JP4862397B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used in an electrophotographic apparatus using an electrophotographic process such as a copying machine, a printer, and a facsimile machine. More specifically, the present invention relates to toner images formed on a plurality of image carriers as intermediate transfer belts. Alternatively, the present invention relates to a so-called tandem-type image forming apparatus that sequentially superimposes and transfers images on a recording medium to form an image.

  A number of methods are known as electrophotographic methods (see, for example, Patent Document 1). In general, the surface of a photoconductor (image carrier) using a photoconductive substance is electrically charged by various means. A latent image is formed, and the formed latent image is developed with toner to form a toner image. The toner image is then applied to the surface of a transfer medium such as paper via an intermediate transfer body. An image is formed through a plurality of steps of transferring and fixing by heating, pressing, heating and pressing, or solvent vapor. 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.

  With the increasing demand for full-color images in recent image formation, higher speed, and higher demands for higher image quality, a developed image is transferred for each color, transferred to an intermediate transfer member, and then transferred to multiple colors. A so-called rotary image forming method has been proposed in which a color image is obtained by transferring all of the images at once. With this method, a high-quality image can be obtained because development and transfer are performed for each color, but it cannot cope with speeding up. For example, the output amount is reduced to a fraction of that of a single color of black only. It is normal to become.

  On the other hand, a primary transfer process is sequentially performed in which a toner image obtained by visualizing an electrostatic latent image formed on an image carrier is transferred to the transfer body by bringing an endless transfer body into contact with the image carrier. A so-called tandem type image forming method has been proposed in which a multilayer transfer toner image is formed continuously on the transfer body, and then the multilayer toner image formed on the transfer body is collectively transferred to a transfer medium. ing. This method has the advantage that the output amount does not change even when compared with a single-color image, corresponding to high speed. However, since the toner transferred in the primary transfer process passes through the transfer nip by the number of the subsequent primary transfer processes, the toner is subjected to external pressure by the number of passes through the transfer nip. Also, as the thickness of the multi-layer toner image increases, the external pressure when passing through the nip increases, and the toner transferred at an early stage is subject to a great deal of external pressure and is liable to change its shape, causing streak image omission due to filming. The problem of being easy to cause occurred.

  In addition, in the high-speed tandem type transfer process, the first transfer position (one on the transfer body) is used in order to prevent voids and scattering during transfer and to avoid filming of the photoconductor (image carrier) and transfer body. A method is disclosed in which the distance and speed of the second transfer position from the nip portion (primary transfer of the color toner image) are defined and the dispersibility of the fixing aid is increased to obtain high transfer efficiency (see FIG. For example, see Patent Document 2). However, this image forming apparatus has not improved any problems relating to toner destruction.

Further, in a tandem type image forming apparatus that sequentially transfers toner images formed on a plurality of image carriers to a recording medium (transfer object), when the number of overlapping toner images on the recording medium increases, The toner image is overlapped between the recording medium and the image carrier, and the thickened toner layer is sandwiched between the recording medium and the image carrier, and the toner image and the surface of the image carrier carried on the image carrier are compressed strongly. In some cases, the adhesion force between the toner images in the transfer toner image on the recording medium is even greater. For this reason, as the number of overlapping toner images on the recording medium increases, the whiteout of the image increases. On the other hand, an image forming apparatus has been reported in which the pressing force at the transfer position (nip portion) on the downstream side in the moving direction of the recording medium is set to be weak for the purpose of improving the image blank (for example, patents). Reference 3).
Japanese Patent Publication No.42-23910 JP 2003-43743 A JP 2002-14515 A

However, when the pressing force is weakened in the downstream direction in which the intermediate transfer member or the recording medium moves, the pressure applied to the toner image is different at each transfer position. This causes a problem that the color reproducibility is inferior and color reproducibility is poor. Specifically, the secondary color formed from the first and second colors and the secondary color formed from the second and third colors have different pressing forces even if the amount of toner to be developed is the same. Therefore, the secondary color formed from the first color and the second color is more reproducible.
Furthermore, the so-called process black, which must reproduce three colors at the same time, has a large amount of toner to be transferred, so that the transfer is insufficient, and the transfer of the yellow toner normally used for the first color tends to be insufficient, resulting in purple. There was a case where it became an image.

  Therefore, an object of the present invention is to solve the above problems. That is, an object of the present invention is to provide an image forming apparatus excellent in color reproducibility.

The above-mentioned subject is achieved by the following present invention. That is, the present invention
<1> A plurality of drum-shaped image carriers that form a toner image on a surface using a color electrostatic charge image developing toner that includes a colorant and a binder resin and is coated with a coating layer; An elastic belt disposed in contact with each other so as to form a nip portion along each shape of the image carrier, and sequentially form toner images formed on the plurality of image carriers at each nip portion. An image forming apparatus for superimposing and transferring, wherein a circumferential width of the nip portion is wider as a downstream nip portion where the elastic belt moves, and a transfer current value to be applied is moved by the elastic belt. The image forming apparatus is characterized by lowering the nip portion in the downstream direction.
<2> Three color toners of yellow, magenta, and cyan are used as the toner for developing an electrostatic charge image of the color, and a toner image is formed on the surface of a different drum-shaped image carrier by each color toner. In the image forming apparatus that sequentially superimposes and transfers at the nip portion, the width in the circumferential direction of the nip portion and the transfer current value to be applied are expressed by the following formulas (1) and (2). ), The image forming apparatus according to <1>.
Formula (1) 1.05 ≦ N3 / N2 ≦ N2 / N1 ≦ 1.5
Formula (2) 0.7 ≦ A3 / A2 ≦ A2 / A1 ≦ 0.95
(Where N1 is the circumferential width of the nip portion where the toner image is transferred first, N2 is the circumferential width of the nip portion where the toner image is transferred second, and N3 is the third toner image. represents the width in the circumferential direction of the nip portion for performing transfer of. Moreover, A1 is first a transfer current value at the nip portion for performing transfer of the toner image, A2 is the transfer current at the nip portion for performing transfer of the toner image to the second (A3 represents the transfer current value at the nip portion where the toner image is transferred third.)

<3> The elastic belt covers at least one surface of a belt base material containing two or more different kinds of elastic materials, and at least one surface of the belt base material, and is at least selected from a fluorine resin and a silicone resin The image forming apparatus according to <1> or <2>, further comprising a protective layer containing one kind.
<4> The image forming apparatus according to any one of <1> to <3>, wherein one of the image carrier and the elastic belt is used as a drive source and the other is driven to rotate. is there.
<5> When the elastic belt is stretched by a plurality of stretching rolls and the circumferential length of the elastic belt in the stretched state is C, and the circumferential length of the elastic belt in the unstretched state is c, The image forming apparatus according to any one of <1> to <4>, wherein the stretch rate represented by Formula (3) is 2 to 5%.
Tension ratio (%) = (C−c) / c × 100 Formula (3)

<6> In any one of the above items <1> to <5>, the spherical coefficient (SF) represented by the following formula (4) in the electrostatic image developing toner is less than 140: The image forming apparatus described.
SF = (πL ² / 4A) × 100 Formula (4)
(In Formula (4), L is the maximum diameter (μm) of the electrostatic image developing toner, and A is the projected area (μm) of the electrostatic image developing toner.)

