Lithographic printing plate precursors and method of use

A lithographic printing plate precursor comprising:

• an aluminum-containing substrate, and
• a radiation-sensitive imageable layer disposed over the aluminum-containing substrate,
• wherein the aluminum-containing substrate comprises:
• an aluminum-containing plate having a grained and etched surface;
• an inner aluminum oxide layer over the grained and etched surface, the inner aluminum oxide layer having an average dry thickness (TO of at least 500 nm and up to and including 1,500 nm;
• and comprising a multiplicity of inner pores having an average inner pore diameter (Di) of more than 0 nm but less than 15 nm;
• a middle aluminum oxide layer over the inner aluminum oxide layer, the middle aluminum oxide layer having an average dry thickness (Tm) of at least 60 nm and up to and including 300 nm;
• comprising a multiplicity of middle pores having an average middle pore diameter (Dm) of at least 15 nm and up to and including 60 nm;
• and having a middle pore density (Cm) of at least 100 middle pores/μm2 and up to and including 2,000 middle pores/m2;
• and
• an outer aluminum oxide layer over the middle aluminum oxide layer, the outer aluminum oxide layer having an average dry thickness (To) of at least 30 nm and up to and including 150 nm;
• comprising a multiplicity of outer pores having an average outer pore diameter (Do) of at least 5 nm and up to and including 35 nm;
• and having an outer pore density (Co) of at least 100 outer pores/μm2 and up to and including 5,000 outer pores/m2;
• wherein the dry thickness of the combination of the middle aluminum oxide layer and the outer aluminum oxide layer is at least 120 nm and up to and including 420 nm,
• wherein the ratio of the outer pore density to the middle pore density (Co/Cm) is at least 1.1:1.0, and
• wherein Dm is larger than Do that is larger than Di, and
• optionally, a hydrophilic layer comprising one or more hydrophilic polymers provided at a dry coverage of at least 0.0002 g/m2 and up to and including 0.1 g/m2.

A method for preparing a lithographic printing plate precursor, the method comprising, in order:

• A) providing an aluminum-containing plate having an electrochemically or mechanically grained and etched surface;
• B) subjecting the aluminum-containing plate to a first anodizing process using phosphoric acid to form an outer aluminum oxide layer over the electrochemically or mechanically grained and etched surface, the outer aluminum oxide layer having an average dry thickness (To) of at least 30 nm and up to and including 150 nm;
• comprising a multiplicity of outer pores having an average outer micropore diameter (Do) of at least 5 nm and up to and including 35 nm;
• and having an outer pore density (Co) of at least 100 outer pores/μm2 and up to and including 5,000 outer pores/μm2;
• C) optionally, rinsing the outer aluminum oxide layer;
• D) subjecting the aluminum-containing plate to a second anodizing process using phosphoric acid to form a middle aluminum oxide layer underneath the outer aluminum oxide layer, the middle aluminum oxide layer having an average dry thickness (Tm) of at least 60 nm and up to and including 300 nm;
• comprising a multiplicity of middle pores having an average middle pore diameter (Dm) of at least 15 nm and up to and including 60 nm;
• and having a middle pore density (Cm) of at least 100 middle pores/μm2 and up to and including 2,000 middle pores/μm2;
• E) optionally, rinsing the middle aluminum oxide layer;
• F) subjecting the aluminum-containing plate to a third anodizing process using sulfuric acid to form an inner aluminum oxide layer underneath the middle aluminum oxide layer, the inner aluminum oxide layer having an average dry thickness (TO of at least 500 nm and up to and including 1,500 nm;
• and comprising a multiplicity of inner pores having an average inner pore diameter (Di) of more than 0 nm but less than 15 nm, to form an aluminum-containing substrate,
• wherein Dm is larger than Do that is larger than Di, and wherein the dry thickness of the combination of the middle aluminum oxide layer and the outer aluminum oxide layer is at least 120 nm and up to and including 420 nm;
• G) optionally, rinsing the inner aluminum oxide layer;
• H) optionally, applying a hydrophilic composition comprising one or more hydrophilic polymers to provide a dry coverage of at least 0.0002 g/m2 and up to and including 0.1 g/m2;
• and
• I) disposing a radiation-sensitive imageable layer over the aluminum-containing substrate.