Lithographic printing plate precursors and methods of use

Abstract

An IR sensitive lithographic printing plate precursor provides a stable printed image using a unique IR sensitive image recording layer. The IR radiation sensitive layer comprises: (1) a free radical initiator composition having an electron donating agent and one or more iodonium cations; (2) a radically polymerizable composition; and (3) a color-changing compound of structure (I) having an indene ring in the conjugated chain between the aromatic end groups. The IR radiation sensitive image recording layer also contains one or more borate ions. After IR imaging, these precursors exhibit desirable print images both when fresh and after dark storage. The lithographic printing plate precursor may be on-press developed after suitable infrared radiation imaging.

Description

Technical Field

[0001] The present invention relates to infrared radiation-sensitive lithographic printing plate precursors that can be imaged using infrared radiation to provide imaged lithographic printing plates. Such precursors include unique infrared radiation-sensitive compositions that provide a stable printout image between exposed and non-exposed areas in an imagewise exposed infrared radiation-sensitive image recording layer. The present invention also relates to methods of using these precursors to provide lithographic printing plates having excellent printout images. Background Art

[0002] In lithography, lithographic ink receiving areas, called image areas, are created on the hydrophilic surface of a planar substrate, such as an aluminum-containing substrate. When the printing plate surface is moistened with water and a lithographic ink is applied, the hydrophilic areas retain the water and repel the lithographic ink, and 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 on which the image is to be reproduced, perhaps using a blanket roller in a printing press.

[0003] Negative-working lithographic printing plate precursors useful for preparing lithographic printing plates typically include a negative-working radiation-sensitive image-recording layer disposed on a hydrophilic surface of a substrate. Such an image-recording layer comprises a radiation-sensitive component that may be dispersed in a suitable polymeric binder material. After image-wise exposure of the precursor to suitable radiation to form exposed and non-exposed areas in the image-recording layer, the non-exposed areas are removed by suitable means to reveal the hydrophilic surface of the underlying substrate. The exposed areas of the image-recording layer that are not removed are lithographic ink-receptive, and the hydrophilic substrate surface revealed by the development process accepts water and aqueous solutions such as fountain solutions, and repels lithographic inks.

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

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

[0006] It is therefore highly desirable that such imaged lithographic printing plate precursors have different colors in exposed and non-exposed areas. The color difference or "contrast" between exposed and non-exposed areas is often referred to as the "print out" or "print out image". A strong print out will facilitate the operator's visual assessment and identification of the imaged printing plate precursor so that the printing plate precursor can be properly connected to a printing press unit.

[0007] Many approaches have been taken to enhance the printout of on-press processable printing plate precursors. It has been observed that they all have certain weaknesses.

[0008] For example, due to the limited efficiency of acid generation in imaging compositions designed for infrared radiation imaging and on-press development, printouts on printing plate precursors having imaging compositions comprising an acid generator and an acid-sensitive color precursor, such as a lactone-based leuco dye, are generally not strong enough. In addition, the concentration of protons generated during infrared radiation imaging is generally reduced after imaging by chemical equilibrium or other post-imaging chemical reactions. As a result, printouts based on proton-induced color changes generally fade after imaging.

[0009] Co-pending and commonly assigned U.S. Patent Application Publication 2021 / 0078350 (Viehmann et al.) describes efforts to increase printout by incorporating more sensitive color-forming compounds into infrared radiation-sensitive imaging compositions that convert from a colorless form to a colored form at lower acid concentrations. Background color formation is suppressed by special additives to stabilize good contrast. The initial printout achieved is quite high, but there is still a need to improve the printout and printout stability obtained using the described chemistry.

[0010] A different approach to producing printouts is based on the use of infrared (IR) decomposable dyes that contain thermally unstable groups and are capable of losing the thermally unstable groups upon exposure to infrared radiation or heat to form compounds of different colors having absorption spectra in the visible spectral region. Examples based on this approach are described in U.S. Patents 8,148,042 (Callant et al.) and 8,178,282 (Callant et al.) and U.S. Patent Application Publication 2010 / 0274023 (Callant et al.). Such IR decomposable dyes should generally be present in the imaging composition in relatively large amounts, or in lower amounts and require high exposure to infrared radiation energy in order to produce sufficient printouts.

[0011] In addition, some IR-decomposable dyes used in such chemicals generate gaseous materials upon decomposition, which are generally harmful to negative-working compositions based on crosslinking of free radical polymerizable compounds in the presence of suitable free radical initiators, resulting in poor image durability during printing operations. In addition, according to a process generally referred to as ablation or partial ablation, the heat pulses generated from exposure to infrared radiation at high energy levels can generally damage the physical integrity of the imaging composition. Ablation or partial ablation generally results in poor image durability. For example, in U.S. Pat. No. 8,148,042 (noted above), it is described that printing plate precursors PPP34 and PPP35 containing IR-decomposable dyes in the imaging composition require 275 mJ / cm 2 Imaging energies were set so as to produce cyan printouts (ΔOD) of 0.43 and 0.60. There is no teaching that such imaging compositions can be used to form printing plates having sufficient durability of the infrared radiation exposed areas after development of any kind.

[0012] It is demonstrated in U.S. Patent Application Publication No. 2020 / 0147950 (Billiet) that the IR-decomposable dyes taught in U.S. Patent No. 8,148,042 (noted above) can be directly incorporated into polymerizable compositions at more practical exposure energies (e.g., 120 mJ / cm 2 or lower), where PPP04 using the IR-decomposable dye IR02 in combination with IR01 as used in PPP03 produced very little printout benefit over PPP03 (e.g. at 120 mJ / cm 2 The ΔE parameter for Billiet is similar to the ΔE parameter defined below.

[0013] In order to avoid the ineffectiveness and undesirable effects of IR-decomposable dyes on negative-working printing plate precursors having polymerizable imaging compositions, WO 2019 / 219560 (Billiet et al.) teaches placing the IR-decomposable dye in a protective overcoat applied on top of an imageable layer comprising an IR-imageable composition. However, the presence of a protective layer in a lithographic printing plate precursor requires additional steps during manufacture, and when present, removal of the protective layer reduces the speed of development. In addition, when the printing plate precursor is developed on-machine, the protective layer may release polymeric or other materials into the fountain solution and cause malfunctions in the lithographic printing operation. Furthermore, the printout generated using infrared radiation at typical exposure doses suitable for such IR-sensitive imageable compositions is still far below what is required.

[0014] U.S. Patent Application Publication 2019 / 0329545 (Shibamoto et al.) teaches the use of certain IR-decomposable dyes that, in their excited state, are capable of accepting 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 are further capable of forming a second wave of free radicals from the IR-decomposable dye by further decomposition thereof or by further reaction with an electron-accepting initiator. The reference demonstrates the color-forming ability of such imaging compositions containing IR-decomposable dyes under the described exposure conditions. Although the disclosure describes certain infrared dyes that are considered IR-decomposable therein, none of the working examples use any IR-decomposable dyes as taught in U.S. Patent 8,148,042 (noted above) or U.S. Patent Application Publication 2010 / 0274023 (noted above). On the other hand, the teachings in U.S. Patent Application Publication 2019 / 0329545 (noted above) consider those taught in U.S. Patent 8,632,941 (Balbinot et al.) to be IR-decomposable infrared dyes.

[0015] U.S. Patent Application Publication 2020 / 0117086 (Nogoshi et al.) describes certain IR-decomposable dyes in combination with certain chromogenic developers. As illustrated in Comparative Examples 1 and 2 thereof, the specified IR-decomposable dyes of this teaching do not have sufficient printout in the absence of the specified chromogenic developer.

[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 thereof, Munnelly et al. demonstrate that at 300 mJ / cm 2 The invention provides good printout (ΔE values ​​of 13.8 to 17.4) at high exposure doses in an imageable composition comprising an IR-decomposable dye containing a combined alkoxycarbonylamino group used in combination with a conventional acid-sensitive dye precursor. However, in the absence of the acid-sensitive dye precursor, Example 4 of Munnelly et al. shows much lower printout (ΔE of 6.6). The use of a comparative IR-decomposable dye containing no alkoxycarbonylamino group as taught by U.S. Pat. No. 8,148,042 (noted above) also provides good printout at 300 mJ / cm even in the presence of an acid-sensitive dye precursor. 2Low printout at imaging energy (ΔE of 4.6). Furthermore, Munnelly et al. only demonstrated a short press run for 200 copies, and it is not obvious whether a printing plate derived from the Munnelly et al. precursor will have sufficient image durability during printing to satisfy customers in the industry, who typically need to print far more than 200 copies in a typical press run.

[0017] Despite all the efforts described in the known literature to provide adequate print-out for press-developable lithographic printing plates with excellent press run durability, there is a continuing need to provide press-developable lithographic printing plate precursors which not only have the desired essential properties such as fast imaging speed, good on-press developability, good lithographic durability and good shelf life, but also exhibit strong and stable print-out using lower exposure energies as required for high productivity. SUMMARY OF THE INVENTION

[0019] The present invention provides a lithographic printing plate precursor, which comprises: a substrate and an infrared radiation-sensitive image recording layer disposed on the substrate, wherein the infrared radiation-sensitive image recording layer comprises the following components (1), (2) and (3):

[0020] (1) a free radical initiator composition capable of generating free radicals upon exposure to infrared radiation, wherein the free radical initiator composition comprises an electron donating agent and one or more iodonium cations;

[0021] (2) a free radical polymerizable composition; and

[0022] (3) A color-changing compound represented by the following structure (I)

[0023]

[0024] in:

[0025] 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;

[0026] Y represents an oxygen atom, a sulfur atom or a 4 R 5 ) represented by a dialkylmethylene group, wherein R 4 and R 5 is independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms;

[0027] R 1 and R 2 are independently substituted or unsubstituted alkyl;

[0028] X represents a single bond or is selected from -S-, -O- and >N(R 6 ) of a divalent linking group, wherein R 6 is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or L;

[0029] L represents -C(=O)-OR 7 Group, -SO 2 -R 3 Group or -SO 2 NR 8 R 9 Group, where R 7 represents a substituted or unsubstituted alkyl group having a -C(=O)OR 7 The secondary or tertiary carbon to which the rest of the group is attached; and R 3 , R 8 and R 9 independently represent substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; and

[0030] Za represents one or more counterions to balance the charge in the rest of the color-changing compound according to structure (I),

[0031] wherein the infrared radiation-sensitive image recording layer comprises one or more borate anions represented by the following structure (IIIa):

[0032] B(R 10 R 11 R 12 R 13 ) -

[0033] Structure (IIIa)

[0034] Where R 10 , R 11 , R 12 and R 13 are independently substituted or unsubstituted alkyl or substituted or unsubstituted aryl, provided that R 10 , R 11 , R 12 and R 13 At least three of the are the same or different substituted or unsubstituted aryl groups, and the substituted aryl groups each have not more than two halogen substituents.

