JP2023069796A - Surface-treated copper foil - Google Patents

Abstract

To provide a surface-treated copper foil in which a bonded surface with a base material has appearance with excellent etching resistance and black color tone and without uneven treatment and a bubble mark in order to be used for a display element in particular.SOLUTION: A surface-treated copper foil 10 comprises a copper foil layer 13, which is an electrolytic copper foil, and a blackening treatment layer 14 covering one surface side of the electrolytic copper foil. The blackening treatment layer 14 is a composite metal layer containing copper, nickel, cobalt, and tungsten. An adhesion amount of nickel of the blackening treatment layer is 120 to 400 μg/dm2, an adhesion amount of cobalt is 400 to 700 μg/dm2, and an adhesion amount of tungsten is 70 to 200 μg/dm2. The blackening treatment layer 14 can be formed by subjecting one surface of the copper foil layer 13 to plating treatment by plating bath containing nickel, cobalt, and tungsten.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a surface-treated copper foil, and more particularly to a surface-treated copper foil for display elements such as touch panels and a method for producing the same.

BACKGROUND ART Conventionally, in the field of display elements, surface-treated copper foils have been used for applications such as wiring forming materials for touch panels. For surface-treated copper foils for other applications, the surface to be adhered to the base material must have an etching resistance that can withstand the chemicals used in etching, which is the wiring formation process, and a surface treatment that has an appearance without unevenness in treatment or bubble traces. Although it is required to be applied to electrolytic copper foil, the surface-treated copper foil used for display elements further has a surface with a black color tone to prevent reflection when used as a display element. It is required that the treatment is applied to the electrolytic copper foil.

As a surface treatment applied to the copper foil, for example, Non-Patent Document 1 describes Ni--W alloy plating as an alternative to hard Cr plating, and depending on the content of W, plating of the Ni--W alloy film is performed. Results of studies on differences in crack behavior are described.

Kazuya Ishii et al., "Influence of Plating Internal Stress on Film Cracking of Ni-W Alloy Plating," Surface Technology, Surface Technology Association, 2014, Vol. 65, No. 8, p. 49-53

However, although the Ni—W alloy plating described in Non-Patent Document 1 is excellent in acid resistance, it does not exhibit a black color tone, so it is not suitable as a surface treatment for electrolytic copper foils used for display elements. do not have. On the other hand, when an electrolytic copper foil is subjected to a surface treatment that exhibits a black color tone, there is also the problem that bubble traces are likely to occur on the surface. Bubble traces are not preferable because they may be erroneously detected as foreign matter in any application.

Therefore, the present invention provides a surface-treated copper foil having excellent etching resistance, a black color tone, and an appearance free from uneven treatment and air bubbles on the surface to be adhered to a substrate, especially for use in display devices. intended to provide

In order to achieve the above object, as one aspect of the present invention, there is provided a surface-treated copper foil comprising an electrolytic copper foil and a blackening treatment layer covering one surface side of the electrolytic copper foil, The blackening treatment layer is a composite metal layer containing copper, nickel, cobalt, and tungsten ^. /dm ² , and the deposition amount of tungsten is 70 to 200 μg/dm ² .

Further, the total amount of nickel, cobalt, and tungsten deposited on the black oxide layer is preferably 700 to 1200 μg/dm ² .

The surface of the surface-treated copper foil on the blackened layer side has an L ^* value of 55.0 to 65.0 and an a ^* value of 0.0 to 10 in the L ^* a ^* b ^* color system. .0 and b ^* values between 0.0 and 10.0 are preferred.

Another aspect of the present invention is a surface-treated copper foil in which 10 or more air bubbles with a diameter of 50 μm or more are not present per 1 m ² on the surface of the surface-treated copper foil on the side of the blackened layer.

