JP2006026602A - Method for forming thin film conductor layer of metallic particulate sintered compact type, and methods for forming metallic wiring and metallic thin film by applying the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a metallic particulate sintered compact exhibiting a good electric conductivity by setting a heat treatment temperature to be used within a range not exceeding at least 200°C at the time of forming a metallic particulate sintered compact layer while a metallic particulate coating layer applied on a substrate is subjected to low-temperature thermal sintering. <P>SOLUTION: After the coating molecules on a surface are removed from the metallic particulates having a surface coating molecule layer included in a coating layer, the metallic particulates are subjected to low-temperature thermal sintering, and at this time, the metallic particulates are irradiated with energy rays from the surface of the coating layer, and thereafter, the metallic particulates are subjected to a heat treatment at a low temperature (below 15°C), and thereby the removal of the coating molecules of the surface is accelerated and the sintering itself of the metallic particulates is rapidly progressed by such low-temperature heating and the metallic particulate sintered compact exhibiting the good electric conductivity is formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for forming a metal fine particle sintered body type thin film conductor layer that can be used for forming a fine metal wiring pattern or a metal thin film. Specifically, fine metal fine particles, in particular, a metal nanoparticle dispersion having a nano-sized particle diameter is used to form an ultrafine pattern or form a thin film coating layer, followed by low-temperature treatment. The present invention relates to a method of forming a sintered compact thin film conductor by sintering various metal fine particles, and a metal wiring and a metal thin film produced by applying the method.

  As one of methods for producing metal fine particles having an extremely small particle diameter, at least an average particle diameter of 100 nm or less, ultrafine metal particles of 10 nm or less prepared by using a gas evaporation method are dispersed in a dispersion solvent. A colloidally dispersed dispersion and a method for producing the same have been reported (see Patent Document 1). Also reported is a method in which metal fine particles having an average particle size of several nanometers to several tens of nanometers are prepared wet by using a reduction precipitation method using an amine compound for reduction, and a method for producing the same is colloidally dispersed. (See Patent Document 2).

  Metal fine particles having an average particle diameter of about several nanometers to several tens of nanometers are called metal nanoparticles, and in general, a temperature much lower than the melting point of the metal material (for example, nanoparticles having a clean surface if silver is used). It is known to sinter at 200 ° C. or lower. This is because in metal fine particles, if the particle diameter is sufficiently reduced, the proportion of the atoms in the high energy state existing on the particle surface will increase, and the surface diffusion of metal atoms will become so large that it cannot be ignored. As a result, due to this surface diffusion, the interface between the particles is stretched and sintered.

  When the metal nanoparticles having an average particle diameter of about several nanometers to several tens of nanometers are brought into direct contact with each other, they are fused to each other to aggregate the nanoparticles and lose uniform dispersibility in the dispersion solvent. Therefore, the surface of the metal nanoparticles is uniformly coated with alkylamine or the like, and the surface is provided with a surface-coated molecular layer, so that the metal nanoparticles exhibit high dispersibility. After coating the dispersion containing metal nanoparticles with the surface coating molecular layer on the substrate surface to form a coating layer having a desired thickness, the surface of the alkylamine or the like that covers and protects the surface of the metal nanoparticles When the coating molecules are removed, the metal nanoparticles exposed to a clean surface come into contact with each other, and a dense sintered body layer between the metal nanoparticles is formed by a low-temperature firing process. Conventionally, by heating to a temperature of about 250 ° C., removal of surface coating molecules such as alkylamine that coats and protects the surface of metal nanoparticles is promoted, and then metal nanoparticles exposed to a clean surface come into contact with each other. As a result, heat treatment conditions are used in which low-temperature firing starts.

  Alternatively, as a conductive medium, a metal nanoparticle type conductive metal paste in which metal nanoparticles having a surface coating molecular layer are blended in a binder resin composition to form a paste-like dispersion liquid has also been proposed. This metal nanoparticle-type conductive metal paste uses a metal fine particle with a particle size of μm as a conductive medium, and its drawing accuracy limit is significantly improved compared to conventional conductive metal pastes. ing. In addition, the conductive layer is formed by forming a dense sintered body layer of metal nanoparticles from metal nanoparticles having a surface-coated molecular layer, and simultaneously solidifying a binder resin to form a sintered body type conductor. As a layer, it is fixed on the substrate surface. In that case, the process which removes a surface coating molecule | numerator from the metal nanoparticle surface, and the solidification process of binder resin are performed continuously by heating to the temperature of about 250 degreeC.

Moreover, the volume resistivity of 3 × 10 ⁻⁶ Ω · cm to 10 × 10 ⁻⁵ Ω · cm is obtained by the sintered metal layers of metal nanoparticles obtained by heat treatment at a temperature of about 250 ° C. A conductor layer having a degree can be produced. Therefore, when heat treatment is possible at a temperature of about 250 ° C., the formed sintered body conductor layer has achieved good conductivity with no problem in practical use.
JP-A-3-34211 JP-A-11-319538

  At present, with the miniaturization of various electronic devices and electronic components, there is a demand for further miniaturization of circuit wiring patterns formed on a wiring board. Furthermore, a method of forming a conductor layer by using a conductive metal paste capable of directly drawing a desired wiring pattern instead of a conductor layer produced by a conventional plating method for forming a wiring pattern. Is being used. For example, using a conductive metal paste using metal nanoparticles with a surface-coated molecular layer as a conductive medium, a conductor layer having a fine wiring pattern in which the minimum line width / wiring interval reaches 20 μm / 20 μm Development of a technique for producing a fine wiring pattern that can achieve stable current-carrying characteristics and has high reproducibility during production is in progress.

  For example, when a dispersion liquid containing metal nanoparticles provided with a surface coating molecular layer is used, a fine wiring pattern can be drawn with high drawing accuracy and reproducibility. Then, by using a technique for producing a dense sintered body layer between metal nanoparticles from metal nanoparticles with a surface coating molecular layer contained in this coating film layer, fine wiring with good reproducibility It has been confirmed that a patterned conductor layer can be formed (see International Publication WO 02/35554 A1 pamphlet). At that time, it is necessary to remove the coating molecular layer on the surface from the metal nanoparticles provided with the surface coating molecular layer, and then proceed with the sintering of the metal nanoparticles, and at least 200 ° C., usually 250 ° C. Heat treatment at a certain temperature is necessary.

  With regard to the substrate material used for the wiring board, for example, a so-called Pb-free solder material is used for solder bonding, and the use of a material having a heat resistance of about 250 ° C. is also progressing. In addition to the heating step in the solder bonding step, when the substrate material having heat resistance is further subjected to heat treatment at about 250 ° C. in order to sinter the metal nanoparticles, the thermal properties of the substrate material are increased. It becomes a factor which raises the frequency which causes deterioration. Therefore, in the step of forming a sintered body-type conductor layer using a dispersion containing metal nanoparticles provided with a surface-coated molecular layer, the heat treatment temperature is selected to be at least 200 ° C. Development of a technique capable of proceeding with the removal of the layer and the subsequent sintering of the metal nanoparticles is desired.

  If the sintered body type conductor layer can be formed from the metal nanoparticles having the surface-coated molecular layer while the heat treatment temperature is suppressed to 200 ° C. or lower, the types of substrate materials that can be used are greatly expanded. Conventionally, due to the problem of heat resistance, a variety of fields that have been used to produce conductive thin film layers using a plating method or the like will open the way to the use of sintered-type conductor layers. .

  The present invention solves the above-mentioned problems, and an object of the present invention is to form a sintered body-type conductor layer on a substrate using a dispersion of fine metal particles having a surface-coated molecular layer. In the step of removing the surface coating molecular layer from the coated metal fine particles having the surface coating molecular layer and then sintering the metal fine particles, the heat treatment temperature used is preferably within a range not exceeding 200 ° C., preferably The object of the present invention is to provide a method that makes it possible to easily and highly reproducibly produce a sintered metal fine particle exhibiting good conductivity in a range of 150 ° C. or lower.

  In order to solve the above problems, the present inventors removed the surface coating molecular layer from the metal fine particles provided with the surface coating molecular layer applied on the substrate and then sintered the metal fine particles. Further examination was made on the factors that determined the heat treatment temperature in the conventional method. As a result of the examination, if metal particles having a clean surface and an average particle diameter of 100 nm or less are brought into close contact and subjected to heat treatment in an inert gas atmosphere, a heating temperature of 200 ° C. or less, for example, 150 ° C. However, it was confirmed that the sintering of the metal fine particles proceeded sufficiently. On the other hand, the process of removing the coating molecular layer from the metal fine particle having the surface coating molecular layer and re-exposing the original clean surface is due to the coordination bond between the coating molecule and the surface metal atom. It was confirmed that the required heating temperature fluctuated depending on the strength of similar intermolecular bonding forces. In order to maintain a stable surface-coated molecular layer in the dispersion, a coating molecule having a high intermolecular bonding force similar to the coordinate bond to the metal atom on the surface of the fine particle is used. For removal, it is necessary to apply higher thermal excitation. Furthermore, in order to suppress the re-adsorption of the coating molecules thermally released from the metal atoms on the surface, a heating temperature at which the transpiration of the coating molecules proceeds has been adopted.

  Based on these findings, the present inventors have conducted further studies. In the dispersion liquid, the present invention shows a high intermolecular bonding force similar to the coordinate bond to the metal atom on the surface of the fine particle, but it is applied on the substrate. After that, when removing the covering molecules, if it becomes possible to greatly reduce the intermolecular bonding force similar to the coordination bond between the covering molecules and the surface metal atoms, the temperature exceeds 250 ° C. It was conceived that the covering molecules could be removed even at a temperature much lower than the conventional heat treatment temperature. Then, after forming a coating layer of metal fine particles having a surface coating molecular layer on the substrate, a negative charge is injected into the metal fine particles from the surface of the coating layer by irradiation of energy rays such as electron beams and ultraviolet rays. Thus, it has been found that the intermolecular bonding force similar to the coordination bond between the coating molecule and the surface metal atom can be greatly reduced. At the same time, a part of the energy of the irradiated energy beam is locally converted into the intramolecular vibrational energy of the coating molecule and the lattice vibrational energy of the metal fine particles. It was also confirmed that the release / removal of water progressed. The penetration depth of energy beams such as electron beams and ultraviolet rays is significantly shallower than the coating thickness of the metal fine particle coating layer. However, if the coating layer thickness is relatively thin, the surface of the metal fine particles has a negative charge. Is injected stepwise, the injected charge is diffused and propagated to the lower metal fine particles, and this effect extends to the entire coating layer thickness. Accordingly, not only the surface portion but also the deep portion of the thin coating layer, although there is a difference in degree, a substantial portion of the covering molecular layer that has protected the surface of the metal fine particles is removed.

