JP2018168269A - Color-developing composition, ithographic printing original plate, and plate-making method - Google Patents

Abstract

To provide a color-developing composition that shows excellent color development, and inhibits the temporal fading of a color development body formed theretiwh; a lithographic printing original plate that offers a lithographic printing plate having excellent plate inspectability, on-press developability, and printing durability; and a plate-making method using the lithographic printing original plate.SOLUTION: A color-developing composition contains (A) an infrared absorption dye, and (B) a color-developing compound having a color development precursor site having an electronic acceptor group that can accept an electron from the excited infrared absorption dye and a releasable site. There are also provided a lithographic printing original plate having an image recording layer containing the color-developing composition, and a plate-making method using the lithographic printing original plate.SELECTED DRAWING: None

Description

  The present invention relates to a color forming composition, a lithographic printing plate precursor, and a plate making method.

  In general, a lithographic printing plate is composed of an oleophilic image area that receives ink and a hydrophilic non-image area that receives dampening water in the printing process. Lithographic printing utilizes the property that water and oil-based ink repel each other, so that the oleophilic image area of the lithographic printing plate is dampened with the ink receiving area and the hydrophilic non-image area is dampened with the water receiving area (ink non-receiving area). ), A difference in ink adhesion is caused on the surface of the lithographic printing plate, the ink is applied only to the image area, and then the ink is transferred to a printing medium such as paper for printing.

  At present, in a plate making process for producing a lithographic printing plate from a lithographic printing plate precursor, image exposure is performed by a CTP (computer to plate) technique. That is, image exposure is performed by scanning exposure or the like directly on a lithographic printing plate precursor using a laser or a laser diode without using a lith film.

  On the other hand, due to the growing interest in the global environment, environmental issues related to waste liquids associated with wet processing such as development processing have been highlighted in relation to plate making of lithographic printing plate precursors, and as a result, development processing has been simplified or eliminated. It is oriented. As one simple development process, a method called “on-press development” has been proposed. On-press development is a method in which the lithographic printing plate precursor is subjected to image exposure and then subjected to the conventional wet development treatment, and is directly attached to the printing press, and the non-image portion of the image recording layer is removed at the initial stage of the normal printing process. is there.

  As a pre-process for attaching a lithographic printing plate to a printing machine, generally, an operation (inspection) for inspecting and identifying an image on the lithographic printing plate is performed to check whether the lithographic printing plate has image recording as intended. In particular, in multicolor printing, it is important in printing work that a register mark (register mark) that serves as a registration mark can be identified.

In a lithographic printing plate precursor with a normal development processing step, a colored image is obtained by development processing by coloring the image recording layer, so that the image can be easily confirmed before mounting the lithographic printing plate on a printing press. it can.
However, in the case of an on-press development type or an unprocessed (no development) type lithographic printing plate precursor that does not involve a normal development processing step, an image on the lithographic printing plate precursor is confirmed at the stage of attaching the lithographic printing plate precursor to the printing machine. It is difficult to perform plate inspection sufficiently. Therefore, on-machine development type or non-processed (no development) type lithographic printing plate precursor, a means for confirming an image at the stage of exposure, that is, a so-called printout image in which an exposed area is colored or decolored is formed. It is requested. Furthermore, from the viewpoint of improving workability, it is also important that the colored or erased exposure area does not change even after a lapse of time and the colored or erased state is maintained.

  Patent Document 1 discloses a dye-forming compound having a specific structure, an infrared-absorbing dye having a specific structure, a binder polymer, an onium-based polymerization initiator having a specific structure, and an infrared coloring property containing a polymerizable compound. A curable composition, a lithographic printing plate precursor, and a plate making method are described.

JP 2013-199089 A

The problem to be solved by the present invention is to provide a color forming composition that is excellent in color developability and in which fading with time of the formed color former is suppressed.
Another problem to be solved by the present invention is that it is excellent in visibility due to color development (plate inspection property), can maintain excellent visibility (plate inspection property) over time, and can be developed on-machine. An object of the present invention is to provide a lithographic printing plate precursor that provides a lithographic printing plate excellent in printing durability and a plate making method using the lithographic printing plate precursor.

Means for solving the above problems will be described below.
(1)
A color-forming composition comprising (A) an infrared-absorbing dye, and (B) a color-forming precursor site having an electron-accepting group capable of accepting one electron from the excited infrared-absorbing dye and a color-forming compound having a leaving site .
(2)
The color forming composition according to (1), wherein the color forming compound is a compound represented by the following formula 1.

In Formula 1, the electron accepting group represents a group that can accept one electron from the excited infrared absorbing dye, and the detachable site represents that the chromogenic compound accepts one electron from the excited infrared absorbing dye. This represents a site that is eliminated due to the color development, and the color-forming precursor site represents a site that forms a color-developing material by the elimination of the detachable site.
(3)
The difference (LB) − (LA) between the lowest empty orbital potential (LB) of the chromogenic compound and the lowest empty orbital potential (LA) of the infrared absorbing dye is 1.10 eV or less (1) or ( The color-forming composition as described in 2).
(4)
The color-forming composition according to any one of (1) to (3), wherein the electron-accepting group of the color-forming compound is an onium group.
(5)
The color-forming composition according to (4), wherein the onium group is a pyridinium group represented by the following formula 2.

In Formula 2, R ¹ represents an organic group, R ² represents an alkyl group, Za represents a counter anion that neutralizes charge, and n represents an integer of 0 to 4.
(6)
The color-forming composition according to any one of (1) to (5), wherein the color-forming compound is a compound represented by the following formula 3.

In Formula 3, R ¹ represents an organic group, R ² represents an alkyl group, and L represents a site where the chromogenic compound is eliminated due to accepting one electron from the excited infrared absorbing dye. , R ³ and R ⁴ together with the carbon atom to which they are bonded and the pyridinium group bonded to the carbon atom, represent the sites that form a chromophore due to elimination of the above-mentioned leaving site, and Za represents The counter anion to sum is represented, n represents the integer of 0-4.
(7)
(C) The color-forming composition according to any one of (1) to (6), further containing a binder polymer.
(8)
(D) The color-forming composition according to any one of (1) to (7), further containing a polymerizable compound.
(9)
(F) The color forming composition according to any one of (1) to (8), further comprising an acid color former.
(10)
The color forming composition according to (9), wherein the acid color former is at least one compound selected from a spiropyran compound, a spirooxazine compound, a spirolactone compound, and a spirolactam compound.
(11)
The chromogenic composition according to any one of (1) to (10), wherein the chromophore formed from the chromogenic compound has a maximum absorption wavelength (λmax) in a region of 500 nm to 600 nm.
(12)
A lithographic printing plate precursor having an image recording layer containing the color forming composition according to any one of (1) to (11) on a support.
(13)
The lithographic printing plate precursor as described in (12), wherein the image recording layer further contains a polymer compound in the form of fine particles.
(14)
The lithographic printing plate precursor as described in (12) or (13), wherein the image recording layer further contains a polymerization initiator.
(15)
The lithographic printing plate precursor as described in any one of (12) to (14), which has a protective layer on the image recording layer.
(16)
The lithographic printing plate precursor as described in (15), wherein the protective layer contains an inorganic stratiform compound.
(17)
(12) to (16) The step of performing image exposure with infrared rays on the lithographic printing plate precursor as described in any one of (16) to develop an exposed portion, and printing ink and fountain solution to the lithographic printing plate precursor subjected to image exposure A plate making method including a step of supplying and developing on-press.

According to the present invention, it is possible to provide a color forming composition that is excellent in color developability and that suppresses fading with time of the formed color former.
Further, according to the present invention, a lithographic printing plate precursor providing a lithographic printing plate having excellent plate inspection properties, excellent on-press developability and excellent printing durability, and the lithographic printing plate precursor are used. A plate making method can be provided.

The present invention is described in detail below.
In this specification, regarding the notation of a group in a compound represented by the formula, if it is not substituted or unsubstituted, and the group can further have a substituent, unless otherwise specified, In addition to an unsubstituted group, a group having a substituent is also included. For example, in the formula, if there is a description that “R represents an alkyl group, an aryl group or a heterocyclic group”, “R is an unsubstituted alkyl group, a substituted alkyl group, an unsubstituted aryl group, a substituted aryl group, an unsubstituted group” Represents a heterocyclic group or a substituted heterocyclic group.

[Coloring composition]
The color-forming composition of the present invention comprises (A) an infrared-absorbing dye, and (B) a color-forming precursor site having an electron-accepting group capable of accepting one electron from the excited infrared-absorbing dye and a detachable site. Contains a chemical compound.
The color-forming composition of the present invention is characterized in that it develops color when irradiated with infrared rays. Here, “color development” means that there is almost no absorption in the visible light region (wavelength range of 400 to 750 nm) before infrared irradiation, but absorption occurs in the visible light region by infrared irradiation. In addition, it also includes that the absorption in the low wavelength region becomes longer in the visible light region.

  In the present specification, the “coloring body” means a colored compound formed from the chromogenic compound according to the present invention by a change in the electron conjugated system caused by electron transfer.

  The mechanism by which the color forming composition of the present invention develops color when irradiated with infrared rays is considered as follows. That is, when the color forming composition of the present invention is irradiated with infrared rays, the infrared absorbing dye is excited by absorbing the infrared rays. One electron transfer occurs from the excited infrared absorbing dye to the chromogenic compound having an electron accepting group. Due to this electron transfer, the detachable site is desorbed from the chromophoric compound, and at the same time, the electron conjugated system in the chromogenic precursor site is changed to form a chromophore and color development occurs.

  Regarding the absorption wavelength range of the color former to be formed, from the viewpoint of visibility, the maximum absorption wavelength (λmax) is preferably in the region of 450 to 650 nm, and more preferably in the region of 500 to 600 nm.

In the color-forming composition of the present invention, as described above, when irradiated with infrared rays, the infrared-absorbing dye absorbs infrared rays and is excited. From the excited infrared-absorbing dye, a color-forming compound having an electron-accepting group One feature is that electron transfer of one electron occurs, and due to this electron transfer, the detachable site is detached from the chromophoric compound, and a color former is formed to cause color development.
On the other hand, in the infrared color-forming curable composition described in Patent Document 1, electrons from a dye-forming compound having a specific structure are compared with an infrared-absorbing dye having a specific structure excited by infrared irradiation. It is described that the donation proceeds, which causes degradation of the dye-forming compound and the formation of a dye.
As described above, the coloring mechanism of the present invention is completely different from that of the infrared coloring curing composition described in Patent Document 1. Due to this difference in color development mechanism, the color developable composition of the present invention is superior in electron transfer efficiency to the infrared color developable curable composition described in Patent Document 1, and as a result has excellent color developability.

[Color-forming compound having an electron-accepting group capable of accepting one electron from an excited infrared-absorbing dye and a leaving part]
A chromogenic compound having an electron accepting group capable of accepting one electron from an excited infrared absorbing dye and a chromogenic compound having a detachable moiety (hereinafter simply referred to as “chromogenic compound”) included in the chromogenic composition of the present invention. Is also composed of a color-forming precursor site and a detachable site that form a color-forming body.

  The chromogenic compound is preferably a compound represented by the following formula 1.

  In Formula 1, the electron accepting group represents a group that can accept one electron from the excited infrared absorbing dye, and the detachable site is derived from accepting one electron from the infrared absorbing dye excited by the chromogenic compound. The site | part which detach | desorbs and the color development precursor site | part represents the site | part which forms a color body by detaching | eliminating a detachable site | part.

(Coloring precursor site with electron accepting group that can accept one electron from excited infrared absorbing dye)
The color-forming precursor site having an electron accepting group that can accept one electron from the excited infrared-absorbing dye constituting the color-forming compound (hereinafter also simply referred to as “color-precursor precursor site”) It is a site | part which forms the mother nucleus of a color development body with the electron-accepting group which can accept.

One of the characteristics of the coloring precursor portion is that it has an electron accepting group that can accept one electron from the excited infrared absorbing dye.
The electron-accepting group (hereinafter also simply referred to as “electron-accepting group”) that can accept one electron from the excited infrared-absorbing dye in the coloring precursor site is a group that can accept one electron from the infrared-absorbing dye excited by infrared irradiation. If it is.
An electron-accepting group is a group having a high ability to accept electrons. Here, “high ability to receive electrons” means that when an electron accepting group is regarded as an independent molecule, the energy that one electron enters and stabilizes in the lowest empty orbit of the molecule (maximum electron affinity, EA). ) Is 0 eV or more.

  As the electron accepting group, an onium group is preferable. Examples of the onium group include a pyridinium group, a sulfonium group, an iodonium group, a phosphonium group, and an azinium group.

  The pyridinium group is preferably a group represented by the following formula 2.

In Formula 2, R ¹ represents an organic group, R ² represents an alkyl group, Za represents a counter anion that neutralizes charge, and n represents an integer of 0 to 4.

In Formula 2, examples of the organic group represented by R ¹ include a halogeno group, an alkyl group, an aryl group, a hydroxyl group, and an alkoxy group. A plurality of R ¹ may be connected to form a ring. when n is 2 to 4, plural ^{R 1} may be the same or different. R ¹ is preferably a halogeno group or a case where a plurality of R ¹ are linked to form a condensed ring, and a chloro group, a bromo group or a benzene ring composed of two R ¹ is condensed (as a whole More preferred is the formation of a quinoline ring.

