JP2007025288A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure good transferability without causing image defects such as image voids due to filming. <P>SOLUTION: An image forming method is provided using an image forming apparatus with a primary transfer means for transfer to an intermediate transfer belt, wherein the intermediate transfer belt is an intermediate elastic transfer belt comprising a belt base material prepared by mixing two or more different elastic materials and a fluorocarbon resin- or silicone resin-based protective layer on one side or both sides of the belt base material, and wherein toner used contains a crystalline polyester and an amorphous polymer as a binder resin and has a core-shell structure of which the surface is covered with a surface layer based on the amorphous polymer. After the toner passes through a nip portion between an image carrier and the intermediate transfer belt, residual toner on the image carrier or the intermediate transfer belt has a coverage of the surface layer of 60-94%, represented by the expression (1): (coverage (%) of the surface layer)=((summation of exposure lengths of the surface layer)/(summation of toner perimeter))×100. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming method using an image forming apparatus such as an electrophotographic apparatus using an electrophotographic process such as a copying machine, a printer, and a facsimile machine.

  Many methods are known as electrophotographic methods (see, for example, Patent Document 1). In general, a latent image is electrically formed by various means on the surface of a photoconductor (latent image holding body) using a photoconductive substance, and the formed latent image is developed with toner. After the toner image is formed, the toner image may be transferred to the surface of a transfer medium such as paper, optionally via an intermediate transfer body, and fixed by heating, pressurization, heat pressurization, solvent vapor, or the like. An image is formed through these steps. Further, the toner remaining on the surface of the photoreceptor is cleaned by various methods as necessary, and is used again for developing the toner image.

  Along with the recent increase in demand for energy saving necessary for image formation, there is a method for lowering the toner fixing temperature as one of the power saving in the fixing process that occupies a certain amount of power. By lowering the toner fixing temperature, in addition to the above power saving, the waiting time until the fixing temperature on the surface of the fixing member such as a fixing roll at the time of power input is shortened, so-called warm-up time is shortened. Long service life is possible.

  However, lowering the fixing temperature of the toner also lowers the glass transition point of the toner particles at the same time, making it difficult to achieve both toner storage stability. In order to achieve both low-temperature fixing and toner storage stability, it is necessary to have a so-called sharp melt property in which the viscosity of the toner rapidly decreases in a desired temperature range while maintaining the glass transition point of the toner. is there.

  However, since the resin used for the toner usually has a certain range in glass transition point, molecular weight, etc., in order to obtain the sharp melt property, it is necessary to make the resin composition and molecular weight extremely uniform. In order to obtain such a highly uniform resin, it becomes necessary to adjust the molecular weight of the resin by using a special production method or by treating the resin with chromatography or the like. In this case, the cost is inevitably high in order to produce such a highly uniform resin, and there is no unnecessary resin (waste) in producing such a highly uniform resin. This is undesirable from the viewpoint of environmental protection in recent years.

  On the other hand, if the copied images are stored over a long period of time, there may be a problem that a part or all of the images are transferred to the back of the upper stacked paper (hereinafter referred to as “document offset”). Called). This phenomenon is particularly accelerated when an image is stored under a high temperature and high humidity condition, and the image storage stability deteriorates. Therefore, an image forming method capable of maintaining a clear image even under a high temperature and high humidity condition is desired.

  Accordingly, there is a strong demand for a so-called wide fixing latitude electrophotographic toner that fixes at a low temperature and does not cause an offset to a higher temperature region, and an image forming method that can provide an image that can withstand document offset.

  As a means for preventing the occurrence of offset, a method using a binder resin blended with a polymer or a cross-linked polymer is known (for example, see Patent Documents 2 and 3). In order to prevent the toner from fusing to the surface of the fixing member by increasing However, although these methods are effective in preventing offset, there arises a problem that the fixing temperature rises.

  In order to improve the releasability from the surface of the fixing member, attempts have been made to add low molecular weight components such as polypropylene, polyethylene, alkylamide compounds, and ester compounds to the toner. However, although these methods can also improve the effect of offset resistance, blocking or the like is likely to occur due to long-term storage in a developing machine, and there is a concern about storage stability.

  On the other hand, as a means for lowering the toner fixing temperature, a technique of lowering the glass transition point of toner resin (binder resin) is generally performed. However, if the glass transition point is too low, powder agglomeration (blocking) tends to occur, and the storability of the toner on the fixed image decreases. Therefore, the lower limit of the glass transition point of the toner is practically about 60 ° C. This level of glass transition point is a design point for many commercially available toner resins. At present, however, it is difficult to obtain a toner that can be fixed at low temperature by a method of lowering the glass transition point. The fixing temperature can also be lowered by using a plasticizer, but there is a problem that toner blocking occurs during storage or in the developing machine.

  As a means for achieving both blocking prevention, image storability, and low-temperature fixability, a method using a crystalline resin as a binder resin has long been known (see, for example, Patent Documents 4 and 5). However, the crystalline resin is difficult to pulverize by the kneading pulverization method and has a low yield, so that there is a problem that it is not practical from the viewpoint of manufacturability. Even if practicality in manufacturing can be ensured, the fixing temperature can be lowered, but sufficient offset resistance cannot always be obtained. That is, the melted toner permeates into the paper to prevent the occurrence of offset, but the melted toner soaks into the paper so that a uniform and high density image cannot be obtained. Arise. In addition, since the mechanical strength of the low melting point binder resin is weaker than that of a general electrophotographic binder resin, the mechanical strength is insufficient in the electrophotographic process, making it difficult to put it into practical use.

  Therefore, the application of a toner having a so-called core-shell structure in which a low melting binder resin is used as a core and a binder resin having a higher melting point and higher mechanical strength than the core binder resin is considered. ing. However, if the shell is made too thick to increase the mechanical strength, the shell will not melt sufficiently in the fixing process, and the function of the low melting point binder resin cannot be exhibited, and the function of the release agent cannot be fully exhibited. As a result, an image defect such as an offset is likely to occur, and not only the intended low-temperature fixing performance and appropriate fixing latitude cannot be obtained, but also it becomes difficult to obtain a good fixed image itself.

  On the other hand, the shell is made thin to some extent in order to exhibit the function of the low melting binder resin as the core, or the low melting binder resin having lower mechanical strength than the conventional binder resin is used as the core. As described above, the mechanical strength is inevitably weak as compared with the conventional toner. For this reason, the toner form tends to change due to mechanical stress at the contact portion with each member such as the developing process and the transfer process in the conventional electrophotographic apparatus. For example, in the transfer process, since the toner is in a state between the image carrier and the transfer member, the nip pressure between the image carrier and the transfer member, the driving of both, and the superimposing speed as necessary Due to the shearing force generated by the ratio, the toner form is changed by applying mechanical stress to the toner. In some cases, the shell is broken and the internal low-melting binder resin is exposed on the toner surface.

If the shell is excessively broken, the low melting point binder resin is excessively exposed on the toner surface, and the low melting point binder resin has a higher mechanical strength than the conventional binder resin. Since it is weak, it easily adheres to the image carrier and the transfer member (so-called filming), and adheres to the member more easily than conventional toners. There was a problem that transferability was remarkably impaired.
Japanese Patent Publication No.42-23910 JP 50-134652 A JP-A-51-23354 Japanese Patent Publication No. 56-13943 Japanese Examined Patent Publication No.62-39428

  An object of the present invention is to solve the above problems. That is, the present invention obtains good transferability without causing image quality defects such as streak-like image omission caused by filming on the image carrier and transfer member due to excessive shell destruction of toner having a core-shell structure. It is an object of the present invention to provide an image forming method that can be used.

The above-mentioned subject is achieved by the following present invention.
That is, the present invention
<1> an image carrier, a charging unit that charges the surface of the image carrier, an exposure unit that forms an electrostatic latent image by exposing the surface of the image carrier charged by the charging unit according to image information, Developing means for developing the electrostatic latent image with a developer containing toner conveyed onto the developer carrying member to form a toner image, and primary transfer the toner image from the surface of the image carrying member to the intermediate transfer belt. An image having primary transfer means, secondary transfer means for electrostatically transferring the toner image transferred to the intermediate transfer belt to the recording material, and fixing means for heating and fixing the toner image transferred to the recording material An image forming method for forming an image on the recording material using a forming apparatus, wherein the intermediate transfer belt includes a belt base material in which two or more different kinds of elastic materials are mixed, and one surface of the belt base material or Fluorine resin or silicon on both sides An intermediate elastic transfer belt comprising a protective layer mainly composed of a resin based on resin, and the toner contains a crystalline polyester and an amorphous polymer as a binder resin, and the surface has the amorphous high transfer belt. A toner having a core-shell structure coated with a surface layer mainly composed of molecules, and further, the image carrier after the toner has passed through the nip portion between the image carrier and the intermediate transfer belt The toner on the upper or intermediate transfer belt is an image forming method characterized in that the coverage of the surface layer represented by the following formula (1) is 60% or more and 94% or less.
Formula (1)
Covering rate of surface layer (%) = (total exposed length of surface layer / total toner peripheral length) × 100

<2> The image forming method according to <1>, wherein one of the image carrier and the intermediate transfer belt is used as a drive source and the other is driven to rotate.

<3> The intermediate transfer belt is stretched by a tension roll in the image forming apparatus, and the intermediate transfer belt stretched by the tension roll is C1, and the intermediate transfer belt is not stretched. The image forming method according to <1> or <2>, wherein the stretching ratio represented by the following formula (2) is 2 to 5% when the circumference of the belt is C2. .
Formula (2)
Tension ratio (%) = (C1-C2) / C2 × 100

<4> The image forming method according to any one of <1> to <3>, wherein a value of a shape factor SF represented by the following formula (3) of the toner is less than 135. is there.
Formula (3)
SF = (πL ² / 4A) × 100
(In Formula (3), L is the maximum diameter (μm) of the toner particles, and A is the projected area (μm ² ) of the toner particles.)

<5> With respect to the particle size range divided based on the particle size distribution, the toner has a volume average particle size D value of 2 μm or more and 9 μm which is 50% cumulative when a cumulative distribution is drawn from the small diameter side with respect to the volume. Any one of <1> to <4>, wherein the amorphous polymer is a polymer having a weight average molecular weight Mw of 50,000 or more and / or a crosslinked polymer. The image forming method according to claim 1.

