JP2011090167A - Liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer which has superior fixability and color reproducibility, exhibits stable electrophoretic properties, electrostatic chargeability and dispersion state of toner particles in the liquid developer, even if the number of printed sheets or print areas are increased, and maintains stable image density without causing fog of a white background, segregation of dispersant components in the liquid developer, or change in developer composition for a long term. <P>SOLUTION: The liquid developer comprises at least a polyester resin, toner particles containing a disproportionated rosin ester and coloring agent, and a carrier liquid. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid developer used for developing an electrostatic latent image in an electronic copying machine, a laser beam printer, an on-demand printing machine, etc., on which an image is formed by using an electrophotographic method, an electrostatic recording method or the like. It relates to the agent. More preferably, the present invention relates to a full color liquid developer having a wide color reproduction region.

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

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

 As is well known, a liquid developer is one in which toner particles are dispersed in an electrically insulating organic liquid, and the toner particles require colorability, chargeability, fixing properties, and dispersion stability. , Resin, and other additives are added to form toner particles. As such a liquid developer for electrostatic charge development, it is important that toner particles are stably dispersed and stably charged. (For example, see Patent Documents 1 and 2)

It has been conventionally known that a rosin ester is used as a binder resin component in toner particles used in a liquid developer. In addition, by using a binder resin that uses a polyester resin and rosin ester in combination, it is possible to easily control the particle size and charge as a liquid developer, and to obtain an excellent dispersion stability, transferability, and fixability. Has been. Here, ester gum, rosin-modified maleic resin, rosin-modified phenol resin, and the like are being studied as rosin esters. (For example, see Patent Documents 3 and 4)
However, the dispersibility of the colorant in the toner particles is insufficient, the charging is unstable due to poor compatibility between the rosin ester and the polyester resin, the toner particles are not fixed well, and there is room for improvement. Was the current situation.

JP 55-153946 A JP-A-5-333607 Japanese Patent Laid-Open No. 10-254186 JP 2009-186970 A

  As described above, the liquid developer has excellent room for improving the image quality, the toner particle fixability, the long-term stability of the image characteristics, and the stability of the developer composition. There is a need for a liquid developer that solves this problem and has good fixability of toner particles, good color reproducibility of output images, color development, printing durability, and electrophoretic stability of toner particles.

  The object of the present invention is excellent in color reproducibility and fixability, and the electrophoretic property, charging property and dispersion state of the toner particles in the liquid developer are stable even when the number of printed sheets and the printing area are increased, and the image density is To provide a liquid developer that is stable, does not cause fogging of a white background portion, does not cause segregation of a dispersant component in the liquid developer, and does not change the developer composition over a long period of time.

 As a result of intensive studies, the present inventors have used a polyester resin and a disproportionated rosin ester, preferably a disproportionated rosin ester having a specific acid value, in the toner particles in the liquid developer. The inventors have found that the above object can be achieved, and have reached the present invention.

  The present invention relates to toner particles including a polyester resin, a disproportionated rosin ester, and a colorant, and a liquid developer including a carrier liquid.

  The present invention further relates to the above liquid developer containing a dispersant.

  The present invention also relates to the above liquid developer, wherein the acid value of the disproportionated rosin ester is 25 mgKOH / g or less.

  The present invention also relates to the above liquid developer, wherein the acid value of the disproportionated rosin ester is 10 to 16 mg KOH / g.

  The present invention also relates to the above liquid developer, wherein the softening point of the disproportionated rosin ester by the ring and ball method is in the range of 110 to 180 ° C.

  The present invention also relates to the liquid developer, wherein the disproportionated rosin ester is contained in the range of 1 to 20 parts by mass with respect to 100 parts by mass of the polyester resin.

  The present invention also provides the liquid developer, wherein the colorant is selected from the group comprising carbon black, phthalocyanine blue pigment, triarylmethane lake pigment, quinacridone pigment, rhodamine lake pigment, naphthol pigment, monoazo pigment, and quinophthalone pigment. About.

  The present invention also relates to the above liquid developer, wherein the acid value of the polyester resin is 5 to 40 mgKOH / g.

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

  The present invention also relates to the above liquid developer, wherein the dry point in the distillation range of the carrier liquid is 210 to 320 ° C.

  The present invention also relates to the liquid developer, wherein the toner particles have a volume average particle size of 0.5 to 4 μm.

As described above, by using a polyester resin and a disproportionated rosin ester in the toner particles used in the liquid developer, excellent images can be obtained over a long period of time with excellent fixability, color developability, and color reproducibility. A liquid developer can be obtained.
In the liquid developer, toner particles in the liquid developer have good development characteristics due to the presence of the toner particles, and a copy image having good image density and color reproduction from the beginning and without fog can be obtained. it can. Furthermore, a preferable liquid developer can be provided in which the balance of the developer is stable and the carrier liquid is not contaminated over a long period of time.

Hereinafter, the present invention will be described in more detail.
The liquid developer of the present invention has been confirmed to have excellent effects in the following points by containing at least a polyester resin, a disproportionated rosin ester, and a colorant in at least toner particles.

The liquid developer of the present invention is greatly characterized in that a polyester resin and a disproportionated rosin ester are used in toner particles.
Since the disproportionated rosin ester is contained in the polyester resin, it is compatibilized and preferably dispersed in the polyester resin, and as an toner particle, an output image having excellent pigment dispersibility, excellent fixability, and glossiness is obtained. It can be obtained.

