WO2020085500A1

WO2020085500A1 - Lithographic printing original plate, layered body of lithographic printing original plates, and method for producing lithographic printing plate

Info

Publication number: WO2020085500A1
Application number: PCT/JP2019/041989
Authority: WO
Inventors: 加奈栢木
Original assignee: 富士フイルム株式会社
Priority date: 2018-10-25
Filing date: 2019-10-25
Publication date: 2020-04-30
Also published as: CN112912249A

Abstract

Provided are: a lithographic printing original plate that comprises a positive-type image recording layer on an aluminum support and in which the Bekk smoothness of the surface of the outermost layer on the side on which the image recording layer is present is 1,000 seconds or less, the outermost layer contains particles, and the modulus of elasticity of the particles is 3.0 GPa or less; a layered body of lithographic printing original plates; a method for producing a lithographic printing plate; and a lithographic printing method.

Description

Lithographic printing plate precursor, lithographic printing plate precursor laminate, and method for producing lithographic printing plate

The present disclosure relates to a lithographic printing plate precursor, a lithographic printing plate precursor laminate, and a method for producing a lithographic printing plate.

《Lithographic printing plate precursors are often stored and transported as a stack of multiple sheets. In this laminate, usually, for the purpose of preventing accumulation deviation of the lithographic printing plate precursor, preventing adhesion between the lithographic printing plate precursors, preventing scratches on the image recording layer side surface of the lithographic printing plate precursor, A slip sheet is inserted between them. However, the use of interleaving paper itself involves problems such as cost increase and disposal processing, and since it needs to be removed before the exposure process, the load of the plate making process and the risk of occurrence of troubles in the interleaf paper peeling defect Will also be. Furthermore, when removing the slip sheet, it is necessary to take care so that the surface of the planographic printing plate precursor on the recording layer side is not damaged. Therefore, it is required to develop a lithographic printing plate precursor that can be laminated even in a mode that does not include interleaving paper (also referred to as "interleaving paperless").

As a matting agent used in a photosensitive lithographic printing plate that can omit the use of interleaving paper, an infrared-sensitive particle mat for a photosensitive lithographic printing plate that is used by being attached to the surface of the photosensitive lithographic printing plate A matting agent characterized by containing an infrared absorbing dye is disclosed (for example, refer to Patent Document 1).
Further, one side of the support has a recording layer containing a water-insoluble and alkali-soluble resin and an infrared absorber and capable of forming an image by infrared irradiation, and a matte layer on the upper recording layer. An organic polymer layer having a film thickness of 1.0 μm to 20 μm is provided on the surface opposite to the surface having the recording layer, and the coefficient of static friction between the recording layer and the organic polymer layer is 0.45 to 0.60. An infrared-sensitive lithographic printing plate precursor characterized by having a range is disclosed (see, for example, Patent Document 2).

Patent Document 1: Japanese Patent Laid-Open No. 2007-114221 Patent Document 2: Japanese Patent No. 4680098

The problem to be solved by one embodiment of the present disclosure is to provide a planographic printing plate precursor excellent in scratch resistance even without interleaving paper, a planographic printing plate laminate, and a method for producing a planographic printing plate. is there.

Means for solving the above problems include the following aspects.
<1> Having a positive image recording layer on an aluminum support,
The Bekk smoothness of the outermost layer surface on the side having the image recording layer is 1,000 seconds or less,
The outermost layer contains particles,
A lithographic printing plate precursor in which the elastic modulus of the particles is 3.0 GPa or less.
<2> The lithographic printing plate precursor as described in <1>, wherein the arithmetic average height Sa of the outermost layer surface on the side having the image recording layer is 0.3 μm or more and 20 μm or less.
<3> The lithographic printing plate precursor as described in <1> or <2> above, wherein the particles contain at least one selected from the group consisting of acrylic resin particles, silica particles and urethane resin particles.
<4> The lithographic printing plate precursor as described in any one of <1> to <3> above, wherein the image recording layer contains a resin having a glass transition temperature of 60 ° C to 230 ° C.
<5> The above-mentioned <1>, wherein the image recording layer contains at least one selected from the group consisting of acetal resin, phenol resin, acrylic resin, and resin having a urea bond, urethane bond or amide bond in the main chain. The lithographic printing plate precursor as described in any one of <4>.
<6> The lithographic printing plate precursor as described in <5>, wherein the image recording layer contains an acrylic resin having a maleimide structure.
<7> The lithographic printing plate precursor as described in any one of the above items <1> to <6>, wherein the image recording layer is a single layer.
<8> The lithographic printing plate precursor as described in any one of <1> to <6> above, wherein the image recording layer is a multi-layer comprising an upper layer and a lower layer on the support.
<9> The lithographic printing plate precursor as described in any one of <1> to <8>, wherein the outermost layer is the image recording layer.
<10> The lithographic printing plate precursor as described in any one of <1> to <9>, further including an overcoat layer on the image recording layer, and the overcoat layer is the outermost layer. .
<11> The lithographic printing plate precursor as described in any one of <1> to <10>, which has a back coat layer on the side opposite to the side having the image recording layer.
<12> A step of exposing the lithographic printing plate precursor according to any one of <1> to <11> above in an imagewise manner to form an exposed portion and an unexposed portion,
developing with an alkaline aqueous solution having a pH of 13.5 or less,
including,
Method of making a lithographic printing plate.
<13> The method for producing a lithographic printing plate as described in <12> above, wherein the alkaline aqueous solution has a pH of 11 or less.
<14> A lithographic printing plate precursor laminate obtained by laminating the lithographic printing plate precursor as described in any one of <1> to <11> above.
<15> The outermost layer on the side having the image recording layer of the lithographic printing plate precursor and the outermost layer on the side opposite to the side having the image recording layer of the other lithographic printing plate precursor were directly contacted and laminated. The lithographic printing plate precursor laminate according to <14> above.

According to an embodiment of the present disclosure, it is possible to provide a lithographic printing plate precursor, a lithographic printing plate precursor laminate excellent in scratch resistance even without a slip sheet, and a method for producing a lithographic printing plate.

The description of the constituent elements described below may be made based on the representative embodiment of the present disclosure, but the present disclosure is not limited to such an embodiment.
In the present specification, “to” indicating a numerical range is used to mean that numerical values described before and after the numerical range are included as a lower limit value and an upper limit value.
In the description of the group (atom group) in the present specification, the notation in which substitution and non-substitution are not included includes not only those having no substituent but also those having a substituent. For example, the “alkyl group” includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).
In the present specification, “(meth) acrylic” is a term used as a concept including both acryl and methacryl, and “(meth) acryloyl” is a term used as a concept including both acryloyl and methacryloyl. Is.
The term "process" in the present specification is included in the term not only as an independent process but also when it cannot be clearly distinguished from other processes as long as the intended purpose of the process is achieved. .
In the present disclosure, a combination of two or more preferable aspects is a more preferable aspect.
In addition, the weight average molecular weight (Mw) and the number average molecular weight (Mn) in the present disclosure use columns of TSKgel GMHxL, TSKgel G4000HxL, and TSKgel G2000HxL (both manufactured by Tosoh Corporation) unless otherwise specified. The gel permeation chromatography (GPC) analyzer was used to detect the solvent THF (tetrahydrofuran) with a differential refractometer, and the molecular weight was calculated using polystyrene as a standard substance.
In the present specification, the term “lithographic printing plate precursor” includes not only the lithographic printing plate precursor but also the discarded plate precursor. In addition, the term "lithographic printing plate" includes not only a lithographic printing plate precursor prepared through an operation such as exposure and development, but also a discarding plate, if necessary. In the case of a waste original plate, the operations of exposure and development are not always necessary. The waste plate is a lithographic printing plate precursor to be attached to a plate cylinder that is not used when a part of the paper surface is printed in a single color or two colors in color newspaper printing, for example.
Hereinafter, the present disclosure will be described in detail.

[Lithographic printing plate precursor]
The lithographic printing plate precursor according to the present disclosure has a positive image recording layer (hereinafter, also simply referred to as “image recording layer”) on an aluminum support (hereinafter also simply referred to as “support”) aluminum support. And the Bekk smoothness of the outermost layer surface on the side having the image recording layer is 1,000 seconds or less, the outermost layer contains particles, and the elastic modulus of the particles is 3.0 GPa or less. The original version.
Further, hereinafter, in the present disclosure, the outermost layer surface of the lithographic printing plate precursor on the side having the image recording layer is also referred to as “front side”, and the outermost layer surface on the side opposite to the side having the image recording layer is also referred to as “back side”. .

As a result of diligent studies by the present disclosure, it has been found that the planographic printing plate precursor according to the present disclosure can provide a planographic printing plate precursor excellent in scratch resistance even with no interleaving paper by adopting the above configuration. Further, it has been found that the planographic printing plate precursor according to the present disclosure is likely to obtain the suppression of ablation.
Although the mechanism by which the above excellent effects are obtained is not clear, it is estimated as follows.

A lithographic printing plate precursor (hereinafter, also simply referred to as “original plate”) is usually used for preventing misalignment of plates during production of the original plate, prevention of adhesion between the original plates, and multiple plate making in the plate making process in which the original plates are taken out one by one from the stack. In order to prevent scratches and prevent scratches in a series of processes such as prevention, master production accumulation, transportation, user plate making, and before printing, the master plates are laminated with a slip sheet interposed between the master plates. There is a case where the interleaving paper is not used for the purpose of preventing the trouble of peeling of interleaving paper at the time of user plate making, improving the plate making speed, and reducing the cost. On the other hand, in the recording layer of the positive lithographic printing plate precursor, the infrared absorbing agent is a dissolution inhibitor that substantially reduces the solubility of the alkali-soluble resin due to the interaction with the alkali-soluble resin in the unexposed area (image area). In the exposed area (non-image area), the generated heat weakens the interaction between the infrared absorbing agent and the alkali-soluble resin and dissolves in the alkali developing solution to form an image. Therefore, the positive type lithographic printing plate precursor has insufficient mechanical strength of the recording layer, and when the plate surface and various members come into strong contact with each other during manufacturing processing, transportation, and handling of the plate, defects occur on the plate surface, and There was a problem that the image part was missing. In the case where interleaving paper is not used in this way, a matting agent is attached to the surface of the photosensitive lithographic printing plate to provide adhesion prevention.
The present inventor, in the positive type lithographic printing plate precursor, simply attaches the matting agent or the like described in Patent Document 1 to the surface of the original plate in order to simply give unevenness to the front surface, and the original plate is made without interleaving paper. When the image recording layer is laminated, the matting agent deforms the image recording layer and the image recording layer becomes thin.Therefore, during development, the image recording layer is dissolved from the thinned portion to expose the support (hereinafter, referred to as “film I also found that there is a problem of "missing." Further, in the lithographic printing plate precursor described in Patent Document 2, it is required to develop a lithographic printing plate precursor that is more excellent in scratch resistance when interleaving paper is omitted.

As a result of intensive studies by the present inventors, in the lithographic printing plate precursor according to the present disclosure, the outermost layer surface on the side having an image recording layer contains particles having a specific elastic modulus or less (that is, moderately soft particles). In addition, by controlling the Bekk smoothness of the outermost layer to a specific number of seconds or less, the occurrence of scratches on the lithographic printing plate precursors can be suppressed when the lithographic printing plate precursors are stacked (when laminated) without interleaving paper, and scratch resistance It is presumed that it has excellent properties.
The lithographic printing original plate according to the present disclosure includes particles having a specific elastic modulus or less on the outermost layer surface on the side having the image recording layer, so that it prevents the components of the image recording layer from scattering during exposure. Conceivable. Further, it is speculated that since the particles spread on the image recording layer at the time of exposure, scattering of components of the image recording layer is suppressed, and thus suppression of ablation can be easily obtained.
Further, since the lithographic printing original plate according to the present disclosure contains particles having a specific elastic modulus or less (that is, particles that are moderately soft), even when the original plates are laminated without interleaving paper, the image recording layer is It is presumed that the film is less likely to be deformed and the film omission is easily suppressed.

The lithographic printing plate precursor according to the present disclosure has an image recording layer (positive type image recording layer) on a support. In the lithographic printing plate precursor according to the present disclosure, the image recording layer may be the outermost layer.
Further, the lithographic printing plate precursor according to the present disclosure may have an undercoat layer between the support and the image recording layer, and also has an overcoat layer (protective layer) on the image recording layer. Alternatively, a resin layer (back coat layer) may be provided on the side (back side) opposite to the side having the image recording layer of the support.
The image recording layer may be a single layer or a multi-layer composed of an upper layer and a lower layer.
The lithographic printing plate precursor according to the present disclosure may be a lithographic printing plate precursor used for on-press development or a lithographic printing plate precursor used for development with a developer.
The outermost layer surface is the surface of the overcoat layer when the above-mentioned overcoat layer is included.

<Bekk smoothness>
[Front side]
The lithographic printing plate precursor according to the present disclosure has a Bekk smoothness of the outermost layer surface (front surface) on the side having an image recording layer (hereinafter, also referred to as “Bekk smoothness a”) from the viewpoint of scratch resistance during stacking without interleaving paper. Is 1,000 seconds or less, preferably 300 seconds or less, and more preferably 100 seconds or less. The Bekk smoothness a is preferably 0 second or more, and more preferably 0.5 second or more, from the viewpoints of plate feeding property for taking out the original plate from the laminate and ease of peeling at the time of laminating without interleaving paper. More preferably, it is more preferably 1 second or longer, and particularly preferably 5 seconds or longer.

[Back side]
The lithographic printing plate precursor according to the present disclosure has a Bekk smoothness b (hereinafter, referred to as “Bekk smoothness b Is also preferably 1,000 seconds or less, more preferably 500 seconds or less, and further preferably 300 seconds or less.

The Bekk smoothness (Bekk seconds) according to the present disclosure is measured according to JIS P8119 (1998). As a specific measuring method, a Beck smoothness tester manufactured by Kumagai Riki Kogyo Co., Ltd. is used, and measurement is performed with an air amount of 1/10 of the standard air amount, that is, 1 mL.

The measurement of the arithmetic mean height Sa in the present disclosure shall be performed according to the method described in ISO 25178. Specifically, using Micromap MM3200-M100 manufactured by Ryoka Systems Co., Ltd., five points are selected from the same sample and measured, and the average value thereof is taken as the arithmetic average height Sa. Regarding the measurement range, a range of 1 cm × 1 cm randomly selected from the sample surface is measured.

<Arithmetic mean height Sa>
[Front side]
The lithographic printing plate precursor according to the present disclosure has an arithmetic average height Sa of the outermost layer surface (front surface) on the side having an image recording layer, from the viewpoint of scratch resistance and peeling ease during interleaving without interleaving paper. It is preferably 0.3 μm or more and 20 μm or less, more preferably 0.5 μm or more and less than 10 μm, further preferably 0.5 μm or more and less than 7 μm, and particularly preferably 0.5 μm or more and less than 3 μm. .
Further, the arithmetic average height Sa of the front surface is preferably smaller than the arithmetic average height Sa of the back surface.
The front surface may be the surface of the image recording layer or the surface of the protective layer when the image recording layer has a protective layer.

