JP4442432B2 - Method for producing liquid developer - Google Patents

Description

The present invention relates to a method for producing a liquid developer .

A dry toner method in which a toner composed of a material containing a colorant such as a pigment and a binder resin is used in a dry state as a developer used to develop the electrostatic latent image formed on the latent image carrier. And a method using a liquid developer in which toner is dispersed in an electrically insulating carrier liquid.
The method using dry toner handles solid-state toner, so there are advantages in handling, but there are concerns about adverse effects on the human body due to powder, as well as contamination due to scattering of toner, and when toner is dispersed There is a problem with uniformity. Also, with dry toners, particle aggregation tends to occur during storage, etc., and it is difficult to sufficiently reduce the size of toner particles, and it is difficult to form a high-resolution toner image. . In addition, when the size of the toner particles is relatively small, the problem due to the powder as described above becomes more remarkable.

  On the other hand, in the method using a liquid developer, toner particles can be effectively prevented from aggregating in the liquid developer during storage, so that fine toner particles can be used. Those having a low softening point (low softening temperature) can be used. As a result, in the method using a liquid developer, fine line image reproducibility is good, gradation reproducibility is good, color reproducibility is excellent, and it is also excellent as a high-speed image forming method. It has characteristics.

Conventionally, a liquid developer has conventionally been obtained by pulverizing a resin to produce a toner (see, for example, Patent Document 1), and polymerizing a monomer component in the electrically insulating liquid, thereby forming the electrically insulating liquid. Polymerization method for forming insoluble resin fine particles (see, for example, Patent Document 2) A solvent insoluble in a resin material is added to a non-aqueous solvent in which a resin material and a pigment are dissolved while stirring. Thus, it has been manufactured by a deposition method for depositing a resin material (see, for example, Patent Document 3).
However, the conventional method for producing a liquid developer has the following problems.

  That is, in the pulverization method, it is difficult to pulverize the toner particles to a sufficiently small size (for example, 5 μm or less), and the effect of using the liquid developer as described above is sufficiently increased. In order to obtain a size that can be exhibited, a very long grinding energy was required for a very long time, and the productivity of the liquid developer was extremely low. Further, in the pulverization method, the particle size distribution of the toner particles tends to be wide (the variation in particle size is large), and the shape of the toner particles tends to be irregular and non-uniform. As a result, variation in characteristics (for example, charging characteristics) among the toner particles tends to increase. Further, it is conceivable to dry pulverize the resin instead of wet pulverization in a nonpolar solvent (insulating liquid). In such a case, even if a fine powder is formed by pulverization, the fine powder is It is easy to agglomerate and it is difficult to make the toner particle size sufficiently small.

  Also, in the polymerization method, it is difficult to make the conditions for the polymerization reaction suitable, so that a resin material having a suitable molecular weight can be formed, toner particles having a desired size can be formed, It is difficult to reduce the variation sufficiently. As a result, the stability and reliability of the toner quality tends to be low. Further, in the polymerization method, it takes a relatively long time to form toner particles, and the productivity of the liquid developer is poor. In addition, the polymerization method generally requires a large production apparatus and production equipment.

In addition, the deposition method has a problem in that each material (particularly, pigment) is likely to aggregate when the resin material is deposited, and variation in composition and characteristics among the toner particles tends to increase. In addition, the precipitation method tends to cause aggregation of the pigment, so that when the obtained liquid developer is used, it is difficult to form a sufficiently transparent (clear) image.
In addition, the liquid developer produced by the conventional method generally has a problem that toner particles are poorly fixed on a recording medium such as paper.

JP-A-7-234551 Japanese Patent Publication No.8-7470 JP 2003-345071 A

  It is an object of the present invention to provide a liquid developer having a narrow particle size distribution, a uniform shape, and excellent toner particle fixability to a recording medium, and efficiently using such a liquid developer. An object of the present invention is to provide a method for producing a liquid developer that can be produced. In particular, an object is to provide a liquid developer that has a narrow particle size distribution, a uniform shape, and excellent fixability of toner particles to a recording medium by an environmentally friendly method.

Such an object is achieved by the present invention described below.
The method for producing a liquid developer of the present invention is a method for producing a liquid developer in which toner particles are dispersed in an insulating liquid,
Preparing an aqueous dispersion in which a dispersoid composed of a material containing a resin material is dispersed in an aqueous dispersion medium composed of an aqueous liquid;
By spraying the aqueous dispersion as droplets, the aqueous dispersion medium is removed, and toner particles obtained as agglomerates of a plurality of the dispersoids contained in the droplets are recovered as powder. And a step of directly dispersing in the insulating liquid.

  This makes it possible to produce a liquid developer having a narrow particle size distribution, a uniform shape, and capable of producing efficiently (highly productive) a liquid developer having excellent fixability of toner particles to a recording medium. A method can be provided. In particular, a method for producing a liquid developer, which is an environmentally friendly method and can produce a liquid developer having a small particle size distribution width, a uniform shape, and excellent toner particle fixability to a recording medium. Can be provided.

In the method for producing a liquid developer according to the aspect of the invention, it is preferable that the toner particles include moisture that is equal to or greater than the water absorption amount of the resin material.
Thereby, the fixing property of the toner particles to the recording medium can be made particularly excellent.
In the method for producing a liquid developer of the present invention, the water content of the toner particles is preferably 0.3 to 5.0 wt%.
As a result, the chargeability of the toner particles can be made sufficiently good, the dispersibility can be improved, and the fixability of the toner particles to the recording medium can be made particularly excellent.

In the method for producing a liquid developer of the present invention, the average particle size of the dispersoid in the aqueous dispersion is preferably 0.01 to 1.0 μm.
As a result, the toner particles can be obtained with a sufficiently high degree of circularity and particularly excellent uniformity in characteristics and shape between each particle (between toner particles). Thereby, the spraying conditions of the aqueous dispersion can be further stabilized.

In the method for producing a liquid developer of the present invention, the average particle diameter of the droplets is preferably 1.0 to 100 μm.
Thereby, removal of an aqueous dispersion medium can be performed more efficiently. In addition, toner particles having an appropriate particle diameter can be more reliably formed.
In the method for producing a liquid developer of the present invention, when the average particle size of the dispersoid in the aqueous dispersion is Dm [μm] and the average particle size of the toner particles is Dt [μm], 0.005 ≦ It is preferable that the relationship of Dm / Dt ≦ 0.5 is satisfied.
Thereby, the variation in shape and size among the toner particles can be particularly reduced.

In the method for producing a liquid developer of the present invention, when the average particle diameter of the droplets is Dd [μm] and the average particle diameter of the dispersoid in the dispersion is Dm [μm], Dm / Dd <0. It is preferable to satisfy the relationship .5.
As a result, it is possible to make the dispersion of the particle diameter of the toner particles smaller while fully exhibiting the characteristics of the dispersion liquid (good liquid drainage, etc.) at the time of toner production.

In the method for producing a liquid developer of the present invention, when the average particle diameter of the droplets is Dd [μm] and the average particle diameter of the toner particles is Dt [μm], 0.05 ≦ Dt / Dd ≦ 1. The method for producing a liquid developer according to claim 1, wherein the relationship of 0 is satisfied.
As a result, toner particles that are sufficiently fine, have a high degree of circularity, and a sharp particle size distribution can be obtained relatively easily.

In the method for producing a liquid developer according to the present invention, the aqueous dispersion includes a step of preparing a kneaded material containing the resin material and a colorant, and the kneading in a solvent capable of dissolving at least a part of the kneaded material. It is preferably prepared through a step of dissolving an object to obtain a solution, a step of dispersing the solution in the aqueous liquid, and a step of removing the solvent.
As a result, inadvertent aggregation between the dispersoids and between the toner particles can be prevented more effectively, and as a result, the uniformity of the shape and size of the toner particles can be made particularly excellent. At the same time, the variation in composition among the toner particles can be made particularly small, and the variation in characteristics (charging characteristics, etc.) among the toner particles can be made particularly small. In addition, the particle size of the toner particles can be further reduced. Further, deaeration treatment can be performed along with the removal of the solvent, and the formation of irregularly shaped toner particles can be more effectively prevented. Further, along with the removal of the solvent, the aqueous dispersion medium (water) can efficiently penetrate (substitute) into the dispersoid, and as a result, the final toner particles can be obtained with an appropriate water content. .
In the method for producing a liquid developer according to the present invention, the kneaded product may include, as the resin material, a self-dispersing resin having a —SO ₃ — group as a group having lyophilicity with respect to the aqueous liquid. preferable.
As a result, the dispersibility of the dispersoid in the aqueous dispersion can be made particularly excellent, and an appropriate amount of water can be included in the dispersoid, so that the final toner particles have an appropriate water content. Can be obtained. In addition, it is possible to effectively prevent the occurrence of problems due to the dispersant contained in the final liquid developer. More specifically, in the liquid developer, it is possible to effectively prevent the dispersant from adversely affecting the charging characteristics of the toner particles. In addition, foaming due to a decrease in defoaming property due to the use of a dispersant in the preparation of the dispersion can be effectively prevented, and ejection at the time of ejection of an aqueous dispersion (aqueous suspension) as described later Stability is improved. Further, when the particles are dispersed in the carrier liquid constituting the liquid developer, it becomes easy to adsorb the dispersant and the charge control agent, and the dispersion and charging can be further stabilized.
In the method for producing a liquid developer of the present invention, the —SO ₃ — group is preferably present in the side chain of the self-dispersing resin.
Thereby, the affinity of the self-dispersing resin with respect to the aqueous liquid can be made particularly excellent, and the dispersoid composed of the self-dispersing resin in the aqueous dispersion (aqueous emulsion or aqueous suspension). Can be made particularly excellent in dispersibility.
In the method for producing a liquid developer of the present invention, the number of —SO ₃ — groups contained in the self-dispersing resin is 0.001 to 0.2 mol with respect to 100 g of the self-dispersing resin. Is preferred.
In the method for producing a liquid developer of the present invention, the content of the self-dispersing resin in the kneaded product is preferably 55 to 95 wt%.
This makes it possible to reliably form a visible image having a sufficient density when the final liquid developer is used while the dispersibility of the dispersoid is sufficiently high.

Hereinafter, a preferred embodiment of a method for producing a liquid developer and a liquid developer according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a longitudinal sectional view schematically showing an example of the configuration of a kneader and a cooler for producing a kneaded product used for preparing an aqueous emulsion (aqueous dispersion), and FIG. 2 is a liquid development of the present invention. FIG. 3 is a longitudinal sectional view schematically showing a preferred embodiment of a liquid developer producing apparatus used for producing the developer, and FIG. 3 is an enlarged sectional view in the vicinity of the head portion of the liquid developer producing apparatus shown in FIG. Hereinafter, in FIG. 1, the left side is assumed to be “base end” and the right side is assumed to be “tip”.

The method for producing a liquid developer according to the present invention includes a step of preparing an aqueous dispersion in which a dispersoid composed of a material including a resin material is dispersed in an aqueous dispersion medium composed of an aqueous liquid, and an aqueous dispersion. And a step of directly dispersing toner particles obtained by spraying to remove the aqueous dispersion medium in the insulating liquid.
The aqueous dispersion used in the present invention may be prepared by any method, but in the present embodiment, a dispersion prepared using a kneaded material containing a colorant and a resin material is used.

<Constituent material of kneaded material>
The kneaded product obtained in the kneading step described later includes a component constituting the toner of the liquid developer, and includes at least a binder resin (resin material) and a colorant.
First, the material used for preparation of a kneaded material is demonstrated.
1. Resin (binder resin)
The toner constituting the liquid developer is made of a material containing a resin (binder resin) as a main component.

In the present invention, the resin (binder resin) is not particularly limited and may be any resin, but is preferably a self-dispersing resin having self-dispersibility with respect to an aqueous liquid described later. By using a self-dispersing resin, the dispersibility of the dispersoid in the aqueous dispersion can be made particularly excellent, and appropriate water can be contained in the dispersoid, so that the final toner particles Can be obtained as having an appropriate water content. In the present specification, “self-dispersibility” refers to a property having dispersibility in a dispersion medium without using a dispersant. The “self-dispersing resin” refers to a resin material having such a self-dispersing property.
Although it does not specifically limit as self-dispersion type resin, For example, resin which has many groups which have the lyophilic property (hydrophilicity) with respect to the aqueous liquid mentioned later is mentioned.

As the group (functional group) having the lyophilic (hydrophilic), for example, -COO ^- _group, ^-SO 3 -, -CO group, -OH group, -OSO ₃ ^- group, -COO- group, - SO ₃ —, —OSO ₃ — group, —PO ₃ H ₂ , —OH group, —OSO ₃ ^— group, —COO— group, —SO ₃ —, —OSO ₃ — group, —PO ₃ ²⁻ , —PO ₄ ^- group, and quaternary ammonium, their salts, etc. are mentioned. Such a self-dispersing resin is particularly excellent in dispersibility in an aqueous liquid, so that an aqueous dispersion (aqueous emulsification) described later can be used without using a dispersant or by using an extremely small amount of a dispersant. Liquid, aqueous suspension) can be suitably prepared. Thereby, for example, it is possible to effectively prevent the occurrence of problems due to the inclusion of the dispersant in the final liquid developer. More specifically, in the liquid developer, it is possible to effectively prevent the dispersant from adversely affecting the charging characteristics of the toner particles. In addition, foaming due to a decrease in defoaming property due to the use of a dispersant in the preparation of the dispersion can be effectively prevented, and ejection at the time of ejection of an aqueous dispersion (aqueous suspension) as described later Stability is improved. Further, when the particles are dispersed in the carrier liquid constituting the liquid developer, it becomes easy to adsorb the dispersant and the charge control agent, and the dispersion and charging can be further stabilized.

Further, the group as described above has a property of being easily charged, and is advantageous in improving the charging property of the toner particles themselves.
Among the groups described above, a —COO— group and a —SO ₃ — group are particularly preferable. The self-dispersing resin having such a group is particularly excellent in dispersibility in an aqueous liquid, has an appropriate water retention ability, is relatively easy to manufacture, and can be obtained relatively inexpensively. Further, it is possible to further reduce the cost of manufacturing the liquid developer.

