JP2005275316A - Electrophotographic liquid developer and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate the designing of a liquid developer capable of achieving high image quality. <P>SOLUTION: The electrophotographic liquid developer is obtained by dispersing toner particles in an electrical insulating carrier liquid, wherein the toner particles comprise coated colorant particles obtained by coating colorant particles with at least one of magnesium abietate and the magnesium salt of an abietic acid derivative, a fixing resin and a charge imparting agent for imparting positive chargeability to the toner particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic developer and a method for producing the same, and more particularly, to an electrophotographic liquid developer and a method for producing the same.

  In the wet electrophotographic technology, a liquid developer containing a highly insulating carrier liquid having a low dielectric constant, such as a petroleum aliphatic hydrocarbon solvent, and toner particles dispersed therein is used. In general, a liquid developer is prepared by mixing a colorant particle composed of a pigment or a dye and a fixing resin in a carrier liquid to prepare a dispersion, and adding a charge imparting agent such as metal soap (or charge control). It is obtained by adding an agent.

  In order to achieve high image quality with wet electrophotographic technology, it is important to optimize the composition of the colorant particles, the chargeability of the toner particles, and the affinity between the colorant particles and the fixing resin. However, the chargeability of the toner particles and the affinity between the colorant particles and the fixing resin vary depending on the type of the colorant particles used. Therefore, it is difficult to design a liquid developer, and there are restrictions on the selection of colorant particles.

In addition, there exists the following patent document 1 as a prior art document relevant to this invention. In this document, metal salts such as aluminum, calcium, magnesium, cobalt, manganese, iron, zinc and copper of organic acids such as rosin acid and fatty acid are exemplified as positive charge control agents. Further, in this document, as a method for producing a liquid developer, a method of diluting a concentrated toner obtained by mixing a colorant, an oil and fat, and a charge control agent and dispersing the mixture in a carrier liquid, A method of dropping the concentrated toner into a carrier liquid and a method of adding a colorant and a charge control agent to the dispersion after producing toner particles by polymerizing monomers in the carrier liquid are described.
JP-A 61-284776

  An object of the present invention is to facilitate the design of a liquid developer capable of realizing high image quality.

  According to a first aspect of the present invention, there is provided a liquid developer for electrophotography in which toner particles are dispersed in an electrically insulating carrier liquid, the toner particles comprising colorant particles of magnesium abietic acid and an abietic acid derivative. An electrophotographic liquid developer comprising: coated colorant particles coated with at least one of magnesium salts; a fixing resin; and a charge imparting agent imparting positive chargeability to the toner particles. Provided.

  According to the second aspect of the present invention, the step of coating the colorant particles with at least one of magnesium abietic acid and a magnesium salt of an abietic acid derivative to obtain coated colorant particles, the coated colorant particles, the fixing resin, and the charge An imparting agent and an electrically insulating carrier liquid are mixed, and the carrier liquid contains the coated colorant particles, the fixing resin, and the charge imparting agent, and imparts positive chargeability by the charge imparting agent. And a method of producing a liquid developer for electrophotography, comprising the step of producing the toner particles.

  According to the present invention, it becomes easy to design a liquid developer capable of realizing high image quality.

Hereinafter, embodiments of the present invention will be described.
The electrophotographic liquid developer according to one embodiment of the present invention contains an electrically insulating carrier liquid and toner particles dispersed therein. Each toner particle includes coated colorant particles obtained by coating the colorant particles with at least one of magnesium abietic acid and a magnesium salt of an abietic acid derivative, a fixing resin, and a charge imparting agent.

  Magnesium abietates and magnesium salts of abietic acid derivatives (hereinafter collectively referred to as “magnesium salts of abietic acids”) are unlikely to cause ionization in a non-aqueous solvent used as a carrier liquid. In addition, the magnesium salt of abietic acid is formed on the surface of the colorant particle because the magnesium forms a strong coordinate bond with both the colorant particle having an acidic substituent and the colorant particle having a basic substituent. Hardly releases from. Therefore, even if the composition of the colorant particles is changed in the liquid developer, the chargeability of the toner particles and the affinity between the colorant particles and the fixing resin do not change due to this change.

