JP2009151006A - Magnetic toner, liquid developer, process cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic toner capable of reducing the size of the toner while suppressing deterioration in magnetic characteristic, a liquid developer using the toner, and a process cartridge and an image forming apparatus using the liquid developer. <P>SOLUTION: The magnetic toner comprises magnetic powder composed of an yttrium-iron-garnet (YIG) and having a peak at 420 in an X-ray diffraction, the half value width of the peak is 0.4 deg or smaller, and a polymer compound including the magnetic powder. The liquid developer uses the magnetic toner. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic toner, a liquid developer, a process cartridge, and an image forming apparatus.

  2. Description of the Related Art A magnetic printing apparatus that can print a required number of copies by forming a latent image once is known. In this magnetic printing apparatus, a magnetic latent image magnetically formed is held on a magnetic recording medium (magnetic latent image holding member), and magnetic toner is supplied to the magnetic recording medium in a developing region to convert the magnetic latent image into toner. It is visualized as an image, a recording medium such as paper is pressed against the magnetic recording medium in the transfer area, the visualized toner image is transferred to the recording medium, and the transferred recording medium is transported to the fixing area and fixed. The print is completed by processing. This method is generally called magnetography.

In the above, the magnetization state in the magnetic recording medium is maintained semi-permanently. Therefore, when a latent image is formed once, an extremely large number of copies can be obtained simply by repeating the development and transfer processes. Further, since there is no need to re-record the latent image in order to obtain a multi-copy, it is possible to cope with high speed. Further, unlike static electricity, magnetism is stable to the environment, and an image with high resolution can be obtained.
On the other hand, since the magnetic latent image can be easily formed and erased magnetically and no printing plate is required, the cost can be reduced.

  Regarding magnetography, so-called dry image forming apparatuses using powdered magnetic toner have been proposed (see, for example, Patent Documents 1 and 2). As a specific process, for example, the magnetic toner is supplied by a supply roller disposed at a distance from the magnetic recording medium. The supply roller holds the magnetic toner layer on the peripheral surface thereof, brings the magnetic toner layer into contact with the magnetic recording medium, and supplies and adheres the magnetic toner to the magnetic latent image of the magnetic recording medium.

  On the other hand, an image forming apparatus (so-called liquid magnetography) using a liquid developer in which a magnetic toner is dispersed in a liquid has been studied (for example, see Patent Documents 3 and 4). In this process, since the toner is contained in the liquid, a problem such as a toner cloud does not occur even if the toner particle size is reduced to improve the image quality.

In order to colorize magnetic toners, proposals have been made to use transparent magnetic materials such as rare earth garnet, ferromagnetic ferrite, yttrium / iron / garnet, cadmium / gallium / tellurium (see, for example, Patent Documents 5 to 8). ).
Japanese Patent Laid-Open No. 6-4008 JP-A-9-156150 Japanese Patent Publication No. 5-87834 Japanese Patent Laid-Open No. 5-18827 JP-A-60-73549 JP 60-73548 A JP-A-63-50856 JP-A-7-114205

  An object of the present invention is to provide a magnetic toner capable of reducing the diameter of the toner while suppressing a decrease in magnetic characteristics, and a liquid developer using the magnetic toner. Another object of the present invention is to provide a process cartridge and an image forming apparatus using the liquid developer.

The above problem is solved by the following means. That is,
The invention according to claim 1
A magnetic powder comprising yttrium, iron, garnet (YIG) and having a half-width of the peak of the plane index (420) of 0.4 deg or less in powder X-ray diffraction;
A polymer compound containing the magnetic powder;
A magnetic toner comprising:

The invention according to claim 2
In the CIE 1976 (L * a * b *) color system of the magnetic powder,
The magnetic toner according to claim 1, wherein L * is 65 or more and 90 or less, a * is −9 or more and 15 or less, and b * is 30 or more and 110 or less.

The invention according to claim 3
The magnetic toner according to claim 2, wherein L * of the magnetic toner in the CIE 1976 (L * a * b *) color system is 80 or more and 90 or less.

The invention according to claim 4
The magnetic toner according to any one of claims 1 to 3,
An aqueous medium in which the magnetic toner is dispersed;
A liquid developer characterized by comprising:

The invention according to claim 5
A magnetic latent image carrier;
Developer storage means for storing the liquid developer according to claim 4;
Developer supplying means for supplying the liquid developer to a magnetic latent image holding member on which a magnetic latent image is formed;
It is a process cartridge characterized by having.

The invention according to claim 6
A magnetic latent image carrier;
Magnetic latent image forming means for forming a magnetic latent image on the magnetic latent image holding member;
Developer storage means for storing the liquid developer according to claim 4;
Developer supplying means for supplying the liquid developer to a magnetic latent image holder on which the magnetic latent image is formed in order to visualize the magnetic latent image as a toner image;
Transfer means for transferring the toner image to a recording medium;
A degaussing means for degaussing the magnetic latent image on the magnetic latent image holder;
An image forming apparatus comprising:

According to the first aspect of the invention, it is possible to reduce the diameter of the toner while suppressing the reduction in magnetic characteristics.
According to the invention of claim 2, the influence of the magnetic powder on the toner hue is suppressed.
According to the third aspect of the invention, a decrease in the brightness of the toner is suppressed.
According to the invention which concerns on Claim 4, while being excellent in developability, high image quality is implement | achieved. In addition, it can support on-demand printing, and not only can obtain high-quality images, but it is also environmentally friendly.
According to the fifth aspect of the present invention, image defects due to poor development are suppressed and high image quality is realized.
According to the sixth aspect of the present invention, image defects due to poor development are suppressed, and high image quality is realized.

(Liquid developer)
The magnetic toner according to this embodiment is a magnetic polymer particle containing a magnetic powder in a polymer compound. And this magnetic powder consists of yttrium, iron, and garnet (YIG), and the half value width of the peak of the surface index (420) is 0.4 deg or less in powder X-ray diffraction. In addition, this characteristic of the magnetic powder may be referred to as “X-ray diffraction characteristic”.

  With the magnetic toner according to the present embodiment, the toner diameter can be reduced while suppressing a reduction in magnetic characteristics by adopting the above configuration. The reason for this is not clear, but is thought to be due to the following reasons.

  In order to improve the image quality, it is necessary to reduce the diameter of the magnetic toner. As an example, in order to reduce the size of the magnetic toner to a number average particle size of, for example, about 0.5 μm to 5 μm, the size of the magnetic powder blended in the toner is also reduced to an average primary particle size of, for example, 2 μm or less. It is necessary to. However, magnetic powder (hereinafter sometimes referred to as YIG particles) made of yttrium, iron, and garnet (YIG particles), for example, has a reduced crystallinity and a reduced magnetization, resulting in deterioration of magnetic properties. This makes it difficult to apply magnetic force to the magnetic toner.

  Here, in the YIG particles, the “surface index (420)” in the powder X-ray diffraction is the strongest of several peaks appearing in the powder X-ray diffraction pattern of YIG, and the half width of this peak is That it is below a predetermined value shows that the reduction of the crystallinity is suppressed. Therefore, when the YIG particles satisfy the X-ray diffraction characteristics, deterioration of the magnetic characteristics is suppressed even when the diameter is reduced.

  For this reason, in the magnetic toner according to the present embodiment, by using the YIG particles having the above characteristics, it is possible to reduce the diameter of the toner while suppressing the reduction of the magnetic characteristics.

  In the magnetic toner according to this embodiment, L * in the CIE 1976 (L * a * b *) color system is preferably 80 or more and 90 or less.

  As a result of accumulating experiments so far, when YIG particles as magnetic powder are reduced in size, it is easy to obtain particles exhibiting a brown color, and if this is included in magnetic toner, it affects the hue of the image (particularly the yellow toner). It has been found that the effect of reducing the brightness). That is, it was found that YIG particles known as a transparent magnetic material having a low influence on the toner color of magnetic powder tend to change from green to brown when the diameter is reduced. If YIG is green, the hue of the color toner (for example, yellow, cyan, magenta) is hardly affected, but if it is brown, the hue of the color toner is affected, and particularly the brightness of the yellow toner is reduced.

  In contrast, the magnetic toner according to the present embodiment satisfies the predetermined CIE 1976 (L * a * b *) color system by applying YIG particles satisfying the X-ray diffraction characteristics (particularly suitable). L * is satisfied), and the magnetic toner in which the influence of the magnetic powder on the color of the toner is suppressed is obtained. This is because the YIG particles satisfying the X-ray diffraction characteristics are reduced in amorphization, in other words, the reduction in crystallinity is suppressed, so that the green YIG particles in which discoloration to brown is suppressed. It is thought that there is.

  The CIE 1976 (L * a * b *) color system is a color space recommended by the CIE (International Lighting Commission) in 1976, and is defined in “JIS Z 8729” by the Japanese Industrial Standard. The same applies hereinafter.

-Magnetic powder-
YIG particles as magnetic powder are made of yttrium, iron, and garnet (YIG). And YIG particle | grains satisfy | fill the characteristic that the half value width of the peak of a surface index (420) is 0.4 deg or less in powder X-ray diffraction.

  The full width at half maximum of this peak is desirably 0.4 deg or less, more desirably 0.38 deg or less, and further desirably 0.35 deg or less. By setting the half width of this peak within the above range, even if the magnetic toner is reduced in diameter, the crystallinity is reduced and the reduction of magnetization is suppressed. Note that the smaller the half-value width of the peak, the sharper the peak and the better. However, the lower limit value is a measurement limit value, for example, 0.1 deg.

