JP5479119B2 - Developer, developing device, developer container, and image forming apparatus - Google Patents

Description

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

  Conventionally, an external additive is generally added to a developer used in an image forming apparatus. By adding an external additive to the developer, the fluidity and chargeability of the developer can be improved. However, the contamination of the member due to the external additive adhering to the member in the developing device, the surface of the developer, etc. It is known that this external additive may cause problems such as drum filming, which damages the photosensitive drum.

  Patent Document 1 proposes to use a developer in which the weight part of silica to be externally added and the specific surface area after external addition are specified in order to cope with drum filming. Here, the specific surface area refers to the surface area per unit mass of a certain object.

JP 2007-183403 A

  However, in the conventional developer described in Patent Document 1, filming by the external additive attached to the developer is supported, but the member contamination by the external additive and the external additive attached to the developer are supported. It does not correspond to a decrease in fluidity due to a decrease in the dosage. This member contamination due to the external additive occurs due to the external additive being detached by pressing and rubbing the developer against the developing member in the developing device. The detached external additive adheres to the surface of the photosensitive drum or the charging roller, and changes the characteristics of the member. Further, the decrease in fluidity occurs due to a decrease in the amount of the external additive adhering to the developer due to the detachment of the external additive. When the fluidity of the toner is lowered, there is a problem that a rubbing phenomenon occurs in which the printing density is lowered from the printing start portion to the printing end portion.

Developer of the present invention, the emulsion having a toner base particles containing a binder resin and a colorant are primary particles, and external additive to improve the fluidity and charging property by adhering to the surface of the toner mother particles A developer by a polymerization aggregation method , wherein a specific surface area of the developer when not used is α, the developer is used under a first condition, and the specific surface area of the developer is β. When the specific surface area of the developer after the agent is used under the second condition where the external additive is desorbed from almost all the toner base particles is γ, the first condition is Using a layer forming member that regulates the thickness of the developer on the developer carrier, the developer is pressed against the developer carrier carrying the developer at a linear pressure of 6.8 [gf / mm]. The developer amount of the developer carrying member is set to 0.40 to 0.50 [mg / cm2], and 150 [m / Sec] at a linear velocity of 25000 rotations of the developer carrier, and the second condition is that the developer is 6.8 by using the layer forming member on the developer carrier. The developer is brought into pressure contact with a linear pressure of [gf / mm], the developer amount of the developer carrier is 0.40 to 0.50 [mg / cm2], and the developer at a linear speed of 150 [mm / sec]. The specific surface area α, β, γ is to rotate the carrier 50000
0.74 ≦ (α−γ) /γ≦1.10.
0.40 ≦ (β−γ) /γ≦0.68
0 ≦ (α−β) /γ≦0.28
Is set to

A developing device of the present invention, the a developer, a rotatable image bearing member configured to bear a latent electrostatic image, a latent image bearing member charging member for charging the surface of the latent image bearing member, the latent image carrier An exposure unit that forms a latent image on the surface of the body, the developer carrier that visualizes the latent image formed on the latent image carrier with the developer, and the developer carrier. It has a said layer forming member to regulate the thickness of the developer, and a developer supplying member for supplying the developer to the developer carrying member.

The developer container of the present invention includes a developer container that stores the developer, a supply port that is disposed between the developer container and the developing unit that develops the developer. was said developer has a supply mechanism for supplying to the developing unit.

The image forming apparatus of the present invention is transferred to the developing device, the developer container, a transfer unit that transfers the developer visualized in the developing device to a printing medium, and the printing medium. and a, a fixing unit for fixing the developer.

According to the developer of the present invention, a toner satisfying 0.74 ≦ (α−γ) /γ≦1.10 is used in a toner having a particle diameter of 4.0 [μm] to 6.5 [μm]. Thus, it is possible to prevent fading and stains due to the amount of the external additive attached to the toner during initial printing. Further, in the toner having a particle diameter of 4.0 [μm] to 6.5 [μm], a toner satisfying 0.40 ≦ (β−γ) /γ≦0.68 is used, so that the developing roller is adjusted to 25, It is possible to prevent blurring due to the amount of the external additive adhering to the toner and smearing in printing after 000 rotations.

Furthermore, by using a toner satisfying 0 ≦ (α−β) /γ≦0.28, it is possible to suppress a change in density due to the detached external additive.

  According to the developing device of the present invention, by using the developer, it is possible to prevent blurring and dirt due to the amount of the external additive attached to the toner, and to change the concentration derived from the detached external additive. Can also be suppressed.

  According to the developer container of the present invention, by storing the developer, it is possible to prevent fading and dirt due to the amount of the external additive attached to the toner, and it is derived from the detached external additive. Concentration change can also be suppressed.

  According to the image forming apparatus of the present invention, by having the developing device and the developer container, it is possible to prevent fading and dirt due to the amount of the external additive attached to the toner, and the detached external additive. It is also possible to suppress the concentration change derived from.

