JP2020086030A - Liquid developer - Google Patents

Abstract

To provide a liquid developer excellent in fixability to a resin film.SOLUTION: A liquid developer contains toner particles containing a colorant and a binder resin containing a polyester resin, a dispersant, an isocyanate hardening agent, and an insulating liquid, and the dispersant has a constitutional part derived from one or more polyamine compounds selected from the group consisting of polyalkylene amine and polyallylamine.SELECTED DRAWING: None

Description

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

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

In recent years, not only paper, but also the applications of printed matter of resin films made of materials such as polyethylene terephthalate (PET), polypropylene (PP), and nylon are expanding. Since the surface of these resin films is smoother than that of paper, the anchor effect is hard to work and the fixing strength of the image is low. On the other hand, there is a method of applying a surface modifier to the resin film to make it easier to fix the image. However, not only is it required to increase the size of the printing apparatus and the system complexity, but also to reduce the image quality. is there.

Patent Document 1 describes a liquid developer in which toner particles containing a polymer having an active hydrogen group and a polymer having a blocked isocyanate group are dispersed in a carrier liquid. It is described that the liquid developer is excellent in low-temperature fixability with respect to a resin film due to a curing reaction during heat fixing.

Patent Document 2 describes a liquid developer in which a colorant, colored particles made of a resin containing an active hydrogen group, and crosslinking agent particles made of a polyisocyanate are dispersed in a carrier liquid. It is described that the liquid developer is excellent in fixability to a metal plate due to a curing reaction during heat fixing.

JP, 2017-67861, A JP-A-6-32861

However, in the techniques disclosed in Patent Documents 1 and 2, the curing reaction at the time of heat fixing does not proceed sufficiently, and the fixability to the resin film is insufficient.

TECHNICAL FIELD The present invention relates to a liquid developer having excellent fixability on a resin film.

The present invention is a liquid developer containing toner particles containing a binder resin containing a polyester resin and a colorant, a dispersant, an isocyanate curing agent, and an insulating liquid, wherein the dispersant is a polyalkylene. The present invention relates to a liquid developer having constituent sites derived from one or more polyamine compounds selected from the group consisting of amines and polyallylamine.

The liquid developer of the present invention has an excellent effect on the fixing property to a resin film. Further, the liquid developer of the present invention exhibits an excellent effect also in dispersion stability when the sum of the primary amine value and the secondary amine value of the dispersant is within a predetermined range.

The liquid developer of the present invention (hereinafter, also simply referred to as “liquid developer”) includes toner particles containing a binder resin containing a polyester resin and a colorant, a specific dispersant, an isocyanate curing agent, and an insulating property. Contains a liquid. With these configurations, the curing reaction proceeds sufficiently during thermal fixing, and thus a thermosetting liquid developer having excellent fixability to the resin film can be obtained.

The reason is not clear, but it can be considered as follows.
In order to sufficiently fix the image on the resin film, high coating film strength and high adhesion between the coating film and the resin film are required. A coating film formed using a conventional liquid developer containing an isocyanate-based compound undergoes a curing reaction due to heat during fixing, resulting in high coating film strength, and adhesion between the coating film and the resin film. Due to insufficient force, the coating film is easily peeled off.
On the other hand, the liquid developer of the present invention contains the dispersant X having a constituent site derived from at least one polyamine compound selected from the group consisting of polyalkyleneamine and polyallylamine. It is considered that when the liquid developer of the present invention is heat-fixed on the resin film, the primary amine site and the secondary amine site in the dispersant X react with the isocyanate curing agent to form polyurea. Urea is a compound having a structure represented by the following general formula (I), and since it has a strongly polarized structure, it has an adhesive action to polar functional groups present on the resin film surface. That is, it is considered that the fixing strength of the image is improved by the polyurea produced by thermosetting acting like an adhesive that bonds the film surface and the coating film. Further, the inventors of the present invention have conducted intensive studies and found that when the sum of the primary amine value and the secondary amine value of the dispersant X is 50 mgKOH/g or more, good film fixing strength can be obtained, while 80 mgKOH/ When it is higher than g, it is clear that the dispersing effect of the dispersant X is lowered, and the liquid developer has a high viscosity and a large particle size. That is, when the sum of the primary amine value and the secondary amine value of the dispersant X is 50 mgKOH/g or more and 80 mgKOH/g or less, a liquid developing liquid having higher fixing stability in addition to good fixing strength on the resin film. An agent is obtained.

[Polyester resin]
Examples of the polyester-based resin include a polyester resin and a composite resin having a polyester resin and another resin such as a styrene-based resin, but the polyester resin is preferable.