  Here, the powder X-ray diffraction pattern of the YIG particles for obtaining the peak and the half width of the peak is obtained as follows. Using an X-ray diffractometer (D8 DISCOVER: manufactured by Bruker AXS Co., Ltd.), measurement is performed by X-ray irradiation of λ = 1.5405 mm with a Cu target. In this powder X-ray diffraction pattern, the peak corresponding to the YIG plane index (420) is a peak showing a diffraction peak at 2θ = 32.3 ° at a Bragg angle (2θ ± 0.2 °), and the maximum intensity is shown. Show. In order to obtain the half width of this peak, the background is approximated by a straight line from 2θ = 30 ° to 35 °, then the height from this straight line to the peak maximum is obtained, and the peak at half the height is obtained. I measured the width of.

  The half width of a peak means a peak width at half the height of a certain peak, and it can be said that the crystallinity is better as the half width becomes smaller.

  The average primary particle size of the YIG particles is preferably in the range of 0.02 μm to 2.0 μm, more preferably 0.05 μm to 1.5 μm, and even more preferably 0.1 μm to 1.0 μm. It is. When the average primary particle size of the YIG particles is within the above range, the magnetic properties required for the magnetic toner can be provided.

  In addition, an average primary particle diameter means the number average diameter at the time of observing and measuring 100 pieces with a transmission electron microscope (TEM) or a scanning electron microscope (SEM). The same applies hereinafter.

  The magnetization of the YIG particles in a magnetic field of 500 Oe is desirably 10 emu / g or more, more desirably 15 emu / g or more, and further desirably 20 emu / g or more. When the magnetization is in the above range, the developability of the magnetic toner is improved.

  Here, the measurement of magnetic characteristics is performed using a vibration sample type magnetometer VSMP10-15 (manufactured by Toei Industry Co., Ltd.). The measurement sample is packed in a cell having an inner diameter of 7 mm and a height of 5 mm and set in the apparatus. The measurement is performed by applying an applied magnetic field, sweeping up to a maximum of 500 Oe (Oersted), and then reducing the applied magnetic field to obtain a hysteresis curve. From this hysteresis curve, the magnetization at 500 Oe (Oersted) is obtained.

  In the CIE 1976 (L * a * b *) color system, YIG particles preferably satisfy L * of 65 to 90, a * of −9 to 15 and b * of 30 to 110, and more preferably. L * is from 68 to 90, a * is from -9 to 13, and b * is from 35 to 110, more preferably L * is from 70 to 90, a * is from -9 to 2, b * Satisfies 60 or more and 110 or less. When this CIE 1976 (L * a * b *) color system is filled with YIG particles, it becomes a green color in which discoloration to brown is suppressed, so that the influence on the hue of the toner is suppressed. Reduction of the brightness of the toner is suppressed.

The surface of YIG particles may be hydrophobized. The method for the hydrophobizing treatment is not particularly limited, and can be performed by coating the surface of the magnetic powder with a hydrophobizing agent such as various coupling agents, silicone oils, and resins. It is preferable to perform a surface coating treatment with an agent.
Since the surface of YIG particles is basically hydrophilic, the hydrophobic treatment increases the affinity of the polymer compound for the hydrophobic monomer. As the compatibility of the functional monomer is improved, the dispersion uniformity of the magnetic powder in the magnetic toner is improved.

  The content of the YIG particles is determined by the magnetic force required for the magnetic toner, but in the present embodiment, it is desirably 2% by mass or more and 50% by mass or less with respect to the total amount of the magnetic toner constituent components. More desirably, it is 4 mass% or more and 30 mass% or less. By setting the content within the above range, a sufficient magnetic force is imparted to the magnetic toner, and the dispersion stability of the magnetic toner as a dispersion medium is enhanced.

  Next, a method for producing YIG particles will be described. Examples of the method for producing YIG particles include a method of producing particles by a bottom-up method such as a coprecipitation method, and a method of producing fine particles by a top-down method such as a pulverization method. Moreover, the YIG particle | grains may use the commercial item mentioned later, if the X-ray-diffraction characteristic is satisfy | filled.

However, when manufacturing YIG particles, in order to satisfy the X-ray diffraction characteristics, for example, it is preferable to employ the following method.
1) In both the bottom-up method and the top-down method, annealing is performed as a post-treatment for the purpose of suppressing the amorphization of the YIG particles that cause the magnetization reduction and promoting the crystallization. Technique. For example, the annealing temperature is preferably 700 ° C. or higher and 1500 ° C. or lower, and more preferably 800 ° C. or higher and 1200 ° C. or lower.
2) In the case of a top-down method, a wet method is carried out for the purpose of reducing the mechanical burden on the raw material YIG particles and suppressing the amorphization of the YIG particles. Examples of the liquid used in this wet process include water, alcohol (eg, isopropyl alcohol, ethanol, etc.) acetone, hexane, and the like. Moreover, the usage-amount of this liquid is about 1g or more with respect to 2g of particle | grains.

  The coprecipitation method represented by the bottom-up method is a method using a coprecipitation phenomenon, and is a method in which a substance that does not precipitate by itself is co-precipitated with a substance that precipitates, thereby causing simultaneous precipitation. Specifically, a coprecipitate is produced by mixing a mixed solution of an aqueous yttrium metal salt solution and a trivalent iron salt aqueous solution with an alkaline aqueous solution.

In addition, as aqueous alkali solution, NaOH aqueous solution is mentioned suitably, for example. Examples of the alkaline aqueous solution include aqueous solutions of NH ₄ OH, (NH ₄ ) ₂ CO ₃ , Na ₂ CO ₃ , NaHCO ₃ , and the like. What is necessary is just to set the alkali concentration of aqueous alkali solution suitably considering the pH at the time of a coprecipitation reaction.
Examples of the yttrium metal salt include halide [chloride (YCl ₃ ), bromide (YBr ₃ )], nitrate [Y (NO ₃ ) ₃ ], salt, and the like.
Examples of the trivalent iron salt include halide [chloride (FeCl ₃ ), bromide (FeBr ₃ ) and the like], sulfate [Fe ₂ (SO ₃ ) ₃ ], nitrate [Fe (NO ₃ ) ₃ ] and the like. Can be mentioned.

Further, when YIG particles are produced by causing a coprecipitation reaction to proceed while dropping an aqueous solution of yttrium metal salt and an aqueous solution of the trivalent iron salt in an alkaline aqueous solution, In order to set the average primary particle size of YIG particles to be 1 nm or more and 500 nm or less, for example, in the coprecipitation reaction, the dropping rate of both metal salt aqueous solutions to the alkaline aqueous solution should be 10 ml / min or more and 100 ml / min or less. More preferably, it is 20 or more and 60 ml / min or less.
The stirring time during and after the dropping is preferably about 10 minutes to 60 minutes, more preferably 30 minutes to 60 minutes.
The final pH value of the aqueous reaction solution during the coprecipitation reaction is 12 or more, preferably 12.5 to 13.8, more preferably 13 to 13.5.
When the coprecipitate is dried, it is preferably heated at 50 ° C. or higher and 200 ° C. or lower, more preferably 100 ° C. or higher and 200 ° C. or lower.

  On the other hand, pulverization represented by a top-down method is performed using various pulverizers. Examples of the pulverization method to be employed include pulverization methods such as a jet mill, a vibration mill, a ball mill, a planetary ball mill, a bead mill, and a disk mill. Among these, the bead mill method, particularly the wet bead mill method, which has a small mechanical burden on the YIG particles is preferable.

The TIG particles used as a raw material to be crushed may be YIG particles obtained by the above coprecipitation method or commercially available YIG particles. Examples of commercially available YIG particles include Yttrium Iron Oxide, nanopowder (manufactured by Aldrich), yttrium / iron / garnet Y ₃ Fe ₅ O ₁₂ (manufactured by Koyo Chemical Co., Ltd.), and the like.

-Polymer compound-
Examples of the polymer compound include resins conventionally used in magnetic recording devices. Specifically, homopolymers of styrene and its substituted products and copolymer resins thereof, copolymer resins of styrene and (meth) acrylate, styrene and (meth) acrylate and other vinyl series Examples include multi-component copolymer resins with monomers, styrene copolymer resins of styrene and other vinyl monomers, and those obtained by crosslinking a part of each of the above resins. Furthermore, polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate resin, polyester resin, epoxy resin, polyamide resin, polyolefin resin, silicone resin, polybutyral resin, polyvinyl alcohol resin, polyacrylic acid resin, phenol resin, aliphatic or finger ring Examples thereof include aromatic hydrocarbon resins, petroleum resins, styrene-vinyl acetate copolymer resins, ethylene-vinyl acetate copolymer resins, wax resins, and the like, or a mixture thereof.

Here, to uniformly and stably disperse the magnetic toner in the aqueous medium is because the polymer compound is hydrophobic, and the magnetic toner surface has characteristics different from ordinary polymer compound particles. There are cases where it cannot be easily achieved with the structure of ordinary polymer compound particles.
In the present embodiment, from the above viewpoint, particularly by using a polymer compound obtained by controlling the monomer species and composition constituting the polymer as described below, good dispersibility of the magnetic toner in the aqueous medium is achieved. And better developability and the like are exhibited. Hereinafter, the structure of the high molecular compound used suitably for this embodiment is demonstrated.

  The polymer compound includes a polymer of an ethylenically unsaturated monomer, the ethylenically unsaturated monomer includes a monomer having a hydroxyl group and a hydrophobic monomer, and the amount of the hydroxyl group of the polymer Is preferably 0.1 mmol / g or more and 5.0 mmol / g or less.

