JP2006317782A - Liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer excellent in charging and fixing properties. <P>SOLUTION: The liquid developer is a liquid developer in which toner particles comprising at least a binder resin and a colorant are dispersed in an insulating liquid, wherein as the colorant, a colorant is used in which pigment particles having a cationic group on the surface thereof are coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group. The colorant is obtained by coating the pigment particles having the cationic group on the surface thereof with the polymer by polymerizing the anionic polymerizable surfactant in an aqueous dispersion in which the pigment particles are dispersed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid developer.

A dry toner method in which a toner composed of a material containing a colorant such as a pigment and a binder resin is used in a dry state as a developer used to develop the electrostatic latent image formed on the latent image carrier. And a method using a liquid developer in which toner is dispersed in an electrically insulating carrier liquid.
The method using dry toner handles solid-state toner, so there are advantages in handling, but there are concerns about adverse effects on the human body due to powder, as well as contamination due to scattering of toner, and when toner is dispersed There is a problem with uniformity. Further, the dry toner has a problem that the particles are likely to aggregate and it is difficult to sufficiently reduce the size of the toner particles, and it is difficult to form a toner image with high resolution. In addition, when the size of the toner particles is relatively small, the problem due to the powder as described above becomes more remarkable.

  On the other hand, in the method using the liquid developer, the toner particles are effectively prevented from aggregating in the liquid developer, so that it is possible to use fine toner particles, and the binder resin has a low softening point. (Low softening temperature) can be used. As a result, in the method using a liquid developer, fine line image reproducibility is good, gradation reproducibility is good, color reproducibility is excellent, and it is also excellent as a high-speed image forming method. It has characteristics.

Conventionally, a liquid developer has conventionally been obtained by pulverizing a resin to produce a toner (see, for example, Patent Document 1), and polymerizing a monomer component in the electrically insulating liquid, thereby forming the electrically insulating liquid. It has been produced by a polymerization method for forming insoluble resin fine particles (for example, see Patent Document 2).
However, with conventional liquid developers, it is difficult to stabilize the charge amount, and problems such as a decrease in image density and fogging are likely to occur. Further, since the colorant contained in the conventional toner particles has a low affinity for the recording medium, there is a problem that the fixing property of the toner particles to the recording medium is hindered depending on the content.

JP-A-7-234551 Japanese Patent Publication No.8-7470

  An object of the present invention is to provide a liquid developer excellent in charging characteristics and fixing characteristics.

Such an object is achieved by the present invention described below.
The liquid developer of the present invention is a liquid developer in which toner particles composed of at least a binder resin and a colorant are dispersed in an insulating liquid,
As the colorant, pigment particles having a cationic group on the surface are coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group. It is characterized by using the same.
Thereby, a liquid developer excellent in charging characteristics and fixing characteristics can be provided.

In the liquid developer according to the aspect of the invention, the colorant may be formed by polymerizing the anionic polymerizable surfactant in an aqueous dispersion in which the pigment particles having the cationic group on the surface are dispersed. It is preferable that is formed by coating with a polymer.
As a result, the charge on the surface of the pigment particles can be surely canceled by the anionic group derived from the anionic polymerizable surfactant, and the electrical stability of the entire liquid developer can be obtained.

これにより、着色剤の耐久性が向上し、例えば、液体現像剤を製造する際に、顔料を被覆するポリマーの不本意な剥がれ等を効果的に防止することができる。 In the liquid developer of the present invention, it is preferable that the polymer further has a repeating structural unit derived from a hydrophobic monomer.
Thereby, the durability of the colorant is improved, and, for example, when the liquid developer is produced, unintentional peeling of the polymer covering the pigment can be effectively prevented.
In the liquid developer of the present invention, it is preferable that the polymer further has a repeating structural unit derived from a crosslinkable monomer and / or a repeating structural unit derived from a monomer represented by the following general formula (1).

Thereby, the durability of the colorant is improved, and, for example, when the liquid developer is produced, unintentional peeling of the polymer covering the pigment can be effectively prevented.

In the liquid developer of the present invention, the pigment constituting the pigment particles is preferably carbon black.
Carbon black has a strong tendency to inhibit the charging characteristics and fixing characteristics of the liquid developer, but by using the microencapsulated one, it is possible to prevent the charging characteristics and fixing characteristics of the liquid developer from being inhibited. .

In the liquid developer of the present invention, the cationic group of the pigment particle is selected from the group consisting of a primary amine cation group, a secondary amine cation group, a tertiary amine cation group, and a quaternary ammonium cation group. It is preferable that
As a result, a liquid developer excellent in charging characteristics and fixing characteristics can be provided more easily.

In the liquid developer of the present invention, the anionic group of the anionic polymerizable surfactant is a sulfonate anion group (—SO ₃ ⁻ ) or a sulfinate anion group (—RSO ₂ ^— : R is C _{1 to} C _12. And an alkyl group or a phenyl group thereof and a modified product thereof) and a carboxylate anion group (—COO ⁻ ) are preferable.
As a result, a liquid developer excellent in charging characteristics and fixing characteristics can be provided more easily.

In the liquid developer of the present invention, the hydrophobic group of the anionic polymerizable surfactant is preferably selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined.
As a result, a liquid developer excellent in charging characteristics and fixing characteristics can be provided more easily.

In the liquid developer of the present invention, the polymerizable group of the anionic polymerizable surfactant is an unsaturated hydrocarbon group capable of radical polymerization, and includes a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, and a propenyl group. , Vinylidene group, and vinylene group are preferable.
As a result, a liquid developer excellent in charging characteristics and fixing characteristics can be provided more easily.

In the liquid developer of the present invention, the colorant is added to the aqueous dispersion of pigment particles having the cationic group on the surface thereof, and the anionic polymerizable surfactant is added and mixed, and then the anionic polymerizable surfactant is further added. It is preferably obtained by emulsifying the agent and then emulsifying, followed by polymerization in water with the addition of a polymerization initiator.
As a result, the charge on the surface of the pigment particles can be canceled by the anionic group derived from the anionic polymerizable surfactant, and the electrical stability of the entire liquid developer can be obtained.

In the liquid developer of the present invention, the colorant is prepared by adding the anionic polymerizable surfactant to the aqueous dispersion of the pigment particles having the cationic group on the surface and mixing the resulting mixture with the hydrophobic monomer and the anionic polymerization. It is preferable that it is obtained by adding and mixing a surfactant and mixing, emulsifying, adding a polymerization initiator, and polymerizing in water.
As a result, the durability of the colorant can be improved more effectively, and the charge on the surface of the pigment particles can be more reliably canceled out by the anionic group derived from the anionic polymerizable surfactant, and the liquid development The electrical stability as the whole agent can be obtained more effectively.

これにより、着色剤の耐久性をより効果的に向上させることができるとともに、顔料粒子表面の電荷を、アニオン性重合性界面活性剤由来のアニオン性基によってより確実に打ち消すことができ、液体現像剤全体としての電気的安定性をより効果的に得ることができる。 In the liquid developer of the present invention, the colorant is prepared by adding the anionic polymerizable surfactant to the aqueous dispersion of pigment particles having the cationic group on the surface and mixing, and then mixing the hydrophobic monomer and the crosslinkable monomer. // It is preferable that the monomer represented by the following general formula (1) and the anionic polymerizable surfactant are added and mixed, and after emulsification, a polymerization initiator is added and polymerized in water. .

As a result, the durability of the colorant can be improved more effectively, and the charge on the surface of the pigment particles can be more reliably canceled out by the anionic group derived from the anionic polymerizable surfactant, and the liquid development The electrical stability as the whole agent can be obtained more effectively.

The liquid developer of the present invention preferably contains a charge control agent.
The contact between the colorant and the charge control agent may inhibit the function of the charge control agent. However, in the liquid developer finally obtained by using microencapsulated pigment as the colorant, In addition, since the colorant and the charge control agent can be present in a state where they are not in direct contact with each other, the obtained liquid developer has excellent charging characteristics while maintaining excellent color developability.

Hereinafter, preferred embodiments of the liquid developer of the present invention will be described in detail with reference to the accompanying drawings.
FIGS. 1 and 3 are diagrams showing a production process of a colorant applied to the liquid developer of the present invention, and FIGS. 2 and 4 are examples of microencapsulated pigments applied to the liquid developer of the present invention. FIG.
The liquid developer of the present invention is one in which toner particles composed of at least a binder resin and a colorant are dispersed in an insulating liquid.

<Insulating liquid>
First, the insulating liquid will be described.
The insulating liquid used in the present invention may be a liquid having a sufficiently high insulating property. Specifically, it is preferable that the electric resistance at room temperature (20 ° C.) is 10 ⁹ Ωcm or more. ^It is more preferably ¹¹ Ωcm or more, and even more preferably 10 ¹³ Ωcm or more.
The dielectric constant of the insulating liquid is preferably 3.5 or less.

  Examples of the insulating liquid that satisfies such conditions include octane, isooctane, decane, isodecane, decalin, nonane, dodecane, isododecane, cyclohexane, cyclooctane, cyclodecane, benzene, toluene, xylene, mesitylene, various silicone oils, Vegetable oil such as linseed oil, soybean oil, Isopar E, Isopar G, Isopar H, Isopar L (Isopar; trade name of Exxon), Cielsol 70, Cielsol 71 (Cielsol; trade name of Ciel Oil), Amsco OMS, Amsco 460 solvent (Amsco; trade name of Spirits), liquid paraffin (Wako Pure Chemical Industries) and the like.

<Constituent material of toner particles>
Next, materials constituting the toner particles will be described.
The toner particles are composed of at least a binder resin (resin) and a colorant.
1. Resin (binder resin)
In the present invention, the resin (binder resin) is not particularly limited, and for example, polystyrene, poly-α-methylstyrene, chloropolystyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer. Polymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid ester -Styrene resins such as methacrylic acid ester copolymer, styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, styrene-vinyl methyl ether copolymer, etc. A homopolymer or copolymer, Polyester resin, epoxy resin, urethane modified epoxy resin, silicone modified epoxy resin, vinyl chloride resin, rosin modified maleic acid resin, phenyl resin, polyethylene resin, polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl Examples include acrylate copolymers, xylene resins, polyvinyl butyral resins, terpene resins, phenol resins, aliphatic or alicyclic hydrocarbon resins. One or more of these can be used in combination.
Although the softening temperature of resin (resin material) is not specifically limited, It is preferable that it is 50-130 degreeC, It is more preferable that it is 50-120 degreeC, It is further more preferable that it is 60-115 degreeC. In the present specification, the softening temperature is a measurement condition in a Koka type flow tester (manufactured by Shimadzu Corporation): temperature increase rate: 5 ° C./min, softening start temperature defined by a die hole diameter of 1.0 mm. Point to.

