JP2008203348A - Platemaking method for planographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a platemaking method for a planographic printing plate by which leachability of a non-image part can be improved without inhibiting development stability, that is, printing performance of an image part, and high image reproducibility in a dot part is maintained as well as visibility of an image part is improved even in a high sensitivity CTP printing plate. <P>SOLUTION: The platemaking method for a planographic printing plate comprises crosslinking an image part by subjecting a photosensitive layer of a planographic printing plate to laser exposure and dissolving and removing an unexposed part by using an alkali developer solution to form a non-image part, wherein after the development processing by an alkali developer solution containing a leaching accelerator, the plate is rinsed with a rinsing liquid containing a basic dye and successively coated with a gum liquid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for making a lithographic printing plate, particularly a lithographic printing plate in which a photosensitive layer forms an image with a laser beam.

  In recent years, direct plate-making systems using various lasers such as ultraviolet, visible, and infrared (computer-to-plate, acronyms are also called CTP systems for directly making computer-generated image information) are available. It has been put into practical use and is widely used in the field of general commercial printing. This direct plate making system is advantageous in comparison with conventional plate making systems using film in terms of speed, cost, stability, etc. by digitizing the system, and is becoming mainstream in today's general commercial printing market.

  Due to these advantages, the direct plate making system is spreading not only in the general commercial printing market but also in the newspaper printing market. In newspaper printing, printing conditions are severer than general commercial printing because of its large number of copies and high printing speed, and high printing durability is required for printing plates. For this reason, negative type photopolymerizable photosensitive materials capable of forming an image with higher strength by a crosslinking reaction than positive type photosensitive materials have been used in conventional film plate making systems. For this reason, a lithographic printing plate having high image strength was indispensable for introducing a direct plate-making system into the newspaper printing market.

  Conventional film-making systems using negative PS plates cause cross-linking reaction of the photosensitive layer by long-time close exposure using a light source with extremely high energy such as a mercury lamp. The image obtained was very strong. In the direct plate making system, since exposure processing is performed with lower exposure energy than these light sources, it was initially difficult to form an image with the same intensity, but in recent years, various photosensitivities have been developed to improve the image intensity. Materials have been developed. In particular, high-power semiconductor lasers that emit light in the infrared region of 750 nm or more are becoming more compact and higher-powered and are very useful as exposure light sources for direct plate-making systems. In the plate making system, the development of photosensitive materials has made remarkable progress, and various proposals have been made.

  For example, the photosensitive material described in JP-A-7-20629 is characterized in that it contains a resole resin, a novolak resin, a latent Bronsted acid, and an infrared absorber, and can be used for both positive and negative plates. The version is described. JP-A-2000-089452 discloses a cross-linkable compound having a unique structure, and a binder is a polymer having an aromatic hydrocarbon ring directly bonded to a hydroxy group or an alkoxy group in a side chain or main chain, In addition, a negative image recording material containing a compound that generates an acid by heat and an infrared absorber is described. JP-A-2001-272778 discloses a photosensitive material comprising a borate complex salt, a trihaloalkyl-substituted compound, and a sensitizing dye having absorption in a wavelength range from near infrared light to infrared light. Are listed.

  The development process of such a negative type laser direct plate making system utilizes the alkali solubility of the binder polymer to be used, and the exposed part is cross-linked by the photopolymerization initiator to attenuate the alkali solubility, thereby removing unnecessary non-image parts. It is removed by dissolution with an aqueous alkaline developer. Thereafter, it is washed with water to wash the alkaline developer component adhering to the image area, the dissolved residue of the non-image area, etc., and further usually an acidic gum solution is applied to the plate surface to make it non-sensitive and protect the plate surface.

  On the other hand, as a problem of a lithographic printing plate (hereinafter referred to as CTP printing plate) corresponding to the direct plate making as described above, the degree of completion of the crosslinking reaction is lower than that of the negative PS plate, and the image strength is not so much as yet. There was a face. Since this is highly sensitive to cope with laser exposure that is exposed in an extremely short time, it is necessary to ensure pre-exposure storage against external factors such as heat, and optimization of cross-linking efficiency and storage stability is required. It is because it is made.

  In order to accelerate curing after laser exposure, a method has been proposed in which after image exposure, heat treatment is performed prior to the development process, radicals remaining in the exposure process are re-reacted, and crosslinking is promoted. It is difficult to supply heat uniformly, causing problems such as image unevenness, particularly dot unevenness, increasing energy required for plate making, and inefficiency and uneconomical problems such as enlargement of the apparatus itself. It was.

  In general, the above-mentioned photosensitive layer is alkali-soluble, but the binder resin has many hydrophobic portions in order to ensure good ink transportability as a lithographic printing plate. For this reason, by adding an organic solvent such as benzyl alcohol having a hydrophobic group and water miscibility, the permeation is increased, the residual film due to poor dissolution is suppressed, and printing stains are prevented. (Patent Document 1).

