JP2002318465A - Electrophotographic toner and method for forming image by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent toner deposition or image flow for a long time in an electrophotographic system using a positive electrification type organic photoreceptor. SOLUTION: In the electrophotographic toner used for a positive electrification type organic photoreceptor, rutile type titanium oxide is incorporated as an external treating agent into the toner particles containing a binder resin and magnetic particles. The amount of the rutile type titanium oxide added is controlled to the range from 5 to 10 vol% of the whole amount of the electrophotographic toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used in an image forming apparatus such as a printer, a copying machine, and a facsimile having a positively charged organic photoreceptor (sometimes simply referred to as "toner"). And an image forming method using the toner for electrophotography.

[0002]

2. Description of the Related Art A positively charged organic photoreceptor performs a positive corona discharge, and thus has the following advantages as compared with a negatively charged laminated organic photoreceptor that performs a negative corona discharge. . Low ozone generation. Non-contact development method,
For example, it is easy to combine with a magnetic jumping method, so that mechanical wear of the photoconductor can be suppressed and durability of the photoconductor can be improved.

However, if image formation is performed for a long period of time, for example, by printing 100,000 sheets of A4 paper using a positively chargeable organic photoreceptor, toner adheres to the photoreceptor and scratches on the surface of the photoreceptor cause Powder accumulates, or ion products generated during charging adhere to the surface of the photoreceptor, increasing water absorption. As a result, the electrostatic latent image leaks in the axial direction in a high-humidity environment, resulting in image deletion. There is a problem that such a problem easily occurs.

Therefore, in order to prevent these problems,
As disclosed in JP-A-3-231282, a method in which a heater is incorporated inside a positively charged organic photoreceptor and heating is performed, or as disclosed in JP-A-61-34579. A method has been proposed in which a sponge roll is pressed against the surface of a photoreceptor to polish the surface of the photoreceptor while providing a linear velocity difference.

[0005] However, even if these proposed methods are adopted, it is not possible to sufficiently and stably prevent toner adhesion and image flow, and on the other hand, the image apparatus becomes large and complicated. Problem was seen. In addition, there has been a problem that the deterioration of the positively charged organic photoreceptor is accelerated by heating the heater, and the positively charged organic photoreceptor is excessively worn due to the pressure contact of the sponge roll.

Further, as disclosed in Japanese Patent Application Laid-Open No. 5-181306, a method of physically fixing metal oxide fine powder such as alumina or zirconia on the surface of a toner to exert a polishing function is also known. Proposed.

However, in the method of physically fixing the metal oxide fine powder, stress is applied to the toner particles at the time of toner production or at the time of physical processing, so that a desired image density can be stably obtained. There was a problem that it could not be done.

Therefore, as disclosed in JP-A-6-208241 and JP-A-7-295293, a non-magnetic monocomponent obtained by adding rutile-type titanium oxide or anatase-type titanium oxide to toner particles. Toner has been proposed.

However, rutile-type titanium oxide generally has high hydrophilicity, and depending on the use environment, there is a possibility that the charging characteristics may be deteriorated. Of course, by using a large amount of the hydrophobizing agent or using a high-viscosity hydrophobizing agent, the degree of hydrophobicity could be improved,
Since the hydrophobization could not be sufficiently performed, such as formation of coalesced particles or non-uniform hydrophobization at the stage of the hydrophobization treatment, the fluidity was poor. Further, when silica is used in combination with rutile-type titanium oxide to supplement the fluidity, there is a problem that the charging characteristics of the toner are further impaired.

On the other hand, anatase-type titanium oxide has problems such as low volume resistivity, rapid charging leakage under high humidity conditions, and unstable charging characteristics.

The non-magnetic one-component toner disclosed in Japanese Patent Application Laid-Open No. 7-295293 requires the use of a specific polyester resin in the toner particles.
In addition, there is also a problem that a proper charging characteristic cannot be obtained because the magnetic powder is not used.

Also, Japanese Patent Application Laid-Open No. Sho 62-113158,
JP-A-64-62667 and JP-A-5-18
No. 8633 discloses a toner to which hydrophobic silica and titanium oxide (anatase type) are externally added.

However, such a toner has a problem in that titanium oxide (anatase type) is buried in the toner due to friction and the charging characteristics become unstable.

Japanese Patent Application Laid-Open No. 2000-128534 discloses a hydrophobic oxidizing treatment in which the surface of a rutile type titanium oxide partially containing hydrous titanium oxide and / or anatase type titanium oxide is treated with a silane coupling agent. A toner using titanium as an external additive is disclosed. And the major axis diameter of the hydrophobic titanium oxide is 0.02 to 0.1 μm,
The axial ratio is set to 2 to 8 to prevent the toner from being embedded in the toner.

However, there has been a problem that such a hydrophobic titanium oxide is not easily manufactured, has a low bulk density, and it is still difficult to exhibit stable charging characteristics.

Japanese Patent Application Laid-Open No. 10-3177 discloses that
A toner in which a titanium compound obtained by a reaction between Ti (OH) ₂ and a silane coupling agent is used as an external additive is disclosed.

However, since the obtained titanium compound has too small an average particle size, there are problems such as easy aggregation and difficulty in handling, and poor polishing effect, which easily causes image deletion.

