Lithographic printing plate precursor and method of use

Abstract

The IR-sensitive lithographic printing plate precursors provide stable print output using a unique IR-sensitive image-recording layer. The IR radiation-sensitive layer contains component (1) a free-radical initiator composition, component (2) a free-radical polymerizable composition, and component (3) a color-changing compound of structure (I) having an indene structure in the conjugated chain between aromatic end groups. A specific group, such as a halo group, is directly or indirectly attached to the indene structure. The IR-sensitive image-recording composition and layer also contain one or more borate ions. After infrared imaging, these precursors exhibit desirable new or initial print output and print output after dark storage. These precursors can be developed on-press.

Description

[Technical Field]

[0001] The present invention relates to an infrared-sensitive lithographic printing plate precursor that can be imaged using infrared light to provide an imaged lithographic printing plate. Such a plate precursor contains a unique infrared-sensitive composition that provides a stable print output image between exposed and unexposed areas of an imagewise exposed infrared-sensitive image-recording layer. The present invention also relates to a method for using such a plate precursor to provide a lithographic printing plate with an excellent print output image. [Background technology]

[0002] In lithographic printing, lithographic ink-receptive areas, also known as image areas, are produced on the hydrophilic surface of a planar substrate, such as an aluminum-containing substrate. When the printing plate surface is moistened with water and lithographic ink is applied, the hydrophilic areas of the aluminum-containing substrate retain the water and repel the lithographic ink, while the lithographic ink-receptive image areas accept the lithographic ink and repel the water. The lithographic ink is transferred to the surface of the material, possibly using a blanket roller on the printing press, thereby reproducing the image.

[0003] Negative-working lithographic printing plate precursors useful for producing lithographic printing plates typically comprise a negative-working radiation-sensitive image-recording layer disposed on the hydrophilic surface of an aluminum-containing substrate. Such image-recording layers comprise radiation-sensitive components that can be dispersed in a suitable polymer binder material. After the precursor is imagewise exposed to suitable radiation to form exposed and unexposed areas in the image-recording layer, the unexposed areas are removed by suitable means to reveal the underlying hydrophilic surface of the aluminum-containing substrate. The unremoved exposed areas of the image-recording layer are lithographic ink-receptive, and the hydrophilic aluminum-containing substrate surface exposed by the development process accepts water and aqueous solutions, such as fountain solution, and repels lithographic printing ink.

[0004] In recent years, the lithographic printing industry has seen an increasing demand for simplification in the manufacture of lithographic printing plates by performing on-press development (identified herein as "DOP") using lithographic ink or a fountain solution, or both, to remove the unexposed areas of the image-recording layer once the lithographic press is initiated. After laser imaging, on-press developable masters can be mounted directly on a printing press without a prior wet chemical step to remove the image-recording layer coating of the master in the non-printing areas.

[0005] Therefore, it is highly desirable for such imaged lithographic printing plate precursors to have different colors, i.e., "contrast," between exposed and unexposed areas. This color difference, i.e., contrast, is typically referred to as a "printed output" or a "printed output image." A dark printed output makes it easier for an operator to visually evaluate and identify the imaged printing plate precursor so that it can be properly mounted in a printing press unit.

[0006] Many approaches have been taken to increase the density and stability of the print output produced with on-press developable printing plate precursors, and all of these approaches have been observed to have certain drawbacks.

[0007] For example, the printout from an imaged master plate having an imaging composition containing an acid generator and an acid-sensitive color precursor, such as a lactone-based leuco dye, is often not sufficiently dense. This is because the efficiency of acid generation is limited in imaging compositions designed for infrared imaging and on-press development. Furthermore, the concentration of protons generated during infrared imaging often decreases after imaging due to chemical equilibrium or other post-imaging chemical reactions. As a result, the printout based on proton-induced color changes often fades after imaging. This printout has limited image stability.

[0008] U.S. Patent Application Publication No. 2021 / 0078350 (Viehmann et al.) describes an approach to increasing print output by incorporating color-forming compounds into infrared-sensitive imaging compositions that are more sensitive and switch from a colorless form to a colored form at lower acid concentrations. Special additives suppress background coloration to stabilize good contrast in the print output. While the initial print output obtained is very high, there remains a need to improve the print output and its stability when using the described chemistry.

[0009] Another approach to producing a printed output is based on the use of infrared (IR) decomposable dyes. These dyes contain heat-labile groups, which can be lost when exposed to infrared light or heat to form compounds of various colors with absorption spectra in the visible spectral region. This approach is described in U.S. Pat. Nos. 8,148,042 (Callant et al.) and 8,178,282 (Callant et al.), and U.S. Patent Application Publication No. 2010 / 0274023 (Callant et al.). To produce a sufficient printed output, such IR decomposable dyes typically must be present in relatively large amounts in the image-forming composition, or higher infrared exposure energy is required at lower amounts.

[0010] Furthermore, some IR-decomposable dyes used in such chemical reactions produce gaseous materials upon decomposition. These gaseous materials are often disadvantageous for negative-tone compositions that utilize crosslinking of free-radical polymerizable compounds in the presence of a suitable free-radical initiator, resulting in reduced image durability during lithographic printing operations. Furthermore, the heat pulses generated from the high-energy levels of exposing infrared radiation can often compromise the physical integrity of the imaging composition, a process commonly referred to as ablation or partial ablation. Ablation or partial ablation typically results in reduced image durability. For example, U.S. Pat. No. 8,148,042 (noted above) describes printing plate precursors PPP34 and PPP35, which contain IR-decomposable dyes in the imaging composition, requiring 275 mJ / cm to produce cyan print outputs (ΔOD) of 0.43 and 0.60. 2 There is no teaching that such imaging compositions are useful for forming printing plates that have sufficient durability in the infrared exposed areas after any type of development.

[0011] When the IR decomposable dyes taught in U.S. Pat. No. 8,148,042 (noted above) are incorporated directly into the polymerizable composition, more practical exposure energies, e.g., 120 mJ / cm 2 The inability to produce a dense print output below this energy level is demonstrated in US Patent Application Publication No. 2020 / 0147950 (Billiet), where PPP04, using the IR-degradable dye IR02 in combination with IR01 used in PPP03, provided only a slight improvement in print output compared to PPP03 (e.g., 120 mJ / cm). 2 (ΔE of 2.99 vs. 2.12). Billiet's ΔE parameter is the same as the ΔE parameter defined below.

[0012] To avoid the ineffectiveness and undesirable effects of IR-decomposable dyes on negative-working printing plate precursors containing polymerizable imaging compositions, WO 2019 / 219560 (Billiet et al.) teaches disposing the IR-decomposable dye in a protective overcoat applied over the imageable layer containing the IR-imageable composition. However, the presence of a protective layer in a lithographic printing plate precursor requires an extra step during manufacturing, and its removal, if present, reduces development speed. Furthermore, the protective layer may release polymeric and other materials into the fountain solution when the printing plate precursor is developed on press, potentially causing malfunctions in the lithographic printing operation. Furthermore, the print output produced with typical infrared exposures suitable for such IR-sensitive imageable compositions is still much smaller than desired.

[0013] U.S. Patent Application Publication No. 2019 / 0329545 (Shibamoto et al.) teaches the use of certain IR-decomposable dyes, which, in an excited state, can accept electrons from an electron-donating initiator upon exposure to infrared radiation to form a first wave of free radicals from the electron-donating initiator, and can further form a second wave of free radicals from the IR-decomposable dye by further decomposition of the IR-decomposable dye itself or by further reaction with an electron-accepting initiator. This publication suggests the color-forming ability of such imaging compositions containing IR-decomposable dyes under demonstrated exposure conditions.

[0014] U.S. Patent Application Publication No. 2020 / 0117086 (Noshi et al.) describes the combination of a specific IR-decomposable dye with a specific color former. In the absence of the specific color former, the specific IR-decomposable dye of this teaching does not produce a suitable printed output, as shown by Comparative Examples 1 and 2 thereof.

[0015] U.S. Patent No. 8,084,182 (Munnelly et al.) teaches the use of certain IR-decomposable dyes in IR-sensitive polymerizable compositions. Munnelly et al., in Examples 1-3, show that an IR-decomposable dye containing an alkoxycarbonylamino group, used in combination with a conventional acid-sensitive dye precursor, can achieve an IR-decomposable dye concentration of 300 mJ / cm. 2 However, without this acid-sensitive dye precursor, Example 4 of Munnelly et al. demonstrated a much lower print output (ΔE 6.6) at a high exposure of 300 mJ / cm 2 . Using a comparative IR-decomposable dye from the teachings of this patent that does not contain an alkoxycarbonylamino group, even in the presence of an acid-sensitive dye precursor, the print output was also significantly lower at 300 mJ / cm 2 . 2 Low print output was produced at an imaging energy of 4.6 (ΔE 4.6). Furthermore, Munnelly et al. demonstrated only a short press run of 200 copies, and it is unclear whether printing plates derived from Munnelly et al.'s masters would have sufficient image durability during printing to satisfy industrial customers who typically require printing runs significantly greater than 200 copies in a typical press run.