2. Colorant The toner contains a colorant.
The colorant used in the liquid developer of the present invention is a repetitive pigment particle having a cationic group on its surface derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group and a polymerizable group. A pigment coated with a polymer having a structural unit, that is, a microencapsulated pigment (hereinafter also simply referred to as a microencapsulated pigment).

As shown in FIG. 2, the microencapsulated pigment 100 includes an anion of a polymer (polymer layer) 60 derived from a cationic group 14 on the surface of the pigment particle 1 and an anionic polymerizable surfactant as described later. The pigment particles 1 are covered with the polymer layer 60 in a state in which the functional group is ionically bonded.
By the way, with a conventional liquid developer, it is difficult to stabilize the charge amount, and problems such as a decrease in image density and fogging are likely to occur. This is because many of the pigments used as the colorant have a cationic group on the surface, and such pigments often deteriorate the electrical characteristics (charging characteristics) of the toner particles. For this reason, it is considered that it is difficult to sufficiently control the charge amount of the toner particles even if the resin or the like is selected in order to reliably control the charge amount of the toner particles. Further, it is considered that even when the charge control agent was added, the charge control agent and the colorant were in contact with each other, and it was difficult to control the charge amount.

  In contrast, the pigment particles were coated with the polymer in a state where the cationic groups on the surface of the pigment particles and the cationic groups of the polymer derived from the cationic polymerizable surfactant were ionically bonded. By using the colorant, the charge on the surface of the pigment particles is canceled out by the anionic group derived from the anionic polymerizable surfactant, so that the colorant becomes electrically stable. As a result, toner particles (liquid developer) excellent in charging characteristics (particularly charging stability) can be obtained.

In addition, the colorant used in the conventional liquid developer has low affinity with the recording medium, and depending on the content, the fixing property of the toner is inhibited. By using such a microencapsulated pigment, Since the affinity of the pigment itself to the recording medium is improved, the fixing characteristics of the toner particles (liquid developer) are improved.
Further, by using the encapsulated pigment as described above, the affinity with the above-described resin is improved and the dispersibility in the resin is improved. As a result, the variation in the content of the colorant among the toner particles can be reduced, and the color developability is improved.

Further, since the colorant conventionally used in liquid developers has a polar group (cationic group) on the surface, toner containing such a colorant is affected by moisture in the air. Although it is easy and environmental stability is low, environmental stability can also be improved by using the above microencapsulated pigment as a colorant.
In addition, since the pigment particles and the polymer are strongly bonded to each other, it is possible to prevent the polymer from being peeled off from the pigment particles, for example, in the manufacturing process of the liquid developer.

  Further, for example, when a charge control agent is contained in the toner particles, depending on the type of the colorant (particularly in the case of carbon black), the colorant and the charge control agent may come into contact with each other, Although the function may be hindered, by using a microencapsulated pigment as the colorant, the colorant and the charge control agent should not be in direct contact with each other in the finally obtained liquid developer. Therefore, the finally obtained liquid developer has excellent charging characteristics while maintaining excellent color developability.

In addition, such a microencapsulated pigment is formed by electrically bonding the cationic group on the surface of the pigment particle and the anionic group of the surfactant. It will be relatively small.
The average particle diameter of these microencapsulated pigments is preferably 400 nm or less, more preferably 300 nm or less, and even more preferably 50 to 200 nm. If the average particle size of the microencapsulated pigment is too large, it may be difficult to make the content of the colorant uniform among the toner particles depending on the size of the toner particles. The description of the particle size is described by the measured value of the laser light scattering method.)

  Further, the aspect ratio (long and short) of the microencapsulated pigment is 1.0 to 1.3, and the Zingg index is 1.0 to 1.3 (more preferably 1.0 to 1.2). It is preferable that Thereby, the dispersibility in the resin is improved, and even when the colorant (microencapsulated pigment) is present on the surface of the toner particles, the influence on the shape of the toner can be reduced. As a result, a toner (liquid developer) with little variation in shape can be provided.

When the short diameter of the microencapsulated pigment particles is b, the long diameter is l, and the thickness is t (l ≧ b ≧ t> 0), the aspect ratio (long / short) is 1 / b (≧ 1), and the flatness is b / t (≧ 1), Zingg index = long / shortness / flatness = (l · t) / b2. That is, the true sphere has an aspect ratio of 1 and a Zingg index of 1.
When the Zingg index is larger than 1.3, the microencapsulated pigment becomes flatter and becomes less isotropy. Therefore, when the microencapsulated pigment is present on the surface of the toner particle, the shape of the toner particle is changed. May have an impact. The method for setting the aspect ratio and Zingg index within the above ranges is not particularly limited. However, a microencapsulated pigment in which pigment particles having an anionic group on the surface are coated with a polymer by the above-described emulsion polymerization method can easily satisfy these conditions. Can meet.

In addition, in a microencapsulated pigment produced by a method other than an emulsion polymerization method such as an acid precipitation method or a phase inversion emulsification method, which will be described later, the aspect ratio and the Zingg index are unlikely to fall within the above ranges.
When the microencapsulated pigment is in the above aspect ratio and Zingg index range, it becomes a true sphere, which improves the dispersibility in the resin and causes the colorant (microencapsulated pigment) to adhere to the toner particle surface. Even if it exists, the influence on the shape and the like of the toner can be reduced. As a result, a toner with less variation in shape can be provided.

Next, the constituent components of the macroencapsulated pigment will be described in detail.
(2-1) Pigment Particles Examples of the pigment constituting the microencapsulated pigment (colorant) used in the present invention include inorganic pigments and organic pigments.
In general, an amine substituent (primary amine, secondary amine, tertiary amine), quaternary ammonium group (—NR ₃ ⁺ ), quaternary phosphonium group (—PR ₃ ) is formed on the surface of the pigment particle. ⁺ ), And a cationic group such as a sulfonium group (—SR ₂ ⁺ ) or a pyridinium group. However, by encapsulating as described above, the surface of the pigment particles can be made electrically stable (neutral). As a result, the charging characteristics of the finally obtained liquid developer can be improved.

  Examples of such inorganic pigments include carbon blacks such as furnace black, lamb black, acetylene black, and channel black (C.I. pigment black 7), iron oxide pigments, and the like. Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxanes). Pigments, thioindigo pigments, isoindolinone pigments, or quinofuranone pigments), dye chelates (for example, basic dye-type chelates or acidic dye-type chelates), nitro pigments, nitroso pigments, or aniline black.

  More specifically, as an inorganic pigment used for black, the following carbon black, for example, No. manufactured by Mitsubishi Chemical Corporation is used. 2300, no. 900, MCF88, No. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, or No2200B, etc .; Columbia-made Raven5750, Raven5250, Raven5000, Raven3500, Raven1255, Raven700, etc .; 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400, etc .; or Color Black FW1, Col Black FW2, Col FW2V, Col 200 or Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, and SpecialBlack 4, and the like.

In particular, since carbon black as described above has a strong tendency to inhibit the charging characteristics and fixing characteristics of the liquid developer, the effect of the present invention by microencapsulation appears significantly.
Examples of the organic pigment for black include black organic pigments such as aniline black (C.I. Pigment Black 1).
Examples of organic pigments for yellow toner include C.I. l. Pigment Yellow 1 (Hansa Yellow), 2, 3 (Hansa Yellow 10G), 4, 5 (Hansa Yellow 5G), 6, 7, 10, 11, 12, 13, 14, 16, 17, 24 (Flavantron Yellow) , 34, 35, 37, 53, 55, 65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 99, 108 (anthrapyrimidine yellow), 109, 110, 113, 117 ( (Copper complex pigment), 120, 124, 128, 129, 133 (quinophthalone), 138, 139 (isoindolinone), 147, 151, 153 (nickel complex pigment), 154, 167, 172, 180, and the like.

  Further, organic pigments for magenta toner include C.I. l. Pigment Red 1 (Paral Red), 2, 3 (Toluidine Red), 4, 5 (lTR Red), 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21 , 22, 23, 30, 31, 32, 37, 38 (pyrazolone red), 40, 41, 42, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 88 (thioindigo), 112 (Naphthol AS series), 114 (Naphthol AS series), 122 (Dimethylquinacridone), 123, 144, 146, 149, 150, 166, 168 (Antanthrone orange), 170 (Naphthol AS series), 171, 175, 176 , 177, 178, 179 (berylene maroon), 184, 185, 187, 202, 209 (dichloroquinacridone), 219, 224 (berylene), 245 (naphthol AS yarn) ) Or C.I. I. Pigment violet 19 (quinacridone), 23 (dioxazine violet), 32, 33, 36, 38, 43, 50 and the like.

Furthermore, as organic pigments for cyan toner, C.I. l. Pigment Blue 1, 2, 3, 15, 15: 1, 15: 2, 15: 3, 15:34, 15: 4, 16 (metal-free phthalocyanine), 18 (alkali blue toner), 22, 25, 60 ( Slen Blue), 65 (Biolantron), 66 (Indigo), C.I. l. Vat blue 4, 60 etc. are mentioned.
Furthermore, as organic pigments used for color toners other than magenta, cyan or yellow toners, C.I. I. Pigment green 7 (phthalocyanine green), 10 (green gold), 36, 37; C.I. I. Pigment brown 3, 5, 25, 26; I. Pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 24, 34, 36, 38, 40, 43, 63, and the like.

In the macroencapsulated pigment used in the toner of the present invention, the above pigments can be used alone or in combination of two or more.
The average particle diameter of the pigment particles having such a cationic group on the surface is preferably 150 nm or less, and preferably 20 nm to 80 nm. Thereby, the average diameter of a microencapsulated pigment can be made suitable.

  Even if the pigment particles are electrically neutral or negatively charged and coated with a conventional resin material, the effect of the present invention cannot be obtained. For example, in the former case, since the average particle diameter of the pigment particles varies due to aggregation of the pigment particles, etc., the content of each toner component among the toner particles may vary. As a result, characteristics such as charging characteristics and fixing characteristics vary. In the latter case, for example, the colorant inhibits the electrical stability of the toner particles, and the charging characteristics of the liquid developer cannot be sufficiently obtained.

  The cationic group may be introduced later. That is, pigment particles having no cationic group or those having a cationic group introduced on the surface of pigment particles having an anionic group may be used. In such a case, a known pigment having no cationic group on the surface or pigment particles having an anionic group can be used as a material for the microencapsulated pigment. Thereby, the variation of the color which can be expressed can be increased.

Examples of the method for introducing a cationic group include the following methods.
The introduction of the cationic group can be performed, for example, by adding an aromatic group to the pigment by diazotization using a diazonium salt and replacing the pigment with a cationic group. Specifically, it can be prepared by reacting a pigment with a diazonium salt in a liquid reaction medium to bond at least one organic ionic group to the pigment surface. The diazonium salt can have an organic ionic group that is bonded to the carbon black.

