JP3352179B2 - Electrophotographic carrier and two-component developer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier in a developer used for developing an electric latent image or a magnetic latent image in an electrophotographic method, an electrostatic printing method, and the like. The present invention relates to a carrier for electrophotography having significantly improved environmental characteristics and a two-component developer using the same.

[0002]

2. Description of the Related Art A carrier constituting a two-component developer is as follows.
The carrier is roughly divided into a conductive carrier and an insulating carrier.As the conductive carrier, oxidized or unoxidized iron powder is usually used.In a developer containing the iron powder carrier as a component,
There is a drawback that the triboelectric charging property with respect to the toner is unstable and that a visible image formed by the developer is fogged. That is, with the use of the developer, the toner particles adhere and accumulate (spent toner) on the surface of the iron powder carrier particles, so that the electric resistance of the carrier particles increases, the bias current decreases, and the triboelectrification property decreases. As a result, the image density of the resulting visible image decreases, and fog increases. Therefore, when copying is continuously performed by an electronic copying apparatus using a developer containing an iron powder carrier, the developer deteriorates in a small number of times, so it is necessary to replace the developer at an early stage, resulting in a high cost. It will be.

[0003] A typical example of an insulating carrier is a carrier obtained by uniformly covering the surface of a carrier core material made of a ferromagnetic material such as iron, nickel, or ferrite with an insulating resin. In a developer using this carrier, toner particles are less likely to fuse to the surface of the carrier than in the case of a conductive carrier, and at the same time, it is easy to control the triboelectric charging property between the toner and the carrier, and the durability is high. This is advantageous in that it is particularly suitable for high-speed electronic copiers in that it has excellent service life and a long service life.

There are various characteristics required for the insulating carrier, but particularly important characteristics are appropriate chargeability, impact resistance, abrasion resistance, good adhesion between the core and the coating material, and good charge distribution. Uniformity and the like.

In view of the above-mentioned required characteristics, conventionally used insulating carriers still have a problem to be improved, and the perfect carrier has not been known so far.
For example, examples in which an acrylic resin or the like is used as a carrier coating material are disclosed in JP-A-47-13954 and JP-A-60-1985.
-208765. In addition, those which particularly describe the molecular weight are disclosed in
It is disclosed in, for example, Japanese Patent Application Laid-Open No. 0-208767, and it is known that the chargeability of a coated carrier is stabilized by controlling the molecular weight to be constant. However, in order to attach the coating resin to the carrier core material, it is easily affected by the conditions of the apparatus and the environment in which the coating is performed, particularly humidity. Even if these are strictly controlled, the resin is stably attached to the core material. At present, there is no satisfactory material for providing sufficient chargeability and durability.

On the other hand, it has been proposed to improve the durability by using a resin having a small surface energy as a coating layer in order to prevent spent of a carrier such as toner fusion or the like. For example, silicone resin is used as a resin having a small surface energy. No.

[0007] Silicone resins have the advantage of being water repellent in addition to having low surface tension. On the other hand, the silicone resin has a problem that it is easily peeled off when used for the coating layer because of poor adhesion.

In order to solve this problem, for example, a method using a resin-modified silicone resin (JP-A-55-12275)
No. 69), a method of containing vinylsilane and reacting with another resin (Japanese Patent Application Laid-Open No. 56-32149), a method of using a mixture of trialkoxysilane and ethylcellulose (US Pat. No. 3,840,644), an organosilicone terpolymer, A method using a mixture with a polyphenylene resin (US Pat. No. 3,849,127) has been proposed. However, a high temperature of 300 ° C. or more is required for forming the coating film, or the phase of the silicone resin and another resin is required. There were problems such as poor solubility and unevenness of the coating film, and the expected characteristics could not be obtained. It has also been proposed to form a coating film at a relatively low curing temperature (JP-A-55-12).
No. 7569) is insufficient in adhesiveness and insufficient in toughness of the coating film, so that it is liable to be worn. For example, strong long-term stirring in a developing section such as a high-speed copying machine causes carrier particles to be formed. If the inner wall of the developing unit or the surface of the photoreceptor collides with each other, or the particles collide with each other, the silicone resin coating layer is worn and peeled off with time, and the frictional charge is changed from the charge between the toner and the silicone resin. , The amount of charge of the developer was not kept constant, and the image quality deteriorated.

