JPH08262812A - Suppressing method of reduction of ph in eluting liquid for electrophotographic planographic printing plate and eluting device therefor - Google Patents

Abstract

PURPOSE: To process a printing plate with stable quality for a long time without causing defect in a plate and further to decrease the exchanging frequency of liquids and to decrease the amt. of waste liquid by supplying air from which acid gas is removed by passing through a trapping agent for acid gas to the eluting liquid so that deterioration in the liquid quality of the eluting liquid cause by absorption of acid gas such as carbon dioxide when the liquid is circulated and reused. CONSTITUTION: Air which is preliminarily passed through acid gas trapping agent is supplied to the liquid surface of an eluting liquid. The supply means of air from which acid gas is removed consists of an aerating means to pass the air through a removing agent containing a acid gas trapping agent, an air taking-in means 125 to recover the air after the acid gas is removed, pipings 127, and a supply and discharge port 129 to supply the recovered air to the upper part of the eluting liquid 29. The air passages consists of two lines and they are the passage 141 to connect a liquid reservoir tank 13 for a removing agent in which the removing agent liquid 132 is stored and a holding means 139 for a solid removing agent which holds a pellet type solid trapping agent for acid gas, and a passage to aerate the removed material 130 stored in a waste liquid tank 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an electrophotographic lithographic printing plate for producing a printing plate by removing the non-image area photoconductive layer of an electrophotographic lithographic printing plate having a toner image formed on the photoconductive layer. Concerning the liquid pH drop suppression method and elution device, stable quality processing can be performed for a long time without the occurrence of plate making defects, and the frequency of liquid replacement and the waste liquid pH reduction of electrophotographic lithographic printing plates can be suppressed. A method and an elution device.

[0002]

2. Description of the Related Art A non-image area alkali-eluting electrophotographic lithographic printing plate generally comprises a photoconductive layer comprising an organic photoconductive compound and an alkali-soluble binder resin, which is provided on a conductive support. After forming a toner image on the photoconductive layer by the method, in the elution step, the non-image portion other than the toner image portion is solubilized with a treatment liquid containing an alkaline agent or the like and eluted.
In the subsequent rinsing step, a washing liquid is supplied to wash the solubilized photoconductive layer component remaining on the plate surface and the eluate, and then, a protective gum treatment is usually carried out for printing. These processes are usually carried out by using an automatic machine, but as a processing method conventionally adopted in a device for plate-making processing of a non-image area alkali-removing planographic printing plate including a photosensitive planographic printing plate (so-called PS plate). Are roughly classified into a liquid circulation reuse system, a new liquid waste disposal system, and a process process residual liquid disposal system described below.

The first liquid circulation and reuse system is a system in which an excessive amount of the processing liquid is brought into contact with the plate surface, and then all the processed liquid is removed from the plate to circulate and reuse it. A squeeze roll squeezing solution is generally used. As a liquid supply method, there is a method of supplying a treatment liquid directly from a spray, a shower or the like onto a printing plate which is held by a roll and conveyed, or through a roll and / or a straightening plate, and JP-A-2-256.
As disclosed in Japanese Patent Publication No. 9 and the like, a method of dipping a printing plate in a processing liquid tank by a submerged guide roll or the like (dip method) and convectively circulating the processing liquid by a submerged shower and supplying it to the plate surface, As disclosed in Kaihei 1-160443, a printing plate is conveyed between a pair of obliquely held guide plates having a large number of protrusions on opposite surfaces, and a method of supplying a liquid from an upper end face in the guide plate conveying direction is used. Various application examples have heretofore been disclosed along with a replenisher replenishing method for preventing and suppressing liquid deterioration due to plate making.

A second new liquid disposal method is disclosed in Japanese Patent Laid-Open No.
As disclosed in JP-A-2-238564, by adjusting the gap of the liquid supply slit, the wire diameter of the wire bar, etc., the minimum necessary amount is pre-measured before the processing liquid is supplied to the plate surface, and a new liquid is prepared for each plate. Is supplied and, if necessary, the treatment promoting means is applied in the treatment process, and then the treated fatigue treatment liquid is removed and discarded together with the solubilized non-image portion.

The method for discarding the residual liquid in the final processing step is as disclosed in Japanese Patent Laid-Open No. 62-59957, in which an excessive amount of the processing liquid is once supplied to the plate surface and then the processing liquid is metered to a fixed amount. The excess solution is circulated and reapplied, and the processing solution on the plate after the measurement is discarded together with the non-image area which has been solubilized after the development is completed. In JP-A-63-163353, the plate-making defect at the plate front part is improved. Therefore, there is also disclosed a method in which the treatment liquid removed at the time of measuring the liquid is circulated and re-supplied to the top of the plate after measuring the liquid.
Further, JP-A-2-93474 discloses JP-A-62-1
No. 59957 and Japanese Patent Laid-Open No. 63-163353 disclose a method in which the technique disclosed is applied to the processing of an electrophotographic lithographic printing plate.

Among these methods, the liquid circulation reuse method circulates and reuses the excess liquid, so that the amount of waste liquid can be apparently reduced, but in the conventional non-image area, almost all of the plate is removed during the dissolution removal process. Since it flows into the circulating processing solution from above, for example, even if the processing solution is replenished with the processing solution itself and the desired processing characteristics are retained, the processing solution containing a large amount of inflowing non-image part components When liquid is adhered to the inside of the tank, the liquid circulation system, the transport part of the processing part, etc., the liquid supply amount is reduced, and if spray is used as the liquid supply method, it has various adverse effects such as clogging of the holes, and non-image area ink. Print stains may be induced by redeposition of the receptive component on the printing plate support.

