JP5590766B2 - Method for producing metal film-forming paint - Google Patents

Description

  The present invention relates to a metal film-forming paint and a metal film that can efficiently form a metal film having excellent reflectivity.

Reflective plates having metallic luster are widely used in the optical field such as a reflective metal film for semiconductor articles, a reflective plate for reflective displays, and a reflective plate for reflective liquid crystal displays. In this case, a smooth and highly reflective reflector is, for example, (1) a dry film-forming technique such as vacuum deposition or sputtering, and (2) a method of applying and baking a paste in which metal fine particles are dispersed to form a metal film. , Etc. are manufactured.
In the dry film forming method such as sputtering (1) described above, since it is often performed under a reduced pressure condition, and the apparatus is inevitably increased in size, the initial introduction cost becomes enormous. Further, in the method for forming a film by firing (2), since the substrate may be deformed or cracked by heat during firing, a substrate having high heat resistance must be selected. There was a practical problem that there was a limit to this.

  Recently, by making metal particles finer, it is easy to cause fusion between particles, and attempts have been made to form metal films by forming metal bonds even at low temperatures (patents). Reference 1).

  However, according to the study by the present inventors, it has been found that the metal film cannot be formed efficiently by the method described in Patent Document 1. That is, the particles described in Patent Document 1 have a low concentration of metal particles in the liquid (20% by mass inside and outside according to the description), and therefore it is necessary to apply metal ink several times when forming the metal film. Since it is not always easy to form the same metal film under the same conditions, the surface property may be deteriorated. Therefore, when such a metal ink is used, it is considered that unevenness is likely to occur on the surface of the formed metal film, and a high reflectance is not always obtained. In view of the process, secondary formation of the metal particles once formed is essential, and it is not necessarily an efficient method for forming a metal film.

  Therefore, it is desired to provide a coating material for forming a metal film that can reflect visible light with high reflectivity and can efficiently form a metal film having a high metal density while being a thin film.

JP 2003-327870 A

  The present invention provides a coating for forming a metal film that is suitable for forming a highly productive metal film while having a high reflectivity while being a thin film that is indispensable as described above, and the coating for forming a metal film. An object is to provide a formed metal film.

Means for solving the problems are as follows. That is,
<1> A metal film-forming paint containing at least metal particles and a solvent,
The number average particle diameter (D _TEM ) calculated from a transmission electron microscope image of the metal particles is 15 nm to 80 nm,
The ratio (D ₅₀ / D ₁₀ ) of the particle size (D ₁₀ ) of 10% of the total number of the metal particles to the particle size (D ₅₀ ) of 50% of the total number of the metal particles is 3 or less, The metal film-forming paint has a metal concentration of 50% by mass or more.
<2> The metal film-forming coating material according to <1>, wherein the ratio of metal particles having a number average particle diameter of 10 nm or less is 10% or less.
<3> The ratio <D _TEM / D _x ) between the crystal particle size (D _x ) of the metal particles and the number average particle size (D _TEM ) of the metal particles is 2.0 or less from <1> to <2 > The metal film-forming paint according to any one of the above.
<4> The coating material for forming a metal film according to any one of <1> to <3>, wherein a ratio of particles causing sintering is 10% or less with respect to the entire metal particles.
<5> The metal film according to any one of <1> to <4>, wherein adjacent metal particles are independent from each other, and a distance between the metal particles is less than 50% of a particle size (D ₅₀ ). It is a paint for forming.
<6> The metal film-forming coating material according to any one of <1> to <5>, wherein an organic compound is interposed between adjacent metal particles.
<7> The metal film according to <6>, wherein the organic compound is present as a protective agent for protecting the metal on the surface of the metal particle, and has at least one of a carbon atom and a nitrogen atom in a molecule of the organic compound. It is a paint for forming.
<8> The metal film-forming coating material according to any one of <1> to <7>, wherein the metal particles are silver particles.
<9> A metal film obtained from the metal film-forming paint according to any one of <1> to <8>.

  According to the present invention, various problems in the prior art can be solved, visible light can be reflected with high reflectivity, and a metal film having a high metal density while being a thin film can reduce the amount of metal used, It is possible to provide a metal film-forming paint that can be efficiently formed, and a metal film formed by the metal film-forming paint.

(Metal film forming paint)
The coating material for forming a metal film of the present invention contains at least metal particles and a solvent, and further contains other components as necessary.

