JPH0627719A - Electrostatic image developer - Google Patents

Abstract

PURPOSE:To provide an electrostatic image developer which hardly causes fluctuation in electrification and is durable by employing a specific inorganic particle having high water repellency and being hardly charged. CONSTITUTION:An inorganic particle is used which is formed by a surface treatment with a compound expressed by a formula: Ar-Si(OCH3)3. In the formula, Ar represents a phenyl group that may have a substituent. This surface treatment agent has a trimethoxyslyl group and is therefore capable of uniformly treating the surface at a high reaction rate. The inorganic particles have a primary grain size of 5 to 100nm. The primary grain size indicates the average grain size of number reference as measured by image analysis through observation by a scanning electron microscope. The material of which the inorganic particles are composed is a silicon oxide, a titanium oxide, an aluminum oxide, a zinc oxide, a zirconium oxide, a cerium oxide, a silicon nitride or a carbon nitride, etc., the titanium oxide, alumina oxide, and zirconium oxide being particularly desirable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic image developer used in electrophotography, electrostatic recording and electrostatic printing.

[0002]

2. Description of the Related Art The development of an electrostatic image has been mostly shifted to dry development for convenience of handling, but as a dry developer, a one-component system containing a magnetic toner capable of forming a visible image and having a magnetic force transporting property. There is a developer and a two-component developer containing a colored toner that forms a visible image and a magnetic carrier that holds and conveys the toner and that contributes to triboelectric charging with the toner.

Such a developer is required to have many functional characteristics in terms of developability and fixability. For example, electrostatic, thermal or strength physical properties, chemical properties, flowability, and blocking of toner are required. The powder characteristics related to the particle size distribution, etc. are problematic, and accordingly, various additives for the shape and material of the toner particles, the forming method, and characteristic complementation are blended and used.

Further, in order to guarantee stability by repetition, the cleaning property must be good without the change of the constituent particles in the developer and the contamination of the photoreceptor and the like.

Originally, it is important to impart fluidity and chargeability to the toner used in electrophotography because of its mechanism. For this reason, it is practiced to add and mix fine inorganic particles to the outside of the toner. By this addition and mixing, the contact area between the toner particles becomes small and the distance between the toner particles becomes large. Further, if water is adsorbed on the surface of the particles to be added, the inorganic fine particles are likely to aggregate due to the effect of water, and the fluidity is lowered. In order to cause such a problem, JP-A-52-135739 discloses a technique in which the surface of fine particles is treated with aminosilane, and JP-A-54-16219 discloses a technique in which silica is hydrophobized for use. Further, JP-A-59-52255 discloses the use of titanium oxide treated with alkyltrialkoxysilane. However, simply making it hydrophobic is not suitable as the inorganic fine particles added to the toner. The reason for this is that when the surface of the inorganic fine particles is surface-treated with these materials, the chargeability of the inorganic fine particles changes and the chargeability of the toner changes. Therefore, it is necessary to consider the change in the charge amount when using the inorganic fine particles. Further, the toner in the developer receives a large stress inside the developing device due to the influence of mechanical stirring or the like, and a phenomenon occurs in which these inorganic fine particles are embedded in the toner. When the embedding occurs, the inorganic fine particles are embedded on the surface of the toner, so that the chargeability of the toner itself changes and the durability decreases.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrostatic charge image developer having a small charge fluctuation and a long durability.

[0007]

In order to achieve the above object, the present invention proposes to use inorganic fine particles having high hydrophobicity and almost no chargeability.

Specifically, the inorganic fine particles formed by treating the surface of the inorganic fine particles with the compound represented by the following general formula (1) are used.

General formula (1) Ar-Si (OCH ₃ ) ₃ Ar represents a phenyl group which may have a substituent.

That is, since the surface treating agent according to the present invention has a trimethoxysilyl group, the reaction rate is fast and the surface can be uniformly treated. Further, unlike the conventionally known alkyl group, since it has a phenyl group, the chargeability of the inorganic fine particles themselves is low. Therefore, there is no influence on the chargeability of the toner, and the charge amount of the toner does not change.

Specifically, the following exemplified compounds can be used.

Example compounds: (1) [C ₆ H ₅ ] -Si (OCH ₃ ) ₃ (2) p-CH _3- [C ₆ H ₄ ] -Si (OCH ₃ ) ₃ (3) p- ( _{tC 4 H 9) - [C} 6 H 4] -Si (OCH 3) 3 (4) p- (nC 8 H 17) - [C 6 H 4] -Si (OCH 3) 3 (5) p- ( C ₄ H ₉ C (C ₂ H ₅ ) HCH ₂ )-[C ₆ H ₄ ] -Si (OCH ₃ ) ₃ (6) pC ₂ H _5- [C ₆ H ₄ ] -Si (OCH ₃ ) ₃ ( 7) o-CH _3- [C ₆ H ₄ ] -Si (OCH ₃ ) ₃ These compounds are preferably added in an amount of 1 to 10 wt% with respect to the inorganic fine particles and coated, preferably 3 to 7 wt%. .
Also, these materials can be used in combination.

