JP3086240B2 - Method for producing electrophotographic lithographic printing plate by reversal development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to a reversal method in which image information output from an electronic editing system or the like is directly written on an organic photoreceptor and a plate is obtained by performing reversal development. The present invention relates to a method for producing an electrophotographic lithographic printing plate by development.

(Prior art) In recent years, with the development of mechanical image processing technology and memory development and transmission technology of large-capacity data, image input, correction, and editing of characters, figures, photographs, etc. are all performed by computer control, and high-speed communication is performed. 2. Description of the Related Art An electronic editing system capable of instantaneously outputting a film to a remote terminal plotter via a network or satellite communication has been adopted and operated particularly in the newspaper printing field and the like.

In the printing field using such an electronic editing system, it is an important issue to produce a printing plate in a shorter time, and in order to meet the demand, image information modulated light emitted from a light source of an output plotter is converted into a film. 2. Description of the Related Art A method for producing an electrophotographic lithographic printing plate, in which writing is performed directly on a high-sensitivity photoconductive electrophotographic photosensitive member instead of an output, has been developed.

As the photoconductive high-sensitivity photosensitive material, an organic photoconductive compound / binder resin material is particularly excellent in terms of printing durability and practical sensitivity, and an organic photoconductive compound as the electrophotographic photosensitive material is excellent. -An organic photoreceptor (OPC) formed by applying a binder resin material on a conductive substrate such as aluminum has been receiving attention. In the image forming step, the organic photoreceptor is first subjected to a charging step to place a uniform charge thereon,
The exposure forms an electrostatic latent image corresponding to the image. This electrostatic latent image is developed using an electrophotographic developer to form a toner visible image. At this time, non-image portions other than the toner visible image are dissolved and removed (eluted) by being treated with a solution containing an alkaline agent or the like, whereby a final printing plate is obtained.

By the way, in the developing step, if a toner image is obtained by so-called reversal development, a good image free from fog and line thinning can be obtained from its developing characteristics. Recently, particularly high resolution and high quality image reproducibility have been demanded, and a method for producing an electrophotographic lithographic printing plate by reversal development is one method that can realize this demand.

When reversal development is performed, first, light is irradiated to a portion where toner is to be adhered (for example, a portion corresponding to a character line) in an exposure step, and the potential of the light irradiated portion is attenuated to almost zero potential. At this time, the portion where light irradiation is not performed (the portion corresponding to the background) maintains the initial charging potential as it is. A predetermined developing bias is applied to the developing process region via an electrode, and a predetermined developing electric field is formed by the developing bias. On the other hand, the toner particles in the developer are charged to the same polarity as the photoconductor side by a predetermined method. In such a state, when the photoconductor is carried into the developing electric field in the developing process area, the toner particles in the developer are transferred to the photoconductor side by the developing electric field, and the light-irradiated portion of the photoconductor is substantially removed. The toner particles adhere to the zero potential portion. At this time, a portion corresponding to the background where the initial charging potential remains remains repelled by the toner particles, thereby avoiding toner adhesion.

As the developer used for such reversal development, either a dry developer or a liquid developer can be employed. However, according to the liquid developer, the toner particles can be made finer, so Good image reproducibility can be obtained with resolving power. The liquid developer is obtained by dispersing pigment (dye) or polymer particles in a highly insulating medium to perform coloring, and adding a charge (charge) controlling agent thereto to impart a predetermined charge.

The development speed, that is, the toner adhesion amount (image density) in the development using such a liquid developer is determined by various image forming conditions. The density is a very important condition for determining the image quality based on the development speed or the image density. As described above, in reversal development,
A substantially zero-potential portion is partially exposed to the initial uniformly charged region on the photoconductor side, and toner is deposited such that the substantially zero-potential portion is filled with charges of toner particles. Therefore, the developing speed (toner adhesion amount) depends on the concentration of the toner particles.
In general, when the concentration of toner particles is low, the developing speed is reduced and the amount of toner particles attached (image density) decreases. When the concentration of toner particles is high, the developing speed is reduced. As a result, the toner particle adhesion amount (image density) increases.

(Problems to be Solved by the Invention) However, in such a liquid developing step, as described in detail below, image reproducibility is inconsistent between a so-called thin line image and a solid image, and it is difficult to obtain a well-balanced image. There is a problem.

