JP3036131B2 - Binder type carrier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a binder type carrier used in an image forming apparatus such as a copying machine and a printer.

[0002]

2. Description of the Related Art In order to obtain an image by an electrophotographic copying machine or a printer, first, the surface of a photoreceptor, which is an image carrier, is uniformly charged, and the surface is exposed based on an original image or output. Is drawn on the photoreceptor with light to form an electrostatic latent image. Next, the surface of the photoreceptor having the electrostatic latent image is developed (visualized) using a developing device.
The obtained toner image is transferred to a transfer material such as paper.

[0003] Developers used in such electrophotographic copying machines and the like include a two-component developer mainly composed of an insulating toner and a magnetic carrier and a one-component developer composed only of an insulating magnetic toner containing a magnetic material. There is.

[0004] Development using a two-component developer is a phenomenon system utilizing a charge generated by frictional charging between a toner and a carrier such as iron powder, and a magnetic brush of carrier particles having magnetism is used as a phenomenon sleeve with a built-in magnet. In this method, the toner is conveyed to a development area while stirring the toner formed on the surface, and the charged toner is brought into contact with and transferred to an electrostatic latent image having the opposite charge formed on the surface of the photoreceptor to perform development.

In such a two-component developing method using an iron powder carrier, the magnetic intensity between the carrier particles is generally too large, and the ears of the magnetic brush become hard. Therefore, there is a problem that carrier particles are aggregated on the sleeve and white stripes are generated in a solid developed image. Further, since the carrier has a low specific volume resistivity of 10 ⁶ Ωcm or less, when the toner concentration in the developer decreases, the charge on the electrostatic latent image carrier (photoconductor) escapes through the carrier to disturb the latent image. There is a problem that an image defect occurs or the carrier adheres to the image portion of the electrostatic latent image carrier due to charge injected from the developing sleeve to the carrier. Furthermore, if hard carrier particles adhere to the electrostatic latent image on the photoconductor, the surface of the photoconductor may be damaged when the surface of the photoconductor is cleaned by a blade cleaner or the like.

[0006] In order to solve the problems of the carrier composed of a magnetic substance such as iron powder alone and to meet the demand for higher image quality, higher speed and longer life, a magnetic powder having a small particle diameter is added to an insulating binder resin. A method has been proposed in which development is carried out using a carrier called a binder-type carrier blended in the above. For example, Japanese Patent Application Laid-Open No. Sho 54-66134 describes that the binder type carrier has effects such as less occurrence of brush stroke due to magnetic spikes and less deterioration of chargeability as compared with the case of using a ferrite carrier. . However, it is difficult to achieve both desired magnetic force and electric resistance even in a binder-type carrier. Particularly, at high humidity, the electric resistance value decreases, and image defects and poor development such as adhesion of the carrier to an image portion occur. In addition, even under a normal environment, the carrier adheres to the photoreceptor, and when an organic photoreceptor is used, the life of the photoreceptor may be reduced, and the image quality may be deteriorated due to carrier development and carrier fog.

Further, in a binder type carrier having a high magnetic force in which a magnetic powder is highly filled in a binder for high-speed development, the electric resistance of the carrier powder is not sufficiently large. For this reason, there is a problem that the carrier is easily developed, the shape is indefinite, and the fluidity is poor because of the irregular shape, and the magnetic powder is released or the particles are pulverized at the time of strong stirring due to cracks or the like generated during the pulverization during the manufacturing process.

Japanese Patent Application Laid-Open No. 56-70556 describes that such a binder-type carrier is heated at a temperature near the glass transition temperature. This technology involves heating after granulation of the binder-type carrier.However, in order to prevent agglomeration and the like, the heating temperature is limited to around the glass transition temperature. And the heating time becomes long.

