JPH09244304A - Liquid developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the fog of the image recorded on a medium to be recorded by dispersing colored particles in the solvent of aliphatic hydrocarbon as the toner. SOLUTION: Colored particles in the aliphatic hydrocarbon are dispersed as the toner to develop the electrostatic latent image formed on a photosensitive material. The mean grain size of the colored particles is preferably in the range of about 1-20μm. The degree of dispersion (the ratio of the volumetric means particle size to the individual mean grain size) measured by a coal tar counter grain size distribution meter of the colored particles is preferably <= about 1.5. The fog of the image recorded on a medium to be recorded can be eliminated, and a large amount of the fixing components to the medium to be recorded which is contained in particles of the developer can be contained by dispersing particles of >=1μm in the organic solvent, and the liquid developer capable of simultaneously performing fixing and coloring to the medium to be recorded can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developer, and more particularly to a liquid developer in which colored particles are dispersed in an aliphatic hydrocarbon solvent.

[0002]

2. Description of the Related Art Conventionally, a liquid developer is known as a developer for developing an electrostatic latent image on a photoconductor, and a colorant composed of a pigment or a dye and resin particles are dispersed in an organic solvent. Has been done. As the organic solvent, an aliphatic hydrocarbon having a high insulating property is generally used. The resin particles are polymerized by dispersing a monomer in an aliphatic hydrocarbon solvent. A colorant is further dispersed in an aliphatic hydrocarbon solvent in which polymerized resin particles are dispersed, and the resin particles and the colorant are aggregated to form a toner. In this case, the solid content concentration of the resin particles and the colorant in the liquid developer is 1 to 10% by weight, and the particle diameter is 1 μm or less. The development on the photoreceptor is such that the resin particles and the agglomerated particles of the colorant are developed with a slight amount of the aliphatic hydrocarbon solvent while contacting the photoreceptor on which the electrostatic latent image based on the image information is formed. It Toner developed on the electrostatic latent image must be transferred to a recording medium and fixed by a heat roller. Therefore, resin particles that are melted by heat should be included in the liquid developer and developed together with the colorant. Will be required.

[0003]

However, since the liquid developer also contacts the portion of the photoreceptor on which the electrostatic latent image is formed and where the toner is not developed, the colorant or resin dispersed in the liquid developer is contacted. The particles adhere with a force different from the electrostatic attraction of the electrostatic latent image. The colorant or resin particles attached to the photoconductor is transferred to the recording medium and fixed by the heat roller, so if the colorant adheres to a portion that is not originally developed, when the image is transferred to the recording medium,
It appears as a fog of colorant on the part that must be white. Further, the resin particles adhered to the photoconductor are not completely removed by transfer or cleaning of the photoconductor, and therefore adhere to the photoconductor. By attaching to the photoconductor,
The potential of the electrostatic latent image becomes unstable, and the colorant and the resin particles are developed in the areas that should not be developed. This also increases the fogging of the image.

The resin particles contained in the liquid developer as a fixing component on the recording medium are contained in an amount sufficient for sufficient fixing to the recording medium due to problems such as increase in viscosity as the liquid developer. However, even if the image is transferred from the photoconductor to the recording medium and fixed, only a fixing strength that can be removed by rubbing is obtained.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a liquid developer capable of eliminating the fog of an image recorded on a recording medium. Another object of the present invention is to provide a liquid developer in which particles having a size of 1 μm or more are dispersed in an organic solvent so that sufficient fixing to a recording medium and coloring can be simultaneously performed. Another object of the present invention is to provide a liquid developer containing uniformly charged developer particles using monodisperse colored particles.

[0006]

In order to achieve this object, the liquid developer according to claim 1 is an electrostatic latent image in which colored particles are formed on a photoreceptor in an aliphatic hydrocarbon solvent. This is achieved by being dispersed as a toner for developing the image.

The liquid developer according to a second aspect of the invention is achieved when the average particle size of the colored particles is in the range of about 1 to 20 μm.

The liquid developer according to claim 3 has a dispersity (ratio of volume average particle diameter to number average particle diameter) of colored particles measured by a Coulter counter particle size distribution meter.
It is achieved by being about 1.5 or less.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The materials constituting the liquid developer of the present invention are colored particles and an aliphatic hydrocarbon solvent. It is also possible to add a charge control agent as needed.