In Formula 2, the alkyl group represented by R ² may be linear, branched or a ring structure. The alkyl group may have a substituent, and preferred examples of the substituent include an alkoxy group and a terminal alkoxy polyalkyleneoxy group.
R ² is preferably an alkyl group having 1 to 12 carbon atoms, more preferably a linear alkyl group having 1 to 12 carbon atoms, and further preferably a linear alkyl group having 1 to 8 carbon atoms. A methyl group or an n-octyl group is particularly preferable.
n is preferably 0-2.

  In Formula 2, the counter anion that neutralizes the charge represented by Za may be any counter anion that neutralizes the charge. Examples of counter anions that neutralize charge include sulfonate ions, carboxylate ions, tetrafluoroborate ions, tetraphenylborate ions, hexafluorophosphate ions, p-toluenesulfonate ions, perchlorate ions, and the like. Hexafluorophosphate ions are particularly preferred. Note that when the electron-accepting group of the chromophoric compound is a pyridinium group represented by Formula 2, Za is not present if the chromophoric compound has a charge-neutral structure throughout the compound.

  Of the onium groups, a pyridinium group is preferred from the viewpoint of accepting one electron from the excited infrared absorbing dye and the stability of the color former formed by elimination of the detachable site. Among these, a pyridinium group represented by Formula 2 is particularly preferable.

  Specific examples of the electron accepting group are given below, but the present invention is not limited thereto. The portion indicated by the wavy line in the formula represents the position where the portion other than the electron accepting group of the coloring precursor site and the carbon atom to which the leaving site is connected are bonded.

  The portion other than the electron-accepting group in the chromogenic precursor site is a portion that mainly forms a chromophore, and specifically, it can form a conjugate with a newly formed double bond by elimination of the detachable site. It is a part that has the property of causing absorption of molecules in the visible light region.

  Specific examples of the portion other than the electron accepting group in the color precursor portion are given below, but the present invention is not limited thereto. The portion indicated by the wavy line in the formula represents the position where the electron accepting group and the leaving site are bonded to the carbon atom to which the electron accepting group and the leaving site are linked.

(Releasable site)
The detachable site constituting the chromogenic compound may be a site that detaches due to accepting one electron from the excited infrared absorbing dye.

  It is considered that homolytic cleavage or heterolytic cleavage occurs in the process of detaching the detachable site from the chromogenic compound. In the case of homolytic cleavage, a polymerization initiating radical is generated, and the polymerization of the polymerizable compound can be promoted. Therefore, in the color forming composition containing the polymerizable compound of the present invention, the polymerization of the polymerizable compound proceeds without using a separate polymerization initiator. In the case of heterolytic cleavage, an anion is generated. Anions can be salts or pigments. Here, the dye indicates that the desorbed anion has absorption in the visible light region and has a function as a colorant.

  Although the specific example of a detachable part is given to the following, this invention is not limited to this. The portion indicated by the wavy line in the formula represents the position where it binds to the coloring precursor site.

  The chromogenic compound is preferably a compound represented by the following formula 3.

In Formula 3, R ¹ represents an organic group, R ² represents an alkyl group, L represents a site that is eliminated due to accepting one electron from the infrared absorbing dye excited by the chromogenic compound, and R ³ and R ⁴ together with the carbon atom to which they are bonded and the pyridinium group bonded to the carbon atom represent a site that forms a chromophore by elimination of the detachable site, and Za is a pair that neutralizes the charge. Represents an anion, and n represents an integer of 0 to 4.

The details of R ¹ , R ² , L, R ³ , R ⁴ , Za and n in Formula 3 are as described above.

  Specific examples of the color forming compound contained in the color forming composition of the present invention are listed below, but the present invention is not limited thereto.

  The content of the chromophoric compound in the chromogenic composition of the present invention is preferably 0.1 to 80% by mass, more preferably 0.5 to 50% by mass, further based on the total solid content of the chromogenic composition. Preferably it is 0.8-30 mass%.

  The color forming compound contained in the color forming composition of the present invention can be synthesized by a known method.

[Infrared absorbing dye]
The infrared-absorbing dye contained in the color-forming composition of the present invention may be any infrared-absorbing dye that has the property of being excited by infrared irradiation and donating one electron to the color-forming compound, and is appropriately selected from known infrared-absorbing dyes Can be used.
The infrared absorbing dye preferably has a maximum absorption in a wavelength range of 750 to 1,400 nm.

As the infrared absorbing pigment, commercially available infrared absorbing dyes and known infrared absorbing dyes described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specifically, infrared rays such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes, etc. Absorbing dyes are mentioned.
Among these dyes, cyanine dyes, squarylium dyes, and pyrylium salts are preferable. Among these, cyanine dyes are preferable, and indolenine cyanine dyes are particularly preferable.

Specific examples of cyanine dyes include compounds described in paragraphs [0017] to [0019] of JP-A No. 2001-133969, paragraph numbers [0016] to [0021] of JP-A No. 2002-023360, JP Compounds described in paragraph Nos. [0012] to [0037] of JP 2002-040638 A, preferably paragraph Nos. [0034] to [0041] of JP 2002-278057 A, paragraph Nos. Of JP 2008-195018 A The compounds described in paragraphs [0035] to [0043] of JP-A-2007-90850 are more preferable.
In addition, compounds described in paragraph Nos. [0008] to [0009] of JP-A No. 5-5005 and paragraph numbers [0022] to [0025] of JP-A No. 2001-222101 can also be preferably used.

  The cyanine dye represented by the following formula 4 is particularly preferable from the viewpoint of improving the color developability of the color developable composition as a whole because it forms a color former by one electron acceptance to the color developable compound.

In Formula 4, R ¹² and R ¹³ each independently represent a hydrogen atom or an alkyl group, R ¹² and R ¹³ may be linked to each other to form a ring, and Ar ¹ and Ar ² are each independently, Represents a group that forms a benzene ring or a naphthalene ring, Y ¹ and Y ² each independently represent an oxygen atom, a sulfur atom, —NR ¹⁰ — or a dialkylmethylene group, and R ¹⁴ and R ¹⁵ each independently represent an alkyl group. R ^{16 to} R ¹⁹ each independently represents a hydrogen atom or an alkyl group, R ¹⁰ represents a hydrogen atom, an alkyl group, or an aryl group, and Za represents a counter ion that neutralizes charges.

In Formula 4, the alkyl group represented by R ^{12 to} R ¹⁹ and R ¹⁰ is preferably an alkyl group having 1 to 30 carbon atoms, more preferably an alkyl group having 1 to 15 carbon atoms, and an alkyl group having 1 to 10 carbon atoms. Groups are more preferred. The alkyl group may be linear, branched or a ring structure.
Specifically, for example, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, hexadecyl group, octadecyl group Group, eicosyl group, isopropyl group, isobutyl group, s-butyl group, t-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclohexyl group, cyclopentyl Group and 2-norbornyl group.
Among the alkyl groups, a methyl group, an ethyl group, a propyl group, or a butyl group is particularly preferable.

  The alkyl group may have a substituent. Examples of substituents include alkoxy groups, aryloxy groups, amino groups, alkylthio groups, arylthio groups, halogeno groups, carboxy groups, carboxylate groups, sulfo groups, sulfonate groups, alkyloxycarbonyl groups, aryloxycarbonyl groups, and Examples include a combination of these.

The aryl group represented by R ¹⁰ is preferably an aryl group having 6 to 30 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms, and still more preferably an aryl group having 6 to 12 carbon atoms.
The aryl group may have a substituent. Examples of substituents include alkyl groups, alkoxy groups, aryloxy groups, amino groups, alkylthio groups, arylthio groups, halogeno groups, carboxy groups, carboxylate groups, sulfo groups, sulfonate groups, alkyloxycarbonyl groups, aryloxycarbonyl groups. And groups combining these.
Specifically, for example, phenyl group, naphthyl group, p-tolyl group, p-chlorophenyl group, p-fluorophenyl group, p-methoxyphenyl group, p-dimethylaminophenyl group, p-methylthiophenyl group, p- A phenylthiophenyl group etc. are mentioned.
Of the aryl groups, a phenyl group, a p-methoxyphenyl group, a p-dimethylaminophenyl group, or a naphthyl group is preferable.

R ¹² and R ¹³ are preferably connected to form a ring. When R ¹² and R ¹³ are linked to form a ring, a 5-membered ring or a 6-membered ring is preferable.

Y ¹ and Y ² each independently represent an oxygen atom, a sulfur atom, —NR ⁰ — or a dialkylmethylene group, preferably —NR ⁰ — or a dialkylmethylene group, and more preferably a dialkylmethylene group.
R ⁰ represents a hydrogen atom, an alkyl group or an aryl group, and an alkyl group is preferable.

R ¹⁴ and R ¹⁵ are preferably the same group.
R ¹⁴ and R ¹⁵ are each independently preferably a linear alkyl group or an alkyl group having a sulfonate group at the terminal, and more preferably a methyl group, an ethyl group or a butyl group having a sulfonate group at the terminal. preferable.
The counter cation of the sulfonate group may be a quaternary ammonium group in Formula 4, or may be an alkali metal cation or an alkaline earth metal cation.

From the viewpoint of improving the water solubility of the compound represented by Formula 4, each of R ¹⁴ and R ¹⁵ is preferably independently an alkyl group having an anion structure, and is an alkyl group having a carboxylate group or a sulfonate group. More preferred is an alkyl group having a sulfonate group at the terminal.
R ¹⁴ and R ¹⁵ are each independently an alkyl group having an aromatic ring from the viewpoint of increasing the maximum absorption wavelength of the compound represented by Formula 4 and from the viewpoint of color developability and printing durability in a lithographic printing plate. The alkyl group having an aromatic ring at the terminal is more preferable, and the 2-phenylethyl group, 2-naphthalenylethyl group, and 2- (9-anthracenyl) ethyl group are particularly preferable.

R ^{16 to} R ¹⁹ each independently represents a hydrogen atom or an alkyl group, and is preferably a hydrogen atom.
Ar ¹ and Ar ² each independently represent a group that forms a benzene ring or a naphthalene ring. A substituent may be present on the benzene ring and naphthalene ring. Examples of the substituent include alkyl group, alkoxy group, aryloxy group, amino group, alkylthio group, arylthio group, halogeno group, carboxy group, carboxylate group, sulfo group, sulfonate group, alkyloxycarbonyl group, aryloxycarbonyl group, and And a group obtained by combining these. As the substituent, an alkyl group is preferable.
Ar ¹ and Ar ² are each independently a naphthalene ring, an alkyl group, or an alkyl group, from the viewpoint of increasing the maximum absorption wavelength of the compound represented by Formula 4 and from the viewpoint of color developability and printing durability in a lithographic printing plate It is preferably a group that forms a benzene ring having an alkoxy group as a substituent, more preferably a naphthalene ring or a group that forms a benzene ring having an alkoxy group as a substituent, such as a naphthalene ring or methoxy. A group that forms a benzene ring having a group as a substituent is particularly preferable.

Za represents a counter ion that neutralizes charge. When an anionic species is indicated, Za represents a sulfonate ion, a carboxylate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a p-toluenesulfonate ion, a perchlorate ion, or the like. And hexafluorophosphate ions are particularly preferred. In the case of indicating a cationic species, alkali metal ions, alkaline earth metal ions, ammonium ions, pyridinium ions or sulfonium ions are preferable, sodium ions, potassium ions, ammonium ions, pyridinium ions or sulfonium ions are more preferable, sodium ions, potassium ions More preferred are ions or ammonium ions.
R ^{12 to} R ¹⁹ , R ¹⁰ , Ar ¹ , Ar ² , Y ¹ and Y ² may have an anion structure or a cation structure, and R ^{12 to} R ¹⁹ , R ¹⁰ , Ar ¹ , Ar ² , If all of Y ¹ and Y ² are charge neutral groups, Za is a monovalent counter anion. For example, R ^{12 to} R ¹⁹ , R ¹⁰ , Ar ¹ , Ar ² , Y ¹ and When Y ² has two or more anion structures, Za can also be a counter cation.

  Specific examples of the infrared absorbing dye contained in the color forming composition of the present invention will be given below, but the present invention is not limited thereto.

Only one infrared absorbing dye may be used, or two or more infrared absorbing dyes may be used in combination. The infrared absorbing dye may be used in combination with an infrared absorbing pigment. As the infrared absorbing pigment, compounds described in paragraph numbers [0072] to [0076] of JP-A-2008-195018 are preferable.
The content of the infrared absorbing dye is preferably 0.05 to 30% by mass, more preferably 0.1 to 20% by mass, and still more preferably 0.2 to 10% by mass with respect to the total solid content of the color forming composition. preferable.

