JPH11242361A - Carrier for electrophotographic developer and electrophotographic developer using that - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic developer carrier which shows little changes in the charge amt. and fluidity under high temp. high humidity conditions and which hardly causes decrease in the image density or image defects by coating a carrier core material with a silicone resin containing a crosslinking agent having phenyl groups. SOLUTION: The carrier core material is coated with a silicone resin containing a crosslinking agent having phenyl groups. As the silicone resin, a methylsilicone resin which is hardened at a normal temp. is used. As for the crosslinking agent having phenyl groups for the silicone resin which is hardened at the normal temp., a dealcohol type or deoxime type agent is preferably used, and a dealcohol type is most preferable considering the reactivity. The amt. of the crosslinking agent having phenyl groups is preferably controlled in such a manner that the total number of phenyl groups in the whole functional groups of the silicone resin containing the crosslinking agent is 0.2 to 15 number %, and preferably 1 to 8 number %, and especially preferably 1 to 5 number %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier for a two-component electrophotographic developer used in a copying machine, a printer and the like, and a developer using the carrier.

[0002]

2. Description of the Related Art An electrostatic image two-component developer used in an electrophotographic system is composed of a toner and a carrier, and the carrier is mixed and stirred with the toner in a developing tank. It is a carrier material that gives a desired charge to the toner, carries the charged toner to an electrostatic latent image on a photoconductor, and forms a toner image.

[0003] The carrier remains on the magnet in the developing tank,
The toner is returned to the developing tank again, mixed and stirred again with the newly supplied toner, and used repeatedly.

Therefore, in order to stably maintain a desired image quality during the printing life, it is required that the characteristics of the carrier be stable during the use period.

[0005] In recent years, most carriers for a two-component dry developer of an electrostatic image have a resin surface coated with a resin in order to obtain a higher quality image.

However, the developer is constantly subjected to stress such as collision between particles or collision with a developing tank and a photoreceptor during the printing life, so that the resin coated on the carrier surface is peeled off. Further, the heat generated by the stress causes toner components to adhere to the surface of the carrier, so-called spent, causing the carrier characteristics to deteriorate with use time and necessitating replacement of the developer itself.

In order to prevent such deterioration of the carrier characteristics, various studies have been made on the types of resins to be coated on the carrier surface. Among them, a silicone resin having a low surface tension is currently used. It is becoming mainstream.

[0008] Such a carrier in which a carrier core material such as a ferrite powder is coated with a silicone resin and an electrophotographic developer using the carrier have a large change in charge amount and fluidity with environmental changes. In particular, fog and toner scattering increase due to a decrease in the charge amount under high temperature and high humidity, and image density decreases due to an increase in the charge amount under low temperature and low humidity. This leads to a fatal image defect due to poor follow-up performance.

As a silicone resin to be coated on the carrier core material as described above, a carrier using a phenyl silicone resin or a methylphenyl silicone resin has been proposed in order to maintain stable charging properties (Japanese Patent Application Laid-Open No. HEI 9-28139). JP-A 64-59238 and JP-A-4-264563) cannot sufficiently solve the above-mentioned problems, and furthermore, the image characteristics greatly change with respect to printing durability.

Accordingly, an object of the present invention is to reduce the change in charge amount and fluidity due to environmental changes, and particularly to reduce the change in charge amount and fluidity under high temperature and high humidity, causing a decrease in image density and image defects. An object of the present invention is to provide a carrier for an electrophotographic developer which does not have a problem and an electrophotographic developer using the carrier.

[0011]

As a result of intensive studies, the present inventors have achieved the above object by using a crosslinking agent having a phenyl group as a crosslinking agent for a silicone resin coated on a carrier core material. I found that.

The present invention has been made based on the above findings, and provides a carrier for an electrophotographic developer, wherein a carrier core material is coated with a silicone resin containing a crosslinking agent having a phenyl group. Things.

[0013] The present invention also provides an electrophotographic developer comprising the above-mentioned carrier and toner.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention, the carrier core material is coated with a silicone resin containing a crosslinking agent containing a phenyl group.

