Patent Publication Number: US-2016230033-A1

Title: Conductive film forming composition, conductive film, organic thin film transistor, electronic paper, display device, and wiring board

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of PCT International Application No. PCT/JP2014/077327 filed on Oct. 14, 2014, which claims priority under 35 U.S.C. §119(a) to Japanese Patent Application No. 2013-221251 filed on Oct. 24, 2013, Japanese Patent Application No. 2013-271971 filed on Dec. 27, 2013, and Japanese Patent Application No. 2014-017288 filed on Jan. 31, 2014. Each of the above application(s) is hereby expressly incorporated by reference, in its entirety, into the present application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a conductive film forming composition and to a conductive film, an organic thin film transistor, electronic paper, a display device, and a wiring board which use the conductive film forming composition. 
     2. Description of the Related Art 
     An organic thin film transistor (organic TFT) is used in a field effect transistor (FET) used in a liquid crystal display or an organic EL display, an apparatus using a logic circuit such as an RF tag (RFID) or a memory, and the like, because the use of the organic thin film transistor makes it possible to reduce the weight of the aforementioned apparatuses, to reduce the costs, and to make the apparatuses flexible. 
     Generally, the organic thin film transistor includes a substrate, a gate insulating film, an organic semiconductor layer, and 3 electrodes (a gate electrode, a source electrode, and a drain electrode). 
     As a method for forming a conductive film such as an electrode or wiring on a substrate, an insulating film, or the like, a method is known in which the conductive film is formed by coating the substrate or the insulating film with a metal particle (for example, silver particle) dispersion and sintering the dispersion. Compared to the conductive film forming method of the related art that is performed by high heat/vacuum processing (sputtering) or a plating treatment, the aforementioned method is performed in a simpler way and saves more energy and resources. Therefore, there are great expectations for the method in regard to the development of next-generation electronics. 
     For example, JP2008-274096A discloses a conductive ink composition containing metal particles and a triarylsulfonium salt, and describes that the composition can be used for the formation of wiring of a circuit board and the like (claim 1, paragraphs “0015” and “0046”, and the like). 
     SUMMARY OF THE INVENTION 
     In recent years, as the organic thin film transistor has been increasingly miniaturized, and the performance thereof has been improved, excellent mobility (particularly, field effect mobility) and stability (for example, insulation reliability) have been required for the organic thin film transistor. 
     Under these circumstances, with reference to JP2008-274096A, the inventors of the present invention prepared an organic thin film transistor by forming electrodes using the composition containing metal particles and a triarylsulfonium salt. As a result, it has become evident that the mobility of the obtained organic thin film transistor does not satisfy the currently required level. Furthermore, as a result of testing the service life of the obtained organic thin film transistor, electrochemical migration of conductive substances markedly occurred between a source electrode and a drain electrode, and accordingly, it has become evident that the insulation reliability of the obtained organic thin film transistor does not satisfy the currently required level. 
     The present invention has been made in consideration of the aforementioned circumstances, and objects thereof are to provide a conductive film forming composition which makes it possible to obtain an organic thin film transistor having excellent insulation reliability and high mobility and to provide a conductive film, an organic thin film transistor, electronic paper, a display device, and a wiring board which use the conductive film forming composition. 
     In order to achieve the aforementioned objects, the inventors of the present invention conducted intensive investigation. As a result, the inventors obtained knowledge that by forming electrodes using a conductive film forming composition containing metal particles and a specific salt, an organic thin film transistor which exhibits excellent insulation reliability and high mobility is obtained. Based on the knowledge, the inventors accomplished the present invention. That is, the inventors found that the aforementioned objects can be achieved by the following constitution. 
     (1) A conductive film forming composition containing metal particles (A) and a compound (B) represented by Formula (I) which will be described later. 
     (2) The conductive film forming composition described in (1), in which the metal particles (A) are particles of a metal selected from the group consisting of Ag, Cu, Al, Ni, and Ta. 
     (3) The conductive film forming composition described in (1) or (2), in which in Formula (I) which will be described later, A m−  is an anion selected from the group consisting of SO 4   2− , R A2 SO 4   − , R A3 SO 3   − , PO 4   3− , R A4 PO 4   2− , (R A5 ) 2 PO 4   − , PO 3   3− , R A6 PO 3   2− , (R A7 ) 2 PO 3   − , [BF 4 ] − , [B(CN) 4 ] − , [B(C 6 H 5 ) 4 ] − , CN − , OCN − , SCN − , [R A8 —COO] − , [(R A9 —SO 2 ) 2 N] − , N(CN) 2   − , and (R A11 ) 2 NCS 2   −  (herein, each of R A2  to R A9  and R A11  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent). 
     (4) The conductive film forming composition described in any one of (1) to (3), in which in Formula (I) which will be described later, C n+  is a cation selected from the group consisting of Formulae (A) to (C). 
     (5) The conductive film forming composition described in any one of (1) to (4), in which in Formula (I) which will be described later, A m−  is an anion selected from the group consisting of SO 4   2− , R A2 SO 4   − , and R A3 SO 3   −  (herein, each of R A2  and R A3  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent). 
     (6) A conductive film formed using the conductive film forming composition described in any one of (1) to (5). 
     (7) An organic thin film transistor including electrodes formed using the conductive film forming composition described in any one of (1) to (5). 
     (8) Electronic paper using the organic thin film transistor described in (7). 
     (9) A display device using the organic thin film transistor described in (7). 
     (10) A wiring board including wiring formed using the conductive film forming composition described in any one of (1) to (5). 
     As will be described below, according to the present invention, it is possible to provide a conductive film forming composition which makes it possible to obtain an organic thin film transistor exhibiting excellent insulation reliability and high mobility and to provide a conductive film, an organic thin film transistor, electronic paper, a display device, and a wiring board which use the conductive film forming composition. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view of an aspect of an organic thin film transistor of the present invention. 
         FIG. 2  is a schematic sectional view of another aspect of the organic thin film transistor of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a conductive film forming composition of the present invention and the organic thin film transistor and the like using the conductive film forming composition will be described. 
     In the present specification, a range of numerical values represented using “to” means a range including the numerical values listed before and after “to” as a lower limit and an upper limit respectively. 
     [Conductive Film Forming Composition] 
     The conductive film forming composition of the present invention (hereinafter, referred to as a composition of the present invention as well) contains metal particles (A) and a compound (B) represented by Formula (I) which will be described later. 
     It is considered that intended effects are obtained because the composition of the present invention is constituted as above. 
     The reason is unclear but is assumed to be as below. 
     When voltage is applied to an electrode of an organic thin film transistor, due to the action of an electric field, a conductive substance such as a metal in the electrode is ionized, and this leads to the movement (migration) of ions in an organic semiconductor layer in some cases. If the migration occurs, the insulating properties between source/drain electrodes deteriorate. That is, the insulation reliability deteriorates. 
     In a case where an electrode (conductive film) is formed using the composition of the present invention, the electrode contains a conductive substance such as a metal and the compound (B) constituted with specific cation and anion. Consequently, even if the conductive substance such as a metal in the electrode is ionized as described above, the substance is trapped in the compound (B) in the electrode, and hence the migration is prevented. That is, the compound (B) functions as an excellent migration inhibitor (anti-migration agent). It is considered that, as a result, the organic thin film transistor having an electrode formed using the composition of the present invention exhibits excellent insulation reliability. The mechanism described above is considered to result from a fact that the specific anion contained in the compound (B) exhibits extremely high affinity with ions of the conductive substance such as a metal. 
     Because of being highly stable in the electrode, and hence the compound (B) does not easily dissociate and move to the adjacent organic semiconductor layer or the like. It is considered that, as a result, the compound (B) substantially does not exert a negative influence on the mobility of the organic thin film transistor, and thus the organic thin film transistor exhibits high mobility. The mechanism described above is considered to particularly result from a fact that the compound (B) has properties in which the specific cation or anion contained in the compound (B) does not easily dissociate even in a state where the ions are trapped in the compound (B). 
     Hereinafter, each component contained in the composition of the present invention will be specifically described. 
     &lt;Metal Particles (A)&gt; 
     The metal particles (A) contained in the composition of the present invention are not particularly limited as long as they have a particle shape. 
     The particle shape refers to the shape of a small particle, and examples thereof include a spherical shape, an elliptical shape, and the like. The particle does not need to be a perfect sphere or ellipse and may be partially distorted. 
     The metal particles (A) are preferably particles of a metal selected from the group consisting of silver (Ag), copper (Cu), aluminum (Al), nickel (Ni), and tantalum (Ta), more preferably silver particles or copper particles, and even more preferably silver particles. 
     The metal particles (A) are preferably conductive nanoparticles. 
     In a case where the metal particles (A) are silver nanoparticles, the method for preparing the particles is not particularly limited. However, for example, the particles can be prepared by a method in which an aqueous solution of a reductant such as N,N-diethylhydroxylamine is added dropwise to an aqueous solution of a silver salt such as silver nitrate in the presence of a dispersing agent such that the silver salt is reduced by the reductant. 
     The average particle size of the metal particles (A) is not particularly limited. However, it is preferably equal to or less than 200 nm, and more preferably equal to or less than 100 nm. The lower limit of the average particle size is not particularly limited but is preferably equal to or greater than 5 nm. 
     In the present invention, the average particle size means an average particle size measured using a concentrated system particle size analyzer FPAR-1000 (manufactured by OTSUKA ELECTRONICS Co., LTD). 
     The content of the metal particles (A) in the composition of the present invention is not particularly limited. However, the content of the metal particles (A) is preferably 5.0% by mass to 80.0% by mass, and more preferably 10.0% by mass to 60.0% by mass, with respect to the total amount of the composition. 
     &lt;Compound (B)&gt; 
     The composition of the present invention contains the compound (B) represented by the following Formula (I). 
         c C n+   a A m−   Formula (I)
 
