JPH10104869A - Electrostatic charge developing toner and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain uniform electrification which prevents fog, to improve environmental dependence of picture quality, to improve durability of a developer and to prevent deposition on a photoreceptor or production of image defects by incorporating at least color particles and fine particles containing titanium oxide of specified pH and positive electrification hydrophobic silica. SOLUTION: This electrostatic charge image developing toner contains at least color particles and fine particles containing titanium oxide of pH=6 to 8 and positive electrification hydrophobic silica. When the pH of titanium oxide is higher than 8, alkali is excessive and positive electrification property increases, which makes as a result, uniform dispersion on the toner surface difficult. Thus, no effect is obtd. If the pH of titanium oxide is lower than 6, deposition on a positive electrification part which is present on the toner surface is largely caused, and as a result, uniform dispersion on the toner surface is decreased and no effect is obtd. The titanium oxide is preferably surface treated with an alkyltrialkoxy silane coupling agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrostatic image developing toner and an image forming method used for forming an image in a copying machine, a printer or the like.

[0002]

2. Description of the Related Art Conventionally, electrophotographic developers used to visualize an electrostatic latent image formed on an electrophotographic photosensitive layer include various resins such as carbon black and phthalocyanine blue. Using pigments or dyes as colorants,
After the melt-kneading, a one-component developer composed of the toner obtained by pulverization, or as a carrier, the average particle diameter is almost the same as the toner particle diameter, or glass beads up to 500 μm,
2. Description of the Related Art A two-component developer in which toner is mixed with particles of iron, nickel, ferrite, or the like, or those obtained by coating these with various resins, is generally known. In particular, the toner developing mechanism using a two-component developer causes the toner to generate a charge having a polarity opposite to that of the latent image due to frictional charging between the toner and the carrier, and develops and transfers the toner to a latent image portion on a photoconductor, thereby developing a visible image. It is a mechanism to make it.

[0003] However, with these developers alone,
Desired charge amount, charge speed, charge exchangeability, charge uniformity,
The image quality does not depend on the environment and the durability of the developer cannot be obtained.
For this reason, a charge controller is often added as an additive.

[0004] For example, in the case of negative charge, silica is used, but there is a problem that developability and charge exchange of toner are poor, toner of opposite polarity is easily generated, and fog is easily generated. It is also known that silica is used for the positively chargeable toner, but in this case, fogging by the opposite polarity toner is also likely to occur, which is more remarkable than in the case of the negatively chargeable toner. Moreover, in recent years, models using an organic photoreceptor (OPC) have become mainstream in copiers, and there is an increasing demand for improvements in positively chargeable toner.

In order to solve these problems, Japanese Patent Laid-Open Publication No.
No. 2-129866 discloses that titania particles having a particle size of 0.05 μm or less are used as an external additive together with silica fine particles, but fog prevention is not sufficient. Also, Japanese Patent Application Laid-Open No. 2-43564 discloses a particle size of 0.0
A technique for preventing fog caused by the opposite polarity toner by attaching silica fine particles having a particle size of 5 μm or less and titania particles having an average particle size of 0.1 μm or more to the surface of the toner particles is described. However, in the techniques of these patents, sufficient prevention of fog, uniformity of charging, environmental dependency of image quality, and durability of the developer have not been achieved, and further improvement is desired.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to improve the environment dependency of fog and image quality (image) by uniform charging, and to improve the developer. An object of the present invention is to provide a toner for developing an electrostatic image with improved durability. Still another object of the present invention is to provide a toner for developing an electrostatic charge image which is less likely to cause problems such as adhesion to a photoreceptor and image defects.

[0007]

The above object of the present invention has been attained by the following constitutions.

(1) At least colored particles and pH = 6
8. A toner for developing an electrostatic charge image, comprising: fine particles having titanium oxide and positively-chargeable hydrophobic silica.

(2) At least colored particles and water content =
0.3-2.0% by weight, specific resistance = 1500-10000
A toner for developing an electrostatic image, comprising fine particles having Ωcm of titanium oxide and positively-charged hydrophobic silica.

