JP7645117B2 - Conductive thin film, its manufacturing method, and conductive sheet - Google Patents

Description

The present invention relates to a conductive thin film, a manufacturing method thereof, 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, conductive thin films of transition metals and/or transition metal compounds produced by a method including a precursor coating step are desirable from the viewpoint of large-scale production.

For example, Patent Document 1 discloses a method for producing a conductive substrate including a conductive thin film in which a dispersion of metal or metal compound particles is printed on a substrate and then fired to fuse at least the outermost metal particles, and discloses that the firing is performed by exposing the substrate to plasma of a gas containing a reducing gas. In this way, by using plasma treatment for firing, even copper, which has a relatively high melting point, can be sintered, and copper oxide, which is relatively stable in air, can be sintered while being reduced.

Patent No. 5354037

Patent Document 1 describes that oxides that remain unreduced during the firing process contribute to the adhesion between the conductive thin film formed in this manner and the substrate. However, the oxide layer in the conductive thin film has lower conductivity than metals, and therefore increases the sheet resistance of the thin film. For this reason, it is difficult to achieve both low sheet resistance and adhesion in a conductive thin film, and there has been a demand for the production of a thin film that has adhesion to a substrate even when the oxide layer in the thin film is small.

The present invention was made in consideration of the above problems, and aims to provide a thin film that has excellent electrical conductivity and excellent adhesion to a substrate.

The inventors conducted extensive research to solve the above problems. As a result, they discovered that the above problems could be solved by forming a concentration gradient of specific phosphorus atoms in the thickness direction of the conductive thin film, and thus completed the present invention.

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

The present invention provides a thin film that has excellent electrical conductivity and excellent adhesion to the substrate.

1 is a schematic cross-sectional view showing an example of a conductive thin film according to an embodiment of the present invention. FIG. 2 is a schematic top view illustrating an example of a conductive thin film according to the present embodiment.

Below, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to this, and various modifications are possible without departing from the gist of the invention. In the drawings, the same elements are given the same reference numerals, and duplicated explanations will be omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right will be based on the positional relationships shown in the drawings. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

1. Conductive thin film The conductive thin film of this embodiment is a conductive thin film containing a transition metal that is laminated on a substrate, and has a phosphorus atom concentration gradient in the thickness direction of the conductive thin film, and the phosphorus atom concentration gradient has a maximum phosphorus atomic concentration _Pm in a range closer to the substrate than half the thickness of the conductive thin film. By having such a phosphorus atom concentration gradient, 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 may contain oxygen atoms and other atoms as necessary. The transition metal may exist in the form of a metal element or in the form of a metal compound such as an oxide. The composition of each atom in the conductive thin film is described in detail below.

The conductive thin film of the present embodiment has a phosphorus atom concentration gradient in the thickness direction of the film thickness. The phosphorus atom concentration gradient has a maximum value _Pm of the phosphorus atom concentration in the range closer to the substrate than the halfway point of the film thickness in the conductive thin film.

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

In this embodiment, "the conductive thin film has a concentration gradient of phosphorus atoms in the thickness direction, and the concentration gradient of phosphorus atoms has a maximum value _Pm of the phosphorus atomic concentration in a range closer to the substrate than half the film thickness in the conductive thin film" means that, as exemplified in the graph of the thickness direction and phosphorus atomic concentration in Figure 1, the concentration of phosphorus atoms tends to increase closer to the substrate side, and the maximum value Pm of phosphorus atoms exists closer to the substrate than half the film thickness (thickness 0.5T).

The graph of thickness direction and phosphorus atom concentration shown in FIG. 1 is a plot of the concentration P(t) of phosphorus atoms contained in a cross section of a conductive thin film when the cross section is obtained at a certain thickness position t. Specifically, the graph of thickness direction and phosphorus atom concentration shown in FIG. 1 is a graph in which the concentration of phosphorus atoms contained in a cross section of a conductive thin film is measured and plotted at each thickness position of 0.1T, 0.2T, 0.3T, ..., and T. Note that the measurement accuracy of the plot is an example, and can be set to a sufficiently high accuracy.

Therefore, the maximum value Pm means the maximum value in the graph plotted in this way, and the average value Pa, which will be described later, means the average value of the phosphorus atom concentration in all thickness directions. In this embodiment, the maximum value is given the subscript "m" (Max), and the average value is given the subscript "a" (average). The same applies to the transition metal atoms, oxygen atoms, and carbon atoms, which will be described later.

It is believed that the adhesion between the conductive thin film and the substrate is improved by having a phosphorus atom concentration gradient such that the maximum value of the phosphorus atomic concentration is present on the substrate side. Although the mechanism by which such improved adhesion is observed is not limited to the following, it is believed that the concentration of phosphorus on the substrate side improves the bonding strength between the transition metals present on the substrate side in the conductive thin film and between the substrate and the transition metal, making it more difficult for condensation breakdown and interfacial peeling to occur. Note that either condensation breakdown or interfacial peeling may be suppressed, or both may be suppressed. In addition, the improvement in bonding strength is not limited to the transition metal itself, and may occur between the transition metal and the transition metal compound, between the transition metal compounds, or between the transition metal compound and the substrate.

It is also believed that the conductivity is improved by having a phosphorus atom concentration gradient such that the maximum value of the phosphorus atomic concentration is present on the substrate side. The mechanism by which such improved conductivity is observed is not limited to the following, but it is believed that the amount of oxygen contained in the conductive thin film is reduced by having a phosphorus atomic concentration gradient as described above, the grain boundary resistance of the transition metal is reduced by phosphorus unevenly distributed on the substrate side, or the conductivity is improved by doping phosphorus into metal compounds with low conductivity such as metal oxides. These reasons may act in combination.

The above-mentioned concentration gradient of phosphorus atoms can be formed by a film formation process in which a precursor thin film containing a phosphorus-based compound is formed, and a specified plasma reaction process. Details of the method for manufacturing a conductive thin film having these processes will be described later, but in general, it is difficult to control the anisotropic movement of phosphorus within the film in the reaction between the precursor thin film and plasma, and it is very surprising that the method described below can be used to obtain a concentration gradient of phosphorus atoms in which phosphorus is highly concentrated on the substrate side as described above.