[0035] In some embodiments of the precursors according to the invention, the infrared radiation-sensitive image recording layer comprises one or more borate anions in such an amount that the molar ratio of one or more borate anions to one or more iodonium cations is at least 0.5:1.

[0036] The present invention also provides a method for providing a lithographic printing plate, the method comprising:

[0037] A) image-wise exposing a lithographic printing plate precursor according to any embodiment of the invention as described herein to infrared radiation to provide exposed areas and non-exposed areas in the infrared radiation sensitive image recording layer, and

[0038] B) removing the non-exposed areas in the infrared radiation sensitive image recording layer from the substrate on-press using a lithographic ink, a fountain solution or a combination of a lithographic ink and a fountain solution.

[0039] The present invention provides print-out images generated in infrared radiation-sensitive image-recording layers in areas exposed to relatively low energy imaging infrared radiation. Such print-out images are strong and do not fade significantly during dark storage. In addition, in many embodiments, the imaging chemistry used to provide excellent print-out images does not negatively affect imaging speed, on-press developability, or lithographic image durability. Further details of the invention and the results obtained therefrom are provided below. DETAILED DESCRIPTION OF THE INVENTION

[0041] The following discussion relates to various embodiments of the invention, and while some embodiments may be desirable for particular uses, the disclosed embodiments should not be interpreted or otherwise considered to limit the scope of the invention as claimed below. In addition, it will be appreciated by those skilled in the art that the following disclosure has broader application than explicitly described in the discussion of any particular embodiment.

[0042] definition

[0043] Unless otherwise indicated, the singular forms "a", "an", and "the" as used herein to define the various components of the infrared radiation-sensitive image recording layer and other materials used in the practice of the invention are intended to include one or more components (i.e., include plural referents).

[0044] Each term not expressly defined in this application should be understood to have a meaning generally accepted by those skilled in the art. If the construction of a term would make it meaningless or essentially meaningless in its context, the term should be interpreted as having a standard dictionary meaning.

[0045] Unless otherwise expressly indicated, the use of numerical values ​​in the various ranges specified herein should be considered approximate, as if both the minimum and maximum values ​​in the stated ranges were preceded by the word "about". In this manner, slight variations above and below the stated ranges may be used to achieve substantially the same results as the values ​​within the ranges. In addition, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values ​​and the endpoints of the ranges.

[0046] Unless the context indicates otherwise, when used herein, the terms "lithographic printing plate precursor," "precursor," and "IR-sensitive lithographic printing plate precursor" refer to equivalent references to embodiments of the present invention.

[0047] As used herein, the term "infrared radiation absorber" refers to a compound or material that absorbs electromagnetic radiation in the near infrared (near IR) and infrared (IR) regions of the electromagnetic spectrum, and generally refers to a compound or material with maximum absorption in the near IR and IR regions.

[0048] As used herein, the terms "near infrared region" and "infrared region" refer to radiation having a wavelength of at least 750 nm and higher. In most cases, the term is used to refer to the region of the electromagnetic spectrum of at least 800 nm and up to and including 1400 nm.

[0049] For the purposes of the present invention, the intensity of the printed image is generally indicated by the parameter ΔE, which is the Euclidean distance in the CIE 1976 L*a*b* color space between the color of the area exposed to radiation and the color of the area not exposed to radiation measured from reflection measurements in 45 / 0 geometry (unpolarized) using a CIE 2° observer and D50 as illuminant according to EN ISO 11664-4 "Colorimetry—Part 4: CIE 1976 L*a*b*Colour space" and other known references. Color measurements can be performed using commercial instruments such as the Techkon SpectroDens. In the CIE 1976 L*a*b color space, colors are expressed as three numeric color values: L* represents the lightness (or brightness) of the color, a* represents the green-red component of the color, and b* represents the blue-yellow component of the color value.

[0050] For the purposes of the present invention, the visible spectral region refers to the spectral region of electromagnetic radiation having a wavelength between 400 nm and 700 nm.

[0051] As used herein, the terms "print out" and "print out image" are meant to be synonymous.

[0052] For clarification of the definition of any term relating to polymers, reference should be made to the "Glossary of Basic Terms in Polymer Science" Pure Appl. Chem. 68, 2287-2311, 1996 as published by the International Union of Pure and Applied Chemistry ("IUPAC"). However, any definition explicitly set forth herein should be considered decisive.

[0053] As used herein, the term "polymer" is used to describe a compound with a relatively large molecular weight formed by linking together many small reactive monomers to form repeating units with the same chemical composition. These polymer chains usually form a coiled structure in a random manner. With the choice of solvent, the polymer can become insoluble as the chain length grows and become polymer particles dispersed in a solvent medium. These particle dispersions can be very stable and can be used to describe the infrared radiation sensitive image recording layer used in the present invention. In the present invention, unless otherwise indicated, the term "polymer" refers to a non-crosslinked material. Therefore, the difference between crosslinked polymer particles and non-crosslinked polymer particles is that the latter can be dissolved in certain organic solvents with good solvation properties, while since the polymer chains are connected by strong covalent bonds, the crosslinked polymer particles can swell but not dissolve in organic solvents.

[0054] The term "copolymer" refers to a polymer comprising two or more different repeating or recurring units arranged along the polymer chain.

[0055] The term "backbone" refers to the chain of atoms in a polymer to which multiple pendant groups may be attached. An example of such a backbone is an "all-carbon" backbone obtained from the polymerization of one or more ethylenically unsaturated polymerizable monomers.

[0056] As used herein, the term "ethylenically unsaturated polymerizable monomer" refers to a compound containing one or more ethylenically unsaturated (-C=C-) bonds that can be polymerized using free radical or acid-catalyzed polymerization reactions and conditions. It is not intended to refer to chemical compounds that have only unsaturated -C=C- bonds that are not polymerizable under these conditions.

[0057] Unless otherwise indicated, the term "weight %" refers to the amount of a component or material based on the total solids of a composition, formulation or layer. Unless otherwise indicated, the percentages may be the same for a dry layer or the total solids of a formulation or composition.

[0058] As used herein, the term "layer" or "coating" may consist of one disposed or applied layer or a combination of several sequentially disposed or applied layers. If a layer is considered to be infrared radiation sensitive and negative-working, it is both sensitive to infrared radiation (as described above with respect to "infrared radiation absorbers") and negative-working in the formation of a lithographic printing plate.

[0059] As used herein, the terms "on-press developable" and "on-press developability" refer to the ability of a precursor according to the present invention to be developed after exposure to infrared radiation (imaging) by mounting the imaged precursor on a suitable printing press and developing it during the first few printed impressions using a fountain solution, a lithographic ink, or a combination of a fountain solution and a lithographic ink.

[0060] use

[0061] The lithographic printing plate precursor according to the present invention can be used to provide a lithographic printing plate that exhibits a desirable printed image after imagewise exposure. These lithographic printing plates can be used for lithographic printing during operation of a printing press. According to the present invention, the lithographic printing plate can be prepared using on-press processing or off-press processing. The lithographic printing plate precursor is prepared using the structure and components described below.

[0062] Lithographic printing plate precursors

[0063] The precursor according to the present invention can be formed by appropriately applying an infrared radiation-sensitive image recording composition (described below) to a suitable substrate (described below) to form a negative-working infrared radiation-sensitive image recording layer. Generally speaking, the infrared radiation-sensitive image recording composition (and the resulting infrared radiation-sensitive image recording layer) comprises: component (1) a free radical initiator composition that is capable of generating free radicals when exposed to infrared radiation, and the free radical initiator composition also comprises an electron donating agent and one or more iodonium cations; component (2) a free radical polymerizable composition; and component (3) a color-changing compound represented by structure (I) described below. All of these components (1), (2) and (3) are defined in detail below, and these components are the only essential components required to achieve the advantages of the present invention. In addition, it is necessary that the infrared radiation-sensitive image recording layer contains one or more borate anions, but optionally contains one or more borate anions in a specific molar ratio to one or more iodonium cations (described in detail below).

[0064] In some embodiments, the infrared radiation-sensitive image recording composition (and the resulting infrared radiation-sensitive image recording layer) may further comprise a component (4) infrared absorbing material (or a mixture of two or more thereof) other than the (3) color-changing compound; and a component (5) acid-sensitive dye precursor (or a mixture of two or more thereof) other than all of the components (1), (2), (3) and (4); and a component (6) non-radical polymerizable polymer material (or a mixture of two or more thereof) other than all of the components (1), (2), (3) and (4); or all of these components (4) to (6), all of which are described below. In some highly useful embodiments, the infrared radiation-sensitive image recording layer consists essentially of all of the indicated components (1) to (6) to provide the desired lithographic printing plate precursor with a desirable printed image and optimal overall imaging and printing properties.

[0065] There is typically only one infrared radiation-sensitive image-recording layer in each precursor. In many embodiments, this layer is typically the outermost layer in the precursor, but in some embodiments, there may be an outermost protective layer (also referred to as a topcoat) as described below disposed above (or directly on and in contact with) the infrared radiation-sensitive image-recording layer.

[0066] Base

[0067] The substrate used to prepare the precursor according to the invention generally has a hydrophilic imaging side surface, or at least a surface that is more hydrophilic than the applied infrared radiation sensitive image recording layer. The substrate generally comprises an aluminum-containing support which may comprise the original aluminum or a suitable aluminum alloy conventionally used for the preparation of lithographic printing plate precursors.

