Lithographic printing plate precursors and methods of use

Abstract

IR-sensitive lithographic printing plate precursors provide stable printed images using a unique IR radiation-sensitive composition in the IR radiation-sensitive image recording layer. The IR radiation-sensitive composition comprises: (1) a free radical initiator composition comprising an electron-donating agent; (2) a free-radically polymerizable composition; and (3) a color-changing compound represented by structure (I) having a conjugated carbon chain between the aromatic end groups. The compound also has a -SO2-R 3 group, where R 3 represents an alkyl, aryl, or heteroaryl group. These precursors exhibit desirable printed images both when fresh and after dark storage following IR imaging. The precursors can be developed off-press or on-press.

Description

Field of the Invention

[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 contain a unique infrared radiation-sensitive composition that provides a stable printout image between exposed and unexposed 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 of the Invention

[0003] In lithographic printing, lithographic ink-receiving areas, called image areas, are created on the hydrophilic surface of a flat substrate (e.g., 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, while the lithographic ink-receiving 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 squeegee in a printing press.

[0004] Negative-working lithographic printing plate precursors useful for preparing lithographic printing plates typically comprise a negative-working radiation-sensitive image-recording layer disposed above 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 imagewise exposure of the precursor to suitable radiation to form exposed and unexposed areas in the image-recording layer, the unexposed areas are removed by suitable means, revealing the underlying hydrophilic surface of the substrate. The exposed areas of the image-recording layer that are not removed are receptive to lithographic inks, and the hydrophilic substrate surface revealed by the development process accepts water and aqueous solutions (e.g., fountain solution) and repels lithographic inks.

[0005] In recent years, there has been an increasing desire in the lithographic printing industry to simplify the manufacture of lithographic printing plates by performing on-press development ("DOP") using lithographic inks and / or fountain solutions to remove unexposed areas of the image-recording layer.

[0006] Thus, in recent decades, on-press processable lithographic printing plate precursors have gained increasing attention in the printing industry due to their many advantages over conventionally processed ("off-press" processing or development) lithographic printing plate precursors, including reduced environmental impact and savings in processing chemicals, processing press floor space, operating and maintenance costs. After laser imaging, the on-press processable precursor can be sent directly to the printing press without any prior wet chemical step to remove the imageable coating on the precursor in the non-printing areas.

[0007] Therefore, it is highly desirable that such imaged lithographic printing plate precursors have different colors in the exposed and unexposed areas. The color difference or "contrast" between the exposed and unexposed areas is often referred to as "printout" or "printout image." A strong printout facilitates the operator's visual evaluation and identification of the imaged printing plate precursor so that the printing plate precursor can be properly attached to the printing press unit.

[0008] Many approaches have been taken to enhance the printout of on-press developable printing plate precursors. It has been observed that all of them have certain weaknesses.

[0009] 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 (e.g., a lactone-based leuco dye) are often not strong enough. Furthermore, the concentration of protons generated during infrared radiation imaging often decreases after imaging through chemical equilibrium or other post-imaging chemical reactions. Consequently, printouts based on proton-induced color changes often fade after imaging.

[0010] 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, however, there remains a need to improve the printout and printout stability achieved using the described chemistry.

[0011] A different approach to producing printouts is based on the use of infrared (IR) decomposable dyes that contain thermally labile groups and are capable of losing these groups upon exposure to infrared radiation or heat to form compounds of different colors with absorption spectra in the visible region of the spectrum. 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 typically be present in relatively large amounts in the imaging composition, or be present in relatively low amounts and require high infrared radiation exposure energies in order to produce sufficient printouts.

[0012] In addition, some of the IR-decomposable dyes used in this type of chemistry generate gaseous materials upon decomposition that are generally detrimental to negative-working compositions based on crosslinking of free-radically polymerizable compounds in the presence of suitable free-radical initiators, resulting in poor image durability during printing operations. Furthermore, the heat pulses generated from exposure to high energy levels of infrared radiation, according to a process commonly referred to as ablation or partial ablation, 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), printing plate precursors PPP34 and PPP35 containing IR-decomposable dyes in the imaging composition are described as requiring 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 are useful for forming printing plates having sufficient durability of infrared radiation exposed areas after development of any kind.

[0013] 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) exhibit IR-decomposable properties 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 yielded very little printout benefit over PPP03 (2.99 vs 2.12 at 120 mJ / cm 2 The ΔE value below). Billiet's parameter ΔE is similar to the ΔE parameter (or value) described below.

[0014] In order to avoid the ineffective 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 the lithographic printing plate precursor requires additional steps during manufacture, and when present, removal of the protective layer reduces the speed of development. Additionally, when the plate precursor is developed on-press, the protective layer can release polymer or other material into the fountain solution and cause malfunctions in the lithographic printing operation. Furthermore, the printout generated using typical exposure doses of infrared radiation suitable for such IR-sensitive imageable compositions remains well below what is required.

[0015] 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 suggests the color-forming ability of such imaging compositions containing IR-decomposable dyes under the indicated exposure conditions. Although the disclosure describes certain infrared dyes that are believed to be IR-decomposable therein, none of the working examples use any IR-decomposable dyes as taught in U.S. Patent 8,148,042 (noted above) and 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.

[0016] U.S. Patent Application Publication 2020 / 0117086 (Nogoshi et al.) describes combinations of certain IR-decomposable dyes with certain chromogenic developers. In the absence of the specified chromogenic developer, as illustrated in Comparative Examples 1 and 2 thereof, the specified IR-decomposable dyes of this teaching do not have sufficient printout.

[0017] US 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 imageable compositions comprising an IR-decomposable dye containing an 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 value of 6.6). The use of a comparative IR-decomposable dye containing no alkoxycarbonylamino group according to the teachings of U.S. Patent 8,148,042 (noted above) only provides a printout at 300 mJ / cm2 even in the presence of the acid-sensitive dye precursor. 2The printout was low (ΔE value of 4.6) at the imaging energy. Furthermore, Munnelly et al. only demonstrated a short press run of 200 copies, and it was not obvious whether a printing plate derived from the precursor of Munnelly et al. would have sufficient image durability during printing to meet the needs of industry customers, who would typically print far more than 200 copies in a typical press run.

[0018] Despite all the efforts described in the known literature to provide adequate printout for press-developable lithographic printing plates with excellent press run durability, there is still a continuing need to provide press-developable lithographic printing plate precursors that not only have the necessary properties required, such as fast imaging speed, good on-press developability, good lithographic durability and good shelf life, but also exhibit adequate and stable printout using lower exposure energies as required for high productivity and are therefore compatible with typical cameras and other reading devices used in printing press automation. SUMMARY OF THE INVENTION

[0020] The present invention provides a lithographic printing plate precursor comprising:

[0021] substrate, and

[0022] An infrared radiation-sensitive image-recording layer provided on a substrate, the infrared radiation-sensitive image-recording layer comprising the following components (1), (2) and (3):

[0023] (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 donor;

[0024] (2) a free radical polymerizable composition; and

[0025] (3) A color-changing compound represented by the following structure (I)

[0026]

[0027] in:

[0028] Ar1 and Ar2 independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or to complete a substituted or unsubstituted heteroaromatic ring;

[0029] R is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;

[0030] R 1 and R 2 is independently substituted or unsubstituted alkyl;

[0031] R3 is a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; 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;

[0032] A 1 and A 2 independently represent substituted or unsubstituted alkyl groups, or together represent the two or three carbon atoms necessary to form a substituted or unsubstituted 5- or 6-membered non-aromatic carbocyclic ring; and

[0033] Za represents one or more counterions to balance the charge in the remainder of the color-shifting compound according to structure (I).

