JP6034660B2 - Method for producing liquid developer - Google Patents

Description

  The present invention relates to a method for producing a liquid developer used for developing a latent image in an image forming apparatus such as an electrophotographic copying machine or a printer.

The electrophotographic developer includes a dry developer that uses a toner component made of a material containing a colorant and a binder resin in a dry state, and a liquid developer in which the toner component is dispersed in an insulating carrier liquid.
The liquid developer can sharpen an image by reducing the particle size of toner particles. In recent years, since the demand for higher image quality has increased, liquid developer has been required to further reduce the toner particle size.

  Patent Document 1 discloses a method for producing a toner dispersion for a liquid developer by roughly pulverizing a kneaded material kneaded with a toner material and wet-pulverizing a mixture with an unsaturated fatty acid monoester as a carrier in a ball mill. Is described. In Patent Document 1, an object is to obtain toner particles having excellent fixability by unevenly distributing unsaturated fatty acid monoesters near the surface of the toner particles.

  In Patent Document 2, a toner kneaded material obtained by kneading a toner material is coarsely pulverized to produce toner coarse particles. Further, the toner coarse particles are transferred to a carrier at a temperature lower by 50 ° C. or more than the glass transition point of the binder resin. A method for producing a toner dispersion of 5 μm or less by pulverizing in a liquid is described. In Patent Document 2, in order to improve heat resistance stability, a binder resin having a high glass transition point is used, and the carrier liquid is made of a binder resin by pulverization at a temperature lower by 50 ° C. or more than the glass transition point of the binder resin. An object of the present invention is to obtain a toner that can penetrate between molecular chains, prevent an apparent glass transition point from decreasing, and suppress a decrease in heat-resistant stability.

JP 2007-232778 A JP 2000-19788 A

However, in the conventional method, there is a problem that the viscosity of the liquid developer increases when trying to produce a liquid developer containing a toner having a small particle diameter at a high concentration. It took a long pulverization time and a complicated process was required.
For example, the method described in Patent Document 1 requires a long pulverization of 200 hours for wet pulverization, and the method described in Patent Document 2 limits the physical properties of the binder resin and is 5 hours for wet pulverization. is necessary.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a production method for efficiently producing a liquid developer having toner particles reduced in size and having a low viscosity.

The present inventors have found that the above problem can be solved by adjusting the temperature in the step of dispersing the toner particles so as to satisfy a specific condition.
That is, the present invention provides the following method [1] for producing a liquid developer.
[1] A method for producing a liquid developer in which toner particles containing at least a resin and a pigment are dispersed in an insulating liquid, the method comprising the following steps 1 to 3.
Step 1: Dry pulverizing a kneaded material obtained by kneading a toner raw material containing at least a resin and a pigment to obtain toner particles (A) Step 2: Insulating the toner particles (A) obtained in Step 1 Step 3: Obtaining the toner particle dispersion (B) by wet dispersion using a media-type disperser in the neutral liquid Step 3: Using the media-type disperser for the toner particle dispersion (B) obtained in Step 2 And the wet dispersion of the toner particle dispersion in step 3 to a temperature lower than the supply temperature of the toner particle dispersion in step 2 to the media disperser. Step of supplying and wet dispersing to obtain toner particle dispersion (C)

  According to the production method of the present invention, it is possible to efficiently produce a liquid developer containing toner particles reduced in size and having a low viscosity.

2 is a photograph of toner particles in a toner particle dispersion (C) obtained in Example 1 taken with an electron microscope. 4 is a photograph of toner particles in a toner particle dispersion (C) obtained in Comparative Example 1 taken with an electron microscope.

The present invention is a method for producing a liquid developer in which toner particles containing at least a resin and a pigment are dispersed in an insulating liquid, and includes the following steps 1 to 3.
Step 1: Dry pulverizing a kneaded material obtained by kneading a toner raw material containing at least a resin and a pigment to obtain toner particles (A) Step 2: Insulating the toner particles (A) obtained in Step 1 Step 3: Obtaining the toner particle dispersion (B) by wet dispersion using a media-type disperser in the neutral liquid Step 3: Using the media-type disperser for the toner particle dispersion (B) obtained in Step 2 And the wet dispersion of the toner particle dispersion in step 3 to a temperature lower than the supply temperature of the toner particle dispersion in step 2 to the media disperser. Step of supplying and wet dispersing to obtain toner particle dispersion (C)

According to the production method of the present invention, it is possible to efficiently produce a liquid developer containing toner particles reduced in size and having a low viscosity. The reason for such an effect is considered as follows.
First, in step 1, toner particles obtained by kneading a toner raw material containing at least a resin and a pigment are dry-pulverized and coarsely pulverized to, for example, about 8 to 20 μm. In order to further reduce the particle size, it is necessary to disperse the toner particles in a wet manner. However, in the first-stage wet pulverization in step 2, an appropriate particle size, for example, 4.0 μm, is used so that thickening does not start. Disperse to about 8.0 μm or less. The toner particles in the toner particle dispersion (B) obtained in step 2 are considered to be dispersed while being rolled flat. If the dispersion is further continued under the conditions of step 2, the toner particles are further stretched to become flat particles having an increased aspect ratio, and it is difficult to reduce the particle size. It also leads to thickening of the liquid developer.
Therefore, in the production method of the present invention, the temperature condition for the first stage wet pulverization in step 2 is changed, and in the second stage wet pulverization in step 3, the toner particle dispersion is applied to the media-type disperser. Supplying the toner particle dispersion at a temperature lower than the supply temperature to the media-type disperser in step 2 to wet disperse the toner particles between the media while suppressing excessive stretching. Or it is estimated that it can fracture between a media and a media mill wall surface.
As a result, for example, it is considered that the toner particles reduced to about 4 μm or less can be dispersed and a liquid developer in which the increase in viscosity is suppressed can be efficiently produced.

<Step 1>
Step 1 is a step of obtaining toner particles (A) obtained by dry-grinding a kneaded product obtained by kneading a toner raw material containing at least a resin and a pigment.
The toner particles (A) contain at least a resin and a pigment, but may contain other components such as a release agent and a charge control agent.

[resin]
As the resin used in the present invention, from the viewpoint of improving the low-temperature fixability of the liquid developer, it is preferable to contain polyester, and it is more preferable to use substantially only polyester.
The polyester content is preferably 90 to 100% by mass, more preferably 95 to 100% by mass, and still more preferably 100% by mass in the total resin contained in the toner particles.
Further, the content of the resin contained in the toner particles is preferably 50 to 98% by mass, more preferably 65 to 96% by mass, and further preferably 75 to 90% by mass.

In addition, in the range which does not impair the effect of this application, other resins other than polyester may be contained.
Examples of resins other than polyester include polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, Styrene resin, epoxy resin, urethane-modified epoxy resin, silicone-modified epoxy resin, rosin-modified maleic acid resin, polyethylene which is a homopolymer or copolymer containing styrene or a styrene substitution product such as styrene-methacrylic acid ester copolymer Examples include resins, polypropylene, ionomer resins, polyurethanes, silicone resins, phenol resins, aliphatic or alicyclic hydrocarbon resins.

(polyester)
In the present invention, the polyester is preferably obtained by polycondensing an alcohol component composed of a divalent or higher alcohol and a carboxylic acid component composed of a divalent or higher carboxylic acid compound.

  Examples of the divalent alcohol include an alkylene oxide adduct of bisphenol A represented by the following formula (I), a diol having 2 to 20 carbon atoms, and the like.

  In the above formula (I), RO and OR are oxyalkylene groups, and R is an alkylene group, preferably an ethylene and / or propylene group. x and y represent the number of added moles of alkylene oxide, each being a positive number. 1-16 are preferable, as for the average value of the sum of x and y, 1-8 are more preferable, and 1.5-4 are still more preferable.

  Examples of the diol having 2 to 20 carbon atoms include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, bisphenol A, hydrogenated bisphenol A, and the like. Among these diols, diols having 2 to 15 carbon atoms are preferable.

  When using trihydric or more alcohol, C3-C20 trihydric or more polyhydric alcohol is mentioned. Examples of the trihydric or higher polyhydric alcohol having 3 to 20 carbon atoms include sorbitol, 1,4-sorbitan, pentaerythritol, glycerol, trimethylolpropane, and the like. Among these polyhydric alcohols, trihydric or higher polyhydric alcohols having 3 to 10 carbon atoms are preferable.

You may use said alcohol component individually or in combination of 2 or more types.
Among these alcohol components, from the viewpoint of improving the low temperature fixability of the liquid developer and from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and obtaining a liquid developer having a high solid content concentration, the above formula ( An alkylene oxide adduct of bisphenol A represented by I) is preferred.