In the present invention, the constituent portion derived from the polyester resin is preferably a polycondensate of an alcohol component containing a divalent or higher valent alcohol and a carboxylic acid component containing a divalent or higher carboxylic acid compound.

Examples of the dihydric alcohol include aliphatic diols, preferably aliphatic diols having 2 to 20 carbon atoms, more preferably 2 to 15 carbon atoms, and formula (II):

In the formula, OR and RO are oxyalkylene groups, R is an ethylene and/or propylene group, x and y represent the average number of added moles of alkylene oxide, each is a positive number, and the sum of x and y. Value of 1 or more, preferably 1.5 or more, and 16 or less, preferably 8 or less, more preferably 6 or less, more preferably 4 or less)
And an alkylene oxide adduct of bisphenol A, bisphenol A, hydrogenated bisphenol A and the like. Specific examples of the aliphatic diol having 2 to 20 carbon atoms include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol and 1,6-hexanediol. Be done.

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 and trimethylolpropane.

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

The trivalent or higher carboxylic acid compound, for example, a carbon number of 4 or more and 20 or less, preferably a carbon number of 6 or more and 20 or less, more preferably a carbon number of 9 or more and 10 or less trivalent carboxylic acid, or their anhydrides. And derivatives such as alkyl esters having 1 to 3 carbon atoms. Specific examples include 1,2,4-benzenetricarboxylic acid (trimellitic acid) and 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid).

The equivalent ratio of the carboxylic group of the carboxylic acid component and the hydroxyl group of the alcohol component (COOH group/OH group) is preferably 0.7 or more, more preferably 0.8 or more, and preferably 1.3 or less, more preferably 1.2 or less. is there. The equivalent ratio of COOH groups and OH groups in the raw material of the polyester resin (alcohol component and carboxylic acid component), from the viewpoint of increasing the softening point of the resulting polyester resin, COOH groups are excessive (the above ratio [COOH groups / OH groups] Is more than 1.0). Further, from the viewpoint of lowering the softening point of the obtained polyester resin, it is preferable that the OH groups are excessive (the above ratio [COOH group/OH group] is less than 1.0).

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 polyester resins grafted or blocked with phenol, epoxy or the like by the methods described in JP-A Nos. 11-133668 and 8-20636.

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, if necessary, in the presence of an esterification promoter, a polymerization inhibitor, etc., at 130° C. It can be produced by polycondensation at a temperature of 250°C or lower and 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, titanium compounds such as titanium diisopropylate bistriethanolaminate, and the tin compounds are preferable. The amount of the esterification catalyst used is preferably 0.01 parts by mass or more, more preferably 0.1 parts by mass or more, and preferably 1.5 parts by mass or less, based on 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is preferably 1 part by mass or less. Examples of the esterification promoter include gallic acid and the like. The amount of the esterification cocatalyst used is preferably 0.001 parts by mass or more, more preferably 0.01 parts by mass or more, and preferably 0.5 parts by mass or less, with respect to 100 parts by mass of the total amount of the alcohol component and the carboxylic acid component. It is more preferably 0.1 part by mass or less.

The softening point of the polyester resin is preferably 160° C. or lower, more preferably 150° C. or lower, further preferably 135° C. or lower, and further preferably 120° C. or lower, from the viewpoint of improving the low-temperature fixability of the liquid developer. From the viewpoint of preventing the toner particles from aggregating when the liquid developer is stored at a high temperature, the temperature is preferably 70°C or higher, more preferably 80°C or higher, still more preferably 90°C or higher.

The glass transition temperature of the polyester resin is preferably 80° C. or lower, more preferably 75° C. or lower, further preferably 70° C. or lower, from the viewpoint of improving the low temperature fixing property of the liquid developer, and the liquid developer is From the viewpoint of preventing toner particles from aggregating when stored at high temperature, the temperature is preferably 45° C. or higher, more preferably 50° C. or higher, and further preferably 55° C. or higher.

The acid value of the polyester resin is preferably 3 mgKOH/g or more, more preferably 5 mgKOH/g or more, further preferably 8 mgKOH/g or more, from the viewpoint of adsorbing the dispersant in the liquid developer and improving the dispersion stability. , More preferably 12 mgKOH/g or more, and preferably 60 mgKOH/g or less, more preferably 50 mgKOH/g or less, further preferably 40 mgKOH/g or less, further preferably 30 mgKOH/g or less, further preferably 25 mgKOH/g. It is below. The acid value of the polyester resin is changed by changing the equivalent ratio of the carboxylic acid component and the alcohol component, changing the reaction time at the time of resin production, or changing the content of the trivalent or higher carboxylic acid compound. Can be adjusted.

