JP2019128534A - Liquid developer - Google Patents

Abstract

To provide a liquid developer that contains a polyester resin, has a small particle diameter and low viscosity, and is excellent in positive chargeability.SOLUTION: A liquid developer contains toner particles containing a binder resin and a colorant, a sucrose fatty acid ester, and an insulating liquid, wherein the binder resin contains a polyester resin; a fatty acid component of the sucrose fatty acid ester has 12 to 24 carbon atoms, inclusive; the viscosity at 25°C of the liquid developer having a solid content concentration of 25 mass% is 50 mPa s or less.SELECTED DRAWING: None

Description

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

  Examples of the electrophotographic developer include a dry developer using toner particles made of a material containing a colorant and a binder resin in a dry state, and a liquid developer in which toner particles are dispersed in an insulating liquid.

  In the liquid developer, since the toner particles are dispersed in oil in the insulating liquid, the particle size can be reduced as compared with the dry developer. Therefore, since a high-quality printed matter that surpasses offset printing can be obtained, it is suitable for commercial printing applications. In recent years, the demand for speeding up has increased, and therefore, there is a demand for lowering the viscosity of the liquid developer. There is also a need for a liquid developer capable of melting and fixing toner particles with a small amount of heat, that is, a liquid developer having excellent low-temperature fixability.

  Patent Document 1 includes a sugar fatty acid ester which is an ester of a sugar and a fatty acid, a fatty acid triglyceride and a fatty acid monoester, and the fatty acid triglyceride is characterized by containing unsaturated fatty acid as a fatty acid component. Liquid is disclosed.

  In Patent Document 2, in a liquid developer for electrostatic latent images, in addition to a colorant and a dispersant, a copolymer segment soluble in an aliphatic hydrocarbon solvent and insoluble in the solvent containing vinyl acetate as a main component. And a dispersion of a nongel-like copolymer which is insoluble in the solvent as a whole, and the mixed dispersion is selected from a ball mill, a sand mill, an attritor and a vibration mill. A method for producing a liquid developer for an electrostatic latent image, characterized in that it is pulverized and dispersed by various means, is disclosed.

JP 2008-170556 A Japanese Patent Laid-Open No. 10-254183

  Although polyester resins are known as binder resins excellent in low-temperature fixability, polyester resins having an acid group tend to be negatively charged, so there is a problem in chargeability when used as a positively chargeable liquid developer. .

  The present invention relates to a liquid developer containing a polyester resin and having a small particle size, a low viscosity, and excellent positive chargeability.

  The present invention provides a liquid developer containing toner particles containing a binder resin and a colorant, a sucrose fatty acid ester, and an insulating liquid, wherein the binder resin contains a polyester resin, and the sucrose fatty acid The present invention relates to a liquid developer having a carbon number of 12 or more and 24 or less of a fatty acid component of an ester, and a viscosity at 25 ° C. at a solid content concentration of 25 mass% of 50 mPa · s or less.

  Even if the liquid developer of the present invention contains a polyester resin, it has an effect of being excellent in small particle size, low viscosity and positive chargeability.

  The liquid developer of the present invention contains a binder resin containing a polyester resin and toner particles containing a colorant, a specific sucrose fatty acid ester, and an insulating liquid, and has a small particle size, low viscosity and It has excellent positive chargeability.

The reason for such an effect is not clear, but is considered as follows.
Sucrose fatty acid ester is a rigid structure because it has a cyclic structure containing a hetero element, and furthermore, there are many oxygen atoms in the molecule, and a hydrogen bond is formed with the polyester resin having an acid group. Highly adsorptive to particles. In addition, the fatty acid component in the molecule has high solubility in the insulating liquid and good dispersibility. Furthermore, it has many oxygen atoms with a high proton demand capability, and can capture protons in the liquid developer. Therefore, the positive chargeability of the liquid developer is excellent even if the binder resin is a polyester resin which is easily negatively charged by the ability of a positively charged sucrose fatty acid ester to be adsorbed by a positive charge by capturing protons. It is presumed that

  The binder resin includes a polyester resin. The polyester resin is preferably a polycondensate of an alcohol component and a carboxylic acid component.

