JP7732564B2 - Transparent Conductive Film - Google Patents

Description

The present invention relates to a transparent conductive film in which a transparent conductive layer of crystalline indium-tin composite oxide is laminated onto a transparent plastic film substrate, and in particular to a transparent conductive film that exhibits excellent pen sliding durability, pen heavy pressure durability, and high definition when used in a resistive touch panel.

Transparent conductive films, which are made by laminating a transparent, low-resistance thin film onto a transparent plastic substrate, are widely used in electrical and electronic applications that utilize their conductivity, such as flat panel displays such as liquid crystal displays and electroluminescence (EL) displays, and as transparent electrodes in touch panels.

Resistive touch panels combine a fixed electrode, made of a glass or plastic substrate coated with a transparent conductive thin film, with a movable electrode (film electrode), made of a plastic film coated with a transparent conductive thin film. These electrodes are layered on top of a display. Pressing the film electrode with a finger or pen, bringing the fixed electrode and the film electrode's transparent conductive thin film into contact, provides input for the touch panel's position recognition. Compared to a finger, a pen often exerts a stronger force on the touch panel. Continuous pen input on a touch panel can cause damage such as cracking, peeling, or wear to the transparent conductive thin film on the film electrode side. Furthermore, applying a force greater than that expected for normal use, such as hitting the touch panel hard with a pen or using very strong pen input force, can cause damage such as cracking or peeling to the transparent conductive thin film. To address these issues, there is a demand for transparent conductive films that combine excellent pen sliding durability with excellent pen heavy pressure durability. Furthermore, high-definition images on touch panels are also required.

One method for improving pen sliding durability is to make the transparent conductive thin film on the film electrode side crystalline (see, for example, Patent Document 1). However, conventional transparent conductive films have achieved excellent pen sliding durability by controlling the crystallinity of indium-tin composite oxide. However, conventional transparent conductive films perform poorly when subjected to the pen heavy pressure durability test described below.

Japanese Patent Application Laid-Open No. 2004-071171

In view of the above-mentioned conventional problems, the object of the present invention is to provide a transparent conductive film that, when used in a touch panel, has excellent pen sliding durability and pen heavy pressure resistance, and is capable of providing high-definition images.

The present invention has been made in view of the above circumstances, and the transparent conductive film of the present invention, which has been able to solve the above problems, has the following configuration.
1. A transparent conductive film comprising a transparent conductive film of indium-tin composite oxide laminated on one surface of a transparent plastic film substrate, wherein the on-resistance of the transparent conductive film in the pen sliding durability test described below is 10 kΩ or less, and further, the rate of increase in the surface resistance of the transparent conductive film in the pen heavy pressure test described below is 1.5 or less, and further, 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 is 250% or more but less than 500%.
(Pen sliding durability test method)
The transparent conductive film according to the present invention is used as one panel plate, and the other panel plate is a transparent conductive thin film consisting of a 20 nm-thick indium-tin composite oxide thin film (tin oxide content: 10% by mass) sputtered onto a glass substrate. The two panel plates are arranged with the transparent conductive thin films facing each other via 30 μm diameter epoxy beads, and the film-side panel plate and the glass-side panel plate are attached with 170 μm thick double-sided tape to produce a touch panel. Next, a polyacetal pen (tip shape: 0.8 mmR) is applied with a load of 2.5 N, and a linear sliding test of 180,000 strokes is performed on the touch panel. In this test, the pen load is applied to the transparent conductive film surface according to the present invention.
The sliding distance at this time is 30 mm, and the sliding speed is 180 mm/sec. After this sliding durability test, the ON resistance (the resistance value when the movable electrode (film electrode) and the fixed electrode come into contact) is measured when the sliding portion is pressed with a pen load of 0.8 N.
(Pen pressure test method)
A 50 mm x 50 mm piece of transparent conductive film according to the present invention was used as one panel plate, and the other panel plate was a 20 nm-thick transparent conductive thin film consisting of an indium-tin composite oxide thin film (tin oxide content: 10% by mass) sputtered onto a glass substrate. These two panels were arranged with the transparent conductive thin films facing each other, with 30 μm diameter epoxy beads sandwiched between them. The film-side panel plate and the glass-side panel plate were attached with double-sided tape adjusted to a thickness of 120 μm to produce a touch panel. A polyacetal pen (tip shape: 0.8 mmR) was used to apply a 35 N load to a position 2.0 mm from the end of the double-sided tape, and linear sliding was performed 10 times (five round trips) parallel to the double-sided tape. In this test, the pen load was applied to the surface of the transparent conductive film according to the present invention. The sliding distance was 30 mm, and the sliding speed was 20 mm/sec. The sliding was performed in a position where there were no epoxy beads. After sliding, the transparent conductive film is removed and the surface resistance (four-terminal method) is measured at any five points on the sliding area, and the average value is calculated. When measuring the surface resistance, four terminals are arranged perpendicular to the sliding area, with the sliding area located between the second and third terminals. The average surface resistance value of the sliding area is divided by the surface resistance value of the non-sliding area (measured using the four-terminal method) to calculate the increase rate of surface resistance.
2. The transparent conductive film according to claim 1, wherein the crystal grain size of the transparent conductive film of indium-tin composite oxide is 10 to 100 nm, the degree of crystallinity of the transparent conductive film of indium-tin composite oxide is 20 to 80%, the transparent conductive film of indium-tin composite oxide contains 0.5 to 10 mass % of tin oxide, the thickness of the transparent conductive film of indium-tin composite oxide is 10 to 30 nm, and when the three-dimensional surface roughness SRa of the transparent conductive film of indium-tin composite oxide is X, X is 1 to 100 nm, and further when the three-dimensional surface roughness SRa of the surface of the transparent plastic film substrate opposite to the transparent conductive film side is Y, ( ^X3 + ^Y3 ) ^1/3 is 140 nm or less.
3. The transparent conductive film according to claim 1 or 2, wherein the transparent conductive film does not peel off when an adhesion test (JIS K5600-5-6:1999) is conducted on the surface of the transparent conductive film, and wherein a bending resistance test (JIS K5600-5-1:1999) is conducted on the indium-tin composite oxide transparent conductive film side of the transparent conductive film, and the mandrel diameter at which cracks or peeling occurs when the bending portion is observed with a 10x magnifying glass is smaller than 20 mm.
4. The transparent conductive film according to any one of the above items 1 to 3, wherein the transparent conductive film has a thickness of 100 to 250 μm.
5. The transparent conductive film according to any one of the above items 1 to 4, which has a curable resin layer between the transparent conductive film of indium-tin composite oxide and the transparent plastic film substrate.

