Transparent electroconductive film

Abstract

Provided is a transparent electroconductive film which has excellent flexibility and fluctuates little in surface resistance value even in severe environments having high temperatures, and high humidities, etc. The transparent electroconductive film comprises a transparent plastic film substrate and a transparent electroconductive film of an indium-tin composite oxide formed on at least one of the surfaces of the transparent plastic film substrate, either directly or with both an easy-to-bond layer and a curing-type resin layer interposed therebetween in this order, wherein the transparent electroconductive film is amorphous. The surface resistance value ratio between before and after a hydrochloric acid immersion test is 0.75 or greater.

Description

Transparent Conductive Film

[0001] The present invention relates to a transparent conductive film in which a transparent conductive film is laminated on a transparent plastic film substrate, and relates to a transparent conductive film that can be suitably used for touch panels.

[0002] Transparent conductive films, which are formed by laminating a transparent, conductive thin film onto a transparent plastic film substrate, are widely used in applications that utilize their conductivity, such as flat panel displays such as liquid crystal displays and electroluminescence (EL) displays, transparent electrodes for touch panels, and transparent electrodes for smart windows, in the electrical and electronic fields.

[0003] Resistive touch panels are often used in mobile devices, car navigation systems, printers, copiers, and other devices. A transparent conductive film is often used on the movable electrode side of resistive touch panels. Some applications, such as car navigation systems, require stable operation even in harsh environments, such as high temperatures and humidity, so films with a crystalline transparent conductive film, which has excellent environmental stability, are often used. However, because films with a crystalline transparent conductive film have poor flexibility, there is a problem that when touch panel input is performed near the double-sided tape that bonds the transparent conductive glass, which is the fixed electrode of the resistive touch panel, to the transparent conductive film, the transparent conductive film can easily crack, causing malfunctions.

[0004] Therefore, in Patent Document 1, the crystallinity of the transparent conductive layer of the transparent conductive film is set to a semi-crystalline state, which is neither too high nor too low, thereby imparting excellent flexibility to the transparent conductive film. However, when the transparent conductive film described in the examples of Patent Document 1 was subjected to a high-temperature, high-humidity treatment at 85°C and 85% RH for 1,000 hours, the surface resistance became more than 1.3 times the value before the high-temperature, high-humidity treatment. Therefore, Patent Document 1 leaves room for further improvement in the stable operation of touch panels under harsh environments such as 85°C and 85% RH for 1,000 hours.

[0005] Patent No. 6172389

[0006] In view of the above-mentioned conventional problems, an object of the present invention is to provide a transparent conductive film that is excellent in flexibility and exhibits little change in surface resistance even under harsh environments such as high temperature and high humidity.

[0007] The present invention has been made in view of the above-described circumstances, and provides a transparent conductive film that can solve the above-described problems, having the following configuration. [1] A transparent conductive film in which a transparent conductive film of indium-tin composite oxide is laminated on at least one surface of a transparent plastic film substrate, either directly or via an easy-adhesion layer and a curable resin layer in that order, wherein the transparent conductive film is amorphous, and the surface resistance ratio before and after a hydrochloric acid immersion test, as determined by Test Method 1 below, is 0.75 or more. [Test Method 1] The surface resistance value R1 of the transparent conductive film before immersion in hydrochloric acid is measured. Next, the transparent conductive film is immersed in 1 mol / L hydrochloric acid at 30°C for 1 minute, and then immediately immersed in pure water for 10 seconds and air-dried. The surface resistance value R2 of the transparent conductive film after air-drying is measured. The value obtained by dividing R1 by R2 is defined as the surface resistance ratio before and after the hydrochloric acid immersion test. If R2 is equal to or greater than the upper limit of the measurement device, R2 is set to ∞, and the surface resistance ratio is set to 0. [2] The transparent conductive film according to [1], wherein the transparent conductive film has a thickness of 14 to 30 nm and a surface resistance ratio of 1.3 or less after high-temperature, high-humidity treatment at 85°C and 85% RH for 1,000 hours. [3] The transparent conductive film according to [1] or [2], wherein the tin oxide concentration in the indium-tin composite oxide is 26 to 60 mass%. [4] The transparent conductive film according to any one of [1] to [3], wherein the surface resistance ratio before and after high-temperature treatment at 80°C for 1,000 hours is 1.3 or less. [5] The transparent conductive film according to any one of [1] to [4], wherein the bending diameter measured by the flexibility test according to Test Method 2 below is 14.0 mm or less. [Test Method 2] A transparent conductive film heat-treated at 120°C for 60 minutes is cut into a rectangular shape measuring 80 mm in the machine direction and 20 mm in the width direction. Next, the short sides of the cut film are connected with a tester to observe the resistance value. The transparent conductive film is bent with the transparent conductive layer facing outward, and the bending diameter (mm) of the transparent conductive film is recorded when the resistance value of the tester begins to increase.[6] The transparent conductive film according to any one of [1] to [5], wherein the dimensional change in both the machine direction and the width direction of the film when heat-treated at 120°C for 30 minutes is 0.10% or more, the dimensional change in at least one of the machine direction and the width direction of the film when heat-treated at 120°C for 30 minutes is 0.35% or more, and the dimensional change in the machine direction of the film after 30 minutes at 120°C, HMD, and the dimensional change in the width direction of the film after 30 minutes at 120°C, HTD, satisfy the following formula (1): 0.00%≦|HMD−HTD|≦0.35% (1).

[0008] According to the present invention, a transparent conductive film is provided which has excellent flexibility and exhibits little change in surface resistance even in harsh environments such as high temperature and high humidity. The obtained transparent conductive film is extremely useful for applications such as resistive touch panels.

[0009] : A cross-sectional schematic diagram showing one embodiment of the laminated structure of the transparent conductive film of the present invention. : A cross-sectional schematic diagram showing another embodiment of the laminated structure of the transparent conductive film of the present invention. : A schematic diagram showing an example of a preferred film-forming apparatus and film-forming method in the present invention. : A schematic diagram showing an evaluation panel in the present invention.

[0010] (Transparent Conductive Film) The transparent conductive film of the present invention is a film in which a transparent conductive film of indium-tin composite oxide is laminated on at least one surface of a transparent plastic film substrate, either directly or via an easy-adhesion layer and a curable resin layer in that order. By having a transparent conductive film on the surface, the film can be widely used in applications in the electrical and electronic fields that utilize its conductivity, such as transparent electrodes in resistive touch panels, etc. The specific layer structure of the transparent conductive film can be set as appropriate, and examples thereof include the laminate structures shown in cross-sectional schematic diagrams such as Figures 1 and 2.

[0011] In some transparent conductive films, a curable resin layer 6 is laminated on one side of a transparent plastic film substrate 7 via an easy-adhesion layer 9 ( FIG. 1 ). The presence of the curable resin layer 6 improves adhesion between the transparent conductive film 5 and the curable resin layer 6, which is preferable because it effectively prevents the transparent conductive film 5 from peeling or being damaged by external forces. The curable resin layer 6 also provides slipperiness, which makes it easier to wind the transparent conductive film into a roll and effectively suppresses wear and tear of the transparent conductive film 5. However, the curable resin layer 6 typically does not have high adhesion to the transparent plastic film substrate 7. Therefore, when the curable resin layer 6 is laminated on the transparent plastic film substrate 7, an easy-adhesion layer 9 is provided on the surface of the transparent plastic film substrate 7 on which the curable resin layer 6 is laminated. For example, as shown in FIG. 1 , by laminating an easy-adhesion layer 9 between a curable resin layer 6 and a transparent plastic film substrate 7, the adhesion between the curable resin layer and the transparent plastic film substrate can be improved, and therefore peeling or wear of the curable resin layer is less likely to occur when a strong external force is applied, thereby suppressing deterioration of the transparent conductive film.

[0012] 2 has a transparent conductive film 5 formed directly on one side of a transparent plastic film substrate 7. The structure in FIG. 2 does not have a curable resin layer, and is therefore preferable because it can be manufactured at low cost.

[0013] When the transparent conductive film 5 is laminated on only one side of the transparent plastic film substrate 7, the transparent conductive film of the present invention preferably has a functional layer 8 laminated via an easy-adhesion layer 9 on the side of the transparent plastic film substrate 7 on which the transparent conductive film 5 is not laminated (FIGS. 1 and 2). The presence of the functional layer 8 suppresses the precipitation of low-molecular-weight components from the transparent plastic film substrate 7 when the transparent conductive film is left in a high-temperature environment, thereby maintaining a good appearance. The presence of the functional layer 8 also effectively reduces peeling or damage to the transparent conductive film 5 due to external forces. The functional layer 8 also imparts slipperiness, making it easier to wind the transparent conductive film into a roll and effectively suppressing wear and tear of the transparent conductive film 5. The easy-adhesion layer 9 improves adhesion between the functional layer 8 and the transparent plastic film substrate 7, making peeling and wear of the functional layer 8 less likely to occur due to external forces, thereby effectively reducing peeling and wear of the transparent conductive film 5.

