Method of making laser imaged printing plates utilizing ultraviolet absorbing layer

• US 5,925,500 A
• Filed: 08/21/1997
• Issued: 07/20/1999
• Est. Priority Date: 06/25/1993
• Status: Expired due to Term

• Current Assignee: Macdermid Printing Solutions LLC (Element Solutions Inc)
• Original Assignee: Polyfibron Technologies, Inc.
• Inventors: Kanga, Rustom Sam, Yang, Michael Wen-Chein, Randall, Alvin Varnard
• Primary Examiner(s): Young, Christopher G.
• Application Number:
  US08/916,101
• Time in Patent Office: 698 Days
• Field of Search: 430/309, 430/512
• US Class Current: 430/300
• CPC Class Codes: G03F 7/202 Masking pattern being obtained by thermal means, e.g. laser ablation
• CPC Class Codes: Y10S 430/146 Laser beam

Abstract

Laser-imageable flexographic printing plates and a method of making same are disclosed. A thin polymeric film doped with a UV absorber is laminated to a photopolymer layer. The film is ablated from the photopolymer using a laser operating at a selected wavelength to create an in situ negative. The resulting negative can be subjected to typical UV flood exposure and development.

Claims

1. A method of making a laser imaged printing plate, the steps comprising

(a) providing a solid, uncured, photocurable printing plate consisting essentially of:

1) a backing;

2) at least one photocurable layer on said backing, said photocurable layer comprising a photopolymer which is unaffected by radiation at a selected wavelength in the range of 300-400 nm and an initiator activatable at the selected wavelength; and

;

3) an ultra-violet radiation absorbing layer over said photocurable layer, said absorbing layer comprising a polymeric matrix that is transparent to ultraviolet radiation and a dopant which is soluble in said polymeric matrix and has a high extinction coefficient in the wavelength range of 300-400 nm, wherein said ultra-violet radiation absorbing layer is capable of being photoablated by a laser operating at a first energy level in the wavelength range of 300-400 nm, and wherein unablated areas of said absorbing layer are capable of absorbing at least 95% of irradiated light in the wavelength range of 300-400 nm from an ultra-violet light source operating at a second energy level lower than said first energy level;

(b) photoablating said absorbing layer using a laser, thereby providing ablated and unablated areas forming an image;

(c) flood exposing said laser imaged printing plate to UV light in the wavelength range of 300-400 nm, without a negative, thereby curing the photocurable layer in areas under ablated areas of said absorbing layer; and

(d) developing said exposed, laser imaged plate.

2. The method of claim 1 wherein the dopant is 2,2'"'"',4,4'"'"'-tetrahydroxybenzophenone;

2,2'"'"'-dihydroxy-4,4'"'"'-dimethoxybenzophenone;

or mixtures thereof.

3. The method of claim 1 wherein unablated areas of said absorbing layer are capable of absorbing more than 97% of irradiated ultra-violet light in the range of 300-400 nm at said second energy level.

4. The method of claim 1 wherein the uncured printing plate further comprises a photocurable overcoat layer disposed between said photocurable layer and said radiation absorbing layer, said overcoat layer comprising a photopolymer which is unaffected by radiation at the selected wavelength and an initiator activatable at the selected wavelength.

5. The method of claim 3 wherein the uncured printing plate further comprises a photocurable overcoat layer disposed between said photocurable layer and said radiation absorbing layer, said overcoat layer comprising a photopolymer which is unaffected by radiation at the selected wavelength and an initiator activatable at the selected wavelength.