The present invention makes it possible to provide a transparent conductive film that has both excellent pen sliding durability and excellent pen heavy pressure durability, and is capable of providing high-definition images. The resulting transparent conductive film is extremely useful for applications such as resistive touch panels.

FIG. 2 is a schematic diagram showing an example (part 1) of the longest part of a crystal grain in the present invention. FIG. 2 is a schematic diagram showing another example (part 2) of the longest part of a crystal grain in the present invention. FIG. 10 is a schematic diagram showing another example (part 3) of the longest part of a crystal grain in the present invention. FIG. 10 is a schematic diagram showing another example (No. 4) of the longest part of a crystal grain in the present invention. FIG. 2 is a schematic diagram illustrating the position of a center roll in an example of a sputtering device preferably used in the present invention.

The transparent conductive film of the present invention is a transparent conductive film in which a transparent conductive film of indium-tin composite oxide is laminated on one surface of a transparent plastic film substrate, and it is preferable that the transparent conductive film of the transparent conductive film has an ON resistance of 10 kΩ or less in the pen sliding durability test described below, and further has an increase rate of the surface resistance value of the transparent conductive film of the transparent conductive film in the pen heavy pressure test described below of 1.5 or less, and further has a total transmitted image clarity of 250% or more but less than 500% at comb widths of 0.125 mm, 0.25 mm, 0.5 mm, 1.0 mm, and 2.0 mm.
(Pen sliding durability test)
A transparent conductive film according to the present invention was used as one panel plate, and a transparent conductive thin film (tin oxide content: 10% by mass) of 20 nm thickness formed on a glass substrate by sputtering was used as the other panel plate. These two panel plates were arranged with the transparent conductive thin films facing each other via 30 μm diameter epoxy beads, and the film-side panel plate and the glass-side panel plate were attached with 170 μm thick double-sided tape to produce a touch panel. Next, a linear sliding test was performed on the touch panel using a polyacetal pen (tip shape: 0.8 mmR) with a load of 2.5 N and 180,000 reciprocations. In this test, the pen load was applied to the transparent conductive film surface according to the present invention. The sliding distance was 30 mm, and the sliding speed was 180 mm/sec. After this sliding durability test, the ON resistance (resistance value when the movable electrode (film electrode) and fixed electrode contact each other) was measured when the sliding portion was pressed with a pen load of 0.8 N.
(Pen heavy pressure test)
A transparent conductive film according to the present invention, cut to a size of 50 mm x 50 mm, was used as one panel plate. The other panel plate was a transparent conductive thin film consisting of a 20 nm-thick indium-tin composite oxide thin film (tin oxide content: 10% by mass) sputtered onto a glass substrate. These two panel plates were arranged with the transparent conductive thin films facing each other, with 30 μm diameter epoxy beads sandwiched between them. The film-side panel plate and the glass-side panel plate were attached with double-sided tape adjusted to a thickness of 120 μm to produce a touch panel. A polyacetal pen (tip shape: 0.8 mmR) was used to apply a 35 N load to a position 2.0 mm from the end of the double-sided tape, and linear sliding was performed 10 times (five round trips) parallel to the double-sided tape. In this test, the pen load was applied to the surface of the transparent conductive film according to the present invention. The sliding distance was 30 mm, and the sliding speed was 20 mm/sec. However, sliding was performed in a position where there were no epoxy beads. After sliding, the transparent conductive film is removed and the surface resistance (four-terminal method) is measured at any five points on the sliding area, and the average value is calculated. When measuring the surface resistance, four terminals are arranged perpendicular to the sliding area, with the sliding area located between the second and third terminals. The average surface resistance value of the sliding area is divided by the surface resistance value of the non-sliding area (measured using the four-terminal method) to calculate the increase rate of surface resistance.

The transparent conductive film of the present invention has excellent pen sliding durability and pen heavy pressure durability. Pen sliding durability and pen heavy pressure durability are contradictory properties. First, we will explain pen sliding durability. Transparent conductive films of indium-tin composite oxide that have excellent pen sliding durability have a high degree of crystallinity in the transparent conductive film and a large crystal grain size. We will explain crystallinity and crystal grain size. When observed under a transmission electron microscope, circular or polygonal regions of the transparent conductive film are defined as crystals (= crystal grains), and the remaining portions are defined as amorphous. A high degree of crystallinity indicates a high proportion of crystals. A large crystal grain size indicates large circular or polygonal regions when observed under a transmission electron microscope. A transparent conductive film with a high degree of crystallinity has a high proportion of hard crystals, and a film with a large crystal grain size has large strain around the crystal grains, making the transparent conductive film harder and resulting in excellent pen sliding durability. Next, we will explain pen heavy pressure durability. Transparent conductive films made of indium-tin composite oxide that have excellent pen-loaded pressure durability require low crystallinity, small crystal grain size, and low three-dimensional surface roughness. Three-dimensional surface roughness will be explained later, but first, transparent conductive films with low crystallinity have a high proportion of soft amorphous material, and those with small crystal grain size have less strain around the crystal grains. This reduces the likelihood of cracks occurring even when a load is applied to the transparent conductive film, resulting in excellent pen-loaded pressure durability. As mentioned above, pen sliding durability and pen-loaded pressure durability are mutually exclusive properties. After careful investigation, we discovered that by controlling the crystallinity and crystal grain size of the transparent conductive film, it is possible to achieve both pen sliding durability and pen-loaded pressure durability. This article describes a transparent conductive film with a transparent conductive film that achieves both pen sliding durability and pen-loaded pressure durability.

