JP2008241776A - Electrostatic latent image developing toner and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic latent image developing toner which suppresses the drop-off or embedding of an external additive and has stable charging property and fluidity over a long term, and to provide an image forming apparatus using the electrostatic latent image developing toner. <P>SOLUTION: The electrostatic latent image developing toner is prepared by a suspension polymerization and comprises toner host particles formed by fixing resin fine particles onto the surface of suspension polymerization particles of which the roundness is 0.970 or more, wherein the average particle size of the resin fine particles is 300 to 700 nm. The image forming apparatus using the electrostatic latent image developing toner is also provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostatic latent image developing toner used for image formation and an image forming apparatus using the same.

  In general, a toner for developing an electrostatic latent image (hereinafter sometimes referred to as “toner”) used for image formation such as electrophotography is not only a binder resin and a colorant but also a wax or a charge control agent as required. In many cases, toner main particles containing the toner are used as a main component, and an external additive (silica particles or the like) for assisting the charging property and fluidity of the toner is added thereto. The toner base particles can be produced by a suspension polymerization method in which the monomer constituting the binder resin is subjected to suspension polymerization in the presence of a colorant, wax, charge control agent, or the like. There is a melt kneading method in which a control agent or the like is melt kneaded and then pulverized.

When such a toner is subjected to stress due to stirring for a long time in a developing container that is replenished during image formation, the external additive attached to the toner base particles is detached or buried in the toner base particles. In other words, the toner deteriorated, and the chargeability and fluidity of the toner were liable to decrease. In particular, in a rotary developing type image forming apparatus, since the developing device rotates, the toner in the developing device (in the developing container) is agitated by the rotation and is in a state of being easily subjected to stress.
In recent years, image forming apparatuses such as printers and multi-function machines have been downsized, and accordingly, developing containers have also been downsized. Therefore, the amount of toner contained in the developing container is reduced, and the toner is more susceptible to stress and deteriorates.

Therefore, a method of adding alumina fine particles having an average particle diameter of 0.1 to 1.0 μm as external additives to the toner base particles (for example, see Patent Document 1), or a small particle diameter of 7 nm or more and less than 20 nm. By the method of adding an external additive comprising an external additive and a large particle size external additive having a particle size of 20 to 80 nm (see, for example, Patent Document 2), the detachment and burying of the external additive are suppressed, It has been studied to prevent toner deterioration.
JP 2006-151562 A JP-A-8-15890

  However, in the methods described in Patent Documents 1 and 2, since the toner raw powder (toner mother particles) is manufactured, the external additive is adhered to the surface of the toner raw powder with a blender such as a blender or Henschel. The larger the diameter, the more difficult the external additive adheres to the surface of the toner raw powder, and it tends to float in the toner. Therefore, the suppression of the detachment and burying of the external additive is not always sufficient.

  As described above, when the external additive is detached or buried due to stirring or aging operation in the developing container and the toner deteriorates, the deteriorated toner and the undegraded toner supplied into the developing container are developed. Since the toner is mixed in the container and toners having different charging capabilities exist in the developing container, charging failure is likely to occur. As a result, there is a problem that image defects such as fogging and image density decrease occur. Such a problem is caused by adopting a non-magnetic one-component developing device and supplying toner to the developing container from the outside (that is, the toner container and developing unit are integrated like a developing cartridge, and they are replaced at the same time. This is especially true if the configuration is different.

  The present invention has been made in view of the above circumstances, and uses an electrostatic latent image developing toner that suppresses the detachment and burying of an external additive and has stable chargeability and fluidity over a long period of time. It is to realize an image forming apparatus.

  As a result of intensive studies, the present inventors have used resin particles fixed on the surface of suspension polymerization particles as mother particles, so that the resin particles serve as a spacer and the toner is subjected to stress. In addition, it was found that detachment and burying of external additives can be suppressed, and the present invention has been completed.

In other words, the toner for developing an electrostatic latent image of the present invention contains a toner base particle in which resin fine particles are fixed on the surface of a suspension polymerization particle produced by suspension polymerization and having a circularity of 0.970 or more. An electrostatic latent image developing toner, wherein the resin fine particles have an average particle diameter of 300 to 700 nm.
The resin fine particles are preferably produced as a by-product during the suspension polymerization.
Furthermore, it is preferable that the number of the resin fine particles fixed to the surface of the suspension polymerization particle is 10 to 40.

The image forming apparatus of the present invention is an image forming apparatus in which the toner for developing an electrostatic latent image is replenished, and a developer container, a developing roller, and the toner for developing an electrostatic latent image on the developing roller. A developing device having a toner supply roller to be supplied and a layer thickness regulating member disposed in contact with the surface of the developing roller; and a replenishing nozzle for replenishing the developing container with the electrostatic latent image developing toner. It is characterized by doing.
Furthermore, the image forming apparatus of the present invention may be a rotary developing system including a plurality of the developing devices.

