JP5879765B2 - Image forming method - Google Patents

Description

  The present invention relates to an electrophotographic image forming method using a two-component developer composed of a toner and a carrier, and measures the toner content (toner concentration) in the developer supplied in the developing device, The present invention relates to an image forming method for replenishing toner to a developing device based on a measurement result.

  Toner used in an electrophotographic image forming method is usually added with inorganic particles or resin particles called external additives on its surface, and the action of these external additives can improve charging properties and fluidity. Maintaining and improving toner performance promotes stable toner image formation. For example, the fluidity and chargeability of the toner are improved by adding a toner having a relatively small particle diameter (small external additive) of about 5 nm to 50 nm to the toner particle surface. In addition, relatively large particles (large-diameter external additives) exceeding 100 nm are also used, and the use of the external additives can improve charging performance and stabilize cleaning performance in a low-temperature, low-humidity or high-temperature, high-humidity environment. (For example, refer patent documents 1 and 2). In addition, the addition of the large-diameter external additive exhibits a spacer effect that avoids the embedding and detachment of the small-diameter external additive when the toner particles contact and collide with each other, so that the surface performance of the toner particles is stabilized. However, it is effective (see, for example, Patent Documents 1 and 2).

  By the way, in the electrophotographic image forming field, it is possible to form a fine and high-resolution image such as a gravure photograph by a technique such as a short wavelength semiconductor laser exposure technique or a toner diameter reduction. With these improvements in performance, a printing market called on-demand printing has recently been formed, and high-quality images on the order of hundreds to thousands of sheets can be speeded up without the work of plate transcription required for conventional printing. Allows you to create. From the viewpoint of maintaining good image quality of the formed image, an image forming apparatus in which a toner concentration detection unit for detecting the content (toner concentration) of toner contained in the developing device is mounted on the developing device is also used. (For example, see Patent Document 3). The toner concentration detection unit disclosed in Patent Document 3 is composed of an LC oscillation circuit in which the central portion of the print pattern coil is hollow, and can detect toner concentration with higher accuracy than the conventional one. Therefore, since the toner density in the developing device can be controlled more strictly, it has been considered that the specification is suitable for a printer compatible with on-demand printing with many opportunities to form high-quality images.

Japanese Patent Laid-Open No. 2005-3726 JP 2007-178470 A JP 2010-26031 A

  However, even in an image forming apparatus in which a toner density detection unit is mounted on a developing device, when an image is formed using toner to which an external additive having a level of several hundred nm is added, a toner image having a predetermined image quality is stably displayed. It was found that it cannot be formed. In other words, the toner density detection unit detects that an appropriate amount of toner is present in the developing device, so that a predetermined toner charge is performed and a toner image of a predetermined density should be formed, but the image density is low and fog occurs. The finished print was created. This is a very disadvantageous problem for on-demand printing in which high-quality printing is continuously performed.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming method capable of stably producing a printed matter with good image quality free from density defects and fog. . In particular, an appropriate amount of toner can be supplied to the developing device and given charge can be applied to an image forming apparatus for on-demand printing or the like in which a toner density detection unit is mounted on the developing apparatus to create a high-quality printed matter. In this way, it is possible to stably produce a printed product having a predetermined finish.

The present inventor has found that the above-described problem can be solved by any of the configurations described below. That is, the invention described in claim 1
“Toner is accommodated in the developing device by supplying toner contained in the developing device to the electrostatic latent image formed on the photoconductor, and the toner image is transferred and fixed on the image support to create a printed matter. ,
In this image forming method, the toner concentration of the developer contained in the developing device is measured by a toner concentration detecting unit provided in the developing device, and the toner is replenished to the developing device based on the measurement result. And
The toner is
At least core-shell toner particles in which a core particle containing a binder resin containing a styrene acrylic copolymer is coated with a resin,
The resin that coats the core particles is
It contains a styrene acrylic modified polyester having a structure in which a styrene acrylic copolymer molecular chain is molecularly bonded to a polyester molecular chain,
An image forming method comprising monodispersed spherical particles having a number average primary particle size of 50 nm to 150 nm as an external additive on the surface of the toner particles. ].

The invention described in claim 2
2. The toner density detector is provided outside the developing device, and includes an LC oscillation circuit having a planar coil having a hollow area at least in the center. Image forming method. ].

The invention according to claim 3
"The styrene acrylic modified polyester is
The image forming method according to claim 1 or 2, wherein the content of the styrene acrylic copolymer is 5% by mass or more and 30% by mass or less. ].

The invention according to claim 4
The said styrene acrylic modified polyester is formed using the aliphatic unsaturated carboxylic acid represented by the following general formula (A), The any one of Claims 1-3 characterized by the above-mentioned. Image forming method.

General formula (A): HOOC- (CR < ¹ > = CR _< ² _> ) _n- COOH
(Wherein R ¹ and R ² are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other. N is an integer of 1 or 2.) ” Is.

The invention described in claim 5
"The styrene acrylic modified polyester is
5. The image forming method according to claim 1, wherein the molecular chain of the styrene acrylic copolymer is molecularly bonded to an end of the polyester molecular chain. ].

The invention described in claim 6
"The styrene acrylic modified polyester is
The styrene acrylic copolymer molecular chain is formed by polymerizing a styrene monomer and an acrylate monomer in the presence of the polyester molecular chain. 6. The image forming method according to any one of 5 above. ].

The invention described in claim 7
The image forming method according to any one of claims 1 to 6, wherein the monodispersed spherical particles are silica particles produced by a sol-gel method. ].

The invention according to claim 8 provides:
“The toner is
The image according to any one of claims 1 to 7, wherein the toner particle surface contains metal oxide particles having a number average primary particle size of 5 nm to 50 nm as an external additive. Forming method. ].

The invention according to claim 9 is:
“The developer is
The volume average particle size is 25 μm or more and 50 μm or less,
The image forming method according to any one of claims 1 to 8, wherein the image forming method comprises a resin-coated carrier having a ferrite particle surface coated with a resin. ].

The invention according to claim 10 is:
The image forming method according to claim 1, wherein toner image formation is performed while replenishing toner to the developing device and replenishing carrier. ].

  According to the present invention, by using the toner having the above-described configuration, the toner density detection unit can accurately detect the toner density in the developing device, and the toner can be appropriately supplied into the developing device. . As a result, since an appropriate amount of toner is triboelectrically charged in the developing device, toner with insufficient charge amount is not used for image formation, and a good finish with an appropriate image density and no fog is achieved. A toner image can be stably formed.

1 is a schematic view of an image forming apparatus capable of performing an image forming method according to the present invention. 2 is a cross-sectional view of a toner having a core-shell structure. FIG. FIG. 3 is a schematic diagram of a developing device capable of mounting a toner concentration detection unit. FIG. 6 is a schematic diagram of a toner concentration detection unit that measures the amount of toner in the developing device. It is the schematic of the carrier manufacturing apparatus which can produce the resin coat carrier. It is a schematic diagram which shows the image layout of the sample for evaluation (printed material) used in the Example.

  The present invention relates to an image forming method using an image forming apparatus equipped with a toner concentration detection unit that detects the concentration of toner contained in a developing device.

  The inventor considered that a mechanism for suppressing the release of the external additive from the surface of the toner particles is necessary, and as a result of the study, the toner having the above-described configuration was able to eliminate the influence of the release of the external additive. That is, in the present invention, a sufficient spacer effect can be exhibited by using monodispersed spherical particles having an average primary particle diameter of 50 nm or more and 150 nm or less as the external additive on the surface of the toner base particles. This could be realized by using a core-shell toner provided with a shell containing a styrene acrylic-modified polyester resin in which a styrene acrylic copolymer molecular chain is bonded to a polyester molecular chain.

  The present inventor is an image forming apparatus in which a toner concentration detection unit is mounted on a developing device when a toner having a large particle diameter of 200 to 300 nm, for example, called a large-diameter external additive is used. Focusing on the fact that a toner image with insufficient density is formed. Then, when a large amount of the external additive is released from the surface of the toner particles by agitation in the developing device, the released external additive is electrostatically attached to the carrier surface, and the flowability of the developer is reduced. It was considered that the developer could not be sufficiently stirred.

  In addition, it was considered that a large amount of the external additive adhered to the carrier surface, and the charge imparting performance of the carrier itself was lowered. In addition, the dispersion of toner in the developer varies due to the suppression of mixing and stirring, and when a low toner density region is detected by the detection device, the toner is excessively supplied into the development device. Was also considered.

  In the present invention, the toner base particles having a core-shell structure provided with a shell containing a styrene acrylic-modified polyester resin in which a styrene acrylic copolymer molecular chain is bonded to a polyester molecular chain are effective. It is considered a thing. That is, due to the styrene acrylic copolymer component in the styrene acrylic modified polyester resin, the affinity between the shell and the core particles is increased, and the shell is likely to adhere uniformly to the core particle surfaces. By uniformly attaching the shell, the surface of the toner base particles is smoothed, and the adhesive force of the external additive to the surface of the toner base particles is made uniform. As a result, even if the external additive has a large particle size, there is no one that adheres to the surface of the toner base particle with a weak adhesive force, and it is considered that the external additive is not released due to stress caused by stirring in the developing device. It is done.

  Further, in the present invention, the smoothness of the toner base particle surface is improved, so that there is no possibility that the small-diameter external additive is buried in the uneven portion of the toner particle surface, and the fluidity and chargeability are improved by the small-diameter external additive. It was thought to be expressed stably. Further, it was considered that if the toner base particle surface is smoothed and the uneven portion is eliminated, the spacer effect can be exhibited without using an external additive exceeding 300 nm, for example. Under such assumptions, the present inventor examined the particle size of the external additive that achieves both the spacer effect and the release suppression for the toner base particles having the core-shell structure. As a result, it has been found that if the average primary particle size is 50 to 150 nm or less, both the spacer effect and the suppression of release can be achieved.

  Hereinafter, the present invention will be described in detail.

  First, an image forming apparatus capable of carrying out the image forming method according to the present invention will be described with reference to FIG.

FIG. 1 is a schematic view showing an example of an image forming apparatus capable of forming a toner image by the image forming method according to the present invention, and is capable of producing a printed matter through at least the following steps. is there. That is,
(1) a step of exposing the photoreceptor to form an electrostatic latent image;
(2) supplying toner to the photosensitive member on which the electrostatic latent image is formed to form a toner image;
(3) a step of transferring a toner image formed on the photosensitive member to an image support;
(4) A printed matter is produced through a step of fixing the toner image transferred to the image support.

  An image forming apparatus 1 shown in FIG. 1 is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 18 as a transfer unit, and And an endless belt-like sheet feeding / conveying means 21 for conveying the image support P and a heat roll type fixing device 24 as a fixing means. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus. The image forming apparatus 1 forms yellow, magenta, cyan, and black toner images by the image forming units 10Y to 10Bk, and transfers and superimposes the toner images formed by the respective image forming units on the intermediate transfer body unit 18. By combining them, a full color image can be formed.

  The image forming unit 10 includes a photoconductor 11, a charging device 12, a developing device 14, a primary transfer device 15, a cleaning device 16, and the like. Specifically, in each of the image forming units 10Y, 10M, 10C, and 10Bk, 11Y, 11M, 11C, and 11Bk are photosensitive members, 14Y, 14M, 14C, and 14Bk are developing devices, and 15Y, 15M, 15C, and 15Bk are primary. The transfer device (primary transfer roll), 16Y, 16M, 16C, and 16Bk are cleaning devices. In the image forming apparatus of FIG. 1, the toner content (toner concentration) contained in the developing device 14 constituting the image forming unit 10 is measured by the toner concentration detecting unit, and the toner is fed into the developing device 14 based on the measurement result. The toner is supplied. Detailed description of the toner density detection method performed in the present invention and image formation by the tandem type image forming apparatus 1 shown in FIG. 1 will be described later.

  Next, the toner used in the present invention will be described.

  The toner used in the present invention comprises toner particles having a core-shell structure in which core particles containing a binder resin containing a styrene acrylic copolymer are coated with a resin. The resin that coats the core particles (shell resin) contains a styrene-acrylic modified polyester having a structure in which a styrene-acrylic copolymer molecular chain is molecularly bonded to a polyester molecular chain. The core shell structure having the above structure forms toner base particles having a smooth surface. Due to this smoothness, monodisperse spherical particles having a number average primary particle size of 50 nm or more and 150 nm or less adhere well to the surface of the toner base particles. be able to. As a result, it is possible to provide a toner that exhibits a stable spacer effect.

  That is, it is presumed that the core particles containing the styrene acrylic copolymer resin constituting the toner have a smooth surface by the production method. Resin containing styrene acrylic modified polyester with styrene acrylic copolymer molecular chain bonded to polyester molecular chain adheres uniformly to the surface of the core particle and forms a shell reflecting the smoothness of the core particle. Presumed to be. This will be described in detail.

  First, the shell will be described. The shell constituting the toner used in the present invention contains a styrene acrylic modified polyester having a structure in which a styrene acrylic copolymer molecular chain is bonded to a polyester molecular chain. That is, the styrene acrylic modified polyester used as the shell resin has a structure in which a styrene acrylic copolymer segment is molecularly bonded to a polyester segment. By using a polyester resin with a structure in which a styrene acrylic copolymer molecular chain is bonded to a polyester molecular chain as a shell resin, the shell is uniformly attached to the surface of the core particle containing the styrene acrylic copolymer. It is possible to make it.

  In the present invention, by using a styrene acrylic modified polyester resin having a structure in which a styrene acrylic copolymer molecular chain is bonded to a polyester molecular chain as a shell resin, the shell is uniformly formed on the core particle surface. Is possible.

  That is, due to the presence of the styrene acrylic copolymer molecular chain bonded to the polyester molecular chain, the shell resin develops affinity with the core particle containing the styrene acrylic copolymer, and the surface of the core particle It becomes possible to attach to any part with the same probability. As a result, the shell resin adheres uniformly to the surface of the core particles with a uniform thickness, thereby realizing a toner that enables both low-temperature fixability and heat-resistant storage stability. In addition, in the shell resin, the presence of styrene acrylic copolymer molecules reduces the affinity between the polyester molecular chains, avoids aggregation of the shell resin particles, and keeps the distance between each other. Conceivable. That is, it is considered that the dispersibility of the resin particles for shell is improved, so that it can be slightly adhered to the surface of the core particles.

  In this way, in the present invention, the shell resin exhibits affinity for the core particles, and the dispersibility is expressed between the shell resins, so that the shell is uniformly formed on the surface of the core particles. The shell can be formed to achieve both low-temperature fixability and heat-resistant storage stability. In the present invention, toner particles having a smooth surface are formed. This is because the shell resin can adhere to any part of the surface of the smooth core particle with the same probability. This is considered to be formed uniformly on the surface.

  Further, in the present invention, by using a resin having a structure in which a polyester molecular chain and a styrene acrylic copolymer molecular chain are molecularly bonded, a high glass transition temperature is maintained as compared to a styrene acrylic copolymer resin of a polyester resin. The softening point of the resin could be lowered. That is, by introducing a styrene acrylic copolymer segment into the polyester segment, a styrene acrylic modified polyester resin having a structure in which the high glass transition temperature and low softening point of the polyester are combined with the molecular chain of the styrene acrylic copolymer molecular chain. By using as a shell resin, the following effects can also be obtained.

  The content ratio of the shell resin in the binder resin constituting the toner used in the present invention is preferably 5% by mass to 50% by mass and more preferably 10% by mass to 40% by mass with respect to the total amount of the binder resin. preferable. A toner having a shell resin content ratio in the above range is supplied with a sufficient amount of the shell resin that covers the entire surface of the core particles. It is possible to realize the coexistence more reliably.

  The content ratio of the styrene acrylic modified polyester in the shell resin is preferably 70% by mass to 100% by mass and more preferably 90% by mass to 100% by mass with respect to 100% by mass of the shell resin. By setting the content ratio of the styrene acrylic modified polyester in the resin for the shell within the above range, it is easy to ensure the affinity between the core particles and the shell, sufficient heat storage stability is obtained, and charging and crush resistance are improved. Effect is also obtained.

  Further, one of the conditions for forming toner particles having a smooth surface is to keep the core particle surface smooth. The smoothing of the core particle surface can be achieved, for example, when the core particles are produced by an emulsion association method. It can be realized by controlling the heating temperature and the fusion time in the aggregation / fusion process. That is, when the resin particles are agglomerated by setting the heating temperature to a high value and a long fusing time, the agglomerated resin particles have a rounded and smooth shape. Further, in the aging step in which the heat treatment of the reaction system is subsequently performed after the aggregation / fusion step, it is possible to smooth the core particle surface by increasing the heating temperature and lengthening the treatment time. .

  Thus, the core-shell structured toner particles defined in the present invention have a smooth surface, and the external additive particles having a number average primary particle size of 50 nm or more and 150 nm or less adhere well and have a stable spacer effect. Can be expressed.

  Hereinafter, a core-shell structure, a styrene-acrylic modified polyester having a structure in which a styrene-acrylic copolymer molecular chain is bonded to a polyester molecular chain contained in the shell, and a styrene-acrylic copolymer contained in the core particle will be specifically described.

  The structure of the core-shell toner used in the present invention will be described. The toner of the core-shell structure is a toner particle having a structure in which a resin layer (shell) having a relatively high glass transition temperature is coated on the surface of a resin particle (core) having a relatively low glass transition temperature containing a colorant or wax. This has the structure shown in FIG. The toner T shown in FIG. 2 is composed of a core A made of a resin A2 containing a colorant A1 and a shell B formed by coating the surface of the core A with a resin B3.

  The toner T shown in FIG. 2A has a structure in which the shell B completely covers the surface of the core A. The toner having the core-shell structure referred to in the present invention is not necessarily limited to the one having the structure in which the shell B shown in FIG. 2A completely covers the core A. For example, the shell B as shown in FIG. The core A is not completely covered, and some of them have a portion where the core A is slightly exposed on the surface.

  The cross-sectional structure of the core-shell toner can be confirmed by a known means such as a transmission electron microscope (TEM) or a scanning probe microscope (SPM). Here, a method for observing the cross-sectional structure of the toner with a transmission electron microscope (TEM) will be described. As for the cross-sectional structure of the toner, the cross-sectional structure of the toner is observed with a transmission electron microscope, for example, in the following procedure.