  Abietic acid is a main component of rosin generally used as a fixing resin. For this reason, magnesium salts of abietic acids have a high affinity for rosin and a high affinity for many other materials generally used as fixing resins.

  That is, once this condition is adopted, once the conditions for achieving good chargeability are determined, even if the composition of the colorant particles is changed, good chargeability and High affinity between the colorant particles and the fixing resin can be realized. For example, in the case of forming a multicolor image, if the conditions under which good chargeability can be achieved for a certain color are investigated, this condition is applied to other colors, so that good chargeability and High affinity between the colorant particles and the fixing resin can be realized. Therefore, according to this aspect, it becomes easy to design a liquid developer capable of realizing high image quality.

The liquid developer can be manufactured, for example, by the following method.
First, the colorant particles are coated with a magnesium salt of abietic acid to obtain coated colorant particles. For example, a colorant and a magnesium salt of abietic acid are kneaded at a temperature equal to or higher than the melting point of the magnesium salt, or kneaded with a small amount of carrier liquid. Alternatively, the colorant particles and the magnesium salt of abietic acid are dispersed in the carrier liquid, and the dispersion liquid is stirred to coat the colorant particles with the magnesium salt. Further, when the colorant particles are coated with a small amount of magnesium salt, for example, less than 1 part by weight per 1 part by weight of the colorant particles, a flushing method may be used.

  Next, a liquid developer in which toner particles are dispersed in the carrier liquid is prepared using the coated colorant particles, the fixing resin, the charge imparting agent, and the carrier liquid. For example, the coated colorant particles, the fixing resin, and the charge imparting agent are added to the carrier liquid and stirred. As a result, toner particles containing the coated colorant particles, the fixing resin, and the charge imparting agent are generated in the carrier liquid. Alternatively, the coated colorant particles, the fixing resin, and the charge-imparting agent are kneaded with a small amount of carrier liquid by a ball mill, sand mill, attritor, or the like, and the resulting concentrate is diluted with the carrier liquid.

  It should be noted that the charge imparting agent may be added to the carrier liquid at any time after the coated colorant particles are prepared. Further, after preparing the coated colorant particles, an auxiliary such as wax may be added to the carrier liquid.

Next, materials that can be used for the liquid developer described above will be described.
The colorant contains a pigment, a dye, or a mixture thereof. There are no particular restrictions on the pigments and / or dyes that can be used as the colorant of the liquid developer. These pigments and dyes may be used alone or in combination of two or more.

  Examples of pigments and dyes that can be used for the colorant include carbon black; I. Pigment yellow 1, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 97, C.I. I. Acetoacetic acid arylamide monoazo yellow pigments such as CI Pigment Yellow 98; I. Imidazolone monoazo yellow pigments such as CI Pigment Yellow 181; I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Acetoacetic acid arylamide disazo yellow pigments such as C.I. Pigment Yellow 17; I. Solvent Yellow 19, C.I. I. Solvent Yellow 77, C.I. I. Solvent Yellow 79, C.I. I. Yellow dyes such as disperse yellow 164; I. Pigment red 48, C.I. I. Pigment red 49: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Pigment red 5, C.I. I. Pigment red 146, C.I. I. Red to red pigments such as C.I. Pigment Red 184; I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Solvent Red 58, C.I. I. Red dyes such as Solvent Red 8; I. Pigment blue 15: 3, C.I. I. A blue pigment of copper phthalocyanine and its derivatives such as CI Pigment Blue 15: 4; I. Pigment green 7, C.I. I. And green pigments such as CI Pigment Green 36 (phthalocyanine green).

  As a magnesium salt of abietic acid, a magnesium salt of abietic acid magnesium and an abietic acid derivative can be used. As this abietic acid derivative, for example, a hydride such as dihydroabietic acid or tetrahydroabietic acid, a dehydrogenated product such as dehydroabietic acid, or an isomer such as neoabietic acid, parastolic acid, levopimaric acid or maleopimaric acid is used. can do. Any of these magnesium salts is substantially insoluble in a carrier liquid usually used in a liquid developer.

  These magnesium salts may be used alone or in combination of two or more. Further, the magnesium salt of abietic acid may be used by mixing with a salt of abietic acid other than magnesium salt and / or abietic acid.