[0018]

That is, the present invention provides:
In view of the above circumstances, by using a positively charged organic photoreceptor and using a predetermined amount of rutile type titanium oxide,
An object of the present invention is to provide an electrophotographic toner, which is optimal for an electrophotographic method and can effectively prevent toner adhesion and image deletion for a long period of time, and to provide an image forming method using the toner.

[0019]

According to the present invention, there is provided an electrophotographic toner used for a positively charged organic photoreceptor.
The toner particles containing the binder resin and the magnetic particles contain rutile-type titanium oxide as an external additive agent, and the added amount of the rutile-type titanium oxide is expressed as a volume ratio of the total amount of the electrophotographic toner. In contrast, the present invention provides an electrophotographic toner characterized by having a value within a range of 5 to 10% by volume, and can solve the above-described problems.

That is, titanium dioxide can be classified into rutile-type titanium oxide, anatase-type titanium oxide and brookite-type titanium oxide from the difference in crystal structure.
In the present invention, among the titanium dioxides having these crystal structures, the use of a predetermined amount of rutile-type titanium oxide effectively prevents toner adhesion and image deletion for a long period of time when a toner for electrophotography is formed. Now you can do it.

In constituting the electrophotographic toner of the present invention, the volume resistivity of the rutile type titanium oxide is 1 ×.
It is preferable that the value be in the range of 10 ⁴ to 1 × 10 ¹⁵ Ω · cm.

With such a configuration, the environmental resistance is improved, and toner adhesion and image deletion can be effectively prevented for a long period of time.

In constituting the electrophotographic toner of the present invention, the average particle diameter of the rutile type titanium oxide is set to 200.
It is preferable to set the value in the range of less than 500 nm.

According to this structure, the toner particles and the rutile type titanium oxide can be uniformly mixed, and as a result, the toner adhesion and the image deletion can be effectively prevented for a longer period of time.

Further, in forming the electrophotographic toner of the present invention, the surface of the rutile type titanium oxide is subjected to a hydrophobizing treatment using a titanium-based coupling agent and a silane-based coupling agent, or one of the surface treatment agents. Is preferably applied.

With such a constitution, the environmental resistance and the fluidity of the rutile type titanium oxide are improved.
It is possible to effectively prevent toner adhesion and image deletion for a longer period.

In constituting the electrophotographic toner of the present invention, the external additive preferably contains fine silica particles.

With this configuration, the fluidity is improved, and therefore, toner adhesion and image deletion can be effectively prevented for a longer period of time.

Heretofore, when silica was used in combination with rutile-type titanium oxide to further supplement the fluidity, there was a problem that the charging characteristics of the toner were impaired. Since the amount of titanium added is strictly limited, there is no such problem even when silica is used in combination.

In constituting the electrophotographic toner of the present invention, the binder resin is preferably a styrene polymer.

With this configuration, the toner particles and the rutile-type titanium oxide can be uniformly mixed, and as a result, toner adhesion and image deletion can be effectively prevented for a longer period of time.

According to another aspect of the present invention, there is provided a method of forming an image by an image forming apparatus using an electrophotographic toner, wherein the electrophotographic toner includes toner particles containing a binder resin and magnetic particles. Rutile-type titanium oxide was added as an addition treatment, and the amount of the rutile-type titanium oxide was set to a value within a range of 5 to 10% by volume with respect to the total amount of the electrophotographic toner, by volume ratio. While using electrophotographic toner, as an image forming apparatus,
Image carrier using positively charged organic photoreceptor, developing means for developing the image carrier in a non-contact manner, transfer means for transferring a developed image formed on the image carrier, and image carrier An image forming method using an image forming apparatus having a cleaning unit for collecting toner remaining in the image forming apparatus.

According to this embodiment, when an image is formed using a positively charged organic photoreceptor, toner adhesion and image deletion can be effectively prevented for a long period of time.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be illustratively described with reference to the drawings. However, dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are schematically described, and the scope of the present invention is limited unless particularly limited. It does not do.

[First Embodiment] A first embodiment is directed to an electrophotographic toner used for a positively charged organic photoreceptor, wherein an external toner is used for toner particles containing a binder resin and magnetic powder. Rutile-type titanium oxide is contained as an additive agent, and the amount of the rutile-type titanium oxide is 5 to 10 parts by volume with respect to the total amount of the electrophotographic toner.
A toner for electrophotography, wherein the value is within a range of volume%. Hereinafter, the toner particles and the external additive will be roughly described. 1. Toner Particles (1) Binder Resin Type The toner particles of the present invention preferably use a polystyrene-based resin as a binder resin because of its good charging characteristics and relatively uniform dispersion of magnetic powder. .

As such a polystyrene resin,
It may be a homopolymer of styrene or a copolymer with another monomer copolymerizable with styrene.

Accordingly, such copolymerized monomers include p-chlorostyrene; vinylnaphthalene; ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene; and vinyl chloride, vinyl bromide and vinyl fluoride. Vinyl halide; vinyl acetate,
Vinyl esters such as vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dotesyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, Phenyl acrylate, α-
(Meth) acrylic esters such as methyl chloroacrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate; other acrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide; vinyl methyl ether, vinyl isobutyl ether Vinyl ethers such as vinyl methyl ketone, vinyl ethyl ketone and methyl isopropenyl ketone; N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidene A single compound or a combination of two or more compounds may be used.

