JP2012242492A - Developer, image forming unit, developer storing body and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the fluidity and durability of a developer from being deteriorated and to prevent the image quality from being deteriorated.SOLUTION: A developer comprises toner base particles composed of at least a binder resin and an external additive adhered on the surface of the toner base particles. As the external additive, hydrophobic silica fine particles, colloidal silic fine particles having an average particle diameter larger than that of hydrophobic silica fine particles and melamine resin fine particles are used. Since hydrophobic silica fine particles, colloidal silic fine particles having an average particle diameter larger than that of hydrophobic silica fine particles and melamine resin fine particles are used as the external additive, the colloidal silica fine particles act as a buffer material against the load applied on the developer in an image forming unit and the load prevent the hydrophobic silica fine particles from being buried in the toner base particles, thereby enabling preventing the fluidity and durability of the developer from being deteriorated and improving the image quality.

Description

  The present invention relates to a developer, an image forming unit, a developer container, and an image forming apparatus.

  Conventionally, an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine, for example, an electrophotographic printer, includes an image forming unit, an LED head, a transfer roller, a fixing device, and the like. The image forming unit includes: a main body of the unit, that is, an image forming unit main body, and a toner cartridge as a developer container that is detachably attached to the image forming unit main body and stores toner as a developer. A photosensitive drum, a charging roller, a developing roller, a toner supply roller, a cleaning blade, and the like are disposed in the main body.

  In the printer, the surface of the photosensitive drum is uniformly charged by the charging roller, exposed by the LED head to form an electrostatic latent image, and the electrostatic latent image is developed by the developing roller. Yes. Then, the toner supplied from the toner cartridge is adhered to the electrostatic latent image on the photosensitive drum to form a toner image, and the toner image is transferred onto a sheet by a transfer roller and fixed in a fixing device. .

  By the way, the toner used in the printer is to add a hydrophobic silica fine powder to the toner base particles as an external additive to increase fluidity, and to suppress the occurrence of fogging on the paper. Further, it is prepared by adding a melamine resin fine powder having a charging polarity opposite to that of the toner base particles (see, for example, Patent Document 1).

JP 2003-295500 A

  However, in the conventional printer, when a load is applied to the toner in the image forming unit, the hydrophobic silica fine powder may be buried in the toner base particles, in which case the fluidity of the toner is reduced. End up.

  In addition, the melamine resin fine powder may be peeled off from the toner base particles, and in this case, the toner is peeled off from the toner base particles together with the hydrophobic silica fine powder. It will be lower. As a result, the image quality is degraded.

  The present invention solves the above-mentioned problems of the conventional printer, can prevent the flowability and durability of the developer from being lowered, and can prevent the image quality from deteriorating, An object is to provide an image forming unit, a developer container, and an image forming apparatus.

  For this purpose, the developer of the present invention has toner base particles made of at least a binder resin and an external additive attached to the surface of the toner base particles.

  As the external additive, there are used hydrophobic silica fine powder, colloidal silica fine powder having an average particle size larger than that of the hydrophobic silica fine powder, and melamine resin fine powder.

  According to the present invention, the developer includes at least toner base particles made of a binder resin and an external additive attached to the surface of the toner base particles.

  As the external additive, there are used hydrophobic silica fine powder, colloidal silica fine powder having an average particle size larger than that of the hydrophobic silica fine powder, and melamine resin fine powder.

  In this case, as the external additive, a hydrophobic silica fine powder, a colloidal silica fine powder having an average particle size larger than the hydrophobic silica fine powder, and a melamine resin fine powder are used. It becomes a buffer material against the load applied to the developer in the unit, and the application of the load can prevent the hydrophobic silica fine powder from being embedded in the toner base particles.

  Therefore, the fluidity of the developer can be prevented from being lowered, so that the image quality can be prevented from being lowered.

  Further, since the hydrophobic silica fine powder and the colloidal silica fine powder are aggregated, even if the melamine resin fine powder is peeled off from the toner base particles, the hydrophobic silica fine powder is not peeled off accordingly.

  Therefore, the durability of the developer can be prevented from being lowered, and the image quality can be prevented from being lowered.

It is sectional drawing for demonstrating the image forming unit in the 1st Embodiment of this invention. 1 is a conceptual diagram of a printer according to a first embodiment of the present invention. It is a 1st conceptual diagram showing the printing density on data. It is a 2nd conceptual diagram showing the printing density on data. It is a conceptual diagram showing the state of generation | occurrence | production of a blur. It is a conceptual diagram showing the state of generation | occurrence | production of a vertical stripe. It is a figure for demonstrating the detection method of fogging. It is a figure which shows the generation | occurrence | production state of dirt.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a printer as an image forming apparatus will be described.

  FIG. 2 is a conceptual diagram of the printer according to the first embodiment of the present invention.

  As shown in the drawing, the printer 40 includes a housing 41, and a paper cassette 50 as a medium accommodating portion is disposed in a lower portion of the housing 41, and a paper P as a medium is placed in the paper cassette 50. Be contained. A feeding roller 51 as a medium supply member is disposed at the front end of the paper cassette 50, and the paper P is fed out to the medium conveyance path 49 by the feeding roller 51.

  The fed paper P is formed with a plurality of image forming units that perform image formation of each color of black, yellow, magenta, and cyan by transport rollers 45 and 46 as medium transport members disposed in the medium transport path 49. As image forming units (developing devices) 55Bk, 55Y, 55M, and 55C, and a transfer unit 53 disposed to face the image forming units 55Bk, 55Y, 55M, and 55C.

  Each of the image forming units 55Bk, 55Y, 55M, and 55C includes a photosensitive drum 12 as an image carrier that is detachably disposed on the main body of the printer 40, that is, the apparatus main body. A toner image as a developer image of each color is formed on the surface of the toner using toner as a developer of each color of black, yellow, magenta, and cyan. An LED head 56 as an exposure device is disposed adjacent to the image forming units 55Bk, 55Y, 55M, and 55C and opposed to the photosensitive drums 12, and the photosensitive drums are provided by the LED heads 56. An electrostatic latent image as a latent image is formed on the surface of 12.

  The transfer unit 53 includes a driving roller R1 as a first roller, a driven roller R2 as a second roller, a conveying member stretched by the driving roller R1 and the driven roller R2, and a first roller A transfer belt 52 serving as a first transfer member, a transfer roller 57 serving as a second transfer member rotatably disposed opposite to the photosensitive drum 12 via the transfer belt 52, and the transfer belt 52; A developer collecting device 58 for scraping off and removing the toner is provided.

  In the transfer unit 53, the paper P is conveyed between the image forming units 55Bk, 55Y, 55M, and 55C and the transfer roller 57 as the transfer belt 52 travels. At this time, the respective color toner images formed in the respective image forming units 55Bk, 55Y, 55M, and 55C are sequentially transferred onto the paper P by the respective transfer rollers 57 to form color toner images.

  Subsequently, the paper P is sent to a fixing device 54 as a fixing device, and a color toner image is fixed in the fixing device 54 to form a color image. For this purpose, the fixing unit 54 includes a heating roller 54a as a first fixing roller and a pressure roller 54b as a second fixing roller, and the color toner image is heated by the heating roller 54a. Then, the image is pressed by the pressure roller 54b and becomes a color image. In addition, a halogen lamp (not shown) as a heating body is disposed in the heating roller 54a. When the halogen lamp is energized, the heating roller 54a is heated and the paper P is heated.

  Then, the paper P discharged from the fixing device 54 is conveyed through the medium discharge path 59 and discharged out of the printer 40 and is stacked on the stacker 60.

  Next, the image forming units 55Bk, 55Y, 55M, and 55C will be described. In this case, since the image forming units 55Bk, 55Y, 55M, and 55C have the same structure, only the image forming unit 55C will be described.

