JP2003015349A - Electrostatic latent image developing toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing toner which prevents the occurrence of BS(black spots) in an intermittent mode, can provide fine-grained good images free from BS, fog and image streaks over a long period of time and has excellent cleanability to a photoreceptor and anti- contamination properties (refreshability) to a carrier and a charge imparting member. SOLUTION: In the electrostatic latent image developing toner obtained by mixing toner particles containing a colorant and a binder resin with at least one additive, the additive is composite particles of strontium titanate and strontium carbonate, the weight ratio between the strontium titanate and strontium carbonate in the composite particles is in the range of (98:2) to (80:20) and the number average particle diameter of the composite particles is 80 to 800 nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic latent image used in electrophotography, electrostatic printing and the like.

[0002]

2. Description of the Related Art In recent years, with respect to digitization and colorization of image forming apparatuses such as copying machines and printers, a toner is required to have high fluidity. Therefore, as a fluidizing agent, inorganic particles such as fine particle silica and fine particle titania are used. Are generally added to the toner. The image forming apparatus includes a two-component developing method in which the toner is charged by mixing and friction between the toner and the carrier, and a one-component charging method in which the toner is charged by passing through the gap between the regulating member such as a regulating blade and the developing roller. A developing method is known.

When the toner is used in any of the two-component developing system and the one-component developing system, the addition amount of the fluidizing agent becomes large in order to secure high fluidity of the toner. Since the fluidizing agent is easily peeled off from the toner, various problems have occurred due to deterioration of the developer. That is, the fluidizing agent that has peeled off migrates to the carrier, the regulating blade, the developing roller and the like and contaminates the toner, so that the toner is not properly charged and fogging occurs on the image. In addition, the fluidizing agent that has peeled off passes through the cleaner section that has a blade cleaning mechanism for cleaning the surface of the photoconductor and is rubbed against the surface of the photoconductor, fixing to the minute scratches on the surface of the photoconductor, etc. As a result, a toner component containing a fluidizing agent accumulates and contaminates the surface of the photoconductor, resulting in an image defect called a black spot (BS) on the image.

In order to solve such problems, various improvement measures have been conventionally proposed. For example, Japanese Patent Laid-Open No. 10-107
Japanese Patent Laid-Open No. 70-70 proposes a technique for preventing BS during cleaning of the photoconductor by adding strontium titanate particles having a number average particle size of 80 to 800 nm. Further, for example, in JP-A-2000-206730, particularly by adding hydrophobic strontium titanate particles completely removed strontium carbonate present as impurities of strontium titanate particles, while improving the chargeability of the toner, Techniques have been proposed for preventing BS during cleaning of the photoconductor.

However, according to the above technique, the BS on the photoconductor when the same image is continuously copied or printed.
However, there is a new problem that BS cannot be completely prevented when images are repeatedly formed for a long time in an intermittent mode in which a different image is formed for each copy or printing.

Therefore, when the particle size of the strontium titanate particles was increased, the BS improving effect in the intermittent mode was slightly recognized, but it was insufficient, and the surface of the photoreceptor was scratched.

On the other hand, in the one-component developing method, since the toner is regulated and charged as described above, the toner is easily fixed to the regulation blade due to the regulation stress, so that the toner on the developing roller can be well conditioned. Formation of a thin toner layer is hindered, and as a result, noise such as image streaks occurs on the image. For the toner of the one-component developing system, the above-mentioned JP-A-10-10770 and 2000-2
Even if the strontium titanate particles described in JP-A-06730 were added, it was difficult to sufficiently solve the above-mentioned problems.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and prevents the occurrence of BS in the intermittent mode, and provides a good image with fine texture without BS, fog, or image streaks for a long period of time. It is an object of the present invention to provide a toner for developing an electrostatic latent image, which is excellent in cleaning property for a photoreceptor and stain resistance (refresh property) for a carrier and a charging member (regulating blade, developing roller, etc.).

[0009]

The present invention provides at least toner particles containing a colorant and a binder resin.
In the electrostatic latent image developing toner obtained by mixing and adding one kind of external additive, the external additive is a composite particle of strontium titanate and strontium carbonate, and the weight ratio of strontium titanate and strontium carbonate in the composite particle is In the range of 98: 2 to 80:20, and the composite particles have a number average particle diameter of 80 to 800 nm.