[0016] Co-pending U.S. patent applications Serial Nos. 17 / 844,953 (filed June 21, 2022 by Simpson et al.) and 17 / 685,570 (filed March 3, 2022 by Simpson et al.), which claim priority from commonly assigned U.S. patent application Serial No. 63 / 169,278, filed April 1, 2021, disclose certain color-changing compounds for producing dark, stable printouts. These color-changing compounds are cyanine dyes characterized by a meso group that can be decomposed by radiation. This decomposition, along with the removal of protecting groups such as triflimide groups, was expected to produce dark, irreversible printouts. However, the indene moiety in the cyanine core structure promotes the formation of phenylated by-products as part of the color development. The ratio of phenylated to decomposed products depends on the amount of borate compound produced in the image-forming chemistry. The aforementioned pending patent applications do not disclose other meso groups that allow the formation of phenylated products. One of the comparative examples described in this publication showed that a cyanine dye having an indenyl core and a diphenylamino meso group gave poor print output, suggesting that the formation of phenylated products is inefficient in the absence of specific degradable meso groups. The degradable meso group typically contains a labile leaving group, the loss of which leads to a stronger electron-donating group at the meso position of the cyanine dye, resulting in a shift in the absorption peak of the cyanine dye. These pending patent applications do not disclose that the phenylated by-products themselves are sufficient to produce print output. Furthermore, cyanine dyes with degradable meso groups require more complex synthetic procedures and expensive reagents, making them more expensive to use in lithographic printing plate precursors.

[0017] Despite all the efforts described in the industry with regard to providing sufficient and stable print output in on-press developable lithographic printing plates together with very good press running durability, there is a continuing need to provide on-press developable lithographic printing plate precursors which not only have the required essential properties such as fast imaging speed, good on-press developability, good lithographic printing durability, and good shelf life, but also show dense and stable print output using lower exposure energy in response to the demands of high productivity, and this print output is realized using relatively inexpensive materials in the imaging chemistry. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 0078350 [Patent Document 2] U.S. Patent No. 8,148,042 [Patent Document 3] International Publication No. 2019 / 219560 [Patent Document 4] US Patent Application Publication No. 2019 / 0329545 [Patent Document 5] US Patent Application Publication No. 2020 / 0117086 [Patent Document 6] U.S. Patent No. 8,084,182 [Patent Document 7] International Publication No. 2021 / 241457 [Patent Document 8] International Publication No. 2021 / 241458 [Patent Document 9] European Patent Application Publication No. 3793829 [Patent Document 10] European Patent Application Publication No. 3184590 [Patent Document 11] European Patent Application Publication No. 3508553 Summary of the Invention

[0019] The present invention provides the following lithographic printing plate precursor: A lithographic printing plate precursor, an aluminum-containing substrate; an infrared-sensitive image-recording layer disposed on an aluminum-containing substrate; and the infrared-sensitive image-recording layer comprises the following components (1), (2), and (3): (1) a free radical initiator composition capable of generating free radicals upon exposure to infrared radiation; (2) a free-radically polymerizable composition, and (3) The following structure (I): [ka] (In the formula, Ar1, Ar2, and Ar3 independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or to complete a substituted or unsubstituted heteroaromatic ring; Y is an oxygen atom, a sulfur atom, or a C(R 4 R 5 ) represents a dialkylmethylene group represented by the formula 4 and R 5 are independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, R 1 and R 2 are independently a substituted or unsubstituted alkyl group; X represents a single bond or a divalent linking group that is -S- or -O-; L is -C(=O)-OR 7 group, -SO2-R 3 group, -SO2NR 8 R 9 group and a group other than -NPh2, where Ph represents a phenyl group, and R 7 is -C(=O)OR 7 represents a substituted or unsubstituted alkyl group having a secondary or tertiary connecting carbon attached to the remainder of the group, R 3 , R 8 , and R 9independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; Za represents one or more counterions to balance the charge in the remainder of the color-changing compound (3) according to structure (I). Including, The infrared-sensitive image-recording layer has the following structure (IIa): B(R 10 R 11 R 12 R 13 ) - Structure (IIa) (In the formula, R 10 , R 11 , R 12 , and R 13 are independently a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, provided that R 10 , R 11 , R 12 , and R 13 at least three of which are the same or different substituted or unsubstituted aryl groups, each of which has no more than two halo substituents A lithographic printing plate precursor comprising one or more borate anions represented by the formula:

[0020] The present invention also provides a method for providing a lithographic printing plate comprising: 1. A method for providing a lithographic printing plate, comprising: A) imagewise exposing a lithographic printing plate precursor according to any of the embodiments of the present invention described herein to infrared radiation to provide exposed and unexposed areas in the infrared-sensitive image-recording layer; and B) On-press removal of the unexposed areas of the infrared-sensitive image-recording layer from the substrate using lithographic printing ink, a fountain solution, or a combination of lithographic printing ink and a fountain solution. A method comprising:

[0021] The present invention provides printout images produced in areas of an infrared-sensitive image-recording layer exposed to relatively low-energy imaging infrared radiation. Such printouts are initially dense and do not fade significantly during dark storage. Furthermore, in many embodiments, the imaging chemistry used to provide superior printout images does not adversely affect imaging speed, on-press developability, or lithographic image durability. Furthermore, the present invention overcomes the above-mentioned problems and provides significant printout benefits using less expensive chemistries. Further details of the present invention and the results achieved thereby are described below. DETAILED DESCRIPTION OF THE INVENTION

[0022] definition As used herein, the term "infrared absorber" refers to a compound or material that absorbs electromagnetic radiation in the near-infrared (near-IR) and infrared (IR) regions of the electromagnetic spectrum, typically having an absorption maximum in the near-IR and IR regions, e.g., wavelengths of 750 nm or greater.

[0023] As used herein, the terms "near-infrared region" and "infrared region" refer to radiation having wavelengths of at least 750 nm or greater. Most often, these terms are used to refer to the region of the electromagnetic spectrum from at least 800 nm to 1400 nm or less.

[0024] In this invention, the density of the printed output is generally indicated by the parameter ΔE, which is the Euclidean distance in the CIE 1976 L*a*b* color space between the color of an area exposed to radiation and an area unexposed to radiation, measured from reflectance measurements in 45 / 0 geometry (unpolarized light) using a CIE 2° observer and D50 as the illuminant, in accordance with EN ISO 11664-4 "Colorimetry—Part 4: CIE 1976 L*a*b* Color Space" and other known literature. Color measurements can be performed using commercially available equipment, such as the Techkon SpectroDens instrument. In the CIE 1976 L*a*b* color space, color is expressed as three color values: L*, the lightness (or brightness) of the color; a*, the green-red component of the color; and b*, the blue-yellow component of the color value.

[0025] In the present invention, the visible spectral region refers to the spectral region of electromagnetic radiation having a peak wavelength between 400 nm and 700 nm.

[0026] As used herein, the terms "printout" and "printout image" are intended to refer to the same feature.

[0027] Unless otherwise indicated, the term "wt %" refers to the amount of an ingredient or material relative to the total solids of a composition, formulation, or layer. Unless otherwise indicated, the percentage can be the same for either the dried layer or the total solids of the layer or coating formulation or composition.

[0028] As used herein, the term "hydrophilic" refers to a surface, layer, or material that is typically "water-loving," in that it can be mixed with, dissolved in, or wetted by water, as opposed to a "hydrophobic" surface, layer, or material that typically repels water and is soluble in oil-based solvents.

[0029] As used herein, the terms "on-press developable" and "on-press developability" refer to the ability to develop a master plate according to the present invention after infrared exposure (imaging) by mounting the imaged master plate on a suitable printing press and carrying out development using a fountain solution, lithographic printing ink, or a combination of fountain solution and lithographic printing ink during the first few prints.

[0030] use The lithographic printing plate precursor according to the present invention is useful for providing a lithographic printing plate that shows desirable stable printing output after imagewise exposure.These lithographic printing plates are useful for lithographic printing during printing operation.The lithographic printing plate can be produced using the on-press or off-press processing according to the present invention.The lithographic printing plate precursor is produced using the structure and components described below.

[0031] Planographic printing plate original plate A master plate according to the present invention can be formed by appropriately applying an infrared-sensitive image-recording composition (as described below) to a suitable hydrophilic aluminum-containing substrate (as described below) to form a negative-working infrared-sensitive image-recording layer. Generally, the infrared-sensitive image-recording composition (and the resulting infrared-sensitive image-recording layer) comprises component (1) a free-radical initiator composition capable of generating free radicals upon exposure to infrared radiation, component (2) a free-radical polymerizable composition, and component (3) a color-changing compound represented by Structure (I) shown below. Components (1), (2), and (3) are all defined in detail below, and are the only essential components required to achieve the benefits of the present invention. Furthermore, the infrared-sensitive image-recording layer must contain one or more borate anions, as described in detail below.

[0032] In some embodiments, the infrared-sensitive image-recording composition (and the resulting infrared-sensitive image-recording layer) can further comprise one or more of the following components (4), (5), and (6): component (4) an infrared-absorbing material (or a mixture of two or more thereof) different from the (3) color-changing compound; component (5) an acid-sensitive dye precursor (or a mixture of two or more thereof) different from all of components (1), (2), (3), and (4); and component (6) a non-free-radically polymerizable polymer material (or a mixture of two or more thereof) different from all of components (1), (2), (3), and (4). These components (4) through (6) are described below. In some highly useful embodiments, the infrared-sensitive image-recording layer consists essentially of all of the above-described components (1) through (4) and (6) to provide a desired lithographic printing plate precursor with the desired print output and the best overall imaging, on-press development, and printing properties.