  FIG. 1 is a sectional view for explaining an image forming unit according to the first embodiment of the present invention.

  In the figure, 11 is a toner cartridge as a developer container, 12 is a photosensitive drum, 13 is a charging roller as a charging device, and 14 is a cleaning member that scrapes off toner t remaining on the surface of the photosensitive drum 12 after transfer. The cleaning blade 15 is disposed in contact with the photosensitive drum 12, and the developing roller 16 as a developer carrying member for holding the toner t is disposed in contact with the developing roller 15. A toner supply roller 17 serving as a developer supply member that supplies t to the developing roller 15 is disposed in pressure contact with the developing roller 15 and develops to thin the toner t supplied by the toner supply roller 16. A developing blade as an agent regulating member and as a layer forming member, 52 is a transfer belt, R1 is a driving roller, 54 is a fixing device, and 54a is Heat roller, 54b is a pressure roller.

  The toner cartridge 11 is provided detachably with respect to the main body of the image forming unit 55C, that is, the image forming unit main body Bd, and includes a toner storage chamber 11a as a developer storage chamber for storing toner t. The toner t stored in the toner storage chamber 11a is supplied to the image forming unit main body Bd through the supply port 18. In the present embodiment, a non-magnetic single component toner is used as the toner t.

  The photosensitive drum 12 includes a conductive support (not shown) formed of a metal pipe made of aluminum, and a photoconductive layer formed of an organic photosensitive member on the conductive support. The photoreceptor comprises a charge generation layer and a charge transport layer formed by sequentially laminating on the conductive support.

  The charging roller 13 is formed of a metal shaft and a semiconductive rubber material that covers the metal shaft, and the developing roller 15 is formed of a metal shaft and a semiconductive urethane rubber material that covers the metal shaft.

  Next, the operation of the printer 40 having the above configuration will be described.

  When a printing instruction is given by a control unit (not shown), first, a motor (not shown) as an image forming drive unit provided in the printer 40 is driven, and the rotation of the motor is performed through several gears (not shown). Is transmitted to the drum gear of the photosensitive drum 12, and the photosensitive drum 12 is rotated in the direction of arrow a. Further, the rotation is transmitted from the drum gear to the developing gear of the developing roller 15 so that the developing roller 15 is transmitted in the direction of arrow b from the developing gear to the supply gear of the toner supply roller 16 via the idle gear. As a result, the rotation of the toner supply roller 16 is transmitted in the direction of arrow c, and the rotation of the toner supply roller 16 is transmitted from the drum gear to the charging gear of the charging roller 13, whereby the charging roller 13 is rotated in the direction of arrow d. The surface of the photosensitive drum 12 is uniformly charged by the charging roller 13 and exposed by the LED head 56 to form an electrostatic latent image. The electrostatic latent image is thinned on the developing roller 16. The layered toner t is electrostatically attached to form a toner image.

  Further, the rotation of the motor is transmitted to the drive gear and the transfer gear via several gears (not shown) provided in the printer 40, whereby the drive roller R1 and the transfer roller 57 are rotated. At the same time, the transfer belt 52 is caused to travel.

  Further, the rotation of the motor is transmitted to the heating gear through several other gears (not shown) provided in the printer 40, the heating roller 54a is rotated, and the pressure roller 54b is rotated. Rotated.

  When a power supply (not shown) of the printer 40 is turned on, the photosensitive drum 12, the charging roller 13, the developing roller 15, the toner supply roller 16, the transfer roller 57, etc. are almost simultaneously with the start of driving of the motor. A predetermined voltage is applied to each, and the halogen lamp is energized.

  Next, a method for creating the toner t will be described.

  In the preparation method, first, a polymer which is a binder resin of toner t in a solvent (aqueous solvent), in the present embodiment, primary particles of a styrene acrylic copolymer resin were prepared by an emulsion polymerization method. Subsequently, the primary particles and a colorant emulsified with an emulsifier (surfactant) are mixed in the solvent, and if necessary, a wax, a charge control agent, and the like are further mixed to agglomerate the mixture. Thus, toner base particles (hereinafter referred to as “base toner”) as toner particles in a solvent were prepared. Then, the base toner was taken out from the solvent, and unnecessary solvent components and by-product components were removed by washing and drying.

  Next, silica is used as the base toner, and in this embodiment, a hydrophobic silica fine powder having a small average particle size (small particle size), and a larger average particle size (large particle size) than the hydrophobic silica fine powder. ) Colloidal silica fine powder and melamine resin, in this embodiment, melamine resin fine powder is added as an external additive, and mixed by a mixer, Henschel mixer (Mitsui Mining Co., Ltd.) in this embodiment And passed through a sieve to prepare toner t. In this way, the toner t in which the external additive is adhered to the surface of the base toner can be created.

  The styrene acrylic copolymer resin was produced from styrene, acrylic acid and methyl methacrylic acid. As the colorant, carbon black was used for black toner, pigment yellow 74 was used for yellow toner, pigment red 238 was used for magenta, and pigment blue 15: 3 was used for cyan toner. As the wax, stearyl stearate, which is a higher fatty acid ester wax, was used.

  The rotation speed of the Henschel mixer was 3200 [rotations / minute], and the Henschel mixer was cooled every time stirring was performed for 5 minutes, and stirring was performed for a total of 15 minutes.

  By the way, the hydrophobic silica fine powder has a function of increasing the fluidity of the toner, and the colloidal silica fine powder is present on the surface of the toner, so that the toner is contained in the image forming units 55Bk, 55Y, 55M, and 55C. It becomes a buffer material against the applied load, and has a function of preventing the hydrophobic silica fine powder from being embedded in the base toner when the load is applied. The melamine resin fine powder has a charging polarity opposite to that of the base toner, The toner has a positive polarity charge and has a function of preventing the sheet P from being fogged. Therefore, in the present embodiment, a hydrophobic silica fine powder having a particle size that can sufficiently increase the fluidity of the toner is used, and the colloidal silica fine powder is sufficiently buffered against the load. It is necessary to form a proper toner by using a material having a particle size as a material and using a melamine resin fine powder having a particle size that sufficiently suppresses the toner from being charged with a positive polarity. There is. A toner that cannot be adhered to the surface of the base toner due to the particle size being too large is not used.

  Accordingly, by determining the respective average particle sizes of the hydrophobic silica fine powder, colloidal silica fine powder and melamine resin fine powder, an appropriate toner t can be formed.

  Therefore, as hydrophobic silica fine powders having different average particle sizes, Aerosil R976S (manufactured by Nippon Aerosil Co., Ltd.) having an average particle size of 7 [nm] and Aerosil R974 (Nippon Aerosil Co., Ltd.) having an average particle size of 12 [nm] are used. And Aerosil R972 (manufactured by Nippon Aerosil Co., Ltd.) having an average particle size of 16 nm was used.

  Further, as colloidal silica fine powders having different average particle diameters, ST-XL (Nissan Chemical Industry Co., Ltd.) having an average particle diameter of 40 [nm], ST-YL (Nissan Chemical Industry Co., Ltd.) having an average particle diameter of 60 [nm] MP-1040 (manufactured by Nissan Chemical Industries, Ltd.) having an average particle diameter of 100 [nm], and MP-2040 (manufactured by Nissan Chemical Industries, Ltd.) having an average particle diameter of 200 [nm] were used. . And as the melamine resin fine powders having different average particle diameters, posters (manufactured by Nippon Shokubai Co., Ltd.) having average particle diameters of 50 [nm], 150 [nm], 300 [nm] and 400 [nm] were used.

