Thermally imageable positive-working lithographic printing plate precursor and method for imaging

• US 6,458,511 B1
• Filed: 06/07/2000
• Issued: 10/01/2002
• Est. Priority Date: 06/07/2000
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Kodak Polychrome Graphics Company Limited (Eastman Kodak Company)
• Inventors: Savariar-Hauck, Celin, Timpe, Hans-Joachim, Wittig, Tobias
• Primary Examiner(s): CHU, JOHN S Y
• Application Number:
  US09/589,335
• Time in Patent Office: 846 Days
• Field of Search: 430/175, 430/302, 430/11, 430/18, 101/457, 101/467, 101/456
• US Class Current: 430/302
• CPC Class Codes: B41C 1/1008 by removal or destruction of lithographic material on the lithographic support, e.g. by laser or spark ablation; by the use of materials rendered soluble or insoluble by heat exposure, e.g. by heat produced from a light to heat transforming system; by on-the-press exposure or on-the-press development, e.g. by the fountain of photolithographic materials
• CPC Class Codes: B41C 2210/02 Positive working, i.e. the exposed (imaged) areas are removed
• CPC Class Codes: B41C 2210/06 Developable by an alkaline solution
• CPC Class Codes: B41C 2210/22 characterised by organic non-macromolecular additives, e.g. dyes, UV-absorbers, plasticisers
• CPC Class Codes: B41C 2210/24 characterised by a macromolecular compound or binder obtained by reactions involving carbon-to-carbon unsaturated bonds, e.g. acrylics, vinyl polymers
• CPC Class Codes: B41N 3/03 Chemical or electrical pretreatment
• CPC Class Codes: B41N 3/038 Treatment with a chromium compound, a silicon compound, a phophorus compound or a compound of a metal of group IVB; Hydrophilic coatings obtained by hydrolysis of organometallic compounds

Abstract

A radiation-sensitive composition comprises: (i) at least one component capable of absorbing IR radiation; and (ii) a diazonium polycondensation product soluble in an organic solvent; with the proviso that the composition does not contain components capable of reacting with decomposition products produced from IR radiation exposure of the diazonium polycondensation product. The composition may additionally comprise a polymeric binder of the type useful for conventional negative-working printing plates. The composition is suitable for preparing thermally imageable printing plate precursors and printing plates and may also be used in a method for providing an image on such plate precursors and printing plates.

Claims

1. A method for providing an image comprising:

(a) coating a substrate with a radiation-sensitive composition comprising;

(i) at least one component capable of absorbing IR radiation, and

(ii) a diazonium polycondensation product soluble in an organic solvent, with the proviso that the composition does not contain components capable of reacting with decomposition products produced from IR radiation exposure of the diazonium polycondensation product;

(b) imagewise exposing the printing plate precursor obtained in step (a) to IR radiation;

(c) subsequently overall exposing the precursor to UV radiation; and

(d) developing the precursor with an aqueous alkaline developing composition.

2. The method according to claim 1, wherein the IR absorbing component is present in an amount of about 1 to about 30 wt % based on the total weight of the radiation-sensitive composition.

3. The method according to claim 1, wherein the diazonium polycondensation product is a diazonium salt condensate which is present in an amount of about 1 to about 60 wt % based on the total weight of the radiation-sensitive composition.

4. The method of claim 1, wherein the diazonium polycondenstation product is a diazo adduct of a diazo resin with sulfonated acrylic polymers or of a diazo resin with sulfonated polyesters, the adduct being present in an amount of about 80 to about 98 wt. % based on the total weight of the composition.

5. The method according to claim 1, wherein the radiation-sensitive composition additionally comprises an alkali soluble resin as a polymeric binder.

6. The method according to claim 5, wherein the polymeric binder is present in an amount of about 1 to about 95 wt % based on the total weight of the radiation-sensitive composition.

7. The method according to claim 1, where the IR absorbing component is a pigment or a dye, or a combination thereof.

8. The method according to claim 1, wherein the IR absorbing component is an IR dye of the formula:

wherein;

each X′

independently represents S, O, NR′

or C(alkyl)₂;

each R¹′

independently is an alkyl group, an alkylsulfonate or an alkylammonium group;

R²′

represents a halogen atom, SR′

, SO₂R′

, OR′

or NR′

₂;

each R³′

independently represents a hydrogen atom, an alkyl group, COOR′

, OR′

, SR′

,

NR′

₂, a halogen atom or a substituted or unsubstituted benzofused ring;

A′

represents an anion;

R⁴′ and

R₅′

are each a hydrogen atom, or are joined together to form a group selected from —

(CH₂)₂—

or —

(CH₂)₃—

;

each R′

independently represents hydrogen, an alkyl or aryl group; and

each n′

independently is 0, 1, 2 or 3.

9. The method according to claim 5, wherein the polymeric binder is a polyvinylacetal binder comprising the following units A, B and C

wherein R¹ is H or C₁-C₄ alkyl, CH═

CHCOOH or

R² is H, C₁-C₄ alkyl, aryl, or of the structure;

wherein R³ and R⁴ are independently selected from hydrogen and methyl,

n is an integer from 1 to 3, and

R⁵ is alkyl, aralkyl, aryl, alkoxyaryl or alkanoyl amide aryl wherein the alkyl moieties have 1 to 8 carbon atoms and the aryl moieties have 6 or 10 carbon atoms R⁶ is hydrogen or an aliphatic, aromatic or araliphatic group having 1 to 10 carbon atoms,

Y is —

CR⁷R⁸—

CR⁹R¹⁰—

, —

CR⁷═

CR⁸—

, or of the structure;

wherein R⁷, R⁸,R⁹, R¹⁰ each are independently hydrogen or C₁-C₄ alkyl and X is —

CH₂, —

CH(CH₃) or —

CH₂CH₂CH₂.

10. The method according to claim 1 further comprising at least one member selected from the group consisting of exposure indicators and dyes for increasing the image contrast.

11. The method according to claim 1, wherein the substrate is a metal or polymeric substrate.

12. The method according to claim 11, wherein the substrate is an aluminium substrate.

13. The method of claim 1, wherein the substrate has been pretreated.

14. The method of claim 12, wherein the aluminium substrate is treated with a silicate, fluorozirconate, phosphate, a phosphate/fluoride composition or an organic compound selected from the group consisting of carboxymethylcellulose, dextrine, gum arabic, amino group-containing phosphonic acids, organic phosphonic acids, organic phosphates, amino acids and hydroxyl group-containing amine hydrochlorides.