JP2549779B2 - Planographic printing plate for back baking - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing plate for back printing, to which a silver complex salt diffusion transfer method is applied.

[0002]

2. Description of the Related Art A lithographic printing plate is composed of an oleophilic image-forming portion that accepts oil-based ink and an oil-repellent non-image-forming portion that does not receive ink. It is composed of sex parts. In ordinary lithographic printing, both water and ink are supplied to the plate surface, the image area selectively receives the coloring ink, and the non-image area selectively receives water, and the ink on the image area, such as paper Printing is performed by transferring it to a printing medium.

Therefore, in order to obtain a good printed matter, the difference in lipophilicity and hydrophilicity between the image area and the non-image area is sufficiently large, and the image area is sufficient when water and ink are supplied to the plate surface. It is necessary to accept a certain amount of ink and not to accept ink in the non-image area.

A lithographic printing plate using a silver complex salt diffusion transfer method (DTR method), particularly a lithographic printing plate having a physical development nucleus layer on a silver halide emulsion layer is described in, for example, US Pat. No. 3,72.
No. 8,114, No. 4,134,769, No. 4,1
No. 60,670, No. 4,336,321, No. 4,
No. 501,811, No. 4,510,228, No. 4,621,041 and the like. The exposed silver halide crystals cause chemical development by DTR development to give a black color. It becomes silver and forms a hydrophilic non-image area, while unexposed silver halide crystals become a silver salt complex by the silver salt complexing agent in the developing solution and diffuse to the physical development nucleus layer on the surface to form nuclei. In the presence of the above, physical development is caused to form an image area mainly composed of ink-receptive physically developed silver.

As described above, in the planographic printing plate, gelatin-
Since the silver image deposited on the physical development nucleus layer on the silver halide emulsion layer is used as the ink-receptive image area, the image area is larger than that of a general lithographic printing plate (eg PS plate). There is a defect that the resistance to mechanical abrasion of the image part is insufficient, the image part is missing, and the ink receiving property of the image part is gradually lost.

In order to overcome this drawback, if the hardness of gelatin is increased or the amount of physical development nuclei is increased, scumming occurs and the printing durability of the lithographic printing plate remarkably decreases.
Further, there are drawbacks such as background stain and deterioration of ink receptivity due to storage for a long period from the production of the lithographic printing plate to the production of the lithographic printing plate, and improvement is desired.

One application of a lithographic printing plate using the silver complex salt diffusion transfer method is in the field of plate making using a commercially available plate making camera having no reversing mirror. Conventionally, a plate making camera installed for a plate making film is used, and a lithographic printing plate for back printing using a silver complex salt diffusion transfer method is used, whereby a direct printing plate can be obtained. In recent years, as typesetting cameras (composer cameras) such as Opticopy have become popular,
The above-mentioned improvement is also demanded for the printability of the lithographic printing plate for back printing.

The effect of the surface irregularities of the lithographic printing plate on the printability is well known in the field of PS plates, but it is also an important factor in the lithographic printing plate using the silver complex salt diffusion transfer method of the present invention. It was revealed. In particular, in a lithographic printing plate using the silver complex salt diffusion transfer method, the non-image area is mainly composed of a gelatin film, and although it is originally highly hydrophilic, it is used to improve the printing durability of the image area. It was general that the agent is designed to have a large matte surface (large unevenness on the surface). Further, in the lithographic printing plate for back printing, a compound that increases the total transmission density of each constituent layer through which light passes when exposed from the back side, such as titanium oxide, is used to reduce printing stains. Even if it is effective, it has a constraint that it cannot be used because it causes a large decrease in sensitivity. The present inventors examined the correlation between the surface matting property and printing stains, and in the present invention, selected the matting agent in the coating layer on the surface side containing the silver halide emulsion layer to carry out the lithographic printing. Plate center line average roughness R
It was found that by specifying the a value, the print stain on the non-image area can be significantly reduced.

Ink / water responsiveness is important for printing,
It is preferable that the responsiveness when changing the ink feed or water feed to set appropriate printing conditions is fast. In particular, in the field of offset rotary presses, in order to prevent paper breakage, etching with dampening water is often omitted at the start of printing,
Ink adheres to the non-image area. Therefore, the desorption speed of the ink is important at the time of rising, and the desorption speed of the ink is required.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithographic printing plate for backing printing using a silver complex salt diffusion transfer method, which has high sensitivity and is excellent in ink / water response and stain resistance. That is.