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

Here, "0T to 0.25T" indicates the range in the thickness direction of the conductive thin film. For example, if the thickness of the conductive thin film is T 100 nm, this means "0 x 100 nm to 0.25 x 100 nm" from the substrate side, that is, a thickness range of 0 to 25 nm from the substrate side.

From the same viewpoint, the maximum value _Pm of the phosphorus atomic concentration is preferably in a range of 100 nm from the side closer to the substrate in the thickness direction of the conductive thin film, more preferably in a range of 50 nm from the side closer to the substrate, and even more preferably in a range of 30 nm from the side closer to the substrate.

The maximum value _Pm 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 _Pm is 0.2% or more, the sheet resistance of the conductive thin film is further reduced, and the adhesion between the conductive thin film and the substrate tends to be further improved. In addition, when the maximum value _Pm is 20% or less, it tends to be easier to adjust the concentration distribution of phosphorus so that the maximum value Pm exists on the substrate side, and the concentration of the transition metal in the conductive thin film is relatively improved, so that the sheet resistance of the conductive thin film tends to be further reduced.

The average value P _a of the phosphorus atomic concentration in the phosphorus atom concentration gradient is preferably 0.1 to 19%, more preferably 0.1 to 10%, even more preferably 0.1 to 5.0%, and still more preferably 0.1 to 1.0%. When the average value P _a of the phosphorus atomic concentration 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 uneven distribution of phosphorus in the thickness direction of the conductive thin film can be expressed by the ratio (P _m /P _a ) of the maximum value P _m to the average value 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 even more 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 toward the substrate side increases, so that the sheet resistance of the conductive thin film is further reduced, and the adhesion between the conductive thin film and 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 opposite side of the conductive thin film from the substrate is relatively improved, so that the sheet resistance of the conductive thin film tends to be further reduced. Furthermore, by having the ratio ( _Pm / _Pa ) be 200 times or less, it tends to be easier to adjust the phosphorus concentration distribution so that the maximum value Pm that satisfies the ratio ( _Pm / _Pa ) exists on the substrate side.

The range of 30 nm from the side closer to the substrate in the thickness direction of the conductive thin film contributes more to improving the adhesion between the conductive thin film and the substrate, and there is a tendency that interfacial peeling can be suppressed by adjusting the concentration of phosphorus atoms in this portion. From this viewpoint, in the concentration gradient of phosphorus atoms, the average value P _a30 of the phosphorus atomic concentration in the range of 30 nm from the side closer to the substrate is preferably 0.2 to 20%, more preferably 1.0 to 15%, even more preferably 1.0 to 10%, and even more preferably 1.5 to 5.0%. By having the average value P _a30 within the above range, there is a tendency that interfacial peeling is further 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 be present in the form of a metal element or a metal compound such as an oxide.

The transition metal atom is not particularly limited as long as it is a metal of Group 3 to Group 11 in the IUPAC periodic table, but preferably contains a metal of Group 11, more preferably contains silver or copper, and even more preferably contains copper. By using such a transition metal, the conductivity of the conductive thin film tends to be further improved. In addition, since the d-orbital of transition metals that are metals of Groups 3 to 11 is not a closed shell, it is thought that the electrons in the d-orbital contribute to bonding with phosphorus, which in turn improves the adhesion between the conductive thin film and the substrate. However, the reason for the improved adhesion is not limited to the above.

The type of metal compound containing a transition metal is 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 manufacture.

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%, even more preferably 70 to 97%, and even more preferably 80 to 95%. When the average value Ma is 40% or more, the sheet resistance of the conductive thin film tends to be further reduced. Also, 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%, even more preferably 5.0 to 40%, and 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. Furthermore, when the maximum value PM _m is 100% or less, 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 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 to 20%, more preferably 2.5 to 15%, even more preferably 3.0 to 10%, and still 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. Furthermore, when the maximum value PMO _m is 20% or less, the sheet resistance of the conductive thin film tends to be further reduced.

The above ratios (P/M) and ratios (P/(M+O)) are values calculated by measuring the atomic concentration M(t) of the transition metal, the atomic concentration O(t) of oxygen, and the atomic concentration P(t) of phosphorus in the cross section of the conductive thin film at the same thickness position. The maximum values _PMm and _PMOm refer to the maximum values among the ratios (P/M) and ratios (P/(M+O)) thus obtained for each thickness position.

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

The average value _Oa 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%, even more preferably 2.0 to 12.5%, and even more preferably 3.0 to 7.5%. When the average value _Oa is 20% or less, the amount of non-conductive transition metal oxide decreases and the amount of conductive transition metal increases relatively, so that the sheet resistance of the conductive thin film tends to be further reduced. In addition, when the average value _Oa is 20% or less, the atomic concentration of phosphorus increases relatively, so that the adhesion between the conductive thin film and the substrate tends to be further improved.

Among the conductive thin films, the oxide layer with 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 this embodiment, the oxide layer is defined as a range in which the atomic concentration of oxygen relative to the atomic concentration of the transition metal is 25% or more. For example, when the transition metal is copper, the value of 25% corresponds to the boundary value at which cuprous oxide and metallic copper exist in a 1:1 ratio. 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, even more preferably 2.0 to 100 nm, even more preferably 3.0 to 50 nm, and even more preferably 3.0 to 20 nm. By having the film thickness of the oxide layer within the above range, the metal layer that relatively contributes to conductivity increases, and the sheet resistance of the conductive thin film tends to decrease further. Note that the metal layer is defined as a range in which the atomic concentration of oxygen relative to the atomic concentration of the transition metal is less than 25% as a concept for the oxide layer.

The thickness of the oxide layer is preferably 35% or less of the thickness of the conductive thin film, more preferably 0.5 to 20%, even more preferably 0.5 to 10%, and even more preferably 0.5 to 5.0%. By having the thickness of the oxide layer 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 PO _m 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%, even 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. In addition, when the maximum value PO _m is 500% or less, it falls within a range that is easy to adjust even when a metal oxide with 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 the present embodiment may have a concentration gradient of carbon atoms in the depth direction of the film thickness, or the carbon atoms may be distributed approximately uniformly.

