JPH0444051A - Image forming method - Google Patents

Abstract

PURPOSE:To sufficiently enhance cleanability without adversely affecting the triboelectrostatic chargeability of a magnetic toner by using not only resin fine particles and hydrophobic silica fine particles but also oxide particles of group IVA as the essential constitution components of the magnetic toner. CONSTITUTION:Not only the resin fine particles and the hydrophobic silica fine particles but also the oxide particles of the group IVA as the 3rd additive are used as the essential constitution components of the magnetic toner. The cleanability of the magnetic toner is enhanced without adversely affecting the triboelectrostatic chargeability in this way. Particularly the oxide particles of group IVA are used as the 3rd additive and since the oxide particles of group IVA have high chemical stability and are amphoteric, the triboelectro- static chargeability of the resin particles themselves is extremely low and, therefore, there is no possibility that the triboelectrostatic chargeability as the magnetic toner fluctuates substantially varies even when the oxide particles are added to the nuclear particles.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an image forming method applied to electrophotography, electrostatic recording, electrostatic photography, etc. The present invention relates to an image forming method including a step of developing a charge image.

[Conventional technology]

In an example of electrophotography, an electrostatic charge image is formed on an image carrier made of a photoconductive photoreceptor by charging and exposure.
This electrostatic charge image is developed with a developer containing toner to form a toner image, which is then transferred to a transfer material and fixed to form a visible image. On the other hand, toner remaining on the photoreceptor without being transferred to the transfer material is cleaned by a cleaning means such as a blade.

Conventionally, known toners used in such electrophotography include a one-component developer made of a magnetic toner and a two-component developer made of a toner and a carrier.

In a one-component developer made of magnetic toner, since no carrier is present, the triboelectric charging property of the magnetic toner itself has a great influence on the quality of the image.

That is, since the magnetic toner is mainly charged by friction with a developer carrier, a member that regulates the layer thickness of the magnetic toner, etc., it is necessary that the magnetic toner itself has excellent triboelectric charging properties.

However, as a technology related to the triboelectric charging properties of magnetic toner, conventionally, core particles consisting of at least a binder resin and magnetic powder are mixed with fine resin particles as a first additive and fine inorganic particles as a second additive. A technique has been proposed for forming a magnetic toner by adding and mixing (Japanese Patent Application Laid-Open No. 1-112
Publication No. 255).

[Problem to be solved by the invention]

However, in the magnetic toner disclosed in JP-A-1-112255, since the abrasive power of the first additive, the fine resin particles, is not sufficient, the inorganic fine particles, which are the second additive, adhered to the surface of the photoreceptor. In order to perform sufficient cleaning with a cleaning means such as a blade, it is necessary to press the blade or the like against the surface of the photoreceptor with a large pressing force.

If the pressing force of the blade, etc. against the surface of the photoconductor is increased in this way, the blade, etc. is usually made of an elastic material such as urethane comb, so it is likely to be deformed, and as a result, the durability of the blade, etc. will be significantly reduced. There was a problem.

The present invention was made based on the above circumstances, and
The purpose of this is to form an image that can effectively clean magnetic toner without reducing the durability of cleaning means such as a blade in an image forming method that includes a step of developing an electrostatic image with a thin magnetic toner layer. The purpose is to provide a method.

[Failure to solve the problem]

In order to achieve the above object, as a result of extensive research by the present inventors, in addition to resin fine particles and inorganic fine particles, as a component of the magnetic toner, oxide particles of Group A, in particular, are used as a third additive. By using it in combination, it is possible to increase the abrasive force of the magnetic toner on the surface of the photoreceptor without adversely affecting the triboelectric charging properties of the magnetic toner, and it is possible to improve the polishing force of the magnetic toner on the surface of the photoreceptor without increasing the pressing force of the blade etc. The present invention was completed based on the discovery that cleaning can be performed.

Therefore, in the image forming method of the present invention, a thin magnetic toner layer is formed on the surface of a developer carrier, this magnetic toner layer is supplied to a development area, and the electrostatic charge image on the photoreceptor is supplied to the development area. In an image forming method comprising a step of developing with a magnetic toner, the magnetic toner comprises core particles comprising at least a binder resin and magnetic powder, hydrophobic silica fine particles having a primary particle diameter of 5 to 20 nm, and an average particle diameter. resin fine particles with a diameter of 0.1 to 3 μm and an average particle diameter of 0.1 to 3 μm.
The present invention is characterized in that a magnetic toner containing Group IVA oxide particles of 01 to 2 μm in diameter is used.

