Lithographic printing plate precursors and methods of use

Abstract

Lithographic printing plate precursors were prepared using a unique aluminum-containing substrate prepared using two separate anodization processes to provide an average dry thickness (T i ) is 300-3,000 nm and has an average internal micropore diameter (D i ) of an inner alumina layer having a large number of inner micropores. Also provided is an inner alumina layer having an average outer micropore diameter (D o ) with a large number of external micropores of 15‑30 nm and a dry thickness (T o ) of the outer aluminum oxide layer. 2 The hydrophilic layer disposed on the outer alumina layer comprises at least a hydrophilic copolymer comprising (a) repeating units having amide groups and (b) repeating units comprising ‑OM groups directly attached to phosphorus atoms, wherein M represents a hydrogen, sodium, potassium or aluminum atom.

Description

Technical Field

[0001] The present invention relates to lithographic printing plate precursors comprising an inventive aluminum-containing substrate that has been prepared using at least two separate anodizing processes to provide different aluminum oxide layers having different structural properties, and having a hydrophilic layer comprising at least one unique hydrophilic copolymer. The present invention also relates to methods for imaging and processing such lithographic printing plate precursors to provide lithographic printing plates; and the invention further relates to methods of preparing such precursors. Background Art

[0002] In lithographic printing, lithographic ink-receptive areas, called image areas, are created on the hydrophilic, flat surface of a substrate. When the 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-receptive image areas accept the lithographic ink and repel the water. A blanket roller may be used to transfer the lithographic ink from the lithographic printing plate to the surface of the material on which the image is to be reproduced.

[0003] The imageable element or lithographic printing plate precursor used to prepare a lithographic printing plate typically comprises one or more radiation-sensitive imageable layers disposed on the outermost hydrophilic surface of a substrate. Such radiation-sensitive imageable layers comprise one or more radiation-sensitive components that can be dispersed together with or dispersed in a polymeric binder material. Alternatively, the radiation-sensitive component can also serve as or form a polymeric binder material. After imaging, a suitable developer can be used to remove the exposed (imaged) area or unexposed (unimaged) area of the one or more radiation-sensitive layers to reveal the outermost hydrophilic surface of the substrate. If the exposed area is removable, the lithographic printing plate precursor is considered to be positive. Conversely, if the unexposed area is removable, the lithographic printing plate precursor is considered to be negative.

[0004] Direct digital thermal imaging of lithographic printing plate precursors has become increasingly important in the printing industry over the past 30 years 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 have been designed to be sensitive to digital imaging using UV or "violet" radiation of at least 250 nm.

[0005] Negative-working lithographic printing plate precursors useful for preparing lithographic printing plates typically comprise a negative-working radiation-sensitive imageable layer disposed on a hydrophilic surface of a substrate. The radiation-sensitive photopolymerizable compositions used in negative-working lithographic printing plate precursors typically comprise a free radically polymerizable component, one or more radiation absorbers, an initiator composition, and optionally one or more polymeric binders different from the other specified components.

[0006] In recent years, there has been an emphasis in the industry on simplifying lithographic printing plate preparation methods, including omitting the pre-development heating step (preheating) and performing on-press development (DOP) using lithographic inks, fountain solutions, 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 a number of features within the element structure to achieve optimal plate run length, on-press developability, and scratch resistance. Achieving high quality across all of these properties is no easy task, as chemical composition or structural features that provide optimal levels of one or two properties may result in the loss of another.

[0007] Independent of the type of lithographic printing plate precursor, lithography is typically performed using a metal-containing substrate comprising aluminum or an aluminum alloy having various metal compositions (e.g., 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 in a "pre-etch" process using an alkali or surfactant solution to remove oil, grease, and other contaminants from the flat surface of the raw aluminum-containing material. The cleaned flat surface is then typically roughened by electrochemical or mechanical graining, followed by a "post-etch" process to remove any contaminants ("smudges") formed during the graining process. Further industrial details of preparing useful substrates for lithographic printing plate precursors can be found in U.S. Patent Application Publication No. 2014 / 0047993A1 (Hauck et al.).

[0008] After further rinsing, the flat 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 properties of the resulting lithographic printing plate precursor once one or more imageable layers are formed thereon.

[0009] One or more anodization treatments are used in some known methods of preparing precursor substrates, such 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.).

[0010] In these known methods for preparing precursor substrates, sulfuric acid, phosphoric acid, or both sulfuric acid and phosphoric acid have been used as electrolytes in combination with various process parameters in order to produce one or more anodic (aluminum oxide) layers having a specific structure and, therefore, to achieve specific properties in the resulting precursors. However, it has been found that lithographic printing plate precursors prepared according to these known methods are still unsatisfactory with respect to one or more precursor properties such as scratch resistance, on-press developability, plate run length, and restart toning (RST).

[0011] Due to the adverse effects of processing chemicals and waste generated during the process of preparing lithographic printing plates, lithographic printing plate precursors that can be developed on-press using ink and / or fountain solution have become significantly more popular in the industry. Early commercial releases of this type of lithographic printing plate precursor were generally limited to printing applications requiring fewer than 100,000 prints. These limitations were attributed to the technical difficulties of achieving both fast on-press development and good image durability.

[0012] The unique anodized substrates described in U.S. Serial No. 15 / 447,651 (noted above), published as U.S. Patent Application Publication 2018 / 0250925 (Merka et al.) and co-assigned as U.S. Patent Application Publication 2018 / 0250925 (Merka et al.) and announced as U.S. Patent Application 10,828,884, and previously published as U.S. Patent Application Publication 2019 / 0016110, co-assigned U.S. Patent Application 10,363,734 (Merka et al.) provide advancements in the art.

[0013] More recently, aluminum-containing substrates having multilayer anodic oxide structures, such as those described in these publications, have been developed. Such substrates, used 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 anodic aluminum oxide structure.

[0014] A typical polymer to be included in the hydrophilic subbing layer is a partially neutralized polyacrylic acid. However, lithographic printing plates prepared from such on-press developable lithographic printing plate precursors have sometimes been shown to experience a problem known as poor "restart toning" (hereinafter identified as "RST"), in which the background becomes sensitive to ink and requires many printed sheets to be cleaned when the lithographic printing operation is restarted after printing has been interrupted or stopped for various reasons.

[0015] Therefore, there still exists a need to provide lithographic printing plates that can be easily restarted after a printing interruption, wherein the noted restart toning problems are reduced or eliminated. It would be particularly desirable if such lithographic printing plates were derived from negative-working lithographic printing plate precursors that can be developed on-press without sacrificing high plate run length and on-press developability. Summary of the Invention

[0016] The present invention provides a lithographic printing plate precursor comprising:

[0017] a substrate having a flat surface, and

[0018] a press-developable radiation-sensitive imageable layer disposed on the planar surface of the substrate,

[0019] The substrate includes:

[0020] an aluminum-containing plate having a ground and etched flat surface;

[0021] An inner aluminum oxide layer disposed on the grained and etched flat surface, the inner aluminum oxide layer having an average dry thickness (T i ), and comprising an average internal micropore diameter (D i ) a large number of internal micropores;

[0022] An outer aluminum oxide layer is disposed on the inner aluminum oxide layer, the outer aluminum oxide layer comprising an average outer micropore size (D) of at least 15 nm and up to and including 30 nm. o ) of a plurality of external micropores and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o );and

[0023] At least 0.0002g / m 2 and up to and including 0.1 g / m 2 A hydrophilic layer is provided on the outer alumina layer with a dry coverage of 100%, and the hydrophilic layer comprises one or more hydrophilic polymers, at least one of which is a hydrophilic copolymer comprising at least (a) repeating units and (b) repeating units, (a) repeating units comprising amide groups, (b) repeating units comprising -OM groups directly attached to phosphorus atoms, wherein M represents a hydrogen, sodium, potassium or aluminum atom.

[0024] Additionally, the present invention provides a method for providing a lithographic printing plate, the method comprising:

[0025] imagewise exposing the lithographic printing plate precursor of any embodiment of the invention to imaging radiation to form an imagewise exposed imageable layer having exposed and unexposed regions, and

[0026] The unexposed areas are removed on-press from the imagewise exposed imageable layer to form a lithographic printing plate.

[0027] Furthermore, the present invention provides a method for preparing a lithographic printing plate precursor, comprising, in sequence:

[0028] providing an aluminum-containing plate having an electrochemically or mechanically ground and etched flat surface;

[0029] The aluminum-containing plate is subjected to a first anodizing treatment to form an outer aluminum oxide layer on the electrochemically or mechanically grained and etched flat surface, the outer aluminum oxide layer comprising an average outer micropore size (D) of at least 15 nm and up to and including 30 nm. o ) of a plurality of external micropores and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o );

[0030] Rinsing the outer aluminum oxide layer;

[0031] The aluminum-containing plate is subjected to a second anodizing treatment to form an inner aluminum oxide layer beneath the outer aluminum oxide layer, the inner aluminum oxide layer having an average dry thickness (T i ); and comprising an average internal micropore diameter (D i ) a large number of internal micropores;

[0032] rinsing the outer aluminum oxide layer and the inner aluminum oxide layer;

[0033] forming a press-developable radiation-sensitive imageable layer on the outer aluminum oxide layer; and

[0034] After rinsing the outer and inner aluminum oxide layers and before forming a press-developable radiation-sensitive imageable layer on the outer aluminum oxide layer, a hydrophilic layer is provided on the outer aluminum oxide layer, the hydrophilic layer comprising one or more hydrophilic polymers, at least one of the hydrophilic polymers being a hydrophilic copolymer 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 is coated with at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 The dry coverage is set on the outer aluminum oxide layer.

