CN110062820B

CN110062820B - Method for forming transparent conductive film and plating solution for electroplating

Info

Publication number: CN110062820B
Application number: CN201780076688.3A
Authority: CN
Inventors: 星野秀树; 大屋秀信; 山内正好; 小俣猛宪; 新妻直人
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2016-12-16
Filing date: 2017-11-16
Publication date: 2021-07-20
Anticipated expiration: 2037-11-16
Also published as: CN110062820A; JP6988826B2; JPWO2018110198A1; WO2018110198A1

Abstract

The invention aims to provide a transparent conductive film forming method and a plating solution for electroplating of a transparent conductive film with excellent conductivity and suppressed plating width. This technical problem is solved as follows. A method of forming a transparent conductive film, comprising: a transparent conductive film intermediate body composed of conductive thin lines is formed on a transparent substrate by a printing method, and then the transparent conductive film intermediate body is electroplated to form a transparent conductive film, and a plating solution for the electroplating contains an oxidizing agent.

Description

Method for forming transparent conductive film and plating solution for electroplating

Technical Field

The present invention relates to a method for forming a transparent conductive film and a plating solution for electroplating, and more particularly, to a method for forming a transparent conductive film and a plating solution for electroplating, which can form a transparent conductive film having excellent conductivity and a suppressed plating width.

Background

Patent document 1 discloses that a conductive thin line pattern formed by a printing method is plated to form a transparent conductive film.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 2015 + 012046

Disclosure of Invention

Technical problem to be solved by the invention

However, the technique of patent document 1 has room for further improvement from the viewpoint of forming a transparent conductive film having excellent conductivity and suppressed plating width. In addition, patent document 1 does not disclose that these technical problems are solved by the formulation of the plating solution.

The present invention addresses the problem of providing a transparent conductive film forming method and a plating solution for electroplating, by which a transparent conductive film having excellent conductivity and a suppressed plating width can be formed.

Other technical problems of the present invention are as follows.

Means for solving the problems

The above-described technical problem can be solved by the following inventions.

1. A method of forming a transparent conductive film, comprising:

a transparent conductive film intermediate containing a conductive thin line is formed on a transparent substrate by a printing method,

then, the transparent conductive film intermediate is subjected to electroplating to form a transparent conductive film,

the plating solution used for the electroplating contains an oxidizing agent.

2. The method for forming a transparent conductive film according to the above 1, wherein the oxidizing agent is one or more selected from the group consisting of sodium persulfate, copper chloride and hydrogen peroxide.

3. The method for forming a transparent conductive film according to the above 1 or 2, wherein the plating solution has an oxidation-reduction potential of 350mV to 700mV (vs Ag/AgCl).

4. The method for forming a transparent conductive film according to any one of the above 1 to 3,

in the printing method, the conductive thin line is formed by selectively depositing the conductive material on the edge of the linear liquid in the process of applying the linear liquid containing the conductive material on the transparent base material and then drying the linear liquid.

5. A plating solution for electroplating contains an oxidizing agent.

6. The plating solution for electroplating according to the above 5, wherein the oxidizing agent is one or more selected from the group consisting of sodium persulfate, copper chloride and hydrogen peroxide.

7. The plating solution for electroplating according to claim 5 or 6, wherein the oxidation-reduction potential is 350mV to 700mV (vs Ag/AgCl).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a transparent conductive film forming method and a plating solution for plating, which can form a transparent conductive film having excellent conductivity and suppressed plating width.

Drawings

FIG. 1 is a view for explaining an example of a method for forming a conductive thin line

FIG. 2 is a diagram for explaining a first mode of forming a mesh pattern

FIG. 3 is a diagram for explaining a second mode of forming a mesh pattern

FIG. 4 is a cross-sectional view conceptually showing an example of a conductive thin line

Detailed Description

Hereinafter, embodiments of the present invention will be specifically described.

1. Method for forming transparent conductive film

In the method for forming a transparent conductive film of the present invention, a transparent conductive film intermediate made of conductive thin lines is plated to form a transparent conductive film. Here, the plating solution for electroplating contains an oxidizing agent, whereby an effect of forming a transparent conductive film having excellent conductivity and suppressed plating width can be obtained. By suppressing the plating width, for example, optical properties of the transparent conductive film such as low visibility (property of being difficult to visually recognize) and transparency can be improved.