  A diazonium salt is an organic compound having one or more diazonium groups. Diazonium salts are typically diazotizing agents such as ammonium nitrite, butyl nitrite, dicyclohexylammonium nitrite, ethyl nitrite, isoamyl nitrite, lithium nitrite, sodium nitrite, potassium nitrite, or zinc nitrite. Any metal or organic nitrite, and can include nitrous acid, nitric oxide, nitrogen dioxide, and mixtures thereof) and is generated by reacting the treating agent / reactant at suitable conditions. The cationic treatment agent itself can contain nitrite, in which case the diazonium salt is made by subsequent addition of acid. Thus, the treating agent can include a diazotizing agent (eg, nitrite) that can be made into a diazonium salt by adding an acid.

  For the method of introducing a cationic group on the surface, WO96 / 18688, US Pat. No. 5,554,739, WO96 / 18696, US Pat. Nos. 5,851,280, 5,837, No. 045, No. 5,803,959, No. 5,672,198, No. 5,571,311, No. 5,630,868, No. 5,707,432, No. No. 5,803,959, No. 5,698,016, No. 5,713,988, WO 97/47697, WO 97/47699.

(2-2) Polymer Layer The polymer layer 60 is composed of a polymer derived from an anionic polymerizable surfactant.
Examples of the anionic polymerizable surfactant used in the present invention include anions as described in JP-B-49-46291, JP-B-1-24142, or JP-A-62-104802. Allyl derivatives, anionic propenyl derivatives as described in JP-A-62-221431, JP-A-62-34947 or JP-A-55-11525 Examples thereof include anionic acrylic acid derivatives and anionic itaconic acid derivatives as described in JP-B-46-34898 or JP-A-51-30284.
As a specific example of the anionic polymerizable surfactant used in the present invention, the general formula (31):

Or a compound represented by formula (32):

The compound represented by these is preferable.
The polymerizable surfactant represented by the formula (31) is described in JP-A-5-320276 or JP-A-10-316909. By appropriately adjusting the type of R21 and the value of X in Formula (31), it is possible to correspond to the degree of hydrophilicity or hydrophobicity of the pigment particle surface. As a preferable polymerizable surfactant represented by the formula (31), a compound represented by the following formula (310) can be exemplified. Specifically, in the following formulas (31a) to (31d) Mention may be made of the compounds represented.

A commercial item can also be used as said anionic polymerizable surfactant. For example, Aqualon HS series (Aqualon HS-05, HS-10, HS-20, HS-1025) from Daiichi Kogyo Seiyaku Co., Ltd. or Adeka Soap SE-10N, SE-20N from Asahi Denka Kogyo Co., Ltd. Can be mentioned.
Asahi Denka Kogyo Co., Ltd. Adekaria Soap SE-10N is a compound represented by the formula (310), in which M ¹ is NH ₄ , R 31 is C ₉ H ₁₉ , and m = 10. Adekaria Soap SE-20N manufactured by Asahi Denka Kogyo Co., Ltd. is a compound represented by formula (310) in which M ¹ is NH ₄ , R 31 is C ₉ H ₁₉ , and m = 20.
Examples of the anionic polymerizable surfactant used in the present invention include a general formula (33):

The compound represented by these is preferable. Preferred examples of the anionic polymerizable surfactant represented by the formula (33) include the following compounds.

A commercial item can also be used as said anionic polymerizable surfactant. For example, Aqualon KH series (Aqualon KH-5, Aqualon KH-10) from Daiichi Kogyo Seiyaku Co., Ltd. can be mentioned. Aqualon KH-5 is a mixture of a compound represented by the above formula wherein r is 9 and s is 5 and a compound where r is 11 and s is 5. Aqualon KH-10 is a mixture of a compound represented by the above formula wherein r is 9 and s is 10, and a compound where r is 11 and s is 10.
Moreover, as an anionic polymerizable surfactant, the compound represented by a following formula (A) is also preferable.

The anionic polymerizable surfactants exemplified above can be used alone or as a mixture of two or more.
The polymer layer 60 may have a repeating structural unit derived from an anionic polymerizable surfactant and a hydrophobic monomer, or may have a repeating structural unit derived from a crosslinkable monomer. May be. These will be described in detail later.

(2-3) Production of Microencapsulated Pigment The microencapsulated pigment described above is prepared by adding an anionic polymerizable surfactant to an aqueous dispersion of pigment particles having a cationic group on the surface and mixing them, and then anionic. It can manufacture suitably by adding a polymerization surfactant and emulsifying, and then adding a polymerization initiator and carrying out emulsion polymerization. In addition, since the pigment particles can be encapsulated even if the pigment particles are relatively small by using such a method, the microencapsulated pigment is compared with the size of the toner particles. Can be made sufficiently small. As a result, the colorant content among the toner particles can be made more uniform.

In the following, description will be made with reference to possible dispersion states of pigment particles in a preferred method for producing a microencapsulated pigment. However, the dispersion state of the pigment particles listed below includes estimation.
First, a possible dispersion state of pigment particles will be described with reference to FIG. The pigment particles 1 having a cationic group 14 as a hydrophilic group dispersed in a solvent containing water as a main component (hereinafter also referred to as an aqueous solvent) are mixed with an anionic group 11, a hydrophobic group 12, and a polymerizable group 13. The anionic group 11 of the anionic polymerizable surfactant 2 having the above is arranged so as to face the cationic group 14 of the pigment particle 1 and adsorbs with a strong ionic bond.
In this state, for example, by adding a polymerization initiator, the polymerizable groups 13 of the adjacent anionic polymerizable surfactant 2 are polymerized to form the pigment particles 1 in the polymer layer 60 as shown in FIG. A microencapsulated pigment 100 coated with is produced.

  According to such an emulsion polymerization method, the arrangement form of the anionic polymerizable surfactant existing around the pigment particles before the polymerization reaction is very highly controlled. Then, the anionic polymerizable surfactant is converted into a polymer by the emulsion polymerization reaction while maintaining this highly controlled form. Therefore, the structure of the microencapsulated pigment is controlled with extremely high accuracy. That is, since the cationic group on the surface of the pigment particle and the anionic group of the anionic polymerizable surfactant are ionically bonded in the polymerization system to form a polymer phase by a polymerization reaction, emulsion polymerization is performed. The arrangement form of the monomers existing around the pigment particles in the front affects the polarization state of the surface of the particles after polymerization, and can therefore be controlled with extremely high accuracy. Thereby, the average particle diameter of the obtained microencapsulated pigment can be made relatively small while preventing aggregation and the like of the pigment particles. The microencapsulated pigment obtained in this manner is sufficiently small compared to the toner particles and has high dispersibility in the resin. Therefore, the content of the colorant between the toner particles is reduced. It can be uniform.

More specifically, the microencapsulated pigment is preferably produced by the following procedure.
(1) First, an anionic polymerizable surfactant is added to a dispersion in which a pigment having a cationic group on its surface is dispersed in water. A part of the added anionic polymerizable surfactant is adsorbed on the cationic group of the “pigment having a cationic group on the surface” and is ionically bound to be immobilized.

  Addition of the anionic polymerizable surfactant to the pigment having the cationic group on the surface when the anionic polymerizable surfactant is added to the aqueous dispersion of pigment particles having the cationic group on the surface The amount is 0 based on the total number of moles of the cationic group relative to the amount of the pigment having a cationic group on the surface (= weight of the pigment used (g) × anionic group on the pigment surface (mol / g)). The range of 0.5 to 2 times mol is preferable, and the range of 0.8 to 1.2 times mol is more preferable. By setting the addition amount to 0.5 times mole or more, the pigment particles having a cationic group are strongly ionically bound and can be easily encapsulated. By setting the addition amount to 2 times or less, the generation of an anionic polymerizable surfactant not adsorbed on the pigment particles can be reduced.

(2) Next, a polymerization initiator is added and polymerized in water. Specifically, emulsion polymerization is performed.
As such a polymerization initiator, a water-soluble polymerization initiator is preferable, and potassium persulfate, ammonium persulfate, sodium persulfate, 2,2-azobis- (2-methylpropionamidine) dihydrochloride, or 4,4 -Azobis- (4-cyanovaleric acid) and the like.
The addition of the polymerization initiator can be suitably carried out by dropping an aqueous solution in which a water-soluble polymerization initiator is dissolved in pure water.

The polymerization initiator is preferably added in an activated state.
The activation of the polymerization initiator can be preferably carried out by raising the temperature of the aqueous dispersion to a predetermined polymerization temperature.
The polymerization reaction preferably uses a reaction vessel equipped with an ultrasonic generator, a stirrer, a reflux condenser, a dropping funnel and a temperature controller.

  After completion of the polymerization, it is preferable to adjust the pH within the range of 7.0 to 9.0 and perform filtration. Here, as described above, the aqueous solvent is a solvent containing water as a main component. In addition to water, the aqueous solvent includes, as an optional component, for example, a water-soluble solvent such as glycerin or glycol. May be. The polymerization temperature is preferably in the range of 60 ° C to 90 ° C. In addition, when the pigment particles having a cationic group as a hydrophilic group on the surface are not in the state of an aqueous dispersion, as a pretreatment, a dispersion treatment is performed using a general disperser such as a ball mill, a roll mill, an Eiger mill, or a jet mill. It is preferable to carry out.

In the microencapsulated pigment obtained as described above, pigment particles having a small average particle diameter are completely covered with a polymer layer (no defect portion).
By the above procedure, a microencapsulated pigment coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant can be suitably produced.
Other comonomer may be added for the purpose of improving the fixing property of the toner particles and improving the storage stability of the microencapsulated pigment.

  In addition, an anionic polymerizable surfactant and a hydrophobic monomer may be present in the aqueous dispersion as necessary during the polymerization. In this case, the polymer layer has an anionic polymerizable surfactant. It becomes a copolymer layer copolymerized from the agent and the hydrophobic monomer. That is, the microencapsulated pigment has a repeating structure in which pigment particles having a cationic group are derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group and a hydrophobic monomer. It is coated with a polymer (copolymer) having structural units.

  In such a microencapsulated pigment, the anionic polymerizable surfactant is added to an aqueous dispersion of pigment particles having a cationic group on the surface and mixed, and then a hydrophobic monomer and an anionic polymerizable surfactant are added. In addition, after emulsification, it can be suitably produced by adding a polymerization initiator and emulsion polymerization. Thereby, a more durable colorant can be manufactured. As a result, unintentional peeling of the polymer covering the pigment can be effectively prevented when the toner is manufactured. Moreover, the affinity with the resin is improved, and the dispersibility in the resin can be further increased.