[0035] The restart toning (RST) problem noted above has been addressed by providing a unique hydrophilic underlayer on a multilayer anodized aluminum structure to form an inventive on-press developable lithographic printing plate precursor. Such a hydrophilic underlayer comprises at least one hydrophilic copolymer comprising at least two repeating units, (a) having an amide group and (b) comprising an -OM group directly attached to a phosphorus atom, wherein "M" is a hydrogen, sodium, potassium, or aluminum atom. Specific details of the materials, including the hydrophilic copolymer, used to prepare the hydrophilic underlayer are provided below. The noted RST improvements are achieved while maintaining acceptable scratch resistance, on-press developability, and high plate run length. DETAILED DESCRIPTION

[0036] The following discussion relates 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. Additionally, those skilled in the art will appreciate that the following disclosure has broader application than the explicitly described and discussion of any embodiments.

[0037] definition

[0038] 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 resulting dried layer), processing solutions, anodizing solutions, hydrophilic layer formulation (and 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).

[0039] Each term not explicitly 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 would make it meaningless or essentially meaningless in its context, the term should be interpreted as having the standard dictionary meaning.

[0040] Unless otherwise expressly indicated, the use of numerical values in the various ranges specified herein should be considered approximate, as if the word "about" were preceding both the minimum and maximum values in the stated ranges. In this manner, slight variations above and below the stated ranges can be used to achieve substantially the same results as the values within the ranges. Additionally, the disclosure of these ranges is intended as a continuous range, including every value between the minimum and maximum values and the endpoints of the range.

[0041] Unless the context indicates otherwise, when used herein, the terms "negative-working radiation-sensitive lithographic printing plate precursor," "positive-working radiation-sensitive lithographic printing plate," "precursor," "radiation-sensitive precursor," and "lithographic printing plate precursor" represent equivalent references to certain embodiments of the invention.

[0042] The term "support" is used herein to refer to an aluminum-containing material 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.

[0043] The average external micropore diameter (D) in nanometers (nm) can be determined from a top-down 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. o It is also possible to determine the external pore size (D) of a lithographic printing plate precursor by o ): After stripping the organic layer with a suitable solvent and optionally removing an outer portion of the outer aluminum oxide layer (approximately 20 nm to 80 nm thick) using a suitable technique such as argon ion beam sputtering, a top-down SEM image is taken. The average value can be determined by examining more than 200 outer micropores.

[0044] The average internal micropore diameter (D) can be determined from cross-sectional SEM images at a magnification of at least 50,000X. i ). A cross section can be generated by bending the lithographic printing plate precursor or its substrate after the imageable layer and optional hydrophilic layer have been removed. During bending, cracks form in the aluminum oxide layer and new surfaces are formed, typically at the weakest locations (which are typically located at the thinnest walls between adjacent internal micropores). The new cracked surface thus provides 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 exposed micropore cross-sections have a width of less than 15 nm.

[0045] Average dry thickness of the outer anodized layer in nanometers (nm) (T o ) and the average dry thickness of the inner anodized 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), a technique well known in the art.

[0046] The number of micropores / μm can be determined from a top-view SEM image at a magnification of at least 50,000X by counting the number of micropores in a square predetermined area having an area of at least 500 nm×500 nm. 2 The micropore density of the external anodized layer (C o ).

[0047] The porosity of the outer alumina layer (P) can be limited by each of the following equations:o ):

[0048] 0.3 < P o < 0.8 or

[0049] 0.3 < P o < 0.6,

[0050] Among them, P o Defined as 3.14(C o )(D o 2 ) / 4,000,000.

[0051] The term "radiation absorber" as used herein refers to a compound or material that absorbs electromagnetic radiation in a defined region, and typically 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.

[0052] As used herein, the term "infrared region" refers to radiation having a wavelength of at least 750 nm and longer. In most cases, the term "infrared" is used to refer to the "near infrared" region of the electromagnetic spectrum, which is defined herein as at least 750 nm and up to and including 1400 nm. Similarly, infrared radiation absorbers provide sensitivity in this infrared region.

[0053] For clarification of the definition of any term relating 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.

[0054] As used herein, the term "polymer" is used to describe a compound with 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. Utilizing the choice of solvent, the polymer can become insoluble as the chain length grows and become polymer particles dispersed in the solvent medium. These particle dispersions can be very stable and are useful for the radiation-sensitive imageable layer described as used in the present invention. In the present invention, unless otherwise indicated, the term "polymer" refers to a non-crosslinked material. Thus, the difference between crosslinked polymer particles and non-crosslinked polymer particles is that the latter are soluble in certain organic solvents with good solvating properties, whereas crosslinked polymer particles can swell but not dissolve in organic solvents because the polymer chains are connected by strong covalent bonds.

[0055] The term "copolymer" refers to a polymer composed of two or more different repeating or recurring units arranged along the copolymer backbone.

[0056] The term "polymer backbone" refers to the chain of atoms in a polymer to which multiple pendant groups can 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 condensation reaction is used to form the polymer with appropriate reactants, some polymer backbones may contain both carbon and heteroatoms.

[0057] 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 can be obtained from various commercial sources or prepared using known chemical synthesis methods. Unless otherwise indicated herein, repeating units derived from the same ethylenically unsaturated polymerizable monomer are, by definition, identical in composition and molecular weight.

[0058] 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.

[0059] 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, can be the same.

[0060] As used herein, the term "layer" or "coating" may consist of one layer disposed or applied or a combination of several layers disposed or applied successively. 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. Similarly, if a layer is considered to be radiation-sensitive and positive-working, it is both sensitive to infrared radiation and positive-working in the formation of a lithographic printing plate.

[0061] use

[0062] The lithographic printing plate precursors of the present invention are useful for forming lithographic printing plates for lithographic printing using lithographic inks and fountain solutions. These precursors are prepared having the structures and components described below. Furthermore, 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 the negative-working radiation-sensitive formulation and imageable layer.

[0063] In addition, the inventive precursors are designed to be developable on-press, such that development of the imaged precursors can be achieved on-press using fountain solution, lithographic ink, or both fountain solution and lithographic ink. However, it is still possible to develop such precursors off-press using a suitable developer if the user so desires.

[0064] The present invention is also useful in making such lithographic printing plate precursors, which can then be sold to consumers for imaging and printing.

[0065] Inventive substrate

[0066] The inventive substrates useful in the present invention are designed to possess key features and properties in order to achieve the advantages described above.

[0067] A general description relating to the production of substrates useful for lithographic printing plate precursors can be found in US Patent Application Publication No. 2014 / 0047993 Al (noted above).

[0068] In general, 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 "raw material") containing aluminum or an aluminum alloy can have any form from which it can be further processed, including sheets, continuous webs, and wound strips, as long as it has at least one flat surface that can be treated as described below to form the hydrophilic flat surface in the inventive substrate. It is also possible to use a polymer film or paper onto which a layer containing pure aluminum or an aluminum alloy is deposited or laminated.

[0069] The resulting substrate should be thick enough to mechanically withstand the conditions in modern printing presses, but thin enough to be mounted on (or wound around) the printing cylinder of such machines. Therefore, the substrate should also have the appropriate tensile strength, elasticity, crystallinity, and conductivity required for lithographic printing. These properties can be achieved by standard methods typically used to make continuous lithographic support strips, webs, or rolls (e.g., heat treatment or hot and cold rolling). The dry thickness of the resulting inventive substrate is typically at least 100 μm and up to and including 600 μm.

[0070] The described aluminum-containing supports can be processed using a typical lithographic printing plate precursor manufacturing process including pre-etching, water rinsing, roughening, water rinsing, post-etching, and a final water rinse in combination with a first and second anodizing treatment described in more detail below.

[0071] Usually the raw material containing aluminum support is subjected to a pre-etching step to remove oil, grease and metal or other pollutants at or near the flat surface. As known in the art, sodium hydroxide or other alkaline aqueous solutions or even some organic solvents can be used to carry out this pre-etching step at known concentrations, time and temperature. Surfactant aqueous solutions can be used to carry out separate or additional degreasing steps when needed. A skilled worker can carry out routine experiments to find optimal pre-etching conditions (e.g., optimal solution concentration, residence time and temperature).

[0072] Typically, after the pre-etching step, the etched support is "roughened" in a suitable manner such as by using known electrochemical or mechanical roughening (or grinding) processes. In the electrochemical grinding process, the etched support can be treated with an alternating current in a 5-20 g / liter hydrochloric acid solution. It is also possible to use a nitric acid (e.g., up to 2.5 wt %) solution or a sulfuric acid solution or mixture for this purpose. Such electrochemical grinding solutions may 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.). A skilled worker can determine the optimal conditions for electrochemical or mechanical grinding by routine experimentation, as such treatments are well known in the art. Mechanical grinding can be performed, for example, using a suitable brush alone or using a combination of a suitable brush and a slurry of an abrasive (e.g., silica particles or aluminum oxide particles). Alternatively, a combination of mechanical and electrochemical graining processes may be used.

