JP2022154511A - Conductive thin film and method for producing the same, and conductive sheet - Google Patents

Abstract

To provide a conductive thin film that has low sheet resistance and high adhesion to a substrate.SOLUTION: A conductive thin film is laminated on a substrate and contains a transition metal. The conductive thin film has a density gradient of phosphorus atoms in the thickness direction of the conductive thin film. The density gradient of phosphorus atoms has a maximum value Pm of the phosphorus density in a range from the half of the thickness of the conductive thin film to the substrate.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a conductive thin film, its manufacturing method, and a conductive sheet.

Conductive thin films composed of transition metals and/or transition metal compounds are used in various electronic devices and are industrially useful. In particular, a conductive thin film of a transition metal and/or a transition metal compound produced by a method including a step of applying a precursor is desirable from the viewpoint of enabling large-scale production.

For example, in Patent Document 1, a dispersion liquid of fine particles of a metal or a metal compound is printed on a base material and fired to fuse at least the fine metal particles on the outermost surface to produce a conductive substrate including a conductive thin film. A method is disclosed wherein calcination is performed by exposure to a plasma of a gas containing a reducing gas. Thus, by using plasma treatment for firing, even copper with a relatively high melting point can be sintered, and even copper oxide, which is relatively stable in the atmosphere, can be sintered while being reduced. can.

Patent No. 5354037

Patent Document 1 describes that an oxide remaining without being reduced during the firing process contributes to the adhesion between the conductive thin film thus formed and the substrate. However, the oxide layer in the conductive thin film increases the sheet resistance of the thin film because the conductivity is lower than that of the metal. Therefore, it is difficult to achieve both low sheet resistance and adhesion of the conductive thin film, and it has been desired to manufacture a thin film having adhesion to a substrate even when the oxide layer in the thin film is small.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a thin film having excellent conductivity and excellent adhesion to a substrate.

The present inventors have made extensive studies to solve the above problems. As a result, the inventors have found that the above problems can be solved by forming a specific concentration gradient of phosphorus atoms in the thickness direction of the conductive thin film, and have completed the present invention.

That is, the present invention is as follows.
[1]
A conductive thin film containing a transition metal, laminated on a substrate,
Having a concentration gradient of phosphorus atoms in the thickness direction in the film thickness of the conductive thin film,
The concentration gradient of the phosphorus atoms has a maximum atomic concentration _Pm of the phosphorus atoms in a range closer to the substrate than half the thickness of the conductive thin film.
Conductive thin film.
[2]
The average value P _a of the atomic concentration of phosphorus in the concentration gradient of phosphorus atoms is 0.1% or more and 19% or less.
The conductive thin film according to [1].
[3]
The ratio of the maximum value P _m to the average value P _a (P _m /P _a ) is 2.0 times or more and 200 times or less.
The conductive thin film according to [2].
[4]
The maximum value P _m is 1.0% or more and 20% or less,
[1] The conductive thin film according to any one of [3].
[5]
In the concentration gradient of the phosphorus atoms, the average value _Pa30 of the atomic concentration of the phosphorus atoms in the range of 30 nm from the side close to the substrate is 0.2% or more and 20% or less.
[1] The conductive thin film according to any one of [4].
[6]
The average oxygen atomic concentration O _a in the thickness direction of the conductive thin film is 20% or less.
[1] The conductive thin film according to any one of [5].
[7]
In the thickness direction of the conductive thin film, the film thickness in the range where the atomic concentration of oxygen relative to the atomic concentration of the transition metal is 25% or more is 200 nm or less.
[1] The conductive thin film according to any one of [6].
[8]
In the thickness direction of the conductive thin film, the thickness in the range where the atomic concentration of oxygen is 25% or more is 35% or less with respect to the thickness of the conductive thin film.
[1] The conductive thin film according to any one of [7].
[9]
In the thickness direction of the conductive thin film, the average value Ma of the atomic concentration of the transition metal is 40% or more and 99% or less.
[1] The conductive thin film according to any one of [8].
[10]
The film thickness is 30 nm or more and 1000 μm or less,
[1] to [9] The conductive thin film according to any one of items.
[11]
wherein the transition metal comprises a metal of Group 11 elements of the IUPAC Periodic Table;
[1] The conductive thin film according to any one of [10].
[12]
wherein the transition metal comprises copper;
The conductive thin film according to [11].
[13]
In the thickness direction of the conductive thin film, the maximum value PM _m of the ratio (P/M) of the atomic concentration P of phosphorus to the atomic concentration M of the transition metal is 1.9% or more and 100% or less.
[1] The conductive thin film according to any one of [12].
[14]
In the thickness direction of the conductive thin film, the maximum value _POm of the ratio (P/O) of the atomic concentration P of phosphorus to the atomic concentration O of oxygen is 60% or more and 500% or less.
[1] The conductive thin film according to any one of [13].
[15]
The maximum value PMO _m of the ratio (P/(M+O)) of the atomic concentration P of phosphorus to the sum of the atomic concentration M of the transition metal and the atomic concentration O of oxygen in the thickness direction of the conductive thin film is 1. 9% or more and 20% or less,
[1] The conductive thin film according to any one of [14].
[16]
wherein the conductive thin film comprises a particle layer to which particles containing the transition metal are bonded;
[1] The conductive thin film according to any one of [15].
[17]
wherein the conductive thin film comprises a continuous pattern with openings;
[1] The conductive thin film according to any one of [16].
[18]
wherein the pattern is a pattern composed of a plurality of intersecting fine lines;
The conductive thin film according to [17].
[19]
The line width of the fine line is 100 nm or more and 1000 μm or less,
The conductive thin film according to [18].
[20]
The fine wires have a pitch of 1.0 μm or more and 1000 μm or less.
[18] or the conductive thin film according to [19].
[21]
Visible light transmittance is 70% or more and 99% or less,
[1] The conductive thin film according to any one of [20].
[22]
Sheet resistance is 0.001 Ωcm ^-2 or more and 20 Ωcm ^-2 or less,
[1] The conductive thin film according to any one of [21].
[23]
A base material and the conductive thin film according to any one of [1] to [22],
conductive sheet.
[24]
the substrate has a plurality of layers,
[23] The conductive sheet described in [23].
[25]
The substrate has a surface layer containing a silicon compound,
The conductive sheet according to [23] or [24].
[26]
The base material is plastic,
[23] The conductive sheet according to any one of [25].
[27]
The plastic is polyethylene terephthalate,
The conductive sheet according to [26].
[28]
[1] comprising the conductive thin film according to any one of [22],
touch panel.
[29]
[1] comprising the conductive thin film according to any one of [22],
display.
[30]
[1] comprising the conductive thin film according to any one of [22],
heater.
[31]
[1] comprising the conductive thin film according to any one of [22],
electromagnetic shield.
[32]
[1] comprising the conductive thin film according to any one of [22],
antenna.
[33]
a film forming step of forming a precursor thin film having a phosphorus weight area density of 6.0 mg·m ⁻² or more and 1000 mg·m ⁻² or less on a substrate;
a plasma reaction step of reacting the precursor thin film with plasma for 150 seconds or more and 60 minutes or less to obtain a conductive thin film;
A method for producing a conductive thin film.
[34]
wherein the precursor thin film contains phosphoric acid and/or a phosphate ester;
[33] The method for producing a conductive thin film according to [33].
[35]
The weight area density of the transition metal in the precursor thin film is 1.0 g·m ⁻² or more and 10 g·m ⁻² or less.
[33] or [34] The method for producing a conductive thin film.
[36]
the atmosphere of the plasma reaction step comprises a gas that is a molecule containing hydrogen atoms;
[33] The method for producing a conductive thin film according to any one of [35].
[37]
the atmosphere of the plasma reaction step comprises a noble gas;
[33] The method for producing a conductive thin film according to any one of [36].
[38]
using microwave plasma in the plasma reaction step;
[33] The method for producing a conductive thin film according to any one of [37].

ADVANTAGE OF THE INVENTION According to this invention, the thin film which is excellent in electroconductivity and the adhesiveness to a base material can be provided.

It is a schematic sectional drawing which shows an example of the electroconductive thin film of this embodiment. It is a schematic top view which shows an example of the electroconductive thin film of this embodiment.

Hereinafter, embodiments of the present invention (hereinafter referred to as "present embodiments") will be described in detail with reference to the drawings as necessary, but the present invention is not limited thereto and the gist thereof. Various modifications are possible without departing from the above. In the drawings, the same elements are denoted by the same reference numerals, and overlapping descriptions are omitted. Moreover, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to the illustrated ratios.

1. Conductive thin film The conductive thin film of the present embodiment is a conductive thin film containing a transition metal that is laminated on a substrate, and has a concentration gradient of phosphorus atoms in the thickness direction in the film thickness of the conductive thin film. The concentration gradient of phosphorus atoms has the maximum value _Pm of the atomic concentration of phosphorus in a range closer to the substrate than half the thickness of the conductive thin film. By having such a concentration gradient of phosphorus atoms, the conductivity is further improved, and the adhesion between the conductive thin film and the substrate is further improved.