[0068] The aluminum-containing substrate may be treated using techniques known in the art, including 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 performed using 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 disposed on the inner aluminum oxide layer), each having a plurality of pores with different depths and shapes of pore openings. Thus, such methods provide an anodized oxide layer or aluminum oxide layer beneath an infrared radiation-sensitive image-recording layer that may be provided as described below. Discussion of such pores and methods for controlling their width is described in, for example, U.S. Patent Publications 2013 / 0052582 (Hayashi), 2014 / 0326151 (Mamba et al.), and 2018 / 0250925 (Merka et al.), and U.S. Patents 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 on providing two sequential anodizing treatments to provide different aluminum oxide layers (e.g., an outer aluminum oxide layer disposed above an inner aluminum oxide layer) in an improved substrate are described in, for example, U.S. Patent Application Publication 2018 / 0250925 (noted above). Teachings on providing three sequential anodization treatments to provide different aluminum oxide layers in an improved substrate are described, for example, in U.S. Patent Application Publication No. 2021 / 0094336.

[0069] Sulfuric acid anodization of the aluminum support generally provides the following aluminum (anodic) oxide weight (coverage) on the surface: at least 1 g / m 2 And up to and including 5g / m 2 , and more usually at least 1.5 g / m 2 And up to and including 4g / m 2 Phosphoric acid anodizing typically provides the following aluminum (anodic) oxide weight on the surface: at least 0.5 g / m 2 And up to and including 5g / m 2 , and more usually at least 1 g / m 2 And up to and including 3g / m 2 .

[0070] The anodized aluminum-containing substrate may be treated with an alkaline pore expansion solution or an acidic pore expansion solution to provide an anodic 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, and such hydrophilic layer may include a non-crosslinked hydrophilic polymer having carboxylic acid side chains.

[0071] Alternatively, the anodized aluminum-containing support can be further treated using a known post-anodizing method, such as post-treatment with an aqueous solution of a hydrophilic material, to seal the anodic oxide pores or to hydrophilize its surface, or both. Representative hydrophilic materials of this type for providing a hydrophilic layer (e.g., a hydrophilic polymer coating) include, but are not limited to, poly(vinylphosphonic acid) (PVPA), vinylphosphonic acid copolymers, poly[(meth)acrylic acid] or its alkali metal salts, or (meth)acrylic acid copolymers or their alkali metal salts, mixtures of phosphates and fluoride salts, or sodium silicate. Such hydrophilic coatings can be disposed on the outermost aluminum oxide layer (e.g., the outer aluminum oxide layer if there are multiple aluminum oxide layers). Post-treatment method materials can also include unsaturated double bonds to enhance adhesion between the treated surface and the infrared radiation exposure area above. Such unsaturated double bonds can be provided in low molecular weight materials, or they can be present in the side chains of polymers. Available post-treatment methods include impregnating the substrate in the case of rinsing, impregnating the substrate in the case of not rinsing, and various coating techniques such as extrusion coating.

[0072] Particularly useful hydrophilic layer or coating materials for this purpose include: a compound having one or more ethylenically unsaturated polymerizable groups, one or more -OM groups (at least one of which is directly attached to a phosphorus atom), and a molecular weight of less than 2000 g / mol, wherein 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) repeating units comprising amide units, and (b) repeating units comprising -OM' groups directly attached to a phosphorus atom, wherein M' represents a hydrogen, sodium, potassium or aluminum atom. The hydrophilic layer may be formed at a molecular weight of at least 0.0002 g / m 2 And up to and including 0.1g / m 2 A dry cover is provided over the outermost aluminum oxide layer.

[0073] Infrared radiation sensitive image recording layer:

[0074] The infrared radiation-sensitive recording layer composition according to the present invention (and the infrared radiation-sensitive image-recording layer prepared therefrom) is designed to be "negative-working", as this term is known in the field of lithography. In addition, the infrared radiation-sensitive image-recording layer can be designed to have a certain combination of components to provide on-press developability for 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.

[0075] The present invention utilizes a component (1) free radical initiator composition that is capable of generating free radicals upon exposure to infrared radiation. Such a component (1) initiator composition may include one or more organic halogen compounds, such as trihaloalkyl compounds; halomethyl triazines; 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 to be capable of generating free radicals upon exposure to infrared radiation. It is essential, however, that the (1) initiator composition include one or more iodonium cations, with or without the other representative listed compounds.

[0076] Representative compounds other than onium salts are described, for example, in

[0087] to

[0102] of U.S. Patent Application Publication 2005 / 0170282 (Inno et al., US '282) and U.S. Patent 6,309,792 (Hauck et al.), and also Japanese Patent Publication 2002 / 107916 and WO 2019 / 179995.

[0077] For example, component (1) free radical initiator composition should include one or more iodonium cations. Available onium salts are described in, for example,

[0103] to

[0109] of the cited disclosed US'282. For example, available iodonium salts include at least one iodonium cation and a suitable anion in the molecule. Examples of iodonium salts include diaryl iodonium salts, such as diphenyl iodonium salts and derivatives thereof, which are obtained by introducing one or more substituents into the phenyl ring of these compounds. Suitable substituents include, but are not limited to, alkyl, alkoxy, alkoxycarbonyl, acyl, acyloxy, chloro, bromo, fluoro and nitro. Particularly available iodonium cations such as diaryl onium cations can have, for example, two substituted or unsubstituted phenyl groups.

[0078] Examples of anions in the onium salt include, but are not limited to, halogen anions, ClO 4 - PF 6 - , BF 4 - , SbF 6 - , CH 3 SO 3- CF 3 SO 3 - , C 6 H 5 SO 3 - , CH 3 C 6 H 4 SO 3 - 、HOC 6 H 4 SO 3 - ,ClC 6 H 4 SO 3 - and boron anions, as described, for example, in U.S. Pat. No. 7,524,614 (Tao et al.). Representative useful iodonium salts are described in columns 6-7 of U.S. Pat. No. 7,524,614 (noted above), where the iodonium cation may contain various listed monovalent substituents "X" and "Y", or a carbocyclic or heterocyclic ring fused to a corresponding phenyl group.

[0079] The usable iodonium salt may be a polyvalent iodonium salt having at least two iodonium cations bonded by a covalent bond in the molecule.

[0080] In addition, the iodonium salts described in paragraphs

[0033] to

[0038] of the specification of Japanese Patent Publication No. 2002-082429 [or U.S. Patent Application Publication No. 2002-0051934 (Ippei et al.)] are useful. Representative iodonium borates are, for example, those listed in column 8 of U.S. Patent No. 7,524,614 (noted above).

[0081] The component (1) free radical initiator composition used in the practice of the present invention should also include one or more electron donating agents, which not only participate in the generation of free radicals for polymerizing the (2) free radical polymerizable compound described below, but also promote the color change reaction of the (3) color change compound described below. For example, electron donating compounds particularly useful in the present invention include borate compounds and other organic compounds, which desirably have an oxidation potential (V) of less than 1.1 relative to the Ag / AgCl electrode. ox ).

[0082] In the practice of the present invention, representative compounds that can serve as electron-donating agents include, but are not limited to, compounds having partial structures in which nitrogen atoms, oxygen atoms or sulfur atoms are directly bonded to aromatic or heteroaromatic groups. Those skilled in the art of chemistry will be able to design compounds having this feature in combination with the electrochemical features described above. Some potentially available electron-donating compounds are described in

[0013] to

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

[0017] to

[0020] of the disclosure. The technician using the teachings provided herein will be able to utilize routine experiments to determine which of any of the compounds will be acceptable or optimal electron-donating compounds according to the present invention.

[0083] Particularly useful compounds that can be used as electron donating agents include organic borate salts, which are organic borate salts represented by the following structure (III).

[0084] [B(R 10 R 11 R 12 R 13 ) - ] n M n+

[0085] Structure (III)

[0086] Where R 10 , R 11 , R 12 and R 13 is independently substituted or unsubstituted alkyl, for example, substituted or unsubstituted alkyl having 1 to 12 carbon atoms, which may be substituted by one or more fluoro, chloro and bromo groups; or substituted or unsubstituted aryl having 6 to 10 carbon atoms in the aromatic ring, and which may be substituted by the following substituents each on one or more aromatic rings: one or more alkyl, alkenyl, alkoxy, alkoxycarbonyl and acyloxy, one or two fluoro, chloro and bromo groups, wherein substituted or unsubstituted 6-membered aromatic (phenyl) groups are the most useful. In most embodiments, R 10 , R 11 , R 12 and R 13 At least three of them are identical or different substituted or unsubstituted aryl groups as defined above, and in the best embodiment, all R 10 , R 11 , R 12 and R 13 are the same substituted or unsubstituted phenyl, and for example wherein all of these groups are the same unsubstituted phenyl.

[0087] In structure (III), n is an integer equal to or greater than 1; and M n+ M 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 having a cationic charge, including a cyanine dye having a cationic charge. n+ and may represent one or more iodonium cations as described above.

[0088] If the other components in the infrared radiation-sensitive image-recording layer do not contain a borate compound represented by structure (III) above, such a borate compound should be present in the component (1) free radical initiator composition.

[0089] One or more electron donating agents useful in the present invention are present in the infrared radiation-sensitive image recording layer in an amount of at least 0.5 wt % or at least 1 wt %, and up to and including 10 wt % or up to and including 20 wt %, based on the total coverage (solids) of the infrared radiation-sensitive image recording layer.

[0090] The component (1) free radical initiator composition is present in the infrared radiation-sensitive image recording layer in an amount (molar ratio or weight ratio) that will be readily apparent to a person skilled in the art of preparing on-press developable lithographic printing plate precursors, and the minimum total amount and the maximum total amount are generally at least 1 weight percent and up to and including 20 weight percent of all components, including the electron donating agent and the iodonium cation, based on the total coverage (solids) of the infrared radiation-sensitive image recording layer.

[0091] Since the component (1) free radical initiator composition can have a variety of components, the useful amounts or dry coverages of the various components of the component (1) free radical initiator composition in the infrared radiation-sensitive image recording layer will be readily apparent to those skilled in the art based on their knowledge and the representative teachings provided herein (including the working examples shown below). Useful component (1) free radical initiator composition materials can be readily obtained from global commercial sources or readily prepared using known starting materials and synthesis methods.

