JPH07104602B2 - How to make a planographic printing plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a lithographic printing material by a scanning exposure system such as a laser beam.

(B) Prior art and its problems A lithographic printing plate which can immediately use a transferred silver image obtained by a silver complex salt diffusion transfer method as an ink accepting property has already been disclosed in JP-B-48-30562 and JP-A-53-21602. 54-103
104, Dosho 56-9750, etc., and is well known.

According to a typical example of a silver complex salt diffusion transfer method suitable for the plate making method of such a lithographic printing plate, a support and an undercoat layer which also serves as an antihalation layer, a silver halide emulsion layer, and a physical development nucleus layer are formed on the support. When a light-sensitive material composed of is exposed to light and developed, the silver halide on which a latent image is formed becomes blackened silver in the emulsion layer. At the same time, the silver halide on which no latent image is formed is dissolved by the action of the silver halide complexing agent contained in the development processing solution, and diffuses to the surface of the photosensitive material. The dissolved and diffused silver complex salt is deposited as a silver image on the physical development nuclei of the surface layer by the reducing action of the developing agent. In order to enhance the ink acceptability of the obtained silver image, a development treatment is followed by an oil sensitization treatment if necessary, and then the ink image is transferred to a printed matter by setting in an offset printing machine.

As a lithographic printing plate for such direct plate making, instead of the plate making method by a plate making camera up to now, scanning with a light source such as a helium-neon laser, an argon laser, a semiconductor laser, a light emitting diode (LED), a cathode ray tube (CRT). A method of exposing and making a plate and a lithographic printing plate therefor have been developed.

For example, U.S. Patent No. 4,501,811, JP-A-59-71056, JP-A-60-75838, JP-A-60-100147, JP-A-60-179744, and Japanese Patent Application No. 60
-244880 and 60-245059 to 245062.

However, the lithographic printing plate used in such a scanning exposure method is, compared to a conventional lithographic printing plate using a plate making camera method,
There is a surface inferior in performance, and further improvement is desired. One of the reasons is that it is necessary to obtain high sensitivity by short exposure with high illuminance such as laser light. Manufacturing conditions for emulsions, especially silver halide emulsions mainly composed of silver chloride, tend to be harsh, and as a result, silver images are removed during printing and scumming occurs, resulting in low printing durability. It is thought that it will end up. In particular, the semiconductor laser has advantages such as small size, low cost, easy modulation, and long life, but since the output is low, the above-mentioned drawbacks are more serious.

Therefore, there is a strong demand for the development of a technique that achieves high printing durability while achieving high sensitivity.

JP-A-60-75838 discloses that the plate life is improved by providing an antihalation layer having a reflectance of 10% or less at the time of plate making with 632.8 nm helium-neon laser light.

Certainly, the use of such a high-concentration antihalation layer gives a lithographic printing plate excellent in printing durability, but naturally causes a great deal of desensitization.

(C) Object of the Invention It is an object of the present invention to provide a lithographic printing plate having high printing durability and high sensitivity in a scanning exposure system such as a laser without silver deficiency or background stain.

(D) Structure of the Invention The above object of the present invention is to subject a lithographic printing plate having a subbing layer, a silver halide emulsion layer and a surface physical development nucleus layer on a support to a silver complex diffusion after a high-intensity short-time scanning exposure. In a plate making method of developing with a transfer developer, the undercoat layer contains a white pigment,
The emulsion layer and / or the undercoat layer contains fine powder having an average particle size of 2 to 10 μm, and the amount necessary for adjusting the reflectance of scanning exposure light to 10% to 40% below the emulsion layer. It was found to be achieved by a plate-making method characterized by using an antihalation lithographic printing plate containing the above light absorber.

According to a preferred embodiment of the present invention, a white pigment, a fine powder and a light absorber are contained in the undercoat layer, and the reflectance of the undercoat layer is 10%.
A lithographic printing plate that is up to 40% is provided.

Hereinafter, the present invention will be described in more detail.