[0033] Typically, there is only one infrared-sensitive image-recording layer in each master, and this layer is generally the outermost layer of the master, although in some embodiments, there may be an outermost protective layer (also known as a topcoat, overcoat, or oxygen barrier layer) disposed on (or directly on and in contact with) the infrared-sensitive image-recording layer, as described below.

[0034] Aluminum-containing substrates: The aluminum-containing substrate used to produce the plate precursor according to the present invention generally has a hydrophilic image-forming surface, or at least a surface that is more hydrophilic than the applied infrared-sensitive image-recording layer. Therefore, the aluminum-containing substrate can also be specified as a "hydrophilic aluminum-containing substrate." The aluminum-containing substrate generally comprises an aluminum-containing support that can be composed of raw aluminum or a suitable aluminum alloy conventionally used to produce lithographic printing plate precursors.

[0035] The aluminum-containing substrate may be treated using techniques known in the art, such as some type of roughening by physical (mechanical) graining, electrochemical graining, or chemical graining, followed by one or more anodizing treatments. Each anodizing treatment is typically carried out using either phosphoric acid or sulfuric acid under conventional conditions to form the desired hydrophilic aluminum oxide (or anodic oxide) layer on the aluminum-containing substrate. There may be a single aluminum oxide (anodic oxide) layer, or multiple aluminum oxide layers (e.g., an inner aluminum oxide layer and an outer aluminum oxide layer disposed on the inner aluminum oxide layer), each of which has multiple pores with varying depths and shapes of pore openings. Thus, such a process provides one or more anodic oxide layers or one or more aluminum oxide layers underneath the infrared-sensitive image-recording layer, which may be provided as described below. Such pores and process considerations for controlling pore width are described, for example, in U.S. Patent Application Publication Nos. 2013 / 0052582 (Hayashi), 2014 / 0326151 (Namba et al.), and 2018 / 0250925 (Merka et al.), as well as U.S. Pat. Nos. 4,566,952 (Sprintschnik et al.), 8,789,464 (Tagawa et al.), 8,783,179 (Kurokawa et al.), and 8,978,555 (Kurokawa et al.), and European Patent No. 2,353,882 (Tagawa et al.).

[0036] In some embodiments, the aluminum-containing substrate may include a hydrophilic layer disposed directly on the grained, anodized, and post-treated aluminum-containing substrate, and such hydrophilic layer may include a non-crosslinked hydrophilic polymer having carboxylic acid side chains.

[0037] Alternatively, the anodized aluminum oxide-containing substrate can be further treated using known post-anodization treatment processes, such as post-treatment with an aqueous solution of a hydrophilic material, to seal the pores of the anodized oxide or to hydrophilize its surface, or both.

[0038] Particularly useful hydrophilic layers or coating materials for this purpose include compounds having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups, at least one of which is directly attached to the phosphorus atom, and a molecular weight of less than 2000 g / mol, where M represents a hydrogen, sodium, potassium, or aluminum atom; and one or more hydrophilic polymers, at least one of which is a hydrophilic copolymer comprising at least (a) a repeat unit comprising an amide group and (b) a repeat unit comprising an -OM' group directly attached to the phosphorus atom, where M' represents a hydrogen, sodium, potassium, or aluminum atom. The hydrophilic layer preferably has a molecular weight of at least 0.0002 g / m. 2 ~0.1g / m 2 The following dry coverages may be placed on the outermost aluminum oxide layer:

[0039] Infrared-sensitive image-recording layer: The infrared-sensitive recording layer composition according to the present invention (and the infrared-sensitive image recording layer produced from the composition) is designed to be "negative-working," a term known in the art of lithographic printing. The infrared-sensitive image recording layer may be designed with a specific combination of components to impart on-press developability to the exposed lithographic printing plate precursor, for example, to enable on-press development using a fountain solution, a lithographic printing ink, or a combination of the two.

[0040] The present invention utilizes component (1), a free radical initiator composition capable of generating free radicals upon exposure to infrared radiation. Such component (1) initiator compositions can include one or more organic halogen compounds, such as bis(trihalomethyl)triazines and trihalomethylarylsulfones, or one or more onium salts, such as iodonium salts and sulfonium salts, many of which are known in the art as being capable of generating free radicals upon exposure to infrared radiation.

[0041] Representative compounds other than onium salts are described, for example, in U.S. Patent Application Publication No. 2005 / 0170282 (Inno et al., U.S. Patent No. '282)

[0087] to

[0102] and U.S. Patent No. 6,309,792 (Hauck et al.), as well as in Japanese Patent Application Publication No. 2002 / 107916 and International Publication No. 2019 / 179995.

[0042] In some embodiments, component (1) the free radical initiator composition should contain one or more iodonium cations. Useful onium salts are described, for example, in U.S. Pat. No. '282, paragraphs

[0103] to

[0109] . For example, useful iodonium salts contain at least one iodonium cation and a suitable anion in the molecule. Examples of iodonium salts include diaryliodonium salts, such as diphenyliodonium salts, and derivatives of these salts obtained by introducing one or more substituents into the benzene ring of these compounds. Suitable substituents include, but are not limited to, alkyl, alkoxy, alkoxycarbonyl, acyl, acyloxy, chloro, bromo, fluoro, and nitro groups. Particularly useful iodonium cations, such as diaryliodonium cations, may have, for example, two substituted or unsubstituted phenyl groups.

[0043] Examples of anions in iodonium salts include halogen anions, ClO4 - , PF6 - , BF4 - , SbF6 - , CH3SO3 - , CF3SO3 - , C6H5SO3 - , CH3C6H4SO3 - , HOC6H4SO3 - , ClC6H4SO3 -and boron anions described, for example, in U.S. Pat. No. 7,524,614 (Tao et al.). Representative useful iodonium salts are described in columns 6-7 of U.S. Pat. No. 7,524,614 (noted above), where the iodonium cation can contain the various monovalent substituents "X" and "Y" listed, or fused carbocyclic or heterocyclic rings each bearing a phenyl group.

[0044] Also useful are the iodonium salts described in paragraphs

[0033] to

[0038] of Japanese Patent Publication No. 2002-082429 (or U.S. Patent Application Publication No. 2002-0051934 (Ippei et al.)). Representative iodonium borate salts are, for example, those listed in column 8 of U.S. Patent No. 7,524,614 (noted above). A particularly useful iodonium salt is diaryliodonium tetraphenylborate.

[0045] Component (1) the free radical initiator composition is present in the infrared-sensitive image-recording layer in an amount (molar ratio or weight ratio) that would be readily apparent to one skilled in the art of manufacturing on-press developable lithographic printing plate precursors, with the minimum and maximum total amounts generally being at least 1 wt % to 20 wt % or less based on the total coverage (solids content) of the infrared-sensitive image-recording layer.

[0046] Another essential feature of the infrared-sensitive image-recording layer is component (2), a free-radically polymerizable composition, which comprises one or more free-radically polymerizable components, each of which contains one or more free-radically polymerizable groups capable of polymerizing using free-radical initiation during infrared exposure. In some embodiments, there are at least two free-radically polymerizable components, each having the same or different numbers of free-radically polymerizable groups in each molecule. Thus, a useful free-radically polymerizable component may contain one or more free-radically polymerizable monomers or oligomers having one or more polymerizable ethylenically unsaturated groups (e.g., two or more such groups). Similarly, crosslinkable polymers having such free-radically polymerizable groups may also be used. Oligomers or prepolymers, such as urethane acrylates and methacrylates, epoxy acrylates and methacrylates, polyester acrylates and methacrylates, polyether acrylates and methacrylates, and unsaturated polyester resins, may be used. In some embodiments, the free-radically polymerizable component contains a carboxyl group.

[0047] The one or more free-radically polymerizable components may have a sufficiently high molecular weight or have sufficient polymerizable groups to provide a crosslinkable polymer matrix that functions as a "polymeric binder" for the other components in the infrared-sensitive image-recording layer. In such embodiments, a separate (6) non-free-radically polymerizable polymeric material (described below) is not required, although it may still be present if desired.

[0048] Useful free-radically polymerizable components include urea urethane (meth)acrylates or urethane (meth)acrylates having multiple (two or more) polymerizable groups. For example, urethane acrylates having 2 to 6 acrylate groups, or even up to 15 acrylate groups, can be prepared by reacting a triisocyanate, such as DESMODUR® N100 (Bayer Corp., Milford, Connecticut), or a diisocyanate, such as hexane-1,6-diisocyanate, with hydroxyethyl acrylate, pentaerythritol triacrylate, or dipentaerythritol pentaacrylate. Such urethane or urea (meth)acrylate compounds have a high number of (meth)acrylate groups per molecule, at 15 or more. Commercially available urethane acrylates having 15 acrylate groups include U-15HA and UA-53H, available from Shin-Nakamura Chemical Co., Ltd. These compounds with a large number of (meth)acrylates have high crosslinking efficiency and can therefore be included in the (2) free-radically polymerizable composition.