[0073] During roughening or graining, stains may form on the flat surface of the support, and treatment with highly acidic or highly alkaline solutions (e.g., to remove 0.01-5.0 g / m 2 The stain is removed by a post-etching step (of the support surface). For example, the following solutions can be used for post-etching: sodium hydroxide, trisodium phosphate, or sulfuric acid. 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 in this step. The post-etching treatment should be sufficient to remove the stain, but it should not excessively damage the surface structure formed in the roughening step. Therefore, there are many combinations of parameters that can be considered by those skilled in the art during routine experimentation to find the optimal post-etching conditions.

[0074] The preceding steps produce an electrochemically or mechanically grained (roughened) and etched flat surface in the aluminum-containing support.

[0075] The subsequent steps performed according to the present invention include at least a first anodizing treatment and a second anodizing treatment (both of which are essential to the present invention) to form an outer aluminum oxide layer and an inner aluminum oxide layer, respectively. The present method does not require additional anodizing treatments (i.e., a third or more anodizing treatments), but one or more additional anodizing treatments are possible and therefore optional. However, in many embodiments, the first anodizing treatment and the second anodizing treatment described herein are the only anodizing treatments.

[0076] The first anodizing treatment and the second anodizing treatment may typically be carried out using sulfuric acid or phosphoric acid (electrolyte) solution 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, which is sufficient to provide up to and including 4 g / m 2 The conditions for both the first anodizing treatment and the second anodizing treatment are as described below.

[0077] The suitable aluminum-containing plate with a flat surface electrochemically or mechanically ground and etched is subjected to a first anodizing treatment to form an outer aluminum oxide layer on the flat surface electrochemically or mechanically ground and etched. The first anodizing treatment can be carried out, for example, using an electrolyte composition containing at least 50 g / liter and up to and including 350 g / liter of phosphoric acid or at least 150 g / liter and up to and including 300 g / liter of sulfuric acid and a suitable amount of aluminum (e.g., 5 g / liter). These solution amounts can be optimized according to the type of acid, acid concentration, aluminum concentration, residence time, and temperature, so as to achieve the desired outer aluminum oxide layer properties as described herein. Representative details of this type of first anodizing treatment are illustrated in the working examples described below. It is particularly useful to use phosphoric acid to carry out the first anodizing treatment.

[0078] The resulting outer aluminum oxide layer comprises an average outer micropore diameter (D) of at least 15 nm and up to and including 30 nm. o ) of a large number of external micropores. In addition, the average dry thickness of the external aluminum oxide layer (T o ) may be at least 30 nm and up to and including 650 nm, or more likely may be at least 130 nm and up to and including 150 nm or up to and including 400 nm. The micropore density (C) of the outer anodized layer o ) can typically be at least 500 micropores / μm 2 and up to and including 3,000 micropores / μm 2 .

[0079] Additionally, the average outer micropore size (D) in nanometers of the outer aluminum oxide layer can be further constrained or related according to any of the following equations: o ) and micropores / μm 2 Micropore density (C o ):

[0080] 0.3 < P o < 0.8 or

[0081] 0.3 < P o < 0.6,

[0082] Among them, P o Defined above.

[0083] Once the first anodizing process has been carried out for the desired time, the formed outer aluminum oxide layer can be rinsed with a suitable solution (such as water) at a suitable temperature and time to remove residual acid and aluminum and to stop the first anodizing process.

[0084] A second anodizing treatment is then performed using a suitable electrolyte composition that may comprise at least 100 g / liter and up to and including 350 g / liter of sulfuric acid or at least 50 g / liter and up to and including 350 g / liter of phosphoric acid, and a suitable amount of aluminum (e.g., 5 g / liter) to form an inner aluminum oxide layer beneath the outer aluminum oxide layer. These solution amounts may be optimized according to acid concentration, aluminum concentration, residence time, and temperature in order to achieve the desired inner aluminum oxide layer properties as described herein. Details of such a second anodizing treatment are exemplified in the working examples described below.

[0085] The resulting inner aluminum oxide layer disposed on the ground and etched flat surface of the substrate comprises an average inner micropore diameter (D i) of a large number of internal micropores. In some embodiments, the average internal micropore diameter (D i ) is less than or equal to 15 nm and smaller than the average external micropore diameter (D o ). In such embodiments, D o With D i The ratio can be greater than 1.1:1, or even greater than 1.5:1, and typically greater than 2:1.

[0086] In other embodiments, the average internal micropore diameter (D i ) is greater than 30 nm and greater than the average external micropore diameter (D o ). In the latter embodiment, D i With D o The ratio can 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 alumina layer (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.

[0087] Once the second anodizing process is performed for the desired time, both the formed outer and inner aluminum oxide layers may be rinsed with a suitable solution (eg, water) at a suitable temperature and time, if necessary, to remove residual acid and aluminum and to stop the second anodizing process.

[0088] In some embodiments of the present invention, the aluminum-containing support is subjected to an additional anodizing treatment using a suitable acid or mixture thereof at a suitable temperature and for a suitable time to provide a "middle alumina layer". This additional anodizing treatment is performed after the first anodizing treatment and before the second anodizing treatment. Thus, the middle alumina layer is typically formed between the outer alumina layer and the later formed inner alumina layer. In such embodiments, the middle alumina layer formed may have an average dry thickness (T of at least 60 nm and up to and including 300 nm). m ), and comprising an average median micropore diameter (D) of at least 20 nm and up to and including 60 nm m ) with a large number of central micropores.

[0089] In such embodiments, D m >D o >D i .

[0090] After forming the middle aluminum oxide layer, the outer and middle aluminum oxide layers may be rinsed as described above for the outer aluminum oxide layer alone, and then the inner aluminum oxide layer may be formed as noted above.

[0091] According to the present invention, it is necessary to provide a hydrophilic layer disposed on the outer aluminum oxide layer. The hydrophilic layer can be provided by a hydrophilic layer formulation comprising one or more hydrophilic polymers and is typically applied or disposed on the outer aluminum oxide layer to provide at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 The dry coverage of the hydrophilic layer is at least 0.005 g / m 2 and up to and including 0.08 g / m 2 Typically, the hydrophilic layer is 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 reside within such micropores and the micropores beneath the outer alumina layer.

[0092] At least one of the hydrophilic polymers used for this purpose is a hydrophilic copolymer comprising (a) repeating units, each of which has at least one amide group and can be derived from one or more corresponding ethylenically unsaturated polymerizable monomers having an amide group, such as methacrylamide, acrylamide, N,N-dimethylacrylamide, N-hydroxyethylacrylamide, and N-(methoxymethyl)acrylamide. A mixture of two or more of these monomers can be used to provide a mixture of (a) repeating units having different compositions or molecular weights, all having at least one amide group in the repeating unit. The amide groups in the monomers generally do not chemically react during the polymerization process to form the (a) repeating units in the hydrophilic copolymer.

[0093] At least one hydrophilic copolymer further comprises (b) repeating units, each of which comprises an -OM group directly bonded to a phosphorus atom, wherein M represents a hydrogen, sodium, potassium, or aluminum atom. The bond within the -OM group may be a covalent bond or an ionic bond. When the bond is an ionic bond, -OM may be written as -O - M + , and M + M is a hydrogen ion, a sodium ion, a potassium ion, or an aluminum ion. Since aluminum atoms typically have three valences, they are typically bonded to other atoms via covalent or ionic bonds. When the hydrophilic copolymer is present in the hydrophilic layer formulation prior to applying the hydrophilic layer formulation to the surface of the multilayer alumina structure as described above, M is typically a hydrogen, sodium, or potassium atom, and more typically a hydrogen atom. Upon application of the hydrophilic layer formulation, it is expected that some of the hydrogen, sodium, or potassium atoms will be converted to aluminum atoms, allowing the hydrophilic copolymer to bond to the multilayer alumina structure.

[0094] Such (b) repeating units may be derived from suitable corresponding ethylenically unsaturated polymerizable monomers, each of which has an -OM group directly linked or attached to the phosphorus atom, or may form an -OM group directly linked or attached to the phosphorus atom after polymerization from a suitable "precursor group" (e.g., -OR in a phosphate group, wherein R is a substituted or unsubstituted alkyl group having 1 to 20 carbons). Such ethylenically unsaturated polymerizable monomers used to provide (b) repeating units may have more than one such -OM group, as long as at least one such -OM group is directly linked or attached to the phosphorus atom. Useful ethylenically unsaturated polymerizable monomers of this type include, but are not limited to, those represented by formula (I).

[0095] CH2=CH(R 1 )-XP(=O)(OM)2(I)

[0096] where R 1 is hydrogen or an alkyl group having 1-4 carbons, M is independently a hydrogen, sodium or potassium atom, and X is a single bond or a divalent linking group. Useful divalent X groups include, but are not limited to, those represented by the following formula (II).

[0097] -C(=O)-(OCH2CH2) n -O-(II)

[0098] Wherein the subscript n is an integer from 1 to 10.

[0099] Specific examples of useful ethylenically unsaturated polymerizable monomers according to formula (I) include vinylphosphonic acid, ethylene glycol acrylate phosphate, and ethylene glycol methacrylate phosphate. Mixtures of such ethylenically unsaturated polymerizable monomers may also be used to form the (b) repeating units, such that the repeating units may have different chemical compositions or molecular weights, as long as each (b) repeating unit has at least one -OM group bonded to a phosphorus atom.

