JP2012128090A - Wet image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet image forming apparatus and wet image forming method, which make it possible to efficiently perform cleaning even in a case of using a liquid developer in which resin is dissolved in a carrier liquid.SOLUTION: In the wet image forming apparatus that develops an electrostatic latent image on the surface of a photoreceptor drum by using a liquid developer, the liquid developer contains at least pigment, resin, and non-volatile carrier liquids of two or more types. Of the carrier liquids of the two or more types, at least the carrier liquid of the one type is different from the carrier liquid of the other types in solubility. The resin is present in the carrier liquid by being dissolved in it. The wet image forming apparatus comprises: means for supplying carrier liquid having the resin whose solubility is highest among the carrier liquids of the two or more types to a residual liquid developer on a developer carrier after development; recovering means for recovering the residual liquid developer after that; and means for supplying remaining carrier liquid after the recovery.

Description

  The present invention belongs to the technical field of a wet developing method which is one of electrophotographic systems that can be employed in a printer, a copying machine, a facsimile machine, or a multifunction machine having these functions.

  In general, a developing method used in an electrophotographic method in which an electrostatic latent image is visualized with charged colored particles is roughly classified into a dry developing method and a wet developing method depending on the form of the developer. Among them, in the wet development method, a liquid developer in which colored particles are dispersed in an electrically insulating carrier liquid is used. The colored particles charged in the liquid developer move from the surface of the developing roller to the surface of the photosensitive drum by the principle of electrophoresis, and the electrostatic latent image on the surface of the photosensitive drum is converted into a toner image (visualized image). The obtained toner image is transferred from the photosensitive drum to a recording medium. The liquid developer has almost no possibility that the colored particles are scattered in the atmosphere, so for example, fine colored particles with an average particle diameter of submicron can be used, and high-quality images with high resolution and excellent gradation. Is obtained.

  Further, conventionally, in a wet image developing apparatus, a liquid developer measured in a predetermined amount is transferred onto a developing roller as a thin layer having a uniform thickness using a supply roller having a fine concave portion on a peripheral surface and a doctor blade. Technology is known. The thin layer of the liquid developer transferred onto the developing roller is subjected to a compaction treatment (developer component in the thin layer) by a charger disposed in the vicinity of the developing roller for the purpose of improving the developing performance on the image carrier. Is developed to the electrostatic latent image on the image carrier. However, since the developing efficiency from the developing roller to the image carrier is not 100%, the developer that has not been developed on the image carrier remains on the developing roller. In a developing roller with such residual developer (residual toner) attached, it is extremely difficult to form a liquid developer layer having a uniform thickness on the peripheral surface, so that the development performance to the image carrier is low. When the peripheral surface of the developing roller is used for the next developing process on the image bearing member, various inconveniences such as dirt are generated on the transfer image on the paper. For this reason, it is necessary to remove (clean) the residual developer from the developing roller.

  As a cleaning method that has been reported so far, in order to clean the residual liquid developer adhering to a developing device or the like, predetermined one or two locations where the liquid developer contacts with the carrier liquid of the liquid developer as the cleaning liquid are used. There is a technology for improving the cleaning property by reducing the viscosity of the residual developer (Patent Document 1).

  On the other hand, when a liquid developer in which a resin is dissolved in a carrier liquid is used in a wet image forming apparatus, there is an advantage that fixing can be performed by non-heating or low-temperature heating. However, when such a liquid developer is used, the liquid developer on the developing roller after development strongly adheres to the developing roller due to charging, but the adhesion force becomes strong because the resin is dissolved, There is a problem that cleaning becomes difficult as compared with general liquid developers.

JP 2000-10446 A

  However, in the above conventional cleaning technique, sufficient cleaning performance cannot be ensured when using a liquid developer that can be fixed by non-heating or low-temperature heating as described above. There was a need for an effective cleaning method. Further, when such a liquid developer is used, it is necessary to improve the recovery rate and transportability in order to use the recovered liquid as a regenerated liquid developer. It is also necessary to suppress the precipitation of the resin due to an increase in the resin concentration in the recovered liquid.

  Therefore, the present invention provides a wet image forming apparatus that can efficiently perform cleaning even when a liquid developer in which a resin is dissolved in a carrier liquid is used, and is excellent in transportability of the liquid developer. It is an object to provide a wet image forming method.

  As a result of intensive studies in view of the above problems, the present inventors have made a liquid developer contain a pigment, a resin, and a carrier liquid in which the solubility of two or more kinds of resins is different, and further a highly soluble carrier liquid. Focusing on the fact that excellent cleaning performance can be achieved even when using a liquid developer containing a resin by supplying to the residual liquid developer on the developer carrying member, the present invention has been completed through further research.

  That is, one aspect of the present invention for solving the above problem is a wet image forming apparatus that develops an electrostatic latent image on the surface of a photosensitive drum using a liquid developer, wherein the liquid developer includes at least a pigment. A resin and two or more types of non-volatile carrier liquids, and at least one of the two or more types of carrier liquids is different in solubility of the resin from other carrier liquids. It is a liquid developer that is dissolved in a carrier liquid, and the solubility of the resin among the two or more kinds of carrier liquids with respect to the residual liquid developer on the developer carrier after development. A wet image forming apparatus comprising: a means for supplying the highest carrier liquid; a recovery means for recovering the residual liquid developer; and a means for supplying the remaining carrier liquid after recovery.

  With such a configuration, since a resin is contained, cleaning can be efficiently performed even when a liquid developer that adheres to the developing roller more strongly than a general liquid developer by being charged. That is, by using only a carrier liquid having a higher resin solubility than a mixture of all the carrier liquids among the carrier liquids, the resin dissolution rate is increased and the cleaning failure such as slipping in the cleaning portion is suppressed. be able to.

  The recovered liquid developer is used as a regenerated liquid developer. According to the above configuration, the recoverability and transportability at that time are also improved.

  Usually, when the resin is deposited at the time of recovery, the resin may not be redissolved even if a liquid mixture of two or more kinds of carrier liquids is added and mixed from the beginning. In that case, the recovered liquid cannot be used as a regenerated liquid developer and must be discarded. In the image forming apparatus according to the present invention, since the highly soluble carrier liquid is added first, the resin can be surely dissolved, and the precipitation of the resin due to the increase in the resin concentration in the recovered liquid can be prevented. Therefore, it is not necessary to discard the recovered liquid, and the recoverability is improved.

  On the other hand, when clogging of the developer occurs in the conveyance path using the liquid developer in which the resin is dissolved, the liquid overflows and the inside of the apparatus is soiled, causing an adverse effect on the image. On the other hand, when a carrier liquid in which the resin dissolves satisfactorily is added, the viscosity of the liquid is lowered and the resin does not precipitate, so that the clogging of the developer in the transport path as described above can be suppressed. That is, the transportability of the recovered liquid is improved.

  Further, when a regenerated liquid developer is produced, it usually takes a considerable time to uniformly dissolve the resin. However, by using the wet image forming apparatus, the stirring time or strength of stirring is increased. (Such as the number of revolutions) can be reduced.

  In the wet image forming apparatus, it is preferable that the collecting unit is a cleaning blade type. Thereby, the cleaning property can be further improved. Furthermore, if resin deposition occurs on the cleaning blade, this also leads to poor cleaning, so the blade may need to be replaced. Therefore, if the precipitation of the resin can be suppressed, there is an advantage that the durability of the blade is also increased.

