JP2013113972A - Liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid developer capable of realizing sufficient image density and fixing strength despite the low amount of attached toner particles.SOLUTION: A liquid developer of the present invention contains toner particles and an insulating liquid; the toner particles contain resin, pigment, and a pigment dispersant; the pigment contains an aniline black structure compound represented by the following general formula (I) (where n represents an integer of 1 to 3, and X represents any one of OH, Cl, and an acid radical); and the pigment dispersant is a basic dispersant.

Description

  The present invention relates to a liquid developer used in an electrophotographic image forming apparatus.

  Various developers are known for use in electrophotographic image forming apparatuses. For example, as a black developer for obtaining a black image, those using aniline black pigments are known (Japanese Patent Application Laid-Open No. 2010-019970 (Patent Document 1), Japanese Patent Application Laid-Open No. 63-285556 ( Patent Document 2), Japanese Patent Application Laid-Open No. 2005-182036 (Patent Document 3)).

JP 2010-019970 A JP-A-63-285556 JP 2005-182036 A

  The developer as described above contains toner particles in which a pigment is dispersed in a resin. Usually, a dry developer consisting only of powders such as toner particles and magnetic material and a liquid in which toner particles are dispersed in a liquid. There are two types of developer and developer.

  In the case of a general dry developer, the content ratio of the pigment contained in the resin of the toner particles is 10 parts by mass or less with respect to 100 parts by mass of the resin. This content ratio is determined by the relationship of the image density to the particle size of the toner particles (that is, the image film thickness). On the other hand, in a liquid developer, since the particle size of toner particles is generally smaller than that of a dry developer, a necessary image density can be obtained unless the pigment content is increased compared to that of a dry developer. Absent.

  Therefore, when a black pigment is used in a black liquid developer for obtaining a black image, the content ratio of the black pigment in the toner particles necessary for securing the image density is approximately 15 parts by mass with respect to 100 parts by mass of the resin. (However, as in the case of the dry developer, the appropriate amount depends on the particle size of the toner particles). However, when the content ratio of the pigment is increased, there is a problem of poor dispersibility of the pigment, and a sufficient image density may not be obtained.

  On the other hand, in order to achieve high image quality, prevention of show-through, and low cost using such a liquid developer, the amount of toner particle adhesion (image film thickness) on a recording material such as paper is further reduced. There is a need. However, even if the adhesion amount of the toner particles is reduced, a desired density is required as the image density. Therefore, it is necessary to further increase the content ratio of the pigment in the toner particles. However, in this case, in addition to the problem of poor dispersibility of the pigment, there is also a problem that the fixing strength is lowered because the amount of resin in the toner particles is lowered.

  Therefore, in the use of such a liquid developer, it is strongly desired to achieve both image density and fixability even under a low adhesion amount of toner particles.

  Patent Document 1 discloses the use of aniline black having a specific structure as a black pigment, but it relates to a dry developer and does not solve the above-described problems related to a liquid developer.

  Patent Document 2 discloses a liquid developer using a sulfonamide derivative such as aniline black as a black pigment. However, since a pigment dispersant is not used, there is a problem in dispersibility of the pigment, and the inclusion of the pigment. There is a limit to increasing the ratio.

  Patent Document 3 discloses a liquid developer using aniline black as a black pigment, but there is a problem in the dispersibility of the pigment because no pigment dispersant is used as in Patent Document 2, and There is a limit to increasing the content ratio.

  The present invention has been made in view of such a current situation, and an object of the present invention is to provide a liquid developer capable of achieving both image density and fixing strength even under a low adhesion amount of toner particles. Is to provide.

  The liquid developer of the present invention includes toner particles and an insulating liquid, and the toner particles include a resin, a pigment, and a pigment dispersant, and the pigment has an aniline black structure represented by the following general formula (I). The pigment dispersant containing a compound is a basic dispersant.

(In the above formula, n represents an integer of 1 to 3, and X represents OH, Cl, or an acid group.)
Here, the pigment is preferably contained in an amount of 25 to 60 parts by mass with respect to 100 parts by mass of the resin, and the aniline black structure compound is contained in a range of 30 to 100% by mass with respect to the total mass of the pigment. It is preferable that

  Since the liquid developer of the present invention has the above-described configuration, it has an excellent effect that both image density and fixing strength can be achieved.

1 is a schematic conceptual diagram of an electrophotographic image forming apparatus.

Hereinafter, embodiments according to the present invention will be described in more detail.
<Liquid developer>
The liquid developer of the present embodiment includes at least toner particles and an insulating liquid, and the toner particles are dispersed in the insulating liquid. Such a liquid developer can contain other arbitrary components as long as these components are contained. Other components include, for example, a toner dispersant (in contrast to a pigment dispersant described later contained in the toner particles, a dispersant contained in the insulating liquid for dispersing the toner particles. And a charge control agent, a thickener, and the like.

  The blending ratio of the liquid developer can be, for example, 1 to 50% by mass of toner particles, and the remainder can be an insulating liquid or the like. If the blending amount of the toner particles is less than 1% by mass, the toner particles are liable to settle, and the stability over time during long-term storage tends to decrease. In order to obtain the required image density, a large amount of liquid development is required. It is necessary to supply the agent, the amount of the insulating liquid adhering to the recording material such as paper increases, it becomes necessary to dry it at the time of fixing, and the generated vapor may cause environmental problems. is there. On the other hand, when the blending amount of the toner particles exceeds 50% by mass, the viscosity of the liquid developer becomes too high, which tends to be difficult in production and handling.

