JP6986941B2 - Liquid developer - Google Patents

Description

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

The electrophotographic developer includes a dry developer that uses toner particles made of a material containing a colorant and a binder resin in a dry state, and a liquid developer in which the toner particles are dispersed in an insulating liquid.

In the liquid developer, the toner particles are dispersed in the oil in the insulating liquid, so that the particle size can be reduced as compared with the dry developer. Therefore, it is possible to obtain a high-quality printed matter that surpasses offset printing, and is suitable for commercial printing applications. Further, in recent years, since the demand for high speed has increased, it is required to reduce the viscosity of the liquid developer. Further, there is a demand 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 provides a liquid developer which is excellent in fixing characteristics of fatty acid particles to a recording medium but is friendly to the environment, and also provides an image forming apparatus using such a liquid developer. An object is a liquid developer in which toner particles mainly composed of a resin material are dispersed in an insulating liquid, wherein the insulating liquid contains an unsaturated fatty acid monoester and is an unsaturated fatty acid monoester. The ester contains an alcohol component having 1 to 8 carbon atoms, the content of the unsaturated fatty acid monoester in the insulating liquid is 10 to 80 wt%, and the volume resistance of the insulating liquid is 10 to 80 wt%. Discloses a liquid developer characterized by having a weight average molecular weight Mw of 10 ¹² Ω cm or more and a weight average molecular weight Mw of the resin material of 5000 to 15000.

Patent Document 2 provides a liquid developer having excellent storage stability and excellent fixing characteristics of toner particles on a recording medium, and also provides an image forming apparatus using such a liquid developer. The insulating liquid contains an insulating liquid and toner particles dispersed in the insulating liquid, and the insulating liquid contains a fatty acid monoester which is an ester of a fatty acid and a monovalent alcohol, and has the insulating property. A liquid developer is disclosed characterized in that the aniline point of the liquid is 5 ° C to 80 ° C.

Patent Document 3 provides a method for producing an insulating liquid, a liquid developer, and a liquid developer, which are excellent in storage stability and long-term stability, and also have excellent fixing characteristics of toner particles on a recording medium. For the purpose of providing an image forming apparatus using such a liquid developer, the liquid developer comprises a lauric acid monoester which is an ester between lauric acid and a monovalent alcohol. Insulating liquids are disclosed.

Patent Document 4 provides a liquid developer that is environmentally friendly, has excellent low-temperature fixability, and can firmly fix toner particles to a recording medium, and can efficiently produce such a liquid developer. For the purpose of providing a method for producing a liquid developer and an image forming apparatus using such a liquid developer, toner particles mainly composed of a resin material and non-volatile insulating property are provided. A liquid developer characterized by having a liquid, the toner particles containing a fatty acid monoester, and the resin material contained in the toner particles being swollen by the fatty acid monoester. It has been disclosed.

Japanese Unexamined Patent Publication No. 2008-26571 Japanese Unexamined Patent Publication No. 2008-203568 Japanese Unexamined Patent Publication No. 2008-20361 Japanese Unexamined Patent Publication No. 2008-299141

However, with the conventional technology, the viscosity of the liquid developer is reduced and the storage stability is insufficient, and it is difficult to cope with the high speed that has been progressing in recent years. Specifically, due to the high viscosity, poor film formation occurs on a roller that rotates at high speed, and when the speed is increased, stress is applied near the blade in the printer and the toner is locally heated to about 50 ° C. Aggregation will occur.

The present invention relates to a liquid developer having a small particle size, low viscosity, and excellent storage stability and low temperature fixability.

The present invention is a liquid developer containing toner particles containing a binder resin and a colorant, a dispersant, and an insulating liquid, wherein the binder resin contains a polyester resin and the insulating liquid is The present invention relates to a liquid developer containing 50% by mass or more of a saturated fatty acid ester, which is an ester of a saturated fatty acid having 8 or more and 16 or less carbon atoms and an alcohol having 3 or more carbon atoms.

The liquid developer of the present invention has the effects of having a small particle size, low viscosity, excellent storage stability and low temperature fixability.

The liquid developer of the present invention is a liquid developer containing toner particles containing a binder resin and a colorant, a dispersant, and an insulating liquid, wherein the binder resin contains a polyester resin and is described above. The insulating liquid contains 50% by mass or more of a saturated fatty acid ester, which is an ester of a saturated fatty acid having 8 or more and 16 or less carbon atoms and an alcohol having 3 or more carbon atoms, and has a small particle size, low viscosity, and storage stability. And it is excellent in low temperature fixing property.

The reason for this effect is not clear, but it is thought to be as follows.
Since the saturated fatty acid ester has an ester bond, it has a high affinity with the polyester resin, and because it penetrates into the resin and plasticizes the resin, it has excellent low-temperature fixability. When the saturated fatty acid ester is present at the interface between the polyester resin and the base material (paper, etc.), the ester bond in the saturated fatty acid ester interacts with both the polyester resin and the base material (paper, etc.), and the resin Excellent low-temperature fixability because it enhances the adhesive effect to the substrate. On the other hand, if the plasticizing effect of the resin becomes excessive, the toner particles are fused or aggregated with each other, and the particles are likely to be coarsened or thickened.
Therefore, as a result of diligent studies by the present inventors, it has been found that the molecular structures of the saturated fatty acids and alcohols constituting the saturated fatty acid ester are important for controlling the degree of plasticization. By using a saturated fatty acid ester, which is an ester of a saturated fatty acid having 8 or more and 16 or less carbon atoms and an alcohol having 3 or more carbon atoms, the molecular chain becomes moderately bulky, and excessive penetration into the resin and plasticization are suppressed. Therefore, it is considered that a small particle size, low viscosity, excellent low temperature fixability and storage stability can be obtained.

The binding resin includes a polyester resin. Examples of the polyester-based resin include a polyester resin, a composite resin having a polyester resin and another resin, preferably a styrene-based resin.

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 an aliphatic diol, preferably an aliphatic diol having 2 or more and 20 or less carbon atoms, and more preferably 2 or more and 15 or less carbon atoms, or the formula (I) :.

(In the formula, OR and RO are oxyalkylene groups, R is ethylene and / or propylene group, x and y indicate the average number of moles of alkylene oxide added, which are positive numbers, respectively, of x and y. The value of the sum is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, still more preferably 4 or less).
Examples thereof include an alkylene oxide adduct of bisphenol A represented by bisphenol A, bisphenol A, hydrogenated bisphenol A and the like. Specific examples of the aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol. An aliphatic diol having a hydroxyl group bonded to a secondary carbon atom having 2 or more and 4 or less carbon atoms is preferable.