The support used for the lithographic printing plate of the present invention is, for example, a paper, a film, for example, a cellulose acetate film, a polyvinyl acetal film, a polystyrene film, a polypropylene film, a polyethylene terephthalate film, or a polyester, polypropylene or polystyrene film coated with a polyethylene film. It can be a support for composite films, metal, metallized paper or metal / paper laminates. A paper support coated with an α-olefin polymer such as polyethylene on one or both sides is also effective.

An undercoat layer containing at least a white pigment is provided between the support and the silver halide emulsion layer.

The silver halide emulsion layer and / or the undercoat layer has an average grain size of 2
Contains fine powder of ˜10 μm. Preferably, 70% by weight or more of the fine powder is contained in the undercoat layer.

At least one of the undercoat layer, the support, and the backing layer is 10% to 10% of scanning exposure light, for example, 780 nm or 632.8 nm laser light.
A light absorber is used to reflect the emulsion layer at a rate of 40%. A more preferable reflectance is 13% to 35%.

The light absorber used in the present invention is a dye, a pigment or the like capable of absorbing scanning exposure light, and carbon black is preferably used.

The white pigment used in the present invention is titanium dioxide,
Average particle size of zinc oxide, calcium carbonate, etc. 0.01-1 μm
Titanium dioxide (either rutile type or anatase type) is preferably used.

The fine powder used in the present invention is silica, starch, polymethylmethacrylate or the like having an average particle size of 2 to 10 μm, and silica is preferably used.

The above-mentioned light reflectance is a value obtained by combining a white pigment, a light absorbing agent and, in some cases, fine powder,
It is preferable that only the light absorbing agent has a light reflectance of about 10% to about 30%, and the light reflectance of a white pigment or the like is added to this to obtain the above-described light reflectance. Generally, the white pigment is about 0.3 g to about 5 g, and preferably about 0.5 g to about 4 g per square meter of subbing layer.
The amount of fine powder is about 0.1 g to about 3 g, and preferably about 0.2 g to about 2 g per square meter of subbing layer or / and emulsion layer.
Is the amount of.

Combining a white pigment such as titanium dioxide in order to prevent desensitization by carbon black is described, for example, in U.S. Pat.No. 4,144,064 and Japanese Patent Laid-Open No. 59-19942 as a light-sensitive material for preparing an original copy. It is known.

The use of fine powder in the undercoat layer of a lithographic printing plate for laser is known, for example, as described in JP-A-60-100147.

However, as described in JP-A-59-19942, a high reflectance halation prevention comprising a large amount of white pigment and a small amount of a light absorber is applied to the undercoat layer described in JP-A-60-100147. However, high sensitivity can be achieved but high printing durability cannot be obtained.

According to the invention, the sensitivity is higher than that of the antihalation layer of the planographic printing plate described in JP-A-60-75838,
Moreover, it is possible to obtain printing durability equal to or higher than that. This is because the white pigment can prevent the reduction of the printing capacity due to the reduction of the amount of the light absorber and the increase of the light reflectance due to the use of the white pigment, and the reduction of the printing durability due to the reduction of the amount of the light absorber. In addition to what was possible, it is considered that the white pigment was finely dispersed in the gaps of the fine powder, and the sufficient adhesion strength of the transferred silver deposit and the effect of retaining the dampening water were improved.

Moreover, according to the present invention, since the high illuminance failure of the silver halide emulsion can be tolerated to some extent, the reduction in printing durability caused by various factors of the emulsion can be reduced.

The silver halide emulsion used in the present invention is silver chloride, silver chloroiodide, silver chlorobromide or silver chloroiodobromide containing silver chloride in an amount of 50 mol% or more, preferably about 70 mol or more. The silver iodide content is preferably in the range of about 0.01 to about 3 mol%. The average grain size of these silver halide grains is in the range of 0.2 to 0.6 μm, preferably 0.25 to 0.5 μm. Further, the silver halide is preferably a monodispersed emulsion in which 90% or more of all grains have a grain size within ± 30% of the average grain size. The silver halide is preferably substantially cubic or tetradecahedral grains, but silver halide having other crystal habit can be used.