[0049] Useful free-radically polymerizable compounds include non-urethane and non-urea (meth)acrylates derived from polyfunctional alcohols, such as NK Ester A-DPH (dipentaerythritol hexaacrylate) available from Kowa American, and Sartomer SR399 (dipentaerythritol pentaacrylate), Sartomer 355 (ditrimethylolpropane tetraacrylate), Sartomer SR295 (pentaerythritol tetraacrylate), Sartomer SR415 (ethoxylated (20) trimethylolpropane triacrylate), and Sartomer SR494 (ethoxylated pentaerythritol tetraacrylate) available from Sartomer Company, Inc. These non-urethane and non-urea (meth)acrylates may also have multiple (meth)acrylate groups per molecule.

[0050] For example, useful free-radically polymerizable components are described in EP 1,182,033 A1 (Fujimaki et al.), paragraphs

[0170] et seq., as well as U.S. Pat. Nos. 6,309,792 (Hauck et al.), 6,569,603 (Furukawa), and 6,893,797 (Munnelly et al.). Other useful free-radically polymerizable components include those described in U.S. Patent Application Publication No. 2009 / 0142695 (Baumann et al.), which contain a 1H-tetrazole group.

[0051] Component (2) The one or more components of the free-radically polymerizable composition are generally present in a total amount of at least 10 wt % or at least 20 wt % and no more than 50 wt % or no more than 70 wt % based on the total coverage (solids) of the infrared-sensitive image-recording layer.

[0052] The third essential component of the infrared-sensitive image recording composition and the infrared-sensitive image recording layer according to the present invention has the following structure (I): [ka] wherein Ar1, Ar2, and Ar3 independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or a substituted or unsubstituted heteroaromatic ring. Component (3) is a color-changing compound represented by the formula (I), or a mixture of two or more thereof. Therefore, generally, to complete a substituted or unsubstituted aromatic ring for any or all of Ar1, Ar2, and Ar3, for example, to complete a benzene (benzo) ring or a naphthalene (naphtho) ring, an appropriate number of carbon atoms are required. Furthermore, to complete a substituted or unsubstituted heteroaromatic ring for any or all of Ar1, Ar2, and Ar3, for example, to complete a pyridin-2-yl ring, a pyridin-3-yl ring, a pyridin-4-yl ring, a pyridazinyl ring, a pyrimidin-2-yl ring, a pyrimidin-4-yl ring, a pyrimidin-5-yl ring, a pyrimidin-6-yl ring, a pyrazine ring, a triazine ring, a pyrrole ring, a furan ring, a thiophene ring, a pyrazole ring, an oxazole ring, an imidazole ring, a thiazole ring, or a triazole ring, an appropriate number of carbon atoms and one or more heteroatoms are required.

[0053] In many useful embodiments of the present invention, Ar1 and Ar2 are the same atoms necessary to complete a substituted or unsubstituted aromatic ring, for example, the same substituted or unsubstituted aromatic ring, for example, a substituted or unsubstituted benzene (benzo) ring. Furthermore, one or both of the aromatic rings completed by the atoms of Ar1 and Ar2 may be substituted, for example, with one or more of the same or different, optionally substituted alkyl groups, alkoxy groups, halo groups (e.g., one or two of the same or different halo groups), cyano groups, -COOR' groups, -S03R' groups, or -S02R' groups, where R' represents a substituted or unsubstituted alkyl group, and these alkyl groups may be the same or different for each of the listed groups. It is particularly useful for one or both of the aromatic rings completed by the atoms of Ar1 and Ar2 to be substituted with one or two halo groups (e.g., chloro groups), which may be the same or different groups. It is also desirable for Ar3 to represent the carbon and hydrogen atoms necessary to complete the benzene (benzo) ring of structure (I).

[0054] In addition, in structure (I), Y is an oxygen atom, a sulfur atom, or a >C(R4 R 5 ) represents a dialkylmethylene group represented by the formula 4 and R 5 are independently substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms. In many useful embodiments of the invention, Y is the same or different dialkylmethylene group or even the same dialkylmethylene group each time it appears, where R 4 and R 5 are the same unsubstituted alkyl groups of 1 or 2 carbon atoms. One skilled in the art would be able to generate numerous compounds in which Y varies among the possible groups, including the many possible dialkylmethylene groups.

[0055] In structure (I), R 1 and R 2 are independently substituted or unsubstituted alkyl groups, each containing 1 to 12 carbon atoms, although in many embodiments one or both of the alkyl groups may contain the same or different ether or ester linkages interrupting the carbon chain, or in the case of ester groups, may be used to terminate the alkyl chain.

[0056] Also in structure (I), X represents a single bond or a divalent linking group selected from -S- and -O-. In certain embodiments used in the present invention, X represents a single bond.

[0057] Also, in structure (I), L is -C(=O)-OR 7 group, -SO2-R 3 group, -SO2NR 8 R 9 group and a group other than -NPh2, where Ph represents a phenyl group, and R 7 is -C(=O)OR 7 R represents a substituted or unsubstituted alkyl group having 1 to 8 carbon atoms and having a secondary or tertiary connecting carbon attached to the remainder of the group. 3 , R 8 , and R 9are independently a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 or 10 carbon atoms in the aromatic ring, or a substituted or unsubstituted heteroaryl group. Under typical imaging conditions, L is stable and does not undergo a decomposition reaction that would result in cleavage of the L group from X. L is typically an electron-withdrawing group.

[0058] In some embodiments, the (3) color-changing compound is represented by the following structure (Ia): [ka] In the formula, Ar1, Ar2, Ar3, R 1 , R 2 , Y, and Za are the same groups as described above for structure (I), and A is -SR 14 , -OR 14 , chloro, bromo, iodo, fluoro, nitro, cyano, trichloromethyl, tribromomethyl, trifluoromethyl, alkylammonium, dialkylammonium, and trialkylammonium groups, wherein each of the same or different alkyl groups contains 1 to 10 carbons and is optionally substituted; R 14 is an optionally substituted aryl group, or an optionally substituted heteroaryl group, or an optionally substituted alkyl group. For synthetic convenience, it is preferred that A is a halo group, e.g., a chloro group or -SR 14 -OR 14 (In the formula, R 14 is an optionally substituted alkyl, an optionally substituted aryl, or an optionally substituted heteroaryl group. 14Color-changing compounds according to structure (Ia) where A is a chloro group can be easily obtained from compounds according to structure (Ia) where A is a chloro group by reaction with an appropriate compound having an -SH or -OH group. Compounds having an -SH group are often used as free radical coinitiators, accelerators, or stabilizers. Examples of such compounds include 3-mercapto-1H-1,2,4-triazole (CAS No. 3179-31-5), 2-mercaptobenzothiazole (CAS No. 149-30-4), and 5-methyl-1,3,4-thiadiazole-2-thiol (CAS No. 29490-19-5). Compounds having a phenolic OH group are often used as free radical initiators or thermal stabilizers. An example of a free radical initiator having a phenolic OH group is 4-hydroxyphenyltribromomethylsulfone, as described in U.S. Patent Application Publication No. 2011 / 0,315,034 A (Heylen et al.). When a compound having one or more -SH groups or one or more -OH groups is included in an infrared-sensitive image-recording layer that also contains a color-forming compound according to structure (Ia) where A is a halo group such as a chloro group, the compound having one or more -SH groups or one or more -OH groups is preferably an infrared-sensitive image-recording layer that also contains a color-forming compound according to structure (Ia) where A is a halo group such as a chloro group. 14 -OR 14 New color-forming compounds with R 14 -SH, wherein R 14 is a substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl group. In order to avoid premature color development in the infrared-sensitive image-recording layer of the lithographic printing plate precursor before infrared exposure, R 14 It is preferred that the group does not contain an -NH- subgroup.

[0059] Useful compounds having one or more -SH groups include, but are not limited to, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 2,2'-dithiobis(benzothiazole), 1-phenyltetrazole-5-thiol, 5-mercapto-1-methyltetrazole, 5-t-butylthio-1,3,4-thiadiazole-2-thiol, 5,5'-dithiobis(1-phenyl-1H-tetrazole), 3-mercapto-4-methyl-1,2,4-triazole, Nt-butyl-2-benzothiazolesulfenamide, and 4-methyl-5-phenyl-4H-1,2,4-triazole-3-thiol.

[0060] R 14 Useful examples of: [ka]

[0061] [ka]

[0062] [ka]

[0063] Finally, in structure (I), Za represents one or more counterions to balance the charge in the remainder of the (3) color-changing compound according to structure (I). If the remainder of the (3) color-changing compound according to structure (I) is positively charged, Za represents an anion. Many useful anions are available, such as halogen anions, ClO4, - , PF6 - , BF4 - , SbF6 - , CH3SO3 - , CF3SO3 - , C6H5SO3 - , CH3C6H4SO3 - , HOC6H4SO3 - , ClC6H4SO3 -Boron-containing anions, such as those described in U.S. Pat. No. 7,524,614 (noted above), are known in the art. Useful boron-containing anions include tetraarylborate anions (e.g., tetraphenylborate) as described above for electron donors. In some embodiments, Za can be provided by the electron donor in the (1) free radical initiator composition. When the remainder of the (3) color-changing compound according to structure (I) is negatively charged, Za represents a cation. Useful cations, such as alkali metal ions, alkaline earth metal ions, tertiary and quaternary ammonium ions, and onium ions, such as iodonium ions, sulfonium ions, or phosphonium ions, are known in the art. In some embodiments, Za can be provided by the onium compound in the above-described component (1) free radical initiator composition.

