Lithographic printing plate precursor and method of use

Abstract

The IR-sensitive lithographic printing plate precursor provides stable printout images using a unique IR-radiation-sensitive composition. The IR-radiation-sensitive composition includes: a) a free-radically polymerizable component; b) an IR-radiation absorber; c) an initiator composition; d) a borate compound; and e) a compound capable of forming a colored boronic acid complex during or after exposure of the IR-radiation-sensitive image-recording layer to infrared radiation. The resulting printout image exhibits excellent color contrast between exposed and unexposed areas. After IR imaging, these precursors can be developed off-press or on-press.

Description

[Technical field]

[0001] The present invention relates to an infrared radiation sensitive lithographic printing plate precursor that can be imaged using infrared radiation to provide an imaged lithographic printing plate. Such a precursor comprises a unique infrared radiation sensitive composition that provides a stable printout image between the exposed and unexposed areas of an imagewise exposed infrared radiation sensitive image recording layer. The present invention also relates to a method of using these precursors to provide a lithographic printing plate with excellent printout images. [Background technology]

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

[0003] Negative-working lithographic printing plate precursors useful for preparing lithographic printing plates typically comprise a negative-working radiation-sensitive image-recording layer disposed on the hydrophilic surface of a substrate. Such image-recording layers comprise a radiation-sensitive component that can be dispersed in a suitable polymeric binder material. After 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 to reveal the underlying hydrophilic surface of the 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 step accepts water and aqueous solutions, such as fountain solution, and repels lithographic ink.

[0004] In recent years, the lithographic printing industry has been highly motivated to simplify the production of lithographic printing plates by using lithographic ink or dampening solution, or both, to remove the unexposed areas of the image recording layer for on-press development ("DOP").Therefore, the use of on-press developable lithographic printing plate precursors is increasingly adopted in the printing industry for many benefits, including less environmental impact and savings in processing chemicals, processing equipment floor space, and operation and maintenance costs.After laser imaging, the on-press developable precursors can be directly loaded into a lithographic printing press.

[0005] It is highly desirable for imaged lithographic printing plate precursors to have different colors in the exposed and unexposed areas of the image recording layer for readability before going to the printing press. The color difference between the exposed and unexposed areas is typically called "printout", "print-out", or "printout image". A strong printout image makes it easier for operators to visually identify imaged lithographic printing plate precursors and properly mount them on the printing press units.

[0006] Many approaches have been taken in the industry to improve the printout of on-press developable printing plate precursors, both immediately after imaging and after storage in the dark, all of which have drawbacks.

[0007] Previously developed masters (wet-processed) using aqueous developers have been designed with incorporated colorants to ensure high contrast between the ink-receptive areas, where the colorant-containing imaging layer is retained, and the hydrophilic support surface, where the colorant-containing imaging layer is removed during wet processing. Such high contrast is required for readability by eye as well as by automatic camera systems. However, in the case of on-press developable masters, the imaging layer is not removed anywhere before the master is mounted on the press, and thus a printout image should be generated. The printout image is usually based on an acid-sensitive leuco dye that can be switched by protons generated by radiation to form a color difference between exposed and unexposed areas. The contrast generated by this concept is much lower than that obtained with wet-processed plates, which tend to fade due to reverse reactions of the color-developing reaction or other undesirable reactions. Therefore, improvements are needed to realize printout images that are strong and do not fade during storage in the dark.

[0008] US Patent Application Publication No. 2020 / 0096865 (Igarashi et al.) describes a negative-working lithographic printing plate precursor that exhibits improved printout images due to the presence of an acid generator, a tetraarylborate, an acid-sensitive dye precursor, and an aromatic diol with electron-withdrawing substituents. In such an imaging composition, the primary color-forming reaction still involves the acid-sensitive dye precursor and protons generated during exposure to imaging radiation. Although the printout value is improved by the presence of the aromatic diol, significant fading still occurs.

[0009] It is desirable to improve printout images beyond the levels produced using acid generators and acid-sensitive color precursors, such as lactone dyes, because printout images may not be strong enough due to inefficient acid generation using infrared radiation-sensitive imaging compositions, followed by on-press development. Furthermore, the concentration of protons generated during infrared radiation imaging often decreases after imaging through chemical equilibrium or other post-imaging chemical reactions. As a result, printout images based on proton-induced color changes often fade after imaging.

[0010] Therefore, there is a need to produce stable printout images using color precursors that change color through reaction with chemical species other than protons generated during infrared radiation imaging. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] US Patent Application Publication No. 2020 / 0096865 Summary of the Invention

[0012] The present invention relates to A substrate; an infrared radiation sensitive image recording layer disposed on a substrate; A lithographic printing plate precursor comprising: an infrared radiation sensitive image recording layer comprising: a) a free radically polymerizable component; b) an infrared radiation absorber; c) an initiator composition capable of generating free radicals; d) with a borate compound; e) a compound capable of forming a colored boronic acid complex during or after exposure of the infrared radiation sensitive image recording layer to infrared radiation; Including, The borate compound has the following structure (I): B - (R 1 )(R2 )(R 3 )(R 4 )Z + (I) (In the formula, R 1 , R 2 , R 3 , and R 4 independently represent an optionally substituted alkyl, aryl, alkenyl, alkynyl, cycloalkyl, or heterocyclic group bonded to the boron atom of the borate anion; or R 1 , R 2 , R 3 , and R 4 two or more of are joined to form a heterocyclic ring containing a boron atom, said heterocyclic ring having up to seven carbon, nitrogen, oxygen, or sulfur atoms; Z + is a cation that balances the charge of the borate anion. The present invention provides a lithographic printing plate precursor represented by the formula:

[0013] The present invention further provides a method of providing a lithographic printing plate comprising the steps of: A) imagewise exposing a lithographic printing plate precursor according to any one of the embodiments of the present invention to infrared radiation to obtain exposed and unexposed areas in an infrared radiation sensitive image recording layer; B) removing the unexposed areas of the infrared radiation sensitive image recording layer from the substrate; The present invention provides a method comprising:

[0014] The present invention provides printout images from colored boronic acid complexes produced in the imaging layer in areas exposed to imaging infrared radiation during or after image-forming exposure, such printout images being strong and not fading during storage in the dark. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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 considered as limiting the scope of the invention as claimed below. Moreover, those skilled in the art will appreciate that the following disclosure has broader applications than are expressly described in the discussion of any particular embodiment.

[0016] definition As used herein to define various components of the infrared radiation sensitive image-recording layer and other materials used in the practice of the present invention, unless otherwise indicated, the singular forms "a," "an," and "the" are intended to include one or more of the components (i.e., include plural referents).

[0017] Each term not expressly defined in this application should be understood to have the meaning generally accepted by those of ordinary skill in the art. If an interpretation of a term would render the term meaningless or essentially meaningless in the context, the term should be interpreted as having its standard dictionary meaning.

[0018] The use of numerical values ​​in the various ranges specified herein, unless expressly indicated, should be considered as approximations, as if the word "about" preceded both the minimum and maximum values ​​in the stated range. Thus, slight variations above and below the stated ranges may be useful to achieve substantially the same results as values ​​within the range. Moreover, the disclosure of these ranges is intended as a continuous range, including all values ​​between the minimum and maximum values, as well as the endpoints of the ranges.

[0019] Unless the context indicates otherwise, as used herein, the terms "lithographic printing plate precursor", "master" and "IR-sensitive lithographic printing plate precursor" are intended as equivalent references to embodiments of the present invention.

[0020] As used herein, the term "infrared radiation absorber" refers to compounds or materials that absorb electromagnetic radiation in the near infrared (near IR) and infrared (IR) regions of the electromagnetic spectrum, and typically have a maximum absorption in the near IR and IR regions.

[0021] As used herein, the terms "near infrared region" and "infrared region" refer to radiation having wavelengths of at least 750 nm or greater. In most instances, these terms are used to refer to the region of the electromagnetic spectrum of at least 750 nm, and possibly at least 750 nm and up to 1400 nm.

[0022] For the purposes of this invention, the intensity of a printout image is generally indicated by ΔE, the Euclidean distance in the CIE 1976 L*a*b* color space between the color of the radiation-exposed area and the color of the radiation-unexposed area measured from reflectance measurements in 45 / 0 geometry (unpolarized light) using a CIE 2° observer and D50 as illuminant, according to EN ISO 11664-4 "Colorimetry--Part 4: CIE 1976 L*a*b* Color space." and other known references. Color measurements can be made using commercially available instruments such as Techkon SpectroDens. In the CIE 1976 L*a*b color space, colors are expressed as three numerical color values: L* for the lightness (or luminance) of the color, a* for the green-red component of the color, and b* for the blue-yellow component of the color value.

