JPS61275862A - Developer for electrophotography - Google Patents

Abstract

PURPOSE:To improve the flowability, electrostatic charging stability and gradient reproducibility of a developer by holding fine titania powder and fine alumina powder each coated with amino modified silicone oil on the surface of the developer. CONSTITUTION:A surface treating agent produced by blending fine titania powder and fine alumina powder each coated with amino modified silicone oil in 1:15-15:1 weight ratio is held on the surface of a developer 7 for electrophotography contg. a fixing medium and a colorant as the principal components by 0.1-2.0pts.wt. per 100pts.wt. developer 7. Thus, the flowability, electrostatic charging stability and gradient reproducibility are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to an electrophotographic developer used in copying machines, printers, etc. This invention relates to a developer for developing a latent image of negative polarity.

(Prior art) In general, electrophotography involves forming an electrostatic latent image on the surface of a photoreceptor made of a photoconductor, applying a developer to the latent image to make it visible, and then reproducing it as needed. , and is transferred to a transfer body and fixed to obtain a copy.

Developers used in such electrophotographic methods include one-component developers in which a colorant, charge control agent, etc. are dispersed in a fixing medium, or two-component developers in which a carrier is mixed. Agents, etc. 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 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.

Conventionally, such surface treatment agents include metal oxides such as silica, alumina, and titania, as well as conductive substances such as carbon, but none of these have yielded satisfactory results. . For example, hydrophobic silica exhibits excellent fluidity properties in the initial stage, but when used for a long period of time, charges accumulate on the silica, causing electrocoagulation of the developer and maintaining the initial properties such as fluidity. It is difficult to do so. Since alumina and chikunia have low electric resistance and low charging properties, they have low charge imparting properties to the developer.

(Summary of the Invention) As a result of intensive research into the current state of the art, the present inventors have discovered that titanium oxide powder and fine aluminum oxide powder, whose surfaces are coated with silicone oil that has been modified together as a surface treatment agent, are simultaneously used as a developer. By supporting it on the surface,
It has been found that it is possible to obtain a developer that has excellent not only fluidity but also charging stability and gradation reproducibility.

That is, according to the present invention, in an electrophotographic developer comprising a fixing medium and a colorant as main components, the surface of the developer is coated with titanium oxide powder and amine-modified silicone oil as a surface treatment agent. There is provided an electrophotographic developer characterized in that fine aluminum oxide powder is supported at a weight ratio of 1:15 to 15:1.

(Example) According to the present invention, titanium oxide powder (hereinafter simply referred to as titania), 71V minium oxide t5F powder (hereinafter referred to as t3+ It is important to use both materials (called alumina) at the same time.

The present inventors recognized the following tendency in the course of research using conventional surface treatment agents. In other words, for positive charging (
Addition of No. 11 surface treatment agent to the intermediate agent tends to reduce the charge amount of the developer itself, and as the number of additive components increases, the charge amount of the developer tends to decrease. The cohesive property is improved. on the other hand,
Since most of the resins selected as fixing media in positively charged developers do not have a very large amount of positive charge, it is necessary to supplement this with other additives. Therefore, the tendency of the surface treatment agent to be negative is not desirable, and on the contrary, there is a need for a surface treatment agent that can impart fluidity without lowering the amount of charge as much as possible.

The surface treatment agent of the present invention is quite unique compared to the above-mentioned conventional trends, and has excellent fluidity for sale, while suppressing the decrease in the amount of charge, and rather , the amount of charge can be increased. A more detailed analysis of these characteristics shows that alumina and titania, which have been subjected to a specific coating treatment, maintain a high charge level in the developer, while alumina increases the fluidity of the developer, and titania works to prevent the charge level from decreasing. It is thought that the above-mentioned specific properties can be obtained by achieving the following.

Among the components of the surface treatment agent used in the present invention, commercially available metal oxides such as alumina and titania can be used. For example, there are vapor-phase silica produced by high-temperature hydrolysis of titanium tetrachloride, vapor-phase alumina produced by high-temperature hydrolysis of anhydrous aluminum chloride, etc.
All of these are preferably ultrafine particles with a secondary particle size of 5 Qmμ or more.

In the present invention, the amino-modified silicone oil used to coat the metal oxide is one in which a part of the methyl groups in the side chains of the siloxane bonds of general silicone oils are modified to at least nitrogen-containing organic groups. It is expressed by the following general formula (1).

However, m': 2] R1; alkylene group having 5 or less carbon atoms R2, Ra; hydrogen, alkyl group or -R4-NH2
(R4: alkylene group having 5 or less carbon atoms) R5: methyl group or me-1-oxy group Representative examples include the following [I] and [TI].