[0064] Without wishing to be bound by any particular theory, it is believed that Ar3 in structure (I) influences the geometry of the polymethine chain in the component (3) color-changing compound, thereby making the compound more reactive in the presence of an organic borate anion according to structure (IIa) described below. For example, in the presence of tetraphenylborate anion, a compound according to structure (I) [color-changing compound 2 of the present invention, i.e., ICCC-2, shown below] can undergo a chemical reaction (shown below) to form the phenylated product ICCC2-Ph during or after irradiation of the infrared-sensitive image-recording layer with an appropriate infrared source. Phenylation of the component (3) color-changing compound can also be achieved by reaction with triphenylalkylborates, such as triphenyl-n-butylborate and tris(3-fluorophenyl)-n-butylborate.

[0065] [ka]

[0066] Phenylated products such as ICCC2-Ph are stable at room temperature for at least one week in the infrared-exposed areas of the infrared-sensitive image-recording layer, and thus provide stable print output from infrared-exposed lithographic printing plate precursors. Furthermore, in the presence of a sufficient amount of borate anion according to the following structure (IIa), the phenylated products can be formed with a much lower input of infrared energy than typically required for decomposition reactions involving cleavage of leaving groups, as described in many of the prior art cited in the Background Art section above.

[0067] Even in the presence of sufficient borate compound, Ar3 in structure (I) remains essential. Without Ar3, the phenylation reaction will be inefficient, if it occurs at all.

[0068] Component (3) color-changing compound represented by Structure (I), alone or as a mixture of two or more thereof, is generally present in the infrared-sensitive image-recording layer in an amount of at least 0.5 wt % or at least 1 wt % and not more than 10 wt % or not more than 15 wt %, based on the total weight of the infrared-sensitive image-recording layer.

[0069] Furthermore, the infrared-sensitive image recording layer according to the present invention must contain one or more borate anions, which have the following structure (IIa): B(R 10 R 11 R 12 R 13 ) - Structure (IIa) (In the formula, R 10 , R 11 , R 12 , and R 13 are independently a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, provided that R 10 , R 11 , R 12 , and R 13at least three of which are the same or different substituted or unsubstituted aryl groups, each of which has no more than two halo substituents. The one or more borate anions can be provided in the infrared-sensitive image-recording layer in various forms. For example, the one or more borate anions can be provided as part of one or more iodonium salts in the component (1) free radical initiator composition. Alternatively, the one or more borate anions can be provided as one or more Za counterions in structure (I) or as part of the component (4) infrared-absorbing material described below. Furthermore, the one or more borate anions can be provided as separate borate salts in the component (1) free radical initiator composition.

[0070] As noted above, in some embodiments, one or more iodonium cations can be provided to the infrared-sensitive image-recording layer as part of the component (1) free-radical initiator composition. Because the borate compound present in the infrared-sensitive image-recording composition can participate in a reaction with the iodonium cation to generate free radicals and can also participate in a reaction with the component (3) color-changing compound represented by structure (I), the amount of borate compound available for the phenylation reaction depends on the amount of both the borate compound and the iodonium cation. Therefore, low exposure energies, e.g., 110 mJ / cm, can be used. 2 To produce adequate print output and image durability at energies of 1000 keV, the infrared-sensitive image-recording layer contains sufficient one or more iodonium cations and one or more borate anions such that the molar ratio of one or more borate anions to one or more iodonium cations is at least 0.25:1, or at least 0.5:1, or even at least 0.8:1, and not more than 2:1, or not more than 4:1.

[0071] The infrared-sensitive image-recording layer according to the present invention may also, although not necessarily, highly desirably contain component (4) an infrared-absorbing material (one or a mixture of two or more) different from the above-described component (3) color-changing compound. Component (4) infrared absorber imparts the desired infrared sensitivity or converts radiation into heat, or both. Useful infrared absorbers may be pigments or, particularly, infrared-absorbing dyes. Suitable dyes of this type are described, for example, in U.S. Patel et al. U.S. Pat. No. 5,208,135, U.S. Pat. No. 6,153,356, U.S. Pat. No. 6,309,792, Hauck et al. U.S. Pat. No. 6,569,603, Furukawa U.S. Pat. No. 6,797,449, Nakamura et al. Tao U.S. Pat. No. 7,018,775, Munnelly et al. Munnelly et al. U.S. Pat. No. 8,632,941, Balbinot et al. Iwai et al. U.S. Pat. App. Pub. No. 2007 / 056457. In some infrared-sensitive embodiments, it is desirable that at least one infrared absorber (component (4)) in the infrared-sensitive image-recording layer is a cyanine dye comprising a suitable cationic cyanine chromophore and a tetraarylborate anion, such as a tetraphenylborate anion. Examples of such dyes include those described in U.S. Patent Application Publication No. 2011 / 003123 (Simpson et al.).

[0072] The total amount of component (4) infrared absorber is at least 0.5% by weight or at least 1% by weight, and not more than 15% by weight or not more than 30% by weight, based on the total weight of the infrared-sensitive image-recording layer.

[0073] Another optional but desirable component of the infrared-sensitive image-recording layer is component (5), an acid-sensitive dye precursor (e.g., a combination of one or more of these). Useful component (5) acid-sensitive dye precursors are compounds that are colorless or nearly colorless in their neutral form and switch to a colored form upon protonation. Many leuco dyes are known for this purpose, including those described in paragraphs

[0209] to

[0222] of EP 3,418,332 A2 (Inasaki et al., corresponding to U.S. Patent Application Publication No. 2018 / 0356730) and paragraphs

[0044] to

[0046] of EP 2,018,365 B1 (Nguyen et al., corresponding to U.S. Patent No. 7,910,768). These component (5) acid-sensitive dye precursors are different from all of the previously defined components (1), (2), (3), and (4).

[0074] In some embodiments, the weight ratio of component (5) acid-sensitive dye precursor to component (3) color-changing compound represented by Structure (I) in the infrared-sensitive image-recording layer is less than 1, or even less than 0.8.

[0075] For example, in some embodiments, at least one of the component (5) acid-sensitive dye precursors includes a lactone moiety. More specifically, useful component (5) acid-sensitive dye precursors include the following structures (C1) and (C2): [ka] wherein R 11 ~R 19are independently hydrogen, an unsubstituted or substituted alkyl group, or an unsubstituted or substituted aryl group. Such substituted or unsubstituted alkyl groups can have 1 to 20 carbon atoms, and the optional one or more substituents can include, but are not limited to, halogen, alkyl, aryl, alkoxy, and phenoxy groups. Useful substituted or unsubstituted aryl groups can be carbocyclic aromatic rings or heterocyclic aromatic rings, and these groups can have two or more fused rings. Useful substituents for the aryl ring include, but are not limited to, those described above for alkyl groups. However, one skilled in the art will be able to use this teaching regarding structures (C1) and (C2) as a guide to design other useful component (5) acid-sensitive dye precursors.

[0076] As noted above, such component (5) acid-sensitive dye precursor may be present, if desired, in any desired amount of at least 0.5% to 10% by weight based on the total coating weight (solids) of the infrared-sensitive image-recording layer.

[0077] In many embodiments of the present invention, the infrared-sensitive image-recording layer optionally, but desirably, further comprises component (6) a non-free-radically polymerizable polymeric material (or polymeric binder), or a mixture of two or more thereof, each of which does not have functional groups that, if present, would render the polymeric material free-radically polymerizable. Such component (6) non-free-radically polymerizable polymeric material is therefore different from all of components (1), (2), (3), and (4) above.

[0078] Useful Component (6) Non-free radically polymerizable polymeric materials generally have a weight average molecular weight (M) determined by gel permeation chromatography (polystyrene standard). w ) is at least 2,000 g / mol or at least 20,000 g / mol and not more than 300,000 g / mol or not more than 500,000 g / mol.

[0079] Such component (6) non-free radically polymerizable polymeric materials can be selected from polymeric binder materials known in the art, including polymers containing repeating units with side chains containing polyalkylene oxide segments, such as those described in U.S. Pat. No. 6,899,994 (Huang et al.). Other useful polymeric binders contain two or more repeating units with different side chains containing polyalkylene oxide segments, as described, for example, in WO 2015-156065 (Kamiya et al.). Some of these polymeric binders may further contain repeating units with pendant cyano groups, as described, for example, in U.S. Pat. No. 7,261,998 (Hayashi et al.).

[0080] Such component (6) non-free-radically polymerizable polymeric materials may also have a backbone comprising a plurality (at least two) of urethane moieties and pendant groups comprising polyalkylene oxide segments.

[0081] The useful component (6) non-free-radically polymerizable polymeric material can be present in particulate form, i.e., in the form of discrete particles (unagglomerated particles). Such discrete particles can have an average particle size of at least 10 nm to 1500 nm, or typically at least 80 nm to 600 nm, and are generally uniformly distributed throughout the infrared-sensitive image-recording layer. The average particle size can be determined using a variety of known methods and nanoparticle measurement devices, including measuring particles in scanning electron microscope images and averaging a set number of measurements.

[0082] Component (6) one or more non-free-radically polymerizable polymeric materials may be present in an amount of at least 10 wt % or at least 20 wt % and not more than 50 wt % or not more than 70 wt % based on the total coverage (solids) of the infrared-sensitive image-recording layer.

