JP5289024B2 - Developer and image forming method - Google Patents

Description

  The present invention relates to a developer and an image forming method. In particular, even when low density printing is performed continuously for a long period of time, adhesion of resin fine particles to a photoreceptor can be effectively suppressed, and development can be performed. The present invention relates to a developer capable of effectively maintaining the triboelectric chargeability of the agent and an image forming method using the developer.

In general, the electrophotographic system is roughly divided into a one-component development system using only insulating toner particles and conductive toner particles and a two-component development system using toner particles and a carrier.
Among these, the two-component development method is superior in friction charge controllability compared to the one-component development method because the toner particles are frictionally charged via the carrier.
In recent years, in order to more stably control the frictional charging of toner particles, a method of externally adding inorganic fine particles and resin fine particles to the toner particles has been performed (for example, Patent Document 1).
That is, a method of more effectively controlling the triboelectric charging of toner particles by improving the chargeability of toner particles with resin fine particles while improving the fluidity of the developer with inorganic fine particles.
However, when resin fine particles are used as an external additive, the resin fine particles are likely to agglomerate with each other. Therefore, depending on the environment at the time of image formation, the chargeability of the toner particles may be adversely affected, which in turn tends to cause fogging. It was observed.

Therefore, a method of using a silica having a large particle size close to the particle size of the resin fine particles in order to suppress aggregation of the resin fine particles is disclosed (for example, Patent Document 2).
More specifically, it is a developer for electrostatic charge development in which two kinds of silica fine particles having different number average particle diameters and resin fine particles are externally added to toner particles. In addition to using the first silica fine particles having a number average particle size of less than 15 nm and the second silica fine particles having a number average particle size in the range of 15 to 150 nm, A resin fine particle having a ratio of the number average particle diameter of the second silica fine particles to the number average particle diameter of the resin fine particles in a range of 1: 0.05 to 20 is used. Developers are disclosed.
JP-A-4-274249 (Claims) JP-A-11-184145 (Claims)

However, although the developer described in Patent Document 2 can suppress the aggregation of resin fine particles to some extent, there is a problem that the resin fine particles are likely to adhere to the surface of the photoreceptor, and as a result, filming is likely to occur. It was seen.
In particular, when low-density printing, more specifically, printing with an average printing rate of less than 2% is repeated, resin fine particles tend to stay on the surface of the photosensitive member, and filming is more likely to occur. The problem of becoming was seen.

Therefore, the inventors of the present invention, as a result of intensive studies, in the developer, as the external additive of the toner particles, two types of silica fine particles each having a predetermined particle size, resin fine particles having a predetermined particle size, In addition, the present inventors have found that the above-described problems can be solved by defining the relationship between the coverage of these external additives to the toner particles within a predetermined range, and have completed the present invention.
That is, an object of the present invention is to effectively suppress the adhesion of resin fine particles to the photoreceptor even when low density printing is performed continuously for a long period of time, and to improve the triboelectric chargeability of the developer. An object of the present invention is to provide a developer that can be effectively held and an image forming method using the developer.

According to the present invention, there is provided a developer including toner particles, resin fine particles as an external additive, first and second silica fine particles as an external additive, and a carrier, wherein the resin fine particles are styrene. And a styrene-acrylic polymer obtained by polymerizing at least one monomer selected from the group consisting of butyl methacrylate and dimethylamino acrylate, and the number average primary particle diameter of the first silica fine particles is Ad (nm). The coverage of the first silica fine particles to the toner particles is Ac (%), the number average primary particle diameter of the second silica fine particles is Bd (nm), and the coverage of the second silica fine particles to the toner particles is Bc (%). ), When the number average primary particle diameter of the resin fine particles is Cd (nm) and the coverage of the resin fine particles to the toner particles is Cc (%), Ad, Ac, Bd, Bc, d and Cc is, there is provided a developing agent characterized by satisfying the following relational expressions (1) to (5), it is possible to solve the problems described above.
16 ≦ Ad ≦ 35 nm (1)
70 ≦ Bd ≦ 100 nm (2)
40 ≦ Cd ≦ 80 nm (3)
1 ≦ Cc ≦ Ac (4)
1 ≦ Cc ≦ Bc (5)
That is, by satisfying the relational expressions (1) to (5), the first silica fine particles exhibit an effect as a spacer between the resin fine particles and the photoconductor, while the second silica fine particles. However, since it exhibits an effect as an abrasive that polishes resin fine particles that have started to adhere to the photoreceptor, adhesion of resin fine particles to the surface of the photoreceptor can be effectively suppressed.
Therefore, the effect of improving the fluidity by the first and second silica fine particles and the effect of improving the chargeability by the resin fine particles can be stably exhibited.
Further, by configuring the resin fine particles in this way, the chargeability of the toner particles can be more effectively improved.
Therefore, with the developer of the present invention, even when low density printing is performed continuously for a long period of time, the adhesion of resin fine particles to the photoreceptor can be effectively suppressed, and the developer friction can be reduced. Chargeability can be effectively maintained.

In constituting the two-component developer of the present invention, it is preferable that Cc satisfies the following relational expression (6).
1 ≦ Cc ≦ 30 (6)
With this configuration, it is possible to effectively suppress adhesion of resin fine particles to the photosensitive member while improving the chargeability of the toner particles.

In constituting the developer of the present invention, it is preferable that a part of the first silica fine particles is externally added to the resin fine particles.
By comprising in this way, the spacer effect by the 1st silica fine particle can be exhibited more reliably.

In constituting the developer of the present invention, it is preferable to further add titanium oxide fine particles to the toner particles.
By comprising in this way, adhesion of the toner particle with respect to a photoreceptor can be suppressed.

In constituting the developer of the present invention, the developer is preferably a two-component developer.
With this configuration, the stability of triboelectric charging of toner particles can be further improved.

Another aspect of the present invention is an image forming method using the developer described above.
That is, in the case of the image forming method of the present invention, since a predetermined developer is used, even when low density printing is performed continuously for a long time, the adhesion of resin fine particles to the photoreceptor is effective. In addition, the triboelectric charging property of the developer can be effectively retained.
Therefore, the image quality can be stably maintained.

In carrying out the image forming method of the present invention, an amorphous silicon photoconductor is preferably used as the photoconductor.
By carrying out in this way, resin fine particles easily adhere to the surface of the photoreceptor, but the present invention can be effectively suppressed.

[First Embodiment]
The first embodiment is a developer including toner particles, resin fine particles as an external additive, first and second silica fine particles as an external additive, and a carrier . A styrene-acrylic polymer obtained by polymerizing styrene and at least one monomer selected from the group consisting of butyl methacrylate and dimethylamino acrylate, and the number average primary particle diameter of the first silica fine particles is Ad (nm). ), The coverage of the first silica fine particles to the toner particles is Ac (%), the number average primary particle diameter of the second silica fine particles is Bd (nm), and the coverage of the second silica fine particles to the toner particles is Bc ( %), The number average primary particle diameter of the resin fine particles is Cd (nm), and the coverage of the resin fine particles on the toner particles is Cc (%), Ad, Ac, Bd, Bc Cd and Cc is a developer and satisfies the following relational expression (1) to (5).
16 ≦ Ad ≦ 35 nm (1)
70 ≦ Bd ≦ 100 nm (2)
40 ≦ Cd ≦ 80 nm (3)
1 ≦ Cc ≦ Ac (4)
1 ≦ Cc ≦ Bc (5)
That is, by satisfying the relational expressions (1) to (5), the state of the developer as shown in FIGS. 1A to 1B is created, and as shown in FIGS. Even when low density printing is performed, the developer can effectively suppress the adhesion of resin fine particles to the photoreceptor and can effectively maintain the triboelectric charging property of the developer. .
Hereinafter, the developer as the first embodiment will be described in detail for each component.

1. Toner Particle (1) Binder Resin The type of binder resin used for the toner particles is not particularly limited. For example, styrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin Use thermoplastic resins such as polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin, N-vinyl resin, styrene-butadiene resin, etc. Is preferred.