(3) a step of developing the electrostatic latent image formed on the photoreceptor with toner, a step of transferring the toner developed on the photoreceptor to a transfer body, a step of cleaning untransferred toner, 3. An image forming method including a step of returning a toner collected by a cleaning unit to a developing unit, wherein the toner is the electrostatic image developing toner according to 1 or 2 above.

The inventors of the present invention have conducted intensive studies and found that factors that cause the chargeability of the positively chargeable toner to change due to environmental changes include the strong positive chargeability of the positively chargeable silica itself, It is presumed that when the positive charging property itself held by is strong, the influence of moisture and the like in the environment is given, and as a result, the charging property fluctuates.

That is, it is presumed that a portion having positive chargeability is easily affected by moisture and the like, and as a result, leakage of charge from the portion is liable to occur.

It has been found that when positively chargeable silica is used, the problem of charge leakage and the like is improved by localizing the chargeability by uniformly attaching the silica to the toner surface. Further, in the present invention, by holding titanium oxide on the surface of the toner, the toner adheres to a positively charged portion on the toner surface, and by slightly lowering the high chargeability of the portion, the moisture of the portion is reduced. It is highly probable that the effects could be prevented. Furthermore, in combination with the positively chargeable silica, the combination of the positively chargeable silica and the above-described titanium oxide allows the silica and the titanium oxide to be uniformly blended on the toner surface, thereby reducing the influence of moisture and the like due to environmental fluctuations. It is estimated that was completed. Although the effect of the titanium oxide itself is not clear, by shifting the pH from neutral to weakly alkaline, it can be attached to the positively charged site on the toner surface,
It is further assumed that the dispersion of the positively chargeable silica itself can be made uniform.

By setting the water content in a specific range, fluctuations due to water adsorption can be prevented. In addition, by making the resistance relatively low, the amount of the positively chargeable silica and the positively chargeable charge control agent becomes excessive. It is presumed that stable chargeability was able to be prevented, and as a result, stable chargeability was maintained for a long period of time.

As described above, in the toner of the present invention, since the positively chargeable silica can be uniformly dispersed, the adhesion to the photosensitive member can be reduced, and the occurrence of abnormalities on the photosensitive member can be prevented. It is presumed that it is also made.

Hereinafter, the present invention will be described in detail.

The first aspect of the present invention is directed to a toner for developing an electrostatic charge image (hereinafter, referred to as a toner) containing at least colored particles and fine particles having a pH of 6 to 8 and titanium oxide and positively charged hydrophobic silica. Toner), and as a second aspect,
A toner for developing an electrostatic charge image, comprising at least colored particles and fine particles having a water content of 0.3 to 2.0% by weight, a specific resistance of 1500 to 10000 Ωcm, and titanium oxide and positively chargeable hydrophobic silica. is there. Further, as an aspect using the toner, a step of developing the electrostatic latent image formed on the photoconductor with the toner, a step of transferring the toner developed on the photoconductor to a transfer body, An image forming method includes a step of cleaning the transfer toner and a step of returning the toner collected by the cleaning unit to the developing unit.

The titanium oxide used as the fine particles constituting the toner according to the first embodiment of the present invention has a pH of 6 to 8.

The method for adjusting the pH of titanium oxide will be described below. The pH of titanium oxide can be adjusted by allowing sodium sulfate to be present on the surface. As a method of leaving sodium sulfate, a step of preparing titanium oxide, that is, treating titanium hydroxide extracted from iron ore with an alkaline solution to prepare titanium oxide, then performing calcination, and further pulverizing Adjust the particle size with. Thereafter, the resultant is dispersed in water, sodium hydroxide is added, and sulfuric acid is further added to adjust the pH, so that sodium sulfate can be present on the surface.

