JP2001109187A - Electrophotographic developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic developing toner which does not contaminate an image or surrounding parts due to splashing of the toner or leaking of a carrier liquid, and to provide toner particles having a small average particle size with which high image quality is easily obtained. SOLUTION: The feature of the electrophotographic developer is that the toner particles essentially consist of a nearly spherical gel containing a liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic developer,
The present invention relates to an electrophotographic method, an image forming method, copying, printing, copier, and printer.

[0002]

2. Description of the Related Art Electrophotography is conventionally known. In electrophotography, an electrostatic latent image is first formed, for example, by imagewise exposing a photoconductive material. Alternatively, for example, a desired imagewise charge may be directly applied on an insulating sheet to form an electrostatic latent image. The charged toner particles adhere to the latent image to form a visible image. Thereafter, an image is directly obtained by transferring the formed toner image to paper or the like or without transferring the toner image.

[0003] Electrophotography is used in copiers and printers, and is now spreading worldwide. As toners used for electrophotography, a dry toner using a powder having an average particle diameter of about 10 μm and a wet toner using a powder having an average particle diameter of about 1 μm dispersed in a carrier liquid are known.

[0004] Wet toners have also been put to practical use quickly, but dry toners are currently the mainstream. The wet toner has a small average particle size and can provide high-quality images with high resolution and gradation.
In addition, there are advantages that a defective image, a failure, and the like hardly occur and maintenance is easy.

However, on the other hand, it is necessary for the carrier liquid to satisfy a high resistance and a low dielectric constant. As a result, various dangers have been pointed out because a flammable and volatile liquid is used. Further, there is a drawback that the odor may give a user discomfort due to the evaporation of the volatile liquid, and the toner may be spilled when the apparatus is moved to easily stain the carpet.

[0006] Dry toner is recognized as being safer because it has no danger of ignition or the like and has almost no unpleasant odor against such disadvantages of wet toner. And expanded the market. However, it is pointed out that the powder scatters to contaminate the background of the image, and that the high average particle size makes it impossible to expect high image quality.

Attempts have been made to achieve high image quality and overcome the disadvantages of the wet method. Japanese Patent No. 262156 proposes a developer that contains a swellable polymer as a component, is substantially solid during storage and transportation, and becomes liquid when heated during use. This is a very useful method. However, when such a developer is used, it is necessary to sufficiently heat the entire path along which the developer moves, and it is necessary to devise a heater for heating and a heat insulating material. Further, in such a developer, the viscosity of the developing solution generally tends to be high and the toner layer tends to be thick, so that it tends to be difficult to obtain the original smooth image quality of the wet type.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised to solve the following problems based on the above prior art. 1. Provided is a toner for electrophotographic development that does not cause contamination of an image or its periphery due to toner scattering or leakage of a carrier liquid. 2. To provide toner particles having a small average particle size, which can easily obtain high image quality.

[0009]

Means for Solving the Problems The object of the present invention is to provide (1) an electrophotographic developer characterized in that the toner particles are mainly composed of a substantially spherical gel containing a liquid.
(2) The electrophotographic developer according to the above (1), wherein the spherical gel has an average particle diameter of 2 to 3 μm and a liquid content of 10 to 90 wt%. The electrophotographic developer according to the above (1) or (2), wherein the toner particles contain a resin having a softening point of 100 ° C. or lower. ”

[0010] The toner particles of the present invention are mainly composed of a substantially spherical gel containing a liquid. The average particle size of the toner particles is preferably 0.5 to 5 μm. The gel may contain various colorants, resins, waxes, polarity control agents, and the like. Such gel particles can be handled as an extremely low-viscosity paste that retains fluidity as a developer that is neither a liquid nor a powder. Therefore, there is no need to worry about scattering of powder or outflow of liquid. The liquid content of the gel is 10 to 90%, preferably 30 to 85%, more preferably 40 to 80%. With such a particle size, it is easy to cope with a case where high resolution and sharpness are required as an electrophotographic developer, and it is easy to obtain high image quality.

When the toner particles contain components such as resins and waxes, their softening points are preferably 100 ° C. or lower. When fixing to a recording medium such as paper or an OHP film, these waxes melt and improve the adhesive force to the recording medium, that is, the fixing property.

The gel, which is the main component of the toner particles, is adjusted by
A polymer of sufficient length, soluble in liquid, alone or
It is obtained by crosslinking with a suitable crosslinkable polyfunctional monomer or polymer. It can also be obtained by allowing a polyfunctional monomer to coexist during the polymerization of the main polymer. The liquid may be a polar liquid such as water or a petroleum-based non-polar liquid. Water is preferred from the viewpoint of safety.

[0013] The progress of the crosslinking reaction may be carried out by irradiating an actinic ray such as an electron beam or an ultraviolet ray, or by adding a radical initiator or the like and reacting with heat or radiation energy. The particle size distribution can be adjusted by known means such as adjusting the polymer concentration in the solution for performing the crosslinking reaction, the mixing ratio of the crosslinking agent, and the like.

