KR101502995B1 - Method for formation of metal coating film, and electrically conductive particle - Google Patents

Abstract

The metal film forming method is a method of forming a metal film by electroless plating on non-conductive particles having a diameter of 0.5 μm to 100 μm. The electroless plating is performed after the pretreatment of attaching the metal nuclei to the non-conductive particles, and at the same time, the metal coating derived from silver is formed in the presence of the silane compound having a thiol group. The conductive particles are imparted with conductivity by the metal coating formed on the entire surface of the non-conductive particles. The diameter of the non-conductive particle ranges from 0.5 μm to 100 μm. Further, the metal coating is composed of a single layer of silver.

Description

METHOD FOR FORMING METAL COATING FILM, AND ELECTRICALLY CONDUCTIVE PARTICLE

The present invention relates to conductive particles usable in conductive materials, electromagnetic shielding materials, and the like, and a method of forming metal coatings on non-conductive particles.

Electroless plating is known as a technique for forming a metal film on non-conductive particles. In order to promote the reaction of the electroless plating, a pretreatment for attaching a catalyst that initiates electroless plating is performed on the surface of the non-conductive particles. In the known treatment method, for example, the non-conductive particles are brought into contact with an aqueous solution of palladium chloride after being brought into contact with an aqueous solution of tin chloride. Through this, the palladium colloid is adsorbed on the surface of the non-conductive particle by the action of reducing tin ions adsorbed on the surface of the non-conductive particle. The palladium colloid acts as a catalyst for initiating electroless plating. The electroless plating bath contains a metal salt, a metal complexing agent, a pH adjuster, a reducing agent, and the like. However, with respect to the electroless plating to be carried out by pretreatment as described above, there is a problem that the thickness of the metal coating is extremely uneven and a continuous film can not be formed.

For example, Patent Document 1 proposes a metal plating powder having a homogeneous and hard coating ability. The metal plating powder specified in this document can be obtained by a catalytic process of carrying noble metal ions on the surface of the substrate and then by electroless plating which is subjected to electroless plating on the substrate. In the catalytic process, noble metal ions are captured on an organic or inorganic substrate, and then the noble metal ions are reduced to carry the noble metal on the substrate. In the electroless plating treatment, the electroless plating solution is composed of at least two liquids, and the electroless plating is carried out by adding them individually or simultaneously.

In addition, Patent Document 2 or Patent Document 3 discloses displacement plating as a technique for forming a noble metal coating on non-conductive particles. As substitution plating, a method of forming a base layer by electroless nickel plating and replacing nickel with a noble metal is generally used. For electroless nickel plating, sodium hypophosphite monohydrate, citric acid and the like are usually added in order to adjust the pH of the plating solution appropriately. On the other hand, in order to control the crystal structure of the noble metal coating on the substitution plating, cobalt is added to the plating solution so that the concentration of cobalt is several hundred ppm. The metal film produced by substitution plating contains nickel having a higher electrical resistance value than silver and gold, impurity phosphorus, cobalt, and the like.

Gold and silver are known as noble metals with high conductivity. In addition to having a higher conductivity than silver, gold is also inexpensive. For this reason, the non-conductive particles and the conductive particles having the metal coating derived from silver on the surface thereof have a high utilization value. When a metal film derived from silver is formed by displacement plating, a metal film containing at least two layers of a nickel layer as a base layer and a silver layer is formed. As described above, the metal coating derived from a plurality of layers is costly disadvantageous. It is also conceivable to form a metal coating derived from silver by performing a pretreatment with non-conductive particles using, for example, a coupling agent followed by electroless plating. However, even if the non-conductive particles of the micron level are pretreated, the metal coating derived from silver can not be formed on the non-conductive particles, or only the discrete metal coating is formed. As described above, with respect to the non-conductive particles of micron size, the technique of forming a metal coating derived from silver as a single layer has not yet been practically achieved.

<Patent Document 1> Japanese Patent Publication No. 6-96771

Patent Document 2: JP-A-2007-242307

[Patent Document 3] JP-A-2004-14409

It is an object of the present invention to provide a method of forming a metal film which is easy to form a metal film derived from silver in a single layer. Another object of the present invention is to provide a conductive particle which is excellent in conductivity and low in cost.

According to a first aspect of the present invention, there is provided a method of forming a metal film by electroless plating of a metal film on non-conductive particles having a diameter of 0.5 to 50 μm. The electroless plating is performed after the pretreatment of attaching the metal nuclei to the non-conductive particles, and at the same time, the metal coating derived from silver is formed in the presence of the silane compound having a thiol group.

