JP2011100000A - Liquid developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid developer that has high fixability and color reproducibility, keeps stable electrophoretic property, electrostatic property, and dispersion state of toner particles in the liquid developer even when the number of printing sheets and the printing area increase, stabilizes the image density, prevents occurrence of fog of a white ground part, prevents segregation of dispersant components in the liquid developer, and prevents variation of the developer composition for a long time. <P>SOLUTION: This liquid developer includes toner particles containing at least polyester resin, ketone resin and colorant, and 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)

In dry toners, it is known to use a ketone resin as a binder resin for toner. It is known that by using a ketone resin, it is possible to improve the fixability and the fixing strength without impairing the offset resistance and blocking resistance of the toner. Further, it is known that the compatibility is excellent and the dispersibility of the material in the toner can be improved. (For example, see Patent Documents 3 and 4)
However, in the case of toner particles used for the liquid developer, the ketone resin is dissolved in the carrier liquid, and thus it has been difficult to use the ketone resin in the liquid developer so far.

JP 55-153946 A JP-A-5-333607 JP-A-5-173364 JP 2002-72556 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 found that the above object can be achieved by using a polyester resin and a ketone resin, preferably a ketone resin having a specific softening point, in the toner particles in the liquid developer. As a result, the present invention has been achieved.

  The present invention relates to toner particles containing a polyester resin, a ketone resin, and a colorant, and a liquid developer containing 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 ketone resin has a softening point by the ring-and-ball method of 70 to 150 ° C.

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

  The present invention also relates to the liquid developer, wherein the ketone resin is contained in a range of 0.3 to 30 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 ketone resin in the toner particles used in the liquid developer, the liquid developer has excellent fixability, color developability, and color reproducibility, and can provide a good image over a long period of time. 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 segregation does not occur for a long 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 ketone resin, 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 ketone resin are used in the toner particles.
When the ketone resin is contained in the polyester resin, it is compatibilized and preferably dispersed in the polyester resin, and as a toner particle, an output image having excellent pigment dispersibility, excellent fixability, and glossiness can be obtained. It can be done.

  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 ketone resin, a polyester resin, and a colorant, and a charge control agent and a pigment dispersant can also be added.

(Ketone resin)

  In the liquid developer of the present invention, the ketone resin is used as a compatibilizing agent and a dispersing agent that can uniformly disperse and mix the colorant in the polyester resin as the binder resin, and also in combination with the polyester 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 ketone resin has not been completely clarified, but the ketone resin has the presence of the carbonyl group in the basic skeleton and the terminal end. Due to the presence of the alcohol group, it has a polar part and a non-polar part, is compatible with the polyester resin, and is also compatible with the colorant, thereby obtaining the effect of preferably dispersing and distributing the colorant in the polyester resin. It is thought that
Here, the polar part is a carbonyl group or an alcohol group, and the nonpolar part is a skeleton derived from cyclohexane or the like. By undergoing a reaction between the polar group of the polyester resin and the carbonyl group or alcohol group of the ketone resin, a binder resin component having excellent fixability can be obtained.

The ketone resin is light in color, has excellent plasticity and adhesion, and is easily soluble in organic solvents.
In the liquid developer of the present invention, at the time of production of toner particles, a polyester resin, a ketone resin, a colorant, etc. are added and then melt kneaded to obtain a toner particle chip. The obtained toner particle chip is further subjected to wet pulverization after dry pulverization. In the wet pulverization step, it is developed and pulverized in a solvent having the same composition as that of the carrier liquid. At this time, the ketone resin present on the surface of the toner particles is dissolved and encapsulated in the toner particles. The existing ketone resin remains as it is. As a result, the ketone resin does not exist on the surface of the toner particles, and the ketone resin exists only in the toner particles. As a result, the surface of the toner particles is in a uniform state without uneven distribution of the resin composition, and stable charging can be imparted to the toner particles.
At this time, since the surface layer of the toner particles is a polyester resin that tends to be negatively charged with respect to the carrier liquid, it is suitable for adsorbing a dispersant exhibiting positive chargeability. Here, the charging polarity may be confirmed by the behavior when electrophoresis is actually performed after selecting the carrier liquid.
Further, since the colorant is uniformly dispersed and blended in the toner particles, the colorant contained in the individual toner particles is not biased, so that the quality as the toner particles can be greatly improved. From the image characteristics, the fog in the non-image area is reduced, and the decrease in image density in a low temperature and low humidity environment can be suppressed.

