JPH02131250A - Developing agent - Google Patents

Abstract

PURPOSE:To obtain a good picture having excellent environmental resistance and durability and stable electrostatic charging property over a long period by coating the surface of a carrier with a specified ceramic coating layer. CONSTITUTION:The ceramic coating layer having 0.05-5mum thickness is formed on the surface of a carrier. When the thickness is controlled to >5mum, the magnetic force of the carrier is not obtained, the adhesion to the carrier is deteriorated, and the coating layer is cracked or released. The effect of the coating layer is not produced at <0.05mum thickness. When the ceramic coating layer is formed on the carrier particles in this way, the durability and environmental resistance of the carrier are improved, a stable electrostatic charge amt. is supplied to a toner over a long period, and a good picture is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Examples] ■Ribun■ The present invention relates to a developer for developing electrostatic images comprising two components, a toner and a carrier.

Conventional technology and issues Currently, copying machines are becoming smaller and faster.
In addition, higher precision is required in terms of image quality. In order to achieve these requirements, it is essential for the developer to (a) have a fast charge build-up, (b) have stable chargeability during durability, and have excellent environmental resistance. It is mentioned as.

Attempts have been made to improve carriers and toners in order to satisfy the above requirements, and techniques for coating the surface of a ferrite carrier with a resin or a glassy layer are known.

With resin-coated carriers, it is generally difficult to form a uniform coating layer, and there are problems such as the coating layer peeling off during mixing and stirring.

Furthermore, in terms of environmental resistance, fully satisfactory characteristics have not yet been achieved.

As a technique for coating the surface of carrier particles with a vitreous layer, for example, Japanese Patent Application Laid-Open No. 78136/1984 is known.

JP-A-54-78136 discloses a carrier material whose surface is coated with an inorganic glass layer.

After melting the glass raw material, the carrier is rapidly cooled to about 2
A carrier that is pulverized with clay (binder) to approximately 00 mesh L (approximately 74 μm), prepares a suspension in which the pulverized material is dispersed, and fluidizes the resulting suspension in a circulating fluidization bed. Spray 120% on the core material with a spray gun.
Dry at a temperature of about °C, then heat in an electric oven at about 950 °C.
After baking for about 10 minutes at a temperature of at least 500℃,
Obtained by standing and cooling.

The above manufacturing method involves adhering glass powder onto a powder of several tens of microns to several hundred microns, and uses a binder, but it is extremely difficult to adhere the glass powder, and it is difficult to apply it uniformly to the surface of the base material. Because glass powder is attached and melted to form a film, the film thickness is several tens of microns.
The thickness is approximately equal to or approximately 80% of the particle size of the glass powder. If the amount to be deposited is reduced, it becomes difficult to form a uniform film layer on the surface of the carrier core material.

In the above manufacturing method, it is difficult to make the glass raw material into a small particle size of about 50 μm or less, and the carrier surface coating layer becomes thick, on the order of several tens of μm. In addition, if a structure is adopted in which a thick glass layer is provided on the surface of the carrier core material,
The magnetic force of the carrier itself decreases, making it unsuitable as a carrier for use in magnetic brush development.

Recently, in cobia and printers, in order to obtain high image quality, the carrier particle size has been required to be smaller than 100μm, preferably 80μm or less, and the surface of the core material with such a particle size has almost the same size. It becomes impossible to attach glass powder of the diameter itself.

As a technique for improving toner, for example, Japanese Patent Application Laid-Open No. 62-2
No. 73581 is known, which discloses a magnetic toner having a thin film containing an organometallic compound as a main component. The magnetic toner can be manufactured by, for example, forming a thin layer on the surface of the magnetic toner by dispersing a metal alcoholate compound in a resin and drying it 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 thin resin film, and the ceramic hard coating that this application seeks to disclose can be obtained. It is completely different from the layer.

Problems to be Solved by the Invention It is an object of the present invention to provide a developer that has a rapid charge build-up, stable charging performance during durability, and excellent environmental resistance. .

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

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

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

In formula [1], M represents a metal ion, specifically L
is B es B SN a1M g%AI2, Si
, P, K, CoSCa, Ti, VSFe, Ga, G
eSY, ZrsNb, SnSSb, LaSHr, Ta,
w, Ce, Nd, Sm, Gd. ．． These are metal ions such as Ho, Er, and Yb.

Preferably Si, Ti. ．． Al2, Mg, Ca, F
e, CoSZr, and other metal ions.