In the metal film forming method, it is preferable to initiate electroless plating after bringing the mixed liquid of the silane compound having a thiol group and water into contact with the non-conductive particles.

With respect to the metal film forming method, it is preferable that the silane compound having a thiol group is 3-mercaptopropyltriethoxysilane.

It is preferable that electroless plating be performed by a silver halide reaction with respect to the above metal film forming method.

In the above-mentioned metal film forming method, the pretreatment is a treatment in which a treatment liquid containing a silane coupling agent, a hydrolysis catalyst and a metal salt is brought into contact with a non-conductive particle and a metal is precipitated by a reducing agent, , And the silane coupling agent preferably has a functional group that forms a chelate with respect to the metal salt.

With respect to the metal film forming method, it is preferable that the metal of the metal nucleus is gold or silver.

According to a second embodiment of the present invention, there is provided a conductive particle imparted with conductivity by a metal coating formed on the entire surface of a non-conductive particle. The diameter of the non-conductive particle ranges from 0.5 μm to 50 μm. Further, the metal coating is composed of a single layer of silver.

As to the above conductive particles, it is preferable that only gold, silver and sulfur are detected as elements other than the elements contained in the non-conductive particles in the fluorescent X-ray analysis of the conductive particles.

The above conductive particles are preferably used as a sealing agent for a liquid crystal display element.

The conductive particles are preferably used as an anisotropic conductive material.

According to the present invention, there is an effect that a metallic coating derived from silver can be formed continuously as a single layer with respect to micron-sized non-conductive particles.

1 is a scanning electron micrograph of silica particles using Example 1,
2 is a scanning electron micrograph of non-conductive particles pretreated with respect to Example 1,
3 is a scanning electron microscope (SEM) image of the conductive particles of Example 1,
4 is an optical microscope photograph showing the dispersion state of the conductive particles of Example 1 in the resin,
5 is a fluorescent X-ray analysis chart showing the detection of silver for the conductive particles of Example 1,
6 is a fluorescent X-ray analysis chart showing the detection of gold for the conductive particles of Example 1,
7 is a fluorescent X-ray analysis chart showing the detection of sulfur against the conductive particles of Example 1,
8 is a scanning electron micrograph showing the state before wet heat test for the silver-coated silica particles of Example 2,
9 is a scanning electron micrograph showing the state after the wet heat test on the silver niter silica particles of Example 2,
10 is a scanning electron microscope photograph of the conductive particles of Example 3,
11 is a scanning electron micrograph of the conductive particles of Example 4,
12 is a scanning electron microscope photograph of the conductive particles of Comparative Example 1,
13 is a scanning electron micrograph of the conductive particles of Comparative Example 2,
14 is a scanning electron micrograph showing the state before the wet heat test for the conductive particles of Comparative Example 3,
15 is a scanning electron microscope photograph showing the state after the wet heat test for the conductive particles of Comparative Example 3,
16 is a scanning electron microscope photograph showing the state before the heat and humidity test for the conductive particles of Comparative Example 4,
17 is a scanning electron microscope photograph showing the state after the wet heat test for the conductive particles of Comparative Example 4,
18 is a scanning electron micrograph of the conductive particles of Comparative Example 5,
19 is a scanning electron micrograph of the conductive particles of Comparative Example 6,
20 is a scanning electron microscope photograph of the conductive particles of Comparative Example 7,
21 is a scanning electron micrograph of the conductive particles of Comparative Example 8,
22 is an optical microscope photograph showing the dispersion state of the conductive particles of Comparative Example 8 in the resin.

Hereinafter, embodiments of the present invention will be described in detail.

&Lt; Method of Forming Metal Film &

The metal film forming method of the present embodiment is a method of forming a metal film on non-conductive particles having a diameter of 0.5 to 50 μm by electroless plating. The electroless plating is performed after the pretreatment of attaching the metal nuclei to the non-conductive particles, and at the same time, the metal coating derived from silver is formed in the presence of the silane compound having a thiol group.

The non-conductive particles are constituted as a base on which a metal coating is formed. Examples of the material of the non-conductive particles include at least one selected from the group consisting of silica, ceramic, glass, and resin. Examples of the silica include, for example, fully crystallized dry silica (cristobalite) and water-dispersed silica (colloidal silica). Examples of the ceramics include alumina, sapphire, mullite, titanium dioxide, silicon carbide, silicon nitride, aluminum nitride and zirconium oxide. Examples of the glass include various kinds of short glass such as BK7, SF11 and LaSFN9, optical crown glass, soda glass, and low expansion borosilicate glass. Examples of the resin stream include a silicone resin, a phenol resin, a natural modified phenol resin, an epoxy resin, a polyvinyl alcohol resin, a cellulose resin, and the like, and a modified material such as a polyolefin resin, a styrene resin, Or a surface treatment by a corona discharge lamp. As non-conductive particles, for example, at least one kind selected from silica, ceramics and glass is preferable from the viewpoint of a small difference in diameter, and silica is more preferable. Examples of the shape of the non-conductive particle include a spherical shape, a rod shape, a plate shape, a needle shape, and a hollow shape. Considering the dispersibility of the non-conductive particles or the dispersibility of the conductive particles that can be obtained, the shape of the non-conductive particles is preferably spherical.