[0014] The transparent conductive film of the present invention preferably has a surface resistance of 100 to 900 Ω / □. If the surface resistance is 100 to 900 Ω / □, the film can function as a resistive touch panel without any problems. A more preferred range of surface resistance is 200 to 800 Ω / □.

[0015] The transparent conductive film of the present invention preferably has a total light transmittance of 83% or more. The higher the total light transmittance, the better the visibility when used in a resistive touch panel or the like. Taking into account production costs and the like, a more preferred total light transmittance suitable for industrial use is 84% ​​or more. The total light transmittance is preferably closer to 100%, but may be 95% or less, or may be 90% or less.

[0016] The transparent conductive film of the present invention preferably has a dimensional change rate of 0.10% or more in both the machine direction and the width direction of the film when heat-treated at 120°C for 30 minutes. Furthermore, the dimensional change rate in at least one of the machine direction (MD) and the width direction (TD) of the film when heat-treated at 120°C for 30 minutes is preferably 0.35% or more, and more preferably 0.35% or more and 1.00% or less. Furthermore, the dimensional change rate HMD in the machine direction of the film after 30 minutes at 120°C and the dimensional change rate HTD in the width direction of the film after 30 minutes at 120°C preferably satisfy the following formula (1): 0.00%≦|HMD-HTD|≦0.35% (1)

[0017] It is preferable that the dimensional change rate of the film in either the MD or TD when heat-treated at 120°C for 30 minutes is 0.10% or more, as this reduces the likelihood of sagging when a transparent conductive film serving as the upper electrode of a resistive touch panel is attached. It is more preferable that the dimensional change rate of the film in either the MD or TD when heat-treated at 120°C for 30 minutes is 0.15% or more, and even more preferable that it is 0.20% or more. It is preferable that the dimensional change rate of at least one of the film's machine direction and width direction when heat-treated at 120°C for 30 minutes is 0.35% or more, as this reduces the likelihood of sagging when a transparent conductive film serving as the upper electrode of a resistive touch panel is attached. It is more preferable that the dimensional change rate of at least one of the film's machine direction and width direction when heat-treated at 120°C for 30 minutes is 0.40% or more. Furthermore, if the dimensional change rate in either the machine direction (MD) or width direction (TD) of the film when heat-treated at 120°C for 30 minutes is 1.00% or less, this is preferable because it can prevent curvature of the glass when the transparent conductive film is attached to transparent conductive glass, which serves as the lower electrode of a resistive touch panel. It is more preferable that the dimensional change rate in either the machine direction (MD) or width direction (TD) of the film when heat-treated at 120°C for 30 minutes is 0.90% or less, and even more preferable that it is 0.70% or less. Furthermore, it is particularly preferable that the dimensional change rates in both the machine direction and width direction of the film when heat-treated at 120°C for 30 minutes are 1.10% or less. It is preferable if the absolute value of the difference between the dimensional change rate HMD in the machine direction of the film at 120°C for 30 minutes and the dimensional change rate HTD in the width direction of the film at 120°C for 30 minutes is 0.00% or more and 0.35% or less, because this makes it less likely for wrinkles to form when the transparent conductive film, which serves as the upper electrode of a resistive touch panel, is attached. A more preferable absolute value of the difference between the dimensional change rate HMD and the dimensional change rate HTD is 0.00% or more and 0.30% or less.

[0018] In the transparent conductive film of the present invention, the transparent conductive film preferably has a thickness of 14 to 30 nm. A thickness of 14 nm or more is preferred because the change in surface resistance tends to be small even in harsh environments such as high temperatures and high humidity. A thickness of 30 nm or less is preferred because transparency is high. A more preferred thickness is 16 to 27 nm, and even more preferably 18 to 25 nm.

[0019] In the transparent conductive film of the present invention, the transparent conductive film is preferably formed from an indium-tin composite oxide, and the tin oxide concentration in the indium-tin composite oxide is preferably 26 to 60% by mass. Increasing the tin oxide concentration tends to make the transparent conductive film more likely to become amorphous and to reduce changes in surface resistance in harsh environments. By adjusting the tin oxide concentration to 26 to 60% by mass, the transparent conductive film becomes amorphous, thereby increasing the flexibility of the transparent conductive film and enabling the surface resistance and total light transmittance to be set to preferred values. Furthermore, adjusting the tin oxide concentration to 26 to 60% by mass is preferred because it tends to reduce changes in surface resistance in harsh environments. A more preferred value for the tin oxide concentration is 30 to 45% by mass.

[0020] When the tin oxide concentration is reduced to make the transparent conductive film crystalline, the change in surface resistance value in a high-temperature environment tends to be small, but it is difficult to suppress the change in surface resistance value in a high-temperature, high-humidity environment.

[0021] The transparent conductive film of the present invention has an amorphous transparent conductive layer. Amorphous transparent conductive layers are softer than crystalline transparent conductive layers, resulting in increased flexibility of transparent conductive films equipped with amorphous transparent conductive layers. The crystallinity of the transparent conductive layer was determined by X-ray diffraction measurement using the standardized integrated intensity value of the diffraction peak of the (222) plane, which is attributed to the crystallinity of indium-tin composite oxide in the transparent conductive layer. Specifically, a standardized integrated intensity value of the diffraction peak of the (222) plane of 10.0 cps·° / nm or less was determined to be amorphous, and a standardized integrated intensity value of more than 10.0 cps·° / nm was determined to be crystalline.

[0022] The standardized integrated intensity value of the (222) diffraction peak was measured using the following method. Because it is difficult to observe the (222) diffraction peak of the transparent conductive film of the present invention using a focusing optical system, a thin-film measurement method was used, in which X-rays were incident on the sample surface at a very shallow angle to limit the penetration depth, thereby minimizing the influence of the transparent plastic film. Measurements were performed using a Rigaku SmartLab horizontal X-ray diffractometer for thin-film evaluation. A parallel beam optical system with a multilayer mirror was used, and CuKα radiation (wavelength: 1.54186 Å) was used as the light source at 40 kV and 30 mA output. The entrance slit system consisted of a 5.0° Soller slit, a 0.2 mm entrance slit, and a 10 mm longitudinal control slit. A parallel slit analyzer (PSA) with a 0.114 deg. angle was used for the receiving slit. The sample was 20 mm square and fixed to the stage with double-sided tape, or alternatively, it may be fixed by suction using a porous suction sample holder. The X-ray incident angle was set to 0.25°, and the scintillation counter detector was scanned in the out-of-plane direction at a step interval of 0.02° and a measurement speed of 2.0° / min. When CuKα radiation was used, the diffraction line from the (222) plane of the ITO film appeared as a peak at approximately 30.5° (2θ). Background removal was performed using the Sonneveld-Visser method (Sonnveld, E.J. & Visser, J.W., J. Appl. Cryst. 8, 1 (1975)), and the integrated intensity of the diffraction peak from the (222) plane was calculated. The value obtained by dividing the integrated intensity by the film thickness of the transparent conductive film was used as the standardized integrated intensity value of the diffraction peak from the (222) plane. The film thickness of the transparent conductive film was measured using the method described below in "(4) Film Thickness of Transparent Conductive Film."

[0023] The transparent conductive film of the present invention has a surface resistance ratio of 0.75 or more before and after a hydrochloric acid immersion test, as determined by Test Method 1 below. [Test Method 1] The surface resistance R1 of the transparent conductive film before immersion in hydrochloric acid is measured. Next, the transparent conductive film is immersed in 1 mol / L hydrochloric acid at 30°C for 1 minute, then immediately immersed in pure water for 10 seconds, and air-dried. The surface resistance R2 of the transparent conductive film after air-drying is measured. The value obtained by dividing R1 by R2 (the value of R1 ÷ R2) is defined as the surface resistance ratio before and after the hydrochloric acid immersion test. If R2 is equal to or greater than the upper limit of the measuring device, R2 is set to ∞, and the surface resistance ratio before and after the hydrochloric acid immersion test is set to 0.