As the alcohol component, the crushability of the toner is improved to obtain toner particles having a small particle size, the low temperature fixability of the toner is improved, and the dispersion stability of the toner particles is improved to improve the storage stability. From the viewpoint, an aliphatic diol or an alkylene oxide adduct of bisphenol A represented by the formula (I) is preferable, from the viewpoint of improving the pulverizability of the toner to obtain toner particles having a small particle size, and the dispersion stability of the toner particles. From the viewpoint of improving storage stability, an aliphatic diol is more preferable, and an aliphatic diol having a hydroxyl group bonded to a secondary carbon atom having 2 or more and 4 or less carbon atoms is further preferable. The content of the aliphatic diol or the alkylene oxide adduct of bisphenol A represented by the formula (I) is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more in the alcohol component. , More preferably 95 mol% or more, still more preferably 100 mol%. When an aliphatic diol and an alkylene oxide adduct of bisphenol A represented by the formula (I) are used in combination, the total content of both is preferably within the above range.

Examples of the divalent carboxylic acid compound include dicarboxylic acids having 3 or more and 30 or less carbon atoms, preferably 3 or more and 20 or less carbon atoms, and more preferably 3 or more and 10 or less carbon atoms, anhydrides thereof, or alkyl groups. Examples thereof include derivatives such as alkyl esters having 1 or more and 3 or less carbon atoms. Specific examples of the dicarboxylic acid include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid, fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, and alkyl having 1 or more and 20 or less carbon atoms. Examples thereof include aliphatic dicarboxylic acids such as succinic acid substituted with a group or an alkenyl group having 2 or more and 20 or less carbon atoms.

As the carboxylic acid component, terephthalic acid and / or fumaric acid is preferable from the viewpoint of improving the low temperature fixability of the toner and improving the dispersion stability of the toner particles to improve the storage stability. The content of terephthalic acid or fumaric acid is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more in the carboxylic acid component. When terephthalic acid and fumaric acid are used in combination, the total content of both is preferably within the above range.

Examples of the trivalent or higher carboxylic acid compound include 4 or more and 20 or less carbon atoms, preferably 6 or more and 20 or less carbon atoms, more preferably 7 or more and 15 or less carbon atoms, still more preferably 8 or more and 12 or less carbon atoms, and further. Preferred examples thereof include trivalent or higher carboxylic acids having 9 or more and 10 or less carbon atoms, anhydrides thereof, or derivatives such as alkyl esters having 1 or more and 3 or less carbon atoms in the alkyl group. Specific examples thereof include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), and acid anhydrides thereof.

The content of the carboxylic acid-based compound having a valence of 3 or more is preferably 60 mol% or less, more preferably 50 mol% or less, still more preferably 30 mol% or less, still more preferably 25 mol% or less, and further. It is preferably 20 mol% or less, more preferably 15 mol% or less.

The alcohol component may contain a monohydric alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid compound as appropriate from the viewpoint of adjusting the molecular weight and 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, still more preferably 0.75 or more from the viewpoint of adjusting the softening point of the polyester resin. Yes, and preferably 1.1 or less, more preferably 1.05 or less.

The polyester resin preferably contains, 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 co-catalyst, a polymerization inhibitor, or the like. 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 diisopropyrate bistriethanol aminated, and tin compounds are preferable. The amount of the esterification catalyst used is preferably 0.01 part by mass or more, more preferably 0.1 part by mass or more, and preferably 1.5 parts by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 1 part by mass or less. Examples of the esterification co-catalyst include gallic acid and the like. The amount of the esterification co-catalyst used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. More preferably, it is 0.1 part by mass or less. Examples of the polymerization inhibitor include t-butylcatechol and the like. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 0.1 parts by mass or less.

In the present invention, the polyester resin may be a polyester resin modified to such an extent that its characteristics are not substantially impaired. Examples of the modified polyester resin include grafting and blocking with phenol, urethane, epoxy and the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636 and the like. Examples thereof include a modified polyester resin, and among the modified polyester resins, a urethane-modified polyester resin obtained by urethane-stretching the polyester resin with a polyisocyanate compound is preferable.

As the composite resin having the polyester resin and the styrene resin, for example, by the method described in JP-A-2017-062379, both reactions can be reacted with either the raw material monomer of the polyester resin or the raw material monomer of the styrene resin. Examples thereof include a resin in which a polyester resin and a styrene resin are chemically bonded via a sex monomer.

The softening point of the polyester resin is preferably 85 ° C. or higher, more preferably 90 ° C. or higher, and improves the low temperature fixability of the toner, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of the temperature, it is preferably 130 ° C. or lower, more preferably 120 ° C. or lower, and further preferably 110 ° C. or lower.

The glass transition temperature of the polyester resin is preferably 45 ° C. or higher, more preferably 50 ° C. or higher, and improves low-temperature fixability, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint, it is preferably 80 ° C. or lower, more preferably 75 ° C. or lower, and further preferably 60 ° 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 from the viewpoint of dispersion stability of the toner particles, it is preferably 90 mgKOH / g or less, more preferably 80 mgKOH / g. Below, more preferably 70 mgKOH / g or less, still more preferably 50 mgKOH / g or less, still more preferably 30 mgKOH / g or less, still more preferably 20 mgKOH / g or less, still more preferably 15 mgKOH / g or less, still more preferably 10 mgKOH / g or less. be.

The content of the polyester-based resin is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 100% by mass, that is, only the polyester-based resin is used in the binder resin. However, a resin other than the polyester resin may be contained as long as the effect of the present invention is not impaired. Examples of resins other than the polyester-based resin 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 acid resin which is a copolymer or copolymer containing a styrene or a styrene substituent such as a coalescence, a styrene-acrylic acid ester copolymer, or a styrene-methacrylic acid ester copolymer. , One or more selected from resins such as polyethylene-based resin, polypropylene-based resin, polyurethane-based resin, silicone-based resin, phenol-based resin, aliphatic or alicyclic hydrocarbon resin.

As the colorant, dyes, pigments and the like used as colorants for toner can be used. Examples thereof include 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, carmin 6B, isoindoline, disazoero and the like. .. In the present invention, the toner particles may be either black toner or color toner.

From the viewpoint of improving the image density, the content of the colorant is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more with respect to 100 parts by mass of the binder resin. Then, from the viewpoint of improving the pulverizability of the toner to make the particle size smaller, improving the low-temperature fixability, and improving the dispersion stability of the toner particles to improve the storage stability, 100 mass of the binder resin. It is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, still more preferably 30 parts by mass or less.

In addition to the binder resin and colorant, the toner particles include mold release agents, charge control agents, charge control resins, magnetic powders, fluidity improvers, conductivity modifiers, reinforcing fillers such as fibrous substances, and antioxidants. Additives such as an agent and a cleaning property improving agent 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 obtained melt-kneaded product is pulverized, preferably wet-pulverized to obtain a toner particle. Examples thereof include a method of mixing the colorant dispersion liquid and combining the binder resin particles and the colorant particles, or a method of stirring the water-based binder resin dispersion liquid and the colorant at high speed. From the viewpoint of improving developability and fixability, a method of melt-kneading the toner raw material and then pulverizing, preferably wet pulverizing is preferable.

First, it is preferable that the toner raw material containing the binder resin, the colorant, the additive used if necessary, etc. is mixed in advance with a mixer such as a Henshell mixer, a super mixer, a ball mill, etc., and then supplied to the kneader. A Henshell mixer is more preferable from the viewpoint of improving the dispersibility of the colorant in the binder resin.

