JP2014092579A - Liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer having excellent fixability, offset resistance and color developing property as well as excellent storage stability, and thereby, capable of providing a stable output image for a long period of time.SOLUTION: The liquid developer comprises at least a binder resin (A), a colorant (B), a polymer dispersant (C), a carrier liquid (D) and a plasticizer (E). The polymer dispersant (C) is prepared by polymerizing at least an ethylenically unsaturated monomer (c-1) having an amino group and an ethylenically unsaturated monomer (c-2) having an alkyl group having 4 to 24 carbon atoms, and the polymer dispersant (C) has an amine value of 5 to 150 mgKOH/g. The plasticizer (E) has a melting point (Tm) of 25°C or higher and is insoluble in the carrier liquid (D) at (Tm+10)°C. Toner particles (F) comprising at least the binder resin (A), the colorant (C) and the plasticizer (E) have a glass transition temperature of 35°C to 70°C.

Description

  The present invention relates to a liquid developer used for developing an electrostatic latent image in an electronic copying machine, a printer, an on-demand printing machine or the like in which an image is formed using an electrophotographic method, an electrostatic recording method, or the like. . More preferably, the present invention relates to a liquid developer that is excellent in fixability, color developability, and color reproducibility while maintaining excellent storage stability.

  An image forming apparatus using a liquid developer can be miniaturized because it is finely pulverized and dispersed under a wet condition as compared with a dry powder toner, and an insulating liquid carrier liquid is used as a carrier. A feature is that high-definition images can be formed without causing problems due to scattering of toner particles in the machine.

  In an electrophotographic image forming apparatus using a liquid developer, a developer in which fine toner particles are dispersed in a carrier liquid is used, and an electrostatic latent image formed by exposure on a photoconductor is used. Development is performed using toner particles in the carrier liquid. After development, the resulting image is transferred, dried and fixed on a recording medium such as paper to form an image.

  The liquid developer is obtained by dispersing toner particles in an electrically insulating carrier liquid, and the toner particles are required to have colorability, fixing properties, charging properties, and dispersion stability. Therefore, the toner particles are composed of additives such as a colorant, a binder resin, and a dispersant. In order to obtain an excellent image, the toner particles must be stably dispersed and charged stably. It is important that (For example, see Patent Documents 1 and 2)

  Further, regarding the fixability of the liquid developer, in order to improve the fixability of the toner particles to the base material, binder resins and plasticizers have been studied. (See, for example, Patent Documents 3 and 4) In particular, when an image is output at high speed, low-temperature fixability of toner particles is required. In order to satisfy low-temperature fixability, the molecular weight of the binder resin is reduced, or glass is used. Reduce the transition temperature. However, these deteriorate the thermal stability of the toner particles and promote the contact and coalescence of the toner particles, and there is a problem that the dispersion stability and storage stability as a liquid developer are lowered. In addition, when using a binder resin that can be fixed with a small amount of heat, the surface of the thermocompression roller and the toner image are in contact with each other when the toner particles are in a molten state. However, there is a problem that a hot offset phenomenon of transfer to the next paper is likely to occur.

  Therefore, in order to achieve both the fixability and the storage stability of the liquid developer, a polymer dispersant has been studied. However, the chargeability of the toner particles decreases due to the influence of the polymer dispersant, the sufficient image density cannot be obtained, the long-term stability of the image deteriorates, and the color developability / color reproducibility is low. There was a problem of being damaged.

  Thus, the fixability and offset resistance of liquid developer, storage stability, color development / color reproducibility, and long-term image stability are in a trade-off relationship, and there is room for improvement to satisfy all of them. There was the present situation.

JP-A-5-333607 Special table 2007-505953 gazette JP 2004-205843 A JP 2002-258542 A JP 2009-145535 A

  As described above, although the liquid developer is excellent in improving the image quality of the image, there is room for improvement in achieving both the fixability and offset resistance, storage stability, color developability and color reproducibility of the liquid developer. . There is a need for a liquid developer that solves this problem and has excellent color developability / color reproducibility of an output image, dispersion stability of toner particles, and excellent storage stability over a long period of time.

  The object of the present invention is excellent in fixability, offset resistance, color development and color reproducibility, and even when the number of printed sheets and the printing area increase, the dispersion state of the toner particles in the liquid developer is stable, and the developer is maintained over a long period of time. An object of the present invention is to provide a liquid developer having a stable image density with no change in composition.

  As a result of intensive studies, the present inventors have determined that a polymer dispersant having a specific amine value is obtained by copolymerizing at least a specific ethylenically unsaturated monomer as a polymer dispersant in a liquid developer. And the toner particles having a specific glass transition temperature, including at least a binder resin, a colorant, and a plasticizer. The inventors have found that it can be achieved and have arrived at the present invention.

The present invention is a liquid developer comprising at least a binder resin (A), a colorant (B), a polymer dispersant (C), a carrier liquid (D), and a plasticizer (E),
The polymer dispersant (C) is at least an ethylenically unsaturated monomer having an amino group (c-1),
Polymerized with an ethylenically unsaturated monomer (c-2) containing an alkyl group having 4 to 24 carbon atoms,
The amine value of the polymer dispersant (C) is 5 to 150 mgKOH / g,
The melting point (Tm) of the plasticizer (E) is 25 ° C. or higher, and is insoluble in the carrier liquid (D) at (Tm + 10) ° C.,
The toner particles (F) including at least the binder resin (A), the colorant (B), and the plasticizer (E) have a glass transition temperature (Tg) of 35 ° C. to 70 ° C. The present invention relates to a liquid developer.

  The present invention also relates to a liquid developer wherein the binder resin (A) contains at least a polyester resin.

  The present invention also relates to a liquid developer, wherein the binder resin (A) contains at least a polyester resin and a styrene-acrylic copolymer resin.

  The present invention also relates to a liquid developer, wherein the binder resin (A) has a weight average molecular weight (Mw) of 2000 ≦ Mw ≦ 100,000.

  The present invention also relates to a liquid developer, wherein the carrier liquid (D) is an aliphatic hydrocarbon.

  The present invention also relates to a liquid developer characterized in that the dry point in the distillation range of the carrier liquid (D) is 200 ° C. to 360 ° C.

  As described above, the polymer dispersant (C) used in the liquid developer is copolymerized containing at least a specific ethylenically unsaturated monomer, has a specific amine value, and has a specific melting point. The toner particles (F) containing at least the binder resin (A), the colorant (B), and the plasticizer (E) are insoluble in the carrier liquid (D). By having a transition temperature (Tg), it is possible to obtain a liquid developer having excellent fixing properties, offset resistance, good color development / color reproducibility and storage stability over a long period of time.

  In this liquid developer, since the plasticizer (E) is insoluble in the carrier liquid (D), the plasticizer (E) is not dissolved in the carrier liquid (D) and is dispersed in the binder resin (A). Therefore, the plasticizing effect on the binder resin (A) is high, the fixing property to the base material is excellent, and the glass transition temperature (Tg) of the toner particles (F) is controlled so that the heat stability The decline in sex can be suppressed. Further, the presence of the polymer dispersant (C) improves the chargeability and dispersion stability of the toner particles (F) in the liquid developer, and the liquid developer has excellent storage stability. Thus, it has been possible to provide a liquid developer having excellent image density, color developability and color reproducibility, and inferior copy image quality.

Hereinafter, the present invention will be described in more detail.
The liquid developer of the present invention is
The polymer dispersant (C) is copolymerized containing at least a specific ethylenically unsaturated monomer, has a specific amine value,
The plasticizer (E) having a specific melting point is insoluble in the carrier liquid (D),
A major feature is that the toner particles (F) including at least the binder resin (A), the colorant (B), and the plasticizer (E) have a specific glass transition temperature (Tg).

  In this liquid developer, since the plasticizer (E) is insoluble in the carrier liquid (D), the toner particles (F) are eluted in the carrier liquid (D) even after the toner particles (F) are wet-dispersed in the carrier liquid (D). Without being present in the binder resin (A). Thereby, the plasticizing effect with respect to binder resin (A) is high, and it is excellent in the low temperature fixability to a base material. Further, since the plasticizer (E) is not present in the carrier liquid (D), it becomes difficult for the toner particles to come into contact with and coalesce during long-term storage of the liquid developer, thereby suppressing a decrease in thermal stability. be able to.

  Furthermore, the presence of the polymer dispersant (C) improves the chargeability and dispersion stability of the toner particles in the liquid developer, and the liquid developer has excellent stability, image density, color developability and color over a long period of time. Reproducibility can be obtained. In order to satisfy the low-temperature fixability, it is known to lower the glass transition temperature (Tg) of the toner particles by using a plasticizer or the like. This results in problems such as insufficient image density and poor color development and color reproducibility. This polymer dispersant (C) is a copolymer containing a specific ethylenically unsaturated monomer and has a specific amine value, so that the adsorption rate of the binder resin (A) is high, and the toner It is possible to suppress a decrease in grindability due to a decrease in the glass transition temperature of the particles and to obtain good dispersion stability.

  Using the polymer dispersant (C) and the plasticizer (E) having such an effect, further including at least a binder resin (A), a colorant (B), and a plasticizer (E). By controlling the glass transition temperature (Tg) of the toner particles (F), the toner particles (F) are excellent in fixability, offset resistance, color development and color reproducibility. Thus, it is possible to obtain a liquid developer having a stable dispersed state of toner particles and having a stable image density with no change in developer composition over a long period of time.

  Hereinafter, the binder resin (A), the colorant (B), the polymer dispersant (C), the carrier liquid (D), the plasticizer (E), and the toner particles (F) constituting the liquid developer of the present invention Will be described in detail.

(Binder resin (A))
In general, the binder resin has a function of uniformly dispersing a colorant such as a pigment or a dye in the resin and a function as a binder when fixing to a substrate such as paper.
Examples of binder resins that can be used include homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and substituted products thereof; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer Styrene-vinyl naphthalene copolymer, styrene- (meth) acrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, Styrene copolymers such as styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, and crosslinked. Styrene copolymer; Polyvinyl chloride , Phenolic resin, natural modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane resin, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral resin Terpene resin, coumarone indene resin, petroleum resin and the like.
As the binder resin (A) used in the liquid developer of the present invention, a polyester resin is particularly preferable from the viewpoint of pigment dispersibility, grindability, and fixability. More preferably, it contains a polyester resin and a styrene-acrylic copolymer resin. Moreover, in order not to disturb the hue of the color material of each color, those exhibiting colorless, transparent, white or light color are preferable.

