JPS6410070B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an insulating toner that is charged with a positive triboelectric charge without using carrier particles to form an electrical latent image in electrophotography, electrostatic recording, or the like. This invention relates to a developing method for obtaining a visible image.

Conventionally, as an electrophotographic method, U.S. Patent No. 2297691
Specification of No. 42-23910 and Special Publication No. 1973
Many methods are known, as described in Japanese Patent No. 24748, etc., but in general, a photoconductive substance is used to form an electrical latent image on a photoreceptor by various means, and then the A latent image is developed using toner, and after the toner image is transferred to a transfer material such as paper as necessary, it is fixed by heat, pressure, solvent vapor, etc. to obtain a copy.

Furthermore, various methods are known for visualizing electrical latent images using toner.

For example, the magnetic brush method described in US Pat. No. 2,874,063, the cascade development method described in US Pat. No. 2,618,552, and US Pat. No. 2,221,776.
A large number of development methods are known, such as the powder cloud method, the fur brush development method, and the liquid development method described in the patent specification.

Among these developing methods, the magnetic brush method, cascade method, liquid developing method, etc., which use a developer mainly consisting of toner and carrier, are in particular widely put into practical use. All of these methods are excellent methods in which good images can be obtained relatively stably, but on the other hand, they have common drawbacks associated with two-component developers, such as deterioration of the carrier and fluctuations in the mixing ratio of toner and carrier.

In order to avoid such drawbacks, various development methods have been proposed that use a one-component developer consisting only of toner.

US Pat. No. 3,909,258 proposes a developing method using an electrically conductive magnetic toner. This supports a conductive magnetic developer in a cylindrical conductive sleeve with magnetism inside.
This is brought into contact with an electrostatic image and developed.
At this time, in the developing section, a conductive path is formed by the toner particles between the recording medium surface and the sleeve surface, and through this conductive path, the sleeve conducts charges to the toner particles, causing a Coulomb force between the electrostatic image and the image area. The toner particles adhere to the image area and are developed.

This developing method using conductive magnetic toner is an excellent method that avoids the problems associated with conventional two-component developing methods, but on the other hand, because the toner is conductive, the developed image can be transferred from the recording medium to the final product such as plain paper. It has the disadvantage that it is difficult to electrostatically transfer it to a permanent support member.

As a developing method using a high-resistance magnetic toner that can be electrostatically transferred, JP-A-52-94140 discloses a developing method that utilizes dielectric polarization of toner particles. However, such a method inherently has drawbacks such as a slow development speed and an inability to obtain a developed image with sufficient density, making it difficult in practice.

Another developing method using high-resistance magnetic toner is a method in which the toner particles are triboelectrified by friction between the toner particles or friction between the toner particles and a sleeve, etc., and the toner particles are brought into contact with an electrostatic image holding member for development. It has been known. However, in these methods, the number of times of contact between the toner particles and the triboelectric charging member is small, which tends to result in insufficient triboelectrification, and the Coulomb force between the charged toner particles and the sleeve increases, making them apt to aggregate on the sleeve. It has the following drawbacks, and there are many practical difficulties.

The present applicant previously proposed a new method in JP-A-54-43036 which eliminates the above-mentioned drawbacks. This involves applying a very thin layer of magnetic toner onto the sleeve, triboelectrically charging it, and then developing it by facing the electrostatic image very close to, but not in contact with, the electrostatic image under the action of a magnetic field.

According to this method, by applying an extremely thin layer of magnetic toner on the sleeve, the chances of contact between the sleeve and the toner are increased, and sufficient frictional electrification is possible.The toner is supported by magnetic force, and the magnet By moving the toner particles relative to each other, the toner particles are disaggregated and the sleeve is sufficiently rubbed, and the toner is supported by magnetic force and is developed by facing the electrostatic image without coming into contact with it. By doing so, excellent images can be obtained by preventing background fog.

However, the performance of this method is largely affected by humidity conditions or the surface properties of the frictional charging member and the toner holding member. For example, when the fluidity of toner is reduced due to high humidity or high temperature, toner agglomeration cannot be sufficiently dissolved by magnetic force, resulting in a decrease in image quality and image density. have Furthermore, in low humidity, unevenness tends to occur in the toner coating layer on the toner holding member.

