JP6757773B2 - Electrolytic copper foil - Google Patents

Description

The present invention relates to an electrolytic copper foil suitable for manufacturing, for example, a lithium ion secondary battery negative electrode current collector, a printed wiring board, and the like.

A printed wiring board (hereinafter, simply referred to as a "wiring board") used in a negative electrode current collector of a lithium ion secondary battery (hereinafter, may be simply referred to as a "battery") and various electronic devices represented by electronic communication devices. Copper foil is widely used for the conductor portion of). In particular, as compared with rolled copper foil, electrolytic copper foil, which is easy to achieve both conductivity and strength and can be thinned at low cost, is widely used.

By the way, various stresses are applied to the copper foil during the manufacture of the lithium ion secondary battery and the charging / discharging of the battery. As a result, the copper foil may be broken such as wrinkles or breaks, and problems such as deterioration of battery cycle characteristics, short circuit, and ignition may occur. In response to such problems, for example, in a lithium ion secondary battery, the tensile strength of the copper foil is set to a predetermined value or more, the tensile strength after heating is set to a predetermined value or more, or the elongation of the copper foil is set to a predetermined value or more. Etc., methods for improving physical properties have been proposed (Patent Documents 1 to 3).

Further, in recent years, the structure of the lithium ion secondary battery has changed as compared with the conventional one with the further increase in capacity and weight reduction of the lithium ion secondary battery. For example, copper foil is increasingly subjected to folding in order to house the electrodes in the battery housing at a higher density.

Specifically, in a cylindrical battery, in order to prevent unwinding and ensure safety at the electrode terminations of the innermost layer and the outermost layer, a separator or, in some cases, a positive electrode aluminum foil is sandwiched between copper foils and folded back. Folding may be performed.
Further, in the square type and laminated type batteries, the electrodes are conventionally folded back to 180 ° (corresponding to FIG. 4 of Patent Document 4, the curved corner portion 12), but in recent years, due to the increase in density, Severe folding processing, such as applying greater tension to the electrodes to make them tightly rotate, pressing after the electrodes to reduce the bending radius, and rotating the electrodes to a range with a smaller bending radius on the inner layer side. May be done.

On the other hand, various electronic devices represented by mobile devices have been rapidly reduced in size and density in recent years, and there is a demand for compact and high-density component storage for mounted members. In particular, in a flexible printed circuit board, the copper foil has been subjected to a folding process in order to house the conductor portion in a narrower housing.

However, such a fold folding process has a problem of causing breakage such as cracks and breaks in the copper foil, and in order to avoid such a problem, development of a copper foil having high durability against the fold fold process Is required.

Here, the "folding process" refers to a bending process in which the surface of the copper foil is folded back at 180 °. It should be noted that such a folding process does not necessarily have to be a close-contact bending, and another member may be sandwiched inside the bent portion. Further, in the following, the durability of the copper foil against such a fold-folding process will be referred to as "fold-folding resistance".

In general, the MIT folding resistance test and the IPC bending test specified in JIS P 8115: 2001 are often used to evaluate the bending property and folding resistance of copper foil. For example, in the MIT folding resistance test, a copper foil is repeatedly bent at a high speed of ± 135 ° under a load, and the number of times of bending is evaluated. In this method, a copper foil having a higher tensile strength tends to be evaluated as having a good folding resistance because the number of times of bending until breaking or an increase in electrical resistance increases. Further, in the IPC bending test, although the bending is 180 °, the bending radius is relatively large, and the bending is applied in the elastic deformation region of the copper foil. In this method, in many cases, the number of bends is evaluated until the electric resistance increases beyond a certain level without breaking.

On the other hand, the fold-folding test is a test by bending at 180 °, and the bending radius is smaller than that of the MIT folding resistance test or the like, and bending is applied in the plastic deformation region of the copper foil. Therefore, the fold resistance is a measurement method of a load mode completely different from the MIT fold resistance test and the IPC bending test, and the test results do not necessarily correspond to each other. Therefore, a copper foil having improved fold resistance in the MIT fold resistance test as disclosed in Patent Document 5 or a copper foil having improved flexibility in the IPC bending test as disclosed in Patent Document 6 can be used. Even if it exists, it cannot be said that it has sufficient fold resistance.

The copper foil folding test is a bending test involving 180 ° bending, but the phenomenon is different from, for example, 180 ° bending of a copper strip or a copper plate having a thickness of more than 50 μm. That is, since the copper foil is very thin (for example, 4 to 30 μm), the number of crystal grains existing in the thickness direction is small, and the compressive stress and tensile stress inside and outside the bending are large. Since the difference is small, it has features that are not found in relatively thick copper products.

In addition, the fold resistance does not correspond to the elongation of the copper foil. For example, in Patent Document 7, assuming that there is a copper foil having a large elongation but poor fold resistance, there is a technique for achieving both tensile strength and fold resistance by controlling the crystal orientation and work hardening index. It is disclosed. However, this technique relates to rolled copper foil, and the relationships generally known in copper products such as the relationship between crystal orientation and bendability cannot be simply applied to electrolytic copper foil. That is, since the electrolytic copper foil has an electrolyzed structure, it is significantly different from the rolled structure in terms of pore density, dislocation density, diffusion coefficient and the like.