  The content of the alkylene oxide adduct of bisphenol A represented by the formula (I) is preferably 50 to 100 mol%, more preferably 70 to 100 mol%, still more preferably 90 to 100 mol% in all alcohol components. Substantially more preferably 100 mol%.

As a bivalent carboxylic acid compound, derivatives, such as dicarboxylic acid and its acid anhydride, a C1-C3 alkyl ester, etc. are mentioned, for example.
3-30 are preferable, as for carbon number of dicarboxylic acid and its acid anhydride, 3-20 are more preferable, and 3-10 are still more preferable.
Specific examples of the divalent carboxylic acid compound include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, and one carbon atom. Aliphatic dicarboxylic acids such as succinic acid substituted with -20 alkyl groups or alkenyl groups, and acid anhydrides thereof.

Examples of the trivalent or higher carboxylic acid compounds include trivalent or higher polyvalent carboxylic acids and acid anhydrides thereof, and derivatives such as alkyl esters having 1 to 8 carbon atoms.
4-30 are preferable, as for carbon number of polyvalent carboxylic acid more than trivalence and its acid anhydride, 6-20 are more preferable, and 8-12 are still more preferable.
Specific examples of the trivalent or higher carboxylic acid compound include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), and these. Acid anhydrides and the like.

You may use said carboxylic acid compound individually or in combination of 2 or more types.
Among these carboxylic acid components, terephthalic acid, fumaric acid, and trimellitic anhydride are preferable from the viewpoint of improving the low-temperature fixability of the liquid developer.

  In addition, from the viewpoint of adjusting the softening point of the polyester, a monovalent alcohol as an alcohol component and a monovalent carboxylic acid compound as a carboxylic acid component may be appropriately contained.

  The equivalent ratio (COOH group / OH group) of the carboxylic acid component and the alcohol component in the polyester is preferably 0.70 to 1.10, more preferably 0.80 to 1.10. preferable.

  The polyester used in the present invention is, for example, an alcohol component and a carboxylic acid component in the presence of an esterification catalyst, an esterification co-catalyst, a polymerization inhibitor, etc. in an inert gas atmosphere such as nitrogen, if necessary. It can be produced by condensation polymerization at a temperature of about ~ 250 ° C.

Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin (II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamate.
The amount of the esterification catalyst used is preferably 0.01 to 1.5 parts by mass and more preferably 0.1 to 1.0 part by mass with respect to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

Examples of the esterification cocatalyst include gallic acid and the like.
The amount of the esterification promoter used is preferably 0.001 to 0.5 parts by mass, more preferably 0.01 to 0.1 parts by mass with respect to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component.

Examples of the polymerization inhibitor include t-butylcatechol.
0.001-0.5 mass part is preferable with respect to 100 mass parts of total amounts of an alcohol component and a carboxylic acid component, and, as for the usage-amount of a polymerization inhibitor, 0.01-0.1 mass part is more preferable.
In addition, it is preferable to add a polymerization inhibitor after adding a raw material monomer, an esterification catalyst, an esterification co-catalyst, etc. and heating to a temperature of 180-250 degreeC in inert gas atmosphere.

  From the viewpoint of improving the low temperature fixability of the liquid developer, the softening point of the polyester thus obtained is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, still more preferably 120 ° C. or lower, and more preferably 105 ° C. or lower. More preferably, from the viewpoint of preventing toner particles from agglomerating, 70 ° C. or higher is preferable, 75 ° C. or higher is more preferable, 80 ° C. or higher is further preferable, 83 ° C. or higher is even more preferable, and 70 ° C. to 160 ° C. Is preferable, 75 ° C to 130 ° C is more preferable, 80 ° C to 120 ° C is further preferable, and 83 ° C to 105 ° C is still more preferable.

  From the viewpoint of improving the low temperature fixability of the liquid developer, the glass transition temperature of the polyester is preferably 80 ° C. or lower, more preferably 70 ° C. or lower, still more preferably 60 ° C. or lower, and the viewpoint of suppressing aggregation of toner particles. Therefore, 35 ° C. or higher is preferable, 40 ° C. or higher is more preferable, 45 ° C. or higher is further preferable, 35 to 80 ° C. is preferable, 40 to 70 ° C. is more preferable, and 40 to 60 ° C. is still more preferable.

  The acid value of the polyester is preferably 100 mgKOH / g or less, more preferably 50 mgKOH / g or less, and 35 mgKOH / g or less from the viewpoint of reducing the viscosity of the toner particle dispersion and improving the solid content concentration of the liquid developer. Is more preferably 20 mgKOH / g or less, and from the same viewpoint, 3 mgKOH / g or more is preferable, 8 mgKOH / g or more is more preferable, 10 mgKOH / g or more is more preferable, and 12 mgKOH / g or more is more preferable. Moreover, 3-100 mgKOH / g is preferable, 8-50 mgKOH / g is more preferable, 10-35 mgKOH / g is still more preferable, 12-20 mgKOH / g is still more preferable.

In addition, the acid value of the polyester is changed by, for example, changing the equivalent ratio of the carboxylic acid component and the alcohol component, changing the reaction time during resin production, or changing the content of the trivalent or higher carboxylic acid compound. Can be adjusted.
Moreover, the softening point, glass transition temperature, and acid value of said polyester mean the value measured by the method as described in an Example.

The polyester used in the present invention may be a polyester modified to such an extent that the characteristics are not substantially impaired.
Examples of the modified polyester include grafting and blocking with phenol, urethane, epoxy and the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Modified polyester and the like.

[Pigment]
The pigment used in the present invention is not particularly limited as long as it is a pigment used as a toner colorant. For example, carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base Solvent Red 49, Solvent Red 146, Solvent Blue 35, Quinacridone, Carmine 6B, Isoindoline, Disazo Yellow and the like.
These pigments may be used alone or in combination of two or more.
The toner of the present invention may be either black toner or color toner.

  From the viewpoint of improving the low temperature fixability of the liquid developer, the content of the pigment in the toner particles (A) is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, with respect to 100 parts by mass of the resin. From the viewpoint of improving the image density of the liquid developer, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more. Moreover, 5-100 mass parts is preferable, 5-70 mass parts is more preferable, 10-50 mass parts is still more preferable, 15-30 mass parts is still more preferable.

[Other ingredients]
The toner particles (A) used in the present invention may further include a release agent, a charge control agent, a magnetic powder, a fluidity improver, a conductivity modifier, a fibrous substance, etc., as long as the effects of the present invention are not impaired. Additives such as reinforcing fillers, antioxidants, and cleaning improvers may be used as appropriate.

[Method for Producing Toner Particles (A)]
The toner particles (A) can be obtained by dry pulverization of a kneaded product obtained by kneading a toner raw material containing a resin and a pigment, etc. From the viewpoint of improving the developability of the developer and improving the low-temperature fixability, it is preferable to melt-knead the toner raw material to obtain a melt-kneaded product, and then dry pulverize the kneaded product.
The melt-kneaded product obtained by melt-kneading can be cooled to such an extent that it can be crushed and then subjected to steps such as a pulverization step and a classification step to obtain toner particles (A).
Further, dry means that substantially no dispersion medium is used, but within the range not impairing the effects of the present invention, the same amount or less of the solvent may be included in the production of the resin. .

(Melting and kneading process)
Melting and kneading of the toner material can be performed using a known kneader such as a closed kneader, a uniaxial or biaxial kneader, and an open roll kneader.
However, in the method for producing a liquid developer of the present invention, an open roll kneader is used from the viewpoint of improving the dispersibility of the pigment in the resin and improving the yield of the toner particles after pulverization and classification. It is preferable to use.

  The toner raw material containing a resin, a pigment, and the like is preferably mixed in advance with a mixer such as a Henschel mixer, a super mixer, or a ball mill, and then supplied to the kneader. Among these mixers, a Henschel mixer is preferable from the viewpoint of improving the dispersibility of the pigment in the resin.

The mixing of the toner raw material in the Henschel mixer can be performed by adjusting the peripheral speed of the stirring and the mixing time.
The peripheral speed of stirring is preferably 10 to 30 m / s, more preferably 15 to 25 m / s, from the viewpoint of improving the dispersibility of the pigment in the resin.
The stirring time is preferably 1 to 10 minutes and more preferably 2 to 5 minutes from the viewpoint of improving the dispersibility of the pigment in the resin.

