JP2018101008A - Liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer capable of high-definition printing with high resistance while maintaining high dispersion stability. A liquid developer containing a binder resin containing a polyester resin, toner particles containing a colorant, a dispersant, and an insulating liquid, wherein the dispersant is a formula (I) :( formula). Among them, R1, R2 and R3 may be the same or different, and are an alkylene group having 1 to 22 carbon atoms) and a basic nitrogen-containing group raw material having a nitrogen-containing group and a dispersion having a polysiloxane chain. A liquid developer containing a reactant X with a sex group raw material and having a number average molecular weight of 250 or more and 5,000 or less of the basic nitrogen-containing group raw material. [Selection diagram] 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.

  As a developer for electrophotography, a liquid developer in which toner particles made of a material containing a colorant and a binder resin are dispersed in an insulating liquid is known. The liquid developer is excellent in terms of image quality because the particle size of the toner can be reduced.

  Generally, in a liquid developer, a dispersant having a polymer amine structure is used as a material for dispersing toner particles in an insulating liquid.

  For example, in Patent Document 1, a dispersant composed of a high molecular amine having a molecular weight of 70,000 or more and a silicone dispersing group is used.

  In Patent Document 2, a dispersant composed of a polyalkyleneimine having a molecular weight of 10,000 to 70,000 and an acrylic polysiloxane copolymer is used.

  Such a dispersant has a feature that it can produce a liquid developer capable of high-definition printing with high resistance because of its high adsorption power to toner particles.

JP 2014-38220 A JP 2011-65135 A

  However, in a liquid developer using a dispersant composed of a high molecular weight amine, as the liquid developer is concentrated in the printing process, the toner particles are cross-linked by the dispersant. There is a problem that continuous printing is impossible. In addition, when a dispersant composed of a low molecular weight amine is used, it is possible to maintain dispersion stability without causing cross-linking even during concentration. (This is also referred to as a free dispersant), and the resistance of the liquid developer is reduced. For example, a printing defect that causes background fogging or the like during printing occurs.

  An object of the present invention relates to a liquid developer that maintains high dispersion stability and enables high-definition printing with high resistance.

  The present invention is a liquid developer containing toner particles containing a binder resin including a polyester resin and a colorant, a dispersant, and an insulating liquid, wherein the dispersant is represented by the formula (I):

(Wherein R ¹ , R ² and R ³ may be the same or different and are alkylene groups having 1 to 22 carbon atoms)
Containing a reaction product X of a basic nitrogen-containing group material having a nitrogen-containing group and a dispersible group material having a polysiloxane chain, wherein the number average molecular weight of the basic nitrogen-containing group material is 250 or more and 5,000 or less This relates to a liquid developer.

  The liquid developer of the present invention has an excellent effect that high dispersion stability can be maintained and high-definition printing can be performed with high resistance. In particular, the liquid developer of the present invention is excellent in that it can maintain dispersion stability even when the liquid developer is concentrated in the printing process, and enables high-definition printing with high resistance. Play.

  In order to achieve high-definition printing in liquid development, a high-resistance liquid developer is required. Thus, as a result of intensive studies by the present inventors, it has been found that the free dispersant in the liquid developer reduces the resistance. That is, for a high-resistance liquid developer, a dispersant that is highly adsorbed with respect to toner particles is desirable. Further, in a general liquid developing device, the liquid developer is concentrated in a process in which toner particles are printed on a fixing medium such as paper. Under this concentration condition, it has been found that if toner particle aggregates are generated, the inside of the liquid developing device is contaminated, and normal printing becomes difficult. That is, for normal printing, a liquid developer that does not aggregate even during concentration and has excellent dispersion stability is desirable.

