JPWO2014157312A1 - Transparent conductive laminated film and method for producing the same - Google Patents

Abstract

The transparent conductive laminate film (100) includes a transparent dielectric layer (21) and a transparent conductive film (24) provided on and in contact with the transparent dielectric layer (21) on at least one surface of the film substrate (10). ) In this order. The transparent dielectric layer (21) in contact with the transparent conductive film (24) is a silicon oxide layer. The transparent conductive film (24) includes, in order from the transparent film substrate (10) side, a first transparent conductive film (22) composed of an indium tin oxide layer having a tin oxide content of 1 wt% or more and less than 6 wt%. A laminated film having a second transparent conductive film (23) composed of an indium tin oxide layer having a tin oxide content of 6 wt% or more and 20 wt% or less. 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 relationships (1) to (3): (1) d1 = 1 to 9 nm; (2) d1 + d2 = 15-37 nm; (3) 2d1 <d2.

Description

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

  A transparent conductive film in which a conductive oxide thin film such as indium tin oxide (ITO) is formed on a transparent film is widely used as a transparent electrode for displays, light emitting elements, photoelectric conversion elements and the like. Such a transparent conductive film is manufactured, for example, by forming a conductive oxide thin film layer on a transparent film substrate by a dry process such as a sputtering method. The conductive oxide thin film that constitutes the transparent electrode is required to have a reliability of resistivity in a high temperature and high humidity environment. In order to meet such required characteristics, the transparent conductive film is often used by crystallizing a conductive oxide.

  For the purpose of improving the quality of the transparent conductive film, it has been proposed that the transparent conductive film provided on the film substrate has a laminated structure. For example, Patent Document 1 discloses that a first transparent conductive film having crystal grains having a small particle diameter on a film substrate and a second transparent conductive film having crystal grains having a larger particle diameter than the first transparent conductive film. A technique for improving pen pressure durability and curling characteristics while maintaining transparency by forming a film is described.

Patent Document 2 discloses a first transparent conductive film made of indium tin oxide having a small tin oxide (SnO ₂ ) content (SnO ₂ : 3 to 8% by weight) on a film substrate, and a SnO ₂ content. A technique is described in which a large (SnO ₂ : 10 to 30 wt%) second transparent conductive film made of indium tin oxide is provided to improve transparency and reduce resistance.

Patent Document 3 discloses a first transparent conductive film made of indium tin oxide having a small SnO ₂ content (SnO ₂ : 2 to 6% by weight) on a film substrate and a large SnO ₂ content (SnO _2). : 6 to 20% by weight) By providing a second transparent conductive film made of indium tin oxide, and setting the film thickness ratio of both to a predetermined range, high temperature and high humidity reliability as a transparent conductive film for a touch panel is achieved. It describes that it is satisfactory and that crystallization is possible by low-temperature heat treatment.

  The transparent conductive films of Patent Documents 1 to 3 are mainly used for resistive touch panels. On the other hand, in recent years, capacitive touch panels capable of multi-touch input and gesture input are rapidly spreading and are used in smartphones, tablet computers, notebook computers, and the like. In the capacitive touch panel, the transparent electrode layer is required to have a low resistance in order to increase the sensitivity and response speed of the sensor.

  Moreover, in the manufacturing process of a transparent conductive film, it is calculated | required to crystallize a conductive oxide in a short time. As a crystallization method, a method of heating after forming an amorphous conductive oxide thin film on a film substrate is generally used. In the transparent conductive film using a resin film base material, it is difficult to heat to high temperature (for example, 200 degreeC or more) from a heat resistant viewpoint of a film base material. Therefore, it is necessary to perform crystallization by heating at a relatively low temperature, and the crystallization time tends to be long.

Patent Document 4 discloses that a transparent conductive film having a laminated structure can achieve both low resistance and crystallization in a short time. Specifically, a configuration in which an ITO layer having a small SnO ₂ content is provided on the surface side of the transparent conductive film (side away from the film substrate) and an ITO layer having a large SnO ₂ content is provided on the substrate side. It is disclosed. According to this configuration, by providing an ITO layer with a small SnO ₂ content on the surface side that is not easily affected by the gas generated from the film substrate, the formation of crystal nuclei is promoted and the crystallization time is shortened. The estimation principle is described that resistance is increased because the carrier is increased by increasing the film thickness of the ITO layer on the substrate side having a large SnO ₂ content.

