JP2009175465A - Lithographic printing plate - Google Patents

Abstract

The present invention provides a lithographic printing plate having a small sensitivity difference depending on the portion of the plate surface of the lithographic printing plate after long-term storage, good storage stability, and good printing image quality.
A lithographic printing plate having at least an undercoat layer, a silver halide emulsion layer and a physical development nucleus layer in this order on one side of a support, and at least one of the layers having the silver halide emulsion layer. In a lithographic printing plate containing a developing agent in one layer and having a backing layer on the other surface of the support, the backing layer contains an inorganic porous compound having pores of less than 2 nm. Lithographic printing plate to do.
[Selection figure] None

Description

  The present invention relates to a lithographic printing plate to which a silver complex diffusion transfer method is applied.

  A lithographic printing plate using a silver complex diffusion transfer method (DTR method), particularly a lithographic printing plate having a physical development nucleus layer on a silver halide emulsion layer is disclosed in, for example, US Pat. No. 3,728,114, US Pat. No. 4,134,769, US Pat. No. 4,160,670, US Pat. No. 4,336,321, US Pat. No. 4,501,811, US Patent The exposed silver halide crystals described in US Pat. No. 4,510,228, US Pat. No. 4,621,041 and the like cause chemical development by DTR development to form black silver and become hydrophilic. On the other hand, unexposed silver halide crystals form a silver salt complex by the silver salt complexing agent in the developer and diffuse to the physical development nucleus layer on the surface due to the presence of nuclei. Ink-receptive physical development silver Forming the image areas of the body.

  DTR development includes a developer type in which a developing agent is added to a processing solution, and an activator type in which a developing agent is added to at least one layer on the side of a lithographic printing plate having a silver halide emulsion layer, and the developing agent is not contained in the solution. However, the activator type is mainly used because of its good storage stability and suitability for running processing. For example, it is described in JP-A-11-295898.

  In the lithographic printing plate, paper, plastic film, and composite materials thereof are generally used as a support, and the back is used for the purpose of improving transportability, antistatic property, and curling property in a plate making apparatus (exposure machine, processor). A coating layer is provided. In order to maintain the curl balance with the hydrophilic colloid binder on the side having the silver halide emulsion layer, these backing layers use approximately the same amount of binder as the silver halide emulsion layer surface.

  In particular, a printing plate using paper or a plastic resin film as a support is inferior in rigidity and plate elongation resistance to an aluminum printing plate, and thus various problems occur in printing on a printing press. In order to improve the registration accuracy at the time of printing, JP-A-11-91256 and JP-A-11-105446 (Patent Documents 1 and 2) describe lithographic printing using a matting agent having a large particle size for the backing layer. There has been proposed a lithographic printing plate using a plate or a backing layer having a large center line roughness Ra. However, when a lithographic printing plate using a backing layer having a large particle size or Ra of the matting agent as described above is used, the developing agent on the photosensitive surface side is transferred to the backing layer, so that the storage stability is lowered. there were.

Japanese Patent Application Laid-Open No. 2000-214589 (Patent Document 3) proposes a DTR lithographic printing plate using a backing layer containing a polymer latex and having a small decrease in sensitivity and printing durability after storage. However, although the DTR lithographic printing plate containing the polymer latex in the above-mentioned backing layer can suppress a decrease in sensitivity and printing durability after storage over time, a difference in sensitivity occurs depending on the portion of the plate surface of the lithographic printing plate over time. There was a problem. Usually, a DTR lithographic printing plate having a support such as paper or a plastic resin film is shipped in a state in which the width is adjusted to the size of the plate making apparatus and wound on a roll. At the time of shipment, there is no difference in sensitivity that causes a practical problem in the width direction of the roll and in the lower winding portion and the upper winding portion of the roll. However, when a backing layer having the above polymer latex is used, the DTR lithographic printing plate stored for a long period of time, particularly at a high temperature or high humidity for a long period of time, has a center portion and both end portions in the width direction of the roll. Or it turned out that a sensitivity difference generate | occur | produces by the upper winding part and lower winding part of a roll. For this reason, uniform plate-making images cannot be obtained at both ends and the center of the plate-making product, or the sensitivity varies during plate-making, resulting in a decrease in reproducibility of fine line images and highlights of color prints, and the print image quality. There was a problem that decreased.
JP-A-11-91256 JP-A-11-105446 JP 2000-214589 A

