JP2005070654A - Quality control method for planographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quality control method for keeping the quality of a planographic printing plate to be constant and for continuously forming a uniform image, by easily deciding the platemaking conditions of a negative planographic printing original plate for IR laser for direct platemaking, in particular, deciding the state of a developing solution and back feeding the result to exposure/development steps. <P>SOLUTION: The quality control method for a planographic printing plate includes steps of: (A) exposing a planographic printing original plate having a photosensitive layer containing an IR absorbent, a compound generating a radical and a polymerizable compound on a supporting body, then developing the plate with a standard alkaline developing solution, and determining the activity of the standard alkaline developing solution from physical properties of the solution; (B) determining the activity of the objective alkaline developing solution to be evaluated under the same conditions, except for using the objective alkaline developing solution instead of the standard one; (C) comparing the activity of the standard alkaline developing solution with the activity of the objective alkaline developing solution; and (D) controlling the exposure/development conditions, according to the difference in the activity if the difference in the activity is equal to or larger than a specified value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a quality control method for a lithographic printing plate, and more particularly, quality control suitable for a negative lithographic printing plate precursor for so-called infrared laser for direct plate making, which can be directly made from a digital signal of a computer or the like. Regarding the method.

In recent years, the development of lasers has been remarkable. In particular, solid lasers and semiconductor lasers having a light emitting region from the near infrared region to the infrared region have been increasing in output and size. Therefore, these lasers are very useful as an exposure light source when making a plate directly from digital data such as a computer.
The negative lithographic printing plate precursor for infrared laser, which uses an infrared laser having a light emitting region in the infrared region as described above as an exposure light source, is composed of an infrared absorbent, a compound that generates radicals by heat, and a polymerizable property on a support. And a photosensitive layer containing the compound.

  Usually, such a negative lithographic printing plate precursor uses a recording method in which a radical generated by heat is used as an initiator to cause a polymerization reaction to cure an exposed portion of a photosensitive layer to form an image portion. ing. Such negative type lithographic printing plate precursors promote the curing reaction such as polymerization because they are less image-forming than the positive type recording method that causes solubilization of the photosensitive layer by the energy of infrared laser irradiation. In order to form a strong image portion, the heat treatment is generally performed before the development step.

In addition, in such negative lithographic printing plate precursors for infrared lasers, the latitude of the developer activity is narrower than that of negative lithographic printing plate precursors made by UV exposure. However, there is a problem that the density of the image area and the printing durability are lowered, and if the activity is low, development defects are easily caused.
Such a problem is caused by an essential difference in the plate making mechanism between the negative lithographic printing plate precursor for infrared laser and the negative lithographic printing plate precursor made by UV exposure as described below.
Many negative lithographic printing plate precursors that are made by UV exposure contain a diazonium compound and a polymer as a binder as essential components. The image forming property varies depending on the diazonium compound and the binder to be used, but generally uses a binder having a large molecular weight and a small copolymerization ratio with a hydrophilic group such as a carboxyl group. Can be easily dissolved and removed with a developer containing an organic solvent such as benzyl alcohol. On the other hand, since the binder and the diazonium compound cause a photoreaction to form a network structure in the exposed area by UV exposure, it is difficult to dissolve even when a developer containing an organic solvent is used. Therefore, in the negative lithographic printing plate precursor for making a plate by UV exposure, the difference in solubility in the developing solution between the exposed portion and the non-exposed portion is very large.

  On the other hand, in the negative lithographic printing plate precursor for infrared laser, at the time of exposure, light is converted into thermal energy by the infrared absorber in the exposed portion (non-image portion), and the heat causes an image portion such as a radical. However, in order to further accelerate the reaction, it is preferable to perform a heat treatment after the exposure, and this heating allows the polymerization reaction to proceed efficiently to form a strong image portion. Thereafter, the negative lithographic printing plate precursor for infrared laser is developed into a lithographic printing plate. However, the conditions of exposure and development treatment that can obtain a level that can be actually used as a lithographic printing plate are very narrow. Furthermore, since the polymerizable compound used here has an overwhelmingly larger number of hydrophilic groups than the binder used in the lithographic printing plate precursor for UV exposure, it is soluble in an alkaline developer even after curing. It's easy to do. For this reason, in the negative planographic printing plate precursor for infrared laser, the difference in solubility between the non-exposed part and the exposed part is small.

For the above reasons, using a lithographic printing plate precursor having a narrow latitude with respect to the activity of the developer, such as a negative lithographic printing plate precursor for infrared laser, in order to continuously form stable quality images Therefore, it is very difficult to control and manage the plate making process.
Usually, when developing a negative photosensitive lithographic printing plate for an infrared laser, an automatic processor having a replenishment mechanism that keeps the developer sensitivity as constant as possible is used. The replenishment mechanism is to add a highly active replenisher to the developer in order to prevent the pH of the developer from being lowered due to the development processing of the lithographic printing plate precursor and the absorption of CO ₂ and the developability to be lowered. .
Specifically, in a normal PS plate processing system, i) a method of managing conductivity and adding a replenisher so that the conductivity is constant (see, for example, Patent Documents 1 to 4), and ii) A method of periodically adding a predetermined amount of replenisher every time the development processing number of a lithographic printing plate precursor reaches a certain number, or after a certain processing time has elapsed (see, for example, Patent Documents 5 to 6). Has been proposed.

However, i) in the method of managing by conductivity, the developer having a larger number of development processes and a large amount of the composition of the photosensitive layer dissolved therein has a different pH and developability even at the same conductivity value compared to the time of development start. There is a fact that it will be different.
In addition, ii) in the method of periodically adding a predetermined amount of replenisher, since the replenishment amount per unit area of the lithographic printing plate precursor is defined, the amount of the photosensitive layer composition that dissolves in the developer varies depending on the image area. In addition, the state of the developing solution slightly changes due to factors such as a difference in the amount of CO ₂ absorbed over time depending on the installation environment (temperature, humidity, CO ₂ concentration, etc.) of the automatic developing machine. For this reason, it is difficult to maintain uniform developability by managing by a method of periodically adding a predetermined amount of replenisher.

Usually, in a general-purpose lithographic printing plate precursor using UV exposure, the latitude with respect to the activity of the developer is wide, and thus the change in developability is not a big problem. However, the negative lithographic printing plate precursor for infrared laser has a narrow latitude with respect to the activity of the developer as described above. Easily cause plate quality problems.
However, a method for effectively preventing image quality deterioration such as a decrease in density of an image portion, a decrease in printing durability, or a development failure by applying it to a general-purpose negative lithographic printing plate precursor for an infrared laser with simple process management. Is not yet found.
JP-A-8-44076 Japanese Patent Publication No. 5-8823 Japanese Patent Publication No. 6-3542 Japanese Patent Publication No. 6-12435 JP 2000-105465 A JP-A-6-43661

An object of the present invention is to solve the above problems and achieve the following object.
That is, the object of the present invention is to easily determine the plate making conditions of the negative lithographic printing plate precursor for infrared laser for direct plate making, particularly the state of the developer, and feed back the result to the exposure / development process. An object of the present invention is to provide a quality control method for continuously forming a uniform image while keeping the quality of a planographic printing plate constant.

  As a result of the study, the inventors made a negative lithographic printing plate precursor for infrared laser with a standard alkaline developer, and then made the same lithographic printing plate precursor with an alkaline developer to be evaluated, The inventors have found that quality control of a lithographic printing plate can be easily performed by comparing the activities of the two developers and feeding back the evaluation results to the plate making conditions for exposure and development, thereby completing the present invention.

The quality control method of the lithographic printing plate of the present invention,
(A) A lithographic printing plate precursor comprising a photosensitive layer containing an infrared absorber, a radical generating compound, and a polymerizable compound on a support is exposed and then developed with a standard alkali developer. Determining the activity of the standard alkaline developer according to its physical properties;
(B) The step of determining the activity of the alkali developer to be evaluated under the same conditions as in the step (A) except that the development is performed with the alkali developer to be evaluated;
(C) comparing the activity of the standard alkali developer with the activity of the alkali developer to be evaluated;
(D) as a result of the comparison, when the difference in activity is a predetermined value or more, adjusting the exposure / development conditions according to the difference in activity; and
It is characterized by having.

Further, the quality control method of the lithographic printing plate of the present invention further comprises:
(E) After the completion of the step (D), the activity of the alkali developer under the adjusted exposure / development conditions is determined by the same index as in the step (A), and the activity of the alkali developer is determined. The step of setting the activity of the alkaline developer to be evaluated in the step (B),
The steps (E), (C) and (D) are performed once or a plurality of times in this order.

Here, as an index for determining the activity of the alkali developer, the physical properties of the alkali developer are used. Specifically, it is preferable to use the pH or conductivity of the alkali developer.
Further, in the step (D), when the difference between the activity of the standard alkali developer and the activity of the alkali developer to be evaluated is 10% to 30%, the exposure / development condition is adjusted. Is practically preferable.

  According to the present invention, it is possible to easily determine the variation in the activity of the alkaline developer, feed back the determination result, and adjust the plate-making conditions to keep the quality of the lithographic printing plate constant and uniform. A quality control method for a lithographic printing plate for continuously forming images can be provided.

The lithographic printing plate quality control method of the present invention (hereinafter referred to as “quality control method” where appropriate) will be described in detail below.
The quality control method of the lithographic printing plate of the present invention,
(A) A lithographic printing plate precursor comprising a photosensitive layer containing an infrared absorber, a radical generating compound, and a polymerizable compound on a support is exposed and then developed with a standard alkali developer. Determining the activity of the standard alkaline developer according to its physical properties;
(B) The step of determining the activity of the alkali developer to be evaluated under the same conditions as in the step (A) except that the development is performed with the alkali developer to be evaluated;
(C) comparing the activity of the standard alkali developer with the activity of the alkali developer to be evaluated;
(D) as a result of the comparison, when the difference in activity is equal to or greater than a predetermined value, adjusting the plate-making conditions according to the difference in activity; and
It is characterized by having.

Moreover, the quality control method of the lithographic printing plate according to the present invention further includes (E) after the completion of the step (D), the activity of the alkaline developer under the adjusted plate making conditions is the same as that in the step (A). And determining the activity of the alkali developer as the activity of the alkali developer to be evaluated in the step (B),
It is a preferred embodiment that the steps (E), (C) and (D) are carried out once or a plurality of times in this order.

Hereafter, each process in this invention is demonstrated sequentially.
First, in step (A), a lithographic printing plate precursor comprising a photosensitive layer containing an infrared absorber, a radical generating compound, and a polymerizable compound on a support is exposed to a standard alkali development after exposure. After developing with a solution, the activity of the standard alkaline developer is determined by its physical properties.
In the present invention, a lithographic printing plate precursor provided with a photosensitive layer containing an infrared absorber, a radical generating compound, and a polymerizable compound on a support is hereinafter simply referred to as “lithographic printing plate”. The support and photosensitive layer will be described in detail later.

  In the step (A), the activity of the standard alkaline developer is determined by using its physical properties as an index. The specific method is to measure the pH, conductivity, and specific gravity of the alkaline developer. Is preferred. Among these, it is preferable to use the pH or conductivity of the alkali developer.

  Thus, the activity of the standard alkaline developer determined in the step (A) is an evaluation criterion for the activity of the alkaline developer to be evaluated, which is determined in the step (B).

The activity of the standard alkaline developer that serves as the evaluation criterion does not need to be determined for each evaluation. If the evaluation and management are to be performed in a continuous process in which the same plate-making process is performed, the first step is required. It may be determined by.
For example, the standard alkaline developer is usually an alkaline developer in an automatic developing machine that performs a continuous development process, and the development process is not performed, or the initial stage of the continuous development process It is preferable that the activity of the alkali developer in such a state be the activity of the standard alkali developer.