On the other hand, although the new liquid disposal method can prevent the processing fluctuation, it requires a larger amount of the processing solution than the liquid circulation reuse method, and inevitably results in a large amount of waste liquid. . In addition, if the amount of liquid is reduced to supply the required minimum amount, the processing liquid may not cover the entire surface of the plate uniformly in some cases, and this tendency particularly strongly appears at the plate leading edge, resulting in processing defects. Become. Particularly, in the plate making process of electrophotographic lithographic printing plate, the electrophotographic photoconductive layer is thicker than the general PS plate photosensitive layer, and the photoconductive layer of the toner image area and the lid are not easily alkaline. Since it is not soluble, the processing condition requires strictness such as the image thinning called side etching is induced when the processing is pressed. Therefore, this processing method is not suitable.

Therefore, the above-mentioned treatment process residual liquid disposal method is a treatment method which solves both drawbacks and has advantages.
In this method, since the alkali developing solution is supplied to the plate and then the measurement is performed while leaving the amount of the solution necessary for the development processing, the non-image area photoconductive layer component is hardly mixed in the measurement removing solution, and the measurement removal plate is used. The remaining fatigued developer is discarded together with the solubilized non-image area, and by replenishing the replenisher in proportion to the amount of waste developer, plate making can be performed in a substantially new liquid state in accordance with the liquid disposable method. It is unlikely to be affected over time like the liquid circulation reuse method. Further, even if a portion where the alkaline developing solution is not supplied onto the plate as a result is generated, the solution is spread by the solution measuring tool before the start of development, so that unevenness in processing is reduced.

[0009]

However, even if this method of discarding the processing residual amount of measuring solution is adopted for the elution method of the electrophotographic lithographic printing plate, in the present method of reusing the measuring removal liquid, it takes a long time. Fatigue deterioration with time occurs due to pH drop due to absorption and dissolution of acidic gas such as carbon dioxide in the air during the circulation and use period. The influence of acidic gas such as carbon dioxide in the air on the circulating eluate depends on the time and contact area where the air and the eluate are in contact with each other. Therefore, when the elution liquid is constantly in contact with air not only while the elution liquid is being circulated during the elution process of the electrophotographic lithographic printing plate, but also during the suspension period, the suspension period is longer than the processing time. The fatigue deterioration of the eluate with time occurred before the number of plate making reached the specified number,
Liquid replacement is required.

In order to suppress the drop in the pH of the eluate due to the acidic gas in the air, it can be suppressed by blocking the contact between the eluate and the air. As an effective method, there is a method of sealing the periphery of the eluate so as not to contact with air. It is difficult to completely seal, and the pH drop will proceed. Therefore, it is necessary to take some means for suppressing the progress of the pH drop even if the eluate and the air slightly contact each other.

An object of the present invention is to recycle and reuse the eluate when a printing plate is prepared by removing the non-image area photoconductive layer of an electrophotographic lithographic printing plate having a toner image formed on the photoconductive layer. Electrophotographic lithographic printing plate that suppresses liquid deterioration caused by absorption of acidic gas such as carbon dioxide, enables stable quality processing for a long period without causing plate making defects, and further reduces liquid replacement frequency and waste liquid. An object of the present invention is to provide a method for suppressing a pH drop of an eluate of a printing plate and an elution device in which a pH drop of an eluate is suppressed.

[0012]

The object of the present invention is achieved by the following method and an elution device for carrying it out. That is, the method for suppressing the eluent pH drop of the electrophotographic lithographic printing plate of the present invention is an eluent for eluting and removing the non-image part of the electrophotographic lithographic printing plate having a toner image formed on the photoconductive layer, In order to suppress liquid deterioration due to absorption of acidic gas such as carbon dioxide due to circulation and reuse of eluate, it is characterized by supplying acid-free air by aerating an acidic gas trapping agent on the liquid surface. And

Further, at least an elution part for supplying an eluate to the image forming surface of the electrophotographic lithographic printing plate and a rinse part for cleaning the image forming surface after elution are provided, and a toner image is formed on the photoconductive layer. In the electrophotographic lithographic printing plate elution device that elutes and removes the non-image area of the electrophotographic lithographic printing plate, in order to suppress the pH drop of the effluent, air is taken in and aerated to the acidic gas trapping agent. The apparatus is characterized by having acid gas removal air supply means for supplying the air from which the acidic gas has been removed to the eluate surface stored in the elution section.

Further, it has a removing means for removing at least the non-image portion eluted before reaching the rinse portion, and a waste liquid tank for collecting the removed matter removed by the removing means,
The non-image area photoconductive layer is swollen and solubilized by supplying an eluent to the image forming surface of the electrophotographic lithographic printing plate on which the toner image is formed on the photoconductive layer, and the photoconductive layer and the plate surface solubilized by the removing means. Is the electrophotographic lithographic printing plate elution device that removes the remaining eluent and discards it in the waste liquid tank, and rinses the printing plate from which the non-image areas have been removed with a rinse liquid. It is also possible to use the eluent used for elution and removal, that is, the eluent waste solution that has been used and exchanged and the removed material containing at least the eluent removed by the removing means, etc. it can.

The eluent pH drop suppressing method and the elution apparatus of the present invention will be described focusing on the material used for suppressing the pH drop of the eluent according to the present invention and the pH drop suppressing method using the same. In view of the fact that the pH drop of the eluate mainly results from the dissolution of the acidic gas mainly composed of carbon dioxide in the air into the eluent, in the present invention, the acidic gas in the air contacting the eluent is removed. Therefore, as a method for suppressing the pH drop of the eluent according to the present invention, a method of supplying air aerated to the acidic gas capturing agent to the surface of the eluate stored in the elution part is adopted. Further, the elution device of the present invention is a device having a series of acid gas removal air supply means for supplying at least the air aerated to the acid gas trapping agent to the elution liquid surface stored in the elution section.