The open roll type kneader refers to an open roll kneading unit that is not sealed and can easily dissipate the kneading heat generated during melt kneading.
As an open roll type kneader used in the present invention, a continuous open roll type kneader having a plurality of raw material supply ports and a kneaded product discharge port provided along the axial direction of the roll from the viewpoint of production efficiency. It is preferable that

  The open roll type kneader used in the present invention preferably has at least two kneading rolls (heating roll and cooling roll) having different temperatures. The roll temperature can be adjusted, for example, by the temperature of the heat medium passed through the inside of the roll, and each roll may be divided into two or more and the heat medium having different temperatures may be passed through each roll.

  In the present invention, the temperature of the kneaded product discharge part of the kneader is preferably set to be equal to or lower than the softening point of the resin in any roll from the viewpoint of improving the mixing property of the toner raw material.

The set temperature on the upstream side of the kneading and the downstream side of the kneading in the heating roll is set so that the upstream set temperature is on the downstream side in order to improve the sticking of the kneaded product to the roll on the upstream side and to knead strongly on the downstream side. It is preferable that the temperature is higher than the set temperature.
As a difference of the setting temperature of the upstream and downstream of kneading in a heating roll, 1-10 degreeC is preferable and 2-7 degreeC is more preferable.

  In a roll having a lower set temperature upstream of kneading (also called a cooling roll), the set temperature upstream of kneading may be the same as or different from the set temperature downstream of kneading. .

It is preferable that the rolls of the open roll kneader have different peripheral speeds.
In an open roll type kneader equipped with a heating roll and a cooling roll, from the viewpoint of improving the low-temperature fixability of the toner, the heating roll is a roll with a higher peripheral speed (high rotation side roll), and the cooling roll is a peripheral roll. A roll having a lower speed (low-rotation side roll) is preferable.

The peripheral speed of the high rotation side roll is preferably 2 to 100 m / min, more preferably 5 to 75 m / min, further preferably 10 to 50 m / min, and still more preferably 20 to 40 m / min.
The peripheral speed of the low rotation side roll is preferably 2 to 100 m / min, more preferably 4 to 60 m / min, still more preferably 8 to 40 m / min, and still more preferably 10 to 30 m / min.
The ratio of the peripheral speeds of the two rolls (low rotation side roll / high rotation side roll) is preferably 1/10 to 9/10, more preferably 3/10 to 8/10, and 4/10 to 6 / 10 is more preferable.

  The gap (clearance) between the two rolls at the end of the kneaded product supply port side (upstream side) is preferably 0.01 to 3 mm, more preferably 0.05 to 1 mm, and still more preferably 0.07 to 0.6 mm. .

In addition, there is no limitation in particular about the structure of each roll, a magnitude | size, material, etc.
Moreover, it is preferable that the roll surface has the groove | channel used for kneading | mixing, and shapes, such as a linear form, a spiral form, a wave form, and an uneven shape, are mentioned as the shape of the said groove | channel.
Since the feed rate and average residence time of the raw material mixture vary depending on the size of the roll used, the composition of the raw material, and the like, optimal conditions may be selected according to these conditions.

(Crushing process)
In the pulverization step of the present invention, fine particles are removed in the classification step after pulverization, and the volume-median particle size (D ₅₀ ) of the toner particles tends to be slightly large. than the particle size (D _50), the volume median particle size after milling step (D ₅₀₎ is, for example, it is preferable to pulverize so that about 0.5~1.0μm reduced.
In the present invention, the volume-median particle size (D ₅₀ ) of toner particles means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size. Specifically, the value measured based on the method described in the examples is shown.

  In the pulverization step in the present invention, the pulverization may be performed in multiple stages. For example, the melt-kneaded product may be further finely pulverized after being roughly pulverized to about 1 to 5 mm. Moreover, in order to improve the productivity at the time of a grinding | pulverization and a classification process, you may grind | pulverize, after mixing melt-kneaded material with inorganic fine particles, such as hydrophobic silica.

It does not specifically limit as a grinder used for a grinding | pulverization process, A well-known grinder can be used.
Examples of the pulverizer suitably used for coarse pulverization include pulverizers such as an atomizer and a rotplex, and a hammer mill or the like may also be used.
Examples of the pulverizer suitably used for fine pulverization include a fluidized bed type counter jet mill, an airflow type jet mill, and a mechanical mill. In the fine pulverization step, it is preferable to pulverize to about 8 to 30 μm.

(Classification process)
Examples of the classifier used in the classification process include an airflow classifier, an inertia classifier, and a sieve classifier. In the classification step, the pulverized product which has been removed due to insufficient pulverization may be subjected to the pulverization step again, and the pulverization step and the classification step may be repeated as necessary.

The volume median particle size (D ₅₀ ) of the toner particles obtained in Step 1 is preferably 8 to 20 μm, more preferably 8 to 18 μm, and still more preferably 8 to 15 μm from the viewpoint of efficient wet pulverization in Step 2. .

<Step 2>
Step 2 is a step in which the toner particles (A) obtained in Step 1 are wet-dispersed in an insulating liquid using a media-type disperser to obtain a toner particle dispersion (B).
In this step, from the viewpoint of stably dispersing the toner particles in the insulating liquid, it is preferably performed in the presence of a basic dispersant, and the toner particles (A) are converted into the insulating liquid in the presence of the basic dispersant. More preferred is a step of mixing and further wet-dispersing using a media-type disperser to obtain a toner particle dispersion (B).

[Basic dispersant]
The basic dispersant is used for stably dispersing the toner particles in the insulating liquid.
In the present invention, a basic dispersant having a basic adsorbing group as an adsorbing group is preferable from the viewpoint of improving the adsorptivity to a resin, particularly polyester.

The basic dispersant preferably has a structure having a basic adsorbing group and a dispersing group in the same molecule, and more preferably has a structure having a basic adsorbing group in the main chain and a dispersing group in the side chain.
Examples of the basic adsorption group include an amino group, an amide group, an imino group, a pyrrolidone group, and a pyridine group. Among these, an amino group, an amide group, and an imino group are preferable from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer.
As the dispersing group, a group compatible with the insulating liquid is preferable, and specifically, a group having a hydrocarbon chain or a hydroxy hydrocarbon chain is more preferable.

Among such basic dispersants, a polyimine-carboxylic acid condensate is preferable from the viewpoint of improving the dispersion stability of toner particles in the liquid developer.
Examples of the polyimine include polyethyleneimine, polypropyleneimine, polybutyleneimine and the like. Among these polyimines, polyethyleneimine is preferable from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer.

The carboxylic acid is preferably a carboxylic acid having 10 to 30 carbon atoms, more preferably a carboxylic acid having 12 to 24 carbon atoms, and more preferably 16 to 22 carbon atoms from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer. The carboxylic acid is more preferable. Moreover, a saturated or unsaturated aliphatic carboxylic acid is preferable, and a linear saturated or unsaturated aliphatic carboxylic acid is more preferable.
The carboxylic acid may have a substituent such as a hydroxy group.

Specific examples of the carboxylic acid include linear saturated aliphatic carboxylic acids such as lauric acid, myristic acid, palmitic acid and stearic acid, and linear unsaturated aliphatic carboxylic acids such as oleic acid, linoleic acid and linolenic acid, Examples thereof include hydroxycarboxylic acids (and their condensates) such as mevalonic acid, ricinoleic acid, and 12-hydroxystearic acid.
Among these, from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer, hydroxycarboxylic acid is preferable, and 12-hydroxystearic acid is more preferable.

As a commercial item of the condensate of polyimine and carboxylic acid, for example, Solsperse 11200, Solsperse 13940 (both are trade names, manufactured by Nippon Lubrizol Co., Ltd.) and the like can be mentioned.
In addition, you may use a basic dispersing agent individually or in combination of 2 or more types.

  The addition amount of the basic dispersant is preferably 4 parts by mass or more with respect to 100 parts by mass of the toner particles (A) from the viewpoint of suppressing aggregation of the toner particles and reducing the viscosity of the liquid developer, and 6 parts by mass. The above is more preferable, 8 parts by mass or more is further preferable, and from the viewpoint of improving the developability of the liquid developer, 25 parts by mass or less is preferable, 20 parts by mass or less is more preferable, 15 parts by mass or less is more preferable, 4-25 mass parts is preferable, 6-20 mass parts is more preferable, and 8-15 mass parts is still more preferable.

[Insulating liquid]
The insulating liquid used in the present invention preferably has a viscosity at 25 ° C. of 3 to 60 mPa · s, and is preferably a liquid having a dielectric constant of 3.5 or less (preferably 3.0 or less).
In the present invention, the viscosity at 25 ° C. of the insulating liquid or toner particle dispersion means a value measured by the method described in Examples.
The dielectric constant of the insulating liquid is a value measured based on an impedance measurement method.