  When a considerable portion of the covering molecular layer that has protected the surface is removed, the remaining surface is removed by heating to a temperature of less than 200 ° C., for example, 150 ° C. Low temperature sintering proceeds from the part where the formed metal fine particles are in direct contact with each other. Finally, the low-temperature sintering of the metal fine particles expands and expands over the entire thickness of the coating layer, including the deep portion of the thin coating layer, and the formation of the dense metal fine particle sintered body layer is completed. In addition, the obtained metal fine particle sintered body is a metal fine particle sintered body layer having good conductivity comparable to that of the metal fine particle sintered body conventionally formed by heat treatment at 250 ° C. or higher. It was also confirmed that The present invention has been completed based on these findings.

That is, the method for forming a metal fine particle sintered body type thin film conductor layer according to the present invention is
A method of forming a metal fine particle sintered body type thin film conductor layer on a substrate,
The metal fine particles used for the production of the metal fine particle sintered body are metal fine particles having an average particle diameter of 1 to 100 nm composed of a metal material having a melting point of at least 200 ° C.,
A liquid phase dispersion medium comprising an organic solvent, wherein a coating molecular layer of a dispersant having a function of preventing aggregation between metal fine particles is provided on the surface of the metal fine particles, and the metal fine particles having the coating molecular layer are used as a dispersoid. Using metal fine particle dispersion liquid dispersed in,
Applying the metal fine particle dispersion at a predetermined thickness on the substrate to form a metal fine particle dispersion coating film layer; and
A step of evaporating the organic solvent contained in the metal fine particle dispersion coating film layer to obtain a dried metal fine particle coating layer;
A process of irradiating the dried metal fine particle coating layer with a predetermined dose of energy rays from the coating layer surface;
The metal fine particle coating layer that has been subjected to the energy beam irradiation treatment comprises a step of performing a low temperature heat treatment at a heating temperature selected in a temperature range not exceeding 50 ° C. and at least not exceeding 200 ° C. in a non-oxidizing gas atmosphere,
By performing the energy beam irradiation treatment and the low-temperature heat treatment, the metal fine particles contained in the metal fine particle coating layer are sintered with each other, and a metal fine particle sintered body type thin film conductor layer is formed. This is a method for forming a metal fine particle sintered body type thin film conductor layer.

that time,
The metal material constituting the metal fine particles and having a melting point exceeding 200 ° C. is at least
A single metal species selected from the group of metal elements consisting of gold, silver, copper, platinum, palladium, rhodium, ruthenium, nickel, and aluminum, or an alloy composed of two or more metal species is preferable. The average particle size of the metal fine particles is more preferably selected in the range of 5 to 20 nm.

In addition, the coating molecular layer of the dispersant, which is provided on the surface of the metal fine particles and has a function of preventing aggregation between the metal fine particles,
As the dispersant,
The boiling point is in the range of 150 ° C. or higher and 350 ° C. or lower,
It is preferably formed using one type of dispersant molecule or two or more types of dispersant molecules selected from the group consisting of amines, alcohols, phenols, and thiols.

on the other hand,
As energy rays used for the energy ray irradiation treatment,
It is preferable to use an electron beam whose acceleration voltage is selected in the range of 50 kV to 200 kV, or an ultraviolet ray selected from the wavelength range of 180 nm to 400 nm.

Moreover, the heating temperature used for the low-temperature heat treatment is
It is desirable to select a temperature range of 50 ° C to 150 ° C.

In the method of forming a metal fine particle sintered body type thin film conductor layer according to the present invention,
In the liquid phase dispersion medium containing the organic solvent,
Along with the irradiation of energy rays used for the energy ray irradiation treatment, an acid generator compound having a function of generating an acid component is added,
The acid generator compound can be contained in the dried metal fine particle coating layer. At that time, as an acid generator compound having a function of generating an acid component with the irradiation of the energy beam,
It is preferable to use one type of compound or two or more types of compounds selected from the group of acid generator compounds consisting of an onium compound, a sulfone compound, a halide, and an iron allene complex having acid generating ability.

Furthermore, in the liquid phase dispersion medium containing the organic solvent,
Along with irradiation of energy rays used for the energy ray irradiation treatment, a radical generator compound having a function of generating radical species is added,
The radical generator compound can be contained in the dried metal fine particle coating layer.

In some cases, in the liquid phase dispersion medium containing the organic solvent,
Along with the irradiation of energy rays used for the energy ray irradiation treatment, a radical generator compound having a function of generating radical species, or an acid generator compound having a function of generating an acid component is added,
In the dried metal fine particle coating layer, the radical generator compound or the acid generator compound is contained,
Further, in response to the irradiation of the energy beam used for the energy beam irradiation treatment, the energy of the irradiated energy beam is received, and the received energy is transmitted to the radical generator compound or the acid generator compound. And adding a sensitizer compound that enables the radical generator compound or the acid generator compound to function,
The sensitizer compound may be contained in the dried metal fine particle coating layer.

In addition, in the liquid phase dispersion medium containing the organic solvent,
When the energy ray irradiation treatment or the low-temperature heat treatment is performed, a binder resin component that can be polymerized and cured is added,
The binder resin component can be contained in the dried metal fine particle coating layer. At that time, when the energy ray irradiation treatment or the low temperature heat treatment is performed, as a binder resin component capable of being polymerized and cured,
It is also possible to use an energy ray curable binder resin component that exhibits polymerization curing activity due to the energy ray irradiation used for the energy ray irradiation treatment.

Moreover, when a binder resin component is added,
By performing the energy beam irradiation treatment and the low-temperature heat treatment, polymerization hardening of the binder resin component contained in the metal fine particle coating layer and sintering of the metal fine particles contained in the metal fine particle coating layer are performed. ,
This is a method for forming a metal fine particle sintered body type thin film conductor layer comprising the polymerized and cured binder resin and the metal fine particle sintered body.

In addition, in the liquid phase dispersion medium containing the organic solvent,
Add an adhesion improver, which has the function of improving the adhesion of the metal fine particle sintered body layer to the surface of the substrate,
The adhesion improver may be contained in the dried metal fine particle coating layer.

Further, the present invention provides an invention of a method for forming a conductive metal thin film or metal wiring, or an invention of a wiring circuit board, which utilizes the method for forming a metal fine particle sintered thin film conductor layer according to the present invention described above. Also offers
That is, the method for forming a conductive metal thin film or metal wiring according to the present invention is as follows.
A method of forming a conductive metal thin film or metal wiring on a substrate,
The conductive metal thin film or metal wiring is formed using a metal fine particle sintered body type thin film conductor layer,
The step of forming the metal fine particle sintered body type thin film conductor layer on the substrate includes:
A method for forming a conductive metal thin film or metal wiring, characterized in that it is carried out using the method for forming a metal fine particle sintered compact type thin film conductor layer according to the present invention having any one of the above-described configurations. .

The invention of the printed circuit board according to the present invention is as follows:
A wiring circuit board in which a wiring circuit pattern made of a conductive metal thin film or metal wiring is formed on the substrate surface,
The wiring circuit pattern formed of the conductive metal thin film or metal wiring formed on the substrate surface is
It is formed using a metal fine particle sintered body type thin film conductor layer,
The metal fine particle sintered body type thin film conductor layer on the substrate is:
A metal fine particle sintered body type thin film conductor layer formed by using the method of forming a metal fine particle sintered body type thin film conductor layer according to the present invention having any one of the above-described configurations. , A printed circuit board.

  The film thickness of the metal fine particle sintered body type thin film conductor layer formed in the embodiment of the present invention is in the range of 0.1 μm to 30 μm, more preferably in the range of 0.5 μm to 20 μm, and still more preferably. It is desirable to select in the range of 0.5 μm to 5 μm.

  In the method of forming a metal fine particle sintered body type thin film conductor layer according to the present invention, taking advantage of high drawing accuracy based on a metal fine particle dispersion using metal nanoparticles of a single metal or an alloy such as gold, silver, and copper, A coating layer of fine metal particles having a fine pattern is formed. In addition, the step of removing the coating molecular layer of the dispersant provided on the surface of the metal fine particles for the purpose of preventing the mutual aggregation of the metal fine particles in the dispersion and performing the sintering of the metal fine particles is applied. Even if the heat treatment temperature is selected to be 200 ° C. or less by performing heat treatment from the surface of the layer after irradiation of energy rays such as electron beams and ultraviolet rays, or simultaneously with the irradiation, It is possible to form a metal fine particle sintered body layer having good conductivity and no inferiority. The effect of reducing the heat treatment temperature due to the irradiation of energy beams such as electron beams and ultraviolet rays is due to the heat resistance of the substrate material used as the base material when the metal fine particle sintered body type thin film conductor layer is produced. The restrictions are greatly relaxed.

  Conventionally, in order to conduct a coating film in a method of forming a conductive metal thin film or metal wiring using metal fine particles, a method by heating has been widely performed. However, a heating temperature of 200 ° C. or higher is required to fuse metal fine particles to each other to produce a low-resistance conductive metal thin film or metal wiring. Therefore, it is difficult to produce a conductive metal thin film or metal wiring using metal fine particles on a substrate such as plastic or paper having poor heat resistance, and the conductive metal thin film or metal wiring using a metal fine particle dispersion is difficult. The forming method could not be used in a wide range of applications. Therefore, the method for forming a metal fine particle sintered body type thin film conductor layer according to the present invention is a conductive metal thin film using a metal fine particle dispersion in a temperature range that can be sufficiently applied to a substrate having poor heat resistance. A method for manufacturing metal wiring is provided. For example, when the method of the present invention is applied, a target drawing pattern is formed on a substrate surface using a metal fine particle dispersion in which metal fine particles of a metal or alloy such as gold, silver, copper, etc. are stably dispersed in a dispersion medium. After applying and drawing directly, by using energy ray irradiation, sintering is performed at a temperature of 50 ° C. to 150 ° C. which does not affect the electronic component, and a good metal thin film is obtained. This advantage can provide further miniaturization of an antenna circuit such as a multilayer wiring board or an IC card, and can improve productivity. In addition, after forming a conventional metal thin film, etching to a desired fine pattern, or using a plating mask of the desired fine pattern, compared to a method of forming a metal thin film by plating, etc. Also from the viewpoint of treatment of waste liquid generated in these processes, it can contribute to reducing the environmental load.