It is also preferable to use a crosslinking agent such as a diisocyanate compound, a dicarboxylic acid compound, or divinylbenzene to obtain a binder resin having a crosslinked structure.

It is also preferable to add another binder resin to the polystyrene resin. Examples of such other binder resins include polyester resins, epoxy resins, polyamide resins, polymethyl methacrylate resins, vinyl acetate resins, polyvinyl butyral resins, and polyvinyl formal resins.

Molecular Weight Distribution The binder resin preferably has at least two or more molecular weight distribution peaks (low molecular weight peak and high molecular weight peak) in the weight average molecular weight measured by gel permeation chromatography (GPC). Specifically, the weight average molecular weight is 3,000-
It is preferred to have a low molecular weight peak in the range of 20,000 and a high molecular weight peak in the range of the weight average molecular weight of 3 × 10 ⁵ to 15 × 10 ⁵ .

The reason for this is that when the low molecular weight peak is within the above range, the fixability of the toner particles is improved. Conversely, if the low molecular weight peak is less than 3,000, offset tends to occur during fixing, and the storage stability of the toner at the service temperature (5 to 50 ° C.) is reduced, resulting in caking. This may result in

On the other hand, when the high molecular weight peak is within the above range, the offset property of the toner particles is improved. Conversely, when the high molecular weight peak is larger than 20,000, the binder resin and the charge This is because the compatibility with the control agent may be reduced and uniform dispersion may not be obtained. Therefore, fog, contamination of the photoreceptor, poor fixing and the like may easily occur.

Further, in the binder resin, the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is preferably 10 or more. The reason for this is that if the ratio of Mw / Mn is less than 10,
This is because the fixing property and the offset property of the toner particles may be reduced, and both properties may not be sufficiently satisfied.

Glass Transition Point The glass transition point of the binder resin is preferably set to a value within the range of 55 to 70 ° C.

The reason is that such a glass transition point is 55 ° C.
If the temperature is lower than 70 ° C., the storage stability of the toner particles may decrease. On the other hand, if the temperature exceeds 70 ° C., the fixability of the toner particles may decrease.

Therefore, the glass transition point of the binder resin is more preferably set to a value in the range of 58 to 68 ° C., and even more preferably to a value in the range of 60 to 66 ° C.

The glass transition point of the binder resin is as follows:
For example, it can be calculated by using a differential scanning calorimeter (DSC) to determine a change point in specific heat.

Addition Amount of the binder resin is preferably in the range of 30 to 80% by weight based on the total amount of the toner particles.

The reason for this is that if the amount of the binder resin is less than 30% by weight, the fixability and charging characteristics of the toner particles may be deteriorated. This is because the storage stability may deteriorate.

Therefore, the amount of the binder resin added is
More preferably, the value is in the range of 30 to 70% by weight based on the total amount of the toner particles.

(2) Magnetic Particles The toner particles of the present invention contain the following magnetic particles, and are characterized in that the positive charge characteristics of the toner can be easily adjusted.

Types Examples of the magnetic particles usable in the toner particles of the present invention include ferromagnetic metals or alloys such as ferrite and magnetite, such as iron, cobalt and nickel, or compounds containing these elements. Can be.

An alloy which does not contain a ferromagnetic element as it is but becomes ferromagnetic when subjected to an appropriate heat treatment, such as chromium dioxide, may be used.

The magnetic particles are preferably surface-treated using a surface treatment agent such as a titanium-based coupling agent or a silane-based coupling agent.

The reason for this is that by performing such a surface treatment, the affinity between the magnetic particles and the binder resin is improved, and the magnetic particles can be more uniformly dispersed in the binder resin. It is. Further, since the magnetic particles are usually hydrophilic, by performing such a surface treatment, it is possible to appropriately make the particles hydrophobic, and as a result, it is possible to improve the moisture resistance of the toner. .

Average Particle Size The average particle size of the magnetic particles is preferably set to a value within the range of 0.1 to 1 μm.

The reason for this is that if the average particle size of such magnetic particles is outside these ranges, it may be difficult to uniformly disperse the toner particles and to uniformly charge them. Therefore, the average particle diameter of the magnetic particles is 0.1 to
More preferably, the value is in the range of 0.7 μm,
More preferably, the value is in the range of 0.1 to 0.5 μm.

When the magnetic particles are applied to a one-component developing system, the amount is preferably in the range of 30 to 70% by weight based on the total amount of the toner particles.

The reason is that the amount of the magnetic particles added is 3
If the content is 0% by weight or less, durability may be reduced and fog may easily occur. On the other hand, if the added amount of the magnetic particles exceeds 70% by weight, the image density and durability may be reduced, or the fixability may be significantly reduced.

Therefore, when applied to the one-component development system, it is more preferable that the amount of the magnetic particles added is in the range of 30 to 60% by weight.

On the other hand, when applied to the two-component developing system, it is not necessary to add magnetic particles.
It is preferable to set the value to not more than% by weight.

The reason is that the amount of the magnetic particles added is 1
If the content exceeds 5% by weight, the durability may be reduced and fog may easily occur.