[0023] For purposes of the present invention, the visible spectral region refers to the spectral region of electromagnetic radiation having wavelengths between 400 nm and 700 nm.

[0024] For clarification of the definitions of terms relating to polymers, reference should be made to the "Glossary of Basic Terms in Polymer Science" published by the International Union of Pure and Applied Chemistry ("IUPAC"), Pure Appl. Chem. 68, 2287-2311 (1996). However, definitions expressly set forth herein should be considered to prevail.

[0025] As used herein, the term "polymer" is used to describe a compound with a relatively large molecular weight formed by linking many small reactive monomers to form repeating units of the same chemical composition. These polymer chains usually form coiled structures in a random manner. Depending on the choice of solvent, the polymer may become insoluble as the chain length increases, resulting in polymer particles dispersed in the solvent medium. These particle dispersions are very stable and may be useful in the infrared radiation sensitive imaging layers described for use in the present invention. In the present invention, the term "polymer" refers to non-crosslinked materials unless otherwise indicated. Thus, crosslinked polymer particles differ from non-crosslinked polymer particles in that non-crosslinked polymer particles can dissolve in certain organic solvents with good solvation properties, while crosslinked polymer particles can swell in organic solvents but do not dissolve because the polymer chains are connected by strong covalent bonds.

[0026] The term "copolymer" refers to a polymer made up of two or more different repeats or repeat units arranged along the polymer chain.

[0027] The term "backbone" refers to a chain of atoms in a polymer to which multiple pendant groups can be attached. An example of such a backbone is an "all-carbon" backbone resulting from the polymerization of one or more ethylenically unsaturated polymerizable monomers.

[0028] As used herein, the term "ethylenically unsaturated polymerizable monomer" refers to a compound that contains one or more ethylenically unsaturated (-C=C-) bonds that are polymerizable using free radical or acid-catalyzed polymerization reactions and conditions. The term is not intended to refer to chemical compounds that have only unsaturated -C=C- bonds that are not polymerizable under these conditions.

[0029] Unless otherwise indicated, the term "wt. %" refers to the amount of a component or material based on the total solids of a composition, formulation or layer. Unless otherwise indicated, the percentage can be the same for either the dry layer or the total solids of the formulation or composition.

[0030] As used herein, the term "layer" or "coating" can consist of one disposed or applied layer, or a combination of several successively disposed or applied layers. When a layer is considered to be infrared radiation sensitive and negative-working, it is both sensitive to infrared radiation (as described above for "infrared radiation absorber") and negative-working in the formation of a lithographic printing plate.

[0031] As used herein, the terms "on-press developable" and "on-press developability" refer to the ability of a master according to the present invention to be developed after exposure to infrared radiation (imaging) by mounting the imaging master on a suitable printing press and developing between the first few prints using a fountain solution, a lithographic ink, or a combination of a fountain solution and a lithographic ink.

[0032] use The lithographic printing plate precursor according to the present invention is useful for providing a lithographic printing plate that shows a desirable printout image after imagewise exposure. These lithographic printing plates are useful for lithographic printing in press operation. The lithographic printing plate can be prepared using on-press or off-press processing according to the present invention. The lithographic printing plate precursor is prepared with the structure and components described as follows:

[0033] Planographic printing plate original plate The master plate 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 an infrared radiation sensitive image recording layer that is negative-working. In general, the infrared radiation sensitive image recording composition (and the resulting infrared radiation sensitive image recording layer) comprises: a) one or more free radically polymerizable components; b) one or more infrared radiation absorbers; c) an initiator composition; d) one or more borate compounds; e) one or more compounds, each of which can form a colored boronic acid complex during or after exposure of the infrared radiation sensitive image recording layer to infrared radiation; and optionally f) a non-free radically polymerizable polymeric material that is different from all of the a), b), c), d), and e) components as defined herein. In some very useful embodiments, the infrared radiation sensitive image recording layer essentially consists of the above-mentioned components a)-e) as the only essential components necessary to provide the desired lithographic image with the desired printout image.

[0034] Generally, there is only one infrared radiation-sensitive image-recording layer in each master. This layer is generally the outermost layer of the master, although in some embodiments there may be an outermost water-soluble hydrophilic protective layer (also known as a topcoat or oxygen barrier layer), described below, disposed over (or directly over and in contact with) the infrared radiation-sensitive image-recording layer.

[0035] substrate: The substrate used to prepare the plate precursor according to the present invention generally has a hydrophilic imaging surface, or at least a surface that is more hydrophilic than the applied infrared radiation-sensitive image-recording layer. The substrate generally comprises an aluminum-containing support which may be composed of raw aluminum or a suitable aluminum alloy conventionally used to prepare lithographic printing plate precursors.

[0036] The aluminum-containing substrate can be treated using techniques known in the art, including some type of roughening by physical (mechanical), electrochemical, or chemical graining, followed by one or more anodization treatments. Each anodization treatment is typically performed using either phosphoric 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 with multiple pores with pore openings of various depths and shapes. Thus, such a process provides an anodic oxide layer or aluminum oxide layer under an infrared radiation-sensitive image-recording layer, which can be provided as described below. Discussions of such pores and methods of controlling their widths are found, for example, in US Patent Publication Nos. 2013 / 0052582 (Hayashi), 2014 / 0326151 (Namba et al.), and 2018 / 0250925 (Merka et al.), as well as in US Patent Nos. 4,566,952 (Sprintschuik et al.), 8,789,464 (Tagawa et al.), 8,783,179 (Kurokawa et al.), and 8,978,555 (Kurokawa et al.), and in EP 2,353,882 (Tagawa et al.). Teachings of providing two successive anodization processes to provide different aluminum oxide layers in an improved substrate are found, for example, in US Patent Publication No. 2018 / 0250925 (Merka et al.).

[0037] By sulfuric acid anodization of the aluminum support, typically at least 1 g / m 2 and 5 g / m 2 or less, more typically at least 3 g / m 2 and 4 g / m 2 The following weight (coverage) of aluminum (anodic) oxide on the surface is obtained: with phosphoric acid anodizing, typically at least 0.5 g / m 2 and 5 g / m 2or less, more typically at least 1 g / m 2 and 3 g / m 2 The following aluminum (anodic) oxide weights on the surface are obtained:

[0038] The anodized aluminum-containing support can be further treated using known post-anodization processes, such as post-treatment with poly(vinylphosphonic acid) (PVPA), vinylphosphonic acid copolymers, poly[(meth)acrylic acid] or its alkali metal salts, or (meth)acrylic acid copolymers or its alkali metal salts, mixtures of phosphate and fluoride salts, or aqueous solutions of sodium silicate, to seal the anodized oxide pores or to hydrophilize the surface, or both. The post-treatment process materials can also contain unsaturated double bonds to enhance adhesion between the treated surface and the overlying infrared radiation-exposed regions. Such unsaturated double bonds can be provided by low molecular weight materials or can be present in the side chains of a polymer. Useful post-treatment processes include immersion of the substrate with rinsing, immersion of the substrate without rinsing, and various coating techniques such as extrusion coating.

[0039] Anodized aluminum-containing substrates can be treated with alkaline or acidic pore-enlarging solutions to provide an anodized oxide layer containing columnar pores. In some embodiments, the treated aluminum-containing substrate can include a hydrophilic layer disposed directly over the grained, anodized, post-treated aluminum-containing support, where such hydrophilic layer can include a non-crosslinked hydrophilic polymer having carboxylic acid side chains.

[0040] The thickness of the substrate can vary, but should be sufficient to withstand the wear from printing and thin enough to wrap around the printing form. Useful embodiments include treated aluminum foils with a thickness of at least 100 μm and up to 700 μm. The backside (non-imaging side) of the substrate can be coated with an antistatic agent, a slippery layer or a matte layer to improve the handling and "feel" of the master.

[0041] The substrate can be formed as a continuous roll (or continuous web) of sheet material suitably coated with the infrared radiation sensitive image recording layer formulation and, optionally, the hydrophilic protective layer formulation, and subsequently cut or slit (or both) to size to provide individual lithographic printing plate masters having a shape or form with four right angle corners (and thus typically a square or rectangular shape or form). Typically, the individual cut masters have a planar or nearly flat rectangular shape.