  Hereinafter, the toner particles, the carrier liquid, the optional dispersant, etc. constituting the liquid developer of the present invention will be specifically described.

(Toner particles)
The toner particles of the present invention comprise at least a disproportionated rosin ester, a polyester resin, and a colorant, and a charge control agent and a pigment dispersant can also be added.

(Disproportionated rosin ester)

  In the liquid developer of the present invention, the disproportionated rosin ester is used in combination with a polyester resin as a compatibilizing agent capable of uniformly dispersing and blending a colorant in a polyester resin as a binder resin. Therefore, it plays a major role as a binder resin component that can obtain toner particles having good fixability and fixing strength.

The reason why the dispersibility of the colorant and the compatibility with the polyester resin are greatly improved by the addition of the disproportionated rosin ester has not been completely clarified, but the disproportionated rosin ester is the disproportionate rosin Stabilization of the structure of dehydroabietic acid, the main component, and esterification of the dehydroabietic acid component have a polar part with acid and a nonpolar part, and are compatible with the polyester resin, and It is considered that the effect of dispersing and distributing the colorant in the polyester resin is obtained by being compatible with the colorant. Here, the part having an acid is a carboxyl group derived from dehydroabietic acid that has not been reacted in the esterification reaction, and the nonpolar part is a disproportionated skeleton of dehydroabietic acid having no unsaturated bond. is there.
By undergoing a reaction between the polar group of the polyester resin and the carboxyl group of the disproportionated rosin ester, a binder resin component having excellent fixability can be obtained.
Further, since the colorant is uniformly dispersed and blended in the toner particles, there is no bias of the colorant contained in the individual toner particles, so that the quality as a toner can be greatly improved. In particular, from the image characteristics, fogging and scattering of the non-image portion are reduced.

The disproportionated rosin ester is an ester of a disproportionated rosin and an alcohol (polyhydric alcohol such as glycerin ester, pentaerythritol ester or diethylene glycol ester, particularly preferably pentaerythritol ester). Among them, an ester of a disproportionated rosin containing 50% by weight or more of dehydroabietic acid and a polyhydric alcohol is preferable.
Disproportionated rosin is a disproportionation reaction product of gum rosin, wood rosin, tall oil rosin based on resin acids such as abietic acid, parastrinic acid, neoabietic acid, pimaric acid, isopimaric acid and dehydroabietic acid. . The disproportionated rosin used in the present invention can be easily produced by subjecting the raw material rosin to a known disproportionation reaction. That is, rosin is heated and reacted in the presence of a disproportionation catalyst. As the disproportionation catalyst, various known catalysts such as supported catalysts such as palladium carbon, rhodium carbon and platinum carbon, metal powders such as nickel and platinum, and iodides such as iodine and iron iodide can be used. The amount of the catalyst used is usually 0.01 to 5% by weight, preferably 0.01 to 1.0% by weight, based on rosin, and the reaction temperature is 100 to 300 ° C., preferably 150 to 290 ° C. .

The disproportionated rosin obtained here is subjected to an esterification step with alcohol. The esterification reaction can employ normal conditions. As an example, the disproportionated rosin and the following various alcohols are usually heated to 150 to 300 ° C. under an inert gas stream, and the generated water is removed from the system.
Examples of the alcohol used herein include monohydric alcohols such as n-octyl alcohol, 2-ethylhexyl alcohol, decyl alcohol, and lauryl alcohol; dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and neopentyl glycol; glycerin, Examples include trihydric alcohols such as trimethylolethane, trimethylolpropane, and cyclohexanedimethanol; and tetravalent alcohols such as pentaerythritol and diglycerin. In the reaction, an esterification catalyst is not necessarily required. However, in order to shorten the reaction time, acid catalysts such as acetic acid and paratoluenesulfonic acid, alkali metal hydroxides such as calcium hydroxide, calcium oxide, and magnesium oxide are used. A metal oxide such as can also be used.

The disproportionated rosin ester that can be preferably used in the present invention preferably has an acid value of 25 mgKOH / g or less. If the acid value exceeds 25 mgKOH / g, the effect of uniformly dispersing and compatibilizing the colorant in the polyester resin is reduced. In addition, the negative chargeability of the toner particles increases, making it difficult to control the toner particles to be positively charged.
A particularly preferred acid value range is 5 to 20 mg KOH / g. The acid value can be adjusted by controlling the type and amount of alcohol added in the esterification reaction step.

In consideration of fixing property, storage stability and productivity as a toner, the softening point of the disproportionated rosin ester by the ring-and-ball method is preferably in the range of 70 to 140 ° C. More preferably, it is 90-130 degreeC. When it becomes lower than 70 degreeC, compatibility with a polyester resin will deteriorate rapidly. The reason is not clear, but it is presumed that at a softening point lower than 70 ° C., the disproportionated rosin ester rapidly dissolves during kneading and becomes incompatible with the polyester resin. On the other hand, if it is lower than 70 ° C., hot offset tends to occur, and satisfactory fixing performance cannot be obtained. Further, if the temperature exceeds 140 ° C., it is necessary to increase the kneading temperature at the time of toner production, so that the toner raw material is not shared and desired kneading cannot be performed, so that the function as a compatibilizing agent cannot be achieved. In addition, the fixing performance (which tends to peel off) is also deteriorated.
In the esterification reaction step, the softening point can be obtained by adjusting the type and amount of alcohol to obtain a disproportionated rosin ester having a desired numerical value. A specific product satisfying this softening point range is Arakawa. Chemical industry Co., Ltd. superester A-125, A-115, T-100, A-75 etc. are mentioned.