[Effect]

In the present invention, not only fine resin particles and hydrophobic phosphor particles are used as the constituent components of the magnetic toner, but also oxide particles of the TVA group are used as a third additive, in particular, as an essential constituent of the magnetic toner. The cleaning properties of the magnetic toner can be improved without adversely affecting the triboelectric charging properties.

To explain in detail, the triboelectric charging property of the magnetic toner is particularly important for achieving good development in the process of developing with a thin magnetic toner layer. In other words, in a one-component developer using magnetic toner, since there is no chimaria, the magnetic toner is charged to a predetermined level by frictional charging with a developer carrier, etc.; May vary widely depending on additives. When the triboelectric charging properties of magnetic toner are significantly affected by additives, the magnetic toner layer supplied to the development area is particularly thin, and the proportion of magnetic toner that actually contributes to development decreases, resulting in lower image density. Problems arise in which the image quality deteriorates or fog tends to occur.

However, in the present invention, since the group IVA oxide particles are particularly used as the third additive, the group IVA oxide particles have high chemical stability and are an amphoteric substance. The triboelectric charging properties of the oxide particles themselves are extremely low, and therefore, even when the oxide particles are added to the core particles, there is no risk that the triboelectric charging properties of the magnetic toner will change substantially.

As a result, the high abrasive power of the TVA group oxide particles is fully exerted, and the lack of abrasive power due to the resin fine particles is fully compensated for, so that the pressing force of the cleaning means such as a blade against the photoconductor is not increased too much. It becomes possible to achieve sufficient leaning without getting tired.

[Specific structure of the invention]

Hereinafter, the configuration of the present invention will be specifically explained.

The magnetic toner used in the present invention has a core particle composed of at least a binder resin and a magnetic powder, and a particle size of 5 to 2Q.
hydrophobic silica fine particles (first additive) of nanometer size, resin fine particles (second additive) with an average particle diameter of 01 to 3 μm,
It consists of Group IVA oxide particles (third additive) having an average particle diameter of 0.01 to 2 μm.

It is necessary that the average particle diameter of the third additive, the oxide particles of group ①Δ, is in the range of 0.01 to 2 μm. If the average particle diameter is within this range, appropriate polishing power will be exhibited. However, when the average particle diameter is too large, the abrasive force becomes excessive, causing scratches on the photoreceptor and producing abnormal images. On the other hand, if the average particle size is too small, the polishing effect will not be exhibited.

Here, the average particle diameter of the rVA group oxide particles was obtained by observation using an electron microscope.

The amount of the TVA group oxide particles to be used is preferably in the range of 0.05 to 20% by weight of the total magnetic material.

Within this range, appropriate polishing power can be exerted and cleaning performance can be further improved. Incidentally, if the amount used is too small, sufficient polishing power will not be exhibited and it will be difficult to improve fishing performance. On the other hand, if the amount used is too large, the rVA group oxide particles may be liberated from the core particles and adhere to the developer carrier, etc., thereby deteriorating the transportability of the thin magnetic toner layer.

As a constituent material of the rVA group oxide particles, for example, T
iO2, ZrO2, H[02, etc. can be used.

The surfaces of these rVA group oxide particles may be particularly subjected to hydrophobic treatment.

The first additive, hydrophobic silica fine particles, needs to have a secondary particle diameter in the range of 5 to 20 nm. −
If the secondary particle size is within this range, the fluidity of the magnetic toner can be sufficiently increased without damaging the surface of the photoreceptor. However, if the secondary particle size is too large, the surface of the photoreceptor will be excessively polished and damaged, and the magnetic toner will be embedded in this damaged area and will not be cleaned.
When forming the next image, black spots occur in the image.

On the other hand, if the secondary particle size is too small, sufficient fluidity will not be exhibited.

Here, the primary particle diameter of the hydrophobic phosphoric acid fine particles was obtained by observation using an electron microscope.

The amount of the hydrophobic silica fine particles used is preferably in the range of 0.01 to 1.0% by weight based on the total weight of the magnetic toner.

Within this range, the fluidity of the magnetic toner can be sufficiently increased without causing separation of the hydrophobic phosphor particles from the core particles. Note that if the amount used is too small, sufficient fluidity will not be exhibited, resulting in a decrease in developability in development with a thin magnetic toner layer, and as a result, the image density will tend to decrease.

