JP6806732B2 - Manufacturing method of transparent conductive laminate - Google Patents

Description

The present invention relates to a method for producing a transparent conductive laminate having a copper-based film patterned on a transparent film substrate.

In recent years, touch panels have come to be installed in various devices such as smartphones, tablets, and personal computers. Conventionally, a touch panel has often used an analog resistance film method for detecting conduction at a touch position between two conductive films (electrode layers) arranged opposite to each other with a dot spacer interposed therebetween (for example, Patent Document 1). ), In recent years, the development of a capacitance type touch panel that detects the touch position of a fingertip by utilizing a change in capacitance has become widespread.

In display devices such as such capacitive touch panels, an indium-tin composite oxide (ITO) thin film having excellent transparency is used as the transparent electrode, but the specific resistance is 10 times that of a single metal. It is said that it is difficult to apply it to a large screen because it is expensive. Therefore, instead of this ITO, a mesh pattern copper line, which is a low-resistance conductor and has excellent mechanical strength as well as being able to increase the sensitivity of capacitance control, has been attracting attention. Recently, a mesh pattern made of polygons has been used. Attempts have been made to commercialize display devices that use surface electrodes (Patent Document 2). The reason for using the mesh pattern for the electrodes is that the conductors are arranged in a plane to improve the capacitance, and the copper line does not transmit light, so it is necessary to geometrically increase the aperture ratio. It is in.

As the transparent conductive laminate having the copper pattern, it is desired to use a film base material as the display device becomes thinner and lighter. On the other hand, it is known that the film and the copper pattern have poor adhesion. Therefore, a thin film made of molybdenum (Mo), chromium (Cr), tantalum (Ta), tungsten (W), nickel (Ni), titanium (Ti) or an alloy thereof is used as the adhesion layer between the film and the copper layer. Has been examined, and measures have been taken to improve adhesion.

Japanese Patent No. 3825487 International Publication No. 2009/108758

When a metal thin film such as a molybdenum layer, a chromium layer, a tantalum layer, a tungsten layer, a nickel layer, or a titanium layer is formed in order to improve the adhesion between the film and the copper layer, the difference in etching rate between the copper layer and the metal thin film is increased. There is a problem that it is difficult to pattern fine lines because they differ greatly. If the metal wiring pattern is not thinned, the wiring pattern traces will be visible when the metal wiring pattern is formed on the transparent film base material, so-called invisibility of the wiring pattern will deteriorate, and the transparency of the transparent conductive film will be improved. It cannot be secured, and there is a problem in using it as a transparent conductive film. Recently, in addition to the problem of adhesion between the film and the copper film, it has been confirmed that the copper film deteriorates due to bleeding from the base material.

In view of such a problem, an object of the present invention is to provide a method for producing a transparent conductive laminate capable of thinning a copper wiring pattern and having excellent reliability.

As an adhesion layer for improving the adhesion between the film substrate and the copper film, a copper oxide film having an etching rate close to that of the copper film is formed under predetermined film forming conditions, so that the adhesion between the film and the copper film is excellent. It is also excellent in moisture and heat resistance, and a transparent conductive laminate in which copper oxide and copper are both formed in a conductive pattern with a line width of 1 to 10 μm can be obtained.

That is, in the present invention, a copper oxide film and a copper film are sequentially provided on at least one side of the transparent film base material, both the copper oxide film and the copper film are patterned with a line width of 1 to 10 μm, and the total light transmittance is 80% or more. The present invention relates to a method for producing a transparent conductive laminate. The copper oxide film is formed by a sputtering method at a substrate temperature of 50 ° C. or higher. At that time, a mixed gas containing argon gas and oxygen gas is used, and the amount of oxygen gas introduced into the mixed gas is 15% by volume to 30% by volume.

Preferably, a step of forming a copper oxide film and a copper film on a transparent film substrate in order under the above conditions, a step of performing a rust preventive treatment on the copper film, and a step of applying a resist film on the copper film and then resisting. It includes a step of forming a wiring pattern, a step of simultaneously etching a copper oxide film and a copper film with the same etchant using the wiring pattern as a mask to form a wiring pattern, and a step of peeling off a resist pattern. Copper oxide is preferably formed into a film using a copper target. A copper oxide film may be formed on both sides of a transparent film base material, and copper may be formed by a wet plating method.

