JPH0310311B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel magnetic toner for use in electrophotography, electrostatic recording, magnetic recording, etc. In electrophotography, an electrostatic latent image is first formed using the properties of photoconductors such as cadmium sulfide, polyvinylcarbazole, selenium, and zinc oxide.
Next, the electrostatic latent image is developed with a powder charged with a polarity opposite to that of the electrostatic latent image, and if necessary, is transferred and fixed onto a transfer sheet. 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 appropriate pressure, the photoreceptor may be scratched or damaged during repeated use.
Development occurs where toner sticks. In order to avoid development in which this toner sticks to the photoreceptor,
No. 48-47345 proposes adding both a friction-reducing developer material and an abrasive material to the toner. Although this method is certainly effective in avoiding toner fixation development, it has the following drawbacks. In other words, if a friction-reducing substance is added to an extent that can avoid toner fixation development, 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. However, 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. Another disadvantage is that the amounts of the friction-reducing substance and the abrasive substance added are delicate, making it difficult to obtain a toner with stable characteristics. It is therefore an object of the present invention to provide a toner which overcomes the above-mentioned drawbacks. Specifically, the present invention reduces the toner weight by 15
Magnetic toner particles containing ~70% by weight of magnetic powder and BET specific surface area due to nitrogen adsorption of 0.8~ ^15m2 /
0.2-10% by weight of strontium titanate fine powder and a BET specific surface area of 40-400 due to nitrogen adsorption.
The present invention relates to a magnetic toner containing 0.03 to 5% by weight of fine silica powder of m ² /g. The BET specific surface area due to nitrogen adsorption used in the present invention is 0.8 to 15 m ² /g (preferably 1.0 to 6.0 m ^{2 /} g).
g) strontium titanate fine powder (hereinafter referred to as fine powder A) has a BET specific surface area of 40 to 400 m ² /g (preferably 50 to 350 m ² /g) by nitrogen adsorption method.
The fine silica powder (hereinafter referred to as fine powder B) of 70 to 300 m ² /g (especially preferably 70 to 300 m 2 /g) is used to scrape off low electrical resistance substances such as paper powder, ozone adducts, and toner that adhere to the surface of the photoreceptor. have a function. especially
Fine powder A, which has a small BET specific surface area, creates fine irregularities on the surface of the photoconductor and effectively acts to reduce the frictional resistance between the photoconductor surface and the cleaning member, preventing toner from sticking, and also has a BET specific surface area of It is thought that the fine powder B having a large particle diameter is effective in removing fine deposits on the surface of the photoreceptor. According to the invention, friction-reducing substances are essentially not necessary and toners with stable properties can be obtained. The reason why the specific surface areas of the fine powders A and B are within the above range is that the above effects are degraded when the specific surface areas are out of this range. As the fine powder A, strontium titanate, which is sparingly water-soluble and does not reduce the chargeability of the toner even in a high-temperature, high-humidity environment, is used. Further, as the fine powder B, a hardly water-soluble silica fine powder is used. Further, the fine powder A is preferably harder than the surface of the photoreceptor, and particularly preferably harder than talc on the Mohs hardness scale. Further, as the silicic acid fine powder B, a silicic acid fine powder is preferable. As the silicic acid fine powder, silicic acid fine powder manufactured by a dry method or a wet method can be used. The dry method mentioned here is a method for producing fine silica powder produced by vapor phase oxidation of a silicon halide compound. For example, this method utilizes the thermal decomposition oxidation reaction of silicon tetrachloride gas in an oxyhydrogen flame, and the basic reaction formula is as follows. SiCl ₄ +2H ₂ +O ₂ →SiO ₂ +4HCl Also, in this manufacturing process, for example, by using other metal halogen compounds such as aluminum chloride or titanium chloride together with silicon halogen compounds, composites of silica and other metal oxides can be formed. It is also possible to obtain fine powders, and these are also included. On the other hand, various conventionally known methods can be applied to the wet manufacturing method. For example, the decomposition of sodium silicate by acid can be expressed using the general reaction formula (the reaction formula is omitted below): Na ₂ O・XSiO ₂ +HCl+H ₂ O→SiO ₂・nH ₂ O
+NaCl In addition, after decomposing sodium silicate with ammonia salts or alkali salts, and producing alkaline earth metal silicate from sodium silicate,
There are methods such as decomposing with an acid to produce silicic acid, using an ion exchange resin to convert a sodium silicate solution into silicic acid, and using natural silicic acid or silicate. As the silicic acid fine powder referred to herein, any of anhydrous silicon dioxide (silica) and other silicates such as aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, and zinc silicate can be used. The surface of these silicic acid fine powders is preferably subjected to an organic treatment such as a coupling treatment, an oil treatment, or a treatment with a fatty acid or a metal salt thereof. It is sufficient that these fine powders A and B exist attached to the surface of the toner particles, but it is preferable that they are mixed with the toner particles before use. The amount of fine powder A (i.e., strontium titanate fine powder) added should be 0.2 to 10% by weight based on the total amount of toner, and the amount of fine powder B (i.e., silica fine powder) added should be 0.2 to 10% by weight based on the total amount of toner. A content of 0.03 to 5% by weight gives good results in terms of toner developability, cleaning properties, and environmental stability. In particular, as shown in Examples below, it is preferable to use more fine powder A than fine powder B. The surfaces of these fine powders A and B 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. Coalescence 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, fatty acid 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 lubricants such as Teflon, zinc stearate, and polyvinylidene fluoride; Auxiliary agents (e.g. low molecular weight polyethylene,
