JP2011150092A - Method for producing liquid developer and liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer excellent in a charging characteristic of positive charging and to provide a method for producing a liquid developer capable of easily producing such a liquid developer. <P>SOLUTION: The method for producing a liquid developer includes a coarse grinding process of coarsely grinding a resin material comprising a polyester resin and a rosin based resin to provide a coarsely ground material and a wet grinding process of performing wet grinding in an insulating liquid comprising polyalkylene imine and a dispersant. A number-average molecular weight of polyalkylene imine is preferably 300 to 200,000. The polyalkylene imine is preferably polyethylene imine. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

As a developer used to develop the electrostatic latent image formed on the latent image carrier, a toner composed of a material containing a colorant such as a pigment and a binder resin is used as an electrically insulating carrier liquid (insulating property). Liquid developers dispersed in (liquid) are known.
As a binder resin used for toner particles constituting such a liquid developer, a polyester resin is generally widely used (see, for example, Patent Document 1). The polyester resin has high transparency, and when used as a binder resin, it has characteristics that the resulting image has good color developability and high fixing characteristics.
However, since the polyester resin itself is generally of a negative chargeability, it has been difficult to apply it to positively chargeable toner particles (liquid developer). In addition, it is conceivable to add a charge control agent to toner particles that use a polyester resin as a binder resin for positive charging, but it is difficult to obtain a sufficient charge amount.

JP 2007-219380 A

  An object of the present invention is to provide a liquid developer excellent in positive charging characteristics, and to provide a method for producing a liquid developer capable of easily producing such a liquid developer. is there.

Such an object is achieved by the present invention described below.
The method for producing a liquid developer of the present invention is characterized in that a resin material containing a polyester resin and a rosin resin is wet-pulverized in an insulating liquid containing a polyalkyleneimine and a dispersant.
Accordingly, it is possible to provide a method for producing a liquid developer capable of easily producing a liquid developer having excellent positive charging characteristics.

The method for producing a liquid developer of the present invention includes a coarse pulverization step of roughly pulverizing a resin material containing a polyester resin and a rosin resin to obtain a coarsely pulverized product,
A wet pulverization step of wet pulverizing the coarsely pulverized product in an insulating liquid containing a polyalkyleneimine and a dispersant.
Accordingly, it is possible to provide a method for producing a liquid developer capable of easily producing a liquid developer having excellent positive charging characteristics.

In the method for producing a liquid developer of the present invention, the number average molecular weight of the polyalkyleneimine is preferably from 300 to 200,000.
As a result, the surface of the toner particles can be more effectively modified (chemically modified), and aggregation of the toner particles can be effectively prevented by steric hindrance due to the relatively long molecular chain of the polyalkyleneimine. In addition, the dispersion stability of the toner particles can be effectively improved.

In the method for producing a liquid developer according to the present invention, the polyalkyleneimine is preferably polyethyleneimine.
As a result, the surface of the toner particles can be more suitably modified, and the long-term dispersion stability and positive charging characteristics of the toner particles can be further improved.
In the method for producing a liquid developer of the present invention, the softening point of the rosin resin is preferably 60 ° C. or higher and 190 ° C. or lower.
As a result, it is possible to achieve a higher level of toner particle fixing characteristics and heat-resistant storage stability while improving the long-term dispersion stability and charging characteristics of the toner particles.

In the method for producing a liquid developer of the present invention, the rosin resin preferably has a weight average molecular weight of 500 or more and 100,000 or less.
As a result, it is possible to achieve a higher level of toner particle fixing characteristics and heat-resistant storage stability while improving the long-term dispersion stability and charging characteristics of the toner particles.
In the method for producing a liquid developer according to the present invention, the dispersant is preferably a graft copolymer of an acrylic polymer and polysiloxane.
Thereby, the dispersion stability of the toner particles in the insulating liquid can be made particularly excellent.

The liquid developer of the present invention is produced by wet-grinding a resin material containing a polyester resin and a rosin resin in an insulating liquid containing a polyalkyleneimine and a dispersant.
Thereby, it is possible to provide a liquid developer excellent in positive charging characteristics.
The liquid developer of the present invention includes a coarse pulverization step of roughly pulverizing a resin material containing a polyester resin and a rosin resin to obtain a coarsely pulverized product, and the insulating material containing a polyalkyleneimine and a dispersant. And a wet pulverization step of performing wet pulverization in an ionic liquid.
Thereby, it is possible to provide a liquid developer excellent in positive charging characteristics.

1 is a schematic diagram illustrating an example of an image forming apparatus to which a liquid developer of the present invention is applied. FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG. 1.

Hereinafter, preferred embodiments of the present invention will be described in detail.
In the present invention, the liquid developer is one in which toner particles are dispersed in an insulating liquid.
<< Method for Producing Liquid Developer >>
First, a preferred embodiment of the method for producing a liquid developer according to the present invention will be described.
The liquid developer production method of the present embodiment includes a kneading step of kneading a resin material containing a polyester resin and a rosin resin and a colorant to obtain a kneaded product, coarsely pulverizing the kneaded product, and coarsely pulverized product. And a wet pulverization step for obtaining a liquid developer by wet pulverizing the coarsely pulverized product in an insulating liquid containing a polyalkyleneimine and a dispersant.

Thus, the present invention is characterized in that a resin material (coarse pulverized product) containing a polyester resin and a rosin resin is wet-pulverized in an insulating liquid containing a polyalkyleneimine and a dispersant. Yes.
By the way, the polyester resin has high transparency, and when used as a binder resin, the resulting image has good color developability and high fixing characteristics. Therefore, the polyester resin is widely used as a resin material constituting toner particles. However, since the polyester resin itself is normally negatively charged, it is difficult to apply it to positively charged toner particles (liquid developer). In addition, it is conceivable to add a charge control agent to toner particles using a polyester resin for positive charging, but it is difficult to obtain a sufficient charge amount.

On the other hand, in the present invention, as described above, a resin material (coarse pulverized product) containing a polyester resin and a rosin resin is wet-pulverized in an insulating liquid containing a polyalkyleneimine and a dispersant. Thus, the surface of the toner particles can be easily chemically modified with the polyalkyleneimine having a positive charge characteristic, and a liquid developer excellent in the positive charge characteristic can be easily manufactured.
Such an effect cannot be obtained when the resin material is composed only of a polyester resin. That is, when the resin material is composed only of a polyester resin, the surface of the toner particles cannot be sufficiently chemically modified with polyalkyleneimine, and sufficient positive chargeability cannot be exhibited.

Further, when the resin material is composed of only the rosin resin, toner particles having stable characteristics cannot be formed.
After wet pulverization in an insulating liquid containing no polyalkyleneimine, simply adding polyalkyleneimine cannot sufficiently modify the toner particle surface with polyalkyleneimine, resulting in sufficient positive chargeability. It cannot be demonstrated.

Hereinafter, each step will be described in detail.
<Kneading process>
In this step, a resin material containing a polyester resin and a rosin resin, and a toner constituent material such as a colorant are kneaded to obtain a kneaded product.
For the kneading of the toner constituent materials, for example, various kneaders such as a biaxial kneading extruder, a kneader, a batch type triaxial roll, a continuous biaxial roll, a wheel mixer, and a blade type mixer can be used.

[Resin material]
(Polyester resin)
As described above, the polyester resin has high transparency, and when used as a binder resin, the polyester resin is a resin that can enhance the color developability of the obtained image.
It also has a functional group that can be chemically modified with a polyalkyleneimine as described below. However, when the toner particles are composed only of the polyester resin, the surface of the toner particles cannot be chemically modified with a sufficient amount of polyalkyleneimine, and sufficient positive chargeability cannot be exhibited. Therefore, by combining with the rosin resin described later, the surface of the toner particles can be sufficiently chemically modified with polyalkyleneimine while exhibiting the characteristics of using the above-described polyester resin, and the resulting liquid developer is , It exhibits excellent positive chargeability.

