JP2022001914A - Liquid developer - Google Patents

Abstract

To provide a liquid developer having excellent fixability at low temperature with which vivid images with high image density can be obtained.SOLUTION: A liquid developer contains: toner particles which contain a binder resin containing a resin having an acid group, and coloring agents; and an insulating liquid. The toner particles contain an ester composition with its acid value equal to or higher than 5 mgKOH/g and its hydroxyl value equal to or lower than 5 mgKOH/g.SELECTED DRAWING: None

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.

Examples of the developer for electrophotographic include a dry developer that uses a toner component made of a material containing a colorant and a binder resin in a dry state, and a liquid developer in which the toner component is dispersed in an insulating liquid. Since the toner particles are dispersed in the oil in the insulating liquid, the particle size can be reduced as compared with the dry developer.

Patent Document 1 discloses a liquid developer having excellent low-temperature fixability, high-temperature fixability, and dispersion stability of toner particles, in which the toner particles contain a synthetic ester wax as a release agent.

Japanese Unexamined Patent Publication No. 2019-012220

Since the thickness of the printed matter produced by the liquid developer becomes thinner due to the smaller particle size of the toner particles, it is necessary to increase the amount of the colorant in the toner in order to obtain the desired image density. However, when the amount of the colorant is large, it becomes difficult to disperse the colorant in the toner, and it is difficult to obtain a high image density.

The present invention relates to a liquid developer having good low temperature fixability, high image density, and a vivid image.

The present invention is a liquid developer containing a binder resin containing a resin having an acidic group, toner particles containing a colorant, and an insulating liquid, wherein the toner particles further have an acid value of 5 mgKOH / g. The above relates to a liquid developer containing an ester composition having a hydroxyl value of 5 mgKOH / g or less.

The liquid developer of the present invention has good low-temperature fixability, has high image density, and is excellent in obtaining a vivid image.

The liquid developer of the present invention contains a binder resin containing a resin having an acidic group, toner particles containing a colorant, and an insulating liquid, and the toner particles are esters having a specific acid value and hydroxyl value. It has a great feature in that it contains a composition, which makes it possible to obtain a vivid image having excellent low-temperature fixability and high image density. Although the reason for achieving such an effect is not clear, the toner particles contain an ester composition that interacts with the resin having an acidic group and the colorant, so that the dispersibility of the colorant in the resin is high. It is presumed that it is due to becoming.

The ester composition is a reaction product of an acid and an alcohol having an acid value of 5 mgKOH / g or more and a hydroxyl value of 5 mgKOH / g or less, preferably a reaction product of a carboxylic acid and an alcohol, and a reaction product of an aliphatic carboxylic acid and an aliphatic alcohol. Is more preferable. The aliphatic carboxylic acid and the aliphatic alcohol may be a saturated aliphatic or an unsaturated aliphatic, but in the present invention, the saturated aliphatic is preferable from the viewpoint of low temperature fixability.

The aliphatic carboxylic acid may be any of an aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid, and a trivalent or higher valent aliphatic carboxylic acid.

The aliphatic monocarboxylic acid has preferably 12 or more carbon atoms, more preferably 14 or more, still more preferably 16 or more, still more preferably 18 or more, and preferably 28 or less, more preferably from the viewpoint of low temperature fixability. It is preferably 26 or less, more preferably 24 or less, still more preferably 22 or less, still more preferably 20 or less.

Examples of the aliphatic monocarboxylic acid include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and montanic acid.

The number of carbon atoms of the aliphatic dicarboxylic acid is preferably 2 or more, more preferably 4 or more, still more preferably 6 or more, still more preferably 8 or more, and from the viewpoint of low temperature fixability, preferably 14 or less, more preferably. Is 12 or less.

Examples of the aliphatic dicarboxylic acid include succinic acid, fumaric acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid and the like.

Examples of the trivalent or higher aliphatic carboxylic acid include citric acid, isocitric acid, and polyacrylic acid.

The carboxylic acid may be subjected to the reaction in the state of an alkyl ester, preferably an alkyl ester having an alkyl group having 1 or more and 3 or less carbon atoms, an anhydride or the like.

The aliphatic alcohol may be any of an aliphatic monoalcohol, an aliphatic diol, and an aliphatic alcohol having a valence of 3 or more.

The aliphatic monoalcohol preferably has 12 or more carbon atoms, more preferably 14 or more, still more preferably 16 or more, still more preferably 18 or more, and preferably 28 or less, more preferably from the viewpoint of low temperature fixability. Is 26 or less, more preferably 24 or less, still more preferably 22 or less, still more preferably 20 or less.

Examples of the aliphatic monoalcohol include lauryl alcohol, stearyl alcohol, and behenyl alcohol.

The aliphatic diol preferably has 2 or more carbon atoms, more preferably 4 or more, still more preferably 6 or more, and from the viewpoint of low temperature fixability, it is preferably 14 or less, more preferably 12 or less, still more preferably. It is 10 or less, more preferably 8 or less.

Examples of the aliphatic diol include ethylene glycol 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, 1,12-dodecanediol, and 1,14-tetradecanediol. Of these, ethylene glycol or 1,6-hexanediol is preferred.