In the present invention, the air supplied to the eluent surface is
Aerate at least the acidic gas scavenger. Normally, the acidic gas mainly composed of carbon dioxide in the air can be removed by passing through a basic medium to such an extent that at least a definite difference in pH drop of the eluate appears. In addition, since many acidic gases are dissolved in mere water even if they are not in a basic atmosphere to some extent, water is used as an acidic gas scavenger in the present invention, and air is simply introduced into water to aerate it. It's just good. Of course, if the water contains a basic substance, the acidic gas can be removed more effectively. Then, by supplying the air from which the acidic gas has been removed to the space above the surface of the eluent, it is possible to substantially reduce the contact between the eluent and the acidic gas, thereby suppressing the pH drop of the eluent. .

The acid gas scavenger according to the present invention includes
As mentioned above, water and basic substances may be mentioned. The basic substance used in the acidic gas scavenger according to the present invention includes silicates represented by the general formula SiO ₂ / M ₂ O (M = Li, Na, K), ammonia, alkali metals and alkaline earth metals. (Hydro) oxides, inorganic alkali agents such as salts of weak acids such as phosphoric acid, phosphorous acid, boric acid and carbonic acid with alkali metals and ammonia, ethylenediamine, diethanolamine, diethylenetriamine, dimethylamine, triethanolamine, triethylenetetramine. , Trimethylamine, 1,2-propanediamine, 1,3-propanediamine, 1,6-hexanediamine, benzylamine, monoethanolamine, and organic alkali agents such as morpholine,
And mixtures thereof.

These acidic gas scavengers are used in the form of the obtained acidic gas scavenger, or dissolved or dispersed in water together with a small amount of a dissolution accelerator or a viscosity reducing agent. When the acidic gas scavenger according to the present invention is used in a solid form, it may be used as it is as long as it is originally solid, or a suitable shaping material (builder) such as silica and alumina regardless of the form of the scavenger or It is used after being adsorbed or supported by a granular or fibrous (acicular, columnar) carrier or the like. The solid material containing the acidic gas scavenger is packed in a column or the like, and air is aerated therein. In the case of a solid material, it is inferior in removal efficiency due to the contact area in comparison with the case of a liquid, and in particular, the acid gas adsorption surface is easily covered and deactivated after aeration, so its shape and size are large. In addition, it is necessary to pay attention to the provision of some means for deactivating the surface such as application of vibration.

When the acidic gas scavenger according to the present invention is used in a liquid form, air may be blown onto the liquid interface, but it is advantageous to disperse the air as fine bubbles in the liquid. is there. As a result, the contact area of gas and liquid is increased, and more acidic gas can be absorbed and removed. The bubble generator preferably has a porous surface shape in order to effectively generate fine bubbles, and the pores have a diameter of preferably 5 to 100 μm, more preferably 10 to 50 μm. As a material thereof, a material which is stable to alkali is preferable, and for example, a fluorine resin, an olefin resin, a glass-coated special alumina-based special bone material or a ceramic is preferably used. In addition, as the means, a blower, a fan, and an air pump may be used by connecting to the bubble generator made of the above-mentioned porous material.

When the acidic gas capturing agent is used in a liquid state as described above, it may be provided only for a tank storing a liquid in which the acidic gas capturing agent is dissolved or dispersed in order to suppress the pH drop of the eluate. In addition to the rinse solution in the rinse part for cleaning the image-forming surface after elution and the eluate-removed product containing the removed solubilized photoconductive layer component, of the waste liquid component during the plate making process and liquid exchange, etc. A basic liquid can also be used. Further, it is preferable to provide a filter at the inlet of the air finally supplied to the eluate surface for the purpose of preventing dust and the like from entering the apparatus.

The rinse solution according to the present invention is set to be slightly basic (around pH 8) from the time of the new solution in order to prevent re-aggregation of the solubilized photoconductive layer components, etc. Even if the photoconductive layer component and the eluate remaining on the plate are removed, they are slightly mixed in the rinse liquid, and the pH value of the rinse liquid itself is further increased. Therefore, the basicity of the rinse liquid becomes strong during long-term circulation use, which may accelerate the elution of the image area even in the rinse step. Therefore, if a rinse liquid that is being used in circulation is used as the acidic gas trapping agent-containing material, not only can the basic substance in the eluate component mixed in the rinse liquid absorb and remove the acidic gas in the air, PH of rinse solution
This is preferable because the effect of suppressing the increase can be expected.

As a material liquid containing an acidic gas scavenger,
Eluents removed such as solubilized photoconductive layer components, eluent waste liquid after reuse of the melt circulation to replace new liquid to maintain eluability, etc., and cleaning liquid for cleaning the removal means A liquid stored in a waste liquid tank for recovering the above may be used. The solubilized photoconductive layer components and eluate waste liquid containing the eluate removed in the removal process are still alkaline even though they are used and fatigued. Therefore, adjust the pH when discarding them. Then need to be discarded. The use of these liquids stored in the waste liquid tank as the acidic gas trapping agent-containing material liquid used for suppressing the pH drop of the eluate is to absorb the acidic gas in the air as in the case of the rinse liquid. The effect of lowering the pH of the waste liquid can be expected, and the waste liquid can be easily discarded.

The acid gas scavenger according to the present invention may be used in a single kind, or may be sequentially aerated in plural kinds of removing materials. Further, the method for suppressing pH drop of the eluent of the present invention may be such that the acid gas-removed air is continuously supplied while the elution device according to the present invention is powered on, even during plate making. May be carried out intermittently only when the level of the eluate changes during the time of supplying to the electrophotographic lithographic printing plate. Further, regardless of whether the supply is continuous or intermittent, the acid gas removal air supply amount may be variable in association with the plate making process.

