JPS60156063A - Method and apparatus for automatically developing photosensitive lithographic plate - Google Patents

Abstract

PURPOSE:To maintain the concn. of a developing soln. in a prescribed range by measuring the AC impedance value of the developing soln. and compensating evaporation of water with a diluent. CONSTITUTION:When a PS plate is inserted in the direction of an arrow 20, a detector 21 actuates to feed a developing soln. in a developing tank 36 to a nozzle tube 28 and spray it. A nonimage part is removed with brush rollers 29, 31. The sprayed developing soln. is freed from insoluble matters with a filter 35, and recovered to the tank 36. A developer replenishing soln. 43 is supplied in accordance with the output of the detector 21. An impedance measuring sensor 38 is installed in the developing soln. 37 in the circulation system, and when a value measured with the meter 39 lowers to a predetermined value, an automatic measuring means 40 actuates in accordance with its output signal to add a prescribed amt. of diluent 41 to the developing soln. As a result, rise of the concn. can be compensated, thus permitting stable development for a long time in cooperation with the replenishment of the developer.

Description

[Detailed Description of the Invention] [Field of the Invention] The present invention relates to a method for developing photosensitive lithographic printing plates (hereinafter referred to as 28 plates), and more specifically, to developing a large number of 28 plates using an automatic developing device. A developing method that maintains the concentration of the developing solution within a certain range at all times by compensating for the evaporation and concentration of water in the developing solution, thereby achieving homogeneous development, and an automatic developing method for that purpose. It is related to the device.

[Prior art]

Generally, when developing 28 plates using an automatic developing device, the frequency of replacing the developer stored in the developing tank of the automatic developing device should be kept as low as possible even if a large number of 28 plates are developed. In order to achieve this, a replenisher is added depending on the amount of 28 plates to be processed and the time required for the process. That is, as the processing amount of 28 plates increases, the effective components of the developer stored in the developing tank are consumed and the developing ability decreases, until the desired development is no longer achieved, so in order to compensate for this, In addition, if the developer is alkaline, it absorbs carbon dioxide gas from the air over time, which deteriorates the developing ability of the developer, so this should be compensated for. For this purpose, the above-mentioned replenisher is added, and these are described in British Patent Application Publication No. 20 Ko6ri J/A Specification, International Patent Application Publication No. WOI 210101t, and Japanese Patent Application Laid-open No. 1987-37. -10≠J publication etc., it is described in detail.

However, even if 28 plates are developed with such compensation, depending on the temperature and humidity conditions of the environment in which the image is processed, water in the developer evaporates and the developer becomes concentrated, resulting in poor exposure to light. The ability to elute the non-image areas of the layer is reduced, resulting in poor development, and new problems arise in which components of the photosensitive layer that have been dissolved in the developer precipitate and become scum that adheres to the plate surface. As a result of experience, water was refilled manually in advance when scum appeared or was expected to occur. However, with manual methods such as this, if you replenish too much water and end up with poor development, or if you replenish after scum appears, you have to discard the plate with the scum and have to start over. The problem was that it didn't.

[Purpose of the invention]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved 28 plate development method that eliminates the problems caused by the evaporation of water in the developer. It is an object of the present invention to provide a 28-plate developing method capable of automatically compensating for evaporation and an automatic developing device therefor.

[Structure and effects of the invention]

The present inventors have conducted repeated research to achieve the above object, and have discovered that the degree of water evaporation in the developer can be determined by measuring the alternating current impedance value of the developer. I came to do this. That is, the present invention provides a method for developing a large number of image-exposed photosensitive lithographic printing plates with a developer consisting of an aqueous solution containing an electrolyte using an automatic developing device. The AC impedance value of the solution is measured, and when the value reaches a predetermined control value, a certain amount of water or at least one of the components contained in the developing solution is added to the developer. The concentration of the liquid is always maintained within a certain range by adding an aqueous solution (hereinafter collectively referred to as a diluent) containing an aqueous solution that is lower in concentration than the concentration in the diluent. This is a method of developing a photosensitive lithographic printing plate.