  The alcohol component preferably contains an aliphatic diol from the viewpoint of compatibility with the insulating liquid.

  The carbon number of the aliphatic diol is preferably 2 or more, more preferably 3 or more from the viewpoint of the positive chargeability of the toner, and preferably 6 or less, from the viewpoint of the particle size reduction and the viscosity reduction. Preferably it is 4 or less.

  Examples of the aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, and the like. Among them, aliphatic diols having a hydroxyl group bonded to a secondary carbon atom having 3 to 5 carbon atoms, such as 1,2-propanediol and 1,3-butanediol, are preferable.

  The content of the aliphatic diol is preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably 95 mol% or more, still more preferably 100 mol%, in the alcohol component.

  Examples of other alcohol components include aromatic diols such as alkylene oxide adducts of bisphenol A, trihydric or higher polyhydric alcohols such as bisphenol A, hydrogenated bisphenol A, and glycerin.

  In the carboxylic acid component, examples of the divalent carboxylic acid compound include dicarboxylic acids having 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 3 to 10 carbon atoms, and anhydrides thereof. Or a derivative such as an alkyl ester having an alkyl group having 1 to 3 carbon atoms. Specific examples of dicarboxylic acids 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, alkyl having 1 to 20 carbon atoms And aliphatic dicarboxylic acids such as succinic acid substituted with a group or an alkenyl group having 2 to 20 carbon atoms.

  The carboxylic acid component is preferably an aromatic dicarboxylic acid compound, more preferably terephthalic acid, from the viewpoint of improving the positive chargeability of the toner and from the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles. . The content of the aromatic dicarboxylic acid compound is preferably 70 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more, further preferably 95 mol% or more, more preferably in the carboxylic acid component. 100 mol%.

  The trivalent or higher carboxylic acid compound includes, for example, 4 to 20 carbon atoms, preferably 6 to 20 carbon atoms, more preferably 7 to 15 carbon atoms, and still more preferably 8 to 12 carbon atoms, and more preferably Preferably, trivalent or higher carboxylic acids having 9 to 10 carbon atoms, their anhydrides, or derivatives such as alkyl esters having 1 to 3 carbon atoms in the alkyl group can be mentioned. Specifically, 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), or their acid anhydrides and the like can be mentioned.

  The content of the trivalent or higher carboxylic acid compound is preferably small from the viewpoint of the low-temperature fixability of the toner, and is preferably 30 mol% or less, more preferably 20 mol% or less, still more preferably in the carboxylic acid component. It is 10 mol% or less.

  The alcohol component may contain a monovalent alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid compound as appropriate from the viewpoint of adjusting the molecular weight and the softening point of the polyester resin.

  From the viewpoint of adjusting the softening point of the polyester resin, the equivalent ratio (COOH group / OH group) of the carboxylic acid component and the alcohol component in the polyester resin is preferably 0.6 or more, more preferably 0.7 or more, and even more preferably 0.75 or more. Yes, and preferably 1.1 or less, more preferably 1.05 or less.

  The polyester resin is preferably, for example, an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and, if necessary, in the presence of an esterification promoter, a polymerization inhibitor, etc. It can be produced by polycondensation at a temperature of 130 ° C. or higher, more preferably 170 ° C. or higher, and preferably 250 ° C. or lower, more preferably 240 ° C. or lower.

  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, and tin compounds are preferred. 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, based on 100 parts by mass of the total of the alcohol component and the carboxylic acid component. Preferably it is 1 mass part or less. Examples of the esterification promoter include gallic acid. The amount of the esterification promoter 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, based on 100 parts by mass of the total 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, based on 100 parts by mass of the total of the alcohol component and the carboxylic acid component. Preferably it is 0.1 mass part or less.

  In the present invention, the polyester resin may be a polyester resin that has been modified to such an extent that its properties are not substantially impaired. As the modified polyester resin, for example, grafting or blocking with phenol, urethane, epoxy or the like according to the method described in JP-A-11-1336668, JP-A-10-239903, JP-A-8-20636, etc. Among the modified polyester resins, a urethane-modified polyester resin in which the polyester resin is urethane-stretched with a polyisocyanate compound is preferable.