  Provided is a lithographic printing plate with little difference in sensitivity depending on the portion of the plate surface of the lithographic printing plate after long-term storage, good storage stability, and good printing image quality.

  The above problem is a lithographic printing plate having at least an undercoat layer, a silver halide emulsion layer and a physical development nucleus layer in this order on one side of a support, and at least one of the layers having the silver halide emulsion layer. A lithographic printing plate containing a developing agent in a layer and having a backing layer on the other side of the support, wherein the backing layer contains an inorganic porous compound having pores of less than 2 nm Achieved by lithographic printing plate.

  Even after long-term storage, a lithographic printing plate with little sensitivity difference depending on the part of the plate surface, good storage stability and good printing image quality can be obtained.

  The present invention is a lithographic printing plate having at least an undercoat layer, a silver halide emulsion layer and a physical development nucleus layer in this order on one side of a support, and at least one layer on the side having a silver halide emulsion layer In a lithographic printing plate containing a developing agent in the substrate and having a backing layer on the other side of the support, the backing layer contains an inorganic porous compound having pores of less than 2 nm in the backing layer. A lithographic printing plate for silver diffusion transfer. The backing layer is composed of a binder and a matting agent, and the inorganic porous compound having pores of less than 2 nm is used as part or all of the matting agent.

  Conventionally, the non-porous hydrophilic metal oxide fine particles such as colloidal silica and the hydrophilic metal oxide fine particles (primary particles) are aggregated in the backing layer of the lithographic printing plate using the silver complex diffusion transfer method. Hydrophilic metal oxide fine particles such as silica matting agent, which are fine particle aggregates (secondary particles), have been used. However, not only moisture but also the developing agent permeates and permeates through the gaps between the colloidal silica particles and the primary particles of the silica matting agent. As a result, when the lithographic printing plate is stored over time, the backing layer is formed from the silver halide emulsion layer side. As a result of the transfer of the developing agent to the side, the amount of the developing agent that contributes to the development is reduced, so that there is a problem that sensitivity and storage stability are lowered. In JP-A-2000-214589 (Patent Document 3), as a result of the transfer of the developing agent from the silver halide emulsion layer side to the adjacent back surface being suppressed by the backing layer containing a polymer latex, the storage stability is improved. However, as described above, there is a problem that a difference in sensitivity occurs depending on the portion of the plate surface after storage. A polymer latex is used to suppress the penetration and permeation of the developing agent into the gap between the conventional hydrophilic metal oxide fine particles and the gap between the primary particles of the silica matting agent. The present inventor has found that the polymer latex suppresses not only the transfer of the developing agent but also the penetration of moisture, and as a result, the moisture is locally confined in the hydrophilic colloid layer on the silver halide emulsion layer side, so that the sensitivity of the plate surface is increased. Based on the hypothesis that a difference may have occurred, the present inventors have sought a method for suppressing the transfer of the developing agent without suppressing the penetration of moisture, and led to the present invention.

  Colloidal silica that has been used for the backing layer has been non-porous and the surface is hydrophilic, but it does not exhibit water permeability by itself. It passes through the gap between the particles, and not only moisture but also the developing agent passes through the gap. In addition, the pores of the silica matting agent formed by the aggregation of primary particles originate from the gaps between the primary particles, have a wide pore distribution in the range of 3 to 50 nm, and have pores of substantially less than 2 nm. Therefore, the pores of the silica matting agent pass not only moisture but also the developing agent. Here, substantially having no pores of less than 2 nm means that the presence of pores of less than 2 nm cannot be confirmed in pore distribution measurement using the molecular probe method described later.

