JP6831233B2 - Liquid developer - Google Patents

Description

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

Electrophotographic developeres 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.

In the liquid developer, the toner particles are dispersed in the oil in the insulating liquid, so that the particle size can be reduced as compared with the dry developer. Therefore, it is possible to obtain a high-quality printed matter that surpasses offset printing, and is suitable for commercial printing applications. Further, in recent years, there is an increasing demand for high speed, so that the viscosity of the liquid developer is required to be reduced. That is, there is a demand for a liquid developer in which toner particles have a small particle size, a low viscosity, and are stably dispersed.

Patent Document 1 aims to provide a liquid developer capable of obtaining a stable output image for a long period of time by having excellent fixability, offset resistance, color development property, and excellent storage stability. A polymer dispersant obtained by polymerizing an ethylenically unsaturated monomer having an amino group and an ethylenically unsaturated monomer containing an alkyl group having 4 to 24 carbon atoms, or a carrier liquid having a melting point of 25 ° C. or higher. A liquid developer containing an insoluble plasticizer is disclosed.

Patent Document 2 provides a crude product containing a binder resin containing polyester and a solid plasticizer for the purpose of providing a method for producing a liquid developer in which a liquid developer containing flat-shaped toner particles can be easily produced. The crude particle preparation step for preparing the particles and the crude particles and the insulating carrier liquid are mixed, and the average temperature is controlled to be (Tg-5) ° C. or higher and Tg ° C. or lower with respect to the glass transition temperature Tg ° C. of the crude particles. However, a method for producing a liquid developer having a crushing step of crushing crude particles by a grinding force to obtain flat-shaped toner particles is disclosed.

Japanese Unexamined Patent Publication No. 2014-92579 Japanese Unexamined Patent Publication No. 2012-103338

In recent years, there has been an increasing demand for high speed, and therefore, a toner that can be melt-fixed with a small amount of heat, that is, a toner having excellent low-temperature fixability is required. Further, since it is necessary to fix the toner without causing a hot offset even at a conventional speed, a toner that can be fixed at a wide temperature is required.

However, when the meltability of the toner is increased to improve the low temperature fixability, hot offset is likely to occur, and it is difficult to obtain a toner that can be fixed at a wide temperature.

The present invention relates to a liquid developer having a small particle size, low viscosity and capable of fixing at a wide range of temperatures.

The present invention is a liquid developer containing toner particles containing a binder resin and a colorant, a liquid plasticant, and an insulating liquid, wherein the binder resin is a polyester resin and a styrene resin. The present invention relates to a liquid developer containing a composite resin chemically bonded via a bireactive monomer capable of reacting with either a raw material monomer of a polyester resin and a raw material monomer of the styrene resin.

The liquid developer of the present invention has an excellent effect that it can be fixed in a wide range of temperatures with a small particle size and low viscosity.

The liquid developer of the present invention is a liquid developer containing toner particles containing a binder resin and a colorant, a liquid plasticizer, and an insulating liquid, and the binder resin is a polyester resin and a styrene resin. It has one feature in that it contains a composite resin that is chemically bonded via a bireactive monomer that can react with either the raw material monomer of the polyester resin and the raw material monomer of the styrene resin. It has a small particle size, low viscosity, and can be fixed at a wide range of temperatures.

The reason for achieving such an effect is not clear, but it is considered as follows.
In order for the liquid plasticizer to plasticize the toner particles, it needs to penetrate into the resin molecules. Among plasticizers, aliphatic plasticizers have a high degree of freedom in molecular motion and easily permeate into resin molecules, so that they are considered to exhibit a plasticizing effect. Furthermore, when a composite resin of a polyester resin and a styrene resin is used, the plasticizer has a polar portion, so that it has a high affinity with the highly polar polyester moiety and selectively acts on the polyester moiety to plasticize. Plasticization occurs. It is considered that this plasticized polyester moiety contributes to low temperature fixability. On the other hand, the plasticizer does not act on the styrene resin, and the styrene portion maintains high elasticity, which contributes to the suppression of hot offset and can maintain the fixability even at high temperatures. Therefore, it is considered that fixing can be performed at a wide range of temperatures.
In addition, the polyester resin in the composite resin has a stronger intermolecular force than the styrene resin and is difficult to wet grind, but the plasticizer selectively acts on the polyester resin to weaken the intermolecular force, so that the wet grindability is improved. , It is considered that the particle size reduction and the viscosity reduction are promoted.
Further, by containing a resin in which a polyester resin and a styrene resin are chemically bonded and composited, it is possible to suppress uneven distribution of two resins having different polarities, and a uniformly dispersed resin can be obtained. As a result, uniform particles can be obtained even when the toner is produced, and it is considered that good wet grindability and fixability can be obtained.

The binder resin contains a composite resin in which a polyester resin and a styrene resin are chemically bonded via a bireactive monomer capable of reacting with either a raw material monomer of the polyester resin or a raw material monomer of the styrene resin. To do.

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 the formula (I):

(In the formula, RO and OR are oxyalkylene groups, R is ethylene and / or propylene group, x and y indicate the average number of moles of alkylene oxide added, which are positive numbers, respectively, of x and y. The value of the sum is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, still more preferably 4 or less).
Examples thereof include an alkylene oxide adduct of bisphenol A represented by. Specific examples of diols having 2 to 20 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, bisphenol A, and hydrogen. Examples thereof include added bisphenol A.

