JPS6064351A - Developing method of photosensitive lithographic printing plate - Google Patents

Abstract

PURPOSE:To develop simultaneously negative type and positive type photosensitive lithographic printing plates by using weak alkaline water having <12pH for a developing soln. of the 1st developing zone and strong alkaline water having >=12pH for a developing soln. of the 2nd develping zone. CONSTITUTION:The 1st developing soln. which is weak alkaline water having <12pH is ejected from nozzle piper 9 and the 2nd developing soln. which is strong alkaline water having >=12pH is ejected from nozzle pipes 9' and a photosensitive lithographic printing plate 7 subjected to a developing treatment is thoroughly washed in a washing zone. A pair of inserting rollers 1'', squeezing rollers and spray pipes 9'' are installed in the washing zone. The city water contained in a tank is fed by a pump 6'' to the pipes 9'' and the 1st developing soln. and the 2nd developing soln. sticking to the developed photosensitive lithographic printing plate are washed away by the city water ejected from the nozzles of said pipes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing a photosensitive lithographic printing plate, and more specifically, a negative photosensitive lithographic printing plate that can be developed with weak alkaline water and a method of developing a photosensitive lithographic printing plate with strong alkaline water N, This invention relates to a common developing method that allows positive photosensitive lithographic printing plates to be simultaneously developed using seven automatic developing machines.

Conventionally, negative-working photosensitive planographic printing plates and positive-working photosensitive planographic printing plates use different developers in most cases, and negative-working photosensitive planographic printing plates use a special developer.

In addition, unless a positive-working photosensitive lithographic printing plate is developed with a special developer, a lithographic printing plate with sufficient performance cannot be obtained. For this reason, printers who use both negative-working photosensitive lithographic printing plates and positive-working photosensitive lithographic printing plates develop each plate using two automatic developing machines. There were complaints that installing an automatic developing machine at a small printing company would make the work space smaller and make it difficult to perform one task. Therefore, an attempt was made to simultaneously develop a special negative-working photosensitive lithographic printing plate and a special positive-working lithographic printing plate with a developer mixture of the two. However, compared to the case where a negative-working printing plate and a positive-working printing plate are developed separately using a dedicated developer, the throughput is low and is not fully satisfactory.

As another attempt, seven automatic developing machines were equipped with tanks for storing negative and positive developing solutions, and when developing negative-type photosensitive planographic printing plates, a switching valve was used to increase the negative image. The solution is introduced into the development zone and developed, and after the development is completed, the developer is collected in a negative storage tank, and the positive planographic printing plate? ]l
- In the case of forming a parent image, a method was proposed in which a positive developing solution was introduced into the developing zone using a switching valve, and this method was actually attempted, but it took a long time to change the developing solution, and positive type photosensitive lithographic printing This method has a disadvantage in that when it is desired to process two or three negative photosensitive lithographic printing plates while processing a large number of plates, it is not possible to process them immediately.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks and to provide a common developing method that can simultaneously develop a negative-working photosensitive lithographic printing plate and a positive-working photosensitive lithographic printing plate. Another object of the present invention is to provide a method by which a large number of negative planographic printing plates and positive planographic printing plates can be developed using seven automatic station imagers.

As a result of repeated research by the present inventors, a negative-working photosensitive lithographic printing plate and/or a negative-working photosensitive lithographic printing plate in which the unexposed area is eluted or swollen and developed with weak alkaline water with p I-1/λ or less, and/or Id
A positive-working photosensitive lithographic printing plate whose light areas are eluted or swollen and depleted by strong alkaline water with a pH of 2 or more is used, and a developer consisting of weakly alkaline water with a pH of less than 12 is added to expose one image. The object of the present invention is achieved by performing development through a horizontal conveyance type automatic developing machine which has a first developing zone which is in series and a second developing zone which is charged with a developing solution made of strong alkaline water having a pH of 2 or higher. was found to be achieved.

The negative-working photosensitive lithographic printing plate whose non-lightened areas are eluted or swollen by weakly alkaline water having a pH of less than pH/j used in the present invention is a negative photosensitive lithographic printing plate containing an organic polymer having an acid value of 10 to 200 and substantially water. A photosensitive layer consisting of an insoluble photosensitive diazo compound (for example, a sulfonate or a Lewis acid salt of a condensate of diphenylamine-+-diazonium salt and formaldehyde) is provided on a hydrophilic support and is photocurable in the absence of light. A photosensitive lithographic printing plate having layers is preferred.