[0009]

SUMMARY OF THE INVENTION The main object of the present invention is to improve the above-mentioned conventional problems, and in particular to provide a durable film having excellent chargeability, mechanical strength and adhesion to a core material under various environments. and to provide a two-component developer using sex of the good electrophotographic career.

[0010]

The present invention has solved the above-mentioned problems by the following constitution.

The present invention relates to a two-component developer having a toner and a carrier, wherein the toner is a negatively chargeable toner containing at least titanium oxide fine particles as an external additive, and the carrier is a carrier core material. an electrophotographic carrier whose surface is coated with a crosslinked silicone resin, the carrier core material, SiO ₂ at least SiO ₂ oxide basis
/ Fe ₂ O ₃ content by weight in the range of 0.01 to 3%,
The crosslinked silicone resin is represented by the following general formula (I): R _m Si—Y _n (I) (wherein R represents an alkoxy group, Y represents a hydrocarbon group containing an amino group, and m represents 1 to 3) of an integer, n represents about two-component developer, wherein the benzalkonium to contain an amino silane coupling agent represented by the indicating.) an integer of 3-1.

The present inventors have conducted various studies and studies to improve the above-mentioned conventional problems. As a result, as a silicone resin as a coating material, a specific cross-linked silicone resin containing an aminosilane coupling agent was replaced with SiO ₂ . The present inventors have found that a carrier coated with a carrier core material having a specific composition containing a specific amount is effective in improving various properties, and have completed the present invention.

It has been proposed to use a modified silicone resin in order to improve the adhesiveness to a carrier core material. Alkyd modification, epoxy modification, acrylic modification, polyester modification, phenol modification, melanin modification, urethane modification There is an example in which a modified silicone resin such as that described above is used, but the toner is liable to stick due to an increase in surface energy, which is not always satisfactory in terms of the durability of the developer.

On the other hand, a method has been proposed in which various additives are used in combination in order to increase the adhesiveness while maintaining a low surface energy (JP-A-2-33159).

These additives impart toughness in addition to adhesiveness by reacting with the silicone resin or itself. However, the one disclosed in Japanese Patent Application Laid-Open No. 2-33159, although having improved resistance as a coating resin, does not necessarily require a carrier core when a thin coating layer is formed on the surface of the carrier core material. The adhesion between the material and the coating resin is not satisfactory, and further improvement is desired.

[0016] Therefore, the present inventors have conducted intensive studies and as a result, SiO SiO ₂ is an oxide basis in the carrier core material ₂
When a crosslinked silicone resin containing a coupling agent represented by the aforementioned general formula (I) is coated on a carrier core material containing 0.01 to 3% by weight / Fe ₂ O ₃ , the coupling agent Are homogeneously compatible in the crosslinked silicone resin,
And, at the same time as the SiO ₂ site in the carrier core material, that is, a part of the SiOH group and the coupling agent react appropriately, the remaining SiOH group in the silicone resin and the coupling agent also react appropriately, resulting in good adhesiveness. It has been found that the chargeability is achieved and a very high-performance long-life carrier can be obtained.

[0017] Also in Japanese Unexamined Patent Publication No. 2-33159, which contains an amino silane coupling agent in the toner, and then as an example of the additive there are described SiO _2, in the present invention, with respect to FeO ₃ Si as an essential component
It is characterized in that O ₂ is contained in a specific weight ratio and is reacted with a coupling agent, and as a result, a coated carrier with improved strength is obtained, which is different from the above invention.

Examples of the aminosilane coupling agent represented by the general formula (I) used in the present invention include the following.