  The viscosity of the liquid developer is preferably 0.1 mPa · s to 10,000 mPa · s at 25 ° C. When it exceeds 10,000 mPa · s, it becomes difficult to stir the liquid developer, and the toner particles cannot be uniformly dispersed in the insulating liquid, and the burden on the apparatus surface for obtaining the liquid developer increases. There is. On the other hand, if it is less than 0.1 mPa · s, the toner particles are liable to settle, the stability over time during long-term storage decreases, and the image density may become unstable.

Such a liquid developer is useful as a developer for an electrophotographic image forming apparatus.
<Toner particles>
The toner particles contained in the liquid developer of the present embodiment include a resin, a pigment, and a pigment dispersant, and the pigment includes an aniline black structure compound represented by the general formula (I), and the pigment dispersant Is a basic dispersant. Since the toner particles of the present embodiment have such a configuration, the pigment content in the toner particles can be increased, so that the adhesion amount of toner particles on a recording material such as paper is small (for example, 2 0.0 g / m ² or less), it is possible to achieve both high image density and fixing strength. Hereinafter, such excellent effects will be described in more detail.

  First, the aniline black structural compound represented by the above general formula (I) has a jet black color tone and excellent coloring power, and has high dispersibility in a resin (for example, a polyester resin). By adding it to the resin together with the basic dispersant as the dispersant, the dispersibility is further improved. Therefore, the pigment content in the toner particles can be dramatically increased as compared with a normal black pigment other than such an aniline black structure compound (for example, blending up to about 60 parts by mass with respect to 100 parts by mass of the resin). Is possible).

The image density on the recording material is greatly affected by the pigment content in the toner particles and the dispersibility of the pigment, and the higher the pigment content and the better the dispersibility, the higher the image density. In the toner particles of the present embodiment, the aniline black structure compound that exhibits excellent dispersibility as described above is further improved in dispersibility due to the action of the basic dispersant, and inherently excellent in coloring power. Can be contained at an extremely high density, so that a sufficient image density can be achieved even if the toner particles have a low adhesion amount (for example, 2.0 g / m ² or less).

  On the other hand, when a normal pigment is used, if the pigment content in the toner particles is increased, the resin content (mixing ratio) decreases, and the fixing strength on the recording material tends to deteriorate. To improve the fixing strength of the liquid developer, improve the pigment dispersibility in the toner particles, reduce the amount of insulating liquid (carrier liquid) retained during fixing, improve the compatibility between the toner particles, and record with the resin. It is thought that the improvement of the adhesiveness of the material contributes. As described above, the toner particles of the present embodiment have good pigment dispersibility, so that the compatibility between the toner particles is improved and the holding amount of the insulating liquid is reduced accordingly. Even though the aniline black structure compound is contained at a high concentration (in other words, the resin content is relatively reduced), the fixing strength is remarkably improved.

  Therefore, the liquid developer of the present embodiment including the toner particles as described above is a highly compatible image density and fixing strength.

  Such toner particles of the present embodiment can contain other optional components as long as they contain a resin, a pigment, and a pigment dispersant. Examples of other components include a wax and a charge control agent. Further, such toner particles preferably have an average particle size of 0.1 to 5 μm, more preferably 0.5 to 3 μm. In addition, the average particle diameter here means a volume average particle diameter.

Hereinafter, each component constituting such a toner particle will be further described.
<Pigment>
The pigment contained in the toner particles of the present embodiment contains at least the aniline black structure compound represented by the general formula (I). As apparent from the general formula (I), the aniline black structure compound is extremely safe because it does not contain heavy metals. In the above formula, n represents an integer of 1 to 3, and X represents OH, Cl, or an acid group.

  As already described, by using the aniline black structure compound having such a structure as the pigment, it is possible to achieve both high image density and fixing strength. In addition to these effects, high image quality, prevention of show-through, and low cost are also achieved.

  Here, the “aniline black structure compound” of the present embodiment is a compound represented by the above general formula (I) having an aniline black structure containing no heavy metal such as chromium or copper in its structure (hereinafter referred to as “the aniline black structure compound”). It is also simply referred to as “aniline black structure compound”).

  When such an aniline black structure compound is added to the liquid developer, an image having a jet black color tone and excellent coloring power can be obtained. The aniline black structure compound of the present embodiment has an absorbance 1.3 to 1.4 times higher than that of conventional aniline black (by the chromium method), for example, when the pigment concentration (pigment / pigment + resin) is 10%. The absorbance at a wavelength of 400 to 800 nm shows a high value of 2.5 to 3.0 (average), which is comparable to that of carbon black.

In the above general formula (I), the acid group refers to a remaining portion obtained by removing one or more hydrogen atoms capable of substituting a metal from various inorganic acid and organic acid molecules. As shown by the general formula (I), this acid group has a negative charge, and has a property of ionic bonding with a nitrogen atom (N ⁺ ) having a positive charge. Here, the organic acid is an acid of an organic compound, for example, formic acid, acetic acid, benzoic acid, benzenesulfonic acid, citric acid, oxalic acid, etc., and an inorganic acid is an acid (mineral acid) of an inorganic compound. For example, hydrochloric acid (in the case of hydrochloric acid, the acid group is Cl), nitric acid, phosphoric acid, sulfuric acid, boric acid, hydrofluoric acid, and the like.

  Such aniline black structure compounds can be used singly or as a mixture of two or more of them (for example, a mixture having different n in general formula (I) or a mixture having different X).

