JPS62238579A - Coated carrier for electrophotography - Google Patents

Abstract

PURPOSE:To obtain coated carrier for electrophotography having high adhesion to an iron powder core and high mechanical strength by using a coating material contg. dispersed fine fluorocarbon resin powder in an F-contg. resin having OH group in the molecule. CONSTITUTION:A core material is covered by a coating material contg. fine fluorocarbon resin powder in an F-contg. resin having OH group in the molecule. The F-contg. resin is a copolymer of an F-contg. unsatd. hydrocarbon with a compd. having a cyclohexylether group, pref. having OH group in the molecule. Suitable fluorocarbon resin to be dispersed in the F-contg. resin is polytetrafluoroethylene, polyvinylidene fluoride, polychloro trifluoroethylene, polyvinyl fluoride, or tetrafluoroethylene/ethylene copolymer, or their mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a carrier for electrophotography, and particularly to a carrier in a two-component developer consisting of a toner and a carrier. More specifically, the present invention relates to a coated carrier for electrophotography with excellent durability.

Conventional techniques and problems Electrophotography uses a corona discharge to apply an electrostatic charge to a photoconductive layer provided on a conductive layer, and then transfers this charged photoconductive layer to an original image (manuscript). Exposure to light to eliminate the electrostatic charge on the exposed area, leaving only the electrostatic latent image, and then depositing toner particles having an electrostatic charge of opposite polarity to that of the photoconductive layer on the electrostatic latent image. It consists of developing an electrostatic latent image.

As a means for developing an electrostatic latent image by adhering toner particles, a cascade method and a magnetic brush method are typically known. In these methods, the developer consists of a mixture of two components: relatively fine toner particles and relatively large carrier particles. When this mixture of toner particles and carrier particles is recycled and used, part or all of the coating peels off from the carrier core due to mechanical friction and deteriorates, and contact and collision between the toner particles and carrier particles causes toner particles to deteriorate. A phenomenon is observed in which the particles adhere firmly to the surface of the carrier particles and gradually accumulate. As a result of these phenomena, the properties of the carrier particles are degraded and the image is adversely affected.

Therefore, the carrier particles are of course required to have desirable and appropriate triboelectric properties;
In addition, it is required to have excellent abrasion resistance and to be free from adhesion and accumulation of toner particles.

As a method of obtaining a carrier having such properties, many proposals have been made to provide a resin coating layer on the surface of carrier particles (core material).

Especially when focusing on triboelectric properties and wear resistance, there are many (
Among the resins, fluororesins are preferred, such as those disclosed in Japanese Patent Application Laid-open No. 47-17434, Japanese Patent Application Laid-open No. 47-17435,
This can be seen in Publications No. 48-90238 and No. 51-117638.

However, the biggest drawback of fluororesins is that they have poor adhesion with the core material. It is described that an epoxy resin, polyurethane, etc. is mixed as a resin for modification in order to improve the adhesion.
90238 discloses that the core material is undercoated in advance and then coated with fluoroethylene, and JP-A-51-117638 discloses that a perfluoro compound having a functional group, e.g. It is described that evaporated perfluoroalcohol, perfluoroamine, etc. are used.

However, in carriers coated by these known methods, the adhesion between the core material and the coating is still not sufficient, and if continuous copying is performed for a long time,
Repeated contact and collision between carrier particles or between carrier particles and mechanical parts may cause the coating layer to peel off and expose the core material. In such a situation, the frictional electrification will be reduced. The problem is that the frictional charging between the toner and the coated carrier changes to the frictional charging between the toner and the core material itself, and the frictional charging characteristics cannot be kept constant, resulting in poor copy image quality. . In addition, the surface of the coated carrier obtained by the above-mentioned known method is not homogeneous, and long-term copying may cause the toner material to adhere firmly to defective areas on the carrier surface, causing stains on the copy screen or blurring of the image. There are also disadvantages that tend to reduce the degree of

SUMMARY OF THE INVENTION An object of the present invention is to provide a coated carrier for electrophotography in which the above-mentioned disadvantages are eliminated or alleviated. More specifically, the first object of the present invention is to provide a coating carrier in which a coating layer that has extremely good adhesion to the iron powder core and has sufficient mechanical strength is supported on the surface of the iron powder core. It is about providing.

A second object of the present invention is to provide a carrier on which a toner film is not firmly formed.

Furthermore, a third object of the present invention is to provide a carrier that has excellent triboelectric charging characteristics with toner particles and is stable over time.

The present invention provides a coated carrier with excellent durability.Furthermore, fine fluororesin powder is dispersed in a fluororesin having hydroxyl groups in its molecules. The present invention provides a carrier in which a core material is coated with a coated material, or a carrier in which the core material is coated by reacting the coating material with polyisocyanate to form a urethane bond.The latter carrier is particularly preferred; It is particularly suitable for use in law.

The fluororesin used in the present invention is preferably a copolymer of a fluorounsaturated hydrocarbon and a compound having a cyclohexyl ether group, and has a hydroxyl group in its molecule.

