JP2011053511A - Liquid developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer having excellent positively charged charge characteristics of toner particles, excellent developing efficiency and excellent long-preservation, and to provide an image forming apparatus using the liquid developer. <P>SOLUTION: This liquid developer includes: toner particles, an insulating liquid containing a hydrogen modified silicone compound with the toner particles dispersed therein; and a graft copolymer of acrylic polymer and polysiloxane. In the toner particles, the surfaces are preferably modified by polyalkylene imine. Preferably resin material contains rosin resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid developer and an image forming apparatus.

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 (insulating 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. Further, the dry toner has a problem that the particles are likely to aggregate and it is difficult to sufficiently reduce the size of the toner particles, and it is difficult to form a toner image with high resolution. 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, the toner particles are effectively prevented from aggregating in the liquid developer, so that fine toner particles can be used, and a dry toner is used as the binder resin. A resin material having a lower softening point (lower softening temperature) than the resin material used 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.

As such a liquid developer, for example, an insulating liquid using silicone oil is known (see, for example, Patent Document 1).
However, with a liquid developer using silicone oil as an insulating liquid, toner particles cannot be sufficiently charged, development efficiency is lowered, and a toner image having a sufficiently uniform image density is stably formed. I couldn't. There are also attempts to improve the charging characteristics by adding a charge control agent, a dispersing agent, etc., but sufficient charging characteristics could not be obtained. In particular, the problem as described above is remarkable in a positively chargeable liquid developer.
On the other hand, since the liquid developer is stored for a long time before being put into the image forming apparatus or stored in the image forming apparatus for a long time, it is required to maintain the performance for a long time.

JP 2009-53638 A

  An object of the present invention is to provide a liquid developer excellent in positive charging characteristics and development efficiency of toner particles and excellent in long-term storage, and an image forming apparatus using such a liquid developer.

Such an object is achieved by the present invention described below.
The liquid developer of the present invention includes toner particles,
An insulating liquid containing a hydrogen-modified silicone compound and dispersing the toner particles;
It contains an acrylic polymer and a graft copolymer of polysiloxane.
As a result, it is possible to provide a liquid developer that is excellent in the positive charging characteristics of the toner particles, the development efficiency, and the long-term storage stability.

In the liquid developer of the present invention, the surface of the toner particles is preferably modified with polyalkyleneimine.
As a result, the positive charging characteristics and dispersion stability of the toner particles are particularly excellent over a long period of time.
In the liquid developer of the present invention, the resin material constituting the toner particles preferably contains a rosin resin.
Since the rosin-based resin is a material having a large number of functional groups (acidic groups) that are highly reactive with polyalkyleneimine, surface modification with polyalkyleneimine can be more suitably performed on the surface of toner particles. As a result of the presence of a large amount of polyalkyleneimine, the positive charging characteristics and dispersion stability of the liquid developer can be made particularly high.

In the liquid developer of the present invention, the graft copolymer is preferably contained in an amount of 0.1 parts by weight or more and 60 parts by weight or less with respect to 100 parts by weight of the hydrogen-modified silicone compound.
Thereby, the effect of the graft copolymer can be sufficiently obtained, and the viscosity of the liquid developer can be made appropriate.

The image forming apparatus of the present invention includes a developing unit that forms a single color image using a liquid developer,
A transfer unit that transfers the monochrome image formed by the developing unit to a recording medium, and forms an unfixed toner image on the recording medium;
A fixing unit that fixes the unfixed toner image on the recording medium,
The liquid developer includes toner particles, an insulating liquid containing a hydrogen-modified silicone compound in which the toner particles are dispersed, and a graft copolymer of an acrylic polymer and polysiloxane.
Accordingly, it is possible to provide a highly reliable image forming apparatus using a liquid developer that is excellent in positive charging characteristics of toner particles, development efficiency, and long-term storage stability.

1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. 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.

≪Liquid developer≫
First, the liquid developer of the present invention will be described. The liquid developer of the present invention is one in which toner particles are dispersed in an insulating liquid. The liquid developer of the present invention contains a hydrogen-modified silicone compound as described later as an insulating liquid, and further contains an acrylic-polysiloxane graft copolymer as described later.

Hereinafter, each component constituting the liquid developer will be described in detail.
<Insulating liquid>
Next, the insulating liquid will be described.
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 constituting the liquid developer of the present invention includes a hydrogen-modified silicone compound.
The hydrogen-modified silicone compound is a compound in which part of the side chain of the polysiloxane is replaced with hydrogen.

By the way, in the conventional liquid developer using silicone oil as the insulating liquid, the toner particles cannot be sufficiently charged, the development efficiency is lowered, and the toner image having a sufficiently uniform image density is stably stabilized. Could not be formed. There are also attempts to improve the charging characteristics by adding a charge control agent, a dispersing agent, etc., but sufficient charging characteristics could not be obtained. In particular, the problem as described above is remarkable in a positively chargeable liquid developer.
In view of the above problems, the present inventors have intensively studied, and as a result, by using a hydrogen-modified silicone compound as the insulating liquid, the positive charging characteristics of the liquid developer can be improved. It was found that the development efficiency of the liquid developer can be improved. This is considered to be due to the following reasons.

  As described above, the hydrogen-modified silicone compound has a hydrogen group in a part of the side chain of the polysiloxane. Part of this hydrogen is liberated as hydrogen ions (protons), and these protons are attracted to the functional group (acidic group) derived from the resin material present on the surface of the toner particles. As a result, the toner particles exhibit excellent positive chargeability and excellent development efficiency.

In addition, since the hydrogen-modified silicone compound has a relatively low viscosity and excellent evaporability, it does not hinder the fixing characteristics during fixing.
In addition, hydrogen ions liberated from the hydrogen-modified silicone compound generally tend to volatilize from the liquid developer as hydrogen molecules. As a result, the properties of the insulating liquid change due to the low molecular weight or chemical modification of the hydrogen-modified silicone compound. As a result, the dispersion stability of the toner particles in the liquid developer during long-term storage and There has been a problem of deteriorating characteristics such as charging characteristics. However, in the present invention, the acrylic polymer portion of the acrylic-polysiloxane graft copolymer can trap hydrogen ions and prevent the hydrogen ions from changing into hydrogen molecules. Therefore, even if the liquid developer contains hydrogen-modified silicone, the change in characteristics is small, and the excellent dispersion stability and charging characteristics of the toner particles are maintained over a long period of time.
Here, “having a hydrogen group at a part of the side chain or terminal” means that a hydrogen group is directly bonded to the Si portion of the polysiloxane skeleton of the hydrogen-modified silicone compound.

Examples of the hydrogen-modified silicone compound include poly (methyl hydrogen siloxane), poly (ethyl hydrogen siloxane), poly (phenyl hydrogen siloxane), and the like.
In the hydrogen-modified silicone compound, the polysiloxane skeleton may be branched or linear.

  Further, as described above, the hydrogen group is bonded to the side chain or the terminal of the polysiloxane skeleton. However, when bonded to the side chain, the hydrogen group easily releases hydrogen ions. The charging characteristics can be made particularly excellent. On the other hand, when a hydrogen group is bonded to the terminal, hydrogen ions are released relatively slowly, so that the hydrogen-modified silicone compound is hardly deteriorated, and the property change of the liquid developer is small over a long period of time. It becomes.