(1) Formation of intermediate (conductive thin line) of transparent conductive film

By forming the conductive thin line on the substrate, a transparent conductive film intermediate body composed of the conductive thin line can be formed. A printing method is used for forming the conductive thin line on the base material, and particularly, a printing method utilizing a coffee stain phenomenon is preferably used.

(printing method)

In the printing method, an ink containing a conductive material may be applied on a substrate to form a conductive fine line.

The printing method is not particularly limited, and examples thereof include: screen printing, relief printing, gravure printing, offset printing, flexographic printing, spray printing, and the like, and among them, spray printing is preferable. The method of ejecting the droplets from the inkjet head in the spray printing method is not particularly limited, and examples thereof include a piezoelectric method and a heating method.

(phenomenon of coffee stain)

In the printing method, when the ink applied to the base material is dried, it is preferable to form a conductive thin line by utilizing the coffee stain phenomenon. This is explained with reference to fig. 1.

First, as shown in fig. 1(a), a linear liquid 2 made of an ink containing a conductive material is applied to a substrate 1.

Then, as shown in fig. 1(b), in the process of drying the linear liquid 2, a conductive material is selectively deposited on the edge of the linear liquid 2 to form a conductive thin line 3. In this example, a pair of conductive

thin lines

3, 3 are formed by selectively depositing a conductive material on both side edges along the longitudinal direction of the linear liquid 2. By uniformly forming the line width of the linear liquid 2, a pair of conductive

thin lines

3, 3 are formed so as to be parallel to each other.

The line width of the conductive thin line 3 may be smaller than the line width of the linear liquid 2, and may be, for example, 20 μm or less, 15 μm or less, and further 10 μm or less. The lower limit of the line width of the conductive thin line 3 is not particularly limited, and may be, for example, 1 μm or more from the viewpoint of providing stable conductivity.

Various patterns may be formed by one or more conductive thin lines 3. Examples of the pattern include a stripe pattern and a mesh pattern. Hereinafter, a first manner of forming the mesh pattern will be described with reference to fig. 2, and then a second manner of forming the mesh pattern will be described with reference to fig. 3.

(first mode of Forming grid Pattern)

In the first embodiment of forming a grid pattern, first, as shown in fig. 2(a), a plurality of linear liquids 2 are formed on a substrate 1 in parallel at predetermined intervals.

Then, as shown in fig. 2(b), when the linear liquid 2 is dried, a pair of conductive

thin lines

3, 3 are formed from the respective linear liquids 2 by the coffee stain phenomenon.

Then, as shown in fig. 2(c), a plurality of linear liquids 2 arranged in parallel at a prescribed interval are formed so as to cross the plurality of conductive thin lines 3 formed previously.

Then, as shown in fig. 2(d), when the linear liquid 2 is dried, a pair of conductive

thin lines

3, 3 are formed from the respective linear liquids 2 by utilizing the coffee stain phenomenon. As described above, a grid pattern may be formed.

In the example of fig. 2, although the linear liquid 2 and the conductive thin line 3 are made straight, it is not limited thereto. The shape of the linear liquid 2 and the conductive thin wire 3 may be, for example, a wavy line or a broken line.

(second mode of Forming grid Pattern)

In the second mode of forming the grid pattern, first, as shown in fig. 3(a), a plurality of quadrangular linear liquids 2 are arranged in parallel on a substrate 1 at predetermined intervals along the longitudinal direction (vertical direction in the drawing) and the width direction (horizontal direction in the drawing) of the substrate 1.

Then, as shown in fig. 3(b), when the thread liquid 2 is dried, a thread unit composed of a pair of conductive threads 3 is obtained from each thread liquid 2 by utilizing the coffee stain phenomenon. In the thin wire unit, one of the conductive thin wires 3 and 3 (the outer conductive thin wire 3) includes the other thin wire (the inner conductive thin wire 3) inside, and is formed concentrically. The conductive

thin lines

3 and 3 form a square shape corresponding to both sides (inner peripheral edge and outer peripheral edge) of the linear liquid 2.

Then, as shown in fig. 3(c), a plurality of quadrangular linear liquids 2 are arranged and formed on the substrate 1 at predetermined intervals in the longitudinal direction and the width direction of the substrate 1. At this time, the linear liquid 2 forming a plurality of quadrangles is formed at a position sandwiched by the previously formed thin line units. At this time, the linear liquid 2 forming a square shape is provided so as to be in contact with the outer conductive thin wire 3 of the thin wire unit adjacent thereto, but not in contact with the inner conductive thin wire 3.