Here, in order to obtain good dispersibility in the aqueous medium while maintaining a magnetic force of a certain level or more as the magnetic toner particles, it is effective to have a hydroxyl group on the particle surface. For this purpose, it is desirable that the constituent component of the polymer compound (polymer) constituting the particles has a hydroxyl group.
Polymers of ethylenically unsaturated monomers that are preferably used as polymer compounds are based on the copolymerization ratio of hydrophilic monomers and hydrophobic monomers having a hydroxyl group, so that dispersibility in aqueous media and stability of magnetic toners are increased. From the viewpoint of the property, and the relationship with the content of the magnetic powder contained in a certain amount in the magnetic toner, the hydroxyl group amount of the polymer is set to an optimum range.

Since the amount of hydroxyl group varies depending on the content of magnetic powder, it is defined as the amount of hydroxyl group of the polymer component excluding the magnetic powder, and is preferably 0.1 mmol / g or more and 5.0 mmol / g or less, It is more preferably 0.2 mmol / g or more and 4.0 mmol / g or less, and further preferably 0.3 mmol / g or more and 3.0 mmol / g or less.
If the amount of hydroxyl groups is less than 0.1 mmol / g, the dispersibility of the magnetic toner in an aqueous medium may deteriorate. When it exceeds 5.0 mmol / g, the swellability of the magnetic toner in water increases and the operability may deteriorate.

  The amount of hydroxyl group is determined by a general titration method. For example, a certain amount of a reagent such as pyridine solution of acetic anhydride is added to the above polymer, heated, hydrolyzed by adding water, separated into particles and supernatant by a centrifuge, and the supernatant is used as an indicator such as phenolphthalein. Is used to determine the amount of hydroxyl groups by titration with an ethanolic potassium hydroxide solution or the like.

An ethylenically unsaturated monomer refers to a monomer having an ethylenically unsaturated group such as a vinyl group. The following hydrophilic monomer and hydrophobic monomer are both included in the ethylenically unsaturated monomer in this embodiment.
Examples of the hydrophilic monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, glycerin di (meth) acrylate, 1,6 -Bis (3-acryloxy-2-hydroxypropyl) -hexyl ether, pentaerythritol tri (meth) acrylate, tris- (2-hydroxyethyl) isocyanuric acid ester (meth) acrylate, polyethylene glycol (meth) acrylate, etc. .
In addition, the said (meth) acrylate is an expression showing an acrylate or a methacrylate here, and applies to this in the following.
Among these, it is possible to use at least one selected from 2-hydroxyethyl (meth) acrylate and polyethylene glycol (meth) acrylate, to control the copolymerization ratio with the hydrophobic monomer described later, and to control the polymerization reaction It is desirable from the viewpoint of sex.

The polymer preferably has a carboxyl group in addition to the hydroxyl group. In this case, it is desirable to use a monomer having a carboxyl group as the ethylenically unsaturated monomer.
Examples of the monomer having a carboxyl group include acrylic acid, methacrylic acid, methacryloyloxyethyl monophthalate, methacryloyloxyethyl monohexahydrophthalate, methacryloyloxyethyl monomaleate, and methacryloyloxyethyl monosuccinate.
Among these, it is desirable to use methacryloyloxyethyl monophthalate from the viewpoints of controlling the copolymerization ratio with the hydrophobic monomer described later, dispersing the magnetic powder in the magnetic toner, and controlling the polymerization reaction.

  Examples of the hydrophobic ethylenically unsaturated monomer include aromatic vinyl monomers such as styrene and α-methylstyrene; alkyl groups having 1 to 18 carbon atoms (more preferably 2 to 16) or aralkyl. (Meth) acrylic acid alkyl ester having a group (for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Lauryl (meth) acrylate, benzyl (meth) acrylate, etc.); (meth) acrylic acid alkoxyalkyl ester having an alkylene group having 1 to 12 carbon atoms (more preferably 2 to 10) (for example, methoxymethyl (meth) ) Acrylate, methoxyethyl (meth) acrylate, Chitosimethyl (meth) acrylate, ethoxyethyl (meth) acrylate, ethoxybutyl (meth) acrylate, n-butoxymethyl (meth) acrylate, n-butoxyethyl (meth) acrylate, etc.); amino group-containing (meth) acrylic acid ester (For example, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, etc.); acrylonitrile, ethylene, vinyl chloride, vinyl acetate and the like can be mentioned.

  Among these, styrene, methyl (meth) acrylate, butyl (meth) acrylate 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, ethoxybutyl (meth) acrylate, benzyl (meth) acrylate, diethylaminoethyl (meth) acrylate Further, styrene, methyl (meth) acrylate, and butyl (meth) acrylate are particularly desirable.

  The content of the hydrophobic monomer copolymerizable with the hydrophilic monomer is desirably 1% by mass or more and 99% by mass or less in all monomer components, and 5% by mass or more and 95% by mass or less. Is more desirable. In particular, when using a monomer having a carboxyl group such as methacryloxyethyl monophthalate in addition to the monomer having a hydroxyl group as an ethylenically unsaturated monomer, the content of the hydrophobic monomer is In all the monomer components, the content is desirably 20% by mass or more and 99% by mass or less, and more desirably 50% by mass or more and 90% by mass or less.

  When the content is less than 1% by mass, the amount of hydroxyl groups in the polymer becomes too large, and there are cases where uniform polymerization cannot be performed during the production of the polymer. Sexual effects may not be obtained.

As another monomer, you may mix a crosslinking agent with the reactive mixture (what contains the said ethylenically unsaturated monomer etc.) disperse | distributed to the aqueous medium mentioned later as needed. By adding a crosslinking agent to the monomer mixture, aggregation during polymerization is suppressed, and dispersion stability is ensured.
As the crosslinking agent, a known crosslinking agent can be selected and used. Examples of suitable crosslinking agents include divinylbenzene, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, methylenebis (meth) acrylamide, and glycidyl. (Meth) acrylate, 2-([1′-methylpropylideneamino] carboxyamino) ethyl methacrylate and the like can be mentioned. Among these, divinylbenzene, ethylene glycol di (meth) acrylate, and diethylene glycol di (meth) acrylate are more preferable, and divinylbenzene is particularly preferable.

Further, the polymer compound may contain a non-crosslinked resin from the viewpoint of improving the fixability. The non-crosslinked resin is not particularly limited as long as it is a polymer that fixes particles on a medium to be fixed such as paper, film by external energy such as heat, ultraviolet rays, and electron beams, solvent vapor, solvent volatilization from the polymer, and the like. .
Specifically, for example, styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl acetate; methyl acrylate , Α-methylene aliphatic monocarboxylic acid esters such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl Examples thereof include homopolymers or copolymers such as vinyl ethers such as methyl ether, vinyl ethyl ether, and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone.

-Other ingredients-
The magnetic toner may further contain a dye for coloring purposes, an organic pigment, carbon black, titanium oxide, and the like. In that case, the respective additives may be directly mixed in a mixture of the monomer and the like in which the magnetic powder is dispersed. For example, in the case of mixing a pigment such as an organic pigment, carbon black, or titanium oxide. For example, it is desirable that the non-crosslinked resin is mixed and dispersed in advance by a known method such as a roll mill, a kneader, or an extruder, and this is mixed with a mixture of the polymerizable monomer or the like.

-Preparation method of magnetic toner-
As a method for producing a magnetic toner containing each of the above monomers, for example, first, an ethylenically unsaturated monomer, a polymerization initiator and other necessary components are mixed to prepare a mixed liquid of monomers and the like. Make it. The mixing method is not particularly limited.
Moreover, a well-known method is applied to dispersion | distribution of the magnetic powder to the said liquid mixture. That is, for example, a dispersing machine such as a ball mill, a sand mill, an attritor, or a roll mill is used. In the case where the monomer component is separately polymerized in advance and the magnetic powder is dispersed in the obtained polymer, a kneader such as a roll mill, a kneader, a Banbury mixer, or an extruder is used.

In order to obtain the magnetic toner, a known method can be used. For example, a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, a seed polymerization method and the like are preferably used. Furthermore, suspension polymerization may be performed using an emulsification method known as a membrane emulsification method.
The magnetic toner thus obtained preferably has a number average particle size of 0.1 μm to 20 μm, more preferably 0.5 μm to 8.0 μm, and more preferably 0.5 μm to 5.0 μm. It is. If the number average particle size is less than 0.5 μm, the particle size may be too small to be handled, and if it exceeds 5 μm, high image quality may not be obtained when used as an image forming material. The number average particle diameter is a number average particle diameter determined by a Coulter Counter Multisizer 3 (Beckman Coulter, Inc.).

When the polymer compound has a carboxyl group, the carboxyl group amount is preferably 0.005 mmol / g or more and 0.5 mmol / g or less. When the amount of carboxyl groups is in the above range, even if the number of functional groups is smaller than that of hydroxyl groups, good dispersibility in an aqueous medium and swelling suppression effect can be obtained, with respect to fluctuations when other functional groups are present. These characteristics are maintained.
The amount of carboxyl groups is more preferably 0.008 mmol / g or more and 0.3 mmol / g or less, and further preferably 0.01 mmol / g or more and 0.1 mmol / g or less.

  The amount of the carboxyl group is determined by a general titration method. For example, a neutralization reaction is carried out by adding a reagent such as an ethanol solution of potassium hydroxide to the above polymer compound, and the supernatant containing excess potassium hydroxide is automatically titrated by separating it into particles and supernatant using a centrifuge. The amount of carboxyl groups can be determined by titrating with an isopropanol hydrochloric acid solution or the like.