Further, in order to solve the above problems, for example, in Patent Document 8 relating to a printed wiring board, the elastic modulus and thickness of the resin layer to be bonded to the metal layer (copper foil) are set within a certain range, and the surface roughness of the metal layer is roughened. In Patent Document 9, the method of setting the value to a predetermined value or less is patented, and the method of keeping the tensile elastic modulus and thickness of the polyimide layer and the tensile elastic modulus, thickness and average crystal grain size of the copper foil within a certain range is patented. Document 10 proposes methods for controlling the thickness, average crystal grain size, and crystal orientation of each copper foil when the copper foils are bonded to both sides of the polyimide layer within a predetermined range. However, these measures greatly contribute to the characteristics of the resin side and the structure as a copper-clad laminate, and the characteristics of the copper foil side have not been sufficiently examined, and improvement of the characteristics of the copper foil side is desired. Was there. If the fold resistance can be improved only by the characteristics of the copper foil side, the degree of freedom in resin selection and board design will increase, so it will be possible to use resin with higher signal transmission performance and more efficient board design. This is because further improvement in performance as a flexible printed circuit board can be expected.

On the other hand, it is generally known that it is effective to reduce the tensile strength of the copper foil as a method for improving the fracture resistance of the copper foil, but the tensile strength can be unnecessarily reduced. There wasn't. That is, in the lithium ion secondary battery, as described above, it is desired that the tensile strength of the copper foil and the tensile strength after heating be constant or higher in terms other than the fracture resistance. This is because, in a flexible substrate, if the tensile strength of the copper foil is low, the handleability in the process of passing the plate or in the process of casting the resin deteriorates in the production of the flexible printed circuit board, which is becoming thinner.

As described above, since the improvement of the fracture resistance and the improvement of the tensile strength of the copper foil are contradictory requirements, the conventional copper foil has a high tensile strength and a tensile strength even after heating. It was difficult to maintain a high level and achieve good fold resistance.

Japanese Patent No. 5588607 Japanese Patent No. 5074611 Japanese Patent No. 4583149 Japanese Patent No. 4863636 Japanese Patent No. 5301886 Japanese Patent No. 5373970 International Publication No. 2012/1280999 Pamphlet Japanese Unexamined Patent Publication No. 2012-006200 Japanese Unexamined Patent Publication No. 2014-080021 JP-A-2015-127120

The present invention has been made in view of the above circumstances, and provides an electrolytic copper foil capable of maintaining high tensile strength even after heating and achieving good fold resistance while having high tensile strength. The purpose is.

As a result of intensive studies on the relationship between the trace components contained in the copper foil and the crease resistance and tensile strength, the present inventors have found that sulfur (S) or nitrogen (N) in the copper foil has been determined. Although the effect of improving the tensile strength is large, the foldability is significantly reduced as the content increases, while carbon (C) and chlorine (Cl) in the copper foil have a large effect of improving the tensile strength. However, even if the content is increased, the fracture resistance is not significantly reduced, and the degree of decrease in the fracture resistance is gradual as compared with sulfur (S) or nitrogen (N). Based on this finding, the contents of carbon (C), sulfur (S), nitrogen (N) and chlorine (Cl), which are trace components contained in the copper foil, are controlled within predetermined ranges. As a result, we succeeded in achieving both excellent fold resistance and high tensile strength, and completed the present invention.

That is, the gist structure of the present invention is as follows.
[1] The content of carbon (C) is 20 to 150 mass ppm, the content of sulfur (S) is 18 mass ppm or less, the content of nitrogen (N) is 40 mass ppm or less, and the content of chlorine (Cl). Is an electrolytic copper foil, characterized in that the amount is 25 to 200 mass ppm.
[2] The ratio of the carbon (C) content to the chlorine (Cl) content [C content / Cl content] is in the range of 0.70 to 1.40, as described in [1]. ] The electrolytic copper foil described in.
[3] The electrolytic copper foil according to the above [1] or [2], wherein the tensile strength measured under normal conditions is in the range of 380 to 600 MPa.
[4] The electrolytic copper foil according to any one of the above [1] to [3], wherein the tensile strength measured in a state after heating at 300 ° C. for 1 hour is in the range of 300 to 550 MPa.
[5] The electrolytic copper foil according to any one of the above [1] to [4], which has a conductivity of 85% IACS or more.
[6] A lithium ion secondary battery having the electrolytic copper foil according to any one of the above [1] to [5] as a negative electrode current collector.
[7] A printed wiring board having the electrolytic copper foil according to any one of the above [1] to [5] as a conductor portion.

According to the present invention, it is possible to provide an electrolytic copper foil which has high tensile strength, maintains high tensile strength even after heating, and can realize good fold resistance. The electrolytic copper foil of the present invention is an electrolytic copper foil that is suitably used, for example, when manufacturing a negative electrode current collector for a lithium ion secondary battery, and can improve the capacity, cycle characteristics, and safety of the battery. Further, for example, it is an electrolytic copper foil that is suitably used when manufacturing a printed wiring board, and can improve the handling property at the time of manufacturing the wiring board and the durability at the time of folding the flexible printed circuit board.

FIG. 1 is a schematic cross-sectional view schematically showing a state when a folding test is performed in an example.

