JPH0296187A - Developing method - Google Patents

Abstract

PURPOSE:To form a distinct image by using carbon black of which volatile component of toner in starting developer and that for replenishing toner are in a specific relation. CONSTITUTION:When the volatile component of the carbon black in the toner in the starting developer is A% and that in the replenishing toner is B%, the carbon black is selected so that 1.1<=A/B<=8.0, and the toner in the starting developer and the replenishing toner are produced. Therefore, an image of high density can be attained since an initial stage, without occurrence of toner scattering nor base fogging, which may be caused by carbon black aggregated by replenishing toner immediately after replenished. Thus, an distinct image of high density can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing method using a two-component developer, and more specifically, to a developing method that uses a two-component developer, and more specifically, it is capable of achieving high density even during long-term continuous copying without causing toner scattering or background fog. This invention relates to a developing method that produces clear images.

(Prior art and its problems) Conventionally, a developing method using a two-component developer has been widely used in the field of electrophotography, and when this is used, the developer is usually placed on the surface of a sleeve that has a magnet inside. The developer is used in the form of a so-called magnetic brush that supports the photoconductive layer.During development, the developer is mixed and stirred in the developing device, and in a mutually frictionally charged state, the rotation of the sleeve or magnet causes the developer to spread on the photoconductive layer. The toner particles are transported to the electrostatic latent image bearing surface, and due to the electrostatic attraction between the triboelectric charge of the toner and the electrostatic latent image, the toner particles are transferred to the latent image, and development is performed.

Furthermore, when making a large number of copies, it is necessary to keep the toner concentration in the developer constant, so a method is used in which only toner is replenished.

However, due to repeated development operations, the developer in the developing device gradually deteriorates, and the carrier surface in particular becomes contaminated with the toner composition, resulting in high resistance of the entire developer and uneven triboelectric charging. , and the bias development efficiency decreases. As a result, the image density may decrease or background fog may occur in the running area.

The present applicant previously wrote in Japanese Patent Application No. 58-75429,
By making the volume resistance of the replenishment toner lower than the volume resistance of the toner in the start developer, the reduction in image density caused by the high resistance of the developer due to continuous copying and the occurrence of background fog due to the edge effect are avoided. We proposed a method to prevent this. In this method, the volume resistivity of the toner in the start developer and the replenishment toner is controlled by particularly changing the content of carbon black contained in the toner.

On the other hand, in recent years, high-resistance ferrite carriers with rich gradation and less characteristic change due to environmental changes have been used in order to obtain higher-quality copies, and With the development of high-speed copying systems that can obtain high-speed copying, developing conditions have become stricter, and further improvements in the various properties of toner are required. Therefore, when the developing method of the above-mentioned Japanese Patent Application No. 58-75429 was applied under such conditions, it was possible to prevent background fogging and a decrease in image density to some extent during running copying, but the carbon black content of the replenishment toner Due to the large amount of carbon black, there were defective particles mainly composed of carbon black, and it was observed that toner scattering and background smearing occurred immediately after toner replenishment.

Furthermore, since the content of carbon black varies during toner production, it is troublesome to control the degree of dispersion, and the image quality of the formed image also varies slightly. Due to the high content of the toner, the fixing performance deteriorates, and it has been recognized that there is a drawback that fixing failure occurs particularly in high-speed copying machines.

Therefore, the present invention has been made in view of the above points,
The purpose of this is to maintain good image quality and fixability over a long period of time without significantly changing the formulation of the toner in the starting developer and the replenishment toner, and to prevent fogging not only during running copying but also immediately after toner replenishment. It is an object of the present invention to provide a developing method capable of forming a clear image with high density without causing toner scattering.

(Means for Solving the Problems) According to the present invention, a starting developer made of a mixture of a magnetic carrier and a toner is brought into contact with an electrostatic latent image bearing surface, and the amount of the toner consumed for development is In an electrophotographic development method that replenishes replenishment toner according to The object of the present invention can be achieved by selecting carbon black in the relationship of 1.1≦A/B≦8.0.

(Function) A feature of the present invention is that each toner is created by determining the volatile content of the carbon black to be used according to the above-mentioned relational expression, without changing the formulations of the starter toner and replenishment toner. It is.

If you select carbon black that satisfies the above relational expression to create the toner in the starting developer and the replenishment toner, a high-density image can be obtained from the beginning, and replenishment occurs due to carbon black agglomerations caused by the replenishment toner. There is no immediate toner scattering or background fog, and the durability of the developer is also good, effectively preventing high resistance due to developer deterioration, and reducing image density due to edge effects during running copying. It is possible to prevent a decrease in bias development efficiency and keep toner developability (transferability) constant.

Furthermore, the fixability of the toner remains good, and the number of sheets to be printed can be increased without causing fixing failure, and furthermore, it is possible to suitably cope with high-speed copying. The volatile matter of carbon black here refers to a complex mixture of oxygen that is strongly bound to the surface by chemisorption, and it has a large effect on the supply and mobility of free electrons that provide conductivity. By creating toners using carboblacks with different volatile contents, toner properties such as coloring properties, fixing properties, and durability can be improved without significantly changing the blending ratio of other constituent materials such as fixing resin and charge control agent. The toner electrical resistance can be effectively controlled while keeping the characteristics constant.