The binder used in the silver halide emulsion of the lithographic printing plate of the present invention is usually gelatin, which is a part of starch, albumin, sodium alginate, hydroxyethyl cellulose, gum arabic, polyvinyl alcohol, polyvinylpyrrolidone, It may be substituted with one or more hydrophilic polymer binders such as carboxymethyl cellulose, polyacrylamide, styrene-maleic anhydride copolymer and polyvinyl methyl ether-maleic anhydride copolymer. Further, an aqueous dispersion of vinyl polymer (latex) can also be used.

The silver halide emulsion can be sensitized in various ways as it is manufactured or coated. It is preferably chemically sensitized by methods well known in the art, such as with sodium thiosulfate, alkyl thioureas, or with gold compounds such as gold rhodanide, gold chloride, or a combination of both. Also,
At any time during the production of silver halide emulsions, the
By using a compound of a metal belonging to Group VIII, for example, a salt of cobalt, nickel, rhodium, palladium, iridium, white, etc., it is possible to obtain preferable properties for a printing plate for direct platemaking, which has high sensitivity, high sharpness, and high resolution. You can Addition amount is 1 silver halide
It is in the range of moles per 10 ^-8 to 10 ^-8 mol. In the silver halide emulsion layer, other additives such as coating aids, hardeners,
The antifoggant, the developing agent, and the white pigment described above may be contained.

For the silver halide emulsion used in the present invention, a sensitizing dye suitable for the wavelength of the light source for scanning exposure is used.

For example, when using a semiconductor laser light as the light source, 700 nm,
In particular, sensitizing dyes having a maximum spectral sensitivity in a wavelength region longer than 750 nm include, for example, U.S. Patent Nos. 2,095,854 and 2,095,856.
No., No. 2,955,939, No. 3,482,978, No. 3,552,97
No. 4, No. 3,573,921, No. 3,582,344, No. 3,623,8
It can be that described in the specification of No. 81 and the like.

Preferably, for example, dyes represented by the following general formulas (I) to (IV) are used.

General formula (I) General formula (II) General formula (III) General formula (IV) In the general formulas (I) to (IV), Z ₁ and Z ₂ may be the same or different and each represents an atomic group necessary for forming a 5- or 6-membered nitrogen-containing heterocycle. . R ₁ and R ₂
May be the same or different and each represents an alkyl group or an alkenyl group. R ₃ represents an alkyl group, an alkenyl group or an aryl group. R _{4 to} R _{10, which} may be the same or different, each represents a hydrogen atom, a halogen atom, an alkyl group, an aryl group or an alkoxy group. However, R ₆ and R ₇ or R ₈ and R ₉ may be connected to each other to form a 5- or 6-membered ring. R ₁₁ and R ₁₂ may be the same or different, and each is an alkyl group,
It represents an aryl group, and R ₁₁ and R ₁₂ may be linked to each other to form a 5- or 6-membered ring. Y represents a sulfur atom, an oxygen atom, or N—R ₁₃ (R ₁₃ is an alkyl group). X represents an acid anion. l, m, n, p and q are each 1
Or represents 2.

Specific examples of Z ₁ and Z ₂ include thiazole, benzothiazole, naphtho [1,2-α] thiazole, naphtho [1,2-
α] thiazole, naphtho [2,12-α] thiazole, selenazole, benzoselenazole, naphtho [2,1-α] selenazole, naphtho [1,2-α] selenazole, oxazole, benzoxazole, naphtho [1,2 -Α] oxazole, naphtho [2,1-α] oxazole, naphtho [2,3-α] oxazole, 2-quinoline, 4-quinoline, 3,3-dialkylindolenine, imidazole, benzimidazole, naphtho [1, 2-α] imidazole,
Nitrogen-containing heterocycles such as pyridine can be mentioned. These heterocycles are alkyl groups (eg methyl, ethyl,
Butyl, trifluoromethyl etc.), hydroxy group, alkoxy group (eg methoxy, ethoxy, butoxy etc.), carboxy group, alkoxycarbonyl group (eg methoxycarbonyl, ethoxycarbonyl etc.), halogen atom (eg fluorine, chlorine, Substituents such as bromine, iodine), aralkyl group (eg, benzyl, phenethyl, etc.) cyano group, alkenyl group (eg, allyl group), etc.
Alternatively, it may have two or more.