Therefore, when applied to the two-component development system, it is more preferable to set the amount of magnetic particles to a value within the range of 0 to 10% by weight (but not including 0% by weight). .

(3) Charge Control Agent Since the electrophotographic toner of the present invention is used for a positively chargeable organic photoreceptor, it is preferable that the toner particles contain a positive charge control agent described below.

Type 1 The type of the positive charge control agent is preferably, for example, a compound containing a repeating unit derived from styrene or α-methylstyrene, or a combination of both.

Further, a compound containing a repeating unit derived from an alkyl (meth) acrylate is preferred. Examples of the alkyl (meth) acrylate include methyl acrylate, ethyl acrylate, n-propyl acrylate, iso-propyl acrylate, n-butyl acrylate, iso-butyl acrylate, and 2-ethylhexyl acrylate. , Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate and the like.

Type 2 Another preferable positive charge controlling agent is a quaternary ammonium salt such as dialkylaminoalkyl (meth)
A compound containing a unit derived from an acrylate through a quaternization step is preferable. Examples of such a dialkylaminoalkyl (meth) acrylate include di (amino) ethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, dibutylaminoethyl (meth) acrylate, and the like. Lower alkyl) aminoethyl (meth) acrylate; dimethyl methacrylamide and dimethylaminopropyl methacrylamide are preferred. Further, a hydroxy group-containing polymerizable monomer such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and N-methylol (meth) acrylamide can be used in combination during polymerization.

Addition amount The addition amount of the charge control agent is determined based on the total amount of the toner particles.
It is preferable to set the value in the range of 1 to 10% by weight.

The reason for this is that if the amount of the charge control agent is less than 1% by weight, it becomes difficult to obtain the required positive chargeability, the charge amount tends to vary among the toner particles, and the fixed image cannot be obtained. This is because it tends to be unclear. In addition, defects such as increased photoreceptor contamination are likely to occur. On the other hand, if the added amount of the charge control agent is more than 10% by weight, environmental resistance and compatibility may be reduced, offset may be easily generated, and defects such as photoreceptor contamination may be easily generated. Because there is.

Therefore, the added amount of the charge controlling agent is 2 to 7
More preferably, the value is in the range of 3 to 6% by weight.
More preferably, the value is in the range of% by weight.

(4) Property Improving Agent In addition to the binder resin, magnetic particles and charge controlling agent described above, the toner particles of the present invention may further comprise a property improving agent for the purpose of further improving the offset property. It is preferable to add a release material such as polyethylene wax or polypropylene wax.

In the toner particles of the present invention, colloidal silica, hydrophobic silica, or the like as a property improver is added, or these colloidal silicas are used for the purpose of improving the fluidity and storage stability of the toner. Or surface treatment.

(5) Average Particle Size The average particle size of the toner particles is preferably set to a value within the range of 5 to 12 μm.

The reason for this is that if the average particle diameter of the toner particles is less than 5 μm, the storage stability of the toner for electrophotography is likely to deteriorate. on the other hand,
If the average particle diameter of the toner particles is larger than 12 μm, the fixed image tends to be unclear.

Therefore, the average particle diameter of the toner particles is set to 6
More preferably, the value is in the range of 11 μm.

2. External Additives (1) Rutile Titanium Oxide The electrophotographic toner of the first embodiment is characterized in that rutile type titanium oxide is used as an external additive.

The reason for this is that, as shown in Table 1, when the toner for electrophotography is constituted by using the rutile type titanium oxide, the image density stability, the toner adhesion, the image running property and the fogging property are reduced. This is because each characteristic can be exhibited with good balance. Conversely, even if titanium dioxide (anatase type titanium oxide) having another crystal structure is used in the same amount as rutile type titanium oxide, the image density is not stable and fogging is likely to occur.

Whether rutile-type titanium oxide is used as an external additive is determined by X-ray analysis of the crystal structure,
It can be determined by measuring the refractive index.

(2) Average Particle Size The average particle size of the rutile type titanium oxide used is 20
It is preferable that the value be in the range of 0 to less than 500 nm.

The reason for this is that if the average particle diameter of the rutile type titanium oxide is less than 200 nm, it becomes difficult to uniformly mix it with the toner particles. On the other hand, the average particle diameter of the rutile type titanium oxide is 500 n.
If the value is not less than m, the image density is not stable and fogging easily occurs when the toner for electrophotography is formed.

Therefore, it is more preferable to set the average particle size of the rutile type titanium oxide to a value within the range of 200 to 300 nm.

The average particle size of the rutile type titanium oxide means the average primary particle size when the rutile type titanium oxide is aggregated. The average particle size of the rutile type titanium oxide can be measured using a particle counter or the like employing a laser method.

(3) Volume resistivity The volume resistivity of the rutile type titanium oxide used is 1
It is preferable to set the value in the range of × 10 ⁴ to 1 × 10 ¹⁵ Ω · cm.

The reason is that when the volume resistivity of the rutile type titanium oxide becomes a value of less than 1 × 10 ⁴ Ω · cm,
This is because when the electrophotographic toner is configured, the charging characteristics may not be stable. On the other hand, if the volume resistivity of the rutile-type titanium oxide is larger than 1 × 10 ¹⁵ Ω · cm, the image density may not be stable when an electrophotographic toner is formed.