  The inorganic porous compound contained in the backing layer of the present invention has a three-dimensional network structure composed of pores of less than 2 nm that allow water molecules to pass through the pores but not a developing agent such as hydroquinone. It is a porous compound. By using the porous compound in the backing layer, the silver halide emulsion layer side can be used without suppressing moisture permeation between the silver halide emulsion layer side and the backing layer side during storage over time even by using a polymer latex. From the developing agent to the side of the undercoat layer can be suppressed.

Preferred inorganic porous compounds having pores of less than 2 nm of the present invention include zeolite and similar compounds. Zeolite is expressed in a general term for crystalline aluminosilicates general formula _{M 2 / n O · Al 2} O 3 · xSiO 2 · yH 2 O, can be used as a natural and synthetic zeolites various. Here, n represents the valence of the cation M, x represents an integer of 2 or more, and y represents an integer of 0 or more. Zeolites generally tetrahedral structure TO ₄ (SiO ₄ and AlO ₄ ^-, etc.) is 4, 6, 8 or 12 connected to share O atoms vertices, 4-membered ring, 6-membered ring, 8-membered ring, A 12-membered ring, a 4-membered double ring in which these 4, 6, 8, 12-membered rings are overlapped each other, a 6-membered double ring, an 8-membered double ring, a 12-membered double ring, etc. It has a three-dimensional network skeleton structure in which pores of 3 to 1.3 nm are continuously connected in three dimensions, and can be exchanged with the skeleton structure basically maintained (exchangeable cation, skeleton). It is characterized by the presence of water molecules that can adsorb and desorb. Since AlO ₄ ⁻ has a negative charge, the electrical neutrality is maintained by the cation M. As the cation, proton, calcium, strontium, barium, sodium, copper, silver, cobalt, nickel, manganese and the like are preferably used. Zeolite-like compounds that do not contain exchangeable cations such as IIB to VB group elements such as P and Ga, and AlPO ₄ can also be used instead of Si and Al of T atom. The pore shapes of various zeolites and zeolite-like compounds have been examined in detail by X-ray diffraction method. You can refer to

As a representative example of the inorganic porous compound having pores of less than 2 nm according to the present invention, zeolite A represented by the composition of Na ₁₂ (Al ₁₂ Si ₁₂ O ₄₈ ) · 27H ₂ O from Union Carbide, Na ₈₆ ( Zeolite X represented by the composition of Al ₈₆ Si ₁₀₆ O ₃₈₄ ) · 264H ₂ O, Zeolite Y represented by the composition of Na ₅₆ (Al ₅₆ Si ₁₃₆ O ₃₈₄ ) · 250H ₂ O, K ₉ (Al ₉ Si ₂₇ Zeolite L represented by a composition of O ₇₂ ) · 22H ₂ O and having a pore diameter of 0.71 nm, Na _n (Al _n Si _96-n O ₁₉₂ ) · 16H ₂ O (where n <27) Zeolite ZSM-5 represented by the composition of the above, synthetic zeolite such as zeolite VSI-5 represented by the composition of Al ₁₈ P ₁₈ O ₇₂ · 42H ₂ O, K ₂ Ca _1.5 Na (Al ₆ Si ₁₀ O ₃₂ ). Philippines represented by a composition of 12H ₂ O _{Pusaito, K 4 Na 4 (Al 8} Si 8 O 32) · 10H 2 O Ami sites represented by a composition of, in the composition of _{Na 2 K 2 Mg 0.5 Ca 2} (Al 9 Si 27 O 72) · 27H 2 O Erionite represented, an anthracite represented by a composition of Na ₁₆ (Al ₁₆ Si ₃₂ O ₉₆ ) · 16H ₂ O, an offretite represented by a composition of KCa ₂ (Al ₅ Si ₁₃ O ₃₆ ) · 15H ₂ O, Biquitite represented by the composition of Li ₂ (Al ₂ Si ₄ O ₁₂ ) · 2H ₂ O, mordenite represented by the composition of Na ₈ (Al ₈ Si ₄₀ O ₉₆ ) · 24H ₂ O, Na _1.5 Mg ₂ (Al _5.5 natural zeolite such as ferrierite represented by the composition of Si _30.5 O ₇₂ ) · 18H ₂ O.

