JP2011082025A - Conductive paste - Google Patents

Abstract

Provided is a conductive paste capable of forming a conductive film having sufficient conductivity, and having leveling resistance that hardly flows on the substrate after application to the substrate (after drawing). .
A conductive paste comprising a metal colloid liquid and a flow inhibitor made of an organic compound that is solid at room temperature and has a boiling point of 300 ° C. or lower.
[Selection figure] None

Description

  The present invention relates to a conductive paste capable of obtaining a film having high conductivity at a low heating temperature, and further relates to a conductive paste excellent in leveling resistance. More specifically, the present invention relates to a conductive paste that can also be used as a conductive ink for forming a conductive film used as, for example, a wiring for solar cell panels and various circuit boards.

  Conventionally, a conductive paste has been used as a conductive material for forming a conductive film constituting a wiring of a solar cell panel wiring, an electrode of a flat panel display, a circuit board or an IC card, for example. As a conventional method for producing such a conductive film, for example, (1) a method such as vacuum deposition of metal, chemical vapor deposition or ion sputtering, (2) a plating method, and (3) a photolithography method are used. ing.

  The above method (1) requires work in a vacuum system or a closed system, and thus is complicated to operate. Since the apparatus is large, a large space is required and the cost is increased. poor. In addition, the method (2) needs to process a large amount of waste liquid, which results in a large material loss and extra cost, and a large burden on the environment. Furthermore, the method (3) requires an extra step of masking a necessary portion of the conductive coating formed on the substrate, and the photosensitive resin used, the removed conductive coating, and Since a large amount of waste liquid generated by dissolution is discharged, processing costs are high and the burden on the environment is large.

  On the other hand, a method of drawing on a substrate using a conductive paste for forming a conductive film as a coating agent has been widely used. In this method, it is not necessary to provide a special apparatus, and manufacturing with simple equipment is possible, so that a large space is not required and the cost can be reduced. Further, this method is advantageous in terms of cost because there is almost no material loss and no waste liquid is generated, and the addition to the environment is small.

  Here, as the coating agent, a conductive paste (or conductive ink) obtained by kneading metal particles such as silver particles, a resin component, and an organic solvent has been conventionally used. In many cases, this conductive paste is applied to a substrate using screen printing or screen printing to form a conductive film. Recently, a method of forming a wiring pattern by drawing a metal colloid liquid having a low viscosity as a conductive paste and drawing it by an ink jet method has been attempted.

  As the conductive paste, for example, Patent Document 1 discloses that a conductive metal paste is sprayed and applied onto a substrate using an ink jet printing method, and has good adhesion and a smooth surface shape when fired. In order to provide a novel circuit pattern forming method capable of forming a low-resistance and ultrafine circuit pattern, the circuit pattern of the wiring board is drawn and formed with a conductive metal paste using an inkjet method. In the method, it has been proposed to use a specific conductive metal paste.

  More specifically, in Patent Document 1, “a conductive metal paste obtained by uniformly dispersing ultrafine metal particles having a fine average particle diameter in a resin composition containing an organic solvent, the fine average The metal ultrafine particles having a particle diameter are selected so that the average particle diameter is in the range of 1 to 100 nm, and the surface of the metal ultrafine particles is nitrogen as a group capable of coordinative bonding with the metal element contained in the metal ultrafine particles. , A conductive metal paste coated with one or more compounds having a group containing oxygen and sulfur atoms has been proposed.

  In Patent Document 2, in the field of electronic materials, a conductive metal film having processing accuracy and reliability comparable to a plating film that can be substituted for various plating films used in various applications is easily and highly reproduced. With the intention of providing a method for forming a metal layer, an “organic ultrafine particle having an average particle diameter of 100 nm or less is provided on its surface with a coating layer such as an amine compound capable of coordinative bonding with a metal element, and organic It has been proposed to use a “dispersion dispersion in which an organic acid anhydride or a derivative thereof or an organic acid is added, which is dispersed in a solvent and shows reactivity with the amine compound of the coating layer”.

  Furthermore, in Patent Document 3, a thin film layer of a conductive silver paste cured body obtained by thermal curing is excellent in flexibility and also exhibits flexibility to withstand repeated bending. The purpose of the present invention is to provide a conductive silver paste whose conductivity is reduced only slightly, “a conductive silver paste comprising silver powder and an epoxy resin component, the epoxy resin component being an essential main component, dimer acid A diglycidyl ester, a curing agent or a curing catalyst thereof, and if necessary, a liquid epoxy resin material other than the diglycidyl ester of dimer acid may be included as a secondary component. A “conductive silver paste” has been proposed.

JP 2002-324966 A JP 2002-334618 A JP 2001-261778 A

  However, depending on the technologies proposed in Patent Documents 1 to 3, although a conductive film having high conductivity can be obtained even at a relatively low heating temperature, the substrate after applying the conductive paste is inclined. When the conductive paste is disposed on the substrate, the conductive paste flows (drops) on the base material, so-called dripping may occur, and there is still room for improvement from the viewpoint of leveling resistance.

  Therefore, an object of the present invention has been made in view of the above-described problems of the prior art, can form a conductive film having sufficient conductivity, and is applied to a substrate (after drawing). It is another object of the present invention to provide a conductive paste having a so-called leveling resistance that hardly flows on the substrate.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor can form a conductive film having sufficient conductivity, and on the base material after application to the base material (after drawing). In order to obtain a conductive paste having a so-called leveling resistance, it is necessary to remove the conductive paste while forming the conductive film by applying and heating the conductive paste while adjusting the viscosity of the conductive paste. The inventors have found that adding a specific compound that can be obtained is extremely effective in achieving the above object, and have reached the present invention. Further, it has been found that if the conductive paste is used, it can be fired even by heating at a relatively low temperature (for example, 300 ° C. or less), and a conductive film having conductivity can be obtained.

That is, the present invention
A metal colloid liquid,
A flow inhibitor comprising an organic compound that is solid at room temperature and has a boiling point of 300 ° C. or lower,
An electrically conductive paste is provided.

  In the conductive paste of the present invention, the “flow inhibitor composed of an organic compound that is solid at normal temperature and has a boiling point of 300 ° C. or lower” is solid at normal temperature, and therefore in the conductive paste prepared at normal temperature. Plays a role of suppressing flow by increasing its viscosity (that is, a role of imparting leveling resistance), and is made of an organic compound having a boiling point of 300 ° C. or lower. When a conductive film is formed at a relatively low heating temperature (preferably higher than the boiling point and not higher than 300 ° C.), the conductivity of the conductive film is not impaired because it is removed by evaporation or decomposition. A conductive film having conductivity can be obtained.