[0024] The indium-tin composite oxide that constitutes the transparent conductive film is known to dissolve in hydrochloric acid. Amorphous transparent conductive films are particularly more soluble in hydrochloric acid than crystalline transparent conductive films. Furthermore, when a transparent conductive film dissolves in hydrochloric acid, its surface resistance increases due to volumetric loss and chemical changes, resulting in a decrease in the surface resistance ratio before and after the hydrochloric acid immersion test, as determined by Test Method 1. Furthermore, the manner in which the volumetric loss and chemical changes of the transparent conductive film occur when it dissolves in hydrochloric acid varies depending on the state of the transparent conductive film. After extensive investigation, we found that an amorphous transparent conductive film with a surface resistance ratio before and after the hydrochloric acid immersion test of 0.75 or higher determined by Test Method 1 is less likely to change in surface resistance even in harsh environments such as high temperatures and high humidity. Furthermore, even in these harsh environments, the surface resistance of the transparent conductive film is less likely to change due to exposure to chemicals generated by components used in touch panels. The preferred value for the surface resistance ratio before and after the hydrochloric acid immersion test, as determined by Test Method 1, is 0.80 or higher. The surface resistance ratio before and after the hydrochloric acid immersion test determined by Test Method 1 is most preferably 1, but may be 0.97 or less, or may be 0.94 or less.

[0025] The transparent conductive film of the present invention preferably has a surface resistance ratio of 1.3 or less when subjected to a high-temperature, high-humidity treatment at 85°C and 85% RH for 1,000 hours (hereinafter sometimes referred to as the "surface resistance ratio before and after the high-temperature, high-humidity treatment"), and more preferably 0.7 to 1.3. The surface resistance ratio before and after the high-temperature, high-humidity treatment is calculated by dividing the surface resistance of the transparent conductive film after 1,000 hours at 85°C and 85% RH by the surface resistance of the transparent conductive film before the 85°C and 85% RH treatment. A surface resistance ratio of 1.3 or less before and after the high-temperature, high-humidity treatment is preferable because electronic devices such as resistive touch panels can operate without problems even in high-temperature, high-humidity environments, such as the inside of a car in the summer in Japan. A more preferable value for the surface resistance ratio before and after the high-temperature, high-humidity treatment is 1.2 or less. Furthermore, a surface resistance ratio of 0.7 or more before and after the high-temperature, high-humidity treatment is preferable because electronic devices such as resistive touch panels can operate without problems even in high-temperature, high-humidity environments, such as the inside of a car in the summer. A more preferable value of the ratio of the surface resistivity before and after the high-temperature, high-humidity treatment is 0.8 or more.

[0026] The transparent conductive film of the present invention preferably has a surface resistance ratio of 1.3 or less when subjected to high-temperature treatment at 80°C for 1000 hours (hereinafter sometimes referred to as the "surface resistance ratio before and after high-temperature treatment"), more preferably 0.7 or more and 1.3 or less. The surface resistance ratio before and after high-temperature treatment is calculated by dividing the surface resistance of the transparent conductive film after 1000 hours at 80°C by the surface resistance of the transparent conductive film before the 80°C treatment. A surface resistance ratio before and after high-temperature treatment of 1.3 or less is preferable because electronic devices such as resistive touch panels can operate without problems even in high-temperature environments such as the inside of a car in a dry and hot region. A more preferable value of the surface resistance ratio before and after high-temperature treatment is 1.2 or less. Furthermore, a surface resistance ratio before and after high-temperature treatment of 0.7 or more is preferable because electronic devices such as resistive touch panels can operate without problems even in high-temperature environments such as the inside of a car in a dry and hot region. A more preferable value of the surface resistance ratio before and after high-temperature treatment is 0.8 or more.

[0027] The transparent conductive film of the present invention preferably has a bending diameter of 14.0 mm or less in a flexibility test determined by Test Method 2 below. [Test Method 2] A transparent conductive film heat-treated at 120°C for 60 minutes is cut into a rectangle measuring 80 mm in the machine direction and 20 mm in the width direction. Next, the short sides of the cut transparent conductive film are connected with a tester, and the resistance value is observed. The transparent conductive film is bent with the transparent conductive layer facing outward, and the bending diameter (mm) of the transparent conductive film is recorded when the resistance value of the tester begins to increase.

[0028] A bending diameter of 14.0 mm or less in the flexibility test corresponds to a suitable degree of flexibility in the transparent conductive film, and is preferable because it can suppress damage to the transparent conductive film when it is handled and can suppress damage to the transparent conductive film due to local deformation of the transparent conductive film when a very strong force is applied to the transparent conductive film, which is the upper electrode of a resistive touch panel, with a pen. It is more preferable that the bending diameter in the flexibility test obtained by Test Method 2 is 12.0 mm or less. The smaller the bending diameter in the flexibility test obtained by Test Method 2, the more preferable it is, but it may be 3.0 mm or more, or 5.0 mm or more.

[0029] Damage to the transparent conductive film, which is the upper electrode of a resistive touch panel, due to local deformation of the transparent conductive film when a very strong force is applied to the transparent conductive film by a pen input can be determined by the heavy load test described below. [Heavy Load Test] A transparent conductive film according to the present invention was cut into a size of 50 mm x 50 mm and used as one panel plate. A panel plate (size 50 mm x 50 mm) having a 20 nm thick indium-tin composite oxide thin film (tin oxide concentration: 10% by mass) formed on one side of a glass substrate by a sputtering method was used as the other panel plate. One panel plate and the other panel plate were attached with a 5 mm wide double-sided tape (No. 500, manufactured by Nitto Denko Corporation) and overlapped so that the conductive films faced each other as shown in Figure 4 to prepare an evaluation panel. The surface of one panel plate of the evaluation panel (the surface of the transparent plastic film substrate) was slid 10 times with a hemispherical polyacetal pen with a 0.8 mm radius tip, applying a load of 50 N (sliding distance: 30 mm, sliding speed: 180 mm / sec). The pen was set so that the midpoint of the 30 mm sliding section coincided with the center of the evaluation panel (marked with an "x" in Figure 4). After sliding, the transparent conductive film was removed, and the surface resistance (four-terminal method) was measured at any five locations on the sliding section of the transparent conductive film, and the average value was calculated. When measuring the surface resistance, four terminals were arranged perpendicular to the sliding section, with the sliding section located between the second and third terminals. The average surface resistance of the sliding section was divided by the surface resistance of the unslided section (measured by the four-terminal method) to calculate the surface resistance ratio before and after sliding.

[0030] In the present invention, the surface resistance ratio of the transparent conductive film before and after sliding in a heavy load test is preferably 1.5 or less. Having such a characteristic is preferable because, for example, even if a very strong force is applied to a transparent conductive film that is the upper electrode of a resistive touch panel using a pen to input data, causing local deformation of the transparent conductive film, damage to the transparent conductive film (such as cracking or peeling) can be suppressed. More preferably, the surface resistance ratio before and after sliding is 1.2 or less. Here, the surface resistance ratio of the transparent conductive film before and after sliding is preferably 1.0 or more.

[0031] In the transparent conductive film of the present invention, the remaining area ratio of the transparent conductive film on the surface of the transparent conductive film is preferably 95% or more, more preferably 99% or more, and particularly preferably 100% in an adhesion test described below in accordance with JIS K5600-5-6: 1999. When the remaining area ratio of the transparent conductive film in the adhesion test is within the above range, the transparent conductive film is in close contact with the transparent conductive film and layers in contact with the transparent conductive film, such as the transparent plastic film substrate and the cured resin layer, and therefore cracking, peeling, wear, etc. of the transparent conductive film are suppressed when an external force is applied to the transparent conductive film, which is preferable.

[0032] The method for forming the transparent conductive film is not particularly limited, but for example, an easy-adhesion layer 9 and a curable resin layer 6 may be formed in this order on the surface of a transparent plastic film substrate 7 as shown in FIG. 1 , or neither the easy-adhesion layer 9 nor the curable resin layer 6 may be formed as shown in FIG. 2 . Hereinafter, the laminate film in which the easy-adhesion layer 9 and the curable resin layer 6 are formed in this order on the surface of the transparent plastic film substrate 7 in FIG. 1 or the transparent plastic film substrate 7 in FIG. 2 may be referred to as a running film 1. A method in which a transparent conductive film of indium-tin composite oxide is formed by sputtering on at least one surface of the running film 1 is preferred. In order to stably form a transparent conductive film, it is preferable to utilize a pulsed DC magnetron sputtering device. As film formation conditions by the sputtering method, the input power relative to the target area is 0.50 to 7.00 W / cm ２ A pulse frequency of 50 to 180 kHz, a pulse width of 0.3 to 4.0 μs, and a pressure during sputtering of 0.2 to 1.5 Pa are preferred because they allow stable deposition of a transparent conductive film and reduce defects in the transparent conductive film. The effects of defects in the transparent conductive film will be described in detail later. In order to produce a transparent conductive film with high productivity, it is preferable to use a so-called roll-type sputtering device in which a running film is supplied from a film roll and, after deposition, is wound up into the shape of a film roll.