According to the present invention, the concentration of the developer is automatically maintained within a certain range at all times, so compared to the conventional manual method, there is no problem with poor development due to excessive replenishment of diluent or replenishment of diluent. Problems such as generation of scum due to shortage no longer occur, and stable development can be performed at all times.

Furthermore, since you are freed from the troublesome work of refilling water, you can improve your work efficiency.

In the present invention, as a method for measuring the AC impedance value of the developer, known means such as an AC impedance meter, an AC bridge meter, or other impedance meter can be used.

In addition, the optimum conditions for the measurement current value and oscillation frequency of the measuring device vary depending on the composition of the developer, etc., but the current value is set to a certain extent depending on the device and to prevent electrolysis of the water-soluble developer. It is preferably low, preferably from several hundred rrLA to several mA.

Also, the frequency is determined by the relationship with the capacitance component in the developer.
A frequency of several hundred Hz to several hundred KHz is preferable.

The impedance value of a developing solution containing an electrolyte depends on the temperature of the aqueous solution, and its value decreases as the temperature of the solution increases. Therefore,
Preferably, a measuring device is provided with a temperature sensor and a temperature guarantee circuit.

The sensor installation position of the AC impedance meter, AC bridge meter, or other impedance meter may be any place where it is immersed in the developer during measurement and where the AC impedance value of the developer can be measured, such as in the developer circulation of an automatic processor. The preferred location is in the system, especially in the developer tank or in the circulation pipe.

The impedance value of the developer decreases as it becomes concentrated, so the impedance value of the initial developer without fatigue (
Hereinafter, this will be referred to as the first impedance value. ) and the impedance value (hereinafter referred to as the second impedance value) at which the developer becomes fatigued and concentrated and begins to generate scum, it is possible to determine the predetermined impedance value that is lower than the first impedance value and higher than the second impedance value. When the impedance value of
activating an automatic metering means, such as an automatic metering pump;
By adding a certain amount of diluent to the developer, the impedance value can be controlled within a certain range. As a general guideline, it is preferable that the predetermined impedance value is set near the median value of the first invinidance value and the second impedance value. Also,
The amount of diluent to be replenished is preferably the amount necessary to reach the first impedance value, and this can be determined by a simple trial test once the composition of the diluent and developer and the amount of developer charged to the developer tank are determined. can be determined.

FIG. 1 is a schematic sectional view of a preferred embodiment of an automatic developing apparatus for carrying out the developing method of the present invention. This automatic developing device uses a conveying means such as a feed roller 1 to process the PS.
In the process of conveying the plate in the direction of the arrow C, a plurality of nozzle blades 3 are provided above the conveyance path, and the developing tank ≠
The developer inside! is sprayed onto the surface of the photosensitive layer of the PS plate from the nozzle of the nozzle pipe 3 by the pump 7, and if necessary, the surface of the photosensitive layer is further rubbed with a brush roller (not shown), etc., thereby performing the development process. In this case, the used developer is passed through a filter T to remove insoluble matter, and then collected into a tank. Then, the sensing means t senses that the PS plate has been inserted into the developing device, and the pump 7 is actuated and starts supplying liquid, and the jetting of the developer from the nozzle starts, and the PS plate is inserted into the developing device.
After the plate has passed through the development zone, the jetting of the developer is stopped.

Is a measuring device used to measure AC impedance values? (Measure the value with a measuring device such as an AC impedance meter or an AC bridge meter, and use automatic measuring means to output the operating signal when necessary.
Output to l. ) and sensor io, and sensor IQ is the developer in the tank! When the AC impedance value measured here drops to a predetermined value, the automatic metering means 1/ is activated by the output signal, and the diluent 12 is immersed in the tank. A certain amount is added to ginseng.・The automatic measuring means is set so that a fixed amount of diluent is added each time it receives an activation signal from the measuring device, and automatically stops when the fixed amount of diluent has been added. It looks like this. As this automatic metering means, for example, a known means such as one consisting of a timer and a liquid feeding pump can be used.

