JPH02157765A - Electrophotographic developing method - Google Patents

Abstract

PURPOSE:To obviate scumming and toner splashing even if a recycled toner is used and to make effective utilization of the toner by using the toner having a specific particle size distribution. CONSTITUTION:The toner in which >=90wt.% of the total particles exists in a 2<-1/3>D to 2<1/3>D range and the content of the toner smaller than 2<-1/3>D is <=5wt.%, where the volume average particle diameter of the toner is designated as D, is used in the two-component developing system by a dry process in which the toner is recycled. The toner to be used in this case has 3 to 20mum volume average particle size D. The effective utilization of the toner is made by using the recycled toner after cleaning in this way and the generation of the scumming and toner splashing is obviated by using the recycled toner.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electrophotographic developing method, and particularly to a dry two-component electrophotographic developing method in which untransferred toner remaining on an image carrier is recovered and reused.

[Prior art]

Generally, in an electrophotographic device, an electrostatic latent image on an image carrier is developed, and then a toner image is transferred to a transfer paper using a biased transfer roller or a corona charger. Approximately 20% by weight of untransferred toner remains on top. Therefore, attempts have been made to clean and recover this untransferred toner (hereinafter referred to as recycled toner) for reuse.

Particularly in high-speed electrophotographic apparatuses, since a large amount of toner is generated after cleaning, the use of recycled toner is being seriously considered. If recycled toner can be used, toner can be used effectively, space inside the machine can be significantly saved, and the machine can be made more compact.

Although the use of recycled toner is desired as described above, the reason why it is not actively used is mainly due to the following reasons. That is, when recycled toner is used, scumming and toner scattering are likely to occur.

Conventionally, it was believed that paper dust, dust, etc. from transfer paper were the cause, so meshes were installed in the recycled toner collection route to remove them.

Further, during cleaning and within the collection path, the toner may be charged to a polarity opposite to that obtained by friction with the carrier. As a countermeasure, it is possible to apply the same frictional charging polarity as the carrier to the member that the toner comes in contact with, or to use a corona charger to remove the charge remaining on the toner or a corona charger with the same polarity as the charge obtained by friction with the carrier. attempt was made to use it.

Furthermore, polarity control agents that are not easily charged to the opposite polarity in the recovery route are also being considered.

However, despite the above measures, background smearing and toner scattering have not been sufficiently improved.

Also, JP-A-63-38947 and JP-A-63-38
No. 948 discloses an invention in which the particle size is specified, but the purpose of specifying the particle size is to improve characteristics such as toner fluidity, image quality, and prevention of filming on the photoreceptor, and the purpose is different from that of the present invention. Essentially different.

(Purpose) The present invention provides an electrophotographic developing method that overcomes the conventional drawbacks by using recycled toner after cleaning to effectively utilize the toner and causing no scumming or toner scattering even when recycled toner is used. The purpose is to provide.

〔composition〕

In order to achieve the above object, the inventors of the present invention conducted a new study on the mechanism by which scumming and toner scattering occur, and found the following.

That is, when a continuous copying test was conducted using an electrophotographic apparatus modified so that recycled toner was returned to the toner replenishing device, background smudging gradually began to occur and toner scattering began to occur. As I continued the copy test, it got worse and worse, and I was finally unable to continue the test.

Therefore, when we measured various characteristics of the developer that had been sampled sequentially from the beginning of the copy test, we found that there were differences in the toner particle size in the developer between the samples before and after the background smudges started to occur. Ta. The sample from the scumming machine had a smaller average particle size as measured by a Coulter counter. Further, when observed with a scanning electron microscope, it was observed that the carrier surface was tightly covered with small particle size toner. When we examined subsequent samples, we found that the small particle size toner that covered the carrier had hardly decreased.

After careful investigation into the cause of such development, we found that among the developed toner, most of the small particle size toner remains on the image carrier without being transferred, and this toner returns to the toner replenishing device, causing the development to occur. By being supplemented in the drug,
It was found that it gradually covered the surface of the carrier. In particular, when the amount of toner in the toner supply tank became low, the amount of small particle size toner covering the carrier increased rapidly.

Furthermore, even if the toner tank is replenished with new toner, once the carrier is covered with small particle size toner, it will not recover.

Therefore, in such a state, even if toner is replenished into the developer, it is difficult for the toner to rub directly against the carrier surface and cannot obtain sufficient charge, resulting in scumming and toner scattering. That's what I found out.

