JP2004109290A - Toner image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a novel toner image forming device for performing image formation suitable for toners which can well reproduce the color tones of projected images. <P>SOLUTION: The toner image forming device is so constituted as to perform the image fomation satisfying the relational expression [1.5×ρr×R≤10×Mmax≤1.2×Br×ρ×R] when the amount of the maximum average toner deposition per unit area in a recording medium P (transparent sheet) of the monochromatic toner image consisting of monochromatic toners is defined as Mmax [mg/cm<SP>2</SP>], the true specific gravity of the toners as ρ[g/cm<SP>3</SP>], the apparent density of the toners as ρr[g/cm<SP>3</SP>], the volume average grain size of the toners as R [μm], and the closest packing rate of the true balls as Br. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly to a toner image forming apparatus that forms a toner image by attaching toner on a recording medium and then fixes the toner image by a fixing unit. .
[0002]
[Prior art]
Conventionally, as this type of toner image forming apparatus, an electrophotographic type is well known. The electrophotographic system is a system in which a latent image carried on a latent image carrier such as a photoreceptor is developed into a toner image by a developing unit and then transferred to a recording medium.
[0003]
Further, a so-called flight recording system is also known (for example, Patent Document 1). The flight recording method is a method of forming a dot image by directly adhering a toner group, which has been ejected in a dot form from a toner flying device, to an intermediate recording medium or a sheet material.
[0004]
On the other hand, with the rapid spread of personal computers in recent years, there has been an increasing demand for creating OHP documents for overhead projectors (hereinafter referred to as OHP) by image output using a toner image forming apparatus. However, a toner image made of a toner is inferior in light transmittance as compared with an ink image, so that it has been difficult to satisfactorily reproduce the color tone of a projected image by OHP. In particular, a toner containing a pigment-based particulate colorant has a very low light transmittance of the particulate colorant, so that it is very difficult to reproduce a color tone in a projected image, and only a dark and unsightly projected image is obtained. .
[0005]
[Patent Document 1]
JP-A-12-23831
[0006]
[Problems to be solved by the invention]
Therefore, the present applicant is developing a novel toner capable of reproducing a color tone well in a projected image by uniformly dispersing a granular colorant having a smaller diameter than in the prior art. However, even with such a toner, depending on the type of the toner image forming apparatus, the amount of toner in the image is excessively large, so that a satisfactory color tone cannot be obtained in the projected image. This is because the conventional toner image forming apparatus is designed with a focus on the color tone of the toner image on the recording medium, and does not consider the color tone of the projected image at all.
[0007]
The present invention has been made in view of the above background, and an object of the present invention is to provide a novel toner image forming apparatus capable of forming an image suitable for a toner capable of well reproducing a color tone of a projected image. It is to provide.
[0008]
[Means for Solving the Problems]
The present inventors have formed single-color toner images of various thicknesses on a transparent OHP sheet using the above-described novel toner, and heat-fixed the images. When the relationship between the color tone reproducibility of the projected image and the enlarged observation result of the fixed image on the OHP sheet was examined, the following was found. That is, in a fixed image having excellent color tone reproducibility of a projected image, one resin layer was formed on the OHP sheet because each toner particle was sufficiently softened and integrated by heating during fixing. In addition, since this resin layer had an appropriate thickness, it exhibited good light transmittance while having a sufficient density of color. On the other hand, in the fixed image having poor color tone reproducibility of the projected image, although the resin layer was formed by integrating the toner particles, the resin layer was thin or thick. The thinner ones do not have a sufficient density of color due to the lack of the granular colorant, so that the color tone reproducibility is deteriorated. Further, in the case of a thick-walled one, sufficient light transmittance could not be exerted due to an excessive amount of the granular colorant, so that color tone reproducibility was deteriorated. In addition, a large number of air bubbles were formed between the resin layer and the OHP sheet because a large amount of toner particles could not be sufficiently adapted to the surface of the OHP sheet at the time of fixing, and this caused irregular reflection of light. Thus, the deterioration of light transmittance was spurred. According to the study of the present inventors, when the thickness of the toner particle layer in the toner image before fixing on the OHP sheet is smaller than 1.5 times the toner particle size, the color tone reproducibility is deteriorated due to insufficient density of the projected image. It became rapidly recognized. Further, when the thickness of the resin layer in the toner image after fixing exceeded 1.2 or less of the toner particle size, deterioration of color tone reproducibility due to insufficient light transmittance of the resin layer became noticeable.
[0009]
Accordingly, in order to achieve the above object, the invention of claim 1 is directed to a method of calculating a maximum average toner adhesion amount per unit area of the recording material of a single color toner image composed of a single color toner to Mmax [mg / cm]. ² ], The true specific gravity of the toner is ρ [g / cm ³ ], The apparent density of the toner is ρr [g / cm ³ 1.5 × ρr × R ≦ 10 × Mmax ≦ 1.2 × Br × ρ × R, where the volume average particle diameter of the toner is R [μm] and the closest packing ratio of true spheres is Br. An image is formed so as to satisfy the following relational expression.
According to a second aspect of the present invention, there is provided the toner image forming apparatus according to the first aspect, wherein the toner image obtained by developing the latent image carried on the latent image carrier by the developing means is directly or intermediately transferred. And transferring the image to the recording medium through the recording medium.
According to a third aspect of the present invention, in the toner image forming apparatus of the second aspect, the maximum average toner adhesion amount per unit area of the single color toner image on the latent image carrier is dMmax [mg / cm]. ² ], The true specific gravity of the toner is ρ [g / cm ³ ], The apparent density of the toner is ρr [g / cm ³ ], The volume average particle diameter of the toner is represented by R [μm], and the closest packing ratio of true spheres is represented by Br, respectively.
1.5 × ρr × R / 0.98 ≦ 10 × dMmax ≦ 1.2 × Br × ρ × R / 0.8
The development is performed so as to satisfy the following relational expression.
The invention according to claim 4 is the toner image forming apparatus according to claim 2 or 3, wherein the developing means develops the latent image using a two-component developer containing a toner and a magnetic carrier. As a two-component developer, the magnetization of a magnetic carrier having a volume average particle size larger than that of the toner in 1 [kOe] is 30 to 1000 [emu / cm]. ³ ] Is used.
According to a fifth aspect of the present invention, there is provided the toner image forming apparatus according to the second, third or fourth aspect, wherein the developing means includes a toner carried on a developer carrier to which a developing bias is applied and a magnetic carrier. The latent image is developed with a two-component developer, and the dynamic resistance between the developer carrier and the latent image carrier when the developing bias is applied is reduced by 10%. ⁷ It is characterized by using a magnetic carrier of [Ω · cm] or less.