FIG. 1 is a configuration diagram showing an outline of the developing device in FIG. 2 in Embodiment 1 of the present invention. FIG. 2 is a block diagram showing an outline of the image forming apparatus in Embodiment 1 of the present invention. FIG. 3 is an explanatory diagram showing a toner durability evaluation print pattern and a print defect example. FIG. 4 is an enlarged view of the print pattern of FIG. FIG. 5 is a graph showing the results of durability evaluation with a toner particle size of 6.5 [μm]. FIG. 6 is a graph showing the results of measuring the specific surface area with a toner particle size of 6.5 [μm]. FIG. 7 is a diagram showing the results of durability evaluation with a toner particle size of 5.5 [μm]. FIG. 8 is a graph showing the results of measuring the specific surface area of the toner with a particle size of 5.5 [μm]. FIG. 9 is a graph showing the results of durability evaluation with a toner particle size of 4.0 [μm]. FIG. 10 is a graph showing the results of measuring the specific surface area of the toner with a particle size of 4.0 [μm]. FIG. 11 is a diagram showing the measurement result of the density change amount.

  Modes for carrying out the present invention will become apparent from the following description of the preferred embodiments when read in light of the accompanying drawings. However, the drawings are only for explanation and do not limit the scope of the present invention.

(Configuration of Image Forming Apparatus of Example 1)
FIG. 2 is a configuration diagram showing an outline of the image forming apparatus in Embodiment 1 of the present invention.

  The image forming apparatus is, for example, an electrophotographic color page printer, and has a paper feed tray 10 below it. The paper feed tray 10 is a tray that stores print media (for example, print paper) P. A hopping roller 11, a paper feed guide 12, transport rollers 13 a and 13 b and a transfer belt 14 are provided above the leading end of the paper feed tray 10, and the printing paper P is fed out from the paper feed tray 10 by the hopping roller 11. Further, it is configured to pass on the transfer belt 14 that is transported by the transport rollers 13 a and 13 b and driven by the drive roller 15.

  Above the transfer belt 14, a plurality of developing devices 30 (= 30K, 30Y, 30M, and 30C) that form unique color images are provided. The plurality of developing devices 30 are arranged in the order of black (K), yellow (Y), magenta (M), and cyan (C) from upstream to downstream. Each developing device 30 has basically the same configuration although there is a difference in the color of an image to be formed.

  Below each developing device 30, a plurality of transfer rollers 16 (= 16K, 16Y, 16M, 16C) are arranged. The transfer belt 14, the drive roller 15, and the transfer roller 16 constitute a transfer portion. A belt cleaner 19 for scraping off the toner 38 attached to the transfer belt 14 is provided below the transfer belt 14.

  A fixing unit including a heating roller 17 and a pressure roller 18 is provided on the downstream side of the developing device 30C. The fixing unit has a function of fixing the developer (for example, toner) 38 of the printing paper P to the printing paper P by heating and pressing the printing paper P. A discharge guide 20 is provided on the downstream side of the fixing unit. The paper discharge guide 20 has a function of guiding the print paper P on which the toner 38 is fixed and discharging it to the outside.

  FIG. 1 is a configuration diagram showing an outline of the developing device in FIG. 2 according to the first embodiment of the present invention, in which a developing device 30C on the downstream side of a plurality of developing devices 30 and its peripheral portion are shown enlarged. Has been.

  Each developing device 30 includes a developing unit 30a that develops the toner 38 on the printing paper P, and a toner cartridge 40 that supplies the toner 38 to the developing unit 30a.

  The developing unit 30 a includes a latent image carrier (for example, a photosensitive drum) 31, a latent image carrier charging member (for example, a charging roller) 32 that charges the photosensitive drum 31, and an exposure unit that forms a latent image on the photosensitive drum 31 ( For example, an exposure apparatus 39, a developer carrier (for example, a developing roller) 33, a developer supply member (for example, a supply roller) 34, and a layer forming member (for example, a developing blade) 35 that is a thin layer forming unit. And a cleaning blade 36 that scrapes off the toner 38 on the photosensitive drum 31, and a toner storage portion 37 that stores the toner 38. The developing roller 33, the supply roller 34, and the developing blade 35 are disposed in the toner storage unit 37.

  The photosensitive drum 31 includes a conductive support using an aluminum metal pipe, a charge generation layer sequentially stacked on the metal pipe, and a photoconductive layer using an organic photoconductor composed of a charge transport layer. Yes. For example, the charging roller 32 includes a metal shaft and a semiconductive rubber layer. The developing roller 33 includes, for example, a metal shaft and a semiconductive urethane rubber material having a hardness of 73 [Asker C], an Rz of 4.0 [μm], and an outer diameter of φ19.6 [mm].

  The supply roller 34 has a semiconductive foamed silicon sponge layer having a hardness of 56 [Asker F] and an outer diameter of φ15.5 [mm]. The developing blade 35 is made of stainless steel with a material of SUS304B-TA, a thickness of 0.08 [mm], a bending angle of the blade tip of 60 [°], and a curvature of the blade 35 tip of 0.20. Has been.