As described above, according to the present invention, a composite metal layer containing copper, nickel, cobalt, and tungsten is formed as a blackening treatment layer on one surface of the electrolytic copper foil (the surface to be bonded to the transparent substrate of the display element). By forming the layer, the etching resistance is excellent, the surface of the surface-treated copper foil on the side of the blackening treatment layer can be blackened, and the appearance can be free from unevenness in treatment and air bubbles.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows typically one embodiment of the surface-treated copper foil which concerns on this invention. 1. It is typical sectional drawing for demonstrating the usage example in the case of using the surface-treated copper foil shown in FIG. 1 as a wiring formation material for touchscreens. 1. It is typical sectional drawing for demonstrating the usage example in the case of using the surface-treated copper foil shown in FIG. 1 as a wiring formation material for touchscreens. 1 is a scanning electron microscope (SEM) image showing a surface to be adhered of a surface-treated copper foil serving as a reference used for evaluating treatment unevenness of the surface-treated copper foil.

An embodiment of the surface-treated copper foil according to the present invention will be described below with reference to the accompanying drawings. However, the present invention is not limited by the embodiments described below.

[Surface-treated copper foil]
The surface-treated copper foil of the present embodiment includes an electrolytic copper foil and a blackened layer covering at least one side of the electrolytic copper foil.

The thickness of the electrolytic copper foil is, for example, preferably in the range of 1 to 35 μm, more preferably in the range of 2.0 to 6.0 μm, still more preferably about 6 μm. If the thickness of the copper foil is less than 6.0 μm, it may become difficult to handle the electrolytic copper foil. Therefore, when using an electrolytic copper foil thinner than 6.0 μm, for example, like the surface-treated copper foil 10 shown in FIG. A copper foil layer 13 is formed as a foil and used. In this case, a blackened layer 14 is formed on the surface of the copper foil layer 13 opposite to the carrier foil 11 . In the copper foil layer 13 with the carrier foil 11, if the thickness of the copper foil layer 13 is less than 1.0 μm, there is a possibility that the carrier foil peel strength becomes unstable. On the other hand, if the electrodeposited copper foil is thicker than 35.0 μm, etching takes a long time and the etching rate tends to be uneven in the in-plane direction, resulting in partial etching and loss of flatness. The problem of fear can arise.

Electrodeposited copper foil generally has a glossy cathode surface, which is the side that was in contact with the electrodeposition drum during the manufacturing process, and a deposition surface formed by plating on the opposite side. The blackened layer may be formed on either the cathode surface or the deposition surface of the electrolytic copper foil, but is preferably formed on the cathode surface of the electrolytic copper foil because the shape is stable.

The blackened layer is a composite metal layer of copper (Cu), nickel (Ni), cobalt (Co), and tungsten (W) because it has excellent etching resistance and exhibits a black color tone. The thickness of the blackened layer is, for example, preferably in the range of 1.0 to 100.0 nm, more preferably in the range of 5.0 to 20.0 nm.

The nickel deposition amount is preferably in the range of 120 to 400 μg/dm ² , more preferably in the range of 170 to 350 μg/dm ² , still more preferably in the range of 200 to 300 μg/dm ² . If the amount of nickel adhered is less than 120 μg/dm ² , the chemical resistance is lowered, and there is a risk that the copper foil that should remain is peeled off during etching. On the other hand, if the amount of nickel adhered exceeds 400 μg/dm ² , unmelted portions may remain at the ends of the wiring formed during etching, which may cause a short circuit between the wirings.

The adhered amount of cobalt is preferably in the range of 400 to 700 μg/dm ² , more preferably in the range of 400 to 600 μg/dm ² , still more preferably in the range of 400 to 500 μg/dm ² . If the amount of cobalt adhered is less than 400 μg/dm ² , there is a possibility that the treated surface will have a bright color tone. On the other hand, if the amount of cobalt adhered exceeds 700 μg/dm ² , undissolved portions may remain at the ends of the wiring formed during etching, which may cause a short circuit between the wirings.

The deposition amount of tungsten is preferably in the range of 70 to 200 μg/dm ² , more preferably in the range of 80 to 150 μg/dm ² and even more preferably in the range of 90 to 130 μg/dm ² . If the deposition amount of tungsten is less than 70 μg/dm ² , the chemical resistance is lowered, and there is a possibility that the copper foil that should remain is peeled off during etching. On the other hand, if the deposition amount of tungsten exceeds 200 μg/dm ² , unmelted portions may remain at the ends of the wiring formed during etching, which may cause a short circuit between the wirings.