According to a sixth aspect of the present invention, in the toner image forming apparatus of the second, third, fourth, or fifth aspect, the latent image carrier is configured to attenuate a potential of an exposed portion of a photosensitive layer formed on a surface of the latent image carrier. An image bearing member that develops the latent image with a developer containing at least a toner carried on a developer bearing member to which a developing bias is applied; Of the non-exposed portion of _D , The potential of the exposed portion _L , The value of the developing bias is E _B 0 <| E _D |-| E _B | <| E _D -E _L | <400 [V] is satisfied.
According to a seventh aspect of the present invention, in the toner image forming apparatus according to any one of the first to sixth aspects, a determining unit for determining the type of the recording medium is provided, and the relational expression is determined based on a determination result by the determining unit. It is characterized in that an image forming operation is performed.
According to an eighth aspect of the present invention, in the toner image forming apparatus according to any one of the first to seventh aspects, the toner to be set in the main body has a number average diameter of the particulate colorant dispersed in the base material of 0.5. [Μm] or less, and those containing the granular colorant having an average diameter of 0.7 [μm] or more in a ratio of 5 [number%] or less are designated.
[0010]
In these toner image forming apparatuses, by satisfying the relational expression of “1.5 × ρr × R ≦ 10 × Mmax”, the thickness of the toner particle layer in the toner image before fixing on the recording medium is reduced by the volume of the toner. Secure at least 1.5 times the average particle size (R). Therefore, if a toner that can reproduce the color tone of a projected image satisfactorily like the above-mentioned novel toner developed by the present applicant is used, it is possible to suppress deterioration in color tone reproducibility due to insufficient density of the projected image. On the other hand, by satisfying the relational expression of “10 × Mmax ≦ 1.2 × Br × ρ × R”, the thickness of the integrated toner layer (for example, the resin layer) in the toner image after fixing on the recording medium is reduced. The volume average particle size (R) is kept at 1.2 times or less. Therefore, if a toner capable of reproducing the color tone of the projected image satisfactorily is used, deterioration of color tone reproducibility due to insufficient light transmittance of the projected image can be suppressed. Therefore, it is possible to form an image suitable for a toner capable of reproducing the color tone of the projected image satisfactorily.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an electrophotographic printer (hereinafter, simply referred to as a “printer”) will be described as an embodiment of an image forming apparatus to which the present invention is applied.
First, a basic configuration of the printer according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram illustrating a printer according to the present embodiment. This printer includes a charging unit 2, an optical writing unit 3, a developing unit 4, a transfer unit 5, a drum cleaning unit 6, and a charge removing unit 7 around a drum-shaped photoreceptor 1 as a latent image carrier. Further, a fixing unit 8 is provided on the left side of the transfer unit 5 in the drawing.
[0012]
The photoreceptor 1, which is driven to rotate clockwise in the figure by a driving unit (not shown), has an organic photosensitive layer formed on a surface of a base tube made of aluminum or the like. Is uniformly charged. Then, the potential of the exposure unit is attenuated by the scanning of the laser beam L emitted from the optical writing unit 3 that constructs optical scanning information based on image information sent from a personal computer (not shown). As a result, an electrostatic latent image having a lower potential than the background portion around the exposed portion is carried. This electrostatic latent image contains toner and a magnetic carrier carried on the developing sleeve 4a of the developing means 4 when passing through a developing position which is a position facing the developing means 4 with the rotation of the photoreceptor 1. To the two-component developer. Then, for example, a negative-polarity toner contained in the two-component developer is electrostatically attached and developed into a toner image.
[0013]
A transfer position where the photoconductor 1 and the transfer unit 5 face each other is formed downstream of the development position in the photoconductor rotation direction. When the toner image developed on the photoreceptor 1 enters the transfer position with the rotation of the photoreceptor 1, the toner image is transferred onto a sheet-shaped recording medium P which is conveyed at an appropriate timing by a paper feed unit (not shown). Superimposed. Then, the image is electrostatically transferred onto the recording medium P under the influence of a transfer electric field formed between the exposed portion of the photoconductor 1 and the transfer unit 5. The recording medium P on which the toner image has been electrostatically transferred in this manner is sent to the fixing unit 8 from the transfer position.
[0014]
The fixing unit 8 forms a fixing nip by contacting a heating roller 8a having a heat source (not shown) therein and a pressing roller 8b pressed by the heating roller 8a. These rollers are rotationally driven so that their surfaces move in the same direction at the contact portions with each other. The recording medium P sent to the fixing unit 8 having such a configuration is conveyed in the direction of movement of the roller surface while being sandwiched by the fixing nip. At this time, the toner image is fixed by the influence of the nip pressure and the heating. The fixed recording medium P is discharged out of the apparatus via a paper discharging means (not shown).
[0015]
When the surface of the photoconductor 1 that has passed the transfer position passes through a position facing the drum cleaning unit 6 with its rotation, the transfer residual toner is cleaned. Then, after the residual charge is removed by the charge removing means, the charge is uniformly charged by the charging means and returns to the initial state.
[0016]
In FIG. 1, the charging unit 2 is of a type in which a bias member such as a charging roller to which a charging bias is applied is brought into contact with the photoconductor 1, but a non-contact type such as a charging charger is used. Is also good. In addition, although the example in which the optical writing unit 3 that forms an electrostatic latent image by irradiating a laser beam is provided has been described, a unit that performs optical writing with LED light from an LED array may be used. Instead of optical writing, an electrostatic latent image may be formed by ion ejection or the like. Further, as the transfer means 5, a roller contact type in which a transfer roller to which a transfer bias is applied is brought into contact with the photoreceptor 1 has been described, but a belt contact type in which a belt is contacted, or a non-contact type such as a transfer charger. May be used. Further, the drum cleaning means 6 has been described as a scraping method using a cleaning blade, but an electrostatic recovery method in which a brush or a roller to which a cleaning bias is applied is brought into contact may be used. Further, the example in which the drum-shaped photoconductor 1 is provided as the latent image carrier has been described, but a belt-shaped photoconductor may be used. Further, the example of the printer in which the photoconductor 1 and the peripheral devices are individually provided has been described. However, a process cartridge in which the photoconductor 1 and the peripheral devices are housed in a common casing as one unit may be used. . For example, the photoconductor 1, the charging unit 2, the developing unit 4, and the drum cleaning unit 6 are configured as one process unit so as to be detachable from the printer main body.