The diameter of the non-conductive particle ranges from 0.5 μm to 100 μm. The diameter of the non-conductive particles is measured using a scanning electron microscope photograph. The average diameter of the non-conductive particles provided by the method for forming a metal film is preferably 1 μm to 50 μm, more preferably 1 μm to 20 μm.

Particularly, when used for a member for a liquid crystal display element, etc., it is necessary to make the diameter of non-conductive particles uniform in advance. In this case, the diameter distribution of the non-conductive particles preferably has a CV value of 10% or less, more preferably 5% or less, in the following expression.

CV value (%) = {standard deviation of particle diameter (μm)] / [average diameter (μm)]} × 100

Electroless plating is carried out after pretreatment to attach metal nuclei to non-conductive particles. As the metal of the metal nucleus to be adhered by the pretreatment, gold or silver is preferable from the viewpoint that the conductivity of silver which is a metal coating hardly adversely affects and the metal coating is stably formed. As a pretreatment, for example, a treatment liquid containing a silane coupling agent, a hydrolysis catalyst and a metal salt is brought into contact with non-conductive particles, and then metal of the metal salt is precipitated by a reducing agent, . Thus, the formation of the metal film by the electroless plating can be uniformly advanced. At this time, as the silane coupling agent, a silane coupling agent having a functional group capable of forming a chelate with respect to the metal salt is used.

Examples of the functional group which forms a chelate with respect to the metal salt include a polar group and a hydrophilic group. Specifically, it is preferably a functional group having at least one or more kinds of atoms selected from a nitrogen atom, a sulfur atom and an oxygen atom. Examples of such functional groups include at least one functional group selected from the group consisting of -SH, -CN, -NH ₂ , -SO ₂ OH, -SOOH, -OPO (OH) ₂ , and -COOH. These functional groups may form salts. When the functional group is an acidic group such as -OH, -SH, -SO ₂ OH, -SOOH, -OPO (OH) ₂ or -COOH, examples of the salt include alkali metal salts such as sodium, potassium and lithium, have. Meanwhile, -NH ₂ , Salts thereof include inorganic acid salts such as hydrochloric acid, sulfuric acid and acetic acid, and organic acid salts such as formic acid, acetic acid, propionic acid and trifluoroacetic acid.

The silane coupling agent is a compound having a hydrolyzable functional group that generates a silanol group by hydrolysis. (-OR) group directly bonded to the Si atom as the hydrolyzable functional group, and the like. As the R constituting the alkoxy group, one of linear, branched and cyclic alkyl groups having 1 to 6 carbon atoms is preferable, Include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert- There are.

Specific examples of the silane coupling agent include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- ) -3-aminopropyltriethoxysilane, and the like. As the silane coupling agent, 3-aminopropyltrimethoxysilane is particularly preferable from the viewpoint of cost and ease of handling.

The hydrolysis catalyst promotes the hydrolysis of the above-mentioned hydrolyzable functional groups. Examples of the hydrolysis catalyst include organic acids such as acetic anhydride, glacial acetic acid, propionic acid, citric acid, formic acid and oxalic acid, aluminum chelate compounds such as aluminum alkyl acetate, and inorganic alkaline compounds such as ammonia water. Among them, ammonia water is preferable considering the reactivity with 3-aminopropyltrimethoxysilane, which is a preferable silane coupling agent, and the cost.

The amount of the hydrolysis catalyst to be used is preferably 0.5 to 5.0 moles, more preferably 1.5 to 2.5 moles per mole of the silane coupling agent. The amount of the metal salt to be used per mole of the silane coupling agent is preferably 0.005 to 0.05 mole, more preferably 0.015 to 0.025 mole. Furthermore, the amount of the reducing agent to be used is preferably 0.025 to 0.25 mol, more preferably 0.075 to 0.125 mol, per mol of the metal salt.

Water or an aqueous solvent may be used as the pretreatment treatment liquid. The aqueous solvent is a mixed solvent of water and an organic solvent. Examples of the organic solvent include lower alcohols such as methanol, ethanol, propanol and butanol, and ketones such as acetone. These organic solvents may be used alone or in combination of plural kinds.