  Then, in order to determine an appropriate range of the average particle size of the hydrophobic silica fine powder, the base toner having an average particle size of 5.5 [μm] and 7.0 [μm] and three types having different average particle sizes are used. In this embodiment, six kinds of toner added with 1.0 [part by weight] and two kinds of toner not added are prepared, and the fluidity of each toner is prepared. Was evaluated. The addition amount of the hydrophobic silica fine powder was set to 1.0 [parts by weight] in determining the appropriate range of the average particle diameter of the hydrophobic silica fine powder from the conventional knowledge (experimental results). This is because it has been found that when 1.0 [parts by weight] of hydrophobic silica fine powder is added, the fluidity increases.

  In this case, “Multisizer III” (manufactured by Beckman Coulter, Inc.) was used as a measuring instrument for measuring the average particle diameter of the base toner. In the “Multisizer III”, a base toner is dispersed in a dispersant (mixture of Isoton II-95 [mass%] and Emulgen-5 [mass%]), and a liquid in which the base toner is dispersed is Isoton II. A small amount added to was used as a measurement sample. The concentration of the base toner in the measurement sample is set to 10% or less. The aperture diameter was 100 [μm]. The measurement was terminated when the number of observed particles in the measurement sample reached 30000 or more, and the median diameter D50 of the obtained measurement result was taken as the average particle diameter.

  Further, a scanning electron microscope “S-2380N” (manufactured by Hitachi, Ltd.) was used as a measuring instrument for measuring the average particle size of the hydrophobic silica fine powder, colloidal silica fine powder and melamine resin fine powder. . In the scanning electron microscope “S-2380N”, each of the primary particles of hydrophobic silica fine powder, colloidal silica fine powder and melamine resin fine powder was photographed at an acceleration voltage of 10 [kV] and a magnification of 100,000 times. Then, 50 photographs taken with primary particles were randomly selected, and the average particle diameter was calculated based on the selected photographs. At that time, image analysis software (manufactured by Mitani Corporation) was used to calculate the diameter of a circle having the same area as the area of each primary particle, and the average value of each diameter was defined as the average particle diameter.

  The toner sample names used here are toners 1A, 1B, 1C, 1D, 1E, 1F, 1G, 1H, the average particle diameter of the base toner, the average particle diameter and the addition amount of the hydrophobic silica fine powder, The degree of toner aggregation is shown in Table 1.

In this case, the degree of aggregation was used as a parameter indicating the fluidity of each toner, and “Multi Tester MT-1001” (manufactured by Seishin Enterprise Co., Ltd.) was used as a measuring instrument for measuring the degree of aggregation. In the “Multi-Tester MT-1001”, three-stage sieves having openings of 250 [μm], 150 [μm], and 75 [μm] are stacked in descending order of openings. Then, each toner is placed on the top sieve at 2.0 ± 0.1 [g], and each sieve is vibrated for a predetermined time, for example, 95 [seconds]. The amplitude of vibration is 1.0 [mm]. The weight of the toner remaining on the sieve having a mesh opening of 250 [μm] after vibration is a [g], and the weight of the toner remaining on the sieve having a mesh opening of 150 [μm] is b [g]. When the weight of the toner remaining on the sieve having a mesh opening of 75 [μm] is c [g] and the weight of the toner first placed on the top sieve is d [g], the aggregation degree η Is
η = (5 × a + 3 × b + c) × 20 ÷ d
become. The lower the aggregation degree η (the smaller the value), the higher the fluidity of the toner.

  In Table 1 and the following tables, small silica represents hydrophobic silica fine powder, colloidal silica represents colloidal silica fine powder, and melamine represents melamine resin fine powder.

  From Table 1, it can be seen that the fluidity is high when the average particle diameter of the hydrophobic silica fine powder is 7 nm or more and 16 nm or less, regardless of the average particle diameter of the base toner. Therefore, when a hydrophobic silica fine powder having an average particle size of 7 nm or more and 16 nm or less is added to the base toner, the fluidity of the toner can be increased and the image quality is lowered. Can be prevented.

  Next, based on this evaluation result, 1.0 [parts by weight] of hydrophobic silica fine powder having an average particle diameter of 16 [nm] is added to the base toner, and further colloidal silica fine powder is added. The average particle diameter of the silica fine powder will be described.

  That is, in order to determine an appropriate range of the average particle size of the colloidal silica fine powder, the average particle size of 16 [nm] is added to the base toner having an average particle size of 5.5 [μm] and 7.0 [μm]. 1.0 [parts by weight] of hydrophobic silica fine powder, and four kinds of colloidal silica fine powders having different average particle diameters were added in a preset amount, in this embodiment, 1.6 [weights]. Part] Eight kinds of added toner and two kinds of toner not added were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated.

  The sample names of the toners used here are toners 2A, 2B, 2C, 2D, 2E, 2F, 2G, 2H, 2I, and 2J, and the addition amount and average particle diameter of the hydrophobic silica fine powder, and the average of the base toner Table 2 shows the particle size, the amount of colloidal silica fine powder added and the average particle size, the initial state aggregation degree ηs, the aggregation degree ηe after the durability test, and the state of occurrence of blurring and vertical stripes.

  The durability of the toner is defined as the change in the degree of aggregation of the toner before and after the endurance test, and the print density on the data is 100% using the image forming units 55Bk, 55Y, 55M, and 55C after the endurance test. The evaluation was made by checking whether or not blurring (white spots) occurred when the printing operation was performed, and whether or not vertical streaks were generated when the printing operation was performed with a printing density of 25%.

  Further, when evaluating durability, A4 size excellent white paper (Oki Data Co., Ltd.) 70 [kg] was used as the paper P.

  FIG. 3 is a first conceptual diagram showing the print density on the data, FIG. 4 is a second conceptual diagram showing the print density on the data, FIG. 5 is a conceptual diagram showing the state of occurrence of fading, and FIG. It is a conceptual diagram showing the state of generation | occurrence | production of.

  In FIGS. 3 and 4, the black circles represent dots on the grid constituting the image. At a printing density of 100 [%], dots are formed in the entire area of the printed part as shown in FIG. 3, and at a printing density of 25 [%], as shown in FIG. Dots are formed in the quarter area.

  When the toner aggregation degree η increases, the amount of toner supplied from the toner supply roller 16 (FIG. 1) to the developing roller 15 becomes insufficient. For example, when a printing operation is performed at a print density of 100%, FIG. As shown in FIG. 4, the actual print density becomes lower toward the upstream side in the printing direction indicated by the arrow, and the phenomenon that the white background of the paper P can be seen in the vicinity of the rear end of the paper P, that is, the blur occurs.

  Further, when the external additive peeled from the toner adheres to the charging roller 13 through the photosensitive drum 12, for example, when a printing operation is performed at a printing density of 25 [%], as shown in FIG. A phenomenon in which vertical lines are formed on the paper P in parallel with the printing direction shown in FIG.

  Next, the printer 40 for performing the durability test will be described.

  In order to evaluate the durability of the toner, in the image forming units 55Bk, 55Y, 55M, and 55C, the photosensitive drum 12 having an outer diameter of 30 [mm], the surface hardness of 73 [Asker C], and the ten-point average roughness A developing roller 15 having an Rz of 4.0 [μm] and an outer diameter of 19.6 [mm], a toner supply roller 16 having a surface hardness of 56 [Asker F] and an outer diameter of 15.5 [mm], and a material thereof The developing blade 17 was SUS304B-TA, the thickness was 0.08 [mm], the tip bending angle was 60 [°], and the tip curvature was 0.20.

  Further, the linear pressure between the developing roller 15 and the toner supply roller 16 is 11.5 [gf / mm], and the linear pressure between the developing roller 15 and the photosensitive drum 12 is 0.48 [gf / mm]. In addition, the linear pressure between the developing roller 15 and the developing blade 17 was set to 6.8 [gf / mm].

