JP5286350B2 - Planographic printing plate precursor, plate making method thereof, and planographic printing method thereof - Google Patents

Description

  The present invention relates to a lithographic printing plate precursor, a plate making method thereof, and a lithographic printing method thereof. In particular, the present invention relates to a lithographic printing plate precursor suitably used for a so-called lithographic printing plate precursor capable of direct plate making, which can be directly made from a digital signal from a computer or the like, a plate making method thereof, and a lithographic printing method thereof.

In general, a lithographic printing plate comprises an oleophilic image area that receives ink in the printing process and a hydrophilic non-image area that receives dampening water. Lithographic printing utilizes the property that water and oil-based inks repel each other, so that the oleophilic image area of the lithographic printing plate is the ink receiving area, and the hydrophilic non-image area is dampened with the water receiving area (ink non-receiving area). In this method, a difference in ink adhesion is caused on the surface of the lithographic printing plate, and after ink is applied only to the image area, the ink is transferred to a printing medium such as paper and printed.
In order to produce this lithographic printing plate, conventionally, a lithographic printing plate precursor (PS plate) in which an oleophilic photosensitive resin layer (image recording layer) is provided on a hydrophilic support is used. After exposure through a mask such as a film, development with an alkaline developer is performed to leave the image recording layer corresponding to the image area, and dissolve and remove the unnecessary image recording layer corresponding to the non-image area. And obtained a lithographic printing plate.

  Due to recent advances in this field, lithographic printing plates are now available with CTP (computer to plate) technology. That is, a lithographic printing plate can be obtained by scanning and exposing a lithographic printing plate precursor directly using a laser or a laser diode without a lith film, and developing it.

  Along with the above progress, problems related to the lithographic printing plate precursor have been changed to improvements in image formation characteristics, printing characteristics, physical characteristics and the like corresponding to the CTP technology. In addition, due to increasing interest in the global environment, environmental issues related to waste liquids associated with wet processing such as development processing have been highlighted as another issue related to lithographic printing plate precursors.

For the above environmental problems, simplification and no processing of development or plate making are directed. As one simple plate making method, a method called “on-press development” is performed. That is, after the exposure of the lithographic printing plate precursor, conventional development is not performed, but it is mounted on a printing machine as it is, and unnecessary portions of the image recording layer are removed at the initial stage of a normal printing process.
In addition, as a simple development method, a method called “gum development” in which unnecessary portions of the image recording layer are removed with a finisher or gum solution having a pH close to neutral instead of a conventional highly alkaline developer is also performed. ing.

  In the simplification of the plate making operation as described above, a system using a lithographic printing plate precursor and a light source that can be handled in a bright room or under a yellow light is preferable in terms of ease of work. A solid-state laser such as a semiconductor laser or a YAG laser emitting an infrared ray of 1200 nm is used.

  As the lithographic printing plate precursor capable of on-machine development or gum development, Patent Document 1 and Patent Document 2 describe a lithographic printing plate precursor using a thermoplastic fine particle polymer in an image forming layer and a plate making method. Patent Document 3 and Patent Document 4 describe a lithographic printing plate precursor and a plate making method using a thermoplastic fine particle polymer having a reactive group as an image forming layer. However, these techniques are still insufficient to obtain both good developability and high printing durability.

JP-A-9-123387 JP 2003-255527 A JP 2001-260554 A Japanese Patent Laid-Open No. 2003-316021

  An object of the present invention is to provide a lithographic printing plate precursor, a lithographic printing plate making method, and a lithographic printing method that can achieve both printing durability and developability.

As a result of diligent research, the present inventor has a star shape in which the main chain is branched into three or more in the image recording layer containing the thermoplastic fine particle polymer, and has a hydrophilic side chain in the branched main chain. The above problem could be solved by including a polymer compound (hereinafter also referred to as a star polymer).
[1]
A lithographic plate having an image recording layer containing a thermoplastic fine particle polymer, an infrared absorber, and a polymer compound on a surface hydrophilic support, and a non-exposed portion in the image recording layer can be removed by development after exposure. A printing plate precursor, wherein the content of the thermoplastic fine particle polymer is 40 to 95% by mass of the solid content of the image recording layer, and the polymer compound has a star shape in which the main chain is branched into three or more A lithographic printing plate precursor having a hydrophilic group in a side chain of a branched polymer main chain.
[2]
The lithographic printing plate precursor as described in [1], wherein the hydrophilic group is at least one of a carboxyl group or a salt thereof, a sulfo group or a salt thereof, and a polyethyleneoxy group.
[3]
The lithographic printing plate precursor as described in [1] or [2], wherein the thermoplastic fine particle polymer has a crosslinkable group.
[4]
A polymer compound having a star shape in which a main chain is branched into three or more has a group that reacts with a crosslinkable group of a thermoplastic fine particle polymer in a side chain of the branched polymer main chain [3 ] The lithographic printing plate precursor as described in the above.
[5]
[4] The crosslinkable group of the thermoplastic fine particle polymer and the group that reacts with the crosslinkable group of the thermoplastic fine particle polymer of the polymer compound having a star shape are both ethylenically unsaturated groups. The lithographic printing plate precursor described.
[6]
The lithographic printing plate precursor as described in any one of [1] to [5], wherein the image recording layer contains a polymerization initiator.
[7]
The lithographic printing plate precursor as described in any one of [1] to [6], wherein the image recording layer can be removed with at least one of printing ink and fountain solution.
[8]
[7] The lithographic printing plate precursor described in [7] is mounted on a printing press and imagewise exposed with a laser or imagewise exposed with a laser and then mounted on a printing press, and the lithographic printing plate precursor A lithographic printing method in which at least one of printing ink and fountain solution is supplied to remove an unexposed portion of the image recording layer and print.
[9]
A lithographic printing plate making method, wherein the lithographic printing plate precursor according to any one of [1] to [6] is imagewise exposed with a laser and then developed with an aqueous solution having a pH of 2 to 12.
[10]
The plate making method of a lithographic printing plate as described in [9], wherein development is carried out with an aqueous solution having a pH of 2 to 12, followed by heat treatment.
Although this invention is invention which concerns on said [1]-[10], it describes also about other matters (for example, the following 1-10) hereafter.

1. A lithographic printing plate precursor having an image recording layer containing a thermoplastic fine particle polymer, an infrared absorber, and a polymer compound on a surface hydrophilic support, wherein the polymer compound is branched into three or more main chains A lithographic printing plate precursor having a star shape and having a hydrophilic group in a side chain of a branched polymer main chain.
2. 2. The lithographic printing plate precursor as described in 1 above, wherein the hydrophilic group is at least one of a carboxyl group or a salt thereof, a sulfo group or a salt thereof, and a polyethyleneoxy group.
3. 3. The lithographic printing plate precursor as described in 1 or 2 above, wherein the thermoplastic fine particle polymer has a crosslinkable group.
4). 3. The polymer compound having a star shape in which the main chain is branched into 3 or more has a group that reacts with the crosslinkable group of the thermoplastic fine particle polymer in the side chain of the branched polymer main chain. The lithographic printing plate precursor described in 1.
5. 5. The above-mentioned 4, wherein the crosslinkable group of the thermoplastic fine particle polymer and the group that reacts with the crosslinkable group of the thermoplastic fine particle polymer of the polymer compound having a star shape are both ethylenically unsaturated groups. Lithographic printing plate precursor.
6). The lithographic printing plate precursor as described in any one of 1 to 5 above, wherein the image recording layer contains a polymerization initiator.
7). The lithographic printing plate precursor as described in any one of 1 to 6 above, wherein the image recording layer can be removed by at least one of printing ink and fountain solution.
8). The lithographic printing plate precursor as described in 7 above is mounted on a printing press and imagewise exposed with a laser, or after imagewise exposure with a laser, mounted on a printing press and printed on the lithographic printing plate precursor A lithographic printing method in which at least one of ink and fountain solution is supplied to remove an unexposed portion of the image recording layer and print.
9. A lithographic printing plate making method, wherein the lithographic printing plate precursor as described in 1 to 6 above is imagewise exposed with a laser and then developed with an aqueous solution having a pH of 2 to 12.
10. 10. The plate making method of a lithographic printing plate as described in 9 above, wherein the development is performed with an aqueous solution having a pH of 2 to 12, followed by heat treatment.

  Although the mechanism of action of the present invention is not clear, since the polymer compound used is a star polymer, the dispersibility of the thermoplastic fine particle polymer in the image recording layer is higher than that of the conventional linear polymer, and it is uniform. It is presumed that the dispersion improved the developability and increased the thermal fusing efficiency of the thermoplastic fine particle polymer and improved the printing durability.

  According to the present invention, it is possible to provide a lithographic printing plate precursor having both printing durability and developability, a lithographic printing plate making method and a lithographic printing method.

It is a schematic diagram which shows the principal chain structure of a star-shaped polymer. It is explanatory drawing which shows the structure of an automatic developing processor.

