JP2020177190A - Liquid developer - Google Patents

Abstract

To provide a liquid developer that contains a polyester resin and is excellent in high resistance and positive chargeability while maintaining a small diameter and low viscosity.SOLUTION: A liquid developer contains toner particles containing a binder resin and a colorant, an amino group-containing copolymer, an inorganic compound including silica, and an insulating liquid. The binder resin contains a polyester resin, and the amino group-containing copolymer is an amino group-containing copolymer that is a polymer of a monomer including a monomer A having an amino group and a monomer B represented by the formula (I), where R1 represents a hydrogen atom or a hydrocarbon group having 1 or more and 5 or less carbon atoms, and R2 represents a hydrocarbon group having 1 or more and 22 or less carbon atoms, which may have a substituent.SELECTED DRAWING: None

Description

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

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

In the liquid developer, the toner particles are dispersed in the oil in the insulating liquid, so that the particle size can be reduced as compared with the dry developer. Therefore, it is possible to obtain a high-quality printed matter that surpasses offset printing, and is suitable for commercial printing applications. Further, in recent years, there has been an increasing demand for high speed, and since toner particles need to be rapidly developed by electrophoresis, it is required to reduce the viscosity and increase the charge of the liquid developer. Further, when toner having insufficient developability and cleanability accumulates on the roller, filming occurs, which causes deterioration of image quality and the like during long-term printing. Therefore, a highly charged toner is required from the viewpoint of suppressing filming and obtaining good printing durability.

Patent Document 1 has an object of providing a white liquid developer having excellent concealing property, transferability, and dispersion stability in a carrier liquid, and as a pigment, titanium oxide (A) and a binder resin (B). A white liquid developer containing white toner particles containing), a basic polymer dispersant (C), and a carrier liquid (D), wherein the titanium oxide (A) is surface-treated with alumina and an organic compound. The white liquid developer is disclosed, wherein the solubility parameter (SP value) of the binder resin (B) is 10 to 13, and the acid value is 20 to 70 mgKOH / g. ing.

According to Patent Document 2, wet development can be easily scraped off by a cleaning blade, does not cause an increase in viscosity of the wet developer or a decrease in fixability of the toner image, and further, wet development with a small variation in the amount of charge of each color toner. For wet development, an object of providing a toner for wet development is that hydrophobic particles having at least a colorant and a binder resin and having a shape coefficient (SF-1) of 100 to 130 are present on the surface. The toner is disclosed.

Patent Document 3 has an object of providing a matte wet developing agent in which resin particles containing a matte pigment are dispersed in an electrically insulating dispersion medium. Discloses a matte wet developer characterized by dispersing resin particles containing a matte pigment.

JP-A-2018-018016 Japanese Unexamined Patent Publication No. 2015-161773 Japanese Unexamined Patent Publication No. 2000-235284

However, with the conventional technology, it is difficult to achieve both small particle size and low viscosity of the liquid developer, and insufficient chargeability and high resistance, and it is difficult to perform high-speed printing while maintaining good image quality. is there. In particular, polyester-based resins, which are widely used as binder resins, are easily negatively charged because they have an acid group, and there is a problem in chargeability when used in a positively charged liquid developer.

The present invention relates to a liquid developer containing a polyester resin, maintaining a small particle size and low viscosity, and having high resistance and excellent positive chargeability.

The present invention is a liquid developer containing toner particles containing a binder resin and a colorant, an amino group-containing copolymer, an inorganic compound containing silica, and an insulating liquid, wherein the binder resin is polyester-based. The resin-containing, amino group-containing copolymer comprises monomer A having an amino group and the formula (I):

(In the formula, R ¹ indicates a hydrogen atom or a hydrocarbon group having 1 or more and 5 or less carbon atoms, and R ² indicates a hydrocarbon group having 1 or more and 22 or less carbon atoms which may have a substituent).
The present invention relates to a liquid developer, which is an amino group-containing copolymer which is a polymer of a monomer containing a monomer B represented by.

Even if the liquid developer of the present invention contains a polyester resin, it has the effect of maintaining a small particle size and low viscosity, and having high resistance and excellent positive chargeability.

The liquid developer of the present invention contains a binder resin containing a polyester resin, toner particles containing a colorant, an insulating liquid, and further contains an amino group-containing copolymer that functions as a dispersant and silica. It contains an inorganic compound, and has high resistance and excellent positive chargeability while maintaining a small particle size and low viscosity.

The reason for achieving such an effect is not clear, but it is considered as follows.
The amino group-containing copolymer is easily adsorbed on the toner particles containing the polyester resin by acid-base interaction. Further, when silica is present in the system, it is considered that the positive chargeability of the particles is improved by the interaction of the acidic moiety of silica with the amino groups of the amino group-containing copolymer adsorbed on the toner particles.
Further, since the amino group-containing copolymer in the present invention has a carbon chain as described later, when it is adsorbed on the toner, the portion of the carbon chain having a high affinity with the insulating liquid expands, and between the toner particles. Expresses the steric repulsive force of. As a result, aggregation of toner particles and thickening of the liquid developer can be suppressed, so that the liquid developer of the present invention is considered to have a small particle size and a low viscosity.