[0017]
FIG. 2 is an enlarged configuration diagram illustrating a configuration of a main part of the developing unit 4. The developing unit 5 has a developing unit and a stirring unit in a casing. The developing section is provided with a developing sleeve 4a that exposes a part of the peripheral surface from the opening of the casing, a doctor blade 4b, and the like. The cylindrical developing sleeve 4a is made of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin, and its surface is roughened by sandblasting or the like to a ten-point average roughness Rz of about 10 to 20 [μm]. Have been. By such a roughening, the frictional resistance with the two-component developer is increased, and a predetermined agent pumping ability is exhibited. Instead of roughening by sandblasting or the like, a surface provided with a plurality of grooves having a depth of several tens to several hundreds [mm] may be used.
[0018]
A magnet roller 4c (not shown) is fixed inside the developing sleeve 4a rotated counterclockwise in the figure by a driving means (not shown) so as not to rotate with the sleeve. This magnet roller 4c has a plurality of magnetic poles divided in the circumferential direction. Due to the influence of these magnetic poles, a plurality of magnetic fields extending in the normal direction are formed around the developing sleeve 4c.
[0019]
The agitating section of the developing means 4 is provided with two conveying screws 4d, a toner concentration sensor (hereinafter, referred to as a T sensor) (not shown), and contains a two-component developer containing a toner and a magnetic carrier. ing. This two-component developer (hereinafter simply referred to as “developer”) has a large number of toners T adhered to the surface of the magnetic carrier C as shown in FIG. Then, in FIG. 2 described above, the toner is frictionally charged while being stirred and transported in the depth direction in the figure by the two transport screws 4d. The two-component developer agitated and transported to the transport screw 4d on the left side in the drawing comes into contact with the surface of the developing sleeve 4d in the axial direction. Then, under the influence of the magnetic field extending from the developing sleeve 4d, the developer is carried on the surface of the sleeve and is pumped up from the stirring section. Then, it is conveyed around the sleeve surface.
[0020]
The doctor blade 4b is fixed to a casing so as to maintain a predetermined gap between the tip and the surface of the developing sleeve 4a. This gap is called a doctor gap, and is set to about 0.4 to 0.7 [mm] in the developing unit 4 of the printer. When the developer pumped up from the agitator passes along the doctor gap along the sleeve surface, the layer thickness is regulated, and the amount of the developer is in a preferable amount for development. Specifically, 20 to 100 [mg / cm ² ]. Then, as the sleeve surface rotates, it is transported to a developing position, which is a position facing a photoconductor (not shown). In this developing area, a developing magnetic field that exerts a strong magnetic force in the normal direction of the sleeve is formed by a developing magnetic pole (not shown) of the magnet roller 4c (magnetic flux density is 60 mT or more). Under the influence of the developing magnetic field, the developer rises and becomes a magnetic brush. Then, the tip is moved while being rubbed against a photoreceptor (not shown) to attach toner to the electrostatic latent image. This adhesion develops the electrostatic latent image into a toner image. The developer that has consumed the toner by the development moves around the surface of the sleeve and moves into the casing, is separated from the surface of the sleeve under the influence of a repelling magnetic field (not shown), and returns to the stirring section.
[0021]
In this printer, the developing gap, which is the distance between the photoconductor (1) and the developing sleeve 4a at the developing position, is set to 0.4 [mm]. If the particle diameter of the magnetic carrier of the developer is 50 [μm], the developing gap is preferably set to about 10 times (0.55 mm) or less. If the developing gap is wider than this, it becomes difficult to obtain a desired image density under the condition of applying a DC developing bias voltage.
[0022]
In the stirring section, a partition wall 4e is provided between the two transfer screws 4d. The inside of the stirring section is divided into two by the partition wall 4e. Of the two transport screws 4d, the one disposed on the left side in the figure supplies the developer to the developing sleeve 4a while transporting the developer from the back side to the near side in the figure, for example, with the rotation. The developer transported to the front end in the figure is passed to the transport screw 4d on the right side in the figure through an opening (not shown) provided in the partition wall 4e. Then, while taking in the replenishing toner falling from the replenishing port 4f while being conveyed from the near side to the far side in the figure, it passes through the other opening (not shown) provided in the partition wall 4e in the figure. It is returned to the upper side of the transport screw 4d. In this manner, the developer is circulated and transported in the stirring section.
[0023]
The toner is supplied from the supply port 4f based on a detection result obtained by a T sensor including a magnetic permeability sensor (not shown). The T sensor is arranged to detect the magnetic permeability of the developer conveyed by the conveying screw 4d on the right side in the figure, and outputs a voltage having a value corresponding to the magnetic permeability. Since the magnetic permeability of the developer shows a certain correlation with the toner concentration, the T sensor outputs a voltage having a value corresponding to the toner concentration of the developer. The value of this output voltage is sent to a control unit (not shown). The control unit includes a RAM, in which Vtref, which is a target value of the output voltage from the T sensor, is stored. Vtref is used for drive control of a toner supply device (not shown). Specifically, the control unit controls the drive of a toner supply device (not shown) so as to replenish the toner in the stirring unit so that the value of the output voltage from the T sensor approaches Vtref. By this replenishment, the toner concentration of the developer in the stirring section is maintained within a predetermined range.
[0024]
Next, the characteristic configuration of the printer will be described.
The applicant of the present invention has determined that the number average particle diameter of the granular colorant dispersed in the binder resin as the base material is 0.5 [μm] or more and the granular colorant having an average diameter of 0.7 [μm] or more is 5 [μm]. %) (Hereinafter referred to as “developed toner”). In this developed toner, a pigment-based particulate colorant having a smaller particle size than in the related art is uniformly dispersed in a binder resin, and light can be transmitted well while reflecting light between the colorant particles. This makes it possible to form a toner image that can reproduce the color tone of the projected image satisfactorily. In addition, the dispersed particle size and shape of the particulate colorant hardly change even after being fixed, and light scattering and diffraction phenomena due to the colorant are remarkably exhibited as compared with those in which the particulate colorant is coarsely dispersed, so that the color tone is clear. An excellent projected image with high transparency can be created. However, even if this developed toner is used, if the amount of toner in the toner image is insufficient, the density of the projected image will be insufficient. Further, if the toner amount is too large, the color tone of the projected image cannot be sufficiently reproduced due to insufficient light transmittance due to excessive colorant. Therefore, the present inventor examined the relationship between the toner adhesion amount per unit area in the unfixed toner image transferred onto the OHP sheet and the image density of the projected image. At this time, the toner adhesion amount was measured by transferring the toner image on the OHP sheet to an adhesive tape. Further, the relationship between the toner adhesion amount per unit area in the toner image fixed on the OHP sheet and the haze (turbidity) of the projected image was examined. At this time, the toner adhesion amount was determined based on the measurement result by measuring the thickness of the resin layer in which each toner particle was softened and integrated with the fixing, and based on the measurement result. The same relationship was also examined for a conventional general toner containing a particulate colorant as a comparative control.
