JPH0359905A - Conductive spherical fine grains, manufacture thereof and conductive paste containing them - Google Patents

Abstract

PURPOSE:To obtain conductive paste being used for highly integrated printed wiring or electrode material while being dispersed in resin or the like by using inorganic oxide spherical fine grains as a core material while carrying a specific metal on the surface of the core material and specifying a grain diameter and making the grain shape spherical. CONSTITUTION:Inorganic oxide spherical fine grains are made a core material while the surface of the core material carries at least one kind of metals to be selected from a group consisting of Ib group, VIII group metals on the periodic table up to the thickness in the range of 0.025 to 0.5mum. An average grain diameter is in the range of 0.1 to 11.0mum. Standard deviation value of a grain diameter is in the range 1.0 to 1.3 and a grain shape is substantially spherical. In this case, grains are substantially spherical while being excellent is dispersivity and very sharp in grain size distribution. Thereby, the subject connective spherical fine grains are effective as a conductive filler for conductive paste which is an electrode material, IC demanding a high printing characteristic, a laminated capacitor and a liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to monodisperse conductive spherical fine particles, a method for producing the same, and a conductive paste using the same. More specifically, the present invention uses inorganic oxide-based spherical fine particles as a core material, and has a specific average particle diameter and standard deviation value of the particle diameter, with a highly conductive metal having a specific thickness supported on the surface of the core material. The present invention relates to monodispersed conductive spherical fine particles having a substantially spherical particle shape, an industrially advantageous manufacturing method thereof, and a conductive paste containing at least the same as a conductive filler.

The conductive spherical fine particles obtained by the present invention are substantially spherical, have excellent dispersibility, and have a very sharp particle size distribution. In addition to being effective as a conductive filler for conductive paste, which is an electrode material, COF
It is filled with conductive adhesives, paints, resins, etc. used in liquid crystals, etc., and is industrially useful as an electromagnetic shield and antistatic agent.

(Prior art) Conventionally, metal particles such as silver powder, platinum powder, and copper powder have been used in dispersed composite conductive materials to impart conductivity, but these metal particles have a scale-like, crushed-like, etc. Not only was the particle shape not constant, but the particle size distribution was also very wide. Recently, spherical metal powders have been developed as atomized powders, but the problems of large particle sizes and extremely wide particle size distributions remain unsolved.

In addition, as a method to improve the disadvantages that noble metal particles are expensive and have a large specific gravity, a method has been proposed in which the surface of spherical fine particles made of polymer is plated with metal (Japanese Patent Application Laid-Open No. 57-49632, etc.). However, there were problems in that it was difficult to plate the surface of the polymer fine particles with noble metals, and the heat resistance was poor when used as conductive particles.

On the other hand, if we limit the base materials to be plated to inorganic oxides and look at the conventional technology, chemical plating is applied to glass, ceramics, clay, etc. by a so-called silver mirror reaction, unless the shape of the base material is concerned. It has been known for a long time that a conductive film can be formed on materials (e.g., page 108 of Chemical Handbook Applied Edition published on October 25, 1965, page 748 of Kirkoo Othmer ELECTROLESS PLATING published in 1979). By the way, as an example of applying the shape of a base material to fine particles, Japanese Patent Application Laid-Open No. 51-87548 discloses a resin composition containing conductive fine particles obtained by chemically plating a metal on a fine particulate base material of an inorganic oxide. The inorganic oxides specifically mentioned are limited to those that dissolve in acid aqueous solutions such as magnesium oxide, zinc oxide, iron oxide, copper oxide, etc., and the manufacturing method of the base material, particle size distribution, and conductive fine particles. Although there is no detailed description of the physical properties, it is assumed that the purpose is to obtain distorted conductive fine particles. On the other hand,
No. 7-41301 discloses an improved method of completely chemically plating a noble metal onto a powder base material such as inorganic oxide fine particles. Although this publication does not provide detailed descriptions of the shape, particle size distribution, monodispersity, etc. of the inorganic oxide fine particles that serve as the core material and the generated conductive fine particles, it is thought that they are simply intended as a substitute for noble metal particles. However, it has the disadvantage that the manufacturing method is complicated.