In R ₁ and R ₂ , the alkyl group is a lower alkyl group such as methyl, ethyl, propyl and butyl, a hydroxyalkyl group such as β-hydroxyethyl and γ-hydroxypropyl, β-methoxyethyl and γ-methoxypropyl. Alkoxyalkyl groups such as, β-acetoxyethyl, γ-acetoxypropyl, β-benzoyloxyethyl and like acyloxyalkyl groups, carboxymethyl, carboxyalkyl groups such as β-carboxyethyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, β- An alkoxycarbonylalkyl group such as ethoxycarbonylethyl,
Examples include sulfoalkyl groups such as β-sulfoethyl, γ-sulfopropyl, and δ-sulfobutyl; aralkyl groups such as benzyl, phenethyl, and sulfobenzyl; and alkenyl groups such as allyl.

Examples of R ₃ include the alkyl groups and alkenyl groups as described above for R ₁ and R ₂ and aryl groups such as phenyl, tolyl, methoxyphenyl, chlorophenyl and naphthyl.

R _{4 to} R ₁₀ are a hydrogen atom, a halogen atom (for example, chlorine, bromine, iodine, fluorine), an alkyl group as described in R ₁ and R ₂ , an aryl group or an alkyl group as described in R ₁ and R _2. An alkoxy group having R ₁ and R ₆ and R ₇
Alternatively, the 5- or 6-membered ring formed by R ₈ and R ₉ may be substituted with a lower alkyl group or the like. R ₁₁ and R
₁₂ represents an alkyl group or an aryl group as described for R ₁ and R ₂ , and R ₁₁ and R ₁₂ may be connected to each other to form a 5- or 6-membered ring. Examples of R ₁₃ include the alkyl groups described for R ₁ and R ₂ .

Examples of the acid anion of X include an alkylsulfate ion such as methylsulfate and ethylsulfate, a thiocyanate ion, a toluenesulfonate ion, a halogen ion such as chlorine, bromine and iodine, and a perchlorate ion. The dye has a betaine-like structure. Does not exist when taking.

Typical specific examples of the sensitizing dye are shown below.

When a helium-neon laser beam is used as the light source, the sensitizing dyes described in JP-A-60-100147 can be preferably used and are represented by the following general formula (V).

General formula (V) (In the formula, R _{1 and} R ₂ are each an alkyl group (for example, methyl group, ethyl group, propyl group, butyl group, β-sulfoethyl group, γ-sulfopropyl group, γ-sulfobutyl group, vinylmethyl group, β-carboxy group. Ethyl group, γ-carboxypropyl group, δ-carboxybutyl group, etc.), alkenyl group, aryl group, aralkyl group, R ₁ and
At least one of R ₂ is a substituted alkyl group having a sulfo group or a carboxyl group. R _{3 to} R ₆ each represent a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a hydroxyl group, an alkoxycarbonyl group, or a halogen atom, and R ₃ and R ₄ or R ₅ and R ₆ form a benzene ring. May be. R ₇ represents an alkyl group, an aryl group or an aralkyl group. Y ₁ and Y ₂ are O atom, S atom, Se atom and N-, respectively.
R ₈ (R ₈ is a lower alkyl group) is represented. X represents a cation such as hydrogen, an alkali metal or ammonium. m and n represent 1 or 0. ) Representative sensitizing dyes are exemplified.

The sensitizing dye used in the present invention can be synthesized by a method known to those skilled in the art. The time of addition to the silver halide emulsion can be any time until the emulsion is coated. The addition amount can be varied over a wide range, but good results are from 1 × 10 ⁻⁵ to 1 × 10 ⁵ per mol of silver halide.
^-In the range of ² moles. The optimum addition amount varies depending on the conditions of the silver halide emulsion, such as the halogen composition, the average grain size of the silver halide grains, and the crystal habit.

The hydrophilic colloid of the undercoat layer may be any one, including those described above. The amount of hydrophilic colloid in the undercoat layer is generally preferably larger than that in the emulsion layer, and is 1 to 1 m ²
It is in the range of 8 g, preferably 2 to 6 g. The dry thickness (μm) of the colloid layer is approximately in agreement with the coating weight (gram) per 1 m ² of the colloid when the specific gravity of the colloid is calculated as 1.