(Liquid developer)
The liquid developer according to the exemplary embodiment includes the magnetic toner according to the exemplary embodiment and an aqueous medium in which the magnetic toner is dispersed. That is, the liquid developer according to the present embodiment is a particle dispersion in which magnetic toner is dispersed in an aqueous medium.

  The concentration of the magnetic toner in the aqueous dispersion is preferably in the range of 0.5% by mass to 40% by mass, and more preferably in the range of 1% by mass to 20% by mass.

  An aqueous medium means the solvent containing 50 mass% or more of water. “Water” means purified water such as distilled water, ion exchange water, ultrapure water, and the like. As the aqueous medium, water or a solution obtained by adding water-soluble organic solvent such as methanol or ethanol to water is preferably used. Of these, water alone is particularly desirable. The amount of water-soluble organic solvent added is preferably 30% by mass or less, more preferably 10% by mass or less based on the total amount of the solvent, although it depends on the properties of the suspended monomer.

  In the aqueous medium, various auxiliary materials used in ordinary aqueous particle dispersions, such as dispersants, emulsifiers, surfactants, stabilizers, wetting agents, thickeners, foaming agents, antifoaming agents, coagulations. In combination with agents, gelling agents, anti-settling agents, charge control agents, antistatic agents, anti-aging agents, softeners, plasticizers, fillers, colorants, flavoring agents, anti-sticking agents, release agents, etc. Also good.

  Specifically, for example, as a surfactant for maintaining the dispersion stability of magnetic polymer particles, any known surfactant such as an anionic surfactant, a nonionic surfactant, a cationic surfactant, etc. Can also be used.

Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether. Sulfate salts and sulfonate salts of the above, higher alkyl sulfosuccinate salts, higher alkyl phosphate ester salts, phosphate ester salts of higher alcohol ethylene oxide adducts, and the like.
Nonionic surfactants include, for example, polypropylene glycol ethylene oxide adduct, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl ether (polyoxyethylene oleyl ether, Polyoxyethylene cetyl ether, polyoxyethylene lauryl ether, etc.), polyoxyethylene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid alkylolamide, oxyethylene adduct of acetylene glycol, and the like.
Examples of the cationic surfactant include tetraalkylammonium salts, alkylamine salts, benzalkonium salts, alkylpyridium salts, imidazolium salts and the like.

  As surfactants, in addition to the above, silicone surfactants such as polysiloxane oxyethylene adducts; fluorine-based surfactants such as perfluoroalkyl carboxylates, perfluoroalkyl sulfonates, and oxyethylene perfluoroalkyl ethers Agents; biosurfactants such as spicrispolic acid, rhamnolipid, lysolecithin; and the like.

Moreover, as a dispersing agent, if it is a polymer which has a hydrophilic structure part and a hydrophobic structure part, it can be used effectively. For example, styrene-styrene sulfonic acid copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl naphthalene-methacrylic acid copolymer. Polymer, vinyl naphthalene-acrylic acid copolymer, acrylic acid alkyl ester-acrylic acid copolymer, methacrylic acid alkyl ester-methacrylic acid, styrene-methacrylic acid alkyl ester-methacrylic acid copolymer, styrene-acrylic acid alkyl ester -Acrylic acid copolymer, styrene-methacrylic acid phenyl ester-methacrylic acid copolymer, styrene-methacrylic acid cyclohexyl ester-methacrylic acid copolymer, etc., and these copolymers are random, block and graft copolymer Coalescence It may also be a structure of deviation.
In order to improve dispersibility and water solubility, these polymers are copolymerized with a polyoxyethylene group, a monomer having a hydroxyl group, a monomer having a cationic functional group, or a hydrophilic group having an acidic group. A certain polymer may have a salt structure with a basic compound.
In the present embodiment, a water-soluble organic solvent can be used for the purpose of controlling evaporation and interface characteristics. The water-soluble organic solvent is an organic solvent that does not separate into two phases when added to water, and examples thereof include mono- or polyhydric alcohols, nitrogen-containing solvents, sulfur-containing solvents, and other derivatives thereof.

  Specifically, polyhydric alcohol derivatives such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerin, etc. As ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, ethylene oxide adduct of diglycerin Monohydric alcohols such as ethanol and isopropyl alcohol , Butyl alcohol, benzyl alcohol, etc., nitrogen-containing solvents such as pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, triethanolamine, etc., sulfur solvents such as thiodiethanol, thiodiglycerol, sulfolane, dimethyl sulfoxide, etc. Examples include propylene carbonate and ethylene carbonate.

For aqueous media, for the purpose of adjusting conductivity, pH of ink, etc., compounds of alkali metals such as potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonium hydroxide, triethanolamine, diethanolamine, ethanolamine, Nitrogen-containing compounds such as 2-amino-2-methyl-1-propanol, alkaline earth metal compounds such as calcium hydroxide, acids such as sulfuric acid, hydrochloric acid and nitric acid, strong acid and weak alkali salts such as ammonium sulfate, etc. Addition is possible.
In addition, benzoic acid, dichlorophen, hexachlorophene, sorbic acid, and the like can be added as necessary for the purpose of mold prevention, antiseptic, rust prevention, and the like. Antioxidants, viscosity modifiers, conductive agents, ultraviolet absorbers, chelating agents, and the like can also be added.

  In particular, in this embodiment, it is preferable to use particles in which metal ions (for example, silver, copper, zinc, and the like) are supported on an inorganic substance (for example, zeolite and the like) having ion exchange properties as the anti-mold agent. A preferred example of particles as such an antifungal agent is silver-supported zeolite. This silver-supported zeolite has a higher antifungal property than other types and is not magnetized, so that it remains in the liquid developer without being developed, and thus has no effect on the formed image.

  Here, the silver supported zeolite preferably has an average primary particle size of 0.1 μm or more and 50 μm or less. That is, it is not technically easy to form a powder having an average primary particle size of less than 0.1 μm, and conversely, if the average primary particle size exceeds 50 μm, the powder tends to settle in the developer, resulting in poor dispersion stability. This is because there is a tendency. Among these, silver-supported zeolite having an average primary particle size of 0.5 μm or more and 10 μm or less is particularly suitable for dispersibility in a developer.

  The content of the silver-supported zeolite is preferably set to about 0.05% by weight or more and 30% by weight or less with respect to the entire liquid developer, although it depends on the required degree of mold prevention (antibacterial). is there. That is, when the content is less than 0.05% by weight, the antibacterial effect is low. Conversely, when the content exceeds 30% by weight, the viscosity of the developer increases and the developability may be lowered.

  As the silver-supported zeolite, for example, one produced according to JP-A-60-202162 can be used, or a commercially available product (for example, antibacterial agent Bactelar BM-101 (particle size 5 μm) manufactured by Fuji Chemical Co., Ltd.) is used. It may be used.

  The dispersed particle diameter of the magnetic toner in the liquid developer is preferably from 0.1 μm to 20 μm, preferably from 0.5 μm to 8 μm, and from 0.5 μm to 5.0 μm. It is more desirable. The dispersion average particle size of the magnetic toner is a number average particle size determined by Coulter Counter Multisizer 3 (Beckman Coulter, Inc.).

In addition, when the magnetic toner suitably designed for the present embodiment is used as the magnetic toner in the liquid developer, the magnetic powder is uniformly dispersed in the particles as described above. There is almost no magnetic powder. Moreover, since it has a hydroxyl group on the particle surface, it exhibits good dispersibility in an aqueous medium.
Therefore, when the above liquid developer is used, there is no variation in micro surface tension in the liquid, and the mobility of particles with respect to the magnetic force during development is small among the particles. Adherence of liquid on the magnetic drum after development based on the water repellency characteristic of the drum surface and occurrence of image fog are more efficiently reduced.

The liquid developer is manufactured by the following procedure, but is not limited thereto.
First, a dispersion medium containing water as a main solvent and the respective additives is prepared using a magnetic stirrer or the like, and the magnetic toner is dispersed in the dispersion medium. A known method is applied to the dispersion. That is, a dispersing machine such as a ball mill, a sand mill, an attritor, or a roll mill is used. Further, as a mixer, a method of rotating a special stirring blade at high speed to disperse, a method of dispersing by the shearing force of a rotor / stator known as a homogenizer, a method of dispersing by ultrasonic waves, and the like can be mentioned.

  After confirming that the magnetic toner is in a single dispersed state in the liquid by microscopic observation of the dispersed liquid, and then confirming that it is dissolved by adding additives such as preservatives, The obtained dispersion liquid is filtered using, for example, a membrane filter having a pore diameter of 100 μm, and dust and coarse particles are removed to obtain a liquid developer as a recording liquid for image formation.

  The viscosity of the liquid developer is preferably 1 mPa · s or more and 500 mPa · s or less, although it depends on the image forming system used. When the viscosity of the liquid developer is less than 1 mPa · s, a sufficient image density may not be obtained because the amount of magnetic toner and the amount of additive are not sufficient. On the other hand, when the viscosity of the liquid developer is greater than 500 mPa · s, handling may be difficult or developability may be deteriorated because the viscosity is too high.

[Image forming apparatus]
Hereinafter, the image forming apparatus according to the present embodiment will be described. The process cartridge will be described together in the embodiments of the image forming apparatus described below.