[0025]
These results are shown in FIG. As shown in the figure, with the conventional toner, if the amount of toner adhering to the toner image is set so that an image density equal to or higher than the target density lower limit is obtained in the projected image ((2) in the figure), the haze degree of the projected image becomes the target. Exceeds the upper limit. If the haze exceeds the target upper limit, the color tone will not be reproduced well in the projected image because the toner image does not transmit light well. FIG. 5 is an enlarged sectional view showing a toner image in which the haze exceeds the target upper limit. In the figure, a resin layer Ly is in close contact with a recording medium P made of a transparent OHP sheet or the like. The resin layer Ly forms a toner image in a planar manner, and is formed by integrating a myriad of toner particles transferred onto the recording medium P by the transfer means (5) by softening accompanying fixing. The thickness of the resin layer Ly exceeds twice the volume average particle diameter R of the toner, and the large particle colorant dispersed therein inhibits light transmission to increase the haze of the projected image. I have. Further, between the resin layer Ly and the recording medium P, air bubbles B are formed in some places, and this diffusely reflects light, thereby increasing the haze degree. FIG. 6 shows a state before fixing of the toner image shown in FIG. As shown in the drawing, the toner image before fixing has a toner particle layer in which about 2.5 toner layers overlap on the recording medium P. With the toner particle layer having such a thickness, a large amount of toner particles cannot be sufficiently adapted to the surface of the OHP sheet at the time of fixing, and many cavities B as shown in FIG. 5 are formed.
[0026]
On the other hand, as shown in FIG. 4, with the developed toner, if the toner adhesion amount in the toner image is secured by (1) or more, an image density lower than the target density lower limit can be obtained in the projected image, and the haze degree is also the target haze. It can be kept lower than the upper limit. However, when the toner adhesion amount exceeds (2), the haze degree exceeds the target upper limit. Therefore, if the toner adhesion amount falls within the range of (1) or more and (2) or less, a toner image capable of realizing a projected image having sufficient image density and excellent light transmittance and having excellent color tone reproducibility can be obtained. Can be formed. The toner adhesion amount {circle around (1)} is an amount capable of forming 1.5 or more toner layers on the recording medium P in the toner image before fixing, as shown in FIG. Further, as shown in FIG. 8, the toner adhesion amount {circle around (2)} is an amount capable of forming the resin layer Ly with a thickness of 1.2 times or less the volume average particle diameter R of the toner in the toner image after fixing. there were. With this thickness, as shown in the figure, at the time of fixing, the respective toner particles are sufficiently adapted to and integrated with the recording medium P, so that the cavity formed between the resin layer Ly and the recording medium P can be eliminated. Understand.
[0027]
Therefore, the present printer is configured to have the following relational expression.
(Equation 1)
1.5 × ρr × R ≦ 10 × Mmax ≦ 1.2 × Br × ρ × R
* However,
Mmax: the maximum average toner adhesion amount per unit area on the recording medium P of a single color toner image composed of a single color toner [mg / cm] ² ]
ρ: True specific gravity of toner [g / cm ³ ]
ρr: apparent density of toner [g / cm ³ ]
R: Volume average particle diameter of toner [μm]
Br: Closest packing ratio of true sphere (68.02%)
[0028]
The apparent density ρr of the toner was determined in accordance with JIS Z2504, in which the filled toner was filled with toner powder naturally dropped in a container, and then dropped on a flat plate. The filling ratio of the toner having good fluidity is increased to about 35%. It is sometimes called loose apparent density. On the other hand, what is measured after applying vibration to the filled toner in order to improve reproducibility is called a compression density. The apparent density ρr of the developed toner is 0.35 to 0.40 [g / cm]. ³ ]. The closest packing of the true sphere is a value when the number of contact points = 8, face centered cubic and dense hexagon are assumed, and is 68.02 [%]. The developed toner has a circularity in the range of 0.90 or more and less than 1.00, and has a shape close to a true sphere, which is difficult to obtain with pulverized toner. For this reason, ρp / ρ obtained by dividing the compressed pressure density ρp when pressed by the doctor gap, the developing gap, the transfer nip, the fixing nip, etc. by the true specific gravity ρ, that is, the toner filling rate is almost the closest packing filling rate Br Has the same value as Further, the true specific gravity ρ = 1.15 to 1.20 [g / cm ³ ], Loose apparent density ρr = 0.35 to 0.40 [g / cm] ³ ], Compression density ρt = 0.65-0.7 [g / cm] ³ ].
[0029]
In the relational expression of the above equation (1), satisfying the condition of “1.5 × r × R ≦ 10 × Mmax” means that the thickness of the toner particle layer in the toner image before fixing on the recording medium P is the volume average of the toner. This means that 1.5 times or more of the particle size R is secured. Further, satisfying the condition of “10 × Mmax ≦ 1.2 × Br × ρ × R” means that the thickness of the resin layer Ly formed on the recording medium P by fixing is set to one of the volume average particle diameters R of the toner. .2 means to keep it below twice. Accordingly, the present printer uses the above-described developed toner to provide a toner image having excellent color tone reproducibility without deterioration in color tone reproducibility due to insufficient density of the projected image or deterioration in color tone reproducibility due to insufficient light transmittance of the projected image. Can be formed.
[0030]
For example, in this printer, the maximum toner adhesion amount of 0.55 [mg / cm ² ] Can be formed. The projected image of the cyan toner image realizes an image density ID of 1.45 which is higher than the lower limit of 1.3 of the target density and has a haze of 20 [%] which is much lower than 35 [%] of the upper limit of the target haze. It was realized. The properties of the developed toner were as follows.
-True specific gravity ρ = 1.2 [g / cm ³ ]
-Apparent density ρr = 0.39 [g / cm ³ ]
・ Volume average particle size R = 7 [μm]
[0031]
When these numerical values are applied to the relational expression of the above expression 1, the following expression can be obtained.