  In the present invention, the pore diameter of less than 2 nm refers to the pore diameter measured by the molecular probe method (MP method) described in JP-A-2007-216118. In the MP method, it is difficult to adsorb an adsorbed molecule having a molecular size larger than the pore size because it does not easily enter the pore. Therefore, the adsorption isotherm is measured using several kinds of gases having different molecular sizes. The pore size distribution is measured from the pore volume, and can be determined, for example, by measurement using a specific surface area / pore distribution measuring device Asap 2020 series manufactured by Shimadzu Corporation.

  The particle size of the inorganic porous compound having pores of less than 2 nm contained in the backing layer of the lithographic printing plate of the present invention can be 10 nm to 10 μm, preferably 50 nm to 5 μm. It is a range. The particle size can be measured using a laser diffraction / scattering particle size distribution measuring apparatus, for example, LA920 manufactured by Horiba, Ltd.

The preferred content of the inorganic porous compound having pores of less than 2 nm contained in the backcoat layer of the planographic printing plate of the present invention is 0.05 to 3.0 g / m ² , preferably 0.1 to 1.5 g. / M ² range.

The backing layer of the lithographic printing plate of the present invention has a hydrophilic colloid as a binder, such as gelatin, starch, dextrin, albumin, sodium alginate, hydroxyethyl cellulose, gum arabic, polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, polyacrylamide, styrene. -Maleic anhydride copolymer, polyvinyl methyl ether-maleic anhydride copolymer, polymer latex described in JP-A No. 2000-214589, and the like can be used. The binder addition amount of the backing layer can be used in the range of 1/100 to 100 parts by mass, preferably 1/20 to 1 part by mass of the inorganic porous compound having pores of less than 2 nm of the present invention. The range is 20 parts by mass. Further, the backing layer contains a hardener. Examples of the hardener include inorganic compounds such as chromium alum, formalin, glyoxal, malealdehyde, aldehydes such as glutaraldehyde, N-methylol compounds such as urea and ethylene urea, mucochloric acid, and 2,3-dihydroxy. Aldehyde equivalents such as -1,4-dioxane, compounds having active halogen such as 2,4-dichloro-6-hydroxy-s-triazine salt and 2,4-dihydroxy-6-chloro-triazine salt, Divinyl sulfone, divinyl ketone, N, N, N-triacroylhexahydrotriazine, compounds having two or more active three-membered ethyleneimino groups and epoxy groups in the molecule, as a polymer hardener One or more of various compounds such as dialdehyde starch can be used. The binder amount in the backing layer is approximately the same as the total binder amount on the photosensitive layer side, and is used in the range of about 0.5 to 8 g / m ² .

  As the matting agent for the backing layer used in the present invention, the inorganic porous compound itself having pores of less than 2 nm can be used alone as the matting agent, and other matting agents can be used in combination. I can do it. Preferable matting agents include silica particles and polymer particles such as polystyrene. Examples of the shape of the matting agent include spherical, amorphous and flat matting agents. The average particle size of the matting agent is about 0.1 to 10 μm, preferably about 0.3 to 7 μm. The addition amount of the matting agent is in the range of 0 to 40 parts by mass, preferably 0 to 20 parts by mass with respect to 100 parts by mass of the inorganic porous compound having pores of less than 2 nm.