[0042] Infrared radiation sensitive image recording layer: The infrared radiation-sensitive recording layer composition (and the infrared radiation-sensitive image recording layer prepared therefrom) according to the present invention is designed to be "negative-working" as that term is known in the lithographic art. Furthermore, the infrared radiation-sensitive image recording layer can be designed with a certain combination of components to provide on-press developability to the lithographic printing plate precursor after exposure, for example to enable development using a fountain solution, a lithographic ink, or a combination of the two.

[0043] The infrared radiation sensitive image recording layer used in the practice of the present invention comprises one or more free radical polymerizable components, each of which contains a) 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 a) free radical polymerizable components, each with the same or different number of free radical polymerizable groups in each molecule. Thus, a useful a) free radical polymerizable component can contain one or more free radical polymerizable monomers or oligomers with one or more polymerizable ethylenically unsaturated groups (e.g., two or more such groups). Similarly, crosslinkable polymers with such free radical polymerizable groups can 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 can be used. In some embodiments, the free radical polymerizable component comprises a carboxyl group.

[0044] It is possible for one or more a) free radically polymerizable components to have a molecular weight large enough, or have sufficient polymerizable groups, to provide a crosslinkable polymer matrix that functions as a "polymeric binder" for the other components in the infrared radiation sensitive image recording layer. In such embodiments, a separate f) non-free radically polymerizable polymeric material (below) is not required, but can still be present if desired.

[0045] The free radical polymerizable component includes urea urethane (meth)acrylates or urethane (meth)acrylates with multiple (two or more) polymerizable groups. A mixture of such compounds can be used, with each compound having two or more unsaturated polymerizable groups, and some of the compounds having three, four or more unsaturated polymerizable groups. For example, the free radical polymerizable component can be prepared by reacting DESMODUR® N100 aliphatic polyisocyanate resin (Bayer Corp., Milford, Conn.) based on hexamethylene diisocyanate with hydroxyethyl acrylate and pentaerythritol triacrylate. Useful free radically polymerizable compounds include NK Ester A-DPH (dipentaerythritol hexaacrylate) available from Kowa American, and Sartomer 399 (dipentaerythritol pentaacrylate), Sartomer 355 (di-trimethylolpropane tetraacrylate), Sartomer 295 (pentaerythritol tetraacrylate) and Sartomer 415 [ethoxylated (20) trimethylolpropane triacrylate] available from Sartomer Company, Inc.

[0046] Many other a) free radically polymerizable components are known in the art and described in a significant literature, including Photoreactive Polymers: The Science and Technology of Resists, A Reiser, Wiley, New York, 1989, pp. 102-177, BM Monroe in Radiation Curing: Science and Technology, edited by S.P.P.appas, Plenum, New York, 1992, pp. 399-440, and "Polymer Imaging" by A.C. Kohen and P. Walker, Imaging Processes and Material, edited by J.M. Sturge et al., Van Nostrand Reinhold, New York, 1989, pp. 226-262. For example, useful free radical polymerizable components are described in EP 1,182,033 (Fujimaki et al.) beginning at paragraph

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

[0047] The one or more a) free radically polymerizable components are generally present in an amount of at least 10% or at least 20% by weight, and not more than 50% or not more than 70% by weight, all based on the total dry coverage of the infrared radiation sensitive image recording layer.

[0048] Useful a) free radically polymerizable components can be obtained from a variety of commercial sources worldwide or can be readily prepared using known starting materials and synthetic methods performed by a skilled synthetic chemist.

[0049] In addition, the infrared radiation sensitive image recording layer comprises one or more b) infrared radiation absorbers to provide the desired infrared radiation sensitivity or convert radiation into heat, or both. Useful infrared radiation absorbers can be pigments or infrared radiation absorbing dyes. Suitable dyes are, for example, those described in U.S. Patel et al., U.S. Pat. No. 5,208,135, U.S. Pat. No. 6,153,356, U.S. Pat. No. 6,309,792, Hauck et al., U.S. Pat. No. 6,569,603, Furukawa, U.S. Pat. No. 6,797,449, Nakamura et al., U.S. Pat. No. 7,018,775, Tao, U.S. Pat. No. 7,368,215, Munnelly et al., U.S. Pat. No. 8,632,941, Balbinot et al., and U.S. Pat. App. Pub. No. 2007 / 056457, Iwai et al. In some infrared radiation sensitive embodiments, it is desirable that at least one b) infrared radiation absorber in the infrared radiation sensitive image recording layer is a cyanine dye that comprises a suitable cationic cyanine chromophore and a tetraarylborate anion, such as a tetraphenylborate anion. Examples of such dyes include those described in US Patent Application Publication No. 2011 / 003123 (Simpson et al.).

[0050] In addition to low molecular weight IR-absorbing dyes, polymer-bound IR-dye chromophores can be used as well. Additionally, IR-dye cations can also be used, i.e., the cation is an IR-absorbing moiety of a dye salt that ionically interacts with a polymer containing a carboxy, sulfo, phospho, or phosphono group in the side chain.

[0051] The total amount of the one or more b) infrared radiation absorbers is at least 0.5% or at least 1% by weight, and not more than 15% or not more than 30% by weight, based on the total dry coverage of the infrared radiation sensitive image recording layer.

[0052] Useful b) infrared radiation absorbers can be obtained from a variety of commercial sources around the world or can be prepared using known chemical synthesis methods and starting materials within the skill of a synthetic chemist.

[0053] Further, the present invention utilizes a c) initiator composition present in the infrared radiation-sensitive image recording layer. Such c) initiator composition can include one or more organic halogen compounds, such as trihaloallyl compounds; halomethyltriazines; bis(trihalomethyl)triazines; and at least one onium salt, such as iodonium salts, sulfonium salts, diazonium salts, phosphonium salts, and ammonium salts, many of which are known in the art as being capable of generating free radicals upon exposure to infrared radiation. For example, representative compounds other than onium salts are described, for example, in U.S. Patent Application Publication No. 2005 / 0170282 (Inno et al., U.S. Patent No. 282)

[0087] to

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

[0054] Useful onium salts are described, for example, in the cited US Pat. No. 282,

[0103] to

[0109] . For example, useful onium salts contain at least one onium cation in the molecule and a suitable anion. Examples of onium salts include diaryliodonium salts, triphenylsulfonium, diphenyliodonium, diphenyldiazonium, compounds obtained by introducing one or more substituents into the benzene ring of these compounds, and their derivatives. Suitable substituents include, but are not limited to, alkyl, alkoxy, alkoxycarbonyl, acyl, acyloxy, chloro, bromo, fluoro, and nitro groups.

[0055] Examples of anions in onium salts include, but are not limited to, halogen anions, ClO4, as described, for example, in U.S. Pat. No. 7,524,614 (Tao et al.).- , PF6 - , BF4 - , SbF6 - , CH3SO3 - , CF3SO3 - , C6H5SO3 - , CH3C6H4SO3 - , HOC6H4SO3 - , ClC6H4SO3 - , and boron anions.

[0056] Representative useful iodonium salts are described in U.S. Pat. No. 7,524,614 (noted above), columns 6-7, where the iodonium cation can contain a variety of recited monovalent substituents "X" and "Y", or fused carbocyclic or heterocyclic rings with the respective phenyl groups.

[0057] Useful onium salts can be polyvalent onium salts having at least two onium ions in the molecule linked through covalent bonds. Among the polyvalent onium salts, those having at least two onium ions in the molecule are useful, and those having sulfonium or iodonium cations in the molecule are useful.

[0058] Additionally, the onium salts described in Japanese Patent Publication No. 2002-082429 [or U.S. Patent Application Publication No. 2002-0051934 (Ippei et al.)], paragraphs

[0033] to

[0038] , or the iodonium borate complexes described in U.S. Patent No. 7,524,614 (noted above), paragraphs 6 and 7, can also be used.

[0059] Representative iodonium borate salts are listed, for example, at column 8 of US Pat. No. 7,524,614 (noted above).

[0060] In some embodiments, a combination of onium salts, such as those described in U.S. Patent Application Publication No. 2017 / 0217149 (Hayashi et al.) as Compound A and Compound B, can be used as part of c) the initiator composition.

