JP2003223002A - Lithographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silver halide lithographic printing plate having high sensitivity and favorable storage property. <P>SOLUTION: The lithographic printing plate having at least a silver halide emulsion layer on a support body and using a silver complex salt diffusion transfer method, is characterized in that the silver halide emulsion layer comprises silver halide particles containing ≥95 mol% of silver chloride, and the silver halide particles have a core-shell structure with respect to rhodium, and ≥80 wt.% of the whole rhodium is included in the shell. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lithographic printing plate utilizing a silver complex salt diffusion transfer method, and more particularly to a lithographic printing plate having high sensitivity and good storage stability.

[0002]

2. Description of the Related Art Most of lithographic printing plates using a silver complex salt diffusion transfer method have a halogen composition mainly composed of silver chloride because they require a hard photographic characteristic in the silver complex salt diffusion transfer process. It is known to dope rhodium (Rh) into a silver halide crystal in order to further enhance the contrast. However, there is a problem that the sensitivity is lowered when Rh is mainly doped with silver chloride.

Further, when silver chloride is the main constituent, there is a problem that the storage stability is poor. The cause is that silver chloride has a high solubility and is easily reduced, so that fog may occur during long-term storage or the sensitivity may change. Therefore, there is a drawback that the intended density and halftone dot% cannot be obtained even if a constant exposure amount is given by a scanning exposure apparatus such as an image setter (also called a plate setter). Further, the rise of fog during storage causes a disadvantage that the printing durability is reduced.

As a technique for producing a silver halide emulsion, R is
It is known to separate and dope h into the core and shell of a silver halide crystal to change the amount thereof. For example, JP-A-1
Japanese Patent No. 254945 discloses that the sensitivity is increased by containing a large amount of Rh in the core. In Examples of JP-A-6-110146 and JP-A-6-138592, emulsions containing a large amount of Rh in the core are introduced. However, these technologies have many Rh
Which is different from the one containing a large amount of Rh in the shell of the present invention. Further, it is not specified what happens to the photographic characteristics and printing characteristics when processed as diffusion transfer. As a result of a supplementary experiment, it was found that the emulsion containing Rh in the core in a larger amount than the emulsion uniformly doped with Rh had low sensitivity and poor storage stability in the diffusion transfer process.

Further, JP-A-63-296031 discloses an emulsion containing a large amount of Rh in the shell. However, this technique uses Rh in the shell to reduce sensitivity.
Is contained in a large amount, and the exposure relates to a plate-making material for contact in a bright room, which has an extremely low sensitivity and uses light having a wavelength shorter than 400 nm which is the intrinsic sensitivity of silver halide. The present invention is 400n
It is intended for high-sensitivity lithographic printing plates with a wavelength longer than m.
The amount of h is two orders of magnitude smaller than that of the previous patent, which is a technology in a different field. More interestingly, as a result of the experiment,
The results show that when a large amount of Rh is contained in the shell, the intrinsic sensitivity is desensitized while the dye sensitization sensitivity is sensitized. Therefore, the above technology and the technology of the present invention are essentially different.

On the other hand, in the field of lithographic printing plates using the silver complex salt diffusion transfer method, JP-A-11-295837 discloses that the core and the shell contain the same kind of V-VIII group metal complex having different ligands. It is disclosed. However, it has not been possible to obtain a lithographic printing plate having sufficiently high sensitivity and excellent storage stability.

[0007]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a lithographic printing plate having high sensitivity and good storage stability.

[0008]

The above object of the present invention is to provide a lithographic printing plate utilizing a silver complex salt diffusion transfer method, which comprises at least a silver halide emulsion layer on a support, wherein the silver halide emulsion layer is chlorinated. A silver halide grain containing silver in an amount of 95 mol% or more, the silver halide grain having a core-shell structure with respect to rhodium, and containing 80% by weight or more of the total amount of rhodium in the shell. Achieved by a lithographic printing plate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The silver halide grains used in the silver halide emulsion layer in the present invention are appropriately selected from silver chloride containing 95 mol% or more of silver chloride, silver chlorobromide, silver chloroiodide and silver chloroiodobromide. However, silver chloroiodide having a silver iodide content of 2 mol% or less is preferable. That is, a preferred embodiment of the present invention is silver halide grains converted by iodine ions after the physical ripening of silver halide.
When the content of silver chloride is less than 95 mol%, a silver image having high printing durability cannot be obtained in the silver complex salt diffusion transfer processing, and when the content of silver bromide or silver iodide is large, the running processing is performed. The characteristics are poor and the high contrast property cannot be obtained.

