JP3206388B2 - Dry developer for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer used for developing an electrostatic latent image formed by an electrophotographic method, an electrostatic recording method or the like.

[0002]

2. Description of the Related Art In a developing method using a two-component developer for electrophotography, toner charged mainly by frictional charging with a carrier such as ferrite adheres to an electrostatic latent image on a photosensitive drum by Coulomb force, and a transfer member is formed. Is developed by being transferred to To perform more efficient development using such a toner, the toner quickly reaches a predetermined charge amount due to friction with the carrier, and the charge amount of each toner is uniform. It is important to keep it long during the process of copying many sheets.

For this purpose, efforts have been made to add an appropriate amount of charge control agent to the toner and to find compatibility between the toner and the carrier. However, it is difficult to optimally control the charging of the toner by the conventional techniques, and when a toner and a carrier having a small particle diameter adopted in recent years to meet the demand for higher image quality are used, there is an adverse effect on the ground. At present, the problem of deterioration in image quality due to poor charging control such as fogging, toner scattering, toner falling, excessive charging, and carrier rising has repeatedly occurred. Further, it is difficult to continue using ferrite carriers containing heavy metals such as Zn, Ni, and Cu, which have been generally used in the past, under the regulations of waste and product liability in recent years. In addition, there is an increasing demand for safety of raw materials for toner.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art, and has no problems caused by poor charging control such as ground fogging, toner scattering, toner falling, carrier rising, and the like. An object of the present invention is to provide a dry developer for electrophotography having safety.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a toner containing a triphenylmethane compound represented by the general formula (1) of Chemical Formula 2, 1 to 10 mol% of MgO and 90% of Fe ₂ O ₃ .
And a ferrite carrier containing up to 99.0 mol% of a ferrite carrier.

[0006]

Embedded image

Hereinafter, the present invention will be described in detail. The toner according to the present invention includes a binder resin, a triphenylmethane-based compound represented by the general formula (1), a colorant, and other additives. At this time, the mixing ratio of the triphenylmethane compound in the toner is preferably 0.1 to 5% by weight. If the content of the triphenylmethane compound is less than 0.1% by weight, the desired charge cannot be obtained in the toner, and a large amount of reversely charged toner tends to be generated, which is not preferable. On the other hand, when the content is more than 5% by weight, the charge amount becomes too high, which causes an image density defect, which is not preferable. Further, the toner of the present invention is preferably implemented as a positively charged toner based on a charge control characteristic peculiar to a triphenylmethane compound. In this case, when a conventionally used nigrosine-based charge control agent is used for the positive polarity toner, the change in the amount of charge of the toner tends to increase, which adversely affects the image quality and reduces mutagenicity (carcinogenicity). It is not preferred because it contains suspected residues.

The thermoplastic resin used as the binder resin for the toner of the present invention includes styrenes such as styrene, parachlorostyrene and methylstyrene, vinyl chloride, vinyl bromide, vinyl fluoride, vinyl acetate, vinyl propionate, and the like. Vinyl esters such as vinyl benzoate,
Methyl acrylate, ethyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate,
2-chloroethyl acrylate, phenyl acrylate, α-
Esters of α-methylene aliphatic monocarboxylic acid such as methyl chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dialkylaminoethyl methacrylate, acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, vinyl Vinyl ethers such as methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; N-vinyl pyrrole;
A homopolymer obtained by polymerizing monomers such as N-vinyl compounds such as -vinylcarbazole, N-vinylindole and N-vinylpyrrolidone, or a copolymer obtained by copolymerizing two or more of these monomers, or A mixture thereof, a rosin-modified phenol formalin resin, an epoxy resin, a polyester resin, a polyurethane resin, a cellulose resin, a non-vinyl-based thermoplastic resin such as a polyether resin, and the like, and a mixture of these and the above-described vinyl resin can be given. .

The coloring agents used in the toner include known pigments and dyes such as carbon black, phthalocyanine blue, indanthrene blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, and permanent yellow. , Benzidine yellow and the like can be widely used.

In the method for producing a toner according to the present invention, for example, the above-mentioned triphenylmethane compound, the above-mentioned binder resin and a colorant are mixed well, and then hot-melt-kneaded with an extruder or the like, then cooled and solidified, and then jet milled. It can be obtained by finely pulverizing and classifying.