(low molecular weight polypropylene, etc.), tin oxide, etc. are appropriately used as a conductivity imparting agent. The magnetic powder contained in the magnetic toner of the present invention is a substance that is magnetized by being placed in a magnetic field, such as powder of ferromagnetic metal such as iron, cobalt, or nickel, or magnetite, γ-iron oxide, or ferrite. There are alloys and compounds such as The content of this magnetic powder is preferably 15 to 70% by weight based on the weight of the toner. The toner of the present invention can be used to develop a latent image on any photoreceptor, including those having an organic polymer layer on the surface, organic photoconductors (OPC), amorphous
There are photoreceptors such as Se, amorphous Si, and zinc oxide.
Particularly preferred are those having a layer containing an organic polymer on the surface. The toner of the present invention can be applied to various developing methods. For example, JP-A-54-42121, JP-A-55-
There are development methods such as those described in Publications No. 18656 and No. 54-43027. The inorganic fine powder A used in the present invention is produced, for example, by a sintering method, and an example of its production will be shown below. [Production example 1] Strontium carbonate 147.6g and titanium oxide 79.9g
Wet-mix g in a ball mill for 8 hours, then filtrate.
Dry. 20 g of this mixture was molded at a pressure of 5 kg/cm ² and calcined at 1100° C. for 8 hours. Thereafter, strontium titanate fine powder having a BET specific surface area of 2.4 m ² /g was obtained by mechanical pulverization. [Production Example 2] 197.3 g of barium carbonate and 79.9 g of titanium oxide were wet mixed in a ball mill for 8 hours, and then filtered and dried. 20 g of this mixture was molded at a pressure of 5 kg/cm ² and calcined at a temperature of 1200° C. for 8 hours. Thereafter, barium titanate having a BET specific surface area of 3.0 m ² /g was obtained by mechanical pulverization. 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, mechanical pulverization or classification can be used, or after dispersing materials such as magnetic powder in a binder resin solution, 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] Styrene-butadiene copolymer 90 parts by weight (weight ratio 84:16) Styrene-dimethylaminoethyl copolymer (weight ratio 90:10) 10 parts by weight Low molecular weight polyethylene 5 parts by weight Magnetite 60 parts by weight Mix and melt-knead using a roll mill. After cooling, it is coarsely ground in a hammer mill, and then finely ground in a jet pulverizer. Next, the mixture is classified using an air classifier to obtain a magnetic colored fine powder colored with 5 to 20 μm of magnetite. This colored fine powder
The specific surface area generated in Production Example 1 per 100 parts is 2.4 m ² /g
A magnetic toner was prepared by mixing 1.5 parts of strontium titanate fine powder and 0.5 parts of colloidal silica (specific surface area 90 m ² /g). On the other hand, an electrostatic latent image was formed on an OPC photoreceptor, and developed by applying the above toner to a developing device as shown in the drawings. The developer carrier was a stainless steel cylindrical sleeve 2 with an outer diameter of 500 mm. The magnetic flux density on the surface of the sleeve 2 is 700 Gauss, and the distance between the ear cutting blade 5 and the sleeve surface is 0.25 mm. This sleeve rotating magnet 3 fixed (sleeve circumferential speed is the same as that of the drum, rotation direction is opposite) type developing device is set at a distance of 0.25 mm between the surface of the photosensitive drum 1 and the surface of the sleeve 2, and the sleeve is connected to an alternating current of 1600 Hz, 1400 V and - A DC bias of 150 to -300V was applied. The toner 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. For fixing, use a commercially available plain paper copier (product name, NP-
200J (manufactured by Canon) was used.
Further, residual toner on the photoreceptor was removed using a blade cleaning method. As a result of the above implementation, a clear image without fogging was obtained. In addition, we conducted a running test on 3,000 sheets in various environments: room temperature and humidity (20℃, 60%), low temperature and low humidity (15℃, 10%), and high temperature and high humidity (30℃, 90%). A good image was obtained, and no image disturbance or fog due to toner adhesion to the photoreceptor surface occurred. Further, the specific surface area produced in the same manner as in Production Example 1 is 0.9 m ² /g, 1.5 ^{m 2} /g, 5.8 m ² /g or 14.3
m ² /g of strontium titanate fine powder and organically treated colloidal silica (specific surface area 200m ² /g)
A magnetic toner was prepared in the same manner as above using g), and when an image printing test was conducted, good results were obtained. In particular, when fine strontium titanate powder having a specific surface area of 1.0 to 6.0 m ² /g was used, a magnetic toner having good developability, cleanability, and environmental stability was obtained. [Comparative Example 1] A magnetic toner was prepared in the same manner as in the example except that the strontium titanate obtained in Production Example 1 was not used, and a running test was conducted under high temperature and high humidity. It was unusable due to the appearance of scratches. [Comparative Example 2] A magnetic toner was obtained in the same manner as in the above Example except that barium titanate having a specific surface area of 3.0 m ² /g produced in Production Example 2 was used. When an image reproduction test was conducted using the obtained magnetic toner in the same manner as in the example, a toner image with a slight fog was generated compared to the case of the example, and the image density was also the same as that of the toner of the example. It was lower than that. Furthermore, using the magnetic toner of Comparative Example 2, a running test of 3,000 sheets was conducted in a high temperature and high humidity environment in the same manner as in the example, and as a result, the toner image quality was found to be distorted compared to the toner image quality of the example. (Image flow)
A toner image was obtained in which some blemishes were observed. The image density of the magnetic toners of Examples and Comparative Examples 1 and 2 under each environment is shown in the table below. As is clear from the table below, the magnetic toner of the present invention has excellent development characteristics and environmental stability.