In the present invention, the addition amount of the disproportionated rosin ester is preferably 0.3 to 20 parts by weight with respect to 100 parts by weight of the polyester resin. If the amount of the disproportionated rosin ester added is less than 0.3 parts by weight, the effect of improving the dispersibility of the colorant and the compatibility with the polyester resin cannot be obtained. On the other hand, if it exceeds 20 parts by weight, the original performance of the polyester resin cannot be obtained, and problems such as deterioration of image characteristics and deterioration of fixing performance (occurrence of hot offset) occur.
The balance between the amount of disproportionated rosin ester added and the amount of colorant added is also important. In order to disperse and dissolve the colorant, the disproportionated rosin ester is preferably added in an amount of 0.3 to 3.5 times the content of the colorant. If the content of the colorant is less than 0.3 times, the effect as a compatibilizer is difficult to obtain, and the colorant may be liberated. When the content exceeds 3.5 times the content of the colorant, the disproportionated rosin ester becomes excessive, which impedes toner formulation and deteriorates image characteristics. A more preferable range is a range of 0.6 to 3 times the content of the colorant.

  The true density of the disproportionated rosin ester used in the present invention is preferably in the range of 1.05 to 1.15 (g / cc). Since the true density of the polyester resin is about 1.15 to 1.35 (g / cc), this value is an approximate numerical value and is an effective numerical range for achieving compatibilization.

(Polyester resin)
The polyester resin as the binder resin used in the liquid developer of the present invention is preferably one that exhibits colorless, transparent, white, or light color so as not to hinder the hue of each color material.

 Examples of the alcohol component constituting the polyester resin include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1, 4-butenediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, bisphenol A, hydrogenated bisphenol A, 1, Diols such as 4-bis (hydroxymethyl) cyclohexane, bisphenol derivatives represented by the following general formula (1), glycerol, diglycerol, sorbit, sorbitan, butanetriol, trimethylolethane, trimethylolpropane, pentae Suritoru, dipentaerythritol, tripentaerythritol, polyhydric alcohols and the like can be mentioned, which are used alone or in combination of two or more.

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

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

  As the acid component, divalent carboxylic acids such as benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and phthalic anhydride or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid Or succinic acid substituted with an alkyl group having 16 to 18 carbon atoms or an anhydride thereof; unsaturated dicarboxylic acid such as fumaric acid, maleic acid, citraconic acid, itaconic acid, glutaconic acid or the anhydride thereof; Cyclohexanedicarboxylic acid; naphthalenedicarboxylic acid; diphenoxyethane-2,6-dicarboxylic acid and the like. Trivalent or higher carboxylic acids that function as crosslinking components include trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, and butanetricarboxylic acid. Acid, hexanetricarboxylic acid Tetra (methylene carboxyl) methane, octane tetracarboxylic acid, and benzophenone tetracarboxylic acid anhydride and the like, which are used alone or in combination of two or more.

  Preferred alcohol components are bisphenol derivatives represented by the above general formula (1), ethylene glycol, neopentyl glycol, etc., and preferred acid components are phthalic acid, terephthalic acid, isophthalic acid or anhydrides thereof, succinic acid, n- Dodecenyl succinic acid or its anhydride, dicarboxylic acids such as fumaric acid, maleic acid and maleic anhydride, and tricarboxylic acids such as trimellitic acid or its anhydride.

  The polyester resin may be a homopolyester or a copolyester alone, or may be a blend of two or more of these. The polyester resin preferably has a weight average molecular weight (Mw) of 5,000 or more in terms of molecular weight measured by gel permeation chromatography (GPC) from the viewpoint of offset resistance and low-temperature fixability. The thing of 000-1,000,000 is more preferable. When the weight average molecular weight of the polyester resin decreases, the offset resistance of the toner tends to decrease, and when the weight average molecular weight increases, the fixability tends to decrease. In addition, the polyester resin used has a type having a molecular weight distribution curve of two peaks composed of a specific low molecular weight condensation polymer component and a specific high molecular weight condensation polymer component, or has a single molecular weight distribution curve. Any type.

The molecular weight distribution by GPC is measured, for example, under the following conditions.
The column is stabilized in a 40 ° C. heat chamber, and tetrahydrofuran (THF) as a solvent is allowed to flow through the column at this temperature at a flow rate of 1 ml / min, and about 100 μl of a sample solution dissolved in THF is injected for measurement. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several monodisperse polystyrene standard samples and the number of counts.

As a standard polystyrene sample for preparing a calibration curve, for example, a standard polystyrene sample having a molecular weight of about 10 ² to 10 ⁷ manufactured by Tosoh Corporation or Showa Denko is used, and it is appropriate to use at least about 10 standard polystyrene samples. . An RI (refractive index) detector is used as the detector. As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns. For example, combinations of shodex GPC KF-801, 802, 803, 804, 805, 806, 807, 800P manufactured by Showa Denko KK, TSKgel G1000H (HXL), G2000H (HXL), G3000H (HXL) manufactured by Tosoh Corporation, A combination of G4000H (HXL), G5000H (HXL), G6000H (HXL), G7000H (HXL), and TSKguardcolumn can be given.

