TW201504067A - Transparent conductive multilayer film and method for producing same - Google Patents

Abstract

This transparent conductive multilayer film (100) sequentially comprises, on at least one surface of a film base (10), a transparent dielectric layer (21) and a transparent conductive film (24) that is provided in contact with the transparent dielectric layer (21), in this order. The transparent dielectric layer (21), which is in contact with the transparent conductive film (24), is a silicon oxide layer. The transparent conductive film (24) is a multilayer film that sequentially has, from the transparent film base (10) side, a first transparent conductive film (22) that is composed of an indium tin oxide layer that has a tin oxide content of 1% by weight of more but less than 6% by weight and a second transparent conductive film (23) that is composed of an indium tin oxide layer that has a tin oxide content of 6-20% by weight (inclusive). The film thickness (d1) of the first transparent conductive film (22) and the film thickness (d2) of the second transparent conductive film (23) satisfy the following relations (1)-(3): (1) d1 = 1-9 nm; (2) d1 + d2 = 15-37 nm; and (3) 2d1 < d2.

Description

Transparent conductive laminated film and method of manufacturing same

The present invention relates to a transparent conductive laminated film which comprises a transparent dielectric layer and a transparent conductive layer on a transparent film substrate, and a method for producing the same.

A transparent conductive film in which a conductive oxide film such as indium tin oxide (ITO) is formed on a transparent film is widely used as a transparent electrode such as a display, a light-emitting element, or a photoelectric conversion element. Such a transparent conductive film is produced by, for example, a dry process such as a sputtering method to form a conductive oxide thin film layer on a transparent film substrate. The conductive oxide film constituting the transparent electrode is required to have reliability of a resistivity in a high-temperature and high-humidity environment. In order to meet such a required characteristic, a transparent conductive film is often used in a state in which a conductive oxide is crystallized.

For the purpose of improving the quality of the transparent conductive film, it is proposed to laminate a transparent conductive film provided on a film substrate. For example, Patent Document 1 discloses that a first transparent conductive film having a small particle size crystal grain and a second transparent conductive film having a larger particle size crystal grain than the first transparent conductive film are formed on the film substrate, and thus A technique that can improve the durability of the writing pressure, the curling property, and the like while maintaining the transparency.

Patent Document 2 discloses that a first transparent conductive film made of indium tin oxide having a small content of tin oxide (SnO ₂ ) (SnO ₂ : 3 to 8 wt%) and a large content of SnO ₂ are provided on a film substrate ( SnO ₂ : 10 to 30% by weight) A second transparent conductive film made of indium tin oxide has a technique of improving the transparency and reducing the resistance.

Patent Document 3 discloses a substrate disposed on the film: made of SnO ₂ content is small: a first transparent conductive film (SnO _{2 2} ~ 6 wt%) composed of indium tin oxide, and a large content of SnO ₂ (SnO _2:. 6 ~20% by weight of a second transparent conductive film made of indium tin oxide, and the film thickness ratio of the two is set to a specific range, in order to satisfy the high temperature and high humidity reliability of the transparent conductive film for a touch panel, or Crystallization of low temperature heat treatment is possible.

The transparent conductive film of the above Patent Documents 1 to 3 is mainly used for a resistive film type touch panel. However, in recent years, the touch panel of the electrostatic capacity type which can be multi-touch input or gesture input has been rapidly popularized, and is used in mobile phones, tablet computers, notebooks, and the like. The capacitive touch panel requires low resistance of the transparent electrode layer to improve the sensitivity or response speed of the sensor.

Further, in the manufacturing process of the transparent conductive film, it is required to crystallize the conductive oxide in a short time. The method of crystallization is usually a method of heating after forming an amorphous conductive oxide film on a film substrate. From the viewpoint of heat resistance of the film substrate, it is difficult to heat the transparent conductive film using the resin film substrate to a high temperature (for example, 200 ° C or higher). Therefore, crystallization is required to be performed under heating at a lower temperature, and the crystallization time tends to be longer.

Patent Document 4 discloses that the composition of the laminated transparent conductive film can achieve both low resistance and crystallization for a short period of time. Specifically, an ITO layer having a small SnO ₂ content is provided on the surface side of the transparent conductive film (on the side away from the film substrate), and an ITO layer having a large SnO ₂ content is provided on the substrate side. According to the presumed principle disclosed in the configuration, the ITO layer having a small SnO ₂ content is provided on the surface side of the film substrate which is less susceptible to the gas generation, thereby promoting the formation of the crystal nucleus and shortening the crystallization time while increasing the SnO. ₂ large content of the thickness of the ITO layer side of the substrate, so the carrier can increase the resistance to reach.

[First technical literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2003-263925

[Patent Document 2] Japanese Patent Laid-Open No. Hei 10-49306

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2006-244771

[Patent Document 4] Japanese Patent Laid-Open Publication No. 2012-114070

According to the disclosure of Patent Document 3, the crystallization time can be effectively shortened by the structure of the laminated transparent conductive film, in addition to improving the transparency and the reliability in a high-temperature and high-humidity environment. However, Patent Document 3 mainly relates to a transparent conductive film used in a resistive film type touch panel, and has a surface resistance of about 300 Ω/□, which is not limited to a reduction in resistance and crystallization time.