The softening temperature of the polyester resin is not particularly limited, but is preferably 50 ° C or higher and 130 ° C or lower, more preferably 50 ° C or higher and 120 ° C or lower, and further preferably 60 ° C or higher and 115 ° C or lower. In the present specification, the softening temperature is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.
The acid value of the polyester resin is preferably 5 mgKOH / g or more and 20 mgKOH / g or less, more preferably 5 mgKOH / g or more and 15 mgKOH / g or less.

  The content of the polyester resin in the resin material is preferably 50 wt% or more and 99 wt% or less, and more preferably 60 wt% or more and 95 wt% or less. As a result, the characteristics obtained by using the above-described polyester resin can be exhibited, and the toner particle surface can be sufficiently chemically modified with polyalkyleneimine. The resulting liquid developer has particularly excellent positive chargeability. Will be demonstrated.

(Rosin resin)
The rosin-based resin is advantageous for improving the fixability of the toner to the recording medium, and is a material that can be easily and reliably modified (chemically modified) by the polyalkyleneimine. In other words, the rosin resin is a material having a large number of functional groups (acidic groups) that are highly reactive with the polyalkyleneimine described later. Therefore, once the rosin resin is modified by the polyalkyleneimine, the polyalkyleneimine and the rosin resin are chemically bonded to each other, so that the polyalkyleneimine is detached and removed from the modified rosin resin. Is very difficult to happen. That is, in the liquid developer obtained by the production method of the present invention, the polyalkylenimine is firmly bonded to the rosin resin (or polyester resin) constituting the toner particles. Accordingly, the toner particles have excellent fixability of the toner particles, and the toner particles have excellent dispersibility, dispersion stability (long-term dispersion stability), and positive charging characteristics of the toner particles in the insulating liquid. can do.
Examples of such rosin resins include rosin-modified phenolic resins, rosin-modified maleic resins, rosin-modified polyester resins, fumaric acid-modified rosin resins, ester gums, etc., and one or more of these are combined. Can be used.

The softening point of the rosin resin as described above is preferably 60 ° C. or higher and 190 ° C. or lower, more preferably 65 ° C. or higher and 170 ° C. or lower, and further preferably 70 ° C. or higher and 160 ° C. or lower. As a result, it is possible to achieve a higher level of toner particle fixing characteristics and heat-resistant storage stability while improving the long-term dispersion stability and charging characteristics of the toner particles.
The weight average molecular weight of the rosin resin is preferably 500 or more and 100,000 or less, more preferably 1000 or more and 80000 or less, and further preferably 1000 or more and 50000 or less. As a result, it is possible to achieve a higher level of toner particle fixing characteristics and heat-resistant storage stability while improving the long-term dispersion stability and charging characteristics of the toner particles.

The acid value of the rosin resin is preferably 40 mgKOH / g or less, more preferably 30 mgKOH / g or less, and further preferably 5 KOH / g or more and 25 mgKOH / g or less. As a result, the surface of the toner base particles can be chemically modified with polyethyleneimine, and the toner particles have excellent long-term dispersion stability and charging characteristics, while the toner particles have excellent fixing characteristics and heat-resistant storage stability. Can be achieved at a higher level.
Further, the content of the rosin resin in the resin material is preferably 1 wt% or more and 50 wt% or less, and more preferably 5 wt% or more and 40 wt% or less. As a result, it is possible to achieve both the fixing characteristics of the toner particles and the heat-resistant storage stability at a higher level while making the long-term dispersion stability and charging characteristics of the toner particles particularly excellent.

[Colorant]
The colorant used in the present invention is not particularly limited, and for example, known pigments and dyes can be used.
[Other ingredients]
Moreover, the kneaded material may contain components other than the above. Examples of such components include known waxes and magnetic powders.
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.

<Coarse grinding process>
Next, the kneaded product obtained in the above step is coarsely pulverized to obtain a coarsely pulverized product.
By using the coarsely pulverized product obtained by roughly pulverizing the kneaded material in this way, the particle size of the toner particles can be reduced more effectively in the wet pulverization step described later. Further, by obtaining a coarsely pulverized product through the kneaded product, it is possible to reduce variations in the characteristics of the toner particles finally formed.

The method of coarse pulverization is not particularly limited, and can be performed using, for example, various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The average particle size of the coarsely pulverized product obtained in the coarse pulverization step is preferably 30 μm or more and 1000 μm or less.
The coarse pulverization step may be performed in multiple steps.

<Wet grinding process (fine grinding process)>
Next, the coarsely pulverized product obtained in the above step is wet-pulverized in an insulating liquid (wet pulverization step). Thereby, toner particles are obtained.
The method of wet pulverization 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 insulating liquid used in this step is a component constituting the finally obtained liquid developer and contains polyalkyleneimine.
In the present invention, the resin material (coarse pulverized product) containing the polyester resin and the rosin resin is wet-pulverized using the insulating liquid containing polyalkyleneimine as described above. Thus, the surface of the toner particles can be chemically modified with polyalkyleneimine while making the average particle size of the obtained toner particles suitable. As a result, a liquid developer having excellent dispersion stability and excellent positive charging characteristics can be obtained.

Thus, by performing wet pulverization, a liquid developer in which toner particles are dispersed in an insulating liquid is obtained.
In addition, wet pulverization may be performed using all of the insulating liquid constituting the liquid developer, or wet pulverization may be performed using a part of the insulating liquid constituting the liquid developer.
Further, for example, after wet pulverization using an insulating liquid containing a dispersant as described later, polyalkyleneimine may be added and further wet pulverization.

Hereinafter, each component will be described.
[Polyalkyleneimine]
Polyalkyleneimine is a compound having a large number of amino groups and can react with acidic groups derived from resin materials (polyester resin, rosin resin) present on the surface of toner particles to chemically modify the surface of toner particles. It is.

Such polyalkyleneimine chemically adheres (bonds) to the surface of the toner particles, so that a large number of positively charged amino groups are present on the surface of the toner particles. It shows the charging characteristics of charging. That is, when the amino group derived from polyalkyleneimine attracts a cation, high positive chargeability can be exhibited. The modification (chemical modification) with polyalkyleneimine is at least a part of amino groups of polyalkyleneimine and at least a part of acidic groups (mainly carboxyl groups) derived from the resin material on the surface of toner particles. Chemically react to form a covalent bond (amide bond), or the acidic group of the resin material and the amino group of the polyalkyleneimine form an ionic bond.
Such a polyalkyleneimine chemically adheres to the surface of the toner particles, so it is difficult to detach from the surface of the toner particles, and the positive charging characteristics of the toner particles can be improved over a long period of time. The toner particles can be stably dispersed in the insulating liquid.

In amino-modified silicones with amino groups (one end, both ends, side chain), the amino group reacts with the acid group on the surface, but around the straight chain structure (side chain, one end, both ends) If the amount of amino is small and the amount of functional groups is increased, the chain length becomes long, causing cross-linking between particles, resulting in a decrease in dispersibility.
Therefore, a structure having a branched structure that bonds to the surface like a network is required even if the amount of functional groups increases structurally, such as polyalkyleneimine.

  Examples of the polyalkyleneimine include polyethyleneimine, polypropyleneimine, polybutyleneimine, polyisopropyleneimine and the like. Of these, polyethyleneimine is preferably used. As a result, the surface of the toner particles can be more suitably modified, and the long-term dispersion stability and positive charging characteristics of the toner particles can be further improved.