  The measurement sample is prepared as follows. That is, after putting a sample in THF and leaving it to stand for several hours, the sample is sufficiently shaken, mixed well with THF until the sample is no longer united, and further allowed to stand for 12 hours or more. At this time, the standing time in THF is set to be 24 hours or longer. Then, GPC measurement was performed on a sample processing filter (pore size 0.45 to 0.5 μm, for example, Mysori Disc H-25-5 manufactured by Tosoh Corp., Excro Disc 25CR manufactured by Gelman Science Japan Ltd., etc.). Sample for use. The sample concentration is adjusted so that the resin component is 0.5 to 5 mg / ml.

The polyester resin used for the toner particles constituting the present invention preferably has a softening temperature Ts by a flow tester of 60 to 90 ° C. This is an effective numerical value for increasing the compatibility with the colorant. When the softening temperature Ts is lower than 60 ° C., the polyester resin is excessively softened at the time of kneading, and the dispersion of the colorant is deteriorated. On the other hand, when the softening temperature Ts is higher than 90 ° C., the polyester resin is not sufficiently melted at the time of kneading, and it becomes difficult to disperse the colorant.
In the present invention, the softening temperature Ts is measured using a flow tester CFT-500D manufactured by Shimadzu Corporation with a starting temperature of 40 ° C. and a temperature increase rate of 6.0 ° C./min. The test load was 20 kg, the preheating time was 300 seconds, the die hole diameter was 0.5 mm, and the die length was 1.0 mm.

  The glass transition temperature (Tg) of the polyester resin is preferably in the range of 50 to 70 ° C. In the present invention, the glass transition temperature (Tg) is an extension of the baseline below Tg when measured with a differential scanning calorimeter (DSC-60, manufactured by Shimadzu Corporation) at a heating rate of 10 ° C./min. And the value of the point of intersection with the tangent of the endothermic curve near Tg.

  The polyester resin in the toner particles used in the present invention preferably has an acid value in the range of 5 to 40 mgKOH / g. When the acid value of the polyester resin is smaller than 5 mgKOH / g, the compatibility with the disproportionated rosin ester is deteriorated, and the electrophoretic property may be lowered. When the acid value of the polyester resin exceeds 40 mgKOH / g, the negative chargeability of the toner particles becomes too strong, and even if a disproportionated rosin ester is added, good positive chargeability cannot be obtained. is there. A more preferred acid value range is 7 to 25 mg KOH / g.

  In the present invention, the acid value of the polyester resin can be measured according to the method of JIS K-0070. The acid value is represented by the number of mg of potassium hydroxide required to neutralize 1 g of toner.

The true density of the polyester resin is preferably 1.1 to 1.4 g / cm ³ considering the balance with the dispersant and the carrier liquid. Here, measurement was performed using AccuPyc 1330 manufactured by Micrometrics.

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

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

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

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

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

Moreover, in order to obtain black with good image density and contrast, it is preferable to add 1 to 10 parts by mass of a blue pigment as a black colorant with respect to 100 parts by mass of the black pigment. As the blue pigment, it is preferable to use a metal phthalocyanine blue compound, a triarylmethane compound, or the like that does not contain a halogen. In addition, the phthalocyanine blue compound and the triarylmethane compound have a stable positive charging property, which is effective in obtaining good black toner particles. Among them, it is preferable to use a copper phthalocyanine compound or a triarylmethane compound. I. Pigment Blue 15: 3, Victoria Pure Blue Lake Pigment (CI Pigment Blue 1), a salt-forming compound (CI Basic Blue 7) comprising a triarylmethane basic dye and a substantially colorless organic acid It is preferable to use a triarylmethane-based oil-soluble dye.
Triarylmethane dyes are effective in controlling the chargeability of toner particles by exhibiting good positive charge, and among them, triarylmethane oil-soluble dyes having excellent dispersibility are preferred.

  The amount of the colorant contained in the toner particles used in the present invention varies depending on the type of polyester resin used, but is usually 5 to 40 parts by weight, preferably 10 to 30 parts by weight with respect to 100 parts by weight of the toner particles. More preferably, it is 15-25 mass parts.

(Other additives)
In addition to the above-described polyester resin and colorant, the toner particles used in the present invention preferably use a charge control agent such as a pigment dispersant or a pigment derivative.
(Pigment dispersant)
As a form of the pigment dispersant internally added to the toner particles, a resin type dispersant such as Solsperse can be used. In particular, in the case of producing a colored master batch through conch, it is a preferable material to be added at the time of producing the master batch.

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

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

In the liquid developer of the present invention, the appropriate addition amount of the dye derivative varies depending on the type of the colorant to be used. Is preferred. Thereby, the dispersion stability of the toner particles is maintained, and the stability of the charging polarity of the toner particles can be maintained.
In the liquid developer of the present invention, it is preferable to use a basic dye derivative since the toner particles have a positive chargeability.

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

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

Further, instead of using the charge control agent, a resin charge control agent can be used.
Of a positively charged, the general formula _{- {CH 2 -CH (C 6} H 5) a} - {CH 2 -CH (COOC 4 H 9)} b- {CH 2 -C (CH 3) COOC 2 H 4 N + CH ₃ (C ₂ H ₅ ) ₂ } cCH ₃ (C ₆ H ₄ ) SO ₃ — (of which quaternary ammonium salt part is 3-35 parts by mass, styrene / acryl part is 97-65 parts by mass, The value of a, b, and c is determined by the above formula), and a styrene / acrylic polymer copolymerized with a styrene / acrylic resin using a quaternary ammonium salt as a functional group.
Specifically, 2-ethylhexyl acrylate / acryloylamino-2-methyl-1-propanesulfonic acid / styrene copolymer, butyl acrylate / N, N-diethyl-N-methyl-2- (methacryloyloxy) ethyl Ammonium = p-toluenesulfonate / styrene copolymer and the like. Since these are colorless and transparent when used with a polyester resin, they are suitable for use in color toners. The resin charge control agent is usually added in an amount of 1.0 to 20 parts by mass, preferably 2.0 to 8 parts by mass with respect to 100 parts by mass of the polyester resin.