[Back side]
In the lithographic printing plate precursor according to the present disclosure, the arithmetic average height Sa of the outermost layer surface (back surface) on the side opposite to the side having the image recording layer is preferably 0.3 μm or more and 20 μm or less.
When the arithmetic mean height Sa of the outermost layer surface on the side opposite to the side having the image recording layer is 0.3 μm or more and 20 μm or less, it is the side opposite to the side having the image recording layer when laminated without interleaving paper. It is possible to suppress the development delay due to the fact that the convex portion of the outermost layer surface (back surface) in (3) is suppressed to the depth of the image recording layer and the image recording layer is damaged.
From the viewpoint of the on-press development delay prevention property and the scratch resistance at the time of stacking without interleaving paper, the arithmetic average height of the back surface is 0.5 μm or more and less than 10 μm, and more preferably 0.5 μm or more and less than 7 μm. It is preferably 0.5 μm or more and less than 3 μm.
The outermost layer surface (back surface) on the side opposite to the side having the image recording layer may be the surface of the support opposite to the side having the image recording layer, or the back coat layer surface. .

[Total value]
In the lithographic printing plate precursor according to the present disclosure, the arithmetic average height Sa of the outermost layer surface on the surface having the image recording layer and the arithmetic average height Sa of the outermost layer surface on the side opposite to the surface having the image recording layer Sa. And the arithmetic mean height Sa of the surface of the outermost layer on the side opposite to the side having the image recording layer is the on-machine development delay prevention property, the plate feeding property for taking out the original plate from the laminate, the particle Is more than 0.3 μm and 20 μm or less, more preferably 0.4 μm to 20 μm, still more preferably 1 μm to 20 μm, from the viewpoints of drop-off prevention property, scratch resistance, and ease of peeling when laminated without interleaving paper. , Particularly preferably 1 μm to 14 μm.

-Specific particles-
<Particles having an elastic modulus of 3.0 GPa or less>
In the lithographic printing plate precursor according to the present disclosure, the outermost layer (front surface) contains particles, and the elastic modulus of the particles is 3.0 GPa or less.
When the elastic modulus of the specific particles is 3.0 GPa or less, the specific particles are appropriately soft, and suppress the occurrence of scratches on the lithographic printing plate precursor when the lithographic printing plate precursors are stacked (when laminated) without interleaving paper, Excellent scratch resistance.
From the above viewpoint, the elastic modulus of the specific particles is preferably 0.001 GPa or more and 3.0 GPa or less, more preferably 0.05 GPa or more and 0.5 GPa or less, and further preferably 0.01 GPa or more and 1.0 GPa or less. is there.
The elastic modulus of the specific particles is obtained by an indentation test, and more specifically, it can be measured by the following method.
A sample in which specific particles are coated on a glass substrate is set in a micro hardness tester. Aiming at one particle of the installed sample, assuming that the plane indenter is sufficiently harder than the particle (sphere), sample particles are compressed with the plane indenter under the following measurement conditions, and a sphere indentation test is performed.
The obtained load variation curve is fitted to the contact formula (Hertz formula) shown in the following formula 1 to calculate the elastic modulus (GPa).

<Measurement conditions>
Equipment: Micro hardness tester HM500 (manufactured by Fisher Instruments Inc.)
Plane indenter: 50 μm x 50 μm plane indenter Load: 1 mN / 20 sec.

Σ ³ , P ² , E ₁ , v ₁ and R ₀ in Formula 1 are as follows.
σ ³ : displacement P ² : load E ₁ : elastic modulus of particle (sphere) v ₁ : Poisson's ratio of particle (sphere) R ₀ : radius of particle

In the lithographic printing plate precursor according to the present disclosure, the outermost layer on the front surface may include one type of specific particles, or may include two or more types in combination.

-Average particle size-
In the outermost layer on the front surface, the average particle diameter of the specific particles is preferably 0.7 μm to 20 μm, more preferably 1 μm to 15 μm, and further preferably 3 μm to 10 μm, from the viewpoint of scratch resistance and film removal prevention property. And particularly preferably 4 μm to 7 μm.
The specific particles may be a combination of two or more specific particles having different average particle sizes.

When the specific particles are contained in the overcoat layer described below, the average particle size of the specific particles is preferably 1.3 times or more, and 1.3 times or more and 10 times or less the thickness of the overcoat layer. Is more preferable.

The average particle size of the specific particles in the present disclosure means a volume average particle size, and the volume average particle size is measured by a laser diffraction / scattering type particle size distribution meter. Specifically, for example, the particle size distribution measurement device “Microtrac MT-3300II” (manufactured by Nikkiso Co., Ltd.) is used.
In addition, in the present disclosure, the average particle size of other particles is also measured by the above measuring method unless otherwise specified.

In the outermost layer on the front surface, the in-plane density of the specific particles is preferably 100 particles / mm ² to 5000 particles / mm ² , and more preferably 100 particles / mm ² to 3000 particles / mm ² .

The in-plane density in the present disclosure can be confirmed by observing the surface of the lithographic printing plate precursor with a scanning electron microscope (SEM). Specifically, the number of specific particles is counted by observing the surface of the lithographic printing plate precursor at 5 points with a scanning electron microscope (SEM), and converted into the number of specific particles per observation visual field area mm ² , and the average value is calculated. It can be done by asking.

In the lithographic printing plate precursor according to the present disclosure, the specific particles are not particularly limited, but from the viewpoint of scratch resistance, at least one kind of particles selected from the group consisting of organic resin particles and inorganic particles may be used. Organic resin particles are more preferable.

<< organic particles >>
Examples of the organic resin particles include poly (meth) acrylic acid esters, polystyrene and its derivatives, polyamides, polyimides, low density polyethylene, high density polyethylene, polypropylene and other polyolefins, polyurethanes, polyureas, polyesters, etc. Preferable examples thereof include particles made of the synthetic resin described above, and particles made of natural polymers such as chitin, chitosan, cellulose, crosslinked starch, and crosslinked cellulose.
Among them, the organic resin particles have advantages such as easy particle size control and easy control of desired surface characteristics by surface modification, and from the viewpoint of excellent scratch resistance, the organic resin particles include urethane resin particles. , Or acrylic resin particles are preferred.

Regarding the production method of organic resin particles, a relatively hard resin such as polymethylmethacrylate (PMMA) can be made into fine particles by a crushing method, but a method of synthesizing particles by an emulsion suspension polymerization method is It is preferably used because of its ease of diameter control and accuracy.
The method for producing organic resin particles is published in "Ultrafine Particles and Materials" edited by Japan Society for Materials Science, published by Sohbo, 1993, "Preparation and application of fine particles and powders" supervised by Haruma Kawaguchi, CMC Publishing, 2005 Etc. in detail.

Organic resin particles are also available as commercial products, for example, cross-linked acrylic resins MX-40T, MX-80H3wT, MX-150, MX-180TA, MX-300, MX-500, MX, manufactured by Soken Chemical Industry Co., Ltd. -1000, MX-1500H, MR-2HG, MR-7HG, MR-10HG, MR-3GSN, MR-5GSN, MR-7G, MR-10G, MR-5C, MR-7GC, styryl resin SX-350H , SX-500H, acrylic resin MBX-5, MBX-8, MBX-12MBX-15, MBX-20, MB20X-5, MB30X-5, MB30X-8, MB30X-20, SBX manufactured by Sekisui Plastics Co., Ltd. -6, SBX-8, SBX-12, SBX-17, polyolefin resin manufactured by Mitsui Chemicals, Inc., Chemipearl (registered trademark) 100, W200, W300, W308, W310, W400, W401, W405, W410, W500, WF640, W700, W800, W900, W950, WP100, and the like.

<< Inorganic particles >>
Examples of the inorganic particles include silica, alumina, zirconia, titania, carbon black, graphite, BaSO ₄ , ZnS, MgCO ₃ , CaCO ₃ , ZnO, CaO, WS ₂ , MoS ₂ , MgO, SnO ₂ , α-Fe ₂ O _3. , Α-FeOOH, SiC, CeO ₂ , BN, SiN, MoC, BC, WC, titanium carbide, corundum, artificial diamond, gemstone, garnet, silica stone, triboli, diatomaceous earth, dolomite, and the like.
Among these, silica particles are preferable as the inorganic particles from the viewpoint of scratch resistance. Further, the silica particles may be silica particles obtained by firing silicone resin particles.
Examples of silica particles obtained by baking the silicone resin particles include Tospearl 2000B, Tospearl 120 (particle diameter 2 μm), Tospearl 145 (particle diameter 4.5 μm) and the like manufactured by Tanac Co., Ltd.

The specific particles may be surface-treated. The surface treatment method is not particularly limited and may be a known method. Further, as the specific particles, two or more kinds of particles having different surface treatments may be used in combination.
From the viewpoint of scratch resistance, the specific particles are preferably organic resin particles coated with at least one inorganic compound selected from the group consisting of silica, alumina, titania and zirconia, and particularly preferably silica-coated organic resin particles. .
The organic resin is preferably at least one resin selected from the group consisting of polyacrylic resins, polyurethane resins, polystyrene resins, polyester resins, epoxy resins, phenol resins and melamine resins.

Hereinafter, the organic resin particles coated with silica (hereinafter, also referred to as “silica-coated organic resin particles”) will be described in detail as an example, but the specific particles in the present disclosure are not limited thereto.

The silica-coated organic resin particles are particles in which particles made of an organic resin are surface-coated with silica. It is preferable that the organic resin particles forming the core do not soften or become sticky depending on moisture in the air or temperature.
Examples of the organic resin forming the organic resin particles in the silica-coated organic resin particles include polyacrylic resin, polyurethane resin, polystyrene resin, polyester resin, epoxy resin, phenol resin, and melamine resin.

As a material for forming the silica layer that coats the surface of the silica-coated organic resin particles, a compound having an alkoxysilyl group such as a condensation product of an alkoxysiloxane-based compound, particularly a siloxane-based material, specifically, silica sol or colloidal silica. Preferred are silica particles such as silica nanoparticles.
Even if the silica-coated organic resin particles have a structure in which silica particles are adhered to the surface of the organic resin particles as a solid component, the siloxane compound layer is formed on the surface of the organic resin particles by condensation reaction of the alkoxysiloxane compound. It may be configured.

Silica does not necessarily have to cover the entire surface of the organic resin particles, and it is preferable that the surface is coated with at least 0.5 mass% of the total mass of the organic resin particles. That is, by virtue of the presence of silica on at least a part of the surface of the organic resin particles, the affinity for the coexisting water-soluble polymer, for example, polyvinyl alcohol (PVA) on the surface of the organic particles is improved, and external stress is applied. Even when the sheet is exposed, falling of particles is suppressed, and excellent scratch resistance and easy peeling at the time of stacking without interleaving paper can be maintained. Therefore, the “silica coating” in the present disclosure includes such a state that silica is present on at least a part of the surface of the organic resin particles.
The surface coverage of silica can be confirmed by morphological observation with a scanning electron microscope (SEM) or the like. The silica coating amount can be confirmed by detecting Si atoms by elemental analysis such as fluorescent X-ray analysis and calculating the amount of silica present therein.

The method for producing the silica-coated organic resin particles is not particularly limited, and a method of coexisting silica particles or a silica precursor compound with a monomer component as a raw material for the organic resin particles to form the organic resin particles and simultaneously form a silica surface coating layer Alternatively, after forming the organic resin particles, silica particles may be physically attached to the surface and then fixed.

The following is an example of a method for producing silica-coated organic resin particles. First, in a water containing a suspension stabilizer appropriately selected from water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and polyacrylic acid, and inorganic suspending agents such as calcium phosphate and calcium carbonate, silica and the raw material resin (more Specifically, a monomer capable of suspension polymerization, a prepolymer capable of suspension crosslinking, or a raw material resin such as a resin liquid, which constitutes the above organic resin, is added, stirred, and mixed to obtain silica and a raw material. A suspension in which a resin is dispersed is prepared. At that time, a suspension having a desired particle size can be formed by adjusting the type of the suspension stabilizer, its concentration, the stirring rotation speed, and the like. Next, the suspension is heated to start the reaction, and the resin raw material is subjected to suspension polymerization or suspension crosslinking to generate resin particles. At this time, the coexisting silica is fixed to the resin particles which are cured by the polymerization or the crosslinking reaction, particularly in the vicinity of the surface of the resin particles due to its physical properties. Thereafter, the suspension is subjected to solid-liquid separation, the suspension stabilizer attached to the particles is removed by washing, and the suspension is dried. Thus, substantially spherical silica-coated organic resin particles having a desired particle size on which silica is immobilized can be obtained.

Thus, the silica-coated organic resin particles having a desired particle size can be obtained by controlling the conditions during suspension polymerization or suspension cross-linking, and the silica-coated organic resin can be strictly controlled without such control. It is also possible to obtain silica-coated organic particles having a desired size by a mesh filtration method or the like after the particles are generated.

Regarding the amount of the raw material added to the mixture when the silica-coated organic particles are produced by the above method, for example, when the total amount of the raw material resin and the silica is 100 parts by mass, first, 200 parts by mass to 800 parts by mass of water as a dispersion medium is used. 0.1 to 20 parts by mass of a suspension stabilizer is added to parts by mass to sufficiently dissolve or disperse the mixture, and the mixture of 100 parts by mass of the raw material resin and silica is added to the solution to prepare dispersed particles. A preferable mode is one in which stirring is performed while adjusting the stirring speed so that the particle size becomes a predetermined particle size, the particle size is adjusted, and then the liquid temperature is raised to 30 ° C. to 90 ° C. and the reaction is performed for 1 hour to 8 hours.

Regarding the method for producing the silica-coated organic resin particles, the above-mentioned method is one example thereof. For example, JP-A-2002-327036, JP-A-2002-173410, JP-A-2004-307837, and The silica-coated organic resin particles obtained by the method described in detail in Japanese Unexamined Patent Publication No. 2006-38246 can also be suitably used in the present disclosure.

Further, the silica-coated organic resin particles are also available as a commercial product, and specifically, as the silica / melamine composite particles, NISSAN CHEMICAL INDUSTRIES CO., LTD. Opto beads 2000M, opto beads 3500M, opto beads 6500M, opto beads are available. Examples include beads 10500M, opto beads 3500S, opto beads 6500S, and the like. Examples of the silica / urethane composite particles include dynamic beads CN5070D manufactured by Dainichiseika Kogyo Co., Ltd., and DAMPRACOAT THU.

Although the organic resin particles used in the present disclosure have been described above by taking the silica-coated organic resin particles as an example, alumina, titania or zirconia is used instead of silica for the organic resin particles coated with alumina, titania or zirconia. It can be carried out similarly.

From the viewpoint of scratch resistance, the specific particles preferably include at least one selected from the group consisting of acrylic resin particles, silica particles and urethane resin particles, and more preferably acrylic resin particles and silica particles. It is preferable to include at least one selected from the group consisting of

<< shape >>
The shape of the specific particles is preferably a true spherical shape, but may be a flat plate shape or a so-called spindle shape such that the projection is elliptical.

The lithographic printing plate precursor according to the present disclosure has an outermost layer (for example, a backcoat layer) on the side opposite to the side having the image recording layer of the support, and by containing the specific particles in the outermost layer, The Bekk smoothness of the outermost layer surface and the arithmetic mean height Sa of the outermost layer surface can be adjusted to the above desired ranges. As a result, the planographic printing plate precursor according to the present disclosure has even more excellent characteristics.

