JP2767837B2 - Developer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer for an electrostatic developer comprising two components, a toner and a carrier. 2. Description of the Related Art At present, copiers are moving toward miniaturization and speeding up, and high precision is also required in terms of image quality. To achieve these requirements, the developer
It is essential that (a) the charge amount rises quickly, (b) the chargeability during durability is stable, and the environment resistance is excellent.

Attempts have been made to improve the carrier and toner in order to satisfy the above requirements. For the carrier, a technique of coating a ferrite-based carrier surface with a resin and a technique of coating a vitreous layer are known.

A resin-coated carrier generally has problems such as difficulty in forming a uniform coat layer and peeling of the coat layer during mixing and stirring. Furthermore, it has not yet reached satisfactory properties in terms of environmental resistance.

As a technique for coating the surface of carrier particles with a vitreous layer, for example, JP-A-54-78136 is known.

JP-A-54-78136 discloses a carrier material having a surface coated with an inorganic glass layer. After melting the glass material, the carrier is rapidly cooled to about 200 mesh (about 74 μm).
m), pulverized together with clay (binder) to prepare a suspension in which the pulverized material is dispersed, and apply the obtained suspension to a carrier core material flowing through a circulating fluidized bed with a spray gun. It is obtained by spraying, drying at a temperature of about 120 ° C., baking in an electric furnace at about 950 ° C. (at least 500 ° C.) for about 10 minutes, and then leaving it to cool.

The above manufacturing method is to attach a glass powder on a powder of several tens μm to several hundred μm, and uses a binder, but the adhesion is very difficult, and the glass is uniformly applied to the surface of the base material. Since the powder is adhered to form a melt film, the film thickness is several tens of μm or more, which is almost equal to the particle diameter of the glass powder or about 80% of the particle diameter. If the amount to be attached is reduced, it becomes difficult to form a uniform film formation layer on the surface of the carrier core material.

In the above manufacturing method, it is difficult to reduce the glass material to a small particle size of about 50 μm or less, and the carrier surface coating layer becomes as thick as several tens μm. In addition, when a thick glass layer is provided on the surface of the carrier core material as described above, the magnetic force of the carrier itself is reduced, and the carrier is not suitable for use in a magnetic brush developing system.

Recently, in copiers and printers, in order to obtain high image quality, the carrier has a particle size of 100 μm or less, preferably 8 μm or less.
It is required to reduce the particle size to 0 μm or less, and it becomes impossible to attach glass powder having substantially the same particle size to the surface of a core material having such a particle size.

As a technique for improving the toner, for example, Japanese Patent Application Laid-Open No. 62-27
No. 3581 is known, which discloses a magnetic toner having a thin film containing an organometallic compound as a main component. The magnetic toner can be produced, for example, by drying a thin layer formed by dispersing a metal alcoholate compound in a resin on the surface of the magnetic toner at a temperature of about 50 ° C. In this manufacturing method, the metal alcoholate compound itself is not reacted to form a film, but the metal alcoholate compound particles are simply contained in a resin thin film. Completely different from layers.

SUMMARY OF THE INVENTION An object of the present invention is to provide a developer which has a rapid rise in charge amount, has stable chargeability during durability, and has excellent environmental resistance.

Means for Solving the Problems The object of the present invention is achieved in a two-component developer comprising a toner and a carrier by coating the surface of the toner and / or the carrier with a ceramic coating layer.

The ceramic coating layer is a layer formed by attaching a metal alkoxide to the surface of a toner or a carrier and then performing a heat treatment.

The metal alkoxide used to form the ceramic coating layer is represented by the following general formula [I]; M (OR) n ... [I] [wherein, M represents a metal ion, R represents a lower alkyl group, n represents the oxidation number of the metal ion].

In the formula [I], M represents a metal ion.
i, Be, B, Na, Mg, Al, Si, P, K, Co, Ca, Ti, V, F
e, Ga, Ge, Y, Zr, Nb, Sn, Sb, La, Hf, Ta, W, C
e, metal ions such as Nd, Sm, Gd, Ho, Er, and Yb. Preferably, they are metal ions such as Si, Ti, Al, Mg, Ca, Fe, Co, and Zr.

R ₁ represents a lower alkyl group such as methyl, ethyl, propyl, butyl and the like.

 n indicates the oxidation number of the metal ion M.