Hereinafter, preferred embodiments of the electrolytic copper foil of the present invention will be described in detail.
The electrolytic copper foil according to the present invention has a carbon (C) content of 20 to 150 mass ppm, a sulfur (S) content of 18 mass ppm or less, a nitrogen (N) content of 40 mass ppm or less, and chlorine ( The content of Cl) is 25 to 200 mass ppm.

In the present specification, the electrolytic copper foil refers to a copper foil produced by electrolytic treatment, and includes untreated copper foil which has not been surface-treated after foil formation and copper foil which has been surface-treated as necessary. It means to include any of (surface-treated electrolytic copper foil). The thickness of the electrolytic copper foil is preferably 30 μm or less, more preferably 4 to 15 μm. In the following, unless otherwise specified, "copper foil" means "electrolytic copper foil". Further, mass ppm is a mass fraction and refers to mg / kg.

<Ingredient composition>
The component composition of the electrolytic copper foil of the present invention and its action are shown.
In the electrolytic copper foil of the present invention, the contents of carbon (C), sulfur (S), nitrogen (N) and chlorine (Cl) are all controlled within the predetermined ranges shown below.

[S content: 18 mass ppm or less] and [N content: 40 mass ppm or less]
S and N are elements having an action of improving tensile strength, but on the other hand, these elements tend to make the grain boundaries of the copper foil brittle, which significantly reduces the crease resistance.

When the S content exceeds 18 parts by mass ppm, the crease resistance is extremely deteriorated. Therefore, the S content is 18 mass ppm or less, preferably 13 mass ppm or less. The smaller the S content, the more preferable, and the lower limit is 0 mass ppm, but from the viewpoint of practicality, it may be 1 mass ppm or more.

When the N content exceeds 40 mass ppm, the fold resistance is extremely deteriorated. Therefore, the N content is 40 mass ppm or less, preferably 30 mass ppm or less. Further, the smaller the N content is, the more preferable it is, and the lower limit value is 0 mass ppm. From the viewpoint of practicality, it may be 1 mass ppm or more.

[C content: 20 to 150 mass ppm] and [Cl content: 25 to 200 mass ppm]
C and Cl are elements having an action of improving the tensile strength, but unlike the cases of S and N described above, the action of brittle the grain boundaries of the copper foil is small, and the fracture resistance is remarkably lowered. There is no.

If the C content is less than 20 mass ppm, the effect of improving the tensile strength is not sufficiently exhibited, and if it exceeds 150 mass ppm, the fold resistance tends to decrease. Therefore, from the viewpoint of achieving both tensile strength and fracture resistance, the C content is set to 20 to 150 mass ppm, preferably 30 to 140 mass ppm, and more preferably 60 to 140 mass ppm.

If the Cl content is less than 25 mass ppm, the effect of improving the tensile strength is not sufficiently exhibited, and if it exceeds 200 mass ppm, the fold resistance tends to decrease. Therefore, from the viewpoint of achieving both tensile strength and fracture resistance, the Cl content is set to 25 to 200 mass ppm, preferably 30 to 180 mass ppm, and more preferably 50 to 150 mass ppm.

Further, the ratio of the C content to the Cl content [C content / Cl content] is preferably in the range of 0.70 to 1.40, and by setting the above range, the copper foil The effect of improving the folding resistance can be further enhanced. It is known that Cl is required to effectively adsorb the organic additive to the copper foil. Although the mechanism is not necessarily clear, Cu + ^- complex organic additives, Cl are specifically adsorbed to the copper base surface ^- electrostatically adsorbed on, as a result, Cl ^- through the Cu ⁺ - It is said that the complex of the organic additive is adsorbed on the copper substrate. Then, when Cu ⁺ indirectly adsorbed on the copper substrate is reduced to Cu atoms and precipitated on the copper substrate, the organic additives (C) and Cl adsorbed together are also simultaneously adsorbed on the copper foil. It is considered to be taken in. Therefore, if the balance of the abundance ratios of C and Cl is lost, the abundance state of C and Cl in the copper foil changes, and it is considered that the effect of improving the crease resistance of the copper foil cannot be sufficiently obtained.

[Other trace components]
The electrolytic copper foil of the present invention may contain components derived from various additives and unavoidable impurities in addition to the above-mentioned components as long as the effects of the present invention are not impaired.
The components derived from the various additives referred to here mean components other than the above-mentioned components among the components derived from the organic additives and inorganic additives used in the production of the electrolytic copper foil. The upper limit of the content of the components derived from such various additives is preferably 100 mass ppm or less.
Further, the unavoidable impurities referred to here mean impurities at a content level that can be unavoidably contained in the manufacturing process. Examples of the components listed as unavoidable impurities include iron (Fe) and oxygen (O). The upper limit of the content of unavoidable impurities is preferably 100 mass ppm or less. Depending on the component and content of unavoidable impurities, it may be a factor that deteriorates the characteristics of the copper foil, so it is preferable to further suppress the content.

<Manufacturing method of electrolytic copper foil>
Next, a preferable manufacturing method of the electrolytic copper foil (or surface-treated electrolytic copper foil) of the present invention will be described.
The electrolytic copper foil of the present invention has, for example, an insoluble anode made of titanium coated with a platinum group element or an oxide element thereof using a sulfuric acid-copper sulfate aqueous solution as an electrolytic solution, and a titanium cathode provided so as to face the anode. The electrolytic solution is supplied between the drum and the cathode drum, and while rotating the cathode drum at a constant speed, copper is deposited on the surface of the cathode drum by applying a DC current between the two electrodes, and the precipitated copper is deposited from the surface of the cathode drum. Manufactured by a method of peeling and continuously winding. The example of this device is an example.

