JP3277213B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a developer used for developing the electrostatic latent image in an electrophotographic method or the like, details related to the polishing surface of the photosensitive member by the toner, and more particularly this
Concerning the the image forming method using the toner.

[0002]

2. Description of the Related Art Electrophotography has been widely known, and a typical Carlson method forms an image through the following steps.

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

(3) A developing step of developing an electrostatic latent image with a developer to attach toner and form a toner image on a photoreceptor. (4) A transfer step of transferring the toner image on the photoreceptor to paper or the like. (5) A fixing step of fixing the transferred toner by heat, pressure, or the like.

Further, a non-Carlson type image forming method in which a developer reservoir is formed on a photoreceptor, charge is injected into the photoreceptor via the developer to charge the photoreceptor, and an image signal is exposed from the back side of the photoreceptor and developed simultaneously. A method is also known, and is usually called an optical back exposure recording system.

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

[0007] On the other hand, however, the a-Si-based photoreceptor tends to leak charge after a long-term use, and tends to cause so-called "image deletion".

The use of abrasives as a countermeasure against such image deletion has been known for a long time. For example, the addition of strontium titanate fine particles to a developer (Japanese Patent Application Laid-Open No. Sho 61-1986)
No. 2,788,861), use of a cleaning member having a Mohs' hardness of 2.5 to 7.0 (Japanese Patent Application Laid-Open No. 59-88776), and a method using abrasives and fine particles of the same degree as the surface layer of an a-Si drum (particularly, And the like, and it has been reported that alkaline earth metals, carbonates, and the like are effective for image flow of an a-Si photoreceptor (Japanese Patent Application Laid-Open No. SHO 61-61). 231564).

However, each of the above-mentioned polishing methods has a weak polishing force, and the effect of preventing the image flow of the a-Si photosensitive member is insufficient. Also, when trying to increase the polishing power,
The image forming apparatus became large and could not be adopted for a small machine.

[0010]

[SUMMARY OF THE INVENTION The present invention is excellent in polishing effect, using Toners useful in particular for the a-Si based photosensitive member
To provide an image forming method .

[0011]

According to the image forming method of the present invention, abrasive fine particles having a hardness equal to or higher than the SiC surface layer of an a-Si photosensitive member for image formation are fixed to the surface of toner base particles. And a toner for developing an electrostatic latent image in which the ratio of the average particle diameter D of the toner base particles to the average particle diameter d of the abrasive particles is in the range of D / d = 10 to 50, and the downstream side of the transfer means. A rubbing roller and a cleaning blade are provided, and the surface of the photoreceptor is polished by the rubbing roller and the cleaning blade with toner remaining on the photoreceptor after transfer.

The toner is supplied and developed on the surface of a photoreceptor having a photosensitive layer of amorphous silicon or the like, and a toner image is formed on the surface of the photoreceptor to form an image.
Polishing of the photoreceptor surface layer is performed simultaneously with image formation.

Further, a toner image is formed on the surface of the photoreceptor,
Then, after the toner image is transferred to the material to be transferred, a pressure-contact member is pressed against the surface of the photoconductor where the untransferred toner remains, and the surface of the photoconductor can be polished with the remaining toner, further improving the polishing effect. I do.

[0014]

FIG. 1 is a sectional view showing a layer structure of a photosensitive layer of an a-Si based photosensitive member 11. On the conductive substrate 13, a laser light absorbing 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 protective layer 21 are sequentially laminated.

The surface protection layer 21 is typically made of SiC. This SiC layer (surface protective layer 21) is not smooth, has many fine projections (cones), has strong hydrophilicity, and adheres ion products generated by corona discharge. Therefore, when continuous printing is repeated or 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, and the charge of the photoconductor leaks, so-called "image deletion" occurs. Moreover, these products have a strong tendency to accumulate between the minute projections of the SiC layer, which is the surface protective layer 21, and the "cleaning of the image" cannot be prevented by ordinary cleaning.

Therefore, according to the present invention, on the surface of the toner particles,
Abrasive fine particles of an appropriate particle size having a hardness equal to or higher than that of the surface protective layer 21 are fixed, and the surface protective layer 21 is polished strongly to prevent image deletion. FIG. 2 is a model diagram of the toner of the present invention.
Abrasive particles 35 are fixedly formed on the surface of.

