JPH0442267A - Electrophotographic reversal developing method by wet process - Google Patents

Abstract

PURPOSE:To improve maintainability by forming a developing device in a simple form with a small number of components by inclining the carrying direction of a photosensitive material against a horizontal direction, and forming a developer storage part with a carried photosensitive material and a squeezing roller clamped on the photosensitive material. CONSTITUTION:The carrying direction of the photosensitive material 1 is inclined against the horizontal direction, and also, the developer storage part 12 is formed with the carried photosensitive material 1 and the squeezing roller 6 clamped on the photosensitive material 1 at the upstream side of the carring direction of the photosensitive material 1. A developing bias electrode 8 is arranged at the developer storage part 8 so as to confront with the carried photosensitive material 1, and developing is performed as applying a bias voltage to the developing bias electrode 8. Thereby, the maintainability can be improved by simplifying a developing device part.

Description

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

(Prior art) An electrophotographic photoreceptor used as a printing plate is made by graining an aluminum plate and anodizing it, and using this as a support, a photoconductive material is dispersed or dissolved in a binder. Obtained by coating and drying a photosensitive solution.

The electrophotographic photoreceptor undergoes a charging process, an exposure process, a developing process,
Depending on the structure of the electrophotographic photoreceptor, it may be made into a printing plate through a fixing process, or may be used in Japanese Patent Publications Nos. 3717162 and 38
No.-7758, No. 46-39405, JP-A-52-2
No. 437, No. 57161863, No. 58-2854, No. 58-28760, No. 58-118658, No. 59-12452, No. 59-49555, No. 62-
No. 217256, No. 63-226668, JP-A-1-
As described in Japanese Patent No. 261659, etc., after the fixing step, the printing plate is produced through an elution step and a gum bowing step.

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 projection 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 light using, for example, a laser beam. In either method, there are positive exposure and negative exposure, and development also includes normal development and reversal development.

(Problems to be Solved by the Invention) It is generally believed that in reversal development in electrophotography, the edge effect is greater than in normal development.

To reduce the edge effect, it is effective to place the developing bias electrode plate close 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 it is not recommended to place it too close. I can't come. Further, if the gap between the developing bias electrode plate and the kite plate becomes small, it may cause transportation failure and sometimes damage to the surface of the electrophotographic photoreceptor. Therefore, the gap between the developing bias electrode plate and the electrophotographic photoreceptor is usually set to 1 to 5 mm. Further, the length of the developing bias electrode plate of the conventional electrophotographic wet type developing device is set to about 100 to 300 rrt m.

Another method for reducing the edge effect is to increase the bias voltage, but with this method, 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. When the developing bias voltage is set in this way, since the surface potential of the photoreceptor is higher than the developing bias voltage in the non-image area, 1 to 10 particles in the developer are developed on the developing bias plate, and the developed toner is The group generates a voltage. The sum of the voltage generated in this group of 1 henna and the developing bias voltage becomes a new developing bias voltage and is applied to the electrophotographic photoreceptor, which also prevents problems such as the negative areas of halftone dots being crushed and the image becoming thicker. arise.

Furthermore, if a large amount of 1-hener is electrodeposited on the developing bias electrode, the developing bias voltage will not be applied properly and image failure will occur. must expend a great deal of effort.

The present invention has been made in order to solve the problems of the prior art, and provides an electrophotographic wet reversal development method that can produce images with less edge effect and excellent gradation reproducibility. With the goal.

Another object of the present invention is to provide an electrophotographic wet reversal developing method that can simplify the developing device and improve maintenance.

(Means for Solving the Problems) The present invention is an electrophotographic wet reversal development method that uses a substantially linear developing bias electrode and performs development while applying a bias voltage to the developing bias electrode. , the conveyance direction of the photoconductor is tilted with respect to the horizontal direction, and the photoconductor being conveyed and the aperture roller that presses the photoconductor,
A developer storage section is formed on the upstream side of the aperture roller in the photoconductor transport direction, and the development bias electrode is arranged in the developer storage section so as to face the photoconductor being transported. It is characterized by performing development while applying a bias voltage.