  The lithographic printing plate of the present invention has an undercoat layer that also serves to prevent halation, a silver halide emulsion layer, and a physical development nucleus layer in this order on a support. The developing agent is contained in a constituent layer on the photosensitive surface side having a silver halide emulsion layer, that is, a silver halide emulsion layer, a physical development nucleus layer and / or an undercoat layer. The amount of the developing agent contained on the photosensitive surface side is an amount necessary for development with an alkaline activating solution (developing solution) that does not substantially contain the developing agent. The content of the developing agent varies depending on the silver halide composition and silver content of the planographic printing plate, the type of physical development nuclei, the pH of the developing solution, the processing conditions such as the temperature, the type of developing agent, etc. Therefore, it is necessary to adjust appropriately.

  As the developing agent, hydroquinone, catechol, chlorohydroquinone, pyrogallol, isopropylhydroquinone, methylhydroquinone and other dihydroxybenzene developing agents, 1-phenyl-3-pyrazolidone, 1-phenyl-4,4-dimethyl-3-pyrazolidone, Examples thereof include pyrazolidones such as 1-phenyl-4,4-dihydroxymethyl-3-pyrazolidone and aminophenols such as paraaminophenol and metol.

In the present invention, it is preferable to contain hydroquinone as a developing agent in the physical development nucleus layer, and the content is suitably in the range of 0.4 to ² g / m ² . Furthermore, it is preferable to use the aforementioned pyrazolidones or aminophenols in combination. Furthermore, it is preferable that the silver halide emulsion layer and / or the undercoat layer contain the pyrazolidone. A preferred combination of developing agents on the photosensitive surface side is to use pyrazolidones in combination in the range of 1/20 to 1/2 part by mass with respect to 1 part by mass of hydroquinone.

Amount of binder in the undercoat layer used in the present invention is preferably in the 0.5 to 8 g / m ^2, more preferably 1 to 5 g / m ^2. The undercoat layer can also contain solid powders (for example, silica particles) having an average particle diameter of 0.1 to 10 μm and further photographic additives such as developing agents to improve printing resistance. As described above, since the undercoat layer also serves as an antihalation layer, it contains carbon black, a coloring dye, or other coloring pigment.

  Any silver halide emulsion layer known in the art can be used, and preferred examples include a high-sensitivity silver halide photosensitive material and an emulsion layer used for a high-speed rapid processing silver halide photosensitive material.

  The silver halide crystals contained in the silver halide emulsion layer are composed of, for example, silver chloride, silver bromide, silver chlorobromide, and crystals containing silver iodide. The silver halide crystal may contain a heavy metal salt such as rhodium salt, iridium salt, palladium salt, ruthenium salt, nickel salt, platinum salt, etc. There is no particular limitation on the crystal form of silver halide, and cubic to 14 It may be a face particle, a core-shell type, or a tabular particle. The silver halide crystals may be either monodispersed or polydispersed crystals, and the average grain size is preferably in the range of 0.2 to 0.8 μm. As a preferred example, monodispersed or polydispersed crystals containing 70% by mole or more of silver chloride containing rhodium salt or iridium salt or both can be used.

  A silver halide emulsion can be sensitized in various ways as it is produced or coated. For example, it is preferable to chemically sensitize with sodium thiosulfate, alkylthiourea, or with a gold compound such as rhodium gold, gold chloride, or a combination of both of these methods well known in the art. The silver halide emulsion can be sensitized with a dye such as cyanine or merocyanine.