  Although it is desirable that the entire surface of the colorant particle is coated with a magnesium salt of abietic acid, the surface of the colorant particle may not be completely coated with the magnesium salt of abietic acid. However, when the magnesium salt of abietic acid that covers the colorant particles is small, the above effect is not remarkably manifested, and the colorant particles tend to aggregate and the original color cannot be obtained. is there. For example, if the colorant particles are coated with the magnesium salt so that the magnesium salt of abietic acid is 1 part by weight or more per 1 part by weight of the colorant particles, the above-mentioned effect is remarkably exhibited and the colorant particles are aggregated. Can be prevented and the original color can be obtained.

  When there are many magnesium salts of abietic acids covering the colorant particles, it is difficult to stably disperse the toner particles in the carrier liquid, and the toner particles may be easily precipitated. In addition, when a general magnesium salt of abietic acid is heated, the melt viscosity is remarkably reduced at around 100 ° C. Therefore, when there is a large amount of magnesium salt of abietic acid covering the colorant particles, a high temperature offset phenomenon occurs during thermal transfer or fixing. May cause. For example, if the colorant particles are coated with the magnesium salt so that the magnesium salt of abietic acid is 1.5 parts by weight or less per 1 part by weight of the colorant particles, precipitation of the toner particles and high temperature offset phenomenon can be prevented. it can.

  As the fixing resin, for example, a resin such as an amphiphilic resin can be used. The amphiphilic resin can be used as a non-aqueous dispersion resin, that is, a colloidal solution dispersed in a non-aqueous solvent.

  As the amphiphilic resin, for example, as described in JP-A-55-71713, a first polymer chain composed of a vinyl polymer soluble in a non-aqueous solvent and a vinyl polymer insoluble in the non-aqueous solvent are used. A graft polymer that has a molecular structure in which a second polymer chain made of a polymer is bonded via an ester bond and is insoluble in the above non-aqueous solvent can be used. Alternatively, the amphiphilic resin has a molecular structure in which the first polymer chain and the second polymer chain are bonded via a urethane bond, as described in, for example, JP-A-58-122557. Things can also be used. In addition to these graft polymers, commercially available olefin copolymers having an ester group or a carboxyl group can also be used.

  When the amount of fixing resin relative to the colorant particles is small, the toner particle diameter is not reduced, and it is difficult to realize good dispersion stability and transferability. For example, when the fixing resin is 0.1 parts by weight or more per 1 part by weight of the colorant particles, good dispersion stability and transferability can be realized.

  When the amount of the fixing resin with respect to the colorant particles is large, the ratio of the colorant particles to the toner particles is small, so that a sufficient concentration cannot be realized. For example, if the fixing resin is 10 parts by weight or less per 1 part by weight of the colorant particles, a sufficient concentration can be realized.

  As the charge imparting agent, for example, a positively chargeable charge imparting agent that imparts positive chargeability to the toner particles can be used. For example, fatty acid zirconium can be used as the positive charge-providing agent. Examples of the fatty acid zirconium include zirconium naphthenate, zirconium octylate, zirconium stearate, zirconium laurate, zirconium oleate and the like.

As the electrically insulating carrier liquid, a liquid mainly composed of a nonpolar hydrocarbon solvent is used. As the nonpolar hydrocarbon solvent, for example, a solvent having a Kauri-butanol value of 30 or less, a resistivity of 10 ⁹ Ω · cm or more, and a dielectric constant of 3 or less can be used. For example, non-polar hydrocarbon solvents such as hexane, pentane, octane, nonane, decane, undecane, dodecane, organic solvents marketed under the trade names such as Isopar H, G, K, L, M and Norper from Exxon Chemical Co., Ltd. As described above, an aliphatic hydrocarbon solvent having a boiling point in the range of 68 ° C. to 250 ° C. may be used. These organic solvents may be used alone or in combination of two or more.

  As the auxiliary agent such as wax, any of those used in ordinary electrophotographic liquid developers can be used. For example, paraffin wax, polyethylene wax, polypropylene wax, ethylene copolymer, propylene copolymer, and a mixture thereof can be used.

