JPH073601B2 - Negatively charged developer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a developer for electrophotography used in a copying machine, a printer, and the like, and more specifically, a positive electrode having excellent fluidity and excellent image stability. And a developer for developing the latent image of

(Prior Art) Generally, the electrophotographic method forms an electrostatic latent image on the surface of a photoconductor made of a photoconductor, and then applies a developer to the latent image to make it a visible image, and if necessary, A copy is obtained by transferring and fixing to a transfer body.

As a developer used in such an electrophotographic method, a one-component system developer in which a colorant, a charge control agent, etc. are dispersed in a fixing medium alone or a two-component system mixed with a carrier is used. Developers and the like are known. Since these developers are required to have fluidity in various developing methods, it has been proposed to apply various fluidizing agents to the developers. Further, the surface characteristics of the developer also greatly contribute to the charging characteristics of the developer itself, and it is no exaggeration to say that the charging characteristics are determined by the material of the surface treatment agent.

Heretofore, as such a surface treatment agent, in addition to metal oxides such as silica, alumina and titania, conductive substances such as carbon have been known, but no satisfactory results have been obtained. . For example, hydrophobic silica has excellent fluidity properties in the initial stage, but in the long-term use, electric charges are accumulated in the silica, causing electrostatic aggregation between developers, and maintaining the initial fluidity properties. It is difficult to get it done. Alumina and titania have low electric resistance and low chargeability, and therefore have low negative charge imparting property to the developer.

Further, these surface treatment agents have drawbacks such as insufficient adhesion to powder particles, the surface treatment agent is likely to fall off during the developing process, and a stable image cannot be obtained for a long period of time. .

(Summary of the Invention) As a result of intensive studies on the above situation, the present inventors have found that a modified silicone oil is used as a surface treatment agent.
By coating the metal oxide and controlling the charge amount of the surface treatment agent within a predetermined range and holding it on the powder surface, it has excellent fluidity as a negatively chargeable developer, and the surface treatment agent does not fall off. It was found that a negatively chargeable developer which is prevented and has excellent image stability can be obtained.

That is, in the fixing medium, a negatively chargeable developer having a surface treatment agent carried on the surface of powder particles mainly composed of a colorant,
The surface treatment agent is obtained by treating at least one metal oxide selected from SiO ₂ , Al ₂ O ₃ , and TiO ₂ with an amino-modified silicone oil, and the metal oxide after the treatment has a blow-off charge amount of −250. A negatively chargeable developer is provided, which is characterized in that it is adjusted to be 50 to 50 μc / g.

Usually, many surface-treating agents for negatively chargeable developers themselves exhibit strong negatively chargeability. However, a treating agent having a strong chargeability is apt to cause cohesion, a bias of charges occurs on the surface of the developer, and the developer tends to coagulate.

According to the present invention, by coating the metal oxide with the amino-modified silicone oil, it is possible to control the charge amount of the metal oxide as a surface treatment agent within a favorable range. Among the metal oxides coated with the amino-modified silicone oil in this manner, a blow-off charge amount of −250 to 25 μc / g, preferably −200 to 30 μc / g, is used as the surface treatment agent to give a negative It is possible to impart excellent fluidity and image stability as a chargeable developer. Moreover, it is also a great feature that the oil-treated metal oxide has an excellent effect on the adhesion to the powder composition. The reason for this good adhesion is
It is considered that the electron-donating amino group (—NH ₂ ) present on the surface of the metal oxide subjected to the coating treatment is strongly retained in the negative polarity portion present on the powder surface of the powder composition. If the blow-off charge amount of the surface treatment agent is more negative than −250 μc / g, the fluidity of the developer is lowered due to the cohesiveness of the surface treatment agent itself, and a stable image cannot be obtained. On the other hand, when it is more positive than 50 μc / g, the negative chargeability as a developer is extremely reduced, and a good image cannot be obtained.

According to the present invention, the charge amount of the powder composition itself treated with the surface treatment agent is determined by the chargeability of the fixing medium and the like. The blow-off charge amount of the material is preferably in the range of -5 to -30 μc / g.