  In the method of forming a metal fine particle sintered body type thin film conductor layer according to the present invention, it is possible for a base material used for a substrate on which the thin film conductor layer is formed or an electronic component already mounted on the substrate. In order to suppress the progress of the material deterioration accompanying the heat treatment and the influence on the performance of electronic components as much as possible, the heat treatment required for forming the metal fine particle sintered body is preferably performed in a temperature range of 50 ° C. to 150 ° C. Yes. Therefore, in the conventional process of removing the surface coating molecular layer of metal fine particles that requires heating at 250 ° C. or higher, and thereafter sintering the metal fine particles themselves, sintering is performed by low-temperature heat treatment at 150 ° C. or lower. In order to proceed, the following means are used.

First, in the method for forming a metal fine particle sintered body type thin film conductor layer according to the present invention,
(1) A step of applying a metal fine particle dispersion on a substrate,
Irradiating energy rays to a layer of fine metal particles applied on a substrate;
Then, through a step of firing the applied metal fine particle layer by low-temperature heat treatment, a metal fine particle sintered body type thin film conductor layer that can be used for a conductive metal thin film or metal wiring is produced.
(2) Since it is used for a conductive metal thin film or a metal wiring, the metal species of the metal fine particles used for the structure of the sintered body is selected from gold, silver, copper, platinum, palladium, rhodium, ruthenium, nickel, and aluminum. By using one kind or two or more kinds of these alloys, a metal fine particle sintered body type thin film conductor layer made of a metal material having excellent conductivity is prepared.
(3) Since the applied metal fine particle layer is fired by a low-temperature heat treatment at 150 ° C. or lower, the metal fine particles having an average particle diameter of 1 to 100 nm are used.
(4) An electron beam or ultraviolet irradiation is used as an energy beam applied to the metal fine particle layer applied on the substrate. Therefore, a high irradiation position where energy beam irradiation is selectively performed on the surface of the metal fine particle layer applied on the substrate and energy beam irradiation is not performed on the other substrate surface. Selectivity is obtained.
(5) A layer of metal fine particles that has been irradiated with energy rays by irradiating a layer of metal fine particles applied on the substrate with energy rays, for example, electron beams or ultraviolet rays, and heating to 50 to 150 ° C. Then, the sintering of the metal fine particles proceeds, and it becomes possible to produce a conductive metal thin film or metal wiring having a desired fine pattern.
(6) A compound that generates an acid component by energy ray irradiation is added to the metal fine particle dispersion, and the acid component is generated when the surface of the metal fine particle layer coated on the substrate is irradiated with energy beam. Thus, the removal of the dispersant covering the surface of the metal fine particles is promoted.

  As described above, as a means for removing the dispersant covering the surface of the metal fine particles, which has been used for the purpose of maintaining the dispersibility of the metal fine particles in the dispersion, heating at a temperature of 250 ° C. or higher has been conventionally performed. It took advantage of the thermal activation and withdrawal process. On the other hand, in the method for forming a metal fine particle sintered body type thin film conductor layer according to the present invention, the surface of the metal fine particles is coated by irradiating the applied metal fine particle layer with an energy beam such as an electron beam or an ultraviolet ray. In addition to directly bringing the dispersing agent into an “activated” state in which vibrational excitation has been performed, the bonding force with the metal atom is also reduced, and the phenomenon that desorption is likely to occur is utilized. The phenomenon in which the bond strength between the dispersant molecule and the metal atom is further reduced is that the bond between the metal atom and the dispersant molecule forms a coordinate bond with the metal element, such as nitrogen, oxygen, or This is derived from the use of a group having a lone pair of electrons on a sulfur atom.

  For example, when a molecular species having a positive charge approaches the dispersant molecule, the lone electron pair on the nitrogen, oxygen, or sulfur atom of the dispersant molecule is utilized to Complex formation is likely to occur. At that time, the binding force between the dispersant molecule and the metal atom is reduced. In addition, when a negative charge is imparted to the metal fine particles, the coordination between the metal atom and the dispersant molecule using the lone electron pair on the nitrogen, oxygen, or sulfur atom that the dispersant molecule has. The binding force is greatly reduced.

  In addition, when the dispersant covering the surface of the metal fine particles is directly in the “activated” state in which vibration excitation is performed, the dissociation process is performed in the same manner as in the case where vibration excitation is performed by thermal “activation”. Is promoted. In addition, when the coated dispersant is removed, the surface of the metal fine particles themselves is activated when irradiated with energy rays, and the phenomenon that the metal fine particles are likely to be fused with each other, The inventors have also found out.

In addition, the surface of the metal fine particle is protected by a coating dispersant, and the presence of an oxide film is usually suppressed on the surface. Even if an oxide film is present on a part of the surface of the metal fine particle, for example, even if an oxide film of silver oxide (AgO) is present on the surface of the silver nanoparticle, when heated to about 100 ° C. under reduced pressure, Silver oxide (AgO) decomposes into metallic silver and oxygen molecules. Alternatively, when a compound having an alcoholic hydroxyl group is present in the system, aldehyde-type -CH ₂ (OH), -CH (OH)-is utilized as a oxidant for silver oxide (AgO). Converted to CHO, ketone type -CO-. On the other hand, a silver oxide (AgO) type oxide film on the surface is reduced to metal Ag. This reaction is also generally promoted when a metal oxide film, for example, silver oxide (AgO), functions as a semiconductor and photocarriers are generated or electrons are injected into the metal oxide film upon excitation with ultraviolet light. The

  Each of these processes is promoted by irradiating the metal fine particle layer coated on the substrate with an energy ray, for example, an electron beam or an ultraviolet ray, and heated to 50 to 150 ° C. A sintered body of fine particles (nanoparticles) can be formed.

  Hereinafter, the present invention will be described in more detail. At that time, for convenience of explanation, the description using the embodiment using “silver nanoparticles having an average particle diameter of 8 nm” as the metal fine particles is included, but the present invention naturally includes the silver. It is not limited to the form using nanoparticles.

[Metal fine particle dispersion]
In the present invention, the metal fine particles are sintered with each other by the low-temperature heat treatment, and the metal fine particle sintered body type thin film conductor layer is formed.

  Therefore, the metal fine particles to be used are metal fine particles having an average particle diameter in the range of 1 to 100 nm, which are sintered with each other by low-temperature heat treatment. In addition, the metal fine particle sintered body type thin film conductor layer to be formed constitutes metal fine particles for use in forming a wiring circuit pattern made of a conductive metal thin film or metal wiring on the surface of the wiring circuit board. It is desirable that the metal material itself does not melt at the temperature at which solder bonding is performed. Therefore, it is desirable to use metal fine particles composed of a metal material having a melting point exceeding 200 ° C. For example, a single metal species selected from the group of metal elements consisting of gold, silver, copper, platinum, palladium, rhodium, ruthenium, nickel, and aluminum, or an alloy consisting of two or more metal species is preferable. .

  As the conditions for performing the sintering between the metal fine particles, a heating temperature selected in a temperature range of 50 ° C. or higher and at least not exceeding 200 ° C., and a low-temperature heat treatment in a non-oxidizing gas atmosphere are used. At that time, the heating temperature is more preferably in the range of 50 ° C to 150 ° C. In order to complete the sintering between metal fine particles having an average particle size of nano size within a practical time after the heating temperature is in the range of 50 ° C. to 150 ° C., the metal fine particles It is desirable to select an average particle size of 20 nm or less.

  The non-oxidizing gas used in the low-temperature heat treatment is not limited as long as it does not cause oxidation of the metal constituting the metal fine particles. Examples of the non-oxidizing gas that can be suitably used include argon gas, helium gas, neon gas, nitrogen gas, nitrogen / hydrogen mixed gas, and carbon dioxide gas. The metal fine particle coating layer that has been subjected to the energy beam irradiation treatment has a high surface activity, and when subjected to a heat treatment at 50 ° C. or higher in the presence of an oxidizing gas such as oxygen molecules, the surface is oxidized. Therefore, the presence of an oxidizing gas in the atmosphere during the low-temperature heat treatment is inappropriate.

  On the other hand, if the average particle diameter of the metal fine particles used is excessively small relative to the thickness of the metal fine particle sintered thin film conductor layer to be produced, the conductivity of the resulting sintered thin film conductor layer is increased. In general, it is not preferable. For example, when the film thickness of the metal fine particle sintered body type thin film conductor layer to be produced is in the range of 0.5 μm to 2 μm, the average particle diameter of the metal fine particles used is at least the film thickness of the thin film conductor layer. It is desirable to select in the range of about 1/100 to 1/500 or more. In other words, the average particle diameter of the metal fine particles to be used is preferably selected in the range of 5 nm or more. Therefore, from a practical viewpoint, the average particle diameter of the metal fine particles to be used is more preferably selected in the range of 5 to 20 nm.

  The metal fine particles include an organic solvent in the form of a metal fine particle having a coating molecular layer provided with a coating molecular layer of a dispersant having a function of preventing aggregation between the metal fine particles on the surface of the metal fine particle. It is dispersed in a liquid phase dispersion medium. According to the film thickness of the thin film conductor layer to be formed and its shape pattern, the metal fine particle dispersion is applied to the substrate surface to form a metal fine particle dispersion coating film layer. Various means such as ink jet, screen printing, dispenser, impregnation, and spin coating are used as means for applying, pattern drawing, and printing of the metal fine particle dispersion.

  It is necessary to appropriately adjust the liquid viscosity of the metal fine particle dispersion in accordance with the application / pattern drawing / printing means to be used. For example, when screen printing is used for drawing a fine coating pattern, it is desirable to select the liquid viscosity of the metal fine particle dispersion in the range of 30 to 300 Pa · s (25 ° C.).

  Moreover, when using offset and resin letterpress printing, it is desirable to select the liquid viscosity in the range of 10 to 500 Pa · s (25 ° C.). When using flexographic printing, it is desirable to select the liquid viscosity in the range of 100 to 5000 mPa · s (25 ° C.). When using gravure printing, it is desirable to select the liquid viscosity in the range of 1 to 100 mPa · s (25 ° C.).

  When using inkjet printing, it is desirable to select the liquid viscosity in the range of 1 to 100 mPa · s (25 ° C.). The liquid viscosity of the metal fine particle dispersion is determined depending on the average particle diameter of the metal fine particles to be used, the dispersion concentration, the dispersion medium being used, for example, the type of the organic solvent (dilution solvent) contained, and the above three types of factors are determined. It can be appropriately selected and adjusted to the target liquid viscosity.