In the present invention, if the ON resistance of the transparent conductive film of the transparent conductive film in the pen sliding durability test is 10 kΩ or less, cracking, peeling, wear, etc. of the transparent conductive film are suppressed even when continuous input is made to the touch panel with a pen. In one embodiment, the ON resistance may be 9.5 kΩ or less, more preferably 5 kΩ or less. For example, the ON resistance may be 3 kΩ or less, 1.5 kΩ or less, and preferably 1 kΩ or less. If the ON resistance is 0 kΩ, the pen sliding durability is very excellent, and in the present invention, the ON resistance can be 0 kΩ. The ON resistance may be, for example, 3 kΩ or more, or 5 kΩ or more.
By keeping the ON resistance within this range, cracks, peeling, wear, etc. on the transparent conductive film can be suppressed even when continuous input is made to the touch panel with a pen.
In one embodiment, these upper and lower limits may be combined as appropriate.

In the present invention, it is desirable that the rate of increase in the surface resistance of the transparent conductive film in a pen heavy pressure test is 1.5 or less. By having such a characteristic, for example, even if a force stronger than that expected in normal use is applied, cracking, peeling, etc. of the transparent conductive film can be suppressed. More preferably, the rate of increase in the surface resistance is 1.2 or less, and particularly preferably 1.0 (no increase).
Here, the rate of increase in the surface resistance of the transparent conductive film according to the present invention is preferably 1.0 or more.

In one embodiment, the ON resistance of the transparent conductive layer of the transparent conductive film in a pen sliding durability test is 0.05 kΩ or more and 9.5 kΩ or less, and the increase rate of the surface resistance value of the transparent conductive layer of the transparent conductive film in a pen heavy pressure (durability) test is 1.0 or more and 1.5 or less.
As described above, pen sliding durability and pen heavy pressure durability are usually contradictory properties. In the present invention, these two durability properties can be balanced within the above ranges. Furthermore, even when continuous input is made to the touch panel with a pen, cracking, peeling, wear, etc. of the transparent conductive film can be suppressed, and excellent durability can be exhibited against loads due to pen sliding and heavy pen pressure. The numerical ranges and values can be selected from those described in this specification.

In the present invention, it is desirable that the sum of the transmission 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 is 250% or more but less than 500%, since this makes it possible to provide high-definition images. The larger the sum of the transmission image clarity, the higher the image clarity, i.e., the higher the high definition. More preferably, the sum of the transmission image clarity of the transparent conductive film is 300% or more. Even more preferably, the sum of the transmission image clarity of the transparent conductive film is 400% or more.
In this specification, the term "comb width" refers to the optical comb width in accordance with JIS-K7105.

In the transparent conductive film of the present invention, the crystal grain size of the transparent conductive film of indium-tin composite oxide is preferably 10 to 100 nm, and the crystallinity of the transparent conductive film of indium-tin composite oxide is preferably 20 to 80%. When the crystal grain size of the transparent conductive film of indium-tin composite oxide is 10 nm or more, the transparent conductive film becomes appropriately hard due to strain around the crystal grains of the transparent conductive film, which is preferable because it has excellent pen sliding durability. More preferably, the crystal grain size of the transparent conductive film of indium-tin composite oxide is 30 nm or more.
On the other hand, if the crystal grain size of the transparent conductive film of indium-tin composite oxide is 100 nm or less, the transparent conductive film is not too hard due to distortion around the crystal grains of the transparent conductive film, and therefore the transparent conductive film has excellent durability against heavy pen pressure, which is preferable. More preferably, the crystal grain size of the transparent conductive film of indium-tin composite oxide is 90 nm or less.
In one embodiment, the crystal grain size of the transparent conductive film of indium-tin composite oxide is 30 nm or more and 95 nm or less, for example, 40 nm or more and 90 nm or less.
A crystallinity of 20% or more for the transparent conductive film of indium-tin composite oxide is preferred because the hard crystals contained in the transparent conductive film make the film moderately hard, resulting in excellent pen sliding durability. A more preferred crystallinity is 25% or more. On the other hand, a crystallinity of 80% or less for the transparent conductive film of indium-tin composite oxide is preferred because, although the amount of hard crystals contained is large, the transparent conductive film is not too hard and therefore excellent pen heavy pressure durability is achieved.
In one embodiment, the crystallinity of the transparent conductive film of indium-tin composite oxide is 25% or more and 78% or less, for example, 25% or more and 76% or less.

In the transparent conductive film of the present invention, where X is the three-dimensional surface roughness SRa of the transparent conductive film, X is preferably 1 to 100 nm. If X is 1 to 100 nm, the surface protrusions of the transparent conductive film are small, which reduces the amount of deformation of the surface protrusions when subjected to a pen-loaded pressure test, thereby suppressing the occurrence of cracks in the transparent conductive film. Furthermore, since the transparent conductive film has some surface protrusions, the film's windability is also maintained, which is preferable. More preferably, X is 1 to 80 nm. Even more preferably, X is 1 to 65 nm.

The transparent conductive film of the present invention is preferably made of indium-tin composite oxide and contains 0.5% to 10% by mass of tin oxide. Tin oxide in indium-tin composite oxide is equivalent to an impurity in indium oxide. The presence of tin oxide impurities increases the melting point of the indium-tin composite oxide. In other words, the presence of tin oxide impurities inhibits crystallization, making it an important factor closely correlated with crystallinity, such as grain size and degree of crystallinity. A tin oxide content of 0.5% by mass or more is preferred, as it ensures that the surface resistance of the transparent conductive film reaches a practical level. A tin oxide content of 1% by mass or more is more preferred, with 2% by mass or more being particularly preferred. A tin oxide content of 10% by mass or less facilitates crystallization during adjustment to the semi-crystalline state described below, and is therefore preferred for improved pen sliding durability. A tin oxide content of 8% by mass or less is more preferred, with 6% by mass or less being even more preferred, and 4% by mass or less being particularly preferred. The surface resistance of the transparent conductive film of the present invention is preferably 50 to 900 Ω/□, and more preferably 50 to 600 Ω/□.

In the present invention, the thickness of the transparent conductive film is preferably 10 nm or more and 30 nm or less. The thickness of the transparent conductive film is an important factor that is strongly correlated with crystallinity, such as crystal grain size and degree of crystallinity. When the thickness of the transparent conductive film is 10 nm or more, the transparent conductive film does not contain too much amorphous material, and it is easy to impart an appropriate crystal grain size and degree of crystallinity to achieve the semi-crystalline state described below, which is preferable because it maintains pen sliding durability. The thickness of the transparent conductive film is more preferably 13 nm or more, and even more preferably 16 nm or more. Furthermore, when the thickness of the transparent conductive film is 30 nm or less, the crystal grain size of the transparent conductive film is not too large and the degree of crystallinity is not too high, making it easy to maintain the semi-crystalline state and maintaining pen heavy pressure durability. The thickness is more preferably 28 nm or less, and even more preferably 25 nm or less.

