Curable polyorganosiloxane composition

Abstract

This is to provide a curable polyorganosiloxane composition which gives a cured product excellent in cold resistance. This relates to a curable polyorganosiloxane composition which comprises (A) an alkenyl group-containing polyorganosiloxane comprising (A1) a linear polyorganosiloxane represented by the formula (1) (wherein Rs independently represent R 1 or R 2 , and among Rs, at least two of which are R 1 s, R 1 s independently represent a C 2 -C 6 alkenyl group, R 2 s independently represent a C 1 -C 6 alkyl group, n is a number which makes a viscosity at 23° C. 10 to 10,000 cP), and (A2) a branched polyorganosiloxane comprising a SiO 4/2 unit and a R′ 3 SiO 1/2 unit, and further optionally a R′ 2 SiO unit and/or a R′SiO 3/2 unit (wherein R′s each independently represent an unsubstituted or substituted, monovalent aliphatic group or alicyclic group), at least three R′s are alkenyl groups per one molecule, a weight ratio of (A2) based on (A1) is 1 to 5, a weight ratio of the SiO 4/2 unit and the optionally existing R′SiO 3/2 unit based on the total weight of (A1) and (A2) is 20 to 60% by weight; (B) a polyorganohydrogensiloxane having hydrogen atoms bonded to a silicon atom in a number of exceeding 2 in the molecule; and (C) a platinum group metal compound.

1 . A curable polyorganosiloxane composition which comprises
 (A) an alkenyl group-containing polyorganosiloxane comprising (A1) a linear polyorganosiloxane represented by the formula (I):   
       
         
           
           
               
               
           
         
         wherein 
         Rs independently represent R 1  or R 2 , and among Rs, at least two of which are R 1 s, 
         R 1 s independently represent a C 2 -C 6  alkenyl group, 
         R 2 s independently represent a C 1 -C 6  alkyl group, 
         n is a number which makes a viscosity at 23° C. 10 to 10,000 cP, and 
         (A2) a branched polyorganosiloxane comprising a SiO 4/2  unit and a R′ 3 SiO 1/2  unit, and optionally a R′ 2 SiO unit and/or a R′SiO 3/2  unit, wherein R′s independently represent, an unsubstituted or substituted, monovalent aliphatic group or alicyclic group, and having at least three R′s are alkenyl groups per one molecule, a weight ratio of (A2) based on (A1) being 1 to 5, and a weight ratio of the SiO 4/2  unit and the optionally existing R′SiO 3/2  unit being 20 to 60% by weight based on the total weight of (A1) and (A2);
 (B) a polyorganohydrogensiloxane having hydrogen atoms bonded to a silicon atom in a number exceeding 2 in the molecule; and 
 (C) a platinum group metal compound. 
 
       
     
     
         2 . The curable polyorganosiloxane composition according to  claim 1 , wherein R 1  of (A) is a vinyl group, and R′ which is an alkenyl group of (A2) is a vinyl group. 
     
     
         3 . The curable polyorganosiloxane composition according to  claim 1 , wherein (B) is a polyorganohydrogensiloxane represented by the formula (II′): 
       
         
           
           
               
               
           
         
         wherein R 3a s independently represent an unsubstituted or substituted, monovalent aliphatic group or alicyclic group containing no aliphatic unsaturated carbon-carbon bond, R 3b s independently represent a hydrogen atom or an unsubstituted or substituted, monovalent aliphatic group or alicyclic group, p is a number of 2 to 100, and q is a number of 0 to 100. 
       
     
     
         4 . The curable polyorganosiloxane composition according to  claim 1 , wherein (C) is a platinum-vinylsiloxane complex. 
     
     
         5 . The curable polyorganosiloxane composition according to  claim 1 , which further comprises an inorganic filler. 
     
     
         6 . An adhesive which comprises the curable polyorganosiloxane composition according to  claim 1 . 
     
     
         7 . A semiconductor device which is encapsulated by the curable polyorganosiloxane composition according to  claim 1 . 
     
     
         8 . The curable polyorganosiloxane composition according to  claim 2 , wherein (B) is a polyorganohydrogensiloxane represented by the formula (II′): 
       
         
           
           
               
               
           
         
         wherein R 3a s independently represent an unsubstituted or substituted, monovalent aliphatic group or alicyclic group containing no aliphatic unsaturated carbon-carbon bond, R 3b s independently represent a hydrogen atom or an unsubstituted or substituted, monovalent aliphatic group or alicyclic group, p is a number of 2 to 100, and q is a number of 0 to 100. 
       
     
     
         9 . The curable polyorganosiloxane composition according to  claim 3 , wherein (C) is a platinum-vinylsiloxane complex. 
     
     
         10 . The curable polyorganosiloxane composition according to  claim 3 , which further comprises an inorganic filler. 
     
     
         11 . The curable polyorganosiloxane composition according to  claim 4 , which further comprises an inorganic filler. 
     
     
         12 . The curable polyorganosiloxane composition according to  claim 9 , which further comprises an inorganic filler. 
     
     
         13 . An adhesive which comprises the curable polyorganosiloxane composition according to  claim 3 . 
     
     
         14 . An adhesive which comprises the curable polyorganosiloxane composition according to  claim 9 . 
     
     
         15 . An adhesive which comprises the curable polyorganosiloxane composition according to  claim 10 . 
     
     
         16 . An adhesive which comprises the curable polyorganosiloxane composition according to  claim 12 . 
     
     
         17 . A semiconductor device which is encapsulated by the curable polyorganosiloxane composition according to  claim 3 . 
     
     
         18 . A semiconductor device which is encapsulated by the curable polyorganosiloxane composition according to  claim 9 . 
     
     
         19 . A semiconductor device which is encapsulated by the curable polyorganosiloxane composition according to  claim 10 . 
     
     
         20 . A semiconductor device which is encapsulated by the curable polyorganosiloxane composition according to  claim 12 .