The binding resin includes a polyester resin.

The polyester-based resin is not particularly limited, and examples thereof include a polyester resin or a composite resin having a polyester resin and another resin such as a styrene resin.

The polyester resin is preferably a polycondensate of an alcohol component containing a divalent or higher alcohol and a carboxylic acid component containing a divalent or higher carboxylic acid compound.

Examples of the divalent alcohol include an aliphatic diol having 2 or more and 20 or less carbon atoms, preferably 2 or more and 15 or less carbon atoms, and the formula (II):

(In the formula, OR and RO are oxyalkylene groups, R is an ethylene group and / or a propylene group, x and y indicate the average number of moles of alkylene oxide added, which are positive numbers, respectively, and x and y. The value of the sum of is 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, still more preferably 4 or less).
Examples thereof include an alkylene oxide adduct of bisphenol A represented by, bisphenol A, hydrogenated bisphenol A and the like. Examples of the aliphatic diol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol, among which the number of carbon atoms is 3 or more. An aliphatic diol having a hydroxyl group bonded to 5 or less secondary carbon atoms is preferable.

As the alcohol component, the pulverizability of the toner is improved to obtain toner particles having a small particle size, the low temperature fixability of the toner is improved, and the dispersion stability of the toner particles is improved to improve the storage stability. From the viewpoint, 1,2-propanediol or an alkylene oxide adduct of bisphenol A represented by the formula (II) is preferable. The content of the alkylene oxide adduct of 1,2-propanediol or bisphenol A represented by the formula (II) is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 in the alcohol component. It is mol% or more, more preferably 95 mol% or more, still more preferably 100 mol%. When 1,2-propanediol and an alkylene oxide adduct of bisphenol A represented by the formula (II) are used in combination, the total content of both is preferably within the above range.

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.

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

As the carboxylic acid component, terephthalic acid and / or fumaric acid are preferable from the viewpoint of improving the low temperature fixability of the toner and improving the dispersion stability of the toner particles to improve the storage stability. The content of terephthalic acid or fumaric acid in the carboxylic acid component is preferably 40 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, and preferably 95 mol% or less, more. It is preferably 93 mol% or less, more preferably 90 mol% or less. When terephthalic acid and fumaric acid are used in combination, the total content of both is preferably within the above range.

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

The content of the trivalent or higher carboxylic acid compound is preferably 1 mol% or more, more preferably 2 mol% or more, among the carboxylic acid components, from the viewpoint of the adsorptivity of the amino group-containing copolymer to the toner particles. It is more preferably 3 mol% or more, and from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, it is preferably 30 mol% or less, more preferably 25 mol% or less, still more preferably 20 mol. % Or less.

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

The equivalent ratio (COOH group / OH group) of the carboxylic acid component and the alcohol component in the polyester resin is preferably 0.6 or more, more preferably 0.7 or more, still more preferably 0.75 or more from the viewpoint of adjusting the softening point of the polyester resin. Yes, and preferably 1.1 or less, more preferably 1.05 or less, and even more preferably 1 or less.

The polyester resin preferably contains, for example, an alcohol component and a carboxylic acid component in an inert gas atmosphere, preferably in the presence of an esterification catalyst, and if necessary, in the presence of an esterification co-catalyst, a polymerization inhibitor, or the like. It can be produced by polycondensation at a temperature of 130 ° C. or higher, more preferably 170 ° C. or higher, and preferably 250 ° C. or lower, more preferably 240 ° C. or lower.

Examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin (II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropyrate bistriethanol aminated, and tin compounds are preferable. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 1 part by mass or less. Examples of the esterification co-catalyst include gallic acid and the like. The amount of the esterification co-catalyst used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. More preferably, it is 0.1 part by mass or less. Examples of the polymerization inhibitor include t-butylcatechol and the like. The amount of the polymerization inhibitor used is preferably 0.001 part by mass or more, more preferably 0.01 part by mass or more, and preferably 0.5 part by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 0.1 parts by mass or less.

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

As the composite resin, a composite resin having the polyester resin and the styrene resin is preferable.

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, 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. The above is more preferably 80% by mass or more, and from the viewpoint of improving the low-temperature fixability of the toner and improving the wet grindability, it is preferably 95% by mass or less, more preferably 93% by mass or less, still more preferably. 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 is present and the case where this group is not present, and it is normal when these groups are not present. Show that. Further, "(meth) acrylic acid" indicates acrylic acid, methacrylic acid, or both.

The content of the (meth) acrylic acid alkyl ester having 7 or more carbon atoms is preferably 5% by mass or more from the viewpoint of improving the low-temperature fixability of the toner and the wet grindability in the raw material monomer of the styrene resin. , More preferably 7% by mass or more, further preferably 10% by mass or more, and preferably 50% by mass or less, more preferably from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. It is 30% by mass or less, more preferably 20% by mass or less.