JP 2003-263925 A Japanese Patent Laid-Open No. 10-49306 JP 2006-244771 A JP 2012-1114070 A

  Patent Document 3 describes that a transparent conductive film having a laminated structure is effective in reducing crystallization time in addition to improving transparency and reliability in a high temperature and high humidity environment. . However, Patent Document 3 relates to a transparent conductive film mainly used for a resistive film type touch panel, and the surface resistance is as high as about 300Ω / □, and it is not possible to achieve both low resistance and shortening of crystallization time. .

  Patent Document 4 describes that a transparent conductive film having a laminated structure can achieve both a reduction in resistance and a reduction in crystallization time. However, with an increase in screen size (increase in area) of a device on which a touch panel is mounted, further reduction in resistance of the transparent conductive film is required for improving response speed. In addition, as the area increases, the uniformity of the in-plane resistivity is also required.

  In view of such problems, the present invention maintains the transparency of the transparent conductive film and the reliability in a high-temperature and high-humidity environment, while shortening the crystallization time, further reducing the resistance, and uniformity of the in-plane resistivity. It aims at providing the transparent conductive film which can implement | achieve improvement.

  In order to solve the above problems, the inventors have intensively studied, and as a result, on the transparent film substrate, an indium tin oxide layer having a small tin oxide content and an indium oxide having a large tin oxide content are interposed via a silicon oxide layer. It is possible to crystallize a transparent conductive film in a short time by providing a tin layer and making these film thicknesses within a predetermined range, and furthermore, the resistivity after crystallization is low and the in-plane resistance is reduced. It was found that the uniformity of rate is also excellent.

  The present invention provides a transparent conductive laminated film comprising, in this order, at least one transparent dielectric layer on at least one surface of a transparent film substrate, and a transparent conductive film provided in contact with the transparent dielectric layer, and It relates to a manufacturing method.

  In the transparent conductive laminated film of the present invention, the transparent dielectric layer in contact with the transparent conductive film is a silicon oxide layer. The thickness of the silicon oxide layer is preferably 2 nm or more and 60 nm or less. The transparent conductive film includes, in order from the transparent film substrate side, a first transparent conductive film composed of an indium tin oxide layer having a tin oxide content of 1 wt% or more and less than 6 wt%, and a tin oxide content of 6 wt%. A laminated film having a second transparent conductive film composed of an indium tin oxide layer of 20 wt% or less.

And the thickness d ₁ of the first transparent conductive film thickness d ₂ of the second transparent conductive film satisfies a relation of the following (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, the transparent conductive laminated film of the present invention is an amorphous film having a crystallization rate of 30% or less. This amorphous film preferably has 90 or more crystal grains per 1 μm ² . The amorphous film preferably has a resistivity of 3.7 × 10 ⁻⁴ Ωcm or less within 2 hours when heated at 150 ° C.

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

  In the method for producing a transparent conductive laminated film of the present invention, the step of forming a transparent dielectric layer on a transparent film substrate (transparent dielectric layer forming step); and the content ratio of tin oxide on the transparent dielectric layer A first transparent conductive film comprising an indium tin oxide layer of 1 wt% or more and less than 6 wt%, and a second transparent conductive film comprising an indium tin oxide layer having a tin oxide content of 6 wt% or more and 20 wt% or less And a step of forming in this order (transparent conductive film forming step).

  In the transparent dielectric layer forming step, the silicon oxide layer is preferably formed by a sputtering method. In the transparent conductive film forming step, the first transparent conductive film is formed directly on the silicon oxide layer, and the second transparent conductive film is formed thereon. Both the first transparent conductive film and the second transparent conductive film are preferably formed by sputtering.

  In one form of the manufacturing method of this invention, it has further the process (crystallization process) in which a transparent conductive film is crystallized by heat processing after a transparent conductive film formation process.

  According to the present invention, there is provided a transparent conductive laminated film having a low resistivity and a uniform in-plane resistance by a short heat treatment. The transparent conductive laminated film of the present invention can be suitably used as an electrode for a capacitive touch panel.

It is a cross-sectional schematic diagram which shows the transparent conductive laminated film (transparent conductive film) which concerns on one Embodiment of this invention. It is a SEM observation image of the transparent conductive laminated body after etching an amorphous component.

  FIG. 1 shows a transparent conductive laminated film 100 having a transparent dielectric layer 21 and a laminated transparent conductive film 24 of a first transparent conductive film 22 and a second transparent conductive film 23 on a transparent film substrate 10. It is a schematic cross section. Hereinafter, with reference to the drawings, the transparent dielectric layer 21, the first transparent conductive film 22, and the second transparent conductive film 23 are rolled onto the transparent film substrate 10 using a winding type sputtering apparatus. -Embodiment of a transparent conductive laminated film is demonstrated centering on the method of forming into a film by a two-roll method.