  The metal particles are preferably silver for obtaining specular reflection, and the particle diameter is 15 nm to 80 nm, preferably 20 nm to 80 nm, as the number average particle diameter calculated from a transmission electron microscope (TEM) image. More preferably, it is 25 nm-75 nm. When the number average particle diameter exceeds 80 nm, the whiteness of the metal becomes high. On the other hand, when the number average particle size is less than 15 nm, a deep blue or a complementary yellow color appears due to metal plasmon absorption, which is not suitable for applications requiring a single color tone.

The ratio (D ₅₀ / D ₁₀ ) of the particle size (D ₁₀ ) of 10% of the total number of the metal particles to the particle size (D ₅₀ ) of 50% of the total number of the metal particles is 3 or less, 1.5-3 are preferable and 1.5-2.5 are more preferable. Since the ratio (D ₅₀ / D ₁₀ ) indicates that the particle size distribution of the particles is good, it is preferably as small as possible. When the ratio (D ₅₀ / D ₁₀ ) exceeds 3, the particle size distribution has a broad shape, and the reflectance decreases when a metal film is formed.

  The proportion of particles having a number average particle diameter of 10 nm or less in the metal particles is preferably 10% or less, and more preferably 8% or less. When the ratio of the particles having a number average particle diameter of 10 nm or less exceeds 10%, the reflection efficiency of the metal film is reduced, and it is not silver-white, and it is dull and the reflectance may be decreased. Absent.

Here, the number average particle diameter _{(D TEM),} D _10, and _{D 50} can be measured by observing the image for example by a transmission electron microscope (TEM).

The ratio (D _TEM / D _x ) between the crystal particle size (D _X ) of the metal particles and the number average particle size (D _TEM ) of the metal particles is preferably 2.0 or less, preferably 0.5 to 1.8. More preferred.
When the ratio (D _TEM / D _x ) exceeds 2.0, it indicates that particles are formed by several crystals, and thus it indicates that crystal grain boundaries are likely to be generated in the particles. Such particles are not preferable because impurities often tend to be mixed between crystal grains.
Here, the crystal grain size (D _X ) of the metal particles represents the size of the crystal particles, and the value is obtained by measuring the half-value width of the diffraction line on the (111) plane of Ag using the X-ray diffraction method. It can be calculated by using a known method.

<Method for producing metal film-forming paint>
The coating material for forming a metal film of the present invention is obtained by forming metal particles and then dispersing the metal particles in a medium. The method for forming metal particles will be described below.

<Reduction process>
First, metal particles are obtained by reducing a metal dissolved in a solvent by a wet method. As the metal salt used, a metal salt exhibiting solubility in a solvent is used. In the case of silver, silver nitrate, silver carbonate and the like can be exemplified. In the reduction, if the solvent is brought to reflux, the reduction can be carried out more efficiently. Therefore, it is preferable that the boiling point of the solvent used individually is as low as possible. Examples of the solvent include isobutyl alcohol and hexanol.

-Organic compounds-
The organic compound is present between adjacent metal particles and exists as a protective agent having a function of protecting the metal on the surface of the metal particles.
The organic compound serves as a protective agent for preventing the metal particles from becoming coarse during the reaction and preventing the metal particles from binding to each other when forming a coating for forming a metal film. If the role as a protective agent is emphasized, it is better to use a polymer with a large molecular weight, but it may remain inside the film as an impurity during the formation of the metal film, which may reduce the reflectivity of the metal film. It is not preferable. As an organic compound having the property of having both a metal particle protecting effect and a metal particle growth suppressing effect, a compound having at least one of a carbon atom and a nitrogen atom in its molecule is preferable. For example, amines are preferably used. Examples of the amines include organic amines having an unsaturated bond in the structure such as oleylamine and octylamine.

By using the organic compound, adjacent metal particles are independent of each other, and the distance between the metal particles can be less than 50% of the particle diameter (D ₅₀ ). If the distance between the metal particles is too long, the independence of the metal particles is ensured, but a high temperature is required when firing the film, which is not preferable.
Further, when the metal particles are dispersed in the liquid, the sintering between the particles is reduced, and the ratio of the particles that cause the sintering (sintered particles) is 10% or less with respect to the entire metal particles. can do. When the ratio of the sintered particles exceeds 10%, the metal film becomes a mottled film, and the metal film may have a low reflectance.
With the sintered particles, the particles do not exist independently, but two or more particles are joined at a point or a surface, and are larger than the average particle size of each individual particle. Refers to particles. At that time, the shape of the particles does not necessarily match the shape of the original independent particles.
Here, the ratio of the sintered particles was determined by applying the state of particles observed in the field of view taken in the transmission electron microscope (TEM) photograph to the above-described method, and sintering the independent particles. Particles can be obtained by counting the number of each.