  Here, “normal temperature” in the present invention refers to a temperature of, for example, about 15 to 30 ° C., and the above-described flow inhibitor of “solid at normal temperature” has a melting point or decomposition point of, for example, 15 to 30 ° C. or higher. Any aqueous dispersion medium such as water and / or an aqueous organic dispersion medium described later, other organic solvents, etc. may be used as long as it is solid (including powder or sherbet) at room temperature below the melting point or decomposition point. It may be dissolved in Moreover, the said flow inhibitor which has a "boiling point of 300 degrees C or less" can evaporate at 300 degrees C or more in principle (a part may remain without evaporating).

  The said flow inhibitor in the electrically conductive paste of this invention is solid at normal temperature, and has a boiling point of 300 degrees C or less. If the flow inhibitor is not solid at room temperature, the viscosity of the conductive paste cannot be increased to give leveling resistance, and if the flow inhibitor has a boiling point of more than 300 ° C., the conductivity after coating is not good. When the conductive paste is baked at a relatively low heating temperature of 300 ° C. or lower (for example, 250 ° C. or lower), it is difficult to obtain a conductive film having sufficient conductivity.

  The melting point of the flow inhibitor can be measured, for example, by a method such as a melting point measuring device or differential scanning calorimetry (DSC). The decomposition point of the flow inhibitor can be measured, for example, by a method called a thermogravimetric apparatus (TGA). Furthermore, the boiling point of the flow inhibitor can be measured by, for example, a Beckmann boiling point measuring device or a Cottrell molecular weight measuring device.

  The conductive paste of the present invention contains a metal colloid liquid. It is known that a film obtained using a metal colloid liquid has good conductivity (for example, see JP-A-2002-245854). Therefore, the conductive paste of the present invention has leveling resistance due to the flow inhibitor and can more reliably form a conductive film having high conductivity.

  Here, the metal colloid liquid in the conductive paste of the present invention includes, for example, a solid content mainly composed of metal colloid particles composed of a metal component (metal particles) and an organic component, and a dispersion medium for dispersing the solid content. Is included. However, in the colloid liquid, the “dispersion medium” may dissolve a part of the solid content. In addition, a main component means a component with most content among structural components.

  According to such a metal colloid liquid, since it contains an organic component, the dispersibility of the metal colloid particles in the metal colloid liquid can be improved. Therefore, the content of the metal component in the metal colloid liquid can be reduced. Even if it is increased, the colloidal metal particles are less likely to aggregate and good dispersion stability can be maintained. The “dispersibility” in the present invention indicates whether or not the dispersion state of the metal particles in the metal colloid liquid is excellent immediately after the metal colloid liquid is prepared (whether or not it is uniform). , "Dispersion stability" indicates whether or not the dispersion state of the metal particles in the metal colloid liquid is maintained after a predetermined time has elapsed after adjusting the metal colloid liquid, It can also be said to be “low sedimentation aggregation”.

  In the electrically conductive paste of this invention, it is preferable that the said flow inhibitor is a trimethylol propane, (epsilon) -caprolactam, ethylene carbonate, or urea. By using these compounds, a conductive paste excellent in leveling resistance can be obtained more reliably, and a conductive film retaining high conductivity due to metal particles in the metal colloid liquid can be more reliably obtained.

  Moreover, it is preferable that the electrically conductive paste of this invention contains the said flow inhibitor in the quantity of 2-50 mass% with respect to solid content of the said metal colloid liquid. If it is 2% by mass or more, it is preferable because it is difficult to flow on the substrate after application on the substrate, that is, it has excellent leveling resistance, and if it is 50% by mass or less, a flow inhibitor is present in the resulting conductive film. Since it is difficult to remain, the volume resistance value is not increased excessively and sufficient conductivity is obtained, which is preferable. More preferably, it is 3-40 mass%, Most preferably, it is 5-30 mass%.

  Here, the “solid content” of the metal colloid liquid in the present invention means that after removing the dispersion medium from the metal colloid liquid using silica gel or the like, for example, it is dried at a room temperature of 30 ° C. or lower (for example, 25 ° C.) for 24 hours. In general, the solid content that remains is usually contained metal particles, residual organic components, residual reducing agent, and the like. Various methods can be employed as a method of removing the dispersion medium from the metal colloid liquid using silica gel. For example, a metal colloid liquid is applied on a glass substrate and placed in a sealed container containing silica gel. What is necessary is just to remove a dispersion medium by leaving a glass substrate with a coating film for 24 hours or more.

  The conductive paste of the present invention preferably further contains 1,3-propanediol, 1,2-propanediol, ethylene glycol or glycerin. These compounds not only improve the dispersibility of the metal colloidal particles, but also suppress the volatilization of the conductive paste when water based colloidal liquid is used for the conductive paste to improve the dispersibility of the metal colloid particles. Has the effect of

  According to the conductive paste of the present invention, it is possible to form a conductive film having sufficient conductivity even when heated and baked at a temperature lower than that of a conventional conductive paste, and applied to a substrate. It is possible to realize a conductive paste having so-called leveling resistance that does not easily flow on the substrate later (after drawing).

  Hereinafter, (1) one preferred embodiment of the conductive paste of the present invention, (2) one preferred embodiment of the method for producing the conductive paste of the present invention, and (3) conductivity using the conductive paste of the present invention. The conductive film and the manufacturing method thereof will be described in detail. In the following description, overlapping description may be omitted.

(1) Conductive paste First, a preferred embodiment of the conductive paste of the present invention will be described. The electrically conductive paste of this embodiment has the structure containing a metal colloid liquid and the flow inhibitor which is solid at normal temperature and has a boiling point of 300 degrees C or less.

  By having such a configuration, the conductive paste of the present embodiment can form a conductive film having sufficient conductivity even when heated and baked at a lower temperature than the conventional conductive paste. And excellent leveling resistance. As will be described later, examples of the dispersion medium constituting the metal colloid liquid of the conductive paste of the present embodiment include water and a water-soluble dispersion medium.

  Here, with the conventional conductive paste (ink), as described above, although a conductive film having high conductivity can be obtained even at a relatively low heating temperature, the substrate after applying the conductive ink is slanted. When the conductive ink is disposed on the substrate, the conductive ink may flow (sag) on the substrate, so-called dripping may occur, and there is still room for improvement from the viewpoint of leveling resistance.

  On the other hand, the electrically conductive paste of this embodiment contains the above "flow control agent which consists of an organic compound which is solid at normal temperature and has a boiling point of 300 degrees C or less." Therefore, as described above, in the conductive paste of the present embodiment, since the flow inhibitor is solid at room temperature, in the conductive paste prepared at room temperature, the viscosity is increased to flow. It plays a role of suppressing (that is, a role of imparting leveling resistance) and is made of an organic compound having a boiling point of 300 ° C. or lower, so that the conductive paste is applied onto a substrate and a relatively low heating temperature. When the conductive film is formed by (preferably the boiling point or higher and 300 ° C. or lower), it is possible to obtain a conductive film having sufficient conductivity that is removed by evaporation or decomposition and does not impair the conductivity of the conductive film. It can be done.