  The softening point of the polyester resin is preferably 75 ° C. or higher, more preferably 80 ° C. or higher from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, and improves the low-temperature fixability of the toner. From the viewpoint, it is preferably 120 ° C. or lower, more preferably 110 ° C. or lower.

  The glass transition temperature of the polyester resin is preferably 35 ° C. or higher, more preferably 40 ° C. or higher, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, and the viewpoint of improving the low-temperature fixability. Therefore, it is preferably 65 ° C. or lower, more preferably 60 ° C. or lower.

  The acid value of the polyester resin is preferably 5 mg KOH / g or more, more preferably 7 mg KOH / g or more, and preferably 60 mg KOH / g or less, more preferably 45 mg KOH / g or less from the viewpoint of dispersion stability of toner particles. More preferably, it is 30 mgKOH / g or less.

  90 mass% or more is preferable in binder resin, as for content of a polyester resin, 95 mass% or more is more preferable, and it is still more preferable to use 100 mass%, ie, only polyester resin. However, as long as the effects of the present invention are not impaired, other resins than the polyester resin may be contained. Examples of resins other than the above polyester resin include polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer A styrene-based resin, an epoxy-based resin, a rosin-modified maleic acid resin which is a homopolymer or a copolymer containing styrene or a styrene-substituted product such as a styrene-acrylic acid ester copolymer or a styrene-methacrylic acid ester copolymer Examples thereof include one or more selected from resins such as polyethylene resins, polypropylene resins, polyurethane resins, silicone resins, phenol resins, aliphatic or alicyclic hydrocarbon resins.

  As the colorant, dyes, pigments and the like used as toner colorants can be used. 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 . In the present invention, the toner particles may be either black toner or color toner.

  The content of the colorant is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, with respect to 100 parts by mass of the binder resin, from the viewpoint of improving the image density. From the viewpoint of improving the pulverization property of the toner to reduce the particle size, improving the low-temperature fixability, and improving the storage stability by improving the dispersion stability of the toner particles, the binder resin is 100 mass. The amount 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 still more preferably 30 parts by mass or less.

  In addition to the binder resin and the colorant, the toner particles include 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, and an antioxidant. An additive such as an agent and a cleaning property improver may be appropriately contained.

  As a method for producing toner particles, a toner raw material containing a binder resin and a colorant is melt-kneaded, and the resulting melt-kneaded product is pulverized, preferably wet-pulverized, an aqueous binder resin dispersion and an aqueous system. The method of mixing a coloring agent dispersion liquid and making a binder resin particle and a coloring agent particle unite, the method of stirring an aqueous binder resin dispersion liquid and a coloring agent at high speed, etc. are mentioned. From the viewpoint of improving developability and fixability, a method of pulverizing, preferably wet pulverizing, after melt-kneading the toner raw material is preferable.

  First, it is preferable that toner raw materials containing a binder resin, a coloring agent, an additive used as needed, etc. are mixed in advance by a mixer such as a Henschel mixer, a super mixer, a ball mill or the like and then supplied to a kneader From the viewpoint of improving the dispersibility of the colorant in the binder resin, a Henschel mixer is more preferable.

  Mixing with a Henschel mixer is carried out while adjusting the peripheral speed of stirring and the stirring time. The peripheral speed is preferably 10 m / sec or more and 30 m / sec or less from the viewpoint of improving the dispersibility of the colorant. The stirring time is preferably 1 minute or more and 10 minutes or less from the viewpoint of improving the dispersibility of the colorant.

  Subsequently, melt kneading of the toner raw material can be performed using a known kneader such as a closed kneader, a uniaxial or twin screw kneader, or a continuous open roll kneader. In the production method of the present invention, an open roll kneader is preferable from the viewpoint of improving the dispersibility of the colorant and the viewpoint of improving the yield of toner particles after grinding.

  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 kneader preferably has at least two kneading rolls having different temperatures.

  From the viewpoint of improving the mixing property of the toner raw material, the set temperature of the roll is preferably 10 ° C. or lower than the softening point of the resin.

  Further, from the viewpoint of improving the sticking of the kneaded product to the roll on the upstream side and kneading strongly on the downstream side, the set temperature of the upstream roll is preferably higher than that on the downstream side.