  In addition, such an aniline black structure compound may be subjected to a coupling treatment for enhancing dispersibility, or may contain other various additives as constituents, if necessary. Moreover, you may use together with other pigments, such as conventionally used carbon black and titanium black. As carbon black, for example, channel black, furnace black, acetylene black, thermal black, lamp black and the like can be used. The proportion of the combined use is preferably 10% by mass or more, more preferably 25% by mass or more, and particularly preferably 30% by mass or more with respect to the total mass of the pigment of the aniline black structure compound of the present embodiment. Of course, only the aniline black structure compound of the present embodiment may be used as the pigment. Therefore, it is preferable that the aniline black structure compound of this Embodiment is contained in 30-100 mass% with respect to the total mass of a pigment.

On the other hand, the pigment (total amount) contained in the toner particles of the present embodiment is preferably contained in an amount of 25 to 60 parts by mass, more preferably 40 to 60 parts by mass with respect to 100 parts by mass of the resin. If the amount is less than 25 parts by mass, it may be difficult to obtain a desired image density when the toner particle adhesion amount is reduced to achieve high image quality (toner particle amount 2 g / m ² or less). In the case of exceeding the above, problems such as deterioration in fixing property, reduction in image density and insufficient glossiness may occur due to a decrease in pigment dispersibility in toner particles. In the present embodiment, as a pigment that can be used together with the aniline black structure compound as a pigment, in addition to carbon black as described above, phthalocyanine-based, quinacridone-based, quinacridone-quinone-based, isoindolinone-based, quinophthalone-based, di- Ketopyrrolopyrrole, perylene, perinone, indigo, thioindigo, dioxazine, anthraquinone, pyranthrone, anthanthrone, flavanthrone, indanthrone, metal complex, etc. Various organic pigments such as benzimidazolone-based, insoluble azo-based, condensed azo-based, soluble azo-based and the like can be used alone or in combination.

  Such an aniline black structure compound can be suitably produced by oxidizing aniline with a persulfate in an aqueous acid solution. In this case, the persulfate used as the oxidizing agent may be any salt such as an ammonium salt; an alkali metal salt such as sodium persulfate or potassium persulfate; an alkaline earth metal salt such as barium persulfate; In particular, ammonium persulfate is preferable. In such a production method, the use amount of persulfate used as an oxidizing agent is 14 moles with respect to 11 moles of aniline, but it can be produced with 14 to 28 moles, twice that theoretical amount. The amount is preferably 16 to 24 mol, which is about 1.2 to 1.7 times the theoretical amount.

  Examples of the acid aqueous solution include mineral acid aqueous solutions such as hydrochloric acid, sulfuric acid, tetrafluoroboric acid, perchloric acid, and periodic acid, and carboxylic acid aqueous solutions such as formic acid, acetic acid, propionic acid, and butyric acid, such as benzenesulfonic acid. Examples thereof include sulfonic acid aqueous solutions such as p-toluenesulfonic acid, methanesulfonic acid, and ethanesulfonic acid, and mineral acid aqueous solution is particularly preferable, and tetrafluoroboric acid aqueous solution is particularly preferable.

  Further, as the acid aqueous solution, a mineral acid (for example, tetrafluoroboric acid) aqueous solution and an organic acid aqueous solution may be used in combination. Further, an aqueous solution of a mineral acid (for example, tetrafluoroboric acid) and an emulsion of higher fatty acids that are insoluble in water such as myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid (with a surfactant) May be used in combination. Furthermore, a mineral acid (for example, tetrafluoroboric acid) aqueous solution and a polymer having a carboxyl group such as polyacrylic acid or polymethacrylic acid or an aqueous solution of a water-soluble salt thereof may be used in combination. In addition, when using the polymer or a water-soluble salt thereof as described above, for example, calcium chloride or the like is added to the reaction solution after the oxidation reaction to make the polymer a water-insoluble salt, and then normal post-treatment is performed. This is preferable because a pigment having good dispersibility can be obtained. The concentration of the aqueous acid solution is usually 1 to 10% by mass, preferably about 2 to 8% by mass, although it depends on the type of acid.

  Moreover, when using a catalyst in said manufacturing method, it is preferable to use an iron salt as a catalyst. Examples of iron salts include ferrous chloride, ferric chloride, ferrous bromide, ferric bromide, ferrous sulfate, ferric sulfate (these iron salts may be anhydrous or hydrous salts (water Inorganic water-soluble iron salts such as (Japanese) or either) may be mentioned. The amount of iron salt used is usually about 0.1 to 5 mol, preferably about 1 to 2.5 mol, per 11 mol of aniline.

  The reaction temperature and reaction time in the above production method are not particularly limited, but are usually 10 to 60 ° C., preferably 20 to 50 ° C., and the persulfate is dropped over 10 to 60 minutes. The reaction may be performed at 50 to 80 ° C. for 1 to 2 hours, and if necessary, at 90 to 95 ° C. for 30 minutes to 1 hour. After the reaction, an unnecessary substance is collected by filtration, washed with water, and if necessary, it is slurried again with water and neutralized with an aqueous alkali solution such as an aqueous sodium hydroxide solution. The mixture is heated and stirred for ˜1 hour, and then filtered again, washed with water, and dried to obtain the aniline black structure compound of the present embodiment.

