JP2011141479A - Mixed developer, developing device and image forming apparatus using the mixed developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce print density difference caused by the difference in the amount of charge of a developer between a developer image formed in initial printing and a developer image formed in ordinary printing. <P>SOLUTION: The mixed developer includes a mixture of a first developer with a low colorant concentration, a slow charge buildup, and a high saturated charge amount absolute value (a developer A for normal printing), a second developer with a high colorant concentration, a rapid charge buildup, with a low saturated charge amount absolute value (a developer B for initial printing), and a carrier for adhesion of the first developer and the second developer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a mixed developer, and a developing device and an image forming apparatus using the mixed developer.

  At the time of initial printing, the developer used in the electrophotographic image forming apparatus is defined by the absolute value of the charge amount by stirring for 1 minute and the absolute value of the charge amount by stirring for 5 minutes when mixed with the carrier. In addition, there is a developer that can form an image free from fogging and smearing during normal printing (see Patent Document 1). “Initial printing” means printing processing performed immediately after startup after the image forming apparatus has been left for a while. “Normal printing” means printing processing performed after the image forming apparatus is continuously operated. In addition, “fogging” means a phenomenon in which the developer adheres to the non-image area. Further, “dirt” means a phenomenon in which black spots made of a developer appear as if scattered.

JP 2008-216582 A

  However, as described below, a conventional developer may cause a difference in print density (color tone) between a developer image formed during initial printing and a developer image formed during normal printing. There was a problem.

  For example, when the image forming apparatus is left for a while, the developer is discharged and the charge amount becomes low. In addition, the developer generally deteriorates in charge rising property during initial printing. For this reason, the image forming apparatus cannot charge the developer up to a saturation charge amount capable of good printing processing in a short time during initial printing, and as a result, a developer image can be formed with an insufficient amount of developer. May form. Therefore, the image forming apparatus may form a developer image having a low print density (light color tone) during initial printing. The print density (color tone) is lightness when the developer color is black, and saturation when the developer color is color.

  On the other hand, the charge amount of the developer is close to the saturation charge amount when the image forming apparatus is continuously operated. Therefore, the image forming apparatus can always charge the developer up to the saturated charge amount in a short time during normal printing, and as a result, forms a developer image with a sufficient amount of developer. Therefore, the image forming apparatus stably forms a developer image having a high printing density (high color tone) during normal printing.

  As described above, the conventional developer has a difference in print density (the color of the developer varies depending on the charge amount of the developer between the developer image formed during initial printing and the developer image formed during normal printing. A difference in brightness may occur in the case of black, and a saturation difference in the case of a color developer.

  Accordingly, the present invention has been made to solve the above-described problems, and is a mixed development that reduces a difference in print density between a developer image formed during initial printing and a developer image formed during normal printing. The main object is to provide a developer, and a developing device and an image forming apparatus using the mixed developer.

  In order to achieve the above object, the first invention is a mixed developer, the first developer having a low colorant concentration, a slow charge rise, and a high saturation charge amount, and A second developer having a higher colorant concentration than the first developer, a fast charge start-up, and a low absolute value of the saturation charge amount; the first developer; and the second developer. The carrier for adhering the agent is mixed.

In this mixed developer, the second developer having a fast charge rise is preferentially used over the first developer at the time of initial printing in which the charge rise property of the developer generally deteriorates. Since the second developer is smaller than the first developer having a low absolute value of the saturation charge amount, it forms a developer image in a smaller amount than the first developer, but it is less than the first developer. Since the concentration of the colorant is high (the color is dark), it is possible to form a developer image having a sufficiently high print density (dark color tone).
On the other hand, in the case of this mixed developer, the first developer having a high absolute value of the saturation charge amount is preferentially used over the second developer during normal printing in which the charge rising property of the developer is restored. Although the first developer has a lower colorant concentration (lighter color) than the second developer, the absolute value of the saturation charge amount is high, so that a sufficient amount of developer image can be formed. This makes it possible to form a developer image having a sufficiently high print density (dark color tone).

  Therefore, this mixed developer has a difference in printing density between the developer image formed during initial printing and the developer image formed during normal printing (lightness difference when the developer color is black, developer color). In the case where is a color, the saturation difference) can be reduced.

  The second invention is a developing device, the developer containing portion for containing the developer, an image carrier on which an electrostatic latent image is formed on the surface, and the supply of the developer from the developer containing portion And a developer carrier that develops the developer by attaching the developer to the electrostatic latent image formed on the surface of the image carrier, and the developer container is colored as the developer. The first developer having a low concentration of the agent, having a slow charge rise and a high absolute value of the saturation charge amount, and having a higher colorant concentration and a faster charge rise than the first developer. And containing a mixed developer in which a second developer having a low absolute value of the saturation charge amount and a carrier that adheres the first developer and the second developer are mixed. To do.

  In this developing device, the mixed developer according to the first invention is accommodated in the developer accommodating portion, and an image is formed using the mixed developer. Therefore, as in the first invention, this developing device can reduce the print density difference between the developer image formed during initial printing and the developer image formed during normal printing.

  According to a third aspect of the present invention, there is provided an image forming apparatus including the developing device according to the second aspect of the present invention, a transfer unit, and a fixing unit.

  This image forming apparatus has the developing device according to the second invention, and forms an image using the mixed developer accommodated in the developer accommodating portion of the developing device. Therefore, as in the second invention, this image forming apparatus can reduce the print density difference between the developer image formed during initial printing and the developer image formed during normal printing.

According to the first aspect of the present invention, it is possible to provide a mixed developer capable of reducing a difference in print density between a developer image formed during initial printing and a developer image formed during normal printing.
According to the second invention, a developing device using the mixed developer according to the first invention can be provided.
Furthermore, according to the third invention, an image forming apparatus using the developing device according to the second invention can be provided.

1 is a diagram illustrating a configuration of an image forming apparatus according to the present invention. 1 is a diagram illustrating a configuration of a developing device according to the present invention. It is a graph which shows the characteristic of the developer which comprises the mixed developing agent which concerns on this invention. It is a figure which shows the structure of the shaker used for stirring of a mixing developing agent. It is explanatory drawing which shows the evaluation method of printing density. It is a figure which shows the evaluation measurement point of printing density.