  It is preferable that the rolls have different circumferential speeds. In the open-roll type kneader equipped with the above two rolls, the heating roll with high temperature is the high rotation side roll and the cooling roll with low temperature is low rotation from the viewpoint of improving the fixability of the liquid developer. Preferably it is a 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, and preferably 100 m / min or less, more preferably 60 m / min or less, and even more preferably 50 m / min or less. It is. Further, the ratio of peripheral speeds of the two rolls (low rotation side roll / high rotation side roll) is preferably 1/10 or more, more preferably 3/10 or more, and preferably 9/10 or less, More preferably, it is 8/10 or less.

  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.

  Next, after cooling the melt-kneaded product to such an extent that it can be pulverized, toner particles can be obtained through a pulverization process, and if necessary, a classification process and the like.

  The grinding process may be divided into 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 a melt-kneaded thing with inorganic fine particles, such as hydrophobic silica.

  As a grinder suitably used for coarse grinding, for example, an atomizer, a rotoplex, etc. may be mentioned, 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.

  Examples of the classifier used in the classification process include an airflow classifier, an inertia classifier, and a sieve classifier. In addition, you may repeat a grinding | pulverization process and a classification process as needed.

The volume median particle size (D ₅₀ ) of the toner particles obtained in this step is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm from the viewpoint of improving the productivity of the wet pulverization step described later. Below, more preferably 12 μm or less. The volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size. The toner particles are preferably further pulverized by wet grinding or the like after being mixed with the dispersant and the insulating liquid.

  The glass transition temperature of the toner particles is preferably 15 ° C. or higher, more preferably 20 ° C. or higher, from the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles, and from the viewpoint of low-temperature fixability. The temperature is preferably 65 ° C. or lower, more preferably 60 ° C. or lower, and still more preferably 55 ° C. or lower.

  In the present invention, the carbon number of the fatty acid component of the sucrose fatty acid ester is 12 or more, preferably 14 or more, more preferably 16 or more, more preferably 18 or more, from the viewpoint of viscosity reduction. Or less, preferably 22 or less, more preferably 20 or less.

  The fatty acid component is preferably an unsaturated fatty acid having an unsaturated bond from the viewpoint of lowering the viscosity and improving the chargeability. Specific examples of unsaturated fatty acids include oleic acid, erucic acid, linoleic acid, linolenic acid, stearidonic acid, bososepentaenoic acid, docosahexaenoic acid and the like, among which oleic acid or erucic acid is preferred.

  The sucrose fatty acid ester may be a monoester or a polyester such as a diester or triester, but having more fatty acid components in the molecule increases the solubility in the insulating liquid and causes dispersion. From the viewpoint of further improving the properties, the polyester is preferably a polyester, and the content of the polyester is preferably 70% or more, more preferably 80% or more, and still more preferably 90% or more in the sucrose fatty acid ester.

  The HLB of the sucrose fatty acid ester is preferably 0 or more, more preferably 0.5 or more from the viewpoint of adsorptivity to the toner, and preferably 3 or less, more preferably 2 from the viewpoint of dispersion stability of the toner. It is as follows.

  The content of the sucrose fatty acid ester is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more based on 100 parts by mass of toner particles, from the viewpoint of dispersion stability of the toner. From the viewpoint of positive chargeability of the toner, it is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and still more preferably 8 parts by mass or less.

  The liquid developer of the present invention contains the sucrose fatty acid ester as a dispersant. Therefore, the liquid developer may contain other liquid developer dispersants as long as the effects of the present invention are not impaired. However, the content of the sucrose fatty acid ester is preferably in the dispersant. Is 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 97% by mass or more, still more preferably 100% by mass, that is, no other dispersant is contained Is preferred.

The insulating liquid in the present invention means a liquid in which electricity does not easily flow, but in the present invention, the conductivity of the insulating liquid is preferably 1.0 × 10 ⁻¹⁰ S / m or less, more preferably 5.0. × 10 ⁻¹¹ S / m or less, and preferably 1.0 × 10 ⁻¹³ S / m or more.