<7> The image forming apparatus according to any one of <1> to <6>, wherein the electrostatic charge image developing toner has a volume average particle diameter of 3 μm to 8 μm.
<8> The image forming apparatus according to any one of <1> to <7>, wherein the elastic belt is an intermediate transfer belt.
<9> The image forming apparatus according to any one of <1> to <7>, wherein the elastic belt is a paper conveyance belt.

  According to the present invention, it is possible to provide an image forming apparatus in which a good color balance is obtained and color reproducibility is excellent.

The image forming apparatus of the present invention includes at least a plurality of drum-shaped image carriers and an elastic belt that is disposed in contact with each other so as to form a nip portion along each shape of the plurality of drum-shaped image carriers. A tandem type color image forming apparatus using at least two or more colors of toner for developing a color electrostatic image having a core-shell structure (that is, a color toner other than black) on each surface of the plurality of drum-shaped image carriers. A toner image forming unit that forms a toner image; and a transfer unit that superimposes and transfers the toner image in the order in which the elastic belt moves in each nip portion. Further, the circumferential width of the nip portion with the elastic belt existing for each of the plurality of image carriers is wider in the downstream nip portion where the elastic belt moves, and the transfer current value applied in each nip portion is The lower nip portion where the elastic belt moves is lower.

  Conventionally, measures have been taken to gradually reduce the pressing force at the nip portion in the downstream direction in order to prevent the destruction of the shell of the core-shell structure toner. However, as described above, simply reducing the pressing force reduces the color balance. In particular, the color reproducibility of secondary colors, process blacks, and the like is remarkably inferior, and the reproducibility of fine lines is not preferable. Therefore, in the present invention, it is possible to obtain both excellent color reproducibility and fine line reproducibility by achieving both the prevention of toner destruction and the color balance by adopting the configuration as described above.

Here, the “width in the circumferential direction of the nip portion” refers to the circumferential length of the elastic belt in the contact area between the image carrier and the elastic belt (hereinafter, “width of the nip portion”). “Nip width” and “nip width”) . Usually, the elastic belt is placed on a plurality of stretching rolls so as to come into contact with the image carrier, so that the width of the nip can be adjusted by the placement of the stretching rolls.

  In addition, the transfer current is applied by using a transfer device (for example, a transfer roll) disposed at a position facing the image carrier via the elastic belt at the nip portion between the image carrier and the elastic belt. It can be done by the method.

  In the present invention, in each nip portion of the plurality of image carriers, the width of the nip portion and the applied transfer current value particularly satisfy the following expressions (1) and (2). preferable.

Formula (1) 1.05 ≦ N3 / N2 ≦ N2 / N1 ≦ 1.5
Formula (2) 0.7 ≦ A3 / A2 ≦ A2 / A1 ≦ 0.95
(Here, N1 is the width of the nip portion where the toner image is transferred first, N2 is the width of the nip portion where the toner image is transferred second, and N3 is the nip portion where the toner image is transferred third. A1 is the transfer current value at the nip portion where the toner image is transferred first, A2 is the transfer current value at the nip portion where the toner image is transferred second, and A3 is the third toner value. (Represents the transfer current value at the nip where the image is transferred.)

  That is, the secondary color formed by the first color and the second color has a narrow nip width compared to the secondary color formed by the second color and the third color. You can make up for it. This tendency is the same for the secondary colors of the first and third colors.

  In the case of a full-color image, an image in which the three colors of toner are appropriately developed or the total amount of applied toner is small, such as halftone, is necessary. The above formulas (1) and (2) By satisfying the above, it is possible to more effectively achieve both the prevention of toner destruction and the color balance, and to obtain excellent color reproducibility and fine line reproducibility.

In the image forming apparatus of the present invention, (A) the toner image formed on each image carrier is sequentially primary-transferred to the intermediate transfer belt, and then the images superimposed on the intermediate transfer belt are collectively put on a recording medium. Or (B) a toner image formed on each image carrier can be sequentially transferred onto a recording medium carried by a paper conveying belt, and then transferred onto the recording medium. A method of superimposing images may be used.
In the case of the method (A), the intermediate transfer belt corresponds to the elastic belt in the present invention, and in the case of the method (B), the paper transport belt corresponds to the elastic belt in the present invention. Even in this case, the effect of achieving both the prevention of toner destruction and the color balance of the present invention can be obtained satisfactorily.

Further, the present invention requires that at least two or more color toners other than black are used as described above. For example, a full color image forming apparatus using yellow (Y), magenta (M), and cyan (C) color toners. Etc. are preferably applied. In this case, three image carriers are provided, and constitute Y, M, and C image forming units, respectively.
The image forming apparatus of the present invention may further include a black (BK) toner and a BK image forming unit. However, the black toner is not transferred so as to overlap with other color toners. From this point of view, it is not necessary to satisfy the requirement that “the transfer current value to be applied is lower in the downstream nip portion”. However, from the viewpoint of influence on toner destruction, it is more preferable to satisfy the requirement that “the width of the nip portion is wider as the nip portion in the downstream direction is wider”.

(Image forming device)
The image forming apparatus of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic diagram showing an example of an image forming apparatus of the present invention provided with an intermediate transfer belt. FIG. 1 shows an image forming apparatus employing a full-color tandem system, each of Y, M, C, and BK image forming units each having a photoconductor drum 11-14, and toner from these photoconductor drums 11-14. In order to primarily transfer the toner on the intermediate transfer belt 2 and the intermediate transfer belt 2 that is in contact with the shape of the photosensitive drums 11 to 14 in a certain region in order to transfer the image. Primary transfer rolls 31 to 34, and as described above, the intermediate transfer belt 2 moves in the downstream direction (showing the rotational direction indicated by arrow A, and in FIG. 1, each of Y, M, and C image forming units). Are arranged in contact with the photosensitive drums 11 to 14 so that the nip width becomes wider toward the nip portion. Further, from the viewpoint of preventing toner destruction, in FIG. 1, the width of the nip portion in the BK image forming unit is preferably wider than the width of the nip portion in the image forming unit.

  In each of the image forming units, the photosensitive drums 11 to 14 are provided with a photosensitive layer whose resistance value is reduced by light irradiation, and around the photosensitive drums 11 to 14 are photosensitive drums 11 to 11. Charging devices 41 to 44 for charging 14, exposure devices L 1 to L 4 for writing electrostatic latent images of respective color components (yellow, magenta, cyan, and black in this example) on charged photosensitive drums 11 to 14, and photosensitive devices Developing devices 51 to 54 that visualize each color component latent image formed on the body drum with each color component toner and cleaning devices 61 to 64 that clean residual toner on the photosensitive drum are provided. Yes.

Here, the photosensitive drums 11 to 14 can be appropriately selected from known photosensitive drums as long as they have a photosensitive layer whose resistance value is reduced by light irradiation.
Further, as the charging devices 41 to 44, for example, charging rolls are used, but chargers such as corotron may be used.
Further, the exposure apparatus may be any photoconductor that can write an image on the ram by light. In this example, for example, a print head tower using LEDs is preferably used, but the present invention is not limited to this. Even with the print head used, it is possible to select an enemy such as a scanner that scans the laser beam with a polygon mirror.