[0083] The infrared-sensitive image-recording layer used in the present invention may also optionally contain crosslinked polymer particles, such materials having an average particle size of at least 2 μm, as described, for example, in U.S. Pat. Nos. 9,366,962 (Hayakawa et al.), 8,383,319 (Huang et al.), and 8,105,751 (Endo et al.).

[0084] The infrared-sensitive image-recording layer may also optionally contain various other additives in conventional amounts, including, but not limited to, dispersants, humectants, biocides, plasticizers, surfactants for coatability or other properties, viscosity-increasing agents, pH adjusters, drying agents, defoamers, development aids, rheology modifiers, or combinations thereof, or any other additives commonly used in the art of lithographic coatings.

[0085] Overcoat: Although the infrared-sensitive image-recording layer can be the outermost layer with no layer disposed thereon, the master of the present invention can be designed with an overcoat disposed over (or directly on) the on-press developable negative-working infrared-sensitive image-recording layer (without an intermediate layer between these two layers). This overcoat, if present, is generally the outermost layer of the master and can be either hydrophilic or hydrophobic in nature.

[0086] The overcoat must be at least 0.1 g / m 2 or at least 0.15 g / m 2 and 2.5 g / m 2 Less than 4g / m 2 In some embodiments, the dry coating coverage is less than 0.1 g / m 2 ~1.5g / m 2 or less, or at least 0.1 g / m 2 ~0.9g / m 2 or less, resulting in a relatively thin overcoat.

[0087] Lithographic printing plate precursor production: The lithographic printing plate precursor according to the present invention can be provided in the following manner. An infrared-sensitive image-recording layer formulation containing the above-mentioned essential components (1), (2), and (3), as well as one or more required iodonium cations and one or more borate anions, and optional components (4), (5), and (6), and optionally other additives, can be applied to the hydrophilic surface of a suitable aluminum-containing substrate using any suitable equipment and procedure, usually in the form of a continuous web as described above. Typically, once the infrared-sensitive image-recording layer formulation has been applied at an appropriate wet coverage, the formulation is dried in an appropriate manner known in the art to provide the desired dry coverage as described below, thereby providing an infrared-sensitive continuous web or continuous article.

[0088] The manufacturing process typically involves mixing the various components required for the infrared-sensitive image-recording layer in a suitable organic solvent or mixtures thereof, with or without water, applying the resulting infrared-sensitive image-recording layer formulation to a continuous aluminum-containing substrate web, and removing the solvent(s) by evaporation under suitable drying conditions.

[0089] After proper drying, the dry coverage of the infrared-sensitive image-recording layer on the aluminum-containing substrate is at least 0.1 g / m 2 or at least 0.4g / m 2 and 2 g / m 2 or less than 4g / m 2 Although other dry coverage amounts can be used to provide the desired dry coverage, if desired.

[0090] As noted above, in some embodiments, a suitable overcoat formulation (described above) can be applied to the dried infrared-sensitive image-recording layer using known coating and drying conditions, equipment, and procedures.

[0091] Image formation (exposure) conditions During use, the infrared-sensitive lithographic printing plate precursor of the present invention can be exposed to an appropriate infrared source depending on the one or more infrared absorbers present in the infrared-sensitive image-recording layer. In some embodiments, the lithographic printing plate precursor can be imaged with one or more infrared-emitting lasers that emit significant infrared radiation within the range of at least 750 nm to 1400 nm, or at least 800 nm to 1250 nm, to create exposed and unexposed areas in the infrared-sensitive image-recording layer. Such infrared-emitting lasers can be used for such imaging in response to digital information provided by a computing device or other digital information source. Laser imaging can be digitally controlled in any suitable manner known in the art.

[0092] Thus, imaging can be carried out using imaging or exposing infrared radiation from an infrared-generating laser (or an array of such lasers). Imaging can also be carried out using imaging radiation at multiple infrared (or near-IR) wavelengths simultaneously, if desired. The laser(s) used to expose the master are typically one or more diode lasers due to the reliability and low maintenance of diode laser systems, although other lasers, such as gas or solid-state lasers, can also be used.

[0093] The infrared imaging device can be configured as a flatbed recorder or a drum recorder, in which an infrared-sensitive lithographic printing plate precursor is attached to the inner or outer cylindrical surface of the drum. Examples of useful imaging devices include the KODAK® Trendsetter platesetter (Eastman Kodak Company) and the NEC AMZISetter X series (NEC Corporation, Japan), which include laser diodes emitting radiation at a wavelength of approximately 830 nm. Other suitable imaging devices include the Screen PlateRite 4300 series or 8600 series platesetters (available from Screen USA, Chicago, Illinois), which operate at a wavelength of 810 nm, or the thermal CTP platesetters manufactured by Panasonic Corporation (Japan).

[0094] When an infrared imaging source is used, the imaging intensity is at least 30 mJ / cm depending on the sensitivity of the infrared-sensitive image-recording layer. 2 ~500mJ / cm 2 or less, typically at least 50 mJ / cm 2 ~300mJ / cm 2 It can be the following:

[0095] On-press processing (developing) and printing After imagewise exposure as described above, the exposed infrared-sensitive lithographic printing plate precursor having exposed and unexposed areas in the infrared-sensitive image-recording layer can be processed on press to remove the unexposed areas (and any hydrophilic protective layer that may be present on said areas). During this processing, and during lithographic printing, the exposed aluminum-containing substrate surface repels ink, while the remaining exposed areas accept lithographic printing ink.

[0096] Thus, the negative-working lithographic printing plate precursor of the present invention can be developed on-press using lithographic printing ink, a fountain solution, or a combination of lithographic printing ink and a fountain solution. In such an embodiment, the imaged (exposed) infrared-sensitive lithographic printing plate precursor of the present invention is mounted on a printing press and the printing run is initiated. After the first printed image is formed, the unexposed areas in the infrared-sensitive image-recording layer are removed with an appropriate fountain solution, a lithographic printing ink, or a combination of both. A representative example of a fountain solution is Varn Litho Etch 142W + Varn PAR (alcohol substitute) (available from Varn International, Addison, Illinois).

[0097] During a typical start-up of a sheet-fed printing press, dampening rollers are first engaged to apply dampening water to the mounted imaged plate master to swell the exposed infrared-sensitive image-recording layer at least in the unexposed areas. After several revolutions, inking rollers are engaged to apply one or more lithographic printing inks to cover the entire printing surface of the lithographic printing plate. Typically, within 5 to 20 revolutions after engagement of the inking rollers, printing paper is applied and the resulting ink-fountain solution emulsion is used to remove the unexposed areas of the infrared-sensitive image-recording layer from the lithographic printing plate and, if present, to remove material from the blanket cylinder.

[0098] The present invention provides at least the following embodiments and combinations thereof, although other combinations of features are contemplated to fall within the scope of the present invention, as one of ordinary skill in the art would understand from the teachings of this disclosure.

[0099] 1. A lithographic printing plate precursor, an aluminum-containing substrate; an infrared-sensitive image-recording layer disposed on an aluminum-containing substrate; and the infrared-sensitive image-recording layer comprises the following components (1), (2), and (3): (1) a free radical initiator composition capable of generating free radicals upon exposure to infrared radiation; (2) a free-radically polymerizable composition, and (3) The following structure (I): [ka] (In the formula, Ar1, Ar2, and Ar3 independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or to complete a substituted or unsubstituted heteroaromatic ring; Y is an oxygen atom, a sulfur atom, or a C(R 4 R 5 ) represents a dialkylmethylene group represented by the formula 4 and R 5 are independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, R 1 and R 2 are independently a substituted or unsubstituted alkyl group; X represents a single bond or a divalent linking group that is -S- or -O-; L is -C(=O)-OR 7 group, -SO2-R 3 group, -SO2NR 8 R 9 group and a group other than -NPh2, where Ph represents a phenyl group, and R 7 is -C(=O)OR 7 represents a substituted or unsubstituted alkyl group having a secondary or tertiary connecting carbon attached to the remainder of the group, R 3 , R 8 , and R 9 independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; Za represents one or more counterions to balance the charge in the remainder of the color-changing compound (3) according to structure (I). Including, The infrared-sensitive image-recording layer has the following structure (IIa): B(R 10 R 11 R 12 R 13 )- Structure (IIa) (In the formula, R 10 , R 11 , R 12 , and R 13 are independently a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, provided that R 10 , R 11 , R 12 , and R 13 at least three of which are the same or different substituted or unsubstituted aryl groups, each of which has no more than two halo substituents A lithographic printing plate precursor comprising one or more borate anions represented by the formula:

[0100] 2. The component (3) color-changing compound has the structure (Ia) [ka] (In the formula, Ar1, Ar2, Ar3, R 1 , R 2 , Y, and Za are the same groups as described above for structure (I), and A is -SR 14 , -OR 14 , chloro, bromo, iodo, fluoro, nitro, cyano, trichloromethyl, tribromomethyl, trifluoromethyl, alkylammonium, dialkylammonium, and trialkylammonium groups, wherein each of the same or different alkyl groups contains 1 to 10 carbons and is optionally substituted; R 14 is an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group.

[0101] 3. A is a halo group or -SR 14 wherein R 14 The lithographic printing plate precursor according to embodiment 2, wherein represents an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group.

