METHODS OF USING PHOTOCURABLE INKS
A method for using a photocurable ink including applying this photocurable ink to a suitable substrate. The photocurable ink can be partially cured during application, or fully cured after application. The photocurable ink contains a colorant dissolved or dispersed within a solvent, a photoinitiator, an organic phosphite, an aldehyde, and a photocurable compound. The organic phosphite is present in a molar excess relative to the aldehyde moieties that are present. The photocurable ink can be used for imaging or other applications where a uniform or patterned image is desired.
1 . A method of applying an ink comprising:
providing a photocurable ink,
curing the photocurable ink by irradiating it with curing radiation, and
before or while partially curing, applying the photocurable ink to a substrate,
wherein the photocurable ink comprises a colorant dissolved or dispersed within a solvent, a photoinitiator, an organic phosphite, an aldehyde, and a photocurable compound, and the organic phosphite is present in a molar excess relative to the aldehyde moieties in the photocurable ink.
2 . The method of claim 1 , wherein the photocurable ink is only partially cured with the curing radiation before application to the substrate.
3 . The method of claim 1 , wherein the photocurable ink is applied to the substrate before any curing.
4 . The method of claim 1 that is carried out in the presence of oxygen.
5 . The method of claim 1 , comprising curing the photocurable ink in an imagewise pattern.
6 . The method of claim 1 , comprising applying the photocurable ink to the substrate in an imagewise pattern.
7 . The method of claim 1 , wherein the organic phosphite is present in the photocurable ink in a molar amount relative to the total aldehyde moieties of at least 1:1 and up to and including 4:1.
8 . The method of claim 1 , wherein the organic phosphite in the photocurable ink is represented by the following Structure (I) or (II):
(R′O) 3 P (I)
wherein the multiple R′ groups are the same or different substituted or unsubstituted alkyl groups or HO[{CH(R)} x O] y groups wherein the multiple R groups are the same or different and can be hydrogen atoms or substituted or unsubstituted alkyl groups, or two R′ groups can form a cyclic aliphatic ring or fused ring system,
wherein the two R 1 groups are the same or different substituted or unsubstituted alkyl groups or HO[{CH(R)} x O] y groups wherein the multiple R groups are the same or different and can be hydrogen atoms or substituted or unsubstituted alkyl groups, or the two R 1 groups can form a substituted or unsubstituted cyclic aliphatic ring or fused ring system, and
x is a number at least 2 and up to and including 20, and y is at least 1 and up to and including 20.
9 . The method of claim 1 , wherein the photocurable ink comprises one or more of trimethyl phosphite, triethyl phosphite, tripropyl phosphite, tributyl phosphite, triisobutyl phosphite, triamyl phosphite, trihexyl phosphite, trinonyl phosphite, tri-(ethylene glycol) phosphite, tri-(propylene glycol) phosphite, tri(isopropylene glycol) phosphite, tri-(butylene glycol) phosphite, tri-(isobutylene glycol) phosphite, tri-(pentylene glycol) phosphite, tri-(hexylene glycol) phosphite, tri-(nonylene glycol) phosphite, tri-(diethylene glycol) phosphite, tri-(triethylene glycol) phosphite, tri-(polyethylene glycol) phosphite, tri-(polypropylene glycol) phosphite, and tri-(polybutylene glycol) phosphite.
10 . The method of claim 1 , wherein the organic phosphite is present in the photocurable ink in an amount of at least 0.5 weight % and up to and including 20 weight %.
11 . The method of claim 1 , wherein the photoinitiator in the photocurable ink is one or more of a benzoin, aryl ketone, α-amino ketone, mono- or bis(acyl)phosphine oxide, benzoin alkyl ether, benzil ketal, phenylglyoxalic ester or derivatives thereof, oxime ester, per-ester, ketosulfone, phenylglyoxylate, borate, and metallocene.
12 . The method of claim 1 , wherein the photocurable ink further comprises a photosensitizer for the photoinitiator that is selected from the group consisting of ketocoumarins, benzophenones, xanthones, thioxanthones, arylketones, and polycyclic aromatic hydrocarbons.
13 . The method of claim 1 , wherein the total amount of photoinitiators in the photocurable ink is generally at least 2 weight % and up to and including 80 weight %, based on the total photocurable ink weight, and the molar ratio of organic phosphite to photoinitiator is at least 0.5:1 and up to and including 50:1.
14 . The method of claim 1 , wherein the photocurable compound in the photocurable acrylic monomer or oligomer.
15 . The method of claim 1 , wherein the aldehyde in the photocurable ink is an alkyl or aryl aldehyde having one or more aldehyde moieties and a molecular weight of less than 500.