(2) Colorant The colorant contained in the toner particles is not particularly limited. For example, carbon black, acetylene black, lamp black, aniline black, azo pigment, yellow iron oxide, ocher, nitro It is preferable to use a dye, an oil-soluble dye, a benzidine pigment, a quinacridone pigment, a copper phthalocyanine pigment, or the like.
Further, the addition amount of the colorant is not particularly limited, but for example, a value within a range of 0.01 to 30 parts by weight with respect to 100 parts by weight of the binder resin of the toner particles is preferable. .
This is because when the amount of the colorant added is less than 0.01 parts by weight, the image density is lowered and it may be difficult to obtain a clear image. On the other hand, when the amount of the colorant added exceeds 30 parts by weight, the fixability may be lowered.
Therefore, it is more preferable that the addition amount of the colorant is a value within the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the binder resin of the toner particles, and within a range of 0.5 to 15 parts by weight. More preferably, the value of

(3) Charge Control Agent It is preferable to add a charge control agent to the toner particles.
The reason for this is that the charge level and the charge rise characteristic (an index for charging to a constant charge level in a short time) can be remarkably improved by adding a charge control agent.
The type of the charge control agent is not particularly limited. For example, positive charge such as nigrosine, a quaternary ammonium salt compound, a resin type charge control agent in which an amine compound is bonded to a resin, and the like. It is preferable to use a charge control agent exhibiting properties.
In addition, the amount of charge control agent added is preferably set to a value in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin of the toner particles.
This is because the effect of the charge control agent may not be sufficiently exhibited when the amount of the charge control agent added is less than 0.5 parts by weight. On the other hand, when the added amount of the charge control agent exceeds 10 parts by weight, charging failure and image failure are likely to occur particularly in a high temperature and high humidity environment.
Therefore, the amount of the charge control agent added is preferably set to a value in the range of 1 to 9 parts by weight with respect to 100 parts by weight of the binder resin of the toner particles, and a value in the range of 2 to 8 parts by weight. More preferably.

(4) Wax It is preferable to add wax to the toner particles.
Such a wax is not particularly limited. A combination of two or more types can be mentioned.
Further, it is preferable that the amount of the wax added is in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the binder resin of the toner particles.
This is because it is difficult to effectively prevent offset (a phenomenon in which toner particles adhere to the fixing roller), image smearing, and the like in the fixing process when the amount of added wax is less than 0.1 parts by weight. This is because there is a case of becoming. On the other hand, when the added amount of the wax exceeds 20 parts by weight, the toner particles are fused together, and the storage stability may be lowered.
Therefore, it is more preferable that the addition amount of the wax is a value within the range of 0.5 to 15 parts by weight with respect to 100 parts by weight of the binder resin of the toner particles, and a value within the range of 1 to 10 parts by weight. More preferably.

(5) Volume average particle diameter The volume average particle diameter of the toner particles is preferably set to a value in the range of 4 to 12 μm.
This is because if the volume average particle diameter of the toner particles is less than 4 μm, the influence of physical or thermal stress becomes excessively large, and it may be difficult to sufficiently suppress the deterioration of the developer. Because there is. On the other hand, if the volume average particle diameter of the toner particles exceeds 12 μm, it may be difficult to obtain a high-quality image.
Therefore, the volume average particle diameter of the toner particles is more preferably set to a value within the range of 5 to 10 μm, and further preferably set to a value within the range of 6 to 9 μm.
The volume average particle diameter of the toner particles can be measured, for example, using a Coulter Multisizer 3 manufactured by Beckman Coulter.

(6) Manufacturing Method As a method for manufacturing toner particles, first, the above-described binder resin, wax, colorant, and if necessary, other additives are preliminarily mixed using a known method. Then, melt-kneading is performed to prepare a resin composition for toner. Next, it is preferable to finely pulverize the obtained resin composition for toner using a known method, and then classify it to obtain toner particles.
Here, the preliminary mixing treatment is preferably performed using, for example, a Henschel mixer, a ball mill, a super mixer, a dry blender, or the like.
Further, the melt-kneading treatment is preferably performed using, for example, a twin screw extruder or a single screw extruder. Further, the fine pulverization treatment is preferably performed using, for example, an airflow pulverizer. Further, the classification process is preferably performed using, for example, an air classifier.

2. Resin Fine Particles The developer of the present invention is characterized by containing resin fine particles as an external additive for toner particles.
This is because inclusion of resin fine particles as an external additive can increase the substantial surface area of the toner particles and effectively improve the triboelectric chargeability.

(1) Binder Resin As the binder resin in the resin fine particles, the same binder resin as that used for the binder resin of the toner particles can be used.
For example, styrene resin, acrylic resin, styrene-acrylic copolymer, polyethylene resin, polypropylene resin, vinyl chloride resin, polyester resin, polyamide resin, polyurethane resin, polyvinyl alcohol resin, vinyl ether resin A thermoplastic resin such as a resin, an N-vinyl resin, and a styrene-butadiene resin can be used.
On the other hand, among the binder resins described above, it is particularly preferable to use an acrylic resin.
This is because, with an acrylic resin, it is easy to adjust the hardness of the resin fine particles to the same degree as that of the toner particles, and it is also possible to easily adjust the frictional charging characteristics and the like of the resin fine particles. This is because it can.
Examples of the acrylic resin include acrylic resin, methacrylic resin, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, and styrene-α-chloromethyl methacrylate copolymer.
More specifically, it includes a styrene-acrylic polymer obtained by polymerizing styrene and at least one monomer selected from the group consisting of butyl methacrylate and dimethylamino acrylate .
This is because the chargeability of the toner particles can be more effectively improved if the resin fine particles use a binder resin composed of these monomers.

The glass transition point of the binder resin in the resin fine particles is preferably set to a value within the range of 80 to 150 ° C.
This is because by setting the glass transition point of the binder resin in the resin fine particles within such a range, it is possible to suppress adhesion of the resin fine particles to the surface of the photosensitive member while maintaining the fixing property of the toner particles. .
That is, if the glass transition point of the binder resin in the resin fine particles is less than 80 ° C., the resin fine particles may be excessively heat-bonded to the photoreceptor. On the other hand, if the glass transition point of the binder resin in the resin fine particles exceeds 150 ° C., it may be easily embedded in the toner particles or may cause a decrease in toner particle fixability. It is.
Therefore, the glass transition point of the binder resin in the resin fine particles is more preferably set to a value within the range of 90 to 145 ° C, and further preferably set to a value within the range of 100 to 140 ° C.

(2) Number average primary particle diameter The number average primary particle diameter Cd of the resin fine particles is set to a value in the range of 40 nm to 80 nm, that is, Cd satisfies the relational expression (3).
The reason for this is that by setting the number average primary particle diameter Cd of the resin fine particles in such a range, the substantial surface area of the toner particles can be increased and the chargeability can be improved efficiently. This is because the first and second silica fine particles can effectively suppress the resin fine particles from adhering to the surface of the photoreceptor.
That is, when the number average primary particle diameter Cd of the resin fine particles is less than 40 nm, it is difficult to sufficiently improve the chargeability of the toner particles, and it is difficult to externally add the resin fine particles using the first silica fine particles. This is because the polishing effect by the second silica fine particles may not be sufficiently exhibited. On the other hand, if the number average primary particle diameter Cd of the resin fine particles becomes an excessively large value, the liberation rate with respect to the toner particles may be excessively increased.
Therefore, the number average primary particle diameter Cd of the resin fine particles is more preferably set to a value in the range of 50 to 80 nm.
In addition, the number average primary particle diameter Cd of the resin fine particles can be measured by, for example, a dynamic scattering type particle size distribution measuring apparatus (LB-550, manufactured by Horiba, Ltd.).
In the present invention, the resin fine particles may be aggregated. In this case, the number average secondary particle diameter is preferably set to a value in the range of 100 to 2000 nm, and in the range of 200 to 1000 nm. A value is more preferable.

(3) Coverage It is preferable that the coverage Cc of the resin fine particles with respect to the toner particles is set to a value in the range of 1 to 30%, that is, Cc satisfies the relational expression (6).
The reason for this is that by setting the resin fine particle coverage Cc to a value within this range, it is possible to more effectively suppress the resin fine particles from adhering to the photoreceptor while improving the chargeability of the toner particles. This is because it can be done.
That is, when the resin fine particle coverage Cc is less than 1%, it may be difficult to sufficiently improve the chargeability of the toner particles, and it may be difficult to suppress fogging, toner scattering, and the like. Because. On the other hand, when the coverage Cc of the resin fine particles exceeds 30%, the spacer effect due to the first silica fine particles is particularly difficult to be exerted sufficiently, and the resin fine particles easily adhere to the photoreceptor. This is because there are cases.
Therefore, the coverage Cc of the resin fine particles to the toner particles is more preferably set to a value within the range of 1.5 to 25%, and further preferably set to a value within the range of 2 to 20%.
In the present invention, the coverage Cc of the resin fine particles to the toner particles means the ratio (%) of the projected area of the resin fine particles externally added to the toner particles to the surface area of the toner particles.
A specific method for calculating the coverage Cc will be described in Examples.