     (Cation) 
     In Formula (I), Cn +  represents an n-valent cation. Herein, n represents an integer of 1 to 6. That is, C n+  is a cation having a valency of 1 to 6. 
     In a case where n in Formula (I) is 1 (that is, in a case where C n+  is a monovalent cation), C n+  represents a cation selected from the group consisting of the following Formulae (A) to (E). Among these, C n+  is preferably a cation selected from the group consisting of Formulae (A) to (C). C n+  is more preferably a cation represented by Formula (A) or (B) because then the obtained organic thin film transistor exhibits better insulation reliability. 
     
       
         
         
             
             
         
       
     
     In Formula (A), each of R 1  to R 4  independently represents a hydrogen atom or a hydrocarbon group (excluding a hydroxyalkyl group) which may have a substituent. Here, there is no case where all of R 1  to R 4  represent a hydrogen atom at the same time. 
     The hydrocarbon group is not particularly limited, and examples thereof include a aliphatic hydrocarbon group, an aromatic hydrocarbon group, a group obtained by combining these, and the like. 
     The aliphatic hydrocarbon group may be linear, branched, or cyclic. The number of carbon atoms of the aliphatic hydrocarbon group is not particularly limited, but is preferably 1 to 12. Specific examples of the aliphatic hydrocarbon group include an alkyl group, an alkenyl group, an alkynyl group, and the like. 
     The number of carbon atoms of the aromatic hydrocarbon group is not particularly limited, but is preferably 6 to 18. Specific examples of the aromatic hydrocarbon group include an aryl group (a phenyl group, a tolyl group, a xylyl group, or the like), a naphthyl group, and the like. 
     Examples of the aforementioned substituent include a substituent Q, which will be described later, and the like. 
     The substituent is preferably a substituent other than a hydroxy group because then the obtained organic thin film transistor exhibits higher mobility. 
     At least one of R 1  to R 4  is preferably and aromatic hydrocarbon group because then the obtained organic thin film transistor exhibits higher mobility. 
     As described above, none of R 1  to R 4  in Formula (A) is a hydroxyalkyl group. The hydroxyalkyl group is an alkyl group having a hydroxy group, and examples thereof include a hydroxyethyl group (—C 2 H 4 —OH) and the like. 
     In a case where any of R 1  to R 4  is a hydroxyalkyl group, carriers moving between electrodes are trapped, and as a result, the mobility of the obtained organic thin film transistor deteriorates. 
     Furthermore, as described above, there is no case where all of R 1  to R 4  in Formula (A) represent a hydrogen atom at the same time. That is, C n+  is not NH 4   + . In a case where C n+  is NH 4   + , dissociated ammonia easily volatilizes. Accordingly, thermal stability decreases, and the compound (B) is easily decomposed at the time when a conductive film (electrode) is formed by sintering or the like. As a result, the insulation reliability of the obtained organic thin film transistor deteriorates. 
     In Formula (A), each of R 1  to R 4  may form a cyclic structure by being bonded to each other. That is, two or more groups selected from the group consisting of R 1  to R 4  may form a cyclic structure by being bonded to each other. In the present specification, forming a cyclic structure by being bonded to each other means that two or more groups form a cyclic structure by being bonded to each other at any position through a single bond, a double bond, or a triple bond or through a divalent linking group. 
     The divalent linking group is not particularly limited, and examples thereof include —CO—, —NH— —NR— (R: substituent (for example, a substituent Q which will be described later)), —O—, —S—, a group obtained by combining these, and the like. 
     Preferred aspects of the cation represented by Formula (A) will be shown below. Herein, each R p  independently represents the group represented by R 1  to R 4  described above. A plurality of R p &#39;s may be the same as or different from each other. Each R independently represents a hydrogen atom or a substituent (for example, a substituent Q which will be described later). 
     
       
         
         
             
             
         
       
     
     In Formula (B), R 5  represents a hydrocarbon group which may have a substituent, —NR 19 R 20 , —N═CR 21 R 22 , —CR 23 ═NR 24 , or —CR B1 R B2 —NR B3 R B4 . Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     Each of R 19  to R 24  and R B1  to R B4  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. R 19  and R 20  may form a cyclic structure by being bonded to each other. 
     In Formula (B), R 6  represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     In Formula (B), R 7  represents a hydrogen atom, a hydrocarbon group which may have a substituent, an alkoxy group, an alkylthio group, a hydroxy group, a mercapto group, or —NR 25 R 26 . Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     Each of R 25  and R 26  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent, and may form a cyclic structure by being bonded to each other. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     In Formula (B), R 8  represents a hydrogen atom, a hydrocarbon group which may have a substituent, an alkoxy group, an alkylthio group, a hydroxy group, a mercapto group, —NR 27 R 28 , —N═CR 29 R 30 , or —CR 31 ═NR 32 . Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     Each of R 27  to R 32  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. R 27  and R 28  may form a cyclic structure by being bonded to each other. 
     Here, there is no case where both of R 7  and R 8  in Formula (B) represent an alkoxy group, a hydroxy group, an alkylthio group, or a mercapto group at the same time. 
     Furthermore, there is no case where all of R 5 , R 7 , and R 8  in Formula (B) represent —NR 19 R 20 , —NR 25 R 26 , or —NR 27 R 28  at the same time. That is, there is no case where R 5 , R 7 , and R 8  represent —NR 19 R 20 , —NR 25 R 26 , and —NR 27 R 28  respectively at the same time. 
     In Formula (B), each of R 5  to R 8  may form a cyclic structure by being bonded to each other. That is two or more groups selected from the group consisting of R 5  to R 8  may form a cyclic structure by being bonded to each other. 
     Two or more groups selected from the group consisting of R 5  to R 8  preferably form a cyclic structure by being bonded to each other. 
     In a case where R 5  forms a cyclic structure, the divalent group derived from R 5  in the cyclic structure is preferably a group selected from the group consisting of the following Formulae (a) to (f). 
     In a case where R 6  forms a cyclic structure, the divalent group derived from R 6  in the cyclic structure is preferably a divalent group selected from the group consisting of the following Formulae (a) to (d). 
     In a case where R 7  forms a cyclic structure, the divalent group derived from R 7  in the cyclic structure is preferably a divalent group selected from the group consisting of the following Formula (a) to (e), (g), and (h). 
     In a case where R 8  forms a cyclic structure, the divalent group derived from R 8  in the cyclic structure is preferably a divalent group selected from the group consisting of the following Formulae (a) to (h). 
     Here, there is no case where both of the “divalent group derived from R 7  in the cyclic structure” and the “divalent group derived from R 8  in the cyclic structure” are represented by the following (g) or (h) at the same time. Furthermore, there is no case where all of the “divalent group derived from R 5  in the cyclic structure”, the “divalent group derived from R 7  in the cyclic structure”, and the “divalent group derived from R 8  in the cyclic structure” are represented by the following Formula (e) at the same time. 
     