As the alcohol component, the viewpoint of improving the grindability of the toner to obtain a liquid developer having a small particle size, the viewpoint of improving the low temperature fixability of the toner, and the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. Therefore, 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, preferably 3 or more and 10 or less carbon atoms. Specific examples thereof include sorbitol, 1,4-sorbitan, pentaerythritol, glycerol, trimethylolpropane and the like.

On the other hand, in the carboxylic acid component, as the divalent carboxylic acid compound, an aromatic dicarboxylic acid compound is preferable from the viewpoint of durability. Further, from the viewpoint of low temperature fixability, an aliphatic dicarboxylic acid compound is preferable.

Examples of the aromatic dicarboxylic acid-based compound include phthalic acid, isophthalic acid, and terephthalic acid; anhydrides of those acids and alkyl (1 to 3 carbon atoms) esters of those acids. Among these, terephthalic acid Alternatively, isophthalic acid is preferable, and terephthalic acid is more preferable. In the present invention, the carboxylic acid compound includes not only free acids, but also anhydrides that decompose during the reaction to generate acids, and alkyl esters having 1 or more and 3 or less carbon atoms.

The content of the aromatic dicarboxylic acid compound is preferably 30 mol% or more in the carboxylic acid component from the viewpoint of durability, and preferably 80 mol% or less, more preferably from the viewpoint of low temperature fixability. It is 75 mol% or less.

The chain hydrocarbon group in the aliphatic dicarboxylic acid compound may be a straight chain or a branched chain, and the aliphatic dicarboxylic acid compound preferably has 4 or more carbon atoms, and is available. From the viewpoint, it is preferably 14 or less, more preferably 12 or less. However, the carbon number of the alkyl group in the alkyl ester portion is not included in the carbon number of the aliphatic dicarboxylic acid compound.

Aliphatic dicarboxylic acid compounds include succinic acid (carbon number: 4), fumaric acid (carbon number: 4), glutaric acid (carbon number: 5), adipic acid (carbon number: 6), and suberic acid (carbon number: 6). : 8), Azelaic acid (carbon number: 9), sebacic acid (carbon number: 10), dodecanedioic acid (carbon number: 12), tetradecanedioic acid (carbon number: 14), alkyl group or alkenyl group on the side chain Examples thereof include succinic acid having a succinic acid, an anhydride of these acids, and an alkyl ester having 1 to 3 carbon atoms thereof.

The content of the aliphatic dicarboxylic acid compound is preferably 5 mol% or more, more preferably 10 mol% or more, and preferably from the viewpoint of storage stability, in the carboxylic acid component from the viewpoint of low temperature fixability. It is less than 50 mol%.

Further, the carboxylic acid component preferably contains an aromatic carboxylic acid compound having a valence of 3 or more from the viewpoint of storage stability and durability.

Examples of trivalent or higher valent aromatic carboxylic acid compounds include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, pyromellitic acid and their acid anhydrides, and lower alkyl. Examples thereof include (1 to 3 carbon atoms) esters, and among these, trimellitic acid-based compounds are preferable.

The content of the trivalent or higher aromatic carboxylic acid compound is preferably 3 mol or more, more preferably 5 mol or more, still more preferably 7 mol or more, with respect to 100 mol of the alcohol component from the viewpoint of improving the softening point. And, from the viewpoint of low temperature fixability, it is preferably 25 mol or less.

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

The equivalent ratio (COOH group / OH group) of the carboxylic acid component and the alcohol component in the polyester resin is preferably 0.6 or more, more preferably 0.70 or more, and more preferably 0.75 or more from the viewpoint of adjusting the softening point of the polyester resin. Yes, and preferably 1.10 or less, more preferably 1.05 or less, and more preferably 1.00 or less.

The polyester resin has, for example, an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and if necessary, in the presence of an esterification co-catalyst, a polymerization inhibitor, etc., at 130 ° C. It can be produced by polycondensation at a temperature of 250 ° C. or higher, preferably 170 ° C. or higher and 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 bistriethanolaminate, and 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 1.0 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 parts by mass or less. Examples of the polymerization inhibitor include t-butylcatechol and the like. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 0.1 parts by mass or less.

The styrene-based resin is an addition polymer of a raw material monomer containing 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”).

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. , More preferably 80% by mass or more, and 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 improving the wet grindability. It is 90% by mass or less.

Further, the styrene resin may contain a (meth) acrylic acid alkyl ester having 7 or more carbon atoms as an alkyl group 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 including both the case where this group exists and the case where this group does not exist, and when these groups do not exist, it is normal. 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 refers to the carbon number 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 vinyl methyl ether; Vinylidene halides such as vinylidene chloride; N- N-vinyl compounds such as vinylpyrrolidone may be contained.

The addition polymerization reaction of the raw material monomer of the styrene resin is 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 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 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 resins.

Further, the bireactive monomer may be one or more (meth) acrylic acid esters selected from acrylic acid esters and methacrylic acid esters having an alkyl group having 6 or less carbon atoms.

The (meth) acrylic acid ester is preferably a (meth) acrylic acid alkyl ester from the viewpoint of reactivity to transesterification, and the number of carbon atoms of the alkyl group is preferably 2 or more, more preferably 3 or more. And it is preferably 6 or less, more preferably 4 or less. The alkyl group may have a substituent such as a hydroxyl group.