  The polyester resin is preferably a thermoplastic polyester, and is obtained by polycondensation of a divalent or trivalent or higher alcohol component and an acid component such as carboxylic acid.

Examples of the alcohol component include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,4-butenediol, Diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, bisphenol A, hydrogenated bisphenol A, 1,4-bis (hydroxy Methyl) cyclohexane, divalent alcohols such as bisphenol derivatives represented by the following general formula (1),
Examples of trihydric or higher alcohols such as glycerol, diglycerol, sorbit, sorbitan, butanetriol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and the like, may be used alone or in combination Used in combination.

(In the formula, R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2 to 10.)

As the acid component, divalent carboxylic acids such as benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and phthalic anhydride or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid Or its anhydride;
And a succinic acid or anhydride thereof further substituted with an alkyl group having 16 to 18 carbon atoms;
Unsaturated dicarboxylic acids such as fumaric acid, maleic acid, citraconic acid, itaconic acid, glutaconic acid or anhydrides thereof;
Examples thereof include cyclohexanedicarboxylic acid; naphthalenedicarboxylic acid; diphenoxyethane-2,6-dicarboxylic acid, and the like as trivalent or higher carboxylic acids acting as a crosslinking component are trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, butanetricarboxylic acid. Hexanetricarboxylic acid, tetra (methylenecarboxyl) methane, octanetetracarboxylic acid, benzophenonetetracarboxylic acid and anhydrides thereof, and the like are used alone or in combination of two or more.

  Preferred alcohol components are those obtained by adding 2 to 3 moles of alkylene oxide to bisphenol A, ethylene glycol, neopentyl glycol, etc., and preferred acid components are phthalic acid, terephthalic acid, isophthalic acid or its anhydride, succinic acid, n-dodecenyl succinic acid or its anhydride, dicarboxylic acids such as fumaric acid, maleic acid and maleic anhydride, and tricarboxylic acids such as trimellitic acid or its anhydride.

  Moreover, as a catalyst used for the polycondensation of the polyester resin, a known and usual reaction catalyst such as at least one metal compound selected from antimony, titanium, tin, zinc and manganese may be used, and the reaction may be promoted. Specific examples of the reaction catalyst include di-n-butyltin oxide, stannous oxalate, antimony trioxide, titanium tetrabutoxide, manganese acetate, and zinc acetate. The addition amount of these reaction catalysts is usually preferably about 0.001 to 0.5 mol% with respect to the acid component in the obtained polyester resin.

  As the polycondensation method, a known bulk polymerization method can be used. To control the molecular weight and softening temperature of the polyester resin, the kind and molar ratio of the alcohol component and carboxylic acid to be reacted, as well as the reaction temperature and reaction time. The reaction pressure, catalyst, etc. may be adjusted. Furthermore, it is also possible to use a commercial item as a polyester resin. For example, there are Diacron ER-502 and Diacron ER-508 (both manufactured by Mitsubishi Rayon Co., Ltd.).

  Furthermore, it is preferable that the binder resin (A) contains a polyester resin and a styrene-acrylic copolymer resin in order to improve the fixability and grindability. The styrene-acrylic copolymer resin is obtained by polymerizing at least one of a styrene monomer and (meth) acrylic acid and (meth) acrylic acid esters.

  Styrene monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-ethyl styrene, 2,4-dimethyl styrene, pn-butyl styrene, p-tert. -Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-phenyl styrene, Examples include p-chlorostyrene and 3,4-dichlorostyrene.

  (Meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) acrylic acid Octyl, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, 2-chloroethyl (meth) acrylate, phenyl (meth) acrylate, acrylic acid Examples include dimethylaminoethyl and diethylaminoethyl (meth) acrylate.

  A preferred styrenic monomer is styrene, and preferred (meth) acrylic acid esters are butyl (meth) acrylate, octyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.

  In order to increase the molecular weight of the styrene-acrylic copolymer resin, a polyfunctional monomer can be used as a crosslinking agent. Specifically, divinylbenzene, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri ( And (meth) acrylate.

  The styrene-acrylic copolymer resin comprising the styrene monomer and (meth) acrylic acid and (meth) acrylic acid esters can be obtained by a known polymerization method such as a suspension polymerization method, a solution polymerization method or an emulsion polymerization method. To control the molecular weight and softening temperature of the styrene-acrylic copolymer resin, the types and molar ratios of the styrene monomer and (meth) acrylic acid and (meth) acrylic acid esters, as well as the reaction temperature, reaction time, and reaction What is necessary is just to adjust a pressure, a polymerization initiator, a crosslinking agent, etc. Furthermore, it is also possible to use a commercial item as a styrene-acrylic copolymer resin. For example, there are ALMATEX CPR100, CPR200, CPR300, CPR600B (Mitsui Chemicals).

In addition, in order to obtain a more uniformly dispersed binder resin (A) by mixing the polyester resin and the styrene-acrylic copolymer resin, the polyester resin and the styrene-acrylic copolymer resin are melt-kneaded. In the presence of either a resin or a styrene-acrylic copolymer resin, there is a method in which the other monomer is added for polymerization. The latter is desirable to obtain a more uniformly dispersed binder resin, usually after polycondensation of the polyester resin by bulk polymerization and then heating as necessary in a system in which the resulting polyester resin is dissolved in a solvent. However, a method of synthesizing the styrene-acrylic copolymer resin by solution polymerization and removing the solvent is preferable.
Furthermore, it is also preferable to synthesize | combine by well-known methods, such as patent 3531980 and Unexamined-Japanese-Patent No. 2006-178296.

  When preparing polyester resin and styrene-acrylic copolymer resin separately, or when using commercially available polyester resin or styrene-acrylic copolymer resin, the polyester resin and styrene-acrylic copolymer resin are mixed together. A resin (A) can be obtained. At this time, either of them may be dissolved in a solvent, mixed and desolvent, or melt-kneaded.

(Softening temperature (T4))
The softening temperature of the binder resin (A) used in the present invention is preferably in the range of 80 to 140 ° C. More preferably, it is the range of 90 to 130 degreeC. The softening temperature in the present invention is as follows. Using a flow tester CFT-500D manufactured by Shimadzu Corporation, a starting temperature of 40 ° C., a heating rate of 6.0 ° C./min, a test load of 20 kg, a preheating time of 300 seconds, and a die hole diameter of 0.5 mm. The temperature when 4 mm of 1.0 g of the sample flows out under the condition of the die length of 1.0 mm is measured as the softening temperature (T4).

  If the softening temperature of the binder resin (A) is lower than 80 ° C., the binder resin (A) is excessively softened during kneading, the dispersion of the colorant (B) is deteriorated, and a sufficient image density as a liquid developer cannot be obtained. Furthermore, the hot offset resistance is deteriorated. On the other hand, when the softening temperature is higher than 140 ° C., there are problems that good fixability cannot be obtained, grindability is deteriorated, and dispersion stability and color developability are deteriorated.

(Weight average molecular weight (Mw))
The binder resin (A) has a weight average molecular weight (Mw) of 2,000 to 100, in terms of molecular weight measured by gel permeation chromatography (GPC) in terms of offset resistance, fixing property and image quality characteristics. 000 is preferable, and 5,000 to 50,000 is more preferable. When the weight average molecular weight (Mw) of the binder resin (A) is smaller than 2,000, hot offset resistance, color reproducibility and dispersion stability are lowered, and when it is larger than 100,000, the fixing property is deteriorated. A problem occurs.

  In addition, the binder resin (A) used in the present invention is a type having a molecular weight distribution curve of two peaks composed of a specific low molecular weight condensation polymer component and a specific high molecular weight condensation polymer component, or one peak. Any of the types having a single molecular weight distribution curve may be used.

In addition, the molecular weight distribution by said GPC was measured on the following conditions using the gel permeation chromatography (HLC-8220) by Tosoh Corporation.
The column is stabilized in a 40 ° C. heat chamber, tetrahydrofuran (THF) as a solvent is allowed to flow through the column at this temperature at a flow rate of 0.6 ml / min, and 10 μl of a sample solution dissolved in THF is injected for measurement. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts.

As standard polystyrene samples for preparing a calibration curve, ten samples having a molecular weight of about 10 ² to 10 ⁷ manufactured by Tosoh Corporation were used. An RI (refractive index) detector is used as the detector. In addition, three TSKgel SuperHM-M (manufactured by Tosoh Corporation) were used for the column.

  A measurement sample was prepared as follows. Place the sample in THF and let stand for several hours, then shake well, mix well with THF until the sample is no longer united, and let stand for more than 12 hours. At this time, the standing time in THF is set to be 24 hours or longer. Then, the sample that has passed through the sample processing filter is used as a GPC measurement sample. The sample concentration was adjusted so that the resin component was 0.5 to 5 mg / ml.

(Acid value)
The acid value of the binder resin (A) is preferably 3 to 70 mgKOH / g, and more preferably 10 to 40 mgKOH / g. When the acid value is lower than 3 mg KOH / g, the polymer dispersant is hardly adsorbed on the binder resin, the dispersion stability of the toner particles is deteriorated, and the storage stability of the liquid developer is deteriorated. When the acid value is higher than 70 mgKOH / g, the chargeability of the toner particles is lowered, and problems such as insufficient image density and poor color development and color reproducibility are caused. The acid value of the binder resin (A) is the number of mg of potassium hydroxide (KOH) necessary for neutralizing the acid contained in 1 g of the binder resin (A), and is an ethanol / toluene mixed solvent. It is the value titrated with KOH solution.

(Colorant (B))
As the colorant (B) used in the liquid developer of the present invention, the following yellow, magenta, cyan, and black organic pigments, organic dyes, particularly salt-forming compounds thereof, carbon black, and magnetic materials are preferably used. . These can be used alone or in admixture of two or more. Further, it is preferably insoluble in the carrier liquid.