The hydroxyl value of the polyester resin is preferably 3 mgKOH/g or more, more preferably 5 mgKOH/g or more, further preferably 8 mgKOH/g or more, from the viewpoint of adsorbing the dispersant in the liquid developer and improving the dispersion stability. , More preferably 12 mgKOH/g or more, more preferably 16 mgKOH/g or more, and preferably 40 mgKOH/g or less, more preferably 35 mgKOH/g or less, further preferably 30 mgKOH/g or less, further preferably 25 mgKOH/g. It is below. The acid value of the polyester resin is changed by changing the equivalent ratio of the carboxylic acid component and the alcohol component, changing the reaction time at the time of resin production, or changing the content of the trivalent or higher carboxylic acid compound. Can be adjusted.

The content of the polyester resin in the binder resin is preferably 90% by mass or more, more preferably 95% by mass or more, and further preferably 100% by mass, that is, it is more preferable to use only the polyester 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 resins include polystyrene, styrene-propylene copolymers, styrene-butadiene copolymers, styrene-vinyl chloride copolymers, styrene-vinyl acetate copolymers, styrene-maleic acid copolymers. , Styrene-acrylic acid ester copolymer, styrene resin such as styrene or styrene-substituted styrene homopolymer or copolymer, such as styrene-methacrylic acid ester copolymer, epoxy resin, rosin-modified maleic acid resin, Examples include one or more selected from resins such as polyethylene resins, polypropylene resins, polyurethane resins, silicone resins, phenol resins, aliphatic or alicyclic hydrocarbon resins.

[Colorant]
As the colorant, a dye, pigment or the like used as a colorant for toner can be used. For example, carbon black, phthalocyanine blue, permanent brown FG, brilliant fast scarlet, pigment green B, rhodamine-B base, solvent red 49, solvent red 146, solvent blue 35, quinacridone, carmine 6B, isoindoline, disazo yellow and the like. .. In the present invention, the toner particles may be black toner or color toner.

From the viewpoint of improving the image density, the content of the colorant is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, with respect to 100 parts by mass of the binder resin, Then, from the viewpoint of improving the pulverizability of the toner to obtain a small particle size, the viewpoint of improving the low temperature fixing property, and the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles, the binder resin 100 mass The amount is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and further preferably 30 parts by mass or less.

In addition to the binder resin and colorant, the toner particles include a release agent, a charge control agent, a charge control resin, a magnetic powder, a fluidity improver, a conductivity adjusting agent, a reinforcing filler such as a fibrous substance, and an antioxidant. Additives such as an agent and a cleaning property improver may be appropriately contained.

Examples of the method for producing the toner particles include a method in which a toner raw material containing a binder resin and a colorant is melt-kneaded, and the obtained melt-kneaded product is pulverized, preferably wet-pulverized. From the viewpoint of improving the 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 a toner raw material containing a binder resin, a colorant, an 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 a kneader. The Henschel mixer is more preferable from the viewpoint of improving the dispersibility of the colorant in the binder resin.

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

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

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

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

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

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

The volume median particle diameter (D ₅₀ ) of the toner particles obtained in this step is preferably 3 μm or more, more preferably 4 μm or more, and preferably 15 μm from the viewpoint of improving the productivity of the wet pulverization step described below. Or less, more preferably 12 μm or less. The volume median particle size (D ₅₀ ) means a particle size at which the cumulative volume frequency calculated by the volume fraction becomes 50% when calculated from the smaller particle size. The toner particles are preferably further finely divided by wet pulverization or the like after mixing with the dispersant and the insulating liquid.

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

[Dispersant]
The dispersant in the present invention has a constituent site derived from one or more polyamine compounds selected from the group consisting of polyalkyleneamine and polyallylamine, and preferably the sum of primary amine value and secondary amine value. It contains Dispersant X which is 50 mgKOH/g or more and 80 mgKOH/g or less.

<Polyamine compound>
Examples of the polyalkylene amine include polyethylene amine, polypropylene amine, polybutylene amine, and the like, and among these, polyethylene amine is preferable.

Examples of the polyethyleneamine include diethylenetriamine, triethylenetetramine, tetraethylenehexamine, pentaethylenehexamine, polyethyleneimine and the like. Among these, tetraethylenepentamine, pentaethylenehexamine, or polyethyleneimine is preferable, and polyethyleneimine is more preferable, from the viewpoint of adsorption to the binder resin having an acidic group.

The polyethyleneimine preferably has a branched structure containing a primary amino group, a secondary amino group, and a tertiary amino group.

Examples of polyallylamine include allylamine polymers.