The hydrophobic monomer has at least a hydrophobic group and a polymerizable group in its structure, and the hydrophobic group is selected from the group consisting of an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Can be illustrated. Examples of the aliphatic hydrocarbon group include a methyl group, an ethyl group, and a propyl group. Examples of the alicyclic hydrocarbon group include a cyclohexyl group, a dicyclopentenyl group, a dicyclopentanyl group, and an isobornyl group, and an aromatic hydrocarbon group. Examples thereof include a benzyl group, a phenyl group, and a naphthyl group.
The polymerizable group is an unsaturated hydrocarbon group capable of radical polymerization, and is preferably selected from the group consisting of a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. .

  Specific examples of the hydrophobic monomer include styrene and methylstyrene, dimethylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, p-chloromethylstyrene, divinylbenzene, and other styrene derivatives; methyl acrylate, ethyl acrylate, acrylic acid n-butyl, butoxyethyl acrylate, benzyl acrylate, phenyl acrylate, phenoxyethyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicyclopentenyl acrylate, dicyclopentenyloxyethyl acrylate, tetrahydrofurfuryl acrylate, isobol Monofunctional acrylic esters such as nyl acrylate; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate Butoxymethyl methacrylate, benzyl methacrylate, phenyl methacrylate, phenoxyethyl methacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate, dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate, tetrahydrofurfuryl methacrylate, isobornyl methacrylate, etc. Monofunctional methacrylate esters of allyl compounds such as allylbenzene, allyl-3-cyclohexanepropionate, 1-allyl-3,4-dimethoxybenzene, allylphenoxyacetate, allylphenylacetate, allylcyclohexane, allyl polycarboxylic acid allyl, etc. ; Ester cheeks of fumaric acid, maleic acid, itaconic acid; radically polymerizable groups such as N-substituted maleimides and cyclic olefins Monomer, and the like that. As the hydrophobic monomer, those satisfying the above-mentioned required characteristics are appropriately selected, and the addition amount thereof is arbitrarily determined.

The amount of the hydrophobic monomer added is preferably in the range of about 5 to 900 parts by weight, more preferably in the range of 10 to 500 parts by weight, and particularly preferably 15 to 200 parts by weight with respect to 100 parts by weight of the pigment. It is a range. The amount of the anionic polymerizable surfactant that forms the outermost shell of the capsule is preferably in the range of about 0.5 to 5 times the mole of the anionic polymerizable surfactant added first, more preferably 1-2. The range is about a double mole. By setting it in the range of 1 mol or more, the dispersibility and dispersion stability of the encapsulated particles are excellent. Since the addition amount of 2 mol or less can suppress the generation of an anionic polymerizable surfactant that does not contribute to encapsulation, the generation of polymer particles in addition to the encapsulated particles can be prevented.
The polymer that coats the pigment particles also preferably has a repeating structural unit derived from a crosslinkable monomer.
By having a repeating structural unit derived from a crosslinkable monomer, a crosslinked structure is formed in the polymer, and the durability of the polymer can be improved.

Examples of the crosslinkable monomer include compounds having two or more unsaturated hydrocarbon groups selected from vinyl group, allyl group, acryloyl group, methacryloyl group, propenyl group, vinylidene group, and vinylene group. , Ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol diacrylate, allyl acrylate, bis (acryloxyethyl) hydroxyethyl isocyanurate, bis (acryloxy neopentyl glycol) adipate 1,3-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, propylene glycol diacrylate Rate, polypropylene glycol diacrylate, 2-hydroxy-1,3-diaacryloxypropane, 2,2-bis [4- (acryloxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy) phenyl] propane 2,2-bis [4- (acryloxyethoxy diethoxy) phenyl] propane, 2,2-bis [4- (acryloxyethoxy polyethoxy) phenyl] propane, hydroxypentylglycol diacrylate, 1 , 4-butanediol diacrylate, dicyclopentanyl diacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, ditrimethylolpropane tetraacrylate, pentaerythritol triacrylate , Tetrabromopisphenol A diacrylate, triglycerol diacrylate, trimethylolpropane triacrylate, tris (acryloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate Methacrylate, polyethylene glycol dimethacrylate, propylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate 2-hydroxy-1,3-dimethacryloxypropane, 2,2 -Bis [41- (methacryloxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxy) phenyl] propane, 2,2-bis [4- (methacryloxyethoxydiethoxy) phenyl] propane, 2, 2-bis [4- (methacryloxyethoxypolyethoxy) phenyl] propane, tetrabromobisphenol A dimethacrylate, dicyclopentanyl dimethacrylate, dipentaerythritol hexamethacrylate, glycerol dimethacrylate, hydroxypentylglycol dipentaglycol dimethacrylate Dipentaerythritol monohydroxypentamethacrylate, ditrimethylolpropane tetramethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, Rig Lise over roll dimethacrylate, trimethylolpropane trimethacrylate, tris (methacryloxyethyl) isocyanurate, allyl methacrylate, divinylbenzene, diallyl phthalate, diallyl terephthalate, diallyl isophthalate, diethylene glycol bis allyl carbonate.
Moreover, it is preferable that the polymer which coat | covers a pigment particle further has the repeating structural unit induced | guided | derived from the monomer represented by following General formula (1).

The R ² group, which is a “bulky” group derived from the monomer represented by the general formula (1) in the polymer, reduces the flexibility of the polymer molecule, that is, restricts the mobility of the molecule. The mechanical strength and heat resistance of the polymer are improved.
In the general formula (1), examples of the alicyclic hydrocarbon group represented by R ² include a cycloalkyl group, a cycloalkenyl group, a benzyl group, a phenyl group, an isobornyl group, a dicyclopentanyl group, a dicyclopentenyl group, and an adamantane. Group, tetrahydrofuran group, naphthyl group, t-butyl group, and the like.

As described above, a polymer having a repeating structural unit derived from a crosslinkable monomer and a polymer having a repeating structural unit derived from the monomer represented by the general formula (1) have high Tg, mechanical strength, and heat resistance. There is an advantage that it is excellent in durability such as resistance and solvent resistance.
Moreover, the following are mentioned as a specific example of the monomer represented by the said General formula (1).

  Moreover, the following hydrophilic monomers can be used with an anionic polymerizable surfactant. As such a hydrophilic monomer, for example, a hydrophilic monomer having an anionic group as a hydrophilic group can be used. In this case, the polymer layer can be a copolymer layer copolymerized from an anionic polymerizable surfactant and / or a hydrophilic monomer having an anionic group and a comonomer.

Preferable specific examples of the hydrophilic monomer having an anionic group include, for example, methacrylic acid, acrylic acid, phosphoric acid group-containing (meth) acrylate, sodium vinyl sulfonate, 2-sulfoethyl methacrylate, 2-acrylamido-2-methyl. And propanesulfonic acid.
Moreover, you may use hydrophilic monomers other than the hydrophilic monomer which has an anionic group. Examples of the hydrophilic monomer other than the hydrophilic monomer having an anionic group include those having a hydroxyl group, an ethylene oxide group, an amide group, or an amino group as the hydrophilic group.

  Specific examples of the hydrophilic monomer include 2-hydroxyethyl methacrylate having an OH group, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and the like, ethyldiethylene glycol acrylate having an ethylene oxide group, polyethylene glycol monomethacrylate, Methoxypolyethylene glycol methacrylate, amide group-containing acrylamide, N, N-dimethylacrylamide, etc., amino group-containing N-methylaminoethyl methacrylate, N-methylaminoethyl acrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl Alkylamines of acrylic acid or methacrylic acid such as methacrylate and diethylaminoethyl methacrylate Esters: N- (2-dimethylaminoethyl) acrylamide, N- (2-dimethylaminoethyl) methacrylamide, N, N-dimethylaminopropylacrylamide, and other unsaturated amides having an alkylamino group, and vinyl Examples thereof include monovinyl pyridines such as pyridine, vinyl ethers having an alkylamino group such as dimethylaminoethyl vinyl ether; vinyl imidazole, N-vinyl-2-pyrrolidone and the like.

  The microencapsulated pigment is produced by adding the anionic polymerizable surfactant to an aqueous dispersion of pigment particles having a cationic group as a hydrophilic group on the surface, and water or water and aqueous as necessary. After adding a solvent and mixing and irradiating ultrasonic waves for a predetermined time, the anionic polymerizable surfactant and / or the hydrophilic monomer (in addition to the above-mentioned hydrophobic monomer, crosslinkable monomer, general formula (1 The monomer represented by) can also be added.) If necessary, water is added and dispersed again by irradiating with ultrasonic waves for a predetermined time, and at a predetermined temperature (polymerization initiator) while performing ultrasonic irradiation and stirring. The temperature can be suitably increased by adding the polymerization initiator to activate the polymerization initiator and emulsion polymerization.

  When the hydrophobic monomer is used, more specifically, an anionic polymerizable property having an anionic group, a hydrophobic group, and a polymerizable group in an aqueous dispersion of pigment particles having the cationic group on the surface. An anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group, a step of adding and mixing a surfactant and irradiating with ultrasonic waves, a step of adding and mixing a hydrophobic monomer, and an anionic group, a hydrophobic group and a polymerizable group It comprises a step of adding and mixing an agent and / or a hydrophilic monomer and irradiating with ultrasonic waves, and a step of emulsion polymerization by adding a polymerization initiator, and it is more preferably produced by carrying out in the order of the steps described above. Can do.

  In the case of using the crosslinkable monomer and / or the monomer represented by the general formula (1), more specifically, an anionic group is added to the aqueous dispersion of pigment particles having the cationic group on the surface. And a step of adding an anionic polymerizable surfactant having a hydrophobic group and a polymerizable group, mixing and irradiating with ultrasonic waves, a crosslinkable monomer and / or the general formula (1) A step of adding and mixing the monomer, a step of adding and mixing the anionic polymerizable surfactant and / or the hydrophilic monomer and irradiating with ultrasonic waves, and a step of emulsion polymerization by adding a polymerization initiator It can comprise more suitably by implementing in order of the said process.

  Further, when the crosslinkable monomer and / or the monomer represented by the general formula (1) is used, more specifically, an anionic group is added to the aqueous dispersion of pigment particles having the cationic group on the surface. And a step of adding an anionic polymerizable surfactant having a hydrophobic group and a polymerizable group, mixing and irradiating with ultrasonic waves, a crosslinkable monomer and / or the general formula (1) A step of adding and mixing a monomer and a monomer having a long-chain alkyl group, a step of adding and mixing an anionic polymerizable surfactant and / or the hydrophilic monomer and irradiating with ultrasonic waves, and a polymerization initiator It can be more suitably manufactured by carrying out the emulsion polymerization step and adding the step.

