JP3245681B2 - Liquid developer for electrophotographic plate making - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developer for electrophotographic plate making, and more particularly, to developing and fixing a printing original plate having an electrophotographic photosensitive layer on a conductive substrate by an electrophotographic method, and then removing a non-image portion. The present invention relates to a liquid developer which is used for producing a printing plate which is eluted with an etching solution to make a plate, and which is particularly excellent in improvement of background stain and etching resistance.

[0002]

2. Description of the Related Art Today, plate offset printing original plates include a bodi-type photosensitive agent containing a diazo compound and a phenol resin as a main component, and a PS plate using a negative photosensitive agent containing an acrylic monomer or a prepolymer as a main component. Although they have been put to practical use, all of them have low sensitivity, and in fact, plate making is performed by contact exposure of a silver halide photographic film on which an image has been recorded in advance.

On the other hand, with advances in computer image processing, large-capacity data storage, and data communication technology, in recent years, computer operations have been consistently performed from document input, correction, editing, layout, to page set, and high-speed communication networks and satellite communication As a result, an electronic editing system that can immediately output to a remote terminal plotter has been put to practical use. In particular, the demand for an electronic editing system is high in the newspaper printing field, which requires immediacy. Also, in fields where the originals are stored in the form of original films and the printing plates are duplicated as necessary, the originals are stored on these recording media with the development of ultra-high capacity recording media such as optical disks. It will be stored as digital data.

However, plate making means for making a printing plate directly from the output of a terminal plotter has hardly been put to practical use, and the output is made to a silver halide photographic film even when an electronic editing system is operating. In reality, the printing plate is indirectly produced by contact exposure to the PS plate. This is because it is difficult to develop a direct-type printing original plate having a sensitivity high enough to produce a printing plate within a practical time using a light source of an output plotter (for example, a He-Ne laser, a semiconductor laser, or the like). ing.

Therefore, an electrophotographic photoreceptor is conceived as an original plate having high photosensitivity from which a direct printing plate can be obtained. Conventionally,
Examples of printing plate materials (printing plates) using electrophotography include, for example, JP-B-47-47610 and JP-B-48-48.
No. 40002, JP-B-48-18325, JP-B-51
Zinc oxide-resin dispersed offset printing plate materials described in publications such as JP-A-15766 and JP-B-51-25761 are known. It is used after being wetted with a desensitizing solution (for example, an acidic aqueous solution having a ferrocyan salt or a ferricyan salt). However, the electrophotographic offset printing plate obtained by such a process has a printing durability of about 5,000 to 10,000 sheets, is not suitable for further printing, and has a light intensity of ZnO-resin dispersion system. If the conductive layer (photosensitive layer) has a composition suitable for desensitization as much as possible, problems such as deterioration of electrostatic characteristics and deterioration of image quality occur. It also has the disadvantage of using a harmful cyanide compound for desensitization treatment.

JP-B-37-17162, JP-B-38-
No. 7758, JP-B-46-39405, JP-B-52-
In an organic photoconductor-resin printing plate material described in Japanese Patent Publication No. 2437 or the like, for example, a photoconductive insulating layer in which an oxazole or oxadiazole compound is bound with a styrene-maleic anhydride copolymer is used for a second time. An electrophotographic photoreceptor provided on an upright aluminum plate is used. After forming a toner image on the photoreceptor by electrophotography, a non-image portion is dissolved and removed with an alkaline organic solvent to form a printing plate.

[0007] As a representative of these systems, Kale Company or Sifasol system is on the market. However, since a dry developer is used, the resolution is poor and a high quality image cannot be obtained. On the other hand, a dry developer generally uses particles having a size of 10 μm to several tens of μm mainly composed of a colorant and a resin, so that the formed toner layer in the non-image area is thick and has excellent resist properties to an etching solution. It is said that there is. As is well known, in a liquid developer, the particle size of a toner for forming an image can be made smaller than that of a dry developer (0.1 to 2 μm). It is known to give an image. However, when a liquid developer is used in these methods, the background is often stained on the non-image portion, and the resolution is excellent when the non-image portion is removed with an alkaline etching solution. Therefore, there is a problem that the image portion is etched. Therefore, in spite of using a liquid developer, it is difficult to obtain a product having excellent resolution as a result. In addition, when a material having excellent etching resistance is used for a liquid developer, there is a problem that it is generally difficult to disperse the material and a high resolving power, which is a feature of the liquid developer, is not provided. As another problem, the toner image becomes more filmy than the photosensitive material surface during the etching operation because the adhesiveness with the photosensitive material is poor despite the excellent dispersibility and the etching resistance described above. Peeled off,
It was also recognized that it would not be used as a resist in the image area.