  According to the present invention, good transferability can be achieved without causing image quality defects such as streak-like image omission caused by filming on the image carrier and the transfer member due to excessive shell destruction of toner having a core-shell structure. An image forming method that can be obtained can be provided.

The image forming method of the present invention forms an electrostatic latent image by exposing an image carrier, charging means for charging the surface of the image carrier, and exposing the surface of the image carrier charged by the charging means according to image information. Developing means for developing the electrostatic latent image with a developer containing toner conveyed on the developer carrying member to form a toner image; electrostatically transferring the toner image from the surface of the image carrying member to the intermediate transfer belt; Primary transfer means for primary transfer, secondary transfer means for electrostatically secondary transfer the toner image transferred to the intermediate transfer belt to the recording material, and heat fixing the toner image transferred to the recording material An image forming method for forming an image on the recording material using an image forming apparatus having a fixing unit, wherein the intermediate transfer belt includes a belt base material in which two or more different kinds of elastic materials are mixed, and the belt On one or both sides of the substrate, An intermediate elastic transfer belt comprising a protective layer mainly composed of a resin or a silicone resin, and the toner contains a crystalline polyester and an amorphous polymer as a binder resin, the surface of which is A toner having a core-shell structure coated with a surface layer mainly composed of a fixed polymer, and further, the image after the toner has passed through a nip portion between the image carrier and the intermediate transfer belt. The toner on the carrier or the intermediate transfer belt is characterized in that the coverage of the surface layer represented by the following formula (1) is 60% or more and 94% or less.
Formula (1)
Covering rate of surface layer (%) = (total exposed length of surface layer / total toner peripheral length) × 100

  Here, the coverage of the toner surface layer on the image carrier or on the intermediate transfer belt is 60% or more and 94% or less. When the coverage of the toner surface layer is the same value, it means that the value is 60% or more and 94% or less, and the coverage of the toner surface layer on the image carrier and the intermediate transfer belt When the coverage of the toner surface layer is a different value, either the coverage of the toner surface layer on the image carrier or the coverage of the toner surface layer on the intermediate transfer belt is 60% or more. Means that both the coverage of the toner surface layer on the image carrier and the coverage of the toner surface layer on the intermediate transfer belt may be 60% or more and 94% or less. .

The coverage of the surface layer is essential to be 60% or more, preferably 70% or more, and more preferably 80% or more. When the coverage of the surface layer is less than 60%, the internal low-melting-point binder resin (core) is excessively exposed on the toner surface, and the low-melting-point binder resin is lower than the conventional binder resin. Because of its low mechanical strength, it easily adheres to the image carrier and the transfer member (so-called filming), and adheres to the member more easily than conventional toners. Image quality defects and remarkably transferability. On the other hand, the coverage of the surface layer must be 94% or less, and preferably 90% or less. When the coverage of the surface layer exceeds 94%, it means that the toner structure has a low-melting-point binder resin (core) that is difficult to be exposed on the toner surface. That is, it means that it is difficult to expose the internal low-melting-point binder resin (core) even in the fixing step. For this reason, when the coverage of the surface layer exceeds 94%, low temperature fixability cannot be obtained.
As described above, as a method for setting the coverage of the surface layer to 60% or more and 94% or less, the amorphous polymer in the toner is polymerized with a polymer having a weight average molecular weight Mw of 50,000 or more and / or crosslinked as described later. The intermediate transfer belt, the method of adjusting the nip pressure between the image carrier and the intermediate transfer belt, and the belt substrate of the intermediate transfer belt are different. Examples thereof include a method of forming a belt base material in which more than one type of elastic material is mixed.

The coating rate of the surface layer is determined by observation with a TEM (transmission electron microscope) and an image analyzer. The procedure is shown below.
First, in a state where the toner passes through the nip portion between the image carrier and the intermediate transfer belt, the image carrier and the intermediate transfer belt through which the toner has passed are cut out as a strip-shaped sample. Subsequently, these samples are vapor-stained in a desiccator charged with a staining agent. The dyeing agent used here is for identifying crystalline polyester (core) and amorphous polymer (surface layer (shell)), as well as the release agent contained in the core. Examples include osmium, ruthenium tetroxide, and iodine. It is necessary to search for conditions of the type and amount of the dyeing agent and the dyeing time sufficiently depending on the toner material. After dyeing, the sample is removed from the desiccator, and excess gas adhering to the sample is exhausted.

  Next, metal vapor deposition is performed on the surface of the vapor-stained sample and embedded with an epoxy resin. After the epoxy resin is cured, the sample tip is trimmed, and a sample slice is prepared with a slice thickness setting of 0.25 μm using a microtome equipped with a diamond knife. The obtained sample section is put on a mesh and used as a sample for TEM observation. As the cutting device, Ultracut N manufactured by Reichert was used. Next, using a Tecnai G2 made by a transmission electron microscope FEI, the acceleration voltage is 100 KV, the magnification is 4500 times, the direction of the sample is the image carrier or the intermediate transfer belt, and the toner on the image carrier or the intermediate transfer belt is removed. Shoot over 20 fields of view.

  Furthermore, particle analysis is performed on the obtained 4500-fold TEM image using an IP-1000PC manufactured by Asahi Kasei Corporation. Specifically, first, the TEM image is adjusted to brightness and contrast suitable for particle analysis. If the image has a tone gradient, shading correction is performed. Subsequently, the image analysis target range is designated as the toner existing area. Then, the image brightness threshold calculation target is automatically set to the entire gradation histogram of the range designation image. Thereafter, the binarization threshold value setting is manually performed while confirming the image of the tissue to be analyzed, that is, the toner that is a low luminance (dark) tissue and the tissue that is not the analysis target, that is, the region other than the toner. When separation, connection, or erasing is required in a binarized image, manual correction is performed and only the toner is extracted. Select the perimeter as the measurement item and execute particle analysis. As a result, the “total toner peripheral length” is obtained. Further, the length of the exposed portion of the amorphous polymer (surface layer) is measured around each extracted toner, and the “total length of the surface layer” is calculated. From the “total toner peripheral length” and the “total length of the surface layer” thus obtained, the coverage of the surface layer can be obtained by the above-described equation (1).

An example of an image forming apparatus used in the image forming method of the present invention is shown in FIG. The image forming apparatus shown in FIG. 1 is an image forming apparatus that employs a full-color four-cycle method, and is primarily used on an image carrier 1 and an intermediate transfer belt 2 that is in contact with the image carrier 1 to transfer a toner image. A primary transfer roll (primary transfer means) 7 for transferring, a secondary transfer roll (secondary transfer means) 5 for secondary transfer of the toner image from the intermediate transfer belt 2 onto the recording material 3, and an opposing ground. And roll 6. The image carrier 1 is provided with a photosensitive layer whose resistance value is reduced by light irradiation. Around the image carrier 1, a charging device (charging means) 9 for charging the image carrier 1 and a charging device are provided. An exposure device (exposure means) 10 for writing an electrostatic latent image of each component (in this example, yellow, magenta, cyan, black) on the image carrier 1 and each color component formed on the image carrier 1 A rotary type developing device (developing means) 11 that visualizes the latent image with each color component toner, an intermediate transfer belt 2, and a cleaning device 12 that cleans residual toner on the image carrier 1 are provided. Yes.
The primary transfer roll 7, the secondary transfer roll 5, and the charging device 9 are connected to a primary transfer roll power source 7a, a secondary transfer roll roll power source 5a, and a charging device roll power source 9a, respectively.

  As the charging device, for example, a charging roll is used, but a charging device such as a corotron may be used. In addition, the exposure apparatus is not limited to this as long as it can write an image on the image carrier with light, and in this example, a scanner that scans a laser beam with a polygon mirror is used. A print head using LED or a print head using LED may be appropriately selected.

  As the developing device, a rotary type developing device 11 is used in this example, and the rotary type developing device 11 has a developing device in which each color component is accommodated in a rotatable state. For example, on the image carrier 1. As long as each color component toner can be attached to the portion where the potential is lowered by the exposure, it may be selected as appropriate. In this example, the rotary developing device 11 is used, but a tandem developing device in which developing devices are arranged in parallel may be used.

  As the cleaning device, a blade cleaning method, a brush cleaning method, or the like may be appropriately selected as long as the toner remaining on the image carrier 1 is cleaned. However, when there is no need for cleaning such as a system with high transfer efficiency or an image forming apparatus using toner, the cleaning apparatus may not be used.

  As shown in FIG. 1, the intermediate transfer belt 2 is stretched over a plurality of stretching rolls (stretching rolls 4 a to 4 c and a stretching and earthing roll 8), and includes a developing device 11, a cleaning device 12, and the like. Are arranged in contact with the surface of the image carrier 1. Further, the intermediate transfer belt 2 may be driven by a separate drive system from the image carrier 1. In a region where the intermediate transfer belt 2 is in contact with the image carrier 1, a primary transfer roll as a primary transfer device 7 is disposed in contact from the back side of the intermediate transfer belt 2, and a predetermined primary transfer bias is applied. A direct current or a superposed alternating current may be applied to the transfer current applied from the intermediate transfer belt to the image carrier. The intermediate transfer belt 2 is provided with an intermediate transfer belt cleaning device 13.

  The intermediate transfer belt 2 may be an intermediate transfer belt (intermediate elastic transfer belt) arranged in contact with the surface of the image carrier 1 as in the image forming apparatus shown in FIG. Due to the elasticity of the elastic transfer belt, compared with polyimide resin or the like used as an intermediate transfer belt of a conventional image forming apparatus, the image transfer body 1 and the intermediate transfer belt 2 pass between the image carrier 1 and the intermediate transfer belt 2. Since the mechanical stress applied to the toner can be suppressed, the core exposure amount on the toner surface accompanying the destruction of the surface layer (shell) of the toner can be suppressed. That is, this form is more preferable for the toner surface layer coating ratio to be 60% or more and 94% or less.

