JP2013205623A - Liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer which is excellent in color developability, color reproducibility and storage stability and is capable of obtaining a stable output image over a long period of time.SOLUTION: There is provided a liquid developer composed of at least a binder resin (A), a colorant (B), a polymer dispersant (C) and a carrier liquid (D), wherein the polymer dispersant (C) is obtained by copolymerizing at least an ethylenically unsaturated monomer (c-1) having an amino group and an ethylenically unsaturated monomer (c-2) containing an alkyl group having 9 to 24 carbon atoms, the alkyl group of the monomer (c-2) has 6 or more carbon atoms of a straight-chain and a total carbon number of the branched alkyl group is 3 or more, and the polymer dispersant (C) has an amine value of 5 to 150 mgKOH/g.

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 color development 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)

In order to uniformly disperse toner particles in an electrically insulating carrier liquid and maintain the storage stability as a liquid developer, a study has been made on a dispersant. On the other hand, in order to improve the fixability of the liquid developer, since the contact and coalescence of the toner particles are promoted, the storage stability as the liquid developer tends to decrease, and the fixability and storage stability It has been a difficult task to achieve compatibility. In view of this, studies have been made on polymer dispersants that do not easily inhibit the fixing property. (For example, see Patent Document 3)
However, due to the influence of the polymer dispersant, there is a problem in that the chargeability of the toner particles is lowered, a sufficient image density cannot be obtained, the long-term stability of the image is deteriorated, and the color developability / color reproducibility is impaired. .

  As described above, there is room for improvement in order to satisfy the storage stability of the liquid developer and the stable color development and color reproducibility.

JP 55-153946 A JP-A-5-333607 JP 2009-145535 A

  As described above, the liquid developer has excellent image quality, and there is room for improvement in achieving both the storage stability of the liquid developer and the color development and color reproducibility. 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 color developability and color reproducibility, and even if the number of printed sheets and the printed area increase, the dispersion state and image density of the toner particles in the liquid developer are stable, and the developer composition changes over a long period of time. It is to provide a liquid developer having a stable image density.

  As a result of intensive studies, the present inventors have at least an ethylenically unsaturated monomer (c-1) having an amino group and an alkyl group having 9 to 24 carbon atoms as a polymer dispersant in the liquid developer. An ethylenically unsaturated monomer (c-2) to be copolymerized, and the alkyl group of the monomer (c-2) has a straight chain carbon number of 6 or more and a branched alkyl The present inventors have found that the above object can be achieved by using a polymer dispersant (C) having a total carbon number of 3 or more and an amine value of 5 to 150 mgKOH / g, and has reached the present invention.

The present invention is a liquid developer comprising at least a binder resin (A), a colorant (B), a polymer dispersant (C), and a carrier liquid (D), wherein the polymer dispersant (C) is And at least an ethylenically unsaturated monomer (c-1) having an amino group and an ethylenically unsaturated monomer (c-2) containing an alkyl group having 9 to 24 carbon atoms,
The alkyl group of the monomer (c-2) has a straight chain carbon number of 6 or more, and the branched alkyl group has a total carbon number of 3 or more, and is an amine of the polymer dispersant (C). The present invention relates to a liquid developer having a value of 5 to 150 mgKOH / g.

The present invention also relates to the liquid developer, wherein the carrier liquid (D) is an aliphatic hydrocarbon.
The present invention also relates to the liquid developer, wherein the binder resin (A) contains at least a polyester resin.
The present invention also relates to the liquid developer, wherein the binder resin (A) has a softening temperature of 80 to 140 ° C.

  As described above, the polymer dispersant (C) used for the liquid developer is copolymerized containing at least a specific ethylenically unsaturated monomer, and has a specific amine value. A liquid developer having excellent color development / color reproducibility and storage stability can be obtained.

  This liquid developer has good charge density and dispersion stability of toner particles in the liquid developer due to the presence of the polymer dispersant (C), and has a good image density and image quality from the beginning. Since the developer has excellent storage stability over a long period of time, a liquid developer that does not deteriorate copy image quality can be provided.