Specific examples of organic polymers having an acid value of 10-200 include Copolymer 1 containing acrylic acid, methacrylic acid, crotonic acid or maleic acid as an essential component, such as US Pat. No. 4Z,/23.

Two hydroxy ether acrylate or λ-hydroxyethyl methacrylate as indicated in λ7,
Ternary or base copolymers of acrylonitrile or methacrylonitrile, acrylic acid or methacrylic acid and optionally further copolymerizable monomers, JP-A-Sho! Acrylic acid or tank IJ/ acid, acrylic acid or methacrylic acid, which has a hydroxyl group at the end and is esterified with a group containing a dicarboxylic acid ester residue as described in No. 3-HAURI No. 03. and, if necessary, a copolymer with other copolymerizable monomers, JP-A-Sho!
≠-216117, a monomer having an aromatic hydroxyl group at the end (for example, N-(≠-hydroxyphenyl) methacrylamide, etc.), acrylic acid or methacrylic acid, and if necessary, other monomers. Copolymer S with at least seven copolymerizable monomers of
≠−! Copolymers of alkyacrylates or methacrylates, acrylonitrile or methacrylonitrile, and unsaturated carboxylic acids as described in No. -/4'i are included. In addition, acidic polyvinyl alcohol derivatives and acidic cellulose derivatives are also useful.

On the other hand, as the photosensitive diazo compound, diazo resins represented by a condensate of p-diazodiphenylamine and formaldehyde are useful, and diazo resins that are substantially water-insoluble and organic solvent-soluble are particularly preferred. Such preferred diazo resins are described in detail in U.S. Pat. No. 3,300,30707 and JP-A-673.

The photosensitive diazo compound is contained in the photocurable photosensitive layer by weight.

It is preferably contained within the range of r-2θ weight f%.

A photosensitive lithographic printing plate is prepared by disposing a photocurable photosensitive layer as described above on a metal support such as an aluminum plate. The surface of the aluminum plate may be subjected to a chemical conversion treatment using an aqueous solution of an alkali 4-gold silicate solution as described in U.S. Pat. i
After anodizing as described in No. ri,≠t1, it is preferable to treat with an aqueous solution of an alkali metal silicate, and on the thus surface-treated aluminum plate, a photosensitive layer as described above is formed with a thickness of 015 to 197 m. , preferably θ, r
~3. evening? /m2 to form a photosensitive lithographic printing plate.

As the developing solution containing weakly alkaline water with a pH of less than 2 for use in the present invention, JP-A No. 1-77≠oi and ll-
No. 40221, same! From an anionic surfactant, an organic solvent whose solubility in water is below the IO weight ratio at room temperature, an alkaline agent, water and, if necessary, a stain preventive agent, as described in No. 3-11Lt202 and No. 1203iII. An aqueous solution is suitable.

Examples of anionic surfactants in the developing solution of weakly alkaline water used in the present invention include sodium salts of lauryl alcohol sulfate, sodium salts of octyl alcohol sulfate, and ammonium salts of lauryl alcohol sulfate.

Carbon number t of secondary sodium alkyl sulfate etc.
, 2.2 higher alcohol sulfate ester salts, aliphatic alcohol phosphate ester salts such as sodium salt of cetyl alcohol phosphate ester, for example sodium salt of dodecylbenzenesulfonic acid, sodium salt of isopropylnaphthalenesulfonic acid, metanitrobenzenesulfone alkylaryl sulfonates such as sodium salts of acids, e.g. C17I(33CON(CH
3) Sulfonic acid salts of alkylamides such as CH2CH2SO3Na, etc.

For example, sodium sulfosuccinate dioctyl ester,
These include sulfonic acid salts of dibasic fatty acid esters such as sodium sulfosuccinate dihexyl ester.

The anionic surfactant is added to the developer solution at the time of use.
It is appropriate to keep the content within the weight range. o,
If it is less than the i weight section, the effectiveness of its use will be lower,
! If it exceeds the weight factor, for example, the dye contained in the photocurable photosensitive layer may elute (color loss) excessively, or the mechanical and chemical strength such as the abrasion resistance of the photolayer image may deteriorate. A juxtaposition occurs, such as deterioration of Therefore, the preferred usage amount is in the range o, t-/, J' weight ratio.

