JP2005114899A - Sensitivity of silver halide emulsion layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum lithographic printing plate excellent in printing durability and antifouling property. <P>SOLUTION: The lithographic printing plate has a physical developing nucleus layer on a surface-roughened and anodically oxidized aluminum support and further has at least two silver halide emulsion layers thereon, wherein the sensitivity of a silver halide emulsion layer closest to the aluminum support is delayed than that of a silver halide emulsion layer located next and the silver halide emulsion layer closest to the aluminum support contains a compound containing at least either a nitrogen-containing heterocycle or a mercapto group. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a lithographic printing plate using a silver complex diffusion transfer method using an aluminum plate as a support.

  For lithographic printing plates using the silver complex diffusion transfer method (DTR method), published by Focal Press, London New York (1972), by Andre Lot and Edith Weide, "Photographic Silver Halide Diffusion Processes", Some examples are described on pages 101-130.

  As described therein, the lithographic printing plate using the DTR method includes a two-sheet type in which a transfer material and an image receiving material are separately provided, or a mono-sheet type in which they are provided on a single support. Two systems are known. The two-sheet type lithographic printing plate is described in detail in JP-A-57-158844. The mono sheet type is described in detail in Japanese Patent Publication Nos. 48-30562, 51-15765, 51-111103, and 52-150105.

  A lithographic printing plate using paper as a support is difficult to print at high quality including printing durability because of plate elongation during printing and penetration of moisture. A film support is used for the purpose of improving these problems and improving printing performance. For example, a cellulose acetate film, a polyvinyl acetal film, a polystyrene film, a polypropylene film, a polyethylene terephthalate film, or a composite film obtained by coating a polyester, polypropylene, or polystyrene film with a polyethylene film can be used as the support.

  However, although lithographic printing plates using a film as a support are improved in terms of plate elongation and moisture penetration, compared to paper-based printing plates, printing durability, water retention, and further to printing presses are improved. The problem remains in terms of printability.

  Therefore, in order to solve the various problems of the lithographic printing plate using the paper or film as a support described above, a silver salt type lithographic printing plate using a metal, particularly an aluminum plate, is known, The details are described in JP-A-57-118244, JP-A-57-158844, JP-A-63-260491, JP-A-3-116151 and JP-A-4-282295. A monosheet type lithographic printing plate (hereinafter referred to as an aluminum lithographic printing plate) using a silver complex diffusion transfer method using these aluminum plates as a support is physically placed on a roughened and anodized aluminum support. A development nucleus layer is provided, and a silver halide emulsion layer is further provided thereon. In a general plate making method of this lithographic printing plate, after exposure, development processing and water washing processing (wash-off: removal of silver halide emulsion layer) are performed. A finishing treatment is usually applied to protect the printing plate.

  Specifically, a metallic silver image portion is formed on the physical development nuclei by the development process, and the silver halide emulsion layer is removed by the subsequent washing treatment, and the metallic silver image portion (hereinafter referred to as a silver image portion) is formed on the aluminum support. Exposed). At the same time, the anodized aluminum surface itself is exposed as a non-image part.

  In the aluminum lithographic printing plate targeted by the present invention, it is necessary that the image silver and the aluminum support are firmly bonded in order for the silver image portion to have a sufficient printing durability. However, the developer of an aluminum lithographic printing plate is usually strongly alkaline, and since aluminum is an amphoteric metal, the aluminum support dissolves in the developer during processing, weakening this adhesion and providing printing durability. I had a problem that I couldn't. In particular, this problem is remarkable in a fine line having a large non-image area compared to a silver image area, a highlight area, and the like.

  Various methods have been proposed for this problem, for example, in JP-A-11-305448, JP-A-2000-181052, and JP-A-2000-275850 (Patent Documents 1, 2, and 3). It wasn't the way.