(4) Addition amount The addition amount of the resin fine particles is preferably set to a value within the range of 0.1 to 1.5 parts by weight with respect to 100 parts by weight of the toner particles.
This is because when the amount of resin fine particles added is less than 0.1 parts by weight, the resin fine particle coverage Cc is excessively lowered, making it difficult to sufficiently improve the chargeability of the toner particles. Because there is. On the other hand, if the amount of the resin fine particles added exceeds 1.5 parts by weight, the resin fine particles may easily adhere to the photoreceptor.
Therefore, it is more preferable that the addition amount of the resin fine particles is set to a value within the range of 0.15 to 1.25 parts by weight with respect to 100 parts by weight of the toner particles, and within a range of 0.2 to 1 part by weight. More preferably, it is a value.

(5) Production Method The resin fine particles can be produced by an emulsion polymerization method, a spray drying method, or a combination thereof, and a particularly preferred production method includes an emulsion polymerization method.
The emulsion polymerization method will be specifically described. For example, polymerization of a surfactant such as sodium lauryl sulfate, diethanolamide laurate and ammonium persulfate, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, etc. Prepare a solution to which an initiator is added. Next, monomer components such as acrylic acid, methyl methacrylate, butyl methacrylate, 2-ethylhexyl acrylate, dimethylamino acrylate, and styrene are dropped into the solution to obtain an emulsion. Finally, resin fine particles can be obtained by drying the emulsion.

3. First Silica Fine Particles The developer of the present invention is characterized by containing first silica fine particles as an external additive for toner particles.
The reason for this is that by including the first silica fine particles as an external additive, the fluidity of the toner particles can be improved, while it functions as a spacer between the resin fine particles and the surface of the photoreceptor. This is because it is possible to effectively prevent the resin fine particles from adhering to the surface of the photoreceptor.

(1) Type The first silica fine particles are preferably spherical silica fine particles that are granulated through vapor or liquid state by reaction heat due to oxidation of metallic silicon.
For the first silica fine particles, dimethylpolysiloxane, 3-aminopropyltrimethoxysilane, hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, and allyl. Hydrophobizing treatment can be performed with an organosilicon compound such as dimethylchlorosilane.
Among these, it is particularly preferable to use dimethylpolysiloxane and 3-aminopropyltrimethoxysilane in combination because the spacer effect of the first silica fine particles can be better exhibited.

(2) Number average primary particle diameter The number average primary particle diameter Ad of the first silica fine particles is set to a value in the range of 16 to 35 nm, that is, Ad satisfies the relational expression (1). And
The reason for this is that the fluidity of the toner particles can be improved by setting the number average primary particle diameter Ad of the first silica fine particles in such a range, while the resin fine particles and the surface of the photoreceptor are in between. This is because the function as a spacer can be exhibited to effectively prevent the resin fine particles from adhering to the surface of the photoreceptor.
That is, when the number average primary particle size Ad of the first silica fine particles is less than 16 nm, the first silica fine particles may be easily embedded in the resin fine particles. On the other hand, when the number average primary particle size Ad of the first silica fine particles exceeds 30 nm, it becomes difficult to uniformly add externally to the resin fine particles. As a result, the resin fine particles, the photosensitive member surface, This is because it may be difficult to exert a function as a spacer between the two.
Accordingly, the number average primary particle diameter Ad of the first silica fine particles is more preferably set to a value within the range of 18 to 37 nm, and further preferably set to a value within the range of 20 to 30 nm.
The number average primary particle size Ad of the first silica fine particles can be measured by, for example, a dynamic scattering type particle size distribution measuring device (LB-550, manufactured by Horiba, Ltd.).
In the present invention, the first silica fine particles may be aggregated. In this case, the number average secondary particle diameter is preferably set to a value in the range of 50 to 2000 nm, and is preferably 100 to 1000 nm. A value within the range is more preferable.

(3) Coverage Further, the coverage Ac of the first silica fine particles with respect to the toner particles is set to a value larger than the coverage Cc of the resin fine particles with respect to the toner particles, that is, Ac and Cc satisfy the relational expression (4). It is characterized by satisfaction.
The reason for this is that the function as the spacer of the first silica fine particles can be stably exhibited by setting the coverage Ac of the first silica fine particles to a value larger than the coverage Cc of the resin fine particles. Because.
That is, when the coverage Ac of the first silica fine particles is smaller than the coverage Cc of the resin fine particles, the amount of the first silica fine particles existing on the surface of the resin fine particles is excessively reduced, and the resin fine particles and the photosensitive particles are exposed. This is because it is easy to make direct contact with the body surface. On the other hand, if the coverage Ac of the first silica fine particles becomes an excessively large value, the first silica fine particles may be easily aggregated or the external addition of the resin fine particles to the toner particles may be hindered.
Therefore, it is necessary to consider the balance with the coverage Cc of the resin fine particles, but in general, the coverage Ac of the first silica fine particles to the toner particles is set to a value within the range of 10 to 60%. Preferably, the value is in the range of 15 to 40%.
The coverage Ac of the first silica fine particles to the toner particles is defined in the same manner as in the case of the resin fine particles.
A specific method for calculating the coverage Ac will be described in Examples.

(4) Addition The addition amount of the first silica fine particles is preferably set to a value within the range of 0.3 to 3 parts by weight with respect to 100 parts by weight of the toner particles.
The reason for this is that when the amount of the first silica fine particles added is less than 0.3 parts by weight, the coverage Ac of the first silica fine particles is excessively decreased, and is larger than the resin fine particle coverage Cc. This is because it may be difficult to adjust to the above. On the other hand, when the amount of the first silica fine particles added exceeds 3 parts by weight, the first silica fine particles are likely to be excessively aggregated or the external addition of the resin fine particles to the toner particles is inhibited. There is.
Therefore, the amount of the first silica fine particles added is more preferably set to a value within the range of 0.4 to 2.5 parts by weight with respect to 100 parts by weight of the toner particles. More preferably, the value is within the range.

(5) External Addition to Resin Fine Particles Further, as shown in FIGS. 1A to 1B, it is preferable that a part of the first silica fine particles 52 is externally added to the resin fine particles 53.
This is because the spacer effect by the first silica fine particles can be more reliably exhibited by such a configuration.
A specific method for obtaining such an externally added state will be described later.

4). Second Silica Fine Particles The developer of the present invention is further characterized by further containing second silica fine particles as an external additive for toner particles.
The reason for this is that by including the first silica fine particles as an external additive, the fluidity of the toner particles can be improved, while the resin fine particles that have started to adhere to the surface of the photoreceptor are efficiently polished and removed. It is because it can do.
Conventionally, titanium oxide fine particles have been used as an abrasive for toner particles. However, the polishing effect is insufficient for resin fine particles that are smaller than toner particles and easily charged.
This is presumed to be due to the fact that the titanium oxide fine particles are very likely to aggregate, and thus the polishing is rougher than the second silica fine particles.

(1) Type The second silica fine particles can be basically configured in the same manner as the first silica fine particles except that the number average primary particle diameter is different.
On the other hand, when the hydrophobizing treatment is performed, it is preferable to use aminopropylethoxysilane and silicon oil in combination as the treating agent because the polishing effect of the second silica fine particles can be better exhibited.

(2) Number average primary particle diameter The number average primary particle diameter Bd of the second silica fine particles is set to a value within the range of 70 nm to 100 nm, that is, Bd satisfies the relational expression (2). And
The reason is that by setting the number average primary particle diameter Bd of the second silica fine particles in such a range, the fluidity of the toner particles can be improved, while the resin fine particles that have started to adhere to the surface of the photoreceptor are This is because it can be polished and removed efficiently.
That is, when the number average primary particle diameter Bd of the second silica fine particles is less than 70 nm, the second silica fine particles are likely to be excessively aggregated and the polishing may be rough. On the other hand, when the number average primary particle diameter Bd of the second silica fine particles becomes an excessively large value, the liberation rate from the toner particles may increase excessively, or the fluidity of the toner particles may be inhibited.
Therefore, the number average primary particle diameter Bd of the second silica fine particles is more preferably set to a value within the range of 80 to 100 nm .

