JPH10282730A - New production of liquid toner used for developing electrostatic latent image and toner produced by the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily produce liq. toner particles having a small particle size and a uniform shape at a low cost by adopting a polymerizing method as a method for producing the toner particles of a liq. developer for developing an electrostatic latent image. SOLUTION: A polymerizing method is adopted as a method for producing the toner particles of a liq. developer for developing an electrostatic latent image. A monomer having a carboxyl or hydroxyl group is preferably used and the polymerizing method is preferably an emulsion polymerizing method, a suspension polymerizing method, a soap-free polymerizing method or a dispersion polymerizing method. It is preferable that polymn. is allowed to proceed using satd. hydrocarbon based on Cn H2n+2 (n=6, 7 or 8) as a solvent in an inverse micelle system and the solvent is used as the solvent of the liq. developer as it is so as to simplify the producing process. In order to practically form a high resolution image, the particle size of the toner particles is preferably regulated to 0.1-5 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid developer used in an image forming apparatus such as a copier, a facsimile, a printer, a printing machine, a printed circuit board manufacturing apparatus, and a photomask manufacturing apparatus of an electrophotographic system or an electrostatic recording system. It is about.

[0002]

2. Description of the Related Art Conventionally, the production of liquid toner particles is generally carried out by a pulverization method. In this method, a polymer pellet is heated and melted while being stirred. Here, if it is necessary to color the toner particles, a pigment such as carbon black is added to the heated and melted polymer, and stirring is performed until the pigment is uniformly dispersed in the polymer. Thereafter, the polymer in which the pigment is dispersed is frozen, and coarse particles having a particle size of several tens of μm are produced by a pulverizer such as a hammer mill or a vibration mill. Next, coarse particles are placed in a non-polar liquid as a liquid toner developer and wet-polished by a ball mill or the like to produce toner particles having a diameter of about 1 to 5 μm. A charge control agent for imparting charge to the toner particles thus produced is mixed to obtain a liquid toner developer.

[0003] The liquid developing method has the advantage of being able to reduce the particle size without the danger of powder explosion and to produce a print with high resolution, as compared with the dry developing method.

[0004]

As described above, the high resolution can be achieved by the wet developing method. However, in the case of high resolution printing, the uniformity of the particle size, that is, the sharpness Particle size distribution is required. Longer pulverization and wet polishing are required to reduce the toner particle diameter by the conventional pulverization method, and repeated classification work (for example, centrifugation) is required to obtain a toner particle having a sharp particle size distribution. Becomes Such pulverizing / polishing operations and classifying operations are not practical for producing toner particles having a very small particle size such as liquid toner, because they are wasteful and increase the production cost. As another means for obtaining toner particles having a smaller particle diameter in a relatively short time, there is a method of mixing wax or the like in a polymer pellet melting step. However, when a wax is added, a hydroxyl group or a carboxyl group present on the surface of the toner particles, which is complex-bonded with the charge control agent, is covered by the wax, and the charge control agent and the toner particles cannot be stably bonded. It becomes toner. Also,
Another problem with the pulverization method is that the shape of the toner particles obtained by the pulverization method is very uneven. When liquid toner particles with non-uniform particle shape are complexed with a charge control agent that gives charge to toner particles, the amount of charge control agent complexed between individual toner particles varies, and each toner particle is charged. Irregularities occur. This uneven charging causes the toner particles to aggregate, lowering the resolution, changing the electrophoretic speed of the toner particles, and causing unevenness in the image and a shortened life. Further, the mechanical frictional force acting between the photoreceptor and the toner particles differs due to the non-uniform shape of the toner particles. This lowers the transfer efficiency from the photosensitive member to the recording medium or from the photosensitive member to the intermediate transfer member, and becomes a serious problem.

The present invention solves the above problems and provides a method for easily and inexpensively producing liquid toner particles having a smaller particle size and a uniform shape, and a method for producing the toner particles produced thereby. The purpose is to provide.