<Transparent film substrate>
The transparent film substrate 10 is preferably transparent and colorless at least in the visible light region. Examples of the transparent film base material include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), cycloolefin resins, polycarbonate resins, polyimide resins, and cellulose resins. Is mentioned. Although the thickness of the transparent film base material 10 is not specifically limited, 10 micrometers-400 micrometers are preferable and 25 micrometers-200 micrometers are more preferable. If the thickness of the transparent film base material 10 is the said range, it may have durability and moderate softness | flexibility. Therefore, it is possible to form the transparent dielectric layer 21 and the transparent conductive film 24 on the transparent film substrate with high productivity by a roll-to-roll method using a winding type sputtering film forming apparatus. . The transparent film substrate 10 may have a functional layer (not shown) such as a hard coat layer formed on one side or both sides.

  In order to improve adhesion on the transparent polymer film substrate, the surface may be previously subjected to surface treatment such as plasma treatment, corona discharge, flame, ultraviolet ray irradiation, electron beam irradiation roughening or the like.

<Dielectric layer>
On the transparent film substrate 10, at least one transparent dielectric layer 21 is formed. The transparent dielectric layer reduces plasma damage to the gas barrier layer that suppresses volatilization of moisture and organic substances from the transparent film substrate 10 and the transparent film substrate when the transparent conductive film 24 is formed thereon. Can act as a protective layer.

  As a 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 is used. As the oxide, an oxide that is colorless and transparent in the visible light region and has a resistivity of 10 Ω · cm or more is preferable. For example, a metal or semi-metal oxide such as Si, Ge, Sn, Al, Ga, In, V, Nb, Ta, Ti, Zr, Zn, and Hf is preferably used.

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

  When the outermost surface layer of the transparent dielectric layer is silicon oxide, it acts as a base layer for film growth of the transparent conductive film 24 formed thereon, and crystallizes the transparent conductive film 24 uniformly in a short time. In addition, the transparent conductive film after crystallization tends to have a low resistance. The silicon oxide layer also has an effect of improving the high temperature and high humidity reliability of the transparent conductive film.

  The formation method of the transparent dielectric material layer 21 on the transparent film base material 10 will not be specifically limited if it is a method in which a uniform thin film is formed. Examples of the film forming method include dry coating methods such as sputtering ring method, vapor deposition method and various CVD methods, and wet coating methods such as spin coating method, roll coating method, spray coating and dipping coating. Among the above, the silicon oxide layer in contact with the transparent conductive film 24 is preferably formed using a dry coating method from the viewpoint of easily forming a nanometer-level thin film. In particular, the sputtering method is preferable from the viewpoint of controlling the film thickness in units of several nanometers and adjusting the hardness and optical characteristics. Further, from the viewpoint of shortening the crystallization time and lowering the resistance of the transparent conductive film 24 formed on the silicon oxide, the silicon oxide layer is preferably formed by a dry coating method, particularly a sputtering method. The silicon oxide layer formed by the dry coating method has a lower impurity concentration such as moisture in the film than that formed by the wet coating. It is considered that the suppression of the mixing of the element contributes to lowering the resistance and shortening the crystallization time.

When the dielectric layer in contact with the transparent conductive film is formed by sputtering, silicon, silicon oxide, silicon carbide, or the like can be used as the target. As the power source, a DC, RF, MF power source or the like can be used. From the viewpoint of productivity, an MF power source is preferable. The power density during film formation can be adjusted within a range that does not give excessive heat to the transparent film substrate and does not impair productivity. Proper value of the power density is dependent on the cathode of the shape and size of such flat plate type or a cylindrical type, in the case of a flat type ^{cathode, 0.5W / cm 2 ~10W / cm} 2 of about preferably, 0. more preferably ^{7W / cm 2 ~4W / cm 2} , more preferably ^{1W / cm 2 ~3W / cm 2} . In particular, when the silicon oxide layer is formed at a low power density of 3 W / cm ² or less, the transparent conductive film formed thereon tends to have a low resistance.

  Sputtering is performed while a carrier gas containing an inert gas such as argon or nitrogen and an oxygen gas is introduced into the film forming chamber. The introduced gas is preferably a mixed gas of argon and oxygen.

