JPS6211864A - Electrophotographic developer - Google Patents

Abstract

PURPOSE:To improve the stability of the titled developer in a continuous copying by preparing the titled developer comprising a toner composed of a binding resin and a charge controlling agent as a main component, and a carrier coated with a specific film on a surface of a magnetic particle. CONSTITUTION:The toner is prepared by melting the binding resin such as an acrylic resin, a polyester resin or an epoxy resin, a coloring agent such as a carbon black and the charge controlling agent under heating, and then, kneading the same, followed by finely dividing and classifying them so as to obtain fine particles having a particle size of 10-20mum. The carrier is prepared by dispersing the charge controlling agent having the same polarity to that of the charge controlling agent contained in the toner, and the magnetic particles in a solution of the binding resin followed by removing the solvent according to a fluidized bed method or a spray dry method to form a coated layer on the surface of the magnetic particles. The titled developer is prepared by mixing the prescribed toner and the obtd. carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic developer used for developing electrostatic latent images in electrophotography.

<Prior Art> Generally, in electrophotography and electrostatic recording, a developer consisting of a toner and a carrier is used to develop an electrostatic latent image formed on an image support -F.

The toner constituting this developer is rubbed against the carrier during the transportation process, and a charge of the opposite polarity to that of the electrostatic latent image is induced in the toner, and during the process of development by the developer, the toner is transferred to the image support. Electrostatic deposition forms a visible image. When developing a negative latent image, a toner containing a positive charge control agent retains a positive charge by friction with the carrier and develops a negative latent image; When developing an image, a toner containing a negative charge control agent is used for development.

However, conventional developers have unstable triboelectric charging properties, and have the disadvantage that during continuous copying, the amount of charge decreases due to the phenomenon of toner spent on the carrier surface, resulting in fogging of images. In this case, the decrease in the charge amount becomes noticeable at a relatively early stage of continuous copying, and thereafter shows a relatively gradual decrease.For example, if the initial charge amount is 15 uc/g, after several hundred copies, 10 uc/g decreases. /g, and then gradually decreases while remaining relatively stable.

As a countermeasure against such deterioration of the charge amount 1f4, it is conceivable to set the initial charge amount high in advance.

However, in this case, although it enters the stable region of continuous copying after several hundred copies have been made, the amount of charge is too high in the initial stage, resulting in poor image density. In order to eliminate this initial image density deficiency, it is possible to (1) lengthen the mixing time of the toner and carrier, (2) to control the amount of charge by coating the toner with additives such as flow control agents. However, in this case as well, the former has problems with poor workability during developer preparation and part of the toner is destroyed due to long-term mixing, while the latter requires an additional developer manufacturing process. The cost is high, and the additive itself has a subtle effect on the triboelectricity between the carriers, so even if it is possible to control the amount of initial charge, it is not always possible to maintain stable triboelectricity during long-term continuous copying. It's not something you get.

Additionally, attempts have been made to blend various charge control agents into the toner, or to blend a charge control agent with the opposite polarity to the toner into the carrier coating agent as in JP-A-53-100242 and JP-A-59-9670. However, these problems have not been fundamentally solved.

<Problems to be Solved by the Invention> The present invention solves the problem of stability during continuous copying, which tends to occur in two-component developers used for developing electrostatic latent images in electrophotography, that is, between the initial stage of copying and the first stage of continuous copying. The objective is to obtain a developer with little variation in the amount of triboelectric charge of the toner, and thereby to obtain copies of good image quality at all times from the initial stage of development.

Means for Solving the Problems> The present invention is characterized in that, in order to solve the above problems, a charge control agent having the same polarity as the charge control agent contained in the toner is added to the coating layer of the coating carrier. Furthermore, the absolute value of the triboelectric charge amount of the toner is 10~10.
It is controlled by the composition of toner and coating carrier so that it becomes 2Q1+c/g.

31 The carrier referred to in the present invention has the following configuration. That is, a coating layer made of a charge control agent and a binder resin is provided on the surface of magnetic particles made of 10 to 500 J+m of iron powder, oxidized iron powder, nickel, cobalt, iron/silicon/aluminum alloy, ferrite particles, etc. A coating carrier is applied.

When a positively chargeable charge control agent is used in the toner, the charge control agent is a positively chargeable charge control agent, i.e., 21 glosine, an azine dye containing an alkyl group having 2 to 6 carbon atoms, C,1
, Ba5ic Violet 1, C,I.

Ba5ic Violet 3, C, T, l1asi
c l1lue 1, C.

1, basic dye f1 such as Ba5ic l1lue 3,
The basic dye Shii-F pigment, quaternary ammonium base, alkoxylated amine, etc. are applied, while when a negatively chargeable charge control agent is used in the toner, a negatively chargeable charge control agent,
Specifically, azo-based metal-containing dyes, non-dye-based metal complexes, chlorinated paraffins, chlorinated polyesters, etc. are applicable.

Examples of the binder resin for fixing these charge control agents to the surface of the magnetic particles include a copolymer of acrylic acid ester and styrene, a copolymer of styrene and butadiene,
Resins commonly used for coating carriers, such as polyvinyl chloride, epoxy resins, polyvinyl butyral, polyurethane, etc., can be used in the present invention.