<Support>
The lithographic printing plate precursor according to the present disclosure has an aluminum support.
A suitable aluminum plate used for the aluminum support is a pure aluminum plate or an alloy plate containing aluminum as a main component and a slight amount of a foreign element, and may be a plastic film on which aluminum is laminated or vapor-deposited. The foreign elements contained in the aluminum alloy include silicon, iron, manganese, copper, magnesium, chromium, zinc, bismuth, nickel and titanium. The content of the foreign element in the alloy is preferably 10 mass% or less.

Aluminum which is particularly suitable in the present disclosure is pure aluminum, but completely pure aluminum is difficult to produce due to refining technology, and thus may contain slightly different elements.
As described above, the aluminum plate applied to the present disclosure is not specified in composition, and an aluminum plate made of a known and publicly known material can be appropriately used. The aluminum plate used in the present disclosure preferably has a thickness of 0.1 mm to 0.6 mm, more preferably 0.15 mm to 0.4 mm, and particularly preferably 0.2 mm to 0.3 mm. preferable.

Such aluminum plate may be subjected to surface treatment such as surface roughening treatment and anodizing treatment, if necessary. Regarding the surface treatment of the aluminum support, for example, a degreasing treatment with a surfactant, an organic solvent or an alkaline aqueous solution, a rough surface as described in paragraphs 0167 to 0169 of JP2009-175195A Chemical treatment, anodization treatment, etc. are appropriately performed.
The aluminum surface that has been subjected to the anodizing treatment is optionally subjected to a hydrophilic treatment.
As the hydrophilic treatment, a method of treating with an alkali metal silicate (for example, sodium silicate aqueous solution) method, potassium fluorozirconate or polyvinylphosphonic acid, as disclosed in paragraph 0169 of JP2009-175195A, is used. Are used.
Further, the support described in JP 2011-245844 A is also preferably used.

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

<Image recording layer>
The lithographic printing plate precursor according to the present disclosure has an image recording layer on a support.
The image recording layer preferably contains a binder polymer. The binder polymer preferably contains a resin having a glass transition temperature of 60 ° C. to 230 ° C., and contains a resin having a glass transition temperature (Tg) of 65 ° C. to 225 ° C., from the viewpoint of scratch resistance and film loss prevention. Is more preferable, and it is further preferable that the resin contains 75 ° C to 220 ° C.
In the present specification, Tg is a value measured by a differential scanning calorimetry (DSC). As the differential scanning calorimeter (DSC), for example, EXSTAR 6220 manufactured by SII Nanotechnology Inc. can be used.

-Acetal resin, phenol resin, acrylic resin, and resin having urea bond, urethane bond or amide bond in the main chain-
The image recording layer is at least one selected from the group consisting of an acetal resin, a phenol resin, an acrylic resin, and a resin having a urea bond, a urethane bond or an amide bond in the main chain (hereinafter, also referred to as “specific binder polymer”). It is preferable to include one.
The specific binder polymers may be used alone or in combination of two or more.
Further, the image recording layer preferably contains the above-mentioned specific binder polymer and an infrared absorbing agent described later.
The image recording layer in the present disclosure can be formed, for example, by applying the specific binder polymer and the infrared absorbing agent on the support and drying the support, if necessary. The drying method is not particularly limited, and examples thereof include natural drying, air drying, and drying by heating.
The image recording layer is preferably a thermal positive type image recording layer capable of imagewise exposure with an infrared laser.

From the viewpoint of developability, the image recording layer according to the present disclosure preferably contains a specific binder polymer having an acid group. The specific binder polymer is preferably an alkali-soluble resin.
In the present disclosure, alkali-soluble refers to being soluble in a 1 mol / L sodium hydroxide solution at 25 ° C.

Here, the specific binder polymer includes a homopolymer containing an acid group in the main chain and / or side chain in a polymer, a copolymer thereof, and a mixture thereof. Therefore, the thermal positive type heat-sensitive layer has a characteristic of being dissolved when it is brought into contact with an alkali developing solution. As the specific binder polymer, those having at least one of the following acid groups (1) to (7) in the polymer main chain and / or side chain are preferable from the viewpoint of solubility in an alkali developing solution. .

(1) Phenolic hydroxy group (-Ar-OH)
(2) Sulfonamide group (-SO ₂ NH-R or divalent group represented by -SO ₂ NH-)
(3) Substituted sulfonamide acid group (—SO ₂ NHCOR, —SO ₂ NHSO ₂ R, —CONHSO ₂ R) (hereinafter referred to as “active imide group”)
(4) Carboxy group (-CO ₂ H)
(5) Sulfo group (-SO ₃ H)
(6) Phosphate group (-OPO ₃ H ₂ )
(7) Phosphonic acid group (-PO ₃ H ₂ )

In the above (1) to (7), Ar represents a divalent aryl group which may have a substituent, and R represents a hydrocarbon group which may have a substituent.

Among the specific binder polymers having an acid group selected from the above (1) to (7), the specific binder polymer having (1) a phenolic hydroxy group, (2) a sulfonamide group or (3) an active imide group is preferable, The specific binder polymer having (1) a phenolic hydroxy group or (2) a sulfonamide group is particularly preferable from the viewpoint of ensuring sufficient solubility in an alkali developing solution and film strength.
From the viewpoint of developability, the acid group contained in the specific binder polymer is at least 1 selected from the group consisting of (4) carboxy group, (2) sulfonamide group, and (1) phenolic hydroxy group. It is preferred that it is a seed acid group.

-Polyurethane or polyurea-
The polyurethane or polyurea contained in the specific binder polymer used in the present disclosure is not particularly limited as long as it is a conventionally known one, but for example, the following urea resin or urethane resin is preferably used. Examples thereof include urea resins and urethane resins disclosed in WO 2015/152209.

<< Urea resin >>
In the present disclosure, a polymer whose main chain is formed by a urea bond is referred to as a urea resin.
In the present disclosure, the “urea bond” is represented by the formula: —NR ¹ CONR ² —. In the present disclosure, R ¹ and R ² are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, And a hydrogen atom or an alkyl group having 5 or less carbon atoms is more preferable.

The urea bond may be formed by any means, but can be obtained by reacting an isocyanate compound with an amine compound. In addition, as in 1,3-bis (2-aminoethyl) urea, 1,3-bis (2-hydroxyethyl) urea, 1,3-bis (2-hydroxypropyl) urea, etc., a hydroxy group at the terminal or A urea compound substituted with an alkyl group having an amino group may be synthesized as a raw material.

The above-mentioned isocyanate compound used as a raw material can be used without particular limitation as long as it is a polyisocyanate compound having two or more isocyanate groups in the molecule, but a diisocyanate compound is preferable.
Examples of the polyisocyanate compound include 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,3-cyclopentane diisocyanate, 9H-fluorene. -2,7-diisocyanate, 9H-fluoren-9-one-2,7-diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,3-phenylene diisocyanate, tolylene-2,4-diisocyanate, Tolylene-2,6-diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 2,2-bis (4-isocyanatophenyl) hexafluoropropane, 1,5-diisocyanato Examples thereof include naphthalene and 4,4′-diamino-3,3′-dihydroxydiphenylmethane.

As the amine compound used as a raw material, any polyamine compound having two or more amino groups in the molecule can be used without particular limitation, but a diamine compound is preferable.
Examples of the polyamine compound include 2,7-diamino-9H-fluorene, 3,6-diaminoacridine, acriflavine, acridine yellow, 2,2-bis (4-aminophenyl) hexafluoropropane, 4,4′-diamino Benzophenone, bis (4-aminophenyl) sulfone, 4,4′-diaminodiphenyl ether, bis (4-aminophenyl) sulfide, 1,1-bis (4-aminophenyl) cyclohexane, 4,4′-diaminodiphenylmethane, 3 , 3'-diaminodiphenylmethane, 3,3'-diaminobenzophenone, 4,4'-diamino-3,3'-dimethyldiphenylmethane, 4- (phenyldiazenyl) benzene-1,3-diamine, 1,5-diaminonaphthalene , 1,3-Phenylenediamine, 2,4-Diaminoto Ruene, 2,6-diaminotoluene, 1,8-diaminonaphthalene, 1,3-diaminopropane, 1,3-diaminopentane, 2,2-dimethyl-1,3-propanediamine, 1,5-diaminopentane, 2-methyl-1,5-diaminopentane, 1,7-diaminoheptane, N, N-bis (3-aminopropyl) methylamine, 1,3-diamino-2-propanol, diethylene glycol bis (3-aminopropyl) Ether, m-xylylenediamine, tetraethylenepentamine, 1,3-bis (aminomethyl) cyclohexane, benzoguanamine, 2,4-diamino-1,3,5-triazine, 2,4-diamino-6-methyl- 1,3,5-triazine, 6-chloro-2,4-diaminopyrimidine, 2-chloro-4,6-diamino- , 3,5-triazine.
You may make these polyamine compounds react with phosgene or triphosgene, synthesize | combine polyisocyanate, and may use it as a raw material.

<< urethane resin >>
In the present disclosure, a polymer whose main chain is formed of urethane bonds is referred to as a urethane resin. In the present disclosure, “urethane bond” is represented by the formula: —OC (═O) NR ³ —. Here, R ³ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms (methyl group, ethyl group, propyl group, isopropyl group, tert-butyl group, pentyl group, hexyl group, cyclohexyl group, etc.) A hydrogen atom or an alkyl group having 5 or less carbon atoms is more preferable, and a hydrogen atom or a methyl group is further preferable.

The urethane bond may be formed by any means, and can be obtained by reacting an isocyanate compound with a compound having a hydroxy group.
The isocyanate compound used as a raw material is preferably a polyisocyanate compound having two or more isocyanate groups in the molecule, and more preferably a diisocyanate compound. Examples of the polyisocyanate compound include the polyisocyanate compounds mentioned as the raw materials for forming the urea bond.
Examples of the compound having a hydroxy group used as a raw material include a polyol compound, an aminoalcohol compound, an aminophenol compound, an alkylaminophenol compound and the like, but a polyol compound or an aminoalcohol compound is preferable.
The polyol compound is a compound having at least two or more hydroxy groups in the molecule, and is preferably a diol compound. Further, it may have an ester bond or an ether bond in the molecule. Examples of the polyol compound include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, polyethylene glycol, polytetramethylene glycol, 1,4-cyclohexane. Dimethanol, pentaerythritol, 3-methyl-1,5-pentanediol, poly (ethylene adipate), poly (diethylene adipate), poly (propylene adipate), poly (tetramethylene adipate), poly (hexamethylene adipate), poly (Neopentylene adipate) and the like.
The amino alcohol compound is a compound having an amino group and a hydroxy group in the molecule, and may further have an ether bond in the molecule. Examples of amino alcohols include amino ethanol, 3-amino-1-propanol, 2- (2-aminoethoxy) ethanol, 2-amino-1,3-propanediol, 2-amino-2-methyl-1,3- Examples thereof include propanediol and 1,3-diamino-2-propanol.
In addition, a diol compound or a polyol compound having a sulfone group such as bis (4- (2-hydroxyethoxy) phenyl sulfone) may be used.

The polyurea or polyurethane used in the present disclosure further has an acid group.
The acid group is preferably at least one group selected from the group consisting of a phenolic hydroxy group, a sulfonamide group, an active imide group and a carboxy group, and a phenolic hydroxy group, a sulfonamide group and a carboxy group It is more preferably at least one group selected from the group consisting of, and further preferably a phenolic hydroxy group or a sulfonamide group.
The acid group may be contained in either the main chain or side chain of the polymer, but it is preferable to have it in the main chain.
In the present disclosure, having a phenolic hydroxyl group in the main chain means having an arylene group bonded to the phenolic hydroxyl group in the main chain. Having a sulfonamide group in the main chain means having a divalent group represented by —SO ₂ NH— in the main chain.

Further, the polyurea or polyurethane used in the present disclosure is at least one selected from the group consisting of a polyurethane containing a constitutional unit represented by the following formula 1 and a polyurea containing a constitutional unit represented by the following formula 1. It is preferable to include a polymer.

In Formula 1, X ¹ represents —CR ² —, —O— or —S—, and R's each independently represent a hydrogen atom or an alkyl group.
The constituent unit represented by the above formula 1 is preferably contained in the main chain of polyurethane or polyurea.
In Formula 1, ^{X 1} is _-CH 2 -, - preferably O- or -S-, -CH ₂ -, or, more preferably -O-, -CH ₂ - that is More preferable. Moreover, the halogen atom of the alkyl group in X ¹ may be substituted with a halogen atom or the like.
In formula 1, the two groups represented by —NHC (═O) — which are bonded to the two benzene rings each bond with —O— to form a urethane bond, or each —NH— It is preferable to combine with to form a urea bond.
In Formula 1, the bonding position of —NHC (═O) — bonded to the two benzene rings is not particularly limited, but is preferably the meta position of X ^{1 in} the benzene ring.
The constitutional unit represented by Formula 1 is preferably a constitutional unit derived from the diisocyanate compound represented by the following Formula 1A. In the production of polyurea or polyurethane, a diisocyanate compound represented by Formula 1A is reacted with an amine compound (for example, a diamine compound) or an alcohol compound (for example, a diol compound) to contain a structural unit represented by Formula 1. It is possible to synthesize polyurea or polyurethane.

Specific examples of polyurethane or polyurea used as the specific binder polymer in the present disclosure are shown below, but the present disclosure is not limited thereto. In the formula below, the numerical value at the lower right of the parentheses represents the molar ratio of the constituent units. Further, the following formulas PU-1 to PU-6 are described in a form in which carbon atoms and hydrogen atoms of hydrocarbon are omitted.

<<< polyamide >>
In the present disclosure, a polyamide resin having an amide bond in the main chain can be used as the specific binder polymer. For example, the polymers described in JP-A-2004-157461 and JP-A-2005-91429 are preferably used. However, as long as it has the above-mentioned acid group and has an amide bond in the main chain because it is soluble in alkali, it is not limited thereto.
Specific examples of these compounds include, but are not limited to, polymers represented by the following formula PA-1.

-Phenolic resin-
The phenol resin used as the specific binder polymer is preferably a phenol resin having a weight average molecular weight of more than 2,000. The phenol resin having a weight average molecular weight of more than 2,000 is a phenol resin containing phenol or a substituted phenol as a constitutional unit, preferably a novolac resin. The novolac resin is preferably used in the lithographic printing plate precursor because it causes a strong hydrogen bonding property in the unexposed area and a part of the hydrogen bonding is easily released in the exposed area.
The novolac resin is not particularly limited as long as it contains phenols as a constituent unit in the molecule.
The novolac resin in the present disclosure is a resin obtained by a condensation reaction of phenol, a substituted phenol shown below, and an aldehyde. Specific examples of the phenol include phenol, isopropylphenol, t-butylphenol, Examples thereof include t-amylphenol, hexylphenol, cyclohexylphenol, 3-methyl-4-chloro-6-t-butylphenol, isopropylcresol, t-butylcresol and t-amylcresol. Preferred are t-butylphenol and t-butylcresol. In addition, examples of aldehydes include aliphatic and aromatic aldehydes such as formaldehyde, acetaldehyde, acrolein, and crotonaldehyde. Formaldehyde and acetaldehyde are preferable.
More specifically, examples of the novolac resin in the present disclosure include a condensation polymer of phenol and formaldehyde (phenol formaldehyde resin), a condensation polymer of m-cresol and formaldehyde (m-cresol formaldehyde resin), p -Polycondensation polymer of cresol and formaldehyde (p-cresol formaldehyde resin), polycondensation polymer of m- / p-mixed cresol and formaldehyde (m- / p-mixed cresol-formaldehyde resin), phenol and cresol (m-, Condensation polymer of p- or m- / p-mixture) and formaldehyde (phenol / cresol (m-, p-, or m- / p-mixture) mixed formaldehyde resin), etc. Is mentioned.
Further, as the novolac resin, as described in US Pat. No. 4,123,279, an alkyl group having 3 to 8 carbon atoms such as t-butylphenolformaldehyde resin and octylphenolformaldehyde resin is further used. Examples thereof include a condensation polymer of phenol and formaldehyde having a substituent.
Among these novolac resins, phenol formaldehyde resin and phenol / cresol mixed formaldehyde resin are particularly preferable.