The inorganic fine particles used in the present invention are particles having a primary particle diameter of 5 to 100 nm. The primary particle diameter of the inorganic fine particles is the number-based average particle diameter observed by a scanning electron microscope and measured by image analysis.

Examples of the material forming the inorganic fine particles include silicon oxide, titanium oxide, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, tungsten oxide, antimony oxide, copper oxide, tellurium oxide, manganese oxide, barium titanate and titanium. Examples include strontium oxide, magnesium titanate, silicon nitride and carbon nitride.

Particularly suitable as these inorganic fine particles are titanium oxide, alumina oxide and zirconium oxide.
The reason for this is that these materials have a small surface area and little water adsorption.

When used by being added to the developer, the amount added is controlled according to the toner surface area. Generally, the amount of the inorganic fine particles of the present invention is 0.01 for a toner having a volume average particle diameter of 11 μm. ˜5 wt%, preferably 0.05 to 1.0 wt%. If the average particle size of the toner is different,
It may be added in a ratio of the surface area based on the surface area of m particles. Specifically, for a toner of 5.5 μm, this addition amount is required to be 4 times. That is, it is advisable to add it as the square of the ratio of the average particle diameter.

The resin material constituting the colored particles is not particularly limited, and various resins can be used. For example, styrene, α-methylstyrene, styrene resin such as divinylbenzene, acrylic resin such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, α -A copolymer of styrene-based monomers such as methylstyrene and divinylbenzene with acrylic-based monomers such as methylmethacrylate, ethylmethacrylate, butylmethacrylate, 2-ethylhexylmethacrylate, methylacrylate, ethylacrylate and butylacrylate. Nitrogen-containing resin containing certain styrene-acrylic copolymer, dimethylaminomethacrylate, diethylaminomethacrylate, vinylpyridine, etc., Teflon, fluorine vinyl Examples thereof include fluorine-containing resins containing lidene, polyolefins such as polypropylene and polyethylene, nylon resins, urethane resins and urea resins.

In the toner used in the present invention, all colorants used in ordinary toners can be used.
Specifically, carbon black, magnetite, nigrosine dye, aniline dye, ferrite and the like can be used. The addition amount of the colorant is controlled as necessary, but generally 0.1 to 10 wt% is added. When it is used as a magnetic toner, it holds 20 to 70 wt% of magnetic powder (magnetite) from the viewpoint of holding the toner on the magnetic brush.
Good to add.

It is also possible to add and use a fluidity improver such as hydrophobic silica or a fatty acid metal salt. When addition and mixing are performed, it is preferable that the particles are present in a free state rather than being fixed to the colored particles. When mixing is performed, it is preferable to use a turbula mixer, a Henschel mixer, or the like.

The colored particles contain a binder resin, a colorant, and other additives such as a charge control agent which are optionally used, and the average particle size thereof is usually in the range of 1 to 30 μm. is there.

The charging polarity of the colored toner particles themselves is determined by the developing method. The chargeability of the colored particles can be controlled by the type and amount of the charge control agent, the combination with the resin and the like. Examples of the charge control agent include salicylic acid derivatives and the like.

Examples of other additives include fixability improving agents such as low molecular weight polyolefins.

In the present invention, when a two-component developer is prepared, a carrier is used in addition to the toner and the inorganic fine particles.

The carrier is not particularly limited, but an uncoated carrier made of magnetic particles, a resin-coated carrier obtained by coating the surface of the magnetic particles with a resin, and magnetic particles dispersed and contained in a binder resin. The magnetic substance-dispersed carrier and the like can be used.

The magnetic particles constituting the carrier include
A substance that is strongly magnetized in that direction by a magnetic field, such as iron,
Ferromagnetic metals such as ferrite and magnetite, nickel or cobalt, or other ferromagnets or alloys, or compounds containing these elements, alloys that do not contain ferromagnetism elements but that exhibit ferromagnetism by appropriate heat treatment For example, particles made of an alloy of a type called a Heusler alloy such as manganese-copper-aluminum or manganese-copper-tin or chromium dioxide can be used.

As the coating resin for the resin-coated carrier or the binder resin for the magnetic substance-dispersed carrier, for example, a styrene-acrylic copolymer, a silicone-based compound fluorine-based resin or the like can be preferably used.

The average particle size of the carrier is preferably 20 to 200 μm, particularly preferably 40 to 150 μm. When the average particle size is too small, the carrier adheres to the electrostatic latent image to form a fixed image, so-called carrier adhesion phenomenon occurs, and as a result, the image may become unclear, while when the average particle size is too large, the image Flow may occur.