  For example, the present inventor compared the conventional conductive paste by measuring the volume resistance value using a DC precision measuring instrument (PORTABLE DOUBLE BRIDGE (portable double bridge) 2769 manufactured by Yokogawa Meter & Instruments Co., Ltd.). In addition, it has been confirmed that the conductive film formed using the conductive paste of the present embodiment (specifically, the conductive paste of Examples described later) is excellent in conductivity. In addition, the present inventor conducted leveling resistance of the conductive paste of the present embodiment (specifically, the conductive paste of Examples described later) by applying to a glass substrate and performing a drying test with the coated surface inclined. It has been confirmed that it has excellent properties.

  Here, “normal temperature” related to the flow inhibitor in the present invention refers to a temperature of, for example, about 15 to 30 ° C., and the above-mentioned flow inhibitor of “solid at normal temperature” has a melting point of, for example, 15 to 30 ° C. or higher. An aqueous dispersion medium such as water and / or an aqueous organic dispersion medium to be described later may be used as long as it has a decomposition point and is solid (including powder or sherbet) in a room temperature atmosphere below the melting point or the decomposition point. In addition, it may be dissolved in an organic solvent or the like. Moreover, the said flow inhibitor which has a "boiling point of 300 degrees C or less" can evaporate at 300 degrees C or more in principle (a part may remain without evaporating).

More specifically, in the conductive paste of this embodiment, the flow inhibitor is trimethylolpropane, ε-caprolactam, ethylene carbonate, or urea. The melting point, decomposition point, and boiling point of these flow inhibitors are as follows.
Melting point (° C) Boiling point (° C) Decomposition point (° C)
Trimethylolpropane 58 292-297 −
ε-caprolactam 69 267 −
Ethylene carbonate 36 261 −
Urea--132.7

  Since these flow inhibitors are solid at room temperature, they can increase the viscosity of the conductive paste prepared at room temperature to impart leveling resistance and have a boiling point of 300 ° C. or less. Even when the subsequent conductive paste is baked at a relatively low heating temperature of, for example, 250 ° C., it is preferable because it is removed by evaporation or the like and a conductive film having sufficient conductivity is obtained.

  Among the above flow inhibitors, for example, a reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. can be used as the trimethylolpropane, and as a ε-caprolactam, for example, a reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. Can be used. Further, as ethylene carbonate, for example, a reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. can be used, and as urea, for example, a reagent special grade manufactured by Wako Pure Chemical Industries, Ltd. can be used.

  From the viewpoint of more reliably obtaining the effects of the present invention, the conductive paste of the present embodiment includes the flow inhibitor in an amount of 2 to 50% by mass with respect to the solid content of the metal colloid liquid. If it is 2% by mass or more, it is preferable because it is difficult to flow on the substrate after application on the substrate, that is, it is excellent in leveling resistance, and if it is 50% by mass or less, the volume resistance value of the conductive film obtained is increased. This is preferable because sufficient conductivity can be obtained. More preferably, it is 3-40 mass%, Most preferably, it is 5-30 mass%.

  Here, the “solid content” of the metal colloid liquid of the present embodiment means that the metal colloid liquid is applied on a glass substrate, and the coated glass substrate is placed in a sealed container containing silica gel at a room temperature of 30 ° C. or lower (for example, 25 The solid content remaining when the dispersion medium is removed by leaving it at 24 ° C. for 24 hours or more.

  In the metal colloid liquid of the present embodiment, the preferred solid content is 1 to 70% by mass. If the concentration of solid content is 1% by mass or more, the metal content in the conductive paste can be ensured, and the conductive efficiency does not decrease. In addition, when the solid content concentration is 70% by mass or less, the viscosity of the metal colloid liquid does not increase and the handling is easy and industrially advantageous. More preferably, the solid content concentration is 10 to 65% by mass.

(1-1) About metal colloid liquid Next, the metal colloid liquid which comprises the electrically conductive paste of this embodiment is demonstrated. Examples of the metal colloid liquid include various metal colloid liquids including a solid content mainly composed of metal colloid particles composed of a metal component (metal particles) and an organic component, and a dispersion medium for dispersing the solid content. Can be used.

  The metal colloid liquid of the present embodiment preferably has a weight loss of 10% by mass or less at 100 to 500 ° C. when thermogravimetric analysis is performed at a rate of temperature increase of 10 ° C./min with respect to the solid content. When the solid is heated to 500 ° C., organic matter and the like are oxidatively decomposed, and most of them are gasified and disappear. For this reason, the reduction | decrease by heating to 500 degreeC can correspond to the quantity of the organic substance in solid content substantially.

  The greater the weight loss, the better the dispersion stability of the metal colloid, but if it is too much, organic matter remains as impurities in the conductive paste, reducing the conductivity of the conductive coating. In particular, in order to obtain a highly conductive film by heating at a low temperature of about 100 ° C., the weight loss is preferably 10% by mass or less. On the other hand, if the weight loss is too small, the dispersion stability in the colloidal state is impaired, so that the content is preferably 0.01% by mass or more. A more preferred weight loss is 0.05 to 4.5% by mass.

  Regarding the form of the metal colloid particles to be included in the solid content of the metal colloid liquid, for example, the metal colloid particles formed by attaching organic components to the surface of the particles composed of the metal components, and the particles composed of the metal components as the core. Examples thereof include, but are not particularly limited to, metal colloid particles having a surface coated with an organic component, metal colloid particles having a metal component and an organic component uniformly mixed, and the like. Metal colloidal particles having a particle composed of a metal component as a core and the surface of which is coated with an organic component, or metal colloidal particles configured by uniformly mixing a metal component and an organic component are preferable. A person skilled in the art can appropriately prepare the metal colloid particles having the above-described form using a well-known technique in the field.

  The average particle diameter of the metal colloid particles (including metal particles) in the metal colloid liquid of this embodiment is preferably 1 to 400 nm or less, and more preferably 70 nm or less. If the average particle diameter of the metal colloid particles is 1 nm or more, a conductive paste capable of forming a good conductive film can be obtained, and the production of metal colloid particles is practical without increasing the cost. Moreover, if it is 400 nm or less, the dispersion stability of a metal colloid particle does not change easily with time, and it is preferable. In the conductive paste obtained using the metal colloid liquid of this embodiment, the average particle diameter (median diameter) of the metal colloid particles (including metal particles) is substantially the same as this range (can be approximated). .