Further, each of the developing devices 51 to 54 contains toner of each color component, and the toner to be used is as described in detail below.
Furthermore, as for the cleaning devices 61 to 64, any device that employs a blade cleaning method may be selected as long as it cleans residual toner on the photosensitive drum. However, there may be a mode in which the cleaning device is not used when toner having a high transfer rate is used.

Further, as shown in FIG. 1, the intermediate transfer belt 2 is stretched over twelve stretching rolls 101 to 112, and extends along the surface of the photosensitive drum positioned between the developing device and the cleaning device. It is closely arranged so as to form a nip portion. In addition, when the circumferential length of the intermediate transfer belt 2 in the stretched state is C and the circumferential length of the intermediate transfer belt 2 in the unstretched state is c, the stretching rate represented by the following formula (3) Is preferably 2 to 5%.
Tension ratio (%) = (C−c) / c × 100 Formula (3)

  Here, the intermediate transfer belt 2 and the photosensitive drums 11 to 14 may be driven by a separate drive system. However, in the present embodiment, the intermediate transfer belt is an elastic belt, and further, Since they are arranged in contact with each other along the peripheral surface, it is preferable that one of the intermediate transfer drum 2 and the photosensitive drums 11 to 14 be a drive source and the other be driven to rotate.

Further, primary transfer rolls 31 to 34 as primary transfer devices are disposed in contact with the nip portion where the intermediate transfer belt 2 is in close contact with the photosensitive drums 11 to 14 from the back side of the intermediate transfer belt 2, and a predetermined primary transfer bias is provided. Is applied. As described above, the primary transfer bias is a nip portion in the downstream direction in which the intermediate transfer belt 2 moves (in the rotation direction indicated by the arrow A, and in the order of the image forming units Y, M, and C in FIG. 1). It is preferably set so as to be lower, and the formula (2) is preferably satisfied.
Further, a secondary transfer roll 7 as a secondary transfer device is disposed opposite to the tension roll 111 of the intermediate transfer belt 2 with the tension roll 111 as a backup roll. The recording medium P is transported to a contact area with the intermediate transfer belt 2 by a paper transport roll tower (not shown). A predetermined secondary transfer bias is applied to the secondary transfer roll 7, and a stretching roll that also serves as the backup roll 111 is grounded.

  Further, a fixing device (not shown) is provided on the downstream side in the traveling direction of the recording medium P, and the toner image transferred onto the recording medium P is fixed by means such as pressurization, heating, and pressure heating.

Here, a mechanism for forming an image in the image forming apparatus will be described.
For example, taking Y as an example, the surface of the photoconductor roll 11 is charged by the charging roll 41. Next, the input image is color-separated (not shown), and only the yellow component is exposed by L1, thereby forming an electrostatic latent image. The developing device 51 develops the electrostatic latent image with a developer containing yellow toner. Next, the toner image is transferred onto the intermediate transfer belt 2 by the primary transfer roll 31. The toner remaining on the photoconductor 11 without being transferred is removed from the photoconductor 11 by a cleaning device (not shown) including a cleaning blade 61.
This is performed for M, C, and BK toners, that is, the photoreceptors 12 to 14, and the intermediate transfer belt 2 on which the transfer images of the four colors of toner are mounted is produced, and the image is transferred onto the recording medium P by the secondary transfer roll 7. The image is transferred and fixed by a fixing device (not shown) to obtain an image.

The present invention is also suitably used as a mode in which toner images formed on the respective image carriers are sequentially transferred onto a recording medium conveyed by a paper conveying belt, and the images are superimposed on the recording medium.
FIG. 2 is a schematic diagram showing an example of the image forming apparatus of the present invention provided with a paper transport belt. FIG. 1 shows an image forming apparatus employing a full-color tandem system, each of Y, M, C, and BK image forming units each having a photoconductor drum 11-14, and toner from these photoconductor drums 11-14. A sheet conveying belt 3 that contacts the shape of the photosensitive drums 11 to 14 in a predetermined area for transferring an image, and a recording medium on which the toner on the photosensitive drums 11 to 14 is conveyed by the sheet conveying belt 3 P has transfer rolls 131 to 134 for transferring onto P. As described above, the sheet conveying belt 3 moves in the downstream direction (showing the rotational direction indicated by arrow A, and in FIG. 2, Y, M, C Are arranged in contact with the photosensitive drums 11 to 14 so that the nip width becomes wider toward the nip portion in the order of the image forming units). From the viewpoint of preventing toner destruction, in FIG. 2, the width of the nip portion in the BK image forming unit is preferably wider than the width of the nip portion in the C image forming unit.

  The configuration in each developing unit, the method of stretching the paper transport belt 3, the method of driving the paper transport belt 3 and the photosensitive drums 11 to 14, and the transfer bias applied by each transfer roll are shown in FIG. Since it is the same, it abbreviate | omits here.

  Further, a fixing device (not shown) is provided on the downstream side in the traveling direction of the recording medium P, and the toner image transferred onto the recording medium P is fixed by means such as pressurization, heating, and pressure heating.

  Here, an image forming mechanism in the image forming apparatus of FIG. 2 will be described. For example, taking Y as an example, the surface of the photoconductor roll 11 is charged by the charging roll 41. Next, the input image is color-separated (not shown), and only the yellow component is exposed by L1, thereby forming an electrostatic latent image. The developing device 51 develops the electrostatic latent image with a developer containing yellow toner. Next, the toner image is transferred onto the recording medium by the transfer roll 131. The toner remaining on the photoconductor 11 without being transferred is removed from the photoconductor 11 by a cleaning device (not shown) including a cleaning blade 61. This is performed for M, C, and BK toners, that is, the photoreceptors 12 to 14, and transfer images of four color toners are produced on the recording medium P and fixed (not shown) to obtain an image.

(Elastic belt)
Next, an elastic belt used as an intermediate transfer belt, a paper transport belt, or the like in the present invention will be described.
The elastic belt preferably includes a belt base material having elasticity and a conductive protective layer covering the surface of the belt base material. Here, examples of the belt base material used in the present invention include ethylene-propylene-diene copolymer rubber (EPDM), natural rubber (NR), isoprene rubber (IR), styrene-butadiene copolymer rubber (SBR), fluorine. Rubber (FKM), silicone rubber, epichlorohydrin rubber (CHR, ECO), polysulfide rubber, urethane rubber, and materials obtained by blending two or more of these are used, but are not limited thereto. . Of these, ethylene-propylene-diene copolymer rubber (EPDM), styrene-butadiene copolymer rubber (SBR), epichlorohydrin rubber (CHR, ECO), and urethane rubber are particularly preferably used. A material obtained by blending more than one kind is preferably used.
The resistance of the material is preferably adjusted by a conductive material (for example, carbon or other metal particles).