  The groups as described above are preferably present in the side chain of the polymer constituting the resin material. As a result, the affinity to the aqueous liquid can be made particularly excellent, and the dispersibility of the dispersoid composed of the self-dispersing resin in the aqueous dispersion (aqueous emulsion, aqueous suspension) is particularly improved. It can be excellent. In addition, even if an organic solvent is not used in the production process, a dispersion in a particularly excellent dispersion state can be obtained, and the effect that the environmental load is small is also obtained.

The self-dispersing resin as described above has, for example, a functional group as described above on a resin material (raw material resin) or a monomer (monomer), a dimer (dimer), an oligomer, or the like as a raw material described later. It can manufacture by combining the material which has.
For example, a self-dispersing resin having a —COO— group is obtained by graft copolymerization or block copolymerization of an unsaturated carboxylic acid with a poorly water-soluble or water-insoluble resin (raw resin), or a single resin constituting a thermoplastic resin. It can be produced by random copolymerization of a monomer and an unsaturated carboxylic acid.

  Examples of unsaturated carboxylic acids include (meth) acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, nadic acid, maleic anhydride, citraconic anhydride and the like. Saturated monocarboxylic acids or dicarboxylic acids or anhydrides thereof, monoesters of unsaturated carboxylic acids such as methyl, ethyl and propyl, esterified products such as diesters, alkali metal salts, alkaline earth metal salts, ammonium salts, etc. Unsaturated carboxylates and the like can be used.

Further, for example, a self-dispersing resin having a —SO ₃ — group can be obtained by graft copolymerization or block copolymerization of an unsaturated sulfonic acid with a thermoplastic resin (raw resin), or an addition polymerizable thermoplastic resin. Random copolymerization of a saturated monomer and a monomer containing an unsaturated sulfonic acid, or a monomer constituting a polycondensation thermoplastic resin and a monomer containing an unsaturated sulfonic acid It can be produced by polycondensation.

  As unsaturated sulfonic acids, for example, styrene sulfonic acids, sulfoalkyl (meth) acrylates, or metal salts, ammonium salts thereof, and the like can be used. Moreover, as a monomer containing sulfonic acids, sulfoisophthalic acids, sulfoterephthalic acids, sulfophthalic acids, sulfosuccinic acids, sulfobenzoic acids, sulfosalicylic acids, or a metal salt or ammonium salt thereof can be used.

  Examples of the raw material resin (raw resin) include (meth) acrylic resin, polycarbonate resin, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, Styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene -Styrene resin such as acrylic ester-methacrylic ester copolymer, styrene-α-chloromethyl acrylate copolymer, styrene-acrylonitrile-acrylic ester copolymer, styrene-vinyl methyl ether copolymer Or a simple substance containing a styrene substitution product Polymer or copolymer, polyester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene resin, polypropylene, ionomer resin, polyurethane resin, silicone Resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, and the like. They can be used in combination.

In addition, the self-dispersing resin as described above, for example, polymerizes a precursor having a functional group as described above (for example, a corresponding monomer (monomer), dimer (dimer), oligomer, etc.). Etc. can also be produced.
The number of the functional groups (hydrophilic groups) contained in the self-dispersing resin is preferably 0.001 to 0.050 mol with respect to 100 g of the self-dispersing resin, and 0.005 to 0.030 mol. It is more preferable that Thereby, it is possible to improve the dispersibility of the dispersoid containing the self-dispersing resin as a main material while more effectively maintaining the characteristics necessary for the toner.

  The content of the self-dispersing resin as described above in the kneaded product (content in the composition used for preparing the kneaded product) is not particularly limited, but is preferably 55 to 95 wt%, and preferably 60 to 90 wt%. % Is more preferable, and 65 to 85 wt% is even more preferable. If the milk content of the self-dispersing resin is less than the lower limit, it may be difficult to make the dispersibility of the dispersoid sufficiently high in an aqueous dispersion (aqueous emulsion or aqueous suspension). There is. On the other hand, when the milk content of the self-dispersing resin exceeds the upper limit, the content of the colorant is relatively lowered, and when a final liquid developer is used, a visible image having a sufficient density can be obtained. It can be difficult to form.

The kneaded product may contain a resin material other than the self-dispersing resin as described above. As such a resin material (resin material other than the self-dispersing resin), for example, those exemplified above as the raw material resin can be used.
Although the softening temperature of resin (resin material) is not specifically limited, It is preferable that it is 50-120 degreeC, It is more preferable that it is 60-115 degreeC, It is further more preferable that it is 65-115 degreeC. In the present specification, the softening temperature refers to a softening start temperature defined by conditions of a heating rate of 5 ° C./min and a die hole diameter of 1.0 mm in the Koka flow tester. When a plurality of types of resin components are included, a weighted average value for these components can be adopted as the softening temperature of the resin (resin material).

2. Colorant The toner contains a colorant. Examples of the colorant that can be used include pigments and dyes. Examples of such pigments and dyes include carbon black, spirit black, lamp black (CI No. 77266), magnetite, titanium black, chrome lead, cadmium yellow, mineral fast yellow, navel yellow, and naphthol yellow S. , Hansa Yellow G, Permanent Yellow NCG, Chrome Yellow, Benzidine Yellow, Quinoline Yellow, Tartrazine Lake, Red Mouth Lead, Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium salt, eosin lake, brilliant carmine 3B, manganese purple, fast violet B, methyl violet lake, bitumen, cobalt blue, al Reblue Lake, Victoria Blue Lake, First Sky Blue, Indanthrene Blue BC, Ultramarine, Aniline Blue, Phthalocyanine Blue, Calco Oil Blue, Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake, Phthalocyanine Green, Final Yellow Green G, Rhodamine 6G, quinacridone, rose bengal (C.I. No. 45432), C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 184, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 5: 1, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic Green 6, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 162, nigrosine dye (CI No. 50415B), metal complex dye, silica, aluminum oxide, magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, Examples thereof include metal oxides such as magnesium oxide and magnetic materials containing magnetic metals such as Fe, Co, and Ni, and one or more of these can be used in combination.

3. Other Components In addition, components other than those described above may be used for preparing the kneaded product. Examples of such components include waxes, charge control agents, magnetic powders, and the like.
Examples of the wax include hydrocarbon waxes such as ozokerite, cercin, paraffin wax, microwax, microcrystalline wax, petrolatum, Fischer-Tropsch wax, carnauba wax, rice wax, methyl laurate, methyl myristate, palmitic acid. Methyl, methyl stearate, butyl stearate, candelilla wax, cotton wax, wood wax, beeswax, lanolin, montan wax, fatty acid ester ester wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax Olefin waxes such as 12-hydroxy stearamide, stearamide, phthalic anhydride amide wax, Lauro , Ketone waxes such as stearone, ether waxes, and the like, can be used singly or in combination of two or more of them.

Examples of the charge control agent include benzoic acid metal salt, salicylic acid metal salt, alkyl salicylic acid metal salt, catechol metal salt, metal-containing bisazo dye, nigrosine dye, tetraphenylborate derivative, quaternary ammonium salt, alkyl Examples include pyridinium salts, chlorinated polyesters, and nitrofunic acid.
Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides, and magnetic materials such as Fe, Co, and Ni. The thing etc. which were comprised with the magnetic material containing a metal are mentioned.

In addition to the above materials, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, etc. are used as the constituent material (component) of the kneaded product. May be.
Moreover, as a constituent material (component) of the kneaded product, for example, a material used as a solvent such as an inorganic solvent or an organic solvent may be used. Thereby, for example, the efficiency of kneading can be improved, and a kneaded product in which the components are more uniformly mixed can be easily obtained.

<Kneaded material>
Next, an example of a method for obtaining the kneaded material K7 by kneading the raw material K5 containing the above components will be described.
The kneaded material K7 can be manufactured using, for example, an apparatus as shown in FIG.
[Kneading process]
The raw material K5 used for kneading contains the components as described above. In particular, since the raw material K5 contains a colorant, air contained in the raw material K5 in this step (especially, air entrapped by the colorant) can be efficiently removed, and bubbles are mixed inside the toner particles ( Remaining) can be effectively prevented. The raw material K5 used for kneading is preferably a mixture of these components.

This embodiment demonstrates the structure which uses a biaxial kneading extruder as a kneading machine.
The kneading machine K1 includes a process part K2 for kneading while conveying the raw material K5, a head part K3 for extruding the kneaded raw material (kneaded material K7) into a predetermined cross-sectional shape, and a raw material K5 in the process part K2. And a feeder K4 to be supplied.
The process part K2 includes a barrel K21, a screw K22 and a screw K23 inserted into the barrel K21, and a fixing member K24 for fixing the head part K3 to the tip of the barrel K21.

In the process part K2, when the screw K22 and the screw K23 rotate, a shearing force is applied to the raw material K5 supplied from the feeder K4, and a uniform kneaded material K7 is obtained.
The total length of the process part K2 is preferably 50 to 300 cm, and more preferably 100 to 250 cm. If the total length of the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the total length of the process part K2 exceeds the upper limit, depending on the temperature in the process part K2, the number of rotations of the screw K22, the screw K23, and the like, the material K5 is easily denatured by heat, and finally obtained. It may be difficult to sufficiently control the physical properties of the liquid developer (toner).

  Moreover, although the raw material temperature at the time of kneading | mixes changes with compositions etc. of the raw material K5, it is preferable that it is 80-260 degreeC, and it is more preferable that it is 90-230 degreeC. Note that the raw material temperature in the process part K2 may be uniform or may vary depending on the part. For example, the process unit K2 includes a first region having a relatively low set temperature and a second region that is provided on the base end side from the first region and whose set temperature is higher than the first region. You may have.

  In addition, the residence time (time required for passage) of the raw material K5 in the process part K2 is preferably 0.5 to 12 minutes, and more preferably 1 to 7 minutes. If the residence time in the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, if the residence time in the process part K2 exceeds the upper limit, the production efficiency is reduced. Depending on the temperature in the process part K2, the rotational speed of the screw K22, the screw K23, etc., the heat of the raw material K5 Modification is likely to occur, and it may be difficult to sufficiently control the physical properties of the finally obtained liquid developer (toner).

  The number of rotations of the screw K22 and the screw K23 varies depending on the composition of the binder resin and the like, but is preferably 50 to 600 rpm. If the rotational speeds of the screws K22 and K23 are less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the rotation speed of the screw K22 and the screw K23 exceeds the upper limit value, the molecular chain of the resin may be cut by shearing, and the resin characteristics may be deteriorated.

  Further, in the kneader K1 used in the present embodiment, the inside of the process unit K2 is connected to the pump P via the deaeration port K25. Thereby, the inside of the process part K2 can be degassed, and an increase in the pressure in the process part K2 due to heating or heat generation of the raw material K5 (kneaded material K7) can be prevented. As a result, the kneading process can be performed safely and efficiently. Further, since the inside of the process part K2 is connected to the pump P via the deaeration port K25, it is possible to effectively prevent bubbles (particularly relatively large bubbles) from being contained in the obtained kneaded material K7. And the properties of the liquid developer (toner) finally obtained can be made more excellent.

[Extrusion process]
The kneaded material K7 kneaded in the process part K2 is pushed out of the kneader K1 through the head part K3 by the rotation of the screw K22 and the screw K23.
The head part K3 has an internal space K31 into which the kneaded material K7 is fed from the process part K2, and an extrusion port K32 from which the kneaded material K7 is extruded.

  The temperature of the kneaded material K7 in the internal space K31 (at least in the vicinity of the extrusion port K32) is not particularly limited, but is preferably a temperature equal to or higher than the softening temperature of the resin material contained in the raw material K5. As a result, the toner particles can be obtained as a mixture of the constituent components more uniformly, and variations in characteristics (charging characteristics, fixing properties, etc.) among the toner particles can be particularly reduced.

The specific temperature of the kneaded material K7 in the internal space K31 (at least the temperature near the extrusion port K32) is not particularly limited, but is preferably 80 to 150 ° C, more preferably 90 to 140 ° C. preferable. When the temperature of the kneaded material K7 in the internal space K31 is a value within the above range, the kneaded material K7 does not solidify in the internal space K31 and is easily extruded from the extrusion port K32.
In the illustrated configuration, the internal space K31 has a cross-sectional area gradually decreasing portion K33 in which the cross-sectional area gradually decreases in the direction of the extrusion port K32. By having such a cross-sectional area gradually decreasing portion K33, the extrusion amount of the kneaded material K7 extruded from the extrusion port K32 is stabilized, and the cooling rate of the kneaded material K7 in the cooling step described later is stabilized. As a result, the toner produced using the toner has a small variation in characteristics among the toner particles, and has excellent overall characteristics.

[Cooling process]
The softened kneaded material K7 extruded from the extrusion port K32 of the head portion K3 is cooled and solidified by the cooler K6.
The cooler K6 includes rolls K61, K62, K63, and K64, and belts K65 and K66.
The belt K65 is wound around a roll K61 and a roll K62. Similarly, the belt K66 is wound around the roll K63 and the roll K64.

  The rolls K61, K62, K63, and K64 rotate around the rotation axes K611, K621, K631, and K641 in the directions indicated by e, f, g, and h in the drawing. Thereby, the kneaded material K7 extruded from the extrusion port K32 of the kneading machine K1 is introduced between the belt K65 and the belt K66. The kneaded material K7 introduced between the belt K65 and the belt K66 is cooled while being formed into a plate shape having a substantially uniform thickness. The cooled kneaded material K7 is discharged from the discharge portion K67. The belts K65 and K66 are cooled by a method such as water cooling or air cooling. When such a belt type is used as the cooler, the contact time between the kneaded product extruded from the kneader and the cooling body (belt) can be increased, and the cooling efficiency of the kneaded product is particularly excellent. Can be.