The voltage applied to the charging roller 13 is -1100 [V], the voltage applied to the developing roller 15 is -200 [V], and the voltage applied to the toner supply roller 16 is -300 [V]. did. It should be noted that the voltage applied to the toner supply roller 16 is made higher in the negative direction than −300 [V] when the toner adhesion amount on the developing roller 15 is less than 0.40 [mg / cm ² ], and development is performed. When the toner adhesion amount on the roller 15 is larger than 0.50 [mg / cm ² ], the toner adhesion amount on the developing roller 15 is set to 0.40 [V]. No change was made when it was not less than mg / cm ² ] and not more than 0.50 [mg / cm ² ]. The peripheral speed of the photosensitive drum 12 was made equal to the conveyance speed of the paper P, and the peripheral speed of the developing roller 15 was 1.6 times the peripheral speed of the photosensitive drum 12.

  And the durability test was done in the following procedures.

  That is, first, the initial aggregation degree ηs of the measurement toner is measured, and then 80 [g] of the measurement toner is supplied to the image forming units 55Bk, 55Y, 55M, and 55C. In this embodiment, in a normal temperature and normal humidity environment, in an environment with a temperature of 22 ° C. and a humidity of 40% (hereinafter referred to as “NN environment”), it was left for 12 hours or more. If necessary, the print data in the initial state was obtained after being left unattended.

  After leaving the printer 40, the printing operation was performed 25,000 times for each page with a blank print pattern (the print density on the data was set to 0 [%]) or based on the print data.

  Subsequently, print data after the durability test was obtained. Then, the toner for measurement was taken out from the image forming units 55Bk, 55Y, 55M, and 55C, and the aggregation degree ηe of the toner after the durability test was measured.

Note that the conveyance speed of the sheet P when performing a printing operation with a blank printing pattern is 150 [mm / sec], and the amount of toner adhered on the developing roller 15 is 0.40 [mg / cm ² ] or more, In addition, the voltage applied to the developing roller 15 and the toner supply roller 16 is adjusted so as to be maintained at 0.50 [mg / cm ² ] or less.

  In Table 2, “x” indicates that the occurrence of fading and vertical stripes can be confirmed by visual observation, and “◯” indicates that the occurrence of fading and vertical stripes cannot be confirmed by visual observation.

  When the colloidal silica fine powder having an average particle size of 200 [nm] is used in the durability evaluation results, the average particle size is too large, and thus the adhesive force to the base toner is weak and easy to peel. In that case, the peeled colloidal silica fine powder adheres to the photosensitive drum 12 or the charging roller 13 to generate vertical stripes. Moreover, when the colloidal silica fine powder whose average particle diameter is 50 [nm] is used, since the average particle diameter is too small, the effect as a buffer material cannot be obtained.

  Therefore, it can be seen that fine colloidal silica powder having an average particle size of 65 nm or more and 100 nm or less is suitable for use.

  That is, when a colloidal silica fine powder having an average particle size of 65 nm or more and 100 nm or less is added to the base toner, the colloidal silica fine powder is contained in the image forming units 55Bk, 55Y, 55M, and 55C. It becomes a buffer material against the load applied to the toner, and the application of the load can prevent the hydrophobic silica fine powder from being buried in the base toner.

  Accordingly, the toner fluidity can be prevented from being lowered, and the image quality can be prevented from being lowered.

  Next, the average particle diameter of the melamine resin fine powder in the case where the hydrophobic silica fine powder is added to the base toner and the melamine resin fine powder is further added will be described.

  That is, in order to determine an appropriate range of the average particle size of the melamine resin fine powder, the average particle size of 16 [nm] is added to the base toner having an average particle size of 5.5 [μm] and 7.0 [μm]. The hydrophobic silica fine powder of 1.0 [parts by weight] is added, and four kinds of melamine resin fine powders having different average particle diameters are added in a preset amount, 0.5 wt. Part] Eight kinds of added toner and two kinds of toner not added were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated. The printer 40 for performing the durability test and the procedure of the durability test are the same as those described above.

  The sample names of each toner used in the durability test are toners 3A, 3B, 3C, 3D, 3E, 3F, 3G, 3H, 3I, and 3J. The amount of hydrophobic silica fine powder added, the average particle size, and the base toner Table 3 shows the average particle size, the added amount of melamine resin fine powder and the average particle size, the state of fogging in the initial state, and the state of fogging and vertical stripes after the durability test.

  In this case, in order to make it easier to compare the influence of the addition of the melamine resin fine powder on the durability of the toner, only 0.5 [part by weight] of the melamine resin fine powder is added without adding the colloidal silica fine powder. Evaluation was performed. The addition amount of melamine resin fine powder was set to 0.5 [parts by weight] from the conventional knowledge (experimental results) when 0.5 [parts by weight] of melamine resin fine powder was added. This is because it is known that durability is increased.

  The durability of the toner is the occurrence of fog when the image forming units 55Bk, 55Y, 55M, and 55C are used and the printing operation is performed with the print density on the data before and after the durability test set to 25%. The evaluation was made by measuring the presence or absence and the presence or absence of fogging when the printing operation was performed with the print density on the data after the durability test being 25%.

  Here, a fog detection method will be described.

  FIG. 7 is a diagram for explaining a fog detection method.

  In the figure, 12 is a photosensitive drum, 15 is a developing roller, 16 is a toner supply roller, and 52 is a transfer belt.

  By the way, fogging is a phenomenon in which toner adheres to a non-printing portion of a sheet regardless of a printing pattern. When the charge amount of the toner is small, a toner charged to a polarity opposite to that of the normal toner, that is, a reversely charged toner is generated, and the reversely charged toner adheres to a non-printing portion and fog occurs. In order to determine whether or not fogging has occurred, first, a printing operation is performed with a blank printing pattern, and the contact portion pa with the developing roller 16 on the photosensitive drum 12 and the transfer belt 52 shown in FIG. The toner adhering to the contact part pb is collected with a scotch tape (manufactured by Sumitomo 3M Co., Ltd.), and the scotch tape is affixed to A4 excellent white paper (manufactured by Oki Data Co., Ltd.) Subsequently, a “CM-2600d spectrocolorimeter” (manufactured by Konica Minolta Sensing Co., Ltd.) is used as a colorimeter, and the color difference between the scotch tape with toner attached and the scotch tape without toner attached is measured. The measurement is performed at a plurality of positions in the axial direction of the body drum 12, in the present embodiment, at five positions of both end portions, the central portion, and the intermediate portion, and the average value is taken as the measurement value. If the measured value is greater than 2.00, it is determined that fogging has occurred, and if it is 2.00 or less, it is determined that fogging has not occurred.

  In Table 3, “x” indicates that the occurrence of vertical stripes can be confirmed by visual observation, and “◯” indicates that the occurrence of vertical stripes cannot be confirmed by visual observation.

  When the average particle size of the melamine resin fine powder is 400 [nm] or more, the adhesive force to the base toner is weak, so that the melamine resin fine powder is easy to peel off, and the peeled melamine resin fine powder adheres to the photosensitive drum 12 and the charging roller 13 to cause fogging. Not only does it generate, but it also causes vertical stripes. Further, even when the average particle diameter is 150 [nm] or less, the occurrence of fog cannot be prevented.

  From Table 3, it can be seen that the toner having an average particle diameter of 200 nm or more and 300 nm or less has high durability.

  Therefore, by adding a melamine resin fine powder having an average particle size of 200 nm or more and 300 nm or less to the base toner, the toner has a positive polarity charge and fog occurs on the paper. Can be suppressed.

  Next, the addition amount of the colloidal silica fine powder and the melamine resin fine powder when adding the hydrophobic silica fine powder to the base toner and further adding the colloidal silica fine powder and the melamine resin fine powder will be described.

