JPH0310312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel image forming method used in electrophotography, electrostatic recording, magnetic recording, etc.

In electrophotography, an electrostatic latent image is first formed by utilizing the properties of photoconductors such as cadmium sulfide, polyvinylcarbazole, selenium, and zinc oxide. For example, applying a charge uniformly on the photoconductor layer,
Imagewise exposure is performed to form an electrostatic latent image, which is then developed with toner powder charged with a polarity opposite to that of the electrostatic latent image, and further transferred and fixed onto a transfer sheet as required.

Among these, in the case of a device that has a transfer process,
Usually, residual toner on the photoreceptor that has not been transferred to the transfer sheet is removed and the photoreceptor is used repeatedly.

The remaining toner on the photoreceptor is generally removed by bringing a cleaning member into contact with the photoreceptor, such as a blade cleaning method, a fur brush cleaning method, or a magnetic brush cleaning method. In this case, since the cleaning member is pressed against the photoreceptor with an appropriate pressure, the photoreceptor may be scratched or the toner may stick to the photoreceptor during repeated use. In order to avoid this phenomenon of toner sticking to the photoreceptor,
No. 47345, it is proposed to add both a friction reducing material and an abrasive material to the toner. Although this method is certainly effective in avoiding the toner sticking phenomenon, it has the following drawbacks. That is,
When a friction-reducing substance is added to an extent that can avoid the toner sticking phenomenon, it becomes difficult to remove low electrical resistance substances such as paper dust and ozone adducts that are generated or adhered to the surface of the photoreceptor due to repeated use.
There is a drawback that the latent image on the photoreceptor is significantly damaged by the low electrical resistance material especially in a high temperature and high humidity environment.

Additionally, the amounts of friction-reducing substances and abrasive substances added are delicate, and adding enough abrasive substances to remove deposits on the photoconductor may damage the photoconductor or the cleaning blade. A phenomenon occurs that causes cleaning failure.

Therefore, it is an object of the present invention to provide a developer which overcomes the above-mentioned drawbacks.

That is, in the present invention, a latent image on an insulator or a photoreceptor is formed by using 0.2 to 10 weight percent of inorganic fine powder having a BET specific surface area of 1.0 to 6.0 m ² /g by a nitrogen adsorption method and produced by a sintering method. and developing using a developer containing magnetic toner, transferring the generated toner image to a transfer member, and then removing the remaining developer on the insulator or photoreceptor by a blade cleaning method. The present invention relates to a characteristic image forming method.

In the present invention, sintering refers to heating the powder at a temperature below its melting point to melt only the vicinity of the surface and create a bond between the particles with the same strength as the inside. The shape of the powder produced by the sintering method has a morphological characteristic of having no corners and being rounded.

For example, the chromium oxide fine powder used in Example 1 described below is prepared by the following manufacturing method. Chromium hydroxide fine powder is heated to approximately 1500℃, which is below the melting point of chromium oxide (Cr ₂ O ₃ ) (approximately 1900 to 2000℃).
Fine chromium oxide powder produced by heating for 12 hours, firing, cooling after firing, crushing aggregates, and sintering with a BET specific surface area of 2.4 m ² /g (average particle size 0.5 μm). You can get a body.

The inorganic powder produced by the above sintering method used in the present invention has the function of scraping off low electrical resistance materials such as paper powder, ozone adducts, and toner. It needs to be hard, especially harder than talc on the Mohs scale. Furthermore, a shape with sharp corners will damage the photoreceptor and the cleaning blade, so a shape with rounded corners is preferable.

Furthermore, when used in combination with an ultrafine powder such as colloidal silica (specific surface area of 40 to 400 m ² /g), the ultrafine powder creates fine irregularities on the surface of the photoreceptor, causing friction between the surface of the photoreceptor and the cleaning member. It works effectively to reduce resistance and is expected to have a greater effect in preventing the adhesion of paper dust, etc.

The reason why the BET specific surface area of the inorganic fine powder produced by the sintering method in the present invention is set to 1.0 to 6.0 m ² /g is that the above-mentioned effects will be degraded if outside this range.