[0100] The at least one hydrophilic copolymer present in the hydrophilic layer may 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%, based on the total number (or moles) of repeating units in the hydrophilic copolymer, including the total amount of (a) repeating units, (b) repeating units, and any other repeating units not defined as (a) repeating units and (b) repeating units.

[0101] The at least one hydrophilic copolymer present in the hydrophilic layer may comprise (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%, based on the total number (or moles) of repeating units in the hydrophilic copolymer, including the total amount of (a) repeating units, (b) repeating units, and any other repeating units not defined as (a) repeating units and (b) repeating units.

[0102] Based on the total number (or mole) of repeating units, the hydrophilic copolymer may include up to 35 mol% of repeating units that are not (a) repeating units or (b) repeating units. Those skilled in the art can determine the suitable monomers for providing these optional repeating units. However, the useful optional repeating units that are not (a) repeating units or (b) repeating units can be repeating units that comprise at least one carboxylic acid group, and the amount of such optional repeating units can be generally less than 30 mol%, and more generally less than 20 mol%, all based on the total number (or mole) of repeating units in the hydrophilic polymer. In some embodiments of the invention, the hydrophilic copolymer incorporated into the hydrophilic layer only contains (a) repeating units and (b) repeating units as defined above.

[0103] Particularly useful hydrophilic copolymers comprise (a) repeating units at least partially derived from one or more of methacrylamide and acrylamide and (b) repeating units at least derived from vinylphosphonic acid. In some embodiments of the invention, the hydrophilic copolymer comprises only such (a) repeating units and (b) repeating units.

[0104] Mixtures of such essential hydrophilic copolymers can be used in the hydrophilic layer in any suitable weight combination. In addition, the hydrophilic layer can include one or more other optional hydrophilic homopolymers or copolymers, each of which is different in composition from those having (a) repeating units and (b) repeating units described above. Such optional hydrophilic polymers are known in the art and, if present, typically account for less than 70 weight % of the total weight of the hydrophilic layer. Therefore, each of the one or more essential hydrophilic copolymers having (a) repeating units and (b) repeating units as described above accounts for at least 30 weight % and more likely at least 70 weight % of the total weight of the hydrophilic layer, particularly after at least 95 weight % of the coating solvent has been removed from the hydrophilic layer formulation provided.

[0105] Ethylenically unsaturated polymerizable monomers useful in preparing the hydrophilic copolymer or mixture of hydrophilic copolymers can be obtained from various commercial sources or prepared using known ethylenically unsaturated polymerizable monomers and polymerization conditions.

[0106] The hydrophilic layer and the hydrophilic layer formulation may contain small amounts of additives such as those readily known in the art, 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 the resulting hydrophilic layers are described below with respect to the working examples.

[0107] The process for forming the hydrophilic layer can be carried out in any suitable manner, such as described, for example, in

[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 such as water directly to the outer alumina layer, and then drying the resulting wet coating. It is expected that during or after the formation of the hydrophilic layer, the -OH groups in the repeating units (b) that are bound or linked to the phosphorus atoms react at least partially with the surface of the multilayer alumina structure to form PO-Al linkages.

[0108] After all these necessary treatments, the resulting inventive substrate in any suitable form (eg, a flat sheet or a continuous web or roll) is ready for the preparation of lithographic printing plate precursors according to the invention.

[0109] Radiation-sensitive imageable layers and precursors

[0110] One or more press-developable radiation-sensitive imageable layers can be formed or disposed on the hydrophilic layer of the inventive substrate in a suitable manner 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.

[0111] Negative-working lithographic printing plate precursors:

[0112] The precursor of the present invention can be formed by suitably applying a negative-working radiation-sensitive composition, as described below, which can be developed on-press, to a suitable inventive substrate (as described above) to form a radiation-sensitive imageable layer on the substrate. Generally speaking, 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 are described in more detail below. Typically, there is only a single negative-working radiation-sensitive imageable layer in the precursor. It is typically the outermost layer in the precursor, but in some embodiments, there may be an outermost hydrophilic overcoat (also known as a topcoat or oxygen barrier layer) disposed on the single negative-working radiation-sensitive imageable layer.

[0113] Thus, the components (type and form of compounds and respective amounts) of the radiation-sensitive imageable layer that can be developed on-press are 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. Further details of on-press developability are described below.

[0114] 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 (and 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.

[0115] Useful free radical polymerizable components can contain one or more free radical polymerizable monomers or oligomers, and it has one or more ethylenically unsaturated groups (such as 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, such as urethane acrylate and urethane methacrylate, epoxide acrylate and epoxide methacrylate, polyester acrylate and polyester methacrylate, polyether acrylate and polyether methacrylate and unsaturated polyester resin.In some embodiments, free radical polymerizable components include carboxyl groups.

[0116] 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 thus make 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 as a particulate material, the component 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 polymer binder (described below) is not necessary but may still be present.

[0117] 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, a free radical polymerizable component can be prepared by using a hexamethylene diisocyanate-based The free radical polymerizable component was prepared by reacting N100 aliphatic polyisocyanate resin (Bayer Corp., Milford, Conn.) with 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.

[0118] Numerous other free radical polymerizable components are known in the art and described in a considerable literature, including PhotoreactivePolymers:TheScienceandTechnologyofResists ,A Reiser,Wiley,NewYork,1989,pp.102-177;BM Monroe, RadiationCuring:ScienceandTechnology , S. P. Pappas, ed., Plenum, New York, 1992, pp. 399-440, A. B. Bohen and P. Walker, "Polymer Imaging" ImagingProcessesandMaterial, 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-tetrazole groups.

[0119] Useful free radically polymerizable components as described above can be readily obtained from various commercial sources or prepared using known starting materials and synthetic methods.

[0120] (a) The 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.

[0121] The on-press developable radiation-sensitive imageable layer used in the present invention further comprises (b) an initiator composition that, in the presence of a suitable radiation absorber, provides free radicals to initiate polymerization of one or more free radically polymerizable components upon exposure of the on-press developable radiation-sensitive imageable layer to suitable imaging radiation. The initiator composition can be a single compound or a combination or system of compounds.

[0122] 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, at least one of which is bonded to the nitrogen, oxygen, or sulfur atom of the aryl moiety; oxime esters and oxime ethers; α-hydroxyacetophenone or α-aminoacetophenone; benzoin ethers and benzoin esters; peroxides; hydroperoxides; azo compounds; 2,4,5-triarylimidazolyl dimers (e.g., "HABIs"); trihalomethyl-substituted triazines; boron-containing compounds; organic borates, such as those described in U.S. Pat. No. 6,562,543 (Ogata et al.); and onium salts.

[0123] Particularly useful in initiator compositions 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 (noted above) and the references cited therein. Examples of onium salts include triphenylsulfonium, diphenyliodonium, diphenyldiazonium, 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 groups.

[0124] 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 Patent 7,524,614 (Tao et al.).

[0125] 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):

[0126]

[0127]

[0128] 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 (noted above) can also be used in the present invention.

[0129] 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.

[0130] Compound A may be represented by structure (I) shown below, and one or more compounds collectively referred to as compound B may be represented by structure (II) or (III) below:

[0131]

[0132] In these structures (I), (II) and (III), R1, R2, R3, R4, R5 and R6 are independently substituted or unsubstituted alkyl groups or substituted or unsubstituted alkoxy groups, each of which has 2-9 carbon atoms (or especially 3-6 carbon atoms). These substituted or unsubstituted alkyl and alkoxy groups can be straight or branched. In many useful embodiments, R1, R2, R3, R4, R5 and R6 are independently substituted or unsubstituted alkyl groups, for example, independently selected substituted or unsubstituted alkyl groups with 3-6 carbon atoms.

[0133] 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 0-4 (i.e., 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 0-4 (i.e., 0, 1, 2, 3 or 4); and X1, X2 and X3 are the same or different anions.

[0134] Useful anions include but are not limited to ClO4 - PF6 - 、BF4 - 、SbF6 - 、CH3SO3 - CF3SO3 - 、C6H5SO3 - 、CH3C6H4SO3 - 、HOC6H4SO3 - 、ClC6H4SO3 - and a borate anion represented by the following structure (IV):

[0135] B - (R 1 )(R 2 )(R 3 )(R 4 )

[0136] (IV)

[0137] where R 1 、R 2 、R 3 and R 4R independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group (including a halogen-substituted aryl group), a substituted or unsubstituted alkenyl group, a substituted or unsubstituted alkynyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted heterocyclic group, or R 1 、R 2 、R 3 and R 4 Two or more of R may be combined together to form a substituted or unsubstituted heterocyclic ring having a boron atom, such ring having up to 7 carbon, nitrogen, oxygen or nitrogen atoms. 1 、R 2 、R 3 and R 4 Optional substituents on may include chloro, fluoro, nitro, alkyl, alkoxy, and acetoxy groups. In some embodiments, all R 1 、R 2 、R 3 and R 4 are identical or different, substituted or unsubstituted aryl groups, such as substituted or unsubstituted phenyl groups, or more likely, all of these groups are unsubstituted phenyl groups. In many embodiments, at least one of X1, X2, and X3 is a tetraarylborate anion containing identical or different aryl groups, or in particularly useful embodiments, one or more is a tetraphenylborate anion or X1, X2, and X3 are each a tetraphenylborate anion.

