JP2007003974A - Method for producing liquid developer and liquid developer obtained by the method - Google Patents

Abstract

When a liquid developer is produced by a coacervation method, when a solvent is distilled off, a colorant such as a pigment is completely embedded in a resin particle while maintaining a finely dispersed state. Further, a method for producing a liquid developer in which the obtained colored resin fine particles have a small particle diameter.
A pigment having a hybrid core-shell structure in which the surface of inorganic particles is coated with an organic pigment or carbon black, a resin having fixability, a solvent (A) for dissolving the resin, a solvent ( A) Hydrocarbon solvent (B) having a lower SP value, at least one dispersant (A) soluble in both the solvent (A) and the solvent (B), and if necessary, further in the solvent (A) Is dissolved, but the solvent (A) is distilled off from the mixed solution containing at least one dispersant (B) that is hardly soluble in the solvent (B) to precipitate the resin in a dissolved state. Thus, the colored resin particles in which the pigment is embedded are dispersed in the solvent (B).
[Selection figure] None

Description

  The present invention relates to a method for producing a liquid developer for electrophotography or electrostatic recording used in printing machines, copiers, printers, facsimiles, and the like, and a liquid developer obtained by the method.

  As the liquid developer, generally, a developer in which colored resin particles containing a colorant such as a pigment are dispersed in an electrically insulating medium is used. As a method for producing such a liquid developer, (1) a polymerization method (a method in which a monomer component is polymerized in an electrically insulating medium in which a colorant is dispersed to form colored resin particles), (2) a wet type Pulverization method (a method in which a colorant and a resin are kneaded at a temperature equal to or higher than the melting point of the resin, followed by dry pulverization, and this pulverized product is wet pulverized in an electrically insulating medium in the presence of a dispersant), (3) precipitation method (core (Cervation method) (colorant, resin, solvent that dissolves the resin, and the solvent is removed from the mixed solution consisting of an electrically insulating medium that does not dissolve the resin, thereby precipitating the resin and electrically insulating the colored resin particles. There are various methods such as a method of dispersing in a functional medium.

  However, the polymerization method (1) has a problem that it requires a step of removing the remaining monomer after the polymerization. Further, in the wet pulverization method (2), since the colorant is not completely embedded in the resin, the colorants are agglomerated and the particle diameter of the colored resin particles becomes non-uniform, and the resulting liquid developer is dispersed. There is a problem that stability and optical characteristics are insufficient. Furthermore, the precipitation method (3) has a problem that the colored resin particles are agglomerated during the precipitation of the resin, and as a result, the particles are coarsened. The wet grinding method (2) The developer obtained in the same manner as above has a problem that the dispersion stability and optical properties are insufficient.

  Therefore, in order to solve the above problem in the precipitation method of (3), the resin is dissolved in a solvent that can be dissolved, and then mixed with an electrically insulating medium in the presence of a colorant and a dispersant to form a mixed solution. Further, a method of dispersing colored resin particles in an electrically insulating medium by further removing the solvent from the mixed solution (for example, see Patent Document 1) has been proposed.

  However, as various printing technologies advance, in order to gain an advantage in competition with other systems, the latest liquid developers are strongly required to increase the density of the developer itself and to increase the resolution of the printed matter. It is becoming a performance. In order to satisfy the required performance, it is necessary to make the colored resin particles finer and higher in concentration, but to produce fine colored resin particles and to disperse more stably at a high concentration. Are both extremely difficult technologies at present, and a new method for producing a liquid developer for realizing them has been demanded.

JP 2003-241439 A

  An object of the present invention is to produce a liquid developer for electrophotography or electrostatic recording by the coacervation method while maintaining a state in which a colorant such as a pigment is finely dispersed when the solvent is distilled off. By providing a production method capable of obtaining a liquid developer that is completely embedded in the interior of resin particles, and that the obtained colored resin fine particles have a small particle size, excellent dispersion stability, and excellent optical properties. is there.

  As a result of various investigations on the production method of the liquid developer, the present inventors have found that in the coacervation method for producing colored resin particles, a hybrid core-shell structure having a very small particle diameter and high optical properties as a pigment. It has been found that a liquid developer capable of solving all of the above problems can be produced by using a material having the above, and the present invention has been completed.

