CN101533236A - Liquid developer and image forming apparatus - Google Patents

Abstract

The invention relates to a liquid developer and an image forming device. The present invention provides a liquid developer having excellent positive charging characteristics and excellent dispersion stability of toner particles, and an image forming apparatus using such a liquid developer. The liquid developer of the present invention is characterized by containing an insulating liquid and toner particles made of a material containing a polyester resin, and containing an alkyldiamine and an amide compound having a hydroxy fatty acid skeleton as a dispersant. The content of the alkyldiamine is preferably 0.1 to 8 parts by weight relative to 100 parts by weight of the toner particles. The content of the amide compound having a hydroxy fatty acid skeleton is preferably 0.1 to 7 parts by weight relative to 100 parts by weight of the toner particles. The hydroxy fatty acid skeleton is preferably a 12-hydroxystearic acid skeleton.

Description

Liquid developer and image forming device

technical field

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

Background technique

As a developer used for developing an electrostatic latent image formed on a latent image carrier, it is known that a colorant such as a pigment and a toner composed of a material containing a binder resin are dispersed in an electrically insulating carrier liquid. (insulating liquid) in the liquid developer.

As a binder resin used in toner particles constituting such a liquid developer, a polyester resin is generally widely used. The polyester resin is characterized by high transparency, and when used as a binder resin, it has excellent color rendering properties of an image obtained, and can also obtain high fixing properties.

Examples of liquid developers include negatively charged liquid developers and positively charged liquid developers. However, in the case of using a negatively charged liquid developer, there is a problem in that the image is formed when a negatively charged liquid developer is used. Ozone is generated inside the forming apparatus, causing environmental problems, adverse effects on peripheral components in the image forming apparatus, and the like.

Therefore, in recent years, a method of forming an image using a positively chargeable liquid developer has been developed because it can reduce the generation of discharge products such as ozone to form an image (for example, refer to Patent Document 1).

The positively chargeable liquid developer described in Patent Document 1 positively charges toner particles by adding a charge control agent.

However, since polyester resins conventionally used for toner particles generally have high negative chargeability, it is difficult to apply them to positively chargeable toner particles (liquid developers). In addition, it is conceivable to add a charge control agent to positively charge toner particles using a conventional polyester resin as a binder resin, but it is difficult to obtain a sufficient charge amount.

In addition, a dispersant is added to the liquid developer in order to improve the dispersibility of the toner particles, but generally, when the dispersant is added, there is a problem that the charging characteristics of the liquid developer are lowered.

Patent Document 1: JP-A-2002-214849 Gazette

Contents of the invention

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

Such objects are achieved by the present invention described below.

The liquid developer of the present invention is characterized in that,

Contains an insulating liquid and toner particles made of a material containing a polyester resin,

As a dispersant, an amide compound having an alkyldiamine and a hydroxy fatty acid skeleton is contained.

In the liquid developer of the present invention, the content of the alkyldiamine is preferably 0.1 to 8 parts by weight relative to 100 parts by weight of the toner particles.

In the liquid developer of the present invention, it is preferable that the alkyldiamine is a compound represented by the following general formula (I).

【Chemical 1】

H ₂ N—R—NH—R’……(I)

(wherein, R is an alkylene group having 2 to 6 carbon atoms, and R' is an alkyl group having 8 to 24 carbon atoms.)

In the liquid developer of the present invention, the content of the amide compound having a hydroxy fatty acid skeleton is preferably 0.1 to 7 parts by weight relative to 100 parts by weight of the toner particles.

In the liquid developer of the present invention, it is preferable that the amide compound having a hydroxy fatty acid skeleton is a compound represented by the following general formula (II).

【Chemical 2】

(In the formula, R1, R2, R3 are H, CH ₃ , OH, OCH ₃ , OCH ₂ CH ₃ , OCH ₂ CH ₂ CH ₃ , or fatty acids with 12 to 18 carbon atoms, a=1 to 5, b=1 ~21, c=1~21, d=1~5, and (b+c)≦26.)

In the liquid developer of the present invention, preferably, the hydroxy fatty acid skeleton is a 12-hydroxystearic acid skeleton.

In the liquid developer of the present invention, it is preferable that the material constituting the toner particles contains a rosin-modified resin in addition to the polyester resin.

In the liquid developer of the present invention, it is preferable that the insulating liquid contains vegetable oil.

In the liquid developer of the present invention, it is preferable that the insulating liquid further contains a fatty acid monoester.

The image forming apparatus of the present invention is characterized by having:

using a plurality of liquid developers with different colors to form a plurality of developing parts corresponding to monochrome images of the plurality of liquid developers;

The multiple monochromatic images formed in the multiple developing parts are sequentially transferred to form an intermediate transfer part of an intermediate transfer image formed by superimposing the transferred multiple monochromatic images;

transferring the intermediate transfer image to a recording medium, forming a secondary transfer portion of an unfixed color image on the recording medium; and

a fixing portion that fixes the unfixed color image on the recording medium,

The liquid developer contains an insulating liquid and toner particles composed of a material containing a polyester resin,

As a dispersant, an amide compound having an alkyldiamine and a hydroxy fatty acid skeleton is contained.

In the image forming apparatus according to the present invention, it is preferable that the developing unit has a supply unit for supplying the liquid developer for forming the monochrome image, and a unit for recovering the liquid developer remaining in the supply unit. part and a partition wall provided between the recovery part and the supply part,

The liquid developer remaining in the supply portion is recovered to the recovery portion through the partition wall.

By satisfying the above configuration, it is possible to provide a liquid developer having excellent positive charging characteristics and excellent dispersion stability of toner particles, and an image forming apparatus using such a liquid developer.

Description of drawings

FIG. 1 is a schematic diagram showing an example 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 .

Fig. 3 is a schematic view showing the state of toner particles in a liquid developer layer on a developing roller.

In the figure, 1—toner particles, 1000—image forming device, 10Y, 10M, 10C, 10K—photoreceptor, 11Y—charging roller, 12Y—exposure unit, 13M, 13Y—photoreceptor squeeze roller, 14M, 14Y —Cleaning knife, 15M, 15Y—developer recovery section, 16Y—static removal unit, 17Y—photoreceptor cleaning knife, 18Y—developer recovery section, 20Y, 20M, 20C, 20K—developing roller, 201Y—liquid developer layer , 21Y—developing roller cleaning knife, 24Y—developer recovery section, 25Y—corona discharger (compression mechanism), 30Y, 30M, 30C, 30K—developing section, 31Y—liquid developer storage section, 31aY—supply section, 31bY—Recovery section, 31cY—Partition, 32Y—Coating roller, 33Y—Fine adjustment knife, 34Y—Developer stirring roller, 35Y—Connecting section, 36Y—Recovery spiral, 40—Intermediate transfer section, 41—Belt driving roller , 49—tension roller, 44, 45—driven roller, 46—intermediate transfer section cleaning knife, 47—developer recovery section, 48—non-contact bias application member, 51Y, 51M, 51C, 51K—1 time Transfer backup roller, 52Y, 52M, 52C, 52K—squeeze device of intermediate transfer part, 53Y—squeeze roller of intermediate transfer part, 55Y—squeeze cleaning knife of intermediate transfer part, 56Y—developer recovery part, 60 —secondary transfer unit, 64—upstream side secondary transfer roller, 65—downstream side secondary transfer roller, 66, 68—secondary transfer roller cleaning knife, 67, 69—developer recovery section, 90Y, 90M, 90C, 90K—liquid developer supply, 91Y, 91M, 91C, 91K—liquid developer storage, 92Y, 92M, 92C, 92K—insulating liquid storage, 93Y, 93M, 93C, 93K—liquid developer Agent mixing tank, 100Y—developing unit, 101Y—photoreceptor squeezer, F40—fixing unit (fixing device), F5—recording medium.

Detailed ways

Preferred embodiments of the present invention will be described in detail below.

"Liquid Developer"

First, the liquid developer of the present invention will be described. The liquid developer of the present invention is a liquid developer in which toner particles are dispersed in an insulating liquid. In addition, the liquid developer of the present invention contains an amide compound having an alkyldiamine and a hydroxy fatty acid skeleton as a dispersant.

<Dispersant>

First, the dispersant will be described.

The liquid developer of the present invention contains an alkyldiamine and an amide compound having a hydroxy fatty acid skeleton as a dispersant.

However, polyester resins conventionally used for toner particles are generally highly negatively chargeable, and it is difficult to apply them to positively chargeable toner particles (liquid developers). In addition, it is considered to add a charge control agent to positively charge conventional toner particles using a polyester resin as a binder resin, but it is difficult to obtain a sufficient charge amount.

In addition, a dispersant is added to the liquid developer in order to improve the dispersibility of the toner particles. However, when the dispersant is added, there is usually a problem that the charging characteristics of the liquid developer are lowered.

On the other hand, as in the present invention, by using an amide compound having an alkyldiamine and a hydroxy fatty acid skeleton as a dispersant, the following effects can be obtained.

A polyester resin constituting toner particles generally has an acidic group (carboxyl group, etc.) in its molecule. The acidic group is ionically bonded to the nitrogen atom of each of the dispersants, and each of the dispersants is chemically attached or adsorbed on the surface of the toner particles. In addition, the nitrogen atoms constituting each dispersant attract protons (H ⁺ ) released from the acidic groups of the polyester resin, so that the toner particles can be positively charged. In this way, the positive charging property of the liquid developer can be made excellent. In addition, since the charging characteristics are excellent, characteristics such as developing efficiency and transfer efficiency are also excellent. Furthermore, the site of the hydroxy fatty acid skeleton of the amide compound having a hydroxy fatty acid skeleton is arranged to face the insulating liquid side because of its particularly high affinity with insulating liquid (especially vegetable oil or fatty acid monoester as described later). Since the respective dispersants are adsorbed on the surface of the toner particles in such a state, the skeleton is interposed between adjacent toner particles, which can effectively prevent the aggregation of the toner particles, etc., thereby making the toner particles The dispersion stability of the toner particles is excellent. In addition, since the dispersion stability can be made excellent in this way, in the image forming apparatus as described later, when the liquid developer recovered in the developing unit etc. is reused, the recovered liquid developer can be easily redispersed. The toner particles can be easily reused.

In this way, the liquid developer of the present invention can achieve both excellent positive charging characteristics and excellent dispersion stability by containing an alkyldiamine and an amide compound having a hydroxy fatty acid skeleton as a dispersant. However, when two types of dispersants are used in combination, usually the properties of one dispersant interfere with the properties of the other dispersant, and it is difficult to balance the properties of both dispersants. However, in the present invention, the characteristics described below of the alkyldiamine and the characteristics described below of the amide compound having a hydroxy fatty acid skeleton can be simultaneously realized, and at the same time, the respective characteristics can be exhibited more remarkably by utilizing a synergistic effect. .

On the other hand, when only one of the alkyldiamine and the amide compound having a hydroxy fatty acid skeleton is used, it is not possible to simultaneously achieve the above-mentioned excellent positive charging characteristics and excellent dispersion stability. That is, when only alkyldiamine is used, dispersion stability cannot be fully exhibited. In addition, in the case of using only an amide compound having a hydroxy fatty acid skeleton, it is difficult to positively charge the toner particles.

Each dispersant will be described in detail below.

[Alkyldiamine]

The alkyldiamine is a component that mainly contributes to the positive charging property of the liquid developer.

As the alkyldiamine, those having various structures can be used, and a compound represented by the following general formula (I) is particularly preferably used.

【Chemical 3】

H ₂ N—R—NH—R’……(I)

(wherein R is an alkylene group having 2 to 6 carbon atoms, and R' is an alkyl group having 8 to 24 carbon atoms.)

By using an alkyldiamine with such a structure, the nitrogen atom at the secondary amine site (-NHR') can effectively attract free protons (H ⁺ ) from the acidic groups of the polyester resin, etc., so that the tuner can be more effectively The toner particles are positively charged. As a result, the positive charging characteristics of the liquid developer can be made particularly excellent.