  Generally, a dispersant having a high molecular weight polyalkyleneimine structure is used for a liquid developer containing a polyester resin. The polyalkyleneimine is a kind of polyamine obtained by ring-opening polymerization of azacycloalkane. Basic functional groups such as amines interact electrostatically with the terminal carboxy group of the polyester resin. Furthermore, the polyalkyleneimine structure expresses strong adsorptivity by multipoint adsorption by creating a large number of interaction sites. As a result, the liquid developer has a low resistance and a high resistance. However, when the liquid developer is concentrated, the distance between the toner particles is shortened, so that the toner particles are crosslinked and aggregated by the polyalkyleneimine.

  In contrast, the present invention has led to the development of a dispersant that exhibits high adsorptivity even with a low molecular weight polyalkyleneimine. The reason for such an effect is considered as follows.

  Amines are classified into primary to tertiary amines depending on the number of substituents, but the magnitude of interaction with carboxylic acids depends on the basicity, secondary amines are larger than primary amines, and The tertiary amine is larger than the secondary amine. In addition, the stronger the electron donating property of the substituent, the greater the interaction.

  Furthermore, in order to facilitate the adsorption, it is important to reduce the morphological change (entropy loss) before and after the adsorption. As a result of intensive studies, it was found that in the polyalkyleneimine structure, the branched structure has less entropy loss and higher adsorptivity than the linear structure.

  Furthermore, it was found that the adsorptivity changes in the polyalkyleneimine structure depending on the chain length of the alkylene group. As a result of intensive studies, an imine having a longer chain alkylene group such as a propyleneimine structure showed higher adsorptivity than an ethyleneimine structure. The dispersant is adsorbed to the carboxy group derived from the polyester resin interposed on the surface of the toner particles. Probably, the long-chain alkyleneimine is more likely to be adsorbed at multiple points relative to the distribution of carboxy groups.

  The dispersant in the present invention has a branched polyalkyleneimine structure, and each imine skeleton is an amine whose substituent is an electron-donating silicone chain, and thus exhibits high adsorptivity even at a low molecular weight. it is conceivable that. Furthermore, it is thought that a higher adsorbability is exhibited by having a propyleneimine structure in the alkyleneimine structure.

  The liquid developer of the present invention is a liquid developer containing toner particles, a dispersant, and an insulating liquid.

  The toner particles contain a binder resin including a polyester resin and a colorant. Polyester resins are excellent in low-temperature fixability, but have a polar group such as a carboxy group, a hydroxyl group, and an ester group, and are therefore difficult to disperse in a nonpolar solvent. However, in the present invention, since the dispersant has a nitrogen-containing group having a branched structure as an adsorbing group, the toner particles can be stably dispersed even when a polyester resin is used.

  Examples of the polyester resin include a polyester resin, a composite resin containing a polyester resin and another resin (preferably a composite resin containing a polyester resin and a styrene resin).

  In the present invention, the polyester resin is preferably a polycondensate 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 (III):

(Wherein R ⁵ O and OR ⁵ are oxyalkylene groups, R ⁵ is an ethylene and / or propylene group, x and y represent the average number of moles of alkylene oxide added, each being a positive number, The sum of x and y is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and even more preferably 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.

  Examples of the trihydric or higher alcohol include trihydric or higher polyhydric alcohols 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.

  As the divalent carboxylic acid-based compound, the number of carbons of 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 3 to 10 carbon atoms, their anhydrides, or the carbon number of the alkyl group 1 or more and 3 or less derivatives such as alkyl esters. Specifically, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, an alkyl group having 1 to 20 carbon atoms, or And aliphatic dicarboxylic acids such as succinic acid substituted with an alkenyl group having 2 to 20 carbon atoms.

  As the trivalent or higher carboxylic acid-based compound, a carboxylic acid having 4 or more and 30 or less carbon atoms, preferably 4 or more and 20 or less carbon atoms, more preferably 4 or more and 10 or less carbon atoms, an anhydride thereof, or Examples thereof include 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 acid anhydrides thereof.

  Note that 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 softening point of the polyester.

