JPH0380262A - Coating carrier - Google Patents

Abstract

PURPOSE:To allow a coated carrier to stably exhibit satisfactory triboelectric chargeability in environment at high temp. and humidity by forming a two- layered resin coating film consisting of inner and outer layers on the surface of each particle of a magnetic body and incorporating a surfactant into the inner layer. CONSTITUTION:A two-layered resin coating film consisting of inner and outer layers is formed on the surface of each particle of a magnetic body and a surfactant is incorporated into the inner layer. Since the surfactant is not exposed to the surface of the resin coating film, the electric resistance reducing effect of the surfactant is stably exhibited even in environment at high temp. and humidity. Even when the resulting carrier is used many times to form images, stable triboelectric chargeability is exhibited and the durability of the carrier can be improved.

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 -0 curve is required, and 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 a surfactant is contained in a resin coating layer (Japanese Unexamined Patent Publication No. 56-1).
No. 43446, No. 56-143447, No. 5
7-40265, etc.).

[Problem to be solved by the invention]

However, in coating carriers that have a resin coating layer containing a surfactant, since the surfactant is highly hygroscopic, the presence of the surfactant exposed on the surface of the resin coating layer causes the coating carrier to The tribo-electrification properties of these materials tend to change easily, and changes in the tribo-electrification properties are particularly noticeable in high-temperature, high-humidity environments.

When the triboelectric charging properties of the coating carrier change in this way, it becomes difficult to impart a suitable triboelectric charge to the toner, resulting in the inconvenience that the coating carrier must be replaced at an early stage.

The present invention has been made based on the above circumstances, and its purpose is to stably exhibit good triboelectric charging properties even when used repeatedly in high temperature and high humidity environments. 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, in which the inner layer contains a surfactant. adopt.

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 contains a surfactant, so that the surfactant is not exposed on the surface of the resin coating layer. In this way, the humidity dependence of triboelectrification is reduced, and as will be understood from the explanation of the examples below, the overall electrical resistance of the coating carrier is reduced even if the surfactant is present in the inner layer. It was completed after confirming that the effect can be obtained calmly.

As described above, according to the present invention, the electrical resistance can be reduced by the inner layer in which the surfactant is present, and the outer layer can prevent the exposure of the surfactant while obtaining preferable low surface energy characteristics. Due to the synergistic effect, it is possible to obtain a developer that has a large slope in the so-called V-0 curve and can stably obtain good triboelectric charging properties even in a high temperature and high humidity environment.

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. .

Furthermore, since no surfactant is present in the outer layer, cracks in the outer layer, which tend to occur when a surfactant is present, do not occur, and the durability of the carrier is improved in terms of mechanical strength.

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

The average particle size of the magnetic particles (the weight is determined from the viewpoint of effectively preventing carrier adhesion and enabling the formation of delicate images,
Approximately 10 to 500 p is preferable.

The resin constituting the inner layer of the resin coating layer (hereinafter referred to as "inner layer resin") is preferably one that has good adhesion to magnetic particles from the viewpoint of increasing film strength, and also enhances the dispersibility of the surfactant. From this point of view, those having high compatibility with the surfactant are preferred. Specifically, styrene resins such as styrene-butadiene resins, styrene-acrylic resins, acrylic resins, etc. can be preferably used.

As the surfactant contained in this inner layer, either an ionic surfactant or a nonionic surfactant can be used, but the effect of reducing the electrical resistance of the coating carrier is remarkable. Therefore, anionic surfactants and cationic surfactants are preferred.

Such anionic surfactants include carboxylic acid salts such as soaps having hydrophilic groups such as -COONa, OS
Hydrophilic groups such as higher alcohol sulfate ester salts, higher alkyl ether sulfate ester salts, sulfated oils, sulfated fatty acid esters, sulfate ester salts such as sulfated olefins, etc., which have a parent group such as Oy N11, etc. Sulfonic acid salts such as alkylbenzene sulfonates, alkylnaphthalene sulfonates, and paraffin sulfonates, which have a hydrophilic group such as -〇PO5Na2, phosphate ester salts such as higher alcohol phosphate ester salts, etc. can be used. can.

