JPH04260057A - Two-component developer for electrophotography - Google Patents

Abstract

PURPOSE:To offer such a two-component developer for electrophotography using a magnetic toner that can maintain good frictional electrification property and causes no picture defects such as splashing, bleeding, etc., by designing a higher density of the magnetic toner in the developer. CONSTITUTION:The two-component developer for electrophotography consists of a negatively (positively) chargeable composite magnetic toner and a magnetic carrier. The composite magnetic toner is obtd. by mixing a magnetic toner (A) and a magnetic toner (B) by 90:10-99:1 mixing ratio. The magnetic powders in the magnetic toner (A) and magnetic toner (B) has such a relative relation that the magnetic powder in the toner (A) is electrified to the negative (positive) polarity because of the frictional electrification series.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a powder developer used for developing electrostatic images, and more specifically, it relates to electrophotographic methods such as copying machines and facsimile machines, electrostatic recording methods, and electrostatic printing. The present invention relates to an improvement in a two-component developer composed of a carrier and a magnetic toner, which is used to develop an electrostatic image formed by a method or the like.

0002

[Prior Art] Generally known conventional electrophotographic technology is
A product that electrostatically forms a latent image on the surface of a photoreceptor (photoreceptor drum), develops the latent image with toner, transfers the toner image onto paper, etc., and then fixes it using heat pressure, etc. to obtain a copied image. be. Developers used in such electrophotography methods include (1) two-component developers in which toner and carrier are mixed in an appropriate ratio (e.g., JP-A-54-110839, JP-A-63);
Two types of developer are known: (2) one-component developer composed only of toner (for example, Japanese Patent Application Laid-Open No. 54-134640 and Japanese Patent Application Laid-Open No. 1-204074).

[0003] The characteristics of the one-component developer are that magnetic powder etc.
% to 70% is used. This magnetic toner can be roughly divided into (1) conductive magnetic toner and (
2) Divided into two types: insulating magnetic toner. Of these, insulating magnetic toner (2) is used in one-component contact development systems, one-component non-contact development systems, and in recent years has been mixed with various carriers and used in two-component development systems.

A two-component developer using magnetic toner has the following advantages. (1) The toner and carrier mixing ratio (toner concentration) has a wide allowable range and does not require a precise concentration sensor. (2) Since a carrier is used, triboelectric charging properties are good. (3) The magnetic brush is easy to form and does not require the precision of the doctor gap or development gap in the developing machine unlike the one-component system. (4) Since the toner contains a magnetic material, there is less toner scattering compared to non-magnetic two-component systems. (5) Since there is almost no need to stir the developer, the structure of the developing machine is simple and compact, similar to the one-component system.

As a proposal for a two-component developer using such a magnetic toner, there is a developing method using a charged magnetic toner and a ferrite carrier in US Pat. No. 4,640,880. In the developer,
When a developer is used with a high toner concentration of 85 to 90%, sufficient frictional charging between the magnetic toner and the magnetic carrier is not achieved, resulting in the phenomenon of magnetic toner scattering around the copied characters (hereinafter referred to as scattering) and characters. The phenomenon of blurring (
(hereinafter referred to as "bleeding") occurred, making it impossible to obtain high image quality.

[0006] In order to improve the above-mentioned scattering and bleeding, it has been proposed to set the concentration of the magnetic toner constituting the developer to be low, and this improves the charging properties of the toner, making it possible to obtain images with less scattering and bleeding. Although this is possible, since it is necessary to strictly control the concentration of the magnetic toner, a concentration sensor is required, resulting in a problem that the cost of the copying machine becomes high.

[0007]

[Problems to be Solved by the Invention] The present invention provides a two-component developer using magnetic toner, in which the magnetic toner in the developer is set at a high concentration to maintain good triboelectric charging properties, thereby preventing images such as scattering and bleeding. An object of the present invention is to provide a defect-free two-component developer for electrophotography.

[0008]

[Means for Solving the Problems] As a result of intensive studies in view of the above points, we have found that by using a mixture of toners containing magnetic powders with different charging series, a good result can be obtained without reducing the concentration of magnetic toner in the developer. It has become possible to maintain good charging properties and obtain good images without scattering or bleeding.

The first two-component developer for electrophotography of the present invention has magnetic toner A and magnetic toner B in a ratio of 90:10 to 99, respectively.
A two-component developer for electrophotography consisting of a negatively charged composite magnetic toner and a magnetic carrier mixed in such a manner that: The second electrophotographic two-component developer is characterized by having a relative relationship in the charging series such that the magnetic powder in the magnetic toner A is charged to the negative polarity side.
Magnetic toner A and magnetic toner B are each 90:10 to 99:
A two-component developer for electrophotography consisting of a positively chargeable composite magnetic toner and a magnetic carrier, which are mixed so that the magnetic toner has a positive charge of 1, and a magnetic carrier. It is characterized by having a relative relationship such that the magnetic powder in the magnetic toner A is positively charged in the series.