The organic solvent used in the developing solution consisting of weakly alkaline water used in the present invention is suitably selected from those having a solubility in water of about 10z@es or less, preferably about λ weight i1 or less. Examples of such organic solvents include l-phenylethanol, λ-phenylethanol, 3-phenylpropanol, 1 μm phenylphthanol, μm
Phenylbutanol-λ, λ-phenylbutanol-7
゜Two phenoxyethanol% λ-penzyloxyethyl alcohol) -A/, 0-methoxybenzyl alcohol.

m-methoxybenzyl alcohol, p-methoxybenzyl alcohol, benzyl alcohol, cyclohexanol, λ-methylcyclohexanol.

Examples include μm methylcyclohexanol and 3-methylcyclohexanol.

The content of the organic solvent in the developing solution is preferably t, r weight - tert. The amount used is closely related to the amount of surfactant used, and it is preferable to increase the amount of surfactant as the amount of organic solvent increases1-7. This is because if the amount of surfactant is small and the amount of organic solvent is large, the organic solvent will not dissolve, and therefore good developability cannot be expected to be ensured.

The alkaline agent used in the developing solution consisting of weakly alkaline water used in the present invention is sodium silicate.

Potassium silicate, potassium hydroxide, sodium hydroxide, lithium hydroxide, tertiary sodium phosphate, dibasic sodium phosphate, tertiary ammonium phosphate, dibasic ammonium phosphate, sodium metasilicate, sodium bicarbonate, sodium borate, ammonium borate.

Inorganic alkaline agents such as ammonia, and monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, n-glythylamine, monoethanolamine, jetanolamine, triethanolamine, mono There are organic amine compounds such as inpro/q-nolamine, io-tubulovanolamine, ethyleneimine, ethylenediamine, pyridine, etc.
These can be used alone or in combination. The content of the alkaline agent in the developing solution is preferably o, or to 3% by weight, preferably 0.1 to 7% by weight. θ, Oj
If the f coefficient is less than that, the removal of the uncured photosensitive layer will be incomplete.

On the other hand, if the amount exceeds 3% by weight, the mechanical and chemical strength of the photocured portion of the photosensitive layer will deteriorate.

For example, in the case of planographic printing plates, this appears as a decrease in printing durability.

The remaining component of the developer of the present invention is water, and if necessary, various additives known in the art may be included. For example, sodium sulfite and the sodium salt of sulfopyrazolone are used as antifouling agents, and ethylenediaminetetraacetic acid II Na salt and N+CH are used as water softeners.
2C00Na)a can be added.

The positive-working photosensitive lithographic printing plate in which the exposed areas are eluted or swollen and developed with strong alkaline water having a pH of pH/- or higher used in the present invention is a combination of an 0-quinonediazide compound and a pH/- or higher.
A photosensitive layer made of an organic polymer compound that is hardly soluble in weak alkaline water but soluble in strong alkaline water with a pH of less than 2 is provided on the hydrophilic support, and the exposed area is adjusted to pH/2 by 1 g of light.
- A photosensitive lithographic printing plate having a photosensitive layer that is soluble in strong alkaline water is desirable. Examples of 0-quinonediazide compounds include 1, for example, U.S. Pat. No. 3,0416,110, U.S. Pat.
No. 1, No. 3, 0≠t, // No. j, No. i, oat,
IIR No. 3,04t6. //R issue, same issue J, a
llt, No. 120, No. 3.0≠t, i, 2i, No. 3,04tt, /Coco, No. J, O Hirot, /23, No. J, ot/, ≠30 , same No. 3. io, 2.
toy issue, same number 3. iot.

Gut! No. 3, 63! , No. 702, No. 31t≠7
, 414tJ, and many other publications. Among these, 0-naphthoquinonediazide sulfonic acid ester or 0-naphthoquinonediazidecarboxylic acid ester of an aromatic hydroxy compound, and 0-naphthoquinonediazide sulfonic acid amide or 0-naphthoquinonediazidecarboxylic acid amide of an aromatic amine compound are particularly preferred. , etc., U.S. Patent No. 3. t3 evening, 7
U.S. Patent No. V, which is obtained by subjecting the condensate of pyrogallol and acetone to an ester reaction with 0-su7toquinonediazide sulfonic acid as described in the specification of No. 02.

