JP6485896B2 - Metal film and method for forming metal film - Google Patents

Description

  The present invention relates to a metal film and a method for forming a metal film, and in particular, for forming a metal film provided on a surface of an insulating base material having a smooth surface such as glass without performing a roughening treatment, and the metal film. The present invention relates to a metal film forming method.

  Conventionally, a metal film is formed on the surface of an insulating substrate such as glass by an electroless plating method or the like. At this time, in order to obtain a metal film having good adhesion on the surface of the insulating base material, it has been generally performed that the surface of the insulating base material is roughened in advance. However, when a roughening process is performed on the surface of a transparent insulating substrate such as glass, the translucency of the transparent insulating substrate decreases. For this reason, in applications where the transparency of the insulating substrate itself is required, such as a black matrix for a color filter such as a liquid crystal display or a transparent electrode of a touch panel, the surface has good adhesion without being roughened. It has been desired to form a metal film. Similarly, even in applications that require smoothness of the surface of an insulating substrate such as a high-frequency circuit, it is possible to form a metal film with good adhesion without subjecting the surface of the insulating substrate to roughening treatment. It was sought after.

  As a method for forming a metal film with good adhesion without subjecting the surface of the insulating base material to roughening, for example, there is a method described in Patent Document 1. In Patent Document 1, first, a conductive film containing an oxide such as ITO (indium tin oxide) is formed on the surface of an insulating base material such as glass, and a reduction layer is formed by reducing the conductive film surface layer. Then, by forming a catalyst layer on the surface of the reduction layer and plating a metal on the conductive film having this catalyst layer, good adhesion without roughening the surface of an insulating substrate such as glass It is said that a simple metal film can be formed.

JP-A-8-120448

  However, in the method described in Patent Document 1, it is necessary to form a conductive film made of an inorganic oxide such as ITO on the surface of the insulating substrate, and further, a reduction treatment is performed on the surface layer of the conductive film such as ITO. There is a need. For this reason, when it is desired to obtain a metal film having good adhesion directly to the surface of an insulating substrate such as glass, the method described in Patent Document 1 cannot be applied.

  In addition, when the inventors of the present invention conducted an experiment and confirmed, if an ITO film was provided on the surface of the insulating substrate, a catalyst was applied, and an electroless nickel plating film was formed. Even if it does not give, the electroless nickel film with good adhesiveness can be formed on the surface of the insulating substrate. However, in order to increase the thickness of the metal coating on the insulating substrate, if the copper plating is performed on the electroless nickel coating by the electrolytic plating method, the electrolytic copper coating is peeled off from the surface of the insulating substrate together with the electroless nickel coating. There was a problem to do. That is, an electroless metal film having good adhesion can be formed on the surface of the insulating base material without roughening treatment, but after that, when an electrolytic metal film is formed on the electroless metal film, the insulating group is formed. There was a problem that the electrolytic metal film peeled off from the surface of the material together with the electroless metal film.

  Accordingly, an object of the present invention is to form a thick metal film with good adhesion on the surface of an insulating substrate by a simple method without performing a roughening treatment.

  As a result of intensive studies, the present inventors have achieved the above-mentioned problem by employing the following metal coating.

  The metal coating according to the present invention is a metal coating provided on an insulating substrate having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less, and is formed on the smooth surface by an electroless plating method. And an electroplating film formed on the surface of the electroless plating film by an electroplating method, wherein the electroplating film has a compressive stress.

  In the metal coating according to the present invention, the electrolytic plating coating preferably contains at least one element of nitrogen, sulfur, and carbon.

  In the metal coating according to the present invention, the electrolytic plating coating preferably contains an alkylamine.

  In the metal coating according to the present invention, the electroless plating coating is preferably an electroless nickel coating, and the electrolytic plating coating is preferably an electrolytic copper coating.

  In the metal coating according to the present invention, a conductive film made of an inorganic oxide is provided on the smooth surface of the insulating substrate, and the electroless plating film is formed on the conductive film. preferable.

  In the metal coating according to the present invention, the electroless plating coating preferably has a thickness of 1 μm or less.

  In the metal coating according to the present invention, the thickness of the electrolytic plating coating is preferably 0.5 μm or more.