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 stored, from the viewpoint of improving the low temperature fixability of the toner. From the viewpoint of stability, it is preferably 12 or less, more preferably 10 or less. The carbon number of the alkyl ester refers to the carbon number derived from the alcohol component constituting the ester.

Raw material monomers of 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; and halovinyl such as vinyl chloride. Classes; vinyl esters such as vinyl acetate and vinyl propionate; ethylenic monocarboxylic acid esters such as dimethylaminoethyl (meth) acrylate; vinyl ethers such as methyl vinyl ether; vinylidene halides such as vinylidene chloride; N-vinylpyrrolidone. N-vinyl compounds and the like may be contained.

The addition polymerization reaction of the raw material monomer of the styrene resin can be carried out 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. 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.

In the present invention, the composite resin can react with either the raw material monomer of the polyester resin or the raw material monomer of the styrene resin from the viewpoint of dispersion stability and pulverizability of the toner particles, and the composite resin and the polyester resin via both reactive monomers. A resin in which a styrene resin is chemically bonded is preferable.

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 alkyl group preferably has 2 or more carbon atoms, more preferably 3 or more carbon atoms, and is preferable. Is 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, "(iso or tertiary)" means to include both the case where these groups are present and the case where these groups are not present, and when these groups are not present, it is normal. Is shown.

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.

The amount of both reactive monomers used is preferably 1 mol or more from the viewpoint of improving the dispersibility of the styrene resin and the polyester resin and improving the durability of the toner with respect to a total of 100 mol of the alcohol component of the polyester resin. , More preferably 2 mol or more, and from the viewpoint of low temperature fixability, preferably 30 mol or less, more preferably 20 mol or less, still more preferably 10 mol or less.
Further, the amount of both reactive monomers used is preferable from the viewpoint of improving the dispersibility between the styrene resin and the polyester resin and improving the durability of the toner with respect to a total of 100 parts by mass of the raw material monomers of the styrene resin. Is 1 part by mass or more, more preferably 2 parts by mass or more, and from the viewpoint of low temperature fixability, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, 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.

Specifically, the composite resin obtained by using the bireactive monomers 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. The raw material monomer of the styrene resin and the bireactive monomer are preferably added into the reaction system at a temperature suitable for the addition polymerization reaction. Both reactive monomers undergo an addition polymerization reaction and also react with a polyester resin.
After the step (B), the reaction temperature is raised again, and if necessary, a raw material monomer of a polyester resin having a valence of 3 or more as a cross-linking agent is added to the reaction 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 to be performed In this method, the steps (A) and (B) are carried out 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 radical 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 step (A) and the step (B) are carried out in parallel, a mixture containing a raw material monomer of a styrene resin is mixed with a mixture containing a raw material monomer of a polyester resin. It 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 crushability 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 polyester 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 of the temperature, 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 polyester resin is preferably 40 ° C. or higher, more preferably 45 ° C. or higher, and improves low temperature fixability, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. From the viewpoint, it is preferably 80 ° C. or lower, more preferably 70 ° C. or lower, and further preferably 60 ° C. or lower.

From the viewpoint of improving the chargeability of the toner, the acid value of the polyester resin is preferably 5 mgKOH / g or more, more preferably 10 mgKOH / g or more, still more preferably 15 mgKOH / g or more, and the dispersion stability of the toner particles is stable. From the viewpoint of improving the properties and the storage stability, it is preferably 70 mgKOH / g or less, more preferably 50 mgKOH / g or less, still more preferably 40 mgKOH / g or less, still more preferably 20 mgKOH / g or less. The acid value of the polyester resin can be adjusted by changing the equivalent ratio of the carboxylic acid component and the alcohol component, changing the reaction time during resin production, or changing the content of the carboxylic acid compound having a valence of 3 or more. Can be adjusted.

The content of the polyester resin is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 100% by mass, that is, only the polyester resin is used in the binder resin. However, a resin other than the polyester resin may be contained as long as the effect of the present invention is not impaired. Examples of resins other than polyester-based resins include polystyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, and styrene-maleic acid copolymer. , Styrene-acrylic acid ester copolymer, styrene-based resin, epoxy-based resin, rosin-modified maleic acid resin, which is a copolymer or copolymer containing styrene or a styrene-substituted product such as a styrene-methacrylic acid ester copolymer, One or more selected from resins such as polyethylene-based resin, polypropylene-based resin, polyurethane-based resin, silicone-based resin, phenol-based resin, aliphatic or alicyclic hydrocarbon resin 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 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more with respect to 100 parts by mass of the binder resin. Then, from the viewpoint of improving the pulverizability of the toner to reduce the particle size, improving the low-temperature fixability, and improving the dispersion stability of the toner particles to improve the storage stability, 100 masses 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, or a method of stirring the aqueous binder resin dispersion liquid and the colorant at high speed. From the viewpoint of improving developability and fixability, a method of melt-kneading the toner raw material and then pulverizing, preferably wet pulverizing is preferable.

