JP2018004696A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of adjusting the glossiness of an image formed on a sheet, while suppressing the increase of the size of an apparatus body.SOLUTION: An image forming apparatus 1 includes color image forming units 62Y, 62C, 62M, and 62K for forming a color toner image, a transparent image forming unit 62T for forming a transparent toner image, a transfer device 7, and a control part 10. In the transfer device 7, the transparent toner image is overlapped on the color toner image and transferred to a sheet S. The control part 10 controls the operation of the transparent image forming unit 62T. The transparent image forming unit 62T includes an image carrier 65 on which an electrostatic latent image is formed and a developing device 64. The developing device 64 develops the electrostatic latent image with first toner and second toner whose melting point is higher than that of the first toner. The control part 10 changes a toner development ratio calculated by the first toner development amount of the first toner used for the development of the electrostatic latent image and the second toner development amount of the second toner used for the development of the electrostatic latent image.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus and an image forming method.

  Among electrophotographic image forming apparatuses, there is an apparatus that can adjust the glossiness of an image formed on a sheet. For example, Patent Document 1 discloses an image forming apparatus that adjusts the glossiness of an image by superimposing a transparent toner image on a colored toner image. Specifically, the image forming apparatus disclosed in Patent Document 1 adjusts the ratio of the gloss type transparent toner and the mat type transparent toner contained in the transparent toner image formed on the sheet, thereby adjusting the glossiness of the image. adjust.

JP 2013-109276 A

  However, the image forming apparatus disclosed in Patent Document 1 includes two image forming units that form a transparent toner image in order to adjust the glossiness. Specifically, the image forming apparatus disclosed in Patent Document 1 includes an image forming unit that forms a glossy transparent toner image and an image forming unit that forms a mat type transparent toner image. Each image forming unit has a developing roller and a photosensitive drum. Therefore, the main body of the image forming apparatus is increased in size.

  The present invention has been made in view of the above problems, and provides an image forming apparatus and an image forming method capable of changing the glossiness of an image formed on a sheet while suppressing an increase in size of the apparatus main body. Objective.

  The image forming apparatus according to the present invention includes a colored image forming unit, a transparent image forming unit, a transfer device, and a control unit. The colored image forming unit forms a colored toner image. The transparent image forming unit forms a transparent toner image. The transfer device transfers the transparent toner image on the colored toner image so as to overlap the sheet. The control unit controls the operation of the transparent image forming unit. The transparent image forming unit includes an image carrier and a developing device. An electrostatic latent image is formed on the image carrier. The developing device develops the electrostatic latent image with a first toner and a second toner having a melting point higher than that of the first toner. The control unit includes a first toner development amount of the first toner used for developing the electrostatic latent image, and a second toner development amount of the second toner used for developing the electrostatic latent image. The toner development ratio calculated by is changed.

  The image forming method according to the present invention includes the following steps. Forming a colored toner image; Forming a transparent toner image; Transferring the transparent toner image onto a sheet on the colored toner image. The step of forming the transparent toner image includes the following steps. Forming an electrostatic latent image on the image carrier; The first toner development amount of the first toner used for developing the electrostatic latent image and the second toner development of the second toner having a melting point higher than that of the first toner used for developing the electrostatic latent image And developing the electrostatic latent image by changing a toner development ratio calculated according to the amount.

  ADVANTAGE OF THE INVENTION According to this invention, the glossiness of the image formed on a sheet | seat can be changed, suppressing the enlargement of an apparatus main body.

1 is a diagram illustrating a configuration of an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a diagram illustrating a configuration of a first toner container according to Embodiment 1 of the present invention. 1 is a diagram illustrating a configuration of a developing device according to a first embodiment of the present invention. It is a figure which shows the image development process which concerns on Embodiment 1 of this invention. 1 is a block diagram illustrating a configuration of an image forming apparatus according to Embodiment 1 of the present invention. It is a figure which shows the developing bias which concerns on Embodiment 1 of this invention. It is a flowchart which shows the glossiness fine adjustment process which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the image forming apparatus which concerns on Embodiment 2 of this invention. It is a flowchart which shows the glossiness rough adjustment process which concerns on Embodiment 2 of this invention.

[Embodiment 1]
Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof is not repeated.

  Hereinafter, a compound and its derivatives may be generically named by adding “system” after the compound name. In addition, when “polymer” is added after the compound name to indicate the polymer name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Furthermore, acryl and methacryl are sometimes collectively referred to as “(meth) acryl”.

In the following, the average value means a number average value unless otherwise specified. Further, an evaluation value (a value indicating a shape or physical property) regarding a powder (for example, toner or toner particles) means a number average value unless specified. The number average value is a value obtained by dividing the sum of the values measured for a considerable number of measurement objects by the number of measurements. Further, the particle diameter of the powder is the equivalent-circle diameter of primary particles measured by an electron microscope unless otherwise specified. The equivalent circle diameter is the diameter of a circle having the same area as the projected area of the particles. The volume median diameter D ₅₀ is a median diameter calculated on a volume basis using a Coulter counter method.

<Configuration of image forming apparatus>
First, the configuration of the image forming apparatus 1 according to the embodiment of the present disclosure will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of the image forming apparatus 1. The image forming apparatus 1 is, for example, a tandem color printer.

  As shown in FIG. 1, the image forming apparatus 1 includes an operation unit 2, a paper feeding unit 3, a transport unit 4, a toner replenishing unit 5, an image forming unit 6, a fixing device 8, a discharge unit 9, and a control unit 10. .

  The operation unit 2 receives an instruction from the user. When the operation unit 2 receives an instruction from the user, the operation unit 2 transmits a signal indicating the instruction from the user to the control unit 10. The operation unit 2 includes a liquid crystal display 21 and a plurality of operation keys 22. The liquid crystal display 21 displays various processing results, for example. The operation keys 22 include, for example, a numeric keypad and a start key. When an instruction indicating the execution of the image forming process is input, the operation unit 2 transmits a signal indicating the execution of the image forming process to the control unit 10. As a result, the image forming operation by the image forming apparatus 1 is started. Further, the user can designate the gloss value of the image formed on the sheet by operating the operation unit 2. When the glossiness value is designated, the operation unit 2 transmits a signal indicating the glossiness value to the control unit 10.

  The paper feed unit 3 includes a paper feed cassette 31 and a paper feed roller group 32. The paper feed cassette 31 can store a plurality of sheets S. The paper feed roller group 32 feeds the sheets S stored in the paper feed cassette 31 to the transport unit 4 one by one.

  The conveyance unit 4 includes a roller and a guide member. The transport unit 4 extends from the paper feed unit 3 to the discharge unit 9. The transport unit 4 transports the sheet S from the paper feed unit 3 to the discharge unit 9 so as to pass through the image forming unit 6 and the fixing device 8.

  The toner supply unit 5 supplies toner to the image forming unit 6. In the present embodiment, the toner includes a colored toner and a transparent toner. The colored toner is a powder composed of a plurality of colored toner particles. The transparent toner is a powder composed of a plurality of transparent toner particles. Hereinafter, the color toner and the transparent toner may be collectively referred to as “toner”. Further, the colored toner particles and the transparent toner particles may be collectively referred to as “toner particles”.

  The transparent toner includes a low melting point transparent toner and a high melting point transparent toner. The low melting point transparent toner is an example of a first toner. The high melting point transparent toner is an example of a second toner.

  The low melting point transparent toner melts at a lower temperature than the high melting point transparent toner. The low melting point transparent toner includes low melting point transparent toner particles. The high melting point transparent toner includes high melting point transparent toner particles. The low melting point transparent toner particles contain a resin having a lower melting point than the resin contained in the high melting point transparent toner particles. The resin contained in the transparent toner particles is, for example, a polyester resin. In this embodiment, the melting point of the polyester resin contained in the low melting point transparent toner particles is 95 ° C., for example. The melting point of the polyester resin contained in the high melting point transparent toner particles is, for example, 105 ° C. The difference between the melting point of the high melting point transparent toner and the melting point of the low melting point transparent toner is preferably 5 ° C. to 15 ° C.

  The toner replenishing unit 5 includes a first mounting unit 51L, a second mounting unit 51H, a third mounting unit 51Y, a fourth mounting unit 51C, a fifth mounting unit 51M, and a sixth mounting unit 51K. The first mounting unit 51L is an example of a first toner supply device, and the second mounting unit 51H is an example of a second toner supply device.

  A first toner container 52L is attached to the first attachment portion 51L. Similarly, the second toner container 52H is provided in the second attachment portion 51H, the third toner container 52Y is provided in the third attachment portion 51Y, the fourth toner container 52C is provided in the fourth attachment portion 51C, and the fifth attachment portion 51M. The fifth toner container 52M is mounted on the sixth mounting portion 51K, and the sixth toner container 52K is mounted on the sixth mounting portion 51K. Note that the configurations of the first mounting unit 51L to the sixth mounting unit 51K are the same except for the types of toner containers to be mounted. For this reason, the first mounting portion 51L to the sixth mounting portion 51K may be collectively referred to as “mounting portion 51”.

  Transparent toner is stored in the first toner container 52L and the second toner container 52H. Specifically, the low-melting point transparent toner is accommodated in the first toner container 52L. The second toner container 52H contains high melting point transparent toner. The high melting point transparent toner may be stored in the first toner container 52L, and the low melting point transparent toner may be stored in the second toner container 52H.

  The third, fourth, fifth, and sixth toner containers 52Y, 52C, 52M, and 52K store colored toners, respectively. In the present embodiment, yellow toner is stored in the third toner container 52Y. The fourth toner container 52C contains cyan toner. The fifth toner container 52M stores magenta toner. The sixth toner container 52K stores black toner.