  The number average molecular weight of the polyalkyleneimine is preferably 300 to 200,000, more preferably 10,000 to 80,000. When the number average molecular weight of the polyalkyleneimine is in such a range, the toner particle surface can be more effectively modified (chemically modified), and due to steric hindrance due to the relatively long molecular chain of the polyalkyleneimine, Aggregation of the toner particles can be effectively prevented, and the dispersion stability of the toner particles can be effectively improved.

  In addition, the above effects cannot be obtained by simply adding polyalkylenimine to the liquid developer. That is, in a process that generates high energy such as wet pulverization, the surface of the toner particles can be chemically modified by allowing the polyalkyleneimine to be present near the toner particles. If it is simply added to the toner particles, it cannot be present on the surface of the toner particles, and a positively charged characteristic cannot be obtained.

  The average particle size of the toner particles formed by such wet pulverization is preferably from 0.5 μm to 3 μm, more preferably from 1 μm to 2.5 μm, and more preferably from 1 μm to 2 μm. Further preferred. When the average particle diameter of the toner particles is within the above range, the variation in characteristics among the toner particles is small, and the liquid developer as a whole is made highly reliable while being formed with the liquid developer. The resolution of the toner image can be made sufficiently high. Further, it is possible to improve the dispersion of the toner particles in the insulating liquid and to improve the storage stability of the liquid developer. In the present specification, “average particle diameter” refers to an average particle diameter based on volume.

The amount of polyalkyleneimine used in this step is preferably from 0.5 to 50 parts by weight, preferably from 1 to 10 parts by weight, based on 100 parts by weight of rosin resin. More preferred. When the usage amount of the polyalkyleneimine is within the above range, it is possible to reliably prevent inconveniences such as excessive polyalkyleneimine leaching into the insulating liquid in the finally obtained liquid developer. On the other hand, the long-term dispersion stability and positive charging characteristics of the toner particles can be made particularly excellent.
The toner particle content in the liquid developer is preferably 10 wt% or more and 60 wt% or less, more preferably 20 wt% or more and 50 wt% or less.

[Insulating liquid]
The insulating liquid functions as a dispersion medium for dispersing the toner particles as described above.
The insulating liquid has a high insulating property in order to transfer charged toner particles during image formation.
The insulating liquid may be a liquid having a sufficiently high insulating property. Specifically, the electric resistance at room temperature (20 ° C.) is preferably 1 × 10 ⁹ Ωcm or more, and preferably 1 × 10 ¹¹ Ωcm. More preferably, it is more preferably 1 × 10 ¹³ Ωcm or more.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

  As the insulating liquid, for example, KF-99, KF-96, KF-995 (Shin-Etsu Chemical Co., Ltd.), AK35, AK50, AK100, AK350, AK1000 (Such, Wacker Chemie AG), SH200, SH510, SH8400 ( As described above, dimethyl silicone oil such as Toray Dow Corning), silicone oil having a degree of polymerization greater than 20 such as hydrogen-modified silicone compound; cyclic siloxane compound such as cyclopentanesiloxane and decamethylcyclopentanesiloxane, and methyltris (trimethylsiloxy) silane Such as low molecular weight siloxane compounds having a polymerization degree of 20 or less; Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon Chemical Co., Ltd.), Cielsol 70, Cielsol 71 (Cie Lusol; trade name of Ciel Oil), Amsco OMS, Amsco 460 solvent (trade name of Amsco; Spirits), mineral oil (hydrocarbon liquid) such as low viscosity / high viscosity liquid paraffin (Wako Pure Chemical Industries); Fatty acid glycerides, fatty acid monoesters, fatty acid esters such as medium chain fatty acid esters or vegetable oils containing them; octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, Examples thereof include mesitylene, butyl acetate, and isopropanol, and one or more of these can be used in combination.

[Dispersant]
In the wet pulverization step, a dispersant is required in the insulating liquid. As a result, the wet pulverization can be efficiently performed, and the dispersion stability of the obtained toner particles can be further increased.
Such a dispersant is not particularly limited, but it is preferable to use a graft copolymer of an acrylic polymer and polysiloxane (hereinafter referred to as an acrylic-polysiloxane graft copolymer). Thereby, the dispersion stability of the toner particles in the insulating liquid can be made particularly excellent. This is considered to be due to the following reasons.

  That is, the (meth) acryl moiety in the acrylic-polysiloxane graft copolymer has a relatively large polarity due to the carbonyl group in its skeleton. On the other hand, the polysiloxane portion has a relatively small polarity. For this reason, by having each of these parts, the acrylic-polysiloxane graft copolymer is such that the (meth) acrylic part has high affinity with the toner particles, and the polysiloxane part has affinity with the insulating liquid. It will be expensive. Further, since the acrylic-polysiloxane graft copolymer is present between the toner particles and the insulating liquid, the dispersion stability of the toner particles in the insulating liquid is excellent.

The monomer component constituting the acrylic polymer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid; acrylic acid or methacrylic acid derivatives such as alkyl acrylate, alkyl methacrylate, etc. Among these, 1 Species or a combination of two or more can be used.
Moreover, as an acrylic polymer comprised by the monomer component mentioned above, it is 1 or more types of monomers chosen from acrylic acid, methacrylic acid, or those alkylesters, Comprising: Carbon number of the alkyl group is 4 Examples thereof include polymers composed of the following monomers (acrylates).

The acrylic-polysiloxane graft copolymer may include a plurality of types of acrylic polymers.
The acrylic polymer constituting the acrylic-polysiloxane graft copolymer is preferably acrylates and alkyl acrylates, more preferably acrylates and ethylhexyl acrylate. As a result, the effects of the acrylic-polysiloxane graft copolymer as described above can be obtained more remarkably, and the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.
In addition, the acrylic polymer may include a monomer component other than the above.

  Further, the polysiloxane constituting the acrylic-polysiloxane graft copolymer is not particularly limited, and examples thereof include dialkylpolysiloxanes such as dimethylpolysiloxane, diarylpolysiloxanes such as diphenylpolysiloxane, and the like. One kind or a combination of two or more kinds can be used. Among the above, the polysiloxane preferably contains a dialkylsiloxane, more preferably dimethylpolysiloxane. As a result, the effects of the acrylic-polysiloxane graft copolymer as described above can be obtained more remarkably, and the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.

The side chain or terminal of the polysiloxane constituting the acrylic-polysiloxane graft copolymer may be substituted with another functional group or the like. For example, acrylic acid or methacrylic acid may be added to the side chain or terminal of polysiloxane. In this case, the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.
The polysiloxane may be linear or branched.

  The acrylic-polysiloxane graft copolymer is obtained by graft polymerization of an acrylic polymer and polysiloxane. As a result, the acrylic-polysiloxane graft copolymer has many branched chains and is bulky. As a result, a portion having a relatively large polarity (acrylic polymer portion) and a portion having a relatively small polarity (polysiloxane portion) can sufficiently exhibit their functions.

More specifically, examples of the acrylic-polysiloxane graft copolymer as described above include KP-541, KP-575, KP-543, KP-545, KP-549, and the like. One or a combination of two or more can be used.
The acrylic-polysiloxane graft copolymer is preferably contained in an amount of 1 to 40 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the toner base particles. More preferred. Thereby, the effect of the acrylic-polysiloxane graft copolymer can be sufficiently obtained, and the viscosity of the liquid developer can be made appropriate.
The liquid developer of the present invention may contain components other than those described above (for example, external additives).

In the above description, the wet pulverization process is performed after the coarse pulverization process. However, the present invention is not limited to this. For example, a polyester resin, a rosin resin, and a polyalkyleneimine are used as an insulating liquid. The liquid developer may be produced by adding and wet pulverizing.
In the above description, the kneaded material is roughly pulverized. However, the present invention is not limited to this, and the kneaded material may not be used.