In the present invention, when the composite particles of strontium titanate and strontium carbonate are used, the abrasiveness of the particles is remarkably improved, so that the cleaning property of the toner on the photoreceptor and the stain resistance of the carrier and the charge imparting member are improved. However, it was found that the life was significantly improved compared with the conventional one, and the lifespan of both the one-component developer and the two-component developer was significantly improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The toner for developing an electrostatic latent image of the present invention comprises toner particles mixed with composite particles of strontium titanate and strontium carbonate. The composite particles of strontium titanate and strontium carbonate used in the present invention are particles obtained by a solid phase reaction between titanium oxide and an excess amount of strontium carbonate.

The solid-state reaction between titanium oxide and strontium carbonate is a known reaction adopted in a general method for producing strontium titanate particles, and the following chemical reaction formula:

[Equation 1] Can be represented by After such solid phase reaction, strontium titanate particles are obtained by sintering the reaction product. In a general method for producing strontium titanate particles, strontium carbonate is usually used in an equimolar amount with respect to titanium oxide, and when the number average particle size is less than 1 μm, an attempt is made to obtain strontium titanate particles at a sintering temperature. It is known that a small amount of strontium carbonate remains in the strontium titanate particles having a relatively small particle size because it is necessary to set the temperature to a relatively low temperature. For example, in JP-A-2000-206730, strontium carbonate is treated as an impurity in strontium titanate particles, and industrially produced strontium titanate particles have a reduced surface activity due to the presence of very small amounts of strontium carbonate. However, it is proposed to remove the remaining strontium carbonate because the surface treatment for uniform hydrophobicity is hindered.

In the method for producing composite particles of strontium titanate and strontium carbonate according to the present invention (hereinafter simply referred to as "composite particles"), the amount of strontium carbonate used in the above solid-phase reaction is set to be in excess of that of titanium oxide. The weight ratio of strontium titanate and strontium carbonate in the obtained composite particles is set to 98:
The residual strontium carbonate amount is intentionally increased so as to be in the range of 2 to 80:20, preferably 95: 5 to 85:15. As described above, the strontium titanate particles (composite particles) in which the residual strontium carbonate amount is positively increased have significantly improved abrasivity, and the toner using the particles as an external additive has a cleaning property for a photoreceptor and a carrier and Since the stain resistance (refreshing property) to the charge imparting member is improved, the surface of the photoconductor, the carrier and the charge imparting member can be used in both the two-component developer and the one-component developer. Pollution can be effectively prevented. As a result, it is possible to prevent the occurrence of BS in the intermittent mode, and it is possible to provide a fine and fine image without BS, fog, and image streaks for a long period of time. In the present specification, the intermittent mode is a method of using an apparatus that forms a different image for each copy or print, and compared to the continuous mode for continuously copying or printing the same image, BS or the like. It can be said that this is a harsh device usage method in which image noise easily occurs.

The reason why the composite particles of strontium titanate and strontium carbonate are superior to the conventional strontium titanate particles in terms of abrasiveness and can provide a good image for a long period of time is not clear in detail, but as shown below. It is considered that this is due to the characteristic difference between strontium titanate and strontium carbonate.

1. Crystal system: Strontium titanate is a colorless cubic crystal, and strontium carbonate is a colorless orthorhombic crystal. Thus, the composite particles of the present invention in which different crystal systems are mixed in a predetermined ratio in one particle have appropriate mechanical properties such as hardness, etc. as an abrasive for the photoreceptor, carrier and charging member. It is believed that it is possible to provide a good image for a long period of time, and as a result, can exhibit more excellent abrasivity. 2. Electrical properties: Strontium titanate is insoluble in water and does not show ionic properties. On the other hand, strontium carbonate is slightly soluble in water and shows alkalinity. Due to such difference in ionic properties, it is considered that the composite particles can appropriately refresh the surface of the carrier or the charge-imparting member electrically (particularly, on the positively chargeable side) while polishing the surface. Due to that, it is considered that a good image can be provided for a long time.

When the content ratio of strontium carbonate in the composite particles is less than 2% by weight, the polishing performance becomes small, which is not desirable, and when the content ratio exceeds 20% by weight, the charge amount is reduced particularly in a high temperature and high humidity environment. It becomes large and is not desirable.

The amount of strontium carbonate in the composite particles can be arbitrarily controlled by increasing or decreasing the excess amount of strontium carbonate as a raw material in the solid phase reaction of titanium oxide and strontium carbonate. When determining the amounts of titanium oxide and strontium carbonate to be charged, refer to Table 1 below, which shows the theoretical ratio between the content (weight%) of strontium carbonate in the composite particles and the amounts of titanium oxide and strontium carbonate to be charged. be able to.

[0018]

[Table 1] For example, to obtain composite particles having a strontium carbonate content of about 10% by weight, 1.14 mol of strontium carbonate may be used with respect to 1 mol of titanium oxide.