In the presence of the silane compound having a thiol group, the electroless plating solution forms a metal film derived from silver. The silane compound having a thiol group is shown in the following general formula (1).

X _m (Y) _{3 m} Si (CH ₂ ) _n SH (1)

(Wherein X is an alkyl group having 1 to 6 carbon atoms, Y is an alkoxy group having 1 to 6 carbon atoms, m is 0 or 1, and n is an integer of 1 to 5)

The alkyl group represented by X is an alkyl group of one of linear, branched and cyclic, and examples thereof include a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, -Butyl group, pentyl group, hexyl group, cyclopentyl group, cyclohexyl group and the like. The alkoxy group represented by Y is represented by -OR, and the R constituting the alkoxy group is an alkyl group of one of linear, branched and cyclic, and examples thereof include a methyl group, ethyl group, n-propyl group, An isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, a cyclopentyl group and a cyclohexyl group. From the viewpoint that the metal coating is stably formed as the mercapto compound represented by the general formula (1), 3-mercaptopropyltriethoxysilane is preferable.

In addition to having a higher conductivity than silver, the price is also cheaper. For this reason, the non-conductive particles and conductive particles having a metal coating derived therefrom on the surface thereof have a high utilization value. A known electroless plating method using a metal salt, a reducing agent, or the like can be applied as electroless plating. As the reducing agent, there may be mentioned, for example, a hydrogenated boronate such as sodium tetrahydroborate (alkali metal hydrogenboride salts such as sodium borohydride, ammonium hydrogenborate salts and the like), hydrazine compounds, inorganic reducing agents such as hypochlorite, Organic reducing agents such as aldehyde, citric acid and sodium citrate are used. These reducing agents may be used alone or in combination of two or more. From the viewpoint that the stability of the reaction is excellent as electroless plating, and impurities can be reduced as much as possible, it is preferable to use the silver halide reaction. The silver halide reaction is a reaction in which silver is precipitated by reducing an anthine complex of silver with a reducing agent. Specifically, silver is precipitated on the surface of the non-conductive particles by adding a reducing agent such as formalin to the aqueous ammonia solution of silver nitrate.

It is preferable to initiate electroless plating after bringing the mixed solution of the silane compound having a thiol group and water into contact with the non-conductive particles. As a result, the silane compound stably works. In consideration of the solubility of the silane compound, an organic solvent compatible with water may be mixed in water. The temperature condition, the reaction time, and the like of the electroless plating using such a mixed solution are set according to a conventional method of electroless plating.

The amount of the metal salt to be used with respect to 1 mole of the silane compound having a thiol group is preferably 0.005 to 0.05 mole, more preferably 0.015 to 0.025 mole. In addition, the amount of the reducing agent to be used is preferably 0.025 to 0.25 mol, more preferably 0.075 to 0.125 mol, per mol of the metal salt.

The metal film obtained by the metal film forming method of the present invention has a lower density than the metal film formed by the bulk material of the metal or the conventional electroless plating method. In detail, although the density ratio of the metal coating of the present invention to the bulk material of the metal (the density of the metal coating of the present invention / the density of the bulk material of the metal (10.5 g / cm ³ ) x 100) is somewhat different, % To 85%, more specifically 50% to 70%. For this reason, for example, when a base material including a metal coating is disposed between opposing electrodes, and the base material is compressed by approaching the positive electrode, the metal film is easily deformed because the density is low. As a result, the ground contact area between the electrode and the metal coating is increased, and the reliability regarding the conductivity between both electrodes through the metal coating is improved.

<Conductive Particle>

A metal film is formed on the entire surface of the non-conductive particle. Conductive particles are imparted with conductivity by the metal coating. The diameter of the non-conductive particle ranges from 0.5 μm to 50 μm. The metal coating is derived from a single layer of silver.

The metal coating is derived from an aggregate of continuous silver microparticles. That is, the metal film is a continuous film made of densely arranged silver fine particles. The aggregate of the continuous fine silver particles refers to an aggregate which is densely arranged so that the metal film to be discontinuous can not be confirmed when the metal film is observed at a magnification of 5,000 to 10,000 times by a scanning microscope. The thickness of the metal film is preferably 50 nm or more from the viewpoint of obtaining stable conductivity.