That is, the present invention provides the following method for producing a liquid developer and the liquid developer obtained thereby.
[1] A pigment having a hybrid core-shell structure in which the surface of inorganic particles is coated with an organic pigment or carbon black, a resin having fixing properties, a solvent (A) that dissolves the resin, a solvent (A ) From a mixed solution containing at least one dispersant (A) that is soluble in both the hydrocarbon solvent (B), the solvent (A), and the solvent (B) having a lower SP value, the solvent (A) The liquid resin is dispersed in the solvent (B) by distilling off the solvent and precipitating the resin in a dissolved state, thereby producing a liquid developer.
[2] Pigments having a hybrid core-shell structure in which the surface of inorganic particles is coated with an organic pigment or carbon black, a resin having fixing properties, a solvent (A) for dissolving the resin, a solvent (A ) Hydrocarbon solvent (B) having a lower SP value, at least one dispersant (A) soluble in both solvent (A) and solvent (B), and soluble in solvent (A) Is obtained by distilling off the solvent (A) from the mixed solution containing at least one dispersant (B) that is hardly soluble in the solvent (B), thereby precipitating the resin in a dissolved state. A method for producing a liquid developer, comprising dispersing colored resin particles embedded in a solvent (B).
[3] Item [1] or [2], wherein a solvent having an SP value of 8.5 or more is used as the solvent (A), and a solvent having an SP value of less than 8.5 is used as the solvent (B). A method for producing a liquid developer.
[4] The dispersant (A) and the dispersant (B) are used in combination so that the mass ratio in the liquid developer is dispersant (A): dispersant (B) = 99: 1 to 1:99. The method for producing a liquid developer according to item [2] or [3].
[5] The method for producing a liquid developer according to any one of [1] to [4], wherein a high-boiling paraffin solvent is used as the solvent (B).
[6] A liquid developer produced by the production method according to any one of [1] to [5].

  Here, embedding means that the pigment particles are completely covered with the resin, and the pigment particles do not exist on the surface of the resin particles.

  According to the method of the present invention, the pigment particles are completely embedded in the resin particles while maintaining the finely dispersed state 43, and the colored resin fine particles are finely and more stable in the electrically insulating medium. Can be dispersed. That is, it is possible to obtain a liquid developer in which resin particles containing a colorant such as a pigment dispersed in an electrically insulating medium have a small particle size, excellent dispersion stability, and excellent optical characteristics. More preferably, by using two types of dispersants that satisfy specific conditions, the resin particles containing a colorant such as a pigment dispersed in an electrically insulating medium have a smaller particle size and stable dispersion. It is possible to obtain a liquid developer that is superior in properties and excellent in optical properties.

  The liquid developer produced by the method of the present invention is characterized by maintaining a sufficiently low viscosity suitable for printing even at a high solid content concentration and achieving higher resolution. In the field of photography or electrostatic recording, it is possible to perform printing at high speed, to have quick drying properties, and to obtain a higher definition image.

  Hereinafter, a method for producing a liquid developer of the present invention and a liquid developer obtained by the method will be described in detail.

  In one embodiment of the method for producing a liquid developer of the present invention (hereinafter referred to as the first embodiment), a pigment having a hybrid core-shell structure in which the surface of inorganic particles is coated with an organic pigment or carbon black, and having fixing properties. Resin, solvent (A) for dissolving the resin, hydrocarbon solvent (B), solvent (A) and solvent (B) which do not dissolve the resin and have a lower SP value than solvent (A) From the mixed liquid containing at least one type of the dispersing agent (A) to be dissolved, the solvent (A) is distilled off to precipitate the resin in a dissolved state, whereby colored resin particles embedded with a pigment are obtained. It is characterized by being dispersed in the solvent (B).

  In another embodiment of the method for producing a liquid developer of the present invention (hereinafter referred to as the second embodiment), the pigment having a hybrid core-shell structure in which the surface of the inorganic particles is coated with an organic pigment or carbon black, and the fixing property. Resin, solvent (A) that dissolves the resin, hydrocarbon solvent (B) that does not dissolve the resin and has a lower SP value than solvent (A), both solvent (A) and solvent (B) From a mixed solution containing at least one dispersant (A) that dissolves in the solvent, and at least one dispersant (B) that dissolves in the solvent (A) but is hardly soluble in the solvent (B). (A) is distilled off, and the resin in a dissolved state is precipitated to disperse the colored resin particles embedded with the pigment in the solvent (B).

  In the present invention, the pigment contained in the colored resin particles is a pigment having a hybrid core-shell structure in which the surface of inorganic particles is coated with an organic pigment or carbon black. The inorganic particles correspond to the core portion, and the organic pigment or carbon black corresponds to the shell layer.

  Materials used as inorganic particles in the core include white pigments such as titanium dioxide and zinc oxide, pearl pigments such as titanium mica and muscovite, silica fine particles such as silicon oxide, white carbon, fine silicic acid, diatomaceous earth, and clay. And extender pigments such as calcium carbonate, barium sulfate, alumina white, talc, and transparent titanium oxide.