The total deposition amount of nickel, cobalt, and tungsten (hereinafter simply referred to as "total amount") is preferably in the range of 700 to 1200 µg/ ^dm2 , more preferably in the range of 730 to 1100 µg/dm2, and 760 to 900 µg/ ^dm2 . A range of dm ² is more preferred. When the total amount is 700 μg/dm ² or more, excellent chemical resistance can be exhibited, and the problem of peeling of the copper foil that should remain during etching can be more reliably prevented. On the other hand, by setting the total amount to 1200 μg/dm ² or less, it is possible to more reliably prevent the problem of short-circuiting between wirings due to undissolved residues at the ends of wirings formed during etching.

Since such a blackening treatment layer is formed on the electrolytic copper foil, the color tone of the adherend surface of the surface-treated copper foil has an L ^* value of 65 or less in the L ^* a ^* b ^* color system. The a ^* value is 10 or less and the b ^* value is 10 or less, and a sufficient black color tone for use in a display element can be exhibited.

The L ^* value is lightness, and the lower the number, the darker the tone. The a ^* and b ^* values indicate the direction of color, with higher a ^* values tending toward red and lower values toward green. Also, the higher the b ^* value, the more yellow, and the lower the b* value, the more blue. The a ^* value and the b ^* value change the color tone depending on their balance, so it cannot be said unconditionally, but the lower the value of both, the more black is exhibited.

More preferably, the L ^* value is 60 or less, the a ^* value is 5.0 or less, and the b ^* value is 5.0 or less, and even more preferably, the L ^* value is 57 or less and the a ^* value is 2.0 or less. , b ^* values of 2.0 or less.

In addition, the surface-treated copper foil provided with the blackening treatment layer of the present embodiment has an excellent appearance in which 10 or more air bubbles with a diameter of 50 μm or more are not present per 1 m ² on the surface on the blackening treatment layer side. be able to. It is preferable that there are not more than 5 bubble traces per 1 m ² , more preferably there are not more than 3 bubbles per 1 m ² , and even more preferably there are not more than 1 bubbles per 1 m ² .

The use of such a surface-treated copper foil having a blackened layer in a display element will be described. As shown in FIG. 2, in order to manufacture a display element, adhesive layers 22 are formed on both sides of a transparent base film 21 such as polyethylene terephthalate (PET), and both sides of the transparent base film 21 are 1, the surface-treated copper foils 10 as shown in FIG. After bonding, the carrier foil 11 is peeled off, and the copper foil layer 13 is etched into a predetermined wiring pattern to manufacture a display element in which the copper foil layer 13 is used as a sensor wiring material.

As shown in FIG. 3, between the copper foil layers 13A and 13B etched into the wiring pattern and the transparent substrate film 21, the blackened layers 14A and 14B similarly etched into the wiring pattern are located. In the display element, the copper foil layer 13B etched into the other wiring pattern is visible from between the copper foil layer 13A etched into the other wiring pattern and the blackened layer 14A. This can be prevented by the hardened layer 14B. As a result, it is possible to prevent reflection of incident light from between the copper wirings on one side, thereby suppressing deterioration in the image quality of the display element. In addition, the surface-treated copper foil of the present invention is not limited to those attached with a carrier foil as shown in FIGS. 1 and 2 .

In addition, the surface-treated copper foil 10 of the present embodiment may be provided with a silane coupling agent-treated layer (not shown) on the surface of the blackened layer 14, if necessary. The silane coupling agent-treated layer may be a layer formed by a silane coupling agent treatment that has been conventionally applied to electrolytic copper foils. The silane coupling agent is not particularly limited, and for example, it is preferable to use an amino-based silane coupling agent or an epoxy-based silane coupling agent.

Moreover, the surface-treated copper foil 10 of this embodiment may be provided with a chromate treatment layer (not shown) between the blackening treatment layer 14 and the silane coupling agent treatment layer, if necessary. The chromate treatment layer may be a layer formed by a chromate treatment conventionally applied to electrolytic copper foils. Chromium trioxide, potassium dichromate, sodium dichromate, or the like is preferably used for the chromate treatment. The chromate treatment layer thus formed contains oxides or hydroxides of trivalent chromium reduced from hexavalent chromium.