The weight average molecular weight of the phenol resin is preferably more than 2,000 and 50,000 or less, more preferably 2,500 to 20,000, and particularly preferably 3,000 to 10,000. . The dispersity (weight average molecular weight / number average molecular weight) is preferably 1.1 to 10.
The number average molecular weight is a polystyrene equivalent number average molecular weight measured by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.
Such phenol resins may be used alone or in combination of two or more.
The content of the phenol resin in the image recording layer in the present disclosure is preferably 1% by mass to 90% by mass based on the total mass of the specific binder polymer, from the viewpoint of obtaining a lithographic printing plate precursor having excellent image forming properties. It is more preferably from 50% by mass to 50% by mass, and particularly preferably from 10% by mass to 30% by mass.

When the specific binder polymer is a phenol resin, specific examples of the phenol resin are shown below, but the present disclosure is not limited thereto.

<< acrylic resin >>
The acrylic resin is not particularly limited as long as it is a resin containing at least a structural unit derived from an acrylic compound. The acrylic resin may have the above acidic group, acrylonitrile group, or styrene group, but it is preferable to have the above acidic group from the viewpoint of developability. As the acrylic resin, known acrylic resins used for the image recording layer of the positive planographic printing plate precursor can be used without particular limitation.
The acrylic resin may be used alone or in combination of two or more.
As the acrylic resin, a polymer produced by polymerizing a monomer containing at least one ethylenically unsaturated monomer having an acidic group or a mixture thereof is preferably used.

As the ethylenically unsaturated monomer having an acidic group, (meth) acrylic acid or a monomer represented by the following formula is preferably exemplified.

In formulas S-1 and S-2, R ^s1 represents a hydrogen atom or an alkyl group. Z represents —O— or —NR ^s2 , and R ^s2 represents a hydrogen atom, an alkyl group, an alkenyl group, or an alkynyl group. Ar ¹ represents an aromatic group, at least one of which is a heteroaromatic group, and X represents a hydrogen atom or an aromatic group. sa and sb each independently represent 0 or 1.

In formula S-1, R ^s1 represents a hydrogen atom or an alkyl group, and the alkyl group is a substituted or unsubstituted alkyl group, and preferably has no substituent. ^Examples of the alkyl group represented by R ^s1 include lower alkyl groups such as a methyl group, an ethyl group, a propyl group and a butyl group. R ^s1 is preferably a hydrogen atom or a methyl group.
Z represents —O— or —NR ^s2 —, preferably —NR ^s2 —. Here, R ^s2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, or a substituted or unsubstituted alkynyl group, preferably a hydrogen atom or an unsubstituted alkyl group, and It is preferably a hydrogen atom.
sa and sb each independently represent 0 or 1, and a preferred embodiment is when sa is 0 and sb is 1, more preferably sa and sb are both 0, and particularly preferably sa And sb are both 1.
More specifically, in the above structural unit, when sa is 0 and sb is 1, Z is preferably O. Further, when both sa and sb are 1, Z is preferably NR ^s2 , and R ^s2 is preferably a hydrogen atom.

Ar ¹ and Ar ² each independently represent an aromatic group, at least one of which is a heteroaromatic group. Ar ¹ is a divalent aromatic group and Ar ² is a monovalent aromatic group. The aromatic group is a substituent formed by replacing one or two hydrogen atoms forming the aromatic ring with a linking group.
The aromatic ring and heteroaromatic ring in the aromatic group may be selected from hydrocarbon aromatic rings such as benzene, naphthalene, and anthracene, and furan, thiophene, pyrrole, imidazole, 1,2,3-triazole. , 1,2,4-triazole, tetrazole, oxazole, isoxazole, thiazole, isothiazole, thiadiazole, oxadiazole, pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine It may be selected from heteroaromatic rings such as 1,2,3-triazine.
A plurality of rings may be condensed to form a condensed ring such as benzofuran, benzothiophene, indole, indazole, benzoxazole, quinoline, quinazoline, benzimidazole, or benzotriazole.

The aromatic group and the heteroaromatic group may have a substituent, and examples of the substituent that can be introduced include an alkyl group, a cycloalkyl group, an alkenyl group, a cycloalkenyl group, an aryl group and a heteroaryl group. A hydroxy group, a mercapto group, a carboxy group or an alkyl ester thereof, a sulfonic acid group or an alkyl ester thereof, a phosphinic acid group or an alkyl ester thereof, an amino group, a sulfonamide group, an amide group, a nitro group, a halogen atom, or these Examples thereof include a substituent formed by combining a plurality of the substituents, and the substituent may further have the substituents described here.

Ar ² is preferably a heteroaromatic group which may have a substituent, more preferably pyridine, pyridazine, pyrimidine, pyrazine, 1,3,5-triazine, 1,2,4-triazine, Heteroaromatic rings containing nitrogen atoms selected from 1,2,3-triazine, tetrazole, oxazole, isoxazole, thiazole, isothiazole, thiadiazole, and oxadiazole.

The content of the constitutional unit represented by the formula S-1 or S-2 (converted as a monomer unit) is preferably 10 mol% to 100 mol% with respect to the total amount of the monomer units in the acrylic resin, 20 mol% to 90 mol% is more preferable, 30 mol% to 80 mol% is still more preferable, and 30 mol% to 70 mol% is particularly preferable.

The number average molecular weight (Mn) of the acrylic resin having at least one of the structural unit represented by the formula S-1 and the structural unit represented by the formula S-2 is preferably 10,000 to 500,000. 10,000 to 200,000 is more preferable, and 10,000 to 100,000 is particularly preferable. The weight average molecular weight (Mw) is preferably 10,000 to 1,000,000, more preferably 20,000 to 500,000, and particularly preferably 20,000 to 200,000.

The content of the structural unit represented by the ethylenically unsaturated monomer having an acidic group is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 25% by mass, because of excellent developability. Mass% is more preferable, and 10 mass% to 20 mass% is further preferable.

As the constitutional unit represented by a monomer other than the ethylenically unsaturated monomer having an acidic group, alkyl (meth) acrylate, (meth) acrylic acid ester having an aliphatic hydroxyl group, (meth) acrylamide, vinyl ester And styrenes, nitrogen atom-containing monomers such as N-vinylpyrrolidone, and constitutional units represented by maleimides. Among the structural units represented by these other monomers, the monomers preferably used are (meth) acrylic acid ester, (meth) acrylamide, maleimide compound, and (meth) acrylonitrile, and more preferably Are (meth) acrylamide and maleimide compounds. ：

The maleimide compound capable of forming a maleimide structure is preferably N-substituted maleimide, and examples of the N-substituted maleimide include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide and Ni-propylmaleimide. , Nn-butylmaleimide, Nt-butylmaleimide, Nn-hexylmaleimide, N-cyclopentylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-1-naphthylmaleimide and the like. Among them, N-cyclohexylmaleimide and N-phenylmaleimide are preferable, and N-phenylmaleimide is more preferable. The N-substituted maleimides may be used alone or in combination of two or more.

The image recording layer preferably contains an acrylic resin having a maleimide structure, and more preferably an acrylic resin having an N-substituted maleimide structure, from the viewpoints of scratch resistance, film detachment suppressing property, and ablation suppressing property.
The content of the structural unit derived from the N-substituted maleimide is preferably 50% by mass or less, more preferably 5% by mass to 50% by mass, further preferably 10% by mass to 40% by mass, based on the total mass of the acrylic resin. .

When it contains a structural unit derived from (meth) acrylamide, the content of the structural unit is preferably 40% by mass or less, more preferably 1% by mass to 40% by mass, based on the total mass of the acrylic resin. More preferably, it is from 30% by mass to 30% by mass.

The weight average molecular weight of the acrylic resin is preferably 2,000 or more, more preferably 10,000 to 100,000, further preferably 30,000 to 60,000.

The content of the acrylic resin in the image recording layer is preferably 1% by mass to 60% by mass, more preferably 5% by mass to 50% by mass, based on the total mass of the image recording layer.

When the specific binder polymer is an acrylic resin, specific examples of the acrylic resin are shown below, but the present disclosure is not limited thereto. In the following formula, Me represents a methyl group.

<< Acetal resin >>
The image recording layer in the present disclosure may further contain an acetal resin.
Examples of the acetal resin include polymer compounds containing a structural unit represented by the following formula EV-1 and the following formula EV-2.

In formula EV-1 or formula EV-2, L represents a divalent linking group, x is 0 or 1, R ¹ represents an aromatic ring group or a heteroaromatic ring group having at least one hydroxy group, R ² and R ³ are each independently a hydrogen atom, a halogen atom, a linear or branched group which may have a substituent, or a cyclic alkyl group, a linear or branched group which may have a substituent, Alternatively, it represents a cyclic alkenyl group, an aromatic ring that may have a substituent, or a heteroaromatic ring that may have a substituent.

In the formula EV-1, R ¹ represents an aromatic ring or a heteroaromatic ring having at least one hydroxy group, and the hydroxy group may be at the ortho, meta or para position with respect to the binding site with L. Good.
Preferred examples of the aromatic ring include phenyl group, benzyl group, tolyl group, o-, m-, p-xylyl group, naphthyl group, anthracenyl group, and phenanthrenyl group.
Preferred examples of the heteroaromatic ring include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group.
These aromatic rings or heteroaromatic rings may have a substituent other than a hydroxyl group, and examples of the substituent include an alkyl group such as a methyl group and an ethyl group, an alkoxy group such as a methoxy group and an ethoxy group, an aryloxy group. Group, thioalkyl group, thioaryl group, -SH, azo group such as azoalkyl group and azophenyl group, thioalkyl group, amino group, ethenyl group, alkenyl group, alkynyl group, cycloalkyl group, aryl group, heteroaryl group, or hetero group Examples thereof include alicyclic groups.
R ¹ is preferably a hydroxyphenyl group having a hydroxy group or a hydroxynaphthyl group, and more preferably a hydroxyphenyl group.
Examples of the hydroxyphenyl group include 2-, 3-, or 4-hydroxyphenyl groups.
Examples of the hydroxynaphthyl group include 2,3-, 2,4-, or 2,5-dihydroxynaphthyl group, 1,2,3-trihydroxynaphthyl group, and hydroxynaphthyl group.
The hydroxyphenyl group or hydroxynaphthyl group may have a substituent, and preferable examples of the substituent include alkoxy groups such as methoxy group and ethoxy group.

In Formula EV-1, L represents a divalent linking group, and is an alkylene group, an arylene group, a heteroarylene group, —O—, —C (═O) —, —C (═O) O—, —C ( = O) -NH-, -NH-C (= O)-, -NH-C (= O) -O-, -OC-(= O) -NH-, -NH-C (= O)- NH-, -NH-C (= S) -NH-, -S (= O)-, -S (= O) 2-, -CH = N-, -NH-NH-, or a combination thereof It is preferred to represent the groups represented.
The alkylene group, the arylene group, or the heteroarylene group may have a substituent, and as the substituent, an alkyl group, a hydroxy group, an amino group, a monoalkylamino group, a dialkylamino group, an alkoxy group, and , Phosphonic acid groups or salts thereof.
L is an alkylene group, an arylene group, or, more preferably heteroarylene _{_{_{group, -CH 2 -, - CH 2}}} -CH 2 -, - CH 2 -CH 2 -CH 2 -, or, phenylene group More preferably,

In Formula EV-2, R ² and R ³ may each independently have a hydrogen atom, a halogen atom, a linear or branched alkyl group which may have a substituent, or a cyclic alkyl group which may have a substituent. It represents a linear, branched, or cyclic alkenyl group, an aromatic ring that may have a substituent, or a heteroaromatic ring that may have a substituent.
Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, a chloromethyl group, a trichloromethyl group, an isopropyl group, an isobutyl group, an isopentyl group and a neopentyl group. , 1-methoxybutyl group, isohexyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, and methylcyclohexyl group.
Examples of the alkenyl group include ethenyl group, n-propenyl group, n-butenyl group, n-pentenyl group, n-hexenyl group, isopropenyl group, isobutenyl group, isopentenyl group, neopentenyl group, 1-methylbutenyl group, isohexenyl group. Group, a cyclopentenyl group, a cyclohexenyl group, and a methylcyclohexenyl group.
A chlorine atom is mentioned as a halogen atom.
The aromatic ring is preferably an aryl group such as a phenyl group, a benzyl group, a tolyl group, an o-, m-, p-xylyl group, a naphthyl group, an anthracenyl group, and a phenanthrenyl group.
Examples of the heteroaromatic ring include a furyl group, a pyridyl group, a pyrimidyl group, a pyrazoyl group, and a thiophenyl group.
R ² and R ³ each independently preferably represent a hydrogen atom, a chlorine atom or a methyl group, and more preferably a hydrogen atom.

Examples of the substituents on the alkyl group, alkenyl group, aromatic ring or heteroaromatic ring include alkoxy groups such as methoxy group and ethoxy group, thioalkyl groups, and —SH.
The aromatic ring or heteroaromatic ring may have an azo group such as an aryloxy group, a thioaryl group, an azoalkyl group and an azoaryl group, or an amino group as a substituent.

The content of the structural unit represented by the formula EV-1 (provided that it is converted into a monomer unit) is preferably 10 mol% or more, and 10 mol% to 55 mol% based on the total amount of the monomer unit in the polymer compound. Is more preferable, 15 mol% to 45 mol% is further preferable, and 20 mol% to 35 mol% is particularly preferable.
The content of the structural unit represented by the formula EV-2 (however, converted as a monomer unit) is preferably 15 mol% or more, and preferably 15 mol% to 60 mol% with respect to the total amount of monomer units in the polymer compound. Is more preferable, 20 mol% to 50 mol% is further preferable, and 25 mol% to 45 mol% is particularly preferable.

Further, the total content of the constitutional unit represented by the formula EV-1 and the constitutional unit represented by the formula EV-2 (however, converted as monomer units) is based on the total amount of the monomer units in the polymer compound. On the other hand, 50 mol% to 90 mol% is preferable, 60 mol% to 80 mol% is more preferable, and 65 mol% to 75 mol% is further preferable.

The weight average molecular weight of the acetal resin is preferably 5,000 or more, more preferably 10,000 to 500,000, further preferably 10,000 to 300,000.

Such acetal resins may be used alone or in combination of two or more.