The average value C _a 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%, even more preferably 2.0 to 12.5%, and still 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 be further reduced, and the adhesion between the conductive thin film and the substrate tends to be further improved.

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

In STEM-EDX analysis, a cross section of a conductive thin film is measured. For example, when the conductive thin film is a thin metal wire pattern described below, the measurement sample is preferably a thin slice including a cross section of the thin metal wire perpendicular to the extension direction of the thin metal wire. When preparing the measurement sample, if necessary, the conductive thin film may be embedded in a support such as an epoxy resin before forming a thin slice.

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

Next, the cross section of the formed thin metal wire is observed using a scanning transmission electron microscope (STEM) to obtain a STEM image of the cross section of the thin metal wire. At the same time, elemental mapping of the cross section of the thin metal wire is measured using energy dispersive X-ray analysis (EDX), allowing STEM-EDX analysis to be performed.

The fact that the thin film of this embodiment has 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) via dry etching. Quantitative values of atomic concentration can be measured by STEM-EDX analysis.

The formation of the cross section of the thin metal wire and the STEM-EDX analysis described below are preferably performed in an inert atmosphere such as argon or in a vacuum in order to prevent oxidation and contamination of the cross section of the thin metal wire.

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

The thickness of the conductive thin film can be determined by the cross-sectional STEM-EDX evaluation of the conductive thin film described below. More specifically, the region in which the atomic concentration of the transition metal in the conductive thin film is 20% or more is defined as the thickness of the conductive thin film, and the average value of the thickness measured at any three locations can be taken as the thickness of the conductive thin film. Note that the conductive thin film of this embodiment may be a thin film having a uniform thickness, or may be a thin film having an uneven surface or having thin portions depending on the position of the conductive thin film.

The conductive thin film may have no voids in the film or may have voids in the film. Of these, the conductive thin film is preferably one having voids in the film. An example of such a conductive thin film is one that includes a particle layer in which particles containing a transition metal are bonded. The particle layer makes the thin film less susceptible to breakage even when stress such as bending of the substrate is applied. 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. The presence of the particle layer can also be evaluated by STEM analysis, etc.

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 refers to a portion where the conductive thin film is not present, and light can pass through the opening portion. In addition, the continuous pattern refers to a connection (contact) confirmed by an optical microscope, and such a pattern is electrically connected.

Among these, it is preferable that the conductive thin film has a continuous pattern with openings. By providing openings in this way, it is possible to make the conductive thin film light-transmitting. In addition, the continuous pattern with openings is not particularly limited, but for example, a pattern formed by a plurality of crossing thin lines is preferable. In this case, the thin lines correspond to the conductive thin film, and the gaps between the thin lines become the openings.

Specific examples of patterns formed from multiple thin wires are described below, but the patterns in this embodiment are not limited to the following. In the following, thin metal wires refer to thin conductive thin films, and thin metal wire patterns refer to patterns formed from multiple thin metal wires.

Figure 2 shows a schematic top view of an example of a conductive thin film of this embodiment. Figure 2 is a top view of a conductive sheet 100 in which a conductive thin film 10 is disposed on a substrate 20, viewed from the side on which the conductive thin film 10 is formed. In Figure 2, the conductive thin film 10 is in the form of thin lines, and is shown as a state in which the thin lines cross on a grid. Here, the conductive thin film 10 in the form of thin lines is called a thin metal wire 10'. The cross section of Figure 1 mentioned above shows the A-A' cross section of this thin metal wire 10'.

As shown in FIG. 2, a continuous pattern refers to, for example, a configuration in which a plurality of fine metal wires 10' cross each other to form a continuous layer, allowing current to flow between any two points on the conductive thin film 10 extending in the planar direction. Also, having an opening refers to, for example, having a discontinuous opening 30 between a plurality of fine metal wires 10'. In this embodiment, the conductive continuous layer and opening formed by the fine metal wires 10' is referred to as a fine metal wire pattern 40.

Here, the line width W of the thin metal wires 10' constituting the thin metal wire pattern 40 refers to the line width of the thin metal wires 10' when projected onto the surface of the substrate 20 from the side of the substrate 20 on which the thin metal wire pattern 40 is arranged. The "line width when projected" is defined as the width of the thin metal wires when the interface between the conductive thin film 10 and the substrate is the widest, for example, as shown in FIG. 1. The pitch P is defined as the sum of the line width W and the distance L between the thin metal wires.

Specific examples of the above-mentioned fine metal wire pattern include a mesh pattern formed by a plurality of fine metal wires crossing each other in a mesh pattern, and a line pattern formed with a plurality of approximately parallel fine metal wires. The fine metal wire pattern may also be a combination of a mesh pattern and a line pattern. The mesh of the mesh pattern may be a square or rectangle, or a polygon such as a diamond. The fine metal wires that make up the line pattern may be straight or curved. Furthermore, the fine metal wires that make up the mesh pattern may also be curved.

The line width W is preferably 100 nm to 1000 μm, more preferably 200 nm to 500 μm, even more preferably 300 nm to 100 μm, still more preferably 400 nm to 50 μm, and even more preferably 500 nm to 5.0 μm. The line width W of a thin metal wire having gently sloping sides as shown in FIG. 1 is the width of the thin metal wire disposed perpendicularly to the substrate, and when the substrate in contact with the thin metal wire is a curved surface, it is the perimeter of the area where the cross section of the thin metal wire contacts the substrate.

By making the line width W of the thin metal wire 100 nm or more, the conductivity of the thin metal wire can be sufficiently ensured, and the sheet resistance tends to be further reduced. In addition, the decrease in conductivity due to oxidation or corrosion of the surface of the thin metal wire can be sufficiently suppressed. Furthermore, for the same aperture ratio, the thinner the line width of the thin metal wire, the more the number of thin metal wires can be increased. This makes the electric field distribution of the conductive sheet more uniform, making it possible to fabricate electronic devices with higher resolution. Furthermore, even if some of the thin metal wires are broken, the other thin metal wires can compensate for the resulting effect.

