JPH11174729A - One-component developer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain one-component developer having good electrostatic charge starting property even at high temp. and high humidity, forming a good image free from unevenness in image density and negative ghost, capable of forming a stable image without imparting excess electric charges even at low temp. and low humidity, not causing image flowing even when paper having an especially high talc content is used and free from secondary trouble such as sticking to a photoreceptor or fog and to further obtain a one-component developer forming a stable image over a long period of time without lowering image density or causing unevenness in image density even when it is allowed to stand at high temp. and high humidity over a long period of time. SOLUTION: The one-component developer consists of toner particles consisting essentially of a bonding resin and a colorant and external additives. At least one of the external additives is magnetic powder having 0.35-0.6 μm number average particle diameter obtd. by surface-treating magnetic particles with an Al compd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a one-component developer used in an electrophotographic apparatus.

[0002]

2. Description of the Related Art In recent years, the dry development method in the electrostatic copying system has been expanded not only to the conventional copying machine as in the past but also to the field of personal use such as a printer, a facsimile, and a multifunction machine with a copying machine. Therefore, there has been a strong demand for smaller and lighter devices. In order to respond to these demands, various improvements of the image forming method or studies of new development have been attempted.

[0003] As dry development methods in various electrostatic copying systems currently in practical use, there are known a two-component development system using a carrier such as toner and iron powder, and a one-component development system using no such carrier. Have been. The two-component development method is the most widely used method, but has the disadvantage that the developer is deteriorated due to toner particles adhering to the carrier surface, and the concentration ratio of the toner in the developer because only the toner is consumed. Therefore, it is difficult to keep the mixing ratio of the carrier and the toner constant, and there is a disadvantage that the developing device becomes large.

On the other hand, the one-component developing method does not have the above-mentioned disadvantage because it does not use a carrier, and is advantageous in miniaturization of an apparatus or the like. The one-component developing method is classified into a non-magnetic one-component developing method using a non-magnetic toner and a magnetic one-component developing method using a magnetic toner. The non-magnetic one-component developing method is suitable for colorization because it does not use a magnetic material for the toner. However, in order to carry the developer on the developer carrying member, the non-magnetic one-component developing method mainly involves the interaction between the developer carrying member and the developer. Since only electrostatic force due to frictional charging is used, when the charge amount of the developer is low, problems such as fogging of the non-image portion and in-machine contamination due to dirt are likely to occur, and it is not yet a mainstream technology in the electrostatic copying method. . On the other hand, the magnetic one-component developing method uses a developer carrying member provided with a magnetic field generating means such as a magnet inside to perform development while holding the magnetic toner. Compared with the one-component developing method, there is a problem that a developing ghost is likely to occur as a common problem of the one-component developing method.

Various attempts have been made to improve this problem. Japanese Patent Application Laid-Open No. Hei 1-276174 discloses a technique in which a ghost is suppressed by providing a resin layer made of phenol resin and carbon and having conductivity and surface lubricity on the surface of a developer carrier. Japanese Patent Application Laid-Open No. Hei 7-281517 proposes a method in which a film having Mo, H, and O is provided on a base of a developer carrying member. These methods can suppress the charge-up of the developer and prevent the occurrence of ghost.

However, although the use of a developer carrier having such a structure can prevent development ghosts from occurring, the developer carrier itself has a low charge-giving ability. When the developer is left unattended, the charge of the developer is reduced, resulting in a problem of low image density and uneven image density.

[0007] In a one-component developer, silica particles or the like subjected to hydrophobic treatment are often added for the purpose of charging and fluidity. The poor distribution has not been improved, and as a result, particularly when an image is formed under high temperature and high humidity, there is a problem that image density unevenness and negative ghost are likely to occur. On the other hand, if adjustment is made to ensure sufficient chargeability under high temperature and high humidity, excessive charge is applied under low temperature and low humidity, and the transport amount on the developer carrying member becomes excessive, resulting in broad charging. Intense, and often causes problems such as deterioration of developability and deterioration of fog.

[0008] Further, in the case of a small machine such as a printer using a one-component developer, it is necessary to set the price of the machine body low.
For example, since the cleaning mechanism for removing the untransferred developer and paper dust on the photoreceptor is constituted by a relatively simple mechanism, if paper dust or the like adheres to the surface of the photoreceptor, an image flow may occur particularly under high temperature and high humidity. There is a problem that it is easy to occur.