As described above, first, an anionic polymerizable surfactant is adsorbed to the cationic group on the surface of the pigment particle having a cationic group on the surface, and then a hydrophobic monomer is added, and then the anionic polymerizable surfactant and / or Alternatively, by adding a hydrophilic monomer and irradiating with ultrasonic waves, the arrangement of the polymerizable surfactant and monomer present around the pigment particles is extremely highly controlled. Then, by emulsion polymerization, the monomer is converted into a polymer in this highly controlled form, and the microencapsulated pigment according to this embodiment is obtained. Thereby, the production | generation of the water-soluble oligomer and polymer which are a by-product can be reduced.
In the microencapsulated pigment obtained as described above, pigment particles having a small average particle diameter are completely covered with a polymer layer (no defect portion).

Next, another dispersion state in which pigment particles can occur in the preferred method for producing a microencapsulated pigment described above will be described with reference to FIG. The anionic group 11 of the anionic polymerizable surfactant 2 having an anionic group 11, a hydrophobic group 12 and a polymerizable group 13 is added to the pigment particle 1 having a cationic group 14 on the surface as a hydrophilic group. It arrange | positions so that it may face 1 cationic group 14, and it adsorb | sucks by a strong ionic bond. Further, the surface of the pigment particle 1 has a cationic group 14 chemically bonded at a specific density, and has a hydrophobic region between the cationic groups 14, and an anionic polymerizable surfactant in the hydrophobic region. The anionic group of another anionic polymerizable surfactant 2 is arranged on the anionic group 11 of the anionic polymerizable surfactant 2. .
In this state, for example, a polymerization initiator is added to polymerize the polymerizable groups 13 of the adjacent anionic polymerizable surfactants 2, whereby the pigment particles 1 become polymer layers 60 as shown in FIG. A microencapsulated pigment 101 coated with 'is produced.

3. Other Components The toner may contain components other than those described above. Examples of such components include waxes, charge control agents, magnetic powders, and the like.
Examples of the wax include hydrocarbon waxes such as ozokerite, cercin, paraffin wax, microwax, microcrystalline wax, petrolatum, Fischer-Tropsch wax, carnauba wax, rice wax, methyl laurate, methyl myristate, palmitic acid. Methyl, methyl stearate, butyl stearate, candelilla wax, cotton wax, wood wax, beeswax, lanolin, montan wax, fatty acid ester ester wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, oxidized polypropylene wax Olefin waxes such as 12-hydroxy stearamide, stearamide, phthalic anhydride amide wax, Lauro , Ketone waxes such as stearone, ether waxes, and the like, can be used singly or in combination of two or more of them.

Examples of the charge control agent include benzoic acid metal salts, salicylic acid metal salts, alkylsalicylic acid metal salts, stearic acid metal salts, catechol metal salts, metal-containing bisazo dyes, nigrosine dyes, tetraphenylborate derivatives, fourth Examples include quaternary ammonium salts, alkylpyridinium salts, chlorinated polyesters, and nitrofunnic acid.
Examples of the magnetic powder include magnetite, maghemite, various ferrites, cupric oxide, nickel oxide, zinc oxide, zirconium oxide, titanium oxide, magnesium oxide, and other metal oxides, and magnetic materials such as Fe, Co, and Ni. The thing etc. which were comprised with the magnetic material containing a metal are mentioned.

In addition to the above materials, the toner may contain, for example, zinc stearate, zinc oxide, cerium oxide, silica, titanium oxide, iron oxide, fatty acid, fatty acid metal salt, and the like.
The other components described above may be contained in the liquid developer. For example, the other components may be contained in the toner particles or in the insulating liquid.

<Method for producing liquid developer>
Next, a preferred embodiment of the method for producing a liquid developer of the present invention will be described.
FIG. 5 is a longitudinal sectional view schematically showing an example of the configuration of a kneader and a cooler for producing a kneaded product.
In the following description, a case where a liquid developer is produced using a kneaded material K7 containing a colorant and a resin material will be described.

Since the colorant (microencapsulated pigment) used in the present invention has a high affinity with the resin material and a high dispersibility in the resin, it can be easily and uniformly dispersed in the kneaded product. Therefore, the liquid developer produced using the kneaded product has a small variation in characteristics among the toner particles.
The kneaded material K7 can be manufactured using, for example, an apparatus as shown in FIG.

(Kneading process)
The raw material K5 used for kneading contains the components as described above. In particular, in a composition containing a colorant, since the colorant easily embeds air, air tends to remain in the composition. However, by kneading in this step, In particular, air entrained by the colorant can be efficiently removed, and bubbles can be effectively prevented from being mixed (remaining) inside the toner particles.

The raw material K5 used for kneading is preferably a mixture of these components.
This embodiment demonstrates the structure which uses a biaxial kneading extruder as a kneading machine.
The kneading machine K1 includes a process part K2 for kneading while conveying the raw material K5, a head part K3 for extruding the kneaded raw material (kneaded material K7) into a predetermined cross-sectional shape, and a raw material K5 in the process part K2. And a feeder K4 to be supplied.

The process part K2 includes a barrel K21, a screw K22 and a screw K23 inserted into the barrel K21, and a fixing member K24 for fixing the head part K3 to the tip of the barrel K21.
In the process part K2, when the screw K22 and the screw K23 rotate, a shearing force is applied to the raw material K5 supplied from the feeder K4, and a uniform kneaded material K7 is obtained.

  The total length of the process part K2 is preferably 50 to 300 cm, and more preferably 100 to 250 cm. If the total length of the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the total length of the process part K2 exceeds the upper limit, depending on the temperature in the process part K2, the number of rotations of the screw K22, the screw K23, and the like, the material K5 is easily denatured by heat, and finally obtained. It may be difficult to sufficiently control the physical properties of the liquid developer (toner).

  Moreover, although the raw material temperature at the time of kneading | mixes changes with compositions etc. of the raw material K5, it is preferable that it is 80-260 degreeC, and it is more preferable that it is 90-230 degreeC. Note that the raw material temperature in the process part K2 may be uniform or may vary depending on the part. For example, the process unit K2 includes a first region having a relatively low set temperature and a second region that is provided on the base end side from the first region and whose set temperature is higher than the first region. You may have.

  In addition, the residence time (time required for passage) of the raw material K5 in the process part K2 is preferably 0.5 to 12 minutes, and more preferably 1 to 7 minutes. If the residence time in the process part K2 is less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, if the residence time in the process part K2 exceeds the upper limit, the production efficiency is reduced. Depending on the temperature in the process part K2, the rotational speed of the screw K22, the screw K23, etc., the heat of the raw material K5 Modification is likely to occur, and it may be difficult to sufficiently control the physical properties of the finally obtained liquid developer (toner).

  The number of rotations of the screw K22 and the screw K23 varies depending on the composition of the binder resin and the like, but is preferably 50 to 600 rpm. If the rotational speeds of the screws K22 and K23 are less than the lower limit, it may be difficult to mix the components in the raw material K5 sufficiently uniformly. On the other hand, when the rotation speed of the screw K22 and the screw K23 exceeds the upper limit value, the molecular chain of the resin may be cut by shearing, and the resin characteristics may be deteriorated.

  Further, in the kneader K1 used in the present embodiment, the inside of the process unit K2 is connected to the pump P via the deaeration port K25. Thereby, the inside of the process part K2 can be degassed, and an increase in the pressure in the process part K2 due to heating or heat generation of the raw material K5 (kneaded material K7) can be prevented. As a result, the kneading process can be performed safely and efficiently. Further, since the inside of the process part K2 is connected to the pump P via the deaeration port K25, it is possible to effectively prevent bubbles (particularly relatively large bubbles) from being contained in the obtained kneaded material K7. And the properties of the liquid developer (toner) finally obtained can be made more excellent.

(Extrusion process)
The kneaded material K7 kneaded in the process part K2 is pushed out of the kneader K1 through the head part K3 by the rotation of the screw K22 and the screw K23.
The head part K3 has an internal space K31 into which the kneaded material K7 is fed from the process part K2, and an extrusion port K32 from which the kneaded material K7 is extruded.

  The temperature of the kneaded material K7 in the internal space K31 (at least in the vicinity of the extrusion port K32) is not particularly limited, but is preferably a temperature equal to or higher than the softening temperature of the resin material contained in the raw material K5. As a result, the toner particles can be obtained as a mixture of the constituent components more uniformly, and variations in characteristics (charging characteristics, fixing properties, etc.) among the toner particles can be particularly reduced.

The specific temperature of the kneaded material K7 in the internal space K31 (at least the temperature near the extrusion port K32) is not particularly limited, but is preferably 80 to 150 ° C, more preferably 90 to 140 ° C. preferable. When the temperature of the kneaded material K7 in the internal space K31 is a value within the above range, the kneaded material K7 does not solidify in the internal space K31 and is easily extruded from the extrusion port K32.
In the illustrated configuration, the internal space K31 has a cross-sectional area gradually decreasing portion K33 in which the cross-sectional area gradually decreases in the direction of the extrusion port K32. By having such a cross-sectional area gradually decreasing portion K33, the extrusion amount of the kneaded material K7 extruded from the extrusion port K32 is stabilized, and the cooling rate of the kneaded material K7 in the cooling step described later is stabilized. As a result, the toner produced using the toner has a small variation in characteristics among the toner particles, and has excellent overall characteristics.

(Cooling process)
The softened kneaded material K7 extruded from the extrusion port K32 of the head portion K3 is cooled and solidified by the cooler K6.
The cooler K6 includes rolls K61, K62, K63, and K64, and belts K65 and K66.

The belt K65 is wound around a roll K61 and a roll K62. Similarly, the belt K66 is wound around the roll K63 and the roll K64.
The rolls K61, K62, K63, and K64 rotate around the rotation axes K611, K621, K631, and K641 in the directions indicated by e, f, g, and h in the drawing. Thereby, the kneaded material K7 extruded from the extrusion port K32 of the kneading machine K1 is introduced between the belt K65 and the belt K66. The kneaded material K7 introduced between the belt K65 and the belt K66 is cooled while being formed into a plate shape having a substantially uniform thickness. The cooled kneaded material K7 is discharged from the discharge portion K67. The belts K65 and K66 are cooled by a method such as water cooling or air cooling. When such a belt type is used as the cooler, the contact time between the kneaded product extruded from the kneader and the cooling body (belt) can be increased, and the cooling efficiency of the kneaded product is particularly excellent. Can be.