(Carrier liquid)
The carrier liquid used in the liquid developer of the present invention is preferably an aliphatic hydrocarbon. Examples of the aliphatic hydrocarbon include a straight chain hydrocarbon, an isoparaffin hydrocarbon, and a naphthene hydrocarbon. Further, those having lipophilic properties, chemically stable and insulating properties are preferred. Further, the carrier liquid needs to be chemically inert with respect to a material or apparatus used in the image forming apparatus, particularly a member around a developing process such as a photoconductor.

It is preferable to use a carrier liquid having a Kauri-butanol value (KB value: ASTM D 1133) of 30 or less. Preferably it is the range of 22-30.
The aniline point (JIS K 2256) is preferably in the range of 60 to 95 ° C. for obtaining a stable carrier liquid.
Specifically describing the insulating properties of the carrier liquid, the dielectric constant is 5 or less, preferably 1 to 5, and particularly preferably 1 to 3.
At the same time, the electric resistivity of the carrier liquid is 10 ⁹ Ω · cm or more, preferably 10 ¹⁰ Ω · cm or more, particularly preferably 10 ¹⁰ to 10 ¹⁶ Ω · cm. Here, the electrical resistivity was measured by combining a universal electrometer MMA-II-17D manufactured by Kawaguchi Electric Manufacturing Co., Ltd. and a liquid electrode LP-05.
Further, the density (JIS K 2249) at 15 ° C. of the carrier liquid is preferably in the range of 0.67 to 0.9 g / cm ³ . More preferably, it is in the range of 0.70 to 0.85 g / cm ³ . In this range, the toner particles and the dispersant can exist stably.

The carrier liquid preferably has a kinematic viscosity (ASTM D445) in the range of 1 to 8. In this range, the charged particles can be moved at the time of the phenomenon, and have sufficient volatility, and can be easily removed from the medium on which the final image is formed by a drying process.
On the other hand, if the viscosity is less than 1, the toner particles after development are likely to move, so that the fineness of the image tends to be lost, which is not preferable. On the other hand, if the viscosity is higher than 8, the fluidity of the toner particles cannot be obtained, and electrophoresis hardly occurs, and a sufficient image density cannot be obtained.
Moreover, it is preferable that the dry point in the distillation range of a carrier liquid is the range of 210-320 degreeC. When the temperature is lower than 210 ° C., the developer is dried at room temperature, solid matter is deposited, and the regulation blade around the development is fixed, thereby causing image contamination. If it is higher than 320 ° C., it becomes difficult to remove the carrier liquid and fixing becomes worse.
Here, the dry point in the distillation range is based on the method defined by ASTM D 86, ASTM D 1078, and JIS K2254.

 Particularly preferred carrier liquids are especially branched paraffin solvent mixtures such as the trade name “Isopar ™ G” (Exxon Corporation), in particular isoparaffinic hydrocarbons, “Exol D80”, “ It is preferably a linear paraffin solvent mixture such as Exol D110 ”,“ Exol D130 ”(Exxsol ™), or a naphthenic hydrocarbon.

(Dispersant)
In the present invention, the dispersant is added to the carrier liquid in which the toner particles are present to uniformly disperse the toner particles and improve the development characteristics. In the liquid developer process of the present invention, toner particles are positively charged.
As a form of using the dispersant, the dispersant having the same polarity as the toner particles is adsorbed on the toner particles, and the dispersant having the opposite polarity to the toner particles is not adsorbed on the toner particles but dispersed in the carrier liquid. It is. At this time, the standard for discussing the polarity is the polarity with respect to the carrier liquid. In addition, this behavior is determined after an actual image test and is obtained empirically.
Specific examples that can be used include fatty acid metal salts such as polyvinylpyrrolidone, cobalt naphthenate, zinc naphthenate, copper naphthenate, manganese naphthenate, cobalt octylate, and zirconium octylate, organics such as lecithin and titanium chelate. These are titanate coupling agents of titanates, alkoxy titanium polymers, polyhydroxy titanium carboxylate compounds, titanium alkoxides, succinimide compounds, fluorine-containing silane compounds, and the like. Of these, titanium alkoxide, succinimide compound, and fluorine-containing silane compound are preferable materials.

  The fluorine-containing silane compound preferably has 2 or more fluorine atoms in one molecule, preferably 2 to 3 fluorine atoms, more preferably 3 fluorine atoms. . More preferably, it is a fluorine-containing alkoxysilane compound. Of these, polyfluoroalkyltri (alkoxy) silanes such as trifluoropropyltrimethoxysilane, trifluorodecyltriethoxysilane, and heptadecafluorodecyltrimethoxysilane are preferable. Here, the structure of the alkoxysilane is preferable in that the fluoroalkyl group can be immobilized and stabilized.