  For this reason, if the curing is insufficient, the developing solution penetrates into the image area in the development process, resulting in a problem of damaging the photosensitive layer. In particular, in the reproducibility of halftone dots and fine lines with high resolution, it is difficult to balance the highlight portion and the shadow portion, and the image reproduction range becomes narrow. This is because if the omission of the shadow part is good, the periphery of the highlight part is a non-image part, so that not only from the surface of the photosensitive layer but also penetration from the surroundings occurs, so that the photosensitive part of the image part is damaged, and the shadow part and This is because the printing durability of the highlight portion is significantly lower than that of the solid portion. However, lowering the permeability of the developer causes undesirable elution of the non-image area, and is liable to cause printing stains.

  In response to these problems, elution accelerators for non-image areas, such as alkanolamines and carbon, which do not inhibit the ink acceptability of the image area or weaken the strength of the image area while promoting elution of the non-image area Addition of compounds having several to 10 alkyl groups and polyalkyleneoxy groups and addition of aromatic anionic surfactants have been proposed (Patent Documents 2 and 3).

However, an elution accelerator such as an organic compound having a hydrophobic group in some cases penetrates into the image area after crosslinking, so that low molecular weight compounds, particularly pigments, contained in the image area may be dissolved and extracted. It was. For this reason, the visibility of the image area after the development processing is lowered, and a defect may occur in the plate inspection after the plate making.
Japanese Patent Publication No.56-39464 JP 2002-278085 A JP 2005-202149 A

  Therefore, the object of the present invention is to improve the development stability, that is, the elution property of the non-image area without impairing the printing performance of the image area, and maintain the high halftone image reproducibility even in the highly sensitive CTP printing plate. At the same time, it is to provide a lithographic printing plate making method that improves the visibility of the image area.

It has been found that the above object of the present invention can be achieved by the plate making method of a lithographic printing plate described below.
1. A method of making a lithographic printing plate that crosslinks an image portion by laser exposure and dissolves and removes an unexposed portion using an alkaline developer to form a non-image portion, after the development treatment with an alkaline developer containing an elution accelerator. A method for making a lithographic printing plate comprising washing with a washing solution having a basic dye and subsequently applying a gum solution having a pH value of 7.5 or less.

  According to the present invention, even when using a high-sensitivity CTP printing plate, development stability, that is, improving the elution of the non-image area without impairing the printing performance of the image area, while maintaining high halftone image reproducibility, At the same time, an excellent effect that the visibility of the image portion can be improved is obtained.

  As a result of intensive studies by the inventor, a method for making a lithographic printing plate, which crosslinks an image area by laser exposure and dissolves and removes an unexposed area using an alkaline developer to form a non-image area, has been studied by the present inventors. Then, after the development treatment with an alkaline developer containing an elution accelerator, use a plate-making method of a lithographic printing plate that is washed with a water-washing solution having a basic dye and subsequently gives a gum solution having a pH value of 7.5 or less. Was found to be extremely useful.

  In general, an alkaline developer contains an organic solvent or a surfactant as an elution accelerator in addition to an alkaline component, and partially dissolves and / or swells and penetrates the photosensitive layer. Although it improves the dissolution and removal performance by helping to penetrate the alkali component, some of it penetrates into the image area after crosslinking, so it is possible to dissolve and extract low molecular weight compounds, especially pigments, contained in the image area. there were. For this reason, compared with the plate surface density before the plate making process, the plate surface (image portion) density of the image portion after plate making may decrease. In the present invention, even if the pigments are extracted during the development process, when the pH of the plate surface is lowered by washing with water, the basic dye is present in the washing solution to cause swelling due to penetration of the elution accelerator. It was found that a basic dye was introduced into the image area due to a rapid pH drop when it was brought into contact with the applied gum solution after washing with water and further washed with water. This is specifically dyed with a basic dye, and hardly dyed with other acidic dyes, reactive dyes or pigments. The same applies if the dye used in the photosensitive layer is not a basic dye. The reason why the basic dye is effective is that the basic group of the basic dye preferably interacts with an alkali-soluble group of an alkali-soluble resin contained in the photosensitive layer of the lithographic printing plate, for example, a carboxylic acid group. Presumed to be captured in the image part.

  The plate making method of the present invention will be described in detail. In general, a lithographic printing plate is developed using an automatic developing machine. The automatic processor consists of a development processing unit, a water washing processing unit, a gum processing unit, and a drying unit in order. The exposed printing plate is transported while being immersed horizontally in each processing tank, or assembled from each processing tank with a pump. Each treatment liquid is sprayed onto the plate surface by spray means to perform each treatment.