The liquid developer described above can be used, for example, in the electrophotographic apparatus of FIG.
FIG. 1 is a diagram schematically illustrating an example of an electrophotographic apparatus that can use a liquid developer according to an aspect of the present invention.

  The electrophotographic apparatus 1 includes an image carrier 10 that is a photoconductor. Around the image carrier 10, a latent image forming device 20, a developing device 30, a densifying device 40, a transfer device 50, and a cleaner 60 are disposed.

  In this example, the image carrier 10 is a photosensitive drum, and can be rotated clockwise in the drawing by a driving mechanism (not shown). By such a rotation operation, the image holding surface of the image carrier 10 moves relative to the cleaner 60, the latent image forming device 20, the developing device 30, the densifying device 40, the transfer device 50, and the like.

  The image carrier 10 includes a substrate 101 having a conductive surface and a photoreceptor layer 102 formed on the conductive surface. The photoreceptor layer 102 contains, for example, a material that changes in a charged state or the like when irradiated with light, for example, an amorphous silicon photosensitive material. The photoreceptor layer 102 can be charged to a positive polarity by a charger 202 described later. The photoreceptor layer 102 can be covered with a release layer (not shown).

The latent image forming apparatus 20 includes a static eliminator (not shown), a charger 201, and a writing device 202.
The static eliminator uniformly eliminates a portion of the photoreceptor layer 102 of the image carrier 10 that is located in front of the static eliminator. That is, the electrostatic latent image is erased from the photoreceptor layer 102 after transfer.

  The charger 201 is, for example, a corona charger represented by a corotron charger or a scorotron charger. The charger 201 uniformly charges a portion of the photoreceptor layer 102 of the image carrier 10 positioned in front of the charger 201 to a positive polarity.

  The writing device 202 includes a light source such as a laser exposure device or an LED, and an optical system that guides light emitted from the light source to the photosensitive layer 102. The writing device 202 irradiates the photoconductor layer 102 with light corresponding to the image information, and thereby neutralizes the light irradiation portion of the photoconductor layer 102. That is, an electrostatic latent image composed of an irradiating portion that is a low potential portion and a non-irradiating portion that is a high potential portion is obtained.

  The developing device 30 supplies the liquid developer to the image holding surface of the image carrier 10. The developing device 30 includes, for example, a container 302 that stores the liquid developer 301, a developing roller 303 that is rotatably arranged with a slight gap from the image holding surface, and a developing roller 303 that rotates counterclockwise in the drawing. And a rotation mechanism (not shown) for applying the voltage and a voltage application mechanism (not shown) for applying a voltage to the developing roller 303.

  When such a configuration is adopted, when the developing roller 303 is rotated counterclockwise in the drawing, a developer layer made of the liquid developer 301 can be formed between the developing roller 303 and the image carrier 10. . At this time, the potential of the developing roller 303 is set to a potential between the surface potential at the irradiation portion of the image carrier 10 and the surface potential at the non-irradiation portion.

  As a result, in the developer layer formed between the developing roller 303 and the image carrier 10, the positively charged toner particles move toward the light irradiation portion of the photoreceptor layer 102. As a result, a developer image is formed on the image holding surface of the image carrier 10 with a pattern corresponding to the electrostatic latent image.

  The densifying device 40 is not necessarily provided. However, when the densifying device 40 is provided, the toner particle layer can be densified. For example, the toner particle layer can be densified by removing at least a part of the carrier liquid from the developer image.

  In this example, the densification device 40 includes a recovery device provided with a squeeze roller 401 and a solvent removal device 402 provided with a porous roller.

  The collection device collects excess toner and solvent from the image holding surface of the image carrier 10. The solvent recovery device includes, for example, a squeeze roller 401 that is rotatably arranged with a slight gap from the image holding surface, a rotation mechanism (not shown) that rotates the squeeze roller 401 clockwise in the drawing, and a squeeze roller. A cleaning blade (not shown) that scrapes off the solvent adhering to the surface of 401, a container (not shown) that receives the solvent scraped off by the cleaning blade, and a voltage application mechanism (not shown) that applies a voltage to squeeze roller 401 (Not shown).