The hydrogen-modified silicone compound has a kinematic viscosity at 25 ° C. of preferably 20 mm ² / s to 500 mm ² / s, more preferably 20 mm ² / s to 80 mm ² / s, and more preferably 20 mm. more preferably not more than ² / s or more 40 mm ² / s. Thereby, the dispersibility of the toner particles can be further improved while improving the positive charging characteristics.

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

Among the above, the insulating liquid preferably contains at least one of silicone oil and a low molecular siloxane compound. As a result, the affinity between the insulating liquid and the acrylic-polysiloxane graft copolymer becomes high, and as a result, the toner particles can be more stably dispersed in the insulating liquid. Further, these components are chemically stable compounds, and the long-term stability of the liquid developer is particularly excellent.
Moreover, as a low molecular siloxane compound, a cyclic siloxane compound is preferable and decamethylcyclopentanesiloxane is more preferable. By including such a compound as the insulating liquid, the dispersion stability of the toner particles in the liquid developer becomes particularly excellent.

  When the insulating liquid contains a component other than the hydrogen-modified silicone compound, the content of the hydrogen-modified silicone compound in the insulating liquid is preferably 20 wt% or more and 90 wt% or less, and 35 wt% or more. More preferably, it is 85 wt% or less, and further preferably 50 wt% or more and 80 wt% or less. As a result, the above-described effects of the hydrogen-modified silicone compound are sufficiently exerted, the alteration of the insulating liquid is more effectively suppressed, and the positive chargeability and long-term storage stability of the liquid developer are particularly effective. It will be excellent.

Further, the liquid developer (insulating liquid) may contain a known antioxidant, a charge control agent and the like in addition to the components described above.
The viscosity of the insulating liquid is not particularly limited, but is preferably 5 mPa · s or more and 1000 mPa · s or less, more preferably 50 mPa · s or more and 800 mPa · s or less, and 50 mPa · s or more and 500 mPa · s or less. More preferably. When the viscosity of the insulating liquid is within the above range, when the liquid developer is squeezed out from the developer container onto the application roller, an appropriate amount of the insulating liquid adheres to the toner particles, and the developability of the toner image , Transferability can be made particularly excellent. Further, the dispersibility of the toner particles can be made higher, and in the image forming apparatus as described later, the liquid developer can be supplied more uniformly to the application roller. It is possible to more effectively prevent the liquid developer from dripping. In addition, aggregation and sedimentation of the toner particles can be more effectively prevented, and the dispersibility of the toner particles in the insulating liquid can be made higher. On the other hand, if the viscosity of the insulating liquid is less than the lower limit, problems such as dripping of the liquid developer from the application roller or the like may occur in an image forming apparatus as described later. On the other hand, when the viscosity of the insulating liquid exceeds the upper limit, the dispersibility of the toner particles cannot be sufficiently increased, and the liquid developer cannot be more uniformly supplied to the application roller in an image forming apparatus as described later. There is a case. However, the viscosity in this specification refers to a value measured at 25 ° C.
The electrical resistance of such an insulating liquid at room temperature (20 ° C.) is preferably 10 ¹¹ Ωcm or more, more preferably 10 ¹² Ωcm or more, and more preferably 10 ¹³ Ωcm or more. More preferably.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

<Acrylic-polysiloxane graft copolymer>
In the present invention, the liquid developer includes a graft copolymer of an acrylic polymer and polysiloxane (hereinafter referred to as an acrylic-polysiloxane graft copolymer).
As described above, in the present invention, the insulating liquid contains a hydrogen-modified silicone compound. A liquid developer containing such a hydrogen-modified silicone compound is generally excellent in positive charging characteristics of toner particles. However, when the liquid developer is stored for a long period of time, there is a problem that the hydrogen group of the hydrogen-modified silicone compound is detached and volatilized as a hydrogen molecule, resulting in the alteration of the hydrogen-modified silicone compound. As a result, there has been a problem that the liquid developer cannot maintain the excellent charging characteristics and viscosity characteristics of the toner particles over a long period of time simply by including the hydrogen-modified silicone compound.

  Therefore, in the present invention, the liquid developer contains an acrylic-polysiloxane graft copolymer together with the hydrogen-modified silicone compound. The acrylic-polysiloxane graft copolymer can capture hydrogen ions released from the hydrogen-modified silicone compound with a carbonyl group in the acrylic portion of the copolymer. As a result, hydrogen ions are prevented from freely moving in the liquid developer, and hydrogen molecules are hardly generated. Further, since the alteration of the hydrogen-modified silicone compound is prevented over a long period of time, the liquid developer can maintain the excellent charging characteristics and viscosity characteristics of the toner particles over a long period of time, and the liquid developer can be maintained over a long period of time. It will be excellent.

  Further, the (meth) acryl moiety in the acrylic-polysiloxane graft copolymer has a relatively large polarity due to the carbonyl group in the skeleton. On the other hand, like the hydrogen-modified silicone compound, the acrylic-polysiloxane graft copolymer has a polysiloxane portion. Therefore, by having each of these parts, the acrylic-polysiloxane graft copolymer is such that the (meth) acrylic part has a high affinity with toner particles having a relatively high polarity, and the polysiloxane part is hydrogenated. It becomes a thing with high affinity with the insulating liquid containing a modified silicone compound. 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 and the long-term storage stability of the liquid developer are particularly excellent. It can be.
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 acrylic-polysiloxane graft copolymer as described above becomes chemically more stable, and the liquid developer is hardly changed over a longer period of time.

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 of the bulky chemical structure, the acrylic-polysiloxane graft copolymer can easily capture hydrogen ions.
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 0.1 to 60 parts by weight, preferably 1 to 50 parts by weight, based on 100 parts by weight of the hydrogen-modified silicone compound. More preferably. Thereby, the effect of the acrylic-polysiloxane graft copolymer can be sufficiently obtained, and the viscosity of the liquid developer can be made appropriate. On the other hand, if the content of the acrylic-polysiloxane graft copolymer in the liquid developer with respect to the toner particles is less than the lower limit, the effect of the acrylic-polysiloxane graft copolymer may not be sufficiently obtained. is there. On the other hand, if the content of the acrylic-polysiloxane graft copolymer in the liquid developer with respect to the toner particles exceeds the upper limit, depending on the type of the acrylic-polysiloxane graft copolymer, the viscosity of the liquid developer may be extremely high. In such an image forming apparatus as will be described later, there is a possibility that problems such as dripping of the liquid developer from a coating roller or the like may occur.

<Toner particles>
Next, toner particles will be described.
[Component material of toner particles]
The toner particles include at least a resin material and a colorant.
1. Resin material (binder resin)
The toner particles are made of a material containing a resin material as a main component.
In the present invention, the resin material (binder resin) is not particularly limited, and for example, a known resin can be used. In particular, a resin having a highly polar functional group such as a carbonyl group or a carboxyl group is used. Is preferred. As a result, when surface modification with polyalkyleneimine, which will be described later, is performed, surface modification with polyalkyleneimine can be suitably performed, and the positive charging characteristics of the liquid developer can be made particularly excellent. .

  Examples of such resins include styrene-acrylic resins, acrylic resins, rosin resins, and polyester resins. In particular, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased. Further, since the polyester resin is a material having a relatively large number of functional groups (acidic groups) highly reactive with the polyalkyleneimine described later, the surface modification with the polyalkyleneimine can be suitably performed, and the liquid The positive charging characteristics of the developer can be improved.