The material of the conductive protective layer is not particularly limited as long as it can achieve the purpose of improving the residual toner cleaning property by reducing the frictional resistance and the surface roughness, but generally includes a powder. It is configured by applying a conductive paint.
Examples of the powder include polytetrafluoroethylene (PTFE) and tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA). Among these, tetrafluoroethylene-perfluoroalkyl vinyl ether (PFA) is particularly preferable.
Examples of the resin used for the conductive paint include silicone resin, fluororesin, fluorosilicone resin, polyacetal resin, urethane emulsion paint, ethylene-vinyl acetate copolymer, alcohol-soluble nylon resin, epoxy resin, polyester resin, acrylic resin, etc. Among these, fluorine resin and silicone resin are preferable, and dimethyl silicone resin and methylphenyl silicone resin are particularly preferable.

  Examples of the method for applying the conductive paint include a spray method, an electrostatic method, a dipping method, a roll coater method, and a curtain flow method.

  Next, an example of an elastic belt manufacturing method will be described. Various additives such as a conductive material are added to the belt base material, and then extruded onto 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, for example, in a hot air oven at 130 to 200 ° C. for about 0.5 to 8 hours. The elastic belt of the present invention is cut into a predetermined length, and the front and back surfaces are polished.

(Static image developing toner)
Next, the toner to be used will be described. The toner used in the image forming apparatus of the present invention is characterized in that it contains at least a binder resin and a colorant and has a surface coated (preferably coated with inorganic particles).

  The toner used in the image forming apparatus of the present invention contains at least a binder resin. In this case, the binder resin contained in the toner may be a commonly used polymer alone, or may be mixed with a crystalline resin, for example. When the crystalline resin is mixed, the content of the crystalline resin is preferably 30% by mass or less. When the content of the crystalline resin contained in the toner exceeds 30% by mass, the amount of deformation of the toner remaining on the photoconductor after passing through the transfer nip increases, and the image quality of image loss due to adhesion of the toner to the photoconductor. A failure may occur.

The glass transition temperature of the toner used in the image forming apparatus of the present invention is preferably in the range of 45 to 70 ° C, and more preferably in the range of 50 to 70 ° C. Since the toner is likely to be deformed due to pressure at the glass transition temperature as a boundary, the amount of deformation of the toner remaining on the photoreceptor after passing through the transfer nip tends to increase in a temperature environment higher than the glass transition temperature. Since heat generated in the apparatus tends to stay due to downsizing of the apparatus in recent years, a relatively high glass transition temperature is necessary to suppress the deformation amount.
This glass transition temperature can be determined as the melting peak temperature of the input compensated differential scanning calorimetry based on “plastic transition temperature measurement method” of JIS K-7121: 87.

The volume average particle size of the toner used in the image forming apparatus of the present invention is preferably 3 to 8 μm, more preferably 4 to 7 μm, and the number average particle size is preferably 3 to 7 μm and more preferably 4 to 6 μm. preferable.
The volume average particle size and number average particle size can be measured by measuring with a Coulter Multisizer II type (manufactured by Beckman Coulter, Inc.) with an aperture diameter of 100 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. The average particle size is defined as the volume average particle size and the number average particle size when the cumulative distribution is drawn from the smaller diameter side with respect to the particle size range divided based on the particle size distribution, and the cumulative distribution is 50%.

The toner for developing an electrostatic charge image in the present invention preferably has a spherical coefficient (SF) represented by the following formula (4) of less than 140, more preferably 135 or less, and 130 or less. It is particularly preferred that
The spherical coefficient SF can be controlled by the heating conditions at the time of toner production, specifically, the heating time and the heating temperature. Generally, the heating time is long, and if the heating temperature is high, the shape becomes nearly spherical. By being in this range, the amount of residual toner at the time of transfer can be reduced, and since it is nearly spherical, there is an advantage that no stress remains in the toner particles and toner deformation hardly occurs.

SF = (πL ² / 4A) × 100 Formula (4)
(In Formula (4), L is the maximum diameter (μm) of the electrostatic image developing toner, and A is the projected area (μm ² ) of the electrostatic image developing toner.)

  The component constituting the toner used in the image forming apparatus of the present invention is not particularly limited as long as it contains at least a binder resin and a colorant, as described above. Other components may be included. 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.

-Binder resin-
The binder resin used for the toner used in the image forming apparatus of the present invention can be used by copolymerizing a polymerizable monomer alone or copolymerized. Specific examples of the polymerizable monomer include homopolymers or copolymers of styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, acrylic Homopolymers of esters having vinyl groups such as n-butyl acid, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate Or copolymers; homopolymers or copolymers of vinyl nitriles such as acrylonitrile and methacrylonitrile; homopolymers or copolymers of vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl methyl ketone, vinyl ethyl Ketone, vinyl isoprop Homopolymers or copolymers of ketone compounds, ethylene, propylene, butadiene, homopolymers or copolymers of olefins such as isoprene; and the like.

  Further, silicone resins including methyl silicone, methyl phenyl silicone, and the like, polyesters containing bisphenol, glycol, etc., epoxy resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, polycarbonate resins, and the like may be used.

  Specifically, among the polymerizable monomers, styrenes such as styrene, parachlorostyrene, and α-methylstyrene; short-chain alkyl acrylates such as methyl acrylate and methyl methacrylate; and acrylic acid n It is preferable to use a copolymer obtained by combining -propyl, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, or the like.

  Further, the binder resin may be crosslinked. By crosslinking, it is possible to adjust the shape at the time of preparation of the toner. In other words, the resin component tends to be spherical when heated, but the shape can be adjusted because crosslinking can suppress the change to a spherical shape.

  Specific examples of the crosslinking agent for crosslinking the binder resin include aromatic polyvinyl compounds such as divinylbenzene and divinylnaphthalene; divinyl phthalate, divinyl isophthalate, divinyl terephthalate, divinyl homophthalate, trimesic acid Polyvinyl esters of aromatic polycarboxylic acids such as divinyl / trivinyl, divinyl naphthalenedicarboxylate, and divinyl biphenylcarboxylate; divinyl esters of nitrogen-containing aromatic compounds such as divinyl pyridinedicarboxylate; vinyl pyromutinate, furancarboxylic acid Vinyl esters of unsaturated heterocyclic compounds such as vinyl, pyrrole-2-carboxylate and vinyl thiophenecarboxylate; butanediol methacrylate, hexanediol acrylate, octanediol methacrylate, deca (Meth) acrylic acid esters of linear polyhydric alcohols such as diol acrylate and dodecane diol methacrylate; branching such as neopentyl glycol dimethacrylate and 2-hydroxy-1,3-diacryloxypropane, substituted polyhydric alcohols (Meth) acrylic acid esters; polyethylene glycol di (meth) acrylate, polypropylene polyethylene glycol di (meth) acrylates; divinyl succinate, divinyl fumarate, vinyl / divinyl maleate, divinyl diglycolate, vinyl itaconate / divinyl , Divinyl acetone dicarboxylate, divinyl glutarate, divinyl 3,3′-thiodipropionate, trans-divinyl aconitic acid / trivinyl, divinyl adipate, divinyl pimelate, dibi suberate Le, azelaic acid, divinyl sebacate, divinyl dodecanedioate divinyl, the polyvinyl esters of polycarboxylic acids such as oxalic acid, divinyl; and the like.

  In this specification, “(meth) acrylate” means “acrylate and methacrylate”, and “(meth) acryl” means “acryl and methacryl”.