  The image forming unit 6 includes an exposure device 61 and a transfer device 7. The image forming unit 6 further includes a first image forming unit 62T, a second image forming unit 62Y, a third image forming unit 62C, a fourth image forming unit 62M, and a fifth image forming unit 62K. The first image forming unit 62T is an example of a transparent image forming unit. The second to fifth image forming units 62Y to 62K are examples of colored image forming units.

  Each of the first to fifth image forming units 62T to 62K includes a charging device 63, a developing device 64, and a photosensitive drum 65. The photosensitive drum 65 is an example of an image carrier.

  The charging device 63 and the developing device 64 are arranged along the peripheral surface of the photosensitive drum 65. In the present embodiment, the photosensitive drum 65 rotates in the direction (clockwise) indicated by the arrow R1 in FIG.

  The charging device 63 uniformly charges the photosensitive drum 65 to a predetermined polarity by discharging. In the present embodiment, the charging device 63 charges the photosensitive drum 65 to a positive polarity. The exposure device 61 irradiates the charged photosensitive drum 65 with laser light. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 65.

  The developing device 64 develops the electrostatic latent image formed on the surface of the photosensitive drum 65 to form a toner image. The developing device 64 is supplied with toner from the toner supply unit 5. The developing device 64 supplies the toner supplied from the toner supply unit 5 to the surface of the photosensitive drum 65. As a result, a toner image is formed on the surface of the photosensitive drum 65.

  In the present embodiment, the ratio (toner development ratio) between the high melting point transparent toner and the low melting point toner contained in the transparent toner used for developing the electrostatic latent image is changed.

  In the present embodiment, the developing device 64 included in the first image forming unit 62T is connected to the first mounting portion 51L and the second mounting portion 51H. Accordingly, transparent toner (low melting point transparent toner and high melting point transparent toner) is supplied to the developing device 64 included in the first image forming unit 62T. Therefore, a transparent toner image is formed on the surface of the photosensitive drum 65 included in the first image forming unit 62T.

  The developing device 64 included in the second image forming unit 62Y is connected to the third mounting portion 51Y. Therefore, yellow toner is supplied to the developing device 64 included in the second image forming unit 62Y. Therefore, a yellow toner image is formed on the surface of the photosensitive drum 65 included in the second image forming unit 62Y.

  The developing device 64 included in the third image forming unit 62C is connected to the fourth mounting portion 51C. Accordingly, cyan toner is supplied to the developing device 64 included in the third image forming unit 62C. Accordingly, a cyan toner image is formed on the surface of the photosensitive drum 65 included in the third image forming unit 62C.

  The developing device 64 included in the fourth image forming unit 62M is connected to the fifth mounting portion 51M. Accordingly, the developing device 64 included in the fourth image forming unit 62M is supplied with magenta toner. Therefore, a magenta toner image is formed on the surface of the photosensitive drum 65 included in the fourth image forming unit 62M.

  The developing device 64 included in the fifth image forming unit 62K is connected to the sixth mounting portion 51K. Therefore, the black toner is supplied to the developing device 64 included in the fifth image forming unit 62K. Therefore, a black toner image is formed on the surface of the photosensitive drum 65 included in the fifth image forming unit 62K.

  The transfer device 7 transfers each toner image formed on the surface of each photosensitive drum 65 included in each of the first to fifth image forming units 62T to 62K on the sheet S in an overlapping manner. In the present embodiment, the transfer device 7 transfers each toner image on the sheet S while being transferred by the secondary transfer method. Specifically, the transfer device 7 includes five primary transfer rollers 71, an intermediate transfer belt 72, a drive roller 73, a driven roller 74, and a secondary transfer roller 75.

  The intermediate transfer belt 72 is an endless belt that is stretched around five primary transfer rollers 71, a driving roller 73, and a driven roller 74. The intermediate transfer belt 72 is driven according to the rotation of the drive roller 73. In FIG. 1, the intermediate transfer belt 72 rotates counterclockwise. The driven roller 74 is driven to rotate according to the driving of the intermediate transfer belt 72.

  The first to fifth image forming units 62T to 62K are arranged facing the lower surface of the intermediate transfer belt 72 along the driving direction D of the lower surface of the intermediate transfer belt 72. In the present embodiment, the first to fifth image forming units 62T to 62K are arranged in the order of the first to fifth image forming units 62T to 62K from the upstream side to the downstream side in the driving direction D on the lower surface of the intermediate transfer belt 72. It is arranged with.

  Each primary transfer roller 71 is disposed to face each photosensitive drum 65 via the intermediate transfer belt 72 and is pressed toward each photosensitive drum 65. Therefore, the toner images formed on the surface of each photoconductor drum 65 are sequentially transferred to the intermediate transfer belt 72. In this embodiment, a transparent toner image, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are transferred onto the intermediate transfer belt 72 in this order. Hereinafter, a toner image in which a transparent toner image, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image are superimposed may be referred to as a “laminated toner image”. Further, a yellow toner image, a cyan toner image, a magenta toner image, and a black toner image may be collectively referred to as a “colored toner image”.

  The secondary transfer roller 75 is disposed to face the drive roller 73 with the intermediate transfer belt 72 interposed therebetween. The secondary transfer roller 75 is pressed toward the drive roller 73. Thereby, a transfer nip is formed between the secondary transfer roller 75 and the driving roller 73. When the sheet S passes through the transfer nip, the laminated toner image on the intermediate transfer belt 72 is transferred to the sheet S. In this embodiment, the transparent toner image, the yellow toner image, the cyan toner image, the magenta toner image, and the black toner image are transferred to the sheet S in this order from the upper layer to the lower layer. That is, the transparent toner image is transferred onto the sheet S so as to overlap the colored toner image. The sheet S to which the laminated toner image has been transferred is conveyed toward the fixing device 8 by the conveyance unit 4.

  The fixing device 8 includes a heating member 81 and a pressure member 82. The heating member 81 and the pressure member 82 are arranged to face each other and form a fixing nip. The sheet S conveyed from the image forming unit 6 is heated and pressed by passing through the fixing nip. As a result, the laminated toner image is fixed on the sheet S. The sheet S is conveyed from the fixing device 8 toward the discharge unit 9 by the conveyance unit 4.

  The discharge unit 9 includes a discharge roller pair 91 and a discharge tray 92. The discharge roller pair 91 conveys the sheet S to the discharge tray 92 through the discharge port 1a. The discharge port 1 a is formed in the upper part of the image forming apparatus 1.

  The control unit 10 controls the operation of each unit included in the image forming apparatus 1.

<Configuration of toner container>
Next, the configuration of the first to sixth toner containers 52L to 52K will be described with reference to FIG. FIG. 2 is a diagram illustrating a configuration of the first toner container 52L. FIG. 2 shows the developing device 64 for easy understanding. The developing device 64 includes a developing container 640 having a toner supply port 640h formed on the upper surface.

  As shown in FIG. 2, the first toner container 52 </ b> L has a main body 520. The main body 520 is provided with a toner supply port 520h.

  A container screw 521 is rotatably provided in the main body 520. The container screw 521 is rotated by a drive mechanism that the toner replenishing unit 5 has. The container screw 521 conveys the toner to the toner supply port 520h by rotating. The toner conveyed to the toner supply port 520h is supplied to the developing container 640 through the toner supply port 640h. For example, the container screw 521 rotates in accordance with the remaining amount of toner in the developing container 640. The remaining amount of toner in the developing container 640 can be detected by, for example, a toner remaining amount detection sensor.

  The first to sixth toner containers 52L to 52K are the same except for the types of toner stored therein. For this reason, the description of the configuration of the second to sixth toner containers 52H to 52K is omitted.

<Developing device>
Next, the configuration of the developing device 64 will be described in detail with reference to FIG. FIG. 3 is a diagram illustrating a configuration of the developing device 64. Specifically, FIG. 3 shows the developing device 64 included in the first image forming unit 62T. In FIG. 3, the photosensitive drum 65 is shown by a two-dot chain line for easy understanding. In the present embodiment, the developing device 64 develops the electrostatic latent image formed on the surface of the photosensitive drum 65 by a touch-down development method. As described above, the developing container 640 included in the first image forming unit 62T is connected to the first mounting portion 51L and the second mounting portion 51H. Accordingly, the low melting point transparent toner and the high melting point transparent toner are supplied to the developing container 640 of the first image forming unit 62T through the toner supply port 640h.

  As illustrated in FIG. 3, the developing device 64 includes a developing roller 641, a magnetic roller 642, a first stirring screw 643, a second stirring screw 644, and a blade 645 inside the developing container 640. Specifically, the developing roller 641 is disposed to face the magnetic roller 642. The magnetic roller 642 is disposed to face the second stirring screw 644. The blade 645 is disposed to face the magnetic roller 642.

  The developing container 640 is partitioned into a first stirring chamber 640a and a second stirring chamber 640b by a partition wall 640c. The partition wall 640 c extends in the axial direction of the developing roller 641. The first agitation chamber 640a and the second agitation chamber 640b communicate with each other outward at both ends in the longitudinal direction of the partition wall 640c.

  A first stirring screw 643 is disposed in the first stirring chamber 640a. A second stirring screw 644 is disposed in the second stirring chamber 640b.

  A magnetic carrier is accommodated in the first stirring chamber 640a and the second stirring chamber 640b.

  Non-magnetic toner is supplied to the first stirring chamber 640a through the toner supply port 640h. In the example shown in FIG. 3, the low-melting point transparent toner and the high-melting point transparent toner are supplied to the first stirring chamber 640a.