First, in the case of a fine line image, a narrow low potential portion (zero potential portion) is linearly formed in the high potential region given by the initial charging, and the narrow low potential portion is formed on both sides of the narrow low potential portion. A high-potential part will be arranged. Then, high-density lines of electric force are formed from the high potential portions on both sides to the entire linear low potential portion.
The electric field generated by the high-density lines of electric force is extremely strong,
It is much larger than the original developing electric field due to the developing bias described above. Therefore, the toner adhesion in the development process of the fine line image is mainly performed along the high-density lines of electric force, and the development by the so-called edge effect is performed. In general, a thin line image is formed so as to swell due to the edge effect.

For this reason, in order to faithfully obtain the highlight portion including the fine line image, it is preferable to lower the solid content concentration in the liquid developer, that is, the toner particle concentration, to lower the developing speed.

On the other hand, in the case of a solid image, a low potential portion (substantially zero potential portion) having a large area is formed in a high potential region formed by initial charging. There is a high-potential portion around this large-area low-potential portion, but the edge effect caused by this high-potential portion only affects the portion along the peripheral portion, and most of the low-potential portion has Only the original development electric field described above is formed.

Therefore, in the case of this solid image, the developing action by the developing bias electric field is mainly performed, and in order to faithfully obtain a halftone dot portion including this solid image, the solid content concentration in the liquid developer, that is, the toner particle concentration is usually adjusted. It is preferable to increase the developing speed by further raising. However, if the toner particle concentration is too high, the halftone dot shadow portion will be crushed.

Thus, the development condition (low toner density) for faithfully obtaining a highlight portion including a fine line image and the development condition (high toner density) for faithfully obtaining a halftone dot portion including a solid image are mutually contradictory. When trying to obtain the highlight part faithfully, the solid black part of the halftone dot shadow part is not reproduced well. Particularly, when trying to obtain a black thin line of the highlight part, the halftone dot shadow part The white part is crushed. In addition, if a halftone dot shadow portion is to be faithfully obtained, a thin black line in a highlight portion is cut off.

The printing plate according to the present invention, the non-image portion other than the toner image portion formed by reversal development is eluted with an alkaline eluent, the surface of the support as a hydrophilic aluminum base is made water-receptive, and the image portion is formed. Ink acceptability. The boundary surface between the toner image portion and the non-image portion has an important influence on the properties of the printing plate formed at the time of alkali elution, for example, image sharpness as well as printing durability. That is, if the image boundary surface does not appear sharply, the boundary of alkali elution is not clear, and sometimes when a printing plate is completed after elution, a whisker-like bleeding occurs from the boundary surface or the image edge becomes uneven. Good printed matter cannot be obtained.

Therefore, for this printing plate, it is necessary to balance the development between the highlight area and the shadow area, and it is necessary to obtain excellent image sharpness during reversal development.

Accordingly, an object of the present invention is to provide a method for producing an electrophotographic lithographic printing plate capable of obtaining both a fine line image and a solid image whose developing conditions are contradictory and excellent in a good balance.

(Means and Actions for Solving the Problems) In order to achieve the above-mentioned object, the present invention provides an organic photoreceptor comprising an organic photoconductive compound bound on a conductive support with a resin material. After charging, exposing the light image to form an electrostatic latent image corresponding to the image on the surface of the organic photoreceptor, the electrostatic latent image is charged using an electrophotographic liquid developer containing charged toner particles in a solvent. In a method for producing an electrophotographic lithographic printing plate by reversal development in which a printing plate is produced by reversal development of an electrostatic latent image, resin particles synthesized by a dispersion polymerization method in a highly insulating medium are used as the toner particles. The total weight of the charged toner particles as measured by electrodeposition is 0.12 to 0.5% with respect to the solvent, and the reversal development is performed using a liquid developer for electrophotography having a weight ratio of 0.12 to 0.5%. ing.

In the present invention, since reversal development is performed using an electrophotographic liquid developer having a lower toner concentration than usual, development is performed at a lower development speed than usual, and the edge effect on a fine line image is reduced. Therefore, the highlight portion including the fine line image is favorably reproduced. The high reproducibility of the highlight portion including the fine line image can be obtained almost independently of the level of the developing bias.

On the other hand, if the original developing electric field is strengthened by increasing the developing bias at this time, even if the electrophotographic liquid developer has a low toner concentration, the toner adhesion amount to the solid image can be obtained properly, and the solid image can be obtained. A halftone shadow portion including an image can be faithfully obtained. Even if the developing bias is increased in this manner, the reproducibility of the highlight portion including the fine line image is not impaired as described above.