  That is, in order to determine an appropriate range of the addition amount of colloidal silica fine powder and melamine resin fine powder, a base toner having an average particle diameter of 5.5 [μm] and a hydrophobic property having an average particle diameter of 16 [nm] 1.0 [parts by weight] of silica fine powder is added, and 1.2 [parts by weight], 1.4 [parts by weight], and 1.8 [parts by weight] of colloidal silica fine powder having an average particle size of 100 [nm]. And 2.0 [parts by weight], and 0.05 [parts by weight], 0.1 [parts by weight] of melamine resin fine powder having an average particle size of 200 [nm] and 300 [nm], Thirty-two types of toner added with 0.3 [parts by weight] and 0.4 [parts by weight] were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated. It was. The printer 40 for performing the durability test and the procedure of the durability test are the same as those described above.

  Sample names of the toners used here are toners 4A, 4B, 4C, 4D, 4E, 4F, 4G, 4H, 4I, 4J, 4K, 4L, 4M, 4N, 4O, 4P, 4a, 4b, 4c, 4d, 4e, 4f, 4g, 4h, 4i, 4j, 4k, 4l, 4m, 4n, 4o, 4p, the average particle size of the base toner, the added amount and average particle size of the hydrophobic silica fine powder, and the colloidal silica fine particle Average particle size of powder, average particle size of melamine resin fine powder, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, fogging in the initial state, occurrence of fog and dirt, blurring after endurance test, fogging Tables 4 to 7 show the state of occurrence of dirt and the determination result of the printing operation.

  In Tables 5 and 7, “x” indicates that the occurrence of fading and dirt can be confirmed by visual observation, and “◯” indicates that the occurrence of fading and dirt cannot be confirmed by visual observation.

  In this case, the decrease in the fluidity of the toner when the amount of the external additive having a large average particle size is excessive is compared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C is compared. To evaluate the above, compare the state of occurrence of blur when printing operation is performed at a printing density of 100%, and compare the state of occurrence of stain when the amount of melamine resin fine powder added is too large. In order to judge whether or not the amount of addition is sufficient to sufficiently suppress the occurrence of fog when adding melamine resin fine powder, the initial state and the occurrence of fog after the durability test were compared.

  FIG. 8 is a diagram showing a state where dirt is generated.

  In this case, the smudge is a phenomenon in which toner adheres to the paper P regardless of the print pattern, as in the case of fogging, but the cause of occurrence differs. The stain is caused when the sum of the surface potential of the developing roller 16 and the toner potential on the developing roller 16 becomes higher than the surface potential of the photosensitive drum 12 when the charge amount of the toner on the developing roller 16 is large. The toner moves from the developing roller 16 to the photosensitive drum 12 so that the total potential of the surface of the developing roller 16 and the toner potential on the developing roller 16 and the surface potential of the photosensitive drum 12 are in an equilibrium state. As shown in FIG. 8, the toner is generated by adhering as shown by a broken line regardless of the print pattern.

  The occurrence of smudges is as shown in FIG. 8 when printing is performed on 70 [kg] of A4 size excellent white paper (manufactured by Oki Data Co., Ltd.) with a printing density of 25 [%]. The broken line was confirmed visually. If no dirt was visually confirmed, it was judged that no dirt was generated.

  From Tables 4 to 7, colloidal silica fine powder having an average particle diameter of 100 nm is added to a base toner having an average particle diameter of 5.5 [μm] at 1.4 [parts by weight] or more and 1.8 [parts]. Parts by weight] or less, and melamine resin fine powder having an average particle size of 200 nm or more and 300 nm or less is added 0.1 parts by weight or more and 0.3 parts by weight or less. In this case, it can be seen that the durability of the toner can be increased and good printing can be performed without fading, fogging and smearing.

  Accordingly, the colloidal silica fine powder having an average particle size of 100 [nm] is added to the base toner in an amount of 1.4 [parts] or more and 1.8 [parts] or less, and the average particle size is 200 [nm]. When a melamine resin fine powder of 300 nm or less is added in an amount of 0.1 parts by weight or more and 0.3 parts by weight or less, hydrophobic silica fine powder and colloidal silica fine powder are aggregated. Therefore, even if the melamine resin fine powder is peeled off from the base toner, the hydrophobic silica fine powder is not peeled off accordingly.

  As a result, the fluidity of the toner can be prevented from being lowered, so that the image quality can be prevented from being lowered.

  Next, when the hydrophobic silica fine powder is added to the base toner, and the colloidal silica fine powder and the melamine resin fine powder are further added, the addition amount of the colloidal silica fine powder and the melamine resin fine powder, and the average of the base toner The particle size will be described.

  That is, in order to determine the appropriate amount of the colloidal silica fine powder and the melamine resin fine powder and the average range of the average particle diameter of the base toner, the average particle diameter is 5.0 [μm], 6.0 [μm] and 1.0 [parts by weight] of hydrophobic silica fine powder having an average particle diameter of 16 [nm] and 1 colloidal silica fine powder having an average particle diameter of 100 [nm] are added to each base toner of 6.5 [μm]. .4 [parts by weight] and 1.8 [parts by weight] 0.1 [parts by weight] and 0.3 [parts by weight] of melamine resin fine powder having an average particle size of 200 [nm] and 300 [nm] added The 32 types of toners were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated. The printer 40 for performing the durability test and the procedure of the durability test are the same as those described above.

  Sample names of the toners used here are toners 5A, 5B, 5C, 5D, 5E, 5F, 5G, 5H, 5I, 5J, 5K, 5L, 5M, 5N, 5O, 5P, 5a, 5b, 5c, 5d, 5e, 5f, 5g, 5h, 5i, 5j, 5k, 5l, 5m, 5n, 5o, 5p, the added amount of the hydrophobic silica fine powder, the average particle diameter of the hydrophobic silica fine powder, the colloidal silica fine powder Average particle size, average particle size of melamine resin fine powder, average particle size of base toner, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, initial state of fogging, fogging and stain occurrence, durability Tables 8 to 11 show the state of occurrence of fading, fogging and smudges after the test, and the determination results of the printing operation.

  In Tables 9 and 11, “x” indicates that the occurrence of fading and dirt can be confirmed by visual observation, and “◯” indicates that the occurrence of fading and dirt cannot be confirmed by visual observation.

  From Tables 8 to 11, a base toner having an average particle diameter of 5.5 [μm] or more and 6.0 [μm] or less is obtained with 1.4 [Colloidal silica fine powder having an average particle diameter of 100 [nm]. Parts by weight] or more and 1.8 [parts by weight] or less, and an average particle size of 200 [nm] or more and 300 [nm] or less of melamine resin fine powder of 0.1 [parts by weight] or more, It can also be seen that when 0.3 [parts by weight] or less is added, the durability of the toner can be increased, and good printing can be performed without causing blurring, fogging and smearing. Therefore, it is possible to prevent the image quality from deteriorating.

  Next, when adding the hydrophobic silica fine powder to the base toner, and further adding the colloidal silica fine powder and the melamine resin fine powder, the colloidal silica fine powder when the average particle size of the colloidal silica fine powder is varied is used. The amount of powder and melamine resin fine powder added will be described.

  That is, in order to determine an appropriate range of the addition amount of colloidal silica fine powder and melamine resin fine powder, a base toner having an average particle diameter of 5.5 [μm] and a hydrophobic property having an average particle diameter of 16 [nm] 1.0 [parts by weight] silica fine powder was added, and 1.2 [parts by weight], 1.4 [parts by weight], and 1.8 [parts by weight] colloidal silica fine powder having an average particle size of 65 [nm]. And 2.0 [parts by weight], and 0.05 [parts by weight], 0.1 [parts by weight] of melamine resin fine powder having an average particle size of 200 [nm] and 300 [nm], Thirty-two types of toner added with 0.3 [parts by weight] and 0.4 [parts by weight] were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated. It was. The printer 40 for performing the durability test and the procedure of the durability test are the same as those described above.