  The intermediate transfer belt 2 shown in FIG. 2 is stretched around a plurality of stretching rolls, and has a predetermined shape along the surface of the image carrier positioned between the developing device and the cleaning device by the stretching rollers 4e and 4d. Only the contact region is closely arranged. Here, the intermediate transfer belt 2 and the image carrier 1 may be driven by a separate drive system. However, since the intermediate transfer belt 2 is disposed in contact along the surface of the image carrier 1, the image carrier One of the body 1 and the intermediate transfer belt 2 can be used as a drive source, and the other can be driven to rotate. If one of the image carrier 1 and the intermediate transfer belt 2 is used as a drive source and the other is driven to rotate, not only the cost can be reduced by consolidating the drive sources, but also the size of the image forming apparatus can be reduced. it can. Further, by causing the intermediate transfer belt 2 to follow the image carrier 1 as much as possible for the driven rotation, the gap before and after the transfer nip region can be suppressed as a result, so that gap discharge can be suppressed. Further, scattering of the toner image can be prevented.

The intermediate transfer belt 2 is stretched by stretching rolls (4a to e and 8 in the image forming apparatus shown in FIG. 2) in the image forming apparatus, and the intermediate transfer belt 2 is stretched by the stretching roll. When the peripheral length of the intermediate transfer belt 2 is C1 and the peripheral length of the intermediate transfer belt 2 is C2, it is preferable that the stretching ratio represented by the following formula (2) is 2 to 5%.
Formula (2)
Tension ratio (%) = (C1-C2) / C2 × 100

  If the stretching ratio is less than 2%, the driving and following of the intermediate transfer belt 2 may be hindered. If the stretching ratio exceeds 5%, the intermediate transfer belt 2 may be in a permanently extended state, or in the daytime. There may be a case where a scratch such as a crack is generated on the surface of the transfer belt 2 and further an image quality defect is caused due to the toner or an external additive being buried in the scratch. The stretching rate is more preferably 3 to 4.5%.

The intermediate transfer belt 2 in the present invention will be described.
In the present invention, the intermediate transfer belt 2 includes a belt base material in which two or more different elastic materials are mixed, and a protective layer mainly composed of a fluororesin or a silicone resin on one or both sides of the belt base material. Are intermediate elastic transfer belts.
Examples of the elastic material in the belt base material include ethylene-propylene-diene copolymer rubber (EPDM), natural rubber (NR), isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), and fluorine rubber (FKM). ), Silicone rubber, epichlorohydrin rubber (CHR, ECO), polysulfide rubber, urethane rubber, and materials obtained by blending two or more of these, among which ethylene-propylene-diene copolymer rubber ( EPDM) is preferred.

  Moreover, as a preferable combination of the two or more kinds of elastic materials, combinations of ethylene-propylene-diene copolymer rubber (EPDM) and chloroprene rubber (CR), ethylene-propylene-diene copolymer rubber (EPDM) and urethane rubber, etc. A combination of ethylene-propylene-diene copolymer rubber (EPDM) and chloroprene rubber (CR) is preferable. As described above, when two or more kinds of elastic materials are mixed and used, dispersion is improved.

  For the belt base material, a conductive material such as carbon or other material whose resistance is adjusted by metal particles is used as the elastic material, but the invention is not limited to this.

  Moreover, it is preferable that the said protective layer has a fluorine resin or a silicone resin as a main component, and is conductive. By making the main component of the protective layer a fluororesin or a silicone resin, the frictional resistance of the surface of the intermediate transfer belt 2 is reduced, and it is easy not only to obtain environmental stability of electrical characteristics, but also to prevent oxidation of elastic materials. This structure is preferable because it improves the cleaning property when untransferred toner remains on the surface of the intermediate transfer belt 2 after the transfer process. In the present invention, “main component” means that the content is 50% by mass or more.

The fluororesin or silicone resin is generally used by adding fine powders such as polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA).
Further, the protective layer may be a fluorosilicone resin, a polyacetal resin, a urethane emulsion paint, an ethylene-vinyl acetate copolymer, an alcohol-soluble nylon resin, an epoxy resin, a polyester resin, An acrylic resin or the like may be used.

  Examples of the method for forming the protective layer on the belt substrate include a spray method, an electrostatic method, a dipping method, a roll coater method, a curtain flow method, and the like.

  The thickness of the belt base material is preferably 50 to 5000 μm, and more preferably 80 to 800 μm. If the belt base material has a thickness of less than 50 μm, the strength of the intermediate transfer belt itself is insufficient, the resistance value is likely to increase, and the belt is easily stretched, so that permanent elongation may easily occur. If it exceeds 5000 μm, the intermediate transfer belt tends to have excessive elasticity, and image quality defects such as image misalignment may occur during image formation.

  The thickness of the protective layer is preferably 1 to 100 μm, and more preferably 3 to 30 μm. If the thickness of the protective layer is less than 1 μm, it may be difficult to form a good coating film, which may cause coating film defects or decrease the dielectric strength. If the thickness exceeds 100 μm, the rigidity of the belt itself changes. Therefore, the coating film is likely to be cracked, and resistance unevenness may be formed.

Next, an example of a method for manufacturing the intermediate transfer belt 2 will be described.
After adding various additives such as a conductive material to the elastic material of the belt base material, it is extruded on a cylinder, followed by primary vulcanization and further secondary vulcanization. Vulcanization is preferably high-pressure steam can vulcanization, but may be other vulcanization methods such as pressureless oven vulcanization and press vulcanization. Vulcanization conditions vary depending on the rubber component and the amount used, but it is usually preferable to carry out at 130 to 170 ° C. for 0.5 to 6 hours. The secondary vulcanization is preferably performed at 130 to 200 ° C. for about 0.5 to 8 hours, for example, in a hot air oven. The transfer belt member of the present invention is cut to a predetermined length, and the front and back surfaces are polished.

Next, toner used in the image forming apparatus will be described.
The toner used in the image forming method of the present invention comprises a core-shell structure containing a crystalline polyester and an amorphous polymer as a binder resin, and having a surface coated with a surface layer composed mainly of the amorphous polymer. Toner.
The toner used in the image forming method of the present invention contains a crystalline polyester and an amorphous polymer as a binder resin. In this case, it is preferable that the content of the amorphous polymer contained in the toner is 40% by mass or more. When the content of the amorphous polymer contained in the toner is less than 40% by mass, the toner on the image carrier or after the toner has passed through the nip portion between the image carrier and the intermediate transfer belt In some cases, the amount of toner deformation on the intermediate transfer belt increases, and an image quality failure such as image omission due to adhesion of the toner to the image carrier may occur.

The melting point of the toner used in the image forming method of the present invention is preferably in the range of 45 to 110 ° C, and more preferably in the range of 60 to 90 ° C. Since the toner sharply decreases in viscosity at the boundary of the melting point, blocking occurs when the toner is stored in a temperature environment equal to or higher than the melting point. Therefore, it is preferable that the melting point of the toner is not less than a lower limit temperature in a general high-temperature environment that is exposed when the toner is stored or after an image is formed, that is, not less than 45 ° C. On the other hand, if the melting point exceeds 110 ° C., low-temperature fixing may not be possible.
This melting point can be determined as the melting peak temperature of input compensated differential scanning calorimetry based on JIS K-7121. The crystalline resin may show a plurality of melting peaks, but the maximum peak is regarded as the melting point.

  “Crystallinity” like the crystalline polyester used in the toner used in the image forming method of the present invention has a clear endothermic peak, not a stepwise endothermic amount change in differential scanning calorimetry (DSC). Specifically, it means that the half-value width of the endothermic peak when measured at a heating rate of 10 ° C./min is within 6 ° C. On the other hand, a resin having a half-value width exceeding 6 ° C. or a resin having no clear endothermic peak means an amorphous resin (amorphous polymer). As an amorphous polymer used in the present invention, It is preferable to use a resin that does not have a clear endothermic peak.

  In addition, the “crystalline polyester resin” used in the toner used in the image forming method of the present invention is a polymer of both a component constituting polyester and other components, in addition to a polymer having a 100% polyester structure as a component. This also means a polymer (copolymer). However, in the latter case, the component other than the polyester constituting the polymer (copolymer) is 50% by mass or less.

  When the crystalline polyester resin is composed of a monomer other than aliphatic, such as aromatic, the melting point of the crystalline polyester resin is increased, resulting in an increase in the melting point of the finally produced toner and an increase in the fixing temperature of the toner. May be invited. In addition, since the emulsifiability of the resin necessary for producing toner by the emulsification granulation method is deteriorated, it is difficult to control the particle size distribution at the time of toner granulation, and uneven distribution of the colorant tends to occur. On the other hand, when an aromatic sulfonic acid monomer is used as a constituent component in order to lower the melting point and impart emulsifying properties, even if the melting point can be lowered and the emulsifying property can be improved, the electrical resistance necessary for imparting toner chargeability can be reduced. As a result, the application range for satisfying the toner characteristics is narrowed. Therefore, in order to enhance the improvement effect on the low-temperature fixability, it is preferable to set the constituent ratio of the aliphatic monomer to 80 mol% or more.

  With respect to the particle size range divided based on the particle size distribution of the toner used in the image forming method of the present invention, the value of the volume average particle diameter D that is 50% cumulative when the cumulative distribution is drawn from the small diameter side with respect to the volume is It is preferably 2 μm or more and 9 μm or less, and more preferably 5 μm or more and 8 μm or less. Further, the number average particle diameter of the toner used in the image forming method of the present invention is preferably 1 μm or more and 20 μm or less, and more preferably 2 μm or more and 8 μm or less. The volume average particle diameter D and the number average particle diameter can be measured, for example, by measuring using a Coulter counter [TA-II] type (manufactured by Beckman Coulter, Inc.) with an aperture diameter of 50 μm. At this time, the measurement is performed after the toner is dispersed in an electrolyte aqueous solution (Isoton-II: manufactured by Beckman-Coulter) and dispersed by ultrasonic waves for 30 seconds.

  As described above, the toner used in the image forming method of the present invention contains a crystalline polyester and an amorphous polymer as a binder resin, but if necessary, contains other components such as a release agent. May be. The method for producing the toner of the present invention is not particularly limited, but it is preferable to use a wet method. Hereinafter, the components and the production method of the toner of the present invention will be described in detail.

  The crystalline polyester resin used for the toner used in the image forming method of the present invention and all other polyester resins are synthesized from a polyvalent carboxylic acid component and a polyhydric alcohol component. In the present invention, a commercially available product may be used as the polyester resin, or an appropriately synthesized product may be used.

