JPS58220146A - Dry developer - Google Patents

Abstract

PURPOSE:To obtain a two-component type dry developer giving a toner image by development and causing no sticking of insulating magnetic powder reverse to the toner in polarity to the periphery of the image during the electrostatic transfer of the image, by mixing specified 2 kinds of insulating magnetic powders after adding fluororesin powder to one of the magnetic powders as a carrier component. CONSTITUTION:A resin component such as styrene-acrylic resin, polyester resin or epoxy resin is kneaded with a fine-grained ferromagnetic body, a colorant, a surface treating agent, etc. by means of a heated roll, and the kneaded material is cooled, pulverized, and classified to form the 1st insulating magnetic powder (toner component) having <=20mum average particle size and the 2nd insulating magnetic powder (carrier component) having <=50mum average particle size. At this time, the 1st and the 2nd powders are provided with different electrostatic charging characteristics by selecting the resin or treating the powders with surface treating agents. <=About 5wt% fluororesin powder such as vinylidene fluoride powder is then dispersed in the 2nd powder, and the 2nd powder is mixed with the 1st powder to obtain a developer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developer that enables transfer using an electrostatically charged developer, and more specifically, the present invention relates to a dry developer that enables transfer using an electrostatic developer. This relates to dry type developers.

Toners for electrophotography include one-component magnetic toner, which contains a magnetic material and does not require a carrier, and two-component toner, which requires a gear.

One-component magnetic toner has the following characteristics: less toner scattering, less fogging, constant image density, and
It has many advantages such as being small and simple and easy to maintain, and many of them are being put into practical use recently. However, since -component magnetic toner is conductive or semi-conductive, it is difficult to electrostatically transfer a developed toner image onto plain paper, and it is difficult to electrostatically transfer a developed toner image onto plain paper. It is widely used as a direct method that does not require the transfer of a developed toner image.

Two-component toners obtain sufficient electric charge through frictional charging with iron powder called carrier, so they often have high resistance and can be easily transferred to plain paper, which is why they are the mainstream in plain paper copiers. occupies .

However, since two-component toner uses iron powder as a carrier, the toner deteriorates significantly, the surface of the photoreceptor is easily damaged, the developing machine is complex and large, and the range of appropriate toner density is narrow and difficult to control. It has many problems, such as being difficult to maintain and requiring complicated maintenance.

The purpose of the present invention is to make it possible to obtain good images without being affected by humidity, to make the structure of the developing machine simple and compact, and to keep the toner image obtained by the development static. It is an object of the present invention to provide a dry developer capable of clearly transferring an image by an electric transfer method without adhering insulating magnetic powder of opposite polarity to the periphery of the image.

In electrophotography, in order to obtain high-quality images, whether using single-component toner or two-component toner, the particles in the toner images must be sufficiently charged and have the same polarity during development. At the time of transfer, each toner forming the toner image is required to be insulating. Among these conditions, it is relatively easy to improve the insulation properties of the toner, but it is extremely difficult to sufficiently charge each toner particle and to make the polarities uniform.

In the case of two-component toner, the above conditions are satisfied due to frictional charging between the iron powder called carrier and the toner. - In the case of component-based toners, those that are subject to distinct triboelectrification, such as iron powder.

It doesn't exist. For example, the toner contacts the air, the sleeve, the blade, and each toner particle. Each toner particle is charged by frictional charging between these particles and the toner, but the uniformity of polarity and the amount of charge are insufficient, and moreover, it is easily affected by temperature and humidity. If the polarities are insufficiently aligned, a fogging phenomenon or a reversed image will occur, and even if the polarities are aligned, if the amount of charge is small, the image density will not increase, and electrostatic transfer will fail. It becomes difficult.

In the present invention, the above object is achieved by mixing two types of insulating magnetic powders having different charging characteristics.