  The resin contained in the liquid developer used in the wet image forming apparatus is more preferably at least one selected from cyclic olefin copolymers, styrene elastomers, cellulose ethers, and polyvinyl butyral. By using such a resin, non-heating or low-temperature fixing can be performed more reliably.

  Further, it is preferable that the wet image forming apparatus has means for adjusting the concentration by measuring the concentrations of the pigment, carrier liquid and resin in the collected liquid developer. Thereby, the recovered liquid can be more efficiently prepared as a regenerated liquid developer.

  According to the wet image forming apparatus and the wet image forming method of the present invention, it is possible to efficiently perform cleaning when a liquid developer in which a resin is dissolved is used, and to obtain a high-quality image.

FIG. 2 is a schematic configuration diagram showing a circulation system of a liquid developer. FIG. 2 is a schematic configuration diagram of a periphery of a liquid developing device provided in the wet image forming apparatus. 1 is a schematic configuration diagram of a wet image forming apparatus. 1 is a schematic cross-sectional view of a wet image forming apparatus excluding a liquid developer circulating device.

<Liquid developer>
First, a liquid developer that can be used in the image forming apparatus according to the present embodiment will be described.

  The liquid developer used in this embodiment has at least a pigment, a resin, and two or more types of nonvolatile carrier liquids as a basic configuration. The resin is present dissolved in the liquid developer, and at least one of the two or more carrier liquids has a different resin solubility from that of the other carrier liquids.

[Pigment]
In the present embodiment, the pigment itself is used as the colored particles. By using the liquid developer according to the present invention, the pigment itself can be included in the liquid developer, so that it is not necessary to go through a heat fixing step as in the case of using a toner containing a binder resin in image formation. It is. That is, since the pigment as the colored particles can be fixed on the recording medium without consuming heat energy or light energy, energy consumption in the wet image forming apparatus can be reduced.

  As a pigment in this embodiment, a conventionally well-known organic pigment and an inorganic pigment can be used, for example, without specifically limiting.

  Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, Tartrazine Lake, etc. It is done. Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK and the like. Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B, and the like. . Examples of purple pigments include Fast Violet B and Methyl Violet Lake. Examples of blue pigments include C.I. I. Pigment Blue 15: 3, cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partial chlorinated product, first sky blue, indanthrene blue BC, and the like. Examples of the green pigment include chrome green, chromium oxide, pigment green B, and malachite green lake.

  The content of the pigment in the liquid developer is preferably 1 to 30% by mass. More preferably, it is 3 mass% or more, More preferably, it is 5 mass% or more. Moreover, More preferably, it is 20 mass% or less, More preferably, it is 10 mass% or less.

[resin]
As the resin that can be used in the liquid developer according to the present embodiment, it can exist stably for a long time in a state dissolved in a carrier liquid, and on the surface of the recording medium after the image is transferred to the recording medium. When the concentration of the resin in the carrier liquid increases and exceeds the saturated dissolution amount, the resin can be used without particular limitation on the condition that the resin stays on the surface of the recording medium and can form a film.

  Note that “recording medium” means any recording medium capable of forming an image, such as high-quality plain paper, print-only paper, copy paper, tracing paper, cardboard, and OHP sheet. In the following description, the term “sheet” may be used simply to indicate those recording media.

  Specific examples include cyclic olefin copolymers, styrene elastomers, cellulose ethers, polyvinyl butyral, and the like. These can be used alone or in combination of two or more.

  In the liquid developer according to this embodiment, the resin exists in a state dissolved in the carrier liquid. The state in which the resin is dissolved in the carrier liquid includes a gel state. Depending on the type and molecular weight of the resin, the resin may be entangled with each other in the carrier liquid, resulting in a gel state with relatively low fluidity. For example, when the concentration of the resin is high, when the affinity between the resin and the carrier liquid is low, or when the temperature is low, a gel state is often obtained. On the other hand, when there is little mutual entanglement of the resin in the carrier liquid and the fluidity is relatively high, it becomes a solution state.

  In this embodiment, since all or most of the resin must be dissolved in the carrier liquid, it is not possible to use a resin that does not dissolve in the carrier liquid (or a carrier liquid that cannot dissolve the resin). Cannot be used). When the resin is present as particles in the carrier liquid, the particles are present only in the image area and are transferred together with the pigment or the like onto the recording medium. Since the non-volatile carrier liquid penetrates into the inside of the recording medium, at least pigments and particles other than the carrier liquid remain on the surface of the recording medium. However, if resin particles are deposited and remain, the particles are not sufficiently fixed. By rubbing, it is detached from the recording medium together with the pigment, and the image is disturbed. However, when the resin is sufficiently dissolved and present in the carrier liquid, when the carrier liquid penetrates into the inside of the recording medium, the resin is entangled and deposited, covering the pigment surface. It is firmly fixed and a high quality image can be obtained.

  The content of the resin in the liquid developer varies depending on the type of resin, but is preferably 1 to 10% by mass, for example. More preferably, it is 2-7 mass%, More preferably, it is 3.5-5 mass%.

  If the resin content is less than 1% by mass, the amount of the resin film remaining on the surface of the recording medium becomes too small, and there is a possibility that the film forming property and thus the fixing property will be excessively insufficient. On the other hand, if the resin content exceeds 10% by mass, the amount of the resin film remaining on the surface of the recording medium becomes excessive, the drying property of the film is excessively lowered, and the adhesiveness (tackiness) of the film is excessive. And the scratch resistance of the image may be excessively lowered. In addition, developability may be insufficient, image density may be low, and fog may increase.

Hereinafter, the resins that can be used in the present embodiment will be described more specifically.
(Cyclic olefin copolymer)
The cyclic olefin copolymer is a non-crystalline thermoplastic olefin resin that has a cyclic olefin skeleton in the main chain, does not contain environmentally hazardous substances, and has excellent transparency, light weight, low water absorption, etc. Is. More specifically, in the present embodiment, the cyclic olefin copolymer is a polymer compound in which the main chain is composed of carbon-carbon bonds and has a cyclic hydrocarbon structure in at least a part of the main chain. This cyclic hydrocarbon structure is introduced by using a compound (cyclic olefin) having at least one olefinic double bond in the cyclic hydrocarbon structure as represented by norbornene or tetracyclododecene as a monomer. Is done.

  As the cyclic olefin copolymer that can be used in the present embodiment, the cyclic olefin copolymer can be stably present for a long time in a state in which it is dissolved in a carrier liquid, and after the image is transferred to the sheet, On the condition that the concentration of the cyclic olefin copolymer in the carrier liquid on the surface of the substrate exceeds the saturation dissolution amount, the cyclic olefin copolymer stays on the surface of the sheet and can form a film. For example, (1) addition (co) polymer of cyclic olefin or hydrogenated product thereof, (2) addition copolymer of cyclic olefin and α-olefin or hydrogenated product thereof, (3) ring opening of cyclic olefin ( Co) polymer or hydrogenated product thereof.

