JPH08272129A - Electrophotography toner composition and image forming method - Google Patents

Abstract

PURPOSE: To improve an electrostatic charge quantity, an electrostatic charge environmental stability, and a stability of the electrostatic charge quantity in repeated use inside a copying machine by containing toner grain consisting of a binding resin and a coloring agent and titania grain doped with metal. CONSTITUTION: Toner grain, which consists of a binding resin and a coloring agent, and titania grain doped with metal are contained. The metal doped titania grain can be formed by plasma, and aluminum is desirably used for doping metal. When the doping metal powder is added and mixed with titanium powder and they are blown into plasma such as an argon-oxygen atmosphere by means of conveying gas such as argon, material powder is evaporated in the plasma so as to be decomposed into a molecular level, and titanium, which is easily oxidized, reacts with oxygen at first so as to be formed into titania. As the titania grain is contained, an environmental stability is improved, and a narrow electrostatic charge distribution is provided under an environment ranging from a high temperature and high humidity one to a low temperature and low humidity one, while a stable electrostatic charge quantity can be maintained in long-term use, and as a result, a copied image with an excellent image quality can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner composition and an image forming method used for developing an electrostatic latent image in a developing process such as electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic developer used to visualize an electrostatic latent image formed on an electrophotographic photosensitive layer is
A one-component developer made of toner and a two-component developer made by mixing toner and carrier are generally used. The toner includes a binder resin such as polystyrene, a styrene-butadiene copolymer, and a polyester, and a colorant including a pigment or a dye such as carbon black and phthalocyanine blue.
After melt-kneading, it is crushed and manufactured. As the carrier, glass beads, particles of iron, nickel, ferrite or the like having an average particle size of about the same as the toner to about 500 μm, or those coated with various resins are used.

However, these developers alone cannot provide sufficient properties such as storage stability (blocking resistance), transportability, developability, transferability and chargeability. Therefore, an additive is externally added to the toner to improve the above characteristics. As the additive, a hydrophobic fine powder typified by hydrophobic silica (JP-A-52-30437), silica fine particles to which alumina or titania is added (JP-A-60-238847), and the like have been proposed. There is. Further, it has been proposed to surface-treat an inorganic compound used as an external additive, such as titania fine particles surface-treated with a coupling agent (Japanese Patent Application Laid-Open No. 4-40467).

Further, not only initial characteristics such as storability (blocking resistance), transportability, developing property, transfer property, charging property, etc., but also charging of the developer by stirring in the developing device due to repeated use of the copying machine. There is also the problem of rising volumes.
In order to improve this, use of conductive powder as an additive (see JP-A-58-40557) and fixing of conductive powder or the like on the toner surface (JP-A-58-40557, JP-A-58-40557). No. 58-66951) has been proposed.

[0005]

By the way, hydrophobic fine powders such as silica, which are often used at present, have long shelf life,
The transportability, developability, transferability, etc. can be controlled considerably, but if an amount sufficient to improve these is used, the chargeability is adversely affected. That is, regarding the charging property, the charging amount, the charging speed, the distribution of the charging amount, the toner admix property,
The use of silica or the like adversely affects the charging speed, the distribution of the amount of charge, the toner admixability, and the environmental stability of the charging, in response to the demand for the environmental stability of the charging.

On the other hand, when trying to improve the above problems by mixing alumina fine particles, titania fine particles and the like into silica fine particles, there is a problem that the charge amount becomes extremely low, and various requirements for chargeability are satisfied. The range is narrow and the improvement curing is not sufficient. In particular, there is a problem that the charging stability is poor.

Further, when rutile type or anatase type titania fine particles are used as an external additive, those whose surface is not treated are hardly charged. Therefore, it is necessary to perform a hydrophobizing treatment with various coupling agents or coat alumina or the like. However, the titania fine particles coated with alumina or the like are not effective in preventing aggregation, and the dispersibility thereof is not good even when added to the toner.

Hydrophobic treatment of alumina with a coupling agent improves the charging property to some extent, but with repeated use of the developer, there is a problem that the charge amount of the developer increases due to stirring in the developing machine. The above problems are remarkable when a polyester resin is used as the resin. Therefore, it has been proposed to add conductive powder to suppress the increase in the charge amount.