[0011]

The above object of the present invention is to use a polyester film coated with an organic copolymer and subjected to a hydrophilic treatment as a support, and at least one undercoat layer and a halogen on the support. In a lithographic printing plate for back printing, which comprises a silver halide emulsion layer and physical development nuclei sequentially coated, the total transmission density of each constituent layer through which light passes when exposed from the back side is about 0.
8 or less, containing 0.1 to 2.0 g / m ² of a matting agent in the coating layer on the side including the silver halide emulsion layer,
The undercoat layer contains a latex that is non-swellable with respect to water,
It was achieved by adjusting the center line average roughness Ra value of the planographic printing plate to 1.2 or less.

The matting agent used in the present invention has an average particle size of 1 to 1.
10 micron solid powder, eg silica particles,
Etc. In the present invention, silica particles having an average particle size of 1 to 5 μm are preferable. In particular, silica particles whose surface is treated with hydrogen fluoride have excellent dispersion stability and are preferred.
Specific examples of silica particles include Syloid manufactured by Fuji Divison Chemical Co., Ltd.

In the present invention, the matting agent may be contained in any coating layer on the side containing the silver halide emulsion layer, but it is preferably underneath between the support and the silver halide emulsion layer. It can be contained in the coating layer and / or the silver halide emulsion layer. The amount of the matting agent added varies depending on various conditions, but is in the range of 0.1 g to 2.0 g per 1 m ² .

The non-swelling latex for water used in the present invention is a latex having a low swelling property for water, and must be transparent in a dry film state. If the dried film is not transparent, it cannot be used as a lithographic printing plate for back printing because it is not suitable for back printing. The latex which is not swellable with water according to the present invention can be specified as follows. That is, a test coating solution having the following composition was prepared, and a wet coating amount of 50 g / m ² was applied onto a polyethylene terephthalate film which had been subbed.
A test sample was prepared by coating. As a comparison, a comparative coating solution containing no test latex was prepared and applied in the same manner to prepare a comparative sample.

<Test coating liquid> Gelatin 40 g Test latex (solid content) 20 g Sidoid (grade 308) manufactured by Fuji Davidson Co., Ltd. 6 g Carbon black dispersion liquid (solid content 32%) 8 g Formaldehyde (30% aqueous solution) 2 g Gliogizar (30%) Aqueous solution) 4 g Water is added to make 500 g.

These samples are immersed in 1N caustic soda for 1 minute, and the increase in weight is measured to obtain the amount of liquid absorption. The ratio of the amount of liquid absorbed between the test sample and the comparative sample is taken and called the swelling ratio. The non-swelling latex for water used in the present invention is a latex having a swelling ratio of 1.2 or less, preferably 1.1 or less.

The non-swellable latex used in the present invention includes, for example, styrene / butadiene latex, polybutadiene latex, polystyrene latex, styrene / isoprene latex.
The amount of non-swelling latex added is converted into solid content,
It is in the range of 0.2 to 5.0 g / m ² .

The gelatin film has a swelling property in water and tends to slow the ink / water response. This is a phenomenon that occurs because the dampening water supplied to the plate surface sucks in the dampening water until the gelatin film reaches saturated swelling, so the dampening water does not work effectively on the plate surface. In addition, since dampening water is exchanged between the plate surface and the gelatin film at the same time, if the amount of gelatin is increased, the ink / water responsiveness becomes slower. On the other hand, a latex that is non-swellable with water hardly swells with dampening water, so that the ink / water responsiveness is less likely to be delayed. On the other hand, the thickness of the binder is required to reduce the matteness of the surface, and it is effective to use a latex that does not swell in water instead of gelatin in order to accelerate the ink / water response. It turned out to be

In the present invention, the center line average roughness Ra value of the planographic printing plate can be measured by using a surface roughness profile measuring instrument, for example, Surfcom 500B manufactured by Tokyo Seimitsu Co., Ltd. From the roughness curve, a portion of the measurement length l is extracted in the direction of the center line, and the center line of the extracted portion is the X axis,
When the direction of longitudinal magnification is taken as the Y axis and the roughness curve is represented by y = f (x), the centerline average roughness Ra value is expressed in units of micrometers and can be calculated by the formula (1).
The center line average roughness Ra value referred to in the present invention is a measured value when the stroke length is 2.5 mm.

[0019]

[Equation 1]

In the present invention, the center line average roughness Ra value of the planographic printing plate must be 1.2 or less. When the center line average roughness Ra value of the planographic printing plate is larger than 1.2, printing stains are likely to occur.