According to the disclosure of Patent Document 4, the composition of the laminated transparent conductive film is used to achieve both the reduction in resistance and the shortening of the crystallization time. However, with the increase in the screen size (large area) of the device mounted on the touch panel, in order to improve the response speed, it is necessary to further reduce the resistance of the transparent conductive film. In addition, with the increase in area, it is also necessary to increase the uniformity of the resistivity in the plane.

The present invention has in view of the subject, and aims to provide a maintenance The transparency of the conductive film and the reliability in a high-temperature and high-humidity environment can simultaneously reduce the crystallization time, further reduce the resistance, and improve the uniformity of the in-plane resistivity.

In order to solve the above-mentioned problems, the inventors have found that an indium tin oxide layer having a small tin oxide content and an indium tin oxide layer having a large tin oxide content are provided on the transparent film substrate via a ruthenium oxide layer. Further, by setting the film thicknesses of the films to a specific range, the transparent conductive film can be crystallized in a short time, and the resistivity after crystallization is also low, and the uniformity of the in-plane resistivity is also good.

The present invention relates to a transparent conductive laminated film which is formed on at least one side of a transparent film substrate, and includes at least one transparent dielectric layer in sequence, and is in contact with the transparent dielectric layer. A transparent conductive film is provided.

In the transparent conductive laminated film of the present invention, the transparent dielectric layer that is in contact with the transparent conductive film is a ruthenium oxide layer. The film thickness of the ruthenium oxide layer is preferably 2 nm or more and 60 nm or less. The transparent conductive film is a laminated film which has, in order from the side of the transparent film substrate, a first transparent conductive film composed of an indium tin oxide layer having a tin oxide content of 1% by weight or more and less than 6% by weight; The tin oxide contains a second transparent conductive film composed of an indium tin oxide layer in a proportion of 6 wt% or more and 20 wt% or less.

The film thickness d ₁ of the first transparent conductive film and the film thickness d _{2 of the} second transparent conductive film are sufficient to be in the relationship of (1) to (3).

(1) d ₁ = 1 to 9 nm; (2) d ₁ + d ₂ = 15 to 37 nm; (3) 2d ₁ < d ₂

In one embodiment of the transparent conductive laminated film of the present invention, the transparent conductive film is an amorphous film having a crystallinity of 30% or less. The amorphous film preferably has an average of 90 or more crystal grains of 1 um ² . Further, when the amorphous film is heated at 150 ° C, the resistivity is preferably 3.7 × 10 ^-4 Ωcm or less within 2 hours.

In one embodiment of the transparent conductive laminated film of the present invention, the first transparent conductive film and the second transparent conductive film are both crystalline. The crystalline transparent conductive film preferably has a resistivity of 3.7 × 10 ^-4 Ωcm or less.

The method for producing a transparent conductive laminated film of the present invention comprises: forming a transparent dielectric layer on a transparent film substrate (transparent dielectric layer forming process); and sequentially forming a first transparent layer on the transparent dielectric layer a conductive film and a second transparent conductive film (transparent conductive film forming process); the first transparent conductive film is composed of an indium tin oxide layer having a tin oxide content of 1% by weight or more and less than 6% by weight, the second The transparent conductive film is composed of an indium tin oxide layer having a tin oxide content of 6 wt% or more and 20 wt% or less.

In the transparent dielectric layer formation process, the hafnium oxide layer is preferably formed by sputtering. In the transparent conductive film forming process, a first transparent conductive film is directly formed on the ruthenium oxide layer, and a second transparent conductive film is formed thereon. The first transparent conductive film and the second transparent conductive film are preferably formed by sputtering.

In one aspect of the production method of the present invention, there is another process (crystallization process) of crystallizing the transparent conductive film by heat treatment after the transparent conductive film formation process.

According to the present invention, a transparent conductive laminated film having a small resistivity and uniform in-plane resistance can be provided by heat treatment for a short period of time. Transparent of the invention The conductive laminated film is suitable for use in an electrode for a touch panel of an electrostatic capacitance type.

10‧‧‧Transparent film substrate

21‧‧‧Transparent dielectric layer (yttria layer)

22‧‧‧First transparent conductive film

23‧‧‧Second transparent conductive film

24‧‧‧Laminated transparent conductive film

100‧‧‧Transparent conductive laminated film

Fig. 1 is a schematic cross-sectional view showing a transparent conductive laminated film (transparent conductive film) according to an embodiment of the present invention.

Fig. 2 shows an SEM observation image of a transparent conductive laminate obtained by etching an amorphous component.

1 is a schematic cross-sectional view showing a transparent conductive laminated film 100 having a transparent dielectric layer 21 on a transparent film substrate 10; and a first transparent conductive film 22 and a second transparent conductive film The transparent conductive film 24 is laminated on the film 23. Hereinafter, an embodiment of a transparent conductive laminated film will be described with reference to the drawings, and a transparent sputtering substrate is used to form a transparent film substrate 10 by a roll-to-roll method. The dielectric layer 21, the first transparent conductive film 22, and the second transparent conductive film 23 will be described as a center.

