Lithographic printing plate precursors and methods of use

Abstract

A lithographic printing plate precursor has an aluminum substrate prepared using two anodization processes to provide an inner aluminum oxide layer having an average dry thickness of 300-3,000 nm and having a plurality of inner micropores having an average inner micropore diameter of <100 nm. An outer aluminum oxide layer is provided with a plurality of outer micropores having an average outer micropore diameter of 15-30 nm and a dry thickness of 30-650 nm. A hydrophilic layer is provided on the outer aluminum oxide layer having (1) a compound having an ethylenically unsaturated polymerizable group, an -OM group directly attached to a phosphorus atom, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and (2) one or more hydrophilic polymers having (a) a repeating unit comprising an amide group, and (b) a repeating unit having an -OM' group directly attached to a phosphorus atom, wherein M' represents a hydrogen, sodium, potassium, or aluminum atom. 2 An outer aluminum oxide layer is provided with a plurality of outer micropores having an average outer micropore diameter of 15-30 nm and a dry thickness of 30-650 nm. A hydrophilic layer is provided on the outer aluminum oxide layer having (1) a compound having an ethylenically unsaturated polymerizable group, an -OM group directly attached to a phosphorus atom, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and (2) one or more hydrophilic polymers having (a) a repeating unit comprising an amide group, and (b) a repeating unit having an -OM' group directly attached to a phosphorus atom, wherein M' represents a hydrogen, sodium, potassium, or aluminum atom.

Description

Technical Field

[0001] The present invention relates to a lithographic printing plate precursor comprising an inventive aluminum-containing substrate that has been prepared using at least two separate anodization processes to provide different aluminum oxide layers having different structural properties. The aluminum-containing substrate also has a unique hydrophilic layer disposed on the aluminum oxide layer, comprising at least one unique hydrophilic copolymer as defined below; and a compound having an -OM group (as defined below) directly attached to a phosphorus atom and at least one ethylenically unsaturated polymerizable group. The present invention also relates to a method for imaging such a lithographic printing plate precursor and processing it to provide a lithographic printing plate. The present invention further relates to a method for making such an inventive precursor. Background of the Invention

[0003] In lithographic printing, lithographic ink-receiving areas, called image areas, are created on the hydrophilic surface of a substrate. When the printing plate surface is moistened with water and a lithographic ink is applied, the hydrophilic areas retain the water and repel the lithographic ink, while the lithographic ink-receiving image areas receive the lithographic ink and repel the water. The lithographic ink is transferred from the lithographic printing plate to the surface of the material on which the image is to be reproduced, perhaps using a blanket roller.

[0004] Imageable elements or lithographic printing plate precursors used to prepare lithographic printing plates typically comprise one or more radiation-sensitive imageable layers disposed on the outermost hydrophilic surface of a substrate. After imaging, either the exposed (imaged) or non-exposed (non-imaged) areas of the one or more radiation-sensitive layers can be removed using a suitable developer to reveal the outermost hydrophilic surface of the substrate. If the exposed areas are removable, the lithographic printing plate precursor is considered positive-working. Conversely, if the non-exposed areas are removable, the lithographic printing plate precursor is considered negative-working.

[0005] Over the past 30 years, direct digital (laser) thermal imaging of lithographic printing plate precursors has become increasingly important in the printing industry due to their stability to ambient light. Such precursors have been designed to be sensitive to imaging near-infrared radiation of at least 750 nm. However, other very useful lithographic printing plate precursors are still designed to be sensitive to digital imaging with UV or "violet" radiation of at least 250 nm.

[0006] Negative-working lithographic printing plate precursors useful for preparing lithographic printing plates typically comprise a negative-working radiation-sensitive imageable layer disposed above a hydrophilic surface of a substrate. Radiation-sensitive photopolymerizable compositions for negative-working lithographic printing plate precursors typically comprise a free radical polymerizable component, one or more radiation absorbers, an initiator composition, and optionally one or more polymeric binders different from the other components. After imaging, precursors of this type having a polymeric interlayer on the substrate and below the imageable layer can be developed in an off-press development apparatus using conventional developers, as described in U.S. Patent Application Publication No. 2012 / 0070779 (Miyamoto et al.).

[0007] In recent decades, the industry has emphasized simplifying the lithographic printing plate manufacturing process, including omitting the pre-development heating step (preheat) and performing on-press development (DOP) using lithographic ink, fountain solution, or both to remove unwanted (unexposed) imageable layer materials from the lithographic printing plate precursor. Such negative-working lithographic printing plate precursors should be designed by balancing many features in the element structure to achieve optimal plate run length, on-press developability, and scratch resistance. Optimizing all of these properties simultaneously is not an easy task, as chemical compositions or structural features that provide optimal levels in one or two properties may result in the loss of another.

[0008] Regardless of the type of lithographic printing plate precursor, lithography is typically performed using a metal-containing substrate comprising aluminum or an aluminum alloy of various metal compositions, for example containing up to 10% by weight of one or more other metals known in the art for this purpose. The raw aluminum-containing material can be cleaned using an alkali or surfactant solution in a "pre-etch" process to remove oil, grease, and other contaminants on the surface of the raw aluminum-containing material. The cleaned surface is then typically roughened by electrochemical or mechanical grinding, followed by a "post-etch" treatment to remove any contaminants ("stains") formed during the grinding process. Further industrial details of preparing substrates that can be used for lithographic printing plate precursors are found in U.S. Patent Application Publication 2014 / 0047993A1 (Hauck et al.).

[0009] After further washing, the treated surface of the aluminum-containing substrate is then anodized one or more times to provide an outermost hydrophilic aluminum oxide coating for abrasion resistance and other desired properties of the resulting lithographic printing plate precursor once one or more imageable layers are formed thereon.

[0010] One or more anodization methods are used in some known methods of making precursor substrates, for example, as described in U.S. Patents 4,566,952 (Sprintschnik et al.) and 8,783,179 (Kurokawa et al.), U.S. Patent Application Publications 2011 / 0265673 (Tagawa et al.), 2012 / 0192742 (Kurokawa et al.), 2014 / 0326151 (Namba et al.), and 2015 / 0135979 (Tagawa et al.), and EP 2,353,882A1 (Tagawa et al.).

[0011] In these known methods for producing precursor substrates, sulfuric acid, phosphoric acid, or both sulfuric acid and phosphoric acid have been used as electrolytes, combined with various process parameters to produce one or more anodic (aluminum oxide) layers with specific structures and thereby achieve specific properties in the resulting precursors. However, it has been found that lithographic printing plate precursors prepared according to these known methods remain unsatisfactory in terms of one or more properties, such as scratch resistance, on-press developability, plate run length, and restart toning (RST).

[0012] Due to the harmful effects of processing chemicals and waste generated during lithographic printing plate manufacturing, lithographic printing plate precursors that can be developed on-press after imaging with lithographic inks and / or fountain solutions have become significantly more desirable in the industry. Early commercialization of this type of lithographic printing plate precursor was generally limited to printing applications requiring fewer than 100,000 impressions. These limitations were due to the technical difficulties in achieving both rapid on-press development and good image durability.

[0013] The unique anodized substrates described in commonly assigned US Patent No. 10,828,884 (Merka et al.) and commonly assigned US Patent No. 10,363,734 (Merka et al.) provide advances in the field of on-press developable lithographic printing plate precursors.

[0014] Recently, aluminum-containing substrates having multilayer anodic oxide structures, such as those described in these publications, have been developed. Such substrates for use in press-developable lithographic printing plate precursors having an on-press developable imageable layer exhibit image durability (good plate run length) while maintaining rapid on-press developability. In such press-developable lithographic printing plate precursors, a hydrophilic subbing layer may be located between the press-developable imageable layer and the multilayer aluminum anodic oxide structure.

[0015] Typical polymers included in this hydrophilic subbing layer are partially neutralized polyacrylic acids. However, lithographic printing plates fabricated from such on-press developable lithographic printing plate precursors have shown to sometimes suffer from a problem known as poor restart toning (identified herein as RST), wherein the background becomes ink receptive and requires many print impressions to become clean when the lithographic printing operation is restarted after a print interruption or stoppage.

[0016] Thus, there remains a need to provide lithographic printing plates that can be easily restarted after a print interruption, wherein the restart toning problem is reduced or eliminated. It is particularly desirable that such lithographic printing plates be derived from on-press developable negative-working lithographic printing plate precursors without sacrificing print durability and on-press developability. SUMMARY

[0018] The present invention provides a lithographic printing plate precursor comprising:

[0019] a substrate having a surface, and

[0020] an on-press developable radiation-sensitive imageable layer disposed over the surface of the substrate,

[0021] wherein the substrate comprises:

[0022] an aluminum-containing plate having a grained and etched surface;

[0023] an alumina inner layer disposed on the grained and etched surface, the alumina inner layer having an average dry thickness (T i ) of at least 300 nm and up to and including 3,000 nm, and comprising a plurality of inner micropores having an average inner micropore diameter (D i ) of less than or equal to 100 nm;

[0024] an alumina outer layer disposed over the alumina inner layer, the alumina outer layer comprising a plurality of outer micropores having an average outer micropore diameter (D o ) of at least 15 nm and up to and including 30 nm, and having an average dry thickness (T o ) of at least 30 nm and up to and including 650 nm; and

[0025] a hydrophilic layer disposed on the alumina outer layer at a dry coverage of at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 and comprising:

[0026] (1) a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, wherein at least one -OM group is directly attached to a phosphorous atom, and a molecular weight of less than 2000 Daltons / mole, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and

[0027] (2) one or more hydrophilic polymers, each comprising at least: (a) a repeating unit comprising an amide group, and (b) a repeating unit comprising an -OM' group directly attached to a phosphorus atom, wherein M' represents a hydrogen, sodium, potassium or aluminum atom.

[0028] Furthermore, the present invention provides a method for providing a lithographic printing plate, the method comprising:

[0029] exposing the lithographic printing plate precursor of any of the embodiments of the invention imagewise to imaging radiation to form an imagewise exposed imageable layer having exposed areas and non-exposed areas, and

[0030] The non-exposed areas are removed on-press from the imagewise exposed imageable layer to form a lithographic printing plate.

[0031] Furthermore, the present invention provides a method for preparing a lithographic printing plate precursor, the method comprising, in sequence:

[0032] providing an aluminum-containing plate having an electrochemically or mechanically ground and etched surface;

[0033] The aluminum-containing plate is subjected to a first anodizing process to form an aluminum oxide outer layer on the electrochemically or mechanically ground and etched surface, the aluminum oxide outer layer comprising a plurality of pores having an average outer pore diameter (D) of at least 15 nm and up to and including 30 nm. o ) and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o );

[0034] rinsing the outer aluminum oxide layer;

[0035] The aluminum-containing plate is subjected to a second anodizing process to form an inner aluminum oxide layer below the outer aluminum oxide layer, the inner aluminum oxide layer having an average dry thickness (T of at least 300 nm and up to and including 3,000 nm). i ); and comprising a plurality of average inner pore diameters (D i ) inner micropores;

[0036] washing the outer aluminum oxide layer and the inner aluminum oxide layer;

[0037] forming an on-press developable radiation-sensitive imageable layer over the aluminum oxide outer layer; and

[0038] After washing the outer aluminum oxide layer and the inner aluminum oxide layer and before forming the on-press developable radiation-sensitive imageable layer over the outer aluminum oxide layer, a hydrophilic layer is provided over the outer aluminum oxide layer, the hydrophilic layer comprising:

[0039] (1) a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, at least one of which is directly attached to a phosphorus atom, and a molecular weight of less than 2000 Daltons / mole, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and

[0040] (2) one or more hydrophilic polymers, each comprising at least: (a) repeating units comprising amide units, and (b) repeating units comprising -OM' groups directly attached to phosphorus atoms, wherein M' represents a hydrogen, sodium, potassium or aluminum atom, and the hydrophilic layer has a surface area of ​​at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 A dry coverage of 1000 nm is provided over the outer layer of aluminum oxide.

[0041] According to the present invention, the above-mentioned restart toning (RST) problem has been successfully solved by providing a unique hydrophilic layer (sometimes referred to as a "bottom" layer) on a multilayer aluminum anodic oxide structure to form an inventive on-press developable lithographic printing plate precursor. Such a hydrophilic layer comprises (2) one or more hydrophilic polymers, the polymer consisting of at least (a) repeating units having an amide group, and (b) repeating units comprising an -OM' group directly attached to a phosphorus atom, wherein M' is a hydrogen, sodium, potassium or aluminum atom. In addition, the hydrophilic layer comprises (1) a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, wherein at least one -OM group is directly attached to a phosphorus atom, and a molecular weight of less than 2000 Daltons / mole, wherein M is a hydrogen, sodium, potassium or aluminum atom. These two components of (1) the compound and (2) one or more hydrophilic polymers comprising at least one hydrophilic copolymer should be used together. Specific details of these necessary components for making the hydrophilic layer are provided below. Significant improvements in RST were achieved while maintaining acceptable scratch resistance, on-press developability and long plate run. Detailed Description of the Invention

[0043] The following discussion is directed to various embodiments of the invention, and while some embodiments may be desirable for particular uses, the disclosed embodiments should not be interpreted or otherwise considered to limit the scope of the invention as claimed below. Furthermore, those skilled in the art will appreciate that the following disclosure has broader applicability than explicitly described in the discussion of any particular embodiment.