  Examples of the polyvalent carboxylic acid component include oxalic acid, succinic acid, glutaric acid, adipic acid, peric acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12 -Aliphatic dicarboxylic acids such as dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,6-dicarboxylic acid, malonic acid, mesaconic acid Aromatic dicarboxylic acids such as dibasic acids such as, and the like, and anhydrides and lower alkyl esters thereof are also included, but not limited thereto.

  Examples of the trivalent or higher carboxylic acids among the polyvalent carboxylic acids include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc. And anhydrides thereof, lower alkyl esters thereof and the like. These may be used individually by 1 type and may use 2 or more types together.

  Furthermore, it is preferable that a dicarboxylic acid component having a sulfonic acid group is contained as the polyvalent carboxylic acid component in addition to the above-mentioned aliphatic dicarboxylic acid and aromatic dicarboxylic acid. The dicarboxylic acid having a sulfonic acid group is effective in that it can favorably disperse a coloring material such as a pigment. Further, when the entire resin is emulsified or suspended in water to produce fine particles, if a sulfonic acid group is present, it can be emulsified or suspended without using a surfactant as described later.

  Examples of the dicarboxylic acid having a sulfone group include, but are not limited to, 2-sulfoterephthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, and sulfosuccinic acid sodium salt. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. The divalent or higher carboxylic acid component having a sulfonic acid group is contained in an amount of 1 to 15 mol%, preferably 2 to 10 mol%, based on all carboxylic acid components constituting the polyester. When the content is low, the stability of the emulsified particles with time deteriorates. On the other hand, when the content exceeds 15 mol%, not only the crystallinity of the polyester resin is deteriorated but also the process of coalescing the particles after aggregation is adversely affected. There is a problem that it becomes difficult to adjust.

  Furthermore, it is more preferable to contain a dicarboxylic acid component having a double bond in addition to the aforementioned aliphatic dicarboxylic acid and aromatic dicarboxylic acid. A dicarboxylic acid having a double bond can be suitably used to prevent hot offset at the time of fixing in that it can be radically cross-linked through the double bond. Examples of such dicarboxylic acids include, but are not limited to, maleic acid, fumaric acid, 3-hexenedioic acid, and 3-octenedioic acid. In addition, these lower esters, acid anhydrides and the like are also included. Among these, fumaric acid and maleic acid are preferable from the viewpoint of cost.

  On the other hand, the polyhydric alcohol component is preferably an aliphatic diol, and more preferably a linear aliphatic diol having 7 to 20 carbon atoms in the main chain portion. When the aliphatic diol is branched, the crystallinity of the polyester resin is lowered and the melting point is lowered, so that toner blocking resistance, image storage stability, and low-temperature fixability may be deteriorated. Further, if the number of carbon atoms is less than 7, when the polycondensation with an aromatic dicarboxylic acid is performed, the melting point becomes high and fixing at a low temperature may be difficult. On the other hand, if it exceeds 20, it is difficult to obtain a practical material. There is a case. The carbon number is more preferably 14 or less.

  Specific examples of the aliphatic diol suitably used for the synthesis of the crystalline polyester used in the toner used in the image forming method of the present invention include ethylene glycol, 1,3-propanediol, and 1,4-butane. Diol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,14-eicosandecanediol, etc., but are not limited thereto. is not. Among these, 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol are preferable in view of availability.

  Examples of the trivalent or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol. These may be used individually by 1 type and may use 2 or more types together.

Among the polyhydric alcohol components, the content of the aliphatic diol component is preferably 80 mol% or more, and more preferably 90 mol% or more. If the content of the aliphatic diol component is less than 80 mol%, the crystallinity of the polyester resin is lowered and the melting point is lowered, so that toner blocking resistance, image storage stability, and low-temperature fixability may be deteriorated. is there.
If necessary, monovalent acids such as acetic acid and benzoic acid, and monovalent alcohols such as cyclohexanol and benzyl alcohol can be used for the purpose of adjusting the acid value and the hydroxyl value.

  Examples of the amorphous polymer used in the toner used in the image forming method of the present invention include conventionally known thermoplastic binder resins, and specifically include styrene, parachlorostyrene, α-methylstyrene. Homopolymers or copolymers of styrenes such as styrene resins; methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methacrylic acid Homopolymers or copolymers (vinyl resins) of esters having a vinyl group such as methyl, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate; acrylonitrile, methacrylonitrile, etc. Homopolymers or copolymers of vinyl nitriles (vinyl resins); vinyl methyl Homopolymers or copolymers of vinyl ethers such as ether and vinyl isobutyl ether (vinyl resins); Homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone (vinyl type) Resins); Homopolymers or copolymers of olefins such as ethylene, propylene, butadiene, and isoprene (olefin resins); Non-vinyls such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, and polyether resins Examples include condensation resins and graft polymers of these non-vinyl condensation resins and vinyl monomers. These resins may be used alone or in combination of two or more. Of these resins, vinyl resins and polyester resins are particularly preferable.

  In the case of a vinyl resin, it is advantageous in that a resin particle dispersion can be easily prepared by emulsion polymerization or seed polymerization using an ionic surfactant or the like. Examples of the vinyl monomer include acrylic acid, methacrylic acid, maleic acid, cinnamic acid, fumaric acid, vinyl sulfonic acid, ethylene imine, vinyl pyridine, vinyl amine, and other vinyl polymer acids and vinyl polymer bases. Examples include monomers that are raw materials.

In the present invention, these resins preferably contain the vinyl monomer as a monomer component. In the present invention, among these vinyl monomers, vinyl polymer acids are more preferable from the viewpoint of ease of formation reaction of vinyl resins, and specifically, acrylic acid, methacrylic acid, maleic acid, cinnamon. A dissociable vinyl monomer having a carboxyl group such as an acid or fumaric acid as a dissociating group is particularly preferred from the viewpoint of controlling the degree of polymerization and the glass transition point.
The concentration of the dissociating group in the dissociable vinyl monomer is determined by, for example, dissolving particles such as toner particles from the surface as described in Chemistry of Polymer Latex (Polymer Publication). Etc. can be determined. It should be noted that the molecular weight of the resin and the glass transition point from the surface of the particle to the inside can also be determined by the above method or the like.

  On the other hand, in the toner used in the image forming method of the present invention, when a polyester resin is used as the amorphous polymer, the resin particles are obtained by emulsifying and dispersing the resin by adjusting the acid value or using an ionic surfactant. This is advantageous in that the dispersion can be easily prepared. The amorphous polyester resin used for emulsification dispersion is synthesized by dehydration condensation of a polyvalent carboxylic acid and a polyhydric alcohol.

  Examples of the polyvalent carboxylic acid in the amorphous polymer include aromatic carboxylic acids such as terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid, maleic anhydride, fumar Examples thereof include aliphatic carboxylic acids such as acid, succinic acid, alkenyl succinic anhydride and adipic acid, and alicyclic carboxylic acids such as cyclohexanedicarboxylic acid. These polyvalent carboxylic acids can be used alone or in combination. Of these polyvalent carboxylic acids, it is preferable to use aromatic carboxylic acids, and in order to take a crosslinked structure or a branched structure in order to ensure good fixability, tricarboxylic or higher carboxylic acids (trimerits) It is preferable to use an acid or an acid anhydride thereof in combination.

  Examples of the polyhydric alcohol in the amorphous polymer include aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentylglycol, glycerin, cyclohexanediol, cyclohexanediene, and the like. Examples thereof include aromatic diols such as alicyclic diols such as methanol and hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A. One or more of these polyhydric alcohols can be used. Among these polyhydric alcohols, aromatic diols and alicyclic diols are preferable, and among these, aromatic diols are more preferable. In order to secure good fixing properties, a trihydric or higher polyhydric alcohol (glycerin, trimethylolpropane, pentaerythritol) may be used in combination with the diol in order to take a crosslinked structure or a branched structure.

  In addition, monocarboxylic acid and / or monoalcohol is further added to the polyester resin obtained by polycondensation of polycarboxylic acid and polyhydric alcohol to esterify the hydroxyl group and / or carboxyl group at the polymerization terminal. The acid value of the polyester resin may be adjusted. Examples of the monocarboxylic acid include acetic acid, acetic anhydride, benzoic acid, trichloroacetic acid, trifluoroacetic acid, propionic anhydride, etc., and examples of the monoalcohol include methanol, ethanol, propanol, octanol, 2-ethylhexanol, trifluoroethanol, Examples include trichloroethanol, hexafluoroisopropanol, and phenol.

  The polyester resin in the amorphous polymer can be produced by subjecting the polyhydric alcohol and polyvalent carboxylic acid to a condensation reaction according to a conventional method. For example, the above polyhydric alcohol and polyvalent carboxylic acid, if necessary, a catalyst, and blended in a reaction vessel equipped with a thermometer, a stirrer, a flow-down condenser, and in the presence of an inert gas (such as nitrogen gas), Heat at 150 to 250 ° C. to continuously remove by-product low-molecular compounds out of the reaction system, stop the reaction when a predetermined acid value is reached, cool, and obtain the desired reactant Can be manufactured.

  Examples of the catalyst used for the synthesis of this polyester resin include esterification catalysts such as organic metals such as dibutyltin dilaurate and dibutyltin oxide, and metal alkoxides such as tetrabutyl titanate. The addition amount of such a catalyst is preferably 0.01 to 1% by mass with respect to the total amount of raw materials.

  The amorphous polymer used in the toner used in the image forming method of the present invention has a weight average molecular weight (Mw) of 50000 as determined by gel permeation chromatography (GPC) method in which tetrahydrofuran (THF) is soluble. The molecular weight distribution Mw / Mn is preferably 1.5 to 30, and more preferably 2 to 20.

When the weight average molecular weight and number average molecular weight are smaller than the above ranges, it is effective for low-temperature fixability, but deteriorates the hot offset resistance and lowers the glass transition point of the toner. While storage stability may be adversely affected, if the molecular weight is larger than the above range, hot offset resistance can be sufficiently imparted, but low-temperature fixability is reduced, and the crystalline polyester phase present in the toner is reduced. Inhibiting bleeding may adversely affect document preservation. Therefore, satisfying the above-described conditions makes it possible to achieve both low-temperature fixability, hot offset resistance, and document storage stability.
In the present invention, the molecular weight of the resin is measured with a THF solvent using a TSO gel GPC / HLC-8120, a Tosoh column / TSKgel SuperHM-M (15 cm), and a monodisperse polystyrene standard sample. The molecular weight was calculated using the prepared molecular weight calibration curve.