[0061] Since the c) initiator composition can have multiple components, useful amounts or dry coverages of the various components of the c) initiator composition in the infrared radiation sensitive image recording layer will be readily apparent to one of ordinary skill in the art based on his or her knowledge and the representative teachings provided herein, including the examples set forth below. Useful c) initiator composition materials can be readily obtained from commercial sources worldwide or can be readily prepared using known starting materials and synthetic methods performed by a skilled synthetic chemist.

[0062] Another essential feature of the infrared radiation sensitive image recording layer is one or more d) borate compounds represented by the following structure (I):

[0063] B - (R 1 )(R 2 )(R 3 )(R 4 )Z + (I) (In the formula, R 1 , R 2 , R 3 , and R 4 independently represent a substituted or unsubstituted alkyl, aryl, alkenyl, alkynyl, cycloalkyl, or heterocyclic group, each bonded to a boron atom; or R 1 , R 2 , R 3 , and R 4 two or more of are joined to form a heterocyclic ring containing a boron atom, each of said heterocyclic rings having up to seven carbon, nitrogen, oxygen, or sulfur atoms; Z + is a cation that balances the charge of the borate anion).

[0064] For example, useful substituted or unsubstituted alkyl groups can contain 1 to 10 carbon atoms; substituted or unsubstituted aryl groups can have 6 or 10 carbon atoms in the carbocyclic ring; substituted or unsubstituted alkenyl groups can have 2 to 10 carbon atoms; substituted or unsubstituted alkynyl groups can have 2 to 10 carbon atoms; and substituted or unsubstituted cycloalkyl groups can contain 5 to 10 carbon atoms in the carbocyclic ring.

[0065] Useful borate compounds of this type include those having a borate anion such as one of those described in paragraphs 7 and 8 of U.S. Pat. No. 7,524,614 (noted above) and Japanese Patent Publication No. 2002 / 107916.

[0066] For example, tetraarylborate compounds, including tetraphenylborate, and triarylalkylborate compounds, such as triphenylalkylborate compounds, are useful.

[0067] Z in Structure (I) + can be part of c) the initiator composition, such as iodonium cations and sulfonium cations, or part of b) the infrared radiation absorber, such as the cyanine dye cations described in US Patent Publication No. 2011 / 003123 (Simpson et al.). More useful cations include, but are not limited to, any chemically possible cation, and such cations will be readily apparent to those skilled in the art. For example, other suitable cations include alkali metal ions, such as sodium and potassium ions, quaternary ammonium and phosphonium cations, such as tetraalkylammonium cations, pyridinium, piperidinium, pyrrolidinium, pyrrolinium, imidazolium, pyrazolium, oxazolium, thiazolium, triazolium, and other organic cations.

[0068] During or after imagewise exposure of the infrared radiation sensitive image recording layer to infrared radiation, one or more d) borate compounds are believed to decompose and generate one or more active boron-containing species that can participate in the formation of colored boronic acid complexes as described below. Examples of useful active boron-containing species include, but are not limited to, boric acid, alkyl boronic acid, aryl boronic acid, dialkyl boric acid, diaryl boric acid, and alkylaryl boric acid, where each of the alkyl and aryl groups may be independently optionally substituted with a substituent such as a halo group, a methyl group, an ester group, an amide group, or a hydroxyl group. In general, unreacted d) borate compounds do not substantially form colored boronic acid complexes during normal storage of the lithographic printing plate precursor according to the present invention. As a result, the molar concentration of colored boronic acid formed in the infrared radiation non-exposed area of ​​the lithographic printing plate precursor is typically less than 50%, more typically less than 70%, lower than the molar concentration of colored boronic acid complex formed in the infrared radiation exposed area 30 minutes after infrared radiation imagewise exposure under ambient conditions.

[0069] In addition to generating active boron-containing species for forming colored boronic acid complexes described below, d) borate compounds according to some embodiments of the present invention can generate free radicals during imagewise exposure to infrared radiation, either alone or in combination with components in the c) initiator composition described above. Useful examples of d) borate compounds that can also generate free radicals include those described in paragraphs 7 and 8 of U.S. Pat. No. 7,524,614 (above), and those described in

[0012] to

[0044] of Japanese Patent Publication No. 2002 / 107916. It is also possible for the d) borate compound and at least one onium salt to form a common salt compound.

[0070] d) Z, in which the borate compound is an infrared absorbing cation + In embodiments that include a counterion, d) the borate compound can also function as an infrared radiation absorber b).

[0071] The total amount of d) one or more borate compounds represented by Structure (I) in the infrared radiation sensitive image recording layer can generally be at least 0.5% by weight or at least 1% by weight, and not more than 10% by weight or not more than 20% by weight, all based on the total dry coverage of the infrared radiation sensitive image recording layer.

[0072] d) In embodiments in which the borate compound can function as a free radical initiator, an infrared radiation absorber, or both a radical initiator and an infrared radiation absorber, a separate non-borate-containing initiator composition c) and a separate non-borate-containing infrared radiation absorber are no longer necessary, but can still be included if desired.

[0073] For the present invention, the molar ratio of d) the borate compound and e) the compound capable of forming a colored boronic acid complex (below) is at least 0.05:1 and no more than 20:1, or perhaps at least 0.1:1 and no more than 10:1.

[0074] Useful d) borate compounds can be obtained from a variety of commercial sources or can be prepared using starting materials and synthetic methods known to those skilled in the art.

[0075] Furthermore, one or more e) compounds capable of forming a colored boronic acid complex during or after exposure to infrared radiation, respectively, are present in the infrared radiation sensitive image recording layer. The colored boronic acid complex during or after exposure of the infrared radiation sensitive image recording layer to infrared radiation has at least one absorption peak in the visible spectral region. Such e) compounds may be compounds that have substantially no absorption peak in the visible spectral region before forming the colored boronic acid complex, or compounds that have at least one absorption peak in the visible spectral region, but at a wavelength substantially different from that of the absorption peak of the colored boronic acid complex.

[0076] Some particularly useful compounds have the following substructures (II), (III), and (IV): [ka] can be defined as a compound containing one or more occurrences of

[0077] Such compounds may have one or more occurrences of one or more of moieties (II), (III), and (IV). e) It may be particularly desirable for compounds capable of forming a coloured boronic acid complex during or after exposure of the infrared radiation sensitive image recording layer to infrared radiation to contain one or more occurrences of moiety (III).

[0078] Useful e) compounds containing one or more occurrences of substructure (II) include, but are not limited to, alizarin, alizarin red S, and pyrocatechol violet. Such compounds typically have one or more absorption peaks in the visible spectrum. Such visible absorption peaks may shift to different wavelengths upon formation of a colored boronic acid complex. The formed boronic acid complex may have the following substructure (IIa) or substructure (IIb): [ka] (In the formula, R a d) for borate compounds, R as defined above for structure (I) 1 , R 2 , R 3 , and R 4 or R a can be an -OH group; R b and R c is e) a residue from a compound capable of forming a colored boronic acid complex; which may be a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. For some embodiments, the R b and R c may be e) a residue from a compound capable of forming a colored boronic acid complex, the colored boronic acid complex having the following partial structure (IIc): [ka] It may contain one or more occurrences of.

[0079] Useful e) compounds containing one or more occurrences of substructure (III) include those having the following structure (V): [ka] wherein Ar1 and Ar2 are independently a substituted or unsubstituted carbocyclic aromatic group or a substituted or unsubstituted heteroaromatic group; m and n are independently 0, 1, 2, or 3. Such substituted or unsubstituted carbocyclic aromatic groups include, but are not limited to, unsubstituted phenyl, unsubstituted naphthyl, or phenyl or naphthyl substituted with one or more of hydroxy, alkyl, halogen, alkoxy, alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyl, aryl, aryloxy, nitro, amino, alkylamino, dialkylamino, arylamino, diarylamino, or acetylamino groups. Such substituted or unsubstituted heteroaromatic groups include, but are not limited to, unsubstituted pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, pyrimidin-2-yl, pyrimidin-4-yl, pyrimidin-5-yl, or pyrimidin-6-yl, pyrazine, furan, thiophene, pyrazole or oxazole, imidazole and thiazole groups, or such groups substituted as described for carbocyclic aromatic groups.