The metal oxide used in the present invention includes SiO ₂ and Al.
₂ O ₃ , TiO _{2 and the} like can be used, and these can be used alone or in combination, and those having a primary average particle size of 50 mμ or less are particularly desirable from the viewpoint of processing uniformity.

In the present invention, the amino-modified silicone oil for coating the aforementioned metal oxide is one in which a part of the side chain or terminal of the siloxane bond of a general silicone oil is modified with an organic group containing at least nitrogen. ,
It is represented by the following general formula (1).

(In the formula, X, ≧ 1, Y, Z ≧ O, R1 represents an alkyl group or an alkoxy group, R2 and R5 represent an alkyl group, R3,
R4 represents an alkyl group or an aryl group, R6 and R7 represent an alkyl group including an alkyl group, an alkoxy group and an amino group, and at least one of the following atomic groups In it, R8 is an alkylene group, an arylene group, R9, R10 represents hydrogen, an alkyl group, or -R11-NH _2: represents the (R11 alkylene groups), respectively. ) Representative examples include the following [I] and [II].

In the production of the surface treating agent of the present invention, the metal oxide is coated with the amino-modified silicone oil described above. The coating process dissolves the oil in a solvent such as toluene,
It is obtained by dispersing the metal oxide and then drying it by heating at 100 to 200 ° C. or vacuum treatment, or by spraying oil in a spray state on the metal oxide. In particular, it is preferable to use a solvent because uniform treatment can be performed.

At this time, the control of the charge amount of the surface treatment agent is based on the electron donating property of the amino-modified silicone oil, and depends on the molecular weight and the amine equivalent. The amine equivalent is the molecular weight divided by the number of amino groups per molecule.

Therefore, the smaller the molecular weight and the smaller the amine equivalent, the more the metal oxide tends to shift to the positively charged side. Therefore, according to the present invention, in order to set the charge amount in a specific range, by appropriately selecting the amount of oil to be dissolved in the solvent, the amine equivalent of the oil, or the molecular weight, depending on the metal oxide used. It can be carried out.

According to the present invention, the above-mentioned surface treatment agent is powder particles 100
Treatment is carried out at a ratio of 0.1 to 2.0 parts by weight, particularly 0.2 to 1.5 parts by weight, based on parts by weight. If the ratio of the surface treatment agent is less than 0.1 parts by weight, the effect as the surface treatment agent cannot be obtained, and
Since the charge amount is insufficient, a good image cannot be obtained.
On the other hand, the toner cannot be carried on the surface of the toner in excess of 2.0 parts by weight, resulting in in-machine contamination, and deterioration of image quality, particularly bleeding.

The developer of the present invention is particularly used for negative charging, and known components such as a fixing medium and a colorant, which are components of the developer, are appropriately selected. As the fixing medium, vinyl aromatic monomers such as styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylnaphthalene and vinylxylene, acrylic acid, methacrylic acid, ethyl acrylate, methyl methacrylate, butyl methacrylate, Homopolymers of acrylic monomers such as butyl acrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate, or copolymers thereof are used. Further, as monomers that can be combined with these resins, butadiene, isoprene, conjugated diolefin-based monomers such as chloroprene, fumaric acid, ethylenically unsaturated carboxylic acids such as maleic anhydride or esters thereof, and acetic acid. Examples thereof include vinyl esters such as vinyl.

In addition, as the fixing medium, 2 to
It is also possible to add various waxes such as low molecular weight olefin resin such as low molecular weight polyproprene and low molecular weight polyethylene, paraffin wax, carnauba wax and the like as an offset preventing agent at a ratio of 20% by weight. At this time, these offset preventing agents can be simply kneaded with the above-mentioned resins, but can also be coexisted during the polymerization of the fixing medium.

As the colorant, various pigments and dyes such as carbon black can be used, and in the one-component developer,
A magnetic material such as magnetite or ferrite may be added in a proportion of 30 to 60% by weight based on the total amount of the developer.

According to the present invention, a charge control agent such as a basic dye such as nigrosine, nigrosine base, and crystal violet can be used in addition to the quaternary ammonium compound, if desired.