Further, as a method for measuring the pH of titanium oxide,
It is measured by the following method. That is, the sample (titanium oxide)
Is a method of measuring the pH of water after adding water and boiling. Specifically, water from which carbon dioxide has been removed (JIS-
5.0 g of a sample to be used for measurement using water free of carbon dioxide specified in 3.6 (3) of K 8001).
Then, 100 ml of the above water is added, and then the mixture is boiled for 5 minutes. After cooling, water containing no carbon dioxide was added to make up the water reduced by boiling, and the supernatant was separated and the pH was adjusted.
The pH value of the titanium oxide can be obtained by measuring.

When the pH of the titanium oxide is high, that is, higher than 8, the alkalinity becomes excessive and the positive charging property becomes high, and as a result, uniform dispersion on the toner surface becomes difficult, and the effect of the present invention is exhibited. Can not. or,
When the pH is low, that is, when the pH is lower than 6, adhesion to a positively charged portion existing on the toner surface becomes strong, and as a result, uniform dispersibility on the toner surface is reduced, and the effect of the present invention is achieved. Can not do.

The surface of the titanium oxide is preferably treated with the following alkyl trialkoxy silane coupling agent. That is, specific compounds include methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, and the like. As a method of surface-treating titanium oxide using these, the above-mentioned alkyl trialkoxysilane coupling agent is added to a solvent such as toluene, and then the titanium oxide is added.
It can be treated by stirring at a temperature of 5 to 100 ° C. for 10 minutes to 10 hours. The treatment amount is 1 to 10% by weight of the above-mentioned coupling agent with respect to titanium oxide. When the amount is small, the effect of the surface treatment cannot be exerted. When the amount is excessive, there arises a problem that the alkyltrialkoxysilane coupling agent is present in a free state.

The titanium oxide used as the fine particles constituting the toner according to the second embodiment of the present invention has a water content of 0.3 to 0.3.
It is characterized by 2.0% by weight and a specific resistance of 1500 to 10000 Ωcm. The pH of the titanium oxide of this embodiment is also preferably in the range of 6 to 8.

A method for measuring the water content of titanium oxide will be described. The moisture content is measured by the following method. That is,
It is carried out by Karl Fischer coulometric titration. Specifically, an automatic thermal vaporized moisture measurement system (AQS
-724 Hiranuma Sangyo Co., Ltd.) at 20 ° C / 50% RH
Titanium oxide left in the environment for 24 hours is made of glass 20m
Weigh accurately into a 1 l sample tube and then stopper with a Teflon-coated silicone rubber packing.
Two empty samples are measured simultaneously to compensate for the moisture present in the sealed environment. Measurement is heating temperature = 110
The measurement is performed for 1 minute under the condition of ° C./carrier gas (nitrogen) flow rate = 150 ml / min. Hydranal Aqualight RS (manufactured by Riedel de Heen) and Aqualite C (manufactured by Kanto Kagaku) were used as reagents.

If the water content of the titanium oxide is excessive, that is, if it is more than 2.0% by weight, a problem of charging leak due to the influence of water occurs, and stable charging can be ensured. On the other hand, when the water content is small, that is, when the
When the amount is less than 3% by weight, the effect of stably maintaining the positive chargeability is reduced, and as a result, uniform chargeability cannot be stabilized.

A method for measuring the specific resistance of titanium oxide will be described. The specific resistance is measured by a measuring method using a parallel electrode to which a voltage of 1 kV is applied after leaving the device for 24 hours or more under environmental conditions at normal temperature and normal humidity (23 ° C./50% RH). The specific resistance itself can be adjusted by treating the surface state of titanium oxide itself with a hydrophobizing agent. When the specific resistance is low, that is, when the specific resistance is lower than 1500 Ωcm, the charge is discharged, and the charge cannot be stably maintained. On the other hand, when the specific resistance is high, that is, 10
When it is higher than 000 Ωcm, although the charge is not released, the charge accumulation becomes large, and as a result, the charge amount cannot be stabilized for a long period of time.

The positively-chargeable hydrophobic silica used as the fine particles constituting the toner according to the first or second embodiment of the present invention will be described.