The viscosity of the insulating liquid at 25 ° C. is preferably from 3 to 55 mPa · s, from the viewpoint of reducing the viscosity of the toner particle dispersion (B) and improving the solid content concentration of the liquid developer, and preferably from 3 to 35 mPa · s. s is more preferable, 3 to 20 mPa · s is more preferable, and 3 to 15 mPa · s is further more preferable. From the viewpoint of removing toner fine particles by centrifugation and reducing toner fine particles in the liquid developer, 5 to 5 mPa · s is preferable. 55 mPa · s is preferred, 8 to 55 mPa · s is more preferred, 10 to 40 mPa · s is still more preferred, and 12 to 20 mPa · s is even more preferred.
In addition, when using combining 2 or more types of insulating liquids, the viscosity of the combined insulating liquid mixture should just be in the said range.

Specific examples of the insulating liquid include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, and polysiloxanes.
Of these, aliphatic hydrocarbons such as liquid paraffin and isoparaffin are preferred from the viewpoints of odor suppression, harmlessness, and cost.

Commercially available insulating liquids include, for example, Isopar G, Isopar H, Isopar L, Isopar K (all trade names, manufactured by Exxon Chemical), Shellsol 71 (trade name, manufactured by Shell Petrochemical), IP Solvent 1620, IP Solvent 2080 (all trade names, manufactured by Idemitsu Petrochemical Co., Ltd.), Moresco White P-55, Moresco White P-70, Moresco White P-100, Moresco White P-150, Moresco White P -260 (all trade names, manufactured by Matsumura Oil Co., Ltd.), Cosmo White P-60, Cosmo White P-70 (all trade names, manufactured by Cosmo Oil Lubricants), Lytol (trade name, manufactured by Sonneborn) It is done.
These insulating liquids can be used alone or in combination of two or more.

  The addition amount of the insulating liquid is preferably 70 parts by mass or more, more preferably 100 parts by mass or more, still more preferably 120 parts by mass or more, with respect to 100 parts by mass of the toner particles (A) from the viewpoint of viscosity reduction. From the viewpoint of increasing the transfer speed by increasing the density, 250 parts by mass or less is preferable, 200 parts by mass or less is more preferable, 180 parts by mass or less is more preferable, and 170 parts by mass or less is more preferable. Furthermore, 70-250 mass parts is preferable, 100-200 mass parts is more preferable, 120-180 mass parts is still more preferable, 140-170 mass parts is still more preferable.

[Method for adjusting toner particle dispersion (B)]
In the present invention, the toner particle dispersion (B) is prepared by mixing the toner particles (A) with an insulating liquid in the presence of a basic dispersant, and further wet-dispersing using a media type dispersing machine.

As a method of mixing the toner particles (A), the basic dispersant, and the insulating liquid, a method of stirring with a stirring and mixing device is preferable.
The stirring and mixing device is not particularly limited, but a high-speed stirring and mixing device is preferable.
Examples of the high-speed stirring and mixing apparatus include Ultra Disper (trade name, manufactured by Asada Tekko Co., Ltd.), Ebara Milder (trade name, manufactured by Ebara Corporation), T.C. K. Homomixer, T.W. K. Homo disperse, T.W. K. ROBOMIX (all trade names, manufactured by PRIMIX), CLEARMIX (trade names, manufactured by MTechnics), KD Mill (trade names, manufactured by Kinetic Dispersion), and the like.

  The number of revolutions when the toner particles (A), the basic dispersant, and the insulating liquid are mixed using a stirring and mixing device is preferably 1,000 to 12,000 r / min, and preferably 3,000 to 10,000 r. / Min is more preferable. Moreover, 1-120 minutes are preferable and the mixing time in this case has more preferable 10-60 minutes.

  The toner particles (A), the basic dispersant, and the insulating liquid are mixed with a stirring and mixing device to preliminarily disperse the toner particles (A) to obtain a preliminarily dispersed toner particle. The productivity of the particle dispersion (B) can be improved.

(Wet grinding)
In the present invention, wet pulverization means a method in which toner particles dispersed in an insulating liquid are mechanically pulverized in a state of being dispersed in the insulating liquid.

In the present invention, a media disperser is used as an apparatus used for wet grinding.
Media-type dispersers are also called media mills, ball mills, bead mills, etc., which retain media in a dispersion chamber (mill), and distribute the dispersion energy of grinding, shearing, and colliding with the preliminary dispersion liquid flowing in the dispersion chamber. It is a disperser that disperses and grinds while giving.

As a typical media type dispersing machine, for example, a plurality of agitator disks (rotors) mounted on a drive shaft are arranged in a cylindrical dispersion chamber having a liquid supply port, and a large number of media are filled in the internal space. It has a structure.
When the toner particle preliminary dispersion is continuously introduced from the supply port into the dispersion chamber while the agitator disk is rotated by the rotation of the drive shaft, a strong shearing force is applied to the media and the preliminary dispersion, and the toner particles are pulverized. Small particle size is dispersed.
The mixed liquid in which the media particles and the reduced toner particles are dispersed is separated from the media particles and conveyed to the outside from a liquid discharge port provided in the upper part of the dispersion chamber. As a method for separating the mixed liquid from the media particles, a centrifugal separation method or a method in which a screen and centrifugal separation are combined can be employed.

Examples of such media-type dispersers include Star Mill (trade name, manufactured by Ashizawa Finetech Co., Ltd.), Ultra Apex Mill (trade name, manufactured by Kotobuki Kogyo Co., Ltd.), Pico Mill (trade name, Asada Iron Works) Company-made), DCP Superflow, Cosmoflow (all trade names, manufactured by Nihon Eirich Co., Ltd.), MSC mill (trade names, manufactured by Nihon Coke Co., Ltd.) and the like.
Among these, a media-type disperser having a media separation mechanism by a centrifugal separation mechanism is preferable from the viewpoint of easy media separation.

There are a circulation method and a continuous method as an operation method in which the dispersion process and the separation process are performed simultaneously and continuously.
Examples of the circulation method include a method in which a tank of one tank and a media-type disperser are installed, and a circulation system is formed by piping to perform a circulation path.
In addition, as a continuous method, a method of installing two tanks and a media-type disperser and passing by a catch ball method, a method of returning the passed dispersion liquid to the original tank again, and repeating the same pass operation, Examples include a method in which the required number of media dispersers are arranged in series to make one pass. In the case where the media type dispersers are arranged in series, it is preferable to install a cooler at the outlet of the disperser because the liquid temperature after the dispersion treatment increases.

The supply temperature (X ₂ ) of the toner particle dispersion to the media-type disperser in Step 2 is a resin contained in the toner particles (A) from the viewpoint of rolling the pigment particles flat and reducing the toner particles. 15 ° C. or lower (X ₂ ≦ Tg−15 ° C.), preferably 18 ° C. or lower (X ₂ ≦ Tg−18 ° C.), more preferably 20 ° C. or lower than the glass transition temperature (Tg). (X ₂ ≦ Tg−20 ° C.) is more preferable, and in view of productivity and flattening of the pigment particles, the temperature is 35 ° C. lower than the glass transition temperature (Tg) of the resin contained in the toner particles (A) ( Tg−35 ° C. ≦ X ₂ ) is preferable, and a temperature 15 to 35 ° C. lower than the glass transition temperature of the resin contained in the toner particles (A) (Tg−35 ° C. ≦ X ₂ ≦ Tg−15 ° C.). Preferably, 18 to 35 ° C lower temperature (Tg _{35 ℃ ≦ X 2 ≦ Tg-} 18 ℃) more preferably, 20 to 35 ° C. lower temperature _{(Tg-35 ℃ ≦ X 2} ≦ Tg-20 ℃) is more preferable.
When there are a plurality of resins contained in the toner particles (A), the glass transition temperatures (Tg) of the resins contained in the toner particles (A) are values obtained by weighted average of the glass transition temperatures of the respective resins. is there.

  The dispersion temperature of the toner particle dispersion in Step 2 is preferably 15 to 40 ° C, more preferably 18 to 35 ° C, and still more preferably 20 to 30 ° C.

In the present invention, the supply temperature of the toner particle dispersion in step 2 to the media-type disperser is the dispersion immediately before being supplied to the media-type disperser when the operation in the circulation method or the continuous method is stabilized. Indicates the temperature of the liquid.
In addition, the dispersion temperature of the toner particle dispersion liquid in step 2 indicates the temperature of the dispersion liquid in the media type dispersing machine or immediately after being discharged from the media type dispersing machine when the operation in the circulation system or the continuous system is stabilized.

