JP2012118393A - Production method of liquid developer and liquid developer - Google Patents

Abstract

To provide a method for producing a liquid developer capable of efficiently producing a liquid developer excellent in positive charging characteristics.
A method for producing a liquid developer according to the present invention is a method for producing a liquid developer containing an insulating liquid and toner particles, wherein a kneaded material containing at least a resin material containing a polyester resin and a colorant is roughened. A coarse pulverization step for obtaining a coarse pulverized product by pulverization, a fine pulverization step for finely pulverizing the coarse pulverized product in the insulating liquid by a wet pulverization method, and a composition provided for the fine pulverization step, Tg [° C.] when the glass transition temperature of the resin material is Tg [° C.] and the softening point of the resin material is Tm [° C.] in the presence of the graft copolymer of polysiloxane and polysiloxane and polyalkyleneimine A heat treatment step of performing a heat treatment at a temperature not lower than Tm and a charge control agent mixing step of mixing a charge control agent having a proton donating group in the molecule and the composition subjected to the heat treatment; Characterized in that it has.
[Selection figure] None

Description

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

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

JP 2007-219380 A

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

Such an object is achieved by the present invention described below.
The method for producing a liquid developer of the present invention is a method for producing a liquid developer containing an insulating liquid and toner particles,
A coarse pulverization step of coarsely pulverizing a kneaded product containing a resin material containing at least a polyester resin and a colorant,
A fine pulverization step of finely pulverizing the coarsely pulverized product in the insulating liquid by a wet pulverization method;
A heat treatment step of subjecting the composition subjected to the fine pulverization step to a heat treatment in the presence of a graft copolymer of an acrylic polymer and a polysiloxane, and a polyalkyleneimine;
And a charge control agent mixing step of mixing the charge control agent having a proton donating group in the molecule with the composition subjected to the heat treatment.
Accordingly, it is possible to provide a method for producing a liquid developer capable of efficiently producing a liquid developer excellent in positive charging characteristics.

In the method for producing a liquid developer of the present invention, it is preferable to use a hydrogen-modified silicone compound as the charge control agent.
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 method for producing a liquid developer of the present invention, it is preferable to use a resin material containing a rosin resin in addition to the polyester resin.
Thereby, the fixing property of the toner to the recording medium can be made particularly excellent. Further, the modification (chemical modification) of the toner base particles with polyalkyleneimine can be easily and reliably performed, and the positive charging characteristics and the stability of the charging characteristics of the toner particles can be made particularly excellent. In addition, the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.

In the method for producing a liquid developer according to the aspect of the invention, it is preferable that the pulverization step is performed in the insulating liquid containing the graft copolymer.
As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

In the method for producing a liquid developer of the present invention, the acrylic polymer preferably contains an alkyl acrylate as a monomer component.
As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

In the method for producing a liquid developer according to the present invention, the polysiloxane is preferably dimethylpolysiloxane.
As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

In the method for producing a liquid developer according to the aspect of the invention, it is preferable that the polysiloxane is obtained by adding an acrylic acid compound to the dimethylpolysiloxane.
As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

In the method for producing a liquid developer of the present invention, it is preferable to use a liquid containing at least one of silicone oil and siloxane compound as the insulating liquid.
As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.
The liquid developer of the present invention is manufactured using the method of the present invention.
Thereby, it is possible to provide a liquid developer excellent in positive charging characteristics.

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

Hereinafter, preferred embodiments of the present invention will be described in detail.
≪Liquid developer manufacturing method≫
First, a method for producing a liquid developer according to the present invention will be described. In the present invention, the liquid developer is one in which toner particles are dispersed in an insulating liquid.
The method for producing a liquid developer according to the present embodiment includes a coarse pulverization step of coarsely pulverizing a kneaded material including a resin material containing at least a polyester resin and a colorant to obtain a coarse pulverized product, and a composition provided for the fine pulverization step The coarsely pulverized product in an insulating liquid in the presence of a graft copolymer of an acrylic polymer and polysiloxane (hereinafter referred to as “acryl-polysiloxane graft copolymer”) and a polyalkyleneimine A fine pulverization step for finely pulverizing the mixture by a wet pulverization method, a heat treatment step for performing a heat treatment, a charge control agent mixing step for mixing the charge control agent having a proton donating group in the molecule and the composition subjected to the heat treatment, have. Thereby, it is possible to efficiently produce a liquid developer having excellent positive charging characteristics.

