JP6202740B2 - Liquid developer - Google Patents

Description

  The present invention relates to a liquid developer used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method, and the like, and a method for producing the same.

  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 is excellent in terms of image quality because it can reduce the particle size of toner particles, and is suitable for commercial printing applications. In recent years, demands for higher speeds have increased, and therefore, there is a demand for lowering the viscosity of liquid developers. That is, there is a need for a liquid developer in which toner particles are stably dispersed with a small particle size and low viscosity.

  In recent years, an insulating liquid having low volatility has been used as a dispersion medium for the liquid developer due to an increase in environmental awareness.

  Patent Document 1 aims to provide a liquid developer that is well dispersed, has a high image density, can stably obtain a high-resolution, high-color image, and suppresses the generation of solvent vapor at the time of fixing. In a liquid developer for electrophotography in which toner particles composed of a colorant and a resin are dispersed in a carrier liquid having a high resistance and a low dielectric constant, the carrier liquid (a) has an initial boiling point of 150 ° C. or higher. Disclosed is a liquid developer for electrostatic images, comprising a naphthenic solvent and (b) at least one organic medium selected from monoesters of alcohols having 3 or more carbon atoms and fatty acids having 5 or more carbon atoms Has been.

  In Patent Document 2, the color development and color reproducibility are excellent, and even when the number of printed sheets and the printing area increase, the dispersion state and image density of the toner particles in the liquid developer are stable, and the developer composition changes over a long period of time. As a liquid developer having a stable image density, a liquid developer comprising at least a binder resin, a colorant, a polymer dispersant, and a carrier liquid, wherein the polymer dispersant has at least an amino group A specific ratio of the unsaturated monomer, the ethylenically unsaturated monomer containing an alkyl group having 9 to 24 carbon atoms, and the ethylenically unsaturated monomer containing an alkyl group having 1 to 8 carbon atoms A liquid developer characterized by having an amine value of 5 to 150 mgKOH / g is disclosed.

JP 2002-251040 A JP 2013-130791 A

  However, in the conventional technique, when using a low-volatile insulating liquid, it is difficult to achieve both dispersion stability, that is, storage stability and low-temperature fixability.

  The present invention relates to a liquid developer excellent in dispersion stability and low-temperature fixability even when a low-volatile insulating liquid is used, and a method for producing the same.

The present invention
[1] A liquid developer in which toner particles containing a resin containing a polyester and a pigment are dispersed in an insulating liquid in the presence of a dispersant,
The insulating liquid contains 5% by mass or more of naphthenic hydrocarbon, and the initial boiling point is 190 ° C. or higher and 300 ° C. or lower,
The dispersant contains a polyimine and carboxylic acid condensate,
A liquid developer, and [2] a method for producing a liquid developer in which toner particles containing a polyester-containing resin and a pigment are dispersed in an insulating liquid in the presence of a dispersant,
Step 1: Melting and kneading resin and pigment and pulverizing to obtain toner particles,
Step 2: A dispersant is added to the toner particles obtained in Step 1 and dispersed in an insulating liquid to obtain a toner particle dispersion. Step 3: The toner particle dispersion obtained in Step 2 is wet-pulverized. And a step of obtaining a liquid developer,
The insulating liquid contains 5% by mass or more of naphthenic hydrocarbon, and the initial boiling point is 190 ° C. or higher and 300 ° C. or lower,
The dispersant contains a polyimine and carboxylic acid condensate,
The present invention relates to a method for producing a liquid developer.

  The liquid developer of the present invention has the effect of being excellent in dispersion stability and low-temperature fixability even when a low-volatile insulating liquid is used.

  The liquid developer of the present invention is a liquid developer in which toner particles containing a polyester-containing resin and a pigment are dispersed in an insulating liquid in the presence of a dispersing agent, and the insulating liquid contains naphthenic hydrocarbons. It is characterized by the fact that it is contained by mass% or more, the initial boiling point is 190 ° C or higher and 300 ° C or lower, and the dispersant contains a polyimine-carboxylic acid condensate, which uses a low-volatile insulating liquid. Even in such a case, the dispersion stability and low-temperature fixability are excellent.

The reason for such an effect is not clear, but is considered as follows.
Naphthenic hydrocarbons are hydrocarbons that contain at least one saturated ring (naphthene ring) in one molecule, and are more polar than chain saturated hydrocarbons (paraffins) and have an affinity for polyester. Is expensive. Therefore, it is considered that the low temperature fixability is improved by containing a specific amount of a naphthenic hydrocarbon so that the toner particles are easily plasticized or swollen even at a lower temperature during fixing. On the other hand, in a liquid developer during storage, excessive plasticization of toner particles is disadvantageous for dispersion stability, but in the present invention, it contains a naphthenic hydrocarbon and the initial boiling point is within a certain range. By using an insulating liquid and a polyimine and carboxylic acid condensate that is strongly adsorbed to the toner particles and has excellent dispersing power in hydrocarbons, the dispersion stability of the toner particles is improved and the storage stability is improved. In addition to the improvement, in the wet pulverization process at the time of manufacture, the toner particles are appropriately plasticized, so that the pulverizability of the toner particles is improved and a liquid developer having a small particle diameter is likely to be obtained. In addition, the generation of the dispersion medium vapor is suppressed during use.

[resin]
The resin in the liquid developer of the present invention is a resin that becomes a binder resin for toner particles, and improves the low-temperature fixability of the liquid developer from the viewpoint of improving the pulverization property of the toner particles and obtaining a liquid developer having a small particle size. From the viewpoint, and from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, the polyester is contained. The polyester content in the resin is preferably 90% by mass or more, more preferably 95% by mass or more, substantially more preferably 100% by mass, and more preferably 100% by mass, that is, only the polyester is used as the resin. However, in the range where the effects of the present application are not impaired, other resins other than polyester may be contained. Examples of resins other than polyester include polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene. -Styrenic resin, epoxy resin, rosin-modified maleic acid resin, polyethylene-based resin which is a homopolymer or copolymer containing styrene or a styrene-substituted product such as acrylic acid ester copolymer and styrene-methacrylic acid ester copolymer , Polypropylene, polyurethane, silicone resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, and the like, and one or more of these can be used in combination.

  In the present invention, the polyester is preferably obtained by polycondensation of an alcohol component containing a divalent or higher alcohol and a carboxylic acid component containing a divalent or higher carboxylic acid compound.