In addition, since the alkyldiamine of the above-mentioned structure has a primary amine site (NH ₂ —), it is bonded to the acidic group on the surface of the toner particle through a strong ionic bond, and thus adheres (adsorbs) more firmly. on the surface of toner particles. As a result, the alkyldiamine can be more reliably present on the surface of the toner particles, so the liquid developer becomes a liquid developer that exhibits a more stable positive charging characteristic. In addition, since the secondary amine site (-NHR') of the alkyldiamine having the above-mentioned structure has a high affinity for the insulating liquid, it is attached (adsorbed) to the surface of the toner particle, and is disposed toward the insulating liquid. liquid side. As a result, together with the dispersibility-improving effect of the amide compound having a hydroxy fatty acid skeleton described later, aggregation of toner particles and the like can be more effectively prevented, thereby making the dispersibility of toner particles particularly excellent.

As described above, in the structural formula (I), R is preferably an alkylene group having 2 to 6 carbon atoms, and R is more preferably an alkylene group having 2 to 4 carbon atoms. In this way, the dispersion stability of the toner particles can be further improved.

In addition, as described above, in the structural formula (I), R' is preferably an alkyl group having 8 to 24 carbon atoms, and R' is more preferably an alkyl group having 8 to 20 carbon atoms. In this way, the dispersion stability of the toner particles can be further improved.

Among them, the alkyldiamine may include a plurality of compounds represented by the above-mentioned structural formula (I) in which the number of carbon atoms of R or the number of carbon atoms of R' is different.

Examples of alkyldiamines having the above structure include Duomin CD, Duomin T, Duomin HT ("Duomin" is a trade name of Lion Akzo Corporation), Asphazol # 10, Asphazol # 20 ("Asphazol" is a trade name of NOF Corporation), and among them, 1 type or a combination of 2 or more types can be used.

The amine value of the alkyldiamine is preferably 50 to 500 mgKOH/g, more preferably 400 to 450 mgKOH/g. In this way, the toner particles can be positively charged more reliably, and at the same time, the dispersion stability of the toner particles can be made higher.

The content of the alkyldiamine in the liquid developer is preferably 0.1 to 8 parts by weight, more preferably 0.3 to 5 parts by weight, and still more preferably 0.6 to 1 part by weight relative to 100 parts by weight of the toner particles. If the content of the alkyldiamine is within the above range, the charging characteristics of positive charging can be made particularly excellent.

[Amide compound having a hydroxy fatty acid skeleton]

The amide compound having a hydroxy fatty acid skeleton is a component that mainly contributes to the dispersion stability of toner particles.

As the amide compound having a hydroxy fatty acid skeleton, amide compounds having a hydroxy fatty acid skeleton having various structures can be used, and a compound represented by the following general formula (II) is particularly preferably used.

【Chemical 4】

(In the formula, R1, R2, R3 are H, CH ₃ , OH, OCH ₃ , OCH ₂ CH ₃ , OCH ₂ CH ₂ CH ₃ , or fatty acids with 12 to 18 carbon atoms, a=1 to 5, b=1 ~21, c=1~21, d=1~5, and (b+c)≦26.)

By using the amide compound with such a structure, the main chain containing nitrogen atoms is more reliably attached (adsorbed) to the surface of the toner particles, and the side chains of the hydroxy fatty acid skeleton are more effectively arranged on the insulating liquid side. As a result, the dispersion stability of toner particles can be made particularly excellent.

In addition, the nitrogen atom of the main chain not only contributes to the adhesion (adsorption) to the surface of the toner particle, but also can attract the free proton (H ⁺ ) in the insulating liquid to some extent, so it can be used with the above The synergistic effect of the above-mentioned alkyldiamine becomes a monomer that makes positive charging more excellent in charging characteristics.

In addition, in the structure, the hydroxy fatty acid skeleton is preferably a 12-hydroxystearic acid skeleton. In this way, the side chain moiety can be more reliably arranged on the insulating liquid side. As a result, the 12-hydroxystearic acid skeleton can be reliably interposed between adjacent toner particles, thereby more effectively preventing aggregation of the toner particles, etc., making the dispersion stability of the toner particles particularly excellent.

Examples of the amide compound having the above structure include SOLSPERSE 11200 and SOLSPERSE 17000 (SOLSPERSE is a trade name of Lubrizol Corporation), and among them, one type may be used or two or more types may be used in combination.

The content of the amide compound in the liquid developer is preferably 0.1 to 7 parts by weight, more preferably 0.5 to 3 parts by weight, and still more preferably 0.6 to 1.5 parts by weight relative to 100 parts by weight of the toner particles. If the content of the amide compound is within the range, the dispersibility of toner particles can be improved more effectively.

<Toner particles>

Next, toner particles will be described.

[Constituent material of toner particles]

The toner particles contain at least a polyester resin-containing resin material.

1. Resin material

In the present invention, the resin material contains polyester resin. Polyester resin has high transparency, and when used as a binder resin, it has good color rendering properties of the obtained image, and also has the characteristics that high fixing properties can be obtained. However, as described above, since polyester resin is a component exhibiting negative chargeability or low chargeability (in the case of low acid value), toner particles composed of such polyester resin generally exhibit negative chargeability. In the present invention, by attaching (adsorbing) each of the above-mentioned dispersants to the surface of the toner particles, the above-mentioned effects can be effectively exerted by using the polyester resin, and at the same time, it can be made to be excellent in positive chargeability. Furthermore, it is a liquid developer having excellent dispersion stability. Among them, the content of the polyester resin in the resin is preferably 50 wt % or more, more preferably 80 wt % or more.

In addition, as the polyester resin, it is preferable to use together a low molecular weight polyester resin having a weight average molecular weight of 3,000 to 12,000 and a high molecular weight polyester resin having a weight average molecular weight Mw of 20,000 to 400,000. In this way, at the time of storage, it is possible to reliably prevent the aggregation of toner particles, and at the same time, it is possible to fix the toner particles to the recording medium at a relatively low temperature.

The low molecular weight polyester resin preferably has ethylene glycol (EG) and/or neopentyl glycol (NPG) as a constituent monomer component. In addition, when the EG content rate W (EG) [wt%] and the NPG content rate W (NPG) [wt%] in all the constituent monomers used in the synthesis of the low molecular weight polyester resin, The value of the weight ratio W(EG)W/(NPG) of EG and NPG is preferably 0 to 1.1, more preferably 0.8 to 1.0. In this way, the preservability of toner particles can be made sufficiently excellent. In addition, it can be stably fixed to the recording medium at low temperature. In addition, such a liquid developer is also more suitable for image formation at high speed.

In addition, the glass transition point Tg of the low molecular weight polyester resin is preferably 30 to 55°C, more preferably 35 to 50°C. By using a low-molecular-weight polyester resin that satisfies the above conditions as a constituent material of toner particles, aggregation and fusion between toner particles can be more reliably suppressed during storage, thereby improving the storage stability of the liquid developer. become better. Furthermore, toner particles can be better fixed to the recording medium at low temperature.

In addition, the softening point T1/2 of the low molecular weight polyester resin is preferably 60 to 120°C, more preferably 80 to 110°C. By using a polyester resin that satisfies the above conditions as a constituent material of toner particles, aggregation and fusion between toner particles can be more reliably suppressed during storage, thereby improving the storage stability of the liquid developer. outstanding. Furthermore, at the time of fixing, the toner particles can be melted with a smaller amount of heat. In this way, toner particles can be fixed more stably at low temperatures. In addition, such a liquid developer becomes also better suited to image formation at high speed.

In addition, in this specification, the glass transition point Tg refers to the measurement conditions in the differential scanning calorimeter DSC-220C (manufactured by SII): sample amount 10 mg, heating rate 10°C/min, measurement temperature range 10 to When measured at 150°C, the temperature at the point of intersection between the extended line of the baseline (baseline) below the glass transition point and the tangent line representing the maximum inclination from the rising portion of the peak to the apex of the peak.

In addition, the softening point refers to the measurement conditions in a Koka flow tester (manufactured by Shimadzu Corporation): temperature rise rate: 5°C/min, and the softening start temperature when the die hole diameter is 1.0mm .

In addition, when the toner particles contain a polyester resin, the content of the low-molecular-weight polyester resin in the polyester resin is preferably 50 to 90 wt%, more preferably 60 to 80 wt%. In this way, the storage stability and low-temperature fixability of the liquid developer can be made particularly excellent.

It is preferable that the above-mentioned high molecular weight polyester resin has ethylene glycol (EG) and/or neopentyl glycol (NPG) as a constituent monomer component. In addition, when the EG content rate W (EG) [wt%] and the NPG content rate W (NPG) [wt%] in all constituent monomers used in the synthesis of such a polyester resin, EG and NPG The value of the weight ratio W(EG)/W(NPG) is preferably 1.2 to 3.0, more preferably 1.5 to 2.0. In this way, the storage stability of the liquid developer can be made particularly excellent. In addition, at the time of fixing, toner particles can be better fixed at a low temperature. Furthermore, the adhesiveness and weather resistance of the fixed toner particles to the recording medium are more excellent, and the obtained toner image has particularly excellent durability.

In addition, the glass transition point Tg of the high molecular weight polyester resin is preferably 45 to 70°C, more preferably 50 to 65°C. By using a high-molecular-weight polyester resin satisfying the above-mentioned conditions as a constituent material of toner particles, during storage, aggregation and fusion between toner particles can be more reliably suppressed, thereby improving the storage stability of the liquid developer. become better. In particular, when the liquid developer is stored at a high temperature, the aggregation of toner particles can be more reliably prevented, and the high-temperature storage property of the liquid developer is particularly excellent. Furthermore, toner particles can be better fixed to the recording medium at low temperature.

In addition, the softening point T1/2 of the high molecular weight polyester resin is preferably 60 to 220°C, more preferably 80 to 190°C. By using a polyester resin that satisfies the above conditions as a constituent material of toner particles, aggregation and fusion between toner particles can be more reliably suppressed during storage, thereby improving the storage stability of the liquid developer. outstanding. Furthermore, at the time of fixing, the toner particles can be more firmly fixed to the recording medium at a low temperature.

The glass transition point Tg of the polyester resin containing the above-mentioned low-molecular-weight polyester resin and high-molecular-weight polyester resin is preferably 35 to 60°C, more preferably 40 to 50°C. By using a polyester resin that satisfies the above conditions as a constituent material of toner particles, aggregation and fusion between toner particles can be more reliably suppressed during storage, thereby improving the storage stability of the liquid developer. outstanding. In addition, toner particles can be better fixed to the recording medium at low temperature.

In addition, when the toner particles contain a polyester resin, the content of the high molecular weight polyester resin in the polyester resin is preferably 10 to 50 wt%, more preferably 20 to 40 wt%. In this way, the storage stability and low-temperature fixability of the liquid developer can be made particularly excellent.

The acid value of the polyester resin used in the present invention is preferably 5 to 15 mgKOH/g, more preferably 5 to 10 mgKOH/g. In this way, the dispersant as described above can be more effectively held on the surface of the toner base particles. On the other hand, if the acid value of the polyester resin is less than the lower limit value, each of the above-mentioned dispersants may not sufficiently adhere to the surface of the toner particles. On the other hand, if the acid value of the polyester resin exceeds the above-mentioned upper limit, the negative chargeability of the polyester resin will become strong, and the desired positive charge characteristics may not be sufficiently obtained.

In addition, the glass transition point Tg of the entire resin material containing the above-mentioned polyester resin is preferably 15 to 70°C, more preferably 20 to 55°C. In this way, the produced liquid developer containing toner particles can more reliably suppress aggregation and fusion of toner particles during storage, thereby improving the storage stability of the liquid developer. Furthermore, toner particles can be better fixed to the recording medium at low temperature.

In addition, the softening point (T1/2) of the resin material containing the above-mentioned polyester resin is not particularly limited, but is preferably 50 to 130°C, more preferably 50 to 120°C, and still more preferably 60 to 115°C.

In addition, as the resin material constituting the toner particles, known resins other than the above-mentioned polyester resin may be contained.

