JP7758239B2 - Transparent Conductive Film - Google Patents

Description

The present invention relates to a transparent conductive film in which a transparent conductive layer of indium-tin composite oxide is laminated onto a transparent plastic film substrate, and in particular to a transparent conductive film that exhibits light operability, excellent pen input stability, and excellent pen sliding durability 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, and are used by overlapping them on top of the 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, is the input for the touch panel's position recognition. Pen sliding durability is particularly important when inputting with a pen.
In addition, as capacitive touch panels have become more common in recent years, resistive touch panels are also expected to be able to input data with a light touch, just like capacitive touch panels. For example, people who have weak finger pressure or writing pressure due to age, illness, or other reasons are expected to be able to input data with a light touch. Furthermore, there is also a demand for stable input from the time a pen or other object is touched to the time it is released (defined as "pen input stability").
However, resistive touch panels require a certain amount of input load to press the film electrode with a finger or pen to bring the fixed electrode and the transparent conductive thin film of the film electrode into contact, which means that they do not have the light and smooth operation feel of capacitive touch panels. Furthermore, the characteristics of transparent conductive films that provide excellent pen input stability are not clear. To solve these problems, there is a demand for transparent conductive films that offer both light operation and excellent pen input stability.

Japanese Patent Application Laid-Open No. 2004-071171

The conventional transparent conductive film disclosed in Patent Document 1 attempts to improve pen sliding durability by controlling the crystallinity of the indium-tin composite oxide. However, when the conventional transparent conductive film was subjected to the input load test and pen input stability test described below, it was found that it was unable to achieve both operability and pen input stability.
Furthermore, in applications such as touch panels, there is a demand for shorthand, for example, reduction of blurred characters that may occur when characters are input continuously.

In view of the above-mentioned conventional problems, an object of the present invention is to provide a transparent conductive film having easy operability, excellent pen input stability, and excellent pen sliding durability.
Another object of the present invention is to provide a transparent conductive film that can reduce the blurring of characters that may occur when characters are input continuously, for example, in shorthand.

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 having a transparent conductive film of indium-tin composite oxide laminated on at least one side of a transparent plastic film substrate,
A transparent conductive film in which an input start load of the transparent conductive film in the following input load test is 3 g or more and 15 g or less, and further, a voltage loss time of the transparent conductive film in the following pen input stability test is 0.00 milliseconds or more and 0.40 milliseconds or less.
(Input load test method)
A transparent conductive film (size: 220 mm × 135 mm) was used as one panel plate, and a transparent conductive thin film A consisting of an indium-tin composite oxide thin film (tin oxide content: 10 mass%) having a thickness of 20 nm and formed by sputtering on a glass substrate (size: 232 mm × 151 mm) was used as the other panel plate.
On the transparent conductive thin film A side of a glass substrate with an indium-tin composite oxide thin film (hereinafter also referred to as ITO glass), epoxy resin (60 μm length × 60 μm width × 5 μm height) is arranged as dot spacers in a square lattice pattern with a pitch of 4 mm.
Next, starting from one of the four corners of the ITO glass, double-sided tape (thickness: 105 μm, width: 6 mm) is attached to the transparent conductive thin film A side of the ITO glass so as to form a rectangle of 190 mm×135 mm.
Next, the transparent conductive film is attached with the transparent conductive layer B side on the double-sided tape attached to the ITO glass, and laminated so that the transparent conductive thin layer A and the transparent conductive layer B face each other.
At this time, one short side of the transparent conductive film is set to protrude from the ITO glass.
Next, connect the ITO glass and transparent conductive film with a tester.
Next, a load is applied from the transparent conductive film side using a polyacetal pen (tip shape: 0.8 mmR), and the load value when the resistance value measured by the tester stabilizes is defined as the input start load.
The position where the load is applied with the pen is the central region surrounded by four dot spacers, and the average value of the input start load at the three points is calculated.
(Pen input stability test method)
A transparent conductive film (size: 220 mm × 135 mm) was used as one panel plate, and a transparent conductive thin film A consisting of an indium-tin composite oxide thin film (tin oxide content: 10 mass%) having a thickness of 20 nm and formed by sputtering on a glass substrate (size: 232 mm × 151 mm) was used as the other panel plate.
On the transparent conductive thin film A side of a glass substrate with an indium-tin composite oxide thin film (hereinafter also referred to as ITO glass), epoxy resin (60 μm length × 60 μm width × 5 μm height) is arranged as dot spacers in a square lattice pattern with a pitch of 4 mm.
Next, starting from one of the four corners of the ITO glass, double-sided tape (thickness: 105 μm, width: 6 mm) is attached to the transparent conductive thin film A side of the ITO glass so as to form a rectangle of 190 mm×135 mm.
Next, the transparent conductive film is attached with the transparent conductive layer B side on the double-sided tape attached to the ITO glass, and laminated so that the transparent conductive thin layer A and the transparent conductive layer B face each other.
At this time, one short side of the transparent conductive film is set to protrude from the ITO glass.
Next, a constant-voltage power supply is connected to the ITO glass and transparent conductive film. A recorder capable of measuring the voltage between the ITO glass and transparent conductive film is then connected. The recorder is used to observe the time-dependent change in voltage. 6 V is then applied to the constant-voltage power supply, and the recorder begins measuring the voltage in 0.02 millisecond increments. A 50 g load is then applied to the transparent conductive film five times per second using a polyacetal pen (tip shape: 0.8 mmR). The pen load is applied to the central area surrounded by the four dot spacers. The data on the time-dependent change in voltage as the pen applies the load to the transparent conductive film is extracted from the recorder. Since the voltage decreases when the pen begins to separate from the transparent conductive film, the time from when the voltage decreases from 6 V to when the voltage reaches 5 V is measured and recorded as the voltage loss time.
2. The transparent conductive film described above, wherein the bending resistance measured by the film bending resistance test described below is 0.23 N cm or more and 0.90 N cm or less, and further, the average maximum peak height of the conductive surface of the transparent conductive film described below satisfies the following formulas (2-1) and (2-2), and further, the value calculated by the contact area ratio evaluation described below satisfies formula (2-3).
(Film bending resistance test method)
A 20 mm x 250 mm test piece is taken from the transparent conductive film and placed on a smooth, horizontal stand with the transparent conductive layer facing up. At this time, only the 20 mm x 20 mm part of the test piece is placed on the horizontal stand, with the 20 mm x 230 mm part outside the horizontal stand. In addition, a weight is placed on the 20 mm x 20 mm part of the test piece. At this time, the weight and size of the weight are selected so that there is no gap between the test piece and the horizontal stand.
Next, the difference between the height of the horizontal table and the height of the tip of the film (hereinafter referred to as δ) is read on the scale, and the value is then substituted into the following formula (1) to calculate the bending resistance.
Formula (1) (g×a×b×L ⁴ )÷8δ (N cm)
g = gravitational acceleration, a = length of the short side of the test piece, b = specific gravity of the test piece, L = length of the test piece, δ = difference in height between the horizontal table and the tip of the film (average maximum peak height evaluation)
The average maximum peak height is the average of the maximum peak heights at five points. To select the five points, first select one arbitrary point A. Next, select two points, one 1 cm upstream and one 1 cm downstream from A in the machine direction (MD) of the film. Next, select two points, one 1 cm to the left and one 1 cm to the right and left of A in the cross-machine direction (TD) of the film. The maximum peak height is specified in ISO 25178 and was determined using a 3D surface profiler, VertScan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x magnification)). Values less than 1 nm were rounded off.
(Contact area ratio evaluation)
The conductive surface of the transparent conductive film is measured for arithmetic mean roughness Ra in accordance with JIS B 0601-2001 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 50x)) over a measurement length range of 100 μm to 200 μm. Ra is measured so that either or both of the following conditions are satisfied: "Rp - average height - Ra ≦ 0.20 μm" or "(Rp - average height) ÷ Ra ≦ 5.0", and Rsm ≦ 30 μm. Here, Rp and Rsm are measured in accordance with JIS B 0601-2001. The average height is the average value of the height over the measurement length. If the above conditions are not satisfied, remeasure at a different point. Next, for the conductive surface of the same transparent conductive film, a 3D surface profiler, Vertscan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x)), is used, and the particle analysis function of the same measuring device is used to determine the sum of the cross-sectional areas using "Ra - 15 nm - average height" as the threshold. The sum of the cross-sectional areas is divided by the area of the measurement field of view, and the result multiplied by 100 is the contact area ratio.
Formula (2-1) Average maximum peak height (μm) ≧ 4.7 x bending resistance - 1.8
Formula (2-2) 0.005 (μm) ≦ Average maximum peak height (μm) ≦ 12.000 (μm)
Formula (2-3) Contact area ratio (%) ≧ 32.6 x bending resistance + 17.2
3. The maximum value of the maximum peak height in the average maximum peak height evaluation is more than 1.0 times but not more than 1.4 times the average maximum peak height, and
The transparent conductive film as described above, wherein the minimum value of the maximum peak height in the average maximum peak height evaluation is 0.6 to 1.0 times the average maximum peak height.
4. The transparent conductive film as described above, wherein the transparent conductive film has a thickness of 10 to 100 nm.
5. The transparent conductive film as described above, wherein the concentration of tin oxide contained in the transparent conductive film is 0.5 to 40% by mass.
6. A curable resin layer is provided between the transparent conductive film and the transparent plastic film substrate,
The transparent conductive film further comprises a functional layer on the opposite side of the transparent plastic substrate from the transparent conductive film.
7. The transparent conductive film according to any one of claims 1 to 5, which has an easy-adhesion layer on at least one side of the transparent plastic film substrate.
8. The transparent conductive film as described above, wherein the easy-adhesion layer is disposed at least at one of the positions between the transparent plastic film substrate and the curable resin layer and the position between the transparent plastic substrate and the functional layer.
9. The transparent conductive film as described above, wherein the transparent conductive layer of the transparent conductive film has an ON resistance of 10 kΩ or less in the pen sliding durability test described below.
(Pen sliding durability test)
A transparent conductive film was used as one panel plate, and a transparent conductive thin film consisting of a 20 nm-thick indium-tin composite oxide thin film (tin oxide content: 10% by mass) was used as the other panel plate, sputtered onto a glass substrate. These two panels were arranged with 30 μm diameter epoxy beads between them, with the transparent conductive thin films facing each other, to produce a touch panel. Next, a polyacetal pen (tip shape: 0.8 mmR) was used to apply a load of 2.5 N to the touch panel, and a linear sliding test was performed 50,000 times. 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 fixed electrode come into contact) was measured when the sliding portion was pressed with a pen load of 0.8 N.
10. The transparent conductive film as described above, wherein in an adhesion test on the surface of the transparent conductive film in accordance with JIS K5600-5-6:1999, the remaining area ratio of the transparent conductive film is 95% or more.