  The metal film forming method according to the present invention is a metal film forming method for forming a metal film on an insulating substrate having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less, and is electroless An electroless plating process for forming an electroless plating film on the smooth surface of the insulating substrate by a plating method; and an electroplating process for forming an electroplating film on the surface of the electroless plating film by an electrolytic plating method. In the electrolytic plating step, an electrolytic plating solution containing 0.02 mol / L or more and 0.3 mol / L or less of a nitrogen compound or 0.001 mol / L or less of a sulfur compound as an additive is used. To do.

  In the method for forming a metal film according to the present invention, the additive is preferably one or more of alkylamines, thiourea and thiourea derivatives.

In the method for forming a metal film according to the present invention, the electrolytic plating process is preferably performed at a current density of 0.1 A / dm ² or more 5A / dm ² or less.

  According to the present invention, a metal coating comprising an electroless plating coating and an electrolytic plating coating having a compressive stress on the surface of an insulating substrate having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less. By providing this, a thick metal film can be provided on the surface of the insulating base material with good adhesion without performing a roughening treatment.

It is a figure for demonstrating the procedure of the metal film formation method which concerns on this invention. It is a scanning electron microscope image (SEM image) which shows an example of the cross section of the metal film which concerns on this invention.

  Hereinafter, embodiments of a metal film and a metal film forming method according to the present invention will be described with reference to the drawings.

1. First, an embodiment of the metal coating according to the present invention will be described. The metal coating according to the present invention is a metal coating provided on an insulating substrate having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less, and is formed on the smooth surface by an electroless plating method. And an electroplating film formed on the surface of the electroless plating film by an electroplating method, wherein the electroplating film has a compressive stress. In the metal film according to the present invention, by providing an electroplating film having compressive stress on the electroless plating film, good adhesion without roughening the smooth surface of the insulating substrate. A conductive film made of a thick metal film can be formed. Moreover, in this invention, it is also preferable that the said smooth surface of an insulating base material is provided with the electrically conductive film which consists of inorganic oxides, and the said electroless-plating film is formed on the said electrically conductive film. Below, it demonstrates in order of an insulating base material, an electrically conductive film, an electroless-plating film, and an electroplating film. However, the electrolytic plating film having a compressive stress in the present invention means having a compressive stress having a value larger than 0 MPa when the stress of the electrolytic plating film is measured.

(1) Insulating base material In this invention, an insulating base material will be specifically limited if it is a base material which consists of an insulating material which has a smooth surface whose arithmetic mean roughness (Ra) is 0.3 micrometer or less. For example, a base material made of an insulating material such as glass, plastic, ceramics, or semiconductor substrate material having a surface arithmetic average roughness (Ra) of 0.3 μm or less can be used. Here, as plastic, it is applied to polyimide resin, polycarbonate resin, polyethylene resin, chlorinated polyethylene resin, polypropylene resin, polystyrene resin, polyvinyl chloride resin, ABS resin, polyphenylene sulfide resin, polybutylene terephthalate resin, liquid crystal polymer, etc. Can do. Examples of the semiconductor substrate material include SiC, GaAs, InP, GaN, Mo, Mo—Cu, and sapphire. In general, the arithmetic roughness (Ra) of the surface of the insulating base material is often 0.3 μm or less, and when the surface of the insulating base material is roughened, the arithmetic average roughness The thickness (Ra) often exceeds 0.3 μm. That is, in the present invention, the insulating base material having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less mainly means an insulating base material whose surface is not subjected to roughening treatment or the like. .

  Moreover, when applying this invention for the use as which translucency is requested | required, it is preferable that the said insulating base material is a transparent insulating base material with a visible light transmittance of 80% or more. The present invention can form a metal film having good adhesion on the surface of the insulating base material by plating without subjecting the surface of the insulating base material to roughening. This is because it can be suitably used for applications requiring transparency of a substrate such as an electrode and a black matrix for a color filter of a liquid crystal display. In applying to these uses, the visible light transmittance of the insulating base material is more preferably 85% or more, and further preferably 90% or more. In addition, when applying this invention for the use for which translucency is not requested | required, of course, the visible light transmittance | permeability of the said insulating base material may be less than 80%.