The number average molecular weight of the polyamine compound is preferably 100 or more, more preferably 300 or more, still more preferably 500 or more, still more preferably 1,000 or more, from the viewpoint of adsorptivity to the binder resin having an acidic group, and, It is preferably 15,000 or less, more preferably 10,000 or less, still more preferably 5,000 or less, further preferably 4,000 or less, further preferably 3,000 or less, still more preferably 2,000 or less.

The sum of the primary amine value and the secondary amine value of the dispersant X having a constituent site derived from the polyamine compound is, as described above, preferably 50 mgKOH/g or more, more preferably from the viewpoint of fixing property to a resin film. It is 60 mgKOH/g or more, more preferably 65 mgKOH/g or more, and from the viewpoint of dispersion stability, it is preferably 80 mgKOH/g or less, more preferably 75 mgKOH/g or less, further preferably 70 mgKOH/g or less. Here, the sum of the primary amine value and the secondary amine value can be calculated from the difference between the total amine value and the tertiary amine value (total amine value−tertiary amine value).

The dispersant X is a constituent moiety derived from one or more long-chain aliphatic compounds selected from the group consisting of a hydrocarbon having a reactive functional group having 16 or more carbon atoms and a polyolefin having a reactive functional group. It is preferable to have

The mass ratio of the constituent site derived from the polyamine compound to the constituent site derived from the long chain aliphatic compound in the dispersant X (the constituent site derived from the polyamine compound/the constituent site derived from the long chain aliphatic compound) is determined by the adsorption to the toner particles. From the viewpoint of stability, preferably 1/99 or more, more preferably 5/95 or more, further preferably 10/90 or more, and from the viewpoint of dispersion stability of toner particles, preferably 42/58 or less, more It is preferably 30/70 or less, more preferably 20/80 or less. The mass ratio of the constituent site derived from the polyamine compound to the constituent site derived from the long chain aliphatic compound in the dispersant X can be measured by NMR of the dispersant X, but the polyamine compound and the long chain aliphatic compound react with each other. In the production of the dispersant X, the mass ratio of the reacted raw material compounds can be regarded as the mass ratio of the constituent sites derived from the respective compounds in the dispersant.

Therefore, the dispersant X is not particularly limited, but for example, one or more polyamine compounds selected from the group consisting of polyalkyleneamines and polyallylamines, and a C 16 having a reactive functional group. It is preferably a reaction product with one or more long-chain aliphatic compounds selected from the group consisting of the above hydrocarbons and polyolefins having a reactive functional group. Here, the reactive functional group includes a carboxy group, an epoxy group, a formyl group, an isocyanate group, and the like. Among these, from the viewpoint of safety and reactivity, an epoxy group or a carboxy group is preferable, and a carboxy group is used. Groups are more preferred.

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

Examples of the polyolefin in the polyolefin having a reactive functional group include, for example, polyethylene, polypropylene, polybutylene, polyisobutene, polymethylpentene, polytetradecene, polyhexadecene, polyoctadecene, polyeicosene, polydococene, and the like. From the viewpoint of availability of raw materials, polyisobutene or polypropylene is preferable, and from the viewpoint of solubility in insulating liquid, polyisobutene is more preferable.

Specific examples of the polyolefin having a reactive functional group include polyethylene succinic anhydride, chlorinated polypropylene, polypropylene succinic anhydride, and polyisobutene succinic anhydride.

As the long-chain aliphatic compound, a polyolefin having a reactive functional group is preferable.

The reaction between the polyamine compound and the long-chain aliphatic compound is carried out by, for example, dropping the long-chain aliphatic compound into the polyamine compound dissolved in an organic solvent and allowing the reaction at 150 to 160° C., and then distilling off the organic solvent under reduced pressure. And the like. The end point of the reaction can be confirmed by, for example, disappearance of a peak derived from an acid anhydride by IR analysis.

The number average molecular weight of the dispersant X is preferably 3,000 or more, more preferably 4,000 or more, still more preferably 5,000 or more from the viewpoint of adsorptivity to the toner particles, and from the viewpoint of dispersion stability of the toner particles, It is preferably 30,000 or less, more preferably 20,000 or less, still more preferably 10,000 or less.

The content of the dispersant X in the dispersant 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.

Examples of the dispersant other than the dispersant X include a copolymer of alkyl methacrylate/amino group-containing methacrylate.

The content of the dispersant X in the liquid developer is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, still more preferably 100 parts by mass of the toner particles, from the viewpoint of dispersion stability of the toner particles. The amount is 4 parts by mass or more, and preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and further preferably 8 parts by mass or less, from the viewpoint of the charging property and fixing property of the toner.