It is desirable that the bias voltage is 80% or more of the photoreceptor surface potential.

(Function) By making the development bias electrode substantially linear and by increasing the transport speed of the photoreceptor, the development time per unit area of the photoreceptor can be shortened. Instead of shortening the development time per unit area, development is performed while applying a relatively high bias voltage to the development bias electrode. The photoreceptor on which the latent image has been recorded is conveyed at an angle with respect to the horizontal direction. When the photoconductor is conveyed to the position of the aperture roller, the photoconductor and the aperture roller form a developer storage section upstream of the photoconductor of the aperture roller. At the same time, development is performed while applying a bias voltage to the development bias electrode disposed in the developer 11'J reservoir.

(Example) Hereinafter, an example of the method of the present invention will be described with reference to the drawings.

As shown in FIG. 2, the electrophotographic photoreceptor 1 includes a support 2 and a photosensitive layer 3 formed on the surface of the support 2. As shown in FIG.

As mentioned above, an aluminum plate is made up of 1 inch of sand and anodized to form the support 2, and a photosensitive liquid in which a photoconductive material is dispersed or dissolved in a binder is used as the support. The electrophotographic photoreceptor 1 can be obtained by coating and drying the photoreceptor 2 to form the photosensitive layer 3.

FIG. 1 shows an example of a developing device used in the method of the present invention, in which squeezing rollers 6 and
7, and the electrophotographic photoreceptor 1 sandwiching the aperture rollers 6 and 7.
A bias voltage is applied to the power feeding pieces 4 and 5 disposed on the upstream and downstream sides of the photoconductor conveyance direction, the development bias electrode 8 disposed on the upstream side of the aperture roller 6 in the photoreceptor conveyance direction, and the development bias electrode 8. It has a bias voltage source 11 for.

As the material of the upper squeezing roller 6, rubber 11, plastic, etc. can be used. Further, as the material of the lower squeezing roller rough, rubber, plastic, metal, etc. can be used.

The rotation center axis 16 of the aperture roller 6 is slightly shifted downstream in the photoconductor conveyance direction from the rotation center axis 17 of the other aperture roller rough, so that the photoconductor 1 is conveyed tilted with respect to the horizontal direction. . More specifically, the conveyance direction”−
It is conveyed diagonally so that the upstream side is higher and the downstream side is lower. Furthermore, the power feeding pieces 4 and 5 are arranged at different heights from each other so that they can come into sliding contact with the photoreceptor 1 that is conveyed in an oblique direction. Although the angle of inclination of the photoreceptor 1 is not particularly limited, it is set within a range of approximately 5° to 80° in order to form an appropriate developer reservoir. Here, it was set to 30°.

In FIG. 1, when the photoreceptor 1 is conveyed from the right side toward the bottom left, the aperture roller pair 6 and 7 press the photoreceptor from above and below, and the photoreceptor 1 and the aperture roller 6, which are conveyed diagonally, almost An inverted triangular space is formed. Therefore, this space is used as a developer storage section 12, and this developer storage section 12 is filled with developer 13. The development bias electrode 8 is arranged within the developer storage section 12 filled with the developer 13.

Further, power feeding pieces 4 and 5 arranged in front and behind the aperture roller pair 6 and 7 are in sliding contact with the support 2 of the photoreceptor 1.

Each component of the developing section described above has a predetermined length in the direction perpendicular to the plane of the paper in FIG. 1, corresponding to the width of the photoreceptor. The developer 13 is supplied evenly in the length direction of the developer storage section 12, and the concentration of the developer 1-3 is constantly maintained by means such as overflowing from both ends of the developer storage section 12 in the length direction. Make sure it's even.

