WO2025134765A1 - Surface modifier, metal foil with surface modified layer, and electronic device - Google Patents

Abstract

A surface modifier according to the present invention forms a surface modified layer between a metal layer and a resin layer. The absolute value of the amount of change in the work function of the copper plate surface before and after application when the surface modifier is applied to the copper plate is in the range of 0.15-1.00 eV.

Description

Surface modifier, metal foil with surface modification layer, and electronic device

The present invention relates to a surface modifier, a metal foil with a surface modification layer, and an electronic device. In particular, the present invention relates to a surface modifier that can prevent metal foils from sticking together during storage and can prevent scratches from occurring during transportation.

In recent years, with the advancement of the data society, there is a demand for printed wiring boards (also called "printed circuit boards") with high density and high definition wiring.
In the manufacturing process of a printed wiring board, a resin material such as an etching resist, a plating resist, a solder resist, a prepreg, etc. is bonded to the surface of a metal layer (metal foil) or a metal wiring. In the manufacturing process of a printed wiring board and in the product after the manufacturing, high adhesion is required between the metal layer and the resin layer.

Therefore, in order to increase the adhesion between the metal layer and the resin layer, a method is known in which a coating is formed on the surface of the metal layer to improve adhesion with the resin layer (see, for example, Patent Document 1). Also, a method is known in which an organic coating is formed on the surface of the metal layer using a treatment liquid containing a nitrogen-containing compound having an amino group, thereby improving the adhesion between the metal layer and the resin layer (see, for example, Patent Document 2).

Incidentally, due to production schedules and other factors, there are cases where metal foils need to be temporarily stored after roughening and cleaning. However, if metal foils are stored stacked or rolled up, they will stick together, and when the metal foil is peeled off, bending or breaking will occur in the areas where stress is concentrated. As a result, the conformability of the resin layer (photosensitive resin film resist) formed on the metal foil will deteriorate, causing a decrease in quality and the occurrence of defects.

Therefore, the present inventors have found that by subjecting the metal foil to a surface treatment, it is possible to prevent the metal foil from sticking during storage.
However, by performing the surface treatment on the metal foil, a problem arises in that the treated surface of the surface-treated metal foil is scratched during transportation.

JP 2017-203073 A JP 2008-274311 A

The present invention has been made in consideration of the above problems and circumstances. The problem to be solved by the present invention is to provide a surface modifier, a metal foil with a surface modification layer, and an electronic device that can prevent metal foil from sticking to each other during storage and prevent scratches during transportation.

In order to solve the above problems, the present inventors have investigated the causes of the above problems, and have found that when the amount of change in the work function of the copper plate surface before and after application of a surface modifier to the copper plate is within a specific range, it is possible to prevent the occurrence of scratches during attachment of metal foils to each other during storage or during transportation.
That is, the above-mentioned problems of the present invention are solved by the following means.

1. A surface modifier that forms a surface modification layer between a metal layer and a resin layer,
A surface modifier in which the absolute value of the change in work function of a copper plate surface before and after application of the surface modifier to a copper plate is within a range of 0.15 to 1.00 eV.

2. A surface modifier according to paragraph 1, which contains a nitrogen-containing heterocyclic compound.

3. The nitrogen-containing heterocyclic compound is a compound having both a nitrogen-containing heterocycle and a functional group containing a nitrogen atom or an oxygen atom,
3. The surface modifier according to item 2, wherein the number of nitrogen atoms in the nitrogen-containing heterocycle is 2 to 4, and at least one of the nitrogen atoms is NH.

4. The functional group is any one of -COOH, _-NH2 , -OH, -NHR, or _-NR2 ;
4. The surface modifier according to claim 3, wherein R represents an alkyl group.

［式中、Ｗ_１～Ｗ_７は、炭素原子又は窒素原子を表し、Ｗ_１～Ｗ_７のうち２～４個が窒素原子を表し、少なくとも１つの窒素原子が水素原子と結合する。
　Ｙ_１～Ｙ_５は、炭素原子又は窒素原子を表し、Ｙ_１～Ｙ_５のうち２～４個が窒素原子を表し、少なくとも１つの窒素原子が水素原子と結合する。
　Ｚ_１は、－ＣＯＯＨ、－ＮＨ_２、－ＯＨ、－ＮＨＲ又は－ＮＲ_２を表す。Ｚ_２は、－ＣＯＯＨ、－ＯＨ、－ＮＨＲ又は－ＮＲ_２を表し、Ｒは、アルキル基を表す。
　Ｌは、単結合、連結基を表す。
　ｎ_１は、３～５の整数を表し、ｎ_２は、１～３の整数を表す。］ 5. The surface modifier according to item 2, wherein the nitrogen-containing heterocyclic compound has a structure represented by the following general formula 1 or 2:

[In the formula, W ₁ to W ₇ represent carbon atoms or nitrogen atoms, two to four of W ₁ to W ₇ represent nitrogen atoms, and at least one nitrogen atom is bonded to a hydrogen atom.
Y ₁ to Y ₅ each represent a carbon atom or a nitrogen atom, and 2 to 4 of Y ₁ to Y ₅ represent nitrogen atoms, with at least one nitrogen atom being bonded to a hydrogen atom.
Z ₁ represents -COOH, -NH ₂ , -OH, -NHR or -NR _2. Z ₂ represents -COOH, -OH, -NHR or -NR ₂ , where R represents an alkyl group.
L represents a single bond or a linking group.
_n1 represents an integer of 3 to 5, and _n2 represents an integer of 1 to 3.

6. The nitrogen-containing heterocyclic compound has a structure represented by General Formula 1,
6. The surface modifier according to item 5, wherein when there are two nitrogen atoms among W ₁ to W ₇ in general formula 1 and the two nitrogen atoms are in W ₅ to W ₇ , W ₅ and W ₇ are nitrogen atoms.