As the yellow colorant, it is preferable to use a yellow organic pigment or a salt forming compound of a yellow dye.
As the yellow organic pigment, compounds represented by benzimidazolone compounds, condensed azo compounds, isoindolinone compounds, anthraquinone compounds, quinophthalone compounds, azo metal complex compounds, methine compounds, and allylamide compounds are used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 138, 139, 147, 150, 168, 174, 176, 180, 181, 191 and the like are preferably used. Of these, quinophthalone compounds, condensed azo compounds, and benzimidazolone compounds are preferably used.
As the yellow dye salt-forming compound, an acid dye salt-forming compound and a basic dye salt-forming compound are used. Examples of the salt forming compound of the acid dye include C.I. I. It is preferable to use a salt-forming compound composed of Acid Yellow 11, 23 (tartrazine) and a quaternary ammonium salt compound. By constituting the quaternary ammonium salt, the toner particles can maintain a stable positive charge.

As the magenta colorant, it is preferable to use a magenta organic pigment or a salt forming compound of a magenta dye.
As magenta organic pigments, condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, lake compounds of basic dyes such as rhodamine lakes, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds are used. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81, 81: 1, 81: 2, 81: 3, 81: 4, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 209, 220, 221, 254, 255, 268, 269, etc., C.I. I. Pigment violet 1, 19 and the like are preferably used. Among them, it is preferable to use a quinacridone compound, a rhodamine lake pigment, a naphthol pigment, or the like. Specifically, naphthol AS (CI Pigment Red 269 etc.), rhodamine lake (CI Pigment Red 81, 81: 1, 81: 2, 81: 3, 81: 4, 169 etc.), quinacridone (C.I. Pigment Red 122 etc.) Carmine 6B (C.I. Pigment Red 57: 1) is a preferred material.
A combination of a quinacridone pigment and a monoazo pigment, Carmine 6B (CI Pigment Red 57: 1), is preferable because it exhibits a good magenta color and red color.
Further, as a salt-forming compound of a magenta dye, a salt-forming compound of a rhodamine-based acidic dye or a salt-forming compound of a rhodamine-based basic dye is preferably used. Examples of the salt forming compound of the basic dye include C.I. I. It is preferable to use a salt-forming compound composed of Basic Red 1 and Basic Violet 10 and colorless (does not inhibit coloring of the pigment) organic sulfonic acid or organic carboxylic acid. Since the basic dye exhibits a good positive charge, the toner particles can maintain a stable positive charge. As the organic sulfonic acid, naphthalenesulfonic acid, naphtholsulfonic acid, naphthylaminesulfonic acid and the like are preferably used. As the organic carboxylic acid, a salicylic acid derivative or a higher fatty acid is used.

As the cyan colorant, it is preferable to use cyan, blue organic pigments, cyan, salt forming compounds of blue dyes, and oil-soluble dyes of cyan and blue dyes.
As the cyan organic pigment, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds, and the like can be used. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 60, 62, 66 and the like are preferably used. Among them, C.I. I. It is preferable to use a copper phthalocyanine compound such as CI Pigment Blue 15: 3.
It is also preferable to use a compound derived from a triarylmethane dye in a form used in combination with the organic pigment. Triarylmethane dyes are effective materials from the viewpoints of both chargeability control and colorability because they have good positive chargeability. In particular, C.I. I. Triarylmethane-based oil-soluble dyes such as Solvent Blue 124 and salt-forming compounds of triarylmethane-based basic dyes are good. C. I. As the solvent blue 124, specifically, COPY BLUE PR manufactured by Clariant is a preferable material. This is C.I. I. It was obtained by condensing Basic Red 9 (paramagenta) and aniline.
Further, in addition to the cyan and blue organic pigments, cyan and blue dye salt forming compounds, and cyan and blue dye oil-soluble dyes, a green pigment can be used as a complementary color for the purpose of adjusting the hue. Specific examples of the green pigment include C.I. I. Halogenated phthalocyanine compounds such as CI Pigment Green 7 and 36 are preferred.

As the black colorant, it is preferable to use organic black pigments such as carbon black and perylene black and organic black dyes such as nigrosine dye and azo metal complex dye from the viewpoint of cost and handling.
As carbon black, various types such as furnace black, channel black, acetylene black, and carbon black derived from biomass can be used, but furnace black carbon and biomass carbon reduce fog (stain on the white background) in image characteristics. This is preferable.
As the nigrosine dye, it is preferable to use a nigrosine base that is refined by wet pulverization or the like and has a volume average particle size of 0.5 to 2 μm. This refined nigrosine dye has a gloss, and a glossy black color can be obtained. Nigrosine refinement can be obtained by the method described in JP-A-2006-171501.
Further, as the black colorant, black can be obtained using the above three colorants of yellow, magenta, and cyan.

Furthermore, in order to obtain black with good image density and contrast, it is preferable to add 1 to 10 parts by mass of a blue dye as a black colorant with respect to 100 parts by mass of the black dye. As the blue pigment, it is preferable to use a halogen-free metal phthalocyanine blue compound, a triarylmethane compound, a dioxazine violet pigment, or the like. In addition, the phthalocyanine blue compound and the triarylmethane compound have a stable positive charging property, which is effective in obtaining good black toner particles. Specifically, C.I. I. Pigment Blue 15: 3, Victoria Pure Blue Lake Pigment (CI Pigment Blue 1), C.I. I. Pigment violet 23, C.I. I. Pigment Violet 19, a salt-forming compound composed of a triarylmethane-based basic dye and a substantially colorless organic acid (a salt-forming compound of CI Basic Blue 7 and an organic acid), a triarylmethane-based oil-soluble dye Is preferably used.
Triarylmethane dyes are effective in controlling the chargeability of toner particles by exhibiting good positive charge, and among them, triarylmethane oil-soluble dyes having excellent dispersibility are preferred.

  The content of the colorant (B) contained in the toner particles used in the present invention varies depending on the type of the binder resin (A) used, but is usually 5 to 40 parts by mass with respect to 100 parts by mass of the toner particles. Preferably it is 10-30 mass parts.

  In the case of obtaining a full-color image in which four colors are superimposed using the liquid developer of the present invention, a preferable image utilizing the fixing property and color developing property in superposition can be obtained by using Y, M, C, and Bk. .

(Polymer dispersant (C))
The dispersant is added to the carrier liquid in which the toner particles are present so as to uniformly disperse the toner particles and improve the development characteristics. The polymer dispersant (C) used in the present invention is a carrier. Even if it is added to the liquid, it can be added to the toner particles (F) during the kneading of the toner production. When added to the carrier liquid and the toner particles are dispersed, the polymer dispersant (C) is adsorbed on the binder resin portion on the toner particle surface, particularly on the polyester resin portion that exhibits excellent dispersion stability. It is inferred that
Thus, the polymer dispersant (C) is preferably present in a state of being adsorbed on the surface of the toner particles or dispersed inside the toner particles.

  The polymer dispersant (C) includes an ethylenically unsaturated monomer (c-1) having an amino group and an ethylenically unsaturated monomer (c-2) containing an alkyl group having 4 to 24 carbon atoms. It is obtained from a copolymerizable monomer containing

As the ethylenically unsaturated monomer having a tertiary amino group in the polymer dispersant (C), for example,
N, such as N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and N, N-diethylaminopropyl (meth) acrylate N-dialkylamino group-containing (meth) acrylic acid esters; and
N, such as N, N-dimethylaminoethyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, and N, N-diethylaminopropyl (meth) acrylamide N-dialkylamino group-containing (meth) acrylamides; and dimethylaminostyrene, diethylaminostyrene and the like.

It can also be obtained by a weight monomer that can be polymerized with an ethylenically unsaturated monomer having a secondary amino group. As an ethylenically unsaturated monomer having a secondary amino group, for example,
Examples thereof include tert-butylaminoethyl (meth) acrylate and tetramethylpiperidinyl methacrylate.

  Among these, N, N-dimethylaminoethyl (meth) acrylate or N, N-diethylaminoethyl (meth) acrylate is preferable from the viewpoint of dispersibility.

  The amine value of the polymer dispersant (C) is preferably 5 to 150 mgKOH / g. More preferably, it is 30-100 mgKOH / g. When the amine value is lower than 5 mgKOH / g, the adsorption to the toner particles (F) is weak, and the pulverizability by wet pulverization is deteriorated. Furthermore, during storage for a long period of time, the toner particles (F) aggregate, the viscosity and average particle diameter of the liquid developer increase, and the storage stability deteriorates. When the amine value is higher than 150 mgKOH / g, the chargeability of the toner particles (F) is deteriorated, the toner particles are hardly transferred to the substrate, and a good image density cannot be obtained. Furthermore, the solubility in the carrier liquid (D) is lowered, and the grindability is deteriorated. The amine value of the polymer dispersant (C) is the total amine value (mgKOH / g) measured according to the method of ASTM D2074.

  Moreover, as for the ethylenically unsaturated monomer (c-2) containing a C4-C24 alkyl group among polymer dispersing agents (C), an alkyl group has the solubility to carrier liquid (D). And improves the pulverization property in wet pulverization, and further suppresses the aggregation of toner particles (F) and the increase in viscosity of the liquid developer during long-term storage, thereby obtaining excellent storage stability. . More preferably, the alkyl group has 9 to 24 carbon atoms. When the alkyl group has less than 4 carbon atoms, the solubility in the carrier liquid (D) is low, and the dispersion stability and storage stability of the toner particles (F) are deteriorated. When the carbon number of the alkyl group is larger than 24, when the liquid developer is fixed to the substrate, the long alkyl group hinders contact and coalescence of the toner particles, and the fixing property is deteriorated. Furthermore, the chargeability of the toner particles is deteriorated, causing the toner particles to be difficult to be transferred to the base material and causing a problem that a sufficient image density cannot be obtained.

