JP2018101006A - Liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer that has a small particle diameter, low viscosity, and can carry out fixing at a wide range of temperature.SOLUTION: A liquid developer contains an insulating liquid and toner particles containing a binder resin, colorant, and solid plasticizer, where the binder resin contains a composite resin in which a polyester resin and a styrene resin are chemically bonded via a bireactive monomer that can be reacted with any one of a raw material monomer of the polyester resin and a raw material monomer of the styrene resin.SELECTED DRAWING: None

Description

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

  Electrophotographic developers 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, since the toner particles are dispersed in the insulating liquid in oil, the particle size can be reduced as compared with the dry developer. Therefore, a high-quality printed matter that surpasses offset printing can be obtained, which is suitable for commercial printing applications. In recent years, the demand for speeding up has increased, and therefore, there is a demand for lowering the viscosity of the liquid developer. That is, there is a need for a liquid developer in which toner particles are stably dispersed with a small particle size and low viscosity.

  In Patent Document 1, for the purpose of providing a liquid developer that is excellent in fixing property, offset resistance, color developability, and has excellent storage stability, a stable output image can be obtained over a long period of time. A polymer dispersant obtained by polymerizing an ethylenically unsaturated monomer having an amino group and an ethylenically unsaturated monomer having 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 a plasticizer that is insoluble in water is disclosed.

  Patent Document 2 discloses a crude developer 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 toner particles is easily produced. The coarse particle preparation step for preparing particles, the coarse particles and the insulating carrier liquid are mixed, and the glass transition temperature Tg ° C. of the coarse particles is controlled to an average temperature of (Tg−5) ° C. to Tg ° C. However, there is disclosed a method for producing a liquid developer having a pulverizing step of pulverizing coarse particles with a grinding force to obtain flat toner particles.

JP 2014-92579 A JP 2012-103338 A

  In recent years, demands for higher speeds have increased, and therefore toners capable of being melt-fixed with a small amount of heat, that is, toners having excellent low-temperature fixability, have been demanded. Furthermore, since it is necessary to fix without causing hot offset even at a conventional speed, a toner that can be fixed at a wide range of temperatures is demanded.

  However, when the low-temperature fixability is improved by increasing the meltability of the toner, hot offset is likely to occur, and it is difficult to obtain a toner that can be fixed at a wide range of temperatures.

  The present invention relates to a liquid developer that has a small particle size, low viscosity, and can be fixed at a wide range of temperatures.

  The present invention is a liquid developer containing toner particles containing a binder resin, a colorant, and a solid plasticizer and an insulating liquid, wherein the binder resin comprises a polyester resin and a styrenic resin. The present invention relates to a liquid developer containing a composite resin chemically bonded via both reactive monomers capable of reacting with both the raw material monomer of the polyester resin and the raw material monomer of the styrenic resin.

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

  The liquid developer of the present invention is a liquid developer containing toner particles containing a binder resin, a colorant, and a solid plasticizer and an insulating liquid, and the binder resin comprises a polyester resin and a styrene resin. However, it has one characteristic in that it contains a composite resin chemically bonded via both reactive monomers capable of reacting with both the raw material monomer of the polyester resin and the raw material monomer of the styrenic resin. , Small particle size, low viscosity and fixable at wide temperature range.

The reason for such an effect is not clear, but is considered as follows.
Since the plasticizer has a polar part, when added to a composite resin of polyester resin and styrene resin, it has high affinity with the highly polar polyester part and selectively acts on the polyester part to plasticize it. Happens. This plasticized polyester portion is considered to contribute to low-temperature fixability. On the other hand, the plasticizer does not act on the styrene-based resin, and the styrene portion maintains a high elasticity, which contributes to the suppression of hot offset and can maintain the fixing property even at a high temperature. 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 stronger intermolecular force than styrene resin and is difficult to wet pulverize, but the plasticizer acts selectively on the polyester resin to weaken the intermolecular force and the solid plasticizer is at the interface. Since pulverization is accelerated, wet pulverization is improved, and it is considered that reduction in the particle size and reduction in viscosity are promoted.
Moreover, by containing the resin which chemically combined and combined the polyester resin and the styrene resin, it is possible to suppress the uneven distribution of two resins having different polarities, and to obtain a uniformly dispersed resin. As a result, uniform particles can be obtained even during the production of the toner, and good wet grindability and fixability can be obtained.

  The binder resin contains a composite resin in which a polyester resin and a styrenic resin are chemically bonded via both reactive monomers capable of reacting with both the raw material monomer of the polyester resin and the raw material monomer of the styrenic 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 aliphatic diols having 2 to 20 carbon atoms, preferably 2 to 15 carbon atoms, and the formula (I):

(In the formula, RO and OR are oxyalkylene groups, R is an ethylene and / or propylene group, x and y are the average number of moles of alkylene oxide added, each being a positive number, The sum value is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, and further preferably 4 or less)
An alkylene oxide adduct of bisphenol A represented by: Specific examples of the diol having 2 to 20 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, bisphenol A, hydrogen Additive bisphenol A etc. are mentioned.

  As the alcohol component, the viewpoint of improving the pulverization property of the toner to obtain a liquid developer having a small particle diameter, 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, further preferably 90 mol% or more, more preferably in the alcohol component. It is 95 mol% or more, more preferably 100 mol%.

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

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

  Examples of aromatic dicarboxylic acid compounds include phthalic acid, isophthalic acid, terephthalic acid; anhydrides of these acids and alkyl (carbon number 1 to 3) esters of these acids. Among these, terephthalic acid Or isophthalic acid is preferable and terephthalic acid is more preferable. In the present invention, the carboxylic acid compound includes not only a free acid but also an anhydride that decomposes during the reaction to produce an acid, and an alkyl ester having 1 to 3 carbon atoms.

