Lithographic printing plate precursor and method of use

Abstract

The IR-sensitive lithographic printing plate precursors provide stable print output images using a unique IR-sensitive image-recording layer. The IR radiation-sensitive layer includes (1) a free radical initiator composition including an electron donor and one or more iodonium cations, (2) a free radical polymerizable composition, and (3) a color-changing compound of structure (I) having an indene ring in a conjugated chain between aromatic end groups. The IR radiation-sensitive image-recording layer also includes one or more borate ions. After IR imaging, these precursors show desirable print output images both when fresh and after dark storage. The lithographic printing plate precursors can be developed on-press after appropriate infrared imaging.

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 comprises a unique infrared-sensitive composition that provides a stable print output image between the exposed and unexposed areas of an imagewise exposed infrared-sensitive image recording layer. The present invention also relates to a method of using these plates to provide a lithographic printing plate with excellent print output image. [Background technology]

[0002] In lithographic printing, lithographic ink-receptive areas, 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 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, perhaps using blanket rollers on a 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 a substrate. Such image-recording layers comprise a radiation-sensitive component that can be dispersed in a suitable polymeric 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 substrate. The unremoved exposed areas of the image-recording layer are lithographic ink-receptive, and the hydrophilic substrate surface exposed by the development process accepts water and aqueous solutions, such as fountain solution, and repels lithographic ink.

[0004] In recent years, there has been an increasing desire in the lithographic printing industry to simplify the manufacture of lithographic printing plates by performing on-press development ("DOP") using lithographic ink or a fountain solution, or both, to remove unexposed areas of the image-recording layer.

[0005] Thus, on-press developable lithographic printing plate precursors have attracted increasing attention in the printing industry over recent decades due to their many advantages over conventionally processed ("off-press" processed or developed) lithographic printing plate precursors, including less environmental impact and savings in processing chemicals, processing machine floor space, and maintenance costs. After laser imaging, on-press developable precursors can be directly mounted on a printing press without a prior wet chemical step to remove the imageable coating on the precursor in the non-printing areas.

[0006] Therefore, it is highly desirable for such imaged lithographic printing plate precursors to have different colors in exposed and unexposed areas. The color difference, or "contrast," between exposed and unexposed areas is typically referred to as the "printed output" or "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 the printing plate precursor can be properly mounted on a printing press unit.

[0007] Many approaches have been taken to increase the print output of on-press developable printing plate precursors, and all of these approaches have been observed to have certain drawbacks.

[0008] For example, the print output on a printing plate precursor having an imaging composition that includes an acid generator and an acid-sensitive color precursor, such as a lactone-based leuco dye, is often not dense enough. This is because the efficiency of acid generation is limited in imaging compositions designed for infrared imaging and on-press development. In addition, 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 print output based on the color change caused by protons often fades after imaging.

[0009] Co-pending and commonly assigned US Patent Application Publication No. 2021 / 0078350 (Viehmann et al.) describes an approach to increase print output by incorporating color-forming compounds into infrared-sensitive imaging compositions that are more sensitive and switch from colorless to colored forms at lower acid concentrations. Special additives suppress background coloration to stabilize good contrast. Although the initial print output obtained is very high, there remains a need to improve the print output and print output stability obtained using the described chemistry.

[0010] Another approach to generate print output is based on the use of infrared (IR) decomposable dyes. These dyes contain thermolabile groups, and when exposed to infrared or heat, they can lose the thermolabile groups to form compounds of various colors with absorption spectra in the visible spectrum. Examples based on this approach are 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 generate sufficient print output, such IR decomposable dyes should typically be present in relatively large amounts in the imaging composition, or higher infrared exposure energy is required at lower amounts.

[0011] Furthermore, some IR decomposable dyes used in such chemical reactions produce gaseous materials upon decomposition. This gaseous material is 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 printing operations. Furthermore, the heat pulses generated from the high energy levels of the exposing infrared radiation can often compromise the physical integrity of the imaging composition, following a process commonly referred to as ablation or partial ablation. Ablation or partial ablation typically results in reduced image durability. For example, in U.S. Pat. No. 8,148,042 (noted above), printing plate precursors PPP34 and PPP35, which contain IR decomposable dyes in the imaging composition, were reported to use 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 having sufficient durability in the infrared exposed areas after any type of development.

[0012] When the IR decomposable dyes taught in U.S. Pat. No. 8,148,042 (noted above) are directly incorporated into the polymerizable composition, more practical exposure energies, e.g., 120 mJ / cm 2 The inability to produce dense print output below energies is demonstrated in US Patent Application Publication No. 2020 / 0147950 (Billiet), where PPP04, using the IR decomposable dye IR02 in combination with IR01 used in PPP03, provided only a slight print output benefit compared to PPP03 (e.g., 120 mJ / cm 2 (ΔE of 2.99 vs. 2.12 for Billiet.) The Billiet ΔE parameter is the same as the ΔE parameter defined below.

[0013] To avoid the ineffectiveness or undesirable effects of IR-decomposable dyes on negative-working printing plate precursors having a polymerizable imaging composition, WO 2019 / 219560 (Billiet et al.) teaches locating 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 manufacture, and its removal, if present, reduces the development rate. In addition, the protective layer may release polymeric and other materials into the fountain solution when the printing plate precursor is developed on press, causing malfunction of 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.

[0014] US Patent Publication No. 2019 / 0329545 (Shibamoto et al.) teaches the use of certain IR-decomposable dyes that, 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 document suggests the color-forming capability of such imaging compositions containing IR-decomposable dyes under the demonstrated exposure conditions. Although this publication describes certain infrared dyes that are believed to be IR-decomposable, none of the examples use IR-decomposable dyes as taught in either US Patent No. 8,148,042 (above) or US Patent Publication No. 2010 / 0274023 (above). On the other hand, the teachings of U.S. Patent Application Publication No. 2019 / 0329545 (noted above) discuss those taught in U.S. Pat. No. 8,632,941 (Balbinot et al.) as IR-decomposable infrared dyes.

[0015] US Patent Application Publication No. 2020 / 0117086 (Nogoshi et al.) describes a combination of a specific IR decomposable dye and 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 print output, as shown by Comparative Examples 1 and 2 thereof.

[0016] U.S. Patent No. 8,084,182 (Munnelly et al.) teaches the use of certain IR-decomposable dyes in IR-sensitive polymerizable compositions. In Examples 1-3, Munnelly et al. describe the use of IR-decomposable dyes containing alkoxycarbonylamino groups in imageable compositions that are used in combination with conventional acid-sensitive dye precursors, with a maximum output of 300 mJ / cm2. 2 However, in the absence of this acid-sensitive dye precursor, Example 4 of Munnelly et al. demonstrated a much lower print output (ΔE value of 6.6). The use of a comparative IR-degradable dye from the teachings of U.S. Pat. No. 8,148,042 (noted above), which does not contain an alkoxycarbonylamino group, also demonstrated a print output of 300 mJ / cm2 even in the presence of an acid-sensitive dye precursor. 2 Low print output was produced at an imaging energy of 100 sq. m (ΔE 4.6). Furthermore, Munnelly et al. demonstrated only a short press run of 200 copies, and it is not clear whether printing plates derived from Munnelly et al.'s masters would have sufficient in-press image durability to satisfy industrial customers who typically require printing significantly more than 200 copies in a typical press run.