  The resin material preferably contains a rosin resin. Since the rosin resin is a material having a large number of functional groups (acidic groups) highly reactive with the polyalkyleneimine described later, the surface modification with the polyalkyleneimine can be more suitably performed. For this reason, the positive charging characteristics and dispersion stability of the liquid developer can be made particularly high. In addition, the rosin-based resin has more acidic groups than the polyester resin, and is more likely to attract protons derived from a hydrogen-modified silicone compound described later, further improving the positive charging characteristics. it can. Further, since the rosin resin has a high affinity with a recording medium such as paper, the toner particles can be further fixed.

Examples of rosin-based resins include rosin-modified phenolic resins, rosin-modified maleic resins, rosin-modified polyester resins, fumaric acid-modified rosin resins, ester gums, etc., and use one or a combination of two or more of these. Can do.
The weight average molecular weight of the rosin resin is preferably 500 or more and 100000 or less, more preferably 1000 or more and 80000 or less, and further preferably 1000 or more and 50000 or less. As a result, the fixing characteristics of the toner particles and the heat-resistant storage stability can be achieved at a higher level.

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 mgKOH / g or more and 25 mgKOH / g or less. As a result, the fixing characteristics of the toner particles and the heat-resistant storage stability can be achieved at a higher level.
Further, the content of the rosin resin in the resin material constituting the toner particles 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, the fixing characteristics of the toner particles and the heat-resistant storage stability can be achieved at a higher level.

  The softening point of the resin material 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 point is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): a temperature increase rate: 5 ° C./min, and a softening start temperature defined by a die hole diameter of 1.0 mm. Point to.

2. Colorant The toner may contain a colorant. The colorant is not particularly limited, and for example, known pigments and dyes can be used.
3. Polyalkyleneimine It is preferable that the surface of the constituted toner particle is modified with polyalkyleneimine. The modification with polyalkyleneimine is a chemical reaction between 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 the toner particles. , A covalent bond (amide bond), or an acidic group of the resin material and an amino group of the polyalkyleneimine form an ionic bond.

Moreover, polyalkyleneimine can show high positive charge property, when an amino group attracts a cation. Then, since the amino group of the polyalkyleneimine and the carbonyl group of the acrylic-polysiloxane graft copolymer are electrically attracted to each other, the amino group and the carbonyl group are further polarized. Especially excellent.
In particular, in the present invention, the insulating liquid contains hydrogen-modified silicone. For this reason, this amino group can efficiently attract protons derived from the hydrogen-modified silicone compound, and the positive charging characteristics of the toner particles can be further improved.

The polyalkyleneimine has a large number of amino groups. Since such polyalkyleneimine is chemically attached (bonded) to the surface of the toner particles, many amino groups are present on the surface of the toner particles. The amino group of the polyalkyleneimine attracts the carbonyl group of the acrylic polymer portion of the acrylic-polysiloxane graft copolymer, and the acrylic-polysiloxane graft copolymer is likely to exist near the surface of the toner particles. In addition, the dispersion stability of the toner particles is particularly excellent.
In addition, since such polyalkyleneimine is chemically attached to the surface of the toner particles, 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. At the same time, the toner particles can be stably dispersed in the insulating liquid over a long period of time.

  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 weight average molecular weight of the polyalkyleneimine is preferably 10,000 or more and 70,000 or less. When the weight 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.

4). Other Components The toner particles may contain components other than those described 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 toner particles. May be.

[Toner particle shape]
The average particle diameter of the toner particles composed of the above materials is preferably 0.5 μm or more and 5 μm or less, more preferably 1 μm or more and 4 μm or less, and 1 μm or more and 3.5 μm or less. 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 content of the toner particles in the liquid developer is preferably 10 wt% or more and 60 wt% or less, and more preferably 20 wt% or more and 50 wt% or less.
The liquid developer of the present invention may contain components other than the components described above (for example, dispersants other than acrylic-polysiloxane graft copolymers, external additives, etc.).

≪Liquid developer manufacturing method≫
Next, a preferred embodiment of the liquid developer manufacturing method as described above will be described.
The liquid developer manufacturing method of the present embodiment includes a resin solution preparation step of preparing a resin solution in which the resin material constituting the toner particles described above is dissolved in an organic solvent, and an aqueous liquid is added to the prepared resin solution. Thus, the O / W emulsion preparation step for preparing the O / W emulsion via the W / O emulsion and the dispersoid contained in the prepared O / W emulsion are combined, and combined. A coalescence step for obtaining particles, an organic solvent removal step for removing the organic solvent contained in the coalesced particles to form toner base particles, and a surface for modifying the surface of the obtained toner base particles with polyalkyleneimine A modifying step and a dispersing step of dispersing the toner particles in an insulating liquid containing an acrylic-polysiloxane graft copolymer and a hydrogen-modified silicone compound.

Hereafter, each process which comprises the manufacturing method of a liquid developer is demonstrated in detail.
[Resin solution preparation process]
First, a resin solution in which a resin material or the like is dissolved in an organic solvent is prepared.
The prepared resin solution contains the above-described toner particle resin material and colorant (material other than polyalkyleneimine), and an organic solvent (organic solvent) as described below.

The organic solvent may be any as long as it dissolves at least a part of the resin material, but it is preferable to use an organic solvent having a boiling point lower than that of the aqueous liquid described later. Thereby, the organic solvent can be easily removed.
The organic solvent is preferably one having low compatibility with an aqueous liquid (aqueous dispersion medium) described later (for example, one having a solubility in 100 g of aqueous liquid at 25 ° C. of 30 g or less). Thereby, in the O / W emulsion liquid (water-based emulsion liquid) described later, the dispersoid composed of the base particle material can be finely dispersed in a stable state.
In addition, the composition of the organic solvent can be appropriately selected according to, for example, the resin material and the colorant composition described above, the composition of the aqueous liquid (aqueous dispersion medium), and the like.
Such an organic solvent is not particularly limited, and examples thereof include ketone solvents such as MEK and aromatic hydrocarbon solvents such as toluene.

The resin solution can be obtained, for example, by mixing a resin material, a colorant, an organic solvent and the like with a stirrer or the like. Examples of the stirrer that can be used for preparing the resin solution include DESPA (manufactured by Asada Tekko Co., Ltd.), T.C. K. Robotics / T. K. Examples thereof include a high-speed stirrer such as a homodisper 2.5-type blade (manufactured by Primex).
The material temperature during stirring is preferably 20 ° C. or higher and 60 ° C. or lower, and more preferably 30 ° C. or higher and 50 ° C. or lower.

  The solid content in the resin solution is not particularly limited, but is preferably 40 wt% or more and 75 wt% or less, more preferably 50 wt% or more and 73 wt% or less, and 50 wt% or more and 70 wt% or less. Is more preferable. When the solid content is within the above range, the dispersoid constituting the dispersion liquid (aqueous dispersion liquid) described later can have a higher sphericity (a shape close to a true sphere). The shape of the toner particles finally obtained can be made more surely suitable.

In preparing the resin solution, all the components of the resin solution to be prepared may be mixed at the same time, or a part of the components of the resin solution to be prepared may be mixed in advance to prepare a mixture (master). After that, the mixture (master) may be mixed with other components.
Further, in the obtained resin solution, some materials such as the colorant may not be dissolved in the organic solvent but may be dispersed in the organic solvent.

