JPH0320750A - Developer and manufacture of the same - Google Patents

Abstract

PURPOSE:To enhance electric chargeability characteristics, fluidity, and cleanability of a binary developer by adding specified fine polymer powder and fine silica powder to a toner. CONSTITUTION:This developer comprises a magnetic carrier and the toner and it is used for developing an electrostatic charge latent image formed on a photosensitive layer having a Vickers hardness of <=50 Hv at a surface temper ature of 30 deg.C, preferably, made of Se-Te, and 0.02 - 0.1 pts.wt. of a fine acrylic polymer powder of 0.1 - 0.3 mum particle diameter and the fine silica powder in a weight ratio of the polymer powder to this silica powder of 1:1 - 1:5 are added to 100 pts.wt. of the toner.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a two-component developer for developing electrostatic latent images, and more particularly, it relates to a two-component developer that develops electrostatic latent images, and more specifically, it has excellent charging properties, fluidity, and cleaning properties, and has excellent blackness due to toner. The present invention relates to a two-component developer that does not cause streaks on copied images.

(Prior art) Conventionally, in electrophotography, electrostatic printing, etc., in order to visualize an electrostatic latent image formed on an image bearing member made of a photoreceptor or dielectric material, binding is used. Development is performed using powder toner in which additives such as colorants are dispersed in resin.

For example, in a copying machine that uses electrophotography, an electrostatic latent image formed on a photoreceptor by charging and exposure is developed with the above-mentioned toner, and the toner image formed on the electrostatic latent image is transferred to a transfer paper or the like. The toner image is transferred onto a support, and the toner image is fixed onto the support by a fixing means such as a heating roller or a pressure roller to obtain a copy. After the toner image is transferred to the support, the toner remaining on the photoreceptor is scraped off by a cleaning means such as a cleaning blade, and the toner is removed to prepare for the next copying process.

In order to obtain a good image shape in the above system,
Toner has various characteristics for each process, such as having good charging stability and maintaining excellent developability without fogging or toner scattering, and ensuring that toner does not remain on the photoreceptor during the post-transfer cleaning process. is required.

In addition, organic and inorganic photosensitive layers are used as the photosensitive layer used in the above photoreceptor, and Se-based photoreceptors are common as inorganic ones, and conventionally Se-Te-based and Se-As
A photoreceptor based on the above-mentioned photoreceptor is used as a photoreceptor for electrophotography. S
E-As type photoreceptors generally have high hardness and excellent photosensitivity, so they are suitable as photoreceptors for high-speed image forming machines. On the other hand, the Se-Te photoreceptor has lower hardness than the Se-As type (vinker hardness of 30Hv or less = 30℃L).It also has inferior photosensitivity, but it has excellent productivity and is low cost. Because of this, the surface of the photosensitive layer does not require excessive hardness, and is used as a photoreceptor for low to medium speed machines that can be used even with low sensitivity.

On the other hand, as described above, in order to obtain a 1.toner image that is stable over repeated use, the toner is required to have excellent developability and cleanability. Therefore, conventional techniques have been proposed in which various additives are externally added to toner to improve its developability and cleanability. As an effective proposal, for example, Japanese Unexamined Patent Publication No. 186851/1983 proposes a toner composition (developer) in which a fine acrylic polymer powder is externally added to a toner.

(Problems to be Solved by the Invention) According to the above proposal, the developer has obtained some good results in terms of prevention of toner scattering, image fogging, and greening properties. However, by using fine acrylic polymer powder together with a magnetic carrier and preparing a two-command developer, Se
- When applied to an image formation system using a photoreceptor drum having a photosensitive layer with low hardness such as a Te-based photoreceptor drum, the medaka phenomenon (black streaks caused by toner) may occur on the copied image along with the repetition of image formation. There is still room for improvement.