In order to solve this problem, a method has been proposed in which strontium titanate, titanium oxide, silicon carbide or the like is added as an abrasive to the surface of toner particles.
Although these can remove paper dust and the like on the surface of the photoreceptor, the effect of preventing image deletion particularly when paper having a large talc component content is used is insufficient, and further, the added external additive itself is exposed to light. It adheres to the body surface and induces secondary obstacles such as image omission and deterioration of fog.

Further, when the developer is stored for a long period of time under high temperature and high humidity, silica fine particles added for the purpose of improving fluidity or the like are embedded in the surface of the toner particles,
As a result, for example, the fluidity of the developer is deteriorated.
There are problems such as a decrease in the charge distribution and charge rise performance of the developer, and a low image density and uneven density.

[0011]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention has been made to solve the problems of the prior art. That is, the first object of the present invention is that even when an image is formed under high temperature and high humidity, the charge rising property of the developer is good, and a good image without image density unevenness and negative ghost can be formed. Another object of the present invention is to provide a one-component developer which does not depend on the environment and can form a stable image without giving excessive charge even at low temperature and low humidity.

Further, even when a paper containing a large amount of talc component is used, particularly at a high temperature and a high humidity, a one-component system which does not cause image deletion and has no secondary obstacles such as photoreceptor adhesion and fog. To provide an agent. It is still another object of the present invention to provide a one-component developer which does not cause image low density or image density unevenness even when the developer is left under high temperature and high humidity for a long period of time and forms a stable image for a long time. .

[0013]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the adhesion of a photoreceptor is reduced by a one-component developer using, as an external additive, at least a magnetic powder surface-treated with an aluminum compound as an external additive. There is no environmental dependency,
Further, they have found that stable image formation can be achieved even after long-term storage.

That is, the present invention provides: (1) a one-component developer comprising at least toner particles comprising a binder resin and a colorant and an external additive, wherein at least one of the external additives comprises an aluminum compound; The magnetic particles are surface-treated, and the number average particle diameter is 0.3
A one-component developer characterized by being a magnetic powder having a size of 5 to 0.6 μm. (2) The one-component developer according to (1), wherein the magnetic particles are one magnetic particle selected from magnetite, ferrite, and iron oxide powder. (3) The one-component developer according to (1), wherein the magnetic particles are magnetite. (4) The one-component developer according to any one of (1) to (3), wherein the shape of the magnetic particles is an octahedron. (5) The one-component system according to any one of (1) to (4), wherein the aluminum compound is one aluminum compound selected from aluminum hydroxide, aluminum chloride, aluminum nitrate, and aluminum sulfate. It is a developer. (6) The one-component developer according to any one of (1) to (4), wherein the aluminum compound is aluminum hydroxide. (7) The toner according to any one of (1) to (6), wherein the amount of the magnetic powder surface-treated with the aluminum compound is 0.1 to 2.0% by weight based on the toner particles. Is a one-component developer. (8) The difference between the BET specific surface area after the surface treatment of the magnetic powder with the aluminum compound and the BET specific surface area before the surface treatment is 4.0 m ² / g or less (1). A one-component developer according to any one of (1) to (7). (9) The one-component developer according to any one of (1) to (8), which is a negatively chargeable developer. (10) The toner according to any one of (1) to (9), wherein the binder resin of the toner particles is a polyester resin.
And the one-component developer described in 1. above. (11) The magnetic one-component developer according to any one of (1) to (10), wherein the volume average particle diameter of the toner particles is 4 to 9 μm. (12) The magnetic one-component developer according to any one of (1) to (11), wherein a magnetic substance is further added to the toner particles. (13) The colorant is a magnetic material (1).
A magnetic one-component developer according to any one of (1) to (11).