The resin material other than polyester resin is not particularly limited, but rosin-modified resin is preferably used.

By using a rosin-modified resin, the following effects can be obtained.

Since the rosin-modified resin has a particularly high affinity with each of the above-mentioned dispersants, it can firmly adhere (adsorb) each of the above-mentioned dispersants to the surface of the toner particles. In addition, such a rosin-modified resin is a component plasticized by the insulating liquid mentioned later. Accordingly, the toner particles having the rosin-modified resin as a constituent can more firmly adhere (adsorb) the respective dispersants described above. As a result, the dispersion stability of the toner particles can be made particularly excellent, and at the same time, the charging characteristics of the positive charge of the liquid developer can be made particularly excellent.

In addition, since the rosin-modified resin has low compatibility with the above-mentioned polyester resin, by using the polyester resin and the rosin-modified resin in combination, the rosin-modified resin can be localized on the surface of the toner particles. By making them localized in this way, each of the above-mentioned dispersants can be reliably present on the surface of the toner particles, so that the dispersion stability and the charging characteristics of positive charging can be made particularly excellent.

Such rosin-modified resins include, for example, rosin-modified phenolic resins, rosin-modified maleic resins, rosin-modified polyester resins, fumaric-acid-modified rosin resins, ester gums, etc., and one of them can be used. Or use 2 or more types together.

The softening point of the rosin-modified resin described above is preferably 80 to 190°C, more preferably 80 to 160°C, and still more preferably 80 to 130°C. In this way, the long-term dispersion stability and charging characteristics of the toner particles are excellent, and at the same time, the fixing characteristics and heat-resistant storage properties of the toner particles can be achieved at a higher level.

In addition, the weight average molecular weight of the rosin-modified resin is preferably 500 to 100,000, more preferably 1,000 to 80,000, and still more preferably 1,000 to 50,000. In this way, the long-term dispersion stability and charging characteristics of the toner particles are excellent, and at the same time, the fixing characteristics and heat-resistant storage properties of the toner particles can be achieved at a higher level.

In addition, the acid value of the rosin-modified resin is preferably 40 mgKOH/g or less, more preferably 30 mgKOH/g or less, and still more preferably 25 mgKOH/g or less.

In addition, the content of the rosin-modified resin in the resin material constituting the toner particles is preferably 1 to 50 wt%, more preferably 5 to 40 wt%. In this way, the rosin-modified resin can be more reliably present on the surface of the toner particles, so that the dispersion stability and positive charging characteristics of the toner particles can be more effectively improved.

2. Colorant

In addition, the toner may also contain a colorant. It does not specifically limit as a coloring agent, For example, a well-known pigment, dye, etc. can be used.

3. Other ingredients

In addition, the toner particles may contain components other than those described above. As such a component, a well-known wax, magnetic powder, etc. are mentioned, for example.

As constituent materials (components) of toner particles, other than the above-mentioned materials, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt and the like can be used.

[Shape of Toner Particles]

The average particle diameter of the toner particles composed of the materials described above is preferably 0.5 to 4.0 μm, more preferably 1 to 4.0 μm, and still more preferably 1 to 3.5 μm. If the average particle size of the toner particles is a value within the above range, the unevenness of the characteristics among the toner particles can be made small, so that the reliability of the liquid developer as a whole is high, and it can also be used The resolution of the toned image formed by the liquid developer is sufficiently high. In addition, the toner particles can be well dispersed in the insulating liquid, and the storage stability of the liquid developer can be improved. However, in this specification, "average particle diameter" means the average particle diameter of a volume basis.

The content of toner particles in the liquid developer is preferably 10 to 60 wt%, more preferably 20 to 50 wt%.

<Insulating liquid>

Next, the insulating liquid will be described.

The insulating liquid may be a liquid with sufficiently high insulating properties. Specifically, the electrical resistance at room temperature (20° C.) is preferably 10 ¹¹ Ωcm or higher, more preferably 10 ¹² Ωcm or higher, and still more preferably 10 ¹³ Ωcm or higher.

In addition, the dielectric constant of the insulating liquid is preferably 3.5 or less.

As the insulating liquid satisfying such conditions, for example, IsoparE, IsoparG, IsoparH, IsoparL (Isopar; trade name of Exxon Chemical Company), Shellsol 70, Shellsol 71 (Shellsol; trade name of Shell Oil Company), AMSCO OMS, AMSCO 460 solvent (AMSCO; trade name of Spirits), low-viscosity and high-viscosity liquid paraffin (Wako Pure Chemical Industries) and other mineral oils (hydrocarbon-based liquids), vegetable oils containing fatty acid glycerides, medium-chain fatty acid esters, etc. , fatty acid monoesters as esters between fatty acids and monoalcohols, octane, isooctane, decane, isodecane, decahydronaphthalene, nonane, dodecane, isododecane, cyclohexane, cyclohexane Octane, cyclodecane, benzene, toluene, xylene, mesitylene, and the like can be used alone or in combination of two or more. Among them, vegetable oil is mainly composed of fatty acid triglyceride, so the affinity (miscibility) with the above-mentioned dispersant (particularly the hydroxy fatty acid skeleton part of the amide compound) is particularly high, so the adjustment can be further improved. Dispersion stability of toner particles. In addition, the affinity with the polyester resin constituting the toner particles is also high, and particularly excellent dispersion stability can be exhibited. In addition, since the fatty acid free from vegetable oil can be used to donate protons to toner particles, it is also advantageous for positive chargeability. In addition, uneven charging characteristics can also be prevented. In addition, vegetable oil is an environmentally friendly ingredient. Therefore, the environmental load of the insulating liquid due to leakage of the insulating liquid to the outside of the image forming apparatus or disposal of the used liquid developer can be reduced. As a result, an environmentally friendly liquid developer can be provided.

In addition, among the above, it is preferable to use an insulating liquid containing a fatty acid monoester as the insulating liquid. Since the fatty acid monoester has a structure similar to the hydroxy fatty acid skeleton part of the amide compound, it can further improve the dispersion stability of the toner particles similarly to the vegetable oil. In particular, the above-mentioned effect can be made more remarkable by using it together with the above-mentioned vegetable oil. In addition, since the fatty acid freed from the fatty acid monoester can be used to donate protons to the toner particles, it is also advantageous for positive chargeability.

In addition, the fatty acid monoester is a component having an effect (plasticizing effect) of plasticizing toner particles (polyester resin, rosin-modified resin). By plasticizing in this way, each of the above-mentioned dispersant components can be firmly adhered (adsorbed) to the surface, thereby further improving the positive charging characteristics of the toner particles and further improving dispersion stability. In addition, the plasticized toner particles can easily adhere to the recording medium, so that the fixability of the toner particles can be made higher.

Examples of such fatty acid monoesters include oleic acid, palmitoleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidonic acid, docosahexaenoic acid (DHA), Alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters of unsaturated fatty acids represented by carbapentaenoic acid (EPA), butyric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid Alkyl (methyl, ethyl, propyl, butyl, etc.) monoesters of saturated fatty acids represented by arachidic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, etc. can be used One selected from these or two or more used in combination.

When the insulating liquid contains fatty acid monoester, the content of fatty acid monoester in the insulating liquid is preferably 1 to 50 wt%, more preferably 5 to 45 wt%. In this way, the toner particles can be favorably plasticized, so that the respective dispersants can be more reliably attached (adsorbed) to the surface of the toner particles. As a result, the dispersion stability of the toner particles can be further improved, so that the charging characteristics of positive charging can be made particularly excellent.

The viscosity of the insulating liquid is not particularly limited, but is preferably 5 to 1000 mPa·s, more preferably 50 to 800 mPa·s, and still more preferably 50 to 500 mPa·s. If the viscosity of the insulating liquid is a value within the above range, when the liquid developer is drawn from the developer container onto the coating roller, an appropriate amount of the insulating liquid adheres to the toner particles, so that the toner particles can be adjusted. The developability and transferability of color images are particularly excellent. However, the viscosity in this specification means the value measured at 25 degreeC.

"Manufacturing method of liquid developer"

Next, preferred embodiments of the method for producing a liquid developer of the present invention will be described.

The method for producing a liquid developer according to this embodiment includes: a dispersion liquid preparation step of preparing a dispersion liquid in which a resin material and a colorant are dispersed in an aqueous dispersion medium; a coalescence step of coalescing several types of dispersed phases to obtain coalesced particles; A desolvation process of removing the organic solvent contained in the coalesced particles to obtain toner particles containing a resin material and a colorant; dispersion of dispersing the toner particles and each of the above-mentioned dispersants in an insulating liquid process.

Each step constituting the manufacturing method of the liquid developer will be described in detail below.

[Dispersion liquid preparation process (aqueous dispersion liquid preparation process)]

First, a dispersion liquid (aqueous dispersion liquid) is prepared.

The aqueous dispersion is a dispersion prepared by any method, for example, dissolving and dispersing constituent materials (toner materials) of toner particles such as a resin material and a colorant in an organic solvent to obtain a resin liquid (resin liquid preparation) treatment), adding an aqueous dispersion medium composed of an aqueous liquid to the resin liquid, forming a dispersed phase (liquid dispersed phase) containing toner materials in the aqueous liquid, thereby obtaining a dispersed dispersion (aqueous dispersion) in which the dispersed phase has been dispersed ) (disperse phase formation treatment).

(resin solution preparation process)

First, prepare a resin solution in which a resin material and a hydrolysis inhibitor are dissolved or dispersed in an organic solvent.

The prepared resin liquid contains the constituent materials of the toner particles as described above and an organic solvent as described below.

The organic solvent may be any organic solvent as long as it dissolves at least a part of the resin material, but it is preferable to use an organic solvent having a lower boiling point than an aqueous liquid described later. In this way, the organic solvent can be easily removed.

In addition, the organic solvent is preferably an organic solvent having low miscibility with an aqueous dispersion medium (aqueous liquid) described later (for example, an organic solvent having a solubility of 30 g or less in 100 g of an aqueous dispersion medium at 25° C.). In this way, the toner material can be finely dispersed in a stable state in the aqueous emulsion.

In addition, the composition of the organic solvent can be appropriately selected according to, for example, the composition of the above-mentioned resin material, colorant, or aqueous dispersion medium.

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 liquid can be obtained, for example, by mixing a resin material, a colorant, an organic solvent, and the like with a mixer or the like. Examples of the stirrer that can be used for the preparation of the resin solution include high-speed stirrers such as DESPA (manufactured by Asada Iron Works Co., Ltd.), and T.K.

In addition, the material temperature during stirring is preferably 20 to 60°C, more preferably 30 to 50°C.

The solid content in the resin liquid is not particularly limited, but is preferably 40 to 75 wt%, more preferably 50 to 73 wt%, and still more preferably 50 to 70 wt%. If the content of the solid content is a value within the above-mentioned range, the dispersed phase constituting the dispersion (emulsion suspension) described later can be a dispersed phase with a higher degree of sphericity (a dispersed phase in a shape close to a sphere), thereby The shape of the finally obtained toner particles can be more reliably made suitable.

In addition, in the preparation of the resin liquid, all the constituents of the resin liquid to be prepared can be mixed at the same time, or a part of the constituents of the resin liquid to be prepared can be mixed in advance to obtain a mixture (master), and then the mixture (master) ) mixed with other ingredients.

(Dispersed Phase Formation Treatment)

Next, an aqueous dispersion (dispersion) is prepared.

By adding an aqueous dispersion medium composed of an aqueous liquid to the resin liquid, a dispersed phase (liquid dispersed phase) containing a toner material is formed in the aqueous liquid to obtain a dispersion in which the dispersed phase is dispersed (aqueous dispersion).

The aqueous dispersion medium is composed of an aqueous liquid.

As the aqueous liquid, an aqueous 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 of 50 parts by weight or more per 100 parts by weight of water at 25° C.).

In addition, an emulsifying dispersant may be added to the aqueous dispersion medium as necessary. Adding an emulsifying dispersant makes it easier to prepare water-based emulsions.