On the other hand, by having the line width W of the thin metal wires be 5.0 μm or less, the visibility of the thin metal wires tends to be reduced, and the transparency of the conductive thin film and the conductive sheet comprising the same tends to be improved.

1.8.2. Aspect ratio The aspect ratio, which is expressed by the thickness T of the metal thin wire relative to the line width W of the metal thin wire, is preferably 0.05 to 1.00, more preferably 0.08 to 0.90, and even more preferably 0.10 to 0.80. When the line width W is constant, the larger the aspect ratio, the more the conductivity tends to improve without decreasing the transmittance. In addition, by having an aspect ratio of 1.00 or less, the decrease in transmittance due to an excessively thick film thickness tends to be suppressed.

1.8.3. Pitch The pitch P is preferably 1.0 to 1000 μm, more preferably 5.0 to 500 μm, even more preferably 50 to 250 μm, and even 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 improved. When the pitch P is 1000 μm or less, the conductivity tends to be improved. In addition, when the shape of the thin metal line pattern is a mesh pattern, the pitch of the thin metal line pattern with a line width of 1 μm is set to 200 μm, so that the aperture ratio can be 99%.

The aperture ratio of the thin metal line 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 thin metal line pattern is 60% or more, the transmittance of the conductive sheet tends to be further improved.

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

The appropriate aperture ratio of the thin metal line pattern varies depending on the shape of the thin metal line pattern. In addition, the aperture ratio of the thin metal line pattern can be appropriately combined with the above upper and lower limits depending on the required performance (transmittance and sheet resistance) of the target electronic device.

The "aperture ratio of the thin metal line pattern" can be calculated for the region on the substrate where the thin metal line pattern is formed by the following formula. The region on the substrate where the thin metal line pattern is formed excludes edges and the like where the thin metal line pattern is not formed.
Aperture ratio of thin metal line pattern=(1−area occupied by thin metal line pattern/area of transparent substrate)×100

The line width W, aspect ratio, and pitch P of the thin metal line pattern can be confirmed by observing the cross section of the conductive sheet with an electron microscope or the like. The line width and pitch of the thin metal line pattern can also be observed with a laser microscope or optical microscope. Since the pitch P and the aperture ratio have a relationship as described below, if one is known, it is possible to calculate the other. Methods for adjusting the line width W, aspect ratio, and pitch P of the thin metal line pattern to the desired range include adjusting the grooves of the plate used in the manufacturing method of the conductive sheet as described below, and adjusting the average particle size of the metal particles in the ink.

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

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 , and preferably 0.1 to 10 Ωcm ⁻² . The lower the sheet resistance, the more improved the conductivity tends to be.

The sheet resistance of a conductive sheet tends to decrease by improving the aspect ratio (height) of the thin metal wires. It can also be adjusted by selecting the type of metal material that makes up the thin metal wires.

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%, and even more preferably 0.01 to 1.00%. When the haze is 5.00% or less, the clouding of the conductive sheet with respect to visible light tends to be further suppressed. The haze in this specification can be measured in accordance with the haze of JIS K 7136:2000.

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

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 conductive film material, and in particular, when the conductive thin film has the above-mentioned metal thin line pattern and has visible light transparency, it becomes a conductive transparent film material. Such a conductive sheet can provide new value by imparting transparency to heaters, electromagnetic shields, antennas, etc., which have not been required to be transparent in the past, in addition to applications requiring transparency such as touch panels and displays.

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

The substrate can be in the form of a plate or a film, with a film being preferred from the viewpoint of excellent freedom in form.

The plastics are not particularly limited, but examples thereof include transparent organic substrates such as acrylic acid esters, methacrylic acid esters, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polyarylate, polyvinyl chloride, polyethylene, polypropylene, polystyrene, nylon, aromatic polyamide, polyether ether ketone, polysulfone, polyethersulfone, polyimide, and polyetherimide.

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

The substrate of the thin film used in this embodiment may be made of one material or may be a laminate of two or more materials. In addition, when the transparent substrate is a multilayer body in which two or more materials are laminated, the transparent substrate may be a laminate of organic substrates or inorganic substrates, or a laminate of an organic substrate and an inorganic substrate.

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 freedom of shape and/or excellent transparency.

The substrate may have multiple layers, and may have a surface layer in the contact area with the conductive thin film. By laminating the surface layer on the substrate, it is possible to prevent etching of the substrate in areas that are not covered with the thin metal line pattern by plasma or the like when the metal components in the ink are sintered by a baking means such as plasma.

The components contained in the surface layer are not particularly limited, but examples thereof include silicon compounds (e.g., (poly)silanes, (poly)silazanes, (poly)silthians, (poly)siloxanes, silicon, silicon carbide, silicon oxide, silicon nitride, silicon chloride, silicate salts, zeolites, silicides, etc.), aluminum compounds (e.g., aluminum oxide, etc.), magnesium compounds (e.g., magnesium fluoride), etc. The polysilanes, polysilazanes, polysilthians, and polysiloxanes may have a linear or branched, cyclic, or mesh-like shape. These components may be used alone or in combination of two or more.

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 components, the durability against plasma is improved, and the adhesion between the conductive thin film and the substrate tends to be improved. In addition, by using such components, the transparency and durability of the conductive sheet tend to be improved, and the productivity, which contributes to the cost reduction effect for manufacturing the conductive sheet, tends to be superior.

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

When a surface layer is included, silicon may be incorporated into the conductive thin film via a plasma reaction. The silicon atoms Si contained in the metal fine wires may exist in the form of silicon atoms or silicon compounds, or in the form of silicon atoms or silicon compounds bonded to metal atoms (e.g., 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, and even 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. In addition, when the thickness of the surface layer is 500 μm or less, the flexibility of the substrate can be ensured.

The surface layer preferably has an antistatic function to prevent disconnection of the thin metal line pattern due to static electricity. From the viewpoint of having the 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 volume resistivity of the surface layer is preferably 100 to 100,000 Ωcm, preferably 1,000 to 10,000 Ωcm, and preferably 2,000 to 8,000 Ωcm. When the volume resistivity of the surface layer is 100,000 Ωcm or less, the antistatic function tends to be further improved. Furthermore, when the volume resistivity of the surface layer is 100 Ωcm or more, the electrical conductivity between the metal fine line patterns is further reduced, making it suitable for use in applications such as touch panels.