Hereinafter, the present invention will be described in more detail.
The liquid developer of the present invention is an ethylenic polymer containing at least an ethylenically unsaturated monomer (c-1) having an amino group and an alkyl group having 9 to 24 carbon atoms as the polymer dispersant (C). An unsaturated monomer (c-2) is copolymerized, and the alkyl group of the monomer (c-2) has a straight chain carbon number of 6 or more, and the total number of branched alkyl groups. A major feature is to use a polymer dispersant (C) having 3 or more carbon atoms and an amine value of 5 to 150 mgKOH / g.

  The polymer dispersant (C) contains an ethylenically unsaturated monomer (c-1) having an amino group and has a specific amine value, so that the polymer dispersant (C) is adsorbed onto the toner particles. The ratio is increased, the dispersion stability of the toner particles is improved, and a liquid developer having a stable copy image and excellent storage stability over a long period of time can be obtained. Further, since the adsorption rate of the polymer dispersant (C) to the toner particles is high, the pulverizability of the toner particles is improved, and a liquid developer having a small average particle diameter and low viscosity can be obtained efficiently. In addition, it is possible to obtain a copy image having excellent color development and color reproducibility.

  Further, the polymer dispersant (C) contains an ethylenically unsaturated monomer (c-2) containing an alkyl group having 9 to 24 carbon atoms, so that the solubility in the carrier liquid (D) is improved. In addition, excellent grindability and dispersion stability of toner particles can be obtained. In addition, the monomer (c-2) has excellent linearity in the carrier liquid (D) by having a linear alkyl group having 6 or more carbon atoms and a total number of carbon atoms in the branched alkyl group of 3 or more. Toner particles having high chargeability while having solubility can be obtained, and a copy image with sufficient image density and high color reproducibility can be obtained. Thereby, a liquid developer having both excellent storage stability and stable color development and color reproducibility can be obtained.

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

(Toner particles)
The toner particles used in the liquid developer of the present invention comprise at least a binder resin (A) and a colorant (B), and in addition, it is also preferable to use additives such as a pigment dispersant and a charge control agent. . The polymer dispersant (C) is preferably added when the toner particles are wet-dispersed in the carrier liquid, but can also be added to the toner particles when the toner particles are produced.

(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 Polymer, styrene-vinyl naphthalene copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl Styrenes such as methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer Copolymer or cross-linked Tylene copolymer; polyvinyl chloride, phenol resin, natural modified phenol resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polyvinyl acetate, silicone resin, polyester resin, polyurethane resin, polyamide resin, furan resin, Examples thereof include epoxy resins, xylene resins, polyvinyl butyral resins, terpene resins, coumarone indene resins, and petroleum resins.
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. Furthermore, 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.

（式中Ｒはエチレンまたはプロピレン基であり、ｘ、ｙはそれぞれ１以上の整数であり、かつｘ＋ｙの平均値は２〜１０である。）

(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;
Cyclohexanedicarboxylic acid; naphthalenedicarboxylic acid; diphenoxyethane-2,6-dicarboxylic acid, and the like.
Trivalent or higher carboxylic acids that serve as crosslinking components include trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, butanetricarboxylic acid, hexanetricarboxylic acid, tetra (methylenecarboxyl) methane, octanetetracarboxylic acid, benzophenonetetracarboxylic acid and An anhydride etc. are mentioned, These are used individually or in combination of 2 or more types.

  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.

  The catalyst used for the polycondensation of the polyester resin may be a known and commonly used reaction catalyst such as at least one metal compound selected from antimony, titanium, tin, zinc and manganese, and the reaction may be accelerated. 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 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 styrene-acrylic copolymer resin, the types and molar ratios of styrene monomer, (meth) acrylic acid and (meth) acrylic acid esters, as well as reaction temperature, reaction time, reaction pressure A polymerization initiator, a crosslinking agent, etc. may be adjusted. 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 order to obtain a more uniformly dispersed binder resin (A) by mixing a polyester resin and a styrene-acrylic copolymer resin, synthesis is performed by a known method such as Japanese Patent No. 3531980 and Japanese Patent Application Laid-Open No. 2006-178296. It is good to do.

(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 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.