In the present invention, it is necessary to adjust the total transmission density of each constituent layer through which light passes when exposing from the back surface to about 0.8 or less. Usually, in a back-printing lithographic printing plate using the silver complex salt diffusion transfer method, the undercoat layer contains a pigment such as carbon black or a dye for the purpose of preventing halation, but the total transmission of each of the above constituent layers is It is necessary to adjust the concentrations of pigments such as carbon black and dyes so that the concentration becomes about 0.8 or less. If the total transmission density of each of the above constituent layers exceeds about 0.8, it becomes difficult to obtain a highly sensitive one.

The mechanism of action of the present invention is presumed as follows. The matting agent added for the purpose of improving printing durability has a tendency to aggregate, which increases the matteness of the surface and makes it easier for ink to accumulate in the recesses on the surface of the non-image area, resulting in printing. Contamination will occur. By reducing the matteness of the surface, ink is less likely to be accumulated in the non-image area, and print stains are less likely to occur. The centerline average roughness Ra value correlates with the matteness of this surface, and this value can specify the range of use of the matting agent.

The lithographic printing plate which is the object of the present invention contains gelatin, and the containing layer may be an undercoat layer, an emulsion layer or a physical development nucleus layer. These gelatin-containing layers can be hardened with a gelatin hardener.
Examples of the gelatin hardener include inorganic compounds such as chromium alum, aldehydes such as formalin, glyoxal, malealdehyde and glutaraldehyde, N-methylol compounds such as urea and ethyleneurea, mucochloric acid, 2,3. Aldehydes such as dihydroxy-1,4-dioxane, 2,4-dichloro-6-hydroxy-
Compounds having an active halogen such as S-triazine salts and 2,4-dihydroxy-6-chloro-S-triazine salts, divinyl sulfone, divinyl ketone and N, N, N
-Triacroylhexahydrotriazine, compounds having two or more active three-membered ethyleneimino groups or epoxy groups in the molecule, one of various compounds such as dialdehyde starch as a polymer hardener, or Two or more kinds can be used.

The hardener can be added to all layers or to some or only one layer.
Of course, in the case of two-layer simultaneous application, the diffusible hardener can be added to only one of the layers. As an addition method, it may be added at the time of emulsion production or in-line at the time of coating.

Gelatin in the gelatin-containing layer of the present invention comprises a part of water-soluble gelatin, starch, dextrin, albumin, sodium alginate, hydroxyethyl cellulose, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, polyacrylamide, styrene. It may be substituted with one or more hydrophilic polymers such as a maleic anhydride copolymer and a polyvinyl methyl ether-maleic anhydride copolymer.

The polymeric binder of the subbing layer is generally 0.5.
It is preferably from 1 to 6 g / m ^2, more preferably from 10 to 10 g / m ² . Further, photographic additives such as developing agents can be included. Further, the undercoat layer is disclosed in JP-A-48-5503 and 48-100.
No. 203, 49-49507.

The silver halide emulsion layer is, for example, silver chloride,
It comprises silver bromide, silver chlorobromide, and those containing silver iodide. The silver halide crystal may contain a heavy metal salt such as a rhodium salt, an iridium salt, a palladium salt, a ruthenium salt, a nickel salt and a platinum salt, and the addition amount is from 10 ^-8 to 10 ^-3 per mol of silver halide. It is a mole. The crystal form of silver halide is not particularly limited, and may be cubic or tetradecahedral grains, or core-shell type or tabular grains. The silver halide crystal may be a monodisperse or polydisperse crystal,
The average particle size is in the range of 0.2 to 0.8 μm. One preferable example is a monodisperse or polydisperse crystal containing rhodium salt or iridium salt and having a silver chloride content of 80 mol% or more.

The silver halide emulsion can be sensitized in various ways as it is manufactured or coated. It is preferable to chemically sensitize by methods well known in the art, for example, with sodium thiosulfate, alkyl thiourea, or with a gold compound such as gold rhodanide, gold chloride, or a combination of both. The silver halide emulsions can also be sensitized or desensitized positively or negatively with dyes such as cyanines, merocyanines. There is no particular limitation on the wavelength range that can be sensitized or desensitized. Therefore, ortho sensitization, panchromatic sensitization, helium-neon laser sensitization, argon laser sensitization, LED sensitization, semiconductor laser sensitization can be performed, and UV sensitization and visible light desensitization for bright rooms. I can feel it.