First, it is preferable that the toner raw material containing the binder resin, the colorant, the additive used as necessary, and the like 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.

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 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.

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. The toner particles are preferably mixed with an amino group-containing copolymer and an insulating liquid, and then further refined by wet pulverization or the like.

The content of the toner particles to be subjected to wet pulverization is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and further preferably 50 parts by mass or more with respect to 100 parts by mass of the insulating liquid from the viewpoint of pulverization efficiency. Yes, 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, still more preferably 60 parts by mass or less.

The amino group-containing copolymer in the present invention comprises monomer A having an amino group and the formula (I):

(In the formula, R ¹ is a hydrogen atom or a hydrocarbon group having 1 or more and 5 or less carbon atoms, preferably a methyl group, and R ² is a hydrocarbon group having 1 or more and 22 carbon atoms or less, which may have a substituent. , Preferably an alkyl group having 1 to 22 carbon atoms or an alkenyl group having 2 to 22 carbon atoms)
It is a polymer of a monomer containing the monomer B represented by.

As the monomer A having an amino group, the formula (III):
CH ₂ = C (R ⁵ ) COYR ⁶ NR ³ R ⁴ (III)
(In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 or more and 4 or less carbon atoms, and they are bonded to each other to form a ring structure. R ⁵ may represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms, preferably a methyl group, and R ⁶ may represent a linear or branched alkylene group having 2 or more and 4 or less carbon atoms, and Y Indicates -O- or -NH-)
A monomer having an amino group represented by, or an acid neutralized product (tertiary amine salt) or a quaternary ammonium salt of this monomer is preferable. Preferred acids for obtaining the above acid neutralized products include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, formic acid, maleic acid, fumaric acid, citric acid, succinic acid, adipic acid, sulfamic acid, toluenesulfonic acid, lactic acid, pyrrolidone-. Examples thereof include 2-carboxylic acid and succinic acid. Preferred quaternary agents for obtaining the above quaternary ammonium salt include alkyl halides such as methyl chloride, ethyl chloride, methyl bromide and methyl iodide, dimethyl sulfate, diethyl sulfate, di-n-propyl sulfate and the like. 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 (I), and in the above formula (I), the carbon number of the alkyl group and the alkenyl group represented by R ² is low viscosity, storage stability, and low temperature. From the viewpoint of fixability, it is preferably 10 or more, more preferably 12 or more, and from the viewpoint of adsorptivity to toner particles, it is 22 or less, preferably 20 or less. The alkyl group or alkenyl group of R ² may be a straight chain or a branched chain, and may have a substituent such as a hydroxyl group.

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

Specific examples of the monomer B include methyl (meth) acrylate, ethyl (meth) acrylate, (iso) propyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (iso or tertiary) butyl (meth) acrylate, and the like. 2-Ethylhexyl (meth) acrylate, (iso) octyl (meth) acrylate, (iso) nonyl (meth) acrylate, (iso) decyl (meth) acrylate, (iso) undecyl (meth) acrylate, (iso) dodecyl (meth) ) Acrylate, (iso) tridecyl (meth) acrylate, (iso) tetradecyl (meth) acrylate, (iso) pentadecyl (meth) acrylate, (iso) hexadecyl (meth) acrylate, (iso) heptadecyl (meth) acrylate, (iso) ) Octadecyl (meth) acrylate, (iso) 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 these groups 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 mass ratio of monomer A to monomer B (monomer A / monomer B) is preferably 20/80 or more, more preferably 35/65 or more, still more preferably 45/55 or more, from the viewpoint of improving the chargeability of the toner. Yes, and from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability, and from the viewpoint of increasing the resistance of the liquid developer, it is preferably 80/20 or less, more preferably 65/35 or less, still more preferable. Is 55/45 or less.

Examples of the monomer other than the monomer A and the monomer B include a monomer having a polysiloxane chain.

The total content of the monomer A and the monomer B in all the monomers used in the amino group-containing copolymer is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and is preferable. Is 100% by mass or less, more preferably 100% by mass.

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

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

The weight average molecular weight of the amino group-containing copolymer is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 12,000 or more from the viewpoint of low viscosity and low-temperature fixability, and preferably 100,000 from the same viewpoint. Below, it is more preferably 50,000 or less, still more preferably 20,000 or less.

From the viewpoint of improving the chargeability of the toner, the amine value of the amino group-containing copolymer is preferably 80 mgKOH / g or more, more preferably 130 mgKOH / g or more, still more preferably 150 mgKOH / g or more, and the toner particles. From the viewpoint of improving the dispersion stability and the storage stability of the liquid developer and increasing the resistance of the liquid developer, the concentration is preferably 300 mgKOH / g or less, more preferably 250 mgKOH / g or less, still more preferably 200 mgKOH / g or less. is there.

The content of the amino group-containing copolymer is preferably 1 part by mass or more, more preferably 2 parts by mass, from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability with respect to 100 parts by mass of the toner particles. It is preferably 10 parts by mass or less, more preferably 8.5 parts by mass or less, and further, from the viewpoint of improving the chargeability of the toner and increasing the resistance of the liquid developer. It is preferably 7 parts by mass or less, more preferably 5 parts by mass or less.