[0092] Another essential feature of the infrared radiation sensitive image recording layer is component (2) a free radical polymerizable composition comprising one or more free radical polymerizable components, each of which contains one or more free radical polymerizable groups that can be polymerized using free radical initiation during infrared radiation exposure. In some embodiments, there are at least two free radical polymerizable components, each of which has the same or different numbers of free radical polymerizable groups in each molecule. Therefore, the available free radical polymerizable components may contain one or more free radical polymerizable monomers or oligomers, each of which has one or more polymerizable ethylenically unsaturated groups (e.g., two or more 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 contains carboxyl groups.

[0093] The one or more free radical polymerizable components may have a sufficiently large molecular weight or have sufficient polymerizable groups to provide a cross-linkable polymer matrix that acts as a "polymer binder" for the other components in the infrared radiation-sensitive image-recording layer. In such embodiments, a different (6) non-free radical polymerizable polymer material (described below) is not necessary, but may still be present if desired.

[0094] 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 two to up to fifteen acrylate groups can be prepared by reacting a triisocyanate such as N100 (Bayer Corp., Milford, Conn.) or a diisocyanate such as hexane-1,6-diisocyanate is reacted with hydroxyethyl acrylate, pentaerythritol triacrylate or dipentaerythritol pentaacrylate. Such urethane or urea (meth) acrylate compounds have a number of (meth) acrylate groups of up to fifteen or more per molecule. Commercially available urethane acrylates having fifteen acrylate groups include U-15HA and UA-53H, which are available from Shin-Nakamura Chemical Co. Ltd. These compounds having a large number of (meth) acrylates can be included in the (2) free radical polymerizable composition due to their high crosslinking efficiency.

[0095] Useful free radical polymerizable compounds include non-urethane (meth)acrylates 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 (di-trimethylolpropane tetraacrylate), Sartomer SR295 (pentaerythritol tetraacrylate), Sartomer SR415 [ethoxylated (20) trimethylolpropane triacrylate], Sartomer SR494 (ethoxylated pentaerythritol tetraacrylate) available from Sartomer Company, Inc. These non-urethane (meth)acrylates and non-urea (meth)acrylates may also have a large number of (meth)acrylate groups per molecule.

[0096] Mixtures of urethane or urea (meth)acrylates and 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.

[0097] Numerous other free radical polymerizable components are known in the art and are described in a wide range of literature including: Photoreactive Polymers: The Science and Technology of Resists, A Reiser, Wiley, New York, 1989, pp. 102-177; BM Monroe, Radiation Curing: Science and Technology, SPP Appas, ed., Plenum, New York, 1992, pp. 399-440; and A. Bohen and P. Walker, "Polymer Imaging", Imaging Processes and Material, JM Sturge et al. (eds.), Van Nostrand Reinhold, New York, 1989, pp. 226-262. For example, useful free radical polymerizable components are also described in EP 1,182,033A1 (Fujimaki et al.) (beginning at paragraph

[0170] ), and in U.S. Pat. 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 include 1H-tetrazolyl groups.

[0098] Component (2) One or more components of the free radically polymerizable composition are typically present in a total amount of at least 10 wt % or at least 20 wt %, and up to and including 50 wt % or up to and including 70 wt %, all based on the total coverage (solids) of the infrared radiation-sensitive image recording layer.

[0099] The third essential component of the infrared radiation-sensitive image recording composition and the image recording layer according to the present invention is component (3) a color-changing compound or a mixture of two or more thereof, each of which is represented by the following structure (I):

[0100]

[0101] Wherein Ar1, Ar2 and Ar3 independently represent the atoms necessary to make the substituted or unsubstituted aromatic ring complete or to make the substituted or unsubstituted heteroaromatic ring complete.Therefore, in general, for any or all of Ar1, Ar2 and Ar3, it is necessary to make the substituted or unsubstituted aromatic ring complete by an appropriate number of carbon atoms, for example, to make benzene (benzo) ring or naphthalene (naphtho) ring complete.In addition, for any or all of Ar1, Ar2 and Ar3, it is necessary to make the substituted or unsubstituted heteroaromatic ring complete by an appropriate number of carbon atoms and one or more heteroatoms, for example, to make the following complete: pyridine-2-yl, pyridine-3-yl, pyridine-4-yl, pyridazinyl, pyrimidine-2-yl, pyrimidine-4-yl, pyrimidine-5-yl or pyrimidine-6-yl, pyrazine, triazine, pyrroles, furans, thiophene, pyrazoles or oxazoles, imidazoles, thiazole or triazole ring.

[0102] In many useful embodiments of the present invention, Ar1 and Ar2 are the same atoms necessary to complete a substituted or unsubstituted aromatic ring, such as the same substituted or unsubstituted aromatic ring, such as 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 by, for example, one or more of the same or different optionally substituted alkyl groups, alkoxy groups, halogen groups (e.g., one or two of the same or different halogen groups), cyano groups, -COOR' groups, -SO 3 R' group or -SO 2 R' groups, wherein R' represents a substituted or unsubstituted alkyl group, which may be the same or different for each indicated group. It is also desirable that Ar3 represents the carbon atoms required to complete the benzene (benzo) ring in structure (I).

[0103] Furthermore, in structure (I), Y represents an oxygen atom, a sulfur atom or a moiety consisting of>C(R 4 R 5 ) represented by a dialkylmethylene group, wherein R 4 and R 5 is independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms. In many useful embodiments of the present invention, each representation of Y is the same or different dialkylmethylene, or even the same dialkylmethylene, wherein R 4 and R 5 is the same unsubstituted alkyl radical having 1 or 2 carbon atoms. A skilled chemist will be able to produce numerous compounds in which Y varies among the possible groups including the many possible dialkylmethylene radicals.

[0104] In structure (I), R 1 and R 2are independently substituted or unsubstituted alkyl groups, each having 1 to 12 carbon atoms, and in many embodiments, one or both of such alkyl groups may contain the same or different ether or ester linkages, which interrupt the carbon chain or, in the case of an ester group, may serve to terminate the alkyl chain.

[0105] Further, in structure (I), X represents a single bond or is selected from -S-, -O- and >N(R 6 ) of a divalent linking group, wherein R 6 is hydrogen, substituted or unsubstituted alkyl having 1 to 12 carbon atoms, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or L (as defined below). In a particular embodiment used in the present invention, X represents>N(R) as defined above 6 ) group, and especially wherein R 6 is hydrogen or an unsubstituted alkyl group having 1 to 8 carbon atoms.

[0106] In structure (I), L represents -C(=O)-OR 7 Group, -SO 2 -R 3 Group or -SO 2 NR 8 R 9 Group, where R 7 represents a substituted or unsubstituted alkyl group having a -C(=O)-OR 7 The rest of the group is attached to 1 to 8 carbon atoms of the secondary or tertiary carbon.

[0107] R 3 , R 8 and R 9 R 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 It may be a haloalkyl group having 1 to 12 carbon atoms, wherein one or more of the hydrogen atoms are replaced by a halogen atom. In some embodiments, L comprises an electron withdrawing group capable of undergoing a redox reaction with the electron donating agent in the free radical initiator composition (1) described above. In a particular embodiment of the present invention, L is -SO 2 -R 3 Group, where R 3 is an unsubstituted alkyl group having 1 or 2 carbon atoms, or a fluorinated alkyl group having 1 or 2 carbon atoms and at least one hydrogen atom replaced by a fluorine atom. 3 It may be trifluoromethyl.

[0108] Finally, in structure (I), Za represents one or more counter ions to balance the charge in the rest of the color-changing compound according to structure (I). For example, when the rest of the color-changing compound according to structure (I) is positively charged, Za represents one or more anions. Many useful anions are known in the art, such as halogen anions, ClO 4 - PF 6 - , BF 4 - , SbF 6 - , CH 3 SO 3 - CF 3 SO 3 - , C 6 H 5 SO 3 - , CH 3 C 6 H 4 SO 3 - 、HOC 6 H 4 SO 3 - ,ClC 6 H 4 SO 3 - And boron-containing anions, such as described in U.S. Patent No. 7,524,614 (noted above). Available boron-containing anions include tetraaryl borate anions (e.g., tetraphenyl borate) as described above for electron-donating agents. In some embodiments, Za can be supplied by an electron-donating agent in (1) a radical initiator composition. When the remainder of the color-changing compound according to structure (I) is negatively charged, Za represents one or more cations. Available cations are known in the art, such as alkali metal ions, alkaline earth metal ions, tertiary ammonium ions, and quaternary ammonium ions; and onium ions, such as iodonium ions, sulfonium ions, or phosphonium ions. In some embodiments, Za can be supplied by an onium compound agent in the radical initiator composition of component (1) as described above. In view of the color formation chemistry 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.

[0109] Some particularly useful embodiments of component (3) the color-changing compound are represented by the following structure (II):

[0110]

[0111] Among them, Ar1, Ar2, Ar3, R 1 , R 2 , R 3 , R 6 , Y and Za are as defined above.

[0112] While not wishing to be bound by a particular theory, it is believed that Ar3 in structure (I) or structure (II) influences the geometry of the polymethine chain in the component (3) color-changing compound and thus renders it more reactive in the presence of an organic borate according to structure (III) as part of component (1). For example, in the presence of a tetraphenylborate anion, a compound according to structure (I) or structure (II) [inventive (3) color-changing compound 2 or ICCC-2 shown below] may undergo a chemical reaction (shown below) to form a phenylated product ICCC 2-Ph during or after irradiation of an infrared radiation-sensitive image recording layer by a suitable infrared source. The UV-visible spectrum of ICCC 2-Ph in methanol has an absorption peak at about 514 nm, which is quite different from the absorption peak of ICCC 2 at 770 nm. It is also possible to phenylate the inventive (3) color-changing compound by reacting with a triphenylalkyl borate, such as triphenyl tert-butyl borate and tris (3-fluorophenyl) n-butyl borate.

[0113]

[0114] The phenylated product, such as ICCC 2-Ph, in the infrared radiation exposed area of ​​the infrared radiation sensitive image recording layer is stable at room temperature for at least one week and thus provides stable printout of the lithographic printing plate precursor exposed to infrared radiation. In addition, in the presence of a sufficient amount of a borate compound according to structure (III) above, the phenylated product can be formed at a much lower infrared radiation energy input than is normally required for decomposition reactions involving cleavage of a leaving group as described in many prior arts listed in the Background of the Invention section above. In addition, the phenylation reaction provides a much larger shift of the absorption peak in the visible spectrum than the decomposition reaction, which can be used to produce large color differences. For example, the phenylation reaction of ICCC-2 provides a peak shift of ~256 nm, while the decomposition reaction of ICCC-2 provides a peak shift of 140 nm and forms the product shown below (λ in methanol): max ~632nm).