Therefore, it is more preferable that the volume resistivity of the rutile type titanium oxide is set to a value within the range of 1 × 10 ⁵ to 1 × 10 ¹⁴ Ω · cm, and 1 × 10 ⁶ to 1 × 10 ¹³ Ω.
More preferably, the value is in the range of cm.

The volume specific resistance of the rutile type titanium oxide was measured using an ULTRA HIGH RESISTANCE METER (R8340A, manufactured by Advantest) under a load of 1 kg.
It can be determined under the condition of an applied voltage of DC10V.

(4) Surface Treatment It is preferable that the rutile type titanium oxide to be used is subjected to a surface treatment in advance.

That is, if the surface of the rutile type titanium oxide is untreated, the hydrophilicity is relatively high, and depending on the use environment, the charging characteristics and the fluidity of the electrophotographic toner may be reduced. is there.

Here, examples of the surface treatment include a surface treatment for imparting hydrophobicity and a surface treatment for imparting fluidity. More specifically, it is preferable to use a surface treatment agent such as a hydrophobic silane coupling agent, a hydrophobic titanium coupling agent, or a hydrophobic silica.

The hydrophobicity defined by the following methanol concentration is preferably set to a value of 60% or more.
More preferably, it is set to a value within the range of 95%. That is, the degree of hydrophobicity of rutile-type titanium oxide is determined by adding 0.1 g of hydrophobized rutile-type titanium oxide to 50 ml of water, and adding methanol to the water at a rate of 2 ml / min with stirring. It can be defined as the methanol concentration at which the type titanium oxide starts to settle.

As the hydrophobizing agent, propyltrimethoxytitanium, propyldimethoxymethyltitanium, propyltriethoxytitanium, butyltrimethoxytitanium,
Butyldimethoxymethyltitanium, butyltriethoxytitanium, vinyltrimethoxytitanium, vinyldimethoxymethyltitanium, vinyltriethoxytitanium, vinyldiethoxymethyltitanium, hexyltrimethoxytitanium, hexyldimethoxymethyltitanium, hexyltriethoxytitanium, hexyldiethoxymethyl Titanium, phenyltrimethoxytitanium, phenyldimethoxymethyltitanium, phenyltriethoxytitanium, phenyldiethoxymethyltitanium, γ-glycidoxypropyltrimethoxytitanium, γ-glycidoxypropyldimethoxymethyltitanium, γ-glycidoxypropyltrititanium Ethoxy titanium, γ
-Glycidoxypropyldiethoxymethyltitanium and the like can be preferably used.

(5) Addition Amount of the rutile titanium oxide is preferably in a range of 5 to 10% by volume with respect to the total amount of the electrophotographic toner.

The reason for this is that if the amount of the rutile-type titanium oxide is less than 5% by volume, the toner adhesion and image flow properties are reduced when an electrophotographic toner is formed.

On the other hand, if the amount of the rutile-type titanium oxide is more than 10% by volume, the image density is not stable and fog tends to occur when an electrophotographic toner is formed.

Therefore, it is more preferable that the amount of the rutile type titanium oxide to be added falls within a range of 5.5 to 9% by volume, and it is even more preferable that the amount falls within a range of 6 to 8% by volume.

Here, referring to FIGS. 2 and 3, the amount (% by volume) of rutile type titanium oxide, the toner adhesion,
The relationship between the image density stability, image flowability and fogging will be described.

The horizontal axis in FIG. 2 shows the amount of addition (volume%) of rutile titanium oxide, and the left axis in FIG.
The evaluation result (relative value) of the toner adhesion is shown, and the evaluation result (relative value) of the image density stability is shown on the right axis of FIG. Similarly, the horizontal axis in FIG. 3 shows the addition amount (volume%) of rutile-type titanium oxide, and the left axis in FIG. 3 shows the evaluation result (relative value) of image flowability.
The evaluation result (relative value) of the fogging property is shown on the right axis of FIG. In addition, the relative value of each characteristic was evaluated as follows.
Is a calculated value, with 0 as the point.

As can be easily understood from FIGS. 2 and 3, when the addition amount of rutile type titanium oxide is in the range of 5 to 10% by volume, toner adhesion, image density stability,
It is possible to obtain a well-balanced result in image flowability and fogging. Further, if the amount of the rutile-type titanium oxide is in the range of 6 to 9% by volume, a more balanced result can be obtained in terms of characteristics, and 6 to 8% by volume.
Within this range, the most excellent results can be stably obtained.

Accordingly, in the electrophotographic toner used for the positively charged organic photoreceptor, it is extremely difficult to limit the amount of the rutile type titanium oxide as the external additive agent to a predetermined range in terms of volume ratio. It is important, on the contrary,
It is surprising that the characteristics can be controlled with such a simple configuration.

(6) Silica Fine Powder It is preferable to add silica fine powder as an external additive. This is because, with such a configuration, the fluidity of the electrophotographic toner can be improved.

It is preferable that the addition amount of the silica fine powder is determined in consideration of the addition amount of titanium oxide. Specifically, the addition amount of the silica fine powder was 1
When it is set to 00% by weight, it is preferable to set the value within the range of 10 to 100% by weight. The reason for this is that if the addition amount of the silica fine particles is less than 10% by weight, the effect of adding the silica fine particles may not be exhibited, while the addition amount of the silica fine particles may be 100% by weight.
If the ratio exceeds the above range, the charging characteristics of the electrophotographic toner may decrease.