Further, as the cationic surfactant, primary amine salts, secondary amine salts, tertiary amine salts, quaternary ammonium salts, etc. can be used.

The content of the surfactant is preferably 0.5 to IO parts by weight, particularly preferably 1 to 8 parts by weight, based on 100 parts by weight of the inner layer resin. Within this range, the electrical resistance reducing effect of the surfactant can be fully exhibited.

The resin constituting the outer layer of the resin coating layer (hereinafter referred to as "outer layer resin") is preferably a resin with low surface energy properties from the viewpoint of effectively preventing the adhesion of toner substances.Specifically, polyvinylidene fluoride , polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, fluorine-containing resins having groups substituted with fluorine atoms in the side chains, etc. can be used. Among these fluorine-containing resins, In particular, acrylic acid-1,1,3-) dihydroperfluoro-n-propyl and acrylic acid-1,1-
Copolymers with dihydroperfluoro-n-propyl, 1,1-dihydroperfluoroethyl acrylate polymers, and the like 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.
The thickness is preferably about 1 to 2.6 nm, and the total thickness of the resin coating layer is preferably about 0.5 to 3.0 nm.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited to these embodiments.

In addition, in the following, "parts" represent "parts by weight".

Example 1 To a solution of 15 g of styrene/methyl methacrylate copolymer dissolved in 300-methyl ethyl ketone, lauric acid alcohol sulfate ester sodium salt (surfactant) I was added.
g was dispersed using a homojetter to prepare a coating liquid for the inner layer.

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

Next, 12 g of acrylic acid-1,1,3-)lihydroperfluoro-n-propyl/acrylic acid-1゜1-dihydroperfluoro-n-propyl copolymer (low surface energy resin) was added to 500 g of acetone. The mixture was dissolved to prepare a coating liquid for the outer layer.

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 forming a coated carrier CI having a resin coating layer with a total average thickness of about 2p and an average particle size of 80 μm. Obtained.

Example 2 In Example 1, the coating liquid for the outer layer was changed to acrylic acid-1, acrylic acid-1,
A coating carrier C2 was obtained in the same manner except that the outer layer coating liquid was prepared by dissolving 12 g of 1-dihydroperfluoroethyl polymer (low surface energy resin) in 500 d of acetone.

Example 3 A coating carrier C3 was obtained in the same manner as in Example 1 except that the surfactant was changed to 1 g of lauryltrimethylammonium chloride.

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 a surfactant.

Comparative Example 2 In a solution of 12 g of 1,1-dihydroperfluoroethyl acrylate polymer dissolved in 50 lrnl of acetone,
A coating solution was prepared by dispersing 1 g of lauric acid alcohol sulfate sodium salt (surfactant) using a homojetter.

Using this coating liquid, a resin coating layer with an average film thickness of 2 μm was formed on the surface of spherical ferrite particles using a Subira coater, and a coating carrier C2 for comparison with an average particle size of 8 μm and consisting of one resin coating layer was prepared. I got it.

Comparative Example 3 In Example 1, the inner layer coating liquid was changed to an inner layer coating liquid prepared in the same manner except that it did not contain a surfactant, and the outer to shoe coating liquids were changed to acrylic acid-1,1, acrylic acid-1,1, 3-) dihydroperfluoro-n-propyl/acrylic acid-1,
1-dihydroperfluoro-n-propyl copolymer 12
g of lauric acid alcohol sulfate sodium salt (surfactant) was added to a solution of 500 g of acetone dissolved in 500 g of acetone.
A comparative coating carrier C3 was obtained in the same manner except that the outer layer coating liquid was changed to 8 g by dispersing it using a homojetter.