<Transparent film substrate>

The transparent film substrate 10 is preferably one which is colorless and transparent at least in the visible light region. The material of the transparent film substrate may be a polyester resin such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT) or polyethylene naphthalate (PEN). An olefin resin, a polycarbonate resin, a polyimide resin, a cellulose resin, or the like. The thickness of the transparent film substrate 10 is not particularly limited, and is preferably 10 um to 400 um, more preferably 25 um to 200 um. The thickness of the transparent film substrate 10 is in the above range, and it can have durability and moderate flexibility. Therefore, it is possible to use a roll-to-roll sputtering apparatus by means of a roll-to-roll film transport method on a transparent film substrate. The transparent dielectric layer 21 and the transparent conductive film 24 are formed with higher production efficiency. The transparent film substrate 10 can form a functional layer (not shown) such as a hard coat layer on one or both sides.

In order to improve the adhesion, a surface treatment such as plasma treatment or corona discharge, flame, ultraviolet irradiation, and electron beam irradiation roughening may be performed on the transparent polymer film substrate in advance.

<dielectric layer>

At least one transparent dielectric layer 21 is formed on the transparent film substrate 10. The transparent dielectric layer functions as a gas barrier layer for suppressing volatilization of moisture or organic substances from the transparent film substrate 10 or to reduce plasma damage to the transparent film substrate when the transparent conductive film 24 is formed thereon. Protective layer.

As the material of the transparent dielectric layer 21, an organic resin material such as a polymer, an inorganic material such as a metal oxide, an organic-inorganic hybrid material, or the like can be used. The oxide is preferably colorless and transparent in the visible light region, and has a resistivity of 10 Ω ‧ cm or more. For example, a metal such as Si, Ge, Sn, Al, Ga, In, V, Nb, Ta, Ti, Zr, Zn, Hf or an oxide of a semimetal is preferably used.

The transparent dielectric layer 21 may be composed of only one layer or a plurality of layers. In the present invention, in the transparent dielectric layer 21, the dielectric layer that is in contact with the transparent conductive film 24 is a ruthenium oxide layer. The ruthenium oxide layer may be composed only of ruthenium oxide or may contain dopants or the like. The total of the content of the oxygen atom and the ruthenium atom in the ruthenium oxide layer is preferably 80% by weight or more, more preferably 90% by weight or more, still more preferably 95% by weight or more.

When the outermost layer of the transparent dielectric layer is yttrium oxide, it functions as a bottom layer of the film which is formed as the transparent conductive film 24 formed thereon, and promotes the transparent conductive film 24 to be uniformly crystallized in a short time, and the transparent conductive after crystallization. Membrane There is a tendency to reduce resistance. In addition, the ruthenium oxide layer also serves to enhance the high temperature and high humidity reliability of the transparent conductive film.

The method of forming the transparent dielectric layer 21 on the transparent film substrate 10 is not particularly limited as long as a uniform film can be formed. The production method may be a dry coating method such as a sputtering method, a vapor deposition method, or various CVD methods, or a wet coating method such as a spin coating method, a roll coating method, spray coating, or dip coating. In view of the ease of formation of the nano-scale film, among the above, the ruthenium oxide layer which is in contact with the transparent conductive film 24 is preferably formed by a dry coating method. In particular, the sputtering method is preferred from the viewpoint of controlling the film thickness in units of nanometers and adjusting the hardness or optical characteristics. Further, from the viewpoint of shortening or lowering the crystallization time of the transparent conductive film 24 formed on the ruthenium oxide, the ruthenium oxide layer is preferably formed by a dry coating method using a sputtering method. Compared with the wet coating manufacturer, the yttrium oxide layer produced by the dry coating method has a low impurity concentration such as moisture in the film, and impurities can be suppressed from being mixed into the transparent conductive film formed thereon, contributing to low resistance. And the shortening of the crystallization time.

When a dielectric layer that is in contact with the transparent conductive film is formed by a sputtering method, germanium, cerium oxide, tantalum carbide or the like can be used as the target. The power supply can use DC, RF, MF power, and the like. The MF power supply is better from the viewpoint of productivity. The power density at the time of film formation can be adjusted without causing excessive heat to the transparent film substrate and without impairing the productivity. The appropriate value of the power density may be affected by the shape or size of the cathode such as a flat plate type or a cylindrical type, and the flat type cathode is preferably about 0.5 W/cm ² to 10 W/cm ² , more preferably 0.7 W/cm ² ~ 4 W/cm ² , more preferably 1 W/cm ² to 3 W/cm ² . In particular, when the ruthenium oxide layer is formed at a low power density of 3 W/cm ² or less, the transparent conductive film formed thereon is likely to have a low resistance.

The sputtering film formation is carried out by introducing a carrier gas containing an inert gas such as argon or nitrogen and an oxygen gas into the film forming chamber. The introduction gas is preferably a mixed gas of argon and oxygen.

The pressure (total pressure) in the film forming chamber at the time of film formation of the dielectric layer is preferably 5.0 × 10 ^-3 Pa to 4.0 × 10 ^-1 Pa, more preferably 1.0 × 10 ^-2 Pa to 1.0 × 10 ^-1 Pa. When the film formation pressure of the dielectric layer is too high, the surface roughness of the transparent conductive film formed thereon is increased by the change in the morphology (fine structure), and the resistivity tends to increase.