The present invention makes it possible to provide a transparent conductive film that offers easy operability, excellent pen input stability, and excellent pen sliding durability. Furthermore, it also improves shorthand writing, reducing the blurring of characters that can occur when entering characters continuously.

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. FIG. 1 is a schematic diagram illustrating a configuration according to one embodiment of the present invention. FIG. 1 is a schematic diagram illustrating a configuration according to one embodiment of the present invention. FIG. 1 is a schematic diagram illustrating a configuration according to one embodiment of the present invention. FIG. 1 is a schematic diagram illustrating a configuration according to one embodiment of the present invention. FIG. 2 is a schematic diagram showing measurement conditions in one embodiment of the present invention. FIG. 1 is a conceptual diagram showing the relationship between voltage and time in one embodiment of the present invention.

The transparent conductive film of the present invention is a transparent conductive film comprising a transparent plastic film substrate and a transparent conductive film of indium-tin composite oxide laminated on at least one side thereof, wherein the input start load of the transparent conductive film in the input load test described below is 3 g or more and 15 g or less, and further the voltage loss time of the transparent conductive film in the pen input stability test described below is 0.00 milliseconds or more and 0.40 milliseconds or less.
(Input load test method)
A transparent conductive film (size: 220 mm × 135 mm) was used as one panel plate, and a transparent conductive thin film A consisting of an indium-tin composite oxide thin film (tin oxide content: 10 mass%) having a thickness of 20 nm and formed by sputtering on a glass substrate (size: 232 mm × 151 mm) was used as the other panel plate.
On the transparent conductive thin film A side of a glass substrate with an indium-tin composite oxide thin film (hereinafter also referred to as ITO glass), epoxy resin (60 μm length × 60 μm width × 5 μm height) is arranged as dot spacers in a square lattice pattern with a pitch of 4 mm.
Next, starting from one of the four corners of the ITO glass, double-sided tape (thickness: 105 μm, width: 6 mm) is attached to the transparent conductive thin film A side of the ITO glass so as to form a rectangle of 190 mm×135 mm.
Next, the transparent conductive film is attached with the transparent conductive layer B side on the double-sided tape attached to the ITO glass, and laminated so that the transparent conductive thin layer A and the transparent conductive layer B face each other.
At this time, one short side of the transparent conductive film is set to protrude from the ITO glass.
Next, connect the ITO glass and transparent conductive film with a tester.
Next, a load is applied from the transparent conductive film side using a polyacetal pen (tip shape: 0.8 mmR), and the load value when the resistance value measured by the tester stabilizes is defined as the input start load.
The position where the load is applied with the pen is the central region surrounded by four dot spacers, and the average value of the input start load at the three points is calculated.
For example, it is preferable to measure the input starting load at three arbitrary points at least 50 mm away from the double-sided tape and take the average value. Also, decimal points may be rounded off.
The position where the load is applied with the pen is the central region of the four dot spacers as shown in FIG.
(Pen input stability test method)
A transparent conductive film (size: 220 mm × 135 mm) was used as one panel plate, and a transparent conductive thin film A consisting of an indium-tin composite oxide thin film (tin oxide content: 10 mass%) having a thickness of 20 nm and formed by sputtering on a glass substrate (size: 232 mm × 151 mm) was used as the other panel plate.
On the transparent conductive thin film A side of a glass substrate with an indium-tin composite oxide thin film (hereinafter also referred to as ITO glass), epoxy resin (60 μm length × 60 μm width × 5 μm height) is arranged as dot spacers in a square lattice pattern with a pitch of 4 mm.
Next, starting from one of the four corners of the ITO glass, double-sided tape (thickness: 105 μm, width: 6 mm) is attached to the transparent conductive thin film A side of the ITO glass so as to form a rectangle of 190 mm×135 mm.
Next, the transparent conductive film is attached with the transparent conductive layer B side on the double-sided tape attached to the ITO glass, and laminated so that the transparent conductive thin layer A and the transparent conductive layer B face each other.
At this time, one short side of the transparent conductive film is set to protrude from the ITO glass.
Next, a constant-voltage power supply is connected to the ITO glass and transparent conductive film. A recorder capable of measuring the voltage between the ITO glass and transparent conductive film is then connected. The recorder is used to observe the time-dependent change in voltage. 6 V is then applied to the constant-voltage power supply, and the recorder begins measuring the voltage in 0.02 millisecond increments. A 50 g load is then applied to the transparent conductive film five times per second using a polyacetal pen (tip shape: 0.8 mmR). The pen load is applied to the central area surrounded by the four dot spacers. The data on the time-dependent change in voltage as the pen applies the load to the transparent conductive film is extracted from the recorder. Since the voltage decreases when the pen begins to separate from the transparent conductive film, the time from when the voltage decreases from 6 V to when the voltage reaches 5 V is measured and recorded as the voltage loss time.
For example, FIG. 7 is a conceptual diagram showing the relationship between voltage and time in one embodiment of the present invention, where the horizontal axis 13 is the time axis, the vertical axis 14 indicates voltage, and the voltage loss time 15 is measured.

In the present invention, when measurements are taken with a tester, a "stable resistance value" is determined when the resistance value fluctuates within a range of, for example, ±5%, depending on external factors such as the measurement environment.

The present invention, which has these characteristics, makes it possible to provide a transparent conductive film that has light operability, excellent pen input stability, and excellent pen sliding durability. The resulting transparent conductive film is extremely useful for applications such as resistive touch panels.

The transparent conductive film of the present invention has easy operability. It has been discovered that the transparent conductive film of indium-tin composite oxide, which has excellent operability, has a maximum peak height on the surface facing the transparent conductive film that is within an appropriate range relative to the height of the dot spacers on the ITO glass for touch panels, has low bending resistance in a film bending resistance test, and has a tin oxide concentration in the transparent conductive film that is close to the tin oxide concentration in the ITO glass for touch panels.