(Image recording layer)
The image recording layer of the lithographic printing plate precursor according to the present invention has a thermoplastic fine particle polymer, an infrared absorber, and a star shape in which the main chain is branched into three or more, and has hydrophilic side chains in the branched main chain. Contains a polymer compound.

[Thermoplastic fine particle polymer]
In the present invention, it is preferable to include a thermoplastic fine particle polymer having a Tg of 60 ° C. or higher. When two or more kinds of thermoplastic fine particle polymers having different Tg are mixed, it is preferable that at least one Tg of these thermoplastic fine particle polymers needs to be 60 ° C. or higher.
As a thermoplastic fine particle polymer having a Tg of 60 ° C. or higher (hereinafter also simply referred to as a thermoplastic fine particle polymer), Research Disclosure No. 333 03 , JP-A-9-123387, JP-A-9-131850, JP-A-9-171249, JP-A-9-171250, EP931647, and the like, and the like. Can do.
Specific examples include homopolymers or copolymers of ethylene, styrene, vinyl chloride, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate, vinylidene chloride, acrylonitrile, vinyl carbazole, or mixtures thereof. Can do. Among them, more preferred are polystyrene and polymethyl methacrylate.

The thermoplastic fine particle polymer contained in the image recording layer of the lithographic printing plate precursor according to the invention may be composed of at least two types having different particle sizes or at least two types having different Tg.
By the above, the film curability of the image portion is further improved, and the printing durability is further improved when a lithographic printing plate is used.
For example, when thermoplastic particles having the same particle size are used as the thermoplastic fine particle polymer, a certain amount of voids exist between the thermoplastic fine particle polymers, and the thermoplastic fine particle polymer is melted and solidified by the heat mode exposure or the like. However, the curability of the film may not be as desired. However, when a thermoplastic fine particle polymer having a different particle size is used, the void ratio between the thermoplastic fine particle polymers can be lowered, and as a result, the film curability of the image area after heat mode exposure is improved. be able to.
Also, when the same Tg is used as the thermoplastic fine particle polymer, when the temperature rise of the image recording layer by the heat mode exposure or the like is insufficient, the thermoplastic fine particle polymer is not sufficiently melted and solidified and the film is cured. Sexuality may not be as desired. On the other hand, when a thermoplastic fine particle polymer having a different Tg is used, the film curability of the image area can be improved even when the temperature rise of the image recording layer due to heat mode exposure or the like is insufficient.

  The average particle size of the thermoplastic fine particle polymer is preferably 0.005 μm to 2.0 μm. This value is also applied as an average particle diameter when two or more kinds are mixed. More preferred is 0.01 μm to 1.5 μm, and particularly preferred is 0.05 μm to 1.0 μm. If the average particle size is too large, the resolution may be deteriorated, and if it is too small, the temporal stability may be deteriorated. The polydispersity when two or more are mixed is preferably 0.2 or more. When the large particles and the small particles are mixed, the generation of voids when heat-sealing is reduced, resulting in high printing durability. Polydispersity and average particle size are calculated by laser light scattering.

  In addition, at least one kind of Tg of these thermoplastic fine particle polymers needs to be 60 ° C. or higher, and particularly preferably 70 ° C. to 140 ° C., more preferably 80 ° C. to 120 ° C. When two or more kinds of thermoplastic fine particle polymers having different Tg are mixed, the difference in Tg is preferably 10 ° C. or more, more preferably 20 ° C. or more. At this time, it is preferable that a thermoplastic fine particle polymer having a Tg of 60 ° C. or more is required to be 70% by mass or more based on the total thermoplastic fine particle polymer. If it is 70% or more, deterioration due to on-press development is reduced with time, which is preferable.

  The thermoplastic fine particle polymer contained in the image recording layer of the lithographic printing plate precursor according to the invention may have a crosslinkable group. The crosslinkable group may be any functional group capable of performing any reaction as long as a chemical bond is formed. For example, an ethylenically unsaturated group that performs a polymerization reaction (for example, acryloyl group, methacryloyl group, vinyl group, allyl group). Etc.), an isocyanate group that performs an addition reaction, or a block thereof and a functional group having an active hydrogen atom that is a reaction partner thereof (for example, an amino group, a hydroxy group, a carboxyl group, etc.), an epoxy group that also performs an addition reaction, and its Examples of the reaction partner include an amino group, a carboxyl group or a hydroxy group, a carboxyl group and a hydroxy group or amino group for performing a condensation reaction, an acid anhydride and an amino group or a hydroxy group for performing a ring-opening addition reaction, and the like.

  As the fine particle polymer having a thermally reactive functional group contained in the image recording layer of the lithographic printing plate precursor according to the present invention, specifically, acryloyl group, methacryloyl group, vinyl group, allyl group, epoxy group, amino group, The thing which has a hydroxyl group, a carboxyl group, an isocyanate group, an acid anhydride, and the group which protected them can be mentioned. Introduction of these functional groups into the polymer particles may be performed at the time of polymerization of the fine particle polymer, or may be performed using a polymer reaction after the polymerization of the fine particle polymer.

When introduced during the polymerization of the fine particle polymer, it is preferable to carry out emulsion polymerization or suspension polymerization of the monomer having these crosslinkable groups.
Specific examples of such a monomer having a crosslinkable group include allyl methacrylate, allyl acrylate, vinyl methacrylate, vinyl acrylate, glycidyl methacrylate, glycidyl acrylate, 2-isocyanate ethyl methacrylate, or block isocyanates based on alcohols thereof, 2-isocyanate ethyl, and the like. Block isocyanate with acrylate or alcohol, 2-aminoethyl methacrylate, 2-aminoethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, acrylic acid, methacrylic acid, maleic anhydride, bifunctional acrylate, bifunctional Although methacrylate etc. can be mentioned, it is not limited to these.
Examples of the polymer reaction used when the crosslinkable group is introduced after polymerization of the fine particle polymer include the polymer reaction described in International Publication No. 96/34316.
These fine particle polymers may react with each other through a crosslinkable group, or a reactive group introduced into the side chain of a star-shaped polymer added to the image recording layer, or a low molecular compound. You may react with. Further, two or more kinds of fine particle polymers may be allowed to react with each other by providing different kinds of crosslinkable groups that are thermally reacted with each other. These functional groups include polymerization reactions with unsaturated groups, addition reactions with isocyanate groups or their blocked compounds and compounds having active hydrogen atoms (eg amines, alcohols, carboxylic acids, etc.), epoxy groups and amino groups / carboxyl groups.・ Addition reaction with hydroxy group, condensation reaction between carboxyl group and hydroxy group or amino group, ring-opening addition reaction between acid anhydride and amino group or hydroxy group, etc., but these form a chemical bond Any reaction is acceptable.

  The amount of the thermoplastic fine particle polymer used in the present invention to the image recording layer is preferably 40 to 95% by mass, more preferably 50 to 90% by mass, and particularly preferably 60 to 85% by mass based on the solid content of the image recording layer. .

[Star polymer]
The polymer compound used in the present invention is a star polymer having a main chain branched into three or more, has a main chain structure as shown in the schematic diagram of FIG. ).

  Here, A represents a branch unit (constituent unit including a branch point) of a star-shaped polymer, and Polymer is a polymer chain constituting the main chain, and has a hydrophilic group in its side chain. n is 3 or more.

[Polymer part above]
As long as the star polymer used in the present invention has the main chain structure as described above, it may have any hydrophilic group in the side chain. The hydrophilic group is preferably contained as a repeating unit having at least one hydrophilic group in the side chain in the Polymer portion.

<Repeating unit having hydrophilic group>
Examples of the hydrophilic group include —COOM ¹ (carboxyl group or a salt thereof), —SO ₃ M ¹ (sulfo group or a salt thereof), —OH, —OSO ₃ M ¹ , —CONR ¹ R ² , —SO ₂ NR. ¹ R ² , —NR ¹ SO ₃ M ¹ , —P (═O) (OM ¹ ) (OM ² ), —OP (═O) (OM ¹ ) (OM ² ), hydroxyethyl group or polyethyleneoxy group Examples thereof include a group having an ethylene oxide structure, a group represented by propylene oxide such as a hydroxypropyl group or a polypropyleneoxy group. Here, M ¹ and M ² represent a hydrogen ion, a metal ion, an ammonium ion, and a phosphonium ion, and R ¹ and R ² each independently represent a hydrogen atom, an alkyl group, an alkenyl group, or an aryl group.

When M ¹ and M ² represent metal ions, specific examples of metal ions include Li ⁺ , Na ⁺ , K ⁺ , and Cu ⁺ . Of these, Li ⁺ , Na ⁺ , and K ⁺ are particularly preferable.
When M ¹ and M ² each represent an ammonium ion, any normal ammonium ion can be preferably used, but an ammonium ion having 24 or less carbon atoms per molecule is preferred, and carbon per molecule is preferred. An ammonium ion having a number of 16 or less is particularly preferred.
When M ¹ and M ² represent a phosphonium ion, any ordinary phosphonium ion can be used suitably, but a phosphonium ion having 24 or less carbon atoms per molecule is preferred, and carbon per molecule is preferred. A phosphonium ion having a number of 16 or less is particularly preferred.

