JP2011053444A - Liquid developer and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer having excellent positively charged charge characteristics, excellent developing efficiency and excellent dispersion stability of toner particles, and to provide an image forming method using the liquid developer. <P>SOLUTION: This liquid developer includes an insulating liquid and toner particles. The insulating liquid is characterized by containing hydrogen modified silicone compound with a weight average molecular weight of 1,500 or more. The content of the hydrogen modified silicone compound in the insulating liquid is preferably 15 wt.% or more. Preferably the insulating liquid contains dimethyl silicone in addition to the hydrogen modified silicone compound. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

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.
Also, with conventional liquid developers, the toner particles aggregate over time, making it difficult to maintain dispersibility over a long period of time.

Japanese Patent Laid-Open No. 3-171149

  An object of the present invention is to provide a liquid developer having excellent positive charging characteristics and excellent development efficiency, and excellent dispersion stability of toner particles, and an image forming method using such a liquid developer. .

Such an object is achieved by the present invention described below.
The liquid developer of the present invention includes an insulating liquid and toner particles,
The insulating liquid contains a hydrogen-modified silicone compound having a weight average molecular weight of 1500 or more.
Thereby, it is possible to provide a liquid developer having excellent positive charging characteristics and excellent development efficiency. Further, the dispersion stability of the toner particles in the liquid developer can be made excellent.

In the liquid developer of the present invention, the content of the hydrogen-modified silicone compound in the insulating liquid is preferably 15 wt% or more.
As a result, the positive charging characteristics can be made particularly excellent, and the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.
In the liquid developer of the present invention, the insulating liquid preferably contains dimethyl silicone in addition to the hydrogen-modified silicone compound.
Thereby, the dispersion stability of the toner particles can be made particularly excellent.

In the liquid developer of the present invention, the content of the hydrogen-modified silicone compound in the insulating liquid is X _H [wt%], and the content of the dimethyl silicone in the insulating liquid is X _DM [wt%]. It is preferable that the relationship 0.18 ≦ X _H / X _DM ≦ 5.6 is satisfied.
As a result, the positively charged characteristics can be made particularly excellent, and the dispersion stability of the toner particles in the liquid developer can be made extremely excellent.

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 of the toner particles can be made particularly excellent. Further, the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.
In the liquid developer of the present invention, the resin material constituting the toner particles preferably contains a rosin resin.
Thereby, the fixing property of the toner particles to the recording medium can be made particularly excellent.

これにより、トナー粒子の分散安定性を特に優れたものとすることができる。 In the liquid developer of the present invention, a silicone compound having a partial structure represented by the following formula (1) and a partial structure represented by the following formula (2) is present near the surface of the toner particles. Preferably it is.

Thereby, the dispersion stability of the toner particles can be made particularly excellent.

The image forming method of the present invention includes a developing step of forming a plurality of single color images corresponding to the plurality of liquid developers using a plurality of liquid developers having different colors,
Transferring a plurality of the monochrome images corresponding to each color to a recording medium, and forming an unfixed toner image formed by superimposing the plurality of monochrome images on the recording medium;
A fixing step of fixing the unfixed toner image on the recording medium,
The liquid developer contains an insulating liquid and toner particles;
The insulating liquid contains a hydrogen-modified silicone compound having a weight average molecular weight of 1500 or more.
Accordingly, it is possible to provide an image forming method capable of performing positively charged image formation that is stable over a long period of time.

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

Hereinafter, preferred embodiments of the present invention will be described in detail.
≪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 as described below.
Hereinafter, each component constituting the liquid developer will be described in detail.

<Insulating liquid>
First, the insulating liquid will be described.
The insulating liquid constituting the liquid developer of the present invention contains a hydrogen-modified silicone compound having a weight average molecular weight of 1500 or more.
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 having a weight average molecular weight of 1500 or more as the insulating liquid, the positive charging characteristics of the liquid developer can be improved. It has been found that the liquid developer can be excellent and the development efficiency of the liquid developer can be excellent. 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. Further, by including a hydrogen-modified silicone compound having a predetermined molecular weight, the dispersion stability of the toner particles in the liquid developer can be made excellent.

Further, since the hydrogen-modified silicone compound having a predetermined molecular weight has a relatively low viscosity and excellent evaporability, it does not hinder the fixing characteristics during fixing.
In addition, since the hydrogen-modified silicone compound having a predetermined molecular weight has a high affinity with the resin material (particularly rosin resin) constituting the toner particles, the dispersibility of the toner particles may be particularly excellent. it can.

As described above, in the present invention, a hydrogen-modified silicone compound having a weight average molecular weight of 1500 or more is used. The weight average molecular weight of the hydrogen-modified silicone compound is preferably 2000 or more and 70000 or less, and preferably 3000 or more and 50000 or less. It is more preferable that Thereby, the effect mentioned above is exhibited more notably.
In addition, as described above, the hydrogen-modified silicone compound may be a compound in which a part of the side chain of the polysiloxane is substituted with hydrogen, but among the many methyl groups of dimethyl silicone, the side chain methyl group It is preferable that a part of (a methyl group other than the terminal) is substituted with a hydrogen atom. Thereby, the effects as described above are more remarkably exhibited.
The insulating liquid may contain a component other than the hydrogen-modified silicone compound as described above.

  The content of the hydrogen-modified silicone compound in the insulating liquid is preferably 15 wt% or more, more preferably 20 wt% or more and 80 wt% or less, and further preferably 30 wt% or more and 70 wt% or less. As a result, the positive charging characteristics can be made particularly excellent, and the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.