Japanese Patent Application Laid-Open No. 1-262863 discloses that the impact on the toner is reduced by using a spherical carrier obtained by melting a binder type carrier composition and spray cooling. Although this technology produces a spherical binder type carrier, it is necessary to adjust the viscosity to be sprayable at the time of production, and it is not possible to substantially fill magnetic powder at a high level, and it is not possible to give sufficient shear stress. In addition, magnetic powder dispersibility is also poor.

An object of the present invention is to provide a binder type carrier having high environmental stability, high electric resistance even at high humidity, and capable of forming an excellent image.

[0011]

Means for Solving the Problems The present inventors have found that the above problems can be solved by applying an instantaneous heating treatment at an unprecedented high temperature to a binder type carrier, and completed the present invention.

That is, according to the present invention , solid particles of a binder type carrier in which magnetic powder is dispersed in a binder resin
The glass transition temperature of the under resin is + 100 ° C. or higher, and
Disperse in a hot air stream having a glass transition temperature of + 500 ° C or less.
Time when the binder type carrier is present in the hot air flow
Another object of the present invention is to provide a binder-type carrier obtained by performing an instantaneous heat treatment so that the time is less than seconds .

The types and amounts of components such as the binder resin and magnetic powder used in the present invention or the charge control agent and the colorant used as required are those conventionally known in the binder type carrier. Good.

As the binder resin (binder resin) used in the present invention, for example, a polystyrene resin,
(Meth) acrylic resin, polyolefin resin, polyamide resin, polycarbonate resin, polyether resin, polysulfone resin, polyester resin, thermoplastic resin such as epoxy resin, or urea resin,
Urethane resins, urea resins, thermosetting resins such as epoxy resins, and their copolymers, block copolymers,
Graft copolymers and polymer blends are used. Further, in order to improve thermal stability, an oligomer or a prepolymer component may be added in addition to the above-mentioned thermoplastic resin, or partially cross-linked.

The magnetic powder used in the binder type carrier of the present invention includes, for example, metals such as iron, nickel and cobalt, and metals such as zinc, ammotin, aluminum, lead, tin, bismuth, beryllium, manganese, selenium, and tungsten. Alloys and mixtures with metals such as zirconium and vanadium, mixtures with metal oxides such as iron oxide, titanium oxide and magnesium oxide, and ferromagnetic ferrites, magnetites and mixtures thereof.

The particle size of these magnetic materials is 2 μm as primary particles.
m or less, preferably 1 μm or less. If the particle size of the magnetic powder is larger than 2 μm, uniform dispersion in the binder becomes difficult due to the relationship with the particle size of the binder type carrier or toner, so that a uniform carrier cannot be obtained and the carrier particles become brittle.

When the carrier is manufactured, the mixing ratio of the binder resin and the magnetic powder is 100 to 900 parts by weight of the magnetic powder, preferably 200 to 8 parts by weight based on 100 parts by weight of the resin.
00 parts by weight. If the mixing amount of the magnetic powder is more than 900 parts by weight, the magnetic powder is formed into secondary particles, which are not uniformly dispersed, the carrier particles become brittle, and the kneading property, that is, the productivity is reduced. On the other hand, if it is less than 100 parts by weight, sufficient magnetism cannot be obtained.

In order to produce a binder-type carrier using these components, for example, the above-mentioned materials are sufficiently mixed by a mixer or the like, pulverized, and then melted and kneaded by using an extruder. After cooling the obtained kneaded material,
Finely pulverized and classified to obtain a developer having a predetermined particle size of 20 to 100 μm.

The carrier of the present invention may further contain a dispersant. As a dispersant, carbon black,
Colloidal silica, colloidal titanium, colloidal alumina and the like can be mentioned.
It is preferable to add 3% by weight.

Next, the binder-type carrier is jetted into a hot air flow to perform an instantaneous heating treatment. The peak temperature of the heating is in the range of the glass transition temperature of the binder resin of the carrier + 100 ° C. to the glass transition temperature + 500 ° C., preferably the glass transition temperature + 200 ° C. to the glass transition temperature + 400 ° C. If the heating peak temperature is lower than the glass transition temperature + 100 ° C., the desired effect cannot be obtained because the binder resin does not sufficiently melt. If the peak temperature is a high temperature exceeding the glass transition + 500 ° C., aggregation of particles occurs.