[0033] Figure 3 is a schematic diagram showing an example of a film formation section in a roll-type sputtering apparatus. In this illustrated example, a running film 1 fed from a film roll (not shown) runs while partially contacting the surface of a center roll 2. An indium-tin sputtering target 4 is placed in a chimney 3 having an opening facing the contact point between the running film 1 and the center roll 2, and a thin film of indium-tin composite oxide is deposited and laminated on the surface of the running film 1 running on the center roll 2. The temperature of the center roll 2 can be controlled by a temperature regulator (not shown).

[0034] As the target, a sintered target of indium-tin composite oxide is preferably used. In order to improve production efficiency, a plurality of sintered targets of indium-tin composite oxide may be placed in the film flow direction.

[0035] To form the film formation atmosphere, it is preferable to flow oxygen gas, an inert gas (such as argon gas), or the like, using a mass flow controller as needed. By flowing oxygen gas, the surface resistance value and total light transmittance of the transparent conductive film can be made more appropriate. Furthermore, if necessary, a hydrogen atom-containing gas (hydrogen, ammonia, a hydrogen + argon mixed gas, or the like, as long as it contains hydrogen atoms, is not particularly limited, except for water) may be flowed. The oxygen partial pressure is preferably 1 to 50 mPa.

[0036] A method for forming a transparent conductive film of amorphous indium-tin composite oxide directly on at least one surface of a transparent plastic film substrate or via an easy-adhesion layer and a curable resin layer in this order, wherein the ratio of the water pressure to the inert gas partial pressure in the film formation atmosphere during sputtering is 8.0 × 10 －３ or less, and further, the ratio of the partial pressure of the gas having a mass number of 28 to the partial pressure of the inert gas in the film formation atmosphere during sputtering is 6.0 × 10 －２ It is desirable to form a transparent conductive film as follows: The gas having a mass number of 28 is nitrogen gas or a gas such as carbon monoxide that is released when a plastic film substrate is exposed to plasma by sputtering.

[0037] If the film-forming atmosphere during sputtering contains a large amount of water and gas with a mass number of 28, defects may easily occur in the transparent conductive film. When the transparent conductive film contains many defects, it may react with oxygen and water in the air, increasing the surface resistance of the transparent conductive film and changing its transparency. In particular, placing a transparent conductive film containing many defects in a high-temperature or high-humidity environment promotes reaction with oxygen and water in the air, making it more likely that the surface resistance of the transparent conductive film will increase and its transparency will decrease in a short period of time. Furthermore, since amorphous transparent conductive films have lower chemical stability than crystalline transparent conductive films, the impact of defects in the transparent conductive film will be even greater. Therefore, it is preferable to control the water and gas with a mass number of 28 contained in the film-forming atmosphere during sputtering in order to reduce defects.

[0038] Furthermore, if the amorphous transparent conductive film has many defects, it may be easily dissolved in hydrochloric acid. When dissolved in hydrochloric acid, the defects in the amorphous transparent conductive film may be easily chemically changed, which may lead to an increase in the surface resistance value.

[0039] To control the amount of water or gas with a mass number of 28 when forming a film on a plastic film, it is desirable to actually observe the amount of water or gas with a mass number of 28 during film formation. Using the degree of vacuum achieved immediately before film formation or the amount of gas with a mass number of 28 to control the amount of water or gas with a mass number of 28 in the film formation atmosphere is inappropriate for the following two reasons.

[0040] First, when a film is formed on a plastic film by sputtering, the film is heated, and the amount of water and gas with a mass number of 28 in the film formation atmosphere increases, and the amount of water and gas with a mass number of 28 both increase compared to just before film formation.

[0041] The second point concerns the case of an apparatus that inputs a large amount of transparent plastic film. In such an apparatus, the film is input in roll form. When the film is input into a vacuum chamber in roll form, water and gas with a mass number of 28 easily escape from the outer portion of the roll, but water and gas with a mass number of 28 do not easily escape from the inner portion of the roll. When measuring the ultimate vacuum and the amount of gas with a mass number of 28 immediately before film formation, the film roll is stopped. However, during film formation, the film roll runs, and the inner portion of the roll, which contains a large amount of water and gas with a mass number of 28, is unwound, increasing the water and gas with a mass number of 28 in the film formation atmosphere. As a result, the amount of water and gas with a mass number of 28 immediately before film formation are both greater than those immediately before film formation. In the present invention, the amount of water and gas with a mass number of 28 in the film formation atmosphere are controlled by observing the ratio of the water pressure to the inert gas partial pressure in the film formation atmosphere during sputtering and the ratio of the gas with a mass number of 28 to the inert gas partial pressure in the film formation atmosphere during sputtering.

[0042] During film formation, it is preferable to cool the running film 1 in FIG. 3 to, for example, below 0°C, preferably below −5°C. Cooling the running film 1 can suppress the release of impurities such as water and organic gases from the film, reducing the amount of water and gas with a mass number of 28 in the film formation atmosphere during sputtering and reducing the occurrence of defects in the transparent conductive film. This suppresses the reaction of the transparent conductive film with oxygen and water in the air when the transparent conductive film is placed in a high-temperature or high-temperature, high-humidity environment, thereby suppressing an increase in the surface resistance of the transparent conductive film and changes in its transparency. The film temperature during film formation can be substituted by the set temperature of a temperature controller that adjusts the temperature of the center roll with which the running film comes into contact. The lower limit of the temperature of the running film 1, i.e., the set temperature of the temperature controller, is preferably −50°C or higher, and preferably −20°C or higher.

[0043] A protective film with low water absorption may be attached to the surface of the running film 1 opposite the surface on which the transparent conductive film is formed. By attaching the protective film, water and gases such as organic gases are less likely to be released from the running film 1, improving the quality of the transparent conductive film. Examples of the base material for the protective film include olefins such as polyethylene, polypropylene, and cycloolefin.

[0044] To prevent impurities such as water and organic gases from being released from the film during deposition, it is preferable to set the magnetic field strength of the outer and inner magnets installed below the target to be the same. If the magnetic field strengths of the outer and inner magnets are the same, a closed equilibrium magnetic field is formed between the outer and inner magnets, allowing a large amount of plasma to be present near the target, thereby reducing thermal damage to the film caused by the plasma and suppressing the release of impurities such as water and organic gases from the film. It is desirable to install outer and inner magnets with the same magnetic field strength and a horizontal magnetic field of 80 mT or less at the target surface, and furthermore, to set the shortest distance between the target surface and the film to 6 cm or more. However, since reducing the horizontal magnetic field at the target surface or widening the shortest distance between the target surface and the film reduces the deposition rate of the transparent conductive film and reduces productivity, it is preferable that the horizontal magnetic field at the target surface be 10 mT or more and the shortest distance between the target surface and the film be 15 cm or less.

[0045] By setting the horizontal magnetic field on the target surface and the shortest distance between the target surface and the film within the above-mentioned ranges, it is possible to suppress the release of impurities such as water and organic gases from the film, thereby reducing the amount of water and gas with a mass number of 28 contained in the film formation atmosphere during sputtering and suppressing the occurrence of defects in the transparent conductive film, and also enabling the transparent conductive film to achieve a high level of both conductivity and transparency.

[0046] Before forming a transparent conductive film, it is desirable to subject the transparent plastic film substrate to a bombardment process. The bombardment process involves applying a voltage to generate a discharge and generate plasma while flowing an inert gas, such as argon gas, or a mixture of a reactive gas, such as oxygen, and an inert gas. Specifically, it is desirable to bombard the film by RF sputtering using a stainless steel target or the like. The bombardment process exposes the film to plasma, which releases water and organic gases from the film. This reduces the amount of water and organic gases released from the film during the formation of the transparent conductive film, thereby reducing defects in the transparent conductive film. Furthermore, the bombardment process activates the layers in contact with the transparent conductive film, improving the adhesion of the transparent conductive film.

[0047] In a film roll for forming a transparent conductive film, the height difference between the most convex and most concave points on the roll end surface is preferably 10 mm or less, more preferably 8 mm or less, and even more preferably 4 mm or less. If it is 10 mm or less, water and organic gases are less likely to be released from the film end surface when the film roll is placed in a sputtering device, which is preferable because the film quality of the transparent conductive film is improved. The height difference between the most convex and most concave points on the roll end surface is most preferably 0 mm, but is also preferably 1 mm or more, and even 2 mm or more.

[0048] The sputtering apparatus is preferably equipped with an exhaust device such as a rotary pump, a turbomolecular pump, a cryopump, etc. The amount of moisture in the film formation atmosphere can be controlled by the exhaust device.