In addition, compared to a two-component developer consisting of toner and carrier, the contact area of the triboelectric charging member that triboelectrically charges the toner is small, so contaminants or non-developing substances deposited on the surface of the triboelectric charging member cause friction between the toner and the carrier. It has the disadvantage that it is susceptible to changes in the triboelectrification series between it and the charging member.

As a means of improving the above drawbacks, the sleeve may be made of a non-adhesive material such as polytetrafluoroethylene,
Most of the problems can be solved by coating with a highly lubricating and water-repellent resin, but on the other hand, the sleeve has another important role, which is to transfer the triboelectrically charged toner to the developing area facing the electrostatic latent image. The conveyance function does not work well due to the reduced coefficient of friction caused by the polytetrafluoroethylene coating, which causes ripple-like unevenness in the toner coating layer on the sleeve in low humidity environments, which adversely affects image quality. Sometimes.

Furthermore, the polytetrafluoroethylene coating is mechanically weak, and as a result of repeated friction when making multiple copies, the coating may be scratched or peeled off.

The object of the present invention is to provide a developing method that improves the above-mentioned drawbacks.

Another object of the present invention is to enable uniform application of toner onto a carrier even under wide temperature and humidity environments;
The object of the present invention is to provide a developing method that can always maintain uniform triboelectric characteristics.

A further object of the present invention is to provide a developing method with high durability and stability that does not change in performance even after repeated copying.

Specifically, an object of the present invention is to transport triboelectrically charged insulating toner without using carrier particles to a developing section for developing an electrical latent image using a developer carrier; In this method, fine particles of fluoropolymer or fluoroelastomer are embedded in pores uniformly provided on the surface of the developer carrier, and the toner is positively charged. The object of the present invention is to provide a developing method characterized in that a positively charged triboelectric charge is applied to the toner on the surface of the developer carrier.

The method of the present invention will be explained below with reference to the drawings.

FIG. 1 shows a schematic configuration of an example of a copying device or a recording device to which the developing method according to the present invention can be applied, but the present invention is not limited thereto.

1 corresponds to an electrostatic image holder, and is a photosensitive drum containing a photoconductive layer.It can be used with or without an insulating layer on the surface. Also possible. 2 is a well-known photoreceptor charging device; 3 is a document image;
Alternatively, it is a light image irradiation device that projects a light image or a light beam modulated by an image signal. As a result, an electrostatic latent image is formed on the photoreceptor 1. A developing device 4 has a developer carrier 4a, and forms a toner particle visible image according to the electrostatic image on the photoreceptor 1. 5 is a device for transferring the toner image onto a transfer material 6. Incidentally, in order to improve the transferability, the visible image may be charged in advance by corona discharge or the like before transfer. It is also possible to adopt a so-called electrostatic transfer method in which the latent image on the photoreceptor 1 is temporarily transferred to another image carrier, and the developing device 4 converts the latent image into a visible image. 7, the toner image is transferred to a member 6;
This is a fixing device for fixing images on a paper, and is composed of at least two rollers having pressure or heating pressure means. Reference numeral 8 denotes a cleaning device for cleaning and removing residual toner on the photoreceptor 1 after transfer, so that the photoreceptor 1 can be reused.

Next, the developing process used in the present invention will be explained. FIG. 2 shows a cross-sectional view of one embodiment of the developing process used in the present invention. In the drawing, when the electrostatic image holding surface 1 moves in the direction of the arrow, the multipolar permanent magnet 9 is fixed so as not to rotate, so the fluoropolymer or A one-component insulating magnetic developer is delivered from the developer container 12 by rotating a non-magnetic cylinder 4b filled with fine particles of fluoroelastomer and permanently fitted with interference in the same direction as the electrostatic image holding surface 1. 11 is applied onto a non-magnetic cylindrical surface, and friction between the cylindrical surface and the toner particles gives the toner particles a charge of opposite polarity to the electrostatic image charge. Furthermore, by arranging an iron doctor blade 10 close to the cylindrical surface (with an interval of 50 μ to 500 μ) and facing one magnetic pole (S pole in the figure) of the multipolar permanent magnet 9, the thickness of the toner layer can be increased. thinner (30μ~
300μ) and uniformly regulated. By adjusting the rotational speed of the cylinder 4b, the surface speed of the developer layer, and preferably the internal speed, are made to be substantially equal to or close to the speed of the electrostatic image holding surface. As the doctor blade 10, a permanent magnet may be used instead of iron to form opposing magnetic poles. Further, in the developing section, an alternating current bias may be applied between the developer carrier and the electrostatic image holding surface.