  When the insulating liquid contains a component other than the hydrogen-modified silicone compound, examples of the component include 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; trade name of Spirits), low viscosity / high viscosity liquid paraffin (Wako Pure Chemical Industries), etc. (hydrocarbon liquid) , Fatty acid glycerides, fatty acid monoesters, fatty acid esters such as medium chain fatty acid esters or vegetable oils containing them, octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xyle , Mesitylene, silicone oil and the like other than the hydrogen-modified silicone compound described above can be used singly or in combination of two or more of them.

Examples of the silicone oil include dimethylsilicone (dimethylpolysiloxane), elcapto-modified dimethylsilicone in which some of the many methyl groups of dimethylsilicone are substituted with mercapto groups, and many methyl groups of dimethylsilicone. Examples thereof include epoxy-modified dimethyl silicone in which a part of them is substituted with an epoxy group.
Among these, by using dimethyl silicone (dimethylpolysiloxane) in combination with the hydrogen-modified silicone compound described above, the dispersion stability of the toner particles can be made particularly excellent.

  In the case where the insulating liquid contains dimethyl silicone in addition to the hydrogen-modified silicone compound, the content of dimethyl silicone in the insulating liquid is preferably 15 wt% or more, and is 20 wt% or more and 80 wt% or less. Is more preferable, and it is further more preferable that it is 30 wt% or more and 70 wt% or less. Thereby, the dispersion stability of the toner particles can be made particularly excellent.

When the insulating liquid contains dimethyl silicone in addition to the hydrogen-modified silicone compound, the content of the hydrogen-modified silicone compound in the insulating liquid is X _H [wt%], and dimethyl silicone in the insulating liquid Is preferably X _DM [wt%], the relationship 0.18 ≦ X _H / X _DM ≦ 5.6 is preferably satisfied, and 0.25 ≦ X _H / X _DM ≦ 4.0 It is more preferable to satisfy the relationship, and it is more preferable to satisfy the relationship of 0.43 ≦ X _H / X _DM ≦ 2.3. By satisfying such a relationship, the positive charging characteristics can be made particularly excellent, and the dispersion stability of the toner particles in the liquid developer can be made extremely excellent. .

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, the developability and transferability of the toner image can be made particularly excellent. Further, aggregation and sedimentation of the toner particles can be prevented more effectively, and the dispersibility of the toner particles in the insulating liquid can be made higher. In an image forming apparatus as will be described later, the liquid developer can be supplied more uniformly to the application roller, and moreover, dripping of the liquid developer from the application roller or the like can be more effectively prevented. it can. 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. By containing the hydrogen-modified silicone compound in the above-described content, the viscosity of the insulating liquid can be easily set to a value within the above range.
The electrical resistance of the 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. Is more preferable.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

<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. Among these, when a polyester resin is used, since the affinity with the hydrogen-modified silicone compound described above is high, the dispersibility of the toner particles in the liquid developer can be made excellent. In addition, the polyester resin generally has a relatively large number of acidic groups and easily attracts protons derived from the hydrogen-modified silicone compound as described above. Can do. Moreover, the polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be made high. 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 property of the developer can be further improved.

  The resin material preferably contains a rosin resin. In general, rosin-based resins have more acidic groups than polyester resins, and are more likely to attract protons derived from the above-described hydrogen-modified silicone compound, 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. Further, 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, and the liquid The charge characteristics of the positive charge of the developer can also be made particularly high.

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. Other Components The toner 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.

[Polyalkyleneimine]
The toner particles may be those obtained by modifying the surface of toner base particles composed of the above materials with polyalkyleneimine.
Since polyalkyleneimine has many amino groups, it is a highly positively charged compound. By modifying the surface of the toner base particles with such polyalkyleneimine, it is possible to improve the positive charging characteristics of the toner particles, and to maintain long-term dispersion stability of the toner particles in the insulating liquid. Can be made particularly excellent. In particular, when the toner base particles are composed of a material containing a rosin resin, the polyalkyleneimine can be firmly bonded to the surface of the toner base particles, and the positive charging characteristics of the toner particles can be stabilized. In addition, the toner particles can have particularly excellent long-term dispersion stability. Although it is conceivable to use a positively chargeable resin material as the constituent material of the toner particles, the positively chargeable resin material has low stability of the resin itself and is difficult to apply as a material constituting the toner particles. It is. It is also conceivable to positively charge the entire toner particles using a positively chargeable charge control agent or dispersant. In such a case, the initial dispersibility of the toner particles is good, but over time. As a result, the charge control agent and the dispersant are detached from the toner particles (toner base particles), and it is difficult to maintain stable positive chargeability for a long period of time. In particular, in an image forming apparatus equipped with a mechanism for reusing the liquid developer collected at the developing unit, which will be described later, since stress is applied to the toner particles during collection, the charging is simply positively charged. In a toner using a control agent or a dispersant, the charge control agent or the dispersant is detached or dropped from the toner particles (toner base particles), and the charging characteristics of the toner particles are likely to be rapidly lowered. In addition, when a positively chargeable charge control agent is used to sufficiently positively charge toner particles, the color of the toner particles may be adversely affected by the influence of the charge control agent.

  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 base particles can be more suitably chemically modified, and the long-term dispersion stability and positive charging characteristics of the toner particles can be further improved.

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

[Silicone compounds]
The toner particle is a silicone compound in which the surface of the toner base particle composed of the material as described above has a partial structure represented by the following formula (1) and a partial structure represented by the following formula (2): The surface may be modified by.

  Thereby, the long-term dispersion stability of the toner particles in the insulating liquid can be made particularly excellent. Further, by developing the surface of the toner base particles with a silicone compound having the above chemical structure, the development efficiency and transfer efficiency of the liquid developer can be made particularly excellent. In addition, the surface of the toner base particles is surface-modified with a silicone compound having the above chemical structure, so that the liquid developer collected in the developing unit or the like is reused in an image forming apparatus as described later. At this time, the toner particles in the collected liquid developer can be easily redispersed and can be easily reused.