[0019]

[Outside 3]

These can be used alone or in combination of two or more. Among them, those preferably used in the present invention include:
The following coupling agents having at least one nitrogen atom having one hydrogen atom in terms of compatibility, reactivity, and stability.

[0021]

[Outside 4]

The amount of addition is preferably 0.1 to 8 parts by weight, more preferably 0.3 to 5 parts by weight, based on 100 parts of the solid siloxane. If the amount is less than 0.1 part by weight, a sufficient effect of addition cannot be obtained, and the charging property is deteriorated and the coating strength is reduced. If the amount is more than 8 parts by weight, sufficient reaction is not performed, and conversely, the coating strength is reduced. I will.

In the present invention, the coupling agent may further be represented by the following general formula (III): R _4-a —Si—X _a (III) (wherein R is a vinyl group, a methacryl group, an epoxy group, a mercapto group) And X represents a halogen or an alkoxy group, and a represents a number of 1 to 3.) may be used in combination.

Examples of such a coupling agent include the following.

(10) CH ₂ ＣＨCH—Si— (OCH ₃ ) ₃ (11) CH ₃ —Si— (OCH ₃ ) ₃ (12) CH ₃ —Si— (OC ₂ H ₅ ) ₃

Further, in order to make the present invention more effective, at least the following general formula (II) may be used as a curing agent for the crosslinked silicone resin.

[0027]

[Outside 5] (Wherein R ₅ is CH ₃ , C ₂ H ₅ ,

[0028]

[Outside 6] And R ₆ and R ₇ represent a substituent selected from the group consisting of CH ₃ , C ₂ H ₅ and their derivatives. The oxime-type curing agents represented by ()) are preferred. That is, the oxime-type silane coupling agent is very excellent in terms of appropriate control of the residual SiOH group in the silicone resin, storage stability, and cost.

Acetic acid type (acetoxy silane), acetone type (propenoxy silane) and the like are known as highly reactive coupling agents, but a stable reaction between the carrier core material and the silicone resin is performed. Achieved, Si
Because it is very difficult to set conditions that allow OH to remain moderately,
It has been found that the production stability is poor, which is not preferable for the present invention.

Examples of the curing agent in the present invention include the following.

[0031]

[Outside 7]

The amount of addition is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts of the solid siloxane. If the amount is less than 0.1 part by weight, a sufficient crosslinking effect cannot be obtained, and if the amount exceeds 10 parts by weight,
Residues cannot be sufficiently removed or a compound with an insufficient reaction remains, and the charging characteristics and strength are reduced.

In order to make the present invention more effective, the coating amount of the crosslinked silicone resin is set to a
g, the carrier specific surface area S after coating (cm ²
(A / S) × 10 ⁴ is preferably 2 to 30, preferably 5 to 20, where a is 0.01 to 1.0, preferably 0.02 to 0.8, more preferably 0. 0.05 to 0.5 is good.

The average particle size of the carrier is 10 to 100.
μm, preferably 20-65 μm, specific surface area of 280
600 cm ² / g is desirable. The particle size distribution measurement of the carrier is based on JIS-H2601. The average particle size is determined from the measured particle size distribution according to the following formula.

[0035]

[Outside 8]

Another feature of the present invention is that the carrier core material has a SiO ₂ / Fe ₂ O ₃ weight ratio in the range of 0.01 to 3% on an oxide basis.

That is, by containing a specific amount of SiO ₂ , the reaction between the surface SiOH groups and the coupling agent was effectively performed, and the coating strength was surprisingly improved. Here, as means for containing a specific amount of SiO ₂ , Fe ₂
O ₃ , CuO, ZnO, MgO, MnO, etc. may be present in a ferrite-forming raw material, or the starting raw material may be used during granulation.
It is also possible to add iO ₂ or a silicate so as to prevent coagulation during firing or to function as a dispersion stabilizer during granulation.

As a carrier core material particularly preferably used in the present invention, a C ₂ of 96% or more containing a specific amount of SiO ₂ is used.
u-Zn-Fe (metal composition ratio (5 to 20): (5 to 2
0): Ferrite particles composed of (30 to 80)) are preferable because the surface can be easily homogenized and spheroidized, and the charging ability is stable.