The residence time of the binder type carrier in the above-mentioned heating atmosphere is 2 seconds or less, preferably 1 second.
Seconds or less. If the residence time exceeds 2 seconds, aggregation of particles occurs. By such instantaneous heating, the binder resin of the carrier is melted into a spherical shape, the magnetic powder exposed on the surface disappears, and the fine powder is united with the carrier. In such instantaneous heating, the time during which the binder resin is in a dissolved state is extremely short, and the particles do not adhere to each other and to the walls of the heat treatment apparatus. As a result, the yield is high,
The cleaning frequency of the manufacturing apparatus can be extremely reduced.

It is preferable that the carrier is heat-treated and then rapidly cooled by a method such as introducing cooling air or cooling a pipe or a collecting tank. By such rapid cooling, adhesion to the device wall and aggregation of particles are further reduced, and the yield is improved. By performing the heat treatment of the carrier in a high-speed hot air stream as described above, the uniformity of the heating is increased, the dispersion between particles is reduced, and the production stability is improved.

In the present invention, the carrier is heated in a state of being dispersed in a hot air stream in a suspended state. The carrier particle concentration in the hot air stream used here is 1000 g / m ^3.
The following is preferred. If the dispersion concentration of the carrier becomes high, carrier particles which are heat-treated in a hot air stream in an aggregated state rather than as individual single particles are generated, which makes it difficult to perform a uniform heat treatment which is the object of the present invention, and furthermore, the particles are not treated with each other. However, it is not preferable because the solidified aggregate is formed.

In the present invention, the flow rate of the pressurized hot air stream and the blowing speed of the carrier may be appropriately selected depending on the temperature of the pressurized hot air stream, the particle size of the carrier, the particle size distribution, the specific gravity, the thermal characteristics of the binder resin, and the like. Further, cooling after the carrier heat treatment is essential. After the heat treatment, the temperature becomes higher than the glass transition temperature of the binder resin due to the residual heat during the heat treatment and the heat generated when turning in the cyclone that collects the carrier, unless the carrier is intentionally cooled. . That is, even if the particles are treated as single particles during the heat treatment, the particles are thermally aggregated without cooling after the heat treatment.

Here, cooling means introducing a carrier into an atmosphere at a temperature not higher than the glass transition temperature of the binder resin and maintaining the carrier at a temperature not higher than the glass transition temperature. Preferably, the glass transition temperature is 10
The carrier is cooled to not more than 20 ° C, more preferably not more than 20 ° C. In addition, after cooling the carrier to cool it,
A method of introducing cooling air at the above temperature, or a method of further cooling the introduction pipe with a liquid such as water and / or air is used. Further, it is desirable that the cyclone itself for collecting the carrier is kept at a temperature equal to or lower than the temperature by using cooling water or the like as needed.

Next, the heat treatment in the present invention is shown in FIG.
This will be specifically described with reference to FIG. As shown in FIG. 1, the high-temperature and high-pressure air prepared by the hot-air generator 1 is injected from the hot-air injection nozzle 6 through the introduction pipe 2. On the other hand, the carrier particles (sample) 5 are conveyed by a predetermined amount of pressurized air from the quantitative supply device 4 through the introduction pipe 2 ′, and are introduced into the hot air stream from the sample injection nozzle 7 provided around the hot air injection nozzle 6. It is injected. In this case, it is preferable to provide the sample injection nozzle 7 with a required inclination so that the jet flow of the sample injection nozzle 7 does not cross the hot air flow. Further, the number of the sample injection nozzles 7 may be one or plural,
In order to improve the dispersion of the sample in the hot air stream, it is desirable to provide a plurality of (preferably two to three) opposed sample injection nozzles 7 having the required inclination. When a plurality of sample injection nozzles are used, each of the nozzles is jetted at the required inclination toward the center of the hot air stream, and the carriers are pressed against each other by an appropriate force at the center of the hot air stream to cause the hot air to flow. Disperse well in the flow, one carrier at a time
It is preferable to perform the two heat treatments uniformly. The carrier injected in this way is instantaneously brought into contact with high-temperature hot air and is uniformly heated. Here, the term “instantaneous” refers to a time during which required carrier reforming (heating treatment) is achieved and aggregation of the carriers does not occur, which varies depending on the processing temperature and the concentration of the sample in the hot air stream. It is preferably less than seconds.