Examples of the trivalent or higher fatty alcohol include glycerin, trimethylolpropane, pentaerythritol, and dipentaerythritol.

Either the carboxylic acid or the alcohol is preferably monovalent. Therefore, the ester composition is preferably a reaction product of a polycarboxylic acid (a carboxylic acid having a divalent value or higher) and a monoalcohol, or a reaction product of a monocarboxylic acid and a polyol (an alcohol having a divalent value or higher), and the polycarboxylic acid and the reaction product. Monoalcoholic reactants are more preferred. The valence of the carboxylic acid is preferably divalent or more and tetravalent or less, more preferably divalent or trivalent, and further preferably divalent.

The ester composition comprises, for example, carboxylic acid and alcohol 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, etc., preferably 130. It can be produced by condensation at a temperature of ° 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. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably more preferably, with respect to 100 parts by mass of the total amount of alcohol and carboxylic acid. It is 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, more preferably, with respect to 100 parts by mass of the total amount of alcohol and carboxylic acid. Is less than 0.1 parts by mass. Examples of the polymerization inhibitor include tert-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, more preferably more preferably, with respect to 100 parts by mass of the total amount of alcohol and carboxylic acid. It is 0.1 parts by mass or less.

The acid value of the ester composition is 5 mgKOH / g or more, preferably 10 mgKOH / g or more, more preferably 15 mgKOH / g or more, and the toner particles, from the viewpoint of dispersibility and low temperature fixability of the colorant. From the viewpoint of dispersion stability, it is preferably 40 mgKOH / g or less, more preferably 30 mgKOH / g or less, and further preferably 25 mgKOH / g or less.

The hydroxyl value of the ester composition is 5 mgKOH / g or less, preferably 3 mgKOH / g or less, more preferably 1 mgKOH / g or less from the viewpoint of dispersion stability of the toner particles, and from the viewpoint of low temperature fixability. It is preferably 0.01 mgKOH / g or more, more preferably 0.05 mgKOH / g or more, and further preferably 0.1 mgKOH / g or more.

The acid value and hydroxyl value of the ester composition can be adjusted by the ratio of alcohol and carboxylic acid and the reaction rate. For example, increasing the proportion of alcohol gives an ester composition with a high hydroxyl value, and increasing the proportion of carboxylic acid gives an ester composition with a high acid value.

The number average molecular weight of the ester composition is preferably 500 or more, more preferably 600 or more, still more preferably 700 or more from the viewpoint of storage stability, and preferably 2,000 or less, more preferably 1,500 from the viewpoint of low temperature fixability. Below, it is more preferably 1,200 or less.

The weight average molecular weight of the ester composition is preferably 500 or more, more preferably 700 or more, still more preferably 800 or more from the viewpoint of storage stability, and preferably 3000 or less, more preferably from the viewpoint of low temperature fixability. Is 2000 or less, more preferably 1500 or less.

The ester composition is preferably crystalline and has a melting point. The melting point of the ester composition is preferably 50 ° C. or higher, more preferably 60 ° C. or higher from the viewpoint of storage stability, and preferably 100 ° C. or lower, more preferably 90 ° C. or lower, from the viewpoint of low temperature fixability. It is more preferably 80 ° C. or lower, still more preferably 70 ° C. or lower. Here, the melting point of the ester composition corresponds to the maximum peak temperature of endotherm described later. Here, the maximum endothermic temperature refers to the temperature of the peak having the largest peak area among the endothermic peaks observed by the differential scanning calorimeter.

The content of the ester composition is preferably 1 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more, and more preferably 3 parts by mass or more, based on 100 parts by mass of the total of the binder resin and the colorant. It is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 10 parts by mass or less.

The content of the ester composition in the toner particles is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass or more, and preferably 30% by mass or less, more preferably. It is 20% by mass or less, more preferably 10% by mass or less.

In the present invention, the binder resin contains a resin having an acidic group.

As the resin having an acidic group, a polyester resin such as a polyester resin or a composite resin having a polyester resin and another resin such as a styrene resin is preferable. Further, the polyester resin may be a modified polyester resin modified to such an extent that the characteristics are not substantially impaired.

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 an aliphatic diol having 2 or more and 20 or less carbon atoms, preferably 2 or more and 15 or less carbon atoms, and more preferably 2 or more and 10 or less carbon atoms, or the formula (I) :.

(In the formula, OR and RO are oxyalkylene groups, R is an ethylene group and / or a propylene group, and x and y indicate the average number of moles of alkylene oxide added, which are positive numbers, respectively, and x and y. The value of the sum of 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 having 2 or more and 20 or less carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol. Be done.

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 liquid developer is improved, and the dispersion stability of the toner particles is improved to improve the storage stability. From the viewpoint of improvement, an alkylene oxide adduct of bisphenol A represented by the formula (I) is preferable. The content of 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, still more preferably 90 mol% or more in the alcohol component. It is 95 mol% or more, more preferably 100 mol%.

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

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

As the carboxylic acid component, terephthalic acid and / or fumaric acid is preferable, and terephthalic acid is more 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. preferable. The content of terephthalic acid or fumaric acid or the total content of both is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more, still more preferably 90 mol% or more in the carboxylic acid component. The above is more preferably 95 mol% or more, still more preferably 100 mol%.