The amount of strontium carbonate in the composite particles can be measured by eluting strontium carbonate in a strong acid solution such as hydrochloric acid and measuring the amount of elution. In order to confirm that the particles are composite particles of strontium titanate and strontium carbonate, it is possible to confirm the existence of peaks specific to strontium titanate and strontium carbonate by qualitative analysis by X-ray diffraction.

The number average particle size of the composite particles used in the present invention is 80 to 800 nm, preferably 100 to 750 nm, more preferably 200 to 700 nm. If the number average particle size is less than 80 nm, the polishing effect of the particles in the cleaner portion of the photoconductor is insufficient. On the other hand, if the number average particle size exceeds 800 nm, the photopolishing effect is too strong to cause photoconductor scratches.

In the present specification, the number average particle size is synonymous with the average primary particle size and means the average particle size of non-aggregated particles, and the number particle size is synonymous with the primary particle size. And the particle size of the particles that have not been aggregated. The number average particle diameter of the particles was obtained by observing the particles with a transmission electron microscope and measuring and averaging the major axis of 100 particles. Magnification at the time of measurement
The particle size was 40,000 to 60,000 times, and particles of 0.5 nm or larger were targeted.

In producing the composite particles, specifically, a predetermined amount of strontium carbonate is added to titanium oxide, and the mixture is thoroughly ground and mixed in a water-based wet type using a mixer such as a ball mill, and then washed with water, Dry at 100-150 ° C for 1-24 hours. Then 750 to 1050 ℃, preferably 800 to 1000 ℃
Sintered with, and pulverized with a mixer such as a jet mill.

Titanium oxide used as a raw material
There is no particular limitation as long as it is a substance having a TiO ₂ composition, and examples thereof include a metatitanic acid slurry (undried titanium oxide) obtained by a sulfuric acid method, and titanium oxide powder. Among these, the metatitanic acid slurry obtained by the sulfuric acid method is preferably used. This is because it is excellent in uniform dispersibility in an aqueous wet system. The particle size of the titanium oxide is preferably 20 to 50 nm in terms of average primary particle size.

Further, as strontium carbonate, SrCO ₃
There is no particular limitation as long as it is a substance having a composition, and any commercially available substance is preferably used. 100 in average primary particle size
Those of ˜500 nm are preferred.

Regarding the sintering temperature, if the temperature is too high, the particle size of the particles obtained becomes too large, while if it is too low, the amount of unreacted components increases and it becomes difficult to produce stable particles.

The amount of the composite particles added to the toner particles as described above is not particularly limited, but the effect of the present invention, that is, the effect of improving the cleaning property with respect to the photoconductor and the stain resistance with respect to the carrier and the charging member is effectively obtained. From the viewpoint, the range of 0.5 to 4% by weight, preferably 0.8 to 3% by weight is desirable. The addition amount may be appropriately adjusted within the above range while considering the balance between the polishing property (cleaning property and stain resistance) and the charging level.

In the present invention, it does not prevent the composite particles from being surface-treated with a hydrophobizing agent which will be described later.

In the toner of the present invention, it is preferable that not only the above composite particles but also a fluidizing agent is mixed and added to the toner particles as an external additive. The fluidizing agent is an additive that can impart fluidity to the toner. As the fluidizing agent, known inorganic fine particles different from the above-mentioned composite particles can be used, and preferably at least one kind of inorganic fine particles selected from the group of silica, titania and alumina is used. The number average particle size of the fluidizing agent is 5 to 40 nm, preferably 5 to 40 nm.
A range of 30 nm is desirable. If the particle size is smaller than 5 nm, it is not preferable because the stress in the one-component development facilitates the embedding in the toner particles.
When it is larger than nm, the effect of giving fluidity to the toner is drastically reduced, which is not preferable.

From the viewpoint of easily securing the fluidity of the toner and effectively preventing carrier deterioration during two-component development and BS generation during cleaning of the photoconductor, the amount of the fluidizing agent added to the toner particles. Is preferably about 0.3 to 4% by weight, and may be appropriately adjusted according to the size of the toner particles. For example, when small toner particles having a size of 3 to 7 μm are used for the purpose of achieving high image quality, the amount of the fluidizing agent added is preferably 0.8 to 4% by weight.

The fluidizing agent is preferably surface-treated with a hydrophobizing agent in order to impart hydrophobicity thereto. As the hydrophobizing agent, a silane coupling agent, a titanate coupling agent, silicone oil, silicone varnish or the like can be used. Examples of the silane coupling agent include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxysilane, and isobutyl. Trimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n
-Butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltrimethoxysilane,
Vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, etc. can be used,
As the silicone oil, for example, dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenylpolysiloxane, etc. can be used.