(2) Conductive Film Next, the conductive film will be described. In the present invention, a conductive film may be provided on the surface of the insulating base material, and a metal film may be formed on the insulating base material through the conductive film. The conductive film is not particularly limited as long as it is a thin film made of a conductive inorganic oxide. However, when considering application to the above-described applications where the transparency of the substrate is required, the conductive film is preferably a transparent conductive film, such as indium tin oxide (ITO), tin oxide (SnO ₂ ), oxidation A transparent conductive film made of a metal oxide such as zinc (ZnO) or titanium oxide (TiO ₂ ) is preferable.

(3) Metal film In this invention, as above-mentioned, a metal film is the electroless plating film formed on the smooth surface of an insulating base material, and the electroplating film formed on the surface of the said electroless plating film Is provided.

i) Electroless plating film An electroless plating film is a metal film formed on the smooth surface of an insulating substrate by an electroless plating method, and is formed directly on the surface of the insulating substrate. Alternatively, it may be formed on the surface of the insulating substrate via the conductive film. In the present invention, the electroless plating film is a metal that can be formed on the surface of the insulating substrate or the conductive film by an electroless plating method such as an electroless nickel film, an electroless copper film, or an electroless copper-nickel alloy film. If it is a film, it will not specifically limit. However, an electroless nickel coating is preferred from the viewpoint that better adhesion to the insulating substrate and / or the conductive film can be obtained. However, the electroless nickel coating means a metal coating mainly composed of nickel formed by an electroless method. In addition to a pure nickel coating, various electroless components mainly composed of nickel such as an electroless nickel-phosphorus coating. It shall contain a nickel alloy coating.

  The thickness of the electroless plating film is preferably 1 μm or less, more preferably 0.8 μm or less, and even more preferably 0.5 μm or less. Moreover, if the said electroless-plating film has a thickness of 0.2 micrometer or more, an electroplating film can be favorably formed in the surface. Accordingly, the lower limit is preferably 0.2 μm or more, but the lower limit is not particularly limited, and if there is conductivity capable of forming an electrolytic plating film on the electroless plating film, The thickness may be less than 0.2 μm.

ii) Electrolytic plating film The electrolytic plating film is a metal film formed on the surface of the electroless plating film by an electrolytic plating method. In the present invention, an electrolytic plating film having compressive stress is provided on the surface of the electroless plating film. Thus, as described above, a thick metal film with good adhesion can be formed on the smooth surface of the insulating substrate without roughening the surface.

  Here, when the compressive stress of the electrolytic plating film is less than 0 MPa, that is, when the electrolytic plating film exhibits tensile stress, the insulating base material of the electroless plating film itself or the insulating base material through the conductive film Even if the adhesion with the electroless plating film is good, the electrolytic plating film cannot be formed on the surface of the electroless plating film, or the insulating group is formed even if the electrolytic plating film is formed on the surface of the electroless plating film. It peels from the surface of the material, and a thick metal film cannot be formed on the surface of the insulating substrate.

  From the above viewpoint, the electrolytic plating film is required to have a compressive stress having a value larger than 0 MPa. From the viewpoint of forming a metal film with higher adhesion, the compressive stress of the electrolytic plating film is preferably 1 MPa or more, and more preferably 2 MPa or more. Moreover, an upper limit is not specifically limited. However, at present, it is difficult to form an electrolytic plating film having a compressive stress greater than 98 MPa. In addition, in order to form an electrolytic plating film with high compressive stress, it is necessary to increase the concentration of additives described later in the electrolytic plating solution. In this case, the content of additive components incorporated into the electrolytic plating film increases. As a result, problems such as an increase in the electrical resistivity of the electrolytic plating film and a decrease in film quality occur. Therefore, from the viewpoint of obtaining an electroplated film having low electrical resistivity and good film quality, the compressive stress of the electroplated film is preferably 60 MPa or less, more preferably 30 MPa or less, and 10 MPa or less. More preferably. However, in this invention, the said compressive stress shall mean the internal stress of the electrolytic plating film measured with the spiral stress meter (spiral contract meter).

  In the present invention, the electrolytic plating film may be an electrolytic plating film made of any metal as long as it has a compressive stress within the above range, but has good adhesion to the surface of the electroless plating film. From the viewpoint that a conductive film can be provided without impairing the smoothness of the surface of the insulating substrate, an electrolytic copper film is preferably provided on the surface of the electroless plating film. However, the electrolytic copper film refers to a metal film mainly composed of copper formed by an electrolysis method. In addition to a pure copper film having a purity of 99.8% or more, various electrolytic copper alloy films such as an electrolytic copper-nickel film. Shall be included.