(Equation 2)
1.5 × ρr × R = 4.095 ≦ 10 × 0.55
[Equation 3]
1.2 × Br × ρ × R = 6.86 ≧ 10 × 0.55
[0032]
0.55 [mg / cm ² It can be seen that the maximum toner adhesion amount in the cyan toner image is within the condition of the above relational expression. The thickness of the toner particle layer in the cyan toner image before fixing was about 2.0. The thickness of the resin layer Ly in the cyan toner image after fixing was about 0.961 times the volume average particle diameter R (7 μm). When the theoretical toner adhesion amount is obtained from these and the relational expression of the above equation 1, the following is obtained.
(Equation 4)
2.0 × ρr × R / 10 = 0.546
(Equation 5)
0.961 × Br × ρ × R / 10 = 0.549
[0033]
It can be seen that the theoretical adhesion amount (0.546, 0.549) and the actual adhesion amount (0.55) are almost the same.
[0034]
On the other hand, the maximum toner adhesion amount is set to 0.80 [mg / cm ² ] To form a cyan toner image. Then, although the image density ID of 1.35, which exceeds the lower limit of 1.3 of the target density, is realized in the projected image, the cyan toner with poor light transmittance of 37 [%], which exceeds the upper limit of 35% of the target haze degree, is realized. It became an image. The properties of the developed toner were as follows.
-True specific gravity ρ = 1.2 [g / cm ³ ]
-Apparent density ρr = 0.35 [g / cm ³ ]
・ Volume average particle size R = 7 [μm]
[0035]
When these numerical values are applied to the relational expression of the above expression 1, the following expression can be obtained.
(Equation 6)
1.5 × ρr × R = 3.68 ≦ 10 × 0.80
(Equation 7)
1.2 × Br × ρ × R = 6.86 (≦ 10 × 0.80 and the condition is not satisfied)
[0036]
It can be seen that as a result of increasing the maximum amount Mmax of applied toner to more than “1.2 × Br × ρ × R”, the haze was deteriorated. The thickness of the toner particle layer in the cyan toner image before fixing was about 3.3. Further, the thickness of the resin layer Ly in the cyan toner image after fixing was about 1.4 times the volume average particle diameter R (7 μm). When the theoretical toner adhesion amount is obtained from these and the relational expression of the above equation 1, the following is obtained.
(Equation 8)
3.3 × ρr × R / 10 = 0.81
(Equation 9)
1.4 × Br × ρ × R / 10 = 0.80
[0037]
It can be seen that the theoretical adhesion amounts (0.81, 0.80) and the actual adhesion amount (0.80) are almost the same.
[0038]
In this printer, by controlling the maximum amount of toner attached from the developing sleeve (4a) to the electrostatic latent image (the electrostatic latent image for a single color toner image) on the photoconductor (1) at the developing position, Equation 1 is provided. Specifically, when the monochromatic toner image on the photoconductor (1) after development is transferred onto the recording medium P, some transfer residual toner is generated on the photoconductor (1). In anticipation of the amount of the transfer residual toner, the maximum toner during development is secured so that a toner adhesion amount of “1.5 × ρr × R ≦ 10 × Mmax” can be secured for the monochromatic toner image transferred on the recording medium P. The amount of adhesion dMmax is controlled. Further, when the monochromatic toner image transferred to the recording medium P is fixed by the fixing unit (8), a slight offset occurs in the heating roller (8a). In view of this offset amount, the maximum toner adhesion amount during development is controlled so that the toner adhesion amount of the monochrome toner image transferred onto the recording medium P is suppressed to “10 × Mmax ≦ 1.2 × Br × ρ × R”. It controls dMmax. In general, an electrophotographic image forming apparatus is designed so that a toner amount transfer rate from a latent image carrier to a recording medium can be secured to 98% or more. In general, the toner amount ratio after fixing is designed so that 80% or more of the toner amount after development can be secured. Therefore, if the developing condition is set such that the maximum toner adhesion amount dMmax of the developed single-color toner image is expressed by the following equation, the above-mentioned relational expression 1 can be easily provided.
(Equation 10)
1.5 × ρr × R / 0.98 ≦ 10 × dMmax ≦ 1.2 × Br × ρ × R / 0.8
[0039]
In this printer, a magnetic carrier having a larger volume average particle diameter than the toner is contained as a two-component developer, and the magnetization in 1 [kOe] is 30 to 1000 [emu / cm]. ³ ] Is used. In such a two-component developer, 30 [emu / cm] in 1 [kOe] is used. ³ By using a magnetic carrier exhibiting the above-described sufficient magnetization, it is possible to effectively suppress carrier adhesion to the photoconductor (1) due to insufficient magnetization. Also, 1000 [emu / cm] in 1 [kOe] ³ By not exhibiting an excessively high degree of magnetization, it is possible to suppress image roughness due to scratching of the toner image on the photoreceptor (1) with the tip of the magnetic brush.
[0040]
Further, the present printer has a dynamic resistance of 10 when a maximum potential difference is generated between the developing sleeve (4a) to which the developing bias is applied and the photoconductor (1). ⁷ It is configured to use a magnetic carrier that can be suppressed to [Ω · cm] or less. This dynamic resistance is a resistance described below. That is, an electrode having an area of 65 mm in width and 1 mm in length is opposed to a developing sleeve (4a: φ20 mm, linear speed: 600 rpm in this example) carrying a two-component developer through a gap of 0.9 mm. The resistance value between the two when a maximum potential difference (400 V for a high-resistance silicon-coated carrier to several V for an iron powder carrier) is generated between the sleeve surface and this electrode. Dynamic resistance of 10 ⁷ Even if the development time (time during which the magnetic brush is brought into contact with the photoconductor at the development position) is reduced to a short time, a sufficient amount of toner corresponding to the development electric field is adhered to the photoconductor by suppressing the resistance to [Ω · cm] or less. be able to.
[0041]
In this printer, the potential of the unexposed portion, which is the background potential of the photoconductor (1), is expressed as E _D , The potential (latent image potential) of the exposed portion _L , The value of the developing bias is E _B In each case, the following equation is provided.
[Equation 11]
0 <| E _D |-| E _B | <| E _D -E _L | <400 [V]
[0042]
In this relational expression, "| E _D |-| E _B | Indicates the potential difference between the background portion and the developing bias value. Also, "| E _D -E _L | "Indicates a potential difference between the background portion and the exposed portion. By making the potential difference of the latter larger than the potential difference of the former, toner adhesion to the background can be effectively suppressed. In addition, by suppressing the latter potential difference to less than 400 [V], it is possible to avoid a discharge between the background portion and the exposed portion due to an excessively large potential difference. This is supported by Paschen's theory of discharge.
