JPH0440486A - Wet type reversal developing method for electrophotography - Google Patents

Abstract

PURPOSE:To obtain an image having a little edge effect by actually making a developing bias electrode into a wire and carrying out development white a bias voltage is applied. CONSTITUTION:The developing bias electrode 6 is actually made into the wire. The range of the actual wire is the projecting width of an electrode 6, that is, <= 30mm. On the other hand, as the material of the developing bias electrode 6, all kinds of metals can be used. The developing bias voltage is applied on the developing bias electrode 6 by a developing bias power source 65, and a contact image exposure is carried out via a negative film. An excess developer is squeezed up by a pair of squeezing rollers 8 and 8' while a developer is carried by a pair of carrying into rollers 7 and 7'. Electrophotographic wet type reversal development is carried out by the developing bias power source 5-the developing bias electrode 6-a developing liquid 9-a sensitive layer 3-a supporting body 2 power feeding pieces 4 and 4'-the closing circuit of the developing bias power source 5. Thus, a printed image having excellent gradation reproducibility without having an edge effect is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application Field The present invention relates to an electrophotographic wet reversal development method, and in particular, an electrophotographic wet reversal method that enables uniform development over the entire surface with little edge effect and excellent gradation reproducibility. This relates to a developing method.

(B) Prior art and its problems An electrophotographic photoreceptor used as a printing plate is made by using an aluminum plate in a grained chamber and anodizing it, using this as a support and using a photoconductive material as a binder. It is obtained by applying and drying a photosensitive liquid dispersed or dissolved in the photosensitive material.

The electrophotographic photoreceptor may undergo a charging process, an exposure process, a development process, and a fixing process to form a printing plate, or depending on the structure of the electrophotographic photoreceptor, for example, Japanese Patent Publication No. 3717162, No. 38-
No. 7758, No. 46-39405, JP-A-52-24
No. 37, No. 57161863, No. 58-2854,
No. 58-28760, No. 58-11'8658, No. 5912452, No. 59-49555, No. 6221
No. 7256, No. 63-226668, JP-A-1-26
As described in Japanese Patent Application No. 1659, etc., after the fixing process, the printing plate is produced through an elution process and a gumming process.

Plate-making machines for obtaining printing plates use the so-called contact printing method, in which the original and the electrophotographic photoreceptor are exposed in close contact with each other, the so-called photographing method, in which the original is projected onto the electrophotographic photoreceptor through a lens, and the image information of the original is transferred electronically. There is a scanning exposure method in which the signal is converted into a signal and an electrophotographic photoreceptor is exposed to, for example, a laser beam. In both methods, there are positive exposure and negative exposure.
It goes without saying that there are two types of development: normal development and reversal development.

It is generally accepted that in reversal development for electrophotography, the edge effect is greater than in normal development. In order to reduce this, it is effective to bring the developing bias electrode plate closer to the electrophotographic photoreceptor, but since a bias voltage is applied to the developing bias electrode plate, there is a risk of short circuit, so do not bring it too close. Actually, I can't do it. Further, if the gap between the developing bias electrode plate and the guide plate becomes small, it may cause transportation failure and sometimes damage to the surface of the electrophotographic photoreceptor. The gap between the developing bias electrode plate and the electrophotographic photoreceptor is usually set to 1 to 5 mm.

The width of the developing bias electrode plate (length in the conveying direction of the photoreceptor) of a conventional electrophotographic wet developing device is 100 mm to 300 mm.
It is set to about.

The edge effect can also be reduced by increasing the bias voltage, but in this case the negative portions of the halftone dots are crushed, resulting in an image with poor gradation reproducibility.

The developing bias voltage of a conventional electrophotographic wet developing device is set to several tens of percent of the surface potential of the electrophotographic photoreceptor. This means that in the non-image area, the surface potential is higher than the development bias voltage, so the toner particles in the developer are developed onto the development bias electrode plate, and the developed toner mass generates a voltage. Since the sum of the generated voltage and the developing bias voltage becomes a new developing bias voltage and is applied to the electrophotographic photoreceptor, there still arise problems such as the negative portions of the halftone dots being crushed and the image becoming thicker.