The conductive thin film contains transition metal atoms and phosphorus atoms, and if necessary, may contain oxygen atoms and other atoms. Moreover, the transition metal may exist in the state of a metal compound such as an oxide in addition to the state of an elemental metal. The composition of each atom in the conductive thin film will be described in detail below.

1.1. Concentration of Phosphorus Atoms The conductive thin film of this embodiment has a concentration gradient of phosphorus atoms in the thickness direction of the film thickness. The concentration gradient of phosphorus atoms has a maximum value _Pm of the atomic concentration of phosphorus in a range closer to the substrate than half the thickness of the conductive thin film.

FIG. 1 shows a schematic cross-sectional view showing an example of the conductive thin film of this embodiment. FIG. 1 shows a schematic cross-sectional view of a conductive sheet 100 in which a conductive thin film 10 is arranged on a substrate 20. As shown in FIG. The conductive thin film 10 shown in FIG. 1 is expressed as a particle layer formed by sintering transition metal particles with plasma, and has pores 11 in its cross section. However, the conductive thin film 10 is not limited to this, and may not have the holes 11 .

In the present embodiment, "the thickness of the conductive thin film has a concentration gradient of phosphorus atoms in the thickness direction, and the concentration gradient of the phosphorus atoms is in a range closer to the substrate than half the thickness of the conductive thin film. In addition, the phrase “has the maximum atomic concentration P _m of phosphorus” means that the concentration of phosphorus atoms increases closer to the substrate side, as exemplified in the graph of the thickness direction and the phosphorus atomic concentration shown in FIG. It means that the maximum value Pm of the phosphorus atoms exists on the substrate side of half the film thickness (thickness 0.5T).

Here, the graph of the thickness direction and the phosphorus atom concentration shown in FIG. It is plotted. Specifically, the graph of the thickness direction and the phosphorus atom concentration shown in FIG. It is the graph which measured the density|concentration of the phosphorus atom contained in a cross section, and plotted it. Note that the plot measurement accuracy is an example, and can be set to sufficiently high accuracy.

Therefore, the maximum value Pm means the maximum value in the graph plotted in this manner, and the average value Pa, which will be described later, means the average value of the phosphorus atomic concentrations in all thickness directions. Further, in this embodiment, the maximum value is denoted by the suffix "m" (Max), and the average value is denoted by the suffix "a" (average). This also applies to transition metal atoms, oxygen atoms, and carbon atoms, which will be described later.

It is considered that the adhesion between the conductive thin film and the substrate is improved by having such a concentration gradient of the phosphorus atoms that the maximum value of the atomic concentration of phosphorus exists on the substrate side. The mechanism by which such an improvement in adhesion is observed is not limited to the following, but by concentrating phosphorus on the substrate side, bonding between transition metals present on the substrate side in the conductive thin film This is thought to be because the bonding strength between the base material and the transition metal is improved, and condensation failure and interfacial peeling are less likely to occur. Here, either one of condensation failure and interfacial peeling may be suppressed, or both may be suppressed. Further, the improvement in bonding strength is not limited to the transition metal itself, and the improvement in bonding strength may occur between a transition metal and a transition metal compound, between transition metal compounds, or between a transition metal compound and a substrate.

In addition, it is considered that the conductivity is improved by having such a concentration gradient of the phosphorus atoms that the maximum value of the atomic concentration of phosphorus exists on the substrate side. The mechanism by which such an improvement in conductivity is observed is not limited to the following. It is conceivable that the grain boundary resistance of the transition metal is reduced by the phosphorus unevenly distributed on the material side, or the conductivity is improved by doping the metal compound with low conductivity such as the metal oxide with phosphorus. . These reasons may act in combination.

The concentration gradient of phosphorus atoms as described above can be formed by a film formation step of forming a precursor thin film containing a phosphorus-based compound and a predetermined plasma reaction step. The details of the method for producing a conductive thin film having these steps will be described later, but in general, it is difficult to control the anisotropic movement of phosphorus in the film in the reaction between the precursor thin film and the plasma, which will be described later. It is very surprising that the method can provide a concentration gradient of phosphorus atoms such that the concentration of phosphorus is higher on the substrate side as described above.

The maximum value P _m of the atomic concentration of phosphorus is in a thickness range (0T to 0.5T) that is 1/2 of the film thickness located on the substrate side, and 1/4 of the film thickness located on the substrate side. It is preferably in the thickness range (0T to 0.25T), and more preferably in the thickness range (0T to 0.1T) that is 1/10 of the film thickness located on the substrate side. When the maximum value _Pm of the atomic concentration of phosphorus is within the above range, the sheet resistance of the conductive thin film is further reduced, and the maximum value Pm exists on the substrate side in the concentration distribution of phosphorus. It tends to be easier to adjust.

Here, "0T to 0.25T" indicates the range in the thickness direction of the conductive thin film. 100 nm to 0.25×100 nm”, ie a thickness range of 0 to 25 nm from the substrate side.

Also, from the same point of view, the maximum value P _m of the atomic concentration of phosphorus is preferably in the range of 100 nm from the side close to the substrate in the thickness direction of the conductive thin film, and 50 nm from the side close to the substrate. It is more preferably in the range, and more preferably in the range of 30 nm from the side closer to the substrate.

The maximum value P _m is preferably 0.2 to 20%, more preferably 1.0 to 15%, even more preferably 1.5 to 10%, and even more preferably 2.0 to 5%. .0%. When the maximum value P _m is 0.2% or more, the sheet resistance of the conductive thin film tends to be further reduced, and the adhesion between the conductive thin film and the substrate tends to be further improved. In addition, when the maximum value P _m is 20% or less, it tends to be easier to adjust the concentration distribution of phosphorus so that the maximum value P m exists on the substrate side. Since the transition metal concentration increases, the sheet resistance of the conductive thin film tends to decrease.

The average value P _a of the atomic concentration of phosphorus in the concentration gradient of phosphorus atoms is preferably 0.1 to 19%, more preferably 0.1 to 10%, and still more preferably 0.1 to 5.0. %, and more preferably 0.1 to 1.0%. When the average value P _a of the atomic concentration of phosphorus is within the above range, the sheet resistance of the conductive thin film tends to be further reduced, and the adhesion between the conductive thin film and the substrate tends to be further improved.

The degree of maldistribution of phosphorus in the thickness direction of the conductive thin film can be expressed using the ratio of the maximum value P _m to the average value P _a (P _m /P _a ) as an index. Such a ratio (P _m /P _a ) is preferably 2.0 to 200 times, more preferably 2.5 to 100 times, even more preferably 5.0 to 50 times, and still more preferably It is preferably 5.0 to 25 times. When the ratio (P _m /P _a ) is 2.0 times or more, the degree of uneven distribution of phosphorus on the substrate side is increased, so that the sheet resistance of the conductive thin film is further reduced, and the conductive thin film and Adhesion to the substrate tends to be further improved. In addition, when the ratio (P _m /P _a ) is 2.0 times or more, the concentration of the transition metal on the side opposite to the substrate of the conductive thin film is relatively improved, so the sheet resistance of the conductive thin film tend to be lower. In addition, since the ratio (P _m /P _a ) is 200 times or less, it is easy to adjust so that the maximum value Pm that satisfies the ratio (P _m /P _a ) exists on the substrate side in the concentration distribution of phosphorus. tend to become

The range of 30 nm from the side close to the substrate in the thickness direction of the conductive thin film is a portion that contributes to the improvement of the adhesion between the conductive thin film and the substrate. can be suppressed. From this point of view, in the concentration gradient of phosphorus atoms, the average value P _a30 of the atomic concentration of phosphorus in the range of 30 nm from the side close to the substrate is preferably 0.2 to 20%, more preferably 1 0 to 15%, more preferably 1.0 to 10%, even more preferably 1.5 to 5.0%. When the average value P _a30 is within the above range, interfacial peeling tends to be more suppressed.

1.2. Concentration of Transition Metal Atoms The conductive thin film of the present embodiment contains a transition metal. As described above, in the conductive thin film, the transition metal may exist in the state of a metal compound such as an oxide in addition to the state of an elemental metal.

The transition metal atom is not particularly limited as long as it is a metal of Group 3 to Group 11 elements in the IUPAC periodic table, but preferably contains a metal of Group 11 elements, more preferably silver or copper. More preferably, it contains copper. The use of such a transition metal tends to further improve the conductivity of the conductive thin film. In addition, since the d orbitals of the transition metals, which are group 3 to 11 element metals, are not closed shells, the electrons in the d orbitals contribute to the bonding with phosphorus, which in turn leads to the formation of a bond between the conductive thin film and the substrate. It is considered that the adhesion is improved. However, the reasons for improving adhesion are not limited to the above.

The types of metal compounds containing transition metals are not particularly limited, but examples include sulfides, selenides, tellurides, nitrides, phosphides, and oxides. Among these, oxides are preferred because they are less harmful to the human body and relatively easy to produce.