On the other hand, the ferrite carrier constituting the present invention is composed of a composite of a metal oxide and an iron oxide having a composition of MO.Fe ₂ O ₃ (where M is a divalent metal ion). MgO) from 1 to 10 mol%
And Fe ₂ O ₃ are those containing from 90 to 99.0 mol%, slightly C as impurities other than MgO and Fe ₂ O ₃
aO, MnO, etc. may be contained.

The ferrite carrier is manufactured, for example, as follows. That is, magnesium oxide is mixed with ferric oxide at a predetermined ratio, calcined at 800 to 1000 ° C. for several hours, then pulverized, and the pulverized powder is added with a binder such as polyvinyl alcohol as necessary. And spray drying in a heated atmosphere to obtain spherical particles. And the spherical particles
The ferrite carrier used in the present invention can be obtained by classifying the sintering component at a temperature of 100 to 1300 ° C.

When the content of magnesium oxide in the ferrite carrier is less than 1 mol%, the composition becomes extremely close to the magnetite composition, so that it is difficult to control the magnetic force such as the saturation magnetization of the carrier, and the image quality deteriorates and the ears are greatly increased. Therefore, there arises a problem that a load is easily applied to the developing machine. In addition, the content of magnesium oxide is 10 mol%
When the amount exceeds the above, it is necessary to increase the sintering temperature during the production of the ferrite carrier, and therefore, the material for the sintering furnace must be able to withstand high temperatures, so that the production cost of the ferrite carrier increases. There is a problem that.

The ferrite carrier constituting the present invention preferably has an electric resistivity in the range of 10 ⁸ to 10 ¹⁴ Ωcm when the average particle diameter is 40 to 100 μm.
If the electric resistivity is less than 10 ⁸ Ωcm, the electric resistance is too low to obtain a high-definition and high-quality image. If the electric resistivity is more than 10 ¹⁴ Ωcm, it becomes difficult to apply a bias voltage, and Undesirably, background stains on the surface of the photoreceptor, background stains on the photoreceptor surface, and a decrease in image density. The electric resistance of the ferrite carrier in the present invention is measured as follows. Ferrite carrier at temperature 20-25 ° C, humidity 50
After leaving for 1 hour in an environmental condition of ６０60% RH, the carrier is filled in the cell, a DC voltage of 200 V is applied, and the electric resistance is calculated from the current value. The average particle diameter is a value measured by the sieve method.

The surface of the ferrite carrier of the present invention may or may not be coated with a resin coating material. Since the ferrite carrier of the present invention has high resistance, the difference in resistivity between the resin-coated product and the non-resin-coated product is small due to its composition. In addition, since there is little peeling of the resin film, there is an advantage that the influence on the toner charge amount can be reduced. Examples of the resin coating material include a fluororesin, an acrylic resin, a styrene-acrylic copolymer resin, a silicone resin, a polyester resin, and a polybutadiene resin. The ferrite carrier of the present invention preferably has a saturation magnetization of 50 to 70 emu / g at an applied magnetic field of 5000 Oe. In this case, if it is less than 50 emu / g, there is a problem of carrier rising. On the other hand, if it is more than 70 emu / g, the problem is that a load is applied to the developing machine because ears are large.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to embodiments. “Parts” means parts by weight.

The ingredients of the above composition are extruded by an extruder.
After melt-kneading and extruding, the mixture is pulverized and classified by a jet mill, and the volume average 50% particle diameter is 9.0 μm by a coulter counter.
Thus, 12% by number of particles having a particle size of 5 μm or less were obtained. Next, Si was used as a fluidizing agent for 100 parts of the fine particles.
O ₂ (manufactured by Nippon Aerosil Co., Ltd., trade name: RA-200H)
S) 0.3 part was mixed with a Henschel mixer to obtain a toner. The toner particle diameter was measured using a Coulter Counter (manufactured by Coulter Electric Co., USA) with a diameter of 10
The measurement was performed using a 0 μm aperture tube.

Example 1 MgO had a composition of 2 mol% and Fe ₂ O ₃ had a composition of 98 mol%, an electric resistivity of 10 ¹¹ Ωcm and a saturation magnetization of 5 mol%.
Five parts of the toner A was mixed with 95 parts of a ferrite carrier coated with a silicone resin having a particle size of 5 emu / g and an average particle diameter of 60 μm to prepare an electrophotographic developer of the present invention.