  In the present invention, the electrolytic plating film preferably has a fine crystal structure having an average grain size of 1.5 μm or less, and more preferably 1.0 μm or less. When the metal is deposited on the electroless plating film by the electroplating method, by adding a predetermined additive, etc., the crystal nuclei are generated one after the other before the crystal grains grow greatly, An electrolytic plating film having a crystal structure can be obtained. An electrolytic plating film having a fine crystal structure is likely to exhibit compressive stress, and it becomes easy to form a thick metal film having good adhesion on the surface of the insulating substrate.

  As described above, the additive contained in the electrolytic solution is taken into the electrolytic plating film. Examples of the additive component include alkylamines, thiourea, and thiourea derivatives as described later. In addition to these, thiosulfate and the like can also be used. Therefore, it is preferable that the electrolytic plating film contains at least one element of nitrogen, sulfur and carbon due to these additive components.

  The thickness of the electrolytic plating film is not particularly limited as long as it can be formed on the surface of the insulating substrate with good adhesion, but is preferably 0.5 μm or more. In this case, a conductive film having a low electrical resistivity can be obtained by forming an electrolytic plating film having a thickness of 0.5 μm or more on the surface of the insulating substrate in addition to the thickness of the electroless plating film. The electrical resistivity can be lowered as the total thickness of the metal coating formed on the insulating substrate increases. For this reason, the thickness of the electrolytic plating film is more preferably 1 μm or more, and further preferably 2 μm or more. As a result of confirmation by experiment, by providing an electrolytic plating film having compressive stress on the surface of the electroless plating film, a 7 μm-thick metal film can be applied to the insulating substrate without peeling off from the surface of the insulating substrate. It was confirmed that a metal film with good adhesion could be obtained. As described above, the upper limit of the thickness of the electrolytic plating film is not particularly limited as long as it can be formed on the surface of the insulating base material with good adhesion. However, even if the electroplating film has the same thickness, the electrical resistivity varies depending on the metal element constituting the electroplating film, the type and concentration of the additive used when forming the electroplating film, and the bath temperature. Therefore, in order to obtain an electrolytic plating film having a lower resistance value, it is required to adjust these.

  The conductive film and metal film described above may be formed on the entire surface of the insulating base material, but may be selectively formed on the surface of the insulating base material, for example. As a method for selectively providing a conductive film and a metal film on the surface of the insulating substrate, for example, after forming these conductive film and metal film on the entire surface of the insulating substrate, a wiring pattern is formed by etching or the like. Examples thereof include a method and a method of selectively forming these conductive films and metal films on the surface of the insulating substrate according to a predetermined wiring pattern.

2. Next, an embodiment of the metal film forming method according to the present invention will be described. The metal film forming method according to the present invention is a metal film forming method for forming a metal film on an insulating substrate having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less, and is electroless An electroless plating process for forming an electroless plating film on the smooth surface of the insulating substrate by a plating method; and an electroplating process for forming an electroplating film on the surface of the electroless plating film by an electrolytic plating method. In the electrolytic plating process, an electrolytic plating solution containing 0.02 mol / L or more and 0.3 mol / L or less of a nitrogen compound or sulfur compound as an additive and / or 0.001 mol / L or more of a sulfur compound as an additive. It is used. Here, since the insulating base and the smooth surface of the insulating base are as described above, the description thereof is omitted here. Further, as described above, a conductive film may be provided on the smooth surface of the insulating substrate, and an electroless plating film may be formed on the surface of the conductive film. Hereinafter, each process including the conductive film forming process will be described in order.

(1) Conductive film formation process
In the case where a conductive film made of an inorganic oxide is provided on the surface of the insulating substrate, a conventionally known thin film forming method such as a sputtering method or a physical vapor deposition method can be appropriately employed. In the present invention, the conductive film has an arbitrary configuration. In the following, when referred to as an insulating substrate, it shall mean the insulating substrate itself or an insulating substrate provided with a conductive film on a smooth surface, and when referred to as the smooth surface of an insulating substrate, insulation When the conductive film is provided on the smooth surface of the conductive base material or the smooth surface of the insulating base material, the surface of the conductive film is meant.