  Examples of the divalent alcohol include diols having 2 to 20 carbon atoms, preferably 2 to 15 carbon atoms, and formula (I):

(In the formula, RO and OR are oxyalkylene groups, R is an ethylene and / or propylene group, x and y indicate the number of added moles of alkylene oxide, each being a positive number, and the sum of x and y. The average value is preferably 1 or more and 16 or less, more preferably 1 or more and 8 or less, and still more preferably 1.5 or more and 4 or less.
An alkylene oxide adduct of bisphenol A represented by: Specific examples of the diol having 2 to 20 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, bisphenol A, hydrogen Additive bisphenol A etc. are mentioned.

  As the alcohol component, the viewpoint of improving the pulverization property of toner particles to obtain a liquid developer having a small particle diameter, the viewpoint of improving the low temperature fixability of the liquid developer, and the dispersion stability of the toner particles in the liquid developer are improved. From the viewpoint of improving storage stability, 1,2-propanediol and an alkylene oxide adduct of bisphenol A represented by the formula (I) are preferable, and 1,2-propanediol is more preferable. The content of 1,2-propanediol is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, further preferably substantially 100 mol%, more preferably in the alcohol component. Is 100 mol%.

  Examples of the trihydric or higher alcohol include trihydric or higher polyhydric alcohol having 3 to 20 carbon atoms, preferably 3 to 10 carbon atoms. Specific examples include sorbitol, 1,4-sorbitan, pentaerythritol, glycerol, trimethylolpropane, and the like.

  Examples of the divalent carboxylic acid compound include, for example, a dicarboxylic acid having 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 3 to 10 carbon atoms, and anhydrides thereof, and 1 or more carbon atoms. Derivatives such as 3 or less alkyl esters and the like can be mentioned. Specifically, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, alkyl groups having 1 to 20 carbon atoms, or carbon Examples thereof include aliphatic dicarboxylic acids such as succinic acid substituted with an alkenyl group having a number of 2 or more and 20 or less.

  Examples of the trivalent or higher carboxylic acid compound include a trivalent or higher polyvalent carboxylic acid having 4 to 20 carbon atoms, preferably 6 to 20 carbon atoms, more preferably 9 to 10 carbon atoms, and their Examples thereof include anhydrides and derivatives such as alkyl esters having 1 to 3 carbon atoms. Specific examples include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), and the like.

  As the carboxylic acid component, terephthalic acid and fumaric acid are preferable 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 improving the storage stability. Terephthalic acid is more preferred. The content of terephthalic acid is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, more preferably substantially 100 mol%, more preferably 100 mol in the carboxylic acid component. %.

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

  From the viewpoint of adjusting the softening point of the polyester, the equivalent ratio of the carboxylic acid component and the alcohol component in the polyester (COOH group / OH group) is preferably 0.70 or more, more preferably 0.75 or more, and preferably 1.10 or less. More preferably, it is 1.05 or less.

  Polyester, for example, contains an alcohol component and a carboxylic acid component in an inert gas atmosphere at a temperature of 130 ° C. to 250 ° C. in the presence of an esterification catalyst, an esterification co-catalyst, a polymerization inhibitor, etc. as necessary. It can be produced by condensation.

  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 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Preferably it is 1.0 mass part or less. Examples of the esterification promoter include gallic acid. The amount of the esterification promoter used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, with respect to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. More preferably, it is 0.1 parts by mass or less. Examples of the polymerization inhibitor include t-butylcatechol. The amount of the polymerization inhibitor used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, more preferably 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Preferably it is 0.1 mass part or less.

  The softening point of the polyester is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, further preferably 120 ° C. or lower, and further preferably 110 ° C. or lower, from the viewpoint of improving the low-temperature fixability of the liquid developer. Further, from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, the temperature is preferably 70 ° C. or higher, more preferably 75 ° C. or higher.

  The glass transition temperature of the polyester is preferably 80 ° C. or lower, more preferably 70 ° C. or lower, and further preferably 60 ° C. or lower, from the viewpoint of improving the low-temperature fixability of the liquid developer. Further, from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, the temperature is preferably 40 ° C. or higher, more preferably 45 ° C. or higher.

  The acid value of the polyester is preferably 110 mgKOH / g or less, more preferably from the viewpoint of reducing the viscosity of the liquid developer and from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability. It is 70 mgKOH / g or less, more preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less. From the same viewpoint, it is preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, and still more preferably 8 mgKOH / g or more. The acid value of the polyester should be adjusted by changing the equivalent ratio of the carboxylic acid component and the alcohol component, changing the reaction time during resin production, changing the content of trivalent or higher carboxylic acid compounds, etc. Can do.

  In the present invention, the polyester 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. Polyester.

[Pigment]
As the pigment, all of the pigments used as toner colorants can be used, such as 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 can be used. In the present invention, the toner particles may be either black toner or color toner.

  The content of the pigment improves the pulverization property of the toner particles to obtain a liquid developer having a small particle diameter, the viewpoint of improving the low temperature fixability of the liquid developer, and the dispersion stability of the toner particles in the liquid developer. From the viewpoint of improving and improving storage stability, it is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and even more preferably 25 parts by mass or less with respect to 100 parts by mass of the resin. is there. Further, from the viewpoint of improving the image density of the liquid developer, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more with respect to 100 parts by mass of the resin.

  In the present invention, as a toner raw material, a release agent, a charge control agent, a charge control resin, a magnetic powder, a fluidity improver, a conductivity modifier, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property Additives such as improvers may be used as appropriate.

[Method for producing toner particles]
As a method for obtaining toner particles, a toner raw material containing a resin or a pigment is melt-kneaded, and the obtained melt-kneaded product is pulverized. A resin-based resin particle and a pigment are mixed by mixing an aqueous resin dispersion and an aqueous pigment dispersion. Examples thereof include a method for uniting the particles and a method for stirring the aqueous resin dispersion and the pigment at high speed. From the viewpoint of improving the developability and fixability of the liquid developer, a method in which the toner raw material is melt-kneaded and then pulverized is preferable.

  The toner raw material can be melt-kneaded using a known kneader such as a closed kneader, a uniaxial or biaxial kneader, or a continuous open roll type kneader. The method for producing the liquid developer of the present invention In order to improve the dispersibility of the pigment in the resin and to improve the yield of the toner particles after pulverization, it is preferable to use an open roll kneader.