The automatic developing device shown in Fig. 7 is a device that only develops PS plates, but it has a developing zone, washing zone, water washing zone,
It goes without saying that in a PS plate processing apparatus having a gum coating zone and/or a drying zone, a dilution means as described above for maintaining the concentration of the developer within a certain range may be incorporated in the development zone. . Further, it is preferable to incorporate a replenishing means for a developer replenisher as conventionally known in these processing apparatuses, since the effects of the present invention can be further exhibited.

FIG. 2 is a sectional view of an automatic developing apparatus according to a particularly preferred embodiment of the present invention, which also incorporates such replenishment means. In this device, when the PS plate is inserted in the direction of the arrow 20, the detection means 21 is activated, and the developer 37 in the developing tank 3 is pumped by a pump 311°K into a plurality of pumps installed above and below the PS plate transport path. nozzle nozzle 2
! r, and spraying of the developer starts. The PS plate held by the insertion roller 2.2 is transferred to the conveyance roller 223.
In the order of 2≠, 3.0132, it is transported through the development zone while being sprayed with developer, and on the way, the brush roller,
After the surface of the photosensitive layer is rubbed by steps 2 and 31 to completely remove the non-image area of the photosensitive layer, the developing solution adhering to the developed PSmK is finally squeezed out by the squeegee roller 2j and then removed. , sent to the next flushing zone. The sprayed developer is collected in a tank 36 after insoluble matter is removed by a filter 3j. An output signal is input from the sensing means 2/ to the automatic measuring means≠2 during the time when the 28th plate is being sensed, and the developer replenisher≠3 is replenished to the developer in proportion to that time.

This compensates for the phenomenon liquid degraded by processing the p and ps plates. On the other hand, the developer 37 in the developer circulation system
Inside, a measurement sensor 3g is installed, and the current commercial liquid 3g is installed.
The impedance of 7 is measured by the measuring device 3, and when the measured value by the measuring device 3 drops to a predetermined value, the automatic measuring means is actuated by the output signal, and the diluent < 4
/ is added in a certain amount to the developer. This compensates for the concentration caused by the evaporation of water in the developer, and together with the compensation due to the addition of the developer replenisher, it becomes possible to perform stable development over a much longer period of time.

After passing through the development zone, the plate is then sent to a washing zone where it is thoroughly washed with water. The washing zone is the insertion roller 2
6 and a squeegee roller 27 are installed between which water is sprayed from a nozzle pipe 33. Rinsing water is either immediately discarded or collected in a tank, etc., and then disposed of after being subjected to necessary treatment.

In the developing method of the present invention, since the AC impedance value of the developer is measured and the concentration is detected from that value, the developer used must be an aqueous solution containing an electrolyte, and is therefore particularly preferred. is composed of 70 to 70% by weight of water and contains inorganic ions. Therefore, the developing method of the present invention can be conveniently applied to 28 plates that can be developed using such a developer.

Preferred examples of the 28th edition include the 28th edition which has a photosensitive layer comprising a diazo resin and a binder having an acidic group such as a carboxy group or an alkali-soluble group. 'The above-mentioned diazo resin includes, for example, an organic sulfonate of a condensate of p-diazodiphenylamine and p-formaldehyde described in U.S. Pat. No. 3,300,302, and Substantially aqueous compounds such as halogenated Lewis salts or perhalogenated salts of condensates of diazo compounds and carbonyl-containing organic condensing agents (e.g. BF, salt% PFa salts) as described in Diazo resins that are insoluble and soluble in organic solvents are preferred. In addition, the above binders include polyamide, polyether, polyester, polycarbonate,
Examples include polystyrene, polyurethane, polyvinyl chloride and copolymer thereof, polyvinyl butyl resin, polyvinyl formal resin, shellac, epoxy resin, phenol resin, acrylic resin and the like.