  First, the toner is sufficiently dispersed in a room temperature curable epoxy resin, embedded, dispersed in styrene fine powder having a particle size of about 100 nm, and then pressure-molded to contain the toner. Is made. If necessary, the prepared block is dyed with ruthenium tetroxide or osmium tetroxide if necessary, and then a microtome having diamond teeth is used to form a flake shape having a thickness of 80 to 200 nm. The sample for a measurement is produced.

  The measurement sample thus thinned is set on a transmission electron microscope (TEM), and the cross-sectional structure of the toner is photographed. At this time, the magnification of the electron microscope is preferably a magnification that allows the cross section of one toner to enter the field of view, and specifically about 10,000 times. Further, it is preferable that the number of toners to be photographed with a transmission electron microscope is at least 10 or more.

  Observation of the cross-sectional structure of the toner with a transmission electron microscope can be sufficiently handled by a model that is generally well known among those skilled in the art. For example, “LEM-2000 type (manufactured by Topcon)” And “JEM-2000FX (manufactured by JEOL Ltd.)”.

  It is also possible to calculate the shell coverage on the core surface by electron microscope observation. That is, it is possible to calculate the image information captured by a transmission electron microscope (TEM) by, for example, processing with a commercially available image processing apparatus “Luzex F” (manufactured by Nireco), and the core area of the captured toner It is calculated from the area of the shell region. The average coverage of the shell is determined by using a cross-sectional structure photograph of at least 10 toners.

  The styrene acrylic modified polyester used as the shell resin in the present invention will be described in detail. Here, the “styrene acrylic modified polyester” is a polyester molecule having a structure in which a styrene acrylic copolymer molecular chain (also referred to as a styrene acrylic copolymer segment) is molecularly bonded to a polyester molecular chain (also referred to as a polyester segment). It is. The styrene acrylic modified polyester used in the present invention has a molecular structure in which a styrene acrylic copolymer molecular chain is bonded to a polyester molecular chain, and a copolymer having a styrene acrylic copolymer segment covalently bonded to a polyester segment. It is a coalescence.

  The styrene acrylic modified polyester used in the present invention is not particularly limited as long as it has a molecular structure in which a styrene acrylic copolymer molecular chain is bonded to a polyester molecular chain. Among them, the styrene-acrylic copolymer segment content is preferably 5% by mass or more and 30% by mass or less. Here, the content ratio of the styrene acrylic copolymer segment in the styrene acrylic modified polyester molecule is also called “styrene acrylic modified amount”, and the ratio (mass ratio) of the styrene acrylic copolymer segment in the styrene acrylic modified polyester molecule. It is. Specifically, it means the ratio of the polymerizable monomer mass used for forming the styrene acrylic copolymer to the total mass of polymerizable monomers used when synthesizing the styrene acrylic modified polyester resin.

  By setting the “styrene acrylic modification amount” within the above range, the above-described shell can be more reliably formed. In other words, the affinity between the styrene-acrylic modified polyester resin and the core particles is moderately controlled to facilitate the formation of a uniform and thin film thickness shell. As a result, the core-shell structure has both low-temperature fixability and heat-resistant storage stability. The toner can be manufactured more stably.

  The styrene acrylic modified polyester used in the present invention is not particularly limited as long as the molecular structure has two types of homopolymer segments, a polyester segment and a styrene acrylic copolymer segment. Specifically, a block copolymer structure in which a styrene acrylic copolymer segment is bonded to the end of a polyester segment, or a graft copolymer structure in which a branched structure of a styrene acrylic copolymer segment is formed on a polyester segment. Is mentioned.

  Among them, the block copolymer structure in which the styrene acrylic copolymer molecular chain is bonded to the end of the polyester molecular chain easily forms a shell having a phase separation structure in which the polyester phase and the styrene acrylic copolymer phase are independent, This is preferable in forming a function-separated shell. That is, the heat resistance imparting performance by the high glass transition temperature and softening point temperature by the polyester phase and the improvement of the adhesive strength between the core particles by the styrene acrylic copolymer phase can be efficiently expressed.

  The method for forming the styrene acrylic modified polyester used in the present invention is not particularly limited as long as it can form a polymer having a structure in which a polyester segment and a styrene acrylic copolymer segment are molecularly bonded. It is not something. Specific examples of the method for forming the styrene acrylic modified polyester include the following methods.

(1) A method of polymerizing a polyester segment in advance and performing a polymerization reaction to form a styrene acrylic copolymer segment in the presence of the polyester segment to form a styrene acrylic modified polyester. A polyester segment is formed by a condensation reaction between an acid and a polyhydric alcohol. Next, in the presence of the polyester segment, a vinyl monomer such as a styrene monomer or an acrylate monomer is polymerized to form a styrene acrylic copolymer segment. At this time, in addition to the styrene monomer and the acrylate monomer, a site capable of reacting with the carboxy group (—COOH) or hydroxy group (—OH) remaining in the polyester segment, and the vinyl monomer A compound having a reactive site is also used. That is, when this compound reacts with a carboxy group (—COOH) or a hydroxy group (—OH) in the polyester segment, the polyester segment has a structure in which the compound is bonded. And a styrene acrylic copolymer segment is formed by carrying out addition reaction, such as radical polymerization, of a styrene-type monomer and an acrylate-type monomer in presence of the polyester segment which combined the said compound. At this time, a styrene acrylic modified polyester having a structure in which the polyester segment and the styrene acrylic copolymer segment are molecularly bonded can be formed through a site capable of reacting with the vinyl monomer of the compound bonded to the polyester segment. it can.

  That is, the method (1) is a method of “forming a styrene acrylic copolymer molecular chain by polymerizing at least a styrene monomer and an acrylate monomer in the presence of a polyester molecular chain”. Applicable. The method (1) includes a method in which the styrene monomer and the acrylate monomer are added to the reaction system before the styrene monomer and the acrylate monomer are added to the reaction system. There is a method in which a monomer is added together to react. The method (1) is a method preferably used for forming a styrene acrylic modified polyester having a block copolymer structure in which a styrene acrylic copolymer molecular chain is molecularly bonded to the end of a polyester molecular chain, as will be described later. It is.

(2) A method of polymerizing a styrene acrylic copolymer segment in advance and performing a polymerization reaction to form a polyester segment in the presence of the styrene acrylic copolymer segment to form a styrene acrylic modified polyester. Then, a styrene-acrylic copolymer segment is formed by addition reaction of a styrene-based monomer and a vinyl-based monomer typified by an acrylate-based monomer. Next, in the presence of the styrene acrylic copolymer segment, a polyvalent carboxylic acid and a polyhydric alcohol are polymerized to form a polyester segment. At this time, in addition to the polyvalent carboxylic acid and the polyhydric alcohol, a compound having a site capable of reacting with the styrene acrylic copolymer segment and a site capable of reacting with the polyvalent carboxylic acid or polyhydric alcohol is also used. That is, by reacting this compound with the styrene acrylic copolymer segment, the styrene acrylic copolymer segment has a structure in which the compound is bonded. And a polyester segment is formed by carrying out the condensation reaction of polyhydric carboxylic acid and a polyhydric alcohol in presence of the styrene acrylic copolymer segment which combined the said compound. At this time, a styrene acrylic modified polyester having a structure in which the styrene acrylic copolymer segment and the polyester segment are molecularly bonded is formed through a site capable of reacting with the carboxylic acid or alcohol of the compound bonded to the styrene acrylic copolymer segment. be able to.

(3) A method of forming a polyester segment and a styrene acrylic copolymer segment in advance and combining them to form a styrene acrylic modified polyester. In this method, first, a polyvalent carboxylic acid and a polyhydric alcohol are subjected to a condensation reaction. To form a polyester segment. In addition to the reaction system for forming the polyester segment, a styrene-acrylic copolymer segment is formed by addition polymerization of a styrene monomer and an acrylate monomer. Next, a system in which the polyester segment and the styrene acrylic copolymer segment coexist is formed, and a compound having a portion that can be bonded to the polyester segment and a portion that can be bonded to the styrene acrylic copolymer segment is added thereto. And the styrene acrylic modified polyester of the structure where the polyester segment and the styrene acrylic copolymer segment were molecularly bonded can be formed through the compound.

  Among the forming methods (1) to (3), the method (1) is easy to form a styrene acrylic modified polyester having a structure in which a styrene acrylic copolymer molecular chain is bonded to the end of a polyester molecular chain and a production process. Can be simplified. In the method (1), since the polyester segment is formed in advance and then the compound is introduced and bonded to the polyester segment, the compound has a very high probability of binding to the end of the polyester segment. Therefore, it is preferable because a styrene acrylic modified polyester having a structure defined in the present invention can be reliably formed.

  In the forming methods (1) to (3), it is preferable to perform heat treatment for uniformly mixing a compound such as a polymerizable monomer used for forming the styrene acrylic modified polyester. Specifically, the temperature is preferably 80 ° C to 120 ° C, more preferably 85 ° C to 115 ° C, and particularly preferably 90 ° C to 110 ° C. Heating under the above temperature range facilitates mixing of polyester molecular chains, styrene monomers, acrylate monomers, and the like, which is preferable for forming a styrene acrylic modified polyester.

  The polyester segment constituting the styrene acrylic modified polyester used in the present invention preferably has a glass transition temperature of 40 ° C to 70 ° C, more preferably 50 ° C to 65 ° C when it is a single polyester molecular chain. . When the glass transition temperature is 40 ° C. or higher, it is possible to form a toner image in which the polyester segments are appropriately aggregated during fixing and the hot offset phenomenon does not occur. In addition, since the glass transition temperature is 70 ° C. or lower, a low-temperature fixing toner that melts a toner image at a lower temperature than before can be produced without inhibiting the melting of the styrene-acrylic copolymer resin during fixing. This is preferable.

  The polyester segment constituting the styrene acrylic modified polyester preferably has a weight average molecular weight (Mw) of 1,500 or more and 60,000 or less, and 3,000 or more and 40,000 or less when it is a single polyester molecular chain. More preferred. By setting the weight average molecular weight to 1,500 or more, an appropriate cohesive force can be imparted to the entire toner resin, and a toner image that does not cause a hot offset phenomenon during fixing can be formed. Further, when the weight average molecular weight is 60,000 or less, sufficient melting can be achieved by heating in a short time, and a firm fixed image can be formed by cooling. Therefore, it is preferable in forming a toner image by low-temperature fixing.

  The styrene acrylic copolymer segment constituting the styrene acrylic modified polyester used in the present invention has a glass transition temperature (Tg) at the time of a single styrene acrylic copolymer molecular chain, which is 35 ° C. or higher as in the case of the core particles described later. The thing of 60 degrees C or less is preferable, and the thing of 30 degrees C or more and 50 degrees C or less is more preferable. The styrene acrylic copolymer segment preferably has a weight average molecular weight (Mw) of 2,000 to 100,000 as in the case of the core particles described later when it is a single styrene acrylic copolymer molecular chain.

  When the styrene acrylic modified polyester is formed by the forming methods (1) to (3), a compound for molecularly bonding the polyester segment and the styrene acrylic copolymer segment is used. This compound is a compound having a site capable of reacting with a carboxy group (—COOH) or a hydroxy group (—OH) remaining in a polyester segment and a site capable of reacting with a vinyl monomer. Is applicable. In addition, in the formation method of the above (2), “in addition to the polyvalent carboxylic acid and the polyhydric alcohol, it has a site capable of reacting with the styrene acrylic copolymer segment and a site capable of reacting with the polyvalent carboxylic acid or polyhydric alcohol. The “compound” is applicable. Furthermore, the formation method (3) corresponds to “a compound having a site capable of binding to a polyester segment and a site capable of binding to a styrene acrylic copolymer segment”.

  This compound includes a functional group capable of performing a condensation reaction with a carboxy group (—COOH) or a hydroxy group (—OH) remaining in a polyester segment, a carbon-carbon double bond capable of performing an addition reaction with a styrene acrylic copolymer segment, and the like. Having an unsaturated structure of Specific examples of such compounds include vinyl compounds having a carboxy group such as acrylic acid, methacrylic acid, fumaric acid and maleic acid, and vinyl carboxylic anhydrides such as maleic anhydride.

  The amount of the compound used for molecularly bonding the polyester segment and the styrene acrylic copolymer segment is 0.1% by mass or more and 5.0% by mass when the total of the compounds used for forming the styrene acrylic modified polyester is 100% by mass. The following is preferable, and 0.5% by mass or more and 3.0% by mass or less is more preferable. Here, the compound used for forming the styrene acrylic modified polyester is a polyester segment, a styrene monomer, an acrylate monomer, and a compound that molecularly bonds the polyester segment and the styrene acrylic copolymer segment.

  Further, the amount of the styrene monomer and the acrylate monomer used in forming the styrene acrylic modified polyester used in the present invention is 5% by mass or more in total when the above-mentioned total is 100% by mass. The content is preferably 30% by mass or less. That is, it corresponds to the ratio (mass ratio) of the styrene acrylic copolymer segment in the styrene acrylic modified polyester molecules described above.

  The polyester segment constituting the styrene acrylic modified polyester used in the present invention is formed by subjecting a known polycarboxylic acid and polyhydric alcohol to a polycondensation reaction in the presence of a catalyst. The polyester segment can be a derivative of the aforementioned polyvalent carboxylic acid or polyhydric alcohol used as a raw material. The polyvalent carboxylic acid derivative includes an alkyl ester, an acid anhydride, or an acid chloride of the polyvalent carboxylic acid. Etc. Polyhydric alcohol derivatives include polyhydric alcohol ester compounds and hydroxycarboxylic acids.

Hereinafter, specific examples of polyvalent carboxylic acid and polyhydric alcohol that can be used for forming the polyester segment will be described. First, examples of the polyvalent carboxylic acid include known divalent carboxylic acids and trivalent or higher carboxylic acids called aliphatic dicarboxylic acids and aromatic dicarboxylic acids. Specific examples of the divalent carboxylic acid include, for example,
Oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid fumaric acid, citraconic acid, diglycolic acid, cyclohexane -3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, malonic acid, pimelic acid, tartaric acid phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, hexahydroterephthalate Acids p-Carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, diphenylacetic acid diphenyl-p, p'-dicarboxylic acid, naphthalene-1, 4-dicarboxylic acid, naphtha Down-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, and the like dodecenylsuccinic acid.

Moreover, as a specific example of carboxylic acid more than trivalence, for example,
Examples include trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

  Among the polyvalent carboxylic acids, by forming a polyester segment using an aliphatic unsaturated dicarboxylic acid having a carbon-carbon unsaturated bond in the molecular structure such as fumaric acid, maleic acid, and mesaconic acid, the following Since it is thought that such an effect is show | played, it is preferable.

  In other words, when forming a shell, a thin shell with a uniform thickness and a smooth surface can be more reliably formed, so that a toner having both heat-resistant storage properties and low-temperature fixability can be more reliably obtained. Can be produced. This is presumably because the presence of a carbon-carbon unsaturated bond in the polyester molecule forms an environment in which the polyester resin particles easily adhere to the surface of the core particles containing the styrene acrylic resin.

  This is because the polyester resin generally has a hydrophobic property, and therefore, when the toner particles are produced by the emulsion association method described later, the polyester resin particles aggregate in an aqueous medium in which the core particles are present, and the polyester resin particles move to the surface of the core particles. Can hardly adhere. However, the presence of a carbon-carbon unsaturated bond in the polyester molecule imparts hydrophilicity to the polyester resin due to the polar action between the unsaturated bonds, avoiding aggregation of the polyester resin particles, and the surface of the core particles. It is thought that it becomes possible to adhere to. Further, by imparting hydrophilicity to the polyester resin, it becomes easy to adopt a form in which the polyester molecular chains are easily oriented toward the aqueous medium, and the polyester resin particles adhere to the core particle surface in a form oriented in the aqueous medium. Is also possible. As a result, the polyester resin particles can be densely attached to the surface of the core particles with a uniform thickness, and it is estimated that a thin shell layer can be formed on the surface of the core particles. Further, the affinity between the styrene acrylic copolymer segment constituting the styrene acrylic modified polyester of the shell and the styrene acrylic copolymer resin constituting the core particle promotes the orientation of the shell to the core particle surface. Conceivable.

  In this way, by having a carbon-carbon unsaturated bond in the polyester molecule, a certain degree of hydrophilicity is imparted to the polyester molecule, and an environment in which the polyester resin particles easily adhere to the core particle surface is formed. It is presumed that the formation of a thin layer of the shell is promoted.

  Further, there is an advantage that a structure in which the polyester segment and the styrene acrylic copolymer segment are molecularly bonded can be formed without preparing the above-mentioned “compound for molecularly bonding the polyester segment and the styrene acrylic copolymer segment”. . Therefore, it is preferable because the number of types of compounds necessary for producing the styrene-acrylic modified polyester is reduced, and the production process of the resin is simplified to contribute to productivity improvement.

Such an aliphatic unsaturated dicarboxylic acid preferably has a structure represented by the following general formula (A). That is,
General formula (A); HOOC- (CR < ¹ > = CR < ² >) n-COOH
R ¹ and R ² in the above formula are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other. N is an integer of 1 or 2.

  The ratio of the aliphatic unsaturated carboxylic acid represented by the general formula (A) to the total polyvalent carboxylic acid used for forming the polyester segment is preferably 25 mol% or more and 75 mol% or less, preferably 30 mol%. More preferred are those of 60 mol% or less.

Next, specific examples of the polyhydric alcohol will be described. Examples of the polyhydric alcohol that can be used to form the polyester segment include known dihydric alcohols and trihydric or higher alcohols. As a specific example of a dihydric alcohol, for example,
Examples include ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, and the like.

Moreover, as a specific example of trihydric or higher alcohol, for example,
Examples include glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, and tetramethylol benzoguanamine.

  The polyester segment is formed by polycondensation reaction of a polyvalent carboxylic acid and a polyhydric alcohol in the presence of a catalyst, and a known catalyst can be used.

  Next, the compound which forms a styrene acrylic copolymer segment is demonstrated. In the present invention, since the shell resin expresses affinity for the core particles to be described later and bonds them firmly, and the shell is formed on the surface of the core particles with a uniform thickness, the shell resin is used. A styrene acrylic modified polyester is used as the resin.