The trivalent or higher carboxylic acid compound preferably has 4 or more and 20 or less carbon atoms, more preferably 6 or more and 20 or less carbon atoms, still more preferably 7 or more and 15 or less carbon atoms, and further preferably 8 or more and 12 or less carbon atoms. More preferably, a trivalent or higher carboxylic acid having 9 or more and 10 or less carbon atoms, an anhydride thereof, or a derivative such as an alkyl ester having 1 or more and 3 or less carbon atoms can be mentioned. 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 compound having a valence of 3 or more is preferably 1 mol% or more, more preferably 2 mol% or more in the carboxylic acid component from the viewpoint of improving the hot offset resistance of the toner and improving the pulverizability of the toner particles. , More preferably 3 mol% or more, and preferably 40 mol% or less, more preferably 35 mol% or less, still more preferably 30 mol% or less.

Further, the carboxylic acid component preferably contains an acid-modified product of the α-olefin polymer from the viewpoint of low-temperature fixability.

The α-olefin has preferably 4 or more carbon atoms, preferably 18 or less, more preferably 10 or less, still more preferably 7 or less, still more preferably 5 or less, still more preferably 4.

Examples of the α-olefin polymer include polyisobutene-based polymers, poly1-butene-based polymers, poly1-pentene-based polymers, poly1-hexene-based polymers, poly1-octene-based polymers, and poly4-methylpentene. Examples thereof include a system polymer, a poly1-dodecene polymer, a 1-hexadecene polymer, a propylene-hexene copolymer and the like, and among these, a polyisobutene polymer is preferable.

On the other hand, as the acid-modified product A, at least the α-olefin polymer was selected from the group consisting of maleic acid, fumaric acid, itaconic acid, and anhydrides of these acids from the viewpoint of reactivity with the polyester resin. An acid-modified product modified with one kind of acid is preferable, and an acid-modified product modified with maleic anhydride is more preferable.

The content of the acid-modified product A is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, still more preferably 1.5 parts by mass with respect to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component other than the acid-modified product A. It is more than parts by mass, and is preferably 30 parts by mass or less, more preferably 25 parts by mass or less, and further preferably 20 parts by mass or less from the viewpoint of hot offset resistance and storage stability.

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 1.2 or less, more preferably 1.05 or less, and even more preferably 1 or less.

The polyester resin, for example, contains 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 1.0 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 tert-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 composite resin containing the polyester resin and the styrene resin, the styrene resin is at least styrene or a styrene derivative such as α-methylstyrene or vinyltoluene (hereinafter, styrene and styrene derivative are collectively referred to as "styrene compound". It is an addition polymer of the raw material monomer containing).

The content of the styrene compound, preferably styrene, is preferably 50% by mass or more, more preferably 70% by mass or more, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability in the raw material monomer of the styrene resin. It is more preferably 80% by mass or more, and is preferably 95% by mass or less, more preferably 93% by mass or less, still more preferably, from the viewpoint of improving the low temperature fixability of the toner and the wet grindability. It is 90% by mass or less.

Further, the styrene resin may contain a (meth) acrylic acid alkyl ester having an alkyl group having 7 or more carbon atoms as a raw material monomer. Examples of the (meth) acrylic acid alkyl ester include (meth) acrylic acid 2-ethylhexyl, (meth) acrylic acid (iso) octyl, (meth) acrylic acid (iso) decyl, and (meth) acrylic acid (iso) stearyl. Can be mentioned. It is preferable to use one or more of these. In addition, in this specification, "(iso)" means to include both the case where this group is present and the case where this group is not present, and it is normal when these groups are not present. Show that. Further, "(meth) acrylic acid" indicates acrylic acid, methacrylic acid, or both.

The carbon number of the alkyl group in the (meth) acrylic acid alkyl ester as the raw material monomer of the styrene resin is preferably 7 or more, more preferably 8 or more, and preferably 8 or more, from the viewpoint of improving the low temperature fixability of the toner. Is 12 or less, more preferably 10 or less. The carbon number of the alkyl ester means the number of carbon atoms derived from the alcohol component constituting the ester.

Raw material monomers for styrene-based resins include raw material monomers other than styrene compounds and (meth) acrylic acid alkyl esters, for example, ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; vinyl chloride and the like. Halovinyls; Vinyl esters such as vinyl acetate and vinyl propionate; Ethylene monocarboxylic acid esters such as dimethylaminoethyl (meth) acrylate; Vinyl ethers such as methyl vinyl ether; Vinylidene halides such as vinylidene chloride; N-vinyl N-vinyl compounds such as pyrrolidone may be contained.

The addition polymerization reaction of the raw material monomer of the styrene resin shall be carried out by a conventional method in the presence of, for example, a polymerization initiator such as dicumyl peroxide, a polymerization inhibitor, a cross-linking agent, etc., in the presence of an organic solvent or in the absence of a solvent. However, the temperature conditions are preferably 110 ° C. or higher, more preferably 140 ° C. or higher, and preferably 200 ° C. or lower, more preferably 170 ° C. or lower.

