JPH10288869A - Method for processing electrostatic charge image developing carrier, manufacture of developer, and, electrostatic charge image developing carrier and developer manufactured by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the method for processing the electrostatic charge image developing carrier and the method for manufacturing the developer and to provide the carrier and the developer capable of obtaining sufficient chargeability in the developer composed of a mixture of the carrier and a toner and especially stabilized image density from the beginning of its use and small in toner scattering. SOLUTION: This electrostatic charge image developing carrier coated with a silicone resin is treated by subjecting only the carrier to stirring treatment before mixing the carrier with the toner to give energy in the range of the following expressions: 1×10<-7> <=E<=5×10<-4> , 1×10<-4> <=Et<=1×10<-1> , where E is an energy amount (kgm<2> s-3) to be given to each carrier grain per unit time (1 sec), and t is a treating time (sec).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a carrier for developing an electrostatic image and a method for producing a developer, and a carrier and a developer for developing an electrostatic image produced by the method.

[0002]

2. Description of the Related Art Methods of visualizing image information via an electrostatic latent image such as electrophotography are currently used in various fields.

[0003] In electrophotography, an electrostatic latent image is formed on a photoreceptor by a charging and exposing process, the electrostatic latent image is developed with an electrostatic image developer containing toner, and visualized through a transfer and fixing process. Is done. The developer used here includes a two-component developer composed of a toner and a carrier, and a one-component developer used alone with a toner such as a magnetic toner. Among these, the two-component developer has features such as good controllability because the carrier shares functions such as stirring, transporting and charging of the developer and is separated as a developer. Have been.

[0004] As a developing method, a magnetic brush method using a magnetic roll as a developer carrier is mainly used. The problem with the magnetic brush method is that the image density is not stable due to fluctuations in the charge of the developer, the background is significantly stained depending on the situation, the image is rough due to the carrier adhering to the image, and the image density unevenness due to the consumption of the carrier. There are problems such as outbreaks, and they have not yet been completely overcome. This is an obstacle to obtaining high quality images.

In order to overcome such problems, it is very important to control the charge of the carrier. In addition, in order to always maintain a high quality image, impact resistance and abrasion resistance are combined. It is necessary to consider the life of the developer. As a carrier that satisfies these required characteristics, a resin-coated carrier that is excellent in charge controllability, environmental dependency and stability over time is relatively easy to study has been actively studied.

As the resin for the resin-coated carrier, a fluorine resin, an acrylic resin, a silicone resin or the like is used. In particular, among the silicone resins, there are three-dimensionally crosslinkable resins, and the three-dimensionally cross-linking has a feature that the wear resistance of the carrier is greatly improved and the developer life is long. Furthermore, silicone resin has low surface energy,
It is difficult to generate toner spent in which toner adheres to the carrier surface, which also extends the life of the developer.

[0007] However, the silicone resin-coated carrier does not have sufficient chargeability when mixed with the toner without any particular pretreatment, so that image fogging occurs early and toner is scattered much. Further, as the continuous image is formed, the chargeability of the developer is improved, the image density is not stabilized, and image fogging occurs.

Japanese Unexamined Patent Publication (Kokai) No. 64-91144 discloses that mechanical stirring is carried out in advance until the toner charge amount Q when the toner and the carrier are mixed and stirred to such an extent that the toner and the carrier are well mixed is 1.2 Q to 2.5 Q. Has been proposed. JP-A-6-19209 proposes a developer in which the bulk density is reduced by 1.0% or more from an initial value by stirring. However, even in the present invention, sufficient chargeability cannot be obtained, image fogging occurs, and toner scattering frequently occurs.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a developer in which a carrier and a toner are mixed, whereby a sufficient chargeability is obtained, and in particular, the image density is stable from the start of use, and the toner is less scattered. An object of the present invention is to provide a method for processing an image developing carrier, a method for producing a developer, and an electrostatic image developing carrier and a developer produced by the method.

[0010]

The object of the present invention is attained by adopting one of the following constitutions.

(1) In a method of treating a carrier for developing an electrostatic charge image coated with a silicone resin, before mixing the toner and the carrier, only the carrier is agitated to give energy within the following range. A method for treating a carrier for developing an electrostatic image, which is characterized by the following.