7. The nitrogen-containing heterocyclic compound has a structure represented by General Formula 2,
6. The surface modifier according to item 5, wherein, in the general formula 2, when _n2 is 2, L does not simultaneously represent a phenylene group.

8. The surface modifier according to paragraph 1, in which the absolute value of the change in the work function is within the range of 0.30 to 0.80 eV.

The surface modifier described in paragraph 1, in which the amount of dissolved oxygen at 9.25°C is within the range of 6.0 to 11.0 ppm by mass.

10. The surface modifier according to paragraph 1, in which, when the surface modifier is applied to the surface of the metal layer, the work function of the surface of the metal layer before and after application changes to a positive value.

11. A surface modifier according to paragraph 1, containing an activator.

12. A surface modifier according to paragraph 1, containing an organic acid.

13. A metal foil with a surface modification layer, comprising a metal foil and a surface modification layer formed on the metal foil,
The metal foil is composed mainly of at least one of gold, silver, and copper,
13. A metal foil with a surface modification layer, wherein the surface modification layer is made of the surface modifier according to any one of items 1 to 12.

14. An electronic device using a laminate having a surface modification layer and a resin layer on a metal layer,
13. An electronic device, wherein the surface modification layer comprises the surface modifier according to any one of items 1 to 12.

According to the above-mentioned means of the present invention, it is possible to provide a surface modifier, a metal foil with a surface modification layer, and an electronic device that can prevent metal foils from sticking to each other during storage and prevent scratches during transportation.
Although the mechanism by which the effects of the present invention are manifested or the mechanism by which the effects of the present invention are acted upon has not been clearly understood, it is speculated as follows.

(Prevents sticking during storage)
When the change in work function before and after the surface treatment with the surface modifier is small, the charge level of the treated surface of the metal layer with the surface modifier and the back surface of the metal layer become close. Therefore, it was inferred that sticking occurs when such surface-modified metal foils are stacked for a certain period of time. Therefore, in the present invention, the absolute value of the change in work function before and after the surface treatment with the surface modifier is set within the range of 0.15 to 1.00 eV, and the change is made large, thereby preventing the metal foils from sticking to each other. As a result, the force required to peel off the metal foils when they are stuck can be reduced. Considering storage for 10 days or more, the absolute value of the change in work function needs to be 0.15 eV or more.

(Prevention of scratches during transportation)
It was found that when the change in work function before and after surface treatment with a surface modifier is large, scratches are likely to occur during transportation. Although the reason is not clear, it is presumed that the change in work function of the treated surface changes the charge level during transportation, making friction with the transport roller, cleaning water, drying water, etc. more likely to occur. Therefore, from the viewpoint of preventing scratches, the change in the work function needs to be 1.00 eV or less.

Diagram showing the process of forming a metal wiring pattern (metal-clad laminate) A diagram showing the process of forming a metal wiring pattern (forming a surface modification layer) A diagram showing the process of forming a metal wiring pattern (forming a resist layer) A diagram showing the process of forming a metal wiring pattern (patterning of the resist layer) FIG. 1 shows a process for forming a metal wiring pattern (etching of the surface modification layer and the metal layer). A diagram showing the process of forming a metal wiring pattern (peeling off the resist layer)

The surface modifier of the present invention is a surface modifier that forms a surface modification layer between a metal layer and a resin layer, and when the surface modifier is applied to a copper plate, the absolute value of the change in work function of the copper plate surface before and after application is within the range of 0.15 to 1.00 eV.
This feature is a technical feature common to or corresponding to each of the following embodiments.

In one embodiment of the present invention, it is preferable to include a nitrogen-containing heterocyclic compound. This allows the nitrogen atoms (N atoms) present in the skeletal structure of the nitrogen-containing heterocyclic compound to interact with the metal of the metal layer, forming coordinate bonds and increasing adhesion.

Furthermore, it is preferable that the nitrogen-containing heterocyclic compound is a compound having both a nitrogen-containing heterocycle and a functional group containing a nitrogen atom or an oxygen atom, and that the number of nitrogen atoms in the nitrogen-containing heterocycle is 2 to 4, at least one of which is NH. This allows the N atom of the NH to interact with the metal in the metal layer, forming a coordinate bond and improving adhesion to the metal layer.

It is preferable that the functional group is any one of -COOH, _-NH2 , -OH, -NHR, and _-NR2 , where R represents an alkyl group. This allows the functional group to form a hydrogen bond or an ionic bond with a polar group present in the resin. As a result, the functional group can adhere to the resin layer with an interaction force stronger than π-π interaction or van der Waals force.
In particular, it is preferable that the nitrogen-containing heterocyclic compound has a structure represented by General Formula 1 or General Formula 2 from the viewpoint of improving the adhesion between the metal layer and the resin layer.

Furthermore, when the nitrogen-containing heterocyclic compound has a structure represented by General Formula 1 and there are two nitrogen atoms among W ₁ to W ₇ in General Formula 1 and the two nitrogen atoms are in W ₅ to W ₇ , it is preferable that W ₅ and W ₇ are nitrogen atoms. This enhances the interaction with the metal, and provides the effect of improving adhesion to the metal layer.
It is also preferred that the nitrogen-containing heterocyclic compound has a structure represented by General Formula 2, and that when _n2 is 2 in General Formula 2, L does not simultaneously represent a phenylene group. This enhances the interaction with the metal, and provides the effect of improving the adhesion to the metal layer.

It is preferable that the absolute value of the change in the work function is within the range of 0.30 to 0.80 eV, as this is more effective in preventing the metal foils from sticking together during storage and preventing scratches during transportation.

It is preferable that the amount of dissolved oxygen at 25° C. is within the range of 6.0 to 11.0 ppm by mass, since sufficient performance can be exhibited and it is more effective in preventing the metal foils from sticking to each other during storage and in preventing scratches during transportation.
When the dissolved oxygen amount is 6.0 ppm by mass or more, the adsorption speed of nitrogen atoms to the metal layer is not too slow, and the distribution density of the nitrogen-containing heterocyclic compound in the surface is not low, so that sufficient performance can be exhibited. On the other hand, when the dissolved oxygen amount is 11.0 ppm by mass or less, the dissolved oxygen amount is not too large, so that the nitrogen-containing heterocyclic compound can be prevented from agglomerating on the surface, and sufficient performance can be exhibited.