-Reduction aid-
As said reduction adjuvant, what has a higher reduction ability than alcohol as a solvent can be used in combination. Since the reducing aid is composed of a substance having a reducing power higher than that of alcohol, it may become very fine particles depending on the amount added. Therefore, it is also possible to adjust by changing the amount of the reducing auxiliary agent as one of the means for adjusting the particle diameter. The reducing aid used is preferably an amine compound having no unsaturated bond and a molecular weight of about 50 to 100. Examples of the amine compound include diethanolamine and triethanolamine.

  The temperature of the reduction reaction is preferably in the range of 50 ° C to 200 ° C, more preferably 75 ° C to 175 ° C. If the reaction temperature is too low, the reducing action of the alcohols is hardly exerted, and the reaction is difficult to proceed, and at the same time, there is a possibility of causing poor reduction. Although the reflux temperature can be adjusted by the reduction temperature, simply increasing the temperature uniformly is not preferable because it may cause a particle group having a poor particle size distribution. In some cases, the reduction can be performed in a so-called multistage process in which the temperature is divided into several stages.

<Solid-liquid separation process>
In the slurry after the reduction reaction, metal particles covered with an organic compound are present. This slurry is subjected to solid-liquid separation, and the metal particles are recovered as a solid content. This solid-liquid separation is effective to be repeated several times in combination with washing. For example, a method of repeating the following procedures (1) to (4) can be adopted.
(1) The slurry after the reduction reaction is subjected to solid-liquid separation by a decantation method or a centrifuge, and the supernatant is discarded.
(2) Methanol is added to the solid content (product) that has been subjected to solid-liquid separation, and ultrasonic dispersion is added to clean and remove impurities adhering to the surface of the product.
(3) The above (1) and (2) are repeated several times to remove surface impurities as much as possible.
(4) Finally, the above (1) is performed again, the supernatant is discarded, and the solid content is collected.

<Dispersing process>
The metal particles obtained by the solid-liquid separation step are redispersed in a dispersion medium to form a metal film-forming paint (metal ink). Specifically, it is obtained through the following steps.

The dispersion medium is not particularly limited and may be appropriately selected depending on the purpose. The dispersion medium is a non-polar or small-polar liquid medium mainly composed of an organic compound, and has a relative dielectric constant of 15 or less at 25 ° C. A certain liquid medium is used, and examples thereof include aliphatic hydrocarbons such as isooctane, n-decane, n-undecane, n-tetradecane, n-dodecane, tridecane, hexane, and heptane; aromatic hydrocarbons such as benzene. It is done. These may be used individually by 1 type and may use 2 or more types together. Among these, tetradecane and n-decane are particularly preferable.
It is also possible to add a dispersion aid such as amines to the dispersion medium as long as the polarity can be kept small as described above.

<Classification process>
In the classification step, the metal film-forming paint (metal ink) obtained through the dispersion step has metal particles with extremely good dispersibility and a metal slightly inferior in dispersibility due to variations in the amount of organic compound attached. Particles are mixed. Therefore, this is a process for producing a dispersion liquid in which only metal particles having extremely good dispersibility are extracted.
Addition of this classification step is advantageous in constructing inks and pastes with good performance.

  As said classification operation, it can select suitably according to the objective, For example, it can carry out using a centrifuge. The centrifugation conditions differ somewhat depending on the scale of the centrifuge and the desired level of dispersibility. For example, the dispersion obtained in the dispersion step is centrifuged at 3,000 rpm for 30 minutes. To separate the supernatant and sediment. Only the highly dispersible metal particles are dispersed in the resulting supernatant. Therefore, a metal particle dispersion with extremely good dispersibility can be obtained by collecting the supernatant.

Further, the metal particle dispersion (supernatant) obtained in the classification step is applied to a vacuum dryer and concentrated until no liquid is confirmed. By dispersing this concentrate in the liquid medium shown above, a dispersion having an appropriately adjusted metal concentration is formed, and a high metal concentration of about 90% by mass can be obtained by the adjustment.
The metal concentration in the metal particle dispersion thus obtained is 50% by mass or more, and by changing the mass of the solvent, the metal concentration relative to the total mass can be further increased to 75% to 90% by mass. Can do. When the metal concentration is less than 50% by mass, the gap between the metal particles is widened at the time of coating, and voids are generated at the time of drying and sintering. It is not preferable because a decrease in reflectance is observed.