When R ¹ and R ² represent an alkyl group, they may be branched or cyclic as long as they are ordinary alkyl groups, and may be a halogen atom, an ether group, a thioether group, a hydroxy group, a cyano group, a keto group, Carboxyl group, carboxylate group, carboxylic acid ester group, carboxylic acid amide group, sulfo group, sulfonate group, sulfonic acid ester group, sulfonamide group, sulfoxide group, phenyl group, phosphonic acid group, phosphonic acid group, phosphoric acid group, It may have a substituent such as phosphate group, amino group, aminocarbonyl group, aminocarboxyl group, aminosulfonyl group. Particularly preferred as the alkyl group is an alkyl group having a total carbon number of 12 or less.

When R ¹ and R ² represent an alkenyl group, they may be branched or cyclic as long as they are ordinary alkenyl groups, and may be halogen atoms, ether groups, thioether groups, hydroxy groups, cyano groups, keto groups, Carboxyl group, carboxylate group, carboxylic acid ester group, carboxylic acid amide group, sulfo group, sulfonate group, sulfonic acid ester group, sulfonamide group, sulfoxide group, phenyl group, phosphonic acid group, phosphonic acid group, phosphoric acid group, It may have a substituent such as phosphate group, amino group, aminocarbonyl group, aminocarboxyl group, aminosulfonyl group. Particularly preferred as the alkenyl group is an alkenyl group having a total carbon number of 12 or less.

When R ¹ and R ² each represents an aryl group, any normal aryl group can be preferably used. Such aryl groups are halogen atoms, ether groups, thioether groups, hydroxy groups, cyano groups, nitro groups, keto groups, carboxyl groups, carboxylate groups, carboxylic acid ester groups, carboxylic acid amide groups, sulfo groups, sulfonate groups, sulfones. Has substituents such as acid ester group, sulfonamide group, sulfoxide group, phenyl group, phosphonic acid group, phosphonic acid group, phosphoric acid group, phosphoric acid group, amino group, aminocarbonyl group, aminocarboxyl group, aminosulfonyl group You may do it. Particularly preferred as the aryl group is an aryl group having a total carbon number of 12 or less.
Among these, —COOM ¹ (carboxyl group or a salt thereof), —SO ₃ M ¹ (sulfo group or a salt thereof), and a polyethyleneoxy group are particularly preferable.

  As long as the repeating unit having at least one hydrophilic group forming the star polymer of the present invention is formed from a repeating unit having at least one of these hydrophilic groups, any repeating unit can be suitably used. Specific examples of the repeating unit having a hydrophilic group used in the present invention are described below. The present invention is not limited to these.

  The star polymer of the present invention may contain only one type of repeating unit having a hydrophilic group as described above, or may contain two or more types.

<Repeating unit having a reactive group>
When the thermoplastic fine particle polymer has a crosslinkable group, it is preferable to have a reactive group that reacts with the crosslinkable group in the side chain of the star polymer of the present invention.
Any reactive group may be used as long as it forms a chemical bond with the crosslinkable group of the fine particles. For example, an ethylenically unsaturated group (for example, acryloyl group, methacryloyl) on which the thermoplastic fine particle polymer undergoes a polymerization reaction. Group, vinyl group, allyl group, etc.), it is preferable to introduce an ethylenically unsaturated group (for example, acryloyl group, methacryloyl group, vinyl group, allyl group) into the side chain of the star polymer. .
When the thermoplastic fine particle polymer has an isocyanate group that undergoes an addition reaction or a block thereof, a functional group having an active hydrogen atom that is the reaction partner on the side chain of the star polymer (for example, an amino group, a hydroxy group, It is preferable to introduce a carboxyl group or the like. When the thermoplastic fine particle polymer has an epoxy group that undergoes an addition reaction, it is preferable to introduce an amino group, a carboxyl group, or a hydroxy group, which is the reaction partner, into the side chain of the star polymer.
When the thermoplastic fine particle polymer has a crosslinkable group having an active hydrogen atom (for example, an amino group, a hydroxy group, a carboxyl group, etc.), an isocyanate group that performs an addition reaction on the side chain of the star polymer or It is preferable to contain the block body or the epoxy group which performs addition reaction similarly.
Similarly, for the functional group of the thermoplastic fine particle polymer, the star polymer has its carboxyl group and hydroxy group or amino group for the condensation reaction, and the acid anhydride and amino group or hydroxy group for the ring-opening addition reaction. It preferably has a functional group that is a reaction partner.
In the present invention, it is preferable that cross-linking is formed between polymer molecules by the ethylenically unsaturated group and curing is accelerated.

(1) Examples of the ethylenically unsaturated groups ethylenically unsaturated group, (meth) acryloyl group, a vinyl group, an allyl group are preferable, these groups may be introduced into the polymer by a polymer reaction or copolymerization it can. For example, a reaction between an acrylic polymer having a carboxyl group in the side chain and glycidyl methacrylate, a reaction between a polymer having an epoxy group and an ethylenically unsaturated group-containing carboxylic acid such as methacrylic acid, or a polymer having a hydroxy group and an isocyanate group Reaction with methacrylate can be used.
From the viewpoint of storage stability and film strength of the polymer compound, (meth) acryloyl group is preferred.

  Specific examples of the repeating unit having a reactive group used in the present invention are described below. The present invention is not limited to these.

  The content of the ethylenically unsaturated group in the polymer compound of the present invention is preferably 0.1 to 10.0 mmol, more preferably 0.25 to 7.0 mmol, most preferably 0, per 1 g of the polymer compound. .5 to 5.5 mmol.

(2) Other reactive groups Specific examples of the repeating units having other reactive groups include the following repeating units.

・ Epoxy group (reacts with amino group, hydroxy group, carboxyl group of fine particle polymer)

・ Isocyanates and blocked isocyanates (reacts with amino group, hydroxy group and carboxyl group of fine particle polymer)

・ Hydroxy group, carboxyl group, amino group (reacts with epoxy group, isocyanate and blocked isocyanate group of fine particle polymer)

・ Compounds with acid anhydride skeleton (react with amino group and hydroxy group of fine particle polymer)

<Other repeating units>
The star polymer used in the present invention may contain other repeating units. Specific examples of such repeating units are described below. The present invention is not limited to these.

  The specific example of the structure of the Polymer part of General formula (1) is given below.

[Branch unit A]
The branch unit represented by A in the general formula (1) is not particularly limited, but preferably has a hubportion that is a residue of a thiol having three or more functionalities. In an idealized structure, the addition polymer backbone extends from each thio moiety in the hub; thus, three or more backbones extend from the thio moiety. That is, the branch unit A preferably has a structure represented by the following general formula (2).

Here, A ₁ is a trivalent or higher organic group, and n is an integer of 3 or higher. Specific examples of A ₁ include the following structures or organic groups constituted by combining a plurality of these structures. n is preferably an integer of 3 to 6, and particularly preferably an integer of 4 to 6.

Trifunctional or higher thiol residues are derived from aromatic or aliphatic thiols. Examples of the aromatic thiol include benzene-1,3,5-trithiol, 3,4,8,9-tetramercaptotetrathiafulvalene and 7-methyltrithiouric acid.
The thiol residue of the aliphatic thiol is preferably an ester residue formed from a trifunctional or higher functional alcohol and a mercaptoalkanoic acid having 2 to 6 carbon atoms.

  Examples of suitable alcohols include glycerin, sorbitol, alcohol represented by formula (3), and alcohol having a group represented by formula (4). In particular, an alcohol represented by the formula (3) and an alcohol having a group represented by the formula (4) are preferable.

In the above formula, R ¹ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a hydroxy-substituted alkyl group. In particular, a methyl group, an ethyl group, a hydroxymethyl group, and a hydroxyethyl group are preferable.

  Examples of mercaptoalkanoic acids having 2 to 6 carbon atoms include 2-mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, 4-mercaptobutyric acid, 5-mercaptovaleric acid, and 6-mercaptocaproic acid. It is done. Of these, 2-mercaptoacetic acid and 3-mercaptopropionic acid are preferable.

Specific examples of esters formed from trifunctional or higher alcohols and mercaptoalkanoic acids having 2 to 6 carbon atoms include 1,2,6-hexanetriol trithioglycolate, 1,3,5-trithiocyanuric acid, 1,3,5-tris (3-mercaptobutyryloxyethyl) -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, trimethylolpropane tris (3-mercaptopropio Nate), trimethylolpropane tristhioglycolate, trimethylolpropane tristhiopropionate, trihydroxyethyltriisocyanuric acid tristhiopropionate, tris-[(ethyl-3-mercaptopropionyloxy) -ethyl] isocyanurate, etc. A compound having three mercapto groups,
It has four mercapto groups such as pentaerythritol tetrakis (3-mercaptopropionate), pentaerythritol tetrakis (3-mercaptobutyrate), pentaerythritol tetrakisthioglycolate, dipentaerythritol hexakis-3-mercaptopropionate. Examples thereof include, but are not limited to, compounds.