  The silicone compound only needs to have a partial structure represented by the above formula (1) and a partial structure represented by the above formula (2), and the partial structure represented by the above formula (1), Although it may have a partial structure other than the partial structure represented by the above formula (2) (hereinafter referred to as “other partial structure”), the partial structure represented by the above formula (1) and the above formula It is preferable that it consists of the partial structure represented by (2). Thereby, the dispersion stability (long-term dispersion stability) of the toner particles in the liquid developer can be made particularly excellent. When the silicone compound includes other partial structures, the proportion of the other partial structures in the silicone compound is preferably 10 wt% or less in terms of the composition formula, and is 5 wt% or less. Is preferred.

[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.

≪Liquid developer manufacturing method≫
Next, a preferred embodiment of the method for producing a liquid developer of the present invention will be described.
The liquid developer manufacturing method of the present embodiment includes a toner base particle preparation step of preparing toner base particles including a colorant and a resin material, and a treatment with polyalkyleneimine on the toner base particles in an acidic liquid. A polyalkyleneimine treatment step and a silicone-based toner particle that has been surface-modified with a silicone compound by subjecting the toner base particles that have been treated with the polyalkyleneimine to a treatment with a silicone compound as described above. A compound treatment step and a dispersion step in the insulating liquid for dispersing the toner particles in the insulating liquid containing the hydrogen-modified silicone compound as described above.

Hereafter, each process which comprises the manufacturing method of a liquid developer is demonstrated in detail.
[Toner base particle preparation process]
First, toner base particles containing a colorant and a resin material are prepared.
In particular, in this embodiment, in this step, a dispersion liquid (aqueous dispersion liquid) in which toner base particles are dispersed in an aqueous dispersion medium is prepared.

  The aqueous dispersion may be prepared by any method, but a resin solution preparation step of preparing a resin solution in which a resin material as a constituent material of toner base particles is dissolved in an organic solvent, and the resin solution The aqueous liquid is added to the O / W emulsion preparation step for preparing the O / W emulsion via the W / O emulsion and the dispersoid contained in the O / W emulsion is combined. The mixture is prepared as a suspension through a coalescing step for obtaining coalesced particles and an organic solvent removing step for removing the organic solvent contained in the coalesced particles to form the toner mother particles. Is preferred. As a result, the size and shape uniformity of the dispersoid contained in the aqueous dispersion can be made particularly high, and the particle size distribution of the toner particles contained in the finally obtained liquid developer can be very sharp. The variation in characteristics among toner particles can be made particularly small. Further, since the polyalkyleneimine treatment step and the silicone compound treatment step, which will be described in detail later, can be performed without going through the toner base particles in a dry state, problems such as aggregation of toner particles (toner base particles) are caused. Generation | occurrence | production can be prevented effectively and a liquid developer can be manufactured with sufficient productivity. Also, the aqueous dispersion prepared as described above (resin solution preparation step, O / W emulsion preparation step, coalescence step, and organic solvent removal step) Since the toner base particles are dispersed in a highly uniform state, each toner base particle can be uniformly treated with a polyalkyleneimine and a silicone compound. For this reason, dispersion of the toner particles contained in the liquid developer and variations in charging characteristics can be suppressed, and the reliability of the entire liquid developer can be made particularly excellent. In the following description, a case where an aqueous dispersion is prepared through a resin solution preparation step, an O / W emulsion preparation step, a coalescence step, and an organic solvent removal step will be representatively described.

(Resin solution preparation process)
First, a resin solution in which a resin material is dissolved in an organic solvent is prepared.
The prepared resin solution contains the constituent material of the toner base particles as described above 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 Homodisper 2.5 type blade (manufactured by PRIMIX Corporation).
In addition, 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.

(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 performed 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 It is preferable to invert the phase to a type 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), 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. It is preferably at least part by weight / minute, more preferably at least 1.5 parts by weight / minute and no 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 agitation of the O / W emulsion, for example, an agitation blade such as an anchor blade, a turbine blade, a fiddler blade, a full zone blade, a max blend blade, or a half moon blade may 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 impurities (such as the amount of volatile organic compound (TVOC)) in the finally obtained toner particles can be made particularly small. In addition, 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.
Note that this step is preferably performed under conditions such that the toner base particles are not dried. Thereby, aggregation of the toner base particles can be prevented more reliably.

[Polyalkyleneimine treatment step]
Next, the toner base particles are treated with polyalkyleneimine in an acidic liquid.
As described above, in the present embodiment, the treatment with the polyalkyleneimine is performed prior to the step of modifying the surface of the toner base particles with the silicone compound (silicone compound treatment step). As a result, the polyalkyleneimine binds to the vicinity of the surface of the toner base particles, and the charging characteristics (particularly the positive charging characteristics) of the toner particles contained in the finally obtained liquid developer are made particularly excellent. it can. In particular, when the toner base particles include a rosin resin, at least a part of the amino groups of the polyalkyleneimine and at least a part of acidic groups (mainly carboxyl groups) derived from the rosin resin on the surface of the toner base particles. Chemically react with each other to form a covalent bond (amide bond), so that the charging characteristics of the toner particles are particularly excellent in stability. Further, in the image forming apparatus described later, when the liquid developer collected in the developing unit or the like is reused, the toner particles in the collected liquid developer can be easily redispersed, and easily Can be reused.

In addition, polyalkyleneimine has a high affinity with the insulating liquid as described above, and the surface stability of the toner base particles can be chemically modified to make the dispersion stability of the toner particles particularly excellent.
The excellent effects as described above are obtained by modifying the surface of the toner base particles with polyalkyleneimine, and can be obtained simply by including polyalkyleneimine in the liquid developer. is not.