In the metal film of the present embodiment, it is preferable that only gold, silver and sulfur are detected as elements other than the elements contained in the non-conductive particles in the fluorescent X-ray analysis. As a result, the purity of the metal coating can be increased and stable electric characteristics can be obtained. From the viewpoint that the average diameter of the conductive particles is suitable as a member for a liquid crystal display element or an anisotropic conductive material, it is preferably 0.5 m to 100 m, and more preferably 1 m to 20 m. The conductive particles obtained by this method can be suitably used for various anisotropically conductive materials in addition to, for example, sealing agents for liquid crystal display elements.

As described above, according to the present embodiment described above, the following effects can be obtained.

(1) The electroless plating as the metal film forming method is carried out after the pretreatment for attaching the metal nuclei to the non-conductive particles, and at the same time, the metal coating derived from silver is formed in the presence of the silane compound having a thiol group. Therefore, even when a metal film is formed on a micron-sized non-conductive particle, a single layer of silver can be easily formed.

(2) electroless plating is initiated after a mixture of the silane compound having a thiol group and water is brought into contact with the non-conductive particles. As a result, the action of the silane compound can be further enhanced, so that the metal film can be stably formed.

(3) For example, by using 3-mercaptopropyltriethoxysilane as a silane compound having a thiol group or electroless plating by a silver halide reaction, the uniformity of the surface of the metal coating can be increased.

(4) Pretreatment of the electroless plating involves contacting a non-conductive particle with a treatment liquid containing a silane coupling agent, a hydrolysis catalyst and a metal salt, and then depositing a metal of the metal salt with a reducing agent, It is preferable that the treatment is treatment for attaching nuclei. As a result, the metal nuclei can be more uniformly attached to the non-conductive particles, and the uniformity of the surface of the metal coating can be further increased.

(5) Metal of metal nucleus is gold or silver. Thus, it is possible to make it difficult to adversely affect the conductivity of the silver that forms the metal film, so that the metal film can be stably formed.

(6) The metal coating constituting the conductive particles is derived from a single layer of silver. For this reason, it is possible to provide conductive particles excellent in conductivity and low in cost. Such conductive particles can be suitably used for sealing an anisotropic conductive material, for example, of a liquid crystal display element, due to stable conductivity and excellent electrical properties.

(7) For the fluorescent X-ray analysis of the conductive particles, it is preferable that only gold, silver and sulfur are detected as elements other than the elements contained in the non-conductive particles. In this case, the electrical characteristics of the conductive particles are clearly exhibited.

(8) Substitution plating, which is one of techniques for forming a noble metal coating on non-conductive particles, is a method in which electroless nickel plating is formed as a base layer and nickel is replaced with a noble metal. However, under high-temperature and high-humidity conditions, the corrosion resistance of nickel is unstable. In addition, silica, ceramics, and glass are more stable than heat in terms of heat and humidity. Therefore, by using silica, ceramics and glass as the non-conductive particles constituting the conductive particles of the present invention, stability against heat and humidity is improved, so that it is possible to provide conductive particles suitable for applications requiring heat stability have.

Incidentally, the above embodiment may be modified as follows.

In the present embodiment, the metal film derived from silver is composed of a single layer, but it may be composed of a plurality of layers. Further, the metal film derived from silver may be formed by one electroless plating or may be formed by electroless plating several times.

Hereinafter, the above embodiments will be described in more detail with reference to examples and comparative examples.

(Example 1)

(A) Pretreatment

63 g of isopropyl alcohol (IPA) was added to a 500 mL Erlenmeyer flask, and 10 g of silica particles (average diameter: 6.40 μm, CV value: 0.96%, measured by scanning electron microscope) And ultrasonicated. Then, 63 g of methanol was added and stirred for 10 minutes by a magnetic stirrer. Further, 50 g of a 25% aqueous ammonia solution was added and stirred for 10 minutes in an oil bath at 30 DEG C to prepare Solution A.

50 ml of methanol was added to 0.23 g of chloroauric acid (HAuCl ₄ .4H ₂ O), and the mixture was stirred with a magnetic stirrer for 10 minutes. Then, 3.5 mL of 3-aminopropyltrimethoxysilane was added and stirred for 10 minutes. Lt; / RTI &gt;

50 mL of methanol was added to 0.107 g of sodium tetrahydroborate (NaBH ₄ ), and the mixture was stirred for 10 minutes on a magnetic stirrer to prepare Solution C.

The liquid A was added to the liquid A, and the mixture was stirred at 30 ° C for 5 minutes. Then, the liquid C was slowly added dropwise, and the reaction system changed to red. C solution was added dropwise, and the oil bath was heated to 65 캜 and stirred for 3 hours. Stirring was stopped and methanol classification was performed three times. Thereafter, silica particles having metal nuclei formed by suction filtration were collected and dried in an oven at 70 DEG C for 3 hours. The obtained particles showed red color.

1 shows a scanning electron microscope photograph of silica particles. 2 is a scanning electron micrograph of silica particles having metal nuclei formed thereon. Referring to FIG. 2, it can be seen that gold fine particles are uniformly adhered to the entire surface of the silica particles. The average diameter of 70 particles was measured by a scanning electron microscope photograph and a CV value indicating the degree of enlargement of the diameter distribution was obtained. The results are shown in Table 1.

Average diameter (占 퐉) CV value (%) 6.42 0.97

(B) Formation of metal film

To 1 g of the particles obtained in the "(A) pretreatment", 200 mL of water was added, and the mixture was ultrasonicated for 10 minutes. Then, 0.015 mL of 3-mercaptotriethoxysilane was added and stirred for 5 minutes by a magnetic stirrer. Thereafter, 0.65 g of silver nitrate was added, and the mixture was further stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

3 is a scanning electron microscope photograph of the conductive particles having the metal coating formed thereon. Referring to FIG. 3, it can be seen that a metal coating is formed on the entire surface of the silica particles.

The average diameter of 70 particles was measured by scanning electron microscope photograph to obtain CV value. The results are shown in Table 2.

Average diameter (占 퐉) CV value (%) 6.64 1.45

The thickness of the metal coating was 0.11 μm.

&Lt; Evaluation of dispersibility in resin &gt;

10 g of Resin (trade name: STRUCT BOND) was stirred for 1 minute in a kneader. To this resin was added 0.2 g of the conductive particles of Example 1 and the mixture was stirred for 1 minute. The resin containing the conductive particles was pressed onto the slide glass, and the cover glass was covered and observed with an optical microscope. An optical microscope photograph is shown in Fig.

According to observation under an optical microscope, the number of adsorbed particles of two or more in 302 particles was four (1.32%), and the dispersibility in the resin was very good.

<Fluorescence X-ray analysis>

The electroconductive particles obtained in Example 1 were subjected to qualitative analysis using a fully automatic fluorescent X-ray analyzer (manufactured by Parent Company, PW2400 type, elongated bulb: Rh, measured element: Na to U, irradiation area: 25 mm) Respectively. First, about 2 g of the conductive particles were sampled and uniformly introduced onto a 6 탆 polypropylene film. Next, the film was placed in a fully automatic fluorescent X-ray analyzer, and the measuring portion was replaced with helium. The element was identified by scanning a wavelength range in which fluorescent X-rays of the elements of Na to U could be detected. As a result, only the three elements of sulfur, silver and gold were detected. Elements other than the above three kinds of elements were not detected. Fluorescence X-ray analysis charts are shown in Figs. 5 to 7. Fig. 5 is a fluorescence X-ray analysis chart showing the detection of silver, FIG. 6 is a fluorescence X-ray analysis chart showing detection of gold, and FIG. 7 is a fluorescence X-ray analysis chart showing detection of sulfur.

&Lt; Measurement of electric resistance value &gt;

The electric resistance value of 20 conductive particles of Example 1 was measured using a micro compression tester (manufactured by Shimadzu Corporation), and an average value was obtained. The results obtained are shown in Table 3 together with the standard deviation.

Average electrical resistance (Ω) Standard Deviation 3.9 2.2

(Example 2)

Layer-coated silica particles were prepared in the same manner as in Example 1 except that silica particles (average diameter: 4.22 占 퐉, CV: 1.13%) were used.

<Wet heat resistance evaluation>

The obtained conductive particles were subjected to a wet heat test under the conditions of 60 占 폚, 90% RH and 240 hours using a constant-humidity constant-temperature heater (Especific). Fig. 8 shows scanning electron microscopic photographs of the conductive particles before the wet heat test, and Fig. 9 shows photographs of the scanning electron microscope of the conductive particles after the wet heat test. As a result of comparison between Fig. 8 and Fig. 9, no change in the state of the silver layer was observed before and after the wet heat test.

The electric resistance value of 50 conductive particles was measured before and after the humid heat test, and the average value of the number of the conductive particles and the electric resistance value of the electric resistance value were obtained. The results obtained are shown in Table 4.

Average electrical resistance (Ω) Number of electrical resistances observed (/ 50) Before wet heat test 3.3 46/50 After moist heat test 5.2 42/50

From the results shown in Table 4, there were only four differences in the number of particles in which the electric resistance value was not observed before and after the wet heat test.