  The particle size of the particles in the metal colloid liquid varies depending on the solid content concentration and is not necessarily constant. In addition, when the conductive paste includes a resin component, an organic solvent, a thickener, a surface tension adjuster, or the like, which will be described later, as an optional component, it may contain a particle component having an average particle diameter of more than 400 nm, As long as it is a component that does not significantly impair the effects of the present invention, a particle component having an average particle diameter of more than 400 nm may be included.

Here, the average particle diameter of the particles in the metal colloid liquid is based on a dynamic light scattering method (Doppler scattered light analysis). For example, a dynamic light scattering particle size distribution measuring apparatus LB-550 manufactured by Horiba, Ltd. The volume-based median diameter (D ₅₀ ) measured in (1) can be expressed. Specifically, several drops of a metal colloid solution are dropped into 10 mL of pure water, and the sample for measurement is prepared by shaking and dispersing by hand. Next, 3 mL of the measurement sample is put into a cell of a dynamic light scattering particle size distribution measuring device LB-550 manufactured by Horiba, Ltd., and measured under the following conditions.

・ Measurement conditions Data reading frequency: 100 times Cell holder temperature: 25 ℃
-Display conditions Distribution form: Standard Number of repetitions: 50 times Particle diameter standard: Volume standard Dispersoid refractive index: 0.200-3.900i (in the case of silver)
Refractive index of dispersion medium: 1.33 (when water is the main component)
・ System condition setting Strength standard: Dynamic
Scattering intensity range upper limit: 10000.00
Scattering intensity range lower limit: 1.00

(1-2) Metal Component The metal component of the metal colloid liquid of this embodiment is not particularly limited, but the conductivity of the film obtained using the conductive paste of this embodiment is improved. Therefore, it is preferable that the metal ionization column is more noble than hydrogen. Examples of the metal whose ionization sequence of the metal is more noble than hydrogen include gold, silver, copper, platinum, palladium, rhodium, iridium, osmium, ruthenium and rhenium. Of these, gold, silver, copper, platinum, and palladium are more preferable. These metals may be used alone or in combination of two or more. As a method to be used in combination, there are a case where alloy particles containing a plurality of metals are used, and a case where metal particles having a core-shell structure or a multilayer structure are used.

  For example, when a silver colloid solution is used as the metal colloid solution, the conductivity of a film formed using the conductive paste of this embodiment is good, but it is necessary to consider the problem of migration. Here, migration can be made difficult to occur by using a mixed colloidal solution made of silver and other metals. The “other metal” is preferably a metal whose ionization sequence is more noble than hydrogen, that is, gold, copper, platinum, palladium, rhodium, iridium, osmium, ruthenium, rhenium, etc., gold, copper, platinum, palladium Is more preferable.

(1-3) Organic Component In the metal colloid liquid of the present embodiment, the “organic component” in the metal colloid particles is an organic substance that substantially constitutes the metal colloid particles together with the metal component. The organic component includes trace organic substances contained in the metal as impurities from the beginning, organic substances adhering to the metal component from trace organic substances mixed in the manufacturing process described later, residual reducing agent that could not be removed in the cleaning process, residual dispersion It does not include organic substances that adhere to trace amounts of metal components such as agents. The “trace amount” is specifically intended to be less than 1% by mass in the metal colloid particles.

  Since the metal colloid particles in this embodiment contain an organic component, the dispersion stability in the metal colloid liquid is high. Therefore, even if the content of the metal component in the metal colloid liquid is increased, the metal colloid particles are less likely to aggregate, and as a result, good dispersibility is maintained.

  The content of the organic component in the metal colloidal particles is preferably 0.5 to 30% by mass. If the content of the organic component is 0.5% by mass or more, the storage stability of the obtained metal colloid particles tends to be improved, and if it is 30% by mass or less, the resulting metal colloid particles are produced. The conductive paste tends to have good conductivity. The more preferable content of the organic component is 1 to 20% by mass, and the more preferable content is 1 to 10% by mass.

  As said organic component, the organic substance used as a dispersing agent or a reducing agent is mentioned, for example. Examples of the dispersant include organic acids such as citric acid, malic acid, tartaric acid and glycolic acid; for example, trisodium citrate, tripotassium citrate, trilithium citrate, monopotassium citrate, disodium hydrogen citrate, Ionic compounds such as potassium dihydrogen citrate, disodium malate, disodium tartrate, potassium tartrate, potassium sodium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, sodium glycolate; for example, sodium dodecylbenzenesulfonate, sodium oleate , Surfactants such as polyoxyethylene alkyl ether and perfluoroalkyl ethylene oxide adducts; for example, polymeric substances such as gelatin, gum arabic, albumin, polyethyleneimine, polyvinylcelluloses, alkanethiols Although the like, dispersed not particularly limited as long to and indicates the dispersion effect dissolved in medium, it may be used in combination of two or more even used alone.

  The dispersant is preferably a hydroxy acid or a salt thereof having a COOH group and an OH group, and (number of COOH groups) ≧ (number of OH groups). When such a dispersant is used, a conductive paste capable of forming a conductive film exhibiting high conductivity even when fired at a low temperature of about 100 ° C. can be obtained. In particular, when a hydroxy acid or a salt thereof having 3 or more COOH groups and OH groups and (number of COOH groups) is (number of OH groups) or more is used, the dispersion stability of the metal colloid particles Therefore, a conductive film having excellent conductivity can be obtained.

  Such dispersants include, for example, organic acids such as citric acid, malic acid, tartaric acid, glycolic acid; for example, trisodium citrate, tripotassium citrate, trilithium citrate, monopotassium citrate, hydrogen citrate Examples include ionic compounds such as disodium, potassium dihydrogen citrate, disodium malate, disodium tartrate, potassium tartrate, sodium potassium tartrate, potassium hydrogen tartrate, sodium hydrogen tartrate, sodium glycolate, trisodium citrate, Tripotassium citrate, trilithium citrate, disodium malate, disodium tartrate and the like are preferable.

  The reducing agent is not particularly limited as long as it is dissolved in a suitable solvent and exhibits a reducing action, but tannic acid or hydroxy acid is preferably used. Tannic acid or hydroxy acid functions as a reducing agent and at the same time exhibits an effect as a dispersing agent. These reducing agents or dispersing agents may be used alone or in combination.

  The tannic acid is not particularly limited as long as it is generally classified as “tannic acid”, and includes gallotannic acid, pentaploid tannin and the like. The content of tannic acid is preferably 0.01 to 6 g with respect to monovalent metal ions / g. For example, in the case of monovalent silver ions, the tannic acid content per gram of silver ions is 0.01 to 6 g, and in the case of trivalent gold ions, the tannic acid content per gram of gold ions is 0.00. 0 3-18 g. If the tannic acid content is too low, the reduction reaction is insufficient, and if it is too high, it may be excessively adsorbed and remain in the conductive paste. A more preferable content of tannic acid is 0.02 to 1.5 g.