(2) Electroless plating step In the electroless plating step, an electroless plating film is formed on the smooth surface of the insulating substrate by an electroless plating method. When a metal film is formed on the surface of an insulating substrate by an electroless plating method, generally, the insulating substrate is subjected to various pretreatments such as degreasing, water washing, conditioner treatment, catalyst application, and accelerator treatment. . Also in the present invention, these various pretreatments can be appropriately performed, and various conventionally known electroless plating methods can be applied. However, in this invention, the roughening process with respect to the insulating base material surface shall not be performed. Further, even when a conductive film is provided on the surface of the insulating base material, the surface of the conductive film is not roughened. However, when an electroless plating film is directly formed on the smooth surface of an insulating substrate such as glass, a surface modification treatment for improving the adhesion with the metal coating on the surface of the insulating substrate ( (Roughening treatment is not included).

  In the electroless plating step, for example, when an electroless nickel coating is formed on the surface of an insulating substrate, an electroless nickel-phosphorous plating solution using hypophosphite as a reducing agent and a borohydride compound are used as the reducing agent. An electroless nickel-boron plating solution or the like can be used. In the electroless plating step, for example, when an electroless copper coating is formed on the surface of an insulating substrate, an electroless copper plating solution using ethylenediamine (EDA) or Rochelle salt as a complexing agent and formalin as a reducing agent. Etc. can be used.

(3) Electrolytic plating step In the electrolytic plating step, an electrolytic plating solution containing 0.02 mol / L or more of nitrogen compound and / or 0.001 mol / L or more of a sulfur compound as an additive is used. An electrolytic plating film is formed on the electroless plating film. The higher the additive concentration tends to have a greater compressive stress, but if the additive concentration becomes too high, as described above, the content of additive components such as nitrogen incorporated into the electrolytic plating film increases, This is not preferable because problems such as an increase in electrical resistivity of the electrolytic plating film and deterioration in film quality occur. From these viewpoints, the additive concentration is required to be within the above range.

  The nitrogen compound or sulfur compound as the additive is preferably, for example, one or more of alkylamines, thiourea and thiourea derivatives. For example, an electrolytic copper plating film having compressive stress can be obtained by adding alkylamines to the electrolytic copper plating solution or the like. Similarly, an electrolytic copper plating film having compressive stress can be obtained by using thiourea as an additive such as an electrolytic copper plating solution. When thiourea is used as an additive, a thick (2 μm or more) electrolytic plating film can be formed on the surface of the insulating substrate with good adhesion via an electroless plating film.

  These additives may be used alone, but any two or more of them can be used simultaneously. For example, compared to the case of using alkylamines alone as an additive, a thicker electrolytic plating film can be formed with better adhesion by using thiourea or a thiourea derivative as an additive together with alkylamines. However, the electrical resistivity of the obtained electrolytic copper plating film becomes smaller when an alkylamine is used alone as an additive. Therefore, from the viewpoint that a metal film having a low electrical resistivity can be formed on the surface of the insulating substrate, it is preferable to use an alkylamine alone as an additive. On the other hand, from the viewpoint of forming a thicker metal film on the surface of the insulating substrate, it is preferable to use thiourea or a thiourea derivative.

Specific examples of alkylamines that can be used include ethylenediamine, diethylenetriamine, and triethylenetetraamine. Further, thiourea is a compound generally represented by CH ₄ N ₂ S, but in the present invention, other compounds having a structure of “> N—C (═S) —N <” are also included. . Specific examples of thiourea derivatives include 1-acetyl-2-thiourea. Even when this thiourea derivative such as 1-acetyl-2-thiourea is used, it is considered that the same effect as that obtained when thiourea is used is obtained.

In the electrolysis step, an insulating base material on which an electroless plating film is formed is immersed in an electrolytic plating solution containing the above additives in the above concentration range, and the electroless plating film is used as a cathode, for example, a stainless electrode or the like is used as an anode. Then, electrolysis of the electrolytic plating solution is performed. In the electrolytic plating step, electrolysis of the electrolytic plating solution is preferably performed at a current density of 0.05 A / dm ² or more and 5 A / dm ² or less. When the electrolytic plating solution is electrolyzed under a lower current density condition, a metal film having better adhesion can be formed on the surface of the insulating substrate. From this viewpoint, the current density during electrolysis is more preferably 3 A / dm ² or less.