[0044] definition

[0045] Unless otherwise indicated, the singular forms "a," "an," and "the" as used herein to define various components of the radiation-sensitive imageable layer formulation (and the resulting dried layer), anodizing solutions, hydrophilic layer formulation (and the resulting dried layer), and other materials used in the practice of the invention are intended to include one or more components (i.e., include plural referents).

[0046] Each term that is not clearly defined in this application should be understood to have the meaning generally accepted by those skilled in the art.If the construction of a term will make it meaningless or essentially meaningless in its context, the term should be interpreted to have the standard dictionary meaning.

[0047] Unless expressly indicated otherwise, the use of numerical values ​​in the various ranges set forth herein should be considered approximate, as if the word "about" were preceding both the minimum and maximum values ​​within the stated ranges. In this manner, slight variations above and below the stated ranges can be useful in achieving substantially the same results as the values ​​within the ranges. Furthermore, the disclosure of these ranges is intended as a continuous range, including every value between the minimum and maximum values, as well as the endpoints of the ranges.

[0048] Unless the context indicates otherwise, when used herein, the terms "negative-working radiation-sensitive lithographic printing plate precursor," "precursor," "radiation-sensitive precursor," and "lithographic printing plate precursor" are intended to refer to certain embodiments of the present invention.

[0049] The term "support" is used herein to refer to an aluminum- or other metal-containing material (sheet, mesh, strip, sheet, foil, or other form) that can be subsequently processed to prepare a "substrate" as described in more detail below.

[0050] The average external pore diameter (D) in nanometers (nm) o ) can be determined from a top view SEM image taken at a magnification of at least 50,000X from the substrate surface prior to application of the optional hydrophilic layer and one or more radiation-sensitive imageable layers. It is also possible to determine the outer micropore diameter (D) of the lithographic printing plate precursor by stripping the organic layer using a suitable solvent and optionally removing a surface portion of the outer aluminum oxide layer of about 20 nm to 80 nm thick using a suitable technique (e.g., argon ion beam sputtering) prior to taking the top view SEM image. o ). The average value can be determined by examining more than 200 external microwells.

[0051] Average inner pore diameter (D i) can be determined from a cross-sectional SEM image at a magnification of at least 50,000X. A cross section can be produced by bending the lithographic printing plate precursor or its substrate after removal of the imageable layer and the optional hydrophilic layer. During bending, cracks form in the alumina layer and new surfaces are formed, typically at the weakest locations (which are typically located at the thinnest walls between adjacent internal micropores). Thus, the new crack surfaces provide a cross-sectional view of many micropores. For the present invention, it is not necessary to determine the exact average internal micropore diameter (D i ), as long as at least 90% of the revealed micropore cross sections have a width below 15 nm.

[0052] Average dry thickness of the anodized outer layer in nanometers (nm) (T o ) and the average dry thickness of the anodized inner layer (T i ) can each be determined from a cross-sectional SEM image at a magnification of at least 50,000X. The cross section of the aluminum oxide layer can be revealed through a crack formed by bending the lithographic printing plate precursor or its substrate. The cross section of the aluminum oxide layer can also be revealed by cutting a slit through the aluminum oxide layer using a focused ion beam (FIB) technique well known in the art.

[0053] Micropores / μm 2 The micropore density of the anodized outer layer (C o ) can be determined from a top-view SEM picture at a magnification of at least 50,000X by counting the number of micropores in a predetermined area of ​​a square having an area of, for example, 500 nm x 500 nm.

[0054] The porosity of the outer layer of alumina (P o ) can be subject to each of the following constraints:

[0055] 0.3≤P o ≤0.8, or

[0056] 0.3≤P o ≤0.6,

[0057] Among them, P o Defined as 3.14(Co ) (D o 2 ) / 4,000,000.

[0058] The term "radiation absorber" as used herein refers to a compound or material that absorbs electromagnetic radiation in a defined region, and generally refers to a compound or material having an absorption maximum in the region of at least 250 nm (UV and violet) and up to and including 1400 nm, or a mixture thereof.

[0059] As used herein, the term "infrared region" refers to radiation having a wavelength of at least 750 nm and higher. In most cases, the term "infrared" is used to refer to the region of the electromagnetic spectrum defined herein as at least 750 nm and up to and including 1400 nm. Similarly, infrared radiation absorbers provide sensitivity in the infrared region.

[0060] For clarification of the definition of any term related to polymers, reference should be made to "Glossary of Basic Terms in Polymer Science", Pure Appl. Chem. 68, 2287-2311 (1996), published by the International Union of Pure and Applied Chemistry ("IUPAC"). However, any definitions explicitly set forth herein should be considered decisive.

[0061] As used herein, the term "polymer" is used to describe a compound having a relatively large molecular weight formed by linking together many small reactive monomers. As the polymer chain grows, it folds back on itself in a random manner to form a coiled structure. Depending on the solvent, the polymer may become insoluble as the chain length increases and become polymer particles dispersed in the solvent medium. These particle dispersions can be very stable and can be used in the radiation-sensitive imageable layer described as being used in the present invention. In the present invention, unless otherwise specified, the term "polymer" refers to a non-crosslinked material. Thus, crosslinked polymer particles differ from non-crosslinked polymer particles in that the latter are soluble in certain organic solvents with good solubility properties, while crosslinked polymer particles can swell but not dissolve in organic solvents because the polymer chains are connected by strong covalent bonds.

[0062] The term "copolymer" refers to a polymer composed of two or more different repeating or recurring units arranged along the copolymer backbone.

[0063] The term "polymer backbone" refers to the chain of atoms in a polymer to which one or more pendant groups may be attached. An example of such a polymer backbone is an "all-carbon" backbone obtained by polymerization of one or more ethylenically unsaturated polymerizable monomers. If a polymer is formed using a polycondensation reaction using appropriate reactants, some polymer backbones may contain both carbon and heteroatoms.

[0064] The repeating units in the polymeric binders described herein are generally derived from corresponding ethylenically unsaturated polymerizable monomers (also identified herein as "monomers") used in the polymerization process, which are available from various commercial sources or can be prepared using known chemical synthesis methods. Unless otherwise specified herein, repeating units derived from the same ethylenically unsaturated polymerizable monomer are, by definition, identical in composition and molecular weight.

[0065] As used herein, the term "ethylenically unsaturated polymerizable monomer" refers to a compound containing one or more ethylenically unsaturated (-C=C-) bonds that can be polymerized using free radical or acid-catalyzed polymerization reactions and conditions. It is not intended to refer to compounds having only unsaturated -C=C- bonds that are non-polymerizable under these conditions.

[0066] Unless otherwise indicated, the term "weight %" refers to the amount of a component or material based on the total solids of a composition, formulation or dry layer. Unless otherwise indicated, the percentages for the total solids of a dry layer or a formulation or composition used to form the dry layer may be the same.

[0067] As used herein, the term "layer" or "coating" may consist of one disposed or applied layer or a combination of several successively disposed or applied layers. If a layer is considered to be radiation-sensitive and negative-working, it is both sensitive to suitable radiation (e.g., infrared radiation) and negative-working in the formation of a lithographic printing plate.

[0068] use

[0069] The lithographic printing plate precursors of the present invention can be used to form lithographic printing plates for lithographic printing, for example, using lithographic inks and fountain solutions (also known as dampening solutions). These precursors are prepared using the structures and components described below. In addition, the lithographic printing plate precursors of the present invention are designed to be negative-working and on-press developable using appropriate materials and manufacturing procedures described below to provide negative-working radiation-sensitive formulations and imageable layers.

[0070] Furthermore, the inventive precursors are designed to be developable on-press, such that development of the imaged precursors can be achieved on-press, for example, using fountain solution, lithographic ink, or both. However, such precursors can still be developed off-press using a suitable developer if desired by the user.

[0071] The present invention can also be used to make such lithographic printing plate precursors, which can then be sold to consumers for imaging and printing.

[0072] Invention Base

[0073] The inventive substrates useful in the present invention are designed to possess key features and properties in order to achieve the advantages described above.

[0074] A general description of the production of substrates useful for lithographic printing plate precursors can be found in US Patent Application Publication No. 2014 / 0047993 Al (noted above).

[0075] Typically, the lithographic printing plate substrate can be derived from aluminum or other metallic materials, such as aluminum alloys containing up to 10% by weight of one or more elements, including but not limited to manganese, silicon, iron, titanium, copper, magnesium, chromium, zinc, bismuth, nickel, and zirconium. The support (or "plate" or "stock") containing aluminum or an aluminum alloy can have any form (including sheet, continuous web, and coiled strip) from which it can be further processed, as long as it has at least one (substantially flat) surface that can be treated as described below to form a hydrophilic surface in the inventive substrate. Polymeric films or papers on which a layer containing pure aluminum or an aluminum alloy is deposited or laminated can also be used.

[0076] The resulting substrate should be thick enough to mechanically withstand the conditions in modern printing presses, but thin enough to be mounted (or wound) on the printing cylinder of such machines. Thus, the substrate should also have the appropriate tensile strength, elasticity, crystallinity, and electrical conductivity required for lithographic printing. These properties can be achieved by standard methods such as heat treatment or cold and hot rolling (typically used to make continuous lithographic support strips, webs, or rolls). The dry thickness of the resulting inventive substrate is typically at least 100 μm and up to and including 600 μm.

[0077] The aluminum-containing support can be processed using a typical lithographic printing plate precursor manufacturing process, which includes pre-etching, water rinsing, roughening, water rinsing, post-etching, and final water rinsing procedures, in combination with the first and second anodization processes described in more detail below.

[0078] The raw material aluminum-containing support is usually subjected to a pre-etching step to remove oil, grease and metal and other contaminants at or near the support surface. As is known in the art, this pre-etching step can be carried out using sodium hydroxide or other alkaline aqueous solutions or even certain organic solvents at known concentrations, times and temperatures. If necessary, a separate or additional degreasing step can be carried out using an aqueous surfactant solution. The skilled person will be able to perform routine experiments to find the best pre-etching conditions (e.g., optimal solution concentration, residence time and temperature).

[0079] Typically, after the pre-etching step, the etched support is "roughened" in a suitable manner, for example, by using a known electrochemical or mechanical roughening (or grinding) process. In the electrochemical grinding process, the etched support can be treated with an alternating current in a solution of 5 to 20 g / l hydrochloric acid. For this purpose, a nitric acid solution (e.g., up to 2.5 wt %) or a sulfuric acid solution or a mixture thereof can also be used. Such electrochemical grinding solutions can also contain additives such as corrosion inhibitors and stabilizers, including but not limited to metal nitrates, metal chlorides, monoamines, diamines, aldehydes, phosphoric acid, chromic acid, boric acid, lactic acid, acetic acid, and oxalic acid. For example, electrochemical grinding can be performed using the method described in U.S. Patent Application Publication No. 2008 / 0003411 (Hunter et al.). The skilled person will be able to determine the optimal conditions for electrochemical or mechanical grinding by routine experimentation, as such methods are well known in the art. The mechanical grinding process can be performed, for example, using a suitable brush (alone or in combination with a slurry of abrasives such as silica particles or aluminum oxide particles). Alternatively, a combination of mechanical and electrochemical graining processes may be used.

[0080] During the roughening or graining process, stains may form on the support surface and these stains may be removed in a post-etching step, for example by treatment with a strongly acidic or alkaline solution to remove 0.01-5.0 g / m 2 The post-etching step is performed by removing the surface of the support. For example, a solution of sodium hydroxide, trisodium phosphate, or sulfuric acid can be used for post-etching. The amount of post-etching can be controlled by setting the residence time, concentration, and temperature of the etching solution. The appropriate amount of post-etching also depends on the amount of roughening and the amount of stain formed during this step. The post-etching treatment should be sufficient to remove the stain, but it should not excessively damage the surface structure formed during the roughening step. Thus, there are many combinations of parameters that a skilled person can consider during routine experimentation to find the optimal post-etching conditions.

[0081] The above steps produce an electrochemically or mechanically grained (roughened) and etched surface in the aluminum-containing support.

[0082] The subsequent steps performed according to the present invention include at least a first anodizing process and a second anodizing process (both of which are essential to the present invention) to form the outer and inner layers of aluminum oxide, respectively. The method of the present invention does not require additional anodizing processes (i.e., a third or more anodizing processes), but one or more additional anodizing processes are possible and thus optional. However, in many embodiments, the first and second anodizing processes described herein are the only anodizing processes.

[0083] Typically, the first and second anodizing processes can be performed using sulfuric acid or phosphoric acid (electrolyte) solutions at a temperature of at least 20°C and up to and including 70°C for a suitable time of at least 1 second and up to and including 250 seconds sufficient to provide up to and including 4 g / m 2 The conditions of the first and second anodizing processes are described as follows.

[0084] A suitable aluminum-containing plate having an electrochemically or mechanically ground and etched surface is subjected to a first anodizing process to form an outer layer of aluminum oxide on the electrochemically or mechanically ground and etched surface. For example, an electrolyte composition containing at least 50 g / l and up to and including 350 g / l phosphoric acid or at least 150 g / l and up to and including 300 g / l sulfuric acid, and a suitable amount of aluminum (e.g., 5 g / l) can be used for the first anodizing process. These solution amounts can be optimized with respect to the type of acid, acid concentration, aluminum concentration, residence time, and temperature to obtain the desired aluminum oxide outer layer properties as described herein. Representative details of such a first anodizing process are illustrated in the following working examples. It is particularly useful to use phosphoric acid for the first anodizing process.