(Average molecular weight)
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, offset resistance, color reproducibility and dispersion stability tend to be lowered, and when it is larger than 100,000, the fixing property is deteriorated. There is a tendency.
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.

(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 consisting of Basic Red 1 and Basic Violet 10 and colorless organic sulfonic acid or organic carboxylic acid (which does not inhibit coloring of the pigment). 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, More preferably, it is 15-25 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 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 9 to 24 carbon atoms. The alkyl group of the monomer (c-2) has a straight chain carbon number of 6 or more and the total carbon number of the branched alkyl group. Have 3 or more.
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 is weak, and the pulverizability by wet pulverization is deteriorated. Further, during long-term storage, toner particles aggregate, the viscosity and average particle size of the liquid developer increase, and storage stability deteriorates. When the amine value is higher than 150 mgKOH / g, the chargeability of the toner particles 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 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, among the polymer dispersant (C), the ethylenically unsaturated monomer (c-2) containing an alkyl group having 9 to 24 carbon atoms has an alkyl group having 9 to 24 carbon atoms as a carrier liquid (D ), The pulverization property in wet pulverization is improved, and the increase in the viscosity of the liquid developer is suppressed. Furthermore, during storage for a long period of time, aggregation of toner particles and increase in the viscosity of the liquid developer can be suppressed, and excellent storage stability can be obtained. When the alkyl group has a carbon number of less than 9, the pulverization property in wet pulverization is lowered, and the aggregation / dispersion stability of the toner particles is deteriorated. When the carbon number of the alkyl group is larger than 24, the chargeability of the toner particles is deteriorated. Furthermore, when the liquid developer is fixed to the substrate, the long alkyl group inhibits contact of the toner particles, and the fixability deteriorates.

  Furthermore, since the monomer (c-2) has a linear alkyl group having 6 or more carbon atoms and a total number of carbon atoms of the branched alkyl group of 3 or more, it has excellent dispersion stability and high chargeability. Toner particles having the following can be obtained. By having a straight-chain alkyl group having 6 or more carbon atoms, solubility in the carrier liquid (D) is improved, and excellent grindability and storage stability can be obtained. If the straight-chain carbon number is smaller than 6, the solubility in the carrier liquid (D) becomes low, and problems such as deterioration in grindability and poor storage stability occur. Further, when the total number of carbon atoms of the branched alkyl group is 3 or more, toner particles having high chargeability can be obtained, and a copy image having sufficient image density and high color reproducibility can be obtained. If the total number of carbon atoms of the branched alkyl group is smaller than 3, the toner particles are not sufficiently charged, and the “fogging phenomenon” in which the toner particles are transferred not only to the image portion but also to the non-image portion, and the transfer property of the toner particle is lowered As a result, a question such as that a sufficient image density cannot be obtained occurs.

As an ethylenically unsaturated monomer (c-2) containing an alkyl group having 9 to 24 carbon atoms in which the straight chain carbon number is 6 or more and the total number of carbon atoms in the branched alkyl group is 3 or more For example,
4-ethyl-1-methylhexyl (meth) acrylate, 4-ethyl-1-methylheptyl (meth) acrylate, 2,4,7-methylheptyl acrylate, 2-ethyl-1-methyloctyl acrylate, 4-ethyl- 1-methyloctyl (meth) acrylate, 4-ethyl-1-methylnonyl (meth) acrylate, 2,4,9-methylnonyl acrylate, 4-ethyl-1-methyldecyl (meth) acrylate, 4-ethyl-1-methyl Undecyl (meth) acrylate, 4-ethyl-1- (2-methylpropyl) octyl acrylate, 4-ethyl-1-butyloctyl acrylate, 4-ethyl-1-methyldodecyl (meth) acrylate, 2-pentyldecyl ( (Meth) acrylate, 2-hexyldecyl (meth) acrylate, 4-ethyl-1-butyldecyl acrylate, 2-hept Rudecyl (meth) acrylate, 2-octyldecyl (meth) acrylate, 2-heptylundecyl (meth) acrylate, 2- (1,3,3 trimethylbutyl) -5,5,7-trimethyl-octyl (meth) acrylate 2-octylundecyl (meth) acrylate, 2-heptyldodecyl (meth) acrylate, 2-octyldodecyl (meth) acrylate, 2-octyltetradecyl (meth) acrylate, 2-octylhexadecyl (meth) acrylate, 2 -[({[(2- (1-Methylbutyl) -5-methyloctyl] oxy} carbonyl) amino] ethyl (meth) acrylate, 2-[({[(2- (4-methylhexyl) -8-methyldecyl ] Oxy} carbonyl) amino] ethyl (meth) acrylate and other alkyl (meth) acrylates having 9 to 24 carbon atoms ( Data) acrylates; and,
N, N-dihexylacrylamide, N, N-dioctylacrylamide, N, N-didecylacrylamide, N, N-didodecylacrylamide, N- (1-butyl-1,3-dimethylbutyl) acrylamide, N- (1 , 1-dipropylpentyl) acrylamide, N- (1,1-dibutylpentyl) acrylamide, N, N-bis (5-methylhexyl) acrylamide, etc., alkyl (meth) acrylamides having 9 to 24 carbon atoms; and ,
N- [4- (1-pyrenyl) butyl] -N-dodecyl (meth) acrylamide, N- (4-phenylbutyl) -N-dodecyl (meth) acrylamide, 4- (4-butylnonyl) phenyl (meth) acrylate Examples thereof include (meth) acrylates and (meth) acrylamides containing an aromatic ring and the like and an alkyl group having 9 to 24 carbon atoms.