The metal concentration in the metal particle dispersion can be calculated from the loss on ignition of the silver particle dispersion. Here, the loss on ignition (%) means a value represented by the following formula.
Loss on ignition (%) = 100 × [(W ₅₀ −W ₃₀₀ ) / W ₅₀ − (W ₅₀ −W ₁₀₀₀ ) / W ₅₀ ]
Here, W ₅₀ , W _300, and W ₁₀₀₀ represent the weight of the dispersion at temperatures of 50 ° C., 300 ° C., and 1000 ° C.
The ignition loss of the metal particle dispersion is less than 10%. That the ignition loss is less than 10% indicates that the organic compound is efficiently burned when the wiring is fired, and impurities in the metal sintered body can be further reduced when the wiring is formed, and It represents that a wiring having good conductivity can be obtained without suppressing sintering. If the ignition loss is 10% or more, the organic compound acts as a sintering inhibitor during firing, and the presence of impurities in the wiring increases the resistance of the wiring. Since it may inhibit, it is not preferable.
The ignition loss can be measured, for example, with a TG-DTA2000 measuring instrument manufactured by Mac Science / Bruker Ax Co. under the following measurement conditions.
・ Sample weight 20 ± 1mg
・ Temperature increase rate 10 ℃ / min
・ Atmosphere: Air (no ventilation)
Standard sample: Alumina 20.0mg
・ Measurement dish: Alumina measurement dish manufactured by Rigaku Corporation ・ Temperature range: 50 ° C to 1000 ° C

(Metal film)
The metal film of the present invention is obtained from the metal film-forming paint of the present invention, and is preferably obtained by applying the metal film-forming paint on a substrate.

There is no restriction | limiting in particular as said base | substrate, According to the objective, it can select suitably, For example, a glass plate, a metal plate, metal films, a plastic plate, a plastic film etc. are mentioned.
There is no restriction | limiting in particular as said application | coating method, According to the objective, it can select suitably, For example, the printing by an inkjet method, roller coating, spin coating, lithography printing, screen printing, offset printing etc. are mentioned.
In the coating, when a metal film is not required on the entire surface of the substrate, that is, when it is desired to partially form a metal film, the metal film may be formed by an ink jet method, or a metal film is formed in a large amount and in a wide range. For this, a method of forming along the purpose and target area, such as a roller coating method, may be appropriately selected. Among these, in order to form fine wiring, an inkjet method, a screen printing method, an offset printing method, and the like are preferable, and an inkjet method is particularly preferable.

The metal film made of the metal particles coated with the organic compound thus formed on the substrate is heated to desorb the organic compound and densify the film. A higher temperature is suitable for reducing the surface resistance value by densification of the metal film, desorbing the organic compound, and shortening the processing time. However, the temperature is appropriately adjusted depending on the properties of the object forming the wiring. It is good. When the substrate is an organic substance (polyethylene film or the like), it is preferable to heat in a region lower than the melting point by 10 ° C. or higher, and more preferable to heat in a region lower than 20 ° C.
A longer heating time is preferable from the viewpoint of forming the metal film, but it is preferable to perform the heating in a short time in order to reduce damage to the substrate as with the heating temperature. In particular, when the metal particles according to the present invention are used, a suitable metal film can be formed in a heating time of 60 minutes at the longest.

-Use-
The metal film of the present invention can reflect visible light with high reflectivity and has a high metal density while being a thin film. For example, a reflective film, a semiconductor device; a plasma display panel (PDP), a liquid crystal display (LCD) It can be widely used for various display devices such as polarizing plates, reflective electrodes, light guide plates, optical disks, reflection films for copying machines, laser light detection mirrors, rear mirrors for projection televisions, and mirrors for reflective liquid crystal displays.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
In the following Examples and Comparative Examples, “number average particle diameter of metal particles (D _TEM ), D ₁₀ , and D ₅₀ ”, “crystal particle diameter of metal particles (Dx)”, and “film thickness of reflective film” are The measurement was performed as follows.

