Aqueous laser-sensitive composition for marking substrates

1. An aqueous composition comprising a color former, a developer, and a binder, wherein

(a) the weight ratio between the developer and the color former is in the range of from 1:1 to 5:1;

(b) the binder comprises an acrylate binder, comprising acrylic acid and styrene, and at least one additional monomer selected from the group consisting of α-methyl styrene, ethyl acrylate and 2-ethylhexyl acrylate; and

(c) at least one of the color former and the developer is present in an un-encapsulated form,

wherein the developer is a sulfonylurea derivative of the formula:

R 1 —S(O) 2 —NH—X—NH-A-B—R 2   (1),

wherein

R 1 is unsubstituted or substituted phenyl, naphthyl or C 1-20 -alkyl,

X is a group of the formula —C(NH)—, —C(O)— or —C(S)—,

A is unsubstituted or substituted phenylene, naphthylene or C 1-12 -alkylene, or is an unsubstituted or substituted heterocyclic group,

B is a linking group of formula —O—SO 2 —, —SO 2 —O—, —NH—SO 2 —, —SO 2 —NH—, —S—SO 2 —, —O—CO—, —O—CO—NH—, —NH—CO—, —NH—CO—O—, —S—CO—NH—, —S—CS—NH—, —CO—NH—SO 2 —, —O—CO—NH—SO 2 —, —NH═CH—, —CO—NH—CO—, —S—, —CO—, —O—, —SO 2 —NH—CO—, —O—CO—O— and —O—PO—(OR 2 ) 2 , and

R 2 is unsubstituted or substituted aryl or benzyl or C 1-20 -alkyl,

wherein if B is not a linking group of formula —O—SO 2 —, R 2 is unsubstituted or substituted phenyl, naphthyl or C 1-8 -alkyl, and wherein if B is —O—, R 2 is not alkyl.

2. The composition according to claim 1 , wherein the color former is a fluoran.

3. The composition according to claim 2 , wherein the fluoran is at least one selected from the group consisting of 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-anilinofluoran, 3-dipentylamino-6-methyl-7-anilinofluoran, and 3-(N-ethyl-N-p-tolylamino)-6-methyl-7-anilinofluoran.

4. A substrate coated with the composition of claim 2 .

5. A process for preparing a coated substrate, which comprises the step of coating a substrate with the composition of claim 2 .

6. A process for preparing a marked substrate, which comprises the steps of i) coating a substrate with the composition of claim 2 , and ii) exposing those parts of the coated substrate, where a marking is intended, to energy in order to generate a marking.

7. The composition according to claim 1 , wherein the weight ratio between the developer and the color former is in the range of from 1.5:1 to 3:1.

8. A process for preparing the composition of claim 1 , which comprises the step of mixing a color former and a developer in a weight ratio in the range of from 1:1 to 5:1; a binder comprising an acrylate binder, comprising acrylic acid and styrene, and at least one additional monomer selected from the group consisting of α-methyl styrene, ethyl acrylate and 2-ethylhexyl acrylate; and wherein at least one of the color former and the developer are present in an un-encapsulated form.

9. A substrate coated with the composition of claim 1 .

10. A process for preparing a coated substrate, which comprises the step of coating a substrate with the composition of claim 1 .

11. A process for preparing a marked substrate, which comprises the steps of i) coating a substrate with the composition of claim 1 , and ii) exposing those parts of the coated substrate, where a marking is intended, to energy in order to generate a marking.

12. The process of claim 11 , wherein the energy is selected from the group consisting of UV, IR, visible and microwave irradiation.

13. A marked substrate, which is obtained by the process of claim 11 .

14. The composition according to claim 1 , wherein R 1 as phenyl or naphthyl is unsubstituted or substituted by C 1-8 -alkyl, C 1-8 -alkoxy or halogen, and wherein R 1 as C 1-20 -alkyl is unsubstituted or substituted by C 1-8 -alkoxy or halogen.

15. The composition according to claim 1 , wherein A as a phenylene or naphthylene group is unsubstituted or substituted by C 1-8 -alkyl, halogen-substituted C 1-8 -alkyl, C 1-8 -alkoxy-substituted C 1-8 -alkyl, C 1-8 -alkoxy, halogen-substituted C 1-8 -alkoxy, C 1-8 -alkylsulphonyl, halogen, phenyl, phenoxy or phenoxycarbonyl.

16. The composition according to claim 1 , wherein R 2 as aryl is phenyl or naphthyl which is unsubstituted or substituted by C 1-8 -alkyl, halogen-substituted C 1-8 -alkyl, C 1-8 -alkoxy-substituted C 1-8 -alkyl, C 1-8 -alkoxy, halogen-substituted C 1-8 -alkoxy or halogen, wherein R 2 as benzyl is unsubstituted or substituted by the substituents given for R 2 as phenyl or naphthyl, and wherein R 2 as C 1-20 -alkyl is unsubstituted or substituted by C 1-8 -alkoxy, halogen, phenyl or naphthyl.

17. The composition according to claim 1 , wherein the developer is N-(p-toluenesulfonyl)-N′-3-(p-toluenesulfonyloxyphenyl)urea.

18. An aqueous composition comprising a color former, a developer, and a binder, wherein

(a) the weight ratio between the developer and the color former is in the range of from 1:1 to 5:1;

(b) the binder comprises an acrylate binder, comprising acrylic acid and styrene, and at least one additional monomer selected from the group consisting of α-methyl styrene, ethyl acrylate and 2-ethylhexyl acrylate; and

(c) at least one of the color former and the developer is present in an un-encapsulated form, and

wherein the developer is selected from at least one of, 4,4′-bis(p-toluenesulphonylaminocarbonylamino)diphenylmethane), 4-hydroxybenzoate derivative of a polypentaerythritol compound with CAS number 378244-93-0, N,N′-[sulfonylbis[4,1-phenylene iminocarbonylimino(methylphenylene)]]bis-,C,C′-diphenyl ester, ZnCl 2 , octylammonium stearate, and ammonium stearate.

19. A process for preparing the composition of claim 18 , which comprises the step of mixing a color former and a developer in a weight ratio in the range of from 1:1 to 5:1; a binder comprising an acrylate binder, comprising acrylic acid and styrene, and at least one additional monomer selected from the group consisting of α-methyl styrene, ethyl acrylate and 2-ethylhexyl acrylate; and wherein at least one of the color former and the developer are present in an un-encapsulated form.

20. A substrate coated with the composition of claim 18 .

21. A process for preparing a coated substrate, which comprises the step of coating a substrate with the composition of claim 18 .

22. A process for preparing a marked substrate, which comprises the steps of i) coating a substrate with the composition of claim 18 , and ii) exposing those parts of the coated substrate, where a marking is intended, to energy in order to generate a marking.

23. The process of claim 22 , wherein the energy is selected from the group consisting of UV, IR, visible and microwave irradiation.

24. A marked substrate, which is obtained by the process of claim 22 .