[Dispersant coating molecular layer]
In the metal fine particle dispersion used in the present invention, the dispersoid metal fine particles are provided with a coating molecular layer of a dispersant having a function of preventing aggregation of metal fine particles on the surface of the metal fine particles. It is dispersed in a liquid phase dispersion medium containing an organic solvent in the form of metal fine particles having a layer.

  The coating molecular layer of the dispersant having a function of preventing mutual aggregation of the metal fine particles can be coordinated to the metal atoms exposed on the surface of the metal material constituting the metal fine particles. Organic compounds are used.

  The organic compound used for the dense coating molecular layer on the surface of the metal fine particle uses a group having a lone electron pair on a nitrogen, oxygen, or sulfur atom when forming a coordinate bond with the metal element. For example, an amino group is mentioned as a group containing a nitrogen atom. Examples of the group containing a sulfur atom include a sulfanyl group (—SH) and a sulfide type sulfanediyl group (—S—). Examples of the group containing an oxygen atom include a hydroxy group and an ether type oxy group (—O—).

  Typical examples of the compound having an amino group that can be used include amine compounds such as alkylamines and diamines. In addition, it is preferable that the amine compound does not desorb in a normal storage environment, specifically, in a range not reaching 40 ° C. in a state in which a coordinate bond is formed with the metal element. Moreover, alkanethiol, alkanedithiol, etc. can be mentioned as a representative of the compound which has sulfanyl group (-SH) which can be utilized. In addition, such alkanethiol and alkanedithiol are preferably those that do not desorb in a normal storage environment, specifically in a range not reaching 40 ° C., in a state in which a coordinate bond is formed with the metal element. . Furthermore, alkanediol can be mentioned as a representative of the compound which has a hydroxyl group which can be utilized. In addition, it is preferable that the alkanediol is not desorbed in a state in which a coordinate bond is formed with the metal element and in a normal storage environment, specifically, in a range not reaching 40 ° C.

  Prior to the low-temperature heating process in which the sintering of the metal fine particles proceeds, the organic compound used as the dispersant is released from the surface of the metal fine particles or is slightly heated by applying energy beam irradiation. It is possible to leave. Thereafter, in the low-temperature heating process, an organic compound that can be transpired and removed after being detached from the surface of the metal fine particles can be suitably used. Accordingly, the coating molecular layer on the surface of the metal fine particles has a boiling point in the range of 150 ° C. or higher and 350 ° C. or lower as the dispersant, and is selected from the group consisting of amines, alcohols, phenols, and thiols. It is preferable to form using one type of dispersant molecule or two or more types of dispersant molecules.

For example, when silver nanoparticles are used as the metal fine particles, amine compounds such as 2-methylaminoethanol, diethanolamine, butoxypropylamine, diethylmethylamine, 2-dimethylaminoethanol, methyldiethanolamine, alkylamines, ethylenediamine, etc. ,
Alkyl alcohols, ethylene glycol, propylene glycol,
Alkyl thiols, alicyclic thiols such as cyclohexyl thiol, ethanedithiol and the like can be suitably used.

  These molecular layers covering the surfaces of the metal fine particles have a function of preventing the metal fine particles from directly contacting the metal surfaces to cause aggregation of the metal fine particles. In addition, when uniformly dispersed in a liquid phase dispersion medium containing an organic solvent, the function as a dispersant for maintaining the dispersibility in the organic solvent is exhibited by utilizing the alkyl chain and the like.

  On the other hand, the compound capable of coordinating and bonding, which covers the surface of the metal fine particles, is, for example, an energy beam, for example, as an excitation energy source in the presence of a compound that generates an acid component upon excitation by energy beam irradiation. When irradiated with an electron beam or ultraviolet light and further heated to about 50 ° C. to 150 ° C., it is possible to cause a chemical reaction using the generated acid and to remove it.

[Energy beam irradiation source]
In the present invention, an electron beam or ultraviolet rays are mainly used in the energy beam irradiation treatment step.

  When using an electron beam, the acceleration voltage is preferably selected in the range of 50 kV to 200 kV.

  In general, as an electron beam source, an ultra-low acceleration voltage electron beam irradiation apparatus having an acceleration voltage of 100 kV or less, a low acceleration voltage electron beam irradiation apparatus having an acceleration voltage of 100 to 300 kV, a medium acceleration voltage electron beam irradiation apparatus of 300 to 800 kV, and 1000 kV The high acceleration voltage electron beam irradiation apparatus described above is known, and among these, an electron beam source suitable for the selected acceleration voltage is selected. Therefore, an electron beam source that can be used in an acceleration voltage range of 50 kV to 200 kV is either an ultra-low acceleration voltage electron beam irradiation apparatus with an acceleration voltage of 100 kV or less, or a low acceleration voltage electron beam irradiation apparatus with an acceleration voltage of 100 to 300 kV. It is.

  When using ultraviolet irradiation in the energy ray irradiation treatment step, it is generally preferable to use a near ultraviolet region having a wavelength of 180 to 400 nm as the light source. In some cases, in addition to the near-ultraviolet region, visible light (wavelength 400 to 500 nm) in the blue and violet regions can be used in combination.

  Examples of the light source of near ultraviolet light having a wavelength of 180 to 400 nm and visible light (wavelength 400 to 500 nm) in the blue and violet regions are low pressure mercury lamps, high pressure mercury lamps, ultrahigh pressure mercury lamps, metal halides. Examples include lamps, chemical lamps, black light lamps, mercury-xenon lamps, excimer lamps, short arc lamps, helium-cadmium lasers, argon lasers, excimer lasers, and UV electrodeless lamps. For example, the atomic beam of mercury shows emission lines at 184.9 nm, 253.7 nm, 365.0 nm, and 435.8 nm.

  The acid generator compound, radical generator compound, and sensitizer compound exemplified below have an aromatic ring, and when these are added, the irradiated ultraviolet rays in the near ultraviolet region are temporarily irradiated with these compounds. To be absorbed. Thereafter, for example, energy transfer can be caused to the coating molecule of the dispersant, and excitation of the intramolecular vibration can be caused. It is also possible to cause energy transfer to the lattice vibration on the surface of the metal fine particles.

In addition, when absorption of ultraviolet rays in the near ultraviolet region occurs with respect to the acid generator compound and radical generator compound, there is an effect that negative charges are injected into the metal fine particles indirectly by electron transfer. Alternatively, protons (H ⁺ ) are indirectly donated to the coating molecules of the dispersant, and the coating molecules that receive the donation of protons (H ⁺ ) have a positive charge as a whole. In any case, the intermolecular bonding force similar to the coordinate bond of the covering molecule to the metal atom on the surface of the metal fine particle can be greatly reduced. As a result, by utilizing the effect of causing energy transfer from the acid generator compound and radical generator compound to the coating molecules of the dispersant and causing excitation of the intramolecular vibration, The withdrawal is promoted.

  The penetration depth of energy beams such as electron beams and ultraviolet rays is significantly shallower than the coating thickness of the metal fine particle coating layer. However, if the coating layer thickness is relatively thin, the surface of the metal fine particles has a negative charge. Is injected stepwise, the injected charge is diffused and propagated to the lower metal fine particles, and this effect extends to the entire coating layer thickness. Therefore, not only the surface portion but also the deep portion of the thin coating layer, although there is a difference in degree, an effect of removing a substantial portion of the covering molecular layer that protects the surface of the metal fine particles can be obtained.

  Therefore, in the present invention, when ultraviolet irradiation is used in the energy beam irradiation treatment step, the irradiated ultraviolet rays are effectively absorbed, and then, in the energy transfer process, with respect to the coating molecules of the dispersant, It is preferable to add an acid generator compound, a radical generator compound, and further a sensitizer compound capable of causing excitation of vibration. The acid generator compound, radical generator compound, and further sensitizer compound are added to the metal fine particle dispersion to form metal fine particles having a surface coating molecular layer in the dried metal fine particle coating layer. On the other hand, it is a form distributed uniformly around it.

  In addition, when using ultraviolet irradiation in an energy-beam irradiation process process, utilization of the acid generator compound which can absorb this ultraviolet rays directly and can generate | occur | produce an acid is desirable. However, the amount of the acid generator compound added is limited, for example, the solubility in the dispersion medium. Instead of suppressing the addition amount of the acid generator compound itself, a sensitizer compound capable of donating absorbed energy is added to the acid generator compound to substantially improve the amount of absorption of ultraviolet rays. You can also In addition, some photoradical generator compounds also exhibit this kind of photosensitization effect, and the photoradical generator compound is added to the acid generator compound to substantially reduce the amount of absorption of ultraviolet rays. It can also be improved.

[Acid generator compound]
In the present invention, as a compound that generates an acid upon irradiation with an energy beam, for example, an acid generator compound used in a chemically amplified photoresist or photocationic polymerization is used (edited by Organic Electronics Materials Research Group, “Imaging”). Organic Materials ", Bunshin Publishing (1993), pages 187-192). In particular, when ultraviolet rays are used, it is preferable to use a compound that directly absorbs the ultraviolet rays and generates an acid.

  Examples of the acid generator compound that can be suitably used in the present invention are shown below.

First, B (C ₆ F ₅ ) ₄ ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ and CF ₃ SO ₃ ⁻ salts of aromatic onium compounds such as diazonium, ammonium, iodonium, sulfonium and phosphonium are listed. be able to. Those having a borate compound as the counter anion are preferred because of their high acid generation ability. On the other hand, as an onium compound, in addition to bis (alkyl (C = 10-14) phenyl) iodonium hexafluorophosphate, 4-methylphenyl [4- (1methylethyl) phenyl] iodonium tetrakis (pentafluorophenyl) borate, The onium compounds exemplified below can be suitably used.

  Secondly, sulfonated products that generate sulfonic acid can be mentioned. An example of a specific compound is illustrated below.

  Thirdly, a halide that generates hydrogen halide can also be used. Examples of specific compounds are shown below.

  Fourthly, iron allene complexes as exemplified below can be mentioned.