  By the way, in the kneading process, since shearing force is applied to the raw material K5, phase separation (particularly macrophase separation) is sufficiently prevented, but the kneaded product K7 that has finished the kneading process is not subjected to shearing force. Therefore, depending on the constituent materials of the kneaded product, phase separation (macrophase separation) or the like may occur again if left for a long period of time. Therefore, it is preferable to cool the kneaded material K7 obtained as described above as soon as possible. Specifically, the cooling rate of the kneaded material K7 (for example, the cooling rate when the kneaded material K7 is cooled to about 60 ° C.) is preferably 3 ° C./second or more, and is preferably 5-100 ° C./second. Is more preferable. Further, the time required from the end of the kneading step (when the shearing force is no longer applied) to the completion of the cooling step (for example, the time required for cooling the temperature of the kneaded product K7 to 60 ° C. or lower) is 20 seconds. Or less, more preferably 3 to 12 seconds.

In the present embodiment, the configuration using a continuous biaxial kneading extruder as the kneading machine has been described, but the kneading machine used for kneading the raw materials is not limited to this. For kneading the raw materials, for example, various kneaders such as a kneader, a batch type triaxial roll, a continuous biaxial roll, a wheel mixer, and a blade type mixer can be used.
In the illustrated configuration, a kneader having two screws has been described. However, the number of screws may be one or three or more. Further, the kneading apparatus may have a disc (kneading disc) portion.

Further, in the present embodiment, the configuration using one kneader has been described, but kneading may be performed using two kneaders. In this case, the heating temperature of the raw material, the rotational speed of the screw, and the like may be different between one kneader and the other kneader.
In the present embodiment, a configuration using a belt type as the cooler has been described. However, for example, a roll type (cooling roll type) cooler may be used. Further, the cooling of the kneaded product extruded from the extrusion port K32 of the kneader is not limited to the one using the above-described cooler, and may be performed by, for example, air cooling.

(Coarse grinding process)
Next, the kneaded material K7 that has undergone the cooling step as described above is roughly pulverized to obtain a coarsely pulverized material.
The method of coarse pulverization is not particularly limited, and can be performed using, for example, various pulverizers and crushers such as a ball mill, a vibration mill, a jet mill, and a pin mill.
The coarse pulverization step may be performed in multiple steps.

(Wet grinding process)
The coarsely pulverized product obtained as described above is put into an insulating liquid as described above and wet pulverized.
By the way, since the colorant conventionally used has low affinity with the resin, it is difficult to remove the main pulverized product and obtain a sufficiently uniform liquid developer during such a pulverization step. However, by using the microencapsulated pigment as described above, such falling off can be prevented, and the variation in the content of the colorant among the toner particles can be reduced. A uniform liquid developer can be obtained.
The wet pulverization method is not particularly limited, and can be performed using various pulverization apparatuses such as a ball mill, a vibration mill, a jet mill, and a pin mill, and a crushing apparatus.
The wet pulverization step may be performed in multiple steps.

  For the purpose of improving the dispersibility of the coarsely pulverized product, a dispersant (surfactant) may be previously dispersed in the insulating liquid. Examples of the surfactant include inorganic mineral dispersants such as viscosity minerals, silica and tricalcium phosphate, nonionic organic dispersants such as polyvinyl alcohol, carboxymethyl cellulose, and polyethylene glycol, and tristearic acid metal salts (for example, aluminum salts). Etc.), distearic acid metal salts (eg, aluminum salts, barium salts, etc.), stearic acid metal salts (eg, calcium salts, lead salts, zinc salts, etc.), linolenic acid metal salts (eg, cobalt salts, manganese salts, lead) Salts, zinc salts, etc.), octanoic acid metal salts (eg, aluminum salts, calcium salts, cobalt salts, etc.), oleic acid metal salts (eg, calcium salts, cobalt salts, etc.), palmitic acid metal salts (eg, zinc salts, etc.) ), Metal salt of dodecylbenzenesulfonic acid (for example, sodium salt), metal salt of naphthenic acid ( For example, calcium salt, cobalt salt, manganese salt, lead salt, zinc salt, etc.), resinate metal salt (eg, calcium salt, cobalt salt, manganese lead salt, zinc salt etc.), polyacrylic acid metal salt (eg, sodium salt) Salt), polymethacrylic acid metal salt (for example, sodium salt), polymaleic acid metal salt (for example, sodium salt), acrylic acid-maleic acid copolymer metal salt (for example, sodium salt), polystyrene sulfonic acid Anionic organic dispersants such as metal salts (for example, sodium salts) and the like, and cationic organic dispersants such as quaternary ammonium salts and the like.

<Liquid developer>
The average particle size of the toner particles in the liquid developer obtained as described above is preferably 0.1 to 5 μm, more preferably 0.4 to 4 μm, and 0.5 to 3 μm. Is more preferable. When the average particle diameter of the toner particles is within the above range, the dispersion of characteristics such as charging characteristics and fixing characteristics among the toner particles is particularly small, and the reliability of the entire liquid developer is particularly high. In addition, the resolution of the image formed by the liquid developer (toner) can be made sufficiently high.

The standard deviation of the particle size between toner particles constituting the liquid developer is preferably 3.0 μm or less, more preferably 0.1 to 2.0 μm, and 0.1 to 1. More preferably, it is 0 μm. As a result, variations in characteristics such as charging characteristics and fixing characteristics among the toner particles are particularly reduced, and the reliability of the entire liquid developer is further improved.
Further, the average value (average circularity) of the circularity R represented by the following formula (I) for the toner particles constituting the liquid developer is preferably 0.85 or more, and 0.90 to 0.00. 99 is more preferable, and 0.95-0.99 is even more preferable.

R = L ₀ / L ₁ (I)
(Where L ₁ [μm] is the circumference of the projected image of the toner particles to be measured, and L ₀ [μm] is the circumference of a perfect circle having an area equal to the area of the projected image of the toner particles to be measured. Represents length)
Thereby, the transfer efficiency and mechanical strength of the toner particles can be made particularly excellent while the particle diameter of the toner particles is sufficiently small.
The standard deviation of the average circularity between the toner particles constituting the liquid developer is preferably 0.15 or less, more preferably 0.001 to 0.10, and 0.001 to 0. More preferably, .05. As a result, variations in characteristics such as charging characteristics and fixing characteristics among the toner particles are particularly reduced, and the reliability of the entire liquid developer is further improved.

Next, a preferred embodiment of the image forming apparatus to which the liquid developer of the present invention as described above is applied will be described.
FIG. 6 shows an example of a contact-type image forming apparatus to which the liquid developer of the present invention is applied. The image forming apparatus P1 includes a drum of a cylindrical photosensitive member P2, and after the surface is uniformly charged by a charger P3 made of epichlorohydrin rubber or the like, information to be recorded by a laser diode or the like In accordance with the exposure P4, an electrostatic latent image is formed.

  The developing device P10 includes a coating roller P12 and a developing roller P13, part of which is immersed in a developer container P11. The application roller P12 is, for example, a metal gravure roller such as stainless steel, and rotates to face the developing roller P13. Further, a liquid developer coating layer P14 is formed on the surface of the coating roller P12, and the thickness thereof is kept constant by the metering blade P15.

  Then, the liquid developer is transferred from the coating roller P12 to the developing roller P13. The developing roller P13 has a low hardness silicone rubber layer on a roller core P16 made of metal such as stainless steel, and a conductive PFA (polytetrafluoroethylene-perfluorovinyl ether copolymer) resin on the surface thereof. A layer is formed, and rotates at the same speed as the photosensitive member P2 to transfer the liquid developer to the latent image portion. The liquid developer remaining on the developing roller P13 after being transferred to the photoreceptor P2 is removed by the developing roller cleaning blade P17 and collected in the developer container P11.

Further, after the transfer of the toner image from the photoconductor to the intermediate transfer roller, the photoconductor is neutralized by the neutralizing light P21, and the residual transfer toner remaining on the photoconductor is a cleaning made of urethane rubber or the like. It is removed by the blade P22.
Similarly, residual toner remaining on the intermediate transfer roller P18 after transfer from the intermediate transfer roller P18 to the information recording medium P20 is removed by a cleaning blade P23 made of urethane rubber or the like.
After the toner image formed on the photoreceptor P2 is transferred to the intermediate transfer roller P18, a transfer current is passed through the secondary transfer roller P19, and the information recording medium P20 such as paper passing between the two. The toner image on the information recording medium P20 such as paper is fixed using the fixing device shown in FIG.

  FIG. 7 shows an example of a non-contact type image forming apparatus to which the liquid developer of the present invention is applied. In the non-contact method, the developing roller P13 is provided with a charging blade P24 made of a phosphor bronze plate having a thickness of 0.5 mm. The charging blade P24 has a function of making frictional charging in contact with the liquid developer layer, and since the application roller P12 is a gravure roll, a developer layer corresponding to the unevenness of the surface of the gravure roll is formed on the development roller P13. Therefore, it functions to uniformly level the unevenness, and the arrangement direction may be either the counter direction or the trail direction with respect to the rotation direction of the developing roller, and may be a roller shape instead of a brate shape.

Further, an interval of 200 μm to 800 μm is provided between the developing roller P13 and the photosensitive member P2, and a frequency of 500 to 3000 Vpp superimposed on a direct current voltage of 200 to 800 V is applied between the developing roller P13 and the photosensitive member P2. An AC voltage of 50 to 3000 Hz is preferably applied. The rest is the same as the image forming apparatus described with reference to FIG.
In FIGS. 6 and 7, the image formation using one color liquid developer has been described. However, in the case of forming an image using a plurality of color toners, each color image is formed using a plurality of color developers. Thus, a color image can be formed.

FIG. 8 is a cross-sectional view of the fixing device. F1 is a heat fixing roll, F1a is a columnar halogen lamp, F1b is a roll base, F1c is an elastic body, F2 is a pressure roll, F2a is a rotating shaft, and F2b is a roll base. F2c is an elastic body, F3 is a heat-resistant belt, F4 is a belt stretching member, F4a is a protruding wall, F5 is a sheet material, F5a is an unfixed toner image, F6 is a cleaning member, F7 is a frame, F9 is a spring, L is It is a pressing part tangent.
As shown in the figure, the fixing device F40 includes a heat fixing roll (hereinafter also referred to as a heating roll) F1, a pressure roll F2, a heat-resistant belt F3, a belt stretching member F4, and a cleaning member F6.

  The heat fixing roll F1 is formed by covering a pipe member having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm with a roll base material F1b and an elastic body F1c having a thickness of about 0.4 mm on the outer periphery thereof. 1,050W as a heat source and two columnar halogen lamps F1a are built in and can be rotated counterclockwise as indicated by an arrow in the figure. Further, the pressure roll F2 has a pipe material having an outer diameter of about 25 mm and a wall thickness of about 0.7 mm as a roll base material F2b with a thickness of 0. The elastic body F2c having a thickness of about 2 mm is formed so as to cover the heat fixing roll F1 and the pressure roll F2 with a pressure contact force of 10 kg or less, a nip length of about 10 mm, and disposed opposite the heat fixing roll F1. It can be rotated in the clockwise direction indicated by an arrow.