When the surface modifier is applied to the surface of the metal layer, it is preferable that the work function of the surface of the metal layer before and after application changes to a positive value, which can prevent foreign matter from adhering to the metal layer.

The surface modifier preferably contains an activator or an organic acid, which allows the absolute value of the change in the work function to be controlled within the range.

The metal foil with a surface modification layer of the present invention is a metal foil with a surface modification layer formed on a metal foil, the metal foil mainly containing at least one of gold, silver, and copper, and the surface modification layer is made of the surface modifier. This makes it possible to provide a metal foil with a surface modification layer that prevents the metal foils from sticking together during storage and prevents scratches from occurring during transportation.

The electronic device of the present invention is an electronic device using a laminate having a surface modification layer and a resin layer on a metal layer, and the surface modification layer is made of the surface modification agent. This makes it possible to provide an electronic device that prevents metal foils from sticking to each other during storage and prevents scratches from occurring during transportation.

The present invention, its components, and the form and mode for implementing the present invention are described below. In this application, "~" is used to mean that the numerical values before and after it are included as the lower and upper limits.

[Overview of the surface modifier of the present invention]
The surface modifier of the present invention is a surface modifier that forms a surface modification layer between a metal layer and a resin layer, and when the surface modifier is applied to a copper plate, the absolute value of the change in work function of the copper plate surface before and after application is within the range of 0.15 to 1.00 eV.
In the present invention, the "surface modifier" is prepared by adding a nitrogen-containing heterocyclic compound described below to a solvent or the like.

<Change in work function>
The surface modifier of the present invention has an absolute value of the change in work function of the copper plate surface before and after application of the surface modifier to the copper plate in the range of 0.15 to 1.00 eV, more preferably in the range of 0.30 to 0.80 eV, and particularly preferably in the range of 0.4 to 0.7 eV.

The work function is measured using an "atmospheric photoelectron spectrometer AC-3" (manufactured by Riken Keiki Co., Ltd.).
The change in the work function is calculated as follows.
(Formation of surface modified layer)
The following steps A and B were carried out to form a surface modified layer.
(1) Process A
A copper-clad laminate (R-1766 manufactured by Panasonic Corporation) having a metal layer formed on an insulating layer was washed with hydrochloric acid using a 5% aqueous hydrochloric acid solution and a spray-type washing device, and then washed with water.
After rinsing with water, the work function of the copper-clad laminate is measured using the atmospheric photoelectron spectrometer, and this value is taken as the work function value of the copper plate surface before coating.

(2) Process B
The prepared surface modifier was applied to the metal layer of the copper-clad laminate that had been washed with hydrochloric acid and rinsed with water using a spray coating device, and then rinsed with water. After rinsing, the surface was drained with a PVA roller and dried with an air knife at 80° C. to form a surface-modified layer with a thickness of 5 nm.
After the surface modification layer is formed, the work function of the copper-clad laminate is measured using the atmospheric photoelectron spectrometer, and this is taken as the work function value of the copper plate surface after coating.

Then, the difference between the work function value before coating and the work function value after coating obtained as described above is calculated, and this is regarded as the change in the work function.

Examples of a means for adjusting the absolute value of the change in the work function to within the range of 0.15 to 1.00 eV include appropriately changing the types and contents of the nitrogen-containing heterocyclic compound, activator, organic acid, and the like contained in the surface modifier.
Preferred embodiments of the nitrogen-containing heterocyclic compound, the activator and the organic acid are as described below.

In addition, in the present invention, when the surface modifier is applied to the surface of the metal layer, it is preferable that the work function of the surface of the metal layer before and after application changes to a positive value. Note that the metal layer to be applied in this case is not limited to a copper plate, but can be a layer containing a metal as its main component, as described below. Furthermore, the measurement of the work function in this case is not limited to the copper-clad laminate described above, but can be performed in a similar manner using any desired metal layer.

<Dissolved oxygen content>
The surface modifier of the present invention preferably has a dissolved oxygen content at 25° C. in the range of 6.0 to 11.0 ppm by mass, and more preferably in the range of 7.0 to 10.0 ppm by mass.
The amount of dissolved oxygen is measured by putting the surface modifier into a 50 ml glass container with a lid to make the total amount 30 g, putting the lid on, shaking for 5 minutes, and measuring the dissolved oxygen concentration (ppm by mass) of this surface modifier.
To measure the dissolved oxygen concentration, a portable dissolved oxygen meter "DO-31P" made by DKK-TOA is used. The sensor part is immersed near the bottom of the surface modifier (measurement liquid) for about one minute, and the measured value is read.

As a means for adjusting the amount of dissolved oxygen to be within the above range, for example, a degassing treatment or aeration treatment of the surface modifier can be mentioned.
Specifically, the degassing treatment may involve reducing the pressure using a water aspirator or the like and degassing while vibrating and suctioning with an ultrasonic cleaner.
A specific example of the aeration treatment is a method in which an appropriate amount of oxygen gas is bubbled from an oxygen cylinder.
Another method for controlling the amount of dissolved oxygen is to adjust the amount of ethanol in the surface modifier. By increasing the amount of ethanol added, the amount of dissolved oxygen increases. Specifically, the amount of ethanol added is preferably within the range of 0 to 50% by mass relative to water.

Furthermore, as a means of controlling the amount of dissolved oxygen, fluctuations in the amount of dissolved oxygen can be suppressed by filling the container containing the surface modifier or during the injection process with an inert gas.