  The system after the reaction is strongly acidic with a pH of 1 to 2, but even if it is filtered, washed with water and dried without neutralization, the filtered material is once again slurried and neutralized. It may be filtered again, washed with water, or dried. However, the aniline black structure compound obtained by adjusting the pH to a neutral range in this step can stabilize the chargeability when used as a liquid developer for an electrophotographic system and has a high quality. An image having a jet-black hue can be obtained.

  In the case of the reaction, in the case of using a mineral acid and a polymer having a carboxyl group or a water-soluble salt thereof as an acid, after reacting at 60 to 80 ° C. for 1 to 2 hours after persulfate dropping, For example, after adding calcium chloride or the like and stirring at the same temperature for about 30 minutes to convert the polymer into a water-insoluble salt and then performing the post-treatment as described above, as described above, aniline black having good dispersibility. Since a structural compound is obtained, it is preferable.

In the above general formula, n can be adjusted by the amount of aniline and persulfate used as an oxidizing agent, and usually n is a mixture of 1 to 3. For example, increasing the amount of persulfate relative to aniline increases the value of n. X can be selected by selecting the type of acid in the aqueous solution of the acid when aniline is oxidized with persulfate. For example, if hydrochloric acid is used, X becomes Cl, and tetrafluoroboric acid is converted. If used, X becomes OH, and if acetic acid is used, X becomes CH ₃ COO (acid group).

<Pigment dispersant>
The pigment dispersant of the present embodiment has a function of uniformly dispersing the pigment in the toner particles, and a basic dispersant is used. Here, the basic dispersant is defined as follows. That is, 0.5 g of pigment dispersant and 20 ml of distilled water are placed in a glass screw tube, shaken for 30 minutes using a paint shaker, and then filtered, and the pH of the filtrate obtained is filtered with a pH meter (product) Name: “D-51” (manufactured by Horiba, Ltd.). In addition, when the pH is smaller than 7, it shall call an acidic dispersing agent.

  The kind of such basic dispersant is not particularly limited. For example, the compound (dispersant) which has functional groups, such as an amino group, an amide group, a pyrrolidone group, an imine group, and a urethane group, in the molecule | numerator of a dispersing agent can be mentioned. The dispersant usually corresponds to a so-called surfactant having a hydrophilic part and a hydrophobic part in the molecule, but various compounds can be used as long as it has an action of dispersing the pigment as described above. Can do.

  Commercially available products of such basic dispersants include, for example, “Ajisper PB-821” (trade name), “Azisper PB-822” (trade name), “Azisper PB-881” (product) manufactured by Ajinomoto Fine Techno Co., Ltd. Name) or “Solspers 28000” (product name), “Solspurs 32000” (product name), “Solspurs 32500” (product name), “Solspurs 35100” (product name), “Solspurs 37500” (product name) Product name).

  The added amount of such a pigment dispersant is preferably 1 to 100% by mass with respect to the pigment. More preferably, it is 1-40 mass%. If it is less than 1% by mass, the dispersibility of the pigment may be insufficient, and the necessary ID (image density) cannot be achieved, and the fixing strength may be lowered. On the other hand, when the amount exceeds 100% by mass, an amount of pigment dispersant more than the necessary amount for pigment dispersion is added, and excess pigment dispersant may be dissolved in the insulating liquid. May adversely affect strength.

  Such pigment dispersants can be used singly or in combination of two or more.

<Resin>
The resin contained in the toner particles of the present embodiment mainly has a function of fixing toner particles (pigments) on a recording material, and a conventionally known resin used as a resin constituting such toner particles. Can be used without any particular limitation. However, it is particularly preferable to use a polyester resin among such resins. This is because not only can the physical properties such as thermal properties be changed over a wide range, but also the resin film after fixing is tough because of its excellent spreadability and viscoelasticity, and it exhibits good adhesion to recording materials such as paper. .

  Such a polyester resin is thermoplastic and can be obtained by polycondensation of a polyhydric alcohol and a polybasic acid (polycarboxylic acid).

  The polyhydric alcohol is not particularly limited. For example, propylene glycol such as ethylene glycol, diethylene glycol, triethylene glycol, and 1,2-propylene glycol, butanediol such as dipropylene glycol and 1,4-butanediol. Of alkylene glycols (aliphatic glycols) such as hexanediol such as neopentyl glycol and 1,6-hexanediol and these alkylene oxide adducts, bisphenols such as bisphenol A and hydrogenated bisphenol, and these alkylene oxide adducts Examples thereof include phenolic glycols, alicyclic or aromatic diols such as monocyclic or polycyclic diols, and triols such as glycerin and trimethylolpropane. These can be used alone or in admixture of two or more. In particular, a bisphenol A alkylene oxide 2-3 mol adduct is preferable because it is suitable as a resin for toner particles of a liquid developer in terms of solubility and stability of the product polyester resin, and is also low in cost. . Examples of the alkylene oxide include ethylene oxide and propylene oxide.

  The polybasic acid (polycarboxylic acid) is not particularly limited, but for example, malonic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, itaconic acid, phthalic acid or the like A dibasic acid such as a modified acid (for example, hexahydrophthalic anhydride), isophthalic acid, terephthalic acid, etc., a polybasic acid having three or more functions such as trimellitic acid, trimesic acid, pyromellitic acid, methylnadic acid, and These acid anhydrides, lower alkyl esters and the like can be mentioned. These can be used alone or in admixture of two or more.

  In particular, since the polyester resin has a three-dimensional structure due to cross-linking by including a trifunctional or higher polybasic acid such as trimellitic acid, trimesic acid, pyromellitic acid, methyl nadic acid, etc., an insulating liquid (carrier liquid) It is preferable because the swellability due to can be suppressed. Also, it is advantageous to use trimellitic acid because it is available at low cost.