[0017] Despite all the efforts described in the known literature with regard to providing sufficient print output for on-press developable lithographic printing plates along 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 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. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] US Patent Application Publication No. 2021 / 0078350 [Patent Document 2] U.S. Patent No. 8,148,042 [Patent Document 3] U.S. Pat. No. 8,178,282 [Patent Document 4] US Patent Application Publication No. 2010 / 0274023 [Patent Document 5] US Patent Application Publication No. 2020 / 0147950 [Patent Document 6] International Publication No. 2019 / 219560 [Patent Document 7] US Patent Application Publication No. 2019 / 0329545 [Patent Document 8] U.S. Patent No. 8,632,941 [Patent Document 9] US Patent Application Publication No. 2020 / 0117086 [Patent Document 10] U.S. Pat. No. 8,084,182 [Patent Document 11] International Publication No. 2020 / 262689 [Patent Document 12] International Publication No. 2021 / 241457 [Patent Document 13] International Publication No. 2021 / 241458 [Patent Document 14] European Patent No. 3793829 Summary of the Invention

[0019] The present invention provides a lithographic printing plate precursor comprising: a substrate; and an infrared-sensitive image-recording layer disposed on the substrate, the infrared-sensitive image-recording layer comprising the following components (1), (2), and (3): (1) a free radical initiator composition capable of generating free radicals upon exposure to infrared radiation, the free radical initiator composition comprising an electron donor and one or more iodonium cations; (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 is independently a substituted or unsubstituted alkyl group; X represents a single bond or -S-, -O-, and >N(R 6 )(wherein, R 6 represents a divalent linking group selected from hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or L; L is -C(=O)-OR 7 group, -SO2-R 3 group, or -SO2NR 8 R 9 represents a group, 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 counter ions for balancing the charge in the remainder of the color-changing compound according to structure (I). Including, The infrared-sensitive image-recording layer has the following structure (IIIa): B(R 10 R 11 R 12 R 13 ) - Structure (IIIa) (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, with the proviso that R 10 , R 11 , R 12 , and R 13 at least three of 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] In some embodiments of the master according to the present invention, the infrared-sensitive image-recording layer comprises one or more borate anions in an amount such that the molar ratio of the one or more borate anions to one or more iodonium cations is at least 0.5:1.

[0021] The present invention also provides a method of providing a lithographic printing plate, comprising the steps of: 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 a lithographic printing ink, a fountain solution, or a combination of a lithographic printing ink and a fountain solution. The present invention provides a method comprising:

[0022] The present invention provides printout images produced in infrared-sensitive image recording layers in areas exposed to relatively low energy imaging infrared radiation. Such printout images are dense and do not fade significantly during dark storage. Furthermore, in many embodiments, the imaging chemistry used to provide excellent printout images does not adversely affect imaging speed, on-press developability, or lithographic image durability. Further details of the present invention and the results it provides are described below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The following discussion is directed to various embodiments of the invention, and while some embodiments may be desirable for particular applications, the disclosed embodiments should not be interpreted or viewed as limiting the scope of the invention as claimed below. Moreover, those of ordinary skill in the art will appreciate that the following disclosure has broader application than is expressly described in the discussion of any particular embodiment.

[0024] definition As used herein to define various components of the infrared-sensitive image-recording layer, and other materials used in the practice of the present invention, unless otherwise indicated, the singular forms "a," "an," and "the" are intended to include one or more of the components (i.e., include plural referents).

[0025] Each term not expressly defined in this application should be understood to have the meaning generally accepted by those skilled in the art. If the interpretation of a term renders the term meaningless or essentially meaningless in the context, the term should be interpreted as having the meaning set forth in a standard dictionary.

[0026] The use of numerical values ​​within the various ranges set forth herein should be considered as approximations, unless expressly indicated otherwise, with the word "about" preceding both the minimum and maximum values ​​within the stated range. As such, slight variations above and below the stated ranges may be useful to achieve substantially the same results as values ​​within the range. Moreover, the disclosure of these ranges is intended to be continuous ranges, including all values ​​between the minimum and maximum values, as well as the endpoints of the ranges.

[0027] Unless the context indicates otherwise, as used herein, the terms "lithographic printing plate precursor," "master," and "IR-sensitive lithographic printing plate precursor" are intended to equally refer to embodiments of the present invention.

[0028] As used herein, the term "infrared absorber" refers to compounds or materials that absorb electromagnetic radiation in the near infrared (near IR) and infrared (IR) regions of the electromagnetic spectrum, and typically have an absorption maximum in the near IR and IR regions.

[0029] 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.

[0030] In the present invention, the darkness of the printed output image is generally indicated by the parameter ΔE, which is the Euclidean distance in the CIE 1976 L*a*b* color space between the colors of radiation-exposed and radiation-unexposed areas measured from reflection measurements in 45 / 0 geometry (unpolarized light) using a CIE 2° observer and D50 as illuminant according to EN ISO 11664-4 "Colorimetry -- Part 4: CIE 1976 L*a*b* color space" and other known literature. Color measurements can be made using commercially available instruments such as Techkon SpectroDens. In the CIE 1976 L*a*b* color space, colors are 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.

[0031] In the present invention, the visible spectral region refers to the spectral region of electromagnetic radiation having wavelengths between 400 nm and 700 nm.

[0032] As used herein, the terms "printout" and "printout image" are intended to be synonymous.

[0033] For a clear definition of any term relating to polymers, please refer to the "Glossary of Basic Terms in Polymer Science" published by the International Union of Pure and Applied Chemistry ("IUPAC"), Pure Appl. Chem. 68, 2287-2311 (1996). However, any definitions expressly set forth herein shall be deemed controlling.

[0034] As used herein, the term "polymer" is used to refer to a compound with a relatively large molecular weight formed by linking many small reactive monomers to form repeating units of the same chemical composition. These polymer chains usually form coiled structures in a random manner. Depending on the choice of solvent, the polymer can become insoluble as the chain length grows, resulting in polymer particles dispersed in the solvent. These particle dispersions can be very stable and useful in the infrared-sensitive image recording layer described for use in the present invention. In the present invention, unless otherwise indicated, the term "polymer" refers to non-crosslinked materials. Thus, crosslinked polymer particles are different from non-crosslinked polymer particles, and this difference is in that non-crosslinked polymer particles can be dissolved in certain organic solvents with good solvation properties, whereas crosslinked polymer particles can swell but not dissolve in organic solvents because the polymer chains are connected by strong covalent bonds.

[0035] The term "copolymer" refers to a polymer composed of two or more different repeating units, ie, repeat units, arranged along the polymer chain.

[0036] The term "backbone" refers to a chain of atoms in a polymer to which multiple pendant groups can be attached. One example of such a backbone is an "all-carbon" backbone resulting from the polymerization of one or more ethylenically unsaturated polymerizable monomers.

[0037] As used herein, the term "ethylenically unsaturated polymerizable monomer" refers to a compound that contains one or more ethylenically unsaturated (-C=C-) bonds that can be polymerized using free radical or acid-catalyzed polymerization reactions and conditions. This term is not intended to refer to compounds that have only unsaturated -C=C- bonds that are not polymerizable under such conditions.

[0038] Unless otherwise indicated, the term "wt. %" refers to the amount of a component or material relative to the total solids of a composition, formulation, or layer. The percentage can be the same for either the dry layer, or the total solids of the formulation or composition, unless otherwise indicated.

[0039] As used herein, the term "layer" or "coating" can consist of one disposed or applied layer, or a combination of several successively disposed or applied layers. When a layer is considered to be infrared-sensitive and negative-working, it is both sensitive to infrared radiation (as described above for "infrared absorber") and negative-working in the formation of a lithographic printing plate.

[0040] 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, a lithographic printing ink, or a combination of a fountain solution and a lithographic printing ink during the printing of the first few sheets.

[0041] use The lithographic printing plate precursor according to the present invention is useful for providing a lithographic printing plate that shows a desirable print output image 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.

[0042] Planographic printing plate original plate The 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 substrate (as described below) to form an infrared-sensitive image recording layer that is negative-working. In general, 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 and comprising an electron donor and one or more iodonium cations, component (2) a free-radical polymerizable composition, and component (3) a color-changing compound represented by structure (I) as described below. All of these components (1), (2), and (3) are defined in detail below, and are the only essential components required to obtain the advantages of the present invention. Additionally, the infrared-sensitive image recording layer must comprise one or more borate anions, as described in detail below, but may optionally comprise one or more borate anions in a specific molar ratio to one or more iodonium cations.

[0043] In some embodiments, the infrared-sensitive image recording composition (and the resulting infrared-sensitive image recording layer) may further comprise component (4) infrared-absorbing material (or a mixture of two or more thereof) different from (3) the color-changing compound, and component (5) 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) non-free-radically polymerizable polymeric material (or a mixture of two or more thereof) different from all of components (1), (2), (3), and (4), or all of these components (4)-(6). All of these components are described below. In some very useful embodiments, the infrared-sensitive image recording layer consists essentially of all of the above-mentioned components (1)-(6) to provide the desired print output image, as well as the desired lithographic printing plate precursor having the best overall imaging and printing properties.