To fix the abrasive fine particles 35 to the surface of the toner base particles 33, for example, the toner base particles 33 and the abrasive fine particles 35 are uniformly mixed, and the abrasive fine particles 35 adhere to the surface of the toner base particles 33. After that, a mechanical and thermal impact force is applied to fix the abrasive fine particles 35 so as to be driven into the toner base particles 33. The abrasive fine particles 35 are not completely embedded in the toner base particles 33, but are fixed so that a part thereof protrudes from the toner base particles 33.

Such a device for fixing the abrasive fine particles 35 is commercially available as a surface reforming device or system, and examples thereof are as follows.

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

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

(3) Wet method: Dispercoat (Nissin Flour Milling Co., Ltd.) Coatmizer (Freund Sangyo Co., Ltd.)

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

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

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

When an image is formed by using the toner 31 as described above, the toner 31 is used as in the case of development and cleaning.
Effectively polishes the photoreceptor surface when it contacts and rubs with the surface layer of the photoreceptor. More specifically, when used for an a-Si photoreceptor having an SiC layer having a large number of microprojections (cones) as a surface layer, the tips of the microprojections are polished by the abrasive fine particles 35 having high hardness. As a result, the photoreceptor surface is smoothed, and at the same time, the ion products deposited between the microprojections are removed to prevent image flow,
Further, it has been found that development stability is also ensured. Moreover, the toner of the present invention having such an effect does not significantly damage the surface of the a-Si photosensitive member even when polished by a cleaning blade, a rubbing roller, or the like.

The operation and effect of the present invention can be attained by externally adding abrasive powder (mixing powder), using an abrasive having a lower hardness, or using an abrasive having an inappropriate particle size ratio. Cannot be obtained when is fixed on the toner surface.

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

As the toner base particles 33, those having the same configuration as the conventional toner itself are used, and for example, a binder resin, a colorant, a charge control agent, an offset preventing 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 resin represented by a polystyrene resin such as a styrene-acryl copolymer, a polyester resin, or the like is used.

Examples of the colorant include carbon black and various pigments and dyes; examples of the charge control agent include quaternary ammonium compounds, nigrosine, nigrosine base, crystal violet, and triphenylmethane compounds; Olefin wax such as low molecular weight polypropylene, low molecular weight polyethylene or a modified product thereof can be used as an auxiliary agent; magnetite, ferrite and the like can be used as a magnetic substance.

The toner base particles of the present invention can be obtained by a conventional method, for example, by melt-kneading the components with a twin-screw extruder, a kneader, or the like, followed by pulverizing with a jet mill or the like 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 photoconductor 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 uniform charging of the surface of the photoconductor 11 by the corona charger 41 and formation of an electrostatic latent image by selective image exposure by the LED head 43, the developer 61 is supplied to the surface of the photoconductor 11 by the developing roller 45, and toner is 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. In addition, since the abrasive fine particles 35 are firmly fixed to the toner base particles 33, they do not fall off and do not cause poor development or image defects.

The toner 31 on the surface of the photoreceptor 11 is transferred to a paper 63 (transfer material) by a transfer device 47 and then fixed on the paper 63 by a 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,
Part of the toner 31 (residual toner) remains on the photoconductor 11. The remaining toner 31 is pressed against the surface of the photoreceptor 11 by the rubbing roller 49 to polish the SiC layer, and the polishing effect of the toner fine particles 35 of the toner 31 is increased.

Next, the remaining toner 31 on the photoreceptor 11 is
Is removed from the surface of the photoreceptor 11 by the cleaning blade 51.
Due to the mechanical force applied between the photoconductor 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. The rubbing roller 49 is pressed against the surface of the photoreceptor 11, and is rotated so as to apply a shear stress to the photoreceptor 11, whereby the photoreceptor 11 is rotated. Is polished and cleaned.

Further, by attaching a heater to the inner surface of the photoreceptor 11 and heating it, the effect of preventing image flow can be further improved. In the above description, an a-Si-based photoreceptor having a SiC layer as a surface layer has been mainly described. However, other types of surface layers or other types of photoreceptors may be used. The hardness of the abrasive particles may be adjusted according to the hardness of the abrasive.

[0038]

According to the present invention, 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 diameter ratio between the toner base particles and the abrasive fine particles to be fixed is adjusted. By specifying this, an excellent polishing effect on the photoreceptor surface can be obtained. Therefore, the image forming apparatus can be designed to be compact, and there is no need to incorporate a special system such as a cleaning brush. In particular, a small machine using a small-diameter photosensitive drum, the hardness of the surface layer is large, and the cleaning brush becomes large It is suitable for an a-Si type photoreceptor which easily causes the above.