The present invention has been made in view of the above points, and its purpose is to provide good charging characteristics, fluidity, and cleaning properties, and to prevent the occurrence of fogging and smearing phenomena (black smudges caused by toner). The objective is to provide a two-component developer that is

(Means for Solving the Problems) According to the present invention, a magnetic carrier for developing an electrostatic latent image formed on a photosensitive drum having a photosensitive layer having a Vickers hardness of 50 Hv or less (surface temperature of 30° C.); In a two-command developer consisting of toner, for 100 parts by weight of toner,
0.02 to 0.15 parts by weight of acrylic polymer fine powder whose secondary particle size is in the range of 0.1 to 0.3 μm, and the weight ratio to the acrylic polymer fine powder is 1:1 to 1:1. A two-command developer is provided, which is characterized in that it is mixed with fine silica powder in a ratio of 1:5.

(Function) The present invention is characterized in that, as a two-component developer consisting of a toner and a magnetic carrier, a specific amount of acrylic polymer fine powder of a specific particle size is externally added to the toner together with silica fine powder, and mixed processing is performed. It has the following.

In general, in the magnetic brush development method using a two-component developer, particles with a small amount of magnetization and particles with a fine particle size are deposited on the photoreceptor together with the toner through repeated development operations, although they are extremely small amounts of the magnetic carrier. May be developed. The carrier developed together with these toners is not transferred in the transfer process, but is scraped off by a blade in the cleaning process and collected in the cleaning box. Therefore, it does not have a large effect on the copied image.

On the other hand, when image formation is repeated using a two-component developer in which acrylic polymer fine powder is added and mixed with toner, extremely good development characteristics are achieved in terms of suppressing the generation of toner with opposite polarity and stabilizing the amount of charge. is obtained, and even in the cleaning process, the toner can be easily scraped off and removed quickly.

However, perhaps because the acrylic polymer fine powder itself has low fluidity, the acrylic polymer fine powder stays in the gap between the cleaning blade and the photoreceptor drum surface, causing the acrylic polymer powder to accumulate between the photoreceptor drum and the blade. Aggregates of coalesced fine powder may accumulate.

For this reason, when using a photoreceptor with poor hardness such as Se-Te (Vickers hardness: 30 HV: surface temperature 30°C), the carrier particles adhering to the photoreceptor are not scraped off by the blade during the cleaning process, and the acrylic The toner is captured by aggregates of fine powder of the polymer, and the surface of the photoreceptor is scratched by these carrier particles, and as the image formation progresses, the toner is embedded in the scratches, causing black streaks of toner on the photoreceptor. It becomes a medaka phenomenon and appears on the copied image.

In the present invention, the particle size of secondary particles of the acrylic polymer fine powder used is 0. 1 to 0.3 μm, preferably 0. By using extremely fine particles in the range of 1 to 0.15 μm and also using a specific amount of fine silica powder according to the amount of fine acrylic polymer powder added, the gap between the cleaning plate and the photoreceptor drum is made of acrylic. This allows most of the polymer fine powder to slip through, reduces the adhesion of the carrier itself to the photoconductor and blade, and improves the fluidity of the developer itself, allowing the carrier to be captured between the photoconductor and the blade. The purpose of this invention is to avoid the above-mentioned problems and enable stable image formation over a long period of time.

Further, as is clear from the Examples and Comparative Examples described below, the developer of the present invention can be applied not only to a photoreceptor drum having an inorganic photosensitive layer such as a Se-Te type, but also to an organic photosensitive layer having a generally low hardness. It can also be suitably used in an image forming system using a photosensitive drum having a Vickers hardness of 20 to 50 Hv at a surface temperature of 30°C.

(Preferred embodiment of the invention) Acrylic polymer fine powder used in the present invention is polymethyl methacrylate, polybutyl methacrylate, styrene-methyl methacrylate copolymer, styrene-butyl methacrylate. Copolymer, methyl methacrylate-butyl methacrylate copolymer, styrene-methyl methacrylate-butyl methacrylate copolymer, etc., and one or two of styrene, methyl methacrylate, methyl acrylate, butyl acrylate, etc. It is obtained by polymerizing more than one type of monomer.

The particle size of the polymer fine powder is 0.1 to 0.3 μm,
Preferably 0. 1 to 0.15. Any form of amorphous or spherical particles within this particle size range can be used, but spherical particles obtained by emulsion polymerization, dispersion polymerization, and soap-free polymerization are particularly preferred. The addition ratio to the toner is 0.000 parts per 100 parts by weight of the toner.
It is preferred to add 0.02 to 0.15 parts by weight, especially 0.05 to 0.1 parts by weight.