  In addition, Asker C and Asker F are one of durometers (spring type hardness testers) defined in SRIS0101 (Japan Rubber Association Standard), and are measuring instruments for measuring hardness. 73 [Asker C] indicates the hardness measured by the measuring instrument. Rz is the average roughness of ten points, extracted from the roughness curve by the reference length in the direction of the average line, measured from the average line of this extracted part in the direction of the vertical magnification, and from the highest peak to the fifth Calculate the sum of the absolute value of the altitude (Yp) of the summit of the mountain and the average value of the absolute value of the altitude (Yv) of the bottom valley from the lowest valley bottom to the fifth, and calculate this value in micrometers (μm) Say what you represent.

  Each member of the developing device 30 has a linear pressure between the developing roller 33 and the supply roller 34 of 11.5 [gf / mm] and a linear pressure between the developing roller 33 and the photosensitive drum 31 of 0.48 [gf / mm]. Thus, the linear pressure between the developing roller 33 and the developing blade 35 is pressed at 6.8 [gf / mm].

  The toner cartridge 40 has a developer accommodating portion (for example, a toner accommodating portion) 41 that accommodates the toner 38, and a supply mechanism (for example, a front and rear surface direction) extending in the longitudinal direction (for example, the front and back sides of the paper) below the toner accommodating portion 41. , A stirring bar) 43 is rotatably supported, and a supply port 42 for supplying the toner 38 in the cartridge to the developing unit 31a is formed below the stirring bar. Further, a slidable shutter 44 for opening and closing the supply port 42 is disposed near the supply port 42.

(Configuration of Toner of Example 1)
The toner 38 according to the first exemplary embodiment is agglomerated by mixing, for example, a binder resin (for example, styrene acrylic copolymer resin) that is a primary particle manufactured by an emulsion polymerization aggregation method, a colorant, and a wax. An external additive (for example, silica) and fine titanium oxide powder are added to toner particles that can be formed (hereinafter referred to as “base toner”) and mixed by a mixer.

Here, the emulsion polymerization aggregation method includes the following steps.

  (1) A binder resin which is a primary particle of a polymer is prepared in an aqueous solvent, and a colorant emulsified with an emulsifier (surfactant) is mixed in the same solvent as the binder resin.

  (2) If necessary, wax, a charge control agent and the like are mixed and agglomerated to form toner particles in the solvent.

  (3) The toner particles are taken out from the solvent, and unnecessary solvent components and by-product components are removed by washing and drying to obtain toner 38.

  The aforementioned styrene acrylic copolymer resin is formed from styrene, acrylic acid, and methyl methacrylic acid. The colorant is carbon black for black, pigment yellow 74 for yellow, pigment red 238 for magenta, and pigment blue 15: 3 for cyan. Further, the wax is composed of stearyl stearate which is a higher fatty acid ester wax.

(Operation of Entire Image Forming Apparatus in Embodiment 1)
The overall operation of the image forming apparatus will be described with reference to FIGS.

  When a printing instruction is issued from a control unit (not shown), a motor (not shown) in the image forming apparatus starts to rotate, driving is transmitted to the drum gear through several gears, and the photosensitive drum 31 rotates in the direction of the arrow. When the drive is transmitted from the drum gear to the developing gear, the developing roller 33 rotates in the direction of the arrow. When the drive is transmitted from the developing gear to the sponge gear via the idle gear, the supply roller 34 rotates in the direction of the arrow. When driving is transmitted from the drum gear to the charge gear, the charging roller 32 rotates in the direction of the arrow.

  On the other hand, the rotation of a motor (not shown) in the image forming apparatus is transmitted to the transfer gear and the drive gear through several different gears, the transfer roller 16 rotates in the direction of the arrow, and the transfer belt 14 rotates. Operate. Further, when the drive is transmitted to the heat roller gear through several gears of different systems, the heat roller 17 rotates in the direction of the arrow, and the pressure roller 18 rotates along with the rotation of the heat roller 17 in the direction of the arrow. Rotate.

  Almost simultaneously with the start of rotation of the motor, each of the rollers 31, 32, 33, 34, 16 in the development / transfer process and the halogen lamp in the heat roller 17 in the fixing process are powered by a power source (not shown) in the image forming apparatus. Each determined bias voltage is applied.

  In the image forming apparatus having the above-described mechanism, the process of forming an image on the printing paper P is as follows.

  The printing paper P set in the paper feed tray 10 is fed out by the hopping roller 11 and conveyed to the transfer belt 14 by the conveying rollers 13a and 13b. The surface of the photosensitive drum 31 is uniformly charged by the charging roller 32. A print job from a host device (not shown) is sent to the exposure device 39 via a control unit (not shown), and an electrostatic latent image corresponding to the print pattern is formed on the photosensitive drum 31.

  The supply roller 34 is in contact with the developing roller 33 and supplies the toner 38 to the developing roller 33 by being driven to rotate while maintaining a constant peripheral speed ratio. The toner 38 on the developing roller 33 is charged by friction with the developing blade 35 in contact with the developing roller 33.

  The developing roller 33 is in contact with the photosensitive drum 31 and causes the toner 38 to adhere to the electrostatic latent image on the photosensitive drum 31. Thereafter, the toner 38 on the photosensitive drum 31 is transferred onto the printing paper P by an electric field with the transfer roller 16, and the toner 38 on the printing paper P is fixed by the fixing unit. The toner 38 remaining on the photosensitive drum 31 after the transfer is scraped off by the cleaning blade 36. The printing paper P is guided by the discharge guide 20 and discharged outside the apparatus.