[0034] The present invention also provides a method for providing a lithographic printing plate, comprising:

[0035] A) imagewise exposing a lithographic printing plate precursor according to any embodiment of the invention as described herein to infrared radiation to provide exposed and unexposed areas in the infrared radiation sensitive image recording layer, and

[0036] B) Removing the unexposed areas of the infrared radiation-sensitive image-recording layer from the substrate.

[0037] The present invention provides printed images produced in an infrared radiation-sensitive image-recording layer in an area exposed to relatively low-energy imaging infrared radiation. Such printed images are not only stable during dark storage but also have an appropriate hue, as indicated by a good cyan ΔOD value, and are therefore more easily read by cameras and other reading devices used in printing press automation and equipped with a light source having a peak emission at approximately 617 nm. Furthermore, in many embodiments, the imaging chemistry used to provide a pleasing printed image does not adversely affect imaging speed, on-press developability, or lithographic image durability. Further details of the invention and the results obtained thereby are provided below. Detailed Description of the Invention

[0039] definition

[0040] 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 having maximum absorption in the near IR and IR regions.

[0041] The terms "near infrared region" and "infrared region" as used herein refer to radiation having a wavelength of at least 750 nm and longer. In most cases, the terms are used to refer to the region of the electromagnetic spectrum of at least 800 nm and up to and including 1400 nm.

[0042] For the purposes of the present invention, the intensity of the printed image is generally indicated by the ΔE parameter or value, which is the Euclidean distance in the CIE 1976 L*a*b* colour space between the colour of the radiation exposed area measured in reflection in 45 / 0 geometry (non-polarized) and the colour of the radiation unexposed area, 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. The colour measurements can be performed using a commercial instrument, such as a Techkon SpectroDens. In the CIE 1976 L*a*b* colour space, the colour is represented as three colour values: L* for the lightness (or value) of the colour, a* for the green-red component of the colour, and b* for the blue-yellow component of the colour value.

[0043] For the purposes of the present invention, the visible spectral region refers to the spectral region of electromagnetic radiation having a wavelength of 400 nm to 700 nm.

[0044] The term "wt.%" refers to the amount of a component or material based on the total solids of the composition, formulation, or layer, unless otherwise indicated. The percentages for the total solids of a dry layer or formulation or composition can be the same, unless otherwise indicated.

[0045] The terms "on-press developable" and "on-press developability" as used herein refer to the ability of the precursors according to the present invention to be developed after infrared radiation exposure (imaging) by mounting the imaged precursor on a suitable printing press and developing using dampening solution, lithographic printing ink, or a combination of dampening solution and lithographic printing ink during the initial few printed impressions.

[0046] Use

[0047] The lithographic printing plate precursors according to the present invention are useful for providing lithographic printing plates that exhibit a desirable printed image after imaging exposure. These lithographic printing plates are useful for lithographic printing during press operation. According to the present invention, the lithographic printing plates can be prepared using on-press processing or off-press processing. The lithographic printing plate precursors are prepared with the structures and components described below.

[0048] Lithographic printing plate precursors

[0049] The precursor according to the present invention can be formed by appropriately applying an infrared radiation-sensitive image recording composition (as described below) to a suitable substrate (as 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 further comprises an electron donor; 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 necessary to achieve the advantages of the present invention.

[0050] 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-shifting compound; and a component (5) acid-sensitive dye precursor (or a mixture of two or more thereof) other than all of components (1), (2), (3), and (4); and a component (6) non-free radically polymerizable polymer material (or a mixture of two or more thereof) other than all of components (1), (2), (3), and (4); or all of these components (4) to (6), all of which are described below. In some very useful embodiments, the infrared radiation-sensitive image-recording layer consists essentially of all of the specified components (1) to (6) to provide the desired lithographic printing plate precursor with a desirable printed image and optimal overall imaging and printing properties.

[0051] Typically, only one infrared radiation-sensitive image-recording layer is present in each precursor. This layer is typically the outermost layer in the precursor, however, in some embodiments, there may be an outermost water-soluble hydrophilic protective layer (also referred to as a topcoat or oxygen barrier layer) as described below disposed above (or directly on and in contact with) the infrared radiation-sensitive image-recording layer.

[0052] substrate :

[0053] The substrate used for the preparation of 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 can consist of raw aluminum or a suitable aluminum alloy conventionally used for the preparation of lithographic printing plate precursors.

[0054] The aluminum-containing substrate can be treated using techniques known in the art, including some type of roughening by physical (mechanical) grinding, electrochemical grinding, or chemical grinding, 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, each having a plurality of pores of varying depths and shapes of pore openings, such as an inner aluminum oxide layer and an outer aluminum oxide layer disposed on the inner aluminum oxide layer. Thus, such methods provide an anodic oxide layer or aluminum oxide layer below the infrared radiation-sensitive image recording layer. Teachings on providing two consecutive anodizing treatments to provide different aluminum oxide layers in the substrate (e.g., an outer aluminum oxide layer disposed on an inner aluminum oxide layer) are described, for example, in U.S. Patent Application Publication 2018 / 0250925.

[0055] Sulfuric acid anodization of the aluminum support typically provides the following aluminum (anodic) oxide weight (coverage) on the surface: at least 1 g / m 2 Up to and including 5g / m 2 , and more usually at least 1.5 g / m 2 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 Up to and including 5g / m 2 , and more usually at least 1 g / m 2 Up to and including 3g / m 2 .

[0056] The anodized aluminum-containing substrate may be treated with an alkaline or acidic pore-enlarging solution to provide an anodic oxide layer containing columnar pores. In some embodiments, the treated aluminum-containing substrate may comprise a hydrophilic layer disposed directly on the grained, anodized, and post-treated aluminum-containing support, and such hydrophilic layer may comprise a non-crosslinked hydrophilic polymer having carboxylic acid side chains.

[0057] Alternatively, the anodized aluminum-containing support can be further treated using known post-anodization processes (e.g., post-treatment using an aqueous solution of a hydrophilic material) to seal the anodic oxide pores and / or hydrophilize its surface. Representative hydrophilic materials of this type for providing a hydrophilic layer (e.g., a hydrophilic polymer coating) include, but are not limited to, polyvinylphosphonic acid (PVPA), vinylphosphonic acid copolymers, poly(meth)acrylic acid or its alkali metal salts, or (meth)acrylic acid copolymers or their alkali metal salts, phosphate and fluoride salt mixtures, or sodium silicate. Such a hydrophilic coating can be provided on the outermost alumina layer (e.g., the outer alumina layer if multiple alumina layers are present). The post-treatment process material can also contain unsaturated double bonds to enhance adhesion between the treated surface and the overlying infrared radiation exposed area. Such unsaturated double bonds can be provided in a low molecular weight material, or they can be present in the side chains of the polymer.