The inorganic fine powder produced by the sintering method is preferably poorly water-soluble, but includes iron oxide, chromium oxide, calcium titanate, strontium titanate, barium titanate, magnesium titanate, cerium oxide, zirconium oxide, and oxidized zirconium. aluminum,
Titanium oxide, zinc oxide, etc. are used alone or in combination.

The inorganic fine powder may be present as long as it adheres to the surface of the toner particles, but it is preferable to use the inorganic fine powder mixed with the toner particles. Addition amount is 0.1 to the total amount of toner
~30 weight percent (more preferably 0.2-10
weight percent).

Furthermore, the surface of the above-mentioned inorganic fine powder may be organically treated with a well-known coupling agent or the like.

In the present invention, the measurement of BET specific surface area by nitrogen adsorption was carried out under appropriate conditions using a commercially available device (Model 2200 manufactured by Micromeritics). However, when the specific surface area exceeded 200 m ² /g, the amount of sample was reduced.

The binder used in the present invention includes homopolymers of styrene and its substituted products, such as polystyrene, poly-P-chlorostyrene, polyvinyltoluene, styrene-P-chlorostyrene copolymer, and styrene-vinyltoluene copolymer. Coalescing and copolymers thereof; styrene-methyl acrylate copolymer;
Copolymers of styrene and acrylic esters such as styrene-ethyl acrylate copolymer, styrene-n-butyl acrylate copolymer; styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene - Copolymers of styrene and methacrylic esters such as n-butyl methacrylate copolymers; multi-component copolymers of styrene and acrylic esters and methacrylic esters; other styrene-acrylonitrile copolymers, styrene-vinyl methyl ether copolymers, etc. Polymer, styrene
Styrenic copolymers of styrene and other vinyl monomers, such as butadiene copolymers, styrene-vinyl methyl ketone copolymers, styrene-acrylonitrile indene copolymers, styrene-maleic acid ester copolymers; Methyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyester, polyamide, epoxy resin,
Polyvinyl butyral, polyacrylic acid, phenolic resin, aliphatic or alicyclic hydrocarbon resin, petroleum resin, chlorinated paraffin, etc. can be used alone or in combination. In particular, low molecular weight polyethylene, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, higher fatty acid, polyamide resin, polyester resin, etc. are used as binder resins for toners used in pressure fixing systems. Can be used alone or in combination.

If necessary, additives may be mixed into the toner of the present invention within a range that does not impair the properties of the toner. Examples of such additives include fluidity imparting agents such as colloidal silica, Teflon, and zinc stearate. Examples include lubricants such as polyvinylidene fluoride, fixing aids (eg, low molecular weight polyethylene, low molecular weight polypropylene, etc.), and tin oxide as conductivity imparting agents.

Colorants used in the developer of the present invention include known dyes and pigments such as carbon black, phthalocyanine blue, indanthrene blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow, benzidine yellow. etc. can be widely used.

Furthermore, in order to use the developer of the present invention as a magnetic toner, it may contain magnetic powder. As such magnetic powder, materials that are magnetized when placed in a magnetic field are used, such as powders of ferromagnetic metals such as iron, cobalt, and nickel, or magnetite, γ
-There are alloys and compounds such as iron oxide ferrite.
The content of this magnetic powder is 15 to 70% of the toner weight.
Weight%.

Toner can be prepared using iron powder, glass beads, or
It is mixed with carrier particles such as nickel powder or ferrite powder and used as a developer for electrical latent images.

The toner of the present invention can be used to develop a latent image on any photoreceptor or insulator, including those having an organic polymer layer on the surface, organic photoconductors (OPC), amorphous Se, amorphous Although there are photoreceptors such as Si and zinc oxide, those having a layer containing an organic polymer on the surface and amorphous silicone photoreceptors are particularly preferred.

The toner of the present invention can be applied to various developing methods. For example, magnetic brush development method, cascade development method, method using conductive magnetic toner described in U.S. Pat. No. 3,909,258, JP-A-53-
Method using high-resistance magnetic toner described in Publication No. 31136, Japanese Patent Application Laid-open No. 54-42121, Publication No. 55-18656
There are methods described in Japanese Patent Application Publication No. 54-43027, a fur brush development method, a powder cloud method, a touch-down development method, an impression development method, and the like.