The polyester segment constituting the styrene acrylic modified polyester used in the present invention is formed by addition polymerization of at least a styrene monomer and an acrylate ester monomer. The styrenic monomer here includes those having a structure having a known side chain or functional group in the styrene structure in addition to styrene represented by the structural formula of CH ₂ ═CH—C ₆ H _5. . In addition to the acrylic ester compounds and methacrylic ester compounds represented by CH ₂ = CHCOOR (R is an alkyl group), the acrylic ester monomers referred to here are acrylic ester derivatives and methacrylic ester derivatives. Such a structure includes a vinyl ester compound having a known side chain or functional group.

  Specific examples of styrene monomers and acrylate monomers capable of forming styrene acrylic copolymer segments are shown below, but they are used to form styrene acrylic copolymer segments used in the present invention. The possibilities are not limited to those shown below.

First, specific examples of the styrene monomer include the following. That is,
Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn- Hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene and the like.

Further, specific examples of the acrylate monomer include the following acrylate monomers and methacrylic acid monomers. Examples of the acrylate monomers include the following: Can be mentioned. That is,
Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, acrylic acid Phenyl and the like.

Examples of the methacrylic acid ester monomer include the following. That is,
Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methacrylic acid Phenyl, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate and the like.

  These acrylic acid ester monomers or methacrylic acid ester monomers can be used alone or in combination of two or more. That is, forming a copolymer using a styrene monomer and two or more kinds of acrylate monomers, and forming a copolymer using a styrene monomer and two or more kinds of methacrylate monomers Either a styrene monomer, an acrylate monomer and a methacrylic acid ester monomer can be used together to form a copolymer.

  Moreover, when forming a styrene acrylic copolymer segment, the relative ratio of these styrene monomers and acrylate monomers is such that the glass transition temperature (Tg) calculated by the FOX equation shown below. It is preferable to adjust so that it may be in the range of 35 ° C to 60 ° C, more preferably in the range of 30 ° C to 50 ° C.

FOX formula: 1 / Tg = Σ (Wx / Tgx)
Wx in the above formula represents the mass fraction of monomer x, and Tgx represents the glass transition temperature of the homopolymer of monomer x. Here, the aforementioned “compound that forms a structure in which a polyester segment and a styrene acrylic copolymer segment are molecularly bonded” is not used when calculating the glass transition temperature.

  Next, physical properties of the shell resin containing the styrene acrylic modified polyester resin used in the present invention will be described. The shell resin used in the present invention has a glass transition temperature of 50 ° C. to 70 ° C. from the viewpoint of fixing properties such as low-temperature fixing properties and fixing separation properties and from the viewpoint of heat resistance such as heat-resistant storage properties and blocking resistance. ° C is preferred, and 50 to 65 ° C is more preferred. From the same viewpoint, the softening point temperature is preferably 80 ° C to 110 ° C.

  The glass transition temperature of the resin for shell can be measured, for example, by the method (DSC method) defined by ASTM (American Society for Testing and Materials) D3418-82.

Moreover, the measurement of the softening point temperature of resin for shells is performed in the following procedure, for example. First, in an environment of 20 ° C. ± 1 ° C. and 50% RH ± 5% RH, 1.1 g of shell resin is placed in a petri dish and leveled, and left for 12 hours or more. Next, pressurization of 3.82 × 10 ⁷ Pa (3820 kg / cm ² ) is performed for 30 seconds with a commercially available molding machine “SSP-10A (manufactured by Shimadzu Corporation)”, and a cylindrical molded sample having a diameter of 1 cm is obtained. create.

Next, this molded sample was subjected to a hole (1 mm diameter) of a cylindrical die by a commercially available flow tester “CFT-500D (manufactured by Shimadzu Corporation)” in an environment of 24 ° C. ± 5 ° C. and 50% RH ± 20% RH. Extrusion is performed from the end of preheating using a 1 cm diameter piston. The offset method was measured with a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, a temperature increase rate of 6 ° C./min, and a melting temperature measurement method of the temperature increase method with an offset value of 5 mm. The temperature T _offset is _defined as the softening point temperature of the shell resin.

Next, the styrene acrylic copolymer contained in the core particles will be described. The styrene acrylic copolymer referred to in the present invention is formed by radical polymerization of at least a styrene monomer and an acrylate monomer described later. The styrenic monomer herein includes styrene represented by the structural formula of CH ₂ ═CH—C ₆ H ₅ , as well as those having a structure having a known side chain or functional group in the styrene structure. Is. In addition, the acrylate ester-based monomer mentioned here has a known side chain or functional group such as a methacrylate ester derivative in addition to an acrylate ester compound represented by CH ₂ = CHCOOR (R is an alkyl group). The vinyl-type ester compound which has is also included.

  Specific examples of the styrene monomer and the acrylate monomer capable of forming a styrene acrylic copolymer are shown below, but for forming the core particles of the toner used in the present invention. Usable ones are not limited to those shown below.

First, examples of the styrene monomer include the following. That is,
Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn- Hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene and the like.

The acrylic ester monomers are typically the following acrylic ester monomers and methacrylic ester monomers. Examples of the acrylic ester monomers include the following. It is done. That is,
Methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, acrylic acid Phenyl and the like.

Examples of the methacrylic acid ester monomer include the following. That is,
Methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, methacrylic acid Phenyl, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate and the like.

  These acrylic acid ester monomers or methacrylic acid ester monomers can be used alone or in combination of two or more. That is, forming a copolymer using a styrene monomer and two or more kinds of acrylate monomers, and forming a copolymer using a styrene monomer and two or more kinds of methacrylate monomers Either a styrene monomer, an acrylate monomer and a methacrylic acid ester monomer can be used together to form a copolymer.

  In addition to the copolymer formed only with the styrene monomer and the acrylate ester monomer, the styrene acrylic copolymer includes the styrene monomer and the acrylate ester monomer. Some are formed by using general vinyl monomers in addition to the body. Although the vinyl monomer which can be used together when forming the styrene acrylic copolymer said by this invention below is illustrated, the vinyl monomer which can be used together is not limited to what is shown below.

(1) Olefins Ethylene, propylene, isobutylene, etc. (2) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate, etc. (3) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether, etc. (4) Vinyl ketones Vinyl methyl ketone, Vinyl ethyl ketone, vinyl hexyl ketone, etc. (5) N-vinyl compounds N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone, etc. (6) Other vinyl compounds such as vinyl naphthalene, vinyl pyridine, acrylonitrile, methacrylo Acrylic acid or methacrylic acid derivatives such as nitrile and acrylamide, etc. Moreover, it is also possible to produce a resin having a crosslinked structure using the following polyfunctional vinyls. Specific examples of the polyfunctional vinyls are shown below. That is,
Divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, etc. It is also possible to use a vinyl monomer having an ionic dissociation group in such a side chain, and specific examples of the ionic dissociation group include, for example, a carboxyl group, a sulfonic acid group, and a phosphoric acid group. It is done. Specific examples of these vinyl monomers having an ionic dissociation group are shown below.

  First, specific examples of the vinyl monomer having a carboxyl group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, and the like. .

  Specific examples of the vinyl monomer having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, and the like. Furthermore, specific examples of the vinyl monomer having a phosphate group include, for example, acid phosphooxyethyl methacrylate and 3-chloro-2-acid phosphooxypropyl methacrylate.

  When forming a styrene acrylic copolymer that can be used in the present invention, the content of the styrene monomer and the acrylate monomer is not particularly limited, and the softening point temperature of the binder resin It is possible to adjust appropriately from the viewpoint of adjusting the glass transition temperature. Specifically, the content of the styrene monomer is preferably 40 to 95% by mass and more preferably 50 to 80% by mass with respect to the entire radical polymerizable monomer. Moreover, 5-60 mass% is preferable with respect to the whole radical polymerizable monomer, and, as for content of an acrylic ester monomer, 10-50 mass% is more preferable.

  The glass transition temperature of the styrene acrylic copolymer formed by radical polymerization is preferably 30 ° C to 60 ° C, more preferably 30 ° C to 50 ° C. The softening point temperature is preferably 80 ° C to 110 ° C, more preferably 90 ° C to 100 ° C. When the glass transition point temperature and softening point temperature are in the above ranges, good fixability can be obtained.

  The molecular weight of the styrene acrylic copolymer formed by radical polymerization is preferably 2,000 to 100,000 in terms of weight average molecular weight (Mw). The weight average molecular weight Mw of the resin constituting the toner can be calculated by a known molecular weight measurement method. Hereinafter, a molecular weight measurement procedure by gel permeation chromatography (GPC) using tetrahydrofuran (THF), which is one of typical examples of the molecular weight measurement method, as a column solvent will be described.

  Specifically, 1 ml of THF (using a degassed sample) is added to 1 mg of a measurement sample, and stirred sufficiently using a magnetic stirrer at room temperature to be sufficiently dissolved. Next, after processing with a membrane filter having a pore size of 0.45 μm to 0.50 μm, it is injected into the GPC apparatus.

  The measurement conditions of GPC are measured by stabilizing the column at 40 ° C., flowing THF at a flow rate of 1 ml / min, and injecting about 100 μl of a sample having a concentration of 1 mg / ml. As the column, it is preferable to use a combination of commercially available polystyrene gel columns. For example, Shodex GPC KF-801, 802, 803, 804, 805, 806, and 807 manufactured by Showa Denko KK, TSKgel G1000H, G2000H, G3000H, G4000H, G5000H, G6000H, G7000H, and TSK guard manufactured by Tosoh Corporation There are combinations.

  As the detector, a refractive index detector (RI detector) or a UV detector is preferably used. In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve created using monodisperse polystyrene standard particles. About 10 points are preferably used as polystyrene for preparing a calibration curve.

  The molecular weight measurement can be performed, for example, under the following measurement conditions.

(Measurement condition)
Apparatus: HLC-8020 (manufactured by Tosoh Corporation)
Column: GMHXLx2, G2000HXLx1
Detector: At least one of RI and UV Eluent flow rate: 1.0 ml / min Sample concentration: 0.01 g / 20 ml
Sample volume: 100 μl
Calibration curve: produced with standard polystyrene As described above, the toner according to the present invention has a core particle surface containing a styrene acrylic copolymer resin and a molecular chain of a styrene acrylic copolymer molecular chain to the end of a polyester molecular chain. And a core-shell toner coated with a modified polyester resin. A toner manufacturing method capable of manufacturing the toner according to the present invention will be described later.

  Next, monodispersed spherical particles having a number average primary particle size of 50 nm to 150 nm used as an external additive in the toner according to the present invention will be described. In the present invention, monodispersed spherical particles having a number average primary particle size of 50 nm or more and 150 nm or less belonging to a class having a small particle size as the large-diameter external additive exhibit a stable spacer effect on the toner particle surface. I found it.

  In the prior art, in order to develop a stable spacer effect, an external additive having a size exceeding 300 nm, for example, is necessary. However, in the present invention, the surface of the toner base particle is smoothed, and thus the external additive having the above particle diameter is used. Thus, it is considered that the spacer effect can be expressed. In the present invention, it is possible to achieve both the spacer effect and the suppression of release by using monodispersed spherical particles having a number average primary particle size of 50 nm or more and 150 nm or less. This is because the smaller the particle size of the external additive, the stronger the adhesion to the toner base particle surface, so that the durability is improved. It is thought that it is difficult to release.

  Due to the expression of the spacer effect by the monodispersed spherical particles, even if the toner is stirred for a long time in the developing device, surface contact between the toner particles is avoided, and metal oxide particles having a number average primary particle size of 5 nm to 50 nm, etc. Prevents burying and detachment of small diameter external additive particles. Therefore, even if the toner is stirred in the developing device for a long time, there is no possibility that the small-diameter external additive is embedded or detached from the toner particle surface, so that the charging property and the fluidity are stably expressed and detached. It is possible to form an image without causing contamination of the carrier and the photoreceptor by the external additive.

  Thus, by using monodispersed spherical particles having a number average primary particle size of 50 nm or more and 150 nm or less as a large-diameter external additive, a toner in which the large-diameter external additive achieves both a spacer effect and suppression of release is obtained. This realizes stable toner image formation. Further, in the present invention, the surface of the toner base particles is smoothed so as not to be uneven, which is considered to promote strong adhesion of a small-diameter external additive having a number average primary particle size of 5 nm to 50 nm. .

  The fact that the external additive particles having a number average primary particle size of 50 nm or more and 150 nm or less used in the present invention are monodispersed spherical particles can be explained by the shape factor SF-1 and particle size distribution described later. Is possible. Preferred examples of the external additive particles having a number average primary particle size of 50 nm to 150 nm are, for example, the external additive having a shape factor SF-1 of 100 to 120 and a particle size distribution contained in the toner particles. 90% or more of the agent particles may have a particle size of ± 10% or less of the number average primary particle size. The method of calculating the shape factor SF-1 of the external additive particles and the particle size distribution will be described in detail later.

  Next, “shape factor SF-1” used for defining that the monodispersed spherical particles used in the present invention are “spherical particles” will be described. The external additive particles having a number average primary particle size of 50 nm or more and 150 nm or less used in the present invention have a shape factor SF-1 of preferably 100 or more and 120 or less, more preferably 100 or more and 110 or less. is there.

  Here, the “shape factor SF-1” is an “spherical” in the present invention, that is, an index indicating the “degree of roundness” of the external additive particle, and is defined by the following formula. The shape factor SF-1 means that when the value is 100, the shape of the external additive particles is a true sphere, and the shape factor is rounded as the value becomes larger than 100. It means becoming an irregular shape.

SF-1 = [{(maximum diameter of particle) ² / (projected area of particle)} × (π / 4)] × 100
The “maximum diameter” in the equation means the width of a particle that maximizes the interval between the parallel lines when the projected image of the particle on the plane is sandwiched between two parallel lines.

  The shape factor SF-1 of the particles can be calculated using a scanning electron microscope and an image analysis processing device, as in the measurement of the number average particle size of the particles described later. That is, the toner is photographed at a magnification of 30,000 times with a scanning electron microscope, the obtained photographic image is taken in with a scanner, and is analyzed and calculated with an image analysis processing apparatus “LUZEX AP (manufactured by Nireco)”. . In the analysis by the image analysis processing device, the external additive particles existing on the toner surface on the photographic image are binarized, SF-1 is calculated for 100 external additive particles, and the average value is externally added. The shape factor SF-1 of the agent particles is used. Specific examples of the scanning electron microscope include a field emission scanning electron microscope “S-4500” manufactured by Hitachi, Ltd.

  Next, “external additive particle size distribution”, which is one of the means for explaining that the external additive particles used in the present invention are “monodispersed particles”, will be described. The external additive particles having a number average primary particle size of 50 nm or more and 150 nm or less used in the present invention have a particle size of 90% or more of the external additive particles contained in the toner particles. It is preferable to be within a range of ± 10% or less of the diameter value.

  Here, “monodispersity” of the external additive particles, that is, “the particle size distribution of the external additive particles is sharp” means that the particle size of the external additive particles added to the toner particles is known. When measured by the method, particles of a certain ratio or more of the measured external additive particles have a particle size within a specific range centered on the peak value with the number average primary particle size as a peak value. It is based on.

  As a preferable particle size distribution of the external additive particles used in the present invention, for example, when the particle size of the external additive particles added to the toner particles is measured, the number average primary particle size is peaked. As a value, it is mentioned that 90% or more of the measured external additive particles have a particle size within a range of ± 10% or less of the peak value.

  Here, “the particle diameter of 90% or more of the measured external additive particles is a value within the range of ± 10% or less of the peak average number average primary particle diameter” specifically. Means as follows. That is, “when the number average primary particle size of the external additive is 100 nm, for example, 90% or more of the external additive particles used in the particle size distribution measurement have a particle size in the range of 90 nm to 110 nm. It means "having". As described above, the method for specifically expressing the “monodispersity” of the external additive particles used in the present invention can be defined by the “particle size distribution” defined as described above.

  The particle size distribution of the external additive particles that can be used in the toner used in the present invention is measured in the same manner as the measurement of the shape factor SF-1 of the external additive particles described above using a commercially available scanning electron microscope and an image. This can be done using an analysis processing device. Specifically, the toner is photographed with a scanning electron microscope at a magnification of 30,000 times, the obtained photographic image is captured with a scanner, and the captured photographic image is converted into a commercially available image analysis processing apparatus “LUZEX AP (Nireco Corporation). Analysis). In the analysis by the image analysis processing device, the external additive particles present on the toner surface on the photographic image are binarized, and the particle size of 100 external additive particles is calculated. The number average primary particle size is calculated from the particle size value of each external additive particle thus calculated, and the obtained number average primary particle size is compared with the particle size of each external additive particle. The particle size distribution of the agent particles is calculated. By such a procedure, the number average primary particle size and particle size distribution of the external additive particles used in the toner can be measured. As a specific example of the scanning electron microscope, for example, there is a field emission scanning electron microscope “S-4500” manufactured by Hitachi, Ltd.

  For example, monodispersed spherical particles having a number average primary particle size used as an external additive in the toner used in the present invention are obtained by hydrophobizing metal oxide particles obtained by a sol-gel method with a hydrophobizing agent. Can be produced. Further, the number average primary particle size of the monodispersed spherical particles can be controlled by reaction conditions, raw material ratios, and the like when producing external additive particles. Hereinafter, a method for producing external additive particles usable in the present invention will be described with reference to production of silica particles by a sol-gel method.

  The production of silica particles by the sol-gel method is performed, for example, by subjecting an alkoxysilane compound or a phenoxysilane compound to hydrolysis or polycondensation reaction, and is generally called the Stöber method. Hereinafter, a method for producing silica particles by the sol-gel method will be specifically described.

  First, a silica sol suspension is prepared by dropping and stirring an alkoxysilane compound or the like heated by adding a catalyst in the presence of water and an organic solvent. The silica sol suspension is then centrifuged to separate into wet silica gel, organic solvent and water. Next, an organic solvent is added to the separated wet silica gel to form a silica sol again, and then a hydrophobizing treatment is performed by adding a hydrophobizing agent. In addition to the above-described method, the hydrophobizing treatment includes a method of adding a hydrophobizing agent after drying the silica sol. And after performing a hydrophobization process, a silica fine particle can be produced by removing an organic solvent. It is also possible to re-hydrophobize the produced silica fine particles.