  The low melting point transparent toner and the high melting point transparent toner are stirred by the first stirring screw 643 and the second stirring screw 644 and mixed with the carrier. As a result, a two-component developer composed of a carrier, a low melting point transparent toner, and a high melting point transparent toner is formed. Hereinafter, the two-component developer is referred to as “developer”.

  The first stirring screw 643 and the second stirring screw 644 stir the developer by circulating between the first stirring chamber 640a and the second stirring chamber 640b. As a result, the toner is charged to a predetermined polarity. In this embodiment, the toner is charged with a positive polarity.

  The magnetic roller 642 includes a nonmagnetic rotating sleeve 642a and a magnet body 642b. The magnet body 642b is fixedly disposed inside the rotating sleeve 642a. The magnet body 642b includes a plurality of magnetic poles. The developer is attracted to the magnetic roller 642 by the magnetic force of the magnet body 642b. As a result, a magnetic brush is formed on the surface of the magnetic roller 642.

  In the present embodiment, the magnetic roller 642 rotates in the direction indicated by the arrow R3 in FIG. The magnetic roller 642 conveys the magnetic brush to a position facing the blade 645 by rotating. The blade 645 is disposed so that a gap (gap) is formed between the blade 645 and the magnetic roller 642. Therefore, the thickness of the magnetic brush is regulated by the blade 645. The blade 645 is disposed on the upstream side in the rotation direction of the magnetic roller 642 from the position where the magnetic roller 642 and the developing roller 641 face each other.

  A predetermined voltage is applied to the developing roller 641 and the magnetic roller 642. When a predetermined voltage is applied and a predetermined potential difference is generated between the developing roller 641 and the magnetic roller 642, the high melting point transparent toner and the low melting point transparent toner contained in the developer move to the developing roller 641. As a result, a thin toner layer composed of the high melting point transparent toner and the low melting point transparent toner is formed on the surface of the developing roller 641.

  The developing roller 641 rotates in the direction indicated by the arrow R2 in FIG. Accordingly, the toner thin layer formed on the surface is conveyed to a position facing the photosensitive drum 65.

  The configuration of the developing device 64 included in each of the first to fifth image forming units 62T to 62K is different only in the type of toner supplied from the toner supply unit 5, and the other configurations are substantially the same. Therefore, the description of the configuration of the developing device 64 included in the second to fifth image forming units 62Y to 62K is omitted.

<Development process>
Next, the development process will be described with reference to FIG. FIG. 4 is a diagram showing a development process.

  As shown in FIG. 4, the image forming apparatus 1 further includes a developing bias applying unit 11. The development bias application unit 11 applies a development bias to the development roller 641. In the present embodiment, the development bias is an AC superposition bias. That is, a voltage obtained by superimposing an AC voltage having a rectangular waveform on a DC voltage is applied to the developing roller 641. Hereinafter, an AC voltage having a rectangular waveform may be referred to as a “rectangular wave AC voltage”.

  The developing bias application unit 11 includes an AC voltage application unit 11a and a DC voltage application unit 11b. The alternating voltage application unit 11a generates a rectangular wave alternating voltage. The DC voltage application unit 11b generates a DC voltage. That is, a voltage obtained by superimposing the rectangular wave AC voltage generated by the AC voltage application unit 11a on the DC voltage generated by the DC voltage application unit 11b is applied to the developing roller 641. In the present embodiment, the voltage value Vpp of the rectangular wave AC voltage generated by the AC voltage application unit 11a is, for example, 1.6 kV. Moreover, the frequency f of the rectangular wave alternating voltage which the alternating voltage application part 11a produces | generates is 2.7 kHz, for example. Also, the duty ratio of the rectangular wave AC voltage generated by the AC voltage application unit 11a, that is, the duty ratio of the developing bias is 55%, for example. The voltage value Vdc of the DC voltage generated by the DC voltage application unit 11b is, for example, 300V. The voltage value Vpp of the rectangular wave AC voltage, the frequency f of the rectangular wave AC voltage, the duty ratio of the rectangular wave AC voltage, and the voltage value Vdc of the DC voltage are stored in the storage device 100 described later with reference to FIG. .

  When a developing bias is applied to the developing roller 641 and the developing roller 641 and the photosensitive drum 65 have a predetermined potential difference, toner flies from the developing roller 641 toward the photosensitive drum 65. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 65 is developed to form a toner image.

<Configuration of image forming apparatus>
Next, the configuration of the image forming apparatus 1 will be further described with reference to FIGS. 5 and 6. FIG. 5 is a block diagram illustrating a configuration of the image forming apparatus 1. FIG. 6 is a diagram illustrating the developing bias. The vertical axis in FIG. 6 indicates the voltage value (V), and the horizontal axis indicates time (t).

  As shown in FIG. 5, the image forming apparatus 1 further includes a storage device 100. The storage device 100 includes an HDD (Hard Disk Drive), a RAM (Random Access Memory), and a ROM (Read Only Memory). In the present embodiment, the storage device 100 stores the glossiness value of an image that is to be formed (hereinafter, the current glossiness value). The glossiness value can be changed by operating the operation unit 2. The storage device 100 also stores a control program for controlling the operation of each unit of the image forming apparatus 1. The control program is executed by the control unit 10.

  The control unit 10 is configured by a CPU (Central Processing Unit) or the like.

  The control unit 10 changes the toner development ratio. The toner development ratio is a ratio between the development amount of the low melting point transparent toner and the development amount of the high melting point transparent toner. The development amount indicates the amount of each toner used for developing the electrostatic latent image formed on the photosensitive drum 65.

  In the present embodiment, the control unit 10 changes the toner development ratio by controlling the operation of the development bias application unit 11. Specifically, the control unit 10 changes the duty ratio of the development bias. In other words, the control unit 10 changes the duty ratio of the rectangular wave AC voltage generated by the AC voltage application unit 11a.

As shown in FIG. 6, the developing bias 110 exhibits a rectangular wave-shaped AC component. The development bias 110 has a positive peak voltage value Vmax and a negative peak voltage value Vmin. The first time t1 indicates a period during which the developing bias voltage value is Vmax. The second time t2 indicates a period during which the developing bias voltage value is Vmin. The duty ratio of the developing bias 110 is obtained by the following formula 1.
Duty ratio = t1 / (t1 + t2) × 100 (Expression 1)

  In one period T of the developing bias, toner particles fly from the developing roller 641 toward the photosensitive drum 65 at the first time t1, and the toner particles are pulled back from the photosensitive drum 65 to the developing roller 641 at the second time t2. It is. Hereinafter, the amount of toner particles flying from the developing roller 641 to the photosensitive drum 65 is referred to as “flying amount”. The amount by which the toner particles are pulled back from the photosensitive drum 65 to the developing roller 641 is referred to as “retraction amount”. The toner development amount is calculated by subtracting the pullback amount from the flying amount. Therefore, in this embodiment, the toner development amount increases as the duty ratio increases, and the toner development amount decreases as the duty ratio decreases.

In general, toner particles having a small volume median diameter D ₅₀ are susceptible to mirror image force and van der Waals force, and are difficult to fly from the developing roller 641 to the photosensitive drum 65. In addition, toner particles having a low degree of circularity have strong adhesion to the developing roller 641 and are likely to remain on the developing roller 641. That is, toner particles having a low degree of circularity hardly fly from the developing roller 641 to the photosensitive drum 65. Accordingly, toner particles having a small volume median diameter D ₅₀ and low circularity are unlikely to fly from the developing roller 641 to the photosensitive drum 65. In contrast, toner particles having a large volume median diameter D ₅₀ and a high degree of circularity easily fly from the developing roller 641 to the photosensitive drum 65.

  In general, when the duty ratio is high, the rate of increase in the flying amount of toner particles that are difficult to fly is greater than the rate of increase in the flying amount of toner particles that are likely to fly. On the other hand, when the duty ratio is low, the rate of decrease in the flying amount of toner particles that are difficult to fly is greater than the rate of decrease in the flying amount of toner particles that are likely to fly.

In the present embodiment, the volume median diameter D ₅₀ of the low-melting transparent toner particles is smaller than the volume median diameter D ₅₀ of the refractory transparent toner particles. The average circularity of the low melting point transparent toner particles is lower than the average circularity of the high melting point transparent toner particles. Therefore, as the duty ratio increases, the ratio of the development amount of the low melting point transparent toner in the toner development ratio increases and the ratio of the development amount of the high melting point transparent toner decreases. In this case, when the toner image is fixed on the sheet S, the transparent toner is easily melted. Therefore, the glossiness of the image formed on the sheet S is increased. On the other hand, when the duty ratio is lowered, the ratio of the development amount of the low melting point transparent toner in the toner development ratio decreases, and the ratio of the development amount of the high melting point transparent toner increases. In this case, when the toner image is fixed on the sheet S, the transparent toner is hardly melted. Accordingly, the glossiness of the image formed on the sheet S is lowered. Volume median diameter D ₅₀ of the low-melting transparent toner particles is an example of a first volume median diameter, volume median diameter D ₅₀ of the refractory transparent toner particles is one example of a second volume median diameter. The average circularity of the low melting point transparent toner particles is an example of the first average circularity, and the average circularity of the high melting point transparent toner particles is an example of the second average circularity. The developing amount of the low melting point transparent toner is an example of the first toner developing amount, and the developing amount of the high melting point transparent toner is an example of the developing amount of the second toner.

<Glossiness fine adjustment processing>
Next, with reference to FIG. 7, the glossiness fine adjustment process according to the present embodiment will be described. FIG. 7 is a flowchart showing the glossiness fine adjustment process. The gloss level fine adjustment process is started before the developing bias is applied to the developing roller 641.