The silver halide grains used in the present invention are
Core shell structure for Rh, 80 layers of total Rh
Included in the shell is greater than or equal to%. Rh amount is silver halide
1 x 10 per mole^-8~ 1 x 10^-6Contains in the molar range
Preferably. 1 x 10 ^-8Lithographic printing plate if it is less than mol
The image does not come out as required. 1 x 10 ^-6
If it is over the molar range, the desired sensitivity cannot be obtained.

The silver halide grains used in the present invention are
Rh may be a core-shell structure, and the halogen composition and the type and content of a doped metal (for example, iridium) other than Rh may be the same or different in the core and the shell.

The silver halide grains of the present invention may have a cubic shape, a tetradecahedral shape, or a flat plate shape, but a cubic shape is preferable. The average grain size of the silver halide grains is preferably in the range of 0.1 to 0.5 μm. With respect to the core-shell structure of the present invention, the shell thickness is preferably ⅛ or less of the entire length of the silver halide crystal. The thinner the shell, the greater the effect, and the greater the proportion of Rh contained in the shell, the greater the effect. However, there is no effect even if Rh is added after the physical ripening is completed.

The core-shell type silver halide grains used in the present invention can be produced by various methods known so far. For example, any of an acidic method, a neutral method, an ammonia method and the like may be used, and as a method of reacting a silver nitrate solution and a halogen solution, a double jet method or a double jet method combined with a single jet method may be used. As one form of the double jet method, a method of keeping pAg constant in a liquid phase where silver halide is produced, that is, a controlled double jet method can be used. Also, British Patent No. 1,53
5,016, Japanese Patent Publication No. 48-36, 890, Japanese Patent Publication No. 5
2-16, 364 and the like, a method of changing the addition rate of silver nitrate or an alkali halide aqueous solution according to the grain formation rate, and US Pat. No. 4,242,4.
A method of changing the concentration of the aqueous solution can be used as described in JP-A No. 45, JP-A-55-158, 124 and the like. Among these production methods, the controlled double jet method is particularly preferably used.

Usually, when Rh is doped in silver halide grains, it is added to a halogen solution, but to dissolve Rh ions in the halogen solution, rhodium chloride, ammonium hexachlororhodate, sodium hexachlororhodate, hexabromo are added. It suffices to dissolve potassium rhodate and the like together with halogen ions. The halogen solution may contain other polyvalent cations. The inclusion of Ir is particularly useful when designing a printing plate for scanning exposure such as an imagesetter.

In the present invention, silver halide grains are preferably chemically ripened. 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 grains used in the present invention are
It is preferable to perform spectral sensitization with a sensitizing dye. The silver halide grains of the present invention have a low sensitivity when there is no sensitizing dye, that is, the sensitivity is rather low when exposed with an intrinsic sensitivity, and conversely, high sensitivity is obtained when spectrally sensitized with a sensitizing dye. As the sensitizing dye, it is possible to use a sensitizing dye that spectrally sensitizes the maximum sensitivity of silver halide grains to visible light in the blue region, green region, red region, or near infrared region. Especially 600
When spectrally sensitized with a sensitizing dye that spectrally sensitizes in the red region or near-infrared region of not less than nm, the silver halide grain of the present invention is excellent in storage stability and sensitivity and has high resistance as a lithographic printing plate. Printability is obtained.

The amount of sensitizing dye added is such that silver halide grains 1
The range of 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol is preferable, and the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻⁴ mol is particularly preferable.

Examples of the sensitizing dye used in the present invention include a cyanine dye, an oxonol dye, a merocyanine dye, a complex trinuclear dye, and a styryl dye. Preferred examples are given below. Among the sensitizing dyes exemplified below, a cyanine dye or a merocyanine dye in which a nitrogen atom of a nitrogen-containing heterocycle is substituted with a hydrophilic group such as a sulfo group or a carboxy group via an alkylene group is preferable.

[0019]

[Chemical 1]

[0020]

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[0021]

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[0022]

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[0023]

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[0024]

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[0031]

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[0032]

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[0033]

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[0034]

[Chemical 16]

[0035]

[Chemical 17]

Although a lithographic printing plate to which the silver complex salt diffusion transfer method (DTR method) of the present invention is applied has been put into practical use, it is roughly 2
It can be divided into two types. One type has a subbing layer, a silver halide emulsion layer and a physical development nucleus layer on a support and is disclosed in U.S. Pat. Nos. 3,721,559 and 3,4.
90,905, 3,385,701, 3,
No. 814,603, No. 3,454,398, No. 3,764,323, No. 3,099,209, JP-B-44-27242, JP-A-48-30562, JP-A-53-53. No. 9603, No. 53-21602, No. 54-
No. 103104, No. 56-9750, etc.

According to a typical implementation method of the silver complex salt diffusion transfer method suitable for the plate making method of such a lithographic printing plate, an undercoat layer also serving as an antihalation layer, a silver halide emulsion layer, a physical development nucleus are formed on a support. When the light-sensitive material consisting of layers is imagewise exposed and developed, the silver halide on which a latent image is formed becomes blackened silver in the emulsion. At the same time, the silver halide on which a latent image is not formed is dissolved by the action of the silver halide solvent contained in the development processing solution and diffuses onto the surface of the photosensitive material. The silver complex salt that has been dissolved and diffused is deposited as image silver on the physical development nuclei of the surface layer by the reducing action of the developing agent.

Another type of lithographic printing plate to which the silver complex salt diffusion transfer method (DTR method) is applied is a mono-sheet type lithographic printing plate having an aluminum plate as a support, which is disclosed in Japanese Patent Laid-Open Publication No.
7-118244, 57-158844, 63
-260491, JP-A-3-116151, 4-
No. 282295, U.S. Pat. Nos. 4,567,131, 5,427,889 and the like, which describe physical development nuclei carried on a roughened and anodized aluminum support. Further, a silver halide emulsion layer is further provided thereon. A general plate-making method for this lithographic printing plate comprises steps of exposure, development, washing with water (wash-off: removal of silver halide emulsion layer) and finishing. That is, a metallic silver image portion is formed on the physical development nuclei by the development treatment, the silver halide emulsion layer is removed by the next water washing treatment, and the metallic silver image portion (hereinafter referred to as the silver image portion) is formed on the aluminum support. Is exposed. At the same time, the anodized aluminum surface itself is exposed as a non-image area.

The silver halide grains of the present invention can be preferably applied to any of the above types.

In the planographic printing plate targeted by the present invention,
Gelatin is preferably used as a hydrophilic binder for the silver halide emulsion layer and the undercoat layer. In addition, a part of gelatin is a protein such as casein, carboxymethyl cellulose, hydroxyethyl cellulose, a cellulose compound such as dextran, agar, sodium alginate,
It may be replaced with a sugar derivative such as a starch derivative, a synthetic hydrophilic colloid such as polyvinyl alcohol, poly-N-vinylpyrrolidone, a polyacrylic acid copolymer, or another hydrophilic polymer such as polyacrylamide.

The above-mentioned gelatin-containing layer 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-S-triazine salt,
Compounds having active halogens such as 2,4-dihydroxy-6-chloro-triazine salts, divinyl sulfone,
Divinyl ketone, N, N, N-triacroylhexahydrotriazine, compounds having two or more active three-membered ethyleneimino groups or epoxy groups in the molecule, dialdehyde starch as a polymer hardener One kind or two or more kinds of various compounds such as

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

The undercoat layer preferably contains carbon black for the purpose of preventing halation, and may contain solid powder (for example, silica particles) having an average particle diameter of 0.1 to 10 microns for improving printing durability. Further, photographic additives such as developing agents can be included.

Physical development nuclei of the physical development nuclei layer include metal colloidal fine particles of silver, antimony, bismuth, cadmium, cobalt, lead, nickel, palladium, rhodium, gold, platinum, etc., and sulfides and polysulfides of these metals. Compound, selenide, a mixture thereof, or a mixed crystal. The physical development core may or may not contain a hydrophilic binder, but gelatin, starch, dialdehyde starch, carboxymethyl cellulose, gum arabic, sodium alginate, hydroxyethyl cellulose, polystyrene sulfonic acid, vinyl imidazole and acrylamide It may contain a polymer, a hydrophilic polymer such as polyvinyl alcohol, or an oligomer thereof, and the content thereof is 0.5 g /
It is preferably m 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.

As the support for the lithographic printing plate of the present invention,
Paper or a synthetic or semi-synthetic polymer film, a metal plate such as aluminum or iron, and the like can be used as long as they can withstand lithographic printing. The surface of the support may be coated on one side or both sides with one or more polymer films or metal thin films. The surface of these supports can be surface-treated in order to improve the adhesion with the coating layer.

The developing solution used in the lithographic printing plate of the present invention contains an alkaline substance such as sodium hydroxide, potassium hydroxide, lithium hydroxide and sodium triphosphate, sulfite as a preservative, and halogen. Silver halide solvents such as thiosulfates, thiocyanates, cyclic imides, 2-mercaptobenzoic acid, amines and the like, thickeners such as hydroxyethyl cellulose and carboxymethyl cellulose, antifoggants such as potassium bromide, JP-A-47. -262
Developers such as hydroquinones, catechol, 1-phenyl-3-pyrazolidone, etc., such as the compounds described in JP-A No. 01-, and development modifiers, such as polyoxyalkylene compounds and onium compounds, can be contained. 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.

In carrying out the silver complex salt diffusion transfer method in the present invention, for example, British Patent No. 1,000,11 is used.
No. 5, No. 1,012,476, No. 1,042,477
As described in the specification of U.S. Pat. No. 4,968,697, a developer is incorporated into a silver halide emulsion layer and / or an image receiving layer or another water permeable layer adjacent thereto. Therefore, in such a material, the processing solution used in the developing stage may be a so-called "alkaline activating solution" containing no developer.

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 a treatment liquid include Japanese Patent Publication No. 48-29723, US Pat.
721,559 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.

[0049]

Example 1 <Production of silver halide emulsion A> The following solutions (1) to (5) were prepared. Solution (1) Pure water 250 ml Gelatin 20 g pH 5.0

Solution (2) Pure water 150 ml 75g of silver nitrate

Solution (3) Pure water 150 ml 75g of silver nitrate

Solution (4) 35 g of sodium chloride Pure water 180 ml 0.1% iridium tetrachloride 1.5 ml

Solution (5) 35 g of sodium chloride Pure water 180 ml 0.1% iridium tetrachloride 1.5 ml 0.001% rhodium chloride trihydrate 4 ml

Solution (2) was added to the above solution (1) by a metering pump.
And (4) were added at a silver potential of 100 mV to the saturated silver chloride electrode potential at 50 ° C. for 30 minutes to give core particles. Further, solutions (3) and (5) were added to the core particles at 50 ° C. for 30 minutes by the same metering pump to form shells. The mixing conditions at this time are the same as those at the time of preparing the core particles. The thickness of the shell of the silver halide grain thus produced is 1/8 of the total length of the crystal. This emulsion contains the silver halide grains of the present invention containing 100% by weight of the total rhodium content in the shell and is designated as emulsion (A).

<Production of Silver Halide Emulsion B> The above solution (1) was prepared, and the following solutions (6) and (7) were added to this solution (1) with a metering pump at a saturated silver chloride electrode potential of 10:
Silver halide grains were prepared by adding at a silver potential of 0 mV at 50 ° C. for 60 minutes. This emulsion is not a core / shell structure, but is a comparative emulsion (B).

Solution (6) Pure water 300 ml Silver nitrate 150g

Solution (7) 70 g of sodium chloride Pure water 360 ml 0.1% iridium tetrachloride 3 ml 0.001% rhodium chloride trihydrate 4 ml

<Production of Silver Halide Emulsion C> It was produced in the same manner as Emulsion A. However, the solutions (4) and (5) were replaced with each other to prepare silver halide grains containing 100% of the total rhodium content in the core. This emulsion is a comparative emulsion (C)
And

<Production of Silver Halide Emulsion D> Emulsion (A)
It was manufactured in the same manner as. However, a part of the rhodium of the solution (5) was put into the solution (4) to prepare an emulsion (D) of the present invention containing 90% by weight of all rhodium in the shell.

<Production of Silver Halide Emulsion E> Emulsion (A)
It was manufactured in the same manner as. However, a part of the rhodium of the solution (5) was put into the solution (4) to prepare a comparative emulsion (E) containing 70% by weight of all rhodium in the shell.

<Production of Silver Halide Emulsion F> Emulsion (A)
It was manufactured in the same manner as. However, after the rhodium in the solution (5) was removed and the silver halide grains were produced, the rhodium removed above was added. This emulsion is referred to as a comparative emulsion (F).

Each of the silver halide grains produced as described above was further converted by adding an aqueous potassium iodide solution so that the amount was 0.01 mol per mol of silver. Each of the silver halide grains thus produced is a cube having an average grain size of 0.3 μm and contains 1.8 × 10 ⁻⁷ mol of rhodium per 1 mol of silver halide.

Next, a coagulation sedimentation and washing with water dehydration step were performed to obtain a physically aged emulsion. Then, a gelatin solution containing gelatin having an average molecular weight of 100,000 was added to these emulsions,
Further, the pH was adjusted to 5.5 with an aqueous solution of NaOH, redissolved, and 3 m of sodium thiosulfate was added per mol of silver.
g, 5 mg of chloroauric acid, and heated at 50 ° C. for 60 minutes,
Chemically aged. After the chemical ripening, the emulsion temperature is adjusted to 38
The temperature was lowered to ℃, the sensitizing dye of Chemical formula 9 was 0.03 mmol per mol of silver, 1-phenyl-3-pyrazolidone 0.1 g / m ² , and 80 mg of N-methylol ethylene urea as a hardening agent. / M ² was added to prepare coating solutions of 6 kinds of silver halide emulsion layers.

As a support, the thickness is 175 μm, which has been undercoated
Using a polyethylene terephthalate film, the backing layer (gelatin 3 g / m ² ) containing 0.3 g / m ² of silica particles having an average particle size of 3.5 μm (Coulter counter method) is provided on one side of the support. It was The surface on the opposite side of the support was subjected to corona discharge machining, and then carbon black was added to 0.
Silica powder (SY445 manufactured by Fuji Sicilia) 0.9 g / m ² having a particle size of 7 g / m ² and an average particle size of 3.5 μ and 2,4-dichloro-6-hydroxy-s-triazine sodium 170
an undercoat layer containing 3.5 mg / m ² (gelatin 3.5 g / m ² ),
On top of that, the five types of emulsions prepared above were changed to 1.2 g / m ² (gelatin 1.0 g / m ² ) as silver nitrate,
Two layers were simultaneously coated.

The undercoat layer and each silver halide emulsion layer were coated and dried, heated at 40 ° C. for 7 days, and then physically developed on the silver halide emulsion layer according to Example 1 of JP-A-8-21114. Core layer coating solution (P- as the polymer
2 was used) and dried to prepare 6 types of lithographic printing plates.

These lithographic printing plates were treated with the following transfer developing solution and neutralizing solution. The sensitivity value was determined as the reciprocal of the exposure amount required to obtain the reflection density of 1.0 of the blackened image obtained by exposure through the step wedge. The fresh sensitivity was expressed as a relative sensitivity (%) when the sensitivity of the emulsion (B) was 100%. Similarly, regarding the evaluation of storage stability, 4
The sensitivity of what was seasoned at 0 ° C. and 85% (RH) for 10 days was evaluated by relative sensitivity (storage sensitivity in the table). Also,
The decrease in printing durability due to the increase in the number of covers during storage has been reduced to 45% at 85%.
(RH) It evaluated by what was seasoned for 10 days.

<Transfer developer> 700 ml of water 20 g of potassium hydroxide Anhydrous sodium sulfite 50g 2-mercaptobenzoic acid 1.5 g 2-methylaminoethanol 15g Add water to make 1 liter.

<Neutralizing liquid> 600 ml of water Citric acid 10g Sodium citrate 35g Colloidal silica (20% liquid) 5 ml Ethylene glycol 5ml Add water to make 1 liter.

For the evaluation of printing durability, the following dampening liquid was used, and the printing machine used was Ryobi 3200CD (trademark of offset printing machine manufactured by Ryobi KK). The number of printed sheets at the time when the image was skipped due to the lack of a copy and the sheet could not be used for printing. The ink used was ABdick3-1012. ⊚ 20,000 sheets or more ○ 15,000 to less than 20,000 sheets △ 10,000 to less than 15,000 sheets × less than 10,000 sheets The printing results are shown in Table 1.

<Moisturizing liquid> o-phosphoric acid 10 g Nickel nitrate 5g Sodium nitrite 5g Ethylene glycol 100g Colloidal silica (20% liquid) 28g Add water to make 2 liters.

[0071]

[Table 1] ───────────────────────────────     Emulsion Fresh sensitivity Storage sensitivity Printing durability Note ───────────────────────────────    (A) 115 113 ◎ The present invention    (B) 100 70 Δ Comparative example    (C) 98 63 Δ Comparative example    (D) 110 106 The present invention    (E) 102 90 Δ Comparative example    (F) 230 60 × Comparative example ───────────────────────────────

As is clear from the above results, by incorporating 80% by weight or more of the total rhodium content in the shell, a lithographic printing plate having high sensitivity and excellent storage stability can be obtained. Further, the emulsion (F) to which rhodium was added after the production of silver halide grains had high sensitivity, but had a soft tone, remarkably inferior in performance as a printing plate, and had very poor storability.

Example 2 The lengths of the entire crystals of silver halide grains were changed by changing the ratio of the solutions (2) and (3) of Example 1 and the ratios of the solutions (4) and (5) variously to change the shell thickness. The ratio of shell thickness to thickness was varied as shown in Table 2. The entire amount of rhodium was contained in the shell. Other operations are the same as in the first embodiment. Table 2 shows the results of evaluation performed in the same manner as in Example 1. The sensitivities in the table are expressed as relative sensitivities (%) when the fresh sensitivity with a shell thickness ratio of 1/8 is 100%.

[0074]

[Table 2] ────────────────────────────     Shell thickness ratio Fresh sensitivity Storage sensitivity Printing durability ────────────────────────────       1/6 94 84 ○       1/8 100 98 ◎       1/10 109 107 ◎       1/16 115 114 ◎ ────────────────────────────

From the results shown in Table 2, it can be seen that the thinner the shell, the higher the sensitivity and the better the storage stability.

[0076]

According to the present invention, a lithographic printing plate having high sensitivity and good storage stability can be obtained.

Claims (4)

[Claims] 1. A lithographic printing plate utilizing a silver complex salt diffusion transfer method, which comprises at least a silver halide emulsion layer on a support, wherein the silver halide emulsion layer contains 95 mol% of silver chloride.
A lithographic printing plate comprising the silver halide grains contained above, which has a core-shell structure with respect to rhodium and contains 80% by weight or more of the total amount of rhodium in the shell. 2. The silver halide grains are silver halide 1
The lithographic printing plate according to claim 1, which contains 1 × 10 ⁻⁸ to 1 × 10 ⁻⁶ mol of rhodium per mol. 3. The lithographic printing plate according to claim 1, wherein the thickness of the shell of the silver halide grains is 1/8 or less of the total length of the crystals. 4. The planographic printing plate according to claim 1, wherein the silver halide grains are spectrally sensitized with a sensitizing dye.