As described above, according to the present invention, the development balance between the highlight portion and the shadow portion is properly performed, and a sharp and high-sharpness image is obtained, and the image boundary surface becomes sharp. Therefore, the boundary of the alkali elution becomes clear, and the printed plate obtained by the elution treatment does not have a whisker-like bleeding at the image boundary surface and the unevenness at the image edge, thereby obtaining a good printed matter.

The present invention is based on reversal development, and in the case of normal development, even if the developing bias is increased as described above, the amount of toner adhering to a solid image cannot be optimized. This is because the developing bias in the normal development is applied in a direction to prevent the toner from adhering to the photoconductor.

 Next, the configuration of the present invention will be described more specifically.

First, as a liquid developer for electrophotography used in the present invention, a pigment such as carbon black is dispersed in a highly insulating hydrocarbon medium together with a dispersing resin, or colored with a dye instead of a pigment, and charged with a charge controlling agent. There are those in which charged colored resin particles are dispersed in a highly insulating carbonized medium, and can be applied to any of them.
According to the latter liquid developer of the resin particle dispersion type, finer toner particles can be obtained, so that they are excellent in resolution and suitable for a printing plate, and also excellent in dispersion stability, charge stability, and fixing property.

The highly insulating hydrocarbon medium used in the present invention is an organic solvent having a low dielectric constant and a high electric insulation, such as a normal paraffinic hydrocarbon, an isoparaffinic hydrocarbon, an alicyclic hydrocarbon, and an aromatic hydrocarbon. Hydrogen, halogen-based aliphatic hydrocarbons and the like can be mentioned, and isoparaffin-based hydrocarbons are preferably used. For example, Shell Sol 71 (manufactured by Shell Petroleum), Isopar G, Isopar H and Isopar K
And Isopar L (manufactured by Esso Oil), IP Solvent (manufactured by Idemitsu Oil), and the like are used.

Examples of the method for producing a toner suitably used in the present invention include JP-A-59-83174, JP-A-59-177572, and JP-A-59-177572.
No. 9-212850, No. 59-212851, No. 60-166477
No. 60-179951, No. 60-185962, No.
The method described in JP-A-60-185963 can be used. These are obtained by polymerizing a monomer that is soluble in the solvent in the presence of a polymer soluble in a highly insulating medium by a so-called dispersion polymerization method, but becomes insoluble when a polymer is formed. It is used as a developer. Further, JP 62
-231266, 62-231267, 62-232660, 63-178258, 63-179368, etc. can also be suitably used. . The liquid developer in this method is excellent in stability in industrial production, dispersion stability and the like.

As the colorant for the dispersed resin particles of the liquid developer used in the present invention, those generally known as wet developer colorants can be arbitrarily used. For example, oil-soluble dyes such as oil black and oil red, basic azo dyes such as bismark brown and chrysoidin, acidic azo dyes such as wool black, amide black green and blue black HF, and direct dyes such as direct black D and congo red And anthraquinone dyes such as Sudan Violet and Acid Blue; carbonium dyes such as Auramine, Malachite Green, Crystal Violet and Victoria Blue; rhodamine dyes such as Rhodan B;

As a method of coloring the dispersed resin particles, there is a method of dissolving in advance a solvent for dissolving the coloring agent to be used and dropping and stirring the colorant solution to the dispersed resin particle solution. Particularly, when an oil dye is dissolved in an aromatic solvent such as toluene or xylene and the mixture is dropped and stirred, coloring can be performed well. At this time, it is desirable that the solvent for dissolving the colorant is mixed with, for example, an isoparaffinic hydrocarbon solvent used as the medium. Further, it is desirable to use a solvent that dissolves the dye, which has relatively insulating properties and a high boiling point.For example, when an oil-soluble dye is used, if a small amount of xylene or the like is used for an aromatic hydrocarbon, Even if the solvent is not removed, a liquid developer for electrophotography which can be used sufficiently can be manufactured. Therefore, if the amount of the solvent that dissolves the dye is reduced using a dye having relatively high solubility in an organic solvent such as an oil-soluble dye, it is not necessary to remove the solvent after coloring the dispersed resin particles.