Hereinafter, each step will be described in detail.
[Coarse grinding process]
First, a kneaded product containing a resin material and a colorant is coarsely pulverized to obtain a coarsely pulverized product.
For pulverization of the kneaded product, for example, various pulverization devices such as a ball mill, a vibration mill, a jet mill, and a pin mill, and a crushing device can be used.

The resin material constituting the kneaded product contains at least a polyester resin.
The polyester resin is a resin that has high transparency, and when used as a binder resin, can improve the color developability of the resulting image.
The polyester resin has high transparency, and when used as a binder resin, the color developability of the obtained image can be increased. Further, since the polyester resin is a material having a relatively large number of functional groups (acidic groups) highly reactive with polyalkyleneimine described later, when the liquid developer contains polyalkyleneimine, Thus, the surface modification can be suitably performed, and the positive charging characteristics of the liquid developer can be improved.

The softening point of the polyester resin is not particularly limited, but is preferably 50 ° C or higher and 130 ° C or lower, more preferably 50 ° C or higher and 120 ° C or lower, and further preferably 60 ° C or higher and 115 ° C or lower. In the present specification, the softening point is defined by measurement conditions in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, die hole diameter 1.0 mm, and pressure 1.96 MPa. Refers to the softening start temperature. Further, the glass transition temperature (Tg) is a glass transition in a differential heat curve obtained by a temperature rise measurement at a temperature rise rate of 5 ° C./min using a differential scanning calorimeter (DSC-60 manufactured by Shimadzu Corporation). It refers to the temperature at the intersection of the baseline before the start temperature and the tangent at the glass transition inflection point.
The acid value of the polyester resin is preferably 5 mgKOH / g or more and 20 mgKOH / g or less, more preferably 5 mgKOH / g or more and 15 mgKOH / g or less.

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

Moreover, the resin material should just contain a polyester resin at least, However, It is preferable that a rosin resin is further included. Thereby, the fixing property of the toner to the recording medium can be made particularly excellent. Further, the modification (chemical modification) of the toner base particles with polyalkyleneimine can be easily and reliably performed, and the positive charging characteristics and the stability of the charging characteristics of the toner particles can be made particularly excellent. In addition, the dispersion stability of the toner particles in the liquid developer can be made particularly excellent.
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 100,000 or less, more preferably 1000 or more and 80000 or less, and further preferably 1000 or more and 50000 or less. As a result, 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% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 40% by mass 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.
Moreover, it does not specifically limit as a coloring agent, For example, a well-known pigment, dye, etc. can be used.
The particle size of the coarsely pulverized product obtained in this step is preferably 5 mm or more and 20 mm or less. As a result, a liquid developer having excellent positive charge characteristics can be produced more efficiently.

[Fine grinding process]
After the coarse pulverization step, the coarsely pulverized product is finely pulverized in an insulating liquid by a wet pulverization method.
This step can be performed using, for example, various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The insulating liquid functions as a dispersion medium for dispersing the toner particles in the finally obtained liquid developer.

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

  Examples of the insulating liquid include KF-96, KF-995 (above, Shin-Etsu Chemical), AK35, AK50, AK100, AK350, AK1000 (above, Wacker Chemie AG), SH200, SH510, SH8400 (above, Toray Dow). Corning) and other dimethyl silicone oils; Cyclic siloxane compounds such as cyclopentasiloxane and decamethylcyclopentasiloxane, and low molecular siloxane compounds having a polymerization degree of 20 or less such as methyltris (trimethylsiloxy) silane; 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; Spirits) Product name), mineral oils (hydrocarbon liquids) such as low-viscosity / high-viscosity liquid paraffin (Wako Pure Chemical Industries); fatty acid glycerides, fatty acid monoesters, fatty acid esters such as medium chain fatty acid esters or vegetable oils containing them; octane , Isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, butyl acetate, isopropanol, etc., and a combination of one or more of these Can be used.

  In this step, it is preferable to use a liquid containing at least one of a silicone oil and a siloxane compound among the above-described insulating liquids. As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

Moreover, among the above-mentioned, it is preferable that an insulating liquid contains at least one among silicone oil and a low molecular siloxane compound. As a result, when the liquid developer contains an acrylic-polysiloxane graft copolymer, which will be described in detail later, the affinity between the insulating liquid and the acrylic-polysiloxane graft copolymer becomes high. As a result, the toner particles Becomes easier to disperse more stably in the insulating liquid.
Moreover, as a low molecular siloxane compound, a cyclic siloxane compound is preferable and cyclopentasiloxane and decamethylcyclopentasiloxane are more preferable. By including such a compound as the insulating liquid, the dispersion stability of the toner particles in the liquid developer becomes particularly excellent.