[0008]

SUMMARY OF THE INVENTION A first object of the present invention is to provide a liquid developer for electrophotographic plate making which has less background stain, and a second object is to provide a resist having a resist property against an alkaline etching solution. It is to provide a liquid developer for electrophotographic plate making which is good.

[0009]

According to the present invention, an electrostatic latent image is formed on the surface of a printing plate having a photoconductive layer (photosensitive layer) provided on a conductive substrate, developed and fixed, and then a non-image area is formed. Is eluted with an alkaline solution to produce a printing plate (a liquid developer in which toner particles containing a colorant and a resin as main components are dispersed in a carrier liquid). It is characterized by containing at least silicone oil.

The present inventors have conducted many studies on a liquid developer for electrophotographic plate making in order to achieve the above object, and as a result, have found that the use of silicone oil gives good results. The present invention has been made based on this. That is, silicone oil has higher electric resistance, lower solubility of resin and additives, and water repellency, oil repellency and the like as compared with the aliphatic hydrocarbon solvent conventionally used. Better than solvent. As a result, the liquid developer for electrophotographic plate making using silicone oil,
It is recognized that there is little background contamination and that the resist properties are good for an alkaline solution.

In general, a liquid developer for electrophotographic plate making comprises a colorant (pigment, dye), a resin (binder resin), a polarity controlling agent, and a dispersing solvent (including a dispersing agent at the time of producing a concentrated toner) as main components. Therefore, in the present invention, silicone oil is used for all or a part of the dispersion solvent in the liquid developer component, or at the time of producing the toner particles subjected to the flashing treatment. As the silicone oil, dialkyl polysiloxane, alkyl phenyl polysiloxane, cyclic alkyl polysiloxane and the like can be used.

The following are examples of commercially available silicone oils. Shin-Etsu Chemical Co., Ltd .: KF96L [0.65, 1.0, 1.5, 2.0, 1
0, 20, 300 (cst: centistokes)] KF56 KF58 KF54 manufactured by Dow Corning Toray: SH-200 SH-400 manufactured by Toshiba Silicone: TSF451 series TSF456 series TSF410, 411, 440, 4420, 484 , 4
83, 431, 433 THF450 series TSF4440, 4001, 401, 4300, 444
5, 4700, 4450, 4702 TSF434, 4600 HS-200

Examples of inorganic pigments used in the colorant include furnace black, acetylene black, channel black and the like as carbon black, and commercially available products thereof include PRINTEX G, PRINTEX V, special black 15, special black 15, and the like. Black 4, Special Black 4-B (made by Degussa), Mitsubishi # 44, #
30, MA-11, MA-100 (made by Mitsubishi Carbon), Raven 30, Raven 40, Conductex SC (made by Columbia Carbon), Regal 40
0, Legal 660, Legal 800, Black Pearl L (all manufactured by Cabot Corporation) and the like. In addition, as inorganic pigments other than carbon black, titanium oxide,
Examples thereof include inorganic white pigments such as silicon oxide, magnetic powders such as zinc oxide and iron tetroxide, metal powders, and metal oxides. Examples of the organic pigment include phthalocyanine blue, phthalocyanine green, rhodamine lake, malachite green lake, methyl violet lake, peacock blue lake, nattole green B, permanent red 4R, Hansa yellow, benzidine yellow, thioindigolet, and alkali blue. .

When silicone oil is used as a carrier liquid for a developer or a dispersion medium for a concentrated toner, it may be used alone or as a mixture with an aliphatic hydrocarbon solvent.