Therefore, when the addition amount of the silica fine powder is 100% by weight and the addition amount of the titanium oxide is 100% by weight,
More preferably, the value is in the range of 90% by weight.
More preferably, the value is in the range of 0 to 80% by weight.

[Second Embodiment] A second embodiment relates to a method for forming an image by an image forming apparatus using an electrophotographic toner, wherein a toner containing a binder resin and magnetic particles is used as the electrophotographic toner. The particles contain rutile-type titanium oxide as an external addition treatment, and the added amount of the rutile-type titanium oxide is in the range of 5 to 10% by volume with respect to the total amount of the electrophotographic toner. An image carrier using a positively chargeable organic photoreceptor as an image forming apparatus, and a developing means for developing the image carrier in a non-contact manner, and the image carrier A transfer unit for transferring a developed image formed on the image carrier, a cleaning unit for collecting toner remaining on the image carrier,
An image forming method using an image forming apparatus having the following.

1. Electrophotographic toner The same electrophotographic toner as described in the first embodiment can be used.

2. 1. Image Forming Apparatus (1) Configuration FIG. 1 shows an embodiment of an image forming apparatus to which the present invention is applied. In the image forming apparatus 1, a developing device 10, a transfer roller 19, a cleaning blade 13, and a developing device 10 are provided around a positively-charged photosensitive drum (photoconductor) 9 rotating clockwise along the rotation direction. A charging unit 8 is provided.

Then, the developing roller 32 is
Is provided, and the surface of the developing roller 32 is
Is separated from the surface of the developing device by a predetermined distance.
For 0, a predetermined amount of toner can be supplied from the toner container 31 as appropriate.

An optical transmission mechanism 5 for forming image dots on the surface of the photoconductor 9 is provided above the photoconductor 9. The optical transmission mechanism 5 is not shown, but the polygon mirror 2 for reflecting the laser light from the laser light source and the laser light are applied to the surface of the photoconductor between the charging unit 8 and the developing roller 32 via the reflection mirror 4. And an optical system 3 for forming image dots.

A base 54 for accommodating a control circuit 71 for controlling the apparatus, which will be described later, is provided below the image forming apparatus 1. Above the base 54, a recording paper container 55 is provided. Are removably arranged from outside.
The recording paper container 55 is provided with a storage 14 for storing recording paper before transfer. Then, the recording paper placed on the pressing spring 52 is transported by the transport rollers 53 and 1.
5, through the passages 16 and 17, the auxiliary roller 30
Is configured to be conveyed to a registration roller 18 provided facing the image forming apparatus.

On the right side of the image forming apparatus 1, a front door 50 is disposed so as to be openable and closable as shown by a virtual line 50 '. When the front door 50 is opened and closed as shown by a virtual line 50',
The recording paper placed on the imaginary line 50 ′ of the front door is configured to be transported to the passage 17 by the transport roller 51.

On the left side of the image forming apparatus 1, a fixing unit is constituted by fixing rollers 23 and 24, and the recording paper passing between the photosensitive member 9 and the transfer roller 19 is fixed by these fixing rollers 23 and 24. Is done. Further, the recording paper after the fixing is configured to pass through the passage 27 by the conveying rollers 25 and 26, and is further accumulated in the transferred recording paper accumulation bin 6 by the rollers 28 and 29.

Further, on the upper part of the image recording device 1,
A display unit 47 for displaying various information, an installation switch 48, and a power switch 49 are provided.

(2) Operation In the image recording apparatus 1 configured as described above, by opening and closing the power switch 49, the main motor (not shown) starts driving, and the photosensitive member is started by the start switch (not shown). The optical transmission mechanism 5 is configured to be able to form an image on the surface of the photoconductor 9 by rotating the clockwise direction 9.

Then, the formed image is developed with toner by the developing roller 32 of the developing device 10, and the developed image is transferred to the recording paper by the transfer roller 19. Further, the recording paper to which the toner has been transferred is
3 and 24, the fixing is fixed, and rollers 25, 27,
By means of 28 and 29, it is conveyed to the storage 6 and collected.

Incidentally, the toner particles not developed by the developing roller 32 are collected by the cleaning blade 13.

Therefore, by forming an image on the positively chargeable organic photoreceptor using the electrophotographic toner in which the addition amount of the rutile type titanium oxide is limited to a predetermined range, the toner adhesion and the image formation for a long time can be achieved. Flow can be effectively prevented.