  In the color forming composition of the present invention, the difference (LB) − (LA) between the lowest unoccupied orbital potential (LB) of the color forming compound and the minimum unoccupied orbital potential (LA) of the infrared absorbing dye is 1.10 eV or less. As a result, the electron transfer efficiency from the infrared absorbing dye to the chromogenic compound is further improved. As a result, the formation efficiency of the chromogen and the detachment efficiency of the detachable site are increased, and the chromogenic and lithographic printing plate precursor It is preferable from the viewpoint of improving the printing durability of a lithographic printing plate. The difference (LB) − (LA) between the lowest orbital potential (LB) of the chromophoric compound and the lowest empty orbital potential (LA) of the infrared absorbing dye is preferably smaller in terms of electron transfer efficiency, and is negative. Numerical values can also be taken. The difference (LB) − (LA) between the lowest empty orbital potential (LB) of the chromogenic compound and the lowest empty orbital potential (LA) of the infrared absorbing dye is more preferably 0.30 eV or less.

Calculation of the potential of the lowest empty orbit of the infrared absorbing dye and the chromogenic compound is performed by the following method.
First, the counter anion in the compound to be calculated is ignored.
The structure optimization is performed by DFT (B3LYP / 6-31G (d)) using quantum chemical calculation software Gaussian09.
The molecular orbital energy calculation is performed by DFT (B3LYP / 6-31 + G (d, p) / CPCM (solvent = ethanol)) with the structure obtained by the above structure optimization.
The molecular orbital energy Epre (unit: hartree) obtained by the molecular orbital energy calculation is converted into Eft (unit: eV) used as the value of the lowest empty orbital in the present invention by the following formula.
Eaf = 0.823168 × 27.2114 × Epre−1.07634
Here, 27.2114 is simply a coefficient for converting hartree to eV, 0.823168 and −1.07634 are adjustment coefficients, and the calculated value of the lowest empty orbit of the compound to be calculated is an actual measurement value. It is a coefficient to make it fit.

  Below, the lowest vacant orbital potential (LB) of the chromogenic compound contained in the chromophoric composition of the present invention, the lowest empty orbital potential (LA) of the infrared absorbing dye, and the difference between them (LB) − (LA) Specific examples are described in Table 1. In Table 1, the chromogenic compound and the infrared absorbing dye are indicated using the symbols described in the above specific examples. For example, C-1 represents the chromogenic compound C-1, and D-1 represents the infrared absorbing dye D-1.

  The color forming composition of the present invention can be suitably used for an image recording layer of a lithographic printing plate precursor. Other components will be described below by taking as an example the case where the color forming composition of the present invention is used in the image recording layer of a lithographic printing plate precursor.

[Binder polymer]
The color forming composition of the present invention preferably contains a binder polymer from the viewpoints of coatability and film formability.
The binder polymer is mainly used for the purpose of improving the film strength of the image recording layer. A conventionally well-known thing can be used for a binder polymer, The polymer which has film property is preferable. Of these, acrylic resins, polyvinyl acetal resins, polyurethane resins and the like are preferable.

  As a suitable binder polymer, as described in JP-A-2008-195018, the main chain or the side chain, preferably the side chain, has a crosslinkable functional group for improving the film strength of the image area. Things. Crosslinking is formed between the polymer molecules by the crosslinkable group, and curing is accelerated.

  The crosslinkable functional group is preferably an ethylenically unsaturated group such as a (meth) acryl group, vinyl group, allyl group, or styryl group, or an epoxy group. The crosslinkable functional group is introduced into the polymer by polymer reaction or copolymerization. can do. For example, a reaction between an acrylic polymer or polyurethane having a carboxy group in the side chain and polyurethane and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be used.

  The content of the crosslinkable group in the binder polymer is preferably 0.1 to 10.0 mmol, more preferably 0.25 to 7.0 mmol, and particularly preferably 0.5 to 5.5 mmol per 1 g of the binder polymer. .

  The binder polymer preferably has a hydrophilic group. The hydrophilic group contributes to imparting on-press developability to the image recording layer. In particular, the coexistence of the crosslinkable group and the hydrophilic group makes it possible to achieve both printing durability and on-press developability.

  Examples of the hydrophilic group include a hydroxy group, a carboxy group, an alkylene oxide structure, an amino group, an ammonium group, an amide group, a sulfo group, and a phosphoric acid group. Among them, an alkylene oxide unit having 2 or 3 carbon atoms. An alkylene oxide structure having 1 to 9 is preferable. The hydrophilic group can be imparted to the binder polymer by, for example, copolymerizing a monomer having a hydrophilic group.

  In the binder polymer, an oleophilic group such as an alkyl group, an aryl group, an aralkyl group, and an alkenyl group can be introduced in order to control the inking property. For example, it can be performed by copolymerizing a lipophilic group-containing monomer such as an alkyl methacrylate ester.

  The binder polymer preferably has a mass average molar mass (Mw) of 2000 or more, more preferably 5000 or more, and still more preferably 10,000 to 300,000.

  The content of the binder polymer is suitably from 3 to 90 mass%, preferably from 5 to 80 mass%, more preferably from 10 to 70 mass%, based on the total solid content of the image recording layer.

  Preferable examples of the binder polymer include a polymer compound having a polyoxyalkylene chain in the side chain. By containing a polymer compound having a polyoxyalkylene chain in the side chain (hereinafter also referred to as a specific polymer compound) in the image recording layer, the permeability of the fountain solution is promoted and the on-press developability is improved.

  The resin constituting the main chain of the specific polymer compound includes acrylic resin, polyvinyl acetal resin, polyurethane resin, polyurea resin, polyimide resin, polyamide resin, epoxy resin, methacrylic resin, polystyrene resin, novolac type phenol resin, polyester Examples thereof include resins, synthetic rubbers, and natural rubbers, and acrylic resins are particularly preferable.

The specific polymer compound is substantially free of a perfluoroalkyl group. “Substantially free of perfluoroalkyl group” means that the mass ratio of fluorine atoms present as a perfluoroalkyl group in the polymer compound is less than 0.5% by mass, and preferably does not contain. The mass ratio of fluorine atoms is measured by elemental analysis.
The “perfluoroalkyl group” is a group in which all hydrogen atoms of an alkyl group are substituted with fluorine atoms.

The alkylene oxide (oxyalkylene) in the polyoxyalkylene chain is preferably an alkylene oxide having 2 to 6 carbon atoms, more preferably ethylene oxide (oxyethylene) or propylene oxide (oxypropylene), and still more preferably ethylene oxide.
2-50 are preferable and, as for the repeating number of the alkylene oxide in a polyoxyalkylene chain, ie, a poly (alkylene oxide) site | part, 4-25 are more preferable.
If the number of alkylene oxide repeats is 2 or more, the permeability of the fountain solution is sufficiently improved, and if the number of repeats is 50 or less, the printing durability due to wear does not deteriorate, which is preferable.
About a poly (alkylene oxide) site | part, the structure of Paragraph Nos. [0060]-[0062] of Unexamined-Japanese-Patent No. 2014-104631 is preferable, The content is integrated in this-application specification.

  The specific polymer compound may have crosslinkability in order to improve the film strength of the image area. The specific polymer compound having crosslinkability is described in paragraphs [0063] to [0072] of JP 2014-104631 A, and the contents thereof are incorporated in the present specification.

  The ratio of the repeating unit having a poly (alkylene oxide) moiety to the total repeating units constituting the specific polymer compound is not particularly limited, but is preferably 0.5 to 80 mol%, more preferably 0.5 to 50 mol. %. Specific examples of the specific polymer compound include those described in paragraphs [0075] to [0076] of JP-A-2014-104631, and the contents thereof are incorporated in the present specification.

  As the specific polymer compound, a hydrophilic polymer compound such as polyacrylic acid and polyvinyl alcohol described in JP-A-2008-195018 can be used in combination as necessary. Further, a lipophilic polymer compound and a hydrophilic polymer compound can be used in combination.

  The form of the specific polymer compound in the image recording layer may exist in the form of fine particles, in addition to being present as a binder that serves as a linking function of the image recording layer components. When present in the form of fine particles, the average particle size is in the range of 10 to 1000 nm, preferably in the range of 20 to 300 nm, and particularly preferably in the range of 30 to 120 nm.

  The content of the specific polymer compound is preferably 3 to 90% by mass, more preferably 5 to 80% by mass, based on the total solid content of the image recording layer. Within the range of 3 to 90% by mass, the permeability of the dampening water and the image formability can be more reliably achieved.

  As another preferred example of the binder polymer, a polymer compound having a polyfunctional thiol having 6 or more and 10 or less functions as a nucleus, a polymer chain bonded to the nucleus by a sulfide bond, and the polymer chain having a polymerizable group (Hereinafter also referred to as a star polymer compound). As the star polymer compound, for example, compounds described in JP2012-148555A can be preferably used.

The star-shaped polymer compound has a polymerizable group such as an ethylenically unsaturated bond for improving the film strength of the image portion as described in JP-A-2008-195018, as a main chain or a side chain, preferably a side chain. What has in a chain | strand is mentioned. Crosslinking is formed between the polymer molecules by the polymerizable group, and curing is accelerated.
As the polymerizable group, an ethylenically unsaturated group such as a (meth) acryl group, a vinyl group, an allyl group, or a styryl group, or an epoxy group is preferable, and a (meth) acryl group, a vinyl group, or a styryl group is polymerizable. It is more preferable from the viewpoint, and a (meth) acryl group is particularly preferable. These groups can be introduced into the polymer by polymer reaction or copolymerization. For example, a reaction between a polymer having a carboxy group in the side chain and glycidyl methacrylate, or a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid can be used. These groups may be used in combination.

  The content of the crosslinkable group in the star polymer compound is preferably 0.1 to 10.0 mmol, more preferably 0.25 to 7.0 mmol, most preferably 0.5, per 1 g of the star polymer compound. ~ 5.5 mmol.

  The star polymer compound preferably further has a hydrophilic group. The hydrophilic group contributes to imparting on-press developability to the image recording layer. In particular, the coexistence of a polymerizable group and a hydrophilic group makes it possible to achieve both printing durability and developability.

As the hydrophilic group, —SO ₃ M ¹ , —OH, —CONR ¹ R ² (M ¹ represents hydrogen, metal ion, ammonium ion, phosphonium ion, R ¹ and R ² each independently represents a hydrogen atom, , alkyl group, alkenyl group, .R ¹ and ^{R 2} representing an aryl group may be bonded to form a ^{ring), -. N + R 3} R 4 R 5 X - (R 3 ~R 5 is represents an alkyl group having 1 to 8 carbon atoms each independently, X ^- represents a counter anion), a group represented by the following general formula (groups and represented by the general formula 1) (2).

  In the above formula, n and m each independently represent an integer of 1 to 100, and R each independently represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

  Here, when the star-shaped polymer compound is a star-shaped polymer compound having a polyoxyalkylene chain (for example, the group represented by the general formula (1) or (2)) on the side, Such a star polymer compound is also a polymer compound having the polyoxyalkylene chain in the side chain.

Among these hydrophilic groups, —CONR ¹ R ² , a group represented by General Formula (1) and a group represented by General Formula (2) are preferable, and represented by —CONR ¹ R ² and General Formula (1) The group represented by the general formula (1) is particularly preferred. Further, among the groups represented by the general formula (1), n is more preferably 1 to 10, and particularly preferably 1 to 4. R is more preferably a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and particularly preferably a hydrogen atom or a methyl group. Two or more of these hydrophilic groups may be used in combination.

  The star polymer compound preferably has substantially no carboxylic acid group, phosphoric acid group or phosphonic acid group. Specifically, it is preferably less than 0.1 mmol / g, more preferably less than 0.05 mmol / g, and particularly preferably 0.03 mmol / g or less. When these acid groups are less than 0.1 mmol / g, developability is further improved.

  In addition, lipophilic groups such as an alkyl group, an aryl group, an aralkyl group, and an alkenyl group can be introduced into the star polymer compound in order to control the inking property. Specifically, a lipophilic group-containing monomer such as alkyl methacrylate ester may be copolymerized.

  Specific examples of the star polymer compound include compounds described in paragraph numbers [0153] to [0157] of JP-A-2014-104631, and the contents thereof are incorporated in the present specification.

  The star polymer compound can be synthesized by a known method such as radical polymerization of the monomer constituting the polymer chain in the presence of the polyfunctional thiol compound.

  The mass average molar mass (Mw) of the star polymer compound is preferably from 5,000 to 500,000, more preferably from 10,000 to 250,000, and particularly preferably from 20,000 to 150,000. In this range, the on-press developability and printing durability become better.

One type of star polymer compound may be used alone, or two or more types may be mixed and used. Moreover, you may use together with a normal linear binder polymer.
The content of the star polymer compound is preferably 5 to 95% by mass, more preferably 10 to 90% by mass, and particularly preferably 15 to 85% by mass with respect to the total solid content of the image recording layer.
In particular, the star polymer compound described in JP-A-2012-148555 is preferred because the permeability of the fountain solution is promoted and the on-press developability is improved.

(Polymerizable compound)
The color-forming composition of the present invention can contain a polymerizable compound. The color-forming composition of the present invention containing a polymerizable compound is obtained by the polymerization of the polymerizable compound by the action of a polymerization initiating radical generated by the elimination of the detachable site resulting from infrared irradiation. It is done.