Next, in step (B), the activity of the alkali developer to be evaluated is determined under the same conditions as in step (A) except that development is performed with the alkali developer to be evaluated.
(B) The activity of the alkaline developer to be evaluated, which is determined in the step, is for confirming the state of the developer's fatigue and changes in physical properties after the passage of time (after the development process is continued). When required, it is determined under the same conditions as in step (A). That is, in the step (B), the same conditions as those in the step (A) are applied as plate making conditions such as exposure conditions and development conditions, except that the activity of the alkali developer is different.
As described above, the activity of the alkaline developer to be evaluated determined in the step (B) is an evaluation target of the activity of the standard alkaline developer determined in the step (A).

  The alkaline developer to be evaluated is usually an alkaline developer in an automatic developing machine that performs a continuous development process, and after a continuous development process for a predetermined period (lithographic printing in the present invention). It is preferable to use a plate precursor that has been subjected to development processing for a predetermined number of sheets continuously) to obtain an alkaline developer for evaluating the activity of the alkaline developer in such a state.

Next, in the step (C), the activity (evaluation criteria) of the standard alkali developer is compared with the activity (evaluation target) of the alkali developer to be evaluated. Thus, by comparing the two, the change in the activity of the alkaline developer can be detected accurately and easily.
As a result, it is possible to determine whether adjustment of exposure / development conditions is necessary.

  Next, in the step (D), when the difference in the activity is a predetermined value or more as a result of the comparison in the step (C), the plate-making conditions are adjusted according to the difference in the activity.

In the step (D), the “predetermined value” is the maximum value of the difference in the activity of the alkaline developer that is allowed to keep the desired image quality constant. Therefore, the specific value may be determined as appropriate according to the image quality desired for the lithographic printing plate that has been made. Only when the difference in the degree of activity equal to or greater than the predetermined value occurs, the step (D) of adjusting the plate-making conditions is performed. Generally, the plate-making conditions are adjusted when the difference in activity between a predetermined value, that is, the standard alkaline developer and the alkaline developer to be evaluated exceeds 10 to 30%. Is preferred.
More specifically, when the activity index of the alkaline developer is pH, the predetermined difference in step (D) is, for example, 0.1.
In addition, when conductivity is used as an index of the activity of the alkaline developer, the predetermined difference in the step (D) is, for example, 4 mS / cm.

The means for adjusting exposure / development conditions in the step (D) are as follows.
In the alkaline developer to be evaluated, when an increase in the activity is observed as compared with the standard alkaline developer, a means for relaxing the developing conditions and increasing the exposure conditions may be employed.
Further, when the alkali developer to be evaluated shows a decrease in activity as compared with the standard alkali developer, a means for activating the developing conditions may be taken.

  In the alkaline developer to be evaluated, the following means can be cited as countermeasures in the case where an increase in the activity is observed as compared with the standard alkaline developer.

<Means Applied to Adjustment in Development Process>
(1) Add water to the developer.
(2) Add dry ice to the developer.
(3) Blow CO ₂ gas.
(4) Reduce the dilution ratio of the replenisher.
(5) Reduce the replenishment amount setting of the automatic processor.
(6) Lower the development temperature.
(7) Shorten the development time (increase the conveyance speed of the automatic processor).
(8) Lower the pressure of the developing brush of the automatic processor.
(9) Reduce the number of developing brushes in the automatic processor.
(10) Lower the spray discharge amount.
(11) Stir the developer.
(12) Replace the developer with a new solution.
<Means Applied to Adjustment in Exposure Step and Pre-Exposure Step>
(13) Increase the exposure amount.
(14) The negative lithographic printing plate precursor for infrared laser is heated before exposure.

  In the alkaline developer to be evaluated, the following means can be cited as countermeasures in the case where a decrease in activity is observed as compared with the standard alkaline developer.

<Means Applied to Adjustment in Development Process>
(1) Add replenisher.
(2) Increase the dilution ratio of the replenisher.
(3) Increase the replenishment amount setting of the automatic processor.
(4) Increase the development temperature.
(5) Increase the development time (lower the conveyance speed of the automatic processor).
(6) Increase the pressure of the developing brush of the automatic processor.
(7) Increase the number of developing brushes in the automatic processor.
(8) Increase the spray discharge amount.
(9) Replace the developer with a new solution.

  Here, in the means applied to the adjustment in the exposure process described above, when performing “increase exposure amount”, the specific exposure amount control is performed under conditions such as laser light output, beam diameter, scanning speed, and exposure time. Is appropriately adjusted.

Further, in the quality control method of the present invention, after the completion of the steps (A) to (D), as the step (E), the activity of the alkaline developer under the adjusted exposure / development conditions is set as (A). ) Determined by the same index as in the step, the activity of the alkaline developer is the activity of the alkali developer to be evaluated in the step (B),
The quality control method for a lithographic printing plate according to claim 1, wherein the steps (E), (C), and (D) are performed once or a plurality of times in this order.
As described above, the results of the image evaluation are fed back, the plate making conditions are adjusted, and the steps (E), (C), and (D) are repeated to stabilize the activity of the alkaline developer. In addition, it can be held constant over a long period of time. As a result, the development processing conditions become constant, so that a lithographic printing plate having a constant quality is produced over a long period of time.

<Lithographic printing plate precursor>
The planographic printing plate precursor to which the planographic printing plate quality control method of the present invention can be applied will be described below.
In the quality control method of the present invention, a lithographic printing plate precursor comprising a photosensitive layer containing an infrared absorber, a radical generating compound, and a polymerizable compound on a support, ie, infrared laser irradiation. Any lithographic printing plate precursor having a negative photosensitive layer in which the part is cured by radical polymerization to form an image part can be applied.
As a preferred embodiment of such a lithographic printing plate precursor, a lithographic plate in which a negative photosensitive layer containing an infrared absorber, a sulfonium salt polymerization initiator, a polymerizable compound, and a binder polymer is provided on a support. It is a printing plate master.
Hereafter, each component which comprises the lithographic printing plate precursor applied to this invention is demonstrated in detail.

[Infrared absorber]
When the lithographic printing plate precursor applied to the present invention is directly drawn (image formation) using a laser emitting infrared rays of 760 to 1,200 nm as a light source, it is usually essential to use an infrared absorber. The infrared absorber has a function of converting absorbed infrared rays into heat. With the heat generated at this time, a compound (polymerization initiator) that generates radicals described later is thermally decomposed to generate radicals. The infrared absorber used in the present invention is a dye or pigment having an absorption maximum at a wavelength of 760 nm to 1200 nm.

As the dye, commercially available dyes and known dyes described in documents such as “Dye Handbook” (edited by the Society for Synthetic Organic Chemistry, published in 1970) can be used. Specifically, dyes such as azo dyes, metal complex azo dyes, pyrazolone azo dyes, naphthoquinone dyes, anthraquinone dyes, phthalocyanine dyes, carbonium dyes, quinoneimine dyes, methine dyes, cyanine dyes, squarylium dyes, pyrylium salts, metal thiolate complexes, etc. Is mentioned.
Examples of preferable dyes include cyanine dyes described in JP-A-58-125246, JP-A-59-84356, JP-A-60-78787, JP-A-58-173696, 58-181690, JP-A-58-194595, etc., methine dyes, JP-A-58-112793, JP-A-58-224793, JP-A-59-48187, JP-A-59- No. 73996, JP-A-60-52940, JP-A-60-63744 and the like, Naphthoquinone dyes described in JP-A-58-112792, etc., British Patent 434,875 And cyanine dyes.

Also, a near infrared absorption sensitizer described in US Pat. No. 5,156,938 is preferably used, and a substituted arylbenzo (thio) pyrylium salt described in US Pat. No. 3,881,924, Trimethine thiapyrylium salts described in JP-A-57-142645 (US Pat. No. 4,327,169), JP-A-58-181051, 58-220143, 59-41363, 59-84248 Nos. 59-84249, 59-146063, 59-146061, pyranlium compounds, cyanine dyes described in JP-A-59-216146, US Pat. No. 4,283,475 The pentamethine thiopyrylium salts described above and the pyrylium compounds disclosed in Japanese Patent Publication Nos. 5-13514 and 5-19702 are also preferably used. . Another example of a preferable dye is a near-infrared absorbing dye described in US Pat. No. 4,756,993 as formulas (I) and (II).
Other preferred examples of the infrared absorbing dye of the present invention include specific indolenine cyanine dyes described in Japanese Patent Application Nos. 2001-6326 and 2001-237840 as exemplified below.

  Particularly 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 preferred, and particularly preferred examples include cyanine dyes represented by the following general formula (a).

In formula (a), X ¹ represents a hydrogen atom, a halogen atom, -NPh _2, X ² -L ¹ or a group shown below. Here, X ² represents an oxygen atom, a nitrogen atom, or a sulfur atom, and L ¹ represents a hydrocarbon group having 1 to 12 carbon atoms, an aromatic ring having a hetero atom, or 1 to 1 carbon atom containing a hetero atom. 12 hydrocarbon groups are shown. Here, the hetero atom represents N, S, O, a halogen atom, or Se. Xa ^- is defined as for Z ^1-to be described later, R ^a represents a hydrogen atom, an alkyl group, an aryl group, a substituted or unsubstituted amino group, substituted or unsubstituted amino group and a halogen atom.

R ¹ and R ² each independently represents a hydrocarbon group having 1 to 12 carbon atoms. From the storage stability of the photosensitive layer coating solution, R ¹ and R ² are preferably hydrocarbon groups having 2 or more carbon atoms, and R ¹ and R ² are bonded to each other to form a 5-membered ring or It is particularly preferable that a 6-membered ring is formed.

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 ¹ and Y ² may be the same or different and each represents a sulfur atom or a dialkylmethylene group having 12 or less carbon atoms. R ³ and R ⁴ may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferred substituents include alkoxy groups having 12 or less carbon atoms, carboxyl groups, and sulfo groups. R ⁵ , R ⁶ , R ⁷ and R ⁸ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 12 or less carbon atoms. From the availability of raw materials, a hydrogen atom is preferred. Z ¹⁻ represents a counter anion. However, when the cyanine dye represented by the general formula (a) has an anionic substituent in its structure and charge neutralization is not necessary, Z ¹⁻ is not necessary. Preferred Z ¹⁻ is halogen ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, and sulfonate ion, particularly preferably perchlorate ion, in view of storage stability of the photosensitive layer coating solution. Hexafluorophosphate ions and aryl sulfonate ions.

Specific examples of the cyanine dye represented by formula (a) that can be suitably used in the present invention include those described in paragraph numbers [0017] to [0019] of JP-A No. 2001-133969. Can do.
Further, other particularly preferable examples include specific indolenine cyanine dyes described in Japanese Patent Application Nos. 2001-6326 and 2001-237840 described above.

  Examples of the pigment used in the present invention include commercially available pigments and color index (CI) manual, “Latest Pigment Handbook” (edited by Japan Pigment Technology Association, published in 1977), “Latest Pigment Application Technology” (CMC Publishing, 1986), “Printing Ink Technology”, CMC Publishing, 1984) can be used.

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

  These pigments may be used without surface treatment, or may be used after surface treatment. The surface treatment method includes a method of surface coating with a resin or wax, a method of attaching a surfactant, a method of bonding a reactive substance (eg, silane coupling agent, epoxy compound, polyisocyanate, etc.) to the pigment surface, etc. Can be considered. The above-mentioned surface treatment methods are described in “Characteristics and Applications of Metal Soap” (Shobobo), “Printing Ink Technology” (CMC Publishing, 1984) and “Latest Pigment Application Technology” (CMC Publishing, 1986). Yes.

  The particle size of the pigment is preferably in the range of 0.01 μm to 10 μm, more preferably in the range of 0.05 μm to 1 μm, and particularly preferably in the range of 0.1 μm to 1 μm. Within this preferred particle size range, excellent dispersion stability of the pigment in the photosensitive layer coating solution can be obtained, and a uniform photosensitive layer can be obtained.

  As a method for dispersing the pigment, a known dispersion technique used in ink production, toner production, or the like can be used. Examples of the disperser include an ultrasonic disperser, a sand mill, an attritor, a pearl mill, a super mill, a ball mill, an impeller, a disperser, a KD mill, a colloid mill, a dynatron, a three-roll mill, and a pressure kneader. Details are described in "Latest Pigment Applied Technology" (CMC Publishing, 1986).