In order to avoid the above-mentioned phenomenon, the present inventors conducted intensive research and found that it is effective to adopt the following developing method.

That is, after the electrostatic latent image on the image carrier is developed and the toner image is transferred to transfer paper, the toner remaining on the image carrier is cleaned, and then this toner is placed in a developing device or a replenishment toner. This is an electrophotographic developing method characterized in that 90 weight percent or more of the total particles are returned to the 3v7''2D range.

The toner used in the present invention has a volume average particle size of 3 to 20μ.
It belongs to m.

When the number of particles decreases, toner with a smaller particle size in the particle size distribution tends to become recycled toner, and by covering the carrier, it becomes more likely to cause scumming and toner scattering, so when recycled toner is used, scumming and toner scattering will occur. Occur.

Methods for cleaning the transfer machine toner from the image carrier include web cleaning, fur brush cleaning, cleaning with an elastic blade, magnetic brush cleaning, and cleaning methods using a combination thereof.

Recycled toner can be used by returning the cleaned toner to the developer, or by returning it to a toner tank for replenishment, stirring well, and then replenishing it into the developer. But it doesn't matter.

The developer used in the present invention is a dry type developer using a carrier.
It is a component-based developer, and all carriers conventionally used for electrophotography can be used.

Further, as the toner used in the present invention, those used as conventional electrophotographic toners can be used. That is,
The toner contains a coloring agent and a polarity control agent in a binder resin, and can also contain a magnetic material to form a magnetic toner.

As the binder resin, conventionally known binder resins can be used. That is, for example, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate. copolymer, styrene-maleic acid copolymer, styrene-acrylic ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene- Octyl acrylate copolymer, styrene
(phenyl acrylate copolymer, etc.), styrene-methacrylate ester copolymer, (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer,
Styrene-based resins (styrene-butyl methacrylate copolymer, styrene-phenyl methacrylate copolymer, etc.), styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, etc. homopolymers or copolymers containing styrene substitutes), vinyl chloride resins, styrene-vinyl acetate copolymers, rosin-modified maleic acid resins, epoxy resins, polyester resins, polyethylene, polypropylene, ionomer resins, polyurethane resins, ketone resins , ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral, etc., and waxes such as natural or synthetic waxes. These may be used alone or in combination.

Coloring agents include carbon black (e.g. channel black, acetylene black, lamp black, etc.), nigrosine dye, aniline blue, calco oil blue, phthalocyanine blue, chrome yellow, ultramarine blue, quinoline yellow,
Examples include methylene blue chloride, Monastral blue, malachite green ozalate, lamp black, rose bengal, Monastral red, Sudan black BM, and the like.

As negative charge control agents, metal complex salts of monoazo dyes,
Nitrohumic acid and its salts, salicylic acid, naphthoic acid,
Dicarboxylic acids Co, Cr.

There are metal complexes such as Fe, sulfonated copper phthalocyanine pigments, nitro groups, styrene oligomers introduced with halogens, chlorinated paraffins, melamine resins, etc., and the following can be used as the positive charge control agent.

Sumizol Black AR (Sumitomo Chemical, oil-soluble dye), Oil Black HBB (Orient Chemical, C, I).

26150-C,1, Solvent Black 3), Nigrosine, Mikethrene Blue R8N (Mitsui Toatsu, C,1,
698QQ,C.

■, Bat Blue 4), Ceres Blue R (Bayer,
C,1,61500,C,1,Solvent Blue 8
), Varifast Blue 1605 (Orient Chemical, oil-soluble dye, C0I, 74180), Oil Blue 2N
(Orient Chemical, oil-soluble dye C, 1, 61555), Rura Quick Rubin B (manufactured by BASF, C, 1, 11)
115, C, 1, Disbirds Red 13), Lurafix Blue FFR (BASF C, 1, 61505,
C, 1, Disper Z Blue 3), Lulafix Pink FF3B (manufactured by BASF, C01,62015, C,
1, Disbird's Red 11), etc.

Magnetic materials include metal powders such as cobalt, iron, and nickel; aluminum, cobalt, and copper.

