Transparent electroconductive film

Abstract

Provided is a transparent electroconductive film that has little surface resistance, has high transparency even without having an optical adjustment layer, suffers from little discoloration, and has appropriate heat shrinkage characteristics.　The transparent electroconductive film is obtained by laminating a transparent electroconductive membrane (5) of an indium-tin composite oxide on at least on one surface of a transparent plastic film substrate (7) directly or via a readily adhesive layer and a curable resin layer, in that order. The transparent electroconductive film does not include an optical adjustment layer, has a surface resistance of 10-100 Ω / □, has a total light transmittance of 80% or more, and has a color difference b of 1.5 or less.

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 in smart windows and capacitive touch panels.

[0002] Transparent conductive films, which are formed by laminating a transparent thin film having low resistance 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] In recent years, the incorporation of capacitive touch panels into mobile devices such as mobile phones and portable music players, as well as into car navigation systems, and the incorporation of smart windows into building and automobile windows has become common. Transparent conductive films used in capacitive touch panels and smart windows are typically layered in the following order: indium-tin oxide (ITO), a high-refractive index layer, a low-refractive index layer, a plastic film, and a hard coat. By optimizing the ITO, high-refractive index layer, and low-refractive index layer, it is easy to achieve a surface resistance of 10 to 100 Ω / □, a total light transmittance of 80% or more, and a color difference b of 1.5 or less. However, the transparent conductive films described above are not suitable for industrial use due to their high manufacturing costs due to their multilayer structure. Furthermore, heating the transparent conductive film to reduce its surface resistance increases manufacturing costs, and the film's thermal shrinkage becomes too small, making it difficult to attach the transparent conductive film to large-screen or three-dimensional smart windows without wrinkles.

[0004] As a measure to solve the above problems, studies are being conducted to achieve both low surface resistance and high transparency in transparent conductive films that do not include optical adjustment layers such as high refractive index layers or low refractive index layers by adjusting the conditions of the transparent conductive film, without heating the transparent conductive film.

[0005] Patent Document 1 describes that a low specific resistance can be achieved by producing a transparent conductive film using krypton gas. According to Example 1 of Patent Document 1, －４ It is possible to produce a transparent conductive film with a low specific resistance of about Ω·cm. However, although a very low surface resistance of about 12 Ω / □ can be achieved and the total light transmittance is 80% or more, the color difference b is greater than 1.5, resulting in a yellowish tint, which poses a transparency issue. Furthermore, because the film is heated at 165°C for 1 hour, the heat shrinkage of the transparent conductive film in both the machine direction and width direction after 30 minutes at 150°C is less than 0.5%, which is undesirable.

[0006] Furthermore, Patent Document 2 describes that a transparent conductive film can be manufactured by optimizing the flow of oxygen in the width direction of the film when manufacturing the transparent conductive film. Example 2 of Patent Document 2 achieves a surface resistance of 100 Ω / □ or less by thickening the transparent conductive film. Example 2 of Patent Document 2 achieves a low surface resistance of 65 Ω / □, and the heat shrinkage rate of the transparent conductive film in the machine direction and width direction after 30 minutes at 150°C is 0.5% or more. However, the total light transmittance is less than 80% and the color difference b is greater than 1.5, indicating issues with transparency. Neither Patent Document 1 nor Patent Document 2 achieves a surface resistance of 10 to 100 Ω / □, a total light transmittance of 80% or more, or a color difference b of 1.5 or less.

[0007] JP 2022-33120 A JP 2019-123243 A

[0008] In view of the above-mentioned conventional problems, an object of the present invention is to provide a transparent conductive film that has low surface resistance, high transparency despite the absence of an optical adjustment layer, little coloration, and moderate heat shrinkage properties.

[0009] The present invention has been made in view of the above circumstances, and provides a transparent conductive film that can solve the above 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, the transparent conductive film does not include an optical adjustment layer and has a surface resistance of 10 to 100 Ω / □, a total light transmittance of 80% or more, and a color difference b of 1.5 or less. [2] The transparent conductive film according to [1], in which a dimensional change rate in at least one of the machine direction and width direction of the film when heat-treated at 150°C for 30 minutes is 0.5% or more. [3] The transparent conductive film according to [1] or [2], in which the transparent conductive film has a thickness of 75 to 115 nm, is formed from indium-tin composite oxide, and the tin oxide concentration in the indium-tin composite oxide is 3 to 40% by mass.

[0010] According to the present invention, a transparent conductive film is provided which has low surface resistance, high transparency despite the absence of an optical adjustment layer, little coloration, and moderate heat shrinkage characteristics. The obtained transparent conductive film is extremely useful for transparent electrodes of capacitive touch panels and smart windows, etc.