  As illustrated in FIG. 7, when the control unit 10 receives a signal indicating execution of image formation from the operation unit 2, the control unit 10 determines whether an instruction to increase the glossiness is input (step S <b> 102). Specifically, the control unit 10 increases the glossiness by comparing the value indicating the current glossiness stored in the storage device 100 with the value indicating the glossiness input from the operation unit 2. It is determined whether or not an instruction is input. Specifically, the control unit 10 determines whether or not a subtraction value obtained by subtracting a value indicating the current glossiness from a value indicating the glossiness input from the operation unit 2 is greater than zero. . When it is determined that the subtraction value is greater than 0, the control unit 10 determines that an instruction for increasing the glossiness is input. On the other hand, when it is determined that the subtraction value is 0 or less, the control unit 10 determines that an instruction to increase the glossiness is not input.

  If the control unit 10 determines that an instruction to increase the glossiness is input (step S102: Yes), the control unit 10 changes the duty ratio of the developing bias stored in the storage device 100 to a higher value (step S106). Next, the developing bias applying unit 11 applies a developing bias to the developing roller 641. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 65 is developed (step S110), and the glossiness fine adjustment process is completed. On the other hand, if it is determined that an instruction to increase the glossiness is not input (step S102: No), the control unit 10 determines whether an instruction to decrease the glossiness is input (step S104). ). Specifically, the control unit 10 calculates a subtraction value in the same manner as the processing in step S102, and determines whether or not the subtraction value is smaller than zero. When it is determined that the subtraction value is smaller than 0, the control unit 10 determines that an instruction for decreasing the glossiness is input. On the other hand, if it is determined that the subtraction value is not smaller than 0, the control unit 10 determines that an instruction to lower the glossiness is not input.

  When the control unit 10 determines that an instruction to lower the glossiness has been input (step S104: Yes), the control unit 10 changes the duty ratio of the developing bias stored in the storage device 100 to a lower value (step S108). Next, the developing bias applying unit 11 applies a developing bias to the developing roller 641. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 65 is developed (step S110), and the glossiness fine adjustment process is completed. On the other hand, when the control unit 10 determines that the instruction to lower the gloss level is not input (step S104: No), the duty ratio stored in the storage device 100 is not changed, and the developing bias applying unit 11 is not changed. Applies a developing bias to the developing roller 641. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 65 is developed (step S110), and the glossiness fine adjustment process is completed.

<Toner>
Next, the configuration of the toner according to the exemplary embodiment will be described. The toner has the following configuration (1). The toner preferably has one or both of the following configurations (2) and (3) in addition to the configuration (1).
Configuration (1): The melting point of the high melting point transparent toner particles included in the high melting point transparent toner (an example of the second toner) is higher than the melting point of the low melting point transparent toner particles included in the low melting point transparent toner (an example of the first toner). .
Configuration (2): The volume median diameter D ₅₀ (an example of the first volume median diameter) of the low melting point transparent toner particles contained in the low melting point transparent toner is the volume of the high melting point transparent toner particles contained in the high melting point transparent toner. It is smaller than the median diameter D ₅₀ (an example of the second volume median diameter).
Configuration (3): The average circularity (an example of the first average circularity) of the low-melting transparent toner particles included in the low-melting transparent toner is the average circularity (the first circularity of the high-melting transparent toner particles included in the high-melting transparent toner). It is lower than an example of 2 average circularity.

When the difference between the volume median diameter D ₅₀ of the high melting point transparent toner particles and the volume median diameter D ₅₀ of the low melting point transparent toner particles becomes large, the charge amount of the high melting point transparent toner particles and the charge amount of the low melting point transparent toner particles There may be a difference between As a result, toner particles that are likely to fly are likely to be scattered, and toner particles that are difficult to fly may adhere to the developing roller 641 and cause image defects. For this reason, the transparent toner preferably has the following configuration (4).

Configuration (4): The difference between the volume median diameter D ₅₀ of the high melting point transparent toner particles included in the high melting point transparent toner and the volume median diameter D ₅₀ of the low melting point transparent toner particles included in the low melting point transparent toner is It is larger than 0.2 μm and smaller than 1.0 μm. This makes it difficult for a difference between the charge amount of the high melting point transparent toner particles and the charge amount of the low melting point transparent toner particles to occur. As a result, image defects are less likely to occur.

The volume median diameter D ₅₀ of the transparent toner particles is measured, for example, by the following method. Using a precise particle size distribution measuring device (for example, “Coulter Counter Multisizer 3” manufactured by Beckman Coulter, Inc.), a volume distribution of the particle diameter of the measurement sample (transparent toner) is obtained. From the volume distribution of the particle diameter of the obtained transparent toner, the volume median diameter D ₅₀ of the transparent toner particles is obtained.

  The average circularity of the transparent toner particles is measured, for example, by the following method. A measurement sample (transparent toner particles) 0.1 g and a dispersion liquid (sheath liquid) 20 mL are mixed to obtain a suspension of transparent toner particles. The number of transparent toner particles contained in the obtained suspension and the circularity of each transparent toner particle were measured using a flow type particle image analyzer (“FPIA (registered trademark) -3000” manufactured by Sysmex Corporation). taking measurement. The sum of the circularity of the measured transparent toner particles is divided by the number of measured transparent toner particles. Thereby, the average circularity of the transparent toner particles is calculated. The average circularity of the transparent toner particles is a number average circularity.

<Colored toner particles>
The colored toner particles contain, for example, a binder resin and a colorant. The colored toner particles may contain a charge control agent as necessary.

<Binder resin>
The binder resin contained in the colored toner particles is preferably a thermoplastic resin. Examples of thermoplastic resins include styrene resins, acrylic resins, olefin resins (specifically, polyethylene resins or polypropylene resins), vinyl resins (specifically, vinyl chloride resins, polyvinyl alcohol resins, vinyl ether resins). Or N-vinyl resin), polyester resin, polyamide resin, urethane resin, styrene acrylic acid resin, or styrene butadiene resin. As the binder resin contained in the colored toner particles, a styrene resin, a styrene acrylic resin or a polyester resin is preferable, and a polyester resin is particularly preferable.

  Hereinafter, the styrene resin and styrene acrylic acid resin used as the binder resin will be described. The styrene resin is a polymer of a styrene monomer. The styrene resin may be a copolymer of a styrene monomer and other monomers (monomers other than styrene monomers and acrylic monomers). The styrene acrylic acid resin is a copolymer of a styrene monomer and an acrylic acid monomer. The styrene acrylic acid resin may be a copolymer of a styrene monomer, an acrylic acid monomer, and another monomer.

  Examples of styrenic monomers include styrene, α-methylstyrene, p-hydroxystyrene, m-hydroxystyrene, vinyltoluene, α-chlorostyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene or p- Ethyl styrene is mentioned.

  Examples of acrylic monomers include (meth) acrylic acid, (meth) acrylic acid alkyl ester, (meth) acrylic acid hydroxyalkyl ester, (meth) acrylic acid 2-chloroethyl, α-chloro (meth) acrylic acid methyl , Phenyl (meth) acrylate or other acrylic acid derivatives. Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, and (meth) acrylic acid n. -Butyl, iso-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate or dodecyl (meth) acrylate. Examples of hydroxyalkyl esters of (meth) acrylic acid include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate or (meth) acrylic acid 4- Hydroxybutyl is mentioned. Examples of other acrylic acid derivatives include acrylonitrile, methacrylonitrile or acrylamide.

  Examples of other monomers include vinyl naphthalene, alkylene monoolefin, vinyl halide, vinyl esters, vinyl alkyl ethers, vinyl ketones, and N-vinyl compounds. Examples of alkylene monoolefins include alkylene (eg ethylene, propylene, butylene or isobutylene) monoolefins. Examples of the vinyl halide include vinyl chloride, vinyl bromide, and vinyl fluoride. Examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl benzoate or vinyl butyrate. Examples of vinyl alkyl ethers include vinyl methyl ether or vinyl isobutyl ether. Examples of vinyl ketones include vinyl methyl ketone, vinyl ethyl ketone, or methyl isopropenyl ketone. Examples of the N-vinyl compound include N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole or N-vinyl pyrrolidene.

  When the binder resin contained in the colored toner particles is a polyester resin, the example of the polyester resin contained in the colored toner particles is the same as the example of the polyester resin contained in the transparent toner particles described later. The alcohol used for preparing the polyester resin contained in the colored toner particles is preferably a dihydric alcohol, more preferably a bisphenol, and particularly preferably a bisphenol A ethylene oxide adduct or a bisphenol A propylene oxide adduct. The carboxylic acid used for preparing the polyester resin contained in the colored toner particles is preferably a divalent carboxylic acid or a trivalent or higher carboxylic acid, such as terephthalic acid, alkenyl succinic acid (preferably dodecenyl succinic acid) or trimellit. Acid is more preferred. Further, as the divalent or trivalent or higher carboxylic acid, an ester-forming derivative of a divalent or trivalent or higher carboxylic acid (for example, acid halide, acid anhydride, or lower alkyl ester) may be used. As the alcohol for preparing the polyester resin, one kind may be used alone, or two or more kinds may be used in combination. As the carboxylic acid for preparing the polyester resin, one kind may be used alone, or two or more kinds may be used in combination.

  The colored toner particles may contain a thermosetting resin as a binder resin. When the colored toner particles contain a thermosetting resin, a partially cross-linked structure is introduced into the binder resin, improving the toner fixability to the recording medium, while maintaining the heat resistant storage stability, shape retention and durability of the toner. It is easy to improve the property. The thermosetting resin that the colored toner particles may contain is the same as the thermosetting resin that the transparent toner particles described later may contain.