  The image forming apparatus according to the present embodiment includes a magnetic latent image holding member (hereinafter sometimes referred to as an “image holding member”), a magnetic latent image forming unit that forms a magnetic latent image on the magnetic latent image holding member, Developer storing means for storing a liquid developer containing magnetic toner and an aqueous medium, and a magnetic latent image holding member on which the magnetic latent image is formed with the liquid developer to visualize the magnetic latent image as a toner image Developer supplying means for supplying the toner image, transfer means for transferring the toner image to a recording medium, and demagnetizing means for demagnetizing the magnetic latent image on the magnetic latent image holding member. The liquid developer according to this embodiment is applied as the liquid developer.

  Here, in so-called liquid magnetography using a liquid developer, since the toner image on the image carrier immediately after development usually contains a large amount of excess developer, the toner image is transferred onto a recording medium such as paper. In some cases, it is necessary to provide a drying step before removing the excess developer.

  Therefore, it is desirable to apply an image carrier having a water-repellent surface as the image carrier. When an aqueous medium is used as a dispersion medium in the liquid developer, since the surface tension of water is large due to hydrogen bonding, the liquid developer can be combined with the image carrier during development by combining with an image carrier having a water-repellent surface. Even when contacted, the liquid that is the dispersion medium hardly transfers to the image carrier, and the toner image is transferred to the recording medium without leaving the liquid on the image carrier. Accordingly, a squeeze roller or the like for removing the residual solvent on the image holding member is unnecessary, and the recording medium on which the toner image is transferred hardly needs to be dried.

  Further, during development, an aqueous medium having a large surface tension is prevented from spreading on the surface of the image carrier, while a magnetic toner having high mobility and being uniformly dispersed in the developer is an image. At the same time as the contact with the holder, only the magnetic latent image is transferred by magnetic force, so that a developing environment in which image fog is hardly generated is created.

  Therefore, it is possible to stably form a high-quality image in which the influence of the residual liquid on the magnetic latent image holding member is suppressed after development and the occurrence of image fogging is reduced while adapting to the use environment such as an office.

  The image forming process applied to the present embodiment includes a so-called electrophotographic process, a process of forming an electrostatic latent image with ions or the like (ionography) on a dielectric, and image information by heat of a thermal head on a charged dielectric. The electrostatic latent image is not used, such as a process of forming an electrostatic latent image according to the above, but a process of forming a toner image by forming a magnetic latent image on the image carrier.

  Hereinafter, an image forming apparatus according to a magnetic developing process using a liquid developer in the present embodiment will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present exemplary embodiment. The image forming apparatus 100 includes a magnetic drum (magnetic latent image holder) 10, a magnetic head (magnetic latent image forming means) 12, a developing device (developer storage means and developer supply means) 14, and an intermediate transfer body (transfer means). 16, a cleaner 18, a demagnetizer (demagnetizer) 20, and a transfer fixing roller (transferr) 28. The magnetic drum 10 has a cylindrical shape, and a magnetic head 12, a developing device 14, an intermediate transfer member 16, a cleaner 18 and a demagnetizing device 20 are sequentially provided on the outer periphery of the magnetic drum 10.
The operation of the image forming apparatus 100 will be briefly described below.

First, the magnetic head 12 is connected to an information device (not shown), for example, and receives binarized image data sent from the information device. The magnetic head 12 forms a magnetic latent image 22 on the magnetic drum 10 by emitting lines of magnetic force while scanning the side surface of the magnetic drum 10. In FIG. 1, the magnetic latent image 22 is indicated by a hatched portion in the magnetic drum 10.
The developing device 14 includes a developing roller (developer supply means) 14a and a developer storage container (developer storage means) 14b. The developing roller 14a is provided so that a part thereof is immersed in the liquid developer 24 stored in the developer storage container 14b.

  In the liquid developer 24, the toner particles are uniformly dispersed. For example, the liquid developer 24 is further stirred by a stirring member provided in the developer storage container 14 b at a predetermined rotation speed, so that the liquid The positional variation in the concentration of toner particles in the developer 24 is reduced. Thus, the liquid developer 24 with reduced toner particle density variation is supplied to the developing roller 14a rotating in the direction of arrow A in the figure.

  The liquid developer 24 supplied to the developing roller 14a is transported to the magnetic drum 10 in a state where the liquid developer 24 is limited to a constant supply amount by a regulating member described later, and the developing roller 14a and the magnetic drum 10 come close (or contact). The magnetic latent image 22 is supplied at the position. As a result, the magnetic latent image 22 is visualized and becomes a toner image 26.

The developed toner image 26 is transported to a magnetic drum 10 that rotates in the direction of arrow B in the figure and transferred to a paper (recording medium) 30. In this embodiment, before transferring to the paper 30, the magnetic drum 26 is transferred to the magnetic drum 10. The toner image is temporarily transferred to the intermediate transfer member 16 in order to improve the transfer efficiency to the recording medium including the separation efficiency of the toner image from the toner 10, and to perform fixing simultaneously with the transfer to the recording medium.
Transfer to the intermediate transfer member 16 is preferably performed by shearing transfer (non-electric field transfer) because the toner particles have almost no charge. Specifically, the magnetic drum 10 rotating in the direction of arrow B and the intermediate transfer member 16 rotating in the direction of arrow C are brought into contact with each other with a certain nip (contact surface having a contact width in the moving direction), and a toner image 26 is obtained. On the other hand, the toner image 26 is transferred onto the intermediate transfer member by an attractive force greater than the magnetic force with the magnetic drum 10. At this time, a peripheral speed difference may be provided between the magnetic drum 10 and the intermediate transfer member 16.

Next, the toner image conveyed in the direction of arrow C by the intermediate transfer member 16 is transferred to the paper 30 at a position where it contacts the transfer and fixing roller 28 and is simultaneously fixed.
The transfer fixing roller 28 sandwiches the paper 30 with the intermediate transfer member 16, and brings the toner image on the intermediate transfer member 16 into close contact with the paper 30. As a result, the toner image is transferred to the paper 30 and simultaneously the toner image is fixed on the paper. The toner image may be fixed only by pressure depending on the characteristics of the toner. The transfer and fixing roller 28 may be provided with a heating element and may be pressed and heated.

On the other hand, in the magnetic drum 10 in which the toner image 26 is transferred to the intermediate transfer member 16, the transfer residual toner is conveyed to a contact position with the cleaner 18 and collected by the cleaner 18. After cleaning, the magnetic drum 10 rotates and moves to the demagnetization position while holding the magnetic latent image 22.
The degaussing device 20 erases the magnetic latent image 22 formed on the magnetic drum 10. The cleaner 18 and the degaussing device 20 return the magnetic drum 10 to a state in which there is no variation in the magnetization state of the magnetic layer before image formation. By repeating the above operation, images successively sent from the information device are continuously formed in a short time. The magnetic head 12, the developing device 14, the intermediate transfer member 16, the transfer fixing roller 28, the cleaner 18, and the demagnetizing device 20 provided in the image forming apparatus 100 are all operated in synchronization with the rotation speed of the magnetic drum 10. ing.

Next, each configuration of the image forming apparatus of the present embodiment will be described sequentially.
(Magnetic latent image holder)
The configuration of the magnetic drum (magnetic latent image holder) 10 is such that a base layer such as Ni or Ni-P is formed on a drum made of a metal such as aluminum with a thickness of about 1 to 30 μm, and is formed thereon. A magnetic recording layer such as Co-Ni, Co-P, Co-Ni-P, Co-Zn-P, Co-Ni-Zn-P is formed to a thickness of about 0.1 to 10 μm, and Ni, A protective layer of Ni—P or the like is formed with a thickness of about 0.1 μm to 5 μm. If there is a defect such as a pinhole in the plating of the underlayer, a defect is also formed in the magnetic recording layer. Therefore, it is preferable to carry out fine and uniform plating. In addition to plating, there are also methods such as sputtering and vapor deposition. Furthermore, the underlayer and the protective layer are preferably nonmagnetic. Maintaining the surface accuracy of the surface of each layer by tape polishing or the like is suitable for maintaining the gap with the magnetic head 12 forming the magnetic latent image with high accuracy.

The film thickness of the magnetic recording layer is preferably in the range of 0.1 μm to 10 μm, and the magnetic characteristics of the magnetic recording layer are such that the coercive force is 16000 A / m or more and 80000 A / m or less (200 Oersted or more and 1000 Oersted (Oe) or less. The residual magnetic flux density is preferably about 100 mT to 200 mT (1000 gauss to 2000 gauss (G)).
The above is the configuration of the magnetic drum 10 in the case of the horizontal magnetic recording type, but in the case of the vertical magnetic recording type, a configuration in which a recording layer such as Co—Ni—P is provided on the nonmagnetic layer, A configuration in which a soft magnetic layer having a high magnetic permeability is provided below the recording layer may be employed, and the present invention is not limited to any one. Further, the magnetic latent image holding member is not limited to the drum shape in the present embodiment, but may be a belt shape.

In this embodiment, the magnetic drum 10 having water repellency is used. Here, water repellency means the property of repelling water, and specifically means that the contact angle with pure water is 70 degrees or more.
In the present embodiment, the contact angle of the magnetic drum 10 with respect to pure water is desirably 70 degrees or more, and more desirably 100 degrees or more. If the contact angle is less than 70 degrees, liquid may remain on the magnetic drum or image fog may occur even after development with a liquid developer using an aqueous medium described later.