Examples of the ethylenically unsaturated monomer containing an alkyl group having 4 to 24 carbon atoms include:
Butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, pentyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, hexyl (meth) Acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, 8-methylnonyl (meth) acrylate, 2-methylnonyl (meth) acrylate, decyl (meth) acrylate, 2- (meth) acrylate methyldecyl (meth) acrylate, undecyl (Meth) acrylate, 2-methylundecyl (meth) acrylate, 9-ethylundecyl (meth) acrylate, dodecyl (meth) acrylate, 2-methyldodecyl (meth) acrylate, 1-methyldodecyl (meth) acrylate, tridecyl (meth) acrylate, 2-methyltridecyl (meth) acrylate, tetradecyl (meth) acrylate, 2-methyltetradecyl (meth) acrylate, pentadecyl (meth) acrylate, 2-methyl Pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, 2-methylhexadecyl (meth) acrylate, heptadecyl (meth) acrylate, 2-methylheptadecyl (meth) acrylate, octadecyl (meth) acrylate, 2-methyloctadecyl ( (Meth) acrylate, nonadecyl (meth) acrylate, 2-methylnonadecyl (meth) acrylate, icosyl (meth) acrylate, heicosyl (meth) acrylate, docosyl (meth) acryl (Meth) acrylates of alkyl (meth) acrylate having a carbon number of 4 to 24, such as over preparative; and,
N-butyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-isopentyl (meth) acrylamide, N-neopentyl (meth) acrylamide, N-hexyl (meth) acrylamide, N-isohexyl (meth) acrylamide, Nn-heptyl (meth) acrylamide, N- (6-methylheptyl) (meth) acrylamide, N-octyl (meth) acrylamide, N- (7-methyloctyl) (meth) acrylamide, N-nonyl (meth) Acrylamide, N- (8-methylnonyl) (meth) acrylamide, N-decyl (meth) acrylamide, N, N-didecyl (meth) acrylamide, N-undecyl (meth) acrylamide, N- (1-methylundecyl) ( (Meth) acrylamide, N-dodecy Ru (meth) acrylamide, N, N-didodecyl (meth) acrylamide, N-tridecyl (meth) acrylamide, N- (1-methyltridecyl) (meth) acrylamide, N-tetradecyl (meth) acrylamide, N, N- Ditetradecyl (meth) acrylamide, N-pentadecyl (meth) acrylamide, N- (1-methylpentadecyl) (meth) acrylamide, N-hexadecyl (meth) acrylamide, N, N-dihexadecylacrylamide, N-heptadecyl (meta) ) Acrylamide, N- (1-methylheptadecyl) acrylamide, N-octadecyl (meth) acrylamide, N, N-dioctadecylacrylamide, N-nonadecyl (meth) acrylamide, N-icosyl (meth) acrylamide, N-henico Alkyl (meth) acrylamides having 4 to 24 carbon atoms such as ru (meth) acrylamide and N-docodecyl (meth) acrylamide; and 4-nonylphenyl (meth) acrylate, 4'-decyl-4-biphenylyl (meth) acrylate 3-pentadecylphenyl (meth) acrylate, N- (10-phenyldecyl) (meth) acrylamide, N- (4-dodecylphenyl) (meth) acrylamide, N- [2- (1-naphthyl) ethyl]- N-dodecyl (meth) acrylamide, N- [4- (1-pyrenyl) butyl] -N-dodecyl (meth) acrylamide, N-octadecyl-N- [2- (1-naphthyl) ethyl] (meth) acrylamide, etc. (Meth) acrylates and (meth) acrylates containing an aromatic ring and an alkyl group having 4 to 24 carbon atoms Ruamido the like; and,
1-pentene, 2-pentene, 1-hexene, 2-hexene, 4-ethyl-2-hexene, 1-heptene, 2-heptene, 1-octene, 2-octene, 1-nonene, 2-nonene, 1- Decene, 2-decene, 1-undecene, 1-dodecene, 2-dodecene, 1-tridecene, 2-tridecene, 1-tetradecene, 2-tetradecene, 4-tetradecene, 1-pentadecene, 2-pentadecene, 4-pentadecene, Carbons such as 1-hexadecene, 2-hexadecene, 4-hexadecene, 1-heptadecene, 2-heptadecene, 4-heptadecene, 1-octadecene, 2-octadecene, 4-octadecene, 1-docosene, 2-docosene, 4-docosene, etc. The alpha olefins containing the alkyl group of several 4-24 can be illustrated.

  Among these, (meth) acrylates such as alkyl (meth) acrylates having 4 to 24 carbon atoms are preferable from the viewpoint of dispersibility.

Other unsaturated compounds that may be included include, for example,
(Meth) acrylates such as alkyl (meth) acrylates having 1 to 3 carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and isopropyl (meth) acrylate;
Polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono (meth) acrylate, poly (ethylene glycol-propylene glycol) mono (meth) acrylate, poly (ethylene glycol-tetramethylene glycol) mono ( (Meth) acrylate, poly (propylene glycol-tetramethylene glycol) mono (meth) acrylate, polyethylene glycol mono (meth) acrylate monomethyl ether, polyethylene glycol mono (meth) acrylate monobutyl ether, polyethylene glycol mono (meth) acrylate monooctyl ether, Polyethylene glycol mono (meth) acrylate monobenzyl ether, polyethylene glycol Mono (meth) acrylate monophenyl ether, polyethylene glycol mono (meth) acrylate monodecyl ether, polyethylene glycol mono (meth) acrylate monododecyl ether, polyethylene glycol mono (meth) acrylate monotetradecyl ether, polyethylene glycol mono (meth) acrylate Monohexadecyl ether, polyethylene glycol mono (meth) acrylate monooctadecyl ether poly (ethylene glycol-propylene glycol) mono (meth) acrylate octyl ether, poly (ethylene glycol-propylene glycol) mono (meth) acrylate octadecyl ether, poly (ethylene Glycol-propyleneglycol) mono (meth) acrylate nonylphenyl Ethylenically unsaturated monomer having an alkylene oxide group having 2 to 4 carbon atoms, such as ether;
Cyclohexyl (meth) acrylate, Tertiarybutylcyclohexyl (meth) acrylate, Dicyclopentanyl (meth) acrylate, Dicyclopentanyloxyethyl (meth) acrylate, Dicyclopentenyl (meth) acrylate, Dicyclopentenyloxyethyl (meth) ) Acrylates or cyclic alkyl (meth) acrylates such as isobornyl (meth) acrylate;
(Meth) acrylates having an aromatic ring such as benzyl (meth) acrylate;
Examples thereof include vinyls such as styrene, α-methylstyrene, vinyl acetate, vinyl (meth) acrylate, and allyl (meth) acrylate.
Unsaturated compounds other than those described above can also be used as long as they do not affect the physical properties.

The polymerization method of the polymer dispersant (C) suitable for the present invention is obtained by ordinary acrylic solution polymerization. However, when the polymer dispersant (C) is used in the present invention, it is preferable that the polymer dispersant (C) can be taken out in a state dissolved in the solvent of the carrier liquid (D) or taken out as a solid. The carrier liquid (D) will be described later. When the polymer dispersant (C) is added when the toner particles (F) are wet-dispersed in the carrier liquid, the polymer dispersant (C) is preferably dissolved in the carrier liquid (D). When the molecular dispersant (C) is added to the toner particles (F) during the production of the toner particles and used, the polymer dispersant (C) is preferably a solid.
There are the following three methods for obtaining the polymer dispersant (C) dissolved in the carrier liquid (D).
As a first method, the carrier liquid (D) used in the liquid developing toner is polymerized using a synthetic solvent.
As a second method, polymerization is performed in a solvent that can be replaced with the carrier liquid (D), and then the carrier liquid (D) is added, and only the solvent used for the polymerization is distilled off.
As a third method, polymerization is performed in a mixed solution of a solvent that can be replaced with the carrier liquid (D) and the carrier liquid (D), and then only the solvent other than the carrier liquid (D) is distilled off.
As a solvent that can be solvent-substituted for the carrier liquid (D), a solvent having a boiling point lower than that of the carrier liquid (D) is preferable. For example, ethyl acetate, n-propyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, ethanol, propanol,
Butanol or the like is used. Two or more kinds of these polymerization solvents may be mixed and used. Among these, n-propyl acetate and toluene are particularly preferable from the viewpoints of polymerization temperature, ease of solvent distillation, and polarity of the solvent.
In order to take it out as a solid, it is obtained by distilling off the solvent after the polymerization of the polymer dispersant (C). The solvent that can be distilled off is not particularly limited, but a solvent that can be easily distilled off as described above is preferable.

Although it does not specifically limit as a polymerization initiator used by superposition | polymerization of a polymer dispersing agent (C), For example, an azo type compound and an organic peroxide can be used. Examples of the azo compounds include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), 2 , 2 '
-Azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate), 4, 4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-
Hydroxymethylpropionitrile), or 2,2′-azobis [2- (2-imidazolin-2-yl) propane]. Examples of organic peroxides include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di (2-ethoxyethyl) peroxy Examples include dicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxybivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, or diacetyl peroxide. These polymerization initiators can be used alone or in combination of two or more. The reaction temperature is preferably 40 to 150 ° C, more preferably 50 to 120 ° C.

  The weight average molecular weight (Mw) of the polymer dispersant (C) is not limited to a specific range, but considering the dispersibility and grindability when the toner particles (F) are wet-dispersed, it is 3000. ~ 100,000 is preferred. If the weight average molecular weight (Mw) is less than 3000, the dispersibility and grindability of the toner particles are deteriorated. If it exceeds 100000, the chargeability of the toner particles is deteriorated and sufficient image density cannot be obtained. Occur.

  The polymer dispersant (C) can be added in an amount of about 0.1 to 10 parts by mass with respect to 100 parts by mass of the liquid developer. More preferably, it is the range of 0.1-5 mass parts. When the amount is less than 0.1 parts by mass, the dispersibility and pulverization properties of the toner particles (F) and the storage stability are deteriorated. It is possible to increase the dispersibility and pulverization properties of the toner particles (F) by changing the dispersion method and increasing the dispersion time, but this causes an increase in the viscosity of the liquid developer, thereby improving transferability and color development. It causes deterioration. When the addition amount is more than 10 parts by mass, the chargeability of the toner particles (F) is lowered, causing problems such as insufficient image density and deterioration of fixing properties.