The substrate temperature at the time of film formation of the cerium oxide layer may be within the range of heat resistance of the transparent film substrate, and is preferably, for example, 60 ° C or lower. The substrate temperature is preferably from -20 ° C to 40 ° C, and more preferably from -10 ° C to 20 ° C. By setting the substrate temperature to the above range, embrittlement or dimensional change of the transparent film substrate can be suppressed, so that a favorable film can be formed.

The film thickness of the ruthenium oxide layer is preferably from 2 to 60 nm, more preferably from 10 to 50 nm, even more preferably from 20 to 40 nm. By setting the film thickness of the ruthenium oxide layer directly under the transparent conductive film to 2 nm or more, the underlayer effect at the time of film formation of the transparent conductive film can be exhibited, and the crystallization time of the transparent conductive film can be shortened and the resistance can be reduced. By increasing the film thickness of the ruthenium oxide layer, the barrier function of the exhaust gas from the film substrate at the time of film formation of the transparent conductive film can be improved, which contributes to shortening of the crystallization time and reduction in resistance. Further, when the film thickness of the ruthenium oxide layer is too large, the multiple reflection of the interface reflection causes the reflection of visible light to become large, which may cause a decrease in the visibility.

<Transparent Conductive Film>

The transparent conductive film 24 is formed on the transparent dielectric layer 21 whose outermost layer is yttrium oxide. The transparent conductive film 24 is composed of at least two layers. The first transparent conductive film 22 that is in contact with the transparent dielectric layer 21 is composed of a tin oxide containing ratio of SnO ₂ /(SnO ₂ +In ₂ O ₃ ) of 1% by weight or more and less than 6% by weight. Composition. The content of tin oxide in the first transparent conductive film is preferably 2% by weight or more and less than 6% by weight, more preferably 3 to 5% by weight. The second transparent conductive film 23 formed on the first transparent conductive film 22 is an indium tin oxide layer having a tin oxide content ratio of SnO ₂ /(SnO ₂ +In ₂ O ₃ ) of 6 wt% or more and 20 wt% or less. Composition. The content of tin oxide in the second transparent conductive film is preferably from 10 to 15% by weight.

The transparent dielectric layer 21 connected to the transparent conductive film is a ruthenium oxide layer, and when the SnO ₂ content of the first and second transparent conductive films is in the above range, heat treatment at a low temperature for a short time can be achieved, and crystallization can be obtained. A transparent conductive layered body having a small resistivity and a good in-plane uniformity of the resistance value.

When the content ratio of SnO _{2 in} the first transparent conductive film is less than 2% by weight, the reliability in a high-temperature and high-humidity environment tends to decrease, and when the content ratio of SnO _{2 in} the second transparent conductive film is less than 6% by weight, the crystal is formed. The resistivity tends to become higher. Further, when the content ratio of SnO ₂ of the first transparent conductive film is 6% by weight or more, or when the content ratio of SnO ₂ of the second transparent conductive film is more than 20% by weight, crystallization requires a long time, or the surface of the resistance value There is a tendency for the internal homogeneity to decrease (the error becomes larger).

When it is desired to crystallize in a short time and to form a laminated conductive film having a low electrical resistance, the film thicknesses of the first and second transparent conductive films need to be in a specific range. The film thickness d ₁ of the first transparent conductive film is 1 to 9 nm, preferably 3 to 7 nm. The total thickness d ₁ + d ₂ of the film thickness d ₁ of the first transparent conductive film and the film thickness d ₂ of the second transparent conductive film is 15 to 37 nm, preferably 17 to 33 nm, more preferably 19 to 30 nm. When the total thickness of the transparent conductive film is small, the crystallization time becomes long and the electric resistance coefficient tends to increase. Further, when the surface resistance of the transparent conductive film is to be reduced, the total thickness of the transparent conductive film must be set to 15 nm or more. When the total film thickness is increased, the light absorption by the transparent conductive film is increased.

The film thickness d ₂ of the second transparent conductive film is greater than twice the film thickness d ₁ of the first transparent conductive film, that is, 2d ₁ <d ₂ . The film thickness d ₂ of the second transparent conductive film is preferably 2.5 times or more the film thickness d ₁ of the first transparent conductive film, more preferably 3 times or more, and even more preferably 3.5 times or more. Further, when the ratio of the film thickness of the first transparent conductive film having a small content of tin oxide is small, crystallization is difficult to proceed, and the in-plane distribution of the electric resistance tends to increase. Therefore, the film thickness d _{2 of} the second transparent conductive film is preferably 15 times or less the film thickness d ₁ of the first transparent conductive film, more preferably 10 times or less, and still more preferably 6 times or less.

When the film thickness d ₁ of the first transparent conductive film having a small tin oxide content ratio is relatively small, the film thickness d ₂ of the second transparent conductive film having a large tin oxide content ratio is relatively large, and the film thickness can be raised. The carrier concentration is low resistance. Further, in the first transparent conductive film 22 that is in contact with the ruthenium oxide layer, crystallization tends to proceed from the ruthenium oxide layer side. Therefore, when the film thickness d _{1 is} set to be smaller than 9 nm, The crystallization of the second transparent conductive film 23 is promoted, and crystallization can be achieved in a short time. In addition, by setting the total film thickness d ₁ +d ₂ to 15 nm or more, the surface resistance can be reduced, and by setting d ₁ +d ₂ to 37 nm or less, absorption of visible light can be suppressed, and transparent conductive layering with high transmittance can be obtained. membrane.