In the depth direction of the conductive thin film, the average value Ma of the atomic concentration of the transition metal is preferably 40 to 99%, more preferably 60 to 98%, still more preferably 70 to 97%, and more More preferably 80 to 95%. When the average value Ma is 40% or more, the sheet resistance of the conductive thin film tends to further decrease. Moreover, when the average value Ma is 99% or less, the adhesion between the conductive thin film and the substrate tends to be further improved.

In the depth direction of the conductive thin film, the maximum value PM _m of the ratio (P/M) of the atomic concentration P of phosphorus to the atomic concentration M of the transition metal is preferably 1.9 to 100%, more preferably 2. 0 to 60%, more preferably 5.0 to 40%, even more preferably 7.5 to 20%. When the maximum value PM _m is 1.9% or more, the adhesion between the conductive thin film and the substrate tends to be further improved. Further, when the maximum value PM _m is 100% or less, the sheet resistance of the conductive thin film tends to be further lowered.

In the depth direction of the conductive thin film, the maximum value PMO _m of the ratio of the atomic concentration P of phosphorus to the sum of the atomic concentration M of the transition metal and the atomic concentration O of oxygen (P/(M+O)) is preferably 1.9. ~20%, more preferably 2.5 to 15%, still more preferably 3.0 to 10%, even more preferably 3.5 to 7.5%. When the maximum value PMO _m is 1.9% or more, the adhesion between the conductive thin film and the substrate tends to be further improved. Further, when the maximum value PMO _m is 20% or less, the sheet resistance of the conductive thin film tends to be further lowered.

Note that the ratio (P/M) and the ratio (P/(M+O)) are the transition metal atomic concentration M(t) and the oxygen atomic concentration O(t) in the cross section of the conductive thin film at the same thickness position. ) and the atomic concentration P(t) of phosphorus. In addition, the maximum value PM _m and the maximum value PMO _m mean the maximum value among the ratios (P/M) and ratios (P/(M+O)) for each thickness position thus obtained. do.

1.3. Concentration of Oxygen Atoms The conductive thin film of the present embodiment may contain oxygen atoms. The conductive thin film of this embodiment may have a concentration gradient of oxygen atoms in the depth direction of the film thickness, or oxygen atoms may be distributed substantially uniformly.

The average oxygen atom concentration _Oa in the depth direction of the conductive thin film is preferably 20% or less, more preferably 1.0 to 15%, and still more preferably 2.0 to 12.5. %, and more preferably 3.0 to 7.5%. When the average value O _a is 20% or less, the amount of non-conductive transition metal oxide is reduced and the amount of conductive transition metal is relatively increased, so that the sheet resistance of the conductive thin film is increased. tend to decline. Further, when the average value O _a is 20% or less, the atomic concentration of phosphorus is relatively increased, so that the adhesion between the conductive thin film and the substrate tends to be further improved.

Among the conductive thin films, an oxide layer having a high oxygen concentration and a small contribution to conductivity can be expressed by using the ratio of oxygen atoms to the transition metal as an index. Specifically, in the present embodiment, the oxide layer is defined as a range in which the atomic concentration of oxygen is 25% or more with respect to the atomic concentration of the transition metal. A value of 25%, for example, when the transition metal is copper, corresponds to a boundary value at which cuprous oxide and metallic copper are present in a ratio of 1:1. The film thickness of this oxide layer in the conductive thin film is preferably 200 nm or less, more preferably 1.0 to 150 nm, still more preferably 2.0 to 100 nm, and even more preferably 3.0 to 150 nm. 50 nm, and more preferably 3.0 to 20 nm. When the film thickness of the oxide layer is within the above range, the amount of the metal layer that contributes relatively more to the conductivity increases, so the sheet resistance of the conductive thin film tends to decrease further. In addition, the metal layer is defined as a range in which the atomic concentration of oxygen is less than 25% with respect to the atomic concentration of the transition metal as a concept of the oxide layer.

The thickness of the oxide layer is preferably 35% or less, more preferably 0.5 to 20%, still more preferably 0.5 to 10%, relative to the thickness of the conductive thin film, Even more preferably 0.5 to 5.0%. When the film thickness of the oxide layer is within the above range, the sheet resistance of the conductive thin film tends to be further reduced.

In the depth direction of the conductive thin film, the maximum value _POm of the ratio (P/O) of the atomic concentration P of phosphorus to the atomic concentration O of oxygen is preferably 60 to 500%, more preferably 70 to 400%. , more preferably 80 to 300%, and even more preferably 100 to 200%. When the maximum value PO _m is 60% or more, the adhesion between the conductive thin film and the substrate tends to be further improved. Further, when the maximum value PO _m is 500% or less, it becomes a range that is easy to adjust even when a metal oxide having relatively excellent stability is used as a precursor.

1.4. Concentration of Carbon Atoms The conductive thin film of the present embodiment may contain carbon atoms. The conductive thin film of this embodiment may have a concentration gradient of carbon atoms in the depth direction of the film thickness, or carbon atoms may be distributed substantially uniformly.

The average value Ca of the concentration of oxygen _atoms in the depth direction of the conductive thin film is preferably 20% or less, more preferably 1.0 to 15%, and still more preferably 2.0 to 12.5. %, and more preferably 3.0 to 8.0%. When the average value C _a is within the above range, the sheet resistance of the conductive thin film tends to decrease, and the adhesion between the conductive thin film and the substrate tends to improve.

1.5. Method for Measuring Atomic Concentration The concentration of each atom described above can be obtained by calculating the atomic concentration for each thickness position by STEM-EDX analysis of the cross section of the conductive thin film. For example, the average value is the average value when the atomic concentration (atomic concentration at a position 1 nm from the substrate side, atomic concentration at a position 2 nm from the substrate, etc.) is calculated for each thickness position in this way. is. Further, the maximum value is a value at which the atomic concentration at each thickness position is maximum. In this embodiment, the concentration of each atom is indicated by element concentration (atom %) unless otherwise specified.

In the STEM-EDX analysis, the cross section of the conductive thin film is measured. For example, when the conductive thin film is a fine metal wire pattern described later, the measurement sample includes the cross section of the fine metal wire perpendicular to the extending direction of the fine metal wire. Thin slices are preferred. In preparing a measurement sample, if necessary, a thin section may be formed after embedding a conductive thin film in a support such as an epoxy resin.

The method for forming the thin piece is not particularly limited as long as it is a method that can suppress damage to the metal fine wire cross section due to the formation and processing of the cross section, but a processing method using an ion beam (for example, BIB (Broad Ion Beam) processing is preferable. method, FIB (Focused Ion Beam) processing method), precision mechanical polishing, an ultramicrotome, and the like can be used.

Next, the cross section of the formed metal fine wire is observed with a scanning transmission electron microscope (STEM) to obtain an STEM image of the cross section of the metal fine wire. At the same time, STEM-EDX analysis can be performed by measuring the cross-sectional elemental mapping of the metal wire by energy dispersive X-ray analysis (EDX).

The thin film of the present embodiment having an atomic concentration distribution in the thickness direction can be evaluated not only by STEM-EDX analysis of the cross section of the thin film but also by X-ray photoelectron spectroscopy (XPS) through dry etching. Also, the quantitative value of the atomic concentration can be measured by STEM-EDX analysis.

From the viewpoint of preventing oxidation and contamination of the cross section of the metal fine wire, it is preferable to perform the formation of the cross section of the fine metal wire and the STEM-EDX analysis, which will be described later, in an inert atmosphere such as argon or in a vacuum.

1.6. Film thickness The film thickness of the conductive thin film is preferably 30 nm to 1000 µm, more preferably 50 nm to 100 µm, still more preferably 100 nm to 10 µm, still more preferably 200 to 1000 nm, still more preferably 300-500 nm. When the film thickness is 30 nm or more, the sheet resistance of the conductive thin film tends to be further lowered. In addition, the thicker the film, the easier it is to adjust the concentration distribution of phosphorus so that the maximum value Pm exists on the substrate side. Further, when the film thickness is 1000 μm or less, the adhesion of the conductive thin film to the substrate tends to be improved. Moreover, when the film thickness is 1000 μm or less, the pattern of the conductive thin film tends to be formed more easily.

The film thickness of the conductive thin film can be determined by cross-sectional STEM-EDX evaluation of the conductive thin film, which will be described later. More specifically, the region where the atomic concentration of the transition metal in the conductive thin film is 20% or more is defined as the film thickness of the conductive thin film, and the average value of the film thicknesses measured at any three locations is It can be the thickness of a conductive thin film. In addition to a thin film having a uniform thickness, the conductive thin film of the present embodiment may be a thin film having unevenness on the surface or having a thin portion depending on the position of the conductive thin film. good.

The conductive thin film may have no voids in the film or may have voids in the film. Among these, the conductive thin film preferably has voids in the film. Such a conductive thin film includes, for example, a layer of particles to which transition metal-containing particles are bonded. By being a particle layer, even when stress such as bending of the base material is applied, disconnection is more difficult to occur. A conductive thin film composed of such a particle layer can be obtained by a thin film manufacturing method using an ink containing transition metal particles, which will be described later. Also, the existence of the particle layer can be evaluated by STEM analysis or the like.