(Other dispersants)
As the dispersant, in addition to the polymer dispersant (C) used in the present invention, a dispersant conventionally used in a liquid developer may be used. Specifically, fatty acid metal salts such as cobalt naphthenate, zinc naphthenate, copper naphthenate, manganese naphthenate, cobalt octylate and zirconium octylate, titanate coupling agents of organic titanates such as lecithin and titanium chelate, alkoxy Examples include titanium polymers, polyhydroxy titanium carboxylate compounds, titanium alkoxides, succinimide compounds, polyimine compounds, fluorine-containing silane compounds, and pyrrolidone compounds. Among them, titanium alkoxide, succinimide compound, fluorine-containing silane compound, and pyrrolidone compound may be mixed and used in an appropriate amount within a range of 5 parts by mass or less with respect to the total mass part of the liquid developer.
In this case, the dispersant is used in such a manner that the dispersant having the same polarity as the toner particles is adsorbed on the toner particles, and the dispersant having the opposite polarity to the toner particles is not adsorbed on the toner particles and dispersed in the carrier liquid. It is something to be made. At this time, the standard for discussing the polarity is the polarity with respect to the carrier liquid. In addition, this behavior is determined after an actual image test and is obtained empirically.

(Carrier liquid (D))
The carrier liquid (D) used in the liquid developer of the present invention is preferably an aliphatic hydrocarbon. Examples of the aliphatic hydrocarbons include linear paraffin hydrocarbons, isoparaffin hydrocarbons, and naphthene hydrocarbons. Among these, paraffinic hydrocarbons with very little residual aromatic hydrocarbon are preferable. Further, those having lipophilic properties, chemically stable and insulating properties are preferred. Further, the carrier liquid needs to be chemically inert with respect to a material or apparatus used in the image forming apparatus, particularly a member around a developing process such as a photoconductor.

The dry point in the distillation range of the carrier liquid (D) is preferably in the range of 200 to 360 ° C. Especially preferably, it is the range of 240 degreeC-330 degreeC. When the temperature is lower than 200 ° C., the liquid developer is dried at room temperature, solid matter is deposited, and the regulation blade around the development is fixed, causing image contamination. On the other hand, when the temperature is higher than 360 ° C., it becomes difficult to remove the carrier liquid and the fixability is deteriorated.
Here, the dry point in the distillation range is based on the method defined by ASTM D 86, ASTM D 1078, and JIS K2254.

Moreover, it is preferable to use a carrier liquid (D) having a Kauri butanol value (KB value: ASTM D 1133) of 30 or less. More preferably, it is the range of 20-30. The aniline point (JIS K 2256) is preferably in the range of 60 to 105 ° C. for obtaining a stable carrier liquid.
When the Kauributanol value exceeds 30 or the aniline point is lower than 60 ° C., the dissolving ability as a solvent is high, the carrier liquid dissolves the toner particles, and the storage stability and color reproducibility of the toner particles (F). This causes problems such as worsening of the quality of the carrier liquid and staining of the substrate such as paper. If the aniline point exceeds 105 ° C, the compatibility with the dispersant / additives added when dispersing the toner particles in the carrier liquid is poor, resulting in problems such as poor dispersion and insufficient image density. To do.

Specifically describing the insulating property of the carrier liquid (D), the dielectric constant is 5 or less, preferably 1 to 5, and more preferably 1 to 3.
At the same time, the electric resistivity of the carrier liquid (D) is 10 ⁹ Ω · cm or more, preferably 10 ¹⁰ Ω · cm or more, particularly preferably 10 ¹⁰ to 10 ¹⁶ Ω · cm. Here, the electrical resistivity was measured by combining a universal electrometer MMA-II-17D manufactured by Kawaguchi Electric Manufacturing Co., Ltd. and a liquid electrode LP-05. When the electrical resistivity is 10 ⁹ Ω · cm or less, the chargeability of the toner particles is deteriorated, a sufficient image density cannot be obtained, and the color reproducibility and color developability are deteriorated.

Further, the density (JIS K 2249) at 15 ° C. of the carrier liquid (D) is preferably in the range of 0.67 to 0.9 g / cm ³ . More preferably, it is in the range of 0.70 to 0.85 g / cm ³ . In this range, the toner particles and the dispersant can exist stably, so that excellent fixability and image density can be obtained.
The carrier liquid (D) preferably has a kinematic viscosity (ASTM D445) in the range of 1 to 25 mm ² / s. Especially preferably, it is the range of 3-15. In this range, the charged particles can be moved during the phenomenon, and the carrier liquid can be easily removed from the medium on which the final image has been formed in the fixing process.
When the kinematic viscosity is less than 1, the viscosity of the liquid developer becomes low, so the transferability to the developing roller is poor, and a sufficient image density cannot be obtained. Furthermore, since the toner particles after development are easy to move, the fineness of the image is easily lost, which is not preferable. On the other hand, if the kinematic viscosity is greater than 25, the fluidity of the toner particles cannot be obtained, electrophoresis is difficult to occur, and a sufficient image density cannot be obtained. Further, the permeability to a substrate such as paper is poor, and it becomes difficult to remove the carrier liquid when the toner particles are fixed, and sufficient fixability cannot be obtained. In particular, the fixability in a superimposed image is greatly deteriorated.

Particularly preferred carrier liquids (D) are especially branched paraffin solvent mixtures such as the trade name “Isopar ^™ M” (Exxon Corporation), in particular isoparaffinic hydrocarbons or “Exol D110”. And naphthenic hydrocarbons such as “Exol D130” (Exxsol ^™ ).

(Plasticizer (E))
It is known that a plasticizer used for a liquid developer is used for the purpose of improving fixability. This is because the plasticizing effect acts on the binder resin, so that the binder resin can be easily dissolved or swollen by low energy heating during fixing to promote low-temperature fixability.

The plasticizer (E) used in the present invention has a melting point (Tm) of 25 ° C. or higher. More preferably, it is 25 ° C. or higher and lower than the fixing temperature.
When the melting point (Tm) of the plasticizer (E) is lower than 25 ° C., the storage stability as a liquid developer is deteriorated. In the toner particle (F) production process, when the binder resin (A), the colorant (B), and the plasticizer (E) are predispersed using a mixer, the plasticizer (E) is uniformly dispersed. This causes problems such as poor pulverization of the toner particles (F) and poor color developability of the liquid developer. The melting point (Tm) of the plasticizer (E) is the melting point (Tm) of the peak top temperature in the endothermic peak of the DSC curve obtained by measurement using a differential operation calorimeter DSC-60 (manufactured by Shimadzu Corporation). It was. The temperature calibration was performed using indium in an aluminum sample container at a heating rate of 10 ° C./min.

  Examples of the plasticizer having a melting point (Tm) of 25 ° C. or more include dioctyl phthalate, dinonyl phthalate, dicyclohexyl phthalate, diundecyl phthalate, diphenyl phthalate, dimethyl sebacate, methyl stearate, ethyl stearate, butyl stearate, Vinyl stearate, divinyl adipate, dibenzyl adipate, o-toluenesulfonamide, p-toluenesulfonamide, m-toluenesulfonamide, N-ethyl-o / p-toluenesulfonamide, Nn-butyl-o / Examples include p-toluenesulfonamide, N-cyclohexyl-p-toluenesulfonamide, sodium p-toluenesulfinate, polyethylene glycol, polypropylene glycol, and polyester polyol.

  The polyester polyol is obtained by condensation of one or more polyhydric alcohol components and one or more carboxylic acid components. Preferred polyhydric alcohol components include ethylene glycol, 1,2-propylene glycol, propylene glycol, 1,4-butanediol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol , Triethylene glycol, neopentyl glycol and the like. Preferred carboxylic acid components include fumaric acid, maleic acid, phthalic acid, adipic acid, sebacic acid, dodecanoic acid and the like.

The plasticizer (E) is characterized by being insoluble in the carrier liquid (D) at (Tm + 10) ° C. Generally, the plasticizer used for the liquid developer is dissolved in the carrier liquid (D), and the toner particles (F) are dispersed in the carrier solution containing the plasticizer, and the plasticizer is dispersed in the toner particles (F). There is a method of dispersing toner particles containing a plasticizer in a carrier liquid. In the present invention, since the plasticizer (E) is insoluble in the carrier liquid (D), the latter method is used. Since the plasticizer (E) contained in the toner particles (F) is insoluble in the carrier liquid (D), in the liquid developer production process, the fixing process during image output, and the liquid developer long-term storage process The toner particles (F) do not elute into the carrier liquid (D) and remain in the state of being taken into the binder resin (A) of the toner particles (F). Thereby, in the fixing process of image output, the plasticizing effect with respect to the binder resin (A) is high, and the low-temperature fixing property to the substrate is excellent. In addition, when a plasticizer is used, the thermal stability of the liquid developer is lowered and the dispersion stability and storage stability are deteriorated, but compared with the case where the plasticizer (E) is present in the carrier liquid (D). As a result, it becomes difficult for the toner particles to come into contact with and coalesce with each other, and a decrease in thermal stability can be suppressed. The criteria for judging that the plasticizer (E) is insoluble in the carrier liquid (D) are as follows.
First, 50 g of carrier liquid (D) and 5 g of plasticizer (E) were mixed and stirred, heated to (Tm + 10) ° C., and further stirred for 1 hour while maintaining the temperature. After stirring for 1 hour, the mixed solution of the plasticizer (E) and the carrier liquid (D) does not become a uniform transparent liquid but becomes an opaque liquid, or the carrier liquid (D) and the plasticizer (E) When the state of layer separation was confirmed, it was judged that the plasticizer (E) was insoluble in the carrier liquid (D).

As the plasticizer (E) satisfying the above-described melting point (Tm) of 25 ° C. or more and insoluble in the carrier liquid (D), o / p-toluenesulfonamide, N-ethyl-o / p -Sulfonamides such as toluenesulfonamide, Nn-butyl-o / p-toluenesulfonamide, sodium p-toluenesulfinate, and the like;
Examples include polyethylene glycol, polypropylene glycol, and polyester polyol. About polyester polyol, it is also possible to use a commercial item. For example, there is polylite OD-X-286 (manufactured by DIC).

  The amount of the plasticizer (E) added is preferably 1 mass with respect to 100 parts by mass of the binder resin (A) from the viewpoint of the pulverization / dispersibility of the toner particles (F) and the fixability of the liquid low developer. Part or more and 20 parts by mass or less, more preferably 5 parts by mass or more and 15 parts by mass or less. When the content is lower than 1 part by mass, the plasticizing effect on the binder resin (A) is low, and the fixability of the liquid developer is deteriorated. When it exceeds 20 parts by mass, the glass transition temperature (Tg) of the toner particles (F) becomes too low, causing problems such as poor pulverizability / dispersibility and poor storage stability.