[0044] Generally, there is only one infrared-sensitive image-recording layer in each master. In many embodiments, 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) disposed over (or directly on and in contact with) the infrared-sensitive image-recording layer, as described below.

[0045] substrate: The substrate used to prepare the plate precursor according to the present invention generally has a hydrophilic imaging surface, or at least a surface which is more hydrophilic than the applied infrared-sensitive image-recording layer. The substrate generally comprises an aluminum-containing support which may be composed of raw aluminum or a suitable aluminum alloy conventionally used to prepare lithographic printing plate precursors.

[0046] 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 and conventional conditions to form the desired hydrophilic aluminum oxide (or anodic oxide) layer on the aluminum-containing support. There may be a single aluminum oxide (anodic oxide) layer, or there may be 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 under an infrared-sensitive image-recording layer, which may be provided as described below. Such pore and pore width control process considerations 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 EP 2,353,882 (Tagawa et al.). Teachings of providing two successive anodization processes to provide different aluminum oxide layers in the improved substrate (e.g., an outer aluminum oxide layer disposed on an inner aluminum oxide layer) are described, for example, in U.S. Patent Application Publication No. 2018 / 0250925 (noted above). Teachings of providing three successive anodization processes to provide different aluminum oxide layers in the improved substrate are described, for example, in U.S. Patent Application Publication No. 2021 / 0094336.

[0047] The sulfuric acid anodization of the aluminum support generally requires at least 1 g / m 2~5g / m 2 or less, more typically at least 1.5 g / m 2 ~4g / m 2 The following aluminum (anodic) oxide weights (coverages) on the surface are given: Phosphoric acid anodizing generally provides at least 0.5 g / m 2 ~5g / m 2 or less, more typically at least 1 g / m 2 ~3g / m 2 The following weights of aluminum (anodic) oxide on the surface are given:

[0048] Anodized aluminum-containing substrates may be treated with alkaline or acidic pore-enlarging solutions to provide an anodized oxide layer containing columnar pores. In some embodiments, the treated aluminum-containing substrate may include a hydrophilic layer disposed directly on the grained, anodized, and post-treated aluminum-containing support, such hydrophilic layer may include a non-crosslinked hydrophilic polymer having carboxylic acid side chains.

[0049] Alternatively, the anodized aluminum oxide-containing support may be further treated using known post-anodization processes, such as post-treatment with an aqueous solution of a hydrophilic material to seal the pores of the anodized oxide or to hydrophilize the surface, or both. Representative hydrophilic materials of this type for providing a hydrophilic layer (e.g., hydrophilic polymer coating) include, but are not limited to, poly(vinyl phosphonic acid) (PVPA), vinyl phosphonic acid copolymers, poly[(meth)acrylic acid] or its alkali metal salts, or (meth)acrylic acid copolymers or their alkali metal salts, mixtures of phosphate and fluoride salts, or sodium silicate. Such hydrophilic coatings may be disposed on the outermost aluminum oxide layer (e.g., the outer aluminum oxide layer, if multiple aluminum oxide layers are present). The post-treatment process material may also contain unsaturated double bonds to enhance adhesion between the treated surface and infrared-exposed areas on the surface. Such unsaturated double bonds may be provided in low molecular weight materials or may be present in the side chains of a polymer. Useful post-treatment processes include immersion of the substrate with rinsing, immersion of the substrate without rinsing, and various coating techniques such as extrusion coating.

[0050] 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, which is directly attached to the phosphorus atom, where M' represents a hydrogen, sodium, potassium, or aluminum atom. The hydrophilic layer has a molecular weight of at least 0.0002 g / m 2 ~0.1g / m 2The following dry coverages may be placed over the outermost aluminum oxide layer:

[0051] 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 said composition) is designed to be "negative-working", a term known in the art of lithographic printing.Furthermore, the infrared-sensitive image recording layer can be designed with a specific combination of components to provide on-press developability to the lithographic printing plate precursor after exposure, for example, to enable on-press development using a fountain solution, a lithographic printing ink, or a combination of the two.

[0052] 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 may include one or more organic halogen compounds, such as trihaloalkyl compounds; halomethyltriazines; bis(trihalomethyl)triazines; or one or more onium salts, such as iodonium salts, sulfonium salts, diazonium salts, phosphonium salts, and ammonium salts, many of which are known in the art as being capable of generating free radicals upon exposure to infrared radiation. However, it is essential that the (1) initiator composition includes one or more iodonium cations, with or without other representative listed compounds.

[0053] 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 '282)

[0087] to

[0102] and U.S. Patent No. 6,309,792 (Hauck et al.), as well as in JP 2002 / 107916 A and WO 2019 / 179995 A.

[0054] For example, component (1) the free radical initiator composition should contain one or more iodonium cations. Useful onium salts are described, for example, in the aforementioned publication, U.S. Pat. No. '282,

[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 such 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.

[0055] Examples of anions in iodonium salts include halogen anions, ClO4 - , PF6 - , BF4 - , SbF6 - , CH3SO3 - , CF3SO3 - , C6H5SO3 - , CH3C6H4SO3 - , HOC6H4SO3 - , ClC6H4SO3 - and boron anions as described, for example, in U.S. Patent No. 7,524,614 (Tao et al.). Representative useful iodonium salts are described in columns 6-7 of U.S. Patent No. 7,524,614 (noted above), where the iodonium cation can include the various monovalent substituents "X" and "Y" listed, or fused carbocyclic or heterocyclic rings each bearing a phenyl group.

[0056] Useful iodonium salts can be polyvalent iodonium salts, having at least two covalently linked iodonium cations in the molecule.

[0057] Also useful are the iodonium salts described in JP 2002-082429 A [or U.S. Patent Application Publication No. 2002-0051934 (Ippei et al.)], paragraphs

[0033] to

[0038] . Representative iodonium borate salts are, for example, those listed in column 8 of U.S. Patent No. 7,524,614 (noted above).

[0058] The component (1) free radical initiator composition used in the practice of the present invention should contain one or more electron donors that not only participate in the generation of free radicals for the polymerization of the (2) free radically polymerizable compound, described below, but also promote the color change reaction of the (3) color-changing compound, described below. For example, electron donor compounds particularly useful in the present invention have an oxidation potential (V) of preferably less than 1.1 versus an Ag / AgCl electrode. ox ) borate compounds and other organic compounds.

[0059] Representative compounds that can act as electron donors in the practice of the present invention include, but are not limited to, compounds having a substructure in which a nitrogen atom, an oxygen atom, or a sulfur atom is directly bonded to an aromatic or heteroaromatic group. A person skilled in the art of chemistry would be able to design a compound having this feature in combination with the electrochemical features described above. Some potentially useful electron donor compounds are described in

[0013] to

[0015] of JP 2005 / 062482 A. Examples of such compounds are described as A-1 to A-25 in

[0017] to

[0020] of this publication. A person skilled in the art using the teachings provided herein would be able to use routine experimentation to determine which compounds are acceptable or optimal electron donor compounds according to the present invention.

[0060] Particularly useful compounds which can be used as electron donors include organic borates, which are represented by the following structure (III): [B(R 10 R 11 R 12 R13 ) - ] n M n+ Structure (III) In the formula, R 10 , R 11 , R 12 , and R 13 are, independently, substituted or unsubstituted alkyl groups, e.g., having 1 to 12 carbon atoms, optionally substituted with one or more fluoro, chloro, and bromo groups, or substituted or unsubstituted aryl groups, having 6 to 10 carbon atoms in the aromatic ring, optionally substituted with one or more alkyl, alkenyl, alkoxy, alkoxycarbonyl, and acyloxy groups, one or two fluoro, chloro, and bromo groups, at one or more of the aromatic rings, with substituted or unsubstituted 6-membered aromatic (phenyl) groups being the most useful. In most embodiments, R 10 , R 11 , R 12 , and R 13 At least three of R are the same or different substituted or unsubstituted aryl groups as defined above, and in the best embodiment, R 10 , R 11 , R 12 , and R 13 are the same substituted or unsubstituted phenyl group, for example, all of these groups are the same unsubstituted phenyl group.