  By the way, in the kneading process, since shearing force is applied to the raw material K5, phase separation (particularly macrophase separation) is sufficiently prevented, but the kneaded product K7 that has finished the kneading process is not subjected to shearing force. Therefore, depending on the constituent materials of the kneaded product, phase separation (macrophase separation) or the like may occur again if left for a long period of time. Therefore, it is preferable to cool the kneaded material K7 obtained as described above as soon as possible. Specifically, the cooling rate of the kneaded material K7 (for example, the cooling rate when the kneaded material K7 is cooled to about 60 ° C.) is preferably −3 ° C./second or more, and is preferably −5 to −100 ° C. / More preferably it is seconds. Further, the time required from the end of the kneading step (when the shearing force is no longer applied) to the completion of the cooling step (for example, the time required for cooling the temperature of the kneaded product K7 to 60 ° C. or lower) is 20 seconds. Or less, more preferably 3 to 12 seconds.

In the present embodiment, the configuration using a continuous biaxial kneading extruder as the kneading machine has been described, but the kneading machine used for kneading the raw materials is not limited to this. For kneading the raw materials, for example, various kneaders such as a kneader, a batch type triaxial roll, a continuous biaxial roll, a wheel mixer, and a blade type mixer can be used.
In the illustrated configuration, a kneader having two screws has been described. However, the number of screws may be one or three or more. Further, the kneading apparatus may have a disc (kneading disc) portion.

Further, in the present embodiment, the configuration using one kneader has been described, but kneading may be performed using two kneaders. In this case, the heating temperature of the raw material, the rotational speed of the screw, and the like may be different between one kneader and the other kneader.
In the present embodiment, a configuration using a belt type as the cooler has been described. However, for example, a roll type (cooling roll type) cooler may be used. Further, the cooling of the kneaded product extruded from the extrusion port K32 of the kneader is not limited to the one using the above-described cooler, and may be performed by, for example, air cooling.

[Crushing process]
Next, the kneaded material K7 that has undergone the cooling process as described above is pulverized. Thus, by pulverizing the kneaded material K7, an aqueous dispersion (aqueous emulsion or aqueous suspension) described later can be obtained as a dispersion of finer dispersoids relatively easily. As a result, the liquid developer finally obtained can also have a smaller toner particle size and can be suitably used for high-resolution image formation.

The pulverization method is not particularly limited, and can be performed using various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The pulverization process may be performed in multiple steps (for example, two stages of a coarse pulverization process and a fine pulverization process). In addition, after such a pulverization step, a classification process or the like may be performed as necessary. For the classification treatment, for example, a sieve, an airflow classifier or the like can be used.

By kneading the raw material K5 as described above, the air contained in the raw material K5 can be effectively removed. In other words, the kneaded material K7 obtained by kneading as described above contains almost no air (bubbles) inside. Thereby, it is possible to effectively prevent the generation of irregularly shaped particles (hollow particles, missing particles, fused particles, etc.) in the aqueous dispersion spraying step described later. As a result, in the finally obtained liquid developer, it is possible to effectively prevent problems such as a decrease in transferability and cleaning property due to irregularly shaped toner particles.
In this embodiment, an aqueous dispersion is prepared using the kneaded material as described above. In particular, in this embodiment, an aqueous emulsion is once prepared using the kneaded material as described above, and then an aqueous suspension is prepared using the aqueous emulsion.

  By using the kneaded material K7 for the preparation of the aqueous dispersion (aqueous emulsion), the following effects can be obtained. That is, even when the toner constituent materials contain components that are difficult to disperse or compatible with each other, each component is sufficiently compatible and finely dispersed in the resulting kneaded product by kneading. State. In particular, pigments (coloring agents) usually have low dispersibility in liquids used as solvents as described later, but are kneaded in advance before being dispersed in the solvent, so that resin particles and the like are surrounded by pigment particles. Thus, the dispersibility of the pigment in the solvent is improved (particularly fine dispersion in the solvent is possible), and the color development property of the finally obtained toner is also improved. For this reason, a component (hereinafter referred to as “hardly dispersible component”) having poor dispersibility with respect to the dispersion medium (aqueous dispersion medium) of the aqueous dispersion liquid (aqueous emulsion liquid, aqueous suspension) described later in the constituent material of the toner. ) And components that are poorly soluble in the solvent contained in the dispersion medium of the aqueous emulsion (hereinafter also referred to as “hardly soluble components”). In particular, the dispersibility of the dispersoid in the aqueous suspension) can be made particularly excellent. As a result, even in the finally obtained liquid developer, variations in composition and characteristics among the toner particles are reduced, and the overall characteristics are particularly excellent.

<Aqueous emulsion preparation process>
Next, using the kneaded material K7 as described above, an aqueous emulsion in which the dispersoid composed of the toner material is dispersed in the aqueous dispersion medium composed of the aqueous liquid is prepared (aqueous emulsion preparation step). .
In an aqueous emulsion, the dispersoid is liquid (has fluidity and can be deformed relatively easily), so the dispersoid has a shape with a large degree of circularity (sphericity) due to its surface tension. Show the trend. Therefore, the suspension (aqueous suspension) prepared using the aqueous emulsion also has a relatively high circularity (sphericity) in the shape of the dispersoid. The circularity (sphericity) is relatively large. In addition, in the case of an emulsion in which the dispersoid is liquid (has fluidity and can be deformed relatively easily), the uniformity of the size of the dispersoid can be relatively easily achieved by, for example, stirring the emulsion. It can be high enough.

The method for preparing the aqueous emulsion is not particularly limited. In this embodiment, a solution of the kneaded product K7 in which at least a part of the kneaded product K7 is dissolved is obtained, and the aqueous emulsion is dispersed by dispersing the solution in the aqueous liquid. Prepare. In the present specification, “emulsion (emulsion, emulsion, emulsion)” refers to a dispersion in which a liquid dispersoid (dispersed particles) is dispersed in a liquid dispersion medium, “Suspension” refers to a dispersion (including suspension colloid) in which a solid (solid) dispersoid (suspension particles) is dispersed in a liquid dispersion medium. Further, when the liquid dispersoid and the solid dispersoid coexist in the dispersion, the total volume of the liquid dispersoid in the dispersion is larger than the total volume of the solid dispersoid. The larger one is used as an emulsified liquid, and in the dispersion liquid, the total volume of the solid dispersoid is larger than the total volume of the liquid dispersoid.
Hereinafter, a method for preparing the aqueous emulsion will be described in detail.

[Preparation of kneaded product solution (solution of kneaded product)]
In this embodiment, first, a kneaded product solution in which at least a part of the kneaded product is dissolved is obtained.
The solution can be prepared by mixing the kneaded product and a solvent capable of dissolving at least a part of the kneaded product.
The solvent used for the preparation of the solution may be any solvent as long as it can dissolve at least a part of the kneaded product, but is usually used with an aqueous liquid described later (an aqueous liquid used for preparing an aqueous emulsion). Those having low compatibility (for example, a liquid having a solubility of 10 g or less in 100 g of an aqueous liquid at 25 ° C.) are used.

  Examples of such solvents include inorganic solvents such as carbon disulfide and carbon tetrachloride, ketone solvents such as methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), and 2-heptanone, pentanol, n-hexanol, Alcohol solvents such as 1-octanol and 2-octanol, ether solvents such as diethyl ether and anisole, aliphatic hydrocarbon solvents such as hexane, pentane, heptane, cyclohexane, octane and isoprene, toluene, xylene, benzene and ethylbenzene , Aromatic hydrocarbon solvents such as naphthalene, aromatic heterocyclic compound solvents such as furan and thiophene, halogen compound solvents such as chloroform, ester solvents such as ethyl acetate, isopropyl acetate, isobutyl acetate, ethyl acrylate, Acrylonitrile, etc. Nitrile solvents, nitromethane an organic solvent such as nitro-based solvents such as nitroethane and the like, can be used a mixture of one or two or more selected from these.

Although the content rate of the solvent in a solution is not specifically limited, It is preferable that it is 5-75 wt%, It is more preferable that it is 10-70 wt%, It is further more preferable that it is 15-65 wt%. If the solvent content is less than the lower limit, depending on the solubility (solubility) of the kneaded product in the solvent, it may be difficult to sufficiently dissolve the kneaded product. On the other hand, when the content of the solvent exceeds the upper limit, the time required for removing the solvent in the subsequent processing becomes longer, and the productivity of the liquid developer is lowered. In addition, if the content of the solvent is too high, components that are sufficiently uniformly mixed may be phase-separated in the above-described kneading step, whereby each toner in the finally obtained liquid developer. It may be difficult to sufficiently reduce the variation in particle characteristics.
In the solution, it is sufficient that at least a part of the components constituting the kneaded material is dissolved (including swelling), and insoluble matter that is not dissolved may exist in the solution.

[Preparation of aqueous emulsion]
Next, an aqueous emulsion is obtained by mixing the above solution with an aqueous liquid. In this aqueous emulsion, the dispersoid containing the solvent and the constituent material of the kneaded material is usually dispersed in an aqueous dispersion medium composed of the aqueous liquid.
In the present invention, the “aqueous liquid” refers to a liquid containing at least water (H ₂ O), and is preferably composed mainly of water. The content of water in the aqueous liquid is preferably 50 wt% or more, preferably 80 wt% or more, and preferably 90 wt% or more. The aqueous liquid may contain components other than water. For example, the aqueous liquid may include a component having excellent compatibility with water (for example, a substance having a solubility in 100 g of water at 25 ° C. of 30 g or more). Examples of such components include alcohol solvents such as methanol, ethanol and propanol, ether solvents such as 1,4-dioxane and tetrahydrofuran (THF), and aromatic heterocyclic compound solvents such as pyridine, pyrazine and pyrrole. Amide solvents such as N, N-dimethylformamide (DMF) and N, N-dimethylacetamide (DMA), nitrile solvents such as acetonitrile, and aldehyde solvents such as acetaldehyde.

Further, for the preparation of the aqueous emulsion (aqueous dispersion), for example, a dispersant may be used for the purpose of improving the dispersibility of the dispersoid. Examples of the dispersant include inorganic dispersants such as tricalcium phosphate, nonionic organic dispersants such as polyvinyl alcohol, carboxymethyl cellulose, and polyethylene glycol, metal tristearate (for example, aluminum salt), and metal distearate. Salt (eg, aluminum salt, barium salt, etc.), stearic acid metal salt (eg, calcium salt, lead salt, zinc salt, etc.), linolenic acid metal salt (eg, cobalt salt, manganese salt, lead salt, zinc salt, etc.) , Octanoic acid metal salts (for example, aluminum salts, calcium salts, cobalt salts, etc.), oleic acid metal salts (for example, calcium salts, cobalt salts, etc.), palmitic acid metal salts (for example, zinc salts, etc.), dodecylbenzenesulfonic acid Metal salts (for example, sodium salts), naphthenic acid metal salts (for example, calcium salts, Baltic salts, manganese salts, lead salts, zinc salts, etc.), resinate metal salts (eg calcium salts, cobalt salts, manganese lead salts, zinc salts etc.), polyacrylic acid metal salts (eg sodium salts), poly Methacrylic acid metal salt (for example, sodium salt), polymaleic acid metal salt (for example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrene sulfonic acid metal salt (for example, Anionic organic dispersants such as sodium salts) and cationic organic dispersants such as quaternary ammonium salts (such as dodecyltrimethylammonium chloride). By using the dispersant as described above for the preparation of the aqueous emulsion, the dispersibility of the dispersoid is improved and the dispersion of the shape and size of the dispersoid in the aqueous emulsion is relatively small. In addition, the shape of the dispersoid can be substantially spherical. As a result, the final liquid developer can be obtained in a substantially spherical shape and composed of toner particles having a uniform shape and size. Further, by using a dispersant as described above for the preparation of the aqueous emulsion, the storage stability of the aqueous emulsion can be made particularly excellent. Mixing of the solution and the aqueous liquid requires at least one of the liquids. It is preferable to carry out with stirring. Thereby, an emulsion (aqueous emulsion) in which a dispersoid having a small variation in size and shape is uniformly dispersed can be easily and reliably obtained.

As a specific method of mixing the solution and the aqueous liquid, for example, a method of adding the solution to the aqueous liquid in the container (for example, a method of dropping), a method of adding the aqueous liquid to the solution in the container (for example, And the like). In these cases, it is preferable to add at least the other liquid to the stirred liquid. Thereby, the effect mentioned above is exhibited more notably.
The content of the dispersoid in the aqueous emulsion is not particularly limited, but is preferably 5 to 55 wt%, and more preferably 10 to 50 wt%. Thereby, the productivity of toner particles (liquid developer) can be made particularly excellent while preventing unintentional bonding (aggregation) between dispersoids in the aqueous emulsion more reliably.

  The average particle size of the dispersoid in the aqueous emulsion is not particularly limited, but is preferably 0.01 to 1.0 μm, and more preferably 0.05 to 0.5 μm. As a result, unintentional bonding (aggregation) between the dispersoids in the aqueous emulsion can be more reliably prevented, and the size of the toner particles finally obtained can be optimized. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.

In the above description, the components in the kneaded product are described as being included in the dispersoid in the aqueous emulsion, but some of the components of the kneaded product may be included in the dispersion medium.
Moreover, components other than the above may be contained in the aqueous emulsion. Examples of such components include a charge control agent and magnetic powder.
Examples of the charge control agent include benzoic acid metal salts, salicylic acid metal salts, alkyl salicylic acid metal salts, catechol metal salts, metal-containing bisazo dyes, nigrosine dyes, tetraphenylborate derivatives, quaternary ammonium salts, Examples thereof include alkyl pyridinium salts, chlorinated polyesters, and nitrohumic acid.

Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides such as Fe, Co, and Ni. The thing comprised with the magnetic material containing a magnetic metal etc. are mentioned.
In addition to the above materials, for example, zinc stearate, zinc oxide, cerium oxide or the like may be added to the aqueous emulsion.

<Aqueous suspension preparation process>
The aqueous emulsion obtained as described above may be used as it is as a spray liquid for producing toner particles, but in this embodiment, an aqueous system (a liquid dispersoid dispersed in an aqueous dispersion medium) is used. An aqueous suspension 3 in which a solid dispersoid 31 is dispersed in a dispersion medium (aqueous dispersion medium) 32 is obtained from the emulsion, and the aqueous suspension 3 is used as a spray liquid for producing toner particles. As a result, inadvertent aggregation between the dispersoids and between the toner particles can be prevented more effectively, and as a result, the uniformity of the shape and size of the toner particles can be made particularly excellent. . Further, deaeration treatment can be performed along with the removal of the solvent, and the formation of irregularly shaped toner particles can be more effectively prevented. Further, along with the removal of the solvent, the aqueous dispersion medium (water) can efficiently penetrate (substitute) into the dispersoid, and as a result, the final toner particles can be obtained with an appropriate water content. .
Hereinafter, a method for preparing the aqueous suspension 3 will be described in detail.