In the transparent conductive laminate, it is preferable that the thickness d ₁ of the copper oxide film and the thickness d _{2 of the} copper film satisfy the relationship of d ₁ = 15 to 50 nm and d ₁ + d ₂ = 600 nm or less. The rate of change in resistance of the transparent conductive laminate after being left in an environment of a temperature of 85 ° C. and a humidity of 85% for 500 hours is preferably ± 10% or less.

According to the present invention, by forming a copper oxide film on a transparent film base material by a predetermined manufacturing method, it is possible to improve the adhesion between the copper wiring pattern and the transparent film base material while maintaining reliability. Moreover, since the etching rates of the copper oxide film and the copper film are close to each other, the wiring pattern can be easily thinned.

It is sectional drawing which shows one Embodiment of a conductive laminate.

[Embodiment of Transparent Conductive Film]
Hereinafter, description will be made with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a conductive film 100 having a copper oxide film 21 and a copper film 22 on a transparent film base material 10. The copper oxide film 21 and the copper film 22 are combined to form a laminated film 23.

<Copper oxide film formation>
A copper oxide film 21 is formed on the transparent film base material 10. The copper oxide film reduces plasma damage to the gas barrier layer that suppresses volatilization of water and organic substances from the transparent film base material 10 or the transparent film base material with respect to the copper film 22 formed on the copper oxide film. Can act as a protective layer. Further, in the present invention, the copper oxide film has an effect of suppressing deterioration of the copper film due to bleeding from the film base material, and further, reliability can be satisfied.

As a method for forming the copper oxide film 21 on the transparent film base material 10, it is preferable to use a dry coating method from the viewpoint that a uniform thin film at the nanometer level can be easily formed. 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. From the viewpoint of improving the adhesion between the transparent film base material 10 and the copper oxide film 21, the surface of the transparent film base material 10 is subjected to surface treatment such as corona discharge treatment or plasma treatment prior to the formation of the copper oxide film. You may.

When the copper oxide film is formed by a sputtering method, for example, in the case of a DC magnetron sputtering apparatus, a copper target can be used. Sputter film formation is performed while introducing a carrier gas containing an inert gas such as argon or nitrogen and an oxygen gas into the film formation chamber. The amount of oxygen gas introduced into the mixed gas of argon gas and oxygen gas is preferably 15% by volume to 30% by volume, more preferably more than 15% by volume and less than 30% by volume. The power density during film formation is adjusted within a range that does not give excessive heat to the transparent film and does not impair productivity. Although 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 ~10.0W / cm} 2 is preferably about. The pressure (total pressure) in the film forming chamber at the time of forming the copper oxide film is preferably 0.1 Pa to 0.8 Pa, more preferably 0.3 Pa to 0.6 Pa. The morphology (microstructure of the surface) changes with the change in the film-forming pressure of the copper oxide film, and the higher the film-forming pressure, the coarser the crystal grains tend to be. It is considered that such a change in morphology affects the specific resistance of the conductive film. The substrate temperature at the time of forming the copper oxide film is preferably 50 ° C. or higher in order to promote the oxidation of the copper oxide film. The upper limit temperature may be in the range where the transparent film base material has heat resistance, and is preferably 90 ° C. or lower, for example. When the substrate temperature is 50 ° C. or higher, the oxidation of the copper oxide film is promoted, which leads to the improvement of the adhesion between the transparent film substrate and the copper oxide film, and when the substrate temperature is 90 ° C. or lower, the film substrate is brittle. Since embrittlement and dimensional change are suppressed, a good quality thin film can be formed.

<Copper film formation>
The copper film is laminated on the copper oxide film. The copper film can be formed by a sputtering method or a plating method. When the film is formed by the take-up sputtering apparatus, the copper oxide film 21 and the copper film 22 may be continuously formed on the transparent film base material 10. When the copper film is formed by the sputtering method, the substrate temperature and power density at the time of forming the copper film are not particularly limited, and may be, for example, in the range of the above-mentioned substrate temperature and power density for forming the copper oxide film. Argon gas is preferable as the introduction gas at the time of forming the copper film. The pressure (total pressure) in the film-forming chamber during copper film-forming is preferably 0.1 Pa to 1.0 Pa, more preferably 0.2 Pa to 0.8 Pa. By setting the film forming pressure within the above range, the conductivity can be improved.