[0058] Particularly useful hydrophilic layer or coating materials for this purpose comprise: 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. Such a hydrophilic layer may be prepared at a density of at least 0.0002 g / m 2 and up to and including 0.1 g / m 2 The dry coverage is set above the outermost aluminum oxide layer.

[0059] The substrate can be formed into a continuous roll (or continuous web) of sheet material suitably coated with an infrared radiation-sensitive image-recording layer formulation and an optional hydrophilic protective layer formulation, and then cut or slit (or both) to size to provide individual lithographic printing plate precursors having a shape or form containing four right angles (thus, typically in a square or rectangular shape or form).

[0060] Infrared radiation sensitive image recording layer:

[0061] The infrared radiation-sensitive image-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 art 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 to the lithographic printing plate precursor after exposure, for example, to enable on-press development using a fountain solution, a lithographic printing ink, or a combination of the two.

[0062] The present invention utilizes component (1) a radical initiator composition that is capable of generating free radicals when exposed to infrared radiation. Such component (1) initiator compositions may include one or more organic halogen compounds (e.g., 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. Representative compounds other than onium salts are described in, for example, U.S. Patent Application Publication 2005 / 0170282 (Inno et al., US'282) at

[0087] to

[0102] and U.S. Patent 6,309,792 (Hauck et al.), as well as Japanese Patent Publication 2002 / 107916 and WO 2019 / 179995.

[0063] Component (1) radical initiator composition can comprise iodonium cation and / or sulfonium cation. Useful onium salt is described in

[0103] to

[0109] of cited U.S. Publication '282. Useful onium salt comprises at least one onium cation and suitable anion in molecule. The example of onium salt comprises diaryl iodonium salt, triphenylsulfonium (salt), diphenyl iodonium (salt), diphenyldiazonium compound and its derivative obtained by introducing one or more substituents into the phenyl ring of these compounds. Suitable substituent includes but is not limited to alkyl, alkoxy, alkoxycarbonyl, acyl, acyloxy, chlorine, bromine, fluorine and nitro. Useful onium cation for onium salt comprises iodonium cation, for example diaryl iodonium cation, for example diaryl iodonium cation with two substituted or unsubstituted phenyl groups.

[0064] Examples of anions in onium salts include, but are not limited to, halogen anions, ClO4 - PF6 - 、BF4 - 、SbF6 - 、CH3SO3 - CF3SO3 - 、C6H5SO3 - 、CH3C6H4SO3 - 、HOC6H4SO3 - 、ClC6H4SO3 - and boron anions as described in U.S. Patent 7,524,614 (Tao et al.). Representative useful iodonium salts are described in columns 6-7 of U.S. Patent 7,524,614 (noted above), where the iodonium cation can contain various listed monovalent substituents "X" and "Y", or a carbocyclic or heterocyclic ring fused to the corresponding phenyl group.

[0065] Useful onium salts may be polyvalent onium salts having at least two onium ions bonded by a covalent bond in the molecule. Among polyvalent onium salts, those having at least two onium ions in the molecule are useful, and those having a sulfonium or iodonium cation in the molecule are useful.

[0066] In addition, onium salts described in paragraphs

[0033] to

[0038] of the specification of Japanese Patent Publication No. 2002-082429 [or U.S. Patent Application Publication No. 2002-0051934 (Ippei et al.)] or iodonium borate complexes described in columns 6 and 7 of U.S. Patent No. 7,524,614 (noted above) can also be used. Representative iodonium borate salts are listed in column 8 of U.S. Patent No. 7,524,614 (noted above).

[0067] In some embodiments, a combination of onium salts may be used as part of the component (1), free radical initiator composition, such as the combination of compounds described as Compound A and Compound B in U.S. Patent Application Publication 2017 / 0217149 (Hayashi et al.).

[0068] The component (1) free radical initiator composition used in the practice of the present invention should contain one or more electron donors that not only participate in the generation of free radicals for polymerizing the (2) free radical polymerizable compound described below, but also promote the color change reaction of the (3) color-changing compound described below. For example, particularly useful electron-donating compounds include borate compounds and other organic compounds that have an oxidation potential (V) of less than 1.1 relative to the Ag / AgCl electrode. ox ).

[0069] In the practice of the present invention, representative compounds that can act as electron donors include compounds having a partial structure in which a nitrogen atom, an oxygen atom, or a sulfur atom is directly bonded to an aromatic group or a heteroaromatic group. Some potentially useful electron donating compounds are described in

[0013] to

[0015] of Japanese Patent Application Publication 2005-062482A, including A-1 to A-25 in

[0017] to

[0020] . A skilled worker using the teachings provided herein will be able to determine which compounds will be acceptable electron donating compounds according to the present invention using routine experiments.

[0070] Useful compounds that can be used as electron donors include organic borates, which are organic borates represented by the following structure (III).

[0071] [B(R 10 R 11 R 12 R 13 ) - ] n Mn+

[0072] Structure (III)

[0073] where R 10 、R 11 、R 12 and R 13 is independently a substituted or unsubstituted alkyl group, for example a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, which may be substituted with one or more fluorine, chlorine and bromine groups; or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms in the aromatic ring, which may be substituted with one or more fluorine, chlorine, bromine, alkyl, alkoxy, alkoxycarbonyl and acyloxy groups, wherein a substituted or unsubstituted 6-membered aromatic (phenyl) group is the most useful. In most embodiments, R 10 、R 11 、R 12 and R 13 At least three of the R 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 all the same substituted or unsubstituted phenyl, and for example wherein all of these groups are the same substituted phenyl.

[0074] In structure (III), n is an integer equal to or greater than 1; and M n+ is an n-valent cation, such as, but not limited to, a monovalent alkali metal cation, an ammonium cation, monomeric and polymeric onium cations (e.g., iodonium, sulfonium, or diazonium cations), or any other inorganic or organic molecule having a cationic charge (including cyanine dyes having a cationic charge). In some embodiments, M n+

[0045] may represent one or more molecules of iodonium anions, for example one or more molecules as described above or a diaryliodonium anion.

[0075] The one or more electron donors useful in the present invention may be 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.

[0076] The component (1) free radical initiator composition may be present in the infrared radiation-sensitive image recording layer in amounts (molar or weight ratios) that will be readily apparent to a person skilled in the art of preparing press-developable lithographic printing plate precursors, and the minimum total amount and the maximum total amount are generally at least 1 wt. % and up to and including 20 wt. % of all components (including the electron donor), based on the total coverage (solids) of the infrared radiation-sensitive image recording layer.

[0077] Since the component (1) free radical initiator composition can have multiple 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 and mixed in appropriate molar or weight ratios for use in the present invention.

[0078] 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 having the same or different numbers of free radical polymerizable groups in each molecule. Thus, useful free radical polymerizable components may contain one or more free radical polymerizable monomers or oligomers having one or more polymerizable ethylenically unsaturated groups (e.g., two or more such groups). Similarly, crosslinkable polymers having such free radical polymerizable groups may also be used. Oligomers or prepolymers such as urethane acrylates and urethane methacrylates, epoxide acrylates and epoxide methacrylates, polyester acrylates and polyester methacrylates, polyether acrylates and polyether methacrylates, and unsaturated polyester resins may be used. Some free radically polymerizable components contain carboxyl groups.