  Examples of the insulating liquid include hydrocarbon-based insulating liquids such as aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, vegetable oils and the like. In the present invention, from the viewpoint of improving the storage stability by improving the dispersion stability of toner particles, the insulating liquid preferably contains a hydrocarbon-based insulating liquid, and contains an aliphatic hydrocarbon-based solvent. More preferably, it is more preferable to contain polyisobutene from the viewpoint of dispersion stability and chargeability.

  In the present invention, polyisobutene is obtained by polymerizing isobutene by a known method, for example, a cationic polymerization method using a catalyst, and then hydrogenating terminal double bonds.

  Examples of the catalyst used in the cationic polymerization method include aluminum chloride, acidic ion exchange resin, sulfuric acid, boron fluoride and complexes thereof. The polymerization reaction can also be controlled by adding a base to the catalyst.

  The degree of polymerization of polyisobutene is preferably 8 or less, more preferably 6 or less, still more preferably 5 or less, still more preferably 4 or less, from the viewpoint of improving the low-temperature fixability of the toner. Further, from the viewpoint of suppressing charger contamination, it is preferably 2 or more, more preferably 3 or more.

  It is preferable that unreacted components of isobutene and high-boiling components having a high degree of polymerization that are generated during the polymerization reaction are removed by distillation. Examples of the method of distillation include a simple distillation method, a continuous distillation method, a steam distillation method and the like, and these methods can be used alone or in combination. The apparatus used for distillation is not particularly limited in material, shape, type and the like, and examples thereof include a distillation column filled with a packing such as Raschig ring, and a tray distillation column having a plate-like shelf. The number of theoretical plates showing the separation ability of the distillation column is preferably 10 or more. In addition, the conditions such as the feed amount to the distillation column, the reflux ratio, and the removal amount can be appropriately selected by a distillation apparatus.

  Since the product obtained by the polymerization reaction has a double bond at the polymerization terminal, a hydrogenated product is obtained by a hydrogenation reaction. The hydrogenation reaction can be performed, for example, using nickel, palladium or the like as a hydrogenation catalyst at a temperature of 180 to 230 ° C. and contacting hydrogen at a pressure of 2 to 10 MPa.

  Examples of commercially available insulating liquids containing polyisobutene include “NAS-3”, “NAS-4”, “NAS-5H” (all of which are manufactured by NOF Corporation). One or more of these can be combined.

  The content of the hydrocarbon-based insulating liquid in the insulating liquid is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, still more preferably 60% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more.

  The boiling point of the insulating liquid, preferably the hydrocarbon-based insulating liquid, is preferably 120 ° C. or higher, more preferably 140 ° C. or higher, from the viewpoint of improving the film formability by suppressing the thickening of the liquid developer on the roller. More preferably, it is 160 ° C. or higher, more preferably 180 ° C. or higher, more preferably 200 ° C. or higher, more preferably 220 ° C. or higher. From the viewpoint of further improving the low-temperature fixability of the toner, the toner is pulverized during wet pulverization. From the viewpoint of further improving the properties and obtaining toner particles having a small particle size, it is preferably 300 ° C. or lower, more preferably 280 ° C. or lower, and further preferably 260 ° C. or lower. When two or more insulating liquids are combined, the boiling point of the combined insulating liquid mixture is preferably within the above range.

  The viscosity at 25 ° C. of the insulating liquid is preferably 1 mPa · s or more, more preferably from the viewpoint of improving the developability and suppressing the increase of the viscosity of the liquid developer on the roller to improve the film formability. 1.5 mPa · s or more, preferably 100 mPa · s or less, more preferably 50 mPa · s or less, still more preferably 20 mPa · s or less, still more preferably 10 mPa · s or less, still more preferably 5 mPa · s or less .

  The liquid developer is obtained by dispersing toner particles in an insulating liquid. From the viewpoint of reducing the particle size of the toner particles, it is preferable to disperse the toner particles in an insulating liquid and then wet pulverize to obtain a liquid developer.

  As a method of mixing the toner particles, the 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 from the viewpoint of improving the productivity and storage stability of the toner particle dispersion. Specifically, Despa (manufactured by Asada Tekko Co., Ltd.), T · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · K. Etc. are preferred.