In the present invention, the colored particles include a pulverizing method for forming a colorant mixed particle by pulverizing a colorant mixture dispersed in a resin by heating and mixing a resin and a colorant, and a solvent in a solvent. A polymerization method in which the dispersed colorant and monomer component are incorporated into the polymerized resin particles by the action of the polymerization initiator to form colorant particles, and the polymerized particles formed only of the resin or the pulverized particles are placed in an organic solvent. It is possible to use a dyeing method in which the coloring agent is dispersed together with the coloring agent and the coloring agent is dyed on the surface of the uncolored resin particles, but in the embodiment of the present invention, the development for a liquid developer having a narrow particle size distribution and a uniform charge amount is possible. From the provision of the agent, dispersion precipitation polymerization, suspension polymerization, mixing the particles polymerized by a polymerization method such as emulsion polymerization with a colorant in a solvent, dye the resin particles to form colored resin particles. For staining method will be described.

Among the various methods for producing polymer particles having the narrowest particle size distribution, dispersion precipitation polymerization is preferable, and 1 μm is preferable.
It is effective as a polymerization method having the above average particle diameter and leaving no impurities in the produced polymer particles. In this embodiment, a non-aqueous precipitation dispersion polymerization in which the particle size of the particles to be polymerized can be controlled is wide among the above-mentioned polymerization methods will be described.

The particles grown by polymerization are separated as particles without being dissolved in the organic solvent. The polymerized particles dispersed in the organic solvent are filtered and then dispersed and dyed again in the organic solvent together with the dye. The dyed polymer particles are filtered, dried, and dispersed again in an aliphatic hydrocarbon solvent to form a liquid developer.

In the non-aqueous precipitation dispersion polymerization, a polymerization initiator and a polymer dispersant are simultaneously dissolved in an organic solvent which dissolves a monomer, and polymerization is initiated while maintaining a constant temperature. If necessary, a surfactant and a crosslinking agent can be added.
Hereinafter, the materials used for the non-aqueous precipitation dispersion polymerization will be described with reference to examples.

(Organic solvent) Examples of the organic solvent in which the polymerizable monomer used in the present invention is dissolved include methanol, ethanol, isopropyl alcohol, n-butanol and s-.
Butanol, t-butanol, n-amyl alcohol,
s-amyl alcohol, t-amyl alcohol, isoamyl alcohol, isobutyl alcohol, isopropyl alcohol, 2-ethylbutanol, 2-ethylhexanol, 2-octanol, n-octanol, n-decanol, cyclohexanol, n-hexanol, 2
-Heptanol, 3-heptanol, 3-pentanol, methylcyclohexanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 3-methyl-1
Alcohols such as -butyn-3-ol, 4-methyl-2-pentanol and 3-methyl-1-pentyn-3-ol may be used alone or in combination of two or more.

Examples of the organic solvent used in combination with these alcohols include hydrocarbon solvents such as hexane, toluene, cyclohexane, benzene and xylene, ethylbenzyl ether, dibutyl ether, dipropyl ether and dibenzdiene. Ethers such as ether, dimethyl ether, tetrahydrofuran, vinyl methyl ether, vinyl ethyl ether, acetaldehyde, acetone, acetophenone, diisobutyl ketone,
Ketones such as diisopropyl ketone and cyclohexanone; esters such as ethyl formate, ethyl acetate, methyl acetate, ethyl stearate, and methyl salicylate; and water. These solvents are used to adjust the SP value of the alcohol.

The weight ratio of organic solvent to monomer is 100:
5-80 is suitable.

(Monomer) As the monomer having a polymerizable functional group, a compound containing a vinyl group can be used, and examples thereof include styrene, methylstyrene, ethylstyrene, 2,4-dimethylstyrene and pn. -Styrene-based monomers such as butyl styrene and pt-butyl styrene, methyl acrylate, ethyl acrylate,
Methyl fatty acid monocarboxylic acid esters such as n-butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methyl vinyl ether, ethyl vinyl ether, Vinyl ethers such as n-propyl vinyl ether and n-butyl vinyl ether, and vinyl compounds such as acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, ethylene, propylene and chloroprene can be used alone or as a mixture of two or more kinds.

(Polymerization Initiator) The polymerization initiator for polymerizing the above monomers is 0.00 based on the total weight of the monomers.
The addition amount of 1 to 20% by weight is suitable, and examples thereof include lauryl peroxide, benzoyl peroxide, and azobisisobutylnitrile.