Furthermore, if a large amount of toner is electrodeposited on the developing bias electrode, the developing bias voltage may not be applied properly, resulting in image failure, or the toner electrodeposited on the electrode must be periodically removed, making maintenance difficult. You have to put in a lot of effort.

(C) Object of the Invention The present invention solves the above-mentioned problems of the prior art, and its object is to provide an electrophotographic wet reversal development method that can produce images with less edge effect.

Another object of the present invention is to provide an electrophotographic wet reversal development method that can produce images with excellent gradation reproducibility.

Still another object of the present invention is to improve maintainability by simplifying the developing device section.

(D) Structure of the Invention The electrophotographic wet reversal development method of the present invention is achieved by making the development bias electrode substantially linear and performing development while applying a bias voltage.

The substantially linear developing bias electrode used in the electrophotographic wet reversal development of the present invention has a projected width of 30 mm or less, preferably 20 mm or less.

The developing bias electrode may be made of any material as long as it is a good electrical conductor. For example, all metals can be used.

The range of bias voltage applied to the electrophotographic wet development of the present invention is preferably 80% of the surface potential of the electrophotographic photoreceptor.
It is above, and more preferably 100% to 500%, but it may be set depending on the amount of charge, polarity, and development speed of the toner, and cannot be generally determined.

The conveyance speed during electrophotographic wet development of the present invention is 0°5 m/m.
in to 20 m/min, preferably 1 m/min
~10 m/rnin.

Examples of the binder for the photosensitive layer of the electrophotographic photoreceptor used in the present invention include styrene-maleic anhydride copolymer, styrene-maleic anhydride half ester copolymer, maleic acid copolymer, and vinyl acetate-crotonic acid copolymer. Examples include copolymers, acrylic resins with acid values, phenolic resins, and the like.

Examples of photoconductive materials for the photosensitive layer of the electrophotographic photoreceptor used in the present invention include inorganic photoconductive materials such as zinc oxide, titanium oxide, and cadmium sulfide, and aromatic tertiary amino compounds such as Phenylamine, diphenylbenzylamine, di(β-naphthyl)benzylamine, diphenylcyclohexylamine, etc., aromatic tertiary diamino compounds such as N, N, N', N'
-tetrabenzyl-p-phenylenediamine, N,
N, N', N'tetrabenzylbenzidine, ], ]'
-bis(1-N,N-dibenzylaminophenyl)
Ethane, 2,2-bis(,IN,N-dibenzylaminophenyl)butane, 4. 4'-bis(di-p-tolylamino)-1,,1,i-triphenylethane, etc.
Aromatic tertiary triamino compounds, such as 4.4', 4
"-tris(diethylaminophenyl)methane, 4-dimethylamino-4,4"bis(diethylamino)-2,
2”-dimethyltriphenylmethane, etc., condensation synthetic organisms,
For example, condensation products of aldehydes and aromatic amines,
Reaction product of aromatic amine and aromatic halide, polyp
-phenylene-1,3,4-oxadiazole, reaction products of formaldehyde and fused polycyclic compounds, etc., metal-containing compounds such as 2-mercaptobenzothiazole zinc salt, 2-mercaptobenzoxazole lead salt, 2- Mercapto-6-medoxybenzimidazole lead salt, S-hydroxyquinoline aluminum salt, 2-hydroxy-4
- methylazobenzene copper salt, etc., polyvinylcarbazole compounds such as polyvinylcarbazole, halogen-substituted polyvinylcarbazole, copolymers of vinylcarbazole and styrene, copolymers of vinylanthracene-vinylcarbazole, etc., heterocyclic compounds, e.g. , 13
,5~triphenylpyrazoline, 1-phenyl-3-(
p-dimethylaminostyryl)-5-(p-dimethylaminophenyl)pyrazoline, J,5-diphenyl-3styrylpyrazoline, 1,3-diphenyl-5styrylpyrazoline, 1,3-diphenyl-5(p- dimethylaminophenyl) pyrazoline, 3-(/l'l dithylaminophenyl)-5,6 di(4''-methoxyphenyl)
-1,2,4 triazine, 3-(4'-dimethylaminophenyl)-5,6-dipyridyl1. , 2.
14 riazine, 2-phenyl-4-(4'-dimethylaminophenyl)quinazoline, 6-hydroxy-2゜3-di(p-methoxyphenyl)benzofuran, etc.
Organic photoconductive materials such as phthalocyanine pigments, quinacridone pigments, indigo pigments, cyanine pigments, perylene pigments, bisbenzimidazole pigments, quinone pigments, azo pigments, etc. are used.

