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 ). 