On the other hand, in the above-mentioned aluminum lithographic printing plate, JP-A-11-305446 (Patent Document 4) proposes to contain a substantially non-photosensitive silver halide emulsion and a photosensitive silver halide emulsion together. However, non-photosensitive silver halide emulsions are physically developed without distinction between image areas and non-image areas. Become. When photosensitive silver halide and non-photosensitive silver halide are mixed in one layer, contamination occurs when there is a large amount of non-photosensitive silver halide. There was no improvement and there was a problem with its stability. Further, when the photosensitive silver halide and the non-photosensitive silver halide are divided into separate layers as in JP-A-62-242946 (Patent Document 5), the implementation of Patent Document 4 is performed before the problem of contamination. As in the comparative example, it is known that, in the aluminum lithographic printing plate, the intended printing durability of the highlight portion is weakened.
JP 11-305448 A (second page) JP 2000-181052 A (2nd page) JP 2000-275850 A (page 2) JP-A-11-305446 (first page, sixth page) JP 62-242946 A (first page)

  An object of the present invention is to provide a lithographic printing plate excellent in printing durability and stain resistance.

  The above object of the present invention is to have a physical development nucleus layer on a roughened and anodized aluminum support and further have at least two silver halide emulsion layers thereon, closest to the aluminum support. A compound in which the sensitivity of the silver halide emulsion layer is slower than that of the next silver halide emulsion layer and the silver halide emulsion layer closer to the aluminum support contains at least one of a nitrogen-containing heterocyclic ring and a mercapto group It was achieved by using a lithographic printing plate characterized in that it contains

  According to the present invention, a lithographic printing plate excellent in printing durability and stain resistance can be provided.

In the present invention, sensitivity can be measured by any method known in the art. For example, the amount of exposure light required to form an image (for example, to obtain a certain density) in the same coating liquid component, the same support, and the photosensitive material manufactured under the same manufacturing conditions with the same amount of coated silver Can be obtained by measuring as follows. In the present invention, when a negative and positive thin line of 50 microns is output in the same coating liquid component, the same support, and the photosensitive material manufactured under the same manufacturing conditions with the same coated silver amount, the thicknesses match. It is expressed by the reciprocal of the required light quantity (unit: J / cm ² ).

  In the present invention, the sensitivity of the silver halide grains in the silver halide emulsion layer (hereinafter referred to as the lower emulsion layer) closest to the aluminum support is higher than that of the silver halide emulsion layer (hereinafter referred to as the upper emulsion layer) positioned thereon. A low value, preferably 5% or less, more preferably 0.1% or less. In the present invention, the slow-sensitive silver halide emulsion can be obtained by any method known in the art. For example, by adding a water-soluble rhodium salt to silver halide grains, by changing the halogen composition of the silver halide grains, and creating silver halide grains with a small particle size, the amount of spectral sensitizing dye added can be reduced. This is achieved by reducing the weight, adding an organic desensitizer, or changing the chemical ripening conditions.

  In the present invention, the lower emulsion layer contains silver halide in an amount of 30 mol% or less, preferably 2 to 10 mol% of the silver ions contained in all layers. The type of silver halide emulsion used in the lower emulsion layer of the present invention is selected from commonly used silver chloride, silver bromide, silver iodide, silver chlorobromide, silver chloroiodobromide, silver iodobromide, etc. Is done. The emulsion type may be either a negative type or a positive type, but a negative type is preferred. These silver halide emulsions can be chemically or spectrally sensitized as necessary.

In the present invention, the lower emulsion layer contains a compound containing at least one of a nitrogen-containing heterocyclic ring and a mercapto group. The amount 1 to 100 mg / m ^2, preferably from 5 to 30 mg / m ^2.

  Examples of the compound containing a nitrogen-containing heterocycle in the present invention include pyrrole, pyridine, pyrimidine, pyrazole, imidazole, benzimidazole, 1.3.5-triazine, and hexahydro-1.3.5. -Triazine series, triazole series, isoxazole series, thiazole series, benzothiazole series, thiazolone series, benzothiazolone series, isothiazolone series, benzisothiazolone series, tetrahydrothiadiazinethione series, azaindene series, etc. Further, alkylallyl derivatives thereof and the like can be mentioned, and among them, a benzimidazole compound is particularly preferable.

  In the present invention, the compound containing a mercapto group is preferably a mercapto derivative of the aforementioned nitrogen-containing heterocyclic compound, an aromatic mercapto compound or the like. Mercapto compounds known to those skilled in the art as sulfur sensitizers such as thioureas are not preferred because they change sensitivity and generate fog.