The pressure (total pressure) in the film forming chamber at the time of forming the dielectric layer is preferably 5.0 × 10 ⁻³ Pa to 4.0 × 10 ⁻¹ Pa, and 1.0 × 10 ⁻² Pa to 1.0. × 10 ⁻¹ Pa is more preferable. When the film forming pressure of the dielectric layer is excessively high, the surface roughness of the transparent conductive film formed thereon increases due to a change in morphology (fine structure), and the resistivity tends to increase.

  The substrate temperature at the time of forming the silicon oxide layer may be in a range in which the transparent film substrate has heat resistance, and is preferably 60 ° C. or less, for example. The substrate temperature is more preferably −20 ° C. to 40 ° C., and further preferably −10 ° C. to 20 ° C. By setting the substrate temperature within the above range, embrittlement and dimensional change of the transparent film substrate are suppressed, so that a high-quality thin film can be formed.

  The thickness of the silicon oxide layer is preferably 2 to 60 nm, more preferably 10 to 50 nm, and still more preferably 20 to 40 nm. By setting the film thickness of the silicon oxide layer immediately below the transparent conductive film to 2 nm or more, the base effect at the time of forming the transparent conductive film is exhibited, and the crystallization time of the transparent conductive film is shortened and the resistance is reduced. In addition, increasing the film thickness of the silicon oxide layer increases the barrier function of outgas from the film substrate when forming a transparent conductive film, which also contributes to shortening the crystallization time and reducing resistance. It is done. On the other hand, when the film thickness of the silicon oxide layer is excessively large, reflection of visible light due to multiple interference of interface reflection increases, and visibility may be reduced.

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

When the transparent dielectric layer 21 in contact with the transparent conductive film is a silicon oxide layer and the SnO ₂ content ratio of the first and second transparent conductive films is in the above range, crystallization by heat treatment at low temperature and short time is performed. It is possible to obtain a transparent conductive laminate having a low resistivity after crystallization and excellent in-plane uniformity of 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 the content ratio of SnO ₂ in the second transparent conductive film is 6 When the content is less than% by weight, the resistivity after crystallization tends to increase. Also, when the content ratio 6% by weight or more of SnO ₂ of and the first transparent conductive film, if the content of SnO ₂ in the second transparent conductive film is more than 20% by weight, a long time crystallization Or the in-plane uniformity of the resistance value tends to decrease (increase variation).

Further, in order to obtain a laminated transparent conductive film that can be crystallized in a short time and has a low resistance, it is necessary to set the film thicknesses of the first and second transparent conductive films within a predetermined range. The film thickness d1 of the _first transparent conductive film is ₁ to 9 nm, preferably 3 to 7 nm. The total 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, and more preferably. Is 19-30 nm. When the total film thickness of the transparent conductive film is small, the crystallization time tends to be long and the resistivity tends to increase. In order to reduce the surface resistance of the transparent conductive film, the total film thickness of the transparent conductive film needs to be 15 nm or more. On the other hand, when the total film thickness increases, light absorption by the transparent conductive film increases.

Thickness d ₂ of the second transparent conductive film is larger than twice the thickness d ₁ of the first transparent conductive film, that is, 2d 1 _{<d 2.} The film thickness d2 of the _second transparent conductive film is more preferably 2.5 times or more of the film thickness d1 of the _first transparent conductive film, more preferably 3 times or more, and 3.5 It is particularly preferable that the number is twice or more. On the other hand, when the film thickness ratio of the first transparent conductive film having a small tin oxide content ratio is small, crystallization hardly proceeds and the in-plane distribution of resistance tends to increase. Therefore, the film thickness d2 of the _second transparent conductive film is preferably 15 times or less, more preferably 10 times or less, and still more preferably 6 times or less the film thickness d1 of the _first transparent conductive film.

The film thickness d ₁ of the first transparent conductive film with a small tin oxide content ratio is relatively small, and the film thickness d ₂ of the second transparent conductive film with a large tin oxide content ratio is relatively large, The medium carrier concentration is increased and the resistance can be reduced. Further, the first transparent conductive film 22 in contact with the silicon oxide layer, since there is a tendency that crystallization proceeds from the silicon oxide layer side, by reducing the thickness d ₁ and 9nm or less, the second transparent conductive Crystallization of the film 23 is also promoted, and crystallization can be performed in a short time. Furthermore, 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 is suppressed, and high transmittance is achieved. A transparent conductive laminated film is obtained.