The present invention will be explained below. The magnetic toner A constituting the composite magnetic toner according to the present invention is made of materials selected so as to have a charging polarity opposite to the polarity of the electrostatic latent image formed on the surface of the photoreceptor. That is, the magnetic toner A is mainly composed of a magnetic material and a binder resin, and contains a charge control agent for controlling charge polarity. As the magnetic material,
Crystallographically, berovskite with a spinel structure, hexagonal garnet, ferrite and magnetite with an orthoferrite structure are applied to the present invention, and their compositions include nickel, zinc, manganese, magnesium, copper, lithium, barium, vanadium, It is a sintered body of oxides such as chromium and calcium and trivalent iron oxide. The binder resin may include polystyrene, polyethylene, polypropylene, vinyl chloride resin, polyacrylate, polymethacrylate, polyvinylidene chloride, polyacrylonitrile, polyether, polycarbonate, thermoplastic polyester, cellulose resin, and monomers thereof. In addition to thermoplastic resins such as copolymer resins, thermosetting resins such as modified acrylic resins, phenol resins, melamine resins, and urea resins can be used. As the charge control agent, monoazo dyes, metal-containing dyes, nigrosine dyes, etc. are used. Furthermore, a colorant such as carbon black, a fluidity modifier such as colloidal silica, or a fatty acid metal salt may be mixed or externally added to the magnetic toner A.

On the other hand, like the magnetic toner A, the magnetic toner B mainly consists of a magnetic material and a binder resin, but the material is selected so that the magnetic powder has a different triboelectrification series from the magnetic powder in the magnetic toner A. It is something. That is, magnetic toner A
When the composite magnetic toner of magnetic toner B and magnetic toner B is negatively charged (
In the first electrophotographic two-component developer), the magnetic powder contained in the magnetic toner A has a triboelectrification series on the more negative polarity side than the magnetic powder contained in the magnetic toner B. In addition, when the composite magnetic toner of magnetic toner A and magnetic toner B is positively chargeable (second electrophotographic two-component developer), the magnetic powder contained in magnetic toner A is the magnetic powder contained in magnetic toner B. It has a triboelectrification series on the positive polarity side compared to the powder.

[0012] The triboelectric charging series as used in the present invention is determined by the blow-off value for a specific carrier. That is, the specific carrier has an average particle size of 74
~105μm, saturation magnetization 60~70emu/g,
Residual magnetization and coercive force are 0, apparent specific gravity is 2.65-2.
75g/cm3, fluidity 20.0~26.0sec
Ferrite powder coated with methyl methacrylate polymer having a physical property value of /50g and a current value of 0.8 to 1.0 μA, specifically the product name F14 manufactured by Powder Tech Co., Ltd.
1-1530H is used. To measure the friction charge series, 100 parts of the specific carrier and 5 parts of magnetic powder were mixed, 0.2 g of the mixture was accurately weighed, and the maximum friction was measured for 30 seconds using a pull-off charge measuring machine (manufactured by Toshiba Chemical Corporation). The amount of electrification is measured, and the triboelectrification series is determined based on the amount of triboelectrification of the magnetic powder.

The material composition of the magnetic powder contained in magnetic toner A and the magnetic powder contained in magnetic toner B does not matter as long as they have different triboelectrification series, and the magnetic powder blended in both magnetic toners is A difference of 10 μc/g or more in the absolute value of the triboelectric charge amount in the charging series, ie, blow-off, is preferable in order to improve the chargeability of the composite magnetic toner.

Methods for varying the triboelectrification series of magnetic powder include changing the material composition of the magnetic powder, incorporating or attaching a charge control agent to the magnetic powder, and attaching a surface treatment agent to the surface of the magnetic powder. Among these, it is particularly preferable to use a surface treatment agent in order to impart good chargeability to the magnetic powder. As the surface treatment agent, a silane coupling agent or a titanium coupling agent having a functional group exhibiting negative chargeability can be suitably used to make the amount of triboelectric charge of the magnetic powder negative. Specifically, γ-chloropropyltrimethoxysilane, γ-
Glycidoxypropyltrimethoxysilane, β-(3,
Examples include 4epoxycyclohexyl)ethyltrimethoxysilane and alkylchlorotitanium coupling agents. Further, there are also products in which a negatively charged polymer such as a copolymer of vinylidene fluoride and tetrafluoroethylene is mixed with a crosslinking agent. On the other hand, as agents for positively charging, there are silane coupling agents containing amino groups and amide groups, and titanium coupling agents, such as γ-aminopropyltriethoxysilane, N-(β -aminoethyl)-γ-aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-anilinopropyltrimethoxysilane, and the like.

The composite magnetic toner constituting the two-component developer for electrophotography of the present invention is a mixture of magnetic toner A and magnetic toner B, with a mixing ratio of 90:10 to 99:
It is 1. When the magnetic toner A content is less than 90%, more magnetic toner is charged to the same polarity as the photoreceptor, which worsens fogging on non-image areas. Moreover, if it exceeds 99%, the charging property becomes insufficient and the desired effect cannot be obtained.