Mixing with a Henschel mixer is performed 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, the melt kneading of the toner raw material can be performed using a known kneader such as a closed kneader, a uniaxial or biaxial kneader, or a continuous open roll kneader. In the production method of the present invention, an open roll type kneader is preferable from the viewpoint of improving the dispersibility of the colorant and improving the yield of toner particles after pulverization.

The open roll type kneader is one in which the melt-kneading portion is not sealed and is open, and the kneading heat generated during melt-kneading can be easily dissipated. The open roll type kneader used in the present invention is provided with a plurality of raw material supply ports and kneaded material discharge ports provided along the axial direction of the roll, and is a continuous open roll type kneader from the viewpoint of production efficiency. Is preferable.

The open roll type 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 higher than the softening point of the resin.

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

It is preferable that the rolls have different peripheral velocities from each other. In the open roll type kneader equipped with the above two rolls, the high temperature heating roll is the high rotation side roll and the low temperature cooling roll is the low rotation side from the viewpoint of improving the fixability of the liquid developer. It is preferably 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, still more preferably 50 m / min or less. Is. Further, the ratio of the 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.

Further, the structure, size, material, etc. of each roll are not particularly limited. The surface of the roll has a groove used for kneading, and the shape thereof may be linear, spiral, corrugated, uneven or the like.

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

The crushing step may be divided into multiple stages. For example, the melt-kneaded product may be coarsely pulverized to about 1 to 5 mm and then further pulverized. Further, in order to improve the productivity in the pulverization step, the melt-kneaded product may be mixed with inorganic fine particles such as hydrophobic silica and then pulverized.

Examples of the crusher preferably used for coarse crushing include an atomizer, a rotoplex and the like, but a hammer mill and the like may also be used. Further, examples of the pulverizer preferably used for fine pulverization include a fluidized bed type jet mill, an airflow type jet mill, and a mechanical type mill.

Examples of the classifying machine used in the classifying process include an air flow type classifying machine, an inertial type classifying machine, and a sieving type classifying machine. If necessary, the crushing step and the classification step may be repeated.

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, it is more preferably 12 μm or less. The volume median particle size (D ₅₀ ) means a particle size in 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 or the like after being mixed 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, still more preferably 30 parts by mass or more, with respect to 100 parts by mass of the insulating liquid from the viewpoint of high-speed printability. 40 parts by mass or more, more preferably 50 parts by mass or more, and from the viewpoint of improving dispersion stability, preferably 100 parts by mass or less, more preferably 80 parts by mass or less, still more preferably 70 parts by mass or less, further. It is preferably 60 parts by mass or less.

The dispersant in the present invention is preferably a basic dispersant having a basic nitrogen-containing group from the viewpoint of high adsorptivity to a resin having an acidic group. The basic nitrogen-containing group includes an amino group (-NH ₂ , -NHR, -NHRR'), an amide group (-C (= O) -NRR'), an imide group (-N (COR) ₂ ), and a nitro group. From the group consisting of _{(-NO 2} ), imino group (= NH), cyano group (-CN), azo group (-N = N-), diazo group (= N ₂ ), and azi group (-N _3). At least one selected is preferred. Here, R and R'represent a hydrocarbon group having 1 to 5 carbon atoms. From the viewpoint of the adsorptivity of the dispersant to the toner particles, the amino group and / or the imino group is preferable, and from the viewpoint of the chargeability of the toner particles, the imino group is more preferable.

Examples of the functional group contained in addition to the basic nitrogen-containing group include a hydroxy group, a formyl group, an acetal group, an oxime group, a thiol group and the like.

From the viewpoint of dispersion stability, the proportion of the basic nitrogen-containing group in the basic dispersant is preferably 70% by number or more, more preferably 80% by number or more, and further preferably 90% by number in terms of the number of heteroatoms. The above is more preferably 95% by number or more, still more preferably 100% by number.

From the viewpoint of dispersibility of the liquid developer, the basic dispersant has 16 or more carbon atoms, a hydrocarbon having 16 or more carbon atoms partially substituted with a halogen atom, and 16 carbon atoms having a reactive functional group. The above hydrocarbons, polymers of hydroxycarboxylic acids with 12 or more carbon atoms, polymers of dibasic acids with 2 or more and 22 or less carbon atoms and diols with 2 or more and 22 or less carbon atoms, alkyl (meth) acrylates with 16 or more carbon atoms. It is preferable that it contains a group derived from the polymer, polyolefin, etc. (hereinafter, also referred to as “dispersible group”).

As the hydrocarbon having 16 or more carbon atoms, a hydrocarbon having 16 or more and 24 or less carbon atoms is preferable, and examples thereof include hexadecene, octadecene, icosane, and docosane.

As the hydrocarbon having 16 or more carbon atoms partially substituted with a halogen atom, a hydrocarbon having 16 to 24 carbon atoms partially substituted with a halogen atom is preferable, for example, chlorohexadecane, bromohexadecane, chlorooctadecane, bromo. Examples thereof include octadecane, chloroeicosan, bromoeikosan, chlorodocane, bromodocosan and the like.

As the hydrocarbon having a reactive functional group and having 16 or more carbon atoms, a hydrocarbon having a reactive functional group and having 16 or more carbon atoms and 24 or less carbon atoms is preferable, for example, hexadecenyl succinic acid and octadecenyl succinic acid. Examples thereof include acid, eicosenyl succinic acid, docosenyl succinic acid, hexadecyl glycidyl ether, octadecyl glycidyl ether, eico syl glycidyl ether, doco syl glycidyl ether and the like.

As the polymer of hydroxycarboxylic acid having 12 or more carbon atoms, a polymer of hydroxycarboxylic acid having 12 or more and 24 or less carbon atoms, preferably 16 or more and 24 or less carbon atoms is preferable, and for example, a polymer of 12-hydroxystearic acid or the like. Can be mentioned.

Examples of the polymer of a dibasic acid having 2 or more and 22 or less carbon atoms and a diol having 2 or more and 22 carbon atoms include a polymer of ethylene glycol and sebacic acid, a polymer of 1,4-butanediol and fumaric acid, 1 Examples thereof include a polymer of 6-hexanediol and fumaric acid, a polymer of 1,10-decanediol and sebacic acid, and a polymer of 1,12-dodecanediol and 1,12-dodecanedioic acid.

As the polymer of alkyl (meth) acrylate having 16 or more carbon atoms, a polymer of alkyl (meth) acrylate having 16 or more carbon atoms and 24 or less carbon atoms is preferable, for example, a polymer of hexadecyl methacrylate, a polymer of octadecyl methacrylate, and doco. Examples thereof include polymers of silmethacrylate.

Examples of the polyolefin include polyethylene, polypropylene, polybutylene, polyisobutene, polymethylpentene, polytetradecene, polyhexadecene, polyoctadecene, polyeicosen, polydocene and the like.