To manufacture the carrier referred to in the present invention using the above materials, a charge control agent and magnetic particles are dispersed in a binder resin solution, and the solvent is removed using a fluidized bed method, spray drying method, etc. A coating layer is provided on the surface of the magnetic particles.

The solvents used at this time are trichlorethylene, toluene,
A wide range of substances can be used, such as methyl ethyl ketone, xylene, cyclohexanone, and acetone. Further, in the coating layer of the carrier referred to in the present invention, there is no need to intentionally incorporate a binder resin in the case where a resin component, such as a resin-acid-modified azine compound, is previously blended with a charge control agent. An example of a resin acid-modified azine compound is Bontron N-04, which is marketed by Orient Chemical Co., Ltd.

The carrier coating material used in the present invention may contain additives such as coloring pigments and plasticizers, if necessary. In addition to the coated carrier used in the present invention, which is coated on the surface of iron oxide powder used in ordinary two-component developers by the above-mentioned method, the coated carrier may also include a binder to which a charge control agent is internally added. It may also be one in which ultrafine particulate magnetic substances such as magnetite are kneaded and then pulverized to a desired size.

The toner used in combination with the carrier having the above structure has the following structure. That is, a binder resin such as an acrylic resin, a polyester resin, or an epoxy resin, a coloring agent such as carbon black, and a charge control agent are hot-melted and kneaded.
The toner of the present invention can be obtained by crushing and classifying the particles to have a particle size of 201 nm. In this case, the charge control agent blended into the toner is required to have the same polarity as that blended into the coating layer of the carrier, but the composition does not necessarily have to be the same.

The developer consisting of the above carrier and toner has an absolute value of triboelectric charge amount of the toner of 10 to 20u by the blow-off method.
It is necessary to design the materials of the carrier and toner so that the ratio of c/g is achieved. In other words, if the photoconductor in the photosensitive layer is P-type, such as selenium, the toner's charge polarity will be negatively charged, whereas if the photoconductor is N-type, such as zinc oxide, the toner's charge polarity will be positively charged. The charge control agent is selected so that

Then, the amount of triboelectric charge of the toner is 10 to 20 uc/
g range, by appropriately selecting and combining the type and amount of charge control agent to be added to the coating layer of toner and carrier, the amount of coating carrier applied, and the type of binder resin used together. It is possible. That is, the charge control agent in the toner is 3 parts by weight per 100 parts by weight of the binder resin.
The amount of charge control agent in the carrier coating layer is 3 to 10 parts by weight per 100 parts by weight of the binder resin.
It is 200 parts by weight, so the selection range for the amount to be added is extremely wide. Also, the coating carrier is applied at a rate of 0.5
The thickness of the film is controlled to be 10III111, preferably 5III11 or less. Although the developer of the present invention having such a structure contains a charge control agent of the same polarity on the toner and carrier surfaces, it is difficult to develop an electrostatic latent image due to the delicate frictional charging series interaction between the two. The present invention was made possible by maintaining suitable triboelectric properties of the toner.

<Examples> The present invention will be further explained in detail with reference to Examples and Comparative Examples below.

Example 1 Styrene/butadiene copolymer resin (Priolide 5
-5A, manufactured by Gutdeyer) and 10 parts by weight of an azine compound (Bontron N-01,
Using a fluidized bed apparatus, a solution of 10 parts by weight (manufactured by Orient Chemical Co., Ltd.) dissolved in 500 parts by weight of toluene,
Iron oxide powder (EFV200/300, manufactured by Nippon Iron Powder Co., Ltd.) 1k
The above solution was sprayed onto a glass plate and dried at a temperature of 80° C. to obtain a gear having a coating layer with a thickness of 1 to 2 μm.

On the other hand, 100 parts by weight of styrene/acrylic ester copolymer resin (Prioride AC, manufactured by Gutdeyer),
5 parts by weight of an azine compound (Pontron N-01, manufactured by Orient Chemical Co., Ltd.) and 3 parts by weight of carbon black (Mitsubishi Carbon Black #40, manufactured by Mitsubishi Kasei Corporation) were hot-melted and kneaded, cooled, and finely pulverized to have an average particle size. A positively chargeable toner having a thickness of 12 um was prepared.

The developer of the present invention was prepared by mixing 100 parts by weight of the above carrier and 5 parts by weight of toner, and the developer was applied to a blow-off charge measuring device (manufactured by Toshiba Chemical Corporation) to measure the amount of triboelectric charge of the toner. It was g. Next, this developer was applied to a PPC copying machine with a zinc oxide photoreceptor and an initial image was taken.
The image density of mφ peta was 1.5, which was a sufficient density, and a clear image without fogging was obtained. Furthermore, this P
When 5,000 sheets were continuously copied using a PC copying machine, the image density and fog remained at their initial state, and clear images were reproduced. The triboelectric charge amount of the toner in this case was 14.5 uc/g, which was almost the same as the initial charge amount, which supported the high image quality.