  The amorphous polymer used in the toner used in the image forming method of the present invention is preferably a crosslinked polymer. When the amorphous polymer is a crosslinked polymer, it becomes easy to obtain surface cohesion when the toner melts in the fixing process, so that it is possible to prevent toner fusion to the surface of the fixing member, so-called offset. This is preferable because it can prevent image quality defects.

  The toner used in the image forming method of the present invention has a volume average particle diameter D value of 2 μm or more and 9 μm or less, and the amorphous polymer is a polymer having a weight average molecular weight Mw of 50000 or more, and / or The crosslinked polymer indicates that the toner on the image carrier or the intermediate transfer belt after the toner passes through the nip portion between the image carrier and the intermediate transfer belt It is preferable in that the coverage of the surface layer represented by 1) is easily set to 60% or more and 94% or less.

  The acid value of the polyester resin as an amorphous polymer (mg number of KOH necessary to neutralize 1 g of resin) is easy to obtain the molecular weight distribution as described above, and the granulation property of toner particles by the emulsion dispersion method. 1 to 30 mgKOH / g is preferable, because it is easy to secure the toner, and it is easy to maintain the environmental stability of the obtained toner (stability of chargeability when temperature and humidity change). . The acid value of the polyester resin can be adjusted by controlling the carboxyl group at the terminal of the polyester according to the blending ratio of the raw polyhydric carboxylic acid and polyhydric alcohol and the reaction rate. Or what has a carboxyl group in the principal chain of polyester is obtained by using trimellitic anhydride as a polyvalent carboxylic acid component.

  The glass transition temperature of the amorphous polymer used in the present invention and the melting point of the crystalline polyester resin are preferably 35 to 100 ° C., and 50 to 80 in terms of the balance between storage stability and toner fixing property. More preferably, it is ° C. If the glass transition temperature and the melting point are less than 35 ° C., the toner tends to be blocked (a phenomenon in which toner particles are aggregated into a lump) during storage or in a developing machine. On the other hand, if the temperature exceeds 100 ° C., the toner fixing temperature may increase.

  The release agent used in the toner used in the image forming method of the present invention is not particularly limited as long as it is a known release agent. For example, natural waxes such as carnauba wax, rice wax, and candelilla wax, low molecular weight Examples include synthesis of polypropylene, low molecular weight polyethylene, sazol wax, microcrystalline wax, Fischer-Tropsch wax, paraffin wax, montan wax, etc. or mineral-petroleum wax, fatty acid ester, ester wax such as montanic acid ester, etc. It is not limited to this. Moreover, these mold release agents may be used individually by 1 type, and may be used together 2 or more types.

  The melting point of the release agent is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, from the viewpoint of storage stability. Moreover, it is preferable that it is 110 degrees C or less from a viewpoint of offset resistance, and it is more preferable that it is 100 degrees C or less.

  The content of the release agent is preferably in the range of 1 to 30 parts by mass, and more preferably in the range of 2 to 20 parts by mass with respect to 100 parts by mass of the binder resin. When the content of the release agent is less than 1 part by mass, there is no effect of adding the release agent, and hot offset at a high temperature may be caused. On the other hand, if it exceeds 30 parts by mass, the chargeability is adversely affected, and the mechanical strength of the toner is reduced. Therefore, the toner is easily destroyed by stress in the developing machine, and may cause carrier contamination. Further, when used as a color toner, a domain tends to remain in a fixed image, which may cause a problem that OHP transparency is deteriorated.

  A colorant can also be used for the toner used in the image forming method of the present invention. The colorant used in the toner of the present invention is not particularly limited as long as it is a known colorant, and examples thereof include carbon black such as furnace black, channel black, acetylene black, and thermal black, bengara, bitumen, and titanium oxide. Inorganic pigments, fast yellow, disazo yellow, pyrazolone red, chelate red, brilliant carmine, para brown and other azo pigments, copper phthalocyanine, metal-free phthalocyanine and other phthalocyanine pigments, flavantron yellow, dibromoanthrone orange, perylene red, quinacridone red, Examples thereof include condensed polycyclic pigments such as dioxazine violet.

  Chrome Yellow, Hansa Yellow, Benzidine Yellow, Slen Yellow, Quinoline Yellow, Permanent Orange GTR, Pyrarozone Orange, Vulcan Orange, Watch Young Red, Permanent Red, Dupont Oil Red, Resol Red, Rhodamine B Lake, Lake Red C Rose Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment 57: 1, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 74, C.I. I. Pigment blue 15: 1, C.I. I. Examples thereof include various pigments such as CI Pigment Blue 15: 3, and these can be used alone or in combination of two or more.

  In the toner used in the image forming method of the present invention, the content of the colorant is preferably 1 to 30 parts by mass with respect to 100 parts by mass of the binder resin. It is also effective to use an agent or a pigment dispersant. By appropriately selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.

  In addition to the above-described components, the toner used in the image forming method of the present invention may further contain various components such as an internal additive, a charge control agent, inorganic powder (inorganic fine particles), and organic fine particles as necessary. Can be added.

  Examples of the internal additive include metals such as ferrite, magnetite, reduced iron, cobalt, nickel, and manganese, alloys, and magnetic materials such as compounds containing these metals.

  Examples of the charge control agent include quaternary ammonium salt compounds, nigrosine compounds, dyes composed of complexes of aluminum, iron, chromium, and triphenylmethane pigments. The inorganic powder is added mainly for the purpose of adjusting the viscoelasticity of the toner. For example, silica, alumina, titania, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide, etc. Examples thereof include all inorganic fine particles used as an external additive on the toner surface.

Examples of the inorganic fine particles externally added to the surface of the toner used in the image forming method of the present invention include the following. For example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, cerium chloride, bengara, chromium oxide, Examples include cerium oxide, antimony trioxide, magnesium oxide, zirconium oxide, silicon carbide, and silicon nitride. Among them, silica fine particles and titanium oxide fine particles are preferable, and hydrophobized fine particles are particularly preferable.
The primary particle diameter of the inorganic fine particles is preferably 1 to 200 nm, and the addition amount is preferably 0.01 to 20 parts by mass with respect to 100 parts by mass of the toner.

The method for producing the toner used in the image forming method of the present invention is not particularly limited, but it is preferably produced by a wet granulation method. Examples of the wet granulation method include known melt suspension methods, emulsion aggregation methods, and dissolution suspension methods. Among these methods, the emulsion aggregation method is preferably used in the present invention.
When the emulsion aggregation method is used, the method for producing a toner for developing an electrostatic charge image according to the present invention includes an aggregation step of forming the aggregated particles containing the crystalline polyester in a dispersion containing the crystalline polyester fine particles, and the aggregated particles. It is preferable to include an adhesion step of adhering amorphous polymer fine particles to the surface, and it is more preferable to include a fusion step of fusing the aggregated particles by heating. Hereinafter, each step will be described in detail.

  First, as an emulsification step, a binder resin emulsified particle (hereinafter abbreviated as “resin particle”) as a raw material dispersion was mixed with an aqueous medium and a dispersion containing a colorant and a release agent as required. It is formed by applying a shearing force to the solution. Therefore, the binder resin needs to be dispersed in advance as resin particles in the raw material dispersion.

  As an average particle diameter of the said resin particle, it is 1 micrometer or less normally, and it is preferable that it is 0.01-1 micrometer. When the average particle size exceeds 1 μm, the particle size distribution of the finally obtained electrostatic image developing toner is broadened or free particles are generated, which tends to deteriorate performance and reliability. On the other hand, when the average particle size is within the above range, there are no disadvantages, and the uneven distribution among the toners is reduced, the dispersion in the toners is improved, and the variation in performance and reliability is advantageous. In addition, the said average particle diameter can be measured using a laser scattering type particle size distribution measuring machine etc., for example.

  Examples of the dispersion medium in the dispersion include an aqueous medium and an organic solvent. Examples of the aqueous medium include water such as distilled water and ion exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together. In the present invention, it is preferable to add and mix a surfactant in the aqueous medium. Although it does not specifically limit as surfactant, For example, anionic surfactants, such as sulfate ester type, sulfonate type, phosphate ester type, soap type; amine salt type, quaternary ammonium salt type, etc. Nonionic surfactants such as polyethylene glycol-based, alkylphenol ethylene oxide adduct-based, polyhydric alcohol-based, and the like. Among these, anionic surfactants and cationic surfactants are preferable. The nonionic surfactant is preferably used in combination with the anionic surfactant or the cationic surfactant. The said surfactant may be used individually by 1 type, and may use 2 or more types together.

  Specific examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate and the like. Specific examples of the cationic surfactant include alkylbenzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, distearyl ammonium chloride and the like. Among these, ionic surfactants such as anionic surfactants and cationic surfactants are preferable. Examples of the organic solvent include ethyl acetate and toluene, which are appropriately selected according to the binder resin.

When the resin particle is a homopolymer or copolymer (vinyl resin) of a vinyl monomer such as the ester having a vinyl group, the vinyl nitrile, the vinyl ether, or the vinyl ketone. By conducting emulsion polymerization or seed polymerization of the vinyl monomer in an ionic surfactant, resin particles made of a vinyl monomer homopolymer or copolymer (vinyl resin) are made ionic. A dispersion obtained by dispersing in a surfactant is prepared.
When the resin particle is a resin other than a homopolymer or a copolymer of the vinyl monomer, the resin can be dissolved in an oily solvent having a relatively low solubility in water. The resin is dissolved in the oily solvent, and this solution is dispersed in water together with an ionic surfactant and polymer electrolyte using a disperser such as a homogenizer, and then the oily solvent is evaporated by heating or decompression. Thus, a dispersion liquid in which resin particles made of resin other than vinyl resin are dispersed in an ionic surfactant is prepared.