02! A product obtained by subjecting a polyester having a hydroxyl group at the end described in No. 111 to an ester reaction with O-naphthoquinonediazide sulfonic acid or O-naphthoquinonediazidecarboxylic acid.

A homopolymer of p-hydroxystyrene or a copolymer of this and other copolymerizable monomers with 0-naphthoquinonediazide sulfonic acid as described in British Patent No. 1,4t Tag, θ≠3 or ester reaction of 0-naphthoquinonediazidecarboxylic acid, from US Pat. No. 3.7.

As described in the specification of No. 7//, 0-naphthoquinonediazide sulfone flit or l3- 0-naphthoquinonediazidecarboxylic acid is added to a copolymer of p-aminostyrene and other copolymerizable monomers. The reactants are very good.

Examples of organic polymer compounds soluble in strong alkaline water used in combination with these O-quinonediazide compounds include novolac type phenol resins. Specifically, phenol formaldehyde m1lb, 0-cresol formaldehyde moh.

Includes m-cresol formaldehyde resin and the like.

Furthermore, as described in @ Kaisho 1O-12jtrot publication, in addition to the above-mentioned phenol resins, phenol or cresol substituted with an alkyl group having 3 to r carbon atoms such as t-butylphenol formaldehyde resin and formaldehyde are used. It is even more preferable to use it in combination with a condensate.

The organic polymer compound soluble in strong alkaline water is present in the photosensitive layer from about jO to about t! Weight, more preferably ≦θ~10% by weight
, may be included.

If necessary, additives such as dyes, plasticizers, and components that provide printout performance may be added to the photosensitive layer consisting of an 0-quinonediazide compound and an organic polymer compound soluble in strong alkaline water. I can do it.

The present fw solution for a positive planographic printing plate in which the non-light areas are eluted or moistened by strong alkaline water with a pH of 2 or more used in the present invention includes alkali metal hydroxides, alkali metal silicate salts,
Alkali metal phosphate or alkali metal aluminate,
A strongly alkaline aqueous solution having a pH of 2 or higher and consisting of water and optionally a surfactant and other additives is suitable. Specifically, Japanese Patent Application Publication No. Sho≠f-/113j, No. J-1233
No. 4A.

Same ra-trxooti issue, same! No. 2-127331,
same! No. 3-44307, jθ-71→02.

Same jj-, 2.27 JP issue, same ta! --rioo issue.

Same evening, Ichita! 911t, same JR-IiroJy, same! Examples include developing solutions made of sodium silicate or potassium silicate described in J-/4'kojλt@, large jjO-jt/Jλg issues.

Both the negative-working photosensitive lithographic printing plate and the positive-working photosensitive lithographic printing plate described above are passed through a horizontal conveyance type automatic developing machine having a first development zone and a first development zone in succession after image exposure. Then, the non-image areas of the photosensitive layer are removed. 1st
The figure is a schematic cross-sectional view of 11 such automatic developing machines, in which a negative and/or positive photosensitive planographic printing plate 7 is first inserted into a first development zone by a pair of insertion rollers and It is transported in the direction of the arrow by a transport roller r or the like.

A plurality of nozzle pipes are installed above the conveyance path, and a first developer consisting of weakly alkaline water with a pH of less than 7λ stored in a tongue puffer is pumped through the nozzle/ξ by a pump B.
The photosensitive lithographic printing plate is exposed through the nozzle. - to the surface of the first version 117! lfi is injected, and the surface of photosensitive F- is further rubbed by a brush roller 3, and finally the first developer is squeezed out by a pair of squeezing rollers λ. The photosensitive lithographic printing plate thus passed through the first development zone is conveyed to the second development zone by a pair of insertion rollers/'.

