JPH05181306A - Electrostatic latent image developing toner - Google Patents

Abstract

PURPOSE:To obtain the excellent polishing effect at the surface of a photoreceptor, and make a device compact without the necessity for assembling a large system such as a cleaning brush, and reduce a diameter of a photoreceptor drum, and prevent the running of image of an a-Si photoreceptor. CONSTITUTION:Polishing material fine-grain such as alumina and zirconia, of which Mohs'hardness is equal or larger to/than that of the a-SiC surface layer of an a-Si group photoreceptor, are fixed to the surface of a toner base grain 33. A grain diameter D of the toner base particle 33 and a grain diameter (d) of a polishing material fine-grain 35 are set so as to satisfy the condition that the ratio of them D/d exists in a range of D/d=10-50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer used for developing an electrostatic latent image in electrophotography or the like, and more particularly to polishing a surface of a photoreceptor with toner.

[0002]

2. Description of the Related Art An electrophotographic method has been generally known, and in a typical Carlson method, an image is formed through the following steps.

(1) A charging step for uniformly charging the surface of the photosensitive member by corona discharge or the like. (2) An exposure step of selectively irradiating the photoconductor with light by image exposure (analog exposure) or signal exposure (digital exposure) such as scanning with laser light to form an electrostatic latent image.

(3) A developing process in which an electrostatic latent image is developed with a developer and toner is made to adhere to the toner to form a toner image on the photoreceptor. (4) A transfer step of transferring the toner image on the photoconductor to paper or the like. (5) A fixing step of fixing the transferred toner by heat, pressure or the like.

Further, a non-Carlsson type image formation is performed in which a developer pool is formed on the photoconductor, and charges are injected into the photoconductor via the developer so that the photoconductor is charged and the image signal is exposed from the back side of the photoconductor and simultaneously developed. A method is also known and is usually called an optical backside exposure recording method.

On the other hand, in addition to the conventional Se-based photoconductor and organic photo-semiconductor, a photoconductor using an amorphous silicon (a-Si) -based photoconductive layer has been receiving attention in recent years. The a-Si type photoconductor has no problem in safety as compared with the Se type photoconductor,
Also, it has excellent durability and has a longer life than the device unit.

On the other hand, on the other hand, the a-Si type photoconductor tends to leak charges due to long-term use and cause so-called "image deletion".

It has been known for a long time to use an abrasive as a measure against such image deletion. For example, addition of strontium titanate fine particles to a developer (Japanese Patent Laid-Open No. 61-
No. 278861), using a cleaning member having a Mohs hardness of 2.5 to 7.0 (Japanese Patent Laid-Open No. 59-88776), a method of using an abrasive and fine particles having the same degree as that of the a-Si drum surface layer (special JP-A-63-29759) and the like, and it has been reported that alkaline earth metals, carbonates and the like are effective for image deletion of an a-Si type photoreceptor (JP-A-61-61). No. 231564).

However, all of the above-mentioned polishing methods have a weak polishing power, and the effect of preventing image deletion of the a-Si photosensitive member is insufficient. Also, when trying to increase the polishing power,
The image forming apparatus has become large and cannot be used in a small machine.

[0010]

SUMMARY OF THE INVENTION The present invention provides a toner which is excellent in polishing effect and is particularly useful for an a-Si type photoreceptor.

[0011]

In the toner for developing an electrostatic latent image of the present invention, fine abrasive particles having hardness equal to or greater than that of the surface layer of an image forming photoreceptor are fixed to the surface of toner mother particles. The ratio of the average particle diameter D of the toner mother particles to the average particle diameter d of the abrasive fine particles is in the range of D / d = 10 to 50.

By supplying the above-mentioned toner to the surface of a photoconductor having a photoconductive layer such as an amorphous silicon type for development, a toner image is formed on the photoconductor surface to form an image,
The surface layer of the photoconductor is polished simultaneously with the image formation.

Further, a toner image is formed on the surface of the photoconductor,
Next, after transferring the toner image to the transfer material, the pressure contact member can be pressed against the surface of the photoconductor where some untransferred toner remains, and the photoconductor surface can be polished with the remaining toner, further improving the polishing effect. To do.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view showing the layer structure of a photosensitive layer of an a-Si photosensitive member 11. On the conductive substrate 13, a laser light absorption layer 15 made of Si: Ge: H or the like,
A carrier injection blocking layer 17 made of Si: H: B: O or the like,
A carrier excitation / transport layer 19 (photoconductive layer) made of Si: H or the like and a surface protection layer 21 are sequentially laminated.