  In this invention, the said crosslinking agent may be used individually by 1 type, and may be used in combination of 2 or more type. Among the cross-linking agents, the cross-linking agent in the present invention is required to be polymerized slower than a normal polymerizable monomer, so that butanediol methacrylate, hexanediol acrylate, octanediol methacrylate, decane (Meth) acrylic acid esters of linear polyhydric alcohols such as diol acrylate and dodecane diol methacrylate; branching such as neopentyl glycol dimethacrylate and 2-hydroxy-1,3-diacryloxypropane, substituted polyhydric alcohols (Meth) acrylic acid esters; polyethylene glycol di (meth) acrylate, polypropylene polyethylene glycol di (meth) acrylates and the like are preferably used.

  The content of the crosslinking agent is preferably in the range of 0.05 to 5% by mass, more preferably in the range of 0.1 to 1.0% by mass, based on the total amount of polymerizable monomers.

Examples of the polymerization initiator when the binder resin used in the toner of the present invention is produced by radical polymerization of a polymerizable monomer include the following.

  There is no restriction | limiting in particular as an initiator for radical polymerization used here. Specifically, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide Ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, tert-butyl hydroperoxide pertriphenyl acetate, tert-butyl formate, Peroxides such as tert-butyl peracetate, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl permethoxyacetate, tert-butyl perN- (3-toluyl) carbamate;

2,2′-azobispropane, 2,2′-dichloro-2,2′-azobispropane, 1,1′-azo (methylethyl) diacetate, 2,2′-azobis (2-amidinopropane) Hydrochloride, 2,2′-azobis (2-amidinopropane) nitrate, 2,2′-azobisisobutane, 2,2′-azobisisobutyramide, 2,2′-azobisisobutyronitrile, 2, Methyl 2′-azobis-2-methylpropionate, 2,2′-dichloro-2,2′-azobisbutane, 2,2′-azobis-2-methylbutyronitrile, dimethyl 2,2′-azobisisobutyrate, 1 , 1′-azobis (sodium 1-methylbutyronitrile-3-sulfonate), 2- (4-methylphenylazo) -2-methylmalonodinitrile, 4,4′-azobis-4-cyano Herbic acid, 3,5-dihydroxymethylphenylazo-2-methylmalonodinitrile, 2- (4-bromophenylazo) -2-allylmalonodinitrile, 2,2′-azobis-2-methylvaleronitrile, 4, 4′-azobis-4-cyanovaleric acid dimethyl, 2,2′-azobis-2,4-dimethylvaleronitrile, 1,1′-azobiscyclohexanenitrile, 2,2′-azobis-2-propylbutyronitrile 1,1′-azobis-1-chlorophenylethane, 1,1′-azobis-1-cyclohexanecarbonitrile, 1,1′-azobis-1-cycloheptanenitrile, 1,1′-azobis-1-phenyl Ethane, 1,1′-azobiscumene, ethyl 4-nitrophenylazobenzylcyanoacetate, phenylazodiphenylmethane, phenol Ruazotriphenylmethane, 4-nitrophenylazotriphenylmethane, 1,1′-azobis-1,2-diphenylethane, poly (bisphenol A-4,4′-azobis-4-cyanopentanoate), poly Azo compounds such as (tetraethylene glycol-2,2′-azobisisobutyrate); 1,4-bis (pentaethylene) -2-tetrazene, 1,4-dimethoxycarbonyl-1,4-diphenyl-2 -Tetrazen etc. are mentioned.

  Among these, preferred are water-soluble compounds, specifically hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, peroxide. Examples thereof include dichlorobenzoyl, bromomethylbenzoyl peroxide, lauroyl peroxide, ammonium persulfate, sodium persulfate, potassium persulfate, and diisopropyl peroxycarbonate.

  When a polyester resin is used for the binder resin of the present invention, the crystalline polyester resin 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 acid include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and the like, and anhydrides thereof. And lower alkyl esters. These may be used individually by 1 type and may use 2 or more types together.

  Moreover, as an acid component, it is preferable that the dicarboxylic acid component which has a sulfonic acid group other than the above-mentioned aliphatic dicarboxylic acid and aromatic dicarboxylic acid is contained. 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 form fine particles, if there are sulfonic acid groups, as described later, emulsification or suspension can be performed without using a surfactant.

  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.

  As the polyhydric alcohol component, an aliphatic diol is preferable, and a linear aliphatic diol having 7 to 20 carbon atoms in the main chain portion is more preferable. 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, when the number of carbon atoms is less than 7, when the polycondensation with aromatic dicarboxylic acid is performed, the melting point becomes high and fixing at low temperature may be difficult. On the other hand, when the number exceeds 20, it is difficult to obtain practical materials. easy. 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 apparatus 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, pentaerythritol and the like. 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% 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.

  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. The monomer used as a raw material is mentioned.

  In the present invention, the resin particles 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 apparatus 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 polycarboxylic acids include terephthalic acid, isophthalic acid, phthalic anhydride, trimellitic anhydride, pyromellitic acid, naphthalenedicarboxylic acid, and other aromatic carboxylic acids, maleic anhydride, fumaric acid, succinic acid, alkenyl Examples thereof include aliphatic carboxylic acids such as 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 polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, glycerin, and other aliphatic diols, cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A And aromatic diols such as bisphenol A ethylene oxide adduct and bisphenol A propylene oxide adduct. 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 and the like, and examples of the monoalcohol include methanol, ethanol, propanol, octanol, 2-ethylhexanol, and trifluoroethanol. , Trichloroethanol, hexafluoroisopropanol, phenol and the like.

  The polyester resin can be produced by subjecting the polyhydric alcohol and polyhydric 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 apparatus of the present invention has a weight average molecular weight (Mw) of 5000 as determined by molecular weight measurement by gel permeation chromatography (GPC) method in which tetrahydrofuran (THF) is soluble. It is preferably ˜1000000, more preferably 7000 to 500,000, the number average molecular weight (Mn) is preferably 2000 to 100,000, and the molecular weight distribution Mw / Mn is preferably 1.5 to 30, More preferably, it is 2-20.

  When the weight average molecular weight and the number average molecular weight are smaller than the above ranges, while effective for low-temperature fixability, not only the hot offset resistance is remarkably deteriorated, but also the glass transition point of the toner is lowered. The storage stability such as toner blocking is also adversely affected. On the other hand, if the molecular weight is larger than the above range, the hot offset resistance can be sufficiently provided, but the low-temperature fixability is deteriorated and the oozing of the crystalline polyester phase present in the toner is inhibited, so that the document storage stability is reduced. May be adversely affected. 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 by using a TOSol 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 acid value of the polyester resin (the number of mg of KOH required to neutralize 1 g of resin) is easy to obtain the molecular weight distribution as described above, and is easy to ensure the granulation property of the toner particles by the emulsion dispersion method. From the standpoint of easy maintenance of the environmental stability (chargeability stability when the temperature and humidity are changed) of the obtained toner, it is preferably 1 to 30 mgKOH / g. 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 melting point of the crystalline polyester resin used in the present invention is preferably 35 to 100 ° C., and more preferably 50 to 80 ° C. from the viewpoint of the balance between storage stability and toner fixing property. 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 increases, which is not preferable.