The positively chargeable hydrophobic silica that can be used in the present invention is a silica capable of having a charge of +10 μC / g or more with respect to iron powder. This silica is
A number average primary particle diameter of 5 to 500 nm hydrophilic silica is treated with the following nitrogen-containing coupling agent, amino-modified silicone oil, amino-modified silicon varnish, ammonium-modified polysiloxane, etc. to increase the chargeability. It can be positively charged. The evaluation of the amount of charge with the iron powder was 100 μm under environmental conditions of normal temperature and normal humidity (20 ° C./50% RH)
1% by weight of the aforementioned silica is added to the spherical iron powder of m
Then, using a glass sample tube, shaker YS-LD
Shake using (manufactured by Yayoi Co., Ltd.) for 20 minutes. Further, using a blow-off charge amount measuring device (manufactured by Toshiba),
The result calculated from the charge amount when blown for seconds is used.

Among the above, examples of nitrogen-containing coupling agents include, for example, 1) γ- (2-aminoethyl) aminopropyltrimethoxysilane, 2) γ- (2-aminoethyl) aminopropylmethyldimethoxysilane 3) γ-
Methacryloxypropyltrimethoxysilane, 4) N-
β- (N-vinylbenzylaminoethyl) γ-aminopropyltrimethoxysilane hydrochloride and the like.

As the ammonium-modified polysiloxane, specifically, a polysiloxane having an ammonium group includes, for example, dimethylpolysiloxane containing a structural unit represented by the general formula (1). It is represented by the structural formula of 2).

[0031]

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Here, R ₁ is a hydrogen atom, a hydroxy group,
An alkyl group, an aryl group, an alkoxy group, or

[0033]

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Wherein R ₂ is a bonding group (for example, an alkylene group, an arylene group, an aralkylene group, -NH-, -N
HCO- or a group obtained by combining these groups arbitrarily) or a mere bond, R _{3 to} R ₅ each represent a hydrogen atom, an alkyl group, or an aryl group, and X represents a halogen atom. Each of the groups represented by R _{1 to} R ₅ includes those having a substituent.

[0035]

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R ₆ and R ₇ each represent a hydrogen atom, a hydroxy group, an alkyl group, an aryl group or an alkoxy group, and these groups include those having a substituent. R ₁
To R ₅ and X have the same meanings as R _{1 to} R ₅ and X in formula (1). m and n each represent an integer of 1 or more. Examples of the group represented by Chemical Formula 2 include, but are not limited to, those represented by the following structural formulas.

[0037]

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[0038]

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[0039]

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As a method for obtaining a polysiloxane having an ammonium salt as a functional group, an organohalogenated silane having an ammonium salt as a functional group and, in particular, an organohalogenated silane having no ammonium base are used in a polymerization step. It can be obtained by a method of introducing by polymerization, a method of partially modifying a polysiloxane obtained by polymerization using an organohalogenated silane with an organic group having an ammonium salt as a functional group, or the like. An organoalkoxysilane may be used instead of the organohalogenated silane. In addition, some compounds can be obtained as commercial products.

Of these, the positively charged hydrophobic silica is preferably treated with ammonium-modified polysiloxane.

The colored particles constituting the toner of the present invention will be described.

The colored particles contain a binder resin, a coloring agent and other additives used as required, and have an average particle size of usually 1 to 30 μm, preferably a volume average particle size, preferably 1 to 30 μm. 5 to 20 μm. There is no particular limitation on the binder resin constituting the colored particles, and various conventionally known resins are used. For example, a styrene resin, an acrylic resin, a styrene / acrylic resin, a polyester resin, and the like can be given. The coloring agent constituting the colored particles is not particularly limited, and various conventionally known materials are used. Examples include carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, rose bengal, and the like. Other additives include a charge control agent, a low molecular weight polyolefin, and a fixability improving agent such as carnauba wax described below.

