A green, safe and environmentally-friendly process and production equipment for industrialized continuous large-scale production of a formaldehyde-free water-based adhesive; the process includes: performing a polymerization reaction on a monomer having a carbon-carbon unsaturated double bond and an acid anhydride group and at least one other monomer containing a carbon-carbon unsaturated double bond that serve as raw materials in the presence of a solvent and an initiator; and performing solid-liquid separation on the polymerization reaction solution under the action of a high-temperature inert carrier gas, vaporizing, condensing, and recovering the solvent for indiscriminate use in polymerization reaction, and performing a gas-solid reaction on the solid material serving as a polymer intermediate and a mixed gas of ammonia gas and air to obtain a solid formaldehyde-free water-based adhesive product.

The present invention aims to provide a curable resin composition capable of providing a cured product that has a high glass transition temperature after curing and is excellent in thermal decomposition resistance, adhesiveness, and long-term heat resistance. The present invention also aims to provide a cured product of the curable resin composition, an adhesive containing the curable resin composition, and an adhesive film, a coverlay film, a flexible copper clad laminate, and a circuit board each formed using the curable resin composition. Provided is a curable resin composition containing: a curable resin; an imide oligomer having an imide skeleton in a main chain and a crosslinkable functional group at an end and having a number average molecular weight of 4,000 or less; and a curing accelerator, a cured product of the curable resin composition having an initial adhesive force to polyimide of 3.4 N/cm or more, the cured product after storage at 200° C. for 100 hours having an adhesive force to polyimide of at least 0.8 times the initial adhesive force.

Adhesive sheets that can adhere to both a smooth surface and a rough surface with sufficient adhesive force and that exhibits smooth visual appearance after adhesion regardless of a surface to be applied are described. In particular, adhesive sheets including a rigid sheet having a thickness of 80 μm or greater and 2 mm or less; and a first pressure-sensitive adhesive layer disposed on one surface of the rigid sheet, the first pressure-sensitive adhesive layer having a thickness of 40 μm or greater and 1.2 mm or less and including a microstructured surface including irregularities are described.

Provided is a curable compound having a low melting temperature, having excellent workability as a result of having good solvent solubility, and being capable of forming a cured product having excellent heat resistance. The curable compound according to an embodiment of the present invention includes the following characteristics (a) to (e). (a) Number average molecular weight (calibrated with polystyrene standard): 1000 to 15000. (b) Proportion of a structure derived from an aromatic ring in the total amount of the curable compound: 50 wt. % or greater. (c) Solvent solubility at 25° C.: 1 g/100 g or greater. (d) Glass transition temperature: 280° C. or lower. (e) 5% Weight loss temperature (T.sub.d5) measured at a rate of temperature increase of 10° C./min (in nitrogen), for a cured product of the curable compound: 300° C. or higher.

The present invention aims to provide a curable resin composition capable of providing a cured product that has a high glass transition temperature after curing and is excellent in thermal decomposition resistance, adhesiveness, and long-term heat resistance. The present invention also aims to provide a cured product of the curable resin composition, an adhesive containing the curable resin composition, and an adhesive film, a coverlay film, a flexible copper clad laminate, and a circuit board each formed using the curable resin composition. Provided is a curable resin composition containing: a curable resin; an imide oligomer having an imide skeleton in a main chain and a crosslinkable functional group at an end and having a number average molecular weight of 4,000 or less; and a curing accelerator, a cured product of the curable resin composition having an initial adhesive force to polyimide of 3.4 N/cm or more, the cured product after storage at 200° C. for 100 hours having an adhesive force to polyimide of at least 0.8 times the initial adhesive force.

A material for a printed circuit board, which is a film composed of a fluorinated resin layer, where the fluorinated resin layer contains a composition containing a fluorinated copolymer having at least one functional group selected from a carbonyl group-containing group, a hydroxy group, an epoxy group and an isocyanate group, has a melt flow rate of at most 15 g/10 min measured at 372 C. under a load of 49N, and has a storage elastic modulus of at least 650 MPa.

A material for a printed circuit board, which is a film composed of a fluorinated resin layer, where the fluorinated resin layer contains a composition containing a fluorinated copolymer having at least one functional group selected from a carbonyl group-containing group, a hydroxy group, an epoxy group and an isocyanate group, has a melt flow rate of at most 15 g/10 min measured at 372 C. under a load of 49N, and has a storage elastic modulus of at least 650 MPa.

A robust hydrogel-solid hybrid formed of a substrate material having a nonporous and non-topographically patterned surface and a tough hydrogel bonded to the surface, the tough hydrogel having over 90 wt % water, and the hydrogel being bonded to provide interfacial toughness over 300 Jm.sup.2, and even over 1000 Jm.sup.2. The hydrogel is formed of polyacrylamide or polyethylene glycol diacrylate, which provide long-chain polymer networks, and chitosan, hyaluronan, or alginate, which provide mechanically dissipative components. An anchor, which can be a silane, a sulfide, or an amine, is disposed between the surface and the hydrogel to provide chemical bonding between the surface and the long-chain networks of the hydrogel.

A robust hydrogel-solid hybrid formed of a substrate material having a nonporous and non-topographically patterned surface and a tough hydrogel bonded to the surface, the tough hydrogel having over 90 wt % water, and the hydrogel being bonded to provide interfacial toughness over 300 Jm.sup.2, and even over 1000 Jm.sup.2. The hydrogel is formed of polyacrylamide or polyethylene glycol diacrylate, which provide long-chain polymer networks, and chitosan, hyaluronan, or alginate, which provide mechanically dissipative components. An anchor, which can be a silane, a sulfide, or an amine, is disposed between the surface and the hydrogel to provide chemical bonding between the surface and the long-chain networks of the hydrogel.

A material having a fluorinated resin layer is subjected to heat treatment. The fluorinated resin layer is composed of a composition containing a fluorinated copolymer (a) having at least one type of functional group selected from a carbonyl group-containing group, a hydroxy group, an epoxy group and an isocyanate group, having a melting point of from 280 to 320 C. and a melt flow rate of at least 2 g/10 min measured at 372 C. under a load of 49 N. The heat treatment is carried out at a temperature of at least 250 C. and lower by at least 5 C. than the melting point of the fluorinated copolymer (a) so that the ratio of the melt flow rate of the fluorinated resin layer after the heat treatment to that before the heat treatment, and the melt flow rate of the fluorinated resin layer after the heat treatment, are respectively within specific ranges.