-Release agent-
The release agent used in the toner 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 polypropylene, and low molecular weight polyethylene. Sazol wax, microcrystalline wax, Fischer-Tropsch wax, paraffin wax, montan wax and the like, or mineral-petroleum wax, fatty acid ester, montanic acid ester and the like, but are not limited thereto It is not a thing. 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.

-Colorant-
A colorant can also be used for the toner used in the image forming apparatus 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 apparatus 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.

-Other additives-
In addition to the above-described components, the toner used in the image forming apparatus 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 apparatus 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.

<Toner production method>
The method for producing the toner used in the image forming apparatus 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 using the emulsion aggregation method, the method for producing a toner for developing an electrostatic charge image of the present invention includes an aggregation step of forming the aggregated particles containing the crystalline polyester in a dispersion containing at least crystalline polyester fine particles, and the aggregation It is preferable to include at least an attachment step of attaching amorphous polymer fine particles to the surfaces of the particles, 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.

-Emulsification process-
In the emulsification step, the raw material dispersion is a solution in which a binder resin emulsified particle (hereinafter abbreviated as “resin particle”) is mixed with a dispersion containing an aqueous medium and, if necessary, a colorant and a release agent. Is formed by applying a shearing force. 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 stabilization at the time of dispersion in the suspension polymerization method, and dispersion stability of the resin particle dispersion, the colorant dispersion, and the release agent dispersion in the emulsion polymerization aggregation method. As the surfactant, a surfactant can be used.
Examples of the surfactant include sulfate surfactants, sulfonates, phosphates, soaps, and the like; amine surfactants, quaternary ammonium salt and other cationic surfactants; polyethylene glycol And nonionic surfactants such as polyphenols, alkylphenol ethylene oxide adducts, and polyhydric alcohols. Among these, an ionic surfactant is preferable, and an anionic surfactant and a cationic surfactant are more preferable.

In the toner used in the present invention, in general, an anionic surfactant has a strong dispersibility and is excellent in dispersion of resin particles and colorants. Therefore, an anionic surfactant is used as a surfactant for dispersing a release agent. It is preferable to use a system surfactant.
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 be used in combination of 2 or more type.

  Specific examples of the anionic surfactant include fatty acid soaps such as potassium laurate, sodium oleate and sodium castor oil; sulfate esters such as octyl sulfate, lauryl sulfate, lauryl ether sulfate and nonyl phenyl ether sulfate; lauryl Alkyl naphthalene sulfonate sodium such as sulfonate, dodecylbenzene sulfonate, triisopropyl naphthalene sulfonate, dibutyl naphthalene sulfonate; naphthalene sulfonate formalin condensate, monooctyl sulfosuccinate, dioctyl sulfosuccinate, lauric acid amide sulfonate, oleic acid amide sulfonate, etc. Sulfonates: lauryl phosphate, isopropyl phosphate, nonylphenyl ether Phosphoric acid esters such as Ruhosufeto; dialkyl sulfosuccinate salts such as sodium dioctyl sulfosuccinate; sulfosuccinate salts such as sulfosuccinate lauryl disodium; and the like.

  Specific examples of the cationic surfactant include amine salts such as laurylamine hydrochloride, stearylamine hydrochloride, oleylamine acetate, stearylamine acetate, stearylaminopropylamine acetate; lauryltrimethylammonium chloride, dilauryldimethyl. Ammonium chloride, distearyldimethylammonium chloride, distearyldimethylammonium chloride, lauryldihydroxyethylmethylammonium chloride, oleylbispolyoxyethylenemethylammonium chloride, lauroylaminopropyldimethylethylammonium ethosulphate, lauroylaminopropyldimethylhydroxyethylammonium perchlorate, Alkylbenzene trimethylammonium chloride Quaternary ammonium salts such as alkyl trimethyl ammonium chloride; and the like.

  Specific examples of the nonionic surfactant include polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether and other alkyl ethers; Alkylphenyl ethers such as oxyethylene nonylphenyl ether; alkyl esters such as polyoxyethylene laurate, polyoxyethylene stearate, polyoxyethylene oleate; polyoxyethylene lauryl amino ether, polyoxyethylene stearyl amino ether, polyoxy Alkylamines such as ethylene oleyl amino ether, polyoxyethylene soybean amino ether, polyoxyethylene beef tallow amino ether; Alkyl amides such as xylethylene lauric acid amide, polyoxyethylene stearic acid amide, polyoxyethylene oleic acid amide; vegetable oil ethers such as polyoxyethylene castor oil ether, polyoxyethylene rapeseed oil ether; lauric acid diethanolamide, stearin Alkanolamides such as acid diethanolamide and oleic acid diethanolamide; sorbitan ester ethers such as polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmiate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate And the like.

  The content of the surfactant in the resin particle dispersion, the colorant dispersion, and the release agent dispersion may be a level that does not inhibit the present invention, and is generally a small amount. It is preferable that it is 0.01-10 mass%, It is more preferable that it is the range of 0.05-5 mass%, It is still more preferable that it is 0.1-2 mass%. When the content of the surfactant is less than 0.01% by mass, each dispersion such as a resin particle dispersion, a colorant dispersion, and a release agent dispersion may become unstable. In some cases, the specific particles may be liberated due to the difference in stability between the particles during aggregation. On the other hand, when the content of the surfactant exceeds 10% by mass, the particle size distribution of the particles may become wide, and the control of the particle size may be difficult. In general, a suspension polymerization toner dispersion having a large particle size is stable even if the amount of the surfactant used is small.

Further, as the dispersion stabilizer used in the suspension polymerization method, a slightly water-soluble and hydrophilic inorganic fine powder can be used. Examples of the inorganic fine powder that can be used include silica, alumina, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate (hydroxyapatite), clay, diatomaceous earth, bentonite and the like. Among these, calcium carbonate, tricalcium phosphate, and the like are preferable from the viewpoints of easy particle size formation and easy removal.
Furthermore, a room-temperature solid aqueous polymer or the like can also be used. Specifically, cellulose compounds such as carboxymethyl cellulose and hydroxypropyl cellulose, polyvinyl alcohol, gelatin, starch, gum arabic and the like can be used. Examples thereof 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.

  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, if the resin particle is a polyester resin, it contains a functional group that can be anionic by neutralization, and if it has self-water dispersibility, a part or all of the functional group that can be hydrophilic is neutralized with a base. A stable aqueous dispersion can be formed under the action of an aqueous medium. Since functional groups that can become hydrophilic groups by neutralization in polyester resins are acidic groups such as carboxyl groups and sulfone groups, examples of neutralizing agents include sodium hydroxide, potassium hydroxide, lithium hydroxide, and calcium hydroxide. And inorganic bases such as sodium carbonate and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine.

  Further, when a polyester resin that does not disperse in water, that is, does not have self-water dispersibility, is used as a binder resin, the resin solution and / or an aqueous medium mixed with the resin solution, as described later, 1 μm easily when dispersed with a polymer electrolyte such as a surfactant, polymer acid, polymer base, etc., heated above the melting point, and treated with a homogenizer or pressure discharge type disperser capable of applying a strong shear force The following microparticles can be made. When this ionic surfactant or polymer electrolyte is used, the concentration in the aqueous medium is suitably about 0.5 to 5% by mass.