Examples of media materials used in the media type disperser include high-hardness metals such as steel and chrome alloys, high-hardness ceramics such as alumina, zirconia, zircon, and titania, and polymer materials such as glass, ultra high molecular weight polyethylene, and nylon. Etc.
Among these, ceramic media are preferable because the specific gravity of the media is relatively large, and zirconia media is more preferable from the viewpoint of wear resistance.
As the media having a higher specific gravity is used, the shearing force, the collision force, and the grinding force for reducing the toner particles tend to be improved.

A desired size can be used as the particle size (diameter) of the media used in the media-type disperser. However, since the kinetic energy per medium increases as the particle size of the medium increases, the grinding force tends to increase. Also, as the particle size of the media particles is smaller, the number of contacts between the media increases, and therefore the dispersion frequency tends to increase.
Therefore, in view of the above matters, the particle diameter (diameter) of the media is preferably 0.3 to 1.0 mm, more preferably 0.3 to 0.9 mm, from the viewpoint of stretching and pulverizing the pigment particles. 0.4 to 0.8 mm is more preferable.

  The peripheral speed of the agitator disk (rotor) tip of the media-type disperser is not particularly limited, but the centrifugal force necessary to separate the media and the dispersion-processed product is maintained while maintaining good mixing and dispersion in the dispersion chamber. From the viewpoint of obtaining, 4 m / s or more is preferable, 6 m / s or more is more preferable, 8 m / s or more is further preferable, and from the same viewpoint, 30 m / s or less is preferable, 20 m / s is more preferable, and 15 m / s or less. Is more preferable, 4-30 m / s is preferable, 6-20 m / s is more preferable, and 8-15 m / s is still more preferable.

  The apparent filling rate of the media particles in the dispersion chamber of the media-type disperser is 50% higher than the space in the dispersion chamber from the viewpoint of improving the effects of pulverization, shearing and collision by the media, and improving the dispersion effect of the toner particles. -100 volume% is preferable and 50-80 volume% is more preferable.

Since the dispersion process and the separation process are performed simultaneously, the average residence time per pass (V (space volume in the dispersion chamber of the media type dispersing machine) / Q (flow rate)) from the viewpoint of suppressing aggregation of toner particles due to heat generation. Is preferably 30 seconds to 5 minutes, more preferably 30 seconds to 2 minutes, and even more preferably 30 seconds to 90 seconds.
The total average residence time obtained by multiplying the average residence time per pass by the number of passes depends on the capacity and size of the disperser, but is preferably 5 to 60 minutes and more preferably 5 to 30 minutes from the viewpoint of productivity. Preferably, 5 to 20 minutes is more preferable.

From the viewpoint of improving the image quality of the liquid developer, the volume median particle size (D ₅₀ ) of the toner particles in the toner particle dispersion (B) obtained in Step 2 is preferably less than 8.0 μm, and 7.0 μm or less. Is more preferably 6.0 μm or less, preferably 4.0 μm or more, more preferably 4.5 μm or more, still more preferably 5.0 μm or more, from the viewpoint of suppressing an increase in the viscosity of the liquid developer. It is preferably 4.0 μm or more and less than 8.0 μm, more preferably 4.5 to 7.0 μm, and even more preferably 5.0 to 6.0 μm.

  The viscosity at 25 ° C. of the toner particle dispersion (B) obtained in Step 2 is preferably 5 to 30 mPa · s, more preferably 7 to 20 mPa · s, from the viewpoint of suppressing the thickening of the dispersion in Step 3. 10-19 mPa * s is still more preferable, and 12-19 mPa * s is still more preferable.

The solid content concentration in the toner particle dispersion (B) obtained in the step 2 is preferably 10 to 50% by mass from the viewpoint of increasing the solid content concentration of the liquid developer and performing dispersion using a media-type disperser. 15-45 mass% is more preferable, and 25-40 mass% is still more preferable.
In the present invention, the solid content concentration in the toner particle dispersion (B) means a value measured based on the method described in Examples.

<Step 3>
Step 3 is a step in which the toner particle dispersion (B) obtained in Step 2 is further wet-dispersed using a media-type disperser to obtain a toner particle dispersion (C) having a further reduced particle size.
The media type disperser used in step 3 may be the same model as that used in step 2 or a different model. Further, the operation method of step 3 may be a circulation method or a continuous method.

The toner particle dispersion (B) obtained in step 2 is considered to contain toner particles that are deformed flat. If the toner particles are continuously dispersed under the same conditions as in step 2, the toner particles continue to be further deformed into a flat shape, making it difficult to reduce the toner particles.
Therefore, in the present invention, when the toner particle dispersion (B) obtained in step 2 is further dispersed using a media type dispersing machine, the toner particle dispersion in step 3 is supplied to the media type dispersing machine. Wet dispersion is performed by setting the temperature to a temperature lower than the supply temperature of the toner particle dispersion liquid to the media type disperser in step 2.
By setting the supply temperature to the toner particle dispersion medium type disperser so as to satisfy the above requirements, breakage due to the media is preferentially generated over flattening, and the toner particles can be made smaller.

In the present invention, the supply temperature of the toner particle dispersion liquid to the media type dispersing machine in step 3 is the dispersion immediately before being supplied to the media type dispersing machine when the operation in the circulation system or the continuous system is stabilized. Indicates the temperature of the liquid.
The reason why this supply temperature is important can be explained as follows.
Inside the media disperser, the internal temperature rises from the inlet toward the outlet. Since the supply of the toner particle dispersion liquid to the media type disperser is usually supplied near the inlet, the dispersion is first performed at the supply temperature to the media type disperser. If the supply temperature at this time is appropriate, the stretched toner particles are broken by the media, so that the toner particles can be made smaller. However, if the supply temperature is higher than an appropriate temperature, the breakage and further stretching of the toner particles proceed at the same time, making it difficult to reduce the particle size of the toner particles or increasing the viscosity.
In the present invention, the final outlet temperature of the media-type disperser is defined as the dispersion temperature of the toner particles. However, if the dispersion temperature is controlled, the supply temperature is excessively lowered.

The supply temperature (X ₃ ) of the toner particle dispersion to the media-type disperser in Step 3 is such that the resin particles contained in the toner particles (A) are reduced from the viewpoint of making the toner particles smaller by breaking the pigment particles. A temperature lower than 35 ° C. (X ₃ <Tg−35 ° C.) is preferable, a temperature lower than 36 ° C. (X ₃ ≦ Tg−36 ° C.) is more preferable, and a temperature lower by 40 ° C. than the glass transition temperature (Tg). The following (X ₃ ≦ Tg−40 ° C.) is more preferable, and from the viewpoint of productivity, the temperature is 50 ° C. lower than the glass transition temperature (Tg) of the resin contained in the toner particles (A) (Tg−50 ° C. ≦ X ₃ ) is preferable, 48 ° C. lower temperature or higher (Tg−48 ° C. ≦ X ₃ ) is more preferable, 46 ° C. lower temperature or higher (Tg−46 ° C. ≦ X ₃ ) is further preferable, and 44 ° C. lower temperature or higher (Tg− 44 ℃ ≦ X ₃₎ is more preferably more, Were, than the glass transition temperature of the resin contained in the toner particles (A), at a temperature lower than the 35 ° C., and preferably 50 ° C. lower temperature than _{(Tg-50 ℃ ≦ X 3} <Tg-35 ℃), A temperature lower by 36 ° C. to 48 ° C. (Tg−48 ° C. ≦ X ₃ ≦ Tg−36 ° C.) is more preferable, and a temperature lower by 36 to 46 ° C. (Tg−46 ° C. ≦ X ₃ ≦ Tg−36 ° C.) is more preferable. A temperature lower by ˜44 ° C. (Tg−44 ° C. ≦ X ₃ ≦ Tg−40 ° C.) is even more preferable.

  In addition, the supply temperature of the toner particle dispersion liquid to the media-type disperser in step 3 is lower than the supply temperature of the toner particle dispersion liquid to the media-type disperser in step 2, but the toner particles are reduced in size. From the supply temperature in step 2, a temperature lower by 1 ° C. or more is more preferable, a temperature lower by 3 ° C. or higher is more preferable, and a temperature lower by 5 ° C. or higher is more preferable. A low temperature is preferable, a low temperature of 10 ° C. or lower is more preferable, a temperature lower by 1 to 20 ° C. is preferable than a supply temperature in Step 2, a temperature lower by 1 to 10 ° C. is more preferable, and a temperature lower by 3 to 10 ° C. Is more preferable, and a temperature lower by 5 to 10 ° C. is even more preferable.