The following describes light operability. Light operability means that input to the resistive touch panel is possible even when the resistive touch panel is pressed lightly with a pen or a finger from the transparent conductive film side. In the present invention, light operability was evaluated by an input load test. In the present invention, if the input start load of the transparent conductive film in the input load test is 3 g or more and 15 g or less, the transparent conductive film has light operability.
The present invention, which has such an input initiation load, allows input by lightly touching the transparent conductive film used for applications such as resistive touch panels, even for people who have weak finger pressure or writing pressure due to age, illness, or other reasons.
An input start load of 15 g or less is preferable because it provides light operability. It is more preferably 13 g or less. Even more preferably 11 g or less. On the other hand, an input start load of 3 g or more is preferable because it prevents erroneous responses of the touch panel. It is more preferably 5 g or more, and even more preferably 8 g or more.

The transparent conductive film of the present invention has excellent pen input stability. It has been found that a transparent conductive film of indium-tin composite oxide with excellent pen input stability has low bending resistance in a film bending resistance test, a high contact area ratio of the transparent conductive film surface in a contact area ratio evaluation, and a tin oxide concentration in the transparent conductive film that is close to the tin oxide concentration in ITO glass for touch panels.

We will explain excellent pen input stability. Excellent pen input stability means that input to the touch panel is stable because the electrical contact between the transparent conductive glass, such as ITO glass, and the transparent conductive film remains stable for a long period of time, from the time a pen or finger presses against the transparent conductive film side of the resistive touch panel until it is released. With excellent pen input stability, for example, when entering characters with a pen on a resistive touch panel, the stroke of the characters can be written without smearing.
In the present invention, the pen input stability was evaluated by a pen input stability test. In the pen input stability test, the change in voltage between the transparent conductive glass and the transparent conductive film when the pen begins to separate from the touch panel is observed. When the transparent conductive glass and the transparent conductive film are in complete contact with each other by the pen, the applied voltage is 6 V, so the voltage remains constant at 6 V. However, when the pen begins to separate from the touch panel, the voltage begins to drop from 6 V.
The present inventors have found that, when the time from when the voltage drop starts until the voltage reaches 5 V, i.e., the voltage loss time, is within the range of the present invention, the time during which stable electrical contact is maintained can be extended, for example, between the transparent conductive thin film A of a glass substrate with an indium-tin composite oxide thin film (ITO glass) and the transparent conductive film B of the transparent conductive film according to the present invention.
Although not limited to a specific theory, it is believed that the voltage loss time within the range of the present invention can extend the electrically stable contact time between a pair of transparent conductive thin films in a touch panel, thereby further reducing electrically unstable contact states. As a result, the time during which input is unstable is shortened, and for example, blurring of characters can be prevented when writing characters continuously. Furthermore, this solves the problem of characters appearing on the touch panel becoming blurred or not being displayed when writing characters on the touch panel. Furthermore, it has excellent shorthand properties, reducing blurring of characters during shorthand writing.

In the present invention, if the voltage loss time of the transparent conductive film in the pen input stability test is 0.00 milliseconds or more and 0.40 milliseconds or less, the film has excellent pen input stability and shorthand properties.
The present invention, which has such pen input stability, makes it possible to vividly draw characters and pictures on a resistive touch panel. For example, it is possible to express the strokes of characters as if they were written with a brush.
The voltage loss time is preferably as short as possible within the scope of the present invention, and is preferably 0.40 milliseconds or less to ensure excellent pen input stability, more preferably 0.35 milliseconds or less, and even more preferably 0.30 milliseconds or less.
It may also be 0.01 milliseconds or more, for example, 0.02 milliseconds or more, or 0.02 milliseconds or more.

In the present invention, it is preferred that the bending resistance in the following film bending resistance test is 0.23 N cm or more and 0.90 N cm or less, and further that the average maximum peak height described below on the transparent conductive film side surface of the transparent conductive film satisfies the following formulas (2-1) and (2-2), and further that the value calculated in the following contact area ratio evaluation satisfies formula (2-3).
First, we will explain the bending resistance measured by the film bending resistance test. In the film bending resistance test, the test piece is placed on a smooth, horizontal table with the transparent conductive layer facing up. This is to align the direction of deformation of the transparent conductive film when it is pressed with a pen or finger from the non-transparent conductive layer side. Even for the same transparent conductive film, the bending resistance value changes depending on whether the transparent conductive layer is facing up or down in the film bending resistance test, so care must be taken when evaluating.
Furthermore, when a curable resin layer is disposed between a transparent plastic substrate and a transparent conductive film, the thickness and hardness of the curable resin layer also affect the bending resistance. Furthermore, when curable resin layers are disposed on both sides of the transparent plastic substrate, the balance between the thicknesses and hardnesses of the curable resin layers on each side also affects the bending resistance.

If the bending resistance of the transparent conductive film is 0.23 N cm or more, the transparent conductive film is less likely to deform when unintentionally touched with a very light force, making it less likely for electrical contact to occur between the transparent conductive film of the transparent conductive film and the transparent conductive film of the ITO glass for touch panels, making it easier to prevent erroneous input, which is preferable. It is also preferable because it provides excellent pen sliding durability. It is more preferable that it is 0.27 N cm or more. Even more preferable that it is 0.30 N cm or more.
On the other hand, if the bending resistance of the transparent conductive film is 0.90 N cm or less, the transparent conductive film is easily deformed even when pressed with a pen or finger from the transparent conductive film side with a low input load, and the transparent conductive film of the transparent conductive film and the transparent conductive film of the ITO glass are easily electrically contacted, which is preferable for easy operability. It is more preferably 0.80 N cm or less. It is even more preferably 0.70 N cm or less. It is particularly preferably 0.60 N cm or less.

(Film bending resistance test method)
A 20 mm x 250 mm test piece is taken from the transparent conductive film and placed on a smooth, horizontal stand with the transparent conductive layer facing up. At this time, only the 20 mm x 20 mm part of the test piece is placed on the horizontal stand, with the 20 mm x 230 mm part outside the horizontal stand. In addition, a weight is placed on the 20 mm x 20 mm part of the test piece. At this time, the weight and size of the weight are selected so that there is no gap between the test piece and the horizontal stand.
Next, the difference between the height of the horizontal table and the height of the tip of the film (= δ) is read using a scale, and the value is then substituted into the following formula (1) to calculate the bending resistance.
Formula (1) (g×a×b×L ⁴ )÷8δ (N cm)
g = gravitational acceleration, a = length of the short side of the test piece, b = specific gravity of the test piece, L = length of the test piece, δ = difference in height between the horizontal table and the tip of the film

In the present invention, when a film bending resistance test is carried out, it is preferred that the bending resistance in the film bending resistance test is 0.23 N cm or more and 0.90 N cm or less, and further that the average maximum peak heights below on the transparent conductive film side surface of the transparent conductive film satisfy the following formulas (2-1) and (2-2):
(Average maximum mountain height rating)
The average maximum peak height is the average of the maximum peak heights at five points. To select the five points, first select one arbitrary point A. Next, select two points, one 1 cm upstream and one 1 cm downstream from A in the machine direction (MD) of the film. Next, select two points, one 1 cm to the left and one 1 cm to the right and left of A in the cross-machine direction (TD) of the film. The maximum peak height is specified in ISO 25178 and was determined using a 3D surface profiler, VertScan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x magnification)). Values less than 1 nm were rounded off.
Formula (2-1) Average maximum peak height ≧ 4.7 × bending resistance − 1.8
Formula (2-2) 0.005 (μm) ≦ Average maximum peak height (μm) ≦ 12.000 (μm)

If the maximum peak height of the surface on the transparent conductive film side satisfies formula (2-1) and formula (2-2), even when pressed with a pen or a finger from the transparent conductive film side with a low input load, electrical contact can be made between the transparent conductive film placed on the protrusion on the transparent conductive film side of the transparent conductive film and the transparent conductive film of the ITO glass for touch panels, which is preferable as it provides easy operability.
More preferably, the y intercept of formula (2-1), i.e., the value shown by "-1.8" in formula (2-1), is -1.7 or more, and even more preferably, the y intercept of formula (2-1) is -1.6 or more.
Furthermore, an average maximum peak height of 0.005 (μm) or more is preferable because the transparent conductive film can be wound into a roll without any problems. More preferably, it is 0.010 (μm) or more. Even more preferably, it is 0.020 (μm) or more. Furthermore, an average maximum peak height of 12,000 (μm) or less is preferable because it is less likely to cause unintended electrical contact between the transparent conductive film arranged on the protrusions on the transparent conductive film side of the transparent conductive film and the transparent conductive film of the ITO glass for touch panels, making it easier to prevent erroneous input. A more preferable average maximum peak height is 11,000 (μm) or less. Even more preferable is 10,000 (μm) or less. From the above, it was found that a moderate balance between bending resistance and average maximum peak height satisfies light operability and other requirements.