[Composition of surface modifier]
The surface modifier of the present invention preferably contains a nitrogen-containing heterocyclic compound, since the N atoms present in the skeleton structure of the nitrogen-containing heterocyclic compound interact with the metal of the metal layer to form coordinate bonds, thereby increasing adhesion.
The surface modifier preferably contains water or an alcohol from the viewpoint of solubility, and preferably contains an organic acid or an activator from the viewpoint of controlling the absolute value of the change in the work function within the above-mentioned range.

<Nitrogen-containing heterocyclic compound>
The nitrogen-containing heterocyclic compound is a compound having a nitrogen-containing heterocycle and a functional group containing a nitrogen atom or an oxygen atom. The number of nitrogen atoms in the nitrogen-containing heterocycle is preferably 2 to 4, at least one of which is NH.

The functional group containing a nitrogen atom or an oxygen atom is preferably, for example, any one of -COOH, -NH ₂ , -OH, -NHR, or -NR _2. The functional group is particularly preferably -COOH, -NH ₂ , or -NR _2. Here, R represents an alkyl group.
The nitrogen-containing heterocyclic compound preferably has a structure represented by the following general formula 1 or 2 in terms of improving adhesion between the metal layer and the resin layer.

In the formula, W ₁ to W ₇ each represent a carbon atom or a nitrogen atom, 2 to 4 of W ₁ to W ₇ represent nitrogen atoms, and at least one nitrogen atom is bonded to a hydrogen atom. W ₁ to W ₇ together form a condensed ring.
Y ₁ to Y ₅ each represent a carbon atom or a nitrogen atom, and 2 to 4 of Y ₁ to Y ₅ each represent a nitrogen atom, and at least one of the nitrogen atoms is bonded to a hydrogen atom. _{Y 1} to Y ₅ together form a condensed ring.
Z ₁ represents -COOH, -NH ₂ , -OH, -NHR or -NR _2. Z ₂ represents -COOH, -OH, -NHR or -NR ₂ , where R represents an alkyl group.
L represents a single bond or a linking group.
_n1 represents an integer of 3 to 5, and _n2 represents an integer of 1 to 3.
Furthermore, L is preferably bonded to a carbon atom among W ₁ to W ₇ and Y ₁ to Y ₅ .

The linking group is composed of an atom or atomic group containing a carbon atom, a nitrogen atom, a sulfur atom, or an oxygen atom. Specific examples include -O-, -S-, -N(R)-, -CO-, _-SO2- , alkylene groups (e.g., methylene, ethylene, propylene, 1,4-cyclohexylene, dodecylene, hexadecylene, 2-ethylhexylene, 2-hexyldecalene, etc.), arylene groups (e.g., phenylene, naphthylene, etc.), and combinations thereof. R represents a hydrogen atom, an alkyl group, or a cycloalkyl group.

The following are exemplary compounds that are examples of nitrogen-containing heterocyclic compounds having a structure represented by general formula 1 or general formula 2, but the nitrogen-containing heterocyclic compounds according to the present invention are not limited to these.

The nitrogen-containing heterocyclic compound has a structure represented by General Formula 1, and when there are two nitrogen atoms among W ₁ to W ₇ in General Formula 1 and the two nitrogen atoms are in W ₅ to W ₇ , it is preferable that W ₅ and W ₇ are nitrogen atoms. That is, it is preferable that adjacent W ₅ and W ₆ are not nitrogen atoms, and it is also preferable that adjacent W ₆ and W ₇ are not nitrogen atoms.
It is preferable that the nitrogen-containing heterocyclic compound has a structure represented by the general formula 2, and when _n2 in the general formula 2 is 2, L does not simultaneously represent a phenylene group.
Among the nitrogen-containing heterocyclic compounds, the above-mentioned exemplary compounds (8), (9), (10), (17), (18), (19) and (25) are more preferable.

The surface modifier may contain only one type of nitrogen-containing heterocyclic compound having a structure represented by general formula 1 or general formula 2, or may contain two or more types of nitrogen-containing heterocyclic compound.

The nitrogen-containing heterocyclic compound is preferably contained in the solvent in an amount ranging from 10 to 300 ppm by mass (0.001 to 0.03% by mass) in terms of film-forming properties. In particular, the nitrogen-containing heterocyclic compound is preferably contained in the solvent in an amount ranging from 50 to 250 ppm by mass in the solvent.

<Water or alcohol>
Examples of the alcohols include methanol, ethanol, 2-propanol, etc. As the solvent, water and two or more of the alcohols may be used in combination.
Specifically, the mass ratio of water to alcohol is preferably within the range of 100:0 to 50:50, and more preferably within the range of 100:0 to 75:25.

<Organic acid>
Examples of the organic acid include saturated fatty acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, and caproic acid; unsaturated fatty acids such as (meth)acrylic acid, crotonic acid, and isocrotonic acid; aliphatic saturated dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, and pimelic acid; aliphatic unsaturated dicarboxylic acids such as maleic acid; aromatic carboxylic acids such as benzoic acid, phthalic acid, and cinnamic acid; oxycarboxylic acids such as glycolic acid, lactic acid, malic acid, citric acid, tartaric acid, and salicylic acid; carboxylic acids having substituents such as β-chloropropionic acid, nicotinic acid, ascorbic acid, hydroxypivalic acid, and levulinic acid; amino acids such as glycine, glutamic acid, and aspartic acid; and organic sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. Examples of the organic acid include barbituric acid and ethylenediaminetetraacetic acid. Among these organic acids, it is preferable to use acetic acid and citric acid.

The amount of the organic acid added is preferably an appropriate ratio in the range of 0.001 to 2.0% by mass relative to the nitrogen-containing heterocyclic compound.

<Activator>
As the activator, various types of surfactants such as nonionic surfactants, cationic surfactants, anionic surfactants, and silicone surfactants can be used.