  The glass transition point (Tg) of the binder resin contained in the colored toner particles is preferably 50 ° C. or higher and 65 ° C. or lower, and more preferably 50 ° C. or higher and 60 ° C. or lower. If the glass transition point of the binder resin is 50 ° C. or higher, the toner particles and other toner particles are difficult to fuse in the developing device. Further, the toner particles hardly adhere to the image carrier. When the glass transition point of the binder resin is 65 ° C. or less, the low-temperature fixability of the toner can be easily improved. The glass transition point of the binder resin is obtained from the change point of the specific heat in the endothermic curve, for example, by measuring the endothermic curve of the binder resin using a differential scanning calorimeter.

<Colorant>
As the colorant contained in the colored toner particles, a known pigment or dye is used according to the color of the colored toner. The content of the colorant is preferably 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the binder resin.

  The colorant contained in the colored toner particles may be a black colorant. An example of a black colorant is carbon black. The black colorant may be a colorant that is toned to black using a yellow colorant, a magenta colorant, and a cyan colorant.

  The colorant contained in the colored toner particles may be a yellow colorant, a magenta colorant, or a cyan colorant.

  Examples of yellow colorants include condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds, or arylamide compounds. Suitable examples of yellow colorants include C.I. I. Pigment Yellow (3, 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155 168, 174, 175, 176, 180, 181, 191 or 194), naphthol yellow S, Hansa yellow G or C.I. I. Bat yellow is mentioned.

  Examples of magenta colorants include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds or perylene compounds. Suitable examples of magenta colorants include C.I. I. Pigment Red (2, 3, 5, 6, 7, 19, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 150, 166, 169, 177 184, 185, 202, 206, 220, 221 or 254).

  Examples of cyan colorants include copper phthalocyanine, copper phthalocyanine derivatives, anthraquinone compounds or basic dye lake compounds. Suitable examples of cyan colorants include C.I. I. Pigment blue (1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62 or 66), phthalocyanine blue, C.I. I. Bat Blue or C.I. I. Acid blue.

  Further, colorants other than yellow, magenta and cyan may be used. Examples of such a colorant include dyes such as Acid Violet.

<Charge control agent>
The colored toner particles may contain a charge control agent. The charge control agent is blended, for example, in order to improve the charge level and charge rise characteristics of the toner and to obtain a toner having excellent durability and stability. The toner charge rising characteristic is an index of whether or not the toner can be charged to a predetermined charge level in a short time. When developing using a positively charged toner, it is preferable to add a positively chargeable charge control agent. In the case of developing using a negatively charged toner, it is preferable to add a negatively chargeable charge control agent.

  Examples of positively chargeable charge control agents include pyridazine, pyrimidine, pyrazine, 1,2-oxazine, 1,3-oxazine, 1,4-oxazine, 1,2-thiazine, 1,3-thiazine, 1, 4-thiazine, 1,2,3-triazine, 1,2,4-triazine, 1,3,5-triazine, 1,2,4-oxadiazine, 1,3,4-oxadiazine, 1,2,6- Oxadiazine, 1,3,4-thiadiazine, 1,3,5-thiadiazine, 1,2,3,4-tetrazine, 1,2,4,5-tetrazine, 1,2,3,5-tetrazine, 1, Azine compounds such as 2,4,6-oxatriazine, 1,3,4,5-oxatriazine, phthalazine, quinazoline or quinoxaline; Azin Fast Red FC, Azin Fast Red 12BK, Azinba Direct dyes composed of azine compounds such as Olet BO, Azine Brown 3G, Azin Light Brown GR, Azin Dark Green BH / C, Azin Deep Black EW or Azin Deep Black 3RL; Nigrosine Compounds such as Nigrosine, Nigrosine Salts or Nigrosine Derivatives An acid dye comprising a nigrosine compound such as nigrosine BK, nigrosine NB or nigrosine Z; metal salts of naphthenic acid or higher fatty acids; alkoxylated amines; alkylamides; or 4 such as benzyldecylhexylmethylammonium and decyltrimethylammonium chloride; A class ammonium salt is mentioned. Two or more of these charge control agents may be combined. Of these positively chargeable charge control agents, a nigrosine compound is preferable from the viewpoint of obtaining a quicker charge rising property of the toner.

  Moreover, you may use the resin or oligomer which has a quaternary ammonium salt, carboxylate, or a carboxyl group as a functional group as a positively chargeable charge control agent. More specifically, a styrene resin having a quaternary ammonium salt, an acrylic acid resin having a quaternary ammonium salt, a styrene acrylic acid resin having a quaternary ammonium salt, a polyester resin having a quaternary ammonium salt, a carvone Styrene resin having acid salt, acrylic acid resin having carboxylate, styrene acrylic resin having carboxylate, polyester resin having carboxylate, polystyrene resin having carboxyl group, having carboxyl group Examples thereof include acrylic resins, styrene acrylic resins having a carboxyl group, and polyester resins having a carboxyl group.

  From the viewpoint of easily adjusting the charge amount to a value within the desired range, a styrene acrylic acid resin having a quaternary ammonium salt as a functional group is preferable. Examples of the acrylic monomer used in the styrene acrylic resin include methyl (meth) acrylate or alkyl (meth) acrylate. Examples of (meth) acrylic acid alkyl esters include ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic. Examples include iso-butyl acid or 2-ethylhexyl (meth) acrylate.

  The quaternary ammonium salt is derived from, for example, a (meth) acrylic acid dialkylaminoalkyl ester through a quaternization step. Examples of the derived (meth) acrylic acid dialkylaminoalkyl ester include, for example, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dipropylaminoethyl (meth) acrylate, or dibutyl (meth) acrylate. Preferred are (meth) acrylic acid di (lower alkyl) aminoethyl such as aminoethyl; dimethyl (meth) acrylamide; dimethylaminopropyl (meth) acrylamide. Further, a hydroxy group-containing polymerizable monomer such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate or N-methylol (meth) acrylamide may be used in combination during polymerization. Good.

  Examples of the negatively chargeable charge control agent include organometallic complexes that are chelate compounds. As the organometallic complex, for example, an acetylacetone metal complex, a salicylic acid metal complex or a salt thereof is preferable, and a salicylic acid metal complex or a salicylic acid metal salt is more preferable. Specific examples include aluminum acetylacetonate, iron (II) acetylacetonate or chromium 3,5-di-tert-butylsalicylate.

  The content of the charge control agent is preferably 0.5 parts by mass or more and 15 parts by mass or less, and 0.5 parts by mass or more and 8.0 parts by mass or less with respect to 100 parts by mass of the total toner. Is more preferable, and most preferably 0.5 parts by mass or more and 7.0 parts by mass or less. When the content of the charge control agent is 0.5 parts by mass or more, the toner is easily and stably charged, so that the image density is easily improved. In addition, it is easy to suppress the occurrence of fog due to poor dispersion of the charge control agent, and it is easy to prevent contamination of the image carrier with toner. When the content of the charge control agent is 15 parts by mass or less, the toner can be easily and stably charged even under high temperature and high humidity. Therefore, image defects can be easily suppressed and contamination of the image carrier with the toner can be easily suppressed.

<Transparent toner particles>
The transparent toner particles contain, for example, a binder resin. Transparent toner particles have translucency. Therefore, it is preferable that the transparent toner particles do not contain a colorant. The transparent toner particles may contain a release agent and a charge control agent as necessary. In this embodiment, the low melting point transparent toner particles contain a binder resin having a lower melting point than that of the high melting point transparent toner particles.

<Binder resin>
As an example of the binder resin contained in the transparent toner particles, a thermoplastic resin is preferable. Examples of such thermoplastic resins include styrene resins, acrylic resins, olefin resins (specifically, polyethylene resins or polypropylene resins), vinyl resins (specifically, vinyl chloride resins, polyvinyl alcohol resins). , Vinyl ether resin or N-vinyl resin), polyester resin, polyamide resin, urethane resin, styrene acrylic acid resin or styrene butadiene resin. The binder resin contained in the transparent toner particles is preferably a polyester resin.

  The polyester resin is obtained by polymerizing a divalent or trivalent or higher alcohol and a divalent or trivalent or higher carboxylic acid.

  Examples of the dihydric alcohol used for preparing the polyester resin include diols or bisphenols.

  Examples of diols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 2-butene-1,4-diol, 1,5 -Pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol or polytetramethylene glycol.

  Examples of bisphenols include bisphenol A, hydrogenated bisphenol A, bisphenol A ethylene oxide adduct or bisphenol A propylene oxide adduct.

  Examples of trihydric or higher alcohols used to prepare polyester resins include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane or 1,3,5-trihydroxymethylbenzene is mentioned.

  Examples of divalent carboxylic acids used to prepare polyester resins include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, adipic acid, sebacin Acid, azelaic acid, malonic acid, succinic acid, alkyl succinic acid (specifically, n-butyl succinic acid, isobutyl succinic acid, n-octyl succinic acid, n-dodecyl succinic acid or isododecyl succinic acid) or alkenyl succinic acid (Specific examples include n-butenyl succinic acid, isobutenyl succinic acid, n-octenyl succinic acid, n-dodecenyl succinic acid or isododecenyl succinic acid).

  Examples of trivalent or higher carboxylic acids used for preparing the polyester resin include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 2,5,7-naphthalenetricarboxylic acid, 1,2,4. -Naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid Examples include acids, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid or emporic trimer acid.

