JPH0373970A - Coating carrier - Google Patents

Abstract

PURPOSE:To stably obtain good triboelectrification and the low surface energy characteristic of a coating resin by incorporating a conductive metal power and/or conductive metal oxide powder into the inner layer of a resin coating layer consisting of two layers. CONSTITUTION:The conductive metal powder and/or conductive metal oxide powder is incorporated into the inner layer of the resin coating layer consisting of the two layers; the inner layer and the outer layer. The exposing of the conductive metal (oxide) powder to the surface of the resin coating layer is obviated to prevent the degradation of triboelectrification. In addition, the effect of decreasing the electric resistance as the entire part of the coating carrier is sufficiently obtd. even if the layer where the conductive metal (oxide) powder exists is in the inner layer and, therefore, the preferable low surface energy is obtd. and the good triboelectrification is stably obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a carrier constituting a developer used in electrophotography, electrostatic recording, electrostatic printing, etc.
The present invention relates to a coated carrier having a resin coating layer on the surface of magnetic particles.

[Conventional technology]

A two-component developer consisting of a toner and a carrier is known as a developer used in electrophotography, etc. However, from the viewpoint of improving durability, such a carrier is made of magnetic particles. A coated carrier having a resin coating layer on its surface is advantageously used.

As the resin for the resin coating layer, it has been proposed to use a fluorine-containing resin with low surface energy properties in order to prevent toner substances from adhering to the carrier surface and stabilize the triboelectric charging properties of the carrier. (Japanese Unexamined Patent Publications No. 58-208754, No. 60-176048)
Publication No. 60-16617, Publication No. 59-2407
(See Publication No. 58, etc.)

However, since the fluorine-containing resin in such a coating carrier has high insulating properties, its electrical resistance as a carrier increases, and as a result, the amount of triboelectric charge imparted to the toner becomes excessive, resulting in poor developability. However, there is also the problem that the bias voltage applied between the photoreceptor and the developing device in the developing area does not act sufficiently, which tends to cause fog in the resulting copied image. In particular, in recent years, devices such as laser printers that carry out the development process by lowering the charged potential of the photoreceptor than before have become popular. The occurrence of fog becomes noticeable.

That is, when the charged potential of the photoreceptor is low, the so-called V, which indicates the correlation between the charged potential V of the photoreceptor and the image density,
A developer with a large slope in the -D curve is required, and in order to achieve this, it is necessary to reduce the electrical resistance of the coating carrier.

However, as a technique for reducing the electrical resistance of a coating carrier, a technique has been proposed in which conductive fine particles are contained in a resin coating layer (Japanese Unexamined Patent Application Publication No. 1986-1999).
No. 200245, No. 57-40267, No. 5
No. 8-108549, No. 55-163544, No. 59-223452, No. 54-7343, No. 61-219055, No. 63-28117
See Publication No. 3, etc.>

[Problem to be solved by the invention]

However, in a coating carrier having a resin coating layer containing conductive fine particles, the conductive fine particles present on the surface of the resin coating layer are easily detached, and the detached conductive fine particles adhere to the toner and cause the toner to become damaged. There is a problem of worsening triboelectric charging properties. Furthermore, since conductive fine particles are present on the surface of the resin coating layer, there is a problem that the low surface energy characteristics of the coating resin are not fully exhibited.

If the triboelectric charging properties of the coating carrier change or the low surface energy characteristics are not exhibited in this way, it becomes difficult to impart a suitable triboelectric charge to the toner, and the coating carrier must be replaced at an early stage. This will cause inconvenience.

The present invention has been made based on the above circumstances, and its purpose is to stably exhibit good triboelectric charging properties and low surface energy properties of the coating resin when used repeatedly many times. The objective is to provide a coated carrier that can

[Means to solve the problem]

In order to achieve the above object, the present invention provides a coating carrier in which a resin coating layer consisting of two layers, an inner layer and an outer layer, is provided on the surface of magnetic particles, wherein the inner layer is made of conductive metal powder and/or conductive metal powder. A structure containing oxide powder is adopted.

The outer layer is preferably made of a low surface energy resin.

That is, in the present invention, the resin coating layer has a two-layer structure of an inner layer and an outer layer, and the inner layer is particularly selected and coated with conductive metal powder and/or conductive metal oxide powder (hereinafter referred to as "conductive metal (oxidized)"). By incorporating the conductive metal (also referred to as "metal) powder") on the surface of the resin coating layer, the conductive metal (
Deterioration of triboelectric charging properties is prevented by not exposing the conductive gold 1jii (oxide) powder, and as will be understood from the explanation of the examples below, the location of the conductive gold 1jii (oxide) powder is in the inner layer. This method was completed after confirming that the overall electrical resistance of the coated carrier could be sufficiently reduced.