  In addition, in the above-mentioned patent document 3 (Unexamined-Japanese-Patent No. 2006-244771), when the film thickness of the transparent conductive film by the side of a film base material is less than 10 nm, it describes that high temperature, high humidity reliability falls. . On the other hand, in the present invention, the silicon oxide layer of the transparent dielectric layer 21 in contact with the first transparent conductive film 22 acts as a film formation base of the first transparent conductive film 22, thereby increasing the temperature and humidity. It is presumed that a transparent conductive laminate having excellent reliability and capable of uniform crystallization in a short time can be obtained.

  In the above-mentioned Patent Document 4 (Japanese Patent Application Laid-Open No. 2012-1114070), considering that the transparent conductive film close to the film base is difficult to crystallize due to the influence of the gas generated from the film base, it is farthest from the film base. ITO with a small tin oxide content ratio is provided at the position (outermost surface side). On the other hand, in the present invention, the silicon oxide layer of the transparent dielectric layer 21 in contact with the first transparent conductive film 22 functions as a barrier layer against the gas generated from the substrate and also functions as a crystallization promoting layer. I think that. Therefore, by reducing the tin oxide content ratio of the first transparent conductive film 22 in contact with the silicon oxide layer, the crystallization time can be shortened and the resistance can be further reduced.

  Actually, when a transparent conductive laminated film was deposited with a scanning electron microscope (SEM) as soon as the transparent conductive film was deposited, an ITO film with a small tin oxide content was formed on the silicon oxide layer. However, it has been confirmed that a larger number of crystal grains are generated than when ITO having a large tin oxide content is formed on silicon oxide. Moreover, when the cross section of the transparent conductive laminated film was observed, many crystal grains were observed near the interface with the silicon oxide layer, so that ITO having a small tin oxide content was formed on the silicon oxide layer. This is thought to promote crystallization. Further, it is considered that the in-plane uniformity of resistance of the transparent conductive film after crystallization is enhanced by the presence of a large number of crystal grains in the plane immediately after the film formation.

The transparent conductive film 24 is an amorphous film immediately after film formation, and the crystallization rate (area ratio occupied by crystal grains) is 30% or less. The amorphous transparent conductive film can be crystallized by heating. In the transparent conductive film immediately after film formation, the number of crystal grains per 1 μm ² is preferably 90 or more, more preferably 100 or more, and even more preferably 110 or more. As the transparent conductive film immediately after film formation contains more crystal grains, the time required for the crystallization time tends to be shorter. However, even when the transparent conductive film immediately after film formation contains a large number of crystal grains, if there is no silicon oxide layer, crystallization tends to take a long time. As described above, ITO having a small tin oxide content ratio is formed by sputtering, so that the number of crystal grains tends to increase. That is, in the present invention, an ITO layer having a small tin oxide content is formed as the first transparent conductive film 22 on the transparent film substrate 10 side, so that a large number of crystal grains are present immediately after film formation and transparent. By promoting the crystallization by the action of the silicon oxide layer of the dielectric layer 21, it is considered that short-time crystallization, low resistance, and in-plane uniformity of resistance value can be satisfied at the same 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 in detail later.

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

The substrate temperature and power density at the time of forming the transparent conductive film are not particularly limited, and may be, for example, the range of the substrate temperature and power density described above for the formation of the transparent dielectric layer. The gas introduced during the formation of the first transparent conductive film and the second transparent conductive film is preferably a mixed gas of argon and oxygen. The amount of oxygen introduced into the film forming chamber is preferably 0.1% by volume to 2.0% by volume, and more preferably 0.4% by volume to 1.5% by volume with respect to the total amount of introduced gas. The pressure (total pressure) in the film-forming chamber when forming the transparent conductive film is preferably 0.1 Pa to 1.0 Pa, and more preferably 0.2 Pa to 0.8 Pa. The oxygen partial pressure in the deposition chamber ^{is, 1 × 10 -3 Pa~2 × 10} -1 Pa , and more preferably ^{3 × 10 -3 Pa~1 × 10 -2} Pa. By setting the film forming pressure and the amount of introduced gas in the above ranges, the transparency and conductivity of the transparent conductive film can be improved. The introduced gas may contain a gas other than oxygen or argon as long as the function of the present invention is not impaired.

<Crystalization of transparent conductive film>
A transparent conductive film made of a metal oxide such as ITO is generally amorphous immediately after sputtering film formation. When the transparent conductive laminated film of the present invention is put to practical use such as formation of a touch panel, the transparent conductive film is preferably crystallized for the purpose of improving transmittance and reducing resistance. 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 set in a range in which the film substrate has heat resistance, and is generally less than 200 ° C. The transparent conductive laminated film of the present invention can be formed into a good crystal film in a short time within 2 hours when heat treatment is performed at 150 ° C.