[0085] The resulting alumina outer layer comprises a plurality of pores having an average outer pore diameter (D o ) of the outer micropores. In addition, the average dry thickness of the outer layer of alumina (T o ) may be at least 30 nm and up to and including 650 nm, or more likely may be at least 130 nm or at least 150 nm and up to and including 400 nm. The micropore density (C o ) can typically be at least 500 micropores / μm 2 and up to and including 3,000 micropores / μm 2 .

[0086] In addition, the average outer pore diameter (D o ) and micropores / μm 2 Micropore density (C o ) can be further constrained or related according to each of the following equations:

[0087] 0.3≤P o ≤0.8, or

[0088] 0.3≤P o ≤0.6,

[0089] The porosity P is defined above. o .

[0090] Once the first anodizing process has been carried out for the desired time, the formed outer aluminum oxide layer can be washed with a suitable solution (such as water) at a suitable temperature and time to remove residual acid and aluminum and stop the first anodizing process, if necessary.

[0091] A second anodization process is then performed to form an inner layer of aluminum oxide beneath the outer layer of aluminum oxide using a suitable electrolyte composition, which may comprise at least 100 g / l and up to and including 350 g / l of sulfuric acid, or at least 50 g / l and up to and including 350 g / l of phosphoric acid, and a suitable amount of aluminum (e.g., 5 g / l). These solution amounts can be optimized with respect to acid concentration, aluminum concentration, residence time, and temperature to obtain the desired inner layer properties of aluminum oxide as described herein. Details of such a second anodization process are illustrated in the following working examples.

[0092] The resulting inner layer of aluminum oxide disposed on the grained and etched surface of the substrate comprises a plurality of pores having an average inner pore diameter (D) of less than or equal to 100 nm. i In some embodiments, the average inner pore diameter (D i ) is less than or equal to 15 nm. In such embodiments, D o To D i The ratio of can be greater than 1.1:1, or even greater than 1.5:1, and often greater than 2:1. In other embodiments, the average inner pore diameter (D i ) is greater than 30 nm, and is greater than the average outer pore diameter (D o ). In these latter embodiments, D i To D o The ratio may be greater than 1.1:1 or even greater than 1.5:1, and is typically greater than 2:1. In addition, the average dry thickness of the inner layer of aluminum oxide (T i ) can be at least 300 nm or at least 650 nm, and up to and including 1500 nm or up to and including 3,000 nm.

[0093] In some embodiments, the outer alumina layer is disposed directly on the inner alumina layer, and the average pore diameter (D i ) is at least 20 nm and larger than the average pore diameter (D o ).

[0094] Once the second anodizing process has been carried out for the desired time, the formed outer and inner aluminum oxide layers can be washed with a suitable solution (such as water) at a suitable temperature and time to remove residual acid and aluminum and stop the second anodizing process, if necessary.

[0095] In some embodiments of the present invention, the aluminum-containing support is subjected to an additional anodizing process using a suitable acid or mixture thereof for a suitable time and at a suitable temperature to provide an "aluminum oxide intermediate layer." This additional anodizing process is performed after the first anodizing process and before the second anodizing process. Thus, an aluminum oxide intermediate layer is typically formed between the aluminum oxide outer layer and the subsequently formed aluminum oxide inner layer. In such embodiments, the aluminum oxide intermediate layer formed may have an average dry thickness (T) of at least 60 nm and up to and including 300 nm. m ), and comprising a plurality of pores having an average median pore diameter (D m ) in the middle of the micropore.

[0096] In such embodiments, D m Greater than D o , D o Greater than D i , and T o It can be less than 150 nm.

[0097] After forming the aluminum oxide intermediate layer, the aluminum oxide outer layer and the aluminum oxide intermediate layer may be rinsed as described above for the aluminum oxide outer layer alone, and before forming the aluminum oxide inner layer as described above.

[0098] According to the present invention, it is essential to provide a hydrophilic layer disposed on the outer layer of aluminum oxide. The hydrophilic layer may be provided by a hydrophilic layer formulation comprising one or more hydrophilic polymers and is typically applied or disposed on the outer layer of aluminum oxide to provide at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 or an amount of at least 0.005 g / m 2 and up to and including 0.08 g / m 2 The hydrophilic layer is typically disposed directly on the outer alumina layer, so that no intermediate layer is present. Because the outer alumina layer contains micropores, some of the hydrophilic layer may be located within such outer micropores and in micropores beneath the outer alumina layer.

[0099] The hydrophilic layer used in the practice of the present invention comprises two essential components, namely: (1) a compound defined as having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, wherein at least one -OM group is directly attached to a phosphorus atom, and a molecular weight of less than 2000 Daltons / mole or less than 1500 Daltons / mole, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and (2) one or more hydrophilic polymers, each of which comprises at least (a) repeating units comprising an amide group, and (b) repeating units comprising an -OM' group directly attached to a phosphorus atom, wherein M' is a hydrogen, sodium, potassium, or aluminum ion. In a given hydrophilic layer formulation, M and M' can be the same or different atoms.

[0100] More particularly, the following defines the necessary (1) compounds having one or more ethylenically unsaturated polymerizable groups. At least one such ethylenically unsaturated polymerizable group is attached to a phosphorus atom directly attached to an -OM group. Thus, at least one ethylenically unsaturated group may be attached to the phosphorus atom directly or via a spacer group as described below.

[0101] Such one or more ethylenically unsaturated polymerizable groups typically contain a carbon-carbon double bond that is polymerizable in the presence of a free radical or cationic initiator, as will be known to those skilled in polymer chemistry. More particularly, such groups may be represented by the formula:

[0102] -C(R')=CH2

[0103] Wherein R 'represents hydrogen atom, or unsubstituted linear or branched alkyl group having 1 to 4 carbon atoms, including but not limited to unsubstituted methyl, ethyl, n-propyl, isobutyl, n-butyl and tert-butyl.In most embodiments, R is hydrogen atom or unsubstituted methyl.

[0104] The (1) compound should also contain one or more (usually only one) -OM groups, where M represents a hydrogen, sodium, potassium or aluminum atom. At least one of the one or more -OM groups should be directly attached to a phosphorus atom within the (1) compound molecule, which may contain one or more such phosphorus atoms.

[0105] Furthermore, the (1) compound should have a molecular weight of less than 2000 Daltons / mole, or at least 150 Daltons / mole and up to and including 1000 Daltons / mole, or up to and including 1500 Daltons / mole.

[0106] Multiple (1) compounds may be present in the hydrophilic layer, and their chemical compositions may differ, including but not limited to different M atoms, different molecular weights, or different numbers or compositions of ethylenically unsaturated groups (e.g., different R groups), or combinations of these differences.

[0107] As noted above, in some embodiments, (1) at least one of the ethylenically unsaturated polymerizable groups in the compound can be attached to the phosphorus atom in the molecule using a spacer group such as, but not limited to, -(-CH2CH2O-)p- wherein the subscript p is an integer of at least 1 and up to and including 10, but can be an integer of at least 1 and up to and including 6. p wherein the subscript p is an integer of at least 1 and up to and including 10, but can be an integer of at least 1 and up to and including 6.

[0108] For example, a useful (1) compound can be represented by the following structure (I):

[0109]

[0110] wherein the subscript m is 1 or 2 for the illustrated hydroxyl groups, the subscript n is an integer of at least 1 and up to and including 10 for the illustrated ethyleneoxy groups, and R is a hydrogen atom or a substituted or unsubstituted methyl group. Mixtures of such (1) compounds having different R groups, different numbers of hydroxyl groups, or different numbers of ethyleneoxy groups can be used if desired.

[0111] The one or more (1) compounds described herein are present in the hydrophilic layer in an amount of at least 10 wt.%, or at least 20 wt.% and up to and including 60 wt.%, or up to and including 80 wt.% based on the total weight of the hydrophilic layer disposed on the outer alumina layer.

[0112] Further, the weight ratio of the one or more (1) compounds to the one or more (2) hydrophilic polymers (described below) in the hydrophilic layer is from 1 :4 to 4: 1, or more likely from 1 :3.5 to 2:3. Such weight ratios will typically be the same for the wet and dry hydrophilic layer formulations.

[0113] Each of the one or more (2) hydrophilic polymers necessary in the hydrophilic layer comprises (a) repeat units each having at least one amide group and which can be derived from one or more corresponding ethylenically unsaturated polymerizable monomers having an amide group such as methacrylamide, acrylamide, N,N-dimethylacrylamide, N-hydroxyethyl methacrylamide, and N-(methoxymethyl)acrylamide. Mixtures of two or more of these monomers can be used to provide a mixture of (a) repeat units of different composition or molecular weight, all of which have at least one amide group. The amide groups in the monomers do not typically chemically react during polymerization to form (a) repeat units in the hydrophilic copolymer.

[0114] Each (2) one or more hydrophilic polymers further comprises (b) repeating units, each (b) repeating unit having an -OM' group directly attached to the phosphorus atom, wherein M' represents a hydrogen, sodium, potassium or aluminum atom. The bond within the -OM' group can be a covalent bond or an ionic bond. The M' atom is typically a hydrogen, sodium or potassium atom, and more typically, when the hydrophilic copolymer is present in the hydrophilic layer formulation as described above before the hydrophilic layer formulation is applied to the surface of the multilayer alumina structure, the M' atom is a hydrogen atom. When the hydrophilic layer formulation is applied, some of the hydrogen, sodium or potassium atoms may be converted to aluminum ions, thereby promoting the binding of the hydrophilic copolymer to the multilayer alumina structure.

[0115] Such (b) repeating units can be derived from suitable corresponding ethylenically unsaturated polymerizable monomers, each of which has an -OM' group directly attached to the phosphorus atom, or the -OM' group can be formed after polymerization from a suitable "precursor group" such as -OR' in a phosphate group, wherein R' is a substituted or unsubstituted alkyl group having 1 to 20 carbons. Such ethylenically unsaturated polymerizable monomers from which (b) repeating units can be derived can have more than one such -OM' group, as long as at least one such -OM' group is directly attached to or attached to the phosphorus atom. Useful ethylenically unsaturated polymerizable monomers of this type include, but are not limited to, those represented by structure (II).

[0116] CH2=CH(R 1 )-XP(=O)(OM')2

[0117] (II)

[0118] where R 1 is hydrogen or a linear or branched alkyl group of 1 to 4 carbons, M' is independently hydrogen, sodium or potassium ion, and X is a single bond or a divalent linking group having a suitable number of linked carbon atoms or a combination of linked carbon atoms and oxygen atoms. Useful divalent X groups include, but are not limited to, those represented by the following structure (III).

[0119] -C(=O)-(OCH2CH2) q -O-

[0120] (III)

[0121] wherein the subscript q is an integer from 1 to 10.

[0122] Specific examples of useful ethylenically unsaturated polymerizable monomers according to structure (II) include vinylphosphonic acid, ethylene glycol acrylate phosphate, and ethylene glycol methacrylate phosphate. Mixtures of such ethylenically unsaturated polymerizable monomers can also be used to form the (b) repeating units, such that the repeating units can have different chemical compositions or molecular weights, as long as each (b) repeating unit has at least one -OM group attached to the phosphorus atom.

[0123] If mixtures of (2) hydrophilic polymers are present, they may have different compositions of (a) and (b) repeat units and / or different amounts of (a) and (b) repeat units, or different amounts of additional repeat units other than (a) and (b) repeat units as described below.

[0124] The (2) one or more hydrophilic polymers present in the hydrophilic layer may each comprise (a) repeating units in an amount of at least 60 mol % or at least 80 mol %, and up to and including 95 mol % or up to and including 97 mol %, all based on the total number (or number of moles) of repeating units in the particular hydrophilic polymer, including the sum of (a) repeating units, (b) repeating units and any other repeating units not defined as (a) and (b) repeating units.

[0125] The (2) one or more hydrophilic polymers present in the hydrophilic layer may each contain (b) repeating units in an amount of at least 3 mol% and up to and including 25 mol%, or up to and including 40 mol%, all based on the total number (or number of moles) of repeating units in the hydrophilic copolymer, including the sum of (a) repeating units, (b) repeating units and any other repeating units not defined as (a) and (b) repeating units.

[0126] Based on the total number (or moles) of repeating units, the (2) one or more hydrophilic polymers may contain up to and including 35 mol% of repeating units that are not (a) repeating units or (b) repeating units. The skilled person will be able to determine suitable monomers that can be used to provide these optional repeating units. However, useful optional repeating units that are not (a) repeating units or (b) repeating units may be repeating units that contain at least one carboxylic acid group, and such optional repeating units may typically be present in an amount of less than 30 mol%, and more typically less than 20 mol%, all based on the total number (or moles) of repeating units in the (2) one or more hydrophilic polymers. In some embodiments of the present invention, the (2) one or more hydrophilic polymers introduced into the hydrophilic layer contain only (a) repeating units and (b) repeating units as defined above.

[0127] Particularly useful (2) hydrophilic polymers comprise (a) repeating units derived at least in part from one or more of methacrylamide and acrylamide, and (b) repeating units derived at least from vinylphosphonic acid. In some embodiments of the present invention, the (2) hydrophilic polymer comprises only such (a) repeating units and (b) repeating units.

[0128] Mixtures of two or more such (2) one or more hydrophilic polymers may be used in the hydrophilic layer in any suitable weight combination.

[0129] Ethylenically unsaturated polymerizable monomers useful in preparing the (2) one or more hydrophilic polymers are available from various commercial sources or can be prepared using known ethylenically unsaturated polymerizable monomers and polymerization conditions.