  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 homogenizer (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 and the content of each of the colorant and the release agent in the dispersion of the colorant and the release agent are usually 5 to 50% by mass. The amount is preferably 10 to 40% by mass. When the content is outside the above range, the particle size distribution may be widened and the characteristics may be deteriorated.

  In the present invention, other components such as the internal additive, the charge control agent, and the inorganic powder as described above may be dispersed in the binder resin dispersion according to the purpose. 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.

-Aggregation process-
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, and as a result, the particle size distribution becomes broad. Further, it is effective to add the dispersion stabilizer separately in both the pre-aggregation step and the heat aggregation step.

-Adhesion process-
In the attaching step, the amorphous polymer particles are attached to the surface of the agglomerated particles containing the crystalline polyester (hereinafter abbreviated as “core agglomerated particles”) formed through the agglomeration step, thereby forming a coating layer ( Hereinafter, the core aggregated particle surface provided with a coating layer is abbreviated as “attached 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.

-Fusion process-
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. Become. 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 less than the softening point or 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, components other than the binder resin contained in the core aggregated particles are 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.

  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% by mass or less, preferably 0.5% by mass or less.

<Developer>
The image forming apparatus of the present invention uses the toner described above 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 these core materials, and magnetic powder-dispersed 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 (mass 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 more specifically with reference to examples. However, the present invention is not limited to the following examples. In the examples, “part” is based on mass.

  In each example and comparative example, the image forming apparatus of the present invention shown in FIG. 1 was used. The four color toners Y (yellow), M (magenta), C (cyan), and BK (black) are manufactured as follows.

-Manufacture of toner base particles-
(Preparation of resin particle dispersion)

Oil layer Styrene (Wako Pure Chemicals) 30 parts n-Butyl acrylate (Wako Pure Chemicals) 10 parts β-Carboethyl acrylate (Rhodia Nikka) 1.1 parts Acrylic acid 0.2 parts Dodecanethiol (Wako Pure) 0.4 parts water layer 1
Ion-exchanged water 17.0 parts Anionic surfactant (Dow Fax, Dow Fax) 0.39 parts Aqueous layer 2
Deionized water 40 parts Anionic surfactant (Dowfax, Dowfax) 0.06 parts Potassium persulfate (Wako Pure Chemical) 0.20 parts Ammonium persulfate (Wako Pure Chemical) 0.20 parts

  The oil layer component and the water layer 1 component were placed in a flask and mixed with stirring to obtain a monomer emulsified dispersion. Furthermore, the components of the aqueous layer 2 were put into a reaction vessel, and the inside of the vessel was sufficiently replaced with nitrogen and stirred, and then heated in an oil bath until the temperature in the reaction system reached 70 ° C. The monomer emulsion dispersion was gradually dropped into the reaction vessel over 3 hours to carry out emulsion polymerization. After completion of the dropping, the polymerization was further continued at 70 ° C., and the polymerization was terminated after 3 hours to obtain a resin fine particle dispersion.

The obtained resin particles were 220 nm when the number average particle diameter D _50n was measured, 51.5 ° C. when the glass transition point was measured, and 32000 when the number average molecular weight (polystyrene conversion) was measured. . From the above, a resin particle dispersion having the above characteristics was obtained.

(Preparation of release agent dispersion)
Polyalkylene wax FNP0092 (melting point: 91 ° C., manufactured by Nippon Seiwa Co., Ltd.) 50 parts Cationic surfactant Neogen RK (Daiichi Kogyo Seiyaku Co., Ltd.) 5 parts Ion-exchanged water 195 parts After sufficiently dispersing at T50, dispersion treatment was performed with a pressure discharge type gorin homogenizer to obtain a release agent dispersion having a center diameter of 190 nm and a solid content of 24.3 mass%.

(Preparation of yellow (Y) colorant dispersion)
C. I. Pigment Yellow 74 (monoazo pigment) ... 100 parts (Daiichi Seika Co., Ltd .: Seika First Yellow 2054)
Anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) ... 10 parts Ion-exchanged water ... 490 parts The above components were mixed and dissolved, and dispersed for 10 minutes using a homogenizer (manufactured by IKA: Ultra Tarrax) to prepare a yellow (Y) colorant dispersant.

(Preparation of magenta (M) colorant dispersion)
The colorant is C.I. I. A magenta (M) colorant dispersion was prepared in the same manner as the yellow (Y) colorant dispersion except that it was changed to CI Pigment Red 122 (quinacridone pigment: manufactured by Dainichi Seika Co., Ltd .: Chromofine Magenta 6887).

(Preparation of Cyan (C) Colorant Dispersion)
The colorant is C.I. I. A cyan (C) colorant dispersion was prepared in the same manner as the yellow (Y) colorant dispersion except that the pigment was changed to Pigment Blue 15: 3 (phthalocyanine pigment: manufactured by Dainichi Seika Co., Ltd .: Cyanine Blue 4937).

(Preparation of black (BK) colorant dispersion)
A black (BK) colorant dispersion was prepared in the same manner as the yellow (Y) colorant dispersion, except that the colorant was changed to Mogal L (carbon black: manufactured by Cabot).

(Manufacture of magenta (M) toner base particles)
The following composition was mixed to produce magenta (M) toner base particles.
-Resin particle dispersion: 130.8 parts-Release agent dispersion: 50 parts-Magenta colorant dispersion: 35 parts-Nonionic surfactant (IGEPAL CA897: manufactured by Rhône-Poulenc): 1.05 parts-Ion Exchanged water: 459 parts Aluminum sulfate: 5.2 parts The above was thoroughly mixed and dispersed in a round stainless steel flask with Ultra Turrax T50 (manufactured by IKA).
While stirring the flask in a heating oil bath, the flask was heated to 49 ° C. at 1 ° C./min. After holding at 49 ° C. for 40 minutes, it was confirmed that aggregated particles having a volume average particle diameter D50 of 5.1 μm were formed.
When the temperature of the heating oil bath was further raised and held at 50 ° C. for 2 hours, the volume average particle diameter D50 of the aggregated particles was 5.4 μm. Thereafter, 65 parts of the resin particle dispersion was added to the dispersion containing the aggregated particles, and then the temperature of the heating oil bath was set to 50 ° C. and held for 30 minutes. After adjusting the pH of the system to 6.5 by adding a 1N sodium hydroxide solution to the dispersion containing the aggregated particles, the stainless steel flask is sealed, and the stirring is continued using a magnetic seal up to 93 ° C. Heated and held for 6 hours.
After cooling, the reaction product was filtered off, washed four times with ion exchange water, and then lyophilized to produce magenta (M) toner base particles. The volume average particle diameter D50 of the toner base particles (1) is 5.5 μm, and the average value of the shape factor SF1 is 131.