[0079] 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 of the infrared radiation-sensitive image-recording layer. In such embodiments, a distinct (6) non-free radical polymerizable polymer material (described below) may be substituted.

[0080] Useful free radical polymerizable components include urea urethane (meth) acrylates or urethane (meth) acrylates having multiple (two or more) polymerizable groups. This can be accomplished by reacting a triisocyanate (e.g. Urethane acrylates having two to fifteen acrylate groups are prepared by reacting N100 (Bayer Corp., Milford, Conn.) or a diisocyanate (e.g., hexane-1,6-diisocyanate) with hydroxyethyl acrylate, pentaerythritol triacrylate, or dipentaerythritol pentaacrylate. Such urethane or urea (meth)acrylate compounds have up to 15 or more (meth)acrylate groups 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.

[0081] Useful free radical polymerizable compounds include non-urethane and non-urea (meth)acrylates derived from polyfunctional alcohols, such as NKEster 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 and non-urea (meth)acrylates may also have a large number of (meth)acrylate groups per molecule.

[0082] Numerous other free radical polymerizable components are known in the art. For example, useful free radical polymerizable components are also described in EP 1,182,033 A1 (Fujimaki et al.) (beginning at paragraph

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

[0083] The one or more components of the free radical polymerizable composition of component (2) may typically be 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.

[0084] A third essential component of the infrared radiation-sensitive image-recording composition and image-recording layer is component (3), a color-changing compound, or a mixture of two or more thereof, each represented by the following structure (I):

[0085]

[0086] wherein Ar1and Ar2independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or to complete a substituted or unsubstituted heteroaromatic ring. For one or both of Ar1and Ar2, an appropriate number of carbon atoms is needed to complete a substituted or unsubstituted aromatic ring, such as a benzene (benzo) or naphthalene (naphtho) ring. In addition, for one or both of Ar1and Ar2, an appropriate number of carbon atoms and one or more heteroatoms is needed to complete a substituted or unsubstituted heteroaromatic ring, such as a pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, pyridazinyl, pyrimidin-2-yl, pyrimidin-4-yl, pyrimidin-5-yl, or pyrimidin-6-yl, pyrazine, triazine, pyrrole, furan, thiophene, pyrazole, oxazole, imidazole, thiazole, or triazole ring.

[0087] In many useful embodiments of the present application, Ar1and Ar2are the same atoms necessary to complete a substituted or unsubstituted aromatic ring, such as a substituted or unsubstituted benzene (benzo) ring. In addition, the aromatic ring of one or both of Ar1and Ar2may be substituted, such as by one or more optionally substituted alkyl, alkoxy, halogen, cyano, -COOR' group, -SO3R' group, or -SO2R' group, where R' represents a substituted or unsubstituted alkyl group, which can be the same or different for each indicated group. It is particularly useful when one or both of Ar1and Ar2are substituted by one or two halogen atoms, such as fluorine atoms.

[0088] Further, in structure (I), Y represents an oxygen atom, a sulfur atom, or a dialkylmethylene group represented by >C(R 4 R 5 ) where R 4 and R 5 are independently substituted or unsubstituted alkyl groups having 1 to 4 carbons. In many useful embodiments of the present application, each occurrence of Y is the same or different dialkylmethylene group, or even the same dialkylmethylene group, where R 4 and R 5 are the same unsubstituted alkyl group having 1 or 2 carbon atoms. Skilled chemists will be able to prepare numerous compounds where Y varies among the possible groups, including many possible dialkylmethylene groups.

[0089] Also in structure (I), R is hydrogen, substituted or unsubstituted alkyl having 1 to 12 carbon atoms, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl. In particular embodiments, R is hydrogen or unsubstituted alkyl having 1 to 8 carbon atoms.

[0090] In structure (I), R 1 and R 2 are independently substituted or unsubstituted alkyl groups, each having from 1 to 12 carbon atoms, and in many embodiments, one or both of such alkyl groups contain an ether or ester linkage, which interrupts the carbon chain or, in the case of an ester group, also terminates the alkyl chain.

[0091] R 3 is 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 an aromatic ring having 6 or 10 carbon atoms in the carbocyclic ring, or a substituted or unsubstituted heteroaryl group having 5 to 10 carbon atoms and heteroatoms in the aromatic ring. For example, R 3 The halogenated alkyl group may be a halogenated alkyl group having 1 to 12 carbon atoms in which one or more hydrogen atoms are replaced by a halogen atom (eg, a fluorine or chlorine atom).

[0092] A 1 and A 2 Each independently represents a substituted or unsubstituted alkyl group, or together they represent the two or three carbon atoms necessary to form a substituted or unsubstituted 5- or 6-membered non-aromatic carbocyclic ring (eg, a cyclohexylene moiety or a cyclopentylene moiety).

[0093] Finally, in structure (I), Za represents one or more counterions to balance the charge of the rest of the color-changing compound according to structure (I). When the rest of the color-changing compound according to structure (I) is positively charged, Za represents an anion. Many useful anions are known, such as halogen anions, ClO4 - PF6 - 、BF4 - 、SbF6 - 、CH3SO3 - CF3SO3 - 、C6H5SO3 - 、CH3C6H4SO3 - 、HOC6H4SO3 - 、ClC6H4SO3 -; And as described in, for example, U.S. Patent 7,524,614 (noted above). Useful boron-containing anions include tetraaryl borate anions (e.g., tetraphenylborate) as described above for electron donors. In some embodiments, Za can be supplied by an electron donor in (1) a radical initiator composition. When the remainder of the color-changing compound according to structure (I) is negatively charged, Za represents a cation. Useful 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. Za can also be supplied by an onium compound in the component (1) radical initiator composition described above.

[0094] The color-changing compound of component (3) (single species or a mixture of two or more thereof) may typically be 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 15 wt %, based on the total weight of the infrared radiation-sensitive image recording layer.

[0095] Although not required, the infrared radiation-sensitive image recording layer may also contain a component (4) infrared absorbing material (one or a mixture of two or more thereof) other than the component (3) color-changing compound described above. The (4) infrared radiation absorber provides the desired infrared radiation sensitivity and / or converts the radiation into heat. Useful infrared radiation absorbers may be pigments or infrared radiation absorbing dyes. Suitable dyes are those described in U.S. Patents 5,208,135 (Patel et al.), 6,153,356 (Urano et al.), 6,309,792 (Hauck et al.), 6,569,603 (Furukawa), 6,797,449 (Nakamura et al.), 7,018,775 (Tao), 7,368,215 (Munnelly et al.), 8,632,941 (Balbinot et al.), and U.S. Patent Application Publication 2007 / 056457 (Iwai et al.). The at least one (4) infrared radiation absorber in the infrared radiation-sensitive image recording layer can be a cyanine dye comprising a suitable cationic cyanine chromophore and a tetraarylborate anion (e.g., tetraphenylborate anion) as described in U.S. Patent Application Publication No. 2011 / 003123 (Simpson et al.).

[0096] The total amount of component (4) infrared radiation absorber can be 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.