  The toner raw material containing a resin and a pigment 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 is performed by adjusting the peripheral speed of mixing and the mixing time. The peripheral speed of stirring is preferably 10 m / sec or more and 30 m / sec or less from the viewpoint of improving the dispersibility of the pigment in the resin. The stirring time is preferably 1 minute or more and 10 minutes or less 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. The open roll type kneader used in the present invention comprises a plurality of raw material supply ports and a kneaded product discharge port provided along the axial direction of the roll, and from the viewpoint of production efficiency, a continuous open roll type kneader. It is preferable that

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

  In the present invention, the temperature of the kneaded product discharge part of the kneader is preferably set to a temperature not higher than 10 ° C. higher 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 such that the upstream set temperature is lower than that on the downstream side from the viewpoint that the kneaded material is firmly attached to the upstream side and kneaded strongly on the downstream side. Is preferably high.

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

  The rolls of the open roll type kneader preferably have different peripheral speeds. In the open roll type kneader provided with the two rolls described above, the temperature is improved from the viewpoint of improving the fixability of the liquid developer. It is preferable that the higher heating roll is the roll with the higher peripheral speed (high rotation side roll), and the cooling roll with the lower temperature is the roll with the lower peripheral speed (low rotation side roll).

  The peripheral speed of the high rotation side roll is preferably 2 m / min or more, more preferably 5 m / min or more, and preferably 100 m / min or less, more preferably 75 m / min or less. The peripheral speed of the low-rotation side roll is preferably 2 m / min or more, more preferably 4 m / min or more, preferably 100 m / min or less, more preferably 60 m / min or less, and even more preferably 50 m / min or less. It is. 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.

  The gap (clearance) between the two rolls is preferably 0.1 mm or more, more preferably 3 mm or less, more preferably 1 mm or less at the upstream end of the kneading.

  Moreover, there is no limitation in particular about the structure of each roll, a magnitude | size, material, etc. The roll surface has grooves used for kneading, and examples of the shape include a linear shape, a spiral shape, a corrugated shape, and an uneven shape.

  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.

  After cooling the melt-kneaded product obtained by melt kneading with an open roll kneader to such an extent that it can be crushed, the toner particles of the present invention are passed through ordinary methods such as a pulverization step and, if necessary, a classification step. Can be obtained.

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

  The pulverizer used in the pulverization step is not particularly limited. For example, examples of the pulverizer suitably used for the coarse pulverization include an atomizer and a rotoplex, but a hammer mill or the like may be used. Moreover, examples of the pulverizer suitably used for fine pulverization include a fluidized bed jet mill, an airflow jet mill, and a mechanical mill.

  The pulverized product may be classified using a classifier as necessary. 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 that 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 the pulverization step and the classification step performed as necessary is preferably 3 μm or more, more preferably from the viewpoint of improving the productivity of the wet pulverization step described later. It is 4 μm or more, preferably 15 μm or less, more preferably 12 μm or less. In the present specification, the volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% when calculated from the smaller particle size.

[Method for producing liquid developer]
Toner particles are dispersed in an insulating liquid in the presence of a dispersant to obtain a liquid developer. From the viewpoint of reducing the particle size of the toner particles in the liquid developer and reducing the viscosity of the liquid developer, the toner particles are dispersed in the insulating liquid, and then the toner particles are wet pulverized to form a liquid developer. Is preferably obtained.

[Insulating liquid]
The viscosity of the insulating liquid at 25 ° C. is to improve the dispersion stability of the toner particles in the liquid developer and improve the storage stability. From the viewpoint of obtaining an agent, it is preferably 1.0 mPa · s or more, more preferably 1.2 mPa · s or more, and further preferably 1.3 mPa · s or more. Further, from the viewpoint of improving the low temperature fixability of the liquid developer, and from the viewpoint of improving the pulverization property of the toner particles during wet pulverization and obtaining a liquid developer having a small particle size, it is preferably 30 mPa · s or less, more preferably 10 mPa · s. s or less, more preferably 5 mPa · s or less, and further preferably 3 mPa · s or less. When two or more insulating liquids are used in combination, the viscosity of the combined insulating liquid mixture may be within the above range. The viscosity of the insulating liquid at 25 ° C. is measured by the method described in the examples described later.

The insulating liquid means a liquid in which electricity does not easily flow. In the present invention, a liquid having a dielectric constant of 3.5 or less and a volume resistivity of 10 ⁷ Ωcm or more is preferable.

  The insulating liquid in the liquid developer of the present invention contains 5% by mass or more of naphthenic hydrocarbon (hereinafter also simply referred to as naphthene) and has an initial boiling point of 190 ° C. or higher and 300 ° C. or lower.

A naphthenic hydrocarbon is a hydrocarbon containing at least one saturated ring (naphthene ring) in one molecule. Specifically, cyclopentane (C ₅ H ₁₀ , one 5-membered ring), cyclohexane (C ₆ H ₁₂ , one 6-membered ring), etc. are known, but naphthene rings are present in petroleum products. There are those with multiple bonds and those with various paraffin side chains, etc., such as phythelite (C ₁₉ H ₃₄ , condensed with 6-membered ring), oleanane (C ₃₀ H ₅₂ , 5 with 6-membered ring) Condensation) and the like are also included in naphthenic hydrocarbons.

  The insulating liquid in the liquid developer of the present invention contains the naphthene-based hydrocarbon, but from the viewpoint of improving the low-temperature fixability of the liquid developer and suppressing the generation of dispersion medium vapor, naphthene-based carbonization. The content of hydrogen is 5% by mass or more in the insulating liquid, preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, further preferably 35% by mass or more, Preferably it is 40 mass% or more, More preferably, it is 45 mass% or more. Further, from the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles in the liquid developer and from the viewpoint of availability, it is preferably 80% by mass or less, more preferably 70% by mass or less.

  Commercially available insulating liquids containing 5% by mass or more of naphthenic hydrocarbons include “Naphthezol 200”, “Naphthezol 220” (all manufactured by JX Nippon Oil & Energy Corporation), “Exor D80”, “Exor” D110 "" Exor D130 "(all of which are manufactured by ExxonMobil Co., Ltd.). One or more of these can be used in combination.

  Specific examples of insulating liquids other than naphthenic hydrocarbons include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, vegetable oils, and the like. Among these, aliphatic hydrocarbons such as liquid paraffin and isoparaffin are preferable from the viewpoints of reducing the viscosity of the liquid developer, odor, harmlessness, and cost.