Furthermore, copolymers of the monomers listed in (1) to Eel below are more preferable.

(1) N-(4'-hydroxyphenyl)acrylamide, N-(4A-hydroxyphenyl)methacrylamide, N-(4'-hydroxynaphthyl)methacrylamide.

(21o-1m-1 or p-hydroxystyrene.

(3) o-1m-1 or p-hydroxyphenyl methacrylate.

(4) Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, and itaconic acid.

(5) Methyl acrylate, ethyl acrylate, propyl acrylate, methyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, acrylic acid-
Alkyl acrylates such as 2-chloroethyl, λ-hydroxyethyl acrylate, glycidyl acrylate, and N-dimethylaminoethyl acrylate.

(6) Methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate,
Amyl methacrylate, cyclohexyl methacrylate, co-hydroxyethyl methacrylate, ≠-hydroxybutyl methacrylate, glycyl methacrylate, N
-Alkyl methacrylates such as dimethylaminoethyl methacrylate and benzyl methacrylate.

(7) Acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N-ethylacrylamide, N-hexylmethacrylamide, N-cyclohexylamide, N-hydroxyethylacrylamide, N-phenylacrylamide,
N-nitrophenyl acrylamide, N-ethyl-N-
Noacrylamide such as phenylacrylamide, methacrylamide.

(8) Ethyl vinyl ether 1.2-chloroethyl vinyl ether, hydroxyethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, octyl vinyl ether, phenyl vinyl ether.

(9) Vinyl acetate, vinyl chloroacetate,
Vinyl esters such as vinyl butyrate and vinyl benzoate.

(Styrenes such as 101 styrene, α-methylstyrene, methylstyrene, and chloromethylstyrene.

Ql) Methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone, phenyl vinyl ketone 7, etc. (7)
Vinyl ketones.

Q21 Olefins such as ethylene, propylene, inbutylene, phtadiene, and isoprene.

(t31 N-vinylpyrrolidone, N-vinylcarbazole, ≠-vinylpyridine, acrylonitrile, methacrylonitrile, etc.)

Furthermore, a monomer that can be copolymerized with the above monomer may be copolymerized. In addition, copolymers obtained by copolymerizing the above monomers, such as glycidyl methacrylate,
Also included are those modified with glycidyl acrylate, etc.

More specific photosensitive layers comprising these diazo resins and binders are described in, for example, US Pat. No. 3.7! l, 217
No., Same No. ≠, No. 123,276, Tokuko Shoyo 7-≠3♂ri No. 0, Same! 7-≠J77, etc.

1 car, 4 works. ,,Kayoyoga□. 5□yu (as mentioned above, an aqueous solution containing an electrolyte, preferably containing an inorganic ion)
It consists of 0-20% by weight of water, and further contains an organic solvent, an alkaline agent, a surfactant, an inorganic salt, an organic salt and/or other additives as necessary.

The inorganic ions mentioned above are preferably alkali metal ions such as sodium ions, potassium ions, and lithium ions, calcium ions, magnesium ions, and ammonium ions, and their sources include anionic surfactants, alkaline agents, inorganic salts, organic salts, etc. can be mentioned.

The above-mentioned organic solvents preferably have a solubility in water of 10% by weight or less at room temperature, such as ethyl acetate, propyl acetate, butyl acetate, amyl acetate, benzyl acetate, ethylene glycol monobutyl ether heptatate, butyl lactate. , butyl levulinate, etc.; more ketones such as ethyl butyl ketone, methyl isobutyl ketone, cyclohexanone; ethylene glycol monobutyl ether, ethylene glycol monobenzyl ether, ethylene glycol monobutyl ether, benzyl alcohol, methylphenyl carbinol , n-amyl alcohol, methyl amyl alcohol, etc. Among these, ethylene glycol monophenyl nitrate henzyl alcohol is particularly preferred. Such an organic solvent is used in the developing solution in a concentration of about 1--0, more preferably λ-i.