  Specific examples of the organic compound containing either a nitrogen-containing heterocyclic ring or a mercapto group are given below. 5-nitrobenzimidazole, imidazole, 2-aminobenzimidazole, 1H-1,2,3-triazole, 1H-tetrazole, 5-phenyl-1H-tetrazole, benzotriazole, 5-methyl-1H benzotriazole, 5-chloro -Benzotriazole, 5-nitrobenzotriazole, 2-methylbenzoxazole, 6-methylpurine, adenine, 1-hydroxy-benzotriazole, 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene, 2- (carbomethoxyamino) -benzimidazole, 2-mercapto-4-phenlimidazole, 2-mercapto-1-benzylimidazole, 2mercapto-1-butyl-benzimidazole, 1 ethyl-2-mercapto-benzimidazole, 2 Capto-benzimidazole, 1,3 diethyl-benzimidazoline-2-thione, 1,3 dibenzyl-imidazolidine-2-thione, 2,2-dimercapto-1,1′-decamethylene-diimidazoline-2-thione, 2 Mercapto-4-phenylthiazol, 2-mercapto-benzothiazole, 2-mercaptonaphthothiazole, 3-ethyl-benzothiazoline-2-thione, 3-dodecyl-benzothiazoline-2-thione, 2-mercapto-4,5 -Diphenyloxazole, 2-mercaptobenzoxazole, 3-pentyl-benzoxazoline-2-thione, 1-phenyl-3-methylpyrazolidone-5-thione, 3-mercapto-4-allyl-5-pentadecyl-1, 2,4-triazole, 3-mercapto-5-nonyl- , 2,4-triazole, 3-mercapto-5-nonyl-5-1,2,4-triazole, 3-mercapto-4-allyl-5-pentadecyl-1,2,4-triazole, 3-mercapto-4 -Amino-5-heptadecyl-1,2,4-triazole, 2-mercapto-5-phenyl-5-pentadecyl-1,3,4-thiadiazole, 2-mercapto-5-n-heptyl-oxathiazole, 2- Mercapto-5-phenyl 1,3,4-oxadiazole, 5-mercapto-1-phenyl-tetrazole, 2-mercapto-5-nitropyridine, 1-methyl-quinoline-2 (1H) -thione, 3-mercapto -4-methyl-6-phenylpyridazine, 2-mercapto-5,6-diphenyl-pyrazine, 2-mercapto-4,6-dipheni 1,3,5 triazine, 2-amino-4-mercapto-6-benzyl-1,3,5-triazine, 1,5-dimercapto-3,7-diphenyl-S-triazolino [1,2-a] -S-triazoline, o-thiosalicylic acid, thiomalic acid and the like.

  Various hydrophilic colloids can be used as protective colloids in the silver halide emulsion layer of the printing plate of the present invention. That is, various gelatins such as acid-treated gelatin, alkali-treated gelatin, gelatin derivatives and grafted gelatin can be used, and hydrophilic polymer compounds such as polyvinyl pyrrolidone, various starches, albumin, polyvinyl alcohol, gum arabic, and hydroxyethyl cellulose. Can be contained. Examples of the hydrophilic colloid used include gelatin, gelatin derivatives, polyvinyl alcohol, polyvinyl pyrrolidone, and the like, but preferably a hardener substantially for facilitating the release of the hydrophilic colloid layer after physical development. It is desirable to use a hydrophilic colloid layer that does not contain.

  In the present invention, the upper emulsion layer has at least one layer on the lower emulsion layer. When there are two or more upper emulsion layers, the lower emulsion layer needs to be less sensitive than all the individual upper emulsion layers, and the comparison of the sensitivity values described above is the upper emulsion having the highest sensitivity with the lower emulsion layer. Do between layers. Further, an intermediate layer or the like may be present between the lower emulsion layer and the upper emulsion layer as necessary. It is also possible to provide a protective layer as the uppermost layer.

  The type of silver halide emulsion used in the upper emulsion layer of the present invention is selected from commonly used silver chloride, silver bromide, silver iodide, silver chlorobromide, silver chloroiodobromide, silver iodobromide, etc. Is done. The emulsion type may be either a negative type or a positive type. These silver halide emulsions can be chemically or spectrally sensitized as necessary. The composition of the silver halide, the degree of chemical sensitization, and the degree of spectral sensitization in the lower emulsion layer and the upper emulsion layer may be the same or different as long as the sensitivity of the lower emulsion layer is low in the final sensitivity. .