  Polyester resin is, for example, a polycondensation of an alcohol component and a carboxylic acid component at a temperature of 180 ° C. or higher and 250 ° C. or lower in an inert gas atmosphere, if necessary, in the presence of an esterification catalyst or a polymerization inhibitor. Can be manufactured.

  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 esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1 part by mass or less, more preferably 100 parts by mass of the total amount of alcohol component and carboxylic acid component. Preferably it is 0.7 mass part or less.

  A cocatalyst may be used to shorten the reaction time. Examples of the cocatalyst include gallic acid. The amount of the cocatalyst 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 relative to the total amount of the alcohol component and the carboxylic acid component. Is 0.3 parts by mass or less. The mass ratio of the cocatalyst to the esterification catalyst (cocatalyst / esterification catalyst) is preferably from 0.01 to 0.5.

  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. Examples of the modified polyester resin include grafting or blocking with phenol, urethane, epoxy or the like by the method described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Among the modified polyester resins, a urethane-modified polyester resin obtained by extending the polyester resin with urethane by a polyisocyanate compound is preferable.

  The softening point of the polyester-based resin is preferably 160 ° C. or less, more preferably 150 ° C. or less from the viewpoint of improving the low-temperature fixability of the liquid developer, and the toner when the liquid developer is stored at a high temperature. From the viewpoint of preventing the particles from aggregating, the temperature is preferably 70 ° C or higher, more preferably 80 ° C or higher. Taking these viewpoints together, the softening point of the polyester resin is preferably 70 ° C. or higher and 160 ° C. or lower, more preferably 80 ° C. or higher and 150 ° C. or lower.

  The glass transition temperature of the polyester-based resin is preferably 80 ° C. or lower, more preferably 75 ° C. or lower, from the viewpoint of improving the low-temperature fixability of the liquid developer, and when the liquid developer is stored at a high temperature. From the viewpoint of preventing toner particles from aggregating, the temperature is preferably 45 ° C. or higher, more preferably 50 ° C. or higher. Taking these viewpoints together, the glass transition temperature of the polyester-based resin is preferably 45 ° C. or higher and 80 ° C. or lower, more preferably 50 ° C. or higher and 75 ° C. or lower.

  The acid value of the polyester resin is preferably 3 mgKOH / g or more, more preferably 5 mgKOH / g or more, and even more preferably 8 mgKOH / g or more, from the viewpoint of adsorbing the dispersant in the liquid developer and improving the dispersion stability. And preferably 60 mgKOH / g or less, more preferably 50 mgKOH / g or less, further preferably 40 mgKOH / g or less, and further preferably 30 mgKOH / g or less. The acid value of the polyester resin is changed by changing the equivalent ratio of the carboxylic acid component and the alcohol component, changing the reaction time during resin production, or changing the content of the carboxylic acid compound having a valence of 3 or more. Can be adjusted.

  The content of the polyester resin is preferably 90% by mass or more, more preferably 95% by mass or more, and more preferably 100% by mass, that is, only the polyester resin is used in the binder resin. However, as long as the effect of the present invention is not impaired, other resins than the polyester resin may be contained. Examples of resins other than polyester resins include polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, and styrene-maleic acid copolymer. A styrene resin, an epoxy resin, a rosin-modified maleic resin, which is a homopolymer or copolymer containing styrene or a styrene-substituted product such as a styrene-acrylic acid ester copolymer, 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, fail 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, and 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 25 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.

  Examples of the method for producing toner particles include a method in which a toner raw material containing a binder resin and a colorant is melt-kneaded, and the obtained melt-kneaded product is pulverized, preferably wet pulverized. 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, the toner raw material containing a binder resin, a colorant, an additive used as necessary is preferably mixed in advance with a mixer such as a Henschel mixer, a super mixer, or a ball mill, 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.

  Next, melt kneading of the toner raw material can be performed using a known kneader such as a closed kneader, a uniaxial or biaxial kneader, a continuous open roll type 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 improving the yield of the toner particles after pulverization.