Specific examples of the monomer are shown below. (Monomer example) Examples of the monomer include styrene compounds such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, sodium p-styrenesulfonate, methyl acrylate, and ethyl acrylate. Acrylate compounds such as n-propyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, glycidyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, methacryl Methacrylic acid ester compounds such as 2-ethylhexyl acid, N-substituted acrylamide compounds such as acrylonitrile, acrylamide, N-isopropylacrylamide, N-piperylacrylamide, divinylbenzene, methylenebisacrylamide Crosslinkable monomer such as 1,3-butanediol dimethacrylate.

(Examples of Initiator) As the polymerization initiator,
2'-azobis-isobutyronitrile, 2,2'-azobis- (2,4-dimethylvaleronitrile), 1,1 '
Diazo compounds such as -azobis- (cyclohexane-1-carbonitrile) and 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile; and peroxides such as benzoyl peroxide and lauroyl peroxide. Can be The amount of these polymerization initiators is generally from 0.1 to 10% by weight of the monomers.

Specific examples of the polymer will be given. Molecules such as polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylonitrile, poly (meth) acrylate oligoethylene oxide, polyethyleneimine, polyalkylene sulfide, polyphosphazenes and polysiloxanes having oligoethylene oxide in the side chain, Nafion and Flemion, etc. And a polymer having an ionic group therein. Further, a copolymer or the like mainly composed of these can also be used. Particularly preferred is a composition that exhibits high ionic conductivity when gelled.

The resin and wax components contained in the toner particles can be used for flushing a coloring agent such as a pigment. The surface treatment of the coloring material can be performed by the flushing treatment, and the ionic components of the gel can be prevented from adsorbing on the surface of the pigment particles and elution of impurities such as unexpected ions can be prevented. It also has the effect of improving the dispersion of the coloring material and improving the degree of coloring of the toner particles.

In the flushing, a pigment slurry or a water-containing paste of the pigment is put together with a resin solution into a kneader called a flasher, mixed well (in this process, water existing around the pigment is replaced by the resin solution), and this is kneaded. After removing the aqueous phase, discarding the aqueous phase, drying the resin in which the pigment is dispersed in the resin solution and removing the solvent, the resulting mass is pulverized. In addition, an allowance for removing water and the solvent under reduced pressure while kneading with a kneader may be adopted. In the flushing treatment, not only the pigment but also the dye is kneaded together with water in a lump to obtain substantially the same result as the pigment, so that the dye can be used as the toner component. The ratio of the dye / pigment to the resin at the time of flushing is desirably 1/1 to 2/8. It is particularly advantageous to carry out the flushing treatment in the presence of humic acid, humates (Na salt, NH ₄ salt, etc.) or humic acid derivatives. The amount of the humic acids to be added is suitably about 0.1 to 30% by weight of the aqueous solution of the dye and pigment.

(Examples of resin used for flushing) Polystyrene, styrene- (meth) acrylate copolymer, styrene-maleate copolymer, (meth) acrylate polymer and copolymer, styrene- Diene copolymers, polyethylene, polypropylene, ethylene-vinyl acetate copolymers, addition polymerization resins such as ethylene-acrylate copolymers, polyester resins, epoxy resins, condensation resins such as phenolic resins, Modified resins such as rosin esters and maleated rosin esters, petroleum resins, higher fatty acid waxes, higher alcohols, higher fatty acids, paraffin waxes, low molecular solids such as carnauba wax and shellac can be used alone or in combination. Among these, polyethylene,
Polyolefins and polyolefin copolymers such as polypropylene, ethylene-acrylate copolymer and ethylene-maleic anhydride copolymer have good dispersibility and good results are obtained. A resin having a softening point of 100 ° C. or less, preferably a softening point of 30 ° C. to 60 ° C., and more preferably a melting point of 60 ° C. to 90 ° C. These have a lower molecular weight than resins conventionally used for dry toners, and generally have a number average molecular weight of 500, although depending on the type of resin.
0 or less.

The mechanism by which such a gel can be favorably developed on an electrostatic latent image on an electrophotographic photosensitive member is still unknown, but the present inventors consider as follows. When the particles are held under the developing electric field, ions existing in the gel particles or in the liquid held between the particles move to the vicinity of the surface of the particles due to the electric field. When the particles have several layers, the ions move to the end of the particle layer. As a result, the toner particles and the particle layer have a strong specific polarity, and adhere to the electrostatic latent image on the photoconductor by electrostatic force.

