Tridimensional structures for an ink jet printhead and relevant manufacturing process

1. A photolithographic process for producing tridimensional structures in a structural layer in photopolymer for an ink jet printhead, said tridimensional structures being made on a substrate having a bottom wall at least in part reflecting, and comprising at least a side wall adjacent to said bottom wall, said process comprising:

depositing on said substrate a photopolymerizable layer comprising a solution of a monomer or oligomer, a photoinitiator, and a polymerization inhibitor basic compound in a quantity less than the stoichiometric value corresponding to the complete neutralization of the acid species generated by the photoinitiator;

masking said layer for defining areas protected by said masking and areas not protected by said masking, intended to make said tridimensional structures;

irradiating with an ultraviolet (UV) radiation for generating acid species suitable for promoting the polymerization of said solution in said areas not protected by said masking;

 in which a fraction of said radiation is reflected by said reflecting part on the inside of said areas protected by the masking, unwanted acid species being generated in a quantity corresponding to said fraction of radiation, on account of said reflected radiation;

neutralizing said unwanted acid species by means of said inhibitor basic compound;

removing said unpolymerized photopolymerizable solution from said areas protected by said masking.

2. A process according to claim 1 , wherein said polymerization inhibitor is chosen from among: N,N-dimethylaniline; piridine; hydroxylamina; 2,6-dimethylpyridine; 4-dimethylamminopyridine; imidazole; morpholine; hydrazine; piperidine; triisopropanolammine; methylamine; ethylamine; diethylamine; triethylamine.

3. A process according to claim 1 , wherein said polymerization inhibitor comprises piperidine.

4. A process according to claim 1 , wherein said polymerization inhibitor comprises 4-dimethylamminopyridine.

5. A process according to claim 1 , wherein said polymerization inhibitor is present in said polymerizable solution in a concentration between 0.05% and 0.4% by weight, with respect to the weight of said polymerizable solution, excluding said solvent.

6. A process according to claim 1 , in which the stoichiometric ratio of said polymerization inhibitor to said photoinitiator is between 1:10 and 9:10.

7. A process according to claim 1 , in which the stoichiometric ratio of said polymerization inhibitor to said photoinitiator is between 1:8 and 3:8.

8. A process according to claim 1 , in which said reflecting part consists of a track of aluminium.

9. A process according to claim 1 , in which said tridimensional structures comprise at least one cavity of at least 20 μm side, having a bottom wall that comprises a reflecting portion.

10. A process according to claim 1 , in which said tridimensional structures have a thickness of at least 5 μm.

11. A photolithographic process for producing tridimensional structures in a structural layer in photopolymer for an ink jet printhead, said tridimensional structures being made on a substrate having a bottom wall at least in part reflecting, and comprising at least a side wall adjacent to said bottom wall, said process comprising:

depositing on said substrate a photopolymerizable layer comprising a solution of a monomer or oligomer, a photoinitiator, and a polymerization inhibitor basic compound in a quantity less than the stoichiometric value corresponding to the complete neutralization of the acid species generated by the photoinitiator, wherein said polymerization inhibitor comprises tris-(2-hydroxy-1-propyl)amine;

masking said layer for defining areas protected by said masking and areas not protected by said masking, intended to make said tridimensional structures;

irradiating with an ultraviolet (UV) radiation for generating acid species suitable for promoting the polymerization of said solution in said areas not protected by said masking;

 in which a fraction of said radiation is reflected by said reflecting part on the inside of said areas protected by the masking, unwanted acid species being generated in a quantity corresponding to said fraction of radiation, on account of said reflected radiation;

neutralizing said unwanted acid species by means of said inhibitor basic compound;

removing said unpolymerized photopolymerizable solution from said areas protected by said masking.

12. A photolithographic process for producing tridimensional structures in a structural layer in photopolymer for an ink jet printhead, said tridimensional structures being made on a substrate having a bottom wall at least in part reflecting, and comprising at least a side wall adjacent to said bottom wall, said process comprising:

depositing on said substrate a photopolymerizable layer comprising a solution of a monomer or oligomer, a photoinitiator, and a polymerization inhibitor basic compound in a quantity less than the stoichiometric value corresponding to the complete neutralization of the acid species generated by the photoinitiator, wherein said polymerization inhibitor has a coefficient of acidity of the conjugate acid (pKa) that is between 5 and 11;

masking said layer for defining areas protected by said masking and areas not protected by said masking, intended to make said tridimensional structures;

irradiating with an ultraviolet (UV) radiation for generating acid species suitable for promoting the polymerization of said solution in said areas not protected by said masking;

 in which a fraction of said radiation is reflected by said reflecting part on the inside of said areas protected by the masking, unwanted acid species being generated in a quantity corresponding to said fraction of radiation, on account of said reflected radiation;

neutralizing said unwanted acid species by means of said inhibitor basic compound;

removing said unpolymerized photopolymerizable solution from said areas protected by said masking.