Further, in order to transfer the developed image using the toner of the present invention to a transfer member as necessary, well-known methods such as corona transfer, bias roll transfer, thermal transfer, and magnetic transfer can be applied.

Further, as a method for removing residual toner on the photoreceptor or insulator, known methods such as a blade cleaning method, a fur brush cleaning method, and a magnetic brush cleaning method can be applied.

Further, in order to fix the toner of the present invention on a transfer member, well-known methods such as oven fixing, hot roll fixing, pressure fixing, flash fixing, microwave fixing, etc. can be applied.

In producing the toner of the present invention, a hot roll,
After thoroughly kneading the constituent materials using a thermal kneader such as a kneader or extruder, the materials can be obtained by mechanical crushing or classification, or by dispersing materials such as magnetic powder in a binder resin solution and then spraying. There are various methods for producing toner, such as a drying method, a polymerization method and toner production method for obtaining a toner by mixing specified materials with the monomers that constitute the binder resin and then polymerizing this emulsified suspension. Can be applied.

EXAMPLES The present invention will be specifically explained below with reference to Examples, but these are not intended to limit the present invention in any way.
Note that all parts in the following formulations are parts by weight.

[Example 1] Styrene-butadiene copolymer (weight ratio 84:
16) 90 parts by weight Styrene dimethylaminoethyl copolymer (weight ratio 90:10) 10 parts by weight Low molecular weight polyethylene 5 parts by weight Magnetite 60 parts by weight The above mixture was kneaded for 30 minutes in a roll mill heated to 160°C, and after cooling, it was hammered. It is coarsely ground in a mill and then finely ground in a jet grinder. The mixture was then classified using an air classifier to obtain a magnetic toner as a colored fine powder of 5 to 20 microns. To 100 parts of this magnetic toner, 1.5 parts of chromium oxide fine powder with a specific surface area of 2.4 m ² /g, which has no corners and is rounded, is synthesized by a wet method with a specific surface area of 90 m ² /g. 0.5 part of colloidal silica was mixed to prepare a developer.

On the other hand, an electrostatic latent image was formed on an OPC photoreceptor, and developed by applying the above developer to a developing device as shown in the drawing. The developer carrier was a stainless steel cylindrical sleeve 2 with an outer diameter of 50 mm. The surface magnetic flux density of the sleeve 2 is 700 Gauss, and the distance between the surfaces of the ear cutting blade 5 and the sleeve 2 is 0.25 mm. This sleeve rotating magnet 3 fixed (sleeve circumferential speed is the same as that of the drum, rotation method is opposite) type developer is connected to the photosensitive drum 1.
Set the distance between the surface and the sleeve 2 surface to 0.25 mm, and apply 1600Hz, 1400V AC and -150 to - to sleeve 2.
A 300V DC bias was applied.

The developer 4 was applied to this developing device to develop the latent image, and then the powder image was transferred while irradiating -7 KV direct current corona from the back side of the transfer paper to obtain a copied image. Fusing is done using a commercially available plain paper copying machine (product name, NP
-200J, manufactured by Canon) was used.

Further, residual toner on the photoreceptor was removed using a blade cleaning method.

When images were formed using the toner of the present invention as described above, clear images without fog were obtained. A running test of 3000 sheets was carried out at room temperature and humidity (20
℃, 60%), low temperature and low humidity (15℃, 10%), and high temperature and high humidity (30℃, 90%).
Good images were obtained in all environments, and no image disturbance or fog due to toner adhesion to the photoreceptor surface occurred.

In place of the silicic acid fine powder synthesized by a wet method with a specific surface area of 90 m ² /g in Example 1, colloidal silica synthesized by a dry method and treated with amine-modified silicone oil and a specific surface area of 100 m ² /g was used. , 170m ² /
The procedure was carried out in almost the same manner as in Example 1 except that a product with a particle size of 210 m ² /g was used, and a good image was obtained, with no image disturbance or fog due to toner adhering to the surface of the photoreceptor. Ta.