  On the other hand, when the resin particle is a crystalline polyester and an amorphous polyester resin, it contains a functional group that can become an anionic type by neutralization, and has a self-water dispersibility. A stable aqueous dispersion can be formed under the action of an aqueous medium, all neutralized with a base. In the crystalline polyester and the amorphous polyester resin, the functional group that can become a hydrophilic group by neutralization is an acidic group such as a carboxyl group or a sulfone group. As the neutralizing agent, for example, sodium hydroxide, potassium hydroxide, water Examples thereof include inorganic bases such as lithium oxide, calcium hydroxide, sodium carbonate and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine.

  Further, as a binder resin, when using a polyester resin that does not disperse in water per se, that is, does not have self-water dispersibility, like a release agent described later, a resin solution and / or an aqueous medium mixed therewith, It is easy to disperse with polymer electrolytes such as ionic surfactants, polymer acids, polymer bases, etc., heat above the melting point, and process using a homogenizer or pressure discharge type disperser that can apply a strong shearing force. Fine particles of 1 μm or less can be formed. When this ionic surfactant or polymer electrolyte is used, it is appropriate that the concentration in the aqueous medium is about 0.5 to 5 wt%.

  As the colorant mixed with the resin dispersion in the emulsification step, the colorants described above can be used. As a method for dispersing the colorant, any method such as a general dispersion method such as a rotary shear type homogenizer, a ball mill having a medium, a sand mill, or a dyno mill can be used, and is not limited at all. If necessary, an aqueous dispersion of these colorants can be prepared using a surfactant, or an organic solvent dispersion of these colorants can be prepared using a dispersant. Hereinafter, such a colorant dispersion may be referred to as a “colored particle dispersion”. As the surfactant and the dispersing agent used for dispersion, the same dispersing agents that can be used when dispersing the binder resin can be used.

  The addition amount of the colorant is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, and still more preferably 2 to 10% by mass with respect to the total amount of the polymer. 2 to 7% by mass is particularly preferable, and as much as possible is preferable as long as the smoothness of the image surface after fixing is not impaired. When the content of the colorant is increased, the thickness of the image can be reduced when an image having the same density is obtained, which is advantageous in terms of prevention of offset. These colorants may be added to the mixed solvent at the same time as other fine particle components, or may be divided and added in multiple stages.

  As the release agent mixed with the resin dispersion in the emulsification step, the release agent described above can be used. As with the case of emulsifying and dispersing a polyester resin that does not have self-water dispersibility, the release agent is dispersed together with an ionic surfactant or the like in water, heated above the melting point, and can be applied with a strong shearing force. Using a pressure discharge type disperser, the dispersed fine particle diameter is adjusted to 1 μm or less. As the dispersion medium in the release agent dispersion, the same dispersion medium as that for the binder resin can be used.

  In the present invention, as an apparatus for mixing and dispersing the binder resin and the release agent with an aqueous medium, for example, a homomixer (Special Machine Industries Co., Ltd.), a slasher (Mitsui Mine Co., Ltd.), Cavitron (stock) Eurotech Co., Ltd., Microfluidizer (Mizuho Industrial Co., Ltd.), Menton Gorin Homizer (Gorin Co., Ltd.), Nanomizer (Nanomizer Co., Ltd.), Static Mixer (Noritake Company), etc. .

The content of the resin particles contained in the binder resin dispersion in the emulsification step, the content of each of the colorant and the release agent in the dispersion of the colorant and the release agent is usually 5 to 50% by mass, Preferably it is 10-40 mass%. When the content is outside the above range, the particle size distribution may be widened and the characteristics may be deteriorated.
Here, according to the purpose, other components such as an internal additive, a charge control agent, and an inorganic powder as described above may be dispersed in the binder resin dispersion. The charge control agent in the present invention is preferably made of a material that is difficult to dissolve in water in terms of controlling ionic strength that affects the stability of the aggregation process and the fusion process and reducing wastewater contamination.

  As an average particle diameter of the said other component, it is 1 micrometer or less normally, and it is preferable that it is 0.01-1 micrometer. When the average diameter exceeds 1 μm, the particle size distribution of the finally obtained electrostatic image developing toner is broadened or free particles are generated, which tends to deteriorate performance and reliability. On the other hand, when the average particle diameter is within the above range, there are no disadvantages, and the uneven distribution among the toners is reduced, the dispersion in the toner is good, and the variation in performance and reliability is advantageous.

In the agglomeration step, the resin particles obtained in the emulsification step, and the colorant and release agent dispersion are mixed (hereinafter, this mixture is referred to as “raw material dispersion”), and the temperature near the melting point of the binder resin. In addition, the particles are heated at a temperature equal to or lower than the melting point to form aggregated particles in which the respective dispersed particles are aggregated.
Aggregated particles are formed by adding a flocculant at room temperature under stirring with a rotary shearing homogenizer to make the pH of the raw material dispersion acidic. The pH is preferably 3.5 to 6 and more preferably 4 to 6 when a vinyl copolymer is used as the amorphous polymer of the binder resin.

  On the other hand, when a polyester resin is used as the binder resin (amorphous polymer), since the pH of the emulsified dispersion of the polyester resin before adjusting the raw material dispersion is 7-8, the crystalline polyester having a pH of 3-5 When an emulsified dispersion of a resin, a colorant, and a release agent dispersion are mixed, the balance of polarity is lost and slow aggregation occurs. Therefore, when the raw material dispersion is mixed, the pH is adjusted to 4 to 6 and heated to form aggregated particles.

  As the aggregating agent used in the aggregating step, a surfactant having a polarity opposite to that of the surfactant used for the dispersing agent, an inorganic metal salt, or a divalent or higher-valent metal complex can be preferably used. In particular, the use of a metal complex is particularly preferable because the amount of the surfactant used can be reduced and the charging characteristics are improved.

  Examples of the inorganic metal salt include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, and polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples thereof include inorganic metal salt polymers. Of these, aluminum salts and polymers thereof are particularly preferred. In order to obtain a sharper particle size distribution, the valence of the inorganic metal salt is bivalent than monovalent, trivalent than bivalent, trivalent than trivalent, and tetravalent than trivalent. The inorganic metal salt polymer is more suitable. In the agglomeration step, it is preferable to adjust the pH at the stage of stirring and mixing at room temperature in order to suppress rapid aggregation due to heating, and add a dispersion stabilizer as necessary (hereinafter, this stage is referred to as “ Called pre-aggregation step).

  As the dispersion stabilizer used in this pre-aggregation step, it is preferable to add 1 to 3% of a known nonionic surfactant so as not to change the polarity. When the dispersion stabilizer is not added, there is a problem that in the heating and agglomeration process, the intake of the fine particles of the raw material particles is deteriorated, resulting in a broad particle size distribution. Further, it is effective to add the dispersion stabilizer separately in both the pre-aggregation step and the heat aggregation step.

  In the attaching step, the amorphous polymer particles are attached to the surface of the agglomerated particles (hereinafter abbreviated as “core agglomerated particles”) containing the crystalline polyester formed through the agglomeration step, thereby forming a surface layer (coating layer). (Hereinafter, the core aggregated particle surface provided with a coating layer is abbreviated as “adhesive aggregated particle”). This coating layer corresponds to the surface layer of the toner of the present invention formed through a fusion process described later. The coating layer can be formed by additionally adding a dispersion containing amorphous polymer particles to the dispersion in which the core aggregated particles are formed in the aggregation process, and other components can be added simultaneously as necessary. It may be added. Also in the adhesion step, the pH and the flocculant are selected in the same manner as in the aggregation step according to the amorphous polymer to be used, and the binder resin having the lowest melting point among the two or more types of binder resins contained in the adhered aggregated particles. Adhesive aggregated particles can be obtained by heating at a temperature below the melting point. This adhesion process is also effective in leading the raw material fine particles that have not been taken into the aggregated particles at the pre-aggregation stage.

  In the fusion step, under the same agitation as in the agglomeration step, the pH of the suspension of the adhered agglomerated particles is set in the range of 6.5 to 8.5 to stop the agglomeration, and then the binder resin The adhered aggregated particles are fused by heating at a temperature equal to or higher than the melting point. Although depending on the liquidity of the dispersion containing the adhered aggregated particles, if the pH at which aggregation is stopped is not an appropriate pH, the adhered aggregated particles will be scattered during the temperature rising process for coalescence, resulting in poor yield. There is a case. Moreover, you may implement a fusion process, after obtaining an aggregation process as needed.

  There is no problem if the heating temperature at the time of fusion is not lower than the melting point of the binder resin contained in the adhered and agglomerated particles. The heating time may be performed so that the fusion is sufficiently performed, and may be performed for about 0.5 to 1.5 hours. If it takes more time, the crystalline polyester contained in the core aggregated particles is likely to be exposed on the toner surface. Therefore, although it is effective for fixing property and document storage property, it is not preferable to heat for a long time because it adversely affects charging property.

  In the fusion step, a crosslinking reaction may be performed when the binder resin is heated to the melting point or higher, or after the fusion is completed. In addition, a crosslinking reaction can be performed simultaneously with the fusion. When the crosslinking reaction is performed, for example, an unsaturated sulfonated crystalline polyester resin obtained by copolymerizing a double bond component as a binder resin is used, and a radical reaction is caused to the resin to introduce a crosslinked structure. . At this time, the following polymerization initiator is used.

  Examples of the polymerization initiator include t-butyl peroxy-2-ethylhexanoate, cumyl perpivalate, t-butyl peroxylaurate, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, di-t. -Butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane 1,1-bis (t-butylperoxy) cyclohexane, 1,4-bis (t-butylperoxyca) Bonyl) cyclohexane, 2,2-bis (t-butylperoxy) octane, n-butyl 4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, , 3-bis (t-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylper) Oxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, di-t-butyldiperoxyisophthalate, 2,2-bis (4,4-di-t-butylperoxy) (Cyclohexyl) propane, di-t-butylperoxy α-methylsuccinate, di-t-butylperoxydimethylglutarate, di-t-butylperoxyhexahydrotereph Tartrate, di-t-butylperoxyazelate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, diethylene glycol-bis (t-butylperoxycarbonate), di-t-butylper Oxytrimethyl adipate, tris (t-butylperoxy) triazine, vinyltris (t-butylperoxy) silane, 2,2'-azobis (2-methylpropionamidine dihydrochloride), 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine], 4,4′-azobis (4-cyanovaleric acid) and the like.