In the present invention, when a film bending resistance test is carried out, it is preferred that the bending resistance in the film bending resistance test is 0.23 N cm or more and 0.90 N cm or less, and further that the average maximum peak heights below on the transparent conductive film side surface of the transparent conductive film satisfy the following formulas (2-1) and (2-2), and further that the value calculated in the contact area ratio evaluation below satisfies formula (2-3).
(Contact area ratio evaluation)
The conductive surface of the transparent conductive film is measured for arithmetic mean roughness Ra in accordance with JIS B 0601-2001 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 50x)) over a measurement length range of 100 μm to 200 μm. Ra is measured so that either or both of the following conditions are satisfied: "Rp - average height - Ra ≦ 0.20 μm" or "(Rp - average height) ÷ Ra ≦ 5.0", and Rsm ≦ 30 μm. Here, Rp and Rsm are measured in accordance with JIS B 0601-2001. The average height is the average value of the height over the measurement length. If the above conditions are not satisfied, remeasure at a different point. Next, for the conductive surface of the same transparent conductive film, a 3D surface profiler, Vertscan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x)), is used, and the particle analysis function of the same measuring device is used to determine the sum of the cross-sectional areas using "Ra - 15 nm - average height" as the threshold. The sum of the cross-sectional areas is divided by the area of the measurement field of view, and the result multiplied by 100 is the contact area ratio.
Formula (2-1) Average maximum peak height (μm) ≧ 4.7 x bending resistance - 1.8
Formula (2-2) 0.005 (μm) ≦ Average maximum peak height (μm) ≦ 12.000 (μm)
Formula (2-3) Contact area ratio (%) ≧ 32.6 x bending resistance + 17.2

Equation (2-3) will be explained in terms of contact area ratio evaluation. When inputting data into a resistive touch panel using a pen, finger, or the like, the transparent conductive glass and the transparent conductive film are in contact. As the pen, finger, or the like moves away from the transparent conductive film of the resistive touch panel, the contact area between the transparent conductive glass and the transparent conductive film decreases. As the contact area decreases, the stability of the electrical contact between the transparent conductive glass and the transparent conductive film also decreases. The larger the contact area between the transparent conductive glass and the transparent conductive film when inputting data into a resistive touch panel using a pen, finger, or the like, the higher the stability of the electrical contact between the transparent conductive glass and the transparent conductive film. Therefore, when the pen, finger, or the like moves away from the transparent conductive film of the resistive touch panel, the longer the contact area becomes until the electrical contact between the transparent conductive glass and the transparent conductive film becomes unstable. This time until the contact area becomes unstable can be considered synonymous with the voltage loss time in this invention. In other words, being within the voltage loss time in this invention means that input to the touch panel is stable.
Even if the size of the pen or finger used to input to the touch panel is the same, the contact area between the transparent conductive glass and the transparent conductive film will be different. We found that there is a strong correlation between the contact area ratio shown below and the stability of pen input.
This section describes the contact area between the transparent conductive glass and the transparent conductive film when inputting data onto a resistive touch panel using a pen or finger. The majority of the transparent conductive film in contact with the transparent conductive glass is made up of protrusions of the average height of the transparent conductive film. Because it is difficult to accurately calculate the contact area with protrusions of average height on the transparent conductive film, we used the cross-sectional area of the transparent conductive film on the transparent conductive film side at a height slightly smaller than the average height of the protrusions on the transparent conductive film (i.e., a height 15 nm lower than the average height of the transparent conductive film) as an alternative indicator. Here, using the arithmetic mean height Sa of ISO 25178 or the arithmetic mean roughness Ra of JIS B 0601-2001 as the average protrusion height of the transparent conductive film is undesirable because Sa and Ra will be larger than the actual average protrusion height of the transparent conductive film due to the influence of the few but very high coarse protrusions on the transparent conductive film side of the transparent conductive film. Therefore, to eliminate the influence of the coarse protrusions, we performed the following.
The conductive surface of the transparent conductive film is measured for its arithmetic mean roughness Ra in accordance with JIS B 0601-2001 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 50x)) over a measurement length range of 100 μm to 200 μm. Ra is measured so that either or both of "Rp - mean height - Ra ≦ 0.20 μm" and "(Rp - mean height) ÷ Ra ≦ 5.0" are satisfied, and further, Rsm ≦ 30 μm is satisfied. Here, Rp and Rsm are measured in accordance with JIS B 0601-2001. The mean height is the average value of the height over the measurement length.
It was discovered that if either or both of "Rp - average height - Ra ≦ 0.20 μm" and "(Rp - average height) ÷ Ra ≦ 5.0" are satisfied, and further if Rsm ≦ 30 μm is satisfied, the influence of coarse protrusions is reduced, making it possible to calculate the average protrusion height of the transparent conductive film. If the above conditions are not satisfied, the influence of coarse protrusions is so great that the average protrusion height of the transparent conductive film cannot be calculated, so measurements are taken again at different points.
Next, the conductive surface of the same transparent conductive film was measured 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)), and the particle analysis function of the same measurement device was used to determine the sum of cross-sectional areas using "Ra - 15 nm - average height" as a threshold. The contact area ratio was calculated by dividing the sum of cross-sectional areas by the area of the measurement field of view and multiplying the result by 100. If the contact area ratio satisfies formula (2-3), the voltage loss time in the pen input stability test falls within the range of the present invention, which is preferable because it results in excellent pen input stability. Formula (2-3) will now be explained. Studies have shown that a high bending resistance increases the speed at which a pen, finger, etc., separates from the transparent conductive film of a resistive touch panel; therefore, it has been found that excellent pen input stability cannot be achieved unless a transparent conductive film with a high contact area ratio is used. To achieve excellent pen input stability, the correlation between the contact area ratio and bending resistance must be as shown in formula (2-3). More preferably, the y-intercept of formula (2-3), i.e., the value shown by "+17.2" in formula (2-3), is +17.5 or more, and even more preferably, the y-intercept of formula (2-3) is +18.0 or more.
It has been found that satisfying all of the formulas (2-1), (2-2), and (2-3) makes it possible to achieve both light operability and excellent stability of pen input.
Formula (2-1) Average maximum peak height (μm) ≧ 4.7 x bending resistance - 1.8
Formula (2-2) 0.005 (μm) ≦ Average maximum peak height (μm) ≦ 12.000 (μm)
Formula (2-3) Contact area ratio (%) ≧ 32.6 x bending resistance + 17.2

In the present invention, the maximum value of the maximum peak height in the average maximum peak height evaluation described below is more than 1.0 times but not more than 1.4 times the average maximum peak height, and
The minimum value of the maximum peak height in the average maximum peak height evaluation is 0.6 to 1.0 times the average maximum peak height. This range is preferable because it keeps the variation in input start load to less than ±5%.
If the minimum value of the maximum peak height in the average maximum peak height evaluation is 0.6 times or more of the average maximum peak height, the in-plane distribution of the tall protrusions on the transparent conductive film side of the transparent conductive film, which contributes to light operability, is uniform, and therefore when pressing from the transparent conductive film side with a pen or a finger, input to the touch panel is possible with the same input load at any location, which is preferable. It is more preferably 0.7 times or more. Even more preferably 0.8 times or more.
On the other hand, if the maximum value of the maximum peak height in the average maximum peak height evaluation is 1.4 times or less the average maximum peak height, the in-plane distribution of the tall protrusions on the transparent conductive film side of the transparent conductive film, which contributes to light operability, is uniform, and therefore when pressing from the transparent conductive film side with a pen or a finger, input to the touch panel is possible with the same input load at any location, which is preferable. It is more preferably 1.3 times or less. It is even more preferably 1.2 times or less.

