JP2020086378A - Liquid developer - Google Patents

Abstract

To provide a liquid developer capable of obtaining an image which is excellent in low temperature fixability and resistance to document offset, and is excellent in electrostatic chargeability.SOLUTION: A liquid developer contains an amorphous composite resin A, a crystalline resin B, toner particles containing a colorant and an insulative liquid, in which the amorphous composite resin A is a resin in which an amorphous polyester resin and a styrenic resin are chemically bonded to each other through a bireactive monomer-derived structural unit capable of reacting both a raw material monomer of the amorphous polyester resin and a raw material monomer of the styrenic resin, the amorphous composite resin A has a styrenic monomer-derived structural unit and an acrylic monomer-derived structural unit, and a mass ratio of the styrenic monomer-derived structural unit to the acrylic monomer-derived structural unit in the amorphous composite resin A (styrenic monomer-derived structural unit/acrylic monomer-derived structural unit) is 75/25 or more and less than 100/0.SELECTED DRAWING: None

Description

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

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

Patent Document 1 discloses a liquid developer containing toner particles, a specific polymer dispersant (C), and a carrier liquid (D), wherein the toner particles are a binder resin (A). Disclosed is a liquid developer containing a colorant (B) and the binder resin (A) containing a crystalline resin (A-1) and an amorphous resin (A-2). Has been done. And, in that example, 800 parts of amorphous polyester resin, 115 parts of styrene, 62 parts of 2-ethylhexyl acrylate, 20 parts of n-butyl acrylate and 3 parts of di-t-butyl peroxide were polymerized, It is disclosed that an amorphous resin containing a polyester resin and a styrene-acrylic copolymer resin is obtained.

Patent Document 2 discloses a liquid developer in which toner particles containing a polyester resin and a pigment are dispersed in an insulating liquid, wherein the polyester resin contains an aliphatic diol having 8 to 14 carbon atoms. Obtained by polycondensing a raw material monomer containing an alcohol component containing from 100 to 100 mol% and a carboxylic acid component containing from 60 to 100 mol% of an aliphatic dicarboxylic acid compound having 8 to 14 carbon atoms. It is disclosed that the polyester resin further comprises an amorphous polyester.

JP, 2005-145985, A JP, 2016-80837, A

In recent years, there has been an increasing demand for high image quality and high speed, so that a toner that can be fused and fixed with a small amount of heat, that is, a toner that is excellent in low-temperature fixability is required. Therefore, by including the crystalline polyester in the amorphous resin, the melt viscosity of the toner particles is lowered and the low temperature fixing can be achieved. However, because the melt viscosity of the toner particles has decreased, the toner particles printed on the media still maintain their meltability. When stored in, there is a tendency that a phenomenon in which images adhere to each other and become difficult to peel off, that is, a phenomenon in which document offset occurs.
In addition, since the crystalline polyester has a low aromatic ring concentration, it cannot hold an electric charge and tends to be inferior in charging property.

The present invention relates to a liquid developer which is excellent in low-temperature fixing property and document offset resistance and which can form an image having excellent charging property.

The present invention provides a liquid developer containing toner particles containing an amorphous composite resin A, a crystalline resin B, and a colorant, and an insulating liquid, wherein the amorphous composite resin A is amorphous. Is a resin in which a high quality polyester resin and a styrene resin are chemically bonded through a constitutional unit derived from a bireactive monomer capable of reacting with both a raw material monomer of an amorphous polyester resin and a raw material monomer of a styrene resin. And the amorphous composite resin A has a structural unit derived from a styrene-based monomer and a structural unit derived from an acrylic monomer, and the structural unit derived from a styrene-based monomer and the acrylic monomer in the amorphous composite resin A are present. The present invention relates to a liquid developer in which the mass ratio of constituent units derived (structural units derived from styrene-based monomer/structural units derived from acrylic monomer) is 75/25 or more and less than 100/0.

The liquid developer of the present invention is excellent in low-temperature fixing property and document offset resistance, and can obtain an image having excellent charging property.

The liquid developer of the present invention includes toner particles containing an amorphous polyester resin and an amorphous composite resin A having a predetermined amount or more of a styrene-based resin containing a structural unit derived from a styrene-based monomer, and a crystalline resin B. It has a great feature in points.
By containing both resins, the crystalline resin B is rapidly melted at the time of fixing, and the low temperature fixability is improved by compatibilizing and plasticizing the amorphous composite resin A containing the amorphous polyester resin. At room temperature after fixing, the compatibility between the amorphous composite resin A containing the styrene resin and the crystalline resin B is lowered, and the crystallization of the crystalline resin B is promoted, so that the amorphous resin once lowered at the time of fixing. It is assumed that the glass transition temperature of the composite resin is easily recovered and the occurrence of document offset is suppressed. Further, it is considered that the combination of the amorphous polyester resin and the styrene-based resin having a high proportion of the structural unit derived from the styrene-based monomer increases the aromatic ring concentration and improves the charging property.

In the liquid developer of the present invention, the toner particles contain the amorphous composite resin A, the crystalline resin B, and the colorant.
The crystallinity of the resin is represented by the ratio of the softening point to the maximum endothermic peak temperature measured by a differential scanning calorimeter, that is, the crystallinity index defined by the value of [softening point/maximum endothermic peak temperature]. The crystalline resin has a crystallinity index of 0.6 or more, preferably 0.7 or more, more preferably 0.9 or more, and 1.4 or less, preferably 1.2 or less, while the amorphous resin has a crystallinity index. The resin is more than 1.4, preferably 1.5 or more, more preferably more than 1.5, still more preferably 1.6 or more, or less than 0.6, preferably 0.5 or less. The crystallinity of the resin can be adjusted by the type and ratio of the raw material monomers, production conditions (for example, reaction temperature, reaction time, cooling rate), and the like. The maximum endothermic peak temperature refers to the temperature of the peak on the highest temperature side among the observed endothermic peaks. In the crystalline resin, the maximum peak temperature of endotherm is the melting point.

The amorphous composite resin A has a constitutional unit derived from a bireactive monomer capable of reacting with the amorphous polyester resin and the styrene resin as both the raw material monomer of the amorphous polyester resin and the raw material monomer of the styrene resin. It is a chemically bonded resin.

In the amorphous composite resin, the amorphous polyester resin is preferably a polycondensate of an alcohol component and a carboxylic acid component.

The alcohol component is used from the viewpoint of improving the low temperature fixing property of the toner, the viewpoint of improving the pulverizability of the toner to obtain a liquid developer having a small particle size, and the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. , Formula (I):

(In the formula, OR and RO are oxyalkylene groups, R is an ethylene and/or propylene group, x and y represent the average number of moles of alkylene oxide added, and each is a positive number. The value of the sum is 1 or more, preferably 1.5 or more, 16 or less, preferably 8 or less, more preferably 4 or less)
It is preferable that the alkylene oxide adduct of bisphenol A represented by

The content of the alkylene oxide adduct of bisphenol A in the alcohol component is 80 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, and further preferably 100 mol%.

Other alcohol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-butene. Examples thereof include diols, aliphatic diols such as 1,3-butanediol and neopentyl glycol, and trivalent or higher alcohols such as glycerin.