  The acid generator compound to be used is desirably used in an added amount that increases the utilization efficiency with respect to energy rays, particularly ultraviolet rays, which are irradiated onto the surface of the dried metal fine particle coating layer. Therefore, when preparing the metal fine particle dispersion, as a raw material for the metal fine particles, for example, a raw material silver nanoparticle dispersion containing 30 to 80 parts by mass of silver nanoparticles in 100 parts by mass of the silver nanoparticle dispersion It is preferable to add an acid generator compound to this raw material silver nanoparticle dispersion at an addition ratio exemplified below. For example, the addition amount of the acid generator compound is in the range of 0.1 to 100 parts by weight, preferably in the range of 0.5 to 30 parts by weight, more preferably in the range of 0.1 to 100 parts by weight per 100 parts by weight of the raw silver nanoparticle dispersion. It is desirable to select in the range of 5 to 10 parts by mass, more preferably in the range of 1 to 10 parts by mass. In addition, when used as a metal fine particle raw material, for example, when the addition amount of the acid generator compound is selected to be 0.1 parts by mass or less per 100 parts by mass of the raw material silver nanoparticle dispersion, energy rays, The effect (function) of supplying an acid into the system using ultraviolet rays is poor. On the other hand, when used as a metal fine particle raw material, for example, when the addition amount of the acid generator compound per 100 parts by mass of the raw silver nanoparticle dispersion is selected to be 100 parts by mass or more, it is a factor that inhibits the sintering of the metal fine particles. Become. For example, as a result of hindering the reduction (shrinkage) of the bulk volume associated with the sintering of metal fine particles, a dense metal fine particle sintered body is not achieved, which hinders achievement of good conductivity.

[Photoradical generator (photoradical polymerization initiator)]
Examples of usable photoradical generator compounds in the present invention are shown below. Here, the photoradical generator can be roughly classified into a photocleavage type and a hydrogen abstraction type.

Examples of photocleavable radical generators include benzoins such as benzoin, benzoin methyl ether, benzoin isopropyl ether, α-acryl benzoin,
Benzyl, 2-methyl-2-morpholino (4-thiomethylphenyl) propan-1-one (Irgacure 907: manufactured by Ciba Specialty Chemicals), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl)- 1-butanone (Irgacure 369: Ciba Specialty Chemicals), benzylmethyl ketal (Irgacure 651: Ciba Specialty Chemicals), 1-hydroxycyclohexyl phenyl ketone (Irgacure 184: Ciba Specialty Chemicals), 2-hydroxy-2 -Methyl-1-phenylpropan-1-one (Darocur 1173: manufactured by Merck), 1- (4-Isopropylphenyl) -2-hydroxy-2-methylpropan-1-one (Darocur 1116: manufactured by Merck), 4- 2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone, 4- (2-acryloyl-oxyethoxy) phenyl-2-hydroxy-2-propylketone, diethoxyacetophenone (ZLI3331: manufactured by Ciba Specialty Chemicals) ), Esacure KIP100 (manufactured by Ramberty), Lucillin TPO (manufactured by BASF), bis (2,6-dimethoxybenzoyl) -2,4,4-trimethyl-pentylphosphine oxide (BAPO1: manufactured by Ciba Specialty Chemicals), Examples include bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide (BAPO2: manufactured by Ciba Specialty Chemicals), BTTB (manufactured by NOF Corporation), CGI1700 (manufactured by Ciba Specialty Chemicals) It is.

Examples of hydrogen abstraction type photo radical generators include benzophenone, p-methylbenzophenone, p-chlorobenzophenone, tetrachlorobenzophenone, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, 4-benzoyl-4'-methyl-diphenyl Aryl ketone initiators such as sulfide, 2-isopropylthioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, acetophenone,
Dialkylaminoaryl ketone initiators such as 4,4′-bis (diethylamino) benzophenone, 4,4′-bis (dimethylamino) benzophenone, isoamyl p-dimethylaminobenzoate, p-dimethylaminoacetophenone,
Examples thereof include thioxanthone, xanthone-based, and halogen-substituted polycyclic carbonyl-based initiators.

  It should be noted that the photo radical generator compounds roughly divided into photo-cleavage type and hydrogen abstraction type are compounds that belong to each type, and those that do not cause interference with each other can be used. , Can be used in combination.

[Sensitizer compounds]
Further, examples of the sensitizer compound used together with the acid generator compound and the radical generator compound include compounds such as anthracene. As the sensitizer compound to be used, a compound capable of effectively absorbing light at the wavelength of irradiated light is used, and is not limited to the anthracene exemplified here.

  The first function of the sensitizer compound to be used is to increase its utilization efficiency with respect to energy rays, particularly ultraviolet rays, which are irradiated onto the surface of the dried metal fine particle coating layer. Therefore, when preparing the metal fine particle dispersion, as a raw material for the metal fine particles, for example, a raw material silver nanoparticle dispersion containing 30 to 80 parts by mass of silver nanoparticles in 100 parts by mass of the silver nanoparticle dispersion It is preferable to add a sensitizer compound in the raw material silver nanoparticle dispersion at an addition ratio exemplified below. For example, the addition amount of the sensitizer compound per 100 parts by mass of the raw silver nanoparticle dispersion is in the range of 0.1 to 100 parts by mass, preferably in the range of 0.5 to 30 parts by mass, and more preferably in the range of 0.0. It is desirable to select in the range of 5 to 10 parts by mass, more preferably in the range of 1 to 10 parts by mass. In addition, when used as metal fine particles, for example, when the addition amount of the sensitizer compound is selected to be 0.1 parts by mass or less per 100 parts by mass of the raw silver nanoparticle dispersion liquid, in many cases, energy rays, particularly ultraviolet rays On the other hand, the effect (function) of increasing the utilization efficiency is poor. On the other hand, for example, when the addition amount of the sensitizer compound is selected to be 100 parts by mass or more per 100 parts by mass of the raw material silver nanoparticle dispersion used as the metal fine particles, it also becomes a factor that inhibits the sintering of the metal fine particles. . For example, as a result of hindering the reduction (shrinkage) of the bulk volume associated with the sintering of metal fine particles, a dense metal fine particle sintered body is not achieved, which hinders achievement of good conductivity.

[Binder resin component]
In the method for forming a metal fine particle sintered body type thin film conductor layer according to the present invention, a binder resin between the metal fine particle sintered body layer and the substrate surface, or the inside of the metal fine particle sintered body layer, if necessary. As a binder resin that fills the gap and connects the entire sintered metal fine particle layer, the binder resin component to be used can be added to the fine metal particle dispersion. This binder resin component is added to the liquid phase component constituting the dispersion medium in the metal fine particle dispersion. Accordingly, a binder resin component itself that exhibits fluidity at room temperature (20 ° C.) and that can be uniformly mixed and dissolved in an organic solvent (dispersion solvent) contained in the dispersion medium is used.

  Accordingly, in the present invention, if necessary, the binder resin is cured by applying an energy ray irradiation treatment and a low-temperature heat treatment to a metal fine particle dispersion, for example, a paste-like dispersion containing silver nanoparticles. A binder resin component that functions as: As the binder resin component added for this purpose, an active energy ray-curable binder as exemplified below, or a compound that develops known photocationic polymerization can be suitably used. On the other hand, when an active energy ray-curable binder or a compound that develops a known photocationic polymerization is added as a binder resin component, at the same time, an acid generator compound, a radical generator compound, and further a sensitizer. By adding a compound, it is also possible to induce a polymerization reaction of these binder resin components by energy beam irradiation treatment.

  The active energy ray-curable binder is a non-reactive resin (innert resin) having a softening point of 50 to 180 ° C. represented by diallyl phthalate resin, or a reactive (radical polymerizable) oligomer, a radical polymerizable monomer, as required. Accordingly, it comprises a radical polymerization initiator, a photosensitizer, a pigment as necessary, and various additives.

  Examples of the non-reactive resin (innert resin) include ortho to isotype diallyl phthalate resins. Examples of the reactive (radical polymerizable) oligomer include alkyd acrylate, polyester acrylate, epoxy acrylate, and urethane-modified acrylate.

  As the radical polymerizable monomer, various (meth) acrylic monomers or acrylic oligomers having an ethylenically unsaturated double bond can be used. Among various (meth) acrylic monomers and oligomers having an ethylenically unsaturated double bond, the following can be exemplified as typical monofunctional monomers. First, alkyl (selected in the range of 1 to 18 carbon atoms) (meth) acrylate, such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) ) Acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate. In addition, alkylphenol ethylene oxide adducts such as benzyl (meth) acrylate, butylphenol, octylphenol or nonylphenol or dodecylphenol (meth) acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, tricyclodecane monomethylol (meth) An acrylate etc. are also illustrated.

Furthermore, the following can be illustrated as a typical bifunctional monomer. First, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate , Tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, butylene glycol di (meth) acrylate, pentyl glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, hydroxypivalyl hydroxypivalate di (Meth) acrylate (commonly called Manda), hydroxypivalyl hydroxypivalate dicaprolactonate di (meth) acrylate, 1,6- Hexanediol di (meth) acrylate over preparative, 1,2-hexanediol di (meth) acrylate, 1,5-hexanediol di (meth) acrylate, 2,5-hexanediol di (meth) acrylate, 1,7 Heptanediol di (meth) acrylate, 1,8-octanediol di (meth) acrylate, 1,2-octanediol di (meth) acrylate di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, 1 , 2-decanediol di (meth) acrylate, 1,10-decanediol di (meth) acrylate, 1,2-decanediol di (meth) acrylate, 1,12-dodecanediol di (meth) acrylate, 1,2 -Dodecanediol di (meth) acrylate, 1,14-tetradecanediol di (Meth) acrylate, 1,2-tetradecanediol di (meth) acrylate, 1,16-hexadecanediol di (meth) acrylate, 1,2-hexadecanediol di (meth) acrylate, 2-methyl-2,4-pentanediol Di (meth) acrylate, 3-methyl-1,5-pentanediol di (meth) acrylate, 2-methyl-2-propyl-1,3-propanediol di (meth) acrylate, 2,4-dimethyl-2, 4-pentanediol di (meth) acrylate, 2,2-diethyl-1,3-propanediol di (meth) acrylate, 2,2,4-trimethyl-1,3-pentanediol di (meth) acrylate, di Methyloloctane di (meth) acrylate, 2-ethyl-1,3-hexanediol di (meth) Acrylate, 2,5-dimethyl-2,5-hexanediol di (meth) acrylate, 2-methyl-1,8-octanediol di (meth) acrylate, 2-butyl-2-ethyl-1,3-propanediol Di (meth) acrylate, 2,4-diethyl-1,5-pentanediol di (meth) acrylate,
Tricyclodecane dimethylol di (meth) acrylate, tricyclodecane dimethylol dicaprolactonate di (meth) acrylate,
Bisphenol A tetraethylene oxide adduct di (meth) acrylate, bisphenol F tetraethylene oxide adduct di (meth) acrylate, bisphenol S tetraethylene oxide adduct di (meth) acrylate, hydrogenated bisphenol A tetraethylene oxide adduct di ( (Meth) acrylate, hydrogenated bisphenol F tetraethylene oxide adduct di (meth) acrylate, hydrogenated bisphenol A di (meth) acrylate, hydrogenated bisphenol F di (meth) acrylate, bisphenol A tetraethylene oxide adduct dicaprolactonate Examples include di (meth) acrylate, bisphenol F tetraethylene oxide adduct dicaprolactonate di (meth) acrylate, and the like.