According to the present invention, it is possible to realize an electrostatic latent image developing toner that suppresses detachment and burying of an external additive and has stable chargeability and fluidity over a long period of time, and an image forming apparatus using the same.
In addition, the electrostatic latent image developing toner of the present invention can prevent image defects such as fogging and a decrease in image density even in an image forming apparatus of a type that replenishes toner from the outside. Further, even with the rotary developing method in which the developing device rotates, image defects such as fogging and image density reduction can be prevented.

Hereinafter, the present invention will be described in detail.
The toner base particles contained in the electrostatic latent image developing toner of the present invention (hereinafter sometimes referred to as “toner”) contain at least a binder resin and a colorant, and if necessary, a charge control agent, Contains wax. Further, the toner base particles are produced by suspension polymerization, and the resin fine particles are formed on the surface of the suspension polymerization particles having a circularity of 0.970 or more, which is produced as a main product by suspension polymerization. The particle shape of the resin fine particles is 300 to 700 nm.

In this way, if the toner base particles are those in which the resin fine particles are fixed on the surface of the suspension polymerized particles, the resin fine particles serve as a spacer, so that the toner is subjected to stress such as stirring for a long time in the developing container. Even if it is received, the external additive can be prevented from being detached or buried, and as a result, the chargeability and fluidity of the toner can be stabilized. Here, when the resin fine particles are not fixed to the suspension polymerization particles but are simply aggregated on the surface of the suspension polymerization particles, the resin fine particles gradually move from the surface of the suspension polymerization particles as the toner is used. Since it is detached, the external additive is detached or buried.
The ratio of the number of the resin particles fixed on the surface of the suspension polymerization particles to the total amount of the toner base particles is preferably 100%. However, the effect of the present invention can be exhibited when the number is at least 80%.

  Further, as described later, such toner base particles are produced by a method (Method 1) in which resin fine particles are by-produced together with the suspension polymer particles by suspension polymerization and are fixed to the surface of the suspension polymer particles. Alternatively, it may be produced by a method (method 2) in which the resin particles produced in another step are fixed to the surface of the suspension polymerization particles, but method 1 is particularly preferred. In such a case, for example, as shown in FIG. 1, the resin fine particles B adhere to the surface of the suspension polymerized particles A in a cassette shape. If the resin fine particles are by-produced at the time of suspension polymerization, the suspension polymer particles and the resin fine particles inevitably have substantially the same composition, so that the resin fine particles themselves are hardly buried or detached. Further, Method 1 is simple, and toner base particles can be obtained at low cost and easily compared to Method 2.

The circularity of the suspension polymerization particles can be determined by a flow type particle analyzer. If the circularity is 0.970 or more, the above-described effects can be obtained, the transfer efficiency at the time of image formation is good, and a toner with excellent image quality can be obtained.
In addition, the particle diameter of the suspension polymerization particles is preferably 5 to 10 μm in terms of volume average particle diameter from the viewpoint of image quality.

  The average particle diameter of the resin fine particles is 300 to 700 nm, preferably 400 to 650 nm. Since the resin fine particles serve as a spacer as described above, the external additive tends to exist in the gap between the resin fine particles. Therefore, when the average particle diameter of the resin fine particles is larger than 700 nm, it is difficult to obtain the effect of the external additive, that is, the effect of charging property and fluidity. On the other hand, when the average particle diameter is smaller than 300 nm, the effect of the spacer is weakened.

In addition, it is preferable that 10 to 40 resin fine particles are fixed to one suspension polymerization particle, and more preferably 20 to 40. When the number of resin fine particles is less than 10, the effect of the spacer is difficult to obtain. On the other hand, when the number exceeds 40, the chargeability of the toner tends to be reduced, or when the toner base particles contain wax, the elution of the wax is hindered and the toner fixability tends to be lowered.
Here, the number of resin fine particles is obtained by the method shown below, and is the number of resin fine particles confirmed by SEM images especially when the magnification of the scanning electron microscope (SEM) is 10,000. .

In addition, it is preferable that 1 to 40 resin fine particles having a particle diameter of 300 to 700 nm are fixed to one suspension polymerization particle, and more preferably 3 to 40. When the number of resin fine particles having a particle diameter of 300 to 700 nm is less than 1, it is difficult to obtain the spacer effect. On the other hand, when the number exceeds 40, the chargeability of the toner tends to be reduced, or when the toner base particles contain wax, the elution of the wax is hindered and the toner fixability tends to be lowered.
Here, the number of resin fine particles having a particle diameter of 300 to 700 nm is measured in the same manner as described above.