The carboxylic acid component preferably contains an aromatic dicarboxylic acid compound from the viewpoint of chargeability. In the present invention, the carboxylic acid compound includes not only a free acid, but also an anhydride that decomposes to form an acid during the reaction, and an alkyl ester having an alkyl group with 1 to 3 carbon atoms.

Examples of the aromatic dicarboxylic acid compound include phthalic acid, isophthalic acid, terephthalic acid; anhydrides of these acids and alkyl (C1 to C3) esters of these acids. Of these, terephthalic acid or isophthalic acid is preferable, and terephthalic acid is more preferable, from the viewpoint of low-temperature fixability.

The content of the aromatic dicarboxylic acid compound in the carboxylic acid component is preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 50 mol% or more, and from the viewpoint of low temperature fixability, It is preferably 95 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less.

Examples of other carboxylic acid components include aliphatic dicarboxylic acids, trivalent or higher carboxylic acids, anhydrides of these acids, and alkyl esters of these acids having 1 to 3 carbon atoms.

From the viewpoint of storage stability and durability, the carboxylic acid component preferably contains a trivalent or higher carboxylic acid compound.

Examples of trivalent or higher carboxylic acid compounds include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid), or acid anhydrides thereof. Etc.

The content of trivalent or higher carboxylic acid compounds in the carboxylic acid component is preferably 3 mol% or more, more preferably 5 mol% or more, more preferably 7 mol% or more, and from the viewpoint of low temperature fixability Therefore, it is preferably 30 mol% or less, more preferably 25 mol% or less, still more preferably 20 mol% or less.

A monovalent alcohol may be contained in the alcohol component, and a monovalent carboxylic acid compound may be contained in the carboxylic acid component 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, and 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 polycondensation reaction of the alcohol component and the carboxylic acid component is, for example, in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and if necessary, in the presence of an esterification promoter, a polymerization inhibitor, etc., preferably It can be carried out 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, titanium compounds such as titanium diisopropylate bistriethanolaminate, and the tin compounds are preferable. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 1 part by mass or less. Examples of the esterification promoter include gallic acid and the like. The amount of the esterification cocatalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, with respect to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is more preferably 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 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, with respect to the total amount 100 parts by mass of the alcohol component and the carboxylic acid component. It is preferably 0.1 part 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. The modified polyester resin is, for example, grafted or blocked with phenol, urethane, epoxy or the like by the method described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636 or the like. Among the modified polyester resins, urethane-modified polyester resins obtained by urethane-extending the polyester resin with a polyisocyanate compound are preferable.

In the amorphous composite resin, the styrene resin is an addition polymer of a raw material monomer containing at least a styrene monomer such as styrene, α-methylstyrene, and a styrene derivative such as vinyltoluene.

The content of styrene-based monomer, preferably styrene, in the raw material monomer of the styrene-based resin, from the viewpoint of chargeability, preferably 70 mass% or more, more preferably 80 mass% or more, more preferably 90 mass% or more, further It is preferably 95% by mass or more, and more preferably 100% by mass.

From the viewpoint of low-temperature fixability, the raw material monomer of the styrene resin preferably further contains at least one acrylic monomer selected from acrylic acid alkyl esters and methacrylic acid alkyl esters.

The number of carbon atoms of the alkyl group in the acrylic acid alkyl ester and methacrylic acid alkyl ester as the raw material monomer of the styrene resin is preferably 7 or more, more preferably 8 or more from the viewpoint of improving the low temperature fixing property of the toner. , And preferably 12 or less, more preferably 10 or less. The carbon number of the alkyl ester refers to the carbon number derived from the alcohol component constituting the ester.

Examples of the (meth)acrylic acid alkyl ester having an alkyl group having 7 or more carbon atoms include 2-ethylhexyl (meth)acrylic acid, (iso)octyl (meth)acrylic acid, (iso)decyl (meth)acrylic acid, and (meth)acrylic acid. ) Examples include (iso)stearyl acrylate. It is preferable to use one or more of these. In the present specification, “(iso)” is meant to include both the case where this group is present and the case where this group is not present, and is normal when these groups are not present. Indicates that. Further, "(meth)acrylic acid" means acrylic acid, methacrylic acid, or both.

The content of the acrylic monomer is preferably 30% by mass or less, more preferably 20% by mass or less, further preferably 10% by mass or less, and further preferably 5% by mass or less in the raw material monomer of the styrene resin.

Raw material monomers other than styrene-based monomers and acrylic-based monomers include ethylenically unsaturated monoolefins such as ethylene and propylene; diolefins such as butadiene; halovinyls such as vinyl chloride; Vinyl esters such as vinyl acetate and vinyl propionate; Ethylenic monocarboxylic acid esters such as dimethylaminoethyl (meth)acrylate; Vinyl ethers such as methyl vinyl ether; Vinylidene halides such as vinylidene chloride; N-vinylpyrrolidone etc. N-vinyl compounds and the like may be contained.

The addition polymerization reaction of the raw material monomer of the styrene resin, for example, in the presence of a polymerization initiator such as dicumyl peroxide, a polymerization inhibitor, a cross-linking agent, etc., in the presence of an organic solvent or without a solvent, by a conventional method However, the temperature condition is 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 or 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 constitutional unit derived from both reactive monomers is chemically bonded to both the amorphous polyester resin and the styrene resin. The constitutional unit derived from the bireactive monomer is, for example, one or more functional groups selected from the carboxy group and the hydroxy group of the amorphous polyester resin, and the hydroxy group, the carboxy group, the epoxy group and the primary amino group of the bireactive monomer. Group and one or more functional groups selected from secondary amino groups are bonded by a chemical reaction, and the ethylenically unsaturated bond of the styrene resin and the ethylenically unsaturated bond of both reactive monomers are chemically reacted. Examples of the constituent units are combined. Examples of the constitutional unit derived from both-reactive monomers include one or more constitutional units selected from acrylic acid-derived and methacrylic acid-derived.

The bireactive monomer has 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 in the molecule, 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. The bireactive monomer is preferably at least one acrylic monomer selected from acrylic acid and methacrylic acid. However, when used together with the polymerization inhibitor, the polyvalent carboxylic acid compound having an ethylenically unsaturated bond such as fumaric acid functions as a raw material monomer for the polyester resin. In this case, fumaric acid or the like is not a bireactive monomer but a raw material monomer for the polyester resin.

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

Specifically, the amorphous composite resin is preferably manufactured by the following method. When the bireactive monomer is used, the bireactive monomer is used in addition polymerization reaction together with the raw material monomer of the styrene resin from the viewpoint of improving the durability of the toner and improving the low temperature fixing property and heat resistant storage stability of the toner. Preferably.

(i) A method in which the step (A) of the polycondensation reaction with the raw material monomer of the polyester resin is followed by the step (B) of the addition polymerization reaction with the raw material monomer of the styrene resin and the bireactive monomer. The step (A) is carried out under reaction temperature conditions suitable for the above, the reaction temperature is lowered, and the step (B) is carried out under temperature conditions suitable for the addition polymerization reaction. It is preferable to add the raw material monomer of the styrene resin and the bireactive monomer to the reaction system at a temperature suitable for the addition polymerization reaction. The bireactive monomer undergoes addition polymerization reaction and also reacts with the amorphous polyester resin.
After the step (B), the reaction temperature is raised again, and if necessary, the raw material monomers of the amorphous polyester resin having a valence of 3 or more serving as a crosslinking agent are added to the polymerization system, and the polycondensation reaction of the step (A) is performed. It is possible to further proceed the reaction with the or both-reactive monomers.