1 × 10 ⁻⁷ ≦ E ≦ 5 × 10 ⁻⁴ 1 × 10 ⁻⁴ ≦ Et ≦ 1 × 10 ⁻¹ E: Energy amount given to one carrier per unit time (1 second) [kgm ^2] s ^-3 ] t: processing time [s] (2) In the carrier for developing an electrostatic image coated with a silicone resin, before mixing the toner and the carrier, only the carrier is subjected to a stirring treatment, and the mixing is performed within the following range. A carrier for developing an electrostatic image, which is provided with energy.

1 × 10 ⁻⁷ ≦ E ≦ 5 × 10 ⁻⁴ 1 × 10 ⁻⁴ ≦ Et ≦ 1 × 10 ⁻¹ E: Energy amount given to one carrier per unit time (1 second) [kgm ^2] s ^-3 ] t: processing time [s] (3) In the method for producing a developer comprising at least an electrostatic charge image developing carrier and a toner, before mixing with the toner using the electrostatic charge image developing carrier according to (2) And a method of mixing the carrier and the toner again by using a device for mixing the carrier and the toner, performing a stirring process on the carrier again, and then adding the toner.

(4) In a developer comprising at least a carrier for developing an electrostatic image and a toner, an apparatus for mixing the carrier and the toner before mixing with the toner using the carrier for developing an electrostatic image according to (2). A developer, wherein the carrier is again subjected to a stirring treatment, and then the toner is added to mix the carrier and the toner.

That is, the inventors of the present invention have conducted intensive studies, and as a result, in order to obtain a developer having a stable chargeability, an impact is applied only to the carrier before mixing the carrier and the toner, and the amount of impact energy to be applied is within a certain range. It has been found that it is important to complete the present invention.

If a carrier and a toner to which no shock is applied are mixed, sufficient chargeability cannot be obtained, image fogging occurs, and toner scattering frequently occurs. When a carrier (processed carrier) subjected to an impact with only the carrier is mixed with the toner, a sufficient charging property can be obtained in a short time, and the charging rise is good.

If the amount of impact energy (E) per unit time added to the carrier is 1 × 10 ⁻⁷ or less, a long processing time is required to obtain sufficient chargeability when the processing carrier and the toner are mixed, resulting in a low productivity. bad. Carriers treated with an impact energy per unit time (E) of more than 5 × 10 ⁻⁴ added to the carrier cannot be sufficiently charged because the film is peeled off, and the carrier is destroyed and the carrier adheres. The amount increases.

On the other hand, if the amount of impact energy (Et) added to the carrier is less than 1 × 10 ⁻⁴ , sufficient chargeability cannot be obtained even if the processing carrier and the toner are mixed, image fogging occurs and toner scattering occurs. Many. Carriers in which the amount of impact energy (Et) added to the carrier exceeds 1 × 10 ⁻¹ have high chargeability and cannot provide a sufficient image density.

Further, if an impact is applied after mixing the carrier and the toner, the toner is fused to the surface of the carrier, so-called toner spent, and sufficient chargeability and durability cannot be obtained.

Further, by applying an impact to the carrier again immediately before mixing the carrier and the toner, the chargeability of the carrier is stabilized.

The amount of impact energy (E) given to one carrier per unit time as referred to herein means the amount of energy consumed to activate one carrier per unit time. m × (v ₁ −v ₂ ) ² × Z / 4 (1)

M: weight of one carrier [kg] v ₁ , v ₂ : velocity before collision of two carriers (relative velocity v ₁ −v ₂ ) [m / s] Z: within unit time Number of times one carrier collides with another carrier [1 / s] Equation (1) was introduced based on the following idea.