[0138] Mixtures of compound B compounds represented by structure (II) or (III) may be used if desired. Many useful compounds represented by structures (I), (II) and (III) are available from commercial sources (e.g., Sigma-Aldrich) or can be prepared using known synthetic methods and readily available starting materials.

[0139] Components useful in the initiator compositions described above can be obtained from various commercial sources or prepared using known synthetic methods and starting materials.

[0140] 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 percent and up to and including 20 weight percent, or typically at least 2 weight percent and up to and including 15 weight percent, or even at least 4 weight percent and up to and including 12 weight percent, all based on the total dry weight of the on-press developable radiation-sensitive imageable layer.

[0141] In addition, the radiation-sensitive imageable layer that can be developed on the press further comprises (c) one or more radiation absorbers to provide the desired radiation sensitivity and / or convert the radiation into heat. In some embodiments, the radiation-sensitive layer that can be developed on the press is sensitive to infrared radiation and comprises one or more different infrared radiation absorbers so that the lithographic printing plate precursor can be imaged with a laser that emits infrared radiation (e.g., in response to digital information). The present invention can also be applied to lithographic printing plate precursors designed for imaging with violet lasers having an emission peak of about 405 nm, lithographic printing plate precursors for imaging with visible lasers (e.g., those having an emission peak of about 488 nm or 532 nm), or lithographic printing plate precursors for imaging with UV radiation having a significant emission peak below 400 nm. In such embodiments, the radiation absorber 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 radiation absorbers of this type are described, for example, in U.S. Patent 7,285,372 (Baumann et al.), column 11 (lines 10-43).

[0142] In most embodiments of the present invention, the on-press developable 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.).

[0143] In addition to low molecular weight IR absorbing dyes, IR dye chromophores bonded to polymers can also be used. Additionally, IR dye cations can be used, i.e., the cation is the IR absorbing portion of a dye salt that ionically interacts with a polymer containing carboxyl, sulfo, phospho, or phosphono groups in the side chains.

[0144] The useful radiation absorbers described above can be readily obtained from a variety of commercial sources or prepared using known starting materials and synthetic methods.

[0145] 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.

[0146] In many embodiments, it is optional but desirable that the radiation-sensitive imageable layer that can be developed on the press further comprises one or more (d) polymer binders (or materials that act as polymer binders) for all materials in the indicated layer. Such polymer binders are different from all of the (a), (b), and (c) materials described above. These polymer binders are generally non-crosslinkable and non-polymerizable.

[0147] 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 in, for example, 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 in, for example, WO Publication No. 2015-156065 (Kamiya et al.). Some of such (d) polymer binders may further comprise repeating units having cyano side groups, such as those described in, for example, U.S. Patent No. 7,261,998 (Hayashi et al.).

[0148] Some useful (d) polymer binders can exist in particulate form (i.e., in the form of discrete non-agglomerated 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 evenly distributed in a radiation-sensitive imageable layer that can be developed on-machine. For example, one or more useful (d) polymer binders can exist 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 micrograph and averaging a set of measured values.

[0149] 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 radiation-sensitive imageable layer that can be developed on-press. The average dry thickness (t) in micrometers (μm) is calculated by the following equation:

[0150] t=w / r

[0151] Where w is the dry coating coverage of the press-developable radiation-sensitive imageable layer (in g / m 2 ), and r is 1 g / cm 3 For example, in such embodiments, the (d) polymeric binder may 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.

[0152] The (d) polymeric binder may also have a backbone comprising a plurality (at least two) of urethane moieties and pendant groups comprising polyoxyalkylene segments.

[0153] Other useful (d) polymeric binders may include polymerizable groups such as acrylate groups, methacrylate groups, vinylaryl groups, 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.).

[0154] 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).

[0155] Useful (d) polymeric binders are available from various commercial sources or they can be prepared using known procedures and starting materials, as described, for example, in the publications described above.

[0156] The total (d) polymeric binder can be present in the on-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 on-press developable radiation-sensitive imageable layer.

[0157] Other polymeric materials known in the art (different from the (d) polymeric binder) may be present in the radiation-sensitive imageable layer that can be developed on the machine, and such polymeric materials are generally 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 with various degrees of saponification. More hydrophobic polymeric binders are less developable than the (d) polymeric binders described above and generally 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 generally contain less than 10% by weight, more generally less than 5% by weight, of segments that contribute to the hydrophilicity of the binder and are selected from the group consisting of 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.

[0158] The other optional additive for the radiation-sensitive imageable layer that can be developed on the machine 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 lactone skeleton (having acid dissociation property lactone skeleton), such as those described in U.S. Patent No. 6,858,374 (Yanaka). Such optional additives can be used as printing out coloring agents, and based on the total dry weight of the radiation-sensitive imageable layer that can be developed on the machine, can be by at least 1 wt % and at most and include 10 wt % amount to exist. Other useful printing out coloring agents are known in the art, and can include azo dyes, triarylmethane dyes, cyanine dyes and as described in, for example, spironolactone or spironolactam coloring agents in U.S. Patent Application Publication 2009 / 0047599 (Horne et al.).

[0159] The on-press developable radiation-sensitive imageable layer may include crosslinked polymer particles 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.), having an average particle size of at least 2 μm or at least 4 μm, and up to and including 20 μm. Such crosslinked polymer particles may be present only in the on-press developable radiation-sensitive imageable layer, only in the hydrophilic overcoat (when present (described below)), or in both the on-press developable radiation-sensitive imageable layer and the hydrophilic overcoat (when present).

[0160] The on-press developable radiation-sensitive imageable layer may also include conventional amounts of various other optional addenda, including but not limited to dispersants, humectants, biocides, plasticizers, surfactants for coatability 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 generally greater than 250, as described in U.S. Pat. No. 7,429,445 (Munnelly et al.).

[0161] Hydrophilic topcoat:

[0162] Although in some embodiments of the negative-working lithographic printing plate precursor, the on-press-developable radiation-sensitive imageable layer is the outermost layer with no layers disposed thereon, it is possible that the precursor can be designed with a hydrophilic layer (also referred to in the art as a hydrophilic overcoat, oxygen barrier layer, or topcoat) disposed directly on the on-press-developable radiation-sensitive imageable layer (with no intervening layers between the two layers). When present, such a hydrophilic overcoat is typically the outermost layer of the precursor.

[0163] Such a hydrophilic topcoat may comprise one or more film-forming water-soluble polymeric binders in an amount of at least 60 wt.-% and up to and including 100 wt.-%, based on the total dry weight of the hydrophilic topcoat. Such film-forming water-soluble (or hydrophilic) polymeric binders may include modified or unmodified polyvinyl alcohol having a saponification degree of at least 30%, or to a degree of at least 75%, or to a degree of at least 90%, and up to and including a degree of 99.9%.

[0164] Furthermore, one or more acid-modified polyvinyl alcohols can be used as the film-forming, water-soluble (or hydrophilic) polymer binder in the hydrophilic overcoat layer. For example, at least one modified polyvinyl alcohol can be modified with an acid group selected from the group consisting of carboxylic acid groups, sulfonic acid groups, sulfate groups, phosphonic acid groups, and phosphate groups. Examples of such materials include, but are not limited to, sulfonic acid-modified polyvinyl alcohols, carboxylic acid-modified polyvinyl alcohols, quaternary ammonium salt-modified polyvinyl alcohols, glycol-modified polyvinyl alcohols, or combinations thereof.

[0165] The hydrophilic overcoat 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.).

[0166] Can be at least 0.1g / 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 / m2 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 0.1g / m 2 and up to and including 0.9 g / m 2 , so that the hydrophilic cover layer is relatively thin.

[0167] The hydrophilic overcoat may optionally comprise organic wax particles dispersed within 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.).

[0168] Preparation of lithographic printing plate precursors

[0169] 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 materials described above (for negative-working or positive-working chemistry) can be applied to the invention substrate (typically in the form of a continuous roll or web of substrate as described above) using any suitable equipment and procedures such as spin coating, knife coating, gravure coating, die coating, slot coating, rod coating, wire rod coating, roller coating, or extrusion hopper coating. The radiation-sensitive imageable layer formulation can also be applied to a suitable substrate by spraying. 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 indicated below, thereby providing a radiation-sensitive continuous article that can be in any suitable form (e.g., a web) from which separate precursors can be prepared using known manufacturing processes.

[0170] The manufacturing process generally comprises mixing the various components required for the 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 organic 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 (noted above).

[0171] After suitable drying, the dry coverage of negative-working, on-press developable radiation-sensitive imageable layers (particularly those sensitive to infrared radiation) on the inventive substrates is typically 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, however other dry coverage amounts may be used if desired.

[0172] As described 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.

[0173] 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 a press-developable radiation-sensitive imageable layer disposed on the inventive substrate described above and any optional layers noted above.

[0174] Individual rectangular lithographic printing plate precursors are formed from this resulting continuous radiation-sensitive web or roll by cutting to form 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 using a cut-to-length process at intervals equal to the other dimension of the rectangular lithographic printing plate precursor, thereby forming individual precursors having a square or rectangular form.

[0175] Imaging (exposure) conditions

[0176] 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, most negative-working lithographic printing plate precursors 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., from 250 nm and shorter than 750 nm). The result of such image-wise exposure is to provide exposed and unexposed regions in one or more radiation-sensitive imageable layers that can be developed on-press.