<Image forming apparatus>
Next, a preferred embodiment of the image forming apparatus will be described. The image forming apparatus forms a color image on a recording medium using the liquid developer of the present invention as described above.
FIG. 1 is a schematic view showing a second embodiment of an image forming apparatus to which the liquid developer of the present invention is applied, and FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, an intermediate transfer unit 40, a secondary transfer unit (secondary transfer unit) 60, and a fixing unit. (Fixing device) F40 and four liquid developer supply portions 90Y, 90M, 90C, and 90K are provided.
The developing units 30Y, 30M, and 30C develop a latent image with a yellow liquid developer (Y), a magenta liquid developer (M), and a cyan liquid developer (C), respectively, and correspond to each color. It has a function of forming a single color image. The developing unit 30K has a function of developing a latent image with a black liquid developer (K) to form a black single color image.

Since the developing units 30Y, 30M, 30C, and 30K have the same configuration, the developing unit 30Y will be described below.
As shown in FIG. 2, the developing unit 30Y includes a photoconductor 10Y as an example of an image carrier, a charging roller 11Y, an exposure unit 12Y, a development unit 100Y, and a photoconductor along the rotation direction of the photoconductor 10Y. The image forming apparatus includes a body squeeze device 101Y, a primary transfer backup roller 51Y, a charge removal unit 16Y, a photoreceptor cleaning blade 17Y, and a developer recovery unit 18Y.

The photoreceptor 10Y is formed on a cylindrical base material and an outer peripheral surface thereof, has a photosensitive layer made of a material such as amorphous silicon, and is rotatable about a central axis. Rotate clockwise as indicated by the arrow in FIG.
The photoreceptor 10Y is supplied with a liquid developer by a developing unit 100Y described later, and a layer of the liquid developer is formed on the surface.

  The charging roller 11Y is a device for charging the photoconductor 10Y, and the exposure unit 12Y is a device for forming a latent image on the photoconductor 10Y charged by irradiating a laser. The exposure unit 12Y includes a semiconductor laser, a polygon mirror, an F-θ lens, and the like, and charges a modulated laser based on an image signal input from a host computer (not shown) such as a personal computer or a word processor. Irradiate onto the photoconductor 10Y.

The developing unit 100Y is a device for developing the latent image formed on the photoreceptor 10Y using the liquid developer of the present invention. Details of the developing unit 100Y will be described later.
The photoconductor squeeze device 101Y is disposed on the downstream side of the developing unit 100Y in the rotation direction so as to face the photoconductor 10Y. The photoconductor squeeze roller 13Y and the photoconductor squeeze roller 13Y are pressed and slidably attached to the surface. The cleaning blade 14Y removes the liquid developer and the developer collection unit 15Y that collects the removed liquid developer. The photoreceptor squeeze device 101Y has a function of collecting excess carrier (insulating liquid) and originally unnecessary fog toner from the developer developed on the photoreceptor 10Y, and increasing the ratio of toner particles in the visible image.

The primary transfer backup roller 51Y is a device for transferring a single color image formed on the photoreceptor 10Y to an intermediate transfer unit 40 described later.
The neutralization unit 16Y is a device that removes residual charges on the photoreceptor 10Y after the intermediate transfer image is transferred onto the intermediate transfer unit 40 by the primary transfer backup roller 51Y.
The photoconductor cleaning blade 17Y is a rubber member that is in contact with the surface of the photoconductor 10Y, and remains on the photoconductor 10Y after the image is transferred onto the intermediate transfer portion 40 by the primary transfer backup roller 51Y. It has a function of scraping off and removing the liquid developer.
The developer recovery unit 18Y has a function of recovering the liquid developer removed by the photoconductor cleaning blade 17Y.

  The intermediate transfer unit 40 is an endless elastic belt member, and is stretched around a belt driving roller 41 and a pair of driven rollers 44 and 45 to which a driving force of a motor (not shown) is transmitted. The intermediate transfer unit 40 is driven to rotate counterclockwise by the belt driving roller 41 while being in contact with the photoreceptors 10Y, 10M, 10C, and 10K by the primary transfer backup rollers 51Y, 51M, 51C, and 51K.

Further, the intermediate transfer unit 40 is applied with a predetermined tension by a tension roller 49 so that slack is removed. The tension roller 49 is disposed downstream of one driven roller 44 in the rotation (movement) direction of the intermediate transfer unit 40 and upstream of the other driven roller 45 in the rotation (movement) direction of the intermediate transfer unit 40. .
A single color image corresponding to each color formed by the developing units 30Y, 30M, 30C, and 30K is sequentially transferred to the intermediate transfer unit 40 by the primary transfer backup rollers 51Y, 51M, 51C, and 51K, and a single color corresponding to each color is transferred. The images are superimposed. As a result, a full-color developer image (intermediate transfer image) is formed on the intermediate transfer portion 40.

  In the intermediate transfer unit 40, the single-color images formed on the plurality of photoconductors 10Y, 10M, 10C, and 10K are secondarily transferred and superposed one after another. Secondary transfer is performed on a recording medium F5 such as paper, film, or cloth. Therefore, when the toner image is transferred to the recording medium F5 in the secondary transfer process, even if the surface of the recording medium F5 is a sheet material that is not smooth due to fiber or the like, the secondary transfer characteristics follow the surface of the non-smooth sheet material. An elastic belt member is employed as means for improving the above.

The intermediate transfer unit 40 is provided with a cleaning device including an intermediate transfer unit cleaning blade 46, a developer recovery unit 47, and a non-contact type bias applying member 48.
The intermediate transfer portion cleaning blade 46 and the developer recovery portion 47 are arranged on the driven roller 45 side.
The intermediate transfer portion cleaning blade 46 scrapes and removes the liquid developer adhering to the intermediate transfer portion 40 after the image is transferred onto the recording medium F5 by the secondary transfer unit (secondary transfer portion) 60. have.
The developer recovery unit 47 has a function of recovering the liquid developer removed by the intermediate transfer unit cleaning blade 46.

  The non-contact type bias applying member 48 is disposed away from the intermediate transfer unit 40 at a position facing the tension roller 49. The non-contact type bias applying member 48 applies a bias voltage having a polarity opposite to that of the toner to the liquid developer toner (solid content) remaining on the intermediate transfer portion 40 after the secondary transfer. As a result, the toner is discharged, and the electrostatic adhesion force of the toner to the intermediate transfer unit 40 is reduced. In this example, a corona charger is used as the non-contact type bias applying member 48.

  The non-contact type bias applying member 48 is not necessarily disposed at a position facing the tension roller 49. For example, a position between the driven roller 44 and the tension roller 49, such as a position between the driven roller 44 and the intermediate transfer unit. It can be disposed at any position downstream in the movement direction and upstream of the driven roller 45 in the movement direction of the intermediate transfer unit. The non-contact type bias applying member 48 may be a known non-contact type charger other than the corona charger.

An intermediate transfer unit squeeze device 52Y is disposed downstream of the primary transfer backup roller 51Y in the moving direction of the intermediate transfer unit 40.
The intermediate transfer unit squeeze device 52Y is provided as a means for removing excess insulating liquid from the transferred liquid developer when the liquid developer transferred onto the intermediate transfer unit 40 has not reached the desired dispersion state. ing.

The intermediate transfer unit squeeze device 52Y is removed by an intermediate transfer unit squeeze roller 53Y, an intermediate transfer unit squeeze cleaning blade 55Y that presses and slides against the intermediate transfer unit squeeze roller 53Y, and an intermediate transfer unit squeeze cleaning blade 55Y. The developer collecting section 56Y collects the liquid developer.
The intermediate transfer unit squeeze device 52Y has a function of recovering excess insulating liquid from the developer primarily transferred to the intermediate transfer unit 40, increasing the toner particle ratio in the image, and recovering originally unwanted toner. Have.