Specific examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylic acid, 2-hydroxyethyl (meth) acrylate, and ( Examples thereof include butyl (iso or tertiary) acrylate (meth) acrylate, and hexyl (meth) acrylate. In addition, in this specification, "(iso or tertiary)" means including both the case where these groups are present and the case where these groups are not present, and when these groups are not present , Indicates that it is normal.

In the present invention, the acrylic acid ester is preferably an acrylic acid alkyl ester having an alkyl group having 2 or more and 6 or less carbon atoms, more preferably butyl acrylate, and the methacrylic acid ester is preferably having an alkyl group having 2 or more carbon atoms. Alkyl methacrylate ester of 2 or more and 6 or less, more preferably butyl methacrylate.

From the viewpoint of low-temperature fixability, the amount of both reactive monomers used is preferably 1 mol or more, more preferably 2 mol or more, and with a styrene resin, based on 100 mol of the total 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, and further preferably 10 mol or less.
From the viewpoint of low-temperature fixability, 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 raw material monomers of the styrene resin. Then, from the viewpoint of enhancing the dispersibility between the styrene resin and the polyester resin and improving the durability of the toner, the amount 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.

In the present invention, the composite resin is a resin in which a polyester resin and a styrene resin are chemically bonded via a bireactive monomer.

Specifically, the composite resin is preferably produced by the following method. Both reactive monomers are preferably used in the 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 fixability and heat storage stability of the toner.

(i) A method in which the step (A) of the polycondensation reaction using the raw material monomer of the polyester resin is followed by the step (B) of the addition polymerization reaction using the raw material monomer of the styrene resin and the bireactive monomer. 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. It is preferable that the raw material monomer of the styrene resin and the bireactive monomer are 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 carried out. The reaction with the sex monomer can be further advanced.

(ii) A method in which a polycondensation reaction step (A) using a polyester resin raw material monomer is performed after the 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. The polycondensation reaction of the step (A) is carried out under the temperature conditions suitable for the polycondensation reaction by raising the reaction temperature by carrying out the step (B) under the reaction temperature conditions suitable for the above. 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 adjusted by adding an esterification catalyst at a temperature suitable for the polycondensation reaction.

(iii) The reaction is carried out under the condition that the step (A) of the polycondensation reaction using the raw material monomer of the polyester resin and the step (B) of the polycondensation reaction using the raw material monomer of the styrene resin and the bireactive monomer proceed in parallel. Method of performing In this method, the steps (A) and (B) are performed in parallel under the reaction temperature conditions suitable for the polycondensation reaction, the reaction temperature is raised, and the temperature conditions suitable for the polycondensation reaction are used. 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 pre-polymerized polycondensation resin may be used instead of the step (A) in which the polycondensation reaction is carried out. In the method (iii) above, when the reaction is carried out under the condition that the steps (A) and (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. The mixture containing the above can also be dropped and reacted.

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

The mass ratio of the styrene resin to the polyester resin (styrene resin / polyester resin) in the composite resin is preferably 3/97 or more, more preferably 7/93 or more, still more preferably 10 from the viewpoint of the grindability of the toner particles. It is / 90 or more, and from the viewpoint of dispersion stability of toner particles, it is preferably 45/55 or less, more preferably 40/60 or less, still more preferably 35/65 or less, still more preferably 30/70 or less, and further. It is preferably 25/75 or less. 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.

The softening point of the composite resin is preferably 70 ° C. or higher, more preferably 75 ° C. or higher, and improves the low temperature fixability of the toner from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint, 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 composite resin is preferably 40 ° C. or higher, more preferably 45 ° C. or higher, and from the viewpoint of improving the low temperature fixability, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. Therefore, it is preferably 80 ° C. or lower, more preferably 70 ° C. or lower, and further preferably 60 ° C. or lower.

The acid value of the composite resin is preferably 3 mgKOH / g or more, more preferably 5 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. , 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. The acid value of the composite 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 a carboxylic acid compound having a valence of 3 or more. can do.

The content of the composite resin is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 100% by mass, that is, only the composite resin is used in the binder resin. However, a resin other than the composite resin may be contained as long as the effect of the present invention is not impaired. Resins other than the composite resin include, for example, polyester resin, polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, and styrene-maleic acid. Styrene-based resin, epoxy-based resin, rosin-modified maleic acid, which is a copolymer or copolymer containing styrene or a styrene-substituted product such as a polymer, a styrene-acrylic acid ester copolymer, or a styrene-methacrylic acid ester copolymer. One or more selected from resins such as resins, polyethylene-based resins, polypropylene-based resins, polyurethane-based resins, silicone-based resins, phenol-based resins, aliphatic or alicyclic hydrocarbon resins can be mentioned.

As the colorant, dyes, pigments and the like used as colorants for toner can be used. For example, carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmin 6B, isoindoline, disazoero, etc. .. 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 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, still more preferably 10 parts by mass or more, based on 100 parts by mass of the binder resin. Is 15 parts by mass or more, and 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. With respect to 100 parts by mass of the binder resin, it is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, still more preferably 30 parts by mass or less.

In addition to the binder resin and colorant, the toner particles include mold release agents, charge control agents, charge control resins, magnetic powders, fluidity improvers, conductivity modifiers, reinforcing fillers such as fibrous substances, and antioxidants. Additives such as an agent and a cleaning property improving agent may be appropriately contained.