As the conductive powder, carbon black, Sn
Although O ₂ , SiC, titania, etc. are used, there is a problem in safety for the human body and there is also a problem in that the inside of the copying machine is contaminated. Furthermore, if an amount sufficient to suppress the increase in the charge amount of the developer is added, the carrier and the developing roll are contaminated. As described above, it has not been possible to simultaneously suppress the increase in the charge amount of the developer and satisfy the environmental stability of the charge.

Therefore, the present invention solves the above problems and provides a toner composition excellent in charge amount, charge environment stability, charge amount stability in repeated use in a copying machine, and the like, and
It is an object of the present invention to provide an image forming method using the toner composition.

[0011]

The present invention has succeeded in solving the above problems by adopting the following constitution. (1) An electrophotographic toner composition containing toner particles composed of a binder resin and a colorant, and metal-doped titania fine particles. (2) The toner composition for electrophotography according to (1) above, wherein the titania fine particles are plasma-synthesized from a titania raw material and a doped metal raw material. (3) The toner composition for electrophotography according to the above (1) or (2), wherein the titania fine particles are anatase crystals.

(4) The toner composition for electrophotography according to any one of (1) to (3) above, wherein the metal-doped titania fine particles are surface-treated. (5) The electrophotographic toner composition as described in (4) above, wherein a coupling agent or silicone oil is used as the surface treatment agent. (6) A silane coupling agent represented by the following general formula is used as the coupling agent.
The toner composition for electrophotography as described above. R _4-x Si (NCO) _x , R _4-x Si (OR ') _x or R _4-x Si (Cl) _x (wherein, X is an integer of 1 to 3 and R is a carbon number of 1 to 16) Alkyl group or fluorine-containing group, OR 'represents an alkoxy group having 1 to 5 carbon atoms.)

(7) The toner composition for electrophotography according to (1) above, wherein a polyester resin is used as the binder resin. (8) A step of forming a latent image on a latent image carrier, a step of developing the latent image with a developer, a step of transferring the developed toner image onto a transfer body, and a heating of the toner image on the transfer body. An image forming method comprising a step of fixing, wherein the toner composition for electrophotography according to any one of the above (1) to (7) is used as the developer.

[0014]

The present inventors have used metal-doped titania fine particles, in particular, titania fine particles obtained by plasma synthesis as an external additive for a toner to improve the charge amount, the stability of the charging environment, and the repeated use in a copying machine. It has become possible to provide a toner composition excellent in stability of the charge amount in the above.

The metal-doped titania fine particles used in the present invention can be synthesized by plasma. As the doped metal, aluminum, boron, gallium, indium, lithium, sodium, potassium, magnesium,
Any metal that is less susceptible to oxidation than titanium such as calcium, strontium, and barium can be used. Among them, aluminum is particularly preferably used. First, a doped metal powder is added to and mixed with titanium powder, and a carrier gas such as argon is used to blow it into a plasma such as an argon / oxygen atmosphere. In the plasma of 3000 to 8000 ° C., the raw material powder is evaporated and decomposed to the molecular level. First, titanium, which is easily oxidized, reacts with oxygen to generate titania.

This titania mainly has an anatase crystal structure, and the doped metal penetrates into it. When using aluminum as the dope metal, when the mixing ratio (weight ratio) of the titania powder and the aluminum powder is 97: 3,
About 1 to 12 of the titania crystals enter the Al base paper.

The titania fine particles obtained by the plasma synthesis method are
The toner exhibits conductivity which is not recognized by the firing method and the like, and the toner to which it is added exhibits stable charging environment. Although the reason why the above conductivity is exhibited is not clear, it is believed that the flow of electrons is faster due to the doped metal. As such plasma-synthesized aluminum-doped titania fine particles, emulsion type "ASTAC" is commercially available from ISAI.

In the synthesis of the titania fine particles of the present invention, the mixing ratio of the doped metal powder to the titanium powder is 1 to 10% by weight, preferably 1 to 4% by weight. Further, the particle size of the titania fine particles of the present invention is appropriately in the range of 5 to 200 nm, preferably 10 to 100 nm.