In particular, the electrolytic copper foil of the present invention is produced under the condition that S and N are not brought into the produced copper foil as much as possible, so that the content of nitrogen (S) in the copper foil is 18 mass ppm or less. It is possible to realize a state in which the nitrogen (N) content is 40 mass ppm or less.

Usually, in order to increase the strength and heat resistance of the copper foil, it is common to add an additive to the electrolytic solution. Examples of such additives include organic additives and inorganic additives, and organic additives are particularly preferably used. Many of these commonly used organic additives contain S or N in their molecular structure. Organic additives containing S or N in their molecular structures are very well incorporated into the copper foil due to their strong adsorptivity to the copper foil. This is believed to be due to the unshared electron pair of S and N.

Therefore, from the viewpoint of obtaining a copper foil in which the contents of S and N in the copper foil are controlled within a predetermined range as described above, it is preferable to use an organic additive that does not contain S and N in the molecular structure. By using such an organic additive, it is possible to effectively prevent S and N derived from the organic additive from being incorporated into the copper foil.

Examples of organic additives that do not contain S and N in their molecular structure include polyethers (polyethylene glycol, polypropylene glycol, etc.), water-soluble polysaccharides (hydroxyethyl cellulose, carboxymethyl cellulose, etc.) and the like. In particular, considering the mass productivity of the electrolytic copper foil, a polymer compound which tends to have higher stability in an electrolytic solution is preferable to a single molecule compound.

From the viewpoint of obtaining a copper foil in which the contents of S and N in the copper foil are controlled within a predetermined range as described above, a method of using an inorganic additive that does not contain S and N in the molecular structure can be considered. However, when an inorganic additive is used, the inorganic additive may precipitate in the electrolytic solution, which deteriorates mass productivity, lowers the conductivity, and does not maintain good fold resistance. Therefore, it is preferable to use the above-mentioned organic additive as the additive.

Furthermore, by using an organic additive that does not contain S and N in the molecular structure as described above, the content of S and N in the obtained copper foil can be controlled within the above range, but further, in the copper foil. From the viewpoint of reducing the S and N contents, the S and N concentrations in the electrolytic solution are reduced as much as possible, for example, by selecting a high-purity reagent and activated carbon type, and pickling the copper raw material before charging. It is preferable to use the method of

Sulfuric acid and copper sulfate reagents used in the preparation of electrolytic solutions and reagent for additives may contain S and N as impurities. In addition, some deposits or impurities of copper raw materials and activated carbon (used in the activated carbon treatment performed during the production of electrolytic copper foil) also contain S and N. Of these, compounds with high reactivity and adsorptivity are appropriately removed by activated carbon treatment and decomposed by electrolytic reaction, so it is unlikely that they will be concentrated in the electrolytic solution, but they are relatively low in reactivity. It is also conceivable that the compound slowly accumulates in the electrolytic solution. Therefore, it is considered that the degree of influence is smaller than that of S and N derived from organic additives that are intentionally added, but S and N derived from reagents, activated carbon, etc. are also removed as much as possible. Is desirable.

Even if these treatments are performed, it is difficult to completely remove impurities containing S and N from the electrolytic solution, and the work load becomes large in keeping the concentration of S and N in the electrolytic solution at zero. Therefore, when considering the actual production, the contents of S and N in the copper foil may be 1 mass ppm or more, respectively, from the viewpoint of practicality. That is, if the S content is 18 mass ppm or less and the N content is 40 mass ppm or less, the foldability is not significantly impaired.

Further, the electrolytic copper foil of the present invention is produced under the condition that the produced copper foil contains appropriate amounts of C and Cl, so that the content of carbon (C) in the copper foil is 20 to 150 mass ppm. It is possible to realize a state in which the chlorine (Cl) content is in the range of 25 to 200 mass ppm.

In general, in order to increase the strength and heat resistance of a copper foil, it is desirable that a large amount of organic additives are incorporated into the copper foil (for example, a large C content). However, the organic additive containing S and N has a lower adsorptivity to copper than the organic additive containing S or N, so that the amount incorporated into the copper foil tends to be smaller. Therefore, in order to increase the content of C and Cl in the copper foil to the extent that the copper foil can be made stronger and more heat resistant by using an organic additive containing no S and N, for example, in an electrolytic solution. It is effective to adjust the chloride ion (Cl ⁻ ) concentration. This is because it is known that chloride ions in the electrolytic solution interact with the organic additive to facilitate the incorporation of the organic additive into the copper foil. On the other hand, if the amount of C and Cl incorporated into the copper foil is too large, the crease resistance tends to deteriorate.