[0061] In structure (III), n is an integer equal to or greater than 1, and M n+ is an n-valent cation, such as, but not limited to, a monovalent alkali metal cation, an ammonium cation, a monomeric and polymeric onium cation, such as an iodonium, sulfonium, or diazonium cation, or any other inorganic or organic molecule bearing a cationic charge, such as a cyanine dye bearing a cationic charge. In some embodiments, M n+ may represent one or more of the iodonium cations described above.

[0062] If the other components in the infrared-sensitive image-recording layer do not include a borate compound represented by Structure (III) above, then such a borate compound should be present in Component (1), the free radical initiator composition.

[0063] The one or more electron donors useful in the present invention are present in the infrared-sensitive image-recording layer in an amount of at least 0.5% by weight, or at least 1% by weight, based on the total coverage (solids) of the infrared-sensitive image-recording layer, and no more than 10% by weight, or no more than 20% by weight.

[0064] 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 amount generally being at least 1% by weight to no more than 20% by weight of all components, including electron donor and iodonium cation, based on the total coverage (solids) of the infrared-sensitive image-recording layer.

[0065] Because the component (1) free radical initiator composition may have multiple components, the useful amounts or dry coverages of the various components of the component (1) free radical initiator composition in the infrared-sensitive image-recording layer will be readily apparent to one of ordinary skill in the art based on their knowledge and the representative teachings provided herein, including the examples set forth below. Useful components (1) free radical initiator composition materials are readily available from commercial sources worldwide or can be readily prepared using known starting materials and synthesis methods.

[0066] Another essential feature of the infrared-sensitive image recording layer is the component (2) free radical polymerizable composition, which comprises one or more free radical polymerizable components, each of which comprises one or more free radical polymerizable groups that can be polymerized using free radical initiation during infrared exposure. In some embodiments, there are at least two free radical polymerizable components, each of which has the same or different number of free radical polymerizable groups in each molecule. Thus, a useful free radical polymerizable component may contain one or more free radical polymerizable monomers or oligomers that have one or more polymerizable ethylenically unsaturated groups (e.g., two or more of such groups). Similarly, crosslinkable polymers having such free radical 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 radical polymerizable component comprises a carboxyl group.

[0067] The one or more free radically polymerizable components can 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 can still be present if desired.

[0068] Useful free radical 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 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, 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 having a high number of (meth)acrylates have high crosslinking efficiency and can be included in the (2) free radical polymerizable composition.

[0069] Useful free radical 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], 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.

[0070] Mixtures of urethane or urea (meth)acrylates with non-urethane and non-urea (meth)acrylates may be used in the (2) free radically polymerizable composition. In some embodiments, mixtures of compounds having different numbers of (meth)acrylate groups may be used.

[0071] Numerous other free radically polymerizable components are known in the art and are described in a significant body of literature, including Photoreactive Polymers: The Science and Technology of Resists, A Reiser, Wiley, New York, 1989, pp. 102-177, Radiation Curing: Science and Technology by BM Monroe, edited by S.P. Pappas, Plenum, New York, 1992, pp. 399-440, and "Polymer Imaging" by A.B. Cohen and P. Walker in Imaging Processes and Material, edited by J.M. Sturge et al., Van Nostrand Reinhold, New York, 1989, pp. 226-262. For example, useful free radical polymerizable components are described in EP 1,182,033 A1 (Fujimaki et al.), paragraphs

[0170] et seq., as well as U.S. Patent Nos. 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 radical polymerizable components include 1H-tetrazole groups.

[0072] Component (2) The one or more components of the free radically polymerizable composition are generally all present in a total amount of at least 10% by weight or at least 20% by weight, and no more than 50% by weight or no more than 70% by weight, based on the total coverage (solids) of the infrared-sensitive image-recording layer.

[0073] The third essential component of the infrared-sensitive image recording composition and 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 (1) or a mixture of two or more thereof. Thus, in general, 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, or a pyrimidin-6-yl ring, a pyrazine ring, a triazine ring, a pyrrole ring, a furan ring, a thiophene ring, a pyrazole ring, or 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.

[0074] In many useful embodiments of the present invention, Ar1 and Ar2 are the same atoms required 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.In addition, 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 (for example, 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 groups described.It is also desirable that Ar3 represents the carbon atoms required to complete the benzene (benzo) ring of structure (I).

[0075] In addition, in structure (I), 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 substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms. In many useful embodiments of the invention, Y at each occurrence is the same or different dialkylmethylene group, or even the same dialkylmethylene group, where R 4 and R 5 are the same unsubstituted alkyl groups having 1 or 2 carbon atoms. One of ordinary skill in the art would be able to make numerous compounds in which Y varies among the possible groups, including the many possible dialkylmethylene groups.

[0076] 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.

[0077] Further, in structure (I), X represents a single bond or is selected from the group consisting of -S-, -O-, and >N(R 6 )(wherein, R 6 represents a divalent linking group selected from hydrogen, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or L (defined below). In certain embodiments used in the present invention, X is >N(R 6 ) group, in particular R 6 is hydrogen or an unsubstituted alkyl group having 1 to 8 carbon atoms.

[0078] Also, in structure (I), L is -C(=O)-OR 7 group, -SO2-R 3 group, or -SO2NR 8 R 9 represents a group, 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 9 each independently represents 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. 3 may be a haloalkyl group having 1 to 12 carbon atoms in which one or more of the hydrogen atoms have been replaced with a halogen atom. In some embodiments, L comprises an electron-withdrawing group capable of undergoing a redox reaction with the electron donor in the (1) free radical initiator composition described above. In certain embodiments of the invention, L is -SO2-R 3 is a group, wherein R 3 is an unsubstituted alkyl group having 1 or 2 carbon atoms, or a fluoroalkyl group having 1 or 2 carbon atoms and at least one hydrogen atom replaced with a fluoro atom. For example, R 3 can be a trifluoromethyl group.

[0079] Finally, in structure (I), Za represents one or more counterions to balance the charge in the remainder of the color-changing compound according to structure (I). For example, if the remainder of the color-changing compound according to structure (I) is positively charged, Za represents one or more anions. Many useful anions are available, such as halogen anions, ClO4 - , PF6 - , BF4 - , SbF6 - , CH3SO3 - , CF3SO3 - , C6H5SO3 - , CH3C6H4SO3 - , HOC6H4SO3 - , ClC6H4SO3 - , and boron-containing anions described, for example, in U.S. Pat. No. 7,524,614 (above) are known in the art. Useful boron-containing anions include tetraarylborate anions (such as 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 color-changing compound according to structure (I) is negatively charged, Za represents one or more cations. 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 component (1) free radical initiator composition described above. In view of the color-developing chemical reactions described below, it is preferred that Za represents one or more anions and the remainder of the color-changing compound according to structure (I) is positively charged.

[0080] Some particularly useful embodiments of the component (3) color-changing compound have the following structure (II): [ka] (In the formula, Ar1, Ar2, Ar3, R 1 , R 2 , R3 , R 6 , Y, and Za are as defined above. It is expressed as:

[0081] Without wishing to be bound by any particular theory, it is believed that Ar3 in structure (I) or structure (II) affects the geometry of the polymethine chain in the component (3) color-changing compound, thus making the compound more reactive in the presence of an organic borate salt according to structure (III) as part of component (1). For example, in the presence of tetraphenylborate anion, a compound according to structure (I) or structure (II) [the (3) color-changing compound 2 of the present invention shown below, i.e., ICCC-2] can undergo a chemical reaction (shown below) to form a phenylated product ICCC2-Ph during or after irradiation of the infrared-sensitive image recording layer with a suitable infrared source. The UV-vis spectrum of ICCC2-Ph in methanol has an absorption peak at around 514 nm, which is significantly different from the absorption peak of ICCC2 at 770 nm. The phenylation of the (3) color-changing compound of the present invention can also be achieved by reaction with a triphenyl alkyl borate salt, such as triphenyl-n-butyl borate and tris(3-fluorophenyl)-n-butyl borate. [ka]

[0082] Phenylation products such as ICCC2-Ph are stable for at least one week at room temperature in the infrared-exposed areas of the infrared-sensitive image recording layer, thus providing a stable print output for infrared-exposed lithographic printing plate precursors. Furthermore, in the presence of a sufficient amount of borate compound according to the above structure (III), the phenylation products can be formed at much lower inputs of infrared energy than typically required for the decomposition reaction involving cleavage of leaving groups as described in many of the prior arts listed in the Background section above. Furthermore, the phenylation reaction results in a much larger shift in the absorption peak in the visible spectrum than the decomposition reaction, which is useful for generating large color differences. For example, the phenylation reaction of ICCC-2 gives a peak shift of about 256 nm, while the decomposition reaction of ICCC-2 gives a peak shift of 140 nm, forming the product shown below (lambda in methanol): max approx. 632nm). [ka]

[0083] As another example, the following decomposition reaction involving a decomposable infrared dye outside the scope of structure (I) can only produce a peak shift of 164 nm, requires high energy input, and produces gaseous by-products. [ka]

[0084] In infrared-sensitive recording layers having both a color-changing compound according to structure (I) or structure (II) and a borate compound according to structure (III), both phenylation reactions and decomposition can occur. 2At an exposure energy level of 100 nm, the amount of phenylation products relative to decomposition products, a metric of print output (e.g., color difference ΔE between exposed and unexposed areas), is determined by the amount of borate compound available for the phenylation reaction. Because borate compounds can also participate in reactions with iodonium cations to produce free radical production, the amount of borate compound available for the phenylation reaction is determined by the amount of both borate compound and iodonium cation.