Next, the processing steps and processing solutions for the elution section and rinse section, etc. relating to the elution apparatus of the present invention will be described in the order of steps. The elution part according to the present invention supplies an eluate to the image forming surface of an electrophotographic lithographic printing plate on which a toner image is formed by an electrophotographic method to swell and solubilize the non-image part photoconductive layer other than the toner image part. . It is desirable that the eluate supply system be soft to prevent the swelling and solubilized photoconductive layer components from diffusing into the eluate. When using a shower, the liquid discharged from the pipe is, for example, a current plate or a roll. A method in which the eluate is rectified and uniformly supplied to the image forming surface via the is preferable.

It is essential that the minimum supply amount of the eluate is such that the eluate flows down from the plate edge during conveyance of the elution part. As a result, a part of the photoconductive layer in the non-image area is swollen and solubilized, and the excess part flows over the plate and partially flows down from the plate edge part while partially replacing the eluate existing in the part to be eluted. Therefore, liquid replacement frequently occurs at the plate edge, and the flow rate of the eluate near the photoconductive layer interface increases, so that not only the elution time is shortened but also the intraplate fluctuation of the elution degree is suppressed.
In addition, in order to prevent liquid supply failure and further shorten the elution time, a flow promoting mechanism is provided during the removal process to replace the eluent on the plate, and the eluate can be used multiple times. It is desirable to supply it.

The eluent according to the present invention preferably contains an alkaline agent and has a buffering capacity. Conventionally, as an alkaline agent used in a developing solution for a photosensitive lithographic printing plate (PS plate), a general formula SiO ₂ / M ₂ O (M = Li, Na,
K) inorganic alkali agents such as silicates, alkali metal hydroxides, alkali metal and ammonium salts of phosphoric acid and carbonic acid, alkylcumines, ethanolamines,
Organic alkaline agents such as ethylenediamine, triethylenetetramine, and morpholine, and mixtures thereof. Of these, the above-mentioned silicates in particular exhibit a strong buffering ability and promote the swelling and solubilization of the photoconductive layer, but can suppress the diffusion of the solubilized product into the liquid, so that the eluent according to the present invention is at least It shall contain a silicate.

In the elution part, the eluate on the plate is not entirely consumed for solubilizing the photoconductive layer, and when a large amount of the eluate or the solubilized photoconductive layer component is mixed in the rinse solution, the rinse solution becomes The elution liquid supplied to the plate surface causes rapid deterioration, and before the photoconductive layer is completely solubilized and reaches the rinse portion, the elution liquid on the plate is removed by the liquid measuring means, leaving a certain amount of the elution liquid. It is preferable to provide a liquid measuring section and a removing section for removing the solubilized photoconductive layer component after measurement and the eluent remaining on the plate. When measuring liquid, it is important to prevent the solubilized photoconductive layer from mixing into the effluent while removing the effluent that was not involved in the solubilization of the photoconductive layer from the plate as much as possible. is there. The activity of the eluate can be further maintained by removing and discarding the eluate that is exhausted due to the mixing of the components of the photoconductive layer together with the solubilized photoconductive layer.

As the removing means according to the present invention, squeeze rolls, scraping blades, roll-shaped and flat brushes,
And contacting means such as Molton, and non-contacting means such as spraying with compressed air. Among these, squeeze rolls and scraping blades are preferably used.

In the electrophotographic lithographic printing plate from which the solubilized photoconductive layer has been removed by the removing means, a rinsing liquid is supplied at the rinsing portion to completely remove the remaining removed material from the plate. As the rinse liquid supply method in the rinse treatment process, a conventionally known liquid supply mechanism such as shower, high pressure spray, dip method, etc. can be used, but unlike the elution treatment, the rinse treatment immediately remains on the plate with the rinse liquid. It must be possible to completely remove the liquid matter. Therefore, the supply liquid may be directly supplied to the plate surface as long as it has a mechanism capable of suppressing scattering, or the treatment liquid may be compressed or supplied together with compressed air. Further, especially when the liquid flow, liquid pressure, or liquid amount is low, the elution promoting member described in JP-B-3-27038 may be used for the rinse treatment mechanism. The treatment method used in the rinse treatment according to the present invention may be a disposable method or a circulation reuse method, or another method can be used if desired.

The electrophotographic lithographic printing plate after the rinsing treatment is treated with a protective gum for the purpose of improving scratch resistance of the plate surface and desensitizing the non-image area. The protective gum solution that can be used in the present invention contains a polymer compound, a lipophilic substance, a surfactant, and the like, and known reagents can be used for all these reagents.

Finally, the electrophotographic lithographic printing plate, electrophotographic processing step and processing liquid composition according to the present invention will be described. The electrophotographic lithographic printing plate according to the present invention has at least a photoconductive layer provided on a conductive support, and can form a toner image by an ordinary electrophotographic development method.
The electroconductive support for an electrophotographic lithographic printing plate according to the present invention comprises a plastic sheet having a conductive surface, a metal plate such as aluminum or the like as a substrate, and at least a surface on which a photoconductive layer is provided is subjected to a hydrophilic treatment. It is a thing. Among these substrates, the aluminum plate is preferably used.
This aluminum plate may contain aluminum as a main component and a slight amount of a foreign element, and a conventionally known material can be used.

An electrophotographic lithographic printing plate can be obtained by providing a desired electrophotographic photoconductive layer on the surface-treated surface of such a support. In the photoconductive layer of the electrophotographic lithographic printing plate according to the present invention, known photoconductive compounds can be used alone or in combination of two or more kinds if desired. In the photoconductive layer, a photoconductive phthalocyanine pigment that can obtain desired electrophotographic characteristics with a small amount is advantageously used. Particularly, χ-type metal-free phthalocyanine and titanyl phthalocyanine which have excellent practical photosensitivity even in a long wavelength region corresponding to a light source such as a laser are suitable.