1.7. Pattern The conductive thin film may have a continuous pattern with openings or a solid pattern without openings. The pattern of the conductive thin film can be designed according to the intended use of the electronic device, and may be a regular pattern or an irregular pattern. Here, the opening means a portion where the conductive thin film does not exist, and light can pass through the opening portion. A continuous pattern means that connection (contact) is confirmed by an optical microscope, and such a pattern is electrically connected.

Among these, the conductive thin film preferably has a continuous pattern with openings. By providing the opening in this manner, a light-transmissive conductive thin film can be formed. Moreover, the continuous pattern having openings is not particularly limited, but for example, a pattern formed by crossing a plurality of fine lines is preferable. In this case, the fine lines correspond to the conductive thin film, and the gaps between the fine lines are the openings.

A specific aspect of the pattern formed by a plurality of fine lines will be described below, but the pattern in this embodiment is not limited to the following. In the following description, a thin metal wire means a thin conductive thin film, and a thin metal wire pattern means a pattern formed by a plurality of thin metal wires.

FIG. 2 shows a schematic top view showing an example of the conductive thin film of this embodiment. FIG. 2 is a top view of the conductive sheet 100 in which the conductive thin film 10 is arranged on the substrate 20, viewed from the side on which the conductive thin film 10 is formed. In FIG. 2, the conductive thin film 10 is in the form of fine lines, and the fine lines are shown crossing over the grid. Here, the thin wire-shaped conductive thin film 10 is referred to as a thin metal wire 10'. The cross section of FIG. 1 described above is a cross section of the thin metal wire 10' taken along the line A-A'.

As shown in FIG. 2, the continuous pattern means that, for example, a plurality of fine metal wires 10' intersect each other to form a continuous layer so that current can flow at any two points on the conductive thin film 10 extending in the plane direction. It means something that is configured to be able to Also, having openings means, for example, having discontinuous openings 30 between a plurality of thin metal wires 10'. In the present embodiment, a conductive continuous layer formed by the fine metal wires 10 ′ and openings is referred to as a fine metal wire pattern 40 .

Here, the line width W of the fine metal wires 10′ constituting the fine metal wire pattern 40 is defined by projecting the fine metal wires 10′ onto the surface of the substrate 20 from the side of the substrate 20 on which the fine metal wire pattern 40 is arranged. It means the line width of the thin metal wire 10' when The "line width when projected" is defined as the line width when, for example, the interface of the conductive thin film 10 in contact with the base material is the thickest as shown in FIG. Also, the pitch P is defined as the sum of the line width W and the distance L between the thin metal lines.

Specific examples of the fine metal wire pattern include a mesh pattern formed by intersecting a plurality of fine metal wires in a mesh pattern, and a line pattern formed by forming a plurality of substantially parallel fine metal wires. Also, the fine metal line pattern may be a combination of a mesh pattern and a line pattern. The meshes of the mesh pattern may be squares, rectangles, or polygons such as rhombuses. Further, the thin metal wires forming the line pattern may be straight lines or curved lines. Further, the thin metal wires forming the mesh pattern can also be curved.

1.8.1. Line Width The line width W is preferably 100 nm to 1000 μm, more preferably 200 nm to 500 μm, still more preferably 300 nm to 100 μm, even more preferably 400 nm to 50 μm, still more preferably 500 nm to 5 .0 μm. As shown in FIG. 1, the line width W of the fine metal wire having a gently sloping side surface is the width of the fine metal wire arranged perpendicular to the substrate, and the substrate in contact with the fine metal wire has a curved surface. In case, it is the length of the perimeter where the cross section of the thin metal wire is in contact with the base material.

When the line width W of the metal fine wire is 100 nm or more, the conductivity of the metal fine wire can be sufficiently ensured, and the sheet resistance tends to be further reduced. In addition, it is possible to sufficiently suppress the decrease in electrical conductivity due to oxidation, corrosion, etc. of the surface of the fine metal wire. Furthermore, when the aperture ratio is the same, the thinner the line width of the metal fine wires, the more the number of the metal fine wires can be increased. As a result, the electric field distribution of the conductive sheet becomes more uniform, making it possible to manufacture electronic devices with higher resolution. Also, even if some of the fine metal wires are broken, the other fine metal wires can compensate for the effects of this breakage.

On the other hand, when the line width W of the fine metal wire is 5.0 μm or less, the visibility of the fine metal wire tends to be further reduced, and the transparency of the conductive thin film and the conductive sheet including the same tends to be further improved.

1.8.2. Aspect Ratio The aspect ratio represented by the thickness T of the fine metal wire to the width W of the fine metal wire is preferably 0.05 to 1.00, more preferably 0.08 to 0.90, and still more preferably is between 0.10 and 0.80. When the line width W is constant, the larger the aspect ratio, the more the conductivity tends to improve without lowering the transmittance. In addition, when the aspect ratio is 1.00 or less, there is a tendency to suppress decrease in transmittance due to excessive film thickness.

1.8.3. Pitch Pitch P is preferably 1.0 to 1000 μm, more preferably 5.0 to 500 μm, even more preferably 50 to 250 μm, still more preferably 100 to 250 μm. When the pitch P is 1.0 μm or more, the transparency of the conductive thin film and the conductive sheet including the same tends to be further improved. Further, when the pitch P is 1000 μm or less, the conductivity tends to be further improved. When the shape of the fine metal line pattern is a mesh pattern, an aperture ratio of 99% can be obtained by setting the pitch of the fine metal line pattern having a line width of 1 μm to 200 μm.

1.8.4. Aperture Ratio The aperture ratio of the fine metal wire pattern is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and particularly preferably 90% or more. When the aperture ratio of the fine metal line pattern is 60% or more, the transmittance of the conductive sheet tends to be further improved.

In addition, the aperture ratio of the fine metal line pattern is preferably less than 100%, more preferably 95% or less, still more preferably 90% or less, still more preferably 80% or less, and even more preferably It is 70% or less, particularly preferably 60% or less. When the opening ratio of the fine metal line pattern is less than 100%, the conductivity of the conductive sheet tends to be further improved.

The appropriate aperture ratio of the fine metal line pattern varies depending on the shape of the fine metal line pattern. The upper limit and lower limit of the aperture ratio of the fine metal line pattern can be appropriately combined according to the required performance (transmittance and sheet resistance) of the intended electronic device.

The "aperture ratio of the fine metal line pattern" can be calculated by the following formula for the area on the substrate where the fine metal line pattern is formed. The area on the substrate where the fine metal line pattern is formed excludes the edges where the fine metal line pattern is not formed.
Aperture ratio of metal fine line pattern = (1-area occupied by metal fine line pattern/area of transparent substrate) x 100

The line width W, aspect ratio, and pitch P of the fine metal line pattern can be confirmed by observing the cross section of the conductive sheet with an electron microscope or the like. Also, the line width and pitch of the metal fine line pattern can be observed with a laser microscope or an optical microscope. Also, since the pitch P and the aperture ratio have a relational expression to be described later, if one is known, the other can be calculated. In addition, methods for adjusting the line width W, aspect ratio, and pitch P of the metal fine line pattern to desired ranges include a method for adjusting the grooves of a plate used in the method for manufacturing a conductive sheet described later, and a method for adjusting the grooves of the metal particles in the ink. and a method of adjusting the average particle size of the.

1.8.5. Visible Light Transmittance The conductive thin film preferably has a visible light transmittance of 70 to 99%, more preferably 75 to 95%, still more preferably 80 to 90%. Here, the visible light transmittance can be measured by calculating the average transmittance in the range of visible light (360 to 830 nm) in accordance with the total light transmittance of JIS K 7361-1:1997. . The visible light transmittance of a patterned thin film tends to be improved by reducing the line width of the fine metal line pattern or by improving the aperture ratio.

1.8.6. Sheet resistance The sheet resistance of the conductive thin film is preferably 0.001 to 20 Ωcm ⁻² , more preferably 0.01 to 17.5 Ωcm ⁻² , still more preferably 0.01 to 15 Ωcm ⁻² , It is preferably 0.1 to 10 Ωcm ^-2 . The lower the sheet resistance, the more the electrical conductivity tends to improve.

The sheet resistance of the conductive sheet tends to be lowered by increasing the aspect ratio (height) of the fine metal wires. Moreover, it can be adjusted by selecting the kind of metal material that constitutes the thin metal wire.

1.8.7. Haze The haze of the conductive thin film is preferably 0.01 to 5.00%, more preferably 0.01 to 3.00%, still more preferably 0.01 to 1.00%. A haze of 5.00% or less tends to further suppress fogging of the conductive sheet against visible light. Haze in this specification can be measured according to JIS K 7136:2000 haze.

1.9. Uses The conductive thin film of the present embodiment can be applied to various uses. Specific examples include conductive sheets, heaters, electromagnetic wave shields, and antennas. In addition, by forming a thin film with a pattern, it can be suitably applied to electronic paper, touch panels, flat panels, and applications requiring transparency.