In the example, the projected area of the developing bias electrode 8 was 5 mm. This corresponds to less than one tenth of the width of the bias electrode used in the conventional electrophotographic wet reversal development method. However, the projected width of the developing bias electrode used in the electrophotographic wet reversal development method of the present invention may be 30 mm or less, preferably 20 mm or less. The material of the developing bias electrode 8 is not particularly limited as long as it is a good electrical conductor. For example, all metals can be used. The gap between the developing bias electrode 8 and the photoreceptor Wj3 of the photoreceptor 1 was set to 2 mm.

Developer 13 is a commercially available electrophotographic wet developer (Mitsubishi Paper Industries (Mitsubishi Paper Industries)
Co., Ltd. LOM, ED-Ill (1 to 1 positively charged particles are dispersed in an insulating solvent)
was used.

The aperture roller pair 6, 7 is driven to rotate in the direction of the arrow shown in FIG. 1, and the photoreceptor 1 is conveyed from the upper right to the lower left in the figure. In the example, the conveyance speed of the photoreceptor 1 was set at 5 m/m.
It was set as in. However, the conveyance speed of the photoreceptor 1 during development by the method of the present invention is 0.5 m/m 1. n~20m
/min is fine.

In this way, by narrowing the width of the developing bias electrode 8, the development time per unit area of the photoreceptor 1 is shortened, and the conveyance speed of the photoreceptor 1 during development is increased as a result.
Furthermore, the developing bias electrode 8 can be considered to be equivalent to a substantially linear photoreceptor whose width in the conveying direction is made very small.

A developing bias voltage is applied to the developing bias electrode 8 from a bias power supply 11 . In the example, the developing bias voltage was set to 400 V, which is considerably higher than the developing bias voltage in the conventional reversal developing method. However, the bias voltage used in the developing method of the present invention may be 80% or more of the surface potential of the electrophotographic photoreceptor 1, and preferably 100% or more. The bias voltage cannot be determined uniformly, but may be set depending on various conditions such as the amount of charge and polarity of the 1-ner, and the development speed.

A positive charge is applied to the photosensitive layer 3 of the photoreceptor by a corona charger (not shown) using a conventionally known method. In the example, the surface potential of the photoreceptor 1 was set to 300 .

Now, the photoreceptor 1 that has been positively charged as described above
on the surface of the negative film (Electronic Photography Society Test Char
No. 1-T 1975) were superimposed and contact image exposure was performed to form a calendar number on the surface of the photoreceptor 1. The photoreceptor 1 is transported to the developing device section shown in FIG. 1, the developer storage section 12 is filled with developer 13, and the aperture roller is The photoconductor 1 is
transport. While the photosensitive layer 3 of the photoreceptor 1 passes through the developer storage section 12, the developer 13 comes into contact with the photosensitive layer 3, and the bias power supply 11-development bias electrode 8-developer 13
- Photosensitive layer 3 - Support 2 - Power supply pieces 4, 5 - Bias power supply 1
A bias voltage is applied to the developing bias electrode 8 through the closed circuit consisting of 1, and wet reversal development is performed. The squeeze roller pair 6, 7 squeezes out excess developer 13 adhering to the photoreceptor 1.

The photoreceptor 1 developed in this manner is subjected to the next processing step. The developer 13 after passing through the photoreceptor 1 is collected in a tray (not shown), circulated by a pump, and used again for development.

As mentioned above, the conveyance speed of the photoreceptor 1 is fast, and the developer]-
3 has a short range of contact with the photoreceptor 1, and the developing bias electrode 8
Since the projected width in the photoreceptor transport direction is narrow and substantially linear, the development time per unit area of the photoreceptor 1 is considerably short.

On the other hand, the bias voltage applied to the developing bias electrode 8 is 4-00 V, which is 300 V of the surface potential of the photoreceptor 1.
, the toner particles in the developer 13 are electrophoresed and adhered to the image area of the surface of the photoreceptor 1 (where the charge is zero), resulting in the desired development. It can be performed.