  The polymerizable compound is an addition polymerizable compound having at least one ethylenically unsaturated double bond, and is selected from compounds having at least one terminal ethylenically unsaturated bond, preferably two or more. These have chemical forms such as monomers, prepolymers, ie dimers, trimers and oligomers, or mixtures thereof. Specifically, the polymerizable compounds described in paragraphs [0109] to [0113] of JP-A-2014-104631 can be used, the contents of which are incorporated herein.

  Among them, tris (acryloyloxyethyl) isocyanurate, bis (acryloyloxyethyl) hydroxyethyl isocyanurate, etc. are excellent in the balance between the hydrophilicity involved in on-press developability and the polymerization ability involved in printing durability. Isocyanuric acid ethylene oxide modified acrylates are particularly preferred.

  Details of the method of use, such as the structure of the polymerizable compound, whether it is used alone or in combination, and the amount added, can be arbitrarily set according to the performance design of the final lithographic printing plate precursor. The polymerizable compound is preferably used in the range of 5 to 75% by mass, more preferably 10 to 70% by mass, and particularly preferably 15 to 60% by mass with respect to the total solid content of the image recording layer.

[Acid color former]
The color forming composition of the present invention can contain an acid color former. By containing the acid color former, the color developability is further improved.

  The “acid color former” used in the present invention means a compound having a property of developing a color by accepting an electron accepting compound (for example, proton such as acid). As the acid color former, in particular, it has a partial skeleton such as lactone, lactam, sultone, spiropyran, ester, amide, etc., and when it comes into contact with an electron-accepting compound, these partial skeletons rapidly open or cleave. Compounds are preferred.

  Examples of such acid color formers include 3,3-bis (4-dimethylaminophenyl) -6-dimethylaminophthalide (referred to as crystal violet lactone), 3,3-bis (4-dimethylamino). Phenyl) phthalide, 3- (4-dimethylaminophenyl) -3- (4-diethylamino-2-methylphenyl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1,2 -Dimethylindol-3-yl) phthalide, 3- (4-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3,3-bis (1,2-dimethylindol-3-yl) ) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9 Ethylcarbazol-3-yl) -6-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -6-dimethylaminophthalide, 3- (4-dimethylaminophenyl) -3- (1-methylpyrrol-3-yl) -6-dimethylaminophthalide,

  3,3-bis [1,1-bis (4-dimethylaminophenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1,1-bis ( 4-pyrrolidinophenyl) ethylene-2-yl] -4,5,6,7-tetrabromophthalide, 3,3-bis [1- (4-dimethylaminophenyl) -1- (4-methoxyphenyl) Ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3,3-bis [1- (4-pyrrolidinophenyl) -1- (4-methoxyphenyl) ethylene-2-yl] -4,5,6,7-tetrachlorophthalide, 3- [1,1-di (1-ethyl-2-methylindol-3-yl) ethylene-2-yl] -3- (4-diethylaminophenyl) ) Phthalide, 3- [1,1-di (1-ethyl-2-methyl) Indol-3-yl) ethylene-2-yl] -3- (4-N-ethyl-N-phenylaminophenyl) phthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-n- Octyl-2-methylindol-3-yl) -phthalide, 3,3-bis (1-n-octyl-2-methylindol-3-yl) -phthalide, 3- (2-methyl-4-diethylaminophenyl) Phthalides such as -3- (1-n-octyl-2-methylindol-3-yl) -phthalide,

  4,4-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl-leucooramine, N-2,4,5-trichlorophenylleucooramine, rhodamine-B-anilinolactam, rhodamine- (4-nitroanilino ) Lactam, rhodamine-B- (4-chloroanilino) lactam, 3,7-bis (diethylamino) -10-benzoylphenoxazine, benzoylleucomethylene blue, 4-nitrobenzoylmethylene blue,

  3,6-dimethoxyfluorane, 3-dimethylamino-7-methoxyfluorane, 3-diethylamino-6-methoxyfluorane, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-7-chlorofluorane, 3 -Diethylamino-6-methyl-7-chlorofluorane, 3-diethylamino-6,7-dimethylfluorane, 3-N-cyclohexyl-Nn-butylamino-7-methylfluorane, 3-diethylamino-7- Dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-di-n-hexylaminofluorane, 3-diethylamino-7-anilinofluorane, 3-diethylamino-7- ( 2'-fluorophenylamino) fluorane, 3-diethylamino- -(2'-chlorophenylamino) fluorane, 3-diethylamino-7- (3'-chlorophenylamino) fluorane, 3-diethylamino-7- (2 ', 3'-dichlorophenylamino) fluorane, 3-diethylamino-7- ( 3'-trifluoromethylphenylamino) fluorane, 3-di-n-butylamino-7- (2'-fluorophenylamino) fluorane, 3-di-n-butylamino-7- (2'-chlorophenylamino) Fluorane, 3-N-isopentyl-N-ethylamino-7- (2′-chlorophenylamino) fluorane,

  3-Nn-hexyl-N-ethylamino-7- (2'-chlorophenylamino) fluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-di-n-butylamino-6- Chloro-7-anilinofluorane, 3-diethylamino-6-methoxy-7-anilinofluorane, 3-di-n-butylamino-6-ethoxy-7-anilinofluorane, 3-pyrrolidino-6 Methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-morpholino-6-methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7- Anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-di-n-butylamino-6-methyl-7-anilinofluorane, 3-di-n Pentylamino-6-methyl-7-anilinofluorane, 3-N-ethyl-N-methylamino-6-methyl-7-anilinofluorane, 3-Nn-propyl-N-methylamino-6-methyl -7-anilinofluorane, 3-Nn-propyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-Nn-butyl-N-methylamino-6-methyl-7 -Anilinofluorane, 3-Nn-butyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-isobutyl-N-methylamino-6-methyl-7-anilinofluor Oran, 3-N-isobutyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-isopentyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N- n-hexyl N-methylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-N-ethylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-propylamino -6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-butylamino-6-methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-hexylamino-6 -Methyl-7-anilinofluorane, 3-N-cyclohexyl-Nn-octylamino-6-methyl-7-anilinofluorane,

  3-N- (2′-methoxyethyl) -N-methylamino-6-methyl-7-anilinofluorane, 3-N- (2′-methoxyethyl) -N-ethylamino-6-methyl-7 -Anilinofluorane, 3-N- (2'-methoxyethyl) -N-isobutylamino-6-methyl-7-anilinofluorane, 3-N- (2'-ethoxyethyl) -N-methylamino -6-methyl-7-anilinofluorane, 3-N- (2'-ethoxyethyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (3'-methoxypropyl) ) -N-methylamino-6-methyl-7-anilinofluorane, 3-N- (3'-methoxypropyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (3′-Ethoxypropyl) -N-me Ruamino-6-methyl-7-anilinofluorane, 3-N- (3′-ethoxypropyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (2′-tetrahydro Furfuryl) -N-ethylamino-6-methyl-7-anilinofluorane, 3-N- (4′-methylphenyl) -N-ethylamino-6-methyl-7-anilinofluorane, 3- Diethylamino-6-ethyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (3′-methylphenylamino) fluorane, 3-diethylamino-6-methyl-7- (2 ′, 6′- Dimethylphenylamino) fluorane, 3-di-n-butylamino-6-methyl-7- (2 ′, 6′-dimethylphenylamino) fluorane, 3-di-n-butylamino-7- ( ', 6'-dimethylphenylamino) fluorane, 2,2-bis [4'-(3-N-cyclohexyl-N-methylamino-6-methylfluorane) -7-ylaminophenyl] propane, 3- [ Fluoranes such as 4 ′-(4-phenylaminophenyl) aminophenyl] amino-6-methyl-7-chlorofluorane, 3- [4 ′-(dimethylaminophenyl)] amino-5,7-dimethylfluorane ,

  3- (2-Methyl-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-n-propoxycarbonylamino-4-di-n) -Propylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-methylamino-4-di-n-propylaminophenyl) -3- (1 -Ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-methyl-4-di-n-hexylaminophenyl) -3- (1-n-octyl-2-methylindole-3- Yl) -4,7-diazaphthalide, 3,3-bis (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide, 3,3-bis (1-n-octyl-2-methylindole- -Yl) -4-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (2-ethoxy-4) -Diethylaminophenyl) -3- (1-octyl-2-methylindol-3-yl) -4 or 7-azaphthalide, 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2- Methylindol-3-yl) -4 or 7-azaphthalide, 3- (2-hexyloxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4 or 7-azaphthalide 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4 or 7-azaphthalide, 3 (2-butoxy-4-diethylaminophenyl) -3- (1-ethyl-2-phenylindol-3-yl) -4 or 7-azaphthalide 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3 -Phenyl-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho- (3-methoxybenzo) spiropyran, 3-propyl-spiro-dibenzopyran-3,6-bis (dimethylamino) fluorene-9 Phthalides such as -spiro-3 '-(6'-dimethylamino) phthalide, 3,6-bis (diethylamino) fluorene-9-spiro-3'-(6'-dimethylamino) phthalide,

  Others 2'-anilino-6 '-(N-ethyl-N-isopentyl) amino-3'-methylspiro [isobenzofuran-1 (3H), 9'-(9H) xanthen-3-one, 2'-anilino -6 '-(N-ethyl-N- (4-methylphenyl)) amino-3'-methylspiro [isobenzofuran-1 (3H), 9'-(9H) xanthen] -3-one, 3'-N , N-dibenzylamino-6′-N, N-diethylaminospiro [isobenzofuran-1 (3H), 9 ′-(9H) xanthen] -3-one, 2 ′-(N-methyl-N-phenyl) And amino-6 ′-(N-ethyl-N- (4-methylphenyl)) aminospiro [isobenzofuran-1 (3H), 9 ′-(9H) xanthen] -3-one.

The acid color former is preferably at least one compound selected from spiropyran compounds, spirooxazine compounds, spirolactone compounds and spirolactam compounds.
The hue of the dye after color development is preferably green, blue or black from the viewpoint of visibility.

  It is also possible to use commercially available products as acid color formers, such as ETAC, RED500, RED520, CVL, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, BLUE220, H -3035, BLUE203, ATP, H-1046, H-2114 (Fukui Yamada Chemical Co., Ltd.), ORANGE-DCF, Vermilion-DCF, PINK-DCF, RED-DCF, BLMB, CVL, GREEN-DCF TH-107 (above, manufactured by Hodogaya Chemical Co., Ltd.), ODB, ODB-2, ODB-4, ODB-250, ODB-BlackXV, Blue-63, Blue-502, GN-169, GN-2, Green -118, Red-40, Red-8 (manufactured by Yamamoto Chemicals Co., Ltd.), crystal violet lactone (manufactured by Tokyo Chemicals Industry Co., Ltd.), and the like. Among these commercial products, ETAC, S-205, BLACK305, BLACK400, BLACK100, BLACK500, H-7001, GREEN300, NIRBLACK78, H-3035, ATP, H-1046, H-2114, GREEN-DCF, Blue-63 , GN-169, and crystal violet lactone are preferable because the formed film has good visible light absorption.

These acid color formers may be used alone or in combination of two or more components.
The content of the acid color former is preferably from 0.1 to 20 mass%, more preferably from 1 to 15 mass%, still more preferably from 2 to 10 mass%, based on the total solid content of the image recording layer.

[Lithographic printing plate precursor]
The planographic printing plate precursor of the present invention has an image recording layer containing the color forming composition of the present invention on a support. The planographic printing plate precursor may have an undercoat layer between the support and the image recording layer and a protective layer on the image recording layer, if necessary.

(Image recording layer)
The image recording layer of the lithographic printing plate precursor is preferably an image recording layer whose non-image area is removed by at least one of acidic to alkaline dampening water and printing ink on a printing press.
According to one embodiment, the image recording layer contains an infrared absorbing dye, a color forming compound, a polymerizable compound, and a binder polymer.
According to another embodiment, the image recording layer contains an infrared absorbing dye, a color forming compound, a polymerizable compound, and a polymer compound in the form of fine particles.

(High molecular compound in the form of fine particles)
The image recording layer of the lithographic printing plate precursor can contain a polymer compound in the form of fine particles. The polymer compound in the form of fine particles is selected from hydrophobic thermoplastic polymer fine particles, thermally reactive polymer fine particles, polymer fine particles having a polymerizable group, microcapsules enclosing a hydrophobic compound, and microgel (crosslinked polymer fine particles). It is preferable. Among these, polymer fine particles and microgels having a polymerizable group are preferable. In a particularly preferred embodiment, the particulate polymeric compound comprises at least one ethylenically unsaturated polymerizable group. Due to the presence of such a polymer compound in the form of fine particles, the effect of improving the printing durability of the exposed portion and the on-press developability of the unexposed portion can be obtained.

Hydrophobic thermoplastic polymer fine particles include Research Disclosure No. 1 of January 1992. 33303, hydrophobic thermoplastic polymer fine particles described in JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250 and European Patent No. 931647 are preferable. .
Specific examples of the polymer constituting the hydrophobic thermoplastic polymer fine particle include ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinyl carbazole, polyalkylene structure Mention may be made of homopolymers or copolymers of monomers such as acrylates or methacrylates or mixtures thereof. Preferable examples include a copolymer containing polystyrene, styrene and acrylonitrile, and polymethyl methacrylate. The average particle size of the hydrophobic thermoplastic polymer fine particles is preferably 0.01 to 3.0 μm.