  The sample names of the toners used here are toners 6A, 6B, 6C, 6D, 6E, 6F, 6G, 6H, 6I, 6J, 6K, 6L, 6M, 6N, 6O, 6P, 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, 6i, 6j, 6k, 6l, 6m, 6n, 6o, 6p, the average particle size of the base toner, the added amount and average particle size of the hydrophobic silica fine powder, the colloidal silica fine Average particle size of powder, average particle size of melamine resin fine powder, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, fogging in the initial state, occurrence of fog and dirt, blurring after endurance test, fogging Tables 12 to 15 show the state of occurrence of dirt and the determination result of the printing operation.

  In Tables 13 and 15, “X” indicates that the occurrence of fading and dirt can be confirmed by visual observation, and “◯” indicates that the occurrence of fading and dirt cannot be confirmed by visual observation.

  From Tables 12 to 15, colloidal silica fine powder having an average particle diameter of 65 nm is added to a base toner having an average particle diameter of 5.5 [μm] at least 1.4 [parts by weight] and 1.8 [parts]. Parts by weight] or less, and melamine resin fine powder having an average particle size of 200 nm or more and 300 nm or less is added 0.1 parts by weight or more and 0.3 parts by weight or less. In this case, it can be seen that the durability of the toner can be increased and good printing can be performed without fading, fogging and smearing. Therefore, it is possible to prevent the image quality from deteriorating.

  Next, when adding the hydrophobic silica fine powder to the base toner, and further adding the colloidal silica fine powder and the melamine resin fine powder, the colloidal silica fine powder when the average particle size of the colloidal silica fine powder is varied is used. The amount of powder and melamine resin fine powder added and the average particle size of the base toner will be described.

  That is, in order to determine the appropriate amount of the colloidal silica fine powder and the melamine resin fine powder and the average range of the average particle diameter of the base toner, the average particle diameter is 5.0 [μm], 6.0 [μm] and To each base toner of 6.5 [μm], 1.0 [part by weight] of hydrophobic silica fine powder having an average particle diameter of 16 [nm] and 1 colloidal silica fine powder having an average particle diameter of 65 [nm] .4 [parts by weight] and 1.8 [parts by weight] 0.1 [parts by weight] and 0.3 [parts by weight] of melamine resin fine powder having an average particle size of 200 [nm] and 300 [nm] added The 32 types of toners were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated. The printer 40 for performing the durability test and the procedure of the durability test are the same as those described above.

  Sample names of the toners used here are toners 7A, 7B, 7C, 7D, 7E, 7F, 7G, 7H, 7I, 7J, 7K, 7L, 7M, 7N, 7O, 7P, 7a, 7b, 7c, 7d, 7e, 7f, 7g, 7h, 7i, 7j, 7k, 7l, 7m, 7n, 7o, 7p, addition amount of hydrophobic silica fine powder, average particle diameter of hydrophobic silica fine powder, colloidal silica fine powder Average particle size, average particle size of melamine resin fine powder, average particle size of base toner, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, initial state of fogging, fogging and stain occurrence, durability Tables 16 to 19 show the state of occurrence of fading, fogging and smudges after the test, and the determination results of the printing operation.

  In Tables 17 and 19, “x” indicates that the occurrence of fading and dirt can be confirmed by visual observation, and “◯” indicates that the occurrence of fading and dirt cannot be confirmed by visual observation.

  From Tables 16 to 19, a colloidal silica fine powder having an average particle size of 65 nm is added to a base toner having an average particle size of 5.5 [μm] or more and 6.0 [μm] or less. Parts by weight] or more and 1.8 [parts by weight] or less, and an average particle size of 200 [nm] or more and 300 [nm] or less of melamine resin fine powder of 0.1 [parts by weight] or more, It can also be seen that when 0.3 [parts by weight] or less is added, the durability of the toner can be increased, and good printing can be performed without causing blurring, fogging and smearing. Therefore, it is possible to prevent the image quality from deteriorating.

  From the above, while adding the hydrophobic silica fine powder having a small average particle diameter to the base toner having an average particle diameter of 5.5 [μm] or more and 6.0 [μm] or less, the average particle diameter is When adding a large colloidal silica fine powder and a melamine resin fine powder together, the addition amount of the colloidal silica fine powder having an average particle size of 65 nm or more and 100 nm or less is 1.4 [parts by weight]. The amount of addition of the melamine resin fine powder having an average particle size of 200 nm or more and 300 nm or less is 0.1 [parts by weight] or more. In addition, when the amount is 0.3 [parts by weight] or less, it can be seen that the durability of the toner can be increased, and good printing without blurring, fogging and smearing can be performed. And since the addition amount of a melamine resin fine powder is made small, it can prevent generating a stain | pollution | contamination. Therefore, it is possible to prevent the image quality from deteriorating.

  In the present embodiment, a base toner having an average particle size of 5.5 [μm] or more and 6.0 [μm] or less is used, but the average particle size is 6.0 [μm]. μm] or more of the base toner, the hydrophobic silica fine powder having a small average particle diameter is added, and the colloidal silica fine powder and the melamine resin fine powder having a large average particle diameter are added together. A second embodiment will be described.

  By the way, as the average particle size of the base toner increases, the surface area per unit weight of the toner as the developer decreases. When the surface area is reduced, the amount of external additive that applies pressure or undergoes friction in the image forming units 55Bk, 55Y, 55M, and 55C (FIG. 2) as the image forming unit is reduced. The amount of external additive that peels from the surface is reduced. As a result, it is possible to prevent the peeled external additive from adhering to the photosensitive drum 12 as the image carrier and the charging roller 13 as the charging device, so that the average particle diameter of the base toner is 5.5 [μm] or more. In addition, an effect of suppressing the generation of vertical stripes can be expected as compared with a toner having a particle size of 6.0 [μm] or less.

  In this embodiment, the average particle diameters of the hydrophobic silica fine powder, colloidal silica fine powder, and melamine resin fine powder added to the base toner are the same as those in the first embodiment. Also, the printer 40 as an image forming apparatus for performing the durability test and the procedure of the durability test are the same as those in the first embodiment.

  First, in order to determine an appropriate range of the addition amount of colloidal silica fine powder and melamine resin fine powder, a hydrophobic toner having an average particle diameter of 16 [nm] is added to a base toner having an average particle diameter of 7.0 [μm]. 1.0 [parts by weight] of silica fine powder is added, and 1.0 [parts by weight], 1.2 [parts by weight], 1.6 [parts by weight] of colloidal silica fine powder having an average particle size of 100 [nm] is added. And 1.8 [parts by weight] are added, and 0.0 [parts by weight] (not added), 0.05 parts by weight of melamine resin fine powder having an average particle size of 200 [nm] and 300 [nm]. Thirty-two types of toner added with [parts by weight], 0.2 [parts by weight] and 0.3 [parts by weight] are prepared, and each toner has durability against the load applied in the image forming units 55Bk, 55Y, 55M and 55C. The sex was evaluated.

  Sample names of the toners used here are toners 8A, 8B, 8C, 8D, 8E, 8F, 8G, 8H, 8I, 8J, 8K, 8L, 8M, 8N, 8O, 8P, 8a, 8b, 8c, 8d, 8e, 8f, 8g, 8h, 8i, 8j, 8k, 8l, 8m, 8n, 8o, 8p, the average particle size of the base toner, the added amount of hydrophobic silica fine powder and the average particle size, colloidal silica fine Average particle size of powder, average particle size of melamine resin fine powder, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, fogging in the initial state, occurrence of fog and dirt, blurring after endurance test, fogging Tables 20 to 23 show the occurrence state of stains and the determination result of the printing operation.

  In Tables 21 and 23, x indicates that the occurrence of fading and dirt can be confirmed by visual observation, and ○ indicates that the occurrence of fading and dirt cannot be confirmed by visual observation.