A ketone resin is a resin obtained as a ketone by condensation of ketones and aldehydes.
Examples of ketones include acyclic ketones such as acetone, methyl ethyl ketone, isobutyl ketone, ethyl methyl ketone, diethyl ketone, and t-butyl methyl ketone, saturated alicyclic ketones such as cyclohexanone and methylcyclohexanone, acetophenone, methyl acetophenone, and methyl naphthyl. Aromatic ketones such as ketone, benzophenone and propiophenone are used.
Examples of aldehydes include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, acrylic aldehyde, and benzaldehyde, and hydrogenated products of ketone resins are also preferably used. As aldehydes, it is preferable to use formaldehyde.

Specific examples include cyclohexanone ketone resins, acetophenone ketone resins, methylcyclohexanone ketone resins, methyl ethyl ketone resins, and methyl isobutyl ketone ketone resins.
Of these, cyclohexanone ketone resins and acetophenone ketone resins are preferably used in terms of excellent compatibility with polyester resins and excellent solubility in carrier liquids. In particular, it is preferable to use cyclohexanone ketone resin.

  The ketone resins preferably used in the present invention are cyclohexanone ketone resins represented by the following chemical formulas 1 and 2, and acetophenone ketone resins using acetophenone instead of cyclohexanone.

  The ketone resin preferably used in the present invention preferably has a degree of polymerization (n) in the range of 1 to 10 in the above chemical formula. When the value of n becomes 0, it does not function as a compatibilizing agent, and when it exceeds 10, it is difficult to dissolve in the carrier liquid, which is not preferable.

  The ketone resin that can be preferably used in the present invention preferably has an acid value of 5 mgKOH / g or less. If the acid value is greater than 5 mgKOH / g, both the polyester resin and the ketone resin exhibit negative polarity, and repulsively charge and the effect of compatibilization with the polyester resin is reduced, thereby improving the fixing property. It becomes difficult to disperse the colorant uniformly in the polyester resin. A more preferable acid value of the ketone resin is 3 mgKOH / g or less.

  In consideration of fixing properties, storage stability, and productivity as toner particles, the softening point of the ketone resin by the ring and ball method is preferably in the range of 70 to 150 ° C. When the temperature is lower than 70 ° C., hot offset is likely to occur, and satisfactory fixing performance cannot be obtained. When the temperature exceeds 150 ° C., it is necessary to similarly increase the kneading temperature during the production of the toner material. The toner raw material does not take a share and the desired kneading cannot be performed, so that the function as a compatibilizing agent is not achieved. In addition, the fixing performance (which tends to peel off) is also deteriorated.

  In this invention, it is preferable that the addition amount of a ketone resin is 0.3-30 weight part with respect to 100 weight part of polyester resins. If the addition amount of the ketone resin 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 30 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 true density of the ketone resin used in the present invention is preferably in the range of 1.05 to 1.15 (g / cc). This numerical value is an approximate numerical value because the true density of the polyester resin is about 1.2 to 1.3 (g / cc), 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.

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

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

  As the acid component, divalent carboxylic acids such as benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid and phthalic anhydride or anhydrides thereof; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and azelaic acid Or 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 and the like, 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 types of 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 ketone resin 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 good chargeability may not be obtained even if a ketone resin is added. 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 between 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 consisting of a triarylmethane basic dye and a substantially colorless organic acid (CI Basic Blue 7) 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, but generally it is used in the range of 0.1% by mass to 30% by mass with respect to 100 parts by mass of the colorant. 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), electron donating substances such as polymers having amino groups, etc. are used alone or in combination of two or more. be able to. Needless to say, the triarylmethane dye described above is preferable.

Further, instead of using the charge control agent, a resin charge control agent can be used.
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 electrical resistivity of the carrier liquid is 10 ⁹ Ω · cm or more, preferably 10 ¹⁰ Ω · cm or more, and 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 “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. In particular, a succinimide compound is preferably used as a dispersant having a function of adsorbing toner particles.

  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.

Examples of the titanium alkoxide 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 and the like to produce 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 master batch for toner particles The dispersion resin, ketone resin and colorant are kneaded with a hot roll or the like at a colorant concentration of 20 to 60% by mass in the master batch and cooled. Post-crushing is performed 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 masterbatch obtained in (1) and a polyester resin, and optionally a ketone resin, are mixed with a mixer such as a super mixer, preliminarily dispersed, and then melt-kneaded, so that the colored masterbatch is added to the polyester resin. Diluted and developed to obtain a chip for toner particles. 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. In the wet pulverization / dispersion step, the dispersant is adsorbed in the toner particles and stabilized in terms of charging.
When performing wet pulverization (dispersion), it is necessary to cool so that the product temperature does not exceed 50 ° C. If the product temperature exceeds 50 ° C., the toner particles are fused, and the particle size distribution cannot be controlled.