  Examples of the pigment for the shell layer include organic pigments such as azo pigments, condensed azo pigments, lake pigments, phthalocyanine pigments, isoindoline pigments, anthraquinone pigments, quinacridone pigments, and carbon black. Examples of organic pigments of various hues include magenta organic pigments, quinacridone pigments such as quinacridone red, azo pigments such as permanent red, condensed azo pigments such as condensed azo red, and perylene pigments such as perylene red. . Examples of cyan organic pigments include phthalocyanine pigments such as metal-free phthalocyanine blue, phthalocyanine blue, and fast sky blue. Examples of yellow organic pigments include monoazo pigments such as Hansa Yellow, disazo pigments such as benzidine yellow and permanent yellow, and condensed azo pigments such as condensed azo yellow. Examples of the green pigment include phthalocyanine pigments such as phthalocyanine green.

  In order to produce a pigment having a hybrid core-shell structure using such a material, for example, a method disclosed in JP 2002-356625 A can be used. That is, for example, after mixing and stirring the inorganic particles in the core and the adhesive to coat the adhesive on the surface of the inorganic particles, the organic pigment or carbon black of the shell layer is added, mixed and stirred, and the adhesive It can be produced by depositing an organic pigment or carbon black on the surface of the coating. According to such a manufacturing method, it is possible to make the particle diameter of the obtained pigment of the hybrid core-shell structure as small as about several tens nm to 100 nm, and higher color density and clear color developability can be obtained. There is a feature.

  In the hybrid core-shell structure pigment, a plurality of shell layers made of an organic pigment or carbon black may be provided on the surface of the inorganic particles in the core portion. For example, the surface of the inorganic particles is coated with an adhesive, and a first shell layer in which an organic pigment or carbon black is attached to the coating is formed. Further, the surface of the first shell layer is coated with an adhesive, A structure in which a second shell layer in which an organic pigment or carbon black is attached to the coating is formed. If necessary, a further shell layer may be formed in the same manner.

  The inorganic particles in the core may be selected according to the required properties and applications. White pigments are preferred for applications where hiding power is required, and pearl pigments for applications where pearly luster is required. For applications where transparency is required, pearl pigments or extender pigments are preferred. Of these, silicon oxide and titanium oxide are preferable. The particle shape of the inorganic particles may be any shape such as a spherical shape, a granular shape, a polyhedral shape, a needle shape, a spindle shape, a rice granular shape, a flake shape, a scale shape, and a plate shape.

  The adhesive is not particularly limited as long as it can adhere an organic pigment or carbon black to the surface of the inorganic particles. Examples thereof include organosilicon compounds such as alkoxysilane, fluoroalkylsilane and polysiloxane, various coupling agents such as silane, titanate, aluminate and zirconate, oligomers or polymer compounds. Considering the adhesion strength of the organic pigment or carbon black to the surface of the inorganic particles, more preferably organosilicon compounds such as alkoxysilane, fluoroalkylsilane, polysiloxane, silane, titanate, aluminate, zirconate, etc. Coupling agents. Thus, the term adhesive in this specification is a broad concept including what are called coupling agents, primers, and the like.

  Depending on the required hue, organic pigments of different hues may be mixed and used. Depending on the required hue, characteristics, etc., pigments of similar colors may be used in combination of two or more.

  Moreover, in the pigment of the hybrid type core-shell structure having a plurality of shell layers, the organic pigment to be adhered to the first shell layer and the organic pigment to be adhered to the second shell layer and after are the same, but different colors and different organic pigments. Or an organic pigment of a different color may be used. Further, by selecting an organic pigment having a function such as light resistance as an organic pigment to be combined, a pigment having a hybrid core-shell structure having a plurality of functions can be obtained.

  In the liquid developer of the present invention, the content of the pigment having a hybrid core-shell structure is not particularly limited, but is 1 to 20% by mass in the final liquid developer from the viewpoint of image density. Is preferred.

  Next, as the resin used in the present invention, a thermoplastic resin having fixability to an adherend such as paper and plastic film is preferable. Specifically, a polyolefin resin is modified to introduce a carboxyl group, Ethylene- (meth) acrylic acid copolymer, ethylene-vinyl acetate copolymer, partially saponified ethylene-vinyl acetate copolymer, ethylene- (meth) acrylic acid ester copolymer, polyethylene resin, polypropylene resin, etc. Styrene resins such as olefin resin, thermoplastic saturated polyester resin, styrene-acrylic copolymer resin, styrene-acrylic modified polyester resin, alkyd resin, phenolic resin, epoxy resin, rosin modified phenolic resin, rosin modified maleic resin, rosin Modified fumaric acid resin, (meth) acrylic acid ester Acrylic resins such as Le resins, vinyl chloride resins, vinyl acetate resins, vinylidene chloride resins, fluorine resins, polyamide resins, and polyacetal resins. These resins can be used alone or in combination of two or more.