[0011] FIG. 1 is a cross-sectional view schematically illustrating one embodiment of the layer structure of a transparent conductive film of the present invention. FIG. 2 is a cross-sectional view schematically illustrating one embodiment of a less preferred layer structure of a transparent conductive film. FIG. 3 is a cross-sectional view schematically illustrating another embodiment of the layer structure of a transparent conductive film of the present invention. FIG. 4 is a cross-sectional view schematically illustrating another embodiment of the layer structure of a transparent conductive film of the present invention. FIG. 5 is a cross-sectional view schematically illustrating another embodiment of the layer structure of a transparent conductive film of the present invention. FIG. 6 is a cross-sectional view schematically illustrating another embodiment of a less preferred layer structure of a transparent conductive film. FIG. 7 is a cross-sectional view schematically illustrating another embodiment of a layer structure of a transparent conductive film of the present invention. FIG. 8 is a cross-sectional view schematically illustrating another embodiment of a layer structure of a transparent conductive film of the present invention. FIG. 9 is a cross-sectional view schematically illustrating another embodiment of a layer structure of a transparent conductive film of the present invention. FIG. 10 is a cross-sectional view schematically illustrating another embodiment of a layer structure of a transparent conductive film of the present invention. FIG. 11 is a cross-sectional view schematically illustrating another embodiment of a less preferred layer structure of a transparent conductive film. FIG. 12 is a cross-sectional view schematically illustrating another embodiment of a layer structure of a transparent conductive film of the present invention.

[0012] (Transparent Conductive Film) The transparent conductive film of the present invention is preferably one in which a transparent conductive film of indium-tin composite oxide is laminated directly on at least one surface of a transparent plastic film substrate, or via an easy-adhesion layer and a curable resin layer in that order. That is, the transparent conductive film of the present invention preferably has a configuration in which a transparent conductive film of indium-tin composite oxide is laminated directly on at least one surface of the plastic film substrate, or a configuration in which an easy-adhesion layer is laminated on at least one surface of the plastic film substrate, a curable resin layer is laminated on the surface of the easy-adhesion layer opposite the plastic film substrate, and a transparent conductive film of indium-tin composite oxide is laminated on the surface of the curable resin layer opposite the easy-adhesion layer (plastic film substrate / easy-adhesion layer / curable resin layer / transparent conductive film of indium-tin composite oxide). By having a transparent conductive film on the surface, the film can be widely used in applications that utilize its conductivity, such as transparent electrodes for capacitive touch panels and smart windows, in electrical and electronic applications. The specific layer structure of the transparent conductive film can be set as appropriate, and examples thereof include the laminate structures shown in the cross-sectional schematic diagrams of FIG. 1, FIGS. 3 to 5, FIGS. 8 to 10, and FIG.

[0013] 1, 3, 4, and 8, a transparent conductive film 5 is formed directly on one side of a transparent plastic film substrate 7. The configuration in Fig. 1 is preferable because it consists only of a transparent conductive film and a transparent plastic substrate and can be manufactured at low cost.

[0014] The transparent conductive film may have a curable resin layer 6 laminated on one side of a transparent plastic film substrate 7 (FIGS. 2, 6, 7, and 11). The presence of the curable resin layer 6 improves adhesion between the transparent conductive film 5 and the curable resin layer 6, effectively preventing the transparent conductive film 5 from peeling or being damaged by external forces, which is preferable. The curable resin layer 6 also provides 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, which is preferable. However, the curable resin layer 6 usually 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, it is preferable to provide an easy-adhesion layer 9 on the surface of the transparent plastic film substrate 7 on which the curable resin layer 6 is laminated. For example, as shown in Figures 5, 9, 10, and 12, 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, making it less likely that the curable resin layer will peel or wear when a strong external force is applied, and therefore, deterioration of the transparent conductive film can be suppressed, which is preferable.

[0015] The transparent conductive film of the present invention may have a functional layer 8 laminated on one side of the transparent plastic film substrate (FIGS. 4 and 10). The presence of the functional layer 8 effectively reduces peeling or damage to the transparent conductive film 5 due to external forces. Furthermore, the functional layer 8 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 5. As shown in FIGS. 4, 7, 8, and 10 to 12, the functional layer 8 is preferably laminated on the surface of the transparent plastic film substrate 7 opposite the surface on which the transparent conductive film 5 is laminated. Furthermore, as shown in FIGS. 8, 11, and 12, for example, an adhesive layer 9 may be laminated between the functional layer 8 and the transparent plastic film substrate 7. The adhesive layer can improve the adhesion between the functional layer and the transparent plastic film substrate, making peeling and wear of the functional layer less likely to occur due to external forces, thereby effectively reducing peeling and wear of the transparent conductive film.

[0016] The transparent conductive film of the present invention may have an easy-adhesion layer 9 laminated on the surface of the transparent plastic film substrate opposite to the surface on which the transparent conductive film 5 is laminated, as shown in Figures 3 and 9. The easy-adhesion layer 9 can impart slipperiness, making it easier to wind up the transparent conductive film into a roll and effectively suppressing the occurrence of wear and deterioration of the transparent conductive film 5.

[0017] The transparent conductive film of the present invention preferably has 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. Having no layer laminated between the transparent conductive film and the transparent plastic film substrate reduces production costs and is therefore more suitable for industrial use. However, if there is a risk of damaging the transparent conductive film of the transparent conductive film during processing of electronic devices such as capacitive touch panels and smart windows, an easy-adhesion layer and a curable resin layer may be laminated between the transparent conductive film and the transparent plastic film substrate in that order from the transparent plastic film substrate side.