As a specific example of the cyclic olefin,
(A) cyclopentene, cyclohexene, cyclooctene;
(B) a monocyclic olefin such as cyclopentadiene and 1,3-cyclohexadiene;
(C) Bicyclo [2.2.1] hept-2-ene (norbornene), 5-methyl-bicyclo [2.2.1] hept-2-ene, 5,5-dimethyl-bicyclo [2.2. 1] Hept-2-ene, 5-ethyl-bicyclo [2.2.1] hept-2-ene, 5-butyl-bicyclo [2.2.1] hept-2-ene, 5-ethylidene-bicyclo [ 2.2.1] hept-2-ene, 5-hexyl-bicyclo [2.2.1] hept-2-ene, 5-octyl-bicyclo [2.2.1] hept-2-ene, 5- Octadecyl-bicyclo [2.2.1] hept-2-ene, 5-methylidene-bicyclo [2.2.1] hept-2-ene, 5-vinyl-bicyclo [2.2.1] hept-2-ene 2 such as ene, 5-propenyl-bicyclo [2.2.1] hept-2-ene Cyclic olefins;
(D) tricyclo [4.3.0.12,5] deca-3,7-diene (dicyclopentadiene), tricyclo [4.3.0.12,5] dec-3-ene;
(E) Tricyclo [4.4.0.12,5] undeca-3,7-diene or tricyclo [4.4.0.12,5] undeca-3,8-diene or a partially hydrogenated product thereof ( Or an adduct of cyclopentadiene and cyclohexene), which is tricyclo [4.4.0.12,5] undec-3-ene;
(F) 5-cyclopentyl-bicyclo [2.2.1] hept-2-ene, 5-cyclohexyl-bicyclo [2.2.1] hept-2-ene, 5-cyclohexenylbicyclo [2.2.1] ] 3 ring cyclic olefins such as hepta-2-ene, 5-phenyl-bicyclo [2.2.1] hept-2-ene;
(G) Tetracyclo [4.4.0.12,5.17,10] dodec-3-ene (tetracyclododecene), 8-methyltetracyclo [4.4.0.12,5.17,10 ] Dodec-3-ene, 8-ethyltetracyclo [4.4.0.12, 5.17,10] dodec-3-ene, 8-methylidenetetracyclo [4.4.0.12,5. 17,10] dodec-3-ene, 8-ethylidenetetracyclo [4.4.0.12,5.17,10] dodec-3-ene, 8-vinyltetracyclo [4,4.0.12. 5.17,10] dodec-3-ene, 4-propenyl-tetracyclo [4.4.0.12, 5.17,10] dodeca-3-ene and the like cyclic olefins;
(H) 8-cyclopentyl-tetracyclo [4.4.0.12,5.17,10] dodec-3-ene, 8-cyclohexyl-tetracyclo [4.4.0.12,5.17,10] dodeca -3-ene, 8-cyclohexenyl-tetracyclo [4.4.0.12, 5.17,10] dodec-3-ene, 8-phenyl-cyclopentyl-tetracyclo [4.4.0.12,5. 17,10] dodec-3-ene;
(I) Tetracyclo [7.4.13,6.01,9.02,7] tetradeca-4,9,11,13-tetraene (1,4-methano-1,4,4a, 9a-tetrahydrofluorene) , Tetracyclo [8.4.14, 7.01, 10.03,8] pentadeca-5,10,12,14-tetraene (to 1,4-methano-1,4,4a, 5,10,10a-) Oxahydroanthracene);
(J) pentacyclo [6.6.1.13,6.02,7.09,14] -4-hexadecene, pentacyclo [6.5.1.13,6.02,7.09,13] -4 -Pentadecene, pentacyclo [7.4.0.02, 7.13, 6.110, 13] -4-pentadecene; heptacyclo [8.7.0.12, 9.14, 7.111, 17.03, 8.012,16] -5-eicosene, heptacyclo [8.7.0.12,9.03,8.14,7.012,17.113, l6] -14-eicosene;
(K) polycyclic cyclic olefins such as a tetramer of cyclopentadiene; and the like. These cyclic olefins can be used alone or in combination of two or more.

  The α-olefin is preferably an α-olefin having 2 to 20 carbon atoms, preferably 2 to 8 carbon atoms. Specific examples thereof include ethylene, propylene, 1-butene, 1-pentene and 1-hexene. 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1- Hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1 -Octadecene, 1-eicosene and the like. These α-olefins can be used alone or in combination of two or more.

  In the present embodiment, there are no particular restrictions on the polymerization method of cyclic olefin, the polymerization method of cyclic olefin and α-olefin, and the hydrogenation method of the obtained polymer, and can be carried out according to known methods. .

  In the present embodiment, the structure of the cyclic olefin copolymer is not particularly limited, and may be a chain, branched, or crosslinked, but is preferably a straight chain.

  In the present embodiment, as the cyclic olefin copolymer, for example, a copolymer of norbornene and ethylene or a copolymer of tetracyclododecene and ethylene can be preferably used. A copolymer is more preferred. In this case, the norbornene content in the copolymer is preferably 60 to 82% by mass, more preferably 60 to 79% by mass, still more preferably 60 to 76% by mass, and still more preferably 60 to 65% by mass. When the norbornene content is less than 60% by mass, the glass transition temperature of the cyclic olefin copolymer film becomes too low, and the film-forming property of the cyclic olefin copolymer film may be lowered. When the norbornene content exceeds 82% by mass, the glass transition temperature of the cyclic olefin copolymer coating film becomes too high, and the fixability of the pigment, that is, the image by the cyclic olefin copolymer coating film may be lowered. Further, the solubility of the cyclic olefin copolymer in the carrier liquid may be excessively lowered.

  In this embodiment, what is marketed can be used as a cyclic olefin copolymer. For example, as a copolymer of norbornene and ethylene, "TOPAS (registered trademark) TM" (norbornene content: about 60% by mass) and "TOPAS (registered trademark) TB" manufactured by Topas Advanced Polymers GmbH (Norbornene content: about 60 mass%), “TOPAS (registered trademark) 8007” (norbornene content: about 65 mass%), “TOPAS (registered trademark) 5013” (norbornene content: about 76 mass%), “ "TOPAS (registered trademark) 6013" (norbornene content: about 76 mass%), "TOPAS (registered trademark) 6015" (norbornene content: about 79 mass%), "TOPAS (registered trademark) 6017" (norbornene content: About 82% by mass). These may be used alone or in combination of two or more depending on the situation.

(Styrene elastomer)
As the styrene-based elastomer that can be used in the present embodiment, conventionally known styrene elastomers can be used without particular limitation. Specific examples thereof include a block copolymer composed of an aromatic vinyl compound and an olefin compound or a conjugated diene compound. As the block copolymer, for example, when A is a polymer block composed of an aromatic vinyl compound and B is a polymer block composed of an olefin compound or a conjugated diene compound, the structure represented by Formula 1 is used. Examples thereof include a block copolymer.

  Examples of the aromatic vinyl compound constituting the block copolymer include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,3-dimethylstyrene, 2,4- Dimethylstyrene, monochlorostyrene, dichlorostyrene, p-bromostyrene, 2,4,5-tribromostyrene, 2,4,6-tribromostyrene, o-tert-butylstyrene, m-tert-butylstyrene, p- Examples thereof include tert-butyl styrene, ethyl styrene, vinyl naphthalene and vinyl anthracene.

  The polymer block A may be comprised from 1 type in the said aromatic vinyl compound, and may be comprised from 2 or more types. Among these, those composed of styrene and / or α-methylstyrene give preferable physical properties to the liquid developer according to this embodiment.

  Examples of the olefin compound constituting the block copolymer include ethylene, propylene, 1-butene, 2-butene, isobutene, 1-pentene, 2-pentene, cyclopentene, 1-hexene, 2-hexene, cyclohexene, Examples include 1-heptene, 2-heptene, cycloheptene, 1-octene, 2-octene, cyclooctene, vinylcyclopentene, vinylcyclohexene, vinylcycloheptene, and vinylcyclooctene.