The surface layer present on top of the silver halide emulsion layer contains physical development nuclei. Physical development nuclei include metal colloidal fine particles such as silver, antimony, bismuth, cadmium, cobalt, lead, nickel, palladium, rhodium, gold, platinum, sulfides, polysulfides, selenides of these metals, or their It may be a mixture or a mixed crystal. The coating amount of physical development nuclei is in the range of 1 to 100 mg / m ^2. The physical development nuclei may or may not contain a hydrophilic binder, but gelatin, starch, dialdehyde starch, carboxymethylcellulose, gum arabic, sodium alginate, hydroxyethylcellulose, polystyrene sulfonic acid, vinyl imidazole and acrylamide It can contain a hydrophilic polymer such as a coalescence or polyvinyl alcohol or its oligomer, and its content is preferably less than 0.5 g / m ² . Further, the physical development nucleus layer may contain a developing agent such as hydroquinone, methylhydroquinone and catechol, and a known hardening agent such as formalin and dichloro-s-triazine.

  The undercoat layer, silver halide emulsion layer, and physical development nucleus layer described above can be hardened with a gelatin hardener. Examples of gelatin hardeners include inorganic compounds such as chromium alum, formalin, glyoxal, malealdehyde, aldehydes such as glutaraldehyde, N-methylol compounds such as urea and ethylene urea, mucochloric acid, 2,3- Aldehyde equivalents such as dihydroxy-1,4-dioxane, compounds having an active halogen such as 2,4-dichloro-6-hydroxy-s-triazine salt and 2,4-dihydroxy-6-chloro-triazine salt, Compounds having two or more divinyl sulfone, divinyl ketone, 1,3,5-triacroylhexahydro-1,3,5-triazine, an active three-membered ethyleneimino group or epoxy group in the molecule, One or more of various compounds such as dialdehyde starch as a polymer hardener can be used. .

  Hardeners can be added to all layers, or only to some or one layer. Of course, the diffusible hardener can be added to only one layer when two or more layers are applied simultaneously. The addition method can be added at the time of emulsion production or in-line at the time of coating.

  The development processing solution used in the present invention is preferably an alkaline activation processing solution that does not substantially contain a developing agent. The pH of the developer is suitably in the range of 12 to 14, and contains sodium hydroxide, potassium hydroxide, lithium hydroxide, trisodium phosphate and the like as an alkaline agent. In addition, preservatives such as sulfites, thiosulfates, thiocyanates, cyclic imides, 2-mercaptobenzoic acid, alkanolamines, meso ions, thioethers and other silver halide solvents, hydroxyethylcellulose, carboxymethylcellulose and other viscous Development inhibitors such as an antifoggant, a polyoxyalkylene compound and an onium compound described in JP-A-47-262201. Further, the developing solution may be a compound or the like that improves ink transfer on the surface silver layer as described in US Pat. No. 3,776,728.

  The surface silver layer after development of the lithographic printing plate of the present invention can be converted to ink acceptability or improved by any known surface treating agent. The printing method, or the desensitizing liquid or moisture absorbing liquid to be used can be applied by a generally well-known method.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but it is needless to say that the present invention is not limited by this description.

On one side of an underdrawn polyethylene terephthalate film having a thickness of 175 μm, 3 g / m ^{2 of} gelatin, 0.6 g / m ^{2 of} styrene-butadiene latex PA 9281 (solid content 48% by mass) manufactured by Japan A & L Co., 2 nm of the present invention A backing layer containing an inorganic porous compound or / and matting agent having less than pores, a hardener (2,4-dichloro-6-hydroxy-s-triazine sodium) and a surfactant was applied. Table 1 shows the types of inorganic porous compounds having pores of less than 2 nm used, the particle diameter, the pore diameter, the pore volume, the addition amount, the particle diameter of the matting agent, and the addition amount. The particle size is measured using a laser diffraction / scattering particle size distribution analyzer LA920 manufactured by Horiba, Ltd., and the pore diameter and pore volume are measured using a molecular probe method (MP method) manufactured by Shimadzu Corporation. The specific surface area / pore distribution measuring apparatus Asap 2020 was used. The DA method (MM Dubinin, VA Astakhov, Adv. Chem. Series, 102, 69 (1970)) was used to calculate the pore volume.

  The inorganic porous compound contained in the backing layer of Comparative Example 1 is mesoporous silica synthesized by the following method based on the method described in Example 3 of JP-A-2000-79756.