The toner of the present invention may contain a magnetic material and be used as a one-component magnetic toner, may be mixed with a carrier to be used as a two-component developer, or may be a non-magnetic toner used alone. Although it is conceivable that any of them can be suitably used, in the present invention, a two-component developer used by mixing with a carrier is preferable. When a magnetic toner is obtained, magnetic particles are contained as additives in the colored particles. As the magnetic particles, particles such as ferrite and magnetite having an average primary particle diameter of 0.1 to 2.0 μm are used. The amount of the magnetic particles added is 20 to 70% by weight of the colored particles.

As the carrier constituting the two-component developer, either an uncoated carrier composed of only magnetic material particles such as iron or ferrite, or a resin-coated carrier in which the surface of the magnetic material particles is coated with a resin or the like is used. You may. Examples of the resin-coated carrier include a fluorine-based resin-coated carrier, a styrene acrylic resin-coated carrier, a silicone resin-coated carrier, and the like, and preferably a silicone resin-coated carrier.

Examples of the charge control agent required to make the toner itself of the present invention positively chargeable are described below, but are not limited thereto.

Nigrosine dyes, quaternary ammonium salt compounds, triphenylmethane compounds and the like can be mentioned. Specific examples of the quaternary ammonium salt compound include compounds represented by the following general formula (3):

[0048]

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(R _{1 to} R ₄ each represent an alkyl group having 1 to 30 carbon atoms having an alkyl group, an alkenyl group, an aryl group, an aralkyl group and an aryl group, and A represents an anion. , R _{1 to} R ₃ are each a long-chain alkyl group or a long-chain alkenyl group having 8 to 22 carbon atoms, and R ₄ is an alkyl group or a benzyl group having 1 to 7 carbon atoms, more preferably R _{1 and} R ₂ are a long-chain alkyl group or a long-chain alkenyl group having 8 to 22 carbon atoms, and R _{3 to} R ₄ are an alkyl group or a benzyl group having 1 to 7 carbon atoms. Examples of the anion include a sulfone group, a molybdate group and a tungstate group.). Specific exemplary compounds are shown below.

1) (C₁₆H₃₃)_TwoN⁺(CH_Three)_Two1/4 @ Mo₈O₃₆｝^Four- 2) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH_Three)_Two1/4 @ Mo₈O₃₆｝^Four- 3) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH_TwoC₆H_Five)_Two1/4 @ Mo₈O₃₆｝^Four- 4) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(C_FourH₉)_Two1/4 @ Mo₈O₃₆｝^Four- 5) (C₁₄H₂₉)_TwoN⁺(CH_Three)_Two1/4 @ Mo₈O₃₆｝^Four- 6) (C₁₆H₃₃)_TwoN⁺(CH_Three)_Two1/10 ｛H_TwoW₁₂O₄₂｝_Ten ^- 7) (C₁₄H₂₉)_TwoN⁺(CH_Three)_Two1/10 ｛H_TwoW₁₂O₄₂｝_Ten ^- 8) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH_Three)_Two1/10 ｛H_TwoW₁₂O₄₂｝_Ten ^- 9) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(CH_TwoC₆H_Five)_Two1/10 ｛H_TwoW₁₂O₄₂｝ _Ten ^- 10) (C₁₆H₃₃) (C₁₄H₂₉) N⁺(C_FourH₉)_Two1/10 ｛H_TwoW₁₂O₄₂｝_Ten ^- In addition, as a triphenylmethane-based compound,
And the compounds represented.

[0051]

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R _{1 to} R ₆ represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. These may be different or the same. Specifically, the following can be mentioned.

[0053]

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Next, an image forming method using the toner according to the first and second aspects of the present invention will be described. FIG. 1 shows an image forming apparatus that can be used for carrying out the image forming method of the present invention.

Around a photoreceptor (latent image carrier) 10 having a positively charged organic photoconductive photosensitive layer, a band electrode 11, a developing mechanism 1
2, a transfer separation pole 13, a cleaning mechanism 14, and a discharge lamp 15 are arranged. The recording material from the paper feed mechanism 16 is transported by transport rollers 17a, 17b, and 17c.
After the toner image is transferred by the transfer / separation pole 13, the toner image is fixed by the fixing mechanism 18 to form an image. The toner remaining on the photoconductor 10 after the transfer is scraped off by the cleaning mechanism 14. The collected toner is recycled by the recycling mechanism 19 to the developing mechanism 12 again.
It is returned to and reused.