(3) Coverage Further, the coverage ratio Bc of the second silica fine particles with respect to the toner particles is set to a value larger than the coverage ratio Cc of the resin fine particles with respect to the toner particles, that is, Bc and Cc are expressed by the relational expression (5). It is characterized by satisfaction.
This is because the function of the second silica fine particles as an abrasive is stably exhibited by setting the coverage ratio Bc of the second silica fine particles to a value larger than the coverage Cc of the resin fine particles. This is because it can.
That is, when the coverage ratio Bc of the second silica fine particles becomes smaller than the coverage ratio Cc of the resin fine particles, the absolute amount of the second silica fine particles is insufficient, and the resin fine particles that have started to adhere to the surface of the photoreceptor are removed. This is because it may be difficult to polish and remove efficiently. On the other hand, when the coverage Bc of the second silica fine particles becomes an excessively large value, the second silica fine particles are likely to aggregate with each other or the external addition of the resin fine particles to the toner particles may be hindered.
Accordingly, it is necessary to consider the balance with the coverage Cc of the resin fine particles, but in general, the coverage Bc of the second silica fine particles with respect to the toner particles is set to a value within the range of 5 to 30%. Preferably, the value is in the range of 10 to 20%.
The coverage Bc of the second silica fine particles to the toner particles is defined in the same manner as in the case of the resin fine particles.
A specific method for calculating the coverage ratio Bc will be described in Examples.

(4) Addition amount The addition amount of the second silica fine particles is preferably set to a value within the range of 0.4 to 5 parts by weight with respect to 100 parts by weight of the toner particles.
The reason for this is that when the amount of the second silica fine particles added is less than 0.4 parts by weight, the coverage ratio Bc of the second silica fine particles is excessively decreased, and is larger than the coverage ratio Cc of the resin fine particles. This is because it may be difficult to adjust to the above. On the other hand, if the amount of the second silica fine particles added exceeds 5 parts by weight, the second silica fine particles may easily aggregate with each other, or the external addition of the resin fine particles to the toner particles may be hindered. .
Accordingly, the amount of the second silica fine particles added is more preferably set to a value within the range of 0.8 to 3 parts by weight, with respect to 100 parts by weight of the toner particles. More preferably.

5. Relational Expression As described above, the developer of the present invention is characterized by satisfying the relational expressions (1) to (5).
Hereinafter, the relationship between the relational expressions (1) to (5) and the effect of the present invention will be described with reference to FIGS.

First, the relationship between the number average primary particle diameter of the resin fine particles and the adhesion of the resin fine particles to the photosensitive member when 100,000 density low density printing is performed will be described with reference to FIG.
That is, in FIG. 2, a characteristic curve A and plot in which the horizontal axis represents the number average primary particle diameter Cd (nm) of the resin fine particles and the vertical axis represents the evaluation value (relative value) of the adhesion of the resin fine particles to the photoreceptor. B to F are shown.
Here, in the characteristic curve A, the number average primary particle diameter Ad of the first silica fine particles is a value in the range of 16 to 35 nm, and the number average primary particle diameter Bd of the second silica fine particles is a value of 70 nm or more. And a characteristic curve in the case of using a developer in which the values of the coverage ratio Ac and Bc of the first and second silica fine particles to the toner particles are larger than the value of the coverage ratio Cc of the resin fine particles to the toner particles. .
That is, the characteristic curve A is a characteristic curve when a developer satisfying the relational expressions (1), (2), (4) and (5) is used.
On the other hand, plot B (marker: ●) shows that the covering ratio Ac of the first silica fine particles to the toner particles is equal to the coverage of the resin fine particles to the toner particles, although the relational expressions (1) to (3) and (5) are satisfied. A plot when using a developer that is smaller than the rate Cc and does not satisfy the relational expression (4) is shown.
The plot C (marker: □) shows that the coverage ratio Bc of the second silica fine particles to the toner particles is higher than the coverage Cc of the resin fine particles to the toner particles, although the relational expressions (1) to (4) are satisfied. The plot when using a small developer that does not satisfy the relational expression (5) is shown.
Plot D (marker: ▲) is a value where the number average primary particle diameter of the first silica fine particles is less than 16 nm, although the relational expressions (2) to (5) are satisfied. The relational expression (1) A plot when using a developer that does not satisfy the above is shown.
Plot E (marker: ◇) is a value in which the number average primary particle diameter of the first silica fine particles exceeds 35 nm, although the relational expressions (2) to (5) are satisfied. The plot when using a developer that does not satisfy () is shown.
Furthermore, plot F (marker: x) is a value in which the number average primary particle diameter of the second silica fine particles is less than 70 nm, although the relational expressions (1) and (3) to (5) are satisfied. The plot at the time of using the developing agent which does not satisfy Formula (2) is shown.
At this time, the amount of resin fine particles added to 100 parts by weight of toner particles was unified to 0.3 parts by weight.
Further, the adhesion evaluation value of the resin fine particles to the photosensitive member (hereinafter referred to as the photosensitive member adhesion evaluation value) is the result when 100,000 low-density printing is performed, and is quantified according to the following evaluation criteria. It is a thing. Details of the evaluation method and the like are described in the examples.
3: No photoconductor adhesion 1: Photoconductor adhesion

First, from the characteristic curve A, as the number average primary particle diameter Cd of the resin fine particles increases, the photosensitive member adhesion evaluation value increases, and the photosensitive member adhesion can be effectively suppressed. Understood.
More specifically, when the number average primary particle size Cd of the resin fine particles increases from 30 nm to 40 nm, the photoreceptor adhesion evaluation value changes from 1 (with photoreceptor adherence) to 3 (without photoreceptor adherence). It is understood that the photosensitive member adhesion evaluation value can be stably maintained at 3 in the range where the number average primary particle diameter Cd of the resin fine particles increases rapidly and is 40 nm or more.
On the other hand, in the case of plots B, C, D and F, it is difficult to obtain a desired photoreceptor adhesion evaluation value even when the number average primary particle diameter Cd of the resin fine particles is increased to 80 nm. It is understood that
Therefore, if it is assumed that the relational expressions (2), (4) and (5) are satisfied, the low density printing was performed continuously for a long time by satisfying the relational expression (3). Even in this case, it is understood that the adhesion of resin fine particles to the photoreceptor can be effectively suppressed.

Next, similarly, FIGS. 3 and 4 show the relationship between the number average primary particle diameter of the resin fine particles and the image density and fog density when 100,000 sheets of low-density printing are performed, respectively. Here, the image density and the fog density are values that serve as indices for determining the chargeability of the developer.
Details of the image density and fog density measuring method will be described in the examples.
Further, the developer used in the characteristic curve A and plots BF shown in FIGS. 3 and 4 is the same as the characteristic curve A and plots BF in FIG.

First, from the characteristic curve A, by setting the number average primary particle diameter Cd of the resin fine particles to a value of 40 nm or more, an image density of 1.3 or more can be stably obtained, and the fog density can also be stabilized. It is understood that the value can be suppressed to 0.008 or less.
On the other hand, in the case of plots B to E, it is understood that it is difficult to obtain desired image density and fog density even when the number average primary particle diameter Cd of the resin fine particles is increased to 80 nm. Is done.
Therefore, if it is assumed that the relational expressions (1), (4) and (5) are satisfied, the low density printing was performed continuously for a long time by satisfying the relational expression (3). Even in this case, it is understood that the triboelectric chargeability of the developer can be stably maintained.
Therefore, if FIGS. 2 to 4 are comprehensively determined, even if low density printing is performed continuously for a long time by satisfying all of the relational expressions (1) to (5), It will be understood that the adhesion of the resin fine particles to the photoreceptor can be effectively suppressed and the triboelectric charging property of the developer can be effectively maintained.
In other words, if any one of the relational expressions (1) to (5) is not satisfied, the resin fine particles adhere to the photosensitive member when the low density printing is performed continuously for a long time, or the developer friction. It is understood that charging problems will occur.

  Further, since it has already been described in the section of the resin fine particles, the content is omitted, but the coverage Cc of the resin fine particles to the toner particles is set to a value within the range of 1 to 30%, that is, Cc is a relational expression (6). Is preferably satisfied.