A binder resin is used in the photoconductive layer of the electrophotographic lithographic printing plate according to the present invention in order to improve the film-forming property and the adhesion to the support. Specific examples of the binder resin include
Styrene / maleic anhydride copolymer, styrene / maleic acid monoalkyl ester copolymer, methacrylic acid / methacrylic acid ester copolymer, styrene / methacrylic acid / methacrylic acid ester copolymer, acrylic acid / methacrylic acid ester copolymer Styrene, methacrylic acid ester, such as polymer, styrene / acrylic acid / methacrylic acid ester copolymer, vinyl acetate / crotonic acid copolymer, and vinyl acetate / crotonic acid / methacrylic acid ester copolymer,
Acrylic ester, vinyl acetate, vinyl benzoate, etc. and acrylic acid, methacrylic acid, itaconic acid, crotonic acid,
Maleic acid, maleic anhydride, a copolymer with a carboxylic acid-containing monomer such as fumaric acid or an acid anhydride group-containing monomer,
Examples thereof include phenolic resins, xylene resins, and vinyl acetal resins such as polyvinyl butyral.

The mixing ratio of the photoconductive compound and the binder resin in the photoconductive layer of the electrophotographic lithographic printing plate according to the present invention is
It may be determined so as to satisfy various characteristics such as desired electrophotographic characteristics and plate-making characteristics, but if the content of the photoconductive compound is too low, the sensitivity becomes low. Since not only improvement cannot be expected but also liquid properties such as coating liquid stability and coating property are deteriorated, the photoconductive compound is preferably 5 to 60 parts by weight, more preferably 15 to 40 parts by weight with respect to 100 parts by weight of the binder resin. A range of parts is preferred. Further, if the photoconductive layer thickness is thin, charging becomes unstable and induces a cover due to leakage, and conversely, if it is thick, side etching is induced during elution, and good image reproducibility cannot be obtained. 0.5-1
The range is preferably 0 μm, more preferably 1.5 to 6 μm.

The electrophotographic lithographic printing plate according to the present invention can be obtained by coating a photoconductive layer-forming coating liquid on a conductive support according to a conventional method. The coating liquid for forming the photoconductive layer is prepared by dissolving and dispersing each component constituting the photoconductive layer in an appropriate solvent. When a substance insoluble in the solvent is contained, the average particle diameter is 0 by a disperser. The particles are dispersed in a particle size of 0.4 μm or less, more preferably 0.2 μm or less. In addition to the photoconductive compound and the binder resin, the photoconductive layer may optionally contain a plasticizer, a surfactant, and the like for the purpose of improving the film properties such as flexibility of the photoconductive layer and the surface state of the coating. You may add the additive of. The coating solution thus prepared is coated on a support by a known method and dried to obtain an electrophotographic lithographic printing plate.

A toner image can be formed on the electrophotographic lithographic printing plate by a known operation. That is, charging is performed substantially uniformly in a dark place, an electrostatic latent image is formed by imagewise exposure, and then toner development is performed. Next, the electrostatic latent image is developed with toner. As a developing method, either a dry developing method or a liquid developing method can be used. In particular, the liquid development method can form a fine toner image and is suitable for producing a printing plate with good reproducibility. Further, positive / positive development by positive development and negative / positive development by reversal development under application of an appropriate bias voltage are also possible. The formed toner image can be fixed by known heat fixing. Using the toner image thus formed as a resist, the non-image area photoconductive layer is removed with an eluent to prepare a printing plate.

The toner used for developing the electrophotographic lithographic printing plate needs to be composed of a resin component having a resist property against the eluate. As the resin component, methacrylic acid, acrylic acid, acrylic resins composed of esters thereof, vinyl acetate resins, copolymers of vinyl acetate with ethylene or vinyl chloride, vinylidene chloride resins, vinyl chloride resins, polyvinyl butyral, etc. Vinyl acetal resin, polystyrene, copolymers of styrene and butadiene, methacrylic acid ester, etc., polyethylene, polypropylene and its chlorides, polyester resin, polyamide resin, phenol resin, xylene resin, alkyd resin, vinyl-modified alkyd resin, etc. Wax etc. are mentioned. Further, the toner may contain a dye or a charge control agent as long as it does not adversely affect development or fixing.

[0038]

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples without departing from the object thereof.

Example 1 JIS 1050 aluminum (thickness: 0.3 mm) was etched with an aqueous sodium hydroxide solution and thoroughly washed with water.
Next, electrolytic surface roughening was performed in a hydrochloric acid aqueous solution, and further anodizing treatment was performed in a sulfuric acid aqueous solution to prepare a printing plate support. After coating the surface-treated surface of the support with the photoconductive composition of Table 1 dispersed for 1 hour with Dynomill with an extrusion coater so that the solid coating amount was 4.0 g / m ² ,
An electrophotographic lithographic printing plate was prepared by drying.

[0040]

[Table 1]

The obtained electrophotographic lithographic printing plate was printed at 398 mm
It was cut into × 560 mm, shielded from light and heated at 50 ° C. for 2 hours, and then cooled to room temperature. This printing plate was charged in a dark place by a corotron so that the surface potential became about +230 V, and then scanning image exposure was performed using a semiconductor laser (780 nm), and immediately a positive charge toner (manufactured by Mitsubishi Paper Mills Ltd., ODP- T
The liquid reversal development was performed in W), the toner dispersion medium was removed by drying with cold air, and the toner was further heat-fixed to form a toner image on the photoconductive layer. The printing plate on which the toner had been developed was subjected to a plate making process using an elution device as shown below.