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

  The chain hydrocarbon group in the aliphatic dicarboxylic acid-based compound may be linear or branched, and the aliphatic dicarboxylic acid-based compound preferably has 4 or more carbon atoms, and is readily 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), suberic acid (carbon number) : 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 in the side chain Succinic acid having these, anhydrides of these acids, alkyl esters having 1 to 3 carbon atoms thereof, and the like.

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

  The carboxylic acid component preferably contains a trivalent or higher aromatic carboxylic acid compound from the viewpoints of storage stability and durability.

  Trivalent or higher 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 alkyls. (C1-C3) ester etc. are mentioned, In these, a trimellitic acid type compound is preferable.

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

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

  From the viewpoint of adjusting the 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, more preferably 0.75 or more. Yes, and preferably 1.10 or less, more preferably 1.05 or less, more preferably 1.00 or less.

  The polyester resin is, for example, an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and further in the presence of an esterification promoter, a polymerization inhibitor, etc. It can be produced by polycondensation at a temperature of 250 ° C. or lower, 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 diisopropylate bistriethanolamate, and tin compounds are preferred. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, more preferably 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Preferably it is 1.0 mass part or less. Examples of the esterification promoter include gallic acid. The amount of esterification promoter 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. More preferably, it is 0.1 parts by mass or less. Examples of the polymerization inhibitor include t-butylcatechol. 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, more preferably 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. Preferably it is 0.1 mass part or less.

  The styrenic 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 derivatives 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 in the styrene resin raw material monomer and improving the storage stability. More preferably, it is 80% by mass or more, and from the viewpoint of improving the low-temperature fixability of the toner and from the viewpoint of improving wet grindability, it is preferably 95% by mass or less, more preferably 93% by mass or less, and still more preferably. 90% by mass or less.

  The styrenic resin may contain (meth) acrylic acid alkyl ester having an alkyl group having 7 or more carbon atoms as a raw material monomer. Examples of (meth) acrylic acid alkyl esters include 2-ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) stearyl (meth) acrylate, and the like. Can be mentioned. It is preferable to use one or more of these. In the present specification, “(iso)” means to include both when this group is present and when it is not present, and is normal when these groups are not present. It shows that. “(Meth) acrylic acid” refers to acrylic acid, methacrylic acid, or both.

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

  Examples of the raw material monomer for the styrene resin 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; ethylenic 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 included.

  The addition polymerization reaction of the raw material monomer of the styrenic resin is carried out by a conventional method, for example, in the presence of a polymerization initiator such as dicumyl peroxide, a polymerization inhibitor, a crosslinking agent, etc., in the presence or absence of an organic solvent. 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.

  Both reactive monomers have 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. Group, more preferably a compound having a carboxy group and an ethylenically unsaturated bond, more preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid and maleic anhydride, From the viewpoint of the reactivity of the polycondensation reaction and the addition polymerization reaction, at least one selected from the group consisting of acrylic acid, methacrylic acid and fumaric acid is more preferable. However, when used 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 the polyester resin. In this case, fumaric acid or the like is not a bireactive monomer but a raw material monomer for a polyester resin.

  The both reactive monomers may be one or more (meth) acrylic acid esters selected from acrylic acid esters and methacrylic acid esters having an alkyl group with 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 carbon number 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) acrylate, 2-hydroxyethyl (meth) acrylate, ( Examples include meth) acrylic acid (iso or tertiary) butyl, hexyl (meth) acrylate, and the like. In the present specification, “(iso or tertiary)” includes both the case where these groups are present and the case where these groups are not present, and in the case where these groups are not present , Indicates normal.

  In the present invention, the acrylate ester is preferably an alkyl acrylate ester having 2 to 6 carbon atoms in the alkyl group, more preferably butyl acrylate, and the methacrylic acid ester preferably has a carbon number in the alkyl group. The alkyl ester is 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 with respect to a total of 100 mol of the alcohol component of the polyester resin. From the viewpoint of enhancing the dispersibility with the polyester resin and improving the durability of the toner, the amount is preferably 30 mol or less, more preferably 20 mol or less, and still more preferably 10 mol or less.
In addition, the amount of both reactive monomers used is preferably 1 part by mass or more, more preferably 2 parts by mass or more, with respect to a total of 100 parts by mass of the raw material monomers of the styrenic resin, from the viewpoint of low-temperature fixability. From the viewpoint of improving the dispersibility of 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 still more 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 styrenic resin are chemically bonded via both reactive monomers.

  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 styrenic resin from the viewpoint of improving the durability of the toner and improving the low temperature fixability and heat resistant storage stability of the toner.

(i) A method of performing a step (B) of an addition polymerization reaction using a raw material monomer of a styrenic resin and an amphoteric monomer after the step (A) of the polycondensation reaction using the raw material monomer of the polyester resin. The step (A) is carried out under the reaction temperature conditions suitable for the reaction, the reaction temperature is lowered, and the step (B) is carried out under the temperature conditions suitable for the addition polymerization reaction. The styrene resin raw material monomer and the both reactive monomers are preferably added to 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 or the like of a trivalent or higher polyester resin that becomes a crosslinking agent is added to the polymerization system, and the polycondensation reaction or both reactions in the step (A). The reaction with the functional monomer can be further advanced.