  Among these, (meth) acrylates such as alkyl (meth) acrylates having 9 to 24 carbon atoms are preferable from the viewpoint of dispersibility.

Other unsaturated compounds that may be included include, for example,
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 are wet-dispersed in the carrier liquid, the polymer dispersant (C) is preferably dissolved in the carrier liquid (D). When (C) is added to toner particles and used at the time of toner particle production, 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 and the like are 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] and the like. 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) does not define a specific range, but dispersibility / pulverizability when the toner particles are wet-dispersed, and fixability as a liquid developer. Is considered to be 3000 to 100,000.

  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 deteriorate, and the storage stability deteriorates. It is possible to increase the dispersibility and pulverization properties of toner particles by changing the dispersion method and increasing the dispersion time, but this causes an increase in the viscosity of the liquid developer and causes deterioration in transferability and color developability. It becomes. When the amount added is more than 10 parts by mass, the chargeability of the toner particles decreases, causing problems such as insufficient image density and poor fixability.

(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 190 to 350 ° C. Especially preferably, it is the range of 210 to 320 degreeC. When the temperature is lower than 190 ° C., the liquid developer is dried at room temperature, solid matter is deposited, and the regulation blade around the development is fixed, thereby causing image contamination. On the other hand, when the temperature is higher than 350 ° C., it becomes difficult to remove the carrier liquid and the fixing property 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 solubility as a solvent is high, and the carrier liquid dissolves the toner particles, so the stability of the toner particles is deteriorated. Color reproducibility 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 ²⁰ mm ² / s. Especially preferably, it is the range of 1-10. 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 20, 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 D80”. It is preferably a naphthenic hydrocarbon such as “Exol D110”, “Exol D130” (Exxsol ^™ ).

(Other additives)
(Pigment dispersant)
As the form of the pigment dispersant internally added to the toner particles, polyamine-based resin type dispersant Solsperse 24000SC, Solspers 32000 (manufactured by Abyssia), Azisper PB821 (manufactured by Ajinomoto Fine Techno Co., Ltd.), resin type dispersion of acrylic copolymer An agent 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, 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 used in the present invention, it is also 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 is maintained, and the stability of the charging polarity of the toner particles can be maintained.
In the liquid developer of the present invention, it is preferable to use a basic dye derivative since the toner particles have a positive chargeability.

(Charge control agent)
The toner particles in the liquid developer of the present invention may contain a colorless or light-colored charge control agent as long as the hue does not hinder the hue. 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 preferably exhibit a positive charge, 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 six processes.

(1) Preparation of colored master batch for toner particles The binder resin (A) and the colorant (B) are kneaded at a concentration of 10 to 60 parts by mass of the colorant in the master batch using a hot roll or the like. After cooling, coarse crushing is performed to obtain a colored master batch. In addition to the binder resin (A) and the colorant (B), a pigment dispersant and a dye derivative can also be added.