In other words, depending on whether two or more types of thermoplastic resins with different charge series are used, whether a dye is added as a charge control agent, or whether a surface treatment agent is used, two types of insulating magnetic powders with different charge series can be used. When thoroughly mixed in a suitable manner, each insulating magnetic powder is charged with opposite polarity due to friction between the two powders. This phenomenon is just like the two-component toner becoming charged due to friction with the iron powder carrier. The insulating magnetic powders each charged with opposite polarity are placed in a developing machine and rotated on a sleeve in the developing machine.

When the charge image on the surface of the photoreceptor reaches the developing section, toner components charged to the opposite polarity to the charge image adhere to the charge image section.

On the other hand, the carrier component charged to the same polarity as the charge image corresponds to the iron powder carrier of a two-component developer, and does not have a strong magnetic force like the iron powder carrier, so the charge reversal that occurs at the periphery of the image occurs. It should stick to the parts, but it actually doesn't stick at all.

-------- If two types of insulating magnetic powders with different charging characteristics are simply mixed, the carrier component charged to the same polarity as the charge image will adhere to the charge reversal area that occurs around the image periphery. . This is particularly noticeable when development is performed by applying a developing bias of the same polarity as the charge image on the photoreceptor in order to remove image fog.

As a result of various studies on development characteristics, the present inventors have found that the problem can be solved by adding fluororesin powder as a third component to both the insulating magnetic powder or at least to the carrier component.

The amount of addition is 5.0 wt % or less, which is the limit at which it does not affect image characteristics. Tsumashi, 6. If it exceeds Qwt%, the developing characteristics are significantly impaired, and only a small amount of the photoreceptor charge image is developed, the image density is not increased, and the photoreceptor does not function as a copy. Commercially available fluororesin powders such as vinylidene fluoride, ethylene tetrafluoride, and propylene hexafluoride can be used.

The method of addition may be to add the first and second insulating magnetic powders and disperse them using any appropriate disperser, and then mix the two, or to mix the two and then add and disperse. You may let them. The particle size of the powder does not have to be ultra-fine like a surface treatment agent, for example, finely powdered silica, and a particle size of about 20 μm is sufficiently effective.

As a means of differentiating the charging characteristics of two types of insulating magnetic powder, there are two methods: selecting two types with different charging series in the resin that serves as the base material, and using a surface treatment agent to mainly create an insulating magnetic powder. A method of varying the charging characteristics in the surface layer of powder,
Another possible method is to knead the charge control agent into the resin, and there are several combinations.

The preferred characteristics of these insulating magnetic powders are as follows.

(1) The average particle size of the first insulating magnetic powder is 20 μm or less, the second insulating magnetic powder is 60 μm or less, and both have electrical conductivities of 10 mho /l:m or less.

(2) The two types of insulating magnetic powder each contain 8°wt% or less of magnetic material.

(3) The two types of insulating magnetic powder have different chargeability. (4) The two types of insulating magnetic powder each have good fluidity, and the mixture of the two also has good fluidity.

(6) The mixing ratio of the first insulating magnetic powder is 6 to 6.
It is desirable to mix at 6Qwt%.

The developer of the present invention is essentially a two-component developer, but since both are insulating magnetic powder and have small particle sizes,
- In addition to being able to use a small developing device like the component developer, it is also possible to prevent scratches on the surface of the photoreceptor and prevent deterioration of the developer. Further, the toner component ratio can be significantly increased, and a good image with excellent reproducibility of halftone fine lines can be obtained.

Next, the materials and manufacturing method of the developer of the present invention will be described.

The developer according to the present invention, like the conventional one-component toner, has a resin component 9 colorant and a fine particle ferromagnetic material as its main components, and as mentioned above, the charging characteristics are different between the two types of insulating magnetic materials. Dyes and surface-treated particles are used depending on the means of providing the difference. Useful resin components include styrene, vinyl chloride, vinyl acetate, methyl acrylate, methyl methacrylate, vinyl methyl ether, and acrylonitrile.