R. represents a lower alkyl group such as methyl, ethyl, proyl, butyl.

n indicates the oxidation number of the metal ion M.

Specific examples of the metal alkoxide represented by the general formula [1] include Li(OEt), Be(OEt)t, B
(OEL). , N a (O E t), Mg (O E
t)-, Aff(O i - P r)3, S i(O
E t)4, P(OEt)s, po(○Me)s, K
(O E t), C a(O E t)t, T i(
O E t)+, T i (O iPr)i, V (O
i P r)4, F e(O E t)3, C a(
O E t)3, G e (O E t)-, Y (O
i-P r)3, Z r(O t-B u)4, Z
r(O n - Bu) a, N b (O E t)
s, S n (O t B u) 4, S n (O n
- Bu)a, Sb(O Et)s, Sb(
O E t)3, La(O i P r)-, H r
(O E t)4, T a(O E t)s, W(O
E t)s, Ce(Oi-Pr)a, Nd(Oi-Pr
)s, S m(O i-P r)3, G d(O i
P r)s, Ho(Oi-Pr)s, E r(O i
-Pr)s, Yb(Oi-Pr)s, and the like.

As the carrier on which the ceramic coating layer is formed, any known carrier can be used, such as glass beads and steel balls used in the cascade development method, ferrite, fine iron powder, microcarriers used in the magnetic brush development method, etc. It is.

As a method for treating these carrier particles with a metal alkoxide, first, the metal alkoxide is added to an alcohol (e.g., ethanol) solvent together with water and an acid (e.g., hydrochloric acid) at a ratio of [water]/[metal alkoxide] of 0.1 to 5
0, preferably 1 to 30, and the ratio of [acid/metal alkoxide/de] is o. Add so that oot ~ 1, and heat at 20°C ~
A homogeneous mixture is prepared by heating to 90°C. Next, carrier particles are added to this solution, and while uniformly mixed and stirred, the temperature of the solution is maintained at 20 to 80°C to proceed with hydrolytic condensation of the metal alkoxide, and the solution on the surface of the carrier particles is gelled. Then, the sample is taken out of the solution tank and heat-treated at an appropriate temperature (100-500°C, preferably 200-400°C). At this time, the alkyl group in the metal alkoxide group should be eliminated. If alkyl groups remain, they may have an adverse effect on environmental resistance.

Other methods include a method in which the above solution or a solution of the metal alkoxide itself is sprayed while carrier particles are transferred in a transfer fluidized tank or the like, and then heat treatment is performed. In this case, the metal alkoxide may be attached to the sample surface in the form of a solution, or the metal alkoxide may be gasified and attached.

Alternatively, a method may be used in which the carrier particles and a metal alkoxide alcohol-water dispersion solution are 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 it is sufficient that the ceramic coating layer has a thickness of at least 0.05 μm or more. If the film thickness is thicker than 5 μm, sufficient magnetic force of the carrier cannot be obtained, and adhesion with the carrier deteriorates, leading to durability problems such as cracking and peeling of the ceramic coating layer. 0605
If the thickness is less than μm, the effect of the ceramic coating layer will not be recognized.

Forming a ceramic coating layer on carrier particles improves the durability and environmental resistance of the carrier, making it possible to supply a stable amount of charge to the toner over a long period of time.
In addition, a good image is formed.

As the toner on which the ceramic coating layer is formed, ordinary toners can be used. For example, after mixing and kneading a thermoplastic resin, a coloring agent, and/or a charge imparting agent, etc., the toner is pulverized and classified. Grinding method for obtaining toner Toner, or suspension polymerization toner obtained by dispersing a colorant and/or charge-imparting agent in a monomer and polymerizing the same, or a colorant and a low softening point substance such as wax, or a fixing resin. It is also possible to use any capsule toner in which a liquid containing .

To form a ceramic coating layer on these toners, metal alkoxides and formation methods similar to those used to form a ceramic coating layer on the carrier surface can be applied, but without forming a ceramic coating layer on the toner surface. The heat treatment temperature for forming is 80~
The temperature is 150°C, preferably 80-120°C. This is 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. Furthermore, if the processing temperature is high, there are problems such as toner aggregation.

Further, the thickness of the ceramic coating layer on the toner surface is formed to be 2 μm or less, preferably 1 μm or less, and it is not necessary that the entire surface of the toner be covered with the ceramic coating layer.
Partial coats are also acceptable.