<< content >>
The content of the specific binder polymer in the present disclosure is preferably 5% by mass to 75% by mass, more preferably 10% by mass to 60% by mass, and further preferably 15% by mass with respect to the total mass of the image recording layer. It is more preferably from about 50% by mass.
When the image recording layer has a multilayer structure having an upper layer and a lower layer, the specific binder polymer is preferably contained in the lower layer at least. The content of the specific binder polymer in the lower layer is preferably 3% by mass or more, more preferably 10% by mass or more, and further preferably 25% by mass or more, based on the total mass of the lower layer. .

-Infrared absorber-
The image recording layer preferably contains an infrared absorber.
The infrared absorbent is not particularly limited as long as it is a pigment or dye that absorbs infrared light and generates heat, and various pigments or dyes known as infrared absorbents can be used.

As the dye, commercially available dyes and known dyes described in documents such as "Handbook of Dyes" (edited by The Society of Synthetic Organic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex salt azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinone imine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, and metal thiolate complex dyes. Is mentioned.
Preferred among these dyes are cyanine dyes, squarylium dyes, pyrylium salts, nickel thiolate complexes, and indolenine cyanine dyes. Further, cyanine dyes and indolenine cyanine dyes are more preferred.
A particularly preferred dye is a cyanine dye represented by the following formula (a).

In formula (a), X ¹ represents a hydrogen atom, a halogen atom, a diarylamino group (—NPh ₂ ), X ² —L ¹ or a group shown below. X ² represents an oxygen atom or a sulfur atom. L ¹ represents a hydrocarbon group having 1 to 12 carbon atoms, an aromatic ring having a hetero atom, or a hydrocarbon group having 1 to 12 carbon atoms containing a hetero atom. In addition, a hetero atom here shows N, S, O, a halogen atom, and Se.

In the above formula, Xa ⁻ is defined in the same manner as Za ⁻ described later, and R ^a is a substituent selected from the group consisting of a hydrogen atom, an alkyl group, an aryl group, a substituted or unsubstituted amino group, and a halogen atom. Represents a group.

R ²¹ and R ²² each independently represent a hydrocarbon group having 1 to 12 carbon atoms. From the viewpoint of storage stability of the positive type lithographic printing plate precursor, R ²¹ and R ²² are preferably a hydrocarbon group having 2 or more carbon atoms, and R ²¹ and R ²² are bonded to each other to form a 5-membered ring. Or, it is particularly preferable to form a 6-membered ring.

Ar ¹ and Ar ² may be the same or different and each represents an aromatic hydrocarbon group which may have a substituent. Preferred aromatic hydrocarbon groups include a benzene ring and a naphthalene ring. Moreover, as a preferable substituent, a C12 or less hydrocarbon group, a halogen atom, and a C12 or less alkoxy group are mentioned.
Y ¹¹ and Y ^{12, which} may be the same or different, each represents a sulfur atom or a dialkylmethylene group having 12 or less carbon atoms. R ²³ and R ^{24, which} may be the same or different, each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferable substituents include an alkoxy group having 12 or less carbon atoms, a carboxyl group and a sulfo group.
R ²⁵ , R ²⁶ , R ²⁷ and R ^{28, which} may be the same or different, each represents a hydrogen atom or a hydrocarbon group having 12 or less carbon atoms. From the availability of raw materials, hydrogen atom is preferable. Za ⁻ represents a counter anion. However, when the cyanine dye represented by the formula (a) has an anionic substituent in its structure and neutralization of charge is not necessary, Za ⁻ is not necessary. Preferred Za ⁻ is a halide ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a sulfonate ion in view of the storage stability of the positive lithographic printing plate precursor, and particularly preferably, perchloric acid. An ion, a hexafluorophosphate ion, and an aryl sulfonate ion.

Specific examples of the cyanine dye represented by the formula (a) which can be preferably used include, for example, paragraphs 0017 to 0019 of JP 2001-133969 A, paragraphs 0012 to 0038 of JP 2002-40638 A, and JP 2002 A. Examples thereof include those described in paragraphs 0012 to 0023 of JP-A-23360.
The cyanine dye A shown below is particularly preferable as the infrared absorber contained in the image recording layer.

The content of the infrared absorbing agent is preferably 0.01% by mass to 50% by mass, more preferably 0.1% by mass to 30% by mass, based on the total mass of the image recording layer. It is particularly preferably from 0.0% by mass to 30% by mass. When the addition amount is 0.01% by mass or more, the sensitivity becomes high, and when the addition amount is 50% by mass or less, the uniformity of the layer is good and the durability of the layer is excellent.

When the image recording layer has a multilayer structure having an upper layer and a lower layer, the exposure sensitivity is improved by including an infrared absorber in the lower layer.
The addition amount of the infrared absorber in the lower layer is preferably 0.01% by mass to 50% by mass, more preferably 0.1% by mass to 30% by mass, based on the total mass of the lower layer. It is particularly preferably from 0.0% by mass to 10% by mass. When the addition amount is 0.01% by mass or more, the sensitivity is improved, and when it is 50% by mass or less, the uniformity of the layer is good and the durability of the layer is excellent.

[Acid generator]
The image recording layer in the present disclosure preferably contains an acid generator from the viewpoint of improving the sensitivity of the lithographic printing plate precursor obtained.
In the present disclosure, the acid generator is a compound that generates an acid by light or heat, and refers to a compound that decomposes to generate an acid when irradiated with infrared rays or heated at 100 ° C. or higher. The generated acid is preferably a strong acid having a pKa of 2 or less such as sulfonic acid and hydrochloric acid. The acid generated from the acid generator enhances the permeability of the developing solution into the image recording layer in the exposed area of the lithographic printing plate precursor, and further improves the solubility of the image recording layer in the aqueous alkaline solution.
The acid generator preferably used in the image recording layer in the present disclosure includes the acid generators described in paragraphs 0116 to 0130 of WO 2016/047392.
Above all, it is preferable to use an onium salt compound as the acid generator from the viewpoint of sensitivity and stability. The onium salt compound will be described below.
Examples of onium salt compounds that can be suitably used in the present disclosure include compounds known as compounds that generate an acid by being exposed to infrared rays and decomposed by thermal energy generated from the infrared absorber upon exposure. Examples of onium salt compounds suitable for the present disclosure include known thermal polymerization initiators and compounds having an onium salt structure described below having a bond with a small bond dissociation energy from the viewpoint of sensitivity.
Examples of onium salts preferably used in the present disclosure include known diazonium salts, iodonium salts, sulfonium salts, ammonium salts, pyridinium salts, azinium salts, and the like. Among them, triarylsulfonium or diaryliodonium sulfonates , Carboxylate, BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ^{− and the} like are preferable.
Examples of onium salts that can be used as an acid generator in the present disclosure include onium salts represented by the following formulas III to V.

In Formula III, Ar ¹¹ and Ar ¹² each independently represent an aryl group having 20 or less carbon atoms, which may have a substituent. When the aryl group has a substituent, a preferable substituent is a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, or an aryloxy group having 12 or less carbon atoms. Is mentioned. Z ^11- is a pair selected from the group consisting of a halide ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a sulfonate ion, and a sulfonate ion having a fluorine atom such as a perfluoroalkylsulfonate ion. It represents an ion, and is preferably a perchlorate ion, a hexafluorophosphate ion, an aryl sulfonate ion, and a perfluoroalkyl sulfonic acid.
In the above formula IV, Ar ²¹ represents an aryl group having 1 to 20 carbon atoms which may have a substituent. Preferred substituents are a halogen atom, a nitro group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryloxy group having 1 to 12 carbon atoms, an alkylamino group having 1 to 12 carbon atoms, Examples thereof include a dialkylamino group having 2 to 12 carbon atoms, an arylamino group having 6 to 12 carbon atoms, and a diarylamino group (the carbon numbers of two aryl groups are each independently 6 to 12). Z ^21- represents a counter ion having the same ^meaning as Z ^11- .
In the above formula V, R ³¹ , R ³² and R ^{33, which} may be the same or different, each represents a hydrocarbon group having 1 to 20 carbon atoms which may have a substituent. Examples of preferable substituents include a halogen atom, a nitro group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, and an aryloxy group having 1 to 12 carbon atoms. Z ^31- represents a counter ion having the same ^meaning as Z ^11- .

Specific examples of the onium salt that can be preferably used in the image recording layer according to the present disclosure are the same as the compounds described in paragraphs 0121 to 0124 of International Publication WO2016 / 047392.

Further, as another example of the compounds represented by the above formulas III to V, the compounds described as examples of the radical polymerization initiator in paragraphs 0036 to 0045 of JP 2008-195018 are related to the present disclosure. It can be suitably used as an acid generator.

More preferred examples of the acid generator usable in the present disclosure include the following compounds (PAG-1) to (PAG-5).

When these acid generators are contained in the image recording layer in the present disclosure, these compounds may be used alone or in combination of two or more kinds.
The content of the acid generator is preferably 0.01% by mass to 50% by mass, more preferably 0.1% by mass to 40% by mass, and 0.5% by mass with respect to the total mass of the image recording layer. More preferably, it is from about 30% by mass. When the content is within the above range, the sensitivity, which is an effect of the addition of the acid generator, is improved, and the generation of the residual film in the non-image area is suppressed.

[Acid multiplying agent]
The image recording layer in the present disclosure may contain an acid multiplying agent. The acid multiplying agent in the present disclosure is a compound substituted with a residue of a relatively strong acid, and is a compound which is easily eliminated in the presence of an acid catalyst to newly generate an acid. That is, it decomposes by an acid-catalyzed reaction to generate an acid again. One or more acids are increased in one reaction, and the acid concentration is accelerated as the reaction progresses, so that the sensitivity is dramatically improved. The strength of the generated acid is preferably 3 or less as an acid dissociation constant (pKa), and more preferably 2 or less. When the acid dissociation constant is 3 or less, the elimination reaction by the acid catalyst is likely to occur.
Examples of the acid used for such an acid catalyst include dichloroacetic acid, trichloroacetic acid, methanesulfonic acid, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid and phenylsulfonic acid.

The usable acid multiplying agent is the same as those described in paragraphs 0133 to 0135 of WO 2016/047392.

When the acid proliferating agent is added to the image recording layer, the content thereof is preferably 0.01% by mass to 20% by mass, and 0.01% by mass to 10% by mass based on the total mass of the image recording layer. Is more preferable, and 0.1% by mass to 5% by mass is further preferable. When the content of the acid proliferating agent is in the above range, the effect of adding the acid proliferating agent is sufficiently obtained, the sensitivity is improved, and the reduction of the film strength of the image area is suppressed.

[Other additives]
The image recording layer in the present disclosure may contain a development accelerator, a surfactant, a printout agent, a colorant, a plasticizer, a wax agent, etc. as other additives.

-Development accelerator-
An acid anhydride, a phenol, or an organic acid may be added to the image recording layer in the present disclosure for the purpose of improving sensitivity.
Cyclic acid anhydrides are preferred as the acid anhydrides, and specific examples of the cyclic acid anhydrides include phthalic anhydride, tetrahydrophthalic anhydride, and hexahydroanhydride described in US Pat. No. 4,115,128. Phthalic acid, 3,6-endooxytetrahydrophthalic anhydride, tetrachlorophthalic anhydride, maleic anhydride, chloromaleic anhydride, α-phenylmaleic anhydride, succinic anhydride, pyromellitic anhydride and the like can be used. Acetic anhydride etc. are mentioned as an acyclic acid anhydride.
Examples of phenols include bisphenol A, 2,2′-bishydroxysulfone, p-nitrophenol, p-ethoxyphenol, 2,4,4′-trihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 4- Examples include hydroxybenzophenone, 4,4 ', 4 "-trihydroxytriphenylmethane, 4,4', 3", 4 "-tetrahydroxy-3,5,3 ', 5'-tetramethyltriphenylmethane. .
Organic acids are described in JP-A-60-88942, JP-A-2-96755, and the like. Specifically, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, p-toluenesulfinic acid, Ethyl sulfuric acid, phenylphosphonic acid, phenylphosphinic acid, phenyl phosphate, diphenyl phosphate, benzoic acid, isophthalic acid, adipic acid, p-toluic acid, 3,4-dimethoxybenzoic acid, phthalic acid, terephthalic acid, 4-cyclohexene Examples include -1,2-dicarboxylic acid, erucic acid, lauric acid, n-undecanoic acid, and ascorbic acid. The proportion of the above-mentioned acid anhydride, phenols and organic acids in the total mass of the image recording layer is preferably 0.05% by mass to 20% by mass, more preferably 0.1% by mass to 15% by mass, and 0.1% by mass. 1% by mass to 10% by mass is particularly preferable.

-Surfactant-
The image recording layer in the present disclosure is described in JP-A-62-251740 and JP-A-3-208514 in order to improve the coating property and to broaden the stability of processing under developing conditions. Such nonionic surfactants, amphoteric surfactants as described in JP-A-59-121044 and JP-A-4-13149, JP-A-62-170950, JP-A-11- Fluorine-containing monomer copolymers as described in JP-A-288093 and JP-A-2003-57820 can be added.
Specific examples of the nonionic surfactant include sorbitan tristearate, sorbitan monopalmitate, sorbitan trioleate, stearic acid monoglyceride and polyoxyethylene nonylphenyl ether.
Specific examples of the amphoteric activator include alkyldi (aminoethyl) glycine, alkylpolyaminoethylglycine hydrochloride, 2-alkyl-N-carboxyethyl-N-hydroxyethylimidazolinium betaine and N-tetradecyl-N, N-betaine. Molds (for example, trade name “Amorgen K”: manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and the like.
The ratio of the surfactant to the total mass of the image recording layer is preferably 0.01% by mass to 15% by mass, more preferably 0.01% by mass to 5% by mass, and 0.05% by mass to 2.0% by mass. % Is more preferable.

-Bakeout agent / colorant-
To the image recording layer in the present disclosure, a printout agent for obtaining a visible image immediately after heating by exposure and a dye or pigment as an image colorant can be added.
Examples of the print-out agent and the colorant are described in detail in paragraphs 0122 to 0123 of JP 2009-229917 A, and the compounds described therein can be applied to the present disclosure.
These dyes are preferably added in a proportion of 0.01 to 10% by mass, more preferably 0.1 to 3% by mass, based on the total mass of the image recording layer.

-Plasticizer-
A plasticizer may be added to the image recording layer in the present disclosure in order to impart flexibility to the coating film. For example, butylphthalyl, polyethylene glycol, tributyl citrate, diethyl phthalate, dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, tetrahydrofurfuryl oleate, acrylic acid or methacrylic acid. Oligomers and polymers are used.
These plasticizers are preferably added in a proportion of 0.5% by mass to 10% by mass, more preferably 1.0% by mass to 5% by mass, based on the total mass of the image recording layer. preferable.

-Wax agent-
To the image recording layer in the present disclosure, a compound that lowers the coefficient of static friction of the surface can be added for the purpose of imparting resistance to scratches. Specifically, as described in US Pat. No. 6,117,913, JP-A 2003-149799, JP-A 2003-302750, or JP-A 2004-12770, Examples thereof include compounds having an ester of a long-chain alkylcarboxylic acid.
The addition amount is preferably 0.1% by mass to 10% by mass, more preferably 0.5% by mass to 5% by mass, based on the total mass of the image recording layer.