Homopolymers obtained from monomers such as vinyl methyl ketone, copolymers obtained by combining two or more of these monomers, mixtures thereof, or, for example, rosin-modified phenol-formalin resins.

Epoxy resin, oil-modified epoxy resin, polyurethane resin, polyether resin, etc., or polyethylene wax, paraffin wax, carnauba wax.

Waxy resins such as stearic acid.

As colorant, any suitable pigment or dye can be used. For example, carbon black, aniline blue, calco oil blue, quinoline yellow, phthalocyanine blue, etc. are used, but it is better to select a material that is effective in controlling the charging characteristics of the insulating magnetic powder. Effective.

Fine particulate magnetic materials include alloys or compounds containing ferromagnetic elements such as iron, cobalt, and nickel, including ferrite and magnetite, or manganese-copper-aluminum that becomes ferromagnetic through appropriate heat treatment. , alloys such as manganese-copper-tin, or chromium dioxide. Since these magnetic substances are generally conductive, it is not advisable to add them in too large a quantity as insulating magnetic powder.

A release agent, a plasticizer, etc. for the heat fixing roller can be added to the insulating magnetic powder, if necessary.

When manufacturing the developer of the present invention, conventional toner manufacturing methods can be applied. For example, resin component 9 colorant, particulate magnetic material, and other additives are premixed in a super mixer, etc., each component is mixed and dispersed uniformly, and then kneaded and melted in a twin screw extruder, etc.
Cool and grind. The pulverized material is classified to obtain the desired particle size.

In order to improve the fluidity of the insulating magnetic powder, it is desirable to make it spherical in shape. For this purpose, the insulating magnetic powder classified by the method described above is sprayed into hot air.
A method is used in which each powder particle is melted and made spherical by surface tension.

Two types of insulating magnetic powders with different charging characteristics are prepared as described above. As mentioned above, the charging characteristics can be adjusted to an appropriate difference between the two types of insulating magnetic powder by selecting the base material thermoplastic resin, coating the surface with surface treatment particles, and adding dye. ing.

Next, fluororesin powder is added to both of the two types of insulating magnetic powder produced as described above or at least to the carrier component, and dispersed by an appropriate method. The developer of the present invention is obtained by mixing these two in a predetermined ratio. The mixing method may be any suitable method.

A magnetic brush method is most suitable for developing using the developer of the present invention. In particular, it is effective to use a developing machine with a structure in which a magnet roll, which is made up of a collection of multiple magnets arranged with different polarities in sequence, is covered with a sleeve made of non-magnetic material. be. In this case, there are three methods: fixing the sleeve and rotating the internal magnet roll, fixing the internal magnet roll and rotating the sleeve, and rotating both. Developers of the invention can be used.

During development, the aforementioned sleeve is grounded, but a bias voltage can also be applied to it. Bias voltage is often effective in removing fog.Next, details and effects of the present invention will be explained using specific examples. Note that the number of parts added in this example is the number of parts by weight.

[Example 1] 100 parts by weight of Almatex XPA-651J (styrene-acrylic resin, manufactured by Mitsui Toatsu Chemical Co., Ltd.) and magnetite (Fe3O4) with a particle size of 0.2 to 0.4 μm 2
The mixture was mixed with 6 parts by weight, kneaded with a hot roll, cooled, and then crushed and classified to prepare a toner component having an average particle size of 13 μm.

[A carrier component was prepared by mixing 6 parts by weight of strained ATR-2005J (polyester resin, manufactured by Kao Atlas Co., Ltd.) and 75 parts by weight of the magnetite in the same manner as described above. However, the average particle size was 41 μm. [Kynar 461 J (polyvinylidene fluoride, manufactured by Pennwalt, USA)] was added to the obtained carrier component for 1.
% and dispersed for 30 minutes using a vibrating mixer. Both of these were mixed at 20 wt % of toner components to prepare a developer.