Contains a large amount of weight.

On the other hand, examples of the alkaline agent include sodium silicate,
Potassium silicate, sodium hydroxide, lithium hydroxide, dibasic is sodium or ammonium salt of tertiary phosphate, inorganic alkaline agent such as sodium metasilicate; mono, di or trimethylamine, mono, dima is triethylamine, mono or There are organic alkaline agents such as diisopropylamine, n-butylamine, monoethanolamine, jetanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triimpropanolamine, ethyleneimine/ethylenediimine, etc. Among these, organic alkaline agents are preferred. The alkaline agent is contained in the developer in an amount of about o, os-+% by weight, more preferably o, s to i% by weight.

The above-mentioned surfactant is preferably an anionic surfactant, such as higher alcohol sulfate ester salts such as sodium salt or ammonium salt of lauryl alcohol sulfate, sodium salt or ammonium salt of octyl alcohol sulfate; for example, cetyl alcohol phosphoric acid. Aliphatic alcohols such as sodium esters, acid x ster salts; alkylaryl sulfonates such as sodium dodecylbenzenesulfonate, sodium isopropylnaphthalenesulfonate, sodium dinaphthalenesulfonate, sodium metanitrobenzenesulfonate; For example, C17H33CO
NlcH3) Alkylamide sulfonates such as CH2CH2SO3Na; sulfonates of dibasic fatty acid esters such as sodium sulfosuccinate dioctyl ester, sodium sulfosuccinate dihexyl ester; formaldehyde condensation of sodium dibutylnaphthalene sulfonate, etc. Examples include formaldehyde condensates of alkylnutthalene sulfonates, such as those having an aromatic sulfonic acid group. Approximately 0 surfactant is present in the developer solution.
．． /, 10% by weight, more preferably 0,3-,! 1:
%□. □Ah. (The above-mentioned inorganic salts include sulfites, sulfates, carbonates, phosphates, etc.; the salt types include sodium salts, potassium salts, ammonium salts, lithium salts, etc.; the organic salts include citric acid Examples include salts, carboxylates such as oxalates, tartrates, benzoates, phthalates, malates, etc., as well as sulfonates, sulfates, etc.

Other additives that can be added to the reaction solution include, for example, polyoxyethylene nitrogen.

For more detailed composition of the developer used in the developing method of the present invention, see, for example, U.S. Patent No. 3,662.660;
J, 73/, No. 237, A, tir6. o
ob, British Patent No. I, ris.

/74A, same number, otr, tJt, West German patent publication s, tori, 774'-4, Japanese Patent Application Publication No. Shoj/-77≠o
No. i, No. j/-90602, No. jl-14j, 2
J issue, 31-320! μ issue, 33-/J17440
Same issue! ! -/! 333;! No. 56-703≠j.

On the other hand, the diluent used in the present invention is water (pure water, tap water, well water, etc.) or an aqueous solution containing at least 1 of the components contained in the developer, and in the aqueous solution. The concentration of the component contained in the developer is lower than that in the developer. For example, when an aqueous solution containing an alkaline agent, a surfactant, an organic solvent, a sulfite, and a chelating agent is used as a developer, an aqueous solution containing at least seven selected from these components,
The concentration of the component contained in the aqueous solution is lower than the concentration threshold of the component contained in the developer, preferably from 1/2 of the degree IIk in the developer.

A diluent containing a concentration of 0/1 is used as a diluent.

The diluent used in a particularly preferred embodiment of the invention is water or a developer solution diluted with water, more specifically one part by volume of developer diluted with one to one part by volume of water. The most preferred is water.