It does not specifically limit as an emulsification dispersant, For example, a well-known emulsification dispersant can be used.

In addition, when preparing an aqueous dispersion, for example, a neutralizing agent can also be used. In this way, for example, the functional groups (such as carboxyl groups) possessed by the resin material can be neutralized, so that the shape and size uniformity of the dispersed phase in the prepared aqueous dispersion liquid and the dispersibility of the dispersed phase can be made particularly excellent. Therefore, the particle size distribution of the obtained toner particles becomes particularly narrow.

The neutralizing agent may be added, for example, to a resin liquid, or may be added to an aqueous liquid.

In addition, the neutralizing agent may be added several times during the preparation of the aqueous dispersion.

As the neutralizing agent, basic compounds can be used, and more specifically, inorganic bases such as sodium hydroxide, potassium hydroxide, and ammonia, or organic bases such as diethylamine, triethylamine, and isopropylamine, etc. can be used. One selected from these or two or more used in combination. In addition, the neutralizing agent may be an aqueous solution containing the above-mentioned compounds.

In addition, the amount of the basic compound used is preferably 1 to 3 times (1 to 3 equivalents) of the amount necessary to neutralize all the carboxyl groups that the resin material has, more preferably 1 to 2 times the amount (1 ~2 equivalents). In this way, the formation of a heterogeneous dispersed phase can be effectively prevented, and the particle size distribution of the particles obtained in the coalescence step described in detail later can be sharpened.

The addition of the aqueous liquid to the resin liquid may be performed by any method, but it is preferable to add the aqueous liquid containing water to the resin liquid while stirring the resin liquid. That is, it is preferable to slowly add (drop) the aqueous liquid to the resin liquid while applying a shearing force to the resin liquid with a stirrer or the like, so as to convert from a W/O type emulsion to an O/W type emulsion. phase, and finally obtain an aqueous dispersion in which the dispersed phase derived from the resin liquid is dispersed in the aqueous liquid.

Examples of agitators that can be used in the preparation of aqueous dispersions include DESPA (manufactured by Asada Iron Works Co., Ltd.), T.K. High-speed mixer or high-speed disperser such as Cavitron (manufactured by Eurotec), etc.

Moreover, when adding an aqueous liquid to a resin liquid, it is preferable to stir at a tip speed of 10-20 m/sec, and it is more preferable to stir at 12-18 m/sec. If the tip speed is a value within the above range, the water-based dispersion can be effectively obtained, and at the same time, the shape and size of the dispersed phase in the water-based dispersion can be made particularly small, thereby preventing excessive generation of fine particles. Dispersed phase, coarse particles, and can also make the uniform dispersion of the dispersed phase particularly excellent.

The solid content in the aqueous dispersion is not particularly limited, but is preferably 5 to 55 wt%, more preferably 10 to 50 wt%. In this way, unintentional aggregation between the dispersed phases in the aqueous dispersion can be more reliably prevented, and at the same time, the productivity of toner particles can be made particularly excellent.

In addition, the material temperature in this treatment is preferably 20 to 60°C, more preferably 20 to 50°C.

[Coalescence process]

Next, the various dispersed phases are coalesced to obtain coalesced particles (coalescing step). The coalescence of the dispersed phase is usually carried out by colliding the dispersed phases containing the organic solvent to integrate them.

Coalescence of several dispersed phases is carried out by adding electrolyte to the dispersion while stirring the dispersion. In this way, coalesced particles can be obtained easily and reliably. In addition, by adjusting the amount of electrolyte added, the particle size and particle size distribution of the coalesced particles can be easily and reliably controlled.

The electrolyte is not particularly limited, and known organic and inorganic water-soluble salts and the like can be used alone or in combination of two or more.

In addition, the electrolyte is preferably a salt of a monovalent cation. In this way, the particle size distribution of the resulting agglomerated particles can be made narrow. In addition, by using a salt of a monovalent cation, the generation of coarse particles can be reliably prevented in this step.

In addition, among the above, the electrolyte is preferably sulfate (such as sodium sulfate, ammonium phosphate) or carbonate, particularly preferably sulfate. In this way, the particle size of the agglomerated particles can be controlled particularly easily.

The amount of the electrolyte added in this step is preferably 0.5 to 3 parts by weight, more preferably 1 to 2 parts by weight, based on 100 parts by weight of solid content contained in the electrolyte-added dispersion liquid. In this way, the particle size of the coalesced particles can be controlled particularly easily and reliably, and at the same time, the occurrence of coarse particles can be reliably prevented.

In addition, the electrolyte is preferably added in the state of an aqueous solution. In this way, the electrolyte can be quickly diffused throughout the entire dispersion liquid, and at the same time, the amount of the electrolyte added can be easily and reliably controlled. As a result, agglomerated particles with a particularly narrow particle size distribution can be obtained with desired particle sizes.

In addition, when the electrolyte is added in the state of an aqueous solution, the concentration of the electrolyte in the aqueous solution is preferably 2 to 10 wt%, more preferably 2.5 to 6 wt%. In this way, the electrolyte can be diffused particularly rapidly throughout the dispersion, so that the amount of electrolyte added can be easily and reliably controlled. In addition, by adding such an aqueous solution, the water content in the dispersion liquid after adding the electrolyte can be made appropriate. Therefore, the growth rate of the aggregated particles after the addition of the electrolyte can be appropriately slowed to such an extent that the productivity is not lowered. As a result, the particle size can be controlled more reliably. In addition, unintended coalescence of coalesced particles can also be reliably prevented.

In addition, in the case of adding the electrolyte with an aqueous solution, the rate of addition of the aqueous electrolyte solution is preferably 0.5 to 10 parts by weight/minute, more preferably 1.5 ~5 parts by weight/min. In this way, it is possible to prevent the uneven concentration of the electrolyte from occurring in the dispersion liquid, and it is possible to reliably prevent the generation of coarse particles. In addition, the particle size distribution of the agglomerated particles becomes particularly narrow. Furthermore, by adding the electrolyte at such a rate, the rate of coalescence can be particularly easily controlled, so that it becomes particularly easy to control the average particle diameter of the coalesced particles, and at the same time, the productivity of the toner can be made particularly excellent.

The addition of the electrolyte may also be performed in fractions. In this way, agglomerated particles of a desired size can be easily and reliably obtained, and at the same time, the circularity of the obtained agglomerated particles can be reliably made sufficiently large.

In addition, this process is performed in the state which stirred the dispersion liquid. In this way, agglomerated particles having particularly small variations in shape and size among particles can be obtained.

In stirring the dispersion, for example, anchor blades, turbine blades, Pfaudler blades, Fullzone (FZ) stirring blades, Maxblend (MB) stirring blades, crescent-shaped stirring blades, etc. can be used. Stirring blades, wherein, preferably maxblend (MB) stirring blades, three-bladed backward curved wings (Pfaudler blade). In this way, the added electrolyte can be quickly and uniformly dispersed and dissolved, and the occurrence of uneven concentration of the electrolyte can be reliably prevented. In addition, it is also possible to effectively coalesce the dispersed phase while more reliably preventing the collapse of temporarily formed coalesced particles. As a result, agglomerated particles having small variations in shape and particle diameter among particles can be efficiently obtained.

The tip speed of the stirring blade is preferably 0.1 to 10 m/sec, more preferably 0.2 to 8 m/sec, and still more preferably 0.2 to 6 m/sec. When the wing tip speed is 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 also possible to more effectively coalesce the dispersed phase while more reliably preventing the collapse of the temporarily formed coalesced particles.

The average particle diameter of the obtained aggregated particles is preferably 0.5 to 5 μm, more preferably 1.5 to 3 μm. In this way, the particle diameter of the finally obtained toner particles can be moderated.

[Desolventization (desolvation of coal) process]

Then, the organic solvent contained in the dispersion liquid is removed. In this way, fine resin particles (toner particles) dispersed in the dispersion liquid can be obtained.

The removal of the organic solvent can also be performed by any method, but can be performed, for example, under reduced pressure. In this way, it is possible to sufficiently prevent modification of constituent materials such as resin materials and the like while effectively removing the organic solvent.

In addition, the treatment temperature in this step is preferably a temperature lower than the glass transition point (Tg) of the resin material constituting the coalesced particles.

In addition, this process can also be performed in the state which added the antifoaming agent to a dispersion liquid. In this way, the organic solvent can be efficiently removed.

As the antifoaming agent, for example, in addition to mineral oil-based antifoaming agents, polyether-based antifoaming agents, and silicone-based antifoaming agents, lower alcohols, higher alcohols, fats and oils, fatty acids, fatty acid esters, Phosphates, etc.

The amount of the antifoaming agent used is not particularly limited, but is preferably 20 to 300 ppm, more preferably 30 to 100 ppm in terms of weight ratio relative to the solid content contained in the dispersion.

In addition, in this step, at least a part of the aqueous liquid may be removed together with the organic solvent.

In addition, in this step, it is not necessary to remove all the organic solvent (the total amount of the organic solvent contained in the dispersion liquid). Even in such a case, the remaining organic solvent can be sufficiently removed in other steps described later.

[washing process]

Next, the resin fine particles (toner particles) thus obtained are washed (washing step).

By performing this step, even if an organic solvent or the like is contained as impurities, they can be effectively removed. As a result, the amount of volatile organic compounds (TVOC) in the finally obtained resin fine particles can be made particularly small.

This step can be achieved by, for example, separating the resin particles by solid-liquid separation (separation from the aqueous liquid), and then performing redispersion of the solid content (resin particles) in water and solid-liquid separation (separation of the resin particles from the aqueous liquid). conduct. Redispersion of solid content in water and solid-liquid separation may be repeated several times.

[drying process]

Thereafter, toner particles can be obtained by performing drying treatment (drying process).

The drying step can be performed using, for example, a vacuum dryer (for example, Ribocone (manufactured by Okawara Seisakusho Co., Ltd.), Naut (manufactured by Hosokawa Micron Co., Ltd.), etc.), a fluidized bed dryer (manufactured by Okawara Seisakusho Co., Ltd.), and the like.

[dispersion process]

Next, the toner particles obtained as described above and each of the dispersants as described above are dispersed in an insulating liquid. In this way, a liquid developer is obtained.

Dispersion of the toner particles and the dispersant in the insulating liquid can be performed by any method, for example, by mixing the insulating liquid, toner particles, and the dispersant with a bead mill, a ball mill, or the like. By mixing by such a method, the dispersant can be more reliably attached or adsorbed to the surface of the toner particles.

In this dispersion, components other than the insulating liquid, toner particles, and the dispersant may be mixed.

In addition, the dispersion of the toner particles and the respective dispersants in the insulating liquid may be performed using the entire amount of the insulating liquid constituting the finally obtained liquid developer, or may be performed using a part of the insulating liquid.

In addition, in the case of using a part of the insulating liquid to disperse the toner particles and the dispersant, the same liquid as the liquid used in the dispersion may be added as the insulating liquid after the dispersion, or may be added after the dispersion. A liquid different from that used in dispersion is added as an insulating liquid. In the latter case, properties such as viscosity of the finally obtained liquid developer can be easily adjusted. In addition, in the case where the liquid used in the dispersion is a fatty acid monoester, it is possible to reliably plasticize the toner particles.

In the case of producing the liquid developer by the method as described above, the contained toner particles become toner particles whose constituent materials are uniformly dispersed, and at the same time, the unevenness of the shape among the toner particles is small. of toner particles. In this way, the surface area of the particle surface becomes relatively uniform among the particles, and the above-mentioned dispersants can be more uniformly attached or adsorbed to the surface of the toner particles. As a result, it is possible to effectively suppress the unevenness of charging characteristics between toner particles and facilitate the configuration in the development and transfer process.

"Image Formation Device"

Next, preferred embodiments of the image forming apparatus of the present invention will be described. The image forming apparatus of the present invention forms a color image on a recording medium using the liquid developer of the present invention as described above.