Next, the carrier that has been subjected to the instantaneous heat treatment is immediately cooled rapidly to the above-mentioned temperature by the cool air introduced from the cooling air introducing section 8. By such rapid cooling, adhesion to the device wall and aggregation of particles are eliminated, and the yield is improved. Next, the carrier is collected by the cyclone 9 through the introduction pipe 2 ″ and stored in the product tank 11. The carrier air after the collection of the carrier further passes through the bag filter 12 to remove fine powder, and then is blown. The cyclone 9 is provided with a cooling jacket 10, and the cooling water is used to maintain the carrier in the cyclone portion in the above-mentioned temperature range to prevent agglomeration of the carrier. Is appropriately performed so that the carrier can be maintained in the above temperature atmosphere, and the method and conditions are not particularly limited.

[0028]

By performing a heat treatment on the binder type carrier, the amount of magnetic powder exposed on the surface of the particles is reduced, and the magnetic powder is not released. In addition, the shape of the carrier becomes spherical by instantaneous melting, the fluidity improves, and the particle size becomes fine,
Fine powder of resin and magnetic powder generated during pulverization is removed, and cracks are eliminated in the particles. By performing the heat treatment in a high-speed air stream, the uniformity of heating is high, the dispersion between particles is reduced, and the production stability is excellent. Since the heat treatment is performed at a high temperature and instantaneously, the time during which the resin is in a molten state is extremely short, and the probability that the particles come into contact with the walls of the heat treatment device and other particles is substantially eliminated.

[0029]

Next, the present invention will be described more specifically based on examples and production examples.

[Toner Production Example (a)] Ingredients Parts by weight Styrene-n-butyl methacrylate resin (softening point: 132 ° C., glass transition temperature: 60 ° C.) 100 carbon black (MA # 8: manufactured by Mitsubishi Kasei Kogyo Co., Ltd.) 8) Low molecular weight polypropylene (Viscol 550P: manufactured by Sanyo Chemical Industry Co., Ltd.) 3 Nigrosine dye (Bontron N-01: manufactured by Orient Chemical Industry Co., Ltd.) 5 After sufficiently mixing the above materials with a ball mill, and heating to 140 ° C. 3 rolls Kneaded above. After cooling the kneaded material,
It was roughly pulverized and then finely pulverized by a jet mill. Next, air classification was performed to obtain a toner (a) having an average particle diameter of 6 μm.

[Toner Production Example (b)] The average particle diameter was obtained in exactly the same manner as in Toner Production Example a except that the nigrosine dye was changed to 5 parts by weight of a chromium complex salt E-81 (manufactured by Orient Chemical Industries, Ltd.). 6 μm of the toner (b) was obtained.

[Production Example (c) of Toner] Component Weight part Polyester resin (Tafton NE-382 manufactured by Kao Corporation) 100 Brilliant carmine 6B (C. 1.15850) 3 Zinc complex salt E-84 (Orient Chemical Industry Co., Ltd.) 5) The above materials were sufficiently mixed by a ball mill, and then kneaded on a three-roll heated to 140 ° C. After cooling the kneaded material,
Coarse pulverization was performed using a feather mill, and further finely pulverized using a jet mill. Thereafter, air classification was performed to obtain a toner (c) having an average particle size of 10 μm.