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 3.0 × 10 ⁻⁴ Ω. More preferably, it is not more than cm, and particularly preferably not more than 2.8 × 10 ⁻⁴ Ω · cm. The lower the resistivity, the better, but generally it is 2.0 Ω · cm or more. The surface resistance of the transparent conductive film 24 after crystallization is preferably 200Ω / □ or less, more preferably 150Ω / □ or less, still more preferably 120Ω / □ or less, and particularly preferably 100Ω / □ or less. When the resistivity and surface resistance of the transparent conductive film are in the above ranges, a high response speed can be realized even when the transparent conductive laminated film is used as a transparent electrode for a large-area capacitive touch panel. .

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

[Measuring method]
<Film thickness>
The film thickness of each layer was determined by performing spectroscopic ellipsometry measurement and fitting using a cauchy model and a tauc-lorentz model.

<Surface resistance and resistivity>
The surface resistance was measured by four-probe pressure welding measurement using a low resistivity meter Loresta GP (MCP-T710, manufactured by Mitsubishi Chemical Corporation). The resistivity was calculated by the product of the value of the surface resistance and the film thickness of the transparent conductive film. In addition, it is known that the resistivity of a transparent conductive film changes with temperature. Therefore, for the sample after crystallization, the sample after crystallization was taken out of the oven and cooled to room temperature, and then 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 to completely etch the amorphous component, and then washed with running water. The surface of this sample was observed with a scanning electron microscope (SEM) at a magnification of 100,000, and the number of points that appeared bright in the range of 1 μm × 1 μm field of view was taken as the number of crystal grains. In addition, the SEM image was binarized by image processing, and the area ratio of the brightly visible part (white part) was defined as the crystallization ratio.

<In-plane resistance distribution>
Cut the transparent conductive laminate into A3 size, take out after heating for a predetermined time in an oven at 150 ° C, divide into 7 equal parts in the long side direction and 5 equal parts in the short side direction, cut into 35 samples in total, using the above equipment The surface resistance of each sample was measured. From the surface resistance of each sample and the average value of the surface resistances of 35 samples, | sample resistivity−average resistivity | ÷ average resistivity × 100 was obtained, and the maximum value was defined as the in-plane resistance distribution.

<Rate of change in resistance>
The transparent conductive laminate was heated in an oven at 150 ° C. for 120 minutes to crystallize ITO. The surface resistance after the measurement, allowed to stand for 500 hours under 85 ° C. 85% of the environment, again measuring the surface resistance after cooling to room temperature, the surface resistivity after the test with respect to the surface resistance before the test (R ₀₎ of (R) The rate of change R / R ₀ was determined.

[Example 1]
(Dielectric layer deposition)
As the transparent film substrate, a biaxially stretched PET film having a thickness of 125 μm and having hard coat layers made of urethane resin on both surfaces was used. Using a silicon target doped with boron on one surface of this PET film, a mixed gas of oxygen (flow rate: 3.0 sccm) and argon (flow rate: 20.0 sccm) is introduced into the apparatus while forming a film. Sputtering was performed under the conditions of room pressure: 5.0 × 10 ⁻² Pa and power density: 1.5 W / cm ² to form a dielectric layer made of silicon oxide. 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) thin film having a tin oxide content of 5% by weight was formed as the first transparent conductive film layer. Using a mixed sintered target of indium oxide and tin oxide (tin oxide content 5% by weight), a mixed gas of oxygen (flow rate: 3.0 sccm) and argon (flow rate: 500 sccm) is introduced into the apparatus while forming a film. Sputtering film formation was performed under conditions of room pressure: 0.4 Pa and power density: 0.8 W / cm ² . The film thickness of the obtained transparent conductive film was 5 nm.

(Formation of second transparent conductive film)
On the first transparent conductive film, an ITO thin film having a tin oxide content of 10% by weight was formed as a second transparent conductive film layer. Using a mixed sintered target of indium oxide and tin oxide (tin oxide content 10% by weight), a mixed gas of oxygen (flow rate: 4.0 sccm) and argon (flow rate: 500 sccm) is introduced into the apparatus while forming a film. Sputtering film formation was performed under conditions of indoor pressure: 0.4 Pa and power density: 1.5 W / cm ² . The film thickness of the obtained transparent conductive film was 25 nm.

