May 5,  2011  12  US 2011/0104454 Al  bonate and diethyl carbonate, which are other water-soluble  flammable liquids not included in the alcohol. As a solvent  other than these solvents, an ether-based solvent, a glycol› based solvent, an amine-based-solvent, a thiol-based solvent,  and a halogen-based solvent may be used together with the  alcohol. Even in the case of using these solvents for combi› nation, it is necessary that the content of alcohol in the mixed  solvent is in the range of from 20% by mass to 99% by mass.  [0145]  Further, in the case of producing the composition for  forming a layer to be plated, that contains a specific polymer  having a cyano group which is a non-polar interactive group,  from the viewpoints of easy handleability, a solvent to be  combined has a boiling point of preferably from 40°  C. to  200°  C., more preferably from 60°  C. to 158°  C., and further  preferably from 65°  C. to 120°  C.  [0146]  The water-soluble flammable solvent for preparing  a mixed solvent used in the invention preferably has the  boiling point of from 60°  C. to 158°  C., and more preferably  from 65°  C. to 120°  C., from the viewpoints of ease of evapo› ration. Especially favorable examples of an alcohol-based  solvent capable of mixing with water include methanol (boil› ing point: 65°  C.), ethanol (boiling point: 78°  C.), isopropyl  alcohol (boiling point: 82° C.), n-propyl alcohol (boiling  point: 97° C.), and l-methoxy-2-propanol (boiling point:  119°  C).  [0147]  In the invention, as described above, a mixed solvent  of water and water-soluble flammable liquid is used, but the  flash point of the water-soluble flammable liquid is preferably  30°  C. or higher, more preferably 40°  C. or higher, and most  preferably 60°  C. or higher, from the viewpoints of ease of  operation.  [  0148]  The flash point used in the invention refers to a value  as measured based on JIS-K 2265 (Tag closed cup method).  [0149]  Water  [0150]  The water used as a solvent in the composition for  forming a layer to be plated according to the invention pref› erably includes no impurities. For example, RO water, deion› ized water, distilled water and purified water are preferred.  Among these, deionized water and distilled water are more  preferred.  [0151]  Additives for Improving Solubility of Specific Poly› mer  [0152]  In the composition for forming a layer to be plated  according to the invention, a mixed solvent of a water-soluble  flammable liquid and water containing at least 20% by mass  to 99% by mass of the water-soluble flammable liquid, and  water is used. Further, an additive may be used for increasing  solubility of a specific polymer.  [0153]  In the invention, in a case in which a specific poly› mer acting as a solute has an acidic group such as a carboxylic  group as an ionic polar group, the acidic group is converted  into a salt thereof such as sodium carboxylate, so that the  specific polymer becomes easy to dissolve in a water-alcohol  mixed solvent. As an additive used for converting the car› boxylic group into sodium carboxylate, a basic compound  may be used. Specific examples of the basic compound to be  used include sodium hydrogen carbonate, sodium carbonate,  sodium hydroxide, tetramethyl ammonium hydroxide, potas› sium hydrogen carbonate, potassium carbonate, potassium  hydroxide, lithium hydrogen carbonate, lithium carbonate,  lithium hydroxide, methylamine, dimethyl amine, trimethyl  amine, ethylamine, diethyl amine, triethyl amine, butyl  amine, dibutyl amine, tributyl amine, ammonia, diazabicy› cloundecene  (DBU),  and diazabicyclononene  (DBN).  Among them, preferable additives include alkali metal salts  such as a sodium salt, a lithium salt, and a potassium salt.  From the viewpoints of degree of water solubilization and  optimal basicity, sodium hydrogen carbonate, sodium car› bonate and sodium hydroxide are particularly preferred.  [0154]  Water-Insoluble Photopolymerization Initiator  [0155]  The composition for forming a layer to be plated  according to the invention contains a water-insoluble photo› polymerization initiator in order to increase sensitivity to  energy application.  [0156]  The water-insoluble photopolymerization initiator  of the invention means a compound, a precipitation of which  is visually observed when 0.1 % by mass of photopolymer› ization initiator is added to water at ordinary temperature (25°  C.), followed by stirring, and then left to stand for 10 minutes.  [0157]  The water-insoluble photopolymerization initiator  to be used is preferably a compound, an absorption wave› length region of which has an absorbance peak in the range of  from 250 nm to 400 nm, and more preferably from 280 nm to  360nm.  [0158]  Specifically, examples of the water-insoluble pho› topolymerization initiator favorably used in the invention  include benzoin compounds and derivatives thereof such as  benzoin ethyl ether, methyl benzoin ether, ethyl benzoin  ether, butyl benzoin ether, and benzoin isopropyl ether; ben› zyl ketal-based compounds and derivatives thereof such as  benzyl dimethyl ketal; hydroxy ketone-based compounds and  derivatives thereof such as I-hydroxy cycohexyl phenyl  ketone; benzophenone-based compounds and derivatives  thereof such  as  benzophene,  4-phenyl-benzophenone,  4-chlorobenzophenone;  acetophenone-based  compounds  and derivatives thereof such as michler’s ketone, anthrone,  1-benzoyl  cyclohexanon-1-ol,  2-hydroxy-2-2-dimethyl  acetophenone,  2,2-dimethoxy-2-pheny lacetophenone;  a-aminoalkyl phenone-based compounds and derivatives  thereof such as 2-benzyl-2-dimethyl amino-1-(4-morpholi- nophenyl)-butanone-l,2-benzyl-2-dimethyl  amino-I-( 4- morpholinophenyl)-butanone-1,2-dimethyl  amino-2-( 4- (methyl-benzyl)-1-( 4-morpholin-4-yl-phenyl)-butan-l-one;  bisacyl phosphinoxide-based compounds and derivatives  thereof such as bis(2,4,6-trimethylbenzoyl)-phenylphosphi› noxide,  bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl  phosphinoxide; acyl phosphinoxide-based compounds and  derivatives thereof such as 2,4,6-trimethylbenzoylphenyl  ethoxyphosphinoxide,  2,4,6-trimethylbenzoyl  diphenyl  phosphinoxide, ethyl-2,4,6-trimethylbenzoylphenyl phos› phinate, and bisacyl phosphinoxide; thioxanthone-based  compounds and derivatives thereof such as isopropyl thiox› anthone,  2,4-diethylthioxanthone;  anthraquinone-based  compounds and derivatives thereof such as  ethylan› thraquinone,  2-methyl-1-[ 4-(methylthio )phenyl]-2-mor› pholinopropan-l-one, ~-methylanthraquinone, and tert-butyl  anthraquinone; oxime ester-based compounds and deriva› tives thereof such as 1,2-octanedione, 1-(4-(phenylthio)-2- ( o-benzoyloxime )),  ethanone,  l-(9-ethyl-6-(2-methylben› zoyl)-9H-carbazol-3-yl)-1-( o-acetyloxime ).  The  water› insoluble photopolymerization initiator is not limited, so long  as it is a water-insoluble initiator.  [0159]  Among them, preferable examples include 2-ben› zyl-2-dimethyl amino- I-( 4-morpholinophenyl)-butanone-l,  2-dimethylamino-2-( 4-(methyl-benzyl)-1-( 4-morpholine-4- yl-phenyl)-butan-l-one, 1,2-octanedione, 1-( 4-(phenylthio )- 2-( o-benzoyloxime )),  ethanone,  and  l-(9-ethyl-6-(2- methylbenzoyl)-9H-carbazol-3-yl)-1-( o-acetyloxime ). 