(Toner particles (F))
The glass transition temperature (Tg) of the toner particles (F) containing at least the binder resin (A), the colorant (B), and the plasticizer (E) used in the present invention is 35 ° C. or higher and 70 ° C. or lower. . More preferably, it is 40 degreeC or more and 60 degrees C or less. When the glass transition temperature (Tg) is lower than 35 ° C., the storage stability of the liquid developer is deteriorated. Further, in the process of wet-dispersing the toner particles (F) in the carrier liquid (D), the pulverizability is deteriorated, and problems such as a sufficient image density cannot be obtained. When the glass transition temperature (Tg) is higher than 70 ° C., the fixing property to the substrate is deteriorated. Further, in the fixing process at the time of image output, the amount of heat necessary for melting the toner particles (F) is insufficient, the toner particles (F) are not in a molten state, and the toner is bonded by the adhesive force between the substrate and the thermocompression roller. A part of the particles (F) adheres to the surface of the thermocompression roller and causes problems such as occurrence of a cold offset phenomenon in which the particles are transferred to the next paper.

  The glass transition temperature (Tg) is a value obtained by measurement according to JIS K-7121 using a differential operation calorimeter DSC-60 (manufactured by Shimadzu Corporation). The temperature calibration was performed using indium in an aluminum sample container at a heating rate of 10 ° C./min. At the endothermic peak of the DSC curve obtained by measurement, draw a tangent point at the point where it begins to deviate from the baseline and the point at which the slope settles down after the peak rises, and the intersection of this tangent and the baseline is the glass transition temperature. (Tg).

(Other additives)
(Pigment dispersant)
As the form of the pigment dispersant internally added to the toner particles (F), polyamine-based resin type dispersant Solsperse 24000SC, Solspers 32000 (manufactured by Abyssia), Azisper PB821 (manufactured by Ajinomoto Fine Techno Co.), acrylic copolymer Resin-type dispersant BYK-116 (manufactured by Big Chemie) or the like can be used. In particular, in the case of producing a colored master batch through conch, it is a preferable material to be added at the time of producing the master batch.
The addition amount of the pigment dispersant is preferably 3 parts by mass or more, more preferably 5 parts by mass or more with respect to 100 parts by mass of the colorant (B) from the viewpoint of improving the dispersibility of the toner particles. Further, from the viewpoint of improving the grindability and productivity of the toner particles (F), the amount is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, with respect to 100 parts by mass of the colorant (B).

(Dye derivative)
In the toner particles (F) used in the present invention, it is possible to use a dye derivative as long as the color developability of the colorant (B) is not impaired.
Examples of the pigment derivative include a compound in which a basic substituent, an acidic substituent, or a phthalimidomethyl group which may have a substituent is introduced into an organic pigment (organic pigment, organic dye), anthraquinone, acridone or triazine. It is done.
In the present invention, a pigment derivative is particularly preferable, and the structure thereof is a compound represented by the following general formula (2).
P-Ln Formula (2)
(However,
P: organic pigment residue, anthraquinone residue, acridone residue or triazine residue L: basic substituent, acidic substituent, or optionally substituted phthalimidomethyl group n: an integer of 1 to 4 is there)
Examples of the organic pigment constituting the organic pigment residue of P include, for example, diketopyrrolopyrrole pigments; azo pigments such as azo, disazo and polyazo; phthalocyanine pigments such as copper phthalocyanine, halogenated copper phthalocyanine and metal-free phthalocyanine Anthraquinone pigments such as aminoanthraquinone, diaminodianthraquinone, anthrapyrimidine, flavantron, anthanthrone, indanthrone, pyranthrone, violanthrone; quinacridone pigments; dioxazine pigments; perinone pigments; perylene pigments; thioindigo pigments; Indoline pigments; isoindolinone pigments; quinophthalone pigments; selenium pigments; metal complex pigments.

Examples of the dye derivative are described in JP-A-63-305173, JP-B-57-15620, JP-B-59-40172, JP-B-63-17102, JP-B-5-9469, and the like. What is currently used can be used, These can be used individually or in mixture of 2 or more types.
The addition amount of the pigment derivative is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the colorant from the viewpoint of improving dispersibility. Further, from the viewpoint of heat resistance and light resistance, the amount is preferably 4 parts by mass or less, more preferably 1.5 parts by mass or less with respect to 100 parts by mass of the colorant.

In the liquid developer of the present invention, the appropriate addition amount of the dye derivative varies depending on the type of the colorant (B) to be used, but generally 0.1 to 30 parts by mass with respect to 100 parts by mass of the colorant (B). It is preferable to use within the range of parts. Thereby, the dispersion stability of the toner particles (F) is maintained, and the stability of the charging polarity of the toner particles (F) can be maintained.
In the liquid developer of the present invention, it is preferable to use a basic dye derivative since the toner particles (F) have a positive chargeability.

(Charge control agent)
The toner particles (F) in the liquid developer of the present invention may contain a colorless or light color charge control agent as long as the hue is not hindered. As the charge control agent, a positive charge control agent or a negative charge control agent is used according to the polarity of the electrostatic image on the electrostatic latent image carrier to be developed.
In the present invention, the toner particles (F) are preferably positively charged, and a positive charge control agent is usually used.

  As the positive charge control agent, quaternary ammonium salt compounds (for example, tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylbenzylammonium tetrafluoroborate), quaternary ammonium salt organic tin oxide (for example, dibutyltin) Oxide, dioctyltin oxide, dicyclohexyltin oxide), diorganotin borate (dibutyltin borate, dioctyltin borate, dicyclohexyltin borate), electron donating substances such as polymers having amino groups, etc. are used alone or in combination of two or more. be able to. Needless to say, the triarylmethane dye described above is preferable.

Further, instead of using the charge control agent, a resin charge control agent can be used.
For positive charging,
Formula _{- {CH 2 -CH (C 6} H 5) a} - {CH 2 -CH (COOC 4 H 9)} b- {CH 2 -C (CH 3) COOC 2 H 4 N + CH 3 (C 2 H ₅ ) ₂ } cCH ₃ (C ₆ H ₄ ) SO ₃ −
(Of these, the quaternary ammonium salt part is 3 to 35 parts by mass, the styrene / acryl part is 97 to 65 parts by mass, thereby determining the values of a, b, and c), Examples of functional groups include styrene / acrylic polymers copolymerized with styrene / acrylic resins.
Specifically, 2-ethylhexyl acrylate / acryloylamino-2-methyl-1-propanesulfonic acid / styrene copolymer, butyl acrylate / N, N-diethyl-N-methyl-2- (methacryloyloxy) ethyl Ammonium = p-toluenesulfonate / styrene copolymer and the like. Since these are colorless and transparent, they are suitable for use in color toners. Further, the resin charge control agent is usually added in an amount of 1.0 to 20 parts by mass, preferably 2.0 to 8 parts by mass with respect to 100 parts by mass of the binder resin (A).

(Production method)
A method for producing the liquid developer of the present invention will be described.
The liquid developer of the present invention is preferably obtained through the following five processes.

(1) Production of colored masterbatch for toner particles (F) A binder resin (A) and a colorant (B) are mixed at a concentration of 10 to 60 parts by mass of the colorant in the masterbatch, and a mixer such as a super mixer. Are mixed, pre-dispersed, kneaded using a hot roll, etc., cooled and roughly crushed to obtain a colored master batch. In addition to the binder resin (A) and the colorant (B), a plasticizer (E), a pigment dispersant, and a dye derivative can also be added.

(2) Preparation of toner particle (F) chips (dilution of colored master batch)
The colored masterbatch obtained in (1), the binder resin (A) and the plasticizer (E) are mixed with a mixer such as a supermixer, preliminarily dispersed, and then melt-kneaded, whereby the colored masterbatch Is diluted in a binder resin and developed to obtain a chip for toner particles (F). A pigment dispersant, a polymer dispersant (C), a charge control agent, and the like may be added at the time of preliminary dispersion and melt kneading. Further, the toner particle (F) chip is preferably 10 mm or less by rough crushing with a hammer mill, a sample mill or the like.
In addition, the steps (1) and (2) can be unified. In this case, all the materials are charged at the time of preliminary dispersion without going through the coloring masterbatch process of (1). What is necessary is just to produce the chip | tip for (F). As the melt-kneading, a known kneader such as a pressure kneader, a Banbury mixer, a uniaxial or biaxial extruder can be used.

(3) Dry pulverization of toner particle (F) chip The toner particle (F) chip obtained in (2) is finely pulverized to an average particle diameter of 7 μm or less. For fine pulverization, it is usually preferable to use a jet airflow pulverizer such as a jet mill or a mechanical pulverizer such as a turbo mill or a kryptron.

(4) Wet pulverization of toner particles (F) The dry pulverized toner particles (F) obtained in (3) are developed in a solvent having the same composition as the carrier liquid (D), and a wet pulverizer (disperser) is used. The pulverization is performed so that the average particle diameter is 0.5 to 4 μm, preferably 1 to 3 μm. At this time, it is also effective to add a polymer dispersant (C) having a function of adsorbing the toner particles (F). Through the wet pulverization and dispersion steps, the dispersant is adsorbed on the toner particles (F) and is also stabilized in terms of charging.
When performing wet pulverization (dispersion), it is necessary to cool so that the product temperature does not exceed 50 ° C. When the product temperature exceeds 50 ° C., the toner particles (F) are likely to be fused, and it becomes difficult to control the particle size distribution.

The wet pulverizer that can be used for wet pulverization of the toner particles (F) uses a pulverization medium, and includes a container drive medium mill and a medium agitation mill. Examples of the container-driven medium mill include a rolling ball mill, a vibrating ball mill, a planetary ball mill, and a centrifugal fluidizing mill, and examples of the medium agitating mill include a tower pulverizer, a stirring tank mill, a flow tank mill (horizontal type, Vertical type), annular mill and the like.
In any of the above-mentioned apparatuses, refinement by wet pulverization is possible, but among these, it is preferable to use a medium stirring mill from the viewpoint of productivity, pulverization ability, control of particle size distribution, etc. It is preferable to use a wet pulverizer classified as a horizontal distribution tank mill that is filled with molds and horizontal microbeads and used as a medium (medium) in order to perform precise wet pulverization and dispersion.
Specific examples include WAB (Shinmaru Enterprises), DYNO-MILL, and sand mill. This is because in a horizontal wet pulverizer, the dispersion medium is hardly affected by gravity, so that a uniform distribution close to ideal can be obtained in the pulverizer. In addition, since it has a completely sealed structure, there is no loss of balance due to foaming or solvent evaporation, and stable pulverization is possible.