Examples of the fluoropolymer or fluoroelastomer used in the present invention include polyvinyl fluoride, polyvinylidene fluoride, polyethylene trifluoride, polytetrafluoroethylene, polychloroethylene trifluoride, and ethylene copolymer chloride trifluoride/ethylene. combination, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer,
Fluoropolymers and fluoroelastomers such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers and hexafluoropropylene-vinylidene fluoride copolymers are preferably used.

The base of the member that imparts triboelectric charge to the toner used in the present invention and simultaneously conveys the toner to the electric latent image surface may be made of metal materials such as stainless steel or aluminum, or polyphenylene oxide, polyphenylene sulfide, Organic materials with excellent mechanical performance, known as engineering plastics, such as polyether sulfone, polyethylene terephthalate, polybutylene terephthalate, polyallyl terephthalate, and polycarbonate, are etched to make them porous.
Alternatively, metal oxides made porous by sintering are used, and the fluoropolymer or fluoroelastomer fine particles are press-fitted and embedded into the pores of the porous substrate. When press-fitting, the porous substrate is heated and the fluoropolymer or fluoroelastomer fine particles are cooled.
The porous substrate absorbs heat from the cooled fluoropolymer or fluoroelastomer fine particles and cools and contracts. Conversely, the fluoropolymer or fluoroelastomer fine particles expand due to the heat of the heated porous substrate, causing the fluoropolymer to shrink. Alternatively, the fluoroelastomer microparticles are permanently embedded in the pores of a porous substrate in a sealed manner.

The one-component insulating toner of the present invention includes a binder resin,
It consists of a colorant and, if necessary, additives such as a charge control agent, a fixing aid, and an anti-caking agent, and any known materials can be used.

For example, as the binder resin, monopolymers of styrene and its substituted products such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene, styrene-P-chlorostyrene copolymers, styrene-propylene copolymers, and styrene-vinyl Toluene copolymer, styrene-vinylnaphthalene copolymer, styrene-acrylic ester copolymer, styrene-methacrylic ester copolymer, styrene-α
Methyl chlormethacrylate copolymer, styrene-
Acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile- Styrenic copolymers such as indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, 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, phenolic resin, aliphatic or alicyclic hydrocarbon resin, Aromatic petroleum resins, chlorinated paraffin, paraffin wax, etc. can be used alone or in combination.

Additives such as colorants, load control agents, fixing aids, and anti-caking agents include carbon black, various dyes and pigments, plasticizers such as colloidal silica, and talc.

Furthermore, when used as a magnetic toner, ferromagnetic elements and alloys and compounds containing them, such as magnetite,
It is sufficient to contain fine powder of substances conventionally known as magnetic materials, such as alloys and compounds of iron such as hematite and ferrite, cobalt, nickel, and manganese, and other ferromagnetic alloys.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1 A stainless steel cylinder with a diameter of 50 mm was coated with hard chrome plating with a thickness of 50 μ, and then immersed in an etching solution consisting of phosphoric acid: sulfuric acid: chromic acid = 1000:100:70 to form pores with a depth of 10 to 20 μ. A porous layer was provided on the surface. Next, this cylinder was heated to 200℃ and −70
Using an electrostatic powder sprayer, spray polytetrafluoroethylene fine particles with an average particle size of 0.2 to 0.3μ cooled to ℃ while pressing the blade against the polytetrafluoroethylene fine particles into the porous layer of the cylinder. was press-fitted. After cooling, a cylinder was obtained in which polytetrafluoroethylene fine particles were fitted into the pores of the porous layer, and this was used as a sleeve.