The titania fine particles of the present invention can be surface-treated as necessary. As the surface treatment agent, a coupling agent or silicone oil can be used. As the coupling agent, one that reacts with a hydroxyl group is used, and a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a zirconium coupling agent, etc. can be used. Agents are particularly suitable.

The silane coupling agent suitable for the present invention is
It is shown in the following formula. R _4-x Si (NCO) _x , R _4-x Si (OR ') _x or R _4-x Si (Cl) _x (wherein, X is an integer of 1 to 3 and R is a carbon number of 1 to 16) An alkyl group or a fluorine-containing group, preferably a perfluoroalkyl group, OR ′ represents an alkoxy group having 1 to 5 carbon atoms, preferably a methoxy group or an ethoxy group.) Specifically, (CH ₃ ) ₂ Si (NCO) ) ₂ , CH ₃ S
i (NCO) ₃ , C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ , CF ₃
Although Si (OCH ₃ ) _{3 and the} like can be mentioned, those having X = 3 in the above formula are preferable from the viewpoint of improving dispersibility.

Examples of the silicone oil used in the present invention include dimethyl silicone oil, methylphenyl silicone oil, methylhydrogen silicone oil and modified silicone oils thereof.

In the surface treatment of the present invention, a coupling agent and silicone oil may be used alone or in combination. The surface treatment amount of the titania fine particles is suitably 2 to 50% by weight, preferably 5 to 30% by weight. In addition, in the toner composition of the present invention, the above-mentioned titania fine particles are 0.5 to 0.5 with respect to the toner particles.
It is preferable to add 4% by weight, preferably 0.5 to 3% by weight. In addition, you may use together with other additives, such as silica and alumina.

The toner particles used in the present invention are mainly composed of a binder resin and a colorant. Examples of the binder resin used include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isobutylene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl acetate; Α-methylene aliphatic monocarboxylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Kinds; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether; homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc. It can be.

Particularly, typical binder resins include polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / styrene. Examples thereof include maleic anhydride copolymer, polyethylene and polypropylene. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin and waxes can be mentioned.

Among them, the polyester resin is particularly effective in the present invention. For example, a polyester resin obtained by polycondensing bisphenol A and a polyvalent aromatic carboxylic acid can be preferably used. This polyester can be produced by the reaction of a polyhydric alcohol and a polybasic carboxylic acid.

Examples of the polyhydric alcohol constituting the polyester include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-
Butanediol, neopentyl glycol, and other diols; bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropyleneized bisphenol A, and other bisphenol A alkylene oxide adducts; other dihydric alcohols You can Also, trimethylolpropane,
1,3,5-trihydroxymethylbenzene and other polyhydric alcohols can also be used.

Examples of the polybasic carboxylic acid constituting the polyester include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid. , Sebacic acid, malonic acids, alkylsuccinic acids, their acid anhydrides, alkyl esters, and other dibasic carboxylic acids.

In addition to these carboxylic acids, a polyhydric alcohol having a valence of 3 or more and / or a polybasic carboxylic acid having a valence of 3 or more is added in order to make the polymer non-linear to the extent that tetrahydrofuran insoluble matter is not generated. You can Examples of trihydric or higher polyhydric alcohols include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, 1,2,4-butanetriol, 1,2,5-. Pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-
1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like can be mentioned.

Examples of the polybasic carboxylic acid having three or more basicities include 1,2,4-benzenetricarboxylic acid,
1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid and the like can be mentioned. The binder resin used in the present invention has a softening point of 70 to 150 ° C. and a glass transition point (Tg).
Is 40 to 70 ° C. and the number average molecular weight (Mn) is 2000 to 5
0000, weight average amount (Mw) is 8000 to 1500
Those having an acid value of 00, an acid value of 5 to 30, and a hydroxyl value of 5 to 40 are particularly suitable.