  As the condensation method, generally known polycondensation methods can be used. Although it depends on the type of raw material monomer, it is generally carried out at a temperature of about 150 ° C to 300 ° C. Moreover, it can carry out on arbitrary conditions, such as using inert gas as atmospheric gas, using various solvent, or making the pressure in reaction container into a normal pressure or pressure reduction. Moreover, you may use an esterification catalyst for reaction promotion. As the esterification catalyst, metal organic compounds such as tetrabutyl zirconate, zirconium naphthenate, tetrabutyl titanate, tetraoctyl titanate, 3/1 stannous oxalate / sodium acetate, etc. can be used, but they are products. Those that do not color the ester are preferred.

  In order to adjust the weight average molecular weight of the product polyester resin, generally the reaction time may be adjusted. Since the polycondensation reaction of polyester is a sequential reaction in which a low molecular weight substance gradually increases the molecular weight, the molecular weight increases with time. The relationship between reaction time and molecular weight varies depending on the type of monomer raw material, polymerization conditions, lot scale, etc. For example, in the case of a polyesterification reaction of hexanediol and sebacic acid, the reaction is performed at a temperature of 200 ° C. for 1 to 2 hours in a nitrogen stream. To give a product with a number average molecular weight (Mn) of about 1000, react for 4-5 hours to give a product with about 2000 Mn, and react for 7-8 hours to give a product with about 3000 Mn. can get. Moreover, when obtaining high molecular weight resin, a polymerization degree becomes high by making the mixing molar ratio of a polyhydric alcohol and a polybasic acid into substantially equal amounts. Furthermore, when the reaction temperature is lowered slightly for a long time, a high molecular weight product can be obtained more efficiently.

  The weight average molecular weight (Mw) of the polyester resin is preferably 30,000 or more and less than 200,000, more preferably 40,000 or more and less than 80,000. Those having an Mw of less than 30,000 are not preferable because they easily interact with the insulating liquid and deteriorate the storage stability. When the Mw is 200,000 or more, the productivity of toner particles deteriorates. Specifically, when toner particles are produced by a granulation method, the solubility when the resin is dissolved in a solvent is deteriorated, so that the desired particle size and shape of the toner particles cannot be controlled. On the other hand, when the toner particles are produced by the pulverization method, the pulverizability of the toner particles is deteriorated and the desired particle size cannot be controlled.

  The glass transition temperature (Tg) of the polyester resin is preferably 50 to 85 ° C. When Tg is lower than 50 ° C., storage stability is deteriorated, and when it is 85 ° C. or higher, the amount of heat required for fixing is remarkably increased and the glossiness is lowered.

  Examples of the resin contained in the toner particles include styrene-acrylic resins, ethylenic acrylic resins, polyethylene resins, and polypropylene resins other than the above polyester resins. These resins can be used alone or in combination of two or more.

<Insulating liquid>
The insulating liquid contained in the liquid developer of the present embodiment preferably has a resistance value (approximately 10 ¹¹ to 10 ¹⁶ Ω · cm) that does not disturb the electrostatic latent image. Moreover, the thing without an odor and toxicity is preferable.

  Examples of such an insulating liquid include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons, polysiloxanes, and the like. In particular, a normal paraffin solvent and an isoparaffin solvent are preferable in terms of odor, harmlessness, and cost. Specifically, Moresco White (trade name, manufactured by Matsumura Oil Research Co., Ltd.), Isopar (trade name, manufactured by Exxon Chemical), Shellsol (trade name, manufactured by Shell Petrochemical), IP Solvent 1620, IP Solvent 2028 (all are trade names, manufactured by Idemitsu Petrochemical Co., Ltd.).

<Toner dispersant>
The liquid developer of the present embodiment preferably contains a dispersant (toner dispersant) soluble in the insulating liquid in order to stably disperse the toner particles in the insulating liquid. Such a toner dispersant is not particularly limited as long as it can stably disperse toner particles. When the acid value of the polyester resin used as the resin contained in the toner particles is relatively high, it is preferable to use a basic polymer dispersant.

<Manufacturing method>
The liquid developer of the present invention can be prepared based on conventionally known techniques such as a granulation method and a pulverization method. Examples of the granulation method include a suspension polymerization method, an emulsion polymerization method, a fine particle aggregation method, a method in which a poor solvent is added to a resin solution, and a spray drying method. In the case of suspension polymerization method or emulsion polymerization method, the continuous phase is aqueous, and after preparing toner particles, the continuous phase is replaced with an insulating liquid, or the toner particles are directly polymerized in the insulating liquid. Can be adopted.

  There is also a method of obtaining toner particles by preparing a resin solution in which a pigment is dispersed in a resin solution, dispersing the resin solution in an insulating liquid, and emulsifying with a suitable dispersant. In this case, a solvent that is incompatible with the insulating liquid is selected as the solvent for the resin solution.

  As a pulverization method, a resin and a pigment are melt kneaded in advance and the mixture is pulverized. The pulverization is preferably performed in a dry state or a wet state in an insulating liquid.

  It is preferable to heat the toner particles to about 40 to 50 ° C. after preparing the toner particles because the arrangement of the resin molecules in the toner particles is aligned.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. In the examples, “part” means “part by mass” unless otherwise specified, and “%” means “% by mass” unless otherwise specified.