[0049] (Transparent Plastic Film Substrate) The transparent plastic film substrate used in the present invention is a film obtained by melt-extruding or solution-extruding an organic polymer into a film shape, and then, as necessary, stretching the film in the longitudinal direction and / or the width direction, cooling, and heat setting. Examples of the organic polymer include polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, and polybutylene terephthalate; polyamides such as nylon 6, nylon 4, nylon 66, and nylon 12; polyimide, polyamideimide, polyethersulfane, polyetheretherketone, polycarbonate, polyarylate, cellulose propionate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyetherimide, polyphenylene sulfide, polyphenylene oxide, polystyrene, syndiotactic polystyrene, and norbornene-based polymers.

[0050] Among these organic polymers, preferred are polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, syndiotactic polystyrene, norbornene-based polymers, polycarbonate, polyarylate, etc. Furthermore, these organic polymers may be copolymerized with a small amount of monomers of other organic polymers, or may be blended with other organic polymers.

[0051] The transparent plastic film substrate may be subjected to surface activation treatment such as corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, or ozone treatment, as long as the object of the present invention is not impaired.

[0052] The thickness of the transparent plastic film substrate is preferably in the range of 75 μm to 250 μm, more preferably 100 μm to 200 μm. A thickness of 75 μm or more of the transparent plastic film substrate is preferable because it has a moderate stiffness, which improves handling during touch panel production, and it maintains mechanical strength, which improves heavy load durability. On the other hand, a thickness of 250 μm or less is preferable because, when used in a touch panel, there is no need to particularly increase the load at which input can be initiated.

[0053] (Curable Resin Layer) The curable resin layer is formed, for example, between a transparent plastic film substrate and a transparent conductive film, and serves as a base layer for the transparent conductive film. The curable resin layer can improve adhesion to the transparent conductive film, thereby effectively preventing the transparent conductive film from peeling or being damaged by external forces. In addition, the curable resin layer can impart slipperiness, making it easier to wind the transparent conductive film into a roll and effectively suppressing wear and tear of the transparent conductive film. Here, when laminating a curable resin layer on a transparent plastic film substrate, it is preferable to previously laminate an easy-adhesion layer on the surface of the transparent plastic film substrate on which the curable resin layer will be laminated. The easy-adhesion layer strongly adheres the curable resin layer to the transparent plastic substrate, making it less likely for the curable resin layer to peel or wear when a strong external force is applied, which is preferable because it can suppress deterioration of the transparent conductive film.

[0054] The resin of the curable resin layer is not particularly limited as long as it is a resin that can be cured by application of energy such as heating, ultraviolet irradiation, or electron beam irradiation, or by a curing agent, and examples thereof include silicone-based resins, acrylic-based resins, methacrylic-based resins, epoxy-based resins, melamine-based resins, polyester-based resins, and urethane-based resins, which may be used alone or in combination of two or more. From the viewpoint of productivity, it is preferable to use an ultraviolet-curable resin as the main component.

[0055] Examples of ultraviolet-curable resins include polyfunctional acrylate resins such as acrylic acid or methacrylic acid esters of polyhydric alcohols, and polyfunctional urethane acrylate resins synthesized from diisocyanates, polyhydric alcohols, and hydroxyalkyl esters of acrylic acid or methacrylic acid, etc. If necessary, these polyfunctional resins can be copolymerized by adding monofunctional monomers such as vinylpyrrolidone, methyl methacrylate, and styrene.

[0056] The curable resin layer preferably contains a curing reaction initiator at least before curing. The curing reaction initiator can be selected depending on the type of curing of the curable resin, and examples thereof include radical polymerization initiators such as thermal polymerization initiators and photopolymerization initiators, and curing agents, with photopolymerization initiators being preferred. The amount of the curing reaction initiator is, for example, 1 part by mass or more and 5 parts by mass or less per 100 parts by mass of the curable resin.

[0057] As the photopolymerization initiator, any known compound that absorbs ultraviolet light and generates radicals can be used without any particular limitation, and examples thereof include various benzoins, phenyl ketones, benzophenones, and the like.

[0058] The curable resin layer may contain particles. The particles can form irregularities on the surface of the curable resin layer. This can impart slipperiness to the curable resin layer, thereby more effectively exhibiting various properties such as improved winding properties of the film and suppression of wear and deterioration of the transparent conductive film.

[0059] Examples of the particles include inorganic particles and organic particles. Examples of inorganic particles include silica particles. Examples of organic particles include particles made of polyester resin, polyolefin resin, polystyrene resin, polyamide resin, etc. The particles may be of one type or two or more types.

[0060] The number-average particle diameter of the particles is, for example, 0.01 μm or more and 10 μm or less. The larger the average particle diameter, the greater the surface roughness of the curable resin layer, so that various properties such as improved film winding properties and suppression of wear deterioration of the transparent conductive film can be more effectively exhibited. The smaller the average particle diameter, the smaller the surface roughness of the curable resin layer, so that the clarity of the appearance of the curable resin layer can be improved. When the number-average particle diameter is large, the amount of water and gas with a mass number of 28 contained in the atmosphere when forming the transparent conductive film may increase.

[0061] The amount of particles in the curable resin layer is, for example, 60% by mass or less relative to 100% by mass of the solid content of the curable resin layer. The greater the amount of particles, the greater the surface roughness of the curable resin layer, so that various properties such as improving the winding property of the film and suppressing wear deterioration of the transparent conductive film can be more effectively exhibited. The smaller the amount of particles, the smaller the surface roughness of the curable resin layer, so that the clarity of the appearance of the curable resin layer can be improved.

[0062] The thickness of the curable resin layer is preferably in the range of 0.1 μm to 15 μm, more preferably 1 μm to 10 μm. When the thickness of the curable resin layer is 0.1 μm or more, the adhesion between the transparent conductive film and the curable resin layer is improved, which is preferable because it effectively prevents the transparent conductive film from peeling or being damaged by external forces. On the other hand, when the thickness of the curable resin layer is 15 μm or less, productivity is good and it is preferable. When the thickness of the curable resin layer is large, the amount of water and gas with a mass number of 28 contained in the atmosphere when forming the transparent conductive film may increase.

[0063] The curable resin layer may contain a resin that is incompatible with the curable resin (hereinafter, simply referred to as an incompatible resin). By dispersing the incompatible resin in the curable resin layer, unevenness can be formed on the surface of the curable resin layer, and the surface roughness can be improved over a wide area. Examples of incompatible resins include polyester resins, polyolefin resins, polystyrene resins, and polyamide resins.

[0064] The curable resin layer is preferably formed by applying a coating liquid obtained by liquefying the curable resin before curing to a lamination target (a transparent plastic film substrate on which an easy-adhesion layer is laminated) and curing the coating liquid. The coating liquid for forming the curable resin layer may contain, in addition to the curable resin, a curing reaction initiator (a radical polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator, a curing agent, etc.; preferably a photopolymerization initiator), particles, a resin incompatible with the curable resin, a solvent, etc. If necessary, other known additives, such as a silicone surfactant or a fluorine-based surfactant, may also be added to the coating liquid. The solvent used is not particularly limited, and examples thereof include alcohol-based solvents such as ethyl alcohol and isopropyl alcohol, ester-based solvents such as ethyl acetate and butyl acetate, ether-based solvents such as dibutyl ether and ethylene glycol monoethyl ether, ketone-based solvents such as methyl isobutyl ketone and cyclohexanone, and aromatic hydrocarbon-based solvents such as toluene, xylene, and solvent naphtha, either alone or in combination.

[0065] The concentration of the curable resin in the coating liquid for forming the curable resin layer (referred to as the solid content concentration) can be appropriately selected taking into consideration the viscosity according to the coating method. The solid content concentration is preferably, for example, 35% by mass or more and 65% by mass or less. By adjusting the solid content concentration within this range, it is preferable to easily obtain a uniform appearance of the curable resin layer over the entire surface.

[0066] The method for coating the coating liquid for forming the curable resin layer onto the lamination target is not particularly limited, and known methods such as bar coating, gravure coating, and reverse coating can be used. The solvent is evaporated and removed from the coated coating liquid in the subsequent drying step. If an incompatible resin (such as a polyester resin) is dissolved in the coating liquid, the incompatible resin becomes particles during this drying step and precipitates in the ultraviolet-curable resin. After drying the coating film, a curable resin layer can be formed by performing an appropriate treatment (e.g., ultraviolet irradiation) depending on the type of curing.

[0067] Before applying the coating liquid for forming the curable resin layer to the surface to be laminated, the easy-adhesion layer may be further treated to improve the adhesion of the curable resin layer, if necessary. Examples of the adhesion improving treatment include a discharge treatment method in which glow or corona discharge is applied to increase carbonyl groups, carboxyl groups, and hydroxyl groups, and a chemical treatment method in which acid or alkali is used to increase polar groups such as amino groups, hydroxyl groups, and carbonyl groups.

