JPH05333588A - Developing agent for electrophotography - Google Patents

Abstract

PURPOSE:To obtain a developer high in image density, good in stability, small in splash of a toner, small in image soiling such as fogging and excellent in life stability by containing a specific toner particle and a zinc sulfide fine powder respectively. CONSTITUTION:The toner particle containing at least a resin and a coloring agent and the fine powdery zinc sulfide coated with copper sulfide on the surface are contained. Styrene based resin, saturated or unsaturated polyester resin and epoxy resin are preferable. An optical adequate pigment or dye is used as the coloring agent and titanium oxide, zinc oxide, aluminum white or the like is preferable. Any fine powdery zinc sulfide coated with copper sulfide on the surface in an uniformly dispersed state is sufficient and a state of solid solution with copper sulfide is preferable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developer used for developing an electrostatic latent image formed in electrophotography or the like.

[0002]

2. Description of the Related Art In a developing process, a developer used in an electronic copying machine or the like is once attached to an image carrier such as a photoconductor on which an electrostatic charge image is formed, and then a photoconductor is used in a transferring process. After being transferred from the sheet to the transfer sheet, it is fixed on the copy sheet surface in the fixing step. At that time, as a developer for developing the electrostatic charge image formed on the latent image holding surface, a two-component developer including a carrier and a toner and a one-component developer (magnetic toner, non-carrier) which does not require a carrier. Magnetic toner) is known.

Toners contained in the developer include positively chargeable toners and negatively chargeable toners. Conventionally, as those imparting positively chargeable toner chargeability, nigrosine dyes, quaternary ammonium salts, etc. A charge control agent as an additive to a toner and a coating agent that imparts a predetermined chargeability to a carrier are known. On the other hand, a charge control agent such as a metal-containing azo dye is used to impart a negative chargeability. Inorganic fine powder, organic fine powder, carrier coating agents and the like are known.

Conventionally, various methods have been proposed for adding conductive fine powder to a developer for the purpose of adjusting the resistance of the toner or controlling the charge amount when the developer is continuously used. For example, JP-B-63-58354 (developer containing conductive ferromagnetic powder), JP-B-1-49941 (developer containing tin oxide), JP-A-59-1684.
No. 60 (developer containing a conductive agent such as tin oxide or zinc oxide), JP-A-59-200250 (color toner containing a tin oxide-antimony oxide-based conductive agent), JP-A-6-200250.
2-258472 (developer containing magnetite), JP-A-63-146048 (developer containing titanium oxide surface-coated with tin oxide-antimony) and the like.

[0005]

However, although the conventional conductive fine powder has a resistance adjusting effect and a charging property controlling effect to some extent, it shows a suitable charging property stably regardless of the environment and the like. It is difficult to obtain a toner exhibiting a preferable morphology with respect to aging, and when the temperature and humidity are changed from a normal temperature / humidity environment to a low temperature / low humidity environment, the image density is remarkably reduced, and stable image density cannot be obtained. Was there.
Further, in recent years, in copying machines, printers, etc. equipped with a photoconductor of organic photo-semiconductor, the photoconductor surface layer is polished and abraded depending on the type of conductive fine particles added to the developer, and the photoconductor life is shortened. There was a problem.

As a result of intensive studies for solving the above problems, the present inventors have shown that by containing a specific zinc sulfide fine powder in the developer, preferable charging characteristics, resistance characteristics, polishing characteristics, etc. are exhibited, and particularly image density is improved. The present invention has been accomplished by finding that a developer excellent in environmental dependence of can be obtained. That is,
An object of the present invention is to provide an electrophotographic developer having high image density, good stability, less toner scattering, less image stain such as fog, and excellent life stability. Still another object of the present invention is to provide an electrophotographic developer having excellent image quality, little change in image quality over time, and excellent charging characteristics. Still another object of the present invention is to provide an electrophotographic developer which is excellent in storage stability against environment such as temperature of use or storage and has little dependence on image change and image quality change.

[0007]

The object of the present invention is, therefore, characterized by containing toner particles containing at least a resin and a colorant, and zinc sulfide fine powder surface-coated with copper sulfide. Easily accomplished with electrophotographic developers.