  Examples of the conjugated diene compound constituting the block copolymer include butadiene, isoprene, chloroprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like.

  The polymer block B may be comprised from 1 type of the said olefin type compound and the said conjugated diene compound, and may be comprised from 2 or more types. Among these, those composed of butadiene and / or isoprene give preferable properties to the liquid developer according to the present embodiment.

  Preferable specific examples of the block copolymer include, for example, polystyrene-polybutadiene-polystyrene triblock copolymer or a hydrogenated product thereof, polystyrene-polyisoprene-polystyrene triblock copolymer or a hydrogenated product thereof, polystyrene-poly (Isoprene / butadiene) -polystyrene triblock copolymer or hydrogenated product thereof, poly (α-methylstyrene) -polybutadiene-poly (α-methylstyrene) triblock copolymer or hydrogenated product thereof, poly (α- Methylstyrene) -polyisoprene-poly (α-methylstyrene) triblock copolymer or hydrogenated product thereof, poly (α-methylstyrene) -poly (isoprene / butadiene) -poly (α-methylstyrene) triblock copolymer Polymer or its hydrogenated product, polystyrene Down - polyisobutene - polystyrene triblock copolymer, poly (alpha-methylstyrene) - polyisobutene - poly (alpha-methylstyrene) triblock copolymer.

  Moreover, as a styrene-type elastomer which can be used by this embodiment, the styrene-butadiene-type elastomer (SBS) in which the polymer block A and the polymer block B have a structure represented by Formula 2 is preferable.

  The styrene-butadiene elastomer can be obtained by copolymerizing a styrene monomer and butadiene which is a conjugated diene compound. Preferred styrene monomers include styrene, α-methyl styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-dodecyl. Styrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene and the like can be mentioned.

  In the molecular weight distribution by GPC (gel permeation chromatography), the styrene-butadiene-based elastomer preferably has a number average molecular weight Mn in the range of 1,000 to 100,000 (see Formula 1), more preferably. , 2,000 to 50,000. The weight average molecular weight Mw is preferably in the range of 5,000 to 1,000,000, more preferably in the range of 10,000 to 500,000. In that case, it is preferable that the weight average molecular weight Mw is in the range of 2,000 to 200,000, and preferably at least one peak is in the range of 3,000 to 150,000.

  In the styrene-butadiene elastomer, the value of the ratio (weight average molecular weight Mw / number average molecular weight Mn) is preferably 3.0 or less, and more preferably 2.0 or less.

  The styrene content (content of the polymer block A) in the styrene-butadiene elastomer is preferably in the range of 5 to 75% by mass (see Formula 2), more preferably 10 to 65% by mass. Within range. When the styrene content is less than 5% by mass, the glass transition temperature of the styrene-based elastomer film becomes too low, and the film-forming property of the styrene-based elastomer film tends to decrease. When the styrene content exceeds 75% by mass, the softening point of the styrene elastomer film becomes too high, and the fixability of the pigment, that is, the image by the styrene elastomer film tends to be lowered.

  In the present embodiment, commercially available styrene elastomers can be used. For example, as a styrene-conjugated diene block copolymer, Kuraray's “Septon” S1001, S2063, S4055, S8007 and “Hibler” 5127, 7311, Shell's “Clayton”, Asahi Kasei Chemicals' “Asuprene ( Registered trademark) "T411, T413, T437," Tufprene (registered trademark) "A, 315P, etc.," JSR TR1086 "," JSR TR2000 "," JSR TR2250 "," JSR TR2827 ", etc. manufactured by JSR; styrene-conjugated As a hydrogenated diene block copolymer, “Dynalon” 6200P, 4600P, 1320P manufactured by JSR, etc .; As a styrene-ethylene copolymer, “Index” manufactured by Dow Chemical Co., etc .; Aron Kasei as a composition "Aron AR" made by the company, three Chemical Co., Ltd. of "Rabalon", and the like. These may be used alone or in combination of two or more depending on the situation. “Septon” S1001, S2063, S4055, S8007 and “Hibler” 5127, 7311 manufactured by Kuraray are hydrogenated products of styrene-conjugated diene block copolymers.

(Cellulose ether)
Cellulose ether is a polymer in which a hydroxyl group in a cellulose molecule is substituted with an alkoxy group. The substitution rate is preferably 45 to 49.5%. Moreover, the alkyl part of the alkoxy group may be substituted with, for example, a hydroxyl group. A cellulose ether film is excellent in toughness, thermal stability, and the like.

  As the cellulose ether that can be used in the present embodiment, the cellulose ether can exist stably for a long time in a state dissolved in the carrier liquid, and the carrier liquid on the surface of the sheet after transferring the image to the sheet. When the concentration of cellulose ether in the solution increases and exceeds the saturated dissolution amount, the cellulose ether remains on the surface of the sheet and can form a film, for example, alkylcellulose such as methylcellulose and ethylcellulose; hydroxyethylcellulose Hydroxyalkyl celluloses such as hydroxypropylcellulose; hydroxyalkylalkylcelluloses such as hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, hydroxyethylethylcellulose; cals such as carboxymethylcellulose Carboxyalkyl cellulose; carboxyalkyl carboxyalkyl hydroxyalkyl cellulose such as methyl hydroxyethyl cellulose; and the like. These may be used alone or in combination of two or more depending on the situation. Among these, alkyl cellulose is preferable, and among the alkyl celluloses, ethyl cellulose is preferable.

  In this embodiment, what is marketed can be used as a cellulose ether. Examples of the ethyl cellulose include “Etocel (registered trademark) STD4”, “Etocel (registered trademark) STD7”, “Etocel (registered trademark) STD10”, etc., manufactured by Nisshinsei. These may be used alone or in combination of two or more depending on the situation.

(Polyvinyl butyral)
The polyvinyl butyral (butyral resin: alkyl acetalized polyvinyl alcohol) that can be used in this embodiment has a hydroxyl group, a hydrophilic vinyl alcohol unit, a butyral group, and a hydrophobic vinyl as shown in Formula 3. It is a copolymer of an acetal unit and a vinyl acetate unit having an acetyl group and having intermediate properties between a vinyl alcohol unit and a vinyl acetal unit. In the liquid developer according to the exemplary embodiment, polyvinyl butyral having a degree of butyralization (determining a ratio between a hydrophilic part and a hydrophobic part) having a film forming ability (film forming property) of 60 to 85 mol% is excellent. Is preferable. Polyvinyl butyral has a vinyl acetal unit that is soluble in a nonpolar solvent and a vinyl alcohol unit that improves binding properties to a recording medium such as paper. And high affinity.

  It does not specifically limit as polyvinyl butyral which can be used by this embodiment. For example, “Mowital (registered trademark)” B20H, B30B, B30H, B60T, B60H, B60HH, B70H manufactured by Hoechst Co., Ltd .; “ESREC (registered trademark)” BL-1 (butyralization degree: 63 ±) manufactured by Sekisui Chemical Co., Ltd. 3 mol%), BL-2 (same: 63 ± 3 mol%), BL-S (same: 70 mol% or more), BL-L, BH-3 (same: 65 ± 3 mol%), BM-1 (same: 65 ± 3 mol%), BM-2 (same: 68 ± 3 mol%), BM-5 (same: 63 ± 3 mol%), BM-S; “Denkabutyral” # 2000-L, # 3000 manufactured by Denki Kagaku Kogyo Co., Ltd. -1, # 3000-2, # 3000-3, # 3000-4, # 3000-K, # 4000-1, # 5000-A, # 6000-C, and the like. These may be used alone or in combination of two or more.