If the amount added is too large beyond the above range, the fluidity of the developer itself will be reduced and fine powder will tend to accumulate between the blade and the photoreceptor. On the other hand, if the amount added is less than the above-mentioned amount, the ratio of toner of opposite polarity tends to increase, and the charging rise characteristics tend to deteriorate.

The fine silica powder used in the present invention has a primary particle size of 0.01 to 0.1 μm, particularly 0.02 to 0.0 μm.
03 μm is preferably used. Further, it is preferably hydrophobic.

The amount of this fine silica powder added should be in the range of 1:1 to 1:5, particularly in the range of 1:2.5 to 1:3.5, in terms of weight ratio of fine acrylic polymer powder to fine silica powder. is preferred.

When the amount added falls outside the above range, the fluidity of the developer itself decreases, and black streaks tend to occur as image formation progresses.

Furthermore, if the amount exceeds the above range, the amount of charge tends to decrease.

The toner used in the present invention is one in which various additives such as colorants are dispersed in a binder resin responsible for electrodetection and fixing properties as shown below. , styrenic polymers, acrylic polymers, styrene-acrylic polymers, chlorinated polyethylene, polyprolene, olefin polymers such as ionomers, polyvinyl chloride, polyester, polyamide, polyurethane, epoxy resin, diallyl phthalate resin , silicone resin, phenol resin, rosin-modified phenol resin, xylene resin, rosin-modified maleic acid resin, rosin ester, petroleum resin, and the like.

The above polymer generally has a glass transition point (Tg) of 40 to 80°C, particularly 50°C, in order to obtain heat resistance and favorable fixing properties.
to 75°C, and the weight average molecular weight is generally 30,000.
Those having a number average molecular weight of 4,500 to iooooo, particularly 4,800 to 9,000 are preferably used, and one or two or more thereof may be used in combination.

Among the above polymers, rosin esters, rosin modified phenolic resins, rosin maleic acid resins, epoxy resins, polyesters, cellulose polymers, polyester resins, etc. are useful in improving the triboelectric properties of toner. be.

In addition, when the toner is a pressure fixable toner, olefin polymers such as polyethylene and polypropylene, etc.
Polymers that are easily plastically deformed are mainly used. This polymer can be used with other polymers such as polyvinyl acetate, ethylene-vinyl acetate copolymer, hydrogenated polystyrene, hydrogenated rosin ester, aliphatic, alicyclic or aromatic petroleum resins. etc. may be included.

As the coloring agent, known coloring agents used in this field are used, such as carbon black, lamp black, chrome yellow, Hanzai Elo, benzidine yellow, permanent orange, pyrazolone orange, watch young red, permanent red, brilliant car. Tan 3B, Brilliant Car 6B, DuPont Oil Red, Vilazolone Red, Lake Red, Rose Bengal, Aniline Blue, Ultramarine Blue Calco Oil Blue, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate, etc.
I. Solvent Yellow 60. C. I
．． Solvent Red 27, C. I. Solv
Examples include oil-soluble dyes such as ENT Blue 35 and the like. These colorants are used alone or in a mixture of two or more, and are generally used in an amount of 1 to 60 parts by weight per 100 parts by weight of the binder resin.
Parts by weight, especially 5 to 30 parts by weight, are preferably used.

Further, an anti-offset agent such as wax may be added to the binder resin in order to prevent offset and improve fixing properties. The waxes used include various waxes such as polyethylene wax, polypropylene wax, ethylene-propylene wax, and paraffin wax, low molecular weight olefin polymers such as olefin monomers having 4 or more carbon atoms, fatty acid amide, silicone oil, etc. is used.

These anti-offset agents are 0 per 100 parts by weight of binder resin.
．． 1 to IO parts by weight can be used.

In addition, in the present invention, in order to control the triboelectric charging characteristics of the toner, oil-soluble dyes such as nigrosine dye, oil black, and soubiron black, naphthenic acid, salicylic acid, fatty acids and resin acids such as manganese and iron are added to the binder resin. ,cobalt,
Known charge control agents such as metal soaps such as lead, zinc, cerium, calcium, and nickel salts, metal alloy azo dyes, pyrimidine compounds, and alkyl salicylic acid metal chelates can also be used. These charge control agents are preferably used in an amount of 0.1 to 5 parts by weight, particularly 1 to 3 parts by weight, per 100 parts by weight of the binder resin.