(Dispersion Stabilizer) At the same time as the polymerization progresses to form particles, a dispersant is mixed in the organic solvent from the initial stage of the polymerization for the purpose of preventing aggregation of the formed polymer particles. The mixing amount is 0.1 with respect to the total monomer weight.
30 WT% is suitable. This dispersion stabilizer is, for example, polystyrene, polyvinyl acetate, polymethylmethacrylate, polydimethylsiloxane, polyvinyl chloride,
Polyethylene, polypropylene, polylauryl methacrylate, polyoxyethylene, polyvinyl alcohol,
Polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylpyrrolidone, polyethyleneimine, polyvinylmethyl ether, poly-4-vinylpyridine,
Examples thereof include polystyrene sulfonic acid.

(Surfactant) A surfactant may be used in combination with the above dispersant. The appropriate addition amount is 0.1 to 30 wt% with respect to the total weight of the monomers. For example, higher alcohol sulfate, alkyl allyl sulfonate, alkyl naphthalene sulfonate, alkyl phosphate, polyoxyethylene alkyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, trimethylaminoethyl alkyl Amido halogen and the like.

(Crosslinking Agent) The polymer particles of the present invention may be crosslinked and polymerized by adding a crosslinking agent. For example, compounds having two or more vinyl groups such as divinylbenzene, divinylnaphthalene, diallyl phthalate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, trimethylolpropane triacrylate, and glycerin trimethacrylate can be mentioned. These cross-linking agents are used alone or in combination of two or more, and are added in the range of 0.01 to 10 wt% with respect to the total weight of the monomers.

The average particle diameter of the polymer particles can be changed by changing the SP value of the organic solvent in which the monomer is dissolved and lengthening the polymerization time.

The polymer particles used as a liquid developer preferably have an average particle size in the range of about 1 to 20 μm, and polymer particles having an average particle size of 1 μm or less are sensitized when the developer is developed. Since it comes into contact with the body, the developer also adheres to a portion of the developer that should not be developed, which causes fog when the image is transferred to the recording medium. When the average particle size exceeds 20 μm, the reproducibility of fine lines in the developed image is poor and the resolution is lowered. If the average particle size is large, the speed at which the dyed particles settle in the liquid developer is increased, and the frequency of stirring the liquid developer is increased. Therefore, the average particle size of 10 μm or less is 20 μm or less. More preferable.

The degree of dispersion represents the ratio of the volume-based average particle diameter to the number-based average particle diameter when measured with a particle size distribution analyzer called a Coulter counter. The Coulter counter is a measuring device that can be obtained by detecting a change in electric resistance flowing in an electrolyte by a particle passing through an aperture as a current value and calculating the particle diameter. Since the Coulter counter measures the particle size of each particle and forms the particle size distribution depending on the number, the volume-based average particle size and the number-based average particle size can be accurately compared.

The volume-based average particle diameter that defines the degree of dispersion is a value obtained by calculating the average particle diameter using a value that represents the total of the particles included in a certain particle diameter range in terms of the volume of the particles. The particle size is a value obtained by calculating the average particle size using a value in which the total number of particles included in a certain particle size range is represented by the number of particles.

The liquid developer of the present invention has a dispersity of about 1.
It is preferably 5 or less and used as an index showing that the particle size has a narrow particle size distribution. When the dispersity is large, the particle size distribution is wide, and large particles and small particles are mixed in the developer. The large particles and the small particles have different charge amounts when present in the liquid developer, so that the charge amount distribution is widened. Since the developer polymer particles are developed based on the charge amount, only the vicinity of the central value of the charge amount distribution is selectively developed. The polymer particles which have not been developed not only remain undeveloped, but also have the opposite polarity and cause fogging. In order to obtain polymer particles that are not selectively developed with a charge amount, it is desirable that the dispersity be 1.5 or less, and more preferably 1.2 or less.

The polymerized particles are filtered with a filter from an organic solvent and dispersed in a solvent to be dyed again. Making the same organic solvent used for polymerization and the organic solvent used for dyeing is advantageous in terms of working steps and cost.

The polymerized particles are dispersed and dyed in an organic solvent in which a dye is dissolved, but the particle size when the polymerization is completed and the particle size when the dyeing is completed do not change.

The dye for dyeing the polymer particles is preferably dissolved or dispersed in the organic solvent in which the polymer particles are dispersed. It is considered that the dissolved and dispersed dye permeates into the polymer particles dispersed in the organic solvent.