As a method for producing the toner particles, a method obtained by melt-kneading a toner raw material containing a binder resin and a colorant and crushing the obtained melt-kneaded product, preferably wet crushing, a water-based binder resin dispersion liquid and an aqueous system Examples thereof include a method of mixing the colorant dispersion liquid and combining the binder resin particles and the colorant particles, and a method of stirring the water-based binder resin dispersion liquid and the colorant at high speed. From the viewpoint of improving developability and fixability, a method of melt-kneading the toner raw material and then pulverizing, preferably wet pulverizing is preferable.

First, it is preferable that the toner raw material containing the binder resin, the colorant, and the 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 supplied to the kneader. A Henschel mixer is more preferable from the viewpoint of improving the dispersibility of the colorant in the binder resin.

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

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

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

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

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

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

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 later. Hereinafter, it is more preferably 12 μm or less. The volume median particle size (D ₅₀ ) means a particle size in which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size. It is preferable that the toner particles are further refined by wet pulverization or the like after being mixed with the dispersant and the insulating liquid.

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

A liquid plasticizer is a substance that shows a liquid state at 25 ° C, and means that the endothermic peak observed by DSC (Differential Scanning Calorimetry) measurement is less than 25 ° C.

In the present invention, the liquid plasticizer preferably contains an aliphatic liquid plasticizer.

Examples of the aliphatic liquid plasticizer include aliphatic ester plasticizers, aliphatic hydrocarbon plasticizers, and aliphatic epoxy plasticizers, from the viewpoint of improving low-temperature fixability and wet grindability of toner. Aliphatic ester plasticizers are preferred.

Examples of the aliphatic ester-based plasticizer include monohydric alcohol esters of fatty acids, monohydric alcohol esters of polybasic acids, fatty acid esters of polyhydric alcohols such as fatty acid esters of glycerin, and the like, which improve low-temperature fixability and chargeability. From the viewpoint of making the ester, a monohydric alcohol ester of polybasic acid or a fatty acid ester of glycerin is preferable.

Examples of monovalent alcohol esters of polybasic acid include diethyl sebacate, dibutyl sebacate, diisobutyl sebacate, diisopropyl sebacate, dioctyl sebacate, diisobutyl adipate, dioctyl adipate, diisononyl adipate, diisodecyl adipate, and tributyl citrate. , Tributyl acetylcitrate and the like.

Examples of the fatty acid ester of glycerin include 2-ethylhexanoic acid triglyceride, caprylic acid triglyceride, and glycerol laurate diacetate.

Examples of other liquid plasticizers include aromatic plasticizers.

Aromatic liquid plasticizers include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diallyl phthalate, di2-ethylhexyl phthalate, diisononyl phthalate, didecyl phthalate, trinormalalkyl trimellitic acid, and trimellitic acid. Examples thereof include triisodecyl and tri2-ethylhexyl trimellitic acid.

As the liquid plasticizer, one or more of the above plasticizers can be used, but the content of the aliphatic liquid plasticizer is preferably 80% by mass or more, more preferably 90% by mass in the liquid plasticizer. % Or more, more preferably 95% by mass or more, still more preferably 100% by mass.

The liquid plasticizer is preferably dissolved in an insulating liquid.

The content of the liquid plasticizer is preferably 2 parts by mass or more, more preferably 3 parts by mass or more, still more preferably 4 parts by mass or more, and the dispersion stability of the toner particles with respect to 100 parts by mass of the toner particles. From the viewpoint of improving storage stability, it is preferably 25 parts by mass or less, more preferably 15 parts by mass or less, and further preferably 10 parts by mass or less.

The insulating liquid in the present invention means a liquid through 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.

The insulating liquid in the liquid developer of the present invention is preferably a non-silicone insulating liquid from the viewpoint of improving fixability and dispersion stability of toner particles. As the non-silicone insulating liquid, for example, an insulating liquid containing polyisobutene is 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.

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 suppressing charger contamination, it is preferably 2 or more, and more preferably 3 or more.

It is preferable that the unreacted component of isobutylene and the high boiling point component having a high degree of polymerization generated during the polymerization reaction are removed by distillation.

Since the product obtained by the polymerization reaction has a double bond at the polymerization terminal, a hydrogenated product is obtained by the hydrogenation reaction.

The content of polyisobutene in the insulating liquid is preferably 5% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, still more preferably 60% by mass or more, from the viewpoint of suppressing charger contamination. More preferably, it is 80% 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). Among these, "NAS-4" is more preferable. One or a combination of two or more of these can be used.

Specific examples of the insulating liquid other than polyisobutene include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, vegetable oils and the like. Among these, aliphatic hydrocarbons such as liquid paraffin and isoparaffin are preferable from the viewpoint of reducing the viscosity of the liquid developer, odor, harmlessness and cost.