Examples of available trifunctional monomers include
Glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane tricaprolactonate tri (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolhexane tri (meth) acrylate, trimethyloloctane Examples include tri (meth) acrylate and pentaerythritol tri (meth) acrylate.

Examples of available tetra- or higher functional monomers include
Pentaerythritol tetra (meth) acrylate, pentaerythritol tetracaprolactonate tetra (meth) acrylate, diglycerin tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, ditrimethylolpropane tetracaprolactonate tetra (meth) Acrylate, ditrimethylolethane tetra (meth) acrylate, ditrimethylolbutanetetra (meth) acrylate, ditrimethylolhexanetetra (meth) acrylate, ditrimethyloloctanetetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol Hexa (meth) acrylate, tripentaerythritol hexa (meth) acrylate, tripentaerythritol Hepta (meth) acrylate, tripentaerythritol octa (meth) acrylate, dipentaerythritol polyalkylene oxide hepta (meth) acrylate and the like.

Furthermore, an alkylene oxide adduct (meth) acrylate monomer of an aliphatic alcohol compound, in particular, an alkylene oxide adduct (meth) acrylate monomer of an aliphatic alcohol compound having a C _{3 to} C ₂₀ alkylene oxide is exemplified.

  The various (meth) acrylate type monomer compounds exemplified above can be used alone or in combination of two or more kinds depending on the intended resin properties. In addition, it is not limited to the (meth) acrylate type monomer compound illustrated above.

  On the other hand, as an example of a compound that causes photocationic polymerization, a photocationically polymerizable monomer can be mentioned. As the excitation light for initiating photocationic polymerization, various known cationically polymerizable monomers that can be used for ultraviolet irradiation can be used. For example, JP-A-6-9714, JP-A-2001-31892, JP-A-2001-40068, JP-A-2001-55507, JP-A-2001-310938, JP-A-2001-310937, Examples thereof include epoxy compounds (aromatic, alicyclic, aliphatic, etc.), vinyl ether compounds, oxetane compounds and the like exemplified in JP-A-2001-220526.

  Some examples of suitable epoxy compounds for the cationic photopolymerizable monomer are shown below.

  Preferred aromatic epoxides are di- or polyglycidyl ethers prepared by reaction of at least one polyhydric phenol having an aromatic nucleus or an alkylene oxide adduct thereof with epichlorohydrin. Examples thereof include di- or polyglycidyl ether of bisphenol A or its alkylene oxide adduct, di- or polyglycidyl ether of hydrogenated bisphenol A or its alkylene oxide adduct, and a novolac type epoxy resin. In addition, ethylene oxide, propylene oxide, etc. are mentioned as alkylene oxide utilized in the said alkylene oxide adduct.

  As the alicyclic epoxide, cyclohexene obtained by epoxidizing at least one compound having a cycloalkene ring such as cyclohexene or cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or peracid. An oxide or a cyclopentene oxide containing compound is mentioned.

Among the aliphatic epoxides, examples of preferable compounds include aliphatic polyhydric alcohols or di- or polyglycidyl ethers of alkylene oxide adducts thereof. As a representative example,
Diglycidyl ether of alkylene glycol such as diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol or diglycidyl ether of 1,6-hexanediol,
Glycerin or polyglycidyl ethers of polyhydric alcohols such as di- or triglycidyl ethers of alkylene oxide adducts thereof,
Polyethylene glycol, or. Examples thereof include diglycidyl ether and polypropylene glycol of the alkylene oxide adduct, and diglycidyl ether of polyalkylene glycol such as diglycidyl ether of the alkylene oxide adduct. In addition, ethylene oxide, propylene oxide, etc. are mentioned as alkylene oxide utilized in the said alkylene oxide adduct.

  Of the various epoxides exemplified above, it is preferable to use aromatic epoxides and alicyclic epoxides in consideration of fast curability. In particular, it is more preferable to use an alicyclic epoxide. As the binder resin component in the present invention, one of the above-mentioned photocation polymerizable epoxides may be used alone, or two or more may be used in appropriate combination.

Moreover, as a vinyl ether compound, for example,
Diethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, propylene glycol divinyl ether, dipropylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether, trimethylolpropane trivinyl ether, etc. Or a trivinyl ether compound,
Ethyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, cyclohexyl vinyl ether, hydroxybutyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexanedimethanol monovinyl ether, propyl vinyl ether, isopropyl vinyl ether, isopropenyl ether-O-propylene carbonate, dodecyl vinyl ether, diethylene glycol mono Examples thereof include monovinyl ether compounds such as vinyl ether and octadecyl vinyl ether.

  As the binder resin component in the present invention, one of the above-mentioned vinyl ether compounds capable of photocation polymerization may be used alone, or two or more may be used in appropriate combination.

  The oxetane compound is a compound having an oxetane (trimethylene oxide) ring, and any known oxetane compound as disclosed in JP-A Nos. 2001-220526 and 2001-310937 can be used in the present invention. Can be used as a binder resin component.

  In the present invention, a binder resin obtained by polymerizing one or two or more of the various polymerizable monomer compounds described above as a binder component and including the polymerized binder resin is contained in the thin film conductor layer of the metal fine particle sintered body type. May be. In preparing the metal fine particle dispersion, as a raw material for the metal fine particles, for example, a raw material silver nanoparticle dispersion containing 30 to 80 parts by mass of silver nanoparticles in 100 parts by mass of the silver nanoparticle dispersion It is preferable to add a binder resin component to the raw material silver nanoparticle dispersion at an addition ratio exemplified below. For example, the amount of the binder resin component added is in the range of 1-50 parts by weight, preferably in the range of 1-40 parts by weight, more preferably in the range of 5-20 parts by weight per 100 parts by weight of the raw silver nanoparticle dispersion. You can choose. In addition, when used as a metal fine particle raw material, for example, when the addition amount of the binder resin component is selected to be 5 parts by mass or less per 100 parts by mass of the raw material silver nanoparticle dispersion, it is often a binder for the entire metal fine particle sintered body. The effect (function) as a resin is poor. On the other hand, when the additive amount of the binder resin component is selected to be 40 parts by mass or more per 100 parts by mass of the raw material silver nanoparticle dispersion, for example, depending on the polymerization rate of the binder resin, It becomes a factor which inhibits sintering. For example, as a result of hindering the reduction (shrinkage) of the bulk volume associated with the sintering of metal fine particles, a dense metal fine particle sintered body is not achieved, which hinders achievement of good conductivity.

  That is, in the obtained metal fine particle sintered body, when a dense sintered body of the metal fine particles is formed, the bulk volume exhibited by the metal fine particles proceeds. Meanwhile, the binder resin component contained in the dried metal fine particle coating layer in which the metal fine particles are densely deposited is also polymerized and cured, and occupies a gap remaining inside the formed metal fine particle sintered body, and the substrate surface. It is also used as an adhesive resin component at the interface with the metal fine particle sintered body layer.

  As described above, when ultraviolet rays are used as energy rays, the acid generator compound is 0.5 to 10 parts by mass and the sensitizer compound is 0 to 10 parts by mass with respect to 100 parts by mass of the raw silver nanoparticle dispersion. It is desirable to select the blending ratio in the range of 0 to 20 parts by mass of the binder resin component.

[Adhesion improver]
In the method for forming a metal fine particle sintered body type thin film conductor layer according to the present invention, the metal fine particle sintered body is bonded to silicon, silicon nitride, silicon oxide, and a phosphorus silicate glass substrate in the metal fine particle dispersion to be used. In order to further improve the properties, an adhesion improver can be added. As this adhesion improver, a general-purpose coupling agent, for example, an amino group and a silane coupling agent having no amino residue, a titanium chelating agent, and the like can be used. At that time, it is desirable to select a general-purpose coupling agent that is used to improve the adhesion between the two depending on the substrate material and the metal material constituting the fine metal particles used.

[Organic solvent (diluted solvent)]
Further, the metal fine particle dispersion to be used is formed by applying a desired pattern on the substrate with a predetermined film thickness to form a metal fine particle dispersion coating film layer. At that time, it is necessary to adjust the viscosity of the metal fine particle dispersion according to the coating means used. In addition, when the above binder resin component, adhesion improver, or acid generator compound, radical generator compound, and sensitizer compound are added, they are prepared into a dispersion in which these additive components are uniformly dissolved. There is a need.

  For this purpose, an organic solvent (diluting solvent) is usually appropriately added to the metal fine particle dispersion. The organic solvent (dilution solvent) used is from various organic solvents that can dissolve the binder resin component and the adhesion improver, or additive components such as an acid generator compound, a radical generator compound, and a sensitizer compound. Selected. Examples of usable organic solvents include aliphatic hydrocarbons such as hexane, cyclohexane, heptane, alcohols, N-methyl-2-pyrrolidone, γ-butyrolactone, N, N-dimethylformamide, N, N-dimethyl. Polar aprotic solvents such as acetamide and dimethyl sulfoxide, ethers such as tetrahydrofuran and dioxane, ketones such as acetone, methyl ethyl ketone and diisobutyl ketone, esters such as ethyl acetate, propylene glycol monomethyl ether acetate and ethyl lactate, toluene, And aromatic hydrocarbons such as xylene.

  In consideration of the type and amount of each additive component added to the metal fine particle dispersion and the target liquid viscosity, one of the organic solvents exemplified, or a mixture of two or more Can be used.

  On the other hand, after applying the metal fine particle dispersion, prior to performing the energy ray irradiation treatment and the low temperature heat treatment, the organic solvent contained in the metal fine particle dispersion coating film layer is evaporated to dry the metal fine particles. Let it be a coating layer. That is, the excessive dilution solvent is evaporated, and the fine metal particles form a dense deposited layer. In the stage of evaporating the organic solvent (diluted solvent), since heating is not performed, it is desirable to use an organic solvent (diluted solvent) exhibiting volatile characteristics that can evaporate by leaving it at room temperature (20 ° C.). .