[Comparative example 3]

The average particle size was 0.1 μm in the same manner as in Production Example 2,
Barium titanate powder with a BET specific surface area of 17 m ² /g was prepared, and 100% of colored fine powder was prepared in the same manner as in the example.
A magnetic toner was prepared by mixing 1.5 parts of barium titanate powder and 1.5 parts of colloidal silica (specific surface area: 90 m ² /g). When a running test was conducted using the prepared magnetic toner in a high temperature and high humidity environment, more disturbance of the toner image (image deletion) occurred than in Comparative Example 2 above.

[Brief explanation of the drawing]

The drawing is a sectional view showing an embodiment of a developing process using the developer of the present invention. 1... Photosensitive drum, 2... Sleeve, 3... Magnet, 4... Toner, 5... Spear cutting blade.

Claims (1)

[Scope of Claims] 1. Magnetic toner particles containing 15 to 70% by weight of magnetic powder based on the weight of the toner, and
Strontium titanate fine powder with a BET specific surface area of 0.8 to 15 m ² /g 0.2 to 10% by weight and silica fine powder with a BET specific surface area of 40 to 400 m ² /g due to nitrogen adsorption
A magnetic toner characterized by containing 0.03 to 5% by weight. 2. The magnetic toner according to claim 1, wherein the magnetic toner particles contain low molecular weight polyethylene or low molecular weight polypropylene. 3. The magnetic toner according to claim 1 or 2, which is used in a developing method in which residual toner on a latent image support is removed by blade cleaning. 4. Claim 1, in which the BET specific surface area of the strontium titanate fine powder is 1.0 to 6.0 m ² /g.
Magnetic toner as described in section.