If the photosensitive layer of the 28th plate to which the developing method of the present invention is applied contains a large amount of inorganic ionic compounds, as the processing amount of the 28th plate increases, the amount of inorganic ionic compounds in the photosensitive layer of the PS plate increases. is eluted into the developer, and this lowers the impedance value of the developer, making it indistinguishable from the decrease in impedance value that accompanies concentration due to evaporation of water in the developer. Therefore, in such a case, the decrease in the impedance value of the phenomenon liquid due to the increase in the processing amount of the PS plate should be calculated in advance, and this can be input into a computer, for example, to calculate the impedance value due to water evaporation. It is only necessary to detect only the decrease in the diluent, and to control the diluent so that it drops to a predetermined value and then replenishes a certain amount of diluent. Needless to say, it is advantageous if the photosensitive layer of the PS plate does not contain an inorganic ionic metal, since such complicated operations are not necessary.

The developing method of the present invention can be used in conjunction with a method of replenishing a developer replenisher as described in, for example, Japanese Patent Laid-Open No. 67760 US.

The present invention will be explained in more detail below. In addition, "person in charge"
indicates weight 1t% unless otherwise specified.

Example 1 Ethylene glycol monomethyl ether 3 under nitrogen flow
Heat 001 to 1oo0c and add co-hydroxyethyl methacrylate 70f1 acrylonitrile rot into it.
, benzyl methacrylate/J Of, methacrylic acid 20? and benzoyl peroxide 1. A mixture of λ1 was added dropwise over 2 hours.

15 minutes after the completion of the dropping, 300 f of ethylene glycol monomethyl ether and 0.3 l of benzoyl peroxide were added, and the reaction was allowed to continue for μ hours. After the reaction is complete, the copolymer is diluted with methanol and poured into water to precipitate the copolymer, which is then dried under vacuum at 700C. The acid number of this 2-hydroxyethyl methacrylate copolymer (I) is 4AO,2.

A 10% aqueous solution of tertiary sodium phosphate kept at a /S aluminum plate 2tro0c with a thickness between 00 and 2μ [Ni3
After degreasing by soaking for a minute and sanding with pumice/water slurry and a nylon brush, tooc's sodium aluminate 3
It was desmutted with an aqueous solution. This aluminum plate IJO
% sulfuric acid at a current density of -2 A/dm2 for 2 minutes, and then treated with a J, 5% aqueous solution of sodium silicate at 700 C for 7 minutes.

The following photosensitive liquid was applied to this aluminum plate and 1oo0
Drying at C for 2 minutes gave psit.

co-hydroxyethyl methacrylate copolymer II) 71 λ-methoxy μm condensate of p-diazodiphenylamine and no-ξ-formaldehyde hydroxy-bennylbenzene sulfonate iov So-thi aqueous solution of phosphorous acid 31 Oil blue #603 (Triphenylmethane oil-soluble dye, manufactured by Orient Chemical Industry Co., Ltd.) 32 2-methoxyethanol 6002 Methanol 6oot Ethylene dichloride AOOf The dry coating amount was 2, OS'/tn. This PS plate, left unexposed, is developed to um2/l by plate development using an alkaline developer having the following composition/l.

Beniquinitrilotrilotriacetic acid sodium 0. ! ? Sodium sulfite 31 Benzyl alcohol 30f Triethanolamine 20? Monoethanolamine 3f ti-y-35% aqueous solution of sodium lunaphthalene sulfonate = 3θ with tap water Ta 2.2a After developing to minimize the loss of liquid removal during this development,
My father, trying to collect the liquid by squeezing the front and back of the plate,
Salt treatment was quickly carried out to prevent water in the developer from evaporating unnecessarily during the treatment process.

As a result, the liquid volume, which was /7 at the start, became Oo trt after the completion of the treatment of μm2/l. A treated solution was obtained in which it was thought that there would be no evaporation of water.

Table 1 shows the AC impedance value of the Sakai 1 dormitory treatment solution up to the treatment and the AC impedance value of the treatment solution after evaporating 70% and 20% of water from the treatment solution up to the 44 m/l treatment. The comparison also shows the AC impedance value of the treatment liquid. In addition, AC impedance value tf
The measurement was carried out using an AC impedance meter using a constant current of 1 kHz and a frequency of 1 kHz. The sensor uses a counter electrode of approximately /cm 2 and the distance between the electrodes is approximately /cm 2 .