(Example 3)

Example 1 200 g of water was added to 1 g of the particles obtained from "(A) Pretreatment" and ultrasonicated for 10 minutes. Then, 0.015 ml of 3-mercaptopropylmethyldimethoxysilane was added and stirred for 5 minutes by a magnetic stirrer. Then, 0.65 g of silver nitrate was added, and the mixture was further stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

Fig. 10 shows a scanning electron microscope photograph of the conductive particles having the metal coating formed thereon. Referring to FIG. 10, a metal film was formed on almost the entire surface of the silica particles.

(Example 4)

Example 1 After adding 200 mL of water to 1 g of the particles obtained in "(A) Pretreatment" and sonicating for 10 minutes, 0.015 mL of 3-mercaptopropyltrimethoxysilane was added and stirred for 5 minutes on a magnetic stirrer. Thereafter, 0.65 g of silver nitrate was added, and the mixture was further stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

11 is a scanning electron microscopic photograph of the conductive particle having the metal coating formed thereon. Referring to FIG. 11, a metal coating was formed on almost the entire surface of the silica particles.

(Comparative Example 1)

Example 1 After adding 200 mL of water to 1 g of the particles obtained in "(A) Pretreatment" and sonicating for 10 minutes, 0.65 g of silver nitrate was added and stirred for 10 minutes on a magnetic stirrer. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

Fig. 12 shows a scanning electron microscope photograph of the conductive particles having the metal coating formed thereon. Referring to FIG. 12, in the conductive particles of Comparative Example 1, no metal film was formed on a part of the surface of the non-conductive particles.

(Comparative Example 2)

(A) Surface treatment

In a 500 mL Erlenmeyer flask, 10 g of silica particles (average diameter of 6.40 μm, measured by MULTISIZER II manufactured by COULTER) as non-conductive particles were added, and 63 g of isopropyl alcohol (IPA) was added and sonicated for 10 minutes. Then, 63 g of methanol was added and stirred for 10 minutes by a magnetic stirrer. Further, 50 g of a 25% aqueous ammonia solution was added and stirred for 10 minutes in an oil bath at 30 DEG C to prepare Solution A.

4.5 mL of 3-mercaptopropyltriethoxysilane was added to the solution A, and the oil bath was heated to 65 DEG C and stirred for 3 hours. Stirring was stopped and methanol classification was performed three times. Then, the silica particles surface-treated with thiol were collected by suction filtration and dried in an oven at 70 ° C for 3 hours.

(B) Formation of metal film

To 1 g of the particles obtained from the surface treatment (A), 200 mL of water was added and the mixture was sonicated for 10 minutes. Then, 0.65 g of silver nitrate was added and stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

13 shows a scanning electron microscope photograph of the obtained silica particles. Referring to FIG. 13, the silica particles were not coated with silver.

(Comparative Example 3)

The base layer was formed on the resin particles by electroless nickel plating and the conductive particles (average diameter: 3.55 μm, CV value: 4.50%) obtained by the replacement gold plating for substituting nickel for gold were subjected to the same conditions Moisture heat evaluation. FIG. 14 shows a scanning electron microscope photograph before the wet heat test, and FIG. 15 shows a scanning electron microscopic photograph after the wet heat test. Referring to Figs. 14 and 15, the state of the metal layer after the wet heat test is largely changed compared to that before the wet heat test. This is thought to be due to the oxidation of nickel and corrosion.

The electric resistance value of 50 conductive particles was measured before and after the humid heat test, and the average value of the number of the conductive particles and the electric resistance value of the electric resistance value were obtained. The results obtained are shown in Table 5.

Average electrical resistance (Ω) Number of electrical resistances observed (/ 50) Before wet heat test 7.5 44/50 After moist heat test 10.4 5/50

From the results in Table 5, the difference in the number of particles was 39 before and after the wet heat test, and the rate of occurrence after the test was only 10% (5/50).

(Comparative Example 4)

The base layer was formed on the silica particles (average diameter: 6.42 μm, CV value: 0.70%) by electroless nickel plating and the conductive particles (average diameter: 6.75 μm, CV Value: 0.77%) was subjected to moisture resistance evaluation under the same conditions as above. FIG. 16 shows a scanning electron microscope photograph before the heat and humidity test, and FIG. 17 shows a scanning electron microscope photograph after the heat and humidity test. Referring to Figs. 16 and 17, the state of the metal layer after the wet heat test greatly changes and becomes rough. This is thought to be due to the oxidation of nickel and corrosion.

The electric resistance value of 50 conductive particles was measured before and after the humid heat test, and the average value of the number of the conductive particles and the electric resistance value of the electric resistance value were obtained. The results obtained are shown in Table 6.

Average electrical resistance (Ω) Number of electrical resistances observed (/ 50) Before wet heat test 7.5 46/50 After moist heat test 10.4 6/50

From the results shown in Table 6, the difference in the number of particles in which the electric resistance value was not observed before and after the wet heat test was 40, and the expression rate after the test was only 12% (6/50).