Now, consider collision and repulsion between two carrier particles moving on the same straight line. Assuming that the weight of one carrier is m and the velocities before collision of the two carriers are v ₁ and v ₂ (relative velocity v ₁ −v ₂ ), the last motion state in the collision process is only the dynamic law Described by According to the law of conservation of momentum, u = (mv ₁ + mv ₂ ) / (m + m) = (v ₁ + v ₂ ) / 2 two carriers collide with respect to the normal direction velocity component u of the contact point at the end of the collision process. difference Ec kinetic energy it had after the collision and have have kinetic energy before the, Ec = (m + m) × u 2 / 2- (mv 1 2 + mv 2 2) / 2 = m × m × (v 1 ^{_{-v 2) 2 / (m +}} m) / 2 = m × (v 1 -v 2) 2/4 is the amount of energy spent on work by deformation of the Ec are two carriers, the energy carrier surface Is the amount of energy expended to activate.

The amount of energy E (the amount of impact energy) consumed to activate one carrier is represented by E = Ec × Z.

The number of times Z that one carrier collides with another carrier in a unit time is Z = πD ² (v ₁ −v ₂ ) × n D: carrier diameter [m] n: number of carriers in unit volume [1 / m ³ ].

The volume referred to here is not the total volume of the container but the volume that the carrier can collide with.

[0027] Thus, per unit time impact energy (E) becomes ^{E = πD 2 mn × (v} 1 -v 2) 3/4 (1 ').

Further, the total impact energy Et becomes ^{Et = πD 2 mn × (v} 1 -v 2) 3/4 × t.

The technology related to the present invention will be further described.

1. Configuration of Core Material of Carrier Specifically, Fe ₂ O ₃ and low-density elements of Periodic Tables IA and IIA, that is, elements Li and B having a density of 2.0 g / cm ³ or less,
e, containing at least one oxide of an element selected from the light metal group consisting of Mg, K, Ca, and Rb, and having these components solid-solubilized with each other to obtain appropriate magnetic properties and low specific gravity. It is something that can be done. Particularly preferred are Li ₂ O.

The low specific gravity mentioned here is 4.9 or less, preferably 4.7 or less. The measurement of the specific gravity was performed by a high-precision automatic volume meter (VM-100 manufactured by S-Tech Co., Ltd.) using a gas phase displacement method.

The light metal oxide is preferably present in a molar ratio of 5 to 50 mol%, particularly preferably 10 to 45 mol%, based on the total amount of the core material composition. When the light metal oxide content is 5 mol% or less,
Low specific gravity is not achieved.

The light metal oxide constituting the composition of the core material is:
It is not always necessary to use an oxide at the time of the raw material, and it is sufficient that the material becomes an oxide after sintering. For example, there are oxyacid salts such as calcium carbonate, magnesium carbonate, lithium carbonate and lithium sulfate, halides, and minerals mainly composed of light metal (lithium) such as lithiachite.

In some cases, a P compound has been added to improve the strength of the carrier. For example, there are yellow phosphorus, red phosphorus, white phosphorus, black phosphorus, purple phosphorus, metal phosphorus, and phosphate oxide. The P compound is preferably at most 2% by weight, particularly preferably at most 1% by weight, based on the total amount of the carrier composition.

By reducing the content of Fe ₂ O ₃ and other components other than the components of the group to 3% by weight or less, the magnetic properties and the specific gravity are not adversely affected.
The effect can be exhibited.

Other components other than Fe ₂ O ₃ and the components of the group include components for controlling the electric resistance and charge amount of the carrier, or V ₂ O ₅ , As as a sintering accelerator.
₂ O ₃ , Bi ₂ O ₃ , Sb ₂ O ₃ , PbO ₂ , CuO, B
_{2 0 3, SiO 2, CaO} , Cs, rare earth compound such as Nb, there are metal compounds such as _{Li 2 CO 3, CuSO 4,} CuCl 2, CaCO 3.

The core material of the carrier can be manufactured by a manufacturing method such as a sintering method or an atomizing method, and can be obtained by mixing and sintering two or more kinds of fine powders as necessary.

In order to accurately develop an electrostatic latent image formed on a photoreceptor by taking such a composition form, 1000
(Oe) (Oersted) magnetization intensity (σ1
k) is preferably from 35 to 100 (emu / g), and more preferably from 45 to 80 (emu / g). 35 (e
When the density is smaller than (mu / g), the magnetic binding force to the developing sleeve is small, so that carrier adhesion occurs and the magnetic brush becomes small, so that a high-density good image cannot be obtained. If it is larger than 100 (emu / g), the magnetic brush becomes hard, and the toner developed on the latent image is swept, that is, a scavenging phenomenon occurs, and a line perpendicular to the developing direction is easily lost.