When an organic solvent is used in the addition polymerization reaction, xylene, toluene, methyl ethyl ketone, acetone and the like can be used. The amount of the organic solvent used is preferably 10 parts by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the raw material monomer of the styrene resin.

The composite resin is preferably a resin in which a polyester resin and a styrene resin are bonded, and is chemically bonded via both reactive monomers that can react with both the raw material monomer of the polyester resin and the raw material monomer of the styrene resin. It is more preferable that it is a resin.

The bireactive monomer contains at least one functional group selected from the group consisting of a hydroxyl group, a carboxy group, an epoxy group, a primary amino group and a secondary amino group, preferably a hydroxyl group and / or a carboxy group. A compound having a group, more preferably a carboxy group and an ethylenically unsaturated bond is preferable, and at least one selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid and maleic anhydride is more preferable. From the viewpoint of the reactivity of the polycondensation reaction and the addition polymerization reaction, at least one selected from the group consisting of acrylic acid, methacrylic acid and fumaric acid is more preferable. However, when used together with a polymerization inhibitor, a polyvalent carboxylic acid compound having an ethylenically unsaturated bond such as fumaric acid functions as a raw material monomer for a polyester resin. In this case, fumaric acid and the like are not bireactive monomers but raw material monomers for polyester resin.

From the viewpoint of low-temperature fixability, the amount of the bireactive monomer used is preferably 1 mol or more, more preferably 2 mol or more, and the styrene-based resin with respect to a total of 100 mol of the alcohol component of the polyester resin. From the viewpoint of enhancing the dispersibility with the polyester resin and improving the durability of the toner, it is preferably 30 mol or less, more preferably 20 mol or less, still more preferably 10 mol or less.
Further, the amount of both reactive monomers used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, based on 100 parts by mass of the total of the raw material monomers of the styrene resin, from the viewpoint of low temperature fixability. Then, from the viewpoint of enhancing the dispersibility between the styrene resin and the polyester resin and improving the durability of the toner, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and further preferably 10 parts by mass or less. Here, the polymerization initiator is included in the total of the raw material monomers of the styrene resin.

Specifically, the composite resin is preferably produced by the following method. When a bireactive monomer is used, the bireactive monomer is used in an addition polymerization reaction together with a raw material monomer of a styrene resin from the viewpoint of improving the durability of the toner and improving the low temperature fixability and heat storage stability of the toner. Is preferable.

(i) A method of performing a polycondensation reaction step (A) using a polyester resin raw material monomer and then an addition polymerization reaction (B) using a styrene resin raw material monomer and a bireactive monomer. In this method, a polycondensation reaction is performed. The step (A) is carried out under the reaction temperature condition suitable for the above, the reaction temperature is lowered, and the step (B) is carried out under the temperature condition suitable for the addition polymerization reaction. The raw material monomer of the styrene resin and the bireactive monomer are preferably added into the reaction system at a temperature suitable for the addition polymerization reaction. Both reactive monomers undergo an addition polymerization reaction and also react with a polyester resin.
After the step (B), the reaction temperature is raised again, and if necessary, a raw material monomer of a polyester resin having a valence of 3 or more as a cross-linking agent is added to the polymerization system, and the polycondensation reaction and both reactions in the step (A) are performed. The reaction with the sex monomer can be further advanced.

(ii) A method of carrying out a polycondensation reaction step (A) using a polyester resin raw material monomer after an addition polymerization reaction step (B) using a styrene resin raw material monomer and a bireactive monomer. In this method, an addition polymerization reaction is performed. Step (B) is carried out under the reaction temperature condition suitable for the above, the reaction temperature is raised, and the polycondensation reaction of the step (A) is carried out under the temperature condition suitable for the polycondensation reaction. Both reactive monomers are involved in the polycondensation reaction as well as the addition polymerization reaction.
The raw material monomer of the polyester resin may be present in the reaction system during the addition polymerization reaction, or may be added to the reaction system under temperature conditions suitable for the polycondensation reaction. In the former case, the progress of the polycondensation reaction can be regulated by adding an esterification catalyst at a temperature suitable for the polycondensation reaction.

(iii) The reaction is carried out under the condition that the polycondensation reaction step (A) using the raw material monomer of the polyester resin and the polycondensation reaction step (B) using the raw material monomer of the styrene resin and the bireactive monomer proceed in parallel. Method of performing In this method, the step (A) and the step (B) are performed in parallel under the reaction temperature condition suitable for the polycondensation reaction, the reaction temperature is raised, and the temperature condition suitable for the polycondensation reaction is performed. If necessary, it is preferable to add a raw material monomer of a trivalent or higher valent polyester resin as a cross-linking agent to the polymerization system to further carry out the polycondensation reaction in the step (A). At that time, under temperature conditions suitable for the polycondensation reaction, a polymerization inhibitor may be added to proceed only with the polycondensation reaction. Both reactive monomers are involved in the polycondensation reaction as well as the addition polymerization reaction.

In the method (i) above, a prepolymerized polycondensation resin may be used instead of the step (A) for carrying out the polycondensation reaction. In the method (iii) above, when the reaction is carried out under the condition that the step (A) and the step (B) proceed in parallel, the raw material monomer of the styrene resin is contained in the mixture containing the raw material monomer of the polyester resin. It is also possible to drop and react the mixture containing the above.