  In the present invention, the solid content concentration in the liquid developer is preferably 10 to 50% by mass, and more preferably 15 to 40% by mass. If the solid content concentration is less than the above range, the image density tends to be insufficient, whereas if it exceeds the above range, the viscosity tends to be too high.

  Next, as a solvent used in the present invention, a solvent (A) that dissolves the resin and a hydrocarbon solvent (B) that does not dissolve the resin and has a lower SP value than the solvent (A) are used in combination. To do.

  As the solvent (A), those having an SP value of 8.5 or more are preferable, and low-boiling solvents that can be easily distilled off from the mixture by distillation are preferable. For example, ethers such as tetrahydrofuran, ketones such as methyl ethyl ketone and cyclohexanone And esters such as ethyl acetate, and aromatic hydrocarbons such as toluene and benzene can also be used if the resin has a dissolving ability. These solvents can be used alone or in combination of two or more.

  On the other hand, the solvent (B) does not dissolve the resin, has electrical insulation, has a lower SP value than the solvent (A) (preferably has an SP value of less than 8.5), and further has a solvent ( A) that does not volatilize when distilling off is preferable, and examples of the solvent that satisfies such conditions include non-volatile to low-volatile hydrocarbons, and more preferable are aliphatic hydrocarbons and alicyclic hydrocarbons. It is. Furthermore, aromatic hydrocarbons and halogenated hydrocarbons can be used as long as they do not dissolve the resin and satisfy the SP value. Among them, in particular, high boiling points (normal boiling point of 150 ° C. or higher) of normal paraffin solvents, isoparaffin solvents, cycloparaffin solvents, and mixtures of two or more of these in terms of odor, harmlessness, and cost Paraffinic solvents are preferred. Examples of commercially available high-boiling paraffinic solvents such as normal paraffinic solvents, isoparaffinic solvents, cycloparaffinic solvents or mixtures thereof include, for example, Isopar G, Isopar H, Isopar L, Isopar M, Exol D130, Exol D140 (all above) Exxon Chemical Co., Ltd.), Shellsol 71 (manufactured by Shell Petrochemical Co., Ltd.), IP Solvent 1620, IP Solvent 2080, IP Solvent 2835 (all manufactured by Idemitsu Petrochemical Co., Ltd.), Moresco White P -40, Moresco White P-55, Moresco White P-80 (all of which are liquid paraffin manufactured by Matsumura Oil Research Co., Ltd.), liquid paraffin No. 40-S, liquid paraffin No. 55-S (all are liquid paraffin manufactured by Chuo Kasei Co., Ltd.).

  Next, as the dispersant used in the present invention, in the first embodiment, the dispersant (A) that is soluble in both the solvent (A) and the solvent (B) is used alone, and in the second embodiment, Uses a dispersant (A) that dissolves in both the solvent (A) and the solvent (B), and a poorly soluble dispersant (B) that dissolves in the solvent (A) but in the solvent (B). . In the second embodiment in which the dispersant (A) and the dispersant (B) are used in combination, the pigment dispersed in the electrically insulating medium, etc., compared to the first embodiment in which the dispersant (A) is used alone, etc. It is possible to obtain a liquid developer in which the resin particles containing the above colorant have a smaller particle size, are excellent in dispersion stability, and are excellent in optical properties.

  As such a dispersant, a known dispersant can be used, and the combination of the dispersant (A) and the dispersant (B) is not particularly limited as long as each condition is satisfied. However, even if the same dispersant is used depending on the solvent to be used, it corresponds to the condition of the dispersant (A), corresponds to the condition of the dispersant (B), or the dispersant (A) or the dispersant (B There is a possibility that different results may be obtained from the case where neither of the conditions is satisfied. Therefore, when the solvent (A) and the solvent (B) are determined, they are classified into those satisfying the conditions as the dispersant (A) and those satisfying the conditions as the dispersant (B) in a preliminary test. It is preferable to select an appropriate combination from each of the classifications.