(ii) Method of performing the step (A) of the polycondensation reaction using the raw material monomer of the polyester resin after the step (B) of the addition polymerization reaction using the raw material monomer of the styrene resin and the both reactive monomers. Step (B) is carried out under the reaction temperature conditions suitable for the step, the reaction temperature is raised, and the polycondensation reaction of step (A) is carried out under the temperature conditions suitable for the polycondensation reaction. Both reactive monomers are involved in the polycondensation reaction as well as the addition polymerization reaction.
The raw material monomer for 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 controlled by adding an esterification catalyst at a temperature suitable for the polycondensation reaction.

(iii) The step (A) of the polycondensation reaction using the raw material monomer of the polyester resin and the step (B) of the addition polymerization reaction using the raw material monomer and both reactive monomers of the styrenic resin are performed under the conditions that proceed in parallel. In this method, the step (A) and the step (B) are performed in parallel under the reaction temperature conditions suitable for the addition polymerization reaction, the reaction temperature is increased, and under the temperature conditions suitable for the polycondensation reaction, If necessary, it is preferable to further add a raw material monomer of a trivalent or higher valent polyester resin to be a crosslinking agent to the polymerization system and further perform the polycondensation reaction in the step (A). At that time, under a temperature condition suitable for the polycondensation reaction, a polymerization inhibitor can be added to advance only the polycondensation reaction. Both reactive monomers are involved in the polycondensation reaction as well as the addition polymerization reaction.

  In the method (i), a prepolymerized polycondensation resin may be used in place of the step (A) for performing the polycondensation reaction. In the above method (iii), when the reaction is carried out under the conditions in which the step (A) and the step (B) proceed in parallel, the raw material monomer for the styrene resin is contained in the mixture containing the raw material monomer for the polyester resin. It is also possible to cause the reaction to be carried out dropwise.

  The methods (i) to (iii) 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, and still more preferably 10 from the viewpoint of pulverizability of the toner particles. From the viewpoint of dispersion stability of the toner particles, it is preferably 45/55 or less, more preferably 40/60 or less, further preferably 35/65 or less, further preferably 30/70 or less, Preferably it is 25/75 or less. In the above calculation, the mass of the polyester resin is an amount obtained by subtracting the amount (calculated value) of the reaction water dehydrated by the polycondensation reaction from the mass of the raw material monomer of the polyester resin to be used. This amount is included in the raw material monomer amount 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 from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, and improves the low-temperature fixability of the toner. From the viewpoint, it is preferably 160 ° C. or lower, more preferably 130 ° C. or lower, further preferably 120 ° C. or lower, and further 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, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, and the viewpoint of improving the low-temperature fixability 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 storage stability by improving the dispersion stability of the toner particles. More preferably, it is 8 mgKOH / g or more, and preferably 60 mgKOH / g or less, more preferably 50 mgKOH / g or less, and further 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 trivalent or higher carboxylic acid compounds. can do.

  The content of the composite resin is preferably 90% by mass or more, more preferably 95% by mass or more in the binder resin, and more preferably 100% by mass, that is, only the composite resin is used. However, a resin other than the composite resin may be contained as long as the effects of the present invention are not impaired. Examples of the resin other than the composite resin include polyester resin, polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, and styrene-maleic acid copolymer. Polymers, styrene resins such as styrene-acrylic acid ester copolymers, styrene-methacrylic acid ester copolymers, and styrene resins, epoxy resins, rosin-modified maleic acids that are styrene or styrene-substituted copolymers or copolymers Examples thereof include one or more selected from resins such as resins, polyethylene resins, polypropylene resins, polyurethane resins, silicone resins, phenol resins, aliphatic or alicyclic hydrocarbon resins.

  As the colorant, dyes, pigments and the like used as toner colorants can be used. Examples include carbon black, phthalocyanine blue, permanent brown FG, brilliant first scarlet, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow. . In the present invention, the toner particles may be either black toner or color toner.

  The content of the colorant is preferably 3 parts by mass or more, more preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, more preferably from 100 parts by mass of the binder resin from the viewpoint of improving the image density. Is 15 parts by mass or more, and from the viewpoint of improving the pulverization property of the toner and reducing the particle size, improving the low-temperature fixability, and improving the dispersion stability of the toner particles and improving the storage stability. 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 with respect to 100 parts by mass of the binder resin.

  In the present invention, the solid plasticizer is a substance that shows a solid state at 25 ° C., and means an endothermic peak temperature observed by DSC (differential scanning calorimeter) measurement of 25 ° C. or higher.

  Examples of the solid plasticizer include a high molecular solid plasticizer and a low molecular solid plasticizer, and a low molecular solid plasticizer is preferable from the viewpoint of improving low-temperature fixability and wet grindability of toner.

  The molecular weight of the low molecular weight solid plasticizer is preferably 150 or more, more preferably 300 or more, further preferably 400 or more, and preferably 1500 or less, more preferably 1300 or less, and still more preferably 1200 or less.

  Examples of the low-molecular solid plasticizer include aliphatic solid plasticizers and aromatic solid plasticizers.

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

  Examples of the aliphatic ester plasticizer include monohydric alcohol esters of fatty acids, monohydric alcohol esters of polybasic acids, fatty acid esters of polyhydric alcohols, and the like. From the viewpoint of improving low-temperature fixability, fatty acids of polyhydric alcohols. Esters are preferred.

  Examples of fatty acid esters of polyhydric alcohol include fatty acid esters of glycerin such as stearic acid monoglyceride, oleic acid monoglyceride, palmitic acid monoglyceride, behenic acid monoglyceride, sorbitan tristearate, sorbitan monostearate, sorbitan monopalmitate, polyoxyethylene sorbitan Examples thereof include tristearate, polyoxyethylene sorbitol tetraoleate, polyethylene glycol monostearate, polyethylene glycol distearate, pentaerythritol monostearate, pentaerythritol tetrapalmitate and the like.