The toner in which additives such as colorants are dispersed in the binder resin has an average particle size of 2 to 20 μm, particularly 6 to 1 μm.
Those having a particle size of 2 μm are preferably used. Further, the shape of the particles may be amorphous or spherical.

As the carrier used in the present invention, various materials can be used, including magnetic materials such as iron oxide, reduced iron, copper, silicon copper, ferrite, nickel, cobalt, etc., and manganese, cobalt, etc. Alloys with zinc, aluminum, etc., such as iron and
Magnetic materials such as nickel alloys, iron-cobalt alloys, iron-aluminum alloys, titanium oxide, aluminum oxide, copper oxide, magnesium oxide, copper oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, titanic acid, etc. Ceramics such as lithium, lead titanate, lead zirconate, lithium diobate, ADP, (NHa
Examples include Hx PO4 ), KDP (KH2PO,) Rossiel's salt, and the like. One or more types of the above carriers may be used.

Further, the surface of the carrier may be coated with a resin component, and a surface-coated high-resistance carrier is suitable for the present invention. The electrical resistance of the carrier is generally IXIO
A range of 1×10 9 to IXIO” Ω·cm, preferably 1×10 9 to IXIO” Ω·cm is used.

In addition, the average particle size of the carrier is 50 to 000 μm.
, particularly preferably 80 to 120 μm. Note that among the above carriers, iron and ferrite such as iron oxide and reduced iron are preferable because they are inexpensive and have excellent image characteristics.

Further, the developer of the present invention is preferably used when a magnetic carrier containing 1% or more of fine particles of 40 um or less is used as the magnetic carrier.

One amount.

In the present invention, the weight ratio to the toner is 50:
1 to 30:1 of acrylic polymer fine powder is added and mixed to form a toner mixture, and a new toner is added and mixed to this toner mixture to maintain a constant concentration of acrylic polymer fine powder relative to the toner. By diluting the acrylic polymer fine powder so that the toner particles are diluted, the fine acrylic polymer powder can be evenly and uniformly adhered to the surface of the toner particles. In other words, when too much acrylic polymer fine powder is mixed, the acrylic polymer fine powder adheres strongly to the toner particle surface and the acrylic polymer fine powder adheres with weak adhesion, resulting in new toner particles. By adding , the new toner firmly adheres to the weakly adhesive acrylic polymer fine powder, resulting in a uniform and uniformly dispersed state as a whole.

The above mixing method is an extremely effective method.If the entire amount of toner and the acrylic polymer zone fine powder are mixed all at once from the beginning, aggregates of the acrylic polymer fine powder are likely to occur, so adjust this toner mixture. If a developer obtained by this method is used, the effects of the present invention tend to be difficult to exhibit.

Then, silica fine powder in the weight ratio described above is added to the mixture of the above toner and acrylic polymer fine powder, and a mixing process is performed. By adding and mixing a specific amount of silica to a toner mixture in which fine acrylic polymer powder is uniformly mixed, it is possible to improve the fluidity of the toner mixture and, ultimately, of the entire developer after the developer is adjusted. By keeping the dispersed structure of the acrylic polymer fine powder stable, more favorable results can be obtained in preventing the occurrence of black streaks, image fogging, poor cleaning, density reduction, etc.

The above toner mixture and magnetic carrier are 1:99 to 15
:85 weight ratio to prepare a developer.

In the present invention, when mixing the toner and the external additive, or the toner mixture and the carrier, a Henschel mixer, a Pitanx mixer, or the like is used as a mixing device, and a Henschel mixer is particularly preferably used.

As explained above, the developer of the present invention can suppress the killifish phenomenon by using a specific amount of acrylic polymer fine powder and silica fine powder of a specific particle size. No more black lines.

Hereinafter, the present invention will be explained in detail with reference to Examples and Comparative Examples.