2. Conductive Sheet The conductive sheet of the present embodiment includes a substrate and the conductive thin film formed on the substrate. Such a conductive sheet becomes a film material having conductivity, and in particular, when the conductive thin film has a metal fine line pattern as described above and has visible light transmission, it has conductivity. It becomes a transparent film material. In addition to applications that require transparency, such as touch panels and displays, such conductive sheets provide new value by imparting transparency to heaters, electromagnetic wave shields, and antennas, for which transparency was not required in the past. can do.

2.1. Substrate The substrate can be appropriately selected according to the application of the conductive sheet, and is not particularly limited. Examples include transparent inorganic substrates such as glass, opaque inorganic substrates such as metal plates, and plastic films. Examples include transparent or opaque organic substrates. Among these, plastic is preferable from the viewpoint of obtaining a flexible and transparent conductive sheet. Moreover, these substrates may have any layer on the surface, or may be subjected to any surface treatment such as corona treatment.

As for the form of the base material, a plate-like one or a film-like one can be used, and a film-like one is preferable from the viewpoint of excellent freedom of form.

Examples of plastics include, but are not limited to, acrylate, methacrylate, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polyvinyl chloride, polyethylene, polypropylene, polystyrene, nylon, and aromatic polyamide. , polyetheretherketone, polysulfone, polyethersulfone, polyimide, and polyetherimide.

Among these, it is preferable to use polyethylene terephthalate (PET) from the viewpoint of high productivity including the cost reduction effect for manufacturing the conductive sheet. Moreover, it is preferable to use a polyimide from a viewpoint of being excellent in the heat resistance of a conductive sheet. Furthermore, it is preferable to use polyethylene terephthalate and/or polyethylene naphthalate from the viewpoint of being advantageous for adhesion between the thin film and the substrate.

The base material of the thin film used in the present embodiment may be made of one kind of material, or may be made of a laminate of two or more kinds of materials. Further, when the transparent substrate is a multilayer body in which two or more kinds of materials are laminated, the transparent substrate may be a laminate of organic substrates or inorganic substrates. The base material may be laminated.

The thickness of the substrate is preferably 5 μm or more and 500 μm or less, more preferably 10 μm or more and 100 μm or less, from the viewpoint of excellent shape flexibility and/or excellent transparency.

2.1.1. Surface Layer The substrate may have a plurality of layers, and may have a surface layer at the contact portion with the conductive thin film. By laminating the surface layer on the base material, when the metal component in the ink is sintered by a baking means such as plasma, the base material is prevented from being etched in places not covered with the fine metal wire pattern by plasma or the like. be able to.

Components contained in the surface layer are not particularly limited, but examples include silicon compounds (e.g., (poly)silanes, (poly)silazanes, (poly)silthianes, (poly)siloxanes, silicon, silicon carbide, silicon oxide, silicon nitride, silicon chloride, silicate, zeolite, silicide, etc.), aluminum compounds (eg, aluminum oxide, etc.), magnesium compounds (eg, magnesium fluoride), and the like. The above polysilanes, polysilazanes, polysilthianes, and polysiloxanes may have a linear or branched, cyclic, or network configuration. These components may be used individually by 1 type, and may be used in combination of 2 or more type.

Among these, silicon compounds, aluminum oxide, and magnesium fluoride are preferred, and silicon oxide, silicon nitride, aluminum oxide, and magnesium fluoride are more preferred. By using such a component, the durability against plasma tends to be further improved, and the adhesion between the conductive thin film and the substrate tends to be further improved. In addition, by using such a component, the transparency and durability of the conductive sheet tend to be further improved, and the productivity that contributes to the cost reduction effect for manufacturing the conductive sheet tends to be more excellent. be.

The surface layer is formed by vapor deposition methods such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), or by coating and drying a composition in which the components contained in the surface layer are dispersed in a dispersion medium. can do. This composition may contain a dispersant, a surfactant, a binder, etc., if necessary.

When the surface layer is included, silicon may be incorporated into the conductive thin film through a plasma reaction. The silicon atom Si contained in the metal fine wire may exist in the form of a silicon atom or a silicon compound, and a form in which the silicon atom or the silicon compound and the metal atom are bonded (for example, Si—M, Si—O— M etc.).

2.1.2. Thickness The thickness of the surface layer is preferably 0.01 to 500 μm, more preferably 0.05 to 300 μm, still more preferably 0.10 to 200 μm. When the thickness of the surface layer is 0.01 μm or more, the adhesion between the conductive thin film and the substrate tends to be further improved. Moreover, the thickness of the surface layer is 500 μm or less, so that the flexibility of the substrate can be ensured.

2.1.3. Volume Resistivity The surface layer preferably has an antistatic function to prevent disconnection of the fine metal wire pattern due to static electricity. From the viewpoint of having an antistatic function, the surface layer preferably contains at least one of a conductive inorganic oxide and a conductive organic compound.

From the viewpoint of antistatic function, the surface layer preferably has a volume resistivity of 100 to 100,000 Ωcm, more preferably 1,000 to 10,000 Ωcm, and more preferably 2,000 to 8,000 Ωcm. When the surface layer has a volume resistivity of 100,000 Ωcm or less, the antistatic function tends to be further improved. In addition, when the surface layer has a volume resistivity of 100 Ωcm or more, the electrical conductivity between the fine metal wire patterns is further reduced, and it can be suitably used for touch panels and the like.

The volume resistivity can be adjusted by the content of the conductive inorganic oxide, conductive organic compound, or the like in the surface layer. For example, when silicon oxide with high plasma resistance (volume resistivity of 1014 Ω·cm or more) and an organic silane compound, which is a conductive organic compound, are included in the surface layer, the volume resistivity is reduced by increasing the content of the organic silane compound. be able to. On the other hand, by increasing the content of silicon oxide, although the volume resistivity increases, it has high plasma resistance, so it can be made into a thin film without deteriorating the optical properties.

2.2. Protective Layer The conductive sheet of the present embodiment may have a protective layer on the conductive thin film. The protective layer can be formed so as to sandwich the conductive thin film with the substrate.

The protective layer is not particularly limited, but is not particularly limited as long as it has transparency and can exhibit good adhesion to a conductive thin film or a substrate, for example, phenol resin, thermosetting type Thermosetting resins such as epoxy resin, thermosetting polyimide, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane, diallyl phthalate resin, silicone resin, urethane acrylate, acrylic resin acrylate, epoxy acrylate, silicone acrylate , UV curable resins such as UV curable epoxy resins, commercially available coating agents, and the like can be used.

3. Method for producing conductive thin film In the method for producing a conductive thin film of the present embodiment, a precursor thin film having a phosphorus weight area density of 6.0 mg·m ⁻² or more and 1000 mg·m ⁻² or less is formed on a substrate. and a plasma reaction step of reacting the precursor thin film with plasma for 150 seconds or more and 60 minutes or less to obtain a conductive thin film. You may have a surface layer formation process of forming a surface layer in .

3.1. Surface Layer Forming Step The surface layer forming step is a step of forming the surface layer described above on the substrate. By forming the surface layer, for example, when a plastic substrate is used, the surface layer can prevent denaturation and etching of the plastic due to plasma reaction.

A specific example of the method for forming the surface layer is to form a film of a component forming the surface layer on the surface of the transparent base material using a vapor deposition method such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). A method of forming a surface layer by Another specific example of the surface layer forming step is a method of forming a surface layer by coating the surface of a transparent base material with a composition in which components for forming the surface layer are dispersed in a dispersion medium, and drying the composition. be done. Moreover, the surface layer forming composition may contain a dispersant, a surfactant, a binder, and the like, if necessary.

In the surface layer forming step, it is preferable to use the silicon compound described above as the component forming the surface layer.

3.2. Film Forming Step The film forming step is a step of forming a precursor thin film having a phosphorus weight area density of 6.0 mg·m ⁻² or more and 1000 mg·m ⁻² or less on the substrate. The weight area density of phosphorus can be adjusted by the amount of the phosphorus-based compound contained in the precursor thin film.

3.2.1. Precursor thin film The precursor thin film contains a transition metal and/or a transition metal compound and a predetermined amount of phosphorus, and is subjected to a plasma reaction process described later to form the conductive thin film of the present embodiment. It becomes. As already described, by subjecting such a precursor thin film containing phosphorus to plasma treatment, the conductive thin film obtained has a phosphorus gradient such that the atomic concentration of phosphorus is the maximum on the substrate side. Due to this phosphorus gradient, it has excellent conductivity and excellent adhesion to the substrate.

The weight area density of phosphorus in the precursor thin film is 6.0 to 1000 mg·m ⁻² , preferably 8.0 to 500 mg·m ⁻² , more preferably 10 to 100 mg·m ⁻² , More preferably, it is 10 to 50 mg·m ^-2 . When the weight area density of phosphorus in the precursor thin film is 6.0 mg·m ⁻² or more, the conductivity of the obtained conductive thin film is further improved, and the adhesion between the conductive thin film and the substrate is further improved. improves. Further, when the weight area density of phosphorus in the precursor thin film is 1000 mg·m ⁻² or less, the transition metal is relatively increased, so that the conductivity of the obtained conductive thin film is further improved.