Furthermore, since the developing time is shortened as described above, there is an advantage that toner does not stick to non-image areas and that no edge effect occurs. On the other hand, if the development time is shortened, the density of the solid area becomes insufficient, so the bias voltage is increased as described above to increase the density of the solid area.

The image obtained in this manner was good, free of edge effects. Furthermore, an image with good gradation reproducibility was obtained without any collapse of the shadow portion of the halftone dots.

Examples of the binder for the photosensitive layer of the electrophotographic photoreceptor used in the method of the present invention include styrene-maleic anhydride copolymer, styrene-maleic anhydride half ester copolymer, maleic acid copolymer, and vinyl acetate-croton. Examples include acid copolymers, acrylic resins having an acid value, and phenolic resins.

Examples of photoconductive materials for the photosensitive layer of the electrophotographic photoreceptor used in the method of the present invention include inorganic photoconductive materials such as zinc oxide, titanium oxide, and cadmium sulfide, and various organic photoconductive materials such as the following: can be used.

Aromatic tertiary amino compounds, such as 1-liphenylamine, diphenylbenzylamine, di(β-naphthyl)
Benzylamine, diphenylcyclohexylamine, etc.

Aromatic tertiary diamino compounds, such as N.

N.

N-dibenzylaminophenyl)ethane, 2゜2-bis(4-N,N-dibenzylaminophenyl)butane, 4
,4'-bis(di-P-1~lylamino)-1,1,1
-triphenylethane, etc.

Aromatic tertiary triamino compounds, such as 4°4', 4
″-1 helis(diethylaminophenyl)methane, 4-
Dimethylamino-4,4'-bis(diethylamino)-
2,2″-dimethyltriphenylmethane, etc.

Condensation products, such as condensation products of aldehydes and aromatic amines, reaction products of tertiary aromatic amines and aromatic halides, poly-p-phenylene-1,3,4-oxadiazole, formaldehyde and Reactants of 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 methyl Azobenzene-copper salt, etc.

Polyvinylcarbazole compounds, such as polyvinylcarbazole, halogen-substituted polyvinylcarbazole, vinylcarbazole and styrene copolymers, vinylanthracene-vinylcarbazole copolymers, and the like.

Heterocyclic compounds, such as 1,3.5-1-rifhenylpyrazoline, 1-phenyl-3-(p-dimethylaminostyryl)-5-(p-dimethylaminophenyl)pyrazoline, 1,5-diphenyl-3 -Styrylpyrazoline, 1
, 3-diphenyl-5-styrylpyrazoline, 1,3diphenyl-5-(p-dimethylaminophenyl)pyrazoline, 3-(4'-dimethylaminophenyl)-5
, 6-di(4″-methoxyphenyl)-1,2,4-triazine, 3-(4′-dimethylaminophenyl)-
5,6-dipyridyl-1,2,4-triazine, 2-phenyl 4-(4-'-dimethylaminophenyl)quinazoline, 6-hydroxy-2,3-di(P-methtriphenyl)pentufuran, and the like.

Phthalocyanine pigments, quinacridone pigments, indigo pigments, cyanine pigments, perylene pigments, bisbenzimidazole pigments, quinone pigments, azo pigments, etc.

The support for the electrophotographic photoreceptor used in the method of 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. However, polymer films such as polyester, cellulose acetate, polystyrene, and polycarbonate 1, polyamide, and polypropylene, as well as processed papers such as synthetic paper and resin-coated paper, can also be used. It is desirable to carry out treatment.

To produce an electrophotographic photoreceptor, one or a mixture of two or more of the above binders is dissolved in a solvent, but if the photoconductive material is not dissolved, a suitable dispersing machine such as a colloid mill, a ball mill, a homogenizer, A sensitizing dye or a chemical sensitizer is added if necessary, and the mixture is coated on the support to a thickness of 1 to 30 μm and dried.