On the other hand, 100 parts by weight of zinc oxide, 20 parts by weight of styrene-butadiene copolymer, n-butyl methacrylate
A mixture consisting of 40 parts by weight, 120 parts by weight of toluene, and 4 parts by weight of 1% rose bengal methanol solution was dispersed and mixed in a ball mill for 6 hours. This is 0.05mm
A zinc oxide binder-based photoreceptor was prepared by coating a thick aluminum plate with a wire bar to a dry coating layer of 40 μm and evaporating the solvent with warm air. This photoreceptor was subjected to -6 KV corona discharge to uniformly charge the entire surface, and then an original image was irradiated to form an electrostatic latent image.

This latent image is transferred to a developing device using the cylinder as a sleeve, with a magnetic flux density on the sleeve surface of 700 Gauss, and a sleeve rotating magnet fixed with a distance between the ear cutting blade and the sleeve surface of 0.2 mm (the peripheral speed of the sleeve is the same as that of the drum, but the direction of rotation is opposite). The distance between the photosensitive drum surface and the sleeve is set to 0.25 mm, and the sleeve is set at 1 KHz.
80 parts by weight of styrene-butyl acrylate copolymer and styrene-butyl acrylate-dimethylaminoethyl methacrylate copolymer in the developer container by applying 1.3 KV AC and -150 V DC bias.
A developer consisting of 20 parts by weight of magnetic powder and 60 parts by weight of magnetic powder is applied to the sleeve in which the aforementioned polytetrafluoroethylene fine particles are fitted, and the electrostatic latent image having the aforementioned negative potential is rubbed against the positive charge of the opposite polarity. The developer is charged by applying an electric charge, the triboelectrically charged developer is conveyed to a developing section by a sleeve, and the electrostatic latent image is developed using the developer,
Next, the powder image was transferred while irradiating -7KV direct current corona from the back side of the transfer paper and fixed by heating.

The images obtained were clear and highly static, and no fogging phenomenon was observed. The toner coating on the developing sleeve was uniform and precise, and the maximum image density of the copied image was as high as 1.35.

Even in a high-humidity environment, there was only a slight decrease in image density, and even in a low-humidity environment, there was no uneven coating of the toner on the sleeve.

Further, even after 10,000 copies were continuously copied, no non-developing material was deposited on the sleeve and there was no change in image quality.

In place of the polytetrafluoroethylene fine particles, polytetrafluorochloroethylene, polytetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, and polytrifluoroethylene fine particles were used, but almost the same effect was obtained. Ta.

Comparative Example 1 A water-based dispersion (product name: Polyflon Dispersion D-1, manufactured by Daikin Industries, Ltd.) in which polytetrafluoroethylene fine powder with a particle size of 0.2 to 0.3 microns was dispersed in a stainless steel cylinder with a diameter of 50 mm. Soak,
The process was carried out in the same manner as in Example 1, except that after being pulled up and dried, the sleeve was baked in an electric furnace at 320°C for 15 minutes.

At room temperature and humidity, the maximum image density is high and the images are clear, but after 10,000 copies were made, some peeling was observed on the polytetrafluoroethylene coating on the sleeve.

In addition, in a low humidity environment of 20℃ and 30%RH,
The toner coating layer on the sleeve became uneven, resulting in uneven density in the copied image.

As seen in this example, by embedding releasable fine particles in a matrix with excellent mechanical strength, it is possible to obtain high mechanical strength, resistance to contamination, and strong charge control properties that are not affected by humidity. Even under environmental conditions, uniform toner coating properties can always be obtained without causing unevenness in the toner coating layer on the carrier.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an example of a copying device or a recording device to which the developing method according to the present invention can be applied. FIG. 2 is a sectional view of one embodiment of the developing process used in the present invention. 1... Photosensitive drum, 4... Developing device, 4a...
Toner carrier, 4b...Nonmagnetic cylinder, 9...Magnet roll, 10...Doctor blade, 11
...Insulating magnetic toner.

Claims (1)

[Claims] 1. A method in which triboelectrically charged insulating toner is transported by a developer carrier to a developing section for developing an electrical latent image without using carrier particles, and the toner is used to develop the electrical latent image. Fine particles of fluoropolymer or fluoroelastomer are embedded in pores uniformly provided on the surface of the developer carrier, and the toner is positively charged. A developing method characterized in that the toner is triboelectrically charged by imparting a positively charged triboelectric charge to the toner.