[0115]

[0116] As another example, the following decomposition reaction involves a decomposable infrared dye that is outside the scope of structure (I), can only produce a peak shift of 164 nm, requires high energy input, and produces gaseous byproducts.

[0117]

[0118] In an infrared radiation-sensitive recording layer having both a color-changing compound according to structure (I) or structure (II) and a borate compound according to structure (III), both phenylation and decomposition may occur. 2 At an exposure energy level of 100 Å, the amount of phenylated products relative to decomposition products, and therefore printout metrics (e.g., ΔE color difference between exposed and non-exposed areas) depends on the amount of borate compound available for the phenylated reaction. Since the borate compound can also participate in the reaction with the iodonium cation to produce free radical generation, the amount of the borate compound available for the phenylated reaction depends on both the amount of the borate compound and the amount of the iodonium cation.

[0119] In some embodiments of the present invention, when it is necessary to expose the sample at a relatively low exposure energy, for example, 110 mJ / cm 2 Sufficient for printing, the molar ratio of one or more borate anions according to structure (IIIa) described below to one or more iodonium cations in the infrared radiation-sensitive image recording layer may be at least 0.5: 1. More desirably, the molar ratio is at least 0.8: 1 and up to and including 4: 1.

[0120] Even in the presence of a sufficient amount of the borate compound, Ar3 is still necessary in both structure (I) and structure (II). In the absence of Ar3 in the decomposable infrared dye, if the phenylation reaction still occurs, it will be inefficient.

[0121] The component (3) color-changing compound (alone or a mixture of two or more thereof) in the infrared radiation-sensitive image recording layer is usually present in an amount of at least 0.5 wt % or at least 1 wt %, and up to and including 10 wt % or up to and including 15 wt %, based on the total weight of the infrared radiation-sensitive image recording layer.

[0122] Thus, in some embodiments of the precursors of the present invention, it is essential that the infrared radiation-sensitive image-recording layer contains sufficient iodonium cation(s) and borate anion(s) so that the molar ratio of borate anion(s) to iodonium cation(s) is at least 0.5:1 or at least 0.8:1, and up to and including 2:1 or up to and including 4:1. The borate anion(s) may be represented by the following structure (IIIa):

[0123] B(R 10 R 11 R 12 R 13 ) -

[0124] Structure (IIIa)

[0125] Where R 10 , R 11 , R 12 and R 13 are independently substituted or unsubstituted alkyl or substituted or unsubstituted aryl, provided that R 10 , R 11 , R 12 and R 13 At least three of the are the same or different substituted or unsubstituted aryl groups, and the substituted aryl groups each have not more than two halogen substituents.

[0126] One or more iodonium cations may be provided to the infrared radiation sensitive image recording layer as part of the (1) free radical initiator composition. However, one or more borate anions may be provided to the infrared radiation sensitive image recording layer in various ways. For example, one or more borate anions may be provided as part of the one or more iodonium salts in the (1) free radical initiator composition. Alternatively, one or more borate anions may be provided as one or more Za counterions in structure (I) or structure (II) or as part of component (4) infrared absorbing material described below. Still further, one or more borate anions may be provided as separate borate salts in the (1) free radical initiator composition.

[0127] Although not necessary, it is highly desirable that the infrared radiation-sensitive image recording layer according to the present invention may also contain a component (4) infrared absorbing material (one or a mixture of two or more thereof) different from the component (3) color-changing compound described above. The (4) infrared radiation absorber provides the desired infrared radiation sensitivity or converts the radiation into heat, or both. Useful infrared radiation absorbers may be pigments or infrared radiation absorbing dyes. Suitable dyes are those described in, for example, U.S. Patents 5,208,135 (Patel et al.), 6,153,356 (Urano et al.), 6,309,792 (Hauck et al.), 6,569,603 (Furukawa), 6,797,449 (Nakamura et al.), 7,018,775 (Tao), 7,368,215 (Munnelly et al.), 8,632,941 (Balbinot et al.) and U.S. Patent Application Publication 2007 / 056457 (Iwai et al.). In some infrared radiation-sensitive embodiments, it is desirable that at least one (4) infrared radiation absorber in the infrared radiation-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.).

[0128] In addition to low molecular weight IR absorbing dyes, IR dye chromophores bound to polymers can also be used. In addition, IR dye cations can also be used, i.e., the cation is the IR absorbing portion of the dye salt that ionically interacts with the polymer containing carboxyl, sulfonyl, phospho or phosphono groups in the side chains.

[0129] The total amount of component (4) infrared radiation absorber is at least 0.5 wt% or at least 1 wt% and up to and including 15 wt%, or up to and including 30 wt%, based on the total weight of the infrared radiation-sensitive image recording layer.

[0130] Another optional but desirable component of the infrared radiation sensitive image recording layer is a component (5) acid-sensitive dye precursor (e.g., alone or in a combination of two or more thereof). Available component (5) acid-sensitive dye precursors are colorless or almost colorless compounds in neutral form, and the compound is converted into a colored form when protonated. Many colorless dyes known for this purpose include, for example, those described in

[0209] to

[0222] of EP 3,418,332A2 (Inasaki et al., corresponding to U.S. Patent Application Publication 2018 / 0356730) and

[0044] to

[0046] of EP 2,018,365B1 (Nguyen et al., corresponding to U.S. Patent 7,910,768). These component (5) acid-sensitive dye precursors are different from all components (1), (2), (3) and (4) defined above.

[0131] For example, in some embodiments, at least one of the component (5) acid-sensitive dye precursors comprises a lactone substructure. More particularly, useful component (5) acid-sensitive dye precursors can be represented by one or more of the following structures (C1) and (C2):

[0132]

[0133]

[0134] Where R 11 To R 19 Be hydrogen, unsubstituted or substituted alkyl or unsubstituted or substituted aryl independently.This type of substituted or unsubstituted alkyl can have 1 to 20 carbon atoms, and possibly, one or more substituents can include but not limited to halogen, alkyl, aryl, alkoxy and phenoxy.Available substituted or unsubstituted aryl can be carbocyclic aromatic ring or heterocyclic aromatic ring, and this type of group can have two or more condensed rings.Available substituents for aromatic ring can include but not limited to those described above for alkyl.But skilled chemists can use this instruction about structure (C1) and (C2) to design other available component (5) acid-sensitive dye precursors as guidance.

[0135] As indicated above, such component (5) acid-sensitive dye precursors may, if desired, be present in any desired amount of at least 0.5 wt % and up to and including 10 wt % based on the total coverage (solids) of the infrared radiation-sensitive image recording layer.

[0136] In many embodiments of the present invention, it is also optional but desirable that the infrared radiation-sensitive image-recording layer further comprises a component (6) non-radical polymerizable polymer material (or polymer binder), or a mixture of two or more thereof, each of which does not have any functional groups (if present) that would enable free radical polymerization of the polymer material. Thus, such component (6) non-radical polymerizable polymer material is different from all of the components (1), (2), (3) and (4) described above.

[0137] Useful component (6) non-free radically polymerizable polymeric materials typically have a weight average molecular weight (M) of at least 2,000 g / mol or at least 20,000 g / mol, and up to and including 300,000 g / mol or up to and including 500,000 g / mol, as determined by gel permeation chromatography (polystyrene standards). w ).

[0138] Such component (6) non-radical polymerizable polymer material may be selected from polymer binder materials known in the art, including polymers comprising repeating units having side chains comprising polyoxyalkylene segments, such as those described in U.S. Pat. No. 6,899,994 (Huang et al.). Other useful polymer binders include two or more types of repeating units having different side chains, the side chains comprising polyoxyalkylene segments, such as described in, for example, WO Publication 2015-156065 (Kamiya et al.). Some such polymer binders may further include repeating units having cyano side groups, such as those described in, for example, U.S. Pat. No. 7,261,998 (Hayashi et al.).

[0139] Such component (6) non-free radical polymerizable polymeric material may also have a backbone comprising a plurality (at least two) of urethane moieties and pendant groups comprising polyoxyalkylene segments.

[0140] The non-radical polymerizable polymer material of component (6) may be present in particulate form, i.e., in the form of discrete particles (non-aggregated particles). Such discrete particles may have an average particle size of at least 10 nm and up to and including 1500 nm, or typically at least 80 nm and up to and including 600 nm, and are typically uniformly distributed in the infrared radiation-sensitive image recording layer. Some of these materials may be present in particulate form and have an average particle size of at least 50 nm and up to and including 400 nm. The average particle size may be determined using various known methods and nanoparticle measuring equipment, including measuring the particles in an electron scanning microscope image and averaging a set number of measurements.

[0141] In some embodiments, component (6) the non-radical polymerizable polymer material may be present in the form of particles having an average particle size that is less than the average dry thickness of the infrared radiation-sensitive image-recording layer.

[0142] Component (6) non-radical polymerizable polymer material may be present in an amount of at least 10 wt%, or at least 20 wt%, and up to and including 50 wt%, or up to and including 70 wt%, based on the total coverage (solids) of the infrared radiation-sensitive image recording layer.

[0143] The infrared radiation-sensitive image-recording layer may also contain various other optional addenda in conventional amounts, including, but not limited to, dispersants, wetting agents, biocides, plasticizers, surfactants for coatability or other properties, tackifiers, pH adjusters, desiccants, defoamers, development aids, rheology modifiers, or combinations thereof, or any other addenda commonly used in the lithographic coating art.

[0144] Top coating:

[0145] Although in most embodiments of the present invention the infrared radiation-sensitive image-recording layer is the outermost layer without a layer disposed thereon (e.g. a topcoat), it is possible that the precursor according to the present invention can be designed to have a protective layer (also referred to in the art as an overcoat, oxygen barrier layer or topcoat) disposed directly on the infrared radiation-sensitive image-recording layer. Any known topcoat composition designed for negative-working image-recording layers of lithographic printing plate precursors based on free radical polymerization in radiation-exposed areas can be used.