The dispersion temperature of the toner particle dispersion in Step 3 is preferably 12 to 35 ° C, and more preferably 15 to 30 ° C.
The dispersion temperature of the toner particle dispersion in step 3 indicates the temperature of the dispersion in the media-type disperser or immediately after being discharged from the media-type disperser when the operation in the circulation method or the continuous method is stabilized.

  The material of the media used in the media type disperser may be appropriately selected from the above materials as in Step 2, but the shearing force, collision force, and grinding force for making the toner particles smaller can be obtained. From the viewpoint of improving the specific gravity of the media particles, ceramic media are preferable, and from the viewpoint of wear resistance, zirconia media is more preferable.

The particle diameter (diameter) of the media used in the media type disperser used in step 3 is smaller than the diameter of the media of the media disperser used in step 2 from the viewpoint of breaking the pigment stretched in step 2. Preferably, it is more preferably 0.1 to 0.4 mm smaller than the diameter of the medium used in step 2.
Moreover, although the desired particle size (diameter) can be used as the particle size (diameter) of the media used in the media type disperser used in the specific step 3, it is 0.1 to 0 from the viewpoint of preventing excessive stretching. 0.8 mm is preferable, 0.15-0.6 mm is more preferable, and 0.2-0.4 mm is still more preferable.
Note that the shape of the media particles is usually a sphere.

  The peripheral speed of the tip of the agitator disk (rotor) of the media type disperser in step 3 is not particularly limited, but it is necessary to maintain a good mixing and dispersion state in the dispersion chamber and to separate the media particles from the dispersion treatment product. From the viewpoint of obtaining a sufficient centrifugal force, 4 m / s or more is preferable, 6 m / s or more is more preferable, 8 m / s or more is more preferable, and from the same viewpoint, 30 m / s or less is preferable, and 25 m / s or less is more preferable. 20 m / s or less is more preferable, 4-30 m / s is preferable, 6-25 m / s is more preferable, and 8-20 m / s is still more preferable.

  The apparent filling rate of the media particles in the dispersion chamber of the media-type disperser in step 3 improves the effects of pulverization, shearing and collision with the media, and improves the dispersion effect of the toner particles. 50 to 100% by volume is preferable, and 50 to 80% by volume is more preferable.

The average residence time per pass in step 3 (V (space volume in the dispersion chamber of the media type dispersing machine) / Q (flow rate)) is 30 seconds to 5 minutes from the viewpoint of suppressing aggregation of toner particles due to heat generation. Is preferable, 30 seconds to 2 minutes is more preferable, and 30 seconds to 90 seconds is still more preferable.
Further, the total average residence time obtained by multiplying the average residence time per pass in Step 3 by the number of passes depends on the capacity and size of the disperser, but is preferably 10 to 100 minutes from the viewpoint of productivity. -70 minutes are more preferable, and 20-60 minutes are still more preferable.

  In step 3, an insulating liquid may be further added and dispersed in the toner particle dispersion. Examples of the insulating liquid used for diluting the toner particle dispersion (B) include those that can be used in Step 2, and the same type of insulating liquid as that used in Step 2 is preferable.

From the viewpoint of improving the image quality of the liquid developer, the volume median particle size (D ₅₀ ) of the toner particles in the toner particle dispersion (C) obtained in Step 3 is preferably less than 4.0 μm, and not more than 3.5 μm. Is more preferably 3.0 μm or less, and preferably 0.1 μm or more, more preferably 0.3 μm or more, and 1.0 μm or more from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer. More preferably, it is preferably 0.1 μm or more and less than 4.0 μm, more preferably 0.3 to 3.5 μm, still more preferably 1.0 to 3.0 μm.

  The viscosity at 25 ° C. of the toner particle dispersion (C) obtained in Step 3 is preferably 5 to 70 mPa · s, more preferably 7 to 50 mPa · s, from the viewpoint of improving the degree of development of the liquid developer. 25 mPa · s is more preferable.

The solid content concentration of the toner particles in the toner particle dispersion (C) obtained in step 3 is preferably 10 to 50% by mass, more preferably 15 to 45% by mass from the viewpoint of increasing the transfer speed by increasing the concentration. Preferably, 25-40 mass% is still more preferable.
The solid content concentration of the toner particle dispersion (C) is a value calculated based on the following formula, and specifically means a value measured based on the method described in the examples.
[Solid concentration (mass%) of toner particle dispersion (C)] = [Solid concentration (mass%) of toner particle dispersion (B)] × [mass of toner dispersion (B)] / ([ Mass of toner particle dispersion (B)] + [mass of insulating liquid added as necessary in step 3])

<Liquid developer>
Without diluting the toner particle dispersion (C) obtained in Step 3, it may be used as a liquid developer as it is, or a solution obtained by diluting the toner particle dispersion (C) may be used as a liquid developer.

From the viewpoint of improving the image quality of the liquid developer, the volume median particle size (D ₅₀ ) of the toner particles in the liquid developer obtained by the production method of the present invention is preferably less than 4.0 μm, and not more than 3.5 μm. Is more preferably 3.0 μm or less, and preferably 0.1 μm or more, more preferably 0.3 μm or more, and 1.0 μm or more from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer. More preferably, it is preferably 0.1 μm or more and less than 4.0 μm, more preferably 0.3 to 3.5 μm, still more preferably 1.0 to 3.0 μm.

  From the viewpoint of improving the developability of the liquid developer, the viscosity of the liquid developer obtained by the production method of the present invention is preferably 5 to 70 mPa · s, more preferably 7 to 50 mPa · s, 25 mPa · s is more preferable.

  The solid content concentration of the toner particles in the liquid developer obtained by the production method of the present invention is preferably 10 to 50% by mass, more preferably 15 to 45% by mass, and still more preferably 25 to 40% by mass.

[Softening point of resin]
Using a flow tester “CFT-500D” (manufactured by Shimadzu Corporation), a 1 g sample was heated at a heating rate of 6 ° C./min, and a load of 1.96 MPa was applied by a plunger, and the diameter was 1 mm and the length was 1 mm. The plunger drop amount of the flow tester was plotted against the temperature at the time of extrusion from the nozzle, and the temperature at which half the sample flowed out was taken as the softening point.

[Glass transition temperature of resin]
Using a differential scanning calorimeter “Q-100” (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of sample (resin) is weighed into an aluminum pan and heated to 200 ° C. Then, the temperature was cooled to 0 ° C. at a rate of temperature decrease of 10 ° C./min. Next, the sample was heated at a heating rate of 10 ° C./min and measured. At this time, the temperature at the intersection of the extended line of the base line below the maximum peak temperature of endotherm and the tangent showing the maximum inclination from the peak rising portion to the peak apex was defined as the glass transition temperature of the resin.

[Acid value of the resin]
Measurement was performed based on JIS K0070-1992 except that a mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)) was used instead of the mixed solvent of ethanol and ether.

[Viscosity of toner particle dispersions (B) and (C), insulating liquid at 25 ° C.]
6-7 mL of measurement liquid was put into a 10 mL-volume screw tube, and the viscosity at 25 ° C. was measured using a rotational vibration viscometer “Viscomate VM-10A-L” (manufactured by CBC).

[Solid concentration of toner particle dispersions (B) and (C)]
10 parts by mass of the toner particle dispersion (B) or (C) is diluted with 90 parts by mass of hexane, and is centrifuged for 20 minutes at a rotational speed of 25000 r / min using a centrifugal separator “H-201F” (manufactured by Kokusan). Rotated. After standing, the supernatant was removed by decantation, then diluted with 90 parts by mass of hexane, and centrifuged again in the same manner. And after removing a supernatant liquid by decantation, the lower layer is dried at 0.5 kPa and 40 degreeC with a vacuum dryer for 8 hours, the mass of the residue after drying is measured, and it is solid from the following formula | equation The partial concentration was calculated.
[Solid content concentration (% by mass)] = [Mass of residue after drying] / [Mass of toner particle dispersion (B) or (C)] × 100

[Volume Median Particle Size (D ₅₀ ) of Toner Particles (A)]
Using a particle size distribution measuring apparatus “Coulter Multisizer II” (manufactured by Beckman Coulter, Inc.), the particle size distribution was determined according to the following method, and the volume median particle size (D ₅₀ ) was measured.
(1) Preparation of Dispersion 10 mg of toner particles (A) are added to 5 mL of a dispersant “Emulgen 109P” (5% by weight polyoxyethylene lauryl ether, manufactured by Kao Corporation), and an ultrasonic disperser is used. Then, 25 mL of an electrolytic solution “Isoton II” (manufactured by Beckman Coulter, Inc.) was added and dispersed again using an ultrasonic disperser for 1 minute to prepare a dispersion.
(2) Measuring device: Coulter Multisizer II (Beckman Coulter, Inc.)
・ Aperture diameter: 100μm
・ Measured particle size range: 2-6 μm
・ Analysis software: Coulter Multisizer AccuComp (Beckman Coulter)
(3) Measurement conditions: 100 mL of electrolyte solution and dispersion were added to a beaker, and 30,000 particles were measured at a concentration that could be measured in 20 seconds.
(4) The volume-median particle size (D ₅₀ ) was determined from the measured value.