[0008]

The present invention will be described in detail below. As the resin component which can be used in the present invention, various known components suitable for the toner of the electrophotographic developer can be used. For example, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer. Copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer and styrene-acrylic Acid phenyl copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer and styrene-phenyl methacrylate copolymer) Polymer, etc.), styrene-α
-Styrene resins such as methyl chloroacrylate copolymer and styrene-acrylonitrile-acrylic ester copolymer (styrene or styrene-substituted homopolymers or copolymers), vinyl chloride resin, rosin-modified maleic acid resin , Phenol resin, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin, silicone resin,
Ketone resin, ethylene-ethyl acrylate copolymer,
There are xylene resin, polyvinyl butyral resin, polycarbonate resin and the like, and as the resin particularly preferable for use in the present invention, styrene resin, saturated or unsaturated polyester resin, epoxy resin and the like can be mentioned. Further, the resin is not limited to use alone,
Two or more types can be used together.

Furthermore, the cross-linking binder resins described in JP-B-51-23354 and JP-A-50-44836, or JP-B-55-6895 and JP-B-63.
The non-crosslinked binder resin described in Japanese Patent No. 32180 can also be used. The glass transition temperature of the binder resin for toner preferably has a transition start (inflection point) of 50 ° C. or higher when measured by a differential thermal analyzer. When the glass transition temperature is lower than 50 ° C., when the toner is left at a high temperature of 40 ° C. or higher for a long time, the toner agglomerates or the toner sticks, which causes a problem in use.

The colorant used in the present invention is not particularly limited as long as it is conventionally used.
Any suitable pigment or dye can be used. For example, titanium oxide, zinc white, alumina white, calcium carbonate, navy blue, carbon black, phthalocyanine blue,
Phthalocyanine green, Hansa yellow G, rhodamine dyes and pigments, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane dyes, anthraquinone dyes, monoazo and disazo dyes, etc. Alternatively, they are mixed and used.

The content of the colorant may be an amount sufficient to color the toner so that a visible image can be formed by development, and is, for example, 3 to 20 parts by weight based on 100 parts by weight of the resin. Is preferred. In addition, if necessary, a small amount of an auxiliary agent may be added for the purpose of improving the thermal properties and physical properties of the toner. For example, polyalkylene wax, paraffin wax, higher fatty acid, fatty acid amide, metal soap and the like can be used. The addition amount is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the toner particles.

In addition to the above, in order to adjust the chargeability of the toner, in the case of a positively chargeable toner, a nigrosine dye, 4
Known charge control agents such as secondary ammonium salts, triaminotriphenylmethane compounds, imidazole compounds, etc., in the case of negatively charged toner, known azo dyes, salicylic acid metal complexes and alkylsalicylic acid metal complexes, etc. An appropriate amount of charge control agent may be added. The addition amount is preferably about 0.05 to 10 parts by weight with respect to 100 parts by weight of the resin.

Among the toners of the present invention, the positively chargeable toner does not necessarily need to contain a positive charge control agent if a resin having a strong tendency to be positively charged, that is, a styrene-diethylamino ethyl methacrylate copolymer is used as a material. However, like the commonly used positively charged toner,
It is preferable to add a positive charge control agent according to the chargeability required by the type of the apparatus such as the photoreceptor and the developing tank and the type of carrier.

As the positive charge control agent, known compounds such as quaternary ammonium salts, triphenylmethane compounds, nigrosine dyes, imidazole derivatives and metal complexes thereof can be selected from a wide range. Further, the negatively chargeable toner may be a known charge control agent, for example, C, depending on the type of copier, carrier, etc., and the chargeability required.
A metal-containing azo dye such as r or Co, a salicylic acid metal complex such as Cr, Al, or Zn, an alkylsalicylic acid metal complex, or the like may be contained.

Generally, the above charge control agent has an average particle size of 0.
It is preferable that the toner has a particle size in the range of 01 to 10 μm, more preferably 0.1 to 5 μm for toner adjustment. As a method of incorporating the above charge control agent into the toner, there are a method of adding it inside the toner and a method of adding it externally. When internally added, the amount of these compounds used is the same as the binder resin 1
It is usually used in an amount of 0.05 to 20 parts by weight, preferably 0.1 to 10 parts by weight, relative to 00 parts by weight. Further, when externally added, the amount of the binder is 100 parts by weight based on 0.
01 to 10 parts by weight is preferable.

Specific zinc sulfide fine powder used in the present invention
With the surface of zinc sulfide evenly dispersed with copper sulfide
It may be coated, preferably solid with copper sulfide.
The state of the solution is good. Primary particles of this specific zinc sulfide fine particle
Child diameter is 1 μm or less, preferably 0.05 to 0.5
μm, and the BET specific surface area is preferably 2 m²/ G or less
Above, more preferably 4m²/ G or more. In particular,
2m in BET specific surface area ²If it is less than / g, continuous copying
Accumulated in the developer, which deteriorates image stability.
Scratches on the photoconductor of organic photo-semiconductor such as stacked type
There are harmful effects such as causing image defects.