[0080] More particularly, e) a compound capable of forming a colored boronic acid complex during or after exposure of the infrared radiation sensitive image recording layer to infrared radiation has the following structure (VI): [ka] (wherein R1 and R2 are independently a substituent selected from the group consisting of hydroxy, halogen, alkyl, alkoxy, alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyl, aryl, aryloxy, nitro, amino, alkylamino, dialkylamino, arylamino, diarylamino, and acetylamino groups, which are located at any of the ortho, meta, and para positions of the benzene ring to which they are attached; m and n are independently 0, 1, 2, or 3; and p and q are independently 0 to 5.) It can be represented by:

[0081] Representative compounds of this type include, but are not limited to, the following compounds, which may be used individually or in any mixture: [ka] [ka] [ka] [ka]

[0082] e) Useful colored boronic acid complexes derived from compounds having the substructure (III), which can form colored boronic acid complexes during or after exposure to infrared radiation, include those having the following substructure (IIIa) or substructure (IIIb): [ka] (In the formula, R a d) for borate compounds, R as defined above for structure (I) 1 , R 2 , R 3 , and R 4 or R a can be an -OH group; R b and R cmay be a residue from a compound capable of forming a colored boronic acid complex, a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group. In some embodiments, R b and R c may be e) a residue from a compound capable of forming a colored boronic acid complex, which may have one or more occurrences of the moiety (IIIc). [ka]

[0083] Useful e) compounds having the moiety (IV) include kermesic acid, Acilan Saphirol SE, Bat Violet 1, CI Disperse Red 60, carminic acid, alizarin, purpurinem quinalizarin, alizarin red, and similar hydroxy-substituted derivatives of anthraquinone. Such compounds typically have one or more absorption peaks in the visible spectrum. Such visible absorption peaks may shift to different wavelengths upon formation of a colored boronic acid complex. The structure of the formed boronic acid complex is similar to that formed by boronic acid compounds composed of the moiety (III) defined, for example, by moieties (IIIa)-(IIIc).

[0084] Representative compounds of this type include, but are not limited to: [ka] [ka] Includes:

[0085] The one or more e) compounds each capable of forming a colored boronic acid complex are present in the infrared radiation sensitive image recording layer at a dry coverage of at least 0.5% by weight and no more than 20% by weight.

[0086] Such e) compound(s) can be obtained from a variety of commercial sources or can be prepared using starting materials and synthetic methods known to those of skill in the art.

[0087] Optionally, but in some embodiments desirably, the infrared radiation-sensitive image-recording layer further comprises one or more f) non-free-radically polymerizable polymeric materials (or polymeric binders) that, if present, do not have any functional groups that would render the polymeric material free-radically polymerizable. Such f) non-free-radically polymerizable polymeric materials are thus distinct from one or more a) free-radically polymerizable components described above, which are distinct materials from all of the b), c), d), and e) components described above.

[0088] Useful f) non-free radically polymerizable polymeric materials generally have a weight average molecular weight (M) of at least 2,000 or at least 20,000, and no more than 300,000 or no more than 500,000, as measured by gel permeation chromatography (polystyrene standard). w ).

[0089] Such f) non-free radically polymerizable polymeric materials can be selected from polymeric binder materials known in the art, including polymers that include repeat units with side chains that include polyalkylene oxide segments, such as those described in U.S. Pat. No. 6,899,994 (Huang et al.). Other useful polymeric binders include two or more types of repeat units with different side chains that include polyalkylene oxide segments, such as those described in WO 2015-156065 (Kamiya et al.). Some of these polymeric binders can further include repeat units with pendant cyano groups, such as those described in U.S. Pat. No. 7,261,998 (Hayashi et al.).

[0090] Such one or more f) polymeric non-free radically polymerizable materials can also have a backbone that includes a plurality (at least two) of urethane moieties, as well as pendant groups that include polyalkylene oxide segments.

[0091] Some useful f) non-free radically polymerizable polymeric materials can be present in particulate form, i.e., in the form of discrete particles (unagglomerated particles). Such discrete particles can have an average particle size of at least 10 nm and no more than 1500 nm, or typically at least 80 nm and no more than 600 nm, and are generally uniformly distributed within the infrared radiation-sensitive image-recording layer. Some of these materials can be present in particulate form and have an average particle size of at least 50 nm and no more than 400 nm. The average particle size can be determined using various known methods and nanoparticle measuring devices, including measuring particles in an electron scanning microscope image and averaging a set number of measurements.

[0092] In some embodiments, f) the non-free-radically polymerizable polymeric material can be present in the form of particles having an average particle size smaller than the average dry thickness (t) of the infrared radiation-sensitive image-recording layer. The average dry thickness (t) in micrometers (μm) is calculated according to the following formula: t=w / r (Wherein, w is g / m 2 is the dry coating coverage of the infrared radiation-sensitive image-recording layer of 1 g / cm 3 (It is.)

[0093] f) The non-free-radically polymerizable polymeric material may be present in an amount of at least 10% or at least 20% by weight, and up to 50% or up to 70% by weight, based on the total dry coverage of the infrared radiation sensitive image recording layer.

[0094] Useful f) non-free-radically polymerizable polymeric materials can be obtained from a variety of commercial sources or can be prepared using known procedures and starting materials, for example, as described in the publications listed above and known by the skilled polymer chemist.

[0095] The infrared radiation sensitive image recording layer may optionally contain crosslinked polymer particles, such materials having an average particle size of at least 2 μm or at least 4 μm, and no greater than 20 μm, as described, for example, 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 polymer particles may be present in the infrared radiation sensitive image recording layer only, in the hydrophilic protective layer (below) only, if present, or in both the infrared radiation sensitive image recording layer and the hydrophilic protective layer, if present.

[0096] The colored boronic acid complexes formed in the infrared radiation exposed areas can provide strong and long-lasting printouts on the lithographic printing plate precursors of the present invention, but can also be used in conjunction with traditional dye precursors to provide additional printouts that can be converted to uniquely colored forms in the presence of acids or free radicals. The acid radicals and free radicals can be generated from c) an initiator composition, d) a borate compound represented by structure (I), or both c) an initiator composition and d) a borate compound. Useful dye precursors include those described in U.S. Serial No. 16 / 572,731, as well as the various classes of color-forming compounds described according to the color-forming mechanism on pages 11 and 12 of U.S. Patent Application Publication No. 2018 / 154,667. These dye precursors typically form colored compounds instantly during image-forming exposure to the infrared radiation master. Printouts generated from such dye precursors typically fade over time, as described in the Background section, but are still desirable when the formation of colored boronic acid complexes according to the present invention is sometimes not instantaneous and takes some time to achieve the full potential of its printout capabilities.

[0097] The infrared radiation sensitive image recording layer can also contain various other optional additives in conventional amounts, including, but not limited to, dispersants, humectants, biocides, plasticizers, surfactants for coverage or other properties, viscosity enhancers, pH adjusters, drying agents, defoamers, development aids, rheology modifiers or combinations thereof, or any other additives commonly used in the lithographic coating art. The infrared radiation sensitive image recording layer can also contain phosphate (meth)acrylates, generally having a molecular weight greater than 250, as described in U.S. Pat. No. 7,429,445 (Munnelly et al.).

[0098] Furthermore, the infrared radiation-sensitive image-recording layer may optionally contain one or more suitable coinitiators, chain transfer agents, antioxidants or stabilizers to prevent or mitigate undesired radical reactions. Antioxidants and inhibitors suitable for this purpose are described, for example, in EP 2,735,903 (Werner et al.)

[0144] to

[0149] and U.S. Pat. No. 7,189,494 (Munnelly et al.), columns 7 to 9.

[0099] Useful dry coverages for the infrared radiation-sensitive image-recording layer are described below.

[0100] Hydrophilic protective layer: In some embodiments of the present invention, the infrared radiation sensitive image recording layer is the outermost layer with no layers disposed thereon, however, it is possible for a master according to the present invention to be designed with a hydrophilic protective layer (also known in the art as a hydrophilic overcoat, oxygen barrier layer or topcoat) disposed directly above the single infrared radiation sensitive image recording layer (with no intermediate layer between these two layers).

[0101] If present, this hydrophilic protective layer is generally the outermost layer of the master, so that when multiple masters are stacked, the hydrophilic protective layer of one master can be in contact with the backside of the substrate of the master immediately above it, and no interleaf paper is present.

[0102] Such hydrophilic protective layers may contain one or more film-forming water-soluble polymeric binders in an amount of at least 60% by weight and up to 100% by weight, based on the total dry weight of the hydrophilic protective layer. Such film-forming water-soluble (or hydrophilic) polymeric binders may include modified or unmodified poly(vinyl alcohol) having a degree of saponification of at least 30%, or at least 75%, or at least 90%, and up to 99.9%.