In order to coat the carrier core material with a resin, the resin composition is dissolved in an appropriate solvent, and the core material is immersed in the resulting solution, followed by solvent removal, drying, and high-temperature baking. A method of suspending the material in a fluidized bed, spray-coating the copolymer solution, drying and baking at a high temperature can be used.

In the present invention, the carrier SiO ₂ / F
The e ₂ O ₃ ratio of the carrier core material was determined by quantifying Fe and Si by the ZAF method of scanning electron microscopy-X-ray analysis (SEM-XMA) as it was and converted to the oxide standard. In addition, in the case of a coated carrier, after the carrier is solidified with an epoxy resin or the like, it is cut by a laser cutter or the like, the coating material is removed, the carrier core material is exposed, and the portion is calculated by quantifying as described above. be able to.

The carrier of the present invention thus obtained is mixed with a toner and used as a magnetic brush developer for developing an electrostatic latent image.

As the toner, any toner commonly used in electrophotography, in which a colorant is dispersed in a binder resin, can be used without any particular limitation.

When a two-component developer is prepared by mixing the carrier and the toner according to the present invention, the mixing ratio is from 1.0% by weight to 12% by weight, preferably 2% by weight, as the toner concentration in the developer. Good results are usually obtained with ９9% by weight. When the toner concentration is less than 1.0% by weight, the image density is low and cannot be used practically. When the toner concentration is more than 12% by weight, fog and scattering in the machine are increased, and the service life of the developer is shortened.

As the coloring agent used in the present invention, known dyes and pigments, for example, phthalocyanine blue, indaslen blue, peacock blue, permanent red, lake red, rhodamine lake, Hanza yellow, permanent yellow, benzine yellow and the like are widely used. can do. The content thereof is 12 parts by weight or less, preferably 0.5 to 9 parts by weight, based on 100 parts by weight of the binder resin so as to reflect sensitively on the permeability of the OHP film.

If necessary, additives may be added to the toner of the present invention as long as the properties of the toner are not impaired. Examples of such additives include Teflon, zinc stearate and polyvinylidene fluoride. And a fixing aid such as low molecular weight polyethylene and low molecular weight polypropylene.

In the production of the toner of the present invention, the constituent materials are kneaded well by a hot kneader such as a hot roll, a kneader, an extruder, etc., and then obtained by mechanical pulverization and classification, or in a binder resin solution. A method in which a material such as a colorant is dispersed and obtained by spray drying, or a method in which a predetermined material is mixed with a monomer to constitute a binder resin, and then the emulsified suspension is polymerized to form a toner. Each method such as a method for producing a polymerized toner can be applied.

As the binder used in the colorant-containing resin particles of the present invention, various material resins conventionally known as toner binder resins for electrophotography are used.

For example, styrene-based copolymers such as polystyrene, styrene-butadiene copolymer and styrene-acrylic copolymer, and ethylene-based copolymers such as polyethylene, ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer Copolymer, phenolic resin, epoxy resin, acrylic phthalate resin, polyamide resin, polyester resin, maleic acid resin and the like. In addition, the production method of any resin is not particularly limited.

The effect of the present invention is remarkable when a polyester resin having a high negative chargeability is used among these resins. That is, the polyester-based resin has excellent fixability and is suitable for a color toner, but on the other hand, the negative charging ability is strong and the charging is liable to be excessively large. A toner is obtained.

In particular, the following equation

[0051]

[Outside 9] (Wherein R is an ethylene or propylene group, x and y are each an integer of 1 or more, and the average value of x + y is 2
10 to 10. A) a carboxylic acid component consisting of a divalent or higher carboxylic acid or an acid anhydride thereof or a lower alkyl ester thereof (for example, fumaric acid, maleic acid,
A polyester resin obtained by co-condensation polymerization of maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, etc.) is more preferable since it has sharp melting properties.