In the present invention, in order to improve the transferability of the toner image from the photoconductor to the recording medium, the number average particle diameter is 30 to 100n.
m inorganic fine particles, preferably the particle size is 10 nm or more larger than the particle size of the fluidizing agent, and 100 nm or less of the inorganic fine particles,
Further, they may be mixed and added to the toner particles. As the inorganic fine particles added for improving the transferability, the same inorganic fine particles as the fluidizing agent can be used. The addition amount of such inorganic fine particles is preferably 0.2 to 1.0% by weight with respect to the toner particles, and the total addition amount of the fluidizing agent is preferably 4% by weight or less.

The toner particles in the toner for developing an electrostatic latent image of the present invention contain at least a binder resin and a colorant. As the binder resin used in the present invention, any known synthetic resin and natural resin can be used. Specifically, styrene resin,
Acrylic resin, olefin resin, diene resin, polyester resin, polyamide resin, epoxy resin, silicone resin, phenol resin, petroleum resin,
Examples include synthetic resins such as urethane resins and natural resins. When used as a full-color toner, polyester resin and styrene-acrylic resin are preferable.

Known pigments and dyes are used as the colorant. For example, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, DuPont oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxalate, lamp black, rose bengal, CI pigment red 48: 1. , CI Pigment Red 122, CI Pigment Red 57: 1, CI
Pigment Red 184, CI Pigment Yellow 9
7, CI Pigment Yellow 12, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Solvent Yellow 162, CI Pigment Blue 15: 1, CI
Pigment Yellow 180, CI Pigment Blue 1
5: 3 etc. can be mentioned. When used as a magnetic toner, a part or all of the colorant may be replaced with a magnetic material. Examples of such magnetic materials include magnetite, ferrite, iron powder, nickel and the like.

In the toner particles of the present invention, additives such as a charge control agent and a release agent may be added to the binder resin depending on the purpose. For example, as the charge control agent, a fluorine-based surfactant, a salicylic acid metal complex, a metal-containing dye such as an azo metal compound, a polymer acid such as a copolymer containing maleic acid as a monomer component, a quaternary Ammonium salt,
An azine dye such as nigrosine, carbon black or the like can be added. The release agent is not particularly limited, but paraffins having 8 or more carbon atoms, olefins and the like are preferable, and for example, paraffin wax, paraffin latex, microcrystalline wax, low molecular weight polypropylene, low molecular weight polyethylene and the like can be used. .

The toner particles of the present invention can be produced by any known method, but in particular, the method of kneading and pulverizing is generally used. That is, generally used is a method in which a binder resin, a colorant, and other additives are melt-kneaded using a kneader, cooled, pulverized, and classified.
The toner particles thus obtained have a volume average particle size of 3
It is preferable to set in the range of up to 12 μm. If it is smaller than this range, the fluidity is likely to be deteriorated and fogging is likely to occur, and if it is larger than this range, the resolution is deteriorated and a high quality image cannot be obtained. It is more preferable that the toner particles satisfying the recent demand for high image quality have a particle size in the range of 3 to 7 μm, particularly 4 to 6 μm.

The toner of the present invention comprising the above toner particles and the external additive (composite particles) has a structure in which the composite particles adhere to the surface of the toner particles. When a fluidizing agent is further used as the external additive, the toner of the present invention preferably has a structure in which the fluidizing agent is attached to the surface of the toner particles and further the composite particles are attached thereon. With such a structure, the effect of the present invention, that is, the effect of improving the cleaning property with respect to the photoconductor and the stain resistance (refresh property) with respect to the carrier and the charging member is effectively obtained. In the present invention, the fluidizing agent does not prevent the fluidizing agent from adhering to the surface of the composite particles or the fluidizing agent and / or a part of the composite particles from adhering to the surface of the toner particles. Adhesion means movably attached, and sticking means attached while being fixed.

In producing the toner of the present invention, the method of mixing the toner particles with the external additive (composite particles, fluidizing agent, etc.) is not particularly limited, and known methods can be used, for example, A known mixer such as a Henschel mixer may be used. At the time of mixing, particularly when the composite particles and the fluidizing agent are used as the external additives, the toner particles and all the external additives may be charged into the mixer at the same time and mixed, but the fluidizing agent is not formed on the surface of the toner particles. From the viewpoint of effectively obtaining a toner having a structure in which the toner adheres and further the composite particles adhere thereon, it is preferable to add and mix the external additive to the toner particles in two or more stages. At this time, the composite particles are added and mixed at a later stage as much as possible. For example, it is preferable that the fluidizing agent is first added to the toner particles and mixed, and then the composite particles are added and further mixed.

