Bonding method employing film adhesives

Claim 1

A method for bonding together two surfaces selected from the group consisting of metals, ceramics, and wood, which comprises (i) applying to a carrier or strippable backing sheet, in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation through consumption of epoxide groups, a layer of (liquid) composition (consisting of) an epoxide resin containing at least one group of the formula ##STR24## directly attached to an atom of oxygen, nitrogen or sulfur, where either R and R 2 each represent a hydrogen atom in which case R 1 denotes a hydrogen atom or a methyl group, or R and R 2 together represent --CH 2 CH 2 --, in which case R 1 denotes a hydrogen atom, a photopolymerisable compound which is an acrylic ester containing at least one group of the formula CH.sub.2 =C(R.sup.3)COO-- where R 3 is a hydrogen, chlorine or bromine atom, or a C 1 -C 4 alkyl group, and a heat-activated curing agent for epoxide resins selected from the group consisting of polycarboxylic acid anhydride, dicyandiamide, an imidazole, a latent boron difluoride chelate, an aromatic polyamine and a complex of an amine with boron trifluoride or with boron trichloride, (ii) exposing said layer to actinic radiation until the composition solidifies to form an essentially solid, continuous, self-supporting adhesive film due to photopolymerisation of the said photopolymerisable compound while the epoxide resin remains substantially in the thermosettable state, (iii) removing the said solid film from the carrier or strippable backing sheet, (iv) sandwiching the said solid film between, and in contact with, the two surfaces, the said solid film, and (v) heating the assembly to cure the epoxide resin.

Claim 2

A method for bonding together two surfaces selected from the group consisting of metals, ceramics, and wood, which comprises (i) applying to a carrier or strippable backing sheet, in the absence of a substance which gives rise to a substantial degree of photoinduced polymerisation through consumption of epoxide groups, a layer of (liquid) composition (consisting of) an epoxide resin containing at least one group of the formula ##STR24## directly attached to an atom of oxygen, nitrogen or sulfur, where either R and R 2 each represent a hydrogen atom in which case R 1 denotes a hydrogen atom or a methyl group, or R and R 2 together represent --CH 2 CH 2 --, in which case R 1 denotes a hydrogen atom, a photopolymerisable compound which is an acrylic ester containing at least one group of the formula CH.sub.2 =C(R.sup.3)COO-- where R 3 is a hydrogen, chlorine or bromine atom, or a C 1 -C 4 alkyl group, and a heat-activated curing agent for epoxide resins selected from the group consisting of polycarboxylic acid anhydride, dicyandiamide, an imidazole, a latent boron difluoride chelate, an aromatic polyamine and a complex of an amine with boron trifluoride or with boron trichloride, (ii) exposing said layer to actinic radiation until the composition solidifies to form an essentially solid, continuous, self-supporting adhesive film due to photopolymerisation of the said photopolymerisable compound while the epoxide resin remains substantially in the thermosettable state, (iii) removing the said solid film from the carrier or strippable backing sheet, (iv) sandwiching the said solid film between, and in contact with, the two surfaces, the said solid film, and (v) heating the assembly to cure the epoxide resin.