[0097] Another optional component of the infrared radiation sensitive image recording layer is component (5) acid-sensitive dye precursor (single or a combination of two or more thereof). Useful component (5) acid-sensitive dye precursor is a colorless or almost colorless compound in a neutral form, and the compound is converted into a colored form when protonated. Many colorless dyes known for this purpose are included in

[0209] to

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

[0044] to

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

[0098] In some embodiments, at least one of the component (5) acid-sensitive dye precursors comprises a lactone substructure. Useful component (5) acid-sensitive dye precursors can be represented by one or more of the following structures (C1) and (C2):

[0099]

[0100] where R 11 to R 19 In some embodiments, the present invention provides the alkyl radical (C1) of the present invention and the alkyl radical (C2) of the present invention.Independently be hydrogen, unsubstituted or substituted alkyl or unsubstituted or substituted aryl.This type of replacement or unsubstituted alkyl can have 1 to 20 carbon atom, and one or more substituting groups can include but not limited to halogen, alkyl, aryl, alkoxyl group and phenoxy group.Useful replacement or unsubstituted aryl can be carbocyclic aromatic ring or heterocyclic aromatic ring, and this type of group can have two or more condensed rings.Useful substituting group for aromatic ring can comprise those described above for alkyl.Yet, skilled chemist can use this instruction about structure (C1) and (C2) to design other useful component (5) acid-sensitive dye precursors as guidance.

[0101] As indicated above, such component (5) acid-sensitive dye precursors may be present in an 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.

[0102] Optionally, 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 lacks any functional group that would enable the polymer material to undergo free radical polymerization. Thus, such component (6) non-radical polymerizable polymer material is different from all of the components (1), (2), (3) and (4) described above.

[0103] Useful component (6) non-radically polymerizable polymeric materials can generally have a weight average molecular weight (Mw) as determined by gel permeation chromatography (polystyrene standards) of at least 2,000 or at least 20,000, and up to and including 300,000 or up to and including 500,000. w ) : at least 2,000 or at least 20,000, and up to and including 300,000 or up to and including 500,000.

[0104] Such component (6) non-radically polymerizable polymeric materials can be selected from include polymeric binder materials including polymers comprising repeat units having pendant chains comprising polyoxyalkylene segments, for example as described in U.S. Patent 6,899,994 (Huang et al.). Other useful polymeric binders include two or more types of repeat units having different pendant chains comprising polyoxyalkylene segments, as described in WO Publication 2015-156065 (Kamiya et al.). Some of such polymeric binders can further include repeat units having pendant cyano groups, as described in U.S. Patent 7,261,998 (Hayashi et al.).

[0105] Such component (6) non-radically polymerizable polymeric materials can also have a backbone comprising a plurality (at least two) urethane moieties and pendant groups comprising polyoxyalkylene segments.

[0106] Some useful component (6) non-radically polymerizable polymeric materials can be present in particulate form, i.e., in the form of discrete particles (non-aggregated particles). Such discrete particles can have an average particle size of at least 10 nm and up to and including 1500 nm, and are typically uniformly distributed within the infrared radiation-sensitive image-recording layer. Average particle size can be determined using various known methods and nanoparticle measurement equipment, including measuring particles in an electron scanning microscope image and averaging a number of measurements.

[0107] Component (6) non-radically polymerizable polymeric materials can 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 (solid) of the infrared radiation-sensitive image-recording layer.

[0108] The infrared radiation-sensitive image-recording layer can also optionally include crosslinked polymeric particles having an average particle size of at least 2 μm or at least 4 μm and up to and including 20 μm, as described in U.S. Patents 9,366,962 (Hayakawa et al.), 8,383,319 (Huang et al.), and 8,105,751 (Endo et al.). Such crosslinked polymeric particles can be present in only one or both of the infrared radiation-sensitive image-recording layer and the hydrophilic protective layer (when present) (described below).

[0109] The infrared radiation-sensitive image-recording layer may also contain conventional amounts of various other optional additives, such as dispersants, humectants, biocides, plasticizers, surfactants for coatability or other properties, tackifiers, pH adjusters, desiccants, defoamers, development aids, rheology modifiers, or any other additives commonly used in the lithographic coating art. The infrared radiation-sensitive image-recording layer may also contain a phosphate (meth)acrylate having a molecular weight generally greater than 250, as described in U.S. Patent 7,429,445 (Munnelly et al.). Useful dry coverages (generally total solids with minimal water and organic solvent) for the infrared radiation-sensitive image-recording layer are described below.

[0110] Hydrophilic protective layer:

[0111] In some embodiments of the present invention, the infrared radiation-sensitive image-recording layer is the outermost layer, with no layers disposed thereon. It is possible that the precursor can be designed with a hydrophilic protective layer (also called a hydrophilic overcoat, oxygen barrier layer, or topcoat) disposed directly on a single infrared radiation-sensitive image-recording layer (without an intermediate layer between the two layers).

[0112] Based on the total dry weight of the hydrophilic protective layer, such a hydrophilic protective layer may contain one or more film-forming water-soluble polymer binders in an amount of at least 60% by weight and up to and including 100% by weight. Such film-forming water-soluble (or hydrophilic) polymer binders may include modified or unmodified polyvinyl alcohol having a saponification degree of at least 30% or a saponification degree of at least 90%, or up to and including a saponification degree of 99.9%.

[0113] One or more acid-modified polyvinyl alcohols can be used as film-forming water-soluble (or hydrophilic) polymer binders. For example, at least one polyvinyl alcohol can be modified with an acid or ester group such as a carboxylic acid, sulfonic acid, sulfate, phosphonic acid, or phosphate group. Useful modified polyvinyl alcohol materials include sulfonic acid-modified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, quaternary ammonium salt-modified polyvinyl alcohol, glycol-modified polyvinyl alcohol, or combinations thereof.

[0114] When present, the hydrophilic protective layer is provided as a hydrophilic protective layer formulation and dried to have a hydrophilic protective layer of at least 0.1 g / m 2 and at most but less than 4g / m 2 In some embodiments, the dry coating coverage is as low as 0.1 g / m 2 and up to and including 1.5 g / m 2 , or at least 0.1g / m 2 and up to and including 0.9 g / m 2 .

[0115] The hydrophilic protective layer may optionally comprise organic wax particles generally uniformly dispersed within one or more film-forming water-soluble (or hydrophilic) polymer binders, as described in US Patent Application Publication No. 2013 / 0323643 (Balbinot et al.).

[0116] Preparation of lithographic printing plate precursors:

[0117] The lithographic printing plate precursor according to the present invention can be provided as follows. An infrared radiation-sensitive image-recording layer formulation comprising the essential components (1), (2) and (3), and optional components (4), (5), (6) and other optional addenda can be applied to the hydrophilic surface of a suitable aluminum-containing substrate, typically in the form of a continuous web, using any suitable equipment and procedure, such as spin coating, knife coating, gravure coating, die coating, slot coating, rod coating, wire rod coating, roller coating, spray coating or extrusion hopper coating. Once the infrared radiation-sensitive image-recording layer formulation is applied at a suitable wet coverage, it is dried in a suitable manner to provide a dry coverage, thereby providing an infrared radiation-sensitive continuous web or an infrared radiation-sensitive continuous article. 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 a lithographic ink and a fountain solution, or a combination of lithographic inks and fountain solutions.

[0118] Prior to application of the infrared radiation-sensitive image recording layer formulation, the substrate may be electrochemically grained and anodized 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.