The one-component developer of the present invention (hereinafter sometimes simply referred to as "developer") has a good charge rising property even when an image is formed under a high temperature and a high humidity, and has an uneven image density and a negative image. The reason why a good image without ghost can be formed will be described below. Generally, magnetic powders such as magnetite particles show negative chargeability by measuring the amount of charge by frictional charging with an iron powder carrier, but the magnetic powders used in the present invention show weak positive chargeability by surface treatment with an aluminum compound. Therefore, in addition to the mutual frictional charging between the developer carrier and the developer, the magnetic powder as an external additive exhibits the same function as the carrier particles used in the two-component developing method for negatively charged toner particles. As a result, it is considered that the charge rising property and the charge amount of the developer on the developer carrying member are sufficient. Therefore, even when an image is formed under high temperature and high humidity, even if silica fine particles or the like are externally added to the developer, for example, the environment dependency due to moisture absorption of the silica fine particles, the charging speed, and the charge distribution are stable and stable. Since the charging characteristics can be obtained, a good image free from uneven image density and negative ghost can be stably obtained. In addition, since the charge providing ability is not excessive, a stable charge amount and charge distribution can be obtained without causing an excessive rise in charge even at low temperature and low humidity. Therefore, a stable image can be obtained without concern about a decrease in developability and fog.

Further, by setting the BET specific surface area within the above-mentioned predetermined range, the surface treatment state of the aluminum compound on the magnetic powder becomes dense and uniform, so that the above-mentioned charging of the developer becomes more uniform. As a result, the charge distribution of the developer on the developer carrier becomes sharp. Therefore, it is possible to more effectively prevent the occurrence of image quality defects such as uneven density.

The reason why the magnetic powder used as an external additive of the developer of the present invention can prevent paper powder and the like from adhering to the surface of the photoreceptor without secondary obstacles is that compared with silica or the like which is a general external additive. The magnetic powder has a relatively large particle diameter, which is considered to be due to the fact that the magnetic powder exerts an abrasive particle effect in a cleaning step or the like to scrape off the surface of the photoreceptor. On the other hand, when a paper having a high talc component content is used, the talc component is smaller than the toner particles and the affinity for an organic substance is strong. There is a problem that it is difficult to remove from the. But,
The talc component has a negative charge property, and the magnetic powder surface-treated with an aluminum compound added as an external additive to the developer of the present invention has a weak positive charge property, so that the talc on the surface of the photoreceptor is weak. The talc component can be removed simultaneously with the cleaning of the developer in the cleaning process as a result of being easily electrostatically attracted to the component. Therefore, without inducing secondary obstacles such as image omission and deterioration of fog,
Good images are stably obtained.

Further, the magnetic powder used as an external additive of the developer of the present invention can form a stable image for a long time without causing image density reduction or image density unevenness even when stored under high temperature and high humidity for a long time. The reason for this is that the main external additive such as silica fine particles added for the purpose of improving the fluidity is embedded in the surface of the toner particles by long-term storage. This is considered to be because it is possible to prevent the deterioration of the fluidity of the developer and the deterioration of the charging performance as a result, and to prevent the image from being reduced in density and the occurrence of density unevenness.

Further, since the magnetic powder in the present invention has a weakly positive charge due to the aluminum compound surface treatment, it is negatively chargeable in addition to the mutual frictional charge between the developer carrier and the developer. Exhibits the same function as the carrier particles used in the two-component development method for the toner particles.As a result, the charge rising property and the charge amount of the developer on the developer carrier are sufficiently increased, and after long-term storage. It is considered that a stable image is formed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. Examples of the magnetic particles serving as the base of the magnetic powder used as the external additive of the developer of the present invention include magnetite, ferrite, and iron oxide powder. The number average particle diameter of such magnetic particles is 0.35 to 0.6 μm, and there is no problem as long as the desired particle diameter is obtained by the surface treatment described below. The shape of the magnetic particles is preferably an octahedron.

Aluminum compounds for surface-treating the magnetic particles include aluminum hydroxide, aluminum chloride,
Examples thereof include aluminum nitrate and aluminum sulfate, with aluminum sulfate being particularly preferred. Aluminum compound, with respect to the magnetic particles, in terms of aluminum,
The surface treatment is preferably performed in the range of 0.01 to 50% by weight.

The surface treatment of the magnetic particles can be performed by dissolving the aluminum compound to be surface-treated in a solvent such as water or alcohol, and mixing with a magnetic particle. As a condition at this time, it is preferable to make the aluminum compound alkaline when adding it. It is desirable that the treatment temperature be equal to or higher than room temperature, preferably equal to or higher than 50 ° C. The processing time is preferably several minutes to several hours.