Further, in the above-mentioned Patent Document 3 (JP-A-2006-244771), when the film thickness of the transparent conductive film on the film substrate side is less than 10 nm, the high-temperature and high-humidity reliability is lowered. In contrast, in the present invention, and the first transparent guide The ruthenium oxide layer of the transparent dielectric layer 21 to which the electric film 22 is connected functions as the bottom layer of the first transparent conductive film 22, so that high temperature and high humidity reliability is also estimated, and uniformity can be obtained in a short time. A crystallized transparent conductive laminate.

In the above-mentioned Patent Document 4 (JP-A-2012-114070), it is considered that the transparent conductive film closest to the film substrate is hardly crystallized by the influence of the gas generated by the film substrate, and is located farthest from the film substrate. The (most surface side) is provided with tin oxide containing a small proportion of ITO. On the other hand, in the present invention, the ruthenium oxide layer of the transparent dielectric layer 21 which is in contact with the first transparent conductive film 22 functions as a barrier layer for generating a gas to the substrate, and also exhibits crystallization. Promote the role of the layer. Therefore, by reducing the tin oxide content ratio of the first transparent conductive film 22 that is in contact with the ruthenium oxide layer, it is possible to achieve a reduction in crystallization time and achieve further reduction in resistance.

In fact, a transparent conductive laminated film which was deposited as a transparent conductive film was observed by a scanning electron microscope (SEM), and as a result, it was confirmed that a cerium oxide layer was formed in comparison with ITO having a large proportion of tin oxide on cerium oxide. When a tin oxide is produced with a small proportion of ITO, a large number of crystal grains can be produced. Further, when the cross section of the transparent conductive laminated film was observed, it was confirmed that a large number of crystal grains appeared in the vicinity of the interface of the ruthenium oxide layer, and it was also presumed that crystallization can be promoted by making ITO having a small proportion of tin oxide on the ruthenium oxide layer. Governing. Further, it can be presumed that the in-plane uniformity of the electric resistance of the transparent conductive film after crystallization can be improved because a large number of crystal grains exist in the surface at the stage after film formation.

The transparent conductive film 24 is an amorphous film after film formation, and the crystallization ratio (area ratio of crystal grains occupied) is 30% or less. The amorphous transparent conductive film can be crystallized by heating. In the transparent conductive film after film formation, the number of crystal grains of 1 um ² average is preferably 90 or more, more preferably 100 or more, still more preferably 110 or more. The more the transparent conductive film after film formation contains a large number of crystal grains, the shorter the time required for crystallization. However, when the transparent conductive film after film formation contains a large number of crystal grains, it takes a long time to crystallize if the ruthenium oxide layer is not present. As described above, by using sputtering to form ITO having a small tin oxide content, the number of crystal grains can be increased. In the present invention, by forming the ITO layer having a small tin oxide content as the first transparent conductive film 22 on the side of the transparent film substrate 10, a large number of crystal grains are present after the film formation, because the transparent dielectric layer 21 The action of the ruthenium oxide layer promotes crystallization, and as a result, it is possible to simultaneously satisfy the in-plane uniformity of crystallization, low resistance, and resistance value in a short period of time.

The transparent conductive film 24 preferably has a resistivity after crystallization of 3.7 × 10 ^-4 Ω ‧ cm or less. The crystallization of the transparent conductive film will be described later in detail.

The first transparent conductive film 22 and the second transparent conductive film 23 are preferably produced by sputtering. When the film formation is performed by the roll-type sputtering apparatus, the first transparent conductive film 22 and the second transparent conductive film 23 can be continuously formed. On the transparent film substrate 10, the transparent dielectric layer 21, the first transparent conductive film 22, and the second transparent conductive film 23 can be continuously formed. Further, another conductive film or the like can be further formed on the second transparent conductive film.

The substrate temperature or power density at the time of film formation of the transparent conductive film is not particularly limited. For example, the production of the transparent dielectric layer may be in the range of the above substrate temperature or power density. The gas to be introduced at the time of film formation of the first transparent conductive film and the second transparent conductive film is preferably a mixed gas of argon and oxygen. The oxygen introduction amount in the film forming chamber is preferably from 0.1% by volume to 2.0% by volume, more preferably from 0.4% by volume to 1.5% by volume, based on the total amount of introduced gas. The pressure (full pressure) in the film forming chamber at the time of film formation of the transparent conductive film is preferably 0.1 Pa to 1.0 Pa, more preferably 0.2 Pa to 0.8 Pa. Further, the oxygen partial pressure in the film forming chamber is preferably from 1 × 10 ^-3 Pa to 2 × 10 ^-1 Pa, more preferably from 3 × 10 ^-3 Pa to 1 × 10 ^-2 Pa. By setting the film forming pressure and the amount of the introduced gas in the above range, the transparency and conductivity of the transparent conductive film can be improved. The introduction gas may contain a gas other than oxygen or argon within a range not impairing the function of the present invention.