On the other hand, if the amount used is too large, the hydrophobic silica fine particles may be released from the core particles and adhere to a developer carrier, etc., thereby deteriorating the transportability of the thin magnetic toner layer.

The first additive, hydrophobic silica particles, is obtained by changing hydrophilic groups such as ○H groups present on the surface of silica particles into hydrophobic groups using a hydrophobizing agent. Dimethylsilane, octylsilane, etc. can be used.

Commercially available hydrophobic Nlica fine particles, which are the first additive, include R-972, R-974, and R-8 manufactured by Aeronle Co., Ltd.
12, R-805, etc.

The resin fine particles that are the second additive have a mean particle size of 0.
It is necessary that the thickness be in the range of 1 to 3 μm. If the average particle diameter is within this range, the cleaning properties of the magnetic 1.sulfur can be sufficiently improved.

However, when the average particle diameter is too large, the cleaning performance tends to worsen. On the other hand, if the average particle diameter is too small, sufficient leaning properties will not be exhibited.

Here, the average particle diameter of the resin fine particles is SYMPATEC
Laser diffraction particle size distribution analyzer rHELO3-
It is the average particle size on a volume basis as measured by cOMPETITION/3J.

The amount of resin fine particles used as the second additive is preferably in the range of 0.05 to 2.0% by weight based on the total weight of the magnetic toner. Within this range, the cleaning properties of the magnetic toner can be sufficiently improved. Note that if the amount used is too small, sufficient leaning properties will not be exhibited and image stains will easily occur.

On the other hand, if the amount used is too large, the fine resin particles may be separated from the core particles and adhere to the developer carrier, etc., resulting in poor conveyance of the thin magnetic toner layer.

As the resin constituting the resin fine particles that are the second additive, vinyl polymers such as polymethyl methacrylate, polystyrene, polyvinylidene fluoride, and polyethylene, and condensation polymers such as polyester, polyurethane, and benzoguanamine can be used. I'll come.

Core particles, which are the main particles of the magnetic toner, are composed of at least a binder resin and magnetic powder. Further, internal additives such as a charge control agent and a fixability improving agent may be contained as necessary.

The binder resin constituting the core particles is not particularly limited, and resins conventionally used as binder resins for toners can be used.

Specifically, styrene resin, acrylic resin, styrene
Examples include acrylic copolymer resins, polyester resins, epoxy/resins, polyurethane resins, polyimide resins, cellulose resins, and polyether resins.

The magnetic powders that make up the core particles include various types of ferrite,
An alloy or compound of iron such as macnetite or hematite, zinc, cobalt, nickel, manganese, etc. can be used. The average particle diameter of the magnetic powder is preferably 1 μm or less, particularly preferably 0.5 μm or less. Moreover, the blending amount of the magnetic powder is preferably in the range of 20 to 70% by weight of the entire core particle.

As the charge control agent, for example, nigrone dyes, metal-containing complex dyes, etc. can be used.

As the fixing property improving agent, for example, polyolefins such as low molecular weight polypropylene and polyethylene can be used.

As a method for producing the core particles, a crushing granulation method, a polymerization granulation method, etc. can be applied.

In the pulverization granulation method, binder resin, magnetic powder, and other toner components used as necessary are mixed, melt-kneaded, pulverized, and classified to obtain a predetermined average particle size (1 to 30 μm).
This is a method for producing core particles of about 1.0 m).

In the polymerization granulation method, magnetic powder and other toner components used as necessary are present in the monomers constituting the binder resin, and a polymerization reaction is carried out by a suspension polymerization method, an emulsion polymerization method, etc. This is a method for producing core particles with an average particle size (about 1 to 30 μm).

The magnetic toner used in the present invention usually includes core particles, hydrophobic silica fine particles as a first additive, resin fine particles as a second additive, and group rVA group as a third additive. These three types of external additives are electrostatically attached to the surface of the core particles by adding and mixing them with oxide particles.

In the image forming method of the present invention, a thin magnetic toner layer is formed on the surface of a developer carrier using the magnetic toner obtained as described above, and this magnetic toner layer is supplied to a development area. In this development area, an image is formed through a step of developing the electrostatic charge image on the image carrier with magnetic toner.