  Examples of the heat-reactive polymer fine particles include polymer fine particles having a heat-reactive group. The thermoreactive polymer fine particles form a hydrophobized region by crosslinking by a thermal reaction and a functional group change at that time.

  The thermally reactive group in the polymer fine particles having a thermally reactive group may be any functional group that performs any reaction as long as a chemical bond is formed, but is preferably a polymerizable group. Ethylenically unsaturated group (for example, acryloyl group, methacryloyl group, vinyl group, allyl group, etc.), cationic polymerizable group (for example, vinyl group, vinyloxy group, epoxy group, oxetanyl group, etc.), addition reaction for radical polymerization reaction An isocyanate group or a block thereof, an epoxy group, a vinyloxy group and a functional group having an active hydrogen atom as a reaction partner thereof (for example, an amino group, a hydroxy group, a carboxy group, etc.), a carboxy group that performs a condensation reaction, and Hydroxy group or amino group that is the reaction partner, acid anhydride that performs the ring-opening addition reaction, and amino acid that is the reaction partner And a group or hydroxy group are preferably exemplified.

  As the microcapsule, for example, as described in JP-A Nos. 2001-277740 and 2001-277742, at least a part of the constituent components of the image recording layer is encapsulated in the microcapsule. The constituent components of the image recording layer can also be contained outside the microcapsules. The image recording layer containing a microcapsule is preferably configured so that a hydrophobic constituent component is encapsulated in the microcapsule and a hydrophilic constituent component is contained outside the microcapsule.

  The microgel (crosslinked polymer fine particles) can contain a part of the constituent components of the image recording layer on at least one of the surface or the inside thereof. In particular, a reactive microgel having a radical polymerizable group on its surface is preferable from the viewpoint of image forming sensitivity and printing durability.

  A known method can be applied to microencapsulate or microgel the constituent components of the image recording layer.

  The average particle size of the polymer compound in the form of fine particles is preferably 0.01 to 3.0 μm, more preferably 0.03 to 2.0 μm, and still more preferably 0.10 to 1.0 μm. In this range, good resolution and stability over time can be obtained.

  The content of the polymer compound in the form of fine particles is preferably 5 to 90% by mass based on the total solid content of the image recording layer.

(Polymerization initiator)
When the lithographic printing plate precursor according to the invention is required to have particularly high printing durability, the image recording layer can contain a polymerization initiator.

The polymerization initiator is a compound that initiates and accelerates the polymerization of the polymerizable compound. The polymerization initiator is a compound that generates polymerization initiation species such as radicals and cations by energy of light, heat, or both, and is a known thermal polymerization initiator, a compound having a bond with a small bond dissociation energy, a photopolymerization initiator. It can select suitably from etc. and can be used. As the polymerization initiator, a radical polymerization initiator is preferable.
Examples of the radical polymerization initiator include organic halides, carbonyl compounds, azo compounds, organic peroxides, metallocene compounds, azide compounds, hexaarylbiimidazole compounds, disulfone compounds, oxime ester compounds, and onium salt compounds. It is done.

As the organic halide, for example, compounds described in paragraphs 0022 to 0023 of JP-A-2008-195018 are preferable.
As the carbonyl compound, for example, compounds described in paragraph 0024 of JP-A-2008-195018 are preferable.
Examples of the azo compound include azo compounds described in JP-A-8-108621.
As the organic peroxide, for example, compounds described in paragraph 0025 of JP-A-2008-195018 are preferable.
As the metallocene compound, for example, compounds described in paragraph 0026 of JP-A-2008-195018 are preferable.
Examples of the azide compound include compounds such as 2,6-bis (4-azidobenzylidene) -4-methylcyclohexanone.
As the hexaarylbiimidazole compound, for example, a compound described in paragraph 0027 of JP2008-195018A is preferable.
Examples of the disulfone compound include compounds described in JP-A Nos. 61-166544 and 2002-328465.
As the oxime ester compound, for example, compounds described in paragraphs 0028 to 0030 of JP-A-2008-195018 are preferable.

  Among the polymerization initiators, preferred compounds include onium salts, especially iodonium salts and sulfonium salts. Preferred specific compounds among the respective salts are the same as the compounds described in paragraphs [0104] to [0106] of JP-A-2014-104631, the contents of which are incorporated herein.

  The content of the polymerization initiator is preferably from 0.1 to 50 mass%, more preferably from 0.5 to 30 mass%, particularly preferably from 0.8 to 20 mass%, based on the total solid content of the image recording layer. Within this range, better sensitivity and better stain resistance of the non-image area during printing can be obtained.

(Radical generation aid)
The image recording layer of the lithographic printing plate precursor may contain a radical generation aid. The radical generation aid contributes to improving the printing durability of a lithographic printing plate produced from the lithographic printing plate precursor. Examples of radical generation aids include the following five types.
(I) Alkyl or aryl art complex: It is considered that a carbon-hetero bond is oxidatively cleaved to generate an active radical. Specific examples include borate compounds.
(Ii) Aminoacetic acid compound: It is considered that the C—X bond on carbon adjacent to nitrogen is cleaved by oxidation to generate an active radical. X is preferably a hydrogen atom, a carboxy group, a trimethylsilyl group or a benzyl group. Specific examples include N-phenylglycines (which may have a substituent on the phenyl group), N-phenyliminodiacetic acid (which may have a substituent on the phenyl group), and the like. It is done.
(Iii) Sulfur-containing compound: A compound obtained by replacing the nitrogen atom of the above-mentioned aminoacetic acid compound with a sulfur atom can generate an active radical by the same action. Specific examples include phenylthioacetic acid (which may have a substituent on the phenyl group).
(Iv) Tin-containing compound: A compound in which the nitrogen atom of the above-mentioned aminoacetic acid compound is replaced with a tin atom can generate an active radical by the same action.
(V) Sulfinic acid salts: An active radical can be generated by oxidation. Specific examples include arylsulfin sodium.

Of the radical generation aids, borate compounds are preferred. As the borate compound, a tetraaryl borate compound or a monoalkyltriaryl borate compound is preferable, and from the viewpoint of compound stability, a tetraaryl borate compound is more preferable.
The counter cation possessed by the borate compound is preferably an alkali metal ion or a tetraalkylammonium ion, more preferably a sodium ion, a potassium ion or a tetrabutylammonium ion.

Specific examples of the borate compound include the following compounds. Here, X _c ⁺ represents a monovalent cation, preferably an alkali metal ion or a tetraalkylammonium ion, and more preferably an alkali metal ion or a tetrabutylammonium ion. Bu represents an n-butyl group.

The radical generation assistant may be used alone or in combination of two or more.
The content of the radical generation aid is preferably 0.01 to 30% by mass, more preferably 0.05 to 25% by mass, and 0.1 to 20% by mass in the total solid content of the image recording layer of the present invention. Further preferred.

(Other ingredients)
The image recording layer can contain other components described below as required.

(1) Low molecular weight hydrophilic compound The image recording layer may contain a low molecular weight hydrophilic compound in order to improve the on-press developability without reducing the printing durability.
As the low molecular weight hydrophilic compound, for example, as the water-soluble organic compound, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol and the like glycols and ether or ester derivatives thereof, glycerin, Polyols such as pentaerythritol and tris (2-hydroxyethyl) isocyanurate, organic amines such as triethanolamine, diethanolamine and monoethanolamine and salts thereof, organic sulfones such as alkylsulfonic acid, toluenesulfonic acid and benzenesulfonic acid Acids and salts thereof, organic sulfamic acids such as alkylsulfamic acid and salts thereof, organic sulfuric acids such as alkylsulfuric acid and alkylethersulfuric acid and salts thereof, phenylphosphonic acid Organic phosphonic acids and salts thereof, tartaric acid, oxalic acid, citric acid, malic acid, lactic acid, gluconic acid, organic carboxylic acids and salts thereof such as amino acids, betaines, and the like.

  Among these, it is preferable to contain at least one selected from the group of polyols, organic sulfates, organic sulfonates, and betaines.

  Specific examples of the organic sulfonates are described in paragraphs [0026] to [0031] of JP-A-2007-276454 and paragraphs [0020] to [0047] of JP-A-2009-154525. Compound etc. are mentioned. The salt may be a potassium salt or a lithium salt.

  Examples of the organic sulfate include compounds described in paragraphs [0034] to [0038] of JP-A-2007-276454.

  As the betaines, compounds having 1 to 5 carbon atoms of the hydrocarbon substituent on the nitrogen atom are preferable. Specific examples include trimethylammonium acetate, dimethylpropylammonium acetate, 3-hydroxy-4-trimethyl. Ammonioobylate, 4- (1-pyridinio) butyrate, 1-hydroxyethyl-1-imidazolioacetate, trimethylammonium methanesulfonate, dimethylpropylammonium methanesulfonate, 3-trimethylammonio-1-propanesulfonate, Examples include 3- (1-pyridinio) -1-propanesulfonate.

  Since low molecular weight hydrophilic compounds have a small hydrophobic part structure and almost no surface activity, dampening water penetrates into the exposed part of the image recording layer (image part), reducing the hydrophobicity and film strength of the image part. The ink receptivity and printing durability of the image recording layer can be maintained well.

The addition amount of the low molecular weight hydrophilic compound is preferably 0.5 to 20% by mass of the total solid content of the image recording layer. 1-15 mass% is more preferable, and 2-10 mass% is still more preferable. In this range, good on-press developability and printing durability can be obtained.
A compound may be used independently and may be used in mixture of 2 or more types.

(2) Grease Sensitizer A grease sensitizer such as a phosphonium compound, a nitrogen-containing low molecular weight compound, or an ammonium group-containing polymer can be used in the image recording layer in order to improve the inking property. In particular, when an inorganic stratiform compound is contained in the protective layer, these compounds function as a surface coating agent for the inorganic stratiform compound, and have an effect of preventing a decrease in the inking property during printing by the inorganic stratiform compound.

  The phosphonium compound, the nitrogen-containing low molecular weight compound, and the ammonium group-containing polymer are specifically described in paragraph numbers [0184] to [0190] of JP-A-2014-104631, and the contents thereof are incorporated in the present specification. .

  The content of the sensitizer is preferably 0.01 to 30.0% by mass, more preferably 0.1 to 15.0% by mass, and more preferably 1 to 10% by mass with respect to the total solid content of the image recording layer. Further preferred.

(3) Others The image recording layer further contains, as other components, a surfactant, a polymerization inhibitor, a higher fatty acid derivative, a plasticizer, inorganic fine particles, an inorganic layered compound, a co-sensitizer, a chain transfer agent, and the like. be able to. Specifically, paragraph numbers [0114] to [0159] of Japanese Patent Application Laid-Open No. 2008-284817, paragraph numbers [0023] to [0027] of Japanese Patent Application Laid-Open No. 2006-091479, and US Patent Publication No. 2008/0311520. The compound and addition amount described in paragraph [0060] of FIG.

<Formation of image recording layer>
For example, as described in paragraphs [0142] to [0143] of JP-A No. 2008-195018, the image recording layer is prepared by dispersing or dissolving the necessary components in a known solvent to prepare a coating solution. The coating liquid is formed on the support directly or through an undercoat layer by a known method such as bar coater coating and then dried. The image recording layer coating amount (solid content) on the support obtained after coating and drying is usually 0.3 to 3.0 g / m ² , although it varies depending on the application.

  The other components of the planographic printing plate precursor are described below.

(Undercoat layer)
In the lithographic printing plate precursor, an undercoat layer can be provided between the image recording layer and the support, if necessary. The undercoat layer enhances the adhesion between the support and the image recording layer in the exposed area and easily peels from the support of the image recording layer in the unexposed area. Contributes to improving the performance. In the case of infrared laser exposure, the undercoat layer functions as a heat insulating layer, thereby preventing the heat generated by the exposure from diffusing to the support and lowering the sensitivity.

Specific examples of the compound used for the undercoat layer include silane coupling agents having an addition-polymerizable ethylenic double bond reactive group described in JP-A-10-282679, and JP-A-2- Examples thereof include phosphorus compounds having an ethylenic double bond reactive group described in Japanese Patent No. 304441. Preferable examples include polymer compounds having an adsorptive group, a hydrophilic group, and a crosslinkable group that can be adsorbed on the surface of the support, as described in JP-A Nos. 2005-125749 and 2006-188038. It is done. Such a polymer compound is preferably a copolymer of a monomer having an adsorptive group, a monomer having a hydrophilic group, and a monomer having a crosslinkable group. More specifically, a phenolic hydroxyl group, a carboxyl _{group, -PO 3 H 2, -OPO 3} H 2, -CONHSO 2 -, - SO 2 NHSO 2 -, - having an adsorptive group such as COCH 2 COCH ₃ Examples thereof include a copolymer of a monomer, a monomer having a hydrophilic group such as a sulfo group, and a monomer having a polymerizable crosslinkable group such as a methacryl group or an allyl group. The polymer compound may have a crosslinkable group introduced by salt formation between a polar substituent of the polymer compound, a substituent having a counter charge and a compound having an ethylenically unsaturated bond. In addition, monomers other than those described above, preferably hydrophilic monomers, may be further copolymerized.