The aqueous suspension 3 can be prepared by removing the solvent constituting the dispersoid from the aqueous emulsion.
The solvent can be removed by, for example, heating (heating) the aqueous emulsion or placing it in a reduced-pressure atmosphere, but it is preferable to remove the solvent by heating the aqueous emulsion under reduced pressure. . Thereby, the aqueous suspension 3 in which the dispersion of the size and shape of the dispersoid 31 is particularly small can be obtained relatively easily. Further, by removing the solvent as described above, deaeration treatment can be performed along with the removal of the solvent. Thereby, the dissolved amount of the gas in the aqueous suspension 3 can be reduced, and the dispersion medium 32 is removed from the droplet 5 of the aqueous suspension 3 in the dispersion medium removing unit M3 of the liquid developer manufacturing apparatus M1. In doing so, it is possible to effectively prevent bubbles and the like from being generated in the aqueous suspension 3. As a result, it is possible to more effectively prevent the irregularly shaped toner particles (hollow particles, missing particles, etc.) from being mixed into the finally obtained liquid developer.

When the aqueous emulsion is heated (warmed), the heating temperature is preferably 30 to 110 ° C, more preferably 40 to 100 ° C. When the heating temperature is a value within the above range, the generation of the irregularly shaped dispersoid 31 is sufficiently prevented (the solvent is surely prevented from evaporating (boiling) from the dispersoid of the aqueous emulsion). However, the solvent can be removed quickly.
Further, when the aqueous emulsion is placed in a reduced pressure atmosphere, the pressure of the atmosphere in which the aqueous emulsion is placed is preferably 0.1 to 50 kPa, and more preferably 0.5 to 5 kPa. When the pressure of the atmosphere in which the aqueous emulsion is placed is a value within the above range, the generation of the irregularly shaped dispersoid 31 is sufficiently prevented (the solvent is rapidly vaporized (boiling from the inside of the dispersoid of the aqueous emulsion). The solvent can be removed quickly, while reliably preventing).

The removal of the solvent may be performed so long as the dispersoid is in a solid state, and may not remove substantially all of the solvent contained in the aqueous emulsion.
The average particle size of the dispersoid 31 in the aqueous suspension 3 is not particularly limited, but is preferably 0.01 to 1.0 μm, and more preferably 0.05 to 0.5 μm. As a result, unintentional bonding (aggregation) between the dispersoids can be prevented more reliably, and the size and circularity of the finally obtained toner particles can be optimized.

<Water-based dispersion spraying process>
Next, an aqueous suspension (aqueous dispersion) 3 is sprayed as droplets 5. As a result, the dispersion medium (aqueous dispersion medium) 32 is removed from the aqueous suspension 3 (droplet 5), and toner particles 8 as aggregates of a plurality of dispersoids 31 contained in the droplet 5 are formed. At the same time, the formed toner particles 8 are directly dispersed in the insulating liquid 9 (aqueous dispersion spraying step). Thereby, the liquid developer 10 in which the toner particles 8 are dispersed in the insulating liquid 9 is obtained. Further, since the dispersion liquid used as the spray liquid is a dispersion medium composed of an aqueous liquid, a liquid developer can be obtained by an environmentally friendly method.

Spraying of the aqueous suspension (aqueous dispersion) may be performed by any method, but it is preferable to intermittently discharge droplets of the aqueous suspension. As a result, the aqueous dispersion medium can be removed more efficiently while effectively preventing unintentional aggregation of the dispersoid, and the productivity of the liquid developer is improved. In addition, even when a part of the solvent remains in the preparation of the aqueous suspension described above, the aqueous dispersion medium is removed by intermittently discharging droplets of the aqueous suspension to remove the aqueous dispersion medium. The remaining solvent can be efficiently removed together with the aqueous dispersion medium.
In particular, in the present embodiment, the aqueous dispersion medium is removed using a liquid developer production apparatus as shown in FIGS.

[Liquid developer production equipment]
As shown in FIG. 2, the liquid developer manufacturing apparatus M1 includes an aqueous suspension (aqueous dispersion) 3 as described above, which intermittently ejects the aqueous suspension 3 as droplets 5, and an aqueous system to the head M2. An aqueous suspension supply unit (aqueous dispersion supply unit) M4 for supplying the suspension 3 and a droplet-form (particulate) aqueous suspension 3 (droplet 5) discharged from the head unit M2 are conveyed. However, it has a dispersion medium removing unit M3 that removes the dispersion medium 32 to form toner particles 8, and an insulating liquid storage unit M5 that stores the insulating liquid 9.

  The aqueous suspension supply unit M4 may have any function as long as it has a function of supplying the aqueous suspension 3 to the head unit M2, but has an agitating means M41 for stirring the aqueous suspension 3 as illustrated. It may be. Thereby, for example, even if the dispersoid 31 is difficult to disperse in the dispersion medium (aqueous dispersion medium) 32, the aqueous suspension 3 in which the dispersoid 31 is sufficiently uniformly dispersed is transferred to the head portion M2. Can be supplied.

The head portion M2 has a function of discharging the aqueous suspension 3 as fine droplets (fine particles) 5.
The head unit M2 includes a dispersion liquid storage unit M21, a piezoelectric element M22, and a discharge unit M23.
The aqueous suspension 3 is stored in the dispersion liquid storage unit M21.

The aqueous suspension 3 stored in the dispersion liquid storage unit M21 is discharged as a droplet 5 from the discharge unit M23 to the dispersion medium removal unit M3 by a pressure pulse (piezoelectric pulse) of the piezoelectric element M22.
As described above, the present invention is characterized in that the dispersion liquid is used as the discharge liquid (spray liquid). Thereby, the following effects are obtained.
That is, by using the dispersion liquid as the discharge liquid, when discharging the discharge liquid (dispersion liquid) from the discharge section, it is selectively cut at the portion of the dispersion medium having a microscopic viscosity and discharged as droplets. The For this reason, the size of the discharged dispersion liquid is small in variation in size among the droplets. Therefore, the toner particles to be formed have small variations in size among the respective particles (toner particles).

  And the droplet discharged from the discharge part becomes spherical shape immediately after discharge by the surface tension of the dispersion medium. Furthermore, the droplets composed of the dispersion liquid contain a large number of dispersoids, and are excellent in shape stability even when transported through the dispersion medium removing unit, and as a whole have a substantially spherical shape. It becomes toner particles in the held state. Therefore, the formed toner particles have a high degree of circularity and a small variation in shape between each particle (between toner particles).

  On the other hand, when a solution or a melt is used as the discharge liquid, such an effect cannot be obtained. That is, since such a discharge liquid has a uniform viscosity even when viewed microscopically, when the liquid is discharged (sprayed) from the discharge portion, the so-called liquid breakage is likely to be in a bad state. Drops tend to have a tail-like shape. Therefore, when a solution or a melt is used as the discharge liquid (spray liquid), the formed toner particles have a large variation in size and shape between each particle (between toner particles), and a small circularity. Easy to be.

In addition, by using a dispersion as a discharge liquid, even when the toner particles to be produced have a sufficiently small particle size, the circularity is easily made sufficiently high and the particle size distribution is sharp. It can be. As a result, the obtained toner has a uniform charge between the particles, and the toner thin layer formed on the developing roller is leveled and densified when the toner is used for printing. Become. As a result, defects such as fog are hardly generated and a sharper image can be formed.
Although the shape of the discharge part M23 is not specifically limited, It is preferable that it is a substantially circular shape. Accordingly, the sphericity of the discharged aqueous suspension 3 and the toner particles 8 formed in the dispersion medium removing unit M3 can be increased.

  When the discharge part M23 is substantially circular, the diameter (nozzle diameter) is, for example, preferably 0.5 to 100 μm, more preferably 0.8 to 50 μm, and 0.8 to More preferably, it is 15 μm. If the diameter of the discharge portion M23 is less than the lower limit value, clogging is likely to occur, and the size variation of the discharged droplets 5 may increase. On the other hand, when the diameter of the discharge part M23 exceeds the upper limit, depending on the force relationship between the negative pressure of the dispersion liquid storage part M21 and the surface tension of the nozzle, the discharged aqueous suspension 3 (droplet 5) There is a possibility of embracing bubbles.

  Further, the vicinity of the discharge portion M23 of the head portion M2 (particularly, the inner surface of the opening of the discharge portion M23 and the surface on the side where the discharge portion M23 of the head portion M2 is provided (the lower surface in the drawing)) The turbid liquid 3 preferably has liquid repellency (water repellency). Thereby, it can prevent effectively that the aqueous suspension 3 adheres to discharge part vicinity. As a result, it is possible to effectively prevent a so-called poor liquid runout or a discharge failure of the aqueous suspension 3. In addition, since the aqueous suspension 3 is effectively prevented from adhering to the vicinity of the discharge portion, the stability of the shape of the discharged droplet is improved (the variation in shape and size among the droplets). The variation in shape and size of the toner particles finally obtained is also reduced.

Examples of such a material having liquid repellency include fluorine resins such as polytetrafluoroethylene (PTFE), silicone materials, and the like.
As shown in FIG. 3, the piezoelectric element M22 includes a lower electrode (first electrode) M221, a piezoelectric body M222, and an upper electrode (second electrode) M223 that are stacked in this order. In other words, the piezoelectric element M22 has a configuration in which the piezoelectric body M222 is interposed between the upper electrode M223 and the lower electrode M221.

The piezoelectric element M22 functions as a vibration source, and the diaphragm M24 vibrates due to the vibration of the piezoelectric element (vibration source) M22 and has a function of instantaneously increasing the internal pressure of the dispersion liquid storage unit M21. It is.
The head unit M2 is in a state where a predetermined ejection signal is not input from a piezoelectric element driving circuit (not shown), that is, a state where no voltage is applied between the lower electrode M221 and the upper electrode M223 of the piezoelectric element M22. Then, the piezoelectric body M222 is not deformed. For this reason, no deformation occurs in the diaphragm M24, and no volume change occurs in the dispersion liquid storage unit M21. Therefore, the aqueous suspension 3 is not discharged from the discharge part M23.

  On the other hand, when a predetermined ejection signal is input from the piezoelectric element drive circuit, that is, when a predetermined voltage is applied between the lower electrode M221 and the upper electrode M223 of the piezoelectric element M22, the piezoelectric body M222 is deformed. Arise. As a result, the diaphragm M24 bends greatly (bends downward in FIG. 3), and the volume of the dispersion liquid storage unit M21 decreases (changes). At this time, the pressure in the dispersion liquid storage part M21 increases instantaneously, and the granular aqueous suspension 3 is discharged from the discharge part M23.

  When one discharge of the aqueous suspension 3 is completed, the piezoelectric element driving circuit stops applying the voltage between the lower electrode M221 and the upper electrode M223. Thereby, the piezoelectric element M22 returns almost to its original shape, and the volume of the dispersion liquid storage part M21 increases. At this time, pressure (pressure in the positive direction) from the aqueous suspension supply unit M4 toward the discharge unit M23 acts on the aqueous suspension 3. For this reason, air is prevented from entering the dispersion liquid storage part M21 from the discharge part M23, and an amount of the aqueous suspension 3 corresponding to the discharge amount of the aqueous suspension 3 is transferred from the aqueous suspension supply part M4 to the dispersion liquid. Supplied to the reservoir M21.

By applying the voltage as described above at a predetermined cycle, the piezoelectric element M22 vibrates and the granular aqueous suspension 3 is repeatedly discharged.
Thus, by discharging (injecting) the aqueous suspension 3 with the pressure pulse generated by the vibration of the piezoelectric body M222, the aqueous suspension 3 can be intermittently discharged one by one. The shape of the droplet 5 of the aqueous suspension 3 is stabilized. As a result, the variation in shape and size among the toner particles can be made particularly small, and the produced toner particles have high sphericity (geometrically close to a perfect sphere). Can be made relatively easy.

Further, by using the vibration of the piezoelectric body to discharge the dispersion liquid (aqueous dispersion liquid), the dispersion liquid can be discharged more reliably at a predetermined interval. For this reason, it is possible to effectively prevent the discharged droplets 5 from colliding with each other and agglomerating, and to more effectively prevent the formation of the irregularly shaped toner particles 8.
The initial velocity of the aqueous suspension 3 (droplet 5) discharged from the head M2 to the dispersion medium removing unit M3 is preferably, for example, 0.1 to 10 m / sec, and is 2 to 8 m / sec. Is more preferable. When the initial speed of the aqueous suspension 3 is less than the lower limit, toner productivity is reduced. On the other hand, when the initial speed of the aqueous suspension 3 exceeds the upper limit, the sphericity of the finally obtained toner particles tends to decrease.

  Further, the viscosity of the aqueous suspension (aqueous dispersion) 3 discharged from the head M2 is not particularly limited, but is preferably 0.5 to 200 [mPa · s], for example, 1 to 25 [mPa · s]. mPa · s] is more preferable. When the viscosity of the aqueous suspension 3 is less than the lower limit, it becomes difficult to sufficiently control the size of the discharged aqueous suspension 3 and the dispersion of finally obtained toner particles becomes large. There is. On the other hand, when the viscosity of the aqueous suspension 3 exceeds the upper limit, the diameter of the formed particles increases, the discharge speed of the aqueous suspension 3 decreases, and the energy required to discharge the aqueous suspension 3 The amount tends to increase. Further, when the viscosity of the aqueous suspension 3 is particularly large, the aqueous suspension 3 cannot be discharged as droplets.