[O / W emulsion preparation process]
Next, an O / W emulsion is prepared via the W / O emulsion by adding an aqueous liquid to the resin solution.
As the aqueous liquid, a liquid mainly composed of water can be used.
The aqueous liquid may contain, for example, a solvent having excellent compatibility with water (for example, a solvent having a solubility in 100 parts by weight of water at 25 ° C. of 50 parts by weight or more).
In addition, an emulsifying dispersant may be added to the aqueous liquid as necessary. By adding an emulsifying dispersant, an aqueous emulsion can be prepared more easily. The emulsifying dispersant is not particularly limited, and for example, a known emulsifying dispersant can be used.

  In preparing the O / W emulsion, for example, a basic substance may be used. Thereby, for example, the functional group (for example, carboxyl group) possessed by the resin material can be neutralized, and the shape and size uniformity of the dispersoid in the prepared O / W emulsion can be improved. Dispersibility can be made particularly excellent. For this reason, the obtained toner particles have a particularly sharp particle size distribution. For example, the basic substance may be added to the resin solution, or may be added to the aqueous liquid. Further, the basic substance may be added in a plurality of times in the preparation of the O / W emulsion.

As a basic substance, sodium hydroxide, potassium hydroxide, ammonia etc. are mentioned, for example, 1 type selected from these, or 2 or more types can be used in combination.
The amount of the basic substance used is preferably an amount equivalent to 1 to 3 times the amount necessary for neutralizing all carboxyl groups of the resin material (1 to 3 equivalents), preferably 1 time. An amount corresponding to 2 times or less (1 equivalent or more and 2 equivalents or less) is more preferable. Thereby, it is possible to effectively prevent the formation of irregular dispersoids, and it is possible to make the particle size distribution of the particles obtained in the coalescence step described in detail later sharper.

The aqueous liquid may be added to the resin solution by any method, but it is preferable to add the aqueous liquid containing water to the resin solution while stirring the resin solution. That is, it is carried out by gradually adding (dropping) an aqueous liquid into the resin solution while applying shear to the resin solution with a stirrer or the like, and from the W / O type emulsion (W / O emulsion) to the O / W type. It is preferable to perform phase inversion to an emulsion (O / W emulsion). Thereby, the uniformity of the size and shape of the dispersoid contained in the O / W emulsion can be made particularly high, and the particle size distribution of the toner particles contained in the finally obtained liquid developer can be greatly increased. Sharpness can be achieved, and variation in characteristics among toner particles can be particularly small.
Examples of the stirrer that can be used for the preparation of the O / W emulsion include DESPA (manufactured by Asada Tekko), T.W. K. Robotics / T. K. Examples thereof include a high-speed stirrer such as a homodisper 2.5-type blade (manufactured by Primics), a slasher (manufactured by Mitsui Mining Co., Ltd.), a Cavitron (manufactured by Eurotech), or a high-speed disperser.

  Further, at the time of adding the aqueous liquid to the resin solution, it is preferable to perform stirring so that the blade tip speed is 10 m / second or more and 20 m / second or less, and stirring is performed so as to be 12 m / second or more and 18 m / second or less. It is more preferable. When the blade tip speed is a value within the above range, an O / W emulsion can be obtained efficiently, and the dispersion of the shape and size of the dispersoid in the O / W emulsion should be particularly small. It is possible to make the uniform dispersibility of the dispersoid particularly excellent while preventing the generation of excessively fine dispersoid and coarse particles.

The solid content in the O / W emulsion is not particularly limited, but is preferably 5 wt% or more and 55 wt% or less, and more preferably 10 wt% or more and 50 wt% or less. Thereby, the productivity of the liquid developer can be made particularly excellent while more reliably preventing unintentional aggregation of dispersoids in the O / W emulsion.
In addition, the material temperature in this treatment is preferably 20 ° C. or more and 60 ° C. or less, and more preferably 20 ° C. or more and 50 ° C. or less.

[Joint process]
Next, a plurality of dispersoids are coalesced to obtain coalesced particles. The coalescence of dispersoids usually proceeds as a result of collision of dispersoids containing an organic solvent so that they are integrated.
The coalescence of a plurality of dispersoids is performed by adding an electrolyte to the O / W emulsion while stirring the O / W emulsion. Thereby, coalesced particles can be obtained easily and reliably. Moreover, the particle diameter and particle size distribution of the coalesced particles can be controlled easily and reliably by adjusting the amount of electrolyte added.

It does not specifically limit as electrolyte, Well-known organic and inorganic water-soluble salt etc. can be used 1 type or in combination of 2 or more types.
The electrolyte is preferably a monovalent cation salt. Thereby, the particle size distribution of the obtained coalesced particles can be made particularly sharp. In addition, by using a monovalent cation salt, it is possible to reliably prevent generation of coarse particles in this step.
Moreover, among the above-mentioned, it is preferable that electrolyte is a sulfate (for example, sodium sulfate, ammonium sulfate) or carbonate, and it is especially preferable that it is a sulfate. Thereby, the particle diameter of the coalesced particles can be controlled particularly easily.

The amount of the electrolyte added in this step is preferably 0.5 parts by weight or more and 3 parts by weight or less with respect to 100 parts by weight of the solid content in the O / W emulsion to which the electrolyte is added. More preferably, it is at least 2 parts by weight. As a result, the particle diameter of the coalesced particles can be controlled particularly easily and reliably, and the generation of coarse particles can be reliably prevented.
The electrolyte is preferably added in the form of an aqueous solution. Thereby, while being able to diffuse an electrolyte to the whole O / W emulsion liquid quickly, the addition amount of an electrolyte can be controlled easily and reliably. As a result, coalesced particles having a desired particle size and a very sharp particle size distribution can be obtained.

  When the electrolyte is added in the form of an aqueous solution, the concentration of the electrolyte in the aqueous solution is preferably 2 wt% or more and 10 wt% or less, and more preferably 2.5 wt% or more and 6 wt% or less. As a result, the electrolyte can be diffused through the entire O / W emulsion particularly quickly, and the amount of electrolyte added can be easily and reliably controlled. In addition, by adding such an aqueous solution, the content of water in the O / W emulsion when the addition of the electrolyte is completed becomes suitable. For this reason, the growth rate of the coalesced particles after the addition of the electrolyte can be made moderately slow to the extent that productivity does not decrease. As a result, the particle size can be controlled more reliably. In addition, unintentional coalescence of coalesced particles can be reliably prevented.

When the electrolyte is added as an aqueous solution, the rate of addition of the aqueous electrolyte solution is 0.5 parts by weight or more and 10 parts by weight per 100 parts by weight of the solid content in the O / W emulsion to which the aqueous electrolyte solution is added. The weight is preferably not more than 1 part by weight, more preferably not less than 1.5 parts by weight and not more than 5 parts by weight / minute. As a result, it is possible to prevent the uneven concentration of the electrolyte from occurring in the O / W emulsion, and to reliably prevent the generation of coarse particles. Further, the particle size distribution of the coalesced particles becomes sharper. Furthermore, by adding the electrolyte at such a rate, the coalescence rate can be controlled particularly easily, and it becomes particularly easy to control the average particle size of the coalesced particles, and the productivity of the liquid developer can be reduced. It can be made particularly excellent.
The addition of the electrolyte may be performed in a plurality of times. As a result, coalescent particles having a desired size can be obtained easily and reliably, and the circularity of the obtained coalescent particles can be surely made sufficiently large.