(ii) Method of performing step (A) of polycondensation reaction with raw material monomer of amorphous polyester resin after step (B) of addition polymerization reaction with raw material monomer of styrene resin and bireactive monomer The step (B) is carried out under reaction temperature conditions suitable for the addition polymerization reaction, the reaction temperature is raised, and the polycondensation reaction of the step (A) is carried out under temperature conditions suitable for the polycondensation reaction. The bireactive monomer participates in the polycondensation reaction as well as the addition polymerization reaction.
The raw material monomer of the amorphous polyester resin may be present in the reaction system during the addition polymerization reaction, or may be added in the reaction system under a temperature condition suitable for the polycondensation reaction. In the former case, the progress of the polycondensation reaction can be controlled by adding an esterification catalyst at a temperature suitable for the polycondensation reaction.

(iii) Conditions under which the step (A) of polycondensation reaction with the raw material monomer of the amorphous polyester resin and the step (B) of addition polymerization reaction with the raw material monomer of the styrenic resin and both reactive monomers proceed in parallel In this method, step (A) and step (B) are performed in parallel under reaction temperature conditions suitable for addition polymerization reaction, the reaction temperature is raised, and temperature conditions suitable for polycondensation reaction are applied. It is preferable that, if necessary, a raw material monomer of a trivalent or higher-valent amorphous polyester resin which serves as a cross-linking agent is added to the polymerization system, and the polycondensation reaction of the step (A) is further performed. At that time, under a temperature condition suitable for the polycondensation reaction, a polymerization inhibitor may be added to proceed only the polycondensation reaction. The bireactive monomer participates in the polycondensation reaction as well as the addition polymerization reaction.

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

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

The mass ratio of the structural unit derived from the styrene monomer and the structural unit derived from the acrylic monomer in the amorphous composite resin A (the structural unit of the styrene monomer/the structural unit of the acrylic monomer) improves the charging property of the toner particles. From the viewpoint, it is 75/25 or more, preferably 80/20 or more, more preferably 82/18 or more, further preferably 85/15 or more, and from the viewpoint of low temperature fixing property, 99/1 or less. , Preferably 98/2 or less, more preferably less than 100/0. Here, the acrylic monomer is acrylic acid, methacrylic acid, or an alkyl ester thereof, and not only the acrylic monomer used as the raw material monomer of the styrene resin, but also the acrylic monomer used as the bireactive monomer. Including system monomers.
The mass ratio of the structural unit derived from the styrene-based monomer and the structural unit derived from the acrylic-based monomer can be calculated from the mass of the raw material monomer of the amorphous composite resin.

The mass ratio of the amorphous polyester resin and the styrene resin in the amorphous composite resin A (amorphous polyester resin/styrene resin) is preferably 60/40 or more, more preferably 70 from the viewpoint of low temperature fixability. /30 or more, more preferably 80/20 or more, and from the viewpoint of pulverizability, it is preferably 98/2 or less, more preferably 97/3 or less, and further preferably 96/4 or less. In the above calculation, the mass of the amorphous polyester resin is the mass of the raw material monomer of the amorphous polyester resin used, excluding the amount of reaction water dehydrated by the polycondensation reaction (calculated value). Yes, the amount of the bireactive monomer is included in the amount of the raw material monomer of the amorphous 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.

The softening point of the amorphous composite resin A is preferably 80° C. or higher, more preferably 85° C. or higher from the viewpoint of storage stability, and preferably 130° C. or lower, from the viewpoint of low temperature fixability. Is below 120°C.

The glass transition temperature of the amorphous composite resin A is preferably 40° C. or higher, more preferably 50° C. or higher from the viewpoint of storage stability, and preferably 80° C. or lower from the viewpoint of low temperature fixability. It is preferably 70°C or lower.

The acid value of the amorphous composite resin A is preferably 5 mgKOH/g or more, more preferably 10 mgKOH/g or more, from the viewpoint of charge rising property, and preferably 50 mgKOH/g or less, from the viewpoint of hygroscopicity. , And more preferably 40 mgKOH/g or less.

The content of the amorphous composite resin A in the toner particles is preferably 55% by mass or more, more preferably 60% by mass or more, further preferably 65% by mass or more, and from the viewpoint of pulverizability, it is preferably It is 97 mass% or less, more preferably 95 mass% or less, and further preferably 90 mass% or less.

As the crystalline resin B, a crystalline polyester resin is more preferable from the viewpoint of low temperature fixability and storability.

As the crystalline polyester resin, a polycondensate of an alcohol component containing an aliphatic diol and a carboxylic acid component containing an aliphatic dicarboxylic acid compound is preferable.

The carbon number of the aliphatic diol is preferably 2 or more, more preferably 4 or more, still more preferably 5 or more, from the viewpoint of crystal recovery of the crystalline polyester, and preferably 9 or less from the viewpoint of low temperature fixability. , More preferably 8 or less, still more preferably 7 or less.

Aliphatic diols having 2 to 9 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol. , 1,7-heptanediol, 1,8-octanediol, neopentyl glycol, 1,9-nonanediol and the like.

Further, the aliphatic diol having 2 or more and 9 or less carbon atoms is preferably an α,ω-aliphatic diol having a hydroxyl group at the end of the carbon chain from the viewpoint of improving the low temperature fixing property of the toner, and the α,ω-linear chain More preferably, it is an alkanediol.

The alcohol component may contain alcohol other than the aliphatic diol, but the content of the aliphatic diol, preferably the aliphatic diol having 2 to 9 carbon atoms, is preferably 80 mol% or more, more preferably Is 90 mol% or more, more preferably 95 mol% or more, and further preferably 100 mol%.

Examples of alcohol components other than the aliphatic diols include aromatic diols such as alkylene oxide adducts of bisphenol A and trivalent or higher alcohols such as glycerin.

Examples of the aliphatic dicarboxylic acid compound include succinic acid (carbon number: 4), fumaric acid (carbon number: 4), glutaric acid (carbon number: 5), adipic acid (carbon number: 6), suberic acid (carbon number: 8), azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), dodecane diacid (carbon number: 12), tetradecane diacid (carbon number: 14), an alkyl group or an alkenyl group on the side chain Examples thereof include succinic acid, anhydrides of these acids, and alkyl esters thereof having 1 to 3 carbon atoms.

The chain hydrocarbon group in the aliphatic dicarboxylic acid compound may be linear or branched, and the carbon number of the aliphatic dicarboxylic acid compound is preferably 1 or more, more preferably from the viewpoint of durability. It is 2 or more, and preferably 22 or less, and more preferably 20 or less from the viewpoint of low temperature fixability. The carbon number of the alkyl group of the alkyl ester portion is not included in the carbon number of the aliphatic dicarboxylic acid compound.

The aliphatic dicarboxylic acid compound is preferably a saturated aliphatic dicarboxylic acid compound from the viewpoint of low temperature fixability.

The carboxylic acid component may contain a carboxylic acid compound other than the aliphatic dicarboxylic acid compound, but the content of the aliphatic dicarboxylic acid compound in the carboxylic acid component is preferably 80 mol% or more, more preferably It is 90 mol% or more, more preferably 95 mol% or more, and further preferably 100 mol%.

