Photosensitive Ink Composition for Screen Printing and Method of Forming Positive Relief Pattern with Use Thereof

Abstract

Disclosed is a photosensitive ink which can form a coated film that is excellent in insulation properties, heat resistance, low warping, low elasticity and adhesion with the substrate, when used as an ink for screen printing, and with which clogging of the screen, bleeding, blur, chipping and the like are unlikely to occur even when the screen printing is repeatedly carried out, so that which has an excellent ease of handling in printing. The ink composition comprises 100 parts by weight of an organic solvent-soluble polyimide block copolymer(s), and 1 to 100 parts by weight of a photoacid generator(s). The polyimide block copolymer(s) and the photoacid generator(s) are dissolved in an organic solvent. The polyimide block copolymer(s) contain(s) in its molecular skeleton a diamine having a siloxane bond, and an aromatic diamine having a hydroxyl group(s) and/or carboxyl group(s) at ortho-position with respect to an amino group.

1 . A photosensitive ink composition for screen printing, said ink composition comprising 100 parts by weight of an organic solvent-soluble polyimide block copolymer(s), and 1 to 100 parts by weight of a photoacid generator(s), said polyimide block copolymer(s) and said photoacid generator(s) being dissolved in an organic solvent, said polyimide block copolymer(s) containing in its molecular skeleton a diamine having a siloxane bond(s), and an aromatic diamine having a hydroxyl group(s) and/or carboxyl group(s) at ortho-position with respect to an amino group. 
   
   
       2 . The composition according to  claim 1 , wherein said polyimide block copolymer(s) is(are) produced by a polycondensation process comprising at least two steps of polycondensation, including a first polycondensation step of dehydration-condensing one or more tetracarboxylic dianhydrides with one or more diamines in the presence of a binary catalyst containing a lactone and a base; and a second polycondensation step of dehydration-condensing the polyimide obtained in said first polycondensation step with one or more tetracarboxylic dianhydrides and one or more diamines in the presence of a binary catalyst containing a lactone and a base. 
   
   
       3 . The composition according to  claim 2 , wherein said polycondensation process is carried out in two steps, and said diamine(s) having a siloxane bond(s) is(are) added in only one of the two steps in said polycondensation process. 
   
   
       4 . The composition according to any one of  claims 1  to  3 , wherein said aromatic diamine having a hydroxyl group(s) and/or carboxyl group(s) is at least one selected from the group consisting of 3,3′-dicarboxy-4,4′-diaminodiphenylmethane, 2,2-bis(3-amino-4-hydroxyphenyl)propane, 1-hydroxy-2,4-diaminobenzene, 3,3′-dihydroxybenzidine, 3,3′-dihydroxy-4,4′-diaminodiphenyl ether, 1,4-bis-(3-hydroxy-4-aminophenoxy)benzene, 2,2-bis(4-amino-3-hydroxyphenyl)propane, bis(3-amino-4-hydroxyphenyl)propane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, bis(3-amino-4-hydroxyphenyl)sulfone, bis(3-amino-4-hydroxyphenyl) sulfide and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. 
   
   
       5 . The composition according to  claim 1 , wherein said diamine having a siloxane bond is one or more diamines having a structure represented by any one of Formulae (I) to (IV) below: 
     
       
         
         
             
             
         
       
     
     (wherein in Formula (I), R 1 , R 2 , R 3  and R 4  each independently represent an alkyl group, cycloalkyl group, phenyl group or a phenyl group substituted by 1 to 3 alkyl groups or by 1 to 3 alkoxyl groups; 1 and m each independently represent an integer of 1 to 4; and n represents an integer of 3 to 30) 
     
       
         
         
             
             
         
       
     
     (wherein in Formulae (II) to (IV), n′ represents an integer of 1 to 30; and p in Formula (II) represents an integer of 1 to 4). 
   
   
       6 . The composition according to  claim 5 , wherein said diamine having a siloxane bond has the structure represented by said Formula (I). 
   
   
       7 . The composition according to  claim 1  wherein the tetracarboxylic dianhydride component(s) constituting said block polyimide block copolymer(s) is(are) at least one selected from the group consisting of bis-(3,4-dicarboxyphenyl)ether diacid dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, p-phenylenebis(trimellitic acid monoester acid anhydride) and bicyclo[2,2,2]oct-2-ene tetracarboxylic dianhydride (BCD). 
   
   
       8 . The composition according to  claim 1  wherein the content of said diamine(s) having a siloxane bond in the molecular skeleton thereof is 15 to 85% by weight based on the total diamine components, and the content of said aromatic diamine(s) having said hydroxyl group(s) and/or carboxyl group(s) is 5 to 20% by weight based on the total diamine components. 
   
   
       9 . The composition according to  claim 1 , wherein said polyimide block copolymer(s) has(have) a weight average molecular weight in terms of polystyrene of 20,000 to 200,000. 
   
   
       10 . The composition according to  claim 1  wherein said polyimide block copolymer(s) is(are) produced by polycondensation of a tetracarboxylic dianhydride component(s) and a diamine component(s) in a polar solvent in the presence of an acid catalyst containing a lactone and a base at a temperature between 150° C. and 220° C., and said polar solvent is said organic solvent in said composition. 
   
   
       11 . The composition according to  claim 10 , wherein said polar solvent is at least one selected from the group consisting of lactone solvents and ether solvents. 
   
   
       12 . A method for forming a positive-type relief pattern, said method comprising:
 coating said composition according to  claim 1  on a substrate;   radiating an active light source in the form of said pattern; and   developing the irradiated regions with an alkaline developer.