When these infrared absorbers are applied to the photosensitive layer of the lithographic printing plate precursor according to the invention, they may be added to the same layer as other components or may be added to the same layer as other components. However, from the viewpoint of the strength (printing durability) of the image area, when a negative lithographic printing plate precursor is prepared, the photosensitive layer has a wavelength range of 760 nm to 1200 nm. Is added so that the absorbance at the maximum absorption wavelength in the range of 0.5 to 1.2 in the reflection measurement method. Preferably, it is the range of 0.6-1.15.
The absorbance of the photosensitive layer can be adjusted by the amount of infrared absorber added to the photosensitive layer and the thickness of the photosensitive layer. Absorbance can be measured by a conventional method. As a measuring method, for example, on a reflective support such as aluminum, a photosensitive layer having a thickness appropriately determined in a range where the coating amount after drying is necessary as a lithographic printing plate is formed, and the reflection density is measured by an optical densitometer. And a method of measuring with a spectrophotometer by a reflection method using an integrating sphere.

  These infrared absorbers are 0.01 to 50% by mass, preferably 0.1%, based on the total solid content constituting the photosensitive layer, from the viewpoints of sensitivity, uniformity in the photosensitive layer and durability of the photosensitive layer. In the case of a dye, particularly preferably in the case of a dye, 0.5 to 10% by mass, and in the case of a pigment, it can be added in a ratio of preferably 0.1 to 10% by mass.

[Compound that generates radicals]
The compound that generates radicals used in the photosensitive layer of the lithographic printing plate precursor applied to the present invention has a function of initiating and proceeding the curing reaction of the polymerizable compound described later by the generated radicals. By using this radical generating compound in combination with the above-described infrared absorber, a mechanism that the infrared absorber converts the infrared rays into heat when irradiated with an infrared laser, and generates a radical by the heat is developed.
Thus, it is preferable that the compound generating radicals is a thermal decomposition type radical generator that decomposes by heat to generate radicals.
In the lithographic printing plate precursor used in the present invention, a sulfonium salt polymerization initiator is preferably used as the radical generating compound.

(Sulfonium salt polymerization initiator)
Examples of the sulfonium salt polymerization initiator suitably used in the present invention include onium salts represented by the following general formula (I).

In general formula (I), R ¹¹ , R ¹² and R ¹³ may be the same or different and each represents a hydrocarbon group having 20 or less carbon atoms which may have a substituent. Preferable substituents include 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. Z ¹¹⁻ represents a counter ion selected from the group consisting of a halogen ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, a carboxylate ion, and a sulfonate ion, preferably a perchlorate ion, Hexafluorophosphate ions, carboxylate ions, and aryl sulfonate ions.

  Specific examples ([OS-1] to [OS-12]) of the onium salt represented by the general formula (I) are shown below, but are not limited thereto.

  In addition to the above, specific aromatic sulfonium salts described in JP-A Nos. 2002-148790, 2002-148790, 2002-350207, and 2002-6482 are also preferably used.

(Other compounds that generate radicals)
Furthermore, in the present invention, as a compound that generates radicals, in addition to the above-mentioned sulfonium salt polymerization initiator, other onium salts other than sulfonium salts, peroxides, azo polymerization initiators, azide compounds, quinonediazides, and the like A conventionally known polymerization initiator (radical generator) can be used. Moreover, these polymerization initiators can be used in combination with the sulfonium salt polymerization initiator as an essential component.
Other onium salts that can be suitably used in the present invention include iodonium salts and diazonium salts. In the present invention, these onium salts function not as acid generators but as radical polymerization initiators.
Other onium salts in the present invention include onium salts represented by the following general formulas (II) and (III).

In general formula (II), Ar ²¹ and Ar ²² each independently represent an aryl group having 20 or less carbon atoms, which may have a substituent. Preferred substituents when this aryl group has a substituent include 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 a carbon atom having 12 or less carbon atoms. An aryloxy group is mentioned. Z ^21- represents a counter ion having the same ^meaning as Z ^11- .

In the general formula (III), Ar ³¹ represents an aryl group having 20 or less carbon atoms which may have a substituent. Preferred examples of the substituent include a halogen atom, a nitro group, an alkyl group having 12 or less carbon atoms, an alkoxy group having 12 or less carbon atoms, an aryloxy group having 12 or less carbon atoms, and 12 or less carbon atoms. Examples thereof include an alkylamino group, a dialkylamino group having 12 or less carbon atoms, an arylamino group having 12 or less carbon atoms, or a diarylamino group having 12 or less carbon atoms. Z ^31- represents a counter ion having the same ^meaning as Z ^11- .

  In the present invention, onium salts represented by general formula (II) ([OI-1] to [OI-10]) and onium salts represented by general formula (III) ([ Specific examples of ON-1] to [ON-5] are given below, but are not limited thereto.

  Specific examples of the onium salt that can be suitably used as the radical-generating compound in the present invention include those described in JP-A No. 2001-133696.

  The radical generating compound used in the present invention preferably has a maximum absorption wavelength of 400 nm or less, and more preferably 360 nm or less. By making the absorption wavelength in the ultraviolet region in this way, the lithographic printing plate precursor can be handled under white light.

  The total content of the radical generating compound in the present invention is 0.1 to 50% by mass with respect to the total solid content constituting the photosensitive layer, from the viewpoint of sensitivity and generation of stains in the non-image area during printing. Preferably it is 0.5-30 mass%, Most preferably, it is 1-20 mass%.

Only 1 type may be used for the compound which generate | occur | produces the radical in this invention, and 2 or more types may be used together. When two or more polymerization initiators are used in combination, for example, only a plurality of suitably used sulfonium salt polymerization initiators may be used, or a sulfonium salt polymerization initiator and another polymerization initiator may be used in combination. Good.
The content ratio (mass ratio) when the sulfonium salt polymerization initiator and another polymerization initiator are used in combination is preferably 100/1 to 100/50, more preferably 100/5 to 100/25.
Moreover, a polymerization initiator may be added to the same layer as other components, or another layer may be provided and added thereto.

  When a highly sensitive sulfonium salt polymerization initiator is contained as a radical generating compound in the photosensitive layer of the lithographic printing plate precursor according to the invention, the radical polymerization reaction proceeds effectively, and the strength of the formed image area is extremely high. It will be expensive. Therefore, combined with a high oxygen blocking function of the protective layer described later, a lithographic printing plate having high image area strength can be produced, and as a result, printing durability is improved. In addition, by using a sulfonium salt polymerization initiator, it is excellent in stability over time, so that it is possible to suppress the occurrence of an undesirable polymerization reaction even when the prepared lithographic printing plate precursor is stored. it can.

[Polymerizable compound]
The polymerizable compound used in the photosensitive layer of the lithographic printing plate precursor applied to the present invention is an addition polymerizable compound having at least one ethylenically unsaturated double bond, and has at least one ethylenically unsaturated bond, Preferably, it is selected from compounds having two or more. Such a compound group is widely known in the industrial field, and can be used without any particular limitation in the present invention. These have chemical forms such as monomers, prepolymers, that is, dimers, trimers and oligomers, or mixtures thereof, and copolymers thereof. Examples of monomers and copolymers thereof include unsaturated carboxylic acids (for example, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, maleic acid, etc.), and esters and amides thereof. In this case, an ester of an unsaturated carboxylic acid and an aliphatic polyhydric alcohol compound, or an amide of an unsaturated carboxylic acid and an aliphatic polyvalent amine compound is used. In addition, an addition reaction product of an unsaturated carboxylic acid ester or amide having a nucleophilic substituent such as a hydroxyl group, amino group or mercapto group with a monofunctional or polyfunctional isocyanate or epoxy, and monofunctional or polyfunctional A dehydration condensation reaction product with a functional carboxylic acid is also preferably used. Further, an addition reaction product of an unsaturated carboxylic acid ester or amide having an electrophilic substituent such as an epoxy group or an epoxy group with a monofunctional or polyfunctional alcohol, amine or thiol, a halogen group or In addition, a substitution reaction product of an unsaturated carboxylic acid ester or amide having a leaving substituent such as a tosyloxy group and a monofunctional or polyfunctional alcohol, amine or thiol is also suitable. As another example, it is also possible to use a group of compounds substituted with unsaturated phosphonic acid, styrene, vinyl ether or the like instead of the unsaturated carboxylic acid.

  Specific examples of the monomer of an ester of an aliphatic polyhydric alcohol compound and an unsaturated carboxylic acid include acrylic acid esters such as ethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butanediol diacrylate, and tetramethylene glycol. Diacrylate, propylene glycol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolpropane tri (acryloyloxypropyl) ether, trimethylolethane triacrylate, hexanediol diacrylate, 1,4-cyclohexanediol diacrylate , Tetraethylene glycol diacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate , Pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol hexaacrylate, sorbitol triacrylate, sorbitol tetraacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, tri (acryloyloxyethyl) isocyanurate, polyester acrylate oligomer.

  Methacrylic acid esters include tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, ethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, Hexanediol dimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol hexamethacrylate, sorbitol trimethacrylate, sorbitol tetramethacrylate, bis [p- (3-methacryloxy- 2-hydroxypro ) Phenyl] dimethyl methane, bis - [p- (methacryloxyethoxy) phenyl] dimethyl methane.

Itaconic acid esters include ethylene glycol diitaconate, propylene glycol diitaconate, 1,3-butanediol diitaconate, 1,4-butanediol diitaconate, tetramethylene glycol diitaconate, pentaerythritol diitaconate And sorbitol tetritaconate.
Examples of crotonic acid esters include ethylene glycol dicrotonate, tetramethylene glycol dicrotonate, pentaerythritol dicrotonate, and sorbitol tetradicrotonate.
Examples of isocrotonic acid esters include ethylene glycol diisocrotonate, pentaerythritol diisocrotonate, and sorbitol tetraisocrotonate.
Examples of maleic acid esters include ethylene glycol dimaleate, triethylene glycol dimaleate, pentaerythritol dimaleate, and sorbitol tetramaleate.

  Examples of other esters include aliphatic alcohol esters described in JP-B-46-27926, JP-B-51-47334, JP-A-57-196231, JP-A-59-5240, JP-A-59-5241. Those having an aromatic skeleton described in JP-A-2-226149 and those containing an amino group described in JP-A-1-165613 are also preferably used. Furthermore, the ester monomers described above can also be used as a mixture.

  Specific examples of amide monomers of aliphatic polyvalent amine compounds and unsaturated carboxylic acids include methylene bis-acrylamide, methylene bis-methacrylamide, 1,6-hexamethylene bis-acrylamide, 1,6-hexamethylene bis. -Methacrylamide, diethylenetriamine trisacrylamide, xylylene bisacrylamide, xylylene bismethacrylamide and the like. Examples of other preferable amide monomers include those having a cyclohexylene structure described in JP-B-54-21726.

  In addition, urethane-based addition polymerizable compounds produced by using an addition reaction of isocyanate and hydroxyl group are also suitable, and specific examples thereof include, for example, one molecule described in JP-B-48-41708. A vinyl urethane containing two or more polymerizable vinyl groups in one molecule obtained by adding a vinyl monomer containing a hydroxyl group represented by the following general formula (1) to a polyisocyanate compound having two or more isocyanate groups. Compounds and the like.

^{_{CH 2 = C (R 4)}} COOCH 2 CH (R 5) OH (1)
(However, R ⁴ and R ⁵ represent H or CH _3. )

  Also, urethane acrylates such as those described in JP-A-51-37193, JP-B-2-32293, and JP-B-2-16765, JP-B-58-49860, JP-B-56-17654, Urethane compounds having an ethylene oxide skeleton described in JP-B-62-39417 and JP-B-62-39418 are also suitable. Further, by using addition polymerizable compounds having an amino structure or a sulfide structure in the molecule described in JP-A-63-277653, JP-A-63-260909, and JP-A-1-105238, It is possible to obtain a photopolymerizable composition excellent in the photosensitive speed.