[Isocyanate curing agent]
The isocyanate curing agent in the present invention is preferably a compound having 2 or more, preferably 5 or less isocyanate groups in one molecule.

Examples of the compound having two or more isocyanate groups in one molecule include, for example, hexamethylene diisocyanate, aliphatic diisocyanate compounds such as trimethylhexamethylene diisocyanate, and biuret type adducts or isocyanurate ring additions of these diisocyanates. Isophorone diisocyanate, 4,4′-methylenebis(cyclohexyl isocyanate), methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 1,3-di(isocyanatomethyl)cyclohexane, 1,4- Alicyclic diisocyanate compounds such as di(isocyanatomethyl)cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, 1,2-cyclohexane diisocyanate, and biuret-type adducts of these diisocyanates and isocyanurate rings Adducts: xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4'-toluidine Diisocyanate, 4,4'-diphenyl ether diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, bis(4-isocyanatophenyl) ) Aromatic diisocyanate compounds such as sulfone and isopropylidene bis(4-phenylisocyanate), and biuret-type adducts or isocyanurate ring adducts of these diisocyanates; triphenylmethane-4,4′,4″-triisocyanate, Three in one molecule such as 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4'-dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate Polyisocyanate compounds having the above isocyanate groups and biuret-type adducts or isocyanurate ring adducts of these polyisocyanates; ethylene glycol, propylene glycol, 1,4-butylene glycol, dimethylolpropionic acid, polyalkylene glycol, tri Methylol propane, hexane Examples thereof include urethanized adducts obtained by reacting a polyisocyanate compound with a hydroxyl group of a polyol such as triol at an excessive ratio of isocyanate groups, and biuret-type adducts or isocyanurate ring adducts of these polyisocyanates. These can be used as one kind or as a mixture of two or more kinds. Of these, from the viewpoint of solubility in an insulating liquid, a biuret type adduct of an aliphatic diisocyanate compound or an isocyanurate ring adduct is preferable, and a biuret type adduct of hexamethylene diisocyanate is more preferable. The biuret type adduct is a compound which is trimerized by adding one molecule of water to three molecules of diisocyanate, and is one of polyisocyanate structures.

The concentration (NCO%) of the isocyanate group in the isocyanate-based curing agent is preferably 10% by mass or more, more preferably 15% by mass or more, further preferably 20% from the viewpoint of reactivity with a primary amine or a secondary amine. From the viewpoint of affinity for the carrier oil, it is preferably 40% by mass or less, more preferably 35% by mass or less, and further preferably 30% by mass or less.

The content of the isocyanate-based curing agent is, with respect to 100 parts by mass of the toner particles, from the viewpoint of improving the coating strength, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and further preferably 15 parts by mass or more. The amount is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 25 parts by mass or less, from the viewpoint of improving dispersion stability of toner particles and improving storage stability.

In the liquid developer, the molar ratio of the isocyanate group to the primary amino group and the secondary amino group (isocyanate group/primary amino group and secondary amino group) is preferably 1 or more from the viewpoint of accelerating the polyurea formation reaction, It is more preferably 5 or more, still more preferably 10 or more, and from the viewpoint of reducing unreacted isocyanate, it is preferably 30 or less, more preferably 25 or less, still more preferably 20 or less. Here, the molar ratio of the isocyanate group to the primary amino group and the secondary amino group is a value calculated from the following formula (1).

(In the formula, X is the content (% by mass) of the isocyanate curing agent in the liquid developer, and Y is the content (% by mass) of the dispersant in the liquid developer).

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

Specific examples of the insulating liquid include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes and the like. In particular, aliphatic hydrocarbons such as normal paraffinic solvents and isoparaffinic solvents are preferable from the viewpoint of odor, harmlessness and cost. Specifically, Isopar G, Isopar H, Isopar L, Isopar K (all manufactured by ExxonMobil), Shellsol 71 (manufactured by Shell Petrochemical Co., Ltd.), IP Solvent 1620, IP Solvent 2080 (all above, all Idemitsu Petrochemical Co., Ltd.), Moresco White P-55, Moresco White P-70 (all above are Matsumura Oil Co., Ltd.), Cosmo White P-60, Cosmo White P-70 (all above, Cosmo Oil Lubricants) Manufactured by the company) and the like.

The viscosity of the insulating liquid at 25° C. is preferably 100 mPa·s or less, more preferably 50 mPa·s or less, further preferably 20 mPa·s or less, from the viewpoint of improving the storage stability of the toner particles in the liquid developer. , More preferably 10 mPa·s or less, further preferably 5 mPa·s or less, and preferably 0.01 mPa·s or more, more preferably 0.1 mPa·s or more.