  In addition to the above-described methods, there are a dry method, a wet method, a mixing method and the like as a method for adding a hydrophobizing agent to silica sol. A typical drying method is a spray drying method in which a hydrophobizing agent or a hydrophobizing agent-containing solution is sprayed onto a silica sol suspended in a gas phase. The wet method is a method in which silica sol is immersed in a hydrophobizing agent-containing solution. Furthermore, the mixing method is a method in which a hydrophobizing treatment is performed by mixing a hydrophobizing agent and silica sol with a mixer.

As the hydrophobizing agent, for example, silane compounds, silicone oils, fatty acids, fatty acid metal salts, and the like can be used. Among these, the silane compound used as a hydrophobizing agent is represented by the following formula, and water-soluble ones are mainly used. That is,
Formula: R _a SiX _4-a
In the formula, a is an integer of 0 to 3, R represents a hydrogen atom, an organic group such as an alkyl group or an alkenyl group, and X represents a hydrolyzable group such as a chlorine atom, a methoxy group or an ethoxy group.

Examples of the silane compound represented by the above formula include a chlorosilane compound, an alkoxysilane compound, a silazane compound, and a special silylating agent. In particular,
(1) Chlorosilane compounds Methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tert-butyldimethylchlorosilane, vinyltrichlorosilane, etc. (2) Alkoxysilane compounds tetramethoxysilane, methyltrimethoxysilane, dimethyl Dimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane,
Vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyl Methyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, etc. (3) Silazane compounds, special silylating agents hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N- Bis (trimethylsilyl) urea and the like.

  Among the silane compounds, dimethyldimethoxysilane, hexamethyldisilazane (HMDS), methyltrimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane and the like are preferable.

  Examples of the silicone oil that can be used as the hydrophobizing agent include linear or branched organosiloxanes such as the following cyclic compounds and organosiloxane oligomers. Specific examples of the cyclic compound include octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, tetravinyltetramethylcyclotetrasiloxane, and the like.

  It is also possible to use a modified silicone oil in which the reactivity is improved by introducing a modifying group into the side chain or one end, both ends, side chain one end, side chain both ends, and the like. Examples of the modifying group include an alkoxy group, a carboxy group, a carbinol group, a phenol group, an epoxy group, a methacryl group, and an amino group. Among the carboxy groups, there are higher fatty acid groups. It is also possible to use a silicone oil having two or more modifying groups such as amino group / alkoxy group.

  It is also possible to use dimethyl silicone oil in combination with these modified silicone oils, and other hydrophobizing agents. Examples of other hydrophobizing agents that can be used in combination include silane coupling agents, titanate coupling agents, aluminate coupling agents, various silicone oils, fatty acids, fatty acid metal salts, esterified products thereof, and rosin acid. is there.

The kinematic viscosity of the silicone oil is preferably 5 cm ² / s or less, more preferably 3 cm ² / s or less, and particularly preferably 2 cm ² / s or less in order to facilitate uniform adhesion to the silica particle surface. is there.

  Hereinafter, as a specific example of the preparation of silica particles by the sol-gel method described above, silica particles having a number average primary particle size of 30 nm are prepared by the sol-gel method. The procedure is shown below. The silica particles can be used as a small-diameter external additive as described later.

In a reaction vessel equipped with a stirrer, a dropping funnel and a thermometer,
Methanol 625 parts by mass Water 40 parts by mass 28% by mass Ammonia water 50 parts by mass are added to prepare a methanol-water mixed solvent containing ammonia water.

While adjusting the temperature of the mixed solvent to 35 ° C. and stirring,
800 parts by mass of tetramethoxysilane, 420 parts by mass of 5.4% by mass of ammonia water are each dropped into the mixed solvent. The addition of these compounds is started simultaneously, tetramethoxysilane is added dropwise over 6 hours, and 5.4 mass% aqueous ammonia is added dropwise over 5 hours.

  Stirring is continued for 0.5 hours after completion of the dropwise addition of tetramethoxysilane, the hydrolysis reaction is allowed to proceed at a temperature of 35 ° C., and then the operation of (2) such as centrifugation is performed, followed by methanol-water mixing. A silica fine particle dispersion in which silica fine particles are dispersed in a solvent is prepared.

Next, after adding 3 mol of hexamethyldisilazane to 1 mol of silica fine particles (SiO ₂ ) in the silica fine particle dispersion, the silica fine particles are heated at 60 ° C. and subjected to a reaction treatment for 3 hours. Hydrophobizing treatment is performed. After performing the reaction treatment for 3 hours, the methanol-water mixed solvent is distilled off from the dispersion under reduced pressure to obtain hydrophobic silica particles having a number average primary particle size of 30 nm.

  Moreover, in the preparation example of the hydrophobic silica particles having the number average primary particle size of 30 nm, the same procedure was performed except that the temperature of the mixed solvent was changed to 30 ° C. and the dropping time of tetramethoxysilane was changed to 3.5 hours. Thus, hydrophobic silica particles having a number average primary particle size of 50 nm are obtained.

  In addition, in the above example of producing hydrophobic silica particles having a number average primary particle size of 30 nm, the amount of tetramethoxysilane added is changed to 1160 parts by mass, and the stirring performed after the completion of tetramethoxysilane dropping is changed to 1.0 hour. Otherwise, the same procedure can be used to obtain hydrophobic silica particles having a number average primary particle size of 100 nm.

  Further, in the above example of producing hydrophobic silica particles having a number average primary particle size of 30 nm, the temperature of the mixed solvent is 40 ° C., the addition amount of tetramethoxysilane is 1260 parts by mass, and the dropping time of tetramethoxysilane is 7 hours. changed. Otherwise, the same procedure can be used to obtain hydrophobic silica particles having a number average primary particle size of 120 nm.

  The external additive that can be used in the present invention is preferably subjected to surface treatment with a known treatment agent such as a coupling agent, and specific examples of the surface treatment agent include the following. . That is, a coupling containing at least one of a silane coupling agent, a titanate coupling agent, a silicone oil, a silicone varnish, a fluorine silane coupling agent, a fluorine silicone oil amino group, and a quaternary ammonium salt. Agents, modified silicone oils and the like.

  The monodispersed spherical particles used as an external additive in the toner according to the present invention will be further described. Monodispersed spherical particles having an average primary particle size of 50 nm or more and 150 nm or less used as an external additive in the toner according to the present invention preferably have an average carbon content of more than 1.0% by mass and 4.0% by mass or less. More preferred is a range of 1.5 mass% to 2.5 mass%. This average amount of carbon can be imparted by performing a hydrophobizing treatment using a hydrophobizing agent.

  A toner externally added with monodispersed spherical particles having an average carbon content in the above range can exhibit excellent charge rising performance and charging stability in both low temperature and low humidity environments and high temperature and high humidity environments. In other words, when the average carbon content is less than the above range, it is difficult to achieve good charging start-up performance and charging stability, particularly during image formation in a high temperature and high humidity environment. From the viewpoint of preventing, it is preferable to set the average carbon amount within the above range. In addition, when the average carbon amount is more than the above range, it may be difficult to develop good charge rising performance particularly during image formation in a low-temperature and low-humidity environment, resulting in toner scattering and photoreceptor contamination. From the viewpoint of preventing the occurrence, it is preferable to set the average carbon amount within the above range.

  For example, in the case of silica particles, the average carbon content of the monodispersed spherical particles can be controlled by adjusting the removal amount of the organic solvent and the addition amount of the hydrophobic treatment agent during the hydrophobic treatment. There is also a method of controlling the average carbon amount by heat-treating the produced silica particles at a temperature of 300 ° C. to 600 ° C. and thermally condensing the silanol groups in the vicinity of the silica particle surfaces and inside the particles. In this method, it is possible to adjust the amount of silanol groups to be thermally condensed by controlling the heat treatment temperature. In this method, the hydrophobization treatment can be performed again after the heat treatment.

The average carbon content of monodispersed spherical particles having an average primary particle size of 50 nm or more and 150 nm or less can be measured by, for example, a combustion method using a solid medium carbon analyzer “EMIA-110 (manufactured by Horiba, Ltd.)”. is there. Specifically, 0.1 g of a monodispersed spherical particle sample having an average primary particle size of 50 nm or more and 150 nm or less is precisely weighed in a magnetic boat, burned at about 1200 ° C., and carbon dioxide (CO ₂ generated at this time) ) The number of carbons can be calculated from the amount.

  The monodispersed spherical particles having an average primary particle size of 50 nm to 150 nm are preferably those having an alkoxy group content of 1.0% by mass to 5.0% by mass, and 1.5% by mass to 4.% by mass. More preferably 0% by mass. The toner to which monodispersed spherical particles having an alkoxy group content in the above range are externally added can exhibit excellent charge rising performance and charging stability in both low temperature and low humidity environments and high temperature and high humidity environments.

The amount of alkoxy groups of monodispersed spherical particles having an average primary particle size of 50 nm or more and 150 nm or less can be measured by, for example, a sealed alkali tracking headspace GC method. The measurement of the amount of alkoxy groups of the monodispersed spherical particles by the sealed alkali tracking headspace GC method is performed through the following steps (1) to (4).
(1) A monodispersed spherical particle sample weighed to 0.2 g is put into a vial with a volume of 20 ml. (2) 1.0 g of 1 mol / liter amyl alcohol potassium solution is added and gently stirred. (3) Head Heat treatment is performed at 80 ° C. for 30 minutes in the space sampler (4) A certain amount of gas generated in the head space sampler is sampled, and gas chromatography (GC) measurement is performed under the following conditions.

Gas chromatography (GC) conditions-Column: Silicone coated capillary column-Carrier: He carrier-Detector: FID detector-GC part temperature: 50 ° C to 280 ° C (temperature increase rate 10 ° C / min)
・ INJECTION section temperature: 250 ℃
The standard addition method in which a fixed amount of methanol is added to the sample is used for quantification using a calibration curve prepared by the same pretreatment.

  The monodispersed spherical particles having an average primary particle size of 50 nm or more and 150 nm or less are preferably those having a degree of hydrophobicity of 40 to 80, and more preferably 50 to 70. A toner externally added with monodispersed spherical particles having a hydrophobization degree in the above range can exhibit excellent charge rising performance and charging stability in both low temperature and low humidity environments and high temperature and high humidity environments.

  In other words, when the degree of hydrophobicity is smaller than the above range, it is conceivable that the performance of maintaining the charged charge is deteriorated particularly in a high-temperature and high-humidity image forming environment, and there is a concern about the occurrence of toner scattering due to a decrease in the toner charge amount. Is done. Further, when the degree of hydrophobicity is larger than the above range, a difference appears in the charge rising performance of the toner, particularly in a low temperature and low humidity image forming environment, and a difference occurs in the developer mixing state during stirring in the developing device. There is a possibility that the charge amount distribution between the toner particles is broadened and the toner is scattered.

The degree of hydrophobicity of monodispersed spherical particles having an average primary particle size of 50 nm or more and 150 nm or less can be measured, for example, by a methanol titration method. Specifically, the hydrophobization degree measurement by the methanol titration method is performed by the following procedure. That is, after adding 50 ml of distilled water to a beaker having a volume of 200 ml, a monodispersed spherical particle sample of 50 nm or more and 150 nm or less weighed to 0.2 g is added. Next, methanol is dripped from the burette whose tip is immersed in the liquid, and dripping is performed until the entire sample is wet and the whole is settled in a state of being slowly stirred. The degree of hydrophobicity can be calculated from the following equation, where the amount of methanol required for the entire sample to settle is a (ml). That is,
Hydrophobic degree = {a / (a + 50)} × 100
The content of monodispersed spherical particles having an average primary particle size of 50 nm or more and 150 nm or less is preferably from 0.1 parts by mass to 3.0 parts by mass with respect to 100 parts by mass of toner particles. 2.0 parts by mass from the part is more preferable.

  As described above, in the present invention, the spacer effect is exhibited by using the monodispersed spherical particles having the above-mentioned constitution and the number average primary particle size of 50 nm or more and 150 nm or less. Surface contact is avoided. As a result, embedding and detachment of small-sized external additive particles such as metal oxide particles having a number average primary particle size of 5 nm to 50 nm, for example, added to the toner particle surfaces are prevented. Therefore, even when the toner is stirred in the developing device for a long time, the small diameter external additive is not embedded or detached from the surface of the toner particles, so that the chargeability and fluidity of the toner can be stably maintained. .

  The toner used in the present invention has, as an external additive, metal oxide particles having a number average primary particle size of 5 nm to 50 nm, preferably a number average primary particle size of 7 nm to 40 nm, together with the above-described monodispersed spherical particles. It is preferable to contain. Examples of such metal oxide particles include fine particles of silica, titania (rutile type, anatase type, amorphous type), metatitanic acid, alumina, silica / titania / alumina composite oxide, and the like.

In addition to the metal oxide particles, for example, the following carbides, nitrides, borides, oxides, and the like can be used as external additives. That is,
(1) Carbide Silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, diamond carbon lactam, etc. (2) Nitride Nitride Boron, titanium nitride, zirconium nitride, etc. (3) Boride Zirconium boride, etc. (4) Sulfide Molybdenum disulfide, etc. (5) Fluoride Carbon fluoride, etc. (6) Oxide Iron oxide, chromium oxide, titanium oxide, oxidation Calcium, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, etc. In addition, some oxides include, for example, composite oxides composed of silica, silica / titania / alumina, etc., colloidal silica, etc. by a vapor phase method. . There are also oxide compounds such as calcium titanate, strontium titanate, and magnesium titanate.

  Furthermore, there are various metal soaps such as aluminum stearate, calcium stearate, zinc stearate and magnesium stearate, various nonmagnetic inorganic materials such as talc and bentonite. These can be used alone or in combination of two or more.

  In addition, these particles are composed of known hydrophobizing agents such as silane coupling agents, titanate coupling agents, silicone oils, silicone varnishes, fluorine silane coupling agents or fluorine silicone oils, amino groups / fourths. It is preferable that the surface is treated with a treating agent such as a secondary ammonium salt-containing coupling agent or a modified silicone oil.

  The metal oxide particles having a number average primary particle size of 5 nm to 50 nm can be used alone or in combination of two or more.

The number average primary particle size of the metal oxide particles having a number primary particle size of 5 nm to 50 nm can be measured, for example, by the following procedure.
(1) Photographing is performed at a magnification according to the average particle size using a transmission electron microscope (TEM), and the photographed photographic image is captured by a scanner.
(2) The image processing analyzer “LUZEX AP (manufactured by Nireco)” binarizes the metal oxide particles present on the toner particle surface on the photographic image. The diameter is calculated, and the calculated value is taken as the number average primary particle diameter. Here, the horizontal ferret diameter is a distance between two vertical lines obtained when a metal oxide particle having a number primary particle size of 5 nm or more and 50 nm or less on a photographic image is sandwiched between two vertical lines. It means that.

  In addition to the above method, the number average primary particle size measurement method for metal oxide particles having a number average primary particle size of 5 nm to 50 nm is not limited to the above method, and the metal oxide particles present on the surface of the toner particles are directly scanned. There is also a method in which a photograph is taken with an electron microscope and calculated in the same procedure from the photograph image.

The metal oxide particles having a number average primary particle size of 5 nm to 50 nm are preferably those having a BET specific surface area of 400 to 50 m ² / g. Here, the BET specific surface area is the specific surface area of the particle calculated by the gas adsorption method. The calculation method is, for example, directly adsorbing gas molecules with a known adsorption area on the particle surface, such as nitrogen gas. The specific surface area of the particles is calculated from the adsorption amount (monomolecular layer adsorption amount).

The BET specific surface area can be calculated from an equation called the BET equation shown below, which shows the relationship between the adsorption equilibrium pressure P when the adsorption equilibrium state is maintained at a constant temperature and the adsorption amount V at that pressure. is there. That is,
P / V (Po−P) = (1 / VmC) + ((C−1) / VmC) (P / Po)
In the above formula, Po is a saturated vapor pressure, Vm is a monolayer adsorption amount (adsorption amount when a gas molecule forms a monolayer on the surface of a metal oxide particle), C (> 0) is a parameter related to heat of adsorption, etc. Is shown. Specifically, the monomolecular adsorption amount Vm is calculated from the above formula, and the BET surface area of the metal oxide particles is calculated by multiplying this by the adsorption occupation area of one gas molecule.

  Moreover, as an apparatus for measuring and calculating the BET specific surface area of the metal oxide particles, for example, there is a commercially available automatic specific surface area measuring apparatus “GEMINI 2360 (manufactured by Shimadzu Micromeritics)”. When measuring and calculating the BET specific surface area using the automatic specific surface area measuring device, first, 2 g of metal oxide particles are filled into a straight sample cell, and the cell is pretreated with nitrogen gas (purity 99.999%) for 2 hours. Replace the inside. After the substitution, nitrogen gas (purity 99.999%) is adsorbed on the metal oxide particles pretreated with the measuring apparatus main body, and the BET specific surface area is calculated by a multipoint method (7-point method).

  The content of the metal oxide particles having a number average primary particle size of 5 nm to 50 nm is preferably 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the toner particles. 4.0 parts by mass is more preferable. By setting the content of the metal oxide particles having a number average primary particle size of 5 nm or more and 50 nm or less within the above range, it becomes easy to impart desired charging characteristics and flow characteristics to the toner particles. In addition, by setting the content of the metal oxide particles in the above range, the metal oxide particles are firmly held on the surface of the toner particles, and there is a risk of causing side effects such as release from the toner particle surface and poor charging. Absent.

  The content of the metal oxide having a number average primary particle size of 5 nm or more and 50 nm or less is such that the total amount of the monodispersed spherical particles having the number average primary particle size of 50 nm or more and 150 nm or less is within the above range. It is preferable to prepare in such a manner. Here, the mass ratio of monodispersed spherical particles having a number average primary particle size of 50 nm to 150 nm and metal oxide particles having a number average primary particle size of 5 nm to 50 nm (monodispersed spherical particles / metal oxide particles) is 3.0 / 0.3 to 0.3 / 3.0 is preferable.