  Other examples include polyester acrylates, epoxy resins and (meth) acrylic acid as described in JP-A-48-64183, JP-B-49-43191, JP-B-52-30490, and JP-A-52-30490. Mention may be made of polyfunctional acrylates and methacrylates such as reacted epoxy acrylates. Further, specific unsaturated compounds described in JP-B-46-43946, JP-B-1-40337 and JP-B-1-40336, vinylphosphonic acid compounds described in JP-A-2-25493, and the like can also be mentioned. . In some cases, a structure containing a perfluoroalkyl group described in JP-A-61-22048 is preferably used. Furthermore, Journal of Japan Adhesion Association vol. 20, no. 7, pages 300 to 308 (1984), which are introduced as photocurable monomers and oligomers, can also be used.

  About these addition polymerizable compounds, the details of usage, such as the structure, single use or combined use, and addition amount can be arbitrarily set according to the final performance design. For example, it is selected from the following viewpoints. From the viewpoint of photosensitive speed, a structure having a high unsaturated group content per molecule is preferable, and in many cases, a bifunctional or higher functionality is preferable. Further, in order to increase the strength of the image area, that is, the cured film, those having three or more functionalities are preferable, and furthermore, different functional numbers and different polymerizable groups (for example, acrylic acid ester, methacrylic acid ester, styrene compound, vinyl ether). It is also effective to adjust both photosensitivity and strength by using a compound of the type). A compound having a large molecular weight or a compound having high hydrophobicity is excellent in photosensitive speed and film strength, but is not preferable in terms of development speed and precipitation in a developer. Further, the selection / use method of the addition polymerization compound is also an important factor for the compatibility and dispersibility with other components in the composition (for example, binder polymer, initiator, colorant, etc.). In some cases, the compatibility can be improved by using a low-purity compound or using two or more of them together.

  As for the compounding ratio of the addition polymerizable compound in the composition, a larger amount is more advantageous in terms of sensitivity, but if it is too much, undesirable phase separation occurs or the photosensitive layer when applied to a lithographic printing plate precursor Problems in the production process due to the adhesive property (for example, transfer of photosensitive layer components, production failure due to adhesion), and precipitation from the developer may occur. From these viewpoints, the addition polymerizable compound is preferably used in the range of 5 to 80% by mass, more preferably 25 to 75% by mass, with respect to the nonvolatile component in the composition. These may be used alone or in combination of two or more. In addition, the use method of the addition polymerizable compound can arbitrarily select an appropriate structure, blending, and addition amount from the viewpoint of polymerization inhibition with respect to oxygen, resolution, fogging property, refractive index change, surface adhesiveness, and the like. Further, the lithographic printing plate precursor according to the invention may be subjected to a layer constitution / coating method such as undercoating or overcoating.

[Binder polymer]
The binder polymer used in the photosensitive layer of the lithographic printing plate precursor according to the invention is contained from the viewpoint of improving the film properties, and various materials are used as long as they have a function of improving the film properties. Can be Especially, as a binder polymer suitable in this invention, it is a binder polymer which has a repeating unit represented by the following general formula (i). Hereinafter, the binder polymer having the repeating unit represented by the general formula (i) is appropriately referred to as a specific binder polymer and will be described in detail.

(In general formula (i), R ¹ represents a hydrogen atom or a methyl group, and R ² is composed of a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, and a halogen atom, and the number of atoms excluding a substituent. Represents a linking group of 2 to 30. A represents an oxygen atom or —NR ³ —, R ³ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms, and n is an integer of 1 to 5. Represents.)

First, R ¹ in the general formula (i) represents a hydrogen atom or a methyl group, and a methyl group is particularly preferable.

The linking group represented by R ² in the general formula (i) is composed of a hydrogen atom, an oxygen atom, a nitrogen atom, a sulfur atom and a halogen atom, and the number of atoms excluding the substituent is 2 to 30. is there. Specific examples include alkylene, substituted alkylene, arylene, substituted arylene, and the like, and a structure in which a plurality of these divalent groups are linked by an amide bond or an ester bond may be used.
Examples of the linking group having a chain structure include ethylene and propylene. A structure in which these alkylenes are linked via an ester bond can also be exemplified as a preferable example.

Among these, the linking group represented by R ² in the general formula (i) is preferably an (n + 1) -valent hydrocarbon group having an aliphatic cyclic structure having 3 to 30 carbon atoms. More specifically, a compound having an aliphatic cyclic structure such as cyclopropane, cyclopentane, cyclohexane, cycloheptane, cyclooctane, cyclodecane, dicyclohexyl, tercyclohexyl, norbornane and the like, which may be substituted by one or more arbitrary substituents And (n + 1) valent hydrocarbon groups by removing (n + 1) hydrogen atoms on an arbitrary carbon atom constituting. R ² preferably has 3 to 30 carbon atoms including a substituent.

One or more arbitrary carbon atoms of the compound constituting the aliphatic cyclic structure may be replaced with a heteroatom selected from a nitrogen atom, an oxygen atom, or a sulfur atom. In terms of printing durability, R ² represents a condensed polycyclic aliphatic hydrocarbon, a bridged cyclic aliphatic hydrocarbon, a spiro aliphatic hydrocarbon, an aliphatic hydrocarbon ring assembly (a plurality of rings are connected by a bond or a linking group). A (n + 1) valent hydrocarbon group having an aliphatic cyclic structure which may have a substituent of 5 to 30 carbon atoms containing two or more rings. . Also in this case, the carbon number includes the carbon atom of the substituent.

As the linking group represented by R ² , those having 5 to 10 atoms are further preferable, and structurally a chain structure having an ester bond in the structure, Those having a cyclic structure are preferred.

Examples of the substituent that can be introduced into the linking group represented by R ² include monovalent nonmetallic atomic groups other than hydrogen, such as halogen atoms (—F, —Br, —Cl, —I), hydroxyl groups. Group, alkoxy group, aryloxy group, mercapto group, alkylthio group, arylthio group, alkyldithio group, aryldithio group, amino group, N-alkylamino group, N, N-dialkylamino group, N-arylamino group, N, N-diarylamino group, N-alkyl-N-arylamino group, acyloxy group, carbamoyloxy group, N-alkylcarbamoyloxy group, N-arylcarbamoyloxy group, N, N-dialkylcarbamoyloxy group, N, N- Diarylcarbamoyloxy group, N-alkyl-N-arylcarbamoyloxy group, alkylsulfoxy , Arylsulfoxy group, acylthio group, acylamino group, N-alkylacylamino group, N-arylacylamino group, ureido group, N′-alkylureido group, N ′, N′-dialkylureido group, N′-aryl Ureido group, N ′, N′-diarylureido group, N′-alkyl-N′-arylureido group, N-alkylureido group, N-arylureido group, N′-alkyl-N-alkylureido group, N ′ -Alkyl-N-arylureido group, N ', N'-dialkyl-N-alkylureido group, N', N'-dialkyl-N-arylureido group, N'-aryl-N-alkylureido group, N ' -Aryl-N-arylureido group, N ', N'-diaryl-N-alkylureido group, N', N'-diaryl-N-arylureido group, N'-al Kill-N′-aryl-N-alkylureido group, N′-alkyl-N′-aryl-N-arylureido group, alkoxycarbonylamino group, aryloxycarbonylamino group, N-alkyl-N-alkoxycarbonylamino group N-alkyl-N-aryloxycarbonylamino group, N-aryl-N-alkoxycarbonylamino group, N-aryl-N-aryloxycarbonylamino group, formyl group, acyl group, carboxyl group and its conjugate base group, Alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, N-alkylcarbamoyl group, N, N-dialkylcarbamoyl group, N-arylcarbamoyl group, N, N-diarylcarbamoyl group, N-alkyl-N-arylcarbamoyl group, Alkylsulfinyl group An arylsulfinyl group, an alkylsulfonyl group, an arylsulfonyl group, a sulfo group (-SO ₃ H) and its conjugated base group, alkoxy sulfonyl group, aryloxy sulfonyl group, sulfinamoyl group, N- alkylsulfinamoyl group, N, N- Dialkylsulfinamoyl group, N-arylsulfinamoyl group, N, N-diarylsulfinamoyl group, N-alkyl-N-arylsulfinamoyl group, sulfamoyl group, N-alkylsulfamoyl group, N, N -Dialkylsulfamoyl group, N-arylsulfamoyl group, N, N-diarylsulfamoyl group, N-alkyl-N-arylsulfamoyl group, N-acylsulfamoyl group and its conjugate base group, N- alkylsulfonylsulfamoyl group (-SO ₂ NHSO ₂ alkyl)) and its conjugated base group, N- aryl sulfonylsulfamoyl group _{(-SO 2 NHSO 2 (aryl)} ) and its conjugated base group, N- alkylsulfonylcarbamoyl group (-CONHSO ₂ (alkyl)) and its conjugate Base group, N-arylsulfonylcarbamoyl group (—CONHSO ₂ (aryl)) and its conjugate base group, alkoxysilyl group (—Si (Oalkyl) ₃ ), aryloxysilyl group (—Si (Oaryl) ₃ ), hydroxysilyl Group (—Si (OH) ₃ ) and its conjugate base group, phosphono group (—PO ₃ H ₂ ) and its conjugate base group, dialkylphosphono group (—PO ₃ (alkyl) ₂ ), diarylphosphono group (— PO ₃ (aryl) _2), alkyl aryl phosphono group _{(-PO 3 (alkyl) (aryl} )) , Monoalkylphosphono group (—PO ₃ H (alkyl)) and its conjugate base group, monoarylphosphono group (—PO ₃ H (aryl)) and its conjugate base group, phosphonooxy group (—OPO ₃ H ₂ ) And its conjugate base group, dialkylphosphonooxy group (—OPO ₃ (alkyl) ₂ ), diarylphosphonooxy group (—OPO ₃ (aryl) ₂ ), alkylarylphosphonooxy group (—OPO ₃ (alkyl) ( aryl)), monoalkylphosphonooxy group (—OPO ₃ H (alkyl)) and its conjugate base group, monoarylphosphonooxy group (—OPO ₃ H (aryl)) and its conjugate base group, cyano group, nitro group, group, ₍₂ -B (alkyl)) dialkyl boryl group, Jiariruboriru group (-B (aryl) _2), alkyl aryl boryl -B (alkyl) (aryl)) , dihydroxy boryl group (-B (OH) ₂₎ and its conjugated base group, an alkyl hydroxy boryl group (-B (alkyl) (OH) ) and its conjugated base group, an aryl hydroxy boryl And the group (—B (aryl) (OH)) and its conjugate base group, aryl group, alkenyl group and alkynyl group.

  Although the lithographic printing plate precursor according to the invention depends on the design of the photosensitive layer, a substituent having a hydrogen atom capable of hydrogen bonding, particularly a substituent having an acid dissociation constant (pKa) smaller than that of a carboxylic acid, , Because it tends to lower the printing durability. On the other hand, hydrophobic substituents such as halogen atoms, hydrocarbon groups (alkyl groups, aryl groups, alkenyl groups, alkynyl groups), alkoxy groups, aryloxy groups and the like are more preferable because they tend to improve printing durability. When the cyclic structure is a monocyclic aliphatic hydrocarbon having 6 or less members such as cyclopentane or cyclohexane, it preferably has such a hydrophobic substituent. If possible, these substituents may be bonded to each other or with a substituted hydrocarbon group to form a ring, and the substituent may be further substituted.