The basic dispersant preferably has a polyolefin skeleton, more preferably a polypropylene skeleton and / or a polyisobutene skeleton, from the viewpoint of dispersibility of the toner particles, and a viewpoint of solubility of the dispersant in an insulating liquid. Therefore, it is more preferable to have a polyisobutene skeleton. Therefore, among the dispersible groups, a group derived from polyolefin is preferable, a group derived from polypropylene and / or a group derived from polyisobutene is more preferable, and a group derived from polyisobutene is further preferable.

The basic dispersant is not particularly limited, but is obtained, for example, by reacting a basic nitrogen-containing base material with a dispersible group material.

Examples of the basic nitrogen-containing base raw material include polyalkyleneimine such as polyethyleneimine, polyallylamine, and polyaminoalkylmethacrylate such as polydimethylaminoethylmethacrylate.

The number average molecular weight of the basic nitrogen-containing group raw material is preferably 100 or more, more preferably 500 or more, still more preferably 1,000 or more, and the dispersion of toner particles, from the viewpoint of the adsorptivity of the acidic group to the resin. From the viewpoint of sex, it is preferably 15,000 or less, more preferably 10,000 or less, still more preferably 5,000 or less.

Dispersible group raw materials include halogenated hydrocarbons with 16 or more carbon atoms, hydrocarbons with reactive functional groups with 16 or more carbon atoms, polymers of hydroxycarboxylic acids with 12 or more carbon atoms, and 2 or more carbon atoms. Polymers of 22 or less dibasic acids and diols with 2 or more carbon atoms and 22 or less carbon atoms, hydrocarbon (meth) acrylate polymers with 16 or more carbon atoms having reactive functional groups, polyolefins having reactive functional groups, etc. Can be mentioned. Among these, from the viewpoint of raw material availability and reactivity, it has a halogenated hydrocarbon having 16 or more carbon atoms, a hydrocarbon having a reactive functional group and having 16 or more carbon atoms, and a reactive functional group. A polymer of an alkyl (meth) acrylate having 16 to 24 carbon atoms or a polyolefin having a reactive functional group is preferable. Examples of the reactive functional group include a carboxy group, an epoxy group, a formyl group, an isocyanate group and the like. Among these, a carboxy group or an epoxy group is preferable, and a carboxy group is more preferable from the viewpoint of safety and reactivity. preferable. Therefore, as the compound having a reactive functional group, a carboxylic acid-based compound is preferable. Examples of the carboxylic acid compound include fumaric acid, maleic acid, ethane acid, propanoic acid, butanoic acid, succinic acid, oxalic acid, malonic acid, tartaric acid, their anhydrides, or alkyl esters having 1 or more and 3 or less carbon atoms thereof. And so on. Specific examples of the dispersible group raw material include halogenated alkanes such as chlorooctadecane, epoxy-modified polyoctadecane methacrylate, polyethylene succinic anhydride, chlorinated polypropylene, polypropylene succinic anhydride, polyisobutene succinic anhydride and the like.

The content of the compound having a polyolefin skeleton in the dispersible base raw material is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 90% by mass or more, from the viewpoint of dispersibility of the toner particles. It is 100% by mass.

The number average molecular weight of the dispersible base material is preferably 500 or more, more preferably 700 or more, still more preferably 900 or more, and the adsorptivity of the dispersant to the toner particles from the viewpoint of the dispersibility of the toner particles. From the viewpoint, it is preferably 5,000 or less, more preferably 4,000 or less, and further preferably 3,000 or less.

The mass ratio of the basic nitrogen-containing group to the dispersible group (basic nitrogen-containing group / dispersible group) in the reaction product is preferably 3/97 or more, more preferably 3/97 or more, from the viewpoint of adsorptivity to toner particles. It is 5/95 or more, and is preferably 20/80 or less, more preferably 15/85 or less, from the viewpoint of dispersion stability of toner particles. The mass ratio of the basic nitrogen-containing group to the dispersible group in the reaction product can be measured by NMR of the reaction product. The mass ratio of the resulting raw material compound can also be regarded as the mass ratio of the basic nitrogen-containing group to the dispersible group (basic nitrogen-containing group / dispersible group) in the dispersant.

Other basic dispersants include monomer A having an amino group and formula (II) :.

(In the formula, R ¹ is a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms, preferably a methyl group, and R ² may have a substituent and is an alkyl group or carbon having 1 or more and 22 or less carbon atoms. Indicates an alkenyl group with a number of 2 or more and 22 or less)
Examples thereof include a copolymer C with the monomer B represented by.

As the monomer A having an amino group, the formula (III):
CH ₂ = C (R ⁵ ) COYR ⁶ NR ³ R ⁴ (III)
(In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 or more and 4 or less carbon atoms, and they are bonded to each other to form a ring structure. R ⁵ may represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms, preferably a methyl group, and R ⁶ may represent a linear or branched alkylene group having 2 or more and 4 or less carbon atoms. Indicates -O- or -NH-)
A monomer having an amino group represented by, or an acid neutralized product (tertiary amine salt) or a quaternary ammonium salt of this monomer is preferable. Preferred acids for obtaining the above acid neutralized products include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, tartaric acid, adipic acid, sulfamic acid, toluenesulfonic acid, lactic acid and pyrrolidone. Examples thereof include 2-carboxylic acid and succinic acid. Preferred quaternary agents for obtaining the above quaternary ammonium salt include alkyl halides such as methyl chloride, ethyl chloride, methyl bromide and methyl iodide, dimethyl sulfate, diethyl sulfate, di-n-propyl sulfate and the like. Common alkylating agents are mentioned.

In the formula (III), R ³ and R ⁴ are each independently preferably a linear or branched alkyl group having 1 or more and 4 or less carbon atoms, and NR ³ R ⁴ is preferably a tertiary amino group. Specific examples of R ³ and R ⁴ include a methyl group, an ethyl group, a propyl group, an isopropyl group and the like, and a methyl group is preferable.

Examples of R ⁶ include an ethylene group, a propylene group, a butylene group and the like, and an ethylene group is preferable.

^{Specific examples of the monomer in which NR 3} R ⁴ is a tertiary amino group in the formula (III) (monomer having a tertiary amino group) include a (meth) acrylic acid ester having a dialkylamino group and a dialkylamino group ( Meta) acrylamide and the like can be mentioned. In addition, "(meth) acrylic acid ester" indicates that acrylic acid ester and methacrylic acid ester are included, and "(meth) acrylamide" includes both cases of acrylamide and methacrylamide.

Examples of the (meth) acrylic acid ester having a dialkylamino group include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, diisopropylaminoethyl (meth) acrylate, and dibutylaminoethyl (). Examples thereof include one or more selected from the group consisting of meth) acrylate, diisobutylaminoethyl (meth) acrylate, and dit-butylaminoethyl (meth) acrylate.

Examples of (meth) acrylamide having a dialkylamino group include dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide, dipropylaminopropyl (meth) acrylamide, diisopropylaminopropyl (meth) acrylamide, and dibutylaminopropyl (meth). Examples thereof include one or more selected from the group consisting of acrylamide, diisobutylaminopropyl (meth) acrylamide, and dit-butylaminopropyl (meth) acrylamide.