As the magnetic carrier constituting the two-component developer for electrophotography of the present invention, those generally used as magnetic carriers for toner can be used, and specifically, iron powder carriers and ferrite carriers are used. Both can be used,
In addition, resin coated carriers whose surfaces are coated with polyester resins, fluorine resins, acrylic resins, silicone resins, etc. using these as core materials, or so-called resins made by kneading iron powder or ferrite with a binder resin and granulating them. Carriers can also be used. The two-component developer for electrophotography of the present invention is produced by mixing 5 to 25% by weight of the magnetic carrier described above and 75 to 95% by weight of the composite magnetic toner.

[0017]

[Examples] Examples of the present invention will be described below. First, Table 1
Based on the formulation table, each material was melt-kneaded using a two-roll kneader, pulverized and classified using a jet mill, and magnetic toner No. 1 with an average particle size of 12 μm was prepared. 1.No. 2,
No. 3 was produced.

[0018]

[Table 1]

In addition, the triboelectric charging series of magnetic powder and magnetic toner in Table 1, namely F141- manufactured by Powder Tech Co., Ltd.
The amount of triboelectric charge for acrylic coated ferrite powder of 1530H was as follows. Magnetic powder a + 4.
6μc/g magnetic powder b
+35.9μc/g magnetic powder c
+67.2 μc/g magnetic toner No.
1 -15.2μc/g Magnetic Toner No. 2-9.9μc
/g magnetic toner No. 3-
4.8 μc/g Next, magnetic toner No. 4.8 μc/g obtained above was applied. 1
, No. 2.No. A composite magnetic toner consisting of magnetic toner A and magnetic toner B was prepared using No. 3 and the mixing ratio shown in Table 2. Table 3 also shows magnetic toner No. 1~No
．． A magnetic toner for comparison was prepared using No. 3.

[0020]

[Table 2]

[0021]

[Table 3]

85% by weight of the above composite magnetic toner or magnetic toner for comparison and 15% by weight of an acrylic coated magnetite carrier were mixed to form two-component developers for electrophotography of the present invention in Examples 1 to 4 and comparative example. Comparative electrophotographic two-component developers 1 to 4 were prepared.

The electrophotographic two-component developers of Examples 1 to 4 and Comparative Examples 1 to 4 thus obtained were installed in a commercially available printer (PC-PR406Lm manufactured by NEC Corporation, bias voltage 475 V). , 10 for the evaluation of the initial characteristics of each developer, Examples 1 and 2, and Comparative Examples 1 and 4.
Evaluation was performed by printing up to 000 sheets. The evaluation results of initial characteristics are shown in Table 4, and the evaluation results of up to 10,000 sheets printed are shown in Table 5. In Tables 4 and 5, the image density was measured using a Macbeth reflection densitometer, the background fog was measured using a Hunter whiteness meter, and the scattering and blurring were evaluated visually by enlarging the text portion of the image with a magnifying glass. As is clear from Tables 4 and 5, the electrophotographic two-component developer of the present invention was able to produce up to 10,000 images free from scattering and bleeding without deteriorating image density or background fog.

[0024]

[Table 4]

[0025]

[Table 5]

Further, the rise of triboelectric charging of the magnetic toner in the developers of Examples 1 and 2 and Comparative Examples 1 and 2 was tested, and the results are shown in FIG. In this test, magnetic toner and magnetic carrier were placed in a plastic container without being mixed, and the plastic container was placed in a rotating device that rotated at a constant speed and rotated, and the magnetic toner and magnetic carrier were mixed in the plastic container. The amount of triboelectric charge of the magnetic toner at a specific mixing time is measured using a blow-off charge amount measuring device (manufactured by Toshiba Chemical Corporation). As is clear from FIG. 1, it was confirmed that the two-component developer for electrophotography of the present invention had an increased triboelectric charge amount and a high saturation value in a short mixing time.

[0027]

Effects of the Invention Since the two-component developer for electrophotography of the present invention is composed of a composite magnetic toner consisting of two types of magnetic toners containing magnetic powders with different triboelectric charge series, the triboelectric chargeability of the composite magnetic toner is Therefore, it is possible to obtain images without splatter or smearing.

[0028]

[Brief explanation of the drawing]

FIG. 1 is a graph showing charging rise characteristics of Examples and Comparative Examples.

Claims (2)

[Claims] [Claim 1] Magnetic toner A and magnetic toner B are each 9
A two-component developer for electrophotography consisting of a negatively chargeable composite magnetic toner and a magnetic carrier mixed in a ratio of 0:10 to 99:1, wherein both components contained in the magnetic toner A and the magnetic toner B are A two-component developer for electrophotography, characterized in that the magnetic powder has a relative relationship in a triboelectrification series such that the magnetic powder in magnetic toner A is negatively charged. [Claim 2] Magnetic toner A and magnetic toner B are each 9
A two-component developer for electrophotography consisting of a positively charged composite magnetic toner and a magnetic carrier mixed in a ratio of 0:10 to 99:1, wherein both components contained in the magnetic toner A and the magnetic toner B are A two-component developer for electrophotography, characterized in that the magnetic powder has a relative relationship in a triboelectrification series such that the magnetic powder in magnetic toner A is positively charged.