  Further, as the divalent or trivalent or higher carboxylic acid, an ester-forming derivative of a divalent or trivalent or higher carboxylic acid (for example, acid halide, acid anhydride, or lower alkyl ester) may be used. Here, the lower alkyl means an alkyl group having 1 to 6 carbon atoms.

  The softening point of the polyester resin is preferably 80 ° C. or higher and 150 ° C. or lower, and more preferably 90 ° C. or higher and 140 ° C. or lower.

  The transparent toner particles may contain a thermosetting resin as a binder resin. By containing a thermosetting resin, a partially cross-linked structure is introduced into the binder resin, improving the toner's heat-resistant storage stability, shape retention and durability while improving the toner's fixability to the recording medium. Easy to do.

  Preferable examples of the thermosetting resin used as the binder resin for the transparent toner particles include an epoxy resin or a cyanate resin. Specific examples include bisphenol A type epoxy resins, hydrogenated bisphenol A type epoxy resins, novolac type epoxy resins, polyalkylene ether type epoxy resins, cycloaliphatic type epoxy resins, and cyanate resins.

  The melting point (Tm) of the binder resin contained in the transparent toner particles preferably satisfies the configuration (1) already described and is preferably 50 ° C. or higher and 110 ° C. or lower. When the melting point of the binder resin is within such a range, it becomes easy to achieve both low-temperature fixability, hot offset resistance, and heat-resistant storage stability of the toner. The melting point of the high melting point transparent toner among the transparent toner particles is more preferably 100 ° C. or higher and 110 ° C. or lower. Of the transparent toner particles, the low melting point transparent toner preferably has a melting point of 90 ° C. or higher and lower than 100 ° C.

  The melting point of the binder resin is measured using, for example, a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.). Specifically, put a measurement sample (binder resin) in an aluminum dish. Set the aluminum pan on the measurement part of the differential scanning calorimeter. Use an empty aluminum pan for reference. The temperature is increased to 170 ° C. at a rate of 10 ° C./min with 30 ° C. as the measurement start temperature. The maximum peak temperature of the heat of fusion observed when the temperature is raised is taken as the melting point of the measurement sample.

  The glass transition point (Tg) of the binder resin contained in the transparent toner particles is preferably 50 ° C. or higher and 70 ° C. or lower. If the glass transition point of the binder resin is 50 ° C. or higher, the toner particles and other toner particles are difficult to fuse in the developing device. Further, the toner particles hardly adhere to the image carrier. If the glass transition point of the binder resin is 70 ° C. or lower, it is easy to maintain the low-temperature fixability of the toner.

  The glass transition point of the binder resin is obtained from the change point of the specific heat in the endothermic curve, for example, by measuring the endothermic curve of the binder resin using a differential scanning calorimeter. As the measuring device, for example, a differential scanning calorimeter (“DSC-6220” manufactured by Seiko Instruments Inc.) is used. 10 mg of a measurement sample (binder resin) is placed in an aluminum pan. Use an empty aluminum pan as a reference. The measurement conditions of the measurement device are set to a measurement temperature range of 25 ° C. or more and 200 ° C. or less and a temperature increase rate of 10 ° C./min. An endothermic curve of the measurement sample is obtained using the measurement device. From the change point of specific heat in the obtained endothermic curve, the glass transition point of the measurement sample is obtained.

<Release agent>
The transparent toner particles contain a release agent. When the transparent toner particles contain a release agent, the hot offset resistance of the toner can be improved.

  Suitable examples of release agents include aliphatic hydrocarbon waxes (eg, low molecular weight polyethylene, low molecular weight polypropylene, olefin copolymers, polyolefins, microcrystalline wax, paraffin wax or Fischer-Tropsch wax), aliphatic hydrocarbon waxes. Oxides (eg, block copolymers of oxidized polyethylene wax or oxidized polyethylene wax), vegetable waxes (eg, candelilla wax, carnauba wax, wood wax, jojoba wax, or rice wax), animal waxes (eg, beeswax, lanolin) Or whale wax), mineral waxes (eg, ozokerite, ceresin or petrolatum), waxes based on fatty acid esters (eg, montanate ester wax or castor wax) or fatty acid esters. Waxes in which some or all of the de-oxidation of ether (e.g., deoxidized carnauba wax) and the like. Two or more of these release agents may be combined. When the transparent toner particles contain such a release agent, it is easy to improve the offset resistance and fixability of the toner and to easily suppress image defects such as image smearing.

  In order to improve the hot offset resistance of the toner, the content of the release agent is preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the whole transparent toner particles. When the addition amount of the release agent is 1 part by mass or more, the offset resistance of the toner is easily improved, and image defects such as image smearing are easily suppressed. When the addition amount of the release agent is 5 parts by mass or less, the toner particles are hardly fused with each other, and the heat resistant storage stability of the toner is easily improved.

<Charge control agent>
The transparent toner particles may contain a charge control agent. The charge control agent contained in the transparent toner particles is not limited as long as it is transparent. Examples of the charge control agent contained in the transparent toner particles are the same as those of the charge control agent contained in the colored toner.

<External additive>
If necessary, an external additive may be attached to the surface of the transparent toner particles and the colored toner particles. The colored toner particles before attaching the external additive may be referred to as colored toner mother particles. Further, an external additive may be attached to the surface of the transparent toner particles as necessary. The transparent toner particles before the external additive is attached may be referred to as transparent toner base particles.

  Examples of the external additive include metal oxides (for example, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate or barium titanate), silicon carbide or silica. Specific examples of the silica include colloidal silica and hydrophobic silica. Examples of the external additive include a salt of a fatty acid and a metal (for example, zinc stearate). The external additive may be surface-treated with a surface treatment agent (for example, aminosilane, silicone oil, hexamethyldisilazane, titanate coupling agent or silane coupling agent) as necessary.

  The particle diameter of the external additive is preferably 0.01 μm or more and 1.0 μm or less. The amount of the external additive used is preferably 0.5 parts by mass or more and 10 parts by mass or less, preferably 1 part by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the colored toner base particles or transparent toner base particles. Is more preferable.

<Toner production method>
The toner production method of the present exemplary embodiment may be implemented with appropriate modifications, and may further include another known process.

<Method for producing colored toner>
Examples of the manufacturing method of the colored toner include an aggregation method or a pulverization method.

  The aggregation method includes, for example, an aggregation process and a coalescence process. In the aggregating step, fine particles containing components constituting the colored toner are aggregated in an aqueous medium to form aggregated particles. In the coalescing step, the components contained in the aggregated particles are coalesced in an aqueous medium to form colored toner base particles. According to the aggregation method, it is easy to obtain colored toner base particles having a uniform shape and a uniform particle diameter. The aggregation method may include an external addition step described later.

  Next, the grinding method will be described. According to the pulverization method, a colored toner can be prepared relatively easily. When producing a colored toner by the pulverization method, the production process of the colored toner includes, for example, a mixing process, a kneading process, a pulverizing process, and a classification process. The manufacturing process of the colored toner may further include an external addition process described later. In the mixing step, for example, a binder resin, a colorant, and an internal additive (for example, a charge control agent) are mixed to obtain a mixture. In the kneading step, the obtained mixture is melted and kneaded to obtain a kneaded product. In the pulverization step, the obtained kneaded product is pulverized to obtain a pulverized product. In the spheronization step, the pulverized product is further pulverized to spheroidize the pulverized product.

  In the classification step, the obtained pulverized product is classified to obtain colored toner base particles. The classification is performed using a classifier (for example, an airflow classifier).

  In the external addition step, the color toner particles are obtained by attaching an external additive to the surface of the color toner base particles. As a suitable method for attaching the external additive, using a mixer (for example, FM mixer, Nauter mixer (registered trademark)) under the condition that the external additive is not buried in the surface of the colored toner base particles, Examples thereof include a method of mixing colored toner base particles and an external additive.

<Manufacturing process of transparent toner>
The transparent toner is manufactured in the same manner as, for example, a colored toner. When the transparent toner is manufactured by the pulverization method, the transparent toner manufacturing process includes, for example, a mixing process, a kneading process, a pulverizing process, and a classification process. The manufacturing process of the transparent toner may further include an external addition process. In the mixing step, for example, a binder resin, a release agent, and an internal additive (for example, a charge control agent) are mixed to obtain a mixture. In the kneading step, the obtained mixture is melted and kneaded to obtain a kneaded product. In the pulverization step, the obtained kneaded product is pulverized to obtain a pulverized product. In the classification step, the obtained pulverized product is classified to obtain transparent toner base particles. The classification is performed using a classifier (for example, an airflow classifier).

  The average circularity of the transparent toner can be adjusted, for example, by reducing the pulverization particle size or increasing the pulverization frequency.

Volume median diameter D ₅₀ of the transparent toner, for example, can be adjusted as follows. Milling conditions of the crusher in the milling step (e.g., material-feeding speed or rotational speed) is adjusted, it is possible to adjust the volume median diameter D ₅₀ of the transparent toner. Further, by adjusting the classification conditions of the classifier in the classifying step, it is also possible to adjust the volume median diameter D ₅₀ of the transparent toner. Specifically, in the classification process for producing the high melting point transparent toner of the transparent toner, the zone width (ΔFht) of the fine powder zone removed on the fine powder side of the classifier, and the zone width of the coarse powder zone removed on the coarse powder side By changing one or more of (ΔMht) and the number of classifications, the volume median diameter D ₅₀ of the high melting point transparent toner particles can be adjusted. Among the transparent toners, in the classification process for producing the low melting point transparent toner, the zone width of the fine powder zone (ΔFlt) removed on the fine powder side of the classifier and the zone width of the coarse powder zone removed on the coarse powder side (ΔMlt) In addition, by changing one or more of the number of times of classification, the volume median diameter D ₅₀ of the low melting point transparent toner particles can be adjusted.