  Incidentally, the candidate for the dispersant (A) or the dispersant (B) is specifically an anionic surfactant, a nonionic surfactant, a cationic surfactant, an amphoteric surfactant, a silicone-based surfactant. Various surfactants such as surfactants and fluorosurfactants and derivatives thereof, polyurethane resins, modified novolak resins having an aromatic ring and a carboxyl group derived from a hydroxycarboxylic acid and having an epoxy group ring-opening structure No. 302259), an acrylic copolymer having a ring-opening structure of an epoxy group with an aromatic ring and a carboxyl group derived from hydroxycarboxylic acid (Japanese Patent Laid-Open No. 9-302259), a polyester such as poly (hydroxycarboxylic acid ester), A dispersant having a polar group such as a base at its end, an amino group of a (poly) amine compound, and / or Or a carbodiimide compound having a (poly) amine derivative having a polyester group introduced into an imino group, a polyester side chain, a polyether side chain or a polyacryl side chain (International Publication WO03 / 07652 pamphlet), a basic nitrogen-containing group And a carbodiimide compound having a side chain having a polyester side chain, a polyether side chain, or a polyacryl side chain (International Publication WO04 / 000950 pamphlet), and a carbodiimide compound having a side chain having a pigment adsorbing portion (International Publication WO04). Polymer type pigment dispersion resin such as / 003085 pamphlet). Examples of commercially available products include BYK-160, 162, 164, 182 (above, manufactured by Big Chemie), EFKA-47, 4050 (above, manufactured by EFKA), Solspers 13940, 17000, 18000, 24000, 28000. (Above, manufactured by Abyssia), Addisper PB-821 (manufactured by Ajinomoto Co., Inc.), and the like.

  The modified novolak resin having a ring-opening structure of an epoxy group by a carboxyl group derived from an aromatic ring and a hydroxycarboxylic acid includes an aromatic ring derived from a novolac resin and an epoxy group by a carboxyl group derived from a hydroxycarboxylic acid in the molecule. Examples thereof include modified novolak resins having at least one group represented by the general formula (1) by ring opening.

(In the formula, the oxygen atom at the left end is derived from the oxygen atom contained in the aromatic hydroxyl group of the novolak resin, and W ¹ and X ¹ are each independently a divalent hydrocarbon group having 1 to 19 carbon atoms. , I and j each independently represent an integer of i = 1 to 30 and j = 0 to 30, and R ¹ represents a hydrogen atom or a methyl group)
The modified novolak resin has at least one group represented by the general formula (1) in the molecule. The number of groups represented by the general formula (1) in the molecule is preferably 1-20. Since the molecular weight control of a novolak resin having a large number of nuclei is very difficult, the total number of aromatic hydroxyl groups of the modified novolak resin (the total of unsubstituted and substituted aromatic hydroxyl groups, the same applies hereinafter) is 20 or less. Is preferred. The modified novolac resin is obtained by reacting an aromatic hydroxyl group with a group other than the group represented by the general formula (1) (for example, reacting an aromatic hydroxyl group with epichlorohydrin or β-methylepichlorohydrin, followed by a monovalent carboxylic acid, etc. Or a group having a reacted structure).

  In general formula (1), general formula (2):

(Wherein W ¹ and i are as defined above) and the general formula (3):

A group represented by the formula (wherein X ¹ and j are the same as defined above) is a hydroxycarboxylic acid having a unsaturated bond and / or a branched structure and having 2 to 20 carbon atoms (for example, 12- Hydroxystearic acid), mixtures thereof, or polycondensates thereof.

  The acrylic copolymer having a ring-opening structure of an epoxy group by a carboxyl group derived from the aromatic ring and hydroxycarboxylic acid is an acrylic copolymer having a weight average molecular weight of 3,000 to 100,000. In the polymer, an amount corresponding to at least 10 mol% of the structural unit represented by the general formula (4) and at least one selected from the structural units represented by the general formula (5) and the general formula (6) And a copolymer containing an amount corresponding to at least 10 mol%.

Wherein W ² and X ² are each independently a divalent hydrocarbon group having 1 to 19 carbon atoms, p and q are each independently an integer of p = 1 to 30, q = 0 to 30, ² , R ³ and R ⁴ are each independently a hydrogen atom or a methyl group, R ⁵ is a hydrogen atom or a halogen atom, R ⁶ and R ⁷ are each independently a hydrogen atom, a hydrocarbon group having 1 to 5 carbon atoms, An alkoxy group having 1 to 5 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or a halogen atom, R ⁸ represents a hydrogen atom or a methyl group, and R ⁹ represents a direct bond or a methylene group)
In general formula (4), general formula (7):

(Wherein W ² and p are as defined above) and the general formula (8):

A group represented by the formula (wherein X ² and q are the same as those described above) may have an unsaturated bond and / or a branched structure, and the hydroxycarboxylic acid having 2 to 20 carbon atoms (for example, 12-hydroxystearic acid, etc.), mixtures thereof, or polycondensates thereof.

  In the first embodiment of the present invention, the amount of the dispersant (A) used is preferably 0.1 to 200% by mass with respect to the amount of the pigment (pigment having a hybrid core-shell structure) in the liquid developer, and more Preferably it is 10-100 mass%. If the amount of the dispersant (A) used is less than the above range, the colored resin particles tend to be coarsened, while if it exceeds the above range, the viscosity tends to be too high.