Then, as shown in fig. 3(d), when the linear liquid 2 is fed, a thin wire unit composed of a pair of conductive

thin wires

3 and 3 is further formed from each linear liquid 2 by the coffee stain phenomenon.

In the pattern shown in fig. 3(d), the outer conductive thin lines 3 are connected to the adjacent outer conductive thin lines 3. On the other hand, the inner conductive thin wire 3 is not connected to the other inner conductive thin wires 3 and the outer conductive thin wires 3. That is, the inner conductive thin lines 3 are provided in an isolated manner.

The pattern shown in fig. 3(d) may be directly used as a grid pattern. In addition, the inner conductive thin lines 3 in the pattern shown in fig. 3(d) may be removed to form a mesh pattern composed of the outer conductive thin lines 3 (fig. 3 (e)). According to the second aspect of forming the mesh pattern, an effect of forming the conductive thin lines 3 with a high degree of freedom can be obtained. Particularly, the arrangement interval of the plurality of conductive thin lines 3 can be set with a high degree of freedom, independent of the line width of the linear liquid 2.

The method of removing the inner conductive thin lines 3 is not particularly limited, and for example, a method of irradiating energy rays such as a laser beam or a method of chemical etching treatment can be used.

When the outer conductive thin wire 3 is plated, a method of removing the inner conductive thin wire 3 with a plating solution may be used. As described above, the inner conductive thin wire 3 is isolated and can be excluded from the energizing circuit for plating the outer conductive thin wire 3. Therefore, when the outer conductive thin line 3 is plated (when conducting electricity), the inner conductive thin line 3 which is not plated can be removed by dissolving or decomposing the plating solution.

In the example of fig. 3, although the linear liquid 2 and the conductive thin line 3 are made quadrangular, it is not limited thereto. The shape of the linear liquid 2 and the conductive thin wire 3 may be a closed geometric figure. As closed geometric figures, mention may be made of: polygons such as triangle, quadrangle, hexagon, and octagon. In addition, the closed geometric figure may include curved elements such as circles, ovals, and the like.

[ base Material ]

As the substrate, a transparent substrate is preferably used. The transparency of the transparent substrate is not particularly limited, and the light transmittance thereof may be an arbitrary value from several% to several tens%, and the spectral transmittance thereof may also be an arbitrary value. These light transmittance and spectral transmittance may be appropriately determined depending on the use and purpose.

The material of the substrate is not particularly limited, and for example, glass, a synthetic resin material, and various other materials can be used. Examples of the synthetic resin material include: polyethylene terephthalate (PET) resin, polyethylene naphthalate (PEN) resin, polybutylene terephthalate resin, cellulose resin (e.g., polyacetyl cellulose, cellulose diacetate, and cellulose triacetate), polyethylene resin, polypropylene resin, methacrylic resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile- (poly) styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin, polyimide resin, polyamide resin, and polyamide-imide resin. These materials can impart good transparency to the substrate.

The shape of the substrate is not particularly limited, and may be, for example, a plate shape (plate material). In the case of using as a plate material, the thickness, size (area), and shape are not particularly limited and may be appropriately determined depending on the application and purpose of the transparent conductive film. The thickness of the plate is not particularly limited, and may be, for example, about 1 μm to 10cm, or about 20 μm to 300 μm.

In addition, the substrate may be surface treated to change the surface energy. Further, a hard coat layer, an antireflection layer, or the like may be provided on the substrate.

[ ink ]

Next, a printing method will be described in detail, particularly an ink suitable for the above-described coffee stain phenomenon.

The conductive material contained in the ink is not particularly limited, and there may be mentioned: conductive fine particles, conductive polymers, and the like.

Examples of the conductive fine particles include: metal particles, carbon particles, and the like.

Examples of the metal constituting the metal fine particles include Au, Pt, Ag, Cu, Ni, Cr, Rh, Pd, Zn, Co, Mo, Ru, W, Os, Ir, Fe, Mn, Ge, Sn, Ga, and In. Among them, Au, Ag and Cu are preferable, and Ag is particularly preferable. The average particle diameter of the metal fine particles may be, for example, 1 to 100nm, and more preferably 3 to 50 nm. The average particle diameter is a volume average particle diameter and can be measured by "Zeta Sizer 1000 HS" manufactured by Malvern.