  In the production method of the present invention, as will be described in detail later, it is sufficient that an acrylic-polysiloxane graft copolymer is contained in the heat treatment step. It is preferable to carry out in an insulating liquid containing a graft copolymer. As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

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

Further, the acrylic-polysiloxane graft copolymer may include a plurality of types of acrylic polymers.
The acrylic polymer that constitutes the acrylic-polysiloxane graft copolymer is preferably acrylates and alkyl acrylates, and more preferably acrylates and ethylhexyl acrylate. As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.
In addition, the acrylic polymer may include a monomer component other than the above.

  The polysiloxane constituting the acrylic-polysiloxane graft copolymer is not particularly limited, and examples thereof include dialkyl polysiloxanes such as dimethylpolysiloxane, diarylpolysiloxanes such as diphenylpolysiloxane, and the like. One kind or a combination of two or more kinds can be used. Among the above, the polysiloxane preferably contains a dialkylsiloxane, more preferably dimethylpolysiloxane. As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

Moreover, the polysiloxane which comprises an acryl-polysiloxane graft copolymer may be substituted by the other functional group etc. in the side chain or the terminal. For example, an acrylic acid compound such as acrylic acid or methacrylic acid may be added to the side chain or terminal of polysiloxane. As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.
The polysiloxane may be linear or branched.

The acrylic-polysiloxane graft copolymer is obtained by graft polymerization of an acrylic polymer and polysiloxane. As a result, the acrylic-polysiloxane graft copolymer has many branched chains and is bulky. As a result, a portion having a relatively large polarity (acrylic polymer portion) and a portion having a relatively small polarity (polysiloxane portion) can sufficiently exhibit their functions.
More specifically, examples of the acrylic-polysiloxane graft copolymer as described above include KP-541, KP-575, KP-543, KP-545, KP-549, and the like. One or a combination of two or more can be used.

  The acrylic-polysiloxane graft copolymer is preferably contained in an amount of 10% by mass to 50% by mass with respect to 100% by mass of the toner particles in the finally obtained liquid developer, and 15% by mass or more. More preferably, the content is 45% by mass or less. Thereby, the effect of the acrylic-polysiloxane graft copolymer can be sufficiently obtained, and the viscosity of the liquid developer can be made appropriate.

  In addition, in the production method of the present invention, as will be described in detail later, it is sufficient that polyalkyleneimine is contained in the heat treatment step, but this step (pulverization step) is performed with an insulating property containing polyalkyleneimine. It is preferable to carry out in a liquid. As a result, the toner particles constituting the finally obtained liquid developer have sufficiently excellent charging characteristics for positive charging, and the dispersion stability of the toner particles in the liquid developer is particularly excellent. Can do. Further, the development and transfer characteristics of the liquid developer can be made particularly excellent.

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

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

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

  The number average molecular weight of the polyalkyleneimine is preferably 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 toner particle surface can be more effectively modified (chemically modified), and due to steric hindrance due to the relatively long molecular chain of the polyalkyleneimine, Aggregation of the toner particles can be effectively prevented, and the dispersion stability of the toner particles can be effectively improved.

  When the resin material contains a rosin resin, the amount of polyalkyleneimine used is preferably 0.5% by mass or more and 50% by mass or less, preferably 1% by mass or more and 10% by mass with respect to 100% by mass of the rosin resin. More preferably, it is less than or equal to parts. When the usage amount of the polyalkyleneimine is within the above range, it is possible to reliably prevent inconveniences such as excessive polyalkyleneimine leaching into the insulating liquid in the finally obtained liquid developer. On the other hand, the long-term dispersion stability and positive charging characteristics of the toner particles can be made particularly excellent.

[Heat treatment process]
Thereafter, the composition subjected to the fine pulverization step is subjected to heat treatment in the presence of a graft copolymer of an acrylic polymer and polysiloxane and a polyalkyleneimine.
As a result, the surface modification of the toner particles with the polyalkyleneimine proceeds efficiently, and the charging characteristics of the finally obtained toner particles can be reliably improved. Further, the dispersion stability of the finally obtained toner particles can be reliably improved, and the storage stability and durability of the liquid developer can be particularly improved.