As mentioned above, conventionally known conductive fine particles, which are metal-plated inorganic oxide fine particles, have irregular shapes, a wide particle size distribution7, and particles that aggregate or are independently dispersed. There were problems such as the thickness of the supported metal was not constant and the thickness of the supported metal was not constant. When these conductive fine particles are applied, for example, to a conductive paste to be used as an electrode material for integrated memory elements, transistors, capacitors, diodes, etc., various undesirable troubles occur. This is because in recent years, as the above-mentioned devices have become more and more miniaturized, layered, and chipped, the number of electrode wires and electrode contacts that are to be formed on the device has increased, resulting in problems with accuracy, reliability, and their performance. There is a demand for improvement in manufacturing speed. Therefore, when using a conductive paste as a printing or bonding material, the flow characteristics of the paste are a particularly important factor, and conventional conductive pastes containing conductive fine particles are unsatisfactory due to the above-mentioned problems with the fine particles. Ta.

(Problems to be Solved by the Invention) The present invention aims to obtain conductive fine particles whose flow characteristics are greatly improved when used in a conductive paste, and to solve the problems of conventional conductive fine particles and We believed that the problem with this manufacturing method lies in the properties of the inorganic oxide fine particles that serve as the core material when chemically plating metals, and we investigated various factors. As a result, particle shape, surface properties, particle size distribution,
By controlling factors such as the degree of aggregation and average particle size,
More preferably, by specifying the method for producing the particles, it has been found that the object can be easily and distantly related, leading to the present invention. However, the use of the conductive fine particles of the present invention is not limited to conductive pastes, but includes polyester, epoxy, (meth)acrylic, phenol, polyethylene,
When added to resins such as PVC, polystyrene, polyimide, polyamide, etc., the fluidity and dispersibility are dramatically improved compared to conventionally known conductive fine particles, so the use of these resins that require conductivity can be expanded. It is something that can be used.

(Means for Solving the Problems) In the first aspect of the present invention, inorganic oxide-based spherical fine particles are used as a core material, and a periodic pattern is formed on the surface of the core material to a thickness in the range of 0.025 to 0.5 μm. At least one metal selected from the group consisting of Group 1b metals, Group VIII metals, and tin is supported, and the average particle diameter is in the range of 0.1 to 11.0 μm, and the standard deviation value of the particle diameter is 1.0 μm. To provide monodisperse conductive spherical fine particles having a particle size of 0 to 1.3 and having a substantially spherical particle shape.

The second invention of the present invention has an average particle diameter of 0.05 to 10 μm.
A suspension of monodispersed inorganic oxide-based spherical fine particles having a standard deviation value of particle diameter in the range of 1.0 to 1.2 is added with a periodic substance that is soluble in the solvent constituting the suspension. Table group Ib, VI
At least one type of compound selected from the group consisting of Group II metals and tin is dissolved, and then the metal compound is chemically reduced to form a 0.0.
An average particle diameter in the range of 0.1 to 11.0 μm, characterized by supporting metal to a thickness in the range of 25 to 0.5 μm,
Provided is a method for producing monodisperse conductive spherical fine particles having a standard deviation value of particle diameter in the range of 1.0 to 1.3 and having a substantially spherical particle shape.

Furthermore, the third invention of the present invention provides at least a conductive filler,
In conductive pastes containing binders and solvents,
As a conductive filler, inorganic oxide-based spherical fine particles are used as a core material, and on the surface of the core material, a material selected from the group consisting of metals of group 1b0 of the periodic table, group VIII metals, and tin is applied to the surface of the core material with a thickness in the range of 0.025 to 0.5 μm. At least one kind of metal is supported on the particles, and the average particle size is 0.
．． Range of 1 to 11.0 μm, standard deviation value of particle size is 1
．． Provided is a conductive paste characterized by using at least one kind of monodispersed conductive spherical fine particles having a particle size of 0 to 1.3 and having a substantially spherical particle shape.

The inorganic oxide-based spherical fine particles that are the core material of the conductive spherical fine particles disclosed in the present invention are not limited in other physical properties or manufacturing method as long as they satisfy the above-mentioned requirements.