<Manufacturing process of transparent conductive laminate>
As a manufacturing step of the transparent conductive laminate of the present invention, preferably, a copper oxide film is formed on a transparent film substrate by a sputtering method at a substrate temperature of 50 ° C. or higher as a first step, and a copper oxide film is formed as a second step. A copper film is laminated on the copper film by a sputtering method or a wet plating method, a rust preventive treatment is performed on the copper film as a third step, a resist is patterned by a photolithography method as a fourth step, and a resist pattern is formed as a fifth step. As a mask, the copper oxide film and the copper film are simultaneously etched with the same etchant to perform patterning, and finally the resist pattern remaining as the sixth step is peeled off.

<Transparent film base material>
The transparent film base material 10 is colorless and transparent at least in the visible light region. Examples of the material 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. Can be mentioned. The transparent film base material 10 may be provided on the outermost surface with a functional layer such as an easy-adhesion layer and a hard coat layer, and an index matching layer that functions as an optical adjustment layer. When the easy-adhesion layer is used, it is presumed that the acrylic resin is bonded to the copper oxide film via carbon and oxygen, and the adhesive force between the transparent film base material and the copper oxide film is strengthened. Is preferable. Further, as the easy-adhesion layer, a layer having a nitrogen atom such as a urethane resin may be formed. It is presumed that the adhesion between the nitrogen atom and the copper oxide film is enhanced by the coordination bond. The thickness of the transparent film base material 10 is not particularly limited, but is preferably 10 μm to 400 μm, more preferably 25 μm to 200 μm. When the thickness of the transparent film base material 10 is within the above range, it has durability and appropriate flexibility, and can be obtained by a roll-to-roll method using a winding sputtering film forming apparatus on the transparent film base material. It is possible to form a film with high productivity.

In addition, the surface of this transparent polymer film substrate is subjected to surface treatment such as roughening treatment by subjecting it to etching treatment such as plasma treatment, corona discharge, flame, ultraviolet irradiation, electron beam irradiation, chemical conversion, and oxidation. For example, the adhesion may be improved.

<Copper oxide film>
The copper oxide film and the copper film formed on the transparent film base material 10 have a copper oxide film thickness d ₁ and a copper film thickness d ₂ as follows (1) d ₁ = 15 to 50 nm, preferably. 20-35 nm,
(2) It may have a relationship of d ₁ + d ₂ = 600 nm or less, preferably 300 nm or more and 500 nm or less. Adhesion is improved and it is preferable to have such a thickness relationship. If the thickness of the copper oxide film is too thin, it will not be formed as a continuous film and will not be able to fully function as an adhesion layer. The adhesion between the material film and the metal film may decrease.

The copper oxide film is Cu _x O (1 ≦ x ≦ 2), and from the viewpoint of improving adhesion, a higher degree of oxidation is preferable. Furthermore, the copper oxide film has conductivity, and a copper film can be formed directly on copper oxide by a wet plating method. Further, when improving the film forming speed of the copper film in the wet plating method, it is desirable to form the sputtered copper film on the copper oxide film and then form the copper film by the wet plating method.

<Copper film>
The average surface roughness Sa of the copper film is preferably 2 nm to 10 nm, and more preferably Sa is 2 nm to 5 nm. If the average surface roughness of the copper film is larger than the above range, the conductivity of the conductive pattern may decrease.

[Transparent conductive laminate]
The transparent conductive laminate of the present invention is particularly preferably used as a position detection electrode for a capacitive touch panel because the invisibility and adhesion of the pattern are improved.

The term "transparent" of the transparent conductive laminate is defined as the total light transmittance of the transparent conductive laminate after the copper oxide film and the copper film are finely patterned to a line width of 1 to 10 μm to be 80% or more. The fine line patterning is preferably performed with a line width of 1 to 10 μm in terms of pattern invisibility and transparency.