The treatment temperature in this step is preferably Tg [° C.] or more and Tm [° C.] or less when the glass transition temperature of the resin material is Tg [° C.] and the softening point of the resin material is Tm [° C.] The temperature is more preferably (Tg + 5) [° C.] or more and (Tm−10) [° C.] or less, and further preferably (Tg + 10) [° C.] or more and (Tm−35) [° C.] or less. As a result, the above-described effects can be exhibited more remarkably, and the productivity of the liquid developer can be made particularly excellent. In addition, when the resin material constituting the coarsely pulverized product is composed of a plurality of types of components (resin components), the glass transition temperature and softening point of the mixture as a whole are adopted as Tg and Tm. It shall be.
The heat treatment time in this step is preferably 10 minutes or more and 180 minutes or less, and more preferably 15 minutes or more and 60 minutes or less. As a result, the effects as described above can be exhibited more remarkably and the productivity of the liquid developer can be made particularly excellent.

Further, this step is preferably performed while applying shear. Thereby, the effects as described above are more remarkably exhibited. Further, the dispersion stability of the toner particles in the insulating liquid can be made particularly excellent. Further, the uniformity of charging characteristics of each toner particle can be made particularly excellent.
When this step is performed while applying shear, it is preferable to apply a shear of 300 rpm to 1200 rpm, and it is more preferable to apply a shear of 400 rpm to 900 rpm.

[Charge control agent mixing process]
Thereafter, a charge control agent having a proton donating group in the molecule and a composition subjected to heat treatment are mixed. Thereby, a liquid developer is obtained. In the liquid developer thus obtained, the charge control agent imparts protons to the polyalkyleneimine that modifies the surface of the toner particles, thereby increasing the charge amount of the toner particles and having excellent charging characteristics. In addition, the development efficiency and transfer efficiency are excellent.

Any charge control agent may be used as long as it has a proton donating group in the molecule. For example, poly (methyl hydrogen siloxane), poly (ethyl hydrogen siloxane), poly (phenyl hydrogen). Siloxane) and the like, carboxy-modified silicone compounds, carbinol-modified silicone compounds, polyether-modified silicone compounds, phenol-modified compounds, silanol-modified compounds, and the like.
Among them, it is preferable to use polyalkyleneimine as the charge control agent. 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 hydrogen-modified silicone compound, the polysiloxane skeleton may be branched or linear.
In addition, the hydrogen group (proton) is bonded to the side chain or terminal of the polysiloxane skeleton, but when bonded to the side chain, the hydrogen ion is easily released, resulting in positive charging characteristics of the toner particles. Can be made particularly excellent. On the other hand, when a hydrogen group is bonded to the terminal, hydrogen ions are released relatively slowly, so that the hydrogen-modified silicone compound is hardly deteriorated, and the property change of the liquid developer is small over a long period of time. It becomes.

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

This step is preferably performed using a rocking mill. As a result, in the finally obtained liquid developer, the amino group of the polyalkyleneimine efficiently attracts protons derived from the hydrogen-modified silicone compound, thereby further improving the positive charging characteristics of the toner particles. it can.
The content of polyalkyleneimine in the liquid developer obtained as described above is preferably 0.2% by mass or more and 10% by mass or less, and preferably 0.4% by mass or more and 2% by mass or less. More preferred. Thereby, the effect by including a polyalkyleneimine as mentioned above can be exhibited more notably, without inhibiting the characteristic of another component.

The content of the acrylic-polysiloxane graft copolymer (pure component) in the liquid developer is preferably 0.5% by mass or more and 8% by mass or less, and preferably 1% by mass or more and 4% by mass or less. Is more preferable. Thereby, the effect by including the above acryl-polysiloxane graft copolymer can be exhibited more significantly, without inhibiting the characteristic of other components.
The content of the charge control agent in the liquid developer is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less. Thereby, the effect by including a charge control agent as mentioned above can be exhibited more notably, without inhibiting the characteristic of other ingredients.