  The contact angle of the surface of the magnetic drum 10 was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd .: CA-X) and pure water was applied to the surface of the magnetic drum in an environment of 25 ° C. and 50% RH. 3.1 μl was dropped and the contact angle after 15 seconds was determined. The measurement was performed at four points in the circumferential direction at the end and center, and the average value of these was taken as the contact angle.

In order to make the surface of the magnetic drum 10 have a suitable contact angle, it is desirable to coat the surface of the magnetic drum configured as described above.
Examples of the surface coat include fluorine lubrication plating and coating using a polymer containing fluorine atoms or silicon atoms. Fluorine lubrication plating is a functional plating in which fluorine resin (polytetrafluoroethylene: PTFE) is combined and co-deposited with electroless nickel plating, and PTFE particles are uniformly deposited in the formed film. Combines the characteristics of electroless nickel plating and PTFE resin.
Examples of the coating using a polymer containing a fluorine atom or a silicon atom include, for example, a polymer having a fluorine-containing cyclic structure, a copolymer of fluoroolefin and vinyl ether, a photopolymerizable fluororesin composition, and the like. It may be applied to the surface of the layer, or may be coated on the entire surface by sputtering a fluorine atom-containing polymer on the surface of the protective layer.

Of these, fluorine lubrication plating is preferable from the viewpoint of adhesion to the lower plating layer, durability, and the like. The fluorine lubrication plating or fluororesin coating may be performed after forming the protective layer, or a layer formed by fluorine lubrication plating or the like may be used as it is.
The film thickness of the surface layer formed by the surface coating is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.3 μm or more and 3 μm or less.

(Magnetic latent image forming means)
The magnetic latent image forming apparatus (magnetic latent image forming means) basically comprises a magnetic head 12 and its drive circuit. The magnetic head 12 mainly includes a full-line type magnetic head and a multi-channel type magnetic head. In the case of a full-line type magnetic head, it is not necessary to scan the magnetic head 12, but in the case of a multi-channel type magnetic head, It is necessary to scan the magnetic head 12 with respect to the magnetic drum 10. Scanning methods include serial scanning and helical scanning. In the helical scanning, the recording speed can be increased by changing the rotational speed of the magnetic drum 10 only in the latent image forming process.

  On the other hand, in the case of a full-line type magnetic head, for example, if the resolution is 600 dpi (dpi: number of dots per inch), a head of about 500 channels is required to cover the recording width in the width direction of A4 size paper. It is. If they are arranged side by side to form a full line, it is not necessary to scan the head, and extremely high-speed recording becomes possible. In order to achieve the above full line, it is necessary to superimpose the head core and the head core. However, as the resolution is increased, the track pitch becomes narrower. A sheet coil is used.

  Leakage magnetic flux is generated from the tip of the magnetic pole when current is passed through the coil of each channel of the magnetic head 12, thereby magnetizing the magnetic recording medium to form a magnetic latent image. The output from the magnetic head 12 needs to be two to three times the coercivity of the magnetic recording layer in the magnetic drum 10. The magnetic latent image formed here does not disappear unless erased by the demagnetizer 20, and has a multi-copy function by repeating the steps of development, transfer, fixing, and cleaning. In addition, since the magnetic latent image is less susceptible to humidity, it has better environmental stability than the electrostatic type.

(Developer storage means, developer supply means)
FIG. 2 shows a schematic diagram in which the development area in FIG. 1 is enlarged.
The developing device (developer supply means) 14 magnetically develops the developer storage container 14b and the liquid developer 24 stored in the developer storage container 14b in a toner supply area (hereinafter sometimes referred to as “supply area”). And a developing roller 14a to be supplied to the drum 10. As shown in FIG. 2, the developing roller 14a holds a layered liquid developer 24 on its peripheral surface, and is disposed at a position separated from the magnetic drum 10 (for example, a process cartridge is formed by the magnetic drum and the developing device). Is configured). Further, a regulating member 13 that maintains the layer thickness of the liquid developer 24 at a predetermined thickness is disposed upstream of the supply region. The regulating member 13 is a plate-like member extending over the entire width in the axial direction of the developing roller 14a, and one edge portion thereof is arranged so as to be separated from the peripheral surface of the developing roller 14a by a predetermined distance corresponding to a desired toner layer thickness. Yes.

In the developing device 14, a liquid developer 24 containing toner particles 26a and an aqueous medium is stored in a developer storage container 14b. The liquid developer 24 is continuously stirred at a predetermined rotational speed by the stirring member 15 provided in the developer storage container 14b, so that the positional variation in the concentration of the toner particles 26a in the liquid developer 24 is reduced. Therefore, the liquid developer 24 with reduced variation in toner particle concentration is supplied to the developing roller 14a.
Although not shown in FIG. 2, in order to supply the liquid developer to the developing roller 14a, a supply roller that rotates in contact with or close to the developing roller 14a may be provided.

The developing roller 14a includes, for example, a plurality of magnetic poles including an S-pole magnetic pole and an N-pole magnetic pole in the circumferential direction, and these magnetic poles are fixed so as not to rotate together with the developing roller 14a. One of these magnetic poles is in particular arranged between the regulating member 13 and the supply area. Therefore, the liquid developer 24 containing the magnetic toner held on the developing roller 14a is held by the magnetic lines of force (developing magnetic field) of these magnetic poles and conveyed toward the magnetic drum 10.
The developing roller 14a need not be a magnetic roller as long as the roller surface itself has a liquid developer conveying force, and an anilox roller or a sponge roller may be used, for example.

  The regulating member 13 is provided at a position from when the developing roller 14 a holds the liquid developer 24 in the developer storage container 14 b until it is supplied to the magnetic drum 10 as described above. The amount of the liquid developer 24 supplied to the magnetic latent image 22 is determined by the gap formed by the regulating member 13 and the developing roller 14a. The material is preferably rubber or phosphor bronze. The liquid developer 24 limited to a constant supply amount by the regulating member 13 is conveyed to the magnetic drum 10 and supplied to the magnetic latent image 22. As a result, the magnetic latent image 22 is visualized and becomes a toner image 26.

  In the development, since the toner particles are magnetic toner, the development can be performed without applying a magnetic field to the developing roller 14a. However, the magnetic field is applied to the developing roller 14a for more efficient development. May be applied.

(Transfer means, fixing means)
The toner image visualized by the developing device 14 is transferred onto the paper 30 by a transfer unit. As described above, in this embodiment, a toner image is not directly transferred from the magnetic drum 10 onto the paper, but is transferred to the intermediate transfer body 16 and then transferred and fixed onto the paper 30. First, transfer to the intermediate transfer member 16 will be described.

  The intermediate transfer member 16 contacts the magnetic drum 10 and transfers the toner image. As the transfer method, there are generally an electrostatic transfer method, a pressure transfer method, and an electrostatic pressure method using both of them. However, as described above, in this embodiment, the toner particles do not have an electric charge. The transfer method and electrostatic pressure method cannot be used. On the other hand, the pressure transfer method is a method in which the toner image is attached to the surface of the transfer medium while being plastically deformed by the pressure between the magnetic drum 10 and the transfer medium, and may be used in combination with shearing transfer.

  In the present embodiment, as described above, the toner image 26 is transferred onto the intermediate transfer member by the attraction force greater than the magnetic force with the magnetic drum 10 with respect to the toner image 26 on the magnetic drum 10. It is preferable to perform adhesive transfer by imparting adhesiveness to the adhesive. For this reason, it is desirable to form, for example, a low hardness silicone rubber layer on the surface of the intermediate transfer member 16.

Next, the toner image 26 transferred to the intermediate transfer body 16 is transferred to a sheet.
A transfer fixing roller 28 is disposed on the opposite side of the magnetic drum 10 across the intermediate transfer member 16 in FIG. 1 so as to form a nip with respect to the intermediate transfer member 16, and the toner image 26 on the intermediate transfer member 16. The sheet 30 is fed to the nip between the intermediate transfer member 16 and the transfer fixing roller 28 at the same timing. The transfer and fixing roller 28 is made of, for example, a stainless steel base, a silicone rubber layer, and a fluororubber layer. By pressing the paper 30 passing through the nip against the intermediate transfer body 16, the toner image on the intermediate transfer body 16 is transferred. It is transferred to the paper 30.

  In the present embodiment, the toner image 26 is transferred from the intermediate transfer body 16 to the paper 30 and the toner image 26 is fixed to the paper 30 at the same time. Specifically, if the intermediate transfer body 16 has a roller shape as shown in FIG. 1, the intermediate transfer body 16 and the transfer fixing roller 28 are each a fixing roller in the fixing device because they constitute a roller pair with the transfer fixing roller 28. The fixing function is exhibited with a configuration according to the pressing roller. That is, when the paper 30 passes through the nip, the toner image is transferred and simultaneously pressed against the intermediate transfer body 16 by the transfer and fixing roller 28, thereby softening the toner particles constituting the toner image and the paper. Infiltrate into 30 fibers.

  Even in this state, fixing to the paper 30 is possible depending on the toner particles to be used. However, when the fixing is not sufficient, the toner image is melted by heating by the transfer fixing roller 28 or the like, and reaches the fiber of the paper 30. The fixed image 29 is formed by entering and fixing. In this state, the fixed image 29 does not peel off even if the paper 30 is bent or peeled off after the adhesive tape is applied.

  In this embodiment, the fixing is performed simultaneously with the transfer to the paper 30. However, the transfer process and the fixing process may be separately performed, and the fixing may be performed after the transfer. In this case, the transfer roller for transferring the toner image from the magnetic drum 10 has a function according to the intermediate transfer body 16.