  Hereinafter, the present invention will be described in more detail with reference to examples. The following examples are examples of the best mode according to the present invention, but the present invention is not limited to the modes shown in these examples.

(Preparation of silver nanoparticle dispersion 1)
Commercially available silver ultrafine particle dispersion (trade name: Independently dispersed ultrafine particle Perfect Silver, Vacuum Metallurgical Co., Ltd.), specifically, 100 parts by mass of silver nanoparticles having an average particle diameter of 8 nm, alkylamine as dodecyl Silver nanoparticle dispersion liquid 1 was prepared by the following procedure using a dispersion of silver nanoparticles containing 15 parts by mass of amine (molecular weight: 185.36; boiling point: 248 ° C.) and 75 parts by mass of toluene as an organic solvent.

  After adding 12 parts by mass of 1-decanol (molecular weight: 158.28; melting point: 6.88 ° C., boiling point: 232 ° C.) per 180 parts by mass of the silver nanoparticle dispersion, toluene was removed by concentration under reduced pressure to obtain a paste. A silver nanoparticle dispersion 1 was prepared. Therefore, the obtained silver nanoparticle dispersion 1 contains 15 parts by mass of dodecylamine as alkylamine and 12 parts by mass of 1-decanol as a dispersion solvent per 100 parts by mass of silver nanoparticles having an average particle diameter of 8 nm. Yes.

(Preparation of silver nanoparticle dispersion 2)
Commercially available silver ultrafine particle dispersion (trade name: Independently dispersed ultrafine particle Perfect Silver, Vacuum Metallurgical Co., Ltd.), specifically, 100 parts by mass of silver nanoparticles having an average particle diameter of 8 nm, alkylamine as dodecyl Silver nanoparticle dispersion 2 was prepared by the following procedure using a dispersion of silver nanoparticles containing 15 parts by mass of amine and 75 parts by mass of toluene as an organic solvent.

  First, 87.5 parts by mass of butoxypropylamine (molecular weight: 131, boiling point: 176 ° C.) (based on Ag solid content: 50 wt%: manufactured by Guangei Chemical Co., Ltd.) is mixed with 500 parts by mass of the raw silver ultrafine particle dispersion. And stirred for 1 hour. After the stirring, toluene was removed by concentration under reduced pressure to prepare 298 parts by mass of a paste-like silver nanoparticle dispersion. As a result of the above-mentioned treatment, 298 parts by mass of the paste-like silver nanoparticle dispersion contains 175 parts by mass of silver nanoparticles, 35 parts by mass of dodecylamine, and 87.5 parts by mass of butoxypropylamine. The coated molecular layer is presumed to be converted to butoxypropylamine.

  After removing the solvent, 298 parts by mass of the paste-like silver nanoparticle dispersion was transferred to a 2 L beaker, 1,000 parts by mass of methanol was added, and the mixture was stirred at room temperature for 3 minutes and allowed to stand. Ag nanoparticles settled to the bottom of the beaker by adding the polar solvent methanol. On the other hand, unnecessary organic components contained in the mixture were dissolved in the supernatant, and a brown methanol solution was obtained. After removing the supernatant layer, 800 parts by mass of methanol was again added to the sediment, and the mixture was stirred and allowed to stand to precipitate Ag nanoparticles, and then the supernatant methanol solution layer was removed. After the above methanol washing step, methanol remaining in the Ag nanoparticle sedimentation layer at the bottom of the beaker was volatilized and dried. When this drying process was completed, the Ag nanoparticles in the sedimentation layer were in the form of blue fine powder.

  By adding 330 parts by mass of toluene and 22 parts by mass of 1-decanol to 205 parts by mass of the blue fine powdered Ag particles that have been subjected to the methanol washing treatment, the Ag nanoparticles are re-applied by heating and stirring at 70 ° C. for 30 minutes. Dispersed. After the completion of stirring, 557 parts by mass of the Ag nanoparticle redispersion liquid was filtered with a 0.2 μm membrane filter to obtain a uniform dark blue dispersion liquid. Furthermore, toluene was removed from the resulting dark blue dispersion by concentration under reduced pressure to prepare paste-like silver nanoparticle dispersion 2. Therefore, the obtained silver nanoparticle dispersion liquid 2 is 14.6 parts by weight of butoxypropylamine constituting a coating molecular layer on the surface of the silver nanoparticles per 100 parts by weight of silver nanoparticles having an average particle diameter of 8 nm. , 10.7 parts by mass of 1-decanol.

(Preparation of conductive inks 1 to 14)
Conductive inks 1 to 14 were prepared using the above silver nanoparticle dispersion 1 and silver nanoparticle dispersion 2. Tables 1 and 2 show the compositions of the conductive inks 1 to 14.

In addition, each component of an acid generator, a sensitizer, a binder component, and an adhesive improvement agent used for preparation of said electroconductive ink is as follows.
Acid generator (1): Photocationic polymerization initiator WPI-113 (bis (alkyl (C = 10-14) phenyl) iodonium hexafluorophosphate) manufactured by Wako Pure Chemical Industries, Ltd.
Acid generator (2): Photoacid generator WPAG199 (bis (p-toluenesulfonyl) diazomethane) manufactured by Wako Pure Chemical Industries, Ltd.
Acid generator (3): Sanwa Chemical Co., Ltd. Photoacid generator TME-triazine sensitizer (1): Ciba Specialty Chemicals Irgacure 184 (1-hydroxycyclohexyl phenyl ketone)
Sensitizer (2): Wako Pure Chemical Industries, Ltd. Reagent special grade Anthracene binder component (1): Toa Gosei Co., Ltd. Aronix M-220 (TPGDA: tripropylene glycol diacrylate)
Binder component (2): Daicel Chemical Industries, Ltd. Celoxide 2021 (3,4-epoxycyclohexenylmethyl-3 ′, 4′-epoxycyclohexene carboxylate)
Adhesion improver: Shin-Etsu Chemical Co., Ltd. KBM-602 (N- (2-aminoethyl) -3-aminopropylmethylmethoxysilane)
(Examples 1-14, Example 14-1)
Using the conductive inks 1 to 14, conductive metal thin films were prepared according to the following procedure.

  On the polyimide film for flexible wiring board, the bar coater No. 2 was used to apply conductive inks 1 to 14 to form a coating film having a uniform thickness. The diluted solvent xylene contained in this coating film was evaporated at room temperature (20 ° C.) to produce a dried conductive ink coating film. In Example 14-1, the bar coater No. 9 is used to apply the conductive ink 14.

  Using the electron beam irradiation device “MinEB” manufactured by Toyo Ink Manufacturing Co., Ltd. on the surface of the dried conductive ink coating film while maintaining the temperature of the substrate polyimide film at room temperature (20 ° C.), an acceleration voltage of 50 kV, Electron dose: Electron beam irradiation was performed under the condition of 1000 kGy. Next, the conductive ink coating film that had been subjected to the electron beam irradiation treatment together with the polyimide film of the substrate was transferred into an oven at 150 ° C. and subjected to heat treatment for 30 minutes in a nitrogen atmosphere.

  As a result of continuously performing this electron beam irradiation treatment, heat treatment at 150 ° C. for 30 minutes, sintering of the silver nanoparticles contained in the conductive ink coating film proceeds, and a uniform sintered body over the entire film Layer formation was taking place. Using the sample obtained by cutting the obtained sintered metal thin film together with the polyimide film of the substrate into a size of 3 mm × 30 mm, the average film thickness and specific resistance value (volume resistivity) of the metal thin film were measured. The film thickness of the metal thin film on the surface of the sample was measured in advance using a needle touch surface shape measuring device (Surfcom), and the average film thickness was calculated. Assuming a uniform conductor layer having this average film thickness, the specific resistance was measured by a four-point measurement method.

  Table 3 summarizes the results of the measured average film thickness and specific resistance of the sintered metal thin film. The measured specific resistance value (volume specific resistivity) is indicated by the following evaluation score.

Specific resistance value (volume resistivity) evaluation score (20 ° C)
◎: Less than 10 ^-5 Ω · cm ○: 10 ^-5 Ω · cm or more, less than 10 ^-4 Ω · cm △: 10 ^-4 Ω · cm or more, less than 10 ^-3 Ω · cm ×: 10 ^-3 Ω · cm cm 2 or more, or the specific resistance value exceeds the measurable range As shown in Table 3, the specific resistance value (volume specific resistivity) evaluation score of the sintered metal thin film produced in Examples 1 to 14 Is “◎” or “◯”, and both are judged to be good conductive metal thin films.

(Examples 15 to 23)
Using conductive inks 3 to 11 containing an acid generator, a conductive metal thin film was prepared according to the following procedure.

  On the polyimide film for flexible wiring board, the bar coater No. 2 was used to apply conductive inks 3 to 11 to form a coating film having a uniform film thickness. The diluted solvent xylene contained in this coating film was evaporated at room temperature (20 ° C.) to produce a dried conductive ink coating film.

The temperature of the substrate polyimide film is kept at room temperature (20 ° C.), and the surface of this dried conductive ink coating film is irradiated with air-cooled high-pressure mercury lamp light with an ultraviolet ray irradiation device manufactured by Eye Graphics Co., Ltd. cm was irradiated while moving at a conveyor speed of 10 m / min. This operation was repeated a total of 5 times. Accordingly, the total irradiation light intensity per unit area corresponds to 5 × 160 × (60/1000) W · s / cm ² . The main peak wavelength in the ultraviolet region irradiated from the high pressure mercury lamp is 365 nm (i-line), 436 nm (g-line), or the like. Next, the conductive ink coating film that had been subjected to the ultraviolet irradiation treatment together with the polyimide film of the substrate was transferred into an oven at 150 ° C. and subjected to a heat treatment in a nitrogen atmosphere for 30 minutes.

  As a result of continuously performing this ultraviolet irradiation treatment and heat treatment at 150 ° C. for 30 minutes, sintering of the silver nanoparticles contained in the conductive ink coating film advances, and a uniform sintered body layer is formed on the entire film. The formation of was happening. Using the sample obtained by cutting the obtained sintered metal thin film together with the polyimide film of the substrate into a size of 3 mm × 30 mm, the average film thickness and specific resistance value (volume resistivity) of the metal thin film were measured. In advance, the film thickness of the metal thin film on the sample surface was measured using a needle touch surface shape measuring instrument (Surfcom 2800DX, manufactured by Tokyo Seimitsu Co., Ltd.), and the average film thickness was calculated. Assuming a uniform conductor layer having this average film thickness, the specific resistance was measured by a four-point measurement method.

