JPH0511508A - Electrophotographic carrier - Google Patents

Abstract

PURPOSE:To cure the uncured components in the resin of the coated carrier and to prevent the contamination of a photosensitive body and the flocculation a developer at the time of agitation by subjecting the carrier to an instantaneous heat treatment at an extremely high temp. CONSTITUTION:The coated carrier having a carrier core material and a coating layer essentially consisting of a thermosetting resin coating the surface of the carrier core material is subjected to the instantaneous heating treatment under the conditions under which the peak temp. is the curing temp. of the thermosetting resin +50 deg.C or above and the curing temp. +50 deg.C or below. Namely, the high-temp. and high- pressure air prepd. in a hot wind generator 1 is injected by a hot wind injection nozzle 6 through an introducing pipe 2. On the other hand, carrier particles are transported through an introducing pipe 2' by the prescribed amt. of the pressurized air from a fixed rate supplying device 4 and are injected into the hot wind current from a sample injection nozzle 7 provided around the hot wind injection nozzle 6. The carrier particles subjected to the instantaneous heat treatment are rapidly cooled by the cold wind immediately introduced from a cooling wind introducing part 8 and are captured by a cyclone 9. These particles store in a product tank 11. The instantaneous heating treatment time is >=2 seconds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic carrier having excellent durability and spent resistance which is used for a two-component type electrostatic image developer for electrophotographic copying machines and printers.

[0002]

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

In such a developing device, a one-component developer composed of only toner or a two-component developer composed of toner and a magnetic carrier is used to uniformly slide the surface of the photosensitive member so that the surface of the photosensitive member is kept static. Make the latent image visible.
Of such developers, the toner usually comprises a thermoplastic resin, a colorant, a charge control agent, a fluidizing agent and the like. The two-component developer is composed of toner and a magnetic carrier such as ferrite. In recent years, electrophotography is required to have high image quality and high speed, and the demand for longer life is increasing.
On the other hand, regarding the carrier, by coating the surface of the carrier with a resin, the fusion of the toner on the surface of the carrier is prevented, and the durability is improved. In particular, when a thermosetting resin is used as the coating material, the coating layer is unlikely to peel off from the carrier core material during stirring in the developing machine, and a robust carrier is obtained.

However, in order to cure the thermosetting resin, it is necessary to bake the coated carrier in an oven or the like. At this time, the carrier easily aggregates, and it is extremely difficult to completely cure the thermosetting resin component. Is. The residual uncured component in such a coated carrier is
Contamination of the photoconductor occurs, the toner is fused to the carrier at the time of stirring, which causes the phenomenon agent to agglomerate, and also leads to a decrease in the charge of the carrier.

In order to completely cure such uncured components, it is necessary to perform treatment at a high temperature for a long time using a fluidized bed or the like. However, even with such a treatment, the uncured component cannot be completely cured. On the other hand, when the resin-coated carrier is treated under the condition where the complete curing is possible, agglomeration of the carriers occurs. Further, when the aggregates of the carriers are crushed and used, the thermosetting resin is partly peeled off, and the effect of the resin coating on the carrier is lost.

Conventionally, as a heat treatment for a carrier, there is a heat treatment for a binder type carrier at a temperature near the glass transition temperature (Japanese Patent Laid-Open No. 56-70556). This technique heats the carrier, but limits the heating temperature to a relatively low temperature near the glass transition temperature in order to prevent aggregation.

An object of the present invention is to cure the uncured component in the resin of the coated carrier without causing the carrier to agglomerate and prevent the contamination of the photoreceptor and the agglomeration of the developer during stirring.

[0008]

Means for Solving the Problems The present inventors have made various studies on the above-mentioned problems and found that such problems are caused by subjecting a carrier coated with a thermosetting resin to instantaneous heat treatment at an extremely high temperature. The inventors have completed the present invention knowing that they can be solved.

The present invention provides a coated carrier having a carrier core material and a coating layer containing a thermosetting resin as a main component for coating the surface of the carrier core material, the peak temperature of which is higher than the curing temperature of the thermosetting resin + 50 ° C. And the curing temperature + 500 ° C
The present invention provides an electrophotographic carrier obtained by instantaneous heat treatment under the following conditions.