EXAMPLE 2 MgO has a composition of 7 mol% and Fe ₂ O ₃ has a composition of 93 mol%, an electric resistivity of 10 ¹¹ Ωcm and a saturation magnetization of 5 mol%.
Five parts of the toner A was mixed with 95 parts of a ferrite carrier coated with a silicone resin having a particle size of 0 emu / g and an average particle diameter of 60 μm to prepare an electrophotographic developer of the present invention.

Example 3 MgO has a composition of 2 mol% and Fe ₂ O ₃ has a composition of 98 mol%, an electric resistivity of 10 ¹¹ Ωcm and a saturation magnetization of 5 mol%.
5 emu / g and 95 parts of a ferrite carrier coated with a silicone resin having an average particle diameter of 60 μm, except that the content of the triphenylmethane compound in the toner A was changed to 3.0 parts. Toner (hereinafter referred to as toner B) (5 parts) was mixed to prepare an electrophotographic developer of the present invention.

Comparative Example 1 A comparative electrophotographic developer was prepared in the same manner as in Example 1 except that a ferrite carrier containing no MgO was used.

Comparative Example 2 A comparative electrophotographic developer was prepared in the same manner as in Example 1 except that a toner in which the triphenylmethane compound of toner A was changed to 0% (hereinafter referred to as toner C) was used. .

Comparative Example 3 A comparative electrophotographic developer was prepared in the same manner as in Example 1 except that a toner in which the triphenylmethane compound of toner A was changed to nigrosine (hereinafter referred to as toner D) was used. The electrophotographic developer obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was used as an electronic copying machine PX-6 manufactured by Sanyo Electric Co., Ltd.
The image density (ID), background stain (BG) in the non-image area, charge amount, toner scattering, and carrier rise were evaluated. Table 1 shows the results.

[0024]

[Table 1]

The measuring methods and evaluation criteria shown in Table 1 are as follows. (1) Image Density (ID) A 40 × 40 mm square solid image was measured with a Macbeth reflection densitometer (trade name: RD-914, manufactured by Macbeth). (2) Background stain on non-image area (BG) It was measured using a Hunter whiteness meter Z-1001DP.

(3) Charge Amount The charge amount is obtained by measuring the frictional charge amount of the toner with a frictional charge measuring device by a blow-off method. (4) Toner scattering The toner scattering was determined by visually observing the toner scattering around the developing device.

<Evaluation Criteria>…: good, no scattering ○: good, slightly scattered but practical △: scattered but practical ×: scattered not practical

(5) Carrier rising Carrier adsorbed on the surface of the photoreceptor was visually observed and judged. <Evaluation criteria> ・ Carrier rising ◎: good, no carrier rising ○: good, slightly carrier rising, but practical △: Carrier rising, but practical ×: Carrier rising markedly impractical

As is clear from Table 1, the developers of Examples 1 to 3 according to the present invention have a stable charge amount during the process of copying 100,000 sheets. D and B. G
Was maintained well, and there was neither toner scattering nor carrier rising. On the other hand, in the case of Comparative Example 1, the charge amount decreased with continuous copying, and B.I. There is an increase in G, toner scattering, and carrier rise.
A sufficient amount of charge was not obtained from the beginning, and the amount of charge increased to D decreased and carrier rise occurred.

[0030]

According to the present invention, even in a large number of copies of 100,000, the image density (ID) and the triboelectric charge (Q / M) characteristics of the background stain (BG) toner are excellent. In addition, it is possible to provide a dry developer for electrophotography which maintains stable image quality and has high product stability, with little toner scattering and very little carrier rise.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 9/097 G03G 9/107

Claims (5)

(57) [Claims] 1. A toner containing a triphenylmethane compound represented by the following general formula (1):
Electrophotography characterized by comprising a 10 mol% and _Fe 2 _{O 3} and a <br/> ferrite carrier consisting of two components with substantially MgO and _Fe 2 _{O 3} containing 90 to 99.0 mol% Dry developer. Embedded image 2. The ferrite carrier having an average particle size of 40
１００100 μm, and the electric resistivity is 10 ⁸ 〜１０10
^{2. The} dry developer for electrophotography according to claim 1, wherein the dry developer is ¹⁴ Ωcm. 3. The dry developer for electrophotography according to claim 1, wherein the ferrite carrier has a saturation magnetization of 50 to 70 emu / g in an applied magnetic field of 5000 Oe. 4. The dry developer for electrophotography according to claim 1, wherein the toner contains 0.1 to 5% by weight of the triphenylmethane compound represented by the general formula (1). 5. The dry developer for electrophotography according to claim 1, wherein the toner is positively chargeable.