If the film thickness is thicker than 2 μm, the fixing properties will be impaired, and in order to obtain the effect of the ceramic coating layer, the film thickness should be at least about 0.01 μm.

When a ceramic coating layer is formed on the surface of the toner particles in this manner, the toner has excellent charge build-up and environmental resistance.

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

Furthermore, in the present invention, various organic and inorganic fine particles can be included as additives in the ceramic coating layer for the purpose of improving various properties of the developer such as chargeability, developability, and transportability.

The fine particles used here include those commonly called charge control agents such as various organic dyes and pigments, such as nigrosine dyes such as Ehanigrosine Base EX (manufactured by Orient Chemical Industry Co., Ltd.), and P-51 (manufactured by Orient Chemical Industry Co., Ltd.). Quaternary ammonium salt such as '12), Sudan chief fish 1 bar BB
(Solvent Black 3: Color Index
26150), positively chargeable charge control agents such as molybdate chelate pigments, imidazole metal complexes, and imidazole derivatives, Eisenspiron Black TRH (manufactured by Hodogaya Chemical Industry Co., Ltd.), S-32, S-33 (manufactured by Orient Chemical Industry Co., Ltd.) ), etc., chromium complex type azo dyes, E-81, E-8
Chromium complex salts such as 2 (manufactured by Orient Chemical Industry Co., Ltd.), E-
Negative charge control agents such as zinc complex salts such as 8 1 (manufactured by Orient Kagaku Kogyo Co., Ltd.); organic resin fine particles such as penzoguanamine, melamine, nylon, epoxy, phenol,
Styrene, acrylic, styrene acrylic, amino acrylic, fluorine acrylic fluorine, silicone, polyester,
Various resin fine particles such as polyethylene; inorganic fine particles, such as magnetic powder such as magnetite and ferrite, various pigments such as copper oxide, titanium oxide, zinc oxide, aluminum oxide, non-magnetic ferrite, tin oxide, silicon oxide, carbon black, and metal oxides. material, metal powder, etc. are used.

The particle size used is preferably 5 μm or less for carriers and 1 μm or less for toners.

The toner and carrier are used in the usual mixing ratio applied to various two-component development systems, and it is possible to use only the carrier, only the toner, or both the toner and the carrier with a ceramic coating layer formed thereon.

(Carrier AX invention) Uncoated ferrite carrier F-250H (average particle size;
50μm. Electric resistance: 3.50 x 10'Ω-OR: manufactured by Nippon Tetsuko Co., Ltd.) was
5) Mix and stir in the ethanol-water monohydrochloric acid mixed solution from step 4, keep this at a temperature near room temperature, air dry for 10 minutes in a transfer fluidized tank, raise the temperature to 300°C, and apply it to the surface of the ferrite carrier. A coating layer with a thickness of 0.5 μm was formed.

The obtained carrier is sieved (sieve opening: 106μs)
The aggregates were removed, and the obtained carrier was designated as carrier A. (Average particle size: 50μm, electrical resistance: 43X10"
Ω・Gm) (Carrier BX invention) Granular iron powder (KG series; manufactured by Kanto Denka Kogyo Co., Ltd.) (average particle size: 5
0 μ-, electrical resistance: 3.5XIO@Ω・cm), and carrier A except that a mixed system of Si (O C , H 5) and Ti (O C , H s) a is used as the metal alkoxide. A coating layer with a thickness of 07 μm was formed on the surface of the granular iron powder using the same method.

The obtained carrier was sieved (sieve opening: 106 μm)
The aggregates were removed, and the resulting carrier was designated as carrier B. (Average particle size: 5lμm1 Electrical resistance: 2.8X10
”Ω-cm) (Carrier C) (Invention) Ferrite carrier F-25 was prepared in the same manner as in Example 1.
0HR (average particle size: 50μm, electrical resistance: 3.50X1
Si (0'Ω・CZ) as a metal alkoxide on the surface of
○CzH-)+ AQ(Oi Pr), T+(Q
A ceramic hard coating layer with a thickness of 0.7 μm was formed using a CzHs)-mixed material in the same manner as for carrier A.