Moreover, this process is performed in the state which stirred the O / W emulsion. Thereby, coalesced particles with particularly small variations in shape and size among the particles can be obtained.
For stirring the O / W emulsion, for example, stirring blades such as anchor blades, turbine blades, fiddler blades, full zone blades, max blend blades, and meniscus blades can be used. preferable. As a result, the added electrolyte can be quickly and uniformly dispersed and dissolved to reliably prevent the uneven concentration of the electrolyte from occurring. Moreover, it is possible to more reliably prevent the coalesced particles once formed from collapsing while efficiently coalescing the dispersoid. As a result, coalesced particles with small variations in shape and particle size among the particles can be obtained efficiently.

The blade tip speed of the stirring blade is preferably from 0.1 m / second to 10 m / second, more preferably from 0.2 m / second to 8 m / second, and from 0.2 m / second to 6 m / second. More preferably, it is as follows. When the blade tip speed is a value within the above range, the added electrolyte can be uniformly dispersed and dissolved, and the occurrence of uneven concentration of the electrolyte can be reliably prevented. In addition, it is possible to more reliably prevent the coalesced particles once formed from collapsing while more efficiently coalescing the dispersoid.
The average particle diameter of the obtained coalesced particles is preferably 0.5 μm or more and 5 μm or less, and more preferably 1.5 μm or more and 3 μm or less. Thereby, the particle diameter of the toner particles finally obtained can be more appropriately set to be appropriate.

[Organic solvent removal step]
Thereafter, the organic solvent contained in the O / W emulsion (particularly in the dispersoid) is removed. Thereby, a dispersion liquid (aqueous dispersion liquid) in which the toner base particles are dispersed in the aqueous dispersion medium is obtained.
The removal of the organic solvent may be performed by any method, but can be performed, for example, under reduced pressure. Thereby, it is possible to efficiently remove the organic solvent while sufficiently preventing the modification of the constituent material such as the resin material.
Moreover, it is preferable that the process temperature in this process is temperature lower than the glass transition point (Tg) of the resin material which comprises coalesced particle.

Moreover, you may perform this process in the state which added the antifoamer to the O / W emulsion (dispersion). Thereby, an organic solvent can be removed efficiently.
Antifoaming agents include, for example, mineral oil-based antifoaming agents, polyether-based antifoaming agents, silicone-based antifoaming agents, lower alcohols, higher alcohols, fats and oils, fatty acids, fatty acid esters, phosphoric acid Esters can be used.
The amount of the antifoaming agent is not particularly limited, but it is preferably 20 ppm or more and 300 ppm or less, and preferably 30 ppm or more and 100 ppm or less in terms of weight ratio with respect to the solid content contained in the O / W emulsion. More preferred.

In this step, at least a part of the aqueous liquid may be removed together with the organic solvent.
In this step, it is not always necessary to remove all of the organic solvent (the total amount of the organic solvent contained in the dispersion). Even in such a case, the remaining organic solvent can be sufficiently removed in the steps described later.

[Washing step (first washing step)]
Next, the toner base particles obtained as described above are washed. As a result, a dispersion liquid (aqueous dispersion liquid) containing the washed toner base particles can be obtained.
By performing this step, even when an organic solvent or the like is contained as an impurity, these can be efficiently removed. Moreover, by performing this process, the electrolyte, basic substance, acidic substance, and salt generated by the acid-base reaction used in the above-described process can be efficiently removed. As a result, the amount of volatile organic compound (TVOC) in the toner base particles finally obtained can be made particularly small. Further, the electrical resistance of the insulating liquid can be made particularly high, and the stability of the characteristics of the toner base particles is improved.

  This step is performed, for example, by separating the toner particles by solid-liquid separation (separation from the aqueous liquid) and then redispersing the solid content (toner mother particles) in the aqueous liquid (aqueous dispersion medium). Can do. The solid-liquid separation and the redispersion of the solid in water may be repeated a plurality of times. The washing is preferably performed until the conductivity of the supernatant of the dispersion (slurry) obtained by redispersing the solid content (toner base particles) in the aqueous liquid (aqueous dispersion medium) is 20 μS / cm or less.

[Surface modification process]
Next, a dispersion liquid (aqueous dispersion liquid) containing toner mother particles as described above and a polyalkyleneimine are mixed, and the toner mother particles as described above are surface-modified with polyalkyleneimine.
This step may be performed by mixing an aqueous dispersion and a polyalkyleneimine, but it is performed in a state where the hydrogen ion index (pH) of the dispersion (aqueous dispersion) is adjusted to 2 or more and 8 or less. preferable. As a result, the reaction between the acid groups present on the surface of the toner particles and the polyalkyleneimine can be more efficiently advanced while reliably preventing unintentional alteration of the constituent material of the toner base particles. The imine can be more firmly bound to the toner base particle surface. As a result, the long-term dispersion stability and charging property stability of the toner base particles can be made particularly excellent. As described above, the hydrogen ion index (pH) of the dispersion (aqueous dispersion) in this step is preferably 2 or more and 8 or less, more preferably 2.5 or more and 6.5 or less. More preferably, it is 4 or more and 5 or less. Thereby, the above effects are more remarkably exhibited.
The pH adjustment of the dispersion liquid described above can be performed by adding, for example, 1N hydrochloric acid or the like.

Further, after mixing the dispersion and the polyalkylenimine, the mixture is preferably stirred for 1 hour or more and 3 hours or less. Thereby, the toner base particle surface can be more uniformly modified (chemically modified).
Moreover, stirring may be performed at normal temperature, and may be performed while heating a liquid mixture at 30 to 40 degreeC. By performing the heating, the surface of the toner base particles can be modified (chemically modified) more efficiently.

  The amount of polyalkyleneimine used in this step is preferably 0.02 to 2.0 parts by weight, preferably 0.06 to 1.2 parts by weight, based on 100 parts by weight of the resin material. More preferably, it is more preferably 0.1 parts by weight or more and 0.6 parts by weight or less. In particular, when the resin material contains a rosin resin, the amount of polyalkyleneimine used in this step is preferably 0.1 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the rosin resin. It is more preferably 0.3 parts by weight or more and 6.0 parts by weight or less, and further preferably 0.5 parts by weight or more and 3.0 parts by weight or less. 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.

[Washing step (second washing step)]
Next, the toner base particles obtained as described above are washed. Thereby, the washed toner particles in the form of a wet cake can be obtained.
By performing this step, it is possible to efficiently remove the excess polyalkyleneimine, electrolyte, salt generated by the acid-base reaction, and the like used in the above-described step. As a result, in the finally obtained liquid developer, the electrical resistance of the insulating liquid can be made particularly high, and the stability of the characteristics of the toner particles is improved.