[Example 2] "Almatex xP Mu 561J" used in Example 1
A toner component was prepared in the same manner as in Example 1 by mixing 100 parts by weight and 26 parts by weight of magnetite with 3.6 parts by weight of 1-Subiron black rua... + (F material, manufactured by Hodogaya Chemical Co., Ltd.). And so. The average particle size was 11 μm. 12.6 parts by weight of [MuTR-2005J and JPCN-1709j (amine modified styrene-acrylic resin, manufactured by Kao Atlas Co., Ltd.) used in Example 1, 12.6 parts by weight. and 76 parts by weight of JPP-7J (Manganf, Elite, manufactured by Kanto Denka Co., Ltd.) were mixed to prepare a carrier component in the same manner as in Example 1. This stuff has 1 fullon L-
0.6 wt% of 169J (polytetrafluoroethylene, manufactured by Asahi Glass Co., Ltd.) was added and dispersed with a vibration mixer.
The average particle size was 38 μm. Both were combined into toner component 1.
The mixture was mixed at 6% to form a developer.

[Example 3] 1.0 wt% of [R-972J (fine powder silica, manufactured by Nippon Aerosil Co., Ltd.) was added to the toner component of Example 2,
Coated with a small super mixer.

Furthermore, 3 wt % of Kynar #461J was added and dispersed using a vibration mixer. The toner components of this invention and the carrier component of Example 2 were mixed at a ratio of 1:4 to form a developer.

[Example 4] 1 and Qw of the above "R-972" were added to the toner components of Example 2.
After adding t% and coating in the same manner as in Example 3, 1.0wt% of the above "Kynar 461" was added,
A similarly prepared product was used as a toner component. A carrier component was prepared in the same manner as in Example 2 by adding 0.6 wt % of Kyker #461J to the carrier component of Example 2. A developer was prepared by mixing both of these at a ratio of 1=2.

Using the developers of Examples 1 to 4, copies were made using an electrostatic copying device, and the image quality was evaluated.

The photoconductor of the copying device is a selenium drum, the developing section is a magnet roll, and the sleeve rotates both ways, with the former rotating at 130 rpm.
0 r,p,m, the latter rotating by 130 r,p,m. The process speed was 125 M/sec, and the developing bias during development was OV and +130 V, respectively.

→ Copying was performed by applying -200V. Evaluation was made by evaluating the number of carrier components attached to the peripheral area of the image when each developing bias was applied in terms of image density, fine lines, and reproducibility of halftones.

The number of carrier components attached is 1.26 resolution cover turns/
The number of adhered particles between the stripes on the plate was examined, and the image density was measured using a Macbeth reflection densitometer manufactured by Konishiroku Co., Ltd. on a copy of the black original portion with a reflection density of 1.60. For fine lines, type 11
The reproducibility of Mincho typeface was evaluated. Regarding the reproducibility of halftones, we used the number of grayscale gradations that can be distinguished from the electrophotography society test sheet. The results are shown in the table below.

(Margins below) As is clear from this table, the image obtained with the dry developer of the present invention has an image density Dmax of 163 or more in terms of reflection density, and when high development is applied, the charge at the periphery of the image decreases. There was very little carrier component adhering to the reversal area. Furthermore, good images with good reproducibility of halftones and fine lines and little fogging were obtained.

As described above, the dry developer of the present invention is a novel developer consisting of two types of insulating magnetic powders with different chargeability and a fluororesin powder as a third component, and is capable of obtaining images with good f quality. 0

Claims (2)

[Claims] (1) Contains magnetic material in resin and has an average particle size of 20 μm
It consists of the following first insulating magnetic powder and a second insulating magnetic powder containing a magnetic substance in a resin and having an average particle size of 50 μm or less, and at least the second insulating magnetic powder A dry developer containing fluororesin powder as a third component. (2) The dry developer according to claim 1, wherein the amount of fluororesin powder added is 6.0 wt% or less.