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

  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 melt-kneaded material with inorganic fine particles, such as hydrophobic silica.

  Examples of a pulverizer that is suitably used for coarse pulverization include an atomizer and a rotoplex, but a hammer mill or the like may also 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. It is preferable that the toner particles are further refined by wet pulverization after mixing with the dispersant and the insulating liquid.

  The content of the toner particles is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, from the viewpoint of high-speed printability with respect to 100 parts by mass of the insulating liquid. From the viewpoint of improving dispersion stability, it is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 70 parts by mass or less, and further preferably 60 parts by mass or less.

  The dispersant in the present invention has the formula (I):

(Wherein R ¹ , R ² and R ³ may be the same or different and are alkylene groups having 1 to 22 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms)
Is a reaction product X of a basic nitrogen-containing group material having a nitrogen-containing group and a dispersible group material having a polysiloxane chain.

  In the formula (I), examples of the alkylene group having 1 to 22 carbon atoms include a methylene group, an ethylene group, and a propylene group.

In addition, as long as the reaction product X does not impair the effects of the present invention, one or two of R ^{1 to} R ³ are divalent at the terminal or central portion of the group derived from the basic nitrogen-containing group raw material. You may have the group which is a hydrogen atom instead of the group of.
The ratio of the group represented by the formula (I) in the basic nitrogen-containing group raw material is preferably 1 mol% or more and 80 mol% or less in the total amount of the group represented by the formula (I) and these groups, and R ¹ The ratio of the group in which one of R ³ is a hydrogen atom is preferably 1 mol% or more and 80 mol% or less, and the ratio of the group in which two of R ^{1 to} R ³ are a hydrogen atom is 1 mol%. The content is preferably 50 mol% or less. This ratio can be calculated from C-NMR measurement.
Further, the ratio of the group represented by the formula (I) in the basic nitrogen-containing group raw material to these groups is such that two of R ^{1 to} R ³ are hydrogen atoms / (formula (I) 1/99 or more and 50/50 or less is preferable in terms of the molar ratio of the group represented by the group + ^{one of} R ^{1 to} R ³ which is a hydrogen atom. This molar ratio can be calculated from H-NMR measurement.

  The number average molecular weight of the basic nitrogen-containing group raw material is 250 or more, preferably 500 or more, more preferably 1,000 or more from the viewpoint of adsorptivity to the toner particles, and 5,000 from the viewpoint of dispersibility of the toner particles. Below, it is preferably 4,000 or less, more preferably 3,000 or less.

  The polysiloxane chain in the dispersible group raw material may be linear or cyclic, and may be modified with a halogen atom, an epoxy group or a glycidyl group, but the dispersible group raw material having a polysiloxane chain is represented by the formula ( II):

(Wherein R ⁴ is a reactive functional group, m is the average number of moles added, and m is 10 or more and 70 or less, preferably 15 or more and 60 or less, more preferably 20 or more and 50 or less)
The compound represented by these is preferable.

  In the formula (II), examples of the reactive functional group include a glycidyl group, an epoxy group, a halogen group, and the like. Among these, a glycidyl group is preferable from the viewpoint of safety and reactivity. Therefore, an epoxy compound is preferable as the dispersible group material having a polysiloxane chain.

  The number average molecular weight of the dispersible group raw material is preferably 1,000 or more, more preferably 1,500 or more from the viewpoint of dispersibility, and preferably 5,000 or less, more preferably 4,000 from the viewpoint of adsorptivity to the toner particles. Hereinafter, it is more preferably 3,000 or less.

  The mass ratio of the basic nitrogen-containing group to the dispersible group in the reactant X (basic nitrogen-containing group / dispersible group) is preferably 1/99 or more, more preferably from the viewpoint of adsorptivity to the toner particles. Is 2/98 or more, more preferably 3/97 or more, and from the viewpoint of dispersion stability of the toner particles, it is preferably 10/90 or less, more preferably 8/92 or less, and still more preferably 5 / 95 or less. Although the mass ratio of the basic nitrogen-containing group and the dispersible group in the reactant X can be measured by NMR of the reactant X, the production of the reactant X by reacting the basic nitrogen-containing group raw material with the dispersible group raw material The mass ratio of the reacted raw material compounds can also be regarded as the mass ratio of the basic nitrogen-containing group to the dispersible group in the dispersant (basic nitrogen-containing group / dispersible group).