Further, the content of the toner particles in the liquid developer is preferably 10% by mass or more and 60% by mass or less, and more preferably 20% by mass or more and 50% by mass or less.
The volume average particle diameter (D ₅₀ ) of the toner particles constituting the liquid developer is preferably 2 μm or more and 4 μm or less.
In particular, in the present invention, the toner particles have a volume average particle diameter (D ₅₀ ) of 2 μm or more and 4 μm or less, and a particle diameter (D ₁₀ ) at a volume cumulative distribution rate of 10% from the fine particle side is 0.8 μm or more. It is preferable that the particle diameter (D ₉₀ ) at a volume cumulative distribution rate of 90% from the fine particle side has a unimodal distribution of 3 μm or more and 7 μm or less. By satisfying such a condition, variation in characteristics (for example, charging characteristics) among toner particles can be made sufficiently small, and optical in a printing part of a printed matter manufactured using a liquid developer. The concentration (OD value) can be made sufficiently high. In the present specification, the volume average particle diameter (D ₅₀ ) means “50% average particle diameter (D ₅₀ ) in terms of sphere by light scattering method”, and is a value obtained as follows. That is, the particles in the dispersion medium are irradiated with light, and the generated diffracted scattered light is measured by detectors arranged in front, side, and rear of the dispersion medium. Using the measured value, assuming that the particles that are originally indefinite are spherical, a cumulative curve is obtained by setting the total volume of the particle population converted to a sphere equal to the volume of the particles as 100%, The point at which the cumulative value becomes 50% is defined as “50% average particle diameter (D ₅₀ ) in terms of sphere by light scattering method”. Examples of the measuring apparatus include a laser diffraction scattering type particle size distribution measuring instrument Microtrac MT-3000. In the present invention, the “unimodal distribution” is a particle size distribution having a stationary point that is not the only extreme value and a single maximum value when the particle size distribution is standardized, and the maximum value It means that the strength satisfies the condition of 0.7 or more.

As described above, the volume average particle diameter (D ₅₀ ) of the toner particles is preferably 2 μm or more and 4 μm or less, more preferably 2.0 μm or more and 3 μm or less. Thereby, the effects as described above are more remarkably exhibited. Further, the resolution of the toner image formed with the liquid developer 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.

The particle diameter (D ₁₀ ) at a volume cumulative distribution rate of 10% from the fine particle side of the toner particles is preferably 0.8 μm or more and 1.8 μm or less, but 1.0 μm or more and 1.5 μm or less. Is more preferable. Thereby, the effects as described above are more remarkably exhibited.
The particle diameter (D ₉₀ ) at a volume cumulative distribution rate 90% from the fine particle side of the toner particles is preferably 3 μm or more and 7 μm or less, more preferably 3.2 μm or more and 5.5 μm or less. . Thereby, the effects as described above are more remarkably exhibited.
Further, the full width at half maximum in the particle size distribution of the toner particles is preferably 3 μm or less, and more preferably 1.0 μm or more and 2.5 μm or less. Thereby, variation in characteristics (for example, charging characteristics) among toner particles can be made particularly small.

A liquid developer containing toner particles satisfying the above conditions can be suitably manufactured by using the method as described above.
Further, the liquid developer may contain components other than those described above. Examples of such components include known waxes, magnetic powders, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acids, fatty acid metal salts, dispersants, external additives, and known oxidation agents. Examples thereof include an inhibitor and a charge control agent. Such a component may be used in any step of the production method described above. That is, such a component may be included in, for example, a kneaded product, or added during a coarse pulverization step, a fine pulverization step, a heat treatment step, or a charge control agent mixing step. It may be.

≪Image forming device≫
Next, a preferred embodiment of an image forming apparatus to which the liquid developer of the present invention is applied will be described.
FIG. 1 is a schematic diagram showing a preferred embodiment of an image forming apparatus to which the liquid developer of the present invention is applied, and FIG. 2 is an enlarged view of a part of the image forming apparatus shown in FIG.
As shown in FIGS. 1 and 2, the image forming apparatus 1000 includes four developing units 30Y, 30M, 30C, and 30K, 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 non-smooth sheet material due to fiber or the like, the secondary transfer characteristics follow the non-smooth sheet surface. An elastic belt member is employed as means for improving the above.

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

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

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

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

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

  The secondary transfer unit 60 includes a pair of secondary transfer rollers that are spaced apart from each other by a predetermined distance along the transfer material movement direction. Of these pair of secondary transfer rollers, the secondary transfer roller disposed on the upstream side in the moving direction of the intermediate transfer unit 40 is the upstream secondary transfer roller 64. The upstream secondary transfer roller 64 can be pressed against the belt drive roller 41 via the intermediate transfer unit 40.