As the liquid developer used in the present invention, if a charge control agent, a dye, and the like are selected, a toner having a positive charge property or a negative charge property can be manufactured. Examples of the charge control agent for the liquid developer used in the present invention include copper oleate, cobalt naphthenate, zinc naphthenate, aluminum stearate, manganese naphthenate, cobalt octylate, lecithin, sodium dioctyl sulfosuccinate, and stevelite. Aluminum base of rosin, etc.
No. 4, JP-A-49-26595, JP-A-60-173558, JP-A-60-175060, JP-A-60-179750, and JP-A-60-175.
No. 182447, No. 60-218662, No. 61-278867, No. 62-30260, No. 62-34170, No. 63-12
The charge control agents listed in 4056 can be used.

To produce a toner having negative charge, a monomer having a base that is soluble in the medium (eg, a copolymer of uraryl methacrylate and dimethylaminoethyl methacrylate), pyromellitic acid, trimellitic acid, Acids insoluble in the medium, such as trimesic acid and benzoic acid, can be used in combination, but are not limited thereto.

The toner particle diameter of the liquid developer used in the present invention is 0.
It is suitably used in the range of 03 to 0.5 μm. More preferably, it is in the range of 0.05 to 0.3 μm.

The solid content concentration of such a liquid developer, that is, the weight ratio of the total weight of the charged toner particles contributing to development to the solvent,
It is measured by the following method.

First, a predetermined amount of the liquid developer is placed in a beaker, and a pair of electrodes made of a new aluminum plate are immersed in the liquid developer and a direct current is applied.
Apply 1000V. The charged toner particles in the liquid developer are electrodeposited on the electrode applied to the opposite polarity side, and accordingly, the toner concentration in the liquid developer in the beaker gradually decreases. When this operation is repeated three times, the toner particles are almost completely recovered, and the liquid developer becomes a red-colored transparent liquid.

Next, the aluminum electrode plate on which the toner particles have been electrodeposited is dried. After the solvent has completely evaporated, the weight change of the aluminum electrode plate is measured. The measured value is used to obtain the solid content weight of the liquid developer, and the solid content concentration of the liquid developer is calculated based on the measured value.

Examples of the lithographic printing plate used in the present invention include, for example, JP-B-37-17162, JP-B-38-6696, and JP-B-38-6961.
-7758, JP-A-41-2426, JP-A-46-39405, JP-A-50-19509, JP-A-50-19510, and 52
No. 2437, No. 54-145538, No. 54-134632, No. 55-105254, No. 55-153948, No. 55-
No. 161250, No. 57-147656, No. 57-161863, No. 58-118658, No. 59-12452, No. 59-4
JP-A-9555, JP-A-62-217256, JP-A-63-226668 and JP-A 1-261659, etc., include electrophotographic printing plate precursors.

(Example) Hereinafter, an example of the present invention will be described in detail.

Example 1 (Synthesis example 1 of emulsion) n-hexyl methacrylate was prepared by a known solution polymerization method.
A 40% xylene solution of a methacrylic acid copolymer (weight ratio 95/5) was obtained.

When 30 g of this solution was added into 1 hexane, a copolymer precipitate was obtained as a slurry.

The slurry washed and decanted several times with hexane was added to a four-necked flask equipped with a N ₂ gas inlet tube, a thermometer, a stirrer, and a cooling tube, and 450 g of IP solvent (manufactured by Idemitsu Petrochemical) was added. added.

Next, 130 g of vinyl acetate and 30 g of lauryl methacrylate were added and stirred well to obtain a uniform transparent solution.
After purging with N ₂ gas at 80 ° C., 1 g of azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and the polymerization started. After about 40 minutes, the solution became cloudy and the internal temperature rose to 110 ° C.
After the internal temperature dropped to 80 ° C., heating was further applied for 2 hours. In order to remove the remaining vinyl acetate monomer, the inside was distilled off under reduced pressure to obtain about 3 g of a distillate. The resulting white emulsion had no precipitate and hardly any monomer odor. When the particle size was measured with an electron microscope, it was found that the particle size was 0.20 μm and there was almost no particle size distribution.

(Production Example of Positively Chargeable Liquid Developer) In 120 g of the emulsion obtained in the above Synthesis Example, 20 g
The emulsion particles were colored by dropping while applying ultrasonic waves to 2 g of oil black HBB (manufactured by Orient Chemical Co., Ltd.) dissolved in xylene.

Subsequently, 1 g of a 1% xylene solution of 4-aminopyridine was added as a charge control agent to obtain a concentrated (concentrated) toner.