  The aliphatic ester plasticizer preferably has a plurality of ester bonds from the viewpoint of improving low-temperature fixability, improving the dispersion stability of toner particles and improving storage stability, and the number of ester bonds is preferably Is 2 or more, more preferably 3 or more, and preferably 5 or less, more preferably 4 or less.

  Examples of the aromatic solid plasticizer include aromatic amide plasticizers and aromatic ester plasticizers, and aromatic amide plasticizers are preferable from the viewpoint of improving the chargeability of the toner. Examples of the aromatic amide plasticizer include p-toluenesulfonamide, N-cyclohexyl-p-toluenesulfonamide, Nn-butylbenzenesulfonamide and the like.

  As the solid plasticizer, one or more plasticizers can be used. In the present invention, a low molecular weight aliphatic solid plasticizer is used from the viewpoint of improving low-temperature fixability and wet grindability of the toner. It is preferable to contain. The content of the low molecular weight aliphatic solid plasticizer 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 in the solid plasticizer. .

  The content of the compound having a plurality of ester bonds in the solid plasticizer is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and further preferably 100% by mass.

  The content of the solid plasticizer in the toner particles is preferably 2% by mass or more, more preferably 3% by mass or more, and further preferably 4% by mass or more, and the dispersion stability of the toner particles is improved and storage stability is improved. From the viewpoint of improving the properties, it is preferably 20% by mass or less, more preferably 15% by mass or less, and further preferably 10% by mass or less.

  In addition to binder resins, colorants, and solid plasticizers, toner particles can be used to reinforce release agents, charge control agents, charge control resins, magnetic powders, fluidity improvers, conductivity modifiers, fibrous materials, etc. An additive such as a filler, an antioxidant, and a cleaning property improver may be appropriately contained.

  As a method for producing toner particles, a toner raw material containing a binder resin, a colorant, and a solid plasticizer is melt-kneaded, and the obtained melt-kneaded product is pulverized, preferably wet-pulverized, and an aqueous binder. Examples include a method of mixing a resin dispersion, an aqueous colorant dispersion, and a solid plasticizer dispersion to unite the binder resin particles and the colorant particles, or a method of stirring the aqueous binder resin dispersion and the colorant at high speed. It is done. From the viewpoint of improving developability and fixability, a method of pulverizing, preferably wet pulverizing, after melt-kneading the toner raw material is preferable.

  First, a toner raw material containing a binder resin, a colorant, a solid plasticizer, 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 supplied to a kneader. The Henschel mixer is more preferable from the viewpoint of improving the dispersibility of the colorant and the solid plasticizer in the binder resin.

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

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

  The open roll type kneader refers to an open roll kneading unit that is not sealed and can easily dissipate the kneading heat generated during melt kneading. The open roll type kneader used in the present invention comprises a plurality of raw material supply ports and a kneaded product discharge port provided along the axial direction of the roll, and from the viewpoint of production efficiency, a continuous open roll type kneader. It is preferable that

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

  The grinding process may be divided into multiple stages. For example, the melt-kneaded product may be coarsely pulverized to about 1 to 5 mm and further finely pulverized. Moreover, in order to improve the productivity at the time of a grinding | pulverization process, you may grind | pulverize, after mixing melt-kneaded material with inorganic fine particles, such as hydrophobic silica.

  Examples of a pulverizer that is suitably used for coarse pulverization include an atomizer and a rotoplex, but a hammer mill or the like may also be used. Moreover, examples of the pulverizer suitably used for fine pulverization include a fluidized bed jet mill, an airflow jet mill, and a mechanical mill.

  Examples of the classifier used in the classification process include an airflow classifier, an inertia classifier, and a sieve classifier. In addition, you may repeat a grinding | pulverization process and a classification process as needed.

The volume median particle size (D ₅₀ ) of the toner particles obtained in this step is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm from the viewpoint of improving the productivity of the wet pulverization step described later. Below, more preferably 12 μm or less. The volume-median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction is 50% calculated from the smaller particle size. It is preferable that the toner particles are further refined by wet pulverization after mixing with the dispersant and the insulating liquid.

  The content of the toner particles is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, still more preferably 30 parts by mass or more, further preferably 100 parts by mass with respect to 100 parts by mass of the insulating liquid. 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, The amount is preferably 60 parts by mass or less.

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

  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 toner particle dispersion stability. 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, cationic polymerization using a catalyst, and then hydrogenating the terminal double bond.

  The degree of polymerization of the polyisobutene is preferably 8 or less, more preferably 6 or less, further preferably 5 or less, further preferably 4 or less, and further 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, more preferably 3 or more.

  It is preferable that unreacted components of isobutene and high-boiling components having a high degree of polymerization that are 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 a hydrogenation reaction.

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

  Specific examples of the insulating liquid other than polyisobutene include, for example, 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 viewpoints of reducing the viscosity of the liquid developer, odor, harmlessness, and cost.

  Examples of commercially available aliphatic hydrocarbons include Isopar M (ExxonMobil), Lytol (Sonneborn), Cactus N12D, Cactus N14 (all of which are manufactured by JX Nippon Oil & Energy Corporation). .

  The boiling point of the insulating liquid is preferably 120 ° C. or higher, more preferably 140 ° C. or higher, more preferably 160 ° C. or higher, more preferably from the viewpoint of further improving the storage stability by further improving the dispersion stability of the toner particles. 180 ° C. or higher, more preferably 200 ° C. or higher, more preferably 220 ° C. or higher, and from the viewpoint of further improving the low-temperature fixability of the toner, liquid development with a small particle size by further improving the toner grindability during wet grinding From the viewpoint of obtaining an agent, it is preferably 300 ° C. or lower, more preferably 280 ° C. or lower, and further preferably 260 ° C. or lower. When two or more insulating liquids are used in combination, the boiling point of the combined insulating liquid mixture is preferably within the above range.

