JPS61275861A - Developer for electrophotography - Google Patents

Abstract

PURPOSE:To improve the flowability and developing characteristics of a developer by holding fine titania powder coated with amino modified silicone oil as a surface treating agent on the surface of the developer. CONSTITUTION:A surface treating agent produced by coating titania with amino modified silicone oil is held on the surface of a developer 7 by 0.1-2.0pts.wt., especially 0.2-1.5pts.wt. per 100pts.wt. developer 7. Thus, the extent of electrostatic charging of the developer is increased and the flowability is 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., and more particularly, to a developer for developing negative polarity latent images with excellent charging stability. Regarding waste developer.

(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. A copy is obtained by transferring and fixing onto a transfer body.

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 initially exhibits excellent fluidity, but after long-term use, charge accumulates on the silica, causing electrostatic aggregation of the developer, which impairs initial properties such as fluidity. Difficult to maintain. Alumina and titania have low electrical resistance.
Since the chargeability is low, the ability to impart charge to the developer is low.

(Summary of the Invention) As a result of intensive research into the above-mentioned current situation, the present inventors used titanium oxide powder coated with modified silicone oil as a surface treatment agent and supported it on the surface of developer particles. It has been found that by doing so, it is possible to obtain a developer particularly excellent in positive charging stability.

That is, according to the present invention, there is provided an electrophotographic developer characterized in that titanium oxide powder coated with amino-modified silicone oil is carried on the surface as a surface treatment agent.

(Example) According to the present invention, it is important to use titanium oxide powder (hereinafter simply referred to as titania) coated with amine-modified silicone oil as a surface treatment agent.

The present inventors recognized the following tendency in the process of researching developers using conventional surface treatment agents. In other words, in the case of old charging developers, the amount of charge of the developer itself tends to decrease due to the addition of a surface treatment agent, the amount of charge of the developer tends to decrease as the number of added components increases, and When the amount of F is low, the non-aggregation property is improved by -1.

On the other hand, in W charging developers, since most of the resins selected as the fixing medium do not have a very large positive chargeability, it is necessary to supplement this with other additives. Therefore, the above-mentioned tendency of surface treatment agents is not favorable, and on the contrary,
There is a need for a surface treatment agent that can impart fluidity without reducing the amount of charge as much as possible.

In contrast to these general trends, titania coated with the amine-modified silicone oil of the present invention has a small charge amount itself, but when used as a surface treatment agent, it can be used as a surface treatment agent without reducing the charge amount of the developer. , rather.”
It has the unique property of having a tendency to increase.

Further, in imparting fluidity to the developer, the fluidity of the developer can be improved compared to titania which is not subjected to any treatment.

Any commercially available titania can be used as the surface treatment agent used in the present invention, such as vapor phase titania produced by high-temperature hydrolysis of titanium tetrachloride.
In particular, those having a -order average particle diameter of 50η1μ or less are desirable from the viewpoint of uniformity of processing.

In the present invention, the amino-modified silicone oil for coating the metal oxide mentioned above is a general silicone oil containing siloxane bonds, (IHm) in which a part of the methyl group is modified with at least a nitrogen-containing organic group. and is expressed by the following general formula (1).

However, m, n; 21 R+; alkylene group having 5 or less carbon atoms R2, R3; hydrogen, alkyl group or -R4-NH2 (
R4: alkylene group having 5 or less carbon atoms) R5, methi/L/
The radical is a me-1-oxy group. Representative examples include CI':l, [Iff'
:There is a 1st prize.

R: CF-(3t is OCF■3) The surface treatment agent of the present invention coats the above-mentioned titania with amino-modified silicone oil.The coating treatment is performed by dissolving the above-mentioned oil in a solvent such as toluene. It can be obtained by dispersing titania and then drying it by heating at 100 to 200'C or by vacuum treatment, or by spraying oil on titania in a spray state.The titania obtained by such treatment is , coated with oil,
The surface becomes hydrophobic, so to speak.

Unfortunately, the charging of the surface treatment agent itself works in the direction of increasing the positive charging, and for example, the untreated titania used in the examples described later has a charge of -18 μC/g.
The value increased to +22 μC/g by the coating treatment.

According to the present invention, the above-mentioned surface treatment agent is used in an amount of 0.1 to 2.0 parts by weight, particularly 0.2 to 1.5 parts by weight, per 100 parts by weight of the developer on the treated surface. .

If the proportion of the surface treatment agent is less than 0.1 parts by weight, no effect as a surface treatment agent can be obtained, the resulting image will be curly and the amount of charge will be insufficient, making it impossible to obtain a good image. On the other hand, if the number exceeds 2.0, the surface of the toner cannot be fully supported, resulting in contamination inside the machine and deterioration of image quality, especially bleeding.

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 styrene,
vinyl/L/l-) renin, a-methylstyrene, α-
To vinyl aromatic Qi-mers such as chlorostyrene, vinylnaphthane, vinylgysylene, acrylic acid, methacrylic acid, ethyl acrylate-1-, methyl methacrylate-1-, butyl methacrylate-1-, butyl acrylate-1-12-ethyl Homopolymers of acrylic monomers such as ginyl acrylate, 2-ethylhexyl methacrylate-1-, and copolymers thereof are used. Furthermore, monomers that can be combined with these resins include conjugated olefin monodisperses such as butadiene, isoprene, and chloroprene, ethylenically unsaturated carboxylic acids and their esters such as fumaric acid and maleic anhydride, 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, halafine wax, carnauba wax, etc. can be offset at a ratio of 2 to 20% by weight based on the entire medium. It is also possible to add it as an inhibitor. In addition,
At this time, these anti-offset agents can be simply kneaded with the above-mentioned resins, or they can be made to coexist during polymerization of the fixing medium.