  The development processing apparatus according to the present invention will be described below with reference to FIG. FIG. 1 is a schematic sectional view showing an example of an automatic processor used in the present invention. The lithographic printing plate 100 subjected to exposure processing (not shown in FIG. 1) is inserted into an automatic developing machine with the photosensitive layer surface facing upward, and is transported into the development processing section by transport rollers 51 and 52, and is transported through transport auxiliary rollers 53 and 54. It is immersed in a developer whose temperature is controlled at a constant temperature.

  The photosensitive layer of the lithographic printing plate 100 immersed in the developer is transported through the liquid by the liquid transport rollers 61 and 62 while the unexposed part, which is a non-image part, is swollen and easily eluted by the developer. Is done. The swollen non-image portion is rubbed by the Molton roll 71, so that elution is promoted. On the other hand, the image portion where the crosslinking reaction has occurred by exposure remains as an image without being eluted in the developer.

  Next, the lithographic printing plate 100 on which an image has been formed by elution of the non-image portion is squeezed with the developer squeeze rolls 9 and 10 to squeeze the excess developer on the plate surface, and is transported to the water washing treatment unit which is the next step. The non-image area of the lithographic printing plate 100 is washed on the surface and the image area is washed by washing water containing a basic dye discharged from the washing shower pipes 14 and 15 while being conveyed by the washing washing rolls 11 and 12 in the washing treatment section. Dyeing with a basic dye is performed.

  Thereafter, the water washing liquid is squeezed by the water washing conveyance rolls 16 and 17 and conveyed to the gum processing unit. A gum solution having a pH of 7.5 or less discharged from the gum solution discharge pipe 22 is applied to the entire surface of the planographic printing plate 100 while being transported by the gum transport rolls 18 and 19 in the gum processing unit, and the pH of the plate surface of the planographic printing plate 100 is increased. Falls sharply. At this time, the image portion of the lithographic printing plate 100 is applied with a washing solution due to rapid pH fluctuation and the basic dye that has penetrated into the film is taken into the image portion, and the non-image portion is insensitive due to the hydrophilizing component contained in the gum solution. It becomes. Subsequently, the excess gum solution is squeezed by the gum conveying rolls 20 and 21 and subsequently conveyed to a drying unit (not shown), and a protective film is formed by the gum solution component while drying the lithographic printing plate surface.

  The washing water in the present invention will be described. The washing solution contains water as a main component and at least a basic dye. Basic dyes are classified by chemical structure, for example, thiazine dyes, azine dyes, xanthene dyes, diallylmethane dyes, triallylmethane dyes, azo dyes, azamethine dyes, anthraquinone dyes, etc. Is mentioned. Among these, thiazine dyes such as methylene blue are particularly preferable because they are excellent in colorability, plate inspection property, stability over time, and the like. The dye used is preferably water-soluble, but if it is difficult to dissolve, it may be added in a dispersed state using a dispersant. The concentration of the dye used is preferably in the range of 0.001 to 10% by mass, particularly 0.01 to 5% by mass in the developer. Further, the pH is preferably in the range of 7 to 10, and is set to be at least 1 lower in pH value than the alkaline developer. More preferably, it is the range of 7.5-9. This is because if the pH is not so different from that of the developer, dissolution by the developer that has penetrated the film surface cannot be stopped, and development proceeds excessively. In addition, preservatives, fungicides, antifoaming agents, pH stabilizers and the like can be added to the washing water in an appropriate amount as necessary.

  The elution accelerator contained in the alkaline developer in the present invention will be described. The development processing of a lithographic printing plate is generally dissolved by a reaction between an alkali-soluble group such as carboxylic acid contained in the binder resin of the lithographic printing plate and an alkali component contained in the alkaline developer, but the binder resin is highly hydrophobic. As a result, it is easy to repel moisture at the interface, the diffusion and penetration of the alkaline developer is inhibited, and it takes time to uniformly dissolve the entire surface. For this reason, the elution promoter referred to in the present invention is a substance that assists and accelerates diffusion and penetration into the lithographic printing plate photosensitive layer in addition to an alkaline developer containing only an alkali component. Such an elution promoter is an organic compound having both a hydrophobic group and a hydrophilic group, and specifically includes alcohols and surfactants. Whether it acts as an elution accelerator is added to a developer containing only an alkali component in consideration of the composition of the planographic printing plate to be used and the film thickness of the photosensitive layer, and diffusion, penetration and dissolution into the planographic printing plate are promoted. You can determine whether or not. For example, by making a developer bath at a constant temperature and immersing the lithographic printing plate in it for a certain period of time to dissolve it, it is determined by performing a simple experiment such as whether or not the dissolution rate has increased after the addition. Can do. The dissolution accelerator contained in the alkaline developer may be used by appropriately mixing a plurality of alcohols or a plurality of surfactants, if not a single one, and the total content thereof is 0.001-50. The range of mass%, and further 0.1-5 mass% is suitable.