[0130] In addition, the hydrophilic layer may include one or more additional hydrophilic homopolymers or copolymers, each of which is compositionally different from the above-mentioned (2) one or more hydrophilic polymers having (a) and (b) repeating units. Such additional hydrophilic polymers are known in the art and, if present, typically comprise less than 70 weight percent, more typically less than 50 weight percent, and even more typically less than 30 weight percent of the total weight of the one or more (2) one or more hydrophilic polymers, and such additional hydrophilic polymers can be purchased from known commercial sources or can be prepared using known raw materials and procedures. The (2) one or more hydrophilic polymers, each having (a) repeating units and (b) repeating units as described above, comprise at least 20 weight percent or at least 40 weight percent of the total weight of the hydrophilic layer, particularly after at least 95 weight percent of the coating solvent has been removed from the provided hydrophilic layer formulation.

[0131] The amount of (2) one or more hydrophilic polymers in the hydrophilic layer can be determined by referring to the amount and weight ratio of the above-mentioned (1) compounds used.

[0132] As will be readily known in the art, the hydrophilic layer and hydrophilic layer formulations may contain small amounts of additives such as inorganic acids (e.g., phosphoric acid in an amount of at least 0.01 wt. %), salts of inorganic acids, and surfactants. Particularly useful hydrophilic layer formulations and resulting hydrophilic layers are described below with respect to working examples.

[0133] The method for forming the hydrophilic layer can be carried out in any suitable manner, such as described in, for example,

[0058] -

[0061] of U.S. Patent Application Publication No. 2014 / 0047993 (noted above). Alternatively, the post-treatment process can be carried out by applying the desired amount of the hydrophilic layer formulation in a suitable solvent (e.g., water) directly to the outer layer of alumina and then drying the resulting wet coating. It is expected that during or after the formation of the hydrophilic layer, the -OM and -OM' groups attached to or directly connected to (1) the phosphorus atoms in the compound and (2) the phosphorus atoms in the repeating units (b) of the one or more hydrophilic polymers will at least partially react with the surface of the multilayer alumina structure to form PO-Al bonds.

[0134] After all these necessary treatments, the resulting inventive substrate, in any suitable form such as a flat sheet or a continuous web or roll, is ready for the preparation of lithographic printing plate precursors according to the invention.

[0135] Radiation-sensitive imageable layers and precursors

[0136] One or more press-developable radiation-sensitive imageable layers can be formed or disposed in a suitable manner over the hydrophilic layer of the inventive substrate using a suitable press-developable radiation-sensitive imageable layer formulation as described in more detail below. Such radiation-sensitive imageable layers are typically negative-working in nature.

[0137] Negative-working lithographic printing plate precursors:

[0138] The precursor of the present invention can be formed by suitably applying a negative-working, press-developable radiation-sensitive composition as described below to a suitable inventive substrate (as described above) to form a negative-working, radiation-sensitive, imageable layer on the substrate. Typically, the negative-working radiation-sensitive composition (and the resulting negative-working radiation-sensitive imageable layer) comprises (a) one or more free-radically polymerizable components, (b) an initiator composition that provides free radicals upon exposure to imaging radiation (e.g., infrared radiation as defined herein), and (c) one or more radiation absorbers (e.g., infrared radiation absorbers) as essential components, and optionally a polymeric binder different from all of (a), (b), and (c), all of which essential and optional components are described in more detail below. Typically, only a single negative-working, press-developable radiation-sensitive imageable layer is present in the precursor. This is typically the outermost layer in the precursor, but in some embodiments, an outermost hydrophilic protective layer (also known as a topcoat or oxygen barrier layer) may be present above the single negative-working, press-developable radiation-sensitive imageable layer.

[0139] Thus, the components of the radiation-sensitive imageable layer can be designed in such a way that, after imagewise exposure, the imaged precursor can be developed on-press using a lithographic ink, a fountain solution, or a combination of a lithographic ink and a fountain solution (type and form of compounds and respective amounts). Further details of on-press developability are described below.

[0140] The negative-working radiation-sensitive composition (and the radiation-sensitive imageable layer prepared therefrom) comprises (a) one or more free radical polymerizable components, each of which contains one or more free radical polymerizable groups (in some embodiments, two or more such groups) that can be polymerized using free radical initiation. In some embodiments, the radiation-sensitive imageable layer comprises two or more free radical polymerizable components having the same or different numbers of free radical polymerizable groups in each molecule.

[0141] Useful free radical polymerizable components can contain one or more free radical polymerizable monomers or oligomers with one or more ethylenically unsaturated groups (for example two or more such groups) that can be addition polymerized. Similarly, crosslinkable polymers with such free radical polymerizable groups can also be used. Oligomers or prepolymers can be used, for example urethane acrylate and methacrylate, epoxide acrylate and methacrylate, polyester acrylate and methacrylate, polyether acrylate and methacrylate, and unsaturated polyester resins. In some embodiments, the free radical polymerizable component comprises a carboxyl group.

[0142] The one or more free radical polymerizable components may have a molecular weight large enough to enhance the mechanical properties of the radiation-sensitive imageable layer and thereby render the corresponding lithographic printing plate precursor suitable for shipping in typical packaging and handling during normal prepress operations. The one or more free radical polymerizable components may also be present in the radiation-sensitive layer in the form of a particulate material having a particle size of at least 10 nm and up to and including 800 nm. In such embodiments, a separate non-polymerizable or non-crosslinkable polymeric binder (described below) is not required but may still be present.

[0143] The free radical polymerizable component includes a urea urethane (meth) acrylate or a urethane (meth) acrylate having multiple (two or more) polymerizable groups. Mixtures of such compounds can be used, each compound having two or more unsaturated polymerizable groups, and some of the compounds having three, four or more unsaturated polymerizable groups. For example, the free radical polymerizable component can be prepared by mixing a hexamethylene diisocyanate-based N100 aliphatic polyisocyanate resin (Bayer Corp., Milford, Conn.) was prepared by reacting hydroxyethyl acrylate and pentaerythritol triacrylate. Useful free radical polymerizable compounds include NK Ester A-DPH (dipentaerythritol hexaacrylate), available from Kowa American, and Sartomer 399 (dipentaerythritol pentaacrylate), Sartomer 355 (di-trimethylolpropane tetraacrylate), Sartomer 295 (pentaerythritol tetraacrylate), and Sartomer 415 (ethoxylated (20) trimethylolpropane triacrylate), available from Sartomer Company, Inc.

[0144] Many other free radically polymerizable components are known in the art and described in the literature, including: Photoreactive Polymers: The Science and Technology of Resists , A Reiser, Wiley, New York, 1989, pp. 102-177; BM Monroe, Radiation Curing: Science and Technology , S. P. Pappas, ed., Plenum, New York, 1992, pp. 399-440; and "Polymer Imaging", A. B. Bohen and P. Walker; Imaging Processes and Material , JM Sturge et al. (eds.), Van Nostrand Reinhold, New York, 1989, pp. 226-262. For example, useful free radical polymerizable components are also described in EP 1,182,033 A1 (Fujimaki et al.) (beginning at paragraph

[0170] ), and U.S. Patents 6,309,792 (Hauck et al.), 6,569,603 (Furukawa), and 6,893,797 (Munnelly et al.). Other useful free radical polymerizable components include those described in U.S. Patent Application Publication No. 2009 / 0142695 (Baumann et al.), which include 1H-tetrazolyl groups.

[0145] Useful free radically polymerizable components as described above are readily available from a variety of commercial sources or can be prepared using known starting materials and synthetic methods.

[0146] The (a) one or more free radical polymerizable components are typically present in the negative-working radiation-sensitive imageable layer in an amount of at least 10 weight percent and up to and including 70 weight percent, or typically at least 20 weight percent and up to and including 50 weight percent, all based on the total dry weight of the negative-working radiation-sensitive imageable layer.

[0147] The on-press developable radiation-sensitive imageable layer used in the present invention further comprises (b) an initiator composition which, in the presence of a suitable radiation absorber, provides free radicals upon exposure of the on-press developable radiation-sensitive imageable layer to suitable imaging radiation to initiate polymerization of one or more free radical polymerizable components. The initiator composition can be a single compound or a combination or system of multiple chemicals.

[0148] Suitable initiator compositions include, but are not limited to, aromatic sulfonyl halides; trihaloalkyl sulfones; trihaloaryl sulfones; imides (e.g., N-benzoyloxyphthalimide); diazosulfonates; 9,10-dihydroanthracene derivatives; N-aryl, S-aryl, or O-aryl polycarboxylic acids having at least two carboxyl groups, wherein at least one carboxyl group is bound to a nitrogen, oxygen, or sulfur atom of the aryl moiety; oxime esters and oxime ethers; α-hydroxyacetophenone or α-aminoacetophenone; benzoin ethers and esters; peroxides; hydroperoxides; azo compounds; 2,4,5-triarylimidazolyl dimers (e.g., "HABIs"); trihalomethyl-substituted triazines; boron-containing compounds; organic borate salts, such as those described in U.S. Pat. No. 6,562,543 (Ogata et al.), and onium salts.

[0149] Useful initiator compositions particularly for infrared radiation sensitive compositions and imageable layers include, but are not limited to, onium salts, such as ammonium, iodonium, sulfonium and phosphonium compounds described in detail in

[0131] of U.S. Patent Application Publication 2014 / 0047993 (above) and the references cited therein. Examples of onium salts include triphenylsulfonium (salt), diphenyliodonium (salt), diphenyldiazonium (salt) and derivatives obtained by introducing one or more substituents into the phenyl ring of these compounds. Suitable substituents include, but are not limited to, alkyl, alkoxy, alkoxycarbonyl, acyl, acyloxy, chlorine, bromine, fluorine and nitro.

[0150] Examples of anions in onium salts include, but are not limited to, halogen anions, ClO4 - PF6 - 、BF4 - 、SbF6 - 、CH3SO3 - CF3SO3 - 、C6H5SO3 - 、CH3C6H4SO3 - 、HOC6H4SO3 - 、ClC6H4SO3 - and boron anions, as described, for example, in US Pat. No. 7,524,614 (Tao et al.).

[0151] Onium salts can be obtained by combining an onium salt having a sulfonium or iodonium cation in the molecule with an onium salt in the molecule. The onium salt may be a polyvalent onium salt having at least two onium ion atoms bonded by a covalent bond in the molecule. Among polyvalent onium salts, those having at least two onium ion atoms in the molecule are useful, and those having a sulfonium or iodonium cation in the molecule are particularly useful. Representative polyvalent onium salts are represented by the following formulas (6) and (7):

[0152]

[0153]

[0154] Furthermore, the onium salts described in paragraphs

[0033] to

[0038] of the specification of Japanese Patent Publication No. 2002-082429 [or U.S. Patent Application Publication No. 2002-0051934 (Ippei et al.)] or the iodonium borate complexes described in U.S. Patent No. 7,524,614 (mentioned above) can also be used in the present invention.

[0155] In some embodiments, the initiator composition may comprise a combination of initiator compounds, such as a combination of iodonium salts, such as a combination of Compound A and Compound B as described below.

[0156] Compound A may be represented by structure (IV) shown below, and one or more compounds collectively referred to as Compound B may be represented by structure (V) or (VI) below:

[0157]

[0158] In these structures (IV), (V) and (VI), R1, R2, R3, R4, R5 and R6 are independently substituted or unsubstituted alkyl or substituted or unsubstituted alkoxy, each of which has 2 to 9 carbon atoms (or particularly 3 to 6 carbon atoms). These substituted or unsubstituted alkyl and alkoxy groups can be straight-chain or branched. In many useful embodiments, R1, R2, R3, R4, R5 and R6 are independently substituted or unsubstituted alkyl, for example, independently selected substituted or unsubstituted alkyl groups having 3 to 6 carbon atoms.

[0159] In addition, at least one of R3 and R4 can be different from R1 or R2; the difference between the total number of carbon atoms in R1 and R2 and the total number of carbon atoms in R3 and R4 is 0 to 4 (that is, 0, 1, 2, 3 or 4); the difference between the total number of carbon atoms (sum) in R1 and R2 and the total number of carbon atoms (sum) in R5 and R6 is 0 to 4 (that is, 0, 1, 2, 3 or 4); and X1, X2 and X3 are the same or different anions.

[0160] Useful anions include, but are not limited to, CIO4 - , PF6 - , BF4 - , SbF6 - , CH3SO3 - , CF3SO3 - , C6H5SO3 - , CH3C6H4SO3 - , HOC6H4SO3 - , CIC6H4SO3 - , and borate anions represented by the following structure (VII): B - (R 1 )(R 2 )(R 3 )(R 4 )

[0161] (VII,

[0162] wherein R 1 , R 2 , R 3 and R 4 independently represent substituted or unsubstituted alkyl, substituted or unsubstituted aryl (including halogen-substituted aryl), substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted cycloalkyl, or substituted or unsubstituted heterocyclyl, or two or more of R 1 , R 2 , R 3 and R 4 may be linked together to form a substituted or unsubstituted heterocycle having a boron atom, such a ring having up to 7 carbon, nitrogen, oxygen or nitrogen atoms. Optional substituents on R 1 , R 2 , R 3 and R 4 may include chloro, fluoro, nitro, alkyl, alkoxy and acetoxy. In some embodiments, R 1 , R 2 , R 3 and R 4 are all the same or different substituted or unsubstituted aryl, e.g., substituted or unsubstituted phenyl, or more likely all of these groups are unsubstituted phenyl. In many embodiments, at least one of X1, X2and X3is a tetraarylborate anion comprising the same or different aryl groups, or in particularly useful embodiments, one or more is a tetraphenylborate anion or each of X1, X2and X3is a tetraphenylborate anion.