[Carrier liquid]
In general, an electrically insulating carrier liquid plays the role of a liquid carrier and is used for the purpose of enhancing the electrical insulating properties of the obtained liquid developer. As the carrier liquid according to this embodiment, a resin described later is dissolved. At least one kind that can be made to be used (one having a relatively high resin solubility) is used.

  The liquid developer according to the exemplary embodiment includes at least two types of carrier liquids, and at least one type of the carrier liquid is different from the other resins in the above-described resin solubility. That is, in this embodiment, as the carrier liquid, a solution having a relatively high solubility of at least one resin (resin good solvent) and a resin having a relatively low solubility (resin poor solvent) are mixed. Use.

Further, in addition to the above physical properties, for example, an electrically insulating organic solvent having a volume resistance at 25 ° C. of 10 ¹² Ω · cm or more (in other words, conductivity of 1.0 pS / cm or less) is preferable.

  As a combination of two or more kinds of carrier liquids, for example, when two kinds of carrier liquids are used, vegetable oil or the like is used as a good solvent for resins, and aliphatic hydrocarbons that are liquid at room temperature as a poor solvent for resins. Can be.

  As the aliphatic hydrocarbon, for example, liquid n-paraffin hydrocarbon, iso-paraffin hydrocarbon, halogenated aliphatic hydrocarbon, aliphatic hydrocarbon having a branched chain, or a mixture thereof is preferable. More specifically, n-hexane, n-heptane, n-octane, nonane, decane, dodecane, hexadecane, heptadecane, cyclohexane, perchloroethylene, trichloroethane and the like can be used. From the viewpoint of environmental measures (measures against VOC), non-volatile organic solvents and organic solvents with relatively low volatility (for example, those having a boiling point of 200 ° C. or higher) are preferable. For example, aliphatics having 16 or more carbon atoms Liquid paraffin or the like containing a relatively large amount of hydrocarbon can be preferably used.

  Specific examples of vegetable oils include tall oil fatty acids (main components: oleic acid, linoleic acid), fatty acid esters derived from vegetable oils, soybean oil, safflower oil, castor oil, linseed oil, tung oil, and the like. Among them, tall oil fatty acid and the like can be preferably used.

  As the carrier liquid, commercially available ones may be used. For example, liquid paraffin “Moresco White P-55”, “Moresco White P-40”, “Moresco White P-70” manufactured by Matsumura Oil Research Co., Ltd. "Molesco White P-200"; tall oil fatty acids "Hartol FA-1", "Hartol FA-1P", "Hartol FA-3" manufactured by Harima Chemicals Co., Ltd .; vegetable oil-based solvent manufactured by Kaneda Corporation " Vegisol MT, Vegisol CM, Vegisol MB, Vegisol PR, vegetable oil “Tung Oil”; “Isopar G”, “Isopar H”, “Isopar K”, “Isopar L”, “Isopar” manufactured by ExxonMobil M ”,“ Isopar V ”; liquid paraffin“ Cosmo White P-60 ”,“ Cosmo White P-70 ”manufactured by Cosmo Oil Co., Ltd. “Cosmo White P-120”; vegetable oil “soybean oil white squeezed oil S”, “linseed oil”, “saflower oil” manufactured by Nisshin Oilio Co., Ltd .; vegetable oil “castor oil LAV”, “castor oil manufactured by ITO EN And the like can be preferably used.

  The liquid developer according to the present embodiment includes two or more types of carrier liquids, but care must be taken so that the conductivity of the entire carrier liquid and the conductivity of the liquid developer do not become excessively high depending on the type of carrier liquid used. For example, tall oil fatty acids, vegetable oils, and the like generally have higher electrical conductivity than aliphatic hydrocarbons such as liquid paraffin. Therefore, in order to dissolve the resin satisfactorily in the carrier liquid, it is necessary to pay attention to the content when the oil is included as the carrier liquid.

  The greater the content of the oil in the entire carrier liquid, the more advantageous in terms of the solubility of the resin, but the disadvantage in terms of conductivity. On the other hand, the smaller the content of the oil in the entire carrier liquid, the more advantageous in terms of conductivity, but the disadvantage in terms of the solubility of the resin.

  As mentioned above, although content of the said oil in the whole carrier liquid is dependent on the kind, content, etc. of resin contained in a liquid developer, it is preferable that it is 2-80 mass%, for example. If it is less than 2% by mass, it becomes difficult to dissolve the resin well in the carrier liquid. On the other hand, if it exceeds 80% by mass, the conductivity of the entire carrier liquid and thus the conductivity of the liquid developer becomes excessively high. If the conductivity of the liquid developer is excessively high, developability may be insufficient, image density may be low, and fog may increase.

  In the present embodiment, the conductivity of the liquid developer is preferably 200 pS / cm or less, for example. Therefore, as a preferred example, a resin is dissolved in the oils such as tall oil fatty acid, and a high electrical resistance aliphatic hydrocarbon is mixed into the obtained solution (hereinafter also referred to as “resin solution”). By doing so, it is preferable to adjust the electrical conductivity of the entire carrier liquid and thus the electrical conductivity of the liquid developer to, for example, 200 pS / cm or less.

  The content of the entire carrier liquid in the liquid developer is not particularly limited, but is about 70 to 95% by mass, preferably about 80 to 90% by mass.

[Dispersion stabilizer]
The liquid developer according to this embodiment may further contain a dispersion stabilizer for promoting and stabilizing the dispersion of particles in the liquid developer. As the dispersion stabilizer that can be used in the present embodiment, for example, “BYK-116” manufactured by Big Chemie is suitable. In addition, “Solsperse 9000”, “Solsperse 11200”, “Solsperse 13940”, “Solspers 16000”, “Solspers 17000”, “Solspers 18000” manufactured by Lubrizol, and “Antarron (registered trademark) V-” manufactured by ISP 216 "," Antaron (registered trademark) V-220 "and the like can be preferably used.

  The content of the dispersion stabilizer in the liquid developer is about 0.5 to 6% by mass, preferably about 1.5 to 3% by mass.

[Production method]
The liquid developer according to the present embodiment uses a carrier liquid, a pigment, a resin, and a dispersion stabilizer depending on the situation, for example, a ball mill, a sand grinder, a dyno mill, a rocking mill, or the like (media using zirconia beads) It may be a dispersion type machine), and can be produced by sufficiently dissolving or mixing and dispersing over several minutes to several tens of hours depending on the situation.

  In the present embodiment, after the resin is dissolved in the carrier liquid, a liquid developer may be produced by mixing and dispersing a pigment (with a dispersion stabilizer depending on the situation), or a resin solution ( Prepared in advance are a pigment dispersion (referred to a mixture of a pigment (with a dispersion stabilizer depending on the situation) mixed and dispersed) in a carrier liquid). In addition, the liquid developer may be manufactured by mixing them at an appropriate mixing ratio (mass ratio).

<Liquid developing apparatus and wet image forming apparatus>
Next, a wet image forming apparatus according to the present embodiment will be described with reference to the drawings. It should be noted that the terms representing the directions such as “upper”, “lower”, “left”, “right” and the like used in the following description are merely for the purpose of clarifying the explanation and limit the present invention in any way. It is not a thing. In addition, the term “sheet” used in the following description refers to any recording medium capable of forming an image, such as high-quality plain paper, print-only paper, copy paper, tracing paper, cardboard, and OHP sheet. means.