Among these, (meth) acrylic acid ester having a dialkylamino group is preferable from the viewpoint of small particle size, low viscosity, storage stability, and low temperature fixability, and dimethylaminoethyl (meth) acrylate is more preferable.

The monomer B is represented by the above formula (II), and in the above formula (II), the carbon number of the alkyl group and the alkenyl group represented by ^{R 2 is low viscosity, storage stability, and low temperature.} From the viewpoint of fixability, it is preferably 10 or more, more preferably 12 or more, and from the viewpoint of adsorptivity to toner particles, it is 22 or less, preferably 20 or less. The alkyl group or alkenyl group of R ² may be a straight chain or a branched chain, and may have a substituent such as a hydroxyl group.

Therefore, ^{it is preferable that the monomer B contains at least the monomer B2 in which R 2} is an alkyl group or an alkenyl group having 10 or more and 22 or less carbon atoms.

In the monomer B, R ² is a monomer B1 which is an alkyl group having 1 or more and 9 carbon atoms or an alkenyl group having 2 or more carbon atoms and 9 or less carbon atoms, and a monomer B2 which is an alkyl group or an alkenyl group having 10 or more and 22 carbon atoms or less. The molar ratio (monomer B1 / monomer B2) is 0.1 or less, preferably 0.07 or less, more preferably 0.05 or less, still more preferably 0.03 or less, still more preferably, from the viewpoint of low viscosity, storage stability, and low temperature fixability. Is 0.01 or less, and is 0 or more, preferably 0.

Specific examples of the monomer B include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, and the like. 2-Ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) nonyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) undecyl (meth) acrylate, (iso) dodecyl (meth) ) Acrylate, (iso) tridecyl (meth) acrylate, (iso) tetradecyl (meth) acrylate, (iso) pentadecyl (meth) acrylate, (iso) hexadecyl (meth) acrylate, (iso) heptadecyl (meth) acrylate, (iso) ) Octadecyl (meth) acrylate, (iso) nonadecyl (meth) acrylate, (iso) icocil (meth) acrylate, (iso) eicocil (meth) acrylate, (iso) henicocil (meth) acrylate, (iso) docosyl (meth) Examples include acrylate. One or more of these can be used. Here, "(iso or tertiary)" and "(iso)" mean that both the case where these groups are present and the case where they are not present are included, and when these groups are not present. Indicates that it is normal. Further, "(meth) acrylate" indicates that the case of both acrylate and methacrylate is included.

The molar ratio of monomer A to monomer B (monomer A / monomer B) functions as a dispersant, and is 2/98 or more, preferably 3/97 or more, more preferably 5 from the viewpoint of low viscosity and storage stability. / 95 or more, more preferably 7/93 or more, 50/50 or less, preferably 40/60 or less, more preferably 35/65 or less, from the viewpoint of low viscosity, storage stability, and low temperature fixability. It is more preferably 25/75 or less, still more preferably 20/80 or less.

The total content of the monomer A and the monomer B in all the monomers used in the copolymer C is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and preferably 100. It is mass% or less, more preferably 100% by mass.

The polymerization of Monomer A and Monomer B is carried out by heating to about 40 to 140 ° C. in a solvent in the presence of a polymerization initiator such as 2,2'-azobis (2,4-dimethylvaleronitrile). Can be made to.

The weight average molecular weight of the basic dispersant is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 15,000 or more from the viewpoint of low viscosity and low temperature fixability, and preferably 100,000 or more from the same viewpoint. Below, it is more preferably 95,000 or less, still more preferably 90,000 or less.

The number average molecular weight of the basic dispersant is preferably 2,000 or more, more preferably 2,500 or more, still more preferably 3,000 or more, still more preferably 3,500 or more, from the viewpoint of low viscosity and low temperature fixability, and From the same viewpoint, it is preferably 10,000 or less, more preferably 9,000 or less, still more preferably 8,000 or less.

The content of the basic dispersant is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and further preferably 2 parts by mass or more with respect to 100 parts by mass of the toner particles from the viewpoint of dispersion stability of the toner particles. From the viewpoint of the chargeability of the toner, it is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 5 parts by mass or less.

The liquid developer of the present invention may contain a known dispersant other than the basic dispersant, but the content of the basic dispersant is preferably 50% by mass or more in the dispersant. More preferably 70% by mass or more, further preferably 90% by mass or more, still more preferably 95% by mass or more, preferably 100% by mass or less, more preferably substantially 100% by mass, still more preferably 100% by mass. be.

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. It is × 10 ^-11 S / m or less, and preferably 1.0 × 10 ^-13 S / m or more.

The insulating liquid in the present invention has 8 or more and 16 or less carbon atoms from the viewpoint of improving the dispersion stability of the toner particles to improve the storage stability, the viewpoint of low temperature fixability, and the viewpoint of increasing the resistance of the liquid developer. Contains a saturated fatty acid ester, which is an ester of a saturated fatty acid of the above and an alcohol having 3 or more carbon atoms.

Examples of the saturated fatty acid having 8 or more and 16 or less carbon atoms include caprylic acid, capric acid, lauric acid, palmitic acid, myristic acid, 2-ethylhexanoic acid and the like.

The carbon number of the saturated fatty acid is 8 or more, preferably 10 or more, more preferably 12 or more, and wet grinding of the toner from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. It is 16 or less, preferably 14 or less, from the viewpoint of improving the properties to obtain toner particles having a small particle size, improving the dispersion stability of the toner particles to improve the storage stability, and the low temperature fixability. Is.

Examples of the alcohol having 3 or more carbon atoms include propanol, isopropanol, hexanol, butanol, isobutanol, octanol, 2-ethylhexyl alcohol, decyl alcohol, isodecyl alcohol, lauryl alcohol, myristyl alcohol, and cetyl alcohol.

The carbon number of the alcohol is 3 or more, preferably 4 or more, more preferably 5 or more, and the wet greasability of the toner from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. It is preferably 16 or less, more preferably 16 or less, from the viewpoint of improving the toner particles having a small particle size, improving the dispersion stability of the toner particles to improve the storage stability, and the low temperature fixability. It is 12 or less, more preferably 10 or less.

The boiling point of the saturated fatty acid ester is preferably 180 ° C. or higher, more preferably 220 ° C. or higher, still more preferably 240 ° C. from the viewpoint of improving the dispersion stability of the toner particles to improve the storage stability and the developability. The temperature is preferably 360 ° C. or lower, more preferably 350 ° C. or lower, still more preferably 350 ° C. or lower, from the viewpoint of low-temperature fixability and improving the wet grindability of the toner to obtain toner particles having a small particle size. It is below 340 ° C.

The viscosity of the saturated fatty acid ester at 25 ° C. is preferably 1 mPa · s or more, more preferably 2 mPa · s or more, still more preferably 3 mPa · s, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. It is preferably 15 mPa · s or less, more preferably 10 mPa · s or less, and further, from the viewpoint of low temperature fixability and improving the wet grindability of the toner to obtain toner particles having a small particle size. It is preferably 6 mPa · s or less.