Examples 2 to 4 The chromium oxide used in Example 1 was replaced by a sintering method that had no corners and rounded edges.
2 calcium titanate with a specific surface area of 1.9 m ² /g
A developer was prepared in the same manner as in Example 1, except that 1.5 parts by weight of zirconium oxide (6.7 m ² /g) and 0.8 parts by weight of cerium oxide (70% purity) of 9.6 m ² /g were used. However, when an image development test was carried out in substantially the same manner as in Example 1, good results were obtained.

Example 5 Styrene-butyl acrylate copolymer (weight ratio 70:30) 100 parts by weight Magnetite 60 parts by weight Alloy dye (Sapon First Black B,
(manufactured by BASF) 2 parts by weight Low molecular weight polypropylene 3 parts by weight Using the above materials, in almost the same manner as in Example 1,
A magnetic toner in the form of colored fine powder with a size of 5 to 20 μm was obtained.

100 parts by weight of this magnetic toner has a specific surface area of 2.4 m ² /
A developer was prepared by mixing 1 part by weight of a rounded chromium oxide fine powder produced by the sintering method of g and 0.4 part by weight of hydrophobic colloidal silica.

This developer was applied to a commercially available copying machine (NP-200J, manufactured by Canon), and a running test of 10,000 sheets was conducted. As a result, clear images were obtained even after the running test was completed.

In addition, good results similar to those in Example 1 were obtained in other test results.

Comparative Example 1 Example 1 except that chromium oxide is not used
When the test was carried out in the same manner as above, a clear image was obtained initially, but after the running test, significant toner sticking occurred at low temperature and low humidity, and significant image disturbance occurred at high temperature and high humidity.

Comparative Example 2 Chromium hydroxide was heated to a temperature below the melting point of chromium oxide,
It was heated and baked at approximately 1800°C for 12 hours. After cooling, the resulting agglomerate was crushed to give an average particle size of approximately 3.5μ,
Chromium oxide with a BET specific surface area of 0.35 m ² /g was obtained.

When a test was conducted in the same manner as in Example 1, a clear image was obtained at the beginning, but an oval-shaped scratch caused by coarse particles appeared on the drum during the running test, and when the test was continued, the image on the drum became clear. Toner stuck to the scratched area.

Comparative Example 3 Fine chromium oxide powder was prepared by the following method other than the sintering method.

Chromium hydroxide was heated for 8 hours at approximately 2100°C, which is above the melting point of chromium oxide. After cooling, the solidified product was crushed using a pulverizer to obtain chromium oxide having an average particle size of about 1 μm and a BET specific surface area of 1.2 m ² /g.

The test was carried out in the same manner as in Example 1. Initially, an image with no problems was obtained, but due to the angular shape of chromium oxide, numerous fine scratches appeared circumferentially on the drum during the running test, causing black fine scratches on the halftone image. It appeared as a line. Furthermore, under high temperature and high humidity conditions, image deletion corresponding to these fine scratches occurred.

Comparative Example 4 Chromium hydroxide was heated at a temperature below the melting point of chromium oxide,
It was calcined by heating at approximately 1500°C for 12 hours. After cooling, it was crushed and further crushed to 0.1μ or less by wet crushing. The BET specific surface area was 34 m ² /g.

When tested in the same manner as in Example 1, a clear image was obtained initially, but in the running test, the image became distorted under high temperature and high humidity conditions.

[Brief explanation of drawings]

The drawing is a sectional view showing an embodiment of a developing process to which the developer of the present invention can be applied. 1... photosensitive drum, 2... sleeve, 3... magnet, 4... toner, 5... ear cutting blade.

Claims (1)

[Scope of Claims] 1. A latent image on an insulator or photoreceptor is formed by a sintering method using an inorganic fine powder having a BET specific surface area of 1.0 to 6.0 m ² /g by a nitrogen adsorption method of 0.2 to 10% by weight. Developing with a developer containing a magnetic toner and transferring the resulting toner image to a transfer member,
An image forming method comprising the step of then removing residual developer on the insulator or photoreceptor by a blade cleaning method. 2. The image forming method according to claim 1, wherein the inorganic fine powder produced by the sintering method has no corners and is rounded. 3. The image forming method according to claim 1, wherein the photoreceptor is an organic photoconductor. 4. The image forming method according to claim 1, wherein the photoreceptor is an amorphous silicone photoreceptor.