When A/B > 8, which deviates from the above relational expression, the resistance of the developer decreases, especially immediately after replenishment, and the charge retention of the toner decreases, making it easy to cause image blurring and image blurring. Further, when A/B is less than 1.1, the resistance of the developer increases and the image density decreases.

The present invention will be explained in detail below.

Examples of the binder resin in which the carbon black of the starting developer toner and the replenishing toner used in the present invention are dispersed include styrene polymers, acrylic polymers, styrene-acrylic polymers, chlorinated polyethylene, Olefin polymers such as polyprolene and ionomers, polyvinyl chloride, polyester, polyamide, polyurethane, epoxy resin, diallyl phthalate resin, silicone resin, phenol resin, rosin modified phenolic resin, xylene resin, rosin modified maleic acid resin, rosin ester,
Examples include various polymers such as petroleum resins.

These polymers generally have a glass transition point (Tg) of 40 to 80°C, particularly 50 to 75°C, and a weight average molecular weight of generally 30,000 to 200,000, particularly 500°C.
00 to 150,000 is preferable, and one type or a mixture of two or more types is used.

Among the above polymers, rosin esters, rosin-modified phenolic resins, rosin maleic acid resins, epoxy resins, polyesters, cellulose polymers, polyester resins, etc. are useful in improving the triboelectric properties of toner. .

In addition, when the toner is a pressure fixable toner, olefin polymers such as polyethylene and polypropylene, etc.
Polymers that are easily plastically deformed are mainly used. This polymer can be used with other polymers, such as polyvinyl acetate, ethylene-vinyl acetate copolymer, hydrogenated polystyrene, hydrogenated rosin ester, aliphatic, alicyclic or aromatic petroleum It may also contain a resin or the like.

The carbon black used in the present invention satisfies the above relational expression in the toner during start development and the replenishment toner, and in particular, the volatile content of the toner used in the start developer is 1 to 40%. Preferably, the volatile content of the toner used for replenishment is 0.1 to 10%.

The binder resin used for these carpo plastics is 10
2 to 30 parts by weight per 0 parts by weight can be used.

In addition, in order to control the triboelectric charge of the toner, oil-soluble dyes such as nigrosine dye, oil black, spirone black, etc., naphthenic acid, salicylic acid, fatty acids and resin acids such as manganese, iron, cobalt, etc. are added to the binder resin. 0.1 to 5 parts by weight of metal soaps such as metal salts of lead, zinc, cerium, calcium, nickel, etc., alloy metal azo dyes, pyrimidine compounds, alkyl salicylic acid metal chelates, etc. per 100 parts by weight of the binder resin. , particularly preferably 1 to 3 parts by weight.

Further, an anti-offset agent such as wax may be added to the binder resin in order to prevent offset and improve fixing properties. Waxes used include various waxes such as polyethylene wax, polypropylene wax, ethylene-propylene wax, and paraffin wax.
Low molecular weight olefin polymers such as olefin monomers having 4 or more carbon atoms, fatty acid amides, silicone oils, etc. are used.

These anti-offset agents are 0 per 100 parts by weight of binder resin.
．． 1 to 10 parts by weight can be used.

Furthermore, when used as a magnetic toner, it is possible to contain a magnetic substance in the toner, and the magnetic substance may be a material that exhibits magnetism or can be magnetized, such as iron such as ferrite and magnetite, cobalt, etc. , nickel, manganese, and other ferromagnetic metals and alloys are used.

These magnetic substances can be used in an amount of 50 to 200 parts by weight per 100 parts by weight of the fixing resin.

Then, the binder resin, carbon black, and other constituent materials are melt-kneaded, for example, and the kneaded product is cooled, pulverized, and classified to obtain a toner having a particle size of 5 to 20 μm.

In addition, the obtained toner may be used as a toner composition by externally adding fluidity improvers such as hydrophobic silica, aluminum oxide, fatty acid metal salts, electrical resistance regulators, cleaning properties improvers, etc., if necessary. can.

Various carriers can be used for the toner (composition) and developer, including magnetic materials such as iron oxide, reduced iron, copper, silicon steel, nickel, ferrite,
Magnetic materials such as cobalt, alloys of these with manganese, zinc, aluminum, etc., such as iron-nickel alloys, iron-cobalt alloys, and iron-aluminum alloys; high dielectric constant materials, such as titanium oxide , aluminum oxide, copper oxide, magnesium oxide, copper oxide, zirconium oxide, silicon carbide, etc., magnesium titanate,
Barium titanate, lithium titanate, lead titanate, lead zirconate, lithium niobate tonoceramics, A
DP, (NH4H2PO4), KD P (KH2P
04) Oy XBv salt, iron, nickel,
Magnetic materials such as cobalt and ferrite are combined with acrylic polymers,
Examples include those coated with polymers such as fluorine polymers, silicone resins, and polyesters. One kind or two or more kinds of the above carriers can be used. The particle size of these carriers is 50 to 150 μm, especially 80 to 100 μm.
m is preferably used. Of the above carriers,
Ferrite is preferably used because it is inexpensive, has excellent image characteristics, and has excellent environmental stability.