Nonionic surfactants include glycerol, trimethylolpropane, trimethylolethane and their ethoxylates and propoxylates (e.g., glycerol propoxylate, glycerol ethoxylate, etc.), polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether, polyethylene glycol dilaurate, polyethylene glycol distearate, and sorbitan fatty acid. Examples of such products include esters, Pluronic (registered trademark) L10, L31, L61, L62, 10R5, 17R2, and 25R2 (manufactured by BASF), Tetronic 304, 701, 704, 901, 904, and 150R1 (manufactured by BASF), Solsperse 20000 (manufactured by Lubrizol Japan Co., Ltd.), NCW-101, NCW-1001, and NCW-1002 (manufactured by Wako Pure Chemical Industries, Ltd.), Paionin D-6112, D-6112-W, and D-6315 (manufactured by Takemoto Oil Co., Ltd.), Olfin E1010, and Surfynol 104, 400, and 440 (manufactured by Nissin Chemical Industry Co., Ltd.).

Specific examples of cationic surfactants include organosiloxane polymer KP341 (manufactured by Shin-Etsu Chemical Co., Ltd.), (meth)acrylic acid (co)polymer Polyflow No. 75, No. 77, No. 90, No. 95, WS, WS-314 (manufactured by Kyoeisha Chemical Co., Ltd.), and W001 (manufactured by Yusho Co., Ltd.).

Specific examples of the anionic surfactant include W004, W005, and W017 (manufactured by Yusho Co., Ltd.), and Sandet BL (manufactured by Sanyo Chemical Industries, Ltd.).
Examples of silicone surfactants include Toray Silicone DC3PA, Toray Silicone SH7PA, Toray Silicone DC11PA, Toray Silicone SH21PA, Toray Silicone SH28PA, Toray Silicone SH29PA, Toray Silicone SH30PA, Toray Silicone SH8400 (manufactured by Dow Corning Toray Co., Ltd.), TSF-4440, TSF-4300, TSF-4445, TSF-4460, TSF-4452 (manufactured by Momentive Performance Materials Co., Ltd.), KP341, KF6001, KF6002 (manufactured by Shin-Etsu Silicone Co., Ltd.), BYK307, BYK323, BYK330, BYK345 (manufactured by BYK-Chemie Co., Ltd.), and the like.
Among the above surfactants, silicone-based surfactants and cationic surfactants (acrylic compounds) are preferred.

The content of the surfactant is preferably 0.001 to 2.0% by mass, more preferably 0.005 to 1.0% by mass, based on the nitrogen-containing heterocyclic compound. Only one type of surfactant may be used, or two or more types may be used. When two or more types of surfactants are used, it is preferable that the total amount is within the above range.

The surface modifier may contain other components in addition to those mentioned above.
The other components include preservatives, stabilizers, acids, bases, pH adjusters, and the like.

<Method of preparing surface modifier>
The surface modifier can be prepared by adding the nitrogen-containing heterocyclic compound to the solvent, and if necessary, the organic acid, activator, or other additives may be added.
After preparing the surface modifier by mixing the solvent, the nitrogen-containing heterocyclic compound, etc., it is preferable to carry out the above-mentioned deaeration or aeration treatment, whereby the amount of dissolved oxygen in the surface modifier can be controlled.

[Laminate]
The laminate according to the present invention is a laminate in which a surface modification layer and a resin layer are provided in this order on a metal layer, and the surface modification layer is made of the above-mentioned surface modifier.

When the surface modification layer is made of the surface modifier, the metal layer and the surface modification layer, and the surface modification layer and the resin layer interact with each other, resulting in improved adhesion between the metal layer and the resin layer.
In particular, it is preferable that the nitrogen-containing heterocyclic compound contained in the surface modifier has a structure represented by General Formula 1 or 2 from the viewpoint of improving the adhesion between the metal layer and the resin layer.

In the laminate, it is preferable that the heterocycle of the nitrogen-containing heterocyclic compound is oriented in a direction approximately perpendicular to the metal layer, and the functional group of the nitrogen-containing heterocyclic compound is oriented in a direction approximately perpendicular to the resin layer. This allows the functional group to get closer to the resin layer, resulting in a stronger interaction, which is preferable in terms of improving adhesion.

The orientation of the nitrogen-containing heterocyclic compound is optimized by using, for example, quantum chemical calculation software Gaussian 16 (manufactured by Gaussian Corporation) and B3LYP (density functional theory) in DFT calculation.
The calculation is performed using SDD (Stuttgart/Dresden ECP) as the basis function for copper, and 6-31G(d) is used for the other elements. The initial position is determined as the position where the copper ion becomes stable in the space around the ligand in the Grid scan module of the software Material Science Suite manufactured by Schrodinger.

The laminate can be applied to, for example, a printed circuit board (printed wiring board) or an electronic device.
The printed circuit board can be formed by a method for forming a metal wiring pattern by photolithography, as described below.

The structure of the laminate will be described below.
The laminate has a configuration in which a surface modification layer and a resin layer are provided in this order on a metal layer, that is, the metal layer and the surface modification layer are adjacent to each other, and the surface modification layer and the resin layer are adjacent to each other.

<Metal layer>
The metal layer is a layer containing a metal as a main component. Here, the main component refers to a component contained in an amount of 50 mass % or more.

The metal used in the metal layer may be, for example, gold, silver, platinum, zinc, palladium, rhodium, osmium, ruthenium, iridium, copper, nickel, cobalt, iron, tin, chromium, titanium, tantalum, tungsten, indium, aluminum, lead, molybdenum, or an alloy thereof. Among these, gold, silver, or copper is preferred, and from the viewpoint of workability and electrical conductivity, it is particularly preferred to use copper or a copper alloy as the main component.

The metal layer can be formed using a metal foil, plating, or a vacuum film forming method.
The thickness of the metal layer is not particularly limited, and may be set to a thickness according to the thickness of the metal wiring pattern to be formed, for example.

In forming the metal wiring pattern, a metal-clad laminate in which a metal layer is formed on an insulating layer is used, so it is preferable that the laminate has an insulating layer below the metal layer. There are no particular limitations on the insulating layer, and a resin sheet or prepreg that is generally used as an insulating layer can be used.