[0018] In the present invention, one preferred embodiment of the transparent conductive film has an easy-adhesion layer and a curable resin layer in this order on a transparent plastic film substrate, and a transparent conductive film thereon. However, the easy-adhesion layer and the curable resin layer are not optical adjustment layers such as high refractive index layers and low refractive index layers intended solely for adjusting the refractive index. In this regard, the functional layer described below is also not an optical adjustment layer intended solely for adjusting the refractive index. The transparent conductive film of the present invention does not include an optical adjustment layer. Here, the optical adjustment layer is a layer formed from raw materials or compositions for forming the optical adjustment layer, and the raw materials or compositions for forming the optical adjustment layer may be organic or inorganic. If the raw materials or compositions are inorganic, for example, SiO ２ , Nb ２ O Ｘ(where 4≦x≦5), etc., is selected according to the target refractive index, and the film is generally formed by a method such as sputtering, vacuum deposition, or ion plating. When it is an organic material, it is often a composition containing a resin and particles, and particles such as silica, zirconium oxide, or titanium oxide are often included in a binder resin and coated depending on the target refractive index. However, the present invention does not have such an optical adjustment layer whose sole purpose is to adjust the refractive index.

[0019] The transparent conductive film of the present invention preferably has a surface resistance of 10 to 100 Ω / □. Lower surface resistance contributes to energy savings when used in capacitive touch panels, smart windows, and the like, and to larger screen sizes for capacitive touch panels and smart windows. Taking into account production costs and other factors, a more preferred range of surface resistance suitable for industrial use is 15 to 90 Ω / □, and even more preferably 20 to 80 Ω / □. Surface resistance can be measured by a four-terminal method in accordance with JIS-K7194:1994. A measuring instrument such as the Loresta (registered trademark) AX MCP-T370 manufactured by Nitto Seiko Analytech Co., Ltd. can be used. The unit of surface resistance measured in this manner is Ω / □.

[0020] The transparent conductive film of the present invention preferably has a total light transmittance of 80% or more. The higher the total light transmittance, the better the visibility when used in capacitive touch panels, smart windows, and the like. Taking production costs and other factors into consideration, a more preferred total light transmittance suitable for industrial use is 81% or more, and even more preferably 82% or more. The closer the total light transmittance is to 100%, the more preferred it is, but 95% or less is also preferred, and even 90% or less is also preferred. The total light transmittance can be measured in accordance with JIS-K7361-1:1997. For example, an NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. can be used as a measuring instrument.

[0021] The transparent conductive film of the present invention preferably has a color difference b of 1.5 or less. The lower the color difference b, the less yellowish the transparent conductive film will be, resulting in a better appearance when used in capacitive touch panels, smart windows, and the like. Taking production costs into consideration, the color difference b suitable for industrial use is more preferably 1.0 or less, and even more preferably 0.5 or less. Furthermore, since the larger the negative color difference b, the more blue the transparent conductive film will appear, a color difference b of -2.5 or more is preferred. The color difference b can be measured in accordance with JIS Z 8722:2009. A Ze 6000 manufactured by Nippon Denshoku Industries Co., Ltd. can be used as a measuring instrument, for example.

[0022] The transparent conductive film of the present invention preferably has a dimensional change rate of 0.5% or more in at least one of the machine direction (MD) and width direction (TD) of the film when heat-treated at 150°C for 30 minutes. ２ This is preferable because the transparent conductive film can be attached without wrinkles to the above-mentioned large-screen smart windows and three-dimensional smart windows such as automobile windshields. A more preferable value for the dimensional change rate is 0.55% or more, and even more preferably 0.6% or more. A particularly preferable embodiment is a dimensional change rate of 0.5% or more in both the machine direction and the width direction of the film when heat-treated at 150°C for 30 minutes. Furthermore, a dimensional change rate of 1.3% or less in either the machine direction (MD) or the width direction (TD) of the film when heat-treated at 150°C for 30 minutes is preferable because it can prevent glass curvature when the transparent conductive film is attached to a glass substrate of a smart window. A more preferable value for the dimensional change rate is 1.1% or less, and even more preferably 0.9% or less. A particularly preferable embodiment is a dimensional change rate of 1.3% or less in both the machine direction and the width direction of the film when heat-treated at 150°C for 30 minutes.

[0023] In the transparent conductive film of the present invention, the film thickness of the transparent conductive film is preferably 75 to 115 nm. In order to achieve a high total light transmittance and a small color difference b value, it is a preferred embodiment to reduce reflected light in the visible light region. In the present invention, the transparent conductive film is adjusted so that it can function as an anti-reflection film. In order to achieve a high total light transmittance and a small color difference b value with a single transparent conductive film as in the present invention, this can be achieved by reducing the reflection of blue light in the visible light region. In order to reduce the reflection of blue light, the film thickness of the transparent conductive film is preferably 75 to 115 nm. The film thickness is more preferably 80 to 110 nm, and even more preferably 90 to 105 nm.

[0024] In the transparent conductive film of the present invention, the transparent conductive layer is preferably formed from an indium-tin composite oxide, and the tin oxide concentration in the indium-tin composite oxide is preferably 3 to 40 mass%. By setting the tin oxide concentration to 3 to 40 mass%, low surface resistance can be achieved, which is preferable. The tin oxide concentration is more preferably 4 to 20 mass%, and even more preferably 5 to 15 mass%.