The surface layer present on top of the emulsion layer contains physical development nuclei. Physical development nuclei include fine particles of metal colloid such as silver, antimony, bismuth, cadmium, cobalt, lead, nickel, palladium, rhodium, gold and platinum, and sulfides, polysulfides, selenides of these metals, or those. It may be a mixture or a mixed crystal. Physical development nuclei may or may not contain a hydrophilic binder, but gelatin, starch, dialdehyde starch, carboxymethyl cellulose, gum arabic, sodium alginate, hydroxyethyl cellulose, polystyrene sulfonic acid, sodium polyacrylate, vinyl It may contain a copolymer of imidazole and acrylamide, a copolymer of acrylic acid and acrylamide, a hydrophilic polymer such as polyvinyl alcohol or an oligomer thereof, and the content thereof is 0.5 g / m.
It is preferably ² or less. Further, the physical development nucleus layer may contain a developing agent such as hydroquinone, methylhydroquinone and catechol, and a known hardener such as formalin and dichloro-s-triazine.

Each of the coating layers such as the undercoat layer, the silver halide emulsion layer and the physical development nucleus layer may contain some of an anion, a cation or a neutral surfactant as a coating aid. , Antifoggants, thickeners, antistatic agents and the like.

As the support of the present invention, a polyester film coated with an organic copolymer and subjected to a hydrophilic treatment is used. This is one in which an undercoating layer having an organic copolymer composition is provided on a polyester film after a surface treatment is performed in order to increase the adhesiveness with a hydrophilic photographic layer. These are the following two. (1) A method of applying a composition comprising an organic copolymer and an organic solvent, which serves as a swelling agent or a dissolving agent for a polyester film (hereinafter referred to as a solvent subbing method). For example, US Pat. No. 2,830,
030, British Patents 772,600 and 776,1
57, 785,789, JP-A-50-1718.
No. 50-8259 and the like. (2) A method of coating in the state of an aqueous composition (so-called latex) of an organic copolymer substantially containing no organic solvent (hereinafter referred to as an aqueous subbing method). For example, Japanese Patent Publications No. 44-13278 and No. 45.
-10988, JP-A-49-11118, 51-
No. 27918, No. 52-114670, No. 54-11
No. 177, No. 55-67745, No. 58-16914.
5 and 59-77439.

The solvent undercoating method of (1) has problems such as deterioration of physical properties of the polyester film during the undercoating process or safety and hygiene in operation due to the above-mentioned organic solvent and pollution problems. It is shifting to law.

The developing solution used in the present invention contains an alkaline substance such as sodium hydroxide or potassium hydroxide,
Lithium hydroxide, sodium triphosphate, etc., sulfites as preservatives, silver halide solvents, such as thiosulfates,
Thiocyanates, cyclic imides, 2-mercaptobenzoic acid, amines, thickeners such as hydroxyethyl cellulose, carboxymethyl cellulose, antifoggants,
For example, potassium bromide, the compounds described in JP-A-47-26201, developers, such as hydroquinones, catechol, 1-phenyl-3-pyrazolidone, development modifiers,
For example, a polyoxyalkylene compound and an onium compound can be included. Further, compounds such as those described in U.S. Pat. No. 3,776,728, which improve ink transfer of the surface silver layer, can be used in the developing solution.

The surface silver layer after development of the lithographic printing plate of the present invention can be converted into ink receptivity or the receptivity can be enhanced with any known surface treating agent. Examples of such treatment liquid include Japanese Patent Publication No. 48-29723 and U.S. Pat. No. 3,7.
21, 559 and the like. The printing method, or the desensitizing liquid, the dampening liquid, or the like to be used may be a commonly known method. The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0035]

【Example】

Example 1 An undercoat layer was formed on a polyester film support which had been subjected to an aqueous undercoating treatment with an undercoating composition containing an epoxy compound disclosed in JP-A-60-213942 for the purpose of hydrophilization. Apply.

<Undercoat liquid> Gelatin 3.5 g Water 20.0 g Fuji Davidson Syroid (Grade 978, average particle size 2.5 μ) 0.6 g Carbon black dispersion liquid (solid content 32%) 0.2 g Formaldehyde ( 30% aqueous solution) 0.2 g Gliogizar (30% aqueous solution) 0.4 g Polylac 752A (styrene / butadiene latex solid content 47.5%) manufactured by Mitsui Toatsu Chemicals Inc. 5.0 g Surfactant 0.6 ml Water is added. The total amount is 50.0 g.