  Commercial products of aliphatic hydrocarbons include Isopar M (manufactured by ExxonMobil), Shellsol TM (manufactured by Shell Chemicals Japan), IP Solvent 2028, IP Solvent 2835 (all of which are manufactured by Idemitsu Kosan Co., Ltd.), Isosol 400 (Manufactured by JX Nippon Oil & Energy Corporation).

  The initial boiling point of the insulating liquid containing naphthenic hydrocarbon is the viewpoint of improving the low temperature fixability of the liquid developer, the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles in the liquid developer. From the viewpoint of improving the pulverization property of the toner particles during wet pulverization and obtaining a liquid developer having a small particle diameter and suppressing the generation of dispersion medium vapor, it is 190 ° C. or higher, preferably 200 ° C. or higher, more preferably 203 The temperature is 300 ° C. or higher, preferably 290 ° C. or lower, more preferably 285 ° C. or lower, and further preferably 280 ° C. or lower.

  The dry point of the insulating liquid containing naphthenic hydrocarbon is the viewpoint of improving the low temperature fixability of the liquid developer, the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles in the liquid developer, From the viewpoint of improving the pulverization property of the toner particles during wet pulverization and obtaining a liquid developer having a small particle diameter and suppressing the generation of the dispersion medium vapor, it is preferably 200 ° C. or higher, more preferably 220 ° C. or higher. Preferably it is 350 degrees C or less, More preferably, it is 330 degrees C or less, More preferably, it is 320 degrees C or less.

[Dispersant]
The liquid developer of the present invention, as a dispersant, improves the dispersion stability of the toner particles in the liquid developer and improves the storage stability, and improves the pulverization property of the toner particles during wet pulverization and reduces the particle size. From the viewpoint of obtaining a liquid developer, it contains a polyimine, which is a basic dispersant, and a condensate of carboxylic acid. The dispersant is used to stably disperse the toner particles in the insulating liquid. The liquid developer of the present invention is a basic adsorbent as an adsorbing group from the viewpoint of improving the adsorptivity to a resin, particularly polyester. It is preferable to contain a basic dispersant having a group, and the polyimine and carboxylic acid condensate is also a kind of basic dispersibility.

  The polyimine used as a raw material for the polyimine-carboxylic acid condensate is preferably a polyalkyleneimine from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability. Specific examples of the polyalkyleneimine include polyethyleneimine, polypropyleneimine, polybutyleneimine and the like. From the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, polyethyleneimine is used. More preferred.

  The carboxylic acid used as a raw material for the polyimine-carboxylic acid condensate is preferably from 10 to 30 carbon atoms, more preferably from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability. Is preferably a saturated or unsaturated aliphatic carboxylic acid having 12 to 24 carbon atoms, more preferably 16 to 22 carbon atoms, and more preferably a linear saturated or unsaturated aliphatic carboxylic acid. Specific carboxylic acids include linear saturated aliphatic carboxylic acids such as lauric acid, myristic acid, palmitic acid and stearic acid; linear unsaturated aliphatic carboxylic acids such as oleic acid, linoleic acid and linolenic acid. It is done.

  In addition, the carboxylic acid used as a raw material for the polyimine-carboxylic acid condensate may have a substituent such as a hydroxy group, which improves the dispersion stability of the toner particles in the liquid developer and improves the storage stability. From the point of view, it is preferably a hydroxycarboxylic acid having a hydroxy group as a substituent. Examples of the hydroxycarboxylic acid include mevalonic acid, ricinoleic acid, hydroxycarboxylic acid such as 12-hydroxystearic acid, and the like. The hydroxycarboxylic acid may be a condensate thereof.

  From the above viewpoint, the carboxylic acid used as a raw material for the polyimine-carboxylic acid condensate is preferably a hydroxy group having 10 to 30 carbon atoms, more preferably 12 to 24 carbon atoms, and still more preferably 16 to 22 carbon atoms. Aliphatic carboxylic acids and their condensates are preferred, and 12-hydroxystearic acid and its condensates are more preferred.

  Specific examples of the condensate of polyimine and carboxylic acid include Solsperse 11200, Solsperse 13040 (all of which are manufactured by Nihon Lubrizol).

  The weight average molecular weight of the polyimine-carboxylic acid condensate is preferably 2000 or more, more preferably 4000 or more, and still more preferably from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability. More than 8000. Further, from the viewpoint of improving the fixability of the liquid developer, it is preferably 50000 or less, more preferably 40000 or less, and further preferably 30000 or less. In addition, the weight average molecular weight of the condensate of polyimine and carboxylic acid is measured by the method as described in the below-mentioned Example.

  The addition amount of the dispersant is preferably 0.5 parts by mass or more, more preferably 1 part by mass as an effective component with respect to 100 parts by mass of the toner particles from the viewpoint of suppressing aggregation of the toner particles and reducing the viscosity of the liquid developer. Part or more, more preferably 2 parts by weight or more. Further, from the viewpoint of improving the developability and fixability of the liquid developer, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, further preferably 10 parts by mass or less, and further preferably 5 parts by mass or less.

  Further, the content of the polyimine and carboxylic acid condensate in the dispersant suppresses the aggregation of the toner particles, reduces the viscosity of the liquid developer, and improves the pulverization property of the toner particles during wet pulverization. From the viewpoint of obtaining a liquid developer having a diameter, preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, further preferably substantially 100% by mass, in the effective component of the dispersant. More preferably, it is 100 mass%.

  As a method of mixing the toner particles, the insulating liquid, and the dispersant, 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 from the viewpoint of improving the productivity and storage stability of the toner particle dispersion, and specifically, Despa (manufactured by Asada Tekko), T. K. homomixer, TK. Homodisper, TK. Robomix (all of which are manufactured by PRIMIX Co., Ltd.), CLEARMIX (manufactured by M Technique Co., Ltd.), KD mill (manufactured by KD International Co., Ltd.) and the like are preferable.

  By mixing the toner particles, the insulating liquid and the dispersant with a high-speed stirring and mixing device, the toner particles are predispersed to obtain a toner particle dispersion, and the productivity of the liquid developer is improved by the next wet grinding. To do.

  From the viewpoint of improving the image density of the liquid developer, the solid content concentration of the toner particle dispersion is preferably 20% by mass or more, more preferably 30% by mass or more, and further preferably 33% by mass or more. Further, from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less. The solid content concentration of the toner particle dispersion is measured by the method described in Examples below.