  This step can be performed by mixing an aqueous dispersion and a polyalkyleneimine. For example, the hydrogen ion index (pH) may be adjusted after mixing, but hydrogen ions are adjusted so that the aqueous dispersion becomes acidic. It is preferable to mix the aqueous dispersion and the polyalkyleneimine while adjusting the index (pH). As a result, the polyalkyleneimine can be more firmly bound to the surface of the toner base particle while reliably preventing unintentional alteration of the constituent material of the toner base particle. As a result, the long-term dispersion stability of toner particles and the stability of charging characteristics can be made particularly excellent.

  This step may be performed by adding the aqueous dispersion to the polyalkyleneimine, but is preferably performed by adding the polyalkylenimine to the aqueous dispersion. As a result, variation in the amount of polyalkyleneimine bonded to the surface among the toner base particles can be more effectively suppressed, and variation in characteristics among the toner particles constituting the liquid developer can be more effectively performed. Can be suppressed.

This step is not particularly limited as long as the toner base particles are treated with the polyalkyleneimine in the acidic liquid. It is preferable to carry out, and it is more preferable to adjust the hydrogen ion index (pH) of the aqueous dispersion to 2.5 or more and 6.5 or less. As a result, the productivity of the liquid developer can be made particularly excellent while the effects as described above are more remarkably exhibited. On the other hand, when the hydrogen ion index (pH) of the aqueous dispersion is less than the lower limit, the effect of the acidic liquid is saturated, and the amount of basic substance used in the silicone compound treatment step described later is used. And the productivity of the liquid developer decreases. On the other hand, when the hydrogen ion index (pH) of the aqueous dispersion exceeds the upper limit, it becomes difficult to bind the polyalkyleneimine more firmly to the toner base particle surface in this step.
The above-described pH adjustment of the dispersion liquid can be performed by using an acidic liquid such as hydrochloric acid (1N hydrochloric acid or the like), for example.

Moreover, after mixing the aqueous dispersion and the polyalkyleneimine, the mixture is preferably stirred for 1 hour to 3 hours. Thereby, the toner base particle surface can be more uniformly modified (chemically modified).
Moreover, stirring may be performed under 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 0.1 parts by weight or more and 10 parts by weight or less, and 0.3 parts by weight or more and 6 parts by weight or less based on 100 parts by weight of the resin material constituting the toner base particles. It is more preferably 0.0 part by weight or less, and further preferably 0.5 part by weight or more and 3.0 part by weight or less. When the amount of polyalkyleneimine used is within the above range, in the finally obtained liquid developer, toner can be surely prevented from inconvenience such as excessive polyalkyleneimine eluting into the insulating liquid. The long-term dispersion stability of the particles and the positive charging characteristics can be made particularly excellent.

[Washing step (second washing step)]
Next, the toner base particles that have been treated with the polyalkyleneimine 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. In addition, by performing this step, the basic substance used in the above-described step can be efficiently removed. As a result, the amount of impurities in the finally obtained toner particles can be made particularly small. In addition, 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.
Note that this step is preferably performed under conditions such that the toner base particles are not dried. Thereby, aggregation of the toner base particles can be prevented more reliably.

[Silicone compound treatment process]
Next, the toner base particles are treated with a silicone compound to obtain toner particles.
As long as the silicone-based compound has the partial structure represented by the above formula (1) and the partial structure represented by the above formula (2) as described above, this step is performed using an alkaline liquid. Among them, the toner base particles are preferably subjected to treatment with an anionic silicone emulsion containing a silicone compound. As a result, the silicone compound as a constituent material of the silicone emulsion can be firmly attached to the surface of the toner mother particles, and the long-term dispersion stability of the toner particles in the finally obtained liquid developer is sufficiently excellent. Can be. In particular, as in the present embodiment, if the toner base particles used in the silicone compound treatment step are treated with a polyalkyleneimine, the constituent material of the silicone emulsion is applied to the surface of the toner base particles. It will be electrostatically coupled. As a result, the dispersion stability (long-term dispersion stability) of the toner particles in the finally obtained liquid developer can be made particularly excellent, and the reliability of the liquid developer can be made particularly excellent. Can do. Further, in the image forming apparatus described later, when the liquid developer collected in the developing unit or the like is reused, the toner particles in the collected liquid developer can be easily redispersed, and easily Can be reused.
Moreover, as what is marketed as an anionic silicone emulsion containing a silicone type compound as mentioned above, KM-9717 (made by Shin-Etsu Chemical Co., Ltd.), X-51302M (made by Shin-Etsu Chemical Co., Ltd.) etc. are mentioned, for example. Can be mentioned. Among these, KM-9717 (manufactured by Shin-Etsu Chemical Co., Ltd.) is particularly preferable as the anionic silicone emulsion.

  This step can be performed by mixing an aqueous dispersion containing toner base particles (toner base particles treated with polyalkyleneimine) and an anionic silicone emulsion. For example, after mixing, a hydrogen ion index ( pH) may be adjusted, but with the hydrogen ion index (pH) adjusted so that the aqueous dispersion containing the toner base particles is alkaline, the aqueous dispersion containing the toner base particles and the anionic silicone emulsion Are preferably mixed. Thereby, the constituent material of the silicone emulsion can be more firmly attached to the surface of the toner base particle while reliably preventing the unintentional alteration or the like of the constituent material of the toner base particle. As a result, the long-term dispersion stability of the toner particles can be made particularly excellent.

  Further, this step may be performed by adding an aqueous dispersion containing toner base particles to the silicone emulsion, but adding the silicone emulsion to an aqueous dispersion containing toner base particles. It is preferable to carry out the above. This makes it possible to more effectively suppress the variation in the amount of the constituent material of the silicone emulsion adhering to the surface between the toner base particles, and the variation in the characteristics among the toner particles constituting the liquid developer. It can be effectively suppressed.