  In addition, the toner used in the present invention is a combination of various organic resin fine particles formed by an emulsion polymerization method, a soap-free emulsion polymerization method, a wet polymerization method such as a non-aqueous dispersion polymerization method, a gas phase method, or the like as an external additive. Is possible. Examples of the organic resin fine particles include styrene resin fine particles, (meth) acrylic resin fine particles, benzoguanamine resin fine particles, melamine resin fine particles, Teflon (registered trademark) resin fine particles, silicone resin fine particles, polyethylene resin fine particles, polypropylene resin fine particles, and the like. is there.

  In the present invention, the toner content (toner concentration) contained in the developing device 14 constituting the image forming unit 10 is measured by the toner concentration detecting unit, and the toner is supplied into the developing device 14 based on the measurement result. Is to be done. Here, the developing device 14 capable of mounting the toner concentration detection unit will be described with reference to FIG.

  The developing device 14 shown in FIG. 3 includes a developing sleeve 141, a transport supply roller 144 that supplies the developer to the developing sleeve 141, a pair of agitation screws 142, and a housing 145 that contains a two-component developer composed of toner and a carrier. 143 are arranged substantially parallel to each other. The developer accommodated in the housing 145 is agitated by the agitating screws 142 and 143 and conveyed in the axial direction (the depth direction in the figure).

  The housing 145 has a partition wall 146 disposed therein, and the partition 146 divides the inside of the developing device 14 into a first chamber 147 in which the stirring screw 142 is disposed and a second chamber 148 in which the stirring screw 143 is disposed. . The first chamber 147 is adjacent to the developing sleeve 141 and the conveyance supply roller 144, but the second chamber 148 is not adjacent.

  The developing sleeve 141 is a cylindrical member using a non-magnetic material such as stainless steel or aluminum, and has an outer diameter of 15 mm to 25 mm and a thickness of 0.5 mm to 1 mm, for example. The developing sleeve 141 maintains a predetermined gap with respect to the circumferential surface of the photosensitive drum 11 by unillustrated abutting rollers provided at both ends, and the rotation of the photosensitive drum 11 (in the direction of the arrow (clockwise in the figure)). Rotate in the opposite direction to direction rotation)). Inside the developing sleeve 141 is disposed a magnet roll 149 provided with a plurality of alternating N and S magnetic poles necessary for image formation. The magnet roll 149 is fixed concentrically with the developing sleeve 141, and applies a magnetic force to the non-magnetic sleeve peripheral surface by the plurality of magnetic poles described above.

  Further, in the developing device 14, a layer thickness regulating member (not shown) is arranged so as to form a predetermined gap with the developing sleeve 141, and the layer thickness regulating member is formed on the peripheral surface of the developing sleeve 141. The thickness (layer thickness) of the agent is regulated.

  The transport supply roller 144 supplies the two-component developer stirred by the stirring screw 142 to the above-described layer thickness regulating member, and is provided with a blade portion that transports the two-component developer.

  The agitating screws 142 and 143 rotate at a constant speed in mutually opposite directions to agitate and mix the toner and the carrier in the developing device 14, and uniformly mix the two-component developer contained in the developing device 14. It is what makes it.

  For example, the developing device 14 is provided with a two-component developer supply port that can be opened at the top of the housing 145 above the stirring screw 143, and the two-component developer is supplied into the housing 145 through the two-component developer supply port.

  The two-component developer supplied into the housing 145 is stirred and mixed with the two-component developer housed in the housing 145 by the stirring screws 142 and 143 rotating at constant speeds in opposite directions. It becomes a two-component developer having a toner concentration. In this way, the two-component developer supplied with the new two-component developer is conveyed to the layer thickness regulating member by the conveyance supply roller 144, and becomes a predetermined layer thickness by the layer thickness regulating member. Then, a developer layer of a two-component developer is formed on the outer peripheral surface of the developing sleeve 141.

  The toner constituting the two-component developer supplied on the outer peripheral surface of the developing sleeve 141 is detached from the developing sleeve 141 corresponding to the latent image formed on the photosensitive drum 11, and electrostatically appears on the photosensitive drum 11. Adsorb. At this time, a developing bias voltage in which a direct current (DC) bias and, if necessary, an alternating current (AC) bias are superimposed is applied to the electrostatic latent image on the photosensitive drum 11, and the photosensitive drum 11 is in a non-contact state. It is possible to perform reversal development (non-contact development method).

  After developing the latent image on the photosensitive drum 11, the two-component developer on the developing sleeve 141 is peeled off from the developing sleeve 141 by the action of a plurality of N magnetic poles constituting the magnet roll 149, and again by the conveyance supply roller 144. It is conveyed to the stirring screw 142.

  When the developing device 14 detects that the toner concentration in the housing 145 has dropped below a predetermined toner concentration by a toner concentration detection unit 17 described later, the two-component developer is supplied. Here, the toner concentration indicates the content (ratio) of toner constituting the two-component developer. That is, in the housing 145, the toner of the two-component developer is consumed by the development, but the carrier is not consumed. Therefore, the toner content (ratio) is decreased by repeating the development, and thus is consumed. One minute of toner will be replenished.

  For example, toner supply to the developing device is performed via a toner supply port 145b provided in the housing 145 from a hopper (not shown). The toner replenished into the developing device 14 is sufficiently stirred and charged by the stirring screws 142 and 143, conveyed to the developing sleeve 141, and supplied to the photoreceptor 11.

  Next, a toner concentration detection unit that measures the toner concentration in the developing device 14 will be described. The present invention forms an image using toner contained in a developing device having a toner density detecting portion. For example, the developing device 14 of FIG. 3 has a toner concentration detection unit 17 attached to the outer surface of the housing 145 below the second chamber 148. This position is outside the portion where the developer accumulates, and the toner concentration detection unit 17 is positioned and fixed by penetrating a protrusion formed on the housing 145.

  In the developing device 14 shown in FIG. 3, the toner density is detected by the toner density detector 17 after the image is formed and the toner is consumed. When the toner density detection unit 17 determines that the toner density in the developing device 14 is lower than a predetermined density, the toner is replenished to increase the toner density, and the toner density in the developing device 14 is appropriately set. Within a certain range.

  The developing device 14 in FIG. 3 is provided with a toner concentration detection unit 17 outside the device. The toner concentration detection unit detects the toner concentration by detecting the apparent magnetic permeability of the developer. Measurement from the outside of the device is possible. The toner concentration detection unit has an LC resonance circuit in which an inductance coil and a capacitor are arranged, and measures the toner concentration by utilizing the fact that the inductance of the coil changes depending on the magnetic permeability of the atmosphere.

Here, the resonance frequency f of the LC resonance circuit is expressed by the following formula (1), which indicates that the toner density can be detected by measuring the resonance frequency f obtained by the LC resonance circuit. That is, the resonance frequency f is
Formula (1); f = 1 / 2π (LC) ^1/2
Where L represents the inductance of the coil and C represents the capacitance of the capacitor.

  The present inventor has found that when a large amount of external additive adheres to the carrier surface, the charge imparting performance of the carrier itself decreases and the permeability of the developer also changes. This change is detected by the LC resonance circuit as a frequency fluctuation, and the toner It was presumed that toner replenishment was performed due to an erroneous determination of density reduction. Therefore, the present inventor prevents the large-diameter external additive from adhering to the carrier surface as much as possible to prevent the large-diameter external additive from adhering to the carrier surface, thereby preventing the fluctuation in the permeability of the developer and detecting the frequency of the LC resonance circuit. Is made stable.

  The toner concentration detector 17 will be further described. FIG. 4 is a schematic diagram illustrating an example of a toner concentration detection unit that measures the amount of toner contained in the developing device 14 that constitutes the electrophotographic image forming apparatus. 4A is an overall view of the toner concentration detector 17, FIG. 4B is an enlarged view of the planar coil 171 constituting the toner concentration detector 17, and FIG. 4C is a resonance circuit used in the toner concentration detector 17. FIG.

  4 detects the toner content (density) stored in the developing device 14 by detecting a change in the resonance frequency of the LC resonance circuit. The toner concentration detection unit 17 in FIG. This is an LC tuned oscillation circuit having a coil and two capacitors. That is, the resonance circuit used as the toner concentration detection unit in the present invention has an inductance coil L, a transistor Q, a resistor R, two capacitors C1, C2, and the like, as shown in FIG.

  As shown in FIG. 4A, the toner density detection unit 17 has a planar coil 172 formed on one surface of a rectangular printed board 171, and the planar coil 172 corresponds to the inductance coil L in FIG. 4C. . As shown in the enlarged view of FIG. 4B, the planar coil 172 has a substantially rectangular outer shape and is formed by a print pattern, and the surface on which the planar coil 172 is formed is the housing 45 of the developing device 14. It is arranged so as to be on the side that touches.

  The planar coil 172 constituting the toner concentration detection unit 17 used in the present invention is not formed up to the central portion 172a, and is a substantially ring-shaped coil as a whole. The central portion 172a is a region where a coil is not formed by a print pattern, and corresponds to a hollow region in the present invention. In other words, the hollow region referred to in the present invention means a region where the coil at the center portion of the planar coil is not formed, and the printed circuit board 171 itself exists. As described above, the toner concentration detection unit 17 provided in the developing device 14 of FIG. 3 does not have a member such as a core in addition to the coil at the central portion 172a of the planar coil 172. The part is air core. Accordingly, the inside of the central portion 172a, which is a hollow region, has a substantially flat sensitivity distribution, so that highly accurate toner concentration detection can be performed.

  Although not shown in FIG. 4A on the other surface of the printed circuit board 171 (the back surface of the surface on which the planar coil 172 is formed), other components of the resonance circuit (transistor Q, resistor R, capacitor C1, C2) is implemented. A connector 173 is attached to the other end of the printed circuit board 171 at the end in the longitudinal direction on the side where the planar coil 172 is not formed. In FIG. 3A, a positioning through-hole 174 is provided in the central portion 172a of the planar coil 172 on the printed circuit board 171. Further, the positioning through-hole 174 is outside the planar coil 172 and substantially corresponds to the central portion of the printed circuit board 171. A long hole-shaped through-hole 175 is also provided at the location.

  Although not shown in the drawing, the outer surface of the housing 145 of the developing device 14 shown in FIG. 3 is provided with two protrusions for positioning to be fitted into the through holes 174 and 175 described above. 17 is positioned in the housing 145. In particular, the positional relationship between the housing 145 and the planar coil 172 is correctly maintained by the through-hole 174 and the protrusion, which are round holes. For example, even if the image forming environment such as temperature changes, the housing of the central portion 172a of the planar coil 172 The position relative to 145 does not change.

  The toner density detector 17 is arranged so that the longitudinal direction of the planar coil 172 is parallel to the longitudinal directions of the developing sleeve 141 and the conveying screws 142 and 143. Further, the toner density detection unit 17 is arranged so that the planar coil 172 is substantially horizontal at the lowest position in the state of being mounted on the image forming apparatus 1 in the developing device 14 or in the tangential direction of the outer surface of the housing 145. May be.

  Next, the size of the planar coil 172 will be described. As shown in FIG. 4B, the planar coil 172 is substantially rectangular (A <B), and is arranged so that the long side B is parallel to the axial direction of the developing device 14. Here, the detection target of the toner concentration detection unit 17 is the developer in the second chamber 148, and the conveyance screw 143 is disposed in the second chamber 148, and the rotation of the conveyance screw 143 moves the upper position of the planar coil 172. The amount of developer present varies periodically. As a result, the detection result by the toner density detector 17 also periodically varies.

  The fluctuation width of the periodic fluctuation varies depending on the relationship between the long side B of the planar coil 172 and the screw pitch of the conveying screw 143, the inner diameter of the planar coil 172, and the like. Specifically, it is preferable to set the long side B within a range larger than 0.5 times the screw pitch of the conveying screw 143 and smaller than 1.5 times. By making the long side B larger than 0.5 times the screw pitch of the conveying screw 143, it is possible to secure one or more developer peaks (where the developer amount becomes maximum) on the coil. . Further, by making the long side B smaller than 1.5 times the screw pitch of the conveying screw 143, the size of the planar coil 172 is made compact, and the toner density detecting unit 17 that can be mounted on the developing device 14 is realized.

  As described above, when the toner concentration detector 17 detects that the toner concentration in the housing 145 is lower than the predetermined toner concentration, the developing device 14 shown in FIG. 3 replenishes toner based on the detection result. It is like.

  In the image forming method according to the present invention, a two-component developer composed of the above-described core-shell toner and carrier is used. Carriers that are magnetic particles used when used as a two-component developer are formed of, for example, metals such as iron, ferrite, and magnetite, alloys of these metals with metals such as aluminum and lead, and among these, Those using ferrite particles are preferred.

  In the present invention, it is preferable to use a resin-coated carrier in which the surface of the magnetic particles such as ferrite is coated with a resin, and the presence of a resin-coated layer formed on the surface of the carrier can exhibit good charge imparting performance to the toner particles. it can. In addition, since the toner described above is used in the present invention, it is difficult for the large-sized external additive to be released from the toner particle surface even if stirring is repeated in the developing device, and charging due to adhesion of the free external additive to the carrier is difficult. Since the deterioration of the application performance is eliminated, stable toner charging can be performed.

  The coating resin that can be used for the resin-coated carrier is not particularly limited. For example, polyolefin resins such as styrene resins and styrene-acrylic resins, silicone resins, polyester resins, and fluorine-containing polymer resins. Etc. can be used.

  The carrier used in the present invention preferably has a volume average particle diameter of 25 μm or more and 50 μm or less. Use of the carrier having the above volume average particle diameter is advantageous in forming a toner image having excellent sharpness because a soft magnetic brush is formed on the developing sleeve during image formation. Further, even if image formation is repeated, adhesion of the free external additive to the surface of the carrier particles does not easily occur. Therefore, the above-described magnetic brush is stably formed, contributing to stable toner image formation. The volume average particle diameter of the carrier can be measured by a known measuring device such as a laser diffraction particle size analyzer “HELOS (manufactured by Sympatec Co., Ltd.)” equipped with a wet disperser. The saturation magnetization value of the carrier used in the present invention is preferably 20 to 80 emu / g. By setting the saturation magnetization value in the above range, a magnetic brush can be easily formed on the developing sleeve. The saturation magnetization value of the carrier can be measured by a known measuring device such as “DC magnetization characteristic automatic recording device 3257-35 (manufactured by Yokogawa Electric Corporation)”.

  The two-component developer used in the present invention can be prepared by mixing the above-described core-shell toner and carrier by a known method. The mixing amount of the toner with respect to the carrier is preferably 2% by mass to 10% by mass. Further, the mixing apparatus is not limited, and for example, a Nauter mixer, a W cone, a V-type mixer, and the like can be used. A method for producing a resin-coated carrier that can be used in the two-component developer used in the present invention will be described in detail later.

  In the present invention, it is preferable that the toner is replenished to the developing device based on the measurement result of the toner density detecting unit described above and the carrier is replenished to the developing device by a known method. In other words, the amount of toner consumed by development is replenished, and a new carrier is also replenished by a known method, and the carrier in the developing device is replaced little by little to maintain the charge imparting performance of the carrier more stably. Is possible. The method of replenishing the developing device with the toner together with the toner is called “auto-refining development method” or “trickle development”, and is used to maintain the charging performance of the two-component developer in the developing device at a predetermined level. It is advantageous.

  Next, a method for producing the toner used in the present invention will be described.

  As described above, in the toner used in the present invention, the surface of the core particle containing the styrene acrylic copolymer resin is coated with the modified polyester resin in which the molecular chain of the styrene acrylic copolymer molecular chain is bonded to the terminal of the polyester molecular chain. The toner has a core-shell structure.

  The toner base particles constituting the toner used in the present invention (toner particles before adding the external additive) are not particularly limited, and can be produced by a conventional toner production method. That is, it can be prepared by a so-called pulverization method in which a toner is prepared through a kneading, pulverization, and classification process, or a so-called polymerization method in which a polymerizable monomer is polymerized and particles are formed while controlling the shape and size. Is possible.

  Among them, the toner production by the polymerization method is a small-diameter toner that can form a desired toner while controlling the shape and size of the particles in the production process, and can faithfully reproduce a minute dot image. It is most suitable for making. In particular, in the present invention, toner base particles having a smooth core-shell structure are required. In order to form a smooth toner particle surface with a shell of a modified polyester resin, the core particle surface needs to be smooth.

  As a toner manufacturing method that satisfies this need, among the toner manufacturing methods by polymerization, resin particles of around 120 nm are formed in advance by emulsion polymerization or suspension polymerization, and the resin particles are aggregated and fused to form particles. It can be said that the emulsification association method for carrying out the above is one of the preferred methods. That is, the emulsion association method makes it possible to produce core particles having a smooth surface by controlling the conditions of the aggregation / fusion process of resin particles and the subsequent aging process.

Hereinafter, an example of preparing a toner having a core-shell structure by an emulsion association method will be described. In the emulsification association method, a toner is generally prepared through the following procedure. That is,
(1) Preparation process of core forming resin particle dispersion (2) Preparation process of colorant particle dispersion (3) Aggregation / fusion process of core resin particles (4) First aging process (5) Shelling process (6) Second aging step (7) Cooling step (8) Washing step (9) Drying step (10) External additive treatment step In the present invention, as described above, when the core particles are produced, aggregation / fusion is performed. By setting the heating temperature higher in the process and setting the fusing time longer, the aggregated resin particles become rounded and at the same time a smooth surface is formed. Further, by setting the heating temperature in the aging step in which the reaction system is heat-treated subsequent to the aggregation / fusion step to a higher temperature for a longer time, core particles having a smooth surface can be produced.

  Hereinafter, each step will be described.

(1) Production process of resin particle dispersion In this process, a polymerizable monomer that forms the resin particles for the core is charged into an aqueous medium and polymerized to form resin fine particles having a size of about 120 nm. It is a process. In the present invention, at this step, at least a styrene monomer and an acrylate monomer are charged and dispersed in an aqueous medium, and these polymerizable monomers are polymerized by a polymerization initiator to thereby styrene acrylic copolymer. The resin particles are prepared. In this way, resin particles for the core are formed.