The support for the electrophotographic photoreceptor used in the present invention is preferably a metal plate such as an aluminum plate, a zinc plate, a magnesium plate, a copper plate, or an iron plate. Furthermore, polymer films such as polyester, cellulose acetate, polystyrene, polycarbonate, polyamide, and polypropylene, as well as processed papers such as synthetic paper and resin-coated paper, can be used, but they must be subjected to conductive treatment or hydrophilic treatment in advance. desirable.

In order to produce an electrophotographic photoreceptor, one or a mixture of two or more of the binders is dissolved in a solvent, and at least one of the photoconductive materials is dissolved in the solvent, but if the photoconductive material is not dissolved. is made into a dispersion liquid using an appropriate dispersion machine (for example, a colloid mill, a ball mill, a homogenizer, an ultrasonic dispersion machine, etc.), and if necessary, a sensitizing dye,
Add a chemical sensitizer to the support to a thickness of 1 to 30 μm.
Apply and dry so that it becomes m.

Those that can be used as solvents include all solvents that are capable of dissolving the binder and capable of dissolving or dispersing the photoconductive material.

For example, alcohols such as methanol, ethanol, propatool, butanol, and hexyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, aromatics such as benzene, toluene, and xylene, and cyclic ethers such as dioxane and tetrahydrofuran. , esters such as ethyl acetate and butyl acetate, ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone, dimethyl formamide, dimethyl sulfoxide, and halogenated hydrocarbons. There is no problem in using one or a combination of two or more of these solvents.

In addition, when used as a printing plate, the toner in the developer must be hydrophobic and ink-receptive, and have sufficient adhesion to the photosensitive layer to withstand back printing, and must also be alkali and/or ink-receptive. Alternatively, when a printing plate is prepared by eluating the non-image area with alcohol or the like, it must have resistivity to the eluate.

Toners that meet these conditions include, for example, carbon black, cyanine blue, nigrosine, oil dyes, and other colorants, pigments, or dyes, which are placed in a highly insulating medium, and which have resistivity to eluates, such as rosin, It is mechanically dispersed with resins such as alkyd resins, acrylic resins, and synthetic rubbers using a ball mill, attritor homogenizer, etc., and then metal soaps, amines, higher fatty acids, etc. are added to stabilize the charge on the dispersed particles of the dispersion. It is added to make toner for liquid development. Also, Special Publication No. 53-54029, No. 57-
1.2985, etc., a polymerizable vinyl group is introduced into a precursor polymer in advance by a polymer reaction, and monomers are polymerized in the presence of this to produce a graft copolymer. , which is made into a liquid developing toner by coloring it with dye.

Furthermore, JP-A-59-83174 and JP-A-59-17757
No. 2, No. 59-21-2850, No. 5921, 285
No. 1, No. 60-164757, No. 60-179751
No. 60-185962, No. 60-1.85963
No. 60-252367, No. 61-i-1, 63
No. 64, No. 61-1-16365, etc., in the presence of a polymer soluble in a highly insulating medium, polymerize a monomer that is soluble in the solvent but becomes insoluble when a polymer is formed, The obtained resin dispersion can be used as a liquid developing toner. Furthermore, JP-A-62-231266, JP-A No. 62-231267, JP-A No. 61-232660, JP-A No. 6
Liquid toners such as those described in Japanese Patent No. 3-1.78258 and Japanese Patent No. 63-1.79368 can be suitably used.

In order to explain in more detail, an example will be given.

(E) Example FIG. 1 is a schematic cross-sectional view of an electrophotographic photoreceptor being developed by the electrophotographic wet reversal developing method of the present invention.