Whether or not the resin fine particles are fixed to the surface of the suspension polymerized particles, the number ratio of such toner base particles, and the average particle diameter and number of the fixed resin fine particles can be confirmed as follows. .
First, to a toner containing toner mother particles, a sufficient amount of methanol is added to disperse the toner to prepare a dispersion, which is sufficiently dispersed using an ultrasonic cleaner. Thereafter, the dispersion is filtered, and the toner on the filter paper is dried under reduced pressure. And this is surface-observed with a scanning electron microscope (SEM), and it confirms individually about each particle | grain whether resin fine particles remain | survive on the surface of suspension polymerization particle | grains. If it remains, it can be determined that the resin fine particles are fixed to the suspension polymerization particles. Further, the number ratio of the toner base particles in such a form and the size and number of the fixed resin fine particles can be measured by SEM observation of such individual particles.
Note that it is sufficient that the SEM observation at this time is performed on 100 randomly selected toners.

As described above, a toner having toner mother particles in which resin fine particles are fixed on the surface of suspension polymer particles having a circularity of 0.970 or more can be produced, for example, as follows.
First, a composition is prepared by mixing a radically polymerizable monomer and a colorant for constituting the binder resin, and, if necessary, a charge control agent and a wax, and further a crosslinking agent and a polymerization initiator with a ball mill or the like. .

  Examples of the monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-dodecylstyrene, etc. Styrene and its derivatives: ethylene, propylene, butylene, isobutylene nadonoethylene unsaturated monoolefins: vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride: vinyl acetate, vinyl propionate, vinyl benzoate Vinyl esters such as methyl methacrylate Ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, methacryl Α-methylene aliphatic monocarboxylic acid esters such as diethylaminoethyl acid: methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, n-octyl acrylate, dodecyl acrylate, acrylic acid Acrylate esters such as 2-ethylhexyl, stearyl acrylate, 2-chloroethyl acrylate, and phenyl acrylate: vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl Vinyl ethers such as ethers: Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone: N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone: Vinyl Naphthalenes: Examples include acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide, and one or more of these can be used.

A conventionally known pigment or dye can be used as the colorant. Examples of pigments include yellow lead, cadmium yellow, mineral fast yellow, navel yellow, naphthol yellow S, Hansa yellow, permanent yellow NCG, tartan rake, red lip yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, benzidine orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Eosole Lake, Brilliant Carmine 3B, Manganese Purple, Fast Bio Red B, Methyl Bio Red Lake, Bitumen, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, First Sky Blue, Indanthrene Blue BC, Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Yellow, final yellow green G, carbon black, acetylene black, and lamp black and the like. Examples of the dye include C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Red, C.I. I. Direct Blue 1, C.I. I. Acid Blue 1, C.I. I. Acid Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic blue, C.I. I. Modern Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic green 6 etc. are mentioned.
The colorant is preferably used in an amount of 5 to 15 parts by mass with respect to 100 parts by mass of the monomer described above.

As the charge control agent, for example, metal-containing dyes, nigrosine dyes, quaternary ammonium compounds, polar group-containing resins and the like can be used.
Examples of the wax include various waxes such as polyhydric alcohol esters of fatty acids, higher alcohol esters of fatty acids, alkylenebisfatty acid amide compounds, natural waxes; number average molecular weights of 1,000 to 10,000, preferably 2,000. Examples include low molecular weight olefin resins such as polypropylene, polyethylene, and propylene-ethylene copolymer in the range of ˜6,000. Among these, low molecular weight polypropylene is preferable.

  Examples of the crosslinking agent include divinylbenzene, divinylnaphthalene, divinyl ether, divinyl sulfone, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1 , 3-butylene glycol dimethacrylate, 1,6-hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2-bis (4-methacryloxydiethoxyphenyl) propane, 2,2-bis (4-acryloxydiethoxyphenyl) propane, trimethyl Propane trimethacrylate, trimethylol propane triacrylate, tetramethylol methane tetraacrylate, dibromoneopentyl glycol dimethacrylate, diallyl phthalate, etc. can be used, and 0.5 to 1.5 with respect to 100 parts by mass of the above monomer. It is preferable to use parts by mass. When the amount of the crosslinking agent used is in such a range, a toner having excellent blocking resistance, durability and fixability and less likely to cause an offset phenomenon can be obtained.

  Examples of the polymerization initiator include azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxide, isopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide. , 2,2-azobis (2,4-dimethylvaleronitrile) can be used, and the amount used is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the monomer.

  Further, when the toner of the present invention is a magnetic toner, magnetic powder may be added to the composition. Examples of magnetic powder include metals or alloys exhibiting ferromagnetism such as iron, cobalt and nickel, or compounds containing these elements (for example, ferrite, magnetite, etc.); An alloy that exhibits ferromagnetism by chromium; chromium dioxide and the like. As for the usage-amount of magnetic powder, 20-100 mass parts is preferable with respect to 100 mass parts of above-mentioned monomers.

  Next, a composition in which a monomer, a colorant, and a charge control agent, a wax, a cross-linking agent, a polymerization initiator, and the like added as necessary are mixed is added to an aqueous medium such as water, and a suspension stabilizer is further added thereto. Is added with a stirrer, homomixer, homogenizer or the like, and suspended and granulated to prepare a dispersion. Under the present circumstances, the quantity of an aqueous medium is about 200-800 mass parts, when a composition is 100 mass parts. The suspension granulation conditions may be any conditions that can form droplets having a desired particle diameter, for example, 3 to 15 μm, and are usually 20 to 50 ° C. and 10 to 30 minutes.

As the suspension stabilizer, an organic dispersant or an inorganic dispersant can be used, and as the organic dispersant, water-soluble cellulose derivatives such as gelatin, denven, and carboxymethyl cellulose, polyvinyl alcohol, anionic, nonionic, cationic, or Amphoteric surfactants can be used. Examples of the inorganic dispersant include hardly soluble inorganic fine particles, for example, various clays such as tribasic calcium phosphate, calcium carbonate, magnesium phosphate, magnesium carbonate, silica, alumina, talc, bentonite, and diatomaceous earth. More than seeds can be used.
The amount of the suspension stabilizer used is preferably in the range of 0.1 to 10% by mass when the aqueous medium is 100% by mass. Within such a range, the dispersibility of the dispersion becomes sufficient, and there is no possibility that the suspension stabilizer will be excessive and remain on the surface of the obtained toner base particles to reduce the moisture resistance of the toner.

  Next, suspension polymerization particles are produced as a main product by suspension polymerization method in which the dispersion is kept under stirring, preferably in an inert atmosphere at 50 to 100 ° C. for 3 to 12 hours, and dissolved in the aqueous phase. Resin fine particles that are presumed to be due to emulsion polymerization of some of the monomers produced are simultaneously produced as a by-product (polymerization step).

  Since fine resin particles are considered to be a by-product of emulsion polymerization of some monomers in the aqueous phase during suspension polymerization, an appropriate amount of a water-soluble polymerization inhibitor is added to the dispersion during the polymerization process. It may be added to control the by-product amount of resin fine particles by-produced during suspension polymerization. However, when a large amount of the polymerization inhibitor is added, the by-production of the resin fine particles is excessively suppressed, and it becomes difficult to generate toner mother particles in which the resin fine particles are fixed on the surface of the suspension polymerization particles. Therefore, when adding a polymerization inhibitor, it is preferable to use in 0.02 mass part or less with respect to 100 mass parts of above-mentioned monomers.

  As a polymerization inhibitor, a water-soluble thing can be used, For example, metal salts, such as cupric chloride, sodium nitrite, and potassium nitrite, hydroquinone, etc. are mentioned, These can be used 1 or more types.

  Thereafter, the obtained dispersion liquid after the polymerization step is filtered, washed, and dried to obtain a toner raw powder containing suspension polymerization particles and resin fine particles. In the toner raw powder thus obtained, the resin fine particles are not fixed to the surface of the suspension polymerization particles. In addition, you may remove the suspension stabilizer contained in a dispersion liquid by washing | cleaning as needed before filtration. Further, the mass ratio of the suspension polymer particles to the resin fine particles in the toner raw powder depends on the amount of the polymerization inhibitor used, but the resin fine particles are usually 0.1% with respect to 100 parts by mass of the suspension polymer particles. About 10 parts by mass.

Next, the obtained toner raw powder is put into a stirrer and stirred at a high speed while being heated, so that the resin fine particles are fixed to the surface of the suspension polymer particles in the toner raw powder (fixing step). The heating temperature at this time is preferably 30 to 50 ° C. Within such a temperature range, the resin fine particles can be sufficiently fixed on the surface of the suspension polymerization particles, and the performance of the toner obtained by this heating is not adversely affected. Moreover, it is preferable to implement stirring under strong shear force, for example, using a Henschel mixer, it is preferable to carry out on the conditions of 1000-5000 rpm and 1 to 10 minutes.
The fixing step may be the above-described method in which the toner raw powder is once obtained from the dispersion after the polymerization step, and then the toner raw powder is stirred under heating, but the dispersion after the polymerization step is filtered, After washing, when drying, the drying treatment and the fixing step may be performed simultaneously by performing the drying treatment in a stirrer such as a Henschel mixer under the above-described conditions.