Hereinafter, each step will be described.

(Developing Step) A one-component developer or a two-component developer constituted by using a toner having resin fine particles fixed as an essential component is transported to a developing area by a developer transporting carrier, and the developer is used as a photosensitive member. Develop the above electrostatic latent image,
An unfixed toner image is formed. The developing method is not particularly limited, and a conventionally known method can be applied.
Specifically, the following method can be mentioned.

(1) Contact Magnetic Brush Development Method In this method, as shown in FIG.
A magnetic brush of developer having a higher height than a gap in the developing area is formed thereon, and the magnetic brush is conveyed to the developing area to rub the electrostatic latent image on the photoreceptor 10 while rubbing the toner in the magnetic brush. Is developed on the electrostatic latent image. Incidentally, 22 is a main stirring roller, 23 is an auxiliary stirring roller, 24 is a toner conveying screw, 25 is a spike regulating plate, and 26 is a doctor blade. Although the photoconductor 10 is not particularly limited,
Is preferred.

(2) Jumping Magnetic Brush Developing Method In this method, a magnetic brush of a developer having a smaller diameter than a gap in a developing area is formed on a developer carrying carrier, and the magnetic brush is transported to the developing area. By applying an oscillating electric field to the developing area, the toner in the magnetic brush flies and adheres to the electrostatic latent image for development.

(Transfer Step) The unfixed toner image on the photoconductor obtained by the development is transferred to a recording material. In this transfer step, either the electrostatic transfer method or the bias transfer method can be applied, but the electrostatic transfer method is particularly preferable. Specifically, for example, a transfer device that causes a DC corona discharge,
An unfixed toner image carried on the surface of the photoreceptor is transferred to the surface of the recording material by arranging the recording material so as to face the photoreceptor with a direct current corona discharge acting from the back side of the recording material. .

(Cleaning Step) The toner remaining on the photoreceptor after the transfer step is cleaned. The cleaning means is not particularly limited, but is preferably a cleaning device having a cleaning blade in contact with the surface of the photoreceptor. According to this cleaning device, the residual toner is scraped off and removed by rubbing the surface of the photoconductor with the cleaning blade.

(Recycling Step) The toner collected by cleaning is returned to the developing mechanism again by an appropriate recycling system and reused.

FIG. 3 is an explanatory diagram showing an example of the recycling system.

10 is a photoreceptor, 12 is a developing mechanism, 14 is a cleaning mechanism, 19 is a recycle mechanism, 31 is a magnetic brush mechanism, 32 is a toner receiving and distributing mechanism, 33 is a screw conveyor, 34 is a first screw, and 35 is a first screw. 2 screws. In this example, the first screw 34 and the second screw 35 supply the toner from the screw conveyor 33 to the toner receiving and distributing mechanism 32. That is, the first screw 34 and the second screw 34
Each of the screws 35 has a rotating shaft and a blade provided spirally along the rotating shaft. The first screw 34 causes the toner sent by the screw conveyor 33 to rotate along with the rotation of the rotating shaft. Are sequentially pushed up and sent to the second screw 35, where the toner is sequentially sent in the horizontal direction according to the same principle as the first screw 34, supplied to the toner receiving and distributing mechanism 32, and collected. The developed toner is again used for developing the electrostatic latent image on the photoconductor 10.

(Fixing Step) The recording material to which the unfixed toner image has been transferred in the transfer step is subjected to fixing processing by a heat fixing mechanism to form a fixed toner image on the recording material.