Specific examples of the aliphatic hydrocarbon include n-hexane, n-decane, isododecane and the like. Commercial products thereof include Shellsol 71 manufactured by Shell Sekiyu, Isopar G, Isopar H manufactured by Exxon, and the like. Isopar L, Isopar K, Isopar M, Isopar V and the like can be mentioned. These can also be used as dispersants.

In general, a liquid developer is prepared by mixing 0.3 to 3 parts by weight of a resin with 1 part by weight of a coloring agent, and mixing the mixture with an aliphatic hydrocarbon carrier solution in an amount of 10 to 20 parts by weight. The toner may be sufficiently dispersed by a dispersing machine such as a ball mill or a Keddy mill to form a concentrated toner, and if necessary, the toner may be diluted 5 to 10 times with a similar solvent. If necessary, a polarity controlling agent such as lecithin, linseed oil, and a surfactant, or a dispersant is added.

As described above, as the coloring agent, ordinary inorganic or organic pigments may be used. However, it is preferable to disperse the pigment particles even to primary particles, and to obtain gradation, resolution, and the like.
In order to further improve the image density and the like, it is effective to use a coloring agent manufactured by the flanking method. The flushing method is a method in which a pigment or a water-containing paste of a pigment is put into a kneader called a flasher together with a resin solution or a resin and mixed well (in this process, water present around the pigment is replaced by the resin solution or the resin). Is removed from the kneader, the aqueous phase is discarded, the pigment in the resin solution or in the resin kneaded and dispersed at room temperature is dried, the solvent is removed, and the resulting mass is pulverized. This is referred to as "flushing colorant" in the present invention. In addition, an allowance for removing water and the solvent under reduced pressure while kneading with a kneader may be adopted.

In the flushing treatment, not only the pigment but also the dye is kneaded with water in a mud-like state, so that almost the same result as the pigment can be obtained. Therefore, in the present invention, the dye to be flushed is also used as a toner component. It is possible to adopt. The ratio of the dye to the resin at the time of flushing is suitably from 10 to 60 parts by weight based on 100 parts by weight of the resin. It is particularly advantageous to carry out the flushing treatment in the presence of humic acid, humates (Na salt, NH ₄ salt, etc.) or humic acid derivatives. The amount of the added humic acid or the like is appropriately about 0.1 to 30% by weight of the aqueous solution of the dye and pigment.

The resin used for flushing includes rosin-modified maleic resin, shellac, beeswax,
Although a binder resin for a wet toner, such as polystyrene, polyacetal, or polyamide resin, which has been conventionally used, can be applied. In the present invention, a coloring agent which is added with silicone oil and flushed is also suitable. Some examples of the production of the flushing-treated coloring agent are as follows.

Preparation Example 1 200 parts by weight of water and ammonium humate 2 in a kneader
0 parts by weight and well melted while carbon Mitsubishi # 44
500 parts by weight (manufactured by Mitsubishi Carbon Corporation) were added and dispersed in a kneader. To this, 500 parts by weight of silicone oil KF96L (300 cst, manufactured by Shin-Etsu Chemical Co., Ltd.) was added and kneaded at about 120 ° C. for 1 hour. Thereafter, the water was separated. After kneading at 150 ° C. for 4 hours, the mixture was dried under vacuum to obtain a colorant.

Colorant Production Examples 2 to 10 In the same manner as in Production Example 1, colorants were obtained according to the formulations shown in Table 1.
The parts in Table 1 are parts by weight.

[Table 1]

A liquid developer using a flushing colorant having a pigment surface treated with silicone oil has a narrow and uniform particle size distribution of toner particles. Further, it is considered that the toner is hardly physically attached to the non-image portion due to the small amount of the fine particles, so that the background stain is hardly generated. Furthermore, after developing the printing original plate with a liquid developer using a flushing colorant having a pigment surface treated with silicone oil, the heat-fixed image area is uniformly developed and has a large contact angle with water. Therefore, the etching resistance with an alkaline aqueous solution is excellent.

Next, known methods for the printing original plate, etching solution, etching method and the like used in the present invention will be described.