At this time, the state of the aluminum surface treatment can be controlled by adjusting the input amount, the input flow rate, the temperature, the time, the pH, etc. of the aluminum compound in the surface treatment step, and the desired surface state can be obtained. What is necessary is just to adjust suitably.

As a specific method for producing the magnetic powder used as an external additive of the developer of the present invention, when the magnetic particles serving as a base are, for example, magnetite, a known method, that is, a reaction between an aqueous solution of iron sulfate and an aqueous solution of caustic soda is used. The obtained iron hydroxide is subjected to steps such as oxidation, washing, drying, degassing, and pulverization to obtain magnetite particles, and further, the obtained magnetite particles are peptized in water, alkalized, and then aluminum. The compound is added and treated, washed with water, dried,
It is obtained through a process such as degassing and crushing.

The magnetic powder used as an external additive of the developer of the present invention is slightly positively charged by the surface treatment with the aluminum compound as compared with the untreated magnetic particles, but becomes too much positively charged. Untreated magnetic particles are preferably slightly negatively charged because the magnetic powder after aluminum compound treatment has a weakly positive charge because it can cause an excessive rise in charge under low temperature and low humidity.

The BE after the surface treatment of the magnetic powder used as an external additive of the developer of the present invention with an aluminum compound is also used.
The difference (increase) between the T specific surface area and the BET specific surface area before surface treatment is preferably 4.0 m ² / g or less. If the difference in the BET specific surface area before and after the surface treatment is greater than 4.0 m ² / g, the coating layer on the surface of the magnetic powder by the aluminum compound becomes too thick, so that a dense surface state cannot be formed, and Is likely to be non-uniform, and as a result, the charge distribution of the developer on the developer carrying member may be broadened, which causes image quality defects such as uneven density.

The amount of the magnetic powder used as an external additive of the developer of the present invention is 0.1 to 2.0 with respect to the toner particles described below.
% By weight, more preferably 0.2 to
1.0% by weight. If the addition amount exceeds 2.0% by weight, the wear of the photoreceptor surface is accelerated, and the life of the photoreceptor may be shortened. If the addition amount is less than 0.1% by weight, the image density under high temperature and high humidity Irregularities, ghosts, and image deletion are likely to occur.
This is not preferable because image density unevenness may be deteriorated.

The number average particle diameter of the magnetic powder used as an external additive of the developer of the present invention is preferably 0.35 to 0.6 μm. When the number average particle diameter of the magnetic powder is smaller than 0.35 μm, image flow when a paper having a large content of talc component, which is an advantage of the magnetic powder external additive of the present invention, is used under high temperature and high humidity, May not sufficiently contribute to the prevention of the adhesion of the photosensitive member. On the other hand, if the number average particle diameter of the magnetic powder is larger than 0.6 μm, the abrasion of the photoconductor becomes too large, which is not preferable.

The developer of the present invention comprises the above-mentioned external additives and toner particles comprising at least a binder resin and a colorant. Examples of the binder resin used for the toner particles include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isobutylene, and vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate. Α-methylene aliphatic monocarboxylic acids such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, etc. Acid esters, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, and vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl isopropenyl ketone; And copolymers. Particularly typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, and styrene- Butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene and polypropylene. further,
Examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, and modified rosin.

The coloring agent used in the developer of the present invention includes
Carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, ポ ン upon oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxalate, lamp black, rose bengal, C.I. I. Pi
gment Red 48: 1, C.I. I. Pigmen
t Red 122, C.I. I. Pigment Red
57: 1, C.I. I. Pigment Yellow
97, C.I. I. Pigment Yellow 12,
C. I. Pigment Yellow 17, C.I.
I. Pigment Blue 15: 1, C.I. I. P
Pigment Blue 15: 3. In the case where the developer is a magnetic one-component developer, the contained magnetic substance described later functions as a colorant.