The content of unsaturated double bonds in the polymer compound for the undercoat layer is preferably 0.1 to 10.0 mmol, more preferably 2.0 to 5.5 mmol, per 1 g of the polymer compound.
The polymer compound for the undercoat layer preferably has a mass average molar mass of 5000 or more, more preferably 10,000 to 300,000.

  In addition to the above compound for the undercoat layer, the undercoat layer is a chelating agent, a secondary or tertiary amine, a polymerization inhibitor, an amino group, or a functional group having a polymerization inhibiting ability and an aluminum support for preventing contamination over time. A compound having a group that interacts with the surface, such as 1,4-diazabicyclo [2,2,2] octane (DABCO), 2,3,5,6-tetrahydroxy-p-quinone, chloranil, sulfophthalic acid , Hydroxyethylethylenediaminetriacetic acid, dihydroxyethylethylenediaminediacetic acid, hydroxyethyliminodiacetic acid, and the like.

The undercoat layer is applied by a known method. The coating amount (solid content) of the undercoat layer is preferably from ^{0.1~100mg / m 2, 1~30mg / m} 2 is more preferable.

[Support]
A known support is used as the support for the lithographic printing plate precursor. Of these, an aluminum plate that has been roughened and anodized by a known method is preferred.
For the aluminum plate, if necessary, the micropore enlargement treatment and sealing treatment of the anodized film described in JP-A-2001-253181 and JP-A-2001-322365, and US Pat. 714,066, 3,181,461, 3,280,734 and 3,902,734, or alkali metal silicates as described in U.S. Pat. , 276,868, No. 4,153,461 and No. 4,689,272, the surface hydrophilization treatment with polyvinylphosphonic acid as described in each specification is appropriately selected and performed. Can do.
The support preferably has a center line average roughness of 0.10 to 1.2 μm.

  A back coat layer containing an organic polymer compound described in JP-A-5-45885 and a silicon alkoxy compound described in JP-A-6-35174 on the back surface of the support, if necessary. Can be provided.

[Protective layer]
In the planographic printing plate precursor, a protective layer can be provided on the image recording layer as necessary. In addition to the function of suppressing the image formation inhibition reaction by blocking oxygen, the protective layer has a function of preventing scratches in the image recording layer and preventing ablation during high-illuminance laser exposure.

The protective layer having such characteristics is described in, for example, US Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729. As the low oxygen permeability polymer used for the protective layer, either a water-soluble polymer or a water-insoluble polymer can be appropriately selected and used, and two or more types can be mixed and used as necessary. it can. Specific examples include polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, water-soluble cellulose derivatives, poly (meth) acrylonitrile, and the like.
As the modified polyvinyl alcohol, acid-modified polyvinyl alcohol having a carboxy group or a sulfo group is preferably used. Specifically, modified polyvinyl alcohols described in JP-A-2005-250216 and JP-A-2006-259137 are preferable.

The protective layer preferably contains an inorganic layered compound in order to enhance oxygen barrier properties. Such an inorganic layered compound is a particle having a thin plate-like shape, for example, mica group such as natural mica and synthetic mica, talc represented by the formula 3MgO · 4SiO · H ₂ O, teniolite, montmorillonite, saponite, Examples include hectorite and zirconium phosphate.
The inorganic layered compound preferably used is a mica compound. Examples of the mica compound include, for example, the general formula: A (B, C) _2-5 D ₄ O ₁₀ (OH, F, O) ₂ [where A is any of K, Na, Ca, and B and C are , Fe (II), Fe (III), Mn, Al, Mg, or V, and D is Si or Al. ] Mica groups such as natural mica and synthetic mica represented by

In the mica group, natural mica includes muscovite, soda mica, phlogopite, biotite, and sericite. Further, as the synthetic mica, non-swelling mica such as fluorine phlogopite mica 3 (AlSi ₃ O ₁₀ ) F ₂ , potassium tetrasilicon mica KMg _2.5 Si ₄ O ₁₀ ) F ₂ , and Na tetrasilicic mica NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ , Na or Li teniolite (Na, Li) Mg ₂ Li (Si ₄ O ₁₀ ) F ₂ , montmorillonite-based Na or Li hectorite (Na, Li) _1/8 Mg _2/5 Li ₁ Swellable mica such as _{/ 8} (Si ₄ O ₁₀ ) F ₂ . Synthetic smectite is also useful.

Of the mica compounds, fluorine-based swellable mica is particularly useful. That is, this swellable synthetic mica has a laminated structure composed of unit crystal lattice layers with a thickness of about 10 to 15 mm, and the intra-lattice metal atom substitution is significantly larger than other clay minerals. As a result, the lattice layer is deficient in positive charge, and in order to compensate for this, cations such as Li ⁺ , Na ⁺ , Ca ²⁺ , and Mg ²⁺ are adsorbed between the layers. The cations present between these layers are called exchangeable cations and exchange with various cations. In particular, when the cation between layers is Li ⁺ or Na ⁺ , the bond between the layered crystal lattices is weak because the ionic radius is small, and the layer swells greatly with water. If shear is applied in this state, it will easily cleave and form a stable sol in water. Swellable synthetic mica has a strong tendency and is particularly preferably used in the present invention.

  The shape of the mica compound is preferably as small as possible from the viewpoint of diffusion control, and the plane size is preferably as long as the smoothness of the coated surface and the transmittance of actinic rays are not impaired. Accordingly, the aspect ratio is 20 or more, preferably 100 or more, particularly preferably 200 or more. The aspect ratio is the ratio of the major axis to the thickness of the particle, and can be measured from, for example, a projection drawing of a micrograph of the particle. The larger the aspect ratio, the greater the effect that can be obtained.

  The average major axis of the mica compound is 0.3 to 20 μm, preferably 0.5 to 10 μm, and particularly preferably 1 to 5 μm. The average thickness of the particles is 0.1 μm or less, preferably 0.05 μm or less, particularly preferably 0.01 μm or less. Specifically, for example, the swellable synthetic mica that is a representative compound has a thickness of 1 to 50 nm and a surface size (major axis) of about 1 to 20 μm.

  0-60 mass% is preferable with respect to the total solid content which comprises a protective layer, and, as for content of an inorganic stratiform compound, 3-50 mass% is more preferable. Even when a plurality of types of mica compounds are used in combination, the total amount of the mica compounds is preferably the above-described mass.

  Further, the protective layer may contain known additives such as a plasticizer for imparting flexibility, a surfactant for improving coating properties, and inorganic fine particles for controlling surface slipperiness. Further, the protective layer can contain the sensitizer described in the description of the image recording layer.

The protective layer is applied by a known method. The coating amount of the protective layer is a coating amount after drying is preferably 0.01 to 10 g / ^{m 2,} more preferably ^{0.02~3g / m 2, 0.02~1g / m} 2 is particularly preferred.

[Plate making method of lithographic printing plate precursor]
The plate making method of the lithographic printing plate precursor according to the present invention is described below. A preferred embodiment of the plate making method of the lithographic printing plate precursor according to the invention includes image exposure and on-press development.

(Image exposure)
The image exposure of the lithographic printing plate precursor can be performed according to the normal image exposure operation of the lithographic printing plate precursor.

Image exposure is performed by laser exposure through a transparent original having a line image, a halftone dot image, or the like, or by laser light scanning using digital data. The wavelength of the light source is preferably 750 to 1400 nm. As a light source of 750 to 1400 nm, a solid laser and a semiconductor laser emitting infrared rays are suitable. Regarding the infrared laser, the output is preferably 100 mW or more, the exposure time per pixel is preferably within 20 microseconds, and the irradiation energy amount is preferably 10 to 300 mJ / cm ² . In order to shorten the exposure time, it is preferable to use a multi-beam laser device. The exposure mechanism may be any of an internal drum system, an external drum system, a flat bed system, and the like. Image exposure can be performed by a conventional method using a plate setter or the like. Alternatively, the exposure may be performed on the printing machine after the planographic printing plate precursor is mounted on the printing machine using a printing machine equipped with an exposure device.
Due to the image exposure using infrared rays, the exposed portion develops color and cures to form an image portion due to the color-forming composition according to the present invention.

(On-machine development)
On-press development of a lithographic printing plate precursor can be performed by a conventional method. That is, when dampening water and printing ink are supplied to the lithographic printing plate precursor subjected to image exposure on a printing machine, the image recording layer cured by exposure has an oleophilic surface in the exposed portion of the image recording layer. A printing ink receiving portion is formed. On the other hand, in the unexposed area, the uncured image recording layer is removed by dissolution or dispersion by the supplied dampening water and / or printing ink, and a hydrophilic surface is exposed in that area. As a result, the fountain solution adheres to the exposed hydrophilic surface, and the printing ink is deposited on the image recording layer in the exposed area and printing is started. The surface of the lithographic printing plate precursor may be supplied first with dampening water or printing ink, but in order to penetrate the dampening water and promote on-machine developability, first supply the dampening water. Is preferred.

  In the lithographic printing plate precursor according to the invention, a lithographic printing plate can be produced by a development treatment using a developer by appropriately selecting a polymer or the like which is a constituent component of the image recording layer. The development process using a developer is at least one selected from the group consisting of an embodiment (also referred to as alkali development) using a developer having a high pH of 14 or less containing an alkali agent, and a surfactant and a water-soluble polymer compound. An embodiment (also referred to as simple development) using a developer having a pH of about 2 to 11 containing a seed compound is included. Alkali development and simple development can be carried out by known methods.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these. In the polymer compound, unless otherwise specified, the molecular weight is a mass average molecular weight (Mw) in terms of polystyrene converted by a gel permeation chromatography (GPC) method, and the ratio of repeating units is a mole percentage. Further, “part” means “part by mass” unless otherwise specified.

Synthesis examples of color forming compounds contained in the color forming composition of the present invention are described below. Other color forming compounds can be synthesized in the same manner by appropriately changing the raw materials, reaction intermediates, and the like.
<Synthesis of chromogenic compound C-12>
A synthesis scheme of the chromogenic compound C-12 is shown below.

3.7 g (19.8 mmol) of di (pyridin-4-yl) methanol (SM-1 above) and 8.0 g (79.2 mmol) of triethylamine were added to 150 ml of CH ₂ Cl ₂ at −5 ° C. The mixture was stirred, and 50 ml of a CH ₂ Cl ₂ solution containing 4.5 g (39.6 mmol) of mesyl chloride (MsCl) was added dropwise. After completion of the dropwise addition, the mixture was stirred for 1 hour, and then separated with a mixture of 250 ml of tert-butyl methyl ether and 250 ml of water. The organic layer was dried over 100 g of magnesium sulfate and filtered, and then the solvent was distilled off under reduced pressure. . After adding 3.0 g (16.1 mmol) and 18.9 g (170 mmol) of CaCl ₂ of the obtained SM-2 to 180 ml of dimethyl sulfoxide, the mixture was reacted at 50 ° C. for 12 hours, and then 600 ml of CH ₂ Cl _2. The organic layer was washed with 1200 ml of water, dried over 100 g of magnesium sulfate and filtered, and then the solvent was distilled off under reduced pressure. 2.0 g (9.76 mmol) of the obtained SM-3, 1.56 g (9.76 mmol) of 2-naphthalenethiol and 1.35 g (9.76 mmol) of potassium carbonate were added to 30 ml of acetonitrile for 30 minutes. After refluxing, the mixture was separated with a mixture of 200 ml of ethyl acetate and 200 ml of water, dried over 100 g of magnesium sulfate, filtered, and then the solvent was distilled off under reduced pressure. 300 mL of a mixture of acetone / hexane (volume ratio 1/2) was added to the obtained solid and allowed to stand for 24 hours. The precipitated crystals were collected by filtration and washed twice with 50 mL of hexane. 1.0 g (3.05 mmol) and 5.0 g (26.8 mmol) of methyl tosylate (MeOTs) of the obtained SM-4 were added to 13 ml of acetone and stirred at room temperature for 8 hours. The precipitated solid was filtered, washed with 500 mL of an ethyl acetate / hexane (volume ratio 2/3) mixed solution, 100 ml of dimethylformamide containing 2 g of KPF ₆ was added, and the mixture was stirred for 10 minutes to dissolve the solid. 300 ml of water was added dropwise, and the precipitated solid was filtered to obtain 0.80 g (1.23 mmol) of chromogenic compound C-12.

[Examples 1 to 18 and Comparative Example 1]
[Preparation of lithographic printing plate precursor]

<Production of support>
In order to remove rolling oil on the surface of an aluminum plate (material JIS A 1050) having a thickness of 0.3 mm, degreasing treatment was performed at 50 ° C. for 30 seconds using a 10 mass% sodium aluminate aqueous solution. After that, the surface of the aluminum plate was grained using three bundled nylon brushes having a bristle diameter of 0.3 mm and a pumice-water suspension (specific gravity 1.1 g / cm ³ ) having a median diameter of 25 μm, and washed thoroughly with water. did. Etching was performed by immersing the aluminum plate in a 25 mass% sodium hydroxide aqueous solution at 45 ° C for 9 seconds, washing with water, and further immersed in a 20 mass% nitric acid aqueous solution at 60 ° C for 20 seconds, followed by washing with water. The etching amount of the grained surface was about 3 g / m ² .

