Photocurable resin composition

Abstract

There is provided a photocurable resin composition comprising (A) an urethane acrylate having three or four acrylate groups in the molecule, (B) a radical polymerizable compound different from the above urethane acrylate; and (C) a photopolymerization initiator, the weight ratio of the urethane acrylate (A) to the radical polymerizable compound (B) being 80:20 to 10:90; and a production process thereof. The said photocurable resin composition can provide moldings and stereolithographed objects having excellent dimensional accuracy with a small volume shrinkage factor at the time of photo-curing and excellent heat resistance with a high thermal deformation temperature as well as excellent transparency and mechanical properties such as tensile strength.

What is claimed is:  
     
         1 . A photocurable resin composition comprising: 
 (A) an urethane acrylate represented by the following formula (I):  
                 
   wherein R 1  is a hydrogen atom or a methyl group, A is a divalent or trivalent organic group which remains after all the hydroxyl groups are removed from a diol or triol, D is a divalent or trivalent organic group which remains after all the isocyanate groups are removed from a diisocyanate or truisocyanate, E is a group represented by the formula —(CH 2 CH 2 O) s — (s is a numeral of 1 to 4),  
                 
   (t is a numeral of 1 to 4), or  
                 
   (u and v are each a numeral of 1 to 3, provided that u+v is 2 to 4), R 2  is a hydrogen atom or an alkyl group, p and q are independently 1 or 2, and r is 3 or 4, provided that at least one of R 1 's is a methyl group when p is 2;    (B) a radical polymerizable compound different from the above urethane acrylate; and    (C) a photopolymerization initiator, the weight ratio of the urethane acrylate (A) to the radical polymerizable compound (B) being 80:20 to 10:90.    
     
     
         2 . The photocurable resin composition of    claim 1   , wherein the proportion of the photopolymerization initiator is 0.1 to 10% by weight based on the total weight of the urethane acrylate and the radical polymerizable compound.  
     
     
         3 . The photocurable resin composition of    claim 1   , which further contains at least one filler selected from solid fine particles and whiskers.  
     
     
         4 . The photocurable resin composition of    claim 3   , which further contains both solid fine particles and whiskers.  
     
     
         5 . The photocurable resin composition of    claim 4   , wherein the solid fine particles are spherical solid fine particles having a smooth surface which hardly causes irregular reflection of light.  
     
     
         6 . The photocurable resin composition of    claim 3    or    4    which contains whiskers having a diameter of 0.3 to 1 μm, a length of 10 to 70 μm and an aspect ratio of 10 to 100.  
     
     
         7 . The photocurable resin composition of    claim 3   , wherein at least one filler selected from solid fine particles and whiskers is treated with a silane coupling agent.  
     
     
         8 . The photocurable resin composition of    claim 3   , wherein the content of the filler is 3 to 70% by volume based on the volume of the photocurable resin composition before it contains the filler.  
     
     
         9 . The photocurable resin composition of    claim 1   , which is a resin composition for optically producing a stereolithographed object.  
     
     
         10 . A method of producing a stereolithographed object from the photocurable resin composition of    claim 1    by an optical stereolithography.  
     
     
         11 . A method of producing a photocurable resin composition which comprises the steps of: 
 (1) allowing a (meth)acrylic acid ester represented by the following formula (II):  
                 
   wherein R 1 , A and p are the same as defined in the formula (I),    and a polyisocyanate represented by the following formula (III):    D—(NCO) q+1   (III)    wherein D and q are the same as defined in the formula (I),    to react each other in such a quantitative ratio that the polyisocyanate has one isocyanate group remaining in its one molecule on the average in the presence or absence of a diluent comprising a radical polymerizable compound which does not show reactivity with the isocyanate group to produce a monoisocyanate represented by the following formula (IV):  
                 
   wherein R 1 , A, D, p and q are the same as defined in the above formula (I);    (2) mixing the monoisocyanate obtained in the above step (1) or the reaction product containing the monoisocyanate and a radical polymerizable compound with a polyol compound represented by the following formula (V):    (HO—E—CH 2  r —C—(R 2 ) 4−r   (V)  wherein E, R 2  and r are the same as defined in the above formula (I),    in a ratio that the isocyanate groups of the monoisocyanate of the formula (IV) is almost equal in equivalent to the hydroxyl groups of the polyol compound and reacting these to produce an urethane acrylate represented by the above formula (I); and      (3) adding to the reaction product containing the urethane acrylate (I) obtained in the above step (2) a photopolymerization initiator and a predetermined amount of a radical polymerizable compound when the reaction product does not contain a radical polymerizable compound or a predetermined amount of a radical polymerizable compound to adjust the weight ratio of the urethane acrylate (I) to the radical polymerizable compound to 80:20 to 10:90.    
     
     
         12 . The method of    claim 11   , wherein the step (1) is carried out in the presence of another radical polymerizable compound which does not show reactivity with the isocyanate group.  
     
     
         13 . The method of    claim 11    which further comprises the step of adding at least one filler selected from solid fine particles and whiskers after the step (3).  
     
     
         14 . An urethane acrylate represented by the above formula (I).