  By the mixing by the high-speed stirring and mixing device, the toner particles can be predispersed to obtain a toner particle dispersion, and the productivity of the liquid developer by the subsequent wet pulverization can be improved.

  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 from the viewpoint of improving the image density, and the dispersion stability of the toner particles From the viewpoint of improving the property and improving the storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less.

  The content of toner particles in the toner particle dispersion is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and still more preferably 30 parts by mass from the viewpoint of high-speed printability with respect to 100 parts by mass of the insulating liquid. Or more, more preferably 40 or more parts, and even more preferably 50 or more parts by weight, and from the viewpoint of improving the dispersion stability, preferably 100 or less parts by weight, more preferably 80 or less parts by weight, still more preferably 70 parts by mass or less, more preferably 60 parts by mass or less.

  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 a device to be used, for example, a generally used stirring and mixing device such as an anchor blade can be used. Among the stirring and mixing devices, high-speed stirring and mixing devices such as Despa (manufactured by Asada Iron Works, Ltd.) and T. K. Homomixer (manufactured by Primix, Inc.), mills, kneaders such as roll mills, beads mills, kneaders, extruders, etc. Etc. A plurality of these devices can be combined.

  Among these, the use of a bead mill is used from the viewpoint of reducing the particle size of the toner particles, improving the storage stability of the toner particles by improving the dispersion stability of the toner particles, and reducing the viscosity of the dispersion. preferable.

  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.

  The solid content concentration of the liquid developer is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more from the viewpoint of improving the image density, and the dispersion stability of the toner particles From the viewpoint of improving the storage stability by improving the content, it is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less.

  The content of toner particles in the liquid developer is preferably 10% by mass or more, more preferably 15% by mass or more, and still more preferably 20% by mass or more from the viewpoint of high-speed printing, and the dispersion stability of the toner particles From the viewpoint of safety, it is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less.

The volume median particle diameter (D ₅₀ ) of the toner particles in the liquid developer is preferably 0.5 μm or more, more preferably 1 μm or more, and still more preferably 1.5 μm or more from the viewpoint of reducing the viscosity of the liquid developer. And, from the viewpoint of improving the image quality of the liquid developer, it is preferably 5 μm or less, more preferably 3 μm or less, and still more preferably 2.5 μm or less.

  The content of the insulating liquid in the liquid developer is preferably 50% by mass or more, more preferably 55% by mass or more, and still more preferably 60% by mass or more from the viewpoint of dispersion stability of the toner particles. From the viewpoint of high-speed printing, it is preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less.

  The viscosity at 25 ° C. of the liquid developer having a solid content concentration of 25% by mass is 50 mPa · s or less, preferably 45 mPa · s or less, more preferably 40 mPa · s, from the viewpoint of improving the fixability of the liquid developer. Or less, more preferably 35 mPa · s or less, still more preferably 25 mPa · s or less, and from the viewpoint of improving the dispersion stability of the toner particles to improve the storage stability, preferably 3 mPa · s or more, more preferably Is 5 mPa · s or more, more preferably 6 mPa · s or more, and further preferably 7 mPa · s or more.

  EXAMPLES Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples. 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), while heating a 1 g sample at a heating rate of 6 ° C./min, a load of 1.96 MPa is applied by a plunger, diameter 1 mm, length 1 mm Extrude from the nozzle. The plunger drop amount of the flow tester is plotted against the temperature, and the temperature at which half of the sample flowed 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 was weighed into an aluminum pan, heated to 200 ° C., and the temperature was reduced to 0 ° C./min. Cool down to ° C. Next, the sample is heated at a heating rate of 10 ° C./min, and the endothermic peak is measured. The temperature at the intersection of the extension of the baseline below the highest endothermic peak temperature and the tangent showing the maximum slope from the rising portion of the peak to the peak of the peak is taken as the glass transition temperature.

[Acid value of resin]
It measures by the method of JIS K 0070: 1992. However, only the measurement solvent is changed to a mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)) from a mixed solvent of ethanol and ether defined in JIS K 0070.