(Toner durability evaluation)
The durability of the toner 38 refers to the friction between the toners 38 in the developing device 30 and the load on the toner 38 due to pressurization at the contact portion between the developing roller 33, the supply roller 34, the developing blade 35, and the photosensitive drum 31. The degree to which the external additive is detached from the base toner. The durability evaluation of the toner 38 is performed, for example, by sequentially executing the following steps (S1) to (S10).

  (S1) The median diameter of the base toner is measured.

  (S2) An evaluation toner is prepared.

  (S3) The specific surface area α is measured.

  (S4) 80 [g] of evaluation toner is put into the developing device 30 and the image forming apparatus is put in an environment (hereinafter referred to as “NN environment”) having a temperature of 22 [° C.] and a humidity of 40 [%]. Leave for more than an hour.

  (S5) Using the image forming apparatus that has been left unattended, in an NN environment, prints are collected for the presence / absence of blurring and the presence / absence of dirt, and periodic data is acquired.

  (S6) Immediately after acquiring the regular data, the blank printing pattern is printed for each page in the NN environment, and the printing operation is performed until the rotation speed of the developing roller 33 reaches 25,000 rotations.

  (S7) Periodic data is acquired immediately after the rotation speed of the developing roller 33 reaches 25,000.

  (S8) 10 [g] of the toner for measuring the specific surface area β is taken out from the developing device 30, and the specific surface area β is measured.

  (S9) From this state, the blank print pattern is printed for each page in the NN environment, and further, the developing roller 33 is rotated 25,000 times, and the total number of rotations of the developing roller 33 reaches 50,000 times. Until printing is performed.

  (S10) 10 [g] of the toner 38 for measuring the specific surface area γ is taken out from the developing device 30, and the specific surface area γ is measured.

  Next, the steps (S1) to (S10) described above will be described in detail.

(1) Measurement of median diameter of base toner (S1)
The median diameter of the base toner is measured using a particle size distribution measuring device (Beckman Coulter, Multisizer III). The measurement sample used is a mixture of 95 [mass%] of Isoton II (Beckman Coulter) and 5 [mass%] of emulgen as a dispersant, and a small amount of toner 38 is added so that the sample concentration is 10% or less. A sample dispersed for 1 minute by an ultrasonic vibrator is used. For the measurement, an aperture diameter of 100 [μm] was used, and the median diameter was calculated in a state where the number of observed particles was 30,000 or more.

  The median diameter (hereinafter referred to as “particle size”) is a particle when the number or mass larger than a certain particle size occupies 50% of the number or mass of all powders in the particle size distribution of the powder. The diameter. Beckman Coulter's Multisizer III is a particle size distribution measuring device based on the Coulter principle. The Coulter principle is called the pore electrical resistance method. A constant current is passed through the pores in the electrolyte solution. In this method, the volume of the particles is measured by measuring the change in the electrical resistance of the pores when the particles pass through the pores.

(2) Preparation of evaluation toner (S2)
Using the base toner when the particle diameter is 6.5 [μm], 5.5 [μm], and 4.0 [μm], the evaluation toners A1 to A16, toners B1 to B16, and toners C1 to C1 are used. C16 is created.

  Aerosil R-972 (Nippon Aerosil Co., Ltd.), which is a hydrophobic silica fine powder, is added to 100 parts by weight of each base toner, mixed with a Henschel mixer (Mitsui Mining Co., Ltd.), and then sieved.

  For each of the three types of base toners, evaluation toners having different external additive adhesion states on the surface of the toner 38 are prepared by changing the amount of hydrophobic silica fine powder and changing the stirring time by a mixer. The Henschel mixer is used at a rotational speed of 3200 revolutions / minute, cooling the apparatus every time it is stirred for 5 minutes.

(A) Preparation of toners A1 to A16 having a particle diameter of 6.5 [μm] To a base toner having a particle diameter of 6.5 [μm], only a predetermined part by weight of hydrophobic silica fine powder is added, and the toner is stirred for a predetermined time. A1 to A16 are created. The predetermined weight part and the predetermined stirring time are as follows. Here, the toners A1 to A16 are simply indicated as A1 to A16.
A1: Addition amount of hydrophobic silica fine powder; 0.5 part by weight, stirring time; 5 minutes A2: Addition amount of hydrophobic silica fine powder; 1.0 part by weight, stirring time; 5 minutes A3: Hydrophobic silica fine powder 1.0 part by weight, stirring time; 15 minutes A4: addition amount of hydrophobic silica fine powder; 1.0 part by weight, stirring time; 25 minutes A5: addition amount of hydrophobic silica fine powder; 1 5 parts by weight, stirring time: 5 minutes A6: addition amount of hydrophobic silica fine powder; 1.5 parts by weight, stirring time; 15 minutes A7: addition amount of hydrophobic silica fine powder; 1.5 parts by weight, stirring Time: 25 minutes A8: Addition amount of hydrophobic silica fine powder; 2.0 parts by weight, stirring time; 5 minutes A9: Addition amount of hydrophobic silica fine powder; 2.0 parts by weight, stirring time; 15 minutes A10: Addition amount of hydrophobic silica fine powder; 2.0 parts by weight, stirring time; 25 minutes A11: Hydrophobic silica fine powder 2.0 parts by weight, stirring time; 5 minutes A12: addition amount of hydrophobic silica fine powder; 2.0 parts by weight, stirring time; 15 minutes A13: addition amount of hydrophobic silica fine powder; 0 parts by weight, stirring time; 25 minutes A14: addition amount of hydrophobic silica fine powder; 4.0 parts by weight, stirring time; 5 minutes A15: addition amount of hydrophobic silica fine powder; 4.0 parts by weight, stirring time 15 minutes A16: Amount of hydrophobic silica fine powder added; 4.0 parts by weight, stirring time; 25 minutes