[0025] The transparent conductive film of the present invention preferably has a total transmitted image clarity of 400 to 500%, as measured in accordance with JIS K7374:2024 using an image clarity measuring device employing optical combs with widths of 0.125 mm, 0.25 mm, 0.5 mm, 1 mm, and 2 mm. Transparent conductive films having a total transmitted image clarity within the above-mentioned range desirably exhibit excellent clarity when used in electrical and electronic applications such as capacitive touch panels and smart windows. The total transmitted image clarity is more preferably 430 to 500%, even more preferably 450 to 500%, and particularly preferably 470 to 500%.

[0026] 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, particularly preferably 99.5% or more, and most preferably 100% in an adhesion test 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 plastic film substrate and the layer in contact with the transparent conductive film, such as 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.

[0027] In the transparent conductive film of the present invention, when the three-dimensional surface roughness SRa of the transparent conductive film is X and the three-dimensional surface roughness SRa of the surface opposite to the transparent conductive film side on the transparent plastic film substrate is Y, (X ３ +Y ３ ) １／３ That is, when the three-dimensional surface roughness SRa of the surface of the transparent conductive film on which the transparent plastic film substrate is not laminated is X, and the three-dimensional surface roughness SRa of the surface of the transparent plastic film substrate on which the transparent conductive film is not laminated is Y, (X ３ +Y ３ ) １／３ Preferably, the mean surface roughness SRa is 70 nm or less. The three-dimensional central plane mean surface roughness SRa is specified in ISO 25178, and can be determined using a three-dimensional surface profiler VertScan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x)). Five measurements are taken, and the average value is calculated. It is preferable to round off to the nearest 0.1 nm to obtain data in the nm digit. To select the five points, first select any one point A. Next, select two points, one point 5 cm upstream and one point downstream of A in the machine direction (MD) of the film. Next, select two points, one point 5 cm to the left and one point 5 cm to the right and left of A in the width direction (TD) of the film. (X ３ +Y ３ ) １／３However, if the comb width is 70 nm or less, the sum of the transmitted image clarity of the transparent conductive film at comb widths of 0.125 mm, 0.25 mm, 0.5 mm, 1.0 mm, and 2.0 mm can be easily adjusted to 400% or more and 500% or less, which is desirable because it is possible to provide high-definition images. (X ３ +Y ３ ) １／３ It was confirmed that the smaller the value of X, the smaller the unevenness on both sides of the transparent conductive film, and therefore the straightness of incident light on the transparent conductive film improves, and the clarity of the transmitted image tends to increase (X ３ +Y ３ ) １／３ The value of (X ３ +Y ３ ) １／３ More preferably, (X ３ +Y ３ ) １／３ is 45 nm or less, and even more preferably (X ３ +Y ３ ) １／３ is 35 nm. (X ３ +Y ３ ) １／３ If the surface protrusions are 1 nm or more, the transparent conductive film has some surface protrusions, which allows the film to be easily wound and various properties such as suppression of wear and deterioration of the transparent conductive film to be more effectively exhibited, which is preferable. (X ３ +Y ３ ) １／３ It is also preferable that the thickness is 2 nm or more.

[0028] The method for forming the transparent conductive film is not particularly limited, but a preferred method is, for example, a method in which a transparent conductive film of indium-tin composite oxide is formed by sputtering on at least one surface of a transparent plastic film substrate 7 (hereinafter sometimes referred to as a running film) on the surface of which an easy-adhesion layer 9 and a curable resin layer 6 may be formed in that order. 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 film formation, is wound up into a film roll.

[0029] Figure 13 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).

[0030] 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.

[0031] 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. Adding oxygen gas can improve the surface resistance and total light transmittance of the transparent conductive film. Increasing the film thickness of the transparent conductive film reduces the amount of gas released from the transparent plastic substrate, which tends to reduce the oxygen partial pressure at which the surface resistance is lowest. After extensive investigation, it was found that selecting an oxygen partial pressure equal to or higher than the oxygen partial pressure at which the surface resistance is lowest when the transparent conductive film is 30 nm thick and depositing a transparent conductive film with a thickness of 75 to 115 nm reduces the absorptance of the transparent conductive film to visible light, thereby achieving a high total light transmittance and a small color difference b. However, since the surface resistance of the transparent conductive film tends to increase as the oxygen partial pressure increases, it is preferable to select an oxygen partial pressure that satisfies the total light transmittance, color difference b, and surface resistance. The preferred oxygen partial pressure conditions cannot be generalized because they vary depending on the power supply conditions of the sputtering device used when forming the transparent conductive film. For example, in a pulsed DC magnetron sputtering device, Advanced Energy's Pinnacle III+, the input power to the target area is 1 W / cm. ２When the pulse frequency is 100 kHz, the pulse width is 2.0 μs, and the pressure during sputtering is 0.6 Pa, the oxygen partial pressure is 8.0 × 10 －３ ~12 x 10 －３ It is desirable to form the film at a pressure of 9.0×10 Pa. －３ ~11 x 10 －３ It is Pa.

[0032] When a transparent conductive film having a transparent conductive film laminated on at least one surface of a transparent film substrate is produced by pulse DC magnetron sputtering, the pulse frequency during sputtering is preferably 60 to 150 kHz.