16 . The method of claim 1 , wherein the photocurable ink comprises:
a colorant dispersed within a solvent,
an alkyl or aryl aldehyde having one or two aldehyde moieties per molecule and a molecular weight of less than 500,
an organic phosphite that is represented by the following Structure (I) or (II):
(R′O) 3 P (I)
wherein the multiple R′ groups are the same or different substituted or unsubstituted alkyl groups or HO[{CH(R)} x O] y groups wherein the multiple R groups are the same or different and can be hydrogen atoms or substituted or unsubstituted alkyl groups, or two R′ groups can form a cyclic aliphatic ring or fused ring system,
wherein the two R 1 groups are the same or different substituted or unsubstituted alkyl groups or HO[{CH(R)} x O] y groups wherein the multiple R groups are the same or different and can be hydrogen atoms or substituted or unsubstituted alkyl groups, or the two R 1 groups can form a substituted or unsubstituted cyclic aliphatic ring or fused ring system, and
x is a number at least 2 and up to and including 20, and y is at least 1 and up to and including 20,
a photoinitiator that is one or more of a benzoin, aryl ketone, α-amino ketone, mono- or bis(acyl)phosphine oxide, benzoin alkyl ether, benzil ketal, phenylglyoxalic ester or derivatives thereof, oxime ester, per-ester, ketosulfone, phenylglyoxylate, borate, and metallocene,
a photosensitizer for the photoinitiator that is selected from the group consisting of ketocoumarins, benzophenones, xanthones, thioxanthones, arylketones, and polycyclic aromatic hydrocarbons, and
a photocurable compound that is an acrylate.
17 . The method of claim 1 , wherein the photocurable ink comprises a colorant dissolved or dispersed within a solvent, a photoinitiator in an amount of at least 0.1 weight % and up to and including 20 weight %, a photosensitizer for the photoinitiator in an amount of at least 0.1 weight % and up to and including 10 weight %, an organic phosphite in an amount of at least 0.5 weight % and up to and including 20 weight %, an aldehyde comprising one or more aldehyde moieties, and a photocurable compound that is an ethylenically unsaturated monomer, oligomer, or crosslinkable polymer, wherein the organic phosphite is present in a molar excess relative to the-aldehyde moieties in the photocurable ink,
wherein:
the colorant is one or more dyes or one or more black, cyan, magenta, yellow, red, blue, green, or brown pigments, or mixtures thereof;
when the colorant comprises one or more dyes, the one or more dyes are present in an amount of at least 1 weight % and up to and including 15 weight % based on the total photocurable ink weight, and when the colorant comprises one or more pigments, the one or more pigments are present in an amount of at least 1% and up to and including 10% based on the total photocurable ink weight;
the organic phosphite is represented by the following Structure (I) or (II):
(R′O) 3 P (I)
wherein the multiple R′ groups are the same or different substituted or unsubstituted alkyl groups or HO[{CH(R)} x O] y groups wherein the multiple R groups are the same or different and can be hydrogen atoms or substituted or unsubstituted alkyl groups, or two R′ groups can form a cyclic aliphatic ring or fused ring system,
wherein the two R 1 groups are the same or different substituted or unsubstituted alkyl groups or HO[{CH(R)} x O] y groups wherein the multiple R groups are the same or different and can be hydrogen atoms or substituted or unsubstituted alkyl groups, or the two R 1 groups can form a substituted or unsubstituted cyclic aliphatic ring or fused ring system, and x is a number at least 2 and up to and including 20, and y is at least 1 and up to and including 20;
the photoinitiator is present in an amount of a molar ratio of the organic phosphite to the photoinitiator of at least 1:1 and up to and including 10:1;
the molar ratio of the photoinitiator to the photosensitizer is at least 1:1 and up to and including 100:1;
the molar ratio of the organic phosphite to the photoinitiator to the photosensitizer is at least 0.1:1:0.1 and up to and including 50:1:1; and
the organic phosphite is present in a molar amount relative to the total aldehyde moieties of greater than 1:1 and up to and including 4:1.
18 . The method of claim 16 , wherein the organic phosphite is present in the photocurable ink in a molar amount relative to the total aldehyde moieties of greater than 1:1 and up to and including 3:1.
19 . The method of claim 1 , wherein the photocurable ink further comprises a black, cyan, magenta, or yellow colorant.
20 . The method of claim 1 , wherein the photocurable ink further comprises a colorant, and if the colorant comprises one or more pigments or dispersions thereof, the one or more pigment particles have a particle average diameter of at least 0.001 μm and up to and including 0.3 μm, provided that at least 70% of the one or more pigment particles have an average diameter of less than about 0.1 μm for carbon black and less than 0.3 μm for other color pigments.