However, even if conventionally known chemical plating methods are applied, it is easy to make the plating uniform, and considering the physical properties of the conductive fine particles after plating, inorganic oxide fine particles manufactured using alkoxy metal compounds or their derivatives as raw materials. is preferred. More preferred are inorganic oxide-based fine particles obtained by hydrolyzing the alkoxy metal compound or the like in an aqueous solution of alcohol. By using inorganic oxide fine particles obtained by such a specified manufacturing method as a core material1, it is possible to easily form a highly conductive metal film with a uniform and controlled thickness on the surface. can. Although the reason for this is not yet clear, it is thought to be due to the unique surface properties of inorganic oxide-based fine particles produced using an alkoxy metal compound or its derivative as a raw material. Specifically, the particles must be truly spherical and have no sharp edges on their surfaces, be porous, have extremely fine irregularities on their surfaces, and have metals that are the constituent units of inorganic oxides. The alkoxy groups partially remaining and bonded to atoms (hereinafter abbreviated as M) and the hydroxyl groups directly bonded to M are very active, so they are usually added when chemically plating metals. Some of the protective colloids, buffers, reducing agents, complexing agents, catalysts, etc. that are applied to the particles are adsorbed or act on the particle surfaces uniformly, and because the particles are spherical and have uniform particle sizes, all particles The chemical and physical properties on the side surfaces are homogeneous, etc.

An alkoxy metal compound is a general formula (%) (where M is a metal element, Ro is a hydrogen atom, and an alkyl group having up to 10 carbon atoms which may have a substituent, an aryl group,
at least one group selected from the group of unsaturated aliphatic residues, R2 represents an alkyl group, m is O or a positive integer, n
represents one or more groups and satisfies the valence of m+n-metal element M. Furthermore, m R1s may be different, and n
The same applies to R2. ), among which compounds of silicon, titanium, zirconium, and aluminum as the metal element M are preferred because they are industrially easy to handle and inexpensive. Alkoxy metal compounds where n is 3 or more can be used alone, but n
The compound represented by -1 or 2 can be used together with a raw material having three or more hydrolyzable organic groups. The above general formula R1゜M
(ORz) Specific examples of alkoxy metal compounds represented by a include tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane, tetrabutoxysilane, trimethoxysilane, triethoxysilane, methyltrimethoxysilane, and trimethoxyvinyl silane. , triethoxyvinylsilane, 3-glycidoxypropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-(2-aminoethyl-5nopropyl)trimethoxysilane, phenyltrimethoxysilane, phenyl Triethoxysilane, dimethoxydimethylsilane, dimethoxymethylsilane, jetoxymethylsilane, jetoxy-3-glycidoxypropylmethylsilane, 3-
Chloropropyldimethoxymethylsilane, dimethoxydiphenylsilane, dimethoxydimethylphenylsilane,
Trimethylmethoxysilane, trimethylethoxysilane, dimethylethoxysilane, dimethoxyjethoxysilane, tetramethyltitanate, tetraethyltitanate, tetraisopropyltitanate, tetrabutyltitanate, diethyldibutyltitanate, tetramethylzirconate, tetraethylzirconate, tetraisopropylzirconate, Examples include tetrabutyl zirconate, tetra(2-ethylhexyl>titanate, 4-trimethyl aluminate, triethyl molulfate, triisopropyl aluminate, and tributyl aluminate).

As derivatives of these alkoxy metal compounds, some alkoxy groups (OR2) are carboxyl groups or β-
These include compounds substituted with a group capable of forming a chelate compound, such as a dicarbonyl group, or low condensates obtained by partially hydrolyzing these alkoxy metal compounds or alkoxy group-substituted compounds.

When the above-mentioned alkoxy metal compound or its derivative is hydrolyzed in an aqueous alcohol solution, methanol, ethanol, isopropanol, butanol, isoamyl alcohol, ethylene glycol, propylene glycol, etc. are used singly or in mixtures. . It is also possible to partially mix an organic solvent such as dioxane, diethyl ether, ethyl acetate, benzene, toluene, hexane, etc. into the solution.

In some cases, NH4'', Na, etc. may be added to the aqueous solution of alcohol for the purpose of controlling the hydrolysis rate.
Catalytic components such as cations such as ``so'', anions such as ``-1H2PO4-, and organic amine compounds such as ethanolamine and tetramethylammonium hydroxide can be added, but their presence or absence and amount vary depending on the raw material, and the particle formation It is appropriately selected in consideration of the influence on the shape and particle size.