This step is performed, for example, by separating the toner base particles by solid-liquid separation (separation from the aqueous liquid), and then redispersing the solid content (toner base particles) in the aqueous liquid (aqueous dispersion medium). be able to. The solid-liquid separation and the redispersion of the solid in water may be repeated a plurality of times. The washing is preferably performed until the conductivity of the supernatant of the dispersion (slurry) obtained by redispersing the solid content (toner base particles) in the aqueous liquid (aqueous dispersion medium) is 20 μS / cm or less.
As described above, the polyalkyleneimine is firmly bonded to the toner particles containing the rosin resin. For this reason, unlike a dispersant or the like used in a conventional liquid developer, it is surely prevented from being detached from or dropped out from the toner particles even if a cleaning process is performed.
In this step, for example, the toner particles are separated by solid-liquid separation (separation from the aqueous liquid), and then the re-dispersion and solid-liquid separation of the solid content (toner particles) in the aqueous liquid (aqueous dispersion medium) are performed. Separation of the toner particles from the aqueous liquid). The redispersion of solids in water and solid-liquid separation may be repeated a plurality of times.

[Drying process]
Thereafter, drying treatment can be performed to obtain dried toner particles. By performing such a process, the water content in the toner particles can be surely made sufficiently low, and the storage stability and characteristic stability of the finally obtained liquid developer are particularly excellent. can do.
The drying step can be performed using, for example, a vacuum dryer (for example, ribocorn (manufactured by Okawara Seisakusho), nauter (manufactured by Hosokawa Micron) etc.), fluidized bed dryer (manufactured by Okawara Seisakusho), etc.

[Dispersion process in insulating liquid]
Next, the toner particles obtained as described above are dispersed in an insulating liquid containing an acrylic-polysiloxane graft copolymer and a hydrogen-modified silicone compound. Thereby, a liquid developer is obtained.
The toner particles can be dispersed in the insulating liquid by any method, for example, by mixing the insulating liquid and the toner particles with a bead mill, a ball mill, or the like.

In addition, components other than the insulating liquid, the acrylic-polysiloxane graft copolymer, and the toner particles may be mixed during the dispersion.
Further, the dispersion of the toner particles in the insulating liquid may be performed by using the whole amount of the insulating liquid constituting the finally obtained liquid developer, or by using a part of the insulating liquid. It may be a thing.
When the liquid developer is manufactured by the method described above, the variation in shape and characteristics between toner particles is small. Further, since the liquid developer contains a hydrogen-modified silicone compound and an acrylic-polysiloxane graft copolymer, it becomes excellent in charging characteristics of toner particles positively charged and long-term storage stability.

≪Image forming device≫
Next, a preferred embodiment of the image forming apparatus of the present invention will be described.
FIG. 1 is a schematic view showing a preferred embodiment of the image forming apparatus of the present invention, 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, a transfer unit (intermediate transfer unit 40 and a secondary transfer unit (secondary transfer unit) 60), and , A fixing unit (fixing device) F40 and four liquid developer replenishing units 90Y, 90M, 90C, and 90K.

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. It 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 in the rotation direction from the developing unit 100Y so as to face the photoconductor 10Y. The photoconductor squeeze roller 13Y is pressed against the photoconductor squeeze roller 13Y and adheres 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 non-smooth sheet material due to fiber or the like, the secondary transfer characteristics follow the non-smooth sheet surface. 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 unit cleaning blade 46 and the developer recovery unit 47 are arranged on the driven roller 45 side.
The intermediate transfer unit cleaning blade 46 scrapes and removes the liquid developer adhering to the intermediate transfer unit 40 after the toner image is transferred onto the recording medium F5 by the secondary transfer unit (secondary transfer unit) 60. It has a function.
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 the intermediate transfer unit squeeze roller 53Y, the intermediate transfer unit squeeze cleaning blade 55Y that presses and slides against the intermediate transfer unit squeeze roller 53Y, and the 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 on the upstream side in the moving direction of the intermediate transfer unit 40 is the upstream secondary transfer roller 64. The upstream secondary transfer roller 64 can be pressed against the belt drive roller 41 via the intermediate transfer unit 40.

Of the pair of secondary transfer rollers, the secondary transfer roller disposed on the downstream side 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 driving 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.

  Therefore, 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 secondary transfer roller 64 and the belt drive roller 41 to the downstream 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.

  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. The secondary transfer unit 60 includes a secondary transfer roller cleaning blade 68 and a developer recovery unit 69 with respect to 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 and remove the liquid developer remaining on the surfaces of the secondary transfer rollers 64 and 65 after the secondary transfer. To do. Further, the developer collecting units 67 and 69 collect 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 (set temperature) is preferably 80 ° C. or higher and 160 ° C. or lower, more preferably 100 ° C. or higher and 150 ° C. or lower, and 100 ° C. or higher and 140 ° C. or lower. Further preferred.

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.

  Further, the liquid developer of the present invention is excellent in dispersion stability because it contains an acrylic-polysiloxane graft copolymer. For this reason, toner particles are prevented from aggregating in the collected liquid developer. For this reason, even if the toner particles are once charged during development and transfer, or the solid content concentration in the liquid developer is changed, the liquid developer collected in the collection unit 31bY is easily added to the toner. The particles are dispersed. That is, the liquid developer is excellent in recyclability.

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 the liquid developer in the supply unit 31aY can be kept constant, and the amount of the 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.
This 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 its diameter is 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 development roller 20Y. To do.

  The regulating blade 33Y contacts 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 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 regulating blade 33Y is about 77 degrees according to JIS-A, and the hardness (about 77 degrees) of the contact portion of the regulating blade 33Y with the surface of the application roller 32Y is about the elasticity of the developing roller 20Y described later. It is lower than the hardness (about 85 degrees) of the press 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 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 top surface does not rise due to blowing, and the liquid The upper surface is held substantially constant, and the developer can be stably supplied to the coating 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). And the quantity of the liquid developer supplied on the developing roller 20Y can be adjusted by changing the rotation speed (linear speed) ratio with 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.

  In the image formation using the above-described apparatus, a plurality of liquid developers having different colors (the liquid developer of the present invention) are used, and a plurality of photoreceptors 10 (10Y, 10M, 10C, 10K) corresponding to the respective colors are used. A developing process for forming a single color image, and a plurality of single color images formed on the photoreceptor 10 are transferred to a recording medium F5, and an unfixed toner image F5a formed by superimposing the plurality of single color images on the recording medium F5 is obtained. The transfer process is performed and the fixing process of fixing the unfixed toner image F5a onto the recording medium F5. By using such a method, an image excellent in color developability can be easily formed.

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.
Further, the liquid developer of the present invention is not limited to those produced by the production method as described above.

Moreover, although embodiment mentioned above demonstrated as what obtains the coalesced particle by obtaining aqueous emulsion and adding electrolyte to this aqueous emulsion, this invention is not limited to this. For example, the coalesced particles are prepared by dispersing a colorant, a monomer, a surfactant, and a polymerization initiator in an aqueous liquid, preparing an aqueous emulsion by emulsion polymerization, and adding an electrolyte to the aqueous emulsion to associate. The emulsion may be prepared using an emulsion polymerization association method, or may be obtained by spray-drying the obtained aqueous emulsion to obtain coalesced particles.
Further, the toner particles are not limited to the above-described embodiment, and for example, toner particles obtained by kneading a resin material and a colorant and pulverizing the obtained kneaded material can be used.

[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
[Dispersion preparation step (aqueous dispersion preparation step)]
(Preparation of colorant master solution)
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.