<Production of aniline black structure compound represented by general formula (I)>
<Production of aniline black structure compound A>
10 g of aniline was dissolved in 260 ml of 3% aqueous hydrochloric acid solution, and 2.7 g of ferrous sulfate heptahydrate was added thereto. And the solution which melt | dissolved 40 g of ammonium persulfate in 250 ml of water was dripped over 15 minutes with respect to this mixture over 15 minutes, Then, it heated at 70-75 degreeC and stirred for 1 hour. Thereafter, insoluble matters were collected by filtration, washed with water, and the obtained cake was reslurried in 300 ml of water, adjusted to pH 7 with 10% aqueous sodium hydroxide solution, and then heated and stirred at 90 ° C. for 30 minutes. Subsequently, insoluble matters were collected by filtration, washed with water, and dried to obtain 9.1 g of a jet-black black pigment having a slight bluish tinge. This black pigment was a compound in which X is Cl and n is 3 in the general formula (I). Hereinafter, this compound is referred to as “aniline black structure compound A”.

  The chemical structure of the aniline black structural compound was identified by NMR (nuclear magnetic resonance) and MS (mass spectrometry) (the same applies hereinafter).

<Production of aniline black structure compound B>
10 g of aniline is dissolved in 250 ml of 6% tetrafluoroboric acid aqueous solution, and a solution obtained by dissolving 40 g of ammonium persulfate in 300 ml of water at 40 ° C. is added dropwise over 20 minutes, followed by heating to 70 to 75 ° C. and stirring for 1 hour. did. Thereafter, insoluble matters were collected by filtration, washed with water, and the obtained cake was reslurried in 300 ml of water, adjusted to pH 7 with 10% aqueous sodium hydroxide solution, and then heated and stirred at 90 ° C. for 30 minutes. Subsequently, insoluble matters were collected by filtration, washed with water, and dried to obtain 9.5 g of a jet-black black pigment having a slight bluish tinge. This black pigment was a compound in which X is OH and n is 3 in the general formula (I). Hereinafter, this compound is referred to as “aniline black structure compound B”.

<Production of aniline black structure compound C>
10 g of aniline was dissolved in 250 ml of a 6% tetrafluoroboric acid aqueous solution, and 2.6 g of ferric chloride hexahydrate was added thereto. A solution of 45 g of ammonium persulfate dissolved in 300 ml of water was added dropwise to this mixture at 40 ° C. over 20 minutes, then heated to 70 to 75 ° C. and stirred for 1 hour, and further stirred at 90 ° C. for 30 minutes. . Thereafter, insoluble matters were collected by filtration, washed with water, and dried to obtain 9.5 g of a jet blackish black pigment having a slight redness. This black pigment was a compound in which X is OH and n is 3 in the general formula (I). Hereinafter, this compound is referred to as “aniline black structure compound C”.

<Production of aniline black structure compound D>
10 g of aniline is dissolved in 250 ml of 6% tetrafluoroboric acid aqueous solution, and a solution obtained by dissolving 40 g of ammonium persulfate in 300 ml of water at 40 ° C. is added dropwise over 20 minutes, followed by heating to 70 to 75 ° C. and stirring for 1 hour. did. Thereafter, the insoluble material was collected by filtration and washed with water. The obtained cake was reslurried in 300 ml of water, adjusted to pH 7 with 10% aqueous potassium hydroxide solution, and then heated and stirred at 90 ° C. for 30 minutes. Subsequently, insoluble matters were collected by filtration, washed with water, and dried to obtain 9.5 g of a jet-black black pigment having a slight bluish tinge. This black pigment was a compound in which X is OH and n is 3 in the general formula (I). Hereinafter, this compound is referred to as “aniline black structure compound D”.

<Production of Reference Compound E>
To a mixture of 5.0 g of aniline black (C.I. 50440), 7.0 g of n-octanesulfonyl chloride, 100 ml of methylene dichloride and 100 ml of dioxane, 7.0 g of triethylamine was maintained for 1 hour while maintaining the temperature at 30 to 35 ° C. It was dripped at. The mixture was further stirred for 2 hours, and then stirred at a temperature of 80 to 85 ° C. for 4 hours. The reaction mixture was concentrated to about 1/3 of the total volume under reduced pressure. Next, this mixture was dropped into 500 ml of water with stirring, and the mixture was stirred as it was for 1 hour, and the precipitated black solid was collected in a furnace. The obtained solid was washed twice with 100 ml of ethyl acetate and then dried at 50 ° C. under reduced pressure. The black material thus obtained is referred to as “reference compound E”. This reference compound E corresponds to the black substance (III) of Example 3 of Patent Document 2.

<Manufacture of resin>
A polyester resin was produced as a resin contained in the toner particles as follows.

  800 parts (polyhydric alcohol) of propylene oxide adduct of bisphenol A (the following general formula (II)) as a monomer in a four-necked flask equipped with a stirring bar, a partial condenser, a nitrogen gas inlet tube, and a thermometer, 320 parts of terephthalic acid (polybasic acid) and 40 parts of trimellitic acid (polybasic acid) were added, nitrogen gas was introduced while stirring, and polycondensation was performed at a temperature of about 170 ° C. When the weight average molecular weight (Mw) reached about 19000, the temperature was lowered to about 100 ° C., and 0.012 part of hydroquinone was added as a polymerization inhibitor to stop polycondensation.

  A polyester resin was thus obtained (hereinafter referred to as “polyester resin A”). It was 21000 when Mw of the polyester resin A was measured, the acid value was 34.2 mgKOH / g, and the glass transition temperature (Tg) was 67 degreeC.