The surface protective layer 21 is typically made of SiC. This SiC layer (surface protection layer 21) is not smooth, has a large number of minute protrusions (cones), is highly hydrophilic, and has ion products generated by corona discharge attached thereto. Therefore, when continuous printing is repeated or when printing is started under high humidity conditions, toner adheres to the photosensitive drum and toner filming occurs,
Adhesion of a hydrophilic compound such as ammonium nitrate as an ion product occurs, the charge of the photoconductor leaks, and so-called "image deletion" occurs. Moreover, these products have a strong tendency to accumulate between the minute protrusions of the SiC layer, which is the surface protection layer 21, and thus "image deletion" cannot be prevented by normal cleaning.

Therefore, in the present invention, on the surface of the toner particles,
Image deletion is prevented by fixing abrasive fine particles having an appropriate particle size having a hardness equal to or higher than that of the surface protective layer 21 and strongly abrading the surface protective layer 21. FIG. 2 is a model view of the toner of the present invention, in which the toner 31 is the toner mother particles 33.
The abrasive fine particles 35 are fixed and formed on the surface of the.

The adhesion of the abrasive fine particles 35 to the surface of the toner mother particles 33 is performed by, for example, uniformly mixing the toner mother particles 33 and the abrasive fine particles 35, and adhering the abrasive fine particles 35 to the surface of the toner mother particles 33. After that, a mechanical and thermal impact force is applied to fix the abrasive fine particles 35 into the toner mother particles 33 so as to be fixed. The abrasive fine particles 35 are not completely embedded in the toner mother particles 33, but are fixed so that a part of the abrasive fine particles 35 protrudes from the toner mother particles 33.

Such a fixing device for the abrasive fine particles 35 is commercially available as a surface modifying device or system, and an example thereof is as follows.

(1) Dry mechanochemical method: Mechanochemical (Okada Seiko Co., Ltd.) Mechanofusion system (Hosokawa Micron Co., Ltd.)

(2) High-speed air impact method: Hybridization system (Nara Machinery Co., Ltd.) Cryptron system (Kawasaki Heavy Industries, Ltd.)

(3) Wet method: Dispercoat (Nisshin Seifun Co., Ltd.) Coatmizer (Freund Sangyo Co., Ltd.)

(4) Heat treatment method: Surfing (Nippon Pneumatic Mfg. Co., Ltd.) (5) Others: Spray dry (Okawara Kakoki Co., Ltd.)

As the abrasive fine particles 35, the surface protective layer 2 is used.
Considering application to an a-Si-based photoreceptor provided with SiC as No. 1, since the SiC layer has a Mohs hardness of about 8, fine particles having a Mohs hardness of 8 or more, preferably 8 to 9, such as alumina and zirconia. Fine particles of the metal oxide are used.

The size of the abrasive fine particles 35 is determined by the relationship with the average particle diameter of the toner mother particles 33. D / d = 10 to 50, preferably 10 to 4, where D is the average particle size of the toner mother particles 33 and d is the average particle size of the abrasive fine particles.
By setting the range to 0, the abrasive fine particles 35 are firmly fixed to the surface of the toner mother particles 33, and the polishing effect of the abrasive fine particles 35 is increased.

When an image is formed by using the toner 31 as described above, the toner 31 is used during development and cleaning.
Effectively abrades the surface of the photoreceptor when the toner contacts and rubs against the surface layer of the photoreceptor. More specifically, when the SiC layer having a large number of fine protrusions (cones) is used as an a-Si-based photoreceptor, the tip of the fine protrusion is polished by the abrasive fine particles 35 having high hardness. The surface of the photoconductor is smoothed, and at the same time, the microscopic projections and the ion products deposited between the microscopic projections are removed to prevent image deletion,
Further, it was found that the development stability is also secured. Moreover, the toner of the present invention having such an effect does not cause a large scratch on the surface of the a-Si photoconductor even when it is abraded by a cleaning blade, a rubbing roller, or the like.

The above-described effects of the present invention are obtained by externally adding (mixing powder) abrasive fine particles, using an abrasive having a smaller hardness, or by using abrasive fine particles having an inappropriate particle size ratio. Is not obtained when is fixed on the toner surface.

If the abrasive fine particles 35 have a specific particle size, the surface of the abrasive fine particles 35 may be subjected to a surface treatment for the purpose of charge adjustment and hydrophobization. Further, other fine particles may be used in combination for the purpose of adjusting fluidity and the like.

As the toner mother particles 33, those having the same constitution as the conventional toner itself are used, and for example, a binder resin, a colorant, a charge control agent, an offset preventive agent and the like can be blended. Further, a magnetic material may be added to obtain a magnetic toner. As the binder resin, a vinyl-based resin represented by polystyrene-based resin such as styrene-acrylic copolymer, a polyester-based resin, or the like is used.

Various pigments and dyes such as carbon black are used as colorants; quaternary ammonium compounds, nigrosine, nigrosine bases, crystal violet, triphenylmethane compounds and the like are used as charge control agents; anti-offset agents and fixation-improving agents. An olefin wax such as low molecular weight polypropylene, low molecular weight polyethylene or a modified product thereof can be used as an auxiliary agent, and magnetite or ferrite can be used as a magnetic material.