[0119] The manufacturing method generally comprises mixing the various components required for the infrared radiation-sensitive image-recording layer in an aqueous or non-aqueous suitable organic solvent or a mixture thereof [e.g., methyl ethyl ketone (2-butanone), methanol, ethanol, 1-methoxy-2-propanol, 2-methoxypropanol, isopropanol, acetone, γ-butyrolactone, n-propanol, tetrahydrofuran, and mixtures thereof], 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.

[0120] 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 , 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.

[0121] In some embodiments, a suitable water-based hydrophilic overcoat formulation (described above) can be applied to the dried infrared radiation-sensitive image-recording layer using known coating and drying conditions, equipment, and procedures.

[0122] Imaging (exposure) conditions

[0123] During use, the infrared radiation-sensitive lithographic printing plate precursors of the present invention may be exposed to an infrared radiation source, depending on the infrared radiation absorber present in the infrared radiation-sensitive image-recording layer. The lithographic printing plate precursors may be imaged using one or more infrared radiation-emitting lasers that emit 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, to produce exposed and unexposed areas in the infrared radiation-sensitive image-recording layer. Imaging may be performed using imaging or infrared radiation exposure from an infrared radiation-generating laser (or an array of such lasers). Imaging may also be performed using imaging radiation at multiple infrared (or near-IR) wavelengths simultaneously, if desired.

[0124] It may be desirable to include an apparatus for reducing or removing ozone in a laser imaging environment as described in U.S. Patent Application Publication 2019 / 0022995 (Igarashi et al.).

[0125] When using an infrared radiation imaging source, the imaging intensity can be at least 30 mJ / cm2, depending on the sensitivity of the infrared radiation sensitive image recording layer. 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 .

[0126] Washing (development) and printing

[0127] After imagewise exposure as described above, the exposed infrared radiation-sensitive lithographic printing plate precursor having exposed and unexposed areas in the infrared radiation-sensitive image-recording layer can be processed off-line or on-press to remove the unexposed areas (and any hydrophilic protective layer over such areas). After this processing and during lithographic printing, the revealed hydrophilic substrate surface repels ink, while the remaining exposed areas accept lithographic printing ink.

[0128] Off-press development and printing:

[0129] Processing can be performed off-line using any suitable developer in one or more successive applications (processing or development steps) of the same or different processing liquids (developers). Such one or more successive processing treatments can be performed for a time sufficient to remove the unexposed areas of the infrared radiation-sensitive image-recording layer to expose the outermost hydrophilic surface of the substrate, but not long enough to remove a significant amount of the hardened exposed areas.

[0130] After or in lieu of any optional preheating, the exposed precursor may be washed (rinsed) to remove any hydrophilic overcoat present.

[0131] Useful developers can be plain water or formulated aqueous solutions and can contain one or more surfactants, organic solvents, alkaline agents, and surface protective agents. Useful organic solvents include reaction products of phenol with ethylene oxide and propylene oxide [e.g., ethylene glycol phenyl ether (phenoxyethanol)], benzyl alcohol, esters of ethylene glycol and propylene glycol with acids having 6 or fewer carbon atoms, and ethers of ethylene glycol, diethylene glycol, and propylene glycol with alkyl groups having 6 or fewer carbon atoms.

[0132] In some cases, an aqueous processing solution can be used off-line to both develop the imaged precursor by removing the unexposed areas and to provide a protective layer or coating over the entire imaged and developed (processed) precursor printing surface. The aqueous solution behaves somewhat like a gum that can protect (or "gum") the lithographic image on the lithographic printing plate.

[0133] After off-press processing and optional drying, the lithographic printing plate can be mounted on a printing press without any contact with further solutions or liquids.

[0134] Printing can be performed by applying lithographic ink and fountain solution to the printing surface of a lithographic printing plate in a suitable manner. The lithographic ink is absorbed by the retained (exposed) areas of the infrared radiation-sensitive image-recording layer and transferred to a suitable receiving material (e.g., cloth, paper, metal, glass, or plastic) to provide the desired image impression thereon. If desired, an intermediate "squeegee" roller can be used to transfer the lithographic ink from the lithographic printing plate to the receiving material (e.g., paper).

[0135] On-press development and printing:

[0136] Alternatively, the negative-working lithographic printing plate precursors 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 is mounted on a printing press and a printing operation is initiated. When the initial printed impression is made, the unexposed areas of 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 desensitizing agent, a surfactant and a wetting agent, a humectant, a low-boiling point solvent, a biocide, a defoaming agent, and a chelating agent. A representative example of a fountain solution is Varn Litho Etch 142W + Varn PAR (alcohol sub) (available from Varn International, Addison, IL).

[0137] In a typical press start-up using a sheet-fed printing press, the dampening rollers are first engaged and fountain solution is supplied to the mounted, imaged precursor to swell the exposed infrared radiation-sensitive image-recording layer at least in the unexposed areas. After several rotations, the inking rollers are engaged and they supply lithographic ink to cover the entire printing surface of the lithographic printing plate. Typically, within 5 to 20 rotations after the inking rollers are engaged, the printing sheet is supplied to remove the unexposed areas of the infrared radiation-sensitive image-recording layer from the lithographic printing plate, as well as material on the blanket cylinder (if present), using the formed ink-fountain solution emulsion.

[0138] The present invention provides at least the following embodiments and combinations thereof:

[0139] 1. A lithographic printing plate precursor comprising:

[0140] substrate, and

[0141] An infrared radiation-sensitive image-recording layer provided on a substrate, the infrared radiation-sensitive image-recording layer comprising the following components (1), (2) and (3):

[0142] (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 donor;

[0143] (2) a free radical polymerizable composition; and

[0144] (3) A color-changing compound represented by the following structure (I)

[0145]

[0146] in:

[0147] Ar1 and Ar2 independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or to complete a substituted or unsubstituted heteroaromatic ring;

[0148] R is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl;

[0149] R 1 and R 2 is independently substituted or unsubstituted alkyl;

[0150] R 3 is a substituted or unsubstituted alkyl, a substituted or unsubstituted aryl, or a substituted or unsubstituted heteroaryl; 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;

[0151] A 1 and A 2 independently represent substituted or unsubstituted alkyl groups, or together represent the two or three carbon atoms necessary to form a substituted or unsubstituted 5- or 6-membered non-aromatic carbocyclic ring; and

[0152] Za represents one or more counterions to balance the charge in the remainder of the color-shifting compound according to structure (I).

[0153] 2. The lithographic printing plate precursor of embodiment 1, wherein R 3 It is trifluoromethyl.

[0154] 3. The lithographic printing plate precursor of embodiment 1 or 2, wherein Ar1 and Ar2 are the same number of carbon atoms necessary to complete the substituted or unsubstituted aromatic ring.

[0155] 4. The lithographic printing plate precursor of any one of embodiments 1 to 3, wherein one or both of the aromatic rings completed through the atoms of Ar1 and Ar2 are substituted with one or two halogen groups which may be the same or different.

[0156] 5. The lithographic printing plate precursor of any one of embodiments 1 to 4, wherein A 1 and A 2 Together they represent the two carbon atoms required to complete the unsubstituted 5-membered non-aromatic carbocyclic ring.