  As the aluminum support used in the present invention, an aluminum support having a purity of 93% by mass or more, preferably 99% by mass or less is used. As the aluminum impurity, elements usually used as an aluminum alloy such as iron, silicon, copper, manganese, magnesium, chromium, zinc, titanium, bismuth, lead, zirconium and nickel can be used. Particularly preferable aluminum alloys include 1050, 1100, and 3003.

  The aluminum support used in the present invention is rolled by a known method. That is, an aluminum ingot is melted and held to cast a slab, and after a surface cutting step of cutting the impurity structure portion on the surface of the slab with a face mill by 3 to 10 mm, in a soaking furnace, 480 to 540 ° C., 6 to A soaking treatment process is performed for 12 hours, and after that, hot rolling is performed to a thickness of 5 to 40 mm, and then cold rolling is performed to a predetermined thickness at room temperature. Moreover, after annealing for homogenizing the structure and homogenizing the rolled structure, etc., cold rolling is performed to a specified thickness, and correction is performed to obtain a plate with good flatness. The thickness of the support is usually in the range of about 0.13 to 0.50 mm.

  The support used in the present invention is subjected to degreasing treatment, roughening treatment, anodizing treatment, etc., which are usually used in this technical field. At least the roughening treatment and anodizing treatment are performed in this order. Use the support made.

  The aluminum plate used in the present invention is degreased to remove fatty substances from the surface. Degreasing treatment includes solvent degreasing such as trichrene and thinner, emulsion degreasing, acid degreasing, and alkaline degreasing mixed with surfactant, kerosene, triethanolamine and sodium hydroxide.

  The aluminum plate used in the present invention is subjected to a roughening treatment in order to improve the adhesion to the photosensitive layer and improve the water retention. The roughening treatment method includes mechanical treatment, chemical treatment, and electrochemical treatment. These treatments are carried out alone or in combination, but it is particularly preferable to combine mechanical polishing in view of cost. The shape of the surface is generally represented by a roughness meter, and its size is suitably a center line average roughness; Ra value of 0.3 to 1.0 μm.

  A ball grain method, a nylon brush method, a buff polishing method, a blast polishing method, or the like can be used as the mechanical surface roughening treatment. Chemical roughening includes a method of chemically dissolving aluminum with chloride, fluoride or the like.

  The electrochemical roughening treatment method is preferably used because it can finely control the shape and surface roughness of the grain according to the electrolyte composition and electrolysis conditions as compared with other methods. The electrochemical surface roughening treatment can be performed by direct current, alternating current or a combination of both. Examples of the AC wave include a single-phase or three-phase commercial AC, or a sine wave, a rectangular wave, a trapezoidal wave, etc. in the range of 10 to 300 Hz including these.

The electric power supplied to the aluminum plate varies depending on the composition of the electrolytic solution, the temperature, the distance between the electrodes, etc., but in order to obtain a suitable grain for a printing plate, generally 1 to 60 A / dm ² for current and 50 for electric quantity. Used in the range of ~ 4000C. The distance between the electrode and the aluminum plate is preferably in the range of 1 to 10 cm.

  As the electrolytic solution, nitric acid or a salt thereof, hydrochloric acid or a salt thereof, or an aqueous solution of one kind or a mixture of two or more kinds thereof can be used. In addition, sulfuric acid, phosphoric acid, chromic acid, boric acid, organic acids or their salts, ammonium salts, amines, surfactants, other corrosion inhibitors, corrosion accelerators, and stabilizers are added as necessary. You can also

  The concentration of the electrolyte is preferably 0.1 to 10%, and the concentration of aluminum ions in the electrolyte is maintained in the range of 0 to 10 g / L. The temperature of the electrolytic solution is preferably 0 to 60 ° C.