The liquid developer of the present invention contains an amino group-containing copolymer as a dispersant. Therefore, the liquid developer may contain other dispersants for liquid developers as long as the effects of the present invention are not impaired, but the content of the amino group-containing copolymer is determined in the dispersant. It 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 97% by mass or more, still more preferably 100% by mass.

The liquid developer of the present invention contains an inorganic compound containing silica (silicon dioxide) from the viewpoint of improving the chargeability of the toner.

As the silica, any one produced by a known method can be used, but from the viewpoint of silica dispersibility, one produced by a dry method or a high-temperature hydrolysis method is preferable.

Further, the silica is preferably hydrophobic silica which has been hydrophobized from the viewpoint of suppressing aggregation in the liquid developer.

Examples of the hydrophobizing agent for hydrophobizing the surface of silica particles include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), dimethylpolysiloxane, butylsilane halide, octylsilane halide, and hexadecyl halide. Examples thereof include silane, halogenated octadecylsilane, octyltriethoxysilane (OTES), and methyltriethoxysilane.

The average particle size of silica is preferably 5 nm or more, more preferably 8 nm or more, still more preferably 12 nm or more, still more preferably 12 nm or more, from the viewpoint of suppressing aggregation in the liquid developer and reducing the viscosity of the liquid developer. It is 15 nm or more, and from the viewpoint of improving the chargeability of the toner, it is preferably 200 nm or less, more preferably 100 nm or less, still more preferably 50 nm or less, still more preferably 30 nm or less. It is preferable that the inorganic compounds other than silica also have an average particle size like silica.

The content of silica is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and further, from the viewpoint of improving the chargeability of the toner with respect to 100 parts by mass of the total amount of the toner particles and the amino group-containing copolymer. It is preferably 1.5 parts by mass or more, preferably 10 parts by mass or less, more preferably 6 parts by mass or less, and further, from the viewpoint of improving the chargeability of the toner and from the viewpoint of lowering the viscosity and increasing the resistance of the liquid developer. It is preferably 4 parts by mass or less.

The mass ratio of the amino group-containing copolymer to silica (amino group-containing copolymer / silica) is preferably 20 / from the viewpoint of improving the chargeability of the toner and increasing the resistance of the liquid developer. 80 or more, more preferably 30/70 or more, still more preferably 40/60 or more, and from the viewpoint of improving the chargeability of the toner and improving the dispersion stability of the toner particles to improve the storage stability. It is preferably 95/5 or less, more preferably 80/20 / or less, and further preferably 70/30 or less.

Examples of inorganic compounds other than silica include titanium dioxide, aluminum oxide, zinc oxide, magnesium oxide, cerium oxide, iron oxide, copper oxide, tin oxide, etc., but from the viewpoint of improving the chargeability of the toner, silica is included. Inorganic compounds are preferred.

The content of silica in the inorganic compound is preferably 30% by mass or more, more preferably 60% by mass or more, further preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more. , More preferably 100% by mass.

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 ^-10 S / m or less, more preferably 5.0. It is × 10 ^-11 S / m or less, and preferably 1.0 × 10 ^-13 S / m or more.

Examples of the insulating liquid include hydrocarbon-based insulating liquids such as aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, and vegetable oils. Further, since the high amine value amino group-containing copolymer is particularly easily adsorbed on toner particles in a non-polar insulating liquid, the amount of free dispersant that is not adsorbed on the toner is reduced, and an increase in conductivity can be suppressed. Therefore, the insulating liquid is preferably non-polar. In addition to these viewpoints, the insulating liquid in the present invention may contain a hydrocarbon-based insulating liquid from the viewpoint of improving the dispersion stability of toner particles and improving the storage stability. preferable. As the hydrocarbon-based insulating liquid, an acyclic hydrocarbon-based insulating liquid is preferable, an aliphatic hydrocarbon-based solvent is more preferable, and polyisobutene is further preferable from the viewpoint of dispersion stability and chargeability.

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, 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.

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

The content of the hydrocarbon-based 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, still more preferably 60% by mass or more in the insulating liquid. It is 80% by mass or more, more preferably 90% by mass or more.

The boiling point of the insulating liquid, preferably the hydrocarbon-based insulating liquid, is preferably 120 ° C. or higher, more preferably 140 ° C. or higher, from the viewpoint of suppressing thickening of the liquid developer on the roller and improving the film-forming property. The temperature is more preferably 160 ° C. or higher, further preferably 180 ° C. or higher, further 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 toner is ground during wet grinding. From the viewpoint of further improving the properties and obtaining toner particles having a small particle size, 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 combined, it is preferable that the boiling point of the combined insulating liquid mixture is within the above range.