  Alcohols used as an elution accelerator contained in the alkaline developer of the present invention are liquid water-soluble organic compounds that are soluble and permeable to the hydrophobic photosensitive layer surface. Include aliphatic alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-methyl-1-propanol, 2-butanol and 1-pentanol, and aromatic alcohols such as benzyl alcohol. , Monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N- (aminoethyl) ethanolamine, N-methylethanolamine, Aminoethylisopropanolamine, N-E Alkanolamines such as ruethanolamine, N-butylethanolamine, N-butyldiethanolamine, N- (t-butyl) ethanolamine, 2-methoxyethanol, 2-ethoxyethanol, 2- (1-propoxy) ethanol, Examples thereof include compounds such as glycol ethers such as 2- (1-butoxy) ethanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol. Among them, preferred alcohols are alkanolamines that have a strong permeability to hydrophobic surfaces and have a good effect on printability.

  Examples of the surfactant used in the elution accelerator contained in the alkaline developer of the present invention include anionic, cationic, nonionic and amphoteric surfactants. Preferred examples of the surfactant include polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, glycerin fatty acid partial esters, sorbitan fatty acid partial esters, and sucrose fatty acids. Partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters, polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid esters, Polyoxyethylene-polyoxypropylene block copolymer, polyoxyethylene-polyoxypropylene block copolymer of ethylenediamine Additives, fatty acid diethanolamides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides and other nonionic surfactants, fatty acid salts, dialkylsulfosuccines Acid salts, alkyl diallyl ether sulfonates, hydroxyalkane sulfonates, N-methyl-N-oleyl taurine sodium salt, sulfated beef tallow oil, fatty acid alkyl ester sulfate ester salts, polyoxyethylene alkyl ether sulfate ester salts, fatty acids Anionic surfactants such as monoglyceride sulfates, alkyl sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, alkylamines, Quaternary ammonium salts such as trabutylammonium bromide, cationic surfactants such as polyoxyethylene alkylamine salts, polyethylene polyamine derivatives, carboxybetaines, aminocarboxylic acids, sulfobetaines, aminosulfuric esters, imidazolines, And amphoteric surfactants. Among the surfactants listed above, those having polyoxyethylene can be read as polyoxyalkylenes such as polyoxymethylene, polyoxypropylene and polyoxybutylene, and these surfactants are also contained. A fluorine-based surfactant containing a perfluoroalkyl group in the molecule can also be used suitably. For example, perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, anionic types such as perfluoroalkyl phosphates, amphoteric types such as perfluoroalkyl betaines, cationic types such as perfluoroalkyltrimethylammonium salts, and perfluoroalkyls Amine oxide, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl group and hydrophilic group-containing oligomer, perfluoroalkyl group and lipophilic group-containing oligomer, perfluoroalkyl group, hydrophilic and lipophilic group-containing oligomer, perfluoroalkyl Nonionic types such as groups and oleophilic group-containing urethanes.

  Further, examples of the surfactant that can be suitably used include aromatic anionic surfactants. These surfactants have particularly strong permeability and effective action on binder polymers having an aromatic ring. Specific examples include alkylbenzene sulfonates, alkyl naphthalene sulfonates, naphthalene sulfonic acid formalin condensate salts, and polyoxyethylene alkyl phenyl ether sulfonates. These surfactants can be appropriately used singly or in combination of two or more or combinations other than the above-mentioned aromatic anionic surfactants.

  Next, other components of the alkaline developer according to the present invention will be described. The component composition of the alkaline developer is as follows: an alkaline agent that mainly dissolves the binder polymer in the photosensitive layer, an alkali agent as described above for the purpose of promoting developability, a dispersion of development residue, and various interfaces for purposes. Consists of activators, organic solvents, and antifoaming agents, metal sequestering agents, antibacterial / antifungal agents, colorants, and additives such as ink riding promotion that enhances the ink affinity of the printing plate image area. . Moreover, the preferable pH range of the alkaline developer of the present invention is 9 to 13, and a low pH value is preferable from the viewpoint of long-term processing stability and disposal. However, if it is too low, the development processing time becomes longer, and more preferable. It is in the range of 10-12.

  As a specific example of the alkali agent, a conventionally known water-soluble alkaline compound can be used. For example, sodium silicate, potassium, tribasic sodium phosphate, potassium, ammonium, dibasic sodium phosphate, potassium, ammonium, sodium carbonate, potassium, ammonium, sodium bicarbonate, potassium, Examples include inorganic alkali salts such as ammonium, sodium borate, 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 listed. These alkaline agents may be used alone or in combination of two or more.