The coating amount was 50 g / m ² in terms of moisture coating amount. When the transmission density of this sample was measured, it was 0.5. When the swelling ratio by addition of Polylac 752A manufactured by Mitsui Toatsu Chemicals, Inc. was determined using the test method described in the present text, it was 1.08, which corresponds to the non-swelling latex for water referred to in the present invention. Was there. An ortho-sensitized high-contrast silver chloride emulsion was coated on these in an amount of 1.5 g / m ² in terms of silver nitrate. After drying, the mixture was heated at 50 ° C. for 2 days, and the core coating solution described in Example 2 of JP-A-58-21602 (containing a copolymer of acrylamide and imidazole of No. 3 as a polymer and hydroquinone as a developing agent) was used. In an amount of 0.8 g / m ² ) and 0.04 g / m ^{2 of} sodium polyacrylate (average molecular weight 260000)
The added liquid was adjusted and coated in the same manner so that
(Sample 1)

As a comparison, an undercoat coating liquid was prepared in the same manner except that Polylac 752A manufactured by Mitsui Toatsu Chemicals, Inc. was not included, and the same coating was performed thereafter. (Comparison a)

Each of the planographic printing plates was subjected to image exposure from the back side using a plate-making camera OS-II manufactured by Mitsubishi Paper Mills Co., Ltd. to develop the plate. The development was carried out with the following diffusion transfer developer at 30 ° C. for 20 tons. Stabilization was carried out by treating with a stabilizing solution having the following composition at 25 ° C. for 20 seconds and drying.

<Diffusion transfer developer> Water 700 g Sodium hydroxide 18 g Potassium hydroxide 7 g Anhydrous sodium sulfite 50 g 2-Mercaptobenzoic acid 1 g Uracil 10 g 2-Methylaminoethanol 30 g 5-Phenyl-2-mercapto-1,3,4 -Oxadiazole 0.1 g Potassium bromide 1 g Water is added to bring the total volume to 1,000 ml.

<Stabilizing Solution> Water 600 g Citric acid 10 g Sodium citrate 35 g Colloidal silica (20%) 5 g Ethylene glycol 5 g Water is added to bring the total volume to 1,000 ml.

The printing evaluation is AB Dick 350.
CD (trademark of AB Dick offset printing machine)
It was used. Regarding printing durability, each lithographic printing plate was treated with the following desensitizing liquid, and then printed with New Champion Ink N manufactured by Dainippon Ink and using the following dampening liquid, The number of printed sheets when the image was skipped due to missing and could not be used for printing was judged according to the following evaluation criteria. (A) 20,000 sheets or more (B) 10,000 to 20,000 sheets (C) 5,000 to 10,000 sheets (D) 2,000 to 5,000 sheets (E) Less than 2,000 sheets The results are shown in Table 1.

<Desensitizing Solution> Water 600 g Isopropyl alcohol 400 g Ethylene glycol 50 g 3-Mercapto-4-acetamido-5-n-heptyl-1,2,4-triazole 1 g

<Moistening liquid> O-phosphoric acid 10 g Nickel nitrate 5 g Sodium nitrite 5 g Ethylene glycol 100 g Colloidal silica (20% liquid) 28 g Water is added to make 2,000 ml.

On the other hand, in order to see the water retention (background stain) of the non-image area, the ink is F Gloss Purple 68S manufactured by Dainippon Ink.
Was used, and 2.5% KPS # 500 aqueous solution manufactured by Rossos Co., Ltd. was used as a moisturizing liquid, and the number of printed sheets when AB Dick350CD became dirty and could not be used for printing was judged by the following evaluation criteria. (A) 3000 sheets or more (B) 1000 to 3000 sheets (C) 500 to 1000 sheets (D) 100 to 500 sheets (E) Less than 100 sheets The printing results are shown in Table 1.

Next, in order to examine the ink / water responsiveness, each lithographic printing plate was not treated with a desensitizing liquid, and the following dampening liquid was used. Was printed and evaluated by the number of stains that can be removed at the time of startup. (A) 10 sheets or less (B) 10 to 20 sheets (C) 20 to 50 sheets (D) 50 to 100 sheets (E) 100 sheets or more The printing results are shown in Table 1.

[0048]

[Table 1]

As is clear from Table 1, Comparative a which does not contain Polylac 752A, which is a styrene-butadiene latex, is inferior in stain resistance, whereas Sample 1 of the present invention is excellent in stain resistance. In addition, the ink / water responsiveness was found to be equivalent.