[0085] In some embodiments of the present invention, relatively low exposure energies, e.g., 110 mJ / cm 2 If sufficient print output is desired, the molar ratio of one or more borate anions according to structure (IIIa) described below to one or more iodonium cations in the infrared-sensitive image-recording layer can be at least 0.5:1, more preferably at least 0.8:1 to no more than 4:1.

[0086] Even in the presence of sufficient borate compounds, Ar3 in both structures (I) and (II) remains essential: without Ar3 in the decomposable infrared dye, the phenylation reaction will be inefficient, if it occurs at all.

[0087] The component (3) color-changing compound, either 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% by weight or at least 1% by weight, and not more than 10% by weight or not more than 15% by weight, based on the total weight of the infrared-sensitive image-recording layer.

[0088] Therefore, in some embodiments of the master of the present invention, it is essential that 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 the one or more borate anions to the one or more iodonium cations is at least 0.5:1 or at least 0.8:1, and not more than 2:1 or not more than 4:1. The one or more borate anions have the following structure (IIIa): B(R 10 R11 R 12 R 13 ) - Structure (IIIa) (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, with the proviso 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 up to two halo substituents.

[0089] One or more iodonium cations can be provided to the infrared-sensitive image-recording layer as part of the (1) free radical initiator composition. However, one or more borate anions can be provided to the infrared-sensitive image-recording layer in various forms. For example, one or more borate anions can be provided as part of one or more iodonium salts in the (1) free radical initiator composition. Alternatively, one or more borate anions can be provided as one or more Za counterions in Structure (I) or Structure (II), or as part of the component (4) infrared absorbing material described below. Furthermore, one or more borate anions can be provided as separate borates in the (1) free radical initiator composition.

[0090] 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 component (3) the color changing compound described above. (4) The infrared absorber provides the desired infrared sensitivity or converts radiation into heat, or both. Useful infrared absorbers may be pigments or infrared absorbing dyes. Suitable dyes are those 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., U.S. Pat. No. 7,018,775, Tao, U.S. Pat. No. 7,368,215, Munnelly et al., U.S. Pat. No. 8,632,941, Balbinot et al., and U.S. Patent Application Publication No. 2007 / 056457, Iwai et al. In some infrared-sensitive embodiments, it is desirable that at least one (4) infrared absorber 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.).

[0091] In addition to low molecular weight IR-absorbing dyes, IR-dye chromophores bound to polymers can be used as well. Additionally, IR-dye cations can be used as well, i.e., the cation is an IR-absorbing moiety of a dye salt that ionically interacts with a polymer containing a carboxy, sulfo, phospho, or phosphono group in the side chain.

[0092] The total amount of component (4) infrared absorbing agent 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.

[0093] Another optional but desirable component of the infrared-sensitive image recording layer is component (5) 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 neutral form and switch to a colored form when protonated. Many leuco dyes are known for this purpose, including those described in EP 3,418,332 A2 (Inasaki et al., corresponding to US Patent Publication No. 2018 / 0356730)

[0209] to

[0222] and EP 2,018,365 B1 (Nguyen et al., corresponding to US Patent No. 7,910,768)

[0044] to

[0046] . These component (5) acid-sensitive dye precursors are different from all of the components (1), (2), (3), and (4) defined above.

[0094] For example, in some embodiments, at least one of the component (5) acid-sensitive dye precursors contains a lactone moiety. More specifically, useful component (5) acid-sensitive dye precursors include the following structures (C1) and (C2): [ka] [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 may have 1 to 20 carbon atoms, and the optional one or more substituents may include, but are not limited to, halogen, alkyl, aryl, alkoxy, and phenoxy groups. Useful substituted or unsubstituted aryl groups may be carbocyclic aromatic rings or heterocyclic aromatic rings, which may have two or more fused rings. Useful substituents for the aryl ring may include, but are not limited to, those described above for alkyl groups. However, one of ordinary skill 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.

[0095] 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 coverage (solids) of the infrared-sensitive image recording layer.

[0096] In many embodiments of the present invention, optionally but desirably, the infrared-sensitive image-recording layer 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, if present, does not have functional groups that would render the polymeric material free-radically polymerizable. Such component (6) non-free-radically polymerizable polymeric material is thus distinct from all of components (1), (2), (3), and (4) above.

[0097] Useful Component (6) Non-free radically polymerizable polymeric materials generally have a weight average molecular weight (M) as 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.

[0098] Such component (6) non-free radically polymerizable polymeric materials can be selected from polymeric binder materials known in the art, including polymers containing repeat 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 repeat units with different side chains containing polyalkylene oxide segments, such as those described in WO 2015-156065 (Kamiya et al.). Some of such polymeric binders can further contain repeat units with pendant cyano groups, such as those described in U.S. Pat. No. 7,261,998 (Hayashi et al.).

[0099] Such component (6) non-free radically polymerizable polymeric materials can also have a backbone that includes a plurality (at least two) of urethane moieties and pendant groups that include polyalkylene oxide segments.

[0100] Useful component (6) non-free radically polymerizable polymeric materials may be present in particulate form, i.e., in the form of discrete particles (unagglomerated particles). Such discrete particles may have an average particle size of at least 10 nm to no more than 1500 nm, or typically at least 80 nm to no more than 600 nm, and are generally uniformly distributed in the infrared-sensitive image-recording layer. Some of these materials may be present in particulate form and may have an average particle size of at least 50 nm to no more than 400 nm. The average particle size may be determined using a variety of known methods and nanoparticle measuring devices, including measuring particles in an electron scanning microscope image and averaging a set number of measurements.

[0101] In some embodiments, component (6), the non-free-radically polymerizable polymeric material, may be present in the form of particles having an average particle size less than the average dry thickness of the infrared-sensitive image-recording layer.

[0102] Component (6) one or more non-free-radically polymerizable polymeric materials may be present in an amount of at least 10% or at least 20% by weight, and up to 50% or up to 70% by weight, based on the total coverage (solids) of the infrared-sensitive image-recording layer.

[0103] The infrared-sensitive image-recording layer may also contain various other optional additives in conventional amounts, including, but not limited to, dispersants, humectants, biocides, plasticizers, surfactants for coatability or other properties, viscosity enhancers, pH adjusters, drying agents, defoamers, development aids, rheology modifiers, or combinations thereof, or any other additives commonly used in the lithographic coating art.

[0104] Top coat: In most embodiments of the present invention, the infrared-sensitive image-recording layer is the outermost layer with no layer (e.g., topcoat) disposed thereon, but master plates according to the present invention can be designed with a protective layer (also known in the art as an overcoat, oxygen barrier layer, or topcoat) disposed directly on the infrared-sensitive image-recording layer. Any known topcoat composition designed for use with a negative-working image-recording layer of a lithographic printing plate master plate utilizing free radical polymerization in the radiation-exposed areas can be used.