  Commercially available products of the above polyfunctional thiol compounds include trimethylolpropane tristhiopropionate (TMTG) (trademark), pentaerythritol tetrakisthiopropionate (PETG) (trademark) (both manufactured by Sakai Chemical Co., Ltd.), penta Erythritol tetrakis (3-mercaptobutyrate) (Karenz MT PE1) (trademark), 1,3,5-tris (3-mercaptobutyryloxyethyl) -1,3,5-triazine-2,4,6 (1H , 3H, 5H) -trione (Karenz MT NR1) (trademark) (all manufactured by Showa Denko KK), trimethylolpropane tris-3-mercaptopropionate (TMMP) (trademark), pentaerythritol tetrakis-3- Mercaptopropionate (PEMP) ™, dipentaerythritol Ruhexakis-3-mercaptopropionate (DPMP) (trademark), tris-[(ethyl-3-mercaptopropionyloxy) -ethyl] isocyanurate (TEMPIC) (trademark) (all manufactured by Sakai Chemical Industry Co., Ltd.), etc. However, the polyfunctional thiol compound of the present invention is not limited thereto.

  Examples of the branch unit represented by the general formula (2) include the following structures.

The mass average molar mass (Mw) of the star polymer used in the present invention is preferably 5,000 to 500,000, and more preferably 10,000 to 250,000.
Specific examples of the star polymer used in the present invention are shown in Table 1. However, the present invention is not limited to these.

  The star polymer of this invention may be used individually by 1 type, and may mix and use 2 or more types. The content of the star polymer of the present invention in the image recording layer is preferably from 3 to 50 mass%, more preferably from 5 to 40 mass%, particularly preferably from 10 to 30 mass%, based on the total solid content of the image recording layer. .

  The star polymer of the present invention 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.

[Infrared absorber]
The lithographic printing plate precursor according to the invention contains an infrared absorber in the image recording layer. The infrared absorber may be further contained in a layer adjacent to the image recording layer (an undercoat layer or an overcoat layer described later). The infrared absorbent may be any substance that absorbs infrared laser light, and various pigments, dyes, and metal fine particles can be used. In particular, a light absorbing material having an absorption band in at least a part of 700 to 1200 nm is preferable.

  Examples of the pigment include black pigments, brown pigments, red pigments, purple pigments, blue pigments, green pigments, fluorescent pigments, metal powder pigments, and other polymer-bonded pigments. Specifically, insoluble azo pigments, azo lake pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, anthraquinone pigments, perylene and perinone pigments, thioindigo pigments, quinacridone pigments, dioxazine pigments, isoindolinone pigments In addition, quinophthalone pigments, dyed lake pigments, azine pigments, nitroso pigments, nitro pigments, natural pigments, fluorescent pigments, inorganic pigments, carbon black, and the like can be used.

  These pigments may be used without surface treatment, or may be used after surface treatment. Surface treatment methods include surface coating with a hydrophilic resin or lipophilic resin, a method of attaching a surfactant, a reactive substance (eg, silica sol, alumina sol, silane coupling agent, epoxy compound, isocyanate compound, etc.) A method of bonding to the pigment surface is conceivable. The above-mentioned surface treatment methods are described in “Characteristics and Applications of Metal Soap” (Shobobo), “Printing Ink Technology” (CMC Publishing, 1984) and “Latest Pigment Application Technology” (CMC Publishing, 1986). Yes. Among these pigments, those that absorb infrared rays are preferable because they are suitable for use in lasers that emit infrared rays. Carbon black is preferable as the pigment that absorbs infrared rays. The particle diameter of the pigment is preferably in the range of 0.01 μm to 1 μm, and more preferably in the range of 0.01 μm to 0.5 μm.

  Examples of the dye include commercially available dyes and literature (for example, “Dye Handbook” edited by the Society for Synthetic Organic Chemistry, published in 1970, “Chemical Industry”, May 1986, P. 45-51, “Near Infrared Absorbing Dye”, “90 Development and market trends of age functional pigments "Chapter 2. 2.3 (1990) CMC) or known dyes described in patents can be used. Specifically, infrared absorbing dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, polymethine dyes, and cyanine dyes are preferable.

  Further, for example, cyanine dyes described in JP-A-58-125246, JP-A-59-84356, JP-A-60-78787, JP-A-58-173696, JP Methine dyes described in JP-A-58-181690, JP-A-58-194595, etc., JP-A-58-112793, JP-A-58-224793, JP-A-59-48187 Naphthoquinone dyes described in JP-A-59-73996, JP-A-60-52940, JP-A-60-63744, etc., and JP-A-58-112792 Squarylium dyes, cyanine dyes described in British Patent 434,875, dyes described in US Pat. No. 4,756,993, US Pat. No. 4,973, Examples include cyanine dyes described in the specification of No. 572, dyes described in JP-A-10-268512, and phthalocyanine compounds described in JP-A-11-235883.

  Further, near-infrared absorption sensitizers described in US Pat. No. 5,156,938 are also preferably used as dyes, and substituted arylbenzoates described in US Pat. No. 3,881,924 are also preferred. (Thio) pyrylium salt, trimethine thiapyrylium salt described in JP-A-57-142645, JP-A-58-181051, JP-A-58-220143, JP-A-59-41363, JP-A-59-84248 No. 59-84249, No. 59-146063, No. 59-146061, Pyrylium compounds, Japanese Patent Publication No. 59-216146, Cyanine dyes, US Pat. No. 4,283. , 475, the pentamethine thiopyrylium salt, etc., and Japanese Patent Publication Nos. 5-13514 and 5-19702. That pyrylium compounds, Eporin Inc. Epolight III-178, Epolight III-130, Epolight III-125 and the like is also preferably used. Among these dyes, water-soluble dyes are preferable, and water-soluble cyanine dyes, particularly cyanine dyes that are water-soluble by sulfonates are particularly preferable. Some specific examples are shown below.

  A preferable addition amount of these infrared absorbers is preferably 0.5 to 30 parts by mass, more preferably 1.0 to 20 parts by mass, and most preferably 2.0 to 100 parts by mass of the total solid content of the image recording layer. It is the range of -10 mass parts.

(Polymerization initiator)
The polymerization initiator used in the present invention is a compound that initiates and accelerates polymerization of a polymerizable compound. As the polymerization initiator that can be used in the present invention, a radical polymerization initiator is preferable, and a known thermal polymerization initiator, a compound having a bond with a small bond dissociation energy, a photopolymerization initiator, and the like can be used.
Examples of the polymerization initiator in the present invention include (a) an organic halide, (b) a carbonyl compound, (c) an azo compound, (d) an organic peroxide, (e) a metallocene compound, (f) an azide compound, (G) hexaarylbiimidazole compounds, (h) organic borate compounds, (i) disulfone compounds, (j) oxime ester compounds, (k) onium salt compounds, and the like.

(A) As the organic halide, compounds described in paragraph numbers [0022] to [0023] of JP-A-2008-195018 are preferable.

(B) As the carbonyl compound, compounds described in paragraph [0024] of JP-A-2008-195018 are preferable.

  (C) As the azo compound, for example, an azo compound described in JP-A-8-108621 can be used.

  (D) As the organic peroxide, for example, compounds described in paragraph [0025] of JP-A-2008-195018 are preferable.

  As the (e) metallocene compound, for example, the compound described in paragraph [0026] of JP-A-2008-195018 is preferable.

(F) Examples of the azide compound include 2,6-bis (4-azidobenzylidene) -4-methylcyclohexanone.
(G) As the hexaarylbiimidazole compound, for example, a compound described in paragraph [0027] of JP-A-2008-195018 is preferable.

  (H) As the organic borate compound, for example, a compound described in paragraph [0028] of JP-A-2008-195018 is preferable.

  (I) Examples of the disulfone compound include compounds described in JP-A Nos. 61-166544 and 2002-328465.

  (J) As the oxime ester compound, for example, compounds described in paragraph numbers [0028] to [0030] of JP-A-2008-195018 are preferable.

  (K) Examples of the onium salt compounds include S.I. I. Schlesinger, Photogr. Sci. Eng. , 18, 387 (1974), T.A. S. Bal et al, Polymer, 21, 423 (1980), diazonium salts described in JP-A-5-158230 (corresponding to NI3 diazonium), US Pat. No. 4,069,055, JP-A-4-365049 Ammonium salts described in U.S. Pat. Nos. 4,069,055 and 4,069,056, EP 104,143, U.S. Patent Application Publication No. 2008/0311520 Nos. 1-150848, JP-A-2-150848, JP-A-2008-195018, or J. Pat. V. Ivonium salt described in Crivello et al, Macromolecules, 10 (6), 1307 (1977), European Patents 370,693, 233,567, 297,443, 297,442, US Patent 4,933,377, 4,760,013, 4,734,444, 2,833,827, German Patent 2,904,626, 3,604,580 Sulphonium salts described in the respective specifications of U.S. Pat. V. Crivello et al, J.A. Polymer Sci. , Polymer Chem. Ed. , 17, 1047 (1979), a selenonium salt described in C.I. S. Wen et al, Teh, Proc. Conf. Rad. Curing ASIA, p478 Tokyo, Oct (1988), and onium salts such as azinium salts described in JP-A-2008-195018.