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

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

The types of grinding media include glass beads (SiO ₂ 70 to 80%, NaO 12 to 16%, etc.), zircon beads (ZrO ₂ 69%, etc.) depending on the viscosity, specific gravity and grinding and dispersion required particle size of the toner particles. SiO ₂ 31%), zirconia beads (ZrO ₂ 95% or more), alumina (Al ₂ O ₃ 90% or more), titania _{(TiO 2 77.7%, Al 2} O 3 17.4%), steel balls or the like Although it can be used, it is preferable to use zirconia beads or zircon beads in order to obtain good grindability.
The particle diameter (diameter) of the pulverization media can be used in the range of 0.1 mm to 3.0 mm, and in particular, the range of 0.3 to 1.4 mm is preferable. If it is smaller than 0.1 mm, the load in the pulverizer increases, and the toner particles melt due to heat generation, making it difficult to pulverize. If it is larger than 3.0 mm, sufficient pulverization cannot be performed. . The filling rate of the dispersion medium is preferably 40 to 85%. If it exceeds 85%, the load in the pulverizer becomes large, the toner particles are melted by heat generation, making pulverization difficult, and if it becomes 40% or less, the pulverization efficiency decreases. Refinement becomes difficult. When the concentration of toner particles in the slurry is high (concentration of 40 to 50%), the filling rate is preferably 40 to 70% by 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. The toner particles having a particle diameter of 2 μm or less are contained in an amount of 50% by volume or less, the toner particles having a particle diameter of 1 to 3 μm are contained in an amount of 5 to 60% by volume, and the toner particles having a particle diameter 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 45 m ² / g) and nigrosine base wet pulverized product (0.5 μm) (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

(Ketone resin)
Cyclohexanone ketone resin 1 K-90 manufactured by Arakawa Chemical
(Acid value 1 or less Softening point 90 ° C. True density 1.10 g / cm ³ )
Cyclohexanone-based ketone resin 2 made by Hitachi Chemical
(Acid value 1 or less, softening point 110 ° C., true density 1.10 g / cm ³ )
Acetophenone-based ketone resin 3 manufactured by Honshu Chemical Co., Ltd. Halon 110H
(Acid value 1 or less, softening point 110 ° C., true density 1.10 g / cm ³ )

(Carrier liquid)
Isopar M Isoparaffinic hydrocarbon Dry point 254 ° C Density 0.790 g / cm ³
Exol D110 Naphthenic hydrocarbons Dry point 267 ° C Density 0.810 g / 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 ketone resin 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 (3 kg in total) was 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 mass

Black Conc 1 50 parts by weight The above materials (5 kg in total) were mixed with a Henschel mixer having a volume of 20 L (3000 rpm, 3 minutes), then fed with a twin-screw kneading extruder (PCM30) at a feed rate of 6 kg / hr, a discharge temperature of 145 ° C. Then, the mixture was cooled and solidified, coarsely pulverized with a hammer mill, and then finely pulverized with an I-type jet mill (IDS-2 type) to obtain a black toner pulverized product 1 having a volume average particle diameter of about 5.0 μm. .
further,
Black toner pulverized product 1 25 parts by mass Isopar M 73 parts by mass Dispersant 1 2 parts by mass were 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 0.1 kg / cm ²
After wet pulverization for 60 minutes, the slurry was taken out and passed through a mesh having an opening of 33 μm (manufactured by SUS304) to obtain a black toner wet pulverized product 1 (including black toner particles 1). When the particle size distribution of the black toner particles 1 was confirmed, D50 (cumulative 50 percent diameter) was 3.0 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 16, 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 a ketone resin 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 (10)

  A liquid developer comprising toner particles containing a polyester resin, a ketone resin, 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, wherein the ketone resin has a softening point of 70 to 150 ° C. according to the ring and ball method.   4. The liquid developer according to claim 1, wherein the acid value of the ketone resin is 5 mg KOH / g or less.   The liquid developer according to claim 1, wherein the ketone resin is contained in an amount of 0.3 to 30 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 8, wherein a dry point of the carrier liquid in a distillation range 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.