       
         
         
             
             
         
       
     
     In Formulae (a) to (f), each of R 35  to R 48  independently represents a hydrogen atom or a substituent. Examples of the substituent include a substituent Q which will be described later. 
     In Formulae (a) to (h), each asterisk (*) represents a binding position. One of two asterisks represents a binding position of each group in Formula (B) and the other asterisk represents a binding position at the time when the groups are bonded to each other to form a cyclic structure. For example, in a case where R 5  and R 6  in Formula (B) form a cyclic structure by being bonded to each other; the divalent group derived from R 5  in the cyclic structure is a group represented by Formula (a); and the divalent group derived from R 6  in the cyclic structure is a group represented by Formula (b), one of the asterisks in Formulae (a) and (b) represents a position of binding to N +  in Formula (B), and the other asterisk in Formulae (a) and (b) represents a binding position at the time when R 5  and R 6  are bonded to each other. 
     Preferred aspects of the cation represented by Formula (B) will be shown below. Herein, R p  represents the group represented by R 5  or R 6  described above; R s  represents the group represented by R 7  or R 8  described above; and each R independently represents a hydrogen atom or a substituent (for example, a substituent Q which will be described later). 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     In Formula (C), R 9  represents either a hydrocarbon group which may have a substituent or —NR C1 R C2 . Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     Each of R C1  and R C2  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     In Formula (C), R 10  represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     In Formula (C), R 11  represents a hydrocarbon group which may have a substituent, —CR 33 ═NR 34 , or —NR C3 R C4 . Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     Each of R 33 , R 34 , R C3 , and R C4  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     In Formula (C), each of R 9  to R 11  may form a cyclic structure by being bonded to each other. That is, two or more groups selected from the group consisting of R 9  to R 11  may form a cyclic structure by being bonded to each other. 
     Preferred aspects of the cation represented by Formula (C) will be shown below. Herein, R p  represents the group represented by R 9  or R 10  described above, and each R independently represents a hydrogen atom or a substituent (for example, a substituent Q which will be described later). 
     
       
         
         
             
             
         
       
     