As specific examples of the metal alkoxide represented by the general formula [I], Li (OEt), Be (OEt) ₂ , B (OEt) ₃ , Na (OE
t), Mg (OEt) ₂ , Al (Oi-Pr) ₃ , Si (OEt) ₄ , P (OE
t) ₃ , PO (OMe) ₃ , K (OEt), Ca (OEt) ₂ , Ti (OEt)
₄ , Ti (Oi-Pr) ₄ , V (Oi-Pr) ₄ , Fe (OEt) ₃ , Ca (O
Et) ₃ , Ge (OEt) ₄ , Y (Oi-Pr) ₃ , Zr (Ot-Bu) ₄ , Z
r (Ot-Bu) ₄ , Nb (OEt) ₅ , Sn (Ot-Bu) ₄ , Sn (Ot-B
u) ₄ , Sb (OEt) ₅ , Sb (OEt) ₃ , La (Oi-Pr) ₃ , Hf (O
Et) ₄ , Ta (OEt) ₅ , W (OEt) ₅ , Ce (Oi-Pr) ₄ , Nd
(Oi-Pr) ₃ , Sm (Oi-Pr) ₃ , Gd (Oi-Pr) ₃ , Ho (Oi
-Pr) ₃ , Er (Oi-Pr) ₃ , Yb (Oi-Pr) _{3 and the} like.

As the carrier on which the ceramic coating layer is formed, any known carrier, for example, glass beads used in a cascade developing system, steel balls, etc., ferrite used in a magnetic brush developing system, fine powdered iron, and any carrier such as a microcarrier can be used. is there.

As a method of treating these carrier particles with a metal alkoxide, first, a metal alkoxide is added to an alcohol (eg, ethanol) solvent with water and an acid (eg, hydrochloric acid).
And the ratio of [water] / [metal alkoxide] is 0.1 to 5
0, preferably 1 to 30, [acid] / [metal alkoxide]
And the mixture is heated to 20 ° C. to 90 ° C. to prepare a homogeneous mixture. Next, the carrier particles are put into this solution, and while performing uniform mixing and stirring, the temperature of the solution is kept at 20 to 80 ° C., and the hydrolysis and condensation of the metal alkoxide is advanced, and the solution on the surface of the carrier particles is gelled. Take the sample out of the solution tank and set the appropriate temperature (100-500
° C, preferably 200 to 400 ° C). At that time, the alkyl group in the metal alkoxide group is eliminated. If the alkyl group remains, it may adversely affect environmental resistance.

As another method, there is a method in which the above-mentioned solution or a solution of the metal alkoxide itself is sprayed while the carrier particles are tumbled in a tumbling fluidized tank or the like, and then a heat treatment is performed. In this case, the metal alkoxide may be attached to the sample surface in a solution state, or the metal alkoxide may be gasified and attached.

Alternatively, the carrier particles and the metal alkoxide-alcohol-water dispersion may be spray-dried in a gas phase by a method such as a spray-drying method, and then subjected to a heat treatment.

The thickness of the ceramic coating layer formed on the carrier particles is 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less, and may be at least 0.05 μm or more. If the thickness is more than 5 μm, the magnetic force of the carrier cannot be sufficiently obtained, the adhesion to the carrier is deteriorated, and problems such as cracking and peeling of the ceramic coating layer occur in terms of durability. When the thickness is less than 0.05 μm, the effect of the ceramic coating layer is not recognized.

When the ceramic coating layer is formed on the carrier particles, the durability and environmental resistance of the carrier are improved, a stable charge amount can be supplied to the toner for a long period, and a good image is formed.

As the toner on which the ceramic coating layer is formed, a conventional toner can be used. For example, a pulverization method of mixing and kneading a thermoplastic resin, a colorant and / or a charge imparting agent, and then pulverizing and classifying to obtain the toner. A suspension polymerized toner obtained by dispersing a colorant and / or a charge imparting agent in a toner or a monomer and polymerizing the same, or a liquid containing a colorant and a low softening point substance such as wax or a fixing resin, etc. Any of capsule toner and the like wrapped with a wall material (capsule shell) having a higher softening point than these can be used.

To form a ceramic coating layer on these toners, the same metal alkoxide and formation method used to form the ceramic coating layer on the carrier surface can be applied, but with the ceramic coating layer formed on the toner surface. Heat treatment temperature is 80 ~
The temperature is 150 ° C., preferably 80 to 120 ° C., because the presence of the alkyl group in the metal alkoxide compound in the ceramic coating layer formed on the toner surface does not affect the developer properties. is there. Further, if the processing temperature is high, there is a problem that toner aggregation occurs.

The thickness of the ceramic coating layer on the surface of the toner is 2 μm or less, preferably 1 μm or less. The entire surface of the toner does not need to be coated with the ceramic coating layer, and may be a partial coating.

If the film thickness is larger than 2 μm, the fixability is impaired. To obtain the effect of the ceramic coating layer, a film thickness of at least about 0.01 μm is provided.