  From Tables 20 to 23, 1.2 [parts by weight] or more and 1.6 [parts] of colloidal silica fine powder having an average particle diameter of 100 [nm] is added to the base toner having an average particle diameter of 7.0 [μm]. [Parts by weight] added below, 0.05 [parts by weight] and 0.2 [parts by weight] or less of melamine resin fine powder with an average particle size of 200 [nm] or more and 300 [nm] or less added In this case, it can be seen that the durability of the toner can be increased and good printing can be performed without fading, fogging and smearing. Therefore, it is possible to prevent the image quality from deteriorating.

  Next, the colloidal silica fine powder and the melamine when the hydrophobic silica fine powder is added to the base toner having a larger average particle diameter than the first embodiment, and further the colloidal silica fine powder and the melamine resin fine powder are added. The amount of resin fine powder added and the average particle size of the base toner will be described.

  That is, in order to determine the appropriate amount of the colloidal silica fine powder and melamine resin fine powder and the average particle diameter of the base toner, the average particle diameter is 6.0 [μm], 6.5 [μm] and 1.0 [parts by weight] of hydrophobic silica fine powder having an average particle diameter of 16 [nm] and colloidal silica fine powder having an average particle diameter of 100 [nm] on a base toner of 7.5 [μm] 0.05 [parts by weight] and 0.2 [parts by weight] of melamine resin fine powders having 2 [parts by weight] and 1.6 [parts by weight] and average particle diameters of 200 [nm] and 300 [nm] were added. Thirty-two types of toners were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated.

  Sample names of the toners used here are toners 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I, 9J, 9K, 9L, 9M, 9N, 9O, 9P, 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, 9i, 9j, 9k, 9l, 9m, 9n, 9o, 9p, the addition amount and average particle size of hydrophobic silica fine powder, the average particle size of colloidal silica fine powder, melamine Average particle size of resin fine powder, average particle size of base toner, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, fogging in the initial state, occurrence of fog and dirt, blurring after endurance test, fogging Tables 24-27 show the occurrence status of smudges and the determination result of the printing operation.

  In Tables 25 and 27, x represents that the occurrence of fading and dirt could be confirmed by visual observation, and ◯ represents that the occurrence of fading and dirt could not be confirmed by visual observation.

  From Tables 24-27, a colloidal silica fine powder having an average particle size of 100 [nm] is added to a base toner having an average particle size of 6.5 [μm] or more and 7.5 [μm] or less to 1.2 [μm]. Parts by weight] or more and 1.6 [parts by weight] or less, and the average particle size of 200 [nm] or more and 300 [nm] or less melamine resin fine powder is 0.05 [parts by weight] or more, Further, it can be seen that when 0.2 [parts by weight] or less is added, the durability of the toner can be increased, and good printing can be performed without blurring, fogging and smearing. Therefore, it is possible to prevent the image quality from deteriorating.

  Next, the colloidal silica fine powder and the melamine when the hydrophobic silica fine powder is added to the base toner having a larger average particle diameter than the first embodiment, and further the colloidal silica fine powder and the melamine resin fine powder are added. The amount of resin fine powder added will be described.

  That is, in order to determine an appropriate range of addition amounts of colloidal silica fine powder and melamine resin fine powder, a base toner having an average particle diameter of 7.0 [μm] and a hydrophobic property having an average particle diameter of 16 [nm] 1.0 [parts by weight] silica fine powder was added, and 1.0 [parts by weight], 1.2 [parts by weight], 1.6 [parts by weight] colloidal silica fine powder having an average particle size of 65 [nm]. And 1.8 [parts by weight] are added, and 0.0 [parts by weight] (not added), 0.05 parts by weight of melamine resin fine powder having an average particle size of 200 [nm] and 300 [nm]. Thirty-two types of toner added with [parts by weight], 0.2 [parts by weight] and 0.3 [parts by weight] are prepared, and each toner has durability against the load applied in the image forming units 55Bk, 55Y, 55M and 55C. The sex was evaluated.

  Sample names of the toners used here are toners 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 10I, 10J, 10K, 10L, 10M, 10N, 10O, 10P, 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 10i, 10j, 10k, 10l, 10m, 10n, 10o, 10p, the average particle diameter of the base toner, the added amount and average particle diameter of the hydrophobic silica fine powder, the colloidal silica fine particle Average particle size of powder, average particle size of melamine resin fine powder, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, fogging in the initial state, occurrence of fog and dirt, blurring after endurance test, fogging Tables 28 to 31 show the occurrence state of stains and the determination result of the printing operation.

  In Tables 29 and 31, “X” indicates that the occurrence of fading and dirt can be confirmed by visual observation, and “◯” indicates that the occurrence of fading and dirt cannot be confirmed by visual observation.

  From Tables 28-31, 1.2 [parts by weight] or more and 1.6 [parts by weight] of colloidal silica fine powder having an average particle diameter of 65 [nm] is added to the base toner having an average particle diameter of 7.0 [μm]. [Parts by weight] added below, 0.05 [parts by weight] and 0.2 [parts by weight] or less of melamine resin fine powder with an average particle size of 200 [nm] or more and 300 [nm] or less added In this case, it can be seen that the durability of the toner can be increased and good printing can be performed without fading, fogging and smearing. Therefore, it is possible to prevent the image quality from deteriorating.

  Next, the colloidal silica fine powder and the melamine when the hydrophobic silica fine powder is added to the base toner having a larger average particle diameter than the first embodiment, and further the colloidal silica fine powder and the melamine resin fine powder are added. The amount of resin fine powder added and the average particle size of the base toner will be described.

  That is, in order to determine the appropriate amount of colloidal silica fine powder and melamine resin fine powder and the average particle diameter of the base toner, the average particle diameter is 6.0 [μm], 6.5 [μm] and 1.0 [parts by weight] of hydrophobic silica fine powder having an average particle diameter of 16 [nm] and colloidal silica fine powder having an average particle diameter of 65 [nm] are added to a base toner of 7.5 [μm]. 0.05 [parts by weight] and 0.2 [parts by weight] of melamine resin fine powders having 2 [parts by weight] and 1.6 [parts by weight] and average particle diameters of 200 [nm] and 300 [nm] were added. Thirty-two types of toners were prepared, and the durability of each toner against the load applied in the image forming units 55Bk, 55Y, 55M, and 55C was evaluated.

  Sample names of the toners used here are toners 11A, 11B, 11C, 11D, 11E, 11F, 11G, 11H, 11I, 11J, 11K, 11L, 11M, 11N, 110, 11P, 11a, 11b, 11c, 11d, 11e, 11f, 11g, 11h, 11i, 11j, 11k, 11l, 11m, 11n, 11o, 11p, and the addition amount and average particle size of hydrophobic silica fine powder, average particle size of colloidal silica fine powder, melamine Average particle size of resin fine powder, average particle size of base toner, addition amount of colloidal silica fine powder, addition amount of melamine resin fine powder, fogging in the initial state, occurrence of fog and dirt, blurring after endurance test, fogging Tables 32 to 35 show the occurrence state of stains and the determination result of the printing operation.

  In Tables 33 and 35, “x” indicates that the occurrence of fading and dirt can be confirmed by visual observation, and “◯” indicates that the occurrence of fading and dirt cannot be confirmed by visual observation.

  From Tables 32 to 35, 1.2 [μm] colloidal silica fine powder having an average particle size of 65 [nm] is added to the base toner having an average particle size of 6.5 [μm] or more and 7.0 [μm] or less. Parts by weight] or more and 1.6 [parts by weight] or less, and the average particle size of 200 [nm] or more and 300 [nm] or less melamine resin fine powder is 0.05 [parts by weight] or more, Further, it can be seen that when 0.2 [parts by weight] or less is added, the durability of the toner can be increased, and good printing can be performed without blurring, fogging and smearing. Therefore, it is possible to prevent the image quality from deteriorating.