  In the wet pulverizer used in the present invention, the major factors that determine the pulverizability include the type of pulverizing media, the particle size of the pulverizing media, the filling rate of the dispersion media in the pulverizer, the type of agitator disk, and the solution of the sample to be pulverized. Concentration, type of solvent, etc. Among these, the type of pulverized media and the particle size of the media greatly contribute to pulverization.

The types of grinding media include glass beads (SiO ₂ 70 to 80%, NaO 12 to 16%, etc.), zircon beads (ZrO ₂ , etc.) according to the required particle size of toner particles (F), specific gravity and grinding and dispersion. 69%, SiO ₂ 31%), zirconia beads (95% or more of ZrO ₂ ), alumina (90% or more of Al ₂ O ₃ ), titania (TiO ₂ 77.7%, Al ₂ O ₃ 17.4%), steel Balls and the like can be used, but among them, zirconia beads and zircon beads are preferably used in order to obtain good grindability.
The particle diameter (diameter) of the pulverization media can be used in the range of 0.1 mm to 3.0 mm, and in particular, the range of 0.3 to 1.4 mm is preferable. If it is smaller than 0.1 mm, the load in the pulverizer increases, and the toner particles melt due to heat generation, making it difficult to pulverize. If it is larger than 3.0 mm, sufficient pulverization cannot be performed. . The filling rate of the dispersion medium is preferably 40 to 85%. If it exceeds 85%, the load in the pulverizer becomes large, the toner particles are melted by heat generation, making pulverization difficult, and if it becomes 40% or less, the pulverization efficiency decreases. Refinement becomes difficult. When the concentration of toner particles in the slurry is high (concentration of 40 to 50%), the filling rate is preferably 40 to 70% by mass.

  An agitator disk inside the wet pulverizer preferably used in the present invention is also important for controlling the pulverization property. The peripheral speed of the disk is preferably 4 to 16 m / s, and if it is less than 4 m / s, it takes time to grind. If it is greater than 16 m / s, heat is generated due to contact with the grinding media. As a result, the toner particles (F) are fused, which is not preferable. As a material of the agitator disk, hardened steel, stainless steel, alumina, zirconia, polyurethane, polyethylene, engineering plastic, and the like can be used. Among them, zirconia is preferable.

  Examples of the material of the grinding cylinder on the inner wall of the wet pulverizer include special hardened steel, stainless steel, alumina, zirconia, ZTA, glass, and polyethylene. Among them, it is preferable to use zirconia reinforced alumina ceramics called ZTA.

(5) Purification of liquid developer The material containing the toner particles (F), carrier liquid, and dispersant obtained by wet pulverization obtained in (4) is mixed with carrier liquid (D) and, if necessary, a dispersant. In addition, the liquid developer is purified by mixing and controlling the concentration of the toner particles (F).
A liquid developer in which toner particles (F) are stably dispersed can be obtained by adding the dispersant to the material obtained in the step (4) together with a carrier liquid for adjustment.

(Liquid developer properties)
The toner particles (F) used in the present invention preferably have an average particle diameter (D50) of 0.5 to 4 μm, and more preferably 1 to 3 μm. The particle size in the present invention is measured using a Nikkiso Co., Ltd. laser diffraction / scattering particle size analyzer Microtrac HRA, and the average particle size (D50) is a cumulative 50 percent diameter value.

  In addition, 60% by volume or less of toner particles having a particle size of 2 μm or less with respect to all toner particles are contained, and 5 to 60% by volume of toner particles having a particle size of 1 to 3 μm are contained and have a particle size of 5 μm or more. The toner particles are more preferably 25% by volume or less from the viewpoint of development characteristics for obtaining color developability. When the amount of toner particles having a particle diameter of 2 μm or less exceeds 60% by volume, the adsorption of the polymer dispersant (C) to the toner particles becomes low, and excellent storage stability cannot be obtained. Furthermore, in the wet pulverization of toner particles, the pulverization property is deteriorated, and it becomes difficult to control the viscosity of the liquid developer. When the amount of toner particles having a particle size of 5 μm or more exceeds 25% by volume, problems such as insufficient image density being obtained and color development / color reproducibility are deteriorated. The toner particles having a particle diameter of 1 to 3 μm are preferably contained in an amount of 5 to 60% by volume in order to obtain dispersion stability of the toner particles and excellent storage stability over a long period of time.

  In the present invention, the concentration of the toner particles (F) in the liquid developer is preferably 10 to 30% by mass with respect to 100% by mass of the liquid developer. More preferably, it is 12-25 mass%. If the amount is less than 10% by mass, it is difficult to remove the carrier liquid, and the toner particles (F) are poorly fixed. If it exceeds 30% by mass, the viscosity of the liquid developer increases, the mobility of the toner particles (F) deteriorates, and a sufficient image density cannot be obtained. Furthermore, aggregation of the toner particles (F) becomes strong and storage stability is deteriorated.

Further, the viscosity (η) of the liquid developer of the present invention is preferably 5 to 180 mPa · s, and the volume specific resistance of the liquid developer is preferably 10 ¹⁰ to 10 ¹⁵ Ω · cm.
The viscosity (η) of the liquid developer can be measured using, for example, an E-type viscometer TV-22 manufactured by Toki Sangyo. The solid content in the liquid developer was adjusted to 25% and fully adjusted to 25 ° C. Then, a 1 ° 34 'cone was set on the TV-22 type viscosity shape, and the viscosity after 1 minute at 20 rpm was measured. . If the viscosity (η) is less than 5 mPa · s, the fineness of the image after development is lacking, and if it exceeds 180 mPa · s, the mobility of toner particles during development is inferior and high-speed development is not possible, and sufficient image density is obtained. Problems such as not occurring.
The volume resistivity can be measured in the same manner as the carrier liquid measuring method described above. If it is 10 ¹⁰ Ω · cm or less, the electrostatic latent image on the photoreceptor cannot be retained, which is not preferable.

  In the use of the liquid developer of the present invention, a development process that can be preferably used is that a liquid developer is supplied to a developing roller made of conductive rubber, and an amorphous silicon photoconductor exposed to LED is used to eliminate static electricity before transfer, intermediate Development is preferably performed via a transfer member. The photoreceptor preferably has a surface potential of +450 to 550 V, a residual potential of +50 V or less, and the bias applied to the developing roller is preferably in the range of +250 to 450 V.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the embodiment of the present invention is not limited to these examples. In the following, all parts represent parts by mass.

  Moreover, in the Example, it carried out using the material described below.

(Binder Resin Synthesis Example 1)
Into a flask equipped with a reflux condenser, distillation, nitrogen gas inlet tube, thermometer, stirrer, polyhydric alcohol and polybasic acid shown in Table 1 and 2 parts of dibutyltin oxide as a catalyst were added and nitrogen gas was stirred. Was heated to 200 ° C. and reacted for 4 hours while maintaining the temperature of the reaction system. Furthermore, it was made to react under reduced pressure for 1 hour. The pressure was returned to normal pressure, the temperature of the reaction system was lowered to 100 ° C. or less, and polycondensation was stopped to obtain a polyester resin binder resin 1.

(Binder Resin Synthesis Example 2)
As in Synthesis Example 1, 2 parts of dibutyltin oxide as a polyhydric alcohol, polybasic acid and catalyst shown in Table 2 were added, nitrogen gas was introduced with stirring, and the mixture was heated to 180 ° C. The reaction was allowed to proceed for 7 hours while maintaining the temperature. Furthermore, it was made to react under reduced pressure for 1 hour. The pressure was returned to normal pressure, the temperature of the reaction system was lowered to 100 ° C. or less, and the polycondensation was stopped to obtain a polyester resin binder resin 2.

(Binder Resin Synthesis Example 3)
The obtained binder resin 1 was put in an equal amount of toluene and heated to be dissolved. Nitrogen gas was introduced with stirring, and the mixture was further heated to the boiling point of toluene, and a mixed solution of styrene monomers and acrylic esters shown in Table 3 and di-t-butyl peroxide as a polymerization initiator was added for 2 hours. Solution polymerization was carried out while dropping. After completion of the dropwise addition, the reaction was further continued at the boiling point of toluene for 2 hours, and 1 part of di-t-butyl peroxide was added to terminate the polymerization. Next, it heated to 180 degreeC and toluene was removed, and the binder resin 3 containing a polyester resin and a styrene-acryl copolymer resin was obtained.

Table 4 shows the weight average molecular weight (Mw), softening temperature (T4), glass transition point (Tg), and acid value of each binder resin.

(Synthesis example 1 of polymer dispersant)
A reaction vessel equipped with a nitrogen gas introduction tube, a thermometer, a condenser, and a stirrer was charged with 90.1 parts of Exol D110 (manufactured by ExxonMobil) and replaced with nitrogen gas. The reaction vessel is heated to 110 ° C., 20.0 parts of N, N-dimethylaminoethyl methacrylate, 80.0 parts of stearyl methacrylate, and 2,2′-azobis (2-methylpropionic acid) as a polymerization initiator A mixture of 9.0 parts of dimethyl (V-601 (manufactured by Wako Pure Chemical Industries, Ltd.)) was dropped over 2 hours to carry out a polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, 0.9 part of V-601 (manufactured by Wako Pure Chemical Industries) was added, and the reaction was further continued at 110 ° C. for 1 hour to obtain a polymer dispersant 1 solution. Got. The weight average molecular weight (Mw) of the polymeric dispersant 1 was about 6940.
1 g of this was sampled, heated and dried at 180 ° C. for 20 minutes to measure the nonvolatile content, and Exol D110 was added so that the nonvolatile content of the polymer dispersant solution was 50%. From this, a 50% nonvolatile solution of the polymer dispersant 1 was obtained.