Therefore, as described above, from the viewpoint of obtaining a copper foil in which the contents of C and Cl in the copper foil are controlled within a predetermined range, it is preferable to control the concentration of chloride ions in the electrolytic solution. Specifically, the chloride ion concentration in the electrolytic solution is preferably 150 to 250 mg / L, more preferably 150 to 200 mg / L. Within the above range, the contents of C and Cl in the copper foil can be efficiently controlled. On the other hand, when the chloride ion is less than 150 mg / L, the amount of C and Cl contained in the copper foil becomes small, and it is difficult to obtain the effects of high strength and high heat resistance. Further, when the chloride ion exceeds 250 mg / L, the amount of C and Cl taken into the copper foil increases, and the fracture resistance deteriorates.

Further, the [C content / Cl content] in the copper foil can be basically controlled by the ratio of the organic additive concentration and the chloride ion concentration in the electrolytic solution, but is in a suitable concentration ratio range. Can be adjusted as appropriate according to other influences such as the type of organic additive.

The following is an example of a preferable composition of the electrolytic solution for producing an electrolytic copper foil.
Copper concentration 50-100g / L
Sulfuric acid concentration 40-120 g / L
Organic additive 0.1 to 100 mg / L
Chloride ion 150-250 mg / L

As described above, it is important to manufacture the foil under the conditions that S and N are not incorporated into the foil as much as possible and that C and Cl can be incorporated in an appropriate amount. For that purpose, organic additives are intended. It is preferable and effective to appropriately control the electrolytic conditions so that the electrolytic conditions are taken in in a state of being taken in.

Usually, a thyristor type DC power supply is generally used for manufacturing copper foil. In principle, the thyristor type DC power supply vibrates (ripples) at an output voltage of 50 or 60 Hz. For example, in the case of a thyristor type DC power supply having a ripple rate of 10%, voltage vibration with a maximum height difference of 10% occurs at 100 or 120 times per second.

Such ripples are known to have a very large effect on potential-responsive reactions such as the adsorption and uptake behavior of organic additives and the precipitation behavior of copper. However, it is extremely difficult to clarify, and in general, copper foil is not manufactured in consideration of the influence of ripple. As a result, due to the influence of ripple, the organic additive may not be taken in efficiently, abnormal segregation may be caused at the grain boundary, or depending on the organic additive, it may be taken in excessively.

Therefore, in the production of the electrolytic copper foil of the present invention, it is preferable to adjust the electrolytic conditions so that the original adsorption behavior of the organic additive appears under the condition of little disturbance. Specifically, it is desirable to manufacture the electrolytic copper foil under electrolytic conditions that do not generate ripples due to the power supply voltage as much as possible, and for example, it is preferable to manufacture the electrolytic copper foil using an inverter type DC power supply.

Since the inverter type DC power supply is controlled in a higher frequency region in principle, it can be considered that there is substantially no influence of ripple. Therefore, by using the inverter type DC power supply, it is possible to easily adjust the situation where there is little disturbance with respect to the organic additive.

Also, even when using a thyristor type DC power supply, electrolysis is performed under conditions with as little ripple as possible, and by selecting additives and electrolysis conditions that are not easily affected by ripple, electrolytic conditions that are less affected by ripple are used. Can be.

In the present invention, it is recommended to use an organic additive that does not contain S and N so that S and N are not incorporated into the copper foil formed as described above as much as possible. Such an organic additive Has a relatively weak adsorption to copper. Therefore, under the influence of ripple as described above, the organic additive is less likely to be incorporated into the copper foil, which is not desirable from the viewpoint of increasing the strength and heat resistance of the copper foil. However, as described above, by performing electrolysis in a manner that minimizes ripple, the organic additive can be efficiently contained in the copper foil even when an organic additive that does not contain S and N is used. And a relatively uniform structure is obtained.

In addition, the temperature of the electrolytic solution is preferably 40 to 60 ° C., and the average current density on the cathode electrode surface is preferably 45 to 60 A / dm ² .

Further, it is preferable that the electrolytic copper foil of the present invention is surface-treated on at least one of its surfaces, if necessary.
The surface treatment of the copper foil includes, for example, chromate treatment, Ni or Ni alloy plating, Co or Co alloy plating, Zn or Zn alloy plating, Sn or Sn alloy plating, and further chromate treatment on the above-mentioned various plating layers. Examples thereof include inorganic rust preventive treatment for things, organic rust preventive treatment such as benzotriazole, and silane coupling agent treatment. In addition to rust prevention, these surface treatments have the role of increasing the adhesion strength with the active material when used as the negative electrode current collector of a lithium ion secondary battery, and further preventing the battery charge / discharge cycle efficiency from decreasing. Fulfill. These rust preventive treatments are generally treated with a thickness very thin with respect to the thickness of the copper foil. Therefore, there is almost no effect on the crease resistance and tensile strength.

It is also possible to roughen the surface of the copper foil, if necessary, before applying the above surface treatment to the copper foil. As the roughening treatment, for example, a plating method, an etching method, or the like can be preferably adopted. These roughening treatments improve the adhesion with the wiring board resin when used as the conductor part of the printed wiring board, and the adhesion with the active material when used as the negative electrode current collector of the lithium ion secondary battery. , Play a role in further improvement.

As the roughening by the plating method, an electrolytic plating method and an electroless plating method can be adopted. Roughened particles can be formed by metal plating consisting of one metal of Cu, Co and Ni, or alloy plating containing two or more of these metals.