The obtained carrier was sieved (sieve opening: 106 μm)
The aggregates were removed, and the obtained carrier was designated as carrier C. (Average particle size; 51μ++t% Li resistance; 3.
3X10"Ω・cl) (Carrier D) (Invention) Ingredients Part by weight Polyester resin 100 (Softening point 123°C, Glass transition point 65°C, AV23, OHV40) Fe-Z n-based ferrite fine particles 500
MFP-2 (manufactured by TDK Corporation) Carbon black 2 (manufactured by Mitsubishi Kasei Corporation, AM#8) The above materials were sufficiently mixed and pulverized using a Henschene mixer, and then cylinder part 180° C1 cylinder head part 17
The mixture was melted and kneaded using an extrusion mixer set at 0°C. After cooling the kneaded material, it was coarsely pulverized using a feather mill, further finely pulverized using a jet mill, and then classified using a classifier to obtain a carrier having an average particle size of 60 μm.

Furthermore, after adjusting the amount of air so that the carrier floats up and transfers in the airflow using a transfer flow device (Subura Coater SP40; manufactured by Okada Seiko Co., Ltd.), Si(OCtH,
4 Ag(0+ Pr)3 HtO HCi2C
t H s O H-based metal alkoxide solution was intermittently sprayed from a spray nozzle to adhere the metal alkoxide to the carrier surface, and the temperature was further heated to 100°C for 10 minutes.
By heating to 00'C and heat-treating for 1 hour, the thickness lμ
A ceramic hard coating layer of m was formed. (Average particle size: 61μm, electrical resistance: 4.IX10''Ω・C
ll) The obtained carrier was designated as carrier D.

(Carrier E) (Comparison) The carrier core material in Example 1 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 method.

(1) Carrier particle size The carrier particle size is Microtrac model 7995-
10SRA (manufactured by Nikkiso Co., Ltd.) was used to determine the average particle size.

(2) Measurement of electrical resistance of carrier Electrical resistance was measured as follows: A sample was placed on a metal circular electrode with a thickness of 1 mm and a diameter of 50 mm, and an electrode with a mass of 895.49 and a diameter of 20 + nm. , inner diameter 38
A guard electrode with an outer diameter of 42 m+n was placed on the sample, and the resistance value after 1 minute when a DC voltage of 500 V was applied was read and converted to the volume resistivity of the sample.

The measurement environment was a temperature of 25°C and a relative humidity of 55±5%, and the measurements were repeated 5 times and averaged.

(Hereinafter, blank space) [Preparation of toner] (-) Part by weight of chargeable toner component (+) Part by weight of chargeable toner component After thoroughly mixing the above materials in a ball mill, knead on three rolls heated to 140°C. did. After leaving the interfering object to cool,
It was coarsely ground using a feather mill and further finely ground using a jet mill. Thereafter, air classification was performed to obtain a fine powder with an average particle size of 13 μm.

The respective polar toners are hereinafter referred to as toner A ((-) chargeable toner) and toner B ((+) chargeable toner).

The average particle size of the toner can be measured using a Coulter Counter ■ (
The relative weight distribution by particle size was determined using a 100 μm aperture tube (manufactured by Coulter Counter).

Note that Toner A and Toner B were post-treated with 0.1 part by weight of Corroiglu Silicry R-974 (manufactured by Nippon Aerosil Co., Ltd.) per 100 parts by weight, and used for evaluation.

Examples 1 to 5, Comparative Examples 1 to 2 [Print durability test] (When using Toner 8) Toner A489 and 552 g of carrier were placed in a 1a polyethylene container, and mixed and stirred by rotating on a stand for 5 hours. Using this, a printing durability test of 50,000 sheets was conducted using a copying machine Ep-870 (manufactured by Minolta Camera Co., Ltd.) having a sleeve rotation type developing device.

(When Toner B is Used) 50 g of Toner B and Carrier 4509 are placed in a 1 g polyethylene container and mixed and stirred by rotating on a stand for 5 hours. Using this, a printing durability test of 50,000 sheets was conducted using a copying machine EP-4702 (manufactured by Minolta Camera Co., Ltd.) having a sleeve rotation type developer.

Using Toner A and Toner B, visually check the image strength during the initial and printing durability tests (1,000 sheets, 5,000 sheets, 10,000 sheets, 30,000 sheets, and 50,000 sheets). The stability of image quality was evaluated by ranking the images based on the image quality evaluation criteria shown in .

○: No fog Δ: Fog is noticeable but practically acceptable.

X: Fog is noticeable and is not practical.

Combining carriers A-E and toners A and B as appropriate,
Performed the above various evaluations (Examples 1 to 5, Comparative Examples 1 to 2),
The results are shown in Table 1.