(Resin solution preparation process)
The above colorant masterbatch: 97.5 parts by weight methyl ethyl ketone: 175 parts by weight, polyester resin: 172.3 parts by weight, rosin modified maleic resin (trade name “Marquide No. 1” manufactured by Arakawa Chemical Industries, Ltd., acid value : 25 mgKOH / g or less, softening point: 120 ° C. or higher and 130 ° C. or lower, weight average molecular weight: 3100): 55.3 parts by weight of a high-speed disperser (manufactured by Primics, TK Robotics / TK Homo Dispers 2 .5 type blades) and 1.38 parts by weight of Neogen SC-F (Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier was added to prepare a resin solution. In this solution, the pigment was uniformly finely dispersed.

(O / W emulsion preparation process)
Next, 72.8 parts by weight of 1N ammonia water was added to the resin solution in the container, and the mixture was stirred with a high-speed disperser (Primics Co., Ltd., TK Robotics / TK homodisper type 2.5 blade). The blade tip speed of the wing was sufficiently stirred at 7.5 m / s, the temperature of the solution in the flask was adjusted to 25 ° C., and the stirring blade blade speed was then 14.7 m / s while stirring. By adding 100 parts by weight of deionized water: 100 parts by weight of deionized water while adding stirring of deionized water by weight and further continuing stirring, the dispersoid containing the resin material is dispersed through the W / O emulsion. / W emulsion was obtained.

(Joint process)
Next, the W / O emulsion was transferred to a stirring vessel having a Max blend blade, and the temperature of the W / O emulsion was adjusted to 25 ° C. while stirring at a blade tip speed of 1.0 m / s. .
Next, while maintaining the same temperature and stirring conditions, 200 parts by weight of a 5.0% aqueous sodium sulfate solution was added dropwise to coalesce the dispersoids to form coalesced particles. After the dropping, stirring was continued until 50% volume particle diameter Dv (50) [μm] of the coalesced particles grew to 2.5 μm. When the Dv (50) of the coalesced particles reached 2.5 μm, 200 parts by weight of deionized water was added to complete the coalescence.
(Organic solvent removal step)
Next, the W / O emulsion containing the coalesced particles was placed in a reduced pressure environment, and the organic solvent was distilled off until the solid content was 23 wt% to obtain a toner particle slurry (dispersion).

[Washing step (first washing step)]
Next, the slurry (dispersion) was subjected to solid-liquid separation, and further washed again by redispersion in water (reslurry) and solid-liquid separation. The washing treatment was performed until the conductivity of the supernatant of the slurry became 20 μS / cm or less.
Thereafter, a wet cake of toner particles (toner particle cake) was obtained by suction filtration, and this wet cake was dispersed in water to obtain a dispersion liquid (aqueous dispersion liquid) containing washed toner particles.

[Surface modification process]
Next, the hydrogen ion index (pH) was adjusted to 4.0 by adding 1N hydrochloric acid to the dispersion (aqueous dispersion) containing the washed toner particles.
Thereafter, polyethyleneimine (weight average molecular weight: 70000) was added dropwise to the dispersion (aqueous dispersion) whose hydrogen ion index (pH) was adjusted to 4.0 while stirring. At this time, polyethyleneimine was added so that it might be 1.0 weight part with respect to rosin-type resin: 100 weight part. Further, stirring was then performed for 2 hours so that the entire dispersion had a sufficiently uniform composition.

[Washing step (second washing step)]
Next, the dispersion liquid in which the toner particles surface-modified with polyethyleneimine are dispersed is subjected to solid-liquid separation, and further subjected to washing treatment by re-dispersion in water (reslurry) and repeated solid-liquid separation. . Thereafter, a wet cake of toner particles (toner particle cake) was obtained by suction filtration. The moisture content of the wet cake thus obtained was 35 wt%. When the liquid phase / filtrate separated by solid-liquid separation was examined, polyethyleneimine was not detected.
[Drying process]
Thereafter, the obtained wet cake was dried using a vacuum dryer to obtain toner particles.

[Dispersion process]
Toner particles obtained by the above method: 50 parts by weight, acrylic-polysiloxane graft copolymer solution (KP-575, manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: acrylates / ethylhexyl acrylate / dimethyl methacrylate polysiloxane) , Solvent: decamethylcyclopentanesiloxane, solid content: 30 wt%: 93 parts by weight, methyl hydrogen silicone oil (poly (methyl hydrogen siloxane) as an insulating liquid, manufactured by Shin-Etsu Silicone, trade name “KF-99” , Kinematic viscosity at 25 ° C .: 20 mm ² / s): 107 parts by weight is placed in a ceramic pot (internal volume 600 ml), and further zirconia balls (ball diameter: 1 mm) are filled in a ceramic pot so that the volume filling rate is 85%. In a tabletop pot mill at a rotation speed of 230 rpm at 24:00 Dispersion was carried out. As a result, a liquid developer was obtained.

The Dv (50) of the toner particles in the obtained liquid developer was 1.95 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 120 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 19)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the composition of the liquid developer, the presence / absence of the surface modification step on the toner base particles, and the conditions were changed as shown in Table 1.

(Example 20)
(Preparation of colorant masterbatch)
First, as a resin material, polyester resin (acid value: 10 mg KOH / g, glass transition point (Tg): 55 ° C., softening point: 107 ° C.): 48 parts by weight, rosin-modified male resin (manufactured by Arakawa Chemical Industries, Ltd., product) The name “Marquide No. 1”, acid value: 25 mgKOH / g or less, softening point: 120 ° C. to 130 ° C., weight average molecular weight: 3100): 12 parts by weight were 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. And the kneaded material 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 toner particles)
The colorant master batch: 15 parts by weight, the polyester resin: 68 parts by weight, and the rosin-modified male resin: 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, and the pulverized product was used as toner particles.

(Dispersion process)
Toner particles obtained by the above method: 50 parts by weight, acrylic-polysiloxane graft copolymer solution (KP-575, manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: acrylates / ethylhexyl acrylate / dimethyl methacrylate polysiloxane) Solvent: Decamethylcyclopentanesiloxane, solid content: 30 wt%): 113 parts by weight, methyl hydrogen silicone oil (poly (methyl hydrogen siloxane) as an insulating liquid, manufactured by Shin-Etsu Silicone Co., Ltd., trade name “KF-99” ”Kinematic viscosity at 25 ° C .: 20 mm ² / s): 87 parts by weight in a propylene wide-mouthed bottle, and φ3 glass beads: 300 parts by weight in a propylene wide-mouthed bottle, rocking mill RM-05S (Seiwa (Manufactured by Giken Co., Ltd.) for 90 minutes with inverter frequency setting of 52Hz I went. Thereafter, the glass beads were removed, and dust and coarse particles were removed from the obtained liquid with a SUS sieve (aperture 150 microns) to obtain a liquid developer.

The Dv (50) of the toner particles in the obtained liquid developer was 4.90 μm. Further, the viscosity of the obtained liquid developer at 25 ° C. was 150 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.
(Comparative Examples 1-3)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that the composition of the liquid developer, the presence / absence of the surface modification step on the toner base particles, and the conditions were changed as shown in Table 1.