The above methods (i) to (iii) are preferably performed in the same container.

The mass ratio of the polyester resin to the styrene resin (polyester resin / styrene resin) in the composite resin is preferably 98/2 or less, more preferably 95/5 or less, still more preferably 90/10 or less from the viewpoint of pulverizability. And, from the viewpoint of low temperature fixability, it is preferably 60/40 or more, more preferably 70/30 or more, and further preferably 80/20 or more. In the above calculation, the mass of the polyester resin is the amount obtained by subtracting the amount of reaction water (calculated value) dehydrated by the polycondensation reaction from the mass of the raw material monomer of the polyester resin used, and is a bireactive monomer. Is included in the amount of raw material monomer of the polyester resin. The amount of the styrene resin is the total amount of the raw material monomer of the styrene resin and the polymerization initiator.

Resins having an acidic group other than polyester resins include acrylic resins such as (meth) acrylic acid polymers, copolymers of (meth) acrylic acid and alkyl esters of (meth) acrylic acid, ethylene, propylene and the like. Examples thereof include a polymer of olefin and (meth) acrylic acid and / or a polymer of an alkyl ester of (meth) acrylic acid, and an ionomer of ethylene and (meth) acrylic acid.

The alkyl group of the (meth) acrylic acid alkyl ester preferably has 1 or more and 5 or less carbon atoms.

The proportion of olefin in the copolymer of olefin and (meth) acrylic acid and / or the copolymer of alkyl ester of (meth) acrylic acid is preferably 80% by mass or more and 99.9% by mass or less.

The softening point of the resin having an acidic group is preferably 70 ° C. or higher, more preferably 75 ° C. or higher, and the liquid developer, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of improving low temperature fixability, it is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, still more preferably 120 ° C. or lower, still more preferably 110 ° C. or lower.

The glass transition temperature of the resin having an acidic group is preferably 40 ° C. or higher, more preferably 45 ° C. or higher, and low temperature fixability from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of improving the temperature, the temperature is preferably 80 ° C. or lower, more preferably 70 ° C. or lower, and further preferably 60 ° C. or lower.

The acid value of the resin having an acidic group is preferably 3 mgKOH / g or more, more preferably 3 mgKOH / g or more, from the viewpoint of reducing the viscosity of the liquid developer and improving the dispersion stability of the toner particles to improve the storage stability. It is 5 mgKOH / g or more, more preferably 8 mgKOH / g or more, and preferably 60 mgKOH / g or less, more preferably 50 mgKOH / g or less, still more preferably 40 mgKOH / g or less, still more preferably 30 mgKOH / g or less. The acid value of the resin is adjusted 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-based compound having a valence of 3 or more. be able to.

The content of the resin having an acidic group is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 100% by mass, that is, only the resin having an acidic group is used in the binder resin. However, a resin other than the resin having an acidic group may be contained as long as the effect of the present invention is not impaired. Examples of the resin other than the resin having an acidic group include polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, and styrene-maleic acid. Polymers, styrene-acrylic acid ester copolymers, styrene-based resins, epoxy-based resins, rosin-modified maleic acid, which are homopolymers or copolymers containing styrene or styrene-substituted products such as styrene-methacrylic acid ester copolymers. One or more selected from resins such as resins, polyethylene-based resins, polypropylene-based resins, polyurethane-based resins, silicone-based resins, phenol-based resins, polyamide resins, aliphatic or alicyclic hydrocarbon resins can be mentioned.

The content of the binder resin is preferably 30% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, and preferably 95% by mass or more in the toner particles. It is mass% or less, more preferably 90% by mass or less, still more preferably 85% by mass or less.

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.

Examples of the method for producing the toner particles include a method of melt-kneading a toner raw material containing a binder resin, a colorant, and an ester composition, and pulverizing the obtained melt-kneaded product. From the viewpoint of improving developability and fixability, a method in which the toner raw material is melt-kneaded and then pulverized is preferable.

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 present invention, an open roll type kneader is preferable from the viewpoint of improving the dispersibility of the colorant and the like 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.

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.

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 4 μm or more, from the viewpoint of improving the productivity of the wet pulverization step described later. It is 15 μm or less, 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 to be subjected to wet grinding is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and further 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. , More preferably 40 parts by mass or more, further 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. Parts or less, more 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 polyester resin. 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 16 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 having 16 or more carbon atoms, a hydrocarbon having a reactive functional group 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 16 or more carbon atoms, a polymer of hydroxycarboxylic acid having 16 or more carbon atoms and 24 or less carbon atoms is preferable, and examples thereof include a polymer of 18-hydroxystearic acid.

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 from the viewpoint of solubility of the dispersant in an insulating liquid. , 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 toner particles, from the viewpoint of the adsorptivity of the polyester resin to the resin. From the viewpoint of dispersibility, 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 16 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, and among these, a carboxy group or an epoxy group is preferable from the viewpoint of safety and reactivity. 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 group raw 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 basic dispersant is preferably 3/97 or more from the viewpoint of adsorptivity to toner particles, and more. It is preferably 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 basic dispersant can be measured by NMR of the basic dispersant, but the basic dispersion in which the basic nitrogen-containing base material and the dispersible group raw material are reacted. In the production of the agent, the mass ratio of the reacted 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.