Examples of the carbon fine particles include: graphite particles, carbon nanotubes, fullerenes, and the like.

The conductive polymer is not particularly limited, and a pi-conjugated conductive polymer is preferable. As the pi-conjugated conductive polymer, there can be mentioned: polythiophenes and polyanilines, and the like. The pi-conjugated conductive polymer can be used, for example, together with a polyanion such as polystyrene sulfonic acid.

The concentration of the conductive material in the ink may be 5 wt% or less, or 0.01 wt% or more and 1.0 wt% or less. This promotes the coffee stain phenomenon, and can provide an effect of making the conductive thin wire finer.

The solvent used for the ink is not particularly limited, and may contain one or more selected from water and organic solvents. As the organic solvent, there may be mentioned: alcohols such as 1, 2-hexanediol, 2-methyl-2, 4-pentanediol, 1, 3-butanediol, 1, 4-butanediol, and propylene glycol, and ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and dipropylene glycol monoethyl ether.

The ink may further contain other components such as a surfactant. The surfactant is not particularly limited, and examples thereof include silicone surfactants. The concentration of the surfactant in the ink may be, for example, 1 wt% or less.

(drying of ink)

The drying method for drying the ink (linear liquid) applied to the substrate may be natural drying or forced drying. The drying method for forced drying is not particularly limited, and for example, a method of heating the surface of the substrate to a predetermined temperature may be used alone or in combination; and a method of forming a gas flow on the surface of the substrate. For example, the air flow may be formed by blowing or sucking using a fan or the like.

(2) Electroplating of

The transparent conductive film intermediate is subjected to electroplating to form a transparent conductive film. In this case, the transparent conductive film intermediate can be electroplated by immersing the transparent conductive film intermediate in a plating solution, bringing the anode into contact with the plating solution, and electrically connecting the cathode to the transparent conductive film intermediate. Therefore, a metal layer (also referred to as a plating film) that may contain a plating metal is laminated on the conductive thin wire constituting the intermediate of the transparent conductive film. By utilizing the conductivity of the transparent conductive film intermediate containing the conductive thin line, plating can be selectively applied to the transparent conductive film intermediate.

By electroplating using a plating solution containing an oxidizing agent, a transparent conductive film having excellent conductivity and suppressed plating width can be obtained. As a result of suppressing the plating width, the following effects are obtained: for example, an increase in the line width of a conductive thin line accompanying plating is suppressed; or the line width of the conductive fine line becomes finer than before the plating. On the other hand, the film thickness of the conductive thin line can be appropriately increased. For example, a metal layer (plating film) having a film thickness larger than that of the conductive thin line before plating may be laminated. This improves the conductivity of the transparent conductive film.

In particular, the conductive thin line formed by a printing method, preferably a printing method utilizing the above-described coffee stain phenomenon, can exhibit particularly excellent effects of excellent conductivity and suppression of plating width by electroplating using a plating solution containing an oxidizing agent. The reason is presumed as follows.

Fig. 4 is a cross-sectional view conceptually showing an example of the conductive thin line, and shows a state in which the conductive thin line 3 formed on the base 1 is cut on a plane perpendicular to the longitudinal direction of the conductive thin line 3. In this case, a pair of conductive

thin lines

3 and 3 formed by a printing method utilizing the coffee stain phenomenon is exemplified.

Although the coffee stain phenomenon causes the conductive material to accumulate along the edge of the linear liquid, the accumulation position is somewhat different, and therefore the film thickness of each conductive thin line 3 is thick at the central portion 31 and thin at the

end portions

32 and 33. In particular, the end 33 provided on the inner side (the center side of the linear liquid) of the pair of conductive

thin lines

3, 3 is likely to be different in the deposition of the conductive material, and thus is likely to form a thin portion.

As a result, the

end portions

32 and 33 of the conductive thin wire 3 have lower conductivity than the central portion 31, and therefore plating is not easily performed. Further, since the

end portions

32 and 33 of the conductive thin line 3 have a sparser distribution of the conductive material than the central portion 31, the conductive material receives a removing action of the oxidizing agent from multiple directions. On the other hand, since the center portion 31 of the conductive thin wire 3 has higher conductivity than the

end portions

32 and 33, the plating is easily performed. Further, since the conductive material is more densely distributed in the central portion 31 of the conductive thin line 3 than in the

end portions

32 and 33, the conductive material is less likely to be affected by the effect of removing the oxidizing agent. The above elements cooperate with each other to stably grow the plating film in the thickness (height) direction and to suppress the growth of the plating film in the width direction. As a result, the effects of exhibiting excellent conductivity and suppressing the plating width are exhibited.