  Hereinafter, an embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings. Each figure is only schematically shown so that the present invention can be fully understood. Therefore, the present invention is not limited to the illustrated example. Moreover, in each figure, the same code | symbol is attached | subjected about the common component and the same component, and those overlapping description is abbreviate | omitted.

[Embodiment 1]
<Configuration of image forming apparatus>
The configuration of the image forming apparatus according to the present invention will be described below with reference to FIG. FIG. 1 is a diagram showing a configuration of an image forming apparatus according to the present invention. Here, the image forming apparatus 100 according to the present invention will be described as an electrophotographic color printer. In the following description, it is assumed that a mixed developer described later for each color of black (B), yellow (Y), magenta (M), and cyan (C) is used as the developer TN. In the following description, when distinguishing the component corresponding to each color, the English letters “B”, “Y”, “M”, and “C” representing each color are added at the end of the code representing each component. It shall be added.

  As shown in FIG. 1, the image forming apparatus 100 includes a paper feeding cassette 2, a discharge tray 3, a paper feeding / conveying mechanism 4, a reversing unit 8, a travel guide 9, an image forming unit 40, and a fixing device 50. Yes.

The paper feed cassette 2 is a medium storage unit that stores a medium P that is used as recording paper in the printing process. In the example shown in FIG. 1, the paper feed cassette 2 is provided below the reversing unit 8.
The discharge tray 3 is a medium stacking unit on which the printed media P are stacked.

The sheet feeding / conveying mechanism 4 performs sheet feeding (that is, a process of feeding the medium P accommodated in the sheet feeding cassette 2 to a conveying path provided inside the image forming apparatus 100), and the medium P is fed to the sheet feeding cassette 2. To the discharge tray 3.
The paper feed transport mechanism 4 includes a paper feed roller 5, a transport roller 6, a discharge roller 7, and a transfer belt 31 on the transport path from the paper feed cassette 2 to the discharge tray 3.

The paper feed roller 5 is a roller member that feeds the medium P accommodated in the paper feed cassette 2 to the transport path.
The transport roller 6 is a roller member that transports the medium P fed to the transport path toward the discharge tray 3.
The discharge roller 7 is a roller member that discharges the medium P to the discharge tray 3 and accumulates the medium P on the discharge tray 3.
The transfer belt 31 is a traveling member that travels during printing and transports the medium P to the fixing device 50 while being in contact with the photosensitive drum 12 described later. The transfer belt 31 is also a component included in a transfer unit 30 described later.

The reversing unit 8 is a mechanism that reverses the medium P having the developer image transferred to one surface thereof and guides it to the image forming unit 40 during duplex printing. The medium P is subjected to a printing process on one side, whereby the developer image is transferred to the one side, and then reversed by the reversing unit 8 and guided to the image forming unit 40 to print on the other side. By performing the processing, the developer image is also transferred to the other surface. As a result, the developer image is transferred onto both sides of the medium P.
The travel guide 9 is a member that guides the conveyance of the medium P. The travel guide 9 is configured to be rotatable in an arbitrary direction, and also functions as a means for switching the conveyance direction of the medium P.

The image forming unit 40 is a mechanism for forming an image.
The image forming unit 40 includes a developing device 10, an exposure unit 20, and a transfer unit 30.

  The developing device 10 develops an electrostatic latent image as a developer image by attaching the developer TN to an electrostatic latent image formed on the surface of a photosensitive drum 12 (see FIG. 2) to be described later. It is. Four developing devices 10 are provided for each color of black (B), yellow (Y), magenta (M), and cyan (C). Details of the developing device 10 will be described later.

  The exposure unit 20 is an exposure unit that partially irradiates the photosensitive drum 12 of the developing device 10 with light to form an electrostatic latent image on the surface of the photosensitive drum 12. Four exposure units 20 are provided for each color of black (B), yellow (Y), magenta (M), and cyan (C).

The transfer unit 30 is a transfer unit that transfers the developer image formed on the surface of the photosensitive drum 12 to the medium P (or the transfer belt 31).
The transfer unit 30 includes a transfer belt 31, a transfer roller 32, a driving roller 33, a belt idle roller 34, a cleaning blade 35, and a waste developer tank 36.

  As described above, the transfer belt 31 is a transport unit that travels during printing and transports the medium P to the fixing device 50 while being in contact with the surface of the photosensitive drum 12 described later. When the density of developer TN is detected, the transfer belt 31 travels in a state where the medium P is not conveyed, so that the developer TN is transferred to the surface. The developer TN transferred to the surface of the transfer belt 31 is measured for density by a density detection sensor (not shown), scraped off from the transfer belt 31 by the cleaning blade 35, and stored in the waste developer tank 36. .

  The transfer roller 32 is a roller member that transfers the developer image formed on the surface of the photosensitive drum 12 to the medium P (or the transfer belt 31). Four transfer rollers 32 are provided in the transfer belt 31 according to each color of black (B), yellow (Y), magenta (M), and cyan (C). The transfer rollers 32B, 32Y, 32M, and 32C are opposed to the photosensitive drums 12B, 12Y, 12M, and 12C, which will be described later, of the developing devices 10B, 10Y, 10M, and 10C, respectively. Each transfer roller 32B, 32Y, 32M, 32C is applied with a voltage having a polarity opposite to the polarity of the developer image of each color formed on the surface of each photosensitive drum 12B, 12Y, 12M, 12C. As a result, the transfer rollers 32B, 32Y, 32M, and 32C draw the developer images of the respective colors from the surfaces of the photosensitive drums 12B, 12Y, 12M, and 12C and transfer them to the medium P (or the transfer belt 31). At this time, if the developer images of the respective colors are formed on the surfaces of the photosensitive drums 12B, 12Y, 12M, and 12C, the developer images of the respective colors are transferred in an overlapping manner. As a result, a color developer image is formed on the medium P.