(Cleaner)
On the other hand, when the transfer efficiency of the toner image from the magnetic drum 10 to the intermediate transfer member 16 does not reach 100%, a part of the toner image 26 remains on the magnetic drum 10 after transfer. The cleaner 18 removes this, and basically comprises a cleaning blade such as rubber and a container of residual magnetic toner.
If the transfer efficiency is close to 100% and residual toner does not cause a problem, the cleaner 18 need not be provided.

(Demagnetizing means)
When a new image is formed again, it is necessary to erase the magnetic latent image before forming the magnetic latent image with the magnetic head 12. There are two types of demagnetizers, a permanent magnet type and an electromagnet type. In the case of the permanent magnet type, it is magnetized in the circumferential direction of the magnetic drum 10 so that the magnetic flux does not leak locally, and energy such as electric power is unnecessary and inexpensive. However, when the magnetic latent image is not erased, it is necessary to move the degaussing device 20 relative to the magnetic drum 10 to increase the magnetic distance and weaken the erasing magnetic field. On the other hand, the electromagnet type is composed of a yoke and a coil, and it is necessary to pass a current. However, when it is not necessary to erase the magnetic latent image, the erasing magnetic field becomes zero by turning off the current, so that the control is relatively Be free.
In the present embodiment, both the permanent magnet type and the electromagnet type may be used.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples do not limit the present invention. In the text, “parts” and “%” represent “parts by mass” and “mass%”, respectively, unless otherwise specified.

[Example A]
(Production of YIG particles)
-YIG particle A1-
As YIG particles, yttrium / iron / garnet Y ₃ Fe ₅ O ₁₂ manufactured by high purity chemical was prepared. As a result of SEM observation of the YIG particles, the average primary particle size of the YIG particles was 2.0 μm.

-YIG particle A2-
As YIG particles, 2 g of high purity chemical yttrium, iron, garnet Y ₃ Fe ₅ O ₁₂ (average primary particle size 2.0 μm) was placed in a planetary ball mill (57 mm of 1 mmφ zirconium beads) together with 2 ml of isopropyl alcohol and pulverized for 43 hours. It was. As a result of TEM observation, the average primary particle size of the ground YIG was 0.32 μm.

-YIG particle A3-
As YIG particles, 400 g of high-purity chemical yttrium / iron / garnet Y ₃ Fe ₅ O ₁₂ (average primary particle size 2.0 μm) and 2 liters of water are placed in a flow-type bead mill (manufactured by Ashizawa Finetech: Star Mill LMZ06) for 30 minutes. Grinding was performed. As a result of TEM observation, the average primary particle size of the ground YIG was 0.24 μm.

-Comparison YIG particle A1-
As YIG particles, 2 g of high purity chemical yttrium / iron / garnet Y ₃ Fe ₅ O ₁₂ (average primary particle size 2.0 μm) was placed in a planetary ball mill (57 mm of 1 mmφ zirconium beads) and pulverized for 48 hours. As a result of TEM observation, the average primary particle size of the pulverized YIG particles was 0.40 μm.

-Comparison YIG particle A2-
As YIG particles, 2 g of yttrium / iron / garnet Y ₃ Fe ₅ O ₁₂ (average primary particle size 2.0 μm) manufactured by high-purity chemical was placed in a planetary ball mill (1 mmφ zirconium beads 57 g) together with isopropyl alcohol, and pulverized for 62 hours. . As a result of TEM observation, the average primary particle size of the pulverized YIG particles was 0.36 μm.

(Evaluation of YIG particles)
-X-ray diffraction profile-
The X-ray diffraction profile of each YIG particle was examined, and the half width of the peak of the plane index (420) was examined. The method of X-ray diffraction is as described above.
FIG. 3 shows X-ray diffraction profiles of YIG particles A1, A2, and A3 and comparative YIG particles A1 and A2. As shown in the X-ray diffraction profile shown in FIG. 3, for YIG particles A1, A2, and A3, a pattern attributed to the garnet structure of YIG is observed, but a peak is observed in the YIG fine particles of Comparative Example 1. Each peak of Comparative Example A2 was broad. This indicates that the crystallinity of the comparative YIG particles A1 and A2 is disturbed.

-Magnetization-
For each YIG particle, the magnetization (emu / g) at 500 Oe was measured. The measuring method is as described above.

-CIE1976 (L * a * b *) color system-
50 parts of each YIG particle and 50 parts of latex particles (styrene-acrylic (St-Ac) particles: weight average molecular weight Mw = 15000, average primary particle size 0.2 μm) were mixed and filtered to obtain a mixture. Was formed into a layer at 4.0 g / m ² , and this was heat-fixed to produce a color sample. Then, the color sample was measured using a reflection densitometer X-rite 939 (manufactured by X-rite), and the CIE 1976 (L * a * b *) color system was examined.

  The results are shown in Table 1.

(Examples A1 to A3, Comparative Examples A1 to A3)
Using each of the YIG particles obtained above as magnetic powder, a magnetic toner and a liquid developer were prepared as follows. These were designated as Examples A1 to A3 and Comparative Examples A1 to A2.
Magnetic toner and liquid developer were prepared using magnetite (trade name: MTS-010, Toda Kogyo Co., Ltd., magnetization 42.2 emu / g at 500 Oe, average primary particle size 0.2 μm) as magnetic powder. Was referred to as Comparative Example A3.

-Preparation of magnetic toner-
First, 400 parts of styrene acrylic resin (ESREC P-SE-0020, manufactured by Sekisui Chemical Co., Ltd.) was added to 600 parts of each YIG particle or magnetite particle, and the surface was resin-coated by kneading with a pressure kneader. Six types of surface-treated magnetic powder (magnetic powder content: 60%) were obtained.

(Preparation of magnetic toner using Example A1)
After mixing 17 parts of hydroxyethyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.), 57 parts of styrene monomer (manufactured by Wako Pure Chemical Industries, Ltd.) and 1 part of divinylbenzene (manufactured by Wako Pure Chemical Industries, Ltd.), 33 parts of the surface-treated magnetic powder of the YIG particles A1 was added thereto and dispersed for 48 hours by a ball mill. To 90 parts of the magnetic powder dispersion, 5 parts of azobisisobutyronitrile (manufactured by Wako Pure Chemical Industries, Ltd.) as a polymerization initiator was added to prepare a mixture containing the monomer and the magnetic powder.

In an aqueous solution obtained by dissolving 28 parts of sodium chloride (manufactured by Wako Pure Chemical Industries, Ltd.) in 160 parts of ion-exchanged water, 30 parts of calcium carbonate (manufactured by Maruo Calcium Co., Ltd., Luminous) as a dispersion stabilizer, carboxymethyl cellulose (first 3.5 parts of Kogyo Seiyaku Co., Ltd., Serogen) was added and dispersed for 24 hours with a ball mill to obtain a dispersion medium.
The mixture was charged into 200 parts of this dispersion medium, and emulsified at 8000 rpm for 3 minutes with an emulsifying device (manufactured by SMT Co., Ltd., HIGH-FLEX HOMOGENIZER).

On the other hand, nitrogen was introduced into the separable flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen introduction pipe from the nitrogen introduction pipe, and the inside of the flask was made a nitrogen atmosphere. The above suspension was placed therein, reacted at 65 ° C. for 3 hours, further heated at 70 ° C. for 10 hours and cooled. The reaction solution was a good dispersion, and no agglomerates could be confirmed during polymerization.
A 10% aqueous hydrochloric acid solution was added to the reaction solution to decompose calcium carbonate, and solid-liquid separation was performed by centrifugation. The obtained particles were washed with 1 L of ion exchange water, and then washed by repeating ultrasonic dispersion and centrifugation in 500 ml of ethanol for 30 minutes three times to obtain a magnetic toner.

  The magnetic toner was dried in an oven at 60 ° C., and then coarse particles were separated through a mesh having a pore diameter of 10 μm. The number average particle diameter was measured and found to be 5.0 μm.

(Production of Magnetic Toner Using Example A2 to Comparative Example A3)
The magnetic toner using YIG particles A2, YIG particles A3, Comparative Example A1, Comparative Example A2, and Comparative Example A3 (magnetite) is the same as the magnetic powder dispersion (magnetic powder dispersion in the production of magnetic toner using Example A1). The amount of surface-treated magnetic powder in (Liquid) was prepared in the same manner as above except that 47 parts, 40 parts, 85 parts, 60 parts, and 40 parts were added.
The diameters of the produced toners are 4.7 μm (Example A2), 3.9 μm (Example A3), 4.7 μm (Comparative Example A1), 4.4 μm, (Comparative Example A2), 3.6 μm (Comparative). Example A3).

-Production of liquid developer-
After 5 parts of polyvinyl alcohol (PVA, manufactured by Kuraray Co., Ltd., Kuraray Poval 217, polymerization degree: 1700, saponification degree: 88 mol%) is added to 95 parts of cooled ion-exchanged water and dispersed while stirring with a magnetic stirrer. Further, the mixture was stirred and dissolved for 3 hours while heating to 70 ° C. in a water bath to prepare an aqueous PVA solution (5% solution).

-Magnetic toner: 5 parts-PVA aqueous solution: 10 parts-Polyoxyethylene (20) cetyl ether (manufactured by Wako Pure Chemical Industries, Ltd.): 0.5 parts-Ion exchange water: 84.5 parts The liquid developer was dispersed with a ball mill for 3 hours to use the magnetic toner as a magnetic toner. 0.1 ml of this liquid developer is sampled, dispersed in 100 ml of a measurement solution Isoton (manufactured by Beckman Coulter, Inc.), and a volume average particle size (by using Coulter Counter Multisizer 3 (manufactured by Beckman Coulter, Inc.)) The dispersion average particle size) was measured and found to be 3.0 μm.