<Crystalization of Transparent Conductive Film>

A transparent conductive film made of a metal oxide such as ITO is usually amorphous after being formed by sputtering. When the transparent conductive laminated film of the present invention is used as a touch panel, it is preferable to crystallize the transparent conductive film for the purpose of improving transmittance or reducing resistance. The crystallization is performed by heating the transparent conductive film 24 formed on the transparent film substrate 10 via the transparent dielectric layer 21.

The heat treatment temperature is a range in which the film substrate has heat resistance, and is generally less than 200 °C. When the transparent conductive laminated film of the present invention is heat-treated at 150 ° C, it can be a good crystal film in a short time of 2 hours.

The resistivity of the transparent conductive film 24 after crystallization is preferably 3.7 × 10 ^-4 Ω ‧ cm or less, more preferably 3.2 × 10 ^-4 Ω ‧ cm or less, and even more preferably 3.0 × 10 ^-4 Ω ‧ Below cm, 2.8 × 10 ^-4 Ω ‧ cm or less is particularly good. The lower the resistivity, the better, but it is usually 2.0 Ω ‧ cm or more. The surface resistance of the transparent conductive film 24 after crystallization is preferably 200 Ω/□ or less, more preferably 150 Ω/□ or less, still more preferably 120 Ω/□ or less, and particularly preferably 100 Ω/□ or less. When the resistivity and surface resistance of the transparent conductive film are in the above range, the transparent conductive laminated film can also achieve a high response speed when used as a transparent electrode for a large-area electrostatic capacitance type touch panel.

[Examples]

The invention will be more specifically described below based on examples, but the invention is not limited to the examples.

[Measurement method] <film thickness>

The film thickness of each layer was measured by Spectroscopic Ellipsometry and adjusted by the Cauchy model and the Tauc-Lorentz model.

<surface resistance and resistivity>

The surface resistance was measured by a four-probe crimp measurement using a low resistivity meter Loresta-GP (MCP-T710, manufactured by Mitsubishi Chemical Corporation). The resistivity is calculated from the product of the value of the surface resistance and the film thickness of the transparent conductive film. Further, it is known that the resistivity of the transparent conductive film changes depending on the temperature. Therefore, for the crystallization sample, the crystallization finished sample was taken out from the oven, and after cooling to room temperature, the above measurement was performed.

<Number of crystal grains and crystallization rate>

The transparent conductive laminate before crystallization was immersed in 1.7% hydrochloric acid for 90 seconds, and the amorphous component was completely etched, followed by running water washing. The surface of the sample was observed at a magnification of 100,000 times using a scanning electron microscope (SEM), and the number of clearly visible dots was set as the number of crystal grains in the field of view of 1 μm × 1 μm. Further, the SEM image is subjected to image processing to be black-and-white binarized, and the area ratio of the clearly visible portion (white portion) is set to the crystallization ratio.

<In-Plane Resistance Distribution>

The transparent conductive laminate was cut into an A3 size, and was taken out in an oven at 150 ° C for a specific period of time, and then taken out, and the longitudinal direction was equally divided into 7, and the short side direction was equally divided into 5, and cut into a total of 35 samples. The device measures the surface resistance of each sample. From the average of the surface resistance of each sample and the surface resistance of 35 samples, the resistivity of the sample - the average resistivity | ÷ average resistivity × 100, and the maximum value was defined as the in-plane resistance distribution.

<resistance change rate>

The transparent conductive laminate was placed in an oven at 150 ° C for 120 minutes to crystallize the ITO. After the surface resistance measurement, it was allowed to stand at 85 ° C for 85% in an environment of 85 ° C. After cooling to room temperature, the surface resistance was measured, and the surface resistance (R) after the test was determined for the surface resistance before the test (R ₀ The rate of change of R/R ₀ .

[Example 1] (film formation of dielectric layer)

The transparent film substrate was used for a biaxially stretched PET film having a thickness of 125 μm including a hard coat layer made of a urethane resin on both sides. On one side of the PET film, a boron-doped ruthenium target was used, and a mixed gas of oxygen (flow rate: 3.0 sccm) and argon (flow rate: 20.0 sccm) was introduced into the apparatus, and the pressure in the film forming chamber was 5.0×. A dielectric layer composed of yttrium oxide was formed by sputtering under the conditions of 10 ^-2 Pa and power density: 1.5 W/cm ² . The film thickness of the obtained dielectric layer was 25 nm.

(film formation of the first transparent conductive film)

On the transparent dielectric layer, an indium tin oxide (ITO) film containing tin oxide in a proportion of 5% by weight was formed as the first transparent conductive film layer. The target was sintered using a mixture of indium acid and tin oxide (tin oxide content: 5% by weight), and a mixed gas of oxygen (flow rate: 3.0 sccm) and argon (flow rate: 500 sccm) was introduced into the apparatus, and pressure in the film forming chamber was: 0.4 Pa, power density: 0.8 W/cm ² was sputter-coated to form a film. The film thickness of the obtained transparent conductive film was 5 nm.

(film formation of the second transparent conductive film)

On the first transparent conductive film, an ITO film containing tin oxide in an amount of 10% by weight was formed as the second transparent conductive film layer. The target was sintered using a mixture of indium acid and tin oxide (tin oxide content: 10% by weight), and a mixed gas of oxygen (flow rate: 4.0 sccm) and argon (flow rate: 500 sccm) was introduced into the apparatus while the pressure in the film forming chamber was: 0.4 Pa, power density: 1.5 W/cm ² was sputter coated. The film thickness of the obtained transparent conductive film was 25 nm.