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

From the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, and the liquid developer of the present invention from the viewpoint of obtaining a liquid developer having a small particle diameter by improving the pulverization property of the toner particles during wet pulverization. It is preferable to contain a basic dispersant. The dispersant is used for stably dispersing the toner particles in the insulating liquid. The liquid developer of the present invention may contain a basic dispersant having a basic adsorbing group from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability and from the viewpoint of improving the chargeability of the toner. preferable. Basic adsorbing groups include amino groups (—NH ₂ , —NHR, —NHRR ′), imino groups (═NH), amide groups (—C (═O) —NRR ′, from the viewpoint of positive chargeability of the toner. ), A cyano group (—CN), an azo group (—N═N—), a diazo group (═N ₂ ), and an azide group (—N ₃ ), at least one nitrogen-containing group selected from the group consisting of 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 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 acid, and a condensate of polyimine and carboxylic acid. 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 include polyethyleneimine, polypropyleneimine, polybutyleneimine, and the like, and polyethyleneimine is more preferable from the viewpoint of improving the dispersion stability of the 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 is preferably from 10 to 30 carbon atoms, more preferably from 12 to 24 carbon atoms, still more preferably 16 carbon atoms from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. A saturated or unsaturated aliphatic carboxylic acid of 22 or less is preferable, and a linear saturated or unsaturated aliphatic carboxylic acid is more preferable. Specific carboxylic acids include linear saturated aliphatic carboxylic acids such as lauric acid, myristic acid, palmitic acid and stearic acid; linear unsaturated aliphatic carboxylic acids such as oleic acid, linoleic acid and linolenic acid. It is done.

  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 preferred. Examples of the hydroxycarboxylic acid include mevalonic acid, ricinoleic acid, hydroxycarboxylic acid such as 12-hydroxystearic acid, and the like. The hydroxycarboxylic acid may be a condensate thereof.

  From the above viewpoint, the carboxylic acid is preferably a hydroxy aliphatic carboxylic acid having 10 to 30 carbon atoms, more preferably 12 to 24 carbon atoms, and still more preferably 16 to 22 carbon atoms, or a condensate thereof. 12-hydroxystearic acid or a condensate thereof is more preferable.

  Specific examples of the condensate include Solsperse 11200, Solsperse 13440 (all of which are manufactured by Nippon Lubrizol Co., Ltd.), and Solsperse 11200 is preferred.

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

(Wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group having 1 to 22 carbon atoms or an alkenyl group having 2 to 22 carbon atoms, which may have a substituent)
And a copolymer C obtained by polymerizing the monomer B represented by the following formula: an α-olefin / vinylpyrrolidone copolymer (Antalon V-216).

As the monomer A having an amino group, the formula (III):
CH ₂ ═C (R ⁵ ) COYR ⁶ NR ³ R ⁴ (III)
(Wherein R ³ and R ⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, which 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—.
Or an acid neutralized product (tertiary amine salt) or quaternary ammonium salt of this monomer. Preferred acids for obtaining the acid neutralized product include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, tartaric acid, adipic acid, sulfamic acid, toluenesulfonic acid, lactic acid, pyrrolidone- Examples thereof include 2-carboxylic acid and succinic acid. Preferred quaternizing agents for obtaining the quaternary ammonium salts 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. The general alkylating agent of these is mentioned.

In the formula (III), R ³ and R ⁴ are each independently preferably a linear or branched alkyl group having 1 to 4 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, and an isopropyl group, and a methyl group is preferable.

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

Specific examples of the monomer in which NR ³ R ⁴ is a tertiary amino group in formula (III) (monomers having a tertiary amino group) include (meth) acrylic acid esters having a dialkylamino group and dialkylamino groups ( And (meth) acrylamide. Note that “(meth) acrylic acid ester” includes both acrylic acid ester and methacrylic acid ester, and “(meth) acrylamide” includes both acrylamide and methacrylamide.

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

  Among these, a (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 formula (II). In the formula (II), the number of carbon atoms of the alkyl group and alkenyl group represented by R ² is reduced in 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, and even more preferably 14 or less. The alkyl group or alkenyl group of R ² may be linear or branched, 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, 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 (Me ) Acrylate, (iso) nonadecyl (meth) acrylate, (iso) icosyl (meth) acrylate, (iso) eicosyl (meth) acrylate, (iso) henicosyl (meth) acrylate, (iso) docosyl (meth) acrylate, etc. It is done. One or more of these can be used. Here, “(iso or tertiary)” and “(iso)” mean that both of these groups are present and not present, and when these groups are not present Indicates normal. Further, “(meth) acrylate” indicates that both acrylate and methacrylate are 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, from the viewpoint of low viscosity and storage stability. Preferably 5/95 or more, more preferably 7/93 or more, and from the viewpoint of low viscosity, storage stability, and low-temperature fixability, preferably 50/50 or less, more preferably 40/60 or less, More preferably, it is 35/65 or less.

  The total content of monomer A and monomer B in all monomers used in copolymer C 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. %.

  Monomer A and monomer B are polymerized by, for example, 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.

  The number average molecular weight of the basic dispersant is preferably 1,000 or more, more preferably 1,500 or more, and further preferably 2,500 or more, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint of the grindability, it is preferably 10,000 or less, more preferably 9,000 or less, further preferably 8,000 or less, further preferably 7,000 or less, and further 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, and still more preferably 8,000 or more, 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, further preferably 30,000 or less, further preferably 20,000 or less, and further preferably 18,000 or less.