Then, the toner (composition) and the carrier particles described above are mixed in a weight ratio of 1=99 to 1515 to form a developer.

The present invention will be explained below with reference to Examples and Comparative Examples.

(Example 1) - 100 parts by weight of a styrene-acrylic copolymer as a binder resin, 9.5 parts by weight of carbon black with a volatile content of 2.4% as a colorant, and a negative polarity as a charge control agent. A toner having an average particle size of 17 μm was prepared by a conventional method using 1.5 parts by weight of a metal monoazo dye and 1.5 parts by weight of low molecular weight polypropylene as a second anti-fset agent.

Then, to 100 parts by weight of the above toner, hydrophobic silica: Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd., trade name) 0.2 parts by weight, aluminum oxide: aluminum oxide C (manufactured by Nippon Aerosil Co., Ltd., trade name) 0.2 parts by weight. Parts by weight were added externally to form a toner composition. Then, a start developer having a toner concentration of 4.5% was prepared using this toner composition and a ferrite carrier having an average particle size of 90 μm.

Side U JLLj 2 In the above-mentioned start developer toner, carbon black with a volatile content of 1.5% was used as carbon black at 9.5%.
A toner having an average particle size of 17 μm was prepared in the same manner except that parts by weight were used.

1.Electronic photocopy machine DC- with a copying speed of 432 pages/minute
3285 (trade name, manufactured by Sanda Kogyo Co., Ltd.), a developing device was loaded with the above-mentioned starting developer, and a 50,000-sheet printing durability test was conducted while replenishing toner from a toner cartridge according to toner consumption.

As a result, a clear image with high density and no capri can be formed from the beginning to the end of printing, and the resulting copy has a well-fixed toner image and is free of stains caused by scattered toner, etc. was gotten.

(Example 2) In Example 1, 11 parts by weight of carbon black with a volatile content of 8.5% was used as the toner for the start developer, and carbon black with a volatile content of 1.1% was used as the replenishment toner. Toners each having an average particle size of 16 μm were prepared in the same manner except that 11 parts by weight of the following were used.

Furthermore, when a 50,000-sheet printing test was conducted in the same manner, clear images with high density and no fogging could be consistently formed from the beginning of copying to the end of printing.

Furthermore, the toner image on the obtained copy was well fixed, and there was no stain on the copy due to scattered toner or the like.

(Comparative Example 1) In Example 1, 8 parts by weight of carbon black with a volatile content of 1.3% was used as the toner for the start developer, and carbon black with a volatile content of 1.3% was used as the replenishment toner. Toners each having an average particle size of 16 μm were prepared in the same manner except that 23 parts by weight of the following were used.

Furthermore, when a 50,000-sheet printing test was carried out in the same manner, a clear image with high density and no fogging could be formed at the beginning of printing, but as the printing progressed, fogging became noticeable.
Copies were smeared due to decreased fixing performance and toner scattering immediately after toner replenishment.

(Comparative Example 2) In Example 1, 10 parts by weight of carbon black with a volatile content of 2.7% was used as the toner for the start developer, and carbon black with a volatile content of 2.6% was used as the refill toner. Toners each having an average particle size of 17 μm were prepared in the same manner except that 10 parts by weight of the following were used.

Furthermore, when a 50,000-sheet printing durability test was conducted in the same manner, almost satisfactory results were obtained in terms of fogging and toner scattering, but the image density was significantly lowered.

(Comparative Example 3) In Example 1, 12 parts by weight of carbon black with a volatile content of 8.5% was used as the toner for the start developer, and carbon black with a volatile content of 0.7% was used as the replenishment toner. Toners each having an average particle size of 16 μm were prepared in the same manner except that 12 parts by weight of the following were used.

Furthermore, when we conducted a 50,000-sheet printing test in the same way, we noticed that as the printing progressed, the occurrence of splatter became more noticeable, and after toner was replenished, toner scattering became more frequent, causing stains on the copies. Ta.

The results of Examples and Comparative Examples are shown in Table 1 below.

(Hereinafter, blank space) (Effects of the Invention) According to the present invention, by using carbon black used for the toner in the starting developer and carbon black used for the replenishment toner, each of which has a specific volatile content relationship. , it is possible to effectively prevent the resistance of the developer from increasing during printing, and also to prevent the toner from scattering or gagging immediately after toner replenishment, thereby making it possible to always form clear images. Further, the fixability can also be stably maintained.

Claims (1)

[Claims] A starting developer made of a mixture of magnetic carrier and toner is brought into contact with the electrostatic latent image bearing surface, and replenishment toner is replenished according to the amount of the toner consumed for development. In the electrophotographic development method, when the volatile content of carbon black in the toner in the starting developer is A% and the volatile content of carbon black in the replenishing toner is B%, 1.1≦A/B≦8. An electrophotographic developing method characterized by satisfying the relational expression: .0.