(Dye) Examples of the dye used include disperse dyes, oil-soluble dyes, and metal-containing dyes. For example, Disperse Yellow 3, 31, 242, Disperse Red 1, 4, 5, 7, 11 , 12, 13, 15, 17,
145, 154, 179, 283, Disperse Blue 1, 3, 6, 7, 43, 44, 52, 60, 68, 8
7, 158, 183, Solvent Yellow 16, 21,
29, 56, 61, 77, 79, 82, 93, Solvent Red 1, 3, 8, 23, 27, 30, 49, 81,
82, 83, 84, 109, 132, 218, Solvent Blue 2, 5, 12, 38, 48, 55, 67, 7
0, 73, and the like.

The dyed polymer particles are dispersed in an aliphatic hydrocarbon solvent. Examples of the aliphatic hydrocarbon solvent include kerosene, ligroin, n-hexane, n-heptane, n-octane, i-octane and i-dodecane.

The aliphatic hydrocarbon solvent has a high insulating property and is required to be a nonpolar solvent. 50 to 50% of liquid developer
The aliphatic hydrocarbon solvent accounting for 99% by weight comes into contact with the dyed polymer particles on the photoreceptor on which the electrostatic latent image is formed according to the image information. When the aliphatic hydrocarbon solvent has no insulating property when contacted with the photoreceptor, the dyed polymer particles are not developed on the photoreceptor.

Further, since the dyed polymer particles are dispersed in an aliphatic hydrocarbon solvent to act as a developer, a material in which the polymer particles are dissolved in the aliphatic hydrocarbon solvent must be avoided.

A charge control agent can be mixed with the aliphatic hydrocarbon solvent in which the colored resin particles are dispersed. For example, lecithin, metal soap, linseed oil, higher fatty acid, etc. can be mentioned.

[0035]

Example 1 “Example of polymerized particle production” 20 parts by weight of polyvinylpyrrolidone (k-30) was dissolved in 500 parts by weight of methanol in a four-necked flask equipped with a stirring blade, a cooler, a thermometer, and a gas introduction tube. Further, 150 parts by weight of styrene, 40 parts by weight of butyl acrylate, and 10 parts by weight of 2,2-azobisisobutyronitrile were added and stirred to obtain a transparent solution. The inside of the flask was replaced with nitrogen gas while stirring, the temperature was raised to 60 ° C., and the polymerization was started at a stirring blade rotation speed of 100 rpm. After 10 minutes from heating, it began to turn cloudy, and polymerization was continued for 5 hours in this state. After 5 hours, 200 parts by weight of a 1: 1 mixed solvent of water and methanol was added dropwise over 1 hour to return to room temperature.
The polymerization was completed. This slurry was filtered for the first time using a 1 μm filter, re-dispersed in a mixed solvent of methanol and water, and then filtered using a 1 μm filter.
It was filtered a second time.

[Example of Colored Particle Production] In a 300 ml beaker, 100 parts by weight of methanol and CERES RED 3R
(Bayer) 3 parts by weight was added and dissolved in a water bath at 40 ° C. with stirring, and the concentration of methanol produced above was about 30.
% Polymer particles 30 parts by weight are dispersed. After dyeing at 40 ° C. for 1 hour, the mixture was filtered through a 1 μm filter for the first time, further redispersed in 100 parts by weight of a 1: 1 solvent of methanol and water, and then subjected to a second filtration. The particles were dried for one day to obtain magenta particles having an average particle diameter of 2.8 μm and a dispersity of 1.03.

As the liquid developer, 100 parts by weight of Isozole was mixed with 20 parts by weight of the magenta color particles prepared above and 2 parts by weight of polystyrene, and a concentrated liquid developer was obtained using Dispermat. Further, 5 parts by weight of this concentrated liquid developer was dispersed in 100 parts by weight of Isosol to complete the liquid developer.

When a voltage of 500 V was applied using an electrophoretic tester, it was possible to confirm the developer particles moving in the aliphatic hydrocarbon solvent.

When the prototype was filled with this liquid developer and developed, a clear image without fog could be formed.