The weight area density of the transition metal in the precursor thin film is preferably 1.0 to 10 g·m ^-2 , more preferably 1.0 to 8.0 g·m ^-2 , and still more preferably 1.0 to 8.0 g·m -2 . 0 to 6.0 g·m ^-2 . When the weight area density of the transition metal in the precursor thin film is within the above range, the conductivity of the obtained conductive thin film is further improved, and the adhesion between the conductive thin film and the substrate tends to be further improved. be.

In this embodiment, the weight density of phosphorus or transition metal in the precursor thin film is the weight density of phosphorus or transition metal in the region where the precursor thin film exists. Portions are not included in the calculation of phosphorus or transition metal weight areal densities.

The phosphorus-based compound contained in the precursor thin film is not particularly limited, but examples thereof include phosphoric acid and/or phosphate esters. By using such a phosphorus-based compound, in the plasma reaction step to be described later, there is a tendency that a phosphorus gradient having the maximum atomic concentration of phosphorus on the substrate side is more likely to be formed.

Such a precursor thin film can be formed using various methods such as a dry method using a vacuum device or the like and a wet method using ink or the like. Among these methods, the method of forming the precursor thin film by printing the ink on the base material is preferable from the viewpoint of suitability for large-scale production and the viewpoint of facilitating adjustment of the amount of phosphorus contained in the precursor thin film.

The printing method that can be used is not particularly limited, but examples thereof include letterpress printing, gravure printing, bar coat printing, spray coating, spin coating, reverse transfer printing, and the like. Among these, from the viewpoint of being able to print a relatively precise pattern, the formation of the precursor thin film by the plate printing method is preferable.

The plate printing method includes, for example, a step of coating the surface of the transfer medium with ink, and contacting the surface of the transfer medium coated with the ink with the surface of the convex portion of the letterpress, so that the surface of the convex portion of the letterpress is coated on the surface of the transfer medium. A step of transferring a part of the ink of , and a step of contacting the surface of the transfer medium and the surface of the base material after the transfer of the part of the ink, and transferring the ink remaining on the surface of the transfer medium to the surface of the base material. is mentioned.

For example, in such a printing method, various shapes such as the thickness, width, and pitch of the precursor thin film and the concentration of each atom contained in the precursor thin film can be controlled by adjusting the printing conditions and ink.

3.2.2. Ink The ink used in the above printing method contains a metal component, a solvent, and a phosphorus component, and may optionally contain a surfactant, dispersant, reducing agent, and the like.

3.2.2.1. Metal Particles The metal component may be contained in the ink as metal particles or may be contained in the ink as a metal complex. Among these, it is preferable to be contained in the ink as metal particles. The metal particles include metal oxides such as copper oxide, other metal compounds, and core/shell particles in which the core portion is copper and the shell portion is copper oxide, as long as they contain the transition metal atoms described above. It may be an aspect. Among these, metal oxides such as copper oxide are preferable from the viewpoint of handleability.

The average primary particle size of the metal particles is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. Although the lower limit of the average primary particle size of the metal particles is not particularly limited, it may be 1 nm or more. The average primary particle size of the metal particles is preferably 100 nm or less from the viewpoint that the line width W of the fine metal wire to be obtained can be made thinner.

The average secondary particle size of the metal particles is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. From the viewpoint of excellent coatability during thin film formation, it is preferable that each particle is monodisperse and that the average secondary particle diameter is close to the average primary particle diameter.

In the present embodiment, the “average primary particle size” refers to the particle size of each metal particle (so-called primary particle), and an aggregate (so-called secondary particle) formed by gathering a plurality of metal particles. is distinguished from the average secondary particle size, which is the particle size of

3.2.2.2. Phosphorus Component The phosphorus component is not particularly limited, but examples thereof include black phosphorus, red phosphorus, phosphoric acid, and phosphate esters. Among these, phosphoric acid and/or phosphate esters are preferred. By using such a phosphorus-based compound, in the plasma reaction step to be described later, there is a tendency that a phosphorus gradient having the maximum atomic concentration of phosphorus on the substrate side is more likely to be formed. The phosphoric acid and/or phosphate ester includes a polymer having a phosphate group and/or a phosphate ester group, a low molecule, a phosphate anion, a phosphate ester anion, a salt containing a phosphate anion, or a phosphate Salts containing an ester anion are included.

Further, for example, surfactants, pH adjusters, viscosity adjusters, drying rate adjusters, dispersants for metal particles, stabilizers, etc. containing phosphorus atoms may be used as the phosphorus component. Examples of such a phosphorus component include a dispersant having a phosphate ester group.

3.2.2.3. Surfactant The surfactant is not particularly limited, but examples thereof include fluorine-based surfactants and silicone-based surfactants. The use of such a surfactant tends to improve the coating properties of the ink on the transfer medium (blanket) and the smoothness of the coated ink, resulting in a more uniform coating film. In addition, it is preferable that the surfactant is capable of dispersing the metal component and is difficult to remain during firing.

3.2.2.4. Solvent The solvent for the ink is preferably an organic solvent in terms of excellent storage stability and low light loss. From the above viewpoint, the organic solvent is preferably alcohol. From the above viewpoint, the number of carbon atoms in the organic solvent is preferably 1 or more and 7 or less, more preferably 2 or more, more preferably 5 or less, or 4 or less, and most preferably 2. Solvents include water, propylene glycol monomethyl ether acetate, 3-methoxy-3-methyl-butyl acetate, ethoxyethyl propionate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol tertiary Butyl ether, dipropylene glycol monomethyl ether, ethylene glycol butyl ether, ethylene glycol ethyl ether, ethylene glycol methyl ether, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2-pentanediol, 2-methylpentane-2 ,4-diol, 2,5-hexanediol, 2,4-heptanediol, 2-ethylhexane-1,3-diol, diethylene glycol, hexanediol, octanediol, triethylene glycol, tri-1,2-propylene glycol , glycerol, ethylene glycol monohexyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl acetate, diethylene glycol monoethyl ether acetate, methanol, ethanol, n-propanol, i-propanol, n-butanol, i-butanol, 2-butanol, t-butanol, n-pentanol, i-pentanol, 2-methylbutanol, 2-pentanol, t-pentanol, 3-methoxybutanol, n-hexanol, 2-methylpentanol, 1- hexanol, 2-hexanol, 2-ethylbutanol, 1-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-ethylhexanol, 2-octanol, n-nonyl alcohol, 2,6 dimethyl-4-heptanol, n-decanol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol, diacetone alcohol, etc., and from the viewpoint of excellent storage stability and low light loss, methanol, ethanol , propanol, butanol, pentanol, hexanol, heptanol, and isomers thereof are more preferred, ethanol, propanol, butanol and isomers thereof are more preferred, and ethanol is most preferred.

3.2.2.5. Dispersant The dispersant is not particularly limited, but includes, for example, a dispersant that non-covalently bonds or interacts with the metal component, and a dispersant that covalently bonds with the metal component. Non-covalently bonding or interacting functional groups include dispersants having phosphate groups. By using such a dispersant, the dispersibility of the metal component tends to be further improved.

3.3. Plasma Reaction Step The plasma reaction step is a step of reacting the precursor thin film formed as described above with plasma for 150 seconds or more and 60 minutes or less to obtain a conductive thin film. As a result, the precursor thin film is fired, and the metal particles in the ink are sintered together to form a particle layer (conductive thin film). of concentration gradient is formed. As a result, a conductive thin film having excellent conductivity and adhesion to the substrate can be obtained. By setting the atmosphere during the plasma reaction to a reducing type, the oxygen concentration contained in the conductive thin film can also be adjusted.

Plasma can be generated by various methods. Among them, microwave plasma and high-frequency plasma are preferred because they are relatively easy to control, and microwave plasma is more preferred from the viewpoint of reducing contamination caused by electrodes for plasma generation in the apparatus.

The microwave power in the microwave plasma is preferably 0.5-10 kW, more preferably 1.0-5.0 kW. When the microwave output is 0.5 kW or more, the adhesiveness between the obtained conductive thin film and the substrate is further improved, and the plasma reaction time can be shortened. Further, when the microwave output is 10 kW or less, etching or denaturation of the base material by the plasma tends to be suppressed.

The plasma reaction treatment time is 150 seconds to 60 minutes, preferably 180 to 600 seconds, more preferably 240 to 360 seconds. When the treatment time is 150 seconds or more, phosphorus tends to be unevenly distributed on the substrate side in the conductive thin film, and the maximum concentration of phosphorus unevenly distributed on the substrate side is increased, thereby forming the conductive thin film. and the adhesion of the substrate tends to be further improved. Further, when the treatment time is 60 minutes or less, the productivity of the conductive thin film tends to be further improved.