[0068] Furthermore, an optical adjustment layer may be provided between the transparent conductive film and the curable resin layer.

[0069] (Functional Layer) The functional layer preferably has the same composition as the curable resin layer, i.e., it is preferable to use the above-described suitable coating liquid for forming a curable resin layer. The coating liquid for forming a functional layer may have the same composition as or a different composition from the coating liquid for forming a curable resin layer. Furthermore, the functional layer is preferably formed on the opposite side of the transparent plastic film substrate from the side on which the curable resin layer is formed, using the same method as the above-described method for forming a curable resin layer. The presence of the functional layer can effectively reduce peeling or damage to the transparent conductive film due to external forces. Furthermore, the functional layer can impart slip properties, which is preferable because it makes it easier to wind the transparent conductive film into a roll and effectively suppresses wear and deterioration of the transparent conductive film.

[0070] In an adhesion test on the surface of the functional layer in accordance with JIS K5600-5-6:1999 (described later), the remaining area ratio of the functional layer is preferably 95% or more, more preferably 99% or more, and most preferably 100%. When the remaining area ratio of the functional layer in the adhesion test is within the above range, the transparent conductive film can adhere closely to the transparent plastic film substrate and the functional layer, effectively reducing peeling or damage of the transparent conductive film due to external forces.

[0071] (Adhesion Layer) The adhesion layer is preferably formed from a composition containing a urethane resin, a crosslinking agent, and a polyester resin. As the crosslinking agent, a blocked isocyanate is preferred, a trifunctional or higher functional blocked isocyanate is more preferred, and a tetrafunctional or higher functional blocked isocyanate is particularly preferred. The thickness of the adhesion layer is preferably 0.001 μm or more and 2.00 μm or less.

[0072] This application claims the benefit of priority based on Japanese Patent Application No. 2024-097738, filed on June 17, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-097738, filed on June 17, 2024, are incorporated herein by reference.

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Various measurements and evaluations in the examples were carried out by the following methods.

[0074] 1. Measurement and Evaluation When a protective film was attached to the functional layer, the protective film was peeled off before the measurement and evaluation.

[0075] (1) Average particle size of particles For the particles contained in the curable resin layer, particles in the cross section of the transparent conductive film were observed using a scanning electron microscope (Keyence Corporation, VE-8800), and 50 particles were randomly selected and their particle sizes were observed. Next, the particle sizes of the 50 observed particles were divided into 0.020 μm intervals, and the total number of particles contained in each interval was determined. A histogram was created with the number of particles on the vertical axis and particle sizes in 0.020 μm intervals on the horizontal axis. For particles with a particle size within ±30% of the absolute value of the center value of the particle size interval where the peak of the normal distribution was reached in the histogram, the number average of the observed particle sizes was taken as the average particle size. The average particle size of the particles contained in the functional layer was also determined in the same manner as for the particles contained in the curable resin layer.

[0076] (2) Thickness of the curable resin layer and the functional layer The thickness of the curable resin layer was determined by observing the cross section of the transparent conductive film with a scanning electron microscope (VE-8800, manufactured by Keyence Corporation) at any five points, and averaging the results to determine the thickness. The same method was used for the thickness of the functional layer.

[0077] (3) Tin oxide concentration (content) in transparent conductive film Cut a sample (approximately 15 cm ２ ) was placed in a quartz Erlenmeyer flask, 20 ml of 6 mol / L hydrochloric acid was added, and the flask was sealed with film to prevent the acid from volatilizing. The flask was left at room temperature for 9 days with occasional shaking to dissolve the transparent conductive film. The remaining film was removed, and the hydrochloric acid in which the transparent conductive film had dissolved was used as the measurement solution. In and Sn in the solution were determined by the calibration curve method using an ICP optical emission analyzer (manufacturer: Rigaku, model: CIROS-120 EOP). Wavelengths with high sensitivity and no interference were selected for the measurement of each element. Furthermore, commercially available standard solutions of In and Sn were diluted and used as the standard solutions. In this example and comparative example, since the transparent conductive film was formed using indium-tin composite oxide, the tin oxide concentration in the transparent conductive film is synonymous with the tin oxide concentration in the indium-tin composite oxide.

[0078] (4) Film Thickness (nm) of Transparent Conductive Film A film sample piece laminated with a transparent conductive layer was cut into a size of 1 mm x 10 mm and embedded in epoxy resin for electron microscopes. This was fixed in a sample holder of an ultramicrotome, and a thin cross-sectional slice parallel to the short side of the embedded sample piece was prepared. Next, a portion of the slice where the thin film was not significantly damaged was photographed using a transmission electron microscope (JEOL, JEM-2010) at an accelerating voltage of 200 kV and a bright field magnification of 10,000 times, and the film thickness was determined from the photograph obtained.

[0079] (5) Total Light Transmittance (%) Total light transmittance was measured in accordance with JIS-K7361-1:1997 using NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0080] (6) Surface Resistivity (Ω / □) Measured by a four-terminal method in accordance with JIS-K7194: 1994. The measuring instrument used was a Loresta (registered trademark) AX MCP-T370 manufactured by Nitto Seiko Analytech Co., Ltd.

[0081] (7) High-temperature, high-humidity treatment (85°C, 85% RH, 1000 hours) After the temperature inside a thermo-hygrostat was set to 85°C and 85% RH, the transparent conductive film was placed in the thermo-hygrostat and removed after 1000 hours. The thermo-hygrostat PR-1KP manufactured by Espec Corporation was used.

[0082] (8) High-temperature treatment (80°C for 1000 hours) After the temperature inside a constant temperature dryer was raised to 80°C, the transparent conductive film was placed in the dryer and removed after 1000 hours. The constant temperature dryer used was a DVS602 manufactured by Yamato Scientific Co., Ltd.

[0083] (9) Surface Resistivity Ratio (Test Method 1) The surface resistance R1 of the transparent conductive film before immersion in hydrochloric acid was measured. Next, the transparent conductive film was immersed in 1 mol / L hydrochloric acid at 30°C for 1 minute, immediately immersed in pure water for 10 seconds, and air-dried. The surface resistance R2 of the transparent conductive film after air-drying was measured. The value obtained by dividing R1 by R2 is shown in Table 3 as the surface resistance ratio before and after the hydrochloric acid immersion test. Note that when R2 was equal to or greater than the upper limit of the measuring device, R2 was set to ∞, and the surface resistance ratio was set to 0. When the high-temperature, high-humidity treatment described in (7) above was performed, the surface resistance values ​​before and after the high-temperature, high-humidity treatment were measured in the same manner as the surface resistance ratio before and after the hydrochloric acid immersion test, and the surface resistance ratio before and after the high-temperature, high-humidity treatment was calculated and shown in Table 3. Furthermore, when the high-temperature treatment described in (8) above was performed, the surface resistance values ​​before and after the high-temperature treatment were measured in the same manner as the surface resistance ratio before and after the hydrochloric acid immersion test, and the surface resistance ratio before and after the high-temperature treatment was calculated and shown in Table 3.

[0084] (10) Bending Diameter (Test Method 2) A transparent conductive film heat-treated at 120°C for 60 minutes was cut into a rectangular shape with a machine direction of 80 mm and a width direction of 20 mm. Next, the short sides of the cut transparent conductive film were connected with a tester, and the resistance value was observed. The transparent conductive film was bent with the transparent conductive film facing outward, and the bending diameter (mm) of the transparent conductive film when the resistance value of the tester began to increase was recorded.

[0085] (11) Adhesion test (transparent conductive film, functional layer) The adhesion test was carried out in accordance with JIS K5600-5-6:1999, except that 100 2 mm square grids (10 × 10) were created on the measurement surface of the adhesion test. The results in Table 3 below show the adhesion as a remaining area ratio (%). The adhesion was judged for each grid, and if more than half of the grid was adhered, it was judged to be adhered. The maximum remaining area ratio is 100%. The closer the remaining area ratio of the adhesion test in Table 3 is to 100%, the smaller the peeled area.

[0086] (12) Dimensional Change Rate In accordance with JIS C 2151:2019, a transparent conductive film was cut so that the measurement direction for dimensional change rate was 150 mm and the direction perpendicular to the measurement direction was 20 mm. The dimension A before heat treatment and the dimension B after leaving the film in a thermostatic chamber maintained at 120±3°C for 30 minutes were measured using an image measuring device (Mitutoyo Corporation: QS-L1020Z / AF), and the dimensional change rate H was calculated using the following formula: H (%) = {(A−B) / A}×100 Using the above measurement method, the dimensional change rate HMD of the transparent conductive film in the machine direction after 30 minutes at 120°C and the dimensional change HTD of the transparent conductive film in the width direction after 30 minutes at 120°C were measured.