Titanium alkoxides include tetra-n-methoxytitanium Ti (OCH ₃ ) ₄ , tetra-n-ethoxytitanium Ti (OC ₂ H ₅ ) 4, tetra-n-propoxytitanium Ti (OC ₃ H ₇ ) ₄ , tetra- i-propoxy titanium Ti [OCH (CH ₃ ) ₂ ] ₄ , tetra-n-butoxy titanium Ti (OCH ₂ CH ₂ CH ₂ CH ₃ ) ₄ , tetrakis (2-ethylhexyloxy) titanium Ti [OCH ₂ CH (C ₂ H ₅ ) C ₄ H ₉ ] _{4 and the} like. These may be used alone or in combination of two or more.
Among them, tetra-i-propoxy titanium (molecular weight 284), tetra-n-butoxy titanium (molecular weight 340), and tetrakis (2-ethylhexyloxy) titanium (molecular weight 564) are preferable.

As the succinimide compound, succinimide, alkenyl succinimide, alkyl succinimide and the like are preferably used.
The alkyl (or alkenyl) succinimide can be obtained by reacting an alkyl (or alkenyl) succinic anhydride with a polyamine such as polyethylene diamine. That is, an alkyl (or alkenyl) anhydride is first synthesized by a reaction between an oligomer of an olefin having a double bond at the terminal and maleic anhydride. This may be appropriately converted to an alkyl (or alkenyl) acid anhydride by reduction such as hydrogenation. The alkyl (or alkenyl) succinic anhydride thus obtained is then reacted with an imidizing agent such as polyalkylene polyamines such as ammonia, ethylenediamine, diethylenetriamine, triethylenetetramine, etc. to give the desired alkyl (or alkenyl) succinic acid. An imide compound can be obtained.

  Specific examples of the succinimide compound include succinimide (succinimide) and Lubrizol 2153, 2160 manufactured by Nihon Librizol.

  Moreover, about 0.1-20 mass parts can be added to a dispersing agent with respect to 100 mass parts of carrier liquids. More preferably, it is the range of 1-10 mass parts.

(Production method)
A method for producing the liquid developer of the present invention will be described.
The liquid developer of the present invention is preferably obtained through the following five processes.
(1) Preparation of colored masterbatch for toner particles The dispersion resin and the colorant are kneaded with a hot roll or the like at a colorant concentration of 20 to 60% by mass in the masterbatch, and then cooled and coarsely crushed. To obtain a colored master batch. In addition to the dispersing resin and the colorant, a resin-type dispersant and a pigment derivative can also be added.

(2) Preparation of toner particle chips (dilution of colored master batch)
The colored master batch obtained in (1) and the polyester resin are mixed with a mixer such as a super mixer, preliminarily dispersed, and then melt kneaded to dilute and develop the colored master batch in the polyester resin. A chip for toner particles is obtained. Here, a charge control agent may be added at the time of preliminary dispersion. Further, it is preferable that the toner particle chip be 10 mm or less by rough crushing with a hammer mill, a sample mill or the like.
In addition, the steps (1) and (2) can be unified. In this case, all the materials are charged at the time of preliminary dispersion without going through the coloring masterbatch process of (1). What is necessary is just to produce the chip for use. As the melt-kneading, a known kneader such as a pressure kneader, a Banbury mixer, a uniaxial or biaxial extruder can be used.

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

(4) Wet pulverization of toner particles The dry pulverized toner particles obtained in (3) are developed in a solvent having the same composition as the carrier liquid, and the volume average particle size is 0 using a wet pulverizer (disperser). The pulverization is performed so as to be in the range of 5 to 4 μm, preferably 1 to 3 μm. At this time, it is effective to add a dispersant having a function of adsorbing the toner particles to obtain stable chargeability of the toner particles. Here, it is preferable to perform wet pulverization by adding titanium alkoxide in a solvent together with dry-pulverized toner particles. In the wet pulverization and dispersion process, the titanium alkoxide is adsorbed in the toner particles and is also stabilized in terms of charging.
When performing wet pulverization (dispersion), it is necessary to cool so that the product temperature does not exceed 50 ° C. If the product temperature exceeds 50 ° C., the toner particles are fused, and the particle size distribution cannot be controlled.

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

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

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

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

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

(5) Purification of developer The toner particles obtained in (4) and the toner particles and carrier liquid that have undergone wet pulverization, and optionally a dispersant-containing material, are further mixed with a carrier liquid and, if necessary, a dispersant. Then, the developer is purified while controlling the concentration of the toner particles.
A liquid developer in which toner particles are stably dispersed can be obtained by adding the dispersant to the material obtained in the step (4) together with a carrier liquid for adjustment.

(Toner physical properties)
The toner particles used in the present invention preferably have a volume average particle size of 0.5 to 4 μm, more preferably 1 to 3 μm. In addition, toner particles having a particle size of 2 μm or less are contained in an amount of 50% by volume or less, toner particles having a particle size of 1 to 3 μm are contained in an amount of 5 to 60% by volume, and toner particles having a particle size of 5 μm or more are 35% by volume. The following is more preferable from the viewpoint of development characteristics. If the amount of toner particles having a particle diameter of 5 μm or more exceeds 35% by volume, the image quality may be deteriorated.
The particle size distribution of the toner can be measured using a laser diffraction / scattering particle size analyzer, for example, Microtrack HRA manufactured by Nikkiso Co., Ltd.

  In the present invention, the concentration of the toner particles in the liquid developer is preferably 15 to 30% by mass with respect to 100% by mass of the developer. By setting the concentration of the toner particles in the developer within this range, a developer having excellent developability can be obtained. It is preferable to set a higher toner particle concentration than conventional ones, which greatly contribute to the presence of two types of dispersants and the characteristics of the toner particles.