-Evaluation of developability-
An image forming apparatus 100 having the configuration shown in FIG. 1 was prepared, and the liquid developer was used as a developer.
As the magnetic drum 10, Ni—P was plated as an underlayer to a thickness of 15 μm and Co—Ni—P as a magnetic recording layer to a thickness of 0.8 μm on an aluminum drum. Fluorine lubrication plating with -P-PTFE particles was performed to form a protective layer having a thickness of 1.5 μm. The magnetic recording layer had a coercive force of 400 Oe and a residual magnetic flux density of 7000 G.
The contact angle of pure water with this magnetic drum 10 surface at 25 ° C. and 50% RH was 110 degrees.

  As the magnetic head 12, a 4-channel full-line magnetic head that forms pixels equivalent to 600 dpi (dpi: number of dots per inch) made of Mn—Zn ferrite was prepared.

  The developing device 14 includes, as a developing roller 14a, a magnet roll in which cylindrical permanent magnets are concentrically arranged in a nonmagnetic sleeve made of aluminum, and stirring the liquid developer inside the developer storage container 14b. A developing device 14 provided with a wing was used. The liquid developer was charged into the developer storage container 14b, and the developing device 14 was arranged so that the gap between the nonmagnetic sleeve surface and the magnetic drum 10 surface was 50 μm.

  As the intermediate transfer member 16, an aluminum intermediate transfer drum having a silicone rubber layer having a thickness of 7.5 mm on the surface and rotating at the same peripheral speed as the magnetic drum 10 was used. Further, as the transfer fixing roller 28, an elastic roll in which a silicone rubber layer and a fluororubber layer are coated in this order on the outer periphery of a stainless steel core material is used, and the elastic roll has a surface temperature of 170 ° C. by a heating element. It was set as the structure heated so that it might become.

The printing conditions were set as follows by the image forming apparatus 100 having the above configuration.
Magnetic drum linear velocity: 100 mm / second.
Developing roller peripheral speed / magnetic drum peripheral speed ratio: 1.2.
Transfer conditions (intermediate transfer): The pressing force of the intermediate transfer member to the magnetic drum is set to 0.147 MPa (1.5 kgf / cm ² ).
Transfer fixing condition: The pressing force of the transfer fixing roller against the intermediate transfer member is set to 0.245 MPa (2.5 kgf / cm ² ).

  Under the above conditions, the magnetic head 12 formed a magnetic latent image (corresponding to a halftone) of 30 .mu.m / line on the magnetic drum 10, and developed by bringing the liquid developer into contact therewith with the developing roller. . The developed toner image was transferred to the intermediate transfer member 16 and then transferred and fixed on a recording sheet to obtain an image. The obtained image was observed and evaluated. As the evaluation criteria, the line width of the fixed image was measured with a microscope, and if it was 45 μm or less, the developability was good.

-Evaluation of CIE1976 (L * a * b *) color system-
The obtained magnetic toner was formed in a layer form at 4.0 g / m ² , and this was heat-fixed (temperature: 157 ° C.) to prepare a color sample. Then, the color sample was measured using a reflection densitometer X-rite 939 (manufactured by X-rite), and the CIE 1976 (L * a * b *) color system was examined.

Further, a toner without magnetic powder prepared in the same manner as described above except that no magnetic powder was blended was prepared, and the color was measured in the same manner, and the color difference ΔE with this was calculated based on the following formula. The toner without magnetic powder had an L * _reference of 92.7, an a * _reference of −8.7, and a b * _reference of 113.5.
ΔE = (ΔL * ² + Δa * ² + Δb * ² ) ^1/2
ΔL * = L * _reference -L * _sample
Δa * = a * _reference -a * _sample
Δb * = b * _reference −b * _sample
(Here, L * _sample, a * _sample , and b * _sample represent the CIE 1976 (L * a * b *) color system of the magnetic toner containing magnetic powder.)

  The results are shown in Table 2.

In Table 2, the blending amount of the surface-treated magnetic powder of YIG particles as the magnetic powder is the blending amount of magnetite (10 cm) with respect to the ratio of YIG particle magnetization to magnetite magnetization (YIG particle magnetization / magnetite magnetization). ² ), a developing toner amount of 4.0 g / m ² , and a blending amount in a case of a magnetite weight ratio of 5% by weight with respect to the whole toner).

  From the above results, compared with the comparative example, the present example realizes a reduction in the toner diameter while suppressing the deterioration of the magnetic properties of the YIG particles as the magnetic powder, has good developability, and forms a high-quality image. I understand that In addition, it can be seen that in this example, the influence of YIG particles as magnetic powder on the hue of the toner, particularly the decrease in lightness of the yellow toner, is suppressed as compared with the comparative example.

[Example B]
(Preparation of magnetic toner)
A magnetic toner prepared in Example A and containing YIG particles as magnetic powder was prepared.

(Preparation of silver supported zeolite)
250 g of each dry powder of type A zeolite fine powder was collected, and a mixture obtained by adding a 0.1 M aqueous silver nitrate solution to each was kept under stirring at room temperature for 3 hours for ion exchange. The silver-supported zeolite thus obtained was filtered and then washed with water to remove excess silver ions. Next, the washed silver-supported zeolite was dried at 100 ° C. and then pulverized to produce a silver-supported zeolite having an average primary particle size of 5 μm.
(Examples B1 to B4)
-Example B1-
-Magnetic toner: 5 parts-Triton-X100 (manufactured by Wako Pure Chemical Industries) solution: 1 part-Silver-supported zeolite: 10 parts-Ion-exchanged water: 89 parts Obtained.

-Example B2-
-Magnetic toner: 5 parts-Triton-X100 (manufactured by Wako Pure Chemical Industries) solution: 1 part-Silver-supported zeolite: 1 part-Ion-exchanged water: 89 parts Obtained.

-Example B3-
-Magnetic toner: 5 parts-Triton-X100 (manufactured by Wako Pure Chemical Industries) solution: 1 part-Silver-supported zeolite: 0.01 part-Ion exchange water: 89 parts An agent was obtained.

-Example B4-
-Magnetic toner: 5 parts-Triton X solution: 1 part-Silver-supported zeolite: None-Ion-exchanged water: 96 parts The above composition was dispersed in a ball mill for 3 hours to obtain a liquid developer.

-Test evaluation of mold resistance-
The fungal resistance test of the liquid developer was performed using a water sampler (MT0010025: for total viable bacteria) manufactured by Tokyo Glass Instrument Co., Ltd. A water sampler was immersed in the prepared developer for 30 seconds to absorb about 1 ml. Subsequently, culture was performed using an incubator set at 35 ° C., and the surface of the sampler after a predetermined time was observed. Specifically, colonies formed on the sampler after 1 day, 10 days, 20 days, and 30 days were counted. The results are shown in Table 3.

From the above results, it can be seen that Examples B1 to B3 in which the silver-supported zeolite was blended were superior in mold resistance as compared to Example B4 that was not blended. Moreover, it turns out that Example B1 and B2 which mix | blended the silver carrying zeolite more than predetermined amount are excellent in especially mold | fungi resistance compared with Example B3.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention. FIG. 3 is an enlarged schematic diagram of a development area in an example of the image forming apparatus of the present invention. It is a figure which shows the X-ray-diffraction profile of YIG particle | grains A1, A2, and A3 produced in the Example, and comparative YIG particle | grains A1 and A2.

Explanation of symbols

10 Magnetic drum (magnetic latent image holder)
12 Magnetic head (magnetic latent image forming means)
13 Restricting member 14 Developing device (developer supply means)
15 Stirring member 16 Intermediate transfer member 18 Cleaner 20 Demagnetizing device (demagnetizing means)
22 Magnetic latent image 24 Liquid developer 26 Toner image 28 Transfer fixing roller (transfer means)
29 fixed image 30 recording medium 100 image forming apparatus

Claims (6)

A magnetic powder comprising yttrium, iron, garnet (YIG) and having a half-width of the peak of the plane index (420) of 0.4 deg or less in powder X-ray diffraction;
A polymer compound containing the magnetic powder;
A magnetic toner comprising: In the CIE 1976 (L * a * b *) color system of the magnetic powder,
The magnetic toner according to claim 1, wherein L * is 65 or more and 90 or less, a * is −9 or more and 15 or less, and b * is +30 or more and 110 or less.   The magnetic toner according to claim 2, wherein L * of the magnetic toner in the CIE 1976 (L * a * b *) color system is 80 or more and 90 or less. The magnetic toner according to any one of claims 1 to 3,
An aqueous medium in which the magnetic toner is dispersed;
A liquid developer comprising: A magnetic latent image carrier;
Developer storage means for storing the liquid developer according to claim 4;
Developer supplying means for supplying the liquid developer to a magnetic latent image holding member on which a magnetic latent image is formed;
A process cartridge comprising: A magnetic latent image carrier;
Magnetic latent image forming means for forming a magnetic latent image on the magnetic latent image holding member;
Developer storage means for storing the liquid developer according to claim 4;
Developer supplying means for supplying the liquid developer to a magnetic latent image holder on which the magnetic latent image is formed in order to visualize the magnetic latent image as a toner image;
Transfer means for transferring the toner image to a recording medium;
A degaussing means for degaussing the magnetic latent image on the magnetic latent image holder;
An image forming apparatus comprising:

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