6). Other External Additives It is preferable to further add titanium oxide fine particles to the toner particles.
This is because adhesion of toner particles to the photoreceptor can be suppressed by further adding titanium oxide fine particles.
Such titanium oxide fine particles are not particularly limited, and may have any crystal type such as a rutile type, anatase type and brookite type.
Further, the number average primary particle diameter of the titanium oxide fine particles is preferably set to a value in the range of 20 to 300 nm, and more preferably set to a value in the range of 50 to 200 nm.
Further, the addition amount of the titanium oxide fine particles is preferably set to a value within the range of 0.5 to 5 parts by weight, and within a range of 1 to 3 parts by weight with respect to 100 parts by weight of the toner particles. Is more preferable.

7). External Addition Conditions Further, external addition conditions when external additives such as resin fine particles and first and second silica fine particles are externally added to the toner particles are shown in FIGS. If such an externally added state is obtained, there is no particular limitation.
As an example, after storing toner particles and a predetermined external additive in a Henschel mixer, the upper limit of the temperature during mixing is set to a value in the range of 5 to 40 ° C., and the rotational speed is 750 to 5000 rpm. The method of mixing for 1 to 30 minutes within the range is mentioned.

7). Two-component developer In constituting the developer of the present invention, the developer is preferably a two-component developer.
This is because the charge stability of toner particles can be further improved with a two-component developer.
The carrier used for such a two-component developer may be a carrier consisting only of a carrier core, but more preferably comprises a carrier core and a resin coating layer covering the carrier core.
The reason for this is that the resin coating layer can improve the insulating properties of the carrier to adjust the triboelectric charging characteristics between the carrier and the toner particles within a suitable range, and further improve the durability of the carrier. This is because it can.

(1) Carrier core As a carrier core, a metal or alloy exhibiting ferromagnetism such as ferrite, magnetite, iron, cobalt and nickel, or a compound containing these ferromagnetic elements, or containing no ferromagnetic elements, is suitable. An alloy or the like that exhibits ferromagnetism when subjected to an appropriate heat treatment can be used.
Moreover, it is also preferable to use what was granulated by disperse | distributing the magnetic powder mentioned above in binder resin, such as polyvinyl alcohol resin and polyvinyl acetal resin, as such a carrier core. That is, after mixing and dispersing magnetic powder, a binder resin, and additives as necessary, the core elementary particles can be obtained by granulation and drying. Thereafter, the obtained carrier core elementary particles can be fired and pulverized using a known method to obtain a carrier core.

(2) Resin coating layer Moreover, as a resin coating layer of a carrier, an epoxy resin, a silicone resin, a fluororesin, etc. are used suitably.
This is because, with these resins, the triboelectric charging characteristics and the like of the carrier can be adjusted to a suitable range.
Moreover, it is preferable to make this resin coating amount into the value within the range of 5-60 weight part with respect to 100 weight part of carrier cores.
The reason for this is that when the resin coating amount is less than 5 parts by weight, the carrier core cannot be sufficiently coated, and the chargeability and durability may be lowered. On the other hand, when the resin coating amount exceeds 60 parts by weight, fluidity may be reduced or spent may be easily generated.
Therefore, the resin coating amount is more preferably set to a value within the range of 10 to 50 parts by weight with respect to 100 parts by weight of the carrier core, and more preferably set to a value within the range of 15 to 45 parts by weight.

(3) Average particle diameter Moreover, it is preferable to make the average particle diameter of a carrier into the value within the range of 20-120 micrometers.
This is because when the average particle diameter of the carrier is less than 20 μm, carrier skipping (a phenomenon in which the carrier moves to the photosensitive member) occurs, and the printed portion may fall out white. On the other hand, when the average particle diameter of the carrier exceeds 120 μm, the developability (development amount) of the developer as a whole may decrease.
Accordingly, the average particle diameter of the carrier is more preferably set to a value within the range of 30 to 110 μm, and further preferably set to a value within the range of 40 to 100 μm.

(4) Addition Amount of addition of the carrier is preferably set to a value in the range of 50 to 5000 parts by weight with respect to 100 parts by weight of the toner particles.
This is because if the amount of carrier added is less than 50 parts by weight, it may be difficult to sufficiently frictionally charge the toner particles with the resin fine particles added externally. On the other hand, when the added amount of the carrier exceeds 5000 parts by weight, the fluidity of the developer as a whole may be lowered, or carrier jump may be likely to occur.
Therefore, the amount of carrier added is more preferably set to a value within the range of 100 to 3000 parts by weight, and more preferably within a range of 200 to 2000 parts by weight with respect to 100 parts by weight of the toner particles.

(5) Manufacturing method Moreover, as a method of forming the resin coating layer on the carrier core, for example, a solution obtained by dissolving the coating resin in an appropriate solvent is used to spray the carrier core using means such as spraying or fluidized bed. It is preferable to coat against. Next, it is preferable to dry and calcinate the mixed mass of the obtained coating resin and carrier core, and then crush using a hammer mill or the like, and further perform classification using an air classifier or the like.

[Second Embodiment]
The second embodiment is an image forming method using the developer described in the first embodiment.
Hereinafter, the image forming method according to the second embodiment will be described with a focus on different points while omitting the same contents as those in the first embodiment.

1. Image Forming Apparatus In carrying out the image forming method of the second embodiment, for example, a tandem type image forming apparatus 2 as shown in FIG. 5 can be suitably used.
Here, FIG. 5 is a schematic diagram showing the overall configuration of the image forming apparatus. The image forming apparatus 2 includes a paper feed cassette 22 disposed in a lower portion of the image forming apparatus main body 2, a paper transport unit disposed on the side and above the paper feed cassette 22, and a paper transport unit of the paper transport unit. An image forming unit disposed above and a fixing unit 24 disposed on the discharge side of the image forming unit are provided.
Then, the sheet feeding cassette 22 is fed out of the plurality of sheet feeding cassettes 22 to the sheet conveying unit side by the rotation operation of the sheet feeding roller, and the sheets are surely fed one by one. It is configured to be fed to the paper transport unit. Note that these three paper feed cassettes 22 are configured to be detachable from the image forming apparatus main body 2.

  Further, the paper fed to the paper transport unit is transported toward the image forming unit via the paper supply path. The image forming unit forms a predetermined toner image on a sheet by an electrophotographic process, and includes a photoconductor 10 that is an image carrier that is rotatably supported in a predetermined direction, and the photoconductor 10. A charging device 12, an exposure device 14, a developing device 3 (3 to 6), a transfer device 16, and a cleaning device 18 are provided around the rotation direction.

  The charging device 12 includes a charging wire to which a high voltage is applied. By applying a predetermined potential to the surface of the photoconductor 10 by corona discharge from the charging wire, the surface of the photoconductor 10 is set to a predetermined potential. It is charged uniformly. Then, the exposure device 14 irradiates the photoconductor 10 with light based on the image data of the document, whereby the surface potential of the photoconductor 10 is selectively attenuated, and the electrostatic latent image is formed on the surface of the photoconductor 10. An image is formed. Next, the developing device 3 attaches toner to the above-described electrostatic latent image and forms a toner image on the surface of the photoconductor 10. The transfer device 16 converts the toner image on the surface of the photoconductor 10 with the photoconductor 10. The image is transferred to a sheet supplied between the transfer device 16.

Further, the sheet on which the toner image is transferred is conveyed from the image forming unit toward the fixing unit 24. The fixing unit 24 is disposed on the downstream side of the image forming unit in the sheet conveyance direction, and the sheet on which the toner image is transferred in the image forming unit is disposed on a heating roller provided in the fixing unit 24 and the heating roller. The toner image is fixed on the sheet by being sandwiched and heated by the pressing pressure roller. Next, the paper on which the image is formed in the fixing unit 24 from the image forming unit is discharged onto the discharge tray 28 by the discharge roller pair 26. On the other hand, the toner remaining on the surface of the photoreceptor 10 after the transfer is removed by the cleaning device 18.
Thereafter, the photoreceptor 10 is charged again by the charging device 12, and image formation is performed in the same manner.

2. As shown in FIG. 6, as an example of the developing device used in the present invention, a developing container 110 for containing a two-component developer and a developer are carried and conveyed to the developing region. A developing roller 140, a magnetic roller 130 for supplying developer to the developing roller 140, and a developer layer thickness regulating member for regulating the layer thickness of the magnetic brush formed on the magnetic roller 130 It is possible to use a developing device 100 that includes 117 and a helical spring 120 that rotates around a predetermined rotation axis to convey the developer in the direction of the rotation axis.
Here, the helical spring 120 includes a first spiral member 124 and a second spiral member 122 which are conveying means for conveying the developer in a predetermined direction.
More specifically, it comprises a spiral blade (not shown) provided on the peripheral surface of a rotatable shaft provided in the stirring chamber 114 for stirring the developer, and is indicated by an arrow in FIG. The first spiral member 124 is provided to convey the developer in the longitudinal direction of the shaft by rotating in the direction.