At the same time, development scum was generated due to evaporation of water.

From Table 1, it can be seen that the change in AC impedance value due to development processing is small when compared with the amount of change in AC impedance value due to liquid evaporation.

Therefore, it is necessary to replenish water equivalent to the amount of the evaporated processing solution.The processing solution concentrated by evaporation from the AC impedance value adheres to the plate as development scum; sludge-like precipitate that causes stains occurred.

And is this water related to the amount of evaporation? When added and stirred, the sludge-like precipitate dissolved into the liquid and disappeared.

A large number of plates were developed using an automatic developing device that added a constant amount of water. That is, the developer t is poured into the developing tank of the automatic developing device shown in Figure 82.
A large number of the photosensitive plates described above were developed.

Attach the impedance measurement sensor (made of stainless steel) to the developer circulation pipe in the automatic developing device.
It was installed so that the impedance value of the developer in the developing tank could be measured at all times. The trap signal obtained by the sensor was activated by the AC impedance meter main unit replenishment device, and water at 0°12 was added using the timer switch.

With this automatic 31i imager, υ the above 1003tHXIθ
0■ thickness 0. 28 exposed images consisting of JOTIMM
The plate was processed at a rate of 20 m/7 days, and running was carried out for 1 month at intervals of 3 to 7 days.

The processing time per day is 5 hours, and 270 td of developer is refilled in addition to water for each processing to prevent poor development.

The AC impedance value decreased as the number of treatment days passed, and when the impedance value reached the control value, o, sl water was replenished, and j, ot water was replenished 10 times during l months. . All of the planographic printing plates obtained by the above-mentioned phenomenon treatment had no adhesion of scum d at all, and no staining occurred during printing, resulting in good printing performance. As a comparison, we carried out the same process in the developing tank as above without replenishing water, but when we processed 28 plates of 100 m, development residue was observed in the developing tank.
The development residue is attached to the non-artist area of the lithographic printing plate.

When the plate was actually printed, residue adhered to it and the trap area became dirty.

Example 2 In Example 1, instead of water, the diluent added by the replenishing device was replaced by a diluent in the ratio of 1 part developer to 2 parts water. Using. Other than that, running was carried out in the same manner as in the experiment fl11.

A total of 7.01 diluents were replenished 1 times in 1 months,
As in Example 1, a plate free from adhesion of family debris was obtained.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of the automatic developing device of the present invention. l...Roller 3...Nozzle feed μ...Developer tank j...Developer liquid...Impedance measurement device #lθ...Sensor/
/... automatic measuring means... detection means n, m...
・Insertion roller 23, JIA, 30, j+2...Conveyance roller 2
1. Core... Squeegee roller comb, J/... Brush roller comb 33... Nozzle no. AC impedance meter) ao, a
K...Automatic measuring means

Claims (2)

[Claims] (1) In a method of developing a large number of image-exposed photosensitive lithographic printing plates using an automatic developing device with a developer consisting of an aqueous solution containing an electrolyte, the alternating current impedance value of the developer in the automatic developing device is measured, and when the developer is concentrated by water evaporation and the value reaches a predetermined control value, a certain amount of water or at least one of the components contained in the developer is added to the developer. 1. A method for developing a photosensitive lithographic printing plate, characterized in that the concentration of the developer is maintained within a certain range by adding an aqueous solution containing one of the two at a concentration lower than that in the developer. (2) In an automatic developing device for a photosensitive lithographic printing plate, which applies a developer to the photosensitive lithographic printing plate during the process of transporting the photosensitive lithographic printing plate, and recycles the developer, the developer is applied to the photosensitive lithographic printing plate. A means for measuring an AC impedance value of the developer is provided in the circulation system of the developer, and a liquid supply means is provided which is actuated by an output signal from the measurement means and supplies a predetermined amount of diluent to the circulation system. An automatic developing device featuring: