JP2009092761A - Toner and image forming apparatus using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide toner capable of preventing amount of electrostatic charging from rising excessively in low humidity environment or being excessively reduced in high humidity environment and providing images having constant density in various environments and to provide an image forming device forming images by using the toner. <P>SOLUTION: A developing device 19 provided in the image forming apparatus 40 develops an electrostatic latent image formed on a photosensitive drum 16 and forms a toner image by using the toner containing binder resin, coloring agent, and internally added water absorbing electrical conductive grains that the toner contains by pts.wt. in a scope of 0.10 pts.wt. or more and 5.0 pts.wt. or less for the binder resin of 100 pts.wt.. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner and an image forming apparatus that uses the toner to form an image based on electrophotography, such as a copying machine, a printer, or a facsimile machine.

  An electrophotographic image forming apparatus that forms an image based on an electrophotographic method includes, for example, a photoconductor and charging, exposing, developing, transferring, cleaning, static eliminating, and fixing devices. The surface of the photoconductor to be rotated is uniformly charged by a charging device, and the charged photoconductor surface is irradiated with laser light by an exposure device to form an electrostatic latent image. Subsequently, the developing device develops the electrostatic latent image on the surface of the photoreceptor using toner, and forms a visible toner image on the surface of the photoreceptor. The toner image on the surface of the photoreceptor is transferred to a transfer material by a transfer device, and then heated and pressurized by a fixing device, and is fixed to the transfer material. As a result, an image is formed on the recording medium.

  With increasing demand for electrophotographic image forming apparatuses in countries around the world, improvement in performance of electrophotographic image forming apparatuses is demanded, and in particular, improvement in toner performance is eagerly desired. Specifically, there is a craving for the toner itself to form a visible image with a quality of a certain level or more without being affected by temperature and humidity. In order to form a visual image of a certain level of quality under any temperature and humidity environment, the toner is not affected by temperature and humidity, and continues to maintain certain physical properties such as chargeability and fluidity. There must be various problems. For example, there are problems such as a decrease in toner charge amount and poor fluidity in a high humidity environment, and an increase in toner charge amount in a low humidity environment. If the change in the charge amount of the toner is excessive, there is a problem that a constant image density cannot be obtained.

  Patent Document 1 discloses a toner using titanium oxide particles having an electrical resistivity relatively lower than that of silica fine particles as an external additive as a means for preventing the toner charge amount from increasing.

  Further, in order to prevent the toner charge amount from increasing, a toner in which carbon black having conductivity is added or added for the purpose of lowering the volume resistivity of the toner is disclosed in Patent Document 2 and has conductivity. Patent Document 3 discloses a toner in which a titanium oxide fine powder having a surface formed with a conductive film of tin oxide doped with an external additive such as antimony is externally added.

JP 2002-214826 A JP-A-6-273969 JP-A-5-119516

  In the techniques disclosed in Patent Documents 1 to 3, it may be possible to suppress an increase in the charge amount of the toner in a low-humidity environment, but there is a problem that the charge amount of the toner decreases in a high-humidity environment. Further, when an external additive such as titanium oxide is externally added as in the techniques disclosed in Patent Documents 1 to 3, the spent component in which the toner component adheres to the carrier and the filming in which the toner component adheres to the photoreceptor are generated. Sometimes.

  In addition, the toner externally added with titanium oxide particles disclosed in Patent Document 1 has little increase in charge amount when images are continuously formed, and can form an image with a constant image density, but an image with low coverage. That is, when the replenished toner is hardly consumed and stirred in the developing tank for a long period of time as in the case of forming a large number of images with a recording material covering rate of about 15%, for example, with toner. In addition, there is a problem in that the charge amount of the toner is reduced, the image is fogged, and the toner is scattered. Further, in the technique disclosed in Patent Document 2, since black carbon black is added, there is a problem that when it is applied to a color toner, the color developability and the color mixing property are lowered.

  The object of the present invention is to prevent a charge amount from excessively increasing in a low humidity environment, and to prevent a charge amount from excessively decreasing in a high humidity environment, and to maintain a constant image density in various environments. An object is to provide a toner capable of realizing an image and an image forming apparatus that forms an image using the toner.

  Another object of the present invention is to suppress an excessive increase in the charge amount in a low humidity environment and an excessive decrease in the charge amount in a high humidity environment, and is excellent in color development and color mixing properties, and is suitable as a color toner. An object is to provide a toner and an image forming apparatus that forms an image using the toner.

  Another object of the present invention is a toner capable of suppressing an excessive increase in the charge amount under a low humidity environment and an excessive decrease in the charge amount under a high humidity environment, and also capable of suppressing the occurrence of spent and filming, And an image forming apparatus that forms an image using the toner.

  The present invention contains a binder resin, a colorant, and water-absorbing conductive particles having water absorption and conductivity. The water-absorbing conductive particles are internally added, and the content of the water-absorbing conductive particles is 0.000 parts by weight with respect to 100 parts by weight of the binder resin. The toner is contained in a weight ratio of 10 parts by weight or more and 5.0 parts by weight or less.

  In the present invention, the water-absorbing conductive particles are characterized in that water-absorbing particles are treated with an ionomer silane coupling agent.

  In the present invention, the water-absorbing conductive particles are silica particles surface-treated with an ionomer silane coupling agent.

In the present invention, the ionomer silane coupling agent is an ionomer silane coupling agent represented by the following general formula (1).
_3/2 OSi—R ¹ —COO ^— M ⁺ (1)
(In the formula, R ¹ represents an alkylene group, and M ⁺ represents a monovalent cation.)

  In the present invention, the water-absorbing conductive particles have a number average particle diameter of 5 nm to 70 nm.

In the present invention, the water-absorbing conductive particles have a volume resistivity of 1 × 10 ¹ Ω · cm to 5 × 10 ⁵ Ω · cm.

The present invention also provides a colored particle containing a colorant and water-absorbing conductive particles in a binder resin;
It is characterized by comprising hydrophobic particles externally added to the colored particles and having hydrophobic properties.

  In the invention, the hydrophobic particles are hydrophobic conductive particles having hydrophobicity and conductivity.

In the present invention, the colored particles have a volume average particle diameter of 5 μm or more and 7 μm or less, and a BET specific surface area of 1.5 m ² / g or more and 1.9 m ² / g or less.

The present invention also provides an image carrier on which an electrostatic latent image is formed,
A latent image forming means for forming an electrostatic latent image on the image carrier;
An image forming apparatus comprising: a developing device that develops an electrostatic latent image formed on an image carrier using the toner to form a toner image.

  According to the present invention, the toner contains a binder resin, a colorant, and water-absorbing conductive particles having water absorption and conductivity. By incorporating the water-absorbing conductive particles having conductivity in the toner in this way, the volume resistivity of the toner is lowered and the volume resistivity of the toner is adjusted as compared with the case of not containing the water-absorbing conductive particles. Can do. In addition, since the water-absorbing conductive particles have water-absorbing properties, water can be adsorbed to the toner, for example, in a low humidity environment by containing the water-absorbing conductive particles in the toner. The water content of the toner can be increased compared to the case where the toner is not contained. As a result, charge leakage can be caused in a low humidity environment, so that an excessive increase in the charge amount of the toner in the low humidity environment can be suppressed. Further, since the water-absorbing conductive particles are internally added to the toner, the exposed amount of water-absorbing conductive particles that are water-absorbing can be reduced on the toner surface as compared with the case where they are externally added. As a result, an excessive decrease in the charge amount of the toner in a high humidity environment can be suppressed. Further, since the water-absorbing conductive particles are contained in the toner in a weight ratio in the range of 0.10 parts by weight or more and 5.0 parts by weight or less with respect to 100 parts by weight of the binder resin, the toner has a sufficient water absorption ability. Therefore, an excessive increase in the charge amount of the toner in a low humidity environment can be suppressed. Therefore, an excessive decrease in the toner charge amount can be suppressed in a high humidity environment, and an excessive increase in the toner charge amount can be suppressed in a low humidity environment. It is possible to stably form an image having

  According to the invention, the water-absorbing conductive particles are obtained by treating water-absorbing particles with an ionomer silane coupling agent. By using such water-absorbing conductive particles, it is possible to realize a toner that can stably form an image having a constant image density regardless of humidity.

  According to the invention, the water-absorbing conductive particles are silica particles surface-treated with an ionomer silane coupling agent. By being such water-absorbing conductive particles, the water-absorbing conductive particles have sufficient adsorbed water retention ability and good dispersibility in the binder resin, so that the toner can be uniformly charged. An excessive increase in the charge amount in a low humidity environment can be suppressed more reliably. Therefore, an image having a constant image density can be more stably formed regardless of humidity. Further, since the water-absorbing conductive particles are silica particles surface-treated with an ionomer silane coupling agent, the influence of the water-absorbing conductive particles on the toner color can be suppressed. Therefore, it is possible to suppress an excessive increase in the charge amount in a low humidity environment and an excessive decrease in the charge amount in a high humidity environment, and to realize a toner that is excellent in color development and color mixing properties and suitable as a color toner. Is possible.

  Moreover, according to this invention, an ionomer silane coupling agent is an ionomer silane coupling agent represented by General formula (1). Since the ionomer silane coupling agent is an ionomer silane coupling agent represented by the general formula (1), the dispersibility of the water-absorbing conductive particles in the binder resin is better. Can be uniformly charged. Further, since the water-absorbing conductive particles have a sufficient adsorbed water holding capacity, the volume resistivity of the toner can be appropriately lowered by the sufficient water-adsorbing water holding capacity of the water-absorbing conductive particles in a low humidity environment. Accordingly, the toner can be charged as uniformly as possible, and an excessive increase in the amount of charge in a low humidity environment can be more reliably suppressed, so that the toner has a constant image density regardless of humidity. An image can be formed more stably.

  According to the invention, the water-absorbing conductive particles have a number average particle diameter of 5 nm to 70 nm. When the number average particle diameter of the water-absorbing conductive particles is within such a range, the water-absorbing conductive particles can be more uniformly dispersed in the binder resin. As a result, the toner charge amount can be stabilized without causing poor dispersion of the water-absorbing conductive particles, and an image having a constant image density can be formed more stably regardless of humidity. can do.

According to the invention, the volume resistivity of the water-absorbing conductive particles is 1 × 10 ¹ Ω · cm or more and 5 × 10 ⁵ Ω · cm or less. Thus, the water-absorbing conductive particles are water-absorbing conductive particles having an appropriate volume resistivity of 1 × 10 ¹ Ω · cm or more and 5 × 10 ⁵ Ω · cm or less. Can be suppressed. Accordingly, it is possible to suppress a decrease in the charge amount of the toner when the charged toner is left, and to prevent an excessive decrease in the charge amount of the toner in a high humidity environment. Further, it is possible to prevent an excessive increase in the charge amount of the toner in a low humidity environment. Therefore, the charge amount of the toner can be stabilized and an image having a constant image density can be stably formed.

  Further, according to the present invention, the toner includes a colored particle in which a colorant and water-absorbing conductive particles are contained in a binder resin, and hydrophobic particles that are externally added to the colored particles and have hydrophobic properties. By externally adding hydrophobic particles having hydrophobicity to the colored particles, the fluidity of the toner can be improved without causing an excessive decrease in the charge amount of the toner in a high humidity environment. Therefore, since the charge amount of the toner is further stabilized, an image having a constant image density can be formed more stably.

  According to the invention, the hydrophobic particles are hydrophobic conductive particles having hydrophobicity and conductivity. By externally adding hydrophobic conductive particles to the colored particles, it is possible to improve the fluidity of the toner and more reliably suppress an excessive increase in the charge amount of the toner in a low humidity environment. Therefore, the toner has excellent fluidity and does not depend on humidity, and can be a toner having a constant charge amount. Therefore, an image having a constant image density can be formed more stably.

According to the invention, the colored particles have a volume average particle diameter of 5 μm or more and 7 μm or less and a BET specific surface area of 1.5 m ² / g or more and 1.9 m ² / g or less. Since such a colored particle has a smooth surface, it is difficult to form a recess on the surface of the colored particle, and the flowability of the toner due to the hydrophobic particle caused by the entry of the hydrophobic particle into the recess is reduced. Can be prevented. Therefore, an image having a constant image density can be formed more stably.

  According to the invention, the image forming apparatus forms an electrostatic latent image on the image carrier by the latent image forming means, and the electrostatic latent image formed on the image carrier using the toner of the invention by the developing device. The image is developed to form a toner image. When an image is formed by such an image forming apparatus, an excessive decrease in the toner charge amount can be suppressed in a high humidity environment, and an excessive increase in the toner charge amount can be suppressed in a low humidity environment. In addition, it is possible to stably form an image having a constant image density by suppressing a decrease in image density and occurrence of fogging throughout the life. For example, when the water-absorbing conductive particles are silica particles surface-treated with an ionomer silane coupling agent, the influence of the water-absorbing conductive particles on the toner color is suppressed, and the color development and color mixing properties are excellent. Images can be formed.

  The toner according to one embodiment of the present invention contains at least a binder resin and a colorant, and further contains water-absorbing conductive particles having water absorption and conductivity. The water-absorbing conductive particles are internally added to the toner, and more specifically are contained in the binder resin. By containing the water-absorbing conductive particles in the toner, the volume resistivity of the toner can be lowered and the volume resistivity of the toner can be adjusted as compared with the case where the water-absorbing conductive particles are not contained. In addition, since the water-absorbing conductive particles have water-absorbing properties, water can be adsorbed to the toner, for example, in a low humidity environment by containing the water-absorbing conductive particles in the toner. The water content of the toner can be increased compared to the case where the toner is not contained. As a result, charge leakage can be caused in a low humidity environment, so that an excessive increase in the charge amount of the toner in the low humidity environment can be suppressed. Also, what is important is that the water-absorbing conductive particles are internally added to the toner, and the exposed amount of water-absorbing conductive particles that are water-absorbing on the toner surface is reduced compared to the case where they are externally added. I can. As a result, an excessive decrease in the charge amount of the toner in a high humidity environment can be suppressed. Therefore, an excessive decrease in the toner charge amount can be suppressed in a high humidity environment, and an excessive increase in the toner charge amount can be suppressed in a low humidity environment. It is possible to stably form an image having Further, since the water-absorbing conductive particles are internally added, the occurrence of spent and filming can be suppressed. Therefore, it is possible to realize a toner that can suppress an excessive increase in the charge amount under a low humidity environment and an excessive decrease in the charge amount under a high humidity environment, and can suppress the occurrence of spent and filming. “Under low humidity environment” refers to an environment with a humidity of 20% or less, and “under high humidity environment” refers to an environment with a humidity of 80% or more.

  As the binder resin, various known styrene / acrylic resins, polyester resins and the like can be used, and linear or nonlinear polyester resins are particularly preferable. The polyester resin is excellent in all of mechanical strength, fixability, and hot offset resistance. Therefore, when the polyester resin is used as a binder resin, fine powder is hardly generated by an external force, for example, an external force applied to the toner by stirring the toner in the image forming apparatus, and the toner is recorded after fixing by the fixing device. It is excellent in that it is difficult to peel off from the medium and the toner does not easily adhere to the heating roll of the fixing device.

  The polyester resin can be obtained, for example, by polymerizing a monomer composition containing a divalent polyhydric alcohol and a divalent polybasic acid. The monomer composition may contain a trihydric or higher polyhydric alcohol or a polybasic acid. “Polybasic acid” includes acids and their derivatives.

  Examples of the divalent alcohol used for polymerization of the polyester resin include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1 Diols such as 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, bisphenol A alkylene such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A and polyoxypropylenated bisphenol A An oxide adduct etc. can be mentioned.

  Examples of the trihydric or higher polyhydric alcohol include sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4- Butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane and 1,3,5-trihydroxymethyl Benzene etc. can be mentioned.

  Examples of the divalent polybasic acid include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, Mention may be made of malonic acid, anhydrides or lower alkyl esters of these acids, alkenyl succinic acids such as n-dodecenyl succinic acid, and alkyl succinic acids such as n-dodecyl succinic acid. “Lower alkyl” refers to alkyl having 1 to 4 carbon atoms.

  Examples of the tribasic or higher polybasic acid include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 2,5,7-naphthalenetricarboxylic acid. 1,2,4-naphthalenetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7 , 8-octanetetracarboxylic acid and anhydrides thereof.

  Known pigments and dyes can be used as the colorant. Specific examples of the black toner colorant include carbon black and magnetite.

  Examples of the colorant for yellow toner include C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 97 and C.I. I. Acetoacetic acid arylamide monoazo yellow pigments such as C.I. Pigment Yellow 98; I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14 and C.I. I. Acetoacetic acid arylamide disazo yellow pigments such as C.I. Pigment Yellow 17; I. Pigment yellow 93, C.I. I. Condensed monoazo yellow pigments such as CI Pigment Yellow 155; I. Pigment yellow 180, C.I. I. Pigment yellow 150 and C.I. I. Other yellow pigments such as CI Pigment Yellow 185, and C.I. I. Solvent Yellow 19, C.I. I. Solvent Yellow 77, C.I. I. Solvent Yellow 79, C.I. I. Examples include yellow dyes such as Disperse Yellow 164.

  Examples of the colorant for magenta toner include C.I. I. Pigment red 48, C.I. I. Pigment red 49: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 81, C.I. I. Pigment red 122, C.I. I. Pigment red 5, C.I. I. Pigment red 146, C.I. I. Pigment red 184, C.I. I. Pigment red 238 and C.I. I. Red or red pigments such as C.I. Pigment Violet 19; I. Solvent Red 49, C.I. I. Solvent Red 52, C.I. I. Solvent Red 58, C.I. I. Examples thereof include red dyes such as Solvent Red 8.

  Examples of the colorant for cyan toner include C.I. I. Pigment blue 15: 3 and C.I. I. Blue dyes and pigments of copper phthalocyanine and its derivatives such as CI Pigment Blue 15: 4; I. Pigment green 7 and C.I. I. Examples thereof include green pigments such as CI Pigment Green 36 (phthalocyanine green). The addition amount of the colorant is preferably 1 part by weight or more and 15 parts by weight or less, and more preferably 2 parts by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the binder resin.

The water-absorbing conductive particles are obtained by surface-treating particles serving as a base (hereinafter referred to as “mother particles”) with an ionomer silane coupling agent. As the base particles, particles having water absorption, more specifically inorganic particles having water absorption are used. In this embodiment, conductivity can be imparted to the mother particles by surface-treating the mother particles with an ionomer silane coupling agent. As the ionomer silane coupling agent, a silane coupling agent having an ionic group can be used. Such a silane coupling agent can be produced, for example, by the method disclosed in JP-A-8-85737. Specifically, the ionomer silane coupling agent is prepared, for example, by mixing an acid functional silane, an acid functional film forming agent, and an ionic compound having a metal cation. Acid functional silanes consist of an acid group covalently bonded to a trialkoxysilane, trihydroxysilane or silsesquioxane structure by an organic linking group. That is, the acid functional silane has one of the structures represented by the following general formulas (a1) to (a3) in the molecule, and includes an oligomeric siloxane condensation product.
Z-Q-Si (OR ² ) ₃ (a1)
Z-Q-Si (OH) ₃ (a2)
Z-Q-SiO _3/2 (a3)

In general formulas (a1) to (a3), Z represents an acid group, and Q represents a divalent organic linking atomic group. In the general formula (a1), R ² represents an alkyl group. The group “—SiO _3/2 ” in the general formula (a3) represents a silsesquioxane structure. “Silsesquioxane” is one type of polysiloxane that is a silicon-containing polymer whose main chain is composed of siloxane bonds. Since silicon in silsesquioxane is bonded to three oxygens and oxygen is bonded to two silicons, it is expressed as “—SiO _3/2 ”.

Examples of the alkyl group represented by the symbol R ² include alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group, and a propyl group. The acid group Z can be any acid group that can be obtained from protonated oxygen acids of carbon, phosphorus, sulfur, selenium or arsenic. Examples of such acid groups include sulfonic acid, selenic acid, arsenic acid, phosphoric acid, phosphonic acid and carboxylic acid functional groups. The acid group Z is preferably a carboxylic acid group (—COOH). Examples of the linking atomic group Q include a short-chain hydrocarbon group such as a dimethylene group and trimethylene. Examples of acid functional film forming agents include carboxylated thermoplastic polymers such as copolymers of styrene and methacrylic acid, and ionic compounds having metal cations include those of metals such as sodium or calcium. A hydroxide is mentioned.

As the ionomer silane coupling agent, an ionomer silane coupling agent represented by the following general formula (1), which is a silane coupling agent having an ionic group, is preferably used. By using the ionomer silane coupling agent represented by the general formula (1), the dispersibility of the water-absorbing conductive particles in the binder resin is good, so that the toner can be charged as uniformly as possible. it can. Further, since the water-absorbing conductive particles have a sufficient adsorbed water holding capacity, the volume resistivity of the toner can be appropriately lowered by the sufficient water-adsorbing water holding capacity of the water-absorbing conductive particles in a low humidity environment. Accordingly, the toner can be charged as uniformly as possible, and an excessive increase in the charge amount in a low humidity environment can be more reliably suppressed, so that the toner has a constant image density regardless of humidity. An image can be formed more stably.
_3/2 OSi—R ¹ —COO ^— M ⁺ (1)
(Wherein R ¹ represents an alkylene group, and M ⁺ represents a monovalent cation)

Examples of the alkylene group represented by the symbol R ¹ include an alkylene group having 1 to 3 carbon atoms such as a dimethylene group and trimethylene. Examples of the monovalent cation represented by the symbol M ⁺ include alkali metal ions such as sodium ion and potassium ion.

  The ionomer silane coupling agent represented by the general formula (1) is preferably used as a surface treatment agent for mother particles when inorganic particles having a hydroxyl group on the surface are used as mother particles. Known inorganic particles such as silica particles, titanium oxide particles and alumina particles can be used as the inorganic particles having water absorption and having hydroxyl groups on the surface. Among them, silica particles are preferable. Silica particles are preferable to other inorganic particles in that they have a high activity of hydroxyl groups on the surface and are therefore highly reactive with a coupling agent and have higher water absorption. That is, the water-absorbing conductive particles are preferably silica particles surface-treated with an ionomer silane coupling agent. By using silica particles as the mother particles, the water-absorbing conductive particles have a sufficient adsorbed water retention capability and better dispersibility in the binder resin, so that the toner can be charged more uniformly. An excessive increase in the charge amount in a low humidity environment can be suppressed more reliably. Therefore, an image having a constant image density can be formed more stably regardless of humidity. Further, since the water-absorbing conductive particles are silica particles surface-treated with an ionomer silane coupling agent, the influence of the water-absorbing conductive particles on the toner color can be suppressed. Therefore, it is possible to suppress an excessive increase in the charge amount in a low humidity environment and an excessive decrease in the charge amount in a high humidity environment, and to realize a toner that is excellent in color development and color mixing properties and suitable as a color toner. Is possible.

  The number average particle diameter of the water-absorbing conductive particles is preferably 5 nm or more and 70 nm or less. Water-absorbing conductive particles having a number average particle diameter of less than 5 nm are difficult to produce mother particles, resulting in high costs. In addition, the water-absorbing conductive particles having a number average particle diameter exceeding 70 nm are difficult to uniformly disperse the water-absorbing conductive particles in the binder resin, so that the toner charge amount is likely to vary and fogging is likely to occur. Become. When the number average particle diameter of the water absorbent conductive particles is 5 nm or more and 70 nm or less, the water absorbent conductive particles can be more uniformly dispersed in the binder resin. As a result, the toner charge amount can be stabilized without causing poor dispersion of the water-absorbing conductive particles, and an image having a constant image density can be stably formed regardless of humidity. Can do.

  Water-absorbing conductive particles can be prepared by surface-treating the mother particles with an ionomer silane coupling agent aqueous solution, and water-absorbing conductive particles exhibiting sufficient water absorbing ability can be obtained. As a method of surface treatment of the mother particles with an ionomer silane coupling agent, for example, when silane is surface treated, an ionomer silane coupling agent aqueous solution obtained by dissolving the ionomer silane coupling agent in water is attached to the surface of the silica particles. The silica particles to which the aqueous solution is adhered are dried at a temperature of 100 to 175 ° C. However, it is not limited to this. The concentration by weight of the aqueous ionomer silane coupling agent solution for treating the mother particles is preferably 1% by weight or more and 10% by weight or less. This amount is determined by routine experimentation.

  The amount of water-absorbing conductive particles added is 0.10 parts by weight or more and 5.0 parts by weight or less with respect to 100 parts by weight of the binder resin. If the amount of water-absorbing conductive particles added to the binder resin is less than 0.10 parts by weight, the number of water-absorbing conductive particles that work effectively is essentially small. There is a possibility that the image density is lowered due to an excessive increase in the toner charge amount below. On the other hand, when the amount of water-absorbing conductive particles exceeds 5.0 parts by weight, there is a risk of poor dispersion of the water-absorbing conductive particles in the binder resin, poor fluidity due to excessive moisture, and reduced charge. In addition, the presence of a large number of water-absorbing conductive particles causes excessive frictional charging and increases the initial toner charge amount. Therefore, the absolute value of the charging potential becomes too large and the density of the initial image becomes insufficient. By adding the water-absorbing conductive particles to the binder resin within the above range, the dispersibility in the toner is improved and the toner can have a sufficient water-absorbing ability, so that the toner can be charged in a low-humidity environment. An excessive increase in the amount can be suppressed. Therefore, an image having a constant image density can be formed more stably.

The volume resistivity of the water-absorbing conductive particles is preferably 1 × 10 ¹ Ω · cm to 5 × 10 ⁵ Ω · cm. When the volume resistivity is less than 1 × 10 ¹ Ω · cm, the electric charge easily leaks, and the toner charge amount decreases when the toner is left in the developing tank containing the developer containing the toner in the image forming apparatus. If an image is formed after being left unattended, image fog is likely to occur. On the other hand, when the volume resistivity of the water-absorbing conductive particles exceeds 5 × 10 ⁵ Ω · cm, the charge amount of the toner tends to increase in a low humidity environment. By using water-absorbing conductive particles having an appropriate resistance of 1 × 10 ¹ Ω · cm to 5 × 10 ⁵ Ω · cm, unnecessary charge leakage can be suppressed. Accordingly, it is possible to suppress a decrease in the charge amount of the toner when the charged toner is left, and to prevent an excessive decrease in the charge amount of the toner in a high humidity environment. Further, it is possible to prevent an excessive increase in the charge amount of the toner in a low humidity environment. Therefore, the charge amount of the toner can be stabilized and an image having a constant image density can be stably formed. The volume resistivity of the water-absorbing conductive particles is measured by a compression method.

In this embodiment, the volume resistivity of the water-absorbing conductive particles by the compression method was measured according to the following procedure. First, the water-absorbing conductive particles after being left for 24 hours in an environment of an air temperature of 20 ° C. and a humidity of 65% are sandwiched between two copper plate electrodes, the pressing pressure is 10 kg / cm ² , and the distance between the copper plate electrodes A compact having a thickness of 8 mm to 10 mm was produced. Next, a voltage of 500 V / cm was applied between the copper plate electrodes as the electric field strength, the volume resistivity 15 seconds after the voltage application start was measured, and the value was taken as the volume resistivity of the water-absorbing conductive particles.

  The toner of the present exemplary embodiment contains a charge control agent and a release agent in the colored particles together with a binder resin, a colorant, and water-absorbing conductive particles. In other embodiments of the present invention, the toner may contain other additives and may not contain a charge control agent and a release agent.

  A known charge control agent can be used as the charge control agent. Specifically, as a charge control agent for negatively chargeable toner that imparts negative chargeability, chromium azo complex dyes, iron azo complex dyes, cobalt azo complex dyes, salicylic acid and derivatives thereof complexes with chromium, zinc, aluminum, and boron And salt compounds, complexes of naphtholic acid and its derivatives with chromium, zinc, aluminum, boron and salt compounds, complexes of benzylic acid and its derivatives with chromium, zinc, aluminum, boron and salts thereof, long-chain alkyl carboxylates And long-chain alkyl sulfonates.

  Examples of charge control agents for positively chargeable toners that impart positive chargeability include nigrosine dyes and derivatives thereof, triphenylmethane derivatives, quaternary ammonium salts, quaternary phosphonium salts, quaternary pyridinium salts, guanidine salts, and amidine salts. Derivatives and the like can be mentioned.

  The addition amount of the charge control agent is preferably in the range of 0.1 to 20 parts by weight and more preferably in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  As release agents, synthetic waxes such as polypropylene and polyethylene, paraffin wax and derivatives thereof, petroleum waxes such as microcrystalline wax and derivatives thereof, and modified waxes thereof, carnauba wax, rice wax, candelilla wax, and other plant systems A wax etc. can be mentioned. By including these release agents in the toner, the releasability of the toner with respect to the fixing roller or the fixing belt can be improved, and high temperature / low temperature offset during fixing can be prevented. The addition amount of the release agent is not particularly limited, but is preferably in the range of 1 to 5 parts by weight with respect to 100 parts by weight of the binder resin.

  Such colored particles can be produced by a known method such as a kneading pulverization method or a polymerization method. For example, in the kneading pulverization method, a binder resin, a colorant, water-absorbing conductive particles, a charge control agent, a release agent are used. And other additives are mixed by a mixer such as a Henschel mixer, a super mixer, a mechano mill, or a Q-type mixer, and the resulting raw material mixture is about 100-180 ° C. by a kneader such as a twin-screw kneader or a single-screw kneader. The resulting kneaded product is cooled and solidified at a temperature of 5 ° C., and the solidified product is pulverized by an air pulverizer such as a jet mill, and the particle size is adjusted as necessary.

  As the colored particles, colored particles having a volume average particle diameter of 3 μm or more and 15 μm or less are used. The volume average particle diameter of the colored particles is measured using a 100 μm aperture with a Coulter counter manufactured by Beckman Coulter.

  The colored particles may be used as a toner as they are, but in the present embodiment, the colored particles are used as a toner with an external additive added thereto. That is, the toner of this embodiment includes colored particles and an external additive that is externally added to the colored particles. By externally adding hydrophobic particles having hydrophobicity to the colored particles, the fluidity of the toner can be improved without causing an excessive decrease in the charge amount of the toner in a high humidity environment. Therefore, since the charge amount of the toner is further stabilized, an image having a constant image density can be formed more stably.

  As an external additive externally added to the colored particles, the surface of inorganic particles such as silica, titanium oxide, and alumina is subjected to a surface treatment with, for example, a silane coupling agent, a titanium coupling agent, or silicone oil to impart hydrophobicity. Hydrophobic particles can be used. In particular, silica particles having hexamethyldisilazane (abbreviation: HMDS) as a silane coupling agent and having a trimethylsilyl group introduced on the surface are excellent in hydrophobicity and insulating properties. In the environment, an excellent effect of more reliably suppressing a decrease in the charge amount of the toner is obtained, and a toner having an effective charge amount is realized. In addition, a toner having excellent fluidity is realized. The volume average particle size of the hydrophobic particles used as the external additive is preferably 5 nm or more and 100 nm or less. In the present invention, the particle size of the external additive is measured using a scanning electron microscope (SEM).

  As specific examples of the hydrophobic particles, Aerosil 50 (volume average particle size: about 30 nm) manufactured by Nippon Aerosil Co., Ltd., which is a hydrophobic particle obtained by surface treatment of silica particles with HMDS, Aerosil 90 (volume average particle size: About 30 nm), Aerosil 130 (volume average particle size: about 16 nm), Aerosil 200 (volume average particle size: about 12 nm), Aerosil 300 (volume average particle size: about 7 nm) and Aerosil 380 (Volume average particle size: about 7 nm) ), Alumina particles C (volume average particle size: about 13 nm) manufactured by Degussa, Germany, which are hydrophobic particles obtained by surface treatment of alumina particles with HMDS, and hydrophobic particles obtained by surface treatment of titanium oxide particles with HMDS Titanium oxide P-25 (volume average particle size: about 21 nm) and MOX170 (volume average particle size: about 15) m), and Ishihara Sangyo Kaisha Ltd. TTO-51 (volume average particle diameter: about 20 nm) and TTO-55 (volume average particle diameter: about 40 nm), and the like.

  The hydrophobic particles are more preferably hydrophobic conductive particles having hydrophobicity and conductivity. Among the hydrophobic particles, titanium oxide P-25 (volume average particle size: about 21 nm) and MOX170 (volume average particle size: about 15 nm), which are hydrophobic particles obtained by surface treatment of titanium oxide particles with HMDS, In addition, TTO-51 (volume average particle size: about 20 nm) and TTO-55 (volume average particle size: about 40 nm) manufactured by Ishihara Sangyo Co., Ltd. correspond to the hydrophobic conductive particles. By externally adding hydrophobic conductive particles to the colored particles, it is possible to improve the fluidity of the toner and more reliably suppress an excessive increase in the charge amount of the toner in a low humidity environment. Therefore, the toner has excellent fluidity and does not depend on humidity, and can be a toner having a constant charge amount. Therefore, an image having a constant image density can be formed more stably.

When external additives such as hydrophobic particles are externally added to the colored particles, the colored particles have a volume average particle size of 5 μm to 7 μm and a BET specific surface area of 1.5 m ² / g to 1.9 m ² / g or less is preferable. When the volume average particle size is 5 μm or less, the fluidity is extremely lowered. When the volume average particle diameter exceeds 7 μm, the transfer efficiency is lowered, and it becomes difficult to uniformly transfer the respective color toners in a full-color image, so that color unevenness may occur. In addition, the color balance may not be stably reproduced. In a colored particle having a volume average particle size of 5 μm or more and 7 μm or less, if the BET specific surface area is less than 1.5 m ² / g, the colored particle surface becomes too smooth, and thus fogging easily occurs due to poor cleaning. Become. On the other hand, if it exceeds 1.9 m ² / g, the colored particle surface will be uneven, and the external additive will enter the concave part of the colored particle surface, making it impossible to adhere the external additive uniformly to the surface. As a result, the roller effect of the external additive, that is, the effect of improving the fluidity and the spacer effect, that is, the effect of preventing charge leakage cannot be sufficiently obtained, and fog and toner scattering are likely to occur. When the volume average particle size of the colored particles is 5 μm or more and 7 μm or less and the BET specific surface area is 1.5 m ² / g or more and 1.9 m ² / g or less, the surface of the colored particles becomes smooth, and the external additive is Since it can prevent entering into the recessed part of the colored particle surface, the roller effect and spacer effect of an external additive can fully be exhibited, and generation | occurrence | production of fog and toner scattering can be prevented. Further, it is possible to prevent the occurrence of defective cleaning and to prevent the occurrence of fogging. Therefore, an image having a constant image density can be formed more stably.

  In the present embodiment, the “BET specific surface area” is a surface area of particles per unit weight measured by the BET method. In this embodiment, the measurement value of the BET specific surface area of the colored particles is a measurement value obtained by a three-point measurement method using a BET specific surface area measurement device Gemini 2360 (manufactured by Shimadzu Corporation). As a method for controlling the BET specific surface area of the colored particles, a known method can be used. For example, the colored particles are rotated in a cylindrical pipe at a high speed to take a corner, or the toner is melted instantaneously in a hot air current. There is a method such as a saffusion system.

The volume resistivity of the hydrophobic particles is preferably 1 × 10 ¹ Ω · cm to 5 × 10 ⁵ Ω · cm. The volume resistivity of the hydrophobic particles can be adjusted by changing the type of surface treatment agent used and the amount of treatment. Hydrophobic particles obtained by treating silica particles with hexamethyldisilazane as a silane coupling agent are preferable because they have high resistance, excellent hydrophobicity, and the toner charge amount is stable even in a high humidity environment.

  The toner of the present exemplary embodiment is manufactured by mixing hydrophobic particles such as silica and titanium oxide and colored particles using an air flow mixer such as a Henschel mixer, that is, performing an external addition process.

  The toner of the present invention can be used as a one-component developer, or mixed with a carrier and used as a two-component developer. The two-component developer can be produced, for example, by mixing toner in a proportion of 3 parts by weight or more and 15 parts by weight or less with respect to 100 parts by weight of the carrier and stirring the mixture with a mixer such as a Nauta mixer.

  Although it does not restrict | limit especially as a carrier, The carrier whose volume average particle diameter is 20 micrometers or more and 100 micrometers or less is preferable. When the particle size of the carrier is too small, the carrier moves from the developing roller to the photosensitive drum at the time of development, thereby causing white spots in the obtained image. On the other hand, when the particle size of the carrier is too large, the dot reproducibility deteriorates and the image becomes rough. Therefore, the volume average particle diameter of the carrier is preferably 20 μm or more and 100 μm or less, and more preferably 30 μm or more and 60 μm or less. The volume average particle diameter of the carrier is a value when measured under the condition of a dispersion pressure of 3.0 bar using a dry dispersion apparatus RODOS (manufactured by SYMPATEC) in a laser diffraction particle size distribution measuring apparatus HELOS (manufactured by SYMPATEC). It is.

  The saturation magnetization of the carrier is preferably 30 emu / g or more and 100 emu / g or less. The lower the saturation magnetization, the softer the magnetic brush in contact with the photosensitive drum, so that an image faithful to the electrostatic latent image can be obtained. However, if the saturation magnetization is too low, carriers will adhere to the surface of the photosensitive drum and white spots will occur. Is likely to occur. If the saturation magnetization is too high, it becomes difficult to obtain an image faithful to the electrostatic latent image due to the stiffening of the magnetic brush. Therefore, the saturation magnetization of the carrier is preferably 30 emu / g or more and 100 emu / g or less.

  The carrier is preferably a coated carrier in which a coating layer is provided on the surface of magnetic core particles.

  As the core particles, known magnetic particles can be used, but ferrite particles are preferred from the viewpoint of chargeability and durability. Known ferrite particles can be used, such as zinc ferrite, nickel ferrite, copper ferrite, nickel-zinc ferrite, manganese-magnesium ferrite, copper-magnesium ferrite, manganese-zinc ferrite, manganese. -Copper-zinc ferrite etc. are mentioned.

These ferrite particles can be produced by a known method. For example, ferrite raw materials such as Fe ₂ O ₃ and Mg (OH) ₂ are mixed, and this mixed powder is heated in a heating furnace and calcined. The obtained calcined product is cooled and then pulverized to a particle size of about 1 μm with a vibration mill, and a dispersant and water are added to the pulverized powder to prepare a slurry. The slurry is wet pulverized with a wet ball mill, and the resulting suspension is granulated and dried with a spray dryer to obtain ferrite particles.

  A known resin material can be used as the coating material constituting the coating layer, and for example, an acrylic resin or a silicone resin can be used. A coated carrier coated with a silicone resin is preferable because the boron compound is hardly spent on the surface, that is, hardly adheres to the surface, and can maintain the charge imparting ability of the toner for a long period of time.

  Known silicone resins can be used, such as silicone varnishes (trade names: TSR115, TSR114, TSR102, TSR103, YR3061, TSR110, TSR116, TSR117, TSR108, TSR109, TSR180, TSR181, TSR187, TSR144 and TSR165, etc. All are manufactured by Momentive Performance Materials Japan, KR271, KR272, KR275, KR280, KR282, KR267, KR269, KR211 and KR212, all manufactured by Shin-Etsu Chemical Co., Ltd.), alkyd-modified silicone varnish (trade name: TSR184, TSR185 etc., both made by Momentive Performance Materials Japan), epoxy modified Ricone varnish (trade names: TSR194 and YS54, etc.), polyester-modified silicone varnish (trade name: TSR187, etc., manufactured by Momentive Performance Materials Japan), acrylic-modified silicone varnish (trade names: TSR170 and TSR171, etc.) , All manufactured by Momentive Performance Materials Japan), urethane-modified silicone varnish (trade name: TSR175, etc., all manufactured by Momentive Performance Materials Japan), reactive silicone resin (trade name: KA1008, KBE1003, KBC1003, KBM303, KBM403, KBM503, KBM602, and KBM603, all manufactured by Shin-Etsu Chemical Co., Ltd.).

  A conductive material is added to the coating layer in order to control the volume resistivity value of the carrier. Examples of the conductive material include silicon oxide, alumina, carbon black, graphite, zinc oxide, titanium black, iron oxide, titanium oxide, tin oxide, potassium titanate, calcium titanate, aluminum borate, magnesium oxide, barium sulfate, Examples include conductive materials such as calcium carbonate.

  Among these conductive materials, carbon black is preferable from the viewpoint of production stability, cost, and low electrical resistance. The type of carbon black is not particularly limited, but those having a dibutyl phthalate (DBP) oil absorption in the range of 90 ml / 100 g or more and 170 ml / 100 g or less are preferable because of excellent production stability. A primary particle size of 50 nm or less is more preferable because of excellent dispersibility. A conductive material can be used individually by 1 type, or can use 2 or more types together. The amount of the conductive material used is preferably 0.1 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the covering material.

  A known method can be employed to coat the coating material on the carrier particles. For example, an immersion method in which carrier particles are immersed in an organic solvent solution of the coating material, a spray method in which the organic solvent solution of the coating material is sprayed on the carrier particles, an organic solvent solution of the coating material in a state where the carrier particles are suspended by flowing air And a kneader coater method in which carrier particles and an organic solvent solution of a coating material are mixed in a kneader coater to remove the solvent. A conductive material for resistance value control is added to the organic solvent solution of the coating material together with the coating material.

Next, the image forming apparatus of the present invention will be described.
FIG. 1 is a schematic view schematically showing one embodiment of an image forming apparatus 40 according to the present invention. As shown in FIG. 1, the image forming apparatus 40 is a tandem color image forming apparatus including four image forming units 1 to 4.

  The image forming apparatus 40 includes, as four image forming units 1 to 4, a first image forming unit 1 for forming a black toner image, a second image forming unit 2 for forming a cyan toner image, and magenta toner. A third image forming unit 3 for forming an image and a fourth image forming unit 4 for forming a yellow toner image are included.

  An intermediate transfer belt 5 which is an endless belt is disposed above the four image forming units 1 to 4 toward the paper surface of FIG. The intermediate transfer belt 5 is stretched over two support rolls 6 and rotates in the direction indicated by the arrow R. A secondary transfer roller 8 is provided opposite to one support roll 6 with the intermediate transfer belt 5 interposed therebetween. Thereafter, the upstream and downstream in the rotational direction of the intermediate transfer belt 5 are defined starting from the secondary transfer position where the secondary transfer roller 8 is disposed. As a material for the intermediate transfer belt 5, a material in which an appropriate amount of an electron conductive material is contained in a resin such as polyimide or polyamide can be used.

  The four image forming units 1 to 4 are a first image forming unit 1 that forms a toner image corresponding to black image information from the upstream side to the downstream side in the rotation direction R of the intermediate transfer belt 5. A second image forming unit 2 that forms a toner image corresponding to the image information, a third image forming unit 3 that forms a toner image corresponding to the magenta image information, and a toner image corresponding to the yellow image information. The fourth image forming units 4 are arranged in this order.

  Inside the intermediate transfer belt 5, a primary transfer roller 7 that transfers the monochromatic toner image formed by each of the image forming units 1 to 4 onto the intermediate transfer belt 5, forms each image with the intermediate transfer belt 5 interposed therebetween. Each is provided so as to face the units 1 to 4. The single color toner images formed by the image forming units 1 to 4 are transferred so as to be superimposed on the intermediate transfer belt 5 to form one color toner image.

  On the downstream side in the rotation direction R of the intermediate transfer belt 5 from the fourth image forming unit 4 that forms a toner image corresponding to yellow image information, the color image formed on the intermediate transfer belt 5 is used as a recording medium. A secondary transfer roller 8 for transferring is provided.

  A belt cleaning unit 10 for cleaning the surface of the intermediate transfer belt 5 is provided downstream of the secondary transfer roller 8 in the rotation direction R of the intermediate transfer belt 5. The belt cleaning unit 10 includes a belt cleaning brush 11 disposed in contact with the intermediate transfer belt 5 and a belt cleaning blade 12. The belt cleaning blade 12 is disposed downstream of the belt cleaning brush 11 in the rotation direction R of the intermediate transfer belt 5.

  A tray 14 for storing a recording medium is disposed below the four image forming units 1 to 4 toward the paper surface of FIG. The recording medium in the tray 14 is conveyed by a plurality of paper feed rollers 13 to a secondary transfer position where the secondary transfer roller 8 faces the intermediate transfer belt 5. An arrow P indicates the conveyance direction of the recording medium.

  A fixing unit 15 for fixing the color toner image transferred to the recording medium to the recording medium is provided downstream of the secondary transfer roller 8 in the conveyance direction P of the recording medium. A discharge roller 13 a for discharging the recording medium on which the color toner image is fixed from the image forming apparatus 40 is provided downstream of the fixing unit 15 in the recording medium conveyance direction P.

  The single color toner images formed by the image forming units 1 to 4 are sequentially transferred onto the intermediate transfer belt 5 to form a color toner image on the intermediate transfer belt 5. The color toner image on the intermediate transfer belt 5 is secondarily transferred to the recording medium conveyed by the paper feed roller 13 at the secondary transfer position, and then fixed to the recording medium by the fixing unit 15. The recording medium on which the color toner image is fixed and the color image is formed is discharged from the image forming apparatus 40 by the paper discharge roller 13a. After the secondary transfer, the toner remaining on the intermediate transfer belt 5 without being transferred to the recording medium is removed by the belt cleaning unit 10.

  FIG. 2 is a schematic diagram showing the first image forming unit 1 shown in FIG. The configurations of the second image forming unit 2, the third image forming unit 3, and the fourth image forming unit 4 are substantially the same. The toner contained in the developer contained in the developing tank 27 is black toner in the first image forming unit 1, cyan toner in the second image forming unit 2, and magenta toner in the third image forming unit 3. In the fourth image forming unit 4, yellow toner is used. Therefore, detailed description of the configuration of the first image forming unit 1, the second image forming unit 2, the third image forming unit 3, and the fourth image forming unit 4 is omitted.

  The first image forming unit 1 includes a cylindrical photosensitive drum 16 that is an image carrier, a charger 17 that is provided around the photosensitive drum 16, and charges the photosensitive drum 16. An exposure device 18 for writing an electrostatic latent image, a developing device 19 for visualizing an electrostatic latent image on the photosensitive drum 16, and a photosensitive drum cleaner 20 for removing a residue including toner remaining on the photosensitive drum 16 after primary transfer. Including. The charger 17 and the exposure device 18 function as a latent image forming unit.

  The charger 17 is a non-contact charger in the present embodiment, and is realized by, for example, a scorotron charger. The charger 17 performs corona discharge on the photosensitive drum 16 to charge the photosensitive drum 16 to a predetermined potential. The charger 17 may be realized by a corotron charger. The charger 17 is not limited to a non-contact type charger, and may be realized by a contact type charger, for example, a charging roller or a charging brush.

  The exposure device 18 is composed of, for example, a laser exposure device, performs exposure by laser scanning according to an image signal, and changes the surface potential of the photosensitive drum 16 charged by the charger 17, thereby changing the surface potential. An electrostatic latent image is formed. An LDE array device or the like can also be used as the exposure device.

  The developing device 19 accommodates a developer containing the toner of the present invention in the developing tank 27, and develops the electrostatic latent image on the surface of the photosensitive drum 16 with the toner contained in the developer to form a toner image. As the developer, there are a two-component developer composed of toner and carrier and a one-component developer containing only the toner without containing the carrier. In the image forming apparatus 40 of the present embodiment, the developing device 19 has a configuration corresponding to the two-component developer by storing the two-component developer in the developing tank 27.

  The photosensitive drum cleaner 20 includes a cleaning blade 21, a cleaner housing 22, and a seal 23.

  The cleaning blade 21 is disposed in pressure contact with the rotation direction Rd of the photosensitive drum 16 in the counter direction, and scrapes off the residue on the surface of the photosensitive drum 16. The cleaner housing 22 accommodates the scraped residue, and the cleaning blade 21 is attached to the cleaner housing 22. The seal 23 seals the inside of the cleaner housing 22. One end of the seal 23 is fixed to the cleaner housing 22 upstream of the cleaning blade 21 in the rotation direction Rd of the photoconductor drum 16, and the other end is the photoconductor drum 16. Is placed in contact.

  FIG. 3 is a schematic diagram showing a configuration around the developing device 19 in the first image forming unit 1 shown in FIG. The developing device 19 includes a developing tank 27 in which a two-component developer (hereinafter sometimes simply referred to as “developer”) is accommodated, and the developing tank 27 faces a peripheral surface of the photosensitive drum 16. In addition, an opening 30 that opens toward the outer peripheral surface of the photosensitive drum 16 is formed.

  A developing roller 24 is provided inside the developing tank 27 so as to face the outer peripheral surface of the photosensitive drum 16 through the opening of the opening 30. The developing roller 24 has a cylindrical shape, and carries the developer on the outer peripheral surface thereof to convey the toner in the developer to the photosensitive drum 16 to develop the electrostatic latent image on the photosensitive drum 16. To do. The developing roller 24 is disposed at a distance from the outer peripheral surface of the photosensitive drum 16.

  The developing roller 24 includes a columnar multipolar magnetized member 25 magnetized in multiple poles, and a nonmagnetic sleeve 26 that is rotatably fitted on the multipolar magnetized member 25. Both ends of the multipolar magnetized member 25 in the axial direction are supported non-rotatably on both side walls of the developing tank 27.

  In the multipolar magnetized member 25, a plurality of magnetic poles are spaced apart from each other at a plurality of positions in the circumferential direction. The magnetic poles of the multipolar magnetized member 25 are formed by, for example, arranging bar magnets having a rectangular cross-sectional shape radially at a plurality of positions in the circumferential direction of the multipolar magnetized member 25. In the present embodiment, the multipolar magnetized member 25 has five magnetic poles, specifically, three N poles N1, N2, N3 and two S poles S1, S2.

  The magnetic pole N1 is disposed at a position facing the photosensitive drum 16. With the rotation axis of the sleeve 26 as the center of rotation, the magnetic pole S1 is arranged at a position displaced, for example, by 59 ° from the magnetic pole N1 in the rotational direction Ra of the sleeve 26, and the magnetic pole N2 is in the rotational direction of the sleeve 26 from the magnetic pole N1. For example, the magnetic pole N3 is disposed on the upstream side of Ra by a 117 ° angular displacement, the magnetic pole N3 is disposed on the upstream side in the rotational direction Ra of the sleeve 26 from the magnetic pole N1, for example, at a position displaced by 224 °, and the magnetic pole S2 is disposed on the magnetic pole N1. For example, the sleeve 26 is arranged at a position displaced by an angle of 282 ° on the upstream side in the rotational direction Ra.

  When the magnetic flux density of the N pole is positive (plus (+)) and the magnetic flux density of the S pole is negative (minus (−)), the peak value of the magnetic flux density of the magnetic pole N1 is, for example, 110 mT, and the magnetic flux of the magnetic pole S1. The peak value of the density is, for example, −78 mT, the peak value of the magnetic flux density of the magnetic pole N2 is, for example, 56 mT, the peak value of the magnetic flux density of the magnetic pole N3 is, for example, 42 mT, and the peak value of the magnetic flux density of the magnetic pole S2. Is, for example, −80 mT.

  Near the opening 30 of the developing tank 27 and upstream of the portion of the developing roller 24 facing the photosensitive drum 16 in the rotational direction Ra of the sleeve 26 and in the rotational direction Ra of the sleeve 26 relative to the pumping pole N2. A regulating member 28 that regulates the thickness of the developer layer carried on the outer peripheral surface of the developing roller 24 and regulates the transport amount of the developer to the electrostatic latent image is located at a position facing the downstream side portion of the developing roller 24. Provided. The regulating member 28 is arranged at a predetermined interval with respect to the outer peripheral surface of the developing roller 24.

  An agitating member 29 that agitates the developer in the developing tank 27 and supplies it to the developing roller 24 is rotatably provided in the developing tank 27 at a position facing the developing roller 24.

  In the image forming apparatus 40, the developing device 19 develops the electrostatic latent image using the toner of the present invention to form an image. Therefore, when a large number of images with low coverage are printed in a low-humidity environment, the change with time changes. The developer can be prevented from causing an increase in charge, and the image density can be prevented from decreasing. Therefore, an image having a constant image density can be formed stably.

The toners of Examples and Comparative Examples of the present invention were prepared by the following method.
[Example 1]
<Production of water-absorbing conductive particles>
After treating silica particles (trade name: TSR115, manufactured by Momentive Performance Materials Japan, number average particle size 16 nm) with an aqueous ionomer silane coupling agent (concentration 20%) represented by the following general formula (2) Filtered and dried to produce water-absorbing conductive particles. The volume resistivity of the obtained water-absorbing conductive particles was 2 × 10 ² Ω · cm. The number average particle diameter of the obtained water-absorbing conductive particles was 60 nm.
_3/2 OSi—CH ₂ CH ₂ CH ₂ —COO ^— Na ⁺ (2)

<Manufacture of toner>
Binder resin (polyester resin obtained by polycondensation using bisphenol A propylene oxide, terephthalic acid and trimellitic anhydride as monomers: glass transition temperature 60 ° C., softening temperature 115 ° C.) 100 parts by weight Colorant (C.I. Pigment Blue 15: 3) 5 parts by weight Charge control agent (boron compound: LR-147 manufactured by Nippon Carlit) 2 parts by weight Release agent (microcrystalline wax: HNP-9 manufactured by Nippon Seiki Co., Ltd.) 3 parts by weight Water-absorbing conductive particles 0.1 parts by weight

The toner material was premixed for 10 minutes with a Henschel mixer, and then melted and kneaded and dispersed using a kneading and dispersing apparatus (Mitsui Mining Co., Ltd .: Knee Dick MOS140-800). The kneaded material is roughly pulverized by a cutting mill, then finely pulverized by a jet type pulverizer (manufactured by Nippon Pneumatic Industry Co., Ltd .: IDS-2 type), and after fine pulverization, an air classifier (manufactured by Nippon Pneumatic Industry Co., Ltd.). : MP-250 type) was used to obtain colored particles having a volume average particle size of 6.6 ± 0.2 μm and a BET specific surface area of 1.8 ± 0.1 m ² / g. The volume average particle diameter was measured with Coulter Multisizer II (manufactured by Beckman Coulter, Inc.).

100 parts by weight of the obtained colored particles were mixed with 1.0 part by weight of silica particles (volume resistivity: 5 × 10 ¹³ Ω · cm) whose surface was treated with HMDS and having a number average particle diameter of 7 nm. The toner of Example 1 was prepared by stirring for 2 minutes with an airflow mixer (manufactured by Mitsui Mining Co., Ltd .: Henschel mixer) with a tip speed set to 15 m / s.

[Example 2]
A toner of Example 2 was produced in the same manner as in Example 1 except that the amount of water-absorbing conductive particles added was changed to 0.3 parts by weight.

[Example 3]
A toner of Example 3 was produced in the same manner as in Example 1 except that the amount of water-absorbing conductive particles added was changed to 0.6 parts by weight.

[Example 4]
A toner of Example 4 was produced in the same manner as in Example 1 except that the amount of water-absorbing conductive particles added was changed to 1.0 part by weight.

[Example 5]
A toner of Example 5 was produced in the same manner as in Example 1 except that the amount of water-absorbing conductive particles added was changed to 2.0 parts by weight.

[Example 6]
A toner of Example 6 was produced in the same manner as in Example 1 except that the amount of water-absorbing conductive particles added was changed to 5.0 parts by weight.

[Comparative Example 1]
A toner of Comparative Example 1 was produced in the same manner as in Example 1 except that the amount of water-absorbing conductive particles added was changed to 7.0 parts by weight.

[Comparative Example 2]
A toner of Comparative Example 2 was produced in the same manner as in Example 1 except that the amount of water-absorbing conductive particles added was changed to 10.0 parts by weight.

[Comparative Example 3]
The toner of Comparative Example 3 was prepared in the same manner as in Example 1 except that colored particles were prepared using silica (trade name: TSR115, manufactured by Shin-Etsu Chemical Co., Ltd.) surface-treated with HMDS instead of water-absorbing conductive particles. Produced.

<Career>
Carriers to be mixed with the toners of Examples and Comparative Examples were produced by the following method.

After mixing the ferrite raw material in a ball mill, calcined at 900 ° C. in a rotary kiln, and pulverized the obtained calcined powder to a volume average particle size of 2 μm or less using a steel ball as a grinding medium by a wet pulverizer. did. The obtained ferrite powder was granulated by a spray drying method, and the granulated product was fired at 1300 ° C. After firing, the mixture was crushed using a crusher to obtain core particles composed of a ferrite component having a volume average particle diameter of about 50 μm and a volume resistivity of 1 × 10 ⁹ Ω · cm.

  Next, as a coating liquid for coating the core particles, 100 parts by weight of a silicone resin (trade name: TSR115, manufactured by Shin-Etsu Chemical Co., Ltd.) and carbon black (primary particle size 25 nm, oil absorption 150 ml / 100 g) 3. 0 part by weight was dissolved and dispersed in toluene to prepare a coating solution for coating.

The prepared coating liquid for coating was coated on the core particles composed of the ferrite component by a spray coating apparatus. Toluene was completely removed by evaporation to prepare a carrier having a volume average particle size of 50 μm, a silicone resin film thickness of 1 μm, a volume resistivity of 2 × 10 ¹⁰ Ω · cm, and a saturation magnetization of 65 emu / g.

<Two-component developer>
Using the toners of Examples and Comparative Examples, 6 parts by weight of toner and 94 parts by weight of the carrier are respectively added to a Nauta mixer (trade name: VL-0, manufactured by Hosokawa Micron Corporation) and mixed by stirring for 20 minutes. A two-component developer was prepared.

<Evaluation>
In the image forming apparatus 40 shown in FIG. 1, a continuous print test was performed for each of the two-component developers produced using the toners of the example and the comparative example. The continuous print test was performed using only the image forming unit 1 out of the four image forming units 1 to 4. As the developing conditions of the image forming apparatus 40, the peripheral speed of the photosensitive drum 16 is 400 mm / s, the peripheral speed of the developing roller 24 is 560 mm / s, the gap between the photosensitive drum 16 and the developing roller 24 is 0.42 mm, and the developing roller 24 and the regulating member 28 are set to be 0.5 mm, the toner adhesion amount on the paper in the solid image portion (100% density) is 0.5 mg / cm ² , and the toner adhesion amount in the white background portion is the smallest. The surface potential and the developing bias of the photosensitive drum 16 were adjusted under the following conditions. As a test paper, an A4 size electrophotographic recording medium (multi receiver: manufactured by Sharp Document System) was used.

  In order to evaluate the performance of the developer, the continuous print test is a constant temperature and humidity test chamber set in a normal temperature and humidity (N / N) environment with a temperature of 20 ° C. and a humidity of 50%, a low temperature of 5 ° C. and a humidity of 20%. Each of the image forming units 1 in a low-temperature and low-humidity test chamber set in a low-humidity (L / L) environment and a high-temperature and high-humidity test chamber set in a high-temperature and high-humidity (H / H) environment at a temperature of 30 ° C. and a humidity of 80%. Was performed by an aging test. Specifically, 30,000 (hereinafter abbreviated as “30k”) print test of a text image in which the coverage of a print image formed on paper, that is, the coverage of the image formable region with toner is 3%. Printing was performed, and the toner charge amount and image density were measured before and after printing 30k sheets. The toner charge amount was measured using a suction type small charge amount measuring device (manufactured by Trek Japan Co., Ltd .: 210HS-2A).

The image density was measured by printing a solid image (100% density) with a side of 3 cm and using a reflection densitometer (Macbeth RD918). The evaluation criteria were as follows.
○: Good. The image density is 1.30 or more and less than 1.40, and the paper fibers are sufficiently covered with toner.
Δ: Yes. The image density is 1.25 or more and less than 1.30, or 1.40 or more and less than 1.45, and the paper fibers are appropriately covered with toner to some extent.
X: Defect. The image density is less than 1.25, or 1.45 or more. When the image density is less than 1.25, the paper fibers are insufficiently covered with toner, and when the image density is 1.45 or more, the paper fibers are excessively covered with toner.

<Result>
Tables 1 and 2 show the results of the continuous print test. However, the content of silica surface-treated with HMDS having hydrophobicity and insulating properties is described in the column of the water-absorbing conductive particle addition amount of Comparative Example 3. Table 1 shows the results before printing 30k sheets as an initial stage, and Table 2 shows the results after printing 30k sheets.

  In the toner continuous print tests of Examples 1 to 6, the toner charge amount showed an appropriate value, and an image density of a certain level or higher could be obtained.

  On the other hand, when the toner of Comparative Example 3 is used, the image density is low in the L / L environment after printing 30k sheets shown in Table 2. This indicates that in Comparative Example 3, the silica contained in the toner is surface-treated with HMDS and does not have water absorption and conductivity, so that effective charge leakage from the toner does not occur. When the toners of Comparative Example 1 and Comparative Example 2 were used, the image density greatly increased under the initial N / N environment shown in Table 1 and the N / N environment after printing 30 k sheets shown in Table 2. I missed it. This is because, in the initial stage, excessive triboelectric charging occurred due to the presence of many water-absorbing conductive particles, and after 30k printing, a large amount of water was adsorbed in an N / N environment. It is mentioned that the leak occurred too much.

1 is a schematic view schematically showing one form of an image forming apparatus 40 according to the present invention. FIG. 2 is a schematic diagram showing a first image forming unit 1 shown in FIG. 1. FIG. 3 is a schematic diagram showing a configuration around a developing device 19 in the first image forming unit 1 shown in FIG. 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st image forming unit 2 2nd image forming unit 3 3rd image forming unit 4 4th image forming unit 5 Intermediate transfer belt 6 Support roll 7 Primary transfer roller 10 Belt cleaning unit 11 Belt cleaning brush 12 Belt cleaning blade 13 Supply Paper roller 13a Paper discharge roller 14 Tray 15 Fixing unit 16 Photosensitive drum 17 Charger 18 Exposure unit 19 Developing device 20 Photosensitive drum 21 Cleaner cleaning blade 22 Cleaner housing 23 Seal 40 Developing device

Claims (10)

Containing a binder resin, a colorant, and water-absorbing conductive particles having water absorption and conductivity,
The toner according to claim 1, wherein the water-absorbing conductive particles are internally added and are contained at a weight ratio in the range of 0.10 parts by weight to 5.0 parts by weight with respect to 100 parts by weight of the binder resin.   The toner according to claim 1, wherein the water-absorbing conductive particles are obtained by treating water-absorbing particles with an ionomer silane coupling agent.   The toner according to claim 1, wherein the water-absorbing conductive particles are silica particles surface-treated with an ionomer silane coupling agent. The toner according to claim 2, wherein the ionomer silane coupling agent is an ionomer silane coupling agent represented by the following general formula (1).
_3/2 OSi—R ¹ —COO ^— M ⁺ (1)
(In the formula, R ¹ represents an alkylene group, and M ⁺ represents a monovalent cation.)   The toner according to claim 1, wherein the water-absorbing conductive particles have a number average particle diameter of 5 nm to 70 nm. The toner according to claim 1, wherein the water-absorbing conductive particles have a volume resistivity of 1 × 10 ¹ Ω · cm to 5 × 10 ⁵ Ω · cm. Colored particles in which a colorant and water-absorbing conductive particles are contained in a binder resin;
The toner according to claim 1, further comprising hydrophobic particles externally added to the colored particles and having hydrophobic properties.   The toner according to claim 7, wherein the hydrophobic particles are hydrophobic conductive particles having hydrophobicity and conductivity. 9. The toner according to claim 7, wherein the colored particles have a volume average particle diameter of 5 μm to 7 μm and a BET specific surface area of 1.5 m ² / g to 1.9 m ² / g. . An image carrier on which an electrostatic latent image is formed;
A latent image forming means for forming an electrostatic latent image on the image carrier;
An image forming apparatus comprising: a developing device that develops an electrostatic latent image formed on an image carrier using the toner according to claim 1 to form a toner image. apparatus.

Images