[0146] When present, the topcoat is provided as a hydrophilic topcoat formulation and dried to provide at least 0.1 g / m 2 And at most but less than 4g / m 2 The dry coating coverage is usually at least 0.15 g / m 2 And up to and including 2.5g / m 2 In some embodiments, the dry coating coverage is as low as 0.1 g / m 2 And up to and including 1.5g / m 2 , or at least 0.1g / m 2 And up to and including 0.9g / m 2 , so that the topcoat is relatively thin for easy removal during off-press development or on-press development.

[0147] Preparation of lithographic printing plate precursors:

[0148] The lithographic printing plate precursor according to the present invention can be provided in the following manner. Any suitable equipment and process such as spin coating, blade coating, gravure coating, die coating, slot coating, rod coating, wire rod coating, roller coating or extrusion hopper coating can be used to apply the infrared radiation sensitive image recording layer formulation containing the necessary components (1), (2) and (3) described above, and the required one or more iodonium cations and one or more borate anions, and optional components (4), (5), (6) and other optional additives to the hydrophilic surface of a suitable aluminum-containing substrate as described above, which is usually in the form of a continuous web. Such formulations can also be applied by spraying onto a suitable substrate. Typically, once the infrared radiation sensitive image recording layer formulation is applied with a suitable wet coverage, it is dried in a suitable manner known in the art to provide the desired dry coverage as indicated below, thereby providing an infrared radiation sensitive continuous web or an infrared radiation sensitive continuous product. The components and addenda of the infrared radiation-sensitive image-recording layer can be designed so that upon imaging, the layer can be readily removed on-press using either or a combination of lithographic inks and fountain solutions.

[0149] As noted above, prior to application of the infrared radiation-sensitive image-recording layer formulation, the substrate (i.e., continuous web or web) may be 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 typically 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.

[0150] The manufacturing method generally comprises mixing the various components required for the infrared radiation-sensitive image recording layer in a suitable organic solvent or a mixture thereof, with or without water [e.g., methyl ethyl ketone (2-butanone), methanol, ethanol, 1-methoxy-2-propanol, 2-methoxypropanol, isopropanol, acetone, γ-butyrolactone, n-propanol, tetrahydrofuran, and other organic solvents and mixtures thereof readily known in the art], applying the resulting infrared radiation-sensitive image recording layer formulation to a continuous substrate web, and removing the solvent by evaporation under suitable drying conditions.

[0151] After suitable drying, the dry coverage of the infrared radiation-sensitive image-recording layer on the substrate may be at least 0.1 g / m 2 , or at least 0.4g / m 2 , and up to and including 2g / m 2 , or up to and including 4g / m 2 , but other dry coverage amounts may be used if desired to provide the desired dry coverage.

[0152] As described above, in some embodiments, a suitable water-based hydrophilic topcoat formulation (described above) may be applied to the dried infrared radiation-sensitive image-recording layer using known coating and drying conditions, equipment, and processes.

[0153] Under actual manufacturing conditions, the result of these coating operations is a continuous radiation-sensitive web (or roll) of infrared radiation-sensitive lithographic printing plate precursor material having only a single infrared radiation-sensitive image-recording layer as the outermost layer or having both a single infrared radiation-sensitive image-recording layer and a hydrophilic top coating layer disposed thereon as the outermost layer. Such a continuous radiation-sensitive web can be cut or slit into appropriately sized precursors for use.

[0154] Imaging (exposure) conditions

[0155] During use, the infrared radiation-sensitive lithographic printing plate precursor of the present invention can be exposed to a suitable infrared radiation source, which depends on the infrared radiation absorber present in the infrared radiation-sensitive image recording layer. In some embodiments, the lithographic printing plate precursor can be imaged using one or more infrared radiation-emitting lasers to produce exposed areas and non-exposed areas in the infrared radiation-sensitive image recording layer, the laser emitting significant infrared radiation in the range of at least 750 nm and up to and including 1400 nm, or at least 800 nm and up to and including 1250 nm. Such infrared radiation-emitting lasers can be used for such imaging in response to digital information provided by a computing device or other digital information source.

[0156] Thus, imaging or exposing infrared radiation from an infrared radiation generating laser (or an array of such lasers) can be used for imaging. If desired, imaging at multiple infrared (or near IR) wavelengths can also be used for imaging simultaneously. The laser used to expose the precursor is typically a diode laser because of the reliability and low maintenance of diode laser systems, but other lasers, such as gas lasers or solid-state lasers, can also be used. The combination of power, intensity, and exposure time for infrared radiation imaging will be readily apparent to those skilled in the art.

[0157] The infrared imaging device can be configured as a flatbed recorder or a drum recorder, wherein the infrared radiation sensitive lithographic printing plate precursor is mounted to the inner or outer cylindrical surface of the drum. An example of a useful imaging device can be a laser diode comprising a laser diode emitting radiation at a wavelength of about 830 nm. The plate setters are available in the form of Trendsetter plate setters (Eastman Kodak Company) and NEC AMZISetter X series (NEC Corporation, Japan). Other suitable imaging devices include Screen PlateRite 4300 series or 8600 series plate setters (available from Screen USA, Chicago, IL) operating at a wavelength of 810 nm or thermal CTP plate setters from Panasonic Corporation (Japan).

[0158] If the infrared radiation sensitive image recording layer is sensitive to the presence of ozone, it may be desirable to include a device for reducing or removing ozone in the environment of laser imaging. Useful devices and systems for achieving this are described, for example, in U.S. Patent Application Publication 2019 / 0022995 (Igarashi et al.).

[0159] Depending on the sensitivity of the infrared radiation sensitive image recording layer, when using an infrared radiation imaging source, the imaging intensity can be at least 30 mJ / cm 2 and up to and including 500 mJ / cm 2 , and usually at least 50 mJ / cm 2 and up to and including 300 mJ / cm 2 .

[0160] Processing (development) and printing

[0161] After imagewise exposure as described above, the exposed infrared radiation-sensitive lithographic printing plate precursor having exposed and non-exposed areas in the infrared radiation-sensitive image-recording layer can be processed on-press to remove the non-exposed areas (and any topcoat layer over both the exposed and non-exposed areas). During this processing and during lithographic printing, the revealed hydrophilic substrate surface repels ink, while the remaining exposed areas accept lithographic ink.

[0162] Thus, the negative-working lithographic printing plate precursor of the present invention can be developed on-press using a lithographic ink, a fountain solution, or a combination of a lithographic ink and a fountain solution. In such embodiments, the imaged (exposed) infrared radiation-sensitive lithographic printing plate precursor according to the present invention is mounted on a printing press and a printing operation is started. When the initial printing plate is performed, the non-exposed areas in the infrared radiation-sensitive image recording layer are removed by a suitable fountain solution, a lithographic ink, or a combination of the two. Typical ingredients of an aqueous fountain solution include a pH buffer, a desensitizer, a surfactant and a wetting agent, a humectant, a low boiling point solvent, a biocide, an anti-foaming agent, and a chelating agent. A representative example of a fountain solution is Varn Litho Etch 142W + Varn PAR (alcohol replacement) (available from Varn International, Addison, IL).

[0163] In a typical press start-up of a sheet-fed press, the dampening rollers are first engaged and dampening solution is supplied to the mounted imaging precursor to swell the exposed infrared radiation-sensitive image recording layer at least in the non-exposed areas. After several rotations, the inking rollers are engaged and they supply lithographic ink to cover the entire printing surface of the lithographic printing plate. Typically, within 5 to 20 rotations after the inking rollers are engaged, the printing sheet is supplied to remove the non-exposed areas of the infrared radiation-sensitive image recording layer and the material on the blanket cylinder (if present) from the lithographic printing plate using the formed ink-fountain solution emulsion.

[0164] The on-press developability of the infrared radiation exposed lithographic precursor is particularly useful when the precursor comprises one or more polymeric binder materials (whether free radical polymerizable or not) in the infrared radiation sensitive image recording layer, at least one of which is present as particles having an average diameter of at least 50 nm and up to and including 400 nm.

[0165] The present invention provides at least the following embodiments and combinations thereof, but other combinations of features as would be understood by a skilled artisan from the teachings of this disclosure are considered to be within the present invention:

[0166] 1. A lithographic printing plate precursor comprising:

[0167] substrate, and

[0168] An infrared radiation-sensitive image recording layer is provided on the substrate, the infrared radiation-sensitive image recording layer comprising the following components (1), (2) and (3):

[0169] (1) a free radical initiator composition capable of generating free radicals upon exposure to infrared radiation, wherein the free radical initiator composition comprises an electron donating agent and one or more iodonium cations;

[0170] (2) a free radical polymerizable composition; and

[0171] (3) A color-changing compound represented by the following structure (I)

[0172]

[0173] in:

[0174] 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;

[0175] Y represents an oxygen atom, a sulfur atom or a 4 R 5 ) represented by a dialkylmethylene group, wherein R 4 and R 5 is independently a substituted or unsubstituted alkyl group having 1 to 4 carbon atoms;

[0176] R 1 and R 2 are independently substituted or unsubstituted alkyl;

[0177] X represents a single bond or is selected from -S-, -O- and >N(R 6 ) of a divalent linking group, wherein R 6 is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or L;

[0178] L represents -C(=O)-OR 7 Group, -SO 2 -R 3 Group or -SO 2 NR 8 R 9 Group, where R 7 represents a substituted or unsubstituted alkyl group having a -C(=O)OR 7 The secondary or tertiary carbon to which the remainder of the group is attached; and R 3 , R 8 and R 9 independently represent substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; and

[0179] Za represents one or more counterions to balance the charge in the rest of the color-changing compound according to structure (I),

[0180] wherein the infrared radiation-sensitive image recording layer comprises one or more borate anions represented by the following structure (IIIa):

[0181] B(R10 R 11 R 12 R 13 ) -

[0182] Structure (IIIa)

[0183] Where R 10 , R 11 , R 12 and R 13 are independently substituted or unsubstituted alkyl or substituted or unsubstituted aryl, provided that R 10 , R 11 , R 12 and R 13 At least three of the are the same or different substituted or unsubstituted aryl groups, and the substituted aryl groups each have not more than two halogen substituents.

[0184] 2. A lithographic printing plate precursor according to embodiment 1, wherein Za represents one or more anions.

[0185] 3. A 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.

[0186] 4. A lithographic printing plate precursor according to any 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 and up to and including 4:1.