[0157] 6. The lithographic printing plate precursor of any one of embodiments 1 to 5, wherein Za comprises a tetraarylborate anion.

[0158] 7. The lithographic printing plate precursor of any one of embodiments 1 to 6, wherein the electron donor is an organic borate represented by the following structure (II).

[0159] (B(R 10 R 11 R 12 R 13 ) - ) n M n+

[0160] Structure (Ⅱ)

[0161] where R 10 、R 11 、R 12 and R 13 are independently substituted or unsubstituted alkyl or substituted or unsubstituted aryl, and R 10 、R 11 、R 12 and R 13 At least three of them are the same or different substituted or unsubstituted aryl groups, n is an integer equal to or greater than 1, and M n+ It is an n-valent cation.

[0162] 8. The lithographic printing plate precursor of embodiment 7, wherein R 10 、R 11 、R 12 and R 13 All are the same or different substituted or unsubstituted aryl groups.

[0163] 9. The lithographic printing plate precursor of embodiment 7 or 8, wherein R 10 、R 11 、R 12 and R 13 All are the same substituted or unsubstituted phenyl groups.

[0164] 10. The lithographic printing plate precursor of any one of embodiments 1 to 9, wherein R 1 and R 2 independently comprises a chain of carbon atoms interrupted by one or more ether or ester linkages.

[0165] 11. The lithographic printing plate precursor of any one of embodiments 1 to 10, wherein the infrared radiation-sensitive image-recording layer further comprises a component (4) infrared absorbing material different from the (3) color-changing compound.

[0166] 12. The lithographic printing plate precursor of any one of embodiments 1 to 11, wherein (1) the free radical initiator composition comprises an onium salt.

[0167] 13. The lithographic printing plate precursor of any one of embodiments 1 to 12, wherein (1) the free radical initiator composition comprises an iodonium cation.

[0168] 14. The lithographic printing plate precursor of embodiment 12 or 13, wherein the iodonium cation is a diaryliodonium cation.

[0169] 15. The lithographic printing plate precursor of any one of embodiments 1 to 14, wherein the infrared radiation-sensitive image-recording layer further comprises a component (5) acid-sensitive dye precursor that is different from all components (1), (2), (3) and (4) defined above.

[0170] 16. The lithographic printing plate precursor of any one of embodiments 1 to 15, wherein the infrared radiation-sensitive image recording layer further comprises a component (6) non-radical polymerizable polymer material different from all components (1), (2), (3) and (4) defined above.

[0171] 17. The lithographic printing plate precursor of embodiment 16, wherein (6) the non-free radically polymerizable polymeric material is in particulate form.

[0172] 18. The lithographic printing plate precursor of any one of embodiments 1 to 17, 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.

[0173] 19. The lithographic printing plate precursor of any one of embodiments 1 to 18, wherein the (3) color-changing compound represented by structure (I) is present in the infrared radiation-sensitive image recording layer in an amount of at least 0.5 weight percent and up to and including 15 weight percent coverage, based on the total weight of the infrared radiation-sensitive image recording layer.

[0174] 20. The lithographic printing plate precursor of any one of embodiments 1 to 19, wherein the infrared radiation-sensitive image-recording layer is the outermost layer.

[0175] 21. The lithographic printing plate precursor of any of embodiments 1 to 20, wherein (2) the free radical polymerizable composition comprises at least two free radical polymerizable components.

[0176] 22. The lithographic printing plate precursor of any one of embodiments 1 to 21, 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.

[0177] 23. The lithographic printing plate precursor of any one of embodiments 1 to 22, wherein the substrate comprises an aluminum-containing substrate comprising at least an inner aluminum oxide layer, an outer aluminum oxide layer disposed on the inner aluminum oxide layer, and a hydrophilic polymer coating disposed on the outer aluminum oxide layer.

[0178] 24. A method for providing a lithographic printing plate, comprising:

[0179] A) imagewise exposing the lithographic printing plate precursor according to any one of embodiments 1 to 23 to infrared radiation to provide exposed and unexposed areas in the infrared radiation-sensitive image-recording layer, and

[0180] B) Removing the unexposed areas of the infrared radiation-sensitive image-recording layer from the substrate.

[0181] 25. The method of embodiment 24, comprising removing the unexposed areas of 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.

[0182] 26. The method of embodiment 24 or 25, wherein the imagewise exposure is performed using one or more lasers emitting infrared radiation.

[0183] The following examples are provided to further illustrate the practice of the present invention and are not intended to be limiting in any way.

[0184] Aluminum-containing substrates for lithographic printing plate precursors were prepared as follows:

[0185] Hydro 1052 aluminum alloy strips or meshes (available from NorskHydro ASA, Norway) with a thickness of 0.28 mm were used as the aluminum-containing "plate" raw material or support. Both the pre-etching and post-etching steps were carried out in alkaline solutions under known conditions. The etched aluminum support was roughened (or grained) by electrochemical means in a hydrochloric acid solution at 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 carried out using phosphoric acid as the electrolyte to form a pore having an average micropore diameter (D o ) and an average dry thickness of 60 nm (T o ) of the outer aluminum oxide layer. A second anodizing treatment was then performed using phosphoric acid as the electrolyte to form an average micropore diameter (D i ) and an average dry thickness of 500 nm (T i). These 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.

[0186] 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 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.

[0187] Table I

[0188]

[0189] Table II

[0190]

[0191] Table II (continued)

[0192]

[0193] Table III

[0194] Example Initiator composition Acid-sensitive dye precursor Color-changing compounds Comparative Example 1 IC1 ASDP1 none Invention Example 1 IC1 none CCC1 Comparative Example 2 IC1 none CCC2 Comparative Example 3 IC1 none CCC3 Comparative Example 4 IC2 none CCC4 Invention Example 2 IC3 none CCC1 Invention Example 3 IC1 ASDP2 CCC1 Comparative Example 5 IC1 none CCC5 Comparative Example 6 IC1 ASDP2 CCC5 Comparative Example 7 IC1 none CCC6 Comparative Example 8 IC1 none CCC7

[0195] The following four tests were used to evaluate each of the inventive and comparative lithographic printing plate precursors: "On-Press Developability" (DOP), "Image Speed," "Print Out Image" (PO), and "Dark Fade." The results are summarized in Table IV below.

[0196] On-press developing capabilities:

[0197] By using Trendsetter 3244x at 15-150 mJ / cm 2Each 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 printing press without developing (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 achieve a clean background, and one of the following qualitative values ​​was given based on the number of printed sheets achieving a clean background. For this test parameter, evaluations of + and 0 were acceptable.

[0198] + <5 printed pages

[0199] 0 15-35 printed pages

[0200] -> 35 printed pages

[0201] Imaging speed:

[0202] Each lithographic printing plate precursor was exposed and developed as described above. Imaging speed was measured on paper after 1000 impressions by measuring the ink density of solids exposed to different energies. The inflection point of ink density vs. exposure energy was considered a measure of imaging speed. The following qualitative values ​​are given as the result of separate experiments, where lower imaging energies were desirable. For this parameter, evaluations of + and 0 were acceptable.