The plasma reaction atmosphere preferably contains a gas or a rare gas that is a molecule containing hydrogen atoms. In particular, a gas containing hydrogen molecules and/or water molecules is more preferable, and a gas containing hydrogen molecules is even more preferable. The gas that is a molecule containing a hydrogen atom is not particularly limited, but for example, a gas containing a hydrogen molecule is preferable. One type or a plurality of types of molecules may be used as the gas that is a molecule containing a hydrogen atom. By using such a gas that is a molecule containing hydrogen atoms, the conductivity of the conductive thin film to be produced tends to be further improved.

Examples of rare gases include, but are not limited to, helium, argon, xenon, and krypton. Among these, helium or argon, which has a relatively small molecular weight, is preferred, and helium is most preferred, from the viewpoint of less sample etching by these plasmas. Using such a rare gas makes it easier to control the plasma reaction.

A gas that is a molecule containing a hydrogen atom and a rare gas may be mixed and used, or another gas may be mixed and used. It is preferable to contain both a gas that is a molecule containing a hydrogen atom and a rare gas from the viewpoint of having reducing properties during the plasma reaction and being able to control the reduction reaction relatively easily. Specifically, it is preferably a gas containing both hydrogen molecules and helium.

The pressure of the plasma reaction may be under increased pressure, under reduced pressure, or under atmospheric pressure. Among these, from the viewpoint of lengthening the mean free path of plasma, it is preferable to be under reduced pressure. Specifically, the pressure is preferably 0.1-1000 Pa, more preferably 1.0-500 Pa, still more preferably 10-300 Pa. When the pressure is 0.1 Pa or more, the mean free path of plasma tends to become longer. In addition, since the pressure is 1000 Pa, it is possible to use more gases and rare gases that are molecules containing hydrogen atoms.

4. Touch Panel The touch panel of the present embodiment is not particularly limited as long as it includes the conductive thin film. For example, in a capacitive touch panel, two conductive sheets (conductive thin films) are present on the front and back surfaces of an insulator. Oppose. The conductive sheet is connected to an extraction electrode, and the extraction electrode 32 connects the thin metal wire and a controller (such as a CPU) for switching the energization of the thin metal wire.

Note that the touch panel of the present embodiment is not limited to the capacitive type, and may be of a resistive film type, a projection type capacitive type, a surface type capacitive type, or the like.

5. Display The display of the present embodiment is not particularly limited as long as it includes the conductive thin film. For example, an organic electroluminescence (EL) display has a structure in which an organic EL film is sandwiched between electrodes, and the conductive thin film can be used as one of the electrodes. A liquid crystal display has a structure in which a liquid crystal layer is sandwiched between electrodes, and the conductive thin film can be used as one of the electrodes.

6. Heater The heater of the present embodiment is not particularly limited as long as it includes the conductive thin film. For example, an electric heater has an electric heating part that generates Joule heat by supplying electricity and a power supply device that supplies electric power to the electric heating part, and a conductive sheet (conductive thin film) is used as the electric heating part. can be used. If the conductive sheet (conductive thin film) is made transparent, the heater will be transparent, and if the conductive sheet is designed to have a high resistance, the heater will generate a large amount of heat.

For example, the use of the transparent heater is not particularly limited. Anti-fogging and anti-freezing heaters are included.

7. Electromagnetic Wave Shield The electromagnetic wave shield of the present embodiment is not particularly limited as long as it includes the conductive thin film. For example, an electromagnetic wave shield has a shielding material that reflects or absorbs incident electromagnetic waves, and the above conductive thin film can be used as the shielding material.

8. Antenna The antenna of this embodiment is not particularly limited as long as it includes the conductive thin film. For example, an RF tag can transmit and receive a specific frequency by having a semiconductor element and an antenna connected thereto, and a conductive sheet (conductive thin film) can be used as the antenna. If the conductive sheet (conductive thin film) is made transparent, it becomes a transparent antenna.

Hereinafter, the present embodiment will be described more specifically with specific examples and comparative examples, but the present embodiment is not limited by these examples and comparative examples as long as the gist thereof is not exceeded. do not have.

(Evaluation of Element Concentration Distribution of Metal Fine Wire Cross Section)
The obtained base material with a conductive thin film was cut out with a razor, embedded in a vapor-deposited carbon layer, and thinly sliced with a thickness of about 100 nm by a focal ion beam. Using the obtained thin section as a measurement sample, STEM-EDX analysis was performed by irradiating an electron beam under the following conditions to prepare an evaluation sample. By this analysis, the concentration distribution of transition metal, phosphorus, oxygen, and carbon in the thickness direction of the conductive thin film was obtained every 2.8 nm or every 3.4 nm. Also, the parameters shown in Table 1 were calculated based on the obtained concentration distribution.
[Apparatus conditions]
STEM: Scanning transmission electron microscope HD-2300A manufactured by Hitachi High-Technologies Corporation
EDX: Energy dispersive X-ray spectrometer Octane T Plus (software: GENESIS) manufactured by EDAX
Accelerating voltage: 200 kV
Measurement magnification: 100,000 times Mapping elements: Cu, O, P, Si, C

(Position in thin film of maximum phosphorus element concentration)
The position of the maximum atomic concentration of phosphorus was evaluated based on the distribution of the atomic concentration of phosphorus obtained in the evaluation of the elemental concentration distribution of the cross section of the metal thin wire. The maximum atomic concentration of phosphorus in the thickness direction of the conductive thin film is in the range of 10% or less from the side closer to the base material. The range from 1/2 to 3/4 was defined as "substrate side", the range from more than 3/4 to the thin film surface was defined as "thin film surface vicinity".

(Average value of P atom concentration at thin film-substrate interface)
Of the film thickness of the conductive thin film, for a region from the side closer to the substrate interface to 30 nm, using the distribution of the atomic concentration of phosphorus obtained by the evaluation of the element concentration distribution of the cross section of the metal fine wire, the phosphorus atoms in this region An average concentration density was obtained.

(thickness of oxide layer)
Based on the oxygen atomic concentration distribution obtained by the evaluation of the element concentration distribution of the cross section of the metal fine wire, the film thickness in the range where the oxygen atomic concentration with respect to the transition metal atomic concentration is 25% or more is the thickness of the oxide layer. identified as Also, the ratio of the film thickness of the oxide layer to the film thickness of the conductive thin film was calculated.

(Morphological evaluation of thin film)
The film thickness of the conductive thin film and the fact that the conductive thin film is a particle layer formed by sintering metal particles together were determined from the STEM image of the cross-sectional STEM-EDX analysis. Furthermore, the pattern shape, line width and pitch of the conductive thin film were evaluated with a laser microscope (OLS-4500 manufactured by OLYMPUS).

(Sheet resistance evaluation)
The sheet resistance was measured using a non-contact resistance meter (NC-700) using eddy current manufactured by NAPSON.

(visible light transmittance)
The visible light transmittance was calculated by the following method.
(visible light transmittance) = (aperture ratio of fine line pattern) x (visible light transmittance of base material)

(Adhesion)
Adhesion of the conductive thin film to the substrate was evaluated by the following tape peeling test and laser microscope observation. Before the tape peeling test, the sample was observed with a laser microscope (OLS-4500 manufactured by OLYMPUS) and the resulting image was recorded. The adhesive surface of an adhesive tape (No. 610 manufactured by 3M) was brought into contact with the conductive thin film, and the tape was fixed by reciprocating the tape twice with a 2N (Newton) roller. The fixed tape was peeled off at a speed of 100 mm/min using a 90° peeling tester (EZ-S, manufactured by Shimadzu Corporation) to perform a tape peeling test. The surface of the base material after peeling off the tape was observed with a laser microscope in the same manner as before the tape peeling test, and the resulting image was recorded. The images obtained before and after the tape peeling test were binarized using Otsu's method to determine the boundaries, and then the areas of the fine metal wires were compared. By obtaining, the peeled area ratio of the fine metal wires was obtained by the tape peeling test. It means that the smaller the peeled area ratio, the better the adhesion of the thin film to the substrate.

<Example 1>
(Preparation of transparent substrate)
Using polyethylene terephthalate (PET) as a transparent substrate, a surface layer forming composition containing silicon oxide nanoparticles and a conductive organic silane compound is applied thereon, and dried to obtain a thickness of 150 nm having an antistatic function. A substrate was obtained by forming a surface layer containing silicon oxide with a volume resistivity of 5000 Ωcm. This base material has a form in which a surface layer is laminated on PET as the base material.

(Ink preparation)
20 parts by mass of cuprous oxide nanoparticles with a primary particle size of 21 nm, a dispersant that is a polymer having a phosphate ester group (manufactured by Big Chemie, product name: Disperbyk-145) 4 parts by mass, and a surfactant (Seimi Chemical Co., Ltd., product name: S-611) 1 part by mass and 75 parts by mass of ethanol were mixed to prepare an ink containing 20% by mass of cuprous oxide nanoparticles.

(Production of precursor thin film)
First, ink is applied to the surface of the transfer medium, then the surface of the transfer medium to which the ink is applied is brought into contact with the plate having the grooves of the fine metal line pattern, and a part of the ink on the surface of the transfer medium is transferred to the convex surface of the plate. let me After that, the surface of the transfer medium coated with the remaining ink was brought into contact with the substrate to transfer the ink in the shape of a metal fine line pattern onto the substrate. This step produced a precursor thin film. The film thickness of this precursor thin film was 680 nm, the deposition concentration of phosphorus was 10 mg·m ⁻² , and the deposition concentration of copper was 1.6 g·m ⁻² . Also, the precursor phosphorus species were phosphoric acid and phosphate esters. Table 1 lists these results.