  The drive roller 33 and the belt idle roller 34 are roller members that stretch the transfer belt 32. The drive roller 33 travels the transfer belt 32 in response to rotational driving from a belt motor (not shown) serving as a belt conveyance drive unit. On the other hand, the belt idle roller 34 applies tension so that the transfer belt 31 does not slack.

The cleaning blade 35 is a member that cleans the surface of the transfer belt 32. The cleaning blade 35 comes into contact with the transfer belt 32 and scrapes off the developer TN adhering to the surface of the transfer belt 32 from the transfer belt 32. The cleaning blade 35 is made of, for example, urethane rubber.
The waste developer tank 36 is a storage unit that stores the developer TN scraped off from the transfer belt 32 by the cleaning blade 35.

  The fixing device 50 is a fixing unit that fixes the developer image on the medium P by heating and pressurizing the medium P on which the developer image has been transferred to melt the developer image.

<Configuration of developing device>
Hereinafter, the configuration of the developing device 10 according to the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a configuration of the developing device according to the present invention.

  The developing devices 10B, 10Y, 10M, and 10C corresponding to the respective colors of black (B), yellow (Y), magenta (M), and cyan (C) have different colors of the developer TN contained therein. Other than that, the structure is the same.

  The developing device 10 includes a developer container 11, a photosensitive drum 12, a charging roller 13, a developing roller 14, a supply roller 15, a developing blade 16, a cleaning blade 17, and a seal member 18.

  The developer container 11 is a container for storing the developer TN inside. The developer container 11 is detachably mounted above the supply roller 15. The developer container 11 has a supply port, and supplies the developer TN to the supply roller 15 through the supply port. Here, the description will be made assuming that the developer TN is a nonmagnetic one-component pulverized developer that is negatively charged.

  The photosensitive drum 12 is a photosensitive member that rotates at a predetermined speed in the arrow direction shown in FIG. The photosensitive drum 12 functions as an image carrier on which an electrostatic latent image and a developer image are formed.

  The charging roller 13 is a roller member that uniformly charges the surface of the photosensitive drum 12. The charging roller 13 is provided in contact with the peripheral surface of the photosensitive drum 12. An exposure unit 20 (see FIG. 1) is provided between the charging roller 13 and the developing roller 14. The exposure unit 20 irradiates the surface of the photosensitive drum 12 charged by the charging roller 13 with light to form an electrostatic latent image on the surface of the photosensitive drum 12. The charging roller 13 includes a metal shaft and an elastic layer formed of semiconductive epichlorohydrin rubber that covers the periphery of the metal shaft.

  The developing roller 14 is a roller member to which a predetermined voltage can be applied. The developing roller 14 rotates along with the photosensitive drum 12, and at this time, the developer TN adheres to the electrostatic latent image formed on the surface of the photosensitive drum 12. Thus, the developing roller 14 functions as a developer carrying member that visualizes (develops) the electrostatic latent image as a developer image. The developing roller 14 is formed of, for example, steel whose surface is nickel-plated as a core, an elastic layer formed of urethane rubber covering the periphery of the core, and an isocyanate covering the surface of the elastic layer. It is the structure which has the made surface layer.

  The supply roller 15 is a roller member that supplies the developer TN supplied from the developer container 11 to the development roller 14. The supply roller 15 is provided so as to be in contact with the peripheral surface of the developing roller 14 and rotates in a direction opposite to the developing roller 14 as indicated by an arrow shown in FIG. At that time, the supply roller 15 causes the developer TN around the supply roller 15 to adhere to the surface of the development roller 14. The supply roller 15 has, for example, a structure in which steel having a surface plated with nickel is used as a core, and the core and an elastic layer formed by silicone foam rubber covering the periphery of the core. In addition, the silicone foam rubber of the supply roller 15 has, for example, open cells having a cell diameter of 300 to 500 μm. Therefore, the supply roller 15 is configured as a sponge roller.

  The developing blade 16 is a regulating member that regulates the layer thickness of the developer TN attached to the surface of the developing roller 14. The developing blade 16 is in pressure contact with the developing roller 14, regulates the layer thickness of the developer TN, and charges the developer TN to a predetermined polarity. The developing blade 16 is configured, for example, by bending a stainless steel (SUS304B-TA) material plate having a thickness of 0.08 mm so as to be divided into a short side and a long side at a bending R of 0.275 mm. The developing blade 16 is disposed so that the short side is on the upstream side and the long side is on the downstream side when viewed from the rotation direction of the developing roller 14, and is bent at the same linear pressure (about 40 to 70 gf / cm). Then, it is pressed against the developing roller 14.

  The cleaning blade 17 is a member that cleans the surface of the photosensitive drum 12. The cleaning blade 17 comes into contact with the photosensitive drum 12 and scrapes off the developer TN remaining on the surface of the photosensitive drum 12 after the transfer process from the photosensitive drum 12. The cleaning blade 17 is made of, for example, urethane rubber.

  The seal member 18 is a sealing member that prevents the developer TN from leaking outside the developing device 10. The seal member 18 is provided in contact with the peripheral surface of the photosensitive drum 12.

<Operation of Image Forming Apparatus>
Hereinafter, the operation of the image forming apparatus 100 will be described.
When the image forming apparatus 100 (see FIG. 1) receives print data from a host device via an interface (not shown), the fixing device 50 starts heating a heater (not shown) and a heating member (not shown) and the heating member (not shown). The rotation of the pressure member that rotates around is started. When the surface temperature of the heating member reaches the set temperature, the image forming apparatus 100 starts feeding and transporting the medium P.

  In the developing device 10, when the feeding of the medium P is started, the photosensitive drum 12, the developing roller 14, and the supply roller 15 rotate in the directions of the arrows shown in FIG. At this time, the charging roller 13 charges the surface of the photosensitive drum 12, and then the exposure unit 20 partially irradiates the surface of the photosensitive drum 12 with the electrostatic latent image on the surface of the photosensitive drum 12. Form. At this time, the supply roller 15 supplies the developer TN to the developing roller 14. The developer TN is triboelectrically charged to the negative electrode on the surface of the developing roller 14 while the layer thickness is regulated by the interaction with the developing blade 16. As a result, a layer of developer TN is formed on the surface of the developing roller 14. The developer TN constituting this layer adheres on the electrostatic latent image formed on the surface of the photosensitive drum 12 from the surface of the developing roller 14 due to a potential difference set between the developing roller 14 and the photosensitive drum 12. To do. As a result, a developer image is formed on the surface of the photosensitive drum 12. This developer image is transferred to the medium P by the transfer unit 30.