Further, according to the present invention, as an external additive of the toner,
It is preferable to contain at least titanium oxide fine particles in order to further stabilize charging. Particularly preferably, fine particles of anatase-type titanium oxide which have been subjected to surface treatment while hydrolyzing a coupling agent in an aqueous system are extremely effective in terms of stabilization of charging, imparting of fluidity, and the like.

Further, the titanium oxide fine particles have an average particle size of 0.01 to 0.2 μm, a hydrophobicity of 20 to 80%,
The light transmittance at μm is preferably 40% or more.

Hereinafter, the measuring method in the present invention will be described.

Fog density measurement method The fog was evaluated by using REFLECTOME manufactured by Tokyo Denshoku Co., Ltd.
The measurement was performed using TER MODELTC-6DS, and the cyan toner image was calculated using the following formula using an amber filter. The smaller the value, the less fog.

Fog (reflectance) (%) = reflectance of standard paper (%) − reflectance of non-image portion of sample (%)

Specific Surface Area Test Method A specific surface area test method is performed using a Shimadzu powder specific surface area measuring device (SS-100 type) according to the following procedure. (1) To charge the test iron powder, turn on the power of the autoslidac of the powder tester and adjust to 100V. (2) Tap the changeover switch of the powder tester and adjust the timer to 1 minute (50 times ± 1 time / 1 minute). (3) Put a sieve plate in a plastic test tube, lay a sheet of filter paper on it, and put a sample on it up to 1/3 of the sample tube. (4) Set the sample tube on the tap stand of the powder tester and press the start button (1 minute tap). (5) Place the sample in the tapped sample tube 2 /
Insert up to 3. (6) Perform the same operation as in the above item 4. (7) Insert a supplementary tube (plastic) onto the sample tube, and put the sample on the heap from above. (8) Perform the same operations as in the above 4 and 6. (9) Take out the tapped sample tube from the tap stand,
Pull out the supplementary cylinder and cut the excess sample with a spatula. (10) Fill up the water up to the S scale of the measuring tube for the specific surface area. (11) Connect the sample tube to the measurement tube (after filling the sample, apply grease to the contact surface). (12) Open the cock of the lower outlet, and start the stopwatch when the water level of the measuring tube passes through the 0 scale (the lower effluent is received in a beaker). (13) Measure the time when the water surface drops to 20 scales (unit is cc). (14) Take out the sample cylinder and measure the weight of the sample. (15) Calculation of specific surface area The specific surface area is calculated by the following formula.

[0058]

[Outside 10]

Examples of the present invention will be shown below, but the present invention is not limited thereto.

[0060]

【Example】

(Manufacturing example 1 of carrier core material) 15 parts by weight of CuO, Zn
Fe containing 15 parts by weight of O and 1.0% by weight of SiO _2
After 70 parts by weight of ₂ O ₃ (Bengara) were each atomized, water was added and mixed, and the mixture was granulated, followed by firing at 1200 ° C.
After adjusting the particle size, a ferrite carrier core material (SiO ₂ / Fe ₂ O ₃ ratio 1.5%) A having an average particle size of 45 μm was obtained.

(Production Example 2 of Carrier Core Material) CuO 1
2.5 parts by weight, ZnO 15 parts by weight, Fe ₂ O ₃ 72
Production Example 1 by mixing and granulating 0.5 part of SiO _{2 to} parts by weight
Ferrite carrier core material B (SiO ₂ / F
was obtained e ₂ O ₃ 0.7%).

(Production Example 3 of Carrier Core Material) CuO 15
Parts by weight, 15 parts by weight of ZnO, and 70 parts by weight of Fe ₂ O ₃ were mixed in an aqueous solution of sodium silicate and then granulated.
Similarly, ferrite carrier core material C (SiO ₂ / Fe ₂ O ₃₎
0.03%).

[0063] Hereinafter the SiO ₂ adding each 0 parts and 4 parts in Production Example 2 (Production example of a carrier core material 4 and 5) the carrier core material in the same manner, a ferrite carrier core D (SiO ₂ / Fe ₂ An O ₃ ratio of 0) and a ferrite carrier core material E (SiO ₂ / Fe ₂ O ₃ ratio of 5.7%) were obtained.