By performing hydrolysis by selecting appropriate conditions, a particle size distribution width such that the average particle size is in the range of 0.05 to 10 μm and the standard deviation value of the particle size is in the range of 1.0 to 1.2 can be obtained. Very small inorganic oxide spherical particles are precipitated in the solution,
An alcoholic solution suspension in which the fine particles are monodispersed is obtained.

In the present invention, the inorganic oxide is not only one in which the M-0 bond is configured three-dimensionally, but also an organic group (R1 when Ro in the general formula is an organic group) that directly bonds to the metal element. This refers to those that exist, those that contain other organic substances or metal elements in their composition, and those that also include hydroxides.

When chemically reducing a compound of group 6 RB and/or group II of the periodic table and/or tin and supporting the metal on the surface of inorganic oxide-based spherical fine particles, the alcohol obtained as described above is used. The suspension can be used as is or after being concentrated. In another embodiment, the fine particles in the suspension are separated by a conventionally known method such as filtration, centrifugation, or solvent evaporation, and then optionally dried or calcined to form a powder, which is then monodispersed in an appropriate solvent. It may also be used as a suspension.

Supported metals include Ib group metals such as copper, silver, and gold;
Group 1 metals such as ruthenium, cobalt, rhodium, nickel, palladium, and platinum, and tin can be used alone or in combination of two or more.

The metal compound serving as the raw material for the supported metal is not limited as long as it has reducibility and is soluble in the solvent constituting the suspension. Examples include the above-mentioned metal chlorides, nitrates, cyanides, sulfates, metal ammonium chloride, various complex compounds, etc., but mineral acid solutions of metals may also be used.

7 The reducing agent is not particularly limited as long as it can reduce the above metal compound and convert it into metal, and formalin, aldehydes such as acetaldehyde and benzaldehyde, glucose,
Reducing sugars such as fructose, hydrazine compounds such as hydrazine, hydrazine sulfate, and hydrazine chloride, sodium tartrate,
Tartaric acid compounds such as potassium tartrate, hydroquinone, sodium sulfite, sodium hyposulfite, sodium hypophosphite, sodium borohydride, and the like can be used.

A method for supporting a metal on the surface of inorganic oxide fine particles is carried out, for example, by adding the above-mentioned metal compound to a suspension of the fine particles, and then adding the above-described reducing agent thereto. Depending on the case, protective colloids such as carboxymethylcellulose, sodium polyacrylate, ammonium polyacrylate, sodium alginate, casein, gelatin, lecithin, soybean protein, methylcellulose, hydroxyethylcellulose, polyvinyl alcohol, starch, ammonium nitrate, sulfuric acid, etc. Ammonium 8, buffering agents such as alkali salts such as formic acid and acetic acid, ammonia, primary amines such as propylamine, secondary amines such as methyl ethyl ketone, complexing agents such as dimethylethylamine, stannous chloride Catalysts such as tin compounds, palladium compounds such as palladium chloride, etc. may be present during reduction, or the inorganic oxide spherical fine particles may be pretreated.

The ratio of the metal compound added to the core material is not generally indicated, but is determined according to the particle size of the core material in order to maintain the electrical conductivity of the resulting metal-supported spherical fine particles within a preferable range and economically advantageous. It needs to change. The preferred addition ratio is shown in Figure 1. In Figure 1, even if the upper limit is exceeded, the effect of improving conductivity is low and it is not economical. On the other hand, if it exceeds the lower limit, the conductivity will decrease, which is not preferable. The metal support thickness of the metal-supported conductive fine particles within the above range is 0.
．． The range is 0.025 to 0.5 μm, and the average particle size is 0.025 to 0.5 μm.
Range of 1-11.0μm, standard deviation value of particle size is 1.0
~1.3, resulting in substantially spherical particles. The conductivity of the 9 conductive spherical fine particles with metal supported within the above range is 10-2 to 10-6 Ω·(1) as the volume resistivity measured by molding only the particles at the bottom, which is suitable for use in conductive pastes. It is ideal as a filler.

When the conductive spherical fine particles obtained in this way are used as at least one type of conductive filler in a conductive paste containing at least a conductive filler, a binder, and a solvent, they exhibit stability that cannot be obtained with conventional pastes. Electrode contacts or wiring with good conductivity, good workability, precision and high reliability can be obtained.