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. It is more preferably 70% by mass or more, further preferably 90% by mass or more, still more preferably 95% by mass or more, still more 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. It is × 10 ^-12 S / m or less, and preferably 1.0 × 10 ^-13 S / m or more.

Examples of the insulating liquid include hydrocarbon-based insulating liquids such as aliphatic hydrocarbons, alicyclic hydrocarbons and aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, vegetable oils and the like. In addition to these viewpoints, the insulating liquid in the present invention may contain a hydrocarbon-based insulating liquid from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. preferable. As the hydrocarbon-based insulating liquid, an acyclic hydrocarbon-based insulating liquid is preferable, an aliphatic hydrocarbon-based solvent is more preferable, and polyisobutene is further preferable from the viewpoint of dispersion stability and chargeability.

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

The content of polyisobutene is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, still more preferably 60% by mass in the insulating liquid from the viewpoint of dispersion stability. As mentioned above, it is more preferably 80% by mass or more, still more preferably 90% by mass or more.

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

Specific examples other than polyisobutene include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, vegetable oils and the like.

The boiling point of the insulating liquid is preferably 120 ° C. or higher, more preferably 140 ° C. or higher, still more preferably 160 ° C. or higher, and from the viewpoint of further improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of further improving the low-temperature fixability of the toner and further improving the pulverizability of the toner during wet grinding to obtain toner particles having a small particle size, the temperature is preferably 300 ° C. or lower, more preferably 280 ° C. or lower, still more preferable. Is below 260 ° C. When two or more kinds of insulating liquids are combined, it is preferable that the boiling point of the combined insulating liquid mixture is within the above range.

The viscosity of the insulating liquid at 25 ° C. is preferably 1 mPa · s or more, and preferably 100 mPa, from the viewpoint of improving the developability and the storage stability of the toner particles in the liquid developer. -S or less, more preferably 50 mPa · s or less, still more preferably 20 mPa · s or less, still more preferably 10 mPa · s or less, still more preferably 5 mPa · s or less.

In addition to binder resins, colorants, ester compositions, dispersants, and insulating liquids, liquid developers include mold release agents, charge control agents, charge control resins, magnetic powders, fluidity improvers, and conductivity adjustments. It may contain an agent, a reinforcing filler such as a fibrous substance, an antioxidant, an additive such as a cleaning property improving agent, and the like as appropriate.

The liquid developer is obtained by dispersing the 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 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.). TK 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 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 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 37 mPa · s or less, more preferably 35 mPa · s or less, still more preferably 32 mPa · s or less, still more preferably 28 mPa · s or less, still more preferably 24 mPa · s or less, still more preferably 20 mPa · s or less, still more preferably. It is 16 mPa · s or less. The viscosity of the liquid developer having a solid content concentration of 25% by mass here means the viscosity measured by adjusting the amount of the insulating liquid to adjust the solid content concentration of the liquid developer to 25% by mass. do. If the solid content concentration of the liquid developer is higher than 25% by mass, it is adjusted by diluting it with the same insulating liquid, and if it is lower than 25% by mass, the insulating liquid is removed by concentration or the like. can do. Here, the solid content concentration refers to the ratio of raw materials other than the insulating liquid in the liquid developer containing the binder resin, the colorant, the ester composition and the insulating liquid. In addition to the binder resin, the colorant, and the ester composition, the raw materials other than the insulating liquid also include additives such as a mold release agent and a charge control agent, which are used as needed.

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 and ester composition]
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)).

[Hydroxy group value of ester composition]
Measure based on 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 tetrahydrofuran.

[Number average molecular weight and weight average molecular weight of ester composition]
Dissolve the sample in tetrahydrofuran to a concentration of 0.5 g / 100 mL. Next, this solution is filtered using a fluororesin filter "DISMIC-25JP" (manufactured by ADVANTEC) having a pore size of 0.2 μm to remove insoluble components, and the sample solution is used.
Using the following measuring device and analytical column, run tetrahydrofuran as an eluent at a flow rate of 1 mL / min to 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.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: GMHXL + G3000HXL (manufactured by Tosoh Corporation)

[Melting point of ester composition (maximum endothermic temperature)]
Using the differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), weigh 0.01 to 0.02 g of the sample in an aluminum pan, and cool down from room temperature (25 ° C) to 10 ° C. Cool to 0 ° C at / min and maintain at 0 ° C for 1 minute. Then, the temperature is measured at a heating rate of 10 ° C./min. Of the observed endothermic peaks, the temperature of the peak with the largest peak area (maximum endothermic temperature) is defined as the melting point.