[0203] + Imaging speed <30mJ / cm 2

[0204] 0 Imaging speed = 30-60mJ / cm 2

[0205] - Imaging speed>60mJ / cm 2

[0206] Printing an image:

[0207] A Trendsetter 800 III Quantum TH 1.7 (available from Eastman Kodak Company) was used at 90 mJ / cm 2Each lithographic printing plate precursor was imagewise exposed to provide exposed and unexposed areas in the negative-working IR-sensitive image-recording layer. For each imagewise exposed lithographic printing plate precursor, the color difference between the exposed and unexposed areas was measured within 10 minutes after the imagewise exposure was completed by measuring the cyan ΔOD value using a Techkon Spectro Dens spectrodensitometer. Cyan ΔOD represents the difference in reflected optical density between the exposed and unexposed areas as viewed through a cyan filter. Visual images on lithographic printing plate precursors with high absolute cyan ΔOD values ​​are expected to be more easily read by cameras and other readers equipped with a diode light source emitting light at approximately 617 nm. The measured values ​​were scored as follows.

[0208] + 0.10≤cyan ΔOD

[0209] 0 0.05≤cyanΔOD<0.10

[0210] - Cyan ΔOD<0.05

[0211] Dark Fade:

[0212] Each lithographic printing plate precursor was imagewise exposed as described above and then stored in the dark for 24 hours.Cyan ΔOD measurements were then performed as described above and the following qualitative scores were given.

[0213] + 0.10≤cyan ΔOD

[0214] 0 0.05≤cyanΔOD<0.10

[0215] - Cyan ΔOD<0.05

[0216] Table IV

[0217] Example DOP Imaging speed Printed image ΔOD cyan Dark faded ΔOD cyan Comparative Example 1 0 0 0 - Invention Example 1 0 0 + + Comparative Example 2 0 0 0 0 Comparative Example 3 0 0 - 0 Comparative Example 4 + - - - Invention Example 2 0 - + + Invention Example 3 0 0 + + Comparative Example 5 0 0 - - Comparative Example 6 0 0 + - Comparative Example 7 0 0 - - Comparative Example 8 0 0 - -

[0218] The results shown in Table IV indicate that the inventive infrared radiation-sensitive imaging compositions containing the inventive (3) color-shifting compounds provided acceptable results in all four tests and particularly improved the printed image after the dark fade test.

Claims

1. A lithographic printing plate precursor comprising: substrate, and An infrared radiation-sensitive image-recording layer 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 donor; (2) a free radical polymerizable composition; and (3) A color-changing compound represented by the following structure (I) in: Ar1 and Ar2 independently represent the atoms necessary to complete a substituted or unsubstituted aromatic ring or to complete a substituted or unsubstituted heteroaromatic ring; R is hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl; R 1 and R 2 is independently substituted or unsubstituted alkyl; R 3 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heteroaryl group; 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; A 1 and A 2 independently represent substituted or unsubstituted alkyl groups, or together represent the two or three carbon atoms necessary to form a substituted or unsubstituted 5- or 6-membered non-aromatic carbocyclic ring; and Za represents one or more counterions to balance the charge in the remainder of the color-shifting compound according to structure (I).

2. The lithographic printing plate precursor of claim 1, wherein R 3 It is trifluoromethyl.

3. The lithographic printing plate precursor of claim 1, wherein Ar1 and Ar2 are the same number of carbon atoms necessary to complete the substituted or unsubstituted aromatic ring.

4. The lithographic printing plate precursor of any one of claims 1 to 3, 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 are the same or different.

5. The lithographic printing plate precursor of any one of claims 1 to 3, wherein A 1 and A 2 Together they represent the two carbon atoms required to complete the unsubstituted 5-membered non-aromatic carbocyclic ring.

6. The lithographic printing plate precursor of any one of claims 1 to 3, wherein Za comprises a tetraarylborate anion.

7. The lithographic printing plate precursor according to any one of claims 1 to 3, wherein the electron donor is an organic borate represented by the following structure (II): (B(R 10 R 11 R 12 R 13 ) - ) n M n+ Structure (Ⅱ) where R 10 、R 11 、R 12 and R 13 are independently substituted or unsubstituted alkyl or substituted or unsubstituted aryl, and R 10 、R 11 、R 12 and R 13 At least three of them are the same or different substituted or unsubstituted aryl groups, n is an integer equal to or greater than 1, and M n+ It is an n-valent cation.

8. The lithographic printing plate precursor of claim 7, wherein R 10 、R 11 、R 12 and R 13 All are the same or different substituted or unsubstituted aryl groups.

9. The lithographic printing plate precursor of claim 8, wherein R 10 、R 11 、R 12 and R 13 All are the same substituted or unsubstituted phenyl groups.

10. The lithographic printing plate precursor of any one of claims 1 to 3 and 8 to 9, wherein R 1 and R 2 independently comprises a chain of carbon atoms interrupted by one or more ether or ester linkages.

11. The lithographic printing plate precursor of claim 1, wherein the infrared radiation-sensitive image-recording layer further comprises a component (4) infrared absorbing material different from the component (3) color-changing compound.

12. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9 and 11, wherein the component (1) free radical initiator composition comprises an onium salt.

13. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9 and 11, wherein the component (1) free radical initiator composition comprises an iodonium cation.

14. The lithographic printing plate precursor of claim 13, wherein the iodonium cation is a diaryliodonium cation.

15. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11 and 14, wherein the infrared radiation-sensitive image-recording layer further comprises a component (5) acid-sensitive dye precursor that is different from all of the components (1), (2) and (3) defined in any one of claims 1 to 3, 8 to 9, 11 and 14 and the component (4) defined in claim 11.

16. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11 and 14, wherein the infrared radiation-sensitive image-recording layer further comprises a component (6) non-radical polymerizable polymer material that is different from all of the components (1), (2) and (3) defined in any one of claims 1 to 3, 8 to 9, 11 and 14 and the component (4) defined in claim 11.

17. The lithographic printing plate precursor of claim 16, wherein the component (6) non-free radical polymerizable polymeric material is present in particulate form.

18. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11, 14 and 17, 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.

19. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11, 14 and 17, wherein the color-changing compound of component (3) represented by structure (I) is 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 weight of the infrared radiation-sensitive image recording layer.

20. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11, 14 and 17, wherein the infrared radiation-sensitive image recording layer is the outermost layer.

21. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11, 14 and 17, wherein the component (2) free radical polymerizable composition comprises at least two free radical polymerizable components.

22. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11, 14 and 17, 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.

23. The lithographic printing plate precursor of any one of claims 1 to 3, 8 to 9, 11, 14 and 17, wherein the substrate comprises an aluminum-containing substrate comprising at least an inner aluminum oxide layer, an outer aluminum oxide layer disposed on the inner aluminum oxide layer, and a hydrophilic polymer coating disposed on the outer aluminum oxide layer.

24. A method for providing a lithographic printing plate, comprising: A) imagewise exposing the lithographic printing plate precursor according to any one of claims 1 to 23 to infrared radiation to provide exposed areas and unexposed areas in the infrared radiation-sensitive image-recording layer, and B) removing the unexposed areas in the infrared radiation-sensitive image-recording layer from the substrate.

25. The method of claim 24, comprising removing the unexposed areas of 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.

26. The method of claim 24 or 25, wherein the imagewise exposure is performed using one or more lasers emitting infrared radiation.

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