  The wet image forming apparatus according to the present embodiment is an image forming apparatus using the above-described liquid developer, and the second liquid developer is applied to the residual liquid developer on the developer carrier after development as described later. A means for supplying a carrier liquid having the highest solubility of the resin among the carrier liquids of more than one species, a recovery means for recovering the residual liquid developer, and a means for supplying the remaining carrier liquid after recovery; If there is any other mechanism, there is no particular limitation.

  Since the wet image forming apparatus according to the present embodiment has such a configuration, since it includes a resin, even when a liquid developer that adheres to the developing roller more strongly than a general liquid developer by charging is used. It becomes possible to clean efficiently. That is, by using only a carrier liquid having a higher resin solubility than a mixture of all the carrier liquids among the carrier liquids, the resin dissolution rate is increased and the cleaning failure such as slipping in the cleaning portion is suppressed. be able to.

  The recovered liquid developer is used as a regenerated liquid developer. According to the above configuration, the recoverability and transportability at that time are also improved.

  Usually, when the resin is deposited at the time of recovery, the resin may not be redissolved even if a liquid mixture of two or more kinds of carrier liquids is added and mixed from the beginning. In that case, the recovered liquid cannot be used as a regenerated liquid developer and must be discarded. In the image forming apparatus according to the present invention, since the highly soluble carrier liquid is added first, the resin can be surely dissolved, and the precipitation of the resin due to the increase in the resin concentration in the recovered liquid can be prevented. Therefore, it is not necessary to discard the recovered liquid, and the recoverability is improved.

  On the other hand, when clogging of the developer occurs in the conveyance path using the liquid developer in which the resin is dissolved, the liquid overflows and the inside of the apparatus is soiled, causing an adverse effect on the image. On the other hand, when a carrier liquid in which the resin dissolves satisfactorily is added, the viscosity of the liquid is lowered and the resin does not precipitate, so that the clogging of the developer in the transport path as described above can be suppressed. That is, the transportability of the recovered liquid is improved.

  Further, when a regenerated liquid developer is produced, it usually takes a considerable time to uniformly dissolve the resin. However, by using the wet image forming apparatus, the stirring time or strength of stirring is increased. (Such as the number of revolutions) can be reduced.

  In the wet image forming apparatus, it is preferable that the collecting unit is a cleaning blade type. Thereby, the cleaning property can be further improved. Furthermore, if resin deposition occurs on the cleaning blade, this also leads to poor cleaning, so the blade may need to be replaced. Therefore, if the precipitation of the resin can be suppressed, there is an advantage that the durability of the blade is also increased.

  More specifically, first, a liquid developer circulation system that supplies liquid developer to the developing device 106 and collects and reuses the liquid developer from the developing device 106 will be described with reference to FIG. . FIG. 1 is a schematic configuration diagram of a liquid developer circulation device LC, which is one of the liquid developer circulation devices described later, and schematically shows a liquid developer circulation system. The other liquid developer circulating devices LY, LM, and LB have the same configuration. The liquid developer circulating device LC is for supplying the liquid developer to the developing device 106 and reusing the liquid developer collected in the reserve tank 108A.

  The liquid developer circulation device LC includes a developer adjustment tank 109, a carrier A tank, a carrier B tank, a pigment dispersion tank, a resin solution tank, developer reserve tanks 108A and 108B, and a cleaning device 104.

  The cleaning device 104 collects the residual liquid developer from the developing roller 102. The collected liquid developer is sent to the developer preparation tank 109 via the reserve tank 108A. The cleaning device 104 is preferably a cleaning blade type cleaning device.

  From the carrier B tank, a carrier liquid having a high resin solubility (a good solvent for the resin, hereinafter also referred to as carrier B) is supplied from the carrier B tank, and the carrier B is a flow path changing member (for example, a three-way cock). The flow path is changed by 110, and the residual liquid developer on the preparation tank 109 or the developer carrier (developing roller) 102 is supplied. When three or more kinds of carrier liquids are used in the liquid developer, a carrier liquid having the highest resin solubility is supplied to the carrier B tank.

  The carrier B is supplied to the front side from the cleaning device 104 as shown in FIG. With such a configuration, the recoverability and transportability of the residual liquid developer are remarkably improved without the resin in the residual liquid developer being precipitated. The supply means used here is not particularly limited, and any normal cleaning liquid supply means can be used. Further, the supply amount of the carrier B is not particularly limited as long as the amount is sufficient to dissolve the resin in the residual liquid developer without precipitation.

  The developer adjustment tank 109 is a developer concentration adjustment system, and by adding a pigment, resin, or carriers A and B having a higher concentration than the developer used in the developing device 106 to the collected liquid developer, The pigment concentration is adjusted to an appropriate range. The liquid developer having the adjusted pigment concentration is supplied again to the developing device 106 via the reserve tank 108B.

  The solid content concentration detection device 111 is a device for detecting the concentration of the pigment and resin of the liquid developer in the developer adjustment tank 109. A solid concentration detector 111 is connected to an annular pipe connected to the developer adjustment tank 109. The liquid developer in the developer adjustment tank 109 is guided to the solid concentration detector 111 and then returned to the developer adjustment tank 109.

  The carrier B tank and the carrier A tank are tanks for storing respective carrier liquids. When the solid content concentration detection device 111 determines that the pigment and resin concentrations in the developer adjustment tank 109 are higher than the appropriate range, carrier liquid is supplied from the respective carrier tanks into the developer adjustment tank 109. The pigment concentration of the liquid developer in the developer adjustment tank 109 is lowered. At this time, the ratio of the carrier B in the carrier liquid of the regenerated liquid developer is adjusted to be in the above-described range.

  The carrier A tank and the developer adjustment tank 109 are connected by a pipe, and a pump is provided in the pipe. The carrier liquid is supplied from the carrier A tank to the developer adjusting tank 109 by driving the pump. Although not shown in the drawing, it may have a carrier tank for storing another carrier liquid. In this case, the other carrier liquid used is a carrier liquid in which the resin is less soluble than the carrier B. Further, the carrier B tank is connected to the developer adjusting tank 109 and is also supplied to the residual liquid developer on the developer carrying member (developing roller) 102 by the flow path changing member 110.

  The resin dispersion tank is a tank that stores a liquid developer having a resin concentration higher than that of the developer used in the developing device 106. When the solid concentration detector 111 determines that the concentration of the resin in the developer adjustment tank 109 is lower than the appropriate range, a resin having a high resin concentration is supplied from the resin tank into the developer adjustment tank 109. The resin concentration of the liquid developer in the developer adjustment tank 109 is increased. The resin tank and the developer adjustment tank 109 are connected by a pipe, and a pump is provided in the pipe. Resin is supplied from the resin tank to the developer adjustment tank 109 by driving the pump.

  The pigment dispersion tank is a tank that stores a liquid developer having a pigment dispersion concentration higher than that of the developer used in the developing device 106. When the solid content concentration detection device 111 determines that the concentration of the pigment dispersion in the developer adjustment tank 109 is lower than the appropriate range, the pigment dispersion concentration is changed from the pigment dispersion tank to the developer adjustment tank 109. A high pigment dispersion is supplied, and the pigment dispersion concentration of the liquid developer in the developer adjustment tank 109 is increased. The pigment dispersion tank and the developer adjustment tank 109 are connected by a pipe, and a pump is provided in the pipe. By driving the pump, the pigment dispersion is supplied from the pigment dispersion tank to the developer adjusting tank 109.