The subbing layer can be a plurality of layers which also serve as intermediate layers.

As the physical development nuclei, known ones such as antimony, bismuth, cadmium, cobalt, palladium, nickel, silver, lead, zinc and like metals and their sulfides can be used. For the image-receiving layer, a hydrophilic colloid such as gelatin, carboxymethyl cellulose, gum arabic, sodium alginate, hydroxyethyl starch, dialdehyde starch, dextrin, hydroxyethyl cellulose, polystyrene sulfonic acid, a copolymer of vinylimidazole and acrylamide, polyvinyl alcohol, etc. is used. You may include 1 type (s) or 2 or more types. The hydrophilic colloid contained in the image receiving layer is preferably 0.5 g / m ² or less.

A hygroscopic substance, for example, a humectant such as sorbitol or glycerol may be present in the image receiving layer. Further, in the image-receiving layer, barium sulfate, titanium dioxide, china clay, silver and the like pigments for preventing skimming, a developing agent such as hydroquinone and a curing agent such as formaldehyde and dichloro-S-triazine may be contained.

The DTR treatment liquid used in the present invention is US Patent No. 4.297,429.
Nos. 4,297,430 and 4,355,090, 2-mercaptobenzoic acid, cyclic imides (e.g., uracil), etc., thiosulfuric acid, thiocyanate silver halide solvents, alkali agents, such as water. Sodium oxide,
Preservatives such as potassium hydroxide, lithium hydroxide, sodium triphosphate, etc., such as sodium sulfite, potassium sulfite, etc., thickeners, such as hydroxyethyl cellulose, carboxymethyl cellulose, antifoggants such as potassium bromide, 1-phenyl- 5-mercaptotetrazole,
Benzotriazole, the compound described in JP-A-47-26201,
Developers such as hydroquinone, 1-phenyl-3-pyrazolidone and development modifiers such as polyoxyalkylene compounds and onium compounds may be included.

In carrying out the silver complex salt diffusion transfer method, for example, British Patent Nos. 1,000,115, 1,012,476, 1,017,273, and
As described in the specification of 1,042,477 and the like, incorporation of a developer into a silver halide emulsion layer and / or an image receiving layer or another water permeable layer adjacent thereto has been carried out. Therefore, in such a material, the processing solution used in the developing step may be a so-called "alkaline activating solution" containing no developer.

The lithographic printing plate produced according to the present invention is, for example, Japanese Patent Publication Sho 48.
-29723, U.S. Pat. No. 3,721,539 and the like can be converted or enhanced to be ink-receptive by a compound as described in the specification.

The printing method or the desensitizing liquid, dampening liquid or the like to be used may be a commonly known method.

(E) Examples Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited thereto.

Example 1 A support having both sides coated with polyethylene resin was provided with a matting layer containing silica particles having an average particle size of 5μ on one side, and carbon black and phenidone were included on the opposite side, and a photographic gelatin was used. Average particle size of 7% by weight
Undercoat layer containing silica powder (adjusted to pH 4.5), chemically sensitized with a gold compound and hypo, then 2-mercaptobenzoic acid, and silica powder with an average particle size of 7 μm to photographic gelatin. And a silver halide emulsion layer (adjusted to pH 4.5) containing 5% by weight.

The silver halide emulsion is prepared by adding the sensitizing dye (6) to the silver halide 1
It contains 1.0 × 10 ^-4 mol per mol, and 5 × 10 ^-7 mol of iridium was added per 1 mol of silver halide during physical ripening. It was a substantially cubic silver chloride crystal in which 90% or more of all grains were distributed in the range of 30%.

The gelatin of the undercoat layer is 3.0 g / m ² , and the gelatin of the emulsion layer is 1.0 g / m ² .
m ^2, and is applied at a rate of silver halide 1.0 g / m ² in terms of silver nitrate. The subbing layer and the emulsion layer contained formalin as a hardening agent in an amount of 5.0 mg / g gelatin based on gelatin.