In the production of the developer of the present invention, a fixing medium, a colorant and the like are mixed at a predetermined ratio, and then kneading is carried out by a three-roll method, a twin-screw extrusion method or the like, and thereafter, pulverization and classification are carried out by heat treatment as desired. Etc. to produce a powder composition having a particle size of 5 to 30 μm. The surface treatment agent can be supported on the surface of the powder by subjecting the powder composition to the above-mentioned surface treatment agent with a super mixer or the like. The surface treatment agent is carried on the surface of the powder by electrostatic attraction such as van der Wamas force, but it may be fixed and carried on the surface of the powder by heat treatment or the like, if desired.

The invention is illustrated by the following example.

Example Styrene-acrylic resin 55 parts by weight Low molecular weight polypropylene 5 〃 Magnetite 40 〃 Negative charge control agent 0.5 〃 The mixture of the above formulation was melt-kneaded with a twin-screw extruder, then pulverized with a jet mill and classified to have a particle size of 5 to 20 μm. A powder composition of The blow-off charge amount of the obtained powder composition was −15 μc / g.

The obtained powder composition was dusted with a surface treatment agent using a super mixer according to the composition shown in Table 2.

The oil treatment of the surface treatment agent was carried out by using the oil in Table 1 and dispersing 10 g of any of the metal oxides in Table 2 in a solution prepared by dissolving 0.5 g of oil in 150 ml of toluene. Heat dry at 150 ° C. After cooling, the aggregated surface treatment agent was pulverized with a mixer, and the aggregate was removed with a 60-mesh sieve.

The charge of the surface treatment agent was measured based on the blow-off method, and iron powder (Z-200, manufactured by Nippon Iron & Powder Co., Ltd.) was used in a constant temperature and humidity bath.
After standing for a period of time, 29.85 g of iron powder and 0.15 g of a surface treatment agent were mixed in a bottle for 1 minute, and then measured with a blow-off electrification meter.

The charge amount of the developer is also the same as in the above measuring method, and the iron powder 2
Measurements were made with 8.50 g and 1.5 g of developer.

The fluidity was measured by measuring the angle of repose with a powder tester (manufactured by Hosokawa Micron).

The adhesiveness to the developer was determined by visually observing the amount of the surface treatment agent which was released from the surface of the developer when the developer was applied to a 100-mesh sieve and remained in the sieve.

The obtained developer was carried on an A1 sleeve having a magnet inside with a layer thickness of 100 to 150 μ, and was faced in a non-contact state with a selenium photoreceptor having a positively charged latent image, and a predetermined bias was applied to the sleeve. And a pulse voltage was applied to cause the developer to fly to the photoconductor for development.

In Table 2, the same metal oxide coated with amino-modified silicone oil and untreated one are shown in parallel. When comparing them,
In any of the metal oxides, the one of the present invention has adhesiveness,
It is understood that both fluidity and image quality are excellent.

However, even if a metal oxide treated with an amino-modified silicone oil was used, if the addition thereof was too much shifted to the positive side, the charge amount of the developer was lowered as shown in No. 16, and the image was deteriorated. On the contrary, even surface treatment agents having a charge amount within the range of the present invention, which has not been oil-treated (No. 6)
Had no effect. Furthermore, when amino-modified silicone oil is used (No.15), the charge amount increases conversely, as is clear from comparison with No.1 and No.2.
It was not so effective.

(Effects of the Invention) As described above, the developer of the present invention uses a metal oxide coated with an amino-modified silicone oil having a specific charge amount as a surface treatment agent, and thus has an extremely stable negative charge. Since it is possible to improve the fluidity and prevent the surface treatment agent from falling off at the same time, it is possible to obtain a stable image for a long period of time.

Claims (1)

[Claims] 1. A negatively-charged developer comprising a fixing medium and powder particles mainly composed of a colorant, the surface of which is coated with a surface-treating agent, wherein the surface-treating agent is SiO ₂ , Al ₂ O ₃ , or TiO _{2. At} least one metal oxide selected from ₂ is treated with amino-modified silicone oil, and the blow-off charge amount of the metal oxide after the treatment is -250 to 50 μc / g. Negatively charged developer.