Other carboxylic acid compounds include aromatic dicarboxylic acid compounds such as terephthalic acid and isophthalic acid, aliphatic dicarboxylic acid compounds having 2 to 3 carbon atoms, aliphatic dicarboxylic acid compounds having 15 or more carbon atoms, trimellitic acid, and pyromellitic acid. Examples thereof include trivalent or higher carboxylic acid compounds such as acids.

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

The equivalent ratio of the carboxylic acid component and the alcohol component in the crystalline polyester resin (COOH group/OH group) is preferably 0.70 or more, more preferably 0.85 or more from the viewpoint of adjusting the softening point of the composite resin, and It is preferably 1.10 or less, more preferably 1.05 or less.

The polycondensation reaction with the carboxylic acid component and the alcohol component is carried out, for example, in the presence of an esterification catalyst, preferably in the presence of an esterification promoter, a polymerization inhibitor, etc., in an inert gas atmosphere. It can be performed at a temperature of 180°C or higher and 250°C or lower.

Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin(II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolaminate. Examples of the esterification promoter that can be used together with the esterification catalyst include gallic acid and the like. 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 part by mass or less, relative to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 0.6 parts by mass or less. The amount of the esterification cocatalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, with respect to the total amount 100 parts by mass of the alcohol component and the carboxylic acid component. It is more preferably 0.1 part by mass or less.

The content of the crystalline polyester resin in the crystalline resin B is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, further preferably 100% by mass.

The melting point of the crystalline resin B is preferably 55° C. or higher, more preferably 75° C. or higher, from the viewpoint of suppressing the document offset by rapidly separating the crystalline polyester resin from the amorphous polyester resin after printing. The temperature is more preferably 90° C. or higher, and from the viewpoint of low-temperature fixability, preferably 130° C. or lower, more preferably 125° C. or lower, still more preferably 120° C. or lower.

The acid value of the crystalline resin B is preferably 1 mgKOH/g or more, more preferably 2 mgKOH/g or more, further preferably 3 mgKOH/g or more from the viewpoint of low temperature fixability, and from the viewpoint of document offset resistance. , Preferably 25 mgKOH/g or less, more preferably 20 mgKOH/g or less.

The mass ratio of the amorphous composite resin A and the crystalline resin B (amorphous composite resin A/crystalline resin B) is preferably 65/35 or more, more preferably 70/30 or more from the viewpoint of document offset resistance. The above is more preferably 80/20 or more, and from the viewpoint of low temperature fixability, it is preferably 97/3 or less, more preferably 95/5 or less, further preferably 90/10 or less.

The total content of the amorphous composite resin A and the crystalline resin B in the toner particles is preferably 50% by mass or more, more preferably 60% by mass or more, further preferably 70% by mass or more, and the document resistance From the viewpoint of offset property, it is preferably 98% by mass or less, more preferably 95% by mass or less, and further preferably 92% by mass or less.

In the present invention, the toner particles contain the above-mentioned amorphous composite resin A and crystalline resin B as a binder resin, and may contain a binder resin other than these resins. The total content of the resin, in the binder resin, preferably 70 mass% or more, more preferably 80 mass% or more, more preferably 90 mass% or more, more preferably 95 mass% or more, more preferably 100 mass%. is there. Other binder resins include vinyl resins such as styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, and composite resins containing two or more of these resins.

As the colorant, a dye, a pigment, a magnetic substance or the like used as a colorant for toner can be used. For example, carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment red 122, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow. Etc. In the present invention, the toner particles may be 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, still more 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 obtain a small particle size, the viewpoint of improving the low temperature fixing property, and the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles, the binder resin 100 mass The amount is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and further preferably 30 parts by mass or less.

As a method for producing toner particles, a method in which a toner raw material containing an amorphous composite resin A, a crystalline resin B, and a colorant is melt-kneaded, and the obtained melt-kneaded product is pulverized to obtain a water-based binder resin. Examples thereof include a method of mixing the dispersion liquid and the aqueous colorant dispersion liquid to combine the binder resin particles with the colorant particles, a method of stirring the aqueous binder resin dispersion liquid and the colorant at high speed, and the like. From the viewpoint of improving the developability and fixability, a method of melting and kneading the toner raw material and then pulverizing is preferable.

First, a toner raw material containing an amorphous composite resin A, a crystalline resin B, a colorant, and additives used as necessary is mixed in advance with a mixer such as a Henschel mixer, a super mixer, or a ball mill, and then kneaded. Henschel mixer is more preferable from the viewpoint of improving the dispersibility of the colorant in the binder resin. The amorphous polyester resin and the crystalline polyester resin may be mixed in advance, or each resin may be directly mixed with the raw material when producing the toner particles.

The mixing with the Henschel mixer is performed while adjusting the peripheral speed of stirring and the stirring time. From the viewpoint of improving the dispersibility of the colorant, the peripheral velocity is preferably 10 m/sec or more and 30 m/sec or less. 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 carried out using a known kneader such as a closed kneader, a uniaxial or biaxial kneader, and 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 improving the yield of toner particles after pulverization.

The open-roll type kneader means that the melt-kneading section is not closed and is open, and the kneading heat generated during the melt-kneading can be easily released. 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 from the viewpoint of production efficiency, a continuous open roll type kneader. Is preferred.

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 materials, the set temperature of the roll is preferably 10° C. or higher 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 strong kneading 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.

The rolls preferably have different peripheral velocities. In the open roll type kneader having the two rolls, from the viewpoint of improving the fixability of the liquid developer, the high temperature heating roll is the high rotation side roll and the low temperature cooling roll is the low rotation speed. It is preferably a side roll.

The peripheral speed of the high-rotation 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, further preferably 50 m/min or less. Is. The ratio of the peripheral speed 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, It is more preferably 8/10 or less.

The structure, size, material, etc. of each roll are not particularly limited. The surface of the roll has grooves used for kneading, and examples of the shape include a linear shape, a spiral shape, a wavy shape, and an uneven shape.

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

The crushing process may be divided into multiple steps. For example, the melt-kneaded product may be roughly pulverized to about 1 to 5 mm and then finely pulverized. Further, in order to improve the productivity in the pulverizing step, the melt-kneaded product may be pulverized after being mixed with inorganic fine particles such as hydrophobic silica.

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

Examples of the classifier used in the classifying process include an airflow classifier, an inertial classifier, and a sieve classifier. The crushing step and the classification step may be repeated if necessary.

The volume median particle diameter (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 below. Or less, more preferably 12 μm or less. The volume median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction becomes 50% when calculated from the smaller particle size. The toner particles are preferably further finely divided by wet pulverization or the like after mixing with the dispersant and the insulating liquid.

The content of the toner particles to be subjected to wet pulverization is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and further preferably 50 parts by mass or more, with respect to 100 parts by mass of the insulating liquid, from the viewpoint of pulverization efficiency. From the viewpoint of improving dispersion stability, the amount is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, further preferably 70 parts by mass or less, and further preferably 60 parts by mass or less.

The liquid developer of the present invention preferably contains a dispersant from the viewpoint of uniformly dispersing the toner particles in the insulating liquid. The dispersant 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, an amino group _{(-NH 2, -NHR, -NHRR '} ), an amide group (-C (= O) -NRR' ), an imido group (-N (COR) _2), a nitro group (-NO ₂ ), imino group (=NH), cyano group (-CN), azo group (-N=N-), diazo group (=N ₂ ), and azido group (-N ₃ ) At least one selected is preferable. 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, an amino group and/or an imino group is preferable, and from the viewpoint of the chargeability of the toner particles, an 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 and a thiol group.