  The basic nitrogen-containing group material and the dispersible group material can be reacted by a conventional method.

  The content of the reactant X is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, further preferably 0.5 parts by mass or more, from the viewpoint of dispersion stability of the toner particles with respect to 100 parts by mass of the toner particles. In view of the charging property and fixing property of the toner, it is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and still more preferably 3.5 parts by mass or less.

  Further, the content of the reactant X in the dispersant is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and further preferably 100% by mass.

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 ⁻¹¹ S / m or less, more preferably 5.0. × 10 ⁻¹² S / m or less, and preferably 1.0 × 10 ⁻¹³ S / m or more.

  Specific examples of the insulating liquid include, for example, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, and the like. In particular, aliphatic hydrocarbons such as normal paraffin solvents and isoparaffin solvents are preferred from the viewpoint of odor, harmlessness and cost. Specifically, Isopar G, Isopar H, Isopar L, Isopar K (all of which are manufactured by ExxonMobil), Shellsol 71 (manufactured by Shell Petrochemical), IP Solvent 1620, IP Solvent 2080 (All of these are all Idemitsu Petrochemical Co., Ltd.), Moresco White P-55, Moresco White P-70 (all are Matsumura Oil Co., Ltd.), Cosmo White P-60, Cosmo White P-70 (all are Cosmo Oil Lubricants) Etc.).

  The viscosity at 25 ° C. of the insulating liquid is preferably 100 mPa · s or less, more preferably 50 mPa · s or less, more preferably 20 mPa · s or less, from the viewpoint of improving the storage stability of the toner particles in the liquid developer. Further, it is preferably 10 mPa · s or less, more preferably 5 mPa · s or less, and preferably 0.01 mPa · s or more, more preferably 0.1 mPa · s or more.

  The liquid developer is obtained by dispersing toner particles in an insulating liquid in the presence of a dispersant. From the viewpoint of reducing the particle size of the toner particles and reducing the viscosity of the liquid developer, 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 from the viewpoint of improving the productivity and storage stability of the toner particle dispersion, a high-speed stirring and mixing device is preferable. Specifically, Despa (manufactured by Asada Tekko Co., Ltd.), TK homomixer, TK homodisper, TK robotics (all of which are manufactured by Primics Co., Ltd.), Claremix (manufactured by M Technique Co., Ltd.), KD Mill (manufactured by KD International) Etc.) are preferred.

  By mixing with a high-speed stirring and mixing device, toner particles are preliminarily dispersed to obtain a toner particle dispersion, and the productivity of the liquid developer by the subsequent wet pulverization is improved.

  The solid content concentration of the toner particle dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, and still more preferably 20% by mass or more from the viewpoint of improving the image density. From the viewpoint of improving the property and improving the storage stability, it is preferably 50% by mass or less, more preferably 40% by mass or less, and still more preferably 30% 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 Tekko Co., Ltd.), TK. 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.

As described above, the liquid developer of the present invention is
Step 1: a step of melt-kneading a binder resin containing a polyester resin and a colorant 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, 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, 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 volume median particle size (D ₅₀ ) of the toner particles in the liquid developer is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more, from the viewpoint of reducing the viscosity of the liquid developer. In view of improving the image quality of the liquid developer, it is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 2.5 μm or less.