Commercially available products of aliphatic hydrocarbons include Isopar M (manufactured by ExxonMobil), Lytol (manufactured by Sonneborn), Cactus N12D, Cactus N14 (all manufactured by JX Nikko Nisseki Energy Co., Ltd.) 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, still more preferably 160 ° C. or higher, from the viewpoint of further improving the dispersion stability of the toner particles and improving the storage stability. It is 180 ° C. or higher, more preferably 200 ° C. or higher, further preferably 220 ° C. or higher, and from the viewpoint of further improving the low-temperature fixability of the toner, the grindability of the toner is further improved during wet grinding to develop a liquid having a small particle size. From the viewpoint of obtaining the agent, the temperature is preferably 300 ° C. or lower, more preferably 280 ° C. or lower, and further preferably 260 ° C. or lower. When two or more kinds of insulating liquids are used in combination, the boiling point of the combined insulating liquid mixture is preferably within the above range.

The viscosity of the insulating liquid at 25 ° C. is preferably 1 mPa · s or more, more preferably 1 mPa · s or more, from the viewpoint of improving the developability of the liquid developer and improving the storage stability of the toner particles in the liquid developer. It is 1.5 mPa · s or more, and preferably 100 mPa · s or less, more preferably 50 mPa · s or less, still more preferably 20 mPa · s or less, still more preferably 10 mPa · s or less, still more preferably 5 mPa · s or less. ..

The liquid developer of the present invention further improves the dispersion stability of the toner particles to improve the storage stability, and further improves the grindability of the toner particles during wet grinding to obtain a liquid developer having a small particle size. , It is preferable to contain a basic dispersant. The dispersant is used to stably disperse the toner particles in the insulating liquid. The liquid developer of the present invention contains a basic dispersant having a basic adsorbent group from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability and improving the chargeability of the toner. Is preferable. The basic adsorbing groups include amino groups (-NH ₂ , -NHR, -NHRR'), imino groups (= NH), and amide groups (-C (= O) -NRR') from the viewpoint of positive chargeability of the toner. ), Cyan group (-CN), azo group (-N = N-), diazo group (= N ₂ ), and at least one nitrogen-containing group selected from the group consisting of azi group (-N ₃ ). 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 or an imino group is preferable, from the viewpoint of increasing the adsorption efficiency of the dispersant and from the viewpoint of suppressing the aggregation of the toner particles and reducing the viscosity of the liquid developer. Is more preferably an imino group. The basic dispersant preferably has a plurality of basic adsorbing groups, and the basic dispersant having an imino group is preferably a condensate of polyimine and an acid, and a condensate of polyimine and a carboxylic acid. Is more preferable.

As the polyimine, polyalkyleneimine is preferable from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. Specific examples thereof include polyethyleneimine, polypropyleneimine, polybutyleneimine, etc., but polyethyleneimine is more preferable from the viewpoint of improving the dispersion stability of toner particles and improving the storage stability. The number of moles of ethyleneimine added is preferably 10 or more, more preferably 100 or more, and preferably 1,000 or less, more preferably 500 or less.

On the other hand, the carboxylic acid preferably has 10 or more and 30 or less carbon atoms, more preferably 12 or more and 24 or less carbon atoms, and further preferably 16 carbon atoms, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. Saturated or unsaturated aliphatic carboxylic acids of 22 or more are preferable, and linear saturated or unsaturated aliphatic carboxylic acids are more preferable. Specific examples of the carboxylic acid include linear saturated aliphatic carboxylic acids such as lauric acid, myristic acid, palmitic acid and stearic acid; and linear unsaturated aliphatic carboxylic acids such as oleic acid, linoleic acid and linolenic acid. Be done.

Further, the carboxylic acid may have a substituent such as a hydroxy group. From the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, a hydroxycarboxylic acid having a hydroxy group as a substituent is preferable. Examples of the hydroxycarboxylic acid include hydroxycarboxylic acids such as mevalonic acid, ricinoleic acid, and 12-hydroxystearic acid. The hydroxycarboxylic acid may be a condensate thereof.

From the above viewpoint, the carboxylic acid is preferably a hydroxyaliphatic carboxylic acid having 10 or more and 30 or less carbon atoms, more preferably 12 or more and 24 or less carbon atoms, and further preferably 16 or more and 22 or less carbon atoms, or a condensate thereof. , 12-Hydroxystearic acid or a condensate thereof is more preferable.

Specific examples of the condensate include Solsparse 11200, Solsparse 13940 (all manufactured by Japan Lubrizol Co., Ltd.), and the like, preferably Solsparse 11200.

In the present invention, as the basic dispersant other than the condensate of polyimine and carboxylic acid, the monomer A having an amino group and the formula (II):

(In the formula, R ¹ indicates a hydrogen atom or a methyl group, and R ² indicates an alkyl group having 1 or more and 22 or less carbon atoms or an alkenyl group having 2 or more and 22 or less carbon atoms, which may have a substituent.)
Examples thereof include a copolymer C obtained by polymerizing the monomer B represented by the above, an α-olefin / vinylpyrrolidone copolymer (Antalon V-216), and the like.

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

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

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

Specific examples of the monomer in which NR ³ R ⁴ is a tertiary amino group in the formula (III) (monomer having a tertiary amino group) include a (meth) acrylate having a dialkylamino group and a dialkylamino group ( Meta) Acrylamide and the like. In addition, "(meth) acrylic acid ester" indicates that the case of acrylic acid ester and methacrylic acid ester, and "(meth) acrylamide" indicates the case of both acrylamide and methacrylamide.