(Comparative Example 1) 100 parts by weight of styrene-acrylic copolymer as a binder resin, 8.5 parts by weight of carbon bra as a colorant, 2 parts by weight of a negative metal-containing azo dye as a charge control agent,
Low molecular weight polypropylene as an anti-offset agent1.
8 parts by weight were mixed and adjusted in a conventional manner, followed by melt-kneading, cooling, pulverization, and classification to produce a toner with an average particle size of 11 μm.

The particle size of the secondary particles is 0 with respect to 100 parts by weight of the above toner.
．． 0.1 part by weight of 4 μm acrylic polymer fine powder,
Fine silica powder (primary particle diameter: 0.02 μm) was added in a weight ratio of 1:2 to fine acrylic polymer powder and mixed with a Henschel ξ Kisser to obtain a toner composition.

Then, a ferrite carrier with an average particle size of 100 μm (
An electrophotographic copying machine with a copying speed of A4: 20 sheets/min, equipped with a Se-Te photoreceptor, which uses a mixture of 1% or more of particles with a particle size of 40 μm or less and a toner concentration of 2.7% as a developer. A running test was conducted using a modified DC-2055 (trade name, manufactured by Sanda Kogyo Co., Ltd.). As a result, 1
After printing 00 to 500 copies, black streaks appeared on the image.

(Comparative Example 2) Using the same developer as in Comparative Example 1, an electrophotographic copying machine DC-4055 equipped with a Se-AS photoconductor and having a copying speed of A4: 40 sheets/min (manufactured by Sanda Kogyo Co., Ltd.) Product name) A running test was conducted using a modified machine. As a result, 3
No black streaks were generated on the copied image even after 10,000 copies of the image were printed.

(Comparative Example 3) Using the same developer as in Comparative Example 1, a photosensitive drum having an organic photosensitive layer with a Binkers hardness of 20 to 30 Hv (surface temperature 30°C) was used. A4 size: 17 sheets/min. A running test was conducted using a modified copying speed electrophotographic copying machine DC-1785 (manufactured by Sanda Kogyo Co., Ltd., trade name).

As a result, black streaks appeared on the images after about 100 sheets.

(Comparative Example 4) Using the same developer as in Comparative Example 1, a photosensitive drum having an organic photosensitive layer with a Vickers hardness of 40 to 50 Hv (surface temperature 30'C) was mounted on A4: 20 sheets/ A running test was conducted using a modified electrophotographic copying machine DC-2055 (manufactured by Sanda Kogyo Co., Ltd., trade name) with a copying speed of 30 minutes. As a result, black streaks appeared on the images after 10,000 sheets were printed. (Example 1) The weight ratio of 100 parts by weight of the same toner as in the comparative example and 0.1 part by weight of acrylic polymer fine powder with a secondary particle size of 0.15 μm to the acrylic polymer fine powder is 1:l
After mixing with silica fine powder (primary particle diameter: 0.02 μm) using a Henschel mixer and preparing a developer in the same manner as in the comparative example, 20 A4 sheets equipped with a Se-Te photoreceptor were prepared. Electrophotocopy machine D with a copying speed of / minute
A running test was conducted using a modified C-2055 (trade name, manufactured by Sanda Kogyo Co., Ltd.). As a result, no black streaks were found even in 30,000 copied images. (Example 2) Fine acrylic polymer powder with a secondary particle size of 0.15 μm was added to 50 parts by weight of the same toner as in the comparative example so that the weight ratio to the toner was 40=1. Then, a new toner is added and further mixed with a Henschel mixer to produce a toner mixture in which 0.1 parts by weight of acrylic polymer fine powder is mixed with 100 parts by weight of toner. I got it. and,
This obtained mixture was mixed with fine silica powder (primary particles having a diameter of 0.5 mm) at a weight ratio of 1:1 to fine acrylic polymer powder.
02 μm) was added thereto and further mixed using a Henschel mixer to obtain toner a.

After adjusting the developer in the same manner as in the comparative example, an A4:17 was prepared with a photoconductor drum having an organic photoconductor layer having a Vickers hardness of 20 to 30Hv (surface temperature 30°C).
Electrophotocopy machine DC-1'78 with copying speed of sheets/minute
5 (manufactured by Sanda Kogyo Co., Ltd., trade name) A running test was conducted using a modified machine, and no black streaks were found even in 50,000 images.