  When such a configuration is employed, for example, when the squeeze roller 401 is rotated in the clockwise direction in the drawing, the excess solvent on the image holding surface of the image carrier 10 is wound up by the squeeze roller 401. The solvent wound up by the squeeze roller 401 is scraped off by the cleaning blade and collected in the container. The solvent recovered in this manner can be reused for the liquid developer.

  The porous roller of the solvent removing device 402 rolls on the image holding surface of the image carrier 10 to absorb and remove the carrier liquid from the developer image. In this example, a porous roller or the like is used as the solvent removing device 402, but an air blower or the like for spraying and drying a developer image may be used, or both of them may be used.

  In this example, the transfer device 50 includes an intermediate transfer medium 501 and a backup roller 502. The transfer device 50 uses pressure to transfer a developer image from the image carrier 10 to the intermediate transfer medium 501 and to transfer a developer image from the intermediate transfer medium 501 onto a recording medium 70 such as paper or an OHP sheet. .

  In this example, the transfer device 50 further includes a heater 503. That is, here, the transfer device 50 transfers the developer image from the image carrier 10 to the intermediate transfer medium 501 and transfers the developer image from the intermediate transfer medium 501 onto a recording medium 70 such as paper or an OHP sheet. The structure that can use pressure and heat is adopted. The transfer device 50 may further include a transport mechanism that moves the recording medium 70 leftward in the drawing.

  The transfer device 50 transfers the developer image on the image carrier 10 onto the recording medium 70 via the intermediate transfer medium 501.

  The intermediate transfer medium 501 is, for example, an intermediate transfer roller or an intermediate transfer belt. In FIG. 1, as an example, an intermediate transfer roller is drawn as the intermediate transfer medium 501. The intermediate transfer medium 501 includes a support 5011 and an elastic layer 5012 provided on the support 5011.

  The intermediate transfer medium 501 is pressed against the image carrier 10 such that the transfer surface is in contact with the image carrier surface of the image carrier 10. Further, the intermediate transfer medium 501 rotates counterclockwise in the drawing as the image carrier 10 rotates.

  The backup roller 502 is pressed against the intermediate transfer medium 501 so that its pressure surface is in contact with the transfer surface of the intermediate transfer medium 501 via the recording medium 70. Further, the backup roller 502 rotates clockwise in the drawing as the intermediate transfer medium 501 rotates.

In this example, the heater 503 is disposed in the intermediate transfer medium 501. As the heater 503, for example, a halogen lamp can be used. The heater 503 is not necessarily provided, but when the heater 503 is provided, the surface of the intermediate transfer medium 501 can be heated to increase the adhesive force of the toner constituting the developer image.
The cleaner 60 removes toner remaining on the image holding surface after transfer.

Examples of the present invention will be described below.
(Example 1)
In this example, first, 40 parts by weight of phthalocyanine blue and 60 parts by weight of magnesium dehydroabietic acid were melt-kneaded using a pressure kneader. Here, KET • BLUE111 commercially available from DIC was used as phthalocyanine blue, and KM-1600 commercially available from Arakawa Chemical was used as magnesium dehydroabietic acid. Subsequently, the obtained colored paste was pulverized using a loadplex. Further, the pulverized product was sieved to obtain coated colorant particles having a particle diameter of 1 mm or less, which was formed by coating phthalocyanine blue with magnesium dehydroabietic acid.

  Next, 95 parts by weight of an organic solvent was added to 5 parts by weight of ethylene vinyl acetate copolymer resin (EVA), and these mixtures were heated and dissolved at 150 ° C. using a container equipped with a reflux stirrer. Here, EV-450 manufactured by Mitsui DuPont was used as EVA, and Isopar L manufactured by Exxon Chemical was used as the organic solvent.

  After cooling the mixed solution, 15 parts by weight of the coated colorant particles, 2 parts by weight of zirconium naphthenate, and 3 parts by weight of Isopar L were added thereto, and mixed with an attritor for 3 hours. Here, zirconium naphthenate manufactured by Dainippon Ink & Chemicals, Inc. having a nonvolatile content of 40% by weight was used as zirconium naphthenate. This gave 120 g of concentrate.

  Further, this concentrated solution was diluted with 880 g of Isopar L. As described above, a positively charged liquid developer for electrophotography was obtained.