  Next, in the present exemplary embodiment, when a base toner having an average particle diameter of 6.5 [μm] or more and 7.0 [μm] or less is used, a toner capable of performing good printing is In the first embodiment, when a base toner having an average particle size of 5.5 [μm] or more and 6.0 [μm] or less is used, it is compared with a toner that can perform good printing. Confirm that the external additive is difficult to peel off.

  In this case, in order to evaluate the difficulty of peeling off the external additive, the printer 40 was used, and an additional durability test was performed on the toners subjected to the durability test in Tables 4 to 35. The toner used in the additional durability test is a toner that can increase the durability of the toner in each of Tables 4 to 34, and that can perform good printing without causing blurring, fogging, and smearing. The toner sample names are Toner 4F, 4G, 4J, 4K, 5E, 5F, 5G, 5H, 8F, 8G, 8J, 8K, 9E, 9F, 9G, 9H, 4f, 4g, 4j, 4k, 5e, 5f. 5g, 5h, 8f, 8g, 8j, 8k, 9e, 9f, 9g, 9h, 6F, 6G, 6J, 6K, 7E, 7F, 7G, 7H, 10F, 10G, 10J, 10K, 11E, 11F, 11G 11H, 6f, 6g, 6j, 6k, 7e, 7f, 7g, 7h, 10f, 10g, 10j, 10k, 11e, 11f, 11g, 11h. In addition, the average particle diameter of the colloidal silica fine powder used in Tables 36 to 39 is 100 [nm], and the average particle diameter of the colloidal silica fine powder used in Tables 40 to 43 is 65 [nm].

  The additional durability test was performed according to the following procedure.

  That is, using the printer 40 and the image forming units 55Bk, 55Y, 55M, and 55C used for the durability test, the printer 40 was first placed in an NN environment and left for 12 hours or more. If necessary, the print data in the initial state was obtained after being left, and the print data was used as print data for an additional durability test.

  After the printer 40 is left unattended, a printing operation is performed 25,000 times for each page with a blank print pattern (the print density on the data is 0 [%]) or based on the print data, and the developing roller The total number of revolutions of 15 was set to 50000 times, and then print data after an additional durability test was obtained.

  In this case, it is difficult for the external additive to be peeled off from the base toner when the printing operation is performed using the image forming units 55Bk, 55Y, 55M, and 55C and setting the print density on the data as 100%. Evaluation was made by confirming the presence or absence of blurring before and after the additional endurance test, and the presence or absence of vertical streaks before and after the additional endurance test when the printing operation was performed at a print density of 25%. .

  As described above, Tables 36 to 40 show the evaluation results for the toners in which the average particle size of the colloidal silica fine powder used is 100 [nm], and the average particle size of the colloidal silica fine powder used is 65 [ nm] is shown in Tables 41 to 44.

  From Tables 36 to 44, the external additive added to the base toner having an average particle diameter of 6.5 [μm] or more and 7.0 [μm] or less has an average particle diameter of 5.5 [μm] or more. In addition, it can be seen that the external additives added to the base toner having a particle size of 6.0 [μm] or less are more difficult to peel off.

  Accordingly, a hydrophobic silica fine powder having a small average particle diameter is added to a base toner having an average particle diameter of 6.5 [μm] or more and 7.5 [μm] or less, and further, a colloidal having a large average particle diameter. When silica fine powder and melamine resin fine powder are added, colloidal silica fine powder having an average particle diameter of 65 nm or more and 100 nm or less is 1.2 [parts by weight] or more and 1.6 [Parts by weight] added below, 0.05 [parts by weight] and 0.2 [parts by weight] or less of melamine resin fine powder having an average particle size of 200 [nm] or more and 300 [nm] or less When added, the durability of the toner can be increased, and good printing can be performed without blurring, fogging and smearing. As a result, it is possible to prevent the image quality from deteriorating.

  In each of the above-described embodiments, the electrophotographic printer 40 has been described. However, the present invention can be applied to a copying machine, a facsimile machine, a multifunction machine, and the like using an electrophotographic system.

  In each of the above-described embodiments, 1.0 [parts by weight] of hydrophobic silica fine powder having an average particle size of 16 [nm] is added as an external additive that can increase the fluidity of the toner. However, in order to further improve the fluidity, it is necessary to use hydrophobic silica fine powder having an average particle size smaller than 16 nm, or to change the amount of hydrophobic silica fine powder added. Can do.

  The present invention is not limited to the above embodiments, and various modifications can be made based on the gist of the present invention, and they are not excluded from the scope of the present invention.

t Toner

Claims (7)

(A) toner base particles comprising at least a binder resin;
(B) having an external additive attached to the surface of the toner base particles,
(C) A developer comprising hydrophobic silica fine powder, colloidal silica fine powder having an average particle size larger than that of the hydrophobic silica fine powder, and melamine resin fine powder as the external additive. (A) The average particle size of the hydrophobic silica fine powder is 7 [nm] or more and 16 [nm] or less,
(B) The average particle diameter of the colloidal silica fine powder is 65 [nm] or more and 100 [nm] or less,
(C) The developer according to claim 1, wherein the melamine resin fine powder has an average particle size of 200 nm or more and 300 nm or less. (A) The average particle size of the toner base particles is 5.5 [μm] or more and 6.0 [μm] or less,
(B) The amount of colloidal silica fine powder added is 1.4 [parts by weight] or more and 1.8 [parts by weight] or less,
(C) The developer according to claim 1 or 2, wherein the addition amount of the melamine resin fine powder is 0.1 [parts by weight] or more and 0.3 [parts by weight] or less. (A) The average particle diameter of the toner base particles is 6.5 [μm] or more and 7.0 [μm] or less,
(B) The amount of colloidal silica fine powder added is 1.2 [parts by weight] or more and 1.6 [parts by weight] or less,
(C) The developer according to claim 1 or 2, wherein the addition amount of the fine melamine resin powder is 0.05 [parts by weight] or more and 0.2 [parts by weight] or less. (A) an image carrier;
(B) a charging device for charging the surface of the image carrier;
(C) a developer carrier for holding the developer;
(D) a layer forming member brought into pressure contact with the developer carrying member;
(E) a developer supply member that is disposed in contact with the developer carrier and supplies the developer to the developer carrier;
(F) The developer includes toner base particles composed of at least a binder resin, and an external additive attached to the surface of the toner base particles.
(G) An image forming unit comprising: a hydrophobic silica fine powder, a colloidal silica fine powder having an average particle size larger than that of the hydrophobic silica fine powder, and a melamine resin fine powder as the external additive. (A) a developer accommodating chamber for accommodating the developer;
(B) a supply port for supplying the developer stored in the developer storage chamber to the image forming unit;
(C) The developer has toner base particles composed of at least a binder resin, and an external additive attached to the surface of the toner base particles.
(D) A developer container comprising a hydrophobic silica fine powder, a colloidal silica fine powder having an average particle size larger than that of the hydrophobic silica fine powder, and a melamine resin fine powder as the external additive. . (A) an image carrier;
(B) a charging device for charging the surface of the image carrier;
(C) a developer carrier for holding the developer;
(D) a layer forming member brought into pressure contact with the developer carrying member;
(E) a developer supply member that is disposed in contact with the developer carrier and supplies the developer to the developer carrier;
(F) having a developer container;
(G) The developer has toner base particles composed of at least a binder resin, and an external additive attached to the surface of the toner base particles.
(H) As the external additive, hydrophobic silica fine powder, colloidal silica fine powder having an average particle size larger than the hydrophobic silica fine powder, and melamine resin fine powder are used,
(I) The developer accommodating body includes a developer accommodating chamber for accommodating a developer, and a supply port for supplying the developer accommodated in the developer accommodating chamber to the image forming unit. An image forming apparatus.

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