[0163] Mixtures of compounds of Compound B represented by structures (V) or (VI) can be used if desired. Many useful compounds represented by structures (IV), (V), and (VI) are available from commercial sources such as Sigma-Aldrich, or they can be prepared using known synthetic methods and readily available starting materials.

[0164] The components that can be used in the above initiator composition are available from various commercial sources or can be prepared using known synthetic methods and starting materials.

[0165] The initiator composition is typically present in the on-press developable radiation- sensitive imageable layer in an amount sufficient to provide one or more polymerization initiators in an amount of at least 0.5 weight % and up to and including 20 weight %, or typically at least 2 weight % and up to and including 15 weight %, or even at least 4 weight % and up to and including 12 weight %, all based on the total dry weight of the on-press developable radiation-sensitive imageable layer.

[0166] In addition, the on-press developable radiation-sensitive imageable layer further comprises (c) one or more radiation absorbers to provide the desired radiation sensitivity, or to convert radiation to heat, or both. In some embodiments, the on-press developable radiation- sensitive layer is sensitive to infrared radiation and comprises one or more different infrared radiation absorbers, such that the lithographic printing plate precursor can be imaged with a laser that emits infrared radiation, for example in response to digital information. The present application is also applicable to lithographic printing plate precursors designed to be imaged using a violet laser having an emission peak at about 405 nm, using visible lasers such as those having an emission peak at about 488 nm or 532 nm, or using UV radiation having a significant emission peak below 400 nm. In such embodiments, the radiation absorbers can be selected to match the radiation source, and many useful examples are known in the art and are sometimes referred to as "sensitizers". Useful such radiation absorbers are described, for example, in U.S. Patent 7,285,372 (Baumann et al.) at column 11 (lines 10-43).

[0167] In most embodiments of the present invention, the on-press developable negative-working radiation-sensitive imageable layer comprises one or more infrared radiation absorbers to provide the desired infrared radiation sensitivity. Useful infrared radiation absorbers can be pigments or infrared radiation absorbing dyes. Suitable dyes may also be those described, for example, in U.S. Patents 5,208,135 (Patel et al.), 6,153,356 (Urano et al.), 6,309,792 (Hauck et al.), 6,569,603 (Furukawa), 6,797,449 (Nakamura et al.), 7,018,775 (Tao), 7,368,215 (Munnelly et al.), 8,632,941 (Balbinot et al.), and U.S. Patent Application Publication No. 2007 / 056457 (Iwai et al.). In some infrared radiation-sensitive embodiments, it is desirable that at least one infrared radiation absorber in the infrared radiation-sensitive imageable layer is a cyanine dye comprising a tetraarylborate anion, such as a tetraphenylborate anion. Examples of such dyes include those described in US Patent Application Publication No. 2011 / 003123 (Simpson et al.).

[0168] In addition to low molecular weight IR absorbing dyes, IR dye chromophores bonded to polymers can also be used. In addition, IR dye cations can also be used, i.e., the cation is the IR absorbing portion of the dye salt that ionically interacts with the polymer containing carboxyl, sulfo, phospho or phosphono groups in the side chains.

[0169] The useful radiation absorbers described above are readily available from a variety of commercial sources or can be prepared using known starting materials and synthetic methods.

[0170] The total amount of one or more radiation absorbers in the press-developable radiation-sensitive imageable layer is at least 0.5 weight percent and up to and including 30 weight percent, or typically at least 1 weight percent and up to and including 15 weight percent, based on the total dry weight of the press-developable radiation-sensitive imageable layer.

[0171] In many embodiments, the on-press developable radiation-sensitive imageable layer optionally but desirably further comprises one or more (d) polymeric binders (or materials that act as polymeric binders) for all materials in the layer. Such polymeric binders are distinct from all of the above-described (a), (b), and (c) materials. These polymeric binders are generally non-crosslinkable and non-polymerizable.

[0172] Such (d) polymer binders can be selected from a wide variety of polymer binder materials known in the art, including polymers comprising repeating units having side chains comprising polyalkylene oxide segments, such as those described, for example, in U.S. Patent No. 6,899,994 (Huang et al.). Other useful (d) polymer binders comprise two or more types of repeating units having different side chains comprising polyalkylene oxide segments, such as those described, for example, in WO Publication No. 2015-156065 (Kamiya et al.). Some of such (d) polymer binders may further comprise repeating units having pendant cyano groups, such as those described, for example, in U.S. Patent No. 7,261,998 (Hayashi et al.).

[0173] Some useful (d) polymeric binders can be present in particulate form, i.e., in the form of discrete, non-aggregated particles. Such discrete particles can have an average particle size of at least 10 nm and up to and including 1500 nm, or typically at least 80 nm and up to and including 600 nm, and are typically uniformly distributed within the imageable layer that can be developed on-machine radiation-sensitive. For example, one or more useful (d) polymeric binders can be present in the form of particles having an average particle size of at least 50 nm and up to and including 400 nm. The average particle size can be determined by various known methods, including measuring the particles in an electron scanning microscope image and taking the average of a certain number of measurements.

[0174] In some embodiments, the (d) polymer binder is present in the form of particles having an average particle size less than the average dry thickness (t) of the on-press developable radiation-sensitive imageable layer. The average dry thickness (t) in micrometers (μm) is calculated by the following equation:

[0175] t=w / r

[0176] Where w is g / m 2 The dry coating coverage of the on-press developable radiation-sensitive imageable layer is calculated, and r is 1 g / cm 3 For example, in such embodiments, the (d) polymeric binder can comprise at least 0.05% and up to and including 80%, or more likely at least 10% and up to and including 50%, of the on-press developable radiation-sensitive imageable layer.

[0177] The (d) polymer binder may also have a backbone comprising a plurality (at least two) of urethane moieties and pendant groups comprising polyalkylene oxide segments.

[0178] Other useful (d) polymeric binders may contain polymerizable groups such as acrylate, methacrylate, vinylaryl, and allyl groups, and alkali-soluble groups such as carboxylic acids. Some of these useful (d) polymeric binders are described in U.S. Patent Application Publication No. 2015 / 0099229 (Simpson et al.) and U.S. Patent No. 6,916,595 (Fujimaki et al.).

[0179] Useful (d) polymeric binders typically have a weight average molecular weight (Mw) of at least 2,000 and up to and including 500,000, or at least 20,000 and up to and including 300,000, as determined by gel permeation chromatography (polystyrene standards).

[0180] Useful (d) polymeric binders can be obtained from various commercial sources, or they can be prepared using known procedures and starting materials, as described, for example, in the above-mentioned publications.

[0181] The total (d) polymer binder can be present in the press-developable radiation-sensitive imageable layer in an amount of at least 10 weight percent and up to and including 70 weight percent, or more likely at least 20 weight percent and up to and including 50 weight percent, based on the total dry weight of the press-developable radiation-sensitive imageable layer.

[0182] Other polymeric materials known in the art (other than the (d) polymeric binder) may be present in the on-machine developable radiation-sensitive imageable layer, and such polymeric materials are typically more hydrophilic or more hydrophobic than the (d) polymeric binder described above. Examples of such hydrophilic polymeric binders include, but are not limited to, cellulose derivatives, such as hydroxypropyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol having various degrees of saponification. More hydrophobic polymeric binders are less developable than the (d) polymeric binder described above, and typically have an acid value of less than 20 mg KOH / g for all acidic groups with a pKa below 7 and their corresponding salts. Such hydrophobic polymeric binders typically contain less than 10% by weight, more typically less than 5% by weight, of segments that contribute to the hydrophilicity of the binder and are selected from hydroxyl groups, -(CH2CH2-O)-, and -C(=O)NH2. Examples of such hydrophobic polymeric binders include, but are not limited to, polymethyl methacrylate, polybenzyl methacrylate, and polystyrene.

[0183] Additional optional additives that can be used in the machine-developed radiation-sensitive imageable layer can include organic dyes or organic dye precursors and chromogenic developers as known in the art. Useful organic dyes or organic dye precursors include, but are not limited to, phthalide and fluoran leuco dyes with a lactone backbone (having an acid-dissociable lactone backbone), such as those described in U.S. Patent No. 6,858,374 (Yanaka). Such optional additives can be used as printout colorants and, based on the total dry weight of the machine-developed radiation-sensitive imageable layer, can be present in an amount of at least 1 wt % and up to and including 10 wt %. Other useful printout colorants are known in the art and can include azo dyes, triarylmethane dyes, cyanine dyes, and spironolactone or spironolactam colorants, such as, for example, described in U.S. Patent Application Publication 2009 / 0047599 (Horne et al.).

[0184] The on-press developable radiation-sensitive imageable layer may include crosslinked polymer particles having an average particle size of at least 2 μm or at least 4 μm and up to and including 20 μm, as described, for example, in U.S. Patents 8,383,319 (Huang et al.), 8,105,751 (Endo et al.), and 9,366,962 (Kamiya et al.). Such crosslinked polymer particles may be present only in the on-press developable radiation-sensitive imageable layer, only in the hydrophilic protective layer (when present) (described below), or in both the on-press developable radiation-sensitive imageable layer and the hydrophilic protective layer (when present).

[0185] The on-press developable radiation-sensitive imageable layer may also include a variety of other optional addenda in conventional amounts, including but not limited to dispersants, humectants, biocides, plasticizers, surfactants for coating or other properties, tackifiers, pH adjusters, desiccants, defoamers, preservatives, antioxidants, development aids, rheology modifiers, or combinations thereof, or any other addenda commonly used in the lithographic art. The on-press developable radiation-sensitive imageable layer may also include a phosphate (meth)acrylate having a molecular weight typically greater than 250, as described in U.S. Patent 7,429,445 (Munnelly et al.).

[0186] Hydrophilic protective layer:

[0187] Although in some embodiments of negative-working lithographic printing plate precursors, the on-press-developable radiation-sensitive imageable layer is the outermost layer with no layers disposed thereon, the precursor may be designed with a hydrophilic layer (also referred to in the art as a hydrophilic protective layer, oxygen barrier layer, or topcoat) disposed above (or directly on) the on-press-developable radiation-sensitive imageable layer (with no intervening layers between the two layers). When present, such a hydrophilic protective layer is typically the outermost layer of the precursor.

[0188] Such a hydrophilic protective layer may comprise one or more film-forming water-soluble polymer binders in an amount of at least 60% by weight and up to and including 100% by weight based on the total dry weight of the hydrophilic protective layer. Such film-forming water-soluble (or hydrophilic) polymer binders may include modified or unmodified polyvinyl alcohol having a saponification degree of at least 30%, or at least 75%, or at least 90%, and up to and including a saponification degree of 99.9%.

[0189] In addition, one or more acid-modified polyvinyl alcohols can be used as film-forming water-soluble (or hydrophilic) polymer binders in the hydrophilic protective layer. For example, at least one modified polyvinyl alcohol can be modified with an acid group selected from carboxylic acid, sulfonic acid, sulfate, phosphonic acid, and phosphate groups. Examples of such materials include, but are not limited to, sulfonic acid-modified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, quaternary ammonium salt-modified polyvinyl alcohol, glycol-modified polyvinyl alcohol, or combinations thereof.

[0190] The hydrophilic protective layer may also include crosslinked polymer particles having an average particle size of at least 2 μm and as described, for example, in US Patents 8,383,319 (Huang et al.) and 8,105,751 (Endo et al.).

[0191] The hydrophilic protective layer may be at least 0.1 g / m 2 and at most but less than 4g / m 2 The dry coating coverage is usually at least 0.15g / m 2 and up to and including 2.5 g / m 2 In some embodiments, the dry coating coverage is as low as 0.1 g / m 2 and up to and including 1.5 g / m 2 , or at least 0.1 g / m 2 and up to and including 0.9 g / m 2 , making the hydrophilic protective layer relatively thin.

[0192] The hydrophilic protective layer may optionally comprise organic wax particles dispersed in one or more film-forming water-soluble (or hydrophilic) polymer binders, as described, for example, in US Patent Application Publication No. 2013 / 0323643 (Balbinot et al.).

[0193] Making lithographic printing plate precursors

[0194] The radiation-sensitive lithographic printing plate precursors of the present invention can be provided in the following manner. The radiation-sensitive imageable layer formulation comprising the above-mentioned materials (for negative-working platemaking chemistry or positive-working platemaking chemistry) can be applied to the invention substrate (typically a continuous substrate roll or web) as described above using any suitable equipment and method, such as spin coating, blade coating, gravure coating, die coating, slot coating, bar coating, wire rod coating, roller coating or extrusion hopper coating. The radiation-sensitive imageable layer formulation can also be applied by spraying onto a suitable substrate. Typically, once the radiation-sensitive imageable layer formulation is applied at a suitable wet coverage, it is dried in a suitable manner known in the art to provide the desired dry coverage as described below, thereby providing a continuous radiation-sensitive article that can be in any suitable form (e.g., a web), from which separate precursors can be prepared using known manufacturing methods.

