JP3290273B2 - Electrophotographic toner - 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 toner, and more particularly, to an electrophotographic toner suitably used for an image forming apparatus using an amorphous silicon photosensitive member.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrostatic copying machine or a laser beam printer, first, the surface of a photoreceptor is uniformly charged (charging step), and then the surface of the photoreceptor is exposed. To form an electrostatic latent image (exposure step). Next, a developer is brought into contact with the surface of the photoconductor by a developing device. Then, the toner contained in the developer is electrostatically attached to the electrostatic latent image, and the electrostatic latent image is visualized as a toner image (developing step). Next, when this toner image is transferred from the photoreceptor surface to the paper (transfer step) and fixed (fixing step), an image corresponding to the electrostatic latent image is formed on the paper surface.
After the toner image has been transferred onto the paper, the photoreceptor is removed from the surface by a cleaning blade or the like pressed against the surface to prepare for the next image formation (cleaning step). .

As the photoreceptor used in the above-mentioned image forming apparatus, those made of various photoconductive materials have been conventionally used. Among the photoreceptors using amorphous silicon, the surface hardness is Vickers hardness (Vickers hardness). Hv) 200
Since it is extremely hard, such as about 0, a highly reliable long-life photoreceptor can be formed, and the amorphous silicon-based material is industrially excellent because it is a non-polluting substance.

However, the surface of the amorphous silicon photoreceptor is oxidized by, for example, ozone generated during a charging step or the like to form a surface oxidized layer. Leakage tends to occur in the surface direction of the body, and as a result, a so-called image flow occurs in the formed image, which deteriorates the image quality. In particular, there is a problem that characters and the like of the formed image are difficult to read.

[0005] Therefore, taking advantage of the fact that the surface hardness of the amorphous silicon photoreceptor is extremely hard as described above, and the polishing is not greatly damaged by a slight polishing, the
Abrasive particles are externally added to the toner of a two-component developer including a carrier circulating in the developing device while the toner is adsorbed, and the surface oxide layer is polished in, for example, a developing step or a cleaning step. Attempts have been made to polish and remove with agent particles.

The abrasive particles include alumina,
It has been reported to use particles of magnetite, cerium oxide, strontium titanate and the like.

[0007]

However, among the above, alumina (α-alumina) particles have a high hardness of about 2000 in Vickers hardness (Hv), and thus are apt to damage a cleaning blade made of rubber or the like. There has been a problem that toner having poor cleaning is pressed against and adheres to the surface of the photoreceptor, thereby causing black spots on the image. The alumina particles have a volume resistivity value of 10 ¹⁵ Ω ·
cm, there is also a problem that the charge amount of the toner is increased to lower the image density of the formed image.

Magnetite particles have a low Vickers hardness (Hv) of about 500, so that they need to be externally added in a large amount in order to obtain a sufficient polishing effect, but their volume resistivity is 10 ³ Ω · Because of the small size, the toner flows forward in the rotation direction of the photoconductor at the time of development, so that there is a problem that a so-called forward pull occurs in a formed image. Although the cause of toner using magnetite particles as abrasive particles is unknown, there is also a problem that the charge amount is reduced particularly in a low-temperature environment of 15 ° C. or less, causing defects such as toner scattering and fog. .

Further, cerium oxide particles have an insufficient polishing effect, particularly when used on a photoreceptor that has been used for a long period of time, and cannot sufficiently prevent image deletion. Further, strontium titanate particles cannot be removed from the toner surface. There is a problem that the photoconductor is easily damaged because the photoconductor is easily detached and remains in a large amount on the surface of the photoconductor even after the transfer. The present invention has been made in view of the above circumstances. Particularly, the surface oxide layer of an amorphous silicon photoreceptor can be reliably polished and removed to sufficiently prevent image deletion and cause various image defects. It is an object of the present invention to provide an electrophotographic toner capable of forming a good image without any problem.