In the transparent conductive film of the present invention, when the three-dimensional surface roughness SRa of the surface opposite to the transparent conductive film side on the transparent plastic film substrate is Y, if ( ^X3 + ^Y3 ) ^1/3 is 140 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 is 250% or more and less than 500%, which is desirable because it enables the provision of high-definition images. It was confirmed and utilized that the smaller the value of (( ^X3 + ^Y3 ) ^1/3 ), the smaller the unevenness on both surfaces of the transparent conductive film, and therefore the linearity of incident light on the transparent conductive film improves, and thus the clarity of the transmitted image tends to increase. More preferably, ( ^X3 + ^Y3 ) ^1/3 is 120 nm or less. Still more preferably, ( ^X3 + ^Y3 ) ^1/3 is 70 nm or less. If ( ^X3 + ^Y3 ) ^1/3 is 1 nm or more, the transparent conductive film will have some surface protrusions, and this is preferable because the film can be easily wound.

The transparent conductive film of the present invention preferably does not peel off even when an adhesion test (JIS K5600-5-6:1999) is conducted on the transparent conductive film surface. Transparent conductive films that do not peel off in an adhesion test are preferred because the transparent conductive film is in close contact with the layer in contact with the transparent conductive film, such as the transparent plastic substrate or the cured resin layer, and therefore cracking, peeling, wear, etc. of the transparent conductive film is suppressed even when continuous input is made to the touch panel with a pen. Furthermore, cracking, peeling, etc. of the transparent conductive film is suppressed even when a force greater than that expected in normal use is applied.

The transparent conductive film of the present invention preferably has a mandrel diameter of less than 20 mm at which cracking or peeling occurs when the bent portion is observed with a 10x magnifying glass in a bending resistance test (JIS K5600-5-1:1999) on the transparent conductive film side of the transparent conductive film. A mandrel diameter of less than 20 mm is preferred because a layer in contact with the transparent conductive film does not crack when a pen pressure test is performed, and cracks do not occur in the transparent conductive film. A mandrel diameter of 18 mm or less is more preferred.
In one embodiment, the value in the flex resistance test may be 1 mm or more, for example, 8 mm or more, 10 mm or more, or 13 mm or more, for example, 15 mm or more.
When the thickness is within this range, the layer in contact with the transparent conductive film does not crack when subjected to a pen heavy pressure test, and cracks do not occur in the transparent conductive film, which is preferable.
It is also possible to provide a transparent conductive film that has both excellent pen sliding durability and excellent pen heavy pressure durability.

The transparent conductive film of the present invention preferably has a transparent plastic film substrate thickness in the range of 100 to 250 μm, and more preferably 130 to 220 μm. A plastic film thickness of 100 μm or more is preferred because it maintains mechanical strength, reduces deformation due to pen input when used in a touch panel, and provides excellent pen sliding durability and pen heavy pressure durability. On the other hand, a thickness of 250 μm or less is preferred because, when used in a touch panel, there is no need to apply a particularly large load to position the film during pen input.

The transparent conductive film of the present invention preferably has a curable resin layer between the transparent conductive film and the plastic film substrate. The presence of the curable resin layer increases the adhesion of the transparent conductive film and distributes the force applied to the transparent conductive film, thereby preventing cracking, peeling, and abrasion of the transparent conductive film in a pen sliding test, and further prevents cracking and peeling of the transparent conductive film in a pen heavy pressure test, which is preferable.

The crystallinity of the transparent conductive film in this invention is neither too high nor too low (this type of crystallinity is referred to as semi-crystalline or semi-crystalline). It is extremely difficult to make a transparent conductive film stably semi-crystalline. This is because semi-crystalline is a state in which the film undergoes a sudden phase change from amorphous to crystalline and is stopped midway. For this reason, the film is sensitive to the amount of moisture in the film-forming atmosphere, a parameter related to crystallinity, and is particularly sensitive to hydrogen-atom-containing gases. Even a small amount of hydrogen-atom-containing gas or moisture in the film-forming atmosphere will result in almost complete crystallinity (high crystallinity), while even a small amount of hydrogen-atom-containing gas or moisture in the film-forming atmosphere will result in amorphousness (low crystallinity).