The volume resistivity can be adjusted by the content of conductive inorganic oxides, conductive organic compounds, etc. in the surface layer. For example, if the surface layer contains silicon oxide (volume resistivity 1014 Ω·cm or more) which has high plasma resistance and an organosilane compound which is a conductive organic compound, the volume resistivity can be reduced by increasing the content of the organosilane compound. On the other hand, although the volume resistivity increases by increasing the content of silicon oxide, the film can be made into a thin film due to its high plasma resistance, and the optical properties are not impaired.

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 together with the substrate.

The protective layer is not particularly limited, but may be any material that is transparent and exhibits good adhesion to the conductive thin film or substrate. Examples of the protective layer include thermosetting resins such as phenolic resin, thermosetting epoxy resin, thermosetting polyimide, melamine resin, urea resin, unsaturated polyester resin, alkyd resin, polyurethane, diallyl phthalate resin, and silicone resin; UV-curable resins such as urethane acrylate, acrylic resin acrylate, epoxy acrylate, silicone acrylate, and UV-curable epoxy resin; and commercially available coating agents.

3. Method for Producing a Conductive Thin Film The method for producing a conductive thin film of the present embodiment includes a film formation step of forming a precursor thin film having a phosphorus weight areal density of 6.0 mg m ^-2 or more and 1000 mg m ^-2 or less 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, and may include a surface layer formation step of forming a surface layer on the substrate before the film formation step, as necessary.

3.1. Surface layer forming step The surface layer forming step is a step of forming the above-mentioned surface layer on the substrate. For example, when a plastic substrate is used, the surface layer can prevent the plastic from being denatured or etched by the plasma reaction.

A specific example of a surface layer forming method is a method in which a component that forms the surface layer is formed on the surface of a transparent substrate using a gas phase film forming method such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). Another specific example of a surface layer forming step is a method in which a composition in which the component that forms the surface layer is dispersed in a dispersion medium is applied to the surface of a transparent substrate and dried to form a surface layer. In addition, the surface layer forming composition may contain a dispersant, a surfactant, a binder, etc., as necessary.

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

The film formation step is a step of forming a precursor thin film having a phosphorus weight areal density of 6.0 mg m ^-2 or more and 1000 mg m ^-2 or less on a substrate. The phosphorus weight areal density can be adjusted by the amount of a 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 turned into the conductive thin film of this embodiment by performing a plasma reaction process described below. As already described, by performing a plasma treatment on such a precursor thin film containing phosphorus, the resulting conductive thin film has a phosphorus gradient with the maximum value of the phosphorus atomic concentration on the substrate side, and this phosphorus gradient gives the conductive thin film excellent conductivity and excellent adhesion to the substrate.

The phosphorus weight areal density of 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 , and even more preferably 10 to 50 mg m ^-2 . When the phosphorus weight areal density of 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. Furthermore, when the phosphorus weight areal density of the precursor thin film is 1000 mg m ^-2 or less, the transition metal is relatively increased, and therefore the conductivity of the obtained conductive thin film is further improved.

The weight areal 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 even more preferably 1.0 to 6.0 g m ^-2 . When the weight areal 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.

In this embodiment, the weight density of phosphorus or transition metal in the precursor thin film refers to the weight density of phosphorus or transition metal in the region where the precursor thin film is present, and if the pattern has openings, the openings are not included in the calculation of the weight area density of phosphorus or transition metal.

The phosphorus-based compound contained in the precursor thin film is not particularly limited, but examples include phosphoric acid and/or phosphoric acid esters. By using such phosphorus-based compounds, a phosphorus gradient with a maximum phosphorus atomic concentration on the substrate side tends to be formed more easily in the plasma reaction process described below.

Such a precursor thin film can be formed using various methods, such as a dry method using a vacuum device, or a wet method using ink. Of these, the method of forming the precursor thin film by printing ink on a substrate is preferred from the viewpoints of suitability for large-scale production and ease of adjusting the amount of phosphorus contained in the precursor thin film.

Printing methods that can be used are not particularly limited, but examples include letterpress printing, gravure printing, bar coating, spray coating, spin coating, and reverse transfer printing. Among these, deposition of the precursor thin film by a plate printing method is preferred from the viewpoint of being able to print relatively precise patterns.

The plate printing method includes, for example, a step of coating the surface of a transfer medium with ink, a step of contacting the ink-coated surface of the transfer medium with the convex surface of a letterpress printing plate to transfer a portion of the ink on the surface of the transfer medium to the convex surface of the letterpress printing plate, and a step of contacting the surface of the transfer medium after some of the ink has been transferred with the surface of a substrate to transfer the ink remaining on the surface of the transfer medium to the surface of the substrate.

For example, in such a printing method, various shapes of the precursor thin film, such as its thickness, width, and pitch, as well as 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 contain a surfactant, a dispersant, a reducing agent, and the like, as necessary.

3.2.2.1 Metal Particles The metal component may be contained in the ink as metal particles or as a metal complex. Of these, it is preferable that the metal component is contained in the ink as metal particles. As the metal particles, as long as they contain the above-mentioned transition metal atoms, they may be metal oxides such as copper oxide or other metal compounds, or core/shell particles in which the core part is copper and the shell part is copper oxide. Of these, metal oxides such as copper oxide are preferable from the viewpoint of handling.

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. The lower limit of the average primary particle size of the metal particles is not particularly limited, but may be 1 nm or more. From the viewpoint of making the line width W of the resulting metal thin wire thinner, it is preferable that the average primary particle size of the metal particles is 100 nm or less.

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 monodispersed and that the average secondary particle size is close to the average primary particle size.

In this embodiment, the "average primary particle size" refers to the particle size of each individual metal particle (a so-called primary particle), and is to be distinguished from the average secondary particle size, which is the particle size of an aggregate (a so-called secondary particle) formed by gathering together multiple metal particles.