The holding power is preferably 100 (Oe) or less, more preferably 50 (Oe) or less. 100
In the case of (Oe) or more, the aggregation of the carrier itself becomes strong, and the mixing property with the toner is reduced, and the carrier adheres strongly on the developing sleeve provided with the fixed magnet, so that the transportability of the developer is greatly reduced. Therefore, image unevenness may occur.

The magnetic characteristics are measured by a DC magnetization characteristics automatic recording device (3257-35, manufactured by Yokogawa Electric Corporation).

The electric resistance of the magnetic particles as the carrier core material is preferably 1 × 10 ⁷ to 1 × 10 ¹³ (Ω · cm). When it is smaller than 1 × 10 ⁷ (Ω · cm), carrier adhesion due to injection of charges from the photoreceptor surface to carrier particles is likely to occur, and when it is larger than 1 × 10 ¹³ (Ω · cm), high concentration It is difficult to obtain an image. In the measurement of electric resistance, under a normal temperature and normal humidity environment, a carrier conditioned at normal temperature and normal humidity is sandwiched between two electrodes at a thickness of about 3 (mm), a DC voltage of 100 (V) is applied, and a current value is measured. Is measured and calculated.

The average particle size of the carrier particles is from 20 to 300.
(Μm) is preferable, and more preferably 30 to 200 μm.
(Μm). If it is less than 30 (μm), carrier adhesion to the photoconductor is likely to occur. If it is larger than 300 (μm), the developing brush on the developing sleeve becomes coarse and a good image cannot be obtained. The average particle size of the carrier is a volume-based average particle size measured by a laser diffraction type particle size distribution analyzer “HELOS” (manufactured by Sympatech) equipped with a wet disperser.

2. Composition of silicone resin The layer thickness of the coating resin (also called coating resin) is 0.0
1 to 2.0 μm is preferred, and particularly 0.01 to 1.0 μm
Is preferred. When the layer thickness is larger than 2.0 μm, the image density is low and a good image cannot be obtained. Layer thickness 0.01μm
If the thickness is smaller, charges are injected from the developing sleeve, and carrier adhesion is likely to occur on the surface of the photoconductor.

The layer thickness of the coating resin was measured by breaking the carrier particles, observing the fractured surface with a scanning microscope, extracting several places at random, and taking the average value as the layer thickness.

Examples of the coating method include a coating method using a dip coating method or a spray drying method. The amount of the coating resin is preferably 0.01 to 15% by weight, particularly 0.05 to 10% by weight, based on the magnetic particles of the core material.
It is preferred that If the amount of the resin is less than 0.01% by weight, a uniform coating layer cannot be formed on the carrier surface, and if the amount exceeds 15% by weight, the coating layer becomes too thick,
Granulation of the carrier particles occurs, and the carrier particles tend to be uneven and have poor fluidity.

3. Configuration of Apparatus for Applying Impact to Carrier As a device for applying impact to the carrier, a Nauter mixer, a turbuler mixer, a V-type mixer, a W-cone type mixer, a stirring mixer having a horizontally rotating body, or the like is used. However, since a device such as a Nauta mixer has a low impact energy per unit time, it takes a long time to obtain a carrier satisfying the performance. Therefore, it is preferable to use a device having a high impact energy per unit time. As a mechanical device for achieving the present invention, a Turbula mixer, a V-type mixer, a W-cone type mixer, and a stirring mixer having a horizontally rotating body are preferable.

4. Device for Mixing Carrier and Toner As a device for mixing carrier and toner, a Nauter mixer, a V-type mixer, a W-cone type mixer, or the like is used.

5. Toner according to the present invention The toner according to the present invention contains a binder resin, a colorant, a release agent, a fluidity-imparting agent, and if necessary, a charge control agent, a magnetic substance, a cleaning aid, and the like.

The electrophotographic toner of the present invention may further contain carnauba wax, bisstearic acid amide wax, rice wax, paraffin wax or the like, if necessary.