Furthermore, in Examples 3 and 4 and Comparative Examples 5 to 7, the particle size and addition amount of the acrylic polymer fine powder, and the addition amount of the silica fine powder were changed, and A4:2G sheets equipped with Se'-Te photoreceptors were prepared. /
DC-2055 electrophotographic copying machine with a copying speed of
A running test was conducted using a modified machine manufactured by Sanda Kogyo Co., Ltd. (trade name).

(Example 3) According to the method of Example 2, acrylic polymer fine powder having an average particle size of 0.3 μm was used, and 0.02 parts by weight of acrylic polymer fine powder was used for 100 parts by weight of toner. A running test was conducted by preparing a developer in which silica powder was mixed in an amount 2.5 times the amount of acrylic polymer fine powder. As a result, no black streaks were found among the 30,000 images.

(Example 4) According to the method of Example 2, acrylic polymer fine powder having an average particle size of 0.1 μm was used, and 0.15 parts by weight of acrylic polymer fine powder was added to 100 parts by weight of toner. A running test was conducted by preparing a developer in which silica powder was mixed in an amount five times that of acrylic polymer fine powder. As a result, no black streaks were found among the 30,000 images.

(Comparative Example 5) According to the method of Example 2, acrylic polymer fine powder having an average particle size of 0.3 μm was used, and }-J--10
A running test was conducted on a developer prepared by mixing 0.2 parts by weight of acrylic polymer fine powder and silica powder in twice the amount of the acrylic polymer fine powder.

As a result, black streaks occurred in the 10,000th image.

(Comparative Example 6) According to the method of Example 2, acrylic polymer fine powder having an average particle size of 0.1 μm was used, and 0.1 part by weight of acrylic polymer fine powder was used per 100 parts by weight of toner. and,
A running test was conducted using a developer mixed with 7 times as much silica powder as the acrylic polymer fine powder. As a result, although no black streaks were observed until the 20,000th image, fogging was severe and clear images could not be obtained.

(Comparative Example 7) According to the method of Example 2, acrylic polymer fine powder having an average particle size of 0.2 μm was used, and 0.01 part by weight of acrylic polymer fine powder was used for 100 parts by weight of toner. A running test was conducted by preparing a developer in which silica powder was mixed in an amount 2.5 times the amount of acrylic polymer fine powder. As a result, although no black streaks occurred until the 20,000th image, the image quality was low and image fogging was observed.

From the above Examples and Comparative Examples, it is clear that the developer of the present invention is Se-
It can be seen that very good results can be obtained with Te-based organic photoreceptors and organic photoreceptors with low hardness. Moreover, preferred adjustment methods can be learned from Examples 1 and 2, and effective ranges of various additives of the present invention can be learned from Examples 3 and 4 and Comparative Examples 5 and 7.

(Effects of the Invention) According to the present invention, in an image format using a Se-Te system or an organic photoreceptor, a good image can be obtained for a long period of time without causing black streaks, image fogging, or a decrease in image density in a copied image. can be obtained.

Claims (3)

[Claims] (1) In a two-component developer consisting of a magnetic carrier and toner for developing an electrostatic latent image formed on a photosensitive drum having a photosensitive layer with a Vickers hardness of 50 Hv or less (surface temperature 30°C), 100 parts by weight of toner. , the particle size of the secondary particles is 0.1
Adding 0.02 to 0.15 parts by weight of acrylic polymer fine powder in the range of 0.3 μm to 0.3 μm and silica fine powder at a weight ratio of 1:1 to 1:5 to the acrylic polymer fine powder. A two-component developer characterized by being mixed. (2) The two-component developer according to claim 1, wherein the photosensitive layer of the photosensitive drum to which it is applied is Se-Te. (3) After adding and mixing acrylic polymer fine powder with a particle size of 0.1 to 0.3 μm in a weight ratio of 50:1 to 30:1 to the toner, new toner is further added. The amount of fine acrylic polymer powder per 100 parts by weight of toner is 0.05 to 0. A developer characterized in that the developer is diluted to 15 parts by weight, and then mixed with silica fine powder in a weight ratio of 1:1 to 1:5 to the acrylic polymer fine powder. Adjustment method.