R ³ in the case where A in formula (i) is NR ³ — represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 10 carbon atoms. Examples of the monovalent hydrocarbon group having 1 to 10 carbon atoms represented by R ³ include an alkyl group, an aryl group, an alkenyl group, and an alkynyl group.
Specific examples of the alkyl group include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, isopropyl group, isobutyl group, sec-butyl group, 1 carbon number such as tert-butyl group, isopentyl group, neopentyl group, 1-methylbutyl group, isohexyl group, 2-ethylhexyl group, 2-methylhexyl group, cyclopentyl group, cyclohexyl group, 1-adamantyl group, 2-norbornyl group Up to 10 linear, branched or cyclic alkyl groups.
Specific examples of the aryl group include carbon having one heteroatom selected from the group consisting of an aryl group having 1 to 10 carbon atoms such as a phenyl group, a naphthyl group, and an indenyl group, a nitrogen atom, an oxygen atom, and a sulfur atom. Examples include heteroaryl groups of 1 to 10, such as furyl, thienyl, pyrrolyl, pyridyl, and quinolyl groups.
Specific examples of the alkenyl group include those having 1 to 10 carbon atoms such as vinyl group, 1-propenyl group, 1-butenyl group, 1-methyl-1-propenyl group, 1-cyclopentenyl group, 1-cyclohexenyl group and the like. A linear, branched, or cyclic alkenyl group is mentioned.
Specific examples of the alkynyl group include alkynyl groups having 1 to 10 carbon atoms such as ethynyl group, 1-propynyl group, 1-butynyl group, and 1-octynyl group. The substituent that R ³ may have is the same as those exemplified as the substituent that R ² can introduce. However, the carbon number of R < ³ > is 1-10 including the carbon number of a substituent.
A in the general formula (i) is preferably an oxygen atom or —NH— because synthesis is easy.

  N in the general formula (i) represents an integer of 1 to 5, and is preferably 1 in terms of printing durability.

  Although the preferable specific example of the repeating unit represented by general formula (i) below is shown, this invention is not limited to these.

  One type of repeating unit represented by the general formula (i) may be contained in the binder polymer, or two or more types may be contained. The specific binder polymer in the present invention may be a polymer composed only of the repeating unit represented by the general formula (i), but is usually used as a copolymer in combination with other copolymerization components. The total content of the repeating unit represented by the general formula (i) in the copolymer is appropriately determined depending on the structure, the design of the composition, etc., but preferably 1 to 99 mol% with respect to the total molar amount of the polymer component. More preferably, it is contained in the range of 5 to 40 mol%, more preferably 5 to 20 mol%.

  As a copolymerization component in the case of using as a copolymer, a conventionally well-known thing can be used without a restriction | limiting, if it is a monomer which can be radically polymerized. Specific examples include monomers described in “Polymer Data Handbook—Basic Edition” (Edition of Polymer Society, Bafukan, 1986). One type of such copolymerization component may be used, or two or more types may be used in combination.

  The molecular weight of the specific binder polymer in the present invention is appropriately determined from the viewpoint of image formability and printing durability. Usually, when the molecular weight increases, the printing durability is excellent, but the image formability tends to deteriorate. On the other hand, if it is low, the image forming property is improved, but the printing durability is lowered. The molecular weight is preferably in the range of 2,000 to 1,000,000, more preferably 5,000 to 500,000, and still more preferably 10,000 to 200,000.

  The binder polymer used in the present invention may be a specific binder polymer alone, or may be used as a mixture by combining one or more other binder polymers. The binder polymer used in combination is used in the range of 1 to 60% by mass, preferably 1 to 40% by mass, and more preferably 1 to 20% by mass with respect to the total mass of the binder polymer component. As the binder polymer that can be used in combination, a conventionally known binder polymer can be used without limitation, and specifically, an acrylic main chain binder, a urethane binder, or the like often used in the industry is preferably used.

Although the total amount of the specific binder polymer in the composition and the binder polymer that may be used in combination can be determined as appropriate, it is usually 10 to 90% by mass, preferably, based on the total mass of nonvolatile components in the composition. It is 20-80 mass%, More preferably, it is the range of 30-70 mass%.
Moreover, as an acid value (meg / g) of such a binder polymer, it is preferable that it is the range of 2.00-3.60.

(Other binder polymers that can be used in combination)
The other binder polymer that can be used in combination with the specific binder polymer is preferably a binder polymer having a radical polymerizable group. The radical polymerizable group is not particularly limited as long as it can be polymerized by radicals, but α-substituted methylacrylic group [—OC (═O) —C (—CH ₂ Z) ═CH ₂ , Z = A hydrocarbon group starting from a hetero atom], an acryl group, a methacryl group, an allyl group, and a styryl group. Among these, an acryl group and a methacryl group are preferable.
The content of the radical polymerizable group in the binder polymer (content of unsaturated double bond capable of radical polymerization by iodine titration) is preferably 0.1 to 1 g per binder polymer from the viewpoint of sensitivity and storage stability. It is 10.0 mmol, More preferably, it is 1.0-7.0 mmol, Most preferably, it is 2.0-5.5 mmol.

  Further, the other binder polymer that can be used in combination is preferably one having an alkali-soluble group. The content of alkali-soluble groups in the binder polymer (acid value by neutralization titration) is preferably from 0.1 to 3.0 mmol, more preferably from 1 to 3.0 g of binder polymer, from the viewpoints of precipitation of developing residue and printing durability. Is 0.2 to 2.0 mmol, most preferably 0.45 to 1.0 mmol.

  The mass average molecular weight of such a binder polymer is preferably from 2,000 to 1,000,000, more preferably from 10,000 to 300, from the viewpoints of film properties (press life) and solubility in a coating solvent. In the range of 20,000 to 200,000.

Further, the glass transition point (Tg) of such a binder polymer is preferably 70 to 300 ° C., more preferably 80 to 250 ° C., and most preferably 90 to 90 ° C. from the viewpoints of storage stability, printing durability, and sensitivity. It is in the range of 200 ° C.
As a means for increasing the glass transition point of the binder polymer, the molecule preferably contains an amide group or an imide group, and particularly preferably contains a methacrylamide methacrylamide derivative.

  In addition to the above basic components, the photosensitive layer of the lithographic printing plate precursor according to the invention may further contain other components suitable for its use and production method. Hereinafter, preferred additives will be exemplified.

[Polymerization inhibitor]
In the photosensitive layer of the lithographic printing plate precursor according to the invention, a compound having a polymerizable ethylenically unsaturated double bond, that is, a small amount of a thermal polymerization inhibitor is added in order to prevent unnecessary thermal polymerization of the polymerizable compound. It is desirable to do. Suitable thermal polymerization inhibitors include hydroquinone, p-methoxyphenol, di-t-butyl-p-cresol, pyrogallol, t-butylcatechol, benzoquinone, 4,4'-thiobis (3-methyl-6-t-butylphenol ), 2,2′-methylenebis (4-methyl-6-tert-butylphenol), N-nitrosophenylhydroxyamine primary cerium salt and the like. The addition amount of the thermal polymerization inhibitor is preferably about 0.01% by mass to about 5% by mass with respect to the mass of the nonvolatile components in the entire composition. If necessary, a higher fatty acid derivative such as behenic acid or behenic acid amide or the like may be added to prevent polymerization inhibition by oxygen and may be unevenly distributed on the surface of the layer in the course of drying after coating. The addition amount of the higher fatty acid derivative is preferably about 0.5% by mass to about 10% by mass with respect to the nonvolatile components in the entire composition.

[Colorant]
Further, a dye or pigment may be added to the photosensitive layer of the lithographic printing plate precursor according to the invention for the purpose of coloring. As a result, it is possible to improve so-called plate inspection properties such as visibility after plate making as a printing plate and suitability for an image density measuring machine. As the colorant, many dyes cause a decrease in the sensitivity of the photopolymerization type photosensitive layer. Therefore, it is particularly preferable to use a pigment as the colorant. Specific examples include pigments such as phthalocyanine pigments, azo pigments, carbon black and titanium oxide, and dyes such as ethyl violet, crystal violet, azo dyes, anthraquinone dyes, and cyanine dyes. The addition amount of the dye and the pigment as the colorant is preferably about 0.5% by mass to about 5% by mass with respect to the non-volatile components in the entire composition.

[Other additives]
Furthermore, you may add well-known additives, such as an inorganic filler for improving the physical property of a cured film, other plasticizers, and a fat-sensitizing agent which can improve the ink deposition property of the photosensitive layer surface. Examples of plasticizers include dioctyl phthalate, didodecyl phthalate, triethylene glycol dicaprylate, dimethyl glycol phthalate, tricresyl phosphate, dioctyl adipate, dibutyl sebacate, triacetyl glycerin, and addition polymerization with binder polymer. Generally, it can be added in a range of 10% by mass or less based on the total mass with the compound. In addition, in the lithographic printing plate precursor described later, in order to enhance the effect of heating and exposure after development for the purpose of improving the film strength (printing durability) described later, a UV initiator, a thermal crosslinking agent, etc. are added. Can also be done.

<Preparation of lithographic printing plate precursor>
The lithographic printing plate precursor according to the invention can be produced by coating a photosensitive layer coating solution containing the above-described components on a suitable support or intermediate layer. In the lithographic printing plate precursor according to the invention, a protective layer may be provided on the photosensitive layer as necessary.

  Solvents used for coating the photosensitive layer in the present invention include acetone, methyl ethyl ketone, cyclohexane, ethyl acetate, ethylene dichloride, tetrahydrofuran, toluene, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol dimethyl ether, propylene Glycol monomethyl ether, propylene glycol monoethyl ether, acetylacetone, cyclohexanone, diacetone alcohol, ethylene glycol monomethyl ether acetate, ethylene glycol ethyl ether acetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether acetate, 3-methoxypropanol, methoxymethoxyethanol , Diethylene Recall monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, 3-methoxypropyl acetate, N, N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, lactic acid Examples include methyl and ethyl lactate. These solvents can be used alone or in combination. The solid content in the coating solution is suitably 2 to 50% by mass.

The coating amount of the photosensitive layer mainly affects the sensitivity of the photosensitive layer, the developability, and the strength and printing durability of the exposed film, and is preferably selected as appropriate according to the application. When the coating amount is too small, the printing durability is not sufficient. On the other hand, if the amount is too large, the sensitivity is lowered, it takes time for exposure, and a longer time is required for development processing, which is not preferable. For the lithographic printing plate precursor for scanning exposure which is the main object of the present invention, the coating amount is suitably in the range of about 0.1 g / m ² to about 10 g / m ² in terms of the mass after drying. More preferably from 0.5 to 5 g / m ^2.

(Physical properties of photosensitive layer)
The physical properties of the photosensitive layer of the lithographic printing plate precursor applied to the present invention are as follows: the development speed of the unexposed area with respect to an alkaline developer having a pH of 10 to 13.5 is 80 nm / sec or more and the exposure of the alkaline developer. The penetration rate in the part is preferably 100 nF / sec or less.
Here, the development speed with an alkaline developer having a pH of 10 to 13.5 is a value obtained by dividing the film thickness (m) of the photosensitive layer by the time (sec) required for development, Is a value indicating the rate of change in capacitance (F) when the photosensitive layer is formed on a conductive support and immersed in a developer.
Hereinafter, a method for measuring “development speed with respect to an alkali developer” and “penetration speed of an alkali developer” in the present invention will be described in detail.

[Measurement of development speed for alkaline developer]
Here, the developing speed of the photosensitive layer with respect to the alkaline developer is a value obtained by dividing the film thickness (m) of the photosensitive layer by the time (sec) required for development.
As a method for measuring the developing speed in the present invention, as shown in FIG. 1, a constant alkali developer (30 ° C.) having an unexposed photosensitive layer on an aluminum support and having a pH in the range of 10 to 13.5. It was immersed in and the dissolution behavior of the photosensitive layer was investigated with a DRM interference wave measuring device. FIG. 1 shows a schematic diagram of a DRM interference wave measuring apparatus for measuring the dissolution behavior of a photosensitive layer. In the present invention, a change in film thickness was detected by interference using light of 640 nm. When the development behavior is non-swelling development from the surface of the photosensitive layer, the film thickness gradually decreases with respect to the development time, and an interference wave corresponding to the thickness can be obtained. Further, in the case of swelling dissolution (film removal dissolution), the film thickness changes due to the penetration of the developer, so that a clean interference wave cannot be obtained.