As the zone width (ΔFht or ΔFlt) of the fine powder zone removed on the fine powder side of the classifier increases, the volume median diameter D ₅₀ of the transparent toner particles increases. As the zone width (ΔMht or ΔMlt) of the coarse powder zone removed on the coarse powder side of the classifier increases, the volume median diameter D ₅₀ of the transparent toner particles decreases. As the number of times of classification increases, the volume median diameter D ₅₀ of the transparent toner particles decreases.

  The first embodiment has been described above. According to this embodiment, the low-melting point transparent toner and the high-melting point transparent toner are respectively supplied to the developing container 640 included in the first image forming unit 62T. Then, the controller 10 changes the duty ratio of the developing bias applied to the developing roller 641 of the first image forming unit 62T to thereby change the developing amount of the low melting point transparent toner used for the development and the high melting point transparent toner. The development amount (toner development ratio) is changed. That is, the image forming apparatus 1 does not need to provide an image forming unit for each of the high melting point transparent toner and the low melting point transparent toner. Therefore, the glossiness can be changed while suppressing the large size of the apparatus main body.

  In general, when the number of toner layers formed on a sheet increases, there is a risk that image disturbance is likely to occur. In contrast, the laminated toner of this embodiment forms a transparent toner image (a toner image in which a high melting point transparent toner and a low melting point transparent toner are mixed) on a colored toner image. Therefore, an increase in the number of toner image layers formed on the sheet S can be suppressed. As a result, the occurrence of image disturbance is suppressed.

  In this embodiment, the low melting point transparent toner and the high melting point transparent toner are replenished from different toner containers. For example, a transparent toner in which a low melting point transparent toner and a high melting point transparent toner are mixed is contained 1. Transparent toner may be supplied to one developing container 640 from one toner container.

  Further, although the toner particles according to the present embodiment have been described by taking the non-capsule toner particles as an example, the toner particles may be capsule toner particles including a toner core and a shell layer formed on the surface of the toner core.

  In this embodiment, the case where the toner is charged with a positive polarity has been described as an example. However, the toner may be charged with a negative polarity. In this case, the photosensitive drum 65 is charged to a negative polarity by the charging device 63.

[Embodiment 2]
<Configuration of image forming apparatus>
Next, the image forming apparatus 1 according to the second embodiment of the present invention will be described with reference to FIGS. 8 and 9. In the second embodiment, the control unit 10 changes the toner development ratio by executing a rough gloss adjustment process instead of the fine gloss adjustment process described in the first embodiment. Specifically, the control unit 10 changes the toner development ratio by changing the amount of high melting point transparent toner supplied to the developing container 640 and / or the amount of low melting point transparent toner. FIG. 8 is a block diagram illustrating a configuration of the image forming apparatus 1 according to the second embodiment.

  As shown in FIG. 8, the control unit 10 changes the toner development ratio by controlling the drive mechanism of the toner supply unit 5. Specifically, by controlling the rotation of the container screw 521 described with reference to FIG. 2, the amounts of the low melting point transparent toner and the high melting point transparent toner supplied to the developing container 640 are changed. Specifically, when increasing the development amount of the low melting point transparent toner at the toner development ratio, that is, when increasing the glossiness, the control unit 10 rotates the container screw 521 included in the first toner container 52L. As a result, the low melting point transparent toner is supplied to the developing container 640. As a result, the development amount of the low melting point transparent toner at the toner development ratio increases.

  On the other hand, when increasing the development amount of the high melting point transparent toner at the toner development ratio, that is, when decreasing the glossiness, the control unit 10 rotates the container screw 521 included in the second toner container 52H. As a result, the high melting point transparent toner is supplied to the developing container 640. As a result, the development amount of the high melting point transparent toner at the toner development ratio increases.

<Glossy rough adjustment process>
Next, the glossiness rough adjustment process will be described with reference to FIG. FIG. 9 is a flowchart illustrating a rough glossiness adjustment process according to the second embodiment. The glossiness rough adjustment process is started, for example, after the glossiness value is input to the control unit 10 and until the development bias application unit 11 applies the development bias to the development roller 641. Note that step S102, step S104, and step S110 shown in FIG. 9 are the same as those described with reference to FIG. 7, and thus the description of step S102, step S104, and step S110 is omitted.

  As shown in FIG. 9, when the control unit 10 determines that an instruction to increase the glossiness has been input (step S102: Yes), the low melting point transparent toner is supplied to the developing container 640 (step S202). Specifically, the control unit 10 rotationally drives the container screw 521 included in the first toner container 52L. As a result, the low melting point transparent toner is supplied to the developing container 640, and the ratio of the low melting point transparent toner contained in the developing container 640 increases. Next, the developing bias applying unit 11 applies a developing bias to the developing roller 641. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 65 is developed (step S110), and the glossiness rough adjustment process is completed.

  In step S104, when the control unit 10 determines that an instruction to lower the glossiness is input (step S104: Yes), high-melting point transparent toner is supplied to the developing container 640 (step S204). Specifically, the control unit 10 rotationally drives the container screw 521 included in the second toner container 52H. As a result, the high melting point transparent toner is supplied to the developing container 640, and the ratio of the high melting point transparent toner contained in the developing container 640 increases. Next, the developing bias applying unit 11 applies a developing bias to the developing roller 641. As a result, the electrostatic latent image formed on the surface of the photosensitive drum 65 is developed (step S110), and the glossiness rough adjustment process is completed.

  The second embodiment has been described above. According to the present embodiment, the ratio of the low melting point transparent toner to the high melting point transparent toner used for development is changed by changing the amount of the high melting point transparent toner and the low melting point transparent toner supplied to one developing container 640. Can be changed. Thereby, the image forming apparatus 1 can change the glossiness of the image formed on the sheet S. That is, the image forming apparatus 1 does not need to be provided with the developing container 640 for storing the high melting point transparent toner and the low melting point transparent toner, respectively, and can suppress the size of the apparatus main body.

  In addition, each item demonstrated in Embodiment 1 and Embodiment 2 can be combined suitably. For example, when the absolute value of the difference between the value indicating the glossiness input via the operation unit 2 and the value indicating the current glossiness is larger than a predetermined value, the image forming apparatus 1 Performs the glossy rough adjustment process described in the second embodiment. On the other hand, when the absolute value of the difference between the value indicating the glossiness input via the operation unit 2 and the value indicating the current glossiness is smaller than a predetermined value, the image forming apparatus 1 in the first embodiment. The gloss fine adjustment process described may be executed.

  The embodiment of the present invention has been described above with reference to the drawings (FIGS. 1 to 9). However, the present invention is not limited to the above-described embodiment, and can be implemented in various modes without departing from the gist thereof.

  For example, in the embodiment of the present invention, the case where the present invention is applied to the secondary transfer method has been described as an example, but the present invention is not limited to this. The present invention is also applicable to a direct transfer type image forming apparatus.

  In the embodiment of the present invention, the case where the present invention is applied to a printer has been described as an example, but the present invention is not limited to this. The present invention can also be applied to an electrophotographic multifunction peripheral.

  Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

<Example 1>
(Manufacture of polyester resin)
A polyester resin to be contained in the colored toner particles was produced by the following method.

  1960 g of bisphenol A propylene oxide adduct, 780 g of bisphenol A ethylene oxide adduct, 257 g of dodecenyl succinic anhydride, 770 g of terephthalic acid, and 4 g of dibutyltin oxide were charged into a container. The air in the container was replaced with nitrogen gas. Under a nitrogen atmosphere, the contents of the container were reacted for 8 hours under the conditions of a temperature of 235 ° C. and normal pressure. Thereafter, the container contents were reacted for 1 hour under conditions of a temperature of 235 ° C. and a pressure of 8.3 kPa. Furthermore, trimellitic anhydride was added to the contents of the container at a temperature of 180 ° C. Thereafter, the container contents were heated to 210 ° C. at a rate of temperature increase of 10 ° C./hour. As a result, a polyester resin was obtained.

(Manufacture of toner)
A toner was manufactured by the following method.

(Manufacturing colored toner)
First, a mixing step was performed. Specifically, 100 parts by mass of a polyester resin as a binder resin, 2 parts by mass of a quaternary ammonium salt (“BONTRON (registered trademark) P-51” manufactured by Orient Chemical Co., Ltd.) as a charge control agent, and a colorant 5 parts by mass of carbon black (“MA-100” manufactured by Mitsubishi Chemical Corporation) was mixed using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.) to obtain a mixture.

  Subsequently, a kneading step was performed. Specifically, the obtained mixture was melted and kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) to obtain a kneaded product. The resulting kneaded product was cooled.

  Subsequently, a pulverization step was performed. Specifically, the kneaded product was coarsely pulverized using a pulverizer (“Rohtoplex (registered trademark) 16/8 type” manufactured by Hosokawa Micron Corporation) to obtain a coarsely pulverized product. The obtained coarsely pulverized product was finely pulverized using a mechanical pulverizer (“Turbo Mill” manufactured by Freund Turbo, Inc.) under the conditions of a material input speed of 10 kg / hour and a rotational speed of 11000 rpm.

Subsequently, a classification process was performed. Specifically, the zone width (ΔFc) of the fine powder zone to be removed on the fine powder side of the classifier (airflow classifier, “Elbow Jet EJ-LABO type” manufactured by Nippon Steel & Mining Co., Ltd.) is set to 12 mm, and the coarse powder side The zone width (ΔMc) of the coarse powder zone to be removed was set to 22 mm. The obtained finely pulverized product was classified twice using a classifier under the condition of a material charging rate of 3.0 kg / hour. As a result, colored toner base particles were obtained. The obtained color toner base particles had a volume median diameter D ₅₀ of 6.50 μm.