(1-4) Dispersion medium The metal colloid liquid of this embodiment contains the dispersion medium which disperse | distributes the solid content which has the metal colloid particle which consists of a metal component (metal particle) and an organic component as a main component. The dispersion medium may dissolve a part of the solid content. Such a dispersion medium is not particularly limited as long as it can disperse metal colloidal particles successfully, and examples thereof include water and / or an aqueous dispersion medium such as a water-soluble organic dispersion medium. It is preferable to use water and / or a water-soluble organic dispersion medium, which is an aqueous dispersion medium, because there are few adverse effects on the environment when producing the conductive paste of this embodiment.

  The water-soluble organic dispersion medium is not particularly limited as long as it does not impair the effects of the present invention. For example, a water-soluble organic solvent described later can be used as an optional component of the conductive paste. However, when used by mixing with water, it is preferable to use, for example, 75% by volume or less of an organic dispersion medium so that the resulting mixture is aqueous.

(1-5) Other components of metal colloid liquid The metal colloid liquid of this embodiment may contain a surfactant different from the organic component. In a multi-component solvent-based conductive paste, surface roughness of the coating film and uneven solid content are likely to occur due to differences in volatilization rate during drying. By adding a surfactant to the metal colloid liquid of this embodiment, a conductive paste capable of suppressing these disadvantages and forming a uniform conductive film is obtained.

  The surfactant that can be used in the present embodiment is not particularly limited, and any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant can be used, for example, an alkylbenzene sulfonate. A quaternary ammonium salt etc. are mentioned. Since the effect can be obtained with a small addition amount, a fluorosurfactant is preferable.

  If the content of the surfactant is too small, the effect cannot be obtained. If the content is too large, the remaining amount of impurities in the coating becomes an impurity, so that the conductivity may be hindered. A preferable surfactant content is 0.01 to 5 parts by mass with respect to 100 parts by mass of the dispersion medium of the metal colloid liquid.

  The viscosity of the conductive paste of this embodiment is desirably in the viscosity range of 1 to 1000 cps, more preferably in the viscosity range of 5 to 900 cps, and particularly preferably in the viscosity range of 30 to 800 cps. By setting it as the said viscosity range, a wide method is applicable as a method of apply | coating a conductive paste on a base material, or a method of drawing on a base material using a conductive paste. For example, select appropriately from dipping, screen printing, spraying method, bar coating method, spin coating method, ink jet method, dispenser method, brush coating method, casting method, flexo method, gravure method, syringe method, etc. It will be possible to adopt. The viscosity can be adjusted by adjusting the solid content concentration, adjusting the blending ratio of each component, adding a thickener, and the like.

  Here, the viscosity of the conductive paste of this embodiment is measured by a vibration viscometer VM-100A-L (for example, VM-100A-L manufactured by CBC Corporation). The measurement may be performed by immersing the liquid in the vibrator, and the measurement temperature may be normal temperature (20 to 25 ° C.).

(2) Manufacturing method of conductive paste In order to manufacture the conductive paste of this embodiment, first, a metal colloid liquid is prepared. Next, the conductive paste of this embodiment can be obtained by mixing the metal colloid liquid and the flow inhibitor.

(2-1) Method for Preparing Metal Colloid Solution The method for preparing the metal colloid solution of the present embodiment is not particularly limited. For example, a dispersion containing metal colloid particles is prepared, and then the dispersion is washed. The method of performing etc. is mentioned. As a process for preparing a solution containing metal colloidal particles, for example, a metal salt (or metal ion) dispersed in a dispersion medium may be reduced using a dispersant as described below. The procedure based on the chemical reduction method may be adopted.

  That is, the metal colloid liquid containing the metal particles and the organic component as described above can be prepared by reducing a raw material aqueous solution containing the metal salt of the metal constituting the metal particles, the organic component, and the dispersion medium. it can. By this reduction, the organic component is localized on at least a part of the surface of the metal particles, and a desired metal colloid liquid is obtained.

  The dispersion medium contained in the raw material aqueous solution for preparing the metal colloid liquid of the present embodiment (a part of the components may be dispersed without being dissolved) is aqueous, for example, water or water and water-soluble An aqueous dispersion medium composed of a mixture with an organic dispersion medium can be used.

  As a starting material for obtaining a metal component for inclusion in a metal colloid solution, various known metal salts or hydrates thereof can be used. For example, silver nitrate, silver sulfate, silver chloride, silver oxide, acetic acid Silver salts such as silver, silver nitrite, silver chlorate and silver sulfide; for example, gold salts such as chloroauric acid, potassium gold chloride and sodium gold chloride; for example, chloroplatinic acid, platinum chloride, platinum oxide and potassium chloroplatinate Platinum salts such as, for example, palladium salts such as palladium nitrate, palladium acetate, palladium chloride, palladium oxide, palladium sulfate, etc., but particularly those that can be dissolved in a suitable dispersion medium and can be reduced. It is not limited. These may be used alone or in combination.

  In addition, the method for reducing these metal salts in the raw material aqueous solution is not particularly limited, and examples thereof include a method using a reducing agent, a method of irradiating light such as ultraviolet rays, an electron beam, ultrasonic waves, or thermal energy. Among these, a method using a reducing agent is preferable from the viewpoint of easy operation.

  Examples of the reducing agent include amine compounds such as dimethylaminoethanol, methyldiethanolamine, triethanolamine, phenidone, and hydrazine; for example, hydrogen compounds such as sodium borohydride, hydrogen iodide, and hydrogen gas; for example, carbon monoxide. Oxides such as sulfurous acid; for example, ferrous sulfate, iron oxide, iron fumaroleate, iron lactate, iron oxalate, iron sulfide, tin acetate, tin chloride, tin diphosphate, tin oxalate, tin oxide, sulfuric acid Low-valent metal salts such as tin; for example, organic compounds such as sugars such as formaldehyde, hydroquinone, pyrogallol, tannin, tannic acid, salicylic acid, D-glucose, etc., but are dissolved in a dispersion medium to reduce the metal salt If it can do, it will not specifically limit. When the reducing agent is used, light and / or heat may be added to promote the reduction reaction.

  As a specific method for preparing the metal colloid liquid using the metal salt, the dispersant and the reducing agent, for example, the metal salt is dissolved in pure water to prepare a metal salt solution, and the metal salt solution is gradually added. And a method of dropping it in an aqueous solution in which a dispersant and a reducing agent are dissolved.

  In the metal colloid liquid obtained as described above, a reducing agent residue and a dispersant are present in addition to the metal colloid particles, and the electrolyte concentration of the whole liquid tends to be high. Since the liquid in such a state has high electrical conductivity, the metal colloid particles are agglomerated and easily settled. Therefore, by washing the solution containing the metal colloid particles to remove excess electrolyte, a metal colloid solution having an electric conductivity of 10 mS / cm or less can be obtained.