Further, the periphery of a rotatable shaft arranged substantially parallel to the axis of the first spiral member 124 provided in the developing chamber 112 provided for applying the developer to the magnetic roller 130 while stirring the developer. And a second spiral member 122 that conveys developer in the longitudinal direction of the shaft by rotating in the direction of the arrow in FIG. 6. Yes.
Note that the first spiral member 124 and the second spiral member 122 are disposed substantially in parallel. Further, between the first spiral member 124 and the second spiral member 122, the axially opposite ends of the first spiral member 124 and the second spiral member 122 are arranged so that the stirring chamber 114 and the developing chamber 112 can communicate with each other. A partition member 113 that partitions the stirring chamber 114 and the developing chamber 112 is provided except for the corresponding portion. Therefore, the toner can be conveyed while being cyclically stirred.
Further, as shown in FIG. 6, the second spiral member 122 is disposed on the drum opening side of the developing container 110, and includes a fixed magnet 134 having a plurality of magnetic poles and the fixed magnet 134. In order to introduce the developer onto the surface of the developing roller 140, a magnetic roller 130 comprising a nonmagnetic magnetic sleeve 132 rotatably supported is provided.
Furthermore, a developer layer thickness regulating member 117 is provided that is made of a plate-like magnetic body, is disposed in the vicinity of the magnetic sleeve 132, and hangs down toward the upper surface of the magnetic sleeve 132.
A thin layer made of toner particles is formed on the surface of the developing container 110 on the drum opening side by the toner particles supplied from the magnetic roller 130, and the toner particles forming the thin layer are transferred to the photoreceptor. A developing roller 140 for electrically developing the electrostatic latent image on the image 10 is provided.

In addition, a toner supply hole (not shown) is opened above the first spiral member 124 so that the developer can be charged from the toner container 100A. That is, the introduced developer is conveyed to the developing chamber 112 by the first spiral member 124 while stirring and charging the toner particles and the carrier. The developer conveyed to the developing chamber 112 is guided to the magnetic sleeve 132 by the second spiral member 122. The developer guided to the magnetic sleeve 132 is carried on the magnetic sleeve 132 using the magnetic force of the fixed magnet 134, and the developer is a developer layer thickness regulating member disposed in the vicinity of the magnetic sleeve 132. The thickness is regulated by 117.
Next, the developer carried on the magnetic sleeve 132 has only toner particles (including external additives) on the developing roller 140 due to the potential difference between the voltages applied to the magnetic roller 130 and the developing roller 140. It moves relative to the peripheral surface to form a thin layer.
The toner particles are guided by the developing roller 140 to a development position, that is, a position close to or in contact with the surface of the photoreceptor 10, and the electrostatic latent image, that is, a portion where the surface potential is attenuated by exposure is developed. Further, when the photoreceptor 10 and the printing paper come into contact with each other, an image is transferred and formed on the printing paper.

3. Photoconductor In the present invention, an amorphous silicon photoconductor is preferably used as the photoconductor.
The reason for this is that, if an amorphous silicon photoconductor is used, resin fine particles are likely to adhere to the surface of the photoconductor, but in the present invention, since a predetermined developer is used, the occurrence of such adhesion is effective. Therefore, it is possible to effectively exhibit the characteristic of long life, which is a feature of the amorphous silicon photoconductor.

  EXAMPLES The present invention will be specifically described below with reference to examples, but it goes without saying that the present invention is not limited to these descriptions.

1. Production of resin fine particles (1) Resin fine particles a
Ion exchange water is contained in a 2 liter separable flask equipped with a stirrer, thermometer, nitrogen inlet tube, reflux condenser and dropping funnel, and lauric acid diethanolamide 1 is added to 100 parts by weight of the ion exchange water. Part by weight was added and the temperature was raised to 80 ° C.
Next, after further adding 0.1 parts by weight of 2,2′-azobis (2-methylpropionamidine) dihydrochloride, 40 parts by weight of styrene, 40 parts by weight of butyl methacrylate, and 20 parts by weight of dimethylaminoacrylate were added dropwise. Emulsion polymerization was carried out at 80 ° C. for 3 hours to obtain an emulsion.
Next, the obtained emulsion was purified by an ultrafiltration device and then dried by a spray drying method to obtain resin fine particles a having a glass transition point of 120 ° C. and a number average primary particle size of 80 nm.
In addition, the number average primary particle diameter of the resin fine particles a was measured using a dynamic scattering type particle size distribution measuring device (manufactured by Horiba, Ltd., LB-550). The same applies to the following resin fine particles b to c.

(2) Resin fine particles b
The fine resin particles a were cut on the coarse powder side with an elbow jet classifier (manufactured by Nittetsu Mining Co., Ltd.) to obtain resin fine particles b having a number average particle diameter of 40 nm.

(3) Resin fine particles c
The fine resin particles a were cut on the coarse powder side with an elbow jet classifier (manufactured by Nittetsu Mining Co., Ltd.) to obtain resin fine particles c having a number average particle diameter of 30 nm.

2. Production of silica fine particles (1) Silica fine particles A
In a container, 100 g of dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) and 100 g of 3-aminopropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) are added and dissolved in 200 g of toluene. This solution was diluted 10 times with toluene to obtain a diluted solution.
Next, 200 g of silica fine particles (manufactured by Nippon Aerosil Co., Ltd., fumed silica aerosil R972) were prepared, and ultrasonic irradiation and stirring were performed for 30 minutes while gradually adding the above-described diluted solution to the silica fine particles. A mixture was obtained.
Subsequently, the obtained mixture was heated in a high-temperature bath at 150 ° C., and then toluene was distilled off using a rotary evaporator. The obtained solid was reduced in weight at a set temperature of 50 ° C. using a vacuum dryer. It was dried until it disappeared to obtain a dry solid.
Next, the obtained dried solid was subjected to a heat treatment at 200 ° C. for 3 hours under a nitrogen stream using an electric furnace to obtain a powder.
Next, the obtained powder was crushed using a jet mill (air volume: 1 m ³ / min) and then collected with a bag filter to obtain silica fine particles A having a number average primary particle size of 20 nm.
In addition, the number average primary particle diameter of the silica fine particles A was measured using a dynamic scattering type particle size distribution measuring apparatus (LB-550, manufactured by Horiba, Ltd.). The same applies to the following silica fine particles B to F.

(2) Silica fine particle B
A silica fine particle B having a number average primary particle diameter of 30 nm was obtained in the same manner as the silica fine particle A except that the air volume during pulverization by a jet mill was changed to 1.2 m ³ / min.

(3) Silica fine particles C
A silica fine particle C having a number average primary particle size of 40 nm was obtained in the same manner as the silica fine particle A except that the air volume at the time of crushing by a jet mill was changed to 1.5 m ³ / min.

(4) Silica fine particles D
A silica fine particle D having a number average primary particle diameter of 13 nm was obtained in the same manner as the silica fine particle A except that the air volume during pulverization by a jet mill was changed to 0.5 m ³ / min.

(4) Silica fine particles E
In the container, finely pulverized silica silica, carbon powder as a reducing agent, and water were accommodated and mixed to obtain a mixed raw material.
Next, the obtained mixed raw material was heat-treated at about 1800 ° C. in an incinerator to generate SiO ₂ gas.
Next, the generated SiO ₂ gas was forcibly cooled using cooling air (flow rate: 80 m ³ / hour), and the precipitated silica fine particles were collected by a bag filter.
Next, aminopropylethoxysilane and silicon oil were added to the obtained silica fine particles, followed by heat treatment to obtain a solid.
Subsequently, the obtained solid was held using a Henschel mixer to obtain silica fine particles E having a number average primary particle size of 100 nm.

(5) Silica fine particle F
The silica fine particles F were produced in the same manner as the silica fine particles E except that the flow rate of the cooling air for forcibly cooling the SiO ₂ gas was changed to 90 m ³ / hour to obtain silica fine particles F having a number average primary particle size of 70 nm.

(6) Silica fine particles G
The silica fine particles G were produced in the same manner as the silica fine particles E except that the flow rate of the cooling air for forcibly cooling the SiO ₂ gas was changed to 110 m ³ / hour to obtain silica fine particles G having a number average primary particle size of 60 nm.