Further, as the roughening by the etching method, for example, a method by physical etching or chemical etching is preferable. For example, as the physical etching, a method of etching by sandblasting or the like can be mentioned. Further, as the chemical etching, a method of etching with a treatment liquid or the like can be mentioned. In particular, in the case of chemical etching, a known treatment liquid containing an inorganic or organic acid, an oxidizing agent, and an additive can be used as the treatment liquid.

<Characteristics of electrolytic copper foil>
Under normal conditions, the electrolytic copper foil according to the present invention preferably has a tensile strength of 380 MPa or more, more preferably 380 to 600 MPa, and even more preferably 400 to 600 MPa. Within the above range, handleability and durability during manufacturing of batteries and wiring boards are further improved. In addition, in the present specification, the "normal state" means that the copper foil is in an unheated state as it is manufactured and also in a state where it has undergone a heat history of 60 ° C. or lower.

Further, the electrolytic copper foil according to the present invention preferably has a tensile strength of 300 MPa or more, more preferably 300 to 550 MPa, still more preferably 350 to 550 MPa in a state after heating at 300 ° C. for 1 hour. Is. Within the above range, handleability and durability during manufacturing of batteries and wiring boards are further improved.

The tensile strength is a value measured in accordance with IPC-TM-650.

Further, the electrolytic copper foil according to the present invention preferably has a conductivity of 85% IACS or more, and more preferably 90% IACS or more. In general, increasing the strength of the electrolytic copper foil tends to lower the conductivity, but in the electrolytic copper foil of the present invention, the decrease in conductivity can be reduced by incorporating a large amount of C and Cl to increase the strength. Since the electrolytic copper foil of the present invention is used as a conductive member, it is desirable that the electrolytic copper foil has a high conductivity. The above conductivity shall be a value measured in accordance with JIS H 0505: 1975.

The electrolytic copper foil according to the present invention is preferably used for manufacturing at least one of a negative electrode current collector of a lithium ion secondary battery and a conductor portion of a printed wiring board. In particular, when used as a negative electrode current collector for a lithium ion secondary battery, it has high strength and high heat resistance, so it has excellent durability during battery manufacturing and charging / discharging, and has excellent fold resistance. This has the advantage of enabling high-density electrode storage. In addition, when used as a conductor part of a printed wiring board, it has high strength and high heat resistance, so it has excellent handleability when manufacturing a printed wiring board, and it has excellent fold resistance, so it can be mounted at a higher density. There is an advantage of becoming. Further, the electrolytic copper foil according to the present invention can be more preferably used for both the negative electrode current collector of the lithium ion secondary battery and the conductor portion of the printed wiring board, and such a highly versatile copper foil is copper. Foil production also has the advantage of being extremely economical because it does not require switching of production conditions or a separate production line.

Although the embodiments of the present invention have been described above, the above-described embodiments show an example of the present invention, and include all aspects included in the concept of the present invention and the scope of claims, and are within the scope of the present invention. Can be modified in various ways.

Next, in order to further clarify the effect of the present invention, Examples , Reference Examples and Comparative Examples will be described.

(Example 1)
An electrolytic solution is supplied between an insoluble anode made of titanium coated with a platinum group element or an oxide element thereof and a titanium cathode drum provided so as to face the anode, and the cathode drum is rotated at a constant speed while rotating. An untreated copper foil having a thickness of 8 μm was produced by depositing copper on the surface of the cathode drum by applying a DC current between the two electrodes.

As the electrolytic solution, a sulfuric acid-copper sulfate-based electrolytic solution having an adjusted copper concentration of 80 g / L and a sulfuric acid concentration of 80 g / L was used. Further, in the electrolytic solution, the additives and their concentrations and the chloride ion (Cl ⁻ ) concentration are adjusted as shown in Table 1, and the DC power supply shown in Table 1 is used as the rectifier, and the temperature of the electrolytic solution is 50. The temperature and current density were adjusted to 40 A / dm ² , and the liquid flow velocity was adjusted to 1.0 m / s.

Further, the untreated copper foil produced under the above conditions was subjected to chromate treatment immediately after the foil formation. Specifically, the untreated copper foil was immersed in a 7 g / L chromic anhydride aqueous solution at 45 ° C. for 5 seconds, and then drained and air-dried.

(Examples 2 to 6 and 8, Reference Example 1 )
In Examples 2 to 6 and 8, in Reference Example 1 , one or more of the conditions of the additive and the chloride ion and the condition of the DC power supply used as the rectifier were changed as shown in Table 1. A copper foil was prepared in the same manner as in Example 1.

(Examples 6 and 7 )
In Examples 6 and 7 , copper was subjected to the same method as in Example 1 except that the conditions of the additive and chloride ion were changed as shown in Table 1 and further roughened under the conditions shown below. A foil was made. The roughening treatment was carried out with a copper concentration of 30 g / L, a sulfuric acid concentration of 180 g / L, a bath temperature of 25 ° C., a current density of 40 A / dm ² , and a treatment time of 4 seconds.

(Comparative Examples 1 to 9)
In Comparative Examples 1 to 9, copper was used in the same manner as in Example 1 except that the conditions of additives and chloride ions and one or more of the DC power supplies used as the rectifier were changed as shown in Table 1. A foil was made.