(Synthesis of mesoporous silica of Comparative Example 1)
As a template, 1 part by mass of hexadecylamine was added and dissolved in 8 parts by mass of ethanol, and then 4 parts by mass of tetraethoxysilane was added with stirring. This mixture was left to react at 20 ° C. for 24 hours. The obtained composite was filtered, washed with water, and then air-dried for 48 hours to obtain a composite powder of silica and template. The obtained white powder was dispersed in 100 parts by mass of ethanol and stirred at 60 ° C. for 30 minutes, and then filtered, and 100 parts by mass of ethanol was added and washed from the top. This operation was repeated twice, followed by drying at 70 ° C. for 24 hours and pulverization with a wet ball mill to obtain a powder sample having an average particle diameter of 2 μm. When the pore distribution and pore volume were determined by the molecular probe method (MP method) using the specific surface area / pore distribution measuring device Asap 2020 manufactured by Shimadzu Corporation in the same manner as in Example 1, the pore diameter was 2 .8 nm and the pore volume were 1.26 g / m ² , and pores of less than 2 nm were not detected.

For the backing layer of Comparative Example 2, Silicia 310 manufactured by Fuji Silysia Chemical was used as a silica matting agent. This is secondary agglomerated silica particles having an average particle diameter of 2 μm and having no pores of less than 2 nm formed by agglomeration of primary particles of several nm. When the pore distribution and pore volume were determined by the molecular probe method (MP method) using the specific surface area / pore distribution measuring device Asap 2020 manufactured by Shimadzu Corporation in the same manner as in Example 1, the pore size and pore volume were determined to be smaller than 2 nm. No holes were detected. In addition, after the adsorption and desorption isotherm of nitrogen was measured using the above Asap 2020, the BJH method (Barett-Joyner-Halenda method, J. Am. Chem. Soc., 73, 373 (1951)) was used. When the pore distribution and pore volume were determined, it had a wide distribution in the range of 3 to 50 nm (average pore diameter of 21 nm), and the pore volume in the range of 3 to 50 nm was 2.6 g / m ² .

Carbon black 0.3 g / m ² and silica matting agent having an average particle size of 3.5 μm (Silicia 445 manufactured by Fuji Silysia Chemical) 0.9 g / m ² are included on the opposite surface of the support provided with the above-mentioned backing layer. A high-sensitivity silver chloride emulsion (gelatin 0) having an undercoat layer (gelatin 3.5 g / m ² ) and long wavelength sensitization (600 nm to 700 nm) having 1-phenyl-3-pyrazolidone 0.1 g / m ² thereon. .8g / m including ²⁾ so that 1.0 g / m ² as silver nitrate, was performed a two-layer simultaneous coating. As the hardener, 2,4-dichloro-6-hydroxy-s-triazine sodium was contained in the undercoat layer at 170 mg / m ² , and the emulsion layer was contained at 80 mg / m ^{2 in} N-methylolethyleneurea. After drying, after heating at 40 ° C. for 5 days, the core coating solution described in JP-A-8-21614, Example 1 (using the polymer of P-2) is applied, dried, cut, and finished. The lithographic printing plate was wound around a plastic core having an outer diameter of 165 mm to prepare a lithographic printing plate having a roll specification having a width of 750 mm and a length of 31 m.

  The lithographic printing plate was forcibly heated at 50 ° C. and 60% RH (relative humidity) for 2 weeks. The fresh (unheated) lithographic printing plate and the forcedly heated lithographic printing plate were each made with a red LD output machine FREDIA (exposure wavelength: 660 nm, exposure method: internal drum) manufactured by Mitsubishi Paper Industries Co., Ltd. For exposure, a 175 lpi dot image is output at 2540 dpi, developed by a built-in processor with a silver complex salt diffusion transfer developer of the following composition at 30 ° C. for 20 seconds, neutralized with a neutralizing solution of the following composition for 20 seconds, and a dryer. And dried a plate of 750 mm (width) × 680 mm (length) to make 45 plates.