The medium P on which the developer image has been transferred is conveyed in the direction of the arrow h shown in FIG. 1 and travels between a heating member and a pressure member (not shown) of the fixing device 50. At this time, the fixing device 50 causes the heat of the heating member to melt the developer image on the surface of the medium P, and further, the pressure between the heating member and the pressure member is applied to the developer TN and the medium P. The developer image is fixed on the medium P.
The image forming apparatus 100 conveys the medium P on which the developer image is fixed to the discharge tray 3 and accumulates it on the discharge tray 3.

<Details of mixed developer>
(Outline of mixed developer)
The developer TN has a low colorant concentration (that is, a light color), a first developer for normal printing that is preferentially used during normal printing, and a high colorant concentration (that is, the color is low). Dark), a mixed developer in which a second developer for initial printing used preferentially at the time of initial printing and a carrier to which the first developer and the second developer are attached are mixed. ing.

(Characteristics of developer constituting mixed developer)
The first developer (hereinafter referred to as “developer A”) and the second developer (hereinafter referred to as “developer B”) have the characteristics shown in FIG. FIG. 3 is a graph showing the characteristics of the developer constituting the mixed developer according to the present invention.
As shown in FIG. 3, the developer A has characteristics that the charge rising is slow and the absolute value of the saturation charge amount Ts1 is high.
On the other hand, the developer B has characteristics that the charge rise is fast and the absolute value of the saturation charge amount Ts2 is low.

(Mixed developer manufacturing method)
Hereinafter, a method for producing the mixed developer TN used in the first embodiment will be described. Here, as an example, a method for producing a black mixed developer TN will be described. Further, here, in order to describe the most preferable configuration as the mixed developer TN, as shown in Table 1, one type of developer A is used as the first developer, and the second developer is used. A plurality of mixed developers are purified using six types of developers B1 to B6, and each mixed developer is comparatively evaluated.

The production method of the mixed developer TN is as follows.
First, the developer A constituting the mixed developer TN is purified by the following processes (1) to (4).
(1) As shown in Table 1, 4.0 parts by weight as a colorant in 100 parts by weight of a binder resin (amorphous polyester resin, number average molecular weight Mn = 3700, glass transition temperature Tg = 62 ° C.) Carbon black (MOGUL-L, manufactured by Cabot), 1.5 parts by weight of a salicylic acid complex (manufactured by Orient Chemical Industries, Bontron E-84) as a charge control agent, and a charge control resin having a quaternary ammonia salt 3.5 parts by weight of the polyester resin and 3.0 parts by weight of carnauba wax (carouba wax No. 1 powder manufactured by Kato Yoko Co., Ltd.) are added.

  (2) These were mixed using a Henschel mixer (FM500E, manufactured by Mitsui Mining Co., Ltd.), then melt-kneaded while heating in a temperature environment of 100 ° C. using a twin-screw extruder, and after cooling, the diameter was 2 mm. Roughly pulverize with a cutter mill having a screen.

  (3) After that, these are pulverized using a collision-type pulverizer “Dispersion Separator” (manufactured by Nippon Pneumatic Industrial Co., Ltd., DSX type), and further classified using an air classifier, and the resulting powder The body is referred to as a developer base a.

  (4) Then, as an external addition step, 100 parts by weight were taken out from the obtained powder (developer base a) and crushed (specifically, inorganic material aggregated by a high-speed stirrer such as a Henschel mixer) 2.5 parts by weight of hydrophobic silica R972 (manufactured by Nippon Aerosil Co., Ltd., average primary particle size 16 nm) and 2.0 parts by weight of hydrophobic silica RY-50 (Japan) Aerosil Co., Ltd., average primary particle size of 40 nm) is added, and the mixture is stirred for 2 minutes at a rotation speed of 3200 revolutions / minute using a 10-liter Henschel mixer. Thereby, the developer A can be obtained.

  For the other developers B1 to B6, the same materials are used, and the addition amounts of the colorant, the charge control agent, and the charge control resin are changed as shown in Table 1, and the same as (1) to (3) above. The powders obtained by executing the processing are respectively used as the developer bases b1 to b6, and the developer bases b1 to b6 are used to perform the same processing as the above (4).

  The average particle sizes of Developer A and Developers B1 to B6 thus obtained were all 5.5 μm. The average particle size was measured using an ISOTON II (manufactured by BECKMAN COULTER) as the electrolyte, an aperture diameter of 100 μm, an aperture current of 1600 μA, a measurement range of 2 to 60 μm, and a total count of 30000. Measurement was performed by the Coulter principle method (pore electrical resistance method) using Multisizer 3 (manufactured by BECKMAN COULTER) as a distribution measuring device.

  In the case of producing a yellow, magenta or cyan mixed developer, for example, instead of carbon black which is a black colorant, for example, Pigment Yellow (Daiichi Seika Kogyo Co., Ltd.) having the same weight part as that of carbon black. Manufactured by ECY-215) or the same part by weight of Pigment Red (Daiichi Seika Kogyo Co., Ltd., ECR-101) or the same part by weight of Pigment Blue (Daiichi Seika Kogyo Co., Ltd., ECB-301) may be used. .

  The mixed developer TN is refined by mixing the developer A, the optimum one type of developer B among the developers B1 to B6, and the carrier. Developer A and developer B have a negative charge due to charge exchange by contact and friction with the surface of the carrier. On the other hand, the carrier has a positive charge commensurate with it. As a result, the developer A and the developer B are attached to the carrier by generating an adhesion force composed of a Coulomb force and a short range van der Waals force.

  As the carrier, iron powder, glass beads, ferrite powder, nickel powder, or the like whose surface is coated with a resin is used. The mixing ratio with the carrier is set as appropriate. In Embodiment 1, ferrite powder (F-60, average primary particle size: 50 μm) was used as a carrier, and the mixing ratio with the carrier was 5% by weight.