When the ceramic coating layer is formed on the surface of the toner particles in this manner, the toner charge is excellent in rising, and the environment resistance is excellent.

The ceramic coating layer formed on the surface of the toner and the carrier is transparent and has a hardness of 6H or more.

Further, in the present invention, various kinds of organic and inorganic fine particles can be contained as an additive in the ceramic coating layer for the purpose of improving various properties such as chargeability, developability, and transportability as a developer.

Examples of the fine particles used herein include those commonly called charge control agents such as various organic dyes and pigments, for example, nigrosine-based dyes such as Nigrosine Base EX (manufactured by Orient Chemical Industry Co., Ltd.), and P-51 (Orient Chemical Industry Co., Ltd.). Quaternary ammonium salts, Sudan Chief Schwarz BB (Solvent Black 3: Color Index 26150), molybdic acid
Positively chargeable charge control agents such as acid pigments, imidazole metal complexes, imidazole derivatives, etc.
Chromium complex salt type azo dyes such as TRH (manufactured by Hodogaya Chemical Industries), S-32 and S-33 (manufactured by Orient Chemical Industries), E-8
1. Negatively chargeable charge control agents such as chromium complex salts such as E-82 (manufactured by Orient Chemical Industries) and zinc complex salts such as E-81 (manufactured by Orient Chemical Industries); organic resin fine particles such as benzoguanamine, melamine and nylon , Epoxy, phenol, styrene, acryl, styrene acryl, amino acryl, fluorine acryl fluorine, silicon, polyester, polyethylene, etc. various resin fine particles; inorganic fine particles, for example, magnetic powder such as magnetite, ferrite, copper oxide, titanium oxide, zinc oxide And various pigments such as aluminum oxide, non-magnetic ferrite, tin oxide, silicon oxide and carbon black, metal oxides, metal powders and the like.

The particle size used is 5 μm in the carrier.
Hereinafter, the thickness of the toner is preferably 1 μm or less.

The toner and the carrier are used in a usual mixing ratio applied to various two-component developing systems, and it is possible to use only the carrier, the toner alone, or the toner and the carrier in each of which a ceramic coating layer is formed.

(Carrier A) (Invention) Powder-coated ferrite carrier F-250H (average particle size: 50
μm, electrical resistance; 3.50 × 10 ⁷ Ω · cm; manufactured by Nippon Iron Powder Co., Ltd.) in a mixed solution of metal alkoxide Si (OC ₂ H ₅ ) ₄ in ethanol-water-hydrochloric acid, and stirred. After maintaining at the temperature, it was air-dried in a tumbling fluidized tank for 10 minutes and then heated to 300 ° C. to form a 0.5 μm thick coating layer on the surface of the ferrite carrier.

The obtained carrier is sieved (screen opening; 106 μm) to remove aggregates, and the obtained carrier is referred to as carrier A. (Average particle size: 50 μm, electric resistance: 4.3 × 10 ¹⁴ Ω · cm) (Carrier B) (Invention) In the method for producing carrier A, granular iron powder (KG series; manufactured by Kanto Denka Kogyo Co., Ltd.) Average particle size; 50
μm, electric resistance: 3,5 × 10 ⁶ Ω · cm), and the same method as that of carrier A except that a mixture of Si (OC ₂ H ₅ ) ₄ and Ti (OC ₂ H ₅ ) ₄ is used as the metal alkoxide. Thus, a coating layer having a thickness of 0.7 μm was formed on the surface of the granular iron powder.

The obtained carrier is sieved (screen opening; 106 μm) to remove aggregates, and the obtained carrier is used as carrier B (average particle size: 51 μm, electric resistance: 2.8 × 10 ¹³ Ω · cm). Carrier C) (invention) Ferrite carrier F-25 in the same manner as in Example 1.
Si (OC ₂ H ₅ ) ₄ -Al (Oi-P) as a metal alkoxide on the surface of 0HR (average particle size: 50 μm, electrical resistance: 3.50 × 10 ⁷ Ω · cm)
r) A ceramic hard coating layer having a thickness of 0.7 μm was formed in the same manner as for the carrier A using a _3- Ti (OC ₂ H ₅ ) ₄ mixed material.