3.2.2.2. Phosphorus component The phosphorus component is not particularly limited, but examples thereof include black phosphorus, red phosphorus, phosphoric acid, and phosphoric acid esters. Among these, phosphoric acid and/or phosphoric acid esters are preferred. By using such phosphorus-based compounds, a phosphorus gradient having a maximum phosphorus atomic concentration on the substrate side tends to be more easily formed in the plasma reaction process described below. The phosphoric acid and/or phosphoric acid ester includes a polymer or low molecule having a phosphoric acid group and/or a phosphoric acid ester group, a phosphate anion, a phosphate ester anion, a salt containing a phosphate anion, or a salt containing a phosphate ester anion.

For example, surfactants, pH adjusters, viscosity adjusters, drying speed adjusters, metal particle dispersants, stabilizers, etc., which contain phosphorus atoms, may be used as phosphorus components. Examples of such phosphorus components include dispersants 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. By using such surfactants, the coatability of the ink on the transfer medium (blanket) and the smoothness of the coated ink tend to be improved, resulting in a more uniform coating film. It is preferable that the surfactant is configured to be capable of dispersing metal components and to be unlikely to remain after baking.

3.2.2.4. Solvent The ink solvent is preferably an organic solvent from the viewpoints of excellent storage stability and small light loss. From the above viewpoints, the organic solvent is preferably an alcohol. From the above viewpoints, the number of carbon atoms in the organic solvent is preferably 1 to 7, more preferably 2 or more, more preferably 5 or less, or 4 or less, and most preferably 2. Examples of the solvent 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 Examples of the alcohol include alcohol, 2,6-dimethyl-4-heptanol, n-decanol, cyclohexanol, methylcyclohexanol, 3,3,5-trimethylcyclohexanol, benzyl alcohol, and diacetone alcohol. From the viewpoints of excellent storage stability and small light loss, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, and isomers thereof are more preferable, ethanol, propanol, butanol, and isomers thereof are even more preferable, and ethanol is the most preferable.

3.2.2.5. Dispersant The dispersant is not particularly limited, but examples thereof include dispersants that form a non-covalent bond or interact with the metal component, and dispersants that form a covalent bond with the metal component. Examples of functional groups that form a non-covalent bond or interact with the metal component include dispersants having a phosphate group. By using such a dispersant, the dispersibility of the metal component tends to be further improved.

3.3. Plasma reaction process The plasma reaction process is a process in which the precursor thin film formed as described above is reacted with plasma for 150 seconds to 60 minutes to obtain a conductive thin film. As a result, the precursor thin film is baked, and the metal particles in the ink are sintered to form a particle layer (conductive thin film), and the phosphorus contained in the precursor thin film migrates to the substrate side, forming a predetermined concentration gradient. This makes it possible to obtain a conductive thin film that is excellent in conductivity and adhesion to the substrate. In addition, by making the atmosphere during the plasma reaction a reducing type, the oxygen concentration contained in the conductive thin film can also be adjusted.

Plasma can be generated by a variety of methods. Among these, microwave plasma and high-frequency plasma are preferred because they are relatively easy to control, and microwave plasma is particularly preferred from the viewpoint of reducing contamination caused by electrodes for generating plasma within the device.

The microwave output of the microwave plasma is preferably 0.5 to 10 kW, and more preferably 1.0 to 5.0 kW. By using a microwave output of 0.5 kW or more, the adhesion between the resulting conductive thin film and the substrate is improved, and the plasma reaction time can be shortened. In addition, by using a microwave output of 10 kW or less, etching or modification of the substrate by the plasma tends to be suppressed.

The processing time for the plasma reaction is 150 seconds to 60 minutes, preferably 180 to 600 seconds, and more preferably 240 to 360 seconds. By setting the processing time to 150 seconds or more, phosphorus tends to be unevenly distributed toward the substrate side in the conductive thin film, and the maximum value of the phosphorus concentration unevenly distributed toward the substrate side becomes larger, which tends to further improve the adhesion between the conductive thin film and the substrate. In addition, by setting the processing time to 60 minutes or less, the productivity of the conductive thin film tends to further improve.

The atmosphere for the plasma reaction preferably contains a gas containing molecules containing hydrogen atoms or a rare gas. 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 containing molecules containing hydrogen atoms is not particularly limited, but is preferably, for example, a gas containing hydrogen molecules. The gas containing molecules containing hydrogen atoms may be one or more types of molecules. By using such a gas containing molecules containing hydrogen atoms, the conductivity of the conductive thin film produced tends to be further improved.

The rare gas is not particularly limited, but examples include helium, argon, xenon, and krypton. Of these, helium or argon, which have a relatively small molecular weight, are preferred, with helium being the most preferred, from the viewpoint of reducing sample etching by these plasmas. By using such a rare gas, it becomes easier to control the plasma reaction.

The gas containing hydrogen atoms and the rare gas may be mixed and used, and other gases may also be mixed therewith. From the viewpoint of having reducing properties during the plasma reaction and being able to control the reduction reaction relatively easily, it is preferable to use a gas containing hydrogen atoms and a rare gas together. Specifically, it is preferable to use a gas containing both hydrogen molecules and helium.

The pressure of the plasma reaction may be under pressure, reduced pressure, or atmospheric pressure. Of these, reduced pressure is preferable from the viewpoint of lengthening the mean free path of the plasma. Specifically, the pressure is preferably 0.1 to 1000 Pa, more preferably 1.0 to 500 Pa, and even more preferably 10 to 300 Pa. A pressure of 0.1 Pa or more tends to lengthen the mean free path of the plasma. Furthermore, a pressure of 1000 Pa makes it possible to use more gases that are molecules containing hydrogen atoms, or rare gases.

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, and the two conductive sheets face each other so that, for example, the line patterns of thin metal wires cross. The conductive sheets are connected to an extraction electrode, and the extraction electrode 32 connects the thin metal wires to a controller (such as a CPU) for switching the current flow to the thin metal wires.

Note that the touch panel of this embodiment is not limited to a capacitive type, and may be a resistive film type, a projected capacitive type, a surface capacitive type, etc.

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. Also, 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 when electricity is supplied thereto, and a power supply device that supplies power to the electric heating part, and a conductive sheet (conductive thin film) can be used as the electric heating part. If the conductive sheet (conductive thin film) is made transparent, it becomes a transparent heater, and if the conductive sheet is designed to have a high resistance, it becomes a heater that generates a large amount of heat.