(2) Step of producing colorant particle dispersion This is a step of producing a colorant particle dispersion having a size of about 110 nm by dispersing a colorant in an aqueous medium.

(3) Aggregation / fusion process of core resin particles (core particle formation)
This step is a step of aggregating the aforementioned resin particles and colorant particles in an aqueous medium, and simultaneously aggregating these particles to produce core particles. In this step, an alkali metal salt or alkaline earth metal salt is added as an aggregating agent to an aqueous medium in which resin particles and colorant particles are mixed, and then heated at a temperature equal to or higher than the glass transition temperature of the resin particles. The agglomeration is advanced to simultaneously fuse the resin particles.

  Specifically, the resin particles and the colorant particles produced by the above-described procedure are added to the reaction system, and a coagulant such as magnesium chloride is added to simultaneously aggregate the resin particles and the colorant particles. They are fused together to form aggregated resin particles (core particles). When the size of the core particles reaches the target size, a salt such as saline is added to stop the aggregation.

  In this step, when the heating temperature is set high and the fusing time is set long, the aggregated resin particles (core particles) become rounded and the surface becomes smooth at the same time. In this way, core particles having a smooth surface can be produced.

(4) First aging step This step is a step of aging until the shape of the core particles is changed to a desired shape by heat-treating the reaction system subsequent to the aggregation / fusion step. Even in this step, it is possible to produce core particles with a smooth surface by setting the heating temperature higher and setting the treatment time longer.

(5) Shelling step In this step, a shell is formed by adding resin particles for shell formation to the dispersion of core particles formed in the first aging step and covering the surface of the core particles with the resin particles. It is a process to do. In the present invention, it is possible to form a shell containing the modified polyester by adding resin particles of a modified polyester in which a styrene acrylic copolymer molecular chain is molecularly bonded to the terminal of the polyester molecular chain in this step.

  As described above, in the present invention, since a modified polyester in which a styrene acrylic copolymer molecular chain is molecularly bonded to a polyester molecular chain is used as a resin for shell formation, an appropriate affinity for the surface of the core particle is obtained. It is considered to form a strong bond when expressed. Further, since moderate dispersibility acts between the shell-forming resin particles, aggregation between the shell-forming resin particles hardly occurs, and it is considered that a thin shell is formed on the surface of the core particles. In this way, toner base particles having a core-shell structure are formed.

(6) Second aging step In this step, following the shelling step, the reaction system is heat-treated to strengthen the shell coating on the core surface, and the toner base particles have a desired shape. It is a process of aging until.

(7) Cooling step This step is a step of cooling (rapid cooling) the dispersion of the toner base particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

(8) Washing step This step includes a step of solid-liquid separating the toner base particles from the toner base particle dispersion liquid cooled to a predetermined temperature in the above step, and a toner base that has been solid-liquid separated into a wet cake-like aggregate It consists of a cleaning process for removing deposits such as surfactants and flocculants from the particle surface.

  In the washing treatment, the washing treatment is performed until the electrical conductivity of the filtrate reaches a level of, for example, 10 μS / cm. As the filtration method, there are known processing methods such as a centrifugal separation method, a vacuum filtration method using Nutsche, etc., a filtration method using a filter press, etc., and there is no particular limitation.

(9) Drying Step This step is a step of drying the washed toner base particles to obtain dried toner base particles. Examples of the dryer used in this step include known dryers such as spray dryers, vacuum freeze dryers, and vacuum dryers, stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, and rotating dryers. It is also possible to use a type dryer, a stirring type dryer or the like.

  Further, the amount of water contained in the dried toner base particles is preferably 5% by mass or less, and more preferably 2% by mass or less. In addition, when the toner base particles that have been dried are agglomerated with a weak interparticle attractive force, the agglomerates may be crushed. Here, as the crushing processing apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

(10) External additive treatment step This step is a step of preparing a toner by adding and mixing external additives as necessary to the surface of the dried toner base particles. In the present invention, monodispersed spherical particles having a number average primary particle size of 50 nm or more and 150 nm are added as external additives in this step.

  Through the above steps, a core-shell toner can be produced by an emulsion association method. For the reasons described above, the core-shell toner according to the present invention is preferably prepared by an emulsion association method.

  Next, colorants and waxes that can be used in the toner used in the present invention will be described with specific examples. First, known colorants can be used for the toner according to the present invention. Specific colorants are shown below.

  As the black colorant, for example, carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite can be used.

  Examples of the colorant for magenta or red include C.I. I. Pigment Red 2, 3, 5, 6, 7, 15, 15, 48: 1, 53: 1, 57: 1, 60, 63, 64, 68, the same 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 139, 144, 149, 150, 163, 166, 170, 177, 178, 184, 202, 206, 207, 209, 222, 238, 269, and the like.

  Examples of the colorant for orange or yellow include C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 12, 14, 15, 17, 74, 83, 93, 94, 138, 155, 162, 180, 185, and the like.

  Further, as a colorant for green or cyan, C.I. I. Pigment Blue 2, 3, 15, 15, 15: 2, 15: 3, 15: 4, 16, 17, 17, 60, 62, 66, C.I. I. Pigment Green 7 etc.

  Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 2, 6, 14, 15, 16, 19, 21, 21, 33, 44, 56, 61, 77, 79, 80, 81, 82, the same 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc.

  These colorants can be used alone or in combination of two or more as required. Further, the amount of the colorant added is in the range of 1 to 30% by mass, preferably 2 to 20% by mass, based on the whole toner, and a mixture thereof can also be used. The number average primary particle size varies depending on the type, but is preferably about 10 to 200 nm.

Next, examples of the wax that can be used for the toner used in the present invention include the following known waxes. That is,
(1) Polyolefin wax Polyethylene wax, polypropylene wax, etc. (2) Long-chain hydrocarbon wax, paraffin wax, sazol wax, etc. (3) Dialkyl ketone wax, distearyl ketone, etc. (4) Ester wax Carnauba wax, Montan Wax, trimethylolpropane tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerol tribehenate, 1,18-octadecanediol di Stearate, trimellitic trimellitic acid, distearyl maleate, etc. (5) Amide wax Ethylenediamine dibehenyl amide, trimellitic acid triste Riruamido like.

  The melting point of the wax is usually 40 to 125 ° C, preferably 50 to 120 ° C, more preferably 60 to 90 ° C. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1% by mass to 30% by mass, and more preferably 5% by mass to 20% by mass.

  Next, the aggregating agent, polymerization initiator, dispersion stabilizer, surfactant, etc. used when the toner used in the present invention is produced by the emulsion association method will be described.

  As described above, the emulsion association method forms toner base particles by agglomerating and fusing resin particles, colorant particles, etc. in a dispersion in which resin particles, colorant particles, etc. are dispersed in an aqueous medium. is there. The aggregating agent that can be used in preparing the toner used in the present invention is not particularly limited, but those selected from metal salts are preferably used. For example, monovalent metal salts such as alkali metal salts such as sodium, potassium and lithium, for example, divalent metal salts such as calcium, magnesium, manganese and copper, and trivalent metals such as iron and aluminum. There is salt. Specific examples of the salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. Among these, divalent metal is particularly preferable. Salt. When a divalent metal salt is used, agglomeration can be promoted with a smaller amount. These may be used alone or in combination of two or more.

When the binder resin constituting the toner used in the present invention is formed using a vinyl polymerizable monomer, a known oil-soluble or water-soluble polymerization initiator can be used. Specific examples of the oil-soluble polymerization initiator include the following azo or diazo polymerization initiators and peroxide polymerization initiators. That is,
(1) Azo or diazo polymerization initiator 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1 -Carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, etc. (2) peroxide-based polymerization initiators benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl Peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4 4-t-butylperoxycyclohexyl) propane, tris (T-butylperoxy) triazine In the case of forming the resin particles by emulsion polymerization is a water-soluble radical polymerization initiators can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

  A known chain transfer agent can also be used for adjusting the molecular weight of the resin particles. Specific examples include octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionic acid ester, terpinolene, carbon tetrabromide, and α-methylstyrene dimer.

  In the present invention, a polymerizable monomer dispersed in an aqueous medium is polymerized, and a resin particle or the like dispersed in the aqueous medium is aggregated and fused to produce a toner. It is preferable to use a dispersion stabilizer that is stably dispersed in the mixture. Examples of the dispersion stabilizer include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, Examples include barium sulfate, bentonite, silica, and alumina. In addition, polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, higher alcohol sodium sulfate and the like which are generally used as surfactants can also be used as the dispersion stabilizer.

  Further, when polymerization is performed using a polymerizable monomer in an aqueous medium, it is necessary to uniformly disperse oil droplets of the polymerizable monomer in the aqueous medium using a surfactant. In this case, usable surfactants are not particularly limited, but for example, the following ionic surfactants can be used as preferable ones. Examples of the ionic surfactant include a sulfonate, a sulfate ester salt, and a fatty acid salt. Examples of the sulfonate include sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, and 3,3-disulfonediphenyl. Urea-4,4-diazo-bis-amino-8-naphthol-6-sulfonate sodium, o-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4 -Sodium diazo-bis-β-naphthol-6-sulfonate.

  Examples of sulfate salts include sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, and sodium octyl sulfate. Fatty acid salts include sodium oleate, sodium laurate, sodium caprate, sodium caprylate, Examples include sodium caproate, potassium stearate, and calcium oleate.

  Nonionic surfactants can also be used. Specifically, polyethylene oxide, polypropylene oxide, a combination of polypropylene oxide and polyethylene oxide, esters of polyethylene glycol and higher fatty acids, alkylphenol polyethylene oxide, higher fatty acids and Examples include polyethylene glycol esters, higher fatty acid and polypropylene oxide esters, sorbitan esters, and the like.

  Next, a method for producing a resin-coated carrier that can be used for the two-component developer used in the present invention will be described. As described above, in the present invention, as a carrier having a volume average particle size of 25 μm or more and 50 μm or less that is preferably used, a resin-coated carrier in which a resin is coated on the surface of magnetic core particles (hereinafter also referred to as core particles) is preferably used. . The resin-coated carrier can stably exhibit good charge imparting performance to the toner particles by the resin coat layer formed on the carrier surface. Further, in the present invention, since the large-sized external additive is not easily released from the toner particle surface even if the stirring is repeatedly performed in the developing device, the reduction in charge imparting performance due to the adhesion of the free external additive to the carrier is eliminated. Is.

  The resin-coated carrier can be manufactured using, for example, a carrier manufacturing apparatus shown in FIG. The carrier manufacturing apparatus of FIG. 5 mixes and stirs the core material particles and the resin particles, electrostatically attaches the resin particles to the surface of the core material particles, and applies stress to the core material particles to which the resin particles are attached. In addition, resin particles are spread on the surface of the magnetic core material particles and coated to prepare a resin-coated carrier.

  The carrier manufacturing apparatus 50 shown in FIG. 5 has a container main body 51 corresponding to the mixing tank referred to in the present invention, and the peripheral surface of the container main body 51 is a heating means referred to in the present invention up to a height of about 3/4. Covered with a warm jacket 57. A bottom portion (also referred to as a container bottom portion) 51a of the container body 51 has a rotary blade 58 for stirring and an outlet 60 for taking out the produced resin-coated carrier. A discharge valve 61 is disposed at the outlet 60. Yes. A main body upper lid 52 is provided on the upper surface of the container main body 51, and a raw material inlet 54 and a filter 55 are provided on the main body upper lid 52, and a discharge valve 64 is provided between the filter 55 and the container upper lid 52. And an in-container outlet 63 is provided at the tip of the filter 55.

  Core material particles and resin particles, which are raw materials for producing the resin-coated carrier, are supplied into the container body 51 from the raw material inlet 54. In addition, the inside of the container main body 51 that actually manufactures the resin-coated carrier is referred to as a chamber, and a thermometer 56 that measures the temperature of the chamber is disposed on the peripheral surface of the container main body 51.

  The rotary blade 58 described above is rotated by a motor 62 as a driving means to stir the core material particles and the resin particles. The central blade 58d of the rotary blade 58 has a stirring blade 58a, 58b at an angular interval of 120 °. And 58c are bonded. These stirring blades are attached to be inclined with respect to the surface of the bottom portion 51a. When the stirring blades 58a, 58b and 58c are rotated at high speed, the raw materials such as the core particles and the resin particles are scraped upward, It collides with the upper inner wall of the container 51 and falls.

  A motor 62 for rotating the rotary blade 58 serving as a stirring means is connected to a control means 40 (not shown) represented by a computer, and the control means 40 controls the operation of the motor 62 by a stored program.

The carrier manufacturing apparatus 50 in FIG. 5 controls the operation of the rotary blade 58 described above, for example, an operation of electrostatically attaching the resin particles to the surface of the core material particles, and the resin particles that have been electrostatically attached to the core material. The operation of strongly adhering to the particle surface can be performed in stages. That is, the carrier manufacturing apparatus in FIG. 5 can produce a resin-coated carrier through at least the following steps.
[1] A step of stirring and mixing the core material particles and the resin particles at room temperature to attach the resin particles to the surface of the core material particles by the action of static electricity. [2] While heating the chamber above the glass transition temperature of the resin particles A step of applying a mechanical impact force to spread and coat resin particles on the surface of core material particles to form a resin coat layer [3] A step of cooling the chamber to room temperature At least the steps of [1] to [3] above As a result, a resin-coated carrier having a structure in which the core particle surface is coated with a resin can be produced. Moreover, the above steps [1] to [3] can be repeated a plurality of times as necessary.

  Next, the image forming method by the image forming apparatus 1 shown in FIG. 1 will be described in detail. As described above, the image forming apparatus 1 shown in FIG. 1 forms yellow, magenta, cyan, and black toner images on the respective photoreceptors using the image forming units 10Y, 10M, 10C, and 10Bk. Each toner image formed on the photoconductor of each image forming unit is transferred onto an endless belt constituting the intermediate transfer body unit 18, and the respective toner images are superimposed (primary transfer). In this way, a full-color toner image is formed in the intermediate transfer unit 18. The toner image transferred and superimposed by the intermediate transfer unit 18 is transferred (secondary transfer) onto the image support P, and further melted and solidified by the fixing device 24 onto the image support P. It is fixed.

  As one of the different color toner images formed on each photoconductor, an image forming unit 10Y that forms a yellow image includes a drum-shaped photoconductor 11Y as a first image carrier, and the photoconductor 11Y. A charging unit 12Y, an exposure unit 13Y, a developing unit 14Y, a primary transfer roll 15Y as a primary transfer unit, and a cleaning unit 16Y are disposed around. Further, an image forming unit 10M that forms a magenta image as another different color toner image is arranged around a drum-shaped photoconductor 11M as a first image carrier, and the photoconductor 11M. The charging unit 12M, the exposure unit 13M, the developing unit 14M, a primary transfer roll 15M as a primary transfer unit, and a cleaning unit 16M are included.

  In addition, an image forming unit 10C that forms a cyan image as one of other different color toner images has a drum-shaped photoconductor 11C as a first image carrier, and around the photoconductor 11C. A charging unit 12C, an exposure unit 13C, a developing unit 14C, a primary transfer roll 15C as a primary transfer unit, and a cleaning unit 16C are disposed. Further, an image forming unit 10Bk that forms a black image as one of other different color toner images is arranged around a drum-shaped photoconductor 11Bk as a first image carrier, and around the photoconductor 11Bk. A charging unit 12Bk, an exposure unit 13Bk, a developing unit 14Bk, a primary transfer roll 15Bk as a primary transfer unit, and a cleaning unit 16Bk.

  The endless belt-shaped intermediate transfer body unit 37 has an endless belt-shaped intermediate transfer body 370 as an intermediate transfer endless belt-shaped second image carrier that is wound around a plurality of rolls and is rotatably supported.

  The respective color images formed by the image forming units 10Y, 10M, 10C, and 10Bk are sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 18 by the primary transfer rolls 15Y, 15M, 15C, and 15Bk to be combined. A colored image is formed. An image support P such as a sheet as a transfer material accommodated in the sheet feeding cassette 20 is fed by a sheet feeding / conveying means 21, passes through a plurality of intermediate rolls 22 A, 22 B, 22 C, 22 D, and a registration roll 23. A color image is transferred onto the recording member P at a time by being conveyed to a secondary transfer roll 19 </ b> A as a next transfer unit. The recording member P to which the color image has been transferred is fixed by the heat roll type fixing device 24, is sandwiched by the paper discharge roll 25, and is placed on the paper discharge tray 26 outside the apparatus.

  On the other hand, after the color image is transferred to the recording member P by the secondary transfer roll 15A, the residual toner is removed by the cleaning unit 189 from the endless belt-shaped intermediate transfer body 18 in which the recording member P is separated by curvature.

  During the image forming process, the primary transfer roll 15Bk is always in pressure contact with the photoreceptor 11Bk. The other primary transfer rolls 15Y, 15M, and 15C are in pressure contact with the corresponding photoreceptors 11Y, 11M, and 11C, respectively, only during color image formation.

  The secondary transfer roll 19A is pressed against the endless belt-shaped intermediate transfer body 18 only when the recording member P passes through the secondary transfer roll 19A and the secondary transfer is performed.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 18 is disposed on the left side of the photoreceptors 11Y, 11M, 11C, and 11Bk in the drawing. Endless belt-shaped intermediate transfer body unit 18 includes endless belt-shaped intermediate transfer body 180 that can be rotated by winding rolls 181, 182, 183, 184, 186, primary transfer rolls 15Y, 15M, 15C, 15Bk and cleaning means. 189.

  In this way, toner images are formed on the photoreceptors 11Y, 11M, 11C, and 11Bk by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer body 180, and are collectively applied to the recording member P. The image is transferred and fixed by the fixing device 24 by pressing and heating. The photoreceptors 11Y, 11M, 11C, and 11Bk after the toner image is transferred to the recording member P are cleaned by the cleaning device 16 after the toner remaining on the photoreceptor is transferred, and then the above charging, exposure, and development cycle. The next image formation is performed.

  The image support used in the present invention is also called a transfer material, and is not particularly limited as long as a toner image can be formed by an electrophotographic image forming method. Specific examples of the image support include known ones such as plain paper from thin paper to thick paper, high-quality paper, art paper, coated printing paper such as coated paper, commercially available Japanese paper and postcards. Examples include paper, plastic films for OHP, and cloth.