The obtained carrier is sieved (screen opening; 106 μm) to remove aggregates, and the obtained carrier is used as carrier C. (Average particle size: 51 μm, electric resistance: 3.3 × 10 ¹³ Ω · cm) (Carrier D) (in the present invention) Component weight part polyester resin 100 (softening point 123 ° C., glass transition point 65 ° C., AV23, OHV40) Zn-based ferrite fine particles 500 MEP-2 (manufactured by TDK) Carbon black 2 (manufactured by Mitsubishi Kasei Co., Ltd., AM # 8) The above materials are sufficiently mixed and pulverized by a hessi-ne mixer, and then the cylinder part is 180 ° C. and the cylinder head part is 170 ° C. Were melted and kneaded by using an extruder kneader set to 1. The kneaded product was left to cool, coarsely pulverized using a feather mill, finely pulverized using a jet mill, and then classified using a classifier to obtain a carrier having an average particle diameter of 60 μm.

Further, after adjusting the amount of air so that the carrier can be lifted and rolled up well in the airflow by a rolling fluidizing device (SPRACOATER SP-40; manufactured by Okada Seiko Co., Ltd.), Si (OC ₂ H ₅ ) ₄ -Al
_{(Oi-Pr) 3 -H 2} O-HCl-C 2 H 5 OH containing metal alkoxide solution intermittently into sprayed carrier surface from a spray nozzle to adhere the metal alkoxide, 300 ° C. for 10 minutes more temperature 100 ° C. The resulting carrier was subjected to a heat treatment for 1 hour to form a ceramic hard coating layer having a thickness of 1 μm (average particle size: 61 μm, electric resistance: 4.1 × 10 ¹⁴ Ω · cm).

(Carrier E) (Comparative) In Example 1, the carrier core material was evaluated as carrier E without coating.

[Evaluation of Carrier] The physical properties of the carriers obtained in Examples and Comparative Examples were measured and evaluated by the following methods.

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

(2) Measurement of the electric resistance of the carrier The electric resistance was measured as follows: A sample was placed on a metal circular electrode so as to have a thickness of 1 mm and a diameter of 50 mm, and an electrode having a mass of 895.4 g and a diameter of 20 mm was used. 38mm inside diameter,
A guard electrode having an outer diameter of 42 mm was placed, and the resistance value one minute after the application of a DC voltage of 500 V was read, and converted to the volume specific resistance of the sample. Measurement environment is temperature 25 ± 1 ℃, relative humidity 55 ± 5%,
The measurement was repeated five times and the average was taken.

After the above materials were sufficiently mixed by a ball mill, they were kneaded on three rolls heated to 140 ° C. After cooling the kneaded material,
Coarse pulverization was performed using a feather mill, and fine pulverization was performed using a jet mill. Thereafter, air classification was performed to obtain a fine powder having an average particle size of 13 μm.

Hereinafter, toner A ((-) chargeable toner) and toner B ((+) chargeable toner) are referred to for each polarity toner.

The average toner particle size was measured using Coulter Counter II.
It was determined by measuring the relative weight distribution by particle size using a 100 μm aperture tube (manufactured by Coulter Counter Co.).

The toner A and the toner B were subjected to post-treatment with 0.1 part by weight of colloidal silica R-974 (manufactured by Nippon Aerosil Co., Ltd.) with respect to 100 parts by weight, respectively, and used for evaluation.

Examples 1 to 5 and Comparative Examples 1 and 2 [Printing endurance test] (When toner A was used) 48 g of the toner A and 552 g of the carrier were put into a polyethylene container, and the mixture was rotated and stirred for 5 hours on a stand. Copier EP with sleeve rotation type developing device using this
A printing durability test of 50,000 sheets was performed by using -870 (manufactured by Minolta Camera).

(When Toner B is Used) 50 g of the toner B and 450 g of the carrier are placed in one polyethylene container, and the mixture is rotated and stirred on a stand for 5 hours. Copier EP with sleeve rotation type developing device using this
A printing durability test of 50,000 sheets was performed using -470Z (manufactured by Minolta Camera Co., Ltd.).

Using the toner A and the toner B at the initial and endurance tests (1,000, 5,000, 10,000, 30,000, 50
The stability of image quality was evaluated by visually ranking the image fog (at the time of 0,000 sheets) based on the following image quality evaluation criteria.

：: no fog Δ: fog is noticeable but practically acceptable.

×: Fog is conspicuous and practically impossible.

Carriers A to E and toners A and B are appropriately combined, and the above various evaluations are performed (Examples 1 to 5, Comparative Examples 1 to 5).
2) and the results are shown in Table 1.

In Comparative Example 2, the printing durability test was stopped because fog was noticeable at the time of 5,000 printing presses, and the practical use was impossible. In each printing test, the toner / carrier mixture ratio was controlled to be constant.