The content of the release agent contained in the toner according to the present invention is preferably 1 to 20 parts by weight, particularly preferably 2 to 15 parts by weight, based on 100 parts by weight of the binder resin.

Colorants used in the toner according to the present invention include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, Dupont oil red, orient oil red, quinoline yellow, methylene blue chloride, Phthalocyanine blue, malachite green oxalate, lamp black, rose bengal and the like.

The fluidity-imparting agent used in the present invention includes metal oxides such as hydrophilic silica, hydrophobic silica, alumina oxide, titanium oxide, magnesium oxide, zinc oxide, chromium oxide and zirconium oxide, and barium titanate. , Magnesium titanate, calcium titanate, strontium titanate and the like.

Examples of the charge control agent used in the toner according to the present invention include a nigrosine dye, a quaternary ammonium salt compound, an alkylpyridium compound, and organic salts or complexes containing a divalent or higher valent metal. Can be.

Examples of the cleaning aid used in the toner according to the present invention include styrene-acrylic fine particles and aliphatic metal salts such as zinc stearate and aluminum stearate.

6. Toner Production Method The toner according to the present invention is produced as follows.

After dry-blending a binder resin component, a colorant, a release agent and, if necessary, a charge control agent, the respective components in the toner are made uniform using an extruder, a kneader, a kneading roll machine, a closed mixer or the like. And melt kneading so that After cooling, the mixture is finely pulverized with a jet mill, a turbo mill or the like, and after classification, the colored particles having a predetermined particle size are dry-blended with a fluidity-imparting agent and, if necessary, a cleaning aid to obtain a toner.
Alternatively, when synthesizing the binder resin by emulsion polymerization or the like, a so-called polymerization toner in which a compound necessary for the toner such as a colorant is added and the produced polymer particles are used as the coloring particles can be preferably used.

[0057]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

Example 1 (Production of carrier core) Raw materials containing Fe ₂ O ₃ and Li ₂ O were weighed and mixed by a ball mill. The obtained mixed powder was calcined and pulverized, a binder was added, and the mixture was granulated by a spray drier. Then, it was fired to obtain a desired core having a volume average particle size of 60 μm and a specific gravity of 4.6 g / cm ³ .

(Manufacture of Carrier) 100 parts by weight of a carrier core was immersed in a coating resin solution obtained by dissolving 1 part by weight of a methyl silicone resin in 50 parts by weight of xylene, and then heated to remove xylene. Heat treatment was performed at 180 ° C. for 3 hours, and then the aggregate was sieved to obtain a carrier. The film thickness was adjusted with the amount of the methyl silicone resin.

(Production of toner) 100 parts by weight of a styrene-acrylic resin were kneaded with 10 parts by weight of carbon black and 4 parts by weight of a low molecular weight polypropylene wax by a kneading machine, followed by cooling, coarse pulverization, and fine pulverization. A toner having a volume average particle diameter D ₅₀ = 8.5 μm was obtained by the machine.

(Examples 1 to 6 and Comparative Examples 1 to 6) In each of Examples and Comparative Examples, the toner concentration was 4% by weight.
Thus, each carrier and the above toner were mixed to prepare a positive charging developer.

Table 1 below shows the conditions under which energy was applied to the carrier and the amount of energy at that time, and Table 2 shows the energy subsequently applied by a mixer with toner.

[0063]

[Table 1]

[0064]

[Table 2]

(Evaluation of Developer) The chargeability was measured with a blow-off powder charge amount measuring device (TB-200, manufactured by Toshiba Chemical Corporation), and it was confirmed that all the developers were positively chargeable developers.

Using a modified electrophotographic copying machine (Konica U-BIX3135 manufactured by Konica) equipped with a negatively chargeable organic photoreceptor, the developing conditions were adjusted to a photoreceptor surface potential of 60.
0 V, developing electric field strength 9000 V / cm (DC bias potential 150 V, developing gap 5 between developing sleeve and photoconductor)
00 μm), and a 100,000 copy actual photography test (environmental conditions: temperature 25 ° C., humidity 55%) was performed, and the following items were evaluated.

Table 3 shows the results of the evaluation.

Image Density Absolute reflection densities of solid black portions of copy images and print images were measured at four points by a Macbeth densitometer (RD-918), and the average value was shown.