[Examples 2 to 4]

In the same manner as in Example 1, except that the film thicknesses of the first transparent conductive film and the second transparent conductive film were changed to those shown in Table 1, a ruthenium oxide film and a two-layer transparent conductive film were formed on the biaxially stretched PET film. Transparent conductive laminated film.

[Comparative Example 1]

In Comparative Example 1, the arrangement of the first transparent conductive film (the content of the tin oxide is 10% by weight) and the second transparent conductive film (the content of the tin oxide is 5% by weight) are opposite to those of the first embodiment.

First, in the same manner as in Example 1, a ruthenium oxide film having a thickness of 25 nm was formed as a dielectric layer by sputtering on a biaxially stretched PET film. A target having a proportion of 10% by weight of tin oxide was used thereon, and an ITO transparent conductive film having a thickness of 25 nm was formed by sputtering, and a target having a tin oxide content of 5% by weight was used thereon by sputtering. An ITO transparent conductive film having a film thickness of 5 nm was formed.

[Comparative Example 2]

No dielectric layer was formed in Comparative Example 2. Specifically, the first transparent conductive film (the tin oxide content: 5% by weight, the film thickness: 25 nm) and the second transparent conductive film (the tin oxide content ratio of 10 parts by weight) are directly formed on the biaxially stretched PET film by sputtering. %, film thickness 5 nm).

[Comparative Example 3]

In Comparative Example 3, except that the film thicknesses of the first transparent conductive film and the second transparent conductive film were changed to those shown in Table 1, a dielectric layer was formed on the biaxially stretched PET film in the same manner as in Comparative Example 2. A transparent conductive laminated film comprising two transparent conductive films.

[Comparative Example 4]

In Comparative Example 4, only ITO transparent conductive film containing 10% by weight of tin oxide was formed on the dielectric layer. Specifically, on the biaxially stretched PET film, a hafnium oxide film having a thickness of 25 nm was formed as a dielectric layer by sputtering, and a target having a tin oxide content of 10% by weight was used thereon to form a film by sputtering. A transparent conductive film having a thickness of 30 nm.

[Comparative Example 5]

In Comparative Example 5, a transparent conductive laminated film was produced in the same manner as in Example 1 except that the film thickness of the first transparent conductive film was reduced. Specifically, a first transparent conductive film (10% by weight of tin oxide) having a film thickness of 0.5 nm is formed on the ruthenium oxide film by sputtering, and a film thickness of 29.5 nm is formed thereon by sputtering. Two transparent conductive films (tin oxide content of 5% by weight).

[Comparative Example 6]

Comparative Example 6 increases the film thickness of the first transparent conductive film. Specifically, a first transparent conductive film (10% by weight of tin oxide) having a film thickness of 8 nm is formed on the transparent dielectric layer by sputtering, and a film thickness of 10 nm is formed thereon by sputtering. A transparent conductive film (tin oxide contains 5% by weight).

〔evaluation result〕

The laminated structure of the transparent conductive laminated film of the above Examples and Comparative Examples, the SEM observation result after the film formation (the number of crystals and the crystallinity), and the measurement of the resistance value after heating at 150 ° C for 90 minutes or 120 minutes The results and the rate of change in resistance (R/R ₀ ) are shown in Table 1. Further, the SEM observation image of the transparent conductive laminate of each of the examples and the comparative examples after the etching of the amorphous component is as shown in Fig. 2 .

As is clear from Table 1, the resistivity of any of the comparative examples after heating at 150 ° C for 120 minutes was 3.8 Ω ‧ cm or more, whereas in Examples 1 to 4, it was 3.1 Ω ‧ cm or less, and the resistance value was in the surface The error is small.

Comparative Example of Forming Transparent Conductive Film Without Transmitting Transparent Dielectric Layer 2, 3, the resistance is greatly reduced after the heat and humidity resistance test. This is because, in addition to the low heat and humidity resistance of the transparent conductive film, crystallization is insufficient in the heat treatment at 150 ° C for 120 minutes. Further, as shown in the number of crystal grains in Table 1 and the SEM image in FIG. 2, in Comparative Examples 2 and 3, the number of crystal grains or the crystallinity after the production of the transparent conductive film was increased as compared with the other comparative examples. However, since the crystallization efficiency is small, the ruthenium oxide layer functions as a film underlayer of ITO to promote the formation of crystal grains, and also has an effect of promoting crystallization when heated and crystallized.

In Comparative Example 1 in which an ITO film having a large proportion of tin oxide was formed on the ruthenium oxide layer and an ITO film having a small tin oxide content was formed thereon, the resistivity was also increased after heating and crystallization at 150 ° C for 120 minutes.

In Comparative Example 5 in which the film thickness of the first transparent conductive film having a small tin oxide content was as small as 0.5 μm, the number of crystal grains after film formation was small, and the electric resistance after crystallization was also high. Further, in Comparative Example 6 in which the film thickness of the first transparent conductive film was 8 μm and d ₂ /d ₁ = 1.25, the number of crystal grains after film formation was large, but the resistivity of the transparent conductive film after crystallization became high. This is because the second transparent conductive film having a large proportion of tin oxide has a small film thickness and a low carrier density.