  Moreover, it is preferable that the bath temperature of the electroplating bath at the time of electrolysis is 20 degreeC or more. As the bath temperature is increased, a metal film having a low electrical resistivity tends to be obtained, and it is more preferably 25 ° C. or higher. On the other hand, when the bath temperature increases, the electrolytic plating bath tends to decompose. From this viewpoint, the bath temperature of the electrolytic plating bath is preferably 60 ° C. or less, and more preferably 30 ° C. or less. However, when a sulfur compound is included as an additive, the bath temperature is preferably 30 ° C. or lower in order to obtain a metal film with good adhesion. In addition, when only a nitrogen compound is included as an additive, even if bath temperature is 30 degreeC or more, the metal film with favorable adhesiveness with respect to an insulating base material can be obtained.

  By the above method, an electrolytic plating film can be formed on the surface of the electroless plating film with a thickness of 0.5 μm or more, and the electroless plating film and the metal film made of the electrolytic plating film are adhered to the surface of the insulating substrate. It can be formed with good properties. The electrolytic plating film formed in the method has a compressive stress. Moreover, the electrolytic plating film formed by the method tends to have a fine crystal structure, and the average particle diameter of the crystal grains constituting the electrolytic plating film is 1.5 μm or less, preferably 1 μm or less. In addition, since a relatively thick electrolytic plating film can be formed on the surface of the insulating substrate, a conductive film having a low electrical resistivity can be obtained.

  Next, the present invention will be specifically described with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

  In Example 1, as shown in FIG. 1, first, an electroless nickel coating 12 is formed on the surface of a glass insulating substrate 10 provided with a transparent conductive film 11 made of ITO by the following electroless plating process. Then, an electrolytic copper coating 13 was formed on the electroless nickel coating 12 by the following electrolytic plating process, and a metal coating composed of the electroless nickel coating 12 and the electrolytic copper coating was provided. The arithmetic average roughness (Ra) of the surface of the transparent conductive film 11 is 1.5 nm. Hereinafter, the electroless plating process and the electrolytic plating process will be described.

(1) Electroless plating step In the electroless plating step, an electroless plating method has an electroless thickness of 0.2 μm on the surface (smooth surface) of the transparent conductive film 11 provided on the surface of the insulating substrate 10 by an electroless plating method. A nickel coating was formed.

(2) Electrolytic plating step On the surface of the electroless nickel coating obtained in the electroless plating step, ethylenediamine with respect to a commercially available electrolytic copper plating solution (Meltex Co., Ltd. electrolytic copper plating solution: Mercapa CF-2170) Was electrolyzed at a current density of 1 A / dm ² using an electrolytic copper plating solution to which 0.05 mol / L was added to form an electrolytic copper film having a thickness of 2 μm. Let the sample obtained at the above process be the sample 1-1. Furthermore, with respect to the commercially available electrolytic copper plating solution, an electrolytic copper plating solution to which 0.05 mol / L of ethylenediamine and 0.001 mol / L of thiourea (CH ₄ N ₂ S) are added is used. A sample formed with an electrolytic copper coating was designated Sample 1-2. In FIG. 2, the SEM image of the cross section of the sample 1-2 is shown.

  In Example 2, the surface of the insulating base material provided with the transparent conductive film was electrolessly treated in the same manner as in Example 1 except that the electrolytic copper plating solution having the composition shown in Table 1 below was used in the electrolytic plating process. A nickel coating was formed, and an electrolytic copper coating was formed on the surface of the electroless nickel coating to obtain Sample 2-1 and Sample 2-2. As shown in Table 1, the electrolytic copper plating solution used when forming Sample 2-1 contains ethylenediamine at a concentration of 0.28 mol / L, and the electrolytic copper used when forming Sample 2-2. In addition to ethylenediamine 0.28 mol / L, the plating solution contains thiourea at a concentration of 0.001 mol / L.

Comparative example

[Comparative Example 1]
As Comparative Example 1, electroless plating was performed on the surface of an insulating substrate provided with a transparent conductive film in the same manner as in Example 1 except that an electrolytic copper plating solution not containing ethylenediamine and thiourea was used in the electrolytic plating step. A nickel coating was formed, and an electrolytic copper coating was formed on the surface of the electroless nickel coating. This is designated as Comparative Sample 1.