[0006]

As a method for producing toner particles of a liquid developer for developing an electrostatic latent image, a polymerization method is used, and a monomer having a carboxyl group or a hydroxyl group as a particularly preferable monomer is used. Any of the emulsion polymerization method, suspension polymerization method, soap-free polymerization method and dispersion polymerization method was used as a preferable method among the polymerization methods. Further, in order to simplify the manufacturing process, CnH2n +
Using a saturated hydrocarbon containing 2 (n = 6, 7, 8) as a main component, the polymerization proceeded in a reverse micelle system, and the solvent used in the production was used as it was for the developer. Furthermore, in order to actually achieve a high-resolution image, the particle size was set to 0.1 μm to 5 μm.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention will be described below. The above shows that the conventional method of grinding and polishing polymers is very inefficient. This is due to the fact that the toner is manufactured from a pre-synthesized polymer mass. Therefore, the present invention introduces a method for producing a toner directly from a polymer monomer.
These monomers are polymerized by using a polymerization initiator as a trigger to form a resin. At this time, the particle size can be freely varied from several tens nm to several μm by changing the reaction time, temperature, surfactant, stirring speed and the like. Further, the shape of the toner particles thus obtained becomes a true sphere due to the interfacial tension between the solvent and the polymer resin. FIG. 1 is a schematic diagram of an emulsion polymerization method among the polymerization methods of the present invention. In the emulsion polymerization method, when surfactant 2 is dissolved in an aqueous phase, at a certain concentration or more, surfactant molecules associate in a specific form in an aqueous solution, and this state is called a micelle. In the aqueous solution, the micelles are arranged with the hydrophilic group on the outside and the hydrophobic group on the inside. Micelles take a spherical structure to minimize surface area. Since the micelle has a hydrophilic group on the outside and a hydrophobic group that is lipophilic on the inside, a lipophilic region is formed in water inside the micelle. In this region, it works the same as in a lipophilic solvent. Also, the size of the micelle at this time is about 0.
005-0.01 μm, which varies with surfactant concentration. When hydrophobic monomer 3 is added to this state, several tens μm
Form droplets of ~ several hundred μm. When this monomer encounters a micelle, it is reversibly incorporated into the micelle due to the lipophilic environment inside the micelle. In this state, when the system is heated and the water-soluble polymerization initiator 4 is added, the initiator is decomposed in the aqueous phase,
Chemically unstable radicals are generated. These radicals attack the monomer and initiate a polymerization reaction inside the micelle. The reaction at this time occurs inside the micelle, and the reaction occurring in the droplet can be ignored. This is because micelles are overwhelmingly larger in number and surface area than droplets. As the reaction proceeds inside the micelle, the consumed monomer is supplied by monomer droplets in the aqueous phase. The inside of the micelles increases in volume as the polymerization proceeds, and subsequently breaks the micelle structure and becomes polymer particles 5. The surfactant migrates to the surface of the polymer particles and stabilizes the particles. If the reaction solution is an aqueous solution, the surface of the polymer particles has exposed hydrophilic groups such as carboxyl groups and hydroxyl groups. A charge control agent that imparts a charge to the toner particles is bonded to such a hydrophilic group,
Liquid toner.

In the suspension polymerization method, a monomer is suspended and dispersed in an aqueous phase containing a surfactant and a dispersion stabilizer to form droplets of the monomer. Polymerization proceeds by radicals generated by decomposition of a polymerization initiator previously dissolved in a monomer to obtain polymer particles. Particles having a larger particle size than the emulsion polymerization method can be obtained. Soap-free emulsion polymerization is a method in which a monomer is added to an initiator radical generated by dissociation and decomposition of a polymerization initiator without using a surfactant and grows, and a polymer chain plays a role of an emulsifier for micelle formation. It is. In the particle formation, the generated polymer chains are aggregated by the effect of the ions in the aqueous solution to form nuclei of the particles, and the monomers are absorbed into the nuclei to promote the polymerization. Since this method does not use a surfactant, there is an advantage that it is not necessary to remove the surfactant (salt-out operation) when synthesizing the liquid toner.

FIG. 2 shows a schematic diagram of the reverse micelle emulsion polymerization method. In this reverse micelle emulsion polymerization method, the polymerization site is replaced with an oil phase from an aqueous phase. When the liquid developer (oil phase) 6 is used as a reaction field, the toner particles produced by polymerization are dried,
Since the liquid developer can be used as it is without performing the dehydrating operation, the operation described above becomes unnecessary.