[0105] The topcoat, if present, is provided as a hydrophilic topcoat formulation and has a coating thickness of at least 0.1 g / m2 when dried. 2 ~4g / m 2 or typically at least 0.15 g / m 2 ~2.5g / m 2 This results in a dry coating coverage of 0.1 g / m. In some embodiments, the dry coating coverage is 0.1 g / m. 2 ~1.5g / m 2 Less than or equal to 0.1 g / m 2 ~0.9g / m 2or less, so that the topcoat is relatively thin for easy removal during off-press or on-press development.

[0106] Lithographic printing plate precursor production: The lithographic printing plate precursor according to the present invention can be provided in the following manner. The infrared-sensitive image recording layer formulation, which comprises the above-mentioned essential components (1), (2), (3), and one or more required iodonium cations and one or more borate anions, and optional components (4), (5), (6), and other additives that may be added, can be applied to the hydrophilic surface of a suitable aluminum-containing substrate, usually in the form of a continuous web as described above, using any suitable equipment and procedure, such as spin coating, knife coating, gravure coating, die coating, slot coating, bar coating, wire rod coating, roller coating, or extrusion hopper coating. Such a formulation can also be applied by spraying onto a suitable substrate. Typically, once the infrared-sensitive image recording layer formulation is applied at a suitable wet coverage, it is dried in a suitable manner known in the art to provide a desired dry coverage as described below, thereby providing an infrared-sensitive continuous web or an infrared-sensitive continuous article. The components and addenda of the infrared-sensitive image-recording layer can be designed so that during imaging, the layer is easily removed on press using either or a combination of lithographic ink and fountain solution.

[0107] As noted above, before the infrared-sensitive image-recording layer formulation is applied, the substrate (i.e., a continuous roll or web) is electrochemically grained and anodized as described above to provide a suitable hydrophilic anodic (aluminum oxide) layer on the outer surface of the aluminum-containing support, and the anodized surface may usually be post-treated with a hydrophilic polymer solution as described above. The conditions and results of these operations are well known in the art, as described above.

[0108] 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 [e.g., methyl ethyl ketone (2-butanone), methanol, ethanol, 1-methoxy-2-propanol, 2-methoxypropanol, isopropyl alcohol, acetone, gamma-butyrolactone, n-propanol, tetrahydrofuran, and others readily known in the art, and mixtures thereof], applying the resulting infrared-sensitive image recording layer formulation to a continuous substrate web, and removing the one or more solvents by evaporation under suitable drying conditions.

[0109] After proper drying, the dry coverage of the infrared-sensitive image-recording layer on the substrate is at least 0.1 g / m 2 or at least 0.4 g / m 2 and 2 g / m 2 Less than or equal to 4g / m 2 Although the preferred range may be less than or equal to 1000 ppm, other dry coverage amounts can be used, if desired, to provide the desired dry coverage.

[0110] As noted above, in some embodiments, a suitable aqueous hydrophilic topcoat formulation (described above) can be applied to the dried infrared-sensitive image-recording layer using known coating and drying conditions, equipment, and procedures.

[0111] In practical manufacturing conditions, the result of these coating operations is a continuous radiation-sensitive web (or roll) of infrared-sensitive lithographic printing plate precursor material having only one infrared-sensitive image-recording layer as the outermost layer, or both one infrared-sensitive image-recording layer and a hydrophilic topcoat disposed thereon as the outermost layer. Such a continuous radiation-sensitive web can be slit or cut into precursors of appropriate size for use.

[0112] Image formation (exposure) conditions In use, the infrared-sensitive lithographic printing plate precursor of the present invention can be exposed to a suitable infrared source depending on the infrared absorber or absorbents 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.

[0113] Thus, imaging can be performed using imaging infrared or exposing infrared from an infrared generating laser (or an array of such lasers). Imaging can also be performed using imaging radiation at multiple infrared (or near-IR) wavelengths simultaneously if desired. The laser or lasers 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. The combination of power, intensity, and exposure time for infrared imaging will be readily apparent to those skilled in the art.

[0114] The infrared imaging device can be configured as a flatbed recorder or drum recorder, with the infrared-sensitive lithographic printing plate precursor attached to the inner or outer cylindrical surface of the drum. One example of a useful imaging device is available as the model KODAK® Trendsetter platesetter (Eastman Kodak Company) and NEC AMZI Setter X series (NEC Corporation, Japan), which includes a laser diode that emits radiation at a wavelength of about 830 nm. Other suitable imaging devices include the Screen PlateRite 4300 series or 8600 series platesetters (available from Screen USA, Chicago, Illinois) that operate at a wavelength of 810 nm, or the thermal CTP platesetters manufactured by Panasonic Corporation (Japan).

[0115] If the infrared-sensitive image-recording layer is sensitive to the presence of ozone, it may be desirable to include a means for reducing or eliminating ozone in the laser imaging environment. Useful means and systems for doing this are described, for example, in U.S. Patent Application Publication No. 2019 / 0022995 (Igarashi et al.).

[0116] 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:

[0117] 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 topcoat that may be present on both the exposed and unexposed areas). During this processing, and during lithographic printing, the exposed hydrophilic substrate surface repels ink, while the remaining exposed areas accept lithographic ink.

[0118] Thus, the negative-working lithographic printing plate precursor of the present invention can be developed on-press using lithographic ink, fountain solution, or a combination of lithographic ink and 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 started. The unexposed areas in the infrared-sensitive image-recording layer are removed by a suitable fountain solution, lithographic ink, or a combination of both, once the first printed image is produced. Typical components of an aqueous fountain solution include pH buffers, desensitizers, surfactants and wetting agents, humectants, low boiling solvents, biocides, defoamers, and sequestering agents. A representative example of a fountain solution is Varn Litho Etch 142W+Varn PAR (alcohol substitute) (available from Varn International, Addison, Illinois).

[0119] During a typical start-up of a sheet-fed printing press, dampening rollers are first engaged to deliver dampening water to the mounted imaged master plate to swell the exposed infrared-sensitive image-recording layer at least in the unexposed areas. After several revolutions, inking rollers are engaged to deliver one or more lithographic printing inks to cover the entire printing surface of the lithographic printing plate. Typically, within 5-20 revolutions after engagement of the inking rollers, a printing sheet is delivered 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 to remove any material present on the blanket cylinder.

[0120] On-press developability of infrared-exposed lithographic printing master plates is particularly useful when the master plate contains one or more polymeric binder materials (whether free-radically polymerizable or not) in the infrared-sensitive image-recording layer, and at least one of these polymeric binders is present as particles having an average diameter of at least 50 nm to no more than 400 nm.

[0121] The present invention provides at least the following embodiments and combinations thereof, however, 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 the present disclosure.

[0122] 1. A lithographic printing plate precursor, A substrate; an infrared-sensitive image-recording layer disposed on a substrate; and 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, the free radical initiator composition comprising an electron donor and one or more iodonium cations; (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 is independently a substituted or unsubstituted alkyl group; X represents a single bond or -S-, -O-, and >N(R6 )(wherein, R 6 represents a divalent linking group selected from hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or L; L is -C(=O)-OR 7 group, -SO2-R 3 group, or -SO2NR 8 R 9 represents a group, 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 counter ions for balancing the charge in the remainder of the color-changing compound according to structure (I). Including, The infrared-sensitive image-recording layer has the following structure (IIIa): B(R 10 R 11 R 12 R 13 ) - Structure (IIIa) (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, with the proviso that R 10 , R 11 , R 12 , and R 13 at least three of 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:

[0123] 2. The lithographic printing plate precursor according to embodiment 1, wherein Za represents one or more anions.

[0124] 3. The lithographic printing plate precursor according to embodiment 1 or 2, wherein the molar ratio of the one or more borate anions to the one or more iodonium cations is at least 0.5:1.

[0125] 4. The lithographic printing plate precursor according to any one of embodiments 1 to 3, wherein the molar ratio of the one or more borate anions to the one or more iodonium cations is at least 0.8:1 to 4:1.

[0126] 5.(3) The color-changing compound has the following structure (II): [ka] (In the formula, Ar1, Ar2, Ar3, R 1 , R 2 , R 3 , R 6 , Y, and Za are as defined above. The lithographic printing plate precursor according to any one of embodiments 1 to 4,

[0127] 6. The lithographic printing plate precursor according to any one of embodiments 1 to 5, wherein Ar1 and Ar2 are the atoms necessary to complete the same or different substituted or unsubstituted aromatic rings.