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

As a method for mixing the toner particles, the dispersant, the isocyanate curing agent, and the insulating liquid, a method of stirring with a stirring and mixing device is preferable.

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

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

The solid content concentration of the toner particle dispersion is preferably 5% by mass or more, more preferably 10% by mass or more, further preferably 20% by mass or more, from the viewpoint of improving the image density, and the dispersion stability of the toner particles. From the viewpoint of improving the properties and improving the storage stability, it is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less.

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

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

Among them, the use of a bead mill is preferred from the viewpoint of reducing the particle size of toner particles, the viewpoint of improving the storage stability by improving the dispersion stability of toner particles, and the viewpoint of reducing the viscosity of the dispersion liquid. preferable.

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

As described above, the liquid developer of the present invention is
Step 1: a step of melt-kneading a binder resin containing a polyester resin and a colorant, and pulverizing to obtain toner particles,
Step 2: a step of adding a dispersant and an isocyanate curing agent to the toner particles obtained in Step 1 and dispersing them in an insulating liquid to obtain a toner particle dispersion, and Step 3: toner particles obtained in Step 2. The dispersion is preferably produced by a method including a step of wet-pulverizing the dispersion to obtain a liquid developer.

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

The volume median particle diameter (D ₅₀ ) of the toner particles in the liquid developer is preferably 0.5 μm or more, more preferably 1.0 μm or more, further 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, still more preferably 2.7 μm or less.

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

The viscosity of the liquid developer having a solid content concentration of 25% by mass at 25° C. is preferably 3 mPa·s or more, more preferably 5 mPa·s from the viewpoint of improving the storage stability by improving the dispersion stability of the toner particles. Or more, more preferably 6 mPa.s or more, more preferably 7 mPa.s or more, and from the viewpoint of improving the fixability of the liquid developer, preferably 35 mPa.s or less, more preferably 32 mPa.s or less, It is preferably 28 mPa·s or less, more preferably 24 mPa·s or less, further preferably 20 mPa·s or less, further preferably 16 mPa·s or less. The viscosity of the liquid developer having a solid content concentration of 25 mass% as used herein means the viscosity measured by adjusting the solid content concentration of the liquid developer to 25 mass%. Adjust the solid concentration of the liquid developer by diluting it with the same insulating liquid if it is higher than 25% by mass, or by removing it by concentration etc. if it is lower than 25% by mass. can do.

The liquid developer of the present invention has excellent fixability on a resin film. Examples of the resin film include polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyethylene, ethylene/vinyl acetate copolymer, polypropylene (PP), cellulose acetate, polyester (polyethylene terephthalate, polybutylene terephthalate, etc.), polycarbonate, nylon and the like. Examples of the film include polyethylene terephthalate (PET) film and nylon film.

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

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

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

[Resin Acid Value and Hydroxyl Value]
Measured according to 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)) and the hydroxyl value is changed to tetrahydrofuran. To do.

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

[Number average molecular weight of polyamine compound and dispersant]
The number average molecular weight (Mn) is determined by measuring the molecular weight distribution by the gel permeation chromatography (GPC) method according to the following method.
Tetrahydrofuran is caused to flow as an eluent at a flow rate of 1 mL per minute using the following measuring device and analytical column to stabilize the column in a constant temperature bath at 40°C. Inject 100 μL of the sample solution into it and perform the measurement. The molecular weight of the sample is calculated based on a calibration curve prepared in advance. At this time, several kinds of monodisperse polystyrene (A-500 (Mw 5.0×10 ² ) manufactured by Tosoh Corporation, A-1000 (Mw 1.01×10 ³ ), A-2500 (Mw 2.63×10 ³ ) were used for the calibration curve. ³ ), A-5000 (Mw 5.97 × 10 ³ ), F-1 (Mw 1.02 × 10 ⁴ ), F-2 (Mw 1.81 × 10 ⁴ ), F-4 (Mw 3.97 × 10 ⁴ ), F-10 (Mw 9.64 x 10 ⁴ ), F-20 (Mw 1.90 x 10 ⁵ ), F-40 (Mw 4.27 x 10 ⁵ ), F-80 (Mw 7.06 x 10 ⁵ ), F-128 (Mw 1.09 x 10 ⁶⁾ )) is used as a standard sample. The molecular weight is shown in parentheses.
Measuring device: HLC-8220GPC (manufactured by Tosoh Corporation)
Analytical column: GMHXL+G3000HXL (manufactured by Tosoh Corporation)