Table 1 shows the composition and the like of the liquid developer for each of the above Examples and Comparative Examples.
In the table, the polyester resin is PEs, the rosin-modified male resin is RM, and the rosin-modified polyester resin (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, side chain hydrogen-modified methyl hydrogen silicone oil is H1, both ends hydrogen-modified methyl hydrogen silicone oil is H2, one end hydrogen-modified methyl hydrogen silicone oil is H3, both ends of the side chain Hydrogen-modified methylhydrogen silicone oil is H4, dimethyl silicone oil (KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) is KF96, mineral oil (Isopar G, manufactured by Exxon Chemical) is ISOPERG, decamethylcyclopentanesiloxane is S1, methyltris (Trimethylsiloxy) Down the S2, showed butyl acetate BuAc, isododecane iD, isopropanol and iP. In the table, KP-575 is an acrylic-polysiloxane graft copolymer solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: acrylates / ethylhexyl acrylate / dimethyl methacrylate polysiloxane, solvent: decamethylcyclopentanesiloxane, Solid content: 30 wt%), KP-543 is an 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-545 is an acrylic-polysiloxane graft copolymer solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: decamethylcyclopentanesiloxane, solid content: 30 wt%), KP-549 is an acrylic-polysiloxane graft copolymer Body solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: methyltris (trimethylsiloxy) silane, solid content: 40 wt%), KP-550 is an acrylic-polysiloxane graft copolymer Solution (manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: isododecane, solid content: 40 wt%), KP-541 is an acrylic-polysiloxane graft copolymer solution (Shin-Etsu Chemical Co., Ltd.) Manufactured, copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: isopropanol, solid content: 60 wt%). In the table, the content of the acrylic-polysiloxane graft copolymer is the content of the net acrylic-polysiloxane graft copolymer contained in the acrylic-polysiloxane graft copolymer solution (the solid content of each solution). Conversion). Moreover, the surface modification (surface modification process) by polyethyleneimine was shown as PEI treatment.

[2] Characteristic Evaluation of Liquid Developer Each liquid developer obtained as described above was evaluated as follows.
[2.1] Development 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 examples 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 photoconductor after the liquid developer layer passed between the photoconductor 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 photoconductor by the sum of the concentration of toner particles collected on the photoconductor 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] Charging characteristics of positive charging 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).

[2.4] Dispersion stability test 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 allowed to stand at room temperature (25 ° C.) for 10 days. The sediment depth was measured and evaluated according to the following four criteria.
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.

[3] Long-term storability evaluation of liquid developer [3.1] Viscosity change With respect to the liquid developer obtained in each Example and each Comparative Example, the viscosity η ₀ [mPa · s] at 25 ° C. was measured. It was. Next, each liquid developer was allowed to stand for 30 days in an environment of atmospheric pressure and 60 ° C. Next, after each liquid developer was cooled to 25 ° C., the viscosity η ₁ [mPa · s] at 25 ° C. was measured. Then, the viscosity change rate: | η ₀ −η ₁ | / η ₀ was determined and evaluated based on the following five-step criteria.

A: | η ₀ −η ₁ | / η ₀ is less than 0.05.
B: | η ₀ −η ₁ | / η ₀ is 0.05 or more and less than 0.10.
C: | η ₀ −η ₁ | / η ₀ is 0.10 or more and less than 0.15.
D: | η ₀ −η ₁ | / η ₀ is 0.15 or more and less than 0.30.
E: | η ₀ −η ₁ | / η ₀ is 0.30 or more.

[3.2] Change in Charging Characteristics For the liquid developers obtained in the respective Examples and Comparative Examples, the potential difference was measured using a “microscopic laser zeta electrometer” ZC-2000 manufactured by Microtic Nichion. .
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.

Next, the liquid developers obtained in each Example and each Comparative Example were allowed to stand for 30 days in an environment of atmospheric pressure and 60 ° C.
Next, for the liquid developer after standing, the potential difference is measured in the same manner as described above, and the rate of decrease in potential difference when compared with the potential difference before standing: {(potential difference before standing)-(after standing) Potential difference)} / (potential difference before standing) × 100. Then, the change in charging characteristics was evaluated based on the following five-step criteria.

A: Reduction rate of potential difference is less than 3%.
B: The decrease rate of the potential difference is 3% or more and less than 6%.
C: The decrease rate of the potential difference is 6% or more and less than 10%.
D: The decreasing rate of the potential difference is 10% or more and less than 20%.
E: Reduction rate of potential difference is 20% or more.

[3.3] Long-term dispersion stability test 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 settled after standing at 60 ° C. for 40 days. The measured depth was measured and evaluated according to the following four-stage criteria.
A: Settling depth is 0 mm.
B: The settled depth is greater than 0 mm and 4 mm or less.
C: The depth of sedimentation is greater than 4 mm and 8 mm or less.
D: The settled depth is larger than 8 mm.
The results are shown in Table 2.

  As is apparent from Table 2, the liquid developer of the present invention was excellent in charging characteristics and dispersion stability, had little change in these characteristics, and was excellent in long-term storage stability. Further, the liquid developer of each example was excellent in development efficiency and transfer efficiency. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.

  1000: Image forming apparatus 10, 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y, 12M, 12C, 12K ... Exposure unit 13M, 13Y ... Photoconductor squeeze roller 14M, 14Y ... Cleaning blade 15M, 15Y ... Development Agent recovery unit 16Y ... Static elimination unit 17Y ... Photoconductor cleaning blade 18Y ... Developer recovery unit 20Y, 20M, 20C, 20K ... Development roller 21Y ... Development roller cleaning blade 24Y ... Developer recovery unit 30Y, 30M, 30C, 30K ... Development Part 31Y ... Liquid developer storage part 31aY ... Supply part 31bY ... Recovery part 31cY ... Partition 32Y ... Application roller 33Y ... Restriction blade 34Y ... Developer stirring roller 35Y ... Communication part 36Y ... Recovery screw 40 ... Intermediate transfer Numeral 41 ... Belt drive roller 44, 45 ... Follower roller 46 ... Intermediate transfer part cleaning blade 47 ... Developer recovery part 48 ... Non-contact type bias applying member 49 ... Tension roller 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 secondary transfer roller 65 ... Downstream secondary transfer roller 66, 68 ... Secondary transfer roller cleaning blade 67, 69 ... Developer recovery unit 90Y, 90M, 90C, 90K ... Liquid developer supply unit 91Y, 91M, 91C, 91K ... Liquid developer tank 92Y 92M, 2C, 92K ... insulation liquid tanks 93Y, 93M, 93C, 93K ... liquid developer mixing tank 100Y ... developing unit 101Y ... photoreceptor squeeze device F 40 ... fixing portion (fixing device) F5 ... recording medium F5a ... toner image

Claims (5)

Toner particles,
An insulating liquid containing a hydrogen-modified silicone compound and dispersing the toner particles;
A liquid developer comprising an acrylic polymer and a polysiloxane graft copolymer.   The liquid developer according to claim 1, wherein the toner particles have a surface modified with polyalkyleneimine.   The liquid developer according to claim 2, wherein the resin material constituting the toner particles includes a rosin resin.   4. The liquid developer according to claim 1, wherein the graft copolymer is contained in an amount of 0.1 to 60 parts by weight with respect to 100 parts by weight of the hydrogen-modified silicone compound. Using a liquid developer, a developing unit that forms a single color image;
A transfer unit that transfers the monochrome image formed by the developing unit to a recording medium, and forms an unfixed toner image on the recording medium;
A fixing unit that fixes the unfixed toner image on the recording medium,
The image forming apparatus, wherein the liquid developer includes toner particles, an insulating liquid containing a hydrogen-modified silicone compound that disperses the toner particles, and a graft copolymer of an acrylic polymer and a polysiloxane. .

Images