[0033] Furthermore, when using a pulsed DC magnetron sputtering device, a lower pulse frequency is desirable because it reduces the number of times excessive voltage rises immediately after application to the sputtering target, thereby reducing the amount of rare gas such as argon absorbed into the transparent conductive film and thereby reducing the surface resistance of the transparent conductive film. However, a pulse frequency of 60 kHz or higher is desirable because it stabilizes pulsed DC magnetron sputtering. A pulse frequency of 150 kHz or lower is desirable because it prevents the amount of rare gas absorbed into the transparent conductive film from becoming too large, making it easier to reduce the surface resistance of the transparent conductive film.

[0034] Furthermore, a hydrogen atom-containing gas (hydrogen, ammonia, a hydrogen + argon mixed gas, or the like, as long as it contains hydrogen atoms, but water is excluded) may be flowed into the film formation atmosphere using a mass flow controller as needed.

[0035] The median value (the intermediate value between the maximum value and the minimum value) of the ratio of water pressure to inert gas in the film formation atmosphere (water pressure / inert gas partial pressure) is, for example, 7.00×10 －３ or less, preferably 5.00 x 10 －３ or less, more preferably 3.00 x 10 －３The following is the reason. The less water there is in the film-forming atmosphere, the more appropriate the film quality of the transparent conductive film, the more likely it is that the surface resistance will be desirable, and the more easily the absorption of visible light will be suppressed. While it is possible to control the moisture content using the ultimate vacuum as a guide, measuring the moisture content (water pressure) during film formation is preferable for the following two reasons. First, when a film is formed on a plastic film by sputtering, the film is heated and moisture is released from the film. The ultimate vacuum does not reflect the effect of this released moisture. Second, the ultimate vacuum does not reflect the effect of moisture in the center of the roll when a film is formed on a film unwound from the film roll. When a film roll is held in a vacuum chamber, water is easily removed from the outer layer of the roll, but it is difficult to remove water from the inner layer of the roll. When the ultimate vacuum is measured, the film is stopped. However, during film formation, the film runs and the inner layer of the film roll, which contains a lot of water, is unwound, increasing the moisture content in the film-forming atmosphere, which is higher than the moisture content measured when the ultimate vacuum is measured.

[0036] 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 components 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.

[0037] 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, releasing water and organic components from the film. This reduces the amount of water and organic components released from the film during the formation of the transparent conductive film, improving the quality of 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.

[0038] 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, gases such as water 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.

[0039] During film formation, it is preferable to cool the running film 1 to, for example, 0°C or below, preferably -5°C or below. By cooling the running film 1, it is possible to suppress the release of impurities such as water and organic gases from the film, thereby ensuring appropriate film quality for the transparent conductive film. 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.

[0040] 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.

[0041] (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 in the longitudinal direction (MD direction) and / or the width direction (TD 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.

[0042] 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.

[0043] 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.

[0044] The thickness of the transparent plastic film substrate is preferably in the range of 20 μm or more and 200 μm or less, and more preferably 50 μm or more and 130 μm or less. A thinner transparent plastic film substrate is desirable because it contributes to thinner electronic devices such as capacitive touch panels and smart windows. Furthermore, a thicker transparent plastic film substrate is preferable because it maintains mechanical strength and therefore suppresses cracking and peeling of the transparent conductive film when an external force is applied to the transparent conductive film. Furthermore, a thicker transparent plastic film substrate is preferable because it improves handleability during the processing of electronic devices such as capacitive touch panels and smart windows.

[0045] (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. The curable resin layer is not an optical adjustment layer solely intended to adjust the refractive index. 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 improving the winding property of the film and suppressing wear and deterioration of the transparent conductive film. Here, the inclusion of these particles in the curable resin layer is not solely for the purpose of adjusting the refractive index.

[0051] 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.

[0052] The number-average particle diameter of the particles is, for example, 0.01 μm or more and 10 μm or less, preferably 0.03 μm or more and 5 μm or less, more preferably 0.05 μm or more and 3 μm or less, and particularly preferably 0.05 μm or more and 1.8 μm or less. The larger the average particle diameter, the larger the three-dimensional center plane average surface roughness SRa 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 average particle diameter, the smaller the three-dimensional center plane average surface roughness SRa of the curable resin layer, so that the clarity of the appearance of the curable resin layer can be improved.

[0053] The amount of particles in the curable resin layer is, for example, 10% by mass or less, based on 100% by mass of the solid content of the curable resin layer. Preferably, it is 5% by mass or less. The greater the amount of particles, the greater the three-dimensional center plane average surface roughness SRa 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 three-dimensional center plane average surface roughness SRa of the curable resin layer, so that the clarity of the appearance of the curable resin layer can be improved.

[0054] The thickness of the curable resin layer is preferably in the range of 0.1 μm to 15 μm. More preferably, it is in the range of 0.5 μm to 10 μm, and particularly preferably in the range of 1 μm to 8 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 peeling or damage to the transparent conductive film due to external force can be effectively prevented. On the other hand, when it is 15 μm or less, productivity is good and it is preferable.

[0055] 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.

[0056] The curable resin layer is preferably formed by liquefying the curable resin before curing, applying it to the lamination target (a transparent plastic film substrate with an easy-adhesion layer laminated thereon), and curing it. In addition to the curable resin, the coating may also contain 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, can be used alone or in combination.