  In the second embodiment of the present invention, the preferred amount ratio of the dispersant (A) and the dispersant (B) tends to differ depending on the combination with the solvent in addition to the performance of the dispersant itself, The mass ratio of dispersant (A): dispersant (B) is preferably about 99: 1 to 1:99, more preferably 95: 5 to 5:95. When the amount ratio of the dispersant (A) and the dispersant (B) is out of the above range, the combined effect tends not to be sufficiently exhibited. Further, the total amount of the dispersants (A) and (B) used is preferably 0.1 to 200% by mass, more preferably 10 to 10% by mass with respect to the pigment (pigment having a hybrid core-shell structure) in the liquid developer. 100% by mass. If the total amount of the dispersants (A) and (B) used is less than the above range, the colored resin particles tend to be coarse, whereas if it exceeds the above range, the viscosity tends to be too high.

  The liquid developer obtained by the method of the present invention may further contain a charge control agent and other additives as necessary in addition to the above materials.

The charge control agent is roughly classified into two types (1) and (2) described below.
(1) A type in which the surface of colored resin particles (toner particles) is coated with a substance that can ionize or adsorb ions. As this type, oils and fats such as linseed oil and soybean oil, alkyd resins, halogenated polymers, aromatic polycarboxylic acids, acidic group-containing water-soluble dyes, and oxidative condensates of aromatic polyamines are suitable.
(2) A type that dissolves in an electrically insulating solvent and coexists with colored resin particles (toner particles) and a substance capable of exchanging ions. Cobalt naphthenate, nickel naphthenate, iron naphthenate, zinc naphthenate , Metal soaps such as cobalt octylate, nickel octylate, zinc octylate, cobalt dodecylate, nickel dodecylate, zinc dodecylate, cobalt 2-ethylhexanoate, etc., metal salts of petroleum sulfonates, metal salts of sulfosuccinates Preferred are sulfonic acid metal salts such as phospholipids such as lecithin, salicylic acid metal salts such as t-butylsalicylic acid metal complex, polyvinylpyrrolidone resin, polyamide resin, sulfonic acid group-containing resin, and hydroxybenzoic acid derivatives.

  Next, a method for producing a liquid developer using the above materials will be described. However, the method described below is an example of a preferred embodiment of the present invention, and the present invention is not limited to this.

  First, preparation of the mixed solution in the present invention will be described. For example, a pigment (a pigment having a hybrid core-shell structure), a dispersant (A), a dispersant (B), and a part of the solvent (A) are mixed as necessary, and an attritor, ball mill, sand mill, bead mill, etc. A pigment dispersion liquid in which pigments are dispersed is obtained using a non-media type dispersing machine such as a high speed mixer or a high speed homogenizer. Furthermore, after adding resin and the remaining solvent (A) to this pigment dispersion, the solvent (B) is added while stirring with a high-speed shearing stirrer to obtain a mixture. In preparing the pigment dispersion, the pigment may be dispersed after previously adding a resin.

  Next, the liquid developer of the present invention can be obtained by distilling off the solvent (A) while stirring the above mixed solution with a high-speed shear stirrer. Further, when the solid concentration in the obtained liquid developer is high, the solvent (B) may be added so as to obtain the required solid concentration. Furthermore, you may add other additives, such as a charge control agent, as needed. The liquid developer of the present invention may be obtained by simultaneously removing the solvent (A) and adding the solvent (B).

  As the high-speed shearing agitation apparatus, a stirring / shearing force can be applied, and a homogenizer, a homomixer, or the like can be used. There are various types such as a capacity, a rotational speed, and a model, and an appropriate one may be used according to the production mode. In addition, as rotation speed at the time of using a homogenizer, 500 rotation (rpm) or more is preferable.

  By the production method as described above, it is possible to produce a liquid developer in which the resin particles containing the pigment dispersed in the electrically insulating solvent have a small particle diameter, excellent dispersion stability, and excellent optical characteristics. The liquid developer thus obtained can be used in the fields of printing machines, copying machines, printers, facsimiles and the like, and is suitable for printing even if the solid content of colored resin particles is high. Since a sufficiently low viscosity can be maintained, it has characteristics that it has high-speed printability and quick-drying properties and can achieve higher resolution.

  From the viewpoint of obtaining a high-definition image, the colored resin particles in the liquid developer in the present invention preferably have an average particle size of 0.1 to 5.0 μm, more preferably 0.1 to 3.0 μm. is there.

  Hereinafter, the liquid developer of the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. In the following description, “part” and “%” represent “part by mass” and “% by mass”, respectively.

  The pigments, dispersants, and fixing thermoplastic resins used in the following examples and comparative examples will be described.

<Pigment>
As a pigment having a hybrid core-shell structure, CS-C200Y, a cyan pigment manufactured by Toda Kogyo Co., Ltd., was used. The average particle size of this pigment was about 20 nm.