FIG. 1 shows a schematic sectional view of an electrophotographic lithographic printing plate elution device used in the plate-making process of this embodiment. The basic structure of this elution device consists of 4 zones: elution section (solubilization step), removal section (removal step), rinse section (rinse step), and protective gum section. The electrophotographic lithographic printing plate is viewed in the direction of the arrow. By being inserted into the printing plate transport line 1, it is sandwiched by a pair of rolls and automatically transported, and at the same time, used for plate making processing.

The elution section further comprises an eluate supply section consisting of an eluate supply pipe 25, a straightening plate 26, and a liquid supply means of the liquid supply roll 10a, and an eluate measurement section composed of a liquid measuring tool 47 and a guide roll 13. Composed of. As the liquid measuring tool 47, a wire bar in which a stainless wire having a diameter of 175 μm was spirally and densely wound around a rotating shaft was used. Forced drive transmission is not performed to the rotating shaft of the wire bar, but rotation is transmitted by contact with a translation plate during liquid measurement. The eluate 29 is branched from the pipe line 110 communicating with the bottom of the eluate storage tank 3 and the pipe 115,
It is rectified by the rectifying plate 26 via the valve 102 and the eluate supply pipe 25, and is supplied to the plate surface via the liquid supply roll 10a. The eluate measured by the eluate measuring unit is again collected in the eluate storage tank 3 and reused. Further, the eluent 29 is discharged from the bottom of the eluate storage tank 3 through the pipe 110 by the operation of the circulation pump 93 to the discharge port arranged below the stored liquid surface, and circulates in the eluate storage tank 3. However, it is adapted to be heated to a specific temperature by a heater (not shown).

The eluate storage tank 3 is configured such that the plate-making reduction amount of the eluate 29 is replenished with the elution replenisher 30.
Replenishment of the eluate replenisher 30 is supplied from the eluate replenisher reservoir 7 through the replenishment pump 62 and the valve 75 to the eluate reservoir 3 when the lower limit of the level sensor (not shown) is reached.
It is set to replenish up to the set amount (liquid level).

The removing section has a scraping blade 37 and a backup roll 14 which are removing means in order from the upstream side of the printing plate conveyance.
A solubilized photoconductive layer removing part, a cleaning / removing liquid supplying means including a cleaning / removing liquid supplying nozzle 36 for supplying a rinsing liquid 45 to the scraping blade 37, a removal waste liquid primary storage tank 4, and a plate are conveyed to the rinsing part. It is composed of a pair of transport rolls 15a and 15b. The contact angle of the scraping blade 37 with respect to the plate surface and the degree of pressurization were adjusted so that the contact width with the backup roll 14 was minimized in a range where the solubilized photoconductive layer was optimally removed. The removed material scraped off by the scraping blade 37 may be temporarily stored in the removed waste liquid primary storage tank 4, or may be disposed in the waste liquid tank 9 through the pipe 94 by opening the valve 77. Has become.

Immediately in front of the scraping blade 37, a nozzle scanning means 35 fixed in parallel to the scraping blade 37 by a holding mechanism (not shown) is arranged, and a liquid supply nozzle 36 is fixed to the movable part thereof. Scraping blade 37
It is movable along. The cleaning of the scraping portion of the scraping blade 37 is performed by scanning the liquid supply nozzle 36 in parallel with the scraping blade 37 by the nozzle scanning means 35 while moving the pump 63, the valve 76, and the pipe 95 from the rinse liquid storage tank 5. After that, from the tip of the liquid supply nozzle 36, a scraping blade 37
The rinse liquid 45 is supplied to the contact portion between the backup roll 14 and the backup roll 14, and the scraping blade 37 and the backup roll 1
4 is to be washed.

The rinsing portion is disposed above the first liquid supplying portion for supplying the rinsing liquid 45 directly from the rinsing liquid supply pipe 40 to the plate surface and substantially in the middle between the transport rolls 17a and 18a, and the unused liquid together with the compressed air. Is supplied from the high-pressure spray 41 to the second liquid supply part, and the rinse liquid is supplied to the joint part of the three pairs of transfer rolls 16, 17, and 18 to rinse the lower surface of the printing plate 3
The rinse liquid supply pipes 42, 43, and 44 are provided, and the rinse liquid storage tank 5 below these liquid supply portions stores the rinse liquid 45. Supply of the rinse liquid 45 is
The rinse liquid is constantly discharged from the rinse liquid storage tank 5 through the pump 65 and the pipe line 97 through the rinse liquid supply pipe 40 during plate making, and is circulated for reuse. The supply of the unused liquid is set by a processing liquid supply control mechanism (not shown) so that the liquid is supplied only while the electrophotographic lithographic printing plate is passing through the second liquid supply section.

The protective gum portion comprises a protective gum solution supply pipe 52, a surface roughening solution measuring roll 22, a liquid supply roll 19a and a lower roll 19b, and a protective gum solution 4.
A protective gum solution storage tank 8 for storing 6 and a primary protective gum solution storage tank 6 for receiving an excess of the protective gum solution. The protective gum solution 46 supplied from the protective gum solution tank 8 through the pump 66, the valve 79 and the protective gum solution supply pipe 52 is measured by the surface roughening solution measuring roll 22 and applied to the printing plate, and the roll pair is used. After being squeezed by 19a and 19b, it is temporarily stored in the protective gum liquid primary storage tank 6 and is discarded in the gum waste liquid tank 20 via the valve 80 and the pipe 99.

As the eluent, the eluent replenisher, and the rinse liquid used in the plate-making process, liquids having the compositions shown in Tables 2 to 4 were prepared and used, and the protective gum liquid was a commercially available gum liquid (Fuji Photo Film (Fuji Photo Film Co., Ltd., GU-7) was used after diluting to a specified ratio. The unused liquid sprayed from the high pressure spray 41 was filled with an unused liquid having the same composition as the rinse liquid. In addition, the elution replenisher and the unused liquid were appropriately replenished in the respective liquid storage tanks according to the amount of use reduction.