[0040]

[Example 2] "Example of polymerized particle production" 20 parts by weight of polyvinylpyrrolidone (k-30) was dissolved in 500 parts by weight of methanol in a four-necked flask equipped with a stirring blade, a cooler, a thermometer, and a gas introduction tube. Further, 150 parts by weight of styrene, 40 parts by weight of butyl acrylate, and 10 parts by weight of 2,2-azobisisobutyronitrile were added and stirred to obtain a transparent solution. The inside of the flask was replaced with nitrogen gas while stirring, the temperature was raised to 60 ° C., and the polymerization was started at a stirring blade rotation speed of 100 rpm.
Ten minutes after heating, the solution began to become cloudy, and polymerization was performed for 10 hours in this state. After 10 hours, 200 parts by weight of a 1: 1 mixed solvent of water and methanol was added dropwise over 1 hour to return to room temperature.
The polymerization was completed. The slurry was filtered for the first time using a 3 μm filter, re-dispersed in a mixed solvent of methanol and water, and then filtered using a 3 μm filter.
It was filtered a second time.

"Colored Particle Production Example" The colored particles obtained by using the same method as in the colored particle production example of Example 1 were dried for one day and night, and had an average particle diameter of 5.7 μm and a dispersity of 1.07. It was possible to obtain magenta particles.

As the liquid developer, 100 parts by weight of Isozole was mixed with 20 parts by weight of the magenta particles prepared above and 2 parts by weight of polystyrene, and a concentrated liquid developer was obtained by using Dispermat. Further, 5 parts by weight of this concentrated liquid developer was dispersed in 100 parts by weight of Isosol to complete the liquid developer.

When a voltage of 500 V was applied using an electrophoretic tester, it was possible to confirm the developer particles moving in the aliphatic hydrocarbon solvent.

When this liquid developer was left to stand, the dyed polymer particles were precipitated, but when it was charged in a prototype machine and developed while stirring, a clear image without fog could be formed.

[0045]

[Comparative Example 1] 500 g of n-hexane was placed in a flask,
Methyl acrylate 100 with heating to 80 degrees and stirring
g, 2-ethylhexyl acrylate 50 g, and azobisisobutyronitrile 5 g were added dropwise over 3 hours. Polymerization was continued for 6 hours while maintaining the temperature at 80 ° C., and 5 g of benzoyl peroxide was added dropwise to 100
The liquid temperature was raised every time and polymerization was carried out for 1 hour.

100 g of this resin dispersion was added to n-hexane 1
00 g and FG7351 (copper phthalocyanine) 10 g were mixed and dispersed in a ball mill for 24 hours. further,
10 g of this concentrated liquid developer solution was added to n-hexane 1000
g to give a cyan liquid developer.

When the image was developed using a prototype as in Example 1, the developer adhered to the portions other than the image or the character forming portion, resulting in an image with conspicuous fog.

[0048]

Comparative Example 2 Polymerization was carried out under the same conditions as in Example 1 except that the amount of butyl acrylate was increased to 60 parts by weight. The average particle diameter was 3.4 μm and the dispersity was 1.74. Polymerized particles of were obtained.

The particles were dyed in the same manner as in Example 1 to obtain magenta dyed particles. Furthermore, when a liquid developer was prepared in the same manner as in Example 1 and developed using a prototype, the developer was attached to areas other than the image or the character forming portion, resulting in an image with conspicuous fog.

[0050]

As is apparent from the above description, by using the liquid developer according to claim 1 of the present invention, a liquid developer capable of eliminating fogging of an image recorded on a recording medium is obtained. Can be provided.

Further, in the liquid developer according to claim 2,
By dispersing particles having a size of 1 μm or more in an organic solvent, a large amount of a fixing component contained in the developer particles to the recording medium can be contained, and a liquid developer capable of fixing to the recording medium and coloring at the same time can be obtained. Can be provided.

Further, in the liquid developer according to claim 3,
Since the developer particles have uniform chargeability by using monodisperse colored particles, it is possible to provide a liquid developer that faithfully develops an electrostatic latent image formed on a photoreceptor.

Claims (3)

[Claims] 1. A liquid developer for developing an electrostatic latent image formed on a photoconductor, characterized in that colored particles are dispersed as a toner in an aliphatic hydrocarbon solvent. Developer. 2. The liquid developer according to claim 1, wherein the average particle size of the colored particles is in the range of about 1 to 20 μm. 3. The dispersity of the colored particles (ratio of volume average particle diameter and number average particle diameter measured by Coulter counter particle size distribution meter) is about 1.5 or less. 1. The liquid developer according to 1.