  By performing the polymerization step and the immobilization step in this manner, toner base particles having resin fine particles fixed on the surface of suspension polymer particles having a circularity of 0.970 or more are obtained.

An external additive is added to the toner base particles thus obtained to obtain a toner.
Examples of the external additive include inorganic oxides such as silica, titanium oxide, and alumina, and metal soaps such as calcium stearate. The amount of the external additive is usually 0.3 to 4 parts by mass with respect to 100 parts by mass of the toner base particles.
The external additive may be added to the stirrer during the above-described fixing step and externally added simultaneously with the fixing of the resin fine particles. Even in such a case, there is a possibility that the external additive is buried in the toner base particles and cannot fully function. Therefore, it is preferable to add and mix separately by the Henschel mixer etc. after an immobilization process.

  The toner of the present invention may be used as a two-component developer in combination with a carrier, or may be used alone as a one-component developer. As the carrier, known materials such as magnetic particles or resin particles in which a magnetic material is dispersed in a binder resin can be used.

Such a toner can be suitably used in an electrophotographic general image forming apparatus, but due to its characteristics, an image forming apparatus configured to replenish toner from the outside to the developing container and a non-magnetic one-component developing apparatus are employed. The image forming apparatus is particularly suitable for a rotary development type image forming apparatus and a combination thereof.
FIG. 1 is a partial schematic view of an image forming apparatus of a rotary development system that is an embodiment of the present invention. The image forming apparatus 1 of this example includes a developing container 11, a developing roller 12, a toner supply roller 14 that supplies toner 13 to the developing roller 12, and a layer thickness regulation that is disposed in contact with the surface of the developing roller 12. The rotary developing system includes a plurality of developing devices 10 each having a member 15. Further, the image forming apparatus 1 includes a supply nozzle 16 that supplies toner 13 to the developing container 11. Further, a drum-shaped photoconductor 17 is disposed so as to face the developing roller 12.

A support (not shown) is connected to each developing device 10 via a clutch, and the support rotates to move the developing roller 12 to a development position that sequentially faces the photoconductor 17. The upper electrostatic latent image is developed to form a toner image on the photoreceptor 17.
The developing container 11 is divided into a toner storage chamber 11a in which the toner 13 of the present invention is stored, and a roller storage chamber 11b in which the developing roller 12 and the toner supply roller 14 are disposed, and the toner storage chamber 11a and the roller storage. The chamber 11b is partitioned by a partition wall 11c.

  The developing roller 12 faces the photoconductor 17 at the developing position, the toner 13 of the present invention is stored in the toner storage chamber 11a, and the toner 13 in the toner storage chamber 11a is stirred by a stirring member (not shown) The toner is supplied to the roller storage chamber 11 b, and the toner 13 is supplied to the developing roller 12 by the toner supply roller 14. The toner layer on the developing roller 12 is regulated by the layer thickness regulating member 15 and is frictionally charged, and the electrostatic latent image on the photoconductor 17 is developed by the developing roller 12.

  When the toner of the present invention is replenished to the developing device 10, the developing device 10 is rotated and positioned at the toner replenishing position. Then, as shown in FIG. 1, the replenishment nozzle 16 is inserted into the developing device 10, and the toner 13 is replenished to the toner storage chamber 11a. The developing container 11 is provided with a supply port (not shown), and the supply nozzle 16 is inserted into the developing device 10 through the supply port.

As described above, in the conventional image forming apparatus, when the toner deteriorates due to stirring or aging operation in the developing container, the deteriorated toner and the undegraded toner newly supplied into the developing container are developed. Therefore, a difference in charging performance between the two toners occurs and charging failure tends to occur. As a result, image defects such as fogging and image density reduction are likely to occur.
However, according to the present invention, even in an image forming apparatus of the type that replenishes toner from the outside, the electrostatic latent image developing toner of the present invention is used. Since it can be suppressed, image defects such as fogging and image density reduction can be prevented. Further, even an image forming apparatus employing a rotary developing system having a plurality of developing devices can prevent image defects such as fogging and image density reduction.

As described above, according to the toner for developing an electrostatic latent image of the present invention, since the toner base particles having the resin fine particles fixed on the surface of the suspension polymer particles having a circularity of 0.970 or more are contained, the toner Even if stress is applied to the metal, it is possible to prevent the external additive from being detached or buried. Therefore, it is possible to keep the chargeability and fluidity of the toner in a stable state over a long period of time. In addition, since the average particle diameter of the resin fine particles fixed to the surface of the suspension polymerization particles is 300 to 700 nm, it can serve as a spacer without impairing the effect of the external additive.
Further, according to the image forming apparatus of the present invention, since the toner of the present invention is used, the toner is hardly deteriorated even in the developing container. Therefore, image defects such as fogging and image density reduction are unlikely to occur. In particular, even in an image forming apparatus configured to replenish toner from the outside to a developing container or a rotary developing type image forming apparatus in which the developing device rotates, image defects are unlikely to occur.