  This step is preferably performed by adjusting the hydrogen ion index (pH) of the aqueous dispersion to 7.3 or more and 13.0 or less, and the hydrogen ion index (pH) of the aqueous dispersion is 8.0 or more and 12.5. It is more preferable to adjust the following, and it is more preferable to adjust the hydrogen ion index (pH) of the aqueous dispersion to 8.5 to 11.5. As a result, the productivity of the liquid developer can be made particularly excellent while the effects as described above are more remarkably exhibited. On the other hand, if the hydrogen ion exponent (pH) of the aqueous dispersion is less than the lower limit, it may be difficult to more firmly bind the constituent material of the silicone emulsion to the toner base particle surface in this step. is there. On the other hand, when the hydrogen ion index (pH) of the aqueous dispersion exceeds the upper limit, the effect of using the alkaline liquid is saturated, and the amount of the cleaning liquid used in the cleaning process (third cleaning process) described later is increased. This increases the productivity of the liquid developer.

When the toner base particles have been subjected to the treatment with the polyalkyleneimine as described above, usually, sufficient washing (dispersion in which solid content (toner base particles) is redispersed in an aqueous liquid (aqueous dispersion medium)) By performing washing such that the conductivity of the supernatant of the liquid (slurry) is 20 μS / cm or less, the hydrogen ion index (pH) of the aqueous dispersion can be set to a value within the above range.
In addition, you may perform pH adjustment of the dispersion liquid mentioned above by using alkaline liquids, such as ammonia water (1N ammonia water etc.), for example.

Moreover, after mixing the aqueous dispersion and the silicone emulsion, the mixture is preferably stirred for 1 hour to 3 hours. Thereby, the toner base particle surface can be more uniformly modified (chemically modified).
Moreover, stirring may be performed under 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 the silicone emulsion 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 resin material (binder resin) constituting the toner base particles. It is more preferably no less than 6.0 parts by weight and no greater than 3.0 parts by weight. When the usage amount of the silicone emulsion is a value within the above range, in the finally obtained liquid developer, while reliably preventing inconveniences such as excessive silicone emulsion leaching into the insulating liquid, The long-term dispersion stability of the toner particles can be made particularly excellent.

[Washing step (third washing step)]
Next, the toner particles obtained as described above are washed.
By performing this step, even when an organic solvent or the like is contained as an impurity, these can be efficiently removed. In addition, by performing this step, the basic substance used in the above-described step can be efficiently removed. As a result, the amount of impurities in the finally obtained toner particles can be made particularly small. In addition, the electrical resistance of the insulating liquid can be made particularly high, and the stability of the characteristics of the toner particles is improved.

As described above, the polyalkyleneimine is firmly bonded to the toner base particles (particularly toner base particles containing a rosin resin), and the silicone compound is chemically bonded to the toner base particles (particularly polyalkyleneimine). It is firmly bonded to the modified toner base particles. Therefore, unlike the dispersants used in conventional liquid developers, the polyalkyleneimine and the silicone compound are sure to be detached from the toner base particles even after being subjected to a cleaning treatment. Has been prevented.
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, by performing a drying treatment, toner particles (dried toner particles) as powder can be obtained. 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. In the present invention, since the toner particles have been treated with the silicone compound as described above, aggregation of the toner particles is reliably prevented even when the drying step is performed.

[Dispersion process in insulating liquid]
Next, the toner particles obtained as described above are dispersed in an insulating liquid containing the hydrogen-modified silicone compound as described above. 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.
Further, at the time of dispersion, components other than the insulating liquid and toner particles may be mixed.
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. In particular, in the manufacturing method of the present embodiment, the toner particles contained in the liquid developer are such that the surface of the toner base particles has a partial structure represented by the above formula (1) and a portion represented by the above formula (2). It is modified with a silicone-based compound having a structure, has excellent long-term dispersion stability of toner particles, and has little variation in shape and characteristics among toner particles. In addition, since the toner particles are uniformly surface-modified with polyalkyleneimine, variation in characteristics such as charging characteristics among the toner particles can be made particularly small. In addition, the dispersion stability of the toner particles can be further improved.

≪Image formation method≫
Next, a preferred embodiment of the image forming method of the present invention will be described.
First, a preferred embodiment of an image forming apparatus applied to the image forming method of the present invention will be described.
FIG. 1 is a schematic diagram showing a preferred embodiment of an image forming apparatus to which the image forming method of the present invention is applied, and FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, 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 and the photoconductor squeeze roller 13Y are pressed and slidably attached to the surface. The cleaning blade 14Y removes the liquid developer and the developer collection unit 15Y that collects the removed liquid developer. The photoreceptor squeeze device 101Y has a function of collecting excess carrier (insulating liquid) and originally unnecessary fog toner from the developer developed on the photoreceptor 10Y, and increasing the ratio of toner particles in the visible image.

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

The intermediate transfer unit 40 is an endless elastic belt member, and is stretched around a belt driving roller 41 and a pair of driven rollers 44 and 45 to which a driving force of a motor (not shown) is transmitted. The intermediate transfer unit 40 is driven to rotate counterclockwise by the belt driving roller 41 while being in contact with the photoreceptors 10Y, 10M, 10C, and 10K by the primary transfer backup rollers 51Y, 51M, 51C, and 51K.
Further, the intermediate transfer unit 40 is applied with a predetermined tension by a tension roller 49 so that slack is removed. The tension roller 49 is disposed downstream of one driven roller 44 in the rotation (movement) direction of the intermediate transfer unit 40 and upstream of the other driven roller 45 in the rotation (movement) direction of the intermediate transfer unit 40. .
A single color image corresponding to each color formed by the developing units 30Y, 30M, 30C, and 30K is sequentially transferred to the intermediate transfer unit 40 by the primary transfer backup rollers 51Y, 51M, 51C, and 51K, and a single color corresponding to each color is transferred. The images are superimposed. As a result, a full-color developer image (intermediate transfer image) is formed on the intermediate transfer portion 40.