[0116]

EXAMPLES Example 1 (1) Preparation of Toner Particles The following raw materials were mixed with a Henschel mixer, and further mixed.
The mixture was melt-kneaded with a screw extruder. After cooling, it was pulverized and classified to obtain an average particle diameter of 7 μm and a bulk specific gravity of 0.60 g / c.
m ³ of the magnetic toner a was obtained. Binder resin (St / Ac resin) 50% by weight Magnetic particles (magnetite) 40% by weight Charge control agent (quaternary ammonium salt) 5% by weight Wax (polyethylene wax) 5% by weight (2) Preparation of toner In a Henschel mixer, toner particles a
And rutile-type titanium oxide (hereinafter, referred to as titanium oxide 1) having a bulk specific gravity of 0.40 g / cm ³ and silica fine particles as a fluidizing agent are accommodated at a peripheral speed of 45 m / sec.
After mixing for about minutes, a toner to which 6.1% by volume of rutile titanium oxide was externally added was obtained. Toner particles a 100% by weight Silica 1.0% by weight Titanium oxide 1 1.5% by weight (3) Evaluation of toner As a positively charged photoreceptor, a charge generating agent, an electron transporting agent and a hole transporting agent are provided on a conductive substrate. A dispersion type single-layer photoreceptor having a photosensitive layer dispersed in a resin binder was prepared.
The positively charged photoreceptor was uniformly charged to 400 V by a scorotron charger, and then irradiated with a laser beam having a wavelength of 780 nm and a light amount of 1.0 μJ / cm ² to form an electrostatic latent image. . Next, a developing bias in which a rectangular wave having a DC voltage of 300 V, an amplitude of 1.4 kV, a frequency of 2.4 kHz, and a duty ratio of 50% was superimposed was applied to the aluminum sleeve, and the electrostatic latent image was developed with toner. At this time, the gap between the drum and the aluminum sleeve was 0.3 mm. Next, the toner developed on the drum was transferred to recording paper by a transfer roll to which DC 800 V to 1200 V was applied. At this time, the transfer residual toner remaining on the drum without being transferred was removed by cleaning with a rubber blade pressed against the drum. This rubber blade uses urethane rubber with a hardness of 65 °, and changes the thickness, free end, and indentation amount,
The pressure was adjusted so that the pressing force against the photoreceptor was 17 g / cm. Next, using such an image forming apparatus, A4
A printing durability test was performed on 20,000 sheets of paper, and the image density stability, toner adhesion, image flowability and fogging property were evaluated based on the following criteria. Image density stability ：: A density fluctuation within 0.2 with respect to the initial density of 20 ° C. and 60%. Δ: Concentration fluctuation within 0.3 with respect to the initial concentration of 20 ° C. and 60%. X: Concentration fluctuation exceeding 0.3 with respect to the initial concentration of 20 ° C and 60%. Toner adhesion ○: No toner adhesion is observed. Δ: Although slight toner adhesion was observed, there was no significant problem in image characteristics. X: Remarkable toner adhesion is observed. Image deletion ○: No image deletion occurs. Δ: Image deletion is slightly generated. X: Remarkable image deletion has occurred. Fogging ○: No fogging occurred. Δ: Some fogging has occurred. X: Remarkable fog is generated.

Comparative Example 1 (1) Preparation of Toner In Comparative Example 1, toner particles a and rutile-type titanium oxide having a bulk specific gravity of 0.40 g / cm ³ (hereinafter, referred to as “titanium oxide”) were mixed in a Henschel mixer at the following ratio. Titanium oxide 1) and silica fine particles as a fluidizing agent are accommodated and mixed at a peripheral speed of 45 m / sec for 6 minutes, with respect to the total amount of toner particles.
There was obtained a toner to which 2.0% by volume of rutile type titanium oxide was externally added. Toner particles a 100% by weight Silica 1.0% by weight Titanium oxide 1 0.5% by weight (2) Evaluation of toner In the same manner as in Example 1, the obtained toner was evaluated. Table 1 shows the obtained results. As you can see from the results,
In Comparative Example 1, since the amount of the rutile-type titanium oxide used was small, the effect of adding the rutile-type titanium oxide was not exhibited.
It is estimated that image deletion and toner adhesion have occurred.

Example 2 (1) Preparation of Toner In Example 2, toner particles a and rutile-type titanium oxide having a bulk specific gravity of 0.65 g / cm ³ (hereinafter, referred to as “titanium oxide”) were mixed in a Henschel mixer at the following ratio. Titanium oxide 2) and silica fine particles as a fluidizing agent are accommodated and mixed at a peripheral speed of 45 m / sec for 6 minutes, with respect to the total amount of toner particles.
A toner to which 6.2% by volume of rutile type titanium oxide was externally added was obtained. Toner particles a 100% by weight Silica 1.0% by weight Titanium oxide 2 2.5% by weight (2) Evaluation of toner In the same manner as in Example 1, the obtained toner was evaluated. Table 1 shows the obtained results. As you can see from the results,
In Example 2, since an appropriate amount of rutile-type titanium oxide was used, even if the type of rutile-type titanium oxide was slightly changed, the image density did not decrease even in a high-humidity environment.
It is estimated that fog did not occur even after the printing durability test of the sheet.

Comparative Example 2 (1) Preparation of Toner In Comparative Example 2, toner particles a and rutile-type titanium oxide having a bulk specific gravity of 0.65 g / cm ³ (hereinafter, referred to as “titanium oxide”) were mixed in a Henschel mixer at the following ratio. After accommodating titanium oxide 2) and silica fine particles as a fluidizing agent, the peripheral speed is 45 m / sec.
After mixing for 6 minutes under the conditions described above, a toner to which 3.5% by volume of rutile type titanium oxide was externally added to the total amount of the toner particles was obtained. Toner particles a 100% by weight Silica 1.0% by weight Titanium oxide 2 1.5% by weight (2) Evaluation of toner In the same manner as in Example 1, the obtained toner was evaluated. Table 1 shows the obtained results. As you can see from the results,
In Comparative Example 2, since the amount of the rutile-type titanium oxide used was small, the effect of adding the rutile-type titanium oxide was not exhibited.
It is estimated that image deletion and toner adhesion have occurred.