  Examples of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.

1. Preparation of “External Additive Particles 1 to 9” First, hydrophobic silica particles having a number average primary particle size of 50 nm and 100 nm shown in the above-mentioned “Specific Examples of Preparation of Silica Particles by Sol-Gel Method” are respectively added to “External Additive Particles”. Agent particles 1 and 2 ”.

  Further, in the above-mentioned preparation example of hydrophobic silica particles having a number average primary particle size of 30 nm, the temperature of the mixed solvent is 45 ° C., the addition amount of tetramethoxysilane is 1460 parts by mass, the dropping time is 7.5 hours, Stirring after completion of dropping of methoxysilane was changed to 1.5 hours. Otherwise, the same procedure is followed to prepare hydrophobic silica particles having a number average primary particle size of 150 nm, which are referred to as “external additive particles 3”.

  Further, in the production of “external additive particles 2” which are hydrophobic silica particles having a number average primary particle size of 100 nm by the sol-gel method described above, the stirring performed after completion of dropping of tetramethoxysilane was changed to 2 hours. Otherwise, the same procedure is used to produce hydrophobic silica particles having a number average primary particle size of 100 nm and a shape factor SF-1 of 100, which are referred to as “external additive particles 4”.

  Further, in the production of “external additive particles 2” performed by the sol-gel method, the stirring performed after the completion of the tetramethoxysilane dropping was changed to 45 minutes, and the other procedures were the same, so that the number average primary particle size was 100 nm. Hydrophobic silica particles having a shape factor SF-1 of 120 were prepared. This is designated as “external additive particles 5”.

  In the preparation of “external additive particles 2” which are hydrophobic silica particles having a number average primary particle size of 100 nm by the sol-gel method described above, the tetramethoxysilane dropping time is changed to 7.5 hours. Otherwise, the same procedure was used to produce hydrophobic silica particles having a number average primary particle size of 100 nm and a particle size distribution sharper than that of “external additive particles 2”. And

  In the preparation of “external additive particles 2” which are hydrophobic silica particles having a number average primary particle size of 100 nm by the sol-gel method described above, the tetramethoxysilane dropping time was changed to 7.5 hours, and tetramethoxysilane was used. The stirring performed after completion of dropping is changed to 2 hours. Otherwise, by using the same procedure, hydrophobic silica particles having a number average primary particle size of 100 nm, a shape factor SF-1 of 100, and a particle size distribution much sharper than that of “external additive particles 2” are obtained. This was prepared and designated as “external additive particles 7”.

  Also, PL-20 (number average primary particle size 220 nm) manufactured by Fuso Chemical Industry Co., Ltd., which is a commercially available sol-gel silica particle, is prepared, and 3 mol of hexamethyldisilazane is added to 1 mol of the silica particles. Then, it is heated to 60 ° C. and subjected to a reaction treatment for 3 hours to carry out a hydrophobic treatment. The silica particles subjected to the hydrophobization treatment are referred to as “external additive particles 8”. In addition, MP-4540M (number average primary particle size 450 nm) manufactured by Nissan Chemical Industries, Ltd., which is a commercially available sol-gel silica particle, was subjected to the same hydrophobizing treatment as “External additive particles 4”. Agent particle 9 ”.

  Table 1 below shows the number average primary particle size, shape factor, 90% and 95% particle size distribution of the “external additive particles 1 to 9” prepared in the above procedure, and the production method. That is,

2. Preparation of “Metal Oxide Particles A to E” Next, metal oxide particles having a number average primary particle size of 5 nm to 50 nm added to the toner base particles together with the “external additive particles 1 to 9” are described below. The silica particles shown were prepared.
・ Metal oxide particles A (commercially available)
Number average primary particle size 7 nm, BET value 300, silica particles / metal oxide particles B (commercially available) hydrophobized with hexamethyldisilazane
Number average primary particle size 10 nm, BET value 90, silica particles / metal oxide particles C hydrophobized with hexamethyldisilazane
Hydrophobic silica particles / metal oxide particles D (commercially available) having a number average primary particle size of 30 nm in the above “specific examples of silica particle production by the sol-gel method”
Number average primary particle size 40 nm, BET value 50, silica particles / metal oxide particles E (commercially available) hydrophobized with hexamethyldisilazane
Number average primary particle size 30 nm, titania particles hydrophobized with dimethyl silicone oil.

3. 3. Production of “toner base particles 1 to 10” 3-1. Preparation of “core resin particle A” (1) First-stage polymerization Sodium lauryl sulfate 2 which is an anionic surfactant is attached to a reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a cooling pipe and a nitrogen introducing device. Mass parts and 2900 parts by mass of ion exchange water were added to prepare an aqueous surfactant solution. The temperature was raised to 80 ° C. while stirring the surfactant aqueous solution under a nitrogen stream at a stirring speed of 230 rpm.

After the temperature increase, an initiator solution in which 9 parts by mass of potassium persulfate (KPS) is dissolved in 200 parts by mass of ion-exchanged water is added, the liquid temperature of the surfactant aqueous solution is set to 78 ° C., and the following compounds are contained. The monomer mixture was added dropwise over 3 hours. That is,
Styrene 540 parts by weight n-butyl acrylate 270 parts by weight Methacrylic acid 65 parts by weight After dispersion, the mixture is heated and stirred at 78 ° C. for 1 hour to conduct a polymerization reaction (first stage polymerization), thereby dispersing “resin fine particles A1”. A liquid was prepared.

(2) Second-stage polymerization Next, 1100 parts by mass of ion-exchanged water and 2 parts by mass of sodium lauryl sulfate were introduced into a reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a cooling tube, and a nitrogen introducing device, and the interface was introduced. An aqueous activator solution was prepared and heated to 90 ° C. After heating, 28 parts by mass of the above-mentioned “resin fine particles (A1)” and the following monomer mixture are added to the above surfactant aqueous solution, and a mechanical dispersion device “Claremix ( M. Technic Co., Ltd.) "for 4 hours to prepare a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm.

The monomer mixture contains the following compounds, and pentaerythritol tetrabehenate, which is a wax having an ester bond, is added after dissolving the following monomers and n-octyl mercaptan and heated to 85 ° C. It is dissolved by warming. That is,
Styrene 94 parts by weight n-butyl acrylate 60 parts by weight Methacrylic acid 11 parts by weight n-octyl mercaptan 5 parts by weight Pentaerythritol tetrabehenate 51 parts by weight In the above emulsified particle dispersion, potassium persulfate (KPS) 2.5 parts by weight An initiator solution having a part dissolved in 110 parts by mass of ion-exchanged water was added, and this system was heated and stirred at 90 ° C. for 2 hours to carry out a polymerization reaction (second stage polymerization). A dispersion was prepared.

(3) Third-stage polymerization Next, an initiator solution in which 2.5 parts by mass of potassium persulfate (KPS) was dissolved in 110 parts by mass of ion-exchanged water in the dispersion of “resin fine particles A2” was added, The liquid temperature was set to 80 ° C., and a monomer mixed solution containing the following compound was added dropwise over 1 hour. That is,
Styrene 230 parts by mass n-butyl acrylate 100 parts by mass n-octyl mercaptan 13 parts by mass The above monomer mixture was added dropwise, followed by heating and stirring for 3 hours at a temperature of 80 ° C. (third stage polymerization). Went. Then, it cooled to 28 degreeC and produced the dispersion liquid of "resin particle A for cores".

  The “core resin particle A” produced by the above procedure is a styrene acrylic copolymer formed by setting the mass ratio of n-butyl acrylate, which is a polymerizable monomer having an ester bond, to 31% by mass, and has a glass transition temperature. Was 43 ° C.

3-2. Preparation of “Shell Resin Particles 1 to 10” (1) Preparation of “Shell Resin Particle 1” A styrene acrylic modified polyester resin in which a styrene acrylic copolymer molecular chain is molecularly bonded to a polyester molecular chain terminal by the following procedure. A dispersion of “shell resin particles 1” containing That is,
To a reaction vessel equipped with a nitrogen introduction device, dehydration tube, stirring device and thermocouple,
Bisphenol A propylene oxide 2-mole adduct 500 parts by weight Terephthalic acid 154 parts by weight Fumaric acid 45 parts by weight Tin octylate 2 parts by weight are charged, a polycondensation reaction is performed at 230 ° C. for 8 hours, and further at 8 kPa for 1 hour. After continuing the polycondensation reaction, it was cooled to 160 ° C. In this way, polyester molecules were formed.

Next, 10 parts by mass of acrylic acid was added at a temperature of 160 ° C., mixed and held for 15 minutes, and then a mixture of the following compounds was added dropwise over 1 hour with a dropping funnel. That is,
Styrene 142 parts by mass n-butyl acrylate 35 parts by mass Polymerization initiator (di-t-butyl peroxide) 10 parts by mass After the addition, the addition polymerization reaction was carried out for 1 hour while maintaining the temperature at 160 ° C., and then 200 ° C. The temperature was raised to 10 kPa and held for 1 hour. In this way, “styrene acrylic modified polyester resin 1” having a styrene acrylic copolymer molecular chain content of 20 mass% was produced.

  Next, 100 parts by mass of the “styrene acrylic modified polyester resin 1” was pulverized by a commercially available pulverization apparatus “Landel mill type: RM (manufactured by Tokuju Kogakusha Co., Ltd.)”. Subsequently, an ultrasonic homogenizer “US-150T (manufactured by Nippon Seiki Seisakusho)” was used while mixing with 638 parts by mass (concentration: 0.26% by mass) of a sodium lauryl sulfate solution prepared in advance and performing a stirring process. Ultrasonic dispersion treatment was performed with V-LEVEL, 300 μA for 30 minutes. In this manner, a “resin particle 1 for shell” dispersion having a volume-based median diameter of 250 nm was prepared.

(2) Production of “Shell Resin Particles 2 to 5” (a) Production of “Shell Resin Particle 2” Used in the production of “Styrene Resin Particle 1” and “Styrene Acrylic Modified Polyester Resin 1” The same procedure was followed except that the added amount of styrene was changed to 30 parts by mass and the added amount of n-butyl acrylate was changed to 7 parts by mass to prepare “resin particles 2 for shell”. “Styrene acrylic modified polyester resin 2” constituting “shell resin particles 2” had a content of styrene acrylic copolymer molecular chain of 5 mass%.

(B) Production of “Shell Resin Particle 3” In the production of “Shell Resin Particle 1”, the amount of styrene used in the production of “styrene acrylic-modified polyester resin 1” was 243 parts by mass, and n-butyl acrylate. The “shell resin particles 3” were prepared by taking the same procedure except that the amount of addition was changed to 61 parts by mass. The “styrene acrylic modified polyester resin 3” constituting the “shell resin particles 3” had a content of styrene acrylic copolymer molecular chain of 30% by mass.

(C) Production of “Shell Resin Particle 4” In the production of “Shell Resin Particle 1”, the amount of styrene used in the production of “styrene acrylic modified polyester resin 1” was 12 parts by mass, and n-butyl acrylate. The “shell resin particles 4” were produced by taking the same procedure except that the amount of addition was changed to 3 parts by mass. The “styrene acrylic modified polyester resin 4” constituting the “shell resin particles 4” had a styrene acrylic copolymer molecular chain content of 2 mass%.

(D) Production of “Shell Resin Particle 5” In the production of “Shell Resin Particle 1”, the amount of styrene used in the production of “styrene acrylic modified polyester resin 1” was 305 parts by mass, and n-butyl acrylate. The “shell resin particles 5” were produced by taking the same procedure except that the amount of addition was changed to 76 parts by mass. The “styrene acrylic modified polyester resin 5” constituting the “shell resin particles 5” had a styrene acrylic copolymer molecular chain content of 35 mass%.

(3) Production of “shell resin particles 6” In the production of “shell resin particles 1”, the amount of the compound added to the reaction vessel when forming the polyester molecules was changed as follows. That is,
Bisphenol A propylene oxide 2 mol adduct 500 parts by mass Terephthalic acid 117 parts by mass Fumaric acid 82 parts by mass Tin octylate 2 parts by mass In addition, the cooling temperature of the reaction system after completion of the polycondensation reaction to form a polyester molecule was changed to 170 ° C. The mixture of the following compounds was then dropped into the reaction system at 170 ° C. over 1 hour using a dropping funnel. That is,
Acrylic acid 10 parts by weight Styrene 142 parts by weight n-butyl acrylate 35 parts by weight Polymerization initiator (di-t-butyl peroxide) 10 parts by weight And addition polymerization reaction for 1 hour while maintaining the temperature after dropping at 170 ° C Changed to something that does. Otherwise, the same procedure was followed to produce “shell resin particles 6”. The “styrene acrylic modified polyester resin 6” constituting the “shell resin particles 6” had a styrene acrylic copolymer molecular chain content of 20% by mass, similarly to the “shell resin particles 1”.

(4) Preparation of “Shell Resin Particles 7 and 8” (a) Preparation of “Shell Resin Particle 7” Used in the preparation of “Shell Resin Particle 6” and “Styrene Acrylic Modified Polyester Resin 6”. The same procedure was followed except that the added amount of styrene was changed to 30 parts by mass and the added amount of n-butyl acrylate was changed to 7 parts by mass to prepare “resin particles 7 for shell”. The “styrene acrylic modified polyester resin 7” constituting the “shell resin particles 7” had a styrene acrylic copolymer molecular chain content of 5 mass%.

(B) Production of “Shell Resin Particle 8” In the production of “Shell Resin Particle 6”, the amount of styrene used in the production of “styrene acrylic modified polyester resin 6” was 243 parts by mass, n-butyl acrylate. The “shell resin particles 8” were produced by following the same procedure except that the amount of addition was changed to 61 parts by mass. “Styrene acrylic modified polyester resin 8” constituting “shell resin particles 8” had a content of styrene acrylic copolymer molecular chain of 30% by mass.

(5) Production of “resin particle 9 for shell” To a reaction vessel equipped with a stirrer, a cooling pipe, and a nitrogen introducing device,
Bisphenol A propylene oxide 2-mole adduct 316 parts by weight Terephthalic acid 80 parts by weight Maleic anhydride 34 parts by weight, and further, 2 parts by weight of titanium tetraisopropoxide, which is a catalyst, are added in 10 portions. Resin formation was performed by performing a polymerization reaction for 10 hours at a temperature of 200 ° C. in an atmosphere. At this time, the reaction was allowed to proceed while distilling off water produced by the condensation reaction.

  Next, the reaction system was depressurized to 13.3 kPa (100 mmHg), and the polymerization reaction was continued under this condition. When the softening point temperature of the formed resin reached 104 ° C., the resin was taken out from the reaction vessel. Let the taken-out polyester resin be "polyester resin (a)."

  100 parts by mass of the “polyester resin (a)” produced by the above procedure was dissolved in 400 parts by mass of ethyl acetate to form a solution. The solution was added to 638 parts by mass of a sodium lauryl sulfate aqueous solution having a concentration of 0.26% by mass prepared in advance and stirred for 30 minutes with an ultrasonic homogenizer “US-150T (manufactured by Nippon Seiki Seisakusho)”. Sonic dispersion treatment was performed. The ultrasonic dispersion treatment was performed by setting the ultrasonic homogenizer to V-LEVEL 300 μA.

  After performing the ultrasonic dispersion treatment, the polyester resin is stirred for 3 hours under reduced pressure using a diaphragm vacuum pump “V-700 (manufactured by BUCHI)” while being heated to 40 ° C. More ethyl acetate was removed. In this way, a dispersion of “shell resin particles 9” containing a resin composed of polyester molecules having a volume-based median diameter of 160 nm and having no segment of styrene-acrylic copolymer was prepared.

(4) Production of “Shell Resin Particle 10” Anionic surfactant 2 used in the production of “core resin particle A” in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device. A surfactant solution was prepared by dissolving 0.0 part by mass in 3000 parts by mass of ion-exchanged water. While this surfactant solution was stirred at a stirring speed of 230 rpm under a nitrogen stream, the internal temperature was raised to 80 ° C.

On the other hand, the following compounds are added and mixed to prepare a “monomer mixed solution”. That is,
Styrene 560 parts by mass n-butyl acrylate 144 parts by mass Methyl methacrylate 96 parts by mass n-octyl mercaptan (NOM) 22 parts by mass

  After adding an initiator solution prepared by dissolving 10 parts by mass of potassium persulfate (KPS) in 200 parts by mass of ion-exchanged water in the surfactant solution, the above “monomer mixed solution” is dropped over 3 hours. did. Then, the system was heated to 80 ° C., and polymerization was performed by heating and stirring for 1 hour to prepare a dispersion of “shell resin particles 10”.

3-3. Preparation of “Colorant Particle Dispersion Bk” While stirring a solution obtained by dissolving 90 parts by mass of sodium dodecyl sulfate in 1600 parts by mass of ion-exchanged water,
420 parts by mass of carbon black “Mogal L (Cabot)” was gradually added. Next, a “colorant particle dispersion Bk” was prepared by carrying out a dispersion treatment using a stirrer “CLEARMIX (M Technique Co., Ltd.)”.

3-4. Preparation of “toner base particles 1 to 10” (1) Preparation of “toner base particles 1” In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction device,
"Core resin particle dispersion A" 270 parts by mass (solid content conversion)
Ion-exchanged water 1400 parts by mass “Colorant particle dispersion Bk” 120 parts by mass (solid content conversion)
Was introduced. Furthermore, a solution of 3 parts by mass of sodium polyoxyethylene-2-dodecyl ether sulfate in 120 parts by mass of ion-exchanged water was added, the temperature of the solution was raised to 30 ° C., and then a 5 mol / liter sodium hydroxide aqueous solution was added. The pH was adjusted to 10.

  Next, an aqueous solution in which 35 parts by mass of magnesium chloride hexahydrate was dissolved in 35 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. The temperature started. The temperature was raised to 90 ° C. over 60 minutes, and the particles were aggregated and fused while maintaining the temperature at 90 ° C.