[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 of basic nitrogen-containing raw materials]
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. At this time, the calibration curve includes several types of standard pullulan (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 ), P-800 (Mw 7.08 × 10 ⁵ )) is used 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 of dispersible group raw materials]
(1) Preparation of sample solution Dissolve the dispersible base material 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 (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 numbers in parentheses indicate the molecular weight.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: TSKgel GMH _XL + TSKgel G3000H _XL (manufactured by Tosoh Corporation)

[Number average molecular weight of dispersant]
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 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 a calibration curve prepared in advance. At this time, the calibration curve includes several types of monodisperse polystyrene (A-500 (Mw 5.0 x 10 ² ), A-5000 (Mw 5.97 x 10 ³ ), F-2 (Mw 1.8 1 x 10) manufactured by Tosoh Corporation. ⁴ ), F-10 (Mw 9.64 × 10 ⁴ ), F-40 (Mw 4.27 × 10 ⁵ )) are used 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)

[Conductivity of insulating liquid]
Put 25 g of insulating liquid 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 attach the electrodes. 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.

[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.

[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%.

Resin production example 1
The raw material monomers of the polyester resin other than fumaric acid and trimellitic anhydride shown in Table 1 and the esterification catalyst were placed in a 10 L volume four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple. After raising the temperature to 230 ° C. using a mantle heater, the reaction was carried out at 230 ° C. for 8 hours, and the pressure was further reduced to 8.3 kPa for 1 hour. The temperature was lowered to 170 ° C., and the raw material monomer of the styrene resin shown in Table 1, the bireactive monomer and the polymerization initiator were added dropwise over 1 hour using a dropping funnel. The addition polymerization reaction was aged for 1 hour while being maintained at 170 ° C. Then, the temperature was raised to 210 ° C., the raw material monomer of the styrene resin was removed at 8.3 kPa for 1 hour, and the reaction between the bireactive monomer and the polyester resin moiety was carried out. Further, at 210 ° C., trimellitic anhydride, fumaric acid and a polymerization inhibitor were added, and the reaction was carried out until the softening point shown in Table 1 was reached to obtain a composite resin (resin P1) having the physical properties shown in Table 1. Obtained.

Resin production example 2
The polyester resin raw material monomers shown in Table 1, the esterification catalyst, and the polymerization inhibitor were placed in a 10 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple, and used with a mantle heater. The temperature is raised from 180 ° C to 210 ° C over 4 hours, the reaction is carried out at 210 ° C for 4 hours, and the reaction is further carried out at 8.3 kPa until the softening point shown in Table 1 is reached. A resin (resin P2) was obtained.

Resin production example 3
BPA-PO and BPA-EO shown in Table 1 are placed in a dehydration tube equipped with a nitrogen introduction tube, a 10 L volume four-necked flask equipped with a stirrer and a thermocouple, heated to 100 ° C., and then Table 1 The terephthalic acid shown in (1) is added, the temperature is raised to 160 ° C, the esterification catalyst and the esterification co-catalyst shown in Table 1 are added, the temperature is raised to 235 ° C, the reaction is carried out at 235 ° C for 10 hours, and then 235 ° C. , 8.0 kPa for 1 hour. After cooling to 160 ° C, polyisobutenyl succinic anhydride shown in Table 1 was added. The temperature is raised to 235 ° C again, and the polycondensation reaction is carried out at 235 ° C for 5 hours, then cooled to 200 ° C, the anhydrous trimellitic acid shown in Table 1 is added, and the polycondensation reaction is further carried out at 200 ° C for 1 hour. A polyester resin (resin P3) was obtained by reacting at 200 ° C. and 8.0 kPa until the softening point shown in Table 1 was reached.

Production Example of Ester Composition The raw material monomer and esterification catalyst shown in Table 2 are placed in a 10 L four-necked flask equipped with a thermometer, a stainless steel stirring rod, a flow-down condenser and a nitrogen introduction tube, and placed in a nitrogen atmosphere. The temperature was raised from 140 ° C to 200 ° C over 8 hours in a mantle heater. Then, the reaction was carried out at 200 ° C. at 8.0 kPa until the acid value shown in Table 2 was reached to obtain ester compositions (E1 and E2).

Dispersant Production Example 1
Polyethylenimine (polyethylenimine 600, manufactured by Genuine Kagaku Co., Ltd.) shown in Table 3 as a basic nitrogen-containing base raw material is equipped with a cooling tube, a nitrogen introduction tube, a stirrer, a dehydration tube, and a thermocouple. It was placed in a mouth flask and the inside of the reaction vessel was replaced with nitrogen gas. While stirring, a solution of polyisobutene succinic anhydride (PIBSA) (H1000, manufactured by Dover) shown in Table 3 as a dispersible base raw material in xylene shown in Table 3 was added dropwise at 25 ° C. over 1 hour. After completion of the dropping, the mixture was kept at room temperature 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. Xylene 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 D having the physical properties shown in Table 3 was obtained.

Examples 1 to 4 and Comparative Example 2
20 parts by mass of the binder resin shown in Table 4, 5 parts by mass of the ester composition, and 20 parts by mass of the colorant "ECB-301" (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue 15: 3). The mixture was stirred and mixed for 3 minutes at a rotation speed of 1500 r / min (peripheral speed 21.6 m / sec) using the Henchel mixer of the above, and then 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) peripheral speed 75r / min (rotation speed 32.4m / min), low rotation side roll (back roll) peripheral speed 35r / min ( The rotation 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 obtained kneaded product 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 and the insulating liquid "NAS-4" (manufactured by Nichiyu Co., Ltd., polyisobutene, conductivity: 1.52 x 10 ^-12 S / m, boiling point: 247 ° C, viscosity at 25 ° C: 2 mPa・ S) Put 63.95 parts by mass and 1.05 parts by mass of dispersant A in a 1 L polyethylene container, and use "TK Robomix" (manufactured by Primix Co., Ltd.) to cool the mixture to 7,000 r / min. The mixture was stirred for 30 minutes 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). After removing the beads by filtration, 44 parts by mass of the insulating liquid "NAS-4" (manufactured by Nichiyu Co., Ltd.) was added to 100 parts by mass of the filtrate to dilute it, and the solid content concentration was 25% by mass. A liquid developer having the physical properties shown in 4 was obtained.