(B) Preparation of toners B1 to B16 when the particle diameter is 5.5 [μm] Similar to the preparation of the evaluation toner having the particle diameter of 6.5 [μm], the base toner having a particle diameter of 5.5 [μm] The toner B1 to B16 for evaluation are prepared by adding a predetermined part by weight of hydrophobic silica fine powder and stirring for a predetermined time. The predetermined part by weight and the predetermined agitation time are the same conditions as when the toner 38 having a particle diameter of 6.5 [μm] is prepared. That is, the predetermined weight part of the hydrophobic silica fine powder and the predetermined stirring time of the toner Bi (= 1 to 16) are the same as those of the toner Ai (= 1 to 16).

(C) Preparation of toners C1 to C16 when the particle diameter is 4.0 [μm] Similarly, toners C1 to C16 are prepared using a base toner having a particle diameter of 4.0 [μm].

(3) Measurement of specific surface area α (S3)
The specific surface area [m2 / g] measured by the nitrogen gas adsorption amount is used as an index indicating the external additive adhesion state of the evaluation toner. For the specific surface area measurement, Tristar 3000 (manufactured by Shimadzu Corporation) is used, and the nitrogen adsorption amount V to the sample (evaluation toner) is measured. The nitrogen adsorption amount V is such that the saturated vapor pressure Po and the adsorption equilibrium pressure P at a liquid nitrogen temperature of −195.8 [° C.], P / Po is 0.5, 1.0, 1.5, 2.0. The nitrogen adsorption amount V is measured at 7 points of 2.5, 3.0, and 3.5. From the measured V and P / Po, an approximate expression of a proportional line with P / Po on the X axis and V on the Y axis is calculated, the slope of the approximate expression, the value of V at P / Po = 0, and the BET The specific surface area is calculated using the adsorption isotherm. The actual calculation is performed using the functions attached to the Tristar 3000.

  First, the specific surface areas α of the evaluation toners A1 to A16, B1 to B16, and C1 to C16 described above in the unused state are measured.

(4) Acquisition of regular data in the initial state (S4), (S5)
80 g of evaluation toner is charged into the developing device 30, and the image forming apparatus is placed in an environment having a temperature of 22 ° C. and a humidity of 40% (hereinafter referred to as “NN environment”) and left for 12 hours or longer. To do. Using the left image forming apparatus, printing is performed in an NN environment, periodic data is acquired, and the presence / absence of blurring and contamination are evaluated.

  FIGS. 3A, 3B, 3C, and 3D are explanatory diagrams showing toner durability evaluation print patterns and examples of printing defects. FIGS. 4A and 4B are FIGS. It is an enlarged view of the printing pattern of (b), (c), (d).

  FIG. 3A is a blank paper print pattern, FIG. 3B is an example of fading (white spots), FIG. 3C is a brush eye stain, and FIG. 3D is an example of background stain. Show. 4A shows a 100% density printing pattern, and FIG. 4B shows a 25% density printing pattern. 4A and 4B, black circles indicate dots to be printed, and blanks indicate dots not to be printed.

  As for the presence or absence of blurring, 100% density printing is printed on 70 kg of A4 excellent white paper (Oki Data Co., Ltd.), and white print as shown in FIG. 3B is seen at the bottom of the obtained paper. Check visually. When white printing is not seen, no blurring is assumed and the printing state is good.

  100% density printing refers to printing on all printable dots as shown in FIG. The stain is a phenomenon in which the toner 38 is developed in the non-printed portion. When the toner charge amount on the developing roller 33 is large, the contamination is on the developing roller 33 when the sum of the potential on the developing roller 33 and the toner potential on the developing roller 33 becomes higher than the potential on the photosensitive drum 31 surface. This refers to a phenomenon in which the toner 38 is developed in the non-printing portion because the toner 38 moves so that the potential and the potential on the photosensitive drum 31 are in an equilibrium state.

  As for the presence or absence of smudges, when a 25% density printing is performed on 70 kg of A4 excellent white paper (Oki Data Co., Ltd.), the printing defects shown in FIGS. 3C and 3D are visually confirmed. “25% density printing” means printing using a dot pattern as shown in FIG. 4B, and means printing on 25% of printable dots. Here, this dot pattern is an enlargement of a part of the printing paper surface, and the 25% density printing pattern is printed on the entire A4 paper surface as a pattern to be actually printed.