The laminate having an insulating layer as described above corresponds to laminate 6 in FIG. 3, which shows the resist layer formation process described below.

<Surface modification layer>
The surface modification layer can be formed by applying the surface modification agent to the surface of the metal layer and drying it.
The thickness of the surface modification layer is not particularly limited, but from the viewpoint of the effects of the present invention, it is preferably within the range of 0.1 to 20 nm.

<Resin Layer>
The resin layer used in the present invention is not particularly limited, and examples thereof include thermoplastic resins such as acrylonitrile/styrene copolymer resin (AS resin), acrylonitrile/butadiene/styrene copolymer resin (ABS resin), fluororesin, polyamide, polyethylene, polyethylene terephthalate, polyvinylidene chloride, polyvinyl chloride, polycarbonate, polystyrene, polysulfone, polypropylene, cyclopolyolefin resin, and liquid crystal polymer, thermosetting resins such as epoxy resin, phenol resin, polyimide, polyurethane, bismaleimide-triazine resin, modified polyphenylene ether, and cyanate ester, and ultraviolet-curable resins such as ultraviolet-curable epoxy resin and ultraviolet-curable acrylic resin. These resins may be modified with a functional group, and may be reinforced with glass fiber, aramid fiber, or other fibers.

When the laminate is a printed circuit board laminate, the resin layer can be a commercially available resin film or prepreg (a sheet-like fiber impregnated with a liquid resin), and resins containing fluororesin, cyclopolyolefin resin, liquid crystal polymer, epoxy resin, phenolic resin, polyimide, bismaleimide-triazine resin, modified polyphenylene ether, and cyanate ester are preferably used.
Furthermore, when the laminate forms wiring for a printed circuit board (when it is a metal wiring pattern), a commercially available liquid resist or dry film resist can be used for the resin layer, and preferably used are ultraviolet-curable epoxy resins containing alkali-soluble resins, ultraviolet-curable acrylic resins, and polyimides.

The method for forming a metal wiring pattern is a method for forming a metal wiring pattern by photolithography, and preferably includes a step of forming a surface modification layer between a metal layer and a resist using the surface modification agent of the present invention.

<Method of forming metal wiring pattern>
Specifically, the metal wiring pattern is formed by the following steps (A) to (F).
Step (A): A step of acid-washing a metal-clad laminate having a metal layer formed on an insulating layer. Step (B): A step of forming a surface-modified layer on the metal layer of the metal-clad laminate using the non-photosensitive surface modifier of the present invention. Step (C): A step of forming a resist layer containing a photosensitive resin on the surface-modified layer. Step (D): A step of patterning the resist layer by exposure and development. Step (E): A step of etching the surface-modified layer and the metal layer through the resist layer. Step (F): A step of peeling off the resist layer from the metal-clad laminate.

Each process will be explained using Figures 1 to 6.

In step (A), a metal-clad laminate 5 (see FIG. 1), in which a metal layer 2 is formed on an insulating layer 1, is acid-washed. This makes it possible to remove dirt, antioxidants, oxide films, and the like adhering to the metal surface that hinder the interaction between the surface modifier and the metal layer. There are no particular limitations on the acid washing solution, and any conventionally known solution can be used. In addition, the solution may be washed with water after acid washing.

The insulating layer 1 is an insulating layer that serves as a base material for a metal wiring pattern. The insulating layer 1 is made of an insulating material such as resin, and may be a prepreg in which a base material such as paper or glass is impregnated with resin.
Metal layer 2 is similar to the metal layer of the laminate described above.

In step (B), the surface modification layer 3 is formed on the metal layer 2 of the metal-clad laminate 5 using the surface modification agent of the present invention (see FIG. 2). Specifically, the surface modification agent is applied onto the metal layer 2 to form the surface modification layer 3.
The thickness of the surface modification layer 3 is not particularly limited, but from the viewpoint of the effects of the present invention, it is preferably within the range of 0.1 to 20 nm.

It is preferable to have a step of washing the metal-clad laminate 5 on which the surface modification layer 3 has been formed with water between step (B) and the next step (C). This allows the non-photosensitive surface modification agent to be removed without sufficient interaction with the metal layer.

In step (C), a resist layer 4 containing a photosensitive resin is formed on the surface modification layer 3 (see FIG. 3). The laminate 6 in this state includes the metal layer 2, the surface modification layer 3, and the resist layer 4, and thus corresponds to the laminate according to the present invention.

The resist layer 4, like the resist layer of the laminate, is not particularly limited as long as it contains a photosensitive resin that can be patterned by photolithography, and can be formed by laminating a dry film resist or applying a liquid resist material.

In step (D), the resist layer 4 is patterned by exposure and development (see FIG. 4). Specifically, the resist layer 4 is exposed using a photomask capable of exposing the resist layer 4 in an arbitrary pattern, and then unnecessary portions of the resist layer 4 are dissolved and removed using a developer, thereby patterning the resist layer 4. It is preferable to wash the resist layer 4 with water after development.
The exposure conditions and development conditions are not particularly limited, and conventionally known conditions can be used.

In step (E), the surface modification layer 3 and the metal layer 2 are etched through the resist layer 4 (see FIG. 5 ). Specifically, the surface modification layer 3 and the metal layer 2 are patterned by dissolving the surface modification layer 3 and the metal layer 2 in the portion where the resist layer 4 has been removed by wet etching using an etching solution.
The etching conditions are not particularly limited, and conventionally known conditions can be applied.

In step (F), the resist layer 4 is peeled off from the metal-clad laminate 5 (see FIG. 6). At this time, due to the effects of the present invention, the surface modification layer 3 is easily peeled off from the resist layer 4, so the surface modification layer 3 is likely to remain on the metal layer 2 of the metal-clad laminate 5, but the surface modification layer 3 may remain on the metal layer 2 or may be peeled off together with the resist layer 4.