(Synthesis example 2 of polymer dispersant)
Synthesis was performed in the same manner as in Synthesis Example 1 except that the raw materials and preparation amounts shown in Table 5 were used, and a polymer dispersant 2 solution was obtained. The amine value and weight average molecular weight of Polymer Dispersant 2 were as shown in Table 6.

(Synthesis Examples 1 to 4 of comparative polymer dispersant)
Synthesis was performed in the same manner as in Synthesis Example 1 except that the raw materials and preparation amounts shown in Table 5 were used, and solutions of comparative polymer dispersants 1 to 4 were obtained. The amine value and weight average molecular weight of each polymer dispersant were as shown in Table 6.

Table 6 shows the physical property values of the obtained polymer dispersant.

(Coloring agent)
Cyan colorant C.I. I. Pigment Blue 15: 3 (copper phthalocyanine blue)
Lionol Blue FG7919 (Toyo Color)

(Pigment dispersant)
Solspers 24000SC Acid value: 25 mgKOH / g
Basic resin type dispersant (polyamine resin)

(Plasticizer)
o / p-Toluenesulfonamide Topsizer No. 5 Melting point (Tm): 112 ° C. Polyethylene glycol PEG10000 manufactured by Fujiamide Chemical Co., Ltd. Melting point (Tm): 61 ° C. Sanyo Chemical Co., Ltd. Sebacic acid dimethyl DMS (Sebacic acid dimethyl ester) Melting point (Tm) ): 30 ° C., Toyokuni Oil Co., Ltd. Nn-butylbenzenesulfonamide Topsizer No. 7 Melting point (Tm): −35 ° C., manufactured by Fujiamide Chemical Co., Ltd.

(Carrier liquid)
Exol D130 Naphthenic hydrocarbon (manufactured by ExxonMobil)
Dry point: 313 ° C. Aniline point: 89 ° C. Kinematic viscosity: 6.12 mm ² / s
Density: 0.824 g / cm ³

[Example 1]
C. I. Pigment Blue 15: 3
(Lionol Blue FG7919) 18 parts by weight binder resin 1 75 parts by weight polyethylene glycol 5 parts by weight (PEG 10000)
Solspers 24000SC 2 parts by mass The above materials (5 kg in total) were mixed with a Henschel mixer having a volume of 20 L (3000 rpm, 3 minutes), then fed with a twin-screw kneading extruder (PCM30) at a feed rate of 6 kg / hr and a discharge temperature of 145 ° C. Then, melt kneading was performed, and further kneading was performed with three rolls having a roll temperature of 140 ° C. After cooling and solidifying, coarsely pulverized with a hammer mill and then finely pulverized with an I-type jet mill (IDS-2 type) to obtain toner particles 1 having an average particle diameter of about 5.2 μm. The toner particles 1 had a glass transition temperature (Tg) of 46 ° C.

further,
Toner Particle 1 25 parts by mass Exol D130 72 parts by mass Polymer Dispersant 1 3 parts by mass were weighed, thoroughly stirred and mixed to disperse cyan toner particles 1 in the Exol D130 solution. (Slurry concentration is 25% by mass)
The slurry in which the toner particles 1 are dispersed is circulated for 90 minutes using a wet pulverizer that is a medium stirring mill, Dino Mill Multilab (Shinmaru Enterprises Co., Ltd., capacity 1.4 L), and wet pulverized. It was.
The wet pulverization conditions at this time were as follows.
Agitator disk (material: zirconia) peripheral speed 10m / s, cylinder ZTA,
Media (Material: Zirconia) Diameter 1.25mm, Filling rate 70%
Solution flow rate 45 kg / h, cooling water 5 l / min, pressure 0.1 kg / cm ²
After performing wet pulverization for 90 minutes, the slurry was taken out and passed through a mesh having a mesh size of 33 μm (manufactured by SUS304) to obtain a liquid developer 1 (including toner particles 1). When the particle size distribution of the toner particles 1 after wet pulverization was confirmed, the average particle size (D50) was 2.3 μm. The viscosity (η) of the liquid developer 1 was 50.

[Examples 2-6, Comparative Examples 1-9]
Using the same method as in Example 1, toner particles and a liquid developer were respectively produced.
Table 7 shows the toner particle composition and physical property values, and Table 8 shows the liquid developer composition.

  In the live-action test, a commercially available liquid developing copier (Savin 870: manufactured by Sabin) was used, an amorphous silicon photoconductor was used under an environmental condition of 23 ° C./50% RH, and the surface potential of the photoconductor was +450. An image test of 1000 sheets was performed from the initial stage with ˜500 V, a residual potential of +50 V or less, and a developing roller bias of +250 to 450 V. At this time, the image was produced in a single color for each color, the paper was OK topcoat made by Oji Paper, and the thermocompression bonding was performed at a speed of 30 m / min and 160 ° C.

  First, the image density was measured with a Gretag Macbeth densitometer (D-196). Here, it is practically preferable that the density value of cyan is 1.4 or more. More preferably, it is 1.5 or more.

For the fixing rate, an image density ID (ID ₁ ) at the time of output was measured using a printed image in which a solid portion of 1 cm × 1 cm was output. Thereafter, a mending tape (Scotch 810 manufactured by 3M) was attached to the printed matter, and a 1 kg cylindrical brass weight was rolled and reciprocated once. Thereafter, the mending tape was removed, the image density ID (ID ₂ ) was measured again, and a value obtained by calculating (ID ₂ ) / (ID ₁ ) × 100 was obtained as a fixing rate (%). Here, if the fixing rate is 80% or more, it is practically preferable, and if it is 90% or more, it is more preferable.

For cold offset resistance, after output by the liquid developing copier, ten output images are continuously thermocompression bonded by an external fixing machine at a speed of 30 m / min and a nip thickness of 6 mm. It was confirmed whether a toner image re-transferred to the paper exists. The temperature at which the re-transferred toner image does not exist was evaluated in four ranks. Here, if the thermocompression-bonding roll temperature is less than 140 ° C, it is practically preferable, and if it is less than 120 ° C, it is more preferable.
A: Thermocompression roll temperature is less than 120 ° C. O: Thermocompression roll temperature is 120 ° C. or more and less than 140 ° C. Δ: Thermocompression roll temperature is 140 ° C. or more and less than 160 ° C. X: Thermocompression roll temperature is 160 ° C. or more.

With respect to hot offset resistance, after being output by the liquid developing copying machine, thermocompression bonding is performed at a speed of 15 m / min and a nip thickness of 6 mm by an external fixing machine, and toner particles begin to adhere to the roll surface to be thermocompression bonded. The temperature was evaluated in four ranks. Here, if the thermocompression-bonding roll temperature is 140 ° C. or higher, it is practically preferable, and if it is 160 ° C. or higher, it is more preferable.
A: Thermocompression roll temperature is 160 ° C. or higher. O: Thermocompression roll temperature is 140 ° C. or higher and lower than 160 ° C. Δ: Thermocompression roll temperature is 120 ° C. or higher and lower than 140 ° C. X: Thermocompression roll temperature is lower than 120 ° C.

The storage stability of the liquid developer was evaluated as follows.
The obtained liquid developer was allowed to stand in a constant temperature and humidity atmosphere at 25 ° C. and 50% for 3 months. The average particle diameter (D50) and viscosity (η) of the liquid developer after 3 months of standing were measured and evaluated at a rate increased from the value before the start of the test.

Average particle size (D50)
○: Average particle size after test (D50) / average particle size before test (D50) is less than 1.2 ×: Average particle size after test (D50) / average particle size before test (D50) is 1. 2 or more

Viscosity (η)
○: Viscosity after test (η) / viscosity before test (η) is less than 1.4 ×: viscosity after test (η) / viscosity before test (η) is 1.4 or more

Table 9 shows detailed physical property values and test results of the liquid developer.

  In Examples 1 to 6, the average particle diameter (D50) and viscosity of the liquid developer are good, and a sufficient image density is obtained. In addition, the fixing property is excellent, the cold offset resistance and the hot offset resistance are both good, and there is no problem in storage stability. As can be seen from Table 9, the polymer dispersant (C) is a plastic containing at least a specific ethylenically unsaturated monomer and copolymerized, having a specific amine value, and a specific melting point. The toner particles (F) containing the agent (E) insoluble in the carrier liquid (D) and containing at least the binder resin (A), the colorant (B), and the plasticizer (E) have a specific glass transition temperature (Tg). ) Only has excellent fixability, anti-offset properties, good color development / color reproducibility and storage stability over a long period of time. It can be seen that either the offset resistance or the storage stability is inferior.

  The liquid developer of the present invention is excellent in fixability, offset resistance, color reproducibility, color developability, and storage stability, and can be used to form an image using an electrophotographic method, an electrostatic recording method, or the like. It can be preferably used as a liquid developer used for developing an electrostatic latent image in a printer, an on-demand printing machine or the like.

Claims (6)

A liquid developer comprising at least a binder resin (A), a colorant (B), a polymer dispersant (C), a carrier liquid (D), and a plasticizer (E),
The polymer dispersant (C) includes at least an ethylenically unsaturated monomer (c-1) having an amino group and an ethylenically unsaturated monomer (c-2) containing an alkyl group having 4 to 24 carbon atoms. ) And polymerized, and
The amine value of the polymer dispersant (C) is 5 to 150 mgKOH / g,
The melting point (Tm) of the plasticizer (E) is 25 ° C. or higher, and is insoluble in the carrier liquid (D) at (Tm + 10) ° C., and
A liquid developer, wherein the toner particles (F) containing at least a binder resin (A), a colorant (B), and a plasticizer (E) have a glass transition temperature of 35 ° C. to 70 ° C.   The liquid developer according to claim 1, wherein the binder resin (A) contains at least a polyester resin.   The liquid developer according to claim 1 or 2, wherein the binder resin (A) contains at least a polyester resin and a styrene-acrylic copolymer resin.   The liquid developer according to claim 1, wherein the binder resin (A) has a weight average molecular weight (Mw) of 2000 ≦ Mw ≦ 100,000.   The liquid developer according to claim 1, wherein the carrier liquid (D) is an aliphatic hydrocarbon.   6. The liquid developer according to claim 1, wherein the dry point in the distillation range of the carrier liquid (D) is 200 ° C. to 360 ° C. 6.