The manufacturing method for obtaining the transparent conductive film of the present invention is not particularly limited, but the following manufacturing method can be exemplified as a preferred example.
Sputtering is a preferred method for forming a transparent conductive film of crystalline indium-tin composite oxide on at least one surface of a transparent plastic film substrate. To produce transparent conductive films with high productivity, it is preferable to use a so-called roll-type sputtering device, which supplies a film roll and then winds it up into a film roll after film formation. A hydrogen atom-containing gas (hydrogen, ammonia, a hydrogen + argon mixed gas, or the like, as long as it contains hydrogen atoms, but excluding water) is introduced into the film formation atmosphere using a mass flow controller in the amount described below. Furthermore, the film temperature during sputtering is kept at 0°C or below, and a sintered target of indium-tin composite oxide containing 0.5 to 10 mass% tin oxide is used. The thickness of the transparent conductive film of indium-tin composite oxide is adjusted to 10 to 30 nm. A transparent conductive film having a three-dimensional surface roughness SRa of 1 to 100 nm is preferably formed on a transparent plastic film. In the film-forming atmosphere during sputtering, a hydrogen atom-containing gas has the effect of inhibiting crystallization of the transparent conductive film. When hydrogen gas is flowed in the film-forming atmosphere, the value of (hydrogen gas flow rate) ÷ (inert gas flow rate + hydrogen gas flow rate) × 100 (sometimes simply referred to as hydrogen concentration) is desirably 0.01 to 3.00%. The hydrogen concentration may be, for example, 0.01% to 2.00%, or 0.01% to 1.00%.
A hydrogen concentration within this range can contribute to obtaining good results in both the ON resistance value in a pen sliding durability test and the heavy pen pressure durability test, for example.
Examples of inert gases include helium, neon, argon, krypton, and xenon. When using a hydrogen-atom-containing gas other than hydrogen gas, the amount of hydrogen gas (= hydrogen molecules) can be calculated by converting the amount of hydrogen atoms contained in the hydrogen-atom-containing gas into the amount of hydrogen gas (= hydrogen molecules). When precisely flowing the hydrogen-atom-containing gas into the film-forming atmosphere using a mass flow controller, positioning the gas outlet so that the hydrogen-atom-containing gas can be uniformly sprayed in a direction perpendicular to the longitudinal direction of the film roll makes it difficult to obtain a transparent conductive film with a mixture of high and low crystallinity. This makes it easy to obtain a uniform semi-crystalline transparent conductive film, thereby enabling the production of a transparent conductive film with both excellent pen sliding durability and pen heavy pressure durability. The amount of moisture in the film-forming atmosphere is also an important factor, as it is known that a high amount of water in the film-forming atmosphere reduces the crystallinity of the transparent conductive film. When a hydrogen atom-containing gas is used, the median value (the intermediate value between the maximum and minimum values) of the ratio of water pressure to inert gas in the film-forming atmosphere during sputtering onto the film roll is controlled to 1.0 × 10 ^-4 to 2.0 × 10 ^-3 , and further, if the difference between the maximum and minimum values of the ratio of water pressure to inert gas in the film-forming atmosphere during sputtering from the start to the end of film formation is 1.0 × 10 ^-3 or less, uniformity of the crystallinity of the transparent conductive film is maintained throughout the entire length of the film. Therefore, in addition to rotary pumps, turbomolecular pumps, and cryopumps commonly used as exhaust devices for sputtering machines, precise control of the water content is not required if the amount of water released from the film during film formation is reduced and a uniform amount of water is released throughout the entire length of the film, such as by using the bombardment process described below and limiting the height difference of the unevenness on the end surface of the film roll described below. However, the median value of the ratio of water pressure to inert gas also depends somewhat on the tin oxide content in the indium-tin composite oxide transparent conductive film and the thickness of the transparent conductive film. When the amount of tin oxide added in the indium-tin composite oxide transparent conductive film is high or the transparent conductive film is thin, it is desirable to set the median value of the ratio of water pressure to inert gas lower within the above range. Conversely, when the tin oxide content in the indium-tin composite oxide transparent conductive film is low or the transparent conductive film is thick, it is desirable to set the median value of the ratio of water pressure to inert gas higher within the above range. It is preferable to form a transparent conductive film on a transparent plastic film by maintaining the film temperature at 0°C or below during sputtering. The film temperature during film formation is substituted for the set temperature of the temperature controller that adjusts the temperature of the center roll with which the running film contacts. Here, Figure 5 shows a schematic diagram of an example of a sputtering device suitable for use in the present invention, in which the running film 1 runs in partial contact with the surface of the center roll 2. An indium-tin sputtering target 4 is installed via a chimney 3, and a thin film of indium-tin composite oxide is deposited and laminated on the surface of the film 1 running on the center roll 2. The temperature of the center roll 2 is controlled by a temperature controller (not shown). A film temperature of 0°C or lower is preferable because it can suppress the release of impurity gases such as water and organic gases from the film, which can cause variations in the crystallinity of the transparent conductive film, and therefore facilitate uniform crystallinity of the transparent conductive film from the start to the end of film formation. When using a hydrogen atom-containing gas, the median value (the intermediate value between the maximum and minimum values) of the ratio of water pressure to inert gas in the film formation atmosphere during sputtering is preferably 1.0×10 ⁻⁴ to 2.0×10 ⁻³ . A ratio of water pressure to inert gas in the film formation atmosphere during sputtering within the above range is desirable because it effectively inhibits the crystallinity of the transparent conductive film. Furthermore, it is preferable to add oxygen gas during sputtering to achieve practical levels of surface resistance and total light transmittance of the transparent conductive film. This manufacturing method focuses on controlling crystallinity using a hydrogen-containing gas, while minimizing the influence of water crystallinity, which causes variations in the crystallinity of the transparent conductive film.

To control the moisture content when depositing an indium-tin composite oxide film on a plastic film, it is preferable to actually observe the moisture content during film deposition rather than observing the ultimate vacuum level, for the following two reasons:

The first reason is that when a film is formed on a plastic film by sputtering, the film is heated and moisture is released from the film, increasing the amount of moisture in the film-forming atmosphere, which is greater than the amount of moisture measured when the ultimate vacuum is reached. Therefore, it is more accurate to express this in terms of the amount of moisture at the time of film formation rather than in terms of the ultimate vacuum.

The second reason is the case with equipment that inputs large amounts of transparent plastic film. In such equipment, the film is input in the form of a film roll. When the film is rolled up and input into the vacuum chamber, water easily escapes from the outer layer of the roll, but water does not easily escape from the inner layer of the roll. When the ultimate vacuum is measured, the film roll is stationary, but during film formation, the film roll runs, and the inner layer of the film roll, which contains a lot of water, is unwound. This increases the amount of moisture in the film formation atmosphere, which is higher than the amount of moisture measured when the ultimate vacuum is measured. In the present invention, the amount of moisture in the film formation atmosphere can be controlled by observing the ratio of water pressure to inert gas pressure in the film formation atmosphere during sputtering.

Before depositing the transparent conductive film, it is desirable to subject the film 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 using RF sputtering with a stainless steel target. 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 deposition of the transparent conductive film, making it easier to achieve uniform crystallinity in the transparent conductive film from the start to the end of deposition, which is desirable. Furthermore, the bombardment process activates the layers in contact with the transparent conductive film, improving the adhesion of the transparent conductive film and improving pen sliding durability and pen heavy pressure durability, which is desirable.

The height difference between the most convex and most concave points on the end face of a film roll used to deposit a transparent conductive film is preferably 10 mm or less. A height difference of 10 mm or less reduces unevenness in the release of water and organic components from the end face of the film when the film roll is placed in a sputtering device, which is preferable because it makes it easier to achieve uniform crystallinity in the transparent conductive film from the start to the end of deposition.