Although there is no particular limitation on the method for removing the resist layer 4, it is preferable to remove the resist layer 4 using a remover liquid. The remover liquid is not particularly limited, and a conventionally known remover liquid can be used.
Through the above steps, the metal wiring pattern 7 can be formed.

The method for forming a metal wiring pattern described above can form a high-density, high-definition metal wiring pattern. Therefore, by attaching electronic components to the metal wiring pattern as required, a high-density, high-definition printed circuit board (printed wiring board) can be manufactured.

Method for forming a printed circuit board laminate
The method for forming a laminate (printed circuit board laminate) according to the present invention is a method for forming a resin layer on a metal layer, and includes a step of forming a surface modification layer between the metal layer and the resin layer using the surface modifier of the present invention.
The metal layer may be a solid layer or may be patterned into a wiring layer, and the lamination method may be a known method such as hot pressing.
As the resin layer, a commercially available resin film or prepreg (a sheet-like fiber impregnated with a liquid resin) can be used, and resins containing fluororesin, cyclopolyolefin resin, liquid crystal polymer, epoxy resin, phenolic resin, polyimide, bismaleimide-triazine resin, modified polyphenylene ether, and cyanate ester are preferably used, and the bonding surface of the resin layer may be subjected to a surface treatment such as a corona treatment or a plasma treatment before lamination.

[Metal foil with surface modification layer]
The metal foil with a surface modification layer of the present invention is a metal foil with a surface modification layer formed on a metal foil, wherein the metal foil is composed mainly of at least one of gold, silver, and copper, and the surface modification layer is composed of the above-mentioned surface modifier.
Here, the term "main component" refers to a component contained in the metal foil in an amount of 50% by mass or more. As the metal other than gold, silver, or copper, the same metals as those listed as the metals used in the metal layer can be used.
The surface modification layer is similar to the surface modification layer of the laminate described above, and therefore a description thereof will be omitted here.

[Electronic Devices]
The electronic device of the present invention is an electronic device using a laminate having a surface modification layer and a resin layer on a metal layer, the surface modification layer being made of the above-mentioned surface modifier. That is, the electronic device uses the above-mentioned laminate.
Examples of the electronic device include a smartphone, a tablet terminal, a personal computer, a server, a router, a communication base station, a display device, and a home appliance.

The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these. In the following examples, unless otherwise specified, operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

<Preparation of Surface Modifier 1>
A surface modifier 1 was prepared by adding 100 mass % ion-exchanged water as a solvent to which the above-mentioned exemplary compound (9), which is a nitrogen-containing heterocyclic compound, was added so as to be at 50 ppm by mass.

<Preparation of Surface Modifiers 2 to 22>
Surface modifiers 2 to 22 were prepared in the same manner as in the preparation of surface modifier 1, except that the type and content of the nitrogen-containing heterocyclic compound, the ratio (content) of ethanol and ion-exchanged water, the type of activator and organic acid, and the presence or absence of aeration or deaeration treatment were changed as shown in Table I below. Note that "water" in Table I below refers to ion-exchanged water.

The activators and organic acids used are as follows: The amounts (% by mass) of the activators and organic acids added are the amounts added relative to the nitrogen-containing heterocyclic compound.
(Activator)
Silicone compound: 0.1% by mass (BYK-345, manufactured by BYK Japan, silicone surfactant)
Acrylic compound: 0.5% by mass (Polyflow WS-314, manufactured by Kyoeisha Chemical Co., Ltd., cationic surfactant)

(organic acid)
Acetic acid: 0.05% by mass
Citric acid: 0.05% by mass

The deaeration and aeration treatments were carried out as follows.
(Aeration treatment)
The aeration treatment was carried out by injecting oxygen into a preparation liquid prepared by adding each compound to a solvent while bubbling the preparation liquid by adjusting the flow rate from an oxygen cylinder.

(Degassing treatment)
The degassing treatment was carried out by reducing the pressure of a preparation liquid in which each compound was added to a solvent using a water aspirator or the like, and by vibrating and sucking with an ultrasonic cleaner to degas the solution.

<Dissolved oxygen content>
The amount of dissolved oxygen was measured for the surface modifier prepared above. The amount of dissolved oxygen was measured by putting the surface modifier into a 50 ml glass container with a lid to make the total amount 30 g, closing the lid, and shaking for 5 minutes, and measuring the dissolved oxygen concentration (ppm by mass) of this surface modifier.
To measure the dissolved oxygen concentration, a portable dissolved oxygen meter "DO-31P" manufactured by DKK-TOA was used. The sensor part was immersed near the bottom of the surface modifier, which was the measurement liquid, and the measurement value was read after holding it for about one minute. The measured dissolved oxygen concentration is shown in the table below.

<Change in work function>
The surface modifier prepared above was applied to a copper plate, and the change in work function of the copper plate surface before and after application was calculated. The change in work function is shown in the table below.
The work function was measured using an "air photoelectron spectrometer AC-3" (manufactured by Riken Keiki Co., Ltd.).
The change in the work function was calculated as follows.
(Formation of surface modified layer)
The following steps A and B were carried out to form a surface modified layer.
(1) Process A
A copper-clad laminate (R-1766, manufactured by Panasonic Corporation) having a metal layer formed on an insulating layer was washed with hydrochloric acid using a 5% aqueous hydrochloric acid solution and a spray-type washing device, and then washed with water.
After rinsing with water, the work function of the copper-clad laminate is measured using the atmospheric photoelectron spectrometer, and this value is taken as the work function value of the copper plate surface before coating.

(2) Process B
The prepared surface modifier was applied to the metal layer of the copper-clad laminate that had been washed with hydrochloric acid and rinsed with water using a spray coating device, and then rinsed with water. After rinsing, the surface was drained with a PVA roller and dried with an air knife at 80° C. to form a surface-modified layer with a thickness of 5 nm.
After the surface modification layer was formed, the work function of the copper-clad laminate was measured using the atmospheric photoelectron spectrometer, which was used as the work function value of the copper plate surface after coating.
Then, the difference between the work function value before coating and the work function value after coating obtained as described above was calculated, and this was defined as the amount of change in the work function.
In addition, Comparative Example 1 shown in the table below is a case where no surface modifier is applied to the copper-clad laminate.

