JPH0220106B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a developing method using an insulating magnetic developer. Conventionally, developing methods for electrophotography, electrostatic recording, etc. are broadly classified into dry developing methods and wet developing methods. The former method is further divided into a method using a two-component developer and a method using a single-component developer. Two-component developing methods include a magnetic brush method using an iron powder carrier, a cascade method using a bead carrier, a fur brush method using fur, etc., depending on the type of carrier for conveying the toner. Furthermore, the one-component development methods include the powder cloud method, in which toner particles are sprayed, and the contact development method, in which toner particles are brought into direct contact with the electrostatic latent image surface. (also referred to as toner development), jumping development method in which toner particles are not brought into direct contact with the electrostatic latent image surface, but are charged and flown toward the latent image surface by the electric field of the electrostatic latent image; magnetic conduction There is the MagneDry method, which develops by bringing a toner into contact with the electrostatic latent image surface. Two-component development methods inevitably use a developer mixture of carrier particles and toner particles, and as the development process progresses, the toner particles are consumed in far larger quantities than the carrier particles, so the mixing ratio of the two changes. However, they inherently have drawbacks such as fluctuations in the density of the visible image and deterioration of image quality due to deterioration of carrier particles that are difficult to consume due to long-term use. On the other hand, a one-component developing method uses magnetic toner. In the Magne Dry method and the contact development method that does not use magnetic toner, the toner comes into contact with the entire surface of the developing surface, that is, the image area and the non-image area, and this causes the toner to adhere even to the non-image area. There was a problem in that the so-called background fog was easily caused by dirt. (This problem of fog staining was also a drawback in two-component development methods.) Also, in the powder cloud method, it is inevitable that powdered toner particles adhere to non-image areas. Similarly, it has the disadvantage that background fog cannot be removed. In this regard, JP-A-54-43027, JP-A-55-
18656, etc., in which an electrostatic image holder that holds an electrostatic image on its surface and a developer carrier that carries an insulating developer on its surface are arranged with a certain gap in a developing section. The method of developing by carrying a developer on a developer carrier to a thickness thinner than the gap and transferring the developer to the electrostatic image holder in a developing section has the advantage that the above-mentioned fog does not occur easily. have. Furthermore, since no carrier particles are used, there is no variation in the mixing ratio as described above, and there is no deterioration of the carrier particles, making it an electrostatic image developing method with high fidelity and stable image quality. In the conventionally known jumping development method, if copying is continued repeatedly, the uniformity of the developer layer carried on the developer carrier may be impaired in some cases, and coating defects may occur with streaks in the direction of the carrier. , or the thickness of the supported developer layer becomes extremely thick in some areas compared to the initial stage, resulting in spot-like unevenness or serpentine-like coating defects. The former is observed as white streaks on the image when developed, and the latter is observed as uneven density in the form of dots or serpentine waves. Although this development hardly occurs during normal repeated copying, it may occur particularly during continuous use over a long period of time under extremely low temperature and low humidity environmental conditions, which is undesirable. Further, even under high temperature and high humidity conditions, the thickness of the developer layer often changes and becomes thinner, which often leads to an undesirable decrease in image density. As a result of repeated studies on this point, we found that one of the causes is the stability and reliability of the charge control component, and that these causes change the adhesion of developer powder onto the sleeve and the transfer of developer powder from the sleeve. I found out that it was for the purpose of More specifically, this phenomenon is caused by the occurrence of non-uniform triboelectric charge in the developer layer supported on the carrier due to changes in environmental conditions. In other words, under ultra-low temperature and low humidity environmental conditions, friction between the surface of the carrier and the developer generates an extremely large component of triboelectric charge, and due to the mirroring force caused by this charge, the area near the carrier Such components with extremely large triboelectric charges tend to accumulate, and this affects the uniformity of developer coating in the upper layer of the developer layer and the ease of development due to continuous durability, etc. As a phenomenon, the above-mentioned sun streaks, uneven spots, and serpentine coating defects occur. Furthermore, the decrease in the thickness of the developer layer at high temperatures and high humidity is also caused by uneven triboelectric charging between the developer and the carrier, and is due to instability in the amount of triboelectricity of the developer near the surface of the carrier. . Static charge control agents used in dry developing toners generally include, for example, quaternary ammonium compounds and organic dyes, particularly basic dyes and their salts. Common positive charge control agents include benzylmethyl-hexadecyl ammonium chloride, decyl-trimethyl ammonium chloride, nigrosine base, nigrosine, safranin gamma and crystal violet. Especially nigrosine base and