In a method for forming a transparent conductive film of crystalline indium-tin composite oxide on at least one surface of a transparent plastic film substrate, it is desirable to introduce oxygen gas during sputtering. Introducing oxygen gas during sputtering prevents defects caused by oxygen deficiency in the transparent conductive film of indium-tin composite oxide, and advantageously reduces the surface resistance of the transparent conductive film and increases its total light transmittance. Therefore, it is desirable to introduce oxygen gas during sputtering in order to achieve a practical level of surface resistance and total light transmittance for the transparent conductive film. The total light transmittance of the transparent conductive film of the present invention is preferably 70 to 95%.

The transparent conductive film of the present invention is preferably obtained by forming a transparent conductive film of indium-tin composite oxide on a transparent plastic film substrate and then heat-treating it in an oxygen-containing atmosphere at 80 to 200°C for 0.1 to 12 hours. A temperature of 80°C or higher facilitates the process of slightly increasing crystallinity to achieve a semi-crystalline state, which is preferable as it improves pen sliding durability. A temperature of 200°C or lower is preferable as it ensures the flatness of the transparent plastic film.

<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 polyethylene, polypropylene, polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, nylon 6, nylon 4, nylon 66, 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.

Of these organic polymers, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, syndiotactic polystyrene, norbornene-based polymers, polycarbonate, polyarylate, etc. are preferred. These organic polymers may also be copolymerized with small amounts of other organic polymer monomers or blended with other organic polymers.

The transparent plastic film substrate used in the present invention may be subjected to surface activation treatments such as corona discharge treatment, glow discharge treatment, flame treatment, ultraviolet irradiation treatment, electron beam irradiation treatment, and ozone treatment, as long as the objective of the present invention is not impaired.

Applying a curable resin layer to a transparent plastic film substrate is preferable because it strengthens the adhesion of the transparent conductive film to the curable resin layer and distributes the force applied to the transparent conductive film, thereby reducing cracking, peeling, and abrasion during pen sliding tests. Furthermore, it also reduces cracking and peeling during pen-loaded pressure tests. Furthermore, forming a transparent conductive film on a curable resin layer with a textured surface reduces the true contact area between the transparent conductive thin film and glass during pen sliding tests, improving the sliding properties between the glass surface and the transparent conductive film, thereby improving pen sliding durability, film roll winding, and anti-Newton ring properties. However, excessive texture increases the deformation of surface protrusions during pen-loaded pressure tests, potentially causing cracks in the transparent conductive film, which is undesirable. Therefore, it is preferable for the surface texture to be 1 to 100 nm, where X is the three-dimensional surface roughness (SRa) of the transparent conductive film. The curable resin layer may also be applied to both sides of the transparent plastic film substrate. If the three-dimensional surface roughness SRa of the curable resin layer on the side opposite the surface on which the transparent conductive film is formed is Y, then Y is preferably 1 to 139 nm. Details of the curable resin layer are described below.

The curable resin preferably used in the present invention is not particularly limited as long as it is a resin that is cured by the application of energy such as heating, ultraviolet radiation, or electron beam radiation, and examples thereof include silicone resin, acrylic resin, methacrylic resin, epoxy resin, melamine resin, polyester resin, and urethane resin. From the viewpoint of productivity, it is preferable to use an ultraviolet-curable resin as the main component.

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

In addition, to improve the adhesion between the transparent conductive thin film and the curable resin layer, it is effective to treat the surface of the curable resin layer using the methods described below. Specific methods include discharge treatment, which involves irradiating with glow or corona discharge to increase the number of carbonyl groups, carboxyl groups, and hydroxyl groups, and chemical treatment, which involves treatment with acid or alkali to increase the number of polar groups such as amino groups, hydroxyl groups, and carbonyl groups.

UV-curable resins are typically used with the addition of a photopolymerization initiator. Any known compound that absorbs UV light and generates radicals can be used as the photopolymerization initiator, with no particular restrictions. Examples of such photopolymerization initiators include various benzoins, phenyl ketones, and benzophenones. The amount of photopolymerization initiator added is typically 1 to 5 parts by weight per 100 parts by weight of UV-curable resin.

In addition, in the present invention, it is preferable to use inorganic or organic particles in addition to the curable resin, which is the main constituent component, in the curable resin layer. By dispersing inorganic or organic particles in the curable resin, it is possible to form irregularities on the surface of the curable resin and improve surface roughness over a wide area.

Examples of the inorganic particles include silica. Examples of the organic particles include polyester resin, polyolefin resin, polystyrene resin, polyamide resin, etc.

In addition to inorganic and organic particles, it is also preferable to use a resin that is incompatible with the curable resin, which is the main constituent component, in combination with the curable resin. By using a small amount of a resin that is incompatible with the curable resin of the matrix, phase separation occurs in the curable resin, allowing the incompatible resin to be dispersed in particulate form. These dispersed particles of the incompatible resin can form irregularities on the surface of the curable resin, improving surface roughness over a wide area.

Examples of incompatible resins include polyester resins, polyolefin resins, polystyrene resins, polyamide resins, etc.

Here, as an example, the blending ratio when inorganic particles are used in the curable resin layer directly below the transparent conductive film is shown. The inorganic particles are preferably 0.1 to 20 parts by mass per 100 parts by mass of the ultraviolet-curable resin, more preferably 0.1 to 15 parts by mass, and particularly preferably 0.1 to 12 parts by mass. When the blending amount of the inorganic particles is 0.1 to 20 parts by mass per 100 parts by mass of the ultraviolet-curable resin, the convex portions formed on the surface of the curable resin layer are not too small, and three-dimensional surface roughness can be effectively imparted. The deformation amount of the surface protrusions is reduced when a pen pressure test is performed, and the occurrence of cracks in the transparent conductive film is suppressed, making it possible to provide high-definition images. Furthermore, since the transparent conductive film has some surface protrusions, film winding properties can be maintained, which is preferable.