[evaluation]
＜Sticking＞
Copper foil (model number: CF-T8G-STD-35) manufactured by Fukuda Metal Foil & Powder Co., Ltd. was cut to 10 cm x 10 cm, and the above-mentioned steps A and B in the amount of change in work function were carried out to subject the copper foil to surface modification treatment. The surface-modified copper foils were stacked and left to stand for 2 hours. Thereafter, when peeling off one sheet of copper foil from the upper layer, it was visually observed whether the copper foil from the lower layer was lifted or not. In the following criteria, "A" and "B" were deemed to be practically acceptable. Comparative Example 1 shown in the table below is a case in which no surface modifier was applied to the copper foil.
(standard)
A: Only the top copper foil was peeled off smoothly.
B: The copper foil on the bottom row rises slightly, but easily returns to its original position.
C: It completely sticks to the copper foil on the upper layer and is lifted up at the same time.

<Damage during transportation>
A copper-clad laminate (R-1766, manufactured by Panasonic Corporation) was subjected to the above-mentioned steps A and B in the change in work function, thereby carrying out a surface modification treatment.
After horizontally transporting the substrate for 5 m in an acid treatment/soft etching device (manufactured by Fuji Kiko Co., Ltd.) with the supply of chemicals stopped, the number of scratches on the substrate surface was visually counted. In the following criteria, "A" and "B" were deemed to be acceptable for practical use. Comparative Example 1 shown in the table below is a case in which no surface modifier was applied to the copper-clad laminate.
(standard)
A: 3 or fewer scratches visible on the entire surface B: 4 to 20 scratches visible on the entire surface C: 21 or more scratches visible on the entire surface

As shown by the above results, it was found that when the surface modifier of the present invention is used, it is possible to prevent the copper foils from sticking to each other during storage and the occurrence of scratches during transportation, compared to when the surface modifier of the comparative example or no surface modifier is applied.
Furthermore, when a gold foil conductive transfer foil manufactured by Murata Gold Foil was used and evaluated in the same manner as described above, it was found that it was possible to prevent the gold foil from sticking to each other during storage and the occurrence of scratches during transportation.

The present invention can be used for a surface modifier, metal foil with a surface modification layer, and electronic devices that can prevent metal foil from sticking together during storage and prevent scratches during transportation.

REFERENCE SIGNS LIST 1: insulating layer 2: metal layer 3: surface modification layer 4: resist layer 5: metal-clad laminate 6: laminate 7: metal wiring pattern

Claims (14)

A surface modifier that forms a surface modified layer between a metal layer and a resin layer,
A surface modifier in which the absolute value of the change in work function of a copper plate surface before and after application of the surface modifier to a copper plate is within a range of 0.15 to 1.00 eV. The surface modifier according to claim 1, which contains a nitrogen-containing heterocyclic compound. the nitrogen-containing heterocyclic compound is a compound having a nitrogen-containing heterocycle and a functional group containing a nitrogen atom or an oxygen atom,
The surface modifier according to claim 2, wherein the nitrogen-containing heterocycle has 2 to 4 nitrogen atoms, at least one of which is NH. the functional group is any of -COOH, _-NH2 , -OH, -NHR, and _-NR2 ;
The surface modifier according to claim 3 , wherein R represents an alkyl group. The surface modifier according to claim 2 , wherein the nitrogen-containing heterocyclic compound has a structure represented by the following general formula 1 or 2:

[In the formula, W ₁ to W ₇ represent carbon atoms or nitrogen atoms, two to four of W ₁ to W ₇ represent nitrogen atoms, and at least one nitrogen atom is bonded to a hydrogen atom.
Y ₁ to Y ₅ each represent a carbon atom or a nitrogen atom, and 2 to 4 of Y ₁ to Y ₅ represent nitrogen atoms, with at least one nitrogen atom being bonded to a hydrogen atom.
Z ₁ represents -COOH, -NH ₂ , -OH, -NHR or -NR _2. Z ₂ represents -COOH, -OH, -NHR or -NR ₂ , where R represents an alkyl group.
L represents a single bond or a linking group.
_n1 represents an integer of 3 to 5, and _n2 represents an integer of 1 to 3. The nitrogen-containing heterocyclic compound has a structure represented by General Formula 1,
The surface modifier according to claim 5, wherein when there are two nitrogen atoms among W ₁ to W ₇ in said general formula 1 and the two nitrogen atoms are in W ₅ to W ₇ , W ₅ and W ₇ are nitrogen atoms. The nitrogen-containing heterocyclic compound has a structure represented by General Formula 2,
6. The surface modifier according to item 5, wherein, in the general formula 2, when _n2 is 2, L does not simultaneously represent a phenylene group. The surface modifier according to claim 1, wherein the absolute value of the change in the work function is within the range of 0.30 to 0.80 eV. The surface modifier according to claim 1, wherein the amount of dissolved oxygen at 25°C is within the range of 6.0 to 11.0 ppm by mass. The surface modifier according to claim 1, wherein when the surface modifier is applied to the surface of the metal layer, the work function of the surface of the metal layer before and after application changes to a positive value. The surface modifier according to claim 1, which contains an activator. The surface modifier according to claim 1, which contains an organic acid. A metal foil with a surface modification layer, comprising a metal foil having a surface modification layer formed on the metal foil,
The metal foil is composed mainly of at least one of gold, silver, and copper,
A metal foil with a surface modification layer, wherein the surface modification layer is made of the surface modifier according to any one of claims 1 to 12. An electronic device using a laminate having a surface modification layer and a resin layer on a metal layer,
An electronic device, wherein the surface modification layer comprises the surface modifier according to any one of claims 1 to 12.

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