  In the first embodiment, in order to identify the most preferable configuration as the mixed developer TN, evaluation of printing density (color tone) and evaluation of charging characteristics of each developer described below were performed.

(Summary of print density evaluation)
In the first embodiment, for each developer A and developers B1 to B6, when each of developer A and developers B1 to B6 are individually mixed in a carrier, and in developer A and developers B1 to B6 Each of these samples was used as a sample when the developer B was mixed with a carrier, and the printing density of each sample was evaluated.

  Evaluation of the print density of each sample is performed by causing the image forming apparatus 100 in which the sample is accommodated to perform solid printing, and the density (hereinafter referred to as “solid density”) of the solid printing (Optical Density value; This was done by measuring the OD value.

(Outline of evaluation of charging characteristics)
Further, in the first embodiment, for each developer A and developers B1 to B6, similarly, when each developer A and each of developers B1 to B6 are individually mixed in a carrier, developer A and developer Each of the samples B1 to B6 was mixed with a carrier and the sample was used as a sample, and the charging characteristics of each sample were evaluated.

  The charging characteristics of each sample were evaluated by stirring each sample to charge it and measuring the charge amount. In the stirring of each sample, a shaker Model-YS-LD (manufactured by Yayoi Co., Ltd.) was used as a stirrer. This shaker has, for example, a configuration shown in FIG. FIG. 4 is a diagram illustrating a configuration of a shaker used for stirring the mixed developer. As shown in FIG. 4, the shaker 60 includes a support portion 61 serving as a base, and a shake portion 62 that shakes (shakes) each sample. The shaking part 62 has a shaking width of 80 mm, a shaking angle of 0 ° to 45 °, and a shaking frequency of 200 times / minute. The shaker 60 agitates and charges the sample by shaking the shaker 62 in a state where the sample is accommodated in the shaker 62.

  In the evaluation of the charging characteristics of each sample, a suction blow type charge amount measuring device TB203 (manufactured by Kyocera Chemical Co., Ltd.) was used as a charge amount measuring device. Moreover, as an evaluation condition, the carrier is F-60 (manufactured by Powder Tech Co., average primary particle size 50 μm), the mixing ratio with the carrier is a mixing weight ratio of 5%, and the temperature and humidity of the measurement environment are 25 ° C. and 40%. (Hereinafter referred to as “25 ° C./40%”), the suction pressure was −40 kPa, the blow pressure was 7.0 kPa, and the measurement time was 10 seconds. The charging characteristics of each sample were evaluated by setting the stirring time of each sample to 60 seconds and 600 seconds, and measuring the charge amounts Q60 and Q600 at that time. The evaluation results are as shown in Table 1 above. In Table 1, Q60 / Q600 represents the charge rising property. Q60 / Q600 indicates that the larger the numerical value, the better the charge rising property.

(Evaluation of each specific sample)
Hereinafter, specific evaluation of each sample will be described. Here, the standing environment (temperature / humidity) of the developer and the standing time before the charge amount measurement (stirring with the carrier) were set to 25 ° C./40% for 12 hours or more. In addition, the environment (temperature / humidity) in which the stirring (shaking) operation with the carrier is performed and the environment (temperature / humidity) in which the charge amount measurement is performed with the suction blow type charge amount measuring device are also 25 ° C./40%, respectively. .

  In the evaluation of the print density (color tone) of each sample, a 100% duty pattern 72 is printed within the printable range 71 of the medium P while the medium P is conveyed in the direction of the arrow shown in FIG. Let The print density of each sample was evaluated by measuring the density of the duty pattern 72. FIG. 5 is an explanatory diagram showing a printing density evaluation method.

Specifically, after the image forming apparatus 100 in which the sample is accommodated is left for 12 hours, the adhesion amount of each sample on the surface of the photosensitive drum 12 is set to 0.50 mg / cm ² . As “evaluation medium after being left”, 100% duty pattern 72 is printed on one medium P, and further, 1% duty pattern 72 is continuously printed on 5,000 sheets of medium P. As a “evaluation medium after continuous printing”, 100% duty pattern 72 was printed on one medium P. The duty of the duty pattern 72 is 100% when solid printing is performed with an area ratio of 100% (that is, when solid printing is performed on the entire printable range 71 of one medium P).

  The evaluation of the print density of each sample is the value of the solid density as the print density at the nine measurement points 73 shown in FIG. 6 with respect to the “evaluation medium after standing” and the “evaluation medium after continuous printing”. This was done by measuring (OD value) and calculating the average. FIG. 6 is a diagram showing evaluation measurement points of print density.

  In the evaluation of the printing density of each sample, X-Rite 528 (manufactured by X-Rite) was used as a density measuring device. As evaluation conditions, the carrier used is F-60 (manufactured by Powdertech, average primary particle size 50 μm), the mixing ratio with the carrier is 5% by weight, and the printing speed of the image forming apparatus 100 is 170 (mm / mm). sec), the temperature and humidity of the printing environment (hereinafter referred to as “RT environment”) were 25 ° C./40%, and the medium P was A4 size Excellent White (manufactured by Oki Data Corporation). Note that the printing speed of the image forming apparatus 100 is the speed of the peripheral surface of the photosensitive drum 12 and also the transport speed of the medium P. Further, the image forming apparatus 100 and the sample were left in an RT environment for 12 hours in order to adjust to the environment. Unless otherwise specified, the evaluation conditions other than the samples are the same.

The solid density value (OD value) as the printing density of each sample was as shown in Table 1 above. Here, “print density” is represented by a common logarithmic value (no unit) of the reciprocal of the transmittance of incident light. Further, here, when the average print density is 1.35 or more and 1.65 or less, the print density is good, and therefore, “pass (hereinafter referred to as“ ◯ ”)” is set. On the other hand, when the average print density is less than 1.35 or higher than 1.65, the print density is too low or too high, and therefore, “fail” (hereinafter referred to as “x”) is set. The evaluation results are shown in Table 2.