[Method for producing surface-treated copper foil]
An embodiment of a method for manufacturing a surface-treated copper foil is described below. The method for producing a surface-treated copper foil of the present embodiment comprises forming a blackened layer on one surface of an electrolytic copper foil to obtain a surface-treated copper foil.

The step of forming the blackened layer is a step of plating the surface of the electrodeposited copper foil on the adherend side to form a composite metal layer of copper, nickel, cobalt, and tungsten. A plating bath containing the metal contained in the composite metal layer described above is used to form the blackened layer. Since the plating treatment can exhibit a blacker color tone, it is preferable to perform the plating treatment twice instead of once.

As the first plating process, for example, a composite metal layer of copper and cobalt is formed. As a specific first plating bath composition for that purpose, for example, a copper concentration of 1.3 to 10.2 g/L, a cobalt concentration of 2.1 to 12.6 g/L, and a pH of 2.5 to 3.5.It is preferable to set the bath temperature to 25 to 33.degree. As for the conditions of the first plating treatment, it is preferable to set the current density to 0.0 to 4.0 A/dm ² and the treatment time to 2.0 to 6.0 seconds. The first plating treatment may be a copper-nickel composite metal layer or a copper-tungsten composite metal layer.

At this time, the supply source of each metal may be in any form such as oxide, sulfate, nitrate, carbonate, isopolyate, and metal oxoate. In addition, sodium sulfate anhydride may be added in order to stabilize the plating performance by stabilizing the ion concentration in the liquid. In this case, the sodium concentration is preferably 5.0 to 30.0 g/L.

Subsequently, as the second plating process, for example, a composite metal layer of nickel, cobalt, and tungsten is formed. As a specific composition of the second plating bath for this purpose, for example, the concentration of nickel is 1.0 to 4.5 g/L, the concentration of cobalt is 1.0 to 3.1 g/L, and the concentration of tungsten is 0.5 g/L. 3 to 2.8 g/L, a pH of 2.5 to 4.0, and a bath temperature of 25 to 33°C are preferred. As for the conditions of the second plating treatment, the current density is preferably 0.3 to 1.5 A/dm ² , more preferably 0.8 to 1.5 A/dm ² . More preferably 0 to 1.4 A/dm ² . Also, the processing time is preferably 2.0 to 4.0 seconds.

At this time, the supply source of each metal may be in any form such as oxide, sulfate, nitrate, carbonate, isopolyate, and metal oxoate. In addition, sodium sulfate anhydride may be added in order to stabilize the plating performance by stabilizing the ion concentration in the liquid. In this case, the sodium concentration is preferably 5.0 to 30.0 g/L.

Theoretically, two layers of the composite metal layer should be formed by performing the plating treatment twice in this way. It is also considered that a blackening treatment layer of is formed. When the amount of nickel, cobalt, and tungsten in the blackening treatment layer was measured from the surface of the blackening treatment layer with a wavelength dispersive X-ray spectrometer (WDX), the amount of each element contained in the two-layer composite metal layer was confirmed.

In addition, in the step of forming the blackening treatment layer, it is preferable to perform washing with water or pickling in advance before any plating treatment. Moreover, after forming the blackened layer, as described above, the silane coupling agent treatment may be performed, or the chromate treatment may be performed before the silane coupling agent treatment. As the treatment conditions for the chromate treatment and the silane coupling agent treatment, known treatment conditions for electrolytic copper foil can be applied.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples of the present invention. However, the invention is not limited to the following examples.

[Example 1]
First, the surface of an electrolytic copper foil (manufactured by Nippon Denki Co., Ltd., product number: SEED foil) having a thickness of 6 μm was immersed in 10 wt % sulfuric acid for 10 seconds for pickling treatment. After washing the copper foil with water, the copper concentration in the liquid is 4.1 to 5.1 g/L, the cobalt concentration is 7.4 to 8.4 g/L, and the sodium concentration is 14.8 to 23.2 g/L. Using the first plating solution adjusted to pH 2.9 and bath temperature 30 ° C., the surface of the copper foil on the cathode side was plated at a current density of 2.4 A / dm ² to form copper and cobalt. A first composite metal layer was formed comprising:

After washing the copper foil with water, the nickel concentration in the liquid is 2.6 to 2.8 g/L, the cobalt concentration is 1.8 to 2.0 g/L, and the tungsten concentration is 0.9 to 1.1 g/L. L, a sodium concentration of 14.1 to 23.7 g / L, using a second plating solution adjusted to pH 2.9 and a bath temperature of 30 ° C., the surface of the copper foil on the cathode side was further heated to 1.0 A /dm ² current density to form a second composite metal layer comprising nickel, cobalt, and tungsten.