Compared with Example 2 in which d ₂ /d ₁ = 12.5, the in-plane error of the resistance value of Example 1 of d ₂ /d ₁ = 5 became small. Further, from the comparison between Comparative Example 2 and Comparative Example 3, it is also known that the in-plane error of the resistance value also becomes small when d ₂ /d ₁ is small. Compared with the other examples, in Example 4, where d ₂ /d ₁ =2.33, the resistivity after crystallization becomes high, and it is also known that the film thickness ratio of the transparent conductive film is low resistance and the in-plane error of the resistance value. It is important to reduce it. Further, in the first embodiment and the third embodiment, although the ratio of d ₁ to d ₂ is the same, the resistivity of the first embodiment is small, and the in-plane error of the resistance value is also small. This is because the total thickness d ₁ +d ₂ of the transparent conductive film of Example 1 is large. As described above, by setting the ratio of the film thicknesses of the first transparent conductive film to the second transparent conductive film and the total film thickness to a specific range, it is possible to obtain a transparent conductive laminated film having low electric resistance and small in-plane error of electric resistance. .

10‧‧‧Transparent film substrate

21‧‧‧Transparent dielectric layer (yttria layer)

22‧‧‧First transparent conductive film

23‧‧‧Second transparent conductive film

24‧‧‧Laminated transparent conductive film

100‧‧‧Transparent conductive laminated film

Claims (10)

A transparent conductive laminated film comprising at least one transparent dielectric layer on at least one side of a transparent film substrate, and a transparent conductive film provided in contact with the transparent dielectric layer; and the transparent conductive film The transparent dielectric layer that is in contact with each other is a ruthenium oxide layer, and the transparent conductive film is a laminated film which is sequentially provided from the side of the transparent film substrate: the content of the tin oxide is 1% by weight or more and less than 6% by weight. a first transparent conductive film made of an indium tin oxide layer; and a second transparent conductive film made of an indium tin oxide layer having a tin oxide content of 6 wt% or more and 20 wt% or less; a film thickness of the first transparent conductive film The film thickness d _{2 of} d ₁ and the second transparent conductive film satisfies the following relationship (1) to (3): (1) d ₁ = 1 to 9 nm; (2) d ₁ + d ₂ = 15 to 37 nm; (3) 2d ₁ <d ₂ The resistivity after crystallization of the above transparent conductive film is 3.7 × 10 ^-4 Ω ‧ cm or less. The transparent conductive laminated film according to claim 1, wherein the ruthenium oxide layer has a film thickness of 2 nm or more and 60 nm or less. The transparent conductive laminated film according to claim 1 or 2, wherein the transparent conductive film is an amorphous film having a crystallinity of 30% or less, and has an average of 90 or more crystal grains per 1 um ² . The transparent conductive laminated film according to claim 1 or 2, wherein the transparent conductive film is an amorphous film having a crystallinity of 30% or less, and when heated at 150 ° C, the resistivity within 2 hours is 3.7 × 10 ^-4 Ω‧cm or less. The transparent conductive laminated film according to claim 1 or 2, wherein the first transparent conductive film and the second transparent conductive film are both crystalline. A method for producing a transparent conductive laminated film, which is a method for producing a transparent conductive laminated film, which is provided on at least one side of a transparent film substrate, and sequentially includes at least one transparent dielectric layer. And a transparent conductive film provided in contact with the transparent dielectric layer; the transparent dielectric layer forming a transparent dielectric layer on the transparent film substrate; and sequentially forming on the transparent dielectric layer Forming a transparent conductive film of the first transparent conductive film and the second transparent conductive film, the first transparent conductive film being composed of an indium tin oxide layer having a tin oxide content of 1% by weight or more and less than 6% by weight, the second The transparent conductive film is composed of an indium tin oxide layer having a tin oxide content of 6 wt% or more and 20 wt% or less; the transparent dielectric layer in contact with the transparent conductive film is a hafnium oxide layer; and the transparent conductive film In the forming process, the first transparent conductive film is directly formed on the yttrium oxide layer by a film thickness d _{1 of} 1 to 9 nm, and the second transparent conductive film is formed thereon by a film thickness d _{2 which is} twice larger than d ₁ Film; the first transparent conductive film The total thickness d ₁ +d ₂ of the film thickness d ₁ and the film thickness d2 of the second transparent conductive film is 15 to 37 nm. The method for producing a transparent conductive laminated film according to claim 6, wherein the ruthenium oxide layer is formed by a sputtering method in the transparent dielectric layer forming process. The method for producing a transparent conductive laminated film according to claim 6 or 7, wherein the first transparent conductive film and the second transparent conductive film are formed by sputtering. The method for producing a transparent conductive laminated film according to claim 6 or 7, further comprising: a crystallization process for crystallizing the transparent conductive film by heat treatment after the transparent conductive film forming process. The method for producing a transparent conductive laminated film according to claim 9, wherein the transparent conductive film after the crystallization process has a resistivity of 3.7 × 10 ^-4 Ω‧ cm or less.