The silicone resin used herein is not particularly limited, but is a methyl silicone resin, a methylphenyl silicone resin, and a modified silicone resin obtained by modifying these resins with acrylic, epoxy, urethane, polyethylene, alkyd resins and the like. Among them, a room temperature-curable silicone resin is preferable, and a room temperature-curable methyl silicone resin is particularly preferable. Various silane coupling agents, conductive carbon and the like may be added to the resin for controlling the resistance and the charge.

On the other hand, the following five kinds of crosslinking agents are generally used as a crosslinking agent for use in a room temperature-curable silicone resin, and R in these structural formulas is a methyl group, an allyl group, a phenyl group or a derivative thereof. And four-functional groups to which free radicals of each type are added.

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The action of these crosslinking agents for cold-setting silicone resins is as follows:

Embedded image Reacting with a terminal OH group of a silicone base polymer having a molecular weight of hundreds to tens of thousands represented by

Embedded image As described above, to crosslink the base polymer three-dimensionally. The crosslinking agent having a phenyl group for a room temperature-curable silicone resin used in the present invention refers to a compound in which R in the above structural formula is a phenyl group, and among these, dealcoholated type and deoxime type are preferably used, Considering the reactivity and the like, the dealcohol type is most preferable.

The content of the crosslinking agent having a phenyl group is determined by the total functional groups R of the entire silicone resin including the crosslinking agent.
Among them, the total number of phenyl groups is preferably 0.2 to 15% by number, more preferably 1 to 8% by number, and particularly preferably 1 to 5% by number. On the other hand, the total number of phenyl groups is 0.2% by number.
If it is less than 1, the number of phenyl groups is too small, and the effect due to the inclusion of phenyl groups cannot be obtained. Also, 15
If it exceeds a certain percentage, the phenyl group becomes excessive and the fluidity becomes poor, and the durability of the cured film also decreases.

In the two-component electrostatic image developing system using the carrier of the present invention, the action of the crosslinking agent having a phenyl group is such that a phenyl group contained as a functional group is much larger than a methyl group or the like. Therefore, when a carrier coating layer is formed by cross-linking a methyl silicone base polymer, as shown in FIG. 1, a silicone base polymer is formed between a phenyl group and a cross-linked silicone base polymer to avoid these steric interferences. Is oriented on the carrier core material side, and the phenyl group is oriented on the upper side, so that the coating layer is smooth. In addition, since the phenyl group is very lipophilic, the effect of moisture on the silicone base polymer can be reduced in a high-temperature and high-humidity environment. The difference in volume and flowability is reduced.

On the other hand, in a conventional coating layer of a methyl silicone polymer containing a cross-linking agent having a functional group such as a methyl group, the functional group such as a methyl group is small, and the silicone base polymer is not functional. As shown in FIG. 2, the silicone-based polymer is three-dimensionally arranged to form a coating layer having irregularities, and thus the cured film is exposed to high temperature and high humidity. In this case, the silicone base polymer is directly affected by moisture, and the difference in charge amount and fluidity of the developer between normal temperature and normal humidity and between high temperature and high humidity is increased.

As a base resin, in the coating layer of methylphenyl silicone polymer, phenyl groups are randomly arranged in the cured product as shown in FIG. 3 in order to avoid steric interference between the phenyl groups. The methylsilicone polymer containing a phenyl group-containing cross-linking agent is characterized in that the film with a large number of phenyl groups is thick and the film with a small number of parts is thin, and the entire coating layer has very large irregularities. And a similar effect cannot be obtained in the charge amount and fluidity of the developer.

The carrier core material used in the present invention is not particularly limited, and examples thereof include iron powder, ferrite powder, and magnetite powder. Cu, Zn, Mg, Mn, Ca, L
Ferrite powder using i, Sr, Sn, Ni, Al, Ba, Co or the like is preferably used. There are no restrictions on the shape, surface properties, particle size, magnetic properties, resistance value, chargeability, etc. of the carrier core material.

The coating amount of the silicone resin with respect to the carrier core material is 0.0
The content is preferably 5 to 10.0% by weight, particularly preferably 0.1 to 7.0% by weight.