For example, the transparent heater is not particularly limited in its use, but examples include anti-fogging and anti-freezing heaters for LED lighting fixtures used in automobile headlamps, taillamps, etc., and anti-fogging and anti-freezing heaters for outdoor LED lighting fixtures used in street lamps, etc.

7. Electromagnetic Wave Shielding The electromagnetic wave shielding of the present embodiment is not particularly limited as long as it includes the conductive thin film. For example, the electromagnetic wave shielding includes a shielding material that reflects or absorbs incident electromagnetic waves, and the 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 is equipped with the conductive thin film. For example, an RF tag has a semiconductor element and an antenna connected thereto, which enables transmission and reception of a specific frequency, 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.

The present embodiment will be explained in more detail below with specific examples and comparative examples, but the present embodiment is not limited in any way by these examples and comparative examples as long as they do not exceed the gist of the present embodiment.

(Evaluation of element concentration distribution in cross section of thin metal wire)
The obtained substrate with the conductive thin film was cut with a razor, embedded in a vapor-deposited carbon layer, and thin slices with a thickness of about 100 nm were formed with a focused ion beam. The obtained thin slices were used as measurement samples, and irradiated with an electron beam under the following conditions to prepare evaluation samples, and STEM-EDX analysis was performed. This analysis obtained the concentration distributions of transition metals, phosphorus, oxygen, and carbon in the thickness direction of the conductive thin film every 2.8 nm or 3.4 nm. In addition, the parameters listed in Table 1 were calculated based on the obtained concentration distributions.
[Apparatus conditions]
STEM: Hitachi High-Technologies Corporation, scanning transmission electron microscope HD-2300A
EDX: Energy dispersive X-ray analyzer Octane T Plus (software: GENESIS) manufactured by EDAX
Acceleration voltage: 200 kV
Measurement magnification: 100,000 times Mapping elements: Cu, O, P, Si, C

(Position of maximum phosphorus concentration in thin film)
Based on the distribution of phosphorus atomic concentration obtained by evaluating the element concentration distribution in the cross section of the metal thin wire, the position of the maximum phosphorus atomic concentration was evaluated. The maximum phosphorus atomic concentration in the conductive thin film was defined as "near the substrate" when it was within 10% of the thickness direction from the side closer to the substrate, as "on the substrate side" when it was within 1/4 to 1/2, as "on the thin film surface side" when it was within 1/2 to 3/4, and as "near the thin film surface" when it was within 3/4 to the surface of the thin film.

(Average value of P atom concentration at the thin film-substrate interface)
For a region of the conductive thin film thickness from the side closest to the substrate interface up to 30 nm, the average phosphorus atomic concentration density in this region was calculated using the distribution of phosphorus atomic concentration obtained by evaluating the element concentration distribution in the cross section of the metal thin wire.

(Thickness of oxide layer)
Based on the distribution of the atomic concentration of oxygen obtained by evaluating the element concentration distribution in the cross section of the metal thin wire, the thickness of the oxide layer was determined to be the thickness within the range in which the atomic concentration of oxygen relative to the atomic concentration of the transition metal was 25% or more. In addition, the ratio of the thickness of the oxide layer to the thickness of the conductive thin film was calculated.

(Evaluation of thin film morphology)
The 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 using a laser microscope (OLYMPUS, OLS-4500).

(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)=(opening ratio of thin line pattern)×(visible light transmittance of substrate)

(Adhesion)
The 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 (OLYMPUS, OLS-4500), and the obtained image was recorded. The adhesive surface of an adhesive tape (3M No. 610) was brought into contact with the conductive thin film, and the tape was fixed by rolling it back and forth twice with a 2N (Newton) roller from above the tape. The fixed tape was peeled off at a speed of 100 mm/min using a 90° peel tester (Shimadzu Corporation, EZ-S), and a tape peeling test was performed. The substrate surface after the tape peeling was observed with a laser microscope in the same manner as that measured before the tape peeling test, and the obtained image was recorded. The obtained images before and after the tape peeling test were subjected to a binarization process to determine the boundary by Otsu's method, and then the areas of the thin metal wire parts were compared, and the area ratio of the thin metal wire parts lost by the tape peeling test was obtained to obtain the peeled area ratio of the thin metal wires by the tape peeling test. The smaller this peeled area ratio, the better the adhesion of the thin film to the substrate.

Example 1
(Preparation of Transparent Substrate)
A surface layer-forming composition containing silicon oxide nanoparticles and a conductive organosilane compound was applied onto a transparent substrate made of polyethylene terephthalate (PET), and then dried to form a surface layer containing silicon oxide having an antistatic function, a thickness of 150 nm, and a volume resistivity of 5000 Ωcm, thereby obtaining a substrate. Note that this substrate has a form in which the surface layer is laminated on the substrate, PET.

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

(Preparation of precursor thin film)
First, ink was applied to the surface of the transfer medium, and then the ink-applied surface of the transfer medium was brought into contact with a plate having grooves of a thin metal line pattern, and a part of the ink on the surface of the transfer medium was transferred to the convex surface of the plate. After that, the surface of the transfer medium coated with the remaining ink was brought into contact with a substrate, and the ink in the form of a thin metal line pattern was transferred onto the substrate. Through this process, a precursor thin film was produced. The 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 . The phosphorus species of the precursor were phosphoric acid and phosphate ester. These results are shown in Table 1.

(Plasma reaction process)
The precursor thin film produced in the above-mentioned process was subjected to a plasma reaction. Specifically, plasma was generated by microwaves generated at an output of 1.5 kW in an atmosphere containing 3 vol% hydrogen and 97 vol% helium gas under reduced pressure, and the plasma was reacted with the precursor thin film for 5 minutes.

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

Example 2
The precursor thin film obtained in the same manner as in Example 1 was subjected to a plasma reaction step, and the procedure was the same as in Example 1, except that the plasma reaction treatment time was 3 minutes. The results are shown in Table 1.

