May 5,  2011  18  US 2011/0104454 Al  talc, aluminum hydroxide and calcium carbonate, and  organic fillers such as cured epoxy resin, crosslinked ben› zoguanamine resin and crosslinked acrylic polymer.  [0253]  The adhesion-aiding layer may also include one or  more additives of various kinds as necessary, such as a colo› rant, a flame retardant, a tackifier, a silane coupling agent, an  antioxidant, an ultraviolet absorbent, or the like.  [0254]  When such a material as described above is added to  the adhesion-aiding layer, an addition amount of each mate› rial is in the range of preferably Oto 200% by mass and more  preferably Oto 80% by mass, with respect to the amount of the  resin as a main component. When the adhesion-aiding layer  and the substrate that are adjacent to each other have the same  or similar physical properties with respect to heat or electric› ity, these additives may not be added. When the above amount  of the additive is more than 200% by mass, properties that are  inherent to the resin, such as strength, may deteriorate.  [0255]  The adhesion-aiding layer preferably includes, as  mentioned above, a resin composition and a compound that  generates radicals upon exposure with light.  [0256]  In the invention, known photopolymerization initia› tors or light-sensitive resins can be used as the compound that  generates radicals upon exposure with light.  [0257]  Examples of the photopolymerization initiator  include acetophenones such as p-tert-butyl trichloroac› etophenone, 2,2’-diethoxyacetophenone, and 2-hydroxy-2- methyl-1-phenylpropan-1-one; ketones such as benzophe› none,  4,4’-bisdimethylaminobenzophenone,  2-chlorothioxanthone, 2-methy lthioxanthone, 2-ethy lthiox› anthone, and 2-isopropylthioxanthone; benzoin ethers such  as benzoin, benzoin methyl ether, benzoin isopropyl ether,  and benzoin isobutyl ether; benzyl ketals such as benzyl  dimethyl ketal and hydroxycyclohexyl phenyl ketone; sulfo› nium salts such as triphenyl sulfonium chloride, triphenyl  sulfonium pentafluoro phosphate; and iodonium salts such as  diphenyl iodonium chloride and diphenyl iodonium sulfate.  [0258]  The photopolymerization initiator (compound that  generates radicals upon exposure with light) is incorporated  in the adhesion-aiding layer preferably at an amount of from  0.1 to 50% by mass, and more preferably from 1.0 to 30% by  mass, in terms of solid content.  [0259]  The thickness of the adhesion-aiding layer accord› ing to the invention is generally from 0.1 to 10 µm, and  preferably from 0.5 to 7 µm.  When the adhesion-aiding layer  has a thickness within this range, a sufficient level of adhesion  to the adjacent substrate or the layer to be plated can be  achieved. Further, a level of adhesion equivalent to that of a  layer formed from a commonly used adhesive can be  achieved, in spite of a thinner layer than the layer formed from  the adhesive.  [0260]  The surface of the adhesion-aiding layer according  to the invention preferably has a surface roughness Rz of3 µm  or less, more preferably 1 µm  or less, as measured in accor› dance with a ten-point average height method as stipulated by  JIS B 0601 (1994), from the viewpoint of improving the  properties of the plated metal film to be formed on the adhe› sion-aiding layer.  [0261]  When a surface roughness of the adhesion-aiding  layer is within the above range, namely the adhesion-aiding  layer has a smooth surface, the adhesion-aiding layer can be  favorably used in the production of a printing circuit board  having an extremely fine circuit (for example, a circuit pattern  having a line/space value of 25/25 µm  or less).  [0262]  The adhesion-aiding layer can be formed on the  substrate by a known method such as a coating method, a  transfer method or a printing method.  [0263]  If desired, the adhesion-aiding layer may be pat› terned by a printing method (such as gravure printing, screen  printing, flexographic printing, inkjet printing and imprint  method), a development method (such as wet etching, dry  etching, ablation, curing/plasticizing (negative/positive) with  light), or the like.  [0264]  The adhesion-aiding layer having been formed on  the substrate may be subjected to a curing process by applying  energy of some kind Examples of the energy to be applied  include light, heat, pressure and electron beams, and heat or  light is generally used in this embodiment. When energy is  applied by heat, heating is preferably conducted at the tem› perature of from 100 to 300°  C. for a period of from 5 to 120  minutes. The conditions for curing by heating may differ  depending on the type of material for the substrate, the type of  resin composition that forms the adhesion-aiding layer, or the  curing temperatures of these materials, but are preferably  selected from the temperature range of from 120 to 220°  C.  and the time range of from 20 to 120 minutes.  [0265]  The curing treatment may be performed immedi› ately after the formation of the adhesion-aiding layer. Alter› natively, by conducting a pre-curing treatment for about 5 to  about 10 minutes after the formation of the adhesion-aiding  layer, the curing treatment can be performed after completion  of all processes subsequent to the formation of the adhesion› aiding layer.  [0266]  After formation of the adhesion-aiding layer, the  surface of the same may be roughened by a dry or wet method  in order to improve its adhesiveness with respect to the layer  to be plated, which is to be formed on the adhesion-aiding  layer. Examples of the  dry  roughening method include  mechanical polishing such as buffing or sand blasting, and  plasma etching. Examples of the wet roughening method  include a chemical treatment using an oxidant such as per› manganate, bichromate, ozone, hydrogen peroxide/sulfuric  acid, or nitric acid; a strong base; or a resin-swelling solvent.  [0267]  Step (2)  [0268]  In step (2) of the method of producing a metal pat› tern material according to the invention, the uncured portion  of the composition on the substrate is removed by developing  with an aqueous solution to form a patterned layer to be  plated.  [0269]  Development with Aqueous Solution  [0270]  Examples of the aqueous solution used in this step  include an acidic aqueous solution, a neutral aqueous solu› tion, and an alkali aqueous solution.  [0271]  Examples of the acidic aqueous solution include an  aqueous solution of hydrochloric acid, sulfuric acid or nitric  acid.  [0272]  Examples of the neutral aqueous solution include a  surfactant that is dissolved in water. Anionic, nonionic or  cationic surfactant may be used.  [0273]  Of the aqueous solution, an alkali aqueous solution  is preferable, and specific examples thereof include an aque› ous solution of sodium hydroxide, potassium hydroxide,  magnesium hydroxide, calcium hydroxide, sodium carbon› ate, potassium carbonate, magnesium carbonate, calcium car› bonate, sodium hydrogen carbonate, potassium hydrogen  carbonate, magnesium hydrogen carbonate and calcium  hydrogen carbonate. 