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

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

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, eicosane, and docosane.

The hydrocarbon having 16 or more carbon atoms partially substituted with a halogen atom is preferably a hydrocarbon having 16 or more and 24 or less carbon atoms partially substituted with a halogen atom, for example, chlorohexadecane, bromohexadecane, chlorooctadecane, bromo. Octadecane, chloroeicosane, bromoeicosane, chlorodocosane, bromodocosane and the like can be mentioned.

The hydrocarbon having 16 or more carbon atoms having a reactive functional group is preferably a hydrocarbon having 16 or more and 24 or less carbon atoms having a reactive functional group, for example, hexadecenyl succinic acid, octadecenyl succinic acid. Acid, eicosenyl succinic acid, docosenyl succinic acid, hexadecyl glycidyl ether, octadecyl glycidyl ether, eicosyl glycidyl ether, docosyl glycidyl ether and the like can be mentioned.

As the polymer of hydroxycarboxylic acid having 16 or more carbon atoms, a polymer of hydroxycarboxylic acid having 16 or more and 24 or less carbon atoms is preferable, and examples thereof include a polymer of 18-hydroxystearic acid.

As the polymer of a dibasic acid having 2 to 22 carbon atoms and a diol having 2 to 22 carbon atoms, for example, a polymer of ethylene glycol and sebacic acid, a polymer of 1,4-butanediol and fumaric acid, 1 Examples thereof include polymers of 6,6-hexanediol and fumaric acid, polymers of 1,10-decanediol and sebacic acid, and polymers 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 and 24 carbon atoms is preferable, for example, a polymer of hexadecyl methacrylate, a polymer of octadecyl methacrylate, or doco Examples thereof include polymers of silmethacrylate.

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

The basic dispersant preferably has a polyolefin skeleton from the viewpoint of dispersibility of toner particles, more preferably a polypropylene skeleton and/or a polyisobutene skeleton, and polyisobutene from the viewpoint of solubility of the dispersant in a carrier. It is more preferable to have a 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 can be obtained, for example, by reacting a basic nitrogen-containing group raw material with a dispersible group raw material.

Examples of the basic nitrogen-containing group 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, from the viewpoint of adsorptivity to the resin having an acidic group, and the dispersion of toner particles. 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.

As the dispersible group raw material, a halogenated hydrocarbon having 16 or more carbon atoms, a hydrocarbon having 16 or more carbon atoms having a reactive functional group, a polymer of a hydroxycarboxylic acid having 16 or more carbon atoms, or 2 or more carbon atoms Polymers of dibasic acids of 22 or less and diols of 2 or more and 22 or less carbon atoms, polymers of alkyl (meth)acrylates of 16 or more carbon atoms having a reactive functional group, polyolefins having a reactive functional group, etc. Can be mentioned. Among these, from the viewpoint of availability and reactivity of raw materials, halogenated hydrocarbons having 16 or more carbon atoms, hydrocarbons having 16 or more carbon atoms having a reactive functional group, and reactive functional groups are included. 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 from the viewpoint of safety and reactivity. Therefore, a carboxylic acid compound is preferable as the compound having a reactive functional group. As the carboxylic acid compound, fumaric acid, maleic acid, ethanoic acid, propanoic acid, butanoic acid, succinic acid, oxalic acid, malonic acid, tartaric acid, their anhydrides, or their carbon number of 1 to 3 alkyl Esters and the like can be mentioned. Specific examples of the dispersible group raw material include halogenated alkanes such as chlorooctadecane, epoxy-modified polyoctadecyl methacrylate, polyethylene succinic anhydride, chlorinated polypropylene, polypropylene succinic anhydride, and polyisobutene succinic anhydride.

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

The number average molecular weight of the dispersible group raw material is, from the viewpoint of dispersibility of the toner particles, preferably 500 or more, more preferably 700 or more, further preferably 900 or more, and the adsorbability of the dispersant to 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 and the dispersible group (basic nitrogen-containing group/dispersible group) in the basic dispersant is preferably 3/97 or more from the viewpoint of adsorbability to the toner particles, and It is preferably 5/95 or more, and preferably 20/80 or less, and more preferably 15/85 or less from the viewpoint of dispersion stability of toner particles. The mass ratio of the basic nitrogen-containing group and 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 group raw material and the dispersible group raw material are reacted with each other. In the preparation of the agent, the mass ratio of the reacted raw material compounds can be regarded as the mass ratio of the basic nitrogen-containing group and the dispersible group in the dispersant (basic nitrogen-containing group/dispersible group).

Further, the number average molecular weight of the basic dispersant is preferably 2,000 or more, more preferably 2,500 or more, further preferably 3,000 or more, further preferably 3,500 or more, from the viewpoint of lowering viscosity and low temperature fixability, and, From the same viewpoint, it is preferably 10,000 or less, more preferably 9,000 or less, and further 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, 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 in the dispersant is preferably 50% by mass or more, The amount is more preferably 70% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, further preferably substantially 100% by mass, further preferably 100% by mass.

The insulating liquid in the present invention means a liquid in which electricity does not easily flow, but in the present invention, the conductivity of the insulating liquid is preferably 1.0×10 ^-11 S/m or less, more preferably 5.0. It is not more than ×10 ^-12 S/m, and preferably not less than 1.0 × 10 ^-13 S/m.

Examples of the insulating liquid C in the liquid developer of the present invention include hydrocarbon-based insulating liquids such as aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, and vegetable oils. Of these, it is preferable to contain a hydrocarbon-based insulating liquid from the viewpoint of dispersion stability and chargeability. 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.

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

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

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

Unreacted components of isobutene and high boiling point components having a high degree of polymerization, which are generated during the polymerization reaction, are preferably removed by distillation. Examples of the distillation method include a single distillation method, a continuous distillation method, a steam distillation method, and the like, and these methods can be used alone or in combination. The apparatus used for distillation is not particularly limited in material, shape, model and the like, and examples thereof include a distillation column filled with a packing such as Raschig rings and a plate distillation column having a plate-shaped shelf. Further, the number of theoretical plates showing the resolution of the distillation column is preferably 10 or more. In addition, conditions such as the feed amount to the distillation column, the reflux ratio, and the take-out amount can be appropriately selected depending on the distillation apparatus.

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

The content of polyisobutene, from the viewpoint of suppressing charger contamination, in the insulating liquid, preferably 5 mass% or more, more preferably 20 mass% or more, more preferably 40 mass% or more, more preferably 60 mass% or more, It is more preferably 80% by mass or more, and further preferably 90% by mass or more.

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

The content of the hydrocarbon-based insulating liquid in the insulating liquid is preferably 80% by mass or more, more preferably 90% by mass or more, further preferably 95% by mass or more, and further preferably 100% by mass.

The boiling point of the insulating liquid C is preferably 120° C. or higher, more preferably 140° C. or higher, further preferably 160° C. or higher, from the viewpoint of further improving the dispersion stability of the toner particles and improving the storage stability. Further, from the viewpoint of further improving the low temperature fixing property of the toner and from the viewpoint of further improving the pulverizability of the toner during wet pulverization to obtain toner particles having a small particle diameter, preferably 300° C. or lower, more preferably 280° C. or lower, It is preferably 260°C or lower. When two or more insulating liquids are combined, the boiling point of the combined insulating liquid mixture is preferably within the above range.