[0057] 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, for example, 35% by mass or more and 65% by mass or less, preferably 45% by mass or more and 55% by mass or less. By adjusting the solid content concentration within the above range, it is preferable because it is easier to obtain a uniform appearance of the curable resin layer over the entire surface.

[0058] 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.

[0059] 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.

[0060] (Functional Layer) The functional layer is preferably the same as the curable resin layer, except that it is formed on the surface of the transparent plastic film substrate opposite to the surface on which the curable resin layer is formed. The presence of the functional layer can effectively prevent the transparent conductive film from peeling or being damaged by external forces. In addition, the functional layer can impart slipperiness, which is preferable because it makes it easier to wind the transparent conductive film into a roll and effectively suppresses the occurrence of wear and deterioration of the transparent conductive film. As described above, the functional layer is not an optical adjustment layer whose sole purpose is to adjust the refractive index.

[0061] In an adhesion test on the surface of the functional layer in accordance with JIS K5600-5-6:1999, the remaining area ratio of the functional layer is preferably 95% or more, more preferably 99% or more, and particularly preferably 99.5% or more. 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.

[0062] When the transparent conductive film has a functional layer and a curable resin layer, it is preferable that the functional layer and the curable resin layer have the same thickness, and it is also preferable that the absolute value of the difference in thickness between the functional layer and the curable resin layer satisfy the following relationship: 0 μm≦|Thickness of curable resin layer−Thickness of functional layer|≦3 μm By making the difference in thickness between the functional layer and the curable resin layer 3 μm or less, the flatness of the transparent conductive film tends to be improved, which is preferable because it provides excellent processability in the processing of electronic devices such as capacitive touch panels and smart windows.

[0063] (Easy-Adhesion Layer) The easy-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 easy-adhesion layer is preferably 0.001 μm or more and 2.00 μm or less. The easy-adhesion layer is not an optical adjustment layer solely intended to adjust the refractive index.

[0064] This application claims the benefit of priority based on Japanese Patent Application No. 2024-35907 filed on March 8, 2024, and Japanese Patent No. 2024-37849 filed on March 12, 2024. The entire contents of the specifications of Japanese Patent Application No. 2024-35907 filed on March 8, 2024, and Japanese Patent No. 2024-37849 filed on March 12, 2024 are incorporated herein by reference.

[0065] 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.

[0066] 1. Measurement and Evaluation In the case where a protective film was attached to the functional layer, the protective film was peeled off before measurement and evaluation.

[0067] (1) Average Particle Diameter Particles in the cross section of a transparent conductive film were observed using a scanning electron microscope (Keyence Corporation, VE-8800), and 50 particles were randomly selected and observed for their particle diameters. Next, the particle diameters 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 diameters on the horizontal axis in 0.020 μm intervals. For particles with particle diameters within ±30% of the absolute value of the center value of the particle diameter interval where the peak of a normal distribution was the maximum, the number average of the observed particle diameters was taken as the average particle diameter. For example, if the histogram had two peaks of a normal distribution, this indicated that two types of particles had been added, and the average particle diameters of the two types were calculated using the same method as described above.

[0068] (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.

[0069] (3) Content of tin oxide 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). A wavelength with high sensitivity and no interference was selected for the measurement wavelength of each element. Furthermore, commercially available standard solutions of In and Sn were diluted and used as standard solutions.

[0070] (4) Thickness of Transparent Conductive Film A film sample piece laminated with a transparent conductive thin film 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 cross-sectional thin section parallel to the short side of the embedded sample piece was prepared. Next, a portion of this section 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.

[0071] (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.

[0072] (6) Surface Resistivity: 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.

[0073] (7) Color Difference b The transmission color difference b of the transparent conductive film was measured using Ze 6000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS Z 8722:2009.

[0074] (8) Dimensional Change Rate In accordance with JIS C 2151:2019, the dimension A before heat treatment and the dimension B after leaving the film in a thermostatic chamber maintained at 150±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} x 100. Samples (20 mm x 150 mm) were taken in the machine direction and width direction of the transparent conductive film, and the dimensional change rate H of the transparent conductive film in the machine direction at 150°C for 30 minutes was calculated. ＭＤ and the dimensional change rate H of the transparent conductive film in the width direction at 150° C. for 30 minutes. ＴＤ was measured.

[0075] (9) Adhesion test (transparent conductive film, functional layer) This test was carried out in accordance with JIS K5600-5-6:1999. The results in the table below show the adhesion as a remaining area ratio (%). The maximum remaining area ratio is 100%. The closer the remaining area ratio in the adhesion test in the table is to 100%, the smaller the peeled area.

[0076] (10) Three-dimensional central plane average surface roughness SRa The three-dimensional central plane average surface roughness SRa is specified in ISO 25178. The three-dimensional central plane average surface roughness SRa was determined using a three-dimensional surface profiler, VertScan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x)). Five measurements were taken, and the average value was calculated. Values ​​less than 1 nm were rounded off. To select the five points, first, an arbitrary point A was selected. Next, two points were selected, one point each 5 cm upstream and downstream of A in the longitudinal (MD) direction of the film. Next, two points were selected, one point each 5 cm to the left and right of A in the width (TD) direction of the film. Here, the three-dimensional surface roughness SRa of the transparent conductive film was designated X, and the three-dimensional surface roughness SRa of the surface opposite the transparent conductive film on the transparent plastic film substrate was designated Y.