Comparative Example 1
A liquid developer was obtained in the same manner as in Example 1 except that the ester composition was not used.

Test Example 1 [Dispersibility of colorant]
A liquid developer is dropped on "OK top coated paper" (manufactured by Oji Paper Co., Ltd., basis weight: 127.9 g / m ² , paper thickness: approx. 103 μm), and the toner mass after drying with a wire bar is 3.4 g / m. ^A thin film was prepared so as to be 2. Then, it was kept in a constant temperature bath at 80 ° C. for 10 seconds.

Subsequently, using a fixing machine taken out from "OKI MICROLINE 3010" (manufactured by Oki Data Corporation), the fixing process was performed at a fixing roll temperature of 100 ° C. and a fixing speed of 280 mm / sec. The image density and saturation of the obtained fixed image were measured by the following methods. The results are shown in Table 4. The higher the image density and saturation, the higher the dispersibility of the colorant.

[Image density]
Using the color meter "Gretag Macbeth Spectroeye" (manufactured by Gretag), the image density of the image print part is measured at 3 points each, and the average value is calculated. The larger the value, the better the image density.

〔saturation〕
Using the colorimeter "Gretag Macbeth Spectroeye" (manufactured by Gretag), the a ^* value and b ^* value of the image printed portion are measured at three points each, and the saturation C ^* is calculated from the following formula. The larger the value, the better the saturation.
C * = √ ((a ^* ) ² + (b ^* ) ² )

Test Example 2 [Low temperature fixability]
A liquid developer is dropped on "OK top coated paper" (manufactured by Oji Paper Co., Ltd., basis weight: 127.9 g / m ² , paper thickness: approx. 103 μm), and the toner mass after drying with a wire bar is 3.4 g / m. ^A thin film was prepared so as to be 2. Then, it was kept in a constant temperature bath at 80 ° C. for 10 seconds.

Subsequently, using a fixing machine taken out from "OKI MICROLINE 3010" (manufactured by Oki Data Corporation), the fixing process was performed at a fixing roll temperature of 80 ° C. and a fixing speed of 280 mm / sec. Then, while raising the fixing roll temperature to 120 ° C. by 10 ° C., the fixing process was carried out in the same manner, and a fixing image was obtained at each temperature.

Attach the mending tape "Scotch Mending Tape 810" (manufactured by 3M Japan Ltd., width 18 mm) to the obtained fixing image, apply pressure to the tape with a roller so that a load of 500 g is applied, and then apply the tape. It peeled off. The image densities before and after the tape peeling were measured using a colorimeter "Gretag Macbeth Spectroeye" (manufactured by Gretag). The image print portion was measured at 3 points each, and the average value was calculated as the image density. The fixing rate (%) is calculated from the value of the image density after peeling / the image density before peeling × 100, and the lowest temperature in the temperature range where the fixing rate is 90% or more and no offset occurs is defined as the minimum fixing temperature. did. The results are shown in Table 4. It is shown that the lower the minimum fixing temperature is, the better the low temperature fixing property is.

From the above results, it can be seen that the liquid developer of Examples 1 to 4 has excellent dispersibility of the colorant and good low-temperature fixability because an image having high image density and saturation is obtained. ..
On the other hand, in Comparative Example 1 in which the ester composition was not used, the dispersibility of the colorant was insufficient, so that the image density and saturation were low, and the adhesiveness to paper was insufficient, so that the low temperature fixability was achieved. Is declining. Further, the ester composition used in Comparative Example 2 is widely used as a synthetic ester wax, but the acid value is too low, so that the dispersibility of the colorant is insufficient, the image density and saturation are low, and the low temperature fixing is performed. The sex is also insufficient.

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 (6)

A liquid developer containing a binder resin containing a resin having an acidic group, toner particles containing a colorant, and an insulating liquid, wherein the toner particles further have an acid value of 5 mgKOH / g or more and a hydroxyl value. A liquid developer containing an ester composition of 5 mgKOH / g or less. The liquid developer according to claim 1, wherein the ester composition is a reaction product of a polycarboxylic acid and a monoalcohol. The liquid developer according to claim 1 or 2, wherein the content of the ester composition is 1% by mass or more and 30% by mass or less in the toner particles. The liquid developer according to any one of claims 1 to 3, wherein the resin having an acidic group is a polyester resin. The liquid developer according to any one of claims 1 to 4, further comprising a basic dispersant having a basic nitrogen-containing group. The liquid developer according to any one of claims 1 to 5, wherein the insulating liquid contains a hydrocarbon-based insulating liquid.