  Table 4 summarizes the results of the measured average film thickness and specific resistance of the sintered metal thin film. The measured specific resistance value (volume specific resistivity) is indicated by the above-described evaluation score.

  As shown in Table 4, the specific resistance value (volume specific resistivity) evaluation score of the sintered metal thin films produced in Examples 15 to 25 is “◎” or “「 ”, and both have good conductivity. It is determined as a metal thin film.

(Comparative Examples 1-5)
Using conductive inks 1, 2, 3, 11, and 14, an attempt was made to produce a sintered metal thin film by the following procedure.

  On the polyimide film for flexible wiring board, the bar coater No. 2 was used to apply conductive inks 1, 2, 3, 11, and 14 to form a coating film having a uniform thickness. The diluted solvent xylene contained in this coating film was evaporated at room temperature (20 ° C.) to produce a dried conductive ink coating film. Next, together with the polyimide film of the substrate, the conductive ink coating film was placed in an oven at 150 ° C. and heat-treated for 30 minutes in a nitrogen atmosphere.

  As a result of the heat treatment at 150 ° C. for 30 minutes, the sintering of the silver nanoparticles contained in the conductive ink coating film proceeds, and within a seeming range, a uniform sintered body layer is formed on the entire film. Was happening. Using the sample obtained by cutting the obtained sintered thin film together with the polyimide film of the substrate into a size of 3 mm × 30 mm, the average film thickness and specific resistance value (volume specific resistivity) of the sintered thin film were evaluated. It was. The film thickness of the sintered compact thin film on the surface of the sample was measured in advance using a needle touch surface shape measuring instrument (Surfcom 2800DX, manufactured by Tokyo Seimitsu Co., Ltd.), and the average film thickness was calculated. Assuming a uniform conductor layer having this average film thickness, an attempt was made to measure specific resistance by a four-point measurement method.

In the four-point measurement method, when the resistance value of the rectangular sample was measured, it exceeded the measurable range, and the specific resistance value (volume resistivity) exceeded at least 10 × 10 ³ μΩ · cm. It is judged that

  Table 5 summarizes the measured average film thickness and specific resistance evaluation results of the sintered compact thin film. The measured specific resistance value (volume specific resistivity) is indicated by the above-described evaluation score.

  As shown in Table 5, the sintered compact thin films prepared in Comparative Examples 1 to 5 have a resistance value of “x” and are determined not to exhibit conductivity. .

(Reference Examples 1 and 2)
Using conductive inks 1 and 2, an attempt was made to produce a sintered metal thin film by the following procedure.

  On the polyimide film for flexible wiring board, the bar coater No. 2 was used to apply conductive inks 1 and 2 to form a uniform coating film. The diluted solvent xylene contained in this coating film was evaporated at room temperature (20 ° C.) to produce a dried conductive ink coating film. Next, together with the polyimide film of the substrate, the conductive ink coating film was placed in an oven at 250 ° C. and subjected to heat treatment for 60 minutes.

  As a result of performing the heat treatment at 250 ° C. for 60 minutes, the sintering of the silver nanoparticles contained in the conductive ink coating film progressed, and a uniform sintered body layer was formed on the entire film.

  In the same manner as in the above example, the resistance value of the rectangular sample was measured in the four-point measurement.

  Table 6 shows the measured average film thickness and specific resistance of the sintered metal thin film. The measured specific resistance value (volume specific resistivity) is indicated by the above-described evaluation score.

  As shown in Table 6, the specific resistance value (volume specific resistivity) of the sintered compact metal thin films prepared in Reference Examples 1 and 2 has an evaluation score of “◎”, both of which are good conductive metal thin films. It is determined that there is.

  In the method of forming a metal fine particle sintered body type thin film conductor layer according to the present invention, taking advantage of high drawing accuracy based on a metal fine particle dispersion using metal nanoparticles of a single metal or an alloy such as gold, silver, and copper, After forming a coating layer of fine metal particles having a fine pattern, it is possible to produce a sintered compact conductor layer of fine metal particles exhibiting good conductivity by heat treatment at a temperature not exceeding 200 ° C. To do. Therefore, the limitation of heat resistance for the substrate material that can be used is greatly relaxed, and the usable range of the sintered compact conductor layer of metal fine particles becomes wider. By applying the method for forming a metal fine particle sintered body type thin film conductor layer according to the present invention, for example, for antenna circuits such as multilayer wiring boards and IC cards, further miniaturization and productivity can be achieved. Improvements can be made.

Claims (16)

A method of forming a metal fine particle sintered body type thin film conductor layer on a substrate,
The metal fine particles used for the production of the metal fine particle sintered body are metal fine particles having an average particle diameter of 1 to 100 nm composed of a metal material having a melting point of at least 200 ° C.,
A liquid phase dispersion medium comprising an organic solvent, wherein a coating molecular layer of a dispersant having a function of preventing aggregation between metal fine particles is provided on the surface of the metal fine particles, and the metal fine particles having the coating molecular layer are used as a dispersoid. Using metal fine particle dispersion liquid dispersed in,
Applying the metal fine particle dispersion at a predetermined thickness on the substrate to form a metal fine particle dispersion coating film layer; and
A step of evaporating the organic solvent contained in the metal fine particle dispersion coating film layer to obtain a dried metal fine particle coating layer;
A process of irradiating the dried metal fine particle coating layer with a predetermined dose of energy rays from the coating layer surface;
The metal fine particle coating layer that has been subjected to the energy beam irradiation treatment comprises a step of performing a low temperature heat treatment at a heating temperature selected in a temperature range not exceeding 50 ° C. and at least not exceeding 200 ° C. in a non-oxidizing gas atmosphere,
By performing the energy beam irradiation treatment and the low-temperature heat treatment, the metal fine particles contained in the metal fine particle coating layer are sintered with each other, and a metal fine particle sintered body type thin film conductor layer is formed. A method of forming a metal fine particle sintered body type thin film conductor layer, characterized in that: The metal material constituting the metal fine particles and having a melting point exceeding 200 ° C. is at least
It is a single metal species selected from the group of metal elements consisting of gold, silver, copper, platinum, palladium, rhodium, ruthenium, nickel, and aluminum, or an alloy composed of two or more metal species. The method of claim 1. The method according to claim 1, wherein an average particle size of the metal fine particles is selected in a range of 5 to 20 nm. As energy rays used for the energy ray irradiation treatment,
2. The method according to claim 1, wherein an accelerating voltage is selected from an electron beam selected in a range of 50 kV to 200 kV or an ultraviolet ray selected from a wavelength range of 180 nm to 400 nm. The heating temperature used for the low-temperature heat treatment is
The process according to claim 1, characterized in that it is selected in the temperature range from 50C to 150C. In the liquid phase dispersion medium containing the organic solvent,
Along with the irradiation of energy rays used for the energy ray irradiation treatment, an acid generator compound having a function of generating an acid component is added,
The method according to claim 1, wherein the acid generator compound is contained in the dried metal fine particle coating layer. As an acid generator compound having a function of generating an acid component with irradiation of the energy beam,
One type of compound selected from the group of acid generator compounds consisting of an onium compound having an acid generating ability, a sulfone compound, a halide, and an iron allene complex, or using two or more types of compounds, The method of claim 6. The coating molecular layer of the dispersant, which is provided on the surface of the metal fine particles and has a function of preventing aggregation between the metal fine particles,
As the dispersant,
The boiling point is in the range of 150 ° C. or higher and 350 ° C. or lower,
It is formed using one type of dispersant molecule selected from the group consisting of amines, alcohols, phenols, and thiols, or two or more types of dispersant molecules. The method of claim 1. In the liquid phase dispersion medium containing the organic solvent,
Along with irradiation of energy rays used for the energy ray irradiation treatment, a radical generator compound having a function of generating radical species is added,
2. The method according to claim 1, wherein the radical generator compound is contained in the dried metal fine particle coating layer. In the liquid phase dispersion medium containing the organic solvent,
Along with the irradiation of energy rays used for the energy ray irradiation treatment, a radical generator compound having a function of generating radical species, or an acid generator compound having a function of generating an acid component is added,
In the dried metal fine particle coating layer, the radical generator compound or the acid generator compound is contained,
Further, in response to the irradiation of the energy beam used for the energy beam irradiation treatment, the energy of the irradiated energy beam is received, and the received energy is transmitted to the radical generator compound or the acid generator compound. And adding a sensitizer compound that enables the radical generator compound or the acid generator compound to function,
The method according to claim 1, wherein the sensitizer compound is contained in the dried metal fine particle coating layer. In the liquid phase dispersion medium containing the organic solvent,
When the energy ray irradiation treatment or the low-temperature heat treatment is performed, a binder resin component that can be polymerized and cured is added,
The method according to claim 1, wherein the binder resin component is contained in the dried metal fine particle coating layer. As the binder resin component that can be polymerized and cured when the energy ray irradiation treatment or the low temperature heat treatment is performed,
The method according to claim 11, wherein an energy ray-curable binder resin component that exhibits polymerization curing activity is used due to energy ray irradiation used for the energy ray irradiation treatment. By performing the energy beam irradiation treatment and the low-temperature heat treatment, polymerization hardening of the binder resin component contained in the metal fine particle coating layer and sintering of the metal fine particles contained in the metal fine particle coating layer are performed. ,
The method according to claim 11, wherein a thin film conductor layer of a metal fine particle sintered body type comprising the polymerized and cured binder resin and a metal fine particle sintered body is formed. In the liquid phase dispersion medium containing the organic solvent,
Add an adhesion improver, which has the function of improving the adhesion of the metal fine particle sintered body layer to the surface of the substrate,
The method according to claim 1, wherein the adhesion improver is contained in the dried metal fine particle coating layer. A method of forming a conductive metal thin film or metal wiring on a substrate,
The conductive metal thin film or metal wiring is formed using a metal fine particle sintered body type thin film conductor layer,
The step of forming the metal fine particle sintered body type thin film conductor layer on the substrate includes:
It implements using the method as described in any one of Claims 1-14, The formation method of a conductive metal thin film or metal wiring characterized by the above-mentioned. A wiring circuit board in which a wiring circuit pattern made of a conductive metal thin film or metal wiring is formed on the substrate surface,
The wiring circuit pattern formed of the conductive metal thin film or metal wiring formed on the substrate surface is formed using a metal fine particle sintered body type thin film conductor layer,
The metal fine particle sintered body type thin film conductor layer on the substrate is:
A printed circuit board comprising a metal fine particle sintered body type thin film conductor layer formed by using the method according to any one of claims 1 to 14.