Each of the toners (a) to (c) is 100
0.3 part by weight of hydrophobic silica R-974 (manufactured by Nippon Aerosil Co., Ltd.) was post-processed using a Henschel mixer with respect to part by weight, and used for evaluation.

[Carrier Production Example (A)] Ingredients Parts by weight Polyester resin 100 (manufactured by Kao Corporation: NE-1110) Inorganic magnetic powder 700 (manufactured by Toda Kogyo Co., Ltd .: EPT-1000) Carbon black 2 (manufactured by Mitsubishi Kasei Corporation) : MA # 8) The above materials were sufficiently mixed with a Henschel mixer and then pulverized. Next, the mixture was melt-kneaded using an extruder kneader set at a cylinder portion of 180 ° C. and a cylinder head portion of 170 ° C. The kneaded material was cooled, coarsely pulverized, and then finely pulverized by a jet mill. Further, the particles were classified using an air classifier to obtain magnetic particles having an average particle size of 55 μm. Further, an instantaneous heating treatment was performed in a hot air stream at 380 ° C. for 0.6 seconds using the instantaneous heating device shown in FIG. 1 to obtain a carrier having an average particle diameter of 55 μm. The obtained carrier is referred to as carrier (A).

[Carrier Production Example (B)] In the carrier production example (A), the inorganic magnetic powder was added to the MFP.
-2 (manufactured by TDK Corporation) was changed to 600 parts by weight in the same manner to obtain magnetic particles having an average particle diameter of 60 μm. Further, an instant heating treatment was performed under the conditions shown in Table 1 to obtain a carrier.
The obtained carrier is referred to as carrier (B).

[Carrier Production Example (C)] (Comparative Production Example) A carrier having an average particle size of 55 μm was obtained in the same manner as in Carrier Production Example (A) except that no heat treatment was performed. The obtained carrier is referred to as a carrier (C).

[Carrier Production Example (D)] (Comparative Production Example) A carrier having an average particle diameter of 60 μm was obtained in the same manner as in Carrier Production Example (B) except that no heat treatment was performed. The obtained carrier is referred to as carrier (D).

[Carrier Production Example (E)] (Comparative Production Example) Carrier heat treatment was performed in the same manner as in Carrier Production Example (A) except that the production conditions were as shown in Table 1. The obtained carrier (E) was judged not to be practically usable because of a large amount of aggregates, and thus various evaluations were not performed.

[0039]

[Table 1]

(Evaluation of Physical Properties) (1) Toner Particle Size The average toner particle size was measured using a Coulter Counter TA-II.
Using a mold (manufactured by Coulter Counter), the relative weight distribution by particle size was measured using a 100 μm aperture tube.

(2) Carrier particle size The carrier particle size is determined by the Microtrac model 7995-
The average particle size was measured using 10 SRA (manufactured by Nikkiso Co., Ltd.).

(3) Charge (Q / M) and Scattering Amount: 100 parts by weight of the obtained toner is subjected to a post-treatment using 0.1 part by weight of colloidal silica R-974 (manufactured by Nippon Aerosil Co., Ltd.). The charge amount (Q / M) and the scattering amount were measured.

The amount of charge was 2 g of toner in the combinations shown in Table 2.
And the above-mentioned carrier 28g in a polyethylene bottle (50cc)
The sample was placed on a rotating base, rotated at 1,200 rpm, and measured after stirring for 10 minutes.

The measurement of the amount of toner scattering is performed by using a digital dust meter P.
It was measured by 5H2 type (manufactured by Shibata Chemical Co., Ltd.). The dust meter and the magnet roll are installed at a distance of 10 cm, and after 2 g of the developer is set on the magnet roll, the dust meter emits toner particles when the magnet is rotated at 2,000 rpm. And it was displayed as a count number per minute (cpm). The scattering amount obtained here is 300 cpm or less, Δ, 500 cpm or less, Δ 5
The case of more than 00 cpm was evaluated as x, and the evaluation was performed in three stages. Although it can be practically used at the rank of Δ or higher, Δ is desirable. Table 2 shows the measurement results of the charge amount and the scattering amount.