(Structure of Cleaning Blade) As the structure of the cleaning blade, any of the structures shown in FIG. 4 or FIG. 5 can be used. 4 or 5, the cleaning blade 14a is held by the holder 14b. The number of photosensitive members is 10. Angle holder 14b and the photoreceptor 10 is formed, both theta ₁ is 20 to 90 ° shown in FIG., Preferably 30 to 75 °. As a material constituting the cleaning blade itself, an elastic body such as silicon rubber or urethane rubber can be used. In this case, it is preferable that the rubber hardness is 30 to 90 °. The thickness is preferably 2 to 10 mm, and the length outside the holder is preferably 5 to 40 mm. The pressure contact force on the photoconductor 10 is preferably 5 to 30 gf / mm.

[0067]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

<< Production of Titanium Oxide >> Titanium oxide shown in Table 1 below was prepared. In addition, the number average primary particle diameter of titanium oxide was 20 nm as a result of measurement using a photograph enlarged 40000 times with a scanning electron microscope.

[0069]

[Table 1]

1 *: octyltrimethoxysilane, 2
*: Dodecyltrimethoxysilane, 3 *: hexyltrimethoxysilane Note) The surface treatment agent was treated at 5% by weight with respect to titanium oxide.

<< Production Example of Colored Particles >> To 100 parts of styrene acrylic resin, 8 parts of carbon black, 6 parts of low molecular weight polypropylene and 1 part of the exemplified compound 1) as a charge control agent were added, and preliminarily mixed, then melt-kneaded and pulverized. And classified to obtain colored particles having a volume average particle size of 8.2 μm. This is referred to as colored particles 1. Also, in the production example of colored particles,
Colored particles having a volume average particle size of 8.1 μm were obtained in the same manner except that the charge control agent was changed to the exemplified compound 3). This is referred to as colored particles 2. Colored particles having a volume average particle size of 8.0 μm were obtained in the same manner as in the colored particle production example, except that the charge control agent was changed to Exemplified compound 6). This is referred to as colored particles 3.

<< Example of Toner Production >> Positively chargeable silica treated with 0.6% by weight of titanium oxide 1 and ammonium-modified polysiloxane with respect to the above colored particles 1 (number average primary particle diameter = 12 nm / charge with iron powder) Amount = 90 μC / g) to 0.8
% By weight and mixed with a Henschel mixer (volume = 10 liters) at a peripheral speed of 40 m / min for 10 minutes to obtain a toner. This is referred to as toner 1. A toner was obtained in the same manner as in the toner production example except that titanium oxide 1 was changed to titanium oxide 2. This is referred to as toner 2. A toner was obtained in the same manner as in the toner production example except that the colored particles 1 were changed to the colored particles 2 and the titanium oxide 1 was changed to the titanium oxide 3. This is referred to as toner 3. In the toner production example, the toner of the present invention was obtained in the same manner except that the colored particles 1 were changed to the colored particles 3, the titanium oxide 1 was changed to the titanium oxide 4, and the addition amount was changed to 0.4% by weight. . This is referred to as toner 4. A toner was obtained in the same manner as in the toner production example except that titanium oxide 1 was changed to titanium oxide 5. This is referred to as toner 5. A toner was obtained in the same manner as in the toner production example except that titanium oxide 1 was changed to titanium oxide 6. This is referred to as toner 6.

<< Preparation of Developer >> A developer was prepared using the toner prepared above. As the carrier, a lithium ferrite carrier having a volume average particle diameter of 61 μm coated with a silicone resin was used. The developer was prepared by mixing the toner and the carrier so that the toner concentration became 5%. The developers corresponding to the toners 1 to 6 are referred to as developers 1 to 6.

The obtained developers 1 to 6 are applied to a copying machine 3135.
(Manufactured by Konica Corporation) and the following experiment was conducted.
The copying machine was modified to a recycling system of the type shown in FIG. 3, and a laminated organic photoreceptor was used as the photoreceptor. The cleaning conditions were as shown in FIG. forming an angle theta ₁ is is 22 °, as the material constituting the cleaning blade itself, using a urethane rubber. Urethane rubber has a rubber hardness of 65 °
And the thickness is 2 mm and the length outside the holder is 8 mm
And The pressing force against the photosensitive member is 15 gf / mm.