FIG. 1 is a schematic diagram showing an example of an image forming apparatus to which the liquid developer of the present invention is applied. 2 is an enlarged view of a part of the image forming apparatus shown in FIG. 1 , and FIG. 3 is a schematic view showing a state of toner particles in a liquid developer layer on a developing roller.

As shown in FIGS. 1 and 2, the image forming apparatus 1000 has four developing sections 30Y, 30M, 30C, and 30K, an intermediate transfer section 40, a secondary transfer unit (secondary transfer section) 60, and a fixing section (fixing device). ) F40, and four liquid developer supply parts 90Y, 90M, 90C, and 90K.

The developing units 30Y, 30M, and 30C respectively have a liquid developer (Y), a liquid developer for magenta (M), and a liquid developer for cyan (C) to develop a latent image and form a monochromatic image corresponding to each color. Function. In addition, the developing unit 30K has a function of developing a latent image with a black-based liquid developer (K) to form a black (black) monochrome 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 has a photoreceptor 10Y as an example of an image carrier, a charging roller 11Y along the rotation direction of the photoreceptor 10Y, an exposure unit 12Y, a developing unit 100Y, a photoreceptor liquid squeezer 101Y, a primary A transfer backup roller 51Y, a static elimination unit 16Y, a photoreceptor cleaning blade 17Y, and a developer recovery section 18Y.

The photoreceptor 10Y has a cylindrical substrate and a photosensitive layer formed on its outer peripheral surface, such as amorphous silicon, and can rotate around the central axis. In this embodiment, as indicated by the arrow in FIG. , turn clockwise.

A liquid developer is supplied to the photoreceptor 10Y 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 photoreceptor 10Y, and the exposure unit 12Y is a device for forming a latent image on the charged photoreceptor 10Y by irradiating laser light. The exposure unit 12Y has a semiconductor laser, a polygon mirror, an F-theta lens, etc., and irradiates the charged photoreceptor 10Y with modulated laser light based on an image signal input from a host (not shown) such as a personal computer or a word processor.

The developing unit 100Y is a device for developing a latent image formed on the photoreceptor 10Y using the liquid developer of the present invention. Note that details of the developing unit 100Y will be described later.

The photoreceptor liquid squeeze device 101Y faces the photoreceptor 10Y on the downstream side of the rotation direction of the developing unit 100Y, and includes a photoreceptor liquid squeeze roller 13Y, which is press-contacted with the photoreceptor liquid squeeze roller 13Y to remove the The cleaning blade 14Y that removes the liquid developer attached thereto and the developer recovery unit 15Y that recovers the removed liquid developer. The photoreceptor squeeze device 101Y recovers the remaining carrier (insulating liquid) and originally unnecessary fogging toner from the developer that has been developed on the photoreceptor 10Y, thereby improving image development. function of the ratio of toner particles within.

The primary transfer backup roller 51Y is a means for transferring the monochrome image formed on the photoreceptor 10Y to the intermediate transfer unit 40 described later.

The charge removing unit 16Y is a device for removing residual charge 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 photoreceptor cleaning blade 17Y is a member made of rubber that is in contact with the surface of the photoreceptor 10Y. function of the liquid developer.

The developer recovery unit 18Y has a function of recovering the liquid developer removed by the photoreceptor cleaning blade 17Y.

The intermediate transfer unit 40 is an endless elastic belt member, and is stretched over a belt drive roller 41 and a pair of driven rollers 44 and 45 that transmit the driving force of a motor (not shown). In addition, the intermediate transfer unit 40 is rotationally driven counterclockwise by the belt drive 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.

Furthermore, predetermined tension is applied to the intermediate transfer unit 40 by the tension roller 49 to remove slack. The tension roller 49 is provided on the downstream side in the rotation (movement) direction of the intermediate transfer section 40 by one driven roller 44 and is provided on the upstream side in the rotation (movement) direction of the intermediate transfer section 40 by the other driven roller 45 .

Using the primary transfer backup rollers 51Y, 51M, 51C, and 51K, monochrome images corresponding to the respective colors formed in the developing portions 30Y, 30M, 30C, and 30K are successively transferred to the intermediate transfer portion 40, and the monochrome images corresponding to the respective colors are superimposed. Hue image. In this way, a full-color developer image (intermediate transfer image) is formed on the intermediate transfer portion 40 .

In this way, in the intermediate transfer section 40, the monochrome images formed on the plurality of photoreceptors 10Y, 10M, 10C, and 10K are sequentially transferred twice, stacked, and loaded, and transferred to the second transfer unit described later. In 60, the secondary transfer is performed on the recording medium F5 such as paper, film, cloth, etc. together. 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 an uneven sheet due to fibers or the like, an elastic belt member can be used as a surface imitating the unevenness. A means to improve the secondary transfer characteristics on the surface of the sheet.

In addition, a cleaning device including an intermediate transfer portion cleaning blade 46 , a developer recovery portion 47 , and a non-contact bias application member 48 is disposed on the intermediate transfer portion 40 .

The intermediate transfer section cleaning blade 46 and the developer recovery section 47 are arranged on the driven roller 45 side.

The intermediate transfer section cleaning blade 46 has a function of scraping and removing the liquid developer adhering to the intermediate transfer section 40 after the image is transferred onto the recording medium F5 by the secondary transfer unit (secondary transfer section) 60 .

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 bias applying member 48 is provided at a position opposed to the tension roller 49 at a distance from the intermediate transfer portion 40 . The non-contact bias applying member 48 applies a bias voltage of opposite polarity to that of the toner (solid content) of the liquid developer remaining on the intermediate transfer portion 40 after the secondary transfer. In this way, the toner is neutralized, and the electrostatic adhesion of the toner to the intermediate transfer portion 40 is reduced. In this example, a corona charger can be used as the non-contact bias applying member 48 .

In addition, the non-contact bias applying member 48 does not necessarily have to be provided at a position opposite to the tension roller 49, for example, it may be provided at a position between the driven roller 44 and the tension roller 49, etc., that is, by utilizing the intermediate rotation of the driven roller 44 Any position on the downstream side in the moving direction of the printing section and on the upstream side in the moving direction of the intermediate transfer section using the driven roller 45 . In addition, a known non-contact charger other than a corona charger may be used as the non-contact bias applying member 48 .

In addition, the intermediate transfer unit liquid squeezer 52Y is disposed on the downstream side of the intermediate transfer unit 40 in the moving direction by the primary transfer backup roller 51Y.

This intermediate transfer unit liquid developer 52Y is provided to remove excess insulating liquid from the transferred liquid developer when the liquid developer transferred on the intermediate transfer unit 40 is not in a desired dispersed state. organization.

The intermediate transfer part squeeze device 52Y includes an intermediate transfer part squeeze roller 53Y, an intermediate transfer part squeeze cleaning knife 55Y that is in pressure contact with the intermediate transfer part squeeze roller 53Y to clean the surface, and a recovering intermediate transfer part. The developer recovery part 56Y of the liquid developer removed by the squeeze cleaning blade 55Y.

The liquid squeezing device 52Y of the intermediate transfer part recovers the remaining insulating liquid from the developer transferred on the intermediate transfer part 40 to increase the ratio of toner particles in the image, and at the same time recovers the originally unnecessary mist. The function of the toner.

The secondary transfer unit 60 includes a pair of secondary transfer rollers arranged with a predetermined partition between them along the transfer material moving direction. Among these pair of secondary transfer rollers, the secondary transfer roller disposed upstream 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 in pressure contact with the belt drive roller 41 via the intermediate transfer unit 40 .

In addition, among the pair of secondary transfer rollers, the secondary transfer roller arranged 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 in 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 respectively bring the recording medium F5 into contact with the intermediate transfer portion 40 hung on the belt drive roller 41 and the driven roller 44, and transfer the material onto the recording medium F5. The secondary transfer is an intermediate transfer image in which colors are superimposed on the intermediate transfer unit 40 .

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

Therefore, the recording medium F5 conveyed by the secondary transfer unit 60 is from the pressure contact start position (nip start position) of the upstream secondary transfer roller 64 and the belt driving roller 41 to the downstream secondary transfer roller 65 and from The pressure contact end position (nip end position) of the moving roller 44 is in close contact with the intermediate transfer unit 40 in a predetermined moving area of the transfer material. In this way, the full-color intermediate transfer image on the intermediate transfer unit 40 is secondary-transferred to the recording medium F5 in close contact with the intermediate transfer unit 40 within a predetermined time, so good secondary transfer can be performed.

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

The toner image (transferred image) transferred on the recording medium F5 by the secondary transfer unit 60 is sent to the fixing unit (fixing device) F40 , heated and pressurized, and fixed on the recording medium F5 .

Among them, specifically, the fixing temperature is preferably 80 to 160°C, more preferably 100 to 150°C, and still more preferably 100 to 140°C.

Next, the developing units 100Y, 100M, 100C, and 100K will be described in detail. However, in the following description, the developing unit 100Y will be described as a representative.

As shown in FIG. 2 , the developing unit 100Y has a liquid developer storage portion 31Y, a coating roller 32Y, a fine adjustment knife 33Y, a developer agitating roller 34Y, a communication portion 35Y, a recovery screw 36Y, a developing roller 20Y, a developing roller cleaning knife 21Y And corona discharger (compression mechanism) 25Y.

The liquid developer storage unit 31Y has a function of storing a liquid developer for developing a latent image formed on the photoreceptor 10Y, and includes a supply unit 31aY for supplying the liquid developer to the developing unit, recovery of the liquid developer in the supply unit 31a, and the like. A recovery portion 31bY for the remaining liquid developer and a partition wall 31cY that separates the supply portion 31aY and the recovery portion 31bY.

The supply portion 31aY has a function of supplying the liquid developer to the coating roller 32Y, and has a concave portion where the developer agitating roller 34Y is provided. In addition, the liquid developer is supplied from the liquid developer mixing tank 93Y to the supply portion 31 aY through the communication portion 35Y.

The recovery unit 31bY recovers the liquid developer excessively supplied to the supply unit 31aY or the surplus liquid developer generated in the developer recovery units 15Y and 24Y. The recovered liquid developer is sent to a liquid developer mixing tank 93Y described later, and then reused. Moreover, the recovery part 31bY has a concave part, and the recovery screw 36Y is provided in the vicinity of the bottom.

A wall-shaped partition wall 31cY is provided at the boundary between the supply part 31aY and the recovery part 31bY. The partition wall 31cY separates the supply part 31aY and the recovery part 31bY, and can prevent the collected liquid developer from being mixed into the fresh liquid developer. In addition, when the excess liquid developer is supplied to the supply portion 31aY, the excess liquid developer may go over the partition wall 31cY and overflow from the supply portion 31aY to the recovery portion 31bY. Therefore, the amount of the liquid developer supplied to the supply part 31aY can be kept constant, and the liquid amount of the liquid developer supplied to the coating roller 32Y can be kept constant. Therefore, the image quality of the finally formed image becomes stable.

In addition, a notch is provided in the partition wall 31cY, 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 liquid developer to the developing roller 20Y.

This coating roller 32Y is a coating roller called an anilox roller (Anilox Roller) with uniformly formed spiral grooves on the surface of a metallic roller such as iron and nickel plating, and its diameter is about 25 mm. . In this embodiment, a plurality of grooves are formed obliquely with respect to the rotation direction of the coating roller 32Y by so-called cutting, rolling, or the like. The coating roller 32Y contacts the liquid developer while rotating counterclockwise, thereby supporting the liquid developer in the supply portion 31 aY in the groove, and conveying the carried liquid developer to the developing roller 20Y.