In addition, in the printing method using the coffee stain phenomenon, a portion of the conductive material may remain on the center side of the thread-like liquid during the drying process of the thread-like liquid without being brought to the edge of the thread-like liquid. In fig. 4, the conductive material remaining on the center side is denoted by reference numeral 4. By adding the oxidizing agent to the plating solution, the effect of removing the conductive material 4 remaining on the center side can be obtained together with the plating. In the second aspect of forming the mesh pattern, when the outer conductive thin wire is plated with the plating solution containing the oxidizing agent, the effect of effectively removing the inner conductive thin wire by the plating solution can be obtained.

As described with reference to fig. 4, the effect will be described with reference to the conductive thin line formed by the printing method using the coffee stain phenomenon, but the effect is also exhibited in the printing method not using the coffee stain phenomenon. For example, in a printing method including a wet process using ink, the thickness of the end portion of the conductive thin line is thinner than the thickness of the central portion of the conductive thin line due to the influence of the ink surface tension, and the same effect as described above can be exhibited.

In a printing method such as an ink jet method, a conductive material may be provided in a non-target region (a region other than a region where a line-shaped liquid is to be formed) on a substrate. For example, satellite ink, which may adhere to non-target areas on a substrate, is ejected from the nozzles of an inkjet head along with a main drop of ink. By adding an oxidizing agent to the plating solution, an effect of removing the conductive material in the non-target region can be obtained together with the plating.

[ oxidizing agent ]

The oxidizing agent contained in the plating solution is not particularly limited. For example, there may be mentioned: persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, hydrogen peroxide, and copper chloride (cupric chloride; CuCl)₂) Iron chloride (ferric chloride; FeCl₃) Potassium permanganate, potassium dichromate, and the like.

In particular, the oxidizing agent is preferably any one or more selected from the group consisting of sodium persulfate, copper chloride, and hydrogen peroxide. Thus, the effect of the present invention can be more favorably exhibited, and the effect that by-products suppressing the action of plating and an oxidizing agent are less likely to be generated can be obtained.

[ Oxidation-reduction potential ]

The redox potential of the plating solution is preferably 350mV to 700mV (vs Ag/AgCl). This makes the effects of the present invention more favorably exhibited.

The amount of the oxidizing agent contained in the plating solution is preferably adjusted so that the oxidation-reduction potential of the plating solution is within the above range. The plating apparatus preferably includes an oxidation-reduction potential measuring device for measuring the oxidation-reduction potential of the plating solution, and the oxidation-reduction potential of the plating solution is preferably monitored without performing the plating so as to be maintained within the above-described range.

[ additives ]

The plating solution may contain an additive, but preferably contains no additive. For example, a copper sulfate plating solution generally contains copper sulfate, sulfuric acid, hydrochloric acid (as a source of chloride ions), and a brightener as an additive. By omitting such an additive, the effects of the present invention can be more effectively exerted. Further, as additives preferably not contained in the plating solution, there can be mentioned: saccharin, benzothiazole, thiourea, JGB, acetylacetone, lead, bismuth having effect of suppressing plating reaction, chloride ion having effect of promoting plating precipitation, CN-, SCN-, sulfide (thiourea, SPS, DMTD, etc.), boric acid, oxalic acid, malonic acid, PEG having effect of film formation, PEGNPE, polyvinyl alcohol, gelatin, unsaturated alcohol (butynediol, propiolic alcohol, coumarin, etc.) having effect of suppressing unevenness of plating surface shape, NO^3-、Fe³⁺And the like.

[ use of oxidizing agent ]

The transparent conductive film intermediate may be plated multiple times with different plating metals. The plating solution containing the oxidizing agent may be used for each of the multiple times of plating, or only a part of the plating solution containing the oxidizing agent may be used. For example, a plating solution containing no oxidizing agent may be used for the first plating, or a plating solution containing an oxidizing agent may be used for the second and subsequent plating.

For example, a plating solution containing an oxidizing agent may be used for the first plating, or a plating solution containing a higher concentration of an oxidizing agent may be used for the second and subsequent plating.