[0102] 4. The lithographic printing plate precursor according to embodiment 2 or 3, wherein A represents a chloro group.

[0103] 5.A is -SR 14 wherein R 14 The lithographic printing plate precursor according to embodiment 2 or 3, wherein represents an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group.

[0104] 6. The lithographic printing plate precursor according to any one of embodiments 1 to 5, wherein the component (1) free radical initiator composition comprises one or more iodonium cations in an amount such that the molar ratio of the one or more borate anions to the one or more iodonium cations is at least 0.4:1.

[0105] 7. The lithographic printing plate precursor according to any one of embodiments 1 to 6, wherein the infrared-sensitive image-recording layer further comprises component (4) an infrared-absorbing material different from component (3) the color-changing compound.

[0106] 8. The lithographic printing plate precursor according to any one of embodiments 1 to 7, wherein Ar3 represents the carbon and hydrogen atoms necessary to complete a benzene ring.

[0107] 9. The lithographic printing plate precursor according to any one of embodiments 1 to 8, wherein Za comprises a tetraarylborate anion.

[0108] 10. Component (1) The free radical initiator composition has the following structure (II): [B(R 10 R 11 R 12 R 13 ) - ] n M n+ Structure (II) (In the formula, R 10 , R 11 , R 12 , and R 13is as defined for structure (IIa), n is an integer equal to or greater than 1, and M n+ is an n-valent cation) 10. The lithographic printing plate precursor according to any one of embodiments 1 to 9, comprising an organic borate represented by the formula:

[0109] 11. R of Structure (II) and Structure (IIa) 10 , R 11 , R 12 , and R 13 11. The lithographic printing plate precursor according to embodiment 10, wherein all of are the same or different substituted or unsubstituted aryl groups.

[0110] 12. R of structure (IIa) and structure (II) 10 , R 11 , R 12 , and R 13 12. The lithographic printing plate precursor according to embodiment 10 or 11, wherein all of are the same substituted or unsubstituted phenyl group.

[0111] 13. The lithographic printing plate precursor according to any one of embodiments 7 to 12, wherein the infrared-sensitive image-recording layer further comprises component (5) an acid-sensitive dye precursor different from all of components (1), (2), (3), and (4) defined above.

[0112] 14. The lithographic printing plate precursor according to any one of embodiments 1 to 13, wherein the component (1) free radical initiator composition comprises a diaryliodonium tetraphenylborate salt.

[0113] 15. The lithographic printing plate precursor according to embodiment 13 or 14, wherein the weight ratio of component (5) the acid-sensitive dye precursor to component (3) the color-changing compound represented by the following structure (I) in the infrared-sensitive image-recording layer is less than 1:

[0114] 16. The lithographic printing plate precursor according to any one of embodiments 7 to 15, wherein the infrared-sensitive image-recording layer further comprises component (6) a non-free-radically polymerizable polymeric material that is present in particulate form and is distinct from all of components (1), (2), (3), and (4) defined above.

[0115] 17. The lithographic printing plate precursor according to any one of embodiments 1 to 16, wherein the infrared-sensitive image-recording layer is the outermost layer.

[0116] 18. The lithographic printing plate precursor according to any one of embodiments 1 to 17, wherein the component (3) color-changing compound represented by structure (I) is present in the infrared-sensitive image recording layer in a coverage of at least 0.5 wt % to 15 wt % or less, based on the total weight of the infrared-sensitive image recording layer.

[0117] 19. A method for providing a lithographic printing plate, comprising: A) imagewise exposing the lithographic printing plate precursor of any one of embodiments 1 to 18 to infrared radiation to provide exposed and unexposed areas in the infrared-sensitive image-recording layer; and B) On-press removal of the unexposed areas of the infrared-sensitive image-recording layer from the substrate using lithographic printing ink, a fountain solution, or a combination of lithographic printing ink and a fountain solution. A method comprising:

[0118] The following examples are provided to further illustrate the practice of the present invention and are not intended to be limiting in any way. Unless otherwise indicated, materials used in the examples were obtained from various commercial sources as indicated, although other commercial sources may also be available.

[0119] An aluminum-containing substrate was prepared for a lithographic printing plate precursor in the following manner.

[0120] A 0.28 mm thick Hydro 1052 aluminum alloy strip or web (available from Norsk Hydro ASA, Norway) was used as the aluminum-containing "plate" material or support. Both the pre-etching and post-etching steps were carried out in alkaline solution under known conditions. The etched aluminum support was roughened (i.e., grained) by electrochemical means in a hydrochloric acid solution at approximately 23°C, resulting in an arithmetic mean roughness (Ra) of 0.5 μm on the surface of the aluminum-containing support. The aluminum-containing support was then subjected to two separate anodizing processes. The first anodizing process was carried out using phosphoric acid as the electrolyte to obtain an average pore diameter (D o ) is 19 nm, and the average dry thickness (T o A second anodization process was then carried out using phosphoric acid as the electrolyte to form an outer aluminum oxide layer with an average pore diameter (D i ) is 70 nm, and the average dry thickness (T i ) formed a 500 nm inner aluminum oxide layer. These two anodization steps were carried out in a continuous process on a typical production line used for the manufacture of lithographic printing plate precursors. The aluminum-containing support thus produced was coated with an aqueous solution of polyacrylic acid to a concentration of 0.03 g / m for substrates useful in the present invention. 2 gave a dry thickness of .

[0121] Next, infrared-sensitive composition formulations with components and amounts shown in Tables I, II, and III below were individually coated using a bar coater to form negative infrared-sensitive image-recording layers on the aluminum-containing substrates, as described below. After drying at 50° C. for 60 seconds, each of the inventive and comparative master plates described below had a coating density of 0.9 g / m 2 A dry coating weight of 1000 mg / kg was obtained. The raw materials listed in Table I are identified in Table II below, and the amounts of the various components are listed in Table III. These materials can be obtained from one or more commercial sources of chemicals or can be prepared using known synthetic methods and starting materials.

[0122] [Table 1]

[0123] [Table 2A]

[0124] [Table 2B]

[0125] [Table 2C]

[0126] [Table 3]

[0127] The lithographic printing plate precursors of the present invention and the comparative lithographic printing plate precursors were each evaluated for the following properties: "On-press developability" (DOP), "imaging speed", "print output" (PO), and "dark fade". The measurement scores for these properties are summarized in Table IV below.

[0128] On-press developability (DOP): On-press development was performed using a Trendsetter 3244x, with each lithographic printing plate precursor at 15 to 150 mJ / cm 2 The image-wise exposed lithographic printing plate precursors were then mounted on a MAN Roland Favorite 04 press without development (processing). Fountain solution (Varn Supreme 6038) and lithographic printing ink (Gans Cyan) were supplied, and lithographic printing was carried out. Since on-press development occurred during printing, on-press development was evaluated by counting the number of printed sheets required to obtain a clean background, and one of the following qualitative values was assigned based on the number of printed sheets that obtained a clean background: + and 0 are acceptable for this test parameter. + Less than 10 printed sheets 0 10-30 sheets of pre-printed paper - Over 30 pre-printed sheets

[0129] Imaging speed: Each of the lithographic printing plate precursors was exposed and developed as described above. The imaging speed was measured on paper by determining the ink density for the solid areas exposed to different energies after printing 1000 sheets. The inflection point of the ink density vs. exposure energy is considered to be a measure of the imaging speed. The following qualitative values were assigned as a result of individual experiments, with lower imaging energies being more desirable. A rating of + or 0 is acceptable for this parameter. + Image forming speed 30mJ / cm 2 less than 0 Image forming speed=30~60mJ / cm 2 - Image forming speed 60mJ / cm 2 super

[0130] Printout: Each lithographic printing plate precursor was exposed to 90 mJ / cm using a Trendsetter 800 III Quantum TH 1.7 (available from Eastman Kodak Company). 2 to provide exposed and unexposed areas in the negative-working IR-sensitive image-recording layer. For each imagewise exposed lithographic printing plate precursor, the ΔE value was determined using a Techkon Spectro Dens spectral densitometer, and the color difference between the exposed and unexposed areas was measured within 10 minutes of completing the imagewise exposure by calculating the Euclidean distance of the measured L*a*b values, and the following qualitative values were assigned immediately after exposure: +++18≦ΔE ++ 11≦ΔE<18 + 8≦ΔE<11 0 5≦ΔE<8 - ΔE<5

[0131] Dark fading: Each lithographic printing plate was imagewise exposed as described above and then stored in the dark for 24 hours. ΔE measurements were then made as described above and the following qualitative values were assigned: +++18≦ΔE ++ 11≦ΔE<18 + 8≦ΔE<11 0 5≦ΔE<8 - ΔE<5

[0132] [Table 4]

[0133] The results shown in Table IV support several conclusions. The data for Comparative Example 1 show that conventional acid-sensitive lactone leuco dyes, such as ASDP-1, typically provide fair or acceptable print output immediately after exposure without long-term storage, but this print output deteriorates after image storage (e.g., considering the consequences of dark fading). Comparative Example 4, which used the highly acid-sensitive lactone dye precursor ASDP-2, provided a dark print output immediately after exposure without long-term storage, but this print output deteriorated after image storage. Comparative Example 5 did not contain any conventional acid-sensitive lactone dye precursor or any other color-changing compound. The corresponding master showed poor print output even immediately after exposure.