  Further, the aqueous suspension (aqueous dispersion) 3 discharged from the head part M2 may be cooled in advance. By cooling the aqueous suspension 3 in this manner, for example, unintentional evaporation (volatilization) of the dispersion medium 32 from the aqueous suspension 3 in the vicinity of the discharge unit M23 can be effectively prevented. As a result, it is possible to effectively prevent a change in the discharge amount of the aqueous suspension 3 due to the decrease in the opening area of the discharge portion over time, and the variation in size and shape among the particles is particularly small. Toner can be obtained.

  In addition, the average particle diameter of the droplets 5 ejected from the head part M2 is 1.0 to 100 μm, although it varies slightly depending on the content of the dispersoid 31 in the aqueous suspension (aqueous dispersion) 3. Is preferably 1.0 to 50 μm, and more preferably 1.0 to 30 μm. By setting the average particle size of the droplets 5 to a value in such a range, the formed toner particles 8 can have an appropriate particle size.

  Incidentally, the droplets 5 ejected (sprayed) from the head part M2 are generally sufficiently larger than the dispersoid 31 in the aqueous suspension (aqueous dispersion) 3. That is, a large number of dispersoids 31 are dispersed in the droplet 5. For this reason, even if the dispersion of the particle size of the dispersoid 31 is relatively large, the ratio of the dispersoid 31 in the discharged droplets 5 is almost uniform in each droplet 5. Therefore, even when the particle size variation of the dispersoid 31 is relatively large, the toner particles 8 have a small particle size variation among the particles by making the discharge amount of the droplets 5 substantially uniform. It becomes. Such a tendency becomes more prominent when the following relationship is satisfied. That is, when the average particle diameter of the droplets 5 is Dd [μm] and the average particle diameter of the dispersoid 31 in the aqueous suspension 3 is Dm [μm], the relationship of Dm / Dd <0.5 is satisfied. And more preferably satisfy the relationship of Dm / Dd <0.2.

  Further, when the average particle size of the droplets 5 is Dd [μm] and the average particle size of the manufactured toner particles 8 is Dt [μm], the relationship of 0.05 ≦ Dt / Dd ≦ 1.0 is satisfied. It is more preferable that the relationship 0.1 ≦ Dt / Dd ≦ 0.8 is satisfied. By satisfying such a relationship, it is possible to relatively easily obtain toner particles 8 that are sufficiently fine, have a large degree of circularity, and have a sharp particle size distribution.

  The frequency (frequency of the piezoelectric pulse) of the piezoelectric element M22 is not particularly limited, but is preferably 1 kHz to 500 MHz, and more preferably 5 kHz to 200 MHz. When the frequency of the piezoelectric element M22 is less than the lower limit, toner productivity is reduced. On the other hand, when the vibration frequency of the piezoelectric element M22 exceeds the upper limit value, the discharge of the granular aqueous suspension 3 cannot follow, and the variation in size of one drop of the aqueous suspension 3 increases, resulting in formation. There is a possibility that the variation in the size of the toner particles 8 will be increased.

The liquid developer manufacturing apparatus M1 having the illustrated configuration has a plurality of head portions M2. From these head portions M2, granular aqueous suspensions 3 (droplets 5) are discharged to the dispersion medium removing portion M3, respectively.
Each head portion M2 may discharge the aqueous suspension 3 (droplet 5) almost simultaneously, but at least two adjacent head portions discharge the aqueous suspension 3 (droplet 5). It is preferable that the timing is controlled to be different. This more effectively prevents the droplets 5 from colliding with each other before the toner particles 8 are formed from the droplets 5 ejected from the adjacent head part M2, and causing unintentional aggregation. Can do.

  Further, as shown in FIG. 2, the liquid developer manufacturing apparatus M1 has a gas flow supply means M10, and the gas supplied from the gas flow supply means M10 passes through the duct M101 to the head portion M2. -It is the structure which injects with substantially uniform pressure from each gas injection port M7 provided between the head parts M2. As a result, the toner particles 8 can be formed while maintaining the interval between the droplets 5 ejected intermittently from the ejection unit M23 and effectively preventing the droplets 5 from colliding with each other. As a result, variations in the size and shape of the toner particles 8 to be formed can be further reduced.

  Further, by injecting the gas supplied from the gas flow supply means M10 from the gas injection port M7, a gas flow that flows in almost one direction (downward in the figure) can be formed in the dispersion medium removal unit M3. . When such a gas flow is formed, the toner particles 8 formed in the dispersion medium removing unit M3 can be transported more efficiently. Thereby, the collection efficiency of the toner particles 8 is improved, and the productivity of the liquid developer is improved.

Further, when gas is ejected from the gas ejection port M7, an airflow curtain is formed between the droplets 5 ejected from each head unit M2, and, for example, between the droplets ejected from adjacent head units. It is possible to more effectively prevent the collision and aggregation.
A heat exchanger M11 is attached to the gas flow supply means M10. Thereby, the temperature of the gas injected from the gas injection port M7 can be set to a preferable value, and the dispersion medium 32 can be efficiently removed from the granular aqueous suspension 3 discharged to the dispersion medium removal unit M3. Can do.
Further, with such a gas flow supply means M10, the removal rate of the dispersion medium 32 from the aqueous suspension 3 discharged from the discharge unit M23 can be easily adjusted by adjusting the supply amount of the gas flow. It is also possible to control.

  The temperature of the gas injected from the gas injection port M7 varies depending on the composition of the dispersoid 31 and the dispersion medium 32 contained in the aqueous suspension (aqueous dispersion) 3, but is usually 0 to 70 ° C. Is preferable, and it is more preferable that it is 15-60 degreeC. If the temperature of the gas ejected from the gas ejection port M7 is within such a range, the resulting toner particles 8 are contained in the droplets 5 while ensuring sufficiently high uniformity and stability of the shape of the toner particles 8. The dispersion medium 32 can be efficiently removed.

  Further, the humidity of the gas injected from the gas injection port M7 is, for example, preferably 50% RH or less, and more preferably 30% RH or less. When the humidity of the gas injected from the gas injection port M7 is 50% RH or less, the dispersion medium 32 included in the aqueous suspension 3 can be efficiently removed in the dispersion medium removal unit M3 described later. The productivity of the toner particles 8 is further improved.

The dispersion medium removing unit M3 is configured by a cylindrical housing M31. For the purpose of keeping the temperature in the dispersion medium removal unit M3 within a predetermined range, for example, a heat source or a cooling source is installed inside or outside the housing M31, or a flow path for the heat medium or the cooling medium is formed in the housing M31. It may be a jacket.
In the illustrated configuration, the pressure in the housing M31 is adjusted by the pressure adjusting means M12. Thus, by adjusting the pressure in the housing M31, the toner particles 8 can be formed more efficiently, and as a result, the productivity of the liquid developer is improved. In the configuration shown in the figure, the pressure adjusting means M12 is connected to the housing M31 by a connecting pipe M121. Further, an enlarged diameter portion M122 having an enlarged inner diameter is formed in the vicinity of the end portion of the connection pipe M121 connected to the housing M31, and a filter M123 for preventing suction of the toner particles 8 and the like is further provided. ing.

The pressure in the housing M31 is not particularly limited, but is preferably 150 kPa or less, more preferably 100 to 120 kPa, and even more preferably 100 to 110 kPa. When the pressure in the housing M31 is within the above range, for example, rapid removal of the dispersion medium 32 from the droplet 5 (boiling phenomenon) can be effectively prevented, and the irregularly shaped toner particles 8 can be prevented. The toner particles 8 can be produced more efficiently while sufficiently preventing the occurrence of the above. Note that the pressure in the housing M31 may be substantially constant at each part or may be different at each part.
The housing M31 is connected to voltage application means M8 for applying a voltage. By applying a voltage having the same polarity as the toner particles 8 (droplets 5) to the inner surface side of the housing M31 by the voltage applying means M8, the following effects can be obtained.

  Usually, the toner particles 8 and the like are charged positively or negatively. For this reason, if there is a charged substance charged with a polarity different from that of the toner particles 8, a phenomenon occurs in which the toner particles 8 are electrostatically attracted and adhered to the charged substance. On the other hand, if there is a charged material charged to the same polarity as the toner particles 8, the charged material and the toner particles 8 repel each other, effectively preventing the phenomenon that the toner particles 8 adhere to the surface of the charged material. be able to. Therefore, by applying a voltage having the same polarity as the granular toner particles 8 to the inner surface side of the housing M31, it is possible to effectively prevent the toner particles 8 from adhering to the inner surface of the housing M31. Thereby, the generation of the irregularly shaped toner particles 8 can be more effectively prevented, and the recovery efficiency of the toner particles 8 can be improved.

  Further, the housing M31 has an enlarged diameter portion M311 in which the inner diameter increases in the downward direction in FIG. 2 in the vicinity of the insulating liquid storage portion M5. By having such an enlarged diameter portion M311, adhesion of the toner particles 8 to the inner wall surface of the liquid developer manufacturing apparatus M1 (particularly, the inner wall surface of the housing M31 or the insulating liquid storage portion M5) is more effectively prevented. can do. As a result, the production efficiency of the liquid developer 10 is improved, and the irregularly shaped toner particles can be effectively prevented from being mixed into the liquid developer 10, thereby improving the reliability of the liquid developer 10. Can do.

  The toner particles 8 formed in the dispersion medium removing unit M3 (in the housing M31) as described above are usually obtained as aggregates of a plurality of dispersoids 31 contained in the droplets 5. Thereby, even when the dispersion and size of the dispersoid contained in the aqueous dispersion (aqueous suspension) are relatively large, the variation in size and shape among the toner particles is reduced. At the same time, variation in characteristics among the toner particles can be reduced, and as a result, the reliability of the entire liquid developer can be improved.

  In addition, as described above, the toner particles 8 are produced using an aqueous dispersion (aqueous emulsion or aqueous suspension) containing a dispersion medium composed of an aqueous liquid. And the water which comprises an aqueous liquid has a comparatively high boiling point among various liquids, and the vapor pressure near room temperature is comparatively low. For this reason, the toner particles 8 formed in the dispersion medium removing portion M3 (inside the housing M31) are obtained as containing a predetermined amount of moisture while having sufficient shape stability. The present inventors have found that toner particles containing a predetermined amount of water are excellent in fixability to a recording medium such as paper. This is considered to be due to the following reasons.

  That is, since the insulating liquid (carrier) constituting the liquid developer is required to be insulating and have a low dielectric constant, it is generally composed of molecules having a structure having no highly polar functional group. . On the other hand, a recording medium such as paper used for image formation with a liquid developer is usually composed of a material having a hydrophilic functional group (for example, a hydroxyl group) such as cellulose. Therefore, in the conventional liquid developer, if the insulating liquid remains on the surface of the toner particles, the insulating liquid deteriorates the fixing property of the toner particles (adhesion between the toner particles and the recording medium). It was. On the other hand, in the present invention, since the toner particles contain a predetermined amount of water, the water contained in the toner particles exhibits a function of increasing the affinity between the toner particles and the recording medium. As a result, the toner particles The fixing property is excellent.

  In the present invention, since toner particles are obtained as agglomerates of a plurality of dispersoids contained in droplets, an appropriate amount of moisture can be reliably retained in the spaces between the dispersoids constituting the toner particles. it can. As described above, in the liquid developer (unfixed toner particles), moisture can be reliably retained, and the moisture is effectively prevented from leaking outside the toner particles. Further, at the time of fixing, moisture can be efficiently released by the applied pressure or the like, and the adhesion of the toner (toner image) to the recording medium can be made particularly excellent.

  The toner particles 8 need only contain a predetermined amount of water, but preferably contain water that is equal to or greater than the water absorption amount of the resin material constituting the toner particles. Thereby, the fixability of the toner particles 8 to the recording medium can be made particularly excellent. In the present invention, the “water absorption amount” refers to the maximum amount of water held by the toner material itself, and the water absorption amount does not include the adsorption amount (such as the amount adsorbed by the functional group on the resin surface).

  The water content of the toner particles 8 is not particularly limited, but is preferably 0.3 to 5.0 wt%, more preferably 0.5 to 2.5 wt%, and 0.5 to 2. More preferably, it is 0 wt%. When the water content of the toner particles 8 is a value within the above range, the toner particles 8 can have a particularly excellent chargeability on the recording medium while the chargeability of the toner particles 8 is sufficiently good. .

  Then, the toner particles 8 formed as described above are introduced into the insulating liquid reservoir M5 and mixed with the insulating liquid 9 here. As a result, a liquid developer 10 in which the toner particles 8 are dispersed in the insulating liquid 9 is obtained. Thus, in the present invention, the formed toner particles are directly mixed with the insulating liquid without being collected as a powder. As a result, it is possible to sufficiently prevent the toner particles from aggregating and to improve the productivity of the liquid developer.

In the configuration shown in the figure, the insulating liquid storage part M5 has a stirring means M51 for stirring the insulating liquid 9. Accordingly, for example, even when the difference in specific gravity between the insulating liquid 9 and the toner particles 8 is relatively large (for example, the absolute value of the difference in specific gravity is 0.3 g / cm ³ or more), the toner particles 8 are sufficiently The liquid developer 10 can be uniformly dispersed, and a good dispersion state of the toner particles 8 can be stably maintained over a long period of time. Further, it is possible to effectively prevent the toner particles 8 from floating near the liquid surface of the insulating liquid 9 and to effectively prevent the toner particles 8 from aggregating.
The insulating liquid 9 may be a liquid having a sufficiently high insulating property, but specifically, the electrical resistance at room temperature (20 ° C.) is preferably 10 ⁹ Ωcm or more, and preferably 10 ¹¹ Ωcm or more. More preferably, it is more preferably 10 ¹³ Ωcm or more.
Moreover, it is preferable that the dielectric constant of the insulating liquid 9 is 3.5 or less.

  Examples of the insulating liquid 9 that satisfies such conditions include octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, and various silicone oils. Vegetable oil such as linseed oil, soybean oil, Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon), Cielsol 70, Cielsol 71 (Cielsol; trade name of Ciel Oil), Amsco OMS, Examples include Amsco 460 solvent (Amsco; trade name of Spirits).