Next, an image output test was performed using this liquid developer in the electrophotographic apparatus of FIG.
Here, a photosensitive drum was used as the image carrier 10, and this was rotated at a peripheral speed of 220 mm / second. The photoreceptor layer 102 of the image carrier 10 was charged by the charger 201 so that the surface potential of the image carrier 10 was about + 750V.

  As the writing device 202, a laser optical device equivalent to 600 dpi (dot per inch) was used. The surface potential at the irradiated portion of the image carrier 10 was lowered to +100 V by laser light irradiation.

  A stainless steel roller was used as the developing roller 303, and the distance between the developing roller 303 and the image holding surface was 100 μm. The potential of the developing roller 303 was set to about +600 V, and the peripheral speed was 220 mm / second.

  A stainless steel roller was used as the squeeze roller 401, and the distance between the squeeze roller 401 and the image holding surface was 50 μm. The peripheral speed of the squeeze roller 401 was set to three times the peripheral speed of the image carrier 10.

  The densifying device 40 was set so that the carrier liquid content in the developer image immediately after passing through the front face was reduced to 0 wt% to 20 wt%.

  As the intermediate transfer medium 501, an elastic body layer 5012 provided with a 200 μm thick silicone rubber layer was used. The peripheral speed of the intermediate transfer medium 501 was 213.4 mm / second.

  A stainless steel roller was used as the backup roller 502. The peripheral speed of the backup roller was equal to the peripheral speed of the intermediate transfer medium 501. Further, the intermediate transfer medium 501 and the backup roller 502 were heated to 130 ° C. by the heater 503.

  As a result of performing an image output test under the above conditions, an image with a very high density (Macbeth density: 1.6) and a high resolution was obtained. Further, no deterioration of the image was observed even after continuously printing 1000 sheets or more. Further, after the developer was left for 1 month, an image output test was performed under the same conditions as described above. As a result, the same image quality as in the initial stage was maintained.

(Example 2)
In this example, first, 20 parts by weight of carbon black, 20 parts by weight of magnesium dehydroabietic acid, and 160 parts by weight of an organic solvent were wet kneaded using an attritor. Here, carbon black # 25 marketed by Mitsubishi Chemical Corporation is used as carbon black, KM-1600 marketed by Arakawa Chemical Co. is used as magnesium dehydroabietic acid, and Exxon Chemical Co., Ltd. is used as the organic solvent. Isopar L was used. As a result, coated colorant particles obtained by coating carbon black with magnesium dehydroabietic acid were obtained.

  Next, 55 parts by weight of an organic solvent was added to 5 parts by weight of ethylene vinyl acetate copolymer resin (EVA), and these mixtures were heated and dissolved at 150 ° C. using a container equipped with a reflux stirrer. Here, Dumira C-2270 manufactured by Takeda Pharmaceutical Company Limited was used as EVA, and Isopar L manufactured by Exxon Chemical Company was used as the organic solvent.

  After cooling the mixed solution, 10 parts by weight of the above-mentioned coated colorant particles, 0.7 parts by weight of zirconium naphthenate, and 13.3 parts by weight of Isopar L are added and mixed for 3 hours with an attritor. did. Here, zirconium naphthenate manufactured by Dainippon Ink & Chemicals, Inc. having a nonvolatile content of 40% by weight was used as zirconium naphthenate. This gave 84 g of concentrate.

  Further, this concentrated solution was diluted with 616 g of Isopar L. As described above, a positively charged liquid developer for electrophotography was obtained.

  Next, an image output test similar to that performed in Example 1 was performed except that this liquid developer was used. As a result, an image with a very high density (Macbeth density: 1.7) and a high resolution was obtained. Further, no deterioration of the image was observed even after continuously printing 1000 sheets or more. Further, after the developer was left for 1 month, an image output test was performed under the same conditions as described above. As a result, the same image quality as in the initial stage was maintained.

(Example 3)
In this example, a positively charged liquid developer for electrophotography was prepared in the same manner as described in Example 1 except that Norper 12 manufactured by Exxon Chemical Co. was used instead of Isopar L manufactured by Exxon Chemical. Obtained.