Example 2 An undercoat layer is coated as follows on a polyester film support which has been subjected to an aqueous undercoating process in the same manner as in Example 1.

<Undercoating liquid> Gelatin 35 g Water 200 g Fuji Dividson Syroid (grade X) Yg Carbon black dispersion (solid content 32%) 2 g Formaldehyde (30% aqueous solution) 2 g Gliogizar (30% aqueous solution) 4 g Mitsui Higashi Pressure Chemical Polylac 752A (Styrene-butadiene latex solid content 47.5%) 5.0 g Surfactant 6 ml Water is added to bring the total amount to 500 g.

The coating amount was 50 g / m ² in terms of moisture coating amount. Table 2 shows the grade X and the addition amount Y of the CYLOID manufactured by Fuji Davidson. When the transmission density of this sample was measured, it was 0.5. The ortho-sensitized high-contrast silver chloride emulsion is converted into silver nitrate, and
5 g / m ^{2 was} applied. After drying, the mixture was heated at 50 ° C. for 2 days, and the core coating solution described in Example 2 of JP-A-58-21602 (containing a copolymer of acrylamide and imidazole of No. 3 as a polymer and hydroquinone as a developing agent) was used. 0.
8 g / m in a proportion of ²⁾ the sodium polyacrylate (average molecular weight 260000) was prepared in the same manner a solution was added to a 0.04 g / m ^2, was coated. (Sample 2,
3, 4, comparison b, c)

A sample was prepared in the same manner as in Example 1 below, and print evaluation was performed. The results are shown in Table 2.

As is clear from Table 2, in Comparative b and Comparative c in which the amount of added siloid is large, the center line average roughness exceeds 1.2, and these are inferior in stain resistance. It was found that Sample 2, Sample 3, and Sample 4 of the present invention had a center line average roughness of 1.2 or less and were excellent in stain resistance.

[0055]

[Table 2]

Example 3 In the undercoating liquid of Example 2, a sample was prepared in the same manner as in Example 2 except that the amounts of gelatin and siloid added and the grade of siloid were as shown in Table 3, and printing evaluation was performed. It was The results are shown in Table 3.

As is clear from Table 3, Samples 5 of the present invention
No. 7 has a center line average roughness Ra value of 1.2 or less and is excellent in stain resistance, while comparison d shows center line average roughness Ra.
The value exceeds 1.2, and the stain resistance is poor.

[0058]

[Table 3]

Example 4 Comparative e was prepared in the same manner as in Sample 2 except that the amount of the carbon black dispersion (solid content: 32%) added to the undercoat coating liquid of Example 2 was 8 g. In the same manner as described above, image exposure was performed from the back side using a plate-making camera OS-II manufactured by Mitsubishi Paper Mills, and printing evaluation was performed. The results are shown in Table 4.

As is clear from Table 4, Comparative e requires an exposure time that is 10 times or more that of Sample 2. On the other hand, Sample 2 showed high sensitivity and excellent stain resistance.

[0061]

[Table 4] Example 5 NIP manufactured by Nippon Zeon Co., Ltd. instead of Polylac 752A manufactured by Mitsui Toatsu Chemicals Inc. (styrene-butadiene latex)
Sample 15 was prepared in the same manner as in Example 1 except that ol1577 (acrylonitrile-butadiene latex) was used, and printing evaluation was performed. When the swelling ratio by the addition of Nipol 1577 manufactured by Nippon Zeon Co., Ltd. was determined by using the test method described in the present text, it was 1.11 which corresponded to the non-swelling latex for water referred to in the present invention. The sample prepared in this manner is the same as in Example 1.
It was excellent in stain and ink / water responsiveness.

[0062]

INDUSTRIAL APPLICABILITY By using the present invention, high sensitivity,
Further, it is possible to provide a lithographic printing plate for back printing, which has excellent ink / water responsiveness and stain resistance.

Claims (1)

(57) [Claims] 1. A polyester film coated with an organic copolymer and subjected to a hydrophilic treatment is used as a support, and at least one undercoat layer, a silver halide emulsion layer and physical development nuclei are sequentially coated on the support. In the lithographic printing plate for back printing, the total transmission density of each constituent layer through which light passes when exposed from the back side is about 0.8 or less, and the surface side including the silver halide emulsion layer Containing 0.1 to 2.0 g / m ² of a matting agent in the coating layer, a non-swelling latex for water in the undercoat layer, and the center line of the planographic printing plate. A planographic printing plate for backing, which has an average roughness Ra value of 1.2 or less.