  The residual liquid developer recovered in this way is prepared as a regenerated liquid developer and used again for development. The regenerated liquid developer is prepared so that the composition ratio in the regenerated liquid developer is the same as that of the liquid developer described above.

  In the developer adjustment tank 109, a stirring device 109a for stirring the liquid developer is disposed. The purpose of the stirring by the stirring device 109a is so that the pigment dispersion or carrier liquid introduced into the developer adjustment tank 109 for density adjustment is uniformly mixed with the existing liquid developer in the developer adjustment tank 109. In order to achieve this, it is also possible to re-disperse the pigment dispersion that may agglomerate in the liquid developer contained in the developer adjustment tank 109. The stirring device 109a includes a rotating shaft and a stirring blade attached to the tip of the rotating shaft.

  The developer reserve tank 108B is a tank that stores a liquid developer to be replenished to the developing device 106 via a liquid developer supply unit. The reserve tank 108B is connected to the developer adjustment tank 109 by a pipe, and a pump is disposed on the pipe. By driving the pump, the liquid developer is supplied from the developer adjustment tank 109 to the reserve tank 108B.

  In addition, although illustration is abbreviate | omitted, each tank is provided with the liquid level detection apparatus for detecting the liquid level height in these tanks.

  Next, FIG. 2 is a schematic configuration diagram of the periphery of the liquid developing device provided in the wet image forming apparatus according to the present embodiment.

  The developing container 112 is supplied with a liquid developer and stores the liquid developer. The liquid developer is supplied into the developing container 112 from the supply nozzle after the carrier liquid, the resin and the pigment are adjusted in concentration as described above.

  The application roller 103 is disposed at substantially the center of the developing container 112 and abuts against the supply roller 105 from below to form a nip portion. The supply roller 105 may be arranged not in a position directly above the application roller 103 but in a direction away from the supply nozzle 278. A groove for holding the liquid developer is provided on the peripheral surface of the supply roller 105.

  The liquid developer supplied from the supply nozzle is temporarily retained on the upstream side in the rotation direction of the application roller 103 at the nip portion between the supply roller 105 and the application roller 103. It is carried upward while being held in the groove. The regulating blade 107 is pressed against the peripheral surface of the supply roller 105 and regulates the amount of the liquid developer held in the groove of the supply roller 105 to be a predetermined amount. Excess liquid developer scraped off by the regulating blade 107 is stored in the bottom of the developing container 112.

  The developing roller 102 is disposed in the upper opening of the developing container 140 so as to be in contact with the supply roller 105. The developing roller 102 is rotated in the same direction as the supply roller 105. As a result, at the nip portion where the developing roller 102 and the supply roller 105 abut, the surface of the developing roller 102 moves in the direction opposite to the surface of the supply roller 105. As a result, the liquid developer held on the peripheral surface of the supply roller 105 is delivered to the peripheral surface of the developing roller 102. Since the amount of liquid developer held in the groove of the supply roller 105 (thickness of the thin layer of liquid developer) is regulated to a predetermined value, the amount of liquid developer carried on the surface of the developing roller 102 (liquid The thickness of the developer thin layer) is also kept at a predetermined value.

  The developing roller 102 is in contact with the photosensitive drum 101, and the toner image based on the image data is transferred to the photosensitive drum due to the potential difference between the electrostatic latent image potential on the surface of the photosensitive drum 101 and the developing electric field applied to the developing roller 102. 10 surfaces.

  The developing cleaning device (cleaning blade) 104 is disposed so as to contact the downstream side in the rotation direction of the contact portion of the developing roller 102 with the photosensitive drum 101, and the developing roller 102 that has completed the developing operation on the photosensitive drum 101 is arranged. The surface liquid developer is removed.

  As described above, the carrier B having a high resin solubility is supplied in front of the cleaning device 104, and the carrier A having a resin solubility lower than that of the carrier B is supplied after the residual liquid developer is recovered.

  The liquid developer removed by the development cleaning device 104 is collected and conveyed to the density adjustment system (developer adjustment tank 109).

  Next, an embodiment of a wet image forming apparatus that can be used in the present embodiment will be described with reference to FIGS. 3 and 4. However, the wet image forming apparatus of the present invention is not limited to this embodiment. 3 is a schematic configuration diagram of the wet image forming apparatus, and FIG. 4 is a schematic cross-sectional view of the wet image forming apparatus excluding the liquid developer circulation device. The wet image forming apparatus described below is a color printer, but can form an image on a sheet, that is, a recording medium, such as a monochrome printer, a copying machine, a facsimile machine, or a multifunction machine having these functions. Any other wet image forming apparatus may be used.

  As shown in FIG. 3, the color printer 1 is arranged in an upper main body 1A (apparatus main body) in which various units and parts for image formation are housed, and a lower portion of the upper main body 1A. The liquid developer circulating devices LY, LM, LC, and LB are configured to accommodate the lower main body 1B. Here, the piping connecting the upper main body 1A and the lower main body 1B is not shown.

  As shown in FIG. 4, the upper main body 1 </ b> A is formed by a tandem image forming unit 2 that forms a toner image based on image data, a paper storage unit 3 that stores paper, and an image forming unit 2. A secondary transfer unit 4 for transferring the transferred toner image onto the paper, a fixing unit 5 for fixing the transferred toner image on the paper, a discharge unit 6 for discharging the fixed paper, and a paper storage unit A paper transport unit 7 for transporting paper from 3 to the discharge unit 6 is arranged.

  The image forming unit 2 includes an intermediate transfer belt 21, a cleaning unit 22 for the intermediate transfer belt 21, and an image forming unit corresponding to each of yellow (Y), magenta (M), cyan (C), and black (Bk). Includes FY, FM, FC, and FB.

  The intermediate transfer belt 21 is a belt-like member that has conductivity and is wider than the maximum length sheet in a direction orthogonal to the sheet conveyance direction, and is an endless, ie, loop-shaped belt. Is circulated and driven clockwise. In the circulation driving of the intermediate transfer belt 21, the surface facing outward is hereinafter referred to as a front surface, and the other surface is referred to as a back surface.

  Four image forming units FY, FM, FC, and FB are arranged near the intermediate transfer belt 21 and disposed between the cleaning unit 22 and the secondary transfer unit 4 of the intermediate transfer belt 21. Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image.

  Each of the image forming units FY, FM, FC, and FB includes a photosensitive drum 10 (image carrier), a charger 11, an LED exposure device 12, a developing device 106, a primary transfer roller 20, and a cleaning device 26. And a static elimination device 13 and a carrier liquid removal roller 30. Further, among the image forming units FY, FM, FC, and FB, the image forming unit FB located closest to the secondary transfer unit 4 is not provided with the carrier liquid removal roller 30, but the other configurations are as follows. Are the same.

  Corresponding to the image forming units FY, FM, FC, and FB, liquid developer circulating devices LY, LM, LC, and LB are provided to supply and collect the liquid developers of the respective colors. Yes. The liquid developer circulating devices LY, LM, LC, and LB will be described in detail later.

  The photosensitive drum 10 is a cylindrical member, and can carry a toner image including a pigment charged (charged to a positive polarity in the present embodiment) on the surface thereof. The photosensitive drum 10 is a member that can rotate counterclockwise in FIGS. 1 and 2. The charger 11 is a device that can uniformly charge the surface of the photosensitive drum 10. The exposure device 12 has a light source such as an LED and irradiates light onto the surface of the uniformly charged photoreceptor drum 10 in accordance with image data input from an external device. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 10.