[0087] (13) Surface Resistivity Ratio Before and After Sliding (Heavy Load Test) A transparent conductive film cut to 50 mm x 50 mm was used as one panel plate, and a panel plate (size 50 mm x 50 mm) with a 20 nm thick indium-tin composite oxide thin film (tin oxide concentration: 10% by mass) formed on one side of a glass substrate by sputtering was used as the other panel plate. The film-side panel plate and the glass-side panel plate were attached with 5 mm wide double-sided tape (Nitto Denko Corporation No. 500) and stacked so that the conductive films faced each other as shown in Figure 4 to prepare an evaluation panel. The transparent conductive film side of this evaluation panel was slid 10 times with a hemispherical polyacetal pen with a 0.8 mm radius tip under a load of 50 N (sliding distance 30 mm, sliding speed 180 mm / sec). At this time, the midpoint of the 30 mm sliding section was set to coincide with the center of the evaluation panel (marked with an x ​​in Figure 4). After sliding, the transparent conductive film was removed, and the surface resistance (four-terminal method) was measured at any five points on the sliding portion, and the average value was calculated. When measuring the surface resistance, four terminals were arranged in a direction perpendicular to the sliding portion, with the sliding portion located between the second and third terminals. The average surface resistance of the sliding portion was divided by the surface resistance of the non-sliding portion (measured by the four-terminal method) to calculate the ratio of the surface resistance before and after sliding.

[0088] (14) Standardized Integrated Intensity Value of the (222) Diffraction Peak. Because it is difficult to observe the (222) diffraction peak of the transparent conductive film of the present invention using a focusing optical system, a thin-film measurement method was used, in which X-rays were incident on the sample surface at a very shallow angle to limit the penetration depth, thereby minimizing the influence of the transparent plastic film. Measurements were performed using a Rigaku SmartLab horizontal X-ray diffractometer for thin-film evaluation. A parallel beam optical system with a multilayer mirror was used, and CuKα radiation (wavelength: 1.54186 Å) was used as the light source at 40 kV and 30 mA output. The entrance slit system consisted of a 5.0° Soller slit, a 0.2 mm entrance slit, and a 10 mm longitudinal control slit. A parallel slit analyzer (PSA) with a 0.114 deg. The receiving slit was a 20 mm square sample, fixed to the stage with double-sided tape, or alternatively, a porous adsorption sample holder was used. The X-ray incident angle was set to 0.25°, and the scintillation counter detector was scanned in the out-of-plane direction at a step interval of 0.02° and a measurement speed of 2.0° / min. When CuKα radiation was used, the diffraction line from the (222) plane of the ITO film appeared as a peak at approximately 30.5° (2θ). Background removal was performed using the Sonneveld-Visser method (Sonnveld, E.J. & Visser, J.W., J. Appl. Cryst. 8, 1 (1975)), and the integrated intensity of the diffraction peak from the (222) plane was calculated. The value obtained by dividing the integrated intensity by the film thickness of the transparent conductive film was used as the normalized integrated intensity value of the diffraction peak from the (222) plane. The film thickness of the transparent conductive film was obtained using the method described above in "(4) Film Thickness of the Transparent Conductive Film."

[0089] 2. Laminated Film In each of the Examples and Comparative Examples, the following transparent plastic film substrates were selected and used, and laminated films were prepared by selectively forming a curable resin layer or functional layer.

[0090] (1) Substrates Any of the following substrates 1 to 4 was used as the transparent plastic film substrate. Substrate 1 (transparent plastic film substrate): A biaxially oriented transparent PET film (manufactured by Toyobo Co., Ltd., A4360, thickness 188 μm) having an easy-adhesion layer on both sides (corresponding to Examples 1, 2, 4, 5, Comparative Examples 2, 4 and 5). Substrate 2 (transparent plastic film substrate): A biaxially oriented transparent PET film (manufactured by Toyobo Co., Ltd., A4160, thickness 188 μm) having an easy-adhesion layer on one side and no easy-adhesion layer on the other side (corresponding to Example 6 and Comparative Example 3). Substrate 3 (transparent plastic film substrate): A biaxially oriented transparent PET film (manufactured by Toyobo Co., Ltd., A4360, thickness 75 μm) having an easy-adhesion layer on both sides (corresponding to Example 3). Substrate 4 (transparent plastic film substrate): A biaxially oriented transparent PET film (manufactured by Toyobo Co., Ltd., A4360, thickness 50 μm) having an easy-adhesion layer on both sides (corresponding to Comparative Example 1).

[0091] (2) Formation of Curable Resin Layer Silica particles having an average particle size as shown in Table 1 were blended into 100 parts by mass of a photopolymerization initiator-containing acrylic resin (Seikabeam (registered trademark) EXF-01J, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) so that the content in the curable resin layer was as shown in Table 1. A mixed solvent of toluene / methyl ethyl ketone (MEK) (8 / 2: mass ratio) was added so that the solids concentration was the value shown in Table 1, and the mixture was stirred to dissolve uniformly, thereby preparing a curable resin layer-forming coating liquid. The curable resin layer-forming coating liquid was applied to one side of a transparent plastic film substrate using a Meyer bar so that the coating thickness was the value shown in Table 1. After drying at 80°C for 1 minute, the coating was irradiated with ultraviolet light (light intensity: 300 mJ / cm) using an ultraviolet irradiation device (manufactured by Eye Graphics Co., Ltd., UB042-5AM-W model). ２ ) and the coating was cured.

[0092] (3) Formation of Functional Layer Silica particles having an average particle size as shown in Table 1 were blended with 100 parts by mass of a photopolymerization initiator-containing acrylic resin (Seikabeam (registered trademark) EXF-01J, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) so as to achieve the content in the functional layer as shown in Table 1. A mixed solvent of toluene / MEK (8 / 2: mass ratio) was added as a solvent so as to achieve the solids concentration as shown in Table 1, and the mixture was stirred to dissolve uniformly, thereby preparing a functional layer-forming coating liquid. The functional layer-forming coating liquid was applied to the surface of a transparent plastic film substrate opposite to the curable resin layer using a Mayer bar. After drying at 80°C for 1 minute, the coating was irradiated with ultraviolet light (light intensity: 300 mJ / cm) using an ultraviolet irradiation device (UB042-5AM-W, manufactured by Eye Graphics Co., Ltd.). ２ The amount of the coating solution for forming the functional layer was adjusted so that the thickness of the coating film would be the value shown in Table 1.

[0093] Example 1 The laminated film was wound into a roll to obtain a film roll. The obtained film roll had a height difference of 2 mm between the most convex and most concave points on the roll end surface. Next, the film roll was placed in a vacuum chamber, and a 1.5 × 10 －４ The pressure measured after oxygen introduction was recorded as the oxygen partial pressure, and then argon was introduced until the total pressure reached 0.6 Pa.

[0094] The film was unwound from the film roll, and as shown in Figure 3, a transparent conductive film was formed by sputtering from a target 4 in a chimney 3 onto a curable resin layer of a running film 1 on a center roll 2. A sintered target of indium-tin composite oxide (tin oxide concentration in the composite oxide: 36 mass %) was used as the target 4, and a magnet was placed directly below the target 4 (omitted from Figure 3) so that the horizontal magnetic field on the target surface was 25 mT and the magnetic field strength of the inner and outer magnets was the same. The shortest distance between the surface of the target 4 and the running film 1 was 7.5 cm, and a Pinnacle III+ from Advanced Energy Corporation was used as a DC pulse sputtering power source with a power of 4.3 W / cm. ２A transparent conductive film was formed on the curable resin layer by pulse DC magnetron sputtering, with a power density of 100 Hz, a pulse frequency of 120 kHz, and a pulse width of 2 μs. The film thickness was controlled by changing the speed at which the film passed over the target. In Example 1, a transparent conductive film was formed with a film thickness of 15 nm. The oxygen partial pressure during film formation in Example 1 was 16 mPa.

[0095] The ratio of the water pressure to argon in the film formation atmosphere during sputtering and the ratio of the partial pressure of a gas with a mass number of 28 to argon were measured using a gas analyzer (Transpector XPR3, manufactured by Inficon Co., Ltd.). The ratio of the water pressure to argon was 3.30 × 10 －３ , the ratio of the partial pressure of the gas with mass number 28 to that of argon is 1.24 × 10 －２ The water vapor pressure ratio and the gas partial pressure ratio of the mass number 28 were adjusted by adopting a bombardment process and adjusting the temperature of the heating medium in a temperature controller that controls the temperature of the center roll with which the film is in contact and runs. In the bombardment process, SUS (stainless steel) was used as a target, and the heating medium temperature was adjusted to 0.5 W / cm ２ RF sputtering was performed at 1000 K. The amount of gas introduced into the RF sputtering was the same as the amount of gas introduced into the vacuum device described in the Examples. The temperature of the hot medium was set to the value (-10°C) described in Table 2, which was exactly halfway between the maximum and minimum temperatures measured from the start to the end of film formation on the film roll.