[Wet grinding]
The wet pulverization is a method in which toner particles dispersed in an insulating liquid are mechanically pulverized in a state of being dispersed in the insulating liquid.

  As an apparatus used for wet pulverization, for example, a generally used stirring and mixing apparatus such as an anchor blade can be used. Among the stirring and mixing apparatuses, high-speed stirring and mixing apparatuses such as Despa (manufactured by Asada Tekko) and TK. . A plurality of these devices can be combined.

  Among these, the viewpoint of reducing the particle size of the toner particles in the liquid developer, the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, and the viscosity of the toner particle dispersion liquid. From the viewpoint of reducing the above, it is preferable to use a bead mill.

  In the bead mill, toner particles having a desired particle size and particle size distribution can be obtained by controlling the particle size and filling rate of the medium used, the peripheral speed of the rotor, the residence time, and the like.

As described above, the liquid developer of the present invention is
Step 1: Melting and kneading resin and pigment and pulverizing to obtain toner particles,
Step 2: A dispersant is added to the toner particles obtained in Step 1 and dispersed in an insulating liquid to obtain a toner particle dispersion. Step 3: The toner particle dispersion obtained in Step 2 is wet-pulverized. However, it is preferable to produce the liquid developer by a method including a step of obtaining a liquid developer.

  From the viewpoint of improving the image density of the liquid developer, the solid concentration of the liquid developer is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more. Further, from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less. The solid content concentration of the liquid developer is measured by the method described in the examples described later. If there is no operation such as dilution or concentration after the preparation of the toner particle dispersion, the solid content concentration of the toner particle dispersion becomes the solid content concentration of the liquid developer.

The volume median particle size (D ₅₀ ) of the toner particles in the liquid developer is preferably 5 μm or less from the viewpoint of reducing the particle size of the toner particles in the liquid developer and improving the image quality of the liquid developer. The thickness is preferably 3 μm or less, more preferably 2.5 μm or less. Further, from the viewpoint of reducing the viscosity of the liquid developer, it is preferably 0.5 μm or more, more preferably 1.0 μm or more, and further preferably 1.5 μm or more. The volume median particle size (D ₅₀ ) of the toner particles in the liquid developer is measured by the method described in Examples described later.

  From the viewpoint of improving the fixability of the liquid developer, the viscosity at 25 ° C. of the liquid developer is preferably 50 mPa · s or less, more preferably 40 mPa · s or less, still more preferably 37 mPa · s or less, more preferably 35 mPa · s. s or less. Further, from the viewpoint of improving the dispersion stability of the toner particles in the liquid developer and improving the storage stability, it is preferably 3 mPa · s or more, more preferably 5 mPa · s or more, further preferably 6 mPa · s or more, and further Preferably, it is 7 mPa · s or more. The viscosity of the liquid developer is measured by the method described in the examples below.

  The present invention further discloses the following liquid developer and method for producing the same with respect to the above-described embodiment.

<1> A liquid developer in which toner particles containing a polyester-containing resin and a pigment are dispersed in an insulating liquid in the presence of a dispersant,
The insulating liquid contains 5% by mass or more of naphthenic hydrocarbon, and the initial boiling point is 190 ° C. or higher and 300 ° C. or lower,
The dispersant contains a polyimine and carboxylic acid condensate,
Liquid developer.