Nigrosine is often used as a positive charge control agent. These are usually added to thermoplastic resins, thermally melted and dispersed, and then finely pulverized and adjusted to a suitable particle size as necessary before use. However, these dyes used as charge control agents have complex structures, inconsistent properties, and poor stability. In addition, it is easily decomposed or deteriorated due to decomposition during thermal kneading, mechanical impact, friction, changes in temperature and humidity conditions, etc., and tends to cause a phenomenon in which charge controllability is deteriorated. Therefore, when a toner containing these dyes as a charge control agent is used for development in a copying machine, as the number of copies increases, the charge control agent decomposes or changes in quality, which may cause deterioration of the toner during durability. Furthermore, most of the substances generally known to be positively chargeable have a dark color and therefore cannot be incorporated into a brightly colored developer. Furthermore, since it is extremely difficult to uniformly disperse these positive charge control agents in a thermoplastic resin, they have the fatal drawback of causing a difference in the amount of frictional charge between toner particles obtained by pulverization. are doing. For this reason, various methods have been used to achieve more uniform dispersion. For example, basic nigrosine dyes are used by forming salts with higher fatty acids in order to improve their compatibility with thermoplastic resins, but unreacted fatty acids or salt dispersion products often remain on the toner surface. When exposed, it contaminates the carrier or toner carrier, causing a decrease in toner fluidity, fog, and a decrease in image density. Alternatively, in order to improve the dispersion of these charge control agents into the resin, a method has also been adopted in which charge control agent powder and resin powder are mechanically pulverized and mixed in advance and then hot melt-kneaded. However, the inherent poor dispersion cannot be avoided, and at present, sufficient uniformity of charge has not yet been obtained for practical use. In addition, many positive charge control agents are hydrophilic, and due to poor dispersion in these resins, after melt-kneading,
When crushed, the dye is exposed on the toner surface. Therefore, when the toner is used under high humidity conditions, it has the disadvantage that a good quality image cannot be obtained because these charge control agents are hydrophilic. In this way, when a conventional positive charge control agent is used in toner, it can be applied to the surface of toner particles between toner particles, between toner and carrier, or between toner and toner carriers such as sleeves. The amount of charge generated varies, and problems such as development fog, toner scattering, and carrier contamination are likely to occur. Further, this problem becomes a noticeable phenomenon when a large number of copies are made, and the result is practically unsuitable for copying machines. Furthermore, under high humidity conditions, the transfer efficiency of toner images decreases significantly, making many toners unusable. Due to the instability of positive charge control agents, they often undergo deterioration and become unusable. An object of the present invention is to provide a developing method with excellent durability such as continuous use characteristics. Another object of the present invention is to provide a developing method that is stable against environmental changes such as high temperature and high humidity, and low temperature and low humidity. Another object of the present invention is to provide a developing method that solves various problems associated with conventional chargeable toners, is uniformly and strongly charged, visualizes electrostatic charge images, and provides high-quality images. The feature is that an electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries an insulating magnetic developer on its surface are arranged with a certain gap in the developing section. A magnetic developer containing an A-B bond or a derivative thereof (A: phthalocyanine or a derivative thereof; B: a nitrogen-containing heterocycle or a derivative thereof) as a positive charge control agent is placed on the developer carrier through the gap. There is also a developing method in which the developer is supported in a thin thickness and the developer is transferred to the electrostatic image holder in a developing section for development. In particular, it is very effective to apply the above developing method to a developing device having a sleeve roller. A-B conjugate (A: phthalocyanine or its derivative; B: nitrogen-containing heterocycle or its derivative)
is thermally and temporally stable, has low hygroscopicity, and has a type of functional separation between the coloring part and the charge control part, so it exhibits bright chromatic colors while maintaining the appropriate amount of charge. It is a high quality positive charge control agent that allows for precise control. The above-mentioned conjugate itself is of course effective, but in consideration of thermal stability, it is preferable that A be copper phthalocyanine or a derivative thereof.