Here, as an example, the blending ratio when inorganic particles are used in the curable resin layer on the side opposite to the side on which the transparent conductive film is formed is shown. The blending amount of the inorganic particles is preferably 0.1 to 25 parts by mass, more preferably 0.1 to 15 parts by mass, and particularly preferably 0.1 to 12 parts by mass per 100 parts by mass of the ultraviolet-curable resin. When the blending amount of the inorganic particles is 0.1 to 25 parts by mass per 100 parts by mass of the ultraviolet-curable resin, the convex portions formed on the surface of the curable resin layer are not too small, effectively imparting three-dimensional surface roughness, making it possible to provide high-definition images, and further, since the transparent conductive film has some surface protrusions, film winding properties can be maintained, which is preferable.

The UV-curable resin, photopolymerization initiator, and resin incompatible with the inorganic particles, organic particles, and UV-curable resin are dissolved in a common solvent to prepare a coating solution. There are no particular restrictions on the solvent used; for example, 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.

The concentration of the resin components in the coating liquid can be appropriately selected taking into account factors such as viscosity depending on the coating method. For example, the total amount of the UV-curable resin, photopolymerization initiator, and high-molecular-weight polyester resin in the coating liquid is typically 20 to 80% by mass. Furthermore, other known additives, such as silicone-based leveling agents, may also be added to the coating liquid as needed.

In the present invention, the prepared coating solution is coated onto a transparent plastic film substrate. There are no particular restrictions on the coating method, and conventional methods such as bar coating, gravure coating, and reverse coating can be used.

The coated coating liquid is then dried, where the solvent is evaporated and removed. During this process, the high-molecular-weight polyester resin, which was uniformly dissolved in the coating liquid, becomes particles and precipitates in the UV-curable resin. After the coating is dried, the plastic film is irradiated with UV light, causing the UV-curable resin to crosslink and harden, forming a hard-coat layer. During this hard-coat process, the high-molecular-weight polyester resin particles are fixed in the hard coat layer, and protrusions form on the surface of the hard-coat layer, improving surface roughness over a wide area.

The thickness of the curable resin layer is preferably in the range of 0.1 to 15 μm. It is more preferably in the range of 0.5 to 10 μm, and particularly preferably in the range of 1 to 8 μm. A thickness of 0.1 μm or more is preferred because sufficient protrusions are formed. On the other hand, a thickness of 15 μm or less is preferred because productivity is good.

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.
(1) Total Light Transmittance The total light transmittance was measured in accordance with JIS-K7136-1:1997 using NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

(2) Surface Resistivity: Measured by a four-terminal method in accordance with JIS-K7194:1994. The measuring instrument used was Lotesta AX MCP-T370 manufactured by Mitsubishi Chemical Analytech Co., Ltd.

(3) Three-dimensional center plane average surface roughness SRa
The three-dimensional central plane average surface roughness SRa is specified in ISO 25178, and 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. Here, the values were rounded to the nearest tenth in nm. Here, the three-dimensional surface roughness SRa of the transparent conductive film is designated X, and the three-dimensional surface roughness SRa of the curable resin layer on the side opposite the transparent conductive film on the transparent plastic film substrate is designated Y.

(4) Crystal grain size A film sample piece laminated with a transparent conductive thin film layer was cut into a size of 1 mm × 10 mm, and attached to the top surface of an appropriate resin block with the conductive thin film surface facing outward. After trimming, ultrathin sections roughly parallel to the film surface were prepared using a general ultramicrotome technique.
The slice was observed under a transmission electron microscope (JEOL, JEM-2010) to select a surface portion of the conductive thin film that was not significantly damaged, and photographed at an acceleration voltage of 200 kV and a direct magnification of 40,000 times.
When observing crystal grains under a transmission electron microscope, the longest part of each crystal grain is measured, and the average of these measurements is taken as the crystal grain size. Figures 1 to 4 show an example of how to determine the longest part when measuring the longest part of a crystal grain. That is, the longest part is determined by the length of the straight line that allows the largest measurement of the grain size of each crystal grain.

(5) Thickness of the transparent conductive film (film thickness)
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.

(6) Pen Sliding Durability Test The transparent conductive film according to the present invention was used as one panel plate, and the other panel plate was a transparent conductive thin film consisting of a 20 nm-thick indium-tin composite oxide thin film (tin oxide content: 10% by mass) sputtered onto a glass substrate. These two panels were arranged with 30 μm diameter epoxy beads between them so that the transparent conductive thin films faced each other, to produce a touch panel. Next, a 5.0 N load was applied to a polyacetal pen (tip shape: 0.8 mmR), and a linear sliding test of 180,000 reciprocations was performed on the touch panel. In this test, the pen load was applied to the transparent conductive film surface according to the present invention. The sliding distance was 30 mm, and the sliding speed was 180 mm/sec. After this sliding durability test, the ON resistance (the resistance value when the movable electrode (film electrode) and the fixed electrode contacted each other) was measured when the sliding portion was pressed with a pen load of 0.8 N. The ON resistance is preferably 10 kΩ or less.
In the comparative examples, the films in the respective comparative examples were used instead of the transparent conductive film according to the present invention.

(7) Pen Pressure Test: A transparent conductive film according to the present invention, cut to a size of 50 mm x 50 mm, was used as one panel plate. The other panel plate was a transparent conductive thin film consisting of a 20 nm-thick indium-tin composite oxide thin film (tin oxide content: 10% by mass) sputtered onto a glass substrate. These two panel plates were arranged with the transparent conductive thin films facing each other, with 30 μm diameter epoxy beads sandwiched between them. A touch panel was fabricated by attaching the film-side panel plate and the glass-side panel plate with double-sided tape adjusted to a thickness of 120 μm. A polyacetal pen (tip shape: 0.8 mmR) was used to apply a 35 N load to a position 2.0 mm from the end of the double-sided tape, and linear sliding was performed 10 times (five round trips) parallel to the double-sided tape. In this test, the pen load was applied to the surface of the transparent conductive film according to the present invention. The sliding distance was 30 mm, and the sliding speed was 20 mm/sec. However, sliding was performed in a position where there were no epoxy beads. After sliding, the transparent conductive film is removed and the surface resistance (four-terminal method) is measured at any five points on the sliding area, and the average value is calculated. When measuring the surface resistance, four terminals are arranged perpendicular to the sliding area, with the sliding area located between the second and third terminals. The average surface resistance value of the sliding area is divided by the surface resistance value of the non-sliding area (measured using the four-terminal method) to calculate the increase rate of surface resistance.
In the comparative examples, the films in the respective comparative examples were used instead of the transparent conductive film according to the present invention.