(Plasma reaction process)
A plasma reaction was applied to the precursor thin film manufactured in the above-described steps. Specifically, plasma is generated by microwaves generated at an output of 1.5 kW in an atmosphere in which a gas of 3% by volume hydrogen and 97% by volume helium is introduced under reduced pressure. reacted for a minute.

The thin film of Example 1 was subjected to atomic concentration analysis, morphology evaluation, sheet resistance measurement, transmittance estimation, and adhesion evaluation of the cross section of the thin film. These results are shown in Table 1.

<Example 2>
The same operation as in Example 1 was performed except that the precursor thin film obtained in the same manner as in Example 1 was subjected to a plasma reaction process, and the plasma reaction treatment time was changed to 3 minutes. Table 1 shows the results.

<Comparative Example 1>
The same operation as in Example 1 was performed except that the precursor thin film obtained in the same manner as in Example 1 was subjected to a plasma reaction step, and the plasma reaction treatment time was changed to 1 minute. Table 1 shows the results.

<Comparative Example 2>
The same operation as in Example 1 was performed except that the precursor thin film obtained in the same manner as in Example 1 was subjected to a plasma reaction process, and the plasma reaction treatment time was changed to 2 minutes. Table 1 shows the results.

Examples 1 and 2 had a distribution in the atomic concentration of phosphorus and had the maximum value of phosphorus on the side closer to the substrate than half the film thickness of the thin film, thus satisfying the present embodiment. On the other hand, Comparative Examples 1 and 2 had the maximum phosphorus value on the side closer to the thin film surface than the half of the thin film thickness, and did not satisfy the present embodiment. Further, Examples 1 and 2 had a small peeled area ratio of 4% or less after the adhesion test, while Comparative Examples 1 and 2 had a large peeled area ratio of 14% or more. Therefore, it was shown that the adhesion of the thin film to the substrate is excellent by satisfying the present embodiment.

In addition, Examples 1 and 2 exhibited lower sheet resistance than Comparative Examples 1 and 2. Therefore, it was shown that the sheet resistance can be reduced and a thin film having excellent conductivity can be obtained by satisfying the present embodiment.

Example 1 that satisfies the present embodiment by subjecting a precursor thin film having a phosphorus weight area density of 6 mg·m ⁻² to 1000 mg·m ⁻² to plasma treatment for 150 seconds to 60 minutes, 2 conductive thin films were obtained. It was shown that the conductive thin film of the present embodiment can be suitably obtained by including this step in the manufacturing method.

As for the amount of oxygen in the thin film, in Examples 1 and 2, compared to Comparative Examples 1 and 2, the average oxygen atomic concentration, oxide layer thickness, and oxide layer thickness ratio in the thin film were smaller. Surprisingly, however, Examples 1 and 2 were superior to Comparative Examples 1 and 2 in adhesion. This is presumed to be due to the uneven distribution of phosphorus on the substrate side.

The conductive thin film of the present invention has industrial applicability as an element constituting a transparent or non-transparent conductive sheet.

DESCRIPTION OF SYMBOLS 10... Conductive thin film, 10'... Metal fine wire, 11... Hole, 20... Base material, 30... Opening, 40... Metal fine line pattern, 100... Conductive sheet

Claims (38)

A conductive thin film containing a transition metal, laminated on a substrate,
Having a concentration gradient of phosphorus atoms in the thickness direction in the film thickness of the conductive thin film,
The concentration gradient of the phosphorus atoms has a maximum atomic concentration _Pm of the phosphorus atoms in a range closer to the substrate than half the thickness of the conductive thin film.
Conductive thin film. The average value P _a of the atomic concentration of phosphorus in the concentration gradient of phosphorus atoms is 0.1% or more and 19% or less.
The conductive thin film according to claim 1. The ratio of the maximum value P _m to the average value P _a (P _m /P _a ) is 2.0 times or more and 200 times or less.
The conductive thin film according to claim 2. The maximum value P _m is 1.0% or more and 20% or less,
The conductive thin film according to any one of claims 1 to 3. In the concentration gradient of the phosphorus atoms, the average value _Pa30 of the atomic concentration of the phosphorus atoms in the range of 30 nm from the side close to the substrate is 0.2% or more and 20% or less.
The conductive thin film according to any one of claims 1 to 4. The average oxygen atomic concentration O _a in the thickness direction of the conductive thin film is 20% or less.
The conductive thin film according to any one of claims 1 to 5. In the thickness direction of the conductive thin film, the film thickness in the range where the atomic concentration of oxygen relative to the atomic concentration of the transition metal is 25% or more is 200 nm or less.
The conductive thin film according to any one of claims 1-6. In the thickness direction of the conductive thin film, the thickness in the range where the atomic concentration of oxygen is 25% or more is 35% or less with respect to the thickness of the conductive thin film.
The conductive thin film according to any one of claims 1-7. In the thickness direction of the conductive thin film, the average value Ma of the atomic concentration of the transition metal is 40% or more and 99% or less.
The conductive thin film according to any one of claims 1-8. The film thickness is 30 nm or more and 1000 μm or less,
The conductive thin film according to any one of claims 1-9. wherein the transition metal comprises a metal of Group 11 elements of the IUPAC Periodic Table;
The conductive thin film according to any one of claims 1-10. wherein the transition metal comprises copper;
The conductive thin film according to claim 11. In the thickness direction of the conductive thin film, the maximum value PM _m of the ratio (P/M) of the atomic concentration P of phosphorus to the atomic concentration M of the transition metal is 1.9% or more and 100% or less.
The conductive thin film according to any one of claims 1-12. In the thickness direction of the conductive thin film, the maximum value _POm of the ratio (P/O) of the atomic concentration P of phosphorus to the atomic concentration O of oxygen is 60% or more and 500% or less.
The conductive thin film according to any one of claims 1-13. The maximum value PMO _m of the ratio (P/(M+O)) of the atomic concentration P of phosphorus to the sum of the atomic concentration M of the transition metal and the atomic concentration O of oxygen in the thickness direction of the conductive thin film is 1. 9% or more and 20% or less,
The conductive thin film according to any one of claims 1-14. wherein the conductive thin film comprises a particle layer to which particles containing the transition metal are bonded;
The conductive thin film according to any one of claims 1-15. wherein the conductive thin film comprises a continuous pattern with openings;
The conductive thin film according to any one of claims 1-16. wherein the pattern is a pattern composed of a plurality of intersecting fine lines;
The conductive thin film according to claim 17. The line width of the fine line is 100 nm or more and 1000 μm or less,
The conductive thin film according to claim 18. The fine wires have a pitch of 1.0 μm or more and 1000 μm or less.
The conductive thin film according to claim 18 or 19. Visible light transmittance is 70% or more and 99% or less,
The conductive thin film according to any one of claims 1-20. Sheet resistance is 0.001 Ωcm ^-2 or more and 20 Ωcm ^-2 or less,
The conductive thin film according to any one of claims 1-21. A substrate and the conductive thin film according to any one of claims 1 to 22,
conductive sheet. the substrate has a plurality of layers,
The conductive sheet according to claim 23. The substrate has a surface layer containing a silicon compound,
The conductive sheet according to claim 23 or 24. The base material is plastic,
The conductive sheet according to any one of claims 23-25. The plastic is polyethylene terephthalate,
27. The conductive sheet according to claim 26. Provided with the conductive thin film according to any one of claims 1 to 22,
touch panel. Provided with the conductive thin film according to any one of claims 1 to 22,
display. Provided with the conductive thin film according to any one of claims 1 to 22,
heater. Provided with the conductive thin film according to any one of claims 1 to 22,
electromagnetic shield. Provided with the conductive thin film according to any one of claims 1 to 22,
antenna. a film forming step of forming a precursor thin film having a phosphorus weight area density of 6.0 mg·m ⁻² or more and 1000 mg·m ⁻² or less on a substrate;
a plasma reaction step of reacting the precursor thin film with plasma for 150 seconds or more and 60 minutes or less to obtain a conductive thin film;
A method for producing a conductive thin film. wherein the precursor thin film contains phosphoric acid and/or a phosphate ester;
34. A method for producing a conductive thin film according to claim 33. The weight area density of the transition metal in the precursor thin film is 1.0 g·m ⁻² or more and 10 g·m ⁻² or less.
35. A method for producing a conductive thin film according to claim 33 or 34. the atmosphere of the plasma reaction step comprises a gas that is a molecule containing hydrogen atoms;
The method for producing a conductive thin film according to any one of claims 33-35. the atmosphere of the plasma reaction step comprises a noble gas;
A method for producing a conductive thin film according to any one of claims 33 to 36. using microwave plasma in the plasma reaction step;
A method for producing a conductive thin film according to any one of claims 33 to 37.

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