Example 2 A solution of 15 parts by weight of a resin acid-modified asine compound (Bontron N-04, manufactured by Orient Chemical Co., Ltd.), which is a positively chargeable charge control agent, dissolved in 500 parts by weight of methyl ethyl ketone was oxidized using a fluidization head device. Iron powder (EFV200
The above solution was sprayed onto 1 kg of Nippon Steel Powder 11-300 (manufactured by Japan Iron Powder 11-) and dried at a temperature of 70 DEG C. to obtain a coating layer having a thickness of 1 to 2 mm.

On the other hand, 5 parts by weight of styrene/acrylic acid co-ester copolymer resin (Bryolide AC, manufactured by Gutdeyer iL), 5 parts by weight of resin acid-modified acine compound (Bontron N-04, manufactured by Orient Chemical Co., Ltd.), Tsunobon Black (manufactured by Orient Chemical Co., Ltd.) After hot-melting and kneading 3 parts by weight of Mitsubishi Tsunobon Black #40 (manufactured by Mitsubishi Kasei Corporation), it was cooled and pulverized to give an average particle size of 14.21°C.
A positively chargeable toner of m was prepared.

A developer of the present invention was prepared by mixing 100 parts by weight of the above carrier and 5 parts by weight of toner, and the developer was measured by a blow-off method and found to be 17 uc/g.

When this developer was applied to a PPC copying machine having a zinc oxide photoreceptor and its image characteristics were examined, excellent effects similar to those of Example 1 were confirmed. The amount of charge on the tree after 5,000 copies was 15 uc/g, confirming the high image quality.

Example 3 Styrene/butadiene copolymer resin (Priory l-
8-5A) and 10 parts by weight of an azo metal complex dye (Metal Black T-1-48, manufactured by Hodogaya Chemical Industry Co., Ltd.), which is a negatively chargeable charge control agent, in 500 parts by weight of toluene. The above solution was sprayed onto 1 kg of iron oxide powder (EFV200/300) using a fluidized bed apparatus and dried at a temperature of 80°C to obtain a carrier having a coating layer with a thickness of 1 to 2 μm.

On the other hand, 100 parts by weight of styrene/acrylic ester copolymer resin (Prioride AC, manufactured by Gutdeyer),
Azo metal complex dye (Metal Black T-4-48) 3
Weight part, Horn Bon Black (Mitsubishi Carbon Black #
40 (manufactured by Mitsubishi Kasei Corporation) = 3 parts by weight (manufactured by Mitsubishi Kasei Corporation) = 11-) was hot-melted and kneaded, cooled, and pulverized to prepare a negatively chargeable toner having an average particle size of 151+m.

The developer of the present invention obtained by mixing 100 parts by weight of the above carrier and 6 parts by weight of toner was applied to a blow-off measuring device to measure the charge amount of the toner, and it was -17 uc/g.
Met.

When this developer was applied to a PPC copying machine having a Se photoreceptor and its image characteristics were observed, excellent effects similar to those of Example 1 were confirmed. Note that the amount of charge of the toner after 5000 sheets of continuous copying was -16 uc/g, which confirmed the high quality images.

Comparative Example Styrene/butadiene copolymer resin (Priolide S
-5A) and 3 parts by weight of azo metal complex dye (T-4--48), which is a negatively chargeable charge control agent, were dissolved in 500 parts by weight of toluene in the same manner as in each of the above examples. A coated carrier was prepared according to the procedure.

On the other hand, 100 parts by weight of a styrene/acrylic ester copolymer resin (Priolide AC), 5 parts by weight of an azine compound (Bontron N-01), and 3 parts by weight of carbon black (Mitsubishi Carbon Black #40) were hot-melted and kneaded. This was pulverized to produce a positively chargeable toner having an average particle size of 12un+.

A comparative developer was prepared by mixing 100 parts by weight of the above carrier and 5 parts by weight of toner, and the amount of triboelectric charge of the toner was measured by a blow-off method and found to be 16.5 sc/g.

When this developer was applied to a PPC copying machine with a zinc oxide photoreceptor and the image characteristics were examined, it was found that the image density was 1 at the initial stage.
．． A good image without fogging was obtained with a value of 5 or more, but a value of 10
Fog occurred after continuous copying of approximately 00 sheets, and it was confirmed that the comparative developer caused problems in practical use. The amount of charge on the toner after 1000 sheets of continuous copying is 1.
It was 0 μc/g, and significant deterioration was confirmed.

<Effects of the Invention> As is clear from the above embodiments, according to the present invention, it is possible to stabilize the triboelectric charging characteristics during continuous copying, and the intended purpose can be achieved.

Claims (1)

[Scope of Claims] 1. A developer consisting of a toner and a carrier whose main components are a binder resin and a charge control agent, in which the carrier is formed on the surface of magnetic particles in the same manner as the charge control agent blended in the toner. An electrophotographic developer comprising a coating containing a polar charge control agent. 2 The absolute value of the triboelectric charge amount of the toner is 10 to 20 μc.
2. The electrophotographic developer according to claim 1, wherein the electrophotographic developer is controlled to have a content of /g.