  The content of the basic dispersant is preferably 0.5 parts by mass or more, more preferably as an effective component with respect to 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, more preferably 10 parts by mass or less. It is.

  In addition, the content of the basic dispersant having an imino group in the basic dispersant suppresses aggregation of the toner particles, reduces the viscosity of the liquid developer, and improves the pulverizability of the toner particles during wet pulverization. From the viewpoint of obtaining a liquid developer having a small particle size, preferably 50% by mass or more, more preferably 70% by mass or more, further preferably 90% by mass or more, further preferably 95% by mass or more, and further preferably 100% by mass. It 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 the insulating liquid and then wet pulverized to obtain the liquid developer. Is preferred.

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

  The stirring and mixing device is not particularly limited, but from the viewpoint of improving the productivity and storage stability of the toner particle dispersion, a high-speed stirring and mixing device is preferable. Specifically, Despa (manufactured by Asada Tekko Co., Ltd.), TK homomixer, TK homodisper, TK robotics (all of which are manufactured by Primics Co., Ltd.), Claremix (manufactured by M Technique Co., Ltd.), KD Mill (manufactured by KD International) Etc.) are preferred.

  By mixing with a high-speed stirring and mixing device, the toner particles are preliminarily dispersed to obtain a toner particle dispersion, 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, and further preferably 33% by mass or more. From the viewpoint of improving the property and improving the storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less.

  The wet pulverization is a method in which toner particles dispersed in an insulating liquid are mechanically pulverized in a state of being dispersed in the insulating liquid.

  As a device to be used, for example, a generally used stirring and mixing device such as an anchor blade can be used. Among the stirring and mixing devices, high speed stirring and mixing devices such as Despa (manufactured by Asada Tekko Co., Ltd.), TK. Etc. A plurality of these devices can be combined.

  Among these, 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. .

  In the bead mill, toner particles having a desired particle size and particle size distribution can be obtained by controlling the particle size and filling rate of the medium used, the peripheral speed of the rotor, the residence time, and the like.

As described above, the liquid developer of the present invention is
Step 1: a step of melt-kneading a binder resin containing a polyester-based resin, a colorant, and a solid plasticizer, and pulverizing to obtain toner particles;
Step 2: A basic dispersant is added to the toner particles obtained in Step 1 and dispersed in an insulating liquid to obtain a toner particle dispersion, and Step 3: the toner particle dispersion obtained in Step 2 is used. It is preferably produced by a method including a step of wet pulverization to obtain a liquid developer.

  From the viewpoint of improving the image density, the solid concentration of the liquid developer is preferably 10% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more, and the dispersion stability of the toner particles. From the viewpoint of improving the storage stability and the storage stability, it is preferably 50% by mass or less, more preferably 45% by mass or less, and still more preferably 40% by mass or less.

The volume median particle size (D ₅₀ ) of the toner particles in the liquid developer is preferably 0.5 μm or more, more preferably 1.0 μm or more, and even more preferably 1.5 μm or more, from the viewpoint of reducing the viscosity of the liquid developer. In view of improving the image quality of the liquid developer, it is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 2.5 μm or less.

  The viscosity at 25 ° C. of the liquid developer is preferably 3 mPa · s or more, more preferably 5 mPa · s or more, 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, it is 7 mPa · s or more, and from the viewpoint of improving the fixability of the liquid developer, it is preferably 50 mPa · s or less, more preferably 40 mPa · s or less, still more preferably 37 mPa · s or less, and still more preferably Is 35 mPa · s or less, more preferably 32 mPa · s or less, more preferably 28 mPa · s or less, more preferably 24 mPa · s or less, still more preferably 20 mPa · s or less, and even more preferably 16 mPa · s or less.

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

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

[Glass transition temperature of resin]
Using a differential scanning calorimeter “DSC210” (manufactured by Seiko Denshi Kogyo Co., Ltd.), 0.01 to 0.02 g of sample was weighed into an aluminum pan, heated to 200 ° C., and the temperature was reduced to 0 ° C./min. Cool to ° C. Next, the sample is heated at a heating rate of 10 ° C./min, and the endothermic peak is measured. The glass transition temperature is defined as the temperature at the intersection of the base line extension below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Acid value of the resin]
Measured by the method of JIS K0070. However, only the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Endothermic peak temperature of plasticizer]
Using a differential scanning calorimeter “Q-100” (manufactured by TA Instruments Japan Co., Ltd.), 0.01 to 0.02 g of plasticizer is weighed into an aluminum pan, and the temperature drop rate is 10 from room temperature (25 ° C.). Cool to -40 ° C at ℃ / min and let stand for 1 minute. Thereafter, the endothermic peak is measured up to 150 ° C. at a temperature rising rate of 10 ° C./min.

[Volume-median particle size of toner particles before mixing with insulating liquid]
Measuring machine: Coulter Multisizer II (manufactured by Beckman Coulter, Inc.)
Aperture diameter: 100μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter, Inc.)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB (Griffin): 13.6) dissolved in the electrolyte to adjust to 5% by mass Dispersion condition: 10 mL of measurement sample in 5 mL of the dispersion Is added for 1 minute with an ultrasonic disperser (machine name: US-1 manufactured by SND Co., Ltd., output: 80 W), and then 25 mL of the electrolyte is added. For 1 minute to prepare a sample dispersion.
Measurement conditions: The sample dispersion was added to 100 mL of the electrolyte so that the particle size of 30,000 particles could be measured in 20 seconds, and 30,000 particles were measured. Determine the median particle size (D ₅₀ ).