Next, an electrochemical roughening treatment was performed continuously using an alternating voltage of 60 Hz. The electrolytic solution was a 1% by mass aqueous nitric acid solution (containing 0.5% by mass of aluminum ions), and the liquid temperature was 50 ° C. The AC power source waveform is electrochemical roughening treatment using a trapezoidal rectangular wave alternating current with a time ratio TP of 0.8 msec until the current value reaches a peak from zero, a duty ratio of 1: 1, and a trapezoidal rectangular wave alternating current. Went. Ferrite was used for the auxiliary anode. The current density was 30 A / dm ² at the peak current value, and 5% of the current flowing from the power source was shunted to the auxiliary anode. The amount of electricity in nitric acid electrolysis was 175 C / dm ² when the aluminum plate was the anode. Then, water washing by spraying was performed.

Subsequently, nitric acid electrolysis was performed with an aqueous solution of 0.5% by mass of hydrochloric acid (containing 0.5% by mass of aluminum ions) and an electrolytic solution having a liquid temperature of 50 ° C. under the condition of an electric quantity of 50 C / dm ² when the aluminum plate was the anode. Electrochemical roughening treatment was performed in the same manner as above, followed by washing with water by spraying.
Next, a 2.5 g / m ² direct current anodic oxide film with a current density of 15 A / dm ² is formed on the aluminum plate as an electrolyte using a 15 mass% aqueous sulfuric acid solution (containing 0.5 mass% of aluminum ions), washed with water, It dried and the support body A was produced. The average pore diameter (surface average pore diameter) in the surface layer of the anodized film was 10 nm.
The pore diameter in the surface layer of the anodized film is measured by using an ultra-high resolution SEM (S-900 manufactured by Hitachi, Ltd.) and performing a vapor deposition process that imparts conductivity at a relatively low acceleration voltage of 12V. Without applying, the surface was observed at a magnification of 150,000 times, and 50 pores were randomly extracted to obtain an average value. The standard deviation error was ± 10% or less.

Thereafter, in order to ensure the hydrophilicity of the non-image area, the support A was subjected to silicate treatment at 60 ° C. for 10 seconds using a 2.5 mass% No. 3 sodium silicate aqueous solution and washed with water to prepare the support B. . The adhesion amount of Si was 10 mg / m ² . When the center line average roughness (Ra) of the support B was measured using a needle having a diameter of 2 μm, it was 0.51 μm.

  In the production of the support A, a support C was produced in the same manner as the production of the support A, except that the electrolytic solution for forming the DC anodized film was changed to a 22 mass% phosphoric acid aqueous solution. When the average pore diameter (surface average pore diameter) in the surface layer of the anodized film was measured by the same method as described above, it was 25 nm.

Thereafter, in order to ensure the hydrophilicity of the non-image area, the support C was subjected to a silicate treatment at 60 ° C. for 10 seconds using a 2.5 mass% No. 3 sodium silicate aqueous solution, and then washed with water to obtain the support D. Produced. The adhesion amount of Si was 10 mg / m ² . When the center line average roughness (Ra) of the support D was measured using a needle having a diameter of 2 μm, it was 0.52 μm.

<Formation of undercoat layer>
On the support, an undercoat layer coating solution (1) having the following composition was applied so that the dry coating amount was 20 mg / m ² to form an undercoat layer.

<Undercoat layer coating solution (1)>
-Polymer (P-1) [below] 0.18 g
・ Hydroxyethyliminodiacetic acid 0.10g
・ Water 61.40g

  The synthesis method of polymer P-1 is described below.

(Synthesis of Monomer M-1)
To a three-necked flask, 200 parts of Ancamine 1922A (diethylene glycol di (aminopropyl) ether, manufactured by Air Products), 435 parts of distilled water and 410 parts of methanol were added and cooled to 5 ° C. Next, 222.5 parts of benzoic acid and 0.025 part of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO) were added, and 280 parts of methacrylic anhydride were added. The reaction solution was added dropwise so that the internal temperature was 10 ° C. or lower. The reaction solution was stirred at 5 ° C. for 6 hours and then stirred at 25 ° C. for 12 hours, and then 70 parts of phosphoric acid was added to adjust the pH to 3.3. The reaction solution was transferred to a stainless beaker, 3,320 parts of ethyl acetate, 1,120 parts of methyl-tertbutyl ether (MTBE) and 650 parts of distilled water were added, and the mixture was vigorously stirred and allowed to stand. After discarding the upper layer (organic layer), 1,610 parts of ethyl acetate (1.8 L) was added, stirred vigorously and allowed to stand, and the upper layer was discarded. Furthermore, 1,350 parts of ethyl acetate was added, stirred vigorously and allowed to stand, and the upper layer was discarded. Next, 1,190 parts of MTBE was added, and after vigorous stirring, the mixture was allowed to stand and the upper layer was discarded. To the obtained aqueous solution, 0.063 part of 4-OH-TEMPO was added to obtain 12,000 parts of an aqueous solution of monomer M-1 (20.1% by mass in terms of solid content).

(Purification of monomer M-2)
After adding 420 parts of light ester P-1M (2-methacryloylethyl acid phosphate, manufactured by Kyoeisha Chemical Co., Ltd.), 1,050 parts of diethylene glycol dibutyl ether and 1,050 parts of distilled water to a separating funnel, and vigorously stirring Left to stand. After discarding the upper layer, 1,050 parts of diethylene glycol dibutyl ether was added, and the mixture was vigorously stirred and allowed to stand. The upper layer was discarded to obtain 13,000 parts of an aqueous monomer M-2 solution (solid content: 10.5% by mass).

(Synthesis of polymer P-1)
In a three-necked flask, 600.6 parts of distilled water, 33.1 parts of the monomer M-1 aqueous solution and 46.1 parts of the following monomer M-3 were added, and the temperature was raised to 55 ° C. in a nitrogen atmosphere. Next, the following dropping solution 1 was dropped over 2 hours and stirred for 30 minutes, then 3.9 parts of VA-046B (manufactured by Wako Pure Chemical Industries, Ltd.) was added, the temperature was raised to 80 ° C., and 1. Stir for 5 hours. After returning the reaction solution to room temperature (25 ° C., the same applies hereinafter), 175 parts of a 30% by mass aqueous sodium hydroxide solution was added to adjust the pH to 8.3. Next, 0.152 parts of 4-OH-TEMPO was added and the temperature was raised to 53 ° C. 66.0 parts of methacrylic anhydride were added and stirred at 53 ° C. for 3 hours. After returning to room temperature, the reaction solution was transferred to a stainless beaker, 1,800 parts of MTBE was added, the mixture was vigorously stirred and allowed to stand, and the upper layer was discarded. In the same manner, the washing operation with 1,800 parts of MTBE was further repeated twice, and then 1,700 parts of distilled water and 0.212 parts of 4-OH-TEMPO were added to the obtained aqueous layer to obtain a polymer P-1 as a homogeneous solution. 41,000 parts (11.0% in terms of solid content) were obtained. The mass average molecular weight (Mw) in terms of polyethylene glycol converted by gel permeation chromatography (GPC) was 200,000.

Dropping solution 1
-Monomer M-1 aqueous solution 132.4 g
-376.9 g of the above monomer M-2 aqueous solution
Monomer M-3 [above] 184.3 g
・ Blemmer PME4000 (manufactured by NOF Corporation) 15.3g
・ VA-046B (Wako Pure Chemical Industries, Ltd.) 3.9 g
・ Distilled water 717.4g

BLEMMER PME4000: Methoxypolyethyleneglycol methacrylate (Repeating number of oxyethylene units: 90)
VA-046B: 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate

<Formation of Image Recording Layer (1)>
On the undercoat layer, an image recording layer coating liquid (1) having the following composition was bar-coated and oven-dried at 100 ° C. for 60 seconds to form an image recording layer (1) having a dry coating amount of 1.0 g / m ² .
The image recording layer coating solution (1) was prepared by mixing and stirring the following photosensitive solution (1) and microgel solution immediately before coating. In addition, when the color forming compound or infrared absorbing dye to be used contains a borate salt portion in the structure, the borate compound (TPB) was not added.

<Photosensitive solution (1)>
-Binder polymer (1) [below] 0.240 g
Color developing compound (described in Table 2) 0.245g
Infrared absorbing dye (described in Table 2) 0.046g
・ Borate compound (TPB [below]) 0.010 g
・ Polymerizable compound 0.192g
Tris (acryloyloxyethyl) isocyanurate (NK ester A-9300, manufactured by Shin-Nakamura Chemical Co., Ltd.)
・ Low molecular weight hydrophilic compound 0.062g
Tris (2-hydroxyethyl) isocyanurate / low molecular weight hydrophilic compound (1) [below] 0.050 g
・ Fat Sensitizer 0.055g
Phosphonium compound (1) [below]
・ Fat Sensitizer 0.018g
Benzyl-dimethyl-octylammonium ・ PF ₆ salt ・ Sensitizer 0.035 g
Ammonium group-containing polymer (1) [below, reduced specific viscosity 44 ml / g]
・ Fluorine-based surfactant (1) [below] 0.008 g
・ 2-butanone 1.091g
・ 1-methoxy-2-propanol 8.609g

<Microgel solution>
・ Microgel (1) 2.640 g
・ Distilled water 2.425g

  Structures of binder polymer (1), TPB, low molecular weight hydrophilic compound (1), phosphonium compound (1), ammonium group-containing polymer (1) and fluorine-based surfactant (1) used in the photosensitive solution (1) Is shown below. In addition, the number on the lower right of the parenthesis of each structural unit of the following polymer represents a molar ratio.

The preparation method of the microgel (1) used for the said microgel liquid is described below.
<Preparation of polyvalent isocyanate compound (1)>
In a suspension of 17.78 g (80 mmol) of isophorone diisocyanate and 7.35 g (20 mmol) of the following polyphenol compound (1) in ethyl acetate (25.31 g), bismuth tris (2-ethylhexanoate) (Neostan U -600, Nitto Kasei Co., Ltd.) 43 mg was added and stirred. When the exotherm had subsided, the reaction temperature was set to 50 ° C., and the mixture was stirred for 3 hours to obtain an ethyl acetate solution (50 mass%) of the polyvalent isocyanate compound (1).

<Preparation of microgel (1)>
The following oil phase component and aqueous phase component were mixed and emulsified at 12000 rpm for 10 minutes using a homogenizer. After stirring the obtained emulsion at 45 ° C. for 4 hours, 10 mass of 1,8-diazabicyclo [5.4.0] undec-7-ene-octylate (U-CAT SA102, manufactured by San Apro Co., Ltd.) % Aqueous solution (5.20 g) was added, and the mixture was stirred at room temperature for 30 minutes and allowed to stand at 45 ° C. for 24 hours. Distilled water was used to adjust the solid content concentration to 20% by mass to obtain an aqueous dispersion of microgel (1). Using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by HORIBA, Ltd.), the number average particle diameter was measured by the light scattering method to be 0.28 μm.

(Oil phase component)
(Component 1) Ethyl acetate: 12.0 g
(Component 2) An adduct obtained by adding trimethylolpropane (6 mol) and xylene diisocyanate (18 mol), and adding methyl-terminated polyoxyethylene (1 mol, repeating number of oxyethylene units: 90) to this ( 50 mass% ethyl acetate solution, manufactured by Mitsui Chemicals, Inc.): 3.76 g
(Component 3) Polyvalent isocyanate compound (1) (as 50% by mass ethyl acetate solution): 15.0 g
(Component 4) 65 mass% ethyl acetate solution of dipentaerythritol pentaacrylate (SR-399, manufactured by Sartomer): 11.54 g
(Component 5) 10% ethyl acetate solution of sulfonate type surfactant (Pionin A-41-C, Takemoto Yushi Co., Ltd.): 4.42 g

(Aqueous phase component)
Distilled water: 46.87g

<Formation of image recording layer (2)>
On the undercoat layer, an image recording layer coating solution (2) having the following composition was bar coated and oven dried at 70 ° C. for 60 seconds to form an image recording layer (2) having a dry coating amount of 0.6 g / m ² . . In addition, when the color forming compound or infrared absorbing dye to be used contains a borate salt portion in the structure, the borate compound (TPB) was not added.