  As the above-mentioned washing method, for example, the obtained metal colloid liquid was allowed to stand for a certain period of time, and the resulting supernatant liquid was removed, and then pure water was added and the mixture was stirred again. Examples include a method of repeating the step of removing the supernatant several times, a method of performing centrifugation instead of the above standing, a method of desalting with an ultrafiltration device, an ion exchange device, and the like. Of these, the desalting method is preferred. Moreover, you may concentrate the liquid which desalted etc. suitably.

(2-2) Manufacturing Method of Conductive Paste The conductive paste of the present embodiment can be manufactured by mixing the metal colloid liquid and the flow inhibitor. The mixing method of the metal colloid liquid and the flow inhibitor is not particularly limited, and can be performed by a conventionally known method using a stirrer, a stirrer, or the like.

  When obtaining a conductive paste containing a plurality of metals, the production method is not particularly limited. For example, when producing a conductive paste composed of silver and other metals, The colloidal solution of silver and the colloidal solution of other metal may be produced separately and then mixed, or the silver ion solution and other metal ion solution may be mixed and then reduced.

  In addition, since the conductive paste of this embodiment includes the metal colloid liquid, the electrical conductivity can be 10 mS / cm or less. Since the conventional conductive paste reacts sensitively to the concentration of the electrolyte component present and aggregates and settles, the dispersion stability (storability) may be impaired. However, by having an electrical conductivity of 10 mS / cm or less, the conductive paste of this embodiment has sufficient dispersion stability, and the alkali outflow due to storage in a glass container, in the air It is possible to prevent deterioration in storage stability due to increase in electrolyte concentration over time due to dissolution of carbon dioxide gas.

  Furthermore, since the conductive paste having an electric conductivity of 10 mS / cm or less has high dispersion stability, it is easy to produce a conductive paste having a high solid content concentration, and the volume can be reduced. Time handling can be made easy. The conductive paste having a high concentration may be adjusted to an optimum concentration for use later using an appropriate dispersion medium.

  In addition to the metal colloid liquid and the flow inhibitor, the conductive paste of the present embodiment has functions such as adhesion, drying properties, and printability within a range that does not impair the effects of the present invention. For example, an optional component such as a resin component that serves as a binder, an organic solvent, a thickener, or a surface tension adjuster may be added. Such optional components are not particularly limited, and examples thereof include polyhydric alcohols that are arbitrarily compatible with water, antifoaming agents, leveling agents, and thickeners.

  Examples of the resin component include polyester resins, polyurethane resins such as blocked isocyanate, polyacrylate resins, polyacrylamide resins, polyether resins, melamine resins, and the like. preferable. These may be used alone or in combination of two or more.

  The organic solvent is preferably a water-soluble solvent, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, 2-propyl alcohol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,2,6-hexanetriol, 1-ethoxy-2-propanol, 2-butoxyethanol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol having a weight average molecular weight in the range of 200 to 1,000, propylene Glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having a weight average molecular weight in the range of 300 to 1,000, N, N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrole Emissions, N, N- dimethylacetamide, glycerin, or acetone, and the like. These may be used alone or in combination of two or more. Of these, the use of a polyhydric alcohol (eg, 1,3-propanediol, glycerin, ethylene glycol, etc.) that is optionally compatible with water allows the conductive paste to dry quickly while maintaining good dispersibility ( From the viewpoint that the (dryability) can be adjusted appropriately. The addition amount of the polyhydric alcohol arbitrarily compatible with water is preferably 20% by mass or less, more preferably 2 to 15% by mass with respect to the entire conductive paste.

  Examples of the thickener include clay minerals such as clay, bentonite or hectorite, for example, emulsions such as polyester emulsion resins, acrylic emulsion resins, polyurethane emulsion resins or blocked isocyanates, methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose. , Cellulose derivatives such as hydroxypropylcellulose and hydroxypropylmethylcellulose, polysaccharides such as xanthan gum and guar gum, and the like. These may be used alone or in combination of two or more. Of these, hydroxyethyl cellulose is preferred among the cellulose derivatives.

  Moreover, as an addition amount of a thickener, it is desirable that it is the range of 0.1-5 mass% with respect to the whole electrically conductive paste. If it is 0.1% by mass or more, the effect of thickening can be obtained more reliably, and if it is 5% by mass or less, the above thickener as an insulator is difficult to inhibit the firing / contact of the metal particles. The conductivity of the conductive film to be obtained can be ensured.

(3) Conductive film (base material with conductive film) and manufacturing method thereof If the conductive paste of the present embodiment is used, a conductive paste application process for applying the conductive paste to the base material, and the base material A conductive film forming step in which the applied conductive paste is baked at a temperature of 300 ° C. or lower (more preferably, more than the boiling point of the actually used flow inhibitor) to form a conductive film; The board | substrate with an electroconductive film containing a material and the electroconductive film formed in at least one part of the surface of the said base material can be manufactured.

  As a result of intensive studies, the present inventor applied the conductive paste of the present embodiment described above as the conductive paste in the conductive paste application step, and applied it to the substrate in the conductive film formation step. It has been found that a conductive film having excellent conductivity can be obtained more reliably even when the conductive paste is baked at a temperature of 300 ° C. or lower.

  Here, “applying to a base material” in the “conductive paste application step of applying a conductive paste to a base material” in the present embodiment means that the conductive paste is applied linearly (drawn) even when applied in a planar shape. ) Is a concept that includes the case of The shape of the coating film made of the conductive paste in a state before being applied and baked by heating can be changed to a desired shape. Therefore, the conductive film of the present embodiment after baking by heating is a concept including both a planar conductive film and a linear conductive film, and these planar conductive film and linear conductive film. The coating may be continuous or discontinuous, and may include a continuous portion and a discontinuous portion.

  The substrate that can be used in the present embodiment is not particularly limited as long as it has at least one main surface on which a conductive paste can be applied and fired by heating to mount a conductive film. Although it is not, it is preferable that it is a base material excellent in heat resistance. In addition, as described above, the conductive paste of this embodiment can obtain a conductive film having sufficient conductivity even when heated and baked at a lower temperature than the conventional conductive paste. Therefore, it is possible to use a base material having a lower heat-resistant temperature than the conventional one in a temperature range higher than this low firing temperature.

  Examples of the material constituting such a base material include polyamide (PA), polyimide (PI), polyamideimide (PAI), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and the like. Polyester, polycarbonate (PC), polyethersulfone (PES), vinyl resin, fluororesin, liquid crystal polymer, ceramics, glass or metal can be used. Further, the substrate may have various shapes such as a plate shape or a strip shape, and may be rigid or flexible. The thickness of the substrate can also be selected as appropriate. In order to improve adhesiveness or adhesion, or for other purposes, a substrate on which a surface layer is formed or a substrate that has been subjected to a surface treatment such as a hydrophilic treatment may be used.