(Average maximum mountain height rating)
The average maximum peak height is the average of the maximum peak heights at five points. To select the five points, first select one arbitrary point A. Next, select two points, one 1 cm upstream and one 1 cm downstream from A in the machine direction (MD) of the film. Next, select two points, one 1 cm to the left and one 1 cm to the right and left of A in the cross-machine direction (TD) of the film. The maximum peak height is specified in ISO 25178 and was determined using a 3D surface profiler, VertScan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x magnification)). Values less than 1 nm were rounded off.

The transparent conductive film of the present invention is made of indium-tin composite oxide. The surface resistance of the transparent conductive film of the present invention is preferably 50 to 900 Ω/□, and more preferably 50 to 700 Ω/□. The total light transmittance of the transparent conductive film of the present invention is preferably 70 to 95%.

In the present invention, the thickness of the transparent conductive film is preferably 10 nm or more and 100 nm or less. A transparent conductive film having a thickness of 10 nm or more is preferred because the transparent conductive film adheres to the entire transparent film substrate or cured resin layer, stabilizing the film quality of the transparent conductive film and resulting in a stable surface resistance value within a preferred range. A more preferred thickness is 13 nm or more, and even more preferred is 16 nm or more. A transparent conductive film having a thickness of 100 nm or less is also preferred because the crystal grain size and degree of crystallinity of the transparent conductive film are appropriate and the total light transmittance is at a practical level. A thickness of 50 nm or less is more preferred, even more preferred is 30 nm or less, and particularly preferred is 25 nm or less.

In the present invention, the tin oxide concentration in the transparent conductive film is preferably 0.5 to 40% by mass. It has been discovered that the closer the tin oxide concentration in the transparent conductive film is to the tin oxide concentration in the ITO glass for touch panels, the easier the electrical contact between the transparent conductive film and the ITO glass becomes, resulting in light operability and excellent pen input stability. The tin oxide concentration in the ITO glass for touch panels is generally 10% by mass.
In the present invention, if the difference between the tin oxide concentration contained in the transparent conductive layer of the transparent conductive film and the tin oxide concentration contained in the ITO glass for touch panels is 30 mass % or less, the transparent conductive layer of the transparent conductive film and the transparent conductive layer of the ITO glass are more likely to come into electrical contact, which is preferable as it provides light operability and excellent pen input stability.
The tin oxide concentration contained in ITO glass for touch panels is often 10% by mass. Therefore, in the present invention, the tin oxide concentration of the transparent conductive film is preferably 40% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less, and particularly preferably 2% by mass or more to 18% by mass. Furthermore, if the tin oxide content is 0.5% by mass or more, the surface resistance of the transparent conductive film becomes a practical level, which is preferable. More preferably, the tin oxide content is 1% by mass or more, and particularly preferably 2% by mass or more.

In one embodiment, the transparent conductive film of the present invention has a curable resin layer between the transparent conductive film and the transparent plastic film substrate.
Furthermore, it is preferable that the transparent plastic substrate has a functional layer on the side opposite to the transparent conductive film.
As shown in the example of the configuration in FIG. 2, the device may have a transparent conductive film 5, a curable resin layer 6, a transparent plastic film substrate 7, and a functional layer 8 in this order.
When a transparent conductive film is heated during the touch panel processing process, monomers and oligomers generated from the transparent plastic film substrate may precipitate onto the transparent conductive film, potentially impairing the touch panel's responsive operability and pen input stability.
Therefore, it is preferable to have a curable resin layer between the transparent conductive film and the transparent plastic film substrate, since this can block the deposition of monomers and oligomers on the transparent conductive film.

Furthermore, since monomers and oligomers precipitated from the transparent plastic substrate may reduce the visibility of the transparent conductive film, it is preferable that the transparent plastic film substrate has a curable resin layer and a functional layer.
Furthermore, by having the curable resin layer and the functional layer, the bending resistance of the transparent conductive film can be adjusted to a more preferable range in the present invention.
The curable resin layer and functional layer according to the present invention can more effectively exhibit various properties such as pen sliding durability, etc. In particular, in the present invention, by having the curable resin layer and functional layer, the bending resistance of the transparent conductive film according to the present invention can be adjusted, the input start load can be adjusted within a predetermined range, and excellent visibility can be achieved.
Although not intended to be limited to any particular theory, the present invention is such that by having both a curable resin layer and a functional layer, a light operation feel and more accurate input performance can be achieved in a resistive touch panel.
Furthermore, by providing a curable resin layer on the transparent plastic film substrate, the adhesive strength of the transparent conductive film can be increased and the force acting on the transparent conductive film can be dispersed, which is preferable because it can suppress cracking, peeling, abrasion, etc. of the transparent conductive film in a pen sliding durability test. Furthermore, by providing a functional layer on the transparent plastic film substrate, it is preferable because it becomes less susceptible to scratches caused by inputting with a pen or the like.

In one embodiment, the transparent conductive film of the present invention has an easy-adhesion layer laminated on at least one side of the transparent plastic film substrate.
For example, the transparent conductive film of the present invention preferably includes an easy-adhesion layer between the transparent plastic film substrate and the curable resin layer, or between the transparent plastic film substrate and the functional layer, or both. Configuration examples are shown in Figures 3, 4, and 5. In these figures, an easy-adhesion layer 9 is disposed. Other reference numerals have the same meanings as in Figure 2.
The presence of the easy-adhesion layer allows the curable resin layer and the functional layer to adhere firmly to the transparent plastic film substrate, which is preferable because peeling of the curable resin layer and the functional layer due to external forces can be more effectively suppressed.

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 at least 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 following pen sliding durability test.
(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 50,000 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.

In the present invention, it is preferable that the ON resistance of the transparent conductive film of the transparent conductive film in a pen sliding durability test is 10 kΩ or less, since 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.
The ON resistance is, for example, 5 kΩ or more, may be 3 kΩ or more, and is preferably 0 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.

For example, the transparent conductive film of the present invention has a remaining area ratio of 95% or more on the surface of the transparent conductive film in an adhesion test conforming to JIS K5600-5-6:1999. When the transparent conductive film of the present invention is subjected to an adhesion test (JIS K5600-5-6:1999) on the transparent conductive film surface, the remaining area ratio of the transparent conductive film is preferably 95% or more, more preferably 99% or more, and particularly preferably 99.5% or more. When the remaining area ratio of the transparent conductive film is within the above range in the adhesion test, the transparent conductive film is in close contact with the transparent plastic film substrate and the cured resin layer, which prevents cracking, peeling, wear, etc. of the transparent conductive film even when continuous input is made with a pen on the touch panel. Furthermore, even when a force greater than that expected for normal use is applied, cracking, peeling, etc. of the transparent conductive film is prevented, which is preferable.

For example, in the transparent conductive film of the present invention, the remaining area ratio of the functional layer on the surface of the functional layer is 95% or more in an adhesion test in accordance with JIS K5600-5-6: 1999. In the transparent conductive film of the present invention, even when an adhesion test (JIS K5600-5-6: 1999) is conducted on the functional layer surface, the remaining area ratio of the functional layer surface is preferably 95% or more, more preferably 99% or more, and particularly preferably 99.5% or more.
Transparent conductive films whose functional layer does not peel off in adhesion tests are preferred because the transparent plastic film substrate and functional layer are in close contact with each other, preventing appearance defects such as cracking, peeling, and wear of the functional layer even when continuous input is made to the touch panel with a pen.Furthermore, even if a force stronger than expected in normal use is applied, the functional layer absorbs the force, preventing cracking, peeling, etc. of the transparent conductive film.

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 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 preferred method for forming a transparent conductive film on a transparent plastic film is to use a mass flow controller in the film formation atmosphere, flow an inert gas and oxygen gas, and use an indium-tin composite oxide sintered target to adjust the thickness of the transparent conductive film of indium-tin composite oxide to 10 to 100 nm. To improve production efficiency, multiple indium-tin composite oxide sintered targets may be placed in the film flow direction. Alternatively, a mass flow controller may be used in the film formation atmosphere to flow 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). The amount of water 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 can adversely affect the quality of the transparent conductive film, such as by causing the surface resistance to fall outside the desired range or preventing crystallization of a transparent conductive film that would normally crystallize. Controlling 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 to 7.00 × 10 ⁻³ or less is preferable, as it can prevent deterioration in the quality of the transparent conductive film. In order to control the amount of water in the film-forming atmosphere, in addition to rotary pumps, turbomolecular pumps, and cryopumps commonly used as exhaust devices for sputtering machines, the bombardment process described below, limiting the height difference of the unevenness on the end surface of the film roll described below, and applying a protective film with low water absorption to the surface opposite the surface on which the transparent conductive film is formed are also preferable, as they reduce the amount of water released from the film during film-forming. Furthermore, 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 by the set temperature of a temperature controller that adjusts the temperature of the center roll with which the running film contacts. Figure 1 shows a schematic diagram of an example of a sputtering apparatus suitable for use in the present invention, in which the running film 1 runs while partially contacting 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 below is preferable because it suppresses the release of impurity gases such as water and organic gases from the film, which degrade the quality of the transparent conductive film. Furthermore, it is desirable to add oxygen gas during sputtering to achieve practical levels of surface resistance and total light transmittance 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, 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, which is desirable because it improves pen sliding durability and pen heavy pressure durability.