As a method for coating the silicone resin, the silicone resin is generally diluted with a solvent and coated on the surface of the carrier core material. The solvent used here may be any solvent that is soluble in the silicone resin, and examples thereof include toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and methanol. Also, on the carrier core material surface,
The method of coating the resin diluted with the solvent is applied by an immersion method, a spray method, a brush application method, a kneading method, or the like, and thereafter, the solvent is volatilized. Note that the surface of the carrier core material can be coated with the resin powder by a dry method instead of a wet method using such a solvent.

When the above-mentioned silicone resin is coated on the surface of the carrier core and then baked, either an external heating method or an internal heating method may be used, for example, a fixed or fluid electric furnace, a rotary kiln electric furnace or a burner furnace. Often,
Alternatively, baking by microwave may be used. The baking temperature depends on the silicone resin used,
It is necessary to raise the temperature to the point where crosslinking and curing proceed sufficiently.

In this way, after the surface of the carrier core material is coated with the silicone resin and baked, the carrier is cooled, crushed, and adjusted for the particle size to obtain the carrier coated with the silicone resin.

The carrier of the present invention is mixed with a toner and used as a two-component developer for electrophotography. The toner used here is a toner in which a charge control agent, a colorant, and the like are dispersed in a binder resin.

[0028] The binder resin used for the toner is not particularly limited.
Chloropolystyrene, styrene-chlorostyrene copolymer, styrene-acrylate copolymer, styrene-methacrylic acid copolymer, rosin-modified maleic resin, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, polyurethane resin, etc. Is mentioned. These are used alone or in combination.

Any appropriate charge control agent can be used. For example, in the case of a positively charged toner, there are a nigrosine dye, a quaternary ammonium salt, and the like.
In the case of a negatively charged toner, a metal-containing monoazo dye or the like can be used.

As the coloring agent, conventionally known dyes and pigments can be used. For example, carbon black,
Examples include phthalocyanine blue, permanent red, chrome yellow, and phthalocyanine green. In addition, external additives such as silica fine powder and titania can be added according to the toner in order to improve the fluidity and aggregation resistance of the toner.

The method for producing the toner is not particularly limited. For example, a binder resin, a charge control agent, and a colorant are sufficiently mixed by a mixer such as a Henschel mixer, and then melt-kneaded by a twin screw extruder or the like. After cooling, pulverizing and classifying, adding an external additive and mixing with a mixer or the like.

The carrier for an electrophotographic developer of the present invention is mixed with a polyester toner among the toners obtained as described above, and an image is formed by an inversion developing method using an OPC photoreceptor as an evaluator. The desired effect can be derived for the method.

[0033]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments and the like.

Example 1 An aminosilane cup was added to a methylsilicone resin having a phenyl crosslinking agent (trimethoxyphenylsilane) prepared so that the total number of phenyl groups among all the functional groups R in the entire silicone resin was 3% by number. Ring agent (3-aminopropyltriethoxysilane)
Was added in an amount of 11.25% by weight based on the resin solid content, and carbon black (trade name: Ketchen Black EC600JD, manufactured by Ketchen Black International) was added at 15% by weight based on the resin solid content.

The core material of a manganese-based ferrite carrier having an average particle size of 90 μm is coated with the above resin 1 at 0.7% by weight,
Carrier 1 was prepared by heating at 260 ° C. for 2 hours.

Example 2 A methylsilicone resin having a phenyl crosslinking agent (trimethoxyphenylsilane) prepared so that the total number of phenyl groups among all the functional groups R in the entire silicone resin was 1.2% by number was used. Unless used,
Resin 2 was obtained in the same manner as in Example 1. Further, using this resin 2, a carrier 2 was prepared in the same manner as in Example 1.

Example 3 A methyl silicone resin having a phenyl cross-linking agent (trimethoxyphenyl silane) prepared so that the total number of phenyl groups in all the functional groups R of the silicone resin was 5% by number was used. Except for the above, a resin 3 was obtained in the same manner as in the example 1. Furthermore, this resin 3
Was used to prepare Carrier 3 in the same manner as in Example 1.

Example 4 A methyl silicone resin having a phenyl cross-linking agent (trimethoxyphenyl silane) prepared so that the total number of phenyl groups in the total functional groups R of the silicone resin was 10% by number was used. A resin 4 was obtained in the same manner as in Example 1 except for the above. Furthermore, this resin 4
Was used to prepare Carrier 4 in the same manner as in Example 1.

