JPH083650B2 - Developer and image forming method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a developer used in electrophotography, electrostatic printing, etc., and an image forming method using the developer, and particularly to a photosensitive drum. The present invention relates to a developer having little mechanical influence and an image forming method using the developer.

[Prior Art] Currently, in electrophotography, an electrostatic latent image is formed by using an optical semiconductor such as cadmium sulfide, amorphous silicon, amorphous selenium, and an organic optical semiconductor as a photoconductor, and then the polarity is opposite to that of the latent image charge. The charged developer is conveyed to the latent image portion and developed by using a mechanical or electrical action. After that, transfer and fixing are performed on paper or the like, if necessary.

Among the devices used in such a method, in the case of a device having a transfer device, the residual toner on the photoconductor that has not been transferred is removed by the cleaning unit, and at that time, a blade cleaning method generally used, Among the fur brush cleaning method and the magnetic brush cleaning method, there is mechanical pressure contact in the blade cleaning method, and particularly when a toner containing magnetic powder such as magnetite is used, problems such as occult and black spots occur.

Here, the occult is the potential unevenness caused by the peeling of the surface oxide film of the photoconductor, and it is recognized as the density unevenness in the copy such as a half-torch chart. Since only the oxide film on the surface becomes a problem in this development, it disappears when the oxide film is regenerated due to a rest state or the like.

Further, the black spots are generated when the toner attached to the photoconductor remains unremoved even after passing through the cleaning unit and is transferred to the subsequent paper material.

These developments are likely to occur when an amorphous photoconductor is used, and are particularly prominent in a photoconductor having a relatively low surface hardness such as an amorphous selenium photoconductor.

[Problems to be Solved by the Invention] An object of the present invention is to provide a developer which has less mechanical influence on a photoreceptor in a cleaning portion without deteriorating image characteristics, and an image forming method using the developer. Especially. In particular, when a magnetic toner is applied to an amorphous photoconductor, a developer capable of preventing occult and black spots generated when cleaning the photoconductor, and an image forming method using the developer.

[Means and Actions for Solving Problems] As a result of studies by the inventors, it has been clarified that the above problems involve the fine powder of the magnetic toner particles contained in the developer. For this reason, it is possible to remove the fine powder side with an air classifier, but it is difficult to completely remove this with the classifiers currently known. Therefore, the classification method improves the above-mentioned problems to some extent, but is still a problem in practical use. Therefore, a system in which magnetic toner particles and vinylidene fluoride polymer (PVDF) particles are mixed was studied, but the system alone has not yet reached a sufficient level.

Therefore, the present invention can solve the above problems by the following configurations.

That is, the present invention relates to a developer applied to an electrophotographic system that removes the residual developer after transfer on the amorphous photoconductor by a cleaning member that is mechanically pressed against the amorphous photoconductor. , Magnetic toner particles containing at least a binder resin and a magnetic substance, and vinylidene fluoride polymer particles having an absolute β crystal content of 0.3 or more, and having a magnetic particle size of 6.35 μm or less in the developer. The present invention relates to a developer, wherein the abundance of toner particles is 25% by number or less, and the vinylidene fluoride polymer particles are contained in the developer in an amount of 0.1 to 0.3% by weight.

Further, the present invention includes: i) developing an electrostatic latent image formed on an amorphous photoconductor with a developer, wherein the developer is a magnetic toner particle containing at least a binder resin and a magnetic substance, and an absolute β crystal. Content ratio is 0.
It has vinylidene fluoride polymer particles of 3 or more, and the abundance of magnetic toner particles having a particle size of 6.35 μm or less in the developer is 25% by number or less, and the vinylidene fluoride polymer particles are 0.1 to 0.3 wt% is contained in the developer, ii) a developed developing image on the amorphous photoconductor is transferred to a transfer machine, and iii) a cleaning member mechanically pressed onto the amorphous photoconductor. The present invention relates to an image forming method, wherein a developing process is performed after removing a residual developer after the transferring process on the amorphous photoconductor.

In other words, PVDF particles are required to have lubricity as well as polishability. To satisfy this requirement, the absolute content ratio of β crystal is 0.30.
It is desired that the content be 0.15 to 0.3% by weight, preferably 0.2 to 0.3% by weight, in the developer.

Further, the abundance of the toner particles of 6.35 μm or less in the developer is 25 number% or less, preferably 15 number% or less.