[Volume-median particle diameter (D ₅₀ ) of toner particles in toner particle dispersions (B) and (C), content of toner particles having a particle diameter of less than 0.1 μm (volume%)]
Using a laser diffraction / scattering particle size measuring device “Mastersizer 2000” (Malvern), Isopar G (ExxonMobil) is added to the measurement cell, and the scattering intensity is 5 to 15%. The volume-median particle size (D ₅₀ ) was measured under the conditions of a particle refractive index of 1.58 (imaginary part 0.1) and a dispersion medium refractive index of 1.42. The content (% by volume) of particles having a particle size of less than 0.1 μm was calculated from the obtained volume particle size distribution.

Production Example 1
The raw material monomer, esterification catalyst, and esterification co-catalyst shown in Table 1 were placed in a 10 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple. In the atmosphere, the temperature was raised to 230 ° C. and the reaction was continued until the reaction rate reached 90%. Then, the reaction was further carried out under a pressure of 8.3 kPa, and after reacting at 230 ° C. by adding a polymerization inhibitor, a resin A made of polyester having physical properties shown in Table 1 was obtained.

Example 1
<Step 1>
85 parts by mass of the resin A and 15 parts by mass of the pigment “ECB-301” (manufactured by Dainichi Seika Co., Ltd., phthalocyanine blue 15: 3) were previously used in a 20 L Henschel mixer at 1500 r / min (21.6 m / s). After stirring and mixing for 3 minutes, the mixture was melt kneaded under the following conditions.

[Melting and kneading conditions]
A continuous two-open roll kneader “NIDEX” (manufactured by Nippon Coke Co., Ltd., roll outer diameter: 14 cm, effective roll length: 55 cm) was used. The operating conditions of the continuous two-open roll type kneader are as follows: high rotation side roll (front roll) peripheral speed 75 r / min (32.4 m / min), low rotation side roll (back roll) peripheral speed 35 r / min (15 0.0 m / min), the roll gap at the end of the kneaded product supply port was 0.1 mm. The heating medium temperature and cooling medium temperature in the roll are 90 ° C. on the raw material input side of the high rotation side roll and 85 ° C. on the kneaded material discharge side, 35 ° C. on the raw material input side of the low rotation side roll and 35 ° C. on the kneaded material discharge side. there were. The feed rate of the raw material mixture to the kneader was 10 kg / h, and the average residence time in the kneader was about 3 minutes.

The kneaded product obtained above was rolled and cooled with a cooling roll, and then roughly pulverized to about 1 mm using a hammer mill. The resulting coarsely pulverized product was finely pulverized by airflow jet mill “IDS” (trade name, manufactured by Nippon Pneumatic Co., Ltd.) and classified to obtain resin A having a volume median particle size (D ₅₀ ) of 10 μm. Toner particles (A) containing were obtained.

<Step 2>
35 parts by mass of the toner particles (A) obtained above and an insulating liquid (liquid paraffin, trade name “Lytole”, manufactured by Sonneborn, viscosity at 25 ° C .: 5 mPa · s, dielectric constant: 2.1) 58 parts by mass, 7 parts by weight of a basic dispersant “Solsperse 11200” (manufactured by Nippon Lubrizol Corporation, effective content of 50% by mass, polyimine and carboxylic acid condensation compound) is placed in a 1 L polyethylene container, and a stirring and mixing apparatus “TK. Using “ROBOMIX” (trade name, manufactured by Primix), the mixture was stirred for 30 minutes under ice cooling at a rotational speed of 7000 r / min to obtain a toner particle preliminary dispersion.

The obtained toner particle preliminary dispersion was wet-dispersed with the following settings using a media-type disperser “Ultra Apex Mill” (trade name, manufactured by Kotobuki Industries).
・ Media particles: Media made of zirconia with a diameter of 0.5 mm. Apparent filling ratio of media particles in the dispersion chamber of the media type disperser: 60 vol%
-Circumferential speed at the rotor tip of the media-type disperser: 10 m / s
・ Average residence time per pass: 60 seconds ・ Total average residence time: 17 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media-type disperser and the supply temperature was adjusted to 13 ° C., the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 35 ° C. The dispersion temperature was 24 ° C.
The volume median particle size (D ₅₀ ) of the toner particles in the toner particle dispersion (B) obtained after the wet dispersion is 5.11 μm, and the viscosity of the toner particle dispersion (B) at 25 ° C. is 15.3 mPa.s. -S and solid content concentration were 38.5 mass%.

<Step 3>
The toner particle dispersion (B) obtained in Step 2 was wet-dispersed using the media type dispersing machine “Ultra Apex Mill” (trade name, manufactured by Kotobuki Kogyo) under the following settings.
-Media particles: 0.2 mm diameter zirconia media-Apparent filling rate of media particles in the dispersion chamber of the media-type disperser: 60 vol%
-Circumferential speed at the rotor tip of the media-type disperser: 10 m / s
・ Average residence time per pass: 60 seconds ・ Total average residence time: 28 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media type dispersing machine and the supply temperature was adjusted to 7 ° C., the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 41 ° C. The dispersion temperature was 25 ° C.
The toner particle dispersion (C) obtained after the wet dispersion has a volume-median particle size (D ₅₀ ) of toner particles of 2.57 μm, and the toner particle dispersion (C) has a viscosity at 25 ° C. of 17.1 mPa · s, the solid content concentration was 38.5% by mass.
The toner particle dispersion (C) obtained in step 3 was used as a liquid developer without being diluted.

Reference example 2
Using the same raw materials as in Example 1, the same operation as in Example 1 was performed until the toner particle preliminary dispersion in Step 2 was obtained. A toner particle dispersion (C) was obtained in the same manner as in Example 1 except that the wet dispersion in Step 2 and Step 3 was changed to the following setting using the toner particle preliminary dispersion. .

<Step 2>
・ Media particles: Zirconia media with a diameter of 0.8 mm ・ Apparent filling rate of media particles in the dispersion chamber of the media-type disperser: 70 vol%
・ Peripheral speed at the rotor tip of the media-type disperser: 8 m / s
-Average residence time per pass: 45 seconds-Total average residence time: 9 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media type dispersing machine and the supply temperature was adjusted to 13 ° C, the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 35 ° C. The dispersion temperature was 29 ° C.
The volume median particle size (D ₅₀ ) of the toner particles in the toner particle dispersion (B) obtained after the wet dispersion is 5.20 μm, and the viscosity of the toner particle dispersion (B) at 25 ° C. is 16.2 mPa. -S and solid content concentration were 38.5 mass%.

<Step 3>
・ Media particles: Media made of zirconia with a diameter of 0.5 mm. Apparent filling ratio of media particles in the dispersion chamber of the media type disperser: 60 vol%
・ Peripheral speed at the rotor tip of the media-type disperser: 8 m / s
-Average residence time per pass: 60 seconds-Total average residence time: 42 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media type dispersing machine and the supply temperature was adjusted to 12 ° C, the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 36 ° C. The dispersion temperature was 20 ° C.
The toner particle dispersion (C) obtained after the wet dispersion has a toner particle volume volume median particle size (D ₅₀ ) of 3.00 μm, and the toner particle dispersion (C) has a viscosity at 25 ° C. of 34.2 mPa · s. s, the solid content concentration was 38.5% by mass.
The toner particle dispersion (C) obtained in step 3 was used as a liquid developer without being diluted.

Reference example 3
Using the same raw materials as in Example 1, the same operation as in Example 1 was performed until the toner particle preliminary dispersion in Step 2 was obtained. A toner particle dispersion (C) was obtained in the same manner as in Example 1 except that the wet dispersion in Step 2 and Step 3 was changed to the following setting using the toner particle preliminary dispersion. .