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

The liquid developer includes, in addition to the amorphous composite resin A, the crystalline resin B, the colorant, the dispersant, and the insulating liquid, a release agent, a charge control agent, a charge control resin, a magnetic powder, and a fluidity improver. An additive such as a conductivity modifier, a reinforcing filler such as a fibrous substance, an antioxidant, and a cleaning property improver may be appropriately contained.

The liquid developer is obtained by dispersing toner particles in an insulating liquid in the presence of a dispersant, if necessary. From the viewpoint of reducing the particle size of the toner particles and the viscosity of the liquid developer, it is preferable to obtain the liquid developer by dispersing the toner particles in the insulating liquid and then wet pulverizing the toner particles.

As a method of mixing the toner particles, the dispersant, and the insulating liquid, a method of stirring with a stirring mixer is preferable.

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

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

From the viewpoint of improving the image density, the solid content concentration of the toner particle dispersion liquid is preferably 20% by mass or more, more preferably 30% by mass or more, further preferably 33% by mass or more, and the toner particles are stable in dispersion. From the viewpoint of improving the properties and improving the storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less.

The 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 a device to be used, for example, a commonly used stirring and mixing device such as an anchor blade can be used. Among the stirring and mixing devices, high-speed stirring and mixing devices such as Despa (manufactured by Asada Iron Works Co., Ltd.) and TK Homomixer (manufactured by Primix Co., Ltd.), pulverizers or kneaders such as roll mills, bead mills, kneaders and extruders Etc. A plurality of these devices can be combined.

Among them, the use of a bead mill is preferred from the viewpoint of reducing the particle size of toner particles, the viewpoint of improving the storage stability by improving the dispersion stability of toner particles, and the viewpoint of 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 packing rate of the medium used, the peripheral speed of the rotor, the residence time, and the like.

From the viewpoint of improving the image density, the solid content concentration of the liquid developer is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% by mass or more, and the dispersion stability of the toner particles. From the viewpoint of improving the storage stability and 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 4 μm or less, still more preferably 3 μm or less.

The content of the toner particles in the liquid developer is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 15% by mass or more, from the viewpoint of high-speed printing, and the dispersion stability of the toner particles. From the viewpoint of properties, it is preferably 45% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less.

The content of the insulating liquid in the liquid developer is preferably 50% by mass or more, more preferably 55% by mass or more, further preferably 60% by mass or more, from the viewpoint of dispersion stability of the toner particles, and From the viewpoint of high speed printing, it is preferably 90% by mass or less, more preferably 85% by mass or less, still more 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 storage stability by improving the dispersion stability of the toner particles. Or more, more preferably 6 mPa.s or more, more preferably 7 mPa.s or more, and from the viewpoint of improving the fixability of the liquid developer, preferably 50 mPa.s or less, more preferably 40 mPa.s or less, It is preferably 30 mPa·s or less, more preferably 25 mPa·s or less. The viscosity of the liquid developer having a solid content concentration of 25 mass% as used herein means the viscosity measured by adjusting the solid content concentration of the liquid developer to 25 mass%. Adjust the solid concentration of the liquid developer by diluting it with the same insulating liquid if it is higher than 25% by mass, or by removing it by concentration etc. if it is lower than 25% by mass. can do.

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.

[Resin softening point]
Using a flow tester "CFT-500D" (manufactured by Shimadzu Corp.), a load of 1.96 MPa was applied by a plunger while heating a 1 g sample at a heating rate of 6°C/min, and a diameter of 1 mm and a length of 1 mm. Push out from the nozzle. The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half the sample flows out is taken as the softening point.

[Maximum peak temperature of resin endotherm]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), weigh 0.01-0.02 g of the sample in an aluminum pan and cool it from room temperature (25°C) to 10°C. Cool to 0°C at /min and hold at 0°C for 1 minute. Then, measurement is performed at a heating rate of 10° C./min. Of the endothermic peaks observed, the temperature of the peak on the highest temperature side is the highest endothermic peak temperature.

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

[Resin Acid Value]
Measured according to the method of JIS K 0070:1992. However, only the measurement solvent is a mixed solvent of ethanol and ether specified in JIS K 0070, the amorphous resin is a mixed solvent of acetone and toluene (acetone:toluene=1:1 (volume ratio)), and the crystalline compound is chloroform. : Change to a mixed solvent of dimethylformamide (chloroform:dimethylformamide = 7:3 (volume ratio)).

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

[Number average molecular weight of basic nitrogen-containing starting material]
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below to determine the number average molecular weight.
(1) Preparation of sample solution The sample is dissolved 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. Then, this solution is filtered using a fluororesin filter “FP-200” (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 0.2 μm to remove insoluble components, to obtain a sample solution.
(2) Molecular weight measurement Using the following measuring device and analytical column, a solution of Na ₂ SO ₄ dissolved in 1% acetic acid aqueous solution at 0.15 mol/L as an eluent, flow at a flow rate of 1 mL per minute, and at 40° C. Stabilize the column in a constant temperature bath. Inject 100 μL of the sample solution into it and perform the measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. At this time, several types of standard pullulan (P-5 (Mw 5.9 × 10 ³ ) manufactured by Showa Denko KK, P-50 (Mw 4.73 × 10 ⁴ ), P-200 (Mw 2.12 × 10 ⁴ ) were used for the calibration curve. ⁵ ), P-800 (Mw 7.08×10 ⁵ )) prepared as a standard sample. The molecular weight is shown in parentheses.
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 material]
(1) Preparation of sample solution Dispersible group raw material is dissolved 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 to obtain a sample solution.
(2) Molecular weight distribution measurement Tetrahydrofuran is caused to flow as an eluent at a flow rate of 1 mL per minute using the following measuring device and analytical column to stabilize the column in a constant temperature bath at 40°C. Inject 100 μL of the sample solution into it and perform the measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. At this time, several kinds of monodisperse polystyrene (A-500 (Mw 5.0×10 ² ) manufactured by Tosoh Corporation, A-1000 (Mw 1.01×10 ³ ), A-2500 (Mw 2.63×10 ³ ) were used for the calibration curve. 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 x 10 ⁴ ), F-20 (Mw 1.90 x 10 ⁵ ), F-40 (Mw 4.27 x 10 ⁵ ), F-80 (Mw 7.06 x 10 ⁵ ), F-128 (Mw 1.09 x 10 ⁶⁾ )) is used as a standard sample. The molecular weight is shown in parentheses.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: TSKgel GMH _XL + TSKgel G3000H _XL (Tosoh Corporation)