The conductive paste of the present invention can be used in any type, such as a room temperature curing type such as an ultraviolet curing type, a heat curing type, or a medium or high temperature baking type.

As the binder used in the present invention, for normal temperature or heat curing type and medium temperature baking type paste, for example, vinyl chloride resin, vinyl acetate resin, polyester resin,
Acrylic resin, urethane resin, epoxy resin, polycarbonate resin, melamine resin, butyral resin, polyide ≧ 0 resin, polysulfone resin, alkyd resin, phenolic resin, polyester resin type resin, polyether sulfone type resin, silicone type resin, or ultraviolet curing resin, and for high temperature baking type paste, glass type powder etc. are used.

Examples of the solvent used in the present invention include ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl n-butyl ketone, diisobutyl ketone, and cyclohexanone, hydrocarbon solvents such as toluene, cyclohexane, and xylene, ethyl acetate, n-propyl acetate, etc. ,
Acetate ester solvents such as isopropyl acetate, cellosolve solvents such as methyl cellosolve and ethyl cellosolve, carpitol solvents such as methyl calpitol and ethyl carpitol, reactive monomers such as styrene and butyl acrylate, etc. It is appropriately selected in consideration of solubility, drying rate of the coating film, adhesion to the painted surface, etc.

Additives 1 which may optionally be added to the conductive paste include leveling agents, colorants, hardeners, defoamers, thixotropic agents, adhesion promoters and other conductive fillers.

The conductive spherical fine particles of the present invention are optionally used together with other conductive fillers and blended with a binder and a solvent, but the ratio of the total conductive filler to the binder is 30 to 90% by weight based on 10 to 70% by weight of the binder. weight%
is preferred. When mixed with other conductive fillers, the effect of the conductive paste of the present invention is that the proportion of the conductive spherical fine particles of the present invention in the conductive filler is 30% by weight or more, preferably 50% by weight or more. is demonstrated.

In that case, it is not preferable that particles having a particle size of 30 μm or more are included in the other conductive filler.

The conductive paste can be blended by dispersing the above-mentioned components using conventionally known methods such as a sand mill, a ball bowl, a high-speed rotation stirrer, a triple roll, and the like. Since the conductive spherical fine particles obtained by the present invention have few aggregated particles, they can be dispersed very easily.

2. The conductive paste of the present invention can be used by a bar code method, a spray method, a roll coating method, a spinner method, a dip method, a Meyer bar method, an air knife method, a dispenser method,
After coating by screen printing, gravure printing, pin transfer, etc., a suitable curing method depending on the type of paste is used to form a conductor.

(Function) The conductive spherical fine particles obtained by the manufacturing method disclosed in the present invention have very uniform shape and conductivity of each particle.
In conductive pastes, electromagnetic shielding agents, and antistatic agents that are dispersed in resins and the like, very homogeneous conductors with good workability are formed. In particular, conductive pastes are used in highly integrated printed wiring or electrode materials to form highly reliable and precise conductors.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples and Reference Examples.

In addition, the particle shape, average particle diameter, standard deviation value, specific surface area of the inorganic oxide spherical fine particles, dispersibility and plating of the conductive spherical fine particles obtained by using the fine particles as a core material and supporting a metal on the surface thereof. Uniformity and volume resistance values were analyzed and evaluated by the following methods.

・Particle shape Judgment was made by observation with an electron microscope at a magnification of 50,000 times.

- Average particle diameter and standard deviation value The particle diameter of 100 arbitrary particles of an image taken with an electron microscope with a magnification of 50,000 times was actually measured and determined from the following formula.

Σ χ5 ·Specific surface area It was measured by the BET method.

4. The dispersibility sample was observed in a slurry state under an optical microscope at a magnification of 1,000 times, and the slurry was evaluated by checking for the presence or absence of coarse particle distribution due to particle aggregation in centrifugal sedimentation particle size distribution measurement.

- Coating uniformity It was determined based on the observation of the uniformity of the distribution of the supported metal on the surface of the core material particles using an electron microscope with a magnification of 50,000 times, and the sharpness of the particle size distribution measured by centrifugal sedimentation particle size distribution measurement of the particle slurry.

The dispersibility and coating uniformity were comprehensively judged from the results of the above evaluation method and evaluated in the following four stages.