By combining these two conditions, damage to the photoreceptor is reduced, and it is possible to obtain a long-life and high-quality image without the occurrence of occult and black spots. Explaining the range of each condition above, if the β crystal of PVDF particles is 0.3 or less, the polishing property is lost and it does not contribute to the suppression of black spots. Regarding the content of PVDF particles,
If it is less than 0.1% by weight, the effect of addition is not observed,
If it exceeds 0.3% by weight, image defects such as light and dark will occur. Regarding the particle size distribution, if the abundance of toner particles of 6.35 μm or less exceeds 25% by number, no improvement is observed in suppressing black spots and occult even if PVDF particles are added.

Examples of the binder resin used in the present invention include homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and substitution products thereof; styrene-p-
Chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-acrylic Butyl acid copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate Copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer Coalesced, styrene-acryloni Styrene-based copolymers such as ril-indene copolymers, styrene-maleic acid copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene ,
Polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax , Carnauba wax and the like, which can be used alone or in combination.

Conventionally known carbon black, copper phthalocyanine iron black or the like can be used as the coloring material used in the toner particles used in the present invention as necessary, and all conventionally known positive or negative charge control agents can be used in the present invention. .

The developer of the present invention can be mixed with carrier particles such as iron powder, glass beads, nickel powder and ferrite powder, if necessary, and used as a developer for an electric latent image.

The magnetic toner particles used in the present invention contain a binder resin and magnetic powder. As the magnetic powder, substances that are magnetized by being placed in a magnetic field are used, and there are powders of ferromagnetic metals such as iron, cobalt and nickel, or alloys and compounds such as magnetite, γ-Fe ₂ O ₃ and ferrite. . In particular, in order to exert the above-mentioned effects, the BET specific surface area by the nitrogen adsorption method is preferably ² to 20 m ² / g, particularly
A magnetic powder having a hardness of 2.5 to 12 m ² / g and a Mohs hardness of 5 to 7 is preferable. The content of this magnetic powder is 10 to 10% by weight of the toner.
70% by weight is good. The combination of such magnetic toner particles and the vinylidene fluoride polymer particles exerts a polishing effect to prevent abnormal adhesion of toner on the photoconductor and damage to the photoconductor plate, resulting in a high-density image free from stains. To be

In the production of the magnetic toner particles, the constituent materials are well kneaded by a heat kneader such as a heat roll, a kneader, an extruder, etc., and then mechanical pulverization and classification are carried out, or the materials are dispersed in a binder resin solution. After that, a method obtained by spray drying, or a polymerization method toner production method or the like to obtain a toner by polymerizing a binder resin by mixing a predetermined material with a monomer to form an emulsion suspension, and the like,
Each method can be applied.

Vinylidene fluoride polymer particles used in the present invention, vinylidene fluoride homopolymer and vinylidene fluoride,
A copolymer with a fluoride such as vinyl fluoride, trifluoroethylene or tetrafluoroethylene, or an olefin monomer such as ethylene, propylene or butene can be used.

As the vinylidene fluoride polymer particles, it is possible to use the powder obtained by the polymerization as it is, or it is effective to use them by annealing them by heat treatment. Further, the effect of the present invention can be exhibited by using a product obtained by stretching a vinylidene fluoride polymer into a film or monofilament and subjecting it to a fine crushing treatment.

The particle size of the vinylidene fluoride polymer particles used in the present invention is
The thickness is 0.05 to 1 μm, preferably 0.1 to 0.5 μm. Particle size 1.
If it is 0 μm or more, the dispersion between the magnetic toner particles is not sufficient, the fluidity and lubricity cannot be imparted to the developer, and the effect is not exhibited. On the other hand, if it is less than 0.05 μm, the surface of the magnetic toner particles will be covered with ultrafine particles, so that the chargeability of the magnetic toner particles will be impaired and the effect cannot be obtained. Further, the shape is preferably powdery and close to a sphere.

Furthermore, a surfactant on the vinylidene fluoride polymer particles,
It is also possible to use those which have been surface-treated with a charge treatment agent or the like.

In the present invention, β in vinylidene fluoride polymer particles
The absolute content ratio of crystals is the characteristic absorption of α crystal and β crystal by a method of obtaining the ratio of α crystal and β crystal from the diffraction line intensity ratio by the usual X-ray diffraction method, and the infrared absorption spectrum.
It can be measured from the peak ratio near m ^-1 , 510 cm ^-1 .

Further, in order to obtain the absolute content ratio, it is necessary to measure the ratio (crystallinity) of the crystallized portion containing α crystal and β crystal. There are various methods of measuring crystallinity, which causes some differences. In the present invention, the crystallinity of the vinylidene fluoride polymer particles is a value derived by measurement by the following measuring method.