     In Formula (D), each of R 12  to R 15  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples and preferred aspects of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     Here, there is no case where all of R 12  to R 15  in Formula (D) represent a hydrogen atom at the same time. That is, C n+  is not PH 4   + . In a case where C n+  is PH 4   + , thermal stability deteriorates, and the compound (B) is easily decomposed at the time when a conductive film (electrode) is formed by sintering or the like. As a result, the insulation reliability of the obtained organic thin film transistor deteriorates. 
     In Formula (D), each of R 12  to R 15  may form a cyclic structure by being bonded to each other. That is, two or more groups selected from the group consisting of R 12  to R 15  may form a cyclic structure by being bonded to each other. 
     In Formula (E), each of R 16  to R 18  independently represents an alkyl group which may have a substituent. The alkyl group may be linear, branched, or cyclic. The number of carbon atoms of the alkyl group is not particularly limited, but is preferably 1 to 12. Examples of the substituent include a substituent Q, which will be described later, and the like. 
     As described above, each of R 16  to R 18  in Formula (E) independently represents an alkyl group which may have a substituent. In a case where any of R 16  to R 18  is a hydrocarbon group (for example, an aromatic hydrocarbon group) other than the alkyl group, the stability of the compound (B) in the electrode deteriorates, and as a result, the mobility of the organic thin film transistor deteriorates. 
     In Formula (E), each of R 16  to R 18  may form a cyclic structure by being bonded to each other. That is, two or more groups selected from the group consisting of R 16  to R 18  may form a cyclic structure by being bonded to each other. 
     Each of R 5  to R 34 , R B1  to R B4 , and R C1  to R C4  described above may be a hydroxyalkyl group. 
     In a case where n in Formula (I) is 2 to 6 (that is, in a case where C n+  is a cation having a valency of 2 to 6), C n+  represents a cation having, as partial structures, n cations selected from the group consisting of Formulae (A) to (E) in the same molecule. That is, in a case where n in Formula (I) is 2 to 6, C n+  represents a cation having n partial structures, which are obtained by removing one or more hydrogen atoms from cations selected from the group consisting of Formulae (A) to (E), in the same molecule. Herein, C n+  may be either a cation having one kind of n partial structures or a cation having two or more kinds of a total of n partial structures. 
     In a case where n in Formula (I) is 2 to 6, C n+  is preferably a cation in which n cations selected from the group consisting of Formulae (A) to (E) are bonded to each other at any position through a single bond, a double bond, a triple bond, or a divalent linking group. Specific examples of the divalent linking group are as described above. Herein, C n+  may be either a cation in which one kind of n cations are bonded to each other or a cation in which two or more kinds of a total of n cations are bonded to each other. 
     (Anion) 
     In Formula (I), A m−  represents an m-valent anion. Herein, m represents an integer of 1 to 3. That is, A m−  is an anion having a valency of 1 to 3. 
     A m−  is not an anion selected from the group consisting of Cl − , Br − , I − , PF 6   − , R A1 CO 3   − , R A10 NHCOO − , SbF 6   − , and AsF 6   − . Herein, each of R A1  and R A10  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     In a case where A m−  is an anion selected from the group consisting of Cl − , Br − , I − , PF 6   − , R A1 CO 3   − , R A10 NHCOO − , SbF 6   − , and AsF 6   − , the mobility or insulation reliability of the obtained organic thin film transistor becomes insufficient. 
     A m−  is preferably an anion selected from the group consisting of SO 4   2− , R A2 SO 4   − , R A3 SO 3   − , PO 4   3− , R A4 PO 4   2− , (R A5 ) 2 PO 4   − , PO 3   3− , R A6 PO 3   2− , (R A7 ) 2 PO 3   − , [BF 4 ] − , [B(CN) 4 ] − , [B(C 6 H 5 ) 4 ] − , CN − , OCN − , SCN − , [R A8 —COO] − , [(R A9 —SO 2 ) 2 N] − , N(CN) 2   − , and (R A11 ) 2 NCS 2   − , and more preferably an anion selected from the group consisting of SO 4   2− , R A2 SO 4   − , R A3 SO 3   − , and (R A5 ) 2 PO 4   − . A m−  is even more preferably an anion selected from the group consisting of SO 4   2− , R A2 SO 4   − , and R A3 SO 3   −  because then the obtained organic thin film transistor exhibits higher mobility. Herein, each of R A2  to R A9  and R A11  independently represents a hydrogen atom or a hydrocarbon group which may have a substituent. Specific examples of the hydrocarbon group which may have a substituent are the same as those of R 1  to R 4  in Formula (A) described above. 
     R A2  is preferably a hydrogen atom or an alkyl group. 
     R A3  is preferably an alkyl group (particularly, an alkyl group having 1 to 12 carbon atoms) which may have a substituent, an aromatic hydrocarbon group (particularly, an aromatic hydrocarbon group having 6 to 18 carbon atoms) which may have a substituent, or a perfluoroalkyl group (a linear or branched alkyl group in which all of the hydrogen atoms are substituted with fluorine atoms). 
     It is preferable that each of R A4  and R A5  independently represents a hydrogen atom or an alkyl group. 
     It is preferable that each of R A6  and R A7  independently represents an aliphatic hydrocarbon group (particularly, an aliphatic hydrocarbon group having 1 to 12 carbon atoms) which may have a substituent. 
     R A8  is preferably a perfluoroalkyl group (a linear or branched alkyl group in which all of the hydrogen atoms are substituted with fluorine atoms). 
     R A9  is preferably an alkyl group (particularly, an alkyl group having 1 to 12 carbon atoms) which may have a substituent, and particularly preferably a perfluoroalkyl group (a linear or branched alkyl group in which all of the hydrogen atoms are substituted with fluorine atoms). 
     Each of R A1  to R A11  may be a hydroxyalkyl group. 
     In Formula (I), c represents an integer of 1 to 3, and a represents an integer of 1 to 6. c, n, a, and m in Formula (I) satisfy a relational expression of c×n=a×m. That is, the compound (B) is a neutrally charged salt composed of a cation (C n+ ) in a number of c and an anion (A m− ) in a number of a. 
     It is preferable that all of c, n, a, and m represent 1. 
     (Substituent Q) 
     In the present specification, examples of the substituent Q include a halogen atom, an alkyl group (including a cycloalkyl group and a perfluoroalkyl group), an alkenyl group (including a cycloalkenyl group and a bicycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group, a cyano group, a hydroxy group, a nitro group, a carboxyl group, an alkoxy group, an aryloxy group, a silyloxy group, a heterocyclic oxy group, an acyloxy group, a carbamoyloxy group, an alkoxycarbonyloxy group, aryloxycarbonyloxy, an amino group (including an anilino group), an acylamino group, an aminocarbonylamino group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino group, alkyl and aryl sulfonylamino groups, a mercapto group, an alkylthio group, an arylthio group, a heterocyclic thio group, a sulfamoyl group, a sulfo group, alkyl and aryl sulfinyl groups, alkyl and aryl sulfonyl groups, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, a carbamoyl group, aryl and heterocyclic azo groups, an imide group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a silyl group, a combination of these, and the like. 
     More specifically, examples of the substituent Q include a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an alkyl group [(it means a substituted or unsubstituted linear, branched, or cyclic alkyl group and a perfluoroalkyl group (a linear or branched alkyl group in which all of the hydrogen atoms are substituted with fluorine atoms); these also include an alkyl group (preferably an alkyl group having 1 to 30 carbon atoms, for example, methyl, ethyl, n-propyl, isopropyl, t-butyl, n-octyl, eicosyl, 2-chloroethyl, 2-cyanoethyl, or 2-ethylhexyl), a perfluoroalkyl group (preferably a perfluoroalkyl group having 1 to 8 carbon atoms, for example, a trifluoromethyl group, a nonafluorobutyl group, or a tridecafluorohexyl group), a cycloalkyl group (preferably a substituted or unsubstituted cycloalkyl group having 3 to 30 carbon atoms, for example, cyclohexyl, cyclopentyl, or 4-n-dodecylcyclohexyl), a bicycloalkyl group (preferably a substituted or unsubstituted bicycloalkyl group having 5 to 30 carbon atoms, that is, a monovalent group obtained by removing one hydrogen atom from bicycloalkane having 5 to 30 carbon atoms, for example, bicyclo[1.2.2]heptan-2-yl or bicyclo[2.2.2]octan-3-yl), a tricyclo structure consisting of a large number of cyclic structures, and the like. An alkyl group in a substituent described below (for example, an alkyl group of an alkylthio group) also means the alkyl group having the concept described above], 
     an alkenyl group [it means a substituted or unsubstituted linear, branched, or cyclic alkenyl group; these also include an alkenyl group (preferably a substituted or unsubstituted alkenyl group having 2 to 30 carbon atoms, for example, vinyl, allyl, prenyl, geranyl, or oleyl), a cycloalkenyl group (preferably a substituted or unsubstituted cycloalkenyl group having 3 to 30 carbon atoms, that is, a monovalent group obtained by removing one hydrogen atom from cycloalkene having 3 to 30 carbon atoms, for example, 2-cyclopenten-1-yl or 2-cyclohexen-1-yl), and a bicycloalkenyl group (a substituted or unsubstituted bicycloalkenyl group and preferably a substituted or unsubstituted bicycloalkenyl group having 5 to 30 carbon atoms, that is, a monovalent group obtained by removing one hydrogen atom from bicycloalkene having one double bond, for example, bicyclo[2.2.1]hept-2-en-1-yl or bicyclo[2.2.2]oct-2-en-4-yl)], an alkynyl group (preferably a substituted or unsubstituted alkynyl group having 2 to 30 carbon atoms, for example, an ethynyl, propargyl, or trimethylsilylethynyl group), 
     an aryl group (preferably a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, for example, phenyl, p-tolyl, naphthyl, m-chlorophenyl, or o-hexadecanoylaminophenyl), a heterocyclic group (preferably a monovalent group obtained by removing one hydrogen atom from a 5-membered or 6-membered substituted or unsubstituted aromatic or non-aromatic heterocyclic compound, more preferably, a 5-membered or 6-membered aromatic heterocyclic group having 3 to 30 carbon atoms, for example, 2-furanyl, 2-thienyl, 2-pyrimidinyl, or 2-benzothiazolinyl), 