Example 5 A methylsilicone resin having a phenyl cross-linking agent (triethylmethylketoxime phenylsilane) prepared so that the total number of phenyl groups among the total functional groups R of the silicone resin was 17% by number was used. Except for using, a resin 5 was obtained in the same manner as in Example 1. Further, using this resin 5, a carrier 5 was prepared in the same manner as in Example 1.

Comparative Example 1 A resin 6 was obtained in the same manner as in Example 1 except that a heat-curable methyl silicone resin having no phenyl crosslinking agent was used. Furthermore, this resin 2
Was used to prepare Carrier 6 in the same manner as in Example 1.

Comparative Example 2 Resin 7 was obtained in the same manner as in Example 1 except that a methyl silicone resin having a methyl crosslinking agent was used. Further, using this resin 7, a carrier 7 was prepared in the same manner as in Example 1.

Comparative Example 3 The same procedure as in Example 1 was carried out except that a methylphenylsilicone resin having a methyl crosslinking agent and having a total number of phenyl groups of 40% by number among all functional groups R of the entire silicone resin was used. Resin 8 was obtained in the same manner. Further, a carrier 8 was prepared using the resin 8 in the same manner as in Example 1.

[Evaluation Results] Carriers 1 to 8 obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were mixed with a polyester toner so that the top sheet concentration was 4%.
The charge amount and the toner density sensor value at room temperature and normal humidity and at high temperature and high humidity were measured. Thereafter, a printing durability test was performed to confirm the life of the developer. The results are shown in Table 1. As a toner density sensor output evaluator and a printing durability tester, AR-5130 manufactured by Sharp Corporation was used.
Was used. From this result, a change in charge amount and a change in sensor value from normal temperature and normal humidity to high temperature and high humidity were calculated, and the results are shown in Table 1.

In the printing durability test results shown in Table 1, the number of printable sheets satisfying an image density of 1.3 or more, a paper fog of 0.8 or less, and a toner consumption of 180 g / 5000 sheets or less was measured. evaluated. ◎: 150,000 sheets or more. ：: 120,000 sheets or more. Δ: 80,000 sheets or more. X: Less than 80,000 sheets.

[0045]

[Table 1]

As shown in Table 1, Examples 1 to 5
Is smaller in the charge amount between normal temperature and normal humidity and high temperature and high humidity than in Comparative Examples 1 to 3, and the difference in the output of the toner density sensor is also small. Furthermore, the number of printable sheets is large in the printing durability test.

[0047]

As described above, the carrier for an electronic developer of the present invention has a small change in charge amount and fluidity due to environmental changes, and particularly a small change in charge amount and fluidity under high temperature and high humidity. . Further, the developer of the present invention using such a carrier does not cause a reduction in image density or image defects.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state of coating a carrier core material surface with a methyl silicone resin containing a crosslinking agent having a phenyl group.

FIG. 2 is a schematic view showing a state in which the surface of a carrier core material is coated with a methyl silicone resin containing a crosslinking agent having a methyl group.

FIG. 3 is a schematic view showing a state in which a methylphenyl silicone resin is coated on the surface of a carrier core material.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiko Kataoka 217 Toyo, Kashiwa-shi, Chiba Powder Powder Co., Ltd. (72) Inventor Tetsuya Uemura 217 Toyo, Kashiwa-shi, Chiba Powder Co., Ltd. (72) Inventor Toshio Honjo 217 Toyoji Kashiwa-shi, Chiba Powder Powder Co., Ltd.

Claims (5)

[Claims] 1. A carrier for an electrophotographic developer, wherein a carrier core material is coated with a silicone resin containing a crosslinking agent having a phenyl group. 2. The carrier for an electrophotographic developer according to claim 1, wherein the silicone resin is a room temperature-curable silicone resin. 3. The electrophotographic development according to claim 1, wherein the proportion of the phenyl group occupied by the crosslinking agent is 0.2 to 15% by number based on all functional groups contained in the silicone resin. Agent carrier. 4. The carrier for an electrophotographic developer according to claim 1, wherein the silicone resin is a methyl silicone resin. 5. An electrophotographic developer comprising the carrier according to claim 1, 2, 3 or 4, and a toner.