The developer of the present invention can be used in combination with various conventionally known developing methods. In particular, a developing method of a thin layer forming system in which the developer is supplied as a thin layer onto a developer carrier. Can be suitably used.

To form a thin layer, it is necessary to form a thin toner layer on the surface of the developing sleeve. Here, the thin layer means a toner layer of 20 to 500 μm in the developing area. In order to form such a thin layer on the developing sleeve, 20 to
It is necessary to regulate the height to around 500 μm. In this case, a method using a magnetic blade that can utilize the magnetic force of the toner is preferable. There is also a toner layer regulation method of pressing a toner layer regulation rod against the surface of the developing sleeve. In this case, it is preferable to use a magnetic force to press the regulating rod against the surface of the developing sleeve. Further, it is possible to form a thin layer by bringing a urethane blade, a phosphor bronze plate or the like into contact with the surface of the developing sleeve.

The gap between the developing sleeve surface and the photoreceptor surface is
It may be larger or smaller than the layer thickness of the toner layer. Further, the developing bias may be only the DC component, but the AC bias may be applied simultaneously.

[0031]

EXAMPLES Hereinafter, more specific examples will be described, but the present invention is not limited to these examples.

The surface-treated inorganic fine particles and colored particles of the developers of the present embodiment and the comparative example were prepared as follows, and magnetic toners were prepared, and their performances were evaluated.

A. Preparation of Surface-treated Inorganic Fine Particles According to the specifications shown in Table 1, 100 parts by weight of each inorganic fine particle was mixed with 200 parts by weight of xylene to which a predetermined amount (wt%) of a surface treatment agent was added and mixed at 20 ° C. for 3 days. Stir for a period of time.

Then, the solvent was dried and removed by a spray dryer, and the surface-treated inorganic fine particles P1 to 10 and P (1) and (2) of Examples and Comparative Examples shown by No. in Table 1 were respectively removed. Got

[0035]

[Table 1]

B. Colored particles Polyester resin 100 parts Magnetite 50 parts Low molecular weight polypropylene 3 parts Metal-containing dye 1 part The above are mixed in a hexshell mixer and then melt-kneaded
The particles were pulverized and classified to obtain colored particles having an average particle size of 11 μm.

C. Preparation of Toner and Preparation of Developer Based on the specifications listed in Table 2, 0.2 wt% of hydrophobic silica and a predetermined amount (wt%) of the surface-treated inorganic fine particles P1 to P10 based on 100 parts by weight of the colored particles. , P (1), (2) were added and mixed with a Henschel mixer to prepare magnetic toners T1-10, T (1), (2) of Examples and Comparative Examples.

[0038]

[Table 2]

Next, the performance of the magnetic toner was evaluated.

Evaluation Konica laser printer LP-3015 was remodeled to have a printing speed of 40 sheets per minute and a developing sleeve made of magnetic stainless steel with a diameter of 25 mm and having a built-in 6-pole fixed magnet. = 0.2 mm, and the toner layer on the surface of the developing device in the developing area was modified to a non-contact developing method with 0.15 mm. In this evaluation, the pressing method using magnetic stainless steel with a diameter of 3 mm was restricted as the toner layer restriction method. The photoreceptor is a laminated organic photoreceptor, the developing potential is -500V, and the developing bias is -50 from peak to peak.
AC bias of -25 to 550V with a frequency of 2kHz
A DC bias of 0V was applied. Evaluation is high temperature and high humidity (33 ℃
・ 80% RH) The changes in concentration under the environment were compared. The evaluation method is to print a pattern having a 5% pixel ratio intermittently on one sheet for 50,000 sheets and compare the densities of the initial and 50,000 sheets.

As the image density, the density of a solid black image is 12
It is a value obtained by measuring points and averaging the values. Absolute concentration is measured by using "RD-918" manufactured by Macbeth.

The results are shown in Table 3 below.

[0043]

[Table 3]

As described above, it is understood that the image density is stable when the inorganic fine particles treated with the compound of the present invention are used.

[0045]

EFFECT OF THE INVENTION A developer having good durability and chargeability can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Watako Ohira Konica Co., Ltd. 2970 Ishikawacho, Hachioji City, Tokyo

Claims (1)

[Claims] 1. A developer comprising colored particles comprising at least a resin and a colorant and surface-treated inorganic fine particles, wherein the surface-treated inorganic fine particles have a primary particle diameter of 5 to 100 nm, and An electrostatic image developer characterized by being surface-treated with a compound represented by the general formula (1). Ar is a phenyl group which may have a substituent in the general formula (1) Ar-Si (OCH _{3) 3} [Formula (1). ]