As described above, according to the present invention, the electrical resistance can be reduced by the inner layer in which the conductive metal (wI oxide) powder is present, and the outer layer can reduce the electrical resistance while preventing the conductive metal (oxide) powder from being exposed. Due to the synergistic effect of these, it is possible to obtain a developer that has a large slope in the so-called V-D curve and can stably obtain good triboelectric charging properties.

Therefore, even when applied to a developing process in which the charged potential of a photoreceptor is lowered, which has become popular in recent years, images can be stably formed many times without causing fog or toner scattering. .

In addition, since there is no conductive metal (oxide) powder in the outer layer, cracks in the outer layer, which tend to occur when conductive metal (oxide) powder is present, do not occur, and the carrier has good mechanical strength. The durability of the material is improved.

As the magnetic particles that are the core material of the coating carrier, conventionally used ones can be used, and specific examples include particles of ferrite, magnetite, and the like.

The resin constituting the inner layer of the resin coating layer (hereinafter referred to as "inner layer resin") is preferably a resin that has good adhesion to magnetic particles from the viewpoint of increasing film strength, and a conductive metal (oxide) powder. From the viewpoint of improving the dispersibility of the conductive metal (oxide) powder, those having high compatibility with the conductive metal (oxide) powder are preferred.

Specifically, styrene resins such as styrene-butadiene resins, styrene-acrylic resins, acrylic resins, etc. can be preferably used.

As the conductive metal (oxide) powder contained in the inner layer, conductive metal powder, conductive metal powder, conductive metal oxide powder, and conductive semimetal oxide powder can be used. Specifically, , silver, iron, antimony, indium, aluminum, magnesium, silicon, zirconium, bismuth, manganese,
Metal powders or metalloid powders such as tin, niobium, cadmium, molybdenum, titanium, selenium, cobalt, nickel, vanadium, tellurium, chromium, lead, tungsten, arsenic, copper, platinum, zinc, germanium, etc., and powders of their oxides, etc. can be mentioned.

Further, from the viewpoint of significantly reducing electrical resistance, conductive metal (oxide) powder whose specific resistance is 1/10' or less of the specific resistance of the inner layer resin is preferable.

In addition, from the perspective of improving dispersion stability, conductive metals (
The average particle size of the powder (oxide) is preferably 0.57/l or less.

The content ratio of conductive metal (oxide) powder is 100% of the inner layer resin.
It is preferably 1 to 200 parts by weight, especially 10 parts by weight.
~50 parts by weight is preferred. Within this range, the electrical resistance reducing effect of the conductive metal (oxide) powder is fully exhibited.

The resin constituting the outer layer of the resin coating layer (hereinafter referred to as "outer layer resin") is preferably a resin having low surface energy properties from the viewpoint of effectively preventing the adhesion of toner substances. polyethylene, tetrafluoroethylene/hexafluoroethylene copolymer, polytrifluorochloroethylene, polyvinylidene fluoride, tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer Silicone resins such as dimethyl silicone resin, methylphenyl silicone resin, fluorine-containing resins having groups formed by substituting fluorine atoms in their side chains can be used.Among the above-mentioned fluorine-containing resins, especially acrylic acid- 1, 1, 3
-) A copolymer of rehydroverfluoro n-propyl and 1,1-dihydroperfluoro-n-propyl acrylate, a 1,1-dihydropurfluoroethyl acrylate polymer, etc. are preferred.

The thickness of the inner layer is about 0.4 to 2.9n, and the thickness of the outer layer is about 0.4nm.
A good thickness is about 1 to 2.6 nm, and the total thickness of the resin coating layer is about 0.5 to 3. It is best to turn it on.

〔Example〕

Examples of the present invention will be described below along with comparative examples, but the present invention is not limited to these embodiments. In addition,
In the following, "parts" represent "parts by weight."

Example 1 A conductive metal oxide powder containing iron oxide (γ 5 g of Fe2es) ultrafine powder was dispersed using an ultrasonic homogenizer to prepare a coating liquid for the inner layer.

Using this inner layer coating liquid, an inner layer having an average thickness of 1 p was formed on the surface of spherical ferrite particles using a Subira coater to obtain a -order carrier.

Then, acrylic acid-1,1,3-)lihy)'.

A coating liquid for the outer layer was prepared by dissolving 02 g of perfluoro-n-propyl/acrylic acid-1-1-dihydroperfluoro-n-propyl copolymer (low surface energy resin) in 500 g of acetone.