[Example 1]
1. Manufacture of toner particles A Henschel mixer (made by Mitsui Mining Co., Ltd.) contains a polyester resin obtained by condensing bisphenol and fumaric acid, and as a release agent for 100 parts by weight of the polyester resin. Fischer-Tropsch wax (manufactured by Nippon Seisaku Co., Ltd., FT-100), 3 parts by weight, copper phthalocyanine pigment as a colorant, 4 parts by weight, and quaternary ammonium salt as a charge control agent (Orient Chemical Co., Ltd.) 2 parts by weight of P-51) were added and mixed for 2 minutes.
Next, the obtained mixture was melt-kneaded using a twin screw extruder to obtain a toner kneaded product.
Next, the obtained toner kneaded product was finely pulverized with an airflow pulverizer and then classified with an air classifier to obtain toner particles having a volume average particle diameter of 8 μm.

2. Production of two-component developer In a Henschel mixer, 100 parts by weight of the obtained toner particles, 1 part by weight of silica fine particles A as first silica fine particles, and 1.7 of silica fine particles E as second silica fine particles Part by weight, 0.3 part by weight of resin fine particles a, and 1 part by weight of titanium oxide fine particles (Ishihara Sangyo Co., Ltd., TTO-55A, number average primary particle size 150 nm) as other external additives are contained. Then, the upper limit of the temperature during mixing was set to 30 ° C., and the mixture was mixed at 3000 rpm for 10 minutes to externally add the external additive to the toner particles.
At this time, the coverage of the silica fine particles A as the first silica fine particles to the toner particles is 33.2%, and the coverage of the silica fine particles F as the second silica fine particles to the toner particles is 11.3%. The coverage of the resin fine particles a with respect to the toner particles was 5.4%.
Next, a ferrite carrier (EF-60B, manufactured by Powder Tech Co., Ltd.) having a number average particle size of 60 μm is added to the toner particles to which the external additive is externally added so that the toner particle concentration becomes 8% by weight. In addition, the mixture was stirred and mixed until uniform to obtain a two-component developer. Table 1 shows the main components of the obtained two-component developer.

3. Calculation of Coverage The coverage in the present invention is defined as the ratio (%) of the projected area of the external additive externally added to the toner particles to the surface area of the toner particles.
Other conditions are not imposed as long as the definition of the coverage ratio is met, but actually, the toner particle and the external additive are calculated from the respective particle diameters, true specific gravity, and the mixing ratio thereof. Finally, it is general to adopt a method of correcting the shape in consideration of the circularity of the toner particles.
Hereinafter, the calculation process will be described focusing on the case where resin fine particles are used as the external additive.

(1) Volume average particle diameter of numerical toner particles used for calculation 8 μm = 8 × 10 ⁻⁴ cm
True specific gravity of toner particles 1.2 g / cm ³
Number average primary particle diameter of resin fine particles 0.08 μm = 8 × 10 ⁻⁶ cm
True specific gravity of resin fine particles 1.04 g / cm ³
Toner: resin fine particle mixing ratio (weight) 1: 0.003
Toner particle shape correction factor 1.6

(2) Calculation of the number of resin fine particles per toner particle First, when the weight per resin fine particle is calculated,
{4 × 3.14 × (4 × 10 ⁻⁶ ) ³ /3}×1.04
= 2.79 × 10 ⁻¹⁶ (g)
Next, when calculating the weight per toner fine particle,
{4 × 3.14 × (4 × 10 ⁻² ) ³ /3}×1.2
= 3.22 × 10 ⁻¹⁰ (g)
Therefore, the number of resin fine particles per toner particle is
{0.003 / 2.79 × 10 ⁻¹⁶ } / {1 / 3.22 × 10 ⁻¹⁰ }
= 3.46 × 10 ³ (pieces)

(3) Calculation of coverage before shape correction Next, when calculating the projected area per resin fine particle,
3.14 × (4 × 10 ⁻⁶ ) ²
= 5.03 × 10 ^-11 (cm ² )
Then, calculating the surface area per toner particle,
4 × 3.14 × (4 × 10 ⁻⁴ ) ²
= 2.01 × 10 ⁻⁶ (cm ² )
Therefore, the coverage before shape correction is
100 × {(3.46 × 10 ³ ) × (5.03 × 10 ⁻¹¹ )} / 2.01 × 10 ⁻⁶
= 8.7 (%)

(4) Shape correction Finally, in order to reflect that the manufactured toner particle is not a true sphere with a circularity of 1 but a circularity of 0.93, its surface area is larger than that of a true sphere. When the coverage before the shape correction is divided by the shape correction coefficient 1.6,
8.7 / 1.6
= 5.4 (%)
The shape correction coefficient can be obtained from the ratio between the surface area of the true sphere and the surface area of the spherical body having a circularity of 0.93.
That is, the BET specific surface area value of ground toner particles having a circularity of 0.93 is 1.255 m ² / g, and the BET specific surface area value of true spherical toner particles is 0.783 m ² / g.
Therefore, the shape correction coefficient 1.6 can be obtained from these values by the following calculation.
1.255 (m ² /g)/0.783(m ² /g)=1.6(-)
The BET specific surface area values when the circularity of the toner particles is 0.98, 0.96, and 0.91 are 0.853, 0.938, and 1.4871.255 m ² / g, respectively. Each shape correction coefficient can be obtained from the value.
Also, when calculating the coverage of silica fine particles as an external additive, the number average particle diameter, true specific gravity (2.26 g / cm ³ ), mixing ratio, etc. are adjusted to the numerical values of the silica fine particles used as appropriate. And calculated. The obtained calculation results are shown in Table 1.

4). Evaluation (1) Evaluation of Image Density (ID) Image density (ID) was evaluated using the obtained two-component developer.
That is, the obtained two-component developer is set in a color multifunction printer (Kyocera Mita Co., Ltd., KM-3232 remodeling machine), and immediately after the machine power is turned on and in a stable state, At a temperature of 25 ± 2 ° C. and a relative humidity of 50 ± 5%), a sample image having a solid portion and a white paper portion was output and used as an initial image.
Subsequently, the image density at three points of the solid portion of the obtained initial image was measured using a reflection densitometer (manufactured by Gretag Macbeth Co., Ltd., RD-19I), and the average value was used as the image density (ID). .
In addition, after the endurance image output of 100,000 sheets with the printing rate of 0.2% under the same environment, the above-described sample image is output as the endurance image, and the image density (ID) is the same as in the case of the initial image. ) Was measured. The obtained results are shown in Table 2.

(2) Evaluation of fog density (FD) Further, the fog density (FD) was evaluated using the obtained two-component developer.
That is, similarly to the evaluation of the image density (ID) described above, after the output of the initial image and the durable image, the fog density at three points in each blank paper portion is measured, and the average value is obtained as the respective fog density. (FD). The obtained results are shown in Table 2.

(3) Evaluation of image defects In addition, image defects were evaluated using the obtained two-component developer.
That is, similarly to the above-described evaluation of the image density (ID), after outputting the initial image and the durable image, it was visually confirmed whether or not the output image was distorted. The obtained results are shown in Table 2.

(4) Comprehensive evaluation Further, the above-described image density evaluation, fog density evaluation, and image defect evaluation were comprehensively evaluated.
That is, comprehensive evaluation was performed according to the following criteria.
○: ID ≧ 1.3 and FD ≦ 0.008 and no image defect Δ: 1.1 ≦ ID <1.3 and 0.009 ≦ FD <0.01 and no image defect ×: ID < 1.1 or FD ≧ 0.01 or image defect