  Of these, more preferred are onium salts, especially iodonium salts, sulfonium salts and azinium salts. Although the specific example of these compounds is shown below, it is not limited to this.

  As an example of the iodonium salt, a diphenyl iodonium salt is preferable, and a diphenyl iodonium salt substituted with an electron donating group such as an alkyl group or an alkoxyl group is particularly preferable, and an asymmetric diphenyl iodonium salt is more preferable. Specific examples include diphenyliodonium = hexafluorophosphate, 4-methoxyphenyl-4- (2-methylpropyl) phenyliodonium = hexafluorophosphate, 4- (2-methylpropyl) phenyl-p-tolyliodonium = hexa. Fluorophosphate, 4-hexyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, 4-hexyloxyphenyl-2,4-diethoxyphenyliodonium = tetrafluoroborate, 4-octyloxy Phenyl-2,4,6-trimethoxyphenyliodonium = 1-perfluorobutanesulfonate, 4-octyloxyphenyl-2,4,6-trimethoxyphenyliodonium = hexafluorophosphate, bis ( -t- butylphenyl) iodonium tetraphenylborate and the like.

  Examples of sulfonium salts include triphenylsulfonium = hexafluorophosphate, triphenylsulfonium = benzoylformate, bis (4-chlorophenyl) phenylsulfonium = benzoylformate, bis (4-chlorophenyl) -4-methylphenylsulfonium = Examples thereof include tetrafluoroborate, tris (4-chlorophenyl) sulfonium = 3,5-bis (methoxycarbonyl) benzenesulfonate, and tris (4-chlorophenyl) sulfonium = hexafluorophosphate.

Examples of azinium salts include 1-cyclohexylmethyloxypyridinium = hexafluorophosphate, 1-cyclohexyloxy-4-phenylpyridinium = hexafluorophosphate, 1-ethoxy-4-phenylpyridinium = hexafluorophosphate, 1-cyclohexyl (2-ethylhexyloxy) -4-phenylpyridinium = hexafluorophosphate, 4-chloro-1-cyclohexylmethyloxypyridinium = hexafluorophosphate, 1-ethoxy-4-cyanopyridinium = hexafluorophosphate, 3,4 -Dichloro-1- (2-ethylhexyloxy) pyridinium = hexafluorophosphate, 1-benzyloxy-4-phenylpyridinium = hexafluorophosphate, 1-phenethylo Ci-4-phenylpyridinium = hexafluorophosphate, 1- (2-ethylhexyloxy) -4-phenylpyridinium = p-toluenesulfonate, 1- (2-ethylhexyloxy) -4-phenylpyridinium = perfluorobutanesulfonate 1- (2-ethylhexyloxy) -4-phenylpyridinium bromide, 1- (2-ethylhexyloxy) -4-phenylpyridinium tetrafluoroborate.
Among these polymerization initiators, water-soluble or water-dispersible polymerization initiators are preferable, and some specific examples of water-soluble azo compounds are shown below.

  The polymerization initiator is preferably 0.1 to 50% by mass, more preferably 0.5 to 30% by mass, and particularly preferably 0.8 to 20% by mass with respect to the total solid content constituting the image recording layer. Can be added. Within this range, good sensitivity and good stain resistance of the non-image area during printing can be obtained.

[Other ingredients]
The image recording layer contains other components such as an additional surfactant, a colorant, a development inhibitor or accelerator, a low molecular weight polymerizable compound that reacts with the crosslinkable group of the thermoplastic fine particle polymer, a catalyst for improving the crosslinkability, or A precursor etc. can be contained.

(Formation of image recording layer)
The image recording layer in the present invention is a coating solution prepared by dispersing or dissolving the necessary components in a known solvent as described in paragraphs [0142] to [0143] of JP-A-2008-195018, for example. This is prepared by coating the substrate by a known method such as bar coater coating and drying. The image recording layer coating amount (solid content) on the support obtained after coating and drying varies depending on the application, but is generally preferably 0.3 to 3.0 g / m ² . Within this range, good sensitivity and good film characteristics of the image recording layer can be obtained.

[Support]
As the support used in the lithographic printing plate precursor according to the invention, a known support is used. Of these, an aluminum plate that has been roughened and anodized by a known method is preferred.
In addition, the above aluminum plate is optionally subjected to micropore enlargement treatment or sealing treatment of an anodized film described in JP-A Nos. 2001-253181 and 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. Surface hydrophilization treatment with polyvinylphosphonic acid or the like as described in each specification of 3,276,868, 4,153,461 and 4,689,272 is appropriately performed and performed. be able to.
The support preferably has a center line average roughness of 0.10 to 1.2 μm.

  If necessary, the support of the present invention includes 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. A backcoat layer can be provided.

[Protective layer]
In the lithographic printing plate precursor according to the invention, a protective layer (overcoat layer) can be provided on the image recording layer. 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 carboxyl 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.

Further, in order to enhance the oxygen barrier property, the protective layer preferably contains an inorganic layered compound such as natural mica and synthetic mica as described in JP-A-2005-119273.
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, the coating amount after drying is preferably in the range of 0.01 to 10 g / ^{m 2,} more preferably in the range of 0.02 to 3 g / ^{m 2,} and most preferably 0. in the range of 02~1g / ^{m 2.}

[Plate making method]
The lithographic printing plate precursor according to the invention is subjected to development processing after image exposure or is developed on a printing machine to be used for printing.

<Image exposure>
The lithographic printing plate precursor is imagewise exposed by laser exposure through a transparent original image having a line image, a halftone dot image or the like, or by laser beam scanning by 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. In the case of on-press development, the lithographic printing plate precursor may be mounted on a printing press and then image exposure may be performed on the printing press.

<On-machine development>
In the on-press development, the image-exposed lithographic printing plate precursor is supplied with at least one of oil-based ink and aqueous component on the printing press, and the image recording layer in the non-image area is removed to produce a lithographic printing plate. The
In other words, after image exposure of the lithographic printing plate precursor, it is mounted on the printing machine without any development processing, or after the lithographic printing plate precursor is mounted on the printing machine, image exposure is performed on the printing machine. When printing is performed by supplying the oil-based ink and the aqueous component, the uncured image recording layer is dissolved or dispersed in the non-image area by the supplied oil-based ink and / or the aqueous component in the initial stage of printing. And a hydrophilic surface is exposed at the portion. On the other hand, in the exposed portion, the image recording layer cured by exposure forms an oil-based ink receiving portion having a lipophilic surface. Oil-based ink or water-based component may be first supplied to the plate surface, but oil-based ink is supplied first in order to prevent the water-based component from being contaminated by the removed image recording layer component. Is preferred. In this way, the lithographic printing plate precursor is subjected to on-press development on a printing machine and used as it is for printing a large number of sheets. As the oil-based ink and the aqueous component, ordinary lithographic printing ink and fountain solution are preferably used.

<Development with pH 2-11 developer>
In a normal development process using a highly alkaline developer, the protective layer is removed by a pre-water washing process, then alkali development is performed, the alkali is washed and removed by a post-water washing process, a gum solution treatment is performed, and a drying process is performed. When drying, but using the planographic printing plate precursor of the present invention and developing with a developer having a pH of 2 to 11, the protective layer and the image recording layer in the non-exposed area are removed at once, and then set in a printing machine and printed. can do. Such a developer having a pH of 2 to 11 can simultaneously perform development and gum solution treatment by containing a surfactant and / or a desensitizing water-soluble polymer in the developer, and after alkali development. The post-washing step that has been performed is not particularly required, and after the development and gum solution treatment with one solution, the drying step can be performed. Drying is preferably performed after the development and gum treatment, after removing excess developer using a squeeze roller. That is, a greatly simplified processing step (gum development) of development / gum processing-drying with a single solution becomes possible.
The development in the present invention is carried out according to a conventional method, such as a method in which a lithographic printing plate precursor subjected to image exposure at a liquid temperature of 0 to 60 ° C., preferably 15 to 40 ° C. is immersed in a developer and rubbed with a brush, or developed by spraying. This is done by spraying the liquid and rubbing with a brush.

  The pH 2 to 11 developer is preferably an aqueous solution containing water as a main component (containing 60% by mass or more of the developer mass), particularly a surfactant (anionic, nonionic, cationic, zwitterionic, etc.). ) And aqueous solutions containing water-soluble polymers are preferred. An aqueous solution containing both a surfactant and a water-soluble polymer is also preferred. The pH of the developer is more preferably 5 to 10.7, still more preferably 6 to 10.5, and most preferably 7.5 to 10.3.

