The present invention relates to novel class of photoinitiators and their use in photopolymerization compositions. The invention also concerns a process for the photopolymerization of compositions comprising said photoinitiators.

The present invention relates to compount (I) comprising at least one functional group A and at least one functional group B, wherein the functional groups A has structural formula A: wherein R.sub.1 is H, R.sub.2, R.sub.3 and R.sub.4 are independently chosen from H, methyl or ethyl, m is 1-6; and the functional groups B has structural formula B: R.sub.5 is H or methyl, X is O or NH, Z′ is a polyalkoxy group or an omega-alkoxy polycaprolacton group, Y′ is a collection of atoms covalently connected in linear or branched configuration n″ is 0 or 1, and m′ is an integer from 1-6; with the proviso that the summed amount of the number of functional groups A and the number of functional groups B in compound (I) is from 2-13; and the compound has a molecular weight in the range from 800-10000 Dalton.

##STR00001##

The present invention relates to compount (I) comprising at least one functional group A and at least one functional group B, wherein the functional groups A has structural formula A: wherein R.sub.1 is H, R.sub.2, R.sub.3 and R.sub.4 are independently chosen from H, methyl or ethyl, m is 1-6; and the functional groups B has structural formula B: R.sub.5 is H or methyl, X is O or NH, Z′ is a polyalkoxy group or an omega-alkoxy polycaprolacton group, Y′ is a collection of atoms covalently connected in linear or branched configuration n″ is 0 or 1, and m′ is an integer from 1-6; with the proviso that the summed amount of the number of functional groups A and the number of functional groups B in compound (I) is from 2-13; and the compound has a molecular weight in the range from 800-10000 Dalton.

##STR00001##

A photocurable inkjet printing ink composition satisfies requirements A to F: A: the total content of compounds selected from vinyl methyl oxazolidinone, N,N-dimethylacrylamide, benzyl acrylate, and N-vinylcaprolactam, is 30.0% by mass or higher; B: the total content of compounds selected from saturated hydrocarbon group-containing monofunctional monomers with 6 or more carbon atoms and saturated hydrocarbon group-containing polyfunctional monomers with 6 or more carbon atoms is 15.0% by mass or higher in the photocurable inkjet printing ink composition; C: the content of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 3.5% by mass or higher; D: the total content of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 6.0 to 12.0% by mass, and their ratio is 0.3 to 1.5; E: the content of amine-modified oligomer is 0.5 to 15.0% by mass in the photocurable inkjet printing ink composition; and F: a colorant is included.

A photocurable inkjet printing ink composition satisfies requirements A to F: A: the total content of compounds selected from vinyl methyl oxazolidinone, N,N-dimethylacrylamide, benzyl acrylate, and N-vinylcaprolactam, is 30.0% by mass or higher; B: the total content of compounds selected from saturated hydrocarbon group-containing monofunctional monomers with 6 or more carbon atoms and saturated hydrocarbon group-containing polyfunctional monomers with 6 or more carbon atoms is 15.0% by mass or higher in the photocurable inkjet printing ink composition; C: the content of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 3.5% by mass or higher; D: the total content of ethoxy(2,4,6-trimethylbenzoyl)phenylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide is 6.0 to 12.0% by mass, and their ratio is 0.3 to 1.5; E: the content of amine-modified oligomer is 0.5 to 15.0% by mass in the photocurable inkjet printing ink composition; and F: a colorant is included.

An example of an ultraviolet (UV) light fusing agent for three-dimensional (3D) printing includes a UV light absorber and a liquid vehicle. The UV light absorber consists of a fluorescent yellow dye. The liquid vehicle includes a surfactant, a co-solvent, and a balance of water. The UV light fusing agent is devoid of a saccharide.

An example of an ultraviolet (UV) light fusing agent for three-dimensional (3D) printing includes a UV light absorber and a liquid vehicle. The UV light absorber consists of a fluorescent yellow dye. The liquid vehicle includes a surfactant, a co-solvent, and a balance of water. The UV light fusing agent is devoid of a saccharide.

An ink jet ink composition contains a metal pigment and at least one liquid medium selected from the group consisting of organic solvents and water. The metal pigment is surface-modified with a surface treatment agent. The metal pigment is in the form of scale-like particles and has a volume average particle size D.sub.50 of 1.0 μm or less. The ratio D.sub.50/Z of the volume average particle size D.sub.50 of the metal pigment to the average thickness Z of the metal pigment particles is 17 or more, and the ratio D.sub.50/L of the volume average particle size D.sub.50 to the nozzle diameter L of the ink jet head is 0.050 or less.

An ink jet recording apparatus including an ink jet head for ejecting and attaching a radiation-curable ink jet composition to a recording medium and an irradiation unit for applying radiation to the recording medium to which the radiation-curable ink jet composition is attached under supply of an inert gas, wherein the irradiation unit has, successively in a transport direction of the recording medium, a nozzle face for ejecting the inert gas and an application face for applying radiation, and h1>h2, where h1 is a distance from the recording medium to the nozzle face and h2 is a distance from the recording medium to the application face.

An ink jet recording apparatus including an ink jet head for ejecting and attaching a radiation-curable ink jet composition to a recording medium and an irradiation unit for applying radiation to the recording medium to which the radiation-curable ink jet composition is attached under supply of an inert gas, wherein the irradiation unit has, successively in a transport direction of the recording medium, a nozzle face for ejecting the inert gas and an application face for applying radiation, and h1>h2, where h1 is a distance from the recording medium to the nozzle face and h2 is a distance from the recording medium to the application face.