(Comparative Example 10)
In Comparative Example 10, a sulfuric acid-copper sulfate-based electrolytic solution in which the copper concentration was adjusted to 80 g / L and the sulfuric acid concentration was adjusted to 140 g / L was used, and the additives, their concentrations, and the chloride ion concentration were shown in Table 1 Adjust as shown in, and use the DC power supply shown in Table 1 as the rectifier, adjust the temperature of the electrolytic solution to 50 ° C, the current density to 52 A / dm ² , and the liquid flow velocity to 0.4 m / s, and untreated. A copper foil was prepared in the same manner as in Example 1 except that the copper foil was produced. In addition, this comparative example corresponds to Example 1 described in Patent Document 5.

(Comparative Example 11)
In Comparative Example 11, a copper foil was produced in the same manner as in Comparative Example 10 except that the DC power supply used as the rectifier was changed as shown in Table 1.

(Comparative Example 12)
In Comparative Example 12, a sulfuric acid-copper sulfate-based electrolytic solution in which the copper concentration was adjusted to 70 g / L and the sulfuric acid concentration was adjusted to 100 g / L was used, and the additives, their concentrations, and the chloride ion concentration were shown in Table 1 Adjust as shown in, and use the DC power supply shown in Table 1 as the rectifier, adjust the temperature of the electrolytic solution to 40 ° C, the current density to 50 A / dm ² , and the liquid flow velocity to 0.4 m / s, and untreated. A copper foil was prepared in the same manner as in Example 1 except that the copper foil was produced. In addition, this comparative example corresponds to Example 5 described in Japanese Patent No. 4796351.

(Comparative Example 13)
In Comparative Example 13, a copper foil was produced in the same manner as in Comparative Example 12, except that the DC power supply used as the rectifier was changed as shown in Table 1.

Among the types of additives listed in Table 1, "HEC1" is hydroxyethyl cellulose having a weight average molecular weight of about 30,000, "HEC2" is hydrolyzed hydroxyethyl cellulose having a weight average molecular weight of about 24500, and "PPG" is weight. Polypropylene glycol with an average molecular weight of about 6000, "2M5S" is 2-mercaptobenzimidazole-5-sulfonate sodium, "PEI" is polyethyleneimine with a weight average molecular weight of about 30,000, and "mixture" is a diallyldimethylammonium chloride polymer. It means that a mixed additive was used in which Na salt of bis (3-sulfopropyl) disulfide and N, N'-diethylthiourea were mixed at a weight ratio of 70:60: 1.
Of the DC power supplies listed in Table 1, the "inverter" is an inverter type DC power supply (power supply equipped with a 20 kHz high frequency inverter), and the "thyristor" is a thyristor type DC power supply (power supply with a ripple rate of 10%). It means that it was used.

[Evaluation]
The following characteristic evaluations were carried out using the electrolytic copper foils according to the above Examples and Comparative Examples. The evaluation conditions for each characteristic are as follows. The results are shown in Table 1.

[1] Analysis of C content and S content Using a carbon / sulfur analyzer (EMIA-810W, manufactured by Horiba Seisakusho Co., Ltd.), measurement is performed by combustion in oxygen stream (tubular electric furnace method) -infrared absorption method. It was. A 0.5 g sample was burned and the amount of impurities was analyzed. The copper foil was handled with great care so that the surface would not be contaminated, and if necessary, pretreatment such as acetone degreasing was performed.

[2] Analysis of N content Measurement was performed by an inert gas melting-thermal conductivity method (TCD) using an oxygen / nitrogen / hydrogen analyzer (EMGA-930, manufactured by Horiba Seisakusho Co., Ltd.). A 0.5 g sample was burned and the amount of impurities was analyzed. The copper foil was handled with great care so that the surface would not be contaminated, and if necessary, pretreatment such as acetone degreasing was performed.

[3] Analysis of Cl content A constant weight of copper foil is dissolved in a constant volume of acid (a mixed solution of 1 mol / L sulfuric acid and 20 ml / L of 35% by mass hydrogen peroxide solution), and the silver nitrate aqueous solution is dissolved in the solution. Using (0.01 mol / L) as a reference solution, potential difference titration was performed using an automatic titrator COM-1600 (manufactured by Hiranuma Sangyo Co., Ltd.), and the Cl content in the copper foil was measured.

[4] Tensile test The tensile test was carried out in accordance with the provisions of IPC-TM-650. Further, the measurement was carried out using a tensile tester (Type 1122, manufactured by Instron) at room temperature (25 ° C. ± 10 ° C.) under the condition of a distance between chucks of 70 mm. The measurement samples were obtained by cutting each copper foil to a size of 0.5 inch × 6 inch under normal conditions, and using an inert gas oven (INH-21CD-S, manufactured by Koyo Thermo System Co., Ltd.) at 300 ° C., 1 After heating for an hour, two types of those cut into a size of 0.5 inch × 6 inch were prepared.
In this example, the tensile strength in the normal state was set to 380 MPa or more as the pass level, and the tensile strength in the state after heating was set to the pass level of 300 MPa or more.

[5] Conductivity The conductivity was measured by the 4-terminal method in accordance with the provisions of JIS H 0505: 1975.
In this example, a conductivity of 85% IACS or higher was evaluated as good.