[0187] 5. The lithographic printing plate precursor according to any of Embodiments 1 to 4, wherein the (3) color-changing compound is represented by the following structure (II):

[0188]

[0189] Among them, Ar1, Ar2, Ar3, R 1 , R 2 , R 3 , R 6 , Y and Za are as defined above.

[0190] 6. A lithographic printing plate precursor according to any of embodiments 1 to 5, wherein Ar1 and Ar2 are atoms necessary to complete the same or different substituted or unsubstituted aromatic rings.

[0191] 7. A lithographic printing plate precursor according to any of embodiments 1 to 6, wherein one or both of the aromatic rings completed by the atoms of Ar1 and Ar2 are substituted by one or two halogen groups which may be the same or different.

[0192] 8. A lithographic printing plate precursor according to any of embodiments 1 to 7, wherein R 3 It is trifluoromethyl.

[0193] 9. A lithographic printing plate precursor according to any of embodiments 1 to 8, wherein Ar3 represents the carbon atoms and hydrogen atoms required to complete the benzene ring.

[0194] 10. The lithographic printing plate precursor according to any of embodiments 1 to 9, wherein Za comprises a tetraarylborate anion.

[0195] 11. The lithographic printing plate precursor according to any of Embodiments 1 to 10, wherein the electron donating agent is an organic borate represented by the following structure (III):

[0196] [B(R 10 R 11 R 12 R 13 ) - ] n M n+

[0197] Structure (III)

[0198] Where R 10 , R 11 , R 12 and R 13 As defined for structure (IIIa), n is an integer equal to or greater than 1, and M n+ It is an n-valent cation.

[0199] 12. A lithographic printing plate precursor according to any of embodiments 1 to 11, wherein R of structure (IIIa) and structure (III) 10 , R 11 , R 12 and R 13 All are the same or different substituted or unsubstituted aryl groups.

[0200] 13. A lithographic printing plate precursor according to any of Embodiments 1 to 12, wherein R of Structure (IIIa) and Structure (III) 10 , R 11 , R 12 and R 13 All are the same substituted or unsubstituted phenyl groups.

[0201] 14. A lithographic printing plate precursor according to any of embodiments 1 to 13, wherein R 1 and R 2 One or both of independently comprise a chain of carbon atoms interrupted by one or more ether or ester bonds.

[0202] 15. The lithographic printing plate precursor according to any of embodiments 1 to 14, wherein the infrared radiation-sensitive image-recording layer further comprises a component (4) infrared absorbing material different from the component (3) color-changing compound.

[0203] 16. A lithographic printing plate precursor according to any of embodiments 1 to 15, wherein the component (1) free radical initiator composition comprises a diaryliodonium tetraphenylborate.

[0204] 17. A lithographic printing plate precursor according to any of embodiments 1 to 16, wherein the infrared radiation-sensitive image recording layer further comprises a component (5) acid-sensitive dye precursor different from all components (1), (2), (3) and (4) defined above.

[0205] 18. A lithographic printing plate precursor according to any of embodiments 1 to 17, wherein the infrared radiation sensitive image recording layer further comprises a component (6) non-free radical polymerizable polymer material which is different from all components (1), (2), (3) and (4) defined above.

[0206] 19. A lithographic printing plate precursor according to embodiment 18, wherein the component (6) non-radical polymerizable polymer material is present in the form of particles.

[0207] 20. The lithographic printing plate precursor according to any of embodiments 1 to 19, wherein after exposure to infrared radiation, the infrared radiation-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.

[0208] 21. A lithographic printing plate precursor according to any of embodiments 1 to 20, wherein the component (3) is a color-changing compound represented by structure (I) present in the infrared radiation-sensitive image recording layer in an amount of at least 0.5 wt. % and up to and including 15 wt. % coverage based on the total dry coverage of the infrared radiation-sensitive image recording layer.

[0209] 22. The lithographic printing plate precursor according to any of embodiments 1 to 21, wherein the infrared radiation-sensitive image-recording layer is the outermost layer.

[0210] 23. The lithographic printing plate precursor according to any of embodiments 1 to 22, wherein the component (2) the free radical polymerizable composition comprises at least two free radical polymerizable components.

[0211] 24. A lithographic printing plate precursor according to any 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.

[0212] 25. A lithographic printing plate precursor according to any of embodiments 1 to 24, wherein the substrate comprises an aluminum-containing substrate, the 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.

[0213] 26. A method for providing a lithographic printing plate, the method comprising:

[0214] A) image-wise exposing the lithographic printing plate precursor according to any of embodiments 1 to 25 to infrared radiation to provide exposed areas and non-exposed areas in the infrared radiation-sensitive image recording layer, and

[0215] B) removing the non-exposed areas in the infrared radiation-sensitive image recording layer from the substrate.

[0216] 27. The method of embodiment 26, comprising removing the non-exposed areas in the infrared radiation-sensitive image-recording layer from the substrate on-press using a lithographic ink, a fountain solution, or a combination of a lithographic ink and a fountain solution.

[0217] 28. A method according to embodiment 26 or 27, wherein the image-wise exposure is performed using at least one laser emitting infrared radiation.

[0218] 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 noted, the materials used in the examples were obtained from various commercial sources as indicated, although other commercial sources are also available.

[0219] An aluminum-containing substrate for a lithographic printing plate precursor was prepared in the following manner:

[0220] Hydro 1052 aluminum alloy strip or web (available from Norsk Hydro ASA, Norway) having a thickness of 0.28 mm was used as an aluminum-containing "printing plate" stock or support. Both the pre-etching and post-etching steps were performed in alkaline solutions under known conditions. The etched aluminum support was roughened (or 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. Thereafter, the aluminum-containing support was subjected to two separate anodizing treatments. The first anodizing treatment was performed using phosphoric acid as the electrolyte to form a pore having an average micropore diameter (DO ) and an average dry thickness (T O ) of the outer aluminum oxide layer. A second anodization treatment was then performed using phosphoric acid as the electrolyte to form an average micropore diameter (D i ) and an average dry thickness (T i ). The two anodization steps are carried out as a continuous process on a typical manufacturing line used to make lithographic printing plate precursors. The aluminum-containing support thus prepared is coated with an aqueous solution of polyacrylic acid to give an anodizing agent of 0.03 g / m 2 for substrates useful in the present invention. 2 Dry thickness.

[0221] A negative-working infrared radiation-sensitive image recording layer was then formed on the aluminum-containing substrate as described by individually coating the infrared radiation-sensitive composition formulations having the components and amounts shown in Tables I, II and III below using a bar coater to provide 0.9 g / m 2 of each of the inventive precursors and comparative precursors described below after drying at 50° C. for 60 seconds. 2 The raw materials indicated in Table I are identified in Table II below, and the amounts of the various components are shown in Table III. These materials can be obtained from one or more commercial sources of chemicals or prepared using known synthetic methods and starting materials.

[0222] Table I

[0223] Components Amount (g) Polymer dispersions [containing non-free radically polymerizable polymeric materials] 1.056 Hydroxypropyl methylcellulose 0.60 Monomer 1 (free radical polymerizable component) 0.501 Monomer 2 (free radical polymerizable component) 0.249 Infrared radiation absorber (see Table III) 0.03 Acid-sensitive dye precursors (see Table III) 0.035 Color-changing compounds (see Table III) 0.035 Surfactant 1 0.069 Initiator composition (see Table III) 0.09 Compound P1 (only in Example 10 of the present invention) 0.008 1-Propanol 4.94 2-Butanone 2.40 1-Methoxy-2-propanol 4.22 γ-Butyrolactone 0.14 water 0.66

[0224] Table II

[0225]

[0226] Table II (continued)

[0227]

[0228] Table II (continued)

[0229]

[0230] Table III

[0231]

[0232] *Example 8 of the present invention contains Compound PI as indicated in Table I above.

[0233] **B - / I + [mol / mol] represents the molar ratio of the one or more borate anions to the one or more iodonium cations, and the one or more borate anions are represented by the above structure (IIIa).

[0234] ***inf represents the infinite case due to zero denominator.

[0235] The following four tests were used to evaluate each of the inventive and comparative lithographic printing plate precursors: "On-Press Developability" (DOP), "Imaging Speed", "Print Out Image" (PO), and "Dark Fade". The results are summarized in Table IV below.

[0236] On-press development capability (DOP):

[0237] By using Trendsetter 3244x at 15-150mJ / cm 2 Each lithographic printing plate precursor was imagewise exposed to evaluate on-press developability. Each imagewise exposed lithographic printing plate precursor was then mounted on a MAN Roland Favorite 04 press without development (rinsing). Fountain solution (Varn Supreme 6038) and lithographic ink (Gans Cyan) were supplied and lithographic printing was performed. On-press development occurred during printing and was evaluated by counting the number of printed sheets required to receive a clean background, and one of the following qualitative values ​​was given based on the number of printed sheets that achieved a clean background. For this test parameter, + and 0 estimates are acceptable.

[0238] +<15 printed pages

[0239] 0 15-35 printed pages

[0240] -> 35 printed pages

[0241] Imaging speed:

[0242] Each lithographic printing plate precursor was exposed and developed as described above. The imaging speed was measured on paper after 1000 printings by determining the ink density of solids exposed to different energies. The inflection point of the ink density with respect to the exposure energy was considered to be a measure of the imaging speed. The following qualitative values ​​are given as the result of separate experiments, where lower imaging energies are desirable. For this parameter, + and 0 estimates are acceptable.

[0243] + Imaging speed <30mJ / cm 2

[0244] 0 Imaging speed = 30-60mJ / cm 2

[0245] - Imaging speed>60mJ / cm 2

[0246] Print out the image:

[0247] A Trendsetter 800III Quantum TH 1.7 (available from Eastman Kodak Company) was used at 90 mJ / 2 Each lithographic printing plate precursor was imagewise exposed to provide exposed areas and non-exposed areas in the negative-working IR-sensitive image recording layer. For each imagewise exposed lithographic printing plate precursor, the color difference between the exposed areas and the non-exposed areas was measured within 10 min after the imagewise exposure was completed by determining the ΔE value using a Techkon Spectro Dens spectrodensitometer, calculating the Euclidean distance of the measured L*a*b values, and giving the following qualitative values ​​immediately after exposure.