[0077] (11) Sum of transmitted image clarity The transparent conductive film was measured in accordance with JIS K7374:2024 using an image clarity measuring instrument (image clarity measuring instrument ICM-1T manufactured by Suga Test Instruments Co., Ltd.) using optical combs with widths of 0.125 mm, 0.25 mm, 0.5 mm, 1 mm, and 2 mm. The sum of the transmitted image clarity of each optical comb was calculated.

[0078] 2. Laminated Films In each of the Examples and Comparative Examples, the following transparent plastic film substrates were selected and used, and laminated films were prepared by selecting and forming a curable resin layer or functional layer depending on the level.

[0079] (1) Substrates Substrate 1 (transparent plastic film substrate): biaxially oriented transparent PET film (manufactured by Toyobo Co., Ltd., A4360, thickness shown in Table 1) having easy-adhesion layers on both sides. (Corresponding to Example 7, Comparative Example 6, and Comparative Example 8) Substrate 2 (transparent plastic film substrate): biaxially oriented transparent PET film (manufactured by Toyobo Co., Ltd., A4160, thickness shown in Table 1) having an easy-adhesion layer on one side and no easy-adhesion layer on the other side. (Corresponding to Examples 3 and 6) Substrate 3 (transparent plastic film substrate): biaxially oriented transparent PET film (manufactured by Toyobo Co., Ltd., A4160, thickness shown in Table 1) having no easy-adhesion layer on one side. The easy-adhesion surface of this film was wiped with a Bemcot (manufactured by Asahi Kasei Corporation) soaked in methyl ethyl ketone to remove the easy-adhesion layer. (Corresponding to Examples 1, 2, 4, 5, and Comparative Examples 1 to 5, and 7)

[0080] (2) Formation of Curable Resin Layer Silica particles having an average particle size as shown in Table 3 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 3. 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 3, and the mixture was stirred and dissolved uniformly to prepare a coating liquid (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 film thickness was the value shown in Table 3. 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.

[0081] (3) Formation of Functional Layer Silica particles having an average particle size as shown in Table 3 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 functional layer was as shown in Table 3. A mixed solvent of toluene / MEK (8 / 2: mass ratio) was added as the solvent so that the solids concentration was the value shown in Table 3, and the mixture was stirred to dissolve uniformly to prepare a coating liquid. The functional layer-forming coating liquid, prepared so that the coating film thickness was the value shown in Table 3, was applied to the surface of the transparent plastic film substrate opposite the curable resin layer using a Meyer 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 (manufactured by Eye Graphics Co., Ltd., UB042-5AM-W model). ２ ) and the coating was cured.

[0082] Example 1 A laminated film was placed in a vacuum chamber and 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.

[0083] As shown in Fig. 13, a transparent conductive film was formed by sputtering from a target 4 in a chimney 3 onto a running film 1 (transparent plastic film substrate, substrate 3, thickness 38 µm) on a center roll 2. A sintered target of indium-tin composite oxide (tin oxide content in the composite oxide: 10 mass%) was used as the target 4, and the sputtering was performed at 1 W / cm using a pulsed DC magnetron sputtering device, Pinnacle III+, manufactured by Advanced Energy Corporation. ２ A transparent conductive film was formed by pulse DC magnetron sputtering with a power density of 100 kHz, a pulse frequency of 100 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. The oxygen partial pressure at which the surface resistance was lowest at a film thickness of 30 nm was confirmed to be 11 mPa. Next, under the film formation conditions for a film thickness of 30 nm, the speed at which the film passed over the target was changed, and in Example 1, a film was formed with a film thickness of 80 nm. The oxygen partial pressure during film formation in Example 1 was 11 mPa.

[0084] The ratio of water vapor pressure to argon pressure in the film formation atmosphere during sputtering was measured using a gas analyzer (Transpector XPR3, manufactured by Inficon Co., Ltd.) and found to be 1.30×10 －３ The water vapor pressure ratio was adjusted by using a bombardment process, and the height difference of the unevenness on the end surface of the film roll was adjusted by 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. In the bombardment process, SUS (stainless steel) was used as a target, and the heating medium temperature was 0.5 W / cm ２ RF sputtering was performed at 1000 W. 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 shown in Table 1, which was exactly halfway between the maximum and minimum temperatures measured from the start to the end of film formation on the film roll.

[0085] The obtained transparent conductive films were evaluated for the film thickness of the transparent conductive film, total light transmittance (%), color difference b, surface resistance (Ω / □), dimensional change rate (%) in the machine direction and width direction of the film when heat-treated at 150°C for 30 minutes, and adhesion to the transparent conductive film. The results are shown in Tables 1 to 3.