<The number average particle size of the metal particles _{(D TEM),} D _10, and _{D 50>}
The number average particle diameter (D _TEM ), D ₁₀ , and D ₅₀ are observed through a transmission electron microscope (TEM; JEOL Co., Ltd., JEM-100CX Mark-II type), and a 300,000 times photograph is taken. Used and measured on 300 particles.

<Crystal particle size of metal particles (Dx)>
The crystal grain size of the metal particles can be obtained from the X-ray diffraction result by the Scherrer equation. How to find it is as follows.
Scherrer's formula is expressed by the following formula.
Dx = K · λ / βcosθ
In the above formula, K represents a Scherrer constant, Dx represents a crystal particle diameter, λ represents a measured X-ray wavelength, β represents a half width of a peak obtained by X-ray diffraction, and θ represents a Bragg angle of the diffraction line.
If K adopts a value of 0.94 and the X-ray tube uses Cu, the above equation can be rewritten as the following equation.
Dx = 0.94 × 1.5405 / βcos θ
The full width at half maximum β used here was measured using diffraction lines on the (111) plane of Ag.

<Evaluation of reflection density>
The reflection density of the obtained reflective film was measured using a densitometer (ND-11, manufactured by Nippon Denshoku Industries Co., Ltd.). Since the reflection film is derived from Ag, the reflection density measured in the black mode was used. The reflection density was expressed as a relative value (%) with the value of the aluminum plate as 100.

<Reflective film thickness>
Measurement was performed using a laser displacement meter LT9000 manufactured by Keyence Corporation and a dedicated stage KS-1100.

Example 1
When isobutanol (made by Wako Pure Chemical Industries, Ltd., special grade reagent) is used as an organic solvent having a reducing power and oleylamine (made by Wako Pure Chemical Industries, Ltd., special grade reagent) is mixed as an organic compound, a silver nitrate crystal as a silver compound (A special grade reagent manufactured by Kanto Chemical Co., Inc.) was added and stirred with a magnetic stirrer to dissolve silver nitrate crystals.
Specifically, a solution A in which 20.59 g of silver nitrate and 96.24 g of isobutyl alcohol were mixed, 99.27 g of oleylamine and 47.00 g of octylamine were prepared.
After these solutions were transferred to a 300 mL container to which a reflux was connected, Solution A was stirred at 100 rpm while adding nitrogen as an inert gas at a flow rate of 400 mL / min into the container with an oil bath. While increasing the liquid temperature at 50 ° C. at a temperature rising rate of 1 ° C./min, the solution B was added, and the temperature was similarly increased to 105 ° C. at a temperature rising rate of 1 ° C./min. The reaction was allowed to proceed while heating. After completion of the reaction, silver particles were produced through the washing, dispersing, and classification steps. The washing was performed twice using methanol.
The obtained silver particles were adjusted with tetradecane as a solvent so that the metal concentration was 85% by mass to prepare a metal film-forming paint (silver ink).

The number average particle diameter (D _TEM ) of the obtained silver particles was 32 nm, the D ₁₀ value was 20 nm, the D ₅₀ value was 32 nm, and the ratio (D ₅₀ / D ₁₀ ) was 1.60. The ratio of the particles having a number average particle size of 10 nm or less was 8.9%, the crystal particle size (D _X ) was 22 nm, and the ratio (D _TEM / D _X ) was 1.5.
Using the obtained silver ink, a film was uniformly formed on a glass substrate by a spin coat method, and dried at room temperature (25 ° C.) to produce a reflective film having a thickness of 13.8 μm. The reflection density of the obtained reflective film was evaluated as follows. The results are shown in Table 1 and FIG.

(Examples 2 to 10)
In Example 1, except that the number average particle diameter (D _TEM ) of the silver particles was changed as shown in Table 1, reflective films of Examples 2 to 10 were produced in the same manner as Example 1.
The reflection density of each obtained reflective film was measured in the same manner as in Example 1. The results are shown in Table 1 and FIG.

( Reference Example 11)
A reflective film was prepared in the same manner as in Example 1 except that the number of cleanings was 5 in the cleaning process of Example 1.
The reflection density of the obtained reflective film was measured in the same manner as in Example 1. The results are shown in Table 1 and FIG.

(Comparative Example 1)
The reflection density was measured in the same manner as in Example 1 using an aluminum plate as the reflection plate. However, since it is a reference in this specification, in Table 1, the reflection density is expressed as 100%.