     a cyano group, a hydroxy group, a nitro group, a carboxyl group, an alkoxy group (preferably a substituted or unsubstituted alkoxy group having 1 to 30 carbon atoms, for example, methoxy, ethoxy, isopropoxy, t-butoxy, n-octyloxy, or 2-methoxyethoxy), an aryloxy group (preferably a substituted or unsubstituted aryloxy group having 6 to 30 carbon atoms, for example, phenoxy, 2-methylphenoxy, 4-t-butylphenoxy, 3-nitrophenoxy, or 2-tetradecanoylaminophenoxy), a silyloxy group (preferably a silyloxy group having 3 to 20 carbon atoms, for example, trimethylsilyloxy or t-butyldimethylsilyloxy), a heterocyclic oxy group (preferably a substituted or unsubstituted heterocyclic oxy group having 2 to 30 carbon atoms, 1-phenyltetrazol-5-oxy or 2-tetrahydropyranyloxy), an acyloxy group (preferably a formyloxy group, a substituted or unsubstituted alkylcarbonyloxy group having 2 to 30 carbon atoms, or a substituted or unsubstituted arylcarbonyloxy group having 6 to 30 carbon atoms, for example, formyloxy, acetyloxy, pivaloyloxy, stearoyloxy, benzoyloxy, or p-methoxyphenylcarbonyloxy), a carbamoyloxy group (preferably a substituted or unsubstituted carbamoyloxy group having 1 to 30 carbon atoms, for example, N,N-dimethylcarbamoyloxy, N,N-diethylcarbamoyloxy, morpholinocarbonyloxy, N,N-di-n-octylaminocarbonyloxy, or N-n-octylcarbamoyloxy), an alkoxycarbonyloxy group (preferably a substituted or unsubstituted alkoxycarbonyloxy group having 2 to 30 carbon atoms, for example, methoxycarbonyloxy, ethoxycarbonyloxy, t-butoxycarbonyloxy, or n-octylcarbonyloxy), an aryloxycarbonyloxy group (preferably a substituted or unsubstituted aryloxycarbonyloxy group having 7 to 30 carbon atoms, for example, phenoxycarbonyloxy, p-methoxyphenoxycarbonyloxy, or p-n-hexadecyloxyphenoxycarbonyloxy), 
     an amino group (preferably an amino group, a substituted or unsubstituted alkylamino group having 1 to 30 carbon atoms, or a substituted or unsubstituted anilino group having 6 to 30 carbon atoms, for example, amino, methylamino, dimethylamino, anilino, N-methyl-anilino, or diphenylamino), an acylamino group (preferably a formylamino group, a substituted or unsubstituted alkylcarbonylamino group having 1 to 30 carbon atoms, or a substituted or unsubstituted arylcarbonylamino group having 6 to 30 carbon atoms, for example, formylamino, acetylamino, pivaloylamino, lauroylamino, benzoylamino, 3,4,5-tri-n-octyloxyphenylcarbonylamino), an aminocarbonylamino group (preferably substituted or unsubstituted aminocarbonylamino having 1 to 30 carbon atoms, for example, carbamoylamino, N,N-dimethylaminocarbonylamino, N,N-diethylaminocarbonylamino, or morpholinocarbonylamino), an alkoxycarbonylamino group (preferably a substituted or unsubstituted alkoxycarbonylamino group having 2 to 30 carbon atoms, for example, methoxycarbonyl amino, ethoxycarbonylamino, t-butoxycarbonylamino, n-octadecyloxycarbonylamino, or N-methyl-methoxycarbonylamino), an aryloxycarbonylamino group (preferably a substituted or unsubstituted aryloxycarbonylamino group having 7 to 30 carbon atoms, for example, phenoxycarbonylamino, p-chlorophenoxycarbonylamino, or m-n-octyloxyphenoxycarbonylamino), a sulfamoylamino group (preferably a substituted or unsubstituted sulfamoylamino group having 0 to 30 carbon atoms, for example, sulfamoylamino, N,N-dimethylaminosulfonylamino, or N-n-octylaminosulfonylamino), alkyl and aryl sulfonylamino groups (preferably substituted or unsubstituted alkylsulfonylamino having 1 to 30 carbon atoms and substituted or unsubstituted arylsulfonylamino having 6 to 30 carbon atoms, for example, methylsulfonylamino, butylsulfonylamino, phenylsulfonylamino, 2,3,5-trichlorophenylsulfonylamino, or p-methylphenylsulfonylamino), 
     a mercapto group, an alkylthio group (preferably a substituted or unsubstituted alkylthio group having 1 to 30 carbon atoms, for example, methylthio, ethylthio, or n-hexadecylthio), an arylthio group (preferably substituted or unsubstituted aryltho having 6 to 30 carbon atoms, for example, phenylthio, p-chlorophenylthio, or m-methoxyphenylthio), a heterocyclic thio group (preferably a substituted or unsubstituted heterocyclic thio group having 2 to 30 carbon atoms, for example, 2-benzothiazolylthio or 1-phenyltetrazol-5-ylthio), a sulfamoyl group (preferably a substituted or unsubstituted sulfamoyl group having 0 to 30 carbon atoms, for example, N-ethylsulfamoyl, N-(3-dodecyloxypropyl)sulfamoyl, N,N-dimethylsulfamoyl, N-acetylsulfamoyl, N-benzoylsulfamoyl, or N—(N′-phenylcarbamoyl)sulfamoyl), a sulfo group, alkyl and aryl sulfinyl groups (preferably a substituted or unsubstituted alkylsulfinyl group having 1 to 30 carbon atoms and a substituted or unsubstituted arylsulfinyl group having 6 to 30 carbon atoms, for example, methylsulfinyl, ethylsulfinyl, phenylsulfinyl, or p-methylphenylsulfinyl), 
     alkyl and aryl sulfonyl groups (preferably a substituted or unsubstituted alkylsulfonyl group having 1 to 30 carbon atoms and a substituted or unsubstituted arylsulfonyl group having 6 to 30 carbon atoms, for example, methylsulfonyl, ethylsulfonyl, phenylsulfonyl, and p-methylphenylsulfonyl), an acyl group (preferably a formyl group, a substituted or unsubstituted alkylcarbonyl group having 2 to 30 carbon atoms, a substituted or unsubstituted arylcarbonyl group having 7 to 30 carbon atoms, or a substituted or unsubstituted heterocyclic carbonyl group having 4 to 30 carbon atoms that is bonded to a carbonyl group through carbon atoms, for example, acetyl, pivaloyl, 2-chloroacetyl, stearoyl, benzoyl, p-n-octyloxyphenylcarbonyl, 2-pyridylcarbonyl, or 2-furylcarbonyl), an aryloxycarbonyl group (preferably a substituted or unsubstituted aryloxycarbonyl group having 7 to 30 carbon atoms, for example, phenoxycarbonyl, o-chlorophenoxycarbonyl, m-nitrophenoxycarbonyl, or p-t-butylphenoxycarbonyl), an alkoxycarbonyl group (preferably a substituted or unsubstituted alkoxycarbonyl group having 2 to 30 carbon atoms, for example, methoxycarbonyl, ethoxycarbonyl, t-butoxycarbonyl, or n-octadecyloxycarbonyl), 
     a carbamoyl group (preferably substituted or unsubstituted carbamoyl having 1 to 30 carbon atoms, for example, carbamoyl, N-methylcarbamoyl, N,N-dimethylcarbamoyl, N,N-di-n-octylcarbamoyl, or N-(methylsulfonyl)carbamoyl), aryl and heterocyclic azo groups (preferably a substituted or unsubstituted arylazo group having 6 to 30 carbon atoms and a substituted or unsubstituted heterocyclic azo group having 3 to 30 carbon atoms, for example, phenylazo, p-chlorophenylazo, and 5-ethylthio-1,3,4-thiadiazol-2-ylazo), an imide group (preferably N-succinimide or N-phthalimide), a phosphino group (preferably a substituted or unsubstituted phosphino group having 2 to 30 carbon atoms, for example, dimethylphosphino, diphenylphosphino, or methylphenoxyphosphino), a phosphinyl group (preferably a substituted or unsubstituted phosphinyl group having 2 to 30 carbon atoms, for example, phosphinyl, dioctyloxyphosphinyl, or diethoxyphosphinyl), a phosphinyloxy group (preferably a substituted or unsubstituted phosphinyloxy group having 2 to 30 carbon atoms, for example, diphenoxyphosphinyloxy or dioctyloxyphosphinyloxy), a phosphinylamino group (preferably a substituted or unsubstituted phosphinylamino group having 2 to 30 carbon atoms, for example, dimethoxyphosphinylamino or dimethylaminophosphinylamino), or a silyl group (preferably a substituted or unsubstituted silyl group having 3 to 30 carbon atoms, for example, trimethylsilyl, t-butyldimethylsilyl, or phenyldimethylsilyl). 
     The content of the compound (B) in the composition of the present invention is not particularly limited. However, a ratio of the content of the compound (B) to the content of the metal particles (A) is preferably 0.1% by mass to 20.0% by mass, more preferably 1.0% by mass to 10.0% by mass because then the obtained organic thin film transistor exhibits better insulating properties, and even more preferably 3.0% by mass to 8.0% by mass. 
     A ratio of the content of the compound (B) to the total amount of the composition is not particularly limited, but is preferably 0.01% by mass to 15% by mass and more preferably 0.5% by mass to 5.0% by mass. The ratio of the content of the compound (B) to the total amount of the composition is even more preferably equal to or greater than 1.0% by mass because then the obtained organic thin film transistor exhibits better insulating properties. 
     &lt;Optional Components&gt; 
     (Solvent) 
     From the viewpoint of ease of regulating viscosity and coating properties, the composition of the present invention preferably contains a solvent. The solvent functions as a dispersion medium of the metal particles (A). 
     The type of the solvent is not particularly limited, and for example, water, organic solvents such as alcohols, ethers, and esters, and the like can be used. Among these, water is preferable. 
     The content of the solvent is not particularly limited. However, it is preferably 20% by mass to 90% by mass with respect to the total amount of the composition because then the increase in viscosity is inhibited and thus the handleability is improved. 
     (Other Components) 
     The composition of the present invention may contain components other than the components described above. For example, the composition of the present invention may contain a dispersing agent, a surfactant, and the like. 
     &lt;Method for Preparing Conductive Film Forming Composition&gt; 
     The method for preparing the composition of the present invention is not particularly limited, and known methods can be adopted. For example, the composition can be obtained by a method in which the metal particles (A) and the compound (B) are added to the aforementioned solvent, and then the solution is stirred by known means such as an ultrasonic method (for example, a treatment performed using an ultrasonic homogenizer), a mixer method, a triple roll method, or a ball mill method. 
     The composition of the present invention is useful as a conductive film forming composition for forming an electrode of a field effect transistor (particularly, an organic thin film transistor). The electrode may be any of a source electrode, a drain electrode, and a gate electrode. Particularly, the composition of the present invention is useful for a source electrode and a drain electrode. 
     Furthermore, as described above, the compound (B) contained in the composition of the present invention functions as a migration inhibitor and hence brings about excellent insulation reliability. Therefore, the composition of the present invention is also useful as a conductive film forming composition for forming wiring of a wiring board (for example, printed wiring board) and the like. 
     [Organic Thin Film Transistor] 
     The organic thin film transistor of the present invention is an organic thin film transistor including electrodes (particularly, a source electrode and a drain electrode) formed using the composition of the present invention described above. The organic thin film transistor may be a bottom contact type (a bottom gate-bottom contact type or a top gate-bottom contact type) or a top contact type (a bottom gate-top contact type or a top gate-top contact type). 