The measurement is continued under these conditions, and the developing speed is expressed by the following equation from the time (s) until the photosensitive layer is completely removed and the film thickness becomes 0 (development completion time) and the film thickness (μm) of the photosensitive layer. It can ask for. It is determined that the higher the development speed, the easier the film is removed by the developer and the better the developability.
Development speed (of unexposed area) = [photosensitive layer thickness (μm) / recording completion time (sec)]

[Measurement of penetration rate of alkaline developer]
The permeation rate of the alkaline developer is a value indicating the rate of change of the capacitance (F) when the photosensitive layer is formed on a conductive support and immersed in the developer.
As shown in FIG. 2, a method for measuring the capacitance, which is a measure of permeability in the present invention, is a predetermined method on an aluminum support in a constant alkaline developer (28 ° C.) in the range of pH 10 to 13.5. There is a method in which the exposure is carried out at the exposure amount, the one provided with the cured photosensitive layer is immersed as one electrode, a lead wire is connected to the aluminum support, and a voltage is applied to the other using a normal electrode. After the voltage is applied, the developer permeates the interface between the support and the photosensitive layer as the immersion time elapses, and the capacitance changes.

From the time (s) required for the capacitance to change and the film thickness (μm) of the photosensitive layer, it can be obtained by the following equation. It is determined that the smaller the permeation rate, the lower the permeability of the developer.
Developer penetration rate (of exposed area) =
[Photosensitive layer thickness (μm) / Time required for capacitance change to be constant (s)]

As a preferable physical property of the photosensitive layer of the lithographic printing plate precursor to be applied to the present invention, the development rate of the unexposed portion with an alkaline developer having a pH of 10 to 13.5 by the above measurement is preferably 80 to 400 nm / sec. The permeation rate of the same alkaline developer into the photosensitive layer is preferably 90 nF / sec or less. Further, the development rate of the unexposed area with an alkaline developer having a pH of 10 to 13.5 as measured above is more preferably 90 to 200 nm / sec, and the penetration rate of the same alkaline developer into the photosensitive layer is 80 nF / sec or less. It is preferable that The upper limit of the development speed or the lower limit of the permeation speed is not particularly limited, but considering the balance between the two, the development speed of the unexposed area is more preferably in the range of 90 to 200 nm / sec. The permeation rate of the alkali developer into the photosensitive layer is preferably 80 nF / sec or less.
Control of the development speed of the unexposed area of the photosensitive layer and the penetration speed of the alkaline developer into the photosensitive layer after curing can be performed by conventional methods, but as a typical example, the development speed of the unexposed area is improved. In addition, addition of a hydrophilic compound is useful, and means for adding a hydrophobic compound is useful for suppressing penetration of the developer into the exposed area.
By using the above-mentioned specific binder polymer, the developing speed of the photosensitive layer and the permeation speed of the developer can be easily adjusted to the above preferred ranges.

[Support]
As the support for the lithographic printing plate precursor in the invention, a conventionally known hydrophilic support for use in the lithographic printing plate precursor can be used without limitation.
The support used is preferably a dimensionally stable plate, for example, paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc). , Copper, etc.), plastic films (eg, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), Paper or plastic film, etc. on which such metals are laminated or vapor-deposited are included. Appropriately known physical and chemical treatments are applied to these surfaces for the purpose of imparting hydrophilicity and improving strength as necessary. You may give it.

  In particular, preferred supports include paper, polyester film or aluminum plate, among which dimensional stability is good, relatively inexpensive, and a surface with excellent hydrophilicity and strength is provided by surface treatment as required. An aluminum plate that can be formed is more preferable. A composite sheet in which an aluminum sheet is bonded on a polyethylene terephthalate film as described in Japanese Patent Publication No. 48-18327 is also preferable.

An aluminum plate is a metal plate mainly composed of dimensionally stable aluminum. In addition to a pure aluminum plate, an alloy plate containing aluminum as a main component and containing a trace amount of foreign elements, or aluminum (alloy) is laminated. Or it is chosen from the vapor-deposited plastic film or paper. In the following description, the above-mentioned support made of aluminum or an aluminum alloy is generically used as an aluminum support. Examples of the foreign element 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 10% by mass or less. In the present invention, a pure aluminum plate is suitable. However, since pure aluminum is difficult to manufacture in terms of refining technology, it may contain slightly different elements. Thus, the composition of the aluminum plate applied to the present invention is not specified, and it is a conventionally known material such as JIS A 1050, JIS A 1100, JIS A 3103, JIS A 3005, etc. Can be used as appropriate.
Moreover, the thickness of the aluminum support body used for this invention is about 0.1 mm-about 0.6 mm. This thickness can be appropriately changed depending on the size of the printing press, the size of the printing plate, and the user's desire. The aluminum support may be subjected to a support surface treatment described later as necessary. Of course, it may not be applied.

(Roughening treatment)
Examples of the roughening treatment method include mechanical roughening, chemical etching, and electrolytic grain as disclosed in JP-A-56-28893. Furthermore, the electrochemical surface roughening method in which the surface is electrochemically roughened in hydrochloric acid or nitric acid electrolyte solution, the aluminum surface is scratched with a metal wire, the wire brush grain method, the surface of the aluminum is polished with a polishing ball and an abrasive. A mechanical graining method such as a pole grain method, a brush grain method in which the surface is roughened with a nylon brush and an abrasive, can be used, and the above roughening methods can be used alone or in combination. Among them, a method usefully used for roughening is an electrochemical method in which roughening is performed chemically in hydrochloric acid or nitric acid electrolyte, and a suitable amount of electricity at the time of anode is 50 C / dm ^{2 to} 400 C / dm ² . It is a range. More specifically, in the electrolytic solution containing from 0.1 to 50% hydrochloric acid or nitric acid, the temperature 20 to 80 ° C., for 1 second to 30 minutes, alternating at a current density of 100C / dm ² ~400C / dm ² It is preferable to perform direct current electrolysis.

  The roughened aluminum support may be chemically etched with acid or alkali. Etching agents suitably used are caustic soda, sodium carbonate, sodium aluminate, sodium metasilicate, sodium phosphate, potassium hydroxide, lithium hydroxide, and the like. Preferred ranges of concentration and temperature are 1 to 50% and 20%, respectively. ~ 100 ° C. Pickling is performed to remove dirt (smut) remaining on the surface after etching. As the acid used, nitric acid, sulfuric acid, phosphoric acid, chromic acid, hydrofluoric acid, borohydrofluoric acid and the like are used. In particular, as a method for removing smut after the electrochemical surface roughening treatment, contact with 15 to 65 mass% sulfuric acid at a temperature of 50 to 90 ° C. as described in JP-A-53-12739 is preferable. And the alkali etching method described in Japanese Patent Publication No. 48-28123. After the treatment as described above, the method condition is not particularly limited as long as the center line average roughness Ra of the treatment surface is 0.2 to 0.5 μm.

(Anodizing treatment)
The aluminum support that has been treated as described above to form an oxide layer is then anodized.
In the anodizing treatment, sulfuric acid, phosphoric acid, oxalic acid, or an aqueous solution of boric acid / sodium borate is used alone or in combination as a main component of the electrolytic bath. In this case, the electrolyte solution may of course contain at least components normally contained in at least an Al alloy plate, an electrode, tap water, groundwater and the like. Further, the second and third components may be added. Here, the second and third components are, for example, metal ions such as Na, K, Mg, Li, Ca, Ti, Al, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn, and ammonium ions. Examples include cations, nitrate ions, carbonate ions, chloride ions, phosphate ions, fluorine ions, sulfite ions, titanate ions, silicate ions, borate ions and the like, and the concentration is 0 to 10,000 ppm. May be included. There are no particular limitations on the conditions of the anodizing treatment, but the treatment is preferably carried out by direct current or alternating current electrolysis at a current density of 0.1 to 40 A / m ² at 30 to 500 g / liter, a treatment liquid temperature of 10 to 70 ° C. . The thickness of the formed anodic oxide film is in the range of 0.5 to 1.5 μm. Preferably it is the range of 0.5-1.0 micrometer. The support prepared by the above treatment is treated so that the pore diameter of the micropores existing in the anodized film is in the range of 5 to 10 nm and the pore density is in the range of 8 × 10 ¹⁵ to 2 × 10 ¹⁶ pieces / m ^2. It is preferred that the conditions are selected.

A widely known method can be applied as the hydrophilic treatment on the surface of the support. As a particularly preferable treatment, a hydrophilic treatment with silicate or polyvinylphosphonic acid is performed. A film | membrane is formed by 2-40 mg / m < ² > as Si or P element amount, More preferably, it is 4-30 mg / m < ² >. The coating amount can be measured by fluorescent X-ray analysis.

  The hydrophilization treatment is carried out by applying an anodized film to an aqueous solution containing 1 to 30% by mass, preferably 2 to 15% by mass of alkali metal silicate or polyvinylphosphonic acid, and having a pH of 10 to 13 at 25 ° C. This is carried out by immersing the aluminum support on which is formed, for example, at 15 to 80 ° C. for 0.5 to 120 seconds.

  As the alkali metal silicate used for the hydrophilization treatment, sodium silicate, potassium silicate, lithium silicate, or the like is used. Examples of the hydroxide used for increasing the pH of the aqueous alkali metal silicate solution include sodium hydroxide, potassium hydroxide, and lithium hydroxide. In addition, you may mix | blend alkaline-earth metal salt or Group IVB metal salt with said process liquid. Alkaline earth metal salts include nitrates such as calcium nitrate, strontium nitrate, magnesium nitrate, and barium nitrate, and water-soluble substances such as sulfate, hydrochloride, phosphate, acetate, oxalate, and borate. Salt. Group IVB metal salts include titanium tetrachloride, titanium trichloride, potassium fluoride titanium, potassium oxalate, titanium sulfate, titanium tetraiodide, zirconium chloride, zirconium dioxide, zirconium oxychloride, zirconium tetrachloride, etc. Can be mentioned.

  Alkaline earth metal salts or Group IVB metal salts can be used alone or in combination of two or more. A preferable range of these metal salts is 0.01 to 10% by mass, and a more preferable range is 0.05 to 5.0% by mass. Silicate electrodeposition as described in US Pat. No. 3,658,662 is also effective. Surface obtained by combining a support with electrolytic grains as disclosed in JP-B-46-27481, JP-A-52-58602, JP-A-52-30503, and the above anodizing treatment and hydrophilization treatment Processing is also useful.

[Intermediate layer (undercoat layer)]
In the lithographic printing plate precursor according to the invention, an intermediate layer (undercoat layer) may be provided for the purpose of improving the adhesion and stain resistance between the photosensitive layer and the support. Specific examples of such an intermediate layer include JP-B-50-7481, JP-A-54-72104, JP-A-59-101651, JP-A-60-149491, JP-A-60-232998, JP-A-3-56177, JP-A-4-282737, JP-A-5-16558, JP-A-5-246171, JP-A-7-159983, JP-A-7-314937, JP-A-8-202025, Special Kaihei 8-320551, JP 9-34104, JP 9-236911, JP 9-269593, JP 10-69092, JP 10-115931, JP 10-161317, JP 10-260536, JP-A-10-282682, JP-A-11-84684, Japanese Patent Application No. 8-225335, Japanese Patent Application No. 8-270098, Japanese Patent Application No. 9-195863, Japanese Patent Application No. 9-195864, Japanese Patent Application No. 9-89646, Japanese Patent Application No. 9-106068, Japanese Patent Application No. 9-183834, Japanese Patent Application No. 9-264411, Japanese Patent Application No. 9 -127232, Japanese Patent Application No. 9-245419, Japanese Patent Application No. 10-127602, Japanese Patent Application No. 10-170202, Japanese Patent Application No. 11-36377, Japanese Patent Application No. 11-165661, Japanese Patent Application No. 11-284091 No., Japanese Patent Application No. 2000-14697, and the like.

[Protective layer]
Since the photosensitive layer of the lithographic printing plate precursor according to the invention is a thermopolymerizable negative photosensitive layer as described above, a protective layer (overcoat) is further formed on the photosensitive layer in order to perform exposure in the air. It is preferable to provide a layer). The protective layer is basically provided to protect the photosensitive layer. However, when the photosensitive layer has a radical polymerizable image forming mechanism as in the present invention, it has a role as an oxygen blocking layer and has a high illuminance. When exposed with an infrared laser, it functions as an ablation preventing layer.
In addition to the properties desired for the protective layer, in addition to the above, the transmission of light used for exposure is not substantially inhibited, it has excellent adhesion to the photosensitive layer, and can be easily removed in the development process after exposure. Is desirable. Such a protective layer has been conventionally devised and described in detail in US Pat. No. 3,458,311 and Japanese Patent Publication No. 55-49729.