<Overcoat layer>
The lithographic printing plate precursor according to the present disclosure preferably further has an overcoat layer on the image recording layer, and the overcoat layer may be the outermost layer on the front surface.

Examples of components of the overcoat include alkali-soluble polyurethane resins and acetal resins, with polyurethane resins having a carboxyl group in the polymer main chain being preferred.
An aromatic diisocyanate such as tolylene diisocyanate is preferable as the isocyanate for producing the polyurethane resin, and 3,5-dihydroxybenzoic acid or 2,2-bis (hydroxymethyl) propionic acid is preferable as the diol.
Examples of the acetal resin include polyvinyl alcohol (PVA) and polyvinyl butyral PVB.

In the lithographic printing plate precursor according to the present disclosure, the thickness of the overcoat layer is preferably 0.2 μm to 10 μm, more preferably 0.3 μm to 5 μm, still more preferably 0.5 μm to 3 μm.

When the overcoat layer contains specific particles, the content of the specific particles is preferably 20% by mass to 80% by mass, more preferably 30% by mass to 60% by mass, based on the total mass of the overcoat layer. Is.

The lithographic printing plate precursor can be manufactured by applying a coating solution for each constituent layer according to a usual method and drying to form each constituent layer. For coating, a die coating method, a dip coating method, an air knife coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, a slide coating method and the like are used.

<Layered planographic printing plate precursor>
In the lithographic printing plate precursor according to the present disclosure, the image recording layer may be a multi-layer including an upper layer and a lower layer.
In the present disclosure, a lithographic printing plate precursor having such a lower layer and an upper layer is also referred to as “a planographic printing plate precursor having a multilayer structure”.
The lower layer and the upper layer are preferably formed by separating the two layers.
As a method for forming the two layers separately, for example, a method of utilizing a difference in solvent solubility between a component contained in the lower layer and a component contained in the upper layer, or a method of applying a solvent rapidly after coating the upper layer Examples of the method include drying and removing. It is preferable to use the latter method together because the separation between layers can be more favorably performed.
The specific binder polymer is preferably contained in either the lower layer or the upper layer, and more preferably contained in the lower layer.
Hereinafter, these methods will be described in detail, but the method of separating and applying the two layers is not limited thereto.

As a method of utilizing the difference in solvent solubility between the component contained in the lower layer and the component contained in the upper layer, a solvent system in which none of the components contained in the lower layer is insoluble is used when the coating liquid for the upper layer is applied. It is a thing. As a result, even if two-layer coating is performed, each layer can be clearly separated to form a coating film. For example, as the lower layer component, a component insoluble in a solvent such as methyl ethyl ketone or 1-methoxy-2-propanol that dissolves the specific binder polymer as the upper layer component is selected, and the lower layer is applied using a solvent system that dissolves the lower layer component. After drying, the upper layer containing the specific binder polymer is dissolved with methyl ethyl ketone, 1-methoxy-2-propanol or the like, coated and dried to form a double layer.

Next, as a method for drying the solvent extremely quickly after applying the second layer (upper layer), high-pressure air is blown from a slit nozzle installed almost at right angles to the running direction of the web, or heating with steam or the like. This can be achieved by applying heat energy as conduction heat from the lower surface of the web from a roll (heating roll) that is internally supplied with the medium, or by combining them.

The coating amount of the lower layer component coated on the support of the lithographic printing plate precursor according to the present disclosure after drying is preferably in the range of 0.5 g / m ² to 4.0 g / m ² , and is 0.6 g. / M ² to 2.5 g / m ² is more preferable. When it is 0.5 g / m ² or more, printing durability is excellent, and when it is 4.0 g / m ² or less, image reproducibility and sensitivity are excellent.
The coating amount after drying of the upper layer component ^is preferably in the range of ^{0.05g / m 2 ~ 1.0g / m} 2, in the range of ^{0.08g / m 2 ~ 0.7g / m} 2 Is more preferable. If it is 0.05 g / ^{m 2} or more, development latitude, and excellent scratch resistance, if it is 1.0 g / ^{m 2} or less, excellent sensitivity.
The combined coating amount of the lower layer and the upper layer after drying is preferably in the range of 0.6 g / m ² to 4.0 g / m ² , and in the range of 0.7 g / m ² to 2.5 g / m ² . Is more preferable. When it is 0.6 g / m ² or more, printing durability is excellent, and when it is 4.0 g / m ² or less, image reproducibility and sensitivity are excellent.

<< Lower layer >>
The lower layer of the planographic printing plate precursor having a multilayer structure in the present disclosure is preferably an infrared-sensitive positive recording layer whose solubility in an aqueous alkali solution is improved by heat.
There is no particular limitation on the mechanism by which the heat in the lower layer improves the solubility in the alkaline aqueous solution, and any mechanism can be used as long as it contains a binder resin and improves the solubility in the heated region. The heat used for image formation includes heat generated when the lower layer containing the infrared absorber is exposed.
The lower layer whose solubility in an aqueous alkali solution is improved by heat includes, for example, novolac, a layer containing an alkali-soluble resin having hydrogen bonding ability such as urethane, a water-insoluble and alkali-soluble resin and a compound having a dissolution inhibiting action. Layers and the like are preferred.

Also, by adding an infrared absorber to the lower layer, the heat generated in the lower layer can be used for image formation. The structure of the lower layer containing an infrared absorbing agent, for example, a layer containing an infrared absorbing agent and a water-insoluble and alkali-soluble resin and a compound having a dissolution suppressing action, an infrared absorbing agent and a water-insoluble and alkali-soluble resin and an acid generator. A layer containing is preferable.

-Water-insoluble and alkali-soluble resin-
The lower layer in the present disclosure preferably contains a water-insoluble and alkali-soluble resin. By containing the water-insoluble and alkali-soluble resin, an interaction is formed between the infrared absorber and the polar group of the water-insoluble and alkali-soluble resin, and a positive photosensitive layer is formed.
The general water-insoluble and alkali-soluble resin will be described in detail below, and among them, for example, a polyamide resin, an epoxy resin, a polyacetal resin, an acrylic resin, a methacrylic resin, a polystyrene resin, a novolac type phenolic resin, etc. are preferred. be able to.
The water-insoluble and alkali-soluble resin that can be used in the present disclosure is not particularly limited as long as it has the property of dissolving when contacted with an alkaline developer, but the main chain and / or side chain in the polymer is acidic. It is preferably a homopolymer containing a group, a copolymer thereof, or a mixture thereof.
The water-insoluble and alkali-soluble resin having such an acidic group preferably has a functional group such as a phenolic hydroxyl group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a sulfonamide group and an active imide group. Therefore, such a resin can be suitably produced by copolymerizing a monomer mixture containing at least one ethylenically unsaturated monomer having the above functional group. As the ethylenically unsaturated monomer having a functional group, a compound represented by the following formula and a mixture thereof can be preferably exemplified in addition to acrylic acid and methacrylic acid. In the formula below, R ⁴⁰ represents a hydrogen atom or a methyl group.

The water-insoluble and alkali-soluble resin that can be used in the present disclosure is preferably a polymer compound obtained by copolymerizing another polymerizable monomer in addition to the above polymerizable monomer. The copolymerization ratio in this case is 10 mol of a monomer that imparts alkali solubility, such as a monomer having a functional group such as a phenolic hydroxyl group, a carboxy group, a sulfonic acid group, a phosphoric acid group, a sulfonamide group, and an active imide group. % Or more, and more preferably 20 mol% or more. When the copolymerization component of the monomer imparting alkali solubility is 10 mol% or more, sufficient alkali solubility is obtained and the developability is excellent.

Examples of other polymerizable monomers that can be used include the compounds listed below.
Alkyl acrylates and alkyl methacrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, benzyl acrylate, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate and benzyl methacrylate. Acrylic acid esters and methacrylic acid esters having an aliphatic hydroxyl group such as 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate. Acrylamide or methacrylamide such as acrylamide, methacrylamide, N-methyl acrylamide, N-ethyl acrylamide, N-phenyl acrylamide. Vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl butyrate and vinyl benzoate. Styrenes such as styrene, α-methylstyrene, methylstyrene and chloromethylstyrene. Other nitrogen atom-containing monomers such as N-vinylpyrrolidone, N-vinylpyridine, acrylonitrile and methacrylonitrile. N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-phenylmaleimide, N-2-methylphenylmaleimide, N-2,6-diethylphenylmaleimide, N-2-chlorophenylmaleimide, Maleimides such as N-cyclohexylmaleimide, N-laurylmaleimide and N-hydroxyphenylmaleimide.
Of these other ethylenically unsaturated monomers, (meth) acrylic acid esters, (meth) acrylamide, maleimide compounds, and (meth) acrylonitrile are preferably used.

Further, as the alkali-soluble resin, the novolak resin mentioned as the other binder polymer mentioned as an optional component of the image recording layer according to the present disclosure is also preferably exemplified.
It is also possible to use the above water-insoluble and alkali-soluble resin in the image recording layer in the present disclosure.

Further, in the lower layer in the present disclosure, other resins can be used in combination as long as the effects according to the present disclosure are not impaired. Since the lower layer itself needs to exhibit alkali solubility, especially in the non-image area, it is necessary to select a resin that does not impair this property. From this viewpoint, water-insoluble and alkali-soluble resins are examples of resins that can be used in combination. The general water-insoluble and alkali-soluble resin will be described in detail below, and among them, for example, a polyamide resin, an epoxy resin, a polyacetal resin, an acrylic resin, a methacrylic resin, a polystyrene resin, a novolac type phenolic resin, etc. are preferred. be able to.
Further, the amount to be mixed is preferably 50% by mass or less with respect to the water-insoluble and alkali-soluble resin.

The water-insoluble and alkali-soluble resin preferably has a weight average molecular weight of 2,000 or more and a number average molecular weight of 500 or more, a weight average molecular weight of 5,000 to 300,000, and a number average molecular weight of 800 to More preferably, it is 250,000. The degree of dispersion (weight average molecular weight / number average molecular weight) of the alkali-soluble resin is preferably 1.1 to 10.
The alkali-soluble resin in the lower layer according to the present disclosure may be used alone or in combination of two or more.
The content of the alkali-soluble resin in the total solid content of the lower layer in the present disclosure is preferably 2.0% by mass to 99.5% by mass, and 10.0% by mass to 99.% by mass, based on the total mass of the lower layer. It is more preferably 0% by mass, further preferably 20.0% by mass to 90.0% by mass. When the addition amount of the alkali-soluble resin is 2.0% by mass or more, the durability of the image recording layer (photosensitive layer) is excellent, and when it is 99.5% by mass or less, both the sensitivity and the durability are improved. Excel.

-Other ingredients-
In addition, the lower layer of the lithographic printing plate precursor having a multi-layer structure may contain an acid generator, an acid multiplying agent, a development accelerator, a surfactant, a printing-out agent / colorant, a plasticizer, a wax agent and the like.
As these components, the above-mentioned respective components used in the image recording layer in the present disclosure can be similarly used, and the preferred embodiments are also the same.

<< Upper layer >>
When the lithographic printing plate precursor has a multi-layer structure, the upper layer of the lithographic printing plate precursor having the multi-layer structure in the present disclosure is preferably an infrared-sensitive positive type image recording layer whose solubility in an alkaline aqueous solution is improved by heat. ..
There is no particular limitation on the mechanism by which the heat in the upper layer improves the solubility in the alkaline aqueous solution, and any mechanism can be used as long as it contains a binder resin and improves the solubility in the heated region. The heat used for image formation includes heat generated when the lower layer containing the infrared absorber is exposed.
The upper layer whose solubility in an aqueous alkali solution is improved by heat includes, for example, a layer containing an alkali-soluble resin having hydrogen bonding ability such as novolac and urethane, a water-insoluble and alkali-soluble resin and a compound having a dissolution suppressing action. A layer, a layer containing a compound capable of suppressing ablation, and the like are preferable.

<Undercoat layer>
The positive lithographic printing plate precursor according to the present disclosure may have an undercoat layer between the support and the image recording layer (or the lower layer in the recording layer), if necessary.
As the undercoat layer component, various organic compounds are used, for example, carboxymethyl cellulose, phosphonic acids having an amino group such as dextrin, organic phosphonic acid, organic phosphoric acid, organic phosphinic acid, amino acids, and a hydroxy group. Preferable examples are the hydrochlorides of the amines that it has. These undercoat layer components may be used alone or in combination of two or more. Details of the compound used for the undercoat layer and the method for forming the undercoat layer are described in paragraphs 0171 to 0172 of JP2009-175195A, and these descriptions also apply to the present disclosure.
The coating amount of the undercoat layer is preferably ² mg / m ² to 200 mg / m ² , and more preferably 5 mg / m ² to 100 mg / m ² . When the coating amount is within the above range, sufficient printing durability can be obtained.

<Backcoat layer>
A back coat layer is provided on the back surface of the support of the lithographic printing plate precursor according to the present disclosure, if necessary. The back coat layer is composed of an organic polymer compound described in JP-A-5-45885 and a metal oxide obtained by hydrolyzing and polycondensing an organic or inorganic metal compound described in JP-A-6-35174. A coating layer is preferably used. Among these coating layers, silicon alkoxy compounds such as Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , Si (OC ₃ H ₇ ) ₄ and Si (OC ₄ H ₉ ) ₄ are inexpensively available. It is particularly preferable because the coating layer of the metal oxide obtained therefrom is excellent in the resistance to developing solution.

[Lithographic printing plate precursor laminate]
The lithographic printing plate precursor laminate according to the present disclosure is a laminate formed by laminating the lithographic printing plate precursor according to the present disclosure, and is formed by laminating a plurality of lithographic printing plate precursors according to the present disclosure. The lithographic printing plate precursor laminate in which the outermost layer on the side having the image recording layer of the original plate and the outermost layer on the side opposite to the side having the image recording layer of the other lithographic printing plate precursor are laminated in direct contact. Preferably there is.
The lithographic printing plate precursor laminate according to the present disclosure is preferably a laminate formed by laminating a plurality of lithographic printing plate precursors according to the present disclosure without interposing interleaving paper.
The number of laminated sheets is not particularly limited, but is preferably 2 to 500 sheets.
The lithographic printing plate precursor according to the present disclosure has excellent properties of the lithographic printing plate precursor according to the present disclosure in terms of prevention of multiple plate feeding and scratch resistance, and is less likely to cause misalignment. It has the characteristic that

(Method of preparing lithographic printing plate)
The method for producing a lithographic printing plate according to the present disclosure, a step of exposing the lithographic printing plate precursor according to the present disclosure imagewise, to form an exposed portion and an unexposed portion (hereinafter, also referred to as "image exposure step"), And a developing step of developing the exposed lithographic printing plate precursor using a developer having a pH of 13.5 or less in this order.
Hereinafter, each step of the manufacturing method according to the present disclosure will be described in detail.

<Image exposure process>
The method for producing a lithographic printing plate according to the present disclosure includes an image exposure step.
As a light source of actinic rays used for image exposure of the lithographic printing plate precursor according to the present disclosure, a light source having an emission wavelength in the near infrared to infrared region is preferable, and a solid laser and a semiconductor laser are more preferable. Among them, in the present disclosure, it is particularly preferable to perform image exposure with a solid-state laser or semiconductor laser that emits infrared rays having a wavelength of 750 nm to 1,400 nm.
The laser output is preferably 100 mW or more, and it is preferable to use a multi-beam laser device in order to shorten the exposure time. The exposure time per pixel is preferably within 20 μsec.
The energy applied to the lithographic printing plate precursor is preferably 10 mJ / cm ² to 300 mJ / cm ² . Within the above range, the solubility of the image recording layer in an alkaline aqueous solution can be sufficiently improved, laser ablation can be suppressed, and image damage can be prevented.