[Comparative Example 2]
As a sample of Comparative Example 2, in the electrolytic plating process, except that an electrolytic copper plating solution not containing ethylenediamine and thiourea was used, in the same manner as in Example 2, the surface of the insulating base material provided with the transparent conductive film was used. An electroless nickel coating was formed, and an electrolytic copper coating was formed on the surface of the electroless nickel coating. This is designated as Comparative Sample 2.

[Evaluation]
Table 2 shows the results of measuring the internal stress of the electrolytic copper coating of each sample obtained in Example 1, Example 2 and Comparative Example with a spiral stress meter. As shown in Table 2, Sample 1-1 to Sample 2-2 obtained in Example 1 and Example 2 exhibited a compressive stress of 0 MPa to 58.8 MPa. On the other hand, Comparative Sample 1 showed a tensile stress of 137.3 MPa to 225.6 MPa, and Comparative Sample 2 showed a tensile stress of 166.7 MPa to 196.1 MPa. Sample 1-1 to Sample 2-2 obtained in Example 1 and Example 2 both have good adhesion to the surface of the insulating substrate, specifically the surface of the transparent conductive film. Did not occur. In particular, the adhesion to the surface of the insulating substrate of Sample 1-2 and Sample 2-2, which were prepared using an electrolytic copper plating solution to which thiourea was added in addition to ethylenediamine, was good. Compared to Sample 2-1, good adhesion could be maintained even when the thickness of the electrolytic copper coating was increased. On the other hand, Comparative Sample 1 and Comparative Sample 2 were both peeled off from the surface of the insulating substrate, and practically sufficient adhesion could not be obtained. In Table 2, “◎” means that adhesion is particularly good, “◯” means that adhesion is good, and “×” means that adhesion cannot be obtained. To do.

  According to the present invention, a metal coating comprising an electroless plating coating and an electrolytic plating coating having a compressive stress on the surface of an insulating substrate having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less. By providing this, a thick metal film can be provided on the surface of the insulating base material with good adhesion without performing a roughening treatment.

Claims (9)

A metal film provided on an insulating base made of glass having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less,
An electroless plating film formed on the smooth surface by an electroless plating method;
An electrolytic plating film formed on the surface of the electroless plating film by an electrolytic plating method;
With
The electrolytic plating film has compressive stress,
A metal coating characterized by   The metal coating according to claim 1, wherein the electrolytic plating film contains at least one element of nitrogen, sulfur, and carbon. The metal film according to claim 1 or 2, wherein the electrolytic plating film contains nitrogen or carbon derived from alkylamines.   The metal film according to any one of claims 1 to 3, wherein the electroless plating film is an electroless nickel film, and the electrolytic plating film is an electrolytic copper film. The smooth surface of the insulating substrate made of glass is provided with a conductive film made of an inorganic oxide,
The metal film according to any one of claims 1 to 4, wherein the electroless plating film is formed on the conductive film. A metal film provided on an insulating substrate having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less,
An electroless plating film formed on the smooth surface by an electroless plating method;
An electrolytic plating film formed on the surface of the electroless plating film by an electrolytic plating method;
With
The electrolytic plating film has a compressive stress,
The smooth surface of the insulating base material is provided with a conductive film made of an inorganic oxide,
A metal film, wherein the electroless plating film is formed on the conductive film. A metal film forming method for forming a metal film on an insulating base made of glass having a smooth surface with an arithmetic average roughness (Ra) of 0.3 μm or less,
An electroless plating step of forming an electroless plating film on the smooth surface of the insulating substrate by an electroless plating method;
An electrolytic plating step of forming an electrolytic plating film on the surface of the electroless plating film by an electrolytic plating method;
With
In the electrolytic plating step, an electrolytic plating solution containing alkylamines in an amount of 0.02 mol / L to 0.3 mol / L as an additive is used,
A metal film forming method characterized by the above. The metal film forming method according to claim 7, wherein the electrolytic plating solution contains 0.001 mol / L or more of thiourea and / or a thiourea derivative as an additive . It said electroplating step, the metal film forming method according to claim 7 or claim 8 carried out at a current density of 0.1 A / dm ² or more 5A / dm ² or less.