[0050]

[Table 2]

[0051]

[Table 3]

[0052]

[Table 4]

The cleaning of the scraping blade 37 is carried out by a treatment liquid supply control mechanism (not shown) after the trailing edge of the printing plate is carried out from the liquid supply roll 19a and the leading part of the printing plate is carried into the liquid supply roll 10a for 60 seconds. If not, the rinse liquid 45 was supplied by the operation of the pump 63 for substantially 15 seconds. The amount of the unused liquid discharged from the high-pressure spray 41 was adjusted to be equal to the amount of the rinse liquid 45 reduced by the supply to the scraping blade 37.

As shown in FIG. 1, the present elution apparatus is provided with an acid gas removal air supply means which is a mechanism for suppressing the pH drop of the eluate. The acid gas removing air supply means is composed of an air intake 120 provided with an air filter and an air pump 1.
21, and ventilation means for aerating air to the removing material containing the acidic gas trapping agent through the pipe 122, acid gas removing air intake means 125 for recovering the air from which the acidic gas has been removed,
It is composed of a pipe 127 and an acid gas removal air supply unit configured by a supply unit discharge port 129 for exhausting the recovered air to the upper portion of the eluate.

The aeration passage in the aeration means is a liquid removing material storage tank 131 capable of storing a removing agent liquid 132 containing an acidic gas capturing agent, and a solid removing material retaining material for holding a pelletized solid acidic gas capturing agent. It comprises a path connecting the means 139 with a pipe 141 and a two-system path for venting the removed material 130 discharged from the removal section and stored in the waste liquid tank 9, both of which are supplied to the supply section via a valve 138 or 137. It is designed to be led to the exit 129.

Waste liquid tank 9 and liquid removing material storage tank 1
Bubble generators 123 and 133 are disposed inside 31 so that they do not come into contact with the bottom, and acid gas removal air intake means 125 and 134 are detachably disposed above them, respectively, and sucked. The tank is structured to prevent air leakage so that air can be efficiently guided to the outlet of the supply unit. Further, as shown in FIG. 2, a valve 94a is provided at the tip of the inside of the waste liquid tank 9 of the pipe 94 for guiding the removed substance from the removed waste liquid primary storage tank 4 to the waste liquid tank 9. The valve 94a is normally closed by the urging of an elastic member, and is opened when at least a certain amount of the removed material is stored in the pipe 94.

The air pump 121 is automatically operated by a signal from a control unit (not shown). Further, the air intake port 120 is disposed above the eluate surface of the eluate storage tank 3, and aerated air can be circulated and used to enhance the effect of suppressing the pH drop. It has become like.

Using the elution device described above, the valves 136 and 138 are closed, and the valves 135 and 137 are opened, and the removal material 130 to be discarded from the removal section is used as the removal material.
The plate making is started in a state where the removed material is stored in the waste liquid tank 9 to the extent that the removed material 130 is immersed in the valve 94a, and the eluent pH drop suppression mechanism is operated continuously while the eluator is operating, The printing plate prepared in advance and having undergone toner development was subjected to continuous plate making for 50 plates at 1-minute intervals and then plate making for 150 plates per day was carried out in a cycle of resting for 2 hours. Under these conditions, plate making was continued for 6 days, plate making was stopped for 1 day, and plate making was made for 4 weeks in total. During the plate-making period, the pH of the eluate was measured each time immediately after the start-up and immediately before the stop. Immediately after the plate making was stopped, it tended to drop slightly immediately after the start-up, but the pH was almost the same as the eluate of the unused liquid throughout the plate making period.

Further, when the dissolution property of the plate-making product was visually evaluated, there was no bluish color in the non-image area, and no defective dissolution called a pigment residue was generated. Furthermore, the 10th edition in total,
100th, 500th, 1500th, and 3500th
When printing was performed on the plate-shaped plate, all the printing plates were good in fine line reproducibility and good in printed matter without printing background stains.

Comparative Example 1 A plate was prepared using the same processing liquid and plate-making conditions as in Example 1, except that the eluator used in Example 1 was used and the eluate pH drop suppressing mechanism was not operated at all.

When the pH of the eluate was measured immediately after the start-up and immediately before the stoppage in the same manner as in Example 1, it tended to decrease slightly with the lapse of plate-making from about the 3rd week. When the pH is increased after 4 weeks, the pH is 0.5 compared to the pH of the eluate of the unused liquid.
It decreased more than that.

Further, the dissolution property of the plate-making product was visually evaluated in the same manner as in Example 1. As a result, it was found that in the first plate immediately after starting the day after the plate-making was stopped, the leading edge of the plate was slightly left in the third week. Remaining pigment was observed, and at the 4th week, some poor dissolution occurred in the non-image area. Further, printing was carried out on the 10th, 100th, 500th, 1500th, and 3500th plates in total under the same conditions as in Example 1. There was no problem, but 3
In the plate-making product of the 500th plate, the printing background was stained and a good printed product could not be obtained.

Example 2 Using the elution apparatus used in Example 1, the eluate pH drop suppressing mechanism was operated for 15 minutes during continuous plate making of 50 plates, and otherwise the same treatment liquid and plate making conditions as in Example 1 were used. Made with.

When the pH of the eluate was measured immediately after the start-up and immediately before the stoppage in the same manner as in Example 1, the pH tended to slightly decrease on the day after the plate making was stopped, and the pH of the eluate of the unused liquid at the fourth week was measured. Although it was slightly lower than the above, the difference was 0.
It was within 1.