In general, when polyester is used as a binder resin for toner particles, the polyester itself has a negative charging property, so that the charging control agent is not used or a small amount is used to obtain the negative charging property. be able to. However, the charge amount is easily affected by changes in temperature and humidity, and the charge amount may excessively increase due to stirring in the developing machine.
In particular, when a pigment other than carbon black is used as a colorant for the toner, the charge amount is remarkably increased. Although the mechanism is not clear, it is considered that the negative chargeability of the polyester is due to the carboxyl group of the polar group of the polyester or the ester bond. Since the chargeability of these polar groups is easily affected by the change in temperature and humidity, it is considered that the chargeability is affected by the change in temperature and humidity only when toner is formed. Further, even if a charge control agent is added to the polyester resin, it is not possible to remarkably improve the temperature and humidity changes of the charge.

However, when the above polyester resin according to the present invention is used, the above drawbacks are eliminated. In the present invention, by externally adding the plasma-synthesized titania fine particles to the toner particles, it is possible to significantly improve the environmental dependency of the charge amount while maintaining the toner charge amount necessary for development at high temperature and high humidity. In addition, it is possible to suppress an excessive increase in the charge amount due to stirring in the developing machine.

Typical colorants for toner particles include carbon black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue,
DuPont Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Malachite Green Oxalate, Lamp Black, Rose Bengal, CI Pigment Red 48: 1, CI Pigment Red
122, CI Pigment Red 57: 1, CI Pigment Yellow 97, CI Pigment Yellow 12, CI Pigment Blue 15: 1, CI Pigment Blue 15: 3 and the like.

For these toner particles, a fluidizing agent such as silica or alumina, or an external additive such as a cleaning aid or a transfer aid such as polystyrene fine particles, polymethylmethacrylate fine particles or polyvinylidene fluoride fine particles can be used. . In particular, hydrophobic silica having a primary average particle diameter of 5 to 30 nm is preferably used.

As an additive, a salicylic acid metal salt,
Components such as a metal-containing azo compound, a charge control agent such as nigrosine or a quaternary ammonium salt, and an anti-offset agent such as low-molecular weight polypropylene, low-molecular weight polyethylene, wax, and high-molecular alcohol can be added. In particular, low molecular weight polypropylene having a weight average molecular weight of 500 to 5000 is preferable.

The average particle size of the toner particles of the present invention is about 30.
It is smaller than μm, preferably in the range of 4 to 20 μm. A high-speed mixer, specifically, a Henschel mixer, a V-type blender, or the like can be used to attach the above additives to the surface of the toner particles.

The toner composition of the present invention can be used as a one-component developer, but it is preferably used as a two-component developer together with a carrier. Examples of the carrier used here include an iron powder-based carrier, a ferrite-based carrier, a surface-coated ferrite carrier, and a magnetic powder-dispersed carrier.

[0037]

【Example】

Example 1-6 (Production of Additives _{a) C 10 H 21 Si (} OCH 3) 3 1.0
g was dissolved in a mixed solvent consisting of 95 parts of methanol and 5 parts of water, and plasma-synthesized titania fine particles (weight ratio of raw material: titania powder / aluminum powder = 97/3) 10
g was added and ultrasonically dispersed to bond the silane coupling agent to the surface of titania particles. Then, after removing methanol and the like with an evaporator, it was heat-treated with a dryer set at 120 ° C. and pulverized with an automatic mortar to obtain an additive a.

(Production of Additive b) Methyl hydrogen silicone oil (KF99, manufactured by Shin-Etsu Silicone Co., Ltd.) 1
After adding g to toluene, 10 g of plasma-synthesized titania fine particles similar to additive a was added and ultrasonically dispersed,
Toluene was desolvated with an evaporator and air-dried.
It heat-processed at 2 degreeC for 2 hours, and it grind | pulverized with the automatic mortar and the additive b was obtained.

(Production of Toner Particles A) 100 parts by weight of styrene / n-butyl methacrylate copolymer (blending ratio 30/70, Tg = 65 ° C., Mn = 15000, Mw = 35000) Magenta pigment (CI Pigment Red 57) 3 parts by weight Potassium tetraphenylboron 1 part by weight The above mixture was kneaded with an extruder, pulverized with a jet mill, and dispersed with a wind classifier to obtain magenta toner particles A having d ₅₀ = 8 μm.