[0195] The manufacturing process generally involves mixing the various components required for a particular radiation-sensitive imageable layer chemistry in a suitable organic solvent or mixture thereof [e.g., methyl ethyl ketone (2-butanone), methanol, ethanol, 1-methoxy-2-propanol, isopropanol, acetone, γ-butyrolactone, n-propanol, tetrahydrofuran, and other solvents readily known in the art, and mixtures thereof], applying the resulting radiation-sensitive imageable layer formulation to a continuous substrate web, and removing the solvent by evaporation under suitable drying conditions. Further details of such manufacturing features are described in U.S. Patent Application Publication No. 2014 / 0047993 (cited above).

[0196] After suitable drying, the negative-working plate can be developed on-press. The dry coverage of the radiation-sensitive imageable layer (especially those sensitive to infrared radiation) on the inventive substrate is generally at least 0.1 g / m 2 Up to and including 4g / m 2 or at least 0.4g / m 2 and up to and including 2g / m 2 , but other dry coverage amounts may be used if desired.

[0197] As noted above, in some negative-working precursor embodiments, a suitable water-based hydrophilic overcoat formulation can be applied to the dried on-press developable radiation-sensitive imageable layer using known coating and drying conditions, equipment, and procedures.

[0198] Under practical manufacturing conditions, the result of these coating operations is a continuous web or roll of radiation-sensitive lithographic printing plate precursor material having an on-press developable radiation-sensitive imageable layer and any optional layers described above disposed on the inventive substrate described above.

[0199] Individual rectangular lithographic printing plate precursors are formed from the resulting continuous radiation-sensitive web or roll by cutting to produce a plurality of longitudinal strips, each having a width equal to one dimension of the rectangular lithographic printing plate precursor. Transverse cuts are made across the strips at intervals equal to the other dimension of the rectangular lithographic printing plate precursor using a cut-to-length process, thereby forming individual precursors having a square or rectangular form.

[0200] Imaging (exposure) conditions

[0201] During use, the radiation-sensitive lithographic printing plate precursors of the present invention can be exposed on-press to a suitable source of exposing radiation, depending on the radiation absorber (or sensitizer) present in one or more radiation-sensitive imageable layers. For example, a negative-working lithographic printing plate precursor containing an infrared radiation absorber can be imaged with an infrared laser that emits significant radiation in the range of at least 750 nm and up to and including 1400 nm, or at least 800 nm and up to and including 1250 nm. However, some negative-working lithographic printing plate precursors that can be developed on-press can be imaged in the UV, "violet" or visible regions of the electromagnetic spectrum using a suitable imaging radiation source (e.g., 250 nm and less than 750 nm). The result of such image-wise exposure is to provide exposed and non-exposed regions in one or more radiation-sensitive imageable layers that can be developed on-press.

[0202] Imaging can be performed using imaging or exposure radiation from a radiation-generating laser (or an array of such lasers). If desired, imaging can also be performed using imaging radiation at multiple wavelengths simultaneously, such as multiple infrared radiation wavelengths. The laser used to expose the precursor is typically a diode laser due to the reliability and low maintenance of diode laser systems, but other lasers, such as gas lasers or solid-state lasers, can also be used. The combination of power, intensity, and exposure time for imaging radiation will be apparent to those skilled in the art.

[0203] The imaging apparatus may be configured as a flatbed recorder or a drum recorder, wherein the radiation-sensitive lithographic printing plate precursor is mounted to the inner or outer cylindrical surface of the drum. Examples of useful infrared imaging apparatus are those comprising a laser diode emitting radiation at a wavelength of about 830 nm. Model Trendsetter platesetters (Eastman Kodak Company) and the NEC AMZI Setter X series (NEC Corporation, Japan) are obtained. Other suitable infrared imaging devices include the Screen PlateRite 4300 series or 8600 series platesetters (available from Screen USA, Chicago, IL) operating at a wavelength of 810 nm or the thermal CTP platesetters from Panasonic Corporation (Japan).

[0204] Depending on the sensitivity of the infrared radiation-sensitive imageable layer, the infrared radiation imaging energy can be at least 30 mJ / cm 2 and up to and including 500 mJ / cm 2 and typically at least 50 mJ / cm 2 and up to and including 300 mJ / cm 2 .

[0205] Useful UV and "violet" imaging devices include the Prosetter (Heidelberger Druckmaschinen, Germany), Luxel V8 / V6 series (Fuji, Japan), Python (Highwater, UK), MakoNews, Mako 2 and Mako 8 (ECRM, US), Micro (Screen, Japan), Polaris and Advantage (AGFA, Belgium), LS Jet (Multiformat) and Smart'n'Easy Jet (Krause, Germany) and VMAX series (DotLine, Germany) imagers.

[0206] Imaging in the UV to visible region, and particularly the UV region (250 nm to 450 nm) of the electromagnetic spectrum can be carried out using an energy of at least 0.01 mJ / cm 2 and up to and including 0.5 mJ / cm 2 at a power density of at least 0.5 kW / cm 3 and up to and including 50 kW / cm 3 .

[0207] Processing (developing) and printing

[0208] After imagewise exposure, the exposed negative-working on-press developable radiation-sensitive lithographic printing plate precursors having exposed and non-exposed regions in the on-press developable radiation-sensitive imageable layer can be processed in a suitable manner to remove the non-exposed regions and any hydrophilic protective layer (if present) and leave the intact hardened exposed regions.

[0209] For example, the negative-working lithographic printing plate precursors of the present invention can be developed on-press using lithographic inks, fountain solutions, or a combination of lithographic inks and fountain solutions. In such embodiments, the radiation-sensitive lithographic printing plate precursors imaged according to the present invention can be mounted on a printing press and the printing run can then be started. When making the initial printing run, the non-exposed areas in the radiation-sensitive imageable layer are removed by a suitable fountain solution, lithographic ink, or a combination of the two. Typical ingredients of aqueous fountain solutions include pH buffers, desensitizers, surfactants and wetting agents, humectants, low-boiling point solvents, biocides, defoamers, and chelating agents. A representative example of a fountain solution is Varn Litho Etch 142W + Varn PAR (alcoholsub) (available from Varn International, Addison, IL).

[0210] In a typical printing press that starts with a sheet-fed press, the dampening rollers are first engaged and dampening solution is supplied to the mounted imaging precursor to swell the exposed radiation-sensitive imageable layer at least in the non-exposed areas. After several rotations, the inking rollers are engaged, which supply lithographic ink to cover the entire printing surface of the lithographic printing plate. Typically, within 5 to 20 rotations after the inking rollers are engaged, a printing sheet is supplied to remove the non-exposed areas of the radiation-sensitive imageable layer and material on the blanket roller (if present) from the lithographic printing plate using the formed ink-fountain solution emulsion.

[0211] The present invention provides at least the following embodiments, alone or in any suitable combination:

[0212] 1. A lithographic printing plate precursor comprising:

[0213] a substrate having a surface, and

[0214] a press-developable radiation-sensitive imageable layer disposed over a surface of the substrate,

[0215] Wherein the substrate comprises:

[0216] an aluminum-containing plate having a ground and etched surface;

[0217] An inner layer of aluminum oxide is provided on the grained and etched surface, the inner layer of aluminum oxide having an average dry thickness (T i ), and comprising a plurality of micropores having an average inner pore diameter (D i ) inner micropores;

[0218] An outer aluminum oxide layer is disposed over the inner aluminum oxide layer, the outer aluminum oxide layer comprising a plurality of pores having an average outer pore diameter (D o ) and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o );and

[0219] At least 0.0002g / m 2 and up to and including 0.1 g / m 2 A hydrophilic layer is provided on the alumina outer layer at a dry coverage of , and the hydrophilic layer comprises:

[0220] (1) a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, at least one of which is directly attached to a phosphorus atom, and a molecular weight of less than 2000 Daltons / mole, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and

[0221] (2) one or more hydrophilic polymers, each comprising at least: (a) a repeating unit comprising an amide group, and (b) a repeating unit comprising an -OM' group directly attached to a phosphorus atom, wherein M' represents a hydrogen, sodium, potassium or aluminum atom.

[0222] 2. The lithographic printing plate precursor of embodiment 1, wherein the hydrophilic layer has a surface area of ​​at least 0.005 g / m 2 and up to and including 0.08 g / m 2 A dry coverage of 100% is provided on the alumina outer layer.

[0223] 3. The lithographic printing plate precursor of embodiment 1 or 2, wherein the outer layer of aluminum oxide has at least 500 micropores / μm 2 and up to and including 3,000 micropores / μm 2 The micropore density (C o ), and having a porosity (P greater than or equal to 0.3 and less than or equal to 0.8 o ), where P o Defined as 3.14(C o )(D o 2 ) / 4,000,000.

[0224] 4. The lithographic printing plate precursor of any one of embodiments 1 to 3, wherein the outer layer of aluminum oxide has at least 500 micropores / μm 2 and up to and including 3,000 micropores / μm 2 The micropore density (C o ), and having a porosity (P greater than or equal to 0.3 and less than or equal to 0.5 o ), where Po Defined as 3.14(C o )(D o 2 ) / 4,000,000.

[0225] 5. The lithographic printing plate precursor of any one of embodiments 1 to 4, wherein the outer layer of aluminum oxide has an average dry thickness (T o ), and the outer aluminum oxide layer is directly disposed on the inner aluminum oxide layer; the average dry thickness of the inner aluminum oxide layer (T i ) is at least 650 nm, and the average inner pore diameter (D i ) is less than or equal to 15 nm and less than the average outer pore diameter (D o ).

[0226] 6. The lithographic printing plate precursor of any one of embodiments 1 to 5, wherein D o To D i The ratio is greater than 1.1:1.

[0227] 7. The lithographic printing plate precursor of any one of embodiments 1 to 6, wherein T i is at least 650 nm and up to and including 1500 nm.

[0228] 8. The lithographic printing plate precursor of any one of embodiments 1 to 7, wherein the substrate further comprises an aluminum oxide intermediate layer disposed between the aluminum oxide inner layer and the aluminum oxide outer layer, wherein the aluminum oxide intermediate layer has an average dry thickness (T m ), and comprising a plurality of pores having an average median pore diameter (D m ) in the middle micropore, where D m Greater than D o , D o Greater than D i , and the average dry thickness of the outer layer of aluminum oxide (T o ) is less than 150nm.

[0229] 9. The lithographic printing plate precursor of any one of embodiments 1 to 8, wherein the outer aluminum oxide layer is directly disposed on the inner aluminum oxide layer, and the average pore diameter (D i ) is at least 20 nm and larger than the average pore diameter (D o ).

[0230] 10. The lithographic printing plate precursor of any one of embodiments 1 to 9, wherein at least one ethylenically unsaturated polymerizable group in the (1) compound is attached to the phosphorus atom to which the -OM group is attached, wherein the spacer group is of the formula -(-CH2CH2O-)p - represents, wherein the subscript p is an integer of at least 1 and up to and including 10.

[0231] 11. The lithographic printing plate precursor of any one of embodiments 1 to 10, wherein the (1) compound has a molecular weight of at least 100 Daltons / mole and up to and including 1500 Daltons / mole.

[0232] 12. The lithographic printing plate precursor of any one of embodiments 1 to 11, wherein the (1) compound has at least one ethylenically unsaturated polymerizable group represented by the following formula:

[0233] -C(R')=CH2

[0234] wherein R' represents a hydrogen atom or an unsubstituted straight-chain or branched-chain alkyl group having 1 to 4 carbon atoms.

[0235] 13. The lithographic printing plate precursor of embodiment 12, wherein R is a hydrogen atom or an unsubstituted methyl group.

[0236] 14. The lithographic printing plate precursor of any one of embodiments 1 to 13, wherein the (1) compound is present in an amount of at least 10 weight % and up to and including 80 weight % based on the total weight (solids) of the hydrophilic layer, or the weight ratio of one or more (1) compounds to (2) one or more hydrophilic polymers in the hydrophilic layer is from 1:4 to 4:1.

[0237] 15. The lithographic printing plate precursor of any one of embodiments 1 to 14, wherein the (1) compound is present in an amount of at least 10 wt. % and up to and including 80 wt. % based on the total weight (solids) of the hydrophilic layer, or the weight ratio of one or more (1) compounds to (2) one or more hydrophilic polymers in the hydrophilic layer is from 1:3.5 to 2:3.

[0238] 16. The lithographic printing plate precursor of any one of embodiments 1 to 15, wherein the (1) compound is represented by the following structure (I):

[0239]

[0240] wherein subscript m is 1 or 2, subscript n is an integer of at least 1 and up to and including 10, and R is a hydrogen atom or a substituted or unsubstituted methyl group.

[0241] 17. The lithographic printing plate precursor of any one of embodiments 1 to 16, wherein the (a) repeating unit is present in the (2) hydrophilic polymer in an amount of at least 60 mol% and up to and including 97 mol%, and the (b) repeating unit is present in the (2) hydrophilic polymer in an amount of at least 3 mol% and up to and including 40 mol%, all based on the total number (or number of moles) of repeating units in the (2) one or more hydrophilic polymers.

[0242] 18. The lithographic printing plate of any one of embodiments 1 to 17, wherein the (a) repeating unit is derived from one or more of methacrylamide, acrylamide, N,N-dimethylacrylamide, N-hydroxyethylmethacrylamide, and N-(methoxymethyl)acrylamide.