  As a material that can be used for the protective layer, for example, a water-soluble polymer compound having relatively excellent crystallinity is preferably used. Specifically, polyvinyl alcohol, vinyl alcohol / vinyl phthalate copolymer, vinyl acetate / Examples include water-soluble polymers such as vinyl alcohol / vinyl phthalate copolymer, vinyl acetate / crotonic acid copolymer, polyvinyl pyrrolidone, acidic celluloses, gelatin, gum arabic, polyacrylic acid, polyacrylamide, etc. They can be used alone or in combination. Of these, the use of polyvinyl alcohol as the main component gives the best results in terms of basic properties such as oxygen barrier properties and development removability.

The polyvinyl alcohol used for the protective layer may be partially substituted with an ester, an ether, and an acetal as long as it contains an unsubstituted vinyl alcohol unit for having necessary oxygen barrier properties and water solubility. Similarly, some of them may have other copolymer components. In particular, a compound obtained by substituting polyvinyl pyrrolidone in a range of 15 to 50% by mass with respect to polyvinyl alcohol is preferable in terms of storage stability.
Specific examples of polyvinyl alcohol include those having a hydrolysis rate of 71 to 100% and a polymerization repeating unit in the range of 300 to 2400. Specifically, Kuraray Co., Ltd. PVA-105, PVA-110, PVA-117, PVA-117H, PVA-120, PVA-124, PVA-124H, PVA-CS, PVA-CST, PVA-HC, PVA-203, PVA-204, PVA-205, PVA-210, PVA-217, PVA-220, PVA-224, PVA-217EE, PVA-217E, PVA-220E, PVA-224E, PVA-405, PVA- 420, PVA-613, L-8 and the like.

Components of the protective layer (selection of PVA, use of additives), coating amount, and the like are selected in consideration of fogging, adhesion, and scratch resistance in addition to oxygen barrier properties and development removability. In general, the higher the hydrolysis rate of the PVA used (the higher the content of unsubstituted vinyl alcohol units in the oxygen barrier layer), the thicker the film thickness, the higher the oxygen barrier property, which is advantageous in terms of sensitivity. is there. However, when the oxygen barrier property is extremely increased, there arises a problem that unnecessary polymerization reaction occurs during production and raw storage, and unnecessary fogging and image line thickening occur during image exposure.
Accordingly, the oxygen permeability A at 25 ° C. and 1 atm is preferably 0.2 ≦ A ≦ 20 (cc / m ² · day).
The molecular weight of the (co) polymer such as polyvinyl alcohol (PVA) can be in the range of 2000 to 10 million, preferably in the range of 20,000 to 3 million.

As another composition of the protective layer, glycerin, dipropylene glycol and the like can be added in an amount corresponding to several mass% with respect to the (co) polymer to provide flexibility. Anionic surfactants such as sodium acid salts; amphoteric surfactants such as alkylaminocarboxylates and alkylaminodicarboxylates; nonionic surfactants such as polyoxyethylene alkylphenyl ethers to the (co) polymer Mass% can be added.
The thickness of the protective layer is suitably from 0.5 to 5 μm, particularly preferably from 0.5 to 2 μm.

  In addition, adhesion to the image area and scratch resistance are also extremely important in handling the plate. That is, when a hydrophilic layer made of a water-soluble polymer is laminated on a new oil-based polymer layer, film peeling due to insufficient adhesion tends to occur, and the peeled part causes defects such as poor film hardening due to inhibition of oxygen polymerization. On the other hand, various proposals have been made to improve the adhesion between these two layers. For example, U.S. Patent Application No. 292,501 and U.S. Patent Application No. 44,563 disclose an acrylic emulsion or a water-insoluble vinylpyrrolidone-vinyl acetate copolymer in a hydrophilic polymer mainly composed of polyvinyl alcohol. It is described that sufficient adhesiveness can be obtained by mixing 20 to 60% by mass and the like and laminating on a polymerization layer. Any of these known techniques can be applied to the protective layer in the present invention. Such a coating method of the protective layer is described in detail in, for example, US Pat. No. 3,458,311 and JP-B-55-49729.

In order to make a lithographic printing plate precursor to be applied to the present invention, at least exposure and development processes are performed.
As a light source for exposing the lithographic printing plate precursor to be applied to the present invention, an infrared laser is preferable, and thermal recording by an ultraviolet lamp or a thermal head is also possible.
In particular, in the present invention, image exposure is preferably performed by a solid-state laser and a semiconductor laser that emit infrared rays having a wavelength of 750 nm to 1400 nm. The laser output is preferably 100 mW or more, and a multi-beam laser device is preferably used in order to shorten the exposure time. The exposure time per pixel is preferably within 20 μsec. The energy applied to the planographic printing plate precursor is preferably 10 to 300 mJ / cm ² . If the exposure energy is too low, the photosensitive layer is not sufficiently cured. If the exposure energy is too high, the photosensitive layer may be laser ablated and the image may be damaged.

  The exposure in the present invention can be performed by overlapping the light beams of the light sources. Overlap means that the sub-scanning pitch width is smaller than the beam diameter. The overlap can be expressed quantitatively by FWHM / sub-scanning pitch width (overlap coefficient), for example, when the beam diameter is expressed by the half width (FWHM) of the beam intensity. In the present invention, the overlap coefficient is preferably 0.1 or more.

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

In the present invention, the development treatment may be performed immediately after exposure, but the heat treatment may be performed between the exposure step and the development step. The heat treatment condition is preferably 5 seconds to 5 minutes in the temperature range of 60 to 150 ° C.
The heat treatment can be appropriately selected from conventionally known various methods. Specific examples include a method of heating the lithographic printing plate precursor while being in contact with a panel heater or a ceramic heater, a non-contact heating method using a lamp or hot air, and the like. By performing the heat treatment, it is possible to reduce the amount of laser energy required for image recording of the laser to be irradiated.

  Moreover, when the lithographic printing plate precursor according to the invention is in an embodiment having a protective layer, pre-water washing for removing the protective layer may be performed before the development step. The pre-water washing is performed, for example, by a method in which water is discharged from the spray pipe onto the surface of the protective layer of the planographic printing plate precursor, and the protective layer is wetted and then removed by a brush roller. For the pre-water washing, for example, tap water is used. Further, when the developing process is performed by an automatic developing machine, a pre-water washing process may be performed in the automatic developing machine.

  The lithographic printing plate precursor according to the invention is developed as it is after being exposed, or after being subjected to a heating step or a pre-water washing step. As the developer used in such development processing, an alkaline aqueous solution having a pH of 14 or less is particularly preferred, and an alkaline aqueous solution having a pH of 8 to 12 containing an anionic surfactant is more preferably used. For example, tribasic sodium phosphate, potassium, ammonium, dibasic sodium phosphate, potassium, ammonium, sodium carbonate, potassium, ammonium, sodium bicarbonate, potassium, ammonium, sodium borate, Examples include inorganic alkaline agents such as potassium, ammonium, sodium hydroxide, ammonium, potassium and lithium. Moreover, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, n-butylamine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, Organic alkali agents such as ethyleneimine, ethylenediamine, and pyridine are also used. These alkali agents are used alone or in combination of two or more.

Moreover, in the development processing of the lithographic printing plate precursor applied to the present invention, 1 to 20% by mass of an anionic surfactant is added to the developer, but more preferably 3 to 10% by mass. If the amount is too small, the developability deteriorates. If the amount is too large, the strength such as the abrasion resistance of the image deteriorates. Anionic surfactants include, for example, sodium salt of lauryl alcohol sulfate, ammonium salt of lauryl alcohol sulfate, sodium salt of octyl alcohol sulfate, such as sodium salt of isopropyl naphthalene sulfonic acid, sodium salt of isobutyl naphthalene sulfonic acid, polyoxy Higher carbon number such as sodium salt of ethylene glycol mononaphthyl ether sulfate ester, sodium salt of dodecylbenzene sulfonic acid, alkylaryl sulfonate such as sodium salt of metanitrobenzene sulfonic acid, secondary sodium alkyl sulfate, etc. Aliphatic alcohol phosphates such as alcohol sulfates, sodium salts of cetyl alcohol phosphates, eg C _{17 H 33 CON (CH 3)} CH 2 CH 2 SO 3 sulfonates of alkylamides such as Na, for example, sodium sulfosuccinate dioctyl ester, sulfonate of dibasic aliphatic esters such as sodium sulfosuccinate dihexyl ester Salts are included.

  Moreover, you may add the organic solvent which mixes with water, such as benzyl alcohol, to a developing solution as needed. As the organic solvent, those having a solubility in water of about 10% by mass or less are suitable, and preferably selected from those having 5% by mass or less. For example, 1-phenylethanol, 2-phenylethanol, 3-phenylpropanol, 1,4-phenylbutanol, 2,2-phenylbutanol, 1,2-phenoxyethanol, 2-benzyloxyethanol, o-methoxybenzyl alcohol, m -Methoxybenzyl alcohol, p-methoxybenzyl alcohol, benzyl alcohol, cyclohexanol, 2-methylcyclohexanol, 4-methylcyclohexanol, 3-methylcyclohexanol and the like can be mentioned. The content of the organic solvent is preferably 1 to 5% by mass with respect to the total mass of the developer at the time of use. The amount used is closely related to the amount of surfactant used, and it is preferable to increase the amount of anionic surfactant as the amount of organic solvent increases. This is because when the amount of the organic solvent is large and the amount of the anionic surfactant is small, the organic solvent is not dissolved, so that it is impossible to expect good developability.

Furthermore, additives such as an antifoaming agent and a hard water softening agent can be further contained as necessary. Examples of the hard water softener include Na ₂ P ₂ O ₇ , Na ₅ P ₃ O ₃ , Na ₃ P ₃ O ₉ , Na ₂ O ₄ P (NaO ₃ P) PO ₃ Na ₂ , Calgon (sodium polymetaphosphate) Such as polyphosphates, aminopolycarboxylic acids (eg, ethylenediaminetetraacetic acid, its potassium salt, its sodium salt; diethylenetriaminepentaacetic acid, its potassium salt, its sodium salt; triethylenetetraminehexaacetic acid, its potassium salt, its sodium salt Hydroxyethylethylenediaminetriacetic acid, its potassium salt, its sodium salt; nitrilotriacetic acid, its potassium salt, its sodium salt; 1,2-diaminocyclohexanetetraacetic acid, its potassium salt, its sodium salt; 1,3-diamino-2 -Propanol tetraacetic acid, its potassium salt, Sodium salt), other polycarboxylic acids (eg 2-phosphonobutanetricarboxylic acid-1,2,4, potassium salt thereof, sodium salt thereof; 2-phosphonobutanone tricarboxylic acid-2,3,4, Potassium salt, sodium salt thereof, etc., organic phosphonic acids (eg, 1-phosphonoethanetricarboxylic acid-1,2,2, potassium salt, sodium salt thereof; 1-hydroxyethane-1,1-diphosphonic acid, Potassium salt, sodium salt thereof; aminotri (methylenephosphonic acid), potassium salt thereof, sodium salt thereof and the like. The optimum amount of such a hard water softener varies depending on the hardness of the hard water used and the amount used, but is generally 0.01 to 5% by weight, more preferably in the developer at the time of use. It is made to contain in 0.01-0.5 mass%.

Furthermore, when developing a lithographic printing plate precursor using an automatic processor, the developer becomes fatigued according to the amount of processing, so that the processing capacity can be restored using a replenisher or fresh developer. Also good. In this case, it is preferable to replenish by the method described in US Pat. No. 4,882,246. This replenishment method is also preferably applied in the present invention. Also when performing this replenishment, adjustment of the plate-making process of the (D) process in the quality control method of this invention can be applied as needed.
Developers described in JP-A-50-26601, 58-54341, JP-B-56-39464, 56-42860, and 57-7427 are also preferable.