The printing original plate used in the present invention can be obtained by coating a photoconductive layer (photosensitive layer) on a conductive substrate. The coating liquid is obtained by dissolving or dispersing the components constituting the photoconductive layer in an appropriate solvent. When a component insoluble in a solvent such as a pigment is used, it can be used after being dispersed to a particle size of 0.1 to 5 μm by a disperser such as a ball mill, a paint shaker, a dyno mill, and an attritor. The binder resin and other additives used in the photoconductive layer can be added during or after the dispersion of the pigment or the like. The coating solution prepared in this manner is applied on a conductive substrate by a known method such as spin coating, blade coating, knife coating, reverse roll coating, dip coating, rod bar coating, spray coating, and dried to form an electrophotographic plate. Printing original plate can be obtained.

Examples of the solution for preparing the coating solution include halogenated hydrocarbons such as dichloromethane, dichloroethane and chloroform: alcohols such as methanol and ethanol: ketones such as acetone, methyl ethyl ketone and cyclohexanone: ethylene glycol monomethyl ether; Glycol ethers such as -methoxyethyl acetate: ethers such as tetrahydrofuran and dioxane; esters such as ethyl acetate and butyl acetate;

The printing plate of the present invention can be made by a generally known process. That is, the photosensitive layer surface of the printing original plate is charged substantially uniformly in a dark place, and an electrostatic latent image is formed by image exposure. As an exposure method, a semiconductor laser, H
Examples include scanning exposure using an e-Ne laser or the like, reflection image exposure using a xenon lamp, a tungsten lamp, a fluorescent lamp or the like as a light source, and contact exposure through a transparent positive film. Next, the electrostatic latent image is developed with the liquid developer of the present invention. The formed toner image can be fixed by a known fixing method (heating fixing, solvent fixing, etc.) as necessary. The printing plate can be prepared by using the toner image thus formed as a resist and removing the electrophotographic photosensitive layer in the non-image area with an etchant.

As the plate making etching solution of the present invention, it is desirable to use an aqueous solution of an organic or inorganic acid or base or a salt thereof or a mixture with an organic solvent miscible therewith. The components of the etchant are determined in consideration of the resist properties of the toner layer in addition to the solubility of the photosensitive layer, and the following are common examples. Sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, potassium silicate, sodium metasilicate, potassium metasilicate, sodium phosphate, potassium phosphate,
Ammonia and amino alcohols such as monoethanolamine, diethanolamine and triethanolamine are well known. Examples of the organic solvent that is miscible with the aqueous solution include alcohols, ketones, esters, and ethers. Examples of alcohols include lower alcohols and aromatic alcohols such as methanol, ethanol, propanol, butanol, benzyl alcohol, and phenethyl alcohol, and cellsolves such as ethylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol, monoethanolamine, Examples thereof include amino alcohols such as diethanolamine and triethanolamine. Examples of ketones include acetone, methyl ethyl ketone, and methyl isobutyl ketone. As esters,
Examples include ethyl acetate, isopropyl acetate, n-propyl acetate, sec-butyl acetate, isobutyl acetate, n-butyl acetate, 1-acetoxy-2-methoxyethane, and ethylene glycol diacetate. Examples of ethers include ethyl ether, tetrahydrolan, dioxane, 2-methoxyethanol, ethylene glycol dimethyl ether, and the like. These organic solvents can be used in a mixture with the above-mentioned aqueous solution at an arbitrary ratio, but are preferably used in a range of 90% by weight or less of the mixed solution. If necessary, a surfactant, an antifoaming agent, a coloring agent, and the like may be added to the etching solution.

The composition of the etching solution should be determined according to the type of the binder resin and the resin for the toner, and the following are representative examples. (1) Potassium silicate 30 parts Potassium hydroxide 10 parts Benzyl alcohol 20 parts Ethanol 90 parts Water 300 parts (2) Potassium silicate 30 parts Phenethyl alcohol 10 parts Benzyl alcohol 30 parts 900 parts of water

Next, the present invention will be described more specifically with reference to examples.