[Sum of primary amine value and secondary amine value of dispersant]
The value obtained by subtracting the tertiary amine value from the total amine value of the dispersant is defined as the sum of the primary amine value and secondary amine value of the dispersant.
Total amine number is measured by the method of ASTM D2074. However, chloroform is used as the dissolution solvent for the sample, and 0.1 mol/L perchloric acid acetic acid standard solution is used as the titration solution.
The tertiary amine value means the mg number of potassium hydroxide equivalent to perchloric acid required to neutralize the tertiary amine contained in 1 g of the sample. It is measured by the following method according to ASTM D2073.
(1) Precisely weigh the sample. [Sample amount: S (g)]
(2) Add 20 mL of acetic anhydride/acetic acid mixed solution (9/1) to dissolve, and leave at room temperature for 3 hours.
(3) Add 30 mL of acetic acid and titrate with 0.1 mol/L perchloric acid/acetic acid solution (titer: f) with a potentiometric titrator. [Titration: A (mL)]
(4) Perform a blank test in the same manner as above. [Titration: B (mL)]
(5) Calculate the tertiary amine value from the following formula.
Tertiary amine value=(AB)×f×0.1×56.108/S

[Concentration of isocyanate group in isocyanate curing agent (NCO%)]
It is measured by the method based on JIS K 6806.

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

[Viscosity of insulating liquid at 25℃]
6 to 7 mL of the measurement liquid is placed in a 10 mL screw tube, and the viscosity is measured at 25° C. using a rotary vibration type viscometer “Viscomate VM-10A-L” (manufactured by Sekonic Co., Ltd.).

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

Resin Production Example The raw material monomer, esterification catalyst, and polymerization inhibitor shown in Table 1 were placed in a 10-liter four-necked flask equipped with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple, and heated to 230°C. The reaction was carried out by heating, and after 12 hours, the reaction was terminated when the softening point reached 100° C., and Resin A having the physical properties shown in Table 1 was obtained.

Toner particle production example: 80 parts by weight of resin A as a binder resin and 20 parts by weight of a coloring agent "ECB-301" (phthalocyanine blue 15:3 manufactured by Dainichiseika Kogyo Co., Ltd.) are used in advance in a 20 L Henschel mixer. Then, the mixture was stirred and mixed at a rotation speed of 1500 r/min (peripheral speed 21.6 m/sec) for 3 minutes, and then melt-kneaded under the following conditions.

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

The kneaded material obtained above was rolled and cooled with a cooling roll, and then roughly pulverized to about 1 mm using a hammer mill. The resulting roughly pulverized product was finely pulverized and classified by air current type jet mill "IDS" (manufactured by Nippon Pneumatic Mfg. Co.), a volume-median particle size (D ₅₀₎ to obtain toner particles A of 10 [mu] m.

Production Example of Dispersant The polyamine compound shown in Table 2 was placed in a 2 L four-necked flask equipped with a cooling tube, a nitrogen introduction tube, a stirrer, a dehydration tube and a thermocouple, and the inside of the reaction vessel was replaced with nitrogen gas. While stirring, polyisobutene succinic anhydride (PIBSA) (OLOA15500, manufactured by Chevron Japan Ltd.) or polypropylene succinic anhydride (PPSA) (X-10065, manufactured by Baker Hughes) shown in Table 2 is used as a long-chain aliphatic compound. The solution dissolved in xylene was added dropwise at room temperature over 1 hour. After the dropping was completed, the mixture was kept at room temperature for 30 minutes. After that, the inside of the reaction vessel was heated to 150° C. and kept for 1 hour, then heated to 160° C. and kept for 1 hour. The solvent was distilled off under reduced pressure to 8.3 kPa at 160°C, the peak of the acid anhydride derived from PIBSA or PPSA (1780 cm ^-1 ) disappeared from IR analysis, and the peak derived from the imide bond (1700 cm ^-1 ) was generated. Dispersants A to E having the physical properties shown in Table 2 were obtained with the time point as the reaction end point.

Examples 1 to 6 and Comparative Example 1
Toner particle A 25 parts by mass, dispersant 1.5 parts by mass shown in Table 3, isocyanate-based curing agent "D-165N" (Mitsui Chemicals, Inc., hexamethylene diisocyanate biuret type adduct, NCO% 23.4% by mass) 5 Parts by mass and 68.5 parts by mass of the insulating liquid "Isopar L" (manufactured by ExxonMobil, isoparaffin, conductivity 6.2 x 10 ^-13 S/m, viscosity 1 mPa·s at 25°C) are put in a 2 L polyethylene container. It was Using "TK Robomix" (manufactured by Primix Co., Ltd.), stirring was performed for 30 minutes at a rotation speed of 7,000 r/min under ice cooling to obtain a toner particle dispersion liquid.