  The lithographic printing plate precursor thus developed is subjected to washing water, surface activity as described in JP-A Nos. 54-8002, 55-11545, 59-58431, and the like. It may be post-treated with a rinsing liquid containing an agent, a desensitizing liquid containing gum arabic, starch derivatives, and the like. These treatments can be used in various combinations for the post-treatment of the lithographic printing plate precursor applied to the present invention.

In plate making of a lithographic printing plate precursor to be applied to the present invention, it is effective to subject the image after development to full post heating or full exposure for the purpose of improving image strength and printing durability.
Very strong conditions can be used for heating after development. Usually, the heating temperature is 200 to 500 ° C. If the heating temperature after development is low, sufficient image strengthening action 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 planographic printing plate obtained by the above processing is loaded on an offset printing machine and used for printing a large number of sheets.
As plate cleaners used for removing stains on the plate during printing, conventionally known plate cleaners for PS plates are used. For example, CL-1, CL-2, CP, CN-4, CN, CG-1, PC-1, SR, IC (made by Fuji Photo Film Co., Ltd.), etc. are mentioned.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.
[Example 1]
[Create support]
<Aluminum plate>
The following surface treatment was performed using a JIS A 1050 aluminum plate having a thickness of 0.30 mm and a width of 1030 mm.

<Surface treatment>
The surface treatment was performed by continuously performing the following various treatments (a) to (j). In addition, after each process and water washing, the liquid was drained with the nip roller.

(A) Alkaline etching treatment The aluminum plate was subjected to an etching treatment by spraying using an aqueous solution having a caustic soda concentration of 2.6 mass%, an aluminum ion concentration of 6.5 mass%, and a temperature of 70 ° C., thereby dissolving the aluminum plate by 5 g / m ² . . Then, it washed with water.

(B) Desmutting treatment The desmutting treatment was performed by spraying with a 1% by weight aqueous solution of nitric acid at a temperature of 30 ° C. (containing 0.5% by weight of aluminum ions), and then washed with water.

(C) Electrochemical roughening treatment An electrochemical roughening treatment was carried out continuously using an alternating voltage of 60 Hz. The electrolytic solution at this time was a 1% by mass aqueous nitric acid solution (containing 0.5 wt% aluminum ions and 0.007 wt% ammonium ions) at a temperature of 30 ° C. The AC power source was subjected to an electrochemical surface roughening treatment using a carbon electrode as a counter electrode using a trapezoidal rectangular wave alternating current with a time TP of 2 msec until the current value reached a peak from zero and a duty ratio of 1: 1. Ferrite was used for the auxiliary anode. The current density was 25 A / dm ² at the peak current value, and the amount of electricity was 250 C / cm ² in terms of the total amount of electricity when the aluminum plate was the anode. 5% of the current flowing from the power source was shunted to the auxiliary anode. Then, it washed with water.

(D) Alkali etching treatment The aluminum plate was etched by spraying at 35 ° C. with a caustic soda concentration of 26 mass% and an aluminum ion concentration of 6.5 mass% to dissolve the aluminum plate by 0.2 g / m ² , The smut component mainly composed of aluminum hydroxide generated when electrochemical roughening was used, and the edge portion of the generated pit was dissolved to smooth the edge portion. Then, it washed with water.

(E) Desmutting treatment A desmutting treatment by spraying was performed with a 25 wt% sulfuric acid concentration aqueous solution (containing 0.5 wt% aluminum ions) at a temperature of 60 ° C., followed by washing with water by spraying.

(F) Anodizing treatment Anodizing treatment was performed for 50 seconds at a sulfuric acid concentration of 170 g / l (containing 0.5 mass% of aluminum ions), a temperature of 33 ° C., and a current density of 5 (A / dm ² ). Then, it washed with water. At this time, the weight of the anodized film was 2.7 g / m ² .

[Photosensitive layer]
Next, the following photosensitive layer coating solution [P-1] was prepared and applied to the above aluminum support using a wire bar. Drying was carried out at 122 ° C. for 27 seconds with a hot air drying apparatus to obtain a lithographic printing plate precursor. The coating amount after drying was in the range of 1.2 to 1.3 g / m ² .

<Photosensitive layer coating solution [P-1]>
・ Infrared absorber (IR-1) 0.074g
Compound that generates radicals (OS-12) 0.311 g
-Polymerizable compound (AM-1) 1.000 g
-Binder polymer (BT-1) 1.000 g
・ Additive (PM-1) 0.151g
・ Ethyl violet (C-1) 0.040g
・ Fluorine-based surfactant 0.015g
(Megafuck F-780-F Dainippon Ink and Chemicals,
Methyl isobutyl ketone (MIBK) 30% by mass solution)
・ Methyl ethyl ketone 10.4g
・ Methanol 4.83g
・ 10.4 g of 1-methoxy-2-propanol

In addition, the compound (OS-12) which generate | occur | produces a radical points out what is mentioned as a compound example of the onium salt represented by the above-mentioned general formula (I).
Infrared absorber (IR-1), polymerizable compound (AM-1), additive (PM-1), binder polymer (BT-1), and ethyl violet (C-1) used in the photosensitive layer coating solution The structure of is shown below.

[Protective layer (overcoat layer)]
A mixed aqueous solution of polyvinyl alcohol (saponification degree: 98 mol%, polymerization degree: 500) and polyvinylpyrrolidone (BASF Corp., Rubiscol K-30) is applied to the surface of the photosensitive layer using a wire bar. It dried at 125 degreeC for 75 second (s) with the wind-type drying apparatus. The content ratio of polyvinyl alcohol / polyvinyl pyrrolidone was 4/1% by mass, and the coating amount (the coating amount after drying) was 2.30 g / m ² .

(exposure)
The resulting negative lithographic printing plate precursor [P-1] (1030 mm × 800 mm × 0.3 mm thickness) is output at 40 W with an external drum rotation speed by a Trendsetter 3244VX manufactured by Creo equipped with a water-cooled 40 W infrared semiconductor laser. The exposure was performed under the conditions of 360 rpm, plate surface energy 100 mJ / cm ² , and resolution 2400 dpi. The exposure was performed under conditions of 25 ° C. and 50% RH.

(developing)
After the exposure, the protective layer was removed by washing with tap water.
Thereafter, development was performed using LP-1310HII manufactured by Fuji Photo Film Co., Ltd. as an automatic developing machine. The developer used was a 1: 4 water-diluted water of DV-2 manufactured by FUJIFILM Corporation, and the 1: 1 water-diluted solution of GN-2K manufactured by FUJIFILM Corporation was used as the finisher.
The pH of the alkali developer before development was adjusted to 11.95, and this was defined as the activity of the standard alkali developer.
In the development process, a developing solution temperature of 30 ° C. and a development time of 12 seconds were set, and 100 plate development processing was performed per day, followed by development processing for 3 months. Further, the development process was performed while adding 40 ml of a replenisher having a higher activity than that of a standard alkaline developer (pH-2.000, Fuji Film Co., Ltd. DV-2RS) per plate.

  During the implementation period, using the quality control method of the present invention, the activities of the alkaline developers are compared daily, the obtained evaluation results are fed back, and the conditions of the exposure / development process, which are platemaking conditions, are fed back. Was appropriately adjusted to perform quality control of the produced lithographic printing plate.

Adjustment of the exposure conditions / development conditions in this example is performed when the pH indicating the activity of the alkaline developer to be evaluated exceeds ± 0.2 from pH 11.95 indicating the activity of the standard alkali developer. That is, when the pH of the alkaline developer to be evaluated exceeded the range of 11.75 to 12.15, the developer temperature, development time, and exposure amount were controlled.
In addition, during the implementation period, the plate making is continued while maintaining the development conditions and the automatic developing machine, and the pH of the alkaline developer before developing the first plate is measured every day, and the alkaline developer to be evaluated is measured. It was set as activity. After the platemaking conditions are adjusted, platemaking is continued under the adjusted conditions, and the pH of the alkaline developer before developing the first plate is measured and evaluated every day from the next day. The activity of the alkaline developer to be used was defined.

Details of quality control in this embodiment are as follows.
On the 17th day, the pH of the alkaline developer to be evaluated was 11.70, and the difference in pH exceeded 0.2, so the developer temperature was adjusted from 30 ° C. to 32 ° C. As a result, although the activity of the alkali developer was lowered, the developer temperature was raised, so that sufficient development was performed and a lithographic printing plate having an image of the same quality as the initial stage could be produced. .
On the 20th day, since the pH changed to 11.80, the developer temperature was returned from 32 ° C. to 30 ° C.
On the 40th day, the pH of the alkaline developer to be evaluated was 12.20, and the difference in pH exceeded 0.2, so the developer temperature was adjusted from 30 ° C. to 28 ° C. As a result, although the activity of the alkali developer was increased, the developer temperature was lowered, so that the lithographic printing plate having an image with the same quality as the initial one could be produced without over-development.
On day 43, the pH changed to 12.10, so the developer temperature was returned from 28 ° C. to 30 ° C.
On the 52nd day, the pH of the alkaline developer to be evaluated was 11.70, and the difference in pH exceeded 0.2, so the development time was adjusted from 12 seconds to 14 seconds. As a result, although the activity of the alkaline developer was lowered, the development time was extended, so that sufficient development was performed, and a lithographic printing plate having an image of the same quality as the initial stage could be produced.
On the 55th day, since the pH changed to 11.80, the development time was returned from 14 seconds to 12 seconds.
On the 60th day, the pH of the alkaline developer to be evaluated was 12.20, and the difference in pH exceeded 0.2, so the development time was adjusted from 12 seconds to 10 seconds. As a result, although the activity of the alkali developer was increased, the development time was shortened, so that the lithographic printing plate having an image with the same quality as the initial one could be produced without over-development.
On day 63, the development time was returned from 10 seconds to 12 seconds because the pH changed to 12.10.
On the 70th day, the pH of the alkaline developer to be evaluated was 12.20, and the difference in pH exceeded 0.2. Therefore, the exposure amount (output) was adjusted from 40 W to 44 W. As a result, although the activity of the alkali developer is increased, the exposure amount is increased, so that the strength of the image portion is increased, and the lithographic printing plate having an image of the same quality as the initial stage is produced without over-development. I was able to.
On day 73, since the pH changed to 12.10, the exposure amount (output) was returned from 44 W to 40 W.
Thereafter, until the 90th day (3 months), the difference in pH did not exceed 0.2 and was stable.

In this example, when the developer pH decreased to 11.70 on the 17th day, if the plate making was continued as it was, a residual film was generated in the non-image area at the center of the plate.
From the above results, in this embodiment, if the lithographic printing plate quality control method of the present invention is not used, a plate making capable of forming a preferable image can only be operated for 16 days.
This shows that the lithographic printing plate quality control method of the present invention is effective in the plate making process using a negative lithographic printing plate precursor for an infrared laser.

It is a schematic block diagram which shows an example of the DRM interference wave measuring apparatus for measuring the dissolution behavior of a photosensitive layer. It is a schematic block diagram which shows an example of the measuring method of the electrostatic capacitance used in evaluating the permeability to the photosensitive layer of a developing solution.

Claims (2)

(A) A lithographic printing plate precursor comprising a photosensitive layer containing an infrared absorber, a radical generating compound, and a polymerizable compound on a support is exposed and then developed with a standard alkali developer. Determining the activity of the standard alkaline developer according to its physical properties;
(B) The step of determining the activity of the alkali developer to be evaluated under the same conditions as in the step (A) except that the development is performed with the alkali developer to be evaluated;
(C) comparing the activity of the standard alkali developer with the activity of the alkali developer to be evaluated;
(D) as a result of the comparison, when the difference in activity is a predetermined value or more, adjusting the exposure / development conditions according to the difference in activity; and
A quality control method for a lithographic printing plate, comprising: (E) After the completion of the step (D), the activity of the alkali developer under the adjusted exposure / development conditions is determined by the same index as in the step (A), and the activity of the alkali developer is determined. A step of setting the degree of activity of the alkaline developer to be evaluated in the step (B),
The quality control method for a lithographic printing plate according to claim 1, wherein the steps (E), (C), and (D) are performed once or a plurality of times in this order.

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