(2) Preparation of toner particle chips (dilution of colored master batch)
The colored master batch obtained in (1) and the binder resin (A) are mixed with a mixer such as a super mixer, pre-dispersed, and then melt-kneaded, whereby the colored master batch is placed in the binder resin. Diluted and developed to obtain a chip for toner particles. 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, it is preferable that the toner particle chip be 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 for use. 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 particles The toner particle chip obtained in (2) is finely pulverized to an average particle size 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 The dry pulverized toner particles obtained in (3) are developed in a solvent having the same composition as that of the carrier liquid, and an average particle size of 0. 0 is obtained using a wet pulverizer (disperser). Grinding is performed so as to be in the range of 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. Through the wet pulverization and dispersion steps, the dispersant is adsorbed in the toner particles and 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. If the product temperature exceeds 50 ° C., the toner particles are fused, and the particle size distribution cannot be controlled.

As a wet pulverizer that can be used for wet pulverization of toner particles, a pulverization medium is used, and examples thereof include 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 pulverization media, the particle size of the pulverization media, the filling rate of the dispersion media in the pulverizer, the type of agitator disk, 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 69%, etc.) depending on the viscosity, specific gravity and grinding and dispersion required particle size of the toner particles. SiO ₂ 31%), zirconia beads (ZrO ₂ 95% or more), alumina (Al ₂ O ₃ 90% or more), titania _{(TiO 2 77.7%, Al 2} O 3 17.4%), steel balls or the like Although it can be used, it is preferable to use zirconia beads or zircon beads 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 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.

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

(Liquid developer properties)
The toner particles used in the present invention preferably have an average particle diameter (D50) of 0.5 to 4 μm, 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.

  Further, toner particles having a particle size of 2 μm or less with respect to all toner particles are contained in an amount of 50% by volume or less, toner particles having a particle size of 1 to 3 μm are contained in an amount of 5 to 60% by volume, and the particle size is 5 μm or more It is more preferable that the toner particles are 35% 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 50% 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 diameter of 5 μm or more exceeds 35% 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 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%. When the amount is less than 10% by mass, it is difficult to remove the carrier liquid, and the toner particles have poor fixability. If it exceeds 30% by mass, the viscosity of the liquid developer becomes high, the mobility of the toner particles deteriorates, and a sufficient image density cannot be obtained. Further, the toner particles are strongly aggregated and the storage stability is deteriorated.

The liquid developer of the present invention preferably has a surface potential of 0.4 kV or more after 1 second of corona charging. The surface potential of the liquid developer was measured as follows. That is, the liquid developer sample is put in a black anodized aluminum container (a cylinder with a diameter of 40 mm and a height of 10 mm) and placed on a grounded metal plate. Set the distance to 10 mm. The particles were charged by corona discharge for 10 seconds under an atmosphere condition of 25 ° C. and 50%, and immediately thereafter, measurement was performed with a surface potential meter (conforming to JIS C 61340-2-1).
When the surface potential after 1 second of corona charging is less than 0.4 kV, the charge amount of the toner particles becomes insufficient, and developability and transferability deteriorate. As a result, problems such as occurrence of fogging phenomenon and insufficient image density are caused.

  The surface potential of the liquid developer greatly depends on the components constituting the liquid developer. In particular, since the dispersant is adsorbed on the surface of the toner particles, it affects the chargeability of the toner particles. The polymer dispersant (C) used in the present invention gives toner particles good chargeability by controlling the amine value and the number of linear and branched alkyl group carbon atoms of the ethylenically unsaturated monomer. is there. If the amine value and the number of carbon atoms of the linear and branched alkyl groups of the ethylenically unsaturated monomer are not controlled, the charge amount of the toner particles adsorbed by the dispersant is lowered, and the surface potential after corona charging is 0. It tends to be below 4 kv.