Using this outer layer coating liquid, an outer layer is formed on the surface of the inner layer of the secondary carrier using a Subira coater, thereby obtaining a coated carrier C1 having a resin coating layer with a total average thickness of about 2n and an average particle size of 100n. Obtained.

Example 2 In Example 1, the coating liquid for the outer layer was changed to acrylic acid-1, acrylic acid-1,
1-dihydroperfluoroethyl polymer 02g of low surface energy resin and 50htf of acetone! A coating carrier C2 was obtained in the same manner except that the coating liquid for the outer layer was changed to the one prepared by dissolving the coating liquid.

Example 3 In Example 1, the conductive metal oxide powder was replaced with iron oxide (iron oxide) having a specific resistance of 1/105 of that of the inner layer resin and an average particle size of 0.05n.
Coating carrier C3 was obtained in the same manner except that 5 g of F es O4) ultrafine powder was used.

Example 4 In Example 2, the conductive metal oxide powder was changed to 5 g of ultrafine iron oxide (Fe304) powder with a specific resistance of 1/10' of the inner layer resin and an average particle size of 0.05μ. Coated carrier C4 was obtained in the same manner.

Example 5 The same procedure as in Example 2 was carried out except that the conductive metal oxide powder was changed to 5 g of ultrafine titanium oxide powder with a specific resistance of 1/10" of the inner layer resin and an average particle size of 0.4 nm. A coating carrier C5 was obtained.

Example 6 The same procedure as in Example 2 was carried out except that the conductive metal oxide powder was changed to 5 g of ultrafine titanium oxide powder with a specific resistance of 1/10" of the inner layer resin and an average particle size of 0.4 tIM. A coating carrier C6 was obtained.

Example 7 The same as in Example 1 except that the conductive metal oxide powder was changed to 5 g of ultrafine iron (Fe) powder with a specific resistance of 1/1022 of that of the inner layer resin and an average particle size of 0.02μ. Coated carrier C7 was obtained.

Example 8 In Example 2, the conductive metal oxide powder was made of iron (F
e) Coated carrier C8 was obtained in the same manner except that 5 g of ultrafine powder was used.

Comparative Example 1 A comparative coating carrier C1 was obtained in the same manner as in Example 1, except that the inner layer coating liquid was prepared without containing the conductive metal oxide powder.

Comparative Example 2 Acrylic acid-1,1,3-)dihydroverfluoro-n
Iron oxide (r
-Fe, ○, ) 5 g of ultrafine powder was dispersed using an ultrasonic homogenizer to prepare a coating liquid.

Using this coating liquid, a coating layer of resin with an average thickness of 2p was formed on the surface of spherical ferrite particles using a Subira coater, and a coating carrier for comparison with an average particle size of 10On and consisting of one resin coating layer was formed. Obtained C2.

Comparative Example 3 In Example 1, the coating liquid for the outer layer was changed to acrylic acid-1, acrylic acid-1,
12 g of 1,3-)dihydroperfluoro-n-propyl/acrylic acid-1,1-dihydroperfluoro-n-propyl copolymer was mixed with 500 mj of acetone! Iron oxide (γFears) ultrafine powder used for the inner layer was added to the solution dissolved in
．． Coated carrier C3 was obtained in the same manner except that the outer layer coating liquid was changed to a coating liquid for outer layer prepared by dispersing 6 g using an ultrasonic homogenizer.

Comparative Example 4 A solution of 15 g of styrene/methyl methacrylate copolymer dissolved in 300 rnl of methyl ethyl ketone was used as the inner layer coating liquid, and an inner layer with an average thickness of 1 p was formed on the surface of spherical ferrite particles using a spira coater. Obtained.

Using the outer layer coating liquid used in Comparative Example 3 on this secondary carrier, an outer layer was formed on the surface of the inner layer of the secondary carrier using a spira coater, so that the total average film thickness was approximately 2 μM.
A coated carrier C4 having a resin coating layer of 100 μm in average particle size was obtained.

Actual Photography Test> Two-component developers were prepared by mixing each of the carriers obtained in the above Examples and Comparative Examples with toner at a ratio such that the toner concentration was 4% by weight. The toner used was obtained as follows.

That is, 100 parts of styrene/methyl methacrylate/butyl acrylate copolymer resin, 10 parts of carbon black, and 3 parts of polypropylene wax were mixed, ground, crushed, and classified to obtain a powder with an average particle size of 10 μm. . Furthermore, 100 parts of this powder and 0.8 parts of hydrophobic silica fine particles
A toner was obtained by mixing the two parts with a Henschel mixer.