     An aspect of the organic thin film transistor of the present invention will be described with reference to a drawing. 
       FIG. 1  is a schematic sectional view of an aspect of the organic thin film transistor of the present invention. 
     In  FIG. 1 , an organic thin film transistor 100 includes a substrate 10, a gate electrode 20 which is disposed on the substrate 10, a gate insulating film 30 which covers the gate electrode 20, a source electrode 40 and a drain electrode 42 which come into contact with the surface, which is opposite to the gate electrode 20 side, of the gate insulating film 30, an organic semiconductor layer 50 which covers the surface of the gate insulating film 30 between the source electrode 40 and the drain electrode 42, and a sealing layer 60 which covers the respective members. The organic thin film transistor 100 is a bottom gate-bottom contact type organic thin film transistor. 
     In  FIG. 1 , the source electrode 40 and the drain electrode 42 are formed using the composition of the present invention described above, but the present invention is not limited to this aspect. It is preferable that at least one of the source electrode 40, the drain electrode 42, and the gate electrode 20 is formed using the composition of the present invention. For example, all of the gate electrode 20, the source electrode 40, and the drain electrode 42 may be formed using the composition of the present invention, or only the source electrode 40 (alternatively, the drain electrode 42) may be formed using the composition of the present invention. 
     Hereinafter, the substrate, the gate electrode, the gate insulating film, the source electrode, the drain electrode, the organic semiconductor layer, the sealing layer, and methods for forming each of these will be specifically described. 
     &lt;Substrate&gt; 
     The substrate plays a role of supporting the gate electrode, the source electrode, the drain electrode, and the like which will be described later. 
     The type of the substrate is not particularly limited, and examples thereof include a plastic substrate, a glass substrate, a ceramic substrate, and the like. Among these, from the viewpoint of the applicability to various devices, a glass substrate or a plastic substrate is preferable. 
     Examples of the material of the plastic substrate include a thermosetting resin (for example, an epoxy resin, a phenol resin, a polyimide resin, or a polyester resin (for example, PET or PEN)) and a thermoplastic resin (for example, a phenoxy resin, polyethersulfone, polysulfone, or polyphenylene sulfone). 
     Examples of the material of the ceramic substrate include alumina, aluminum nitride, zirconia, silicon, silicon nitride, silicon carbide, and the like. 
     Examples of the material of the glass substrate include soda glass, potash glass, borosilicate glass, quartz glass, aluminosilicate glass, lead glass, and the like. 
     &lt;Gate Electrode&gt; 
     Examples of the material of the gate electrode include a metal such as gold (Au), silver, aluminum (Al), copper, chromium, nickel, cobalt, titanium, platinum, magnesium, calcium, barium, or sodium; a conductive oxide such as InO 2 , SnO 2 , or ITO; a conductive polymer such as polyaniline, polypyrrole, polythiophene, polyacetylene, or polydiacetylene; a semiconductor such as silicon, germanium, or gallium arsenide; a carbon material such as fullerene, carbon nanotubes, or graphite; and the like. Among these, a metal is preferable, and silver or aluminum is more preferable. 
     The thickness of the gate electrode is not particularly limited but is preferably 20 nm to 200 nm. 
     The method for forming the gate electrode is not particularly limited. Examples of the method include a method of vacuum vapor-depositing or sputtering an electrode material onto a substrate, a method of coating a substrate with a composition for forming an electrode, a method of printing a composition for forming an electrode on a substrate, and the like. Furthermore, in a case where the electrode is patterned, examples of the patterning method include a photolithography method; a printing method such as ink jet printing, screen printing, offset printing, or relief printing; a mask vapor deposition method; and the like. 
     &lt;Gate Insulating Film&gt; 
     Examples of the material of the gate insulating film include a polymer such as polymethyl methacrylate, polystyrene, polyvinylphenol, polyimide, polycarbonate, polyester, polyvinylalcohol, polyvinyl acetate, polyurethane, polysulfone, polybenzoxazole, polysilsesquioxane, an epoxy resin, or a phenol resin; an oxide such as silicon dioxide, aluminum oxide, or titanium oxide; a nitride such as silicon nitride; and the like. Among these materials, in view of the compatibility with the organic semiconductor layer, a polymer is preferable. 
     In a case where a polymer is used as the material of the gate insulating film, it is preferable to concurrently use a cross-linking agent (for example, melamine) By the concurrent use of the cross-linking agent, the polymer is cross-linked, and the durability of the formed gate insulating film is improved. 
     The film thickness of the gate insulating film is not particularly limited, but is preferably 100 nm to 1,000 nm. 
     The method for forming the gate insulating film is not particularly limited, but examples thereof include a method of coating a substrate, on which the gate electrode is formed, with a composition for forming a gate insulating film, a method of vapor-depositing or sputtering the material of the gate insulating film onto the substrate on which the gate electrode is formed, and the like. The method for coating the aforementioned substrate with the composition for forming a gate insulating film is not particularly limited, and it is possible to use a known method (a bar coating method, a spin coating method, a knife coating method, or a doctor blade method). 
     In a case where the gate insulating film is formed by coating the substrate with the composition for forming a gate insulating film, for the purpose of removing the solvent, causing cross-linking, or the like, the composition may be heated (baked) after coating. 
     &lt;Source Electrode and Drain Electrode&gt; 
     As described above, the source electrode and the drain electrode are formed using the composition of the present invention described above. 
     The channel length of the source electrode and the drain electrode is not particularly limited, but is preferably 5 μm to 100 μm. 
     The channel width of the source electrode and the drain electrode is not particularly limited, but is preferably 50 μm to 500 μm. 
     The method for forming the source electrode and the drain electrode is not particularly limited, but examples thereof include a method including a coating film forming step and a sintering step. Hereinafter, each of the steps will be described. 
     (Coating Film Forming Step) 
     This is a step of coating the substrate, on which the gate electrode and the gate insulating film are formed, with the composition of the present invention described above. 
     The method for forming a coating film by coating the substrate with the composition of the present invention is not particularly limited, and known methods can be adopted. 
     Examples of the method of coating includes a coating method, a screen printing method, a dip coating method, a spray coating method, a spin coating method, an ink jet method, and the like using a double roll coater, a slit coater, an air knife coater, a wire bar coater, a slide hopper, a spray coater, a blade coater, a doctor coater, a squeeze coater, a reverse roll coater, a transfer roll coater, an extrusion coater, a curtain coater, a dip coater, a die coater, and a gravure roll. 
     After the substrate is coated with the composition of the present invention, if necessary, in order to remove the solvent, a drying treatment may be performed. As the method of the drying treatment, methods known in the related art can be used. 
     (Sintering Step) 
     This is a step of forming a conductive film by sintering the metal particles (A) in the composition by applying heat energy or light energy to the coating film formed by the coating film forming step by means of heating or light irradiation. 
     The heating conditions are not particularly limited. However, the heating temperature is preferably 100° C. to 300° C., and the heating time is more preferably 10 minutes to 60 minutes. 
     The heating means is not particularly limited, and known heating means such as an oven and a hot plate can be used. 
     The light source used for the light irradiation treatment is not particularly limited, and examples thereof include a mercury lamp, a metal halide lamp, a xenon (Xe) lamp, a chemical lamp, a carbon arc lamp, and the like. 
     &lt;Organic Semiconductor Layer&gt; 
     The organic semiconductor material constituting the organic semiconductor layer is not particularly limited, and known materials used as an organic semiconductor layer of organic semiconductor transistors can be used. Specific examples of the organic semiconductor material include pentacenes such as 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS pentacene), tetramethyl pentacene, and perfluoropentacene, anthradithiophenes such as TES-ADT and diF-TES-ADT (2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene), benzothienobenzothiophenes such as DPh-BTBT and Cn-BTBT, dinaphthothienothiophenes such as Cn-DNTT, dioxaanthanthrenes such as peri-xanthenoxanthene, rubrenes, fullerenes such as C60 and PCBM, phthalocyanines such as copper phthalocyanine and fluorinated copper phthalocyanine, polythiophenes such as P3RT, PQT, and P3HT, polythienothiophenes such as poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT), and the like. 
     The thickness of the organic semiconductor layer is not particularly limited but is preferably 10 nm to 200 nm. 
     The method for forming the organic semiconductor layer is not particularly limited. Examples of the method include a method of coating the substrate, on which the gate electrode, the gate insulating film, the source electrode, and the drain electrode are formed, with a composition for an organic semiconductor layer obtained by dissolving an organic semiconductor material in a solvent, and the like. Specific examples of the method of coating the substrate with the composition for an organic semiconductor layer are the same as the method of coating the substrate with the composition for forming a gate insulating film. In a case where the organic semiconductor layer is formed by coating the substrate with the composition for an organic semiconductor layer, for the purpose of removing the solvent, causing crosslinking, or the like, the composition may be heated (baked) after coating. 
