LITHOGRAPHIC PRINTING PLATE PRECURSOR AND METHOD OF USE

1 . A lithographic printing plate precursor comprising an aluminum-containing substrate, and an infrared radiation-sensitive image-recording layer disposed on the aluminum-containing substrate,

the infrared radiation-sensitive image-recording layer comprising:

g) one or more free radically polymerizable components;

h) one or more infrared radiation absorbers;

i) an initiator composition;

j) one or more color-forming compounds;

k) one or more compounds, each being represented by the following Structure (P):

wherein X is the group —O—, —S—, —NH—, or —CH 2 —, Y is the group >N— or >CH—, R 1 is hydrogen or a substituted or unsubstituted alkyl, R 2 and R 3 are independently halo, thioalkyl, thiophenyl, alkoxy, phenoxy, alkyl, phenyl, thioacetyl, or acetyl, groups, and m and n are independently 0 or an integer of from 1 to 4; and

l) optionally, a non-free radically polymerizable polymeric material different from the a), b), c), d), and e) components defined above,

wherein the infrared radiation-sensitive image-recording layer, upon exposure to infrared radiation to provide exposed regions and non-exposed regions, exhibits a color contrast between the exposed regions and non-exposed regions of a ΔE greater than 8, and wherein a ΔE of at least 5 is maintained between the exposed regions and the non-exposed regions after storage of the exposed image-recording layer under white light for at least one hour.

2 . The lithographic printing plate precursor of claim 1 , provided that at least one of the d) one or more color-forming compounds is not a compound represented by the following Structure (C′):

wherein A and A′ are the same or different group represented by the following Structure (AA′):

R 4 is an unsubstituted alkyl group, R 5 is an unsubstituted alkyl group, and R 6 is a halogen or an alkyl sulfonyl group.

3 . The lithographic printing plate precursor of claim 1 , provided that at least one of the d) one or more color-forming compounds is not a compound represented by one of the following Structures (X) and (Y):

4 . The lithographic printing plate precursor of claim 1 , wherein at least one of the d) one or more color-forming compounds comprises a lactone substructure.

5 . The lithographic printing plate precursor of claim 1 , wherein the d) one or more color-forming compounds and the e) one or more compounds represented by Structure (P) are present in the infrared radiation-sensitive image-recording layer at a d) to e) molar ratio of at least 1.1:1 to and including 50:1.

6 . The lithographic printing plate precursor of claim 5 , wherein the d) one or more color-forming compounds are present in the infrared radiation-sensitive image-recording layer in a dry coverage amount of at least 2 weight % and up to and including 10 weight %.

7 . The lithographic printing plate precursor of claim 1 , wherein the f) polymeric material is present in particulate form.

8 . The lithographic printing plate precursor of claim 1 , wherein the infrared radiation-sensitive image-recording layer is the outermost layer.

9 . The lithographic printing plate precursor of claim 1 , that is on-press developable.

10 . The lithographic printing plate precursor of claim 1 , wherein the a) one or more free radically polymerizable components comprise at least two free radically polymerizable components.

11 . The lithographic printing plate precursor of claim 1 , wherein the c) initiator composition comprises a diaryliodonium salt.

12 . The lithographic printing plate precursor of claim 1 , wherein the aluminum-containing substrate comprises an aluminum oxide layer provided by phosphoric acid anodization, and a hydrophilic polymer coating is disposed on the aluminum oxide layer.

13 . The lithographic printing plate precursor of claim 1 , wherein X is —S— or —NH—, and Y is >N—.

14 . The lithographic printing plate precursor of claim 1 , wherein m and n are independently 0, 1, or 2, and R 2 and R 3 are independently a chloro, a thioalkyl having 1 or 2 carbon atoms, or an acetyl, group.

15 . The lithographic printing plate precursor of claim 1 , wherein the d) one or more color-forming compounds are represented by one or both of the following Structures (C1) and (C2):

wherein R 11 through R 19 are independently hydrogen, unsubstituted or substituted alkyl groups, or unsubstituted or substituted aryl groups.

16 . The lithographic printing plate precursor of claim 1 , wherein the e) one or more compounds represented by Structure (P) are one or more of the following Compounds 1 through 4:

17 . The lithographic printing plate precursor of claim 1 , wherein the c) initiator composition comprises a tetraaryl borate.

18 . A method for providing a lithographic printing plate, comprising:

A) imagewise exposing the lithographic printing plate precursor according to claim 1 to infrared radiation, to provide exposed regions and non-exposed regions in the infrared radiation-sensitive image-recording layer, and

B) removing the non-exposed regions in the infrared radiation-sensitive image-recording layer from the aluminum-containing substrate.

19 . The method of claim 18 , comprising removing the non-exposed regions in the infrared radiation-sensitive image-recording layer from the aluminum-containing substrate on-press using a lithographic printing ink, a fountain solution, or a combination of a lithographic printing ink and a fountain solution.

20 . A method for providing a lithographic printing plate, comprising:

A) imagewise exposing the lithographic printing plate precursor according to claim 5 to exposing infrared radiation, to provide exposed regions and non-exposed regions in the infrared radiation-sensitive image-recording layer, and

B) removing the non-exposed regions in the infrared radiation-sensitive image-recording layer from the aluminum-containing substrate on-press.