<Dispersant 1>
In a reaction vessel, 30 parts of epoxy-modified novolak resin (Epicoat 154, manufactured by Yuka Shell Epoxy Co., Ltd.), 75 parts of polyester having an acid value of 30 and a weight average molecular weight of 4,500 obtained by condensation polymerization of 12-hydroxystearic acid , 35 parts of stearic acid and 0.2 parts of tetraethylammonium bromide were charged. Next, a modified novolak resin having a weight average molecular weight of 8,000 was obtained by heating and stirring under a nitrogen stream at 130 to 150 ° C. for 3 hours and then removing the catalyst by vacuum filtration.

<Dispersant 2>
Commercially available Ajisper PB821 (Ajinomoto Co., Inc./Amine number 8 to 10) was used. Azisper PB821 corresponds to a (poly) amine derivative in which a polyester group is introduced into the amino group and / or imino group of the (poly) amine compound.

<Dispersant 3>
Commercially available Solspers 13940 (Avicia Co., Ltd./Amine value 80-90) was used. Solspers 13940 corresponds to a (poly) amine derivative in which a polyester group is introduced into the amino group and / or imino group of the (poly) amine compound.

<Thermoplastic resin>
Epoxy resin (AER6064, manufactured by Asahi Kasei Corporation) was used.

Example 1
10 parts of CS-C200Y, 1 part of the dispersant 1 as a dispersant (A) and 89 parts of tetrahydrofuran (SP value 9.1, hereinafter referred to as “THF”) are mixed, and steel beads having a diameter of 5 mm are used. After kneading for 15 minutes with a paint shaker, the mixture was further kneaded with an ultra apex mill (manufactured by Kotobuki Industries Co., Ltd.) using zirconia beads having a diameter of 0.05 mm. To 50 parts of the kneaded product, 14.5 parts of a thermoplastic resin was added and further diluted with 35.5 parts of THF. The diluted product was stirred while diluting with 80 parts of Moresco White P-80 (manufactured by Matsumura Petrochemical Laboratories, Inc., SP value 8.5 or less) to obtain a mixed solution. Next, using a device in which a solvent evaporating device (connected to a decompression device) is connected to a homogenizer consisting of a closed stirring tank, the temperature of the mixture is adjusted by the decompression device while stirring the mixture at high speed (revolution: 5,000 rpm). The pressure was reduced to 50 ° C., and THF was completely distilled off from the sealed stirring tank to obtain the liquid developer of Example 1 (solid content concentration 20%).

Example 2
10 parts of CS-C200Y, 1 part of the above dispersant 3 as a dispersing agent (A), 89 parts of THF are mixed, kneaded for 15 minutes in a paint shaker using 5 mm diameter steel beads, and then zirconia beads having a diameter of 0.05 mm Was further kneaded for 2 hours with an ultra apex mill (manufactured by Kotobuki Industries). To 50 parts of the kneaded product, 14.5 parts of a thermoplastic resin was added and further diluted with 35.5 parts of THF. The diluted product was stirred while diluting with 80 parts of Moresco White P-80 (manufactured by Matsumura Petrochemical Laboratories, Inc., SP value 8.5 or less) to obtain a mixed solution. Next, using a device in which a solvent evaporating device (connected to a decompression device) is connected to a homogenizer consisting of a closed stirring tank, the temperature of the mixture is adjusted by the decompression device while stirring the mixture at high speed (revolution: 5,000 rpm). The pressure was reduced to 50 ° C., and THF was completely distilled away from the sealed stirring tank to obtain a liquid developer of Example 2 (solid content concentration 20%).

Example 3
Paint 10 parts of CS-C200Y, 2 parts of Dispersant 1 as Dispersant (A), 2 parts of Dispersant 2 as Dispersant (B), and 86 parts of THF, and paint using 5 mm diameter steel beads. After kneading with a shaker for 15 minutes, zirconia beads having a diameter of 0.05 mm were used and further kneaded with an ultra apex mill for 2 hours. To 50 parts of this kneaded product, 13 parts of a thermoplastic resin was added and further diluted with 37 parts of THF. The diluted product was stirred while being diluted with 80 parts of Moresco White P-80 to obtain a mixed solution. Next, using a device in which a solvent evaporating device (connected to a decompression device) is connected to a homogenizer consisting of a closed stirring tank, the temperature of the mixture is adjusted by the decompression device while stirring the mixture at high speed (revolution: 5,000 rpm). The pressure was reduced to 50 ° C., and THF was completely distilled off from the sealed stirring tank to obtain a liquid developer of Example 3 (solid content concentration 20%).