[0010]

Example 1 An example of a method for producing toner particles by an emulsion polymerization method is described below. Using water as a dispersion solvent, 90 parts of methyl methacrylate as a monomer of the resin constituting the toner, 10 parts of methylacrylic acid so that the charge control agent and the toner particles form a complex bond, and azobisisobutyro as a polymerization initiator. 3 parts by weight of nitrile was added, and the aqueous solution was stirred for 8 hours,
Heated to 70 degrees. The toner particles polymerized in this way were spherical. Thereafter, the toner particles were dried to a powder state. This powder was dispersed in Isopar H. Al (acac) (DIP
S) 2 was used. Where acac is acetylacetonate, DIP
S2 is 3,5-diisopropyl salicylate. The mixture was mixed in Isopar and stirred for about 10 minutes by an ultrasonic cleaner to obtain a liquid toner developer. The obtained liquid toner exhibited good electrophoretic characteristics, and a product having high transfer efficiency and high resolution was obtained.

[0011]

Example 2 In Example 1, copolymerization was carried out using styrene and acrylic acid as monomers. The particles obtained by polymerization were treated in the same manner as in Example 1 to obtain a liquid toner developer.

[0012]

Example 3 Iso-butyl methacrylate 90 as a monomer
Parts and 10 parts of methyl acrylate, azobisisobutyronitrile was used as a polymerization initiator, and the aqueous solution was heated to about 60 ° C. while stirring to carry out copolymerization. The particles obtained by polymerization were treated in the same manner as in Example 1 to obtain a liquid toner developer. Both Examples 2 and 3 had good development characteristics as in Example 1.

[0013]

Example 4 An example in which the reaction proceeds by the reverse micelle system is shown below. Isopar H (manufactured by Esso Corporation), which is a dispersion medium of a liquid toner developer, was used as a solvent, acrylic acid was used as a monomer, and AIBN was used as a polymerization initiator. Further, an emulsifier (used as a charge control agent) used for dispersing micelles was mixed. The same emulsifier as the charge control agent shown in Example 1 was used. The solvent was heated to about 60 ° C. with stirring and polymerization was carried out for 6 hours to obtain particles having a particle size of 0.1 to 5 μm, which were used as liquid toner particles. Excess charge control agent (emulsifier) inserted in the polymerization stage was removed by salting out.

When the liquid toner developer thus obtained was actually used for high-resolution printing, it was found that the transfer efficiency and the resolution were excellent. In the above examples, the emulsion polymerization method has been described. However, similar results were obtained in other suspension polymerization methods, sop-free polymerization methods, and dispersion polymerization methods.

[0015]

According to the present invention, when the particles are complexed with the charge control agent because they have extremely uniform spheres, all the toner particles have the same number of complexed bonds, so that the charge uniformity is excellent.

[Brief description of the drawings]

FIG. 1 is a schematic view of an emulsion polymerization method used in the present invention.

FIG. 2 is a schematic view of a reverse micelle polymerization method used in the present invention.

[Explanation of symbols]

 1; aqueous phase 2; surfactant 3; monomer 4; polymerization initiator 5; polymer particles 6;

Claims (6)

[Claims] 1. A method for producing toner particles of a liquid developer for developing an electrostatic latent image, comprising using a polymerization method. 2. The method according to claim 1, wherein toner particles are produced using a monomer having a carboxyl group or a hydroxyl group. 3. Toner particles, wherein the toner particles produced by the production method according to claim 1 have a particle size of 0.1 μm to 5 μm. 4. A method for producing toner particles according to claim 1, wherein said polymerization method is any one of an emulsion polymerization method, a suspension polymerization method, a soap-free polymerization method and a dispersion polymerization method. 5. The method for producing toner particles according to claim 1, wherein the polymerization proceeds in a reverse micelle system. 6. A solvent comprising CnH2n + 2 (n = 6, 7, 8)
6. The method for producing toner particles according to claim 5, wherein a saturated hydrocarbon containing as a main component is used.