The toner of the present invention can be applied to either a two-component developer used with a carrier or a one-component developer without a carrier. In particular, it is preferably used as a full-color toner. In this case, it is used as a two-component developer or a non-magnetic toner for a one-component developing device in which a toner regulating member (blade) is arranged in pressure contact with a toner carrier (developing roller). It is preferably used as a one-component developer.

[0039]

EXAMPLES The present invention will be specifically described below with reference to examples. <Manufacture of toner particles> (Manufacture of polyester resin) A 2-liter four-necked flask was equipped with a reflux condenser, a water separator, a nitrogen gas inlet tube, a thermometer, and a stirrer. Propylene (2,2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2,
0) -2,2-bis (4-hydroxyphenyl) propane,
Fumaric acid and terephthalic acid were charged together with a polymerization initiator (dibutyltin oxide) in a molar ratio of 9: 2: 5: 4, heated and stirred while introducing nitrogen into the flask to react, Average molecular weight Mn is 4500, weight average molecular weight
The ratio Mw / Mn of Mw to the number average molecular weight Mn is 3.0, and the glass transition point is
A low molecular weight polyester resin having a softening point of 59.5 ° C. and 97.6 ° C. was obtained.

Further, polyoxypropylene (2,2) -2,2
-Bis (4-hydroxyphenyl) propane, polyoxyethylene (2,0) -2,2-bis (4-hydroxyphenyl) propane, terephthalic acid and trimellitic acid,
The number average molecular weight Mn is 5400, the weight average molecular weight Mw and the number average molecular weight are the same except that the molar ratio is 7: 3: 7: 2.
Ratio of Mn to Mw / Mn is 14.7, glass transition point is 66 ℃, softening point is 1
A high molecular weight polyester resin having a temperature of 19.9 ° C. was obtained. A mixture of the obtained low molecular weight polyester resin and high molecular weight polyester resin at a ratio of 8: 2 (weight ratio) was used as a polyester resin used as a binder resin.

(Pigment masterbatch) 70 parts by weight of the above polyester resin 30 parts by weight of magenta pigment (CI Pigment Red 184) A mixture having the above composition was charged and kneaded in a pressure kneader. The obtained kneaded product was cooled and then ground with a feather mill to obtain a pigment masterbatch.

(Toner Particles 1) 93 parts by weight of the polyester resin 10 parts by weight of the pigment master batch 2 parts by weight of polypropylene wax (TS-200, manufactured by Sanyo Kasei Co., Ltd.) Materials having the above composition are mixed with a Henschel mixer. After that, the mixture was kneaded with a vent biaxial kneader. The obtained kneaded product was cooled, coarsely pulverized with a feather mill, finely pulverized with a jet mill, and further classified to obtain toner particles having a volume average particle diameter of 5.5 μm.

(Toner particles 2) 93 parts by weight of the polyester resin 10 parts by weight of the pigment master batch The materials having the above composition were mixed by a Henschel mixer, and then the mixture was kneaded by a vent biaxial kneading device. The obtained kneaded product was cooled, coarsely pulverized with a feather mill, finely pulverized with a jet mill, and further classified to obtain toner particles having a volume average particle diameter of 5.5 μm.

<Production of Carrier> (Carrier 1) 100 parts by weight of methyl ethyl ketone was charged into a flask having a capacity of 500 ml equipped with a stirrer, a condenser, a thermometer, a nitrogen introducing tube, and a dropping device. 80 ° C under nitrogen atmosphere
Then, 36.7 parts by weight of methyl methacrylate, 5.1 parts by weight of 2-hydroxyethyl methacrylate, 58.2 parts by weight of 3-methacryloxypropyltris (trimethylsiloxy) silane and 1 part by weight of 1,1′-azobis (cyclohexane-1-carbonitrile), The solution obtained by dissolving in 100 parts by weight of methyl ethyl ketone was dropped into the reactor over 2 hours and aged for 5 hours. Isophorone diisocyanate / trimethylolpropane adduct (IPDI / TMP system: NCO% = 6.1%) was adjusted as a cross-linking agent to the obtained resin so that the OH / NCO molar ratio was 1/1, and then methyl ethyl ketone was used. A coating resin solution having a solid ratio of 3% by weight was prepared by dilution.

As the core material, fired ferrite powder F-300 (volume average particle size: 50 μm, manufactured by Powder Tech Co., Ltd.) was used, and the above coating resin solution was added to a spira coater (so that the coating resin amount to the core material was 1.5% by weight). It was applied and dried by Okada Seiko. The obtained carrier was left in a hot air circulation type oven at 160 ° C. for 1 hour for firing. After cooling, the ferrite powder bulk was crushed using a sieve shaker equipped with screen meshes of 106 μm and 75 μm openings to obtain a resin-coated carrier 1.