  Next, an image output test similar to that performed in Example 1 was performed except that this liquid developer was used. As a result, an image with a very high density (Macbeth density: 1.6) and a high resolution was obtained. Further, no deterioration of the image was observed even after continuously printing 1000 sheets or more. Further, after the developer was left for 1 month, an image output test was performed under the same conditions as described above. As a result, the same image quality as in the initial stage was maintained.

Example 4
In this example, zirconium octylate manufactured by Nippon Kagaku Sangyo Co., Ltd. having a nonvolatile content of 55% by weight was used instead of zirconium naphthenate manufactured by Dainippon Ink Chemical Co., Ltd. having a nonvolatile content of 40% by weight. In the same manner as described in Example 2, a positively charged liquid developer for electrophotography was obtained.

  Next, an image output test similar to that performed in Example 1 was performed except that this liquid developer was used. As a result, an image with a very high density (Macbeth density: 1.6) and a high resolution was obtained. Further, no deterioration of the image was observed even after continuously printing 1000 sheets or more. Further, after the developer was left for 1 month, an image output test was performed under the same conditions as described above. As a result, the same image quality as in the initial stage was maintained.

(Comparative Example 1)
In this example, a positively charged liquid developer for electrophotography was obtained by the same method as described in Example 1 except that calcium dehydroabietic acid was used instead of magnesium dehydroabietic acid.

  Next, an image output test similar to that performed in Example 1 was performed except that this liquid developer was used. As a result, an initial image with a very high density (Macbeth density: 1.5) and a high resolution was obtained. However, after continuously printing 1000 sheets or more, the density gradually decreased (Macbeth density: 1.0). In addition, when this developer was left for one month and then an image output test was performed under the same conditions as described above, a large amount of fog was generated on the white background.

(Comparative Example 2)
In this example, instead of adding the coating colorant particles to the mixture of EVA and Isopar L, instead of adding phthalocyanine blue and magnesium dehydroabietic acid to this mixture, it was explained in Example 1. In the same manner, a positively charged liquid developer for electrophotography was obtained. The amounts of phthalocyanine blue and magnesium dehydroabietic acid in this liquid developer were the same as those of the liquid developer prepared in Example 1.

  Next, an image output test similar to that performed in Example 1 was performed except that this liquid developer was used. As a result, the density was slightly low from the beginning (Macbeth density: 1.2), and the image edge portion was blurred. Also, fog was seen on the white background.

1 is a diagram schematically illustrating an example of an electrophotographic apparatus that can use a liquid developer according to one embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electrophotographic apparatus, 10 ... Image holding body, 20 ... Latent image forming apparatus, 30 ... Developing apparatus, 40 ... Densification apparatus, 50 ... Transfer apparatus, 60 ... Cleaner, 70 ... Recording medium, 101 ... Substrate, 102 ... Photosensitive layer, 201 ... Charger, 202 ... Writing device, 301 ... Liquid developer, 302 ... Container, 303 ... Developing roller, 401 ... Squeeze roller, 402 ... Solvent removing device, 501 ... Intermediate transfer medium, 502 ... Backup Roller, 503... Heater, 5011... Support, 5012.

Claims (4)

An electrophotographic liquid developer in which toner particles are dispersed in an electrically insulating carrier liquid,
The toner particles are coated colorant particles obtained by coating the colorant particles with at least one of magnesium abietic acid and a magnesium salt of an abietic acid derivative, a fixing resin, and charge imparting that imparts positive chargeability to the toner particles. A liquid developer for electrophotography characterized by comprising an agent.   The electrophotographic liquid developer according to claim 1, wherein the coated colorant particles are formed by coating the colorant particles with magnesium dehydroabietic acid.   3. The electrophotographic liquid developer according to claim 1, wherein the charge imparting agent contains fatty acid zirconium. Coating the colorant particles with at least one of magnesium abietic acid and a magnesium salt of an abietic acid derivative to obtain coated colorant particles;
The coated colorant particles, the fixing resin, the charge imparting agent, and the electrically insulating carrier liquid are mixed, and the coated colorant particles, the fixing resin, and the charge imparting agent are contained in the carrier liquid. And a process for producing toner particles imparted with a positive charge by the charge imparting agent.

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