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

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

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

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

The toner image (transfer image) 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 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 apparatus, a plurality of single color images corresponding to the respective colors are applied to the photoreceptors 10Y, 10M, 10C, and 10K using a plurality of liquid developers having different colors (the liquid developer of the present invention). And a transfer step of transferring a plurality of single color images formed on the photosensitive member to the recording medium F5 and forming 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.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.
For example, the liquid developer of the present invention is not limited to that applied to the image forming apparatus as described above.
In addition to the above-described steps (coarse pulverization step, fine pulverization step, heat treatment step, charge control agent mixing step), the liquid developer manufacturing method of the present invention may have other steps. For example, the insulating liquid used in the pulverization step after the pulverization step (between the pulverization step and the heat treatment step, between the heat treatment step and the charge control agent mixing step, after the charge control agent mixing step) May have a step of mixing insulating liquids having different compositions. That is, the insulating liquid used in the pulverization step and the insulating liquid constituting the finally obtained liquid developer may have different compositions. By having such a process, the composition of the finally obtained liquid developer can be made particularly preferable while making the processing efficiency of the pulverization process particularly high.

[1] Production of Liquid Developer A liquid developer was produced as follows. About the process in which temperature is not described, it performed at room temperature (25 degreeC).
Example 1
[Coarse grinding process]
First, a polyester resin (acid value: 10 mg KOH / g, glass transition temperature: 55 ° C., softening point: 120 to 130 ° C.): 60% by mass was prepared as a resin material.

Next, a mixture (mass ratio 50:50) of the resin material and a black pigment (Degussa, Printex L 15: 3) as a colorant 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 kneader extruded from the extrusion port of the biaxial kneading extruder was cooled.
The kneaded product cooled as described above was roughly 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.

  Colorant masterbatch: 15% by mass, polyester resin: 68% by mass, rosin-modified maleic resin (Arakawa Chemical Industries, trade name “Marquide No. 1”, acid value: 25 mgKOH / g or less, glass transition temperature: 55 ° C., softening point: 120 to 130 ° C., weight average molecular weight: 3100): 17% by mass were kneaded using a biaxial kneading extruder. And the kneaded material extruded from the extrusion port of the biaxial kneading extruder was cooled. The obtained kneaded product was pulverized with a hammer mill to obtain a coarsely pulverized product having an average particle diameter of 15 mm.

[Fine grinding process]
Coarse pulverized product obtained by the above method: 32% by mass, acrylic-polysiloxane graft copolymer solution (KP-545, manufactured by Shin-Etsu Chemical Co., Ltd., copolymer component: alkyl acrylate / dimethylpolysiloxane, solvent: Cyclopentasiloxane, solid content: 30% by mass): 14% by mass, dimethyl silicone oil as an insulating liquid (KF-96-50cs: manufactured by Shin-Etsu Chemical Co., Ltd.): 70% by mass, polyalkyleneimine (number average molecular weight; 1800): 1.2 mass% is put in a ceramic pot (contents 1600 ml), and further zirconia balls (ball diameter: 2 mm) are put in a ceramic pot so that the volume filling rate is 40%, and rotated by a planetary ball mill. Wet grinding was performed at a speed of 200 rpm for 24 hours.
The volume average particle diameter (D ₅₀ ) of the fine particles contained in the obtained composition (composition subjected to the fine pulverization step) was 3.2 μm. The particle size of the fine particles contained in the composition 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.

[Heat treatment process]
The finely pulverized composition was transferred to a beaker and placed on a hot stirrer and heated at 60 ° C. At that time, a shear of 600 rpm was applied. The heat treatment was performed for 30 minutes. Thereafter, it was naturally cooled to room temperature to obtain a liquid developer. The resulting liquid developer has a viscosity at 25 ° C. of 155 mPa.s. s. The toner particles have a volume average particle diameter (D ₅₀ ) of 2.1 μm, a particle diameter (D ₁₀ ) at a volume cumulative distribution rate of 10% from the fine particle side is 1.0 μm, and the volume from the fine particle side. The particle size (D ₉₀ ) at a cumulative distribution rate of 90% was 3.5 μm and had a unimodal distribution. Further, the full width at half maximum in the particle size distribution of the toner particles was 1.9 μm. The viscosity of the liquid developer at 25 ° C. was determined by measurement under the condition of 10 mm / s using an mE type viscometer.
[Charge control agent mixing process]
Thereafter, 10% by mass of KF-99 (manufactured by Shin-Etsu Chemical Co., Ltd.) as a hydrogen-modified silicone compound is added to the composition subjected to the above heat treatment, and the mixture is stirred with a rocking mill at 52 Hz for 10 minutes, whereby liquid development. An agent was obtained.