The specific zinc sulfide fine powder is added in an amount of 10 to 0.05 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the toner particles. 0.05
If it is less than 10 parts by weight, it is difficult to achieve the object of the present invention. If it is more than 10 parts by weight, the resistance of the developer is too low, and the absolute charge amount of the toner is too low to deteriorate the image stability. Are generated, and image defects are generated, which is not preferable.

Further, the specific zinc sulfide fine powder can be treated with a known surface treatment agent for the purpose of improving dispersibility and hydrophobicity. Examples of such surface treatment agents include higher fatty acids, anionic surfactants, silane coupling agents, titanate coupling agents and the like. In addition, known additives as external additives may be added to the toner particles, but in order to effectively act the present invention, inorganic fine particles such as titania, silica and alumina are added for the purpose of imparting a fluidity improving function. By using the powder, it is possible to improve the storage stability of the toner, improve the toner replenishment performance, and further improve the transportability of the developer to improve the image characteristics. Therefore, BE of inorganic fine powder
The T specific surface area is preferably in the range of 50 to 500 m ² / g,
If it is less than 50 m ² / g, a sufficient fluidity improving function cannot be imparted to the toner, and if it is more than 500 m ² / g, the partition effect between the toner particles is reduced and the toner tends to agglomerate and adhere during storage at high temperature. is there.

As the inorganic fine powder, one or more kinds selected from silica, titanium and alumina prepared by a known wet method or dry method can be used, and silica is preferably used. Further, in consideration of improving the environmental dependence, the inorganic fine powder is preferably subjected to a hydrophobic treatment by a known method, and the surface treatment agent is a silane coupling agent,
Examples thereof include titanate-based coupling agents, higher fatty acids, anionic surfactants, silicone oils, and the like, but silane-based coupling agents and silicone oils are preferable in terms of hydrophobicity and chargeability. Of these, a silane coupling agent is more preferable from the viewpoint of environment dependence and fluidity.

The use of the silane coupling agent as the surface treatment agent for the inorganic fine powder has a high degree of imparting the hydrophobic function and is excellent in the fluidity improving function of the inorganic powder. Surface treatment agents other than silane coupling agents are inferior in fluidity improving function to silane coupling agents and are not preferred. A conventionally known method is used for the surface treatment of the inorganic fine powder with a silane coupling agent. For example, as the silane coupling agent, an organoalkoxylane (methoxytrimethylsilane, dimethoxydimethylsilane, trimethoxymethylsilane, ethoxytrimethylsilane, etc.) is used. , Organochlorosilane (trichloromethylsilane, dichlorodimethylsilane, chlorotrimethylsilane, trichloroethylsilane, dichlorodiethylsilane, chlorotriethylsilane, trichlorophenylsilane, etc.), organosilazane (triethylsilazane, tripropylsilazane, triphenylsilazane) , Hexamethyldisilazane, hexaethyldisilazane, hexaphenyldisilazane, etc.), organodisilane, organosilane, etc.
Used as a seed or a mixture of two or more kinds. The silane coupling agent is preferably organochlorosilane or organosilazane.

The surface treatment of the inorganic fine powder with silicone oil may be carried out by a conventionally known method. For example, as the silicone oil, general straight silicone oil such as dimethyl silicone oil, methylphenyl silicone oil, methylhydrogen silicone oil, And modified silicone oils such as methacryl modified silicone oil, alkyl modified silicone oil, epoxy modified silicone oil and amino modified silicone oil.
Used in mixtures of more than one species. The silicon oil is preferably straight silicone oil.

The amount of the inorganic fine powder mixed is preferably 0.005 to 7 parts by weight, more preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the toner. Inorganic fine powder is 0.0
If it is less than 05 parts by weight, there is no fluidity improving effect, and if it is more than 7 parts by weight, the inorganic powder liberated may cause filming on the photoconductor or adhere to the carrier to cause problems such as deterioration of the charging function. In addition, in the case of positively chargeable toner, there is a problem that the charge amount is remarkably lowered, the fog is deteriorated, and the toner scattering amount is increased, and in the case of the negatively chargeable toner, the charge amount is significantly increased. However, there is a problem that the image density is lowered.