Also in the second development zone, a number of nozzle pipes' are installed above the conveyance path of the photosensitive planographic printing plate.
A first developer consisting of strong alkaline water with a pH of 2 or higher is supplied to the nozzle pipe 2 by a pump 6' and is stored in a tank j.
', the λth developer is injected from the nozzle onto the surface of the photosensitive layer of the photosensitive lithographic printing plate, and then the brush roller 3'
The surface of the photosensitive layer is rubbed, and finally the λth developer is squeezed out by a squeeze roller λ'. The photosensitive lithographic printing plate 7 that has passed through the first development zone and the second development zone and has been subjected to development processing is then sufficiently washed with water in a water washing zone. The water washing zone is equipped with a pair of insertion rollers and a squeezing roller, and is equipped with a spray pipe.The tap water stored in the tank is sent to the nozzle pipe by a pump, and is sprayed from the nozzle. The first developer and/or the λ-th developer adhering to the developed photosensitive lithographic printing plate are thoroughly washed away by the tap water.

Even though the first developing zone and the λth developing zone of the above-mentioned horizontal conveyance type automatic developing machine are equipped with replenishing devices suitable for each developing solution in order to recover from the decrease in performance due to processing of developer slag. good. Further, the horizontal conveyance type automatic developing machine used in the present invention has a washing zone continuous after the developing zone, if necessary.

Fixing zone, protective gum application zone or drying zone 7
- Can be used with attached.

Furthermore, the present invention will be elucidated in detail with examples. Note that the examples merely show examples of specific embodiments and do not limit the present invention.

Example 1 ♀ Ethylene glycol monomethyl ether J under bare air flow
Heat the old part of the ooz to 100c, add 10 parts by weight of λ-hydroxyethyl methacrylate, 7 parts by weight of acronitrile, 7 parts by weight of methyl methacrylate,
10°J' parts by weight of methacrylic acid and 1 part by weight of benzoyl peroxide
1.2 parts by weight of the mixed solution was added dropwise over 2 hours.

75 minutes after the completion of the dropwise addition, 300 parts by weight of ethylene glycol monomethyl ether and 0.3 parts by weight of benzoyl peroxide were added, and the mixture was allowed to react for several hours.

After the reaction was completed, the copolymer was diluted with methanol and poured into water to precipitate the copolymer, followed by vacuum drying at 700C.

This λ-hydroxyethyl methacrylate copolymer (I
) had an acid value of 21.

A 28 aluminum plate with a thickness of 0/IrTnTI was erected to a temperature of 0.000 m and then desmutted with 30% of sodium aluminate water at Aθ0C. This aluminum plate was anodized in λθ-containing acid at a current density of 2 A/dm2 for 1 minute, and then anodized at 700 C sodium silicate at 2°! The sample was treated with an aqueous solution of water for 7 minutes.

The following photosensitive liquid was applied to this aluminum plate, and 1000
After drying at C for 2 minutes, a negative photosensitive lithographic printing plate was obtained.

Two-hydroxyethyl methacrylate copolymer (1) r7 parts by weight Condensate of p-diazodiphenylamine and paraformaldehyde One-methoxy l-hydroxy-j-benzoylbenzenesulfonic acid 10M amount m Oil Blue #603 (Orient Chemical Industry Co., Ltd. tJJ, triphenylmethane oil-soluble dye) 3M parts Comethoxyethanol 600 parts by weight Methanol 1
00 parts by weight of ethylene dichloride too=i part The dry coating weight is ko, evening? /m2. A transparent negative original image was brought into close contact with this photosensitive lithographic printing plate, and the image was illuminated for ≠0 seconds from a distance of 70 cfn using a 3θ ambore carbon arc lamp.

U.S. Patent No. 3, t3 as partially positive photosensitive lithographic printing plate
In the evening, 1 part of 7 parts of naphthoquinone-/,j-')azido r-sulfonic acid ester of polyhydroxyphenyl obtained by condensation polymerization of acetone and pyrogallol described in Example 1 of the 70th edition of the Meiji Ra book and novolak. Type cresol formaldehyde resin 2 parts by weight, oil pull kilo 0
3 A photosensitive solution prepared by dissolving 0.03 parts by weight in 2ON parts of λ-methoxyethyl acetate and 20 parts by weight of methyl ethyl ketone was applied to an anodized aluminum plate after graining and dried for 2 minutes at tOoC. Dry coating weight λ
, ! A photosensitive lithographic printing plate of f/m was obtained. A transparent positive original image was brought into close contact with this photosensitive lithographic printing plate and imagewise exposed for 40 seconds from a distance of 70 cm using a 30 ampere carbon arc lamp.