  The anionic surfactant used in the developer is not particularly limited, but fatty acid salts, abietic acid salts, hydroxyalkane sulfonic acid salts, alkane sulfonic acid salts, dialkyl sulfosuccinic acid salts, linear alkyl benzene sulfonic acid salts, branched Chain alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkyl diphenyl ether (di) sulfonates, alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, sodium N-methyl-N-oleyl taurine N-alkylsulfosuccinic acid monoamide disodium salts, petroleum sulfonates, sulfated castor oil, sulfated beef tallow oil, sulfate esters of fatty acid alkyl esters, alkyl sulfate esters Tellurium salts, polyoxyethylene alkyl ether sulfates, fatty acid monoglyceride sulfates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene styrylphenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates Salt, polyoxyethylene alkylphenyl ether phosphate ester salt, styrene-maleic anhydride copolymer partial saponification products, olefin-maleic anhydride copolymer partial saponification products, naphthalene sulfonate formalin condensates, etc. Can be mentioned. Among these, alkylbenzene sulfonates, alkyl naphthalene sulfonates, and alkyl diphenyl ether (di) sulfonates are particularly preferably used.

  Although it does not specifically limit as a cationic surfactant used for the said developing solution, A conventionally well-known thing can be used. Examples thereof include alkylamine salts, quaternary ammonium salts, alkyl imidazolinium salts, polyoxyethylene alkylamine salts, and polyethylene polyamine derivatives.

The nonionic surfactant used in the developer is not particularly limited, but is a polyethylene glycol type higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, alkyl naphthol ethylene oxide adduct, phenol ethylene oxide adduct, naphthol. Ethylene oxide adduct, fatty acid ethylene oxide adduct, polyhydric alcohol fatty acid ester ethylene oxide adduct, higher alkylamine ethylene oxide adduct, fatty acid amide ethylene oxide adduct, fat and oil ethylene oxide adduct, polypropylene glycol ethylene oxide adduct, Dimethylsiloxane-ethylene oxide block copolymer, dimethylsiloxane- (propylene oxide-ethylene oxide ) Fatty acid ester of polyglycol type glycerol, fatty acid ester of pentaerythritol, fatty acid ester of sorbitol and sorbitan, fatty acid ester of sucrose, alkyl ether of polyhydric alcohol, fatty acid amide of alkanolamines, etc. Can be mentioned. Among these, those having an aromatic ring and an ethylene oxide chain are preferable, and an alkyl-substituted or unsubstituted phenol ethylene oxide adduct or an alkyl-substituted or unsubstituted naphthol ethylene oxide adduct is more preferable.
The zwitterionic surfactant used in the developer is not particularly limited, and examples thereof include amine oxides such as alkyldimethylamine oxide, betaines such as alkylbetaines, and amino acids such as alkylamino fatty acid sodium. In particular, alkyldimethylamine oxide which may have a substituent, alkylcarboxybetaine which may have a substituent, and alkylsulfobetaine which may have a substituent are preferably used. Specific examples of these are described in paragraph numbers [0255] to [0278] of JP2008-203359, paragraph numbers [0028] to [0052] of JP2008-276166, and the like. More preferable specific examples include 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, alkyldiaminoethylglycine hydrochloride, lauryldimethylaminoacetic acid betaine, N-lauramidopropyldimethylbetaine, and N-lauric acid. And amidopropyldimethylamine oxide.

  Two or more surfactants may be used, and the ratio of the surfactant contained in the developer is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass.

  Examples of the water-soluble polymer used in the developer having a pH of 2 to 11 include soybean polysaccharide, modified starch, gum arabic, dextrin, fibrin derivatives (for example, carboxymethylcellulose, carboxyethylcellulose, methylcellulose, etc.) and modified products thereof, pullulan. , Polyvinyl alcohol and its derivatives, polyvinyl pyrrolidone, polyacrylamide and acrylamide copolymer, vinyl methyl ether / maleic anhydride copolymer, vinyl acetate / maleic anhydride copolymer, styrene / maleic anhydride copolymer, etc. It is done.

  A well-known thing can be used for the said soybean polysaccharide, for example, there exists a brand name Soya Five (made by Fuji Oil Co., Ltd.) as a commercial item, and the thing of various grades can be used. What can be preferably used is one in which the viscosity of a 10% by mass aqueous solution is in the range of 10 to 100 mPa / sec.

  As the modified starch, known ones can be used, and starch such as corn, potato, tapioca, rice, and wheat is decomposed with acid or enzyme in the range of 5 to 30 glucose residues per molecule, and further in an alkali. It can be made by a method of adding oxypropylene or the like.

  Two or more water-soluble polymers can be used in combination. The content of the water-soluble polymer in the developer is preferably 0.1 to 20% by mass, more preferably 0.5 to 10% by mass.

The pH 2 to 11 developer used in the present invention may further contain a pH buffer.
Any pH buffering agent can be used without particular limitation as long as it exhibits a buffering effect at pH 2-11. In the present invention, weakly alkaline buffering agents are preferably used. For example, (a) carbonate ions and hydrogen carbonate ions, (b) borate ions, (c) water-soluble amine compounds and ions of the amine compounds, and their Combination use etc. are mentioned. That is, for example, (a) a combination of carbonate ion-bicarbonate ion, (b) borate ion, or (c) a combination of water-soluble amine compound-ion of the amine compound exhibits pH buffering action in the developer. Even when the developer is used for a long period of time, fluctuations in pH can be suppressed, and deterioration in developability due to fluctuations in pH, development of development residue, etc. can be suppressed. Particularly preferred is a combination of carbonate ions and bicarbonate ions.

  In order to allow carbonate ions and hydrogen carbonate ions to be present in the developer, carbonate and hydrogen carbonate may be added to the developer, or by adjusting the pH after adding carbonate or bicarbonate, Ions and bicarbonate ions may be generated. The carbonate and bicarbonate are not particularly limited, but are preferably alkali metal salts. Examples of the alkali metal include lithium, sodium, and potassium, and sodium is particularly preferable. These may be used alone or in combination of two or more.

  When (a) a combination of carbonate ions and bicarbonate ions is employed as the pH buffer, the total amount of carbonate ions and bicarbonate ions is preferably 0.05 to 5 mol / L relative to the total mass of the developer. 1-2 mol / L is more preferable, and 0.2-1 mol / L is particularly preferable.

The developer may contain an organic solvent. Examples of organic solvents that can be contained include aliphatic hydrocarbons (hexane, heptane, “Isopar E, H, G” (Esso Chemical Co., Ltd.)), aromatic hydrocarbons (toluene, xylene, etc.) Or halogenated hydrocarbons (methylene dichloride, ethylene dichloride, trichlene, monochlorobenzene, etc.) and polar solvents. Examples of polar solvents include alcohols (methanol, ethanol, propanol, isopropanol, 1-butanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1 -Nonanol, 1-decanol, benzyl alcohol, ethylene glycol monomethyl ether, 2-ethoxyethanol, diethylene glycol monoethyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monomethyl ether, polyethylene glycol monomethyl Ether, polypropylene glycol, tetraethylene glycol, ethylene glycol monobutyl ether Ter, ethylene glycol monobenzyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, methylphenyl carbinol, n-amyl alcohol, methyl amyl alcohol, etc.), ketones (acetone, methyl ethyl ketone, ethyl butyl ketone, methyl isobutyl ketone) , Cyclohexanone, etc.), esters (ethyl acetate, propyl acetate, butyl acetate, amyl acetate, benzyl acetate, methyl lactate, butyl lactate, ethylene glycol monobutyl acetate, propylene glycol monomethyl ether acetate, diethylene glycol acetate, diethyl phthalate, butyl levulinate Etc.), others (triethyl phosphate, tricresyl phosphate, N-phenylethanolamine) N- phenyl diethanolamine, N- methyldiethanolamine, N- ethyldiethanolamine, 4- (2-hydroxyethyl) morpholine, N, N- dimethylacetamide, N- methylpyrrolidone and the like) and the like.
Two or more organic solvents can be used in combination in the developer.

  If the organic solvent is insoluble in water, it can be used after being solubilized in water using a surfactant or the like. If the developer contains an organic solvent, safety, ignition, From the viewpoint of property, the concentration of the solvent is preferably less than 40% by mass.

  In addition to the above, the developer having a pH of 2 to 11 may contain a preservative, a chelate compound, an antifoaming agent, an organic acid, an inorganic acid, an inorganic salt, and the like. Specifically, compounds described in paragraph numbers [0266] to [0270] of JP-A-2007-206217 can be preferably used.

  The developer can be used as a developer and a development replenisher for the exposed lithographic printing plate precursor, and is preferably applied to an automatic processor described later. When developing using an automatic processor, the developing solution becomes fatigued according to the amount of processing, and therefore the replenishing solution or fresh developing solution may be used to restore the processing capability.