The fine adjustment blade 33Y is in contact with the surface of the application roller 32Y, and finely adjusts the amount of the liquid developer on the application roller 32Y. That is, the fine blade 33Y functions to scrape off the remaining liquid developer on the coating roller 32Y and measure the liquid developer on the coating roller 32Y to be supplied to the developing roller 20Y. The fine adjustment blade 33Y is made of urethane rubber which is an elastic body, and is supported by a fine adjustment blade support member made of metal such as iron. In addition, the fine blade 33Y is provided on the side where the coating roller 32Y rotates to enter and exit the liquid developer (ie, the right side in FIG. 2 ). Here, the rubber hardness of the fine blade 33Y is about 77 degrees based on JIS-A, and the hardness (about 77 degrees) of the contact portion of the fine blade 33Y to the surface of the coating roller 32Y becomes lower than the elasticity of the developing roller 20Y described later. The hardness (approximately 85 degrees) of the pressure-bonded portion of the layer of the body to the surface of the coating roller 32Y. In addition, the remaining liquid developer scraped off is recovered to the supply portion 31aY, and further reused.

The developer agitating roller 34Y has a function of agitating the liquid developer into a uniformly dispersed state. In this way, even in the case where a plurality of toner particles 1 are aggregated, the toner particles 1 can be dispersed well among themselves. In particular, the liquid developer of the present invention has high dispersibility of the toner particles, and thus can be better dispersed. In addition, even if it is a reused liquid developer, it can be easily dispersed.

In the supply portion 31aY, the toner particles 1 in the liquid developer have a positive charge, and the liquid developer is agitated by the developer agitating roller 34Y to be in a uniformly dispersed state. 31Y is pulled up, and the liquid developer amount is finely adjusted by a fine adjustment knife 33Y, and then supplied to the developing roller 20Y. In addition, by stirring with the developer stirring roller 34Y, the liquid developer can be stably overflowed to the recovery portion 31bY side over the partition wall 31cY, thereby preventing stagnation and compression of the liquid developer.

Furthermore, a developer stirring roller 34Y is provided near the communication portion 35Y. Therefore, the liquid developer supplied from the communication portion 35Y can be quickly diffused, and even when the liquid developer is replenished to the supply portion 31aY, the liquid level of the supply portion 31aY can be stabilized. By providing such a developer agitating roller 34Y near the communication portion 35Y, the communication portion 35Y becomes negative pressure, whereby the liquid developer can be naturally sucked.

The communication portion 35Y is provided vertically below the developer stirring roller 34Y, communicates with the liquid developer storage portion 31Y, and sucks the liquid developer from the liquid developer mixing tank 93Y to the supply portion 31aY.

By disposing the communication portion 35Y below the developer agitating roller 34Y, the liquid developer supplied from the communication portion 35Y becomes stopped by the developer agitating roller 34Y, there is no swelling of the upper surface of the liquid caused by the ejection, and the upper surface of the liquid is cleared. By keeping it constant, the developer can be stably supplied to the coating roller 32Y.

In addition, the recovery screw 36Y provided near the bottom of the recovery part 31bY is composed of a cylindrical member with helical ribs on the outer periphery, and has the function of maintaining the fluidity of the recovered liquid developer and at the same time, has the function of promoting the development of liquid developer. The function of transporting the liquid developer in the agent mixing tank 93Y.

The developing roller 20Y carries the liquid developer and conveys it to a developing position facing the photoreceptor 10Y in order to develop the latent image carried on the photoreceptor 10Y with the liquid developer.

In the developing roller 20Y, the liquid developer layer 201Y is formed by supplying the liquid developer from the aforementioned coating roller 32Y to the surface of the developing roller 20Y.

The developing roller 20Y is provided with a layer of a conductive elastic body on the outer peripheral portion of an inner core made of metal such as iron, and has a diameter of about 20 mm. In addition, the elastomer layer is composed of a two-layer structure. As its inner layer, it has polyurethane rubber with a rubber hardness of about 30 degrees based on JIS-A and a thickness of about 5 mm. As its surface layer (outer layer), it has a rubber hardness based on JIS-A. A is urethane rubber with an angle of about 85 degrees and a thickness of about 30 μm. Next, the surface layer of the developing roller 20Y serves as a pressure contact portion, and is in pressure contact with the application roller 32Y and the photoreceptor 10Y in a state of being elastically deformed.

In addition, the developing roller 20Y is rotatable about its center axis which is located below the rotation center axis of the photoreceptor 10Y. In addition, the developing roller 20Y rotates in a direction (counterclockwise in FIG. 2 ) opposite to the rotational direction of the photoreceptor 10Y (clockwise in FIG. 2 ). Further, when developing the latent image formed on the photoreceptor 10Y, an electric field is formed between the developing roller 20Y and the photoreceptor 10Y.

The corona discharger (compression mechanism) 25Y is a device having a function of bringing the toner of the liquid developer carried on the developing roller 20Y into a compressed state. In other words, the corona discharger 25Y applies an electric field of the same polarity as the toner particles 1 to the liquid developer layer 201Y, as shown in FIG. 3 , in the liquid developer layer 201Y, the toner particles 1 Means that are biased near the surface of the developing roller 20Y. By making the toner particles localized in this way, the development density (development efficiency) can be increased, and as a result, a high-quality clear image can be obtained.

In addition, in the developing unit 100Y, the coating roller 32Y and the developing roller 20Y are respectively driven by different power sources (not shown). Next, the amount of the liquid developer supplied to the developing roller 20Y can be adjusted by changing the ratio of the rotational speed (linear velocity) of the application roller 32Y to that of the developing roller 20Y.

In addition, the developing unit 100Y has a developing roller cleaning blade 21Y made of rubber that contacts the surface of the developing roller 20Y, and a developer recovery portion 24Y. The developing roller cleaning blade 21Y is a device for scraping and removing the liquid developer remaining on the developing roller 20Y after developing at the developing position. The liquid developer removed by the developing roller cleaning blade 21Y is recovered in the developer recovery unit 24Y.

In addition, as shown in FIGS. 1 and 2 , image forming apparatus 1000 includes liquid developer supply units 90Y, 90M, 90C, and 90K that supply liquid developer to developing units 30Y, 30M, 30C, and 30K. These liquid developer supply units 90Y, 90M, 90C, and 90K respectively include liquid developer tanks 91Y, 91M, 91C, and 91K, insulating liquid tanks 92Y, 92M, 92C, and 92K, and liquid developer mixing tanks 93Y, 93M, 93C, 93K.

High-concentration liquid developers corresponding to respective colors are stored in the liquid developer tanks 91Y, 91M, 91C, and 91K, respectively. In addition, insulating liquids are stored in the insulating liquid tanks 92Y, 92M, 92C, and 92K, respectively. Furthermore, to each of the liquid developer mixing tanks 93Y, 93M, 93C, and 93K, predetermined amounts of high-concentration liquid developers from the liquid developer storages 91Y, 91M, 91C, and 91K and high-concentration liquid developers from the insulating liquid storage tank 92Y are supplied. , 92M, 92C, 92K of the specified amount of each insulating liquid.

Next, each liquid developer mixing tank 93Y, 93M, 93C, and 93K mixes and stirs each high-concentration liquid developer and each insulating liquid supplied separately by using a stirring device installed separately, and prepares a liquid developer corresponding to each supply unit 31aY, 31aM, 31aC, Various liquid developers used in 31aK. The respective liquid developers prepared in the respective liquid developer mixing tanks 93Y, 93M, 93C, and 93K are supplied to the respective supply parts 31aY, 31aM, 31aC, and 31aK.

In addition, in the liquid developer mixing tank 93Y, the liquid developer recovered in the recovery part 31bY is recovered and reused. The same applies to the liquid developer mixing tanks 93M, 93C, and 93K.

As mentioned above, although this invention was demonstrated based on preferable embodiment, this invention is not limited to these.

For example, the liquid developer of the present invention is not limited to be applicable only to the above-mentioned image forming apparatus.

In addition, the liquid developer of the present invention is not limited to being produced by the above-mentioned production method.

In addition, in the above-mentioned embodiment, a mode in which agglomerated particles are obtained by obtaining an aqueous emulsion and adding an electrolyte to the aqueous emulsion has been described, but the present invention is not limited thereto. For example, the coalescing particles can be obtained by dispersing a colorant, a monomer, a surfactant, and a polymerization initiator in a water-based liquid, utilizing emulsion polymerization to prepare a water-based emulsion, adding an electrolyte to the water-based emulsion, and causing them to associate. It is formulated by emulsion polymerization association method, and coalesced particles can also be obtained by spray-drying the obtained water-based emulsion.

In addition, in the above-mentioned embodiments, the configuration including the corona discharger as the image forming apparatus has been described, but the corona discharger may not be required.

【Example】

[1] Manufacture of liquid developer

A liquid developer was produced as follows.

(Example 1)

First, production of toner particles is performed. In addition, the process which does not describe temperature was performed at room temperature (25 degreeC).

<Dispersion adjustment process>

(Preparation of coloring liquid mixing (master) solution)

First, polyester resin (acid value: 10 mgKOH/g, glass transition point (Tg): 55° C., softening point: 107° C.): 60 parts by weight was prepared as a resin material.

Next, a mixture (mass ratio 50:50) of the resin material and a cyan pigment (manufactured by Dainichi Seika Co., Ltd., pigment blue 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) is kneaded using a twin-screw kneading extruder. Cool the kneaded product extruded from the extrusion port of the twin-screw kneading extruder.

The kneaded product cooled as above is coarsely pulverized to obtain a colorant masterbatch (average particle diameter: 1.0 mm or less). A hammer mill was used for coarse pulverization of the kneaded product.

(resin solution preparation process)

Using a high-speed disperser (manufactured by Plaimic, T.K.ROBOMIX/T.K.HOMODISPER 2.5 type wing), mix methyl ethyl ketone: 175 parts by weight, the poly Ester resin: 172.3 parts by weight Rosin-modified phenolic resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "KG2212", acid value: 22 mgKOH/g or less, softening point: 172-182, weight-average molecular weight: 100000): 55.3 parts by weight , NEOGENSC-F (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.): 1.38 parts by weight was added as an emulsifier to prepare a resin solution. Here, in this solution, the pigment is finely dispersed uniformly.

(Dispersed Phase Formation Treatment)

Then, add 1 equivalent of ammonia water to the resin liquid in the container: 72.8 parts by weight, utilize a high-speed disperser (manufactured by Spectrum, T.K.ROBOMIX/T.K.HOMO DISPER2.5 type wing), so that the tip speed of the stirring blade is 7.5m/s, stir fully, adjust the temperature of the solution in the flask to 25°C, then make the tip speed of the stirring wing become 14.7m/s, continue to stir, and simultaneously drip 400 parts by weight of deionized water, Phase inversion emulsification occurs. Continue stirring while further adding deionized water: 100 parts by weight relative to the resin solution. In this way, an aqueous dispersion in which the dispersed phase containing the resin material is dispersed is obtained.

<Coalescence process>

Next, the aqueous dispersion liquid was transferred to a stirring vessel having a Maxblend (MB) stirring blade, and the temperature of the aqueous dispersion liquid was kept at 25° C. while stirring at a tip speed of the stirring blade at 1.0 m/s.

Next, while maintaining the same temperature and stirring conditions, 5.0% sodium sulfate aqueous solution: 200 parts by weight was dripped at the same time to coalesce the dispersed phase to form coalesced particles. After dropping, stirring was continued until the 50% volume particle diameter Dv(50) [μm] of the toner particles of the coalesced particles grew to 3.5 μm. When the Dv(50) of the coalesced particles became 3.5 μm, 200 parts by weight of deionized water was added to terminate the coalescence.

<Desolventization process>

The organic solvent was distilled off under reduced pressure from the obtained coalesced particle dispersion until the solid content became 23% by weight to obtain a slurry of fine resin particles.

<Washing process>

Next, the slurry is subjected to solid-liquid separation, and further redispersion in water (reslurry) and solid-liquid separation are repeated to perform washing treatment. Thereafter, a wet cake of colored resin particles (resin particle cake) was obtained by suction filtration. Wherein, the moisture content of the wet filter cake is 35wt%.

<Drying process>

After that, the obtained wet cake was dried by using a vacuum dryer to obtain toner particles.