[Number average molecular weight of dispersant]
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below to determine the number average molecular weight.
(1) Preparation of sample solution Dispersant is dissolved in chloroform so that the concentration becomes 0.2 g/100 mL. Then, this solution is filtered using a fluororesin filter “FP-200” (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 0.2 μm to remove insoluble components, to obtain a sample solution.
(2) Measurement of molecular weight Using the following measuring device and analytical column, a chloroform solution of 1.00 mmol/L of Pharmine DM2098 (manufactured by Kao Corporation) as an eluent was flowed at a flow rate of 1 mL per minute, and kept in a constant temperature bath at 40°C. Stabilize the column in. Inject 100 μL of the sample solution into it and perform the measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. At this time, several kinds of monodisperse polystyrene (A-500 (Mw 5.0×10 ² ) manufactured by Tosoh Corporation, A-5000 (Mw 5.97×10 ³ ), F-2 (Mw 1.81×10 ³ ) were used for the calibration curve. ⁴ ), F-10 (Mw 9.64 × 10 ⁴ ) and F-40 (Mw 4.27 × 10 ⁵ )) prepared as standard samples. The molecular weight is shown in parentheses.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: K-804L (Showa Denko KK)

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

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

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

[Solid content of toner particle dispersion and liquid developer]
10 parts by mass of the sample is diluted with 90 parts by mass of hexane, and is rotated for 20 minutes at a rotation speed of 25,000 r/min using a centrifugal separator “H-201F” (manufactured by Kokusan Co., Ltd.). After standing, the supernatant is removed by decantation, diluted with 90 parts by mass of hexane, and centrifuged again under the same conditions. After removing the supernatant liquid by decantation, the lower layer is dried with a vacuum dryer at 0.5 kPa and 40° C. for 8 hours, and the solid content concentration is calculated from the following formula.

[Volume median particle diameter (D ₅₀ ) of toner particles in liquid developer]
Using a laser diffraction/scattering particle size analyzer “Mastersizer 2000” (Malvern), add Isopar L (ExxonMobil, isoparaffin, viscosity at 25° C. 1 mPa·s) to the measurement cell, and measure the scattering intensity. At a concentration of 5 to 15%, the volume median particle diameter (D ₅₀ ) is measured under the conditions of a particle refractive index of 1.58 (imaginary number part 0.1) and a dispersion medium refractive index of 1.42.

Production Example 1 of amorphous resin
The raw material monomer of the amorphous polyester resin shown in Table 1, the esterification catalyst, and the esterification promoter were placed in a 10 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, and the temperature was 230°C. The temperature was raised to 230° C., the reaction was carried out at 230° C. for 8 hours, the pressure was further reduced to 8.3 kPa, and the reaction was carried out for 1 hour. The temperature was lowered to 170° C., and the raw material monomer of the styrene resin, the bireactive monomer and the polymerization initiator shown in Table 1 were added dropwise over 1 hour. After aging the addition polymerization reaction for 1 hour while maintaining it at 170°C, the temperature was raised to 210°C and the reaction between both reactive monomers and the polyester resin part was carried out at 8.3 kPa for 1 hour to reach the softening point shown in Table 1. The reaction was continued until the temperature reached, and amorphous composite resins (resins A1 to A7, A9, A11) having the physical properties shown in Table 1 were obtained.

Production Example 2 of amorphous resin
The raw material monomer of the amorphous polyester resin shown in Table 1, the esterification catalyst, and the esterification co-catalyst were placed in a 10 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple, and 210°C. The reaction is carried out until the reaction rate reaches 90%, and the reaction is further carried out at 8.3 kPa. When the target softening point is reached, the reaction is terminated and the amorphous polyester having the physical properties shown in Table 1 is used. A resin (resin A8) was obtained.

Production Example 3 of amorphous resin
10 liters of xylene was placed in a 20 liters four-necked flask equipped with a thermometer, a stainless steel stirring rod, a downflow condenser, a dropping funnel and a nitrogen introducing tube, and the styrene resin raw material monomer shown in Table 1 was added. The bireactive monomer and the radical polymerization initiator were placed in a dropping funnel equipped with a four-necked flask. Then, the xylene in the four-necked flask was heated to 135° C. under a nitrogen atmosphere, and the mixture of the raw material monomer and the polymerization initiator was dropped into the xylene from the dropping funnel over 1 hour. The temperature was further raised to 200° C. and maintained at 200° C. for 2 hours. After that, xylene was removed by further holding for 1 hour under a reduced pressure of 8 kPa to obtain a styrene resin (Resin A10).

Production Example 1 of crystalline resin
The raw material monomers, the esterification catalyst, and the polymerization inhibitor shown in Table 2 were placed in a 10-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, and reacted at 160°C for 5 hours. .. Then, the temperature was raised to 200° C. and the reaction was carried out for 1 hour, and then the reaction was continued for another 1 hour under a reduced pressure of 8.3 kPa to obtain crystalline polyester resins (resins B1 to B3).

Dispersant Production Example 1
Polyethyleneimine (polyethyleneimine 600, manufactured by Junsei Kagaku Co., Ltd.) shown in Table 3 as a basic nitrogen-containing base material is equipped with a cooling pipe, a nitrogen introduction pipe, a stirrer, a dehydration pipe, and a thermocouple. It was placed in a flask and the inside of the reaction vessel was replaced with nitrogen gas. While stirring, a solution of polyisobutene succinic anhydride (PIBSA) (OLOA15500, manufactured by Chevron Japan Ltd., effective content: 78 mass%) shown in Table 3 as a dispersible group raw material in xylene shown in Table 3 was prepared at 25°C. It was added dropwise over 1 hour. After the dropping was completed, the mixture was kept at room temperature for 30 minutes. After that, the inside of the reaction vessel was heated to 150° C. and kept for 1 hour, then heated to 160° C. and kept for 1 hour. Xylene was distilled off at 160°C under reduced pressure to 8.3 kPa. The peak of acid anhydride derived from PIBSA (1780 cm ^-1 ) disappeared from the IR analysis, and the peak derived from the imide bond (1700 cm ^-1 ) occurred. As a reaction end point, a dispersant A having the physical properties shown in Table 3 was obtained.

Examples 1-10 and Comparative Examples 1-4
70 parts by mass of the amorphous resin A and 10 parts by mass of the crystalline resin B shown in Table 4, and 20 parts by mass of the coloring agent "ECB-301" (phthalocyanine blue 15:3 manufactured by Dainichiseika Kogyo Co., Ltd.) Using a 20 L Henschel mixer in advance, the mixture was stirred and mixed at a rotation speed of 1500 r/min (peripheral speed of 21.6 m/sec) for 3 minutes, and then melt-kneaded under the following conditions. The amorphous resin A of Comparative Example 3 was a combination of 66.5 parts by mass of resin A8 and 3.5 parts by mass of resin A10.

[Conditions for melt-kneading]
A continuous two-roll open-roll type kneader "Kneedex" (manufactured by Nippon Coke Industry Co., Ltd., roll outer diameter: 14 cm, effective roll length: 55 cm) was used. The operating conditions of the continuous two-roll 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 of the kneaded material supply port side was 0.1 mm. The heating medium temperature and the cooling medium temperature in the rolls are 90°C on the raw material input side of the high rotation side roll and 85°C on the kneaded material discharge side, and 35°C on the raw material input side of the low rotation side roll and 35°C on the kneaded material discharge side. there were. The feed rate of the raw material mixture to the kneader was 10 kg/h, and the average residence time in the kneader was about 3 minutes.

The obtained kneaded product was rolled and cooled with a cooling roll, and then roughly crushed to about 1 mm using a hammer mill. The obtained coarsely pulverized product was finely pulverized and classified by an air flow type jet mill “IDS” (manufactured by Nippon Pneumatic Co., Ltd.) to obtain toner particles having a volume median particle diameter (D ₅₀ ) of 10 μm.