  The secondary transfer unit 60 includes a pair of secondary transfer rollers that are spaced apart from each other by a predetermined distance along the transfer material movement direction. Of these pair of secondary transfer rollers, the secondary transfer roller disposed upstream of the moving direction of the intermediate transfer unit 40 is the upstream secondary transfer roller 64. The upstream secondary transfer roller 64 can be brought into pressure contact with the belt driving roller 41 via the intermediate transfer unit 40.

Of the pair of secondary transfer rollers, the secondary transfer roller disposed downstream in the moving direction of the transfer material is the downstream secondary transfer roller 65. The downstream secondary transfer roller 65 can be brought into pressure contact with the driven roller 44 via the intermediate transfer unit 40.
That is, the upstream side secondary transfer roller 64 and the downstream side secondary transfer roller 65 bring the recording medium F5 into contact with the intermediate transfer unit 40 that is hung on the belt drive roller 41 and the driven roller 44, respectively. The intermediate transfer image formed by superimposing colors on 40 is secondarily transferred to the recording medium F5.

  In this case, the belt driving roller 41 and the driven roller 44 also function as backup rollers for the upstream side secondary transfer roller 64 and the downstream side secondary transfer roller 65, respectively. That is, the belt drive roller 41 is also used as an upstream backup roller disposed in the secondary transfer unit 60 on the upstream side of the driven roller 44 in the moving direction of the recording medium F5. The driven roller 44 is also used as a downstream backup roller disposed in the secondary transfer unit 60 on the downstream side in the moving direction of the recording medium F5 from the belt driving roller 41.

  Accordingly, the recording medium F5 conveyed to the secondary transfer unit 60 is moved from the pressure contact start position (nip start position) between the upstream side secondary transfer roller 64 and the belt driving roller 41 to the downstream side secondary transfer roller 65 and the driven roller. In close contact with the intermediate transfer portion 40 in a predetermined movement region of the transfer material up to the press-contact end position (nip end position) with 44. As a result, the full-color intermediate transfer image on the intermediate transfer unit 40 is secondarily transferred to the recording medium F5 in close contact with the intermediate transfer unit 40 over a predetermined time, so that good secondary transfer is performed.

  Further, the secondary transfer unit 60 includes a secondary transfer roller cleaning blade 66 and a developer recovery unit 67 with respect to the upstream side secondary transfer roller 64. Further, the secondary transfer unit 60 includes a secondary transfer roller cleaning blade 68 and a developer recovery unit 69 for the downstream side secondary transfer roller 65. The secondary transfer roller cleaning blades 66 and 68 are in contact with the secondary transfer rollers 64 and 65, respectively, and scrape off and remove the liquid developer remaining on the surfaces of the secondary transfer rollers 64 and 65 after the secondary transfer. To do. The developer recovery units 67 and 69 recover and store the liquid developer scraped off from the secondary transfer rollers 64 and 65 by the secondary transfer roller cleaning blades 66 and 68, respectively.

The toner image (transfer image) F5a transferred onto the recording medium F5 by the secondary transfer unit 60 is sent to a fixing unit (fixing device) F40, and is heated and pressurized to be fixed on the recording medium F5.
Specifically, the fixing temperature is preferably 80 to 160 ° C., more preferably 100 to 150 ° C., and further preferably 100 to 140 ° C.

Next, the developing units 100Y, 100M, 100C, and 100K will be described in detail. In the following description, the developing unit 100Y will be typically described.
As shown in FIG. 2, the developing unit 100Y includes a liquid developer storage unit 31Y, a coating roller 32Y, a regulating blade 33Y, a developer stirring roller 34Y, a communication unit 35Y, a recovery screw 36Y, and a developing roller 20Y. And a developing roller cleaning blade 21Y.

The liquid developer storage unit 31Y has a function of storing a liquid developer for developing the latent image formed on the photoreceptor 10Y. The supply unit 31aY supplies the liquid developer to the development unit, and the supply unit A recovery unit 31bY that recovers excess liquid developer generated at 31aY and the like, and a partition 31cY that partitions the supply unit 31aY and the recovery unit 31bY are provided.
The supply unit 31aY has a function of supplying the liquid developer to the application roller 32Y, and has a concave portion in which the developer stirring roller 34Y is installed. Further, the liquid developer is supplied from the liquid developer mixing tank 93Y to the supply unit 31aY through the communication unit 35Y.
The collection unit 31bY collects the liquid developer that is excessively supplied to the supply unit 31aY and excess liquid developer generated in the developer collection units 15Y and 24Y. The collected liquid developer is conveyed to a liquid developer mixing tank 93Y described later and reused. The recovery unit 31bY has a concave portion, and a recovery screw 36Y is installed near the bottom.

A wall-shaped partition 31cY is provided at the boundary between the supply unit 31aY and the recovery unit 31bY. The partition 31cY partitions the supply unit 31aY and the recovery unit 31bY and can prevent the recovered liquid developer from being mixed into the fresh liquid developer. Further, when an excessive liquid developer is supplied to the supply unit 31aY, the excess liquid developer can overflow from the supply unit 31aY to the recovery unit 31bY beyond the partition 31cY. For this reason, the amount of liquid developer in the supply unit 31aY can be kept constant, and the amount of liquid developer supplied to the application roller 32Y can be kept constant. For this reason, the image quality of the finally formed image becomes stable.
Further, the partition 31cY is provided with a notch, and the liquid developer can overflow from the supply part 31aY to the recovery part 31bY through the notch.

The coating roller 32Y has a function of supplying a liquid developer to the developing roller 20Y.
The application roller 32Y is a so-called anilox roller in which grooves are uniformly and spirally formed on the surface of a metallic roller such as iron and nickel-plated, and has a diameter of about 25 mm. . In the present embodiment, a plurality of grooves are formed obliquely with respect to the rotation direction of the application roller 32Y by so-called cutting or rolling. The application roller 32Y contacts the liquid developer while rotating counterclockwise, thereby supporting the liquid developer in the supply unit 31aY in the groove and transporting the supported liquid developer to the developing roller 20Y. To do.

  The regulating blade 33Y is in contact with the surface of the coating roller 32Y and regulates the amount of liquid developer on the coating roller 32Y. That is, the regulation blade 33Y plays a role of scraping off the excess liquid developer on the application roller 32Y and measuring the liquid developer on the application roller 32Y supplied to the development roller 20Y. The restriction blade 33Y is made of urethane rubber as an elastic body, and is supported by a restriction blade support member made of metal such as iron. The regulating blade 33Y is provided on the side where the application roller 32Y rotates and advances from the liquid developer (that is, the right side in FIG. 2). The rubber hardness of the regulation blade 33Y is about 77 degrees according to JIS-A, and the hardness (about 77 degrees) of the contact portion of the regulation blade 33Y with the surface of the coating roller 32Y is about the elasticity of the developing roller 20Y described later. It is lower than the hardness (about 85 degrees) of the pressure contact portion of the body layer to the surface of the application roller 32Y. Further, the excess liquid developer scraped off is collected in the supply unit 31aY and reused.

  The developer stirring roller 34Y has a function of stirring the liquid developer in a uniformly dispersed state. Thus, even when a plurality of toner particles are aggregated, the toner particles can be suitably dispersed. In particular, since the liquid developer of the present invention is excellent in dispersion stability and redispersibility, even a reused liquid developer can be easily dispersed.

  In the supply unit 31aY, the toner particles in the liquid developer have a positive charge, and the liquid developer is stirred by the developer stirring roller 34Y to be in a uniformly dispersed state, and the coating roller 32Y rotates. Thus, the liquid developer is stored in the liquid developer storage unit 31Y, and the amount of the liquid developer is regulated by the regulating blade 33Y and supplied to the developing roller 20Y. In addition, by stirring with the developer stirring roller 34Y, the liquid developer can be stably overflowed to the collection unit 31bY side beyond the partition 31cY, and the liquid developer can be prevented from staying and being compressed. it can.