[0103] Furthermore, one or more acid-modified poly(vinyl alcohols) can be used as a film-forming water-soluble (or hydrophilic) polymeric binder in the hydrophilic protective layer. For example, at least one poly(vinyl alcohol) can be modified with an acid group selected from the group consisting of carboxylic acid, sulfonic acid, sulfate ester, phosphonic acid and phosphate ester groups. Examples of useful modified poly(vinyl alcohol) materials include, but are not limited to, sulfonic acid-modified poly(vinyl alcohol), carboxylic acid-modified poly(vinyl alcohol) and quaternary ammonium salt-modified poly(vinyl alcohol), glycol-modified poly(vinyl alcohol) or combinations thereof.

[0104] The optional hydrophilic overcoat may also include crosslinked polymer particles, as described above, having an average particle size of at least 2 μm.

[0105] When present, the hydrophilic protective layer is provided as a hydrophilic protective layer formulation and has a dry coating density of at least 0.1 g / m 2 and 4 g / m 2 Dry coating coverage of less than 0.15 g / m 2 and 2.5 g / m 2 In some embodiments, a dry coating coverage of 0.1 g / m is provided so that the hydrophilic protective layer is relatively thin for easy removal during off-press or on-press development. 2 and as low as 1.5g / m 2 Less than or equal to 0.1 g / m2 and 0.9 g / m 2 The following is the result.

[0106] The hydrophilic protective layer can optionally comprise organic wax particles generally uniformly dispersed within one or more film-forming water-soluble (or hydrophilic) polymeric binders, as described, for example, in U.S. Patent Application Publication No. 2013 / 0323643 (Balbinot et al.).

[0107] Preparation of lithographic printing plate precursor: The lithographic printing plate precursor according to the present invention can be provided in the following manner. The infrared radiation-sensitive image recording layer formulation comprising the above-mentioned essential components a), b), c), d), and e), and optional component f), and other optional additions, can be applied to the hydrophilic surface of a suitable aluminum-containing substrate, usually in the form of a continuous web as described above, using any suitable equipment and procedure, such as spin coating, knife coating, gravure coating, die coating, slot coating, bar coating, wire rod coating, roller coating, or extrusion hopper coating. Such a formulation can also be applied onto a suitable substrate by spraying. Typically, once the infrared radiation-sensitive image recording layer formulation is applied at a suitable wet coverage, it is dried by a suitable method known in the art to obtain a desired dry coverage as described below, thereby obtaining an infrared radiation-sensitive continuous web or an infrared radiation-sensitive continuous article.

[0108] As noted above, prior to application of the infrared radiation-sensitive image recording layer formulation, the substrate (i.e., a continuous roll or web) is electrochemically grained and anodized as described above to provide a suitable hydrophilic anodic (aluminum oxide) layer on the outer surface of the aluminum-containing support, and the anodized surface can usually be post-treated with a hydrophilic polymer solution as described above. The conditions and results of these operations are well known in the art as described above.

[0109] The manufacturing process typically involves mixing the various components required for the infrared radiation sensitive image recording layer in a suitable organic solvent or mixtures thereof, with or without water, such as methyl ethyl ketone (2-butanone), methanol, ethanol, 1-methoxy-2-propanol, 2-methoxypropanol, iso-propyl alcohol, acetone, gamma-butyrolactone, n-propanol, tetrahydrofuran and others readily known in the art, 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.

[0110] After proper drying, the dry coverage of the infrared radiation sensitive image recording layer on the substrate is at least 0.1 g / m 2 or at least 0.4 g / m 2 , and 2 g / m 2 Less than or equal to 4g / m 2 Although the dry coverage can be less than or equal to 100%, other dry coverage amounts can be used if desired to provide the desired dry coverage.

[0111] As noted above, in some embodiments, a suitable water-based hydrophilic protective layer formulation (described above) can be applied to the dried infrared radiation-sensitive image-recording layer using known coating and drying conditions, equipment and procedures.

[0112] In practical 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, or having both a single infrared-radiation-sensitive image-recording layer and a hydrophilic protective layer disposed as the outermost layer. Such a continuous radiation-sensitive web can be slit or cut into precursors of appropriate size for use.

[0113] Image formation (exposure) conditions In use, the infrared radiation sensitive lithographic printing plate precursor of the present invention can be exposed to a suitable infrared radiation source according to the infrared radiation absorber present in the infrared radiation sensitive image recording layer.In some embodiments, the lithographic printing plate precursor can be imaged with one or more lasers that emit significant infrared radiation within the range of at least 750nm and 1400nm or less, or at least 800nm ​​and 1250nm or less, to create exposed and unexposed areas in the infrared radiation sensitive image recording layer.Such infrared emitting lasers can be used for such imaging according to digital information provided by a computing device or other digital information source.Laser imaging can be digitally controlled by any suitable method known in the art.

[0114] For example, imaging can be performed using imaging or exposing infrared radiation from an infrared radiation generating laser (or an array of such lasers). Imaging can also be performed using imaging radiation of multiple infrared (or near-IR) wavelengths simultaneously if desired. The laser used to expose the master is typically a diode laser due to the reliability and low maintenance of diode laser systems, although other lasers such as gas or solid state lasers can also be used. Power, intensity and exposure time combinations for infrared radiation imaging will be readily apparent to one skilled in the art.

[0115] The infrared imaging device can be configured as a flatbed recorder or drum recorder, with the infrared radiation sensitive lithographic printing plate precursor attached to the inner or outer cylindrical surface of the drum. Examples of useful imaging devices are available as models of Kodak® Trendsetter platesetters (Eastman Kodak Company) and NEC AMZI Setter X series (NEC Corporation, Japan) that include a laser diode that emits radiation at a wavelength of 830 nm. Other suitable imaging devices include Screen PlateRite 4300 series or 8600 series platesetters (available from Screen USA, Chicago, Illinois) that operate at a wavelength of 810 nm, or thermal CTP platesetters manufactured by Panasonic Corporation (Japan).

[0116] If the infrared radiation sensitive image recording layer is sensitive to the presence of ozone, it may be desirable to include a means for reducing or eliminating ozone in the laser imaging environment. Useful means and systems for doing this are described, for example, in U.S. Patent Application Publication No. 2019 / 0022995 (Igarashi et al.).

[0117] When an infrared radiation imaging source is used, the imaging intensity is at least 30 mJ / cm depending on the sensitivity of the infrared radiation sensitive image recording layer. 2 and 500 mJ / cm 2 or less, typically at least 50 mJ / cm 2 and 300 mJ / cm 2 It could be the following:

[0118] Processing and printing 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-press or on-press to remove the unexposed areas (and any hydrophilic protective layer on 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.

[0119] Off-press development and printing: Processing can be carried out off-press using any suitable developer in one or more successive applications (processing or development steps) of the same or different processing solutions (developers). Such one or more successive processing steps can be carried out for a time sufficient to remove the unexposed areas of the infrared radiation-sensitive image-recording layer to reveal the outermost hydrophilic surface of the substrate, but not long enough to remove a significant amount of the exposed areas that have been hardened within the same layer.

[0120] Prior to such off-press processing, the exposed master may be subjected to a "preheat" process to further harden the exposed areas of the infrared radiation-sensitive image-recording layer. Such optional preheating may generally be carried out at a temperature of at least 60°C and not more than 180°C, using any known process and equipment.

[0121] Following this optional pre-heating, or in lieu of pre-heating, the revealed master can be washed (rinsed) to remove any hydrophilic overcoat present. Such optional washing (or rinsing) can be carried out using any suitable aqueous solution (such as water or an aqueous surfactant solution) at a suitable temperature for a suitable period of time, as would be readily apparent to one skilled in the art.

[0122] Useful developers can be ordinary water or formulated aqueous solutions. Formulated developers can include one or more components selected from surfactants, organic solvents, alkaline agents, and surface protectants. For example, useful organic solvents include reaction products of phenols with ethylene oxide and propylene oxide, such as 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, such as 2-ethylethanol and 2-butoxyethanol.

[0123] In some instances, the aqueous processing solution can be used off-press to both develop the imaging master by removing the unexposed areas, and to provide a protective layer or coating over the entire imaged and developed (processed) master printing surface. In this embodiment, the aqueous solution acts like a rubber that can somewhat protect (or "gumming") the lithographic image on the lithographic printing plate from contamination or damage (e.g., from oxidation, fingerprints, dust or scratches).