When the developer of the present invention is used in the non-magnetic one-component developing system, the toner particles may be composed of only the binder resin and the colorant, but are used in the magnetic one-component developing system. In such a case, it is constituted as a coloring agent or further added with a magnetic substance. As the magnetic material, any known magnetic material that has been generally used can be used. For example, metals such as iron, cobalt and nickel and alloys thereof, Fe
A material formed of a metal oxide such as ₃ O ₄ , γ-Fe ₂ O ₃ , or cobalt-added iron, or various ferrites such as MnZn ferrite or NiZn ferrite is used. These magnetic materials may have a surface treated with a coupling agent such as a silane coupling agent or a titanate coupling agent, an inorganic fine particle such as silica or alumina, or a fatty acid compound or an organic compound such as a resin. Is generally 0.
A range of from 0.5 to 0.5 μm is appropriate. Octahedrons, hexahedrons, and spheres are used as the shape of these magnetic bodies.
In the present invention, the content of the magnetic substance is used in a range of 30 to 70% by weight, preferably 40 to 60% by weight, based on the total weight of the toner particles. If the content is less than 30% by weight, particularly under a low-temperature and low-humidity environment, the image density is reduced and fogging is caused. If the content exceeds 70% by weight, the fixing property of the toner is deteriorated, which causes practical problems.

Further, a releasing agent may be added to the toner particles used in the present invention for the purpose of improving gloss and offset. The release agent is preferably a paraffin having 8 or more carbon atoms, polyolefin, or the like. Examples thereof include paraffin wax, paraffin latex, microcrystalline wax, and the like, and polypropylene, polyethylene, and the like. These may be used alone or in combination. The addition amount is preferably in the range of 0.3 to 10% by weight.

Further, a charge controlling agent may be added to the toner particles in the present invention, if necessary. As the charge control agent, known ones can be used, but high charge such as a fluorine-containing surfactant, a metal-containing dye such as a salicylic acid metal complex or an azo-based metal compound, or a copolymer containing maleic acid as a monomer component can be used. A molecular acid, a quaternary ammonium salt, an azine dye such as nigrosine, carbon black, or a charge control resin is used. A salicylic acid complex of Zn and Al, and a quaternary ammonium salt are particularly preferable, and 0.1 to 10% by weight. Used in the range.

The toner particles used in the present invention have a volume average particle diameter D50 of 4 to 9 μm, preferably ₅ to 7 μm.
Can be used. When the volume average particle diameter D ₅₀ is in this range, the surface area per unit weight of the toner particles is large, even faster charge rise in less contact and friction charging opportunity, sufficient charge amount can be obtained to be developed . In addition, since there is little reduction or broadening of the charge amount due to deterioration of the surface of the toner particles, it is possible to solve problems such as a decrease in density during continuous use, uneven density and fog.
Further, even when the developer carrying member and the layer forming blade are deteriorated and the charge applying ability is reduced, a sufficient amount of charge for developing the toner is obtained, and the image quality retention can be improved. . When the volume average particle diameter D ₅₀ is less than 4 [mu] m, tends to charge up too high charge quantity of the toner particles fogging and low concentration of the problem is likely to occur. In addition, the fluidity of the toner particles is significantly deteriorated, which causes fogging of density unevenness due to poor layer formation. On the other hand, when the volume average particle diameter D ₅₀ exceeds 9 .mu.m, the surface area per unit weight of the toner particles is decreased, rapid and uniform charge quantity not only eliminated resulting et al, high in the resolution is lowered It is difficult to obtain image quality.

The toner particles used in the present invention can be produced by any known method, but a kneading and pulverizing method is particularly preferable. That is, a method is preferred in which a binder resin and a colorant are melted and kneaded with a kneader such as a kneader or an extruder, cooled, pulverized and classified, and an external additive is added and mixed.

The developer of the present invention can be obtained by adding and mixing the above-mentioned magnetic powder used as an external additive to the above-mentioned toner particles, and the mixing is carried out by, for example, a V-type blender, a Henschel mixer, a Loedige mixer. And the like. At this time, for the purpose of improving fluidity and chargeability, inorganic fine powders such as silica, titania, and alumina, organic fine powders such as fatty acids or derivatives thereof and metal salts, fluorine-based resins, and acrylic resins, as necessary. Alternatively, various additives such as fine powder of a styrene resin or the like may be added alone or in combination.

[0037]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto. The particle size of the magnetic particles and the magnetic powder was determined using an electron microscope (manufactured by Hitachi, Ltd .: S-4100) in the range of 20,000 to 3
Take a 0000-fold enlarged photo and use this Image
It was determined by image analysis using an Analyzer LUZEX III (manufactured by NIRECO). Also, B
ET specific surface area is beta soap automatic surface area meter MODEL
4200 (manufactured by Nikkiso Co., Ltd.). Further, the number average particle diameter of the toner particles was measured using a particle size analyzer TA-II manufactured by Coulter Counter Co., Ltd.
m.