<Dispersion process>

The toner particles obtained in the above method were added to a ceramic tank (inner volume: 600 ml): 37.5 parts by weight of alkyldiamine (manufactured by Lion Akzo Corporation, trade name "DUOMINCD" as a dispersant, amine value: 437 mgKOH /g): 0.24 parts by weight and an amide compound having a 12-hydroxystearic acid skeleton (manufactured by Japan Lubrizol Corporation, trade name "SOLSPERSE11200"): 0.48 parts by weight, rapeseed oil (manufactured by Nissin Oilio Co., trade name "High-oleic rapeseed oil"): 90 parts by weight, soybean oil fatty acid methyl ester (manufactured by Nissin Oilio Co., Ltd.): 60 parts by weight, and then put zirconia beads (ball diameter: 1mm) into the ceramic tank to make the volume The filling rate was 85%, and it was dispersed for 24 hours at a rotation speed of 230 rpm using a table-top tank grinder. In this way, a liquid developer is obtained.

The Dv(50) of the toner particles in the obtained liquid developer was 3.2 μm. Here, the 50% volume particle diameter Dv(50) [µm] of the obtained toner particles was measured using a Mastersize R1000 particle analyzer (manufactured by Malvern Instruments Ltd.). In addition, the particle diameters were obtained in the same manner for the particles obtained in each of the examples and comparative examples described below.

In addition, the viscosity at 25° C. of the obtained liquid developer was 65 mPa·s.

In addition, instead of cyan-based pigments, magenta-based pigments: Pigment Red 238 (manufactured by Sanyo Color Co., Ltd.), yellow-based pigments: Pigment Yellow 180 (manufactured by Klein Co.), and black-based pigments: carbon black (Degussa Co., Ltd. Manufactured by Printex L), except that, it was carried out in the same manner as above to produce a magenta-based liquid developer, a yellow-based liquid developer, and a black-based liquid developer.

(Example 2-5)

Except that the addition amount of the dispersant was as shown in Table 1, it carried out similarly to the said Example 1, and manufactured the liquid developer corresponding to each color.

(Example 6)

As the rosin-modified resin, a rosin-modified phenolic resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "Tamanor 135", acid value: 18 mgKOH/g or less, softening point: 130-140, weight-average molecular weight: 15000) was used. Other than that, it carried out similarly to the said Example 1, and produced the liquid developer corresponding to each color.

(Example 7)

As the rosin-modified resin, a rosin-modified phenolic resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "Tamanor 145", acid value: 18 mgKOH/g or less, softening point: 140-155, weight-average molecular weight: 20000) was used. Other than that, it carried out similarly to the said Example 1, and produced the liquid developer corresponding to each color.

(Embodiment 8)

As the rosin-modified resin, rosin-modified maleic resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "Malkyd No. 1", acid value: 25 mgKOH/g or less, softening point: 120 to 130, weight average molecular weight: 3100) was used. , except that, it was carried out in the same manner as in Example 1, and a liquid developer corresponding to each color was produced.

(Example 9)

As the alkyldiamine, except that DUOMIN T (manufactured by Lion Akzo, amine value: 364 mgKOH/g) was used, it carried out similarly to the said Example 1, and manufactured the liquid developer corresponding to each color.

(Example 10)

As the alkyldiamine, except that Asphazol #10 (manufactured by NOF Corporation, amine value: 320 mgKOH/g) was used, it was carried out in the same manner as in Example 1 to manufacture liquid developers corresponding to each color.

(Example 11)

As the alkyldiamine, except that Asphazol #20 (manufactured by NOF Corporation, amine value: 325 mgKOH/g) was used, it was carried out in the same manner as in Example 1 to manufacture liquid developers corresponding to each color.

(Example 12, 13)

Except having changed the compounding ratio of a polyester resin and a rosin-type resin as shown in Table 1, it carried out similarly to the said Example 1, and manufactured the liquid developer corresponding to each color.

(Example 14)

As the insulating liquid, instead of soybean oil fatty acid methyl ester and rapeseed oil, liquid paraffin (manufactured by COSMO Petroleum Co., Ltd., trade name "COSMO WHITE P-70") was used, except that it was carried out in the same manner as in Example 1, Manufactures liquid developers corresponding to each color.

(Example 15)

Liquid developers corresponding to each color were produced in the same manner as in Example 1 except that liquid paraffin (manufactured by COSMO Petroleum Corporation, trade name "COSMOWHITE P-70") was used instead of rapeseed oil.

(Example 16)

As the amide compound having a hydroxy fatty acid skeleton, except that SOLSPERSE 17000 (manufactured by Lubrizol Corporation) was used, it carried out similarly to the said Example 1, and produced the liquid developer corresponding to each color.

(comparative example 1)

Except not having added a dispersant (an alkyldiamine and an amide compound having a 12-hydroxystearic acid skeleton), it carried out similarly to the said Example 1, and manufactured the liquid developer corresponding to each color.

(comparative example 2)

Except not adding the amide compound which has a 12-hydroxystearic-acid skeleton as a dispersant, it carried out similarly to the said Example 1, and manufactured the liquid developer corresponding to each color.

(comparative example 3)

Except not having added the alkyldiamine as a dispersant, it carried out similarly to the said Example 1, and manufactured the liquid developer corresponding to each color.

Table 1 shows the composition and the like of the liquid developer for each of the above Examples and Comparative Examples. Wherein, in the table, polyester resin is shown as PES, rosin modified phenolic (trade name "KG2212") is shown as RP1, rosin modified phenolic (trade name "Tamanor 135") is shown as RP2, rosin modified phenolic (trade name "Tamanor 135") is shown as RP2, rosin modified Phenolic (trade name "Tamanor 145") is shown as RP3 and rosin-modified maleic resin is shown as RM. In addition, SOLSPERSE is shown as S. In addition, soybean oil fatty acid methyl ester is shown as MONO, rapeseed oil is shown as VO, and liquid paraffin is shown as LP.

【Table 1】

[2] Evaluation

The following evaluations were performed on each of the liquid developers obtained as described above.

[2.1] Developing efficiency

Using the image forming apparatus shown in FIG. 1 and FIG. 2 , a liquid developer layer using the liquid developer obtained in the respective examples and comparative examples described above was formed on a developing roller of the image forming apparatus. Next, the surface potential of the developing roller was set to 300V, the surface potential of the photoreceptor was uniformly charged at 500V, and the photoreceptor was exposed to light to attenuate the charge on the surface of the photoreceptor to bring the surface potential to 50V. The belt collects the toner particles on the developing roller after the liquid developer layer passes between the photoreceptor and the developing roller and the toner particles on the photoreceptor. Each tape used for collection was attached to a recording paper, and the concentration of toner particles was measured respectively. After the measurement, divide 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, and multiply by 100, this value was determined as the developing efficiency, and the evaluation was performed according to the following 4-level standard.

A: The developing efficiency is 90% or more, and the developing efficiency is particularly excellent.

B: The developing efficiency is 85% or more and less than 90%, and the developing efficiency is excellent.

C: The developing efficiency is 80% or more and less than 85%, and there is no practical problem.

D: The developing efficiency is less than 80%, and the developing efficiency is poor.

[2.2] 1 transfer efficiency

Using the image forming apparatus shown in FIGS. 1 and 2 , a liquid developer layer using the liquid developer obtained in each of the examples and comparative examples described above was formed on a photoreceptor of the image forming apparatus. Next, the toner particles on the photoreceptor after the liquid developer layer has passed between the photoreceptor and the intermediate transfer portion and the toner particles on the intermediate transfer portion are collected with the belt. Each tape used for collection was attached to a recording paper, and the concentration of toner particles was measured respectively. After the measurement, the concentration of toner particles collected on the intermediate transfer portion is divided by the sum of the concentration of toner particles collected on the photoreceptor and the concentration of toner particles collected on the intermediate transfer portion to obtain The obtained numerical value was multiplied by 100, and the value was determined as the primary transfer efficiency, and the evaluation was performed according to the following 4-level scale.

A: The primary transfer efficiency is 90% or more, and the primary transfer efficiency is particularly excellent.

B: The primary transfer efficiency is 85% or more and less than 90%, and the primary transfer efficiency is excellent.

C: The primary transfer efficiency is 80% or more and less than 85%, and there is no practical problem.

D: The primary transfer efficiency is less than 80%, and the primary transfer efficiency is poor.

[2.3] Second transfer efficiency

Using the image forming apparatus shown in FIGS. 1 and 2 , toner images using the liquid developers obtained in the above-described Examples and Comparative Examples were formed on the intermediate transfer portion of the image forming apparatus. Next, toner particles on the intermediate transfer portion after the toner image passed between the intermediate transfer portion and recording paper (manufactured by Seiko Epson Corporation, high-quality paper LPCPPA4) were collected with a belt. Each tape used for collection was attached to other recording paper than the above, and the concentration of toner particles was measured. On the other hand, the concentration of toner particles on the recording paper on which the toner image was transferred from the intermediate transfer portion was also measured. After the measurement, the sum of the concentration of toner particles collected on the intermediate transfer portion and the concentration of toner particles on the recording paper on which the toner image was transferred from the intermediate transfer portion was divided into The concentration of toner particles on the recording paper to which the toner image was transferred was multiplied by 100 to obtain the value as the secondary transfer efficiency, and evaluated according to the following 4-level scale.

A: The secondary transfer efficiency is 70% or more, and the secondary transfer efficiency is particularly excellent.

B: The secondary transfer efficiency is 60% or more and less than 70%, and the secondary transfer efficiency is excellent.

C: The secondary transfer efficiency is 55% or more and less than 60%, and there is no practical problem.

D: The secondary transfer efficiency is less than 55%, and the secondary transfer efficiency is poor.

[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 "microscope laser Z-potentiometer" ZC-2000 manufactured by Microtec Nition, and evaluated in accordance with the following 5-level criteria.

Measured by diluting the liquid developer with a diluent solvent, putting it into a square transparent tank (ce1l) with a side length of 10mm, applying a voltage of 300V at a distance of 9mm between the electrodes, and observing the moving speed of the particles in the tank with a microscope at the same time, thus calculating The speed of movement, from which the zeta potential is obtained.

A: The potential difference is +100 mV or more (very good).

B: The potential difference is more than +85 mV and less than +100 mV (good).

C: The potential difference is more than +70 mV and less than +85 mV (general).

D: The potential difference is more than +50 mV and less than +70 mV (slightly poor).

E: The potential difference is less than +50 mV (very poor).

[2.5] Dispersion stability test - 1

Put 10 mL of the liquid developer obtained in each example and each comparative example into a test tube (caliber 12 mm, length 120 mm), let it stand for 1 week, observe the depth of sedimentation, and evaluate according to the following 4-level standard.

A: The depth of settlement is 0 mm.

B: The depth of subsidence is greater than 0 mm and less than 2 mm.

C: The depth of settlement is more than 2 mm and less than 5 mm.

D: The depth of settlement is greater than 5 mm.

[2.6] Dispersion stability test - 2

45.5 mL of the liquid developer obtained in each of Examples and Comparative Examples was put into a centrifuge tube, and the depth of sedimentation was measured by loading at 900 G for 60 seconds using a centrifuge (manufactured by Kokusan Co., Ltd.). The sedimentation velocity S [m/s] was calculated from the obtained sedimentation depth, and the evaluation was performed according to the following criteria.

A: S≦3.0×10 ^-4

B: 3.0×10 ^-4 <S≦9.0×10 ^-4

C: 9.0×10 ^-4 <S≦1.0×10 ^-3

D: 1.0×10 ^-3 <S

These results are shown in Table 2.

【Table 2】

Developing efficiency 1 transfer efficiency 2 transfer efficiency Positively charged characteristics Dispersion Stability-1 Dispersion Stability-2 Example 1 A A A A A A Example 2 A B B B B B Example 3 B B B A A A Example 4 B B B B A B Example 5 B B B B A A Example 6 A A A A A A Example 7 A A A A A A Example 8 A A A A A A Example 9 A A A B A A Example 10 A B B B A A Example 11 A A B B A A Example 12 B B B B A A Example 13 A B B B A A Example 14 B B B B B B Example 15 A A A A B B Example 16 A A A A B B Comparative example 1 D. D. D. E. D. D. Comparative example 2 C C C C D. D. Comparative example 3 D. D. D. E. B B

As can be seen from Table 2, the liquid developer of the present invention is excellent in charging characteristics (positive charging characteristics) and dispersion stability of toner particles. In addition, the liquid developer of the present invention is also excellent in developing efficiency and transfer efficiency. On the other hand, satisfactory results could not be obtained in the liquid developers of the comparative examples.