◎ Very good ○ Good △ Bad × Very bad Volume resistivity sample was pressed at 10 tons/cj for 5 minutes to form a bottom mold.
The volume resistance value was measured by the DC four-terminal method.

5 Production of inorganic oxide spherical fine particles <Reference Example 1> Ethanol 16β and 1.5 kg of a 28% ammonium aqueous solution were added and mixed in a 3ON glass reactor equipped with a stirrer, a dropping port, and a thermometer. The mixture was heated to 20°C.
While adjusting the temperature to ±0.5°C and stirring, a solution of 1.4 kg of tetraethyl silicate diluted with 21 parts of ethanol was added dropwise from the dropping port over 1 hour. After addition, stirring was continued for 2 hours to further hydrolyze the silica. An alcoholic solution suspension (1a) of spherical fine particles was produced. At this time, the concentration of each raw material relative to the total amount of the final solution was 0.32% tetraethylsilicate.
mol/l, water 2.90 mol/11 ammonia 1.19 mol/l. The organic solvent containing ethanol, water, catalyst, etc. was evaporated from the suspension using a 5Il jacket equipped kneader under normal pressure at a jacket temperature of 120°C to obtain a fine dry powder. The dry powder was fired in an electric furnace set at 250°C for 5 hours and then passed through a jet pulverizer to crush the agglomerated particles to obtain a powder of silica spherical fine particles (1b
) was manufactured.

6 Table 1 shows the reaction conditions and particle analysis results.

<Reference Example 2-4> A 28% ammonium aqueous solution was added to the fine particle suspension obtained in Reference Example 1 so that the composition as shown in Table 1 was obtained, and the components shown in Table 1 were added to the mixed suspension. An alcoholic solution suspension (22-4a) and a powder (2b-4b) of sequentially grown silica spherical fine particles were produced in the same manner as in Reference Example 1, except that the amount of tetraethylsilicate having the composition shown was used. did.

The reaction conditions and analysis results are shown in Table-1.

<Reference Example 5-8> Silica spherical Suspensions (5a to 8a) and powders (5a to 8a) of fine particles, titania spherical fine particles, zirconia spherical fine particles, aluminum spherical fine particles
b-8b) were produced.

The reaction conditions and analysis results are shown in Table-1.

7 Production of conductive spherical fine particles <Example 1> Silica spherical fine particles obtained in Reference Example 3 (3b> 100 g
was dispersed in a metal complex liquid having the composition shown below (A), and then mixed with the reducing liquid shown below (B). After stirring at room temperature for about 10 minutes, the resulting slurry was centrifuged and washed with water to produce a water slurry of conductive spherical particles (3c). The conductive spherical fine particles in the slurry were monodispersed without agglomeration, and were particles that were coated on the metal core material with good uniformity. Further, the powder produced by drying the slurry at 100° C. for 5 hours showed good conductivity.

(A) Metal complex liquid Silver nitrate 240g 28%-ammonia water 280g Sodium hydroxide 20g Water 10+r(
B) Reduced liquid glucose 130g gelatin
5g 8 Water 10g The analysis results of the obtained conductive spherical fine particles are shown in Table 2.

Furthermore, as can be seen from the XMA analysis results (Figure 3) of the conductive spherical fine particles produced in Example 1, silver is present almost uniformly on the surface of the fine particles.

Furthermore, a transmission electron micrograph (FIG. 4) of the cross section of the fine particles shows that a silver film of about 0.1 μm is formed on the surface of the core substance. Furthermore, the surface state of the conductive spherical fine particles produced in Example 1 was observed using a scanning electron microscope, and the results are shown in FIG.

<Example 2> After adding 1 kg of silver nitrate and 30 g of sodium hydroxide to 18.4 kg of the silica spherical fine particle alcoholic solution suspension (3a) obtained in Reference Example 3, an aqueous solution containing 550 g of glucose and 25 g of gelatin was added. By adding and stirring at room temperature for about 15 minutes, conductive spherical fine particles (3d) were manufactured. The analysis results are shown in Table-2.

9 <Example 3-9> Reference example 1. 2. The silica spherical fine particles 1b, 2b, 4b, 5b, titania spherical fine particles 6b, zirconia spherical fine particles 7b, and aluminum spherical fine particles 8b obtained in steps 4 to 8 were used as core materials, and the metal weight percentage in the conductive spherical fine particles was Conductive spherical fine particles were prepared in the same manner as in Example 1, except that the silver nitrate concentration was adjusted to the value shown in Table 2, and the reducing agent amount was adjusted to A mole of the silver nitrate. 1
c, 2c4c-8c were produced. The analysis results are shown in Table-2.