R; CF-T3 or OCHa [1] In the surface treatment agent used in the present invention, the aforementioned titania or alumina is coated with amino-modified silicone oil. The coating treatment is performed by dissolving the above-mentioned oil in a solvent such as toluene, dispersing the titania or alumina separately, and then drying by heating or vacuum treatment at 100 to 200°C, or by shattering. This is done by spraying oil onto titania and alumina. The titania and alumina obtained by such treatment are coated with oil, and their surfaces are rendered hydrophobic.

Additionally, due to this coating treatment, the amount of charge of the surface treatment agent itself is generally shifted in the positive direction, and in the case of titania, the amount of charge is approximately 40%.
A shift of μ(2/g) was detected, but for alumina there was almost no shift.

According to the present invention, it is preferable that the above-mentioned surface treatment agent contains chikunia and alumina in a weight ratio of 1:15 to 15:1. If the amount of titania is smaller than the above range,
A decrease in the amount of charge occurs, resulting in deterioration of image quality such as a decrease in density, blurring, and fogging. On the other hand, when the amount of alumina decreases, fluidity decreases and image quality also decreases. It also poses a problem in handling.

The surface treatment agent is carried on the surface of the developer in an amount of 01 to 2.0 parts by weight, particularly 0.2 to 1.5 parts by weight, per 100 parts by weight of the developer before treatment. If the proportion of the surface treatment agent is less than 0.1 part by weight, the surface treatment effect cannot be achieved, and the image quality may deteriorate due to a decrease in fluidity and charging stability.
Produce a subordinate. On the other hand, if the amount exceeds 2.0 parts by weight, the surface treatment agent will separate from the developer surface, causing contamination inside the machine.

The developer of the present invention is particularly used for positive charging, and components of the developer such as a fixing medium, colorant, etc. are appropriately selected from known ones. The fixing medium is methylene,
Vinyl aromatic tjA fA forms such as vinyl IV l-luene, α-methylstyrene, a-chlorostyrene, vinylnaphthalene, vinylkylene, acrylic acid, methacrylic acid, ethyl acrylate, methyl methacrylate-1, butyl methacrylate, bunalac Homopolymers of acrylic monomers such as relay 1-12-ethylhexyl acrylate, 1/-1-12-ethylhexyl methacrylate, or copolymers thereof are used. Furthermore, monomers that can be combined with these resins include conjugated diolefin yarn single bodies such as butadiene, isoprene, and chloroprene, ethylenically unsaturated carboxylic acids such as fumaric acid and maleic anhydride, their nistyl derivatives, and acetic acid. Examples include vinyl esters such as vinyl.

In addition, as a fixing medium, various waxes such as low molecular weight polypropylene, low molecular weight polyethylene, paraffin wax, carnauba wax, etc. -Anti-■ 1- It is also possible to add it as an agent.

At this time, these anti-offset agents can be simply kneaded with the above-mentioned fats, but they can also be made to coexist during the polymerization of the fixing medium.

As a coloring agent, various pigments and dyes can be used, including carbon black.In addition, in the case of a -component type developer, 30 to 60% by weight of magnetite, ferrite, etc. can be used as a coloring agent. They can also be blended in proportions.

As the charge control agent, in addition to metal complex azo dyes such as chromium, iron, and cobalt, and quaternary ammonium compounds, basic dyes such as nicrosine, nicrosine base, and crystal violet can be used.

In producing the developer of the present invention, the fixing medium, colorant, etc. are mixed in a predetermined ratio, and then kneaded by a three-roll, twin-screw extrusion method, etc., followed by pulverization, classification, and, if desired, heat treatment. By performing the above steps, a powder composition having a particle size of 5 to 30 μm is manufactured. By subjecting this powder composition to a grinding treatment using the above-mentioned surface treating agent and a super mixer, the surface treating agent can be supported on the surface of the powder.

The surface treatment agent is supported on the powder surface by electrostatic force such as van der Waals force, but if desired, it can also be fixed and supported on the powder surface by heat treatment or the like.

The developer of the present invention can be used in any developing method, but is particularly suitable for developing methods that require fluidity and charging stability, such as the method previously proposed by the applicant in Japanese Patent Application No. 59-202977. Effective for developing methods. This developing method will be explained based on FIG.

A cylindrical non-magnetic sleeve 2 made of A6 or the like is arranged close to the photoreceptor 1. Inside the sleeve 2, a N-pole repelling magnetic pole 3 is disposed close to the photoconductor 1, and magnets 4 with different polarities alternately magnetized at other locations are disposed inside the sleeve 2. An ear cutting member 5 made of a magnetic material is arranged above the sleeve. To explain the behavior of the developer here, the developer 7 accommodated in the hopper 6 is regulated to a predetermined layer thickness by the cutting member 5, and then conveyed to the developing area 8 as the sleeve 2 rotates. . In the developing area 8, as shown in the enlarged view of FIG. 2, the developer layer 9 is stripped off by the repulsive magnetic field 3 of the magnet 4, and a floating l/toner 10 is formed between it and the photoreceptor.