35 parts by mass of the obtained toner particles and an insulating liquid “NAS-4” (manufactured by NOF CORPORATION, polyisobutene, conductivity: 1.52×10 ⁻¹² S/m, boiling point: 247° C., viscosity at 25° C.: 2 mPas・S) 63.95 parts by mass and 1.05 parts by mass of dispersant A were put in a polyethylene container having a volume of 1 L, and using "TK Robomix" (manufactured by Primix Co., Ltd.) under ice cooling, at a rotation speed of 7,000 r/min. And stirred for 30 minutes to obtain a toner particle dispersion liquid having a solid content concentration of 36 mass %.

Next, the obtained toner particle dispersion liquid was rotated with a 6-cylinder sand mill “TSG-6” (manufactured by AIMEX Co., Ltd.) at a volume filling rate of 60% by volume using zirconia beads having a diameter of 0.8 mm. Wet grinding 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 NOF CORPORATION) was added to 100 parts by mass of the filtrate to dilute it, and liquid development with a solid concentration of 25% by mass was performed. I got an agent.

Test Example 1 [Low temperature fixability]
Liquid developer is dropped on "OK Top Coat Paper" (Oji Paper Co., Ltd., basis weight: 127.9 g/m ² , paper thickness: about 103 μm), and the toner mass after drying is 3.4 g/m with a wire bar. ^A thin film was prepared so as to be ² . Then, it hold|maintained for 10 second in 80 degreeC thermostat.
Then, using a fixing machine taken out from "OKI MICROLINE 3010" (manufactured by Oki Data Co., Ltd.), fixing processing was performed at a fixing roll temperature of 80°C and a fixing speed of 280 mm/sec. After that, the fixing process as described above was performed while increasing the temperature of the fixing roll by 10° C. to 160° C., and a fixed image was obtained at each temperature.
Attach the mending tape "Scotch Mending Tape 810" (3M Japan Ltd., width 18 mm) to the obtained fixed image, press the tape with a roller so that a load of 500 g is applied, and then remove the tape. Peeled off. The image density before and after tape peeling was measured using a colorimeter "Gretag Macbeth Spectroeye" (manufactured by Gretag). The image-printed portion was measured at three points, and the average value was calculated as the image density. The fixing ratio (%) is calculated from the value of image density after peeling/image density before peeling×100, and the temperature of the fixing roll at which the fixing ratio first reaches 90% or more is set as the minimum fixing temperature, and low-temperature fixability is determined. evaluated. The results are shown in Table 4. The lower the minimum fixing temperature is, the better the low temperature fixing property is.

Test Example 2 [Document offset resistance (DO resistance)]
A liquid developer was dropped on "POD gloss coated paper" (manufactured by Oji Paper Co., Ltd.), and a thin film was prepared by a wire bar so that the mass after drying was 1.2 g/m ² . Then, it hold|maintained for 10 second in 80 degreeC thermostat. Then, using a fixing device taken out from "OKI MICROLINE 3010" (manufactured by Oki Data Co., Ltd.), fixing processing was performed at a fixing roll temperature of 120°C and a fixing speed of 280 mm/sec.
Two sheets of the same were prepared, and a sample in which two sheets of paper were overlapped so that the fixed image parts faced each other, and a sample was placed for 1 day under an environment of a temperature of 50°C under a load of a surface pressure of 80 g/cm ² . .. Then, the superposed sheets were taken out and peeled off. Ten samples were prepared, the state of the fixed image portion after opening was visually observed, and the document offset resistance was evaluated according to the following evaluation criteria. The results are shown in Table 4.

〔Evaluation criteria〕
A: No peeling noise was observed in all 10 samples during peeling, and no image loss was observed. B: 1 or 2 samples out of 10 were peeling noise during peeling, but no image loss was observed. C: 3 or more samples out of 10 have peeling noise when peeling, but no image defect is seen D: 3 or more samples out of 10 peeling noise when peeling, 10 samples (paper Image defects are seen in an area less than 1/3 of the total area of the image part (20 sheets) E: At the time of peeling, peeling noise is generated in 3 or more samples out of 10 and 10 samples (20 sheets of paper) Image loss is seen in 1/3 or more of the total area of the image part of

Test Example 3 [Charging property]
A liquid developer with a solid content concentration of 25% by mass was weighed 0.03 g in an aluminum pan (diameter: 10 mm) using a charge decay property measuring device (made by Nanoseed Co.), and the surface potential was measured at a measuring time of 10 seconds. Then, the charge decay rate (1/√sec) from the maximum surface potential was calculated from the following formula. The results are shown in Table 4. The smaller the value, the better the charge retention.

V＝V ₀・exp(-α√t)
V: surface potential
V ₀ : initial surface potential α: decay rate t: decay time

From the above results, it is understood that the liquid developers of Examples 1 to 10 have good low-temperature fixability, chargeability, and document offset resistance. Among them, it can be seen from the comparison between Examples 1 and 7 to 10 that the higher the ratio of the structural unit derived from the styrene-based monomer in the amorphous composite resin, the higher the charging property.
On the other hand, Comparative Example 1 in which the amorphous resin does not have a styrenic resin lacks chargeability, and Comparative Example 2 in which the proportion of acrylic monomer in the amorphous resin is high is crystalline polyester. Since the crystallization of the resin is not promoted, the document offset resistance is low, and the ratio of the styrene-based monomer is low, so the chargeability is also low. In Comparative Example 3 in which the amorphous polyester resin and the styrene resin are not composite, the crystalline polyester resin is compatible only with the styrene resin, and the crystallization of the crystalline polyester resin is not promoted. Missing. Further, Comparative Example 4, which does not use the crystalline polyester resin, lacks low-temperature fixability.

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

Claims (6)

A toner developer containing an amorphous composite resin A, a crystalline resin B, and a colorant, and a liquid developer containing an insulating liquid, wherein the amorphous composite resin A is an amorphous polyester resin. The styrene resin is a resin chemically bonded through a constitutional unit derived from a bireactive monomer capable of reacting with both the raw material monomer of the amorphous polyester resin and the raw material monomer of the styrene resin, The crystalline composite resin A has a structural unit derived from a styrene monomer and a structural unit derived from an acrylic monomer, and the structural unit derived from a styrene monomer and the structural unit derived from an acrylic monomer in the amorphous composite resin A. Liquid developer having a mass ratio of (structural unit derived from styrene-based monomer/structural unit derived from acrylic-based monomer) of 75/25 or more and less than 100/0. The liquid development according to claim 1, wherein the mass ratio of the amorphous polyester resin and the styrene resin in the amorphous composite resin A (amorphous polyester resin/styrene resin) is 60/40 or more and 98/2 or less. Agent. The liquid developer according to claim 1, wherein the raw material monomer of the styrene-based resin in the amorphous composite resin A contains at least one acrylic monomer selected from alkyl acrylate and alkyl methacrylate. The liquid developer according to claim 1, wherein the bireactive monomer is at least one acrylic monomer selected from acrylic acid and methacrylic acid. The liquid developer according to claim 1, wherein the crystalline resin B contains a crystalline polyester resin. The liquid according to claim 1, wherein the mass ratio of the amorphous composite resin A and the crystalline resin B (amorphous composite resin A/crystalline resin B) is 65/35 or more and 97/3 or less. Developer.