<Example 10> Same as Example 1 except that the silver nitrate concentration was adjusted so that the metal ratio in the conductive spherical fine particles was 30%, and the reducing agent amount was adjusted to be % mole of the silver nitrate. Conductive spherical fine particles were produced. The results are shown in Table-2.

<Example 11> Same as Example 0 and 1 except that the silver nitrate concentration was adjusted so that the metal ratio in the conductive spherical fine particles was 80%, and the reducing agent amount was adjusted so that the silver nitrate amount was A mole. Conductive spherical fine particles were produced. The results are shown in Table-2.

Example 10.11 shows that when the core material is spherical and the particle size distribution is sharp, the overall physical properties of the resulting conductive spherical fine particles are influenced by the particle size and metal ratio of the core material. .

<Comparative Example 1> Metal coating was carried out in the same manner as in Example 5 except that crushed silica was used as the core material, but as shown in Table 2, the dispersibility and coating uniformity of the particles produced were The conductivity was poor, and even though the metal ratio in the particles was comparable to that of Example 5, the conductivity was poor.

Comparative Example 2> Metal coating treatment was carried out in the same manner as in Example 4 except that fibrous silica was used as the core material, but as shown in Table 2, particles with good dispersibility and coating uniformity were used. was not obtained.

<Comparative Example 3> Metal coating treatment was carried out in the same manner as in Example 5 except that silica spherical fine particles with a relatively wide distribution of particle size 1 obtained from water glass were used as the core material, but as shown in Table 2. The dispersibility, coating uniformity, and conductivity of the produced particles were inferior to those of the particles obtained in Example 5.

<Example 12> 0 g of silica spherical fine particles 3b obtained in Reference Example 3
．． 01wt%-PdCj! , immersed in an aqueous solution for 15 minutes,
After washing with water and dispersing in a solution consisting of the following composition, 95°
The mixture was stirred at C for 2 hours to produce nickel-coated particles.

Nickel chloride 760g Sodium citrate 400g Sodium succinate 400g Sodium hypophosphite 1200g Water 20kg The coating uniformity and dispersibility of the obtained particles were good, and the volume resistivity was 9. It was 1×10 −5 Ω mark.

2 3075 parts by weight of the conductive spherical fine particles produced in Example 1, 15 parts of epoxy resin, and 10 parts of ethyl cellosolve were kneaded for 30 minutes using a triple roll to produce a conductive paste. This was screen printed onto an epoxy resin board to a width of 1m.
A conductive line with a thickness of about 25 μm was formed, and the coating was cured by heating at 180° C. for about 1 hour. The volume resistance value of the conductive line thus obtained was 4.3×10−′Ωσ. Furthermore, when the line edges after curing were observed under an electron microscope, they were sharp with almost no irregularities.

<Comparative Example 4> In Example 13, instead of using the conductive spherical particles 3c, crushed metal-coated particles 9c manufactured in Comparative Example 1 were used.
A conductive paste was prepared in the same manner as in Example 13, except that a conductive line was formed on an epoxy substrate.The volume resistance value was as high as 8.7×10-2Ω, and the line edge was sharp. There was considerable unevenness due to the protrusions.

<Comparative Example 5> 3 The same as Example 13 except that instead of using the conductive spherical fine particles 3C in Example 13, the conductive spherical fine particles 11C obtained in Comparative Example 3 and having a relatively wide particle size distribution were used.
A conductive paste was prepared in the same manner as described above, and conductive lines were formed on an epoxy substrate, but the line edges included large irregularities.

<Example 14> Everything except that 3035 parts by weight of the conductive spherical fine particles produced in Example 1 and 11C40 parts by weight of the conductive spherical fine particles with a relatively wide particle size distribution obtained in Comparative Example 3 were used as the conductive filler. A conductive paste was prepared in the same manner as in Example 13, a conductive line was formed on an epoxy substrate, and when observed, the line edge was sharp.

This means that by adding conductive spherical fine particles with a sharp particle size distribution in addition to the conductive spherical fine particles with a wide particle size distribution as used in Comparative Example 5, the printing resolution when forming conductive lines is improved. It shows.