[0086] Examples 2 to 7, Comparative Examples 1 to 8 Experiments were conducted for each Example and Comparative Example by varying the conditions as shown in Tables 1 to 3 relative to Example 1. The type and thickness of the transparent plastic substrate film were selected. In each Example and Comparative Example, in the case where both a curable resin layer and a functional layer were provided, the curable resin layer and the functional layer were laminated on opposite sides of the transparent plastic substrate film. In the case where a curable resin layer was provided, a transparent conductive film was laminated on the side of the curable resin layer where the transparent plastic film substrate was not laminated. In the case where a curable resin layer was not provided, the transparent conductive film was laminated directly on the transparent plastic substrate. In the case where a protective film was provided, a 65 μm-thick polyethylene film 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 where the transparent conductive film was not formed. The order of laminating these layers was as follows: lamination of the curable resin layer on the transparent plastic film substrate, lamination of the functional layer, attachment of the protective film, and formation of the transparent conductive film.

[0087] In each example and comparative example, the content of tin oxide in the indium-tin composite oxide, the pulse frequency, pulse width, and running film speed during sputtering were changed, and the film thickness of the transparent conductive film was changed and adjusted. In all examples and comparative examples, the oxygen partial pressure at which the surface resistance was lowest when the film thickness was 30 nm was 11 mPa.

[0088] In addition, the ratio of water pressure to argon pressure in the film formation atmosphere during sputtering was adjusted by adjusting whether or not a bombardment process was used, whether or not a protective film was used, the unevenness of the film roll end surface, and the temperature of the heating medium in the temperature regulator that controls the temperature of the center roll with which the film runs in contact. Each example and comparative example level is basically the same as Example 1 except for the changes in conditions shown in Tables 1 to 3.

[0089] The transparent conductive films obtained in each Example and Comparative Example were evaluated for the film thickness of the transparent conductive film, total light transmittance (%), color difference b, surface resistance (Ω / □), dimensional change rate (%) in the machine direction and width direction of the film when heat-treated at 150°C for 30 minutes, adhesion to the transparent conductive film, and adhesion to the functional layer in the case of a film having a functional layer, in the same manner as in Example 1. The results are shown in Tables 1 to 3.

[0090] The transparent conductive films obtained in Examples 1 to 7 were preferable transparent conductive films that had low surface resistance, high transparency and little coloration despite the absence of an optical adjustment layer, and could be subjected to moderate heat shrinkage.

[0091] The transparent conductive film obtained in Comparative Example 1 had a small total light transmittance because the transparent conductive film had a small thickness.

[0092] The transparent conductive film obtained in Comparative Example 2 had a large color difference b, possibly due to the fact that the oxygen partial pressure during the formation of the transparent conductive film was somewhat low and the film thickness of the transparent conductive film was thick.

[0093] The transparent conductive film obtained in Comparative Example 3 had a slightly low total light transmittance and a slightly large color difference b, possibly due to the slightly low oxygen partial pressure during the formation of the transparent conductive film.

[0094] The transparent conductive film obtained in Comparative Example 4 had a slightly low total light transmittance and a slightly large color difference b, probably because the oxygen partial pressure during transparent conductive film formation was slightly high and the transparent conductive film was slightly thin.

[0095] The transparent conductive film obtained in Comparative Example 5 had a low total light transmittance, a slightly high surface resistance, and a large color difference b because the oxygen partial pressure during transparent conductive film formation was low.

[0096] The transparent conductive film obtained in Comparative Example 6 did not employ the bombardment process, and the power supply conditions, water pressure / argon partial pressure ratio, temperature conditions, etc. during sputtering were inappropriate, so the surface resistance was large and the color difference b was also large.

[0097] The transparent conductive film obtained in Comparative Example 7 had a slightly low total light transmittance, a slightly high surface resistance, and a slightly high color difference b because the proportion of tin oxide contained in the sputtering target was low and the oxygen partial pressure was low during transparent conductive film formation.

[0098] The transparent conductive film obtained in Comparative Example 8 had a high surface resistance and a large color difference b because the sputtering target contained a high proportion of tin oxide, the bombardment process was not adopted, and the power supply conditions, water pressure / argon partial pressure ratio, temperature conditions, etc. during sputtering were inappropriate.

[0099]

[0100]

[0101]

[0102] The transparent conductive film of the present invention has low surface resistance, and despite the absence of an optical adjustment layer, it is highly transparent, has little coloration, and can be moderately heat-shrunk. Therefore, when used in a capacitive touch panel, it contributes to larger size, improved touch sensitivity, and reduced manufacturing costs. When used in a large-screen smart window or a three-dimensional smart window, it contributes to energy savings and reduced manufacturing costs. The transparent conductive film of the present invention can be applied without wrinkles and is extremely useful.

[0103] 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

Claims

1. A transparent conductive film in which a transparent conductive film of indium-tin composite oxide is laminated on at least one side of a transparent plastic film substrate, either directly or via an easy-adhesion layer and a curable resin layer in that order, and which does not include an optical adjustment layer, has a surface resistance of 10 to 100 Ω / □, a total light transmittance of 80% or more, and a color difference b of 1.5 or less.

2. The transparent conductive film according to claim 1, wherein the dimensional change rate in at least one of the machine direction and width direction of the film when heat-treated at 150° C. for 30 minutes is 0.5% or more.

3. The transparent conductive film according to claim 1 or 2, wherein the transparent conductive film has a thickness of 75 to 115 nm, is formed from an indium-tin composite oxide, and has a tin oxide concentration of 3 to 40 mass %.

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