The developer of the present invention preferably has a viscosity of ¹⁰ to 200 mPa · s, and the developer has a volume resistivity of 10 ¹⁰ to 10 ¹⁵ Ω · cm.
The viscosity of the developer can be measured using, for example, an E-type viscometer TV-22 manufactured by Toki Sangyo. The solid content in the developer was adjusted to 25% and sufficiently adjusted to 25 ° C., then a 1 ° 34 ′ cone was set in the TV-22 viscosity type, and the viscosity after 1 minute at 20 rpm was measured. If the viscosity is 10 mPa · s or less, the fineness of the image after development is lacking, and if it is 200 mPa · s or more, the mobility of the toner during development is poor and high-speed development cannot be performed.
The volume resistivity can be measured in the same manner as the carrier liquid measuring method described above. If it is 10 ¹⁰ Ω · cm or less, the electrostatic latent image on the photoreceptor cannot be retained, which is not preferable.

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

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

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

(Polyester resin)
Thermoplastic polyester resin 1
Polyester resin composed of terephthalic acid, isophthalic acid, trimellitic acid, propylene oxide-added bisphenol A, and ethylene glycol.
Acid value: 10 mg KOH / g OH value: 43 mg KOH / g Tg 58 ° C. Softening temperature Ts 65 ° C. True density 1.32 g / cc Molecular weight Mw: 28200 Mn: 2500
Thermoplastic polyester resin 2
Polyester resin composed of terephthalic acid, isophthalic acid, trimellitic acid, propylene oxide-added bisphenol A, and ethylene glycol.
Acid value: 18 mg KOH / g OH value: 36 mg KOH / g Tg 59 ° C. Softening temperature Ts 66 ° C. True density 1.31 g / cc Molecular weight Mw: 32000 Mn: 2600

(Coloring agent)
Black colorant 1
Carbon black (Monarch 280 BET specific surface area 45 m ² / g manufactured by Cabot) and C.I. I. Solvent Blue 124 (Clariant COPY BLUE PR)
Black colorant 2
Carbon black (Cabot Monarch 280 BET specific surface area 45m ² / g) and nigrosine base wet pulverized product (0.5μm) (Orient Chemical's Bontron N-07 refined by wet pulverization)
Yellow colorant 1
C. I. Pigment Yellow 138
Cyan colorant 1
C. I. Pigment blue 15: 3 and C.I. I. Solvent Blue 124 (Clariant COPY BLUE PR)
Cyan colorant 2
C. I. Pigment blue 15: 3 and C.I. I. Pigment Blue 1
Magenta colorant 1
C. I. Pigment red 269 and C.I. I. Pigment Violet 1
Magenta colorant 2
C. I. Pigment red 122 and C.I. I. Pigment Red 57: 1

(Disproportionated rosin ester)
Disproportionated rosin ester 1 Super ester A-125 made by Arakawa Chemical
(Acid value 12.2 Softening point 126 ° C. True density 1.097 g / cm ³ )
Disproportionated rosin ester 2 Super ester A-115 made by Arakawa Chemical
(Acid value 17.8 Softening point 118 ° C. True density 1.098 g / cm ³ )
Disproportionated rosin ester 3 Super ester A-100 manufactured by Arakawa Chemical
(Acid value 5.4 Softening point 100 ° C. True density 1.099 g / cm ³ )
Disproportionated rosin ester 4 Super ester A-75 made by Arakawa Chemical
(Acid value 6.7 Softening point 78 ° C. True density 1.096 g / cm ³ )

(Carrier liquid)
Isopar M Isoparaffinic hydrocarbon Dry point 254 ° C Density 0.790g / cm ³
Exol D110 Naphthenic hydrocarbons Dry point 267 ° C Density 0.810g / cm ³

(Dispersant)
Dispersant 1 Succinimide compound Lubrizol 2153 Acid value: 70 mg KOH / g
Number average molecular weight: 3000 or less Dispersant 2 Titanium alkoxide (titanium tetraisopoloxide)
Ti (O-i-C ₃ H ₇ ) ₄
Dispersant 3 Trifluoropropyltrimethoxysilane CF ₃ CH ₂ CH ₂ Si (OCH ₃ ) ₃ Molecular weight: 218.2 Specific gravity: 1.14 (25 ° C.)
Boiling point: 144 ° C