<Step 2>
・ Media particles: Media made of zirconia with a diameter of 0.5 mm. Apparent filling ratio of media particles in the dispersion chamber of the media type disperser: 60% by volume
・ Peripheral speed of rotor tip of media type disperser: 9m / s
・ Average residence time per pass: 60 seconds ・ Total average residence time: 17 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media-type disperser and the supply temperature was adjusted to 13 ° C., the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 35 ° C. The dispersion temperature was 21 ° C.
The volume median particle size (D ₅₀ ) of the toner particles in the toner particle dispersion (B) obtained after the wet dispersion is 5.19 μm, and the viscosity of the toner particle dispersion (B) at 25 ° C. is 16.7 mPas. -S and solid content concentration were 38.5 mass%.

<Step 3>
-Media particles: 0.2 mm diameter zirconia media-Apparent filling rate of media particles in the dispersion chamber of the media-type disperser: 60 vol%
-Circumferential speed at the rotor tip of the media-type disperser: 10 m / s
-Average residence time per pass: 60 seconds-Total average residence time: 34 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media type dispersing machine and the supply temperature was adjusted to 12 ° C, the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 36 ° C. The dispersion temperature was 28 ° C.
The toner particle dispersion (C) obtained after the wet dispersion has a volume-median particle size (D ₅₀ ) of toner particles of 2.94 μm, and the viscosity of the toner particle dispersion (C) at 25 ° C. is 46.7 mPa · s. s, the solid content concentration was 38.5% by mass.
The toner particle dispersion (C) obtained in step 3 was used as a liquid developer without being diluted.

Comparative Example 1
Using the same raw materials as in Example 1, the same operation as in Example 1 was performed until the toner particle preliminary dispersion in Step 2 was obtained. A toner particle dispersion (C) was obtained in the same manner as in Example 1 except that the wet dispersion in Step 2 and Step 3 was changed to the following setting using the toner particle preliminary dispersion. .

<Step 2>
・ Media particles: Zirconia media with a diameter of 0.8 mm ・ Apparent filling rate of media particles in the dispersion chamber of the media-type disperser: 70 vol%
-Circumferential speed at the rotor tip of the media-type disperser: 8.5 m / s
・ Average residence time per pass: 60 seconds ・ Total average residence time: 10 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media type dispersing machine and the supply temperature was adjusted to 17 ° C., the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 31 ° C. The dispersion temperature was 25 ° C.
The volume median particle size (D ₅₀ ) of the toner particles in the toner particle dispersion (B) obtained after the wet dispersion is 5.10 μm, and the viscosity at 25 ° C. of the toner particle dispersion (B) is 20.6 mPa. -S and solid content concentration were 38.5 mass%.

<Step 3>
・ Media particles: Zirconia media with a diameter of 0.2 mm. Apparent filling ratio of media particles in the dispersion chamber of the media type disperser: 70% by volume.
・ Peripheral speed of rotor tip of media type disperser: 9m / s
-Average residence time per pass: 45 seconds-Total average residence time: 29 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media-type disperser and the supply temperature was adjusted to 17 ° C, the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 31 ° C. The dispersion temperature was 30 ° C.
The toner particle dispersion (C) obtained after the wet dispersion has a toner particle volume median particle size (D ₅₀ ) of 3.60 μm, and the toner particle dispersion (C) has a viscosity at 25 ° C. of 100 mPa · s or more. Viscosity increased to Moreover, solid content concentration was 38.5 mass%.
Since the viscosity increase was remarkable, the toner particle dispersion (C) obtained in Step 3 could not be used as a liquid developer.

Comparative Example 2
Using the same raw materials as in Example 1, the same operation as in Example 1 was performed until the toner particle preliminary dispersion in Step 2 was obtained. Then, using the toner particle preliminary dispersion, the wet dispersion in step 2 was changed to the setting shown below, and toner particle dispersion was performed in the same manner as in Example 1 except that Step 3 of Example 1 was not performed. A liquid was obtained.
<Step 2>
・ Media particles: Media made of zirconia with a diameter of 0.5 mm. Apparent filling ratio of media particles in the dispersion chamber of the media type disperser: 60% by volume
・ Peripheral speed at the rotor tip of the media-type disperser: 8 m / s
-Average residence time per pass: 60 seconds-Total average residence time: 53 minutes In addition, since the cooling water was passed through the jacket of the raw material tank and the media type dispersing machine and the supply temperature was adjusted to 17 ° C, the supply temperature And the glass transition temperature of the resin A contained in the toner particles (A) was 31 ° C. The dispersion temperature was 25 ° C.
The volume median particle size (D ₅₀ ) of the toner particles in the toner particle dispersion obtained after wet dispersion is 5.10 μm, the viscosity of the toner particle dispersion at 25 ° C. is 18.6 mPa · s, and the solid content concentration Was 38.5% by mass.

From Table 1, the toner particle dispersion liquid (C) (liquid developer) obtained in Example 1 and Reference Examples 2 to 3 has toner particles contained therein having a reduced particle size and reduced viscosity. You can see that. FIG. 1 is a photograph of the toner particles in the toner particle dispersion liquid (C) obtained in Example 1 taken with an electron microscope. It can be seen that diameter toner particles are obtained.
On the other hand, the toner particle dispersion (C) obtained in Comparative Example 1 could not be made into a liquid developer because of a significant increase in viscosity. FIG. 2 is a photograph of the toner particles in the toner particle dispersion (C) obtained in Comparative Example 1 taken with an electron microscope. The toner particles are stretched and flat particles having an increased aspect ratio. It turns out that it is.
Further, it can be seen that the toner particle dispersion (C) (liquid developer) obtained in Comparative Example 2 contains larger toner particles and has a higher viscosity than the Examples.

  The liquid developer obtained by the production method of the present invention contains toner particles reduced in size, has a low viscosity, and can sharpen an image. Therefore, the liquid developer is suitable as a liquid developer used for developing a latent image in an image forming apparatus such as an electrophotographic copying machine or a printer.

Claims (8)

At least toner particles containing a resin and a pigment is a method for producing a liquid developer having dispersed in the insulating liquid, have a following step 1-3, and, wherein the toner particle dispersion in step 2 The supply temperature to the media type dispersing machine is set to be 15 to 35 ° C. lower than the glass transition temperature of the resin contained in the toner particles (A), and the media type dispersion of the toner particle dispersion in step 3 is performed. The supply temperature to the machine is lower than the glass transition temperature of the resin contained in the toner particles (A) by more than 35 ° C. and 3 ° C. or more lower than the supply temperature in step 2. A method for manufacturing a liquid developer to be set .
Step 1: Dry pulverizing a kneaded material obtained by kneading a toner raw material containing at least a resin and a pigment to obtain toner particles (A) Step 2: Insulating the toner particles (A) obtained in Step 1 Step 3: Obtaining the toner particle dispersion (B) by wet dispersion using a media-type disperser in the neutral liquid Step 3: Using the media-type disperser for the toner particle dispersion (B) obtained in Step 2 And the wet dispersion of the toner particle dispersion in step 3 to a temperature lower than the supply temperature of the toner particle dispersion in step 2 to the media disperser. Step of supplying and wet dispersing to obtain toner particle dispersion (C) 2. The method for producing a liquid developer according to claim 1, wherein the diameter of the media of the media type dispersing machine used in step 3 is smaller than the diameter of the media of the media dispersing machine used in step 2. Step 2 is a step in which the toner particles (A) are mixed with an insulating liquid in the presence of a basic dispersant, and further wet-dispersed using a media-type disperser to obtain a toner particle dispersion (B). method for producing a liquid developer according to claim 1 or 2. Volume median particle size of the toner particle dispersion liquid obtained in Step 2 _{(B) (D 50)} is less than or 4.0 .mu.m 8.0 .mu.m, the liquid developer according to any one of claims 1 to 3 Production method. Toner particle dispersion liquid obtained in the step 3 is a volume median particle size _{(D 50)} of (C), or more and less than 0.1 [mu] m 4.0 .mu.m, the liquid developer according to any one of claims 1-4 Production method. The solid content of the toner particles in the toner particle dispersion liquid obtained in the step 3 (C) is 10 to 50 wt%, the liquid developer producing method according to any one of claims 1-5. The resin comprises a polyester, the glass transition temperature of the polyester is 35 to 80 ° C., the liquid developer producing method according to any one of claims 1-6. Toner particle dispersion liquid obtained in step 3 viscosity at 25 ° C. of (C), a 5~70mPa · s, the liquid developer producing method according to any one of claims 1-7.