  The brush eye stain in FIG. 3C is a phenomenon in which a vertical line appears as if it was scratched with a nail having a higher print density than the surrounding when 25% density printing was performed. Regardless of the above, the toner 38 is developed on the photosensitive drum 31 and a vertical line appears on the print medium. In addition, in the trouble which belongs to dirt, the brush eye dirt is a minor trouble compared with background dirt. If no brush eye stains and background stains are visually confirmed, the print state is considered good as no stains.

  (5) Acquisition of regular data immediately after the rotation speed of the developing roller 33 reaches 25,000 rotations (S6), (S7)

  Immediately after acquiring the regular data in the initial state, the blank printing pattern is printed for each page in the NN environment, and the printing operation is performed until the rotation speed of the developing roller 33 reaches 25,000. Periodic data is acquired immediately after the rotation speed of the developing roller 33 reaches 25,000.

  As shown in FIG. 3A, the blank paper printing pattern refers to operating the developing device 30 with blank paper on which nothing is printed, and the developing roller 33, the supply roller 34, and the photosensitive drum 31 have a bias voltage. Means that the rollers 31, 32, 33, and 34 of the developing device 30 rotate. P thick paper A4 (Fuji Xerox Co., Ltd.) is used for the blank paper printing operation. The paper passing speed of the printing paper P when printing the regular data and the blank paper printing pattern is 150 [mm / sec].

  Since the external additive attached to the toner 38 is detached and the fluidity of the toner 38 is reduced, it becomes difficult for the toner 38 to be supplied from the supply roller 34 to the developing roller 33. Is likely to occur.

(6) Measurement of specific surface area β (S8)
10 [g] of toner for evaluation of the specific surface area β is taken out from the developing device 30, and the specific surface area β is measured. The measuring method is the same as the measuring method of the specific surface area α.

(7) Measurement of specific surface area γ (S9), (S10)
After measuring the specific surface area β, a blank print pattern is printed for each page in the NN environment, and the developing roller 33 is rotated 25,000 times until the total number of rotations of the developing roller 33 reaches 50,000 rotations. Perform the printing operation. 10 [g] of the toner 38 for measuring the specific surface area γ is taken out from the developing device 30 and the specific surface area γ is measured. The measuring method is the same as the measuring method of the specific surface area α. When the developing roller 33 is rotated 50,000 times and an excessive load is applied to the toner 38, almost all of the external additive on the toner 38 can be removed.

  From the above (4) acquisition of regular data in the initial state to (7) measurement of the specific surface area γ, the toner adhesion amount on the developing roller 33 is maintained at 0.40 to 0.50 [mg / cm 2]. The bias voltage applied to each roller is adjusted. In the first embodiment, for example, the charging roller bias is −1100 [V], the developing roller bias is −220 [V], and the supply roller bias is −350 [V]. However, when the toner adhesion amount on the developing roller 33 decreases, the toner adhesion amount is adjusted by changing the supply roller bias in increments of 20 [V].

(Effect of Example 1)
According to the first embodiment, the following effects (1) and (2) can be obtained.

(1) Results of Toner Durability Evaluation FIG. 5 is a diagram showing the results of durability evaluation with a toner particle system of 6.5 [μm].

  In FIG. 5, for each of the toners A1 to A16, the amount of added external additive (= silica amount), the stirring time (= external addition time), the presence / absence of blurring, and the presence / absence of dirt are described. . The presence / absence of smearing and the presence / absence of dirt are described separately after the initial state and after 25,000 rotations.

FIG. 6 is a diagram showing the results of measuring the specific surface area of a toner particle system of 6.5 [μm].
In FIG. 6, for each of the toners A1 to A16, the specific surface area α, the specific surface area β, the specific surface area γ, and the parameters indicating the amount of the external additive attached to the toner in the initial state are shown. This is a parameter indicating the parameter (α−γ) / γ related to dirt and fading and the amount of external additive adhering to the toner 38 when the developing roller 33 rotates 25,000, and 25,000 of the developing roller 33. The parameter (β−γ) / γ related to dirt and blurring during rotation is described.

  According to FIG. 6, the specific surface area γ is 1.02 ± 0.03 [m 2 / g] in the toners A1 to A16, and the external additive adhered to the toner 38 by rotating the developing roller 33 by 50,000 times. It can be seen that the agent is almost completely removed.

  In the parameter (α−γ) / γ of FIG. 6, referring to the initial state of FIG. 5 and the presence of blurring and dirt after 25,000 rotations, the use of toner 38 of 0.74 or more prevents blurring. It can be seen that the use of the toner 38 of 1.10 or less causes no contamination.

  Similarly, in the parameter (β−γ) / γ of FIG. 6, blurring can be prevented by using the toner 38 of 0.40 or more, and no stain is generated by using the toner 38 of 0.63 or less. I understand that.