[Examples 2 to 4]
A silicon oxide film and a biaxially stretched PET film were formed on the biaxially stretched PET film 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 as shown in Table 1. A transparent conductive laminated film provided with a two-layer transparent conductive film was produced.

[Comparative Example 1]
In Comparative Example 1, the arrangement of the first transparent conductive film (tin oxide content 10% by weight) and the second transparent conductive film (tin oxide content 5% by weight) was opposite to that in Example 1.
First, in the same manner as in Example 1, a 25 nm-thickness silicon oxide film as a dielectric layer was formed by sputtering on a biaxially stretched PET film. On top of that, an ITO transparent conductive film having a film thickness of 25 nm was formed by sputtering using a target having a tin oxide content ratio of 10% by weight, and a film thickness was formed thereon by using a target having a tin oxide content of 5% by weight. A 5 nm ITO transparent conductive film was formed by sputtering.

[Comparative Example 2]
In Comparative Example 2, no dielectric layer was formed. Specifically, on the biaxially stretched PET film, the first transparent conductive film (tin oxide content 5 wt%, film thickness 25 nm) and the second transparent conductive film (tin oxide content 10 wt%, A film thickness of 5 nm) was formed by sputtering.

[Comparative Example 3]
In Comparative Example 3, on the biaxially stretched PET film in the same manner as in Comparative Example 2, except that the film thicknesses of the first transparent conductive film and the second transparent conductive film were changed as shown in Table 1. A transparent conductive laminated film including two transparent conductive films without using a dielectric layer was produced.

[Comparative Example 4]
In Comparative Example 4, only an ITO transparent conductive film having a tin oxide content of 10% was formed on the dielectric layer. Specifically, on a biaxially stretched PET film, a silicon oxide film having a film thickness of 25 nm is formed as a dielectric layer by sputtering, and a film having a film thickness of A 30 nm transparent conductive film was formed by sputtering.

[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 (tin oxide content 10% by weight) is formed on a silicon oxide film by sputtering to a thickness of 0.5 nm, and a second transparent conductive film (oxidized) is formed thereon. Sputtering was performed at a film thickness of 29.5 nm.

[Comparative Example 6]
In Comparative Example 6, the film thickness of the first transparent conductive film was increased. Specifically, on the transparent dielectric layer, a first transparent conductive film (tin oxide content 10% by weight) is formed by sputtering with a film thickness of 8 nm, and a second transparent conductive film (tin oxide) is formed thereon. Sputtering was performed at a film thickness of 10 nm.

[Evaluation results]
Laminated structure of transparent conductive laminated films of the above examples and comparative examples, SEM observation results (number of crystals and crystallization rate) immediately after film formation, measurement results of resistance value after heating at 150 ° C. for 90 minutes or 120 minutes Table 1 shows the resistance change rate (R / R ₀ ). Moreover, the SEM observation image of the transparent conductive laminated body of each Example after etching an amorphous component and a comparative example is shown in FIG.

  As is clear from Table 1, in each of the comparative examples, the resistivity after heating at 150 ° C. for 120 minutes is 3.8 Ω · cm or more, whereas in Examples 1 to 4, 3.1 Ω · It can be seen that it is not more than cm and the in-plane variation in resistance value is small.

  In Comparative Examples 2 and 3 in which the transparent conductive film was formed without using the transparent dielectric layer, the resistance was greatly reduced after the wet heat resistance test. This is due to the fact that the heat treatment at 150 ° C. for 120 minutes was insufficient for crystallization in addition to the low wet heat resistance of the transparent conductive film. In addition, 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 and crystals after forming the transparent conductive film compared to other Comparative Examples. It can be seen that the conversion rate is large. Nevertheless, since the crystal acceleration is small, the silicon oxide layer promotes the formation of crystal grains as the ITO film formation base, and also has the action of promoting crystallization during crystallization by heating. Conceivable.

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

In Comparative Example 5 in which the film thickness of the first transparent conductive film having a small tin oxide content ratio was as small as 0.5 μm, the number of crystal grains immediately after film formation was small, and the resistivity after crystallization was also high. In Comparative Example 6 where the thickness of the first transparent conductive film is as large as 8 μm and d ₂ / d ₁ = 1.25, the number of crystal grains immediately after film formation is large, but the transparent conductive film after crystallization The resistivity was high. This is considered to be due to the low carrier density because the film thickness of the second transparent conductive film having a large tin oxide content ratio is small.