[6] MIT fold resistance test The MIT fold resistance test is performed at room temperature (25 ° C ± 10 ° C) with a bending radius R of 0.08 mm, a bending angle of ± 135 °, and bending in accordance with JIS P 8115: 2001. The test was performed under the conditions of a speed of 175 times / minute and a load of 500 g. The measurement sample was prepared by heating the above copper foil in an inert gas oven (same as above) at 300 ° C. for 1 hour, and cutting the heated copper foil into a size of 130 mm in length × 15 mm in width. Was used.
In this test, the number of bends until the sample for measurement was cut was counted, and the number of bends when the sample was cut was evaluated.
In this example, a bending frequency of 800 or more was evaluated as good.

[7] Folding test The flicking test was performed at room temperature (25 ° C. ± 10 ° C.) according to the following procedures <S1> to <S5>. In addition, <S1> to <S4> of FIG. 1 correspond to the following <S1> to <S4>.
<S1> First, the copper foil is heated in an inert gas oven (same as above) at 300 ° C. for 1 hour, and the heated copper foil is cut into a size of 0.5 inch × 6 inch to prepare a sample for measurement. did.
Next, a polyimide film having a thickness of 100 μm was used as a spacer having a bending radius of 0.2 mm, and as shown in FIG. 1, a measurement sample 10 was placed on the spacer 20, and both ends on the longitudinal side of the spacer 20 were placed on the spacer 20. It was fixed to 20 to prepare a laminate of the spacer 20 and the copper foil 10.
<S2> Next, as shown in FIG. 1, with the spacer 20 inside, the laminate of the spacer 20 and the copper foil 10 is bent at 180 °, and a rubber roller (diameter 95 mm × width 45 mm, weight 2 kg, rubber hardness) is bent. A load was applied using 80 Hs (manufactured by Tayu Equipment Co., Ltd.) 30.
<S3> After that, the presence or absence of breakage (cracking) was observed using an optical microscope (VHX-1000, manufactured by KEYENCE CORPORATION) in the vicinity of the bent portion (dotted line region X) of the copper foil shown in FIG.
<S4> Then, for those that did not break in <S3>, the laminated body after bending was reopened as shown in FIG. 1 and stretched flat using the roller 30.
<S5> After that, the steps <S2> to <S4> were repeated until the fracture was observed in <S3>, the number of repetitions was counted, and the number of observations when the fracture was observed was evaluated.
In this example, 40 or more observations were evaluated as a passing level, and 50 or more observations were evaluated as even better.

As shown in Table 1, the electrolytic copper foils according to Examples 1 to 8 and Reference Example 1 of the present invention have carbon (C), sulfur (S), nitrogen (N) and chlorine (Cl) contents. Since it was controlled within a predetermined range, it was confirmed that it had high tensile strength before and after heating and was also excellent in fracture resistance.

On the other hand, the electrolytic copper foils according to Comparative Examples 1 to 13 have a content of any one or more of carbon (C), sulfur (S), nitrogen (N) and chlorine (Cl) within a predetermined range. Since it was not controlled, it was confirmed that any one or more of the tensile strength and the crease resistance before and after heating were inferior to those of the electrolytic copper foils according to Examples 1 to 9. In particular, the electrolytic copper foils according to Comparative Examples 2 to 4, 10 and 11 can exhibit excellent bending resistance in the conventional MIT folding resistance test, but are more severe bending tests. In the test, it was confirmed that sufficient bending resistance could not be exhibited.

As described above, the electrolytic copper foil according to the present invention has high tensile strength, maintains high tensile strength even after heating, and can realize good fold resistance, so that it is a collection of negative electrodes of lithium ion secondary batteries. It can be suitably used as an electrolytic copper foil for manufacturing an electric body or a wiring board.

Claims (10)

The carbon (C) content is 60 to 150 mass ppm, the sulfur (S) content is 18 mass ppm or less, the nitrogen (N) content is 40 mass ppm or less, and the chlorine (Cl) content is 25 to mass ppm. An electrolytic copper foil characterized by a weight of 200 mass ppm. The first aspect of the present invention, wherein the ratio of the carbon (C) content to the chlorine (Cl) content [C content / Cl content] is in the range of 0.70 to 1.40. Electrolytic copper foil. The electrolytic copper foil according to claim 1 or 2, wherein the tensile strength measured in a normal state is in the range of 380 to 600 MPa. The electrolytic copper foil according to any one of claims 1 to 3, wherein the tensile strength measured in a state after heating at 300 ° C. for 1 hour is in the range of 300 to 550 MPa. The electrolytic copper foil according to any one of claims 1 to 4, which has a conductivity of 85% IACS or more. After heating at 300 ° C for 1 hour, it is bent 180 ° so that the bending radius is 0.2 mm under room temperature (25 ° C ± 10 ° C) conditions. The number of repeated bendings until breaking is 40 times by the foil folding test. The electrolytic copper foil according to any one of claims 1 to 5, which is the above. The electrolytic copper foil according to any one of claims 1 to 6, which is used for manufacturing a negative electrode current collector of a lithium ion secondary battery. The electrolytic copper foil according to any one of claims 1 to 6, which is used for manufacturing a conductor portion of a printed wiring board. A lithium ion secondary battery having the electrolytic copper foil according to any one of claims 1 to 7 as a negative electrode current collector. A printed wiring board having the electrolytic copper foil according to any one of claims 1 to 6 and 8 as a conductor portion.

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