[0128] 7. The lithographic printing plate precursor according to any one of embodiments 1 to 6, wherein one or both of the aromatic rings completed by the atoms Ar1 and Ar2 are substituted with one or two halo groups, which may be the same or different.

[0129] 8.R 3 The lithographic printing plate precursor according to any one of embodiments 1 to 7, wherein is a trifluoromethyl group.

[0130] 9. The lithographic printing plate precursor according to any one of embodiments 1 to 8, wherein Ar3 represents the carbon and hydrogen atoms necessary to complete a benzene ring.

[0131] 10. The lithographic printing plate precursor according to any one of embodiments 1 to 9, wherein Za comprises a tetraarylborate anion.

[0132] 11. The electron donor has the following structure (III): [B(R 10 R 11 R 12 R 13 ) - ] n M n+ Structure (III) (In the formula, R 10 , R 11 , R 12 , and R 13 is as defined for Structure (IIIa), n is an integer equal to or greater than 1, and M n+ is a cation with a valence of n) The lithographic printing plate precursor according to any one of embodiments 1 to 10, wherein the organic borate is represented by the formula:

[0133] 12. R of Structure (IIIa) and Structure (III) 10 , R 11 , R 12 , and R 13 12. The lithographic printing plate precursor according to any one of embodiments 1 to 11, wherein all of are the same or different substituted or unsubstituted aryl groups.

[0134] 13. R of structure (IIIa) and structure (III) 10 , R 11 , R 12 , and R 13 13. The lithographic printing plate precursor according to any one of embodiments 1 to 12, wherein all of are the same substituted or unsubstituted phenyl group.

[0135] 14.R 1 and R 2 14. The lithographic printing plate precursor according to any one of embodiments 1 to 13, wherein one or both of independently comprise a chain of carbon atoms interrupted by one or more ether or ester linkages.

[0136] 15. The lithographic printing plate precursor according to any one of embodiments 1 to 14, wherein the infrared-sensitive image recording layer further comprises component (4) an infrared-absorbing material different from component (3) the color-changing compound.

[0137] 16. The lithographic printing plate precursor according to any one of embodiments 1 to 15, wherein the component (1) free radical initiator composition comprises a diaryliodonium tetraphenylborate.

[0138] 17. The lithographic printing plate precursor according to any one of embodiments 1 to 16, 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.

[0139] 18. The lithographic printing plate precursor according to any one of embodiments 1 to 17, wherein the infrared-sensitive image-recording layer further comprises component (6) a non-free-radically polymerizable polymeric material different from all of components (1), (2), (3), and (4) defined above.

[0140] 19. The lithographic printing plate precursor according to embodiment 18, wherein the component (6) non-free-radically polymerizable polymeric material is present in particle form.

[0141] 20. The lithographic printing plate precursor according to any one of embodiments 1 to 19, wherein after infrared exposure, the infrared-sensitive image recording layer is developable on-press using a lithographic ink, a fountain solution, or a combination of a lithographic ink and a fountain solution.

[0142] 21. The lithographic printing plate precursor according to any one of embodiments 1 to 20, 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% by weight to 15% by weight or less based on the total dry coverage of the infrared-sensitive image recording layer.

[0143] 22. The lithographic printing plate precursor according to any one of embodiments 1 to 21, wherein the infrared-sensitive image-recording layer is the outermost layer.

[0144] 23. The lithographic printing plate precursor according to any one of embodiments 1 to 22, wherein the component (2) free radically polymerizable composition comprises at least two free radically polymerizable components.

[0145] 24. The lithographic printing plate precursor according to any one of embodiments 1 to 23, wherein the substrate comprises an aluminum-containing substrate comprising at least one aluminum oxide layer and a hydrophilic polymer coating disposed on the at least one aluminum oxide layer.

[0146] 25. The lithographic printing plate precursor according to any one of embodiments 1 to 24, wherein the substrate comprises an aluminum-containing substrate comprising at least an inner aluminum oxide layer, an outer aluminum oxide layer disposed on the inner aluminum oxide layer, and a hydrophilic polymer coating disposed on the outer aluminum oxide layer.

[0147] 26. A method for providing a lithographic printing plate, comprising the steps of: A) imagewise exposing the lithographic printing plate precursor according to any one of embodiments 1 to 25 to infrared radiation to provide exposed and unexposed areas in the infrared-sensitive image recording layer; and B) Removing the unexposed areas of the infrared-sensitive image-recording layer from the substrate. A method comprising:

[0148] 27. The method of embodiment 26, comprising the step of on-press removing the unexposed areas in the infrared-sensitive image-recording layer from the substrate using a lithographic printing ink, a fountain solution, or a combination of a lithographic printing ink and a fountain solution.

[0149] 28. The method according to embodiment 26 or 27, wherein the imagewise exposing is carried out using at least one infrared-emitting laser. EXAMPLES

[0150] 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. An aluminum-containing substrate was prepared for a lithographic printing plate precursor in the following manner.

[0151] Hydro 1052 aluminum alloy strips or webs (available from Norsk Hydro ASA, Norway) with a thickness of 0.28 mm were used as the aluminum-containing "plate" material or support. Both pre-etching and post-etching steps were carried out in alkaline solutions under known conditions. The etched aluminum support was roughened (i.e. grained) 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 surface of the aluminum-containing support. The aluminum-containing support was then subjected to two separate anodization processes. A first anodization process was carried out using phosphoric acid as the electrolyte to obtain an average pore size (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 size (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 manufacturing 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 give a concentration of 0.03 g / m for substrates useful in the present invention. 2 The dry thickness was 1.01 mm.

[0152] Then, infrared-sensitive composition formulations having 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, with a coating weight of 0.9 g / m2 after drying at 50° C. for 60 seconds for each of the master plates of the present invention and the comparative master plates described below. 2 A dry coating weight of 100 g was obtained. The raw materials set forth in Table I are identified below in Table II, and the amounts of the various components are set forth in Table III. These materials may be obtained from one or more commercial sources of chemicals or may be prepared using known synthetic methods and starting materials.

[0153] [Table 1]

[0154] [Table 2]

[0155] [Table 3]

[0156] [Table 4]

[0157] [Table 5]

[0158] Each of the lithographic printing plate precursors of the present invention and the comparative example was evaluated using four tests: "on-press developability" (DOP), "imaging speed", "print output image" (PO) and "dark fade". The results are summarized in Table IV below.

[0159] 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 Each imagewise exposed lithographic printing plate precursor was 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. As 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 ratings are acceptable for this test parameter. + Less than 15 printed sheets 0 15-35 sheets of printed paper - Over 35 pre-printed sheets

[0160] 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 taken as a measure of the imaging speed. The following qualitative values ​​were given as a result of the individual experiments, with lower imaging energies being more desirable. A rating of + and 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

[0161] Print output image: Each lithographic printing plate precursor was photoirradiated at 90 mJ / cm using a Trendsetter 800 III Quantum TH 1.7 (available from Eastman Kodak Company). 2to 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: +++20≦ΔE ++11≦ΔE<20 + 8≦ΔE<11 0 5≦ΔE<8 - ΔE<5

[0162] 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: +++20≦ΔE ++11≦ΔE<20 + 8≦ΔE<11 0 5≦ΔE<8 - ΔE<5

[0163] [Table 6]

[0164] The results shown in Table IV support several conclusions. The data in Comparative Example 1 show that conventional acid-sensitive lactone-based leuco dyes, such as Acid-Sensitive Dye Precursor 1, typically give fair or acceptable print output images immediately after exposure without extended storage, but the print output images degrade (e.g., considering dark fade results) after storage of the images. Comparative Example 8, which used the highly acid-sensitive lactone-based dye precursor ASDP2, gave dark print output images immediately after exposure, but the print output images degraded after storage of the images.