For film rolls used to deposit transparent conductive films, the height difference between the most convex and most concave points on the roll edge is preferably 10 mm or less. A height difference of 10 mm or less is preferable because it reduces the release of water and organic components from the film edge when the film roll is placed in a sputtering device, improving the quality of the transparent conductive film.

For films (transparent plastic film substrates) on which a transparent conductive film is formed, it is desirable to apply a protective film with low water absorption to the side opposite the surface on which the transparent conductive film is formed. Applying a protective film with low water absorption makes it less likely for gases such as water to be released from the film substrate, improving the quality of the transparent conductive film, which is preferable. Materials such as polyethylene, polypropylene, and cycloolefin are preferred as substrates for protective films with low water absorption.

In a method for forming a transparent conductive film of 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 of 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 is preferred when it is necessary to increase the crystallinity of the transparent conductive film in order to improve pen sliding durability. A temperature of 200°C or lower is preferred because 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.

The transparent conductive film of the present invention preferably has a transparent plastic film substrate thickness in the range of 100 μm or more and 240 μm or less, and more preferably 120 μm or more and 220 μm or less. 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. On the other hand, a thickness of 240 μm or less is preferred because it maintains light operability and excellent pen input stability when used in a touch panel.

Laminating a curable resin layer on a transparent plastic film substrate is preferable because it prevents monomers and oligomers generated from the transparent plastic film substrate from precipitating on the transparent conductive film, thereby not impairing the smooth operability of the touch panel. It is also preferable because it provides strong adhesion between the transparent conductive film and the curable resin layer and distributes the force applied to the transparent conductive film, thereby reducing cracking, peeling, and abrasion of the transparent conductive film in pen sliding durability tests. To improve the adhesion between the transparent plastic film substrate and the curable resin layer, it is preferable to provide an easy-adhesion layer between the transparent plastic film substrate and the curable resin layer.

Laminating a functional layer on a transparent plastic film substrate is preferable because it can block the precipitation of monomers and oligomers generated from the transparent plastic film substrate, thereby suppressing a decrease in visibility of the transparent conductive film. It is preferable to have a functional layer on the transparent plastic film substrate in order to adjust the bending resistance of the transparent conductive film. It is also preferable to have a functional layer on the transparent plastic film substrate because it makes it less susceptible to scratches caused by writing with a pen or the like.

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

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 the present invention, the curable resin layer and the functional layer preferably contain inorganic particles or organic particles in addition to the curable resin, which is the main component. By dispersing inorganic particles or organic particles in the curable resin, unevenness can be formed on the surfaces of the curable resin layer and the functional layer, thereby improving surface roughness over a wide area.
In the present invention, by improving the surface roughness of the curable resin layer, the bending resistance of the transparent conductive film can be adjusted to a more preferred range in the present invention, and various properties such as pen sliding durability, anti-Newton ring properties, and film winding properties can be more effectively exhibited.
In the present invention, by improving the surface roughness of the functional layer, the bending resistance of the transparent conductive film can be adjusted to a more preferable range in the present invention, and various properties such as the film's winding properties, writing comfort with a pen, and fingertip feel can be more effectively exhibited.

Examples of the inorganic particles include silica. Examples of the organic particles include polyester resin, polyolefin resin, polystyrene resin, polyamide resin, etc. The particles contained in the curable resin layer and the functional layer may be the same or different.

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 particle form. These dispersed particles of the incompatible resin create irregularities on the surfaces of the curable resin layer and functional layer, 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 is shown. The inorganic particles are preferably present in an amount of 0.1 to 30 parts by weight per 100 parts by weight of the UV-curable resin, more preferably 0.1 to 25 parts by weight, and particularly preferably 0.1 to 20 parts by weight. When the blending amount of the inorganic particles is 0.1 to 30 parts by weight per 100 parts by weight of the UV-curable resin, the convex portions formed on the surface of the curable resin layer are not too small, providing an effective average maximum peak height, providing easy operability for the touch panel, and furthermore, since the transparent conductive film has some surface protrusions, film winding properties are maintained, which is preferable. Furthermore, when inorganic particles are used in the curable resin layer, the higher the blending ratio within the above range, the higher the average maximum peak height of the curable resin layer tends to be.
Furthermore, when inorganic particles are used in the curable resin layer, the higher the blending ratio within the above range, the more likely it is that the bending resistance of the transparent conductive film will increase.

Here, as an example, the blending ratio when inorganic particles are used in the functional layer is shown below: It is preferable that the inorganic particles are 0.1 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the ultraviolet curable resin.
When inorganic particles are used in the functional layer, a higher blending ratio within the above range tends to reduce the bending resistance of the transparent conductive film. Furthermore, the lower the blending amount of inorganic particles, the higher the contact area ratio of the transparent conductive film tends to be. When the blending amount of the inorganic particles is 0.1 parts by mass or more and 60 parts by mass or less per 100 parts by mass of the ultraviolet-curable resin, the bending resistance of the transparent conductive film can be adjusted to an appropriate value according to the present invention, which is preferable. Furthermore, since surface protrusions can be formed on the functional layer within a range that does not impair the effects of the present invention, the film can also be wound easily, which is preferable.

Here, as an example, the size of inorganic particles when inorganic particles are used in the curable resin layer is shown. The size of the inorganic particles is preferably an average particle size of 0.010 to 10,000 μm. When inorganic particles are used in the curable resin layer, inorganic particles with different average particle sizes may be mixed. The larger the average particle size, the larger the average maximum peak height of the curable resin layer tends to be. The more uniform the average particle size of the inorganic particles used in the curable resin layer, the larger the contact area ratio of the transparent conductive film tends to be.
In one embodiment, inorganic particles A having an average particle size of 1.0 μm or more and 10,000 μm can be used in combination with inorganic particles B having an average particle size of 0.010 μm or more and less than 1.0 μm. For example, the average particle size of inorganic particles B is preferably 0.05 μm or more.
Furthermore, when the curable resin layer contains inorganic particles A and inorganic particles B, the amount of inorganic particles A in the curable resin layer is, for example, 0.1 wt % or more and 5 wt % or less relative to 100 wt % of the solid content of the curable resin layer. The amount of inorganic particles B in the curable resin layer is preferably greater than the amount of inorganic particles A in 100 wt % of the solid content of the curable resin layer, for example, more than 5 wt % and 30 wt % or less.
By satisfying this relationship, it is possible to increase the average maximum peak height of the curable resin layer while increasing the contact area ratio of the transparent conductive film, thereby shortening the voltage loss time. Furthermore, since the voltage loss can be reduced within the range of the present invention, the time during which input is unstable is shortened, and for example, when characters are written continuously, it is possible to more effectively prevent blurring of characters.

Here, as an example, the size of inorganic particles when inorganic particles are used in the functional layer is shown. The size of the inorganic particles is preferably an average particle size of 0.010 to 10,000 μm. When inorganic particles are used in the functional layer, inorganic particles with different average particle sizes may be mixed.

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 component 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. The higher the concentration of the resin component, the higher the average maximum peak height of the curable resin layer tends to be. Furthermore, other known additives, such as silicone-based leveling agents, may 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, turns into 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 resin layer and functional 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 surfaces of the hard-coat resin layer and functional layer, improving surface roughness over a wide area.

The thickness of the curable resin layer is preferably in the range of 0.1 μm to 15 μm. It is more preferably in the range of 0.5 μm to 10 μm, and particularly preferably in the range of 1 μm 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. A thick curable resin layer also tends to increase the bending resistance of the transparent conductive film.