  FIG. 7 is a diagram showing the results of durability evaluation with a toner particle system of 5.5 [μm], and FIG. 8 is a diagram showing the results of measuring the specific surface area of the toner with a particle system of 5.5 [μm]. .

  7 and FIG. 8 are the same as the views of FIG. 5 and FIG. That is, the specific surface area γ of FIG. 8 is 1.21 ± 0.02 [m2 / g] in the toners B1 to B16, and the external additive attached to the toner 38 by rotating the developing roller 33 by 50,000 rotations. It can be seen that the agent is almost completely removed.

  In the parameter (α−γ) / γ in FIG. 8, it is possible to prevent fading by using the toner 38 of 0.74 or more, and it is possible to prevent contamination by using the toner 38 of 1.10 or less. I understand.

  In the parameter (β−γ) / γ in FIG. 8, it is possible to prevent blur by using the toner 38 of 0.40 or more, and it is possible to prevent the stain by using the toner 38 of 0.68 or less. I understand.

  FIG. 9 is a diagram showing the results of durability evaluation with a toner particle system of 4.0 [μm], and FIG. 10 is a diagram showing the results of measuring the specific surface area of the toner with a particle system of 4.0 [μm]. .

  The specific surface area γ of FIG. 10 is 1.62 ± 0.02 [m2 / g] in the toners C1 to C16, and the external additive attached to the toner 38 is detached by 50,000 rotations of the developing roller 33. You can see that it is almost complete.

  In the parameter (α−γ) / γ in FIG. 10, it is possible to prevent blur by using the toner 38 of 0.40 or more, and it is possible to prevent contamination by using the toner 38 of 0.81 or less. I understand.

  In the parameter (β−γ) / γ in FIG. 10, it is possible to prevent fading by using the toner 38 of 0.74 or more, and it is possible to prevent contamination by using the toner 38 of 0.57 or less. I understand.

(2)
According to the developer of Example 1, 0.74 ≦ (α−γ) /γ≦1.10 which is the condition 1 in the toner 38 having a particle diameter of 4.0 [μml] to 6.5 [μm]. By using the toner 38 that satisfies the condition, it is possible to prevent fading and stains due to the amount of the external additive attached to the toner 38 in the initial printing. Further, in the toner 38 having a particle diameter of 4.0 [μm] to 6.5 [μm], the toner 38 satisfying the condition 2 of 0.40 ≦ (β−γ) /γ≦0.68 is used. When the developing roller 33 is rotated 25,000 times, the developing member presses and rubs the toner 38 to prevent the external additive from detaching and smearing.

  By satisfying the above two conditions, the toner 38 with good durability can be obtained.

(Configuration of Image Forming Apparatus of Example 2)
The configurations of the image forming apparatus and the developing device 30 in the second embodiment are the same as those in the first embodiment. Further, the configuration of the toner 38 is the same as that of the first embodiment.

  In Example 1, by setting the amount of the external additive attached to the toner 38 to be in a specific range, the occurrence of dirt and fading was prevented. However, even when the toner 38 having an attached amount of the external additive in a specific range is used, the external additive is detached.

  In general, the external additive detached from the toner 38 adheres to the photosensitive drum 31, passes through the cleaning blade 36, and adheres from the photosensitive drum 31 to the charging roller 32. In the portion where the external additive is attached on the charging roller 32, the ability of the charging roller 32 to charge the photosensitive drum 31 is reduced. Therefore, the development amount when the toner 38 on the developing roller 33 is developed on the photosensitive drum 31. Will increase. As a result, density unevenness occurs on the printing paper P, and density changes occur after initial printing and durability evaluation.

  In order to eliminate these inconveniences, in the second embodiment, a parameter for improving the printing density change by examining the relationship between the density change after the initial printing and the durability evaluation and the amount of the external additive desorbed. Clarify the range of (α-β) / γ.

(Measurement of toner print density in Example 2)
In the second embodiment, for example, the print density change amount of the toner 38 is measured by the following procedures (1) to (5).

  (1) The measurement toner 38 of 80 [g] is put into the developing device 30.

  (2) The image forming apparatus is placed in an NN environment having a temperature of 22 ° C. and a humidity of 40% and left for 12 hours or more.

  (3) Periodic data is acquired in an NN environment using the image forming apparatus that has been left unattended.

  (4) Immediately after acquiring the regular data, the blank print pattern is printed for each page in the NN environment, and the printing operation is performed until the rotation speed of the developing roller 33 reaches 25,000 rotations.

  (5) Periodic data is collected immediately after the rotation speed of the developing roller 33 reaches 25,000.

The conditions for performing blank paper printing and the measurement conditions of the developing device 30 are the same as in the first embodiment.
The periodic data, unlike the first embodiment, collects and evaluates the print density change. The change in printing density was measured by printing 25% density printing on 70 kg A4 Excellent White Paper (Oki Data Co., Ltd.), and measuring the density at the three positions of the top and bottom edges of the paper. The average value is taken as the measured value.

  If the difference between the initial density and the density of the developing roller 33 at 25,000 rotations is 0.05 or less, the print density change is good.