In Example 1 where d ₂ / d ₁ = 5, the in-plane variation of the resistance value is smaller than that in Example 2 where d ₂ / d ₁ = 12.5. Further, from the comparison between Comparative Example 2 and Comparative Example 3, it can be seen that the smaller the d ₂ / d ₁ , the smaller the in-plane variation of the resistance value. Since Example 4 where d ₂ / d ₁ = 2.33 has a higher resistivity after crystallization than other examples, the film thickness ratio of the transparent conductive film is reduced in resistance and resistance value. It can be seen that this is important for reducing the in-plane variation. In Example 1 and Example 3, the ratio of d ₁ and d ₂ is the same, but Example 1 has a smaller resistivity and smaller in-plane variation in resistance value. This is considered to be due to the fact that Example 1 has a larger total film thickness d ₁ + d _{2 of the} transparent conductive film. Thus, by setting the ratio of the film thickness of the first transparent conductive film to the second transparent conductive film and the total film thickness within a predetermined range, the transparent conductive laminated film has low resistance and small in-plane variation in resistance. It can be seen that

DESCRIPTION OF SYMBOLS 100 Transparent conductive laminated film 10 Transparent film base material 21 Transparent dielectric material layer (silicon oxide layer)
22 First transparent conductive film 23 Second transparent conductive film 24 Laminated transparent conductive film

Claims (10)

A transparent conductive laminated film comprising, in this order, at least one transparent dielectric layer on at least one surface of the transparent film substrate, and a transparent conductive film provided in contact with the transparent dielectric layer,
The transparent dielectric layer in contact with the transparent conductive film is a silicon oxide layer;
The transparent conductive film includes, in order from the transparent film substrate side, a first transparent conductive film composed of an indium tin oxide layer having a tin oxide content of 1 wt% or more and less than 6 wt%; and a tin oxide content of 6 A laminated film comprising: a second transparent conductive film comprising an indium tin oxide layer having a weight percent of 20% by weight or less;
And the thickness d ₁ of the first transparent conductive film and the film thickness d ₂ of the second transparent conductive film satisfies a relation of the following (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 transparent conductive laminated film whose resistivity after crystallization of the said transparent conductive film is 3.7 * 10 <^-4> ohm * cm or less.   The transparent conductive laminated film according to claim 1, wherein the silicon oxide layer has a thickness of 2 nm to 60 nm. The transparent conductive laminated film according to claim 1, wherein the transparent conductive film is an amorphous film having a crystallization rate of 30% or less, and has 90 or more crystal grains per 1 μm ² . The transparent conductive film is an amorphous film having a crystallization rate of 30% or less, and when heated at 150 ° C., the resistivity becomes 3.7 × 10 ⁻⁴ Ω · cm or less within 2 hours. The transparent conductive laminated film of any one of Claims 1-3.   The transparent conductive laminated film according to claim 1 or 2, wherein both the first transparent conductive film and the second transparent conductive film are crystalline. A method of producing a transparent conductive laminated film comprising at least one transparent dielectric layer on at least one surface of a transparent film substrate and a transparent conductive film provided in contact with the transparent dielectric layer in this order. ,
A transparent dielectric layer forming step in which a transparent dielectric layer is formed on the transparent film substrate; and an indium tin oxide layer having a tin oxide content of 1 wt% to less than 6 wt% on the transparent dielectric layer; A transparent conductive film forming step in which a first transparent conductive film made of 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 are formed in this order; Have
The transparent dielectric layer in contact with the transparent conductive film is a silicon oxide layer;
In the transparent conductive film forming step, the first transparent conductive film is directly formed on the silicon oxide layer with a film thickness d ₁ of ₁ to 9 nm, and the second transparent conductive film is is a film ₁ of 2 times greater than the thickness d _2,
It said first sum d _{1 +} d ₂ of the film thickness d ₂ of the film thickness d ₁ of the transparent conductive film second transparent conductive film is 15～37Nm, method for producing a transparent conductive laminated film.   The method for producing a transparent conductive laminated film according to claim 6, wherein in the transparent dielectric layer forming step, the silicon oxide layer is formed by a sputtering method.   The method for producing a transparent conductive laminated film according to claim 6 or 7, wherein, in the transparent conductive film forming step, the first transparent conductive film and the second transparent conductive film are both formed by a sputtering method.   The manufacturing method of the transparent conductive laminated film of any one of Claims 6-8 which further has the crystallization process in which the said transparent conductive film is crystallized by heat processing after the said transparent conductive film formation process. The manufacturing method of the transparent conductive laminated film of Claim 9 whose resistivity of the said transparent conductive film after a crystallization process is 3.7 * 10 <^-4> ohm * cm or less.