Next, this copper foil was washed with water, and a chromium solution containing 3.5 g/L of sodium dichromate adjusted to pH 5.4 and bath temperature of 28° C. was applied on the first and second composite metal layers. , the surface of the copper foil on the cathode side was plated at a current density of 0.9 A/dm ² to form a chromate treatment layer.

Further, this copper foil was washed with water, and the chromate treated layer was immersed in a silane coupling agent solution containing 0.25 wt % 3-aminopropyltriethoxysilane for 10 seconds to form a silane coupling agent treated layer. Thus, a surface-treated copper foil of Example 1 was obtained.

[Examples 2 to 4]
As shown in Table 1, under the same conditions as in Example 1, except that the current density of the second plating treatment was changed to 1.1 A/dm ² , 1.2 A/dm ² and 1.4 A/dm ² . The electrolytic copper foil was treated to obtain surface-treated copper foils of Examples 2-4.
[Example 5]
As shown in Table 1, the surface-treated copper foil of Example 5 was obtained by treating the electrolytic copper foil under the same conditions as in Example 3, except that the first plating treatment was not performed.

[Comparative Examples 1 to 4]
As shown in Table 1, except that the current density of the second plating treatment was changed to 1.6 A/dm ² , 1.9 A/dm ² , 2.5 A/dm ² and 0.5 A/dm ² , Electrolytic copper foils were treated under the same conditions as in Example 1 to obtain surface-treated copper foils of Comparative Examples 1-4.

[Comparative Example 5]
As shown in Table 1, the electrolytic copper foils were treated under the same conditions as in Example 1, except that the second plating treatment was not performed, to obtain surface-treated copper foils of Comparative Examples 1 to 5.

The plating time in each example and comparative example was adjusted in the range of 0.0 to 8.0 seconds while adjusting the adhesion amount.

For the surface-treated copper foils of Examples 1 to 5 and Comparative Examples 1 to 5, the amounts of the components Ni, Co, and W adhered to the adherend surface of the surface-treated copper foil were measured by the method described below. The color tone, etching resistance, and appearance of treatment unevenness and air bubble traces on the adherend surface of the surface-treated copper foil were evaluated.

(1) Measurement of adhesion amount The adhesion amount (μg/dm ² ) on the adherend surface of the surface-treated copper foil was measured using a scanning fluorescent X-ray spectrometer (manufactured by Rigaku, product number ZSX Primus IVi). Table 1 shows the adhesion amount of each component of Ni, Co, and W, and the total amount thereof.

(2) Measurement of color tone The color tone of the adherend surface of the surface-treated copper foil is measured using a color difference meter (manufactured by Konica Minolta, product number CR-400), and L ^* a ^* b ^* table in accordance with JIS Z 8781. The L ^* value, a ^* value, and b ^* value of the color system were measured. Table 2 shows the results.

(3) Etching resistance The adherend surface of the surface-treated copper foil is laminated to a laminate film (BH907, manufactured by Asuka Co., Ltd.) using a laminator (LPD3226N, manufactured by Fujipla Co., Ltd.) to form a copper-clad laminate, and a test piece is prepared. made. This test piece was immersed in a 40% aqueous solution of ferric chloride for 10 minutes and etched to form a wiring with a width of 1 mm. In this process, when the copper foil wiring was peeled off, it was evaluated as "×", and when it was not peeled off, it was evaluated as "◯". After etching, a residue of 1 μm or more in width at the end of the wiring was evaluated as “×”, and a “◯” was given when there was no residue of 1 μm or more in width. Table 2 shows the results.