(Hereinafter referred to as margins) In Comparative Example 2, the printing durability test was discontinued because the force bleed was noticeable after printing 5000 sheets and reached a level that was practically unusable. In addition, during each printing test, toner/
The carrier mixing ratio was controlled to be constant.

In general, if toner has a poor charging start-up, even if the initial image is good, fogging will occur immediately during continuous printing because the charging level of the replenished toner is low. Further, as the carrier becomes svent-like, the charging stability is lost during the printing durability test, resulting in fogging. As shown in the table above, when the carrier shown in the present invention was used, stable images were obtained at the initial stage and during printing.

Toner C and Toner D (present invention) Polyester resin (softening point (Tm): 125°C, glass transition point (Tg)
: 68°C) : 100 parts by weight Carbon black MA#8 (manufactured by Mitsubishi Chemical Industries, Ltd.): 5 parts by weight Viscoel TS-200 (manufactured by Sanyo Chemical Industries, Ltd.); 2 parts by weight The above materials were thoroughly mixed in a ball mill. Thereafter, the mixture was kneaded on three rolls heated to 135°C. After cooling the kneaded material, it was roughly pulverized with a feather mill, then pulverized with a fine pulverizer using a jet stream, and further classified by air to obtain an average particle size of 11.
．． An insulating toner C having a thickness of 5 μm was obtained.

The toner C obtained here was placed in a granulation coating device (Spirer Flow S FC-1 type 5; manufactured by Freund Sangyo Co., Ltd.), in which air at a temperature of 50°C was sent from an air outlet to generate an air current. Adjust the amount of air so that the toner floats and transfers properly.

Next, Si(QC,H,). -H,O-HCQ-C,H
A 50H metal alkoxide solution is intermittently sprayed from a spray nozzle.

After spraying, heated air at about 80'C was sent to form a Sin-based coating layer on the toner surface layer. At this time, the average particle size of the toner was 11.8 μm. The toner obtained here is referred to as toner D.

(Charge amount and printing durability evaluation) Example 6 Using carrier E and the above-mentioned toner D, a developer with a toner mixing ratio of 7% by weight was obtained. The toner charge amount of this developer was measured after being mixed for 3, 10, and 30 minutes, and the results were 13 μC/9, -14 μC/9, and -14 μC/9. It was found that the charge rise was quick and stable.

Furthermore, this developer was heated at 30'C and 85% RH for 2 hours.
The toner charge amount after storage for 4 hours is -141lC/9
Met. This showed that even under such high humidity, the charging property was the same as under normal environment.

In addition, using this developer, a positive electrostatic charge image is developed by a magnetic brush development method using a copying machine equipped with a (+) chargeable Se-based photoreceptor and a Teflon-coated heating fixing roll. 60,000 copies were made continuously.

As a result, the image quality was excellent in the initial stage, with no carrier adhesion or carrier development, and this was maintained even after 60,000 sheets were printed. Further, there was no carrier adhesion to the photoreceptor.

Comparative Example 3 The same evaluation as in Example 6 was performed using Carrier E and the above-mentioned Toner C.

As a result, the amount of charge after mixing for 3 minutes, 10 minutes, and 30 minutes was measured, and the results were -6μC/9, -9μC/9, 12μC/9
Met.

Further, after the developer was stored for 24 hours under high humidity at 30 DEG C. and 185% RH, the toner's chargeability was -8 .mu.C/9.

Also, when the initial image was evaluated, there was a lot of fogging and it was not at a level that could withstand a printing durability test.

Effects of the Invention The developer obtained according to the present invention has good charging start-up, excellent environmental resistance and durability, and stable charging properties, and can provide good images over a long period of time.

Claims (1)

[Claims] 1. In a two-component developer consisting of at least a carrier and a toner, the carrier has a diameter of 5 μm or less and 0.05 μm.
A developer characterized by having a ceramic coating layer on its surface with a thickness of m or more. 2. In a two-component developer consisting of at least a carrier and a toner, the toner surface has a particle size of 2 μm or less and 0.01
A developer characterized in that a ceramic coating layer with a thickness of μm or more is formed. 3. Attach metal alkoxide to the carrier surface, 10
2. The method for manufacturing a carrier according to claim 1, wherein the ceramic coating layer is formed by heating to 0 to 500[deg.]C. 4. Attach metal alkoxide to the toner surface, and
3. The method for producing a toner according to claim 2, wherein the ceramic coating layer is formed by heating to 150[deg.] C.