Hereinafter, the present invention will be specifically described with reference to examples. “Part” means “part by mass”.
[Example 1]
A toner was manufactured as follows.
(Polymerization process)
80 parts of styrene, 20 parts of 2-ethylhexyl methacrylate, 5 parts of carbon black (MA-77, manufactured by Mitsubishi Chemical), 3 parts of low molecular weight polypropylene (Sunwax LEL-250, manufactured by Sanyo Chemical Industries), charge control agent (Bontron) A mixed solution of 2 parts of S-34, manufactured by Orient Chemical Co., Ltd. and 1 part of divinylbenzene (crosslinking agent) was sufficiently dispersed by a ball mill, and then 2,2-azobis (2,4-dimethylvaleronitrile) ( Polymerization initiator) 3 parts were added to prepare a composition.
Next, this composition was added to 400 parts of ion-exchanged water, and further 5 parts of calcium triphosphate and 0.1 part of sodium dodecylbenzenesulfonate were added as suspension stabilizers thereto, and TK Homomixer (Special Machine Industries, Ltd.) was added. For 45 minutes at a rotational speed of 6000 rpm to obtain a dispersion.
Then, after holding at 70 ° C. and 100 rpm for 5 hours under a nitrogen atmosphere, 0.01 part of cupric chloride (polymerization inhibitor) was added and held for another 5 hours to carry out suspension polymerization reaction, followed by acid washing. And tricalcium phosphate was removed.
Next, this dispersion was filtered, washed, and dried to obtain a toner raw powder containing suspension polymer particles as a main product and resin fine particles as a by-product. Of the obtained toner raw powder, the volume average particle diameter of the suspension polymer particles was 7.8 μm, and the circularity was 0.974. The volume average particle diameter was measured with Multisizer III (manufactured by Coulter Counter), and the circularity was measured with a flow particle image analyzer (FPIA-2100, manufactured by Sysmex Corporation).

(Immobilization process)
500 g of the obtained toner raw powder is put into a Henschel mixer (FM-10C type, manufactured by Mitsui Mining Co., Ltd.) and stirred at 45 ° C. and 3500 rpm for 10 minutes to fix the resin fine particles in the toner raw powder to the suspension polymerization particles. Toner mother particles were obtained.

(Addition of external additives)
A mixture obtained by adding 0.8 part of silica (R974, manufactured by Nippon Aerosil Co., Ltd.) having a particle diameter of 12 nm as an external additive to 100 parts of the obtained toner base particles was used as a Henschel mixer (FM-10C type, Mitsui Mining Co., Ltd.). And stirred for 2 minutes at 20 ° C. and 2000 rpm to obtain a toner.

(Confirmation of resin fine particles)
A dispersion obtained by adding 20 g of methanol to 1 g of the obtained toner was further dispersed for 1 minute using an ultrasonic cleaner. Next, this dispersion was filtered, and the toner on the filter paper was dried under reduced pressure. The surface of 100 randomly selected toners was observed with an SEM (10,000 times), and it was confirmed for each particle whether or not resin fine particles remained on the surface of the suspension polymerization particles. For the remaining particles, it was judged that the resin fine particles were fixed, the particle diameter and the number of the fixed resin fine particles were measured, and the average value was obtained for the particle diameter.
As a result, it was confirmed that the resin fine particles were fixed on the surface of the suspension polymerization particles in all (100%) toner base particles. The average particle size of the resin fine particles was 500 nm. Further, an average of 30 resin fine particles were fixed to each suspension polymerized particle.

(Evaluation of toner)
The obtained toner was evaluated for the degree of toner deterioration, fogging, and image density unevenness using the following evaluation machine (image forming apparatus). The results are shown in Table 1.
(1) Evaluation machine Model: Canon LBP-2410 modified machine (negative charging system)
Line speed: 1660 mm / min Drum: Negatively charged Amorphous silicon drum Development: Non-magnetic one-component development Layer thickness regulating member: SUS (2) Image output condition Toner weight in developer container: 40 g
Toner replenishment amount: 5g
Development Vdc: 90V
Duty: 37%
S / D: 1.1
Vpp: 1.1 kV
Bright potential of photoconductor: 10V
Dark potential of photoconductor: 300V