[Number average molecular weight (Mn) and weight average molecular weight (Mw) of polyimine and carboxylic acid condensate]
The molecular weight distribution is measured by the gel permeation chromatography (GPC) method shown below to determine the number average molecular weight and the weight average molecular weight.
(1) Preparation of sample solution Dissolve the condensate in chloroform so that the concentration is 0.2 g / 100 mL. Next, this solution is filtered using a PTFE type membrane filter “DISMIC-25JP” (manufactured by Toyo Roshi Kaisha, Ltd.) having a pore size of 0.20 μm to remove insoluble components, thereby obtaining a sample solution.
(2) Molecular weight measurement Using the following measuring device and analytical column, a chloroform solution of 100 mmol / L Farmin 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. To stabilize the column. Measurement is performed by injecting 100 μl of the sample solution. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. The calibration curves at this time include several types of monodisperse polystyrene (A-500 (Mw 5.0 × 10 ² ), A-5000 (Mw 5.97 × 10 ³ ), F-2 (Mw 1.81 × 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 to determine the number average molecular weight and the weight average molecular weight.
(1) Preparation of sample solution A 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. Subsequently, this solution was filtered using a fluororesin filter “FP-200” (manufactured by Sumitomo Electric Industries, Ltd.) having a pore size of 2 μm to remove insoluble components to obtain a sample solution.
(2) Molecular weight distribution measurement Using the following measuring device and analytical column, tetrahydrofuran is flowed as an eluent at a flow rate of 1 mL per minute, and the column is stabilized in a constant temperature bath at 40 ° C. Inject 100 μL of the sample solution into the sample and perform measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. The calibration curve at this time includes several types of monodisperse polystyrene (A-500 (5.0 × 10 ² ), A-1000 (1.01 × 10 ³ ), A-2500 (2.63 × 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 )) prepared as standard samples are used. 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 Marum Co., Ltd.), and use a non-aqueous conductivity meter “DT-700” (manufactured by Dispersion Technology) 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 a differential scanning calorimeter “DSC210” (manufactured by Seiko Denshi Kogyo Co., Ltd.), a sample of 6.0 to 8.0 mg was weighed into an aluminum pan, heated to 350 ° C. at a heating rate of 10 ° C./min, and an endothermic peak was obtained. taking measurement. The endothermic peak on the highest temperature side is defined as the boiling point.

[Viscosity of insulating liquid and liquid developer at 25 ° C]
Put 7 mL of the measuring solution into a 10 mL screw tube, and use the rotational vibration viscometer “Viscomate VM-10A-L” (manufactured by Seconic Co., Ltd., detection terminal: titanium, φ8 mm). Fix the screw tube at the position where the liquid level reaches 15mm above, and measure the viscosity at 25 ℃.

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

[Volume Median Particle Size (D ₅₀ ) of Toner Particles in Liquid Developer]
Using a laser diffraction / scattering particle size measuring device “Mastersizer 2000” (Malvern), add Isopar L (ExxonMobil, isoparaffin, viscosity 1 mPa · s at 25 ° C.) to the measurement cell, and the scattering intensity The volume median particle size (D ₅₀ ) is measured under the conditions of a particle refractive index of 1.58 (imaginary part 0.1) and a dispersion medium refractive index of 1.42 at a concentration of 5 to 15%.

Resin Production Example 1 [Composite Resin A]
Polyester resin raw material monomers other than fumaric acid and trimellitic anhydride shown in Table 1, esterification catalyst and esterification co-catalyst, 10 L four-neck flask equipped with nitrogen introduction tube, dehydration tube, stirrer and thermocouple The mixture was heated to 230 ° C. using a mantle heater, reacted at 230 ° C. for 8 hours, further depressurized to 8.3 kPa, and reacted for 1 hour.
The temperature was lowered to 170 ° C., and the styrene resin raw material monomer, the bireactive monomer and the polymerization initiator shown in Table 1 were added dropwise over 1 hour using a dropping funnel. After aging the addition polymerization reaction for 1 hour while maintaining at 170 ° C, the temperature was raised to 210 ° C, the raw material monomer of the styrene resin was removed at 8.3 kPa for 1 hour, and the reaction of both reactive monomers and the polyester part was performed. went.
Further, at 210 ° C., trimellitic anhydride, fumaric acid, and 5 g of a polymerization inhibitor were added, and the reaction was performed until the softening point shown in Table 1 was reached. Thus, composite resin A having physical properties shown in Table 1 was obtained. .

Resin Production Example 2 [Polyester Resin A]
The polyester resin raw material monomer, esterification catalyst, and esterification co-catalyst 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 a mantle heater was used. The temperature is raised from 180 ° C. to 210 ° C. over 4 hours, reacted at 210 ° C. for 4 hours, further reacted at 8.3 kPa until the softening point shown in Table 1 is reached, and has the physical properties shown in Table 1. Polyester resin A was obtained.

Resin Production Example 3 [Polyester Resin B]
Polyester resin raw material monomers other than fumaric acid and trimellitic anhydride shown in Table 1, esterification catalyst and esterification co-catalyst, 10 L four-neck flask equipped with nitrogen introduction tube, dehydration tube, stirrer and thermocouple The mixture was heated to 230 ° C. using a mantle heater, reacted at 230 ° C. for 8 hours, depressurized to 8.3 kPa, and reacted for 1 hour.
Furthermore, at 210 ° C., trimellitic anhydride, fumaric acid and a polymerization inhibitor 5 g were added and reacted until reaching the softening point shown in Table 1 to obtain a polyester resin B having 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. A mixture of the styrene resin raw material monomer and the polymerization initiator shown in Table 1 was added dropwise over 1.5 hours while stirring at 130 ° C., and the addition polymerization reaction was carried out while maintaining the same temperature for 1.5 hours. After raising the temperature to 160 ° C. and carrying out the reaction for 1 hour, the temperature was raised to 200 ° C. and maintained for 1 hour to remove xylene. Further, the remaining xylene was removed at 8.3 kPa to obtain styrene acrylic resin A having the physical properties shown in Table 1.