Example 4
Paint 10 parts of CS-C200Y, 2 parts of Dispersant 3 as Dispersant (A), 2 parts of Dispersant 2 as Dispersant (B), and 86 parts of THF, and paint using 5 mm diameter steel beads. After kneading with a shaker for 15 minutes, zirconia beads having a diameter of 0.05 mm were used and further kneaded with an ultra apex mill for 2 hours. To 50 parts of this kneaded product, 13 parts of a thermoplastic resin was added and further diluted with 37 parts of THF. The diluted product was stirred while being diluted with 80 parts of Moresco White P-80 to obtain a mixed solution. Next, using a device in which a solvent evaporating device (connected to a decompression device) is connected to a homogenizer consisting of a closed stirring tank, the temperature of the mixture is adjusted by the decompression device while stirring the mixture at high speed (revolution: 5,000 rpm). The pressure was reduced to 50 ° C., and THF was completely distilled off from the sealed stirring tank to obtain a liquid developer of Example 4 (solid content concentration 20%).

Example 5
Paint 20 parts of CS-C200Y, 2 parts of Dispersant 1 as Dispersant (A), 2 parts of Dispersant 2 as Dispersant (B) and 76 parts of THF, and paint using 5 mm diameter steel beads. After kneading with a shaker for 15 minutes, zirconia beads having a diameter of 0.05 mm were used and further kneaded with an ultra apex mill for 2 hours. To 50 parts of this kneaded product, 18 parts of a thermoplastic resin was added and further diluted with 34 parts of THF. The diluted product was stirred while being diluted with 70 parts of Moresco White P-80 to obtain a mixed solution. Next, using a device in which a solvent evaporating device (connected to a decompression device) is connected to a homogenizer consisting of a closed stirring tank, the temperature of the mixture is adjusted by the decompression device while stirring the mixture at high speed (revolution: 5,000 rpm). The pressure was reduced to 50 ° C., and THF was completely distilled off from the sealed stirring tank to obtain a liquid developer of Example 5 (solid content concentration 30%).

Comparative Example 1
In Example 1, a liquid developer (solid content concentration 20%) of Comparative Example 1 was obtained by the same method as Example 1 except that Dispersant 2 was used instead of Dispersant 1.
Comparative Example 2
In Example 3, an attempt was made to produce a liquid developer by the same method as in Example 3 except that the dispersants (A) and (B) were not used. However, since an aggregate was formed, a liquid developer was obtained. There wasn't.

<Evaluation method>
Each liquid developer was evaluated by the following evaluation method. The results are shown in Table 1.

(viscosity)
The viscosity at 25 ° C. was measured as the viscosity after 60 seconds with an E-type viscometer (50 rpm).

(Average volume particle diameter D50 of colored resin particles)
The particle size distribution was measured using Microtrac UPA (Honeywell).

(State of colored resin particles)
It was confirmed whether or not the colored resin particles were completely embedded using an optical microscope BH-2 (manufactured by Olympus Corporation).

Claims (6)

Pigment having a hybrid core-shell structure in which the surface of inorganic particles is coated with an organic pigment or carbon black, a resin having a fixing property, a solvent (A) for dissolving the resin, a solvent that does not dissolve the resin, and lower than the solvent (A) The solvent (A) is distilled off from the mixed solution containing at least one dispersant (A) that is soluble in both the solvent (B), the solvent (A), and the solvent (B), which is an SP value. Then, the colored resin particles in which the pigment is embedded are dispersed in the solvent (B) by precipitating the resin in a dissolved state. Pigment having a hybrid core-shell structure in which the surface of inorganic particles is coated with an organic pigment or carbon black, a resin having a fixing property, a solvent (A) for dissolving the resin, a solvent that does not dissolve the resin, and lower than the solvent (A) The hydrocarbon solvent (B) having an SP value, at least one dispersant (A) that dissolves in both the solvent (A) and the solvent (B), and the solvent (A) that dissolves in the solvent (A) In B), the solvent (A) is distilled off from the mixed solution containing at least one of the poorly soluble dispersant (B) to deposit the resin in a dissolved state, thereby embedding the pigment. A method for producing a liquid developer, comprising dispersing the colored resin particles in a solvent (B). The method for producing a liquid developer according to claim 1 or 2, wherein a solvent having an SP value of 8.5 or more is used as the solvent (A), and a solvent having an SP value of less than 8.5 is used as the solvent (B). The dispersant (A) and the dispersant (B) are used in combination such that the mass ratio in the liquid developer is dispersant (A): dispersant (B) = 99: 1 to 1:99. 4. A method for producing a liquid developer according to 2 or 3. The method for producing a liquid developer according to claim 1, wherein a high-boiling paraffin solvent is used as the solvent (B). A liquid developer produced by the production method according to claim 1.