  In the present invention, the development treatment with a developer having a pH of 2 to 11 can be suitably carried out by an automatic processor equipped with a developer supply means and a rubbing member. An automatic processor using a rotating brush roll as the rubbing member is particularly preferable. Further, the automatic processor is preferably provided with a means for removing excess developer such as a squeeze roller and a drying means such as a hot air device after the development processing means.

The lithographic printing plate precursor according to the invention can be subjected to a heat treatment in a post-heating step (baking process) after the development treatment in order to improve printing durability.
The baking process can be performed at a temperature higher than the coagulation temperature of the thermoplastic polymer particles, for example, 100 ° C. to 230 ° C. for 5 to 40 minutes. For example, the exposed and developed plate can be baked at a temperature of 230 ° C. for 5 minutes, at a temperature of 150 ° C. for 10 minutes, or at a temperature of 120 ° C. for 30 minutes. Baking can be done in a conventional hot stove or by irradiation with a lamp emitting in the infrared or ultraviolet spectrum.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these. In the polymer compound, the molecular weight is a mass average molar mass (Mw), and the ratio of repeating units is a mole percentage, except for those specifically defined.

[Synthesis example of star polymer]

Synthesis of star polymer (P-4) 1-methoxy-2-propanol heated to 80 ° C. under nitrogen flow: 330 g, acrylic acid: 283 g, tetrakis (mercaptoacetic acid) pentaerythritol: 2.3 g, V-601 (Wako Pure Chemical Industries, Ltd.): A mixed solution consisting of 2.4 g and 1-methoxy-2-propanol: 330 g was added dropwise over 2 hours and 30 minutes. After completion of the dropwise addition, the reaction was continued for another 3 hours. The mass average molar mass (Mw) of the obtained polymer was 50,000.

Synthesis of Star Polymer (P-16) 1-Methoxy-2-propanol heated to 80 ° C. under a nitrogen stream: 200 g, acrylic acid: 144 g, tetrakis (mercaptoacetic acid) pentaerythritol: 2.3 g, V-601 (Wako Pure Chemical Industries, Ltd.): A mixed solution consisting of 2.4 g and 1-methoxy-2-propanol: 100 g was added dropwise over 2 hours and 30 minutes. V-601: 0.143g was further added after completion | finish of dripping, and it heated up at 90 degreeC, and continued reaction for 2 hours. After the reaction, it is cooled to 50 ° C., 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxide free radical: 0.971 g, glycidyl methacrylate: 28.4 g, and 1-methoxy-2-propanol: A liquid for mixing consisting of 13.6 g was added and stirred for 5 minutes. The reaction mixture was heated to 90 ° C. and stirred for 10 minutes. Then, tetraethylammonium bromide: 2.21 g was added, and tetraethylammonium bromide adhering to the reaction vessel wall was washed away with 1-methoxy-2-propanol: 30.47 g. It was. After stirring at 90 ° C. for 18 hours, 1-methoxy-2-propanol was further added to dilute the reaction mixture so that the solid content concentration was 24.5%. The weight average molecular weight measured by GPC of the polymer compound (P-16) solution represented by the above structural formula was 80,000.

[Examples 1 to 16 and Comparative Examples 1 to 3]

[Preparation of lithographic printing plate precursors (1) to (19)]
(1) Production of support First, 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 with a 10 mass% sodium aluminate aqueous solution, and 30 mass%. Neutralization and smut removal treatment was performed with an aqueous sulfuric acid solution at 50 ° C. for 30 seconds.

Next, in order to improve the adhesion between the support and the image recording layer and to provide water retention to the non-image area, a so-called graining treatment was performed to roughen the surface of the support. An aqueous solution containing 1% by mass of nitric acid and 0.5% by mass of aluminum nitrate is kept at 45 ° C., and an aluminum web is allowed to flow in the aqueous solution, while an indirect power feeding cell has a current density of 20 A / dm ² and a duty ratio of 1: 1. Electrolytic graining was performed by applying an anode side electric quantity of 240 C / dm ² in an alternating waveform. Thereafter, etching treatment was carried out with a 10% by mass sodium aluminate aqueous solution at 50 ° C. for 30 seconds, and neutralization and smut removal treatment were carried out with a 30% by mass sulfuric acid aqueous solution at 50 ° C. for 30 seconds.

Furthermore, in order to improve wear resistance, chemical resistance and water retention, an oxide film was formed on the support by anodic oxidation. An anodization of 2.5 g / m ² by using a 20% by weight sulfuric acid aqueous solution as an electrolyte at 35 ° C. and carrying out an aluminum web through the electrolyte and performing an electrolytic treatment at a direct current of 14 A / dm ² by an indirect power supply cell. A film was prepared.
Thereafter, a silicate treatment was performed in order to ensure hydrophilicity as a non-image portion of the printing plate. In the treatment, a 1.5 mass% aqueous solution of sodium silicate No. 3 was kept at 70 ° C. so that the contact time of the aluminum web was 15 seconds, and further washed with water. The adhesion amount of Si was 10 mg / m ² . Ra (center line surface roughness) of the support prepared as described above was 0.25 μm.

(2) Formation of image recording layer The following image recording layer coating solution (1) or (2) is selected and coated on the support as shown in Table 2, followed by oven drying and dry coating. An image recording layer having an amount of 0.6 g / m ² was formed to obtain lithographic printing plate precursors (1) to (19).

<Image recording layer coating solution (1)>
・ Particulate polymer aqueous dispersion (described in Table 2) Solid conversion 12.5g
Infrared absorbing dye (3) [following structure] 1.0 g
-Polymer compound represented by the general formula (1) (described in Table 2) 2.0 g
・ 1,5-Naphthalenedisulfonic acid disodium 0.1g
・ Pure water 10.0g

<Image recording layer coating solution (2)>
・ Particulate polymer aqueous dispersion (described in Table 2) Solid conversion 12.5g
Infrared absorbing dye (3) [above structure] 1.0 g
-Polymer compound represented by the general formula (1) (described in Table 2) 2.0 g
・ 0.5 g of the following water-soluble azo compounds
・ 1,5-Naphthalenedisulfonic acid disodium 0.1g
・ Pure water 10.0g

(Synthesis of fine particle polymer (1))
A stirrer, thermometer, dropping funnel, nitrogen inlet tube, reflux condenser is applied to a 1000 ml four-necked flask, and 350 mL of distilled water is added while deoxygenating by introducing nitrogen gas, and the internal temperature becomes 80 ° C. Until heated. 1.5 g of sodium dodecyl sulfate was added as a dispersant, 0.45 g of ammonium persulfide was added as an initiator, and then 45.0 g of styrene was dropped from the dropping funnel over about 1 hour. After the completion of the dropwise addition, the reaction was continued as it was for 5 hours, and then the unreacted monomer was removed by steam distillation. Thereafter, the mixture was cooled and adjusted to pH 6 with ammonia water, and finally pure water was added so that the nonvolatile content was 15% by mass to obtain a fine particle polymer aqueous dispersion (1). The particle size distribution of the fine particle polymer had a maximum value at a particle size of 60 nm.

  Here, the particle size distribution is obtained by taking an electron micrograph of polymer fine particles, measuring a total of 5000 fine particle sizes on the photograph, and logarithm between 0 and the maximum value of the obtained particle size measurement values. The frequency of appearance of each particle size was plotted by dividing it into 50 on the scale. For non-spherical particles, the particle size of spherical particles having the same particle area as that on the photograph was used as the particle size.

(Synthesis of fine particle polymer (2) having a thermally reactive functional group)
7.5 g of allyl methacrylate, 7.5 g of butyl methacrylate and 200 ml of polyoxyethylene nonylphenol aqueous solution (concentration: 9.84 × 10 ⁻³ mol ⁻¹ ) are added, and the system is replaced with nitrogen gas while stirring at 250 rpm. After the temperature of this liquid is 25 ° C., 10 ml of an aqueous cerium (IV) ammonium salt solution (concentration: 0.984 × 10 ⁻³ mol ⁻¹ ) is added. At this time, an aqueous ammonium nitrate solution (concentration 58.8 × 10 ⁻³ mol ⁻¹ ) is added to adjust the pH to 1.3 to 1.4. This was then stirred for 8 hours. The liquid thus obtained had a solid content concentration of 9.5% by mass and an average particle size of 0.4 μm.

(Synthesis of fine particle polymer (3) having a thermally reactive functional group)
7.5 g of glycidyl methacrylate, 7.5 g of butyl methacrylate and 200 ml of a polyoxyethylene nonylphenol aqueous solution (concentration: 9.84 × 10 ⁻³ mol ⁻¹ ) are added, and the system is replaced with nitrogen gas while stirring at 250 rpm. After the temperature of this liquid is 25 ° C., 10 ml of an aqueous cerium (IV) ammonium salt solution (concentration: 0.984 × 10 ⁻³ mol ⁻¹ ) is added. At this time, an aqueous ammonium nitrate solution (concentration 58.8 × 10 ⁻³ mol ⁻¹ ) is added to adjust the pH to 1.3 to 1.4. This was then stirred for 8 hours. The liquid thus obtained had a solid content concentration of 9.5% by mass and an average particle size of 0.4 μm.