Fog A relative density of a copy image or print image corresponding to a white background portion (reflection density: 0.0) of the transfer paper was measured by a Sakura Densitometer (manufactured by Konica Corporation).
Less than 0.01 is a level that is not a problem, while 0.01
The above are practically problematic levels.

Carrier Attachment The presence or absence of carrier attachment was visually determined from the copy image.

Toner scattering A blank sheet is placed under the developing area of the copying machine, scattering toner is adhered, the blank sheet is fixed under the same fixing conditions as in the evaluation machine, and the density is measured by a Sakura densitometer.
The relative density corresponding to a white background portion (reflection density 0.0) of the paper was measured.
The case where the value was 01 or more and less than 0.02 was marked with “△”, and the case where it was 0.02 or more was marked with “x”.

(Productivity) Evaluation was made on the basis of the stirring time required for the production of the developer. "○" is within the practical allowable range,
"X" has a problem in practice.

[0073]

[Table 3]

As is apparent from Table 3, in Examples 1 to 6, the image density was high and stable up to 10,000 copies, and high quality images were obtained without fogging, carrier adhesion and toner scattering. Was. Also, there was almost no occurrence of spent, and sufficient durability (200,000 copies or more) was obtained as a carrier.

On the other hand, in Comparative Examples 1 and 2, sufficient chargeability was not obtained even when the processing carrier and toner were mixed, image fogging occurred, and toner scattering was large. In Comparative Example 3, the processing time is long to obtain sufficient chargeability when the processing carrier and the toner are mixed, resulting in poor productivity. In Comparative Example 4, the treatment carrier was not peeled off because the film was peeled off, so that sufficient chargeability could not be obtained, image fogging occurred, and toner scattering was large. Also,
Since the carrier is destroyed, the amount of carrier attached increases.
In Comparative Example 5, the processing carrier has high chargeability, and a sufficient image density cannot be obtained. Furthermore, in Comparative Example 6, the treated carrier was not peeled off because of the film peeling, and thus did not have sufficient durability, causing image fogging and toner scattering. In addition, since the carrier is destroyed, the amount of the carrier attached increases.

[0076]

According to the present invention, a method of treating a carrier for developing an electrostatic charge image, in which a developer obtained by mixing a carrier and a toner, has a sufficient chargeability, and in particular, has a stable image density from the start of use and little toner scattering. And a method for producing a developer, and a carrier and a developer for electrostatic image development produced by the method.

Claims (4)

[Claims] 1. A method of treating a carrier for developing an electrostatic charge image coated with a silicone resin, characterized in that, before mixing the toner and the carrier, only the carrier is agitated to give energy within the following range. Of a carrier for developing an electrostatic image. 1 × 10 ⁻⁷ ≦ E ≦ 5 × 10 ⁻⁴ 1 × 10 ⁻⁴ ≦ Et ≦ 1 × 10 ⁻¹ E: Energy amount given to one carrier per unit time (1 second) [kgm ² s ^-3] T: Processing time [s] 2. A carrier for developing an electrostatic image coated with a silicone resin, wherein the carrier is agitated only before mixing the toner and the carrier, and energy is applied within the following range. Carrier for developing electrostatic images. 1 × 10 ⁻⁷ ≦ E ≦ 5 × 10 ⁻⁴ 1 × 10 ⁻⁴ ≦ Et ≦ 1 × 10 ⁻¹ E: Energy amount given to one carrier per unit time (1 second) [kgm ² s ^-3] T: Processing time [s] 3. A method for producing a developer comprising at least a carrier for developing an electrostatic image and a toner, wherein the carrier and the toner are mixed before mixing with the toner using the carrier for developing an electrostatic image according to claim 2. A method for producing a developer, wherein the carrier is again subjected to a stirring treatment using an apparatus, and then the toner is added to mix the carrier and the toner. 4. A developer comprising at least a carrier for developing an electrostatic image and a toner, wherein an apparatus for mixing the carrier and the toner is used before mixing with the toner using the carrier for developing an electrostatic image. The carrier is again subjected to a stirring treatment, and then the toner is added to mix the carrier and the toner.