The toner base particles of the present invention can be obtained by a conventional method, for example, by melt-kneading the respective components with a twin-screw extruder, a kneader, etc., and then pulverizing with a jet mill etc. and classifying. The toner of the present invention can be used as a one-component developer or as a two-component developer by mixing with a carrier.

Next, an image forming method using the toner of the present invention will be described with reference to FIG. FIG. 3 is the same as a conventional general image forming apparatus except that a rubbing roller (pressing member) is provided.

As a surface protective layer, S of about 0.3 to 1 μm
Around the drum-shaped a-Si photoreceptor 11 having the iC layer, a corona charger 41, an LED head 43 (exposure device), a developing roller 45, a transfer device 47, a rubbing roller 49,
A cleaning blade 51 is provided. After the surface of the photoconductor 11 is uniformly charged by the corona charger 41 and the electrostatic latent image is formed by the selective image exposure by the LED head 43, the developing roller 45 supplies the developer 61 to the surface of the photoconductor 11, and the toner is developed. A visible image consisting of 31 is formed. At this time, the surface of the photoconductor 11 is rubbed by the toner 31 in the developer 61, and the SiC layer on the surface is polished. Further, since the abrasive fine particles 35 are firmly fixed to the toner mother particles 33, the abrasive fine particles 35 do not fall off and do not cause development defects, image defects and the like.

The toner 31 on the surface of the photoconductor 11 is transferred to the paper 63 (material to be transferred) by the transfer device 47, and then fixed on the paper 63 by the fixing device (not shown).

In the transfer step, not all the toner 31 on the surface of the photoconductor 11 is transferred to the paper 63, but
Part of the toner 31 (residual toner) remains on the photoconductor 11. The residual toner 31 is pressed against the surface of the photoconductor 11 by the rubbing roller 49 to polish the SiC layer, and the polishing effect of the abrasive fine particles 35 of the toner 31 is increased.

Then, the residual toner 31 on the photoconductor 11
Are removed from the surface of the photoconductor 11 by the cleaning blade 51.
By the mechanical force applied between 1 and the photoconductor 11,
The surface SiC layer of the photoconductor 11 is polished by the abrasive fine particles 35 of the toner 31.

An elastic roller is used as the rubbing roller 49, and the rubbing roller 49 is brought into pressure contact with the surface of the photoconductor 11 and rotated so that a shear stress is applied to the photoconductor 11, whereby the photoconductor 11 is rotated. The surface is polished and cleaned.

Further, by attaching a heater to the inner surface of the photoconductor 11 to heat it, the effect of preventing image deletion can be further improved. In the above description, the a-Si-based photoconductor having the SiC layer as the surface layer has been mainly described, but other types of surface layers or photoconductors of other types may be used. The hardness of the abrasive fine particles may be adjusted according to the hardness of the.

[0038]

According to the present invention, the abrasive fine particles having a hardness equal to or higher than that of the photoreceptor surface layer are fixed to the surface of the toner, and the particle ratio of the fixed toner mother particles to the fine abrasive particles is set. By specifying, an excellent polishing effect can be obtained on the surface of the photoconductor. Therefore, the image forming apparatus can be designed compactly, and it is not necessary to incorporate a special system such as a cleaning brush. Especially, a small machine using a small-diameter photosensitive drum, a large surface layer hardness, and a large cleaning brush. It is suitable for an a-Si-based photoconductor that is liable to cause the above problems.

Further, since the abrasive fine particles are firmly fixed to the toner surface, the image stability does not occur due to the removal of the abrasive fine particles during development and the development stability can be secured for a long time.

[0040]

【Example】

 Example 1 Styrene / n-butyl acrylate copolymer (copolymerization ratio 80/20) 100 parts by weight Carbon black (MA-100, manufactured by Mitsubishi Kasei Co., Ltd.) 5 parts by weight Polypropylene wax (Viscole 550P, Sanyo Kasei) Industrial Co., Ltd.) 4 parts by weight Triaminotriphenylmethane compound 2 parts by weight (Copy Blue PR, manufactured by Hoechst)

The toner materials having the above compounding ratios are mixed by a super mixer, kneaded by using a twin-screw extruder (PCM-30, manufactured by Ikegai Tekko Co., Ltd.), cooled, pulverized and classified,
Toner mother particles having an average particle diameter of 10 μm were obtained.

2% by weight of abrasive fine particles (listed in Tables 1 and 2) were mixed at high speed with the toner base particles, and then treated with a surface reforming device (Hybridizer, Nara Machinery Co., Ltd.). Thus, a toner having fine abrasive particles adhered to the surface thereof was obtained.