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

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

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

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

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

The intermediate transfer unit squeeze device 52Y is removed by 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) 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.

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 particular, since the liquid developer of the present invention has excellent dispersion stability and redispersibility of toner particles, the toner particles can be easily dispersed (redispersed) even with reused liquid developers. Can be made.

  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 being stirred by 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.

  Further, 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. Development 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 to form an unfixed toner image formed by superimposing the plurality of single-color images on the recording medium F5. And a fixing step of fixing an unfixed toner image on the recording medium F5. By using such a method, an image excellent in color developability can be easily formed. Further, since the liquid developer described above is excellent in long-term dispersion stability of toner particles, stable image formation can be performed over a long period of time.

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. The toner base particles prepared in the toner base particle preparation step may be prepared by, for example, a pulverization method.
In the above-described embodiment, the configuration having the corona discharger as the image forming apparatus has been described. However, the corona discharger may be omitted.

[1] Production of Liquid Developer A liquid developer was produced as follows. About the process in which temperature is not described, it performed at room temperature (25 degreeC).
Example 1
[Toner base particle preparation process]
(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 then the blade tip speed of the stirring blade was 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% sodium sulfate aqueous solution was dropped, and the dispersoids were coalesced to form coalesced particles. After the dropping, stirring was continued until the 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 toner mother 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 mother particles (toner mother particle cake) is obtained by suction filtration, and the wet cake is dispersed in water to obtain a dispersion (water-based dispersion) containing the washed toner mother particles. It was. This step was performed under the condition that the toner base particles were not dried.

[Polyalkyleneimine treatment step]
Next, the hydrogen ion index (pH) was adjusted to 4.0 by adding 1N hydrochloric acid to the dispersion containing the washed toner base particles (aqueous dispersion).
Thereafter, polyethyleneimine (number average molecular weight Mn: 70000) was added dropwise to the dispersion liquid (aqueous dispersion liquid) whose hydrogen ion index (pH) was adjusted to 4.0 and stirred. At this time, the polyethyleneimine was added so as to be 1.0 part by weight with respect to 100 parts by weight of the resin material (binder resin) constituting the toner base particles. Thereafter, the mixed liquid was stirred for 2 hours so that the entire dispersion had a sufficiently uniform composition.

[Washing step (second washing step)]
Next, the dispersion containing the toner base particles treated with polyalkyleneimine is subjected to solid-liquid separation, and further subjected to washing treatment by redispersion in water (reslurry) and repeated solid-liquid separation. did. The washing treatment was performed until the conductivity of the supernatant of the dispersion became 20 μS / cm or less.

  Thereafter, a wet cake of toner base particles (toner base particle cake) that has been treated with polyalkyleneimine is obtained by suction filtration, and the wet cake is dispersed in water to contain the washed toner base particles. A dispersion (aqueous dispersion) was obtained. The hydrogen ion exponent (pH) of the aqueous dispersion thus obtained was 9.5. This step was performed under the condition that the toner base particles were not dried. Further, when the liquid phase / filtrate separated by solid-liquid separation was examined, polyethyleneimine was not detected.

[Silicone compound treatment process]
Next, a partial structure represented by the above formula (1) is added to an aqueous dispersion (toner dispersion having a hydrogen ion index (pH) of 9.5) containing toner base particles treated with polyalkyleneimine. KM-9717 (manufactured by Shin-Etsu Chemical Co., Ltd.) as an anionic silicone emulsion containing a silicone compound having a partial structure represented by the above formula (2) was added dropwise and stirred. At this time, the silicone emulsion was added so as to be 2.0 parts by weight with respect to 100 parts by weight of the resin material (binder resin) constituting the toner base particles. Thereafter, the mixture is stirred for 2 hours to disperse the toner particles in which the toner base particles are modified with the polyalkyleneimine and the silicone compound, thereby obtaining an aqueous dispersion having a sufficiently uniform composition as a whole. It was.

[Washing step (third washing step)]
Next, the aqueous dispersion in which the toner particles are dispersed was subjected to solid-liquid separation, and further subjected to washing treatment by re-dispersing in water (reslurry) and repeating 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 and the silicone compound were not detected.
[Drying process]
Thereafter, the obtained wet cake was dried using a vacuum dryer to obtain toner particles in which the toner base particles were surface-modified with polyethyleneimine and the constituent material of the silicone compound.

[Dispersion process in insulating liquid]
Toner particles obtained by the above method: 50 parts by weight, as an insulating liquid, among the many methyl groups of dimethyl silicone, some of the side chain methyl groups (methyl groups other than the terminal) are replaced with hydrogen atoms The hydrogen-modified compound (weight average molecular weight Mw: 20000): 80 parts by weight and dimethyl silicone (kinematic viscosity at 25 ° C .: 20 mm ² / s): 120 parts by weight were placed in a ceramic pot (internal volume 600 ml), and further zirconia Balls (ball diameter: 1 mm) were placed in a ceramic pot so that the volume filling rate was 85%, and dispersed for 24 hours at a rotational speed of 230 rpm in a desktop pot mill. 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, 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 12)
Each color was the same as in Example 1 except that the materials (resin material, anionic silicone emulsion, polyalkyleneimine, insulating liquid) used for the production of the liquid developer and the production conditions were changed as shown in Table 1. A liquid developer corresponding to the above was manufactured.

(Comparative Example 1)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that only dimethyl silicone (kinematic viscosity at 25 ° C .: 20 mm ² / s) was used as the insulating liquid.
(Comparative Examples 2 and 3)
Liquid developers corresponding to the respective colors were produced in the same manner as in Comparative Example 1 except that the dimethyl silicone shown in Table 1 was used.