(4) Image evaluation (fogging on image)
Carriers were mixed at a ratio of 5/95 to prepare a two-component developer. As a developer using the toners of Examples 1 and 4 and Comparative Example 1, a copying machine EP-470Z (manufactured by Minolta Camera Co., Ltd.) was used. For Examples 2 and 5 and Comparative Example 2, a copying machine EP-570Z (Minolta Camera Co., Ltd.)
For Example 3 and Comparative Example 3, an EP-570Z fixing device improved to an oil coating method was used. Initial image formation was performed using these. Regarding the fog on the image, the toner fog on the white background image was evaluated and ranked. Although it can be practically used at the rank of Δ or higher, it is preferable that the rank is at least ○. Table 2 shows the results.

(5) Moisture resistance test After leaving each copying machine at 35 ° C. and a high humidity of 85% relative humidity for 24 hours, (i) the charge amount and (i)
i) scattering properties and (iii) image evaluation were performed. The symbols in Table 2 are the same as described above.

(6) Printing durability test Using a chart having a B / W ratio of 6%, a printing durability test was performed on up to 100,000 sheets to evaluate the charge amount, image and fog, and carrier adhesion. In the table, ○ means a practically usable area, and × means a practically problematic area. Table 2 shows the measurement results.

Carrier adhesion is performed by using the above-described copying machine for the combination of each of the toner and the carrier.
The carrier adhered on the image was visually evaluated and ranked. Although practical use is possible with a rank of △ or more, a grade of ○ or more is desirable.

[0049]

[Table 2]

[0050]

According to the present invention, carrier development becomes difficult due to the high resistance of the carrier, the image quality is improved, and the carrier is reduced in particle size and magnetic powder is filled with high speed, so that high-speed copying can be supported. .

Further, in the present invention, since the instantaneous heating treatment is used, the yield of the carrier is very high, and the frequency of cleaning the manufacturing apparatus is extremely reduced. Further, if rapid cooling is performed after the heat treatment, the adhesion to the device wall and the aggregation of particles are further reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a hot air flow surface reforming apparatus.

[Explanation of symbols]

 6 Hot air injection nozzle 7 Sample injection nozzle 8 Cooling air inlet 9 Cyclone

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-164052 (JP, A) JP-A-62-296156 (JP, A) JP-A-59-37553 (JP, A) JP-A-59-37553 125741 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/10

Claims (5)

(57) [Claims] 1. A method according to claim 1, wherein the solid particles of the binder type carrier in which the magnetic powder is dispersed in the binder resin are mixed with the glass transition temperature of the binder resin + 100 ° C. or higher and the glass transition temperature +
Dispersed in a hot air stream of 500 ° C or less,
Time of under-type carrier is less than 2 seconds
The binder-type carrier obtained by heating moment. 2. The method according to claim 1, wherein the temperature of the hot air stream is the same as that of the binder resin.
Glass transition temperature of + 200 ° C or higher and glass transition temperature
The binder type carrier according to claim 1, wherein the temperature is + 400 ° C or lower . 3. The binder-type carrier according to claim 1, which is obtained by immediately cooling the binder-type carrier subjected to the instantaneous heat treatment to a temperature equal to or lower than the glass transition temperature of the binder resin. 4. The instantaneous heating process is performed by dispersing a binder-type carrier in a hot air flow, and the dispersion concentration of the binder-type carrier in the hot air flow is 1000 g.
2. The binder-type carrier according to claim 1, which is not more than / m ³ . 5. The content of the magnetic powder in the binder type carrier is 100 to 9 parts by weight per 100 parts by weight of the binder resin.
2. The binder type carrier according to claim 1, wherein the amount is 00 parts by weight.