  In the present invention, development is performed using an automatic developing device, but an aqueous solution (replenisher) having high alkali strength can be added to the alkaline developer. Accordingly, a large amount of lithographic printing plate can be suitably processed without changing the developer in the developing tank for a long time.

  In the alkaline developer used in the present invention, various development stabilizers are preferably used. Preferred examples thereof include polyethylene glycol adducts of sugar alcohols described in JP-A-6-282079, phosphonium salts such as tetrabutylphosphonium bromide, and iodonium salts such as diphenyliodonium chloride. Furthermore, anionic surfactants or amphoteric surfactants described in JP-A-50-51324, water-soluble cationic polymers described in JP-A-55-95946, and JP-A-56-142528 are described. There are water-soluble amphoteric polyelectrolytes that have been described. Further, an organic boron compound to which an alkylene glycol is added as described in JP-A-59-84241, a polyethylene glycol having a mass average molecular weight of 300 or more as described in JP-A-61-215554, and a cation as described in JP-A-63-175858. And a water-soluble ethylene oxide adduct obtained by adding 4 mol or more of ethylene oxide to an acid or alcohol disclosed in JP-A-2-39157, a water-soluble polyalkylene compound, and the like.

  It is advantageous in terms of transportation that the alkaline developer used in the present invention is a concentrated solution in which the content of water is less than that in use, and is diluted with water at the time of use. The degree of concentration in this case is suitably such that each component does not cause separation or precipitation, and depending on its composition, it can be usually concentrated to a concentrated solution: water = 1: 0 to 1:10. In addition, since the container is alkaline, it is preferable to use a material that does not permeate carbon dioxide and that does not break during transportation for safety. Usually, a resin container such as a hard bottle or a cubicener is preferably used.

  Next, the gum solution used in the present invention will be described. The gum solution used in the present invention is imparted for the purpose of desensitizing the non-image area and protecting the plate surface, and mainly comprises a desensitizing agent, a surfactant, an antiseptic, an antifungal agent, a parent agent. It is composed of oily substances, wetting agents, chelating agents, antifoaming agents, pH adjusting agents and the like. The gum solution used in the present invention is used in the range of pH 7.5 or less. However, if the acidity is too strong, the aluminum support used in the lithographic printing plate may be corroded. Therefore, the pH is adjusted to 3 to 7.5 by adding a pH adjuster such as mineral acid, organic acid or inorganic salt. And preferably used. Furthermore, it is preferable that the difference with the pH value of the washing solution is large, that is, the acidity is strong, and the range of 3 to 6 is more preferable.

  As the desensitizing agent for the gum solution used in the present invention, a water-soluble resin having hydrophilicity and film-forming ability is preferably used. Examples of water-soluble resins include gum arabic, dextrin, stellabic, stratane, alginates, polyacrylates, hydroxyethylcellulose, polyvinylpyrrolidone, polyacrylamide, methylcellulose, hydroxypropylcellulose, hydroxymethylcellulose, carboxyalkylcellulose salt, soybean Water-soluble polysaccharides extracted from these okaras are preferred, and pullulan or pullulan derivatives and polyvinyl alcohol are also preferred.

  Further, as modified starch derivatives, roasted starch such as British gum, enzyme modified dextrins such as enzyme dextrin and shardinger dextrin, oxidized starch shown in solubilized starch, modified starch pregelatinized and unmodified gelatinized starch , Phosphate starch, fat starch, sulfate starch, nitrate starch, xanthate starch, carbamic acid starch and other esterified starch, carboxyalkyl starch, hydroxyalkyl starch, sulfoalkyl starch, cyanoethyl starch, allyl starch, benzyl starch, carbamyl Etherified starch such as ethyl starch and dialkylamino starch, methylol cross-linked starch, hydroxyalkyl cross-linked starch, phosphoric acid cross-linked starch, dicarboxylic acid cross-linked starch and other cross-linked starch, starch polyacrylamide copolymer, starch polyacrylic acid copolymer Starch polyvinyl acetate copolymer, starch polyacrylonitrile copolymer, chaotic starch polyacrylic acid ester copolymer, chaotic starch vinyl polymer copolymer, starch polystyrene maleic acid copolymer, starch polyethylene oxide copolymer, Starch graft polymers such as starch polypropylene copolymers are preferred. Natural polymer compounds include starches such as candy starch, potato starch, tapioca starch, wheat starch and corn starch, carrageenan, laminaran, seaweed mannan, funari, Irish moss, agar and algae such as sodium alginate. , Plant mucilage such as troroaoy, mannan, quince seed, pectin, tragacanth gum, karaya gum, xanthine gum, guar bin gum, locust bin gum, carob gum, benzoin gum, homopolysaccharides such as dextran, glucan, levan and succinoglucan and santango gum Preferred are microbial mucilages such as hetropolysaccharides, proteins such as glue, gelatin, casein and collagen. These water-soluble resins can be used in combination of two or more, and can be contained in the gum solution in an amount of preferably 5 to 40% by mass, more preferably 10 to 30% by mass.