The exposure in the present disclosure can be performed by overlapping the light beams of the light source. The overlap means that the sub-scanning pitch width is smaller than the beam diameter. The overlap can be quantitatively expressed by FWHM / sub-scanning pitch width (overlap coefficient) when the beam diameter is expressed by the full width at half maximum (FWHM) of the beam intensity. In the present disclosure, this overlap coefficient is preferably 0.1 or more.

The light source scanning method of the exposure apparatus that can be used in the present disclosure is not particularly limited, and a cylinder outer surface scanning method, a cylinder inner surface scanning method, a flat surface scanning method, or the like can be used. The light source channel may be a single channel or a multi-channel, but in the case of the cylindrical outer surface system, the multi-channel is preferably used.

<Developing process>
The method of preparing a lithographic printing plate according to the present disclosure includes a developing step of developing the exposed positive lithographic printing plate precursor using a developer having a pH of 13.5 or less.
The pH of the developer used in the developing step is preferably 11 or less.
The developing solution used in the developing step is not particularly limited as long as it is a developing solution of 13.5 or less.
The developer is preferably an aqueous solution.
The lithographic printing plate precursor according to the present disclosure may be developed using a developer having a pH of more than 13.5. For example, development can be performed using a known developing solution such as the developing solutions described in paragraphs 0270 to 0292 of JP-A-2003-1956.

Further, in order to improve the developability, the developer may contain a surfactant.
The surfactant used in the developer may be any of anionic, nonionic, cationic, and amphoteric surfactants, but as described above, anionic and nonionic surfactants. Agents are preferred.
As the anionic, nonionic, cationic and amphoteric surfactants used in the developing solution in the present disclosure, those described in paragraphs 0128 to 0131 of JP2013-134341A can be used.

Further, from the viewpoint of stable solubility or turbidity in water, the HLB value is preferably 6 or more, more preferably 8 or more.
As the surfactant used in the developing solution, anionic surfactants and nonionic surfactants are preferable, and anionic surfactants containing sulfonic acid or sulfonate, and nonionics having an aromatic ring and an ethylene oxide chain. Surfactants are especially preferred.
The surfactants can be used alone or in combination.
The content of the surfactant in the developer is preferably 0.01% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass.

The developing solution used in the developing step is not particularly limited as long as it is a developing solution having a pH of 13.5 or less, but is preferably a developing solution having a pH of 11 or less, and a developing solution having a pH of 8.0 to 10.0. The developer having a pH of 9.0 to pH 9.9 is more preferable, and the developer is further preferable.
When a developer having a relatively low pH, such as a developer having a pH of 8.0 to 10.0, is used, for example, as compared with a developer having a high pH of about 12, the dissolution of CO _{2 in} the atmosphere, etc. It is easy to suppress the lowering of the derived pH. That is, it can be said that the low pH provides excellent stability during use or storage of the developer.
In the low pH developer, the decrease in the pH of the developer is suppressed as described above, so that the deterioration of the developability and the generation of development residue are suppressed.
Further, in order to keep the pH of the low pH developer at an initial value, it is preferable to use the developer as a buffer solution. The buffer solution is preferably a carbonate buffer system.
In the present disclosure, the carbonate buffer system refers to a buffer solution containing carbonate ion and hydrogen carbonate ion as a buffering agent.
In order to allow the carbonate ion and the hydrogen carbonate ion to be present in the developing solution, carbonate and hydrogen carbonate may be added to the developing solution, or the carbonate may be added by adjusting the pH after adding the carbonate or hydrogen carbonate. Ions and hydrogen carbonate ions may be generated. The carbonate and hydrogen carbonate are not particularly limited, but are preferably alkali metal salts. Examples of the alkali metal include lithium, sodium and potassium, with sodium being particularly preferred. These may be used alone or in combination of two or more.

The total amount of carbonate and hydrogen carbonate is preferably 0.3% by mass to 20% by mass, more preferably 0.5% by mass to 10% by mass, and more preferably 1% by mass to 5% by mass, based on the total mass of the developer. % Is particularly preferred. If the total amount is 0.3% by mass or more, developability and processing ability are not deteriorated, and if the total amount is 20% by mass or less, it becomes difficult to generate a precipitate or a crystal. It does not easily gel and does not interfere with waste liquid treatment.

Further, for the purpose of finely adjusting the alkali concentration and assisting the dissolution of the image recording layer in the non-image area, other alkali agents, for example, organic alkali agents may be supplementarily used. As the organic alkaline agent, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, Examples thereof include diisopropanolamine, ethyleneimine, ethylenediamine, pyridine, tetramethylammonium hydroxide and the like. These other alkaline agents may be used alone or in combination of two or more.
In addition to the above, the developer may contain a wetting agent, a preservative, a chelate compound, a defoaming agent, an organic acid, an organic solvent, an inorganic acid, an inorganic salt and the like. However, when the water-soluble polymer compound is added, the plate surface tends to become sticky, especially when the developer is fatigued.

As the wetting agent, the wetting agent described in paragraph 0141 of JP2013-134341A can be preferably used. The wetting agents may be used alone or in combination of two or more. The wetting agent is preferably used in an amount of 0.1% by mass to 5% by mass, based on the total mass of the developer.

As the preservative, the preservative described in paragraph 0142 of JP2013-134341A can be preferably used. It is preferable to use two or more preservatives in combination so as to be effective against various molds and sterilizations. The addition amount of the preservative is an amount that exerts a stable effect on bacteria, molds, yeasts and the like, and varies depending on the types of bacteria, molds, yeasts, but it is 0 for the total mass of the developer. A range of 0.01% by mass to 4% by mass is preferable.

As the chelate compound, the chelate compound described in paragraph 0143 of JP2013-134341A can be preferably used. The chelating agent is selected so that it stably exists in the developer composition and does not impair the printability. The addition amount is preferably 0.001% by mass to 1.0% by mass with respect to the total mass of the developer.

As the defoaming agent, the defoaming agent described in paragraph 0144 of JP2013-134341A can be preferably used. The content of the defoaming agent is preferably in the range of 0.001% by mass to 1.0% by mass with respect to the total mass of the developer.

As the organic acid, the defoaming agent described in paragraph 0145 of JP2013-134341A can be preferably used. The content of the organic acid is preferably 0.01% by mass to 0.5% by mass with respect to the total mass of the developer.

Examples of the organic solvent include aliphatic hydrocarbons (hexane, heptane, “Isopar E, H, G” (manufactured by Esso Chemical Co., Ltd.), gasoline, or kerosene), aromatic hydrocarbons (toluene, Xylene) or halogenated hydrocarbons (methylene dichloride, ethylene dichloride, trichlene, monochlorobenzene, etc.) and polar solvents.

Examples of polar solvents include alcohols (methanol, ethanol, propanol, isopropanol, benzyl alcohol, ethylene glycol monomethyl ether, 2-ethoxyethanol, etc.), ketones (methyl ethyl ketone, cyclohexanone, etc.), esters (ethyl acetate, methyl lactate, propylene). Glycol monomethyl ether acetate, etc.) and others (triethyl phosphate, tricresyl phosphate, N-phenylethanolamine, N-phenyldiethanolamine, etc.) and the like.

If the above organic solvent is insoluble in water, it can be solubilized in water with a surfactant or the like before use. When the developer contains an organic solvent, the concentration of the solvent is preferably less than 40 mass% from the viewpoint of safety and flammability.

As the inorganic acid and the inorganic salt, phosphoric acid, metaphosphoric acid, monobasic ammonium phosphate, dibasic ammonium phosphate, monobasic sodium phosphate, dibasic sodium phosphate, monobasic potassium phosphate, dibasic potassium phosphate, Examples thereof include sodium tripolyphosphate, potassium pyrophosphate, sodium hexametaphosphate, magnesium nitrate, sodium nitrate, potassium nitrate, ammonium nitrate, sodium sulfate, potassium sulfate, ammonium sulfate, sodium sulfite, ammonium sulfite, sodium hydrogensulfate and nickel sulfate. The content of the inorganic salt is preferably 0.01% by mass to 0.5% by mass with respect to the total mass of the developer.

The developing temperature is not particularly limited as long as it can be developed, but is preferably 60 ° C. or lower, more preferably 15 ° C. to 40 ° C. In a developing process using an automatic developing machine, the developing solution may become fatigued depending on the processing amount, and therefore the replenishing solution or a fresh developing solution may be used to recover the processing ability. As an example of the development and the treatment after the development, a method of performing alkali development, removing the alkali in the post-water washing step, performing gum treatment in the gumming step, and drying in the drying step can be exemplified. As another example, a method of simultaneously performing pre-washing, developing and gumming can be preferably exemplified by using an aqueous solution containing carbonate ion, hydrogen carbonate ion and a surfactant. Therefore, the pre-water washing step does not have to be particularly carried out, and it is preferable to carry out the pre-water washing, development and gumming in one bath only after using one solution, and then to carry out the drying step. After the development, it is preferable to remove excess developer using a squeeze roller or the like and then perform drying.

Development process can be preferably carried out by an automatic processor equipped with a rubbing member. As the automatic processor, for example, the automatic processor described in JP-A-2-220061 and JP-A-60-59351, which performs rubbing treatment while conveying the planographic printing plate precursor after image exposure, and a cylinder The lithographic printing plate precursor after image exposure set on the above is subjected to a rubbing treatment while rotating a cylinder, and the automatic processor described in each specification of US Pat. Nos. 5,148,746, 5,568,768, and British Patent 2,297,719 is Can be mentioned. Above all, an automatic processor using a rotating brush roll as the rubbing member is particularly preferable.

The rotating brush roll used in the present disclosure can be appropriately selected in consideration of the scratch resistance of the image area, the rigidity of the support of the planographic printing plate precursor, and the like. As the rotating brush roll, a known roll formed by planting a brush material on a plastic or metal roll can be used. For example, a metal or plastic in which brush materials are implanted in rows, as described in JP-A-58-159533 and JP-A-3-100554, and JP-B-62-167253. It is possible to use a brush roll in which the groove-shaped material is wound around a plastic or metal roll serving as a core in a radial pattern without a gap.
As the brush material, plastic fibers (for example, polyester type such as polyethylene terephthalate and polybutylene terephthalate, polyamide type such as nylon 6.6 and nylon 6.10, polyacryl type such as polyacrylonitrile, alkyl poly (meth) acrylate) Polyolefin-based synthetic fibers such as polypropylene and polystyrene) can be preferably used. For example, fibers having a hair diameter of 20 μm to 400 μm and a hair length of 5 mm to 30 mm can be preferably used.
The outer diameter of the rotating brush roll is preferably 30 mm to 200 mm, and the peripheral speed of the tip of the brush rubbing the plate surface is preferably 0.1 m / sec to 5 m / sec. It is preferable to use a plurality of rotating brush rolls.

The rotating brush roll may be rotated in the same direction or in the opposite direction with respect to the conveying direction of the lithographic printing plate precursor, but when using two or more rotating brush rolls, at least one rotating brush roll is used. It is preferable that the rotating brush rolls of 1 rotate in the same direction and at least one rotating brush roll rotate in the opposite direction. This further ensures removal of the image recording layer in the non-image area. Further, it is also effective to swing the rotating brush roll in the rotation axis direction of the brush roll.

After the developing step, it is preferable to provide a drying step continuously or discontinuously. Drying is performed with hot air, infrared rays, far infrared rays, or the like.
As an automatic processor preferably used in the method for producing a lithographic printing plate according to the present disclosure, an apparatus having a developing unit and a drying unit is used, and a lithographic printing plate precursor is developed and gummed in a developing tank. And then dried in the drying section to obtain a lithographic printing plate.

Further, the printing plate after development can be heated under extremely strong conditions for the purpose of improving printing durability. The heating temperature is preferably in the range of 200 ° C to 500 ° C. If the temperature is low, a sufficient image strengthening effect cannot be obtained, and if it is too high, problems such as deterioration of the support and thermal decomposition of the image area may occur.
The lithographic printing plate thus obtained is set on an offset printing machine and is suitably used for printing a large number of sheets.

Hereinafter, the present disclosure will be described in detail with reference to examples, but the present disclosure is not limited thereto. In the examples, "%" and "parts" mean "mass%" and "parts by mass", respectively, unless otherwise specified. In the polymer compound, the molecular weight is a weight average molecular weight (Mw) and the ratio of the constitutional repeating units is a molar percentage, except for those specified otherwise. The weight average molecular weight (Mw) is a value measured as a polystyrene conversion value by a gel permeation chromatography (GPC) method.

(Examples 1 to 36 and Comparative Examples 1 and 2)
<Preparation of support>
A support was produced by the same method as in paragraphs 0224 to 0297 of WO 2015/152209. This support was used in all examples and comparative examples.

<Synthesis of specific binder polymer>
[Binder polymer P1-1]
Binder polymer P1-1 was synthesized by a method similar to the method described in paragraph 0221 of Japanese Patent No. 6243010 to obtain binder polymer P1-1 having the structural units shown below.
In addition, in the following structural units, parenthesized subscripts represent the content (molar ratio) of each structural unit. The same applies hereinafter.

[Binder polymer P2-1]
As the binder polymer P2-1, a binder polymer (commercially available product) having a constitutional unit shown below (manufactured by Sumitomo Bakelite Co., Ltd., trade name: Sumilite Resin PR54046) was used.

[Binder polymer P3-1]
As the binder polymer P3-1, a binder polymer P3-1 having the constitutional units shown below was synthesized by the method described in JP-A-2011-186139.

[Binder polymer P4-1]
Under a nitrogen stream, 26.25 g of N-phenylmaleimide, 7.95 g of acrylonitrile, 10.65 g of acrylamide and 4.3 g of methacrylic acid were added to 133.1 g of 2-methoxyethanol and heated to 70 ° C., then α, α′- 0.25 g of azobisisobutyronitrile was added and a polymerization reaction was carried out for 8 hours. After the reaction solution was purified, a binder polymer P4-1 having a structural unit shown below with a weight average molecular weight of 43,000 was obtained.

[Binder polymer P4-2]
In a three-necked flask equipped with a condenser and a stirrer, 5.80 g of N, N'-dimethylformamide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was weighed and stirred at 65 ° C for 30 minutes while flowing nitrogen. Next, in the dropping funnel, 7.21 g of 4-methacrylamidobenzenesulfonamide (manufactured by FUJIFILM Fine Chemicals Co., Ltd.), 3.00 g of methyl methacrylate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and acrylonitrile (manufactured by Tokyo Chemical Industry Co., Ltd.) 2.12 g, N, N'-dimethylformamide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) 23.0 g, and 0.324 g of asobisisobutyronitrile (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) , Dissolved, and added dropwise to the flask over 2 hours. The mixture was further stirred at 65 ° C for 3 hours. The reaction solution was added dropwise to a mixed solution of 0.5 L of pure water and 0.5 L of methanol to precipitate a polymer. This was collected by filtration, washed and dried to obtain 11.2 g of a binder polymer P4-2 having the following structural unit with a weight average molecular weight of 50,000.