[0010]

In order to solve the above problems, the present inventors have studied the blending of alumina particles and magnetite particles among the conventional abrasive particles. That is, the alumina particles have the above-mentioned disadvantages because the hardness is too high and the volume resistivity is too large, while the magnetite particles have the hardness too low and the volume resistivity is too small. Since there are inconveniences such as the above, if both are blended and the appropriate hardness as a whole, that is, the polishing force, and the appropriate electric resistance, that is, the chargeability of the toner, are adjusted, the disadvantages of both can be solved. We thought that we could draw only the merits.

Therefore, the electrophotographic toner of the present invention is
It is characterized in that alumina particles having an average particle size of 0.1 to 2 μm and magnetite particles having an average particle size of 0.1 to 2 μm are externally added to the toner particles. In the electrophotographic toner of the present invention, the ratio of alumina particles to magnetite particles is preferably in the range of 1: 5 to 5: 1 by weight. The total external addition amount of the alumina particles and the magnetite particles is preferably 1 to 5 parts by weight based on 100 parts by weight of the toner particles.

Hereinafter, the present invention will be described. In the present invention, both the alumina particles and the magnetite particles used as the abrasive particles have a particle size limited to the range of 0.1 to 2 μm as described above. If the particle size of both abrasive particles is less than 0.1 μm, the polishing effect of the small abrasive particles decreases,
Image deletion cannot be prevented.

Conversely, if the particle size of both abrasive particles exceeds 2 μm, the abrasive particles are likely to separate from the toner particles, the toner charging characteristics are deteriorated, and the transfer efficiency is reduced. And image fogging and contamination inside the image forming apparatus due to toner scattering. Of the two abrasive particles, as the alumina particles, α-type, β-type and γ-type crystal types can be used, any of which can be used, but in particular, the surface oxide layer of the amorphous silicon photoreceptor is surely polished, To ensure sufficient hardness for removal, α-type alumina particles are mainly used.

The fine particles externally added to the conventional electrophotographic toner as a fluidizing agent or a charge controlling agent include alumina, and the externally added alumina is externally added as abrasive particles in the present invention. The particles are significantly smaller than the alumina particles, for example, those produced by a gas phase method (such as those manufactured by Nippon Aerosil Co., Ltd.).
Since this corresponds to a particle diameter of less than 1 μm, it is distinguished from alumina particles having a particle diameter of 0.1 to 2 μm in the present invention. As will be described later, fine particles such as the above-mentioned externally added alumina can be externally added to the electrophotographic toner of the present invention as a fluidizing agent or a charge adjusting agent, as described below.

The magnetite particles to be blended with the alumina particles include various types of conventionally known magnetite particles, such as natural products naturally produced as zite ores, and synthetic products synthesized from iron, iron (III) oxide and the like. Magnetite particles can be used. The ratio of the alumina particles to the magnetite particles is not particularly limited in the present invention, but in order to obtain the effect of using both abrasive particles in combination, as described above, the weight ratio is 1: 5 to 5: 1.
Is preferably within the range.

If the proportion of the alumina particles is smaller than the above range, the disadvantages of the magnetite particles appear more strongly, and there is a possibility that the formed image will be pre-painted, and that defects such as toner scattering and fogging will occur particularly in a low temperature environment. Conversely, when the proportion of the magnetite particles is small, the disadvantages of the alumina particles appear more strongly, which may cause image black spots in the formed image or reduce the image density of the formed image.

The ratio of the two abrasive particles is preferably in the above range, and more preferably in the range of 1: 3 to 3: 1 by weight. The total external addition amount of the two abrasive particles is preferably 1 to 5 parts by weight based on 100 parts by weight of the toner particles. If the sum of the external addition amounts of the two abrasive particles is less than the above range, the effect of the addition cannot be sufficiently obtained, and the surface oxide layer of the amorphous silicon photoreceptor cannot be sufficiently polished or removed. There is a risk.
Conversely, if the sum of the external addition amounts of the two abrasive particles exceeds the above range, the amount of the abrasive particles detached from the toner particles increases, and the toner charging characteristics deteriorate. Or contamination inside the apparatus due to toner scattering may occur.