  Examples of the surfactant contained in the gum solution include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic surfactant. Anionic surfactants include fatty acid salts, abietic acid salts, hydroxyalkane sulfonates, alkane sulfonates, α-olefin sulfonates, dialkyl sulfosuccinates, alkyl diphenyl ether disulfonates, linear alkyl benzene sulfonates, branched Chain alkylbenzene sulfonates, alkylnaphthalene sulfonates, alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, sodium N-methyl-N-oleyl taurate, disodium N-alkylsulfosuccinate monoamide Salts, petroleum sulfonates, sulfated castor oil, sulfated beef tallow oil, fatty acid alkyl ester sulfate esters, alkyl sulfate esters, polyoxy Ethylene alkyl ether sulfates, fatty acid monoglyceride sulfates, polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene styryl phenyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene Examples thereof include alkyl phenyl ether phosphate esters, partially saponified products of styrene-maleic anhydride copolymers, partially saponified products of olefin-maleic anhydride copolymers, naphthalene sulfonate formalin condensates, and the like. Among these, dialkyl sulfosuccinates, alkyl sulfate esters, alkyl naphthalene sulfonates, α-olefin sulfonates, and alkyl diphenyl ether disulfonates are particularly preferably used. As the cationic surfactant, alkylamine salts, quaternary ammonium salts and the like are used. As the amphoteric surfactant, alkylcarboxybetaines, alkylimidazolines, alkylaminocarboxylic acids and the like are used. Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ether, polyoxyethylene polyoxypropylene alkyl ether, glycerin fatty acid partial esters, sorbitan fatty acid partial esters , Pentaerythritol fatty acid partial esters, propylene glycol monofatty acid esters, sucrose fatty acid partial esters, polyoxyethylene sorbitan fatty acid partial esters, polyoxyethylene sorbitol fatty acid partial esters, polyethylene glycol fatty acid esters, polyglycerin fatty acid partial esters , Polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanol Mides, N, N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, trialkylamine oxides, polypropylene glycol having a molecular weight of 200 to 5000, trimethylolpropane, glycerin or sorbitol And polyoxyethylene or an adduct of polyoxypropylene, acetylene glycol type, and the like. Fluorine-based and silicon-based nonionic surfactants can also be used in the same manner. Two or more surfactants can be used in combination. The amount used is not particularly limited, but a preferable range is 0.01 to 20% by mass, preferably 0.05 to 10% by mass, based on the total weight of the gum solution.

  Next, the planographic printing plate used in the present invention will be described. The lithographic printing plate used in the present invention is a so-called negative CTP printing plate in which the image portion is crosslinked by laser exposure. The photosensitive layer of the lithographic printing plate is crosslinked in the image portion by laser exposure, and an alkaline developer is used. A lithographic printing plate that is used to dissolve and remove unexposed portions of the photosensitive layer to form non-image portions. Therefore, in order to dissolve and remove the non-image area with an alkaline developer, it is preferable that the photosensitive layer is alkali-soluble, and particularly sensitive ones and those requiring high printing durability used for newspaper printing are preferable.

  Examples of these printing plates include a lithographic printing plate characterized by containing a resole resin, a novolak resin, a latent Bronsted acid, and an infrared absorber described in JP-A-7-20629, and JP-A 2000-2000. The compound having crosslinkability described in Japanese Patent No. 089452 has a unique structure, and the binder is a polymer having an aromatic hydrocarbon ring directly bonded to a hydroxy group or an alkoxy group in a side chain or main chain, and an acid is generated by heat. A lithographic printing plate containing a generated compound and an infrared absorber, a borate complex salt described in JP-A-2001-272778, a trihaloalkyl-substituted compound, and an increase having absorption in a wavelength range from near infrared light to infrared light region. Examples thereof include a lithographic printing plate characterized by containing a dye-sensitive dye.

  In particular, the photosensitive layer of a lithographic printing plate has a copolymer of a monomer having a polymerizable double bond in the side chain and a carboxyl group-containing monomer as a polymerizable polymer, and lithographic printing having an organic boron salt as a photopolymerization initiator The plate can be applied effectively because it is more sensitive.

  Further, as the outermost layer of the lithographic printing plate, a water-soluble polymer compound having relatively excellent crystallinity, such as polyvinyl alcohol, polyvinyl pyrrolidone, acidic cellulose, gelatin, gum arabic, polyacrylic acid and the like as a main component. A blocking protective layer can also be provided.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples as well as the effects.