<Liquid developer>
The liquid developer obtained as described above is excellent in fixability of toner particles to a recording medium. Further, the liquid developer obtained as described above has small variations in the shape and size of the toner particles. Therefore, such a liquid developer easily migrates in the insulating liquid (in the liquid developer), and is advantageous for high-speed development. Further, since the variation in the shape and size of the toner particles is small, the toner particles are excellent in dispersibility, and the toner particles are effectively prevented from settling or floating in the liquid developer. Therefore, such a liquid developer is excellent in long-term stability.

  The average particle diameter of the toner particles 8 in the liquid developer 10 obtained as described above is preferably 0.1 to 5 μm, more preferably 0.4 to 4 μm, and 0.5 to 3 μm. More preferably. When the average particle diameter of the toner particles 8 is within the above range, the variation in characteristics such as charging characteristics and fixing characteristics among the toner particles 8 is particularly small, and the reliability of the liquid developer 10 as a whole is improved. In particular, the resolution of the image formed by the liquid developer (toner) can be sufficiently high while the resolution is high.

  The standard deviation of the particle size between the toner particles 8 constituting the liquid developer 10 is preferably 1.0 μm or less, more preferably 0.1 to 1.0 μm, and more preferably 0.1 to 1.0 μm. More preferably, it is 0.8 μm. As a result, variation in characteristics such as charging characteristics and fixing characteristics among the toner particles 8 is particularly reduced, and the reliability of the liquid developer 10 as a whole is further improved.

  Further, when the average particle size of the dispersoid 31 in the aqueous suspension 3 is Dm [μm] and the average particle size of the toner particles 8 is Dt [μm], 0.005 ≦ Dm / Dt ≦ 0.5. It is preferable to satisfy the relationship, and it is more preferable to satisfy the relationship of 0.01 ≦ Dm / Dt ≦ 0.2. By satisfying such a relationship, the liquid developer 10 can be obtained with a particularly small variation in shape and size between the toner particles 8.

The average value (average circularity) of the circularity R represented by the following formula (I) for the toner particles 8 constituting the liquid developer 10 is preferably 0.85 or more, and 0.90 to More preferably, it is 0.99, and it is further more preferable that it is 0.95-0.99.
R = L ₀ / L ₁ (I)
(Where, L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is a perfect circle having an area equal to the area of the projected image of the toner particles 8 to be measured) Represents the perimeter.)
Thereby, it is possible to make the transfer efficiency and mechanical strength of the toner particles 8 particularly excellent while making the particle diameter of the toner particles 8 sufficiently small.

The standard deviation of the average circularity between the toner particles 8 constituting the liquid developer 10 is preferably 0.15 or less, more preferably 0.001 to 0.10, and 0.001. More preferably, it is -0.05. As a result, variation in characteristics such as charging characteristics and fixing characteristics among the toner particles 8 is particularly reduced, and the reliability of the liquid developer 10 as a whole is further improved.
Next, a preferred embodiment of the image forming apparatus to which the liquid developer of the present invention as described above is applied will be described.

FIG. 4 shows an example of a contact-type image forming apparatus to which the liquid developer of the present invention is applied. The image forming apparatus P1 includes a drum of a cylindrical photosensitive member P2, and after the surface is uniformly charged by a charger P3 made of epichlorohydrin rubber or the like, information to be recorded by a laser diode or the like In accordance with the exposure P4, an electrostatic latent image is formed.
The developing device P10 includes a coating roller P12 and a developing roller P13, part of which is immersed in a developer container P11. The application roller P12 is, for example, a metal gravure roller such as stainless steel, and rotates to face the developing roller P13. Further, a liquid developer coating layer P14 is formed on the surface of the coating roller P12, and the thickness thereof is kept constant by the metering blade P15.

  Then, the liquid developer is transferred from the coating roller P12 to the developing roller P13. The developing roller P13 has a low hardness silicone rubber layer on a roller core P16 made of metal such as stainless steel, and a conductive PFA (polytetrafluoroethylene-perfluorovinyl ether copolymer) resin on the surface thereof. A layer is formed, and rotates at the same speed as the photosensitive member P2 to transfer the liquid developer to the latent image portion. The liquid developer remaining on the developing roller P13 after being transferred to the photoreceptor P2 is removed by the developing roller cleaning blade P17 and collected in the developer container P11.

Further, after the transfer of the toner image from the photoconductor to the intermediate transfer roller, the photoconductor is neutralized by the neutralizing light P21, and the residual transfer toner remaining on the photoconductor is a cleaning made of urethane rubber or the like. It is removed by the blade P22.
Similarly, residual toner remaining on the intermediate transfer roller P18 after transfer from the intermediate transfer roller P18 to the information recording medium P20 is removed by a cleaning blade P23 made of urethane rubber or the like.
After the toner image formed on the photoreceptor P2 is transferred to the intermediate transfer roller P18, a transfer current is passed through the secondary transfer roller P19, and the information recording medium P20 such as paper passing between them. The toner image on the information recording medium P20 such as paper is fixed using the fixing device shown in FIG.

  FIG. 5 shows an example of a non-contact type image forming apparatus to which the liquid developer of the present invention is applied. In the non-contact method, the developing roller P13 is provided with a charging blade P24 made of a phosphor bronze plate having a thickness of 0.5 mm. The charging blade P24 has a function of making frictional charging in contact with the liquid developer layer, and since the application roller P12 is a gravure roll, a developer layer corresponding to the unevenness of the surface of the gravure roll is formed on the development roller P13. Therefore, it functions to uniformly level the unevenness, and the arrangement direction may be either the counter direction or the trail direction with respect to the rotation direction of the developing roller, and may be a roller shape instead of a brate shape.

Further, an interval of 200 μm to 800 μm is provided between the developing roller P13 and the photosensitive member P2, and a frequency of 500 to 3000 Vpp superimposed on a direct current voltage of 200 to 800 V is applied between the developing roller P13 and the photosensitive member P2. An AC voltage of 50 to 3000 Hz is preferably applied. The rest is the same as the image forming apparatus described with reference to FIG.
In FIGS. 4 and 5, image formation using a single color liquid developer has been described. However, when an image is formed using a plurality of color toners, each color image is formed using a plurality of color developing devices. Thus, a color image can be formed.

FIG. 6 is a cross-sectional view of the fixing device, F1 is a heat fixing roll, F1a is a halogen lamp, F1b is a roll base, F1c is an elastic body, F2 is a pressure roll, F2a is a rotating shaft, F2b is a roll base, F2c is an elastic body, F3 is a heat-resistant belt, F4 is a belt tension member, F4a is a protruding wall, F5 is a sheet material, F5a is an unfixed toner image, F6 is a cleaning member, F7 is a frame, F9 is a spring, and L is pressing It is a part tangent.
As shown in the figure, the fixing device F40 includes a heat fixing roll (hereinafter also referred to as a heating roll) F1, a pressure roll F2, a heat-resistant belt F3, a belt stretching member F4, and a cleaning member F6.

  The heat fixing roll F1 is formed by covering a pipe member having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm with a roll base material F1b and an elastic body F1c having a thickness of about 0.4 mm on the outer periphery thereof. 1,050W as a heat source and two columnar halogen lamps F1a are built in and can be rotated counterclockwise as indicated by an arrow in the figure. Further, the pressure roll F2 has a pipe material having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm as a roll base material F2b with a thickness of 0. The elastic body F2c having a thickness of about 2 mm is formed so as to cover the heat fixing roll F1 and the pressure roll F2 with a pressure contact force of 10 kg or less, a nip length of about 10 mm, and disposed opposite the heat fixing roll F1. It can be rotated in the clockwise direction indicated by an arrow.

  Thus, since the outer diameters of the heat fixing roll F1 and the pressure roll F2 are configured to be as small as about 25 mm, the sheet material F5 after fixing does not wrap around the heat fixing roll F1 or the heat-resistant belt F3. A means for forcibly removing the sheet material is not necessary. Further, by providing a PFA layer of about 30 μm on the surface layer of the elastic body F1c of the heat fixing roll F1, the rigidity is improved accordingly. Thereby, although the thicknesses of the elastic bodies F1c and 2c are different, the elastic bodies F1c and 2c are substantially uniformly elastically deformed to form a so-called horizontal nip, and with respect to the peripheral speed of the heat fixing roll F1. Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the sheet material F5, extremely stable image fixing is possible.

  In addition, two halogen lamps F1a and F1a constituting a heating source are built in the heat fixing roll F1, and the heating elements of these halogen lamps F1a and F1a are arranged at different positions. The halogen lamps F1a and F1a are selectively turned on, so that the fixing nip portion where the heat-resistant belt F3 is wound around the heat fixing roll F1 and the portion where the belt stretching member F4 is in sliding contact with the heat fixing roll F1 are different. Temperature control can be easily performed under conditions and different conditions between a wide sheet material and a narrow sheet material.

  The heat-resistant belt F3 is an endless annular belt which is stretched around the outer periphery of the pressure roll F2 and the belt tension member F4 and is movable, and is sandwiched between the heat fixing roll F1 and the pressure roll F2. is there. The heat-resistant belt F3 has a thickness of 0.03 mm or more, and its front surface (the surface on which the sheet material F5 comes into contact) is formed of PFA, and the back surface (contacts with the pressure roll F2 and the belt stretching member F4). It is formed of a seamless tube having a two-layer structure in which the surface on the side to be formed is made of polyimide. The heat-resistant belt F3 is not limited to this, and can be formed of other materials such as a metal tube such as a stainless steel tube or a nickel electroformed tube, or a heat-resistant resin tube such as silicon.

  The belt stretching member F4 is disposed upstream of the fixing nip portion between the heat fixing roll F1 and the pressure roll F2 in the conveying direction of the sheet material F5, and has an arrow P around the rotation axis F2a of the pressure roll F2. It is arranged so that it can swing in the direction. The belt stretching member F4 is configured to stretch the heat-resistant belt F3 in the tangential direction of the heat fixing roll F1 in a state where the sheet material F5 does not pass through the fixing nip portion. If the fixing pressure is large at the initial position where the sheet material F5 enters the fixing nip portion, the entry may not be smoothly performed and the sheet material F5 may be fixed with the leading end of the sheet material F5 broken. By adopting a configuration in which F3 is stretched in the tangential direction of the heat fixing roll F1, an introduction port portion of the sheet material F5 through which the sheet material F5 smoothly enters can be formed, and to the stable fixing nip portion of the sheet material F5. Can enter.

  The belt stretching member F4 is inserted into the inner periphery of the heat-resistant belt F3 and cooperates with the pressure roll F2 to apply a tension f to the heat-resistant belt F3 (the heat-resistant belt F3 is a belt). Sliding on the tension member F4). The belt stretching member F4 is disposed at a position where the heat-resistant belt F3 is wound around the heat fixing roll F1 side from the pressing portion tangent L between the heat fixing roll F1 and the pressure roll F2 to form a nip. The protruding wall F4a protrudes from one end or both ends of the belt stretching member F4 in the axial direction. The protruding wall F4a is formed by the heat-resistant belt F3 when the heat-resistant belt F3 approaches one of the axial ends. The contact to the end of the heat-resistant belt F3 is regulated by contacting the wall F4a. A spring F9 is contracted between the end of the protruding wall F4a opposite to the heat fixing roll F1 and the frame, and the protruding wall F4a of the belt stretching member F4 is lightly pressed by the heat fixing roll F1, so that the belt tension is increased. The frame member F4 is positioned in sliding contact with the heat fixing roll F1.

  In order to stretch the heat-resistant belt F3 with the pressure roll F2 and the belt stretching member F4 and drive it stably with the pressure roll F2, the friction coefficient between the pressure roll F2 and the heat-resistant belt F3 is changed to the belt stretching member. It is good to set larger than the friction coefficient of F4 and heat-resistant belt F3. However, the friction coefficient is such that foreign matter enters between the heat-resistant belt F3 and the pressure roll F2 or between the heat-resistant belt F3 and the belt stretching member F4, or the heat-resistant belt F3, the pressure roll F2, and the belt stretching member. It may become unstable due to wear of the contact portion with F4.

  Therefore, the belt tension member F4 and the heat-resistant belt F3 have a winding angle smaller than the winding angle of the pressure roll F2 and the heat-resistant belt F3, and the diameter of the belt stretching member F4 is smaller than the diameter of the pressure roll F2. Set as follows. As a result, the length that the heat-resistant belt F3 slides on the belt stretching member F4 is shortened, which can be avoided from instability factors such as changes with time and disturbances, and the heat-resistant belt F3 is stably driven by the pressure roll F2. Will be able to.

  Further, a cleaning member F6 is disposed between the pressure roll F2 and the belt stretching member F4. The cleaning member F6 is in sliding contact with the inner peripheral surface of the heat-resistant belt F3, and foreign matter on the inner peripheral surface of the heat-resistant belt F3. It cleans and wear powder. By cleaning the foreign matter, wear powder, and the like in this way, the heat-resistant belt F3 is refreshed, and the above-described factor of instability of the friction coefficient is removed. Further, the belt tension member F4 is provided with a recess F4f, and the recess F4f is suitable for storing foreign matter, abrasion powder, and the like removed from the heat-resistant belt F3.

  The position where the belt tension member F4 is lightly pressed against the heat fixing roll F1 is the nip initial position, and the position where the pressure roll F2 is pressed against the heat fixing roll F1 is the nip end position. Then, the sheet material F5 enters the fixing nip portion from the initial nip position, passes between the heat-resistant belt F3 and the heat fixing roll F1, and exits from the nip end position, whereby an unfixed sheet formed on the sheet material F5. The toner image F5a is fixed, and then discharged in the tangential direction L of the pressing portion of the pressure roll F2 to the heat fixing roll F1.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, each part constituting the liquid developer manufacturing apparatus can be replaced with an arbitrary one that exhibits the same function, or another configuration can be added.
Further, the liquid developer of the present invention is not limited to those applied to the image forming apparatus as described above.