(Evaluation) Evaluation items were high temperature and high humidity (33 ° C. /
Under an environmental condition of 80% RH), 100,000 sheets of a document having a pixel ratio of 5% were continuously printed, and the image density, the fogging state, and the presence / absence of image defects due to scratches on the photoreceptor were evaluated. . An image defect was determined as having a defect when a black spot of 0.2 mmφ or more occurred on the image. The image density was indicated by absolute reflection density using RD-918 manufactured by Macbeth Co., and the fog density was indicated by relative reflection density when the density of the support (paper) was set to "0".

The results are shown in Table 2 below.

[0077]

[Table 2]

As is clear from the results in Table 2, when the pH was 6
Developers 1 to 4 using titanium oxide of No. 8 to No. 8 have substantially no change in the image density and fog density in the initial stage and after 100,000 sheets, and the toner on the photoreceptor after processing 100,000 sheets. It has good durability such as no adhesion and defects,
It can be seen that it has excellent overall performance. Further, the water content = 0.3 to 2.0% by weight and the specific resistance = 1500 to 10
It can be seen that developers 1-4 using titanium oxide of 000 Ωcm also have excellent performance. However, after the load conditions of processing 100,000 sheets of the developers 5 and 6 outside these ranges, the image density and the fog density are not sufficient, and the image defects at that time may be considerable. I understand.

[0079]

According to the present invention, it is possible to provide a toner for developing an electrostatic image in which the charge is made uniform to improve the fog and the environment dependency of the image and the durability of the developer is improved. It has the effect. Also, it is possible to provide a toner for developing an electrostatic charge image which is less likely to cause problems such as adhesion to a photoreceptor and image defects.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an image forming apparatus.

FIG. 2 is a diagram showing a contact magnetic brush development method.

FIG. 3 is a diagram illustrating an example of a recycling system.

FIG. 4 is a diagram illustrating a configuration of a cleaning blade.

FIG. 5 is a diagram illustrating a configuration of a cleaning blade.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor 11 band electrode 12 developing mechanism 13 transfer separation electrode 14 cleaning mechanism 14 a cleaning blade 14 b holder 15 static elimination lamp 16 paper feed mechanism 17 a, b, c transport roller 18 fixing mechanism 19 recycling mechanism 21 developer transport carrier 22 main stirring roller Reference Signs List 23 auxiliary stirring roller 24 toner transport screw 25 spike regulating plate 26 doctor blade 31 magnetic brush mechanism 32 toner receiving and distributing mechanism 33 screw conveyor 34 first screw 35 second screw

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 9/08 371 375 (72) Inventor Yuji Marukawa 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation

Claims (8)

[Claims] 1. A toner for developing an electrostatic image, comprising at least colored particles and fine particles having a pH of 6 to 8 and having titanium oxide and positively charged hydrophobic silica. 2. The toner according to claim 1, wherein said titanium oxide is surface-treated with an alkyl trialkoxysilane. 3. The toner for developing an electrostatic image according to claim 1, further comprising a charge control agent for positive charge. 4. At least colored particles and water content = 0.3
~ 2.0% by weight, specific resistance = 1500-10000Ωcm
And a fine particle having positively charged hydrophobic silica. 5. The toner for developing an electrostatic image according to claim 4, wherein the pH of the titanium oxide is 6 to 8. 6. The electrostatic image developing toner according to claim 4, further comprising a charge control agent for positive charge. 7. The electrostatic image developing toner according to claim 1, wherein the positively charged hydrophobic silica is treated with ammonium-modified polysiloxane. 8. A step of developing the electrostatic latent image formed on the photoconductor with toner, a step of transferring the toner developed on the photoconductor to a transfer body, a step of cleaning untransferred toner, and a cleaning step. 8. An image forming method comprising: a step of returning the toner collected in the image forming section to the developing section, wherein the toner is the toner for developing an electrostatic image according to any one of claims 1 to 7. Forming method.