This conc toner was diluted with Isopar G to obtain eight kinds of positively charged liquid developers having different solid contents. The solid content concentrations of these positively chargeable liquid developers A, B, C, D, E, F, G and H are as shown in Table 1 below. However, the solid content concentration at this time refers to the weight ratio of charged toner particles contributing to development to the solvent.

(Preparation of a photoreceptor printing original plate) The following photoconductive layer composition dispersed on a surface-treated surface of an aluminum support anodized to have a center line average roughness (Ra) of 0.55 μm with a paint shaker for 1 hour was added to a bar. After coating with a coater, the coating was dried at 90 ° C for 5 minutes to prepare a photoreceptor printing original plate as an electrophotographic planographic printing plate. At this time, the coating amount of the photoconductive layer was 4.5 g / m ² .

Photoconductive layer coating solution composition Butyl methacrylate / methacrylic acid copolymer (methacrylic acid 40% by weight) 18 parts by weight x-type metal-free phthalocyanine 4 parts by weight 1,4-dioxane 60 parts by weight 2-propanol 18 parts by weight (toner reversal development After applying the corona discharge to the obtained photoreceptor printing plate in a dark place to charge it so that the surface potential (V ₀ ) becomes about +300 V, a scanning image is obtained at a density of 2000 DPI using a semiconductor laser (780 nm). Exposure was performed to form various electrostatic latent images from a highlight image area where halftone dots had an area ratio of 7% to a shadow image area where halftone dots had an area ratio of 90%.

Immediately, liquid reversal development was performed using any of the above liquid developers A, B, C, D, E, F, G and H. The developing bias in this reversal development was set by changing variously from 0 to +300 V for one liquid developer. The gap between the electrodes was set to 1 to 5 mm. If the gap between the electrodes is smaller than this, the printing plate comes into contact with the electrodes, and if it is wider, air enters, which is not preferable.

After the toner development, drying with cold air was performed, and then heat fixing was performed using an infrared lamp. Thus, a toner image was obtained on the photoconductor layer.

The results of toner development using the above eight liquid developers of A, B, C, D, E, F, G and H are as follows.

First, when the liquid developer A was used, the development itself was performed well, but the toner concentration of the liquid developer was too low, so that the development could not be performed before a predetermined number of sheets had been processed. In this case, if the toner replenishment is appropriately continued, good development can be obtained similarly to the liquid developers B, C, and D described below.

When the liquid developers B, C, and D were used, good and clear images were obtained, and high reproducibility was obtained for both highlight portions including fine line images and halftone dot portions including solid images.
This will be considered below.

First, the highlight portion including the fine line image was well reproduced because the toner concentration of the liquid developer in this case was lower than the toner concentration of the commonly used liquid developer (solid concentration was about 1%). Probably because it is set.
That is, the development speed is reduced by the low toner density, and the edge effect on the fine line image is reduced. Therefore, the swelling of the black fine line portion as in the normal development is reduced, and the toner adhesion to the non-image portion is also reduced. It is considered that the images of both the black thin line portion and the non-image portion are reproduced well. The high reproducibility of the highlight portion was obtained irrespective of the level of the developing bias, that is, the level of the original developing electric field.

On the other hand, for a halftone dot portion including a solid image, good reproducibility was obtained when the original developing electric field was increased by setting the developing bias higher. That is, toner is mainly applied to the solid image by the developing bias, and the edge effect that occurs independently of the developing bias is as follows.
It affects only the periphery of the solid image.
Therefore, even when a liquid developer having a low toner concentration is used as in the present invention, as long as the developing bias is strengthened and the original developing electric field is set to a large value, the toner adhesion amount to the solid image is properly maintained. Things. Further, even if the developing bias is increased in this manner, the reproducibility of a highlight portion including a thin line image is not impaired as described above.

Further, when the liquid developer E was used, a certain degree of image reproducibility was obtained. However, compared to the case where each of the liquid developers B, C, and D was used, the non- The sharpness of the part decreased.

When the liquid developers F, G, and H are used, the highlight portion including the fine line image is formed so as to swell by an edge effect, and the halftone dot shadow portion including the solid image is crushed and faithful. Image reproducibility was not obtained. This is probably because the toner concentration of the liquid developer was too high and the developing speed was increased more than necessary, so that the development balance between the fine line image portion and the shadow portion was not achieved.