(3) Evaluation of Deterioration Level of Toner Evaluation of the deterioration level of toner is a measurement for judging how much of the external additive attached to the toner base particles is buried in the toner base particles. The more external additives are buried. The evaluation method is shown below.
The toner was set in the developing container of the evaluation machine and after aging for 60 minutes, 200 sheets were printed with a printing rate of 6% under the above-mentioned image output conditions. The BET specific surface area of the toner remaining in the developing container was measured with a BET specific surface area measuring device (fully automatic BET specific surface area measuring device, manufactured by Mountech Co., Ltd.). The BET specific surface area of the toner before aging (before use) was also measured in advance in the same manner, and the BET value change rate was obtained from the following formula as an index of the degree of toner deterioration. It is determined that the toner is deteriorated as the BET value change rate is larger. Note that if the BET value change rate is 0.3 or less, fogging is unlikely to occur.
BET value change rate = (BET specific surface area of toner before use−BET specific surface area of toner remaining in developing container) / BET specific surface area of toner before use

(4) Fog evaluation After the toner was set in the developing container of the evaluation machine and aged for 60 minutes, 200 sheets were printed on the above-mentioned image printing conditions. Next, 5 g of new toner was replenished, and after aging for another minute, a sample image was output under the above-described image output conditions.
Using a reflection densitometer (TC-6D, manufactured by TEPCO), the fog density FD of the same paper (base paper) as that used for outputting the sample image and the non-image portion (margin portion) in the sample image is used. The difference was taken as the fogging FD value. The fogging occurred when the fogging FD value was 0.010 or more.

(5) Image density unevenness evaluation Toner was set in the evaluation machine, and a black image (solid patch) of 15 cm × 15 cm was output on the leading edge of the paper under the image output conditions. The density unevenness of the black image was visually observed and evaluated in four stages of ◎, ○, Δ, and × in order from the best. In addition, (double-circle) and (circle) were set as the pass.

[Example 2]
A toner was produced and evaluated in the same manner as in Example 1 except that the addition amount of the polymerization inhibitor was changed to 0.02 part.
As a result, in the obtained toner raw powder, the volume average particle size of the suspension polymer particles was 7.8 μm and the circularity was 0.973.
Further, it was confirmed that the resin fine particles were fixed on the surface of the suspension polymerization particles in all (100%) of the toner base particles. The average particle diameter of the resin fine particles was 330 nm. Further, an average of 37 resin fine particles were fixed to each suspension polymerized particle.
Each evaluation result is shown in Table 1.

[Example 3]
A toner was produced and evaluated in the same manner as in Example 1 except that the addition amount of the polymerization inhibitor was changed to 0.005 part.
As a result, the volume average particle diameter of the suspension polymer particles in the obtained toner raw powder was 7.5 μm, and the circularity was 0.980.
Further, it was confirmed that the resin fine particles were fixed on the surface of the suspension polymerization particles in all (100%) of the toner base particles. The average particle size of the resin fine particles was 500 nm. Further, an average of 5 resin fine particles were fixed to each suspension polymerized particle.
Table 1 shows the evaluation results.

[Example 4]
A toner was produced and evaluated in the same manner as in Example 1 except that the stirring time in the fixing step was changed to 20 minutes.
As a result, in the obtained toner raw powder, the volume average particle diameter of the suspension polymer particles was 7.4 μm and the circularity was 0.982.
Further, it was confirmed that the resin fine particles were fixed on the surface of the suspension polymerization particles in all (100%) of the toner base particles. The average particle size of the resin fine particles was 500 nm. Further, an average of 70 resin fine particles adhered to each suspension polymerized particle.
Each evaluation result is shown in Table 1.

[Example 5]
In the same manner as in Example 1 except that the addition amount of the polymerization inhibitor was changed to 0.02 parts, the stirring speed in the suspension polymerization reaction was changed to 50 rpm, and the stirring time in the immobilization step was changed to 20 minutes. Toner was manufactured and evaluated.
As a result, of the obtained toner raw powder, the volume average particle diameter of the suspension polymer particles was 7.7 μm and the circularity was 0.980.
Further, it was confirmed that the resin fine particles were fixed on the surface of the suspension polymerization particles in all (100%) of the toner base particles. The average particle size of the resin fine particles was 650 nm. Furthermore, an average of 40 resin fine particles were fixed to each suspension polymerized particle.
Each evaluation result is shown in Table 1.

[Comparative Example 1]
A toner was produced and evaluated in the same manner as in Example 1 except that the polymerization inhibitor was not added and the external additive was added without performing the fixing step.
As a result, of the obtained toner raw powder, the volume average particle diameter of the suspension polymer particles was 8.5 μm and the circularity was 0.985.
However, resin fine particles were not fixed on the surface of the suspension polymerization particles.
Each evaluation result is shown in Table 1.