  In the step of applying the conductive paste to the substrate, various methods can be used. As described above, for example, dipping, screen printing, spray method, bar coating method, spin coating method, ink jet method, A dispenser method, a brush coating method, a casting method, a flexo method, a gravure method, a syringe method, or the like can be appropriately selected and used.

  In addition, the shape of the coating film made of the conductive paste in a state before being applied and baked by heating can be changed to a desired shape. Therefore, “application” in the present embodiment is a conductive state. The coating film and the conductive film of this embodiment are applied to the surface and the linear coating film and the conductive film. It is a concept that includes both. Moreover, these planar and linear coating films and conductive coating films may be continuous or discontinuous, and may include a continuous part and a discontinuous part.

  The coating film applied as described above is baked by heating to a temperature of 300 ° C. or lower to obtain the conductive film (substrate with a conductive film) of the present embodiment. In this embodiment, as described above, since the conductive paste of this embodiment is used, a conductive film having excellent conductivity and leveling resistance can be obtained even when baked at a temperature of 300 ° C. or lower. It is definitely obtained. By this firing, the bonding between metal particles can be enhanced and sintered.

  In the present embodiment, when the conductive paste contains a binder component, the binder component is also sintered from the viewpoint of improving the strength of the conductive film and improving the adhesive strength with the base material. The main purpose of the binder component is to adjust the viscosity of the conductive paste for application to various printing methods, and the binder component may be entirely removed by controlling the firing conditions.

  The method for performing the baking is not particularly limited. For example, using a conventionally known gear oven or the like, baking is performed so that the temperature of the conductive paste applied or drawn on the substrate is 300 ° C. or lower. By this, a conductive film can be formed. The lower limit of the firing temperature is not necessarily limited, and is a temperature at which a conductive film can be formed on a substrate, and the temperature at which the flow inhibitor can be removed by evaporation or decomposition within a range that does not impair the effects of the present invention. (A part may remain within a range that does not impair the effects of the present invention, but it is desirable that all be removed desirably).

  According to the conductive paste of the present embodiment, a conductive film that exhibits high conductivity can be formed even by a low-temperature heat treatment at about 100 ° C. Therefore, a conductive film can be formed even on a relatively heat-sensitive substrate. Can be formed. Further, the firing time is not particularly limited as long as the conductive film can be formed on the base material and the flow inhibitor can be evaporated or decomposed according to the firing temperature.

In addition, the remaining amount of the flow inhibitor in the produced conductive film can be calculated by the following method. First, a conductive paste containing no flow inhibitor is prepared as a blank. After applying the conductive paste to the substrate, or after drawing on the substrate using the conductive paste, firing, scraping off the conductive film formed on the substrate using a metal spatula, It is subjected to thermogravimetric analysis (TG) measurement (temperature increase rate 10 ° C./min, nitrogen atmosphere). The weight reduction rate is determined from the weight of the coating before and after thermogravimetric analysis. Next, the conductive paste of this embodiment containing a flow inhibitor is prepared, and the film treated under the same conditions as the blank is subjected to thermogravimetric analysis under the same conditions as the blank. The difference is taken as the remaining amount of the flow inhibitor in the conductive film.
Formula: Residual amount of flow inhibitor (% by mass) = (Weight reduction ratio of conductive film of this embodiment (%) − (Weight reduction ratio of blank conductive film (%)))

  In this embodiment, in order to further improve the adhesion between the substrate and the conductive film, the substrate may be subjected to a surface treatment. Examples of the surface treatment method include a method of performing dry treatment such as corona treatment, plasma treatment, UV treatment, and electron beam treatment, and a method of previously providing a primer layer and a conductive paste receiving layer on a substrate.

  Thus, the electroconductive film (base material with an electroconductive film) of this embodiment can be obtained. Thus, the conductive film of this embodiment obtained is about 0.1-5 micrometers, for example, More preferably, it is 0.1-1 micrometer. If the conductive paste of this embodiment is used, a conductive film having sufficient conductivity can be obtained even if the thickness is about 0.1 to 5 μm. In addition, the volume resistance value of the conductive film of this embodiment is 15 μΩ · cm or less.

In addition, the thickness t of the conductive film of this embodiment can be calculated | required, for example using a following formula (The thickness t of a conductive film is measured with a laser microscope (for example, laser microscope VK-9510 by Keyence). It is also possible to do this.)
Formula: t = m / (d × M × w)
m: Weight of the conductive film (measured with an electronic balance the weight of the conductive film formed on the slide glass)
d: Conductive film density (g / cm ³ ) (10.5 g / cm ^{3 in} the case of silver)
M: Conductive film length (cm) (Measured length of conductive film formed on slide glass on a scale equivalent to JIS class 1)
w: Conductive film width (cm) (Measured width of the conductive film formed on the slide glass on a scale equivalent to JIS class 1)

  Hereinafter, although an Example and a comparative example are given and the manufacturing method of the electroconductive paste of this invention and the electroconductive film (base material with an electroconductive film) of this invention is further demonstrated, this invention is not limited to these Examples at all. Is not to be done.

<< Preparation Example 1 >>
34.1 g of trisodium citrate dihydrate (special grade manufactured by Wako Pure Chemical Industries, Ltd.) and 32.3 g of ferrous sulfate heptahydrate (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) And about 200 mL of an aqueous solution in which the solution is dissolved at room temperature while stirring, 15 mL of a 0.66 g / mL aqueous solution of silver nitrate (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) is added dropwise to the solution. Agitation was performed for a time to prepare a silver colloid solution. The obtained silver colloid solution was desalted by dialysis until the electrical conductivity was 30 μS / cm or less. After dialysis, the solution was further concentrated and centrifuged at 2100 rpm (920 G) for 10 minutes to remove coarse metal colloid particles. The silver colloid solution after removing the coarse metal colloid particles was designated as silver colloid solution A.

  The solid content in the silver colloid liquid was determined by a dry weight method. About the solid content obtained here, the thermogravimetric change in the air | atmosphere from room temperature to 500 degreeC was calculated | required at a temperature increase rate of 10 degree-C / min using TG / DTA300 by Seiko Electronics Industry Co., Ltd. The weight loss up to 500 ° C was calculated. The solid content in the silver colloidal liquid was 55% by mass, and the weight loss when the temperature was raised at 500 ° C. by thermogravimetric analysis was 2.0% by mass.