(Plate making process) Next, a plate making process was performed using an eluate, a washing solution and a rinsing solution as shown below.

(1) eluent composition of sodium silicate solution (S _i O ₂ minutes 30 _{wt%, S i O 2 / Na} 2 O
Molar ratio 2.5) 20 parts by weight Potassium hydroxide 1 part by weight Pure water 79 parts by weight (2) Washing liquid composition (20 dm ³ ) Na dioctylsulfosuccinate 0.1 part by weight 2-methyl-3-isothiazolone 0.01 part by weight to pure water A solution prepared by dispersing and dissolving to 100 parts by weight was charged into a washing tank, and after making the plate for 100 plates, 15 ml of a 5% by weight glycine aqueous solution was added each time the plate was processed for 10 plates (A2 size).

(3) Rinse liquid composition (20 dm ³ ) 0.5 parts by weight of succinic acid 0.5 parts by weight of phosphoric acid (85% aqueous solution) 0.05 parts by weight of decaglyceryl monolaurate 0.01 parts by weight of 2-methyl-3-isothiazolone 0.01 parts by weight of sodium hydroxide The solution was adjusted to pH 4.7, and then adjusted to 100 parts by weight with pure water.

When plate making was performed using the above processing solution (elution time was set to 8 seconds), no failure such as elution delay (pigment remaining) in the non-image area was observed. Thus, a printing plate was obtained.

Printing was performed using the eight types of printing plates thus obtained. As a result, with the printing plates obtained according to the present invention, it was possible to obtain printed matter having good, clear and high-quality images. On the other hand, in the case of using a printing plate outside the present invention, good printed matter could not be obtained. In particular, in a printing plate in which a shadow portion of a halftone dot was crushed, only an extremely inappropriate copy was obtained.

Example 2 (Production Example of Negatively Charged Liquid Developer) Up to coloring of the emulsion particles, the same procedure as in Example 1 was carried out, and 0.08 g of dioctyl sulfosuccinate sodium salt was added as a negatively chargeable charge control agent. A conc (concentrated) toner was obtained.

This conc toner was diluted with Isopar G to obtain eight types of negatively chargeable liquid developers having different solid contents. The solid content concentration of each of these negatively chargeable liquid developers J, K, L, M, N, P, Q and R was as shown in Table 2 below. However, the solid content concentration at this time refers to the weight ratio of charged toner particles contributing to development to the solvent.

(Preparation of a photoreceptor printing original plate) The following photoconductive layer composition dispersed on a surface-treated surface of an aluminum support anodized to have a center line average roughness (Ra) of 0.55 μm with a paint shaker for 1 hour was added to a bar. After coating with a coater, the coating was dried at 90 ° C. for 5 minutes to prepare a photoreceptor printing original plate as an electrophotographic lithographic printing plate. At this time, the coating amount of the photoconductive layer was 4.5 g / m ² .

Photoconductive layer coating liquid composition Butyl methacrylate / methacrylic acid copolymer (methacrylic acid 40% by weight) 18 parts by weight 1,4-dioxane 60 parts by weight 2-propanol 18 parts by weight (toner reversal development) A corona discharge is applied to the obtained photoreceptor printing original plate in a dark place so that the surface potential (V ₀ ) becomes about −350 V. After exposure to a scanning image using a He-Ne laser (633 nm) at a density of 2000 DPI, a halftone dot has an area ratio of 90% from a highlight image portion having an area ratio of 7%. A shadow image portion was formed.

Immediately, liquid reversal development was performed using any of the liquid developers J, K, L, M, N, P, Q and R. The developing bias in this reversal development was set while varying variously between 0 and -300V. The gap between the electrodes was set to 1 to 5 mm.

After the toner development, drying with cold air was performed, and then heat fixing was performed using an infrared lamp. Thus, a toner image was obtained on the photoconductor layer.

The results of toner development using the eight liquid developers of J, K, L, M, N, P, Q and R are as follows.

First, when the liquid developer J was used, the development itself was performed well, but the toner concentration of the liquid developer was too low, so that the development could not be performed before the predetermined number of sheets had been processed. In this case, if the toner replenishment is continued as appropriate, good development can be obtained similarly to the liquid developers K, L, and M described below.

When the liquid developers K, L, and M were used, good and clear images were obtained, and high reproducibility was obtained for both highlight portions including fine line images and halftone dot portions including solid images.
The high reproducibility of the highlight portion was obtained irrespective of the level of the developing bias, that is, the level of the original developing electric field.