<Transfer developer>
Water 700 parts by mass Potassium hydroxide 20 parts by mass Anhydrous sodium sulfite 50 parts by mass 2-Mercaptobenzoic acid 1.5 parts by mass 2-Aminoethylaminoethanol 15 parts by mass Water to make 1000 parts by mass.

<Neutralizing solution>
Water 600 parts by weight Citric acid 10 parts by weight Sodium citrate 35 parts by weight Colloidal silica (20% by weight liquid) 5 parts by weight Ethylene glycol 5 parts by weight Add water to make 1000 parts by weight.

<Evaluation of sensitivity>
The sensitivity of four points of the above-mentioned fresh and heated chronographic lithographic printing plates in the upper winding center, upper winding end, lower winding central, and lower winding end was determined. Sensitivity is represented by the reciprocal (relative value) of the laser power value when the dot sizes of 5% and 95% are the same, and the sensitivity at the center of the upper part of the planographic printing plate of Comparative Example 2 is 100. The relative sensitivity was expressed as an average value. Here, the upper winding center portion, upper winding end portion, lower winding center portion, and lower winding end portion of the lithographic printing plate represent the following portions, respectively. The results are shown in Table 2.
Upper winding center: part 375 mm inside from both ends of the first to fifth plates Upper winding end: part 50 mm inside from both ends of the first to fifth plates Lower winding central part: partial lower winding end 375 mm inside from both ends of the 40th to 45th plates Part: 50mm inner part from both ends of 40th to 45th plates

<Evaluation of image reproducibility>
The rolls of the upper and lower rolls are printed at the laser power values when the size of the halftone dots of 5% and 95% are the same in the center of the upper roll of each of the roll-shaped lithographic printing plates. Made a plate. Here, the upper winding portion and the lower winding portion refer to the 1st to 5th and 40th to 45th plates, respectively. The lithographic printing plate was mounted on an offset printing machine Lithlon 26 manufactured by Komori Corporation, and the following oil-sensitizing solution was applied to the entire plate surface, and printing was performed using the following moisturizing solution. Trans-GN (black) manufactured by Dainippon Ink Manufacturing Co., Ltd. was used as the ink, and Pearl Coat A manufactured by Mitsubishi Paper Industries, Ltd. was used as the printing paper.

<Fat Sensitizing Solution>
Water 600 parts by mass Isopropyl alcohol 400 parts by mass Ethylene glycol 50 parts by mass 3-mercapto-4-acetamido-5-n-heptyl-1,2,4-triazole
1 part by mass

<Moisturizing liquid>
o-phosphoric acid 5 parts by mass Nickel nitrate 2.5 parts by mass Sodium nitrite 2.5 parts by mass Ethylene glycol 50 parts by mass Colloidal silica (20 mass% liquid) Add 14 parts by mass water to make 1000 parts by mass.

  The halftone dot area ratios on the printed matter with 5% halftone dots at the upper winding center, upper winding edge, lower winding middle, and lower winding edge of each lithographic printing plate were measured. Table 2 shows the average dot area ratio.

  From the results shown in Table 2, the planographic printing plate of the present invention containing an inorganic porous compound having pores of less than 2 nm in the backing layer is sensitive to changes in sensitivity after forced heating and sensitivity of the plate surface after forced heating. It can be seen that there is little difference between the two, and the halftone dot reproducibility is uniform over the entire plate surface.

Claims (1)

  A lithographic printing plate having at least an undercoat layer, a silver halide emulsion layer, and a physical development nucleus layer in this order on one side of the support, and developing on at least one of the layers having the silver halide emulsion layer A lithographic printing plate containing an active ingredient and having a backing layer on the other side of the support, wherein the backing layer contains an inorganic porous compound having pores of less than 2 nm .