The crystallinity was determined from the heat of fusion obtained from the melting peak of a differential scanning calorimeter (DSC). Using about 20 mg of sample, 50
˜200 ° C. is measured at a temperature rising rate of 10 ° C./min, and the heat of fusion ΔH (cal / g) of this sample is calculated from the ratio of the area of the melting peak at this time and the area of the melting peak of the standard indium. The heat of fusion of the complete crystal was set to ΔHc = 15 cal / g, and the value obtained from the crystallinity = ΔH / ΔHc × 100 (%) was used.

Example 1 100 parts by weight of a styrene-acrylic-BMA copolymer, 60 parts by weight of BET specific surface area of 5 m ² / g magnetite, and 4 parts by weight of chromium salicylate salt were melt mixed at 160 ° C. by a roll mill. After cooling, coarsely crushed with a hammer mill, then finely crushed with a jet stream, and then using an air classifier to obtain a volume average diameter of 10
A black powder (magnetic toner particles) containing 15% by number of particles having a particle size of -12 μm and 6.35 μm or less was obtained. To 100 parts by weight of this black powder, 0.3 parts by weight of hydrophobic colloidal silica and 0.3 parts by weight of vinylidene fluoride polymer particles having an absolute β crystal content ratio of 0.40 were added and mixed by shearing force.

This mixture (developer) was used in a commercially available copying machine (trade name: Selex-602; made by Copia) using an amorphous selenium photoconductor and a cleaning member that mechanically press-contacts the photoconductor.
When a running test was performed on ten thousand sheets, good images were obtained. In addition, neither toner adhesion nor scratches were observed on the photoconductor.

Example 2 In the same manner as in Example 1, except that the addition amount of the vinylidene fluoride polymer particles was changed to 0.1 part by weight, a similar image was obtained. In addition, neither toner adhesion nor scratches were observed on the photoconductor.

Comparative Example 1 When vinylidene fluoride polymer particles were not added in Example 1 and the same experiment was performed, the diameter number on the image was about 1000 sheets.
Black spots of about mm occurred and increased with the number of durable sheets. Further, fusion of the developer was recognized on the photoreceptor.

Comparative Example 2 When the amount of vinylidene fluoride polymer particles added in Example 1 was changed to 0.4 parts by weight and the same experiment was carried out, black spots and occult were good, but the copy density was 1.1 relative to the original. It was below 0.9, which was a practical problem.

Comparative Example 3 In Example 1, 30 particles having a particle size distribution of 6.35 μm or less were used.
When the experiment was repeated in the same manner with the number% changed, an occult was generated on about 500 sheets and rubbing scratches were also found on the photoconductor.

Comparative Example 4 When the same experiment was performed by changing the β crystal content ratio of the vinylidene fluoride polymer particles to 0.18 in Example 1, the same experiment was performed, and many black spots occurred in about 5000 sheets.

[Effects of the Invention] As described above, the present invention is applied to an electrophotographic system in which a cleaning member that mechanically presses against an amorphous photoconductor removes residual developer after transfer on the amorphous photoconductor. Since the developer to be used has a magnetic toner having a specific particle size distribution and specific vinylidene fluoride polymer particles having an abrasive property, it suppresses the occurrence of occult and black spots peculiar to the above electrophotographic system. It is possible to

Claims (2)

[Claims] 1. A developer applied to an electrophotographic system for removing a residual developer after transfer on the amorphous photoconductor by a cleaning member mechanically pressed against the amorphous photoconductor, wherein the developer is: A magnetic toner having at least a binder resin and a magnetic toner, and a vinylidene fluoride polymer particle having an absolute β crystal content of 0.3 or more, and having a particle size of 6.35 μm or less in the developer. A developer characterized in that the abundance of particles is 25% by number or less, and the vinylidene fluoride polymer particles are contained in the developer in an amount of 0.1 to 0.3% by weight. 2. An electrostatic latent image formed on an amorphous photoconductor is developed with a developer, and the developer contains magnetic toner particles containing at least a binder resin and a magnetic material, and an absolute β crystal. The vinylidene fluoride polymer particles have a ratio of 0.3 or more, and the abundance of magnetic toner particles having a particle size of 6.35 μm or less in the developer is 25 number% or less. Is contained in the developer in an amount of 0.1 to 0.3% by weight, ii) the developed image on the amorphous photoconductor is transferred to a transfer machine, and iii) cleaning is performed by mechanically pressing the amorphous photoconductor. An image forming method, characterized in that a developing step is performed after removing a residual developer on a member after the transfer step on the amorphous photosensitive member.