The content of the saturated fatty acid ester is 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 90% by mass or more in the insulating liquid from the viewpoint of environmental safety and low temperature fixability. It is 95% by mass or more, more preferably 100% by mass.

Examples of the insulating liquid other than the saturated fatty acid ester include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, vegetable oils and the like.

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 the toner particles to obtain a liquid developer.

As a method for mixing the toner particles, the dispersant, and the insulating liquid, a method of stirring with a stirring / mixing device or the like is preferable.

The stirring / mixing device is not particularly limited, but a high-speed stirring / mixing device is preferable from the viewpoint of improving the productivity and storage stability of the toner particle dispersion, and specifically, Despa (manufactured by Asada Iron Works Co., Ltd.), T. .K. Homo Mixer, TK Homo Disperser, TK Robomix (all manufactured by Primex Co., Ltd.), Claire Mix (manufactured by M Technique Co., Ltd.), Kady Mill (manufactured by Kady International Co., Ltd.) Etc. are preferable.

By mixing with the high-speed stirring and mixing device, the toner particles are pre-dispersed, the toner particle dispersion liquid can be obtained, and the productivity of the liquid developer by the next wet grinding is improved.

From the viewpoint of improving the image density, 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, and the toner particles are stably dispersed. From the viewpoint of improving the properties and the storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less.

Wet pulverization is a method of mechanically pulverizing toner particles dispersed in an insulating liquid in a state of being dispersed in the insulating liquid.

As the device to be used, for example, a commonly used stirring / 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 Co., Ltd.) and TK Homomixer (manufactured by Primix Corporation), crushers or kneaders such as roll mills, bead mills, kneaders, and extruders. And so on. 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 dispersion stability of the toner particles to improve the storage stability, and reducing the viscosity of the dispersion liquid. 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 to be 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, still more preferably 20% by mass or more, and the dispersion stability of the toner particles from the viewpoint of improving the image density. From the viewpoint of improving storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less.

The content of the toner particles in the liquid developer is preferably 10% by mass or more, more preferably 15% by mass or more, still more preferably 20% by mass or more, and the dispersion stability of the toner particles is preferable from the viewpoint of high-speed printing. From the viewpoint of sex, it is preferably 50% by mass or less, more preferably 45% by mass or less, and further 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, still more preferably 1.5 μm or more, from the viewpoint of reducing the viscosity of the liquid developer. 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 further preferably 2.5 μm or less.

The glass transition temperature of the toner particles in the liquid developer is preferably 15 ° C. or higher, more preferably 20 ° C. or higher, and a low temperature from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of fixability, the temperature is preferably 50 ° C. or lower, more preferably 40 ° C. or lower, and further preferably 30 ° C. or lower.

The content of the insulating liquid in the liquid developer is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more, and 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 of the liquid developer having a solid content concentration of 25% by mass at 25 ° C. is preferably 3 mPa · s or more, more preferably 5 mPa · s, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. The above is more preferably 6 mPa · s or more, further 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, and further. It is preferably 30 mPa · s or less, more preferably 25 mPa · s or less, still more preferably 20 mPa · s or less.

^{The conductivity of the liquid developer is preferably 5.0 × 10 -8} S / m or less, more preferably 3.0 × 10 ^-8 S / m or less, and even more preferably 1.0 × 10 from the viewpoint of the developability and image quality of the liquid toner. ^-8 S / m or less.

Hereinafter, the present invention will be specifically described 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 methods.

[Plastic softening point]
Using the 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 was applied by a plunger to a diameter of 1 mm and a length of 1 mm. Extrude from the nozzle of. 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 used as the softening point.

[Resin glass transition temperature]
Using the differential scanning calorimeter "DSC210" (manufactured by Seiko Electronics Inc.), weigh 0.01 to 0.02 g of the sample in an aluminum pan, raise the temperature to 200 ° C, and then lower the temperature from that temperature to 0 at a temperature reduction rate of 10 ° 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 temperature at the intersection of the extension of the baseline below the maximum peak temperature of heat absorption and the tangent line indicating the maximum slope from the rising portion of the peak to the peak of the peak is defined as the glass transition temperature.

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

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

[Number average molecular weight (Mn) of basic nitrogen-containing base material]
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below, and the number average molecular weight is determined.
_{(1) Preparation of sample solution Dissolve the sample at 0.15 mol / L in a solution of Na 2} SO ₄ in a 1% acetic acid aqueous solution so that the concentration becomes 0.2 g / 100 mL. Next, this solution is filtered using a fluororesin filter "FP-200" (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 0.2 μm to remove insoluble components, and a sample solution is used.
(2) Molecular weight measurement Using the following measuring device and analysis column, a solution of Na ₂ SO ₄ dissolved in a 1% acetic acid aqueous solution at 0.15 mol / L as an eluent was flowed at a flow rate of 1 mL per minute at 40 ° C. Stabilize the column in a constant temperature bath. Inject 100 μL of the sample solution into it and measure. The molecular weight of the sample is calculated based on the calibration curve prepared in advance. The calibration curve at this time includes several types of standard pullulan (P-5 (5.9 x 10 ³ ), P-50 (4.73 x 10 ⁴ ), P-200 (2.12 x 10 ⁵ ) manufactured by Showa Denko KK). Use a sample prepared using P-800 (7.08 × 10 ⁵ )) as a standard sample. The numbers in parentheses indicate the molecular weight.
Measuring device: HLC-8320GPC (manufactured by Tosoh Corporation)
Analytical column: α + α-M + α-M (manufactured by Tosoh Corporation)

[Number average molecular weight (Mn) of dispersible base material]
(1) Preparation of sample solution Dissolve the sample in tetrahydrofuran so that the concentration becomes 0.5 g / 100 mL. Next, this solution is filtered using a fluororesin filter "FP-200" (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 2 μm to remove insoluble components, and used as a sample solution.
(2) Measurement of molecular weight distribution Using the following measuring device and analytical column, flow tetrahydrofuran as an eluent at a flow rate of 1 mL / min and stabilize the column in a constant temperature bath at 40 ° C. Inject 100 μL of the sample solution into it and measure. The molecular weight of the sample is calculated based on the calibration curve prepared in advance. At this time, the calibration curve includes several types of monodisperse polystyrene (A-500 (5.0 x 10 ² ), A-1000 (1.01 x 10 ³ ), A-2500 (2.63 x 10 ³ ) manufactured by Tosoh Corporation). A-5000 (5.97 x 10 ³ ), F-1 (1.02 x 10 ⁴ ), F-2 (1.81 x 10 ⁴ ), F-4 (3.97 x 10 ⁴ ), F-10 (9.64 x 10 ⁴ ), F-20 (1.90 × 10 ⁵ ), F-40 (4.27 × 10 ⁵ ), F-80 (7.06 × 10 ⁵ ), F-128 (1.09 × 10 ⁶ )) are used as standard samples. The numbers in parentheses indicate the molecular weight.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (manufactured by Tosoh Corporation)