<Production of Composite Particles> (Composite particle A: 1% strontium carbonate product) A metatitanic acid slurry (average primary particle diameter of TiO ₂ particles of 20 nm) obtained by the sulfuric acid method had a molar ratio of 1.01 to TiO _2. Add strontium carbonate (average primary particle size 100nm) so that it doubles, thoroughly grind and mix with a ball mill in an aqueous wet system, wash with water, dry for 1 day at 110 ° C, and sinter at 900 ° C. Let
When pulverized with a jet mill, composite particles A of strontium titanate and strontium carbonate having a number average particle diameter of 300 nm were obtained. Qualitative analysis of the resulting composite particles A by X-ray diffraction, the peaks of strontium titanate and strontium carbonate were detected, and the strontium carbonate weight loss due to the elution of hydrochloric acid was measured to show that the composite particles contained 0.6% by weight of strontium carbonate. Was recognized.

(Composite particle B: 3% strontium carbonate product)
Composite particle B was produced in the same manner as the above composite particle A except that strontium carbonate was added so that the molar ratio to TiO ₂ was 1.05 times. The content of strontium carbonate in the composite particles was 2.6% by weight.

(Composite particles C1: 6% strontium carbonate)
(Product) Composite particles C1 were produced in the same manner as the above-mentioned production of composite particles A, except that strontium carbonate was added so that the molar ratio to TiO ₂ was 1.08. The content of strontium carbonate in the composite particles was 5.4% by weight.

(Composite particle C2: strontium carbonate 6%
Product) Anatase type titanium oxide with an average primary particle size of 40 nm, Ti
Strontium carbonate (average primary particle size 100 nm) was added so that the molar ratio to O ₂ was 1.08, and the mixture was thoroughly ground and mixed using a ball mill in an aqueous wet system, then washed with water, and 110
After drying at ℃ for 1 day, it was sintered at 1000 ℃ and pulverized by a jet mill to obtain composite particles C2 of strontium titanate and strontium carbonate having a number average particle diameter of 700 nm. Qualitative analysis of the obtained composite C2 by X-ray diffraction, the peaks of strontium titanate and strontium carbonate were detected, and the strontium carbonate weight loss was measured by elution of hydrochloric acid, and it was found that the composite particles contained 5.8% by weight of strontium carbonate. Admitted.

(Composite Particle D: Strontium Carbonate 10%
(Product) A composite particle D was produced in the same manner as the production of the composite particle A except that strontium carbonate was added so that the molar ratio to TiO ₂ was 1.14 times. The content of strontium carbonate in the composite particles was 8.9% by weight.

(Composite particle E: Strontium carbonate 15%
(Product) Composite particle E was produced in the same manner as the above-mentioned composite particle A except that strontium carbonate was added so that the molar ratio to TiO ₂ was 1.22 times. The content of strontium carbonate in the composite particles was 13.2% by weight.

(Composite particle F: strontium carbonate 25%
Goods) Composite particles F were manufactured in the same manner as the above-described preparation of composite particles A, except that strontium carbonate was added so that the molar ratio to TiO ₂ was 1.41 times. The content of strontium carbonate in the composite particles was 24.2% by weight.

(Strontium titanate particles 1: Strontium carbonate 0% product) The above composite particles A were stirred in hydrochloric acid,
Elute all residual strontium carbonate, wash with water, dry and crush with a jet mill to obtain a number average particle size of 300n
m strontium titanate particles 1 were obtained. When the particles were analyzed by an X-ray diffractometer, no strontium carbonate was detected and it was confirmed that the particles were complete strontium titanate particles.

(Strontium titanate particles 2: 0% strontium carbonate product) Strontium carbonate was added to anatase type titanium oxide having an average primary particle size of 40 nm so that the molar ratio to TiO ₂ was 1.00 times, and the mixture was placed in a water-based wet system. After thoroughly grinding and mixing with a ball mill, wash with water. The cake thus obtained was dried at 110 ° C. for 1 day, calcined and sintered at 1100 ° C., and further pulverized by a jet mill to obtain strontium titanate particles 2 having a number average particle diameter of 1000 nm. When the obtained particles were qualitatively analyzed by X-ray diffraction, the peak of strontium carbonate was not detected, and it was confirmed that the particles were pure strontium titanate.