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

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

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

The monomer B is represented by the above formula (II), and in the above formula (II), the carbon number of the alkyl group and the alkenyl group represented by R ² is low viscosity, storage stability, and low temperature. From the viewpoint of fixability, it is preferably 10 or more, more preferably 12 or more, and from the viewpoint of low temperature fixability, it is 22 or less, preferably 18 or less, more preferably 16 or less, still more preferably 14 or less. The alkyl group or alkenyl group of R ² may be a straight chain or a branched chain, and may have a substituent such as a hydroxyl group.

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

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

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

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

The number average molecular weight of the basic dispersant is preferably 1,000 or more, more preferably 1,500 or more, still more preferably 2,500 or more, and the toner, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of grindability, it is preferably 10,000 or less, more preferably 9,000 or less, still more preferably 8,000 or less, still more preferably 7,000 or less, still more preferably 6,000 or less.

The weight average molecular weight of the basic dispersant is preferably 2,000 or more, more preferably 4,000 or more, still more preferably 8,000 or more, and the toner, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of grindability, it is preferably 50,000 or less, more preferably 40,000 or less, still more preferably 30,000 or less, still more preferably 20,000 or less, still more preferably 18,000 or less.

The content of the basic dispersant is preferably 0.5 parts by mass or more, more preferably 0.5 parts by mass or more, based on 100 parts by mass of the toner particles, from the viewpoint of suppressing aggregation of the toner particles and reducing the viscosity of the liquid developer. 1 part by mass or more, more preferably 2 parts by mass or more, and from the viewpoint of improving developability and fixability, preferably 20 parts by mass or less, more preferably 15 parts by mass or less, still more preferably 10 parts by mass or less. Is.

In addition, the content of the basic dispersant having an imino group in the basic dispersant suppresses the aggregation of the toner particles, reduces the viscosity of the liquid developer, and improves the pulverizability of the toner particles during wet grinding. From the viewpoint of obtaining a liquid developer having a small particle size, it is preferably 50% by mass or more, 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. Is.

The liquid developer is obtained by dispersing toner particles in an insulating liquid. From the viewpoint of reducing the particle size of the toner particles in the liquid developer and reducing the viscosity of the liquid developer, the toner particles are dispersed in an insulating liquid and then wet-ground to obtain a liquid developer. Is preferable.

As a method for mixing the toner particles, the liquid plasticizer, and the insulating liquid, preferably the basic dispersant, a method of stirring with a stirring and mixing device 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 a 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 pulverization 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 preferable 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. ..

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 media used, the peripheral speed of the rotor, the residence time, and the like.

As described above, the liquid developer of the present invention is
Step 1: A step of melt-kneading a binder resin containing a polyester resin and a colorant and pulverizing them to obtain toner particles.
Step 2: A step of adding a liquid plasticizer and a basic dispersant to the toner particles obtained in step 1 and dispersing them in an insulating liquid to obtain a toner particle dispersion liquid, and a step 3: the toner obtained in step 2. It is preferable to produce by a method including a step of wet-grinding the particle dispersion liquid to obtain a liquid developer.

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, still more preferably 20% by mass or more, and the dispersion stability of the toner particles. From the viewpoint of improving storage stability, the content 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 1.0 μm or more, still more preferably 1.5 μm or more, from the viewpoint of reducing the viscosity of the liquid developer. Yes, and from the viewpoint of improving the image quality of the liquid developer, it is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 2.5 μm or less.

The viscosity of the liquid developer at 25 ° C. is preferably 3 mPa · s or more, more preferably 5 mPa · s or more, still more preferably 6 mPa · s or more, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. , 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, still more preferably 37 mPa · s or less, still more preferable. Is 35 mPa · s or less, 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 16 mPa · s or less.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The physical properties of the resin and the like were measured by the following methods.

[Resin 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, and the diameter was 1 mm and the length was 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 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 Co., Ltd.), 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]
Measure by the method of JIS K0070. However, only the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Endothermic peak temperature of plasticizer]
Using a differential scanning calorimeter "Q-100" (manufactured by TA Instruments Japan Co., Ltd.), weigh 0.01 to 0.02 g of plasticizer in an aluminum pan, and cool down from room temperature (25 ° C) to a temperature reduction rate of 10. Cool to -40 ° C at ° C / min and let stand for 1 minute. After that, the endothermic peak is measured up to 150 ° C at a heating rate of 10 ° C / min.

[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: 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. Dispersion conditions: 10 mg of measurement sample in 5 mL of the dispersion Was added and dispersed with an ultrasonic disperser (machine name: US-1, manufactured by SND Co., Ltd., output: 80 W) for 1 minute, then 25 mL of the electrolytic solution was added, and the mixture was further added to the ultrasonic disperser. Disperse for 1 minute to prepare a sample dispersion.
Measurement conditions: Add the sample dispersion to 100 mL of the electrolytic solution so that the particle size of 30,000 particles can be measured in 20 seconds, measure 30,000 particles, and measure the volume from the particle size distribution. Determine the medium particle size (D ₅₀ ).