  Table 2 shows a case where each of the developer A and developers B1 to B6 is mixed with a carrier alone at a mixing weight ratio of 5%, and 50 parts by weight of developer A and 50 parts by weight at a mixing weight ratio of 5%. Each of the case where any one type of developer B among the developers B1 to B6 is mixed with a carrier is used as a sample. Table 2 shows all the evaluation results when the developers B1 to B6 are individually mixed with the carrier because the evaluation results are all the same.

  (1) Table 2 shows that the average printing density of the evaluation medium after being left is “density after leaving” and the average printing density of the evaluation medium after continuous printing is “density after continuous printing”. The evaluation results of “density after standing” and “density after continuous printing” are shown. In Table 2, a case where the print density is less than 1.35 is indicated as “× (low)”, and a case where the print density is higher than 1.65 is indicated as “x (high)”.

  (2) Table 2 shows, for each sample, the difference between the average print density of the evaluation medium after standing and the average print density of the evaluation medium after continuous printing is “print density difference”. The evaluation results are shown. In Table 2, since the print density difference with time is small and good when the print density difference is less than 0.3, it is “◯”, and when the print density difference is higher than 1.65, Since the print density difference is large and not good, it is indicated as “x”.

  (3) Table 2 shows “overall evaluation” for each sample. Table 2 shows that when the sample is “◯” in all items of “density after standing”, “density after continuous printing”, and “print density difference”, the print density is good even over time. Since stable color development is possible, if the overall evaluation is “◯” and the sample is “x” in any one item, stable color development can be achieved with good print density over time. Since it is not possible, the overall evaluation is indicated as “×”.

  As shown in Table 2, the sample when developer A is mixed alone with the carrier (hereinafter referred to as “developer A single sample”) is too low after standing, and therefore “× (low)”. It became.

  Further, a sample in which each of the developers B1 to B6 is mixed with a carrier alone (hereinafter referred to as “developer Bn single sample (where n = 1, 2,..., 6)”) is the developer B. The density of this colorant was high (the color was dark), so the density after standing was “◯”, but the density after continuous printing was too high, and “× (high)”.

  Further, a sample in which developer A and any one of developer B 1 among developers B1 to B6 are mixed in a carrier (hereinafter referred to as “developer A + Bn sample (where n = 1, 2,..., 6) ”), the developer A + B3 sample was“ ◯ (good) ”in all items. As shown in FIG. 3, this is generally during initial printing in which the charge rising property of the developer deteriorates (that is, during printing processing performed immediately after the image forming apparatus 100 is left for a while). Developer B for initial printing having good charge rise characteristics is preferentially used, and printing processing performed during normal printing in which the charge rise characteristics of the developer is restored (that is, after the image forming apparatus 100 is continuously operated). This is because the normal printing developer A having a saturation charge amount Ts1 larger than the saturation charge amount Ts2 of the initial printing developer B is preferentially used.

  Further, in the developer A + Bn sample (where n = 1, 2,..., 6), the developer A and the developer B whose charge rising property is worse than or equivalent to that of the developer A (specifically, the developer) B1, B2, B4, B5, B6) and a sample mixed with a carrier (that is, developer A + B1 sample, developer A + B2 sample, developer A + B4 sample, developer A + B5 sample, developer A + B6 sample) However, during initial printing (that is, during printing processing performed immediately after the image forming apparatus 100 is left for a while), the developer A having a low colorant concentration is preferentially used, or Since the developer A and the developer B are used at approximately the same rate, the printing density is lowered. That is, the density of the developer A + B1 sample, the developer A + B2 sample, the developer A + B4 sample, the developer A + B5 sample, and the developer A + B6 sample was “× (low)” after being left standing.

  Further, in the developer A + Bn sample (where n = 1, 2,..., 6), the developer A and the developer B having a saturated charge amount larger than or equivalent to the developer A (specifically, the developer) Samples (ie, developer A + B4 sample, developer A + B5 sample, developer A + B6 sample) mixed with carrier (any one of B4, B5, and B6) during normal printing (ie, image forming apparatus 100 is continuous) Developer B4, B5, B6 having a high colorant concentration is preferentially used during printing processing performed after printing), or the ratio of developer A and developer B is approximately the same. The print density increased because it was used in That is, the density after continuous printing of the developer A + B4 sample, the developer A + B5 sample, and the developer A + B6 sample was “× (high)”.

  This evaluation was performed using the black developers A and B in the above-described RT environment. However, the same results may be obtained using another color developer in the RT environment under different conditions. Results were obtained.

  However, the charge rising property and the saturation charge amount are closely related to each other. For this reason, it has not been possible to produce a developer that improves one of the charge rising property and the saturated charge amount while maintaining the other, or a developer that improves both the charge rising property and the saturated charge amount.

Thus, the most suitable sample as the mixed developer TN is the developer A + B3 sample. The developer A + B3 sample is defined as follows.
That is, the most suitable sample as the mixed developer TN is that the charging characteristics of the developer A as the first developer and the developer B as the second developer are the same as shown in FIG. When the developer A and the developer B are mixed independently at the same mixing weight ratio with respect to the carrier CR, and the time t is shorter than the saturation charging time Ts2 at which the developer B reaches the saturation charge amount. In this case, the charge amount of the developer A is qt, the charge amount of the developer B is Qt, and the charge amount of the developer A when the developer B is stirred for a time T longer than the saturation charge time Ts2 of the developer B is qT. In addition, when the charge amount of the developer B is QT, | qT |> | QT | and a combination satisfying the relationship of qt / qT <Qt / QT.

Specifically, when the charging characteristics of developer A and developer B are each set to a mixing weight ratio of 5%, time t is set to 60 seconds, and time T is set to 600 seconds, q600 |> | Q600 | and a combination satisfying the relationship of q60 / q600 <Q60 / Q600.
The mixed developer TN in a combination that satisfies this relationship can stably obtain a print quality with a good print density over time.