[Binder polymer P5-1]
As the binder polymer P5-1, a binder polymer (commercially available product) having a constitutional unit shown below (manufactured by Sekisui Chemical Co., Ltd., trade name: S-REC BL-1H) was used.

<Formation of undercoat layer>
After coating the undercoat layer coating liquid 1 shown below on the support, it was dried at 80 ° C. for 15 seconds to form an undercoat layer. The coating amount after drying was 15 mg / m ² .

[Undercoat layer coating liquid 1]
-The following copolymer having a weight average molecular weight of 28,000: 0.3 part-Methanol: 100 parts-Water: 1 part

In the above chemical formula, the subscripts in parentheses indicate the content (mass%) of each structural unit. Et represents an ethyl group.

<Preparation of photosensitive resin composition>
Photosensitive resin composition (I) was prepared by mixing the components described in the following composition. The photosensitive resin composition (I) is a positive type photosensitive resin composition.

[Photosensitive resin composition (I)]
-Specific binder polymer shown in Table 1 or Table 2: Amount shown in Table 1 or Table 2-Infrared absorber (IR dye (1): structure below): 0.045 part-Megafac F-780: 0. 03 parts Methyl ethyl ketone: 13.0 parts 1-Methoxy-2-propanol: 30.0 parts 1- (4-methylbenzyl) -1-phenylpiperidinium 5-benzoyl-4-hydroxy-2-methoxy Benzene sulfonate: 0.01 part

<Formation of image recording layer (single layer)>
In each of the Examples or Comparative Examples, the above-mentioned support with an undercoat layer was coated with the above-mentioned photosensitive resin composition (I) using a wire bar, and then dried in a drying oven at 150 ° C. for 40 seconds to give a table. The coating amount of the specific binder polymer shown in (3) was applied to provide an image recording layer and an overcoat layer to obtain a lithographic printing plate precursor.

(Particle coating method)
The particles shown in Table 1 or Table 2 were added to the following overcoat layer coating liquid (I) at an adjusted addition amount so as to have the in-plane density shown in Table 1 or Table 2.
An overcoat layer coating solution having the following composition was bar-coated on the image recording layer and oven-dried at 125 ° C. for 75 seconds to form an overcoat layer having a dry coating amount of 0.15 g / m ² .

[Overcoat layer coating liquid (I)]
-Polyvinyl alcohol (CKS-50 (product name), saponification degree 99 mol%, polymerization degree 300, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 0.29 parts by mass-Daiichi Kogyo Seiyaku Co., Ltd. Serogen (registered trademark) ) PR: 0.12 parts by mass Surfactant-1 (manufactured by Nippon Emulsion Co., Ltd., Emalex 710 (trade name)): 0.025 parts by mass Particles shown in Table 1 or Table: 0.10. Parts by mass / pure water: 69.2 parts by mass

(Example 37)
<Formation of image recording layer (multilayer)>
The following lower layer forming composition (I) was applied onto a support similar to those in Examples 1 to 36 and Comparative Examples 1 and 2 with a wire bar, and then dried in a drying oven at 150 ° C. for 40 seconds to specify. After coating so that the coating amount of the binder polymer becomes the amount shown in Table 3 and providing the lower layer, the wire bar so that the coating liquid composition (I) for forming the upper layer having the following composition is 0.22 g / m ^2. After coating, the coating was dried at 150 ° C. for 40 seconds. A lithographic printing plate precursor of Example 37 was obtained by providing a lower layer and an upper layer and further providing an overcoat layer.

[Coating liquid composition for forming lower layer (I)]
-Specific binder polymer shown in Table 3: amount shown in Table 3-infrared absorber (IR dye (1): the above structure): 0.045 part-Megafac F-780: 0.03 part-methyl ethyl ketone: 13 0.0 parts 1-methoxy-2-propanol: 30.0 parts 1- (4-methylbenzyl) -1-phenylpiperidinium 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonate: 0 .01 copy

[Coating liquid composition for forming upper layer (I)]
-Novolak resin (m-cresol / p-cresol / phenol = 3/2/5, weight average molecular weight 8,000): 0.34 parts-Infrared absorber (IR dye (1): the above structure): 0.023 Parts-Fluorosurfactant (Megafuck F-780, manufactured by DIC Corporation): 0.02 parts-Methylethylketone: 15.0 parts-Methoxy-2-propanol: 30.0 parts-1- (4 -Methylbenzyl) -1-phenylpiperidinium 5-benzoyl-4-.hydroxy-2-methoxybenzenesulfonate: 0.01 part

(Particle coating method)
The particles described in Table 3 were added to the following overcoat layer coating liquid (II) at an addition amount adjusted so that the in-plane density described in Table 3 was obtained.
An overcoat layer coating solution (II) having the following composition was applied onto the image recording layer by a bar and oven-dried at 125 ° C. for 75 seconds to form an overcoat layer having a dry coating amount of 0.15 g / m ² .

[Overcoat layer coating liquid (II)]
-Polyvinyl alcohol (CKS-50 (product name), saponification degree 99 mol%, polymerization degree 300, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.): 0.29 parts by mass-Daiichi Kogyo Seiyaku Co., Ltd. Serogen (registered trademark) ) PR: 0.12 parts by mass Surfactant-1 (manufactured by Nippon Emulsion Co., Ltd., Emarex 710 (trade name)): 0.025 parts by mass Particles shown in Table 3: 0.10 parts by mass Pure water: 69.2 parts by mass

(Example 38)
The composition for forming an underlayer (I) was applied onto a support similar to those in Examples 1 to 36 and Comparative Examples 1 and 2 with a wire bar, and then dried in a drying oven at 150 ° C. for 40 seconds to specify. The coating amount of the binder polymer was applied so as to be the amount shown in Table 3, and after the lower layer was provided, the particles shown in Table 3 in the coating liquid composition (II) for forming the upper layer having the following composition are shown in Table 3. After coating with a wire bar so as to have the in-plane density as described, the coating was dried at 150 ° C. for 40 seconds to obtain a lithographic printing plate precursor of Example 38 having an image recording layer as a lower layer and an upper layer. .

[Coating liquid composition for forming upper layer (II)]
Novolak resin (m-cresol / p-cresol / phenol = 3/2/5, weight average molecular weight 8,000): 0.34 parts Infrared absorber (IR dye (1): the above structure): 0.023 Parts-Fluorosurfactant (Megafuck F-780, manufactured by DIC Corporation): 0.02 part-Methyl ethyl ketone: 15.0 parts-Particles shown in Table 3: 0.1 parts by mass-1-Methoxy- 2-propanol: 30.0 parts 1- (4-methylbenzyl) -1-phenylpiperidinium 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonate: 0.01 parts

The following evaluation was performed using the obtained planographic printing plate precursor. The results are shown in Tables 1 to 3.
In the lithographic printing plate precursors of Examples 1 to 38 and Comparative Examples 1 and 2, Bekk smoothness and arithmetic mean height Sa of the outermost layer surface on the side having the image recording layer are shown in Tables 1 to 3, respectively.

<Evaluation of original planographic printing plate>
-Evaluation of scratch resistance-
The lithographic printing plate precursor was conditioned at 25 ° C. and 60% RH for 2 hours, and then punched into 2.5 cm × 2.5 cm, and the continuous weighted scratch strength tester TYPE-18 manufactured by Shinto Kagaku Co., Ltd. was used. Set so that the back surface of the punched lithographic printing plate precursor is in contact with the surface of the lithographic printing plate precursor that has not been attached or punched, and the lithographic printing plate precursor is applied at a pressure of 0 gf to 1,500 gf (0N to 14.7N). I scratched several places. The lithographic printing plate precursor with scratches was set on the Trendsetter 3244 manufactured by Creo, and the output was 7 W at the resolution of 2,400 dpi (dot per inch, 1 inch was 2.54 cm), the outer surface drum rotation speed was 150 rpm (revolutions per minute), and the plate surface energy was set. Image exposure was performed at 110 mJ / cm ² . The lithographic printing plate precursor after image exposure was mounted on an offset rotary printing machine manufactured by Tokyo Kikai Seisakusho, and Soybee KKST-S (red) manufactured by Inktec Co., Ltd. was used as printing ink for newspapers, and Sakata Inx as dampening water ( Using Eco Seven N-1 manufactured by Co., Ltd., printing was performed on newsprint paper at a speed of 100,000 sheets / hour. In the printing process, the 1,000th printed material was sampled, and the degree of scratch stains caused by scratches was visually observed.
The scratch resistance is evaluated by a sensory evaluation of 1 to 5, and 3 or more is a practically preferable level.
5: No scratch stains.
4: Although it cannot be visually confirmed, there is one scratch stain that can be confirmed with a magnifying glass of 6 magnifications.
3: Although it cannot be visually confirmed, there are several scratches that can be confirmed with a magnifying glass of 6 magnifications.
2: There are scratch stains that can be visually confirmed at multiple locations.
1: There are scratches and stains on the entire surface.

-Evaluation of membrane detachment suppression-
The planographic printing plate precursor was developed using Fuji Film Co., Ltd. PS plate processor LP940H in which developer XP-D (diluted to have an electric conductivity of 43 mS / cm) was prepared. Development was performed at a temperature of 30 ° C. and a development time of 20 seconds. The lithographic printing plate after development was cut into 5.0 cm × 5.0 cm, and the presence or absence and degree of omission of the image area were visually observed.
The evaluation of the film omission suppressing property is performed by the following sensory evaluations 1 to 5, and 4 or more is a practically preferable level.
5: No omission was observed in the image area.
4: The omission of the image area cannot be visually confirmed, but one omission of the film was confirmed with a magnifying glass of 6 magnifications.
3: Although the omission of the image area cannot be visually confirmed, several omissions of the film which were observable with a magnifying glass of 6 magnifications were observed.
2: Visually visible omission of the image area was confirmed at multiple locations.
1: Visually visible omission of the image area was observed on the entire surface.

-Ablation suppression evaluation-
A transparent polyethylene terephthalate film (manufactured by Fuji Film Co., Ltd.) having a thickness of 0.1 mm was brought into close contact with the surface of the lithographic printing plate precursor, and a drum rotating speed of 150 rpm and a beam intensity of 10 W were applied by a Creo Trendsetter. The entire surface was exposed.
After the exposure, the polyethylene terephthalate film was removed and visually inspected to observe the degree of dirt on the surface. The case where no stain was observed was 5, the case where a little stain was observed was 4, and the case where the film was contaminated to the extent that it was not visible through the film through the film was rated as 3.
It can be said that the less the dirt is, the more excellent the abrasion resistance is. Therefore, the evaluation is preferably 5 or 4, and more preferably 5.

In Tables 1 to 3 above, the description in the type column indicates the type of the specific binder polymer or particles used. For example, in Example 15, Art Pearl C-800 and Art Pearl J-7PY were contained at a ratio of 50:50 (molar ratio), the elastic modulus (GPa) of Art Pearl C-800 was 0.03 GPa, and the particle diameter was (Μm) is 6.0 μm, the elastic modulus (GPa) of Art Pearl J-7PY is 0.55 GPa, and the particle size (μm) is 6.5 μm.
In Table 2, the examples in which "-" is written in the column of particles indicate that particles were not added.
The details of the particles are as follows.
Art Pearl C-800; Urethane resin, Negami Kogyo Co., Ltd. Art Pearl J-7PS; Medium cross-linked acrylic resin, Negami Kogyo Co., Ltd. Tospearl 2000B; Silica, Tanac Co. Art Pearl J-7PY; Highly cross-linked acrylic Resin, Negami Kogyo Co., Ltd. Optobeads 6500M; Composite spherical particles composed of melamine resin and silica, Nissan Chemical Industries, Ltd. Art Pearl J-4P; Medium cross-linked acrylic resin, Negami Kogyo Co., Ltd. Art Pearl J- 5P: Medium-crosslinked acrylic resin, manufactured by Negami Kogyo Co., Ltd. Art Pearl J-6P; Medium-crosslinked acrylic resin, manufactured by Negami Kogyo Co., Ltd. Art Pearl GR600; Medium-crosslinked acrylic crosslinked (PMMA) resin, manufactured by Negami Kogyo Co., Ltd. Art Pearl P-800T: Urethane resin, Negami Kogyo Co., Ltd. Art Pearl CE-800T: Urethane resin, Negami Product

From the results shown in Tables 1 to 3, it can be seen that the lithographic printing plate precursor according to the present disclosure has excellent scratch resistance even without interleaving paper. Further, it can be seen that the lithographic printing plate precursor according to the present disclosure is also excellent in the prevention of film omission and the ablation.

The disclosure of Japanese Patent Application No. 2018-200690 filed on October 25, 2018 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference. Are incorporated herein by reference.

Claims

Having a positive image recording layer on an aluminum support,
The Bekk smoothness of the outermost layer surface on the side having the image recording layer is 1,000 seconds or less,
The outermost layer contains particles,
The elastic modulus of the particles is 3.0 GPa or less,
Original planographic printing plate.
The lithographic printing plate precursor according to claim 1, wherein the arithmetic average height Sa of the outermost layer surface on the side having the image recording layer is 0.3 μm or more and 20 μm or less.
The lithographic printing plate precursor according to claim 1 or 2, wherein the particles include at least one selected from the group consisting of acrylic resin particles, silica particles, and urethane resin particles.
The lithographic printing plate precursor according to any one of claims 1 to 3, wherein the image recording layer contains a resin having a glass transition temperature of 60 ° C to 230 ° C.
The image recording layer contains at least one resin selected from the group consisting of acetal resin, phenol resin, acrylic resin, and resin having urea bond, urethane bond or amide bond in the main chain. The lithographic printing plate precursor as described in any one of 4 above.
The lithographic printing plate precursor according to claim 5, wherein the image recording layer contains an acrylic resin having a maleimide structure.
The lithographic printing plate precursor according to any one of claims 1 to 6, wherein the image recording layer is a single layer.
The lithographic printing plate precursor as claimed in any one of claims 1 to 6, wherein the image recording layer is a multilayer consisting of an upper layer and a lower layer.
The planographic printing plate precursor according to any one of claims 1 to 8, wherein the outermost layer is the image recording layer.
The lithographic printing plate precursor according to any one of claims 1 to 9, further comprising an overcoat layer on the image recording layer, and the overcoat layer is the outermost layer.
The lithographic printing plate precursor according to any one of claims 1 to 10, which has a back coat layer on the side opposite to the side having the image recording layer.
A step of imagewise exposing the lithographic printing plate precursor according to any one of claims 1 to 11 to form an exposed portion and an unexposed portion;
developing with an alkaline aqueous solution having a pH of 13.5 or less,
including,
Method of making a lithographic printing plate.
The method for preparing a lithographic printing plate according to claim 12, wherein the pH of the alkaline aqueous solution is 11 or less.
A lithographic printing plate precursor laminate in which the lithographic printing plate precursors according to any one of claims 1 to 11 are laminated.
The outermost layer on the side having the image recording layer of the planographic printing plate precursor and the outermost layer on the side opposite to the side having the image recording layer of the other planographic printing plate precursor are directly contacted and laminated. 14. The lithographic printing plate precursor laminate according to 14.