[0124] After off-press processing and optional drying as described, the resulting lithographic printing plate can be mounted on a printing press without contact with additional solutions or liquids. It is optional to further bake the lithographic printing plate, with or without a blanket or flood-wise exposure to UV or visible radiation.

[0125] A print can be produced by applying lithographic ink and fountain solution to the printing surface of the lithographic printing plate in a suitable manner. The fountain solution is incorporated into the hydrophilic surface of the substrate revealed by the exposure and treatment steps, and the lithographic ink is incorporated into the remaining (exposed) areas of the infrared radiation-sensitive image-recording layer. The lithographic ink is then transferred to a suitable receiving material (such as cloth, paper, metal, glass or plastic) to provide the desired impression of the image thereon. If desired, an intermediate "blanket" roller can be used to transfer the lithographic ink from the lithographic printing plate to the receiving material (e.g., paper).

[0126] On-press development and printing: Alternatively, the negative-working lithographic printing plate precursor of the present invention can be developed on-press using lithographic ink, fountain solution, or a combination of lithographic ink and fountain solution. In such an embodiment, the image-forming (exposed) infrared radiation-sensitive lithographic printing plate precursor of the present invention is mounted on a printing press and the printing run is started. The unexposed areas of the infrared radiation-sensitive image-recording layer are removed by a suitable fountain solution, lithographic ink, or a combination of both when the first print is made. Typical components of the aqueous fountain solution include pH buffers, desensitizers, surfactants and wetting agents, humectants, low boiling solvents, biocides, defoamers, and sequestering agents. A representative example of a fountain solution is Varn Litho Etch 142W+Varn PAR (alcohol sub) (available from Varn International, Addison, IL).

[0127] In a typical press start-up using a sheet-fed press, the dampening rollers are first engaged and dampening solution is applied to the mounted imaging master to swell the exposed infrared radiation sensitive image recording layer at least in the unexposed areas. After several revolutions, the inking rollers are engaged and lithographic ink is applied to cover the entire printing surface of the lithographic printing plate. Typically, within 5 to 20 revolutions after the inking rollers are engaged, the printing sheet is fed to use the ink-dampening solution emulsion formed 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.

[0128] On-press developability of infrared radiation-exposed lithographic printing masters is particularly useful when the master comprises one or more polymeric binder materials (whether free-radically polymerizable or not) in the infrared radiation-sensitive image-recording layer, and at least one of the polymeric binders is present as particles having an average diameter of at least 50 nm and no greater than 400 nm.

[0129] The present invention provides at least the following embodiments and combinations thereof, however, as one of ordinary skill in the art will recognize from the teachings of this disclosure, other combinations of features are contemplated to be within the scope of the present invention: 1. A lithographic printing plate precursor comprising a substrate and an infrared radiation-sensitive image recording layer disposed on the substrate, the infrared radiation-sensitive image recording layer comprising: a) a free radically polymerizable component; b) an infrared radiation absorber; c) an initiator composition capable of generating free radicals; d) with a borate compound; e) a compound capable of forming a colored boronic acid complex during or after exposure of the infrared radiation sensitive image recording layer to infrared radiation; Including, The borate compound has the following structure (I): B - (R 1 )(R 2 )(R 3 )(R 4 )Z + (I) (In the formula, R 1 , R 2 , R 3 , and R 4 independently represent an optionally substituted alkyl, aryl, alkenyl, alkynyl, cycloalkyl, or heterocyclic group bonded to the boron atom of the borate anion; or R 1 , R 2 , R 3 , and R 4two or more of are joined to form a heterocyclic ring containing a boron atom, said heterocyclic ring having up to seven carbon, nitrogen, oxygen, or sulfur atoms; Z + is a cation that balances the charge of the borate anion. A lithographic printing plate precursor represented by:

[0130] 2.e) Compounds capable of forming colored boronic acid complexes are represented by the following substructures (II), (III), and (IV): [ka] 2. The lithographic printing plate precursor according to embodiment 1, comprising one or more occurrences of one or more of:

[0131] 3. The lithographic printing plate precursor according to embodiment 1 or 2, wherein the infrared radiation-sensitive image-recording layer further comprises one or more f) non-free-radically polymerizable polymeric materials different from the a), b), c), d) and e) components defined above.

[0132] 4. The lithographic printing plate precursor according to embodiment 3, wherein the one or more f) non-free-radically polymerizable polymeric materials are present in particle form.

[0133] 5.c) The lithographic printing plate precursor according to any of embodiments 1 to 4, wherein the initiator composition comprises at least one onium salt capable of generating free radicals.

[0134] 6. The lithographic printing plate precursor according to embodiment 5, wherein the onium salt is a diaryliodonium salt.

[0135] 7.d) The lithographic printing plate precursor according to embodiment 5 or 6, wherein a borate compound and at least one onium salt are used as common salt compounds.

[0136] 8. The lithographic printing plate precursor according to any of embodiments 1 to 7, 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.

[0137] 9.d) The lithographic printing plate precursor according to any one of embodiments 1 to 8, wherein the borate compound is present in the infrared radiation sensitive image recording layer in an amount of at least 0.5% by weight and no more than 20% by weight, based on the total dry coverage of the infrared radiation sensitive image recording layer.

[0138] 10.e) The lithographic printing plate precursor according to any of embodiments 1 to 9, wherein the compound capable of forming a colored boronic acid complex is present in the infrared radiation-sensitive image-recording layer at a dry coverage of at least 0.5% by weight and no more than 20% by weight.

[0139] 11. The lithographic printing plate precursor according to any of embodiments 1 to 10, wherein the molar ratio of d) the borate compound and e) the compound capable of forming a colored boronic acid complex is at least 0.05:1 and not more than 20:1.

[0140] 12. The lithographic printing plate precursor according to any one of embodiments 1 to 11, wherein the infrared radiation-sensitive image-recording layer is the outermost layer.

[0141] 13. The lithographic printing plate precursor according to any one of embodiments 1 to 12, wherein the infrared radiation-sensitive image-recording layer comprises at least two a) free-radically polymerizable components.

[0142] 14. The lithographic printing plate precursor according to any of embodiments 1 to 13, wherein the substrate comprises an aluminum-containing substrate comprising an aluminum oxide layer and a hydrophilic polymer coating disposed on the aluminum oxide layer.

[0143] 15.e) A lithographic printing plate precursor according to any of embodiments 2 to 14, wherein the compound capable of forming a coloured boronic acid complex comprises one or more occurrences of moiety (III).

[0144] 16.e) A compound capable of forming a colored boronic acid complex has the following structure (V): [ka] wherein Ar1 and Ar2 are independently a substituted or unsubstituted carbocyclic aromatic group or a substituted or unsubstituted heteroaromatic group; m and n are independently 0, 1, 2, or 3. 16. The lithographic printing plate precursor according to embodiment 15, represented by:

[0145] 17.e) A compound capable of forming a colored boronic acid complex has the following structure (VI): [ka] (wherein R1 and R2 are independently a substituent selected from the group consisting of hydroxy, halogen, alkyl, alkoxy, alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyl, aryl, aryloxy, nitro, amino, alkylamino, dialkylamino, arylamino, diarylamino, and acetylamino groups, which are located at any of the ortho, meta, and para positions of the benzene ring to which they are attached; m and n are independently 0, 1, 2, or 3; and p and q are independently 0 to 5.) 17. The lithographic printing plate precursor according to embodiment 15 or 16, represented by:

[0146] 18.e) A compound capable of forming a colored boronic acid complex is the following compound: [ka] [ka] [ka] [ka] 18. The lithographic printing plate precursor according to any one of embodiments 15 to 17, comprising one or more of:

[0147] 19. The lithographic printing plate precursor according to any of embodiments 1 to 18, wherein the infrared radiation-sensitive image-recording layer further comprises one or more acid-sensitive dye precursors.

[0148] 20.d) The lithographic printing plate precursor according to any one of embodiments 1 to 19, wherein the borate compound is a tetraarylborate or a triarylalkylborate.

[0149] 21. A method for providing a lithographic printing plate, comprising the steps of: A) imagewise exposing the lithographic printing plate precursor according to any one of embodiments 1 to 20 to infrared radiation to obtain exposed and unexposed areas in the infrared radiation sensitive image recording layer; B) removing the unexposed areas of the infrared radiation sensitive image recording layer from the substrate; The method includes:

[0150] 22. The method of embodiment 21, comprising the step of 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.