<Fluidizer> In the examples of the present invention,
The following fluidizing agents were used.・ Hydrophobic silica: H2000 (Clariant Japan Co., Ltd.); primary particle size 12 nm ・ Hydrophobic titania: STT-30A (Titanium Industry Co., Ltd.); primary particle size 30 nm ・ Hydrophobic alumina: Aluminum oxide C (Japan Aerosil Co., Ltd.) Manufactured by HMDS (hexamethyldisilazane) having a primary particle diameter of 13 nm and subjected to a hydrophobic surface treatment. These fluidizing agents are simply referred to in Table 2 as “silica”,
Indicated as "titania" and "alumina".

Examples 1 to 10 and Comparative Examples 1 to 4 <Production of Toner> Composite particles, a fluidizing agent, etc. having the composition shown in Table 2 were added to toner particles 1 and 2 as external additives, and the production conditions described below were used. To produce a magenta toner.・ Production equipment: Henschel mixer FM10B ・ Production conditions: To a batch of 1 kg of toner particles, a fluidizing agent was added and mixed for 3 minutes at a blade rotation speed of 3640 rpm, then composite particles were added and mixed for 2 minutes, and then Sifted through a circular vibrating screen. The magenta toner obtained by using the toner particles 1 was used in the evaluation using the one-component developing system, and the magenta toner obtained using the toner particles 2 was used in the evaluation using the two-component developing system.

<Evaluation in one-component developing system> (Initial HH fog) The toner of each Example / Comparative Example was set as a one-component developer in a magenta developing device of a color laser printer LP-3000C (manufactured by Epson Corporation), Under HH environment (30 ℃ / 8
After left at 0%) for 6 hours, a magenta monochromatic character image was printed, and the fog on the image was visually evaluated based on the following criteria. ◯: Fog is not recognized at all; Δ: Fog is slightly recognized, but it is at an acceptable level for practical use; ×: Fog is severe and cannot be used for practical purposes.

(Fixation) The toner of each of the examples and comparative examples was set as a one-component developer in a magenta developing device of a color laser printer LP-3000C (manufactured by Epson Corporation), and an image area ratio of 6 was obtained.
% Magenta monochromatic character image after printing 2000 sheets and the developing device sleeve roller were observed, and image streaks (fixation) generated by toner adhered to the regulation blade were evaluated based on the following criteria. ◯: No image streaks were observed on the image, and no sticking streaks were found on the sleeve roller of the developing device; Δ: Slight sticking streaks were not found on the image, but on the sleeve roller of the developing device Is observed; x: Thick image streaks are generated due to fixation, and practical use cannot be endured.

(Fog after Durability) Color laser printer LP-300 using the toner of each of the examples and comparative examples as a one-component developer.
Set it in a magenta developing unit of 0C (manufactured by Epson), and print a magenta monochromatic character image with an image area ratio of 6% in the NN environment (20 ° C / 50
%), The image fog was evaluated based on the following criteria. ◯: Fog is not recognized at all; Δ: Fog is slightly recognized, but it is at an acceptable level for practical use; ×: Fog is severe and cannot be used for practical purposes.

(BS) The toner of each of the examples and comparative examples was set as a one-component developer in a magenta developing device of a color laser printer LP-3000C (manufactured by Epson Corp.), and the image area ratio was 6%.
Magenta single color character image under NN environment (20 ℃ / 50%), 2
After printing in the 000-sheet intermittent mode, the BS generated on the photoconductor was observed. ◯: BS was not generated at all; Δ: A small amount of BS was observed on the photoconductor, but there was no problem on the image; ×: A large amount of BS was generated, which is not practical.

(Photoreceptor scratches) The surface of the organic photoreceptor after the evaluation of fog after durability using a one-component developer was visually evaluated. If the photoreceptor surface was not scratched, the surface of the photoreceptor was clouded. What was visible was evaluated as Δ, and what was scratched on the surface of the photoreceptor was evaluated as x.

<Evaluation in Two-Component Development System> (HH Fogging) The toners of the respective Examples and Comparative Examples were mixed and stirred with Carrier 1 so that the T / C ratio was 6% to prepare a starter. The starter was set in the magenta developing unit of the full-color copying machine CF-910 (Minolta Co., Ltd.), left for 6 hours in the HH environment, and the character image was copied in magenta single color. It was evaluated based on. ◯: Fog is not recognized at all; Δ: Fog is slightly recognized, but it is at an acceptable level for practical use; ×: Fog is severe and cannot be used for practical purposes.

(Fog after Durability) The toners of Examples and Comparative Examples were mixed and stirred with Carrier 1 so that the T / C ratio was 6% to prepare a starter. The starter is a full color copier CF
-Set the image on the Magenta developing unit of 910 (Minolta Co., Ltd.) and copy 10,000 copies of a document with an image area ratio of 15% in a magenta single color under NN environment (20 ° C / 50%). It was evaluated based on the standard. ◯: Fog is not recognized at all; Δ: Fog is slightly recognized, but it is at an acceptable level for practical use; ×: Fog is severe and cannot be used for practical purposes.