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, cyclic ethers such as dioxane and tetrahydrofuran, Examples include esters such as ethyl acetate and butyl acetate, ketones such as acetate, methyl ethyl ketone, and methyl isobutyl ketone, dimethyl formamide, dimethyl sulfoxide, and halogenated hydrocarbons, but they are not suitable for solubility, cost, safety, etc. was selected in consideration of
There is no problem in using one type 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, ink-receptive, and have sufficient adhesion to the photosensitive layer to withstand printing, and must also have alkali and/or alcohol When a printing plate is prepared by eluating the non-image area using a method such as the above, it must have resistivity to the eluent.

A toner that satisfies these conditions is, for example, a rosin having a resistive property to an eluent, in which a colorant pigment or dye such as carbon black, cyanine blue, nigrosine, or oil dye is mixed in a highly insulating medium. , alkyd resin, acrylic resin, synthetic rubber, etc., using a ball mill, 71-Reiter homogenizer, etc., and then adding metal soap, amine, higher resin acid, etc. to the dispersed particles of the dispersion. There are toners to which a charge is stably applied and used for liquid development. In addition, special public service 53-540
No. 29, No. 57-12985, etc., a vinyl group that can be polymerized by a polymer reaction is introduced into the precursor polymer in advance, and monomers are polymerized in the presence of the vinyl group. There are products that are made into liquid developing agents by forming a polymer and coloring it with a dye.

Furthermore, JP-A-59-83174, JP-A No. 5917757
No. 2, No. 59-21-2850, No. 59-21.28
No. 51, No. 60-164757, No. 60-17975
No. 1, No. 60-185962, No. 60-185963
No. 60-252367, No. 61-116364, No. 61-116365, etc., the polymer is soluble in the highly insulating medium in the presence of the polymer. A resin dispersion obtained by polymerizing monomers that become insoluble when formed can be used as a liquid developing toner. Furthermore, JP-A-61-231266, JP-A-62
-231267, 62-232660, 63-
Liquids 1 to 3 described in Japanese Patent No. 178258, No. 631, No. 79368, etc. can be suitably used.

(Effects of the Invention) According to the present invention, the development bias electrode is made substantially linear to shorten the development time per unit area of the photoreceptor, and the bias voltage applied to the development bias electrode is adjusted to the surface potential of the photoreceptor. Since the ratio is set as high as 80% or more, it is possible to provide an electrophotographic wet reversal developing method that is free from edge effects and has excellent gradation reproducibility.

In addition, the conveyance direction of the photoconductor is tilted with respect to the horizontal direction, and the developer storage section is formed by the photoconductor being conveyed and the aperture roller that presses against the photoconductor, so the member forming the developer storage section is There is no need to add a special component, and the developing device for carrying out the method of the present invention can be formed in a simple form with a small number of parts. Therefore, it is possible to provide an electrophotographic wet reversal developing method with good maintainability.

Furthermore, since no member comes into contact with the calendar surface of the photoreceptor until development is completed, there is no problem of damaging the calendar surface.

[Brief explanation of drawings]

FIG. 1 is a side view schematically showing an example of a developing device section for implementing the method of the present invention, and FIG. 2 is a side view showing an example of a photoreceptor to which the method of the present invention is applied.

Claims (1)

[Claims] 1. An electrophotographic wet reversal development method in which development is performed while applying a bias voltage to the development bias electrode using a substantially linear development bias electrode, the method comprising: The direction is tilted with respect to the horizontal direction, and a developer storage section is formed by the conveyed photoconductor and a squeeze roller that presses against the photoconductor, on the upstream side of the squeeze roller in the photoconductor conveyance direction, and the developing bias is An electrophotographic wet reversal developing method characterized in that an electrode is disposed in the developer storage section so as to face the photoconductor being transported, and development is performed while applying a bias voltage to the development bias electrode. 2. The electrophotographic wet reversal developing method according to claim 1, wherein the bias voltage is 80% or more of the photoreceptor surface potential.