     &lt;Sealing Layer&gt; 
     From the viewpoint of durability, the organic thin film transistor of the present invention preferably includes a sealing layer as the outermost layer. For the sealing layer, a known sealant can be used. 
     The thickness of the sealing layer is not particularly limited but is preferably 0.2 μm to 10 μm. 
     The method for forming the sealing layer is not particularly limited. Examples of the method include a method of coating the substrate, on which the gate electrode, the gate insulating film, the source electrode, the drain electrode, and the organic semiconductor layer are formed, with a composition for forming a sealing layer, and the like. Specific examples of the method of coating the substrate with the composition for forming a sealing layer are the same as the examples of the method of coating the substrate with the composition for forming a gate insulating film. In a case where the organic semiconductor layer is formed by coating the substrate with the composition for forming a sealing layer, for the purpose of removing the solvent, causing crosslinking, or the like, the composition may be heated (baked) after coating. 
       FIG. 2  is a schematic sectional view of another aspect of the organic thin film transistor of the present invention. 
     In  FIG. 2 , an organic thin film transistor 200 includes the substrate 10, the gate electrode 20 which is disposed on the substrate 10, the gate insulating film 30 which covers the gate electrode 20, the organic semiconductor layer 50 which is disposed on the gate insulating film 30, the source electrode 40 and the drain electrode 42 which are disposed on the organic semiconductor layer 50, and the sealing layer 60 which covers the respective members. Herein, the source electrode 40 and the drain electrode 42 are formed by using the composition of the present invention described above. The organic thin film transistor 200 is a top contact-type organic thin film transistor. 
     The substrate, the gate electrode, the gate insulating film, the source electrode, the drain electrode, the organic semiconductor layer, and the sealing layer are as described above. 
     The organic thin film transistor described above can be suitably used in electronic paper, a display device, and the like. 
     EXAMPLES 
     Hereinafter, examples will be described, but the present invention is not limited thereto. 
     &lt;Preparation of Silver Ink A1&gt; 
     As a dispersing agent, Disperbyk-190 (manufactured by BYK) (7.36 g as nonvolatile matter) was dissolved in water (100 mL) (solution a). Then, 50.00 g (294.3 mmol) of silver nitrate was dissolved in water (200 mL) (solution b). The solution a and the solution b were mixed and stirred together. To the obtained mixture, 85% by mass aqueous N,N-diethylhydroxylamine solution (78.71 g) (750.5 mmol as N,N-diethylhydroxylamine) was slowly added dropwise at room temperature. Thereafter, a solution obtained by dissolving Disperbyk-190 (7.36 g) in water (1,000 mL) was slowly added dropwise thereto at room temperature. Through an ultrafiltration unit (Vivaflow 50 manufactured by Sartorius Stedim Biotech, molecular weight cut-off: 100,000, number of units: 4), the obtained suspension was purified by passing purified water through the unit until approximately 5 L of leachate was obtained from the ultrafiltration unit. The supply of the purified water was stopped, and concentration was performed, thereby obtaining 50 g of silver nanoparticle dispersion (silver ink A1). The content of solids in the silver ink A1 was 32% by mass. Furthermore, as a result of measuring the content of silver in the solids by TG-DTA, it was confirmed that the content of silver was 97.0% by mass. Herein, as a result of measuring the particle size of the silver nanoparticles by using a concentrated system particle size analyzer FPAR-1000 (manufactured by OTSUKA ELECTRONICS Co., LTD), it was confirmed that the average particle size of the silver nanoparticles was 60 nm. 
     Examples 1 to 9 and Comparative Examples 1 to 11 
     Silver inks A2 to A7 and A19 to A21 (conductive film forming compositions of Examples 1 to 9) and silver inks A8 to A18 (conductive film forming compositions of Comparative examples 1 to 11) were prepared according to the same procedure as used in the preparation of the silver ink A1, except that at the time of mixing the solution a with the solution b, in addition to the solution a and the solution b, a migration inhibitor shown in Table 1 was also formulated according to the “ratio of content of migration inhibitor to total amount of silver ink” shown in Table 1. 
     &lt;Evaluation of Insulation Reliability&gt; 
     By a spray coating method, a substrate obtained by laminating ABF-GX13 (manufactured by Ajinomoto Fine-Techno Co., Inc.) on an FR 4  glass epoxy sheet was coated with the silver ink A1 by using STS-200 (manufactured by YD Mechatronic Solutions Inc.) such that the film thickness after sintering became 200 nm. Then, the silver ink A1 was sintered (210° C., 1 hour) using an oven, thereby forming a silver film on the substrate. The formed silver film was etched in a comb shape at L/S=50/50 μm by a photolithography method, thereby forming a comb-shaped silver film (silver wiring). At this time, Photec 7025 (manufactured by Hitachi Chemical Co., Ltd.) was used as a dry photoresist, and Agrip 940 (manufactured by Meltex Inc.) was used as a silver etching solution. In addition, the silver wiring was spin-coated with Cytop CTL107MK (manufactured by ASAHI GLASS CO., LTD.) such that the film thickness after drying became 1 μm, followed by drying at 140° C. for 20 minutes in an oven, thereby forming a sealing layer. In this way, a wiring board for evaluating insulation reliability was prepared. 
     For the obtained wiring board, a service life test was performed under the conditions of a humidity of 85%, a temperature of 85° C., a pressure of 1.0 atm, and a voltage of 60 V (used apparatus: EHS-221MD manufactured by ESPEC Corp). Specifically, in the aforementioned environment, the aforementioned voltage was applied to the silver wirings adjacent to each other. Then, a time taken for a short circuit to occur between the silver wirings due to electrochemical migration (time T taken for a value of resistance between silver wirings to become 1×10 5 Ω) was measured. A time T taken in a case where the silver ink A1 was used was denoted by T1 (standard). 
     Subsequently, by using silver inks A2 to A21 (conductive film forming compositions of examples and comparative examples) to which the migration inhibitor was added, wiring boards for evaluating insulation reliability were prepared in the same manner as in the case of the silver ink A1, and the service life thereof was measured. A time T taken in a case where a silver ink An (n=2 to 21) was used was denoted by Tn. 
     For silver inks A2 to A21 (conductive film forming compositions of examples and comparative examples), Tn/T1 was calculated, and the insulation reliability was evaluated according to the following criteria. The results are shown in Table 1. For practical use, the silver ink is preferably evaluated to be A to C, more preferably evaluated to be A or B, and even more preferably evaluated to be A. 
     “A”: a case where Tn/T1≧5 
     “B”: a case where 5&gt;Tn/T1≧2 
     “C”: a case where 2&gt;Tn/T1≧1 
     “D”: a case where 1≧Tn/T1 
     &lt;Evaluation of Mobility&gt; 
     A1 to be a gate electrode was vapor-deposited (thickness: 50 nm) onto a glass substrate (Eagle XG: manufactured by Corning). The A1 was spin-coated with a composition for forming a gate insulating film (a propylene glycol monomethyl ether acetate (PGMEA) solution (concentration of solid content: 2% by mass) of polyvinylphenol/melamine=1 part by mass/1 part by mass (w/w)), followed by baking for 60 minutes at 150° C., thereby forming a gate insulating film having a film thickness of 400 nm. Onto the gate insulating film, by using the silver ink A1, patterns of a source electrode and a drain electrode (channel length: 40 μm, channel width: 200 μm) were drawn using an ink jet apparatus DMP-2831 (manufactured by FUJIFILM Dimatix, Inc.). The silver ink A1 was then sintered by being baked for 30 minutes at 180° C. in an oven, thereby forming source and drain electrodes. The source electrode and the drain electrode were spin-coated with a toluene solution of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (manufactured by Sigma-Aldrich Co, LLC.), followed by baking for 15 minutes at 140° C., thereby forming an organic conductive layer having a thickness of 100 nm. The organic semiconductor layer was spin-coated with Cytop CTL-107MK (manufactured by ASAHI GLASS CO., LTD.), followed by baking for 20 minutes at 140° C., thereby forming a sealing layer (uppermost layer) having a thickness of 2 μm. In this way, an organic thin film transistor (bottom contact-type) was prepared. 
     The electrodes of the obtained organic thin film transistor were respectively connected to the terminals of a manual prober connected to a semiconductor parameter/analyzer (4155C, manufactured by Agilent Technologies Inc.), thereby evaluating the field effect transistor (FET). Specifically, by measuring the drain current-gate voltage (Id-Vg) characteristics, the field effect mobility ([cm 2 /V·sec]) was calculated. A total of five organic thin film transistors were prepared in the same manner as described above, and the field effect mobility thereof was calculated. The average of the field effect mobility of the five organic thin film transistors, in which the silver ink A1 was used for the source electrode and the drain electrode, was denoted by μl. 
     Then, by using the silver inks A2 to A21 (conductive film forming compositions of examples and comparative examples) to which the migration inhibitor was added, organic thin film transistors were prepared in the same manner as in the case of the silver ink A1, and the average of the field effect mobility thereof was calculated. The average of the field effect mobility in a case where a silver ink An (n=2 to 21) was used was denoted by μn. 
     For the silver inks A2 to A21 (conductive film forming compositions of examples and comparative examples), μn/μl was calculated, and the mobility was evaluated according to the following criteria. The results are shown in Table 1. For practical use, the silver ink is preferably evaluated to be A to C, more preferably evaluated to be A or B, and even more preferably evaluated to be A. 
     “A”: μn/μl≧0.8 
     “B”: 0.8&gt;μn/μl≧0.5 
     “C”: 0.5&gt;μn/μl≧0.1 
     “D”: 0.1&gt;μn/μl 
     Details of the migration inhibitors in Table 1 are as below.
         M1: tosic acid pyridinium salt       