[0177] 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 of multiple wavelengths simultaneously (e.g., using 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 radiation imaging will be readily apparent to those skilled in the art.

[0178] The imaging apparatus can be configured as a flatbed recorder or a drum recorder, wherein the radiation-sensitive lithographic printing plate precursor is mounted on the inner cylindrical surface or the outer cylindrical surface of the drum. An example of a useful infrared imaging apparatus can be a laser diode that emits radiation having a wavelength of about 830 nm. Suitable infrared imaging devices include the Trendsetter platesetter (Eastman Kodak Company) and the NEC AMZISetter X series (NEC Corporation, Japan). Other suitable infrared imaging devices include the Screen PlateRite 4300 series or 8600 series platesetters (available from Screen USA, Chicago, IL) or thermal CTP platesetters from Panasonic Corporation (Japan), which operate at a wavelength of 810 nm.

[0179] The infrared radiation imaging energy can be at least 30mJ / cm 2 and up to and including 500 mJ / cm 2 , and usually at least 50 mJ / cm 2 and up to and including 300 mJ / cm 2 , which depends on the sensitivity of the infrared radiation sensitive imageable layer.

[0180] Useful UV and "violet" imaging devices include 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) imagesetters.

[0181] Can use at least 0.01mJ / cm 2 and up to and including 0.5 mJ / cm 2 Energy of at least 0.5kW / cm 3 and up to and including 50kW / cm 3 Imaging in the UV to visible region of the electromagnetic spectrum and in particular in the UV region (250 nm-450 nm) is performed with a power density of 100 nm.

[0182] Washing (development) and printing

[0183] Exposed negative-working precursor:

[0184] Following image-wise exposure, the exposed negative-working, radiation-sensitive, on-press developable lithographic printing plate precursor having exposed and unexposed areas in the on-press developable radiation-sensitive imageable layer can be processed in a suitable manner to remove the unexposed areas and any hydrophilic overcoat, if present, and to leave the hardened exposed areas intact.

[0185] For example, the negative-working lithographic printing plate precursor of the present invention is developed on-press using a lithographic ink, a fountain solution, or a combination of a lithographic ink and a fountain solution. In such embodiments, the imaged radiation-sensitive lithographic printing plate precursor according to the present invention can be mounted on a printing press and then the printing operation can be started. When preparing the initial printed sheets, the unexposed areas in the radiation-sensitive imageable layer are removed by a suitable fountain solution, a 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).

[0186] In a typical printing press starting with a sheet-fed press, the dampening rollers are first engaged and fountain solution is supplied to the mounted imaged precursor to swell the exposed radiation-sensitive imageable layer at least in the unexposed areas. After several rotations, the inking rollers are engaged and they 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, the printing sheet is supplied to remove the unexposed areas of the radiation-sensitive imageable layer from the lithographic printing plate, as well as material on the blanket cylinder (if present), using the formed ink and fountain solution emulsion.

[0187] The present invention provides at least the following embodiments:

[0188] 1. A lithographic printing plate precursor comprising:

[0189] a substrate having a flat surface, and

[0190] a press-developable radiation-sensitive imageable layer disposed on the planar surface of the substrate,

[0191] The substrate includes:

[0192] an aluminum-containing plate having a ground and etched flat surface;

[0193] An inner aluminum oxide layer disposed on the grained and etched flat surface, the inner aluminum oxide layer having an average dry thickness (Ti ), and comprising an average internal micropore diameter (D i ) a large number of internal micropores;

[0194] An outer aluminum oxide layer is disposed on the inner aluminum oxide layer, the outer aluminum oxide layer comprising an average outer micropore size (D) of at least 15 nm and up to and including 30 nm. o ) of a plurality of external micropores and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o );and

[0195] At least 0.0002g / m 2 and up to and including 0.1 g / m 2 A hydrophilic layer is provided on the outer alumina layer with a dry coverage of 100%, and the hydrophilic layer comprises one or more hydrophilic polymers, at least one of which is a hydrophilic copolymer comprising at least (a) repeating units and (b) repeating units, (a) repeating units comprising amide groups, (b) repeating units comprising -OM groups directly attached to phosphorus atoms, wherein M represents a hydrogen, sodium, potassium or aluminum atom.

[0196] 2. The lithographic printing plate precursor of embodiment 1, wherein the outer aluminum oxide layer 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.

[0197] 3. The lithographic printing plate precursor of embodiment 2, wherein the outer aluminum oxide layer 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 internal micropore diameter (D i ) is less than 15 nm and smaller than the average external micropore diameter (D o ).

[0198] 4. The lithographic printing plate precursor of embodiment 2 or 3, wherein the substrate further comprises a middle aluminum oxide layer disposed between the inner aluminum oxide layer and the outer aluminum oxide layer, wherein the middle aluminum oxide layer has an average dry thickness (T m), and comprising an average median micropore diameter (D) of at least 20 nm and up to and including 60 nm m ) of a large number of central micropores, among which D m >D o >D i , and the average dry thickness of the outer aluminum oxide layer (T o ) is less than 150nm.

[0199] 5. The lithographic printing plate precursor of any of embodiments 2-4, wherein the outer alumina layer is disposed directly on the inner alumina layer, and the average micropore size (D i ) is at least 20 nm and is larger than the average pore size (D o ).

[0200] 6. The lithographic printing plate precursor of any of embodiments 1-5, wherein (a) the repeating unit is present in the copolymer in an amount of at least 60 mol% and up to and including 97 mol%, and (b) the repeating unit is present in the copolymer 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 hydrophilic copolymer.

[0201] 7. The lithographic printing plate precursor of any of embodiments 1-6, wherein the press-developable radiation-sensitive imageable layer is negative-working and comprises:

[0202] (a) one or more free radically polymerizable components;

[0203] (b) an initiator composition that provides free radicals when the radiation-sensitive imageable layer is exposed to imaging radiation;

[0204] (c) one or more radiation absorbers; and optionally

[0205] (d) A polymer binder different from all of (a), (b) and (c).

[0206] 8. The lithographic printing plate precursor of any of embodiments 2-7, wherein P o Greater than or equal to 0.3 and less than or equal to 0.6.

[0207] 9. The lithographic printing plate precursor of any of embodiments 1 to 8, wherein the hydrophilic copolymer in the hydrophilic layer comprises (a) repeating units derived from at least one or more of methacrylamide and acrylamide and (b) repeating units derived from at least vinylphosphonic acid.

[0208] 10. The lithographic printing plate precursor of any of embodiments 1-9, 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.

[0209] 11. The lithographic printing plate precursor of any of embodiments 7 to 10, wherein the on-press developable negative-working radiation-sensitive layer further comprises (d) a polymeric binder in the form of microparticles.

[0210] 12. The lithographic printing plate precursor of any of embodiments 1-11 further comprising a hydrophilic overcoat disposed on the on-press developable radiation-sensitive imageable layer.

[0211] 13. The lithographic printing plate precursor of any of embodiments 7 to 12, wherein the on-press developable radiation-sensitive layer is infrared radiation-sensitive and comprises two or more free radical polymerizable components.

[0212] 14. A method for providing a lithographic printing plate, comprising:

[0213] imagewise exposing the lithographic printing plate precursor of any of embodiments 1-13 to imaging radiation to form an imagewise exposed imageable layer having exposed regions and unexposed regions, and

[0214] The unexposed areas are removed on-press from the imagewise exposed imageable layer to form a lithographic printing plate.

[0215] 15. The method of embodiment 14, wherein the unexposed areas of the imagewise exposed imageable layer are removed on-press using a lithographic ink, a fountain solution, or both.

[0216] 16. The method of embodiment 14 or 15, wherein the image-wise exposure is performed using infrared radiation.

[0217] 17. The method of claim 14, wherein the imagewise exposing is performed off-press using infrared radiation and the unexposed areas of the imagewise exposed imageable layer are removed on-press using lithographic ink, fountain solution, or both.

[0218] 18. A method for preparing the lithographic printing plate precursor of any of embodiments 1 to 13, comprising, in order:

[0219] providing an aluminum-containing plate having an electrochemically or mechanically ground and etched flat surface;

[0220] The aluminum-containing plate is subjected to a first anodizing treatment to form an outer aluminum oxide layer on the electrochemically or mechanically grained and etched flat surface, the outer aluminum oxide layer comprising an average outer micropore size (D) of at least 15 nm and up to and including 30 nm.o ) of a plurality of external micropores and having an average dry thickness (T of at least 30 nm and up to and including 650 nm) o );

[0221] Rinsing the outer aluminum oxide layer;

[0222] The aluminum-containing plate is subjected to a second anodizing process to form an inner aluminum oxide layer beneath the outer aluminum oxide layer, the inner aluminum oxide layer having an average dry thickness (T i ); and comprising an average internal micropore diameter (D i ) a large number of internal micropores;

[0223] rinsing the outer aluminum oxide layer and the inner aluminum oxide layer;

[0224] forming a press-developable radiation-sensitive imageable layer on the outer aluminum oxide layer; and

[0225] After rinsing the outer and inner aluminum oxide layers and before forming a press-developable radiation-sensitive imageable layer on the outer aluminum oxide layer, a hydrophilic layer is provided on the outer aluminum oxide layer, the hydrophilic layer comprising one or more hydrophilic polymers, at least one of the hydrophilic polymers being a hydrophilic copolymer 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 is coated with at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 The dry coverage is set on the outer aluminum oxide layer.