[Example 2]
In Example 2, a two-component developer was produced and evaluated in the same manner as in Example 1 except that when the two-component developer was produced, silica fine particles B were used as the first silica fine particles. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Example 3]
In Example 3, a two-component developer was produced and evaluated in the same manner as in Example 1 except that when the two-component developer was produced, silica fine particles F were used as the second silica fine particles. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Example 4]
In Example 4, a two-component developer was produced and evaluated in the same manner as in Example 1 except that the resin fine particles b were used as the resin fine particles when producing the two-component developer. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Example 5]
Example 5 was the same as Example 1 except that when the two-component developer was produced, the amount of the first silica fine particles was changed to 0.3 parts by weight with respect to 100 parts by weight of the toner particles. Two-component developers were manufactured and evaluated. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Example 6]
In Example 6, the two-component developer was prepared in the same manner as in Example 1, except that the amount of the second silica fine particles added was changed to 1 part by weight with respect to 100 parts by weight of the toner particles. Developers were manufactured and evaluated. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Example 7]
In Example 7, when the two-component developer is manufactured, the amount of the second silica fine particles added is changed to 4 parts by weight with respect to 100 parts by weight of the toner particles, and the amount of the resin fine particles added is changed to the toner particle 100. A two-component developer was produced and evaluated in the same manner as in Example 1 except that the amount was changed to 1.4 parts by weight with respect to parts by weight. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Example 8]
In Example 8, the two-component developer was prepared in the same manner as in Example 1 except that when the two-component developer was produced, the amount of resin fine particles added was 0.2 parts by weight with respect to 100 parts by weight of the toner particles. Were manufactured and evaluated. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 1]
In Comparative Example 1, a two-component developer was produced and evaluated in the same manner as in Example 1 except that when the two-component developer was produced, silica fine particles C were used as the first silica fine particles. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 2]
In Comparative Example 2, a two-component developer was produced and evaluated in the same manner as in Example 1 except that silica fine particles G were used as the second silica fine particles when producing the two-component developer. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 3]
In Comparative Example 3, when the two-component developer is produced, the amount of the second silica fine particles added is 2.4 parts by weight with respect to 100 parts by weight of the binder resin, and the resin fine particles c are used as the resin fine particles. A two-component developer was produced and evaluated in the same manner as in Example 1 except that it was used. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 4]
In Comparative Example 4, the same procedure as in Example 1 was performed except that, when the two-component developer was produced, the amount of the first silica fine particles added was changed to 0.15 parts by weight with respect to 100 parts by weight of the toner particles. Two-component developers were manufactured and evaluated. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 5]
In Comparative Example 5, the same procedure as in Example 1 was conducted except that the amount of the second silica fine particles added was changed to 0.7 parts by weight with respect to 100 parts by weight of the toner particles when the two-component developer was produced. Two-component developers were manufactured and evaluated. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 6]
In Comparative Example 6, when the two-component developer is manufactured, the amount of the second silica fine particles added is changed to 4 parts by weight with respect to 100 parts by weight of the toner particles, and the amount of the resin fine particles added is changed to the toner particle 100. A two-component developer was produced and evaluated in the same manner as in Example 1 except that the amount was changed to 1.8 parts by weight with respect to parts by weight. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 7]
In Comparative Example 7, two-component development was performed in the same manner as in Example 1 except that when the two-component developer was produced, the amount of resin fine particles added was changed to 0.05 parts by weight with respect to 100 parts by weight of the toner particles. Agents were manufactured and evaluated. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

[Comparative Example 8]
In Comparative Example 8, a two-component developer was produced and evaluated in the same manner as in Example 1 except that when the two-component developer was produced, silica fine particles D were used as the first silica fine particles. Tables 1 and 2 show main structures and evaluation results of the obtained two-component developer.

As understood from Tables 1 and 2, in all of Examples 1 to 8, good image density (ID) and fog density (FD) can be maintained through 100,000 sheet printing, and It was also possible to suppress image defects.
On the other hand, in Comparative Example 1 in which the number average primary particle diameter of the first silica fine particles was increased, the image density was lowered and fogging occurred. This is presumably because toner fluidity could not be maintained.
In Comparative Example 2, drum adhesion occurred. This is probably because the polishing effect was not sufficiently obtained because the second silica fine particles having a relatively small size were used.
In Comparative Example 3, image defects due to adhesion of the photoconductor occurred. This is presumably because the resin fine particles used were relatively small in size, and thus passed through the photoconductor cleaning blade to cause adhesion of the photoconductor.
In Comparative Example 4, since the coverage with the first silica fine particles is low, the spacer function between the resin fine particles and the surface of the photoconductor does not work, and it is considered that the photoconductor adheres. Further, although the image density is lowered and the fog is generated, it is considered that the toner fluidity is insufficiently maintained.
In Comparative Example 5, it is considered that the polishing effect of the second silica fine particles was insufficient and the photosensitive member adhered.
In Comparative Example 6, since the coverage of the resin fine particles is large, the spacers and the polishing effect by the first and second silica fine particles cannot be sufficiently obtained, and it is considered that adhesion of the photoreceptor occurred as a result. Further, since there are many resin beads having relatively high thermal characteristics (Tg), it is considered that fixing failure has occurred from the beginning.
In Comparative Example 7, fogging and toner scattering occurred. This is presumably because the resin fine particle coverage was small and a sufficient charge maintaining effect could not be obtained.
In Comparative Example 8, the image density decreased after the endurance, and the photoconductor adhered. Regarding the reduction in image density, since the first silica fine particles having a relatively small size were used, the first silica fine particles were buried in the surface of the toner particles, and the fluidity of the developer was not sufficiently maintained. This is probably because In addition, with respect to adhesion of the photoreceptor, the first silica fine particles are buried in the surface of the toner particles, and the first silica fine particles can sufficiently exhibit a spacer function between the resin fine particles and the surface of the photoreceptor. This is thought to be because it was not possible.

According to the developer of the present invention, two types of silica fine particles each having a predetermined particle diameter and resin fine particles having a predetermined particle diameter are used as external additives for toner particles, and these external additives are used. By defining the relationship between the coverage of the agent and the toner particles within a predetermined range, the adhesion of resin fine particles to the photoreceptor can be effectively suppressed.
As a result, even when low density printing is performed continuously for a long time, the adhesion of resin fine particles to the photoreceptor can be effectively suppressed, and the triboelectric charging property of the developer is effectively retained. I was able to do it.
Therefore, the developer of the present invention and the image forming method using the developer are expected to contribute to high performance and high durability in various image forming apparatuses such as copying machines and printers.

FIGS. 1A to 1B are diagrams for explaining the state of the developer of the present invention on the surface of the photoreceptor. FIG. 2 is a diagram provided to explain the relationship between the number average primary particle diameter of resin fine particles and the photoreceptor adhesion. FIG. 3 is a diagram for explaining the relationship between the number average primary particle diameter of resin fine particles and the image density (ID). FIG. 4 is a diagram for explaining the relationship between the number average primary particle diameter of the resin fine particles and the fog density (FD). FIG. 5 is a diagram for explaining the image forming apparatus according to the present invention. FIG. 6 is a diagram provided for explaining the developing device according to the present invention.

Explanation of symbols

2: image forming device, 3: developing device, 10: photoconductor, 12: charging device, 14: exposure device, 16: transfer device, 18: cleaning device, 22: paper feed cassette, 24: fixing unit, 26: discharge Roller pair, 28: discharge tray, 100: developing device, 100A: toner container, 110: developing container, 112: developing chamber, 113: partition member, 114: stirring chamber, 117: developer layer thickness regulating member, 120: helical spring 122: second spiral member, 124: first spiral member, 130: magnetic roller, 132: magnetic sleeve, 134: fixed magnet, 140: developing roller

Claims (7)

A developer comprising toner particles, resin fine particles as an external additive, and first and second silica fine particles as an external additive,
The resin fine particles include a styrene-acrylic polymer obtained by polymerizing styrene and at least one monomer selected from the group consisting of butyl methacrylate and dimethylamino acrylate,
The number average primary particle diameter of the first silica fine particles is Ad (nm),
The coverage ratio of the first silica fine particles to the toner particles is Ac (%),
The number average primary particle size of the second silica fine particles is Bd (nm),
The coverage of the second silica fine particles to the toner particles is Bc (%),
The number average primary particle diameter of the resin fine particles is Cd (nm),
The coverage of the resin fine particles to the toner particles is Cc (%),
In the developer, the Ad, Ac, Bd, Bc, Cd and Cc satisfy the following relational expressions (1) to (5).
16 ≦ Ad ≦ 35 nm (1)
70 ≦ Bd ≦ 100 nm (2)
40 ≦ Cd ≦ 80 nm (3)
1 ≦ Cc ≦ Ac (4)
1 ≦ Cc ≦ Bc (5) The developer according to claim 1, wherein the Cc satisfies the following relational expression (6).
1 ≦ Cc ≦ 30 (6) It said portion of the first silica particles, the developer according to claim 1 or 2, characterized in that it is externally added to the resin particles. The developer according to any one of claims 1 to 3 , wherein titanium oxide fine particles are further externally added to the toner particles. The developer according to any one of claims 1 to 4 , wherein the developer is a two-component developer. An image forming method using the developer according to any one of claims 1 to 5 . The image forming method according to claim 6 , wherein an amorphous silicon photoconductor is used as the photoconductor.

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