[Number average molecular weight (Mn) and weight average molecular weight (Mw) of dispersant]
<Dispersants A and B>
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) are determined.
(1) Preparation of sample solution Dissolve the dispersant in chloroform so that the concentration becomes 0.2 g / 100 mL. Next, this solution is filtered using a fluororesin filter "FP-200" (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 0.2 μm to remove insoluble components, and a sample solution is used.
(2) Molecular weight measurement Using the following measuring device and analysis column, a chloroform solution of 1.00 mmol / L Fermin DM2098 (manufactured by Kao Corporation) was flowed at a flow rate of 1 mL per minute in a constant temperature bath at 40 ° C. Stabilize the column inside. Inject 100 μL of the sample solution into it and measure. The molecular weight of the sample is calculated based on the calibration curve prepared in advance. At this time, the calibration curve includes several types of monodisperse polystyrene (A-500 (5.0 x 10 ² ), A-5000 (5.97 x 10 ³ ), F-2 (1.81 x 10 ⁴ ), manufactured by Tosoh Corporation. Use F-10 (9.64 x 10 ⁴ ), F-40 (4.27 x 10 ⁵ )) as standard samples. The numbers in parentheses indicate the molecular weight.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: K-804L (manufactured by Showa Denko KK)

<Dispersant C>
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method by the following method, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) are obtained.
(1) Preparation of sample solution The dispersant (the insulating liquid was distilled off from the dispersant solution) was dissolved in tetrahydrofuran so that the concentration became 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, and used as a sample solution.
(2) Measurement of molecular weight distribution Using the following measuring device and analytical column, flow tetrahydrofuran as an eluent at a flow rate of 1 mL / min and stabilize the column in a constant temperature bath at 40 ° C. Inject 100 μL of the sample solution into it and measure. The molecular weight of the sample is calculated based on the calibration curve prepared in advance. At this time, the calibration curve includes several types of monodisperse polystyrene (A-500 (5.0 x 10 ² ), A-1000 (1.01 x 10 ³ ), A-2500 (2.63 x 10 ³ ), manufactured by Tosoh Corporation. A-5000 (5.97 × 10 ³ ), F-1 (1.02 × 10 ⁴ ), F-2 (1.81 × 10 ⁴ ), F-4 (3.97 × 10 ⁴ ), F-10 (9.64 × 10 ⁴ ), F-20 (1.90 × 10 ⁵ ), F-40 (4.27 × 10 ⁵ ), F-80 (7.06 × 10 ⁵ ), F-128 (1.09 × 10 ⁶ )) are used as standard samples. The numbers in parentheses indicate the molecular weight.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: TSKgel GMHXL + TSKgel G3000HXL (manufactured by Tosoh Corporation)

[Conductivity of insulating liquids and liquid developers]
Place 25 g of the sample in a 40 mL glass sample tube "Screw No. 7" (manufactured by Maruemu Co., Ltd.) and use a non-aqueous conductivity meter "DT-700" (manufactured by Dispersion Technology) to insulate the electrodes. Immerse in a liquid and measure 20 times at 25 ° C to calculate the average value and measure the conductivity. The smaller the value, the higher the resistance.

[Boiling point of insulating liquid]
Using the differential scanning calorimeter "DSC210" (manufactured by Seiko Electronics Inc.), weigh 6.0 to 8.0 mg of the sample into an aluminum pan, raise the temperature to 350 ° C at a heating rate of 10 ° C / min, and set the endothermic peak. Measure. The endothermic peak on the highest temperature side is the boiling point.

[Viscosity of insulating liquids and liquid developers at 25 ° C]
Put 6 to 7 mL of the measuring solution in a 10 mL screw tube, and use the rotary vibration viscometer "Viscomate VM-10A-L" (manufactured by Seconic Co., Ltd., detection terminal: titanium, φ8 mm) at the tip of the detection terminal. Fix the screw tube at the position where the liquid level comes 15 mm above the part, and measure the viscosity at 25 ° C.

[Solid concentration of toner particle dispersion and liquid developer]
Dilute 10 parts by mass of the sample with 90 parts by mass of hexane and rotate for 20 minutes at a rotation 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 liquid by decantation, the lower layer is dried in a vacuum dryer at 0.5 kPa at 40 ° C. for 8 hours, and the solid content concentration is calculated from the following formula.

[Volume medium particle size of toner particles in liquid developer (D ₅₀ )]
Using the laser refraction / scattering particle size measuring device "Mastersizer 2000" (Malburn), Isopar L (Exxon Mobile, Isoparaffin, viscosity at 25 ° C, 1 mPa · s) is added to the measuring cell, and the scattering intensity is increased. _{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%.

[Glass transition temperature (Tg) of toner particles in liquid developer]
Using the differential scanning calorimeter "DSC210" (manufactured by Seiko Electronics Inc.), weigh 0.025 to 0.035 g of the liquid developer on an aluminum pan and raise the temperature from 0 ° C to 100 ° C at a temperature rise rate of 10 ° C / min. Then measure the endothermic peak. The temperature at the intersection of the extension of the baseline below the maximum peak temperature of heat absorption and the tangent line indicating the maximum slope from the rising portion of the peak to the peak of the peak is defined as the glass transition temperature.

Resin production example 1
The raw material monomers and esterification catalysts shown in Table 1 are placed in a 10 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, heated to 180 ° C. using a mantle heater, and then heated to 180 ° C. The temperature was raised to 220 ° C. over 10 hours, and the reaction was carried out at 220 ° C. Further, the reaction was carried out at 8.3 kPa until the softening point shown in Table 1 was reached to obtain a polyester resin (resin A) having the physical characteristics shown in Table 1.

Resin production example 2
Put the raw material monomers other than trimellitic anhydride shown in Table 1, the esterification catalyst and the polymerization inhibitor into a 10 L volume four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, and use a mantle heater. Then, the temperature was raised from 180 ° C. to 200 ° C. over 1 hour, the reaction was carried out at 200 ° C., then trimellitic anhydride was added, and the reaction was carried out at 200 ° C. until the softening point shown in Table 1 was reached. , A polyester resin (resin B) having the physical properties shown in Table 1 was obtained.

Dispersant Production Example 1
The polyalkyleneimine shown in Table 2 was placed in a 2 L four-necked flask equipped with a cooling tube, a nitrogen introduction tube, a stirrer, a dehydration tube and a thermocouple, and the inside of the reaction vessel was replaced with nitrogen gas. With stirring, a solution of polyisobutene succinic anhydride (PIBSA) shown in Table 2 dissolved in xylene was added dropwise at 25 ° C. over 1 hour. After completion of the dropping, the temperature was maintained at 25 ° C. for 30 minutes. Then, the inside of the reaction vessel was heated to 150 ° C. and held for 1 hour, then heated to 160 ° C. and held for 1 hour. The solvent was distilled off under reduced pressure to 8.3 kPa at 160 ° C., and the time point at which the peak of acid anhydride derived from PIBSA (1780 cm ^-1 ) disappeared from IR analysis and the peak derived from imide bond (1700 cm ^-1 ) occurred. As the reaction end point, a dispersant A having the physical properties shown in Table 2 was obtained.