As shown in FIG. 7, an acoustic lens (concave lens) M25 may be installed in the head portion M2. By installing such an acoustic lens M25, for example, the pressure pulse (vibration energy) generated by the piezoelectric element M22 can be converged by the pressure pulse converging unit M26 in the vicinity of the ejection unit M23. As a result, the vibration energy generated by the piezoelectric element M22 can be efficiently used as energy for discharging the aqueous suspension 3. Therefore, even if the aqueous suspension 3 stored in the dispersion liquid storage unit M21 has a relatively high viscosity, it can be reliably discharged from the discharge unit M23. Further, even if the aqueous suspension 3 stored in the dispersion liquid storage unit M21 has a relatively large cohesive force (surface tension), it can be discharged as fine droplets. In addition, the particle diameter of the toner particles 8 can be controlled to a relatively small value.
In this way, by adopting the configuration as shown in the figure, the toner particles 8 can have a desired shape, even when a material having a higher viscosity or a material having a high cohesive force is used as the aqueous suspension 3. Since the size can be controlled, the range of material selection is particularly wide, and a toner having desired characteristics can be obtained more easily.

  Further, in the case of the configuration shown in the figure, since the aqueous suspension 3 is discharged by the converged pressure pulse, the aqueous suspension to be discharged is discharged even when the area (opening area) of the discharge portion M23 is relatively large. The size of the liquid 3 can be made relatively small. That is, even when it is desired to make the particle size of the toner particles 8 relatively small, the area of the discharge portion M23 can be increased. Thereby, even if the aqueous suspension 3 has a relatively high viscosity, it is possible to more effectively prevent the occurrence of clogging in the discharge part M23.

The acoustic lens is not limited to a concave lens, and for example, a Fresnel lens, an electronic scanning lens, or the like may be used.
Furthermore, as shown in FIGS. 8 to 10, a diaphragm member M13 having a converging shape or the like may be disposed between the acoustic lens M25 and the ejection unit M23 toward the ejection unit M23. Thereby, the convergence of the pressure pulse (vibration energy) generated by the piezoelectric element M22 can be assisted, and the pressure pulse generated by the piezoelectric element M22 can be used more efficiently.
In the above-described embodiment, the toner component is described as a solid component contained in the dispersoid. However, at least a part of the toner component may be contained in the dispersion medium.

  In the above-described embodiment, the dispersion liquid (aqueous suspension) is intermittently ejected from the head portion by the piezoelectric pulse. However, another method is used as the dispersion liquid ejection method (spraying method). You can also For example, as a method of discharging (spraying) the dispersion liquid, a spray drying method, a so-called bubble jet (“Bubble Jet” is a registered trademark) method, or the like, “the dispersion liquid is pressed against a smooth surface with a gas flow. A method of spraying the dispersion liquid into droplets using a nozzle that sprays the thin laminar flow as fine droplets apart from the smooth surface (Japanese Patent Application No. 2002-321889). Or the like) ”or the like. The spray drying method is a method of obtaining liquid droplets by spraying (spraying) a liquid (dispersion) using a high-pressure gas. Moreover, as a method to which a so-called bubble jet (“bubble jet” is a registered trademark) method is applied, a method described in the specification of Japanese Patent Application No. 2002-169348 can be cited. That is, as a method for discharging (spraying) the dispersion liquid, a “method for intermittently discharging the dispersion liquid from the head portion by a change in gas volume” can be applied.

  Moreover, the preparation method of the aqueous dispersion as a spray liquid is not limited to the method as described above. For example, by heating a dispersion (suspension) in which a solid state dispersoid is dispersed, the dispersoid is once liquefied to obtain an aqueous emulsion, and the aqueous emulsion is cooled to obtain an aqueous suspension as a spray liquid. A suspension may be obtained. Moreover, you may use an aqueous emulsion as a spray liquid as it is, without making it into a suspension. Even when a suspension is used as the spray liquid, the suspension may be prepared without using an emulsion (aqueous emulsion). For example, a suspension obtained by dispersing a pulverized product of the kneaded material as described above in an aqueous liquid may be used as the spray liquid. Further, the aqueous dispersion as the spray liquid may contain fine particles produced by an emulsion polymerization method as a dispersoid. Thereby, the size of the dispersoid can be made sufficiently small, and the variation in the size of the dispersoid can be reduced. As a result, the variation in shape and size among the toner particles can be particularly reduced.

[1] Production of liquid developer (Example 1)
First, as a self-dispersing resin, a polyester resin having a number of —SO ₃ ^— groups (sulfonic acid Na group) in the side chain (glass transition point: 58 ° C., softening temperature: 120 ° C., water absorption: 0.3 wt% ): 80 parts by weight and a cyan pigment as a colorant (Dainipei Seika Co., Ltd., Pigment Blue 15: 3): 20 parts by weight were prepared. The self-dispersing resin had 0.2 mol of —SO ₃ ^— group in 100 g of the self-dispersing resin.

These components were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.
Next, this raw material (mixture) was kneaded using a twin-screw kneading extruder as shown in FIG.
The total length of the process part of the biaxial kneading extruder was 160 cm.
Moreover, it set so that the temperature of the raw material in a process part might be 125-135 degreeC.

The screw rotation speed was 120 rpm, and the raw material charging speed was 20 kg / hour.
The time required for the raw material to pass through the process part, determined from such conditions, is about 4 minutes.
The kneading as described above was performed while degassing the inside of the process unit by operating a vacuum pump connected to the process unit via a degassing port.

The raw material (kneaded material) kneaded in the process part was extruded outside the biaxial kneading extruder through the head part. The temperature of the kneaded material in the head part was adjusted to 130 ° C.
Thus, the kneaded material extruded from the extrusion port of the biaxial kneading extruder was cooled using a cooling machine as shown in FIG. The temperature of the kneaded material immediately after the cooling step was about 40 ° C.
The cooling rate of the kneaded product was −9 ° C./second. In addition, the time required from the end of the kneading process to the end of the cooling process was 10 seconds.

The kneaded material cooled as described above was coarsely pulverized to obtain a powder having an average particle size of 1.5 mm. A hammer mill was used for coarse pulverization of the kneaded product.
Next, 100 parts by weight of the coarsely pulverized product of the kneaded product is added to 250 parts by weight of toluene, and the mixture is treated for 1 hour using an ultrasonic homogenizer (output: 400 μA), whereby the self-dispersing resin of the kneaded product is obtained. A dissolved solution was obtained. In this solution, the pigment was uniformly finely dispersed.
On the other hand, an aqueous liquid composed of 700 parts by weight of ion-exchanged water was prepared.
The stirring speed of the aqueous liquid was adjusted with a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.).
The above solution (a kneaded toluene solution) was dropped into the agitated aqueous liquid. As a result, an aqueous emulsion in which the dispersoid having an average particle diameter of 0.8 μm was uniformly dispersed was obtained.

  Thereafter, toluene in the aqueous emulsion was removed under the conditions of temperature: 100 ° C. and atmospheric pressure: 80 kPa, and further cooled to room temperature to obtain an aqueous suspension in which solid fine particles were dispersed. In the obtained aqueous suspension, substantially no toluene remained. The solid content (dispersoid) concentration of the obtained aqueous suspension was 29.1 wt%. The average particle size of the dispersoid (solid fine particles) dispersed in the suspension was 0.5 μm. The average particle size of the dispersoid was measured using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.).

  The suspension obtained as described above was charged into the aqueous suspension supply unit of the toner manufacturing apparatus having the configuration shown in FIGS. While stirring the aqueous suspension in the aqueous suspension supply unit with the stirring means, the aqueous suspension was supplied to the head unit by a metering pump and discharged (injected) from the discharge unit to the dispersion medium removal unit. The discharge part had a circular shape with a diameter of 25 μm. Further, as the head portion, a head portion that has been subjected to a hydrophobic treatment with a fluororesin (polytetrafluoroethylene) coat in the vicinity of the discharge portion is used. The temperature of the aqueous suspension in the aqueous suspension supply unit was adjusted to 35 ° C.

  The aqueous suspension is discharged at a dispersion temperature of 35 ° C. in the head, the frequency of the piezoelectric body is 10 kHz, the initial velocity of the dispersion discharged from the discharge is 3 m / second, and the aqueous suspension discharged from the head is used. The discharge amount of one drop of the turbid liquid was adjusted to 2 pl (particle size: 15 μm). In addition, the aqueous suspension was discharged so that the discharge timing of the aqueous suspension was shifted at least between the head portions adjacent to each other among the plurality of head portions.

Further, when discharging the aqueous suspension, air having a temperature of 35 ° C., a humidity of 27% RH, and a flow velocity of 3 m / sec was jetted vertically downward from the gas jetting port. The temperature (atmosphere temperature) in the housing was set to 40 ° C. The pressure in the housing was about 105 kPa. The length of the dispersion medium removing portion (length in the transport direction) was 1.5 m.
Further, a voltage is applied to the housing of the dispersion medium removing unit so that the potential on the inner surface side becomes −100 V so as to prevent the aqueous suspension liquid droplets (toner particles) from adhering to the inner wall. I made it.

In the dispersion medium removing section, the dispersion medium is removed from the droplets of the discharged aqueous suspension, and toner particles are formed and formed as aggregates in which a plurality of dispersoids contained in each droplet are aggregated. The toner particles were introduced into an insulating liquid storage part in which Isopar H (manufactured by Exxon Chemical Co., Ltd.) as an insulating liquid was stored, and stirred with a stirring means to obtain a liquid developer. The water content of the toner particles formed in the dispersion medium removing part was 1.8 wt%. The insulating liquid (Isoper H) had an electric resistance of 10 ¹⁴ Ωcm at room temperature (20 ° C.), and the insulating liquid had a relative dielectric constant of 2.3. Further, the ratio of the toner particles in the liquid developer was 20 wt%.

(Examples 2 to 6)
The amount of toluene used during preparation of the toluene solution of the kneaded product, the stirring conditions of the aqueous liquid during preparation of the aqueous emulsion, the dropping rate of the solution, the temperature of the aqueous suspension in the head, and the amount of air injected from the gas injection port A liquid developer was prepared in the same manner as in Example 1 except that the average particle size of the dispersoid, the content, the water content of the toner particles, and the like were changed as shown in Table 1 by changing the temperature. Was prepared.

(Example 7)
In preparation of a raw material (kneaded material) for toner production, an epoxy resin (glass transition point: 52 ° C., softening temperature: 80.5 ° C., water absorption amount: 0.8%) which is not a self-dispersing resin, instead of the self-dispersing resin. 2 wt%), and a liquid developer was produced in the same manner as in Example 1 except that 0.5 part by weight of dodecyltrimethylammonium chloride as a dispersant was used.

(Example 8)
An aqueous suspension was prepared by an emulsion polymerization method as described below.
A mixed solution of octadecyl methacrylate: 100 g, toluene: 150 g and isopropanol: 50 g was heated to a temperature of 75 ° C. with stirring under a nitrogen stream. 2,2′-Azobis (4-cyanovaleric acid): 30 g was added and reacted for 8 hours. After cooling, it was reprecipitated in 2 liters of methanol, and the white powder was agglomerated and dried. A mixture of the obtained white powder: 50 g, vinyl acetate: 3.3 g, hydroquinone: 0.2 g and toluene: 100 g was heated to a temperature of 40 ° C. and reacted for 3 hours. Next, the temperature was raised to 70 ° C., 100% sulfuric acid: 3.8 × 10 ⁻³ ml was added and reacted for 10 hours. After cooling to 25 ° C. and adding 0.02 g of sodium acetate trihydrate and stirring for 30 minutes, methanol was reprecipitated in 1 liter, agglomerated and dried to obtain a dispersion stabilizing resin.

Next, 12 g of the obtained resin for dispersion stabilization: 100 g of vinyl acetate: 100 g, octadecyl methacrylate: 1.0 g, and Isopar H: 384 g were heated to a temperature of 70 ° C. while stirring under a nitrogen stream. 2,2′-azobis (isovaleronitrile): 0.8 g was added and reacted for 6 hours. 20 minutes after the addition of the initiator, white turbidity occurred, and the reaction temperature rose to 88 ° C. The temperature was raised to 100 ° C. and stirred for 2 hours to distill off unreacted vinyl acetate. After cooling, white latex particles were obtained through a 200-mesh nylon cloth. The average particle was 0.3 μm.
30 g of the above white latex particles were dispersed in water.
A liquid developer was produced in the same manner as in Example 1 except that the aqueous suspension obtained as described above was used as a spray solution.

(Comparative Example 1)
In the same manner as in Example 1, except that the toluene solution prepared in Example 1 was used as the spray liquid instead of the aqueous suspension, fine particles mainly composed of a resin material were dispersed in the insulating liquid. A dispersion was obtained.
Thereafter, the dispersion was stirred and placed in an environment of temperature: 100 ° C. and atmospheric pressure: 80 kPa, thereby obtaining a liquid developer from which toluene was removed.

(Comparative Example 2)
First, a coarsely pulverized kneaded product (average particle size: 1.5 mm) was obtained in the same manner as in Example 1.
Next, this coarsely pulverized product was finely pulverized using a jet mill to obtain a fine powder having an average particle size of 4.5 μm.
Thereafter, 20 parts by weight of the finely pulverized product obtained as described above was mixed with 80 parts by weight of Isopar H (Exxon Chemical Co., Ltd.) and 1 part by weight of a dispersant (dodecyltrimethylammonium chloride). A liquid developer was obtained by dispersing.

(Comparative Example 3)
First, a coarsely pulverized kneaded product (average particle size: 1.5 mm) was obtained in the same manner as in Example 7.
Next, this coarsely pulverized product was finely pulverized using a jet mill to obtain a fine powder having an average particle size of 4.2 μm.
Thereafter, 20 parts by weight of the finely pulverized product obtained as described above was mixed with 80 parts by weight of Isopar H (Exxon Chemical Co., Ltd.) and 1 part by weight of a dispersant (dodecyltrimethylammonium chloride). A liquid developer was obtained by dispersing.