Ferromagnetic materials such as iron and ferrite carriers are used as the core material of the coated carrier obtained in the present invention. Examples of such carrier materials include alloys or mixtures of metals such as iron, nickel and cobalt with metals such as zinc, antimony, aluminum, lead, tin, bismuth, beryllium, manganese, selenium, tungsten, zirconium, vanadium and vanadium, and oxidation. Materials, metal oxides such as titanium oxide and magnesium oxide, chromium nitride,
Examples thereof include nitrides such as vanadium nitride, mixtures with carbides such as silicon carbide and tungsten carbide, ferromagnetic ferrites, and mixtures thereof.

Thermosetting resins for coating these core materials include polycarbonate resin, epoxy resin, urea resin,
Examples thereof include silicone resin, acrylic resin, melamine resin, styrene (meth) acrylic resin and the like.

Further, various organic and / or inorganic materials may be dispersed and / or dissolved for coating in order to improve chargeability and other various developer characteristics, and these materials may be fixed on the surface of the coated carrier. You may use what was done. As a device for carrying out carrier coating and immobilization treatment of various materials, various coating devices such as a spray dryer and a rolling flow tank, and the above-mentioned various surface modifying devices are used.

The particle diameter of the carrier core material is preferably 20 to 80 μm. Further, the coating layer of the thermosetting resin is preferably 1/10 or less of the particle diameter of the core material. It is necessary that the coat layer uniformly covers the carrier surface and does not peel off during mixing and stirring. The coating layer thickness is 1 of the carrier core material
When it is thicker than / 10, it is difficult to form a uniform coat layer, and it is necessary to repeatedly coat a plurality of times, which is difficult in terms of technology and productivity. Further, if the coat layer is thickened, the holding power on the sleeve is reduced and carrier development occurs, which causes a problem as image noise.

The average particle size of the carrier is generally 20.
Although the thickness is up to 200 μm, it is appropriately set according to the developing method and the like. Generally, if the carrier particle size is smaller than 20 μm,
Development of the carrier itself occurs, and if it is larger than 200 μm, problems such as coarse image texture occur.

The coated carrier is jetted into the air stream for instantaneous heat treatment. The peak temperature of heating is the curing temperature of the thermosetting resin coating the carrier + 50 ° C to the curing temperature +500.
The temperature is in the range of 0 ° C, and preferably + 100 ° C to + 400 ° C. If the curing temperature is lower than this, the desired effect will not be sufficiently obtained, and if it is too high, a problem will occur in which carriers are aggregated.

The time during which the carrier is present in the atmosphere above the curing temperature is 2 seconds or less, preferably 1 second or less.
If the residence time exceeds 2 seconds, the carriers are likely to aggregate with each other, the production yield is deteriorated, and the carrier performance is easily deteriorated.

Decomposition of the coating layer by such instantaneous heating,
The uncured component remaining in the coating resin layer of the carrier is completely removed without causing the carrier to aggregate. By carrying out such instantaneous heating, the time during which the resin is exposed to a high temperature is extremely short, and particles do not adhere to each other and to the vessel wall of the heat treatment apparatus. As a result, the yield is high and the cleaning frequency of the manufacturing apparatus is extremely low.

After the heat treatment, the carrier is preferably rapidly cooled by introducing cooling air or cooling the pipe and the collecting tank from the outside. By such rapid cooling, adhesion to the device wall and particle agglomeration are reduced and the yield is improved. Further, by heating the carrier in a high-speed air stream, the heating uniformity is improved, the variation between particles is reduced, and the manufacturing stability is excellent.

In the present invention, the carrier is dispersed in a hot air stream in a suspended state and heat-treated. The particle concentration of the dispersed air flow used here is preferably 1000 g / m ³ or less. If the dispersion concentration of the carrier becomes high, particles that are heat-treated in an agglomerated state will not be generated as individual particles in the hot air stream, but it will be difficult to perform the uniform heat treatment for the purpose of the present invention and particles Becomes a nodule and becomes a problem.