The viscosity of the insulating liquid at 25 ° C. is preferably 1 mPa · s or more, more preferably 1 mPa · s or more, from the viewpoint of improving the developability and suppressing the thickening of the liquid developer on the roller to improve the film forming property. 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 is obtained by dispersing toner particles in an insulating liquid. From the viewpoint of reducing the particle size of the toner particles, it is preferable to disperse the toner particles in an insulating liquid and then wet-pulverize the toner particles to obtain a liquid developer.

In the production of the liquid developer of the present invention, it is preferable that the amino group-containing copolymer is mixed with the insulating liquid together with the toner particles. Further, even if the inorganic compound containing silica is mixed with the insulating liquid together with the toner particles and the amino group-containing copolymer, after the toner particles, the amino group-containing copolymer and the insulating liquid are mixed and wet-ground, Although they may be mixed, the latter method is preferable from the viewpoint of improving the chargeability of the toner.

Therefore, the liquid developer of the present invention is a method in which toner particles, an amino group-containing copolymer and an insulating liquid are mixed, the obtained toner particle dispersion is wet-ground, and then an inorganic compound containing silica is mixed. preferable.

As a method for mixing the toner particles, the amino group-containing copolymer, and the insulating liquid, a method of stirring with a stirring mixer or the like is preferable.

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

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

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

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

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

Among these, the use of a bead mill is used from the viewpoint of reducing the particle size of the toner particles, improving the dispersion stability of the toner particles to improve the storage stability, and reducing the viscosity of the dispersion liquid. preferable.

The means for mixing silica after wet pulverization is not particularly limited, and a ball mill or the like can be used.

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, it is preferably 50% by mass or less, more preferably 45% by mass or less, and further preferably 40% by mass or less.

The volume median particle diameter (D ₅₀ ) of the toner particles in the liquid developer is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 1.5 μm or more, from the viewpoint of reducing the viscosity of the liquid developer. From the viewpoint of improving the image quality of the liquid developer, it is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 2.5 μm or less.

From the viewpoint of high-speed printing, the content of the toner particles in the liquid developer is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, and the toner particles are dispersed and stable. From the viewpoint of sex, it is preferably 45% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less.

The content of the insulating liquid in the liquid developer is preferably 50% by mass or more, more preferably 55% by mass or more, still more preferably 60% by mass or more, and from the viewpoint of dispersion stability of the toner particles. From the viewpoint of high-speed printing, it is preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less.

The viscosity of the liquid developer having a solid content concentration of 25% by mass at 25 ° C. is preferably 50 mPa · s or less, preferably 45 mPa · s or less, more preferably 40 mPa · s, from the viewpoint of improving the fixability of the liquid developer. Below, it is more preferably 35 mPa · s or less, further preferably 25 mPa · s or less, and preferably 3 mPa · s or more, more preferably from the viewpoint of improving the dispersion stability of the toner particles and improving the storage stability. Is 5 mPa · s or more, more preferably 6 mPa · s or more, still more preferably 7 mPa · s or more.

The conductivity of the liquid developer is preferably 5.0 × 10 ^-9 S / m or less, more preferably 5.0 × 10 ^-10 S / m or less, and even more preferably 1.0 × 10 from the viewpoint of the developability and image quality of the liquid toner. ^{It is -10} S / m or less. And it is preferably 1.0 × 10 ^-13 S / m or more.

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. Extrude from the nozzle of. The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is used as the softening point.

[Resin glass transition temperature]
Using the differential scanning calorimeter "DSC210" (manufactured by Seiko Electronics 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 endothermic peak temperature and the tangent line indicating the maximum slope from the rising portion of the peak to the peak of the peak is defined as the glass transition temperature.

[Acid value of resin]
Measured by the method of JIS K 0070: 1992. However, only the measurement solvent is changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Volume medium particle size of toner particles before mixing with insulating liquid]
Measuring machine: Coulter Multi-Sizar II (manufactured by Beckman Coulter Co., Ltd.)
Aperture diameter: 100 μm
Analysis software: Coulter Multi-Sizar AccuComp version 1.19 (manufactured by Beckman Coulter Co., Ltd.)
Electrolyte: Isoton II (manufactured by Beckman Coulter Co., Ltd.)
Dispersion solution: Emalgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB (griffin): 13.6) was dissolved in an electrolytic solution to adjust to 5% by mass. Dispersion condition: 10 mg of measurement sample in 5 mL of the dispersion solution Is added and dispersed for 1 minute with an ultrasonic disperser (machine name: US-1, manufactured by SND Co., Ltd., output: 80 W). Then, 25 mL of the electrolytic solution is added and further dispersed with an ultrasonic disperser 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 amino group-containing copolymer]
The molecular weight distribution is measured by gel permeation chromatography (GPC) by the following method, and the number average molecular weight (Mn) and the weight average molecular weight (Mw) 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 Toso Co., Ltd.). A-5000 (5.97 x 10 ³ ), F-1 (1.02 x 10 ⁴ ), F-2 (1.81 x 10 ⁴ ), F-4 (3.97 x 10 ⁴ ), F-10 (9.64 x 10 ⁴ ), Use F-20 (1.90 × 10 ⁵ ), F-40 (4.27 × 10 ⁵ ), F-80 (7.06 × 10 ⁵ ), F-128 (1.09 × 10 ⁶ )) as standard samples. The molecular weight is shown in parentheses.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: TSKgel GMHXL + TSKgel G3000HXL (manufactured by Tosoh Corporation)

[Amine value of amino group-containing copolymer and dispersant A]
Measured by the method of ASTM D2074. However, chloroform is used as the dissolution solvent of the sample, and 0.1 mol / L acetic acid perchlorate standard solution is used as the titration solution.