(Comparative Example 4)
First, Isopar H (manufactured by Exxon Chemical) was prepared as an electrically insulating liquid. This electrical insulating liquid had an electric resistance of 10 ¹⁴ Ωcm at room temperature (20 ° C.), and the insulating liquid had a relative dielectric constant of 2.3.
A mixed solution of octadecyl methacrylate: 100 g, toluene: 150 g and isopropanol: 50 g was heated to a temperature of 75 ° C. with stirring under a nitrogen stream. 2,2′-Azobis (4-cyanovaleric acid): 30 g was added and reacted for 8 hours. After cooling, it was reprecipitated in 2 liters of methanol, and the white powder was agglomerated and dried. A mixture of the obtained white powder: 50 g, vinyl acetate: 3.3 g, hydroquinone: 0.2 g and toluene: 100 g was heated to a temperature of 40 ° C. and reacted for 2 hours. Next, the temperature was raised to 70 ° C., 100% sulfuric acid: 3.8 × 10 ⁻³ ml was added, and the reaction was carried out for 10 hours. After cooling to 25 ° C. and adding 0.02 g of sodium acetate trihydrate and stirring for 30 minutes, methanol was reprecipitated in 1 liter, agglomerated and dried to obtain a dispersion stabilizing resin.

  Next, 12 g of the obtained resin for dispersion stabilization: 100 g of vinyl acetate: 100 g, octadecyl methacrylate: 1.0 g, and Isopar H: 384 g were heated to a temperature of 70 ° C. while stirring under a nitrogen stream. 2,2'-azobis (isovaleronitrile): 0.8 g was added and reacted for 6 hours. 20 minutes after the addition of the initiator, white turbidity occurred, and the reaction temperature rose to 88 ° C. The temperature was raised to 100 ° C. and stirred for 2 hours to distill off unreacted vinyl acetate. After cooling, it was diluted with Isopar to obtain a liquid developer.

(Comparative Example 5)
Partially saponified resin of ethylene-vinyl acetate copolymer (trade name: Dumiran C-2280, manufactured by Takeda Pharmaceutical Co., Ltd.): 80 parts by weight of 2-ethylhexanoic acid ester (trade name: Exepal HO, manufactured by Kao Corporation) : Cyan pigment as a colorant (dissolved by Dainichi Seika Co., Ltd., Pigment Blue 15: 3): dissolved in 200 parts by weight when heated, mixed with 20 parts by weight and heated to 80 ° C. Dispersed by Inoue Seisakusho). 70 parts by weight of Isopar H (manufactured by Exxon Chemical Co., Ltd.): 70 parts by weight with stirring and mixing at 7000 rpm with a homogenizer was added to 30 parts by weight of the pigment dispersion solution heated to 40 ° C., and then further with a homogenizer. The mixture was stirred and mixed at 7000 rpm for 30 minutes. Next, a salicylic acid Al salt (trade name: Bontron E-88, manufactured by Orient Chemical Co., Ltd.): A solution prepared by dissolving 1 part by weight in Isopar H: 100 parts was added while stirring and dispersing at 7000 rpm with a homogenizer, and then further added to the homogenizer. The liquid developer was obtained by stirring and dispersing at 7000 rpm for 30 minutes.

(Comparative Example 6)
Table 1 shows the average particle size and content of the dispersoid in the aqueous emulsion by changing the amount of toluene used when preparing the toluene solution of the kneaded product and the stirring conditions of the aqueous liquid during the preparation of the aqueous emulsion. The above implementation is performed except that the droplets to be sprayed are prevented from containing a plurality of dispersoids and the toner particles are formed in a size and shape corresponding to one dispersoid. A liquid developer was prepared in the same manner as in Example 1.

  For each of the above Examples and Comparative Examples, the manufacturing conditions of the liquid developer are shown in Table 1 together with the evaluation of the discharge stability of the dispersion. In addition, the evaluation of the discharge stability of the droplets was “◯” when the droplets having an average particle size variation of less than 20% could be stably discharged over 6 hours or more, and the discharge of the dispersion liquid was started. From 6% to 6% from the start of the discharge of the dispersion, the variation of the average particle diameter of the discharged droplets was 6% from the start of the dispersion discharge. What was 40% or more was shown by "x".

  As is apparent from Table 1, in the present invention, it was possible to stably discharge droplets. In particular, in Examples 1 to 6, it was possible to discharge droplets with particularly excellent stability even though no dispersant was used.

[2] Evaluation Each liquid developer obtained as described above was evaluated for fixing strength, transparency, and storage stability.
[2.1] Fixing Strength Using an image forming apparatus as shown in FIG. 4, an image of a predetermined pattern with a liquid developer obtained in each of the above examples and each of the comparative examples was recorded on a recording paper (manufactured by Seiko Epson Corporation, It was formed on fine paper LPCPPA4). Thereafter, the image formed on the recording paper was thermally fixed by an oven. This heat fixing was performed under the condition of 120 ° C. × 30 minutes.

Thereafter, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) with a pressing load kgf, and the residual ratio of the image density is determined as X -Measured by "X-Rite model 404" manufactured by Rite Inc, and evaluated according to the following four-stage criteria.
○: Image density residual ratio is 90% or more.
Δ: Image density remaining ratio is 70% or more and less than 90%.
X: Image density residual ratio is less than 70%.

[2.2] Transparency Using the image forming apparatus as shown in FIG. 4 and the fixing apparatus as shown in FIG. 6, images of a predetermined pattern using the liquid developers obtained in the respective examples and the comparative examples. Was formed on an OHP sheet (manufactured by A-One, 27081).
Then, the HAZE value was measured with a HAZE meter (manufactured by Nippon Denshoku Industries Co., Ltd., MODEL1001DP), and evaluated according to the following four criteria. The HAZE value is a value obtained by dividing the diffuse transmittance by the total transmittance, and this value becomes smaller as the dispersibility of each component in the toner is better.
A: HAZE value is less than 47.
○: HAZE value is 47 or more and less than 50.
Δ: HAZE value is 50 or more and less than 53.
X: HAZE value is 53 or more.

[2.3] Storage Stability The liquid developers obtained in the above Examples and Comparative Examples were allowed to stand for 6 months in an environment at a temperature of 15 to 20 ° C. Thereafter, the state of the toner in the liquid developer was visually confirmed and evaluated according to the following four criteria.
A: No aggregation or sedimentation of toner particles is observed.
○: Almost no aggregation or sedimentation of toner particles is observed.
Δ: Slight aggregation and sedimentation of toner particles is observed.
X: Aggregation and sedimentation of toner particles are clearly recognized.

These results are shown in Table 2 together with the water content of the toner particles, the average circularity R, the circularity standard deviation, the volume-based average particle diameter, and the particle diameter standard deviation. The circularity was measured using a flow type particle image analyzer (FPIA-2000, manufactured by Toa Medical Electronics Co., Ltd.). However, the circularity R is represented by the following formula (I).
R = L ₀ / L ₁ (I)
(Wherein, L ₁ [μm] is the circumference of the projected image of the particle to be measured, and L ₀ [μm] is the circumference of a perfect circle having an area equal to the area of the projected image of the particle to be measured. To express.)

  As is clear from Table 2, in all of the liquid developers according to the present invention, the circularity of the toner particles is large and the width of the particle size distribution is small. Further, the variation in the shape of the toner particles (standard deviation of circularity) was small. Further, the liquid developer of the present invention was excellent in fixing strength, transparency, and storage stability. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples. In particular, in Comparative Example 6 in which each toner particle corresponds to one dispersoid, the variation in size and characteristic among the toner particles are large, and the reliability of the entire liquid developer is low. .

In addition, the liquid developer was manufactured and evaluated in the same manner as described above except that Pigment Red 122, Pigment Yellow 180, and Carbon Black (Printex L, manufactured by Degussa) were used as the colorant instead of the cyan pigment. As a result, the same result as above was obtained.
Further, the structure in the vicinity of the head portion of the liquid developer manufacturing apparatus is changed from the structure shown in FIG. 3 to the structure shown in FIGS. As a result of the production and evaluation, the same results as above were obtained. Moreover, in the liquid developer manufacturing apparatus provided with the head part as shown in FIGS. 7 to 10, even a dispersion liquid having a relatively high viscosity (a high dispersoid content) could be suitably discharged.

It is a longitudinal cross-sectional view which shows typically an example of a structure of the kneading machine for manufacturing the kneaded material used for preparation of an aqueous emulsion (aqueous dispersion), and a cooler. 1 is a longitudinal sectional view schematically showing a preferred embodiment of a liquid developer production apparatus used for producing a liquid developer of the present invention. FIG. 3 is an enlarged cross-sectional view of the vicinity of a head portion of the liquid developer manufacturing apparatus shown in FIG. 2. 1 is a cross-sectional view illustrating an example of a contact-type image forming apparatus to which a liquid developer of the present invention is applied. 1 is a cross-sectional view illustrating an example of a non-contact type image forming apparatus to which a liquid developer of the present invention is applied. FIG. 3 is a cross-sectional view illustrating an example of a fixing device to which the liquid developer of the present invention is applied. It is a figure which shows typically the other examples of the structure of the head part vicinity of a liquid developer manufacturing apparatus. It is a figure which shows typically the other examples of the structure of the head part vicinity of a liquid developer manufacturing apparatus. It is a figure which shows typically the other examples of the structure of the head part vicinity of a liquid developer manufacturing apparatus. It is a figure which shows typically the other examples of the structure of the head part vicinity of a liquid developer manufacturing apparatus.

Explanation of symbols

K1 ... kneading machine K2 ... process part K21 ... barrel K22, K23 ... screw K24 ... fixing member K25 ... deaeration port K3 ... head part K31 ... internal space K32 ... extrusion port K33 ... cross-sectional area gradually decreasing part K4 ... feeder K5 ... raw material K6 ... Coolers K61, K62, K63, K64 ... Rolls K611, K621, K631, K641 ... Rotating shafts K65, K66 ... Belts K67 ... Discharge part K7 ... Kneaded product M1 ... Liquid developer production apparatus M2 ... Head part M21 ... Dispersion Storage unit M22 ... Piezoelectric element M221 ... Lower electrode M222 ... Piezoelectric body M223 ... Upper electrode M23 ... Discharge unit M24 ... Vibration plate M25 ... Acoustic lens M26 ... Pressure pulse converging unit M3 ... Dispersion medium removing unit M31 ... Housing M311 ... Expanding part M4: aqueous suspension supply unit (aqueous dispersion supply unit) M41: stirring means M5 Insulating liquid storage part M51 ... Stirring means M7 ... Gas injection port M8 ... Voltage application means M10 ... Gas flow supply means M101 ... Duct M11 ... Heat exchanger M12 ... Pressure adjusting means M121 ... Connection pipe M122 ... Expanded diameter part M123 ... Filter M13 ... Squeezing member P ... Pump 3 ... Aqueous suspension (aqueous dispersion) 31 ... Dispersoid 32 ... Dispersion medium (aqueous dispersion medium) 5 ... Droplet 8 ... Toner particle 9 ... Insulating liquid 10 ... Liquid developer P1 ... Image forming apparatus P2 ... Photoconductor P3 ... Charger P4 ... Exposure P10 ... Developer P11 ... Developer container P12 ... Application roller P13 ... Development roller P14 ... Liquid developer application layer P15 ... Metering blade P16 ... Roller core P17 ... developing roller cleaning blade P18 ... intermediate transfer roller P19 ... secondary transfer roller P20 ... information recording medium P21 ... static elimination P22 ... Cleaning blade P23 ... Cleaning blade P24 ... Charging blade F40 ... Fixing device F1 ... Thermal fixing roll (heating roll) F1a ... Column-shaped halogen lamp F1b ... Roll base material F1c ... Elastic body F2 ... Pressure roll F2a ... Rotating shaft F2b ... Roll base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt tension member F4a ... Projection wall F4f ... Recess F5 ... Sheet material F5a ... Unfixed toner image F6 ... Cleaning member F9 ... Spring

Claims (13)

A method for producing a liquid developer in which toner particles are dispersed in an insulating liquid,
Preparing an aqueous dispersion in which a dispersoid composed of a material containing a resin material is dispersed in an aqueous dispersion medium composed of an aqueous liquid;
By spraying the aqueous dispersion as droplets, the aqueous dispersion medium is removed, and toner particles obtained as agglomerates of a plurality of the dispersoids contained in the droplets are recovered as powder. And a step of directly dispersing the insulating liquid in the insulating liquid.   The method for producing a liquid developer according to claim 1, wherein the toner particles contain moisture that is greater than or equal to the water absorption amount of the resin material.   The method for producing a liquid developer according to claim 1, wherein the water content of the toner particles is 0.3 to 5.0 wt%.   The method for producing a liquid developer according to claim 1, wherein an average particle size of the dispersoid in the aqueous dispersion is 0.01 to 1.0 μm.   The method for producing a liquid developer according to claim 1, wherein the droplets have an average particle diameter of 1.0 to 100 μm.   When the average particle size of the dispersoid in the aqueous dispersion is Dm [μm] and the average particle size of the toner particles is Dt [μm], the relationship of 0.005 ≦ Dm / Dt ≦ 0.5 is satisfied. A method for producing a liquid developer according to claim 1.   The relationship of Dm / Dd <0.5 is satisfied, where Dd [μm] is an average particle size of the droplets and Dm [μm] is an average particle size of the dispersoid in the dispersion. 7. A method for producing a liquid developer according to any one of 6 above.   8. The relationship of 0.05 ≦ Dt / Dd ≦ 1.0 is satisfied, where Dd [μm] is the average particle size of the droplets and Dt [μm] is the average particle size of the toner particles. A method for producing a liquid developer according to any one of the above. A step of preparing a kneaded product in which the aqueous dispersion contains the resin material and a colorant; a step of obtaining the solution by dissolving the kneaded product in a solvent capable of dissolving at least a part of the kneaded product; 9. The method for producing a liquid developer according to claim 1, wherein the liquid developer is prepared through a step of dispersing the solution in the aqueous liquid and a step of removing the solvent .   The kneaded product is -SO as a group having a lyophilic property to the aqueous liquid as the resin material. ₃ The method for producing a liquid developer according to claim 9, comprising a self-dispersing resin having a group.   -SO ₃ The method for producing a liquid developer according to claim 10, wherein the group is present in a side chain of the self-dispersing resin.   The -SO contained in the self-dispersing resin ₃ The method for producing a liquid developer according to claim 10 or 11, wherein the number of groups is 0.001 to 0.2 mol with respect to 100 g of the self-dispersing resin.   The method for producing a liquid developer according to claim 10, wherein the content of the self-dispersing resin in the kneaded product is 55 to 95 wt%.

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