[3] Manufacture of liquid developer

The liquid developer was produced as follows.

(Example 17)

First, production of toner particles is performed. In addition, the process which does not describe temperature was performed at room temperature (25 degreeC).

<Dispersion adjustment process>

(Preparation of colorant mixed solution)

First, as the polyester resin, low molecular weight polyester resin L1 (acid value: 8.5 mgKOH/g, weight average molecular weight Mw: 5,200, glass transition point Tg: 46°C, softening point T1/2: 95°C) was prepared: 48 parts by weight of high molecular weight polyester resin H1 (acid value: 16.0mgKOH/g, weight average molecular weight Mw: 237,000, glass transition point Tg: 63°C, softening point T1/2: 182°C): 12 parts by weight mixture.

Next, a mixture (mass ratio 50:50) of the mixture of the polyester resin and a cyan pigment (Pigment Blue 15:3 manufactured by Dainichi Seika Co., Ltd.) 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) is kneaded using a twin-screw kneading extruder. Cool the kneaded product extruded from the extrusion port of the twin-screw kneading extruder.

The kneaded product cooled as described above is coarsely pulverized to obtain a colorant masterbatch having an average particle diameter of 1.0 mm or less. A hammer mill was used for coarse pulverization of the kneaded product.

(resin solution preparation process)

Using a high-speed disperser (manufactured by Primix, T.K.ROBOMIX/T.K.HOMO DISPER2.5 type wing), mix methyl ethyl ketone: 175 parts by weight in the colorant masterbatch: 97.5 parts by weight , the mixture of the polyester resin: 172.3 parts by weight, rosin modified phenolic resin (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "KG2212", acid value: below 22mgKOH/g, softening point: 172～182, weight average molecular weight: 100000): 55.3 parts by weight, NEOGEN SC-F (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.): 1.38 parts by weight was added as an emulsifier to prepare a resin solution. Here, in this solution, the pigment is finely dispersed uniformly.

(Dispersed Phase Formation Treatment)

Then, add 1 equivalent of ammonia water to the resin liquid in the container: 72.8 parts by weight, utilize a high-speed disperser (manufactured by Spectrum, T.K.ROBOMIX/T.K.HOMO DISPER2.5 type wing), so that the tip speed of the stirring blade is 7.5m/s, stir fully, adjust the temperature of the solution in the flask to 25°C, then make the tip speed of the stirring wing become 14.7m/s, continue to stir, and simultaneously drip 400 parts by weight of deionized water, Phase inversion emulsification occurs. Continue stirring while further adding deionized water: 100 parts by weight relative to the resin solution. In this way, an aqueous dispersion in which the dispersed phase containing the resin material is dispersed is obtained.

<Coalescence process>

Next, the aqueous dispersion liquid was transferred to a stirring vessel having a Maxblend (MB) stirring blade, and the temperature of the aqueous dispersion liquid was kept at 25° C. while stirring at a tip speed of the stirring blade at 1.0 m/s.

Next, while maintaining the same temperature and stirring conditions, 5.0% sodium sulfate aqueous solution: 200 parts by weight was dripped at the same time to coalesce the dispersed phase to form coalesced particles. After dropping, stirring was continued until the 50% volume particle diameter Dv(50) [μm] of the toner particles of the coalesced particles grew to 3.5 μm. When the Dv(50) of the coalesced particles became 3.5 μm, 200 parts by weight of deionized water was added to terminate the coalescence.

<Desolventization process>

The organic solvent was distilled off under reduced pressure from the obtained coalesced particle dispersion until the solid content became 23% by weight to obtain a slurry of fine resin particles.

<Washing process>

Next, the slurry is subjected to solid-liquid separation, and further redispersion in water (reslurry) and solid-liquid separation are repeated to perform washing treatment. Thereafter, a wet cake of colored resin particles (resin particle cake) was obtained by suction filtration. Wherein, the moisture content of the wet filter cake is 35wt%.

<Drying process>

After that, the obtained wet cake was dried by using a vacuum dryer to obtain toner particles.

<Dispersion process>

Add the toner particles obtained in the above method to a ceramic tank (inner volume: 600 ml): 37.5 parts by weight of alkyldiamine (manufactured by LionAkzo Corporation, trade name "DUOMINCD" as a dispersant, amine value: 437 mgKOH/ g): 0.24 parts by weight and an amide compound having a 12-hydroxystearic acid skeleton (manufactured by Lubrizol Corporation, trade name "SOLSPERSE11200"): 0.48 parts by weight, rapeseed oil (manufactured by Nissin Oilio Co., Ltd., trade name " High-oleic rapeseed oil"): 90 parts by weight, soybean oil fatty acid methyl ester (manufactured by Nisshin Oilio Co., Ltd.): 60 parts by weight, and then put zirconia beads (ball diameter: 1 mm) into the ceramic tank to fill the volume The ratio was 85%, and it was dispersed at 230 rpm for 24 hours using a table-top tank grinder. In this way, a liquid developer is obtained.

The Dv(50) of the toner particles in the obtained liquid developer was 3.1 μm. Here, the 50% volume particle diameter Dv(50) [μm] of the obtained toner particles was measured using a MastersizeR1000 particle analyzer (manufactured by Malvern Instruments Ltd.). In addition, the particle diameters were obtained in the same manner for the particles obtained in each of the examples and comparative examples described below.

In addition, the viscosity at 25° C. of the obtained liquid developer was 65 mPa·s.

In addition, instead of cyan-based pigments, magenta-based pigments: Pigment Red 238 (manufactured by Sanyo Color Co., Ltd.), yellow-based pigments: Pigment Yellow 180 (manufactured by Klein Co.), and black-based pigments: carbon black (Degussa Co., Ltd. Manufactured by Printex L), except that, it was carried out in the same manner as above to produce a magenta-based liquid developer, a yellow-based liquid developer, and a black-based liquid developer.

(Example 18)

Instead of polyester resin L1, low molecular weight polyester resin L2 shown in Table 3 was used, and instead of polyester resin H1, high molecular weight polyester resin H2 was used, except that it was carried out in the same manner as in Example 17 to produce Corresponds to various liquid developers.

(Example 19)

Instead of polyester resin L1, low-molecular-weight polyester resin L3 shown in Table 3 was used, and instead of polyester resin H1, high-molecular-weight polyester resin H3 was used in an amount as shown in Table 4. In addition, the same as In the same manner as in Example 17, liquid developers corresponding to each color were produced.

The ratio of terephthalic acid (TPA) to isophthalic acid (IPA), ethylene glycol (EG) in all monomer components used in the synthesis of the polyester resins used in the above Examples 17 to 19, Table 3 shows the ratio to neopentyl glycol (NPG), physical parameters of each resin, and the like. In addition, in each of Examples 17 to 19, Table 3 shows the weight-average molecular weight Mw, glass transition point Tg, and softening point T1/2 of the low-molecular-weight polyester resin and high-molecular-weight polyester resin used.

In addition, the evaluation of the glass transition point Tg of the polyester resin in Table 3 used a DSC (DSC-220C manufactured by SII Corporation) as a measuring device, and about 10 mg of the resin material was taken in an alumina pan, and the temperature increase rate: 10 ° C / min , Measuring temperature range: 30 ~ 150 ℃ conditions, the measurement is carried out. However, for the measurement, values measured under the same conditions were used for the second time by temperature rise and fall (10° C. to 150° C. to 10° C.) for the first time.

In addition, the softening point T1/2 of the polyester resin in Table 3 was measured using a Koka rheometer (manufactured by Shimadzu Corporation) under the conditions of a temperature increase rate of 5°C/min and a die hole diameter of 1.0 mm. Determination.

In addition, about Examples 17-19, the composition etc. of a liquid developer are shown in Table 4. Wherein, in the table, polyester resins L1, L2, L3 are shown as L1, L2, L3 respectively, polyester resins H1, H2, H3 are shown as H1, H2, H3 respectively, and rosin modified phenolic (trade name " KG2212") is indicated as RP1. In addition, SOLSPERSE is shown as S. In addition, soybean oil fatty acid methyl ester is shown as MONO, and rapeseed oil is shown as VO.

【table 3】

In addition, the same evaluation as the above [2] was performed on each of the liquid developers obtained in Examples 17 to 19, and the results are shown in Table 5.

【table 5】

Developing efficiency 1 transfer efficiency 2 transfer efficiency Positively charged characteristics Dispersion Stability-1 Dispersion Stability-2 Example 17 A A A A A A Example 18 A A A A A A Example 19 A A A A A A

As can be seen from Table 5, the liquid developer of the present invention is excellent in charging characteristics (positive charging characteristics) and dispersion stability of toner particles. In addition, the liquid developer of the present invention is also excellent in developing efficiency and transfer efficiency.

Claims (11)

1. a liquid developer is characterized in that,

The toner-particle that contains insulativity liquid and constitute by the material that contains vibrin,

As spreading agent, contain alkyl diamine and amide compound with hydroxy fatty acid skeleton.

2. liquid developer according to claim 1, wherein,

The content of described alkyl diamine is 0.1～8 weight portion with respect to described toner-particle 100 weight portions.

3. liquid developer according to claim 1 and 2, wherein,

Described alkyl diamine is the compound shown in the following general formula (I),

H ₂N—R—NH—R’……(I)

Wherein, R is the alkylidene of carbon number 2～6, and R ' is 8～24 alkyl for carbon number.

4. according to any described liquid developer in the claim 1～3, wherein,

Described content with amide compound of hydroxy fatty acid skeleton is 0.1～7 weight portion with respect to described toner-particle 100 weight portions.

5. according to any described liquid developer in the claim 1～4, wherein,

Described amide compound with hydroxy fatty acid skeleton is the compound shown in the following general formula (II),

In the formula, R1, R2, R3 are H, CH ₃, OH, OCH ₃, OCH ₂CH ₃, OCH ₂CH ₂CH ₃Or the fatty acid of carbon number 12～18, a=1～5, b=1～21, c=1～21, d=1～5, and (b+c) ≦ 26.

6. according to any described liquid developer in the claim 1～5, wherein,

Described hydroxy fatty acid skeleton is 12-hydroxy stearic acid skeleton.

7. according to any described liquid developer in the claim 1～6, wherein,

In the material that constitutes described toner-particle, except described vibrin, also contain modified rosin resin.

8. according to any described liquid developer in the claim 1～7, wherein,

Contain vegetable oil in the described insulativity liquid.

9. liquid developer according to claim 8, wherein,

Also contain fatty-acid monoester in the described insulativity liquid.

10. an image processing system is characterized in that,

Have: use the different multiple liquid developer of color, form a plurality of development sections of the filtergram of corresponding multiple described liquid developer;

The a plurality of described filtergram that forms at a plurality of described development sections is transferred successively, forms the intermediate transfer portion of the intermediate transfer picture that a plurality of described filtergram of transfer printing is formed by stacking;

To the described intermediate transfer picture of recording medium transfer printing, on described recording medium, form fixedly 2 transfer printing portions of coloured image; With

On described recording medium, fix the photographic fixing portion of described fixedly coloured image,

The toner-particle that described liquid developer contains insulativity liquid and is made of the material that contains vibrin as spreading agent, contains alkyl diamine and the amide compound with hydroxy fatty acid skeleton.

11. image display device according to claim 10, wherein,

Described development section has: the supply unit of supplying with the described liquid developer that is used to form described filtergram;

Recovery is positioned at the recoverer of the remaining described liquid developer of described supply unit; With

The next door that between described recoverer and described supply unit, is provided with,

The remaining described liquid developer that is positioned at described supply unit is recovered to described recoverer by described next door.

Images