(Examples 2 to 15)
A liquid developer was produced in the same manner as in Example 1 except that the material used for producing the liquid developer was changed and the heat treatment conditions in the heat treatment step were changed as shown in Table 1.
(Comparative Example 1)
A liquid developer was produced in the same manner as in Example 1 except that the charge control agent mixing step was omitted.

(Comparative Example 2)
A liquid developer was produced in the same manner as in Example 1 except that the heat treatment step was omitted.
(Comparative Examples 3 and 4)
A liquid developer was produced in the same manner as in Example 1 except that the material used for producing the liquid developer was changed and the heat treatment conditions in the heat treatment step were changed as shown in Table 1.

Table 1 shows the composition and the like of the liquid developer for each of the above Examples and Comparative Examples.
In the table, polyester resin (acid value: 10 mg KOH / g, glass transition temperature: 55 ° C., softening point: 120 to 130 ° C.) is PES1, rosin modified maleic resin (manufactured by Arakawa Chemical Industries, Ltd., trade name “Marquide No. 1 ”, acid value: 25 mgKOH / g or less, glass transition temperature: 54 ° C., softening point: 120 to 130 ° C., weight average molecular weight: 3100), RM1, acrylic-polysiloxane graft copolymer solution (KP-545, Shin-Etsu) Acrylic-polysiloxane graft copolymer component contained in a copolymer component: (alkyl acrylate / dimethylpolysiloxane) copolymer, solvent: cyclopentasiloxane, solid content: 30% by mass) manufactured by Kagaku Kogyo Co., Ltd. is used as KP-545. KF-99 (manufactured by Shin-Etsu Chemical Co., Ltd., 25 ° C.) as a charge control agent (hydrogen-modified silicone compound) Kicking kinematic viscosity: 20mm ² / s) and KF-99, x-22-170DX (manufactured by Shin as charge control agents, 25 kinematic viscosity at ° C.: a 65mm ² / s) 170DX, as charge control agents x-22-162C (manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity at 25 ° C .: 220 mm ² / s) 162C, x-22-160As (manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity at 25 ° C .: 35 mm) ² / s) was 160 As, and x-22-4039 (manufactured by Shin-Etsu Chemical Co., Ltd., kinematic viscosity at 25 ° C .: 90 mm ² / s) as a charge control agent was converted to 4039x dimethyl silicone oil (KF-96-50cs, Shin-Etsu Chemical). Kogyo Co., Ltd.) was indicated as KF-96-50cs, and polyethyleneimine (number average molecular weight: 1800) was indicated as PEI.

[2] Evaluation The following evaluation was performed on the liquid developer obtained as described above.
[2.1] Charging characteristics of positive charge With respect to the liquid developers obtained in the respective examples and comparative examples, the charge amount of toner particles is measured using PEA (PEA space charge measuring device manufactured by Fibrabo Co., Ltd.). Went. It can be said that the larger this value, the better the charging characteristics.

[2.2] Storage stability The liquid developers obtained in each Example and each Comparative Example were placed in a test tube (12 mm in diameter and 120 mm in length) and allowed to stand at 50 ° C. for 2 days.
Thereafter, the charge amount of the toner particles was measured by the same method as in [2.1] above, and evaluated according to the following four criteria.
A: Change in charge amount is less than 10%.
B: Change in charge amount is 10% or more and less than 20%.
C: Change in charge amount is 20% or more and less than 50%.
D: Change in charge amount is 50% or more.

[2.3] 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 photosensitive member after the liquid developer layer passed between the photosensitive member and the developing roller were collected with a tape. Each tape used for sampling was affixed on a recording paper, and the concentration of each toner particle was measured. After the measurement, the value obtained by dividing the concentration of toner particles collected on the photoreceptor by the sum of the concentration of toner particles collected on the photoreceptor and the concentration of toner particles collected on the developing roller is multiplied by 100. Was determined as development efficiency, and evaluated according to the following four-stage criteria.
A: The development efficiency is 96% or more, and the development efficiency is particularly excellent.
B: The development efficiency is 90% or more and less than 96%, and the development efficiency is excellent.
C: The development efficiency is 80% or more and less than 90%, and there is no practical problem.
D: The development efficiency is less than 80% and the development efficiency is inferior.

[2.4] Transfer Efficiency Liquid developer using the liquid developer obtained in each of the examples and comparative examples on the photoreceptor of the image forming apparatus using the image forming apparatus as shown in FIGS. 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.