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

[Average particle size of inorganic compounds]
The average particle size refers to the average particle size of the number of primary particles, and the particle size (average value of major axis and minor axis) of 500 particles is measured from a scanning electron microscope (SEM) photograph, and the average value of the number of the particles is used. To do.

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

[Boiling point of insulating liquid]
Using the differential scanning calorimeter "DSC210" (manufactured by Seiko Electronics 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. taking measurement. The endothermic peak on the highest temperature side is the boiling point.

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

[Solid concentration of toner particle dispersion and liquid developer]
Dilute 10 parts by mass of the sample with 90 parts by mass of hexane and rotate for 20 minutes at a rotation speed of 25,000 r / min using a centrifuge "3-30KS" (manufactured by Sigma). After standing, the supernatant is removed by decantation, diluted with 90 parts by mass of hexane, and centrifuged again under the same conditions. After removing the supernatant 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 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
Four ports of 10 L volume equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple for the raw material monomer, esterification catalyst and esterification co-catalyst of polyester resin other than fumaric acid and trimellitic anhydride shown in Table 1. It was placed in a flask, heated to 230 ° C. using a mantle heater, reacted at 230 ° C. for 8 hours, further reduced to 8.3 kPa and reacted 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 a polymerization inhibitor were added, and the reaction was carried out until the softening point shown in Table 1 was reached to obtain a composite resin (resin A) having the physical properties shown in Table 1. Obtained.

Resin production example 2
The raw material monomer and esterification catalyst of the polyester resin shown in Table 1 are placed in a 10 L four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple, and the temperature is raised to 180 ° C. using a mantle heater. After that, the temperature was raised to 220 ° C. over 10 hours, and the reaction was carried out at 220 ° C. Further, the reaction was carried out at 8.3 kPa until the softening point shown in Table 1 was reached to obtain a polyester resin (resin B) having the physical properties shown in Table 1.

Resin production example 3
Four ports of 10 L volume equipped with nitrogen introduction tube, dehydration tube, stirrer and thermocouple containing raw material monomers of polyester resin other than trimellitic anhydride shown in Table 1, esterification catalyst, esterification auxiliary catalyst and polymerization inhibitor Place in a flask, raise the temperature from 180 ° C to 200 ° C over 1 hour using a mantle heater, react at 200 ° C, add trimellitic anhydride, and soften at 200 ° C as shown in Table 1. The reaction was carried out until the point was reached to obtain a polyester resin (resin C) having the physical properties shown in Table 1.

Example of production of amino group-containing copolymer 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 the mixture of the raw material monomer and the polymerization initiator shown in Table 2 was added dropwise over 2 hours to carry out the polymerization reaction. After completion of the dropping, the reaction was carried out at 80 ° C. for another 3 hours. The solvent was distilled off at 80 ° C. to obtain amino group-containing copolymers (copolymers A and B) having the physical properties shown in Table 2.

Examples 1-6, 8, 9
Rotate 80 parts by mass of the binder resin and 20 parts by mass of the colorant "ECB-301" (manufactured by Dainichi Seika Kogyo Co., Ltd., phthalocyanine blue 15: 3) shown in Table 5 in advance using a 20 L Henschel mixer. After stirring and mixing at a speed of 1500 r / min (peripheral speed 21.6 m / sec) for 3 minutes, the mixture was melt-kneaded under the conditions shown below.

[Melting and kneading conditions]
A continuous double open roll type kneader "Kneedex" (manufactured by Nippon Coke Industries Co., Ltd., roll outer diameter: 14 cm, effective roll length: 55 cm) was used. The operating conditions of the continuous double open roll type kneader are high rotation side roll (front roll) rotation speed 75r / min (peripheral speed 32.4m / min), low rotation side roll (back roll) rotation speed 35r / min ( The peripheral speed was 15.0 m / min), and the roll gap at the end on the side of the kneaded material supply port was 0.1 mm. The heating medium temperature and cooling medium temperature in the roll are 90 ° C on the raw material input side of the high rotation side roll and 85 ° C on the kneaded material discharge side, 35 ° C on the raw material input side of the low rotation side roll and 35 ° C on the kneaded material discharge side. there were. The supply speed of the raw material mixture to the kneader was 10 kg / h, and the average residence time in the kneader was about 3 minutes.