The flow rate of the pressurized hot air stream and the blowing rate of the carrier in the present invention are the temperature of the pressurized hot air stream, the particle size of the carrier, the particle size distribution, the specific gravity and the thermal characteristics of the coated thermosetting resin, It may be appropriately selected depending on the film thickness and the like. In addition, cooling after heat treatment of carrier particles is essential. If you do not intentionally cool after the heat treatment, due to the residual heat during heat treatment,
Alternatively, the carrier particles are thermally aggregated by the heat generated when the carrier particles are swirled in the cyclone.
That is, although the particles are treated as single particles during the heat treatment, they are thermally aggregated unless cooling is performed after the heat treatment. Here, cooling means introducing carrier particles into an atmosphere having a temperature not higher than the curing temperature of a thermosetting resin used as a carrier coating material, and maintaining the carrier particles at a temperature not higher than the curing temperature. Further, in order to cool the carrier particles, a method of introducing a cooling air of the above temperature after heat treatment, or a method of further cooling the carrier introducing pipe with a liquid such as water and / or air is used. Further, it is desirable that the cyclone itself, which collects the carrier particles if necessary, is also kept at the temperature or lower by using cooling water or the like.

Next, the heat treatment in the present invention 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, carrier particles (sample) are conveyed from the constant quantity feeder 4 by a predetermined amount of pressurized air through the introduction pipe 2 ′, and are jetted into the hot air stream from the sample jet nozzle 7 provided around the hot air jet nozzle 6. It 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 more, but in order to improve the dispersibility of the sample in the hot air flow, a plurality of the nozzles facing each other with the required inclination (preferably It is desirable to provide 2 to 3 sample injection nozzles 7. When using multiple sample injection nozzles, each jets toward the center of the hot air stream at the required inclination, and the carrier particles collide with each other with an appropriate force at the center of the hot air stream, so that the carrier particles are heated. It is preferable that the carrier particles are sufficiently dispersed in the flow and the carrier particles are heat-treated uniformly. The carrier particles thus jetted are brought into contact with the hot air of high temperature instantaneously and uniformly heat-treated. Here, the term "instantaneous" refers to the time during which the required modification of carrier particles (heat treatment) is achieved and the agglomeration of carrier particles does not occur, depending on the treatment temperature and the concentration of the sample in the hot air flow. It is preferably 2 seconds or less.

Next, the carrier particles subjected to the instant heat treatment are immediately cooled rapidly by the cold air introduced from the cooling air introduction section 8. Due to such rapid cooling, adhesion to the device wall and aggregation of particles are eliminated, and the yield is also improved. Next, the carrier particles are collected by the cyclone 9 through the introduction pipe 2 ″ and stored in the product tank 11. The carrier air after the carrier particles are collected further passes through the bag filter 12 to remove fine powder. After that, the cyclone 9 is released into the atmosphere through the blower 13. The cyclone 9 is provided with a cooling jacket 10 to keep the carrier particles in the cyclone in the above temperature range by cooling water to prevent the carrier particles from aggregating.
The cooling is appropriately performed so that the carrier particles can be held in the above temperature atmosphere, and the method and conditions thereof are not particularly limited.

The toner used with the carrier of the present invention may be a conventionally known one, and any conventionally known one may be used as the binder resin, the charge control agent, the colorant and the like.

[0024]

The uncured component in the thermosetting resin layer is completely cured by instantaneously heating the carrier coated with the thermosetting resin at a high temperature.

[0025]

EXAMPLES Next, the present invention will be described more specifically based on Examples and Production Examples.

[Toner Production Example 1] Component weight part Styrene-n-butylmethacrylate 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 (Viscor 550P: Sanyo Kasei Co., Ltd.) 3 Nigrosine dye (Bontron N-01: Orient Chemical Co., Ltd.) 5 After thoroughly mixing the above materials with a ball mill, on a three-roll heated to 140 ° C. Kneaded After leaving the kneaded mixture to cool,
It was roughly crushed and then finely crushed with a jet mill. Next, air classification was performed to obtain a toner a having an average particle size of 6 μm.

[Toner Production Example 2] Except that the nigrosine dye was changed to 5 parts by weight of the chromium complex salt E-81 (manufactured by Orient Chemical Co., Ltd.) in Toner Production Example 1, the same method was used, and the average particle size was 6 μm. Toner b was obtained.

[Toner Production Example 3] In the toner production example 1, the Nigrosine dye was used as Eisenspirone Black T.
A toner c having an average particle size of 7 μm was obtained by the same method except that the amount of RH (manufactured by Hodogaya Chemical Co., Ltd.) was changed to 5 parts by weight.