     
       
         
         
             
             
         
       
         
         
           
             M2: tosic acid tetramethyl ammonium salt 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             M3: phosphoric acid diethyltetramethyl ammonium salt 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             M4: tosic acid dimethylphenyl ammonium salt 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             M5: triaryl sulfonium trifluoromethanesulfonate 
             M6: octadecyl benzoate 
             M7: fluoroantimonic acid salt (following structure) 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             M8: N-butylpyridinium hexafluorophosphate 
             M9: dodecylsulfonic acid triethanolamine salt 
             M10: hexoxybenzoic acid (following structure) 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             M11: 2-ethylhexylammonium 2-ethylhexylcarbamate 
             M12: hexafluorophosphoric acid triethanolamine salt 
             M13: p-toluenesulfonic acid ammonium salt 
             M14: 1-ethyl-1-methylpyrrolidinium bromide 
             M15: tetrabutylammonium chloride 
             M16: a compound represented by the following formula 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             M17: a compound represented by the following formula 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             M18: a compound represented by the following formula 
           
         
       
    
     
       
         
         
             
             
         
       
     
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Table 1 (part 1) 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Example 1 
                 Example 2 
                 Example 3 
                 Example 4 
                 Example 5 
                 Example 6 
                 Example 7 
                 Example 8 
                 Example 9 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
            
               
                 Silver ink 
                 A2 
                 A3 
                 A4 
                 A5 
                 A6 
                 A7 
                 A19 
                 A20 
                 A21 
               
               
                 Migration inhibitor 
                 M1 
                 M1 
                 M2 
                 M2 
                 M3 
                 M4 
                 M16 
                 M17 
                 M18 
               
               
                 Ratio of content of 
                 2 
                 5 
                 0.5 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 migration inhibitor to 
               
               
                 total amount of silver 
               
               
                 ink (% by mass) 
               
               
                 Insulation reliability 
                 A 
                 A 
                 B 
                 A 
                 B 
                 A 
                 A 
                 B 
                 B 
               
               
                 Mobility 
                 A 
                 A 
                 B 
                 B 
                 A 
                 A 
                 B 
                 A 
                 A 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Table 1 (part 2) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                 Comparative 
                 Comparative 
                 Comparative 
                 Comparative 
                 Comparative 
                 Comparative 
               
               
                   
                 example 1 
                 example 2 
                 example 3 
                 example 4 
                 example 5 
                 example 6 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Silver ink 
                 A8 
                 A9 
                 A10 
                 A11 
                 A12 
                 A13 
               
               
                 Migration inhibitor 
                 M5 
                 M6 
                 M7 
                 M8 
                 M9 
                 M10 
               
               
                 Ratio of content of 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 migration inhibitor to 
               
               
                 total amount of silver ink 
               
               
                 (% by mass) 
               
               
                 Insulation reliability 
                 B 
                 D 
                 B 
                 B 
                 B 
                 D 
               
               
                 Mobility 
                 D 
                 C 
                 D 
                 D 
                 D 
                 C 
               
               
                   
               
            
           
         
       
     
     [Table 3] 
     
       
         
           
               
            
               
                   
               
               
                 Table 1 (part 3) 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 Compar- 
                 Compar- 
                 Compar- 
                 Compar- 
                 Compar- 
               
               
                   
                 ative 
                 ative 
                 ative 
                 ative 
                 ative 
               
               
                   
                 exam- 
                 exam- 
                 exam- 
                 exam- 
                 exam- 
               
               
                   
                 ple 7 
                 ple 8 
                 ple 9 
                 ple 10 
                 ple 11 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Silver ink 
                 A14 
                 A15 
                 A16 
                 A17 
                 A18 
               
               
                 Migration 
                 M11 
                 M12 
                 M13 
                 M14 
                 M15 
               
               
                 inhibitor 
               
               
                 Ratio of 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 content of 
               
               
                 migration 
               
               
                 inhibitor to 
               
               
                 total amount 
               
               
                 of silver ink 
               
               
                 (% by mass) 
               
               
                 Insulation 
                 D 
                 B 
                 D 
                 D 
                 D 
               
               
                 reliability 
               
               
                 Mobility 
                 B 
                 D 
                 B 
                 D 
                 D 
               
               
                   
               
            
           
         
       
     
     As is evident from Table 1, all of the organic thin film transistors having electrodes formed using the conductive film forming compositions of Examples 1 to 9 containing the compound (B) exhibited excellent insulation reliability and high mobility. 
     Through the comparison between Examples 3 and 4, it was confirmed that the insulation reliability was better in Example 4 in which the ratio of the content of the compound (B) to the total amount of the composition (ratio of the content of the migration inhibitor to the total amount of the silver ink) was equal to or greater than 1.0% by mass. 
     Furthermore, through the comparison between Examples 4 and 5, it was confirmed that the insulation reliability was better in Example 4 in which A m−  in Formula (I) was an anion selected from the group consisting of SO 4   2− , RA 2 SO 4   − , and R A3 SO 3   − . 
     In addition, through the comparison between Examples 4 and 6, it was confirmed that the mobility was higher in Example 6 in which at least one of R 1  to R 4  in Formula (I) was an aromatic hydrocarbon group. 
     In contrast, in the organic thin film transistors having electrodes formed using the conductive film forming compositions of Comparative examples 1 to 11 not containing the compound (B), either or both of the insulation reliability and the mobility were insufficient. 
     EXPLANATION OF REFERENCES 
     
         
         
           
               10 : substrate 
               20 : gate electrode 
               30 : gate insulating film 
               40 : source electrode 
               42 : drain electrode 
               50 : organic semiconductor layer 
               60 : sealing layer 
               100 ,  200 : organic thin film transistor