When the developer of the present invention is used as a two-component developer, the toner and the magnetic carrier may be mixed and used, and the content ratio of the carrier to the toner in the developer is 10%.
0: 1 to 10 parts by weight is preferable. As the magnetic carrier, conventionally known ones such as iron powder, ferrite powder, magnetite powder and magnetic resin carrier having a particle diameter of about 20 to 200 μm can be used. Further, those whose surface is coated with a known silicone resin, acrylic resin, fluorine resin, styrene resin, or the like, or a mixture of these resins can also be suitably used.

The present invention works effectively when a developer obtained by mixing a positively charged toner and a carrier coated with a fluororesin or a silicone resin is used. The toner of the present invention can also be used as a one-component magnetic toner or non-magnetic toner that does not use a carrier. As a method for producing the toner particles, various conventionally used toner production methods can be applied. The mixture may be dispersed and mixed, and then the mixture may be melt-kneaded by a closed kneader or a uniaxial or biaxial extruder, cooled, pulverized, and classified.

The average particle diameter of the toner is preferably 3 to 20 μm. When the toner is externally added, the classified toner and the external additive may be stirred and mixed with a high-speed stirrer such as a super mixer or a Henschel mixer, and a start developer toner and a replenishment toner are used as necessary. The type of external additive and the amount added may be different, and the number of rotations for stirring,
The mixing conditions such as the time and the order of addition of the external additives may be appropriately determined according to the toner performance. Further, it is more preferable that the external additive is subjected to a crushing treatment in advance before it is used in the external addition work in order to reduce aggregation.

When the external additive floating after the external addition of the toner exists in the toner, it may be removed by a vibrating screen or the like, if necessary. The two-component start developer can be prepared by mixing and stirring the toner obtained in the above steps and the carrier with a ball mill, a V-type mixer, or the like for a predetermined time. The BET specific surface area of the fine powder can be measured by using a commercially available BET specific surface area measuring apparatus based on nitrogen adsorption. and so on.

[0027]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the following examples, simply "parts" means "parts by weight".

A black toner was obtained by the following procedure before the toner external addition step.

[Table 1] Styrene / n-butyl acrylate copolymer resin 100 parts (flow softening point 127 ° C, glass transition point 60 ° C) Colorant carbon black MA-7 5 parts (manufactured by Mitsubishi Kasei Co., Ltd.) Polyalkylene Viscole 550P 2 parts (polypropylene manufactured by Sanyo Kasei Co., Ltd.)-Charge control agent Bontron P51 2 parts (quaternary ammonium salt manufactured by Orient Chemical Co., Ltd.) was blended, kneaded, pulverized, classified using a continuous twin-screw extruder, and averaged particles A black toner having a diameter of 8 μm was obtained. Hereinafter, this black toner was used as a base toner before external addition in Examples and Comparative Examples.

Example 1 For 100 parts of black toner
Silica fine powder surface-treated with dimethyldichlorosilane
(R972, BET specific surface area manufactured by Nippon Aerosil Co., Ltd. =
110m²/ G) 0.2 parts and zinc sulfide surface with copper sulfide
Fine powder subjected to covering treatment (BET specific surface area = 6 m ²/ G, volume
Resistivity = 2Ω · cm) 0.2 part with Henschel mixer
Toner A was obtained by mixing with stirring and externally added. Obtained
Silicone tree with 4 parts of Na A and an average particle size of about 100 μm
Mix with 100 parts of grease-coated ferrite carrier,
Stirring was performed to prepare Start Developer A.

Next, with respect to this developer A, a laminated organic photoconductor is used as a photoconductor, and a copying machine with a blade cleaning system and a copying speed of 50 sheets / min is used. (1) Normal environmental test: temperature 25 ° C. 50,0 under the condition of humidity 60% RH
00 copy live copy test, and (2) low temperature and low humidity environment test: 50,000 copy live copy test was performed under conditions of temperature 10 ° C. and humidity 20% RH. The replenishment toner used for the actual copying test was the same toner as the toner used for the above-mentioned start developer.

(1) Results of normal environmental test From the initial stage to 50,000 sheets, the uniformity of the black portion of the copy is good, the defect is good, the image density is high and stable, and the fog which is the stain on the white portion of the copy is increased. In addition, the toner and the developer were excellent in durability performance, with little pollution due to toner scattering inside the machine. Furthermore,

(2) Low-temperature low-humidity environment test results From the initial stage to 50,000 copies, the density of the black portion is relatively stable and high, there is no increase in fog which is a stain on the white background of the copy, and the inside of the copying machine is not increased. There was no contamination due to toner scattering, which was good. Moreover, there was almost no difference between the normal environment and the low temperature and low humidity environment.