Dispersant Production Example 2
100 g of the solvent (methyl ethyl ketone) was placed in a 2 L four-necked flask equipped with a cooling tube, a nitrogen introduction tube, a stirrer and a thermocouple, and the inside of the reaction vessel was replaced with nitrogen gas. The inside of the reaction vessel was heated to 80 ° C., and a mixture of the raw material monomer shown in Table 3 and the polymerization initiator was added dropwise over 2 hours to carry out the polymerization reaction. After completion of the dropping, the reaction was carried out at 80 ° C. for another 3 hours. The solvent was distilled off at 80 ° C. to obtain a dispersant C made of a copolymer having the physical characteristics shown in Table 3.

Examples 1 to 6 and Comparative Examples 1 to 5 (Examples 5 and 6 are reference examples)
Rotate 80 parts by mass of the binder resin and 20 parts by mass of the colorant "ECB-301" (manufactured by Dainichi Seika Kogyo Co., Ltd., Phthalocyanine Blue 15: 3) shown in Table 5 in advance using a 20 L volume Henchel mixer. After stirring and mixing at a number of 1500 r / min (peripheral speed 21.6 m / sec) for 3 minutes, the mixture was melt-kneaded under the conditions shown below.

[Melting and kneading conditions]
A continuous double open roll type kneader "Kneedex" (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 double open roll type kneader are high rotation side roll (front roll) rotation speed 75r / min (peripheral speed 32.4m / min), low rotation side roll (back roll) rotation speed 35r / min ( The peripheral speed was 15.0 m / min), and the roll gap at the end on the side of the kneaded material 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 supply speed 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 coarsely pulverized to about 1 mm using a hammer mill. The obtained coarsely pulverized product was finely pulverized and classified by an air flow jet mill "IDS" (manufactured by Nippon Pneumatic Co., Ltd.) to obtain toner particles having _{a volume medium particle size (D 50) of 10 μm.}

35 parts by mass of the obtained toner particles, 63.95 parts by mass of the insulating liquid shown in Table 5 (62.9 parts by mass only in Example 4), and 1.05 parts by mass of the dispersant shown in Table 5 (2.1 parts by mass only in Example 4) (toner). Put 3 parts by mass for 100 parts by mass of particles in a 1 L polyethylene container, and use "TK Robomix" (manufactured by Primix Co., Ltd.) under ice cooling at a rotation speed of 7,000 r / min for 30 minutes. Stirring was carried out to obtain a toner particle dispersion having a solid content concentration of 36% by mass.

Next, the obtained toner particle dispersion was rotated by a 6-cylinder sand mill "TSG-6" (manufactured by IMEX Co., Ltd.) at a volume filling rate of 60% by volume using zirconia beads having a diameter of 0.8 mm. Wet pulverization was performed at 1300 r / min (peripheral speed 4.8 m / sec) _{until the volume medium particle size (D 50) shown in Table 5 was reached.} After removing the beads by filtration, 44 parts by mass of the insulating liquid shown in Table 5 was added to 100 parts by mass of the filtrate to dilute the liquid, and the solid content concentration was adjusted to 25% by mass. The liquid having the physical properties shown in Table 5. A developer was obtained. However, in Comparative Examples 1 and 4, a liquid developer could not be obtained because the toner particle dispersion liquid solidified immediately after the start of wet pulverization.

Details of the insulating liquid used in Examples and Comparative Examples are as follows.

Test Example 1 [Storage stability]
5 g of the liquid developer was placed in a 10 mL screw tube and stored in a constant temperature bath at 50 ° C. for 15 hours. _{The volume median particle size (D 50} ) of the toner particles before and after storage was measured, and the storage stability was evaluated from the value (%) _{of D 50} after storage / D _{50 × 100 before storage.} The results are shown in Table 5. The closer the value is to 100%, the better the storage stability.

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

After holding the prepared thin film in a constant temperature bath at 80 ° C for 10 seconds, the temperature of the fixing roll was set to 90 ° C with an external fixing machine that took out the fixing machine of "OKI MICROLINE 3010" (manufactured by Oki Data Corporation) to the outside. It was set to and fixed at a fixing speed of 140 mm / sec. After that, the fixing roll temperature was set to 95 ° C., and the same operation was performed. While raising this to 140 ° C. by 5 ° C., the unfixed image was fixed at each temperature to obtain a fixed image.

The mending tape "Scotch Mending Tape 810" (manufactured by 3M, width 18 mm) was attached to the obtained fixed image, pressure was applied to the tape with a roller so that a load of 500 g was applied, and then the tape was peeled off. The image densities before and after the tape was applied were measured with a colorimeter "Gretag Macbeth Spectroeye" (manufactured by Gretag). The image printing unit measured each of three points and calculated the average value as the image density. The fixing rate (%) is calculated from the value of the image density after peeling / the image density before pasting × 100, and the temperature of the fixing roll at which the fixing rate first reaches 90% or more is set as the minimum fixing temperature, and the low temperature fixing property is evaluated. did. The results are shown in Table 5. The smaller the value, the better the low temperature fixability.

From the above results, it can be seen that the liquid developers of Examples 1 to 6 have a small particle size, a low viscosity, and good storage stability and low temperature fixability.
On the other hand, in Comparative Examples 1 and 4 in which methyl ester or ethyl ester was used as the saturated fatty acid ester, the toner particle dispersion was solidified due to poor dispersion of the toner particles during production, and a liquid developer was not obtained. Further, in Comparative Example 2 using an unsaturated fatty acid ester, the liquid developer becomes highly viscous due to aggregation of toner particles, and both storage stability and low-temperature fixability are insufficient, and Comparative Example using liquid paraffin. Comparative Example 5 using the liquid developer of No. 3 and the unsaturated fatty acid ester which is an ester of an unsaturated fatty acid having 18 carbon atoms and an alcohol having 4 carbon atoms lacks low-temperature fixability.

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

Claims (2)

A liquid developer containing toner particles containing a binder resin and a colorant, a dispersant, and an insulating liquid, wherein the binder resin contains a polyester resin.
The polyester-based resin is a polyester resin or a composite resin having a polyester resin and a styrene-based resin, and the polyester resin is a carboxylic acid component containing an alcohol component containing an aliphatic diol and a carboxylic acid-based compound having a valence of 2 or more. Is a polycondensate of
The dispersant contains a basic dispersant having an imino group,
The insulating liquid contains 50% by mass or more of a saturated fatty acid ester which is an ester of a saturated fatty acid having 8 or more and 16 or less carbon atoms and an alcohol having 3 or more and 6 or less carbon atoms.
The solid content concentration is 10% by mass or more and 50% by mass or less.
Solid concentration Ru der viscosity less 3 mPa · s or more 40 mPa · s at 25 ° C. of 25% by weight of the liquid developer, a liquid developer. Conductivity of the liquid developer is not more than 5.0 × 10 ^-8 S / m, the liquid developer according to claim 1 Symbol placement.