  Thus, since the outer diameters of the heat fixing roll F1 and the pressure roll F2 are configured to be as small as about 25 mm, the sheet material F5 after fixing does not wrap around the heat fixing roll F1 or the heat-resistant belt F3. A means for forcibly removing the sheet material is not necessary. Further, by providing a PFA layer of about 30 μm on the surface layer of the elastic body F1c of the heat fixing roll F1, the rigidity is improved accordingly. Thereby, although the thicknesses of the elastic bodies F1c and 2c are different, the elastic bodies F1c and 2c are substantially uniformly elastically deformed to form a so-called horizontal nip, and with respect to the peripheral speed of the heat fixing roll F1. Since there is no difference in the conveyance speed of the heat-resistant belt F3 or the sheet material F5, extremely stable image fixing is possible.

  In addition, two columnar halogen lamps F1a and F1a constituting a heat source are built in the heat fixing roll F1, and the heating elements of these columnar halogen lamps F1a and F1a are arranged at different positions. Yes. Then, by selectively lighting each columnar halogen lamp F1a, F1a, a fixing nip portion where the heat-resistant belt F3 is wound around the heat fixing roll F1 and a portion where the belt stretching member F4 is in sliding contact with the heat fixing roll F1 are formed. Temperature control can be easily performed under different conditions or different conditions between a wide sheet material and a narrow sheet material.

  The heat-resistant belt F3 is an endless annular belt which is stretched around the outer periphery of the pressure roll F2 and the belt tension member F4 and is movable, and is sandwiched between the heat fixing roll F1 and the pressure roll F2. is there. The heat-resistant belt F3 has a thickness of 0.03 mm or more, and its front surface (the surface on which the sheet material F5 comes into contact) is formed of PFA, and the back surface (contacts with the pressure roll F2 and the belt stretching member F4). It is formed of a seamless tube having a two-layer structure in which the surface on the side to be formed is made of polyimide. The heat-resistant belt F3 is not limited to this, and can be formed of other materials such as a metal tube such as a stainless steel tube or a nickel electroformed tube, or a heat-resistant resin tube such as silicon.

  The belt stretching member F4 is disposed upstream of the fixing nip portion between the heat fixing roll F1 and the pressure roll F2 in the conveying direction of the sheet material F5, and has an arrow P around the rotation axis F2a of the pressure roll F2. It is arranged so that it can swing in the direction. The belt stretching member F4 is configured to stretch the heat-resistant belt F3 in the tangential direction of the heat fixing roll F1 in a state where the sheet material F5 does not pass through the fixing nip portion. If the fixing pressure is large at the initial position where the sheet material F5 enters the fixing nip portion, the entry may not be smoothly performed and the sheet material F5 may be fixed with the leading end of the sheet material F5 broken. By adopting a configuration in which F3 is stretched in the tangential direction of the heat fixing roll F1, an introduction port portion of the sheet material F5 through which the sheet material F5 smoothly enters can be formed, and to the stable fixing nip portion of the sheet material F5. Can enter.

  The belt stretching member F4 is inserted into the inner periphery of the heat-resistant belt F3 and cooperates with the pressure roll F2 to apply a tension f to the heat-resistant belt F3 (the heat-resistant belt F3 is a belt). Sliding on the tension member F4). The belt stretching member F4 is disposed at a position where the heat-resistant belt F3 is wound around the heat fixing roll F1 side from the pressing portion tangent L between the heat fixing roll F1 and the pressure roll F2 to form a nip. The protruding wall F4a protrudes from one end or both ends of the belt stretching member F4 in the axial direction. The protruding wall F4a is formed by the heat-resistant belt F3 when the heat-resistant belt F3 approaches one of the axial ends. The contact to the end of the heat-resistant belt F3 is regulated by contacting the wall F4a. A spring F9 is contracted between the end of the protruding wall F4a opposite to the heat fixing roll F1 and the frame, and the protruding wall F4a of the belt stretching member F4 is lightly pressed by the heat fixing roll F1, so that the belt tension is increased. The frame member F4 is positioned in sliding contact with the heat fixing roll F1.

  In order to stretch the heat-resistant belt F3 with the pressure roll F2 and the belt stretching member F4 and drive it stably with the pressure roll F2, the friction coefficient between the pressure roll F2 and the heat-resistant belt F3 is changed to the belt stretching member. It is good to set larger than the friction coefficient of F4 and heat-resistant belt F3. However, the friction coefficient is such that foreign matter enters between the heat-resistant belt F3 and the pressure roll F2 or between the heat-resistant belt F3 and the belt stretching member F4, or the heat-resistant belt F3, the pressure roll F2, and the belt stretching member. It may become unstable due to wear of the contact portion with F4.

  Therefore, the belt tension member F4 and the heat-resistant belt F3 have a winding angle smaller than the winding angle of the pressure roll F2 and the heat-resistant belt F3, and the diameter of the belt stretching member F4 is smaller than the diameter of the pressure roll F2. Set as follows. As a result, the length that the heat-resistant belt F3 slides on the belt stretching member F4 is shortened, which can be avoided from instability factors such as changes with time and disturbances, and the heat-resistant belt F3 is stably driven by the pressure roll F2. Will be able to.

  Further, a cleaning member F6 is disposed between the pressure roll F2 and the belt stretching member F4. The cleaning member F6 is in sliding contact with the inner peripheral surface of the heat-resistant belt F3, and foreign matter on the inner peripheral surface of the heat-resistant belt F3. It cleans and wear powder. By cleaning the foreign matter, wear powder, and the like in this way, the heat-resistant belt F3 is refreshed, and the above-described factor of instability of the friction coefficient is removed. Further, the belt tension member F4 is provided with a recess F4f, and the recess F4f is suitable for storing foreign matter, abrasion powder, and the like removed from the heat-resistant belt F3.

  The position where the belt tension member F4 is lightly pressed against the heat fixing roll F1 is the nip initial position, and the position where the pressure roll F2 is pressed against the heat fixing roll F1 is the nip end position. Then, the sheet material F5 enters the fixing nip portion from the initial nip position, passes between the heat-resistant belt F3 and the heat fixing roll F1, and exits from the nip end position, whereby an unfixed sheet formed on the sheet material F5. The toner image F5a is fixed, and then discharged in the tangential direction L of the pressing portion of the pressure roll F2 to the heat fixing roll F1.

As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to this.
For example, in the above-described embodiment, the liquid developer is obtained by wet pulverization. However, the present invention is not limited to this. For example, toner particles are manufactured by using an emulsion polymerization method, and this is used as an insulating liquid. It may be produced by dispersing in.

[1] Production of toner (Example 1)
<Manufacture of colorant (microencapsulated pigment)>
Prior to toner production, the following colorants were produced.
First, a carbon black pigment composed of pigment particles having a cationic group on the surface was prepared.

4 g of Aqualon KH-10 represented by the following general formula as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion obtained by dispersing 15 g of this carbon black pigment in 75 g of ion-exchanged water. Was irradiated for 15 minutes. Next, 2 g of anionic polymerizable surfactant Aqualon KH-10 and 20 g of ion-exchanged water were added and mixed, and then ultrasonic waves were irradiated again for 30 minutes. This was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After the internal temperature of the reaction vessel was raised to 80 ° C., an aqueous potassium persulfate solution in which 0.03 g of potassium persulfate was dissolved as a polymerization initiator was added dropwise to 10 g of ion-exchanged water. Polymerized for hours. After the polymerization is completed, the pH is adjusted to 8 and unreacted substances are removed by ultrafiltration. Then, coarse particles are removed by a membrane filter having a pore size of 1 μm to obtain a dispersion of the target microencapsulated pigment “AMP carbon black”. Obtained.
The volume average particle diameter of the obtained dispersion was measured using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 130 nm.
Thereafter, the dispersion was heated and dried under reduced pressure to obtain an AMP carbon black pigment.

<Manufacture of toner>
First, 70 parts by weight of a styrene acrylic copolymer (softening temperature T _f : 125.6 ° C.) as a binder resin and 30 parts by weight of an AMP carbon black pigment as a colorant were prepared.
These components were mixed using a 20 L type Henschel mixer to obtain a raw material for toner production.

Next, this raw material (mixture) was kneaded using a twin-screw kneading extruder as shown in FIG.
The total length of the process part of the biaxial kneading extruder was 160 cm.
Moreover, it set so that the temperature of the raw material in a process part might be 105-115 degreeC.
The screw rotation speed was 120 rpm, and the raw material charging speed was 20 kg / hour.
The time required for the raw material to pass through the process part, determined from such conditions, is about 4 minutes.

The kneading as described above was performed while degassing the inside of the process unit by operating a vacuum pump connected to the process unit via a degassing port.
The raw material (kneaded material) kneaded in the process part was extruded outside the biaxial kneading extruder through the head part. The temperature of the kneaded material in the head part was adjusted to 135 ° C.
Thus, the kneaded material extruded from the extrusion port of the biaxial kneading extruder was cooled using a cooling machine as shown in FIG. The temperature of the kneaded material immediately after the cooling step was about 45 ° C.
The cooling rate of the kneaded product was 9 ° C./second. In addition, the time required from the end of the kneading process to the end of the cooling process was 10 seconds.
The kneaded material cooled as described above was coarsely pulverized to obtain a powder having an average particle size of 1.0 mm or less (coarse pulverized product). A hammer mill was used for coarse pulverization of the kneaded product.

Next, the coarsely pulverized product obtained as described above: 100 parts by weight, soybean oil as an insulating liquid (trade name “soybean oil” manufactured by Kanto Chemical Co., Ltd.): 100 parts by weight, and surfactant Of polyoxyethylene alkyl ether: 2 parts by weight and aluminum stearate as a charge control agent: 1.5 parts by weight were prepared. The electrical resistance of the insulating liquid at room temperature (20 ° C.) was 5.2 × 10 ¹³ Ωcm, and the relative dielectric constant of the insulating liquid was 2.8.
These components were put into a ball mill and wet pulverized for 72 hours.
Thereafter, 300 parts by weight of soybean oil (manufactured by Kanto Chemical Co., Ltd., trade name “soybean oil”) was added and wet pulverized for 1 hour to obtain a liquid developer. The volume standard average particle size of the toner particles in the liquid developer was 1.2 μm.

(Example 2)
A toner was produced in the same manner as in Example 1 except that the colorant produced as described below was used, and dehydrated castor oil (made by Ito Oil Co., Ltd .: trade name “DOC”) was used as the insulating liquid. . The finally obtained toner had a weight-based average particle size of 1.2 μm.