[0165] The results of Comparative Example 4, compared to those of Example 2 of the present invention, show that the presence of an N-triflamide (i.e., trifluoromethylsulfonamide) group in the color-changing compound of structure (I) (3) results in improved print output image and dark fade. Compounds having an indene ring connected to a diphenylamino group instead of an N-triflamide group, such as Comparative Example color-changing compound 2, typically give a moderate or acceptable print output immediately after imaging, but the print output image deteriorates after dark fade storage. The difference between Comparative Example 4 and Example 2 of the present invention demonstrates that the specific -XL group in addition to the Ar3 group in structure (I) is also important for the efficiency of the phenylation reaction to form stable colored species as explained above. The inferior print output image and dark fade values ​​of the master of Comparative Example 4 relative to the master of Example 9 of the present invention further supports the importance of the -XL group of the present invention. The color-changing compound CCC3 of Comparative Example 4 and the color-changing compound CCC5 of Example 9 of the present invention have the same structure except for the different -XL groups. ICCC3 is outside the scope of structure (I) above, since it has a diphenylamino group as the -XL group.

[0166] The results of Comparative Example 2, compared to those of Inventive Example 2, show that the presence of tetraphenylborate anion is desirable to obtain a dark print output image immediately after imaging and after dark storage. As explained above, tetraphenylborate anion can react with the inventive color-changing compound 2 to form a colored phenylated product. A typical initiator composition such as that used in Comparative Example 2 provides 90 mJ / cm 2 At the given exposure energy level of , the tetraphenylborate anion is not effective in inducing a chemical change to each of the (3) color-changing compounds of the present invention. In other words, at this exposure energy level, the color-changing compound 2 of the present invention does not undergo sufficient chemical conversion of the triflamide group [-XL group in structure (I)] for color-developing purposes under heat or in the presence of an acid generated by the iodonium salt of the initiator composition 2. Furthermore, the unacceptable imaging speed used in Comparative Example 2 indicates that the tetraphenylborate anion is necessary even for optimal imaging speed.

[0167] The results of Comparative Example 9, and Inventive Examples 9, 10, 11, and 12 also demonstrate that decreasing the molar ratio of borate anion to iodonium cation results in decreased print output image production, whereas increasing the borate concentration to a molar ratio of borate anion to iodonium cation greater than 4, as demonstrated in Comparative Example 10, produces a darker print output image but reduces the development rate.

[0168] The results of Comparative Example 3 also show that (1) even if there is no iodonium cation in the free radical initiator composition, the presence of the electron donor tetraphenylborate anion can cause the color-forming reaction of the (3) color-changing compound. Of course, the presence of the iodonium cation is still essential for sufficient image formation speed, or other known components for enhancing the generation of free radicals must be added to the free radical initiator composition.

[0169] Compared with Inventive Example 1, the results of Comparative Example 5 showed lower print output both immediately after imaging and after dark storage. These differences demonstrate that the presence of (3) color-changing compound "Inventive Dye 1" according to structures (I) and (II) having an indene ring (benzene as Ar3 in structure (I)) in the conjugated chain results in improved print output image compared to Comparative Example color-changing compound 3 having a cyclopentene ring in the conjugated chain. The difference between Comparative Example 5 and Inventive Example 1 demonstrates that Ar3 in structures (I) and (II) affects the geometry of the polymethine chain of the color-changing compound, making it react more easily with tetraphenylborate anion to form a stable colored phenylated product as explained above. 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 having an absorption peak around 514 nm in the visible spectrum. The lithographic printing plate precursors in other Inventive Examples also have a reddish hue in the infrared-exposed areas. On the other hand, Comparative Example 5 had a bluish hue, which is believed to be due to the low conversion rate of the N-methyltriflamide group to the N-methylamino group in the color-changing compound 2 of the comparative example.

[0170] Comparative Examples 6 and 7 show that the borate anions provided by IC6 and IC7 are not effective in producing good print output images from color-changing compound CCC2. These borate anions are outside the scope of structure (IIIa) above, and therefore B - / I + It is not included in the mole ratio calculation.

[0171] Compared with the results of Example 1 of the present invention, Example 3 of the present invention showed lower print output images both immediately after imaging ("fresh") and after dark storage. It is believed that these differences may be caused by less than desired IR absorption by (3) color-changing compound 1 under certain imaging conditions and energies. However, it is also believed that improved results may be obtained by combining various (3) color-changing compounds according to the present invention with other infrared absorbing dyes.

[0172] Compared with the results of Example 1 of the present invention, the results of Example 4 of the present invention showed higher print output image immediately after image formation ("fresh"). This result shows that the advantage of using the (3) color-changing compound of the present invention can be further enhanced by its combination with the conventional (5) acid-sensitive dye precursor. Meanwhile, the contribution of the acid-sensitive dye precursor 2 to ΔE print output is known to decrease over time, so the improvement from the added acid-sensitive dye precursor is still temporary. After 24 hours of dark fading, Examples 1 and 4 of the present invention showed comparable ΔE print output values, which is largely contributed by the (3) color-changing compound 1 of the present invention.

Claims

1. A lithographic printing plate precursor, A substrate; an infrared-sensitive image-recording layer disposed on said substrate; and said 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, the free radical initiator composition comprising an electron donor and one or more iodonium cations; (2) a free radically polymerizable composition, and (3) The following structure (I) 【Chemistry 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 ) wherein R 4 and R 5 are independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms; R 1 and R 2 is independently a substituted or unsubstituted alkyl group; X represents a single bond, or -S-, -O-, and >N(R 6 ) (where R 6 represents a divalent linking group selected from hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or L; L is -C(=O)-OR 7 Group, -SO 2 -R 3 group, or -SO 2 NR 8 R 9 represents a group, 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 counter ions for balancing the charge in the remainder of the color-changing compound according to structure (I). Including, The infrared-sensitive image recording layer has the following structure (IIIa): B(R 10 R 11 R 12 R 13 ) － Structure (IIIa) (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, with the proviso that R 10 , R 11 , R 12 , and R 13 at least three of are the same or different substituted or unsubstituted aryl groups, each of said substituted aryl groups having no more than two halo substituents; A lithographic printing plate precursor comprising one or more borate anions represented by the formula:

2. The lithographic printing plate precursor according to claim 1 , wherein Za represents one or more anions.

3. 3. The lithographic printing plate precursor according to claim 1, wherein a molar ratio of the one or more borate anions to the one or more iodonium cations is at least 0.5:

1.

4. The lithographic printing plate precursor according to any one of claims 1 to 3, wherein a molar ratio of the one or more borate anions to the one or more iodonium cations is at least 0.8:1 to 4:1 or less.

5. The (3) color-changing compound has the following structure (II): 【Chemistry 2】 (In the formula, Ar1, Ar2, Ar3, R 1 , R 2 , R 3 , R 6 , Y, and Za are as defined above. The lithographic printing plate precursor according to any one of claims 1 to 4, wherein the lithographic printing plate precursor is represented by the formula:

6. The lithographic printing plate precursor according to any one of claims 1 to 5, wherein Ar1 and Ar2 are the atoms necessary to complete the same or different substituted or unsubstituted aromatic rings.

7. 7. The lithographic printing plate precursor according to claim 1, wherein one or both of the aromatic rings completed by the atoms of Ar1 and Ar2 are substituted with one or two halo groups, which may be the same or different.

8. R 3 The lithographic printing plate precursor according to any one of claims 1 to 7, wherein is a trifluoromethyl group.

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

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

11. The electron donor has the following structure (III): [B(R 10 R 11 R 12 R 13 ) － ] n M n＋ Structure (III) (In the formula, R 10 , R 11 , R 12 , and R 13 is as defined for Structure (IIIa), n is an integer equal to or greater than 1, and M n＋ is a cation with a valence of n) The lithographic printing plate precursor according to claim 1 , wherein the organic borate is represented by the formula:

12. R of structure (III) and structure (IIIa) 10 , R 11 , R 12 , and R 13 The lithographic printing plate precursor according to claim 1 , wherein all of are the same or different substituted or unsubstituted aryl groups.

13. R of structure (III) and structure (IIIa) 10 , R 11 , R 12 , and R 13 The lithographic printing plate precursor according to claim 1 , wherein all of the are the same substituted or unsubstituted phenyl group.

14. The lithographic printing plate precursor according to any one of claims 1 to 13, 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.

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

16. The lithographic printing plate precursor according to any one of claims 1 to 15, 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.

17. 17. The lithographic printing plate precursor according to any one of claims 1 to 16, 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 the components (1), (2), (3), and (4) defined above.

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

19. 19. The lithographic printing plate precursor according to any one of claims 1 to 18, 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 a total weight of the infrared-sensitive image recording layer.

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

Images