(Comparative Example 4)
A liquid developer corresponding to each color was produced in the same manner as in Example 1 except that a hydrogen-modified silicone compound having a weight average molecular weight of 1300 was used.
(Comparative Example 5)
A liquid developer was produced in the same manner as in Comparative Example 1 except that the silicone compound treatment step and the third washing step were omitted.

(Comparative Example 6)
A liquid developer was produced in the same manner as in Comparative Example 5 except that the polyalkyleneimine treatment step and the second washing step were omitted.
(Comparative Example 7)
A liquid developer corresponding to each color was produced in the same manner as in Comparative Example 6 except that Arachid 251 (manufactured by Arakawa Chemical Industries, Ltd.) was used instead of the anionic silicone emulsion.

For each of the above Examples and Comparative Examples, the resin material used for the preparation of the liquid developer, an anionic silicone emulsion (for Comparative Example 7, a dispersant, not a silicone emulsion), polyalkyleneimine, insulating liquid Conditions, hydrogen ion index (pH after dispersion adjustment) of a dispersion (aqueous dispersion) in which the hydrogen ion index (pH) was adjusted when being used in the silicone compound treatment process, and the polyalkyleneimine treatment process Table 1 shows the hydrogen ion index (pH after adjustment of the dispersion) of the dispersion (aqueous dispersion) in which the hydrogen ion index (pH) was adjusted. In the table, polyester resin (acid value: 10 mgKOH / g, glass transition point (Tg): 55 ° C., softening point: 107 ° C.) is PES, styrene-acrylate copolymer is ST-AC, and rosin. Modified polyester resin (trade name “Traffus 4102”, manufactured by Arakawa Chemical Industries, Ltd., acid value: 15 mg KOH / g, softening point: 98 ° C. or higher and 104 ° C. or lower, weight average molecular weight: 1600) RPES and rosin modified phenolic resin ( Product name “Tamanol 135”, manufactured by Arakawa Chemical Industries, Ltd., acid value: 18 mg KOH / g or less, softening point: 130 ° C. or higher and 140 ° C. or lower, weight average molecular weight: 15000, RPH and rosin modified maleic resin (Arakawa Chemical Industries, Ltd.) Product name “Marquide No. 1”, acid value: 25 mg KOH / g or less, softening point: 120 ° C. or more and 130 ° C. or less, weight average Amount: 3100) RM, KM-9717 (made by Shin-Etsu Chemical Co., Ltd.) as an anionic silicone emulsion, KM9717, X-51302M (made by Shin-Etsu Chemical Co., Ltd.) as an anionic silicone emulsion, X511302M, Polyethyleneimine is PEI, Arachid 251 is DA, Hydrogen modified compound (weight average molecular weight: 20000) is A, Hydrogen modified compound (weight average molecular weight: 50000) is B, Hydrogen modified compound (weight average molecular weight) : 1600) C, hydrogen-modified compound (weight average molecular weight: 60000), D, hydrogen-modified dimethyl silicone (weight average molecular weight: 1300) and E, dimethyl silicone (kinematic viscosity at 25 ° C .: 20 mm ² / s) with F and dimethyl Ricorn (kinematic viscosity at 25 ° C .: 50 mm ² / s) was indicated as G, dimethyl silicone (kinematic viscosity at 25 ° C .: 100 mm ² / s) was indicated as H, and Isopar E (manufactured by Exxon Chemical) was indicated as I. The hydrogen-modified compounds A to D described above are hydrogens in which a part of the side chain methyl groups (methyl groups other than the terminals) among the many methyl groups of dimethyl silicone are substituted with hydrogen atoms. It was a modifying compound. Further, for the liquid developers of Examples 1 to 12, the toner particles were filtered and washed, and then analyzed by NMR. As a result, a portion represented by the above formula (1) was found near the surface of the toner base particles. It was confirmed that a silicone compound having a structure and a partial structure represented by the above formula (2) was present. On the other hand, when the insulating liquid was analyzed by NMR, the presence of the silicone compound comprising the partial structure represented by the above formula (1) and the partial structure represented by the above formula (2) was confirmed. There wasn't. Moreover, about the comparative example 7, the conditions of the dispersing agent were shown in the column of the anionic silicone emulsion. In addition, the insulating liquid constituting the liquid developer of each of the examples had a viscosity of 50 mPa · s to 500 mPa · s at 25 ° C.

[2] Evaluation 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 five-step criteria.
A: The development efficiency is 96% or more, and the development efficiency is particularly excellent.
B: The development efficiency is 91% or more and less than 96%, and the development efficiency is excellent.
C: The development efficiency is 85% or more and less than 91%, and there is no practical problem.
D: The development efficiency is 55% or more and less than 85%, and the development efficiency is inferior.
E: The development efficiency is less than 55%, and the development efficiency is particularly inferior.

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

[2.3] Fixing Strength Using an image forming apparatus as shown in FIGS. 1 and 2, an image of a predetermined pattern with a liquid developer obtained in each of the examples and the comparative examples is recorded on a recording paper (Seiko Epson). It was formed on a high-quality paper LPCPPA4) manufactured by the company. Thereafter, the fixing temperature was set to 100 ° C., and thermal fixing was performed.
Then, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) twice with a pressing load of 1.2 kgf, and the remaining ratio of image density Was measured by “X-Rite model 404” manufactured by X-Rite Inc, and evaluated according to the following five-step criteria.

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

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

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

[2.5] Dispersion stability test [2.5.1] Method 1
10 mL of the liquid developer obtained in each example and each comparative example was placed in a test tube (12 mm in diameter and 120 mm in length), and the sedimented depth after standing for 14 days was measured. According to the following five-stage criteria evaluated.