[0243] 19. The lithographic printing plate of any one of embodiments 1 to 18, wherein the (b) repeating unit is derived from one or more ethylenically unsaturated polymerizable monomers represented by the following structure (II):

[0244] CH2=CH(R 1 )-XP(=O)(OM')2

[0245] (II)

[0246] where R 1 is hydrogen or a linear or branched alkyl group of 1 to 4 carbons, M' is independently hydrogen, sodium or potassium ion, and X is a single bond or a divalent linking group having an appropriate number of linked carbon atoms or a combination of linked carbon atoms and oxygen atoms.

[0247] 20. The lithographic printing plate precursor of embodiment 19, wherein the X divalent group is represented by the following structure (III):

[0248] -C(=O)-(OCH2CH2) q -O-

[0249] (III)

[0250] wherein the subscript q is an integer from 1 to 10.

[0251] 21. The lithographic printing plate precursor of any one of embodiments 1 to 20, wherein the on-press developable radiation-sensitive imageable layer is negative-working and comprises:

[0252] (a) one or more free radically polymerizable components;

[0253] (b) an initiator composition that provides free radicals when the radiation-sensitive imageable layer is exposed to imaging radiation,

[0254] (c) one or more radiation absorbers, and optionally

[0255] (d) a polymeric binder that is different from the polymeric binder of (a), (b), and (c).

[0256] 22. The lithographic printing plate precursor of any one of embodiments 1 to 21, wherein the (2) one or more hydrophilic copolymers in the hydrophilic layer comprises at least (a) repeat units derived from one or more of methacrylamide and acrylamide, or (b) repeat units derived from vinyl phosphonic acid.

[0257] 23. The lithographic printing plate of any one of embodiments 1 to 22, wherein the on- press developable radiation-sensitive imageable layer is negative-working and is sensitive to infrared radiation and comprises one or more infrared radiation absorbers.

[0258] 24. The lithographic printing plate precursor of any one of embodiments 21 to 23, wherein the on-press developable negative-working radiation-sensitive layer further comprises (d) a polymeric binder in particulate form.

[0259] 25. A method of providing a lithographic printing plate comprising:

[0260] exposing the lithographic printing plate precursor of any one of embodiments 1 to 24 to imaging radiation in an image-wise manner to form an image-wise exposed imageable layer having exposed regions and non-exposed regions, and

[0261] removing the non-exposed regions from the image-wise exposed imageable layer on-press to form a lithographic printing plate.

[0262] 26. The method of embodiment 25, wherein the lithographic printing plate precursor comprises one or more infrared radiation absorbers and the image-wise exposure is performed using infrared radiation.

[0263] 27. A method of making the lithographic printing plate precursor of any one of embodiments 1 to 24, comprising in order:

[0264] providing an aluminum-containing plate having an electrochemically or mechanically grained and etched surface;

[0265] subjecting the aluminum-containing plate to a first anodization process to form an outer aluminum oxide layer on the electrochemically or mechanically grained and etched surface, the outer aluminum oxide layer comprising a plurality of outer micropores having an average outer micropore diameter (D o ) of at least 15 nm and up to and including 30 nm, and having an average dry thickness (T o ) of at least 30 nm and up to and including 650 nm;

[0266] rinsing the outer aluminum oxide layer;

[0267] The aluminum-containing plate is subjected to a second anodizing process to form an inner aluminum oxide layer below the outer aluminum oxide layer, the inner aluminum oxide layer having an average dry thickness (T of at least 300 nm and up to and including 3,000 nm). i ); and comprising a plurality of average inner pore diameters (D i ) inner micropores;

[0268] washing the outer aluminum oxide layer and the inner aluminum oxide layer;

[0269] forming an on-press developable radiation-sensitive imageable layer over the aluminum oxide outer layer; and

[0270] After washing the outer aluminum oxide layer and the inner aluminum oxide layer and before forming the on-press developable radiation-sensitive imageable layer over the outer aluminum oxide layer, a hydrophilic layer is provided over the outer aluminum oxide layer, the hydrophilic layer comprising:

[0271] (1) a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, at least one of which is directly attached to a phosphorus atom, and a molecular weight of less than 2000 Daltons / mole, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and

[0272] (2) one or more hydrophilic polymers, each comprising at least: (a) repeating units comprising amide units, and (b) repeating units comprising -OM' groups directly attached to phosphorus atoms, wherein M' represents a hydrogen, sodium, potassium or aluminum atom, and the hydrophilic layer has a surface area of ​​at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 A dry coverage of 1000 nm is provided over the outer layer of aluminum oxide.

[0273] The following examples are provided to illustrate the practice of the invention and are not intended to be limiting in any way.

[0274] Inventive Examples 1-3 and Comparative Examples 1-8:

[0275] The aluminum-containing substrates A and B used to prepare the negative-working lithographic printing plate precursors used in the Inventive and Comparative Examples were prepared according to the general method described above.

[0276] Type 1 support:

[0277] This aluminum-containing support was used to prepare the precursors for Inventive Examples 1, 2, and 5-7 and Comparative Examples 1-5. Hydro 1052 aluminum alloy strips or meshes having a thickness of 0.28 mm (available from Norsk Hydro ASA, Norway) were used as the aluminum-containing "plate" raw material or support. Both the pre-etching step and the post-etching step were performed in an alkaline solution under known conditions. These etched aluminum supports were roughened (or stenciled) by electrochemical means in a hydrochloric acid solution at approximately 23° C. to obtain an arithmetic mean roughness (Ra) of 0.5 μm on the surface of the aluminum-containing support. Subsequently, the aluminum-containing support was subjected to two separate anodizing treatments as described in U.S. Patent No. 10,828,884 (noted above). The first anodizing process was performed using phosphoric acid as the electrolyte to form a pore having an average micropore diameter (D) of 19 nm. o ) and an average dry thickness of 190 nm (T o ) of the outer layer of aluminum oxide. A second anodization process was then performed using sulfuric acid as the electrolyte to form an average micropore diameter (D i ) and an average dry thickness of 800 nm (T i The two anodization steps are performed in a continuous process on a typical production line for the manufacture of lithographic printing plate precursors.

[0278] Type 2 support:

[0279] This support was used to prepare the precursor of Inventive Example 3. Hydro 1052 aluminum alloy strip or mesh having a thickness of 0.28 mm (available from Norsk Hydro ASA, Norway) was used as the aluminum-containing "plate" raw material or support. Both the pre-etching step and the post-etching step were performed in an alkaline solution under known conditions. The etched aluminum support was roughened (or plated) by electrochemical means in a hydrochloric acid solution at approximately 23° C. to obtain an arithmetic average roughness (Ra) of 0.5 μm on the surface of the aluminum-containing support. Subsequently, the aluminum-containing substrate was subjected to two separate anodizing treatments. The first anodizing process was performed using phosphoric acid as the electrolyte to form a pore having an average micropore diameter (D) of 19 nm. o ) and an average dry thickness of 60 nm (T o ) of the outer layer of aluminum oxide. A second anodization process was then performed using phosphoric acid as the electrolyte to form an average micropore diameter (D i ) and an average dry thickness of 500 nm (T i The two anodization steps are performed in a continuous process on a typical production line for the manufacture of lithographic printing plate precursors.

[0280] Type 3 support:

[0281] This support was used to prepare the precursor for Inventive Example 4. Hydro 1052 aluminum alloy strip or mesh having a thickness of 0.28 mm (available from Norsk Hydro ASA, Norway) was used as the aluminum-containing "plate" raw material or support. Both the pre-etching step and the post-etching step were performed in an alkaline solution under known conditions. The etched aluminum support was roughened (or plated) by electrochemical means in a hydrochloric acid solution at approximately 23° C. to obtain an arithmetic mean roughness (Ra) of 0.5 μm on the surface of the aluminum-containing support. Subsequently, the aluminum-containing substrate was subjected to two separate anodizing treatments as described in commonly assigned U.S. Patent No. 10,828,884 (Merka et al.) and commonly assigned U.S. Patent No. 11,117,423 (Merka, Mueller, Kemmling and Blum). The first anodizing process was performed using phosphoric acid as the electrolyte to form a pore having an average micropore diameter (D o ) and an average dry thickness of 60 nm (T o ) of the outer layer of aluminum oxide. A second anodization process was then performed using phosphoric acid as the electrolyte to form an average micropore diameter (D m ) and an average dry thickness of 160 nm (T m ) of the aluminum oxide intermediate layer. A third anodization process was performed using sulfuric acid as the electrolyte to form an average micropore diameter (D i ) and an average dry thickness of 800 nm (T i These three anodization steps are carried out in a continuous process on a typical production line for manufacturing lithographic printing plate precursors.

[0282] Preparation of hydrophilic layer formulation:

[0283] The hydrophilic layer formulations HL-1 to HL-10 evaluated below were prepared having the materials and amounts shown in Tables I and II below.

[0284] Table I: Hydrophilic Layer Formulation**

[0285] Hydrophilic polymer Amount of hydrophilic polymer (g) Non-polymeric compound Amount of non-polymeric compound (g) HL-1 1 0.3237 2 0.0971 HL-2 1 0.2525 2 0.1683 HL-3 3 0.3237 2 0.0971 HL-4 4 0.3237 2 0.0971 HL-5 5 0.3237 2 0.0971 HL-6 6 0.4209 None 0 HL-7 6 0.3237 7 0.9711 HL-8 8 0.3237 2 0.0971 HL-9 None 0 2 0.4209 HL-10 8 0.4209 None 0 HL-11 1 0.4209 None 0 HL-12 4 0.4209 None 0 HL-13 5 0.4209 None 0

[0286] * Compounds that may include the (1) compound of the present invention having an ethylenically unsaturated polymerizable group.

[0287] **The hydrophilic layer formulations each contained 0.0291 g of Surfactant 10G (a nonionic surfactant available from DIXIE CHEMICAL COMPANY, INC, Houston, TX) and deionized water to make a total of 100 g of hydrophilic layer formulation.

[0288] Table II: Materials listed in Table I

[0289]

[0290] Each hydrophilic layer formulation shown in Table 1 was coated onto a sample of one of the Type 1, Type 2, or Type 3 supports using a re-wound coating rod and dried at 70°C for 2 minutes and cooled to 20-27°C to provide a hydrophilic layer on the alumina outer layer, followed by drying to provide 0.03 g / m2 of the hydrophilic layer in the Type 1, Type 2, or Type 3 substrate. 2 coverage of the hydrophilic layer.

[0291] Preparation of negative-working on-press developable precursors:

[0292] Coating formulations for negative-working, on-press developable infrared radiation-sensitive imageable layers were prepared using a rod coater using the components and amounts shown in Tables III and IV below to provide a 0.9 g / m² film after drying at 50° C. for 60 seconds. 2 of dry coating weight.

[0293] The starting materials identified in Tables III and IV below can be obtained from one or more commercial sources of chemicals or can be prepared using known synthetic methods and starting materials.

[0294] Table III

[0295]

[0296] Table IV

[0297]

[0298]

[0299] Inventive and comparative examples were prepared according to the general method described above, and after applying the hydrophilic layer formulation to the grained, etched, and doubly or triple anodized aluminum-containing support, the infrared radiation-sensitive image-recording layer was prepared as described above. Table V below identifies each of these examples.

[0300] Table V

[0301] Type of substrate Hydrophilic layer Inventive Example 1 1 HL-1 Inventive Example 2 1 HL-2 Inventive Example 3 2 HL-2 Inventive Example 4 3 HL-2 Inventive Example 5 1 HL-3 Inventive Example 6 1 HL-4 Inventive Example 7 1 HL-5 Comparative Example 1 1 HL-6 Comparative Example 2 1 HL-7 Comparative Example 3 1 HL-8 Comparative Example 4 1 HL-9 Comparative Example 5 1 HL-10 Comparative Example 6 1 HL-11 Comparative Example 7 1 HL-12 Comparative Example 8 1 HL-13

[0302] Using the following test methods, each of the above inventive and comparative precursors was evaluated for plate run, on-press developability, water-ink balance (restart toning or RST test), and shelf life, and the results of these evaluations are shown in Table VI below.

[0303] On-press development capability (DOP):

[0304] To evaluate on-press developability, a Trendsetter 800III Quantum (available from Eastman Kodak Company) was used to segment the image at a range of 50 mJ / cm 2 and 300mJ / cm 2 Each lithographic printing plate precursor (both inventive and comparative) was imagewise exposed at different energies between 1 and 20° and then mounted on a Heidelberg Speedmaster SM 74 press (available from Heidelberg) without any development process in between. In other words, the plates were printed using Varn Supreme 6038+Par fountain solution and OF Kodak Kreide black lithographic ink ( Each imaged precursor was developed on-press using a printing press operated by Schneemann Druckfarben GmbH. Each resulting lithographic printing plate was subjected to an on-press developability print test for up to 1,000 impressions. For the first 10 revolutions, the press was operated with fountain solution alone, after which lithographic ink was supplied to the lithographic printing plate and printing paper was fed into the machine. During on-press development, non-exposed areas of the infrared radiation-sensitive image-recording layer initially transferred the lithographic ink to the printed sheet. The on-press developability was assessed by counting the number of printed sheets required to obtain a clean background and assigning one of the following qualitative values ​​based on the number of printed sheets:

[0305] (++) Development was completed using 5 or fewer sheets of paper;

[0306] (+) Development is completed using more than 5 sheets but 10 or fewer sheets;

[0307] (0) Development is accomplished using more than 10 sheets but 15 or fewer sheets;

[0308] (-) Development is completed using more than 15 sheets but 30 sheets or less; and

[0309] (--) Development was completed using more than 30 sheets but 50 sheets or less.