(Texture of image quality) The toner of each Example / Comparative Example is used.
A starter was prepared by mixing and stirring with Carrier 1 so that the T / C ratio was 6%. The starter is a full-color copying machine CF-910.
The image was set in a magenta developing device (manufactured by Minolta Co., Ltd.), a photographic image was copied in a single color of magenta, and the texture of the image was evaluated based on the following criteria. ◯: A uniform and fine image with no graininess; Δ: A slight graininess is recognized, but it is at an acceptable level for practical use; ×: The grainy image has no fineness and cannot be used practically.

(BS) The toners of Examples and Comparative Examples were mixed and stirred with Carrier 1 so that the T / C ratio was 6% to prepare a starter. The starter was set on the magenta developing unit of CF-910 (a Minolta Co., Ltd.) full-color copying machine, and the image area ratio was set.
6% of the character image was copied in a single center color in intermittent mode in 10,000 sheets in an NN environment, and the BS generated on the photoconductor was observed. ◯: BS was not generated at all; Δ: A small amount of BS was observed on the photoconductor, but there was no problem on the image; ×: A large amount of BS was generated, which is not practical.

(Photoreceptor scratches) The surface of the organic photoreceptor after the evaluation of fog after durability using a two-component developer was visually evaluated. When the surface of the photoreceptor was not scratched, the surface of the photoreceptor was clouded. What was visible was evaluated as Δ, and what was scratched on the surface of the photoreceptor was evaluated as x.

[0067]

[Table 2]

Method for measuring glass transition point (Tg) of resin Using a differential scanning calorimeter (DSC-200: manufactured by Seiko Denshi KK), alumina was used as a reference, and a 10 mg sample was heated at a rate of 10 ° C./min. It was measured under the conditions of 20 to 120 ° C., and the shoulder value of the main endothermic peak was taken as the glass transition point.

Method for measuring softening point (Tm) of resin Using a flow tester (CFT-500: Shimadzu), pores of die (diameter 1 mm, length 1 mm), pressure 20 kg / cm ² , temperature rise The softening point was defined as the temperature corresponding to half the height from the outflow start point to the outflow end point when a 1 cm ² sample was melted and outflowed at a rate of 6 ° C / min. The particle size of the toner particles was measured using Coulter Multisizer 2.

[0070]

Since the toner of the present invention contains the composite particles of strontium titanate and strontium carbonate whose polishing property is remarkably improved, the cleaning property for the photoconductor and the stain resistance (refresh property) for the carrier and the charge imparting member are improved. Is significantly improved. Therefore, it is possible to effectively prevent the occurrence of BS in the intermittent mode, and it is possible to provide a fine and fine image free from BS, fog, and image streaks for a long period of time.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Minoru Nakamura             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture             Osaka International Building Minolta Co., Ltd. (72) Inventor Hiroaki Kato             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture             Osaka International Building Minolta Co., Ltd. F term (reference) 2H005 AA08 CA26 CB07 CB08 CB13                       EA05 EA07

Claims (6)

[Claims] 1. A toner for developing an electrostatic latent image comprising toner particles containing a colorant and a binder resin mixed with at least one external additive, wherein the external additives are strontium titanate and strontium carbonate. In the composite particles, the weight ratio of strontium titanate and strontium carbonate in the composite particles is in the range of 98: 2 to 80:20, and the number average particle diameter of the composite particles is 80 to 800 nm. Toner for electrostatic latent image development. 2. The weight ratio of strontium titanate to strontium carbonate in the composite particles is 95: 5 to 85: 1.
The toner for developing an electrostatic latent image according to claim 1, wherein the toner has a range of 5. 3. The number average particle diameter of the composite particles is 100 to 750.
The toner for developing an electrostatic latent image according to claim 1 or 2, wherein the toner is nm. 4. The hydrophobic inorganic fine particles obtained by surface-treating inorganic fine particles different from the composite particles with a hydrophobizing agent are further mixed and added to the toner particles as the external additive. 5. The toner for developing an electrostatic latent image according to any one of 1. 5. The toner for developing an electrostatic latent image according to claim 4, wherein the inorganic fine particles are at least one kind of inorganic fine particles selected from the group consisting of silica, titania and alumina. 6. The volume average particle diameter of the toner particles is 3 to 7 μm.
6. The electrostatic latent image developing toner according to claim 1, wherein the toner is m.