Using each of the above two-component developers, an electrophotographic copying machine rU-Bix 1017J (manufactured by -Nika) was used.
The potential of the black background part (image part) of the photoreceptor is -400V, and the potential of the white background part (
Non-Image Area〉Potential: 150V1 A photographic test was conducted under conditions of a bias voltage of 1,150V in the development area, and the following items were evaluated.

(2) Durability of carrier Carrier durability was determined by measuring the change in the amount of charge of the developer when a 100,000-sheet photographic test was conducted. In other words, the carrier having a smaller change in charge amount has better durability.

■Image fog This was determined by measuring the change in relative density of the white background area (non-image area) of the copied image when a 100,000-sheet photocopy test was conducted.In other words, the smaller this change is, the more likely the carrier is triboelectrically charged. and its stability is excellent.

■ Developability The judgment was made by measuring the change in relative density of the black background area (image area) of the copied image when a live copy test was conducted on 10,000 copies.In other words, the smaller the change, the better the carrier's developability and frictional electrification. Excellent properties and stability.

■Toner scattering When a 100,000-sheet photo shooting test was conducted, the state of toner scattering after the test was completed was evaluated on the following 6 scales.

That is, the less toner scatters, the better the triboelectric charging properties and stability of the carrier.

A: No scattering was observed at all.

B: Some scattering is observed around the developing device, but no scattering is observed in other areas.

C: Scattering is observed around the developing device and some scattering is also observed in other parts, but no problems are observed in both copy quality and maintainability.

D: Scattering is observed throughout the copying machine, and some ground blurring is observed due to dirt in the optical system.

E: Considerable scattering occurred throughout the copying machine, and soil blur due to contamination of the optical system was clearly observed, and copies were stained due to contamination of the conveyance section.

F: Scattered toner is discharged outside the copying machine and contaminates the surrounding area.

The results are shown in Table 1.

As can be understood from Table 1, the coated carriers of Examples 1 to 8 not only have a resin coating layer consisting of two layers, an inner layer and an outer layer, on the surface of the magnetic particles, but also have an electrically conductive layer in the inner layer. Since it contains metal (oxide) powder, it exhibits stable triboelectric chargeability and developability even when images are formed many times, allowing stable high-density images to be produced without fogging or toner scattering. The durability of the carrier is greatly improved.

On the other hand, the coating carrier of Comparative Example 1 does not contain any conductive metal (oxide) powder, so
Since the bias voltage does not act sufficiently and the developability is poor, the image density is low and the occurrence of fog is significant.

Since the coating carrier of Comparative Example 2 contains conductive gold (oxide) powder in one resin coating layer, the amount of triboelectric charge decreases significantly after 100,000 copies, resulting in a decrease in image density. The decrease is also significant, and the occurrence of fog and toner scattering is significant.

The coated carrier of Comparative Example 3 contains conductive metal (oxide) powder not only in the inner layer but also in the outer layer, and the coated carrier of Comparative Example 4 contains conductive metal (oxide) powder in the outer layer instead of the inner layer. ) powder, conductive metal (oxide) powder will be present on the surface of the resin coating layer in any coating carrier, so after 100,000 copies, the amount of triboelectric charging will be large. The image density decreases significantly, and the occurrence of fog and toner scattering is significant.

〔Effect of the invention〕

According to the invention of claim 1, the resin coating layer has a two-layer structure of an inner layer and an outer layer, and in particular, the inner layer contains conductive metal powder and/or conductive metal oxide powder. The conductive metal powder and/or conductive metal oxide powder is not exposed on the surface, so the electrical resistance reduction effect of the conductive metal powder and/or conductive metal oxide powder is stably exhibited, and many Even when images are formed over and over again, stable developability and triboelectric charging properties are exhibited, fogging and toner scattering do not occur, and the durability of the carrier is improved. The outer layer is made of conductive gold 1jK.
Since no (oxide) powder is present, cracks in the outer layer are less likely to occur, and the durability of the carrier is improved in terms of mechanical strength.

These excellent performances can be stably exhibited even when applied to a developing process where the photoreceptor is charged at a low potential, such as in a laser printer.

According to the second aspect of the invention, the low surface energy property of the outer layer effectively prevents adhesion of toner substances, so that even more excellent durability is exhibited.

Claims (2)

[Claims] (1) A coating carrier in which a resin coating layer consisting of two layers, an inner layer and an outer layer, is provided on the surface of magnetic particles, wherein the inner layer contains conductive metal powder and/or conductive metal oxide powder. A coated carrier characterized by: (2) The coated carrier according to claim 1, wherein the outer layer is made of a low surface energy resin.