  These polymerization initiators can be used alone or in combination of two or more. The amount and type of the polymerization initiator are selected depending on the amount of unsaturated sites in the polymer and the type and amount of the coexisting colorant. The polymerization initiator may be mixed with the polymer in advance before the emulsification step, or may be incorporated into the aggregate in the aggregation step. Further, it may be introduced after the fusion step or after the fusion step. In the case where the polymerization initiator is introduced after the aggregation step, the adhesion step, the fusion step, or the fusion step, a solution in which the polymerization initiator is dissolved or emulsified is added to a particle dispersion (resin particle dispersion or the like). These polymerization initiators may be added with known crosslinking agents, chain transfer agents, polymerization inhibitors and the like for the purpose of controlling the degree of polymerization.

  The fused particles obtained by fusing can be made into toner particles through a solid-liquid separation process such as filtration and, if necessary, a washing process and a drying process. In this case, in order to ensure sufficient charging characteristics and reliability as a toner, it is preferable to sufficiently wash in the washing step.

  In the drying process, an arbitrary method such as a normal vibration type fluidized drying method, a spray drying method, a freeze drying method, or a flash jet method can be adopted. It is desirable that the toner particles have a moisture content after drying of 1.0% or less, preferably 0.5% or less.

The shape factor SF represented by the following formula (3) of the toner used in the image forming method of the present invention is preferably less than 135. When the shape factor SF is 135 or more, the toner charge distribution is difficult to be sharp, and problems such as transfer efficiency are likely to be deteriorated. As a result, high quality image formation may be adversely affected. is there.
Formula (3)
SF = (πL ² / 4A) × 100
(In Formula (3), L is the maximum diameter (μm) of the toner particles, and A is the projected area (μm ² ) of the toner particles.)

In the image forming method of the present invention, the toner described above is used as it is as a one-component developer or as a two-component developer. When used as a two-component developer, it is used by mixing with a carrier.
There is no restriction | limiting in particular as a carrier which can be used for a two-component developer, A well-known carrier can be used. Examples thereof include magnetic metals such as iron oxide, nickel and cobalt, magnetic oxides such as ferrite and magnetite, resin-coated carriers having a resin coating layer on the surface of the core material, and magnetic dispersion carriers. Further, a resin-dispersed carrier in which a conductive material or the like is dispersed in a matrix resin may be used.

  Coating resins and matrix resins used for carriers include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic. Examples thereof include, but are not limited to, acid copolymers, straight silicone resins composed of organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenol resins, epoxy resins and the like.

  Examples of the conductive material include metals such as gold, silver and copper, carbon black, titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, and carbon black. It is not limited.

  Examples of the core material of the carrier include magnetic metals such as iron, nickel, and cobalt, magnetic oxides such as ferrite and magnetite, and glass beads. However, in order to use the carrier for the magnetic brush method, it is a magnetic material. It is preferable. The volume average particle size of the core material of the carrier is generally 10 to 500 μm, preferably 30 to 100 μm.

  In order to coat the surface of the core material of the carrier with a resin, there may be mentioned a method of coating with a coating layer forming solution in which the coating resin and, if necessary, various additives are dissolved in an appropriate solvent. The solvent is not particularly limited and may be appropriately selected in consideration of the coating resin to be used, coating suitability, and the like.

  Specific resin coating methods include an immersion method in which the carrier core material is immersed in the coating layer forming solution, a spray method in which the coating layer forming solution is sprayed onto the surface of the carrier core material, and the carrier core material is fluidized air. And a kneader coater method in which the carrier core material and the coating layer forming solution are mixed in a kneader coater and the solvent is removed in a kneader coater.

  The mixing ratio (weight ratio) of the toner of the present invention and the carrier in the two-component developer is in the range of toner: carrier = 1: 100 to 30: 100, and about 3: 100 to 20: 100. A range is more preferred.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited to the following examples. In each of the examples and comparative examples, the four color toners of Y (yellow), M (magenta), C (cyan), and K (black) are toners manufactured as follows.

Preparation of crystalline polyester resin dispersion In a heat-dried 5 L flask, 1939 parts by mass (9.6 mol) of sebacic acid, 1180 parts by mass (10 mol) of 1,6-hexanediol, dimethyl-5-sulfonate sodium isophthalate Add 118.4 parts by mass (0.4 mol) and 0.7 parts by mass of dibutyltin oxide, depressurize the air in the container by a depressurization operation, make it in an inert atmosphere with nitrogen gas, and reflux at 180 ° C. for 6 hours. went. Subsequently, the temperature was gradually raised to 220 ° C. under reduced pressure and stirred for 4 hours. When the mixture became viscous, the molecular weight was confirmed by GPC. When the weight average molecular weight reached 30000, the vacuum distillation was stopped, Air-cooled to obtain a crystalline polyester resin. The acid value of the obtained resin was 7.8 mgKOH / g, and there was no THF-insoluble matter. Further, the melting point (DSC peak top) of the obtained resin was 70 ° C., the measurement result of the content of dimethyl 5-sodium phthalate by NMR was 2 mol% (with respect to the total constituent monomers), and the ester concentration was 0.00. 11.

The obtained crystalline polyester resin was transferred in a molten state to Cavitron CD1010 (manufactured by Eurotech Co., Ltd.) at a rate of 100 g / min. A separately prepared aqueous medium tank is filled with 5% by weight diluted ammonia water obtained by diluting reagent ammonia water with ion exchange water, adjusted to pH 8.6, and heated to 120 ° C. with a heat exchanger. The polyester resin melt was transferred to the Cavitron at a speed of 0.1 liter per minute. In this state, the Cavitron was operated under the conditions where the rotor rotation speed was 60 Hz and the pressure was 5 kg / cm ² , and a crystalline polyester resin dispersion (resin particle concentration: 20% by mass) having an average particle diameter of 0.89 μm was obtained. Obtained.

-Preparation of amorphous polymer dispersion 280 parts by mass of styrene, 120 parts by mass of n-butyl acrylate and 6 parts by mass of acrylic acid were prepared to prepare a solution. On the other hand, nonionic surfactant (Nonipol 400, Sanyo Kasei) 8 parts by mass) and 12 parts by mass of an anionic surfactant (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were dissolved in 550 parts by mass of ion-exchanged water, and the previous solution was added and dispersed in the flask. After receiving and mixing slowly for 10 minutes, 50 parts by mass of ion-exchanged water in which 4 parts by mass of ammonium persulfate (manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved was added, and after nitrogen substitution, the contents were stirred while stirring the flask. Was heated in an oil bath until the temperature reached 70 ° C., and emulsion polymerization was continued for 5 hours. Thereafter, the reaction solution was cooled to room temperature to prepare an amorphous polymer dispersion.
The weight average molecular weight of the amorphous polymer was 400,000.

-Preparation of Colorant Dispersion (Y) 90 parts by weight of yellow pigment (CI Pigment Yellow 180), 5 parts by weight of cationic surfactant Neogen RK (Daiichi Kogyo Seiyaku), 200 parts by weight of ion-exchanged water After mixing and dissolving, a colorant dispersion (Y) was prepared by dispersing the colorant by dispersing for about 1 hour using a high-pressure impact disperser Ultimateizer (manufactured by Sugino Machine Co., Ltd., HJP30006).

-Preparation of Colorant Dispersion (M) Instead of the yellow pigment, 2 parts of 30 parts by weight of quinacridone pigment (CI Pigment Red 122) and 20 parts by weight of Carmine 6B pigment (CI Pigment Red 57: 1) A colored dispersion (M) was prepared in the same manner as the colorant dispersion (Y) except that the types of pigments were used.

-Preparation of Colorant Dispersion (C) Colored in the same manner as Colorant Dispersion (Y), except that 45 parts by mass of copper phthalocyanine pigment (CI Pigment Blue 15: 3) was used instead of the yellow pigment. A dispersion (C) was prepared.

-Preparation of colorant dispersion (K) 30 parts by mass of carbon black (Cabot Corp .: Regal 330), 2 parts by mass of an anionic surfactant (Newlex R: manufactured by NOF Corporation), 220 parts by mass of ion-exchanged water Were mixed and dissolved, and a colorant dispersion (K) was prepared by dispersing the colorant by dispersing for about 1 hour using a high-pressure impact disperser Ultimateizer (manufactured by Sugino Machine Co., Ltd., HJP30006).

Preparation of core agglomerated particles (Y) Crystalline polyester resin dispersion: 550 parts by weight Release agent dispersion: 50 parts by weight Colorant dispersion (Y): 22.87 parts by weight Nonionic surfactant ( IGEPAL CA897): 1.05 parts by mass The components having the above composition are placed in a 5 L cylindrical stainless steel container, dispersed and mixed for 30 minutes while applying a shear force at 8000 rpm by Ultraturrax, and 0.14 aqueous solution of 10% polyaluminum chloride as a flocculant. The pre-aggregation was promoted while dropping the mass part. When the thickening of the raw material dispersion itself accompanying agglomeration was confirmed, dropping of the aggregating agent was continued while confirming the agglomerated particle diameter with an optical microscope each time. At this time, the pH of the raw material dispersion was controlled to about 4.5, and the pH was adjusted with 0.3 N nitric acid or 1 N sodium hydroxide aqueous solution as necessary. The core agglomerated particles (Y) were produced by holding for 2 hours.

-Preparation of toner base particles (Y) 25 parts by mass of an amorphous polymer dispersion is added to an aqueous dispersion containing 100 parts by mass of the obtained core aggregated particles (Y), and an amorphous polymer is formed on the surface of the core aggregated particles. The particles were adhered, and the raw material dispersion was transferred to a polymerization kettle equipped with a stirrer and a thermometer, and heated to 40 ° C. with a mantle heater to promote the growth of adhered aggregated particles. Thereafter, granulation is performed while confirming the size and form of the adhered aggregated particles with an optical microscope and a Coulter counter, and when the volume average particle diameter becomes 5 to 6 μm, the pH is adjusted to 9.0 for the fusion of the adhered aggregated particles. Thereafter, the temperature was raised to 90 ° C., and when it was confirmed that the particles were fused with a microscope, the pH was lowered to 6.5 while maintaining the temperature at 90 ° C., and the heating was stopped after 1 hour and the mixture was allowed to cool. Then, after sieving with a 45 μm mesh, washing with water was repeated and dried with a vacuum dryer to prepare toner mother particles (Y).
The volume average particle diameter D of the toner base particles (Y) was 6.1 μm.