(Production Examples 1 to 5 of Carrier) Toluene 20
Parts, 20 parts of butanol, 20 parts of water and 40 parts of ice were placed in a four-necked flask, and while stirring, 40 parts of a mixture of 15 mol of CH ₃ SiCl _{3 and} 10 mol of (CH ₃ ) ₂ SiCl ₂ were added, and further 30 minutes. After stirring, a condensation reaction was performed at 60 ° C. for 1 hour. Thereafter, the siloxane was sufficiently washed with water and dissolved in a mixed solvent of toluene-xylene-butanol to prepare a silicone varnish having a solid content of 10%.

The silicone varnish was added in an amount of 2.0% by weight based on the siloxane solid content.

[0066]

[Outside 11] And 3.0% by weight

[0067]

[Outside 12] Was added simultaneously to prepare a carrier coating solution.

This coating solution was applied to the above-mentioned carrier cores A to E using a coating machine (Spiracoater manufactured by Okada Seiko Co., Ltd.) so that the resin coating amount was 0.3% by weight. I got Table 1 shows the respective carrier compositions.

(Toner Production Example 1) 100 parts of a polyester resin obtained by condensation of propoxylated bisphenol and fumaric acid 4 parts of phthalocyanine pigment 4 parts of chromium complex of di-tert-butylsalicylic acid 4 parts were sufficiently premixed with a Henschel mixer. The mixture was melt-kneaded by a twin-screw extruder, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet pulverizer. Further, the obtained finely pulverized product was classified to obtain a negatively triboelectrically charging cyan powder having a weight average particle size of 8.3 μm.

100 parts of the above colored powder and nC ₄ H in an aqueous system
₉ parts of anatase type titanium oxide fine powder treated with 15 parts by weight of _9- Si- (OCH ₃ ) ₃ was mixed with a Henschel mixer to obtain cyan toner a.

Example 1 The above-described cyan toner and carrier 1 were mixed at a toner concentration of 5% to prepare a developer, and a color copier CLC500 (manufactured by Canon) was used. 30 ° C / 80% under 23 ° C / 65% RH using 25% original manuscript
Table 2 shows the results of 10,000 images output at 20 ° C./10% RH under RH. From Table 2, it can be seen that the above-mentioned developer has a small variation in the printing durability test, has no problem of scattering after 10,000 sheets, and is very good. Table 2 shows the evaluation results.

In Table 2, the evaluation results of the image density and the capri are shown over the entire environment, the durability is shown at 23 ° C./65% RHF, and the toner scattering is shown at 30 ° C./80% RHF. The evaluation results are shown. For solid homogeneity, 20 ° C./10% RH
The evaluation result in F is shown.

(Examples 2 and 3 and Comparative Examples 1 and 2) The carriers 2 shown in Table 1 were used instead of the carriers 1 used in Example 1.
Example 1 except that 3, 4 and 5 were used, respectively.
A developer was prepared in the same manner as described above and evaluated in the same manner. Table 2 shows the evaluation results.

(Carrier Production Examples 6 to 8) Carriers 6 to 8 were obtained in the same manner as in Carrier Production Example 1, except that the curing agents were changed to those shown in Table 1.

(Carrier Production Examples 9 and 10) Carriers 9 and 10 were obtained in the same manner as in Carrier Production Example 1, except that the amount of the aminosilane coupling agent was changed to those shown in Table 1, respectively.

(Examples 4 to 6 and Comparative Examples 3 and 4) Except for using carriers 6, 7, 8, 9 and 10 shown in Table 1 in place of carrier 1 used in Example 1, respectively. A developer was prepared in the same manner as in Example 1 and evaluated in the same manner. Table 2 shows the evaluation results.

(Carrier Production Examples 11 to 13) Carriers 11 to 13 were prepared in the same manner as in Carrier Production Example 1 except that the aminosilane coupling agent was changed to those shown in Table 1.
13 was obtained.