  Furthermore, the developer stirring roller 34Y is provided in the vicinity of the communication portion 35Y. For this reason, the liquid developer supplied from the communication unit 35Y can quickly diffuse, and even when the liquid developer is supplied to the supply unit 31aY, the liquid level of the supply unit 31aY is stabilized. can do. By providing such a developer agitation roller 34Y in the vicinity of the communication portion 35Y, the communication portion 35Y has a negative pressure, and the liquid developer can be sucked up naturally.

The communication unit 35Y is provided in the vertical direction below the developer stirring roller 34Y, communicates with the liquid developer storage unit 31Y, and sucks the liquid developer from the liquid developer mixing tank 93Y to the supply unit 31aY.
By providing the communication portion 35Y below the developer stirring roller 34Y, the liquid developer supplied from the communication portion 35Y is stopped by the developer stirring roller 34Y, and the liquid upper surface does not rise due to the blowing, and the liquid The upper surface is held substantially constant, and the developer can be stably supplied to the application roller 32Y.
The recovery screw 36Y provided in the vicinity of the bottom of the recovery unit 31bY is made of a cylindrical member, has a spiral rib on the outer periphery, and has a function of maintaining the fluidity of the recovered liquid developer. It has a function of promoting the conveyance of the developer to the liquid developer mixing tank 93Y.

The developing roller 20Y carries the liquid developer and conveys it to the developing position facing the photoconductor 10Y in order to develop the latent image carried on the photoconductor 10Y with the liquid developer.
The developing roller 20Y forms a liquid developer layer on its surface by supplying the liquid developer from the coating roller 32Y described above.
The developing roller 20Y includes a conductive elastic layer on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. The elastic body layer has a two-layer structure. As the inner layer, urethane rubber having a rubber hardness of about 30 degrees JIS-A and a thickness of about 5 mm is used, and as the surface layer (outer layer), the rubber hardness is JIS. A urethane rubber having a thickness of about 30 μm at about 85 ° A is provided. The developing roller 20Y is in pressure contact with the coating roller 32Y and the photoreceptor 10Y in a state of being elastically deformed with the surface layer serving as a pressure contact portion.

Further, the developing roller 20Y can rotate around its central axis, and the central axis is below the rotational central axis of the photoconductor 10Y. Further, the developing roller 20Y rotates in a direction (counterclockwise in FIG. 2) opposite to the rotation direction of the photoreceptor 10Y (clockwise in FIG. 2). When developing the latent image formed on the photoconductor 10Y, an electric field is formed between the developing roller 20Y and the photoconductor 10Y.
In the developing unit 100Y, the coating roller 32Y and the developing roller 20Y are separately driven by different power sources (not shown). The amount of the liquid developer supplied onto the developing roller 20Y can be adjusted by changing the rotation speed (linear speed) ratio between the application roller 32Y and the developing roller 20Y.

  The developing unit 100Y includes a rubber developing roller cleaning blade 21Y that is in contact with the surface of the developing roller 20Y, and a developer recovery unit 24Y. The developing roller cleaning blade 21Y is a device for scraping off and removing the liquid developer remaining on the developing roller 20Y after development is performed at the developing position. The liquid developer removed by the developing roller cleaning blade 21Y is collected in the developer collecting unit 24Y.

  As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes liquid developer replenishing units 90Y, 90M, 90C, and 90K that replenish liquid developer to the developing units 30Y, 30M, 30C, and 30K. . These liquid developer replenishers 90Y, 90M, 90C, and 90K are respectively provided with liquid developer tanks 91Y, 91M, 91C, and 91K, insulating liquid tanks 92Y, 92M, 92C, and 92K, and a liquid developer mixing tank 93Y. , 93M, 93C, 93K.

  Each of the liquid developer tanks 91Y, 91M, 91C, and 91K stores a high concentration liquid developer corresponding to each color. Insulating liquid tanks 92Y, 92M, 92C, and 92K contain insulating liquids, respectively. Further, in each liquid developer mixing tank 93Y, 93M, 93C, 93K, a predetermined amount of each high-concentration liquid developer from each liquid developer tank 91Y, 91M, 91C, 91K, and each insulating liquid tank 92Y, A predetermined amount of each insulating liquid from 92M, 92C, and 92K is supplied.

  The liquid developer mixing tanks 93Y, 93M, 93C, and 93K are respectively mixed and stirred by the stirrers provided with the supplied high-concentration liquid developer and the insulating liquid, respectively, and the supply units 31aY. , 31aM, 31aC, and 31aK, a liquid developer corresponding to each color is prepared. The liquid developers prepared in the liquid developer mixing tanks 93Y, 93M, 93C, and 93K are supplied to the supply units 31aY, 31aM, 31aC, and 31aK, respectively.

  Further, the liquid developer recovered by the recovery unit 31bY is recovered and reused in the liquid developer mixing tank 93Y. The same applies to the liquid developer mixing tanks 93M, 93C, and 93K. Here, as described above, the surface of the toner base particles containing the rosin resin is modified with polyalkyleneimine, and the toner particles are firmly bonded to the surface of the toner base particles. ing. For this reason, even when the toner particles are subjected to stress accompanying recovery (for example, stress due to a cleaning blade), the polyalkyleneimine is reliably prevented from detaching / dropping from the toner base particles, The toner particles as described above have high redispersibility in the insulating liquid. Therefore, the collected toner particles can be suitably reused for image formation.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, the liquid developer of the present invention is not limited to that applied to the image forming apparatus as described above.
In the above-described embodiment, the configuration having the corona discharger as the image forming apparatus has been described. However, the corona discharger may be omitted.

[1] Production of Liquid Developer A liquid developer was produced as follows. About the process in which temperature is not described, it performed at room temperature (25 degreeC).
Example 1
[Coarse grinding process]
(Preparation of colorant masterbatch)
First, as a resin material, a polyester resin (acid value: 10 mgKOH / g, glass transition point (Tg): 55 ° C., softening point: 107 ° C.): 60 parts by weight was prepared.

Next, a mixture (mass ratio 50:50) of the resin material and a cyan pigment as a colorant (manufactured by Dainichi Seika Co., Ltd., Pigment Blue 15: 3) was prepared. 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. The kneaded product extruded from the extrusion port of the biaxial kneading extruder was cooled.
The kneaded material cooled as described above was coarsely pulverized to obtain a colorant master batch having an average particle size of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.

(Preparation of coarsely pulverized product)
15 parts by weight of the above colorant master batch, 68 parts by weight of the above polyester resin, rosin-modified male resin (manufactured by Arakawa Chemical Industries, trade name “Marquide No. 1”, acid value: 25 mgKOH / g or less, softening point: 120 ˜130, weight average molecular weight: 3100): 17 parts by weight were kneaded using a biaxial kneading extruder. And the kneaded material extruded from the extrusion port of the biaxial kneading extruder was cooled. The obtained kneaded product was pulverized with a hammer mill to obtain a coarsely pulverized product.

[Wet grinding process]
Coarse pulverized product obtained by the above method: 40 parts by weight, acrylic-polysiloxane graft copolymer solution as a dispersant (KP-545, manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethyl poly Siloxane, solvent: decamethylcyclopentanesiloxane, solid content: 30 wt%): 40 parts by weight, dimethyl silicone oil as an insulating liquid (KF-96, manufactured by Shin-Etsu Chemical Co., Ltd., 50 cs): 150 parts by weight, polyethyleneimine ( Number average molecular weight: 1800); 3 parts by weight are placed in a ceramic pot (internal volume 600 ml), and zirconia balls (ball diameter: 10 mm) are placed in a ceramic pot so that the volume filling rate is 40%. Then, wet pulverization was performed at a rotational speed of 230 rpm for 48 hours. As a result, a liquid developer was obtained.