Example 1 [Production of Magnetic Powder as External Additive] Magnetic powder surface-treated with an aluminum compound was produced as follows. As a starting material, magnetite (octahedron, number average particle size 0.41 μm, BET specific surface area =
2.5 m ² / g). 100 parts by weight of the magnetite is put into 1000 parts by weight of water, deflocculated by a mixer, the temperature of the obtained slurry is adjusted to 80 ° C., the pH is adjusted to 8.5, and then an aluminum sulfate solution (concentration of aluminum: 3.
(5%) 30 parts by weight, and sodium hydroxide were added so that the pH was 8 or more. This solution was surface-treated for about 1 hour while being kept at 80 ° C. to produce a magnetic powder as an external additive used in this example (octahedron, number average particle diameter 0.41 μm, BET ratio before and after surface treatment). Surface area difference =
0.5 m ² / g, aluminum content 1.0% by weight).

[Production of Toner Particles] Binder resin: 50 parts by weight of styrene-butyl acrylate copolymer (weight average molecular weight Mw: about 140,000, Tg: 57 ° C.) Magnetic powder: magnetite (hexahedral, average particle) Diameter: 0.15 μm, BET: 7 m ³ / g) 47 parts by weight ・ Negatively chargeable charge control agent z: 1 part by weight of azo-based Fe dye ・ Release agent: 2 parts by weight of polypropylene wax The above materials were mixed with a Henschel mixer. After that, set temperature 140 ° C with an extruder, screw rotation speed 30
The mixture was melt-kneaded at 0 rpm at a supply speed of 250 kg / h. After cooling, coarsely pulverized, finely pulverized by a jet mill, and further pulverized, the pulverized material is classified into a classified product having a volume average particle diameter D ₅₀ of 7.0 μm and particles of 5 μm or less 22% by number ( Toner particles).

[Manufacture of Developer] With respect to 100 parts by weight of the obtained toner particles, 0.5 parts by weight of the magnetic powder as the above-mentioned external additive and 1.
0 parts by weight was externally added and mixed with a Henschel mixer to obtain a developer.

[Evaluation Test of Developer] The obtained developer was subjected to a laser printer Laser manufactured by Fuji Xerox Co., Ltd.
Press 4150PS under high temperature and high humidity environment (28 ° C., 85% RH) and low temperature and low humidity environment (10
(15 ° C., 15% RH), an evaluation test was performed by copying the test pattern on about 5,000 PPC sheets. The results are shown in Tables 1 and 2. The evaluation items are as follows.

1) Image density Under both high temperature, high humidity and low temperature, low humidity environments,
The initial image density and the image density at the time of printing 5,000 sheets are Xr
It was measured with an item densitometer and evaluated according to the following criteria. ：: Image density of 1.4 or more Δ: Image density of 1.2 or more and less than 1.4 ×: Image density of less than 1.2

2) Ghost In both high-temperature, high-humidity and low-temperature, low-humidity environments,
The density difference between the initial image and the non-image portion at the time of printing 5,000 sheets was measured with respect to the paper itself, and evaluated based on the following criteria. ：: Image density difference of less than 0.05 Δ: Image density difference of 0.05 or more and less than 0.10 ×: Image density difference of 0.10 or more

3) Density unevenness Under both high-temperature, high-humidity and low-temperature, low-humidity environments,
In the initial and 5,000 print image areas,
The image density was measured, the difference between the maximum value and the minimum value was determined, and evaluated according to the following criteria. ：: Image density difference of less than 0.10 Δ: Image density difference of 0.10 or more and less than 0.20 ×: Image density difference of 0.20 or more

4) Adhesion of developer to photoreceptor surface Under both high-temperature, high-humidity and low-temperature, low-humidity environments,
At the time of printing 5,000 sheets, the state of adhesion of the developer to the photoreceptor surface was visually checked, and evaluated according to the following criteria. ：: No developer adhesion was confirmed on the photoreceptor surface. Δ: Developer adhesion to the photoreceptor surface is slightly observed. ×: Adhesion of the developer to the photoreceptor surface was confirmed, and a problem occurred in the obtained image.