On the other hand, for a halftone dot portion including a solid image, good reproducibility was obtained when the original developing electric field was increased by setting the developing bias higher. Further, even if the developing bias is increased in this manner, the reproducibility of a highlight portion including a thin line image is not impaired as described above.

Further, when the liquid developer N was used, although a certain degree of image reproducibility was obtained, compared with the case where each of the liquid developers K, L, and M was used, the non-image quality in the halftone dot shadow area was particularly high. The sharpness of the part decreased.

When the liquid developers P, Q, and R are used, the highlight portion including the fine line image is formed so as to swell by the edge effect, and the halftone dot shadow portion including the solid image is flattened. Image reproducibility was not obtained.

(Plate making process) Next, a plate making process was performed using the following eluate, water washing, and rinsing solution.

(1) eluent composition of sodium silicate solution (S _i O ₂ 30 _{wt%, S i O 2 / Na} 2 O molar ratio of 2.5) 20 parts by weight of potassium hydroxide, 1 part by weight of pure water 79 parts by weight (2) rinsing solution composition Dioctyl sulfosuccinate Na 0.1 parts by weight 2-Methyl-3-isothiazolone 0.01 parts by weight was dispersed and dissolved in pure water to make up to 100 parts by weight, and the solution was charged into a washing tank. Every time the plate was treated, 15 ml of a 5% by weight aqueous glycine solution was added.

(3) Rinse liquid composition (20 dm ³ ) 0.5 parts by weight of succinic acid 0.5 parts by weight of phosphoric acid (85% aqueous solution) 0.05 parts by weight of decaglyceryl monolaurate 0.01 parts by weight of 2-methyl-3-isothiazolone 0.01 parts by weight of sodium hydroxide The solution was adjusted to pH 4.7 and then adjusted to 100 parts by weight with pure water.

When plate making was performed using the above processing solution (elution time was set to 8 seconds), no failure such as elution delay (pigment remaining) in the non-image area was observed. Thus, a printing plate was obtained.

Printing was performed using the eight types of printing plates thus obtained. As a result, with the printing plates obtained according to the present invention, it was possible to obtain printed matter having good, clear and high-quality images. On the other hand, in the case of using a printing plate outside the present invention, good printed matter could not be obtained. In particular, in a printing plate in which a shadow portion of a halftone dot was crushed, only an extremely inappropriate copy was obtained.

Example 3 (Synthesis example 2 of emulsion) 150 g of a 20% Isopar G solution of a stearyl methacrylate-methacrylic acid copolymer (97/3 by weight), 95 g of vinyl acetate, 5 g of N-vinylpyrrolidone, and 1.0 g of AIBN The mixture was placed in a four-necked flask, and the total amount was adjusted to 650 g with Isopar G. When heated to 80 ° C after N ₂ gas replacement, polymerization starts,
The internal temperature rose to 105 ° C., and a stable cloudy emulsion was formed. After the internal temperature dropped to 80 ° C., heating was further applied for 2 hours. The resulting emulsion had no precipitate, and the particle size of the emulsion particles was 0.18 μm.

(Production of Positively Chargeable Liquid Developer) Five kinds of positively chargeable liquid developers having different solid content concentrations were obtained in the same manner as in Example 1 using such emulsion particles. Each of these positively chargeable liquid developers X ₁ , X
The respective solid contents at ₂ , X ₃ , X ₄ and X ₅ were as shown in Table 3 below. However, the solid content concentration at this time refers to the weight ratio of charged toner particles contributing to development to the solvent.

The results of toner development using the five types of liquid developers of X ₁ , X ₂ , X ₃ , X ₄ and X ₅ were as follows.

In the case of using a liquid developer X ₁ first, the development itself satisfactorily performed, too low toner concentration of the liquid developer, no longer able to perform development in less through predetermined processing sheets . In this case, if to continue the toner replenishment appropriate, as with the liquid developer X ₂ and X ₃ which will be described next good development obtained.

In the case of using a liquid developer X ₂ and X ₃ are good clear image is obtained, the highlight portion and both high reproducibility dot shadow portion including a solid image including the fine line images were obtained. The high reproducibility of the highlight portion was obtained irrespective of the level of the developing bias, that is, the level of the original developing electric field.

On the other hand, for a halftone dot portion including a solid image, good reproducibility was obtained when the original developing electric field was increased by setting the developing bias higher. Further, even if the developing bias is increased in this manner, the reproducibility of a highlight portion including a thin line image is not impaired as described above.