[Evaluation of planographic printing plate precursor]
(1) On-machine developability The obtained lithographic printing plate precursor was subjected to an external drum rotation speed of 1000 rpm, a laser output of 70%, and a resolution of 2400 dpi on a Fujifilm Corporation Luxel PLASETTER T-6000III equipped with an infrared semiconductor laser. Exposed. The exposure image included a solid image and a 50% halftone dot chart of a 20 μm dot FM screen.
The obtained exposed original plate was attached to a plate cylinder of a printing machine LITHRONE 26 manufactured by Komori Corporation without developing. Standard automatic of LITHRONE 26 using dampening water of Equality-2 (Fuji Film Co., Ltd.) / Tap water = 2/98 (volume ratio) and Values-G (N) black ink (made by DIC Corporation) After dampening water and ink were supplied by the printing start method and developed on the machine, 100 sheets were printed on Tokuhishi art (76.5 kg) paper at a printing speed of 10,000 sheets per hour.
The number of print sheets required until the on-press development on the printing press of the unexposed portion of the image recording layer was completed and the ink was not transferred to the non-image portion was measured as on-press developability. The results are shown in Table 2.

(2) Printing durability After the above-described evaluation of on-press developability, the printing was further continued. As the number of printed sheets was increased, the image recording layer was gradually worn out, so that the ink density on the printed material decreased. Printing durability was evaluated using the number of printed copies when the value measured by the Gretag densitometer for the 50% halftone dot area ratio of the FM screen in the printed material was 5% lower than the measured value for the 100th printed sheet. . The results are shown in Table 2.

[Examples 17 to 32 and Comparative Examples 4 to 6]
The lithographic printing plate precursor produced as described above was exposed, developed and processed to make a plate for printing.

(1) Exposure, development, and printing The above lithographic printing plate precursors were transferred to FUJIFILM Electronic Imaging Ltd. Image exposure was performed with a Violet semiconductor laser plate setter Vx9600 (equipped with an InGaN-based semiconductor laser (emission wavelength 405 nm ± 10 nm / output 30 mW)) manufactured by (FFEI). Image drawing was performed at a resolution of 2,438 dpi, using an FM screen (TAFFETA 20) manufactured by Fuji Film Co., Ltd., with a plate surface exposure of 0.05 mJ / cm ² so that the dot area ratio was 50%.
Next, after preheating at 100 ° C. for 30 seconds, development processing was performed with an automatic developing processor having a structure as shown in FIG.
Here, the automatic development processor includes a developing unit 6 that develops a planographic printing plate precursor (hereinafter referred to as “PS plate”) 4 and a drying unit 10 that dries the developed PS plate 4. An insertion port is formed in the side plate of the automatic developing machine (the left portion in FIG. 2), and the PS plate 4 inserted from the insertion port is fed by a carry-in roller 16 provided on the inner side surface of the side plate of the automatic developing machine. It is conveyed to the developing unit 6. In the developing tank 20 of the developing unit 6, a conveyance roller 22, a brush roller 24, and a squeeze roller 26 are sequentially provided from the upstream side in the conveyance direction, and a backup roller 28 is provided at an appropriate position therebetween. The PS plate 4 is developed by being immersed in the developer while being conveyed by the conveying roller 22 and rotating the brush roller 24 to remove the protective layer and the image recording layer unexposed portion of the PS plate 4. The developed PS plate 4 is conveyed to the next drying unit 10 by a squeeze roller (unloading roller) 26.
The drying unit 10 is provided with a guide roller 36 and a pair of skewer rollers 38 in order from the upstream side in the transport direction. The drying unit 10 is provided with drying means such as hot air supply means and heat generation means (not shown). The drying unit 10 is provided with a discharge port, and the PS plate 4 dried by the drying means is discharged, and the automatic development processing for the PS plate is completed. The automatic processor used in the examples has one brush roller having an outer diameter of 50 mm in which fibers made of polybutylene terephthalate (hair diameter: 200 μm, hair length: 17 mm) are implanted in the same direction as the conveying direction. 200 revolutions per minute (peripheral speed of the brush tip: 0.52 m / sec). The temperature of the developer was 30 ° C. The planographic printing plate precursor was transported at a transport speed of 82 cm / min (the transport speed was changed when developing properties were evaluated). After the development processing, drying was performed in a drying section. The drying temperature was 80 ° C.

  Next, the lithographic printing plate was attached to a printing machine SOR-M manufactured by Heidelberg, and dampening water (EU-3 (Etchi solution manufactured by FUJIFILM Corporation) / water / isopropyl alcohol = 1/89/10 (volume ratio)). And TRANS-G (N) black ink (manufactured by DIC Corporation), printing was performed at a printing speed of 6000 sheets per hour.

(Developer)
Table 3 below shows the composition of the developer 1 used in Examples and Comparative Examples. The following New Coal B13 (manufactured by Nippon Emulsifier Co., Ltd.) is polyoxyethylene β-naphthyl ether (oxyethylene average number n = 13), and gum arabic has a mass average molar mass (Mw) of 20 Ten thousand things were used.

(2) Evaluation The developability and printing durability were evaluated as follows. The results are shown in Table 4.

<Developability>
Development was performed at various conveying speeds, and the cyan density of the non-image area was measured with a Macbeth densitometer (manufactured by Gretag Macbeth). The conveyance speed at which the cyan density of the non-image area is equal to the cyan density of the aluminum substrate is obtained, and the leading edge of the original is immersed in the developer at this conveying speed, and then the leading edge of the original comes out of the developing liquid. The development time was defined as the development time.

<Print durability>
Printing was performed after evaluating the developability described above. As the number of printed sheets was increased, the image recording layer was gradually worn out, so that the ink density on the printed material decreased. Printing durability was evaluated using the number of printed copies when the value measured by the Gretag densitometer for the 50% halftone dot area ratio of the FM screen in the printed material was 5% lower than the measured value for the 100th printed sheet. . The results are shown in Table 4.

[Examples 33 to 39]
The lithographic printing plate precursors (4) and (11) to (16) were exposed and developed as described above, and then heated in an oven at 130 ° C. for 2 minutes. When the printing durability was tested under the same conditions as in Example 17, the results shown in Table 5 were obtained.

4 Planographic printing plate precursor (PS version)
DESCRIPTION OF SYMBOLS 6 Developing part 10 Drying part 16 Carry-in roller 20 Developing tank 22 Carrying roller 24 Brush roller 26 Squeeze roller (unloading roller)
28 Backup roller 36 Guide roller 38 Skewer roller

Claims (10)

  A lithographic plate having an image recording layer containing a thermoplastic fine particle polymer, an infrared absorber, and a polymer compound on a surface hydrophilic support, and a non-exposed portion in the image recording layer can be removed by development after exposure. A printing plate precursor, wherein the content of the thermoplastic fine particle polymer is 40 to 95% by mass of the solid content of the image recording layer, and the polymer compound has a star shape in which the main chain is branched into three or more A lithographic printing plate precursor having a hydrophilic group in a side chain of a branched polymer main chain.   The lithographic printing plate precursor as claimed in claim 1, wherein the hydrophilic group is at least one of a carboxyl group or a salt thereof, a sulfo group or a salt thereof, and a polyethyleneoxy group.   The lithographic printing plate precursor as claimed in claim 1 or 2, wherein the thermoplastic fine particle polymer has a crosslinkable group.   The polymer compound having a star shape in which the main chain is branched into three or more has a group that reacts with a crosslinkable group of the thermoplastic fine particle polymer in a side chain of the branched polymer main chain. 3. The lithographic printing plate precursor as described in 3.   The crosslinkable group of the thermoplastic fine particle polymer and the group that reacts with the crosslinkable group of the thermoplastic fine particle polymer of the polymer compound having a star shape are both ethylenically unsaturated groups. The lithographic printing plate precursor described.   The lithographic printing plate precursor as claimed in any one of claims 1 to 5, wherein the image recording layer contains a polymerization initiator.   The lithographic printing plate precursor as claimed in any one of claims 1 to 6, wherein the image recording layer is removable by at least one of printing ink and fountain solution.   The lithographic printing plate precursor according to claim 7 is mounted on a printing press and exposed imagewise with a laser, or after imagewise exposure with a laser and mounted on a printing press, the lithographic printing plate precursor A lithographic printing method in which at least one of printing ink and fountain solution is supplied to remove an unexposed portion of the image recording layer and print. A lithographic printing plate making method, wherein the lithographic printing plate precursor according to any one of claims 1 to 6 is imagewise exposed with a laser and then developed with an aqueous solution having a pH of 2 to 12.   The plate making method of a lithographic printing plate according to claim 9, wherein the plate is developed with an aqueous solution having a pH of 2 to 12, followed by heat treatment.

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