The fluorounsaturated hydrocarbon used in the production of the fluororesin of the present invention is preferably tetrafluoroethylene, and may also be chlorotrifluoroethylene. Further, a typical copolymerizable compound having a cyclohexyl ether group is cyclohexyl hinyl ether. In addition, the fluorine content of the fluororesin used in the present invention is 15 to 35
It is preferable that the weight percent and the amount of hydroxyl groups are 10 to 100 in terms of OH value.

The fluororesin of the present invention may have a carboxyl group in its molecule (the presence of the carboxyl group improves core material adhesion, pigment dispersibility, etc.).

The fluororesin to be dispersed in the fluororesin is preferably polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, or a mixture thereof. good.

More specific commercially available products include Polyflon TFE, Lublon, Guiflon CTFE manufactured by Daikin Industries, Tef1on manufactured by Mitsui Fluorochemicals, and Kyn manufactured by Pennwalt.
ar, 3M KEL-F81 Asahi Glass 7707C
Examples include OP, and the fluorine content in the molecule is 30 to 80.
% is preferred.

Further, in consideration of the thickness of the coating layer, it is preferable that the primary particle diameter as measured by an electron microscope is 1 μm or less.

Furthermore, the amount of fluororesin powder to be dispersed in the fluororesin is preferably 10 to 100 parts based on the fluororesin; if it is less than 10 parts, the dispersion will not be effective, and if it is more than 100 parts, the strength of the coating layer will decrease. It is not desirable because

When a fluororesin is reacted with a polyisocyanate to form a urethane bond, the amount of polyisocyanate to be blended is 0.8 to 1.2 inocyanate groups in the polyincyanate per 1 hydroxyl group in the fluororesin (equivalent ratio). ) is preferable. The polyincyanates used may be conventional ones, such as tolylene diisocyanate, hexamethylene diisocyanate, and other polyisocyanates of the polyhydric alcohol addition type.

One advantage of the present invention is that the fluororesin, which is the binder resin, has good affinity with the fluororesin, so uniform dispersion is possible. Since it is soluble in water, it can be easily formed into a uniform coating film, and the coating film also exhibits good adhesion to the core material.

In other words, since the fluororesin is a binder, the dispersibility and adhesion of the fluororesin powder, which had conventional drawbacks, are improved, and the low surface energy effect of the fluororesin powder prevents the carrier particle surface from being contaminated by toner. This makes it possible to provide a carrier that can withstand long-term use.

In addition, not only pigments but also various additives generally exhibit good dispersibility in the coating material used in the present invention, and for example, a conductive agent can be added thereto.

The coating material of the present invention is dissolved in a solvent such as ethyl acetate, toluene, xylene, etc., then coated on the core material by dipping or spraying the core material, and then dried or cured by heating.

The coating amount is preferably about 0.05 to 6% by weight, more preferably about 0.1 to 4% by weight based on the core material.

The core material used in the present invention has a particle size of 30 to 200.
Micron iron powder, magnetite or ferrite is used.

The toner used in combination with the coated carrier according to the invention may be any known electrophotographic toner.

In the coated carrier for electrophotography of the present invention constructed as described above, the coating material has extremely good adhesion to the iron powder core material and has sufficient mechanical strength, so even if the core material has a flat shape, It shows sufficient resistance to peeling and abrasion at the edges, even if In addition, since the surface of the coating material is uniform and smooth, it is difficult to form a fixed toner film.
Furthermore, the triboelectric charging properties caused by friction with the toner have excellent stability over time.

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

The current value in each example was measured using a current value measuring circuit shown in the attached drawings. In the drawings, MR is a mag roll, D is an aluminum drum, ■ is a DC 100 volt power supply, R is a 1 kilohm resistor, and m is a millivolt meter or millivolt recording device. The measurement was made with the distance between MR and D being 5 mm, M
The test was carried out under the same conditions with the R rotation speed being 150 rpm.

Example-1 Fluorine resin in which 50 parts of polytetrafluoroethylene resin powder is dispersed in Furan-based resin paint New Garmetsu 2000 (OH value of hydroxyl group = 52, solid content 240% by weight) per 100 parts of the above resin. 37.5.5' is incyanate curing agent for the same paint, OI is toluene 20
0mA! A coating solution was prepared by dissolving it in

Using a fluidized coach ink device, this coating solution was sprayed onto 300 (l) of flat amorphous iron powder with a particle size ranging from 44 to 105 microns, and fluidized and heated at a temperature of 110° C. for 30 minutes to produce a carrier having a coating layer. The obtained carrier was non-adhesive, did not form agglomerates, and had good fluidity.

A developer was prepared by weighing 940 g of this coated carrier into a commercially available positive donor 601 for magnetic brushes and stirring it at 120 rpm for 15 minutes in a 11 polyethylene bottle. At this time, the amount of charge of the toner measured with a blow-off powder charge amount measuring device (Model TB-200 manufactured by Toshiba Chemical) was 2.
It was 5.0μe/g. Also, the current value of the developer is 0.50
It was μA.