In the same electroplating as the metal to be electroplated, the electroplating is continued using a plating solution containing no oxidizing agent, and then the electroplating may be continued with the oxidizing agent contained in the plating solution.

For example, in the case of electroplating which is the same as the metal to be electroplated, the electroplating is continued using a plating solution containing an oxidizing agent, and then the electroplating is further continued by increasing the oxidizing agent concentration of the plating solution.

As described above, the plating initially performed on the transparent conductive film intermediate may contain no oxidizing agent, or may contain an oxidizing agent at a lower concentration than the plating solution used in the subsequent plating. This can provide an effect of appropriately preventing the conductive thin line from being broken.

[ Multi-layer Metal layer ]

By subjecting the transparent conductive film intermediate to a plurality of plating treatments with different plating metals, a plurality of metal layers can be stacked on the conductive thin line. In the case of laminating a plurality of metal layers, by laminating a first metal layer formed of copper and a second metal layer formed of nickel or chromium in this order on the conductive thin wire, an effect of improving conductivity by copper, an effect of improving weather resistance by nickel or chromium, and an effect of removing color can be obtained. The plating solution for electroplating may contain an oxidizing agent such as sodium persulfate, copper chloride, or hydrogen peroxide. Further, by using an oxidizing agent, the conductivity of the conductive thin line can be improved, and the plating width can be suppressed. The effect is exhibited well when a conductive thin line formed by the coffee stain phenomenon is used as an object.

(3) Others

[ firing treatment ]

The conductive thin wire formed on the substrate may be subjected to firing treatment. The firing treatment may be performed as a pretreatment for plating, for example. Examples of the firing treatment include: light irradiation treatment, heat treatment, and the like. As the light irradiation treatment, the heat treatment, and the like, for example, there can be used: gamma rays, X rays, ultraviolet rays, visible light, Infrared Rays (IR), microwaves, radio waves, and the like. For the heat treatment, for example, hot air, a heating stage, a heating press, or the like can be used.

[ use ]

The use of the substrate with the transparent conductive film and the transparent conductive film is not particularly limited, and for example, the substrate can be used for various devices and the like in various electronic machines. Here, "transparent" does not mean that the conductive thin lines themselves constituting the transparent conductive film are transparent, but that the entire transparent conductive film (for example, through regions where no conductive thin lines are provided) transmits light.

The conductive thin wire constituting the transparent conductive film can be used as, for example, an electric wire constituting a circuit.

In addition, for example, a transparent conductive film may be used as one transparent electrode (planar electrode).

For example, the transparent electrode can be used as a transparent electrode for displays of various types such as liquid crystal, plasma, organic electroluminescence, and field emission. In addition, the transparent electrode can be used as a transparent electrode for touch panels, mobile phones, electronic paper, various solar cells, various electroluminescence control elements, and the like. In particular, the transparent electrode may be used as a touch panel sensor of an electronic device such as a smart phone, a tablet terminal, or the like. When used as a touch panel sensor, the transparent electrodes may be used as position detection electrodes (X electrodes and Y electrodes).

2. Plating solution for electroplating

The plating solution for electroplating of the present invention is characterized by containing an oxidizing agent. By performing electroplating using the plating solution, the plated product has excellent conductivity and the effect of suppressing the plating width can be obtained. As a more detailed description of the plating solution, the description of "1. method for forming transparent conductive film" can be cited.

Examples

Examples of the present invention will be described below, but the present invention is not limited to these examples.

(example 1)

1. Formation of transparent conductive film intermediate

A transparent conductive film intermediate comprising a grid pattern was formed in a region of 5cm by 10cm of a polyethylene terephthalate (PET) substrate having a thickness of 125 μm using an ink jet head (KM 1024i LHE-30 manufactured by Konica Minolta corporation, standard droplet volume: 30pL) filled with an ink containing 1.0 wt% of silver nanoparticles (average particle diameter: 20nm) and 99.0 wt% of 1-butanol, in the same manner as shown in FIG. 2.

2. Formation of metal layer

(1) Preparation of plating solution

As an oxidizing agent, sodium persulfate is added to an aqueous solution (general copper sulfate plating solution) containing copper sulfate, sulfuric acid, hydrochloric acid, and a brightening agent as an additive to prepare a plating solution. The pH of the plating solution was 3.2 to 3.4 (the pH was the same in other examples and comparative examples).