With respect to the conductive laminates obtained in the following Examples and Comparative Examples, the resistivity of the surface of the conductive laminate, the total light transmittance after patterning of the metal electrode, the high temperature and high humidity reliability, and the adhesion were evaluated.
The results are shown in Table 1.

<Resistivity>
The resistivity of the conductive laminate was calculated by measuring the sheet resistance. It was calculated from the relationship of resistivity = sheet resistance x film thickness. The surface resistance was measured by four-probe pressure contact measurement using a low resistivity meter Loresta GP (MCP-T710) (manufactured by Mitsubishi Chemical Corporation), and each film thickness was measured using a transmission electron microscope.

<Light transmittance>
The total light transmittance of the laminated film after patterning was measured by a turbidity meter type NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd. based on Tt: JIS K7105 (1981). Those having a transmittance of 80% or more were designated as "○", and those having a transmittance of less than 80% were designated as "x".

<High temperature and high humidity reliability>
After laminating the copper oxide film and the copper film on the transparent film substrate, a test was conducted in which the unpatterned conductive laminate was left to stand in an environment of a temperature of 85 ° C. and a humidity of 85% for 500 hours. The rate of change of the surface resistance value (R) after the test [that is, R / R ₀ ] with respect to the surface resistance value (R ₀ ) before the test was determined, and the high temperature and high humidity reliability was evaluated.

<Adhesion>
According to the cross-cut test method described in JIS K5600, 10 scratches are made on each of the laminated films using a cutter knife at 1 mm intervals in each of the vertical and horizontal directions, and cellophane tape is attached and peeled off. It was observed whether the film peeled off from the substrate.
Adhesion was ranked from the highest strength level 0 to the lowest strength level 5, with 1 or less being good.
Definition of adhesion See JIS K5600.
0 ... The edges of the cut are completely smooth, and there is no peeling in the eyes of any grid.
1 ... Small peeling of the coating film at the intersection of cuts. The area affected by the crosscut does not clearly exceed 5%.
2 ... The coating film is peeled off along the edge of the cut and / or at the intersection. The cross-cut area is clearly affected by more than 5%, but not more than 15%.
3 ... The coating film is partially or wholly peeled off along the edge of the cut, and / or various parts of the eyes are partially or wholly peeled off. The cross-cut portion is clearly affected by more than 15% but not more than 35%.
4 ... The coating film has a large peeling partially or wholly along the edge of the cut, and / or some eyes are partially or wholly peeled off. The cross-cut portion is clearly not affected by more than 35%.
5 ... Peeling that cannot be classified even in classification 4.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[Example 1]
(Copper oxide film formation)
As the transparent film base material, a biaxially stretched PET film having a thickness of 125 μm in which easy-adhesion layers made of an acrylic resin were formed on both sides was used. Copper oxide films were formed on both sides of this PET film.

Using copper as a target, while introducing a mixed gas of oxygen gas (flow rate: 90 sccm) and argon gas (flow rate: 270 sccm) into the device, the film forming chamber pressure: 0.4 Pa, power density: 1.7 W / cm ² , Sputtering film formation was performed under the condition of a roll temperature of 90 ° C. during film formation. The film thickness of the obtained copper oxide film was 20 nm.

(Copper film formation)
A copper film was formed on the above copper oxide film. Using a copper target, while introducing argon gas (flow rate: 270 sccm) into the apparatus, under the conditions of film forming chamber pressure: 0.4 Pa, power density: 4.2 W / cm ² , and roll temperature during film forming at 90 ° C. , Sputtering was performed. The film thickness of the obtained copper film was 300 nm.

(Metal electrode patterning)
After forming the above copper film, rust prevention treatment is performed on the copper film, the resist film is patterned by a photolithography method, the resist pattern is used as a mask, and the copper oxide film and the copper film are used with 5% of an iron (III) chloride aqueous solution. At the same time, etching was performed to pattern the metal wiring, and the last remaining resist wiring pattern was peeled off to make the line width 5 μm.

[Example 2]
With respect to Example 1, the amount of oxygen introduced during the copper oxide film formation was changed to 50 sccm, and a transparent conductive laminate was produced without changing other conditions.

[Comparative Example 1]
A transparent conductive laminate was produced without changing other conditions except that the copper oxide film was not formed with respect to Example 1.