[Comparative Example 2]
A toner was produced and evaluated in the same manner as in Example 1 except that the addition amount of the polymerization inhibitor was changed to 0.07 part.
As a result, the volume average particle diameter of the suspension polymer particles in the obtained toner raw powder was 7.5 μm and the circularity was 0.975.
Further, it was confirmed that the resin fine particles were fixed on the surface of the suspension polymerization particles in all (100%) of the toner base particles. The average particle diameter of the resin fine particles was 80 nm. Further, an average of 2000 resin fine particles adhered to each suspension polymerized particle.
Each evaluation result is shown in Table 1.

[Comparative Example 3]
A toner was produced and evaluated in the same manner as in Example 1 except that the addition amount of the polymerization inhibitor was changed to 0.1 part and the stirring speed in the suspension polymerization reaction was changed to 66.7 rpm.
As a result, of the obtained toner raw powder, the volume average particle diameter of the suspension polymerization particles was 7.2 μm, and the circularity was 0.978.
Further, it was confirmed that the resin fine particles were fixed on the surface of the suspension polymerization particles in all (100%) of the toner base particles. The average particle diameter of the resin fine particles was 900 nm. Further, an average of 10 resin fine particles were fixed to each suspension polymerized particle.
Each evaluation result is shown in Table 1.

As is apparent from Table 1, toner base particles containing resin fine particles (average particle size: 300 to 700 nm) fixed on the surface of suspension polymer particles produced by suspension polymerization and having a circularity of 0.970 or more are contained. According to the toners of the examples, the evaluation of the degree of toner deterioration, fogging, and image density unevenness was good. In particular, the toners of Examples 1, 2, and 5 in which the number of resin fine particles fixed to one suspension polymerization particle is 10 to 40 have a BET value change rate of 0.3 or less, The burial of the additive could be further suppressed. Also, by using these toners, image defects such as fogging and image density unevenness can be effectively suppressed.
On the other hand, in the toner obtained in Comparative Example 1 in which the fixing process was not performed, the external additive was buried and the toner was easily deteriorated. This is thought to be a result of the resin fine particles gradually dropping off because the resin fine particles initially aggregated on the surface of the suspension polymerized particles, but the immobilization process was not performed. Further, when the toner of Comparative Example 1 was used in an image forming apparatus, fogging occurred and image density was uneven.
In the toner of Comparative Example 2, since the amount of the polymerization inhibitor used was large, 2000 resin fine particles were fixed on the surface of the suspension polymerization particles. The average particle size of the resin fine particles was 80 nm, which was smaller than that of the example. For this reason, when toner is used in the image forming apparatus, fog occurs.
In the toner of Comparative Example 3, since the amount of the polymerization inhibitor used is larger and the stirring speed in the suspension polymerization reaction is slower, the average particle diameter of the resin fine particles fixed on the surface of the suspension polymerization particles is 900 nm. It was larger than that of the example. For this reason, when toner is used in the image forming apparatus, blurring occurs and image density becomes uneven.
As described above, since the toner of each embodiment can suppress the burying of the external additive, the charging property and the fluidity can be maintained in a stable state for a long time even when subjected to stress such as stirring and aging in the developing container. .

FIG. 3 is a diagram illustrating an appearance of toner mother particles. 1 is a partial schematic diagram illustrating an example of an image forming apparatus of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Developing apparatus 11 Developing container 12 Developing roller 13 Toner 14 Toner supply roller 15 Layer thickness regulating member 16 Supply nozzle 17 Photoconductor

Claims (5)

An electrostatic latent image developing toner comprising toner mother particles having resin fine particles fixed on the surface of suspension polymerization particles produced by suspension polymerization and having a circularity of 0.970 or more,
An electrostatic latent image developing toner, wherein the resin fine particles have an average particle size of 300 to 700 nm.   The electrostatic latent image developing toner according to claim 1, wherein the resin fine particles are a by-product generated during the suspension polymerization.   3. The electrostatic latent image developing toner according to claim 1, wherein the number of the resin fine particles fixed to the surface of the suspension polymerization particle is 10 to 40. 4. An image forming apparatus to which the electrostatic latent image developing toner according to claim 1 is replenished,
A developing device comprising: a developing container; a developing roller; a toner supply roller that supplies the developing roller with toner for developing the electrostatic latent image; and a layer thickness regulating member that is disposed in contact with the surface of the developing roller. An image forming apparatus comprising: a replenishing nozzle for replenishing the developing container with the electrostatic latent image developing toner. The image forming apparatus according to claim 4, wherein the image forming apparatus is a rotary developing system including a plurality of the developing devices.

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