[2.5] Evaluation of image density of printed matter Recording paper (manufactured by Seiko Epson Corporation, fine quality) by applying a liquid developer to the image forming apparatus as shown in FIGS. 1 and 2 so that the thickness becomes 5 μm. A printing part was formed on paper LPCPPA4).
The image density of the printed portion thus formed was measured with X-Rite (“X-Rite model 404” manufactured by Inc.).
These results are shown in Table 2 together with the particle size distribution of the toner particles constituting the liquid developer.

  As is apparent from Table 2, the liquid developer of the present invention was excellent in charging characteristics of toner particles, excellent in storage stability, and excellent in development efficiency and transfer efficiency. Further, it could be suitably used for producing a printed matter having a sufficient optical density. On the other hand, satisfactory results were not obtained with the liquid developers of the comparative examples.

  1000: Image forming apparatus 10Y, 10M, 10C, 10K ... Photoconductor 11Y ... Charging roller 12Y, 12M, 12C, 12K ... Exposure unit 13M, 13Y ... Photoconductor squeeze roller 14M, 14Y ... Cleaning blade 15M, 15Y ... Developer recovery Section 16Y ... Static elimination unit 17Y ... Photoconductor cleaning blade 18Y ... Developer collection section 20Y, 20M, 20C, 20K ... Development roller 21Y ... Development roller cleaning blade 24Y ... Developer collection section 30Y, 30M, 30C, 30K ... Development section 31Y Liquid developer storage unit 31aY Supply unit 31bY Recovery unit 31cY Partition 32Y Application roller 33Y Restricting blade 34Y Developer stirring roller 35Y Communication unit 36Y Recovery screw 40 Intermediate transfer unit 4 ... belt drive rollers 44, 45 ... driven rollers 46 ... intermediate transfer section cleaning blade 47 ... developer recovery section 48 ... non-contact type bias applying member 49 ... tension rollers 51Y, 51M, 51C, 51K ... primary transfer backup roller 52Y ... Intermediate transfer unit squeeze device 53Y ... Intermediate transfer unit squeeze roller 55Y ... Intermediate transfer unit squeeze cleaning blade 56Y ... Developer recovery unit 60 ... Secondary transfer unit 64 ... Secondary transfer roller on upstream side 65 ... Secondary transfer roller on downstream side 66, 68 ... Secondary transfer roller cleaning blade 67, 69 ... Developer recovery unit 90Y, 90M, 90C, 90K ... Liquid developer supply unit 91Y, 91M, 91C, 91K ... Liquid developer tank 92Y, 92M, 92C, 92K ... Insulation Liquid liquid tongue 93Y, 93M, 93C, 93K ... liquid developer mixing tank 100Y ... developing unit 101Y ... photoreceptor squeeze device F 40 ... fixing portion (fixing device) F5 ... recording medium

Claims (9)

A method for producing a liquid developer comprising an insulating liquid and toner particles, comprising:
A coarse pulverization step of coarsely pulverizing a kneaded product containing a resin material containing at least a polyester resin and a colorant,
A fine pulverization step of finely pulverizing the coarsely pulverized product in the insulating liquid by a wet pulverization method;
A heat treatment step of subjecting the composition subjected to the fine pulverization step to a heat treatment in the presence of a graft copolymer of an acrylic polymer and a polysiloxane, and a polyalkyleneimine;
A method for producing a liquid developer, comprising: a charge control agent mixing step of mixing a charge control agent having a proton donating group in the molecule and the composition subjected to the heat treatment.   The method for producing a liquid developer according to claim 1, wherein a hydrogen-modified silicone compound is used as the charge control agent.   The method for producing a liquid developer according to claim 1, wherein the resin material includes a rosin resin in addition to the polyester resin.   The method for producing a liquid developer according to any one of claims 1 to 3, wherein the pulverizing step is performed in the insulating liquid containing the graft copolymer.   The method for producing a liquid developer according to claim 1, wherein the acrylic polymer contains an acrylic acid alkyl ester as a monomer component.   The method for producing a liquid developer according to claim 1, wherein the polysiloxane is dimethylpolysiloxane.   The method for producing a liquid developer according to claim 1, wherein the polysiloxane is obtained by adding an acrylic acid compound to the dimethylpolysiloxane.   The method for producing a liquid developer according to any one of claims 1 to 7, wherein a liquid containing at least one of silicone oil and a siloxane compound is used as the insulating liquid.   A liquid developer produced by using the method according to claim 1.

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