Comparative Example 3 (1) Preparation of Toner In Comparative Example 3, toner particles a and rutile-type titanium oxide having a bulk specific gravity of 0.65 g / cm ³ (hereinafter, referred to as “titanium oxide”) were mixed in a Henschel mixer at the following ratio. Titanium oxide 2) and silica fine particles as a fluidizing agent are accommodated and mixed at a peripheral speed of 45 m / sec for 6 minutes, with respect to the total amount of toner particles.
A toner to which 11.3% by volume of rutile type titanium oxide was externally added was obtained. Toner particles a 100% by weight Silica 1.0% by weight Titanium oxide 2 4.5% by weight (2) Evaluation of toner In the same manner as in Example 1, the obtained toner was evaluated. Table 1 shows the obtained results. As you can see from the results,
In Comparative Example 3, since a large amount of rutile-type titanium oxide was used, it is presumed that the image density was reduced in a high-humidity environment and that fog occurred.

Comparative Example 4 (1) Preparation of Toner In Comparative Example 4, toner particles a and anatase-type titanium oxide having a bulk specific gravity of 0.37 g / cm ³ (hereinafter, referred to as “a”) were mixed in a Henschel mixer at the following ratio. Titanium oxide 3) and silica fine particles as a fluidizing agent are contained, and the peripheral speed is 45 m / sec.
Was mixed for 6 minutes under the conditions described above to obtain a toner to which 6.3% by volume of anatase type titanium oxide was externally added with respect to the total amount of the toner particles. Toner a 100% by weight Silica 1.0% by weight Titanium oxide 3 1.6% by weight (2) Evaluation of Toner The obtained toner was evaluated in the same manner as in Example 1. Table 1 shows the obtained results. As you can see from the results,
In Comparative Example 4, since anatase-type titanium oxide having a different crystal structure was used, it is presumed that the image density decreased in a high-humidity environment and fog occurred.

[0122]

[Table 1]

[0123]

According to the electrophotographic toner of the present invention, the rutile type titanium oxide is externally added so that the volume ratio is 5 to 10% by weight with respect to the total amount of the toner particles. 2. Description of the Related Art In an electrophotographic system using a chargeable organic photoconductor, it has become possible to prevent toner adhesion and image deletion that occur when the photoconductor is used for a long period of time.

Further, according to the image forming method using the electrophotographic toner of the present invention, in an electrophotographic system using a positively charged organic photoreceptor, toner adhesion which occurs when the photoreceptor is used for a long period of time is reduced. Image deletion can now be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an image forming apparatus to which the electrophotographic toner of the present invention is applied.

FIG. 2 is a diagram showing an example of the relationship between the volume ratio of rutile-type titanium oxide and toner adhesion and image density stability.

FIG. 3 is a diagram showing an example of the relationship between the volume ratio of rutile-type titanium oxide, image flowability, and fog.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Polygon mirror 5 Optical transmission mechanism 7 Top door 9 Photoconductor 10 Developing device 31 Toner container 32 Developing roller 33 Supply roller 39 Toner sensor 47 Display part

Claims (7)

[Claims] 1. An electrophotographic toner used for a positively charged organic photoreceptor, wherein the toner particles containing a binder resin and magnetic particles contain rutile-type titanium oxide as an external additive agent. An electrophotographic toner, characterized in that the amount of the rutile titanium oxide added is, by volume ratio, a value within the range of 5 to 10% by volume based on the total amount of the electrophotographic toner. 2. The electrophotographic toner according to claim 1, wherein the volume resistivity of the rutile type titanium oxide is set to a value within a range of 1 × 10 ⁴ to 1 × 10 ¹⁵ Ω · cm. 3. The electrophotographic toner according to claim 1, wherein the average particle diameter of the rutile type titanium oxide is set to a value within a range of 200 to less than 500 nm. 4. The surface of the rutile type titanium oxide is subjected to a hydrophobizing treatment using a titanium-based coupling agent and a silane-based coupling agent, or one of surface treatment agents. The toner for electrophotography according to any one of claims 1 to 3. 5. The toner for electrophotography according to claim 1, wherein the external additive contains silica fine particles. 6. The electrophotographic toner according to claim 1, wherein the binder resin is a styrene-based polymer. 7. A method for forming an image by an image forming apparatus using an electrophotographic toner, wherein the electrophotographic toner includes toner base particles containing a binder resin and magnetic particles, and a rutile type as an external addition process. An electrophotographic toner containing titanium oxide and having an addition amount of the rutile type titanium oxide in a volume ratio of 5 to 10% by volume with respect to the total amount of the electrophotographic toner is used. In addition, as the image forming apparatus, an image carrier using a positively charged organic photoreceptor, a developing unit for developing the image carrier in a non-contact manner, and a device for transferring a developed image formed on the image carrier. An image forming method, comprising: using an image forming apparatus having a transfer unit of (1) and a cleaning unit for collecting toner remaining on the image carrier.