-Preparation of toner base particles (M) In the preparation of toner base particles (Y), the colorant dispersion (Y) used for preparation of the core aggregated particles (Y) is changed to the colorant dispersion (M). Toner base particles (M) were prepared in the same manner as toner base particles (Y).
The volume average particle diameter D of the toner base particles (M) was 6.3 μm.

-Preparation of toner base particles (C) In the preparation of toner base particles (Y), the colorant dispersion (Y) used for the preparation of core aggregate particles (Y) is changed to the colorant dispersion (C). Toner base particles (C) were prepared in the same manner as toner base particles (Y).
The volume average particle diameter D of the toner base particles (C) was 6.0 μm.

-Preparation of toner base particles (K) In the preparation of toner base particles (Y), the colorant dispersion (Y) used for the preparation of core aggregated particles (Y) is changed to the colorant dispersion (K). Toner mother particles (K) were produced in the same manner as toner mother particles (Y).
The volume average particle diameter D of the toner base particles (K) was 6.4 μm.

-Determination of resin composition in toner base particles-
In each of the obtained toner base particles (Y), (M), (C), and (K), the resin composition of the toner base particles prepared using two types of binder resin dispersions was quantified using NMR. . Specifically, about 20 mg of toner base particles were weighed into a sample bottle, 1 ml of heavy THF as a solvent was added thereto and dissolved sufficiently, the solution was transferred to an NMR tube, and NMR spectrum measurement was performed. As a result, the content of the amorphous polymer in each toner base particle was 56% by mass.

-Manufacture of toner-
In each of the obtained toner base particles (Y), (M), (C), and (K), 1.2 mass of fine titania powder having a primary particle diameter of 20 nm as an external additive with respect to 100 parts by mass of the toner base particles. Partly added and mixed with a Henschel mixer to produce toners (Y), (M), (C), and (K), respectively. The obtained toners (Y), (M), (C), and (K) had shape factors SF of 129, 127, 132, and 130, respectively.

-Production of developer-
2 parts by mass of the obtained toner (Y), (M), (C), (K) are mixed with 100 parts by mass of resin-coated ferrite particles (average particle diameter: 35 μm). Component developers (Y), (M), (C), and (K) were produced.

<Example 1>
An image forming apparatus similar to the image forming apparatus shown in FIG. 2 is operated using 200 g of the two-component developers (Y), (M), (C), and (K), and the surface layer coverage of the toner is adjusted. Asked. In the image forming apparatus shown in FIG. 2, an organic photoreceptor having a diameter of 47 mm is used as the image carrier, and 8 parts by mass of chloroprene rubber and 10 parts by mass of ethylene-propylene-diene copolymer rubber (EPDM) are used as the intermediate transfer belt 2. In addition, an elastic belt in which a protective layer (tetrafluoroethylene resin) having a thickness of 11 μm was provided by a spray method on a surface of the belt base material made of an elastic material having a thickness of 520 μm in contact with the image carrier was used. Further, the intermediate transfer belt 2 was set so that the stretching ratio was 3.8% and the nip width between the image carrier 1 and the intermediate transfer belt 2 was 36 mm. Further, the nip pressure formation from the intermediate transfer belt 2 to the image carrier 1 applied from the both end support portions of the primary transfer roll 7 was performed by a spring pressing load 260 gf × 2 from the both end support portions of the primary transfer roll 7. As a result, the coverage of the toner surface layer on the intermediate transfer belt 2 after passing through the nip portion between the image carrier 1 and the intermediate transfer belt 2 for four cycles is 91%. The coverage of the surface layer was 90%.

  Next, the image forming apparatus used A4 size P paper (manufactured by Fuji Xerox) as a recording material and performed a running test of 16000 sheets with 14 patterns of full-color images such as letters, halftones, and photographic images. Then, the state of filming on the surface of the image carrier and the image quality were evaluated. At this time, a slight amount of toner was confirmed on the image carrier, but there was no problem in image quality.

<Example 2>
An operation and running test were performed in the same manner as in Example 1 except that the nip width between the intermediate transfer belt 2 and the image carrier 1 was changed to 31 mm. At this time, the surface shell coverage of the toner on the intermediate transfer belt after passing through the image carrier and the intermediate transfer belt for 4 cycles is 84%, and the coverage of the surface layer of the toner on the image carrier 1 is 82. %Met.
After a running test similar to that in Example 1, a small amount of toner was confirmed on the image carrier, but there was no problem in image quality.

<Example 3>
An operation and running test were performed in the same manner as in Example 1 except that the nip width between the intermediate transfer belt 2 and the image carrier was changed to 18 mm. At this time, the surface shell coverage of the toner on the intermediate transfer belt after passing through the image carrier and the intermediate transfer belt for 4 cycles is 63%, and the coverage of the surface layer of the toner on the image carrier 1 is 63. %Met.
After a running test similar to that in Example 1, a small amount of toner was confirmed on the image carrier, but there was no problem in image quality except that very slight image omission was observed after 14,000 sheets.

<Comparative Example 1>
A driving test and a running test were performed in the same manner as in Example 1 except that the nip width between the intermediate transfer belt 2 and the image carrier 1 was changed to 15 mm. At this time, the surface shell coverage of the toner on the intermediate transfer belt after passing through the image carrier and the intermediate transfer belt for 4 cycles is 54%, and the coverage of the surface layer of the toner on the image carrier 1 is 51%. %Met.
After a running test similar to that in Example 1, toner filming was confirmed on the image carrier, and slight image omission began to be observed after 10,000 sheets, and clear image omission could be visually confirmed after 16,000 sheets. There was a problem with the image quality.

<Comparative example 2>
An operation and running test were performed in the same manner as in Example 1 except that the nip width between the intermediate transfer belt 2 and the image carrier was changed to 10 mm. At this time, the surface shell coverage of the toner on the intermediate transfer belt after passing through the image carrier and the intermediate transfer belt for 4 cycles is 42%, and the coverage of the surface layer of the toner on the image carrier 1 is 37. %Met.
After a running test similar to that in Example 1, toner filming adhesion was confirmed on the image carrier, and slight image omission was observed after 6000 sheets, and obvious streak image omission was observed after 12000 sheets. There was a significant problem with image quality, such as visual confirmation.

<Comparative Example 3>
The image forming apparatus is changed to an image forming apparatus similar to the image forming apparatus shown in FIG. 1, and the belt substrate of the intermediate transfer belt 2 is changed to a belt substrate made of a composition containing polyimide as a main component. The driving and running tests were conducted in the same manner as in Example 1 except that a transfer roll made of a composition mainly composed of epichlorohydrin rubber was set so as to be supported at both ends so that one-side spring load was 1.47 N (150 gf). .
After the same running test as in Example 1, toner film adhesion was confirmed on the image carrier, image omission and density unevenness began to be observed after 1000 sheets, and stripe image omission and density were observed after 3000 sheets. Significant problems occurred in image quality, such as unevenness and insufficient density could be confirmed visually.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus used in an image forming method of the present invention. It is a schematic block diagram which shows the other example of the image forming apparatus used for the image forming method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Intermediate transfer belt 3 Recording material 4a-4e Stretching roll 5 Secondary transfer roll 5a Secondary transfer roll power supply 6 Ground roll 7 Primary transfer roll 7a Primary transfer roll power supply 8 Stretching and earth roll 9 Charging Device 9a Charging device power supply 10 Exposure device 11 Developing device 12 Cleaning device 13 Cleaning device for intermediate transfer belt

Claims (5)

An image bearing member; a charging unit that charges the surface of the image bearing member; an exposure unit that forms an electrostatic latent image by exposing the surface of the image bearing member charged by the charging unit according to image information; Developing means for developing an image into a toner image by developing with a developer containing toner carried on the developer carrying member, and primary transfer means for electrostatically transferring the toner image from the surface of the image carrying member to an intermediate transfer belt. An image forming apparatus comprising: a secondary transfer unit that electrostatically transfers the toner image transferred onto the intermediate transfer belt to a recording material; and a fixing unit that heat-fixes the toner image transferred onto the recording material. An image forming method for forming an image on the recording material, comprising:
The intermediate transfer belt includes a belt base material in which two or more different types of elastic materials are mixed, and a protective layer mainly composed of a fluorine-based resin or a silicone-based resin on one or both surfaces of the belt base material. Intermediate elastic transfer belt,
The toner includes a core-shell structure including a crystalline polyester and an amorphous polymer as a binder resin, and the surface is coated with a surface layer mainly composed of the amorphous polymer.
Further, the toner on the image carrier or the intermediate transfer belt after the toner has passed through the nip portion between the image carrier and the intermediate transfer belt is a surface layer represented by the following formula (1): An image forming method characterized in that the covering ratio is from 60% to 94%.
Formula (1)
Coverage ratio of surface layer (%) = (total exposed length of surface layer / total toner peripheral length) × 100   2. The image forming method according to claim 1, wherein one of the image carrier and the intermediate transfer belt is used as a drive source, and the other is driven to rotate. The intermediate transfer belt is stretched by a tension roll in the image forming apparatus. The circumferential length of the intermediate transfer belt stretched by the tension roll is C1, and the intermediate transfer belt is not stretched. 3. The image forming method according to claim 1, wherein when the length is C <b> 2, the stretching rate represented by the following formula (2) is 2 to 5%.
Formula (2)
Tension ratio (%) = (C1-C2) / C2 × 100 4. The image forming method according to claim 1, wherein the shape factor SF represented by the following formula (3) of the toner is less than 135. 5.
Formula (3)
SF = (πL ² / 4A) × 100
(In Formula (3), L is the maximum diameter (μm) of the toner particles, and A is the projected area (μm ² ) of the toner particles.) The toner has a volume average particle diameter D value of 2 μm or more and 9 μm or less when the cumulative distribution is drawn from the small diameter side with respect to the particle size range divided based on the particle size distribution. ,
5. The amorphous polymer according to claim 1, wherein the amorphous polymer is a polymer having a weight average molecular weight Mw of 50,000 or more and / or a crosslinked polymer. Image forming method.

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