The kneaded product obtained above was rolled and cooled with a cooling roll, and then 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, 62.2 parts by mass of the insulating liquid shown in Table 5 and 1.4 parts by mass of the dispersant (4 parts by mass with respect to 100 parts by mass of the toner particles) were placed in a 1 L volume polyethylene container. Using "TK Robomix" (manufactured by Primix Co., Ltd.), 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 5 was reached. After removing the beads by filtration, 44 parts by mass of the insulating liquid shown in Table 5 was added to 100 parts by mass of the filtrate to dilute the mixture, and the solid content concentration was adjusted to 25% by mass.

Next, 0.5 parts by mass of the inorganic compound shown in Table 5 (2 parts by mass with respect to 100 parts by mass of solid content (toner particles and amino group-containing copolymer)) was added to 100 parts by mass of the obtained dispersion. , The mixture was mixed with a ball mill for 12 hours to obtain a liquid developer having the physical properties shown in Table 5.

Example 7
A liquid developer having the physical properties shown in Table 5 was obtained in the same manner as in Example 1 except that the amount of silica 1 used was changed to 1.25 parts by mass (5 parts by mass with respect to 100 parts by mass of solid content).

Comparative Example 1
A liquid developer having the physical properties shown in Table 5 was obtained in the same manner as in Example 1 except that silica 1 was not added.

Comparative Example 2
Except for changing the amount of insulating liquid used to 60.8 parts by mass and using 2.8 parts by mass of dispersant A (4 parts by mass of effective component for 100 parts by mass of toner particles) instead of copolymer A as a dispersant. Obtained a liquid developer having the physical properties shown in Table 5 in the same manner as in Example 1.

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

Test example [Positive charge]
Two electrodes (stainless steel, W4 cm x) whose mass was measured in advance in a Teflon (registered trademark) container (outer dimensions W: 6.3 cm x D4 cm x H6.3 cm, inner dimensions: W5 cm x D1.1 cm x H5 cm) (D0.5 cm x H5 cm) was inserted (distance between electrodes 0.1 cm). 2.5 g of a liquid developer was injected between the two electrodes, and a DC voltage of ± 250 V was applied to both electrodes for 60 seconds using a DC power supply device "TMK1.5-50" (manufactured by Takasago Seisakusho). Both electrodes were taken out and dried in a vacuum dryer at 0.5 kPa at 100 ° C. for 15 minutes, and the mass of each electrode after drying was measured. The value of (mass of electrode after drying)-(mass of electrode before voltage application) was obtained for each of the positive and negative electrodes, and used as the mass of toner particles adhering to each electrode. The results are shown in Table 5. It is shown that the larger the mass of the toner particles on the negative electrode and the smaller the mass of the toner particles on the positive electrode, the better the positive charge property.

From the above results, it can be seen that the liquid developing agents of Examples 1 to 9 maintain a small particle size and low viscosity, have high resistance, and are excellent in positive chargeability. On the other hand, the liquid developer of Comparative Example 1 containing no silica has a low positive charge property. Further, the liquid developer of Comparative Example 2 which does not contain a predetermined amino group-containing copolymer but contains a dispersant having an amino group exhibits negative chargeability instead of positive chargeability. Also, the conductivity is too high.

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

Claims (6)

A liquid developer containing toner particles containing a binder resin and a colorant, an amino group-containing copolymer, an inorganic compound containing silica, and an insulating liquid, wherein the binder resin contains a polyester resin. , The amino group-containing copolymer has a monomer A having an amino group, and the formula (I):

(In the formula, R ¹ indicates a hydrogen atom or a hydrocarbon group having 1 or more and 5 or less carbon atoms, and R ² indicates a hydrocarbon group having 1 or more and 22 or less carbon atoms which may have a substituent).
A liquid developer which is an amino group-containing copolymer which is a polymer of a monomer containing a monomer B represented by. Monomer A having an amino group has the formula (III):
CH ₂ = C (R ⁵ ) COYR ⁶ NR ³ R ⁴ (III)
(In the formula, R ³ and R ⁴ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 or more and 4 or less carbon atoms, and they are bonded to each other to form a ring structure. R ⁵ may represent a hydrogen atom or an alkyl group having 1 or more and 5 or less carbon atoms, R ⁶ may represent a linear or branched alkylene group having 2 or more and 4 or less carbon atoms, and Y may be −O− or -NH- is shown)
The liquid developer according to claim 1, which is a monomer having an amino group represented by, or an acid neutralized product or a quaternary ammonium salt of this monomer. The liquid developer according to claim 1 or 2, wherein the amine value of the amino group-containing copolymer is 80 mgKOH / g or more. The liquid developer according to any one of claims 1 to 3, wherein the mass ratio of monomer A to monomer B (monomer A / monomer B) is 20/80 or more and 80/20 or less. The liquid developer according to any one of claims 1 to 4, wherein the polyester-based resin is a polyester resin or a composite resin having a polyester resin and a styrene-based resin. The liquid developer according to any one of claims 1 to 5, wherein the polyester resin has an acid value of 5 mgKOH / g or more and 70 mgKOH / g or less.