(Comparative Example 2)
A glass-plated Ag plating film (thickness 1.1 μm) was prepared, and the reflection density was measured in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Examples 3-5)
In Example 1, except that the number average particle diameter (D _TEM ) of the silver particles was changed as shown in Table 1, the reflective films of Comparative Examples 3 to 5 were prepared in the same manner as in Example 1. .
The reflection density of each obtained reflective film was measured in the same manner as in Example 1. The results are shown in Table 1 and FIG.

(Comparative Example 6)
In Example 2, a reflective film was produced in the same manner as in Example 2 except that the rate of temperature increase during reduction during particle formation was 2.5 ° C./min.
The reflection density of the obtained reflective film was measured in the same manner as in Example 1. The results are shown in Table 1 and FIG.

(Comparative Example 7)
A reflective film was produced in the same manner as in Example 1 except that the dilution rate in the ink production process of Example 1 was increased and the metal concentration was changed to 35.8% by mass.
The reflection density of the obtained reflective film was measured in the same manner as in Example 1. The results are shown in Table 1 and FIG.

表１及び図１の結果から、実施例１〜１０、参考例１１は、アルミニウム板（比較例１）及びＡｇめっき（比較例２）と比べて、金属粒子を用いているので、反射濃度の向上が見られた。また、数平均粒径（Ｄ_ＴＥＭ）が１５ｎｍ〜８０ｎｍの金属粒子が特に優れた反射率を示すことが分かった。

From the results of Table 1 and FIG. 1, Examples 1 to 10 and Reference Example 11 use metal particles as compared with the aluminum plate (Comparative Example 1) and Ag plating (Comparative Example 2). An improvement was seen. The number average particle diameter _{(D TEM)} was found to exhibit a particularly excellent reflective metal particles are 15Nm～80nm.

  The metal film obtained by the coating composition for forming a metal film of the present invention can reflect visible light with high reflectivity and has a high metal density while being a thin film. For example, a reflective film, a semiconductor device; a plasma display panel ( Various display devices such as PDP) and liquid crystal displays (LCDs); polarizing plates, reflective electrodes, light guide plates, optical disks, reflection films for copying machines, laser light detection mirrors, rear mirrors for projection televisions, mirrors for reflective liquid crystal displays It can be used widely.

FIG. 1 is a graph showing the relationship between the number average particle diameter of metal particles and the reflection density in Examples and Comparative Examples.

Claims (9)

The metal salt is reduced in a solution containing a metal salt, an organic solvent having a reducing power, and organic amines to form metal particles, washed, and then the obtained metal particles are dispersed with a dispersion medium and classified. A method for producing a coating for forming a metal film, comprising:
The metal concentration in the coating for forming a metal film is 50% by mass or more,
The ratio of particles that cause sintering state, and are 10% or less with respect to the entire metal particles,
The metal particles are silver particles;
The number average particle diameter (D _TEM ) calculated from the transmission electron microscope image of the metal particles is 15 nm to 80 nm, the particle diameter (D ₁₀ ) is 10% of the total number of the metal particles, and the total number of the metal particles A method for producing a coating for forming a metal film , wherein the ratio (D ₅₀ / D ₁₀ ) to the 50% particle size (D ₅₀ ) is 3 or less . The method for producing a coating for forming a metal film according to claim 1, wherein the organic solvent having a reducing power is either isobutyl alcohol or hexanol.   The method for producing a coating for forming a metal film according to claim 1, wherein the organic amine is at least one selected from oleylamine and octylamine.   The method for producing a coating material for forming a metal film according to any one of claims 1 to 3, wherein the dispersion medium is either n-tetradecane or n-decane.   The method for producing a coating for forming a metal film according to any one of claims 1 to 4, wherein the temperature of the reduction reaction is 75 ° C to 175 ° C. The method for producing a coating for forming a metal film according to any one of claims 1 to 5, wherein the proportion of metal particles having a particle size of 10 nm or less is 10% or less. Crystal grain size of metal particles (D _x ) And the number average particle size (D _TEM ) (D) _TEM / D _x ) Is 2.0 or less, The manufacturing method of the coating material for metal film formation in any one of Claim 1 to 6. Adjacent metal particles are independent from each other, and the distance between the metal particles is 50% (D ₅₀ The method for producing a coating material for forming a metal film according to any one of claims 1 to 7. The method for producing a coating for forming a metal film according to any one of claims 1 to 8, wherein an organic amine is interposed between adjacent metal particles.

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