[0151] The following examples are provided to further illustrate the practice of the present invention and are not intended to be limiting in any way. Unless otherwise indicated, materials used in the examples were obtained from various commercial sources as indicated, although other commercial sources may also be available.

[0152] Inventive and Comparative Examples An aluminum-containing substrate was prepared for use as a lithographic printing plate precursor in the following manner: The surface of the aluminum alloy sheet (support) was subjected to electrolytic roughening treatment using hydrochloric acid to obtain an average roughness Ra of 0.5 μm. The resulting grained aluminum sheet was subjected to anodizing treatment using an aqueous phosphoric acid solution to obtain an average roughness Ra of 2.5 g / m 2An aluminum oxide layer with a dry coverage was formed, followed by post-coating with a poly(acrylic acid) solution to obtain an aluminum-containing substrate.

[0153] Then, for each of the invention master plate and the comparative master plate described below, a negative infrared radiation-sensitive image recording layer was formed on the aluminum-containing substrate by individually coating an infrared radiation-sensitive composition formulation having the components shown in Table I below using a bar coater, and after drying at 50° C. for 60 seconds, the dry coating weight was 0.9 g / m 2 The raw materials listed in Table I are identified below in Table II. These materials can be obtained from one or more commercial sources of chemicals or can be prepared using known synthetic methods.

[0154] [Table 1]

[0155] [Table 2]

[0156] [Table 3]

[0157] [Table 4]

[0158] Table III below shows e) compounds capable of forming colored boronic acid complexes on exposure to infrared radiation, their amounts, the amount of leuco dye 1, and borate compounds used in various inventive and comparative examples of negative-working lithographic printing plate precursors.

[0159] [Table 5]

[0160] [Table 6]

[0161] WinCon Red can be obtained from Connect Chemicals.

[0162] Curcumin and pyrocatechol violet were purchased from Sigma Aldrich.

[0163] Each of the invention and comparative lithographic printing plate precursors was evaluated using two tests: "On-press developability" (DOP) and "Printed out image" (PO).

[0164] On-press developability: Each lithographic printing plate precursor was exposed to 120 mJ / cm using a Trendsetter 800 III Quantum TH 1.7 (available from Eastman Kodak Company). 2 On-press developability was evaluated by imagewise exposing the plate precursor at 100° C. for 10 min at 100° C. Each imagewise exposed lithographic printing plate precursor was then mounted on a MAN Roland Favorite 04 press without development (processing). Fountain solution (Varn Supreme 6038) and lithographic printing ink (Gans Cyan) were supplied and lithographic printing was performed. On-press development occurred during printing. Acceptable on-press developability was evaluated by counting the number of printing sheets required to obtain a clean background and given one of the following qualitative values ​​based on the number of printing sheets to achieve a clean background: + Less than 30 sheets of printing paper 0 30-100 sheets of printing paper - Over 100 sheets of printing paper

[0165] Printout Image: Each of the lithographic printing plate precursors was exposed to 150 mJ / cm 2 using a Trendsetter 800 III Quantum TH 1.7 (available from Eastman Kodak Company).2 to obtain exposed and unexposed areas in the negative IR-sensitive imaging layer. For each imagewise exposed lithographic printing plate precursor, the color difference between the exposed and unexposed areas was measured by determining the ΔE value using a Techkon Spectro Dens spectrodensitometer and calculating the Euclidean distance of the measured L*a*b values ​​to give the following qualitative values ​​immediately after exposure and after 1 hour of exposure (storage in the dark):

[0166] Initial Contrast + ΔE > 12 0 ΔE=7-12 - ΔE < 7 Contrast after storage ++ Over 10% increase in initial Delta E + Over 2% increase in initial Delta E 0 + / - 2% of initial Delta E - A decrease of more than 2% - A decrease of more than 10%

[0167] [Table 7]

[0168] As can be seen from the data presented in Table IV, practice of the present invention provides lithographic printing plates with the same level of printout image as currently known methods (see, e.g., Inventive Example 7 vs. Comparative Example 3). The production of printout images using the present invention proceeds via a parallel mechanism and is therefore applicable in addition to currently known methods, thus resulting in improved printout images when used in addition to already known methods (e.g., Inventive Example 1 vs. Comparative Example 2).

[0169] Inventive Examples 5 and 6 demonstrate that a variety of boronic acid compounds can be used to form printout images. From the data obtained in Inventive Example 7, it can be concluded that an iodonium compound is not necessary for printout imaging of colored boronic acid complexes. Data from Inventive Examples 8, 9, and 10 demonstrate that the color-forming effect is not significantly affected by the substitution of the color-forming phenyl ring. Data from Comparative Example 4 demonstrate that the combination of a curcumin derivative and a borate compound is necessary for successful printout imaging, since the absence of a borate compound according to structure (I) resulted in low printout even in the presence of curcumin. Data from Comparative Example 6 show that a d) borate compound according to structure (I) is necessary to generate a reactive boronic acid compound, since the addition of phenylboronic acid, which is outside the scope of structure (I), results in an initially very colorful lithographic printing plate precursor that does not allow for differentiation between infrared radiation-exposed and non-exposed areas.

Claims

1. A substrate; an infrared radiation sensitive image recording layer disposed on said substrate; A lithographic printing plate precursor comprising: said infrared radiation sensitive image recording layer comprising: a) a free radically polymerizable component; b) an infrared radiation absorber; c) an initiator composition capable of generating free radicals; d) a borate compound; e) a compound capable of forming a colored boronic acid complex during or after exposure of the infrared radiation-sensitive image recording layer to infrared radiation; Including, The borate compound has the following structure (I): B － (R 1 )(R 2 )(R 3 )(R 4 )Z ＋ (I) (In the formula, R 1 , R 2 , R 3 , and R 4 independently represent an optionally substituted alkyl, aryl, alkenyl, alkynyl, cycloalkyl, or heterocyclic group bonded to the boron atom of the borate anion; or R 1 , R 2 , R 3 , and R 4 two or more of are joined to form a heterocyclic ring containing a boron atom, said heterocyclic ring having up to seven carbon, nitrogen, oxygen, or sulfur atoms; Z ＋ is a cation that balances the charge of the borate anion. is represented by The compound capable of forming a colored boronic acid complex has the following partial structures (III) and (IV): 【Chemistry 1】 【Chemistry 2】 A lithographic printing plate precursor comprising one or more occurrences of one or more of:

2. 2. The lithographic printing plate precursor according to claim 1, wherein the c) initiator composition comprises at least one onium salt capable of generating free radicals.

3. 3. The lithographic printing plate precursor according to claim 1 or 2, 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.

4. The lithographic printing plate precursor according to any one of claims 1 to 3, wherein the molar ratio of d) the borate compound to e) the compound capable of forming a colored boronic acid complex is at least 0.05:1 and not more than 20:

1.

5. The lithographic printing plate precursor according to any one of claims 1 to 4, wherein the e) compound capable of forming a colored boronic acid complex comprises one or more occurrences of the partial structure (III).

6. e) a compound capable of forming a colored boronic acid complex having the following structure (V): 【Chemistry 3】 (In the formula, Ar 1 and Ar 2 are independently a substituted or unsubstituted carbocyclic aromatic group or a substituted or unsubstituted heteroaromatic group; m and n are independently 0, 1, 2, or 3. The lithographic printing plate precursor according to claim 5, which is represented by:

7. e) a compound capable of forming a colored boronic acid complex having the following structure (VI): 【Chemistry 4】 (In the formula, R 1 and R 2 are independently substituents selected from the group consisting of hydroxy, halogen, alkyl, alkoxy, alkylcarbonyl, alkylcarbonyloxy, alkoxycarbonyl, aryl, aryloxy, nitro, amino, alkylamino, dialkylamino, arylamino, diarylamino, and acetylamino groups, which are located at either the ortho, meta, or para positions of the benzene ring to which they are attached; m and n are independently 0, 1, 2, or 3; and p and q are independently 0 to 5. The lithographic printing plate precursor according to claim 5, which is represented by:

8. The lithographic printing plate precursor according to any one of claims 1 to 7, wherein the infrared radiation-sensitive image-recording layer further comprises one or more acid-sensitive dye precursors.

9. 1. A method for providing a lithographic printing plate, comprising the steps of: A) imagewise exposing the lithographic printing plate precursor according to any one of claims 1 to 8 to infrared radiation to obtain exposed and unexposed areas in the infrared radiation sensitive image recording layer; B) removing the unexposed areas of the infrared radiation sensitive image recording layer from the substrate; The method includes:

Images