(4) Appearance The appearance of the adherend surface of the surface-treated copper foil was evaluated from the viewpoint of treatment unevenness and air bubble marks. For the evaluation of uneven processing, a digital camera was used to observe the surface of the surface-treated copper foil to be adhered, and the uneven processing of the image shown in FIG. "X" was given, and weaker cases were given "O". For evaluation of bubble traces, a magnified image (field of view 6 mm x 8 mm) was taken using a USB camera, and when bubble traces with a diameter of 50 µm or more were present, it was marked as "x", and no bubble traces with a diameter of 50 µm or more were present. The case was marked as “〇”. Table 2 shows the results.

As shown in Tables 1 and 2, each of the surface-treated copper foils ^of Examples 1 to 5 has an L ^* value of 65 or less, an a ^* value of 10 or less, and a b ^* value of 10 or less in the L ^* a*b ^* color system. The value was 10 or less, indicating a blackish color tone that can be used for display devices. In particular, in Example 4, the color tone values L ^* , a ^* , and b ^* were lower, and the possibility of reflection when used as a display device was low. In the evaluation of etching resistance, no residue or peeling occurred in any of the surface-treated copper foils of Examples 1-5. Furthermore, in the evaluation of the appearance, any of the surface-treated copper foils of Examples 1 to 5 had no bubble traces or treatment unevenness. In particular, in comparison with Example 5 in which the first plating treatment was not performed, Examples 1 to 4 in which the first plating treatment was performed had lower a ^* values and b ^* values and were superior in color tone.

On the other hand, in the surface-treated copper foils of Comparative Examples 1 to 3, since the current density of the second plating treatment is high, the adhesion amount of each component increases, and in the evaluation of color tone, L ^* value, a ^* value, b The ^* values were generally lower than those of Examples 1 to 4, and while there was no problem with color tone, the increased amount of adhesion reduced the solubility in the etchant, resulting in the formation of residues after etching. In addition, since hydrogen gas was more likely to be generated on the copper foil side during the plating process by increasing the current density, bubble traces and uneven processing occurred in the appearance evaluation. In particular, in all of the surface-treated copper foils of Comparative Examples 1 to 3, there were 10 or more bubble traces per 1 m ² .

In the surface-treated copper foil of Comparative Example 4, since the current density of the second plating treatment is low, the amount of each component adhered is reduced, and in the evaluation of color tone, the L ^* value greatly exceeds 65, and the color tone is blackish. could not get Furthermore, the decrease in the adhesion amount increased the solubility in the etchant, and the copper foil was peeled off during etching. On the other hand, by lowering the current density, it became difficult for hydrogen gas to be generated on the copper foil side during the plating process.

Since the surface-treated copper foil of Comparative Example 5 was not subjected to the second plating treatment, the L ^* value greatly exceeded 65 in the color tone evaluation, and a black color tone could not be obtained. In addition, peeling of the copper foil was found in the evaluation of the etching resistance.

10 surface-treated copper foil 13 copper foil layer (electrolytic copper foil)
REFERENCE SIGNS LIST 14 blackened layer 20 touch panel 21 transparent substrate film 22 adhesive layer

Claims (4)

A surface-treated copper foil comprising an electrolytic copper foil and a blackening treatment layer covering one surface side of the electrolytic copper foil,
The blackened layer is a composite metal layer containing copper, nickel, cobalt, and tungsten,
Surface-treated copper having a nickel deposition amount of 120 to 400 μg/dm ² , a cobalt deposition amount of 400 to 700 μg/dm ² , and a tungsten deposition amount of 70 to 200 μg/dm ² in the blackened layer. foil. 2. The surface-treated copper foil according to claim 1, wherein the total amount of nickel, cobalt, and tungsten in the blackened layer is 700 to 1200 μg/dm ² . The surface of the surface-treated copper foil on the blackened layer side has an L* value of 55.0 to 65.0 and an ^{a* value} of 0.0 to 10 in the L ^* a ^* b ^* color system. .0, and a b ^* value of 0.0 to 10.0. A surface-treated copper foil free from 10 or more bubble traces with a diameter of 50 μm or more per 1 m ² on the surface of the surface-treated copper foil on the side of the blackened layer.

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