<Comparative Example 1>
The precursor thin film obtained in the same manner as in Example 1 was subjected to a plasma reaction process, and the procedure was the same as in Example 1, except that the plasma reaction treatment time was 1 minute. The results are shown in Table 1.

<Comparative Example 2>
The precursor thin film obtained in the same manner as in Example 1 was subjected to a plasma reaction step, and the procedure was the same as in Example 1, except that the plasma reaction treatment time was set to 2 minutes. The results are shown in Table 1.

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

In addition, Examples 1 and 2 showed lower sheet resistance than Comparative Examples 1 and 2. This shows that by satisfying the present embodiment, it is possible to obtain a thin film with low sheet resistance and excellent conductivity.

The conductive thin films of Examples 1 and 2, which satisfy the present embodiment, were obtained by performing plasma treatment for 150 seconds to 60 minutes on a precursor thin film having a phosphorus weight areal density of 6 mg m ^-2 to 1000 mg m ^- 2. It was shown that the conductive thin films of the present embodiment can be preferably obtained by including this step in the manufacturing method.

Regarding the amount of oxygen in the thin film, the average oxygen atomic concentration in the thin film, the oxide layer thickness, and the oxide layer thickness ratio were smaller in Examples 1 and 2 than in Comparative Examples 1 and 2. However, surprisingly, Examples 1 and 2 had better adhesion than Comparative Examples 1 and 2. This is presumably due to the effect of phosphorus being unevenly distributed 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.

10...conductive thin film, 10'...metallic thin wire, 11...hole, 20...substrate, 30...opening, 40...metallic thin wire pattern, 100...conductive sheet

Claims (38)

A conductive thin film containing a transition metal is laminated on a substrate,
the conductive thin film has a concentration gradient of phosphorus atoms in a thickness direction;
the concentration gradient of the phosphorus atoms has a maximum value _Pm of the atomic concentration of the phosphorus atoms in a range closer to the substrate than the halfway point of the film thickness in the conductive thin film;
Conductive thin film. The average value _Pa of the phosphorus atomic concentration in the phosphorus atom concentration gradient is 0.1% or more and 19% or less.
The conductive thin film according to claim 1 . The ratio (P _m /P _a ) of the maximum value P _m to the average value P _a is 2.0 times or more and 200 times or less.
The conductive thin film according to claim 2 . The maximum value _Pm 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, an average value _P of the atomic concentration of the phosphorus atoms in a range of 30 nm from the side closer 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. a thickness of the conductive thin film in a range in which the atomic concentration of oxygen relative to the atomic concentration of the transition metal is 25% or more in a thickness direction of the conductive thin film is 200 nm or less;
The conductive thin film according to any one of claims 1 to 6. a thickness of the conductive thin film in a range in which the atomic concentration of oxygen is 25% or more in a thickness direction of the conductive thin film 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 to 7. an average atomic concentration Ma of the transition metal in a thickness direction of the conductive thin film is 40% or more and 99% or less;
The conductive thin film according to any one of claims 1 to 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 to 9. The transition metal comprises a metal of Group 11 of the IUPAC Periodic Table;
The conductive thin film according to any one of claims 1 to 10. The transition metal comprises copper.
The conductive thin film according to claim 11. a maximum value _PMm of a ratio (P/M) of an atomic concentration P of the phosphorus to an atomic concentration M of the transition metal in a thickness direction of the conductive thin film is 1.9% or more and 100% or less;
The conductive thin film according to any one of claims 1 to 12. a maximum value _POm of a ratio (P/O) of the atomic concentration P of phosphorus to the atomic concentration O of oxygen in a thickness direction of the conductive thin film is 60% or more and 500% or less;
The conductive thin film according to any one of claims 1 to 13. a maximum value PMOm of a ratio (P/(M+O)) of the atomic concentration _P of the phosphorus to the sum of the atomic concentration M of the transition metal and the atomic concentration O of oxygen in a 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 to 14. the conductive thin film includes a particle layer to which particles containing the transition metal are bonded;
The conductive thin film according to any one of claims 1 to 15. the conductive film includes a continuous pattern having openings;
The conductive thin film according to any one of claims 1 to 16. The pattern is a pattern formed by intersecting a plurality of thin lines.
The conductive thin film according to claim 17. The line width of the thin line is 100 nm or more and 1000 μm or less.
The conductive thin film according to claim 18. The pitch of the thin lines is 1.0 μm or more and 1000 μm or less.
20. The conductive thin film according to claim 18 or 19. The visible light transmittance is 70% or more and 99% or less.
The conductive thin film according to any one of claims 1 to 20. The sheet resistance is 0.001 ^Ωcm to 20 ^Ωcm .
The conductive thin film according to any one of claims 1 to 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 substrate is a plastic.
The conductive sheet according to any one of claims 23 to 25. The plastic is polyethylene terephthalate.
The conductive sheet according to claim 26. The conductive thin film according to any one of claims 1 to 22 is provided.
Touch panel. The conductive thin film according to any one of claims 1 to 22 is provided.
display. The conductive thin film according to any one of claims 1 to 22 is provided.
Heater. The conductive thin film according to any one of claims 1 to 22 is provided.
Electromagnetic wave shielding. The conductive thin film according to any one of claims 1 to 22 is provided.
antenna. a film-forming step of forming a precursor thin film on a substrate, the precursor thin film having a phosphorus weight area density of 6.0 mg m ^-2 or more and 1000 mg m ^-2 or less;
and a plasma reaction step of reacting the precursor thin film with plasma for 150 seconds to 60 minutes to obtain a conductive thin film.
A method for producing a conductive thin film. The precursor thin film comprises phosphoric acid and/or a phosphoric acid ester;
The method for producing the 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 to 10 ^g m.
The method for producing a conductive thin film according to claim 33 or 34. The atmosphere of the plasma reaction process contains a gas that is a molecule containing a hydrogen atom.
The method for producing a conductive thin film according to any one of claims 33 to 35. The atmosphere of the plasma reaction step includes a rare gas.
The method for producing a conductive thin film according to any one of claims 33 to 36. In the plasma reaction step, microwave plasma is used.
The method for producing a conductive thin film according to any one of claims 33 to 37.