The above toners a to c are toner 1 respectively.
For 100 parts by weight, 0.3 part by weight of hydrophobic silica R-974 (manufactured by Nippon Aerogel Co., Ltd.) was post-treated with a Henschel mixer and used for evaluation.

[Production Example 1 of carrier] Component weight part Silicone resin (KR-251; manufactured by Shin-Etsu Chemical Co., Ltd.) 100 Aminosilane (H ₂ NCH ₂ CH ₂ CH ₂ Si (OCH ₃ ) ₃ ) 1 Toluene 100 The above mixture (Curing temperature 30 ° C.) was stirred with a homomixer for 20 minutes to prepare a coating layer forming liquid. This solution was applied to the surface of ferrite particles F-300 (manufactured by Powder Tech Co., Ltd.) having an average particle size of 50 μm using a fluidized bed type coating apparatus, the solvent was evaporated, and the mixture was baked at 150 ° C. for 2 hours to obtain an average film. A coated carrier having a thickness of 1.0 μm was obtained.

Next, the obtained coated carrier was subjected to instantaneous heat treatment under the conditions shown in Table 1 using the apparatus shown in FIG. 1 to obtain a carrier having an average particle size of 52 μm. The carrier obtained here is called carrier A.

[Production Example 2 of carrier] Component by weight Epoxy resin (Epiclon 1050-75T; Dainippon 100 Ink Chemical Industry Co., Ltd., epoxy equivalent; 450-500) Curing agent B-101 (aliphatic polyamine type) Epiclon curing agent) 3 Toluene 1,000 A carrier having an average particle size of 51 μm was obtained from the above material (curing temperature 100 ° C.) in the same manner as in Carrier Production Example 1. The carrier obtained here is called carrier B.

[Production Example 3 of carrier] Component parts by weight Butylurea resin (Beckroll G-1850; Dainippon 20 Ink Chemical Industry Co., Ltd.) Alkyd resin (Beckosol J-579; Dainippon 80 Ink Chemical Industry Co., Ltd.) Amino resin curing accelerator 1 (P-198; manufactured by Dainippon Ink and Chemicals, Inc.) Toluene 1,000 Using the above materials (curing temperature 150 ° C.), the average particle size was 52 μm in the same manner as in Production Example 1 of the carrier. Got a career. The carrier obtained here is called carrier C.

[Manufacturing Example 4 of Carrier] The same procedure as in Manufacturing Example 1 of Carrier except that F-250HR (average particle size 50 μm, manufactured by Powder Tech Co.) was used as the ferrite particles, the average particle size was 52 μm. Got a career. The carrier obtained here is called carrier D.

[Manufacturing Examples 5 and 6 of Carrier] Carriers having an average particle diameter of 52 μm and an average particle diameter of 51 μm were obtained in the same manner as in Manufacturing Examples 1 and 2 of Carrier except that the instantaneous heat treatment was not performed. The carriers obtained here are referred to as carrier E and carrier F, respectively.

[Manufacturing Example 7 of Carrier] A carrier G was manufactured by the same composition and method as in Manufacturing Example 1 of Carrier except that the firing conditions were 300 ° C. and 5 hours. The obtained carrier could not be used because of its large amount of aggregate.

[Production Example 8 of Carrier] Production Example 1 of Carrier
A carrier was manufactured by the same method except that the heat treatment conditions in Table 1 were changed as shown in Table 1. The obtained carrier (Carrier H) was determined to be practically unusable because aggregates were generated, so various evaluations were not performed.

[0038]

[Table 1]

[0039]Evaluation of the physical properties   (1) Toner particle size Toner average particle size is measured by Coulter Counter TA-II
Type (manufactured by Coulter Counter, Inc.)
The relative weight distribution by particle size was measured with a patcher tube.

(2) Carrier particle size The carrier particle size is Microtrack model 7995-
It measured using 10 SRA (made by Nikkiso Co., Ltd.), and calculated | required the average particle diameter.

(3) Charge amount (Q / M) and scattering amount The charge amount is the combination shown in Table 2 and 2 g of toner and 28 g of the carrier are put in a polyethylene bottle (50 cc) and placed on a rotary mount, 1,200 rpm. It was rotated at 10 minutes and stirred for 10 minutes before measurement.