The Dv (50) of the toner particles in the obtained liquid developer was 2.31 μm. The 50% volume particle diameter Dv (50) [μm] of the obtained toner particles was measured with Microtrac MT-3000 (manufactured by Nikkiso Co., Ltd.). Moreover, the particle diameter was similarly calculated | required about the particle | grains obtained by each Example and each comparative example demonstrated below.
Further, the viscosity of the obtained liquid developer at 25 ° C. was 100 mPa · s.

  Further, instead of cyan pigment, magenta pigment: Pigment Red 238 (manufactured by Sanyo Dye), yellow pigment: Pigment Yellow 180 (manufactured by Clariant), black pigment: carbon black (printex L, manufactured by Degussa) In addition, a magenta liquid developer, a yellow liquid developer, and a black liquid developer were produced in the same manner as described above except that the respective changes were made.

(Examples 2 to 20)
Example 1 except that the type and content of rosin resin, the content of polyester resin, the molecular weight and amount of polyethyleneimine, the type of dispersant, the type of insulating liquid, etc. were changed as shown in Table 1. In the same manner, liquid developers corresponding to the respective colors were produced.
(Comparative Example 1)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the rosin resin was not used and the amount of the polyester resin used was increased accordingly.

(Comparative Example 2)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that no polyethyleneimine was added.
(Comparative Example 3)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the dispersant was not added.

  Table 1 shows the manufacturing conditions such as the resin material, polyethyleneimine, type of dispersant, type of insulating liquid, etc. used in the preparation of the liquid developer for the above Examples and Comparative Examples. In the table, rosin-modified polyester resin (manufactured by Arakawa Chemical Industries, trade name “TFS-015”, acid value: 11.8 mg KOH / g, softening point: 79 ° C., weight average molecular weight: 1300) is RPES and rosin. Modified phenolic resin (Arakawa Chemical Industries, trade name “Tamanol 135”, acid value: 18 mg KOH / g or less, softening point: 130 to 140, weight average molecular weight: 15000) RPH and rosin modified maleic resin (Arakawa Chemical Industries) Product name "Marquide No. 1", acid value: 25 mgKOH / g or less, softening point: 120 to 130, weight average molecular weight: 3100), RM, acrylic-polysiloxane graft copolymer (KP-545, Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: decamethylcyclopentanesiloxane , Solid content: 30 wt. Eulio, trade name “High Oleic Rapeseed Oil”) is indicated as NT, soybean oil fatty acid methyl (Nisshin Oillio) as ME, and Cosmo White P70 (insulating liquid) as P70.

[2] Evaluation Each liquid developer obtained as described above was evaluated as follows.
[2.1] Developing efficiency Using the image forming apparatus as shown in FIGS. 1 and 2, the liquid developer by the liquid developer obtained in each of the embodiments and comparative examples on the developing roller of the image forming apparatus. A layer was formed. Next, the surface potential of the developing roller was set to 300V, the surface potential of the photoconductor was uniformly charged at 500V, the photoconductor was exposed, the charge on the surface of the photoconductor was attenuated, and the surface potential was set to 50V. The toner particles on the developing roller and the toner particles on the photosensitive member after the liquid developer layer passed between the photosensitive member and the developing roller were collected with a tape. Each tape used for sampling was affixed on a recording paper, and the concentration of each toner particle was measured. After the measurement, the value obtained by dividing the concentration of toner particles collected on the photoreceptor by the sum of the concentration of toner particles collected on the photoreceptor and the concentration of toner particles collected on the developing roller is multiplied by 100. Was determined as development efficiency, and evaluated according to the following four-stage criteria.
A: The development efficiency is 96% or more, and the development efficiency is particularly excellent.
B: The development efficiency is 90% or more and less than 96%, and the development efficiency is excellent.
C: The development efficiency is 80% or more and less than 90%, and there is no practical problem.
D: The development efficiency is less than 80% and the development efficiency is inferior.

[2.2] Transfer efficiency Using the image forming apparatus as shown in FIGS. 1 and 2, a liquid developer using the liquid developer obtained in each of the above examples and comparative examples on the photoreceptor of the image forming apparatus. A layer was formed. Next, the toner particles on the photoconductor and the toner particles on the intermediate transfer portion after the liquid developer layer passed between the photoconductor and the intermediate transfer portion were collected with a tape. Each tape used for sampling was affixed on a recording paper, and the concentration of each toner particle was measured. After the measurement, a value obtained by dividing the concentration of the toner particles collected on the intermediate transfer portion by the sum of the concentration of the toner particles collected on the photoconductor and the concentration of the toner particles collected on the intermediate transfer portion is 100. A value obtained by multiplying by is obtained as transfer efficiency, and evaluated according to the following four criteria.
A: The transfer efficiency is 96% or more, and the transfer efficiency is particularly excellent.
B: The transfer efficiency is 90% or more and less than 96%, and the transfer efficiency is excellent.
C: The transfer efficiency is 80% or more and less than 90%, and there is no practical problem.
D: Transfer efficiency is less than 80% and inferior to transfer efficiency.

[2.3] Fixing Strength Using an image forming apparatus as shown in FIGS. 1 and 2, an image of a predetermined pattern with a liquid developer obtained in each of the examples and the comparative examples is recorded on a recording paper (Seiko Epson). It was formed on a high-quality paper LPCPPA4) manufactured by the company. Thereafter, the fixing temperature was set to 100 ° C., and thermal fixing was performed.
Then, 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.) twice with a pressing load of 1.2 kgf, and the remaining ratio of image density Was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.

A: Image density residual ratio is 96% or more (very good).
B: Image density residual ratio is 90% or more and less than 96% (good).
C: Image density remaining rate is 80% or more and less than 90% (normal).
D: Image density residual ratio is 70% or more and less than 80% (slightly bad).
E: Image density residual ratio is less than 70% (very bad).

[2.4] Charging characteristics of positive charge For the liquid developers obtained in each of the examples and comparative examples, the potential difference was measured using a “microscopic laser zeta electrometer” ZC-2000 manufactured by Microtic Nichion. The evaluation was made according to the following five criteria.
Measurement is performed by diluting the liquid developer with a diluting solvent, placing it in a 10 mm transparent cell, applying a voltage of 300 V at 9 mm between the electrodes, and simultaneously observing the moving speed of the particles in the cell with a microscope. Was obtained by calculating the zeta potential from the calculated value.

A: The potential difference is +100 mV or more (very good).
B: Potential difference is +85 mV or more and less than +100 mV (good).
C: The potential difference is +70 mV or more and less than +85 mV (normal).
D: The potential difference is +50 mV or more and less than +70 mV (somewhat bad).
E: Potential difference is less than +50 mV (very bad).

[2.5] Dispersion stability test [2.5.1] Method 1
10 mL of the liquid developer obtained in each example and each comparative example was placed in a test tube (12 mm in diameter and 120 mm in length), and the settling depth after standing for 10 days was measured. According to the following four-stage criteria evaluated.
A: Settling depth is 0 mm.
B: The settled depth is greater than 0 mm and 2 mm or less.
C: The settled depth is larger than 2 mm and 5 mm or less.
D: The settled depth is larger than 5 mm.