[0043]
In FIG. 1 described above, the photosensitive member 1 is driven to rotate at a linear velocity of 200 [mm / sec], and the developing sleeve 4a is driven to rotate at a linear velocity of 300 [mm / sec]. The diameters of the photoconductor 1, the developing sleeve 4a, and the stirring screw (FIG. 2) are 50, 16, and 18 [mm], respectively. Further, the thickness of the photosensitive layer of the photosensitive member 1 is 28 [μm], the beam spot system using the laser light L is 50 × 60 [μm], and the laser light amount is 0.23 [mW].
[0044]
In a conventional image forming apparatus, a binary process has been generally performed by using a method of performing exposure by narrowing a beam diameter so that a laser light amount is as high as possible. However, when the laser light amount is increased, a means for narrowing the beam diameter of the high-density light amount is required, and the precision in assembling the parts is strictly required, resulting in a large cost increase. Furthermore, since the amount of laser light is increased, a so-called electrostatic hazard is caused due to an increase in the amount of electric charge on the photosensitive member 1, and there is a problem that the life of the photosensitive member 1 is shortened. Therefore, in this printer, the potential of the background portion of the photoreceptor 1 is kept as low as possible, and the laser light amount is also kept low, so that a high-definition latent image can be formed even when general-purpose optical components are used, and the photoreceptor can be statically applied. Electric hazards are reduced and the service life is extended. Looking at the γ curve (development amount with respect to the development potential difference) showing the development characteristics of the printer, it can be seen that development is possible even at a relatively large slope and a relatively low potential. This indicates that the toner can be efficiently transferred to the electrostatic latent image even in a solid image with the toner amount on the developing sleeve 4a kept constant. Even when a small-diameter dot is formed, the background potential can be suppressed to a low level, and a uniform dot image can be formed with about half the amount of laser light compared to the related art.
[0045]
As the developing bias, an oscillating bias voltage in which an AC voltage is superimposed on a DC voltage is used. The background portion potential and the exposed portion potential are located between the maximum value and the minimum value of the vibration bias potential. As a result, an alternating electric field whose direction is alternately reversed is formed between the exposed portion and the developing sleeve 4a. In this alternating electric field, the toner and the carrier of the developer vibrate violently, and the toner separates from the magnetic carrier on the developing sleeve 4a and flies and adheres to the electrostatic latent image on the photoconductor 1. The difference (peak-to-peak voltage) between the maximum value and the minimum value of the oscillation bias voltage is preferably 0.5 to 5 [KV], and the frequency is preferably 1 to 10 [kHz]. The waveform of the oscillation bias voltage may be any of a rectangular wave, a sine wave, and a triangular wave. The DC voltage component of the vibration bias is a value between the background portion potential and the exposed portion potential. A value closer to the background portion potential than the exposed portion potential suppresses the adhesion of the fogging toner to the background portion. be able to. When the waveform of the oscillation bias voltage is a rectangular wave, the duty ratio is desirably set to 50% or less. The duty ratio is the ratio of the time during which the toner goes to the photoconductor 1 during one cycle of the vibration bias. By setting the duty ratio to 50% or less, the difference between the peak value and the time average value of the bias can be increased in order to direct the toner to the photoconductor 1. As a result, the movement of the toner can be activated, and the resolution can be improved while the roughness is suppressed by faithfully attaching the toner to the potential distribution on the latent image surface. Further, the difference between the peak value of the carrier having the opposite polarity to that of the toner and the time average of the bias can be reduced. Carrier adhesion to the substrate can be greatly reduced.
[0046]
The printer performs printing to satisfy the above relational expression only when the “transparent sheet output mode” is set. This setting is performed, for example, by a user's input operation on an operation panel (not shown) provided in the printer body. Further, for example, when the “output paper information” sent together with the image information from a personal computer or the like (not shown) is a “transparent sheet”, a control unit (not shown) of the printer body automatically sets. As described above, by providing the relational expression of Expression 1 only in the “transparent sheet output mode”, for a paper output image that does not need to obtain a projected image, the maximum toner adhesion amount Mmax for a single color toner image is obtained. Can be increased. As a result, the image density of the paper output image can be increased.
[0047]
FIG. 9 is a schematic diagram showing the developed toner. In the developed toner T, a particulate colorant is finely dispersed in a binder resin as a base material. In addition, a release accelerator and a charge control agent are also dispersed. External additives are applied to the outer surfaces of the particles of the binder resin.
[0048]
The developed toner T is manufactured as follows. That is, first, at least a polyester-based prepolymer A containing an isocyanate group is dissolved in an organic solvent, and then a granular colorant is dispersed (dispersion liquid 1). Then, an aqueous medium in which an oil-based dispersion in which a release accelerator is dissolved or dispersed in the presence of inorganic fine particles or polymer fine particles is added to dispersion 1. As a result, the prepolymer A is reacted with the polyamine or the monoamine B having an active hydrogen-containing group to form a urea-modified polyester resin having a urea group, and is contained in the dispersion containing the urea-modified polyester resin C. The developed toner T is obtained by removing the liquid medium. As the urea-modified polyester resin, those having a glass transition point Tg of 40 to 65 [° C], more preferably 45 to 60 [° C] are used. Its number average molecular weight Mn is 2,500 to 50,000, more preferably 2,500 to 30,000. The weight average molecular weight Mw is 10,000 to 500,000, preferably 30,000 to 100,000. The developed toner T contains, as a binder resin, a urea-modified polyester resin C having a urea bond and having a high molecular weight by a reaction between the prepolymer A and the monoamine B. The particulate colorant is evenly dispersed in the binder resin.
[0049]
The granular colorant can be evenly dispersed in the binder resin by adding and dispersing a polymer dispersant or a synergist, and exerts a strong interaction with the pigment with this synergist. In addition, the compound exhibits a strong interaction with a polymer dispersant. By using such a synergist and a polymer dispersant in combination, the synergist can be interposed between the granular colorant and the polymer dispersant, and uniform dispersion can be promoted more effectively. The synergist is not particularly limited as long as it is a compound that exhibits a strong interaction with the granular colorant and also exhibits a strong interaction with the polymer dispersant. As the polymer dispersant, those conventionally used generally for toner can be used. The amount of the synergist and polymer dispersant used is 0.1 to 100 parts by weight based on 100 parts by weight of the granular colorant. If the amount is less than 0.1 part by weight, a sufficient effect cannot be obtained.