At this time, as shown in Table 1 below, various types of abrasive fine particles and average particle diameter were variously changed to obtain respective toners. Further, the developers shown in Table 2 were prepared in the same manner as above except that the average particle size of the toner mother particles was 7 μm.

The obtained toner was sufficiently mixed with a non-coated ferrite carrier at a concentration of 4% to prepare a two-component developer. Using the obtained developer, continuous printing was performed on 300,000 sheets using the apparatus shown in FIG. 3, and image density, fog, black spots on the drum, and image deletion were evaluated according to the following criteria. The film thickness of the surface SiC layer after printing was measured by XPS.

As the photoconductor, a laser light absorption layer (Si: Ge: H, 0.2-5 μm) and a carrier injection blocking layer (Si: H: B: O, 0.2-) are formed on a conductive substrate. 4μ
m), carrier excitation / transport layer (Si: H, 15 to 30 μm)
m), an a-Si-based photoconductor in which a SiC surface protective layer was sequentially laminated was used, and the film thickness of the SiC surface protective layer was unified to 5000Å.

In addition, the surface of the a-Si photosensitive member was scanned with an electron microscope (SE) both at the initial stage and after printing 30 sheets.
When observed with M) at a magnification of 5000, the number of cones was reduced and the surface was smoothed after printing 300,000 sheets compared to the initial stage.

(1) Image density ◯: Initial density is maintained Δ: Density is slightly decreased ×: Density is significantly decreased

(2) Fog ○: Fog is not observed at all Δ: Fog is slightly observed ×: Fog is large

(3) Black spots ◯: No black spots are seen Δ: Some black spots are seen ×: Many black spots

(4) Image deletion ○: No image deletion occurs Δ: Image deletion occurs slightly ×: Image deletion occurs on the entire surface

[0051]

[Table 1]Table 1: When the average particle diameter of the toner mother particles is 10 μm Abrasive fine particles Evaluation results Early stageCharacteristics after printing 300,000 sheets Type Mohs Average particle size D / d Image Image Fog Black spot Image flow SiC layer thickness Kind Hardness d (μm)   concentration concentration       (Å) 9 0.02 500 ○ △ △ ○ × 5000 A 9 0.1 100 ○ ○ △ ○ × 5000 R 9 0.3 33.3 ○ ○ ○ ○ ○ 4000 Mi 9 0.5 20 ○ ○ ○ ○ ○ 3500 NA 9 0.8 12.5 ○ ○ ○ ○ ○ 3500 9 1.1 9.1 ○ △ × × △ 4500 D 9 0.1 100 ○ △ △ ○ × 5000 R 9 0.3 33.3 ○ ○ ○ ○ ○ 4000 9 9 16.7 ○ ○ ○ ○ ○ 3500 D 9 1.2 8.3 ○ △ △ × △ 4500 A 6 6 3 33.3 ○ ○ △ ○ × 5000 Data 6 0.8 12.5 △ △ △ ○ × 5000 D 6 1.2 3.3 △ △ △ ○ × 5000 A

[0052]

[Table 2]Table 2: When the average particle diameter of the toner mother particles is 5 μm Abrasive fine particles Evaluation results Early stageCharacteristics after printing 300,000 sheets Type Mohs Average particle size D / d Image Image Fog Black spot Image flow SiC layer thickness Kind Hardness d (μm)   concentration concentration       (Å) 9 0.02 250 ○ △ △ ○ × 5000 Rule 9 0.2 25 ○ ○ ○ ○ ○ 4500 Mi 9 0.4 12.5 ○ ○ ○ ○ ○ 4000 NA 9 0.8 6.3 △ × △ ○ △ 4500

[Brief description of drawings]

FIG. 1 is an explanatory cross-sectional view showing an example of a layer structure of an a-Si based photoreceptor.

FIG. 2 is a model cross-sectional view showing an example of the toner of the present invention.

FIG. 3 is an explanatory diagram showing an example of an image forming apparatus for carrying out the present invention.

[Explanation of symbols]

 11 Photoconductor 13 Conductive Substrate 15 Laser Light Absorption Layer 17 Carrier Injection Blocking Layer 19 Carrier Excitation / Transport Layer 21 Surface Protective Layer 31 Toner 33 Toner Mother Particles 35 Abrasive Fine Particles 41 Corona Charger 43 LED Head 45 Developing Roller 47 Transfer Device 49 rubbing roller 51 cleaning blade 61 developer 63 paper

Claims (1)

[Claims] 1. An average particle diameter D of the toner base particles and an average of the abrasive fine particles are formed by fixing abrasive fine particles having a hardness equal to or higher than that of the surface layer of the image forming photoreceptor to the surface of the toner base particles. A toner for developing an electrostatic latent image, which has a ratio with a particle diameter d in a range of D / d = 10 to 50.