Comparative Example 4 In Example 1, the coating liquid for the outer layer was changed to acrylic acid-1, acrylic acid-1,
To a solution of 12 g of 1,3-) dihydroperfluoro-n-propyl/1,1-dihydroperfluoro-n-propyl acrylate copolymer dissolved in 500 ml of acetone, was added lauric acid alcohol sulfate sodium salt. A comparative coating carrier C4 was obtained in the same manner except that the coating liquid for the outer layer was changed by dispersing 0.8 g of the surfactant using a homojetter.

<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 5% by weight. The toner used was obtained as follows.

That is, 100 parts of styrene/methyl methacrylate/butyl acrylate copolymer resin, carbon black 101iFIS, and 3 parts of polypropylene wax,
The mixture was mixed, ground, crushed, and classified to obtain a powder with an average particle size of 10 nm. Further, 100 parts of this powder and 0.8 parts of hydrophobic silica fine particles were mixed in a Henschel mixer to obtain a toner.

Using each of the two-component developers mentioned above, an electrophotographic copying machine R: U-Bix 1017J (manufactured by Konica ■) was used to set the black background area (image area) of the photoreceptor to a potential of -400V, and the white background area (non-image area) to a potential of -400 V. An actual photographic test was conducted under the condition that the bias voltage in the 150V1 development area was 1150V, 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 1-layer, 10,000-sheet photocopy test was conducted in a high-temperature, high-humidity environment with a temperature of 33° C. and a relative humidity of 80%. In other words, the carrier having a smaller change in charge amount has better durability.

(2) 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 10,000-layer photocopy test was conducted.

That is, the smaller this change is, the better the carrier triboelectricity and its stability are.

■ Developability: Judgment was made by measuring the change in the relative density of the black background area (image area) of the copied image when a live copy test was carried out on 10,000 copies. In other words, the smaller this change is, the better the developability of the carrier and the frictional electrification. Excellent properties and stability.

■Toner scattering When a 1-layer, 10,000-sheet live photo 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.

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 blur due to dirt in the optical system is observed.

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 this fi1 table, the coated carriers of Examples 1 to 3 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 a surfactant especially in the inner layer. Because of this, stable triboelectric chargeability and developability are exhibited even when images are formed many times in high temperature and high humidity environments.
High-density images can be stably formed without fogging or toner scattering, and the durability of the carrier is significantly improved.

On the other hand, since the coating carrier of Comparative Example 1 does not contain any surfactant, the bias voltage does not act sufficiently, resulting in low image density and significant fogging.

Since the coating carrier of Comparative Example 2 contains a surfactant in one resin coating layer, after 100,000 copies, the amount of triboelectric charge decreases significantly, the image density decreases significantly, and fogging and The occurrence of toner scattering is noticeable.

The coated carrier of Comparative Example 3 contains a surfactant in the outer layer rather than the inner layer, and the coated carrier of Comparative Example 4 contains a surfactant not only in the inner layer but also in the outer layer. Even in the coating carrier of
The amount of triboelectric charge decreases significantly, and the image density decreases significantly.
Fog and toner scattering are noticeable.

〔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 a surfactant, so that the surfactant is not exposed on the surface of the resin coating layer. Therefore, even in high temperature and high humidity environments, the electrical resistance reduction effect of the surfactant is stably exhibited.
Stable triboelectric charging properties are exhibited even when images are formed many times, and fogging and toner scattering do not occur.
The durability of the carrier is improved. Furthermore, since no surfactant is present in the outer layer, cracks in the outer layer are less likely to occur, and the durability of the carrier is improved in terms of mechanical strength as well.

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 comprising a resin coating layer consisting of two layers, an inner layer and an outer layer, on the surface of magnetic particles, wherein the inner layer contains a surfactant. (2) The coated carrier according to claim 1, wherein the outer layer is made of a low surface energy resin.