Example 1 A mixture consisting of 100 parts of a colorant (produced in Example 1), 100 parts of KF96L (1.0 cst), 500 parts of nickel naphthenate and 3 parts of nickel was dispersed for 6 hours by an aspirator to prepare a concentrated toner. 100 g of the concentrated toner is applied to the carrier liquid KF9.
The developer was dispersed in 6 L (1.0 cst) of 1000 ml to prepare a developer. On the other hand, a printing original plate was prepared as follows.
First, the surface of a JIS1050 aluminum sheet was grained with a rotating nylon brush using a Pumice-water suspension as an abrasive. At this time, the surface roughness (center line average roughness) was about 0.5 μm. After washing with water, dipped in a 10% aqueous solution of caustic soda at 70 ° C. to dissolve about 6 g / m of aluminum.
Etching was performed to obtain ² . After washing with water, it was neutralized by immersion in a 30% nitric acid aqueous solution for 1 minute, and the voltage at the time of cathode was 6
Using the rectangular wave alternating waveform of the bolt (JP-B-55-191)
The surface was roughened for 20 seconds, immersed in a solution of 20% nitric acid at 50 ° C. to wash the surface, and then washed with water. Further, the substrate was subjected to anodizing treatment in a 20% aqueous nitric acid solution so that the weight of the anodized film became about 3.0 g / m ² , washed with water, and dried to prepare a conductive substrate. On this conductive substrate, a photosensitive layer in which a copper phthalocyanine pigment was dispersed in a phenol resin was formed to a thickness of about 5 μm to obtain a printing original plate. Next, the printing original plate obtained here was charged to +200 V by a corona charger in a dark place, and then subjected to image exposure with tungsten light. Subsequently, development was carried out using the above-mentioned liquid developer according to a conventional method, and the obtained image was heated and fixed at 140 ° C. for 5 minutes. This was immersed in an etching solution obtained by diluting 45 parts of potassium silicate, 10 parts of potassium hydroxide, 15 parts of benzyl alcohol and 100 parts of ethanol in 1,000 parts of water (for 1 minute) to remove non-image portions, and thoroughly washed with water. To obtain a printing plate. Table 1 summarizes the results of evaluation of the resist properties of the image areas and others.

Comparative Example 1 A liquid developer was prepared and a printing plate was prepared in exactly the same manner as in Example 1 except that a colorant not based on the flushing method was used and that Isopar H was used instead of silicone oil. The evaluation was performed. Table 2 summarizes the results.

[0032]

[Table 2]

Examples 2 to 6 Using the materials shown in Table 3 below, liquid developers were prepared in the same manner as in Example 1.

[Table 3] Subsequently, when the printing plate obtained by plate making using the liquid developer was mounted on a commercial printing machine (manufactured by Ricoh Company) and subjected to printing, favorable results as shown in Table 4 were obtained. .

[Table 4]

[0034]

According to the first and second aspects of the present invention, a printing plate prepared by using the liquid developer has little background stain and excellent resist resistance. The printing plate made using the liquid developer according to claim 3 has excellent resist resistance. The printing plate made by using the liquid developer according to the fourth aspect is particularly one having less background stain and excellent resist resistance.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hidemi Uematsu 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-58-139155 (JP, A) JP-A Heihei 2-74957 (JP, A) JP-A-63-4249 (JP, A) JP-A-61-39059 (JP, A) JP-A-3-43749 (JP, A)

Claims (4)

(57) [Claims] A printing plate is prepared by forming an electrostatic latent image on the surface of a printing original plate having a photoconductive layer provided on a conductive substrate, developing and fixing the non-image portion with an alkaline solution. Used in the liquid developer in which the toner particles containing at least a colorant and a resin as main components are dispersed in a carrier liquid.
A liquid developer for electrophotographic plate making characterized by containing a silicone oil. 2. The liquid developer according to claim 1, wherein the silicone oil is used as a carrier liquid or as a part of the carrier liquid. 3. The liquid developer according to claim 1, wherein the colorant is dispersed in a resin insoluble or hardly soluble in silicone oil. 4. The liquid developer for electrophotographic plate making according to claim 1, wherein the coloring agent is subjected to a flushing treatment by adding silicone oil.