In the liquid developer of the present invention, the adsorption rate of the polymer dispersant (C) to the toner particles is preferably 50% or more. More preferably, it is 70% or more. If it is less than 50%, the dispersion stability of the toner particles is poor, causing aggregation of the toner particles during long-term storage, and stable color development and color reproducibility cannot be obtained.
In order to obtain a liquid developer having an adsorption rate of 50% or more, it is necessary to control the amine value of the polymer dispersant (C) and the number of straight and branched alkyl group carbon atoms of the ethylenically unsaturated monomer. is there.

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.

(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 was heated to 110 ° C., 20.0 parts of N, N-dimethylaminoethyl methacrylate, 80.0 parts of 2-octyldecyl methacrylate, and 2,2′-azobis (2-methyl) as a polymerization initiator. A mixture of 9.0 parts of dimethyl propionate (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, and then 0.9 part of 2,2′-azobis (2-methylpropionic acid) dimethyl was added, and the reaction was further continued at 110 ° C. for 1 hour. A solution of Dispersant 1 was obtained. The weight average molecular weight (Mw) of the polymeric dispersant 1 was about 7100.
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 Examples 2-6 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 2 were used, and solutions of polymer dispersants 2 to 6 were obtained. The amine value and weight average molecular weight of each polymer dispersant were as shown in Table 3.

(Comparative Polymer Dispersant Synthesis Examples 1-6)
Synthesis was performed in the same manner as in Synthesis Example 1 except that the raw materials and preparation amounts shown in Table 2 were used, and solutions of comparative polymer dispersants 1 to 5 were obtained. The amine value and weight average molecular weight of each polymer dispersant were as shown in Table 3.

Table 3 shows the physical property values of the obtained polymer dispersant.
As a polymer dispersant, a commercially available Antaron V-216 (manufactured by ISP) was used as the comparative polymer dispersant 7.

(Coloring agent)
Cyan colorant C.I. I. Pigment Blue 15: 3 (copper phthalocyanine blue)
Lionol Blue FG7919 (manufactured by Toyo Ink)
Magenta colorant C.I. I. Pigment Red 122 (Quinacridone Magenta)
Hosterperm Pink E (manufactured by Clariant)
C. I. Pigment Red 57: 1 (Kermin 6B)
Permanent Rubin L6B (manufactured by Clariant)
Yellow colorant C.I. I. Pigment Yellow 180 (Benz Imidazolone Yellow)
Novoperm Yellow P-HG (manufactured by Clariant)
Black colorant carbon black NIPEX150 (Degussa)
As the blue component, C.I. I. Pigment Blue 15: 3 added

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

(Carrier liquid)
Exol D110 Naphthenic hydrocarbons Dry point: 267 ° C. Aniline point: 83 ° C. Kinematic viscosity: 3.50 mm ² / s
Density: 0.810 g / cm ³

[Example 1]
C. I. Pigment Blue 15: 3
(Lionol Blue FG7919) 18 parts by weight binder resin 1 80 parts by weight Solspers 24000SC 2 parts by weight The above materials (total 5 kg) were mixed (3000 rpm, 3 minutes) with a Henschel mixer having a volume of 20 L, and then a twin-screw kneading extruder (PCM30) was melt-kneaded at a supply rate of 6 kg / hr and a discharge temperature of 145 ° C., and further kneaded with three rolls at a roll temperature of 140 ° C. After cooling and solidifying, coarsely pulverizing with a hammer mill and then finely pulverizing with an I-type jet mill (IDS-2 type) to obtain a pulverized cyan toner having an average particle size of about 5.0 μm.

further,
Cyan toner pulverized product 25 parts by mass Exol D110 72 parts by mass Polymeric dispersant 1 3 parts by mass were weighed and mixed thoroughly to disperse the cyan toner pulverized product in the Exol D110 solution. (Slurry concentration is 25% by mass)
The slurry in which the cyan toner pulverized product is dispersed is subjected to a circulation operation for 60 minutes using a wet pulverizer which is a medium agitating mill, Dino Mill Multilab (manufactured by Shinmaru Enterprises Co., Ltd., capacity 1.4 L), and wet pulverization is performed. went.
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 wet pulverization for 60 minutes, the slurry was taken out and passed through a mesh having an opening of 33 μm (manufactured by SUS304) to obtain a liquid developer 1C (including cyan toner particles). When the particle size distribution of the cyan toner particles was confirmed, the average particle size (D50) was 2.7 μm. The viscosity (η) of the liquid developer 1C was 54 mPa · s.