[Number average molecular weight (Mn) and weight average molecular weight (Mw) of condensate of polyimine and carboxylic acid]
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below, and the number average molecular weight and the weight average molecular weight are determined.
(1) Preparation of sample solution Dissolve the condensate in chloroform so that the concentration becomes 0.2 g / 100 mL. Next, this solution is filtered using a PTFE type membrane filter "DISMIC-25JP" (manufactured by Toyo Filter Paper Co., Ltd.) having a pore size of 0.20 μm to remove insoluble components, and the sample solution is used.
(2) Molecular weight measurement Using the following measuring device and analysis column, a chloroform solution of 100 mmol / L Fermin DM2098 (manufactured by Kao Corporation) was flowed as an eluent at a flow rate of 1 mL per minute in a constant temperature bath at 40 ° C. Stabilize the column with. 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. The calibration curve at this time 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 molecular weight is shown in parentheses.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: K-804L (manufactured by Showa Denko KK)

[Number average molecular weight (Mn) and weight average molecular weight (Mw) of dispersants A and B]
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below, and the number average molecular weight and the weight average molecular weight are determined.
(1) Preparation of sample solution The dispersant (the insulating liquid was distilled off from the dispersant solution) was dissolved in tetrahydrofuran so that the concentration was 0.5 g / 100 mL. Next, this solution was filtered using a fluororesin filter "FP-200" (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 2 μm to remove insoluble components, 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 per minute 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 a calibration curve prepared in advance. The calibration curve at this time includes several types of monodisperse polystyrene (A-500 (5.0 x 10 ² ), A-1000 (1.01 x 10 ³ ), A-2500 (2.63 x 10 ³ ), manufactured by Tosoh Corporation. A-5000 (5.97 × 10 ³ ), F-1 (1.02 × 10 ⁴ ), F-2 (1.81 × 10 ⁴ ), F-4 (3.97 × 10 ⁴ ), F-10 (9.64 × 10 ⁴ ), F-20 (1.90 × 10 ⁵ ), F-40 (4.27 × 10 ⁵ ), F-80 (7.06 × 10 ⁵ ), F-128 (1.09 × 10 ⁶ )) are used as standard samples. The molecular weight is shown in parentheses.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: TSKgel GMH _XL + TSKgel G3000H _XL (manufactured by Tosoh Corporation)

[Conductivity of insulating liquid]
Put 25 g of insulating liquid into a 40 mL glass sample tube "Screw No. 7" (manufactured by 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, 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 Co., Ltd.), 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 liquid and liquid developer at 25 ° C]
Put 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, and measure the viscosity at 25 ° C.

[Solid concentration of toner particle dispersion and liquid developer]
10 parts by mass of the sample is diluted with 90 parts by mass of hexane, and the sample is rotated for 20 minutes at a rotation speed of 25000 r / min using a centrifuge "H-201F" (manufactured by Kokusan Co., Ltd.). After standing, the supernatant is removed by decantation, diluted with 90 parts by mass of hexane, and centrifuged again under the same conditions. After removing the supernatant by decantation, the lower layer is dried in a vacuum dryer at 0.5 kPa at 40 ° C. for 8 hours, and the solid content concentration is calculated from the following formula.

[Volume medium particle size of toner particles in liquid developer (D ₅₀ )]
Using the laser diffraction / scattering particle size measuring device "Mastersizer 2000" (manufactured by Malvern), Isopar L (manufactured by Exxon Mobile, isoparaffin, viscosity at 25 ° C, viscosity 1 mPa · s) is added to the measuring cell to obtain scattering intensity. The volume median particle diameter (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 [Composite Resin A]
A 10-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple containing raw material monomers, esterification catalysts, and esterification auxiliary catalysts for polyester resins other than fumaric acid and trimellitic anhydride shown in Table 1. 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. After aging the addition polymerization reaction for 1 hour while keeping it at 170 ° C, the temperature is raised to 210 ° C, and the raw material monomer of the styrene resin is removed at 8.3 kPa for 1 hour, and the reaction between the bireactive monomer and the polyester moiety is carried out. went.
Further, at 210 ° C., trimellitic anhydride, fumaric acid and 5 g of 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 A having the physical properties shown in Table 1. ..

Resin Production Example 2 [Polyester Resin A]
The polyester raw material monomers, esterification catalysts, and esterification auxiliary catalysts shown in Table 1 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 was raised from 180 ° C to 210 ° C over 4 hours, reacted at 210 ° C for 4 hours, and further reacted at 8.3 kPa until the softening point shown in Table 1 was reached. Polyester having the physical properties shown in Table 1. Resin A was obtained.

Resin Production Example 3 [Polyester Resin B]
A 10-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple containing raw material monomers, esterification catalysts, and esterification auxiliary catalysts for polyester resins other than fumaric acid and trimellitic anhydride shown in Table 1. 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 reduced to 8.3 kPa for 1 hour.
Further, at 210 ° C., trimellitic anhydride, fumaric acid and 5 g of a polymerization inhibitor were added, and the reaction was carried out until the softening point shown in Table 1 was reached to obtain a polyester resin B having the physical properties shown in Table 1. ..

Resin Production Example 4 [Styrene Acrylic Resin A]
1567 g of xylene was placed in a 5 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, and the temperature was raised to 130 ° C. The mixed solution of the raw material monomer of the styrene resin and the polymerization initiator shown in Table 1 was added dropwise at 130 ° C. over 1.5 hours while stirring, and the addition polymerization reaction was carried out while maintaining the same temperature for another 1.5 hours. The temperature was raised to 160 ° C. and the reaction was carried out for 1 hour, then the temperature was raised to 200 ° C. and held for 1 hour to remove xylene. Further, the remaining xylene was removed at 8.3 kPa to obtain a styrene acrylic resin A having the physical characteristics shown in Table 1.