5) Image Deletion In a high-temperature, high-humidity environment, image quality evaluation (image deletion) at the time of printing 5,000 sheets on a high talc-containing paper (talc content: 5% by weight) was performed according to the following criteria. ：: No image deletion is observed at all. Δ: Image deletion is confirmed only at the end of the sheet. X: Image deletion occurs in the entire image area.

6) Storage stability After storing the developer in an environment of 45 ° C./90% RH for 48 hours, the image quality was evaluated in the initial stage in a low-temperature and low-humidity environment in the same manner as in 3) density unevenness. Was.

Example 2 A binder resin used for producing toner particles was a polyester resin (polycondensation product of ethylene oxide adduct of bisphenol A and terephthalic acid: Tg = 67 ° C., Mw = 10,0).
A developer was produced in the same manner as in Example 1 except that the developer was replaced with (00). Using the obtained developer, a developer evaluation test was performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 1 A developer was produced in the same manner as in Example 1 except that the magnetic compound as an external additive was not treated with an aluminum compound. Example 1 was prepared using the obtained developer.
An evaluation test of the developer was performed in the same manner as described above. The results are shown in Tables 1 and 2.

Comparative Example 2 As an external additive, magnetite (octahedron, number average particle diameter 0.27 μm, BET specific surface area 5.
A developer was produced in the same manner as in Example 1 except that 0 m ² / g) was used. Using the obtained developer, a developer evaluation test was performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 3 A developer was produced in the same manner as in Example 1 except that no magnetic powder was externally added. Example 1 was prepared using the obtained developer.
An evaluation test of the developer was performed in the same manner as described above. The results are shown in Tables 1 and 2.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

The one-component developer of the present invention uses a magnetic powder treated with an aluminum compound as an external additive so that the photoreceptor adheres to paper powder or the like, and particularly when high talc content paper is used. Secondary obstruction such as image deletion can be prevented, image quality does not deteriorate after storage of the one-component developer, and there are no problems such as image density, uneven image density, and ghost. Therefore, the one-component developer of the present invention has excellent environmental dependence, and can provide excellent image quality over a long period of time.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsu Torigoe 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. (72) Inventor Tomohiro Takeda 1600 Takematsu, Minamiashigara-shi, Kanagawa Fuji Xerox Co., Ltd. Inventor Shinpei Takagi 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd.

Claims (13)

[Claims] 1. A one-component developer comprising at least toner particles comprising a binder resin and a colorant, and an external additive, wherein at least one of the external additives has its magnetic particles surface-treated with an aluminum compound. And a magnetic powder having a number average particle diameter of 0.35 to 0.6 μm. 2. The one-component developer according to claim 1, wherein the magnetic particles are one magnetic particle selected from magnetite, ferrite, and iron oxide powder. 3. The one-component developer according to claim 1, wherein the magnetic particles are magnetite. 4. The one-component developer according to claim 1, wherein the shape of the magnetic particles is octahedron. 5. The one-component system according to claim 1, wherein the aluminum compound is one aluminum compound selected from aluminum hydroxide, aluminum chloride, aluminum nitrate and aluminum sulfate. Developer. 6. The one-component developer according to claim 1, wherein the aluminum compound is aluminum hydroxide. 7. The amount of magnetic powder surface-treated with an aluminum compound is 0.1 to 2.0 with respect to toner particles.
The one-component developer according to any one of claims 1 to 6, wherein the amount is 1% by weight. 8. The method according to claim 1, wherein the difference between the BET specific surface area after the magnetic powder is surface-treated with an aluminum compound and the BET specific surface area before the surface treatment is 4.0 m ² / g or less. Item 13. The one-component developer according to any one of Items 1 to 7. 9. The one-component developer according to claim 1, which is a negatively chargeable developer. 10. The one-component developer according to claim 1, wherein the binder resin of the toner particles is a polyester resin. 11. The volume average particle diameter of the toner particles is from 4 to 9.
The magnetic one-component developer according to any one of claims 1 to 10, wherein the magnetic monocomponent developer is μm. 12. The magnetic one-component developer according to claim 1, further comprising a magnetic substance added to the toner particles. 13. The magnetic one-component developer according to claim 1, wherein the colorant is a magnetic material.