The thickness of the functional layer is preferably in the range of 0.1 μm to 15 μm. It is more preferably in the range of 0.5 μm to 15 μm, and particularly preferably in the range of 1 μm to 10 μm. A thick functional layer tends to reduce the bending resistance of the transparent conductive film. A functional layer 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 it allows for good productivity.

The bending resistance of the transparent conductive film can be adjusted to the above-mentioned appropriate value by appropriately selecting the amounts of inorganic particles, organic particles, and incompatible resin added to the curable resin layer and the thickness of the curable resin layer, in consideration of the influence of these amounts on the bending resistance of the transparent conductive film.
Therefore, in the present invention, the effect of the present invention cannot be obtained simply by providing a functional layer, but the characteristics of the present invention can effectively contribute to the bending resistance of the transparent conductive film.

In one embodiment, the thickness of the curable resin layer and the thickness of the functional layer may be the same. In another embodiment, for example, the absolute value of the difference between the thickness of the curable resin layer and the thickness of the functional layer has the following relationship:
0.1 μm≦|thickness of curable resin layer−thickness of functional layer|≦3 μm
In this way, in the present invention, by providing a difference in thickness between the curable resin layer and the functional layer, the bending resistance of the transparent conductive film can be adjusted to a more preferred range in the present invention, and various properties such as pen sliding durability can be more effectively exhibited, and a transparent conductive film having easy operability can be obtained.
Furthermore, it is preferable that the particle mass per unit volume of the curable resin layer and the particle mass per unit volume of the functional layer are different.

The adhesive layer according to the present invention is preferably formed from a composition containing a urethane resin, a crosslinking agent, and a polyester resin. The crosslinking agent is preferably a blocked isocyanate, more preferably a trifunctional or higher functional blocked isocyanate, and particularly preferably a tetrafunctional or higher functional blocked isocyanate. The thickness of the adhesive layer is preferably from 0.001 μm to 2.00 μm.

The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples. Various measurements and evaluations in the examples were performed using the following methods.

(1) Total Light Transmittance The total light transmittance was measured in accordance with JIS-K7361-1:1997 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) Average Maximum Peak Height Evaluation The average maximum peak height is the average of the maximum peak heights at five points. To select the five points, first select one arbitrary point A. Next, select two points, one 1 cm upstream and one 1 cm downstream from A in the machine direction (MD) of the film. Next, select two points, one 1 cm to the left and one 1 cm to the right and left of A in the cross-machine direction (TD) of the film. The maximum peak height is specified in ISO 25178 and was determined using a 3D surface profiler, VertScan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x magnification)). Values less than 1 nm were rounded off.

(4) Crystallinity of Transparent Conductive Film A film sample having a transparent conductive thin film layer laminated thereon was cut into a size of 1 mm × 10 mm, and attached to the top surface of a suitable resin block with the conductive thin film surface facing outward. After trimming, ultrathin sections approximately 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.
The crystallinity of the transparent conductive film was evaluated by observing the proportion of crystal grains under a transmission electron microscope, that is, the degree of crystallinity.

(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 A transparent conductive film was used as one panel plate, and 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 was used as the other panel plate. 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 polyacetal pen (tip shape: 0.8 mmR) was applied with a load of 2.5 N, and a linear sliding test of 50,000 strokes was performed on the touch panel. 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 contact each other) was measured when the sliding portion was pressed with a pen load of 0.8 N. An ON resistance of 10 kΩ or less is desirable.

(7) 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.

(8) Input Load Test Method A transparent conductive film (size: 220 mm × 135 mm) was used as one panel plate, and a transparent conductive thin film A consisting of an indium-tin composite oxide thin film (tin oxide content: 10 mass%) having a thickness of 20 nm and formed by sputtering on a glass substrate (size: 232 mm × 151 mm) was used as the other panel plate.
On the transparent conductive thin film A side of a glass substrate with an indium-tin composite oxide thin film (hereinafter also referred to as ITO glass), epoxy resin (60 μm length × 60 μm width × 5 μm height) was arranged as dot spacers in a square lattice pattern with a pitch of 4 mm.
Next, double-sided tape (thickness: 105 μm, width: 6 mm) was attached to the transparent conductive thin film A side of the ITO glass so as to form a rectangle of 190 mm×135 mm, starting from one of the four corners of the ITO glass.
Next, the transparent conductive film is attached with the transparent conductive layer B side on the double-sided tape attached to the ITO glass, and laminated so that the transparent conductive thin layer A and the transparent conductive layer B face each other.
At this time, one short side of the transparent conductive film is set to protrude from the ITO glass.
Next, connect the ITO glass and transparent conductive film with a tester.
Next, a load is applied from the transparent conductive film side using a polyacetal pen (tip shape: 0.8 mmR), and the load value when the resistance value measured by the tester stabilizes is defined as the input start load.
The position where the load is applied with the pen is the central region surrounded by four dot spacers, and the average value of the input start load at the three points is calculated.
The position where the load was applied with the pen was the central region of the four dot spacers as shown in Figure 6. The input start load was measured at three arbitrary points at least 50 mm away from the double-sided tape and the average value was calculated. Decimals were rounded off.

(9) Film bending resistance test method: A 20 mm x 250 mm test piece is taken from the transparent conductive film and placed on a smooth horizontal stand with the transparent conductive layer facing up. At this time, only the 20 mm x 20 mm portion of the test piece is placed on the horizontal stand, with the 20 mm x 230 mm portion being placed outside the horizontal stand. In addition, a weight is placed on the 20 mm x 20 mm portion of the test piece. At this time, the weight and size of the weight are selected so that there is no gap between the test piece and the horizontal stand. Next, the difference in height between the horizontal stand and the tip of the film (= δ) is read on a scale. Next, the bending resistance is calculated by substituting the values into the following formula (1).
Formula (1) (g×a×b×L ⁴ )÷8δ (N cm)
g = gravitational acceleration, a = length of the short side of the test piece, b = specific gravity of the test piece, L = length of the test piece, δ = difference in height between the horizontal table and the tip of the film

(10) Evaluation of the maximum and minimum values of the maximum peak height relative to the average maximum peak height The maximum and minimum values of the maximum peak heights measured at five points in the average maximum peak height evaluation are divided by the average maximum peak height.

(11) Adhesion Test The adhesion test was carried out in accordance with JIS K5600-5-6:1999.
The results in the table below show the adhesion as a percentage of the remaining area. The maximum percentage of the remaining area is 100%. The closer the percentage of the remaining area in the adhesion test in the table is to 100%, the smaller the peeled area.

(12) Pen Input Stability Test Method A transparent conductive film (size: 220 mm × 135 mm) was used as one panel plate, and a transparent conductive thin film A consisting of an indium-tin composite oxide thin film (tin oxide content: 10% by mass) having a thickness of 20 nm was used as the other panel plate, which was formed on a glass substrate (size: 232 mm × 151 mm) by a sputtering method.
On the transparent conductive thin film A side of a glass substrate with an indium-tin composite oxide thin film (hereinafter also referred to as ITO glass), epoxy resin (60 μm length × 60 μm width × 5 μm height) is arranged as dot spacers in a square lattice pattern with a pitch of 4 mm.
Next, starting from one of the four corners of the ITO glass, double-sided tape (thickness: 105 μm, width: 6 mm) is attached to the transparent conductive thin film A side of the ITO glass so as to form a rectangle of 190 mm×135 mm.
Next, the transparent conductive film is attached with the transparent conductive layer B side on the double-sided tape attached to the ITO glass, and laminated so that the transparent conductive thin layer A and the transparent conductive layer B face each other.
At this time, one short side of the transparent conductive film is set to protrude from the ITO glass.
Next, a constant-voltage power supply is connected to the ITO glass and transparent conductive film. A recorder (Keyence GR-7000) capable of measuring the voltage between the ITO glass and transparent conductive film is then connected. The recorder is used to observe the time course of the voltage. 6 V is then applied to the constant-voltage power supply, and the recorder begins measuring the voltage in 0.02 millisecond increments. Next, a 50 g load is applied to the transparent conductive film side five times per second using a polyacetal pen (tip shape: 0.8 mmR). The pen load is applied to the central area surrounded by the four dot spacers. The data of the time course of the voltage as the pen applies the load to the transparent conductive film is extracted from the recorder. The voltage decreases as the pen begins to separate from the transparent conductive film. The time from when the voltage decreases from 6 V to when the voltage reaches 5 V is measured and recorded as the voltage loss time. See Figure 7.