  As described above, according to the mixed developer TN according to the first embodiment, the second developer (developer B) having a fast charge rise is generally obtained during initial printing in which the charge rise property of the developer is generally deteriorated. It is used preferentially over the first developer (Developer A). Since the second developer is smaller than the first developer having a low absolute value of the saturation charge amount, it forms a developer image in a smaller amount than the first developer, but it is less than the first developer. Since the concentration of the colorant is high (that is, the color is dark), it is possible to form a developer image having a sufficiently high print density (dark tone).

  Further, according to this mixed developer TN, the first developer having a higher absolute value of the saturation charge amount is used preferentially over the second developer during normal printing in which the charge rising property of the developer is restored. Is done. Although the first developer has a lower colorant concentration than the second developer (that is, the color is light), since the absolute value of the saturation charge amount is high, a sufficient amount of developer image is formed. Thus, it is possible to form a developer image having a sufficiently high printing density (dark color tone).

  Therefore, according to this mixed developer TN, there is a difference in print density between the developer image formed during initial printing and the developer image formed during normal printing (lightness difference, development when the developer color is black). When the color of the agent is a color, the saturation difference) can be reduced, and a print quality with a good print density can be obtained stably over time.

Further, according to the developing device 10 that stores the mixed developer TN in the developer container 11, the difference in print density is reduced between the developer image formed during initial printing and the developer image formed during normal printing. Can be made.
Similarly, according to the image forming apparatus 100 using the developing device 10, it is possible to reduce the print density difference between the developer image formed during initial printing and the developer image formed during normal printing.

[Embodiment 2]
In Embodiment 1, two types of developer A and developer B were mixed in the same amount. On the other hand, in the second embodiment, developer A (in this second embodiment, any one of developers A2 to A5 described later) having a physical property value (for example, saturation charge amount) deviated from the target value is used. By changing the mixing ratio of developer B (developer C or D, which will be described later in the second embodiment) with respect to developer, the entire physical property value as mixed developer TN is adjusted.

In the second embodiment, five sets of developer A were purified as samples under the same conditions and the same manufacturing method as those of the first embodiment, and these were designated as developers A1 to A5. In the second embodiment, the charge amount Q600 of each sample when the sample was stirred for 600 seconds as the saturated charge amount of each sample (developers A1 to A5) was evaluated by the same evaluation method as in the first embodiment. Further, in the second embodiment, each sample is accommodated in the developing device 10 (see FIG. 2), and the developing device 10 is sufficiently obtained in the RT environment under the same conditions as in the first embodiment until each sample reaches the saturation charge amount. , The 100% duty pattern 72 is further printed on one medium P, and nine measurement points 73 (see FIG. 5) of the duty pattern 72 are printed in the same manner as in the first embodiment. The print density (color tone) of each sample was evaluated by measuring the print density of 6) and calculating the average print density. The evaluation results are shown in Table 3.

Table 3 shows the saturation charge amount (charge amount Q600) and the solid density value (OD value) of each sample (developers A1 to A5).
As shown in Table 3, each sample (developers A1 to A5) has a variation in charging characteristics despite being purified under the same conditions and the same manufacturing method as in the first embodiment. Therefore, there is a difference in the solid density value (OD value) between the samples. Each sample (developers A1 to A5) is refined with the target of a physical property value of Q600 = −30 μC / g and a solid density value (OD value) of 1.40.

Further, in the second embodiment, two sets of developer B are purified as samples by changing the addition amount of the salicylic acid complex that is the charge control agent, and the same manufacturing method as that of the first embodiment. It was. These developers C and D are refined under the same conditions and the same production method as developer B except that the addition amount of the salicylic acid complex as the charge control agent is different. Developer C has 0.6 parts by weight of a salicylic acid complex added to 100 parts by weight of the binder resin, and Developer D has 2.4 parts by weight of 100 parts by weight of the binder resin. A salicylic acid complex is added. In Embodiment 2, developer A2 to A5 having physical property values that deviate from the target values are mixed with developer C or D at an arbitrary ratio. Each charge amount Q600 and printing density were evaluated by the same evaluation method as A1 to A5. The evaluation results are shown in Table 4. In the example shown in Table 4, each sample is mixed with each combination of developer A2 and developer D, developer A3 and developer C, developer A4 and developer D, and developer A5 and developer C. It has been configured.

  Table 4 shows the saturation charge amount (charge amount Q600) and solid density of each sample (developer A2 + developer D, developer A3 + developer C, developer A4 + developer D, and developer A5 + developer C). The value (OD value) is shown. Table 4 also shows evaluation results in the case of developers A1 to A5 alone, developer C alone, and developer D alone. In the example shown in Table 4, the saturation charge amount of developer C (charge amount Q600) is −15 μC / g, and the saturation charge amount of developer D (charge amount Q600) is −45 μC / g.

  As shown in Table 4, each developer A2 to A5 having a physical property value deviated from the target value is mixed with developer C or D as developer B at an arbitrary ratio. Is adjusted to a constant value (-30 μC / g in the example shown in Table 4).

  As described above, in the second exemplary embodiment, the first developer (developer A) has a physical property value deviated from the target value (here, any one of the developers A2 to A5). Even so, by mixing a second developer (here, developer C or D) having a different saturation charge amount with respect to the first developer at an arbitrary ratio, the mixed developer TN The total saturation charge amount can be adjusted from the saturation charge amount of the first developer to a charge amount corresponding to the mixing ratio of the first developer and the second developer.

  Therefore, in the second embodiment, even when the first developer (developer A) has a physical property value deviated from the target value, the mixing ratio of the second developer (developer C or D) By changing the above, it is possible to obtain the mixed developer TN having the same characteristics as those of the first embodiment. As a result, in the second embodiment, similarly to the first embodiment, there is a difference in print density between the developer image formed during initial printing and the developer image formed during normal printing (when the developer color is black). Can reduce the difference in lightness, and the saturation difference when the developer color is color), and it is possible to obtain a print quality with a good print density stably over time.

  This evaluation was performed using the black developers A and B in the above-described RT environment. However, the same results may be obtained using another color developer in the RT environment under different conditions. Results were obtained.

  As described above, according to the second embodiment, even when the first developer is a developer having a physical property value deviated from the target value, the mixed developer is changed by changing the mixing ratio of the second developer. The overall characteristics of TN can be adjusted, and as a result, the print density can be adjusted.