Next, the obtained toner particle dispersion liquid was rotated with a 6-cylinder sand mill “TSG-6” (manufactured by AIMEX Co., Ltd.) at a volume filling rate of 60% by volume using zirconia beads having a diameter of 0.8 mm. It was wet-milled for 4 hours at 1300 r/min (peripheral speed 4.8 m/sec). The beads were removed by filtration to obtain a liquid developer having the physical properties shown in Table 3 and a solid content concentration of 25% by mass.

Test Example 1 [Dispersion stability]
The volume median particle size of the toner particles and the viscosity of the liquid developer were measured by the following methods. The smaller the volume median particle size of the toner particles and the lower the viscosity of the liquid developer, the better the dispersion stability.

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

[Viscosity of liquid developer at 25°C]
6 to 7 mL of the measurement liquid is placed in a 10 mL screw tube, and the viscosity is measured at 25° C. using a rotary vibration type viscometer “Viscomate VM-10A-L” (manufactured by Sekonic Co., Ltd.).

Test Example 2 [Fixability to resin film]
(1) Drop the liquid developer on the corona-treated surface of PET film "FE2000-25" (Futamura Chemical Co., Ltd.), and apply a thin film with a wire bar to a dry weight of 1.2 g/m ^2. It was made. Then, it was held in a constant temperature bath at 120° C. for 6 minutes for fixing.
(2) A liquid developer was dropped on the corona-treated surface of PP film "FOR25" (manufactured by Futamura Chemical Co., Ltd.), and a thin film was prepared by a wire bar so that the mass after drying was 1.2 g/m ² . .. After that, it was held in an 80° C. constant temperature bath for 6 minutes to be fixed.
(3) Drop the liquid developer on the corona-treated surface of Nylon film "Emblem ON-25" (manufactured by Unitika Ltd.), and apply a thin film with a wire bar to a dry weight of 1.2 g/m ^2. It was made. Then, it was held in a constant temperature bath at 120° C. for 6 minutes for fixing.

Stick the mending tape "Scotch Mending Tape 810" (3M Japan Ltd., width 18 mm) on each fixed image obtained in (1) to (3), and use a roller to apply a load of 500 g. After applying pressure to the tape, the tape was peeled off. The image density before and after tape peeling was measured using a colorimeter "Gretag Macbeth Spectroeye" (manufactured by Gretag). The image printed portion was measured at each of 3 points, and the average value was calculated as the image density. The fixing ratio (%) was calculated from the value of image density after peeling/image density before peeling×100. The results are shown in Table 3. It is indicated that the larger the numerical value of the fixing rate is, the more excellent the fixing property is.

From the above results, it is found that the liquid developers containing the dispersant having a high sum of the primary amine value and the secondary amine value of Examples 1 to 5 are excellent in the fixing property to the resin film and the dispersion stability. I understand. Further, while the liquid developer of Example 6 has excellent fixability on the resin film, the liquid developer has a slightly high viscosity because the sum of the primary amine value and the secondary amine value of the dispersant is slightly high. There is a tendency that the particle size becomes larger and the particle size becomes slightly larger. On the other hand, the liquid developer of Comparative Example 1 containing the non-amine dispersant could not be fixed on the resin film.

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

Claims (7)

A toner developer containing a binder resin containing a polyester resin and a colorant, a dispersant, an isocyanate curing agent, and a liquid developer containing an insulating liquid, wherein the dispersant is polyalkyleneamine and polyallylamine. A liquid developer having constituent sites derived from at least one polyamine compound selected from the group consisting of: The liquid developer according to claim 1, wherein the sum of the primary amine value and the secondary amine value of the dispersant X is 50 mgKOH/g or more and 80 mgKOH/g or less. The dispersant X comprises at least one polyamine compound selected from the group consisting of polyalkyleneamine and polyallylamine, a hydrocarbon having a reactive functional group of 16 or more carbon atoms and a polyolefin having a reactive functional group. The liquid developer according to claim 1, which is a reaction product with one or more long-chain aliphatic compounds selected from the group consisting of: The liquid developer according to claim 1, wherein the polyamine compound is polyethyleneimine. The liquid developer according to claim 1, wherein the isocyanate curing agent is a compound having two or more isocyanate groups in one molecule. The liquid developer according to claim 1, wherein the isocyanate curing agent is a biuret type addition product or an isocyanurate ring addition product of an aliphatic diisocyanate compound. 7. The liquid developer according to claim 1, wherein the molar ratio of the isocyanate group to the primary amino group and the secondary amino group (isocyanate group/primary amino group and secondary amino group) is 1 or more and 30 or less.