As shown in Figure 1, 10 Jl of the weakly alkaline aqueous developer shown below was charged into the 7th developing zone of a horizontal conveyance type automatic acid developing machine which has λ dust image zones and a water washing or fixing zone after that, and the developer temperature was set to 30 liters. °CK11ll was adjusted.

Benzyl alcohol 300gr Triethanolamine 100gr Isopropylnaphthalene sulfonate 100gr Sodium phosphate sodium sulfite, 20gr Trisodium nitrilotriacetate jgr Ion exchange water
Ta≠rOgr Next, add potassium silicate (20% to Sing/) to the first development zone.
Molar ratio/2) A strong alkaline aqueous developer consisting of a diluted aqueous solution was charged with ion and the developer temperature was adjusted to 0C.

The transport speed of this automatic processor was set so that the developing time for both the first developing zone and the first developing zone was 2θ seconds, and the first developing zone was followed by a water washing zone. I put it in.

To prevent the washing water from becoming extremely dirty, a portion of fresh water was always replenished and drained through the overflow.

In addition, the strongly alkaline aqueous developer in the second development zone is continuously replenished with a 12% aqueous solution of potassium silicate (20 molar ratio 1.0% to SiO2) during development in order to recover from deterioration caused by processing and carbon dioxide gas in the air. Ta.

The imagewise exposed negative photosensitive lithographic printing plates and the positive photosensitive lithographic printing plates were indiscriminately passed through the above automatic processor for processing. With this processing method, negative-working photosensitive planographic printing plates can be processed up to 41 m271, and positive-working photosensitive planographic printing plates can be processed up to i.

We were able to process up to m27t. When the lithographic printing plates developed in this manner were coated with a protective gum and printed, it was possible to obtain beautiful printed matter with no stains in the non-image areas of each printing plate.

Example 2 In the same manner as in Example 1, 11 hydroxyethyl me+2.
2- Tafrylate/Acrylonitrile/Ether methacrylate/Methacrylic acid=,! 0. A 2-hydroxyethyl methacrylate copolymer i) of /20/λj/I/L weight % (monomer charge ratio) was obtained. Using this λ-hydroxyethyl methacrylate copolymer (n), the following photosensitive solution was coated on the sodium silicate treated aluminium plate of Example 1, and dried for 1000 C to obtain a negative photosensitive lithographic printing plate.

Diazo resin consisting of p-diazodiphenylamine of Example 1 o, ri parts by weight Cotardoxyethyl methacrylate copolymer (II)! , 00 tt Victoria Pure Blue BDH (manufactured by Hodogaya Chemical ■) 0,10 1t-7' Sodium tilnaphthalene sulfonate θ, 03 N Tricredidyl phosphonate 0 protection oN Phosphoric acid 0,10 # Fluorine surfactant (FC-≠JO) 0.03 parts by weight ethylene glycol monomethyl ether methanol/Att methyl ethyl ketone 3+2 water/s The dry coating weight was 2.527 m2. When this negative photosensitive lithographic printing plate was used in place of the negative photosensitive lithographic printing plate of Example 1, almost the same results as in Example 1 were obtained.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of an automatic developing machine suitable for carrying out the developing method of the present invention. /, /', /”... Insertion roller λ, 2', 2
“...Aperture roller 3.3'...Brush roller lag!...Development tank 4.4', 4”...
... Pump 7 ... Photosensitive planographic printing plate it
, r'... Conveyance roller ta, P', r'...
... Spray pipe IO ... Overflow outlet / / ... Tap water inlet Patent applicant Fuji Photo Film Co., Ltd. -

Claims (1)

[Claims] Negative photosensitive lithographic printing plates that are developed with unexposed areas eluted or swollen by weak alkaline water with pH less than H/λ and/or I) Exposed areas are eluted or swelled with strong alkaline water of H/j or higher. After the image is removed, the positive-working photosensitive lithographic printing plate to be imaged is passed through a horizontal conveyance type automatic imager having a first development zone and a second image zone in succession to remove the non-image area. This is an image method that consists of applying the same amount of water to the surface, and the developer in the first zone is p)I/
A common developing method for negative-working and positive-working photosensitive lithographic printing plates, characterized in that the developer in the first development zone is made of strong alkaline water with a p )I /λ or more.