[Volume median particle size of toner particles before mixing with insulating liquid]
Measuring machine: Coulter Multisizer II (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 100 μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter, Inc.)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion solution: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB (glyphin): 13.6) dissolved in electrolyte to adjust to 5% by mass Dispersion conditions: 10 mg of measurement sample in 5 mL of the dispersion And is dispersed for 1 minute with an ultrasonic disperser (machine name: US-1 manufactured by SND Corporation, output: 80 W). Thereafter, 25 mL of the electrolytic solution is added and further dispersed for 1 minute with an ultrasonic disperser to prepare a sample dispersion.
Measurement conditions: The sample dispersion is added to 100 mL of the electrolyte so that the particle size of 30,000 particles can be measured in 20 seconds, 30,000 particles are measured, and the volume is determined from the particle size distribution. Determine the median particle size (D ₅₀ ).

[Glass transition temperature of toner particles]
Using a differential scanning calorimeter “DSC210” (manufactured by Seiko Denshi Kogyo Co., Ltd.), 0.025 to 0.035 g of liquid developer is weighed into an aluminum pan and heated from 0 ° C to 100 ° C at a heating rate of 10 ° C / min. And measure the endothermic peak. The temperature at the intersection of the extension of the baseline below the highest endothermic peak temperature and the tangent showing the maximum slope from the rising portion of the peak to the peak of the peak is taken as the glass transition temperature.

[Conductivity of Insulating Liquid]
25 g of a sample is put in a 40 mL glass sample tube “screw No. 7” (manufactured by Marumu Co., Ltd.), and the non-aqueous conductivity meter “DT-700” (manufactured by Dispersion Technology) is used to insulate the electrode. Immerse in a liquid, measure 20 times at 25 ° C, calculate the average value, and measure the conductivity. The smaller the value, the higher the resistance.

[Boiling point of insulating liquid]
Using a differential scanning calorimeter “DSC210” (manufactured by Seiko Denshi Kogyo Co., Ltd.), a sample of 6.0 to 8.0 mg was weighed into an aluminum pan, heated to 350 ° C. at a heating rate of 10 ° C./min, and an endothermic peak was obtained. taking measurement. The endothermic peak on the highest temperature side is taken as the boiling point.

[Viscosity of Insulating Liquid and Liquid Developer at 25 ° C.]
Put 6 to 7 mL of the measured solution in a 10 mL screw tube, and use the rotational vibration viscometer “Viscomate VM-10A-L” (manufactured by Seconic, detection terminal: titanium, φ8 mm), and the tip of the detection terminal Fix the screw tube at the position where the liquid level is 15mm above the part, and measure the viscosity at 25 ° C.

[Solid Content Concentration of Toner Particle Dispersion and Liquid Developer]
10 parts by mass of the sample is diluted with 90 parts by mass of hexane, and is rotated for 20 minutes at a rotational speed of 25,000 r / min using a centrifuge “3-30KS” (manufactured by Sigma). 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 L (ExxonMobil, isoparaffin, viscosity 1 mPa · s at 25 ° C.) to the measurement cell, and then 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 combined with a nitrogen introduction tube, a dehydration tube equipped with a fractionation tube through which hot water of 98 ° C was passed, a 10L four-necked flask equipped with a stirrer and a thermocouple. Put in. After the temperature was raised to 180 ° C., the temperature was raised to 210 ° C. over 5 hours, and the reaction was continued until the reaction rate reached 90%. Furthermore, the reaction was performed at 8.3 kPa, and when the target softening point was reached, the reaction was terminated, and a polyester resin (Resin A) having physical properties shown in Table 1 was obtained. In the resin production example, the reaction rate means a value of the amount of generated reaction water (mol) / theoretical generated water amount (mol) × 100.

Examples 1 to 6 and Comparative Examples 1 and 2
As a binder resin, 80 parts by mass of resin A and 20 parts by mass of a colorant “ECB-301” (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue 15: 3) were used in advance using a 20 L Henschel mixer, and the number of rotations After stirring and mixing at 1500 r / min (circumferential speed 21.6 m / sec) for 3 minutes, the mixture was melt-kneaded under the following conditions.