The floating toner 10 forms an electrostatic latent image 1 due to its own charge.
1 electrostatically and selectively, converting the latent image 11 into a visible image 12. The developer 7 that has passed through the development area 8 is transferred to the sleeve 2
As the image rotates, it is returned to the flopper 6 and waits for the next development.

According to this developing method, the photoreceptor sleeves must be placed close to each other, and the layer thickness must be set so that the developer layer does not come into contact with the photoreceptor. It is set to a very thin layer of 30 to 200 μm. In order to form such a thin layer, it is at least necessary that the developer does not aggregate at the panicle cutting position.

Unfortunately, since the transfer to the photoreceptor 1 in the development zone 8 is controlled by the amount of charge of the developer layers, it is necessary to maintain a stable amount of charge at all times.

According to this developing method, by using the developer with excellent fluidity and charging stability of the present invention, it is possible to stably form the layer thickness described above, and moreover, in the development zone 8, the charging property stabilization is achieved, making it possible to supply stable images over a long period of time.

According to this developing method, the coercive force of the developer is set in the range of 40 to 3000 e in relation to the magnetic attraction force by the magnet 4 in the developing area 8 or the conveyance property on the sleeve 2. is preferred.

The developing method of the present invention is not limited to the configuration shown in FIG. 1, and any modifications can be made. For example, it is also possible to use a flexible part such as a film or a thin metal plate in place of the cutting part set 5 to control the layer of the developer by surface contact. If desired, for the purpose of improving fine line reproducibility and gradation of images, the bias applying means 13 applies a direct current or pulse voltage of the same polarity as the latent image polarity of the photoreceptor to the sleeve 2 in a range below the potential of the photoreceptor. It is also possible to apply with

The invention is illustrated by the following example.

Example Styrene butyl methacrylate-maleic acid copolymer 6
A mixture of 0 parts by weight, low molecular weight polypropylene, 5 parts by weight, magnetite, 35 liters of crocin dye, and the above formulation was melt-kneaded in a twin-screw extruder to obtain a jet mill μ powder composition. The coercive force of the powder composition is 1
000e, and the saturation magnetization was 32 emu 7 g.

The obtained powder composition was coated with a surface treatment agent using a supermigizer according to the composition shown in Table 2.

For the oil treatment of the surface treatment agent, use the oil shown in Table 1 and add 5 g of oil to 1-50 m6 of toluene.
After dispersing 10 g of any of the metal oxides listed in Table 2 in a solution dissolved in water, the mixture is heated and dried at 100°C.

After cooling, the aggregated surface treatment agent was pulverized using a mixer, and then the aggregates were removed.

As the surface treatment agent, the silicone oils shown in Table 1 were used.

Engraving of the statement (no changes to the contents) Table 1 The metal oxides listed in Table 2 were used.

Table 2)L A copying test was conducted using the surface-treated developer according to the formulation shown in Table 3 using the developing device shown in FIG. The development conditions were as follows: developer layer thickness 100μ, PC photoconductor, maximum surface potential -450V, repulsion magnetic field (maximum drop height j) 100x, photoconductor-sleeve distance 200μ, bias voltage 300V, frequency 1. I set it to 2B.

The results are shown in Table 3.

(Hereinafter, 1-4E3) As is clear from Table 3, when alumina coated with amino-modified silicone oil or titania is used alone, alumina alone (ib, s
) shows excellent fluidity, but a decrease in the amount of charge is observed, and there is some fogging and bleeding, and titania alone (7';
, 9) showed a noticeable decrease in fluidity and lacked uniformity in image quality. In addition, with hydrophobic silica and hydrophilic silica coated with amine-modified silicone oil, positive charging was difficult (and the image quality was poor. (bian),,
, 2, 3. 4. ) were all excellent in positive chargeability, fluidity, and image quality.

(Effects of the Invention) Second, as mentioned above, the developer of the present invention improves fluidity by simultaneously using alumina and titania coated with amino-modified silicone oil within a specific range as surface treatment agents. A developer with excellent charging stability is obtained,
In particular, image stability and image uniformity during continuous copying can be achieved for negatively charged electrostatic latent images.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a developing device that can use the developer of the present invention, and FIG. 2 shows an enlarged view of the developing area thereof. 1. Photoreceptor, 2... Sleeve, 4... Magnet 7...
developer

Claims (2)

[Claims] (1) In an electrophotographic developer consisting mainly of a fixing medium and a colorant, the surface of the developer is coated with amino-modified silicone oil as a surface treatment agent. Fine titanium oxide powder and fine aluminum oxide powder 1. An electrophotographic developer, characterized in that it carries the following in a weight ratio of 1:15 to 15:1. (2) The surface treatment agent is 0.00 parts by weight per 100 parts by weight of the developer.
The electrophotographic developer according to claim 1, wherein the electrophotographic developer is carried in an amount of 1 to 2.0 parts by weight.