  Subsequently, an external addition process was performed. Specifically, 97.1 parts by mass of the obtained colored toner base particles, 1.8 parts by mass of dry silica fine particles (“AEROSIL (registered trademark) REA200” manufactured by Nippon Aerosil Co., Ltd.) as an external additive, and external additives 1.0 parts by mass of conductive titanium oxide fine particles ("EC-100" manufactured by Titanium Industry Co., Ltd.) and 0.1 parts by mass of zinc stearate (manufactured by NOF Corporation) as an external additive, Mixing was performed using a mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.). The mixing conditions were set at a rotation speed of 30 m / sec and a mixing time of 5 minutes. As a result, the external additive was adhered to the surface of the colored toner base particles.

(Manufacture of transparent toner)
(Manufacture of high melting point transparent toner)
First, a mixing step was performed. Specifically, 100 parts by mass of a polyester resin (melting point Tm: 105 ° C., glass transition point Tg: 65 ° C.) as a binder resin and carnauba wax (“Carnauba Wax No. 1” manufactured by Hiroyuki Kato) ) 6 parts by mass and 2 parts by mass of a quaternary ammonium salt (“BONTRON (registered trademark) P-51” manufactured by Orient Chemical Co., Ltd.) as a charge control agent, and FM mixer (“FM manufactured by Nippon Coke Industries, Ltd.”) -20B ") to obtain a mixture.

  Subsequently, a kneading step was performed. Specifically, the obtained mixture was melted and kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) to obtain a kneaded product. The resulting kneaded product was cooled.

Subsequently, a pulverization step was performed. Specifically, the kneaded product was coarsely pulverized using a pulverizer (“Rohtoplex (registered trademark) 16/8 type” manufactured by Hosokawa Micron Corporation) to obtain a coarsely pulverized product. The obtained coarsely pulverized product was finely pulverized using a mechanical pulverizer (“Turbo Mill” manufactured by Freund Turbo, Inc.) under the conditions of a material input speed of 10 kg / hour and a rotational speed of 11000 rpm. The obtained finely pulverized product had a volume median diameter D ₅₀ of 6.0 μm.

Subsequently, a classification process was performed. Specifically, the zone width (ΔFht) of the fine powder zone to be removed on the fine powder side of the classifier (airflow classifier, “Elbow Jet EJ-LABO type” manufactured by Nippon Steel & Mining Co., Ltd.) is set to 12 mm, and the coarse powder side The zone width (ΔMht) of the coarse powder zone to be removed was set to 22 mm. The obtained finely pulverized product was classified twice using a classifier under the condition of a material charging speed of 3 kg / hour. As a result, high melting point transparent toner base particles were obtained. The obtained high melting point transparent toner mother particles had a volume median diameter D ₅₀ of 6.9 μm. The average circularity of the high melting point transparent toner base particles was 0.960.

(Manufacture of low melting point transparent toner)
First, a mixing step was performed. Specifically, 100 parts by mass of a polyester resin (melting point Tm: 95 ° C., glass transition point Tg: 58 ° C.) as a binder resin and carnauba wax (“Carnauba Wax No. 1” manufactured by Hiroyuki Kato) ) 6 parts by mass and 2 parts by mass of a quaternary ammonium salt (“BONTRON (registered trademark) P-51” manufactured by Orient Chemical Co., Ltd.) as a charge control agent, and FM mixer (“FM manufactured by Nippon Coke Industries, Ltd.”) -20B ") to obtain a mixture.

  Subsequently, a kneading step was performed. Specifically, the obtained mixture was melted and kneaded using a twin-screw extruder (“PCM-30” manufactured by Ikegai Co., Ltd.) to obtain a kneaded product. The resulting kneaded product was cooled.

Subsequently, a pulverization step was performed. Specifically, the kneaded product was coarsely pulverized using a pulverizer (“Rohtoplex (registered trademark) 16/8 type” manufactured by Hosokawa Micron Corporation) to obtain a coarsely pulverized product. The obtained coarsely pulverized product was finely pulverized using a mechanical pulverizer (“Turbo Mill” manufactured by Freund Turbo, Inc.) under the conditions of a material input speed of 10 kg / hour and a rotational speed of 10,000 rpm. The obtained finely pulverized product had a volume median diameter D ₅₀ of 6.4 μm.

  Subsequently, a classification process was performed. Specifically, the zone width (ΔFlt) of the fine powder zone to be removed on the fine powder side of the classifier (airflow classifier, “Elbow Jet EJ-LABO type” manufactured by Nippon Steel Mining Co., Ltd.) is set to 10 mm, and the coarse powder side The zone width (ΔMlt) of the coarse powder zone to be removed was set to 20 mm. The obtained finely pulverized product was classified once using a classifier under the condition of a material charging speed of 3 kg / hour. As a result, low melting point transparent toner base particles were obtained. The obtained low melting point transparent toner base particles had a volume median particle size of 6.5 μm. The circularity of the low melting point transparent toner base particles was 0.948.

1 part by mass of a high melting point transparent toner and 1 part by mass of a low melting point transparent toner were mixed, and then further mixed using an FM mixer (“FM-20B” manufactured by Nippon Coke Industries, Ltd.) to obtain a mixture. . As a result, a mixture having a volume median diameter D ₅₀ of 6.7 μm was obtained.

<Evaluation method>
The method for evaluating the change in glossiness is as follows.

  The two-component developer used for the evaluation was prepared by mixing 100 parts by mass of ferrite carrier (manufactured by Powder Tech Co., Ltd.) and 10 parts by mass of toner using a ball mill for 30 minutes.

(Glossiness evaluation)
The glossiness was evaluated in a normal environment (temperature 20 ° C., humidity 65% RH). As an evaluation machine, a multifunction machine (a modified machine of “FS-C8026” manufactured by Kyocera Document Solutions Inc.) was used. The amount of the two-component developer initially charged in the developing container of the evaluation machine was 220 g. 220 g of the two-component developer was a mixture of 10 g of high melting point transparent toner, 10 g of low melting point transparent toner, and 200 g of ferrite carrier. The voltage value of the DC voltage applied to the developing roller included in the evaluation machine is 300 V, the value of the AC voltage is 1.6 kV, the frequency f of the AC voltage is 2.7 kHz, and the duty ratio is 55. %Met. The image I forming process was executed on one sheet (90 g / m ² , A4 size). The image I was a solid image in a direction orthogonal to the transport direction, and the printing rate was 20%. The gloss value (glossiness) of the image I printed on the paper was measured using a gloss meter (“Handy Gloss Meter Gloss Checker IG-331” manufactured by HORIBA, Ltd.).

  In Example 2 and Example 3, as shown in Table 1, the image forming process was executed by changing the duty ratio of the developing bias. Then, the gloss value of each image formed on the sheet was measured.

In Example 4, as shown in Table 1, the image forming operation was executed by changing the ratio of the amount of the high melting point transparent toner and the amount of the low melting point transparent toner. Then, the gloss value of the image formed on the sheet was measured.

  As described above, as shown in Table 1, it is shown that the gloss value of the image can be changed by changing the duty ratio of the developing bias or the ratio of the high melting point transparent toner and the low melting point transparent toner contained in the developing container 640. It was.

  From the above, according to the present invention, it was shown that the gloss value of the image can be changed by changing the duty ratio and the ratio of the high melting point transparent toner and the low melting point transparent toner contained in the developing container 640. .

  The present invention is useful for an electrophotographic image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 7 Transfer apparatus 10 Control part 62Y-62K Colored image forming unit 62T Transparent image forming unit 64 Developing apparatus 65 Photosensitive drum S Sheet

Claims (6)

A colored image forming unit for forming a colored toner image;
A transparent image forming unit for forming a transparent toner image;
A transfer device that superimposes the transparent toner image on the colored toner image and transfers it to a sheet;
A controller for controlling the operation of the transparent image forming unit,
The transparent image forming unit includes:
An image carrier on which an electrostatic latent image is formed;
A developing device for developing the electrostatic latent image with a first toner and a second toner having a melting point higher than that of the first toner;
The control unit includes a first toner development amount of the first toner used for developing the electrostatic latent image, and a second toner development amount of the second toner used for developing the electrostatic latent image. An image forming apparatus for changing the toner development ratio calculated by A bias application unit for applying a development bias to the developing roller of the developing device;
The image forming apparatus according to claim 1, wherein the control unit changes the toner development ratio by changing a duty ratio of the development bias. A first toner supply device for supplying the first toner to the developing device;
A second toner replenishing device for replenishing the second toner to the developing device;
The controller changes a first supply amount of the first toner supplied from the first toner supply device and a second supply amount of the second toner supplied from the second toner supply device. The image forming apparatus according to claim 1, wherein the toner development ratio is changed according to the method.   4. The image forming apparatus according to claim 1, wherein a first volume median diameter of the first toner is smaller than a second volume median diameter of the second toner. 5.   The image forming apparatus according to claim 1, wherein a first average circularity of the first toner is lower than a second average circularity of the second toner. Forming a colored toner image;
Forming a transparent toner image;
Transferring the transparent toner image on the colored toner image and transferring it to a sheet,
Forming the transparent toner image comprises:
Forming an electrostatic latent image on the image carrier;
The first toner development amount of the first toner used for developing the electrostatic latent image and the second toner development of the second toner having a melting point higher than that of the first toner used for developing the electrostatic latent image And developing the electrostatic latent image by changing a toner development ratio calculated according to the amount.

Images