In this state, using “Multisizer 3 (manufactured by Beckman Coulter)”, the particle size of the agglomerated particles growing in the reaction vessel was measured, and when the volume-based median diameter was 6.0 μm,
"Resin particle dispersion 1 for shell" 30 parts by mass (solid content conversion)
Was added and heating and stirring were continued until the “shell resin particles 1” adhered to the surface of the aggregated particles. Then, a small amount of the reaction solution was taken out and centrifuged, and when the supernatant became transparent, an aqueous solution in which 150 parts by mass of sodium chloride was dissolved in 600 parts by mass of ion-exchanged water was added to stop particle growth. Furthermore, as the aging treatment, the liquid temperature was set to 90 ° C., and the mixture was heated and stirred to promote particle fusion. In this state, the fusion of the particles was advanced until the average circularity was 0.965 as measured by “FPIA-2100 (manufactured by Sysmex Corporation)”.

  Thereafter, the liquid temperature was cooled to 30 ° C., the pH of the liquid was adjusted to 2 using hydrochloric acid, and stirring was stopped. In this manner, “toner base particle dispersion 1” was produced.

  The “toner base particle dispersion 1” produced through the above steps is subjected to solid-liquid separation with a basket type centrifuge “MARKIII model number 60 × 40 (manufactured by Matsumoto Kikai Co., Ltd.)”, and the “toner base particle 1” is wet. A cake was formed.

  The wet cake was washed with ion exchange water at 45 ° C. until the electric conductivity of the filtrate reached 5 μS / cm using the basket-type centrifuge. After that, it is transferred to “Flash Jet Dryer (manufactured by Seishin Enterprise Co., Ltd.)” and dried until the water content becomes 0.5% by mass to produce “toner base particle 1” having a volume-based median diameter of 6.3 μm. did.

(2) Preparation of “toner base particles 2 to 10” In the preparation of “toner base particles 1”, a resin particle dispersion for shell added when the volume-based median diameter of the aggregated particles becomes 6.0 μm is prepared. , “Resin particle dispersions for shells 2 to 10”. Otherwise, the same procedure was used to prepare “toner base particles 2 to 10”. The volume-based median diameter of “toner base particles 2 to 10” was 6.3 μm in the same manner as “toner base particle 1”.

  By the above procedure, “toner base particles 1 to 10” having a core-shell structure were produced.

4). Production of “toner particles 10-19, 20-80, 110”, “toner particles 210, 211” and “toner particles 310, 311” 4-1. Preparation of “Toner Particles 10-19, 20-80, 110” (1) Preparation of “Toner Particle 10” External additive particles and metal oxide particles shown below with respect to 100 parts by mass of “toner base particle 1”. Was added and the peripheral speed of the stirring blade of the Henschel mixer “FM10B (Mitsui Miike Chemical Co., Ltd.)” was set to 40 m / sec, the processing temperature was 30 ° C., and the processing time was 20 minutes, and external addition processing was performed. After the external addition process, coarse particles were removed using a sieve having an opening of 90 μm to prepare “toner particles 10”. The external additive particles and metal oxide particles to be added are as follows.

External additive particle 1 1.0 part by weight Metal oxide particle 1 0.5 part by weight Metal oxide particle 2 0.7 part by weight Metal oxide particle 3 0.15 part by weight Metal oxide particle 5 0.15 part by weight (2) Preparation of “Toner Particles 11 to 19” The “Toner Particles 10” were prepared under the same conditions except that “External Additive Particles 1” were changed to “External Additive Particles 2 to 9” described above. By performing the addition treatment, “toner particles 11 to 18” were produced. Further, in the production of the “toner particle 10”, an external additive treatment was performed under the same conditions except that the external additive and the metal oxide particle to be added were changed as follows, and “toner particle 19” was produced. That is,
External additive particles 2 1.0 parts by weight Metal oxide particles 1 0.5 parts by weight Metal oxide particles 3 0.15 parts by weight Metal oxide particles 4 0.7 parts by weight Metal oxide particles 5 0.15 parts by weight (3) Preparation of “Toner Particles 20-80” In the preparation of “Toner Particles 10”, “Toner Base Particles 1” is changed to “Toner Base Particles 20-80” described above, and the external toner used for external addition processing is changed. “Toner particles 20 to 80” were prepared with the same types and amounts of additive particles and metal oxide particles as those used in the preparation of “toner particles 11”.

(4) Production of “toner particle 110” For the purpose of comparison, the “external additive particle 1” is not added in the production of the “toner particle 10”, and an external treatment is performed using the other external additives. “Toner Particles 110” was prepared.

4-2. Preparation of “Toner Particles 210, 211” and “Toner Particles 310, 311” “Toner Base Particle 1” used in the preparation of “Toner Particle 12” is referred to as “Toner Base Particle 2” and “Toner Base Particle 3”, respectively. The toner particles 210 and the toner particles 310 were prepared by performing an external addition process under the same conditions as those for the production of the “toner particles 12”.

  Further, the “toner base particle 1” used in the preparation of the “toner particle 16” is changed to the “toner base particle 2” and the “toner base particle 3”, respectively, and the external condition is the same as that of the “toner particle 16”. Addition processing was performed to produce “toner particles 211” and “toner particles 311”.

  Table 2 below shows toner base particles (shell resin particles), external additive particles, and metal oxide particles used in the 22 types of toner particles prepared by the above procedure.

5). Production of “Resin Coated Carriers 1-5” Five types of resin coated carriers having different volume average particle diameters were produced by the following procedure.

5-1. Preparation of Ferrite Core Particles Ferrite particles (commercially available) having a volume average particle size of 20 μm, 25 μm, 35 μm, 50 μm, and 55 μm were prepared as magnetic core particles for a resin-coated carrier. This ferrite particle has a manganese content of 21.0 mol% in terms of MnO, a magnesium content of 3.3 mol% in terms of MgO, a strontium content of 0.7 mol% in terms of SrO, and an iron content in terms of Fe2O3. It was 75.0 mol%. The volume average particle diameter is measured by a commercially available laser diffraction particle size distribution measuring apparatus “HELOS (manufactured by Sympatec)” equipped with a wet disperser.

5-2. Preparation of resin particles for coating A surfactant aqueous solution in which 1.7 parts by mass of sodium dodecyl sulfate was dissolved in 3000 parts by mass of ion-exchanged water was prepared in a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction apparatus. . The internal temperature was raised to 80 ° C. while stirring the aqueous surfactant solution at a stirring speed of 230 rpm under a nitrogen stream. In this surfactant aqueous solution, an initiator solution in which 10 parts by mass of potassium persulfate (KPS) is dissolved in 400 parts by mass of ion-exchanged water is added, the temperature of the liquid is set to 80 ° C., and a monomer mixture composed of the following compounds is added. The solution was added dropwise over 2 hours. That is,
Cyclohexyl methacrylate 400 parts by weight Methyl methacrylate 400 parts by weight After the dropwise addition of the above monomer mixture, heating and stirring are performed at 80 ° C. for 2 hours, and a polymerization reaction is performed to prepare a dispersion of coating resin particles. did. The dispersion was dried with a spray dryer to prepare coating resin particles.

5-3. Production of each resin-coated carrier (1) Production of “resin-coated carrier 1” 3000 parts by mass of the ferrite particles having a volume average particle diameter of 20 μm and 120 parts by mass of the resin particles for coating are transferred to a horizontal rotary blade type mixing apparatus shown in FIG. The peripheral speed of the horizontal rotary blade was set to 4 m / second, and the mixture was stirred for 15 minutes at a temperature of 22 ° C. After the mixing and stirring, a stirring process was performed for 40 minutes while heating at 120 ° C. to prepare “Resin Coated Carrier 1” having a volume average particle diameter of 20 μm.

(2) Production of “Resin Coated Carriers 2 to 5” Instead of the ferrite particles having a volume average particle diameter of 20 μm used in the production of the “resin coated carrier 1”, ferrite particles having a volume average particle diameter of 25 μm were used. “Resin-coated carrier 2” having a volume average particle diameter of 25 μm was produced in the same procedure. Similarly, in place of the ferrite particles having a volume average particle size of 20 μm used in the production of “resin coated carrier 1”, the same procedure was adopted except that ferrite particles having a volume average particle size of 35 μm, 50 μm, and 55 μm were used. “Resin-coated carriers 3 to 5” were produced.

6). Evaluation experiment 6-1. Preparation of “Developer 1-26” “Resin Coated Carriers 1-5” having different volume average particle diameters from “Toner Particles 10-19, 20-80, 110, 210, 211, 310, 311” are shown in Table 3. “Developers 1 to 26” were prepared in combination as shown. The toner concentration of “Developers 1 to 26” was changed as follows according to the volume average particle diameter to be used. That is,
-Resin coated carrier 1 (volume average particle size 20 μm) 8.0% by mass
Resin-coated carrier 2 (volume average particle size 25 μm) 7.6% by mass
-Resin coated carrier 3 (volume average particle size 35 μm) 7.0% by mass
Resin-coated carrier 4 (volume average particle size 50 μm) 6.0% by mass
-Resin-coated carrier 5 (volume average particle size 55 μm) 5.6% by mass
6-2. Evaluation Conditions As an evaluation machine, the image forming apparatus shown in FIG. 4 is placed outside the developing apparatus of a commercially available multifunction machine “bizhub PRO C6500 (manufactured by Konica Minolta Business Technologies, Inc.)” corresponding to the two-component development type image forming apparatus shown in FIG. A toner concentration detector was used. The toner concentration detection unit attached to the evaluation machine has an LC oscillation circuit using a planar coil having a hollow area in the center. In the evaluation machine, the toner density detection unit detects the toner density in the developing device, and is controlled so that new toner is replenished based on the detection result.

  Each of “Developers 1 to 26” was loaded into the developing device, and each toner prepared in the above procedure was used as a toner for replenishing the corresponding developer. As shown in Table 3 below, those evaluated using "Developers 1-7, 10-14, 20-26" are referred to as "Examples 1-19" and "Developers 8, 9, 15-19" What was evaluated using was set as “Comparative Examples 1 to 6”. Table 3 below shows each developer used in each example and each comparative example, toner particles and resin-coated carrier used in preparing the developer, and shell resin particles used in preparing the toner particles.

(1) Evaluation experiment 1
In Evaluation Experiment No. 1, the presence or absence of image defects due to liberation of external additives was evaluated. Specifically, 20,000 sheets are continuously printed for each type of developer in a room temperature and normal humidity environment at a temperature of 20 ° C. and a relative humidity of 55% RH, and the agitation is repeated in the developing device. It was evaluated from the following prepared images that the additive particles were not released and the spacer effect was stably expressed.

  Images created by continuous printing are divided into four equal parts: a human face photo image, a halftone image with a relative reflection density of 0.4, a white background image, and a solid image with a relative reflection density of 1.3 on an A4 size image support. It was made to output. The relative reflection density of the halftone image and the solid image is based on the Macbeth densitometer. At the end of continuous printing of 20,000 sheets, 10 printed materials shown in FIG. 6 were output, and the finish of the fine line images, dot images, and graphic images having the vertices described in the printed materials was evaluated.

<Halftone image density unevenness and human image finish>
The occurrence of density unevenness and the finished state of human images (occurrence of image unevenness) on the halftone images of 10 prints created at the start and end of the continuous printing were evaluated by visual observation. The occurrence of density unevenness on the halftone image is 3 or less, and the human image is accepted when no image unevenness of a level detectable with the naked eye has passed. What was not 1 sheet was made especially excellent.

<Solid image density>
The average value is calculated by measuring the solid image density of each of the 10 prints created at the start and end of the above-mentioned continuous printing, and if the average density difference at the start and end is less than 0.10 did.

<Fog>
Using a Macbeth reflection densitometer “RD-918”, the density of 20 sheets on which printing has not been performed is measured, and the average value is defined as the blank paper density. Next, 20 white background images of 10 prints created at the start and end of continuous printing were measured in the same procedure at 20 locations, and the value obtained by subtracting the white paper density from the average density (fog density) was evaluated as fog. .

  A fog density of less than 0.01 was accepted, and a fog density of less than 0.005 was particularly excellent.

<Fine line image, dot image finish>
The finished images Sa to Si output to the image sample shown in FIG. 6 were visually evaluated using a loupe. Note that the images Sa and Sb are line images, and the Sc is a dot image. These images were evaluated for image omission within the line and within the dots, and image sticking between the lines and between the dots. In addition, the triangular image Sd, the square image Se, the rhombus image Sf, the star image Sg, and the crescent moon image Si were evaluated to be reproduced with rounded corners. Further, for the rhombus image Sf, it was evaluated that the line drawing was not stuck in the gap between the rhombuses and that there was no omission of fine lines. Further, in the two-circle image Sh, it was evaluated that the corner portion was reproduced without being rounded at the portion where the two circles overlapped. Of the 10 printed materials, those that cleared all of the above evaluation items passed 7 or more, and all 10 sheets cleared all of the above evaluation items as excellent.

  The above results are shown in Tables 4 and 5.

  As shown in Tables 4 and 5, “Examples 1 to 19” performed under the conditions for producing the print having the configuration of the present invention, the results satisfying the criteria for all the evaluation items were obtained. It was confirmed that the additive particles were not released and the spacer effect was stably expressed. On the other hand, “Comparative Examples 1 to 7” performed under the conditions for producing the print without the configuration of the present invention resulted in the external additive particles being liberated and affecting the image quality.

(2) Evaluation experiment 2
Evaluation experiment No. 2 was that 20,000 continuous prints were made for each type of developer in a high-temperature and high-humidity environment with a temperature of 30 ° C. and a relative humidity of 80% RH. Image finish, solid image density, and fog were evaluated. These evaluation methods are the same as those in the first evaluation experiment.

  In evaluation experiment 2, continuous printing was performed while replenishing the carrier together with the toner. In addition, evaluation was performed for the “Examples 1 to 8, 13 to 19” and “Comparative Examples 1 to 7” using a resin-coated carrier having a volume average particle diameter of 35 μm, and the toner content was adjusted to 75% by mass. The toner and the carrier were replenished using the developer.

  The results are shown in Table 6.

  As shown in Table 6, in "Examples 1 to 8, 13 to 19", in addition to replenishment with a new carrier during continuous printing, no external additives were released due to stirring, and thus charged to a predetermined level. Printing with toner could be performed stably. On the other hand, in “Comparative Examples 1 to 7”, it is not possible to create a printed matter having the image quality as obtained in “Examples 1 to 8 and 13 to 19” even though a new carrier is replenished during continuous printing. The result was.

1 Image forming apparatus 10 (10Y, 10M, 10C, 10Bk) Image forming unit 11 (11Y, 11M, 11C, 11Bk) Photoconductor 12 (12Y, 12M, 12C, 12Bk) Charging means 13 (13Y, 13M, 13C, 13Bk) ) Exposure means 14 (14Y, 14M, 14C, 14Bk) Developing device 141 Developing sleeve 142, 143 Conveying screw 144 Conveying supply roller 145 Housing 145b Toner replenishing port 146 Separator 147 First chamber 148 Second chamber 149 Magnet roll 15 (15Y, 15M, 15C, 15Bk) Primary transfer roll 16 (16Y, 16M, 16C, 16Bk) Cleaning device 17 Toner concentration detector 171 Substrate 172 Planar coil 172a Hollow portion 18 Endless belt-shaped intermediate transfer body unit 180 Endless belt-shaped Transfer member 19A 2 transfer roller 24 fixing device 50 carrier manufacturing apparatus 51 the container body (mixing tank) (chamber)
51a Container bottom 52 Container upper lid 53 Input valve 54 Raw material input port 55 Filter 57 Temperature control jacket (heating means)
58 Rotating blade (stirring means)
61 Discharge valve 62 Motor (drive means)
P Image support T Toner A Core particle A1 Colorant A2 Resin B Shell B3 Resin

Claims (10)

The toner contained in the developing device is supplied to the electrostatic latent image formed on the photoreceptor to form a toner image, and the toner image is transferred and fixed on the image support to create a printed matter.
In this image forming method, the toner concentration of the developer contained in the developing device is measured by a toner concentration detecting unit provided in the developing device, and the toner is replenished to the developing device based on the measurement result. And
The toner is
At least core-shell toner particles in which a core particle containing a binder resin containing a styrene acrylic copolymer is coated with a resin,
The resin that coats the core particles is
It contains a styrene acrylic modified polyester having a structure in which a styrene acrylic copolymer molecular chain is molecularly bonded to a polyester molecular chain,
An image forming method comprising monodispersed spherical particles having a number average primary particle size of 50 nm to 150 nm as an external additive on the surface of the toner particles.   2. The toner density detection unit according to claim 1, wherein the toner concentration detection unit includes an LC oscillation circuit that is provided outside the developing device and includes a planar coil having a hollow area at least in the center. Image forming method. The styrene acrylic modified polyester is
The image forming method according to claim 1 or 2, wherein the content of the styrene acrylic copolymer is 5% by mass or more and 30% by mass or less. The said styrene acrylic modified polyester is formed using the aliphatic unsaturated carboxylic acid represented by the following general formula (A), The any one of Claims 1-3 characterized by the above-mentioned. Image forming method.
General formula (A): HOOC- (CR < ¹ > = CR _< ² _> ) _n- COOH
(In the formula, R ¹ and R ² are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other. N is an integer of 1 or 2.) The styrene acrylic modified polyester is
The image forming method according to any one of claims 1 to 3, wherein the styrene acrylic copolymer molecular chain is molecularly bonded to an end of the polyester molecular chain. The styrene acrylic modified polyester is
The styrene acrylic copolymer molecular chain is formed by polymerizing a styrene monomer and an acrylate monomer in the presence of the polyester molecular chain. 6. The image forming method according to any one of 5 above.   The image forming method according to claim 1, wherein the monodispersed spherical particles are silica particles produced by a sol-gel method. The toner is
The image according to any one of claims 1 to 7, wherein the toner particle surface contains metal oxide particles having a number average primary particle size of 5 nm to 50 nm as an external additive. Forming method. The developer is
The volume average particle size is 25 μm or more and 50 μm or less,
The image forming method according to any one of claims 1 to 8, wherein the image forming method comprises a resin-coated carrier having a ferrite particle surface coated with a resin.   The image forming method according to claim 1, wherein toner image formation is performed while replenishing toner to the developing device and replenishing carrier.

Images