Here, the term "the magnetic toner layer is thin" refers to a state in which the thickness of the magnetic toner layer supported on the developer carrier and supplied to the development area is 150 μm or less. In such a thin magnetic toner layer, the number of magnetic toner particles arranged in the thickness direction is approximately 15 or less.

Examples of means for forming a thin magnetic toner layer include arranging the edges of blades facing each other on the surface of the developer carrier with a gap of 100 μm or less in between, and using urethane comb, stainless steel, etc. It is possible to employ means such as placing one surface of an elastic plate in pressure contact with each other, or placing rod-like bodies made of stainless steel or the like facing each other on the surface of the developer carrier.

FIG. 1 schematically shows a developing section of a semiconductor laser printer that can be used in the image forming method of the present invention.
2 is a developing sleeve (developer carrier), 3 is a cylindrical rod-shaped thin layer forming member, 4 is a toner agitator, 15 is a toner pumper, and 6 is a toner cartridge.

The thin layer forming member 3 is made of an elastic material such as stainless steel, and is disposed opposite to the developing sleeve 3 with a slight gap therebetween.

In this device, magnetic toner present in a toner hopper 5 is agitated by a toner agitator 4 and conveyed to a developing sleeve 2. The thickness of the magnetic toner carried by magnetic force on the surface of the developing sleeve 2 is regulated by the thin layer forming member 3 to form a thin magnetic toner layer. triboelectrically charged. This magnetic toner layer is supplied to a development region where the organic photoreceptor 1 and the development sleeve 2 face each other, and development is performed.

The minimum value of the gap between the organic photoreceptor 1 and the developing sleeve 2 in the developing area, that is, the developing gap Dsd is 50 to 300.
The thickness of the magnetic toner layer, whose thickness is regulated by the thin layer forming member 3, is 150 μm or less.

It is preferable to apply a developing bias consisting of a DC component and an AC component to the developing sleeve 2.

Further, in the image forming method of the present invention, as the cleaning means, a means for disposing a cleaning blade in pressure contact with the surface of the photoreceptor can be particularly preferably employed.

As a constituent material of the cleaning blade, an elastic body such as urethane rubber can be preferably used.

Pressure force of the cleaning blade against the surface of the photoreceptor (
The linear pressure) is preferably in the range of 10 to 35 g/cm. If this pressing force causes damage, the durability of the IJ-ning plate tends to decrease. Furthermore, if the pressing force of the leaning blade is too small, it will be difficult to achieve sufficient cleaning of the magnetic toner.

〔Example〕

Examples of the present invention will be described below along with comparative examples, but the embodiments of the present invention are not limited thereto. In addition, in the following, "part" represents "part by weight".

Core particle 1> Styrene/acrylic copolymer resin 65 parts Magnetic powder
35 copies (EPT-100
02 manufactured by Toda Kogyo Co., Ltd.) Charge control agent 1 part (Bontron E-82, manufactured by Orient Chemical Industry Co., Ltd.) Polypropylene 3 parts (Viscol 660P
, manufactured by Sanyo Chemical Industries, Ltd.) were mixed, mixed, crushed, and classified to obtain core particles 1 having a volume average particle diameter of 11 μm.

<Nuclear particle 2> Polyester resin 65 parts Magnetic powder
35 copies (EPT-
1000, manufactured by Toda Kogyo Co., Ltd.) Charge control agent
1 part (Bontron 5-34. Manufactured by Orient Chemical Industry Co., Ltd.) Polypropylene
Core particles 2 were obtained by treating 3 parts or more of the material (Viscol 660P, manufactured by Sanyo Chemical Industries, Ltd.) in the same manner as in the case of core particles 1.

<Core particle 3> Styrene/acrylic copolymer resin 65 parts Magnetic powder
35 parts (Mapico Black B L-100, manufactured by Titan Kogyo Co., Ltd.) Charge control agent
1 part (spiron black TRH,
(manufactured by Sakudogaya Chemical Industry Co., Ltd.) or more than 3 parts of polypropylene (Viscol 550P, manufactured by Sanyo Chemical Industries, Ltd.)
Nuclear particles 3 were obtained by processing in the same manner as nuclear particles 1.

<Nuclear particle 4> Polyester resin 65 parts Magnetic powder
35 copies (MAT-305
HD, manufactured by Toda Kogyo Co., Ltd.) Charge control agent
1 part (Bontron S-34, manufactured by Orient Chemical Industry Co., Ltd.) Polypropylene
Core particles 4 were obtained by treating 3 parts or more of the material (Viscol 660P, manufactured by Sanyo Chemical Industries, Ltd.) in the same manner as in the case of core particles 1.