[Example 1]
Thermoplastic polyester resin 1 52 parts by weight disproportionated rosin ester 1 8 parts by weight carbon black (specific surface area 45 m ² / g: Monarch 280 manufactured by Cabot Corporation) 37 parts by weight Copy Blue PR (CI Solvent Blue 124) 3 parts by weight Part The above materials (3 kg in total) were taken out by mixing and kneading in a pressure kneader at a set temperature of 150 ° C. for 10 minutes. Further, the mixture was kneaded with three rolls at a roll temperature of 95 ° C., and after cooling, coarsely crushed to 10 mm or less to obtain Black Conc 1 as a black colorant dispersion.
further,
Thermoplastic polyester resin 1 50 parts by weight Black concrete 1 50 parts by weight The above materials (5 kg in total) are mixed with a Henschel mixer having a volume of 20 L (3000 rpm, 3 minutes) and then supplied with a twin-screw kneading extruder (PCM30). Melted and kneaded at 6 kg / hr, discharge temperature of 145 ° C., cooled and solidified, then coarsely pulverized with a hammer mill, then finely pulverized with an I-type jet mill (IDS-2 type) and a volume average particle size of about 5.0 μm A black toner ground product 1 was obtained.
further,
Black toner pulverized product 1 25 parts by mass Isopar M 73 parts by mass Dispersant 1 2 parts by mass Weighed, sufficiently stirred and mixed, and Black toner pulverized product 1 was dispersed in the Isopar M solution. (Slurry concentration is 25% by mass)
The slurry in which the black toner pulverized product 1 is dispersed is subjected to a circulation operation for 60 minutes using a wet pulverizer which is a medium agitating mill, Dino Mill Multilab (Shinmaru Enterprises Co., Ltd., capacity 1.4 L), and wet pulverized. Went.
The wet pulverization conditions at this time were as follows.
Agitator disk (material: zirconia) peripheral speed 10m / s, cylinder ZTA,
Media (Material: Zirconia) Diameter 1.25mm, Filling rate 70%
Solution flow rate 45 kg / h, cooling water 5 l / min. , Pressure 0.1Kg / cm ²
After wet pulverization for 60 minutes, the slurry was taken out and passed through a mesh having an opening of 33 μm (manufactured by SUS304) to obtain a black toner wet pulverized product 1 (including black toner particles 1). When the particle size distribution of the black toner particles 1 was confirmed, the D50 (cumulative 50 percent diameter) was 2.9 μm.
Further, 1 part by mass of the dispersant 3 was added to 100 parts by mass of the obtained black toner wet pulverized product 1 and stirred to obtain a liquid developer 1.

  In the live-action test, a commercially available liquid developing copier (Savin 870: manufactured by Sabin) was used, an amorphous silicon photoconductor was used under an environmental condition of 23 ° C./50% RH, and the surface potential of the photoconductor was +450. An image test of 10,000 sheets was performed from the initial stage with ˜500 V, residual potential +50 V or less, and developing roller bias set to +250 to 450 V. At this time, the image was produced with each color as a single color.

  The image density is measured using a Macbeth photometer (RD-918). The density is 1.5 or more for black, 1.1 or more for yellow, 1.25 or more for cyan, and 1 for magenta. The concentration may be 25 or more. Scattering was visually confirmed using a loupe.

As for the fixing rate, first, an image density ID (ID ₁ ) at the time of output was measured using a printed image obtained by outputting a solid portion of 1 cm × 1 cm at OD = 1.1 after 1000 sheets. Thereafter, a mending tape (Scotch 810 manufactured by 3M) was attached to the printed matter, and a 1 kg cylindrical brass weight was rolled and reciprocated once. Thereafter, the mending tape was removed, the image density ID (ID ₂ ) was measured again, (ID ₂ ) / (ID ₁ ) × 100 was calculated, and the fixing rate (%) was obtained. Here, if the fixing rate is 80% or more, it is practically preferable, and if it is 90% or more, it is preferable.

Detailed experimental conditions, compositions, and physical property results are shown in Tables 1-4. Table 1 shows the colorant concentrate composition, Table 2 shows the composition of the toner pulverized product (dry pulverization step), Table 3 shows the composition of the wet pulverized product and toner particle properties, and Table 4 shows the composition of the liquid developer and the image test results.
Moreover, about Examples 2-17 and Comparative Examples 1-3, experimental conditions, a composition, and a physical-property result are shown to Tables 1-4 similarly. The conditions other than those listed in Tables 1 to 4 were the same as in Example 1.

In Examples 1 to 17, even when an image test of 10,000 sheets was performed from the beginning, the image density was stable at 1.3 or more, and no scattering was observed. The fixing rate was also good.
As can be seen from Table 3, unless the disproportionated rosin ester is added, a sufficient image density cannot be obtained and the fixing strength is inferior.

  The liquid developer of the present invention is compatible with high-speed machines, has excellent printing durability, and development characteristics, and is static in electrophotographic copying machines, laser beam printers, and the like where images are formed using electrophotography, electrostatic recording, and the like. It can be preferably used as a liquid developer used for developing an electrostatic latent image.

Claims (11)

  A liquid developer comprising toner particles containing a polyester resin, a disproportionated rosin ester, and a colorant, and a carrier liquid.   The liquid developer according to claim 1, further comprising a dispersant.   The liquid developer according to claim 1 or 2, wherein the acid value of the disproportionated rosin ester is 25 mgKOH / g or less.   The liquid developer according to claim 1, wherein the disproportionated rosin ester has an acid value of 5 to 20 mg KOH / g.   The liquid developer according to any one of claims 1 to 4, wherein a softening point of the disproportionated rosin ester by the ring and ball method is in a range of 70 to 140 ° C.   6. The liquid developer according to claim 1, wherein the disproportionated rosin ester is contained in an amount of 0.3 to 20 parts by mass with respect to 100 parts by mass of the polyester resin.   The colorant is selected from the group comprising carbon black, phthalocyanine blue pigment, triarylmethane lake pigment, quinacridone pigment, rhodamine lake pigment, naphthol pigment, monoazo pigment and quinophthalone pigment. Liquid developer.   The liquid developer according to claim 1, wherein the polyester resin has an acid value of 5 to 40 mg KOH / g.   The liquid developer according to claim 1, wherein the carrier liquid is an aliphatic hydrocarbon.   The liquid developer according to any one of claims 1 to 9, wherein a dry point in a distillation range of the carrier liquid is 210 to 320 ° C.   The liquid developer according to claim 1, wherein the toner particles have a volume average particle diameter of 0.5 to 4 μm.