Various pigments and dyes such as carbon black can be used as colorants, and in -component developers, magnetic substances such as magnetite and ferrite are blended at a ratio of 30 to 60% of the total amount of the developer. You can also.

As charge control agents, in addition to quaternary ammonium compounds,
Nigrosine, Nicrosine base, Crystal Violeno 1
Basic dyes such as - 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 applying the above-mentioned surface treating agent to this powder composition using a supermigizer or the like, the surface treating agent can be supported on the surface of the powder.

Note that the surface treatment agent is supported on the powder surface by electrostatic attraction such as van der Waals force, but if desired, it is also possible to make it supported on the powder surface in a solid Mt state by heat treatment or the like.

The developer of the present invention can be used in any developing method, but particularly in a developing method that requires fluidity and charge stability, for example, the developing method previously proposed by the applicant in Japanese Patent Application No. 59-202977. It is effective for This developing method will be explained based on FIG.

A cylindrical non-magnetic sleeve 2 made of M or the like is placed close to the photoreceptor 1. Inside the sleeve 2, a N-pole repelling magnetic pole 3 is provided at a position close to the photoreceptor, and magnets 4 with different polarities alternately magnetized at other locations.

An ear cutting member 5 made of a magnetic material is arranged above the sleeve. Here, the behavior of the developer will be explained. After the developer 7 stored in the hopper 6 is regulated to a predetermined layer thickness by the shaving member 5, it is transported 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 floating toner 10 is formed between it and the photoreceptor 1. The floating toner 10 is electrostatically and selectively attracted to the electrostatic latent image 11 due to its own charge, converting the latent image 11 into a visible image 12.
become The developer 7 that has passed through the development area 8 is returned to the flopper 6 as the sleeve 2 rotates, and waits for the next development.

According to this development method, the photoreceptor cleaves must be placed close to each other, and the layer thickness must be set so that the developer layer does not touch the photoreceptor. It is set to an extremely 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 development method, by using the developer of the present invention, it is possible to stably form the layer thickness described above, and moreover, stabilization of charging characteristics is achieved in the development zone 8, and it is possible to achieve long-term stability. , it becomes possible to supply stable images.

According to this developing method, the coercive force of the developer is set in the range of 40 to 3000 e due to the magnetic attraction force by the magnet 4 in the developing area 8 and the transportability on the sleeve 2. is friendly.

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, instead of the ear cutting member 5, a burnable member such as a film or a thin metal plate may be used to line up with the developer and control the layer by surface contact. If desired, for the purpose of improving fine line reproducibility and gradation of images, a DC or pulse voltage of the same polarity as the latent image polarity of the photoreceptor is applied to the sleeve 2 by the bias applying means 13 at a voltage lower than the potential of the photoreceptor. It is also possible to apply within a range.

The invention is illustrated by the following example.

Example: Styrene butyl methacrylate-maleic acid co-FF 60 parts by weight Low molecular weight polypropylene 5 (1 magnetite 35 u Nigrosine dye 0.5 ti) After melt-kneading the mixture of the above formulation in a twin-screw extruder, (No change in content) A powder composition with a particle size of 5 to 25μ was obtained by pulverization and classification using a jet mill.The coercive force of the powder composition was 1000μ.
e, the saturation magnetization was 3Qemu/g"?'.

Regarding the obtained powder composition - according to the composition in Table 2,
Add the surface treatment agent to a super mixer (- treatment was performed.

For the oil treatment of the surface treatment agent, use the oil in Table 1 to disperse 10 g of any of the metal oxides in Table 2 in a solution of 110.5 g of oil dissolved in 150 parts of toluene. After that, it 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.

Reprint of Specification (No change in content) A copying test was conducted using the developer obtained according to the formulations shown in Tables 2 and 3 using the developing device shown in FIG. In addition, the development conditions are
Developer layer thickness 100μ, ○PC photoreceptor, maximum surface potential -4
50■, repulsion magnetic field (maximum drop height) 100 Gauss, photoconductor-sleeve distance 200μ JP-A-6L-2758F
;1(5) zu)^ha→ gu((Ttsutiffl) For 1., 3, 4., and 6.7 in Table 3, the relationship between surface potential and image density is shown in Table 3. It is shown in Figure 3.

As is clear from Table 3 and FIG. 3, 761 using titania without any treatment had no effect of improving fluidity and the image quality was low. The same result was obtained for alumina (stripe 2). In addition, in the case of titania treated with unmodified silicone oil (Na,
4) The amount of charge was low and the image quality was not satisfactory. Even when wet silica was used instead of titania (j67), the amount of charge was low and the capri was intense. On the other hand, when conventionally used hydrophobic silica was used, as is clear from FIG. 3, the image density in the high density region decreased, and the decrease in density was severe. IG of the present invention other than these, 2.3
, ], and O all had excellent image quality.

(Effects of the Invention) According to the present invention, by using titanium oxide coated with amino-modified silicone oil as a surface treatment agent, developer band 7) 3 knees 417
In particular, it is possible to maintain a high charge level, stabilize the charge level, and improve fluidity. As a result, image 1 image/image 1 with high rA degree
Copies with excellent image stability can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a developing device that can use the developer of the present invention, FIG. 2 is an enlarged view of the developing area, and FIG.
FIG. 3 is a diagram showing the relationship between surface type A☆ and image density. 1... Photoreceptor, 2... Sleeve, 4... Magnet, 7...
・Developer

Claims (2)

[Claims] (1) An electrophotographic developer characterized in that a fine titanium oxide powder coated with amino-modified silicone oil is carried on the surface as a surface treatment agent. (2) The electrophotographic developer according to claim 1, wherein the titanium oxide fine powder is supported at a ratio of 0.1 to 2.0 parts by weight per 100 parts by weight of the developer.