(Production of Toner Particles B) Linear Polyester Resin 100 parts by weight (linear polyester resin obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexyne dimethanol, Tg = 62 ° C., Mn = 4000, Mw = 35,000, acid value = 12, hydroxyl value = 25) Magenta pigment (CI Pigment Red 57) 3 parts by weight The above mixture was kneaded with an extruder, pulverized with a jet mill, and dispersed with a wind classifier. Magenta toner particles B having d ₅₀ = 8 μm were obtained.

(Production of Toner Compositions 1 and 2) To 100 parts by weight of each of toner particles A and B, hydrophobic silica R9 is added.
1.0 parts by weight of 72 (manufactured by Nippon Aerosil Co., Ltd.) and 0.6 parts by weight of plasma-synthesized surface-untreated titania fine particles (weight ratio of raw material: titania powder / aluminum powder = 97/3) were added and mixed with a Henschel mixer. Toner composition 1
And 2 were obtained.

(Production of Toner Compositions 3 and 4) To 100 parts by weight of each of the toner particles A and B, 0.6 part by weight of the additive a (surface-treated titania fine particles by plasma synthesis) was added and mixed by a Henschel mixer. Toner compositions 3 and 4 were obtained.

(Production of Toner Compositions 5 and 6) To 100 parts by weight of each of the toner particles A and B, 0.6 part by weight of the additive b (surface-treated titania fine particles by plasma synthesis) was added and mixed by a Henschel mixer. Toner compositions 5 and 6 were obtained.

(Preparation of Developer) Toner Compositions 1 to 4 above
And a carrier composed of a ferrite having a particle size of about 50 μm and coated with a methylmethacrylate / styrene copolymer.
Parts by weight were added and mixed with a tumbler shaker mixer to obtain the developers of Examples 1 to 6 for evaluation.

(Evaluation) A copy test was carried out using an electrophotographic copying machine (A-color 630, manufactured by Fuji Xerox Co., Ltd.) using the above six developers, and high temperature and high humidity (30 ° C., 85 ° C.).
% RH), medium temperature / humidity (22 ° C., 55% RH) and low temperature / low humidity (10 ° C., 10% RH) environment after 10 copies, and medium temperature / humidity (22 ° C., 55% RH). )
Of the amount of charge after 5000 copies under the following environment,
The results are shown in Table 1. The charge amount is a value obtained by image analysis of CGS (charge spectrograph method).

When the toner composition of the present invention is used,
The charge amount hardly changed even at low temperature and low humidity, medium temperature and medium humidity, and high temperature and high humidity. 5 using these toner compositions
When a 000-copy test was conducted, stable images could be obtained without fluctuations in image density or scumming on the whole.

[Comparative Example 1] With respect to the toner particles B of Example 1, the same as Example 1 except that the plasma-synthesized untreated titania fine particles were replaced with titania TTO55 (manufactured by Ishihara Sangyo Co., Ltd.) obtained by a sintering method. A toner composition was obtained in the same manner. Using this toner composition and the carrier used in Example 1, a developer of Comparative Example 1 was obtained. This developer was evaluated in the same manner as in Examples, and the results are shown in Table 1. The developer of Comparative Example 1 had large fluctuations in the charge amount due to changes in the environment, and large fluctuations in image density.

Comparative Example 2 A toner composition was obtained in the same manner as in Example 1 except that only hydrophobic silica R972 (manufactured by Nippon Aerosil Co., Ltd.) was added to Toner Particle B of Example 1. Using this toner composition and the carrier used in Example 1, a developer of Comparative Example 2 was obtained. This developer was evaluated in the same manner as in Examples, and the results are shown in Table 1.
The developer of Comparative Example 2 had large fluctuations in the charge amount due to changes in the environment, and large fluctuations in the image density. Furthermore, copy 5
After 000 sheets, the charge amount was increased and the image density was insufficient, resulting in poor stability.