Melting and kneading conditions
A continuous double-open-roll type kneader "Kinedex" (manufactured by Nippon Coke Industry 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 speed roll (front roll) rotation speed 75 r / min (circumferential velocity 32.4 m / min), low speed roll (back roll) rotation speed 35 r / min ( The peripheral speed was 15.0 m / min), and the roll clearance at the end of the kneaded product supply port was 0.1 mm. The temperature of the heating medium and the temperature of the cooling medium in the roll are 90 ° C for the raw material input side of the high rotation side roll and 85 ° C for the kneaded material discharge side, 35 ° C for the raw material input side of the low rotation side roll and 35 ° C for 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 obtained kneaded product was rolled and 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 a pneumatic jet mill "IDS" (manufactured by Nippon Pneumatic Mfg. Co., Ltd.) to obtain toner particles having a volume median particle size (D ₅₀ ) of 10 μm. The glass transition temperature of the toner particles was 45.degree.

35 parts by mass of the obtained toner particles and insulating liquid “NAS-4” (manufactured by NOF Corporation, polyisobutene, conductivity: 1.52 × 10 ⁻¹² S / m, boiling point: 247 ° C., viscosity at 25 ° C .: 2 mPa S) 62.9 parts by mass of the dispersant and 2.1 parts by mass of the dispersant shown in Table 2 (6 parts by mass with respect to 100 parts by mass of toner particles) are placed in a 1 L polyethylene container, and "TK Robomix" (Primix Co., Ltd.) The mixture was stirred for 30 minutes at a rotational speed of 7,000 r / min under ice-cooling, to obtain a toner particle dispersion having a solid content concentration of 37% by mass.

Next, the obtained toner particle dispersion is rotated at a volume packing ratio of 60% by volume using zirconia beads of diameter 0.8 mm with a six-cylinder sand mill “TSG-6” (manufactured by Imex Co., Ltd.) Wet grinding was performed at 1300 r / min (circumferential speed 4.8 m / sec) until the volume-median particle size (D ₅₀ ) shown in Table 2 was obtained. After removing the beads by filtration, 48 parts by mass of insulating liquid "NAS-4" (manufactured by NOF Corporation) is added to 100 parts by mass of the filtrate to dilute, and the solid content concentration is 25% by mass. A liquid developer having physical properties shown in 2 was obtained.

Test example (positive chargeability)
A 45 mm × 70 mm (3 mm thick) copper electrode pair was opposed with a 1 mm gap, and 3 g of liquid developer was injected into the gap. A voltage of ± 250 V was applied for 1 minute between the electrodes, the state (migration property) of the toner particles attached to each electrode was visually confirmed, and the positive chargeability of the liquid developer was evaluated according to the following evaluation criteria. The results are shown in Table 2.

〔Evaluation criteria〕
A: Toner particles adhere only to the negative electrode side B: Many toner particles adhere to the negative electrode side C: Toner particles adhere to the same extent to both the negative electrode and positive electrode D: Many toner particles adhere to the positive electrode side E: Toner particles only to the positive electrode side Is attached

  From the above results, as compared with Comparative Examples 1 and 2 using polyglycerin fatty acid ester instead of sucrose fatty acid ester as a dispersant, the liquid developers of Examples 1 to 6 have a small particle size and low viscosity. It can be seen that the positive chargeability is also good.

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

Claims (5)

  A liquid developer containing toner particles containing a binder resin and a colorant, a sucrose fatty acid ester, and an insulating liquid, wherein the binder resin contains a polyester resin, and the fatty acid component of the sucrose fatty acid ester The liquid developer has a carbon number of 12 to 24 and a viscosity at 25 ° C. at a solid content concentration of 25 mass% is 50 mPa · s or less.   The liquid developer according to claim 1, wherein the fatty acid component of the sucrose fatty acid ester is an unsaturated fatty acid.   The liquid developer according to claim 1 or 2, wherein the sucrose fatty acid ester has an HLB of 3 or less.   The liquid developer according to claim 1, wherein the acid value of the polyester resin is 5 mgKOH / g or more and 60 mgKOH / g or less.   The liquid developer according to any one of claims 1 to 4, wherein the polyester resin is a polycondensate of an alcohol component containing 80 mol% or more of an aliphatic diol and a carboxylic acid component.