<2> The content of the polyester is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 100% by mass, and 100% by mass, that is, only the polyester is used as the resin. Is more preferable, The liquid developer according to <1>.
<3> The alcohol component of the polyester preferably contains 1,2-propanediol and / or an alkylene oxide adduct of bisphenol A represented by the formula (I), and contains 1,2-propanediol. More preferably, the liquid developer according to <1> or <2>.
<4> The content of 1,2-propanediol is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, further preferably substantially 100 mol% in the alcohol component. The liquid developer according to <3>, more preferably 100 mol%.
<5> The liquid developer according to any one of <1> to <4>, wherein the carboxylic acid component of the polyester preferably contains terephthalic acid and / or fumaric acid, and more preferably contains terephthalic acid.
<6> The content of terephthalic acid in the carboxylic acid component is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, still more preferably substantially 100 mol%, still more preferably The liquid developer according to <5>, wherein is 100 mol%.
<7> The softening point of the polyester is preferably 160 ° C or lower, more preferably 130 ° C or lower, further preferably 120 ° C or lower, more preferably 110 ° C or lower, preferably 70 ° C or higher, more preferably 75 ° C or higher. The liquid developer according to any one of <1> to <6>, wherein
<8> The glass transition temperature of the polyester is preferably 80 ° C. or lower, more preferably 70 ° C. or lower, further preferably 60 ° C. or lower, preferably 40 ° C. or higher, more preferably 45 ° C. or higher, <1 The liquid developer according to any one of> to <7>.
<9> The acid value of the polyester is preferably 110 mgKOH / g or less, more preferably 70 mgKOH / g or less, further preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less, preferably 3 mgKOH / g or more, more The liquid developer according to any one of <1> to <8>, which is preferably 5 mgKOH / g or more, more preferably 8 mgKOH / g or more.
<10> The content of the pigment is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, further preferably 25 parts by mass or less, with respect to 100 parts by mass of the resin. The liquid developer according to any one of <1> to <9>, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 15 parts by mass or more.
<11> The liquid developer according to any one of <1> to <10>, wherein the toner particles are obtained by a method comprising a step of melting and kneading the toner raw material and then pulverizing.
<12> The viscosity of the insulating liquid at 25 ° C. is preferably 1.0 mPa · s or more, more preferably 1.2 mPa · s or more, further preferably 1.3 mPa · s or more, preferably 30 mPa · s or less, more preferably The liquid developer according to any one of <1> to <11>, wherein is 10 mPa · s or less, more preferably 5 mPa · s or less, and further preferably 3 mPa · s or less.
<13> The content of naphthenic hydrocarbon in the insulating liquid is preferably 10% by mass or more, more preferably 20% by mass or more, further preferably 30% by mass or more, further preferably 35% by mass or more, and further preferably Is 40% by mass or more, more preferably 45% by mass or more, preferably 80% by mass or less, more preferably 70% by mass or less, according to any one of <1> to <12>.
<14> The liquid developer according to any one of <1> to <13>, wherein the insulating liquid further preferably contains an aliphatic hydrocarbon.
<15> The initial boiling point of the insulating liquid is preferably 200 ° C. or higher, more preferably 203 ° C. or higher, preferably 290 ° C. or lower, more preferably 285 ° C. or lower, more preferably 280 ° C. or lower, The liquid developer according to any one of <1> to <14>.
<16> The dry point of the insulating liquid is preferably 200 ° C. or higher, more preferably 220 ° C. or higher, preferably 350 ° C. or lower, more preferably 330 ° C. or lower, and further preferably 320 ° C. or lower. The liquid developer according to any one of 1> to <15>.
<17> The liquid developer according to any one of <1> to <16>, wherein the polyimine that is a raw material of the condensate of polyimine and carboxylic acid is preferably a polyalkyleneimine, more preferably polyethyleneimine.
<18> The carboxylic acid used as the raw material for the polyimine-carboxylic acid condensate is preferably a hydroxy aliphatic having 10 to 30 carbon atoms, more preferably 12 to 24 carbon atoms, and even more preferably 16 to 22 carbon atoms. The liquid developer according to any one of <1> to <17>, wherein a carboxylic acid and / or a condensate thereof is preferable, and 12-hydroxystearic acid and / or a condensate thereof is more preferable.
<19> The weight average molecular weight of the polyimine and carboxylic acid condensate is preferably 2000 or more, more preferably 4000 or more, still more preferably 8000 or more, preferably 50000 or less, more preferably 40000 or less, and further preferably 30000. The liquid developer according to any one of <1> to <18>, which is the following.
<20> The amount of the dispersant added is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 2 parts by mass or more, preferably 20 parts by mass or more as an effective component with respect to 100 parts by mass of the toner particles. The liquid developer according to any one of <1> to <19>, wherein the liquid developer is at most 15 parts by mass, more preferably at most 15 parts by mass, even more preferably at most 10 parts by mass, even more preferably at most 5 parts by mass.
<21> The content of the polyimine-carboxylic acid condensate is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and still more preferably substantially, in the effective content of the dispersant. The liquid developer according to any one of <1> to <20>, wherein the content is 100% by mass, more preferably 100% by mass.
<22> The solid concentration of the liquid developer is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, preferably 50% by mass or less, more preferably 45% by mass. Hereinafter, the liquid developer according to any one of <1> to <21>, further preferably 40% by mass or less.
<23> The volume median particle size (D ₅₀ ) of the toner particles in the liquid developer is preferably 5 μm or less, more preferably 3 μm or less, still more preferably 2.5 μm or less, preferably 0.5 μm or more, more preferably Is 1.0 μm or more, more preferably 1.5 μm or more, the liquid developer according to any one of <1> to <22>.
<24> The viscosity of the liquid developer at 25 ° C. is preferably 50 mPa · s or less, more preferably 40 mPa · s or less, further preferably 37 mPa · s or less, further preferably 35 mPa · s or less, preferably 3 mPa · s or less. The liquid developer according to any one of <1> to <23>, which is s or more, more preferably 5 mPa · s or more, further preferably 6 mPa · s or more, and further preferably 7 mPa · s or more.
<25> A method for producing a liquid developer in which toner particles containing a polyester-containing resin and a pigment are dispersed in an insulating liquid in the presence of a dispersant,
Step 1: Melting and kneading resin and pigment and pulverizing to obtain toner particles,
Step 2: A dispersant is added to the toner particles obtained in Step 1 and dispersed in an insulating liquid to obtain a toner particle dispersion. Step 3: The toner particle dispersion obtained in Step 2 is wet-pulverized. And a step of obtaining a liquid developer,
The insulating liquid contains 5% by mass or more of naphthenic hydrocarbon, and the initial boiling point is 190 ° C. or higher and 300 ° C. or lower,
The dispersant contains a polyimine and carboxylic acid condensate,
A method for producing a liquid developer.
<26> The solid content concentration of the toner particle dispersion is preferably 20% by mass or more, more preferably 30% by mass or more, still more preferably 33% by mass or more, preferably 50% by mass or less, more preferably 45% by mass. % Or less, more preferably 40% by mass or less, the liquid developer according to <25>.
<27> The method for producing a liquid developer according to <25> or <26>, wherein a bead mill is preferably used for wet pulverization.

  The physical properties of the resin and the like were measured by the following method.

[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, a 1.96 MPa load was applied by a plunger, a nozzle with a diameter of 1 mm and a length of 1 mm Extrude from. The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Glass transition temperature of resin]
Using a differential scanning calorimeter “DSC210” (manufactured by Seiko Denshi Kogyo Co., Ltd.), 0.01 to 0.02 g of sample is weighed into an aluminum pan, heated to 200 ° C, and from that temperature to 0 ° C at a cooling rate of 10 ° C / min. Cooling. Next, the sample is heated at a heating rate of 10 ° C./min, and the endothermic peak is measured. The glass transition temperature is defined as the temperature at the intersection of the base line extension below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Acid value of the resin]
Measured by the method of JIS K0070. However, only the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Volume-median particle size of toner particles before mixing with insulating liquid]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 100μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) is dissolved in the electrolyte so as to have a concentration of 5% by mass.
Dispersion conditions: 10 mg of a measurement sample was added to 5 ml of the dispersion, and dispersed for 1 minute with an ultrasonic disperser, then 25 ml of the electrolyte was added, and further dispersed for 1 minute with an ultrasonic disperser. Prepare sample dispersion.
Measurement conditions: The sample dispersion is added to 100 ml of the electrolytic solution so that the particle size of 30,000 particles can be measured in 20 seconds, and 30,000 particles are measured. Determine the median particle size (D ₅₀ ).

[Viscosity of insulating liquid and liquid developer at 25 ° C]
Put 4-5mL of measuring solution into 6mL glass sample tube "Screw No.2" (manufactured by Maruemu Co., Ltd.) and use rotational vibration viscometer "Viscomate VM-10A-L" (manufactured by Seconic) Measure the viscosity at 25 ° C.

[Initial boiling point and dry point of insulating liquid]
Measured by the method specified in ASTM D86.

[Content of naphthenic hydrocarbon in insulating liquid]
Measure by the method specified in JIS K2536-2.

[Solid content concentration of dispersant solution]
10 parts by mass of the dispersant solution is dried at 8.3 kPa and 100 ° C. for 4 hours in a vacuum dryer, and the solid content concentration is calculated from the following formula.