As the toner particles to which both abrasive particles are externally added, any of the known toners conventionally used in dry development methods can be used. Such a toner is usually manufactured by dispersing additives such as a colorant in a fixing resin. Examples of the fixing resin include styrene-based polymers, acrylic-based polymers, styrene-acryl-based polymers, olefin-based polymers such as chlorinated polystyrene, polypropylene, and ionomers, polyvinyl chloride, polyester, polyamide, polyurethane, and epoxy. Resin, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, phenol resin, rosin modified phenol resin, xylene resin, rosin modified maleic resin, rosin ester and the like. Among them, an acrylic polymer or a styrene-acrylic polymer is preferable, and a styrene-acrylic polymer is particularly preferable, because of easy pulverization and control of the molecular weight distribution.

Colorants dispersed in the fixing resin include, for example, carbon black, lamp black, chrome yellow, Hansa yellow, benzidine yellow, bethlen yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange,
Watching Red, Permanent Red, Brilliant Carmine 3B, Brilliant Carmine 6B, Dupont Oil Red Pyrazolone Red, Risor Red, Rhodamine B Lake, Lake Red C, Rose Bengal,
Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate, etc. or CISolvent Yellow 60, CISolv
oil-soluble dyes such as ent Red 27 and CISolvent Blue 35. The addition amount of these coloring agents is 1 to 30 parts by weight, preferably 2 to 30 parts by weight based on 100 parts by weight of the fixing resin.
20 parts by weight.

Typical additives other than the coloring agent include a charge control agent and an anti-offset agent. The charge control agent is compounded to control the triboelectric charging property of the toner, and is classified into two types, one for positive charge control and the other for negative charge control. Examples of the charge control agent for controlling the positive charge include organic compounds having a basic nitrogen atom, such as basic dyes, aminopyrine, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, and fillers surface-treated with each of the above compounds. Is raised.

Nigrosine base (CI5045), oil black (CI26150)
), Bontron S, oil-soluble dyes such as spiron black; charge control resins such as styrene-styrene sulfonic acid copolymers; compounds containing carboxy groups (eg, alkyl salicylate metal chelates); metal complex dyes; Soaps, resin acid soaps, metal naphthenates and the like can be mentioned.

The amount of charge control agent added is
0.1 to 10 parts by weight, preferably 0.5 to 10 parts by weight
８8 parts by weight. The anti-offset agent is blended to give the toner an anti-offset effect. Examples of the offset preventing agent include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, various waxes and the like. Among them, the weight average molecular weight is 1,000 to 10,000
A degree of aliphatic hydrocarbon is preferred. Specifically, one or a combination of two or more of low-molecular-weight polypropylene, low-molecular-weight polyethylene, paraffin wax, a low-molecular-weight olefin polymer composed of olefin units having 4 or more carbon atoms, and silicone oil are suitable.

The addition amount of the offset preventing agent is 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight based on 100 parts by weight of the fixing resin. When the magnetic powder is added, 1
A magnetic toner as a component developer is obtained. The magnetic substance is a substance that is strongly magnetized in the direction by a magnetic field, and is preferably chemically stable, and is a fine powder having a particle diameter of 1 μm or less, particularly about 0.01 to 1 μm. Typical magnetic materials include iron oxides such as magnetite, hematite, and ferrite, as well as metals such as iron, cobalt, and nickel, or metals such as aluminum, cobalt, copper, lead, magnesium, tin, zinc, and antimony. , Beryllium, bismuth, cadmium, calcium, manganese, selenium, alloys with titanium, tungsten, and vanadium, or mixtures thereof.