  The automatic plate making machine in the present embodiment will be described below with reference to FIG. FIG. 1 is a schematic sectional view showing an example of an automatic plate making machine used in the present invention. The lithographic printing plate 100 subjected to exposure processing in FIG. 1 is inserted into an automatic developing machine with the photosensitive layer surface facing upward, and is immersed in a developer kept at a liquid temperature of 30 degrees while being transported to the development processing tank 2. Dissolution is accelerated by the Molton roll 71 which is driven separately from the transport of the lithographic printing plate 100, and the non-image portion of the plate surface is dissolved and removed.

  Next, the lithographic printing plate 100 squeezes excess developer on the plate surface with developer squeeze rolls 9 and 10 and transports it to the water-washing processing section as the next step. The surface of the non-image part of the lithographic printing plate 100 is washed with rinsing water containing a basic dye discharged from the rinsing shower pipes 14 and 15 while being conveyed by the rinsing conveying rolls 11 and 12 in the rinsing processing section. Part is dyed with a basic dye.

  Thereafter, the water washing liquid is squeezed by the water washing conveyance rolls 16 and 17 and conveyed to the gum processing unit. The acidic gum solution discharged from the gum solution discharge pipe 22 is applied to the entire surface of the planographic printing plate 100 while being transported by the gum transport rolls 18 and 19 in the gum processing unit, and the pH of the plate surface is drastically lowered. At this time, the image portion of the lithographic printing plate 100 is tightened due to rapid pH fluctuations, and the basic dye that has been applied with the washing liquid and penetrated into the film is taken in. It becomes. Subsequently, the excess gum solution is squeezed by the gum conveying rolls 20 and 21 and subsequently conveyed to the drying unit, so that a protective film is formed by the gum solution component while drying the planographic printing plate surface. .

The lithographic printing plate produced as described below was subjected to laser irradiation energy of 50 mJ / mm at a drum rotation speed of 1000 rpm using an external drum type plate setter (PT-R4000 manufactured by Dainippon Screen Mfg. Co., Ltd.) equipped with an 830 nm semiconductor laser. The exposure processing was carried out with a setting of cm ² , and subsequently the development processing was carried out with the above-mentioned automatic plate making machine.

[Preparation of planographic printing plate]
An aluminum plate (material 1050) having a thickness of 0.3 mm was degreased, and then the surface was grained using a nylon brush and a 400 mesh pumice-water suspension and thoroughly washed with water. This plate was etched with a 25% aqueous sodium hydroxide solution at 45 ° C., washed with water, further immersed in 20% nitric acid for 20 seconds, washed with water, and 7% sulfuric acid as an electrolytic solution at a current density of 15 A / dm ² and 3 g / m. After providing the direct current anodic oxide film of ² , it was washed with water and dried to prepare an aluminum support. The following photosensitive solution material was applied to this support so as to have a dry film thickness of 1.8 μm and dried to prepare a lithographic printing plate.

<Photosensitive material>
Polymer (10% dioxolane solution of the compound shown in Chemical formula 1) 300 parts by mass Organic boron salt (compound shown in Chemical formula 2) 4 parts by mass Ethylenically unsaturated compound (compound shown in Chemical formula 3) 15 parts by mass Pentaerythritol tetraacrylate 10 parts by mass Part Sensitizing dye (compound shown in Chemical formula 4) 0.8 part by weight Colorant (25% phthalocyanine pigment MEK dispersion) 15 parts by weight Colorant (oil Yellow 105) 3 parts by weight Polymerization inhibitor (2,6-di-t -Butylcresol) 0.1 part by weight Trihaloalkyl-substituted compound (compound shown in Chemical formula 5) 1 part by weight Matting agent (silicone resin dispersion: GE Toshiba Silicone Tospearl 145)
0.6 parts by weight 1,3-dioxolane 70 parts by weight cyclohexanone 20 parts by weight Surfactant (Surflon S381 manufactured by Seimi Chemical) 0.02 parts by weight

  The followings were used as the developer, washing solution and gum solution.

<Developer 1>
Potassium hydroxide is 0.5% by weight as an alkali component, benzyl alcohol is 2% by weight as an elution accelerator, aromatic anionic surfactant (Perex NB-L manufactured by Kao Corporation) is 3% by weight, and a metal sequestering agent as other components. The solution was diluted with water so that (Crewat DA, manufactured by Nagase ChemteX Corporation) was 0.1%, and the pH was adjusted to 11.5 with a pH adjuster.

<Developer 2>
0.5% by mass of potassium hydroxide as an alkaline component, 2% by mass of N-methylethanolamine as an elution accelerator, 3% by mass of an aromatic anionic surfactant (Perex NB-L manufactured by Kao Corporation) and other components The metal sequestering agent (Crewat DA, manufactured by Nagase ChemteX Corporation) was diluted with water so as to be 0.1%, and the pH was adjusted to 11.5 with a pH adjuster.