  In the present invention, it is preferable to perform a desmut treatment between the roughening treatment and the anodizing treatment. Desmutting refers to a chemical etching process performed between roughening and anodizing. Desmutting can be performed using an acid or an alkali, but acid treatment is preferred. As the acid, nitric acid, phosphoric acid, chromic acid, sulfuric acid, hydrochloric acid, hydrofluoric acid and the like can be used alone or in combination. As the alkali desmut, sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, tribasic potassium phosphate, sodium aluminate, sodium silicate and the like can be used alone or in combination. In addition, the concentration of the desmut solution and the treatment time must be such that the smut can be completely removed. Since the amount of smut generated depends on the roughening treatment method in the previous stage, the required degree of desmutting depends on the roughening method. However, since the degree of removal of the smut can be easily observed with a scanning microscope, the degree of desmut from which the smut is completely removed can be easily determined by observing the surface of the treated aluminum. Actually, there is a relationship with the treatment of waste liquid, and the total of acid or alkali is about 5 to 40%, and the treatment time is preferably 30 seconds to 2 minutes. The treatment temperature is preferably 40-60 ° C.

  In the present invention, the desmutting step can be divided into two or more times. In this case, it is possible to combine an acid desmut and an alkali desmut, but it is preferable to use the alkali desmut first.

  After performing such roughening treatment and desmut treatment, anodization treatment is performed. As the electrolytic solution for anodic oxidation, sulfuric acid, phosphoric acid, oxalic acid, chromic acid, organic acid (for example, sulfamic acid, benzenesulfonic acid, etc.) or a mixture thereof is preferable, and an acid with low solubility of the generated oxide film is particularly preferable .

Since the anodic oxide film is formed only on the anode, a direct current is usually used. As conditions for anodization, a liquid concentration of 1 to 40%, a current density of 0.1 to 10 A / dm ² , and a voltage of 10 to 100 V are used. The thickness of the anodic oxide film is changed by the current density and time, it is adjusted appropriately by printing grade of the printing plate, 3 g / m ² or less, preferably ^{2.8g / m 2 ~1g / m 2} , more preferably preferably the 2.3g / m ² ~1g / m ² required. The temperature affects the hardness of the anodic oxide film, and the hardness is high at low temperatures, but is inferior in flexibility and is usually processed at a temperature near room temperature. The amount of these anodized films can be measured based on JIS H86807 “film mass method”.

  Further, after the anodizing treatment, a post-treatment can be performed as necessary. As the post-treatment, methods known to those skilled in the art, for example, post-treatment with inorganic salts such as silicate treatment and hydrofluoric zirconate treatment, organic polymer treatment such as gum arabic, polyvinyl phosphonic acid and polyvinyl sulfonic acid, hydration There is a sealing treatment.

  In the present invention, the physical development nuclei may be those used in a known silver complex diffusion transfer method, such as colloids such as gold and silver, metal sulfides obtained by mixing sulfides with water-soluble salts such as palladium and zinc, and the like. Can be used. For details and manufacturing methods thereof, reference can be made to, for example, “Photographic Silver Halide Diffusion Processes”, published by Focal Press, London New York (1972), by Andre Lot and Edith Weide.

As the binder for the physical development nucleus layer in the present invention, hydrophilic polymers such as starch, carboxymethylcellulose, gum arabic, sodium alginate, hydroxyethylcellulose, polystyrenesulfonic acid, sodium polyacrylate, a copolymer of vinylimidazole and acrylamide A copolymer of acrylic acid and acrylamide, a hydrophilic polymer such as polyvinyl alcohol, polyvinyl pyrrolidone, protein, polyvinyl phosphonic acid, or an oligomer thereof, and a hydrophilic polymer described in JP-A-8-21614 can be used. The amount of the binder is preferably 1 mg / m ² or less, more preferably 0.5 mg / m ² or less.

  In the present invention, each physical development nucleus layer may further contain a surfactant, a known development stabilizer, and various salts such as nitrate or nitrite.

  Developers used in the present invention include developing agents such as polyhydroxybenzenes, 3-pyrazolidinones, alkaline substances such as potassium hydroxide, sodium hydroxide, lithium hydroxide, tribasic sodium phosphate, or amine compounds. Fixing agents such as sodium sulfite, thickeners such as carboxymethyl sesulose, antifoggants such as potassium bromide, 1-phenyl-5-mercaptotetrazole, development modifiers such as additives such as polyoxyalkylene compounds, etc. Can be included.