The amount of the magnetic powder added is 100
20 to 300 parts by weight, preferably 50 to 300 parts by weight based on parts by weight
It is 150 parts by weight. In addition, various additives such as a stabilizer may be blended at an appropriate ratio. The above toner particles,
In order to treat with the above-mentioned two types of abrasive particles, the necessary amount of the toner particles and the abrasive particles and all the other external additives may be put into a mixer to perform the surface treatment at a time.

As the external additives other than the abrasive particles, as described above, silica, titanium oxide or alumina fine particles (particles) used as a fluidizing agent or a charge controlling agent in the conventional electrophotographic toner. (The diameter is much smaller than 0.1 μm), but any of them can be used. The particle size of these external additives is not particularly limited, but is expressed as a BET specific surface area of 20 to 400 m ² / g, preferably 50 to 200 m ² / g.
m ² / g. The addition amount of these external additives is 0.05 to 2 parts by weight, preferably 0.1 to 1 part by weight, based on 100 parts by weight of the toner. If the added amount exceeds 2 parts by weight, filming or charger contamination will occur, and if it is less than 0.05 part by weight, the fluidity of the toner will be insufficient, and neither is preferable.

The toner for electrophotography of the present invention thus obtained is suitably used for both a one-component developer and a two-component developer. When used as a one-component developer, the toner for electrophotography of the present invention in which toner particles containing or not containing a magnetic substance are surface-treated as described above may be used as it is.

On the other hand, to obtain a two-component developer, the electrophotographic toner of the present invention, which has been surface-treated as described above, may be mixed with a carrier. Carriers include, for example, glass beads, oxidized or unoxidized iron powder, ferrite,
Magnetic particles such as cobalt, or particles whose surface is coated with a synthetic resin (eg, an acrylic, fluorine, silicone, or polyester resin) are used. Such carriers generally have a particle size of 50 to 2000 μm. When a two-component developer is used, the toner concentration is preferably 2 to 15% by weight.

[0028]

The present invention will be described below based on examples and comparative examples. Examples 1 to 5 and Comparative Examples 3 and 4 <Production of Toner Particles> 85 parts by weight of a styrene-acrylic copolymer as a fixing resin, 10 parts by weight of carbon black, an anti-offset agent (release agent) ), 3 parts by weight of a low-molecular-weight polypropylene and 2 parts by weight of a chromium-containing azo dye as a charge control agent were melted, kneaded, pulverized, and then classified to produce toner particles having an average particle diameter of 10 μm. . <Production of electrophotographic toner> 100 parts by weight of the toner particles obtained in the production of the above toner particles, 0.5 part by weight of hydrophobic silica as a fluidizing agent, and alumina particles having the compounding amount shown in Table 1 below (Average particle size: 0.6 μm) and magnetite particles (average particle size: 0.6 μm) were sufficiently stirred, mixed and dispersed by a Henschel mixer to obtain an electrophotographic toner.

[0029]

[Table 1]

Examples 6 and 7, Comparative Examples 1 and 2 In place of alumina particles and magnetite particles having an average particle size of 0.6 μm, 1.25 parts by weight of alumina particles having an average particle size shown in Table 2 below, and magnetite 1.25 of particles
An electrophotographic toner was obtained in the same manner as in Examples 1 to 5 except that parts by weight were externally added.

[0031]

[Table 2]

Comparative Example 5 In place of alumina particles having an average particle diameter of 0.6 μm, alumina fine particles having a particle diameter of 0.02 μm (alumina-C manufactured by Nippon Aerosil Co., Ltd.) produced by a gas phase method. 2
5 parts by weight of magnetite particles (average particle size 0.6 μm)
Example 1 except that it was externally added together with 1.25 parts by weight of
To 5, an electrophotographic toner was obtained.

The electrophotographic toners of the above Examples and Comparative Examples were mixed with a ferrite carrier having an average particle diameter of 70 μm to prepare a two-component developer having a toner concentration of 5% by weight. Using the two-component developer, the following tests were performed to evaluate the characteristics of the electrophotographic toner. Image evaluation An electrostatic copying machine (DC70 manufactured by Mita Kogyo Co., Ltd.) in which the two-component developer was replaced with an amorphous silicon photoconductor.
85 remodeling machine) as a start developer, and using the electrophotographic toner of the same example and comparative example as a replenishing toner, when performing continuous copying of 100,000 sheets, image deletion, black spots and The presence or absence of forward pulling was visually observed.