<Manufacture of colorant (microencapsulated pigment)>
First, a magenta pigment (CI Pigment Red 122) composed of pigment particles having a cationic group on the surface was prepared.
4 g of Aqualon KH-10 as an anionic polymerizable surfactant was added to and mixed with an aqueous dispersion obtained by dispersing 15 g of this magenta pigment particle in 75 g of ion-exchanged water, and then irradiated with ultrasonic waves for 15 minutes. Next, 6 g of benzyl methacrylate, 4 g of dodecyl methacrylate, 2 g of anionic polymerizable surfactant Aqualon KH-10, 0.5 g of 2-acrylamido-2-methylpropanesulfonic acid and 50 g of ion-exchanged water as hydrophilic monomers were added. Then, the mixture was again irradiated with ultrasonic waves for 30 minutes. This was put into a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, a temperature controller, a nitrogen introduction tube and an ultrasonic generator. After the internal temperature of the reaction vessel was raised to 80 ° C., an aqueous potassium persulfate solution in which 0.4 g of potassium persulfate was dissolved as a polymerization initiator was added dropwise to 20 g of ion-exchanged water. Polymerized for hours. After the polymerization is completed, the pH is adjusted to 8, and unreacted substances are removed by ultrafiltration. Then, coarse particles are removed by a membrane filter having a pore size of 1 μm to obtain a dispersion of the target microencapsulated pigment “AMP magenta pigment”. Obtained.
The volume average particle diameter of the obtained dispersion was measured using a laser Doppler type particle size distribution analyzer Microtrac UPA150 manufactured by Leeds & Northrop Co. As a result, it was 130 nm.
Thereafter, the dispersion was heat-dried under reduced pressure to obtain an AMP magenta pigment.

(Comparative Example 1)
A liquid developer was produced in the same manner as in Example 1 except that a non-encapsulated pigment was used as the colorant.
(Comparative Example 2)
A liquid developer was produced in the same manner as in Example 2 except that a non-encapsulated pigment was used as the colorant.

[2] Evaluation Each liquid developer obtained as described above was evaluated for charging uniformity, fogging, and fixing strength.
[2.1] Uniformity of charging A glass electrode deposited on a parallel plate ITO film is immersed in the liquid developer obtained in each of the examples and comparative examples. The distance between the electrodes is 2.0 mm, the applied voltage is 200 V, and the voltage is applied for 10 hours. The toner adhesion amounts m1 [g / m ² ] and m2 [g / m ² ] per unit area on both electrode surfaces were measured under conditions of seconds. The uniformity was evaluated as (m1 / (m1 + m2)) × 100. The larger this value, the more uniform the chargeability.

[2.2] Cover evaluation A mending tape manufactured by Sumitomo 3M Co., Ltd. is affixed to plain paper manufactured by Fuji Xerox Office Supply Co., Ltd. (product name J). The color of this tape was measured with a color difference meter CR-221 manufactured by Minolta Co., Ltd., and this value was used as a reference value.
Using the image forming apparatus as shown in FIG. 6, the liquid developer to be evaluated was put in a developing machine, and the entire surface white (solid white) was printed. Stop the printer during printing, take out the photoconductor, and place the mending tape in the area between the point where the photoconductor and the intermediate transfer roller are in contact (transfer nip) and the point where the developing roller and photoconductor are close (development nip). Affixing and fogging toner were adhered, and this was affixed to J paper. The color difference between this tape and the reference value was measured. Note that the smaller the color difference, the less the fogging.

[2.3] Fixing Strength Using an image forming apparatus as shown in FIG. 6, images of a predetermined pattern using the liquid developer obtained in each of the above examples and each of the above comparative examples were printed on a recording paper manufactured by Seiko Epson Corporation. Paper LPCPPA4). Thereafter, the image formed on the recording paper was thermally fixed by an oven. This heat fixing was performed under the condition of 120 ° C. × 30 minutes.
Thereafter, after confirming the non-offset area, the fixed image on the recording paper is erased twice (rubber eraser “LION 261-11” manufactured by Lion Business Machine Co., Ltd.) with a pressing load kgf, and the residual ratio of the image density is X -Measured by "X-Rite model 404" manufactured by Rite Inc, and evaluated according to the following three-stage criteria.
○: Image density residual ratio is 90% or more.
Δ: Image density remaining ratio is 70% or more and less than 90%.
X: Image density residual ratio is less than 70%.
These results are shown in Table 1.

As is apparent from Table 1, all of the liquid developers of the present invention (Examples 1 and 2) were excellent in charging uniformity, fogging and fixing strength. On the other hand, all of the liquid developers of the comparative examples were inferior in charging uniformity, fogging, and fixing strength.
In each example and each comparative example, as a colorant, C.I. I. Pigment Blue 15: 3, copper phthalocyanine pigment, Pigment Red 57: 1, C.I. I. A liquid developer was prepared in the same manner except that Pigment Yellow 93 was microencapsulated, and each of these liquid developers was evaluated in the same manner as described above. As a result, the same results as those of the respective Examples and Comparative Examples were obtained.

It is a figure which shows the manufacturing process of the coloring agent applied to the liquid developer of this invention. It is a figure which shows an example of the microencapsulation pigment applied to the liquid developer of this invention. It is a figure which shows the manufacturing process of the coloring agent applied to the liquid developer of this invention. It is a figure which shows an example of the microencapsulation pigment applied to the liquid developer of this invention. It is a longitudinal cross-sectional view which shows typically an example of a structure of the kneading machine used for the manufacturing method of the liquid developer of this invention, and a cooler. 1 is a cross-sectional view illustrating an example of a contact-type image forming apparatus to which a liquid developer of the present invention is applied. 1 is a cross-sectional view illustrating an example of a non-contact type image forming apparatus to which a liquid developer of the present invention is applied. FIG. 3 is a cross-sectional view illustrating an example of a fixing device to which the liquid developer of the present invention is applied.

Explanation of symbols

K1 ... kneading machine K2 ... process part K21 ... barrel K22, K23 ... screw K24 ... fixing member K25 ... deaeration port K3 ... head part K31 ... internal space K32 ... extrusion port K33 ... cross-sectional area gradually decreasing part K4 ... feeder K5 ... raw material K6 ... Cooling machines K61, K62, K63, K64 ... Rolls K611, K621, K631, K641 ... Rotating shaft K65, K66 ... Belt K67 ... Discharge part K7 ... Kneaded material 1 ... Pigment particles 11 ... Anionic group 12 ... Hydrophobic group 13 ... polymerizable group 14 ... cationic group 2 ... anionic polymerizable surfactant 60 ... polymer layer 100, 101 ... microencapsulated pigment P1 ... image forming apparatus P2 ... photoconductor P3 ... charger P4 ... exposure P10 ... developer P11 ... developer container P12 ... coating roller P13 ... developing roller P14 ... liquid developer coating layer P1 ... Metering blade P16 ... Roller core P17 ... Development roller cleaning blade P18 ... Intermediate transfer roller P19 ... Secondary transfer roller P20 ... Information recording medium P21 ... Static elimination light P22 ... Cleaning blade P23 ... Cleaning blade P24 ... Charging blade F40 ... Fixing Apparatus F1 ... Heat fixing roll (heating roll) F1a ... Column-shaped halogen lamp F1b ... Roll base material F1c ... Elastic body F2 ... Pressure roll F2a ... Rotating shaft F2b ... Roll base material F2c ... Elastic body F3 ... Heat-resistant belt F4 ... Belt tension Mounting member F4a ... Projection wall F4f ... Recess F5 ... Sheet material F5a ... Unfixed toner image F6 ... Cleaning member F9 ... Spring

Claims (13)

A liquid developer in which toner particles composed of at least a binder resin and a colorant are dispersed in an insulating liquid,
As the colorant, pigment particles having a cationic group on the surface are coated with a polymer having a repeating structural unit derived from an anionic polymerizable surfactant having an anionic group, a hydrophobic group, and a polymerizable group. A liquid developer characterized by using the above.   The colorant is obtained by coating the pigment particles with a polymer by polymerizing the anionic polymerizable surfactant in an aqueous dispersion in which the pigment particles having a cationic group on the surface are dispersed. The liquid developer according to claim 1.   The liquid developer according to claim 1, wherein the polymer further has a repeating structural unit derived from a hydrophobic monomer. The liquid according to any one of claims 1 to 3, wherein the polymer further has a repeating structural unit derived from a crosslinkable monomer and / or a repeating structural unit derived from a monomer represented by the following general formula (1). Developer.

  The liquid developer according to claim 1, wherein the pigment constituting the pigment particles is carbon black.   The cationic group of the pigment particles is selected from the group consisting of a primary amine cation group, a secondary amine cation group, a tertiary amine cation group, and a quaternary ammonium cation group. The liquid developer according to any one of 5. The anionic group of the anionic polymerizable surfactant is a sulfonate anion group (—SO ₃ ^— ), a sulfinate anion group (—RSO ₂ ^— : R is a C _{1 to} C ₁₂ alkyl group or a phenyl group, and The liquid developer according to claim 1, which is selected from the group consisting of a modified product) and a carboxylate anion group (—COO ⁻ ).   8. The liquid developer according to claim 1, wherein the hydrophobic group of the anionic polymerizable surfactant is selected from the group consisting of an alkyl group, an aryl group, and a group in which these are combined. .   The polymerizable group of the anionic polymerizable surfactant is an unsaturated hydrocarbon group capable of radical polymerization, and includes a vinyl group, an allyl group, an acryloyl group, a methacryloyl group, a propenyl group, a vinylidene group, and a vinylene group. The liquid developer according to claim 1, which is selected from the group.   The colorant is mixed after adding the anionic polymerizable surfactant to the aqueous dispersion of pigment particles having the cationic group on the surface, and then emulsifying after adding the anionic polymerizable surfactant and starting polymerization. The liquid developer according to claim 1, which is obtained by adding an agent and polymerizing in water.   The colorant is prepared by adding the anionic polymerizable surfactant to an aqueous dispersion of pigment particles having the cationic group on the surface and mixing, and then adding a hydrophobic monomer and the anionic polymerizable surfactant. The liquid developer according to claim 1, which is obtained by mixing, emulsifying, adding a polymerization initiator and polymerizing in water. The colorant is prepared by adding the anionic polymerizable surfactant to an aqueous dispersion of pigment particles having the cationic group on the surface and mixing the mixture, and then mixing the hydrophobic monomer and the crosslinkable monomer and / or the following general formula (1) The monomer represented by the above formula and the anionic polymerizable surfactant are added and mixed, and after emulsification, a polymerization initiator is added and polymerization is performed in water. Liquid developer.

The liquid developer according to claim 1, comprising a charge control agent.

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