  The viscosity at 25 ° C. of the liquid developer having a solid content concentration of 25% by mass is preferably 3 mPa · s or more, more preferably 5 mPa · s, from the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles. Or more, more preferably 6 mPa · s or more, more preferably 7 mPa · s or more, and from the viewpoint of improving the fixability of the liquid developer, preferably 50 mPa · s or less, more preferably 40 mPa · s or less, Preferably it is 37 mPa · s or less, more preferably 35 mPa · s or less, more preferably 32 mPa · s or less, more preferably 28 mPa · s or less, more preferably 24 mPa · s or less, more preferably 20 mPa · s or less, more preferably 16 mPa · s or less.

  Further, the liquid developer of the present invention can maintain a low viscosity even when the solid content concentration increases. From such a viewpoint, for example, the viscosity at 25 ° C. of the liquid developer having a solid content concentration of 45% by mass is preferably 70 mPa · s or less, more preferably 50 mPa · s or less, from the viewpoint of improving the cleaning property in the developing machine, More preferably, it is 30 mPa · s or less.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to 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), a 1 g sample was heated at a heating rate of 6 ° C./min, and a 1.96 MPa load was applied by a plunger, and the diameter was 1 mm and the length was 1 mm. Extrude from the nozzle. 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 was weighed into an aluminum pan, heated to 200 ° C., and the temperature was reduced to 0 ° C./min. Cool to ° C. 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 (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 100μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter, Inc.)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB (Griffin): 13.6) dissolved in the electrolyte to adjust to 5% by mass Dispersion condition: 10 mL 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 was added to 100 mL of the electrolyte so that the particle size of 30,000 particles could be measured in 20 seconds, and 30,000 particles were measured. Determine the median particle size (D ₅₀ ).

[Number average molecular weight (Mn) of basic nitrogen-containing raw material]
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below to determine the number average molecular weight.
(1) Preparation of sample solution To a concentration of 0.2 g / 100 mL, polyalkylenimine is dissolved in a solution of 0.15 mol / L Na ₂ SO ₄ dissolved in 1% acetic acid aqueous solution. 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) using the analytical column the molecular weight measurement following measurement apparatus, a solution prepared by dissolving over Na ₂ SO ₄ in 1% acetic acid aqueous solution at 0.15 mol / L as the eluent, at a flow rate per minute 1 mL, of 40 ° C. Stabilize the column in a constant temperature bath. Inject 100 μL of the sample solution into the sample and perform measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. There are several standard pullulans (P-5 (Mw 5.9 × 10 ³ ), P-50 (Mw 4.73 × 10 ⁴ ), P-200 (Mw 2.12 × 10) manufactured by Showa Denko KK). ⁵ ) Use P-800 (Mw 7.08 × 10 ⁵ )) as a standard sample. The molecular weight is shown in parentheses.
Measuring device: HLC-8320GPC (manufactured by Tosoh Corporation)
Analysis column: α + α-M + α-M (manufactured by Tosoh Corporation)

[Number average molecular weight of dispersible group raw material (Mn)]
(1) Preparation of sample solution The dispersible group raw material was dissolved in tetrahydrofuran so that the concentration was 0.5 g / 100 mL. Next, this solution was filtered using a fluororesin filter “FP-200” (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 2 μm to remove insoluble components to obtain a sample solution.
(2) Molecular weight distribution measurement Using the following measuring device and analytical column, tetrahydrofuran is flowed as an eluent at a flow rate of 1 mL per minute, and the column is stabilized in a constant temperature bath at 40 ° C. Inject 100 μL of the sample solution into the sample and perform measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. The calibration curves at this time include 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) manufactured by Tosoh Corporation. ³ ), 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. The molecular weight is shown in parentheses.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (manufactured by Tosoh Corporation)

[Conductivity of insulating liquid]
Put 25 g of insulating liquid into a 40 mL glass sample tube “Screw No. 7” (manufactured by Marumu Co., Ltd.), and use a non-aqueous conductivity meter “DT-700” (manufactured by Dispersion Technology) to connect the electrode. Immerse in an insulating liquid, measure 20 times at 25 ° C, calculate the average value, and measure the conductivity. The smaller the value, the higher the resistance.