(2) Electroplating of

The substrate with the transparent conductive film intermediate is immersed in the plating solution, the anode is placed in the plating solution, the cathode is electrically connected to the transparent conductive film intermediate, and electroplating is performed by applying a current using a rectifier so that the conductivity is 1A · min (0.1A × 10 min). Thereby, a transparent conductive film (transparent conductive film intermediate to which plating is applied) was obtained.

3. Evaluation method

The obtained transparent conductive film was evaluated by the following method. The transparent conductive film intermediate before plating was also evaluated by the same method.

(1) Line width of conductive thin line

The line width of the conductive thin line is an average value of 20 points of the line width of the conductive thin line measured at 5000 times at random using a conductive optical Microscope ("Digital Microscope VHX-5000" manufactured by keyence corporation).

(2) Resistance of grid pattern

The resistance of the mesh pattern was an average value of 20 points measured at random at both ends of the mesh pattern by using a tester ("Digital Multimeter CD 770" manufactured by mitsui and electric meter corporation).

The results are shown in Table 1.

(example 2)

The same procedure as in example 1 was repeated except that copper chloride was used as an oxidizing agent for the plating solution instead of sodium persulfate in example 1. The results are shown in Table 1.

(example 3)

The same procedure as in example 1 was repeated except that hydrogen peroxide was used as an oxidizing agent for the plating solution instead of sodium persulfate in example 1. The results are shown in Table 1.

(example 4)

The same procedure as in example 1 was repeated, except that the addition of the additive (brightener) to the plating solution was omitted in example 1. The results are shown in Table 1.

Comparative example 1

The same procedure as in example 1 was repeated, except that the mixing of the oxidizing agent in the plating solution was omitted in example 1. The results are shown in Table 1.

Comparative example 2

In comparative example 1, the same procedure as in comparative example 1 was carried out, except that as the pretreatment for plating, etching treatment was performed on the transparent conductive film intermediate using sodium persulfate. The results are shown in Table 1.

Comparative example 3

Comparative example 2 was performed in the same manner as comparative example 2 except that etching treatment was performed as post-treatment instead of plating pretreatment. The results are shown in Table 1.

TABLE 1

< evaluation >

As can be seen from table 1, examples 1 to 4, which are methods for forming the transparent conductive film of the present invention, are superior in conductivity and suppressed in plating width as compared with comparative examples 1 to 3.

(example 5): confirmation test 1 of dependence of Oxidation-reduction potential

The operation was carried out in the same manner as in example 1 except that the oxidation-reduction potential of the plating solution was adjusted to 350mV (vs Ag/AgCl) in example 1. The results are shown in Table 2.

(example 6): confirmation test 2 of dependence of Oxidation-reduction potential

The operation was carried out in the same manner as in example 5 except that the oxidation-reduction potential of the plating solution was adjusted to 800mV (vs Ag/AgCl) in example 5. The results are shown in Table 2.

TABLE 2

< evaluation >

As is clear from table 2, the higher the oxidation-reduction potential of the plating solution, the thinner the line width of the conductive thin line. Therefore, the following steps are carried out: the oxidation-reduction potential is 350mV (vs Ag/AgCl) or more, thereby appropriately suppressing the increase in line width of the conductive thin line and appropriately suppressing the plating width. On the other hand, when the oxidation-reduction potential is 800mV (vs Ag/AgCl), the line width of the conductive thin line becomes small, but the resistance of the transparent conductor slightly increases. Thus, it can be seen that: the oxidation-reduction potential of the plating solution is preferably 350mV to 700mV (vs Ag/AgCl) from the viewpoint of more favorably achieving the improvement in conductivity and the suppression of the plating width.

Description of the marks

1: base material

2: linear liquid

3: conductive thin wire

Claims

1. A method of forming a transparent conductive film, comprising:

the plating solution used for the electroplating contains an oxidizing agent.

2. The method for forming a transparent conductive film according to claim 1, wherein the oxidizing agent is one or more selected from the group consisting of sodium persulfate, copper chloride, and hydrogen peroxide.

3. The method for forming a transparent conductive film according to claim 1 or 2, wherein the oxidation-reduction potential of the plating solution is 350mV to 700mV (vs Ag/AgCl).

4. The method for forming a transparent conductive film according to claim 1 or 2,