1 is an electrophotographic photoreceptor; 2 is a support for the electrophotographic photoreceptor; 3
is a photosensitive layer of an electrophotographic photoreceptor.

As the electrophotographic photoreceptor 1, an electrophotographic photoreceptor having the following composition was applied to the support 2, which was prepared by roughening a 0.3 mm thick aluminum plate by a conventional method and anodizing it. After drying, an electrophotographic lithographic printing plate provided with the photosensitive layer 3 was obtained. The coating weight of the photosensitive layer after drying is 4.5 grams/square meter.

Butyl methacrylate/methacrylic acid copolymer (molecular weight 50,000, acid value 200) 1.8 parts by weight metal-free phthalocyanine 4 parts by weight acetic acid]. -butyl
60 parts by weight 2-Proper Tools
18 parts by weight The developing bias electrode 6 has a projected width of 0.1 mm, 1 mm, and 5 mm as shown in Table 1.
s 20 rom, 30 mm. As a comparative example, a sample of 50 mm% and 100 mm was also conducted.

As the developer 9, a commercially available electrophotographic wet developer (LOM ED-m manufactured by Mitsubishi Paper Industries, Ltd., in which positively charged toner particles are dispersed in an insulating solvent) was used.

Carrying roller pair 7.7゛ and squeezing roller pair 8.8゛
was rotated in the direction of the arrow in the figure, and the conveyance speed of the electrophotographic photoreceptor 1- was set to 3.5 m/min.

The diameters of the input roller pair 7.7' and the exit roller pair 8.8'' are 20 mm, but are not particularly limited.

The distance between the roller centers of the carry-in roller pair and the squeeze roller pair was set by adding 20 mm to the projected width of each developing bias electrode.

The carry-in roll 7, the squeeze roll 8, and the electrophotographic photoreceptor 1 form a developer reservoir.

A developing bias voltage is applied to the developing bias electrode 6 by a developing bias power source 5 . The developing bias voltage is
As shown in Table 1.

The photosensitive layer 3 of the electrophotographic photoreceptor 1 is positively charged by a conventional method using a corona charger (not shown) to have a surface potential of 300 cm.
And so.

Next, negative film' (electronic photography society test chart N
o, 1-T 1975), and the excess developer is squeezed out by the squeezing roller pair 8.8' while being conveyed by the input roller pair 7.7'. Remove and proceed to the next process.

Development bias power supply 5 - Development bias electrode 6 - Developer solution 9 -
Electrophotographic wet reversal development was carried out by a closed circuit of photosensitive layer 3 - support 2 - power supply piece 4.4' development bias power supply 5.

Table 1: The obtained electrophotographic printing plate was eluted with an eluent (20 parts by weight of sodium silicate aqueous solution, 1 part by weight of potassium hydroxide, diluted with water to 100 parts by weight) to elute the non-image areas. When lithographic printing was performed, in Examples 1, 2, 3, and 4, printed materials with excellent gradation reproducibility and good image quality were obtained.

In Example 5, the shadow portions of the halftone dots were clogged, but this was not a practical problem.

On the other hand, in the printed matter of Comparative Examples 1 and 2, the shadow portions of the halftone dots were completely clogged, and the printed matter had no gradation reproducibility at all.

(F) Effects of the Invention According to the present invention, it is possible to provide an electrophotographic wet reversal developing method that is free from edge effects and can produce printed images with excellent gradation reproducibility. Furthermore, since the developing device is simple, maintainability is also good.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a situation in which electrophotographic wet reversal development of the present invention is performed. 1...Electrophotographic photoreceptor 2...Support 3...Photosensitive layer 4.4' 5 . . . 6 . . . 7.7"8.8' 9 . . . Power feeding piece Developing bias power supply Developing bias electrode Carrying roller vs. aperture roller vs. developer

Claims (1)

[Claims] 1. An electrophotographic wet reversal developing method, characterized in that in an electrophotographic wet reversal developing apparatus having a developing bias electrode, the developing bias electrode is substantially linear and development is performed while applying a bias voltage.