Metals such as iron, lead, nickel, magnesium, tin, zinc, gold, silver, selenium, titanium, tungsten and zirconium, and mixtures thereof; metal oxides and metal compounds containing them, such as iron oxide and nickel oxide; Mention may be made of magnetic ferrites as well as mixtures thereof. Further, a fluidizing agent such as SiliH fine powder, a metal oxide such as titanium oxide or aluminum oxide, an abrasive such as silicon carbide, a lubricant such as fatty acid metal salt, etc. may be added to the toner.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to the following examples, but the present invention is not limited thereto. Note that all parts are parts by weight.

Example 1 Styrene resin (D-125 manufactured by Esso Corporation) 100 parts by weight Carbon black (#44 manufactured by Mitsubishi Carbon Corporation) 10
Part by weight chromium-containing monoazo dye
3 parts by weight A mixture having the above composition was thoroughly stirred and mixed in a Henschel mixer, and then melted and kneaded in a hot roll mill to obtain bulk toner A.

Next, bulk toner A was pulverized and classified into 1 part with a volume average particle size of 1
The toner (a) was 1.2 μm.

8.9μ■ or less is 2.4% by weight.

There are 7.2 weight percent particles in the 14.1 μm and larger range.

On the other hand, using a carrier in which ferrite particles each having a particle size of 100 μm are coated with methyl methacrylate resin to a thickness of 1 μm, toner (a) is mixed with this carrier at a ratio of 3.0% by weight, and the mixture is placed in a ball mill pot for 30 minutes. The mixture was stirred for a minute to prepare a developer.

Next, the Ricoh FT5510 was modified so that the recycled toner could be returned to the toner replenishment tank.

When we conducted a continuous copy test using this electrophotographic device and the developer mentioned above, we found that even after copying 100,000 sheets, there was no background smudge.
There was no toner scattering, and the same high image quality as the initial version was maintained. When I checked the toner consumption during the copy test, it was 2630 sheets/100g of A4 size.

Comparative example 1 The bulk toner A prepared in Example 1 was pulverized.

The toner (b)' was classified and had a volume average of 11.2 μm and a particle size distribution shown in Table 1. Next, a continuous copy test was conducted in exactly the same manner as in Example 1, and after approximately 30,000 copies had been made, scumming and toner scattering occurred. Toner consumption during the copy test was 1810 A4 size sheets/100g.
Met.

Comparative Example 2 Bulk toner A produced in Example 1 was pulverized and classified to produce toner (c) shown in Table 1.

Next, when a continuous copy test was conducted in the same manner as in Example 1, scumming and toner scattering occurred after approximately 20,000 copies.
The results are shown in Table 1.

Comparative Example 3 A continuous copy test of 100,000 copies was conducted in exactly the same manner as in Example 1, except that recycled toner was prevented from returning to the toner supply tank. Although there was no problem with the copy quality, only 2060 copies could be made per 100 g of toner, which was a decrease of about 22% compared to Example 1.

Example 2 Carbon black 10 parts by weight Di-tert-butylsalicylic acid zinc salt 3 parts by weight A mixture having the above composition was sufficiently stirred and mixed in a Henschel mixer, and then melted and kneaded with a hot roll to obtain bulk toner B.

This bulk toner B was pulverized and classified to form the toner shown in Table 1 (
d) was obtained.Next, a continuous copying test was conducted in the same manner as in Example 1, and as shown in Table 1, even after copying 100,000 sheets, no scumming or toner scattering occurred, and the level was the same as that at the beginning. Image quality was maintained. The toner consumption amount was 2850 sheets/100g of A4 size.

Comparative Examples 4 to 5 Bulk toner B prepared in Example 2 was crushed and classified to obtain toner (a) and toner (f) shown in Table 1. Next, a continuous copy test was conducted in exactly the same manner as in Example 1. The results are shown in Table 1.

(The following is a blank space) [Effects] As described above, by using a toner having a specific particle size distribution as described in the claims of the present invention, background smudges and toner particles can be prevented even when recycled toner is used. Since no scattering occurs, toner can be used effectively by using recycled toner, and the number of copies per unit weight of toner can be increased.

Claims (1)

[Claims] 1. After developing the electrostatic latent image on the image carrier and transferring the toner image to transfer paper, clean the toner remaining on the image carrier, and then transfer this toner to a developing device or a replenishing toner. In a dry two-component developing method in which the toner is returned to the original state and reused, when the volume average particle diameter of the toner is D, D/■√2
Electrophotographic development characterized by using toner powder in which 90 weight percent or more of all particles are in the range of ~■√2D, and particles smaller than D/■√2 are 5 weight percent or less Method.