Furthermore, in consideration of charge controllability, it is preferable that B be a nitrogen-containing unsaturated heterocycle or a derivative thereof. As is well known, the phthalocyanine derivatives used in the developer used in the present invention include halides such as chloro group, arylates such as phenyl group, mercapto group, thiocyan group, cyan group, amino group, etc. Hydrocarbon groups, halogenated hydrocarbon groups, nitro groups, sulfone groups, etc. can be introduced singly or in combination.
Further, a form such as a so-called sulfur dye in which two molecules are bonded by a disulfide group is also possible. or,
Various metals can be used as metal complexes in addition to the commonly known copper complexes, but nickel, zinc,
Stable complexes with cobalt, aluminum, platinum, iron, vanadium, etc. are preferred. Many nitrogen-containing heterocycles have been known in the past for the developer used in the present invention, and in addition to nitrogen, the developer can also contain oxygen, phosphorus, silicon, sulfur, and the like. for example,

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[Example 1]

100 parts by weight of zinc oxide, 20 parts by weight of styrene-butadiene copolymer, 40 parts by weight of n-butyl methacrylate, 120 parts by weight of toluene, 1% by weight of rose bengal.
A mixture consisting of 4 parts by weight of methanol solution was dispersed and mixed in a ball mill for 6 hours. This was applied to a 0.05 mm thick aluminum plate using a wire bar to a dry coating thickness of 40 μm, and the solvent was evaporated with hot air to create a zinc oxide binder photoreceptor in the form of a drum. 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. The developer carrier has an outer diameter according to the configuration shown in Figure 1.
It is a 50mm stainless steel cylindrical sleeve. The magnetic flux density on the sleeve surface is 700 Gauss, and the distance between the ear cutting blade and the sleeve surface is 0.2 mm. This sleeve rotating magnet fixed (sleeve circumferential speed is the same as that of the drum, rotation direction is opposite) type developing device is set at a distance between the photosensitive drum surface and the sleeve surface of 0.25 mm,
An alternating current of 400 Hz, 1000 V and a direct current bias of -150 V were applied to the sleeve. Next, a sulfonyl chloride group was introduced into copper phthalocyanine using chlorosulfonic acid, and the mixture was reacted with aminophenylguanamine to obtain the following compound (1). Using (1), a toner with an average particle size of 10 μm was prepared with the following ingredients. Styrene-n-butyl methacrylate 100 parts Magnetite 60 parts Compound (1) 5 parts This toner was developed using the above-mentioned developing device, and then the powder image was transferred while irradiating -7KV DC corona from the back side of the transfer paper. , a duplicate image was obtained. Fixing was carried out using a commercially available plain paper copying machine (trade name: NP-5000, manufactured by Canon). The resulting transferred image had a sufficiently high reflected image density of 1.45, had no fogging, and had no toner scattering around the image, resulting in a good image with high resolution. Transfer images were continuously created using the above developer to examine durability, but the transferred images after 20,000 sheets were also completely dull compared to the initial images. In addition, when the environmental conditions were set to 35℃ and 58%, the image density was 1.38, a value that was almost unchanged from normal temperature and humidity, and clear images were obtained without fogging or scattering, and the durability was almost unchanged up to 30,000 sheets. Nakatsuta.
Next, when a transferred image was obtained at a low temperature and low humidity of 10°C and 10%, the image density was as high as 1.62, solid black was developed and transferred extremely smoothly, and the image was excellent with no scattering or hollow spots. Durability tests were conducted under these environmental conditions, and copies were made both continuously and intermittently, and the density variation was ±0.2 up to 30,000 copies, which was sufficient for practical use. [Example 2] Example 1 except that substance (2) was used instead of (1).
I did the same thing and got good results.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of a developing process applicable to the present invention. 1... Electrostatic image holder, 2... Non-magnetic cylinder, 5...
...Doctor blade, 6...Insulating magnetic developer.

Claims (1)

[Claims] 1. An electrostatic image carrier that holds an electrostatic image on its surface and a developer carrier that carries an insulating magnetic toner on its surface are arranged with a certain gap in a developing section, and A
An insulating magnetic toner containing a -B conjugate or a derivative thereof (A: phthalocyanine or a derivative thereof; B: a nitrogen-containing heterocycle or a derivative thereof) as a positive charge control agent is placed on the developer carrier from the above-mentioned gap. A developing method characterized in that the toner is supported in a thin thickness and the toner is transferred to the electrostatic image holder in a developing section for development.