A: Settling depth is 0 mm.
B: The settled depth is greater than 0 mm and 2 mm or less.
C: The depth of sedimentation is greater than 2 mm and 4 mm or less.
D: The depth of sedimentation is greater than 4 mm and 6 mm or less.
E: The settled depth is larger than 6 mm.

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

A: 0 ≦ k <0.003
B: 0.003 ≦ k <0.005
C: 0.005 ≦ k <0.008
D: 0.008 ≦ k <0.011
E: k ≧ 0.011

[2.6] Recyclability Using the liquid developers obtained in each of the above examples and comparative examples, 50,000 sheets of images with a predetermined pattern were obtained using an image forming apparatus as shown in FIGS. Recording paper (manufactured by Seiko Epson Corporation, high-quality paper LPCPPA4). This image formation was performed in a state where supply of the liquid developer from the liquid developer tank of each color to the corresponding stirring device of each color was stopped. After image formation on 50,000 sheets of recording paper, a liquid developer (recycled) regenerated by diluting the toner particles collected in the stirrer with an insulating liquid so that the solid content is 20 wt% The liquid developer was tested by the following two methods (Method 1 and Method 2) to evaluate the adaptability (recyclability) for recycling.

[2.6.1] Method 1
Recycled liquid developer 10 mL for each example and each comparative example was placed in a test tube (12 mm in diameter and 120 mm in length), and the sedimentation depth after standing for 10 days was measured and evaluated according to the following five-stage criteria. did.
A: Settling depth is 1 mm or less.
B: The settled depth is larger than 1 mm and 3 mm or less.
C: The depth of sedimentation is greater than 3 mm and 5 mm or less.
D: The depth of sedimentation is greater than 5 mm and 7 mm or less.
E: The settled depth is larger than 7 mm.

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

A: 0 ≦ k <0.005
B: 0.005 ≦ k <0.009
C: 0.009 ≦ k <0.012
D: 0.012 ≦ k <0.014
E: k ≧ 0.014
These results are shown in Table 2.

  As is apparent from Table 2, the liquid developer of the present invention was excellent in positively charged characteristics, excellent in development efficiency, and excellent in toner particle dispersion stability (long-term dispersion stability). The liquid developer of the invention was also excellent in recyclability. Further, the liquid developer of the present invention was excellent in transfer efficiency and fixing strength. On the other hand, satisfactory results were not obtained with the liquid developer of the comparative example.

  In addition, recording paper (manufactured by Seiko Epson Corporation) is supplied by the image forming apparatus as shown in FIGS. 1 and 2 so that the liquid developer is supplied from the liquid developer mixing tank of each color to the supply unit of each corresponding color. When high-quality paper LPCPPA4) was subjected to continuous image formation of 100,000 sheets, the present invention was able to form an image with excellent image quality even on the 100,000th sheet, whereas no deterioration in image quality was observed. In the comparative example, a clear decrease in image quality was observed.

  1000: Image forming apparatus 10, 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y ... Exposure unit 13M, 13Y ... Photoconductor squeeze roller 14M, 14Y ... Cleaning blade 15M, 15Y ... Developer recovery unit 16Y ... Static elimination Unit 17Y ... Photoconductor cleaning blade 18Y ... Developer collection unit 20Y, 20M, 20C, 20K ... Development roller 21Y ... Development roller cleaning blade 24Y ... Developer collection unit 30Y, 30M, 30C, 30K ... Development unit 31Y ... Liquid developer Storage part 31aY ... Supply part 31bY ... Recovery part 31cY ... Partition 32Y ... Applying roller 33Y ... Regulator blade 34Y ... Developer stirring roller 35Y ... Communication part 36Y ... Recovery screw 40 ... Intermediate transfer part 41 ... Belt drive low -49 ... tension roller 44, 45 ... driven roller 46 ... intermediate transfer part cleaning blade 47 ... developer recovery part 48 ... non-contact type bias applying member 51Y, 51M, 51C, 51K ... primary transfer backup roller 52Y ... intermediate transfer part 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 ... 2 Next 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, 92C, 92K ... Insulating liquid tank 93Y, 93M, 93C, 93K ... Liquid developer mixing tank 100Y ... Development unit 101Y ... Photoconductor squeeze device F40 ... Fixing unit (fixing device) F5 ... Recording medium

Claims (8)

Including an insulating liquid and toner particles;
The liquid developer, wherein the insulating liquid contains a hydrogen-modified silicone compound having a weight average molecular weight of 1500 or more.   The liquid developer according to claim 1, wherein the content of the hydrogen-modified silicone compound in the insulating liquid is 15 wt% or more.   The liquid developer according to claim 1, wherein the insulating liquid contains dimethyl silicone in addition to the hydrogen-modified silicone compound. When the content of the hydrogen-modified silicone compound in the insulating liquid is X _H [wt%] and the content of the dimethyl silicone in the insulating liquid is X _DM [wt%], 0.18 ≦ The liquid developer according to claim 3, wherein the relationship of X _H / X _DM ≦ 5.6 is satisfied.   The liquid developer according to claim 1, wherein the toner particles have a surface modified with polyalkyleneimine.   The liquid developer according to claim 1, wherein the resin material constituting the toner particles includes a rosin resin. 7. A silicone compound having a partial structure represented by the following formula (1) and a partial structure represented by the following formula (2) is present near the surface of the toner particles. Liquid developer according to any one of the above.

A development step of forming a plurality of single color images corresponding to the plurality of liquid developers using a plurality of liquid developers having different colors;
Transferring a plurality of the monochrome images corresponding to each color to a recording medium, and forming an unfixed toner image formed by superimposing the plurality of monochrome images on the recording medium;
A fixing step of fixing the unfixed toner image on the recording medium,
The liquid developer contains an insulating liquid and toner particles;
The image forming method, wherein the insulating liquid contains a hydrogen-modified silicone compound having a weight average molecular weight of 1500 or more.

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