In general, if the charge rise of the toner is poor, even if the initial image quality is good, the recharged toner has a low charge level, so that fog occurs immediately at the end of printing. Also,
When the spent carrier is advanced, the stability of charging is lost during the printing test, so that fogging occurs. When the carrier shown in the present invention was used, a stable image was obtained at the initial stage and at the end of printing as shown in the above table.

Toner C and Toner D (Invention) Polyester resin (softening point (Tm): 125 ° C, glass transition point (Tg): 68 ° C): 10
0 parts by weight Carbon black MA # 8 (Mitsubishi Kasei Kogyo): 5 parts by weight Viscol TS-200 (manufactured by Sanyo Chemical Co., Ltd.): 2 parts by weight After thoroughly mixing the above materials with a ball mill, 135 ° C
And kneaded on three heated rolls. The kneaded product was left to cool, coarsely pulverized with a feather mill, then pulverized with a fine pulverizer using a jet stream, and further classified by wind power to an average particle size of 11.5.
μm of insulating toner C was obtained.

The toner C obtained here is fed into a granulating coating apparatus (spiral flow SFC-15 type; manufactured by Freund Corporation) through air at a temperature of 50 ° C. from an air outlet to generate an air current. Adjust the amount of air so that it rolls up.

Then, sprayed intermittently from spray nozzles _{Si (OC 2 H 5) 4} -H 2 O-HCl-C 2 H 5 OH containing metal alkoxide solution.

After spraying, send heated air at approx.
An O ₂ -based coating layer was provided. At this time, the average particle size of the toner was 11.8 μm. The toner obtained here is referred to as toner D
And

(Evaluation of charge amount and printing durability) Example 6 Using the carrier E and the toner D, the toner mixing ratio was 7
% By weight of the developer was obtained. As a result of measuring the charge amount of the toner after mixing the developer for 3, 10, and 30 minutes, it was -13 μC / g, -14 μC / g, and -14 μC / g. It was found that the rise of charging was fast and stable.

Further, the toner charge amount after storing this developer under high humidity of 30 ° C. and 85% RH for 24 hours was −14 μC / g. This indicated that even under such high humidity, the chargeability was the same as in a normal environment.

Using this developer, a positive electrostatic image is developed by a magnetic brush developing method using a copier equipped with a (+) chargeable Se-based photoreceptor and a Teflon-coated heated fixing roll. Sixty thousand continuous copies were made. As a result, in the initial stage, the image quality was excellent, there was no carrier adhesion or carrier development, and this was maintained after 60,000 sheets. In addition, no carrier adhered to the photoreceptor.

Comparative Example 3 The same evaluation as in Example 6 was performed using the carrier E and the toner C.

As a result, the charge amount after mixing for 3, 10 and 30 minutes was measured to be -6 μC / g, -9 μC / g and -12 μC / g.

Further, the toner charge amount after storing the developer under high humidity of 30 ° C. and 85% RH for 24 hours was −8 μC / g.

In addition, when the initial image was evaluated, fogging was large and the level was not at a level that could withstand the printing test.

Effects of the Invention The developer obtained according to the present invention has a good charge rise, excellent environmental resistance and durability, and stable chargeability, and can provide a good image over a long period of time.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hideaki Ueda 2-30 Azuchicho, Higashi-ku, Osaka-shi, Osaka Osaka International Building Minolta Camera Co., Ltd. (56) References JP-A-60-247649 (JP, A) JP-A-57-176753 (JP, A) JP-A-54-78136 (JP, A) JP-A-60-96591 (JP, A) JP-A-63-25972 (JP, A) (58) Int.Cl. ⁶ , DB name) G03G 9/10 G03G 9/08

Claims (4)

(57) [Claims] 1. A two-component developer comprising at least a carrier and a toner, wherein the carrier has a thickness of 0.05 μm or more and 5 μm or less and has the following general formula [I]: M (OR) n [I] (where M is A metal ion, R represents a lower alkyl group, and n represents an oxidation number of the metal ion.) A developer comprising a metal alkoxide represented by the following formula: 2. A two-component developer comprising at least a carrier and a toner, wherein the toner has a thickness of 0.01 μm or more.
μm or less, the following general formula [I]: M (OR) n [I] (where M represents a metal ion, R represents a lower alkyl group, and n represents the oxidation number of the metal ion). A developer having on its surface a ceramic coating layer formed from a metal alkoxide to be formed. 3. The method for producing a carrier according to claim 1, wherein a metal alkoxide is adhered to the surface of the carrier, and the ceramic coating layer is formed by heating to 100 to 500 ° C. 4. A method for producing a toner according to claim 2, wherein a metal alkoxide is adhered to the surface of the toner, and the ceramic coating layer is formed by heating to 80 to 150 ° C.