[0134] The results of Comparative Example 2, compared to those of Inventive Example 1, demonstrate that the presence of a specific -XL group in the color-changing compound of Structure (I) or a specific -A group in Structure (Ia) results in improved print output and dark fading. Compounds with an indene ring connected to a diphenylamino group instead of a chloro group, such as Comparative Color-Changing Compound CCC-2, typically yielded fair or acceptable print output immediately after imaging, but the print output image deteriorated after dark fading storage. The differences between Comparative Example 2 and Inventive Example 1 demonstrate that the specific -XL or -A group, in addition to the Ar3 group in Structure (I) or Structure (Ia), is also important for the efficiency of the phenylation reaction to form stable colored species, as previously described. Because CCC-2 has a diphenylamino group as the -XL or -A group, it falls outside the scope of Structure (I) or Structure (Ia) described above.

[0135] Compared with Inventive Example 1, the results of Comparative Example 3 showed lower print output both immediately after imaging and after dark storage. These differences demonstrate that the presence of the (3) color-changing compound CCC-1 according to structures (I) and (Ia), which has an indene ring (benzene as Ar3 in structure (I)) in the conjugated chain, results in improved print output compared to the comparative color-changing compound CCC3, which has a cyclopentene ring in the conjugated chain. The differences between Comparative Example 3 and Inventive Example 1 demonstrate that Ar3 in structures (I) and (Ia) affects the geometry of the color-changing compound's polymethine chain and, therefore, the efficiency of the phenylation reaction with the tetraphenylborate anion, resulting in the formation of a stable colored phenylated product, as previously described. In addition to the difference in ΔE, it should also be noted that the exposed areas of Inventive Example 1 have a reddish hue, which is likely due to the phenylated product. The lithographic printing plate precursors in other Inventive Examples also have a reddish hue in the infrared-exposed areas.

[0136] Compared with the results of Inventive Example 1, the results of Inventive Example 2 showed somewhat higher print output images immediately after imaging and after dark fading. These differences are believed to be due to the reaction of color-changing compound CCC-1 with mercaptan compound M-1 to obtain the novel color-changing compound CCC-1 / M-1 of the present invention, as shown below. [ka]

[0137] The results from Example 2 of the present invention show that CCC-1 / M-1 is more effective than CCC-1 in the phenylation reaction with tetraphenylborate anion.

[0138] Examples 4 to 6 of the present invention demonstrate that M compounds other than M-1 can also react with the mesochloro group of CCC-1 to form a thioether bond, improving the print output image compared to the print output image obtained in Example 1 of the present invention.

[0139] Example 3 of the present invention demonstrates that when the color-changing compound according to the present invention provides the printing plate precursor with adequate absorption of infrared light, a separate infrared absorber can be omitted while maintaining a good print output image and imaging speed.

[0140] Comparative Example 6 shows that in the absence of a suitable borate compound according to the present invention, the printed output image may be insufficient even in the presence of a specific discoloration compound.Comparative Example 7 shows that in the absence of a suitable onium cation, such as diaryliodonium, a dense printed output image can be obtained, but the image formation speed is insufficient.Therefore, in order to obtain both a good image formation speed and a good printed output image, both a suitable borate anion and an onium cation, such as diaryliodonium, are required.

Claims

1. A lithographic printing plate precursor, an aluminum-containing substrate; an infrared-sensitive image-recording layer disposed on the aluminum-containing substrate; wherein the infrared-sensitive image-recording layer comprises the following components (1), (2), and (3): (1) a free radical initiator composition capable of generating free radicals upon exposure to infrared radiation; (2) a free-radically polymerizable composition, and (3) The following structure (I) 【Chemical 1】 (In the formula, Ar1, Ar2, and Ar3 independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or to complete a substituted or unsubstituted heteroaromatic ring; Y is an oxygen atom, a sulfur atom, or a C(R 4 R 5 ) represents a dialkylmethylene group represented by the formula 4 and R 5 are independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms, R 1 and R 2 are independently a substituted or unsubstituted alkyl group; X represents a single bond or a divalent linking group which is —S— or —O—; L is -C(=O)-OR 7 group, -SO 2 -R 3 group, -SO 2 NR 8 R 9 group, and -NPh 2 In the formula, Ph represents a phenyl group, and R 7 is -C(=O)OR 7 represents a substituted or unsubstituted alkyl group having a secondary or tertiary connecting carbon attached to the remainder of the group, R 3 , R 8 , and R 9 independently represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; Za represents one or more counterions to balance the charge in the remainder of the color-changing compound (3) according to structure (I). Including, The infrared-sensitive image recording layer has the following structure (IIa): B(R 10 R 11 R 12 R 13 ) － Structure (IIa) (In the formula, R 10 , R 11 , R 12 , and R 13 are independently a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, provided that R 10 , R 11 , R 12 , and R 13 at least three of which are the same or different substituted or unsubstituted aryl groups, each of which has no more than two halo substituents. A lithographic printing plate precursor comprising one or more borate anions represented by the formula:

2. The component (3) color-changing compound has the structure (Ia) 【Chemistry 2】 (In the formula, Ar1, Ar2, Ar3, R 1 , R 2 , Y, and Za are the same groups as described above for structure (I), and A is -S-R 14 , -O-R 14 , chloro, bromo, iodo, fluoro, nitro, cyano, trichloromethyl, tribromomethyl, trifluoromethyl, alkylammonium, dialkylammonium, and trialkylammonium groups, wherein each of the same or different alkyl groups contains 1 to 10 carbons and is optionally substituted; R 14 The lithographic printing plate precursor according to claim 1 , wherein R 1 is an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group.

3. A is a halo group or -S-R 14 wherein R 14 3. The lithographic printing plate precursor according to claim 2, wherein represents an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group.

4. 4. The lithographic printing plate precursor according to claim 2, wherein A represents a chloro group.

5. A is -S-R 14 wherein R 14 4. The lithographic printing plate precursor according to claim 2 or 3, wherein represents an optionally substituted alkyl group, an optionally substituted aryl group, or an optionally substituted heteroaryl group.

6. 6. The lithographic printing plate precursor according to claim 1, wherein the component (1) free radical initiator composition comprises one or more iodonium cations in an amount such that a molar ratio of the one or more borate anions to the one or more iodonium cations is at least 0.4:

1.

7. The lithographic printing plate precursor according to any one of claims 1 to 6, wherein the infrared-sensitive image-recording layer further comprises a component (4) an infrared-absorbing material different from the component (3) the color-changing compound.

8. The lithographic printing plate precursor according to any one of claims 1 to 7, wherein Ar3 represents the carbon and hydrogen atoms necessary to complete a benzene ring.

9. The lithographic printing plate precursor according to claim 1 , wherein Za comprises a tetraarylborate anion.

10. The component (1) free radical initiator composition has the following structure (II): [B(R 10 R 11 R 12 R 13 ) － ] n M n＋ Structure (II) (In the formula, R 10 , R 11 , R 12 , and R 13 is as defined for structure (IIa), n is an integer equal to or greater than 1, and M n＋ is an n-valent cation) The lithographic printing plate precursor according to any one of claims 1 to 9, comprising an organic borate represented by the formula:

11. R of structure (II) and structure (IIa) 10 , R 11 , R 12 , and R 13 The lithographic printing plate precursor according to claim 10, wherein all of are the same or different substituted or unsubstituted aryl groups.

12. R of structure (IIa) and structure (II) 10 , R 11 , R 12 , and R 13 The lithographic printing plate precursor according to claim 10, wherein all of are the same substituted or unsubstituted phenyl group.

13. 13. The lithographic printing plate precursor according to claim 7, wherein the infrared-sensitive image-recording layer further comprises a component (5) an acid-sensitive dye precursor different from all of the components (1), (2), (3), and (4) defined above.

14. The lithographic printing plate precursor according to any one of claims 1 to 13, wherein the component (1) free radical initiator composition comprises a diaryliodonium tetraphenylborate salt.

15. 15. The lithographic printing plate precursor according to claim 13, wherein the weight ratio of the component (5) acid-sensitive dye precursor to the component (3) color-changing compound represented by the following structure (I) in the infrared-sensitive image-recording layer is less than 1:

16. 16. The lithographic printing plate precursor according to claim 7, wherein the infrared-sensitive image-recording layer further comprises a component (6) a non-free-radically polymerizable polymeric material that is present in particulate form and is distinct from all of the components (1), (2), (3), and (4) defined above.

17. The lithographic printing plate precursor according to any one of claims 1 to 16, wherein the infrared-sensitive image-recording layer is the outermost layer.

18. 18. The lithographic printing plate precursor according to any one of claims 1 to 17, wherein the Component (3) color-changing compound represented by Structure (I) is present in the infrared-sensitive image-recording layer in a coverage of at least 0.5 wt % to 15 wt % or less, based on the total weight of the infrared-sensitive image-recording layer.

19. 1. A method for providing a lithographic printing plate, comprising: A) imagewise exposing the lithographic printing plate precursor according to any one of claims 1 to 18 to infrared light to provide exposed and unexposed areas in the infrared-sensitive image-recording layer; and B) on-press removing the unexposed areas of the infrared-sensitive image-recording layer from the substrate using lithographic printing ink, a fountain solution, or a combination of lithographic printing ink and a fountain solution. A method comprising:

Images