  The pH of the developer is usually about 10 to 14, preferably about 12 to 14, but the pretreatment (for example, anodization) conditions of the aluminum support of the lithographic printing plate used, the photographic element, the desired image, in the developer Depending on the type and amount of various compounds, development conditions and the like.

  In the present invention, the development treatment is followed by a water washing treatment to remove the silver halide emulsion layer, exposing the silver image and the aluminum support which is the non-image area. The washing solution may contain a buffer that buffers the pH in the range of 4-8, preferably 4.5-7, such as phosphate buffer, citrate buffer, or mixtures thereof. Moreover, you may contain a preservative. The washing solution may further contain a proteolytic enzyme (for example, pepsin, rennin, trypsin, chymotrypsin, cathepsin, papain, ficin, thrombin, renin, collagenase, bromelain, bacterial proteinase) and the lipophilic agent described above. it can.

  Between the development process and the water washing process, a neutralization stabilization process for stopping the progress of development may be performed, or the oleophilic agent may be contained in the neutralization solution.

  The above washing solution is used to completely remove the silver halide emulsion layer on the aluminum support, and is a method of spraying a washing solution of 25 to 35 ° C. by a jet method or an emulsion layer with a scrub roller while blowing the washing solution. The method of peeling is generally used.

  The silver image portion and the non-image portion exposed by the water washing treatment are treated with a finishing solution in order to increase the lipophilicity and hydrophilicity of each and to protect the plate surface. In the present invention, the finishing solution contains arabic gum, dextrin, sodium alginate, propylene glycol ester of alginic acid, hydroxyethyl starch, carboxymethylcellulose, hydroxyethylcellulose, polyvinyl for the purpose of protecting the anodized layer in the non-image area and improving hydrophilicity. It is preferable to contain protective colloids such as pyrrolidone, polystyrene sulfonic acid, and polyvinyl alcohol. Further, in order to further improve the lipophilicity of the image area, it is preferable to contain the oleophilic agent. Further, the enzyme can be contained.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. In addition,% shows the mass% unless there is a notice.

A 1050 aluminum plate is degreased with a 4% aqueous sodium hydroxide solution at 50 ° C. for 1 minute, washed with water, then polished with a rotating nylon brush using a 400 mesh pumiston suspension, and a 2.5% aqueous hydrochloric acid solution. Electrolytic surface roughening treatment was performed for 60 seconds at an AC density of 50 A / dm ² at 20 ° C., and desmutted with 20% phosphoric acid at 50 ° C. for 1 minute. Thereafter, an anodization treatment was performed in a 25% sulfuric acid solution at a temperature of 20 ° C., a current density of 3 A / dm ² , and a treatment time of 45 seconds to prepare an aluminum support. Subsequently, an aqueous sodium thiosulfate solution and an aqueous palladium chloride solution were mixed at 40 ° C. for 5 minutes to prepare a palladium sulfide colloid solution, which was applied to an aluminum support so that the amount of palladium sulfide was 0.5 mg / m ^2. An aluminum support coated with development nuclei was prepared.

  The silver halide emulsion was prepared by using alkali-processed gelatin as a protective colloid, and using a control double jet method doped with 0.006 mmol of potassium hexachloroiridium (III) per mol of silver having an average particle size of 0.3 μm. A silver chloroiodobromide emulsion of 84.8 mol% silver, 15 mol% silver bromide, and 0.2 mol% silver iodide was prepared. The emulsion was then flocculated and washed. The emulsion was further subjected to gold-sulfur sensitization, 1-phenyl-5-mercaptotetrazole was added, and then a red-sensitive sensitizing dye represented by Chemical Formula 1 was added in various amounts as shown in Table 1, Sensitized.