When the plate-making product was visually evaluated for elution in the same manner as in Example 1, no elution failure called a pigment residue in the non-image area did not occur. Also, the 10th edition in total,
100th, 500th, 1500th, and 3500th
When printing was carried out on the plate-making product, Example 1
In all printing plates, the fine line reproducibility was excellent, and good prints without printed background stains were obtained.

Example 3 Using the elution device used in Example 1, valves 135 and 1 were used.
37 is closed and valves 136 and 138 are opened, and the liquid removal material storage tank 131 uses an alkaline component in the eluate as an acidic gas trap, and the eluate used in the first embodiment is used. Liquid was injected as a removing material, and nothing was put in the solid removing material holding means 139. Air pump 121
By the operation of the air, the air is fed from the air intake 125 to the pipe 1
22, the bubble generator 133, the acid gas removal air intake means 134, and the pipe 127 so that the gas is supplied to the supply unit discharge port 129. Other than that, plate making was carried out under the same treatment liquid and plate making conditions as in Example 1.

As in Example 1, the pH of the eluate was measured immediately after the start and immediately before the stop. The pH of the eluate was measured every time during the plate making, immediately after the start and immediately before the stop of the day. Immediately after the plate making was stopped, it tended to drop slightly immediately after the start-up, but the pH was almost the same as the eluate of the unused liquid throughout the plate making period.

The dissolution property of the plate-making product was visually evaluated in the same manner as in Example 1. As a result, no dissolution defect such as a pigment residue was generated in the non-image area, and the plate-making total 10th plate, 100th plate,
Printing was performed on the 500th, 1500th, and 3500th plate-making products. As a result, a good printed matter having the same fine line reproducibility as that of Example 1 and excellent printing line scum in all printing plates was obtained. Was given.

Example 4 Using the elution device used in Example 1, valves 135 and 1 were used.
37 is closed, valves 136 and 138 are opened, solid sodium removal material holding means 139 is filled with about 5 mm of granular sodium hydroxide as an acid gas trap, and liquid removal material storage tank 131 I didn't put it in. Then, from the second week onward, at the beginning of the plate making week, the solid removing material holding means 139.
The used sodium hydroxide stored in was transferred to the liquid removing material storage tank 131, and new sodium hydroxide was added to the solid removing material holding means 139. Other than that, plate making was carried out under the same treatment liquid and plate making conditions as in Example 3.

As in Example 1, the pH of the eluate was measured immediately after the start and immediately before the stop. The pH of the eluate was measured every time during the plate making, immediately after the start and immediately before the stop. Immediately after the plate making was stopped, it tended to drop slightly immediately after the start-up, but the pH was almost the same as the eluate of the unused liquid throughout the plate making period.

The dissolution property of the plate-making product was visually evaluated in the same manner as in Example 1. As a result, no dissolution defect such as a pigment residue was found in the non-image area, and the plate-making total 10th plate, 100th plate,
Printing was performed on the 500th, 1500th, and 3500th plate-making products. As a result, a good printed matter having the same fine line reproducibility as that of Example 1 and excellent printing line scum in all printing plates was obtained. Was given.

[0072]

As described above, when the electrophotographic lithographic printing plate is treated by the method and apparatus for suppressing the eluent pH drop of the electrophotographic lithographic printing plate of the present invention, the deterioration of the liquid property of the effluent can be suppressed for a long period of time. Therefore, not only is it possible to obtain a good printing plate that does not cause scumming during printing by preventing plate-making process defects, it also significantly reduces the frequency of replacement of the processing liquid, which results in waste liquid processing and maintenance management. It has excellent effects such as reduced burden.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an elution device used for carrying out a method for suppressing a pH drop of an eluent of an electrophotographic lithographic printing plate according to the present invention.

FIG. 2 is a schematic configuration diagram of a waste liquid tank that constitutes an eluate pH drop suppressing mechanism according to the elution device of the present invention.

[Explanation of symbols]

 1 Printing plate transport line 3 Eluent storage tank 4 Removal waste liquid primary storage tank 5 Rinsing liquid storage tank 6 Protective gum liquid primary storage tank 9 Waste liquid tank 29 Eluent 45 Rinse liquid 94a valve 120 Air intake 121 Air pump 123, 133 Air bubble generator 125,134 Acidic gas removing air intake means 129 Supply section discharge port 130 Removed material 131 Liquid removing material storage tank 139 Solid removing material holding means

Claims (4)

[Claims] 1. An eluent for eluting and removing a non-image portion of an electrophotographic lithographic printing plate on which a toner image is formed on a photoconductive layer, the air having an acidic gas trapping agent supplied to the liquid surface thereof. Eluent pH of electrophotographic lithographic printing plate characterized by
Descent control method. 2. The suppression of pH drop of the eluent of the electrophotographic lithographic printing plate according to claim 1, wherein the acidic gas trapping agent for treating the air for removing the acidic gas supplied to the surface of the eluent is at least the eluent used for the elution removal. Method. 3. A toner image is formed on the photoconductive layer, having at least an elution part for supplying an elution liquid to the image forming surface of the electrophotographic lithographic printing plate and a rinse part for cleaning the image forming surface after elution. In the elution device of electrophotographic lithographic printing plate, which elutes and removes the non-image part of the electrophotographic lithographic printing plate, the air is sucked into the acidic gas trapping agent and the air from which the acidic gas is removed is eluted An elution device for an electrophotographic lithographic printing plate, comprising an acidic gas removing air supply means for supplying to the surface of the eluate stored in. 4. The elution device has a removing means for removing at least the non-image part eluted before reaching the rinse part, and a waste liquid tank for recovering the removed matter removed by the removing means. An electrophotographic lithographic printing plate elution device according to claim 3.