The optical reflection density of the undercoat layer at 780 nm was 1.26. After drying and heating at 40 ° C. for 14 days, 0.8 g / m of hydroquinone was added to the core coating solution of plate No. 11 in Example 1 of JP-A-54-103104 on the emulsion layer. ^The added liquid is adjusted in the same manner so as to be ² and applied (Comparative planographic printing plate A).

On the other hand, a comparative planographic printing plate B was prepared in exactly the same manner as the planographic printing plate A except that the optical reflection density of the undercoat layer was 0.82.

Next, titanium dioxide was added to the undercoat layer of the planographic printing plate B at 2.0 g / m ²
Of the present invention having an optical reflection density of 0.77.
Was produced.

A dark red filter that transmits light having a wavelength longer than about 700 nm was attached to a light source, and each lithographic printing plate was exposed for 10 ⁻⁵ seconds through a wedge having a density difference of 0.15. This was used as a sample for sensitometry.

On the other hand, Uitre Sett, a laser diode scanner that emits a proper exposure according to the sensitivity of each lithographic printing plate at 780 nm
er (manufactured by Uitre, USA). This was used as a printing sample.

Each of the imagewise exposed printing plates was
It was developed at 30 ° C. for 30 seconds. After the development treatment, the original plate is passed between two squeezing rollers to remove excess developer, immediately treated with a neutralizing solution having the following composition at 25 ° C. for 20 seconds, and squeezing rollers remove excess liquid. , Dried at room temperature.

Each printing sample was attached to one sheet, this sheet was mounted on an offset printing machine, and the following desensitizing solution was applied all over the plate surface, using the following dampening solution that was made a dilute solution than usual. Printed.

The printing machine is ABCD 350CD (AB
A trademark of an offset printing machine manufactured by the company) was used.

The printing durability shows the number of printed sheets in which a minute transferred silver image is missing and the number of printed sheets in which background stain occurs, and the sensitivity is shown in Table 1 as a relative sensitivity when the planographic printing plate A is 100.

It can be seen that the lithographic printing plate C of the present invention has higher sensitivity than the comparative lithographic printing plates A and B, and has high printing durability in terms of missing silver and background stain.

Example 2 The sensitizing dye (6) in the lithographic printing plate A of Example 1 was replaced with the sensitizing dye (3), and the reflection density of the undercoat layer was 0.65. A lithographic printing plate E (comparative) having a reflection density of 0.34 was prepared.

On the other hand, 1.3 g / m ^{2 of} titanium dioxide was added to the undercoat layer of planographic printing plate D.
A lithographic printing plate F of the present invention containing (reflection density of 0.62) and a comparative lithographic printing plate G containing 1.3 g / m ^{2 of} titanium dioxide in the undercoat layer of the lithographic printing plate E (reflection density of 0.32) were prepared.

Thereafter, the same test as in Example 1 was conducted, and the results are shown in Table 2. The relative sensitivity was set to 100 for the planographic printing plate D.

Example 3 A lithographic plate prepared by replacing the sensitizing dye (6) in the lithographic printing plates A to C of Example 1 with the sensitizing dye (15) (3 × 10 ⁻⁴ mol per mol of silver halide). The printing plates were sequentially designated as H to J.

Table 3 shows the results of a test conducted according to Example 1 using a helium-neon laser beam. The relative sensitivity was 100 for the printing plate H.

It can be seen that the lithographic printing plate J of the present invention has high sensitivity and high printing durability even in plate making with a helium-neon laser beam.

(F) Effects of the Invention According to the plate-making method of the present invention, a lithographic printing plate having improved sensitivity to laser light and printing durability can be obtained.

Claims (1)

[Claims] 1. A plate making method in which a lithographic printing plate having an undercoat layer, a silver halide emulsion layer and a surface physical development nucleus layer on a support is subjected to scanning exposure with high illuminance for a short time and then developed with a developer for silver complex diffusion transfer. In the method, the undercoat layer contains a white pigment, the emulsion layer and / or the undercoat layer contains fine powder having an average particle size of 2 to 10 μm, and scanning exposure is performed below the emulsion layer. Light reflectance of 10
A plate-making method comprising using a lithographic printing plate that has been subjected to halation prevention and contains a necessary amount of a light absorber in an amount of 40% to 40%.