[0021]

The present invention will be described in more detail with reference to the following examples. [Example 1] Isopar H50 as a polymerization solvent in a reaction vessel
0 parts were taken and heated to 90 ° C., 100 parts of LMA (lauryl methacrylate), 10 parts of GMA (glycidyl methacrylate) and 2 parts of BPO (benzoyl peroxide) were completely dissolved, and then added dropwise to the reactor over 3 hours. After completion of the dropwise addition, polymerization was carried out at 90 ° C. for further 6 hours. To this, 5 parts of MAA (methacrylic acid) was added dropwise over 1 hour, and 130 parts of MMA (methyl methacrylate), 30 parts of Pigment Red 146 (naphthol carmine FBB, Fuji dye) and 5 parts of AIBN (azobisisobutylnitrile) were mixed. 80
It was added dropwise at 2 ° C. over 2 hours. Pigment Red 146 is 10
It was dried in a vacuum oven at 0 ° C., irradiated with UV, activated, and used. After dropping, 85 ° C
Was further polymerized for 4 hours to obtain red polymerized colored particles having an average particle diameter of 2.3 μm, a negative polarity and containing 60 wt% of isoper.

Example 2 800 parts of Isopar L was used as a polymerization solvent in a reaction vessel and heated to 85 ° C.
(2 ethylhexyl methacrylate) 80 parts, SMA
After 30 parts of (stearyl methacrylate), 7 parts of GMA (glycidyl methacrylate) and 2 parts of BPO (benzoyl peroxide) were completely dissolved, they were dropped into the reaction vessel over 3 hours. After the completion of the dropwise addition, the mixture was further polymerized at 85 ° C. for 4 hours. To this, 3 parts of MAA (methacrylic acid) was added dropwise over 1 hour, 110 parts of MMA (methyl methacrylate), and a flushed Pigment Blue 15: 3 (copper phthalocyanine).
A mixture of 30 parts and 5 parts of AIBN (azobisisobutylnitrile) was added dropwise at 80 ° C. over 2 hours. After completion of the dropwise addition, polymerization was carried out at 85 ° C. for another 4 hours, and the average particle size was 1.8.
Blue polymerized colored particles having μm, positive polarity and containing 40% by weight of isoper were obtained. Pigment that has been flushed
Blue15: 3 was created as follows. 50 parts of water, Pi
gment Blue 15: 3 20 parts and ammonium humate 3 parts were taken in a flasher and mixed and dispersed well. Next, 80 parts by weight of an ethylene-vinyl acetate copolymer (Eva Flec 210, manufactured by Du Pont-Mitsui Co., Ltd.) and 50 parts by weight of toluene were added.
Dispersed at 00 ° C. for 2 hours. After dispersion, the pressure was reduced, water and toluene were removed, and the mixture was pulverized to obtain a flushing colorant.

Example 3 To 120 parts of ethanol was added 35 parts of carbon black (Cabot, Regal 330), and the mixture was sufficiently dispersed by ultrasonic waves for 50 minutes. This was transferred to a reaction tank capable of reducing pressure, and 250 parts of toluene and Isopar M60 were added.
0 parts, 5 parts of a styrene-methacrylic copolymer having a softening point of about 60 ° C., and 5 parts of manganese naphthenate were added. After stirring at 90 ° C. for about 5 hours, the liquid temperature was lowered to 40 ° C., and the degree of vacuum in the vessel was raised to 1 degree.
The pressure was reduced to mmHg, ethanol and toluene were removed, and the average particle diameter was 2.1 μm.
And black polymer particles having a low softening point were obtained.

Using the polymer particles of Examples 1 to 3, an image was formed on paper by electrophotography. As a developing device, a roller having a 10 μm-thick polyfluoroethylene layer formed on an aluminum base material was prepared, and a roller and
A device for continuously supplying the polymer particles in a uniform layer on the roller by a regulating member was prepared. An electrostatic latent image was formed on a commercially available OPC by a known means. The surface was uniformly charged with a corona charger, and the image was exposed imagewise on the OPC, and charges were left only in the non-exposed areas except for the exposed areas. When a uniform layer of the polymer particles was brought into contact with such an OPC using the developing device, and various biases were applied between the developing roller and the OPC substrate, the OPC was placed on the OPC in accordance with the latent image. The polymer particles adhered and formed a good image. Further, the obtained image was transferred to a commercially available PPC paper (PPC paper manufactured by Ricoh Co., Ltd.) by static electricity, and then fixed by a fixing device for a laser printer (NX-100 manufactured by Ricoh Co., Ltd.). All showed good fixability.

[0025]

As is apparent from the above detailed and specific description, the present invention provides a toner for electrophotographic development which does not cause contamination of an image or its periphery due to toner scattering or leakage of a carrier liquid. This provides an extremely excellent effect of providing toner particles having a small average particle size, which can easily obtain high image quality.

Claims (3)

[Claims] 1. An electrophotographic developer, wherein the toner particles are mainly composed of a substantially spherical gel containing a liquid. 2. The electrophotographic developer according to claim 1, wherein said spherical gel has an average particle size of 2 to 3 μm and a liquid content of 10 to 90% by weight. 3. The electrophotographic developer according to claim 1, wherein the toner particles contain a resin having a softening point of 100 ° C. or lower.