(8) Measurement of the tin oxide content in the transparent conductive film. A sample (approximately 15 ^cm2 ) was cut and placed in a quartz Erlenmeyer flask. 20 ml of 6 mol/L hydrochloric acid was added and 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 spectrometer (manufacturer: Rigaku, model: CIROS-120 EOP). A wavelength with high sensitivity and no interference was selected for the measurement wavelength for each element. Commercially available standard solutions of In and Sn were diluted and used as standard solutions.

(9) Adhesion Test The adhesion test was carried out in accordance with JIS K5600-5-6:1999.

(10) Bending resistance test: This test was carried out in accordance with JIS K5600-5-1: 1999. However, if no cracking or peeling occurred up to a mandrel diameter of 13 mm, further bending resistance tests were not carried out, and all tests were recorded as 13 mm.

(11) Transmission Image Clarity Test According to JIS-K7105, the transmission image clarity of the transparent conductive film was measured at comb widths of 0.125 mm, 0.25 mm, 0.5 mm, 1.0 mm, and 2.0 mm, and the sum of the transmission image clarity for each comb width was calculated. The measuring machine used was an image clarity measuring instrument ICM-1T manufactured by Suga Test Instruments Co., Ltd.

The transparent plastic film substrate used in the examples and comparative examples was a biaxially oriented transparent PET film (A4340, manufactured by Toyobo Co., Ltd., thickness listed in Table 1) having easy-adhesion layers on both sides. As the curable resin layer, 100 parts by mass of a photopolymerization initiator-containing acrylic resin (Seikabeam (registered trademark) EXF-01J, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) was blended with silica particles (Snowtex ZL, manufactured by Nissan Chemical Industries, Ltd.) in the amount listed in Table 1. A mixed solvent of toluene/MEK (8/2: mass ratio) was added as a solvent to a solids concentration of 50% by mass, and the mixture was stirred to dissolve uniformly to prepare a coating solution (hereinafter referred to as Coating Solution A). The prepared coating solution was applied using a Meyer bar to a coating thickness of 5 μm. After drying at 80°C for 1 minute, the coating was cured by irradiating ultraviolet light (light intensity: 300 mJ/cm ² ) using an ultraviolet irradiation device (UB042-5AM-W, manufactured by iGraphics Co., Ltd.). The curable resin layers were provided on both sides of the transparent plastic substrate.

(Examples 1 to 8)
Each example was carried out under the conditions shown in Table 1 as follows.
The film was placed in a vacuum chamber, and the chamber was evacuated to 1.5×10 ⁻⁴ Pa. Next, oxygen was introduced, followed by introduction of argon as an inert gas and hydrogen gas as a hydrogen-containing gas at the concentrations shown in Table 1, until the total pressure reached 0.6 Pa.
A transparent conductive film was formed by DC magnetron sputtering using a sintered target of indium-tin composite oxide or a sintered target of indium oxide containing no tin oxide, with power input at a power density of ³ W/cm². Film thickness was controlled by varying the speed at which the film passed over the target. The ratio of water vapor pressure to inert gas in the film-forming atmosphere during sputtering was measured using a gas analyzer (Transpector XPR3, manufactured by INFICON). In each example, the ratio of water vapor pressure to inert gas in the film-forming atmosphere during sputtering was adjusted by adjusting the presence or absence of a bombardment process, 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 in contact with the film, as shown in Table 1. The temperature exactly midway between the maximum and minimum temperatures from the start to the end of film formation on the film roll was listed as the median value in Table 1.
The film on which the transparent conductive film was formed and laminated was subjected to the heat treatment shown in Table 1, and then measurements were carried out. The measurement results are shown in Table 1.

(Comparative Examples 1 to 9)
Transparent conductive films were prepared and evaluated in the same manner as in Example 1 under the conditions shown in Table 1. However, in Comparative Example 7, no curable resin layer was provided. However, in Comparative Example 8, the thickness of the coating of the curable resin layer was adjusted to 20 μm. The results are shown in Table 2.

As shown in Tables 1A and 1B, the transparent conductive films of Examples 1 to 8 have excellent pen sliding durability, pen heavy pressure durability, and high resolution, combining all of these properties. However, as shown in Table 2, Comparative Examples 1 to 9 do not satisfy all of the pen sliding durability, pen heavy pressure durability, and high resolution requirements.

As described above, the present invention makes it possible to produce a transparent conductive film that has excellent pen sliding durability, pen heavy pressure durability, and high resolution, which is extremely useful for applications such as resistive touch panels.

1. Film 2. Center roll 3. Chimney 4. Indium-tin composite oxide target

Claims (4)

A transparent conductive film having a transparent conductive film of indium-tin composite oxide laminated on one surface of a transparent plastic film substrate,
a transparent conductive film comprising an indium-tin composite oxide having a crystal grain size of 10 to 100 nm, a crystallinity of 20 to 80%, a content of tin oxide of 0.5 to 10 mass %, a thickness of 10 to 30 nm, a three-dimensional surface roughness SRa of the transparent conductive film of indium-tin composite oxide of 10 to 100 nm, and a curable resin layer containing 0.1 to 25 parts by mass of inorganic particles per 100 parts by mass of ultraviolet-curable resin on the surface opposite to the transparent conductive film side of the transparent plastic film substrate, wherein, when the three-dimensional surface roughness SRa of the curable resin layer is Y, ( ^X3 + ^Y3 ) ^1/3 is 140 nm or less. The transparent conductive film according to claim 1, wherein the transparent conductive film does not peel off when subjected to an adhesion test (JIS K5600-5-6:1999) on the surface of the transparent conductive film, and wherein the mandrel diameter at which cracking or peeling occurs when the indium-tin composite oxide transparent conductive film side of the transparent conductive film is subjected to a bending resistance test (JIS K5600-5-1:1999) and the bent portion is observed with a 10x magnifying glass is smaller than 20 mm. The transparent conductive film according to claim 1 or 2, wherein the thickness of the transparent conductive film is 100 to 250 μm. 4. The transparent conductive film according to claim 1 , further comprising a curable resin layer between the transparent conductive film of indium-tin composite oxide and the transparent plastic film substrate.