Coating compositions for marking substrates
The present invention provides coating compositions for marking substrates, which comprise a colour former in an amount of from 0.01 to 50%, a metal salt of a carboxylic acid in an amount of from 0.01 to 50%, a binder in an amount of from 1 to 80% and an organic solvent in an amount of from 1 to 99%, wherein each amount is by weight based on the weight of the composition. The present invention also provides a process for the preparation of the composition of the present invention, substrates coated with these compositions and a process for preparing a marked substrate using these compositions.
1. A composition comprising a colour former in an amount of from 0.01 to 50%, a metal salt of a carboxylic acid in an amount of from 0.01 to 50%, a binder in an amount of from 1 to 80% and an organic solvent in an amount of from 1 to 99%, wherein each amount is by weight based on the weight of the composition, and wherein the composition is a clear solution.
2. The composition of claim 1 , wherein the carboxylic acid is a carboxylic acid of formula
or a mixture of carboxylic acids of formula (I) in which
n is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 or 14, m is 0, 1, 2, 3 or 4,
R 1 and R 5 are the same or different and can be hydrogen, hydroxy, C 1-12 -alkyl, carboxy, C 1-4 -alkoxycarbonyl, carbamoyl, C 1-4 -alkylaminocarbonyl, acyl, amino, (C 1-4 -alkyl)-CO—NH or ureido, R 2 and R 3 are the same or different and can be hydrogen, C 1-4 -alkyl or (C 1-4 -alkyl)-CO—NH, R 4 is hydrogen, C 1-12 -alkyl, carboxy, C 1-4 -alkoxycarbonyl, carbamoyl, C 1-4 -alkylamino-carbonyl, acyl, amino, (C 1-4 -alkyl)-CO—NH, ureido, phenyl, 2-, 3-, or 4-pyridyl, or 1-, 2- or 3-naphthyl, whereby phenyl, pyridyl or naphthyl can be unsubstituted or mono-, di- or tri-substituted with C 1-4 -alkyl, phenyl, C 1-4 -alkoxy, hydroxy, di(C 1-4 -alkyl)amino or halogen.
3. The composition of claim 1 , wherein the colour former is selected from the group consisting of phthalides, fluorans, triarylmethanes, benzoxazines, quinazolines, spiropyrans, quinones, thiazines, oxazines and mixtures thereof.
4. The composition of claim 1 , wherein the binder is a polymeric binder.
5. The composition of claim 1 , wherein the organic solvent is a polar organic solvent or a mixture of polar organic solvents.
6. A process for preparing the composition of claim 1 , comprising the step of mixing the metal carboxylate, the colour developer, the binder and the organic solvent.
7. A substrate coated with the coating composition of any of claim 1 .
8. The substrate of claim 7 , wherein the coating is transparent.
9. A process for preparing a marked substrate comprising the steps of i) coating a substrate with the composition of any of claim 1 , and ii) exposing those parts of the coated substrate, where a marking is intended, to energy in order to generate a colour marking.
10. The process of claim 9 , wherein the energy is IR irradiation.
11. A marked substrate obtained by a process of claim 9 .
12. The marked substrate of claim 11 , wherein the coating is transparent.
13. The process of claim 9 , wherein the coating is transparent.