[0050]
The dispersion particle size and particle size distribution of the particulate colorant in the developed toner T were measured as follows. That is, a measurement sample is prepared in which the developed toner T is embedded in an epoxy resin and the toner particles are ultra-thin sliced to about 100 [nm] with a microtome MT6000-XL (manufactured by Alliwa Shoji Co., Ltd.). This is photographed by an electron microscope (H-9000NAR manufactured by Hitachi, Ltd.) at an acceleration voltage of 100 [kV] at a magnification of 10,000 to 40,000 to obtain a TEM photograph. Then, the image information is converted into image data by an image processing / analyzing device LUZEX III of IMAGE ANALYZER. The above operation was repeated until the number of samples of the toner particles in the epoxy resin sampled at random exceeded 300, and the average particle size and the particle size (particle size) distribution were obtained.
[0051]
Then, the developed toner T has a weight average particle diameter (Dv) of 4 to 8 [μm] and a ratio (Dv / Dn) to the number average particle diameter (Dn) of 1.00 ≦ Dv / Dn ≦. 1.25. By keeping Dv / Dn within such a range, a high-resolution and high-quality toner can be obtained. Further, the weight average particle diameter (Dv) of the granular colorant is 4 to 8 [μm], Dv / Dn = “1.00 ≦ Dv / Dn ≦ 1.25”, and the number% of particles having a particle size of 3 μm or less = 1 to 1 When the number was set to 10% by number, higher quality images could be obtained. More preferably, when the weight average particle diameter is 4 to 6 [μm] and Dv / Dn = 1.00 ≦ Dv / Dn ≦ 1.15, a monochromatic toner image having extremely excellent color tone reproducibility of a projected image is formed. I was able to. The developed toner T satisfying these conditions is excellent in heat storage stability, low-temperature fixability, and hot offset resistance, and particularly excellent in glossiness of an image when used in a full-color copying machine or the like. Further, in the case of the two-component developer, even if the toner balance is performed for a long time, the fluctuation of the particle diameter of the toner in the developer is reduced, and good and stable developability can be obtained even when the developing device is stirred for a long time. Can be
[0052]
Generally, it is said that the smaller the particle size of the toner is, the more advantageous it is to obtain a high-resolution and high-quality image. It is. Further, when the volume average particle diameter R is relatively small as in the case of the developed toner T, the magnetic carrier may be fused to the surface of the carrier with long-term stirring with the magnetic carrier, and the charging ability of the magnetic carrier may be reduced. . Further, when used as a one-component developer containing no magnetic carrier, filming and fusion to the developing sleeve 4a and the doctor blade are likely to occur. These phenomena are largely related to the content of the fine powder in the toner. Particularly, when the content of the particles having a particle size of 3 μm or less exceeds 10%, the toner hardly adheres to the carrier. Furthermore, it is difficult to achieve a high level of charging stability. Conversely, if the particle size of the toner exceeds 8 [μm], it becomes difficult to obtain a high-resolution image with high resolution, and the fluctuation of the toner particle size accompanying the toner balance in the developer becomes large. . In addition, it was also found that the same problem occurs even when the ratio of weight average particle diameter / number average particle diameter is larger than 1.25.
[0053]
The average particle size and the particle size distribution of the developed toner T were measured by a Car Coulter counter method. Examples of the measuring device include Coulter Counter TA-II and Coulter Multisizer II (both manufactured by Coulter Inc.). In the present embodiment, a Coulter Counter TA-II was used to connect and measure an interface (manufactured by Nikka Giken Co., Ltd.) for outputting the number distribution and volume distribution, and a PC9801 personal computer (manufactured by NEC).
[0054]
The number distribution and volume distribution of the toner were measured as follows. That is, first, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution. The electrolyte is an approximately 1% NaCl aqueous solution formed using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter Corporation) can be used. 2 to 20 mg of a measurement sample is further added to the obtained liquid. Then, the electrolytic solution in which the sample was suspended was subjected to a dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the volume and number of the toner particles were measured by using the above-described measuring device with a 100 μm aperture as an aperture. The volume distribution and number distribution were calculated. As the channels, the following 13 channels were used.
・ 2.00 to less than 2.52 μm
・ 2.52 to 3.17 μm or less
・ 3.17 to less than 4.00 μm
・ 4.0 to less than 5.04 μm
・ 5.04 to less than 6.35 μm
・ 6.35 to less than 8.00 μm
・ 8.00 to less than 10.08 μm
・ 10.08 to less than 12.70 μm
・ 12.70 to less than 16.00 μm
・ 16.0 to less than 20.20 μm
・ 20.20 to less than 25.40 μm
・ 25.40 to less than 32.00 μm
・ 32.00 to less than 40.30 μm
[0055]
Various studies have been made on the hot offset resistance at the time of fixing the toner, including control of the molecular weight distribution of the binder resin. As a method for achieving compatibility between the contradictory properties of low-temperature fixing property and hot offset resistance, a method using a binder resin having a wide molecular weight distribution, a high molecular weight component having a molecular weight of several hundred thousand to several million, There is a method using a mixed resin having at least two molecular weight peaks containing several thousand to tens of thousands of low molecular weight components. When the high molecular weight component has a crosslinked structure or is in a gel state, it is more effective for hot offset. However, in a full-color toner requiring gloss and transparency, it is not preferable to introduce a large amount of a high molecular weight component. On the other hand, since the developed toner T contains a high molecular weight urea-modified polyester resin having a urea bond, it is possible to achieve hot offset resistance while satisfying transparency and glossiness.
[0056]
The main peak molecular weight in the molecular weight distribution of the binder resin contained in the developed toner T was usually 2500 to 10000, preferably 2500 to 8000, and more preferably 2500 to 6000. When the amount of the component having a molecular weight of less than 1,000 increases, the heat-resistant storage stability tends to deteriorate. On the other hand, when components having a molecular weight of 30,000 or more increase, the low-temperature fixability tends to decrease, but the decrease can be suppressed as much as possible by balance control. The content of the component having a molecular weight of 30,000 or more is 1 to 10% and varies depending on the toner material, but is preferably 3 to 6%. If it is less than 1%, sufficient hot offset resistance cannot be obtained, and if it exceeds 10%, the gloss and the transparency deteriorate. The Mn of the binder resin is preferably 2,500 to 50,000, and the value of Mw / Mn is preferably 10 or less. If it exceeds 10, sharp melt properties are lacking and gloss is impaired.