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

[0040]

【Example】

 Example 1 100 parts by weight of styrene / n-butyl acrylate copolymer (copolymerization ratio 80/20) 5 parts by weight of carbon black (MA-100, manufactured by Mitsubishi Chemical Industry Co., Ltd.) 5 parts by weight of polypropylene wax (Viscol 550P, Sanyo Chemical) 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 using a twin screw extruder (PCM-30, manufactured by Ikegai Iron Works Co., Ltd.), cooled, pulverized and classified.
Toner toner particles having an average particle diameter of 10 μm were obtained.

After 2% by weight of abrasive particles (described in Tables 1 and 2) were mixed at a high speed with respect to the toner base particles, the mixture was treated with a surface reforming device (Hybritizer, manufactured by Nara Machinery Co., Ltd.). Thus, a toner having fine abrasive particles fixed on the surface was obtained.

At this time, as shown in Table 1 below, the types and average particle diameters of the abrasive fine particles were variously changed to obtain respective toners. Further, a developer shown in Table 2 was prepared in the same manner as above, except that the average particle size of the toner base 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 of 300,000 sheets was performed using the apparatus shown in FIG. 3, and the image density, fogging, black point due to the drum, and image deletion were evaluated based on the following criteria. The thickness of the surface SiC layer after printing was measured by XPS.

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

The surface of the a-Si photosensitive member was scanned with a scanning electron microscope (SE) both at the initial stage and after printing 30 sheets.
Observation at 5000 magnifications using M) showed that after printing 300,000 sheets, the number of cones was reduced and the surface was smoothed.

(1) Image density ：: Maintain initial density △: Slightly lower density X: Severely lower density

(2) Fog ：: Fog is not observed at all Δ: Fog is slightly observed X: There are many fogs

(3) Black spots 全 く: No black spots are observed at all △: Black spots are slightly observed ×: Many black spots are observed

(4) Image deletion ：: No image deletion occurs Δ: Slight image deletion ×: Image deletion occurs over the entire surface

[0051]

[Table 1]Table 1: When the average particle size of the toner base particles is 10 μm Abrasive particles Evaluation results EarlyCharacteristics after printing 300,000 sheets Species 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 l 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 9 9 0.3 33.3 ○ ○ ○ ○ ○ 4000 90.6 16.7 ○ ○ ○ ○ ○ 3500 D 9 1.2 8.3 ○ △ △ × △ 4500 A H 6 0.3 33.3 ○ ○ △ ○ × 5000 60.8 12.5 △ △ △ ○ × 5000 D 6 1.2 3.3 △ △ △ ○ × 5000 A

[0052]

TABLE 2: Mean particle When the size 7μm abrasive particles Evaluation results Initial 300,000 sheets characteristic species after printing Morse average particle diameter D / d Image fog black spots image flow SiC layer thickness such toner base particles Hardness d (μm) Concentration Concentration (Å) A 9 0.02 250 ○ △ △ ○ × 5000 5000 9 0.225 ○ ○ ○ ○ ○ 4500 M 9 0.4 12.5 ○ ○ ○ ○ ○ 4000 na 9 0.8 6.3 △ × △ ○ △ 4500

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view illustrating an example of a layer configuration of an a-Si-based photoconductor.

FIG. 2 is a model sectional view showing an embodiment of the toner of the present invention.

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

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 photoconductor 13 conductive substrate 15 laser light absorbing layer 17 carrier injection blocking layer 19 carrier excitation / transport layer 21 surface protection layer 31 toner 33 toner base particles 35 abrasive particles 41 corona charger 43 LED head 45 developing roller 47 transfer device 49 Rubbing roller 51 Cleaning blade 61 Developer 63 Paper

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-15154 (JP, A) JP-A-63-244054 (JP, A) JP-A-64-20586 (JP, A) JP-A-60-1985 150076 (JP, A) JP-A-60-107675 (JP, A)

Claims (1)

(57) [Claims] An abrasive particle having a hardness equal to or greater than a SiC surface layer of an a-Si photosensitive member for image formation is fixed to the surface of toner base particles. The ratio of the abrasive particles to the average particle diameter d is D / d = 10
, A rubbing roller and a cleaning blade are provided downstream of the transfer means, and the toner remaining on the photoreceptor after transfer is sensitized by the rubbing roller and the cleaning blade. An image forming method, characterized by polishing the surface of a body.