[0310] Shelf life:

[0311] To evaluate shelf life, the same imagewise exposure conditions as described above for the on-press developability test were used, except that, prior to imagewise exposure, each lithographic printing plate precursor (both inventive and comparative precursors) was subjected to accelerated aging by storing them at 40° C. and 80% relative humidity for 5 days after coating. Each precursor was then imaged and used for printing on a printing press as described above for the on-press developability print test, using the same scoring as follows:

[0312] (++) Development was completed using 5 or fewer sheets of paper;

[0313] (+) Development is completed using more than 5 sheets but 10 or fewer sheets;

[0314] (0) Development is accomplished using more than 10 sheets but 15 or fewer sheets;

[0315] (-) Development is completed using more than 15 sheets but 30 sheets or less; and

[0316] (--) Development was completed using more than 30 sheets but 50 sheets or less.

[0317] Plate durability:

[0318] To evaluate the plate run length, a Trendsetter 800III Quantum (available from Eastman Kodak Company) was used at 120 mJ / cm 2 Each lithographic printing plate precursor (both inventive and comparative) was imagewise exposed and then mounted on a Heidelberg Speedmaster SM 74 press (available from Heidelberg) without any development process. In other words, the plates were printed using Varn Supreme 6038+Par fountain solution and OF Kodak Kreide black lithographic ink ( Each imaged precursor was developed on-press on a printing press operated by Schneemann Druckfarben GmbH. Each resulting lithographic printing plate was subjected to a plate runout test for up to 150,000 impressions. The lithographic printing plates gradually wore out as the printing progressed. The plate runout of each lithographic printing plate was defined as the number of printed sheets achieved before the tonal values ​​of the printed sheets in a 50% FM20 screen decreased to 70% or less of the tonal values ​​obtained on the 1000th sheet. A Techkon Spectro DENS spectrodensitometer was used to measure the tonal values, and the results were scored as follows:

[0319] (++) Equal to or greater than 80,000 sheets;

[0320] (+) Equal to or greater than 60,000 sheets but less than 80,000 sheets;

[0321] (0) Equal to or greater than 40,000 sheets but less than 60,000 sheets;

[0322] (-) Equal to or greater than 20,000 sheets but less than 40,000 sheets; and

[0323] (--)Less than 20,000 sheets.

[0324] Re-start toning (RST):

[0325] For evaluation of restart toning, the same exposure conditions as described for the plate run length test were applied. A sample of each imagewise exposed lithographic printing plate precursor (both inventive and comparative) was mounted on a SpeedMaster SM 52 press and printed using a Fount S-3021 fountain solution and OF Kodak Kreide Black Lithographic Ink ( + Schneemann Druckfarben GmbH) on-press development. After 3,000 impressions, the printing press was stopped without post-wetting. After 15 minutes, the restart toning (RST) was tested without pre-wetting each lithographic printing plate. For the restart toning test, the water content was manipulated to near the smearing limit to enhance the differences in restart toning. The printed sheets were evaluated using a large format scanner and subsequent brightness analysis in specific areas. Non-image areas and 20 μm checkerboards were analyzed. When the brightness in the specified area reached a maximum, the plate was assessed as clean, and the results were scored as follows:

[0326] (++) Less than 20 pieces;

[0327] (+) Equal to or greater than 20, but less than 30;

[0328] (0) Equal to or greater than 30, but less than 40;

[0329] (-) equal to or greater than 40 sheets, but less than 50 sheets; and

[0330] (--) Equal to or greater than 50 sheets.

[0331] Table VI below shows the results of the DOP, shelf life, plate run length, and RST tests for each of the inventive and comparative examples, given the evaluations identified above.

[0332] Table VI

[0333] DOP Shelf life Plate durability RST Inventive Example 1 (++) (+) (++) (+) Inventive Example 2 (++) (+) (++) (++) Inventive Example 3 (+) (+) (-) (++) Inventive Example 4 (++) (+) (+) (+) Inventive Example 5 (++) (+) (+) (+) Inventive Example 6 (+) (+) (++) (+) Inventive Example 7 (+) (+) (++) (+) Comparative Example 1 (++) (0) (+) (--) Comparative Example 2 (+) (--) (+) (-) Comparative Example 3 (++) (--) (0) (-) Comparative Example 4 (+) (--) (--) (++) Comparative Example 5 (+) (0) (-) (--) Comparative Example 6 (+) (0) (+) (-) Comparative Example 7 (+) (+) (++) (-) Comparative Example 8 (++) (+) (-) (+)

[0334] The results show that it is critical to use (1) the compound and (2) one or more hydrophilic polymers together to obtain overall improved results in several important characteristics of press-developable lithographic printing plate precursors, such as fast DOP, good shelf life, long run, and good restart toning behavior. The best embodiments of the invention provide improvements in multiple characteristics without undesirably diminishing other characteristics.

Claims

1. A lithographic printing plate precursor comprising: a substrate having a surface, and an on-press developable radiation-sensitive imageable layer disposed over said surface of said substrate, wherein the substrate comprises: an aluminum-containing plate having a ground and etched surface; An inner layer of aluminum oxide is disposed on the grained and etched surface, the inner layer of aluminum oxide having an average dry thickness (T i ), and comprising a plurality of micropores having an average inner pore diameter (D i ) inner micropores; An outer aluminum oxide layer is disposed over the inner aluminum oxide layer, the outer aluminum oxide layer comprising a plurality of pores having an average outer pore diameter (D) of at least 15 nm and up to and including 30 nm. o ) and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o );and At least 0.0002g / m 2 and up to and including 0.1 g / m 2 A hydrophilic layer is provided on the alumina outer layer at a dry coverage of , and the hydrophilic layer comprises: (1) a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, at least one of which is directly attached to a phosphorus atom, and a molecular weight of less than 2000 Daltons / mole, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and (2) one or more hydrophilic polymers, each comprising at least: (a) a repeating unit comprising an amide group, and (b) a repeating unit comprising an -OM' group directly attached to a phosphorus atom, wherein M' represents a hydrogen, sodium, potassium or aluminum atom.

2. The lithographic printing plate precursor of claim 1 , wherein the outer layer of aluminum oxide has at least 500 micropores / μm 2 and up to and including 3,000 micropores / μm 2 The micropore density (C o ), and having a porosity (P greater than or equal to 0.3 and less than or equal to 0.8 o ), where P o Defined as 3.14(C o )(D o 2 ) / 4,000,000.

3. The lithographic printing plate precursor of claim 1 or 2, wherein the outer layer of aluminum oxide has an average dry thickness (T o ), and the outer aluminum oxide layer is directly disposed on the inner aluminum oxide layer; the average dry thickness of the inner aluminum oxide layer (T i ) is at least 650 nm, and the average inner pore diameter (D i ) is less than or equal to 15 nm and less than the average outer pore diameter (D o ).

4. The lithographic printing plate precursor of claim 1 or 2, wherein the substrate further comprises an aluminum oxide intermediate layer disposed between the aluminum oxide inner layer and the aluminum oxide outer layer, wherein the aluminum oxide intermediate layer has an average dry thickness (T m ), and comprising a plurality of pores having an average median pore diameter (D m ) in the middle micropore, where D m Greater than D o , D o Greater than D i , and the average dry thickness of the alumina outer layer (T o ) is less than 150nm.

5. The lithographic printing plate precursor of claim 1 or 2, wherein the outer aluminum oxide layer is directly disposed on the inner aluminum oxide layer, and the average inner pore diameter (D i ) is at least 20 nm and larger than the average outer pore diameter (D o ).

6. The lithographic printing plate precursor of claim 1 or 2, wherein at least one ethylenically unsaturated polymerizable group in the (1) compound is attached to the phosphorus atom to which the -OM group is attached via a spacer group, wherein the spacer group is of the formula -(-CH2CH2O-) p - represents, wherein the subscript p is an integer of at least 1 and up to and including 10.

7. A lithographic printing plate precursor as described in claim 1 or 2, wherein the (1) compound is present in an amount of at least 10 weight % and up to and including 80 weight % based on the total weight (solids) of the hydrophilic layer, or the weight ratio of one or more (1) compounds to the (2) one or more hydrophilic polymers in the hydrophilic layer is from 1:4 to 4:

1.

8. The lithographic printing plate precursor according to claim 1 or 2, wherein the (1) compound is represented by the following structure (I): wherein subscript m is 1 or 2, subscript n is an integer of at least 1 and up to and including 10, and R is a hydrogen atom or a substituted or unsubstituted methyl group.

9. A lithographic printing plate precursor as described in claim 1 or 2, wherein the (a) repeating unit is present in the (2) one or more hydrophilic polymers in an amount of at least 60 mol% and up to and including 97 mol%, and the (b) repeating unit is present in the (2) one or more hydrophilic polymers in an amount of at least 3 mol% and up to and including 40 mol%, all based on the total number (or number of moles) of repeating units in the (2) one or more hydrophilic polymers.

10. The lithographic printing plate precursor of claim 1 or 2, wherein the on-press developable radiation-sensitive imageable layer is negative-working and comprises: (a) one or more free radically polymerizable components; (b) an initiator composition that provides free radicals when the radiation-sensitive imageable layer is exposed to imaging radiation, (c) one or more radiation absorbers, and optionally (d) A polymeric binder other than the owner of (a), (b) and (c).

11. The lithographic printing plate precursor of claim 1 or 2, wherein the hydrophilic copolymer in the hydrophilic layer comprises at least the (a) repeating units derived from one or more of methacrylamide and acrylamide, or at least the (b) repeating units derived from vinylphosphonic acid.

12. The lithographic printing plate precursor of claim 1 or 2, wherein the on-press developable radiation-sensitive imageable layer is negative-working and sensitive to infrared radiation and comprises one or more infrared radiation absorbers.

13. The lithographic printing plate precursor of claim 10, wherein the on-press developable negative-working radiation-sensitive layer further comprises the (d) polymer binder in particulate form.

14. A method of providing a lithographic printing plate, comprising: imagewise exposing the lithographic printing plate precursor of any one of claims 1 to 13 to imaging radiation to form an imagewise exposed imageable layer having exposed and non-exposed areas, and The non-exposed areas are removed on-press from the imagewise exposed imageable layer to form a lithographic printing plate.

15. The method of claim 14, wherein the lithographic printing plate precursor comprises one or more infrared radiation absorbers and the image-wise exposing is performed using infrared radiation.

16. A method of preparing a lithographic printing plate precursor, comprising, in sequence: providing an aluminum-containing plate having an electrochemically or mechanically ground and etched surface; The aluminum-containing plate is subjected to a first anodizing process to form an outer aluminum oxide layer on the electrochemically or mechanically ground and etched surface, the outer aluminum oxide layer comprising a plurality of pores having an average outer pore diameter (D) of at least 15 nm and up to and including 30 nm. o ) and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o ); washing the outer layer of aluminum oxide; The aluminum-containing plate is subjected to a second anodizing process to form an inner aluminum oxide layer below the outer aluminum oxide layer, the inner aluminum oxide layer having an average dry thickness (T i ); and comprising a plurality of average inner pore diameters (D i ) inner micropores; flushing the outer aluminum oxide layer and the inner aluminum oxide layer; forming an on-press developable radiation-sensitive imageable layer over the aluminum oxide outer layer; and After rinsing the outer aluminum oxide layer and the inner aluminum oxide layer and before forming the on-press developable radiation-sensitive imageable layer over the outer aluminum oxide layer, a hydrophilic layer is provided over the outer aluminum oxide layer, the hydrophilic layer comprising: (1) a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, at least one of which is directly attached to a phosphorus atom, and a molecular weight of less than 2000 Daltons / mole, wherein M represents a hydrogen, sodium, potassium, or aluminum atom; and (2) one or more hydrophilic polymers, each comprising at least: (a) repeating units comprising an amide unit, and (b) repeating units comprising an -OM' group directly attached to a phosphorus atom, wherein M' represents a hydrogen, sodium, potassium, or aluminum atom, and the hydrophilic layer has a surface area of ​​at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 A dry coverage of 500 nm is provided over the alumina outer layer.

17. The method of claim 16, wherein the on-press developable radiation-sensitive layer is infrared radiation-sensitive and negative-working and comprises: (a) one or more free radically polymerizable components; (b) an initiator composition that provides free radicals when the radiation-sensitive imageable layer is exposed to imaging radiation, (c) one or more radiation absorbers, and optionally (d) A polymeric binder other than the owner of (a), (b) and (c).

18. The method of claim 16 or 17, wherein the (2) one or more hydrophilic polymers in the hydrophilic layer comprise the (a) repeating units derived from at least one or more of methacrylamide and acrylamide, and the (b) repeating units derived from at least vinylphosphonic acid, and the (a) repeating units are present in the (2) one or more hydrophilic polymers in an amount of at least 60 mol% and up to and including 97 mol%, and the (b) repeating units are present in the (2) one or more hydrophilic polymers in an amount of at least 3 mol% and up to and including 40 mol%, all based on the total number (or moles) of repeating units in the (2) one or more hydrophilic polymers.

19. The method of claim 16 or 17, wherein the compound (1) is represented by the following structure (I): wherein subscript m is 1 or 2, subscript n is an integer of at least 1 and up to and including 10, and R is a hydrogen atom or a substituted or unsubstituted methyl group.

20. The method of claim 16 or 17, wherein the weight ratio of the one or more (1) compounds to the (2) one or more hydrophilic polymers in the hydrophilic layer is 1:4 to 4:1.

Images