4

[Brief explanation of drawings]

FIG. 1 is a graph showing a preferable addition ratio of a metal compound to the particle size of inorganic oxide particles. FIG. 2 is a diagram showing the surface state of conductive spherical fine particles (3C) observed with a scanning electron microscope. Figure 3 shows conductive spherical fine particles (3c) examined by XMA.
) is a diagram showing the distribution state of silver on the surface. FIG. 4 is a diagram showing a cross-sectional state of the conductive spherical fine particles (3c) observed with a transmission electron microscope.

Claims (7)

[Claims] (1) Inorganic oxide-based spherical fine particles are used as a core material, and on the surface of the core material, metals selected from the group consisting of metals of group Ib and group VIII of the periodic table and tin are coated on the surface of the core material with a thickness in the range of 0.025 to 0.5 μm. The average particle diameter is in the range of 0.1 to 11.0 μm, the standard deviation value of the particle diameter is in the range of 1.0 to 1.3, and the particle shape is substantially the same. Monodisperse conductive spherical fine particles characterized by their spherical shape. (2) The inorganic oxide-based spherical fine particles include silicon, titanium,
The conductive spherical fine particles according to claim 1, characterized in that the main component is an oxide of aluminum or zirconium, or a composite oxide thereof. (3) Inorganic oxide-based spherical fine particles have the general formula R_1_mM(OR_2)_n (where M is a metal element, R_1 is a hydrogen atom, and an alkyl group with up to 10 carbon atoms which may have a substituent, an aryl group, an unsaturated At least one group selected from the group of aliphatic residues, R_2 represents an alkyl group, m is 0 or a positive integer, n is an integer of 1 or more, and m + n = valence of the metal element M is satisfied. In addition, the m R_1's may be different, and the n R_2's are also the same.) Fine particles obtained by hydrolyzing an alkoxy metal compound or its derivative represented by The conductive spherical fine particles according to claim 1 or 2, characterized in that: (4) A suspension of monodispersed inorganic oxide-based spherical fine particles with an average particle diameter in the range of 0.05 to 10 μm and a standard deviation value of particle diameter in the range of 1.0 to 1.2 is added to the suspension. At least one compound selected from the group consisting of metals of groups Ib and VIII of the periodic table and tin that is soluble in the solvent constituting the turbid body is dissolved, and then the metal compound is chemically reduced. 0.025 to 0.5 μm on the surface of inorganic oxide-based spherical fine particles.
The average particle size is in the range of 0.1 to 11.0 μm, the standard deviation value of the particle size is in the range of 1.0 to 1.3, and the particle shape is in the range of 1.0 to 1.3. A method for producing monodisperse conductive spherical fine particles that are substantially spherical. (5) The conductivity according to claim (4), wherein the inorganic oxide-based spherical fine particles are mainly composed of an oxide of silicon, titanium, aluminum, or zirconium, or a composite oxide thereof. Method for producing spherical particles. (6) Inorganic oxide-based spherical fine particles have the general formula R_1_mM(OR_2)n (where M is a metal element, R_1 is a hydrogen atom, and an alkyl group with up to 10 carbon atoms which may have a substituent, an aryl group, an unsaturated At least one group selected from the group of aliphatic residues, R_2 represents an alkyl group, m is 0 or a positive integer, n is an integer of 1 or more, and m + n = valence of the metal element M is satisfied. In addition, the m R_1's may be different, and the n R_2's are also the same.) Fine particles obtained by hydrolyzing an alkoxy metal compound or its derivative represented by The method for producing conductive spherical fine particles according to claim 4 or 5, characterized in that: (7) In a conductive paste containing at least a conductive filler, a binder, and a solvent, the conductive filler is made of inorganic oxide-based spherical fine particles as a core material, and the surface of the core material has a thickness in the range of 0.025 to 0.5 μm. periodic table of thickness
At least one metal selected from the group consisting of Ib group metals, VIII group metals, and tin is supported, and the average particle size is 0.
．． In the range of 1 to 11.0 μm, the standard deviation value of particle diameter is 1.
1. A conductive paste characterized by using at least one type of monodispersed conductive spherical fine particles having a particle size of 0 to 1.3 and having a substantially spherical particle shape.