[Viscosity at 25 ° C. of insulating liquid and liquid developer with a solid content concentration of 25 mass%]
Put 6-7 mL of the measuring solution into a 10 mL screw tube, and measure the viscosity at 25 ° C. using a rotational vibration viscometer “Viscomate VM-10A-L” (manufactured by Seconic).

[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 centrifugal separator “H-201F” (manufactured by Kokusan Co., Ltd.). 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 10 liter capacity equipped with raw material monomers shown in Table 1, 25.0 g of esterification catalyst (dibutyltin oxide) and 2.5 g of cocatalyst (gallic acid), equipped with nitrogen introduction tube, dehydration tube, stirrer and thermocouple The reaction was carried out by raising the temperature to 230 ° C. and after 12 hours, the reaction was terminated when the softening point reached 100 ° C. to obtain a resin A having the physical properties shown in Table 1. .

Example of toner particle production 80 parts by mass of resin A as binder resin and 20 parts by mass of colorant “ECB-301” (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue 15: 3) are used in a 20 L Henschel mixer in advance. The mixture was stirred and mixed for 3 minutes at a rotational speed of 1500 r / min (circumferential speed 21.6 m / sec) and then melt-kneaded under the following conditions.

[Melting and kneading conditions]
A continuous two-open roll kneader “NIDEX” (manufactured by Nippon Coke Industries 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 clearance at the end of the kneaded product supply port was 0.1 mm. The heating medium temperature and cooling medium temperature in the roll are 90 ° C. on the raw material input side of the high rotation side roll and 85 ° C. on the kneaded material discharge side, 35 ° C. on the raw material input side of the low rotation side roll and 35 ° C. on the kneaded material discharge side. there were. The feed rate of the raw material mixture to the kneader was 10 kg / h, and the average residence time in the kneader was about 3 minutes.

The kneaded product obtained above was rolled and cooled with a cooling roll, and then roughly pulverized to about 1 mm using a hammer mill. The 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 A having a volume median particle size (D ₅₀ ) of 10 μm.

Production Examples of Dispersant Basic nitrogen-containing base material, dispersible base raw material shown in Table 2 and 100 parts by mass of ethanol equipped with 1L capacity equipped with cooling pipe, nitrogen introduction pipe, stirrer, dehydration pipe and thermocouple The flask was placed in a neck flask, heated to 75 ° C. and stirred for 12 hours. Thereafter, ethanol was removed at 75 ° C. and 8.3 kPa. From the NMR analysis, dispersants 1 to 6 were obtained with the reaction end point being the point at which the peak (2.5 ppm) derived from the epoxy group disappeared.

Examples 1-3 and Comparative Examples 1-3
25 parts by mass of toner particles A, 0.75 parts by mass of the dispersant shown in Table 3, and insulating liquid “Isopar L” (exxonmobile, isoparaffin, conductivity 6.2 × 10 ⁻¹³ S / m, viscosity at 25 ° C. 1 mPa S) 74.25 parts by mass were placed in a 2 L polyethylene container. Using “TK Robomix” (manufactured by Primix Co., Ltd.), the mixture was stirred for 30 minutes under ice cooling at a rotation speed of 7000 r / min to obtain a toner particle dispersion having a solid content concentration of 25 mass%.

  Next, the obtained toner particle dispersion was rotated with a 6-cylinder sand mill “TSG-6” (manufactured by IMEX Co., Ltd.) using zirconia beads having a diameter of 0.8 mm at a volume filling rate of 60% by volume. Wet pulverization was carried out at 1300r / min (circumferential speed 4.8m / sec) for 4 hours. The beads were removed by filtration to obtain a liquid developer having the physical properties shown in Table 3.

  The following physical properties were measured for the obtained liquid developer. The results are shown in Table 3.