FIG. 11 is a diagram illustrating the measurement result of the density change amount.
In FIG. 11, for the evaluation toners A5, A6, A9, B6, B9, B12, and C6 that were judged to be good in Example 1, the particle diameters of the base toners used for the toner 38 and the charged toners were added. The external additive amount (= silica amount), the stirring time (= external addition time), the printing density, and the parameter (α−β) / γ, which is an index of the amount of detached external additive, are described. .

  In the print density, the density in the initial state, the density after the developing roller 33 is rotated 25,000, and the density change amount are described. The parameter (α 1 β) / γ is a parameter representing the amount of the external additive detached from the initial toner 38 during 25,000 rotations of the toner 38 for each evaluation toner 38. The specific surface areas α, β, and γ of the toners 38 for evaluation were those measured in Example 1.

  From this result, it can be seen that the density change is good when 0 ≦ (α−β) /γ≦0.28.

(Effect of Example 2)
According to the toner 38 of Example 2, in the toner 38 having a particle diameter of 4.0 [μm] to 6.5 [μm], 0.74 ≦ (α−γ) /γ≦1.10. In the toner 38 having good durability satisfying 40 ≦ (β−γ) /γ≦0.68, the toner 38 satisfying 0 ≦ (α−β) /γl≦0.28 is further used. It is possible to prevent fading and dirt caused by the amount of the external additive adhering to 38, and to suppress the concentration change derived from the detached external additive.

(Modification)
The present invention is not limited to the above-described embodiments, and various usage forms and modifications are possible. For example, the following forms (a) and (b) are used as the usage form and the modified examples.

  (A) In the first and second embodiments, a color page printer has been described as an example of the image forming apparatus. However, the present invention is not limited to this, and a facsimile machine, a copier, or an MFP (MultiFunction Printer / Product / Peripheral) is used. ) Etc.

  (B) In Examples 1 and 2, the amount of external additive to be added and the stirring time (= external addition time) were adjusted in order to adjust the external additive adhesion amount of the toner 38, but this is merely an example. The amount of the external additive attached may be adjusted according to the ambient temperature at which the external addition is performed.

30 Developing Device 31 Photosensitive Drum 32 Charging Roller 33 Developing Roller 34 Supply Roller 40 Toner Cartridge

Claims (9)

In the developer according to an emulsion polymerization aggregation method with the external additive, the increase and the toner base particles, the fluidity and chargeability by adhering to the surface of the toner mother particles containing a binder resin and a colorant are primary particles There,
The specific surface area of the developer when not used is α,
The specific surface area of the developer after using the developer under the first condition is β,
When the developer is used under the second condition in which the external additive is detached from almost all the toner base particles, the specific surface area of the developer is γ,
The first condition is:
A layer forming member that regulates the thickness of the developer on the developer carrier is used for the developer carrier that carries the developer, and the developer has a linear pressure of 6.8 [gf / mm]. And the developer carrying body of the developer carrying body is set to 0.40 to 0.50 [mg / cm2], and the developer carrying body is rotated 25000 at a linear velocity of 150 [mm / sec]. Yes,
The second condition is:
Using the layer forming member, the developer is brought into pressure contact with the developer carrier at a linear pressure of 6.8 [gf / mm], and the developer amount of the developer carrier is set to 0.40 to 0.00. 50 [mg / cm2], the developer carrier is rotated 50000 at a linear speed of 150 [mm / sec],
The specific surface areas α, β, γ are:
0.74 ≦ (α−γ) /γ≦1.10.
0.40 ≦ (β−γ) /γ≦0.68
0 ≦ (α−β) /γ≦0.28
The developer characterized by being set to. The toner base particles are
The developer according to claim 1, wherein the developer is formed by mixing and aggregating the binder resin formed by the emulsion polymerization aggregation method, the colorant, and a wax. The developer is
3. The developer according to claim 1, wherein the developer is formed by adding a predetermined amount of the external additive to the toner base particles and stirring for a predetermined time. The developer is
The developer according to claim 3, wherein the external additive and titanium oxide fine powder are added to the toner base particles and stirred. The developer according to claim 1, wherein the binder resin is a styrene acrylic copolymer resin. The developer is
6. The developer according to claim 1, wherein a particle diameter is in a range of 4.0 to 6.5 [μm], and silica is used as the external additive. The developer according to any one of claims 1 to 6,
A rotatable latent image carrier carrying an electrostatic latent image;
A latent image carrier charging member for charging the surface of the latent image carrier;
Exposure means for forming a latent image on the surface of the latent image carrier;
The developer carrying body that visualizes the latent image formed on the latent image carrying body with the developer; and
The layer forming member for regulating the thickness of the developer on the developer carrying member;
A developer supply member for supplying the developer to the developer carrier;
A developing device comprising: A developer accommodating portion for accommodating the developer according to any one of claims 1 to 6;
A supply port disposed between the developer accommodating portion and a developing portion that develops using the developer;
A supply mechanism for supplying the developer stored therein to the developing unit;
A developer container characterized by comprising: A developing device according to claim 7;
The developer container according to claim 8;
A transfer unit that transfers the developer visualized in the developing device to a print medium;
A fixing unit for fixing the developer transferred to the print medium;
An image forming apparatus comprising:

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