  The developing device 106 opposes a liquid developer in which a pigment dispersion (dispersoid) as a solid content is dispersed in a carrier (dispersion medium) of a dielectric liquid to the electrostatic latent image on the surface of the photosensitive drum 10. By holding in this manner, the pigment is attached to the electrostatic latent image. Thereby, the electrostatic latent image is developed as a toner image.

  The primary transfer roller 20 is disposed on the back surface of the intermediate transfer belt 21 so as to face the photosensitive drum 10. A voltage having a polarity opposite to that of the pigment in the toner image (minus in this embodiment) is applied to the primary transfer roller 20 from a power source (not shown). That is, the primary transfer roller 20 applies a voltage having a polarity opposite to that of the pigment to the intermediate transfer belt 21 at a position in contact with the intermediate transfer belt 21. Since the intermediate transfer belt 21 has conductivity, the applied voltage attracts the pigment to the surface side of the intermediate transfer belt 21 and its periphery. The intermediate transfer belt 21 functions as an image carrier that carries a toner image and conveys it to a sheet.

  The photosensitive drum cleaning device 26 is a device for cleaning the liquid developer remaining without being transferred from the photosensitive drum 10 to the intermediate transfer belt 21, and the residual liquid developer on the surface of the photosensitive drum 10. And a cleaning blade 262 for scraping off.

  The static eliminator 13 has a light source for static elimination, and removes the liquid developer by the cleaning blade 262 and removes the surface of the photosensitive drum 10 with light from the light source in preparation for the next round of image formation.

  The carrier liquid removal roller 30 is a substantially cylindrical member that can rotate in the same direction as the photosensitive drum 10 around a rotational axis parallel to the rotational axis of the photosensitive drum 10. The carrier liquid removing roller 30 is disposed on the side where the secondary transfer unit 4 is disposed with respect to the position where the photosensitive drum 10 and the intermediate transfer belt 21 are in contact with each other, and the carrier liquid is removed from the surface of the intermediate transfer belt 21. The member to be removed.

  The paper storage unit 3 is a part for storing a paper for fixing a toner image, and is disposed below the upper main body 1A. The paper storage unit 3 has a paper feed cassette that stores paper.

  The secondary transfer unit 4 is a part that transfers the toner image formed on the intermediate transfer belt 21 to a sheet, and is disposed opposite to the support roller 41 that supports the intermediate transfer belt 21 and the support roller 41. And a secondary transfer roller 42.

  The fixing unit 5 is a part for fixing the toner image on the sheet, and is disposed on the upper side of the secondary transfer unit 4. The fixing unit 5 includes a heating roller 43 and a pressure roller 44 disposed to face the heating roller 43. In this embodiment, since the liquid developer that can be fixed without heat is used, the fixing unit 5 can be omitted.

  The discharge unit 6 is a portion from which the paper on which the toner image has been fixed by the fixing unit 5 is discharged, and is disposed at the top of the color printer 1. The paper transport unit 7 includes a plurality of transport roller pairs, and transports the paper from the paper storage unit 3 to the secondary transfer unit 4, the fixing unit 5, and the discharge unit 6.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

1. Manufacture of liquid developer Ethyl cellulose as cellulose ether (“Etocel (registered trademark) STD4” (ethoxylation ratio: 45 to 49.5%) manufactured by Nihon Kasei Co., Ltd.) 3.8 parts by mass, Toll as carrier liquid B A resin solution was prepared by dissolving in 15.2 parts by mass of an oil fatty acid (“Hartol FA-1” manufactured by Harima Chemicals). On the other hand, 18 parts by mass of liquid paraffin as carrier liquid A (“Moresco White P-200” manufactured by Matsumura Oil Research Co., Ltd.) and 5 mass of cyan pigment (CI Pigment Blue 15: 3) as colored particles. A pigment dispersion was prepared by mixing and dispersing 2 parts by weight of “Antaron (registered trademark) V-216” manufactured by ISP manufactured by Lubrizol as a dispersion stabilizer. The average particle diameter (D ₅₀ ) of the pigment in the pigment dispersion was 0.5 μm. Then, by mixing 19 parts by mass of the resin solution and 25 parts by mass of the pigment dispersion and 56 parts by mass of the tall oil fatty acid, as shown in Table 1, the pigment contained 5% by mass and ethyl cellulose 3.8% by mass. A cyan liquid developer in which the content of tall oil fatty acid in the entire carrier liquid was 79.8% by mass was produced.

2. Image formation 2-1. Conventional method (when carrier B is not used for collection)
Using the experimental machine (linear speed: 116 mm / s) of a wet image forming apparatus (color printer) manufactured by Kyocera Mita Co., Ltd., the cyan liquid developer is charged into the cyan image forming unit FC and placed on the developing roller. A 5 μm developer layer was formed. The developer was charged on the developing roller with a corona charger (4 kV applied), and then the blank paper image was developed from the developing roller to the photoreceptor for 10 minutes. Other image forming conditions are shown below.

Photoconductor: Dark potential: + 550V, Bright potential: + 10V
Developing roller: + 400V
Then, when the recovered liquid after development was recovered with a cleaning blade, a cleaning failure occurred (the developer adhered to the developing roller).

2-2. This embodiment An image was formed in the same manner as in 2-1, except that tall oil fatty acid (carrier liquid B) was slowly dropped onto the developing roller (3 g in 10 minutes) before the cleaning blade. As a result, the above-described cleaning failure did not occur.

  In addition, 0.76 g of liquid paraffin (carrier liquid A) was added to the liquid recovered after the cleaning with the cleaning blade, followed by stirring to prepare a regenerated liquid developer. (The ratio of carrier A to carrier B added after development is 20.1: 79.8).

2-3. Consideration From the above, it has been clarified that the wet image forming apparatus according to the present embodiment does not cause cleaning failure even when a liquid developer in which a resin is dissolved is used, and exhibits good recoverability and transportability.

  INDUSTRIAL APPLICABILITY The present invention can be used in a wide range of industries in the technical field of a wet developing method which is one of electrophotographic systems that can be employed in color printers, printers, copiers, facsimile machines, and multifunction machines having these functions. Have sex.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 1A Upper side main-body part (apparatus main body)
DESCRIPTION OF SYMBOLS 101 Photosensitive drum 102 Developing roller 103 Coating roller 104 Cleaning device 105 Supply roller 106 Developing device 109 Developer preparation tank 108 Reserve tank 110 Flow path changing member 111 Solid content concentration detection device

Claims (4)

A wet image forming apparatus for developing an electrostatic latent image on the surface of a photosensitive drum using a liquid developer,
The liquid developer includes at least a pigment, a resin, and two or more kinds of non-volatile carrier liquids, and at least one of the two or more kinds of carrier liquids has a solubility of the resin and other carrier liquids. And the resin is a liquid developer present dissolved in a carrier liquid, and the two or more types of carrier liquids with respect to the residual liquid developer on the developer carrier after development. Means for supplying a carrier liquid having the highest solubility of the resin,
A wet image forming apparatus, comprising: a collecting means for collecting the remaining liquid developer after that; and a means for supplying the remaining carrier liquid after the collection.   The wet image forming apparatus according to claim 1, wherein the collecting unit is a cleaning blade type.   The wet image forming apparatus according to claim 1 or 2, wherein the resin is at least one selected from a cyclic olefin copolymer, a styrene-based elastomer, a cellulose ether, and polyvinyl butyral. The wet image forming apparatus according to claim 1, further comprising means for measuring the concentrations of the pigment and the resin in the collected liquid developer and adjusting the concentration.

Images