The present invention is not limited to the above-described embodiment, and various changes and modifications can be made without departing from the gist of the present invention.
For example, the present invention is not limited to a printer, and can be used in an image forming apparatus such as a copying machine, a FAX, and an MFP. Note that “MFP” is an abbreviation for Multi Function Peripheral (or Product), and is an apparatus in which a facsimile function, a scanner function, a copy function, and the like are added to a printer.
The order of the colors of the developer stored in the developing device 10 can be different from the order shown in FIG.
Further, the color of the developer stored in the developing device 10 may be a color other than black (B), yellow (Y), magenta (M), and cyan (C).

2 Paper cassette (medium container)
DESCRIPTION OF SYMBOLS 3 Discharge tray 4 Paper feed conveyance mechanism 5 Paper feed roller 6 Conveyance roller 7 Discharge conveyance roller 8 Reverse unit 9 Traveling guide 10 (10B, Y, M, C) Developing device 11 Developer container (developer container)
12 Photosensitive drum (image carrier)
13 Charging roller (Charging part)
14 Development roller (developer carrier)
DESCRIPTION OF SYMBOLS 15 Supply roller 16 Developing blade 17 Cleaning blade 18 Seal material 20 Exposure unit (exposure part)
30 Transfer unit (transfer section)
31 Transfer belt (first transfer member)
32 Transfer roller (second transfer member)
33 Driving roller 34 Belt idle roller 35 Transfer belt cleaning blade 36 Waste developer tank 40 Image forming unit 50 Fixing unit (fixing unit)
51 Heating roller 52 Pressure roller 60 Shaker (stirrer)
61 Supporting Unit 62 Shaking Unit 71 Printable Range 72 Duty Pattern 73 Measuring Point 100 Image Forming Apparatus (Printer)
P Medium (Recording paper)
TN Developer (toner)
qt, Qt, Qt, QT Charge amount Qs1, Qs2 Saturation charge amount t, T Stirring time Ts1, Ts2 Saturation charge time

Claims (13)

A first developer having a low colorant concentration, a slow charge rise, and a high absolute value of the saturation charge amount;
A second developer having a colorant concentration higher than that of the first developer, a rapid charge start-up, and a low absolute value of the saturation charge amount;
A mixed developer, wherein a carrier for adhering the first developer and the second developer is mixed. The mixed developer according to claim 1,
A mixed developer, wherein the color of the colorant is a color, and the chroma of the second developer is darker than the chroma of the first developer. The mixed developer according to claim 1,
A mixed developer, wherein the brightness of the second developer is higher than the brightness of the first developer when the color of the colorant is black. The mixed developer according to any one of claims 1 to 3,
The charging characteristics of the first developer and the second developer are respectively
When the first developer and the second developer are mixed independently at the same mixing weight ratio with respect to the carrier of the same material, and the second developer reaches the saturation charge amount Qt is the charge amount of the first developer when t is stirred for a time t shorter than the saturation charge time of the second developer, and Qt is the charge amount of the second developer. When the charge amount of the first developer when the stirring time T is longer than the saturation charge time of the developer 2 is qT and the charge amount of the second developer is QT,
| QT |> | QT | and a mixed developer characterized by satisfying the relationship of qt / qT <Qt / QT. The mixed developer according to claim 4,
The charging characteristics of the first developer and the second developer are respectively
When the mixing weight ratio is 5%, and when the time t is 60 seconds and the time T is 600 seconds,
| Q600 |> | Q600 | and a mixed developer characterized by satisfying the relationship of q60 / q600 <Q60 / Q600. In the mixed developer according to claim 4 or 5,
A mixed developer, wherein an overall saturation charge amount is adjusted by changing a mixing ratio of the first developer and the second developer. A developer accommodating portion for accommodating the developer;
An image carrier on which an electrostatic latent image is formed on the surface;
A developer carrier that receives the developer from the developer container and attaches the developer to the electrostatic latent image formed on the surface of the image carrier, and performs development.
The developer container is
As the developer,
A first developer having a low colorant concentration, a slow charge rise, and a high absolute value of the saturation charge amount;
A second developer having a colorant concentration higher than that of the first developer, a rapid charge start-up, and a low absolute value of the saturation charge amount;
A developing device containing a mixed developer in which a carrier for adhering the first developer and the second developer is mixed. The developing device according to claim 7,
The developer container is
As the developer,
A developing device that contains a mixed developer in which the saturation of the second developer is higher than the saturation of the first developer when the color of the colorant is a color. The developing device according to claim 7,
The developer container is
As the developer,
A developing device that contains a mixed developer in which the brightness of the second developer is higher than the brightness of the first developer when the color of the colorant is black. The developing device according to any one of claims 7 to 9,
The developer container is
As the developer,
The charging characteristics of the first developer and the second developer are respectively
When the first developer and the second developer are mixed independently at the same mixing weight ratio with respect to the carrier of the same material, and the second developer reaches the saturation charge amount. The charge amount of the first developer when the stirring time t is shorter than the saturation charge time of the second developer is qt, the charge amount of the second developer is Qt, and the second developer When the charge amount of the first developer is qT and the charge amount of the second developer is QT when the developer is stirred for a time T equal to or longer than the saturation charge time of the developer,
A developing device containing a mixed developer satisfying a relationship of | qT |> | QT | and qt / qT <Qt / QT. The developing device according to claim 10,
The developer container is
As the developer,
The charging characteristics of the first developer and the second developer are respectively
When the mixing weight ratio is 5%, and when the time t is 60 seconds and the time T is 600 seconds,
A developing device containing the mixed developer satisfying a relationship of | q600 |> | Q600 | and q60 / q600 <Q60 / Q600. The developing device according to claim 10 or 11,
The developer container is
As the developer,
A developing device that accommodates the mixed developer in which the total saturation charge amount is adjusted by changing a mixing ratio of the first developer and the second developer. A developing device according to any one of claims 7 to 12,
A transcription section;
An image forming apparatus comprising: a fixing unit.

Images