<Manufacture of magnetic toner> External additives were added to the core particles according to the formulation shown in Table 1 below, and these were mixed using a turbular mixer to produce magnetic toners 1 to 9 for the present invention and magnetic toner 1 for comparison.
0 to 12 were manufactured.

<Image Formation Test> Using magnetic toners 1 to 9 for the present invention and magnetic toners 10 to 12 for comparison, a development sleeve (development A thin magnetic toner layer is formed on the surface of an organic photoreceptor (image carrier), and this magnetic toner layer is supplied to a development area, where the electrostatic charge image on the organic photoreceptor (image carrier) is developed with the magnetic toner. A test was conducted to form an image under low temperature and low humidity environmental conditions of 10° C. and 20% relative humidity, and the cleaning performance and image density were evaluated. The results are shown in Table 2 below.

The developing section of rLP-3015J has a structure similar to that shown in FIG. 1, and the thin layer forming member is a cylindrical bar made of stainless steel, and the thickness of the magnetic toner layer is reduced by this thin layer forming member to approximately It is regulated to about 150 μm. The development gap Dsd in the development area is 100 μm.

In addition, this printer has a structure that uses a reversal development method, and the development sleeve has a DC component of 300 V,
A developing bias with an AC component of -400 to -200 Vp-p is applied. And the surface potential of the organic photoreceptor is
The unexposed area is 1580V, and the exposed area is 80V.

In the cleaning section of this printer, a cleaning blade made of urethane comb is placed in pressure contact with the surface of the organic photoreceptor.

The cleaning performance was evaluated by forming an image while changing the pressing force (linear pressure) of the cleaning blade against the organic photoreceptor, and measuring the minimum pressing force when sufficient leaning was achieved.

Further, image density was evaluated by measuring reflection density.

As a result of the tests shown in Table 2 and above, when magnetic toners 1 to 9 of the present invention are used, sufficient leaning can be achieved with a small pressing force of the cleaning blade.
Moreover, it is clear that an image with sufficiently high image density can be obtained. The reason why the image density is sufficiently high even though the magnetic toner layer supplied to the development area is thin is because the magnetic toner has Group IVA oxide particles added as a third additive. This is because the triboelectrification properties of the particles are not substantially affected.

On the other hand, when Comparative Magnetic Toner 10 is used, since there are no resin particles as the second additive, cleaning cannot be achieved without increasing the pressing force of the cleaning blade. First, it is clear that the durability of the cleaning blade decreases.

It is clear that when Comparative Magnetic Toner 11 was used, an image with high image density could not be obtained because the third additive was CuO rather than Group IVA oxide particles. This is because the addition of CuO deteriorates the triboelectric charging properties of the magnetic toner.

When Comparative Magnetic Toner 12 was used, since the third additive, rVA group oxide particles, was not present, cleaning could be achieved without increasing the pressing force of the cleaning blade. First, it is clear that the durability of the cleaning blade decreases.

〔Effect of the invention〕

As explained above, in the present invention, not only fine resin particles and fine hydrophobic silica particles are used as constituent components of the magnetic toner, but also oxide particles of Group IVA are used as a third additive, in particular, as an essential constituent. As a result, the cleaning performance of the magnetic toner can be sufficiently improved without adversely affecting the triboelectric charging properties of the magnetic toner, and therefore, high-density images can be formed with a thin magnetic toner layer without cleaning defects. can do.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing a developing section of a printer that can be used in the image forming method of the present invention. 1...Organic photoreceptor 2...Developing sleeve 3.
...Thin layer forming member 4...Toner agitator-5
... Toner hopper 6 ... Toner cartridge

Claims (1)

[Scope of Claims] A thin magnetic toner layer is formed on the surface of a developer carrier, this magnetic toner layer is supplied to a development area, and the electrostatic charge image on the image carrier is formed in this development area by the magnetic toner. In an image forming method including a step of developing, the magnetic toner includes core particles comprising at least a binder resin and magnetic powder, hydrophobic silica fine particles having a primary particle size of 5 to 20 nm, and an average particle size of 0.1 to 20 nm. An image forming method characterized by using a magnetic toner containing fine resin particles of 3 μm and Group IVA oxide particles having an average particle diameter of 0.01 to 2 μm.