Image Density Measurement The image density (ID) of the 100,000th copy image was measured using a reflection densitometer (TC-6D, manufactured by Tokyo Denshoku Co., Ltd.). Blow-off charge amount measurement The blow-off charge amount (μC / g) of the developer after the above-mentioned continuous copying of 100,000 sheets was measured using a blow-off charge amount measuring device manufactured by Toshiba Chemical Corporation.

Measurement of fog density at low temperature When 100,000 sheets of continuous copying were performed in a low temperature environment of 10 ° C., the fog density (FD) of the blank portion of the 100,000th copy image was determined by the reflection density. Total (TC-6D manufactured by Tokyo Denshoku Co., Ltd.)
It measured using. Table 3 shows the above results.

[0036]

[Table 3]

From the results shown in Table 3 above, the particle size of the externally added alumina particles and magnetite particles was 0.1 μm in both cases.
In the electrophotographic toner of Comparative Example 1 having a particle diameter of less than m, image deletion occurred. Also, the image density slightly decreased. In addition, the electrophotographic toner of Comparative Example 2 in which both the alumina particles and the magnetite particles each had a particle size of more than 2.0 μm generated image black spots and pre-drawing, and increased the fog density at low temperatures. In addition, the charge amount slightly decreased.

In the electrophotographic toner of Comparative Example 3 containing no alumina particles, fogging density at a low temperature was remarkably increased while pre-pulling occurred. Further, the electrophotographic toner of Comparative Example 4, which did not contain magnetite particles, caused image black spots and greatly reduced image density. Also, the charge amount increased significantly.

Further, the electrophotographic toner of Comparative Example 5 in which fine alumina particles used as a fluidizing agent and a charge controlling agent in the conventional toner were added instead of the alumina particles, the image deletion and the leading edge occurred. In addition, the fog density at low temperature increased. Also, the charge amount decreased.
On the other hand, all of the electrophotographic toners of Examples 1 to 7 did not cause image defects such as image deletion, black spots, and forward pulling, and provided good images with high image density and low fog density at low temperatures. And had a sufficient charge amount.

[0040]

As described in detail above, the toner for electrophotography of the present invention has two types of toner particles, alumina particles having an average particle size of 0.1 to 2 μm and magnetite particles having an average particle size of 0.1 to 2 μm. Since the abrasive particles are externally added, the surface oxide layer of the amorphous silicon photoreceptor is surely polished and removed to prevent image deletion and to form a good image.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takeshi Arakawa 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka Inside Mita Kogyo Co., Ltd. (72) Inventor Hiroaki Yamaguchi 1-2-2 Tamazo, Chuo-ku, Osaka-shi, Osaka No. 28 Mita Kogyo Co., Ltd. (72) Koji Kuramasu, Inventor 1-2-2 Tamatsuzo, Chuo-ku, Osaka-shi, Osaka Mita Kogyo Co., Ltd. (56) References JP-A-4-68359 (JP, A) JP JP-A-3-67268 (JP, A) JP-A-5-216270 (JP, A) JP-A-4-204658 (JP, A) JP-A-5-181306 (JP, A) JP-A-2-59768 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (2)

(57) [Claims] A toner for electrophotography, wherein alumina particles having an average particle size of 0.1 to 2 μm and magnetite particles having an average particle size of 0.1 to 2 μm are externally added to the toner particles. 2. The weight ratio of the alumina particles to the magnetite particles is in the range of 1: 5 to 5: 1, and the total external addition amount of both is 1 to 5 with respect to 100 parts by weight of the toner particles.
2. The electrophotographic toner according to claim 1, which is in parts by weight.