[0226] 19. The method of embodiment 18, wherein the on-press developable radiation-sensitive layer is infrared radiation-sensitive and negative-working, and comprises:

[0227] (a) one or more free radically polymerizable components;

[0228] (b) an initiator composition that provides free radicals when the radiation-sensitive imageable layer is exposed to imaging radiation;

[0229] (c) one or more radiation absorbers; and optionally

[0230] (d) A polymer binder different from all of (a), (b) and (c).

[0231] The following examples are provided to illustrate the practice of the invention and are not intended to be limiting in any way.

[0232] Inventive Examples 1-3 and Comparative Examples 1-5:

[0233] The aluminum-containing substrates A and B used to prepare the negative-working lithographic printing plate precursors of Inventive Examples 1-3 and Comparative Examples 1-5 were prepared according to the general method described above.

[0234] Type A substrate:

[0235] Hydro 1052 aluminum alloy strips or meshes (available from Norsk Hydro ASA, Norway) with a thickness of 0.28 mm were used as aluminum-containing "plate" raw materials or supports. Both the pre-etching and post-etching steps were performed in alkaline solutions under known conditions. Roughening (or grinding) of these etched aluminum supports was performed by electrochemical means in a hydrochloric acid solution at about 23° C. to obtain an arithmetic mean roughness (Ra) of 0.5 μm on the flat surface of the aluminum-containing support. Thereafter, the aluminum-containing support was subjected to two separate anodizing treatments as described in U.S. Patent Application Publication 2018 / 0250925 (noted above). The first anodizing treatment was performed using phosphoric acid as the electrolyte to form an average micropore size (D o ) is 19 nm and the average dry thickness (T o ) of an outer aluminum oxide layer of 190 nm. A second anodizing treatment was then performed using sulfuric acid as an electrolyte to form an average micropore diameter (D i ) is <10 nm and the average dry thickness (T i ) is an inner aluminum oxide layer of 800 nm. These two anodization steps are performed in a continuous process on a typical manufacturing line for making lithographic printing plate precursors.

[0236] Type B substrate:

[0237] Hydro 1052 aluminum alloy strips or meshes with 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 and post-etching steps were carried out in alkaline solutions under known conditions. Roughening (or grinding) of the etched aluminum support was performed by electrochemical means in a hydrochloric acid solution at about 23° C. to obtain an arithmetic mean roughness (Ra) of 0.5 μm on the flat surface of the aluminum-containing support. Thereafter, the aluminum-containing substrate was subjected to two separate anodizing treatments. The first anodizing treatment was performed using phosphoric acid as the electrolyte to form an average micropore size (D o ) is 19 nm and the average dry thickness (T o ) of an outer aluminum oxide layer of 60 nm. A second anodization treatment was then performed using phosphoric acid as an electrolyte to form an average micropore size (D i ) is 70 nm and the average dry thickness (T i) is an inner aluminum oxide layer of 500 nm. These two anodization steps are performed in a continuous process on a typical manufacturing line for making lithographic printing plate precursors.

[0238] Synthesis of polymer 1 for use in the hydrophilic layer:

[0239] Polymer 1 is a hydrophilic copolymer derived from vinylphosphonic acid and acrylamide (molar ratio of 1:9) as ethylenically unsaturated polymerizable monomers. Ethanol (3500g) is loaded into a 10-liter reaction vessel with a condenser and heated at 70°C. Vinylphosphonic acid (231.1g) and acrylamide (1368.9g) monomers are mixed into 1000g of ethanol. AIBN (52g) polymerization initiator is dissolved in the resulting monomer mixture and then added dropwise to the reaction vessel at 70°C over 4 hours. After adding this monomer mixture, the reaction mixture is kept at 70°C for 2 hours and then cooled to room temperature. The precipitated white powder is separated by filtration and washed with 1 liter of ethanol to provide a yield of 1550g of polymer 1.

[0240] Synthesis of polymer 2 for use in the hydrophilic layer:

[0241] Polymer 2 is a copolymer derived from vinylphosphonic acid and methacrylic acid (molar ratio of 2:8) monomers and is outside the scope of the present invention. Ethyl acetate (3650g) is loaded into a 10-liter reaction vessel with a condenser and heated to 70°C. Vinylphosphonic acid monomer (390g) and methacrylic acid (1243g) are mixed into 1000g of ethyl acetate. AIBN (52g) polymerization initiator is dissolved in the resulting monomer mixture. The monomer mixture is added dropwise to the reaction vessel at 70°C over 4 hours. After the monomer mixture is added, the reaction mixture is kept at 70°C for 2 hours and cooled to room temperature. The precipitated white powder is separated by filtration and washed with 1 liter of ethyl acetate to provide a yield of 1580g of polymer 2.

[0242] Preparation of hydrophilic layer formulation:

[0243] Hydrophilic layer formulations HL-1 to HL-6 were prepared having the materials and amounts shown in Table I below.

[0244] Table 1: Hydrophilic layer formulation

[0245] 1000 polymer is an aqueous solution of polyacrylic acid (50 wt%) obtained from The Dow Chemical Company.

[0246] PVPS30 is an aqueous solution of polyvinylphosphonic acid (30 wt %) obtained from Merck Performance Materials GmbH.

[0247] D-410-GL is a leveling agent obtained from Takemoto Oil & Fat Co., Ltd.

[0248] Each hydrophilic layer formulation shown in Table 1 was coated onto a Type A substrate sample or a Type B substrate sample as described above. Each hydrophilic layer formulation was coated using a re-wound coating bar and dried at 80°C for 2 minutes to provide a hydrophilic layer on the outer aluminum oxide layer, and then dried to a 0.03 g / m 2 As shown in Table II below, inventive substrate samples or comparative substrate samples having a hydrophilic layer were prepared.

[0249] Table II

[0250] Substrate type hydrophilic layer Invention Example 1 Type A HL-1 Invention Example 2 Type A HL-2 Invention Example 3 Type B HL-1 Comparative Example 1 Type A HL-3 Comparative Example 2 Type A HL-4 Comparative Example 3 Type A HL-5 Comparative Example 4 Type A HL-6 Comparative Example 5 Type B HL-3

[0251] Preparation of negative-working on-press developable infrared radiation-sensitive coating formulations:

[0252] Coating formulations for negative-working, press-developable, infrared radiation-sensitive imageable layers were prepared using the components and amounts shown in Tables III and IV below, dissolved or dispersed at a total solids content of 5 weight percent in a coating medium containing a solvent mixture of 35 weight percent n-propanol, 20 weight percent 2-methoxypropanol, 35 weight percent 2-butanone, and 10 weight percent water.

[0253] The starting materials identified in Table IV below can be obtained from one or more commercial sources of chemicals or prepared using known synthetic methods and starting materials.

[0254] Table III

[0255] Table IV

[0256]

[0257] Negative-working, press-developable, radiation-sensitive imageable layers were prepared by coating the formulations described in Table III onto the substrate samples indicated above in Table II using a wire-wound coating rod and drying the coatings at 80° C. for 2 minutes to provide the indicated infrared radiation-sensitive imageable layers having a % RI of 1 g / m². 2 The dry coverages were provided for evaluation of the lithographic printing plate precursors as Inventive Examples 1-3 and Comparative Examples 1-5.

[0258] After imaging, samples of each of the prepared lithographic printing plate precursors were evaluated for plate run, on-press developability (DOP) and restart toning (RST) properties using the test methods described below, and the results are shown in Table V below.

[0259] A commercially available Kodak Magnus 800 imagesetter was used with a 150 mJ / cm2 solid area 2 The infrared radiation exposure energy was used to image respective samples of the prepared lithographic printing plate precursors.

[0260] On-press developability (DOP):

[0261] Samples of the lithographic printing plate precursors (both inventive and comparative) were imaged as described above and mounted on a commercial Roland R-201 printing press for on-press development. The press was supplied with a fountain solution of Presarto WS100 (DIC Graphics) / isopropyl alcohol / water (1 / 1 / 98 by volume), an S-7400 rubber blanket (Kin-yo-sha), OK Top Coated Matt N Grade paper (Oji paper) as the printing paper, and lithographic ink Fusion G Magenta N (DIC Graphics), and printing was carried out at a print rate of 9,000 sheets / hour. On-press developability was assessed by recording the number of printed sheets from the start of printing, after which no ink transfer was observed in the unimaged (unexposed) areas. A DOP of less than 50 sheets is preferred, and a DOP of more than 100 sheets is unacceptable for the stated press conditions.

[0262] Restart color grading (RST):

[0263] Samples of each lithographic printing plate precursor (both inventive and comparative) were imaged as described above and mounted on a commercial Roland R-201 printing press for on-press development. The press was supplied with a fountain solution of Presarto WS100 (DIC Graphics) / isopropyl alcohol / water in a volume ratio of 1:1:98, an S-7400 rubber blanket (Kin-yo-sha), Oji paper (OK Top Coated Matt N Grade), and lithographic ink Fusion G Magenta N (DIC Graphics), and printing was carried out at a print rate of 9,000 sheets per hour. When 1,000 sheets had been printed under these printing conditions, printing was stopped. Each lithographic printing plate on the press cylinder was then heated for 30 minutes using hot air generated by a dryer, and printing was then restarted for each heated lithographic printing plate. Restart toning (RST) properties were evaluated by observing the number of printed sheets required to achieve a perfect clean in the unimaged area after restarting printing. A satisfactory result for RST is less than 100 printed impressions under the indicated printing conditions, which are commonly used in the industry for negative-working, on-press developable lithographic printing plate precursors that have been imaged using infrared radiation.