[0049]

[Table 1]

Example 7 Styrene / n-butyl methacrylate copolymer 97 parts by weight (compounding ratio 70:30, Tg = 60 ° C., Mn = 7000, Mw = about 40,000) Cyan pigment (β-type phthalocyanine: CI pigment) Blue 15: 3) 3 parts by weight After the above mixture is melt-kneaded, finely pulverized, classified and ad ₅₀
= 8 μm cyan toner particles were obtained. To 100 parts by weight of the cyan toner particles, 0.9 part by weight of the additive a (surface-treated titania fine particles by plasma synthesis) obtained in Example 1, hydrophobic silica R972 (manufactured by Nippon Aerosil Co., Ltd.)
A cyan toner composition was obtained by mixing 9 parts by weight with a Henschel mixer.

6 parts by weight of the above cyan toner composition was mixed with 100 parts by weight of the carrier used in Example 1 to obtain a developer. An electrophotographic copying machine (A-
When a copy test was performed using color630, manufactured by Fuji Xerox Co., Ltd., there was no stain on the background part from the initial condition under conditions of high temperature and high humidity (30 ° C., 85% RH) to low temperature and low humidity (10 ° C., 10% RH). A high quality image could be obtained at high density. Further, when 8,000 sheets were continuously copied, almost no change in image quality was observed.

[Examples 8 and 9] The cyan pigment of Example 7 was replaced by a magenta pigment (Brilliant Carmine 6BC: CI).
Pigment Red 57) and a yellow pigment (Disazo Yellow: CI Pigment Yellow 12), and other conditions were the same as in Example 5 to obtain magenta toner particles and yellow toner particles having an average particle diameter of 8 μm.

To 100 parts by weight of the magenta toner particles and yellow toner particles, 1.0 part by weight of surface-untreated titania fine particles used in Example 1 by plasma synthesis,
1.1 parts by weight of hydrophobic silica R972 (manufactured by Nippon Aerosil Co., Ltd.) was added and mixed with a Henschel mixer to obtain a magenta toner composition and a yellow toner composition. These toner compositions showed good flowability.

Using these toner compositions, a developer was prepared in the same manner as in Example 7, and a copy test was conducted in the same manner as in Example 5. As a result, a high temperature and high humidity (30 ° C., 85% RH) was obtained.
From low temperature to low humidity (10 ° C., 10% RH), there was no stain on the background, and a high-quality image could be obtained from the initial stage with high density. Further, when 8,000 sheets were continuously copied, almost no change in image quality was observed.

[0055]

According to the present invention, by adopting the above-mentioned constitution and externally adding titania fine particles doped with a metal such as aluminum, in particular, plasma synthesized titania fine particles to the toner particles, the chargeability of the toner particles is improved. In particular, the environmental stability is improved, the charge distribution range is narrow under the environment of high temperature and high humidity to low temperature and low humidity, and the stable charge amount is maintained even when continuously used for a long time, and excellent image quality is achieved. You can now get a copy of the image.

Claims (7)

[Claims] 1. A toner composition for electrophotography, comprising toner particles composed of a binder resin and a colorant, and titania fine particles doped with a metal. 2. The toner composition for electrophotography according to claim 1, wherein the titania fine particles are plasma-synthesized from a titania raw material and a doped metal raw material. 3. The toner composition for electrophotography according to claim 1, wherein the metal-doped titania fine particles are surface-treated. 4. A coupling agent or silicone oil is used as the surface treatment agent.
The toner composition for electrophotography as described above. 5. The toner composition for electrophotography according to claim 4, wherein a silane coupling agent represented by the following general formula is used as the coupling agent. R _4-x Si (NCO) _x , R _4-x Si (OR ') _x or R _4-x Si (Cl) _x (wherein, X is an integer of 1 to 3 and R is a carbon number of 1 to 16) Alkyl group or fluorine-containing group, OR 'represents an alkoxy group having 1 to 5 carbon atoms.) 6. The toner composition for electrophotography according to claim 1, wherein a polyester resin is used as the binder resin. 7. A step of forming a latent image on a latent image carrier, a step of developing the latent image with a developer, a step of transferring the developed toner image onto a transfer body, and a toner image on the transfer body. An image forming method comprising a step of heating and fixing the toner, wherein the electrophotographic toner composition according to any one of claims 1 to 6 is used as the developer.