Production Example of Dispersant 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 and the polymerization initiator shown in Table 2 was dropped over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 80 ° C. for 3 hours. The solvent was distilled off at 80 ° C. to obtain dispersants A and B composed of copolymers having physical properties shown in Table 2.

Examples 1-4 and Comparative Examples 1-4
The amount of binder resin and solid plasticizer shown in Table 3 (not used in Comparative Example 1) and 20 parts by mass of pigment “ECB-301” (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue 15: 3) Then, using a 20 L Henschel mixer in advance, the mixture was stirred and mixed for 3 minutes at a rotational speed of 1500 r / min (circumferential speed 21.6 m / sec), and then melt-kneaded under the following conditions.

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

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

35 parts by mass of the obtained toner particles and 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 mPa・ S) Put 62.9 parts by mass and 2.1 parts by mass of the basic dispersant shown in Table 3 in a 1 L polyethylene container and rotate under ice-cooling using “TK Robotics” (manufactured by Primics Co., Ltd.). The mixture was stirred for 30 minutes at several 7000 r / min to obtain a toner particle dispersion having a solid content concentration of 36% by mass.

Next, the obtained toner particle dispersion was rotated with a 6-cylinder sand mill “TSG-6” (manufactured by IMEX Co., Ltd.) using zirconia beads having a diameter of 0.8 mm at a volume filling rate of 60% by volume. Wet grinding was performed at 1300 r / min (circumferential speed 4.8 m / sec) until the volume-median particle size (D ₅₀ ) shown in Table 3 was obtained. After removing the beads by filtration, 100 parts by mass of the filtrate was diluted by adding 40 parts by mass of the insulating liquid “NAS-4” (manufactured by NOF Corporation), and the solid content concentration was 26% by mass. A liquid developer having the physical properties shown in 3 was obtained.

Examples 5 and 6
The same method as in Example 1 except that the basic dispersant was changed to the dispersant shown in Table 3, the basic dispersant usage was changed to 1.05 parts by mass, and the insulating liquid usage was changed to 63.95 parts by mass. Thus, a liquid developer having a solid content concentration of 26% by mass and having the physical properties shown in Table 3 was obtained.

Comparative Example 5
Liquid development having the physical properties shown in Table 3 in the same manner as in Example 1 except that the binder resin was changed to 67.5 parts by mass of polyester resin B and 7.5 parts by mass of styrene acrylic resin A, and the solid content concentration was 26% by mass. An agent was obtained.

Test example (fixability)
A liquid developer was dropped onto “POD gloss coated paper” (manufactured by Oji Paper Co., Ltd.), and a thin film was prepared with a wire bar so that the mass after drying was 1.2 g / m ² . Then, it hold | maintained for 10 second in an 80 degreeC thermostat.

  Subsequently, 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 80 ° C. and a fixing speed of 280 mm / sec. Thereafter, while the fixing roll temperature was increased to 160 ° C. by 10 ° C., the fixing process as described above was performed, and a fixed image was obtained at each temperature.

  Affix the mending tape “Scotch Mending Tape 810” (manufactured by 3M Japan Co., Ltd., width 18mm) to the fixed image obtained, apply pressure to the tape with a roller to apply a load of 500g, It peeled. The image density before and after tape peeling was measured using a color meter “GretagMacbeth 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 rate (%) is calculated from the value of image density after peeling / image density before peeling x 100, and the fixing temperature is 90% or more and the temperature range where no offset occurs is the fixing temperature. The value obtained by subtracting the lower limit from the value was defined as the fixing width. The results are shown in Table 3. The larger the value, the wider the fixing width and the better the fixing property.

From the above results, it can be seen that the liquid developers of Examples 1 to 6 have a small particle size and low viscosity, and can be fixed at a wide range of temperatures.
On the other hand, the liquid developer of Comparative Example 1 that does not use a solid plasticizer, and the liquid developer of Comparative Examples 2 to 4 that uses a polyester resin or a styrene acrylic resin instead of a composite resin as a binder resin, The diameter is large, the viscosity is high, and the fixing width is narrow. Similarly, the liquid developer of Comparative Example 5 in which a polyester resin and a styrene resin are melt-kneaded instead of the composite resin has a large particle size and a high viscosity.

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

Claims (7)

  A liquid developer containing toner particles containing a binder resin, a colorant, and a solid plasticizer, and an insulating liquid, wherein the binder resin comprises a polyester resin and a styrenic resin. A liquid developer comprising a composite resin chemically bonded via a bi-reactive monomer capable of reacting with both the raw material monomer and the raw material monomer of the styrene resin.   The liquid developer according to claim 1, wherein the content of the solid plasticizer is 2% by mass or more and 20% by mass or less in the toner particles.   The liquid developer according to claim 1, wherein the solid plasticizer contains an aliphatic solid plasticizer having a molecular weight of 1500 or less.   The liquid developer according to claim 3, wherein the aliphatic solid plasticizer is an aliphatic ester plasticizer having two or more ester bonds.   The liquid developer according to claim 1, further comprising a basic dispersant.   The liquid developer according to claim 5, wherein the basic dispersant is a basic dispersant having an imino group.   The liquid developer according to claim 5 or 6, wherein the basic dispersant has a weight average molecular weight of 8,000 or more.