Inkjet-type 3D printing method using urea reaction

An inkjet-type three-dimensional (3D) printing method of printing a 3D structure using a urea reaction between amine and isocyanate, the inkjet-type 3D printing method comprising:

• applying by a slot coating method a subject ink on a build platform to form a subject ink layer, the subject ink consisting of a high molecular weight oligomer or a high molecular weight polymer containing an amine group (—NH2) or an isocyanate group (—NCO) on an least one end;
• spraying a hardener ink, according to patterns set in advance for a shape of a 3D structure layer of the 3D structure to be manufactured, onto a surface of the subject ink layer through an inkjet nozzle, the hardener ink consisting of a monomer or an oligomer containing the other of the isocyanate group (—NCO) or the amine group (—NH2) from that of the subject ink on at least one end and curing the 3D structure layer through cross-linking by the urea reaction between amine and isocyanate groups contained in the subject ink and the hardener ink, respectively;
• and
• repeatedly applying subsequent layers of the subject ink on the 3D structure layer previously cured by the urea reaction, and then curing the subsequently applied layers by spraying thereon the hardener ink through the inkjet nozzle,
• wherein the subject ink is made of a temperature phase change ink composition that is maintained in a liquid state at a temperature above the phase change temperature and is frozen and gelled at a temperature equal to or lower than the phase change temperature,
• the printing of the 3D structure is performed in a chamber in which the temperature is equal to or lower than the phase change temperature,
• using cooling means to maintain a surface temperature of the build platform in a range of 0° C. to 10° C.;
• and
• whereby each applied ink layer and the correspondingly sprayed hardener ink are supported by the prior layers of the 3D structure which are at a temperature below the phase change temperature.