[Weight average molecular weight (Mw) of polyimine and carboxylic acid condensate]
The molecular weight distribution is measured by gel permeation chromatography (GPC) method to determine the weight average molecular weight.
(1) Preparation of sample solution Dissolve the dispersant in chloroform so that the concentration is 0.2 g / 100 ml. Next, this solution is filtered using a fluororesin filter “FP-200” (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 0.2 μm to remove insoluble components to obtain a sample solution.
(2) Molecular weight measurement Using the following measuring device and analytical column, a chloroform solution of 100 mmol / L Farmin DM2098 (manufactured by Kao Corporation) was flowed as an eluent at a flow rate of 1 ml per minute, and the column was placed in a constant temperature bath at 40 ° C. To stabilize. Measurement is performed by injecting 100 μl of the sample solution. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. There are several types of monodisperse polystyrene (A-500 (Mw 5.0 × 10 ² ), A-5000 (Mw 5.97 × 10 ³ ), F-2 (Mw 1.81 × 10 ⁴ ) manufactured by Tosoh Corporation) , F-10 (Mw 9.64 × 10 ⁴ ), F-40 (Mw 4.27 × 10 ⁵ )) are used as standard samples.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: K-804L (Showa Denko)

[Weight Average Molecular Weight of Dispersant A (Mw)]
The molecular weight distribution is measured by gel permeation chromatography (GPC) method to determine the weight average molecular weight.
(1) Preparation of sample solution A dispersant (the insulating liquid was distilled off from the dispersant solution) was dissolved in tetrahydrofuran so that the concentration was 0.5 g / 100 ml. Subsequently, this solution was filtered using a fluororesin filter “FP-200” (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 0.2 μm to remove insoluble components to obtain a sample solution.
(2) Molecular weight measurement Using the following measuring device and analytical column, tetrahydrofuran is flowed as an eluent at a flow rate of 1 ml / min, and the column is stabilized in a constant temperature bath at 40 ° C. Measurement is performed by injecting 100 μl of the sample solution. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. There are several types of monodisperse polystyrene (A-500 (Mw 5.0 × 10 ² ), A-1000 (Mw 1.01 × 10 ³ ), A-2500 (Mw 2.63 × 10 ³ ) manufactured by Tosoh Corporation) , A-5000 (Mw 5.97 × 10 ³ ), F-1 (Mw 1.02 × 10 ⁴ ), F-2 (Mw 1.81 × 10 ⁴ ), F-4 (Mw 3.97 × 10 ⁴ ), F-10 (Mw 9.64 × 10 ⁴ ), F-20 (Mw 1.90 × 10 ⁵ ), F-40 (Mw 4.27 × 10 ⁵ ), F-80 (Mw 7.06 × 10 ⁵ ), F-128 (Mw 1.09 × 10 ⁶ )) Is used as a standard sample.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (manufactured by Tosoh Corporation)

[Solid content concentration of toner particle dispersion and liquid developer]
Dilute 10 parts by weight of the sample with 90 parts by weight of hexane, and rotate for 20 minutes at a rotational speed of 25000 r / min using a centrifugal separator “H-201F” (manufactured by Kokusan). After standing, the supernatant is removed by decantation, diluted with 90 parts by mass of hexane, and centrifuged again under the same conditions. After removing the supernatant by decantation, the lower layer is dried in a vacuum dryer at 0.5 kPa and 40 ° C. for 8 hours, and the solid content concentration is calculated from the following formula.

[Volume Median Particle Size (D ₅₀ ) of Toner Particles in Liquid Developer]
Using a laser diffraction / scattering particle size measuring device “Mastersizer 2000” (Malvern), add Isopar G (ExxonMobil, isoparaffin, viscosity 1 mPa · s at 25 ° C.) to the measurement cell, and the scattering intensity The volume median particle size (D ₅₀ ) is 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 at a concentration of 5 to 15%.

Example of resin production The raw material monomer and esterification catalyst shown in Table 1 were used as a 10L four-neck equipped with a nitrogen introduction tube, a dehydration tube equipped with a fractionation tube through which hot water of 98 ° C was passed, a stirrer and a thermocouple. Put in a flask, raise the temperature to 180 ° C, raise the temperature to 210 ° C over 5 hours, react until the reaction rate reaches 90%, further react at 8.3 kPa, softening point to 87 ° C When it reached, the reaction was completed, and a resin A was obtained. Table 1 shows the physical properties of Resin A. The reaction rate means a value of the amount of generated reaction water (mol) / theoretical generated water amount (mol) × 100.

Dispersant production example 90.5g of insulating liquid "Exsol D110" (ExxonMobil Co., Ltd.) is placed in a 2L four-necked flask equipped with a cooling tube, nitrogen inlet tube, stirrer and thermocouple, and reacted with nitrogen gas. The inside of the container was replaced. The inside of the reaction vessel was heated to 95 ° C., and a mixture of the raw material monomer and the polymerization initiator shown in Table 2 was dropped over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 95 ° C. for 3 hours to obtain a dispersion A solution. The weight average molecular weight of the dispersant A was 9600, and the solid content concentration of the dispersant A solution was 62% by mass. In addition, the weight average molecular weight of the dispersing agent A measured using chloroform as a solvent was 1200 like the condensate of polyimine and carboxylic acid.

  Table 3 shows insulating liquids used in Examples and Comparative Examples.

Examples 1 to 5 and Comparative Examples 1 and 3
85 parts by weight of Resin A and 15 parts by weight of pigment “ECB-301” (Phtalocyanine Blue 15: 3, manufactured by Dainichi Seika Co., Ltd.) using a 20 L Henschel mixer in advance, with a rotation speed of 1500 r / min (circumferential speed 21.6 m) / sec) for 3 minutes under stirring and then melt-kneaded under the conditions shown below.

[Melting and kneading conditions]
A continuous two-open roll kneader “NIDEX” (manufactured by Nippon Coke Kogyo 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: high rotation side roll (front roll) rotation speed 75r / min (circumferential speed 32.4m / min), low rotation side roll (back roll) rotation speed 35r / min ( The peripheral speed was 15.0 m / min), and the roll gap at the raw material charging side end 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 cooled with a cooling roll and then roughly pulverized to about 1 mm using a hammer mill. The obtained coarsely pulverized product was finely pulverized and classified by an airflow jet mill “IDS” (manufactured by Nippon Pneumatic Co., Ltd.) to obtain toner particles having a volume median particle size (D ₅₀ ) of 10 μm.