[Adsorption rate]
10 g of liquid developer was transferred to a centrifuge tube, and centrifuged for 2 hours at 25,000 r / min and 25 ° C. using a centrifuge (manufactured by Sigma, 3-30KS). 4 g of the supernatant was taken out of an aluminum dish and dried in a vacuum dryer “DRV422DB” manufactured by ADVANTEC at 100 ° C. for 4 hours at 8.3 kPa. From the amount of the remaining dispersant, the adsorption rate was calculated from the following formula.

[Viscosity at 25 ° C. of a liquid developer having a solid content concentration of 45 mass%]
Assuming a liquid developer concentrated in the developing tank during printing, the solid content concentration of the liquid developer was adjusted from 25 mass% to 45 mass%.
Add 6-7 mL of liquid developer with a solid content of 45% by mass into a 10 mL screw tube, and use a rotational vibration viscometer “Viscomate VM-10A-L” (manufactured by Seconic Co., Ltd.), 25 The viscosity was measured at ° C. The higher the viscosity is, the more aggregates are generated when printing is repeated, so the viscosity is preferably low.

[Resistance of liquid developer]
25 g of liquid developer with a solid content of 25% by mass is placed in a 40 mL glass sample tube “Screw No. 7” (manufactured by Maruemu Co., Ltd.), and a non-aqueous conductivity meter “DT-700” (Dispersion Technology) The electrode was immersed in a liquid developer and measured 20 times at 25 ° C., the average value was calculated, the conductivity was measured, and the reciprocal thereof was taken as the resistance. The higher the numerical value, the higher the resistance, and the less background fogging occurs during printing.

  From the above results, it can be seen that the liquid developers of Examples 1 to 3 have a high adsorption rate of the dispersant, a high resistance, and a low viscosity and a good dispersion stability even when the solid concentration is high. I understand. On the other hand, the liquid developer of Comparative Example 1 in which the basic nitrogen-containing group raw material of the dispersant does not have the group represented by the formula (I) and the number average molecular weight is too small is the adsorption of the dispersant. Comparative Example 2 in which the rate is low, the resistance is low, the number average molecular weight of the basic nitrogen-containing group raw material of the dispersant is too large, and the basic nitrogen-containing group raw material has a group represented by the formula (I) In addition, the liquid developer of Comparative Example 3 whose number average molecular weight is too large has a low adsorption rate and low resistance. However, particularly when the solid content concentration is high, the increase in viscosity is remarkable, and the high resistance and low viscosity. That is, it can be seen that the dispersion stability is not compatible.

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

Claims (7)

A toner comprising a binder resin including a polyester resin and a colorant, a dispersant, and a liquid developer containing an insulating liquid, wherein the dispersant is represented by the formula (I):

(Wherein R ¹ , R ² and R ³ may be the same or different and are alkylene groups having 1 to 22 carbon atoms)
Containing a reaction product X of a basic nitrogen-containing group material having a nitrogen-containing group and a dispersible group material having a polysiloxane chain, wherein the number average molecular weight of the basic nitrogen-containing group material is 250 or more and 5,000 or less A liquid developer. The dispersible group raw material having a polysiloxane chain has the formula (II):

(Wherein R ⁴ is a reactive functional group, m is the average number of moles added, and m is 10 or more and 70 or less)
The liquid developer according to claim 1, which is a compound represented by:   The liquid developer according to claim 1, wherein the number average molecular weight of the dispersible group raw material is 1,000 or more and 5,000 or less.   The liquid developer according to claim 1, wherein the content of the reactant X is 0.1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the toner particles.   The liquid developer according to any one of claims 1 to 4, wherein the acid value of the polyester-based resin is 5 mgKOH / g or more and 60 mgKOH / g or less.   The liquid developer according to claim 1, wherein the polyester resin contains a polyester resin or a composite resin containing a polyester resin and a styrene resin.   The liquid developer according to claim 6, wherein the polyester resin is a polycondensate of an alcohol component containing a divalent or higher alcohol and a carboxylic acid component containing a divalent or higher carboxylic acid compound.