Example 2 As Example 1 except that the fine powder (BET specific surface area = 6 m ² / g, volume resistivity = 2 Ω · cm) obtained by coating the surface of zinc sulfide with copper sulfide was 1.0 part. Toner B was obtained by the same operation. After that, a start developer was prepared in the same manner as in Example 1, and the same tests (1) and (2) were performed. As a result, the normal environment test of (1) was good as in Example 1, and the low temperature and low humidity environment test of (2) was also stable and good in image density maintenance.

Example 3 A fine powder (BET specific surface area = 7 m ² / g, volume resistivity = 1) obtained by coating the surface of zinc sulfide with copper sulfide and then surface-treating it with a silane coupling agent.
(Toner C) was obtained in the same manner as in Example 1 except that the amount was 1.0 part. After that, a start developer was prepared in the same manner as in Example 1, and the same tests (1) and (2) were performed.
As a result, the normal environment test of (1) was good as in Example 1, and the low temperature and low humidity environment test of (2) was also stable and good in image density maintenance. In particular, the image change due to the environmental difference between (1) and (2) was extremely small and good.

Comparative Example 1 100 parts of a black toner, silica fine powder surface-treated with dimethyldichlorosilane (manufactured by Nippon Aerosil Co., Ltd., R972, BET specific surface area =
110 parts of 110 m ^{2 /} g) was stirred and mixed with a Henschel mixer and externally added to obtain a toner F. After that, a start developer was prepared in the same manner as in Example 1, and the same tests (1) and (2) were performed. As a result, in the normal environment test (1), the initial image density was slightly low, the charge amount increased due to continuous copying, and as a result, the image density slightly decreased. In the low-temperature and low-humidity environment test (2), the initial image density was considerably low, and the charge amount increased remarkably even during continuous copying, resulting in a marked decrease in image density.

<Comparative Example 2> Silica fine powder surface-treated with dimethyldichlorosilane on 100 parts of a black toner (R972, BET specific surface area manufactured by Nippon Aerosil Co., Ltd.)
110 m ^{2 /} g) 0.2 parts and magnetite fine powder (BE
T specific surface area = 6 m ² / g, volume resistivity = 2 × 10 ⁶ Ω
cm) was stirred and mixed in a Henschel mixer and externally added to obtain a toner E.

Thereafter, a start developer was prepared in the same manner as in Example 1 and the same tests (1) and (2) were carried out. As a result, in the normal environment test (1), the image density tended to be slightly low and the fog tended to be slightly high. Further, after about 40,000 sheets, polishing scratches were noticeable on the photoconductor and streaks were generated on the black portion of the copy. In the low temperature and low humidity environment test of (2), the image density was slightly low and the change amount was small as in the normal environment of (1), but the fog increased. Further, after about 30,000 sheets, polishing scratches were noticeable on the photoconductor, and streaks were generated on the black portion of the copy.

<Comparative Example 3> Silica fine powder surface-treated with dimethyldichlorosilane on 100 parts of black toner (R972, BET specific surface area manufactured by Nippon Aerosil Co., Ltd.)
110 parts of m ^{2 /} g) and a fine powder obtained by coating the surface of titanium oxide with tin oxide-antimony (BET specific surface area =
Toner E was obtained by externally mixing and stirring 1.0 part of 20 m ² / g and volume resistivity = 2 × 10 Ω · cm) with a Henschel mixer.

Thereafter, a start developer was prepared in the same manner as in Example 1 and the same tests (1) and (2) were carried out. As a result, in the normal environment test of (1), it was almost the same as in Example 2 and was good. In the low temperature and low humidity environment test of (2), the image density was slightly lower and the amount of change was larger than in the normal environment of (1).

[0040]

INDUSTRIAL APPLICABILITY The electrophotographic developer of the present invention has good charging performance such as always showing a proper and stable charge amount, and also has a suitable fluidity, so that the storage stability and the image stability are stable. In addition, it provides a great industrial benefit because it is excellent in maintaining the image density at low temperature and low humidity, is stable, and has high reliability against environmental dependence.

Claims (1)

[Claims] 1. A developer for electrophotography, comprising toner particles containing at least a resin and a colorant, and zinc sulfide fine powder surface-coated with copper sulfide.