(Carrier Production Examples 14 and 15) Carrier 1 was prepared in the same manner as in Carrier Production Example 1 except that the amount of the aminosilane coupling agent was changed as shown in Table 1.
4-15 were obtained.

(Examples 7 to 10 and Comparative Examples 5 and 6) The carrier 1 shown in Table 1 was used in place of the carrier 1 used in Example 1.
A developer was prepared in the same manner as in Example 1 except that 1, 12, 13, 14, and 15 were used, respectively, and evaluated in the same manner. Table 2 shows the evaluation results.

(Carrier Manufacturing Example 16) In Carrier Manufacturing Example 1,

[0081]

[Outside 13] Was obtained in the same manner as above except that 1.0 part was further added.

Example 11 A developer was prepared in the same manner as in Example 1 except that each of the carriers 16 shown in Table 1 was used instead of the carrier 1 used in Example 1, and evaluation was performed in the same manner. Was done. Table 2 shows the evaluation results.

(Production Example 2 of Toner)

[0084]

[Outside 14] A cyan toner b was obtained in the same manner as in Production Example 1 of the toner except that the amorphous titanium oxide fine powder (primary particle size: 17 nm) treated with 12 parts by weight was used.

(Production Example 3 of Toner) In Production Example 1 of the toner, instead of the fine powder of anatase type titanium oxide,

[0086]

[Outside 15] A cyan toner c was obtained in the same manner except that silica (primary particle size: 12 mm) treated with 15 parts by weight was used.

[0087]

Example 12 and Reference Example 1 Example 1 was repeated except that the cyan toner a used in Example 1 was replaced by each of the cyan toners b to c described above.
A developer was prepared in the same manner as described above and evaluated in the same manner. Table 2 shows the evaluation results.

[0089]

[Table 1]

[0090]

[Table 2]

[0091]

[Table 3]

[0092]

According to the carrier for electrophotography of the present invention, at least the surface of a carrier core material containing a specific amount of SiO ₂ is coated with a silicone resin containing a coupling agent having a specific structure, thereby toughening the coating. It has high durability and excellent durability in environmental characteristics.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-33159 (JP, A) JP-A-4-172366 (JP, A) JP-A-4-204551 (JP, A) JP-A-62-162 182759 (JP, A) JP-A-60-227267 (JP, A) JP-A-63-184764 (JP, A) JP-B-47-19398 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/113 G03G 9/08

Claims (3)

(57) [Claims] 1. A two-component developer having a toner and a carrier, wherein the toner comprises at least titanium oxide fine particles as an external additive.
A negatively chargeable toner containing, the carrier is a electrophotographic carrier obtained by coating the surface of the carrier core material with crosslinked silicone resin, the carrier core material, SiO ₂ at least SiO ₂ oxide basis / Fe ₂ O _{3 in a} weight ratio of 0.01 to 3%, and the crosslinked silicone resin has the following general formula (I): R _m Si—Y _n (I) (wherein R represents an alkoxy group shows, Y represents a hydrocarbon group containing an amino group, m represents an integer of 1 to 3, n is a Turkey to contain an amino silane coupling agent represented by the indicating.) an integer of 3-1 Characteristic two-component developer. 2. The crosslinked silicone resin has at least the following general formula (II): (Wherein R ₅ is CH ₃ , C ₂ H ₅ , And R ₆ and R ₇ represent a substituent selected from the group consisting of CH ₃ , C ₂ H ₅ and their derivatives. 2. The two-component developer according to claim 1, comprising a crosslinked silicone resin cured with a curing agent of the compound represented by the formula ( 1 ). Wherein when the a (g) the coverage of the crosslinking silicone resin relative to the carrier 100 g, relative to the specific surface area S of the key <br/> Yaria after coating ^(cm 2 / g) (a / S)
Two-component developer according to claim 1 or <br/> 2 wherein the × 10 ⁴ is 2 to 30.