[Comparative Example 2]
A transparent conductive laminate was produced without changing other conditions except that the film forming temperature of the copper oxide film was changed to 30 ° C. with respect to Example 1.

[Comparative Example 3]
A transparent conductive laminate was prepared without changing other conditions except that the amount of oxygen at the time of forming the copper oxide film was changed to 30 sccm with respect to Example 1.

[Comparative Example 4]
A transparent conductive laminate was prepared without changing other conditions except that the amount of oxygen at the time of forming the copper oxide film was changed to 120 sccm with respect to Example 1.

[Comparative Example 5]
With respect to Example 1, a transparent conductive laminate was prepared without changing other conditions except that a nickel layer was formed instead of the copper oxide film. The nickel layer was formed by a sputtering method, and the nickel layer and the copper film were continuously formed in-line.

As is clear from Table 1 above, it can be seen that the transparent conductive laminate of the example satisfies the adhesion for the touch panel and the total light transmittance, and is excellent in high temperature and high humidity reliability.

From Examples and Comparative Examples, a strong adhesive force can be obtained by increasing the degree of oxidation of the copper oxide film. It is considered that this is because the carbon and oxygen atoms on the surface of the transparent film base material are bonded to the oxygen atoms of the copper oxide film. However, if the amount of oxygen in the film formation is excessively introduced from a predetermined range in order to increase the degree of oxidation, the high temperature and high humidity reliability deteriorates. It is considered that this is because the copper oxide film has excess oxygen and oxygen is supplied from the copper oxide film to the copper film, and the resistivity changes. Further, if a metal film such as a nickel layer is formed as the base layer instead of copper oxide, patterning failure occurs due to the difference in etching rate with the copper film, and the total light transmittance deteriorates.

100 Conductive laminate 10 Transparent film base material 21 Copper oxide film 22 Copper film 23 Laminated film

Claims (4)

A method for producing a transparent conductive laminate having a wiring pattern having a line width of 1 to 10 μm on at least one side of a transparent film base material and having a total light transmittance of 80% or more.
The transparent film base material is provided with an acrylic-based easy-adhesion layer on the forming surface of the wiring pattern.
The wiring pattern is a pattern in which a copper oxide film and a copper film provided in order are both patterned on the easy-adhesion layer of the transparent film base material.
The copper oxide film is formed by a sputtering method at a substrate temperature of 50 ° C. or higher using a copper target, and at that time, a mixed gas containing argon gas and oxygen gas is used, and the amount of the oxygen gas introduced into the mixed gas. There Ri 15 vol% to 30 vol% der method for producing a transparent electroconductive laminate composition of copper oxide and said _{Cu x O (1 ≦ x ≦} 2) der Rukoto. A method for producing a transparent conductive laminate having a wiring pattern having a line width of 1 to 10 μm on at least one side of a transparent film base material and having a total light transmittance of 80% or more.
The transparent film base material is provided with an acrylic-based easy-adhesion layer on the forming surface of the wiring pattern.
A step of forming a copper oxide film on the easily adhesive layer of a transparent film substrate by a sputtering method at a substrate temperature of 50 ° C. or higher using a copper target .
The step of laminating a copper film on the copper oxide film and
The process of performing rust prevention treatment on the copper film and
A step of forming a resist pattern after applying a resist film on the copper film after the rust prevention treatment, and
Using the resist pattern as a mask, the copper oxide film and the copper film are simultaneously etched by the same etching to form a wiring pattern having a line width of 1 to 10 μm.
The steps of peeling the resist pattern are included in order.
Wherein in the step of forming the copper oxide film, using a mixed gas containing argon gas and oxygen gas, Ri the introduction amount of oxygen gas is 15 vol% to 30 vol% der for the gas mixture, the composition of the copper oxide Cu _{x O (1 ≦ x ≦ 2} ) der Rukoto characterized method for producing a transparent electroconductive laminate. The method for producing a transparent conductive laminate according to claim 1 or 2 , wherein the thickness of the copper oxide film is 15 to 60 nm, and the total thickness of the copper oxide film and the copper film is 600 nm or less. .. The method for producing a transparent conductive laminate according to any one of claims 1 to 3 , wherein the copper oxide film and the copper film are formed on both surfaces of the transparent film base material.