Thermally developable materials stabilized with crown ethers
View Patent ↗Incorporating a crown ether-alkali metal complex cation of an enolate anion of an aldehyde having at least one electron withdrawing group in the alpha (α) position, provides thermally developable materials with imaging properties that have little change with changes in humidity. Both photothermographic and thermographic materials are provided, and particularly photothermographic materials having lower silver coverage.
1. A thermally developable material comprising a support having on at least one side thereof, one or more thermally developable imaging layers comprising in reactive association:
a. a non-photosensitive source of reducible silver ions,
b. a reducing agent for said reducible silver ions,
c. a polymeric binder, and
d. a co-developer compound that is a crown ether-alkali metal complex cation and an enolate anion of an aldehyde having at least one electron withdrawing group in the alpha (α) position.
2. The thermally developable material of claim 1 wherein said crown ether-alkali metal complex cation of an enolate anion of an aldehyde having at least one electron withdrawing group in the alpha (α) position, is represented by the following Structure (I):
wherein M + is an alkali metal cation, the CROWN ETHER is a substituted or unsubstituted 12-crown-4, a substituted or unsubstituted 15-crown-5, or a substituted or unsubstituted 1 8-crown-6, and at least one of V and W is an electron-withdrawing group, or V and W can be combined to form a ring containing an electron-withdrawing group.
3. The thermally developable material of claim 2 wherein M + is lithium, sodium, or potassium.
4. The thermally developable material of claim 2 wherein said CROWN ETHER is:
5. The thermally developable material of claim 2 , wherein CROWN ETHER is a substituted or unsubstituted 12-crown-4 when M + is a lithium cation, a substituted or unsubstituted 15-crown-5 when M + is a sodium cation, and a substituted or unsubstituted 1 8-crown-6 when M + is a potassium cation, W is a cyano group or a carboxyalkyl group having from 1 to 20 carbon atoms, and V is a cyano group.
6. The thermally developable material of claim 2 that is a photothermographic material and further comprises a photosensitive silver halide.
7. The thermally developable material of claim 1 further comprising a high contrast enhancing agent.
8. The thermally developable material of claim 7 wherein said high contrast enhancing agent is an hydroxylamine, alkanolamine, ammonium phthalamate, hydroxamic acid, N-acylhydrazine, or hydrogen atom donor compound.
9. The thermally developable material of claim 1 wherein the total amount of silver is equal to or less than 1.6 g/m 2 .
10. The thermally developable material of claim 1 further comprising a protective overcoat layer disposed over said photothermographic layer.
11. The thermally developable material of claim 1 wherein said co-developer compound is present in one or more layers in a total amount of from about 0.0005 to about 0.15 g/m 2 .
12. The thermally developable material of claim 1 that is a photothermographic material and further comprises a photosensitive silver halide.
13. The thermally developable material of claim 1 wherein the molar ratio of said reducing agent to said co-developer compound is from about 1000:1 to about 100:1.
14. A method of forming a visible image comprising:
A) imagewise exposing the material of claim 1 that is a photothermographic material to electromagnetic radiation to form a latent image, and
B) simultaneously or sequentially, heating said exposed photothermographic material to develop said latent image into a visible image.
15. The method of claim 14 wherein said development is carried out for up to 25 seconds.
16. The method of claim 14 wherein said imagewise exposing is carried out using laser imaging at from about 700 to about 950 nm.
17. A method of forming a visible image comprising thermal imaging of the material of claim 1 that is a thermographic material.
18. A photothermographic material comprising a support having on at least one side thereof, one or more thermally developable imaging layers comprising in reactive association:
a. a photosensitive silver halide,
b. a non-photosensitive source of reducible silver ions,
c. a reducing agent for said reducible silver ions,
d. a polymeric binder, and
e. a co-developer compound that is a crown ether-alkali metal complex cation and an enolate anion of an aldehyde having at least one electron withdrawing group in the alpha (α) position, having a Hammett σ p value that is at least 0.35.
19. The photothermographic material of claim 18 wherein said co-developer compound is present in an amount of from about 0.001 g/m 2 to about 0.05 g/m 2 .
20. A black-and-white, organic solvent based photothermographic material comprising a support and having on at least one side thereof a photothermographic layer and comprising, in reactive association:
a. a photosensitive silver bromide or iodobromide,
b. a non-photosensitive source of reducible silver ions, comprising at least silver behenate,
c. one or more reducing agents for said reducible silver ions,
d. a polyvinyl butyral or polyvinyl acetal binder, and
e. one or more co-developer compounds represented by Structure (1)
wherein CROWN ETHER is a substituted or unsubstituted 18-crown-6, M + is a potassium cation, W is a carboxyalkyl group having 1 to 20 carbon atoms and V is a cyano group,
the total amount of silver is present in an amount equal to or less than 1.6 g/m 2 , and
said co-developer compound is present in an amount of at least 0.0005 g/m 2 .
21. The photothermographic material of claim 20 wherein said one or more co-developer compounds comprises one or more of compounds (CNR-1 to (CNR-11) or mixtures thereof