[0264] Printing plate run strength:

[0265] At 150mJ / cm 2 Samples of each lithographic printing plate precursor (both inventive and comparative precursors) were exposed as indicated above at an energy rate of 1.5 Å. Each imaged precursor was then mounted on a commercial Komori S-26 printing press at 8,000 rpm, and the press life of the printing plates was evaluated using a fountain solution of 1% Presarto WS100 (DIC Graphics) and a 10% isopropyl alcohol in water mixture, an S-7400 rubber blanket (Kin-yo-sha), OK Top Coated Matt N Grade paper (Oji paper) as the printing paper, and a lithographic ink, Fusion G Magenta N (DIC Graphics). The lithographic printing plates were developed on-press in the early stages of printing. As the number of printed sheets (printed sheets) increased through continuous printing, the imaged radiation-sensitive layer of each lithographic printing plate gradually wore away, and its ink receptivity deteriorated. Consequently, as printing continued for extended periods, the ink density on the printed sheets decreased. The plate run length is determined by observing the number of printed sheets when the reflection density of the solid areas on the printed sheet has dropped to 90% of the reflection density observed on the printed sheet at the start of printing.

[0266] Table V below shows the results of RST, plate run length, and DOP for each of the inventive and comparative examples, measured in terms of the number of sheets (or press sheets) printed.

[0267] Table V

[0268] RST Printing plate run DOP Invention Example 1 50 100,000 30 Invention Example 2 50 100,000 30 Invention Example 3 50 95,000 28 Comparative Example 1 200 100,000 30 Comparative Example 2 200 100,000 30 Comparative Example 3 200 100,000 30 Comparative Example 4 350 100,000 35 Comparative Example 5 150 95,000 28

[0269] The results show that the precursors of Inventive Examples 1, 2, and 3 having an inventive substrate containing a unique hydrophilic layer disposed on an outer aluminum oxide layer exhibit faster RST recovery than Comparative Examples 1-5, while the plate run and on-press developability properties remain acceptable.

Claims

1. A lithographic printing plate precursor comprising: a substrate having a flat surface, and a press-developable radiation-sensitive imageable layer disposed on the planar surface of the substrate, wherein the substrate comprises: an aluminum-containing plate having a ground and etched flat surface; An inner aluminum oxide layer disposed on the grained and etched planar surface, the inner aluminum oxide layer having an average dry thickness T of at least 300 nm and at most 3,000 nm i , and comprising an average internal micropore diameter D less than or equal to 100 nm i A large number of internal micropores; An outer aluminum oxide layer is disposed on the inner aluminum oxide layer, the outer aluminum oxide layer comprising an average outer micropore diameter D of at least 15 nm and at most 30 nm. o a large number of external micropores and having an average dry thickness T of at least 30 nm and at most 650 nm o ;and At least 0.0002g / m 2 And at most 0.1g / m 2 A hydrophilic layer is provided on the outer alumina layer with a dry coverage of , and the hydrophilic layer comprises one or more hydrophilic polymers, at least one of the hydrophilic polymers is a hydrophilic copolymer comprising at least repeating units a and b, the repeating units a comprising an amide group, the repeating units b comprising an -OM group directly connected to the phosphorus atom, wherein M represents a hydrogen, sodium, potassium or aluminum atom.

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

3. The lithographic printing plate precursor of claim 2, wherein the outer aluminum oxide layer has an average dry thickness T of at least 130 nm. o , and the outer aluminum oxide layer is directly disposed on the inner aluminum oxide layer; the average dry thickness T of the inner aluminum oxide layer i is at least 650 nm, and the average internal pore diameter D i Less than 15nm and smaller than the average external micropore diameter D o .

4. The lithographic printing plate precursor of claim 2, wherein the substrate further comprises a middle aluminum oxide layer disposed between the inner aluminum oxide layer and the outer aluminum oxide layer, wherein the middle aluminum oxide layer has an average dry thickness T of at least 60 nm and at most 300 nm. m , and comprising an average median micropore diameter D of at least 20 nm and at most 60 nm m A large number of central micropores, among which D m >D o >D i , and the average dry thickness of the outer aluminum oxide layer is T o Less than 150nm.

5. The lithographic printing plate precursor of claim 2, wherein the outer aluminum oxide layer is directly disposed on the inner aluminum oxide layer, and the average micropore size D of the inner aluminum oxide layer is i At least 20 nm and larger than the average micropore size D of the outer aluminum oxide layer o .

6. The lithographic printing plate precursor of claim 1 , wherein the repeating unit a is present in the copolymer in an amount of at least 60 mol % and at most 97 mol %, and the repeating unit b is present in the copolymer in an amount of at least 3 mol % and at most 40 mol %, all based on the total number of repeating units in the hydrophilic copolymer.

7. The lithographic printing plate precursor of claim 1 wherein the on-press developable radiation-sensitive imageable layer is negative-working and comprises: one or more free radical polymerizable components; an initiator composition that provides free radicals when the radiation-sensitive imageable layer is exposed to imaging radiation; one or more radiation absorbers; and optionally a polymeric binder that is distinct from all of the free radically polymerizable components, the initiator composition, and the radiation absorber.

8. The lithographic printing plate precursor of claim 2, wherein P o Greater than or equal to 0.3 and less than or equal to 0.

6.

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

10. The lithographic printing plate precursor of claim 1 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.

11. The lithographic printing plate precursor of claim 7 wherein the on-press developable radiation-sensitive imageable layer further comprises a polymeric binder in the form of microparticles.

12. The lithographic printing plate precursor of claim 1 further comprising a hydrophilic overcoat disposed on the on-press developable radiation-sensitive imageable layer.

13. The lithographic printing plate precursor of claim 7 wherein the on-press developable radiation-sensitive imageable layer is infrared radiation sensitive and comprises two or more free radically polymerizable components.

14. A method for providing a lithographic printing plate, comprising: imagewise exposing the lithographic printing plate precursor of claim 1 to imaging radiation to form an imagewise exposed imageable layer having exposed regions and unexposed regions, and The unexposed 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 unexposed regions in the imagewise exposed imageable layer are removed on-press using lithographic ink, fountain solution, or both lithographic ink and fountain solution.

16. The method of claim 14, wherein the imagewise exposure is performed using infrared radiation.

17. The method of claim 14 wherein the imagewise exposing is performed off-press using infrared radiation and the unexposed areas of the imagewise exposed imageable layer are removed on-press using lithographic ink, fountain solution, or both.

18. A method for preparing a lithographic printing plate precursor comprising, in sequence: providing an aluminum-containing plate having an electrochemically or mechanically ground and etched flat surface; The aluminum-containing plate is subjected to a first anodizing treatment to form an outer aluminum oxide layer on the electrochemically or mechanically grained and etched flat surface, the outer aluminum oxide layer comprising an average outer micropore size D of at least 15 nm and at most 30 nm. o a plurality of external micropores and having an average dry thickness T of at least 30 nm and at most 650 nm o ; rinsing the outer aluminum oxide layer; The aluminum-containing plate is subjected to a second anodizing treatment 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 at most 3,000 nm. i ; and comprising an average internal micropore diameter D less than or equal to 100 nm i A large number of internal micropores; rinsing the outer aluminum oxide layer and the inner aluminum oxide layer; forming a radiation-sensitive imageable layer that is developable on-press on the outer aluminum oxide layer; and After rinsing the outer and inner aluminum oxide layers and before forming the press-developable radiation-sensitive imageable layer on the outer aluminum oxide layer, a hydrophilic layer is provided on the outer aluminum oxide layer, the hydrophilic layer comprising one or more hydrophilic polymers, at least one of the hydrophilic polymers being a hydrophilic copolymer comprising at least repeating units a and b, the repeating units a comprising amide units, the repeating units b comprising -OM groups directly attached to phosphorus atoms, wherein M represents a hydrogen, sodium, potassium, or aluminum atom, and the hydrophilic layer having a density of at least 0.0002 g / m 2 And at most 0.1g / m 2 A dry coverage of 500 nm is provided on the outer alumina layer.

19. The method of claim 18 wherein the on-press developable radiation-sensitive imageable layer is infrared radiation-sensitive and negative-working and comprises: one or more free radical polymerizable components; an initiator composition that provides free radicals when the radiation-sensitive imageable layer is exposed to imaging radiation; one or more radiation absorbers; and optionally a polymeric binder that is distinct from all of the free radically polymerizable components, the initiator composition, and the radiation absorber.

20. The method of claim 18, wherein the hydrophilic copolymer in the hydrophilic layer comprises at least repeating units a derived from one or more of methacrylamide and acrylamide and at least repeating units b derived from vinylphosphonic acid, and the repeating units a are present in the hydrophilic copolymer in an amount of at least 60 mol% and at most 97 mol%, and the repeating units b are present in the hydrophilic copolymer in an amount of at least 3 mol% and at most 40 mol%, all based on the total number of repeating units in the hydrophilic copolymer.

Images