When further using the liquid developer X ₄ are those obtained some degree of image reproducibility, each of liquid developers X ₂ and
Compared to the case of using the X _3, in particular the sharpness of the non-image area of the halftone dot shadow portion is lowered.

In the case of using a liquid developer X ₅ is a highlight portion including a fine line image will be formed as swollen by the edge effect and faithful image reproducibility caused a collapse in dot shadow portion including a solid image Was not obtained.

Example 4 (Synthesis example 3 of emulsion) 60 g of dodecyl methacrylate, 100 g of vinyl acetate, AIBN
1.6 g was put into a four-necked flask, and the whole amount was adjusted to 650 g with Isopar G. When heating after replacing the N ₂ gas, the internal temperature
About 1 hour after the temperature rose to 80 ° C., the internal temperature rose to 105 ° C., and a stable cloudy emulsion was formed. Internal temperature is 80
After the temperature was lowered to ° C, heating was further applied for 2 hours. There was no precipitate in the obtained emulsion, and the particle size of the emulsion particles was 0.10 μm.

(Production of Positively Chargeable Liquid Developer) Five kinds of positively chargeable liquid developers having different solid content concentrations were obtained in the same manner as in Example 3 using such emulsion particles. Each of these positively charged liquid developers Y ₁ , Y
The respective solid content concentrations of ₂ , Y ₃ , Y ₄ and Y ₅ were as shown in Table 4 below. However, the solid content concentration at this time refers to the weight ratio of charged toner particles contributing to development to the solvent.

The results of toner development using the above five types of liquid developers Y ₁ , Y ₂ , Y ₃ , Y ₄ and Y ₅ are as follows.

When using a liquid developer Y _1, Y ₂ and Y ₃ are first good clear image is obtained, both high reproducibility obtained halftone shadow portion including the highlight portion and the solid image containing the fine line image Was done. The high reproducibility of the highlight portion was obtained irrespective of the level of the developing bias, that is, the level of the original developing electric field.

On the other hand, for a halftone dot portion including a solid image, good reproducibility was obtained when the original developing electric field was increased by setting the developing bias higher. Further, even if the developing bias is increased in this manner, the reproducibility of a highlight portion including a thin line image is not impaired as described above.

When further using the liquid developer Y ₄ are those obtained some degree of image reproducibility, as compared with the case of using the above liquid developers Y _1, Y ₂ and Y _3, in particular dot shadows The sharpness of the non-image portion in the portion was reduced.

In the case of using a liquid developer Y ₅ is a highlight portion including a fine line image will be formed as swollen by the edge effect and faithful image reproducibility caused a collapse in dot shadow portion including a solid image Was not obtained.

(Effects of the Invention) As described above, the present invention sets the toner solid content concentration of the liquid developer used for reversal development to a predetermined value or less, so that a highlight portion including a fine line image and a solid image can be formed. High reproducibility can be obtained in both the halftone and shadow areas, and a toner image can be formed on the photoreceptor printing original plate very satisfactorily, and a high quality printed matter can be obtained.

Continuation of front page (56) References JP-A-61-49895 (JP, A) JP-A-57-147656 (JP, A) JP-A-55-35383 (JP, A) JP-A-55-36847 (JP, A) JP-A-57-73746 (JP, A) JP-A-63-96668 (JP, A) JP-A-63-173075 (JP, A) JP-A-2-66566 (JP, A) 60-185963 (JP, A) JP-A-59-212851 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/26-13/28 G03G 9/12-9 / 135

Claims (1)

(57) [Claims] An electrostatic latent image corresponding to an image by uniformly charging the surface of an organic photoreceptor obtained by binding an organic photoconductive compound on a conductive support with a resin material and exposing the light image. After forming on the surface of the organic photoreceptor, to produce a printing plate by reversal development of the electrostatic latent image using an electrophotographic liquid developer containing charged toner particles in a solvent and In the method for producing an electrophotographic lithographic printing plate by reversal development, resin particles synthesized by a dispersion polymerization method in a highly insulating medium are used as the toner particles, and all of the charged toner particles measured by electrodeposition are used. A method for producing an electrophotographic lithographic printing plate by reversal development, wherein reversal development is performed using an electrophotographic liquid developer having a weight ratio of 0.12 to 0.5% with respect to a solvent.