In formula (II), R ¹ and R ² represent a propylene group, m and n each independently represent 0 or a positive integer, and the sum of the two is a mixture of 1 to 16.

  The weight average molecular weight (Mw), acid value, and glass transition temperature (Tg) were measured as follows.

<Measurement of weight average molecular weight (Mw)>
It measured according to the following conditions with the gel permeation chromatograph (GPC).
DETECTOR: RI (refractive index) detector
COLUMN: ShodexKF-404HQ + ShodexKF-402HQ (made by Showa Denko)
Solvent: Tetrahydrofuran flow Speed: 0.3ml / min
Calibration curve: Standard polystyrene <Measurement of acid value>
The acid value was measured under conditions based on JIS K5400 method.

<Measurement of glass transition temperature (Tg)>
The glass transition temperature (Tg) was measured using a differential scanning calorimeter (trade name: “DSC-6200”, manufactured by Seiko Instruments Inc.) under the conditions of a sample amount of 20 mg and a heating rate of 10 ° C./min.

<Example 1>
100 parts of polyester resin A, 500 parts of acetone, 45 parts of aniline black structural compound A, a basic dispersant as a pigment dispersant (trade name: “Ajisper PB-821”, manufactured by Ajinomoto Fine Techno Co., amine-based basic Compound) 500 parts of glass beads were added to 25 parts and dispersed for 2 hours using a paint conditioner to prepare a resin solution X in which the pigment was dispersed in the resin.

  Next, N-vinylpyrrolidone / alkylene copolymer (trade name: “Antaron V-216”, manufactured by GAF / ISP Chemicals), which is a basic polymer dispersant having an N-vinylpyrrolidone group as a toner dispersant, 5 The part was dissolved in 70 parts of an insulating liquid (trade name: “IP Solvent 2028”, manufactured by Idemitsu Petrochemical Co., Ltd.), and the homogenizer was started. 150 parts of the above resin solution X was charged into a starting homogenizer and dispersed for 5 minutes to prepare a liquid developer precursor.

  Subsequently, when acetone was removed from the liquid developer precursor by an evaporator, the average particle size of the toner particles became 2.3 μm. Then, the liquid developer precursor of the present invention was obtained by storing the liquid developer precursor in a thermostatic bath at 50 ° C. for 4 hours. The average particle size of the toner particles was measured using a particle size distribution measuring device (trade name: “SALD2200”, manufactured by Shimadzu Corporation) (the same applies to the following examples).

<Example 2>
In Example 1, “45 parts of aniline black structural compound A” was changed to “15 parts of aniline black structural compound B and 30 parts of carbon black (trade name:“ Mulul-L ”, manufactured by Cabot Specialty Chemicals, Inc.). The liquid developer of the present invention was obtained in the same manner as in Example 1 except that the amount of the pigment dispersant was changed from “25 parts” to “20 parts”. The average particle size of the toner particles was 2.2 μm.

<Example 3>
In Example 1, “45 parts of aniline black structural compound A” was replaced with “10 parts of aniline black structural compound B and 30 parts of carbon black (trade name:“ Mulul-L ”, manufactured by Cabot Specialty Chemicals, Inc.). ) ”, And“ basic dispersant (Ajisper PB-821) 25 parts ”is replaced with“ basic dispersant (trade name: “SOLSPERS 32000”, manufactured by Nippon Lubrizol Corporation) 20 parts ” In all other respects, the liquid developer of the present invention was obtained in the same manner as in Example 1. The average particle size of the toner particles was 2.3 μm.

<Example 4>
In Example 1, “45 parts of aniline black structure compound A” was replaced with “65 parts of aniline black structure compound C”, and “basic dispersant (Ajisper PB-821) 25 parts” was replaced with “basic dispersant”. Except for replacing with “Solspers 32000” 10 parts ”, everything else was obtained in the same manner as in Example 1 to obtain the liquid developer of the present invention. The average particle size of the toner particles was 2.4 μm.

<Example 5>
100 parts of polyester resin A, 20 parts of aniline black structure compound D, 15 parts of basic dispersant as a pigment dispersant (trade name: “Ajisper PB-822”, manufactured by Ajinomoto Fine Techno Co., Ltd., amine-based basic compound) Was sufficiently mixed with a Henschel mixer, and then melt kneaded using a same-direction rotating twin-screw extruder having a heating temperature in the roll of 100 ° C. Next, the obtained mixture was cooled and then coarsely pulverized to obtain coarsely pulverized toner Y.

  Subsequently, the toner particles Y were obtained by pulverizing the coarsely pulverized toner Y using a counter jet mill (trade name: “200AFG”, manufactured by Hosokawa Micron Corporation). The particle diameter of the toner particles Y was 2.3 μm.

  Thereafter, 70 parts of an insulating liquid (IP solvent 2028), 30 parts of toner particles Y, and 1 part of an N-vinylpyrrolidone / alkylene copolymer (Antaron V-216) as a toner dispersant are mixed, and the mixture is shaken for 1 hour. By dispersing, the liquid developer of the present invention was obtained.

<Comparative Example 1>
A liquid developer of a comparative example was obtained in the same manner as in Example 1 except that “aniline black structure compound A” in Example 1 was replaced with “carbon black (Mogul-L)”. The average particle size of the toner particles was 2.5 μm.