  105 g of the toner particles obtained, 187.1 g of the insulating liquid shown in Table 4, and a dispersant “Solsperse 13040” (manufactured by Lubrizol, polyimine and carboxylic acid condensate, effective content 40%, weight average molecular weight 24200) 7.9 g Into a 2L polyethylene container, and use TK Robotics (Primics) to stir for 30 minutes at 7000r / min under ice-cooling to solidify toner particles with a solid content of 36.1% by mass A dispersion was obtained.

  Next, the obtained toner particle dispersion was rotated with a 6-cylinder sand mill “TSG-6” (manufactured by Imex) at a volume filling rate of 60% by volume using zirconia beads having a diameter of 0.8 mm. Wet milled for 4 hours at min (circumferential speed 4.8 m / sec). The beads were removed by filtration, and the solid content concentration was diluted to 25% by mass with an insulating liquid to obtain a liquid developer having the physical properties shown in Table 4.

Example 6
In Example 1, the amount of the insulating liquid shown in Table 4 was added to 6.3 g of the dispersant “Solsperse 11200” (manufactured by Lubrizol, polyimine and carboxylic acid condensate, effective content 50%, weight average molecular weight 10400). A liquid developer having the physical properties shown in Table 4 was obtained in the same manner as in Example 1, except that the weight was changed to 188.7 g.

Comparative Example 2
In Example 4, the properties shown in Table 4 were obtained in the same manner as in Example 4 except that the amount of insulating liquid used was changed to 189.9 g, the dispersant and the amount used were changed to 5.1 g of Dispersant A, respectively. A liquid developer was obtained.

Test Example 1 [Crushability]
The grindability was evaluated according to the following evaluation criteria from the value of the volume median particle size (D ₅₀ ) of the toner particles in the liquid developer after wet grinding for 4 hours shown in Table 4. The results are shown in Table 5. The smaller the value, the better the grindability (dispersing performance of the dispersant).

A: Volume median particle size of less than 2.0 μm B: Volume median particle size of 2.0 μm or more and less than 2.5 μm C: Volume median particle size of 2.5 μm or more and less than 3.0 μm D: Volume median particle size of 3.0 μm or more

Test Example 2 [storage stability]
10 g of the liquid developer was placed in a 20 mL glass sample tube “Screw No. 5” (manufactured by Maruemu Co., Ltd.) and stored in a constant temperature bath at 40 ° C. for 12 hours. The volume-median particle size before and after storage was measured, and storage stability was evaluated from the difference value. The results are shown in Table 5. The closer the value is to 0, the better the storage stability.

Test Example 3 [Low-temperature fixability]
A liquid developer was dropped onto “POD gloss coated paper” (manufactured by Oji Paper Co., Ltd.), and a thin film was prepared with a wire bar so that the mass after drying was 1.2 g / m ² .

  The prepared thin film is held in a constant temperature bath at 60 ° C for 10 seconds, and then the fixing roll temperature is set to 90 ° C with an external fixing device that takes out the fixing device of "OKI MICROLINE 3010" (Oki Data). And fixing at a fixing speed of 140 mm / sec. Thereafter, the fixing roll temperature was set to 100 ° C., and the same operation was performed. While the temperature was increased by 10 ° C. up to 160 ° C., the fixing process of the unfixed image was performed at each temperature to obtain a fixed image.

  A mending tape “Scotch Mending Tape 810” (manufactured by 3M, width 18 mm) was affixed to the obtained fixed image, pressure was applied to the tape with a roller so that a load of 500 g was applied, and then the tape was peeled off. The image density before and after tape peeling was measured with a color meter “Spectroeye” (manufactured by X-Rite). The image printing unit measured three points each, and the average value was calculated as the image density. Calculate the fixing rate (%) from the value of image density after peeling / image density before peeling x 100, and set the temperature of the fixing roll at which the fixing rate first reaches 90% or more as the minimum fixing temperature, and evaluate low-temperature fixability did. The results are shown in Table 5. Smaller values indicate better low temperature fixability. When the fixing rate is 90% or more and an offset to the fixing roll occurs, “no fixing window” is set.

  As is clear from the results in Table 5, it can be seen that the liquid developers of Examples 1 to 6 are excellent in grindability and low-temperature fixability and excellent in storage stability as compared with Comparative Examples 1 to 3.

  The liquid developer of the present invention is suitably used for developing a latent image formed in electrophotography, electrostatic recording method, electrostatic printing method and the like.

Claims (7)

A liquid developer in which toner particles containing a polyester-containing resin and a pigment are dispersed in an insulating liquid in the presence of a dispersant,
The polyester is a polycondensate of an alcohol component and a carboxylic acid component containing 50 mol% or more of 1,2-propanediol,
The insulating liquid contains 5% by mass or more of naphthenic hydrocarbon, and the initial boiling point is 190 ° C. or higher and 300 ° C. or lower,
The dispersant contains a polyimine and carboxylic acid condensate,
Liquid developer. The content of the condensation product of a polyimine and a carboxylic acid, dispersant, at least 50 wt%, the liquid developer according to claim 1.   The liquid developer according to claim 1, wherein the liquid developer has a viscosity at 25 ° C. of 3 mPa · s to 50 mPa · s.   The liquid developer according to claim 1, wherein the insulating liquid has a viscosity at 25 ° C. of 1.0 mPa · s to 30 mPa · s.   The liquid developer according to claim 1, wherein the polyester content is 90% by mass or more in the resin.   The liquid developer according to claim 1, wherein the polyester has an acid value of 3 mgKOH / g or more and 110 mgKOH / g or less. A method for producing a liquid developer in which toner particles containing a polyester-containing resin and a pigment are dispersed in an insulating liquid in the presence of a dispersant,
Step 1: Melting and kneading resin and pigment and pulverizing to obtain toner particles,
Step 2: A dispersant is added to the toner particles obtained in Step 1 and dispersed in an insulating liquid to obtain a toner particle dispersion. Step 3: The toner particle dispersion obtained in Step 2 is wet-pulverized. And a step of obtaining a liquid developer,
The polyester is a polycondensate of an alcohol component and a carboxylic acid component containing 50 mol% or more of 1,2-propanediol,
The insulating liquid contains 5% by mass or more of naphthenic hydrocarbon, and the initial boiling point is 190 ° C. or higher and 300 ° C. or lower,
The dispersant contains a polyimine and carboxylic acid condensate,
A method for producing a liquid developer.