[0248]

[0249] Dark Fade:

[0250] The individual lithographic printing plates were imagewise exposed as described above and then stored in the dark for 24 hours. The ΔE measurements were then carried out as described above and the following qualitative values ​​are given.

[0251]

[0252] Table IV

[0253]

[0254]

[0255] The results shown in Table IV support many of the conclusions. The data for Comparative Example 1 show that conventional acid-sensitive lactone-based leuco dyes such as Acid-Sensitive Dye Precursor 1 generally provide a moderate or acceptable printout image immediately after exposure without any long-term storage, but after the printout image is stored, the image becomes poor (e.g., considering dark fading results). In Comparative Example 8, in which the highly acid-sensitive lactone-based dye precursor ASDP2 was used, a strong printout image was obtained immediately after exposure, but after the printout image was stored, the image became poor.

[0256] The results for Comparative Example 4, compared to those for Example 2 of the present invention, indicate that the presence of an N-trifluoromethanesulfonamide group (or trifluoromethylsulfonamide group) in the color-changing compound of (3) Structure (I) provides improvements in printout image and dark fading. Compounds having an indene ring attached to a diphenylamino group rather than an N-trifluoromethanesulfonamide group, such as Comparative Color-changing Compound 2, generally provide moderate or acceptable printout immediately after imaging, but the printout image becomes poor after dark fading storage. The difference between Comparative Example 4 and Example 2 of the present invention demonstrates that, in addition to the Ar3 group in Structure (I), the specified -XL group is also important for the efficiency of the phenylation reaction to form the stable colored species explained above. These values ​​for the precursor in Comparative Example 4 are poor relative to the printout image and dark fading of the precursor in Example 9 of the present invention, which further supports the importance of the -XL group of the present invention. The color-changing compound CCC3 in Comparative Example 4 and the color-changing compound CCC5 in Example 9 of the present invention have the same structure except for the different -XL groups. ICCC3 has a diphenylamino group as the -XL group and thus falls outside the scope of structure (I) as described above.

[0257] The results for Comparative Example 2, compared to those for Example 2 of the present invention, indicate that the presence of tetraphenylborate anions is desirable in order to have a strong print-out image both immediately after imaging and after dark storage. As explained above, tetraphenylborate anions can react with the color-changing compounds 2 of the present invention to form colored phenylated products. At a given 90 mJ / cm 2 At exposure energies of 100 Å, typical initiator compositions, such as that used in Comparative Example 2, are ineffective in inducing chemical changes in the respective (3) color-changing compounds of the present invention. In other words, at this exposure energy level, the color-changing compounds 2 of the present invention do not have sufficient chemical conversion of the trifluoromethanesulfonamide groups [-XL groups in structure (I)] for color formation purposes under heating or in the presence of an acid generated by the iodonium salt of the initiator composition 2. In addition, the unacceptable imaging speed for Comparative Example 2 indicates that the tetraphenylborate anion is also required for optimal imaging speed.

[0258] The results of Comparative Example 9 and Inventive Examples 9, 10, 11 and 12 also demonstrate that reducing the molar ratio of borate anions to iodonium cations results in a reduction in the production of printout images. On the other hand, as demonstrated in Comparative Example 10, increasing the borate concentration until the molar ratio of borate anions to iodonium cations is greater than 4 results in the production of a strong printout image, but at the expense of optical speed.

[0259] In addition, the results for Comparative Example 3 show that even in the absence of iodonium cations in the (1) free radical initiator composition, the presence of tetraphenylborate anions as electron donors can induce the color formation reaction of the (3) color-changing compound. Of course, the presence of iodonium cations is still necessary for sufficient imaging speed, or other known ingredients for enhancing free radical generation need to be added to the free radical initiator composition.

[0260] The results of Comparative Example 5 show lower printout both immediately after imaging and after dark storage relative to Example 1 of the present invention. These differences demonstrate that the presence of the (3) color-changing compound "Dye 1 of the present invention" having an indene ring in the conjugated chain according to structures (I) and (II) (benzene as AR3 in structure I) provides an improvement in printout of the image compared to the comparative color-changing compound 3 having a cyclopentene ring in the conjugated chain. The difference between Comparative Example 5 and Example 1 of the present invention demonstrates that Ar3 in structures (I) and (II) affects the geometry of the polymethine chain of the color-changing compound and makes it more easily react with the tetraphenylborate anion to form a stable colored phenylated product as explained above. In addition to the ΔE difference, it should also be noted that the exposed area of ​​Example 1 of the present invention has a slightly reddish hue, which may be attributed to the phenylated product having an absorption peak of about 514 nm in the visible spectrum. The lithographic printing plate precursors in other embodiments of the present invention also have a slightly reddish hue in the infrared radiation exposed area. On the other hand, Comparative Example 5 has a slightly bluish hue, which is believed to be caused by the low conversion rate of the N-methyltrifluoromethanesulfonamide group in Comparative Color-changing Compound 2 to the N-methylamino group.

[0261] Comparative Examples 6 and 7 show that the borate anions provided by IC6 and IC7 are ineffective for forming a good printout image from the color-changing compound CCC2. These borate anions are outside the scope of structure (IIIa) above and are therefore not included in B - / I + Calculation of molar ratio.

[0262] Relative to the results for Example 1 of the present invention, Example 3 of the present invention shows lower printout images both immediately after imaging ("fresh") and after dark storage. It is believed that these differences may be caused by lower than desired IR absorption of (3)chromic compound 1 under certain imaging conditions and energies. However, it is also believed that the use of various (3)chromic compounds according to the present invention in combination with other infrared absorbing dyes may produce improved results.

[0263] The results for Example 4 of the present invention show even higher immediate ("fresh") printout images after imaging relative to the results for Example 1 of the present invention. This result shows that the advantages of using the (3) color-changing compound of the present invention can be further enhanced by its combined use with the conventional (5) acid-sensitive dye precursor. On the other hand, since the contribution of the acid-sensitive dye precursor 2 to ΔE printout is known to weaken over time, the improvement from the added acid-sensitive dye precursor is still temporary. After 24 hours of dark fading, Example 1 of the present invention and Example 4 of the present invention show comparable ΔE printout values, which are mainly contributed by the (3) color-changing compound 1 of the present invention.

Claims

1. A lithographic printing plate precursor comprising: substrate, and An infrared radiation-sensitive image recording layer is provided on the substrate, the infrared radiation-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, wherein the free radical initiator composition comprises an electron donating agent and one or more iodonium cations; (2) free radical polymerizable compositions; and (3) A color-changing compound represented by the following structure (I) in: 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 represents an oxygen atom, a sulfur atom or a 4 R 5 ) represented by a dialkylmethylene group, wherein R 4 and R 5 are independently substituted or unsubstituted alkyl groups having 1 to 4 carbons; R 1 and R 2 are independently substituted or unsubstituted alkyl; X represents a single bond or is selected from -S-, -O- and >N(R 6 ) of a divalent linking group, wherein R 6 is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or L; L represents -C(=O)-OR 7 Group, -SO2-R 3 Group or -SO2NR 8 R 9 Group, where R 7 represents a substituted or unsubstituted alkyl group having a -C(=O)OR 7 The secondary or tertiary carbon to which the remainder of the group is attached; and R 3 , R 8 and R 9 independently represent substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; and Za represents one or more counterions to balance the charge in the rest of the color-changing compound according to structure (I), wherein the infrared radiation-sensitive image recording layer comprises one or more borate anions represented by the following structure (IIIa): B(R 10 R 11 R 12 R 13 ) - Structure (IIIa) Where R 10 , R 11 , R 12 and R 13 are independently substituted or unsubstituted alkyl or substituted or unsubstituted aryl, provided that R 10 , R 11 , R 12 and R 13 At least three of the are the same or different substituted or unsubstituted aryl groups, and the substituted aryl groups each have not more than two halogen substituents.

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

3. The lithographic printing plate precursor of claim 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.

4. The lithographic printing plate precursor of any one of claims 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 and up to and including 4:

1.

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

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

7. A lithographic printing plate precursor as claimed in any one of claims 1 to 6, wherein one or both of the aromatic rings completed by the atoms of Ar1 and Ar2 are substituted by one or two halogen groups which may be the same or different.

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

9. A lithographic printing plate precursor as claimed in any one of claims 1 to 8 wherein Ar3 represents the carbon and hydrogen atoms required to complete the benzene ring.

10. The lithographic printing plate precursor of any one of claims 1 to 9, wherein Za comprises a tetraarylborate anion.

11. The lithographic printing plate precursor of any one of claims 1 to 10, wherein the electron donating agent is an organic borate represented by the following structure (III): [B(R 10 R 11 R 12 R 13 ) - ] n M n+ Structure (III) Where R 10 , R 11 , R 12 and R 13 As defined for structure (IIIa), n is an integer equal to or greater than 1, and M n+ It is an n-valent cation.

12. The lithographic printing plate precursor according to any one of claims 1 to 11, wherein R of structures (III) and (IIIa) 10 , R 11 , R 12 and R 13 All are the same or different substituted or unsubstituted aryl groups.

13. The lithographic printing plate precursor according to any one of claims 1 to 12, wherein R of structures (III) and (IIIa) 10 , R 11 , R 12 and R 13 All are the same substituted or unsubstituted phenyl groups.

14. The lithographic printing plate precursor according to any one of claims 1 to 13, wherein the infrared radiation-sensitive image-recording layer further comprises a component (4) infrared absorbing material different from the component (3) color-changing compound.

15. The lithographic printing plate precursor of 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 of any one of claims 1 to 15, wherein the infrared radiation sensitive image recording layer further comprises a component (5) acid-sensitive dye precursor different from all of the components (1), (2), (3) and (4) defined above.

17. The lithographic printing plate precursor of any one of claims 1 to 16, wherein the infrared radiation sensitive image recording layer further comprises a component (6) of a non-radical polymerizable polymer material, the component (6) being different from all of the components (1), (2), (3) and (4) defined above, and being present in a particle form.

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

19. A lithographic printing plate precursor as described in any one of claims 1 to 18, wherein the component (3) is a color-changing compound represented by structure (I) and is present in the infrared radiation-sensitive image recording layer in a coverage amount of at least 0.5 wt. % and up to and including 15 wt. %, based on the total weight of the infrared radiation-sensitive image recording layer.

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

Images