[2.5.2] Method 2
45.5 mL of the liquid developer obtained in each example and each comparative example was put into a centrifuge tube, and a centrifuge (Kokusan Co., Ltd.) was used under the conditions of a rotation radius of 5 cm, a rotation speed of 500, 1000, 2000, 4000, 5000 rpm for 3 minutes. The depth of sedimentation at each rotational speed was measured.
Centrifugal acceleration rω ² (rω ² = 1118 × rotation radius (cm) × number of revolutions per minute (rpm) ² × 10 ⁻⁸ × g (gravity acceleration)) is taken on the horizontal axis, and the sedimentation depth is taken on the vertical axis. Plotted based on the measurement results. Based on each plot, the slope k was determined by first-order approximation and evaluated according to the following criteria. It can be said that the lower the value of k, the higher the dispersion stability.
A: 0 ≦ k <0.004
B: 0.004 ≦ k <0.008
C: 0.008 ≦ k <0.012
D: k ≧ 0.012

[2.6] Recyclability 10,000 images of a predetermined pattern are obtained using the liquid developers obtained in each of the examples and the comparative examples, respectively, using an image forming apparatus as shown in FIGS. Recording paper (manufactured by Seiko Epson Corporation, high-quality paper LPCPPA4). This image formation was performed in a state where supply of the liquid developer from the liquid developer tank of each color to the corresponding stirring device of each color was stopped. After image formation on 10,000 sheets of recording paper, a liquid developer (recycled) regenerated by diluting the toner particles collected in the stirring device with an insulating liquid so that the solid content is 20 wt% The liquid developer was tested by the following two methods (Method 1 and Method 2) to evaluate the adaptability (recyclability) for recycling.

[2.6.1] Method 1
10 mL of the recycled liquid developer for each Example and each Comparative Example was put in a test tube (12 mm in diameter and 120 mm in length), and the sedimentation depth after standing for 10 days was measured and evaluated according to the following four criteria. did.
A: Settling depth is 1 mm or less.
B: The settled depth is larger than 1 mm and 3 mm or less.
C: The settled depth is larger than 3 mm and 6 mm or less.
D: The settled depth is larger than 6 mm.

[2.6.2] Method 2
Recycled liquid developer 45.5 mL for each example and each comparative example was put in a centrifuge tube, and a centrifuge (manufactured by Kokusan Co., Ltd.) under conditions of a rotation radius of 5 cm, a rotation speed of 500, 1000, 2000, 4000, 5000 rpm for 3 minutes. ), The sedimentation depth at each rotational speed was measured.
Centrifugal acceleration rω ² (rω ² = 1118 × rotation radius (cm) × number of revolutions per minute (rpm) ² × 10 ⁻⁸ × g (gravity acceleration)) is taken on the horizontal axis, and the sedimentation depth is taken on the vertical axis. Plotted based on the measurement results. Based on each plot, the slope k was determined by first-order approximation and evaluated according to the following criteria. It can be said that the lower the value of k, the higher the dispersion stability.

A: 0 ≦ k <0.006
B: 0.006 ≦ k <0.010
C: 0.010 ≦ k <0.014
D: k ≧ 0.014
These results are shown in Table 2.

As is apparent from Table 2, the liquid developer of the present invention was excellent in charging characteristics (positive charging characteristics) and long-term dispersion stability of toner particles. The liquid developer of the invention was also excellent in recyclability. The liquid developer of the present invention was also excellent in development efficiency, transfer efficiency, and fixing strength. On the other hand, satisfactory results were not obtained with the liquid developer of the comparative example.
In addition, recording paper (manufactured by Seiko Epson Corporation) is supplied by the image forming apparatus as shown in FIGS. 1 and 2 so that the liquid developer is supplied from the liquid developer mixing tank of each color to the supply unit of each corresponding color. As a result of continuous image formation of 50000 sheets on high-quality paper LPCPPA4), in the present invention, an image with excellent image quality could be formed even on the 50000th sheet, whereas no deterioration in image quality was observed. In the comparative example, a clear decrease in image quality was observed.

  In addition, the dispersant of Example 1 was changed to KP-575 (acrylic-polysiloxane graft copolymer solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: acrylates / ethylhexyl acrylate / dimethyldimethylpolymethacrylate, solvent: deca Methylcyclopentanesiloxane, solid content: 30 wt%), KP-543 (acrylic-polysiloxane graft copolymer solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: butyl acetate) , Solid content: 50 wt%)), KP-549 (acrylic-polysiloxane graft copolymer solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: methyltris (trimethylsiloxy) silane) , Solid content: 40 wt%)), KP-550 (acrylic-poly Resiloxane graft copolymer solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: isododecane, solid content: 40 wt%), KP-541 (acrylic-polysiloxane graft copolymer) Each of the combined developers (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: isopropanol, solid content: 60 wt%)) was produced, and each liquid developer When the same evaluation as above was performed, the same evaluation was obtained.

  1000: Image forming apparatus 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y ... Exposure unit 13M, 13Y ... Photoconductor squeeze roller 14M, 14Y ... Cleaning blade 15M, 15Y ... Developer recovery unit 16Y ... Static elimination unit 17Y ... Photoconductor cleaning blade 18Y ... Developer collection unit 20Y, 20M, 20C, 20K ... Development roller 21Y ... Development roller cleaning blade 24Y ... Developer collection unit 30Y, 30M, 30C, 30K ... Development unit 31Y ... Liquid developer storage unit 31aY ... Supply unit 31bY ... Recovery unit 31cY ... Partition 32Y ... Applying roller 33Y ... Regulator blade 34Y ... Developer stirring roller 35Y ... Communication unit 36Y ... Recovery screw 40 ... Intermediate transfer unit 41 ... Belt drive roller 49 ... Tension Rollers 44, 45 ... driven roller 46 ... intermediate transfer portion cleaning blade 47 ... developer recovery portion 48 ... non-contact type bias applying member 51Y, 51M, 51C, 51K ... primary transfer backup roller 52Y, 52M, 52C, 52K ... intermediate Transfer unit squeeze device 53Y ... Intermediate transfer unit squeeze roller 55Y ... Intermediate transfer unit squeeze cleaning blade 56Y ... Developer recovery unit 60 ... Secondary transfer unit 64 ... Upstream side secondary transfer roller 65 ... Downstream side secondary transfer roller 66, 68 ... secondary transfer roller cleaning blade 67, 69 ... developer recovery unit 90Y, 90M, 90C, 90K ... liquid developer replenishment unit 91Y, 91M, 91C, 91K ... liquid developer tank 92Y, 92M, 92C, 92K ... insulation Liquid tank 93Y, 93M, 93C, 9 3K: Liquid developer mixing tank 100Y: Development unit 101Y: Photoconductor squeeze device F40: Fixing unit (fixing device) F5: Recording medium

Claims (9)

  A method for producing a liquid developer, comprising wet-grinding a resin material containing a polyester resin and a rosin resin in an insulating liquid containing a polyalkyleneimine and a dispersant. A coarse pulverization step of roughly pulverizing a resin material containing a polyester resin and a rosin resin to obtain a coarse pulverized product
And a wet pulverization step of wet pulverizing the coarsely pulverized product in an insulating liquid containing a polyalkyleneimine and a dispersant.   The method for producing a liquid developer according to claim 1, wherein the polyalkyleneimine has a number average molecular weight of 300 or more and 200,000 or less.   The method for producing a liquid developer according to claim 1, wherein the polyalkyleneimine is polyethyleneimine.   The method for producing a liquid developer according to claim 1, wherein the rosin resin has a softening point of 60 ° C. or higher and 190 ° C. or lower.   6. The method for producing a liquid developer according to claim 1, wherein the rosin resin has a weight average molecular weight of 500 or more and 100,000 or less.   The method for producing a liquid developer according to claim 1, wherein the dispersant is a graft copolymer of an acrylic polymer and polysiloxane.   A liquid developer produced by wet pulverizing a resin material containing a polyester resin and a rosin resin in an insulating liquid containing a polyalkyleneimine and a dispersant.   Coarse pulverization of a resin material containing a polyester resin and a rosin resin to obtain a coarse pulverized product, and wet pulverization of the coarsely pulverized product in an insulating liquid containing a polyalkyleneimine and a dispersant A liquid developer produced by a production method comprising a pulverization step.

Images