[0096] The tin oxide concentration in the transparent conductive film and the film thickness of the transparent conductive film obtained are shown in Table 2. The total light transmittance (%), surface resistivity (Ω / □), the standardized integrated intensity of the (222) diffraction peak, the surface resistivity ratio before and after a hydrochloric acid immersion test, the surface resistivity ratio before and after a high-temperature, high-humidity treatment, the surface resistivity ratio before and after a high-temperature treatment, the dimensional change rate (%) in the machine direction and width direction of the film when heat-treated at 120°C for 30 minutes, the adhesion of the transparent conductive film, the adhesion of the functional layer, a flexibility test, and a heavy load test were also evaluated. The results are shown in Table 3.

[0097] Examples 2 to 6 and Comparative Examples 1 to 5: Various conditions were changed relative to Example 1 as shown in Tables 1 and 2. The type and thickness of the transparent plastic substrate film were selected. In each Example and Comparative Example, when both a curable resin layer and a functional layer were provided, the curable resin layer and the functional layer were provided on opposite sides of the transparent plastic substrate film. In addition, a transparent conductive film was laminated on the side of the curable resin layer on which the transparent plastic film substrate was not laminated. However, in Example 6 and Comparative Example 3, no curable resin layer was provided, and the functional layer was laminated on the adhesive layer on the adhesive layer on the side of the substrate film on which the adhesive layer was present, and the transparent conductive film was formed on the surface of the substrate film on which the adhesive layer was not present. When a protective film was provided, a polyethylene film with a thickness of 65 μm was used as the protective film. An acrylic adhesive was applied to one side of the protective film. The protective film was attached to the outermost surface of the transparent plastic substrate film on the side on which the transparent conductive film was not formed. The order in which these layers were laminated was as follows: lamination of a curable resin layer on a transparent plastic film substrate, lamination of a functional layer, attachment of a protective film, and formation of a transparent conductive film.

[0098] In each example and comparative example, the film thickness of the transparent conductive film was adjusted by changing the horizontal magnetic field on the target surface, the difference in magnetic field strength between the inner magnet and the outer magnet, the oxygen partial pressure, the tin oxide concentration in the indium-tin composite oxide, and the shortest distance between the surface of the target 4 and the running film 1.

[0099] In addition, the ratio of water pressure to argon and the ratio of gas partial pressure of mass number 28 to argon in the film formation atmosphere during sputtering were adjusted by adjusting the horizontal magnetic field on the target surface, the difference in magnetic field strength between the inner and outer magnets, whether a bombardment process was used, the presence or absence of a protective film, the difference in unevenness in the edge surface of the film roll, the temperature of the heating medium in the temperature regulator that controls the temperature of the center roll in contact with which the film runs, and the thickness of the curable resin layer and functional layer. Each example and comparative example is basically the same as Example 1 except for the changes in conditions shown in Tables 1 and 2.

[0100] The transparent conductive films obtained in each Example and Comparative Example were evaluated for the tin oxide concentration in the transparent conductive film, the film thickness of the transparent conductive film, the total light transmittance (%), the surface resistivity (Ω / □), the standardized integrated intensity value of the diffraction peak of the (222) plane, the surface resistivity ratio before and after the hydrochloric acid immersion test, the dimensional change rate (%) in the machine direction and width direction of the film when heat-treated at 120°C for 30 minutes, the adhesion to the transparent conductive film, the adhesion of the functional layer, the flexibility test, and the heavy load test in the same manner as in Example 1. The results are shown in Tables 2 and 3.

[0101] The transparent conductive films obtained in Examples 1 to 6 have high chemical stability, as their surface resistance values ​​do not change much before and after the hydrochloric acid immersion test, and therefore the change in surface resistance value is small even in harsh environments such as high temperature and humidity, high temperature, etc. Furthermore, the integrated intensity normalized value of the diffraction peak of the (222) plane is small, so the transparent conductive film has high amorphousness, and therefore the transparent conductive film has excellent flexibility and heavy load durability.

[0102] The transparent conductive films obtained in Comparative Examples 1, 2, 4, and 5 had a large change in surface resistance before and after the hydrochloric acid immersion test because the ratio of water pressure to argon during transparent conductive film formation, the ratio of the partial pressure of the gas with a mass number of 28 to argon, the tin oxide concentration in the transparent conductive film, and the film thickness were all outside of the preferred ranges. Because these films had low chemical stability, the change in surface resistance was also large even under harsh environments such as high temperature and humidity. Furthermore, the integrated intensity standard value of the (222) diffraction peak was small and the transparent conductive film was highly amorphous, resulting in excellent flexibility and a transparent conductive film that satisfied heavy load durability. However, in Comparative Example 1, the heavy load durability was poor due to the thin thickness of the transparent plastic substrate.

[0103] The transparent conductive film obtained in Comparative Example 3 had a high crystalline state due to the low tin oxide concentration in the transparent conductive film, resulting in a large integrated intensity standard value for the diffraction peak of the (222) plane, but the change in surface resistance before and after the hydrochloric acid immersion test was small due to the low tin oxide concentration. Furthermore, the film had poor flexibility due to its crystalline state, resulting in poor heavy load durability.

[0104]

[0105]

[0106]

[0107] The transparent conductive film of the present invention exhibits little change in surface resistance even in harsh environments such as high temperature and high humidity, is flexible, and has an appropriate dimensional change rate in at least one of the machine direction and width direction of the film. Therefore, when used in a touch panel, it is extremely useful because it contributes to stable input performance in harsh environments, durability against heavy load input using a pen or the like, and a good appearance with reduced wrinkles and sagging.

[0108] REFERENCE SIGNS LIST 1 Running film 2 Center roll 3 Chimney 4 Target 5 Transparent conductive film 6 Curable resin layer 7 Transparent plastic film substrate 8 Functional layer 9 Easy-adhesion layer 10 Evaluation panel 11 Double-sided tape

Claims

1. A transparent conductive film having a transparent conductive film of indium-tin composite oxide laminated on at least one surface of a transparent plastic film substrate, either directly or via an easy-adhesion layer and a curable resin layer in that order, wherein the transparent conductive film is amorphous and the surface resistance ratio before and after a hydrochloric acid immersion test, as determined by Test Method 1 below, is 0.75 or more. [Test Method 1] The surface resistance value R1 of the transparent conductive film before immersion in hydrochloric acid is measured. Next, the transparent conductive film is immersed in 1 mol / L hydrochloric acid at 30°C for 1 minute, immediately immersed in pure water for 10 seconds, and air-dried. The surface resistance value R2 of the transparent conductive film after air-drying is measured. The value obtained by dividing R1 by R2 is defined as the surface resistance ratio before and after the hydrochloric acid immersion test. If R2 is equal to or greater than the upper limit of the measurement device, R2 is set to ∞, and the surface resistance ratio is set to 0.

2. The transparent conductive film according to claim 1, wherein the transparent conductive film has a thickness of 14 to 30 nm and a surface resistance ratio of 1.3 or less when subjected to high-temperature, high-humidity treatment at 85°C and 85% RH for 1,000 hours.

3. The transparent conductive film according to claim 1 or 2, wherein the concentration of tin oxide in the indium-tin composite oxide is 26 to 60 mass %.

4. The transparent conductive film according to claim 1 or 2, wherein the surface resistance ratio before and after high-temperature treatment at 80° C. for 1,000 hours is 1.3 or less.

5. The transparent conductive film according to claim 1 or 2, wherein the bending diameter in the flexibility test determined by the following Test Method 2 is 14.0 mm or less. [Test Method 2] A transparent conductive film heat-treated at 120°C for 60 minutes is cut into a rectangle measuring 80 mm in the machine direction and 20 mm in the width direction. Next, the short sides of the cut film are connected with a tester, and the resistance value is observed. The transparent conductive film is bent with the transparent conductive layer facing outward, and the bending diameter (mm) of the transparent conductive film is recorded when the resistance value of the tester begins to increase.

6. The transparent conductive film according to claim 1 or 2, wherein the dimensional change in both the machine direction and width direction of the film when heat treated at 120°C for 30 minutes is 0.10% or more, the dimensional change in at least one of the machine direction and width direction of the film when heat treated at 120°C for 30 minutes is 0.35% or more, and the dimensional change in the machine direction of the film after 30 minutes at 120°C, HMD, and the dimensional change in the width direction of the film after 30 minutes at 120°C, HTD, satisfy the following formula (1): 0.00%≦|HMD-HTD|≦0.35% ... (1)

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