Printing plate blank and image sheet by laser transfer

The method of making a printing plate from a receptor sheet of a type having a hydrophilic surface comprising:

• providing small cavities in one surface of the receptor sheet to relieve high pressure effects resulting from the generation of gases;
• providing a transfer sheet transparent to a laser beam;
• coating one face of the transfer sheet with a substance which in response to laser beam radiation passing through said transfer sheet emits gases and produces a material capable of adhering to said receptor sheet;
• applying the coated face of the transfer sheet to said one surface of the receptor sheet;
• applying an electrostatic charge to one of said sheets to effect adherence of the sheets;
• selectively applying a laser beam through said transfer sheet to said substance to thus produce gases and said material and cause said material to adhere to the receptor sheet to provide said receptor sheet with a printing configuration, the gases dispersing into said cavities;
• and
• removing the transfer sheet thereby rendering said receptor sheet a printing plate.

A method of making a printing plate by applying a beam of laser radiation for transferring a selected pattern of oleophilic material from a transfer sheet onto a receptor sheet in the form of a lithographic plate, said method comprising:

• forming a transfer sheet by coating one side of a sheet of material that is transparent to said beam of laser radiation with a coating consisting of an oleophilic material, a material which absorbs said laser radiation and a self-oxidizing binder such that combustion of the self-oxidizing binder is initiated by said laser radiation absorbed by said absorbent material;
• providing a receptor sheet having a lithographic printing surface that is grained;
• selecting said transparent sheet and the coating material thereon and said plate so that one will hold an electrostatic charge and the other is electrically conductive;
• placing an electrostatic charge on at least one of said sheets;
• placing the transfer sheet with its coated side in intimate contact with the grained lithographic surface of the receptor sheet whereby the two sheets are held electrostatically together in said intimate contact;
• and
• directing a laser beam on the coated side of said transfer sheet in accordance with a configuration of the subject matter to be printed to effect said combustion and for applying the solid products of said combustion onto the receptor sheet to provide a printing surface thereon.

A printing plate blank comprising

• receptor sheet means having a multiplicity of raised areas separated by troughs which will provide relief from excessive gas pressure generated therein during further processing of the blank,
• a transfer sheet,
• said transfer sheet comprising electrostatic means holding said transfer sheet to said multiplicity of raised areas while bridging said troughs so that the transfer sheet does not preclude the dispersion of gases to said troughs,
• said transfer sheet comprising means which, in response to predetermined irradiation, releases gases between the first named means and the transfer sheet and also forms a printing plate by changing the character of the surface area of said first named means that is in contact with the portion of the transfer sheet which received the predetermined irradiation, whereby in response to selective application of said predetermined irradiation certain portions of the surface area of the first named means are changed in character to thereby form a printing plate.

The method of making a printing plate from a receptor sheet of a type having a hydrophilic surface comprising

• providing small cavities in one surface of the receptor sheet to relieve high pressure effects resulting from the generation of combustion gases,
• providing a transfer sheet transparent to a laser beam,
• coating one face of the transfer sheet with a mixture of carbon and a self-oxidizing binder which is sufficiently absorbed by the carbon to effect combustion of the mixture in response to laser beam radiation passing through said transfer sheet and impinging on said mixture,
• applying the coated face of the transfer sheet to said one surface of the receptor sheet,
• applying an electrostatic charge to one of said sheets to effect adherence of the sheets,
• selectively applying a laser beam through said transfer sheet to said mixture effecting combustion thereof and adhering combustion products to the receptor sheet to provide it with a printing configuration, the combustion gases dispersing into said cavities, and
• removing the transfer sheet thereby rendering said receptor sheet a printing plate.