<Comparative example 2>
In Example 1, except that “aniline black structure compound A” is replaced with “aniline black by conventional chromium method (CI Pigment Black 1, manufactured by Tokyo Color Materials Co., Ltd.)”, everything else is the same as in Example 1. Similarly, a liquid developer of a comparative example was obtained. The average particle size of the toner particles was 2.4 μm.

<Comparative Example 3>
In Example 2, except that “aniline black structure compound B” is replaced with “aniline black by conventional chromium method (CI Pigment Black 1, manufactured by Tokyo Color Materials Co., Ltd.)”, everything else is the same as in Example 2. Similarly, a liquid developer of a comparative example was obtained. The average particle size of the toner particles was 2.6 μm.

<Comparative example 4>
In Example 1, except that “45 parts of aniline black structure compound A” was replaced with “25 parts of reference compound E” and no pigment dispersant was added, Comparative Example was the same as in Example 1. A liquid developer was obtained. The average particle size of the toner particles was 2.8 μm.

<Comparative Example 5>
In Example 5, except that “15 parts of basic dispersant (Ajisper PB-822)” is replaced with “15 parts of sodium dodecyl sulfate (manufactured by Wako Pure Chemical Industries, Ltd., non-basic dispersant)” A liquid developer of Comparative Example was obtained in the same manner as Example 5 except for the above. The average particle size of the toner particles was 2.4 μm.

<Evaluation>
The fixing strength and image density of each liquid developer obtained in the above examples and comparative examples were evaluated as follows.

<Evaluation of fixing strength>
Using the image forming apparatus of FIG. 1, a single color solid (solid) pattern (10 cm × 10 cm, adhesion amount: 1.2 g / m ² ) of each liquid developer of Example and Comparative Example is formed on coated paper as a recording material. did. Subsequently, the image was fixed by a heat roller. The fixing conditions were 180 ° C. and a nip time of 50 msec.

After that, an eraser (made by Lion Koki Co., Ltd., sand eraser “LION 26111”) is rubbed twice with a pressing load of 1 kgf on the image portion (single color solid pattern), and a reflection densitometer (trade name: “X-Rite model 404”). The residual ratio of image density (image density after rubbing twice with an eraser relative to the image density before rubbing with an eraser) was measured using X-Rite. Evaluation was made in the following three stages. A higher image density remaining rate indicates a higher fixing strength. The results are shown in Table 1.
A: Image density remaining rate is 90% or more.
B: Image density remaining rate is 80% or more and less than 90%.
C: Image density remaining rate is less than 80%.

<Evaluation of image density>
A single color solid (solid) pattern (10 cm × 10 cm, adhesion amount: 1.2 mg / m ² ) is formed on the coated paper as a recording material by using the liquid developers of the example and the comparative example, using the image forming apparatus of FIG. did. Subsequently, the image was fixed by a heat roller. The fixing conditions were 180 ° C. and a nip time of 50 msec.

Then, the image density of the black solid portion of the monochromatic solid pattern (that is, the fixed image) thus obtained is measured using a reflection densitometer (trade name: “X-Rite model 404”, manufactured by X-Rite). Measurement was performed and the following three ranks were evaluated. A higher numerical value indicates a higher image density. The results are shown in Table 1 below.
A: Image density of 1.8 or more B: Image density of 1.7 or more and less than 1.8 C: Image density of less than 1.7 The process conditions and process of the image forming apparatus are as follows.

<Process conditions>
System speed: 40 cm / s
Photoconductor: negatively charged OPC
Charging potential: -700V
Development voltage (developing roller applied voltage): -450V
Primary transfer voltage (transfer roller applied voltage): + 600V
Secondary transfer voltage: + 1200V
Pre-development corona CHG: appropriately adjusted at a needle application voltage of -3 to 5 kV.

<Outline of the process>
FIG. 1 is a schematic conceptual diagram of an electrophotographic image forming apparatus 1. First, the liquid developer 2 is scraped by the regulating blade 4, and a thin layer of the liquid developer 2 is formed on the developing roller 3. Thereafter, the toner particles move at the nip between the developing roller 3 and the photoreceptor 5, and a toner image is formed on the photoreceptor 5.

  Next, the toner particles move at the nip between the photosensitive member 5 and the intermediate transfer member 6, and a toner image is formed on the intermediate transfer member 6. Subsequently, the toner particles are superimposed on the intermediate transfer member 6, and an image is formed on the recording medium 10. Then, the image on the recording medium 10 is fixed by the heat roller 11.

  In addition to the above, the image forming apparatus 1 includes a cleaning blade 7, a charging device 8, and a backup roller 9.

  As is clear from Table 1, it was confirmed that the liquid developers of the examples were highly compatible in image density and fixing strength as compared with the liquid developers of the comparative examples.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 2 Liquid developer, 3 Developing roller, 4 Control blade, 5 Photoconductor, 6 Intermediate transfer body, 7 Cleaning blade, 8 Charging apparatus, 9 Backup roller, 10 Recording medium, 11 Heat roller

Claims (2)

Including toner particles and an insulating liquid;
The toner particles include a resin, a pigment, and a pigment dispersant,
The pigment includes an aniline black structure compound represented by the following general formula (I):
The pigment dispersant is a liquid developer, which is a basic dispersant.

(In the above formula, n represents an integer of 1 to 3, and X represents OH, Cl, or an acid group.) The pigment is contained in an amount of 25 to 60 parts by mass with respect to 100 parts by mass of the resin.
The liquid developer according to claim 1, wherein the aniline black structure compound is contained in a range of 30 to 100% by mass with respect to the total mass of the pigment.

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