The amount of toner scattered is measured by a digital dust meter P
It was measured with a 5H2 type (manufactured by Shibata Chemical Co., Ltd.). The dust meter and the magnet roll are installed at a distance of 10 cm, 2 g of the developer is set on the magnet roll, and the dust meter generates toner particles generated when the magnet is rotated at 2,000 rpm. It was read as and was displayed by the number of counts per minute (cpm). The scattering amount obtained here is ◯ when it is 300 cpm or less, and Δ when it is 500 cpm or less.
The case of more than 00 cpm was evaluated as x and evaluated in three stages. It is practically usable with a rank or more, but ◯ is desirable. Table 2 shows the measurement results of the charge amount and the scattering amount.

(4) Image Evaluation (Fogging on Image) The predetermined toner and carrier shown in Table 2 were mixed at a ratio of toner / carrier = 5/95 to prepare a two-component developer. For Examples 1 and 4 and Comparative Example 1, a copying machine EP
-470Z (manufactured by Minolta Camera Co., Ltd.) was used. For Examples 2, 3 and 5 and Comparative Examples 2 and 3, a copying machine EP-570Z (manufactured by Minolta Camera Co., Ltd.) was used. Using these, an initial image was drawn. Regarding the fogging on the image, the toner fogging on the white background image was evaluated and ranked. It can be practically used in a rank or more, but is preferably in a rank or more. Image fogging after the 100,000-sheet printing durability test was also evaluated in the same manner. The results are shown in Table 2.

(5) Humidity resistance test After each copying machine was left under high humidity of 35 ° C. and relative humidity of 85% for 24 hours, (i) charge amount, (i
i) Scatterability and (iii) Image evaluation were performed. The results are shown in Table 2.
Shown in. The symbols in the table are the same as above. (6) During printing durability Using a chart having a B / W ratio of 6%, a printing durability test was performed on up to 100,000 sheets, and the charge amount and image fog were evaluated. The results are shown in Table 2. The circles in the table are practically usable areas,
X means that it is a practically problematic area.

(7) Cohesive toner of carrier / 50 g of developer consisting of carrier = 5/95
The mixture was placed in a 00 ml plastic bottle and stirred vigorously for 60 minutes with a paint conditioner, a paint conditioner (manufactured by Red Devil). Next, 30 g of this developer was taken, and the amount of residue after sieving with a sieve having an opening of 106 μm was measured. When the amount of residue is within 3%, it is ◯, within 5% is △, and when it is more than 5%, it is 3
A graded evaluation was performed. The results are shown in Table 2.

[0046]

[Table 2]

[0047]

In the coated carrier of the present invention, the coated thermosetting resin component is completely cured and the residual uncured component is eliminated. For this reason, contamination of the photoreceptor and aggregation of the carrier during stirring of the developer are eliminated, and the spent resistance is excellent.

[Brief description of drawings]

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

[Explanation of symbols]

6 hot air jet nozzle 7 Sample injection nozzle 8 Cooling air introduction section 9 cyclones

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor, Hoichi Sano             2-3-3 Azuchi-cho, Chuo-ku, Osaka             Kokusai Building Minolta Camera Co., Ltd. (72) Inventor Yukio Tanigami             2-3-3 Azuchi-cho, Chuo-ku, Osaka             Kokusai Building Minolta Camera Co., Ltd.

Claims (3)

[Claims] 1. A coated carrier having a carrier core material and a coating layer containing a thermosetting resin as a main component for coating the surface of the carrier core material, wherein a peak temperature is a curing temperature of the thermosetting resin + 50 ° C. or more, An electrophotographic carrier obtained by instantaneous heat treatment under the curing temperature + 500 ° C or lower. 2. A carrier core material made of a ferromagnetic material having an average particle diameter of 20 to 80 μm, and thermosetting in which the surface of the carrier core material is coated and the film thickness is 1/10 or less of the average particle diameter of the carrier core material. The electrophotographic carrier according to claim 1, which is obtained by instantaneously heating a coated carrier having a coating layer containing a conductive resin as a main component. 3. A coated carrier is dispersed in a high-speed air stream,
After instantaneous heat treatment of the coated carrier for 2 seconds or less,
The electrophotographic carrier according to claim 1, which is obtained by immediately cooling.