<Developer 3>
Potassium hydroxide is 0.5% by mass as the alkaline component, and the metal sequestering agent (Crewat DA manufactured by Nagase ChemteX Corporation) is 0.1% as the other component, and the pH is adjusted to 11 with a pH adjuster. .5.

<Washing liquid 1>
The basic dye, methylene blue, was diluted with water so as to be 5% by mass, and the pH was adjusted to 8.5 with a pH adjuster.

<Washing liquid 2>
As a dye, a phthalocyanine dye (WATER BLUE3 manufactured by Orient Chemical Co., Ltd.) was diluted with water so as to be 5% by mass, and the pH was adjusted to 8.5 with a pH adjuster.

<Washing liquid 3>
The acid dye (Kayakayl pure blue FGA manufactured by Nippon Kayaku Co., Ltd.) was diluted with water so as to be 5% by mass, and the pH was adjusted to 8.5 with a pH adjuster.

<Washing liquid 4>
The dye was not added, and only water was prepared with a pH adjuster so that the pH was 8.5.

<Gum solution>
The mixture was diluted with water so that gum arabic was 5% by mass and 85% phosphoric acid was 3% by mass, and prepared using a pH adjuster so that the pH was 4.5.

  As confirmation of the effect of the dissolution accelerator, test pieces obtained by cutting the lithographic printing plate into 10 cm × 5 cm were prepared, each of which had a liquid temperature of 30 ° C., and each of the developer solutions 1 to 3 placed in a 500 ml beaker was tested. Half of the sample was immersed and the time required for dissolution was confirmed. In developer 1 and 2, the photosensitive layer was dissolved in 6 seconds, but in developer 3 it took 10 seconds.

  Table 1 shows the results of performing plate-making processes in combination with Table 1 using the automatic plate-making machine and each processing solution, and evaluating the plate surface density (image part) before and after plate-making using a commercially available reflection densitometer. Shown in Visual observation of the lithographic printing plate made from the lithographic printing plate of each Example showed that the plate surface reflection density did not decrease and the image portion / non-image portion contrast was sufficient to perform plate inspection. In both cases, the image portion / non-image portion contrast is low, and in Comparative Examples 1 to 4, there are some that cannot be read with 2-point size characters.

  Next, 50,000 sheets of these were printed using an offset printing machine (Sprint 226 manufactured by Komori Corporation), ink (Super TEKPLUS Magenta L manufactured by T & K TOKA), and a moisturizer (ASTROMARK 3 manufactured by Nikken Chemical Laboratory). Was printed, and the area ratios of dot portions 1 to 9% and 90 to 99% of the dot line density 175 lines of the printed matter were measured in increments of 1%. In the case of using the plate-making products of Examples 1 and 2 and Comparative Examples 1 to 4, good reproducibility was obtained from the printed material immediately after the start of printing, and the area ratio of the halftone dots in the printed material after printing 50,000 sheets was reduced. However, there was no problem in practical use. On the other hand, in the case of using the plate-making products of Comparative Examples 5 and 6, the printed material immediately after the start of printing has good reproducibility, but in the printed material after printing 50,000 sheets, the halftone dot area ratio of the 1-2% portion is particularly high. The decrease was large and was hardly reproduced. Also, in the plate making performed in the same manner except that water was used in place of the gum solution used in Example 1, scumming occurred from the start of printing, and partial omission of images occurred when 10,000 sheets were printed. Occurred and could not be used (Comparative Example 7). Furthermore, even in the plate making performed in the same manner except that the pH of the gum solution used in Example 1 was adjusted to 8, partial missing of the image occurred at the time when 10,000 sheets were printed, and it could not be used ( Comparative Example 8).

  As an application example of the present invention, it can be used as a plate making method for CTP printing plates for commercial printing or newspaper printing fields.

1 is a schematic cross-sectional view showing an example of an automatic processor used in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Planographic printing plate 2 Development processing tank 3 Washing tank 4 Gum tank 51, 52 Transport roll 53, 54 Transport auxiliary roll 61, 62 Submerged transport roll 71 Molton roll 72 Guide plate 9, 10, Development squeeze roll 11, 12, 16, 17 Flushing rolls 14, 15 Flushing shower pipes 18, 19, 20, 21 Gum conveyance rolls 22 Gum liquid discharge pipe

Claims (1)

  A method of making a lithographic printing plate that crosslinks an image portion by laser exposure and dissolves and removes an unexposed portion using an alkaline developer to form a non-image portion, after the development treatment with an alkaline developer containing an elution accelerator. A method for making a lithographic printing plate, comprising washing with a washing solution having a basic dye and subsequently applying a gum solution having a pH value of 7.5 or less.

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