All copies obtained by developing electrostatic latent images on OPC photoreceptors using this developer had excellent images with no fog. Table 1 shows the number of times of development, characteristics of the developer, and actual results when developing the electrostatic latent image on the OPC photoreceptor.

Example-2 The coating material of the present invention obtained in Example-1 was coated with 75 to 150
A carrier having a coating layer was prepared by spray coating spherical magnetite having a particle size in the micron range and heating it in a fluidized state at 110° C. for 30 minutes. The obtained carrier was non-adhesive and had good fluidity without agglomeration, as in Example-1. Commercially available magnetic brush positive donor 40! for this coated carrier 960I! j was weighed into a 14 polyethylene bottle and stirred at 120 rpm for 15 minutes to prepare a developer.

All copies obtained by developing electrostatic latent images on the PC photoreceptor using this developer had excellent images with no fog. Table 1 shows the number of times of development, characteristics of the developer, and actual results when developing the electrostatic latent image on the PC photoreceptor.

Example-3 The coating material of the present invention obtained in Example-1 was coated with 75 to 150
A carrier having a coating layer was prepared by spray coating a spherical ferrite having a particle size in the micron range and heating it in a fluidized state at 110° C. for 30 minutes. The obtained carrier was non-adhesive and had good fluidity without agglomeration, as in Example-1.

For this coated carrier 9601, commercially available positive donor for magnetic brushes 40.9 was weighed into a 11 polyethylene bottle and stirred at 12 Orpm for 15 minutes to prepare a developer. All copies obtained by developing electrostatic latent images on the PC photoreceptor using this developer had excellent images with no fog.

Table 1 shows the number of times of development, characteristics of the developer, and actual results when developing the electrostatic latent image on the OPC photoreceptor.

Comparative Example-1 Furan-based resin paint New Garmetsu) 2000 (OH value of hydroxyl group = 52, solid content 240% by weight) 37.51, incyanate-based curing agent for the same paint 7.5g, toluene 20
A coating solution was prepared by dissolving in 0ml. A carrier was manufactured by spray coating the same core as in Example-1.

The obtained carrier was non-adhesive, did not form agglomerates, and had good fluidity. A developer was prepared from this coated carrier in the same manner as in Example 1, and the electrostatic latent image on the OPC photoreceptor was developed. The copy obtained was initially a clear image with no fog, but After 2QOOO times of development, a copy image with many chipped edges was obtained, and obvious deterioration of the developer was observed. The results are shown in Table-1.

Comparative Example-2 Fluorine-based resin paint New Garmet 2000 (OH value of hydroxyl group = 52, solid content 340% by weight) was mixed with polytetrafluoroethylene resin powder in an amount of 1 part per 100 parts of the resin.
20 parts of fluorocarbon resin (37.59 g), an isocyanate curing agent for the same paint (375 g), and toluene (200 ml)
A coating solution was prepared by dissolving it in A developer was prepared using this coated carrier in the same manner as in Example 1, and the electrostatic latent image on the oPC photoreceptor was developed. The copy obtained was initially a clear image without fog, but after 5000 After the first development, an unclear copy image was obtained, similar to that seen when the resistance was low, and obvious scratches of the developer were observed. The results are shown in Table-1.

[Brief explanation of drawings]

The attached figure is a conceptual diagram of the device used for measuring the current value of the carrier in the example. Patent Applicant: Kanto Denka Kogyo Co., Ltd. Patent Applicant: Toa Investment India Co., Ltd. (5 others) Procedures Amendment Book 1986! Commissioner of the Japan Patent Office, July 2-9, 1986 Patent No. 31ft No. 81866 2, Name of the invention, Coated carrier for electrophotography 3, Relationship with the person making the amendment Patent application Person Address Name Kanto Denka Kogyo Co., Ltd. (1 other person) 4. Agent 5. Specification to be amended 8F Detailed description of the invention] column 6. Contents of amendment (1) Amended the following description in the specification. do. Page Line Before correction After correction 8 3
Poly 8 3 Ride Tetra Ride or Tetra 8 9 F81 Asahi
F81, End of Asahi 10 Iron powder core Core (2) The above in the 3rd column and 8th column from the left of Table 1 on page 17 of the same

Claims (1)

[Scope of Claims] 1) A coated carrier for electrophotography comprising a core material carrying a coating layer in which fine fluororesin powder is dispersed in a fluororesin having a hydroxyl group in the molecule. 2) Fluororesin is a copolymer of a fluorounsaturated hydrocarbon and a compound having a cyclohexyl ether group,
The carrier according to claim 1, which has a hydroxyl group in its molecule. 3) The fluororesin powder is one or two of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, and polyvinyl fluoride.
The carrier according to claim 1 or 2, which is a mixture of more than one species. 4) The carrier according to any one of claims 1 to 3, wherein the coating layer is cured by a urethane-forming reaction between a fluororesin and a polyisocyanate on the surface of the core material. 5) The carrier according to any one of claims 1 to 4, wherein the amount of the coating layer is in the range of 0.05 to 6% by weight based on the core material. 6) The carrier according to any one of claims 1 to 5, wherein the core material is iron powder, magnetite, or ferrite.