[Examples 2 to 9, Comparative Examples 1 to 10]
Using the raw materials shown in Tables 4 and 5 in the same manner as in Example 1, toner pulverized products and liquid developers were produced, respectively.

  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.

  The image density was measured with a Gretag Macbeth densitometer (D-196). Here, it is practically preferable that the density value of each color is 1.2 or higher for yellow, 1.4 or higher for magenta / cyan, and 1.6 or higher for black. More preferably, yellow is 1.3 or more, magenta / cyan is 1.5 or more, and black is 1.7 or more.

  The fog phenomenon in which the toner particles are transferred not only to the image portion but also to the non-image portion was evaluated by measuring the reflectance with a photovolt 577. If it is less than 1.0%, it is practically preferable, and if it is less than 0.5, it is more preferable.

◎: Reflectance is less than 0.5 ○: Reflectance is 0.5% or more and less than 1.0% Δ: Reflectance is 1.0% or more and less than 1.5% ×: Reflectance is 1.5% that's all

  The surface potential of the liquid developer was measured with a surface potential meter immediately after charging the particles by corona discharge for 10 seconds. The value one second after the end of charging by corona discharge was taken as the surface potential of the liquid developer. The surface potential after 1 second is preferably 0.4 kv or more, more preferably 0.8 kv or more.

The adsorption rate of the polymer dispersant (C) to the toner particles was measured as follows.
10 g of the liquid developer was weighed and carried out at 19000 rpm for 20 minutes using a Hitachi Koki centrifuge CR22H, and the supernatant was collected. 1 g of the separated supernatant solution was weighed and Exol D110 was volatilized in an oven at 160 ° C. for 1 hour. The residual polymer dispersant (C) was weighed, and the adsorption rate to the toner particles was calculated from the obtained value. If the adsorption rate is 50% or more, it is practically preferable, and if it is 70% or more, it is more preferable.

◎: Adsorption rate is 70% or more ○: Adsorption rate is 50% or more and less than 70% Δ: Adsorption rate is 30% or more and less than 50% ×: Adsorption rate is less than 30%

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

  Detailed physical property values and test results of the liquid developer are shown in Table 6.

  In Examples 1 to 9, the surface potential of the liquid developer is high, a sufficient image density is obtained, and the fog phenomenon does not occur. Furthermore, the adsorption rate to the toner particles is high, and the storage stability is excellent. As can be seen from Table 6, as the polymeric dispersant (C), at least an ethylenically unsaturated monomer (c-1) having an amino group and an ethylenically unsaturated group containing an alkyl group having 9 to 24 carbon atoms. Copolymerized with a saturated monomer (c-2), the alkyl group of the monomer (c-2) has a linear carbon number of 6 or more, and the total carbon of the branched alkyl group When the polymer dispersant (C) having a number of 3 or more and having an amine value of 5 to 150 mg KOH / g is not used, it can be seen that any of image density, fog phenomenon, and storage stability is inferior.

  The liquid developer of the present invention is excellent in color reproducibility, color developability, and storage stability, and is an electronic copying machine, printer, on-demand printing machine in which an image is formed 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 the above.

Claims (4)

A liquid developer comprising at least a binder resin (A), a colorant (B), a polymer dispersant (C), and a carrier liquid (D),
The polymer dispersant (C) is at least an ethylenically unsaturated monomer having an amino group (c-1),
Copolymerized with an ethylenically unsaturated monomer (c-2) containing an alkyl group having 9 to 24 carbon atoms,
The alkyl group of the monomer (c-2) has a linear carbon number of 6 or more, and the branched alkyl group has a total carbon number of 3 or more;
A liquid developer, wherein the polymer dispersant (C) has an amine value of 5 to 150 mgKOH / g.   The liquid developer according to claim 1, wherein the carrier liquid (D) is an aliphatic hydrocarbon.   The liquid developer according to claim 1, wherein the binder resin (A) contains at least a polyester resin.   The liquid developer according to any one of claims 1 to 3, wherein the softening temperature of the binder resin (A) is 80 to 140 ° C.