<< Preparation Example 2 >>
A silver colloid solution was prepared by carrying out the same method as in Preparation Example 1 except that disodium malate (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) was used instead of trisodium citrate dihydrate. B was obtained. The obtained silver colloidal liquid had a solid content of 55% by mass, and the weight loss upon heating at 500 ° C. by thermogravimetric analysis was 4.9% by mass.

<< Preparation Example 3 >>
90 mL of ion exchange of 0.44 g of glycine (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) and 3.2 g of ferrous sulfate heptahydrate (special grade reagent manufactured by Wako Pure Chemical Industries, Ltd.) After dissolving in water and adjusting the pH to 7 with an aqueous sodium hydroxide solution (special grade reagent made by Wako Pure Chemical Industries, Ltd. adjusted to an appropriate concentration with ion-exchanged water), ion-exchanged water is added to make the total amount. 128 mL. Next, 2 mL of an aqueous solution containing 1 g of silver nitrate (reagent special grade manufactured by Wako Pure Chemical Industries, Ltd.) was dropped while stirring with a magnetic stirrer at room temperature to prepare a silver colloid solution.

  The obtained silver colloid solution was filtered using an ultrafiltration membrane (Advantech Toyo Co., Ltd.) having a molecular weight cut off of 50,000 to remove impurity ions. The silver colloid solution after removing the impurity ions was designated as silver colloid solution C. The filtration was performed 20 times with 100 mL ion-exchanged water for a total of 2000 cc ion-exchanged water. The obtained silver colloidal liquid had a solid content of 55% by mass, and the weight loss upon heating at 500 ° C. by thermogravimetric analysis was 9.7% by mass.

<< Examples 1-8 and Comparative Examples 1-4 >>
As shown in Table 1, any one of the silver colloid liquids A to C obtained as described above and the compound shown in Table 1 are mixed, and ion-exchanged water and other additions are added to the obtained mixture. Things were added and it adjusted so that the last solid content might be 40 mass%, and the conductive pastes 1-8 and the comparative conductive pastes 1-4 were obtained.

[Evaluation test]
(1) Conductivity evaluation of conductive film Using conductive pastes 1 to 8 or comparative conductive pastes 1 to 4, dispenser (SHOTMASTER300 manufactured by Musashi Engineering Co., Ltd., needle: SNA-30G (inner diameter 0. 14 mm)), a line having a line width of 300 μm and a length of 10 cm was drawn to obtain a coating film. The obtained coating film was naturally dried and then heated in a gear oven at 250 ° C. for 1 hour. Then, the volume resistivity was calculated | required by the double bridge method using the portable double bridge 2769 made from Yokogawa Meter & Instruments. Specifically, based on the following formula, the volume resistance value was converted from the distance between the measurement terminals and the thickness of the conductive coating. The case where the volume resistance value was 15 μΩ · cm or less was evaluated as “◯”, and the case where the volume resistance value was more than 15 μΩ · cm was evaluated as “X”. The results are shown in Table 2.
Formula: (volume resistivity ρv) =
(Resistance value R) × (film width w) × (film thickness t) / (terminal distance L)

(2) Leveling resistance evaluation (drip evaluation)
On a glass substrate (trade name: AN100, manufactured by Asahi Glass Co., Ltd.), 1 μL of conductive pastes 1 to 8 or comparative conductive pastes 1 to 4 is dropped so as to form a circle with a diameter of about 3 mm, Inclined by 45 degrees and dried in a gear oven at 60 ° C. for 2 hours. After drying, the presence or absence of ink dripping was visually evaluated. The case where the liquid was not dripping was evaluated as “◯”, and the case where it was dripping was evaluated as “×”. The results are shown in Table 2.

(3) Viscosity The viscosity of the conductive pastes 1 to 8 or the comparative conductive pastes 1 to 4 was measured with a vibration viscometer VM-100A-L (manufactured by CBC). The measurement was performed by immersing the liquid in the vibrator, and the measurement temperature was normal temperature (20 to 25 ° C.).

* 1) Special grade reagent manufactured by Wako Pure Chemical Industries, Ltd., mp: 58 ° C, bp: 292-297 ° C
* 2) Special grade reagent manufactured by Wako Pure Chemical Industries, mp: 69 ° C, bp: 267 ° C
* 3) Special grade reagent manufactured by Wako Pure Chemical Industries, Ltd., mp: 36 ° C, bp: 261 ° C
* 4) Special grade reagent manufactured by Wako Pure Chemical Industries, Ltd. Decomposition point: 132.7 ° C
* 5) Special grade reagent manufactured by Wako Pure Chemical Industries, Ltd., mp: -12.9 ° C, bp: 197.3 ° C
* 6) Wako Pure Chemical Industries, Ltd., solid, molecular weight: 180, mp: 146 ° C, bp:> 300 ° C

  As is apparent from the results shown in Table 2, when the conductive paste of the present invention is used, a conductive film having sufficient conductivity even when fired at a relatively low heating temperature by including a specific flow inhibitor. Further, it can be seen that a conductive paste having leveling resistance that hardly flows on the base material after application (after drawing) to the base material can be obtained.

  The conductive paste obtained by the present invention can form a conductive film having sufficient conductivity even by firing at a relatively low heating temperature by including a specific flow inhibitor, and further to the substrate. It has leveling resistance that hardly flows on the substrate after coating (after drawing). Thereby, as a base material which apply | coats the electrically conductive paste of this invention, the application | coating and baking to resin base materials with low heat resistance other than glass, such as PET or a polyimide, are possible.

  The conductive paste of the present invention includes, for example, solar cell panel wiring, electrodes for flat panel displays, conductive materials for forming wiring for circuit boards or IC cards, through holes or circuits themselves, electromagnetic wave shielding for cathode ray tubes and plasma displays Suitable as a coating agent for infrared rays, a coating material for building materials or automobiles, an antistatic agent for electronic devices and mobile phones, a coating agent for heat rays of frosted glass, or a coating material for imparting conductivity to a resin material Can be used. In addition, since the conductive paste of the present invention can form a film exhibiting high conductivity, it is possible to form a conductive pattern excellent in conductivity without being restricted by the type of substrate. In addition, since it has excellent leveling resistance and can be adjusted to various viscosity ranges, it can be used in a wide range of drawing apparatuses, printing machines, and the like.

Claims (4)

A metal colloid liquid,
A flow inhibitor comprising an organic compound that is solid at room temperature and has a boiling point of 300 ° C. or lower,
A conductive paste characterized by The flow inhibitor is trimethylolpropane, ε-caprolactam, ethylene carbonate or urea;
The conductive paste according to claim 1. Containing the flow inhibitor in an amount of 2 to 50% by weight based on the solid content of the metal colloid liquid,
The conductive paste according to claim 1 or 2. Further comprising 1,3-propanediol, 1,2-propanediol, ethylene glycol or glycerin,
The electrically conductive paste in any one of Claims 1-3 characterized by these.