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

Examples 1 to 3 and Comparative Examples 2 to 3
80 parts by mass of the binder resin and 20 parts by mass of the pigment "ECB-301" (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue 15: 3) shown in Table 3 are rotated in advance using a 20 L volume Henschel mixer. After stirring and mixing at 1500 r / min (peripheral speed 21.6 m / sec) for 3 minutes, the mixture was melt-kneaded under the conditions shown below.

[Melting and kneading conditions]
A continuous double open roll type kneader "Kneedex" (manufactured by Nippon Coke Industries Co., Ltd., roll outer diameter: 14 cm, effective roll length: 55 cm) was used. The operating conditions of the continuous double open roll type kneader are high rotation side roll (front roll) peripheral speed 75r / min (32.4m / min), low rotation side roll (back roll) peripheral speed 35r / min (15.0m). / min), the roll gap at the end of the kneaded material supply port side 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, and 35 ° C on the raw material input side and 35 ° C on the kneaded material discharge side of the low rotation side roll. there were. The supply speed of the raw material mixture to the kneader was 10 kg / h, and the average residence time in the kneader was about 3 minutes.

The kneaded product obtained above was rolled and cooled with a cooling roll, and then roughly 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 median particle diameter (D ₅₀ ) of 10 μm.

35 parts by mass of the obtained toner particles and 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 61.15 parts by mass, 1.75 parts by mass of the liquid plasticizer and 2.1 parts by mass of the basic dispersant shown in Table 3 in a 1 L volume polyethylene container, and use "TK Robomix" (manufactured by Primix Co., Ltd.). Then, the mixture was stirred for 30 minutes at a rotation speed of 7,000 r / min under ice cooling to obtain a toner particle dispersion having a solid content concentration of 36% by mass.

Next, the obtained toner particle dispersion was rotated by a 6-cylinder sand mill "TSG-6" (manufactured by Imex Co., Ltd.) at a volume filling rate of 60% by volume using zirconia beads having a diameter of 0.8 mm. Wet pulverization was performed at 1300 r / min (peripheral speed 4.8 m / sec) until the volume medium particle size (D ₅₀ ) shown in Table 3 was reached. After removing the beads by filtration, 40 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 26% by mass. A liquid developer having the physical properties shown in 3 was obtained.

Examples 4, 5
The solid content concentration was increased by the same method as in Example 1 except that the basic dispersant was changed to the dispersant shown in Table 3, the basic dispersant was changed to 1.05 parts by mass, and the insulating liquid was changed to 63.95 parts by mass. A liquid developer having 26% by mass and the physical characteristics shown in Table 3 was obtained.

Comparative Example 1
A liquid developer was obtained in the same manner as in Example 1 except that the amount of the insulating liquid used was changed to 62.9 parts by mass without using the liquid plasticizer.

Comparative Example 4
Liquid development having the physical properties shown in Table 3 with a solid content concentration of 26% by mass by the same method as in Example 1 except that the binding resin was changed to 72 parts by mass of polyester resin B and 8 parts by mass of styrene acrylic resin A. I got the agent.

Test example [Fixability]
A liquid developer was added dropwise to "POD gloss coated paper" (manufactured by Oji Paper Co., Ltd.), and a thin film was prepared with a wire bar so that the mass after drying was 1.2 g / m ² . 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 160 ° C. by 10 ° C., the fixing treatment as described above was performed, 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 fixed 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 (%) was calculated from the value of the image density after peeling / the image density before peeling × 100, and the fixing rate was defined as a temperature range in which the fixing rate was 90% or more and no offset occurred. The value obtained by subtracting the lower limit value from the upper limit value of the fixing temperature was defined as the fixing width. The results are shown in Table 3. The larger the value, the wider the fixing width.

From the above results, it can be seen that the liquid developing agents of Examples 1 to 5 have a small particle size and a low viscosity, and can be fixed at a wide range of temperatures.
On the other hand, the liquid developer of Comparative Example 1 which does not use a liquid plasticizer and the liquid developer of Comparative Examples 2 and 3 which used a polyester resin instead of a composite resin as the binder resin have a large particle size and a high particle size. It has a viscosity and a narrow fixing width. Further, the liquid developer of Comparative Example 4 in which a polyester resin and a styrene resin are melt-kneaded instead of the composite resin also has a large particle size, a high viscosity, and a narrow fixing width.

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 (5)

A liquid developer containing toner particles containing a binder resin and a colorant, a liquid plasticizer, and an insulating liquid, wherein the binder resin is a polyester resin and a styrene resin as a raw material for the polyester resin. It contains a composite resin that is chemically bonded via a bireactive monomer that can react with either the monomer and the raw material monomer of the styrene resin, and the liquid plasticizer is a monovalent alcohol ester of polybasic acid or a fatty acid of glycerin. A liquid developer containing an aliphatic liquid plasticizer that is an ester . Liquid content of the plasticizer is, the toner particles 100 parts by weight, more than 25 parts by mass or more, 2 parts by mass claim 1 Symbol placement of the liquid developer. The liquid developer according to claim 1 or 2 , further comprising a basic dispersant. The liquid developer according to claim 3 , wherein the basic dispersant is a basic dispersant having an imino group. The liquid developer according to claim 3 or 4 , wherein the basic dispersant has a weight average molecular weight of 8,000 or more.