(Comparative Example 5)

200 g of water was added to 1 g of the particles obtained in "(A) pretreatment" of Example 1 and ultrasonicated for 10 minutes. Then, 0.020 ml of 2-mercaptoethanol was added and stirred for 5 minutes on a magnetic stirrer. Then, 0.65 g of silver nitrate was added, and the mixture was further stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

18 is a scanning electron microscope photograph of the conductive particles having the metal coating formed thereon. Referring to Fig. 18, silver particles were not coated on the surface of the silica particles.

(Comparative Example 6)

Example 1 200 g of water was added to 1 g of the particles obtained in "(A) pretreatment" and ultrasonicated for 10 minutes. Then, 0.015 ml of 2-mercaptoethyl octanoate was added and stirred for 5 minutes on a magnetic stirrer. Thereafter, 0.65 g of silver nitrate was added, and the mixture was further stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

Fig. 19 shows a scanning electron microscope photograph of the conductive particle having the metal coating formed thereon. Referring to Fig. 19, silver was not coated on the surface of the silica particles.

(Comparative Example 7)

Example 1 After adding 200 mL of water to 1 g of the particles obtained in "(A) Pretreatment" and sonicating for 10 minutes, 0.013 g of calcium mercaptoacetate trihydrate was added and stirred for 5 minutes on a magnetic stirrer. Thereafter, 0.65 g of silver nitrate was added, and the mixture was further stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

Fig. 20 shows a scanning electron microscope photograph of the conductive particles having the metal coating formed thereon. Referring to Fig. 20, silver particles were not coated on the surface of the silica particles.

(Comparative Example 8)

Example 1 200 g of water was added to 1 g of the particles obtained in "(A) pretreatment" and ultrasonicated for 10 minutes. Then, 0.015 ml of 3-aminopropyltrimethoxysilane was added and stirred for 5 minutes by a magnetic stirrer. Then, 0.65 g of silver nitrate was added, and the mixture was further stirred for 10 minutes. Next, 13 mL of a 25% ammonia aqueous solution was added, then 20 mL of a 0.24 mmol / L formalin aqueous solution was added, and the mixture was stirred for 5 minutes. The precipitated silver-coated silica particles were collected by suction filtration, washed with methanol, and then dried in an oven at 70 DEG C for 3 hours.

21 is a scanning electron micrograph of a conductive particle having a metal coating formed thereon. Referring to FIG. 21, no metal film was formed on a part of the surface of the non-conductive particles.

The resulting conductive particles were evaluated for dispersibility in the resin. 22 shows an optical microscope photograph used for evaluation of dispersibility. Referring to Fig. 22, a state in which the conductive particles are aggregated is observed. This suggests that the yield of the monodisperse conductive particles used as a sealing agent for a liquid crystal display element is low.

Claims (10)

A metal film is formed by electroless plating on a non-conductive particle having a diameter of 0.5 mu m to 100 mu m,
Wherein the electroless plating is performed after the pretreatment of attaching the metal nuclei to the non-conductive particles and that the metal coating derived from silver is formed in the presence of the silane compound having a thiol group .
The method for forming a metal film according to claim 1, wherein the electroless plating is initiated after the mixture of the silane compound having thiol group and water is brought into contact with the non-conductive particles.
The method for forming a metal film according to claim 1 or 2, wherein the silane compound having a thiol group is 3-mercaptopropyltriethoxysilane.
The method for forming a metal film according to claim 1 or 2, wherein the electroless plating is performed by a silver halide reaction.
The method according to claim 1 or 2, wherein the pretreatment comprises depositing a metal of the metal salt by a reducing agent after bringing a treatment liquid containing a silane coupling agent, a hydrolysis catalyst and a metal salt into contact with the non- ,
Wherein the silane coupling agent has a functional group that forms a chelate with respect to the metal of the metal salt.
The method for forming a metal film according to claim 1 or 2, wherein the metal of the metal nuclei is gold or silver.
Conductive particles that are imparted with conductivity by a metal coating formed on the entire surface of the non-conductive particles,
The diameter of the non-conductive particle ranges from 0.5 μm to 100 μm,
Wherein the metal coating is comprised of a single layer of silver,
Wherein only gold, silver and sulfur are detected as elements other than the elements contained in the non-conductive particles in the fluorescent X-ray analysis of the conductive particles.
delete The conductive particle according to claim 7, which is used as a sealing agent for a liquid crystal display element.
The conductive particle according to claim 7, which is used as an anisotropic conductive material.

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