The obtained silver halide emulsion was coated on an aluminum support coated with a physical development nucleus layer and dried on a slot coater so that the coating amount was 3.0 g / m ² as AgX in terms of silver nitrate. Created a version. Each lithographic printing plate was subjected to 50 micron negative-positive line image exposure with an image setter (equipped with a red LD laser with a SDP-α2400 wavelength of 633 nm manufactured by Mitsubishi Paper Industries). Next, it was processed with a plate making processor (P-α880 manufactured by Mitsubishi Paper Industries Co., Ltd.) with a developer immersion time of 10 seconds. The plate-making processor consists of a development process (22 ° C.), a washing process (washing off the emulsion layer with a scrub roller while showering 35 ° C. washing water), a finishing process (21 ° C., shower) and a drying process. It is composed of The washing process is a closed type in which 20 L of washing water stored in a storage tank is circulated with a pump, showered onto a planographic printing plate, filtered through a filtration filter, collected in a storage tank, and reused. .

The composition of the developer, washing solution and finishing solution used is as follows.
<Developer>
Sodium hydroxide 20g
Hydroquinone 20g
1-phenyl-3-pyrazolidinone 2g
80 g of anhydrous sodium sulfite
Sodium thiosulfate 5g
N-methylethanolamine 6g
Ethylenediaminetetraacetic acid sodium salt 5g
Bring to 1000 mL with deionized water.
pH (25 ° C.) = 13.4

<Washing liquid>
2-mercapto-5-nheptyloxanediol 0.5 g
Triethanolamine 13g
Sodium bisulfite 10g
40g potassium dihydrogen phosphate
Proteolytic enzyme 1g
Add water to adjust total volume to 1000cc. The pH was adjusted to 6.0.
Bioprolase AL-15 (bacterial proteinase, manufactured by Nagase Sangyo Co., Ltd.) was used as a proteolytic enzyme.

<Finishing liquid>
Arabic gum 10g
Phosphoric acid 0.5g
Sodium nitrate 20g
Polyethylene glycol # 400 100g
2-mercapto-5-nheptyloxanediol 0.5 g
Bring to 1000 mL with deionized water.
The pH was adjusted to 6.5 with sodium hydroxide.

  Table 1 shows the relative sensitivity of each silver halide emulsion when the sensitivity is the reciprocal of the amount of light with which the negative and positive lines have the same thickness in the obtained image and the sensitivity of the silver halide emulsion A is 100%. .

After adding benzotriazole to the obtained silver halide emulsion as shown in Table 2 and coating it as a lower emulsion layer on an aluminum support coated with physical development nuclei, the upper emulsion layer without adding benzotriazole as shown in Table 2 Was applied. The coating amount of the lower emulsion and the upper emulsion was set to 3 g / m ² in total in terms of silver nitrate as the coating silver amount.

  The lithographic printing plate thus obtained is subjected to image exposure at 2400 dpi and 175 lpi with an image setter SDP-α2400 (manufactured by Mitsubishi Paper Industries) whose light source is a red semiconductor laser, and then a plate-making processor (P -Α880) for a processing time of 10 seconds to produce a lithographic printing plate.

  The planographic printing plate prepared in this way was printed with a printing machine Sprint 226 (manufactured by Comorico Corporation). The ink is GEOS G Cyan H type (Dainippon Ink Co., Ltd.) for printing durability test, High Unity soy gold red M (T & K Co.) for stain test, and Astro Mark 3 (Japan) A 2% aqueous solution of Kenken) was used.

  Table 3 shows the printing results. Printing durability was printed, 50 micron fine line images were faded, and the number of changes such as dropout was printed. Dirt was printed after 3000 sheets x. What was attached was △, and what was hardly adhered was made ○.

  From Table 3, it can be seen that the planographic printing plate of the present invention is excellent in printing durability and stain resistance.

The same procedure as in Example 1 was carried out except that 15 mg / m ² of the compound in Table 4 was used instead of benzotriazole, the lower emulsion was C emulsion, the upper emulsion was A emulsion, and the silver ratio of C emulsion was 5%. . As a result, as shown in Table 4, the planographic printing plate of the present invention was excellent in printing durability and stain resistance.

Claims (1)

A silver halide emulsion layer closest to the aluminum support having a physical development nucleus layer on the roughened and anodized aluminum support and further having at least two silver halide emulsion layers thereon; The silver halide emulsion layer having a sensitivity lower than that of the next silver halide emulsion layer and closest to the aluminum silver support contains a compound containing at least one of a nitrogen-containing heterocyclic ring and a mercapto group. A lithographic printing plate featuring.