(13) Contact Area Ratio Evaluation The conductive surface of the transparent conductive film is measured for its arithmetic mean roughness Ra in a measurement length range of 100 μm to 200 μm 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 50x)) in accordance with JIS B 0601-2001. Ra is measured so that either or both of the following conditions are satisfied: "Rp - average height - Ra ≦ 0.20 μm" or "(Rp - average height) ÷ Ra ≦ 5.0", and Rsm ≦ 30 μm. Here, Rp and Rsm are measured in accordance with JIS B 0601-2001. The average height is the average value of the height over the measurement length. If the above conditions are not satisfied, the measurement is repeated at a different point. Next, for the conductive surface of the same transparent conductive film, a 3D surface profiler, Vertscan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x)), is used, and the particle analysis function of the same measuring device is used to determine the sum of the cross-sectional areas using "Ra - 15 nm - average height" as the threshold. The sum of the cross-sectional areas is divided by the area of the measurement field of view, and the result multiplied by 100 is the contact area ratio.

The transparent plastic film substrate used in the examples and comparative examples was a biaxially oriented transparent PET film (A4380, manufactured by Toyobo Co., Ltd., thickness shown in Table 2) 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 the amount of silica particles having the average particle size shown in Table 2. 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 2, 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 achieve the coating thickness shown in Table 3. After drying at 80°C for 1 minute, the coating was cured by irradiating it with ultraviolet light (light intensity: 300 mJ/cm ² ) using an ultraviolet irradiation device (UB042-5AM-W, manufactured by iGraphics Co., Ltd.).
Under the conditions shown in Table 3, a functional layer was formed on the surface of the transparent plastic substrate opposite to the curable resin layer.

Examples 1 to 7
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 argon as an inert gas, 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 Tables 1 to 3.

(Comparative Examples 1 to 8)
Transparent conductive films were prepared and evaluated in the same manner as in Example 1 under the conditions shown in Tables 1 to 3. The results are shown in Tables 1 to 3.

As shown in Tables 1 to 3, the transparent conductive films described in Examples 1 to 7 have an input start load within the range of the present invention, which means they offer excellent, smooth operability when used in a resistive touch panel. Also, because the voltage loss time is within the range of the present invention, they offer excellent pen input stability and pen sliding durability, combining all of these properties. However, Comparative Examples 1 to 8 do not satisfy all of the requirements for smooth operability, pen input stability, and pen sliding durability.

As described above, the present invention makes it possible to provide a transparent conductive film that has light operability, excellent pen input stability, and excellent pen sliding durability, which is extremely useful for applications such as resistive touch panels.

1. Film 2. Center roll 3. Chimney 4. Indium-tin composite oxide target 5. Transparent conductive film 6. Curable resin layer 7. Transparent plastic film substrate 8. Functional layer 9. Easy-adhesion layer 10. ITO glass 11. Dot spacer 12. Position where load is applied with a pen 13. Time 14. Voltage 15. Voltage loss time

Claims (9)

A transparent conductive film having a transparent conductive film of indium-tin composite oxide laminated on at least one surface of a transparent plastic film substrate,
A transparent conductive film having a bending resistance of 0.23 N cm or more and 0.90 N cm or less in the following film bending resistance test, and further having an average maximum peak height of the conductive surface of the transparent conductive film that satisfies the following formulas (2-1) and (2-2), and further having a value calculated in the following contact area ratio evaluation that satisfies formula (2-3).
(Film bending resistance test method)
A 20 mm x 250 mm test piece is taken from the transparent conductive film and placed on a smooth, horizontal stand with the transparent conductive layer facing up. At this time, only the 20 mm x 20 mm part of the test piece is placed on the horizontal stand, with the 20 mm x 230 mm part outside the horizontal stand. In addition, a weight is placed on the 20 mm x 20 mm part of the test piece. At this time, the weight and size of the weight are selected so that there is no gap between the test piece and the horizontal stand.
Next, the difference between the height of the horizontal table and the height of the tip of the film (hereinafter referred to as δ) is read on the scale, and the value is then substituted into the following formula (1) to calculate the bending resistance.
Formula (1) (g×a×b×L ⁴ )÷8δ (N cm)
g = gravitational acceleration, a = length of the short side of the test piece, b = specific gravity of the test piece, L = length of the test piece, δ = difference in height between the horizontal table and the tip of the film (average maximum peak height evaluation)
The average maximum peak height is the average of the maximum peak heights at five points. To select the five points, first select one arbitrary point A. Next, select two points, one 1 cm upstream and one 1 cm downstream from A in the machine direction (MD) of the film. Next, select two points, one 1 cm to the left and one 1 cm to the right and left of A in the cross-machine direction (TD) of the film. The maximum peak height is specified in ISO 25178 and was determined using a 3D surface profiler, VertScan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x magnification)). Values less than 1 nm were rounded off.
(Contact area ratio evaluation)
The conductive surface of the transparent conductive film is measured for arithmetic mean roughness Ra in accordance with JIS B 0601-2001 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 50x)) over a measurement length range of 100 μm to 200 μm. Ra is measured so that either or both of the following conditions are satisfied: "Rp - average height - Ra ≦ 0.20 μm" or "(Rp - average height) ÷ Ra ≦ 5.0", and Rsm ≦ 30 μm. Here, Rp and Rsm are measured in accordance with JIS B 0601-2001. The average height is the average value of the height over the measurement length. If the above conditions are not satisfied, remeasure at a different point. Next, for the conductive surface of the same transparent conductive film, a 3D surface profiler, Vertscan (R5500H-M100, manufactured by Ryoka Systems Co., Ltd. (measurement conditions: wave mode, measurement wavelength 560 nm, objective lens 10x)), is used, and the particle analysis function of the same measuring device is used to determine the sum of the cross-sectional areas using "Ra - 15 nm - average height" as the threshold. The sum of the cross-sectional areas is divided by the area of the measurement field of view, and the result multiplied by 100 is the contact area ratio.
Formula (2-1) Average maximum peak height (μm) ≧ 4.7 x bending resistance - 1.8
Formula (2-2) 0.005 (μm) ≦ Average maximum peak height (μm) ≦ 12.000 (μm)
Formula (2-3) Contact area ratio (%) ≧ 32.6 x bending resistance + 17.2 The maximum value of the maximum peak height in the average maximum peak height evaluation is more than 1.0 times but not more than 1.4 times the average maximum peak height, and
2. The transparent conductive film according to claim 1 , wherein the minimum value of the maximum peak height in the average maximum peak height evaluation is 0.6 to 1.0 times the average maximum peak height. 3. The transparent conductive film according to claim 1, wherein the transparent conductive film has a thickness of 10 nm or more and 100 nm or less. 4. The transparent conductive film according to claim 1, wherein the concentration of tin oxide contained in the transparent conductive film is 0.5% by mass or more and 40% by mass or less. A curable resin layer is provided between the transparent conductive film and the transparent plastic film substrate,
5. The transparent conductive film according to claim 1, further comprising a functional layer on the opposite side of the transparent plastic film substrate from the transparent conductive film. 6. The transparent conductive film according to claim 1, further comprising an easy-adhesion layer on at least one side of the transparent plastic film substrate. The transparent conductive film according to claim 6 , wherein the easy-adhesion layer is disposed at least one position between the transparent plastic film substrate and the curable resin layer or between the transparent plastic substrate and the functional layer. 8. The transparent conductive film according to claim 1, wherein the transparent conductive film has an ON resistance of 10 kΩ or less in the following pen sliding durability test.
(Pen sliding durability test)
A transparent conductive film was used as one panel plate, and a transparent conductive thin film consisting of a 20 nm-thick indium-tin composite oxide thin film (tin oxide content: 10% by mass) was used as the other panel plate, sputtered onto a glass substrate. These two panels were arranged with 30 μm diameter epoxy beads between them, with the transparent conductive thin films facing each other, to produce a touch panel. Next, a polyacetal pen (tip shape: 0.8 mmR) was used to apply a load of 2.5 N to the touch panel, and a linear sliding test was performed 50,000 times. 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 fixed electrode come into contact) was measured when the sliding portion was pressed with a pen load of 0.8 N. 9. The transparent conductive film according to claim 1 , wherein the remaining area ratio of the transparent conductive film on the surface of the transparent conductive film is 95% or more in an adhesion test according to JIS K5600-5-6:1999.