Subsequently, except that the magenta (M) colorant dispersion was changed to a yellow (Y) colorant dispersion, a cyan (C) colorant dispersion, and a black (K) colorant dispersion, respectively. Yellow (Y), cyan (C) and black (BK) toner base particles were produced.
The volume average particle diameter and shape factor SF of each toner base particle are shown below. (Volume average particle diameter, shape factor SF)
Magenta (M) toner base particles (5.5 μm, 131)
Yellow (Y) toner base particles (5.5 μm, 133)
Cyan (C) toner base particles (5.7 μm, 130)
Black (BK) toner base particles (5.8 μm, 131)

-Manufacture of toner-
To each of the toner base particles, 1.2 parts of titania particles having a primary particle diameter of 20 nm as an external additive were added with respect to 100 parts of the toner, and mixed with a Henschel mixer to obtain a toner.

-Carrier manufacturing-
Adjust the mixture of SR2410 and SR2411 (both manufactured by Toray Dow Corning Silicone Co., Ltd.) 1: 1 to 100 parts of ferrite core (Powder Tech: F-300) so that the solid content is 1.5 parts. Further, 50 parts of toluene was added, and the above was heated, put in a vacuum kneader, sealed, heated and mixed until it reached 70 at normal pressure, heated to 90 ° C., allowed to stand for 30 minutes, and then the internal pressure Was reduced to 100 Pa, and the solvent was distilled off. After 1 hour, the internal temperature was raised to 150 ° C. and left for another 1 hour, and then cooled to obtain a carrier.

-Production of developer-
5 parts of each toner and 100 parts of the carrier were mixed and used as a negatively chargeable two-component developer.

As the photoconductors 11 to 14, an organic photoconductor having a diameter of 47 mm is used, the intermediate transfer belt 2 is an elastic belt containing chloroprene rubber as a main component, and the stretch rate represented by the above formula (3) is 3. Set to 8%.
In the following examples and comparative examples, the nip width of the nip portion formed between the photoconductor 11 and the intermediate transfer belt 2 (that is, the Y image forming unit) in FIG. The nip width of the nip portion formed in the forming unit is denoted as Nm, the nip width of the nip portion formed in the C image forming unit is denoted as Nc, and the nip width of the nip portion formed in the BK image forming unit is denoted as Nk. Further, the transfer current value in the Y image forming unit is Ay, and thereafter, similarly, Am, Ac, and Ak.

Example 1
The nip widths Ny, Nm, Nc, Nk between the photoconductors 11, 12, 13, and 14 of the image forming apparatus shown in FIG. 1 and the intermediate transfer belt 2, and transfer current values Ay, Am, Ac and Ak were set as shown in Table 1, respectively.
Next, by using the image forming apparatus, an A3 size P paper (manufactured by Fuji Xerox) was used as a recording material, and an electrophotographic society test chart No. A 10000 running test was performed on a full-color image of 5-1, and color reproducibility was evaluated according to the following criteria.
The evaluation results are shown in Table 1 together with the calculated values of the above formulas (1) and (2) showing the preferable conditions of the nip width and the transfer current value.

[Color reproducibility]
The color reproducibility of the secondary color red, green, and blue portions of the test chart and the number of sheets when the color tone of the process black portion of the person background changed were confirmed every 200 sheets. However, although there was no problem after outputting 10,000 sheets, the evaluation was 10000 or more, and no more was performed. Moreover, if it was 6000 or more, it was set as the pass.

(Examples 2 to 15 and Comparative Examples 1 to 3)
Each of the nip widths Ny, Nm, Nc, Nk and the transfer current values Ay, Am, Ac, Ak at each nip part were changed as shown in Table 1, and the running test was performed in the same manner as in Example 1. Performed and evaluated. The evaluation results are shown in Table 1.

1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention including an intermediate transfer belt. 1 is a schematic diagram illustrating an example of an image forming apparatus according to the present invention including a sheet conveying belt.

Explanation of symbols

2 Intermediate transfer belt 3 Paper transport belt 7 Secondary transfer roll 11, 12, 13, 14 Photosensitive roll 31, 32, 33, 34 Primary transfer roll 41, 42, 43, 44 Charging roll 51, 52, 53, 54 Development Machine 61, 62, 63, 64 Cleaning blade 131, 132, 133, 134 Transfer roll 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112 Stretch roll

Claims (9)

A plurality of drum-shaped image carriers that form a toner image on the surface using a toner for color electrostatic charge image development that includes a colorant and a binder resin and is coated with a coating layer;
An elastic belt disposed in contact with each other so as to form a nip portion along each shape of the plurality of drum-shaped image carriers,
An image forming apparatus that sequentially superimposes and transfers toner images formed on the plurality of image carriers at respective nip portions,
The width in the circumferential direction of the nip portion is increased as the nip portion in the downstream direction in which the elastic belt moves,
An image forming apparatus, wherein a transfer current value to be applied is lowered toward a nip portion in a downstream direction in which the elastic belt moves. Three color toners of yellow, magenta and cyan are used as toners for developing electrostatic images of the color, and toner images are formed on the surface of different drum-shaped image carriers by the respective color toners. An image forming apparatus that sequentially superimposes and transfers, wherein in each of the nip portions, the circumferential width of the nip portion and the applied transfer current value satisfy the following expressions (1) and (2): The image forming apparatus according to claim 1.
Formula (1) 1.05 ≦ N3 / N2 ≦ N2 / N1 ≦ 1.5
Formula (2) 0.7 ≦ A3 / A2 ≦ A2 / A1 ≦ 0.95
(Where N1 is the circumferential width of the nip portion where the toner image is transferred first, N2 is the circumferential width of the nip portion where the toner image is transferred second, and N3 is the third toner image. represents the width in the circumferential direction of the nip portion for performing transfer of. Moreover, A1 is first a transfer current value at the nip portion for performing transfer of the toner image, A2 is the transfer current at the nip portion for performing transfer of the toner image to the second (A3 represents the transfer current value at the nip portion where the toner image is transferred third.)   The elastic belt covers at least one surface of a belt base material comprising two or more different kinds of elastic materials and at least one surface of the belt base material, and includes at least one selected from a fluororesin and a silicone resin The image forming apparatus according to claim 1, further comprising: a protective layer contained therein.   4. The image forming apparatus according to claim 1, wherein one of the image carrier and the elastic belt is used as a drive source, and the other is driven to rotate. 5. When the elastic belt is stretched by a plurality of stretching rolls and the circumferential length of the elastic belt in the stretched state is C, and the circumferential length of the elastic belt in the unstretched state is c, the following formula (3 5. The image forming apparatus according to claim 1, wherein a stretch rate represented by 2) is 2 to 5%.
Tension ratio (%) = (C−c) / c × 100 Formula (3) 6. The image formation according to claim 1, wherein a value of a spherical coefficient (SF) represented by the following formula (4) in the electrostatic image developing toner is less than 140. apparatus.
SF = (πL ² / 4A) × 100 Formula (4)
(In Formula (4), L is the maximum diameter (μm) of the electrostatic image developing toner, and A is the projected area (μm) of the electrostatic image developing toner.)   7. The image forming apparatus according to claim 1, wherein the electrostatic charge image developing toner has a volume average particle diameter of 3 μm to 8 μm.   The image forming apparatus according to claim 1, wherein the elastic belt is an intermediate transfer belt.   The image forming apparatus according to claim 1, wherein the elastic belt is a paper conveyance belt.

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