<Image recording layer coating solution (2)>
Color developing compound (described in Table 2) 0.245g
Infrared absorbing dye (described in Table 2) 0.046g
・ Borate compound (TPB [above]) 0.010 g
・ Polymerizable compound 0.192g
Tris (acryloyloxyethyl) isocyanurate (NK ester A-9300, manufactured by Shin-Nakamura Chemical Co., Ltd.)
-Polymer fine particle aqueous dispersion (1) (22% by mass) [below] 10.0 g
Polymerizable compound (SR-399, manufactured by Sartomer) 1.50 g
・ Mercapto-3-triazole 0.2g
・ Byk 336 (byk Chemie) 0.4g
・ Klucel M (Hercules) 4.8g
・ ELVACITE 4026 (manufactured by Ineos Acrylics) 2.5g
・ N-propanol 55.0g
・ 2-butanone 17.0g

The compounds described under the trade names used in the image recording layer coating solution (2) are as follows.
SR-399: Dipentaerythritol pentaacrylate Byk 336: Modified dimethylpolysiloxane copolymer (25% by mass xylene / methoxypropyl acetate solution)
・ Klucel M: Hydroxypropyl cellulose (2% by mass aqueous solution)
ELVACITE 4026: Hyperbranched polymethyl methacrylate (10% by mass 2-butanone solution)

A method for preparing the polymer fine particle aqueous dispersion (1) used in the image recording layer coating liquid (2) is described below.
<Preparation of aqueous polymer fine particle dispersion (1)>
A four-necked flask is equipped with a stirrer, thermometer, dropping funnel, nitrogen inlet tube, reflux condenser, and introduced with nitrogen gas, deoxygenated, and polyethylene glycol methyl ether methacrylate (PEGMA, average repeating unit of ethylene glycol) Number: 50) 10 g, distilled water 200 g and n-propanol 200 g were added and heated until the internal temperature reached 70 ° C. Next, a premixed mixture of 10 g of styrene (St), 80 g of acrylonitrile (AN) and 0.8 g of 2,2′-azobisisobutyronitrile was added dropwise over 1 hour. After completion of the dropwise addition, the reaction was continued for 5 hours, and then 0.4 g of 2,2′-azobisisobutyronitrile was added to raise the internal temperature to 80 ° C. Subsequently, 0.5 g of 2,2′-azobisisobutyronitrile was added over 6 hours. Polymerization progressed 98% or more on a molar basis at the stage of reaction for a total of 20 hours, and a polymer fine particle aqueous dispersion (1) having a mass ratio of PEGMA / St / AN = 10/10/80 was prepared. Using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by HORIBA, Ltd.), the number average particle diameter was measured by a light scattering method to be 0.15 μm.

<Formation of image recording layer (3)>
On the undercoat layer, an image recording layer coating aqueous solution (3) having the following composition after coating is bar-coated, oven dried at 50 ° C. for 60 seconds, and an image recording layer having a dry coating amount of 0.93 g / m ² ( 3) was formed. In addition, when the chromogenic compound or infrared absorbing dye to be used contains a borate salt site in the structure, the borate compound (TPB) was not used.

<Image recording layer coating solution (3)>
Color developing compound (described in Table 2) 0.245 g / m ²
Infrared absorbing dye (described in Table 2) 0.046 g / m ²
Borate compound (TPB [above]) 0.015 g / m ²
-Polymer fine particle aqueous dispersion (2) [below] 0.693 g / m ²
・ Glascol E15 0.09 g / m ²
(Allied Colloids Manufacturing)
・ ERKOL WX48 / 20 (manufactured by ERKOL) 0.09 g / m ²
・ Zonyl FSO100 (manufactured by DuPont) 0.0075 g / m ²

The compound described in the trade name and the polymer particle aqueous dispersion (2) used in the image recording layer coating aqueous solution (3) are as follows.
・ Glascol E15: Polyacrylic acid ・ ERKOL WX48 / 20: Polyvinyl alcohol / polyvinyl acetate copolymer ・ Zonyl FSO100: Surfactant ・ Polymer fine particle aqueous dispersion (2): Styrene stabilized with an anionic wetting agent / Acrylonitrile copolymer (molar ratio 50/50, average particle size 61 nm, solid content about 20%)

<Formation of image recording layer (4)>
On the undercoat layer, the following image recording layer coating solution (4) was bar coated and oven dried at 100 ° C. for 60 seconds to form an image recording layer (4) having a dry coating amount of 1.0 g / m ² . The image recording layer coating solution (4) was prepared by mixing and stirring the following photosensitive solution (2) and microgel solution immediately before coating. In addition, when the color forming compound or infrared absorbing dye to be used contains a borate salt portion in the structure, the borate compound (TPB) was not added.

<Photosensitive solution (2)>
-Binder polymer (1) [above] 0.240 g
Color developing compound (described in Table 2) 0.245g
Infrared absorbing dye (described in Table 2) 0.023g
・ Borate compound (TPB [above]) 0.057 g
・ Polymerizable compound 0.192g
Tris (acryloyloxyethyl) isocyanurate (NK ester A-9300, manufactured by Shin-Nakamura Chemical Co., Ltd.)
・ Low molecular weight hydrophilic compound 0.062g
Tris (2-hydroxyethyl) isocyanurate / low molecular weight hydrophilic compound (1) [above] 0.050 g
・ Fluorosurfactant (1) [above] 0.008 g
・ Acid color developer [below] 0.029 g
・ 2-butanone 1.091g
・ 1-methoxy-2-propanol 8.609g

<Microgel solution>
Microgel (1) [above] 2.640 g
・ Distilled water 2.425g

  The acid color formers used in the photosensitive solution (2) are as follows.

(CL-1): S-205 (Fukui Yamada Chemical Co., Ltd.)
(CL-2): GN-169 (manufactured by Yamamoto Kasei Co., Ltd.)
(CL-3): Black-XV (manufactured by Yamamoto Kasei Co., Ltd.)
(CL-4): Red-40 (manufactured by Yamamoto Kasei Co., Ltd.)

<Formation of protective layer>
A protective layer coating solution having the following composition was applied onto the image recording layer by bar coating and oven-dried at 120 ° C. for 60 seconds to form a protective layer having a dry coating amount of 0.15 g / m ² .

<Protective layer coating solution>
Inorganic layered compound dispersion (1) [below] 1.5 g
-Polyvinyl alcohol (CKS50, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.,
Modified with sulfonic acid, saponification degree 99 mol% or more, polymerization degree 300) 6 mass% aqueous solution 0.55 g
・ Polyvinyl alcohol (PVA-405, manufactured by Kuraray Co., Ltd.,
Degree of saponification 81.5 mol%, degree of polymerization 500) 6% by weight aqueous solution 0.03 g
・ Surfactant (polyoxyethylene lauryl ether, Emalex 710,
Nippon Emulsion Co., Ltd.) 1% by weight aqueous solution 0.86g
・ Ion-exchanged water 6.0g

A method for preparing the inorganic layered compound dispersion (1) is described below.
<Preparation of inorganic layered compound dispersion (1)>
6.4 g of synthetic mica (Somasif ME-100, manufactured by Co-op Chemical Co., Ltd.) was added to 193.6 g of ion-exchanged water, and dispersed using an homogenizer until the average particle size (laser scattering method) became 3 μm. The aspect ratio of the obtained dispersed particles was 100 or more.

  The lithographic printing plate precursors were prepared by combining the supports A to D and the image recording layers (1) to (4) as shown in Table 2 below. Although a protective layer was formed on the image recording layer (1), no protective layer was formed on the image recording layers (2) to (4).

[Evaluation of planographic printing plate precursor]
Each lithographic printing plate precursor was evaluated for color developability, on-press developability, and printing durability as follows. The evaluation results are shown in Table 2.

(1) Color development The lithographic printing plate precursor was output to a Creo Trendsetter 3244VX equipped with a water-cooled 40W infrared semiconductor laser, the output was 11.7 W, the outer drum rotation speed was 250 rpm, and the resolution was 2,400 dpi (dotper inch, 1 inch = 25.4 mm). The exposure was performed under the following conditions. The exposure was performed in an environment of 25 ° C. and 50% RH.
The color development of the lithographic printing plate precursor was measured immediately after exposure and after storage for 2 hours in a dark place (25 ° C.) after exposure. The measurement was performed by a SCE (regular reflection light removal) method using a spectrocolorimeter CM2600d manufactured by Konica Minolta Co., Ltd. and operation software CM-S100W. The color developability was evaluated by the difference ΔL between the L ^* value of the exposed area and the L ^* value of the unexposed area using the L ^* value (brightness) of the L ^* a ^* b ^* color system. Table 2 shows the numerical values of ΔL. The larger the value of ΔL, the better the color developability. The larger the value of ΔL after 2 hours of exposure (the numerical value described in the column of “color development (after storage for 2 hours)” in the table), the more color fading is suppressed. Further, it can be said that the larger the value of ΔL, the better the plate inspection property.

(2) On-machine developability The lithographic printing plate precursor was exposed under the conditions of an external drum rotation speed of 1000 rpm, a laser output of 70%, and a resolution of 2400 dpi using Fujifilm's Luxel PLASETTER T-6000III equipped with an infrared semiconductor laser. The exposure image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The exposed lithographic printing plate precursor was mounted on the plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Equality-2 (manufactured by FUJIFILM Corporation) / tap water = 2/98 (volume ratio) dampening water and Values-G (N) black ink (manufactured by DIC Graphics Co., Ltd.) Dampening water and ink were supplied by the standard automatic printing start method, and 100 sheets were printed on Tokishi Art Paper (76.5 kg) (Mitsubishi Paper Co., Ltd.) at a printing speed of 10,000 sheets per hour. .
The on-machine development of the unexposed part of the image recording layer on the printing machine was completed, and the number of printing sheets required until the ink was not transferred to the non-image part was measured and evaluated as on-machine developability. The smaller the number, the better the on-press developability.

(3) Printing durability After the on-press developability was evaluated, printing was further continued. As the number of printed sheets increased, the image recording layer gradually worn out, so that the ink density on the printed material decreased. The number of printed sheets was measured until the dot area ratio of the 50% halftone dot on the printed matter was 5% lower than the value measured with the Gretag densitometer, and evaluated as printing durability. .

I-1 ^* : In Example 13 and Comparative Example 1, when forming the image recording layer (1), 0.245 g of a polymerization initiator I-1 (triphenylsulfonium hexafluorophosphate) was added to the photosensitive solution (1). ).

From the results shown in Table 2, the lithographic printing plate precursor having the image recording layer containing the color forming composition containing the color forming compound of the present invention is excellent in color developability, and the formed color former is fading over time. It is suppressed and has excellent plate inspection properties, excellent on-press developability, and excellent printing durability. In contrast, a lithographic printing plate precursor having an image recording layer containing a color-forming composition containing a known compound instead of the color-forming compound of the present invention is inferior in color development, on-press development and printing durability. You can see that

Claims (17)

  (A) Infrared absorbing dye, and (B) a chromophoric composition comprising a chromogenic compound having a chromogenic precursor site having an electron accepting group capable of accepting one electron from the excited infrared absorbing dye and a detachable site. . The color forming composition according to claim 1, wherein the color forming compound is a compound represented by the following formula 1.

In Formula 1, an electron-accepting group represents a group capable of accepting one electron from the excited infrared absorbing dye, and a detachable site represents that the chromogenic compound accepts one electron from the excited infrared absorbing dye. This represents a site that is eliminated due to the color development, and the color-forming precursor site represents a site where a color former is formed by the elimination of the detachable site.   3. The difference (LB) − (LA) between the lowest empty orbital potential (LB) of the chromogenic compound and the lowest empty orbital potential (LA) of the infrared absorbing dye is 1.10 eV or less. The color-forming composition as described in 1.   The color-forming composition according to claim 1, wherein the electron-accepting group of the color-forming compound is an onium group. The color forming composition according to claim 4, wherein the onium group is a pyridinium group represented by the following formula 2.

In Formula 2, R ¹ represents an organic group, R ² represents an alkyl group, Za represents a counter anion that neutralizes charge, and n represents an integer of 0 to 4. The color-forming composition according to claim 1, wherein the color-forming compound is a compound represented by the following formula 3.

In Formula 3, R ¹ represents an organic group, R ² represents an alkyl group, and L represents a site that is released due to the chromogenic compound receiving one electron from the excited infrared absorbing dye. , R ³ and R ⁴ together with the carbon atom to which they are bonded and the pyridinium group bonded to the carbon atom, represent a site that forms a chromophore by the elimination of the detachable site, and Za represents a medium charge. The counter anion to sum is represented, n represents the integer of 0-4.   (C) The color-forming composition according to any one of claims 1 to 6, further comprising a binder polymer.   (D) The color-forming composition according to any one of claims 1 to 7, further comprising a polymerizable compound.   (F) The color-forming composition according to any one of claims 1 to 8, further comprising an acid color former.   The color forming composition according to claim 9, wherein the acid color former is at least one compound selected from a spiropyran compound, a spirooxazine compound, a spirolactone compound, and a spirolactam compound.   The chromogenic composition according to any one of claims 1 to 10, wherein the chromophore formed from the chromophoric compound has a maximum absorption wavelength (λmax) in a range of 500 nm to 600 nm.   A lithographic printing plate precursor having an image recording layer containing the color forming composition according to any one of claims 1 to 11 on a support.   The lithographic printing plate precursor according to claim 12, wherein the image recording layer further contains a polymer compound in the form of fine particles.   The lithographic printing plate precursor according to claim 12 or 13, wherein the image recording layer further contains a polymerization initiator.   The lithographic printing plate precursor as claimed in any one of claims 12 to 14, further comprising a protective layer on the image recording layer.   The lithographic printing plate precursor as claimed in claim 15, wherein the protective layer contains an inorganic stratiform compound. A step of performing image exposure with infrared rays on the lithographic printing plate precursor according to any one of claims 12 to 16 to develop an exposed portion, and supplying printing ink and fountain solution to the lithographic printing plate precursor subjected to image exposure A plate making method including an on-press development process.