[0057]
The circularity of the developed toner T can be measured as follows. That is, the suspension containing the toner particles is passed through the detection zone on the flat plate, and a particle image is optically captured by a CCD camera. Based on the projected area of the toner particles thus obtained, it can be obtained using the following equation.
(Equation 12)
Circularity = perimeter of a circle having the same area as the projected area of the particle / perimeter of the projected image of the particle
[0058]
However, recently, the average circularity can be easily obtained by a flow type particle image analyzer FPIA-2000 (manufactured by Sysmex Corporation). Specifically, first, 0.1 to 0.5 ml of a surfactant, preferably an alkylbenzenesulfonate, is added as a dispersant to 100 to 150 ml of water from which impurity solids have been removed in advance in a container, and then, About 0.1 to 0.5 g of a measurement sample is added. Then, the suspension after addition of the sample is subjected to dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the dispersion is applied to the above-mentioned apparatus at a concentration of 3000 to 10,000 / μl. Also in the present embodiment, the average circularity was determined by this method.
[0059]
As a result of this measurement, the average circularity was 0.900 or more and less than 1.00. If the average degree of circularity is less than 0.900, the shape of the toner becomes indefinite, so that it was not possible to obtain a high quality image without satisfactory transferability and dust. Amorphous toner particles have many points of contact with the photoreceptor to the smooth medium, and charge is concentrated on the tip of the protrusion, so that the van der Waals force and the mirror image force are higher than the relatively spherical particles. Therefore, in the electrostatic transfer step, in the toner in which the irregular particles and the spherical particles are mixed, the spherical particles selectively move, and a character portion or a line portion image is missing. In addition, the remaining toner must be removed for the next development step, which causes problems such as the necessity of a cleaner device and a low toner yield (the ratio of toner used for image formation). . The circularity of the pulverized toner is usually 0.910 to 0.920 when measured by this apparatus. In addition,
[0060]
As the granular colorant used in the developed toner T, a conventionally known one can be used. For example, carbon black, nigrosine dye, anthraquinone green, titanium oxide, zinc white, lithobone, a mixture thereof, and the like. The content of the particulate colorant is 1 to 15% by weight, preferably 3 to 10% by weight.
[0061]
Examples of the release accelerator used for the developed toner T include wax such as polyolefin wax and dialkyl ketone (such as distearyl ketone). Preferred are polyalkanoic esters. The melting point of the wax is usually from 40 to 160 ° C, preferably from 50 to 120 ° C, and more preferably from 60 to 90 ° C. A wax having a melting point of less than 40 ° C adversely affects heat-resistant storage stability, and a wax having a melting point of more than 160 ° C tends to cause cold offset during fixing at a low temperature. The melt viscosity of the wax is preferably 5 to 1000 cps, more preferably 10 to 100 cps, as a value measured at a temperature 20 ° C. higher than the melting point. Waxes exceeding 1000 cps have poor improvement effects on hot offset resistance and low-temperature fixability. The content of the wax in the toner is usually from 0 to 40% by weight, and preferably from 3 to 30% by weight.
[0062]
Examples of the charge control agent used in the developed toner include the following. That is, it is a nigrosine dye, a triphenylmethane dye, a quinacridone, an azo pigment, or a polymer compound having a functional group such as a sulfonic acid group, a carboxyl group, or a quaternary ammonium salt. The amount of the charge control agent used is preferably determined by the type of the binder resin, the presence or absence of an additive used as necessary, and the toner manufacturing method including the dispersion method. Absent. However, as a guide, the range is 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. Preferably, the range is 0.2 to 5 parts by weight. When the amount exceeds 10 parts by weight, the chargeability of the toner is too large, the effect of the main charge control agent is reduced, the electrostatic attraction with the developing sleeve 4a is increased, the flowability of the developer is reduced, and the image density is reduced. Causes a decrease in The charge control agent, the release accelerator and the charge control agent described above may be melt-kneaded together with the master batch and the resin, or may be added when dissolved and dispersed in an organic solvent.
[0063]
As the external additive used in the developed toner T to assist the fluidity and chargeability of the particles, inorganic fine particles are preferable. The primary particle diameter of the inorganic fine particles is preferably from 5 nm to 2 μm, and particularly preferably from 5 nm to 500 nm. The specific surface area by the BET method is 20 to 500 [m ² / G]. The usage ratio of the inorganic fine particles is preferably from 0.01 to 5% by weight of the toner, and particularly preferably from 0.01 to 2.0% by weight. Specific examples of the inorganic fine particles include, for example, silica and silicon nitride. In addition, polymer-based fine particles can be used. Examples of such materials include soap-free emulsion polymerization, suspension polymerization, and polystyrene obtained by dispersion polymerization, methacrylate and acrylate copolymers, silicone, benzoguanamine, and polycondensation systems such as nylon, and thermosetting resins. Polymer particles.
[0064]
The external additive can be subjected to a surface treatment to increase the hydrophobicity and prevent deterioration of its flow characteristics and charging characteristics even under high humidity. Preferred surface treatment agents include, for example, silane coupling agents, silylating agents, silane coupling agents having an alkyl fluoride group, organic titanate coupling agents, aluminum coupling agents, silicone oil, and modified silicone oil. It can be mentioned as.
[0065]
A resistance reducing agent may be applied to the developed toner T for the purpose of improving the cleaning property of the transfer residual toner from the photoconductor 1 and the intermediate transfer body. Examples thereof include metal salts of fatty acids such as zinc stearate, calcium stearate, and stearic acid, and polymer fine particles produced by soap-free emulsion polymerization of polymethyl methacrylate fine particles, polystyrene fine particles, and the like. The polymer fine particles preferably have a relatively narrow particle size distribution and a volume average particle size of 0.01 to 1 μm. In order to increase the average circularity and obtain a so-called spherical toner, a known polymerization method such as an emulsion polymerization method, a suspension polymerization method, or a dispersion polymerization method may be used.
[0066]
The mixing ratio of the magnetic carrier and the developed toner T is preferably 1 to 10 parts by weight of the toner with respect to 100 parts by weight of the carrier. As the magnetic carrier, conventionally known ones such as iron powder, ferrite powder, magnetite powder, and magnetic resin carrier having a particle diameter of about 20 to 200 μm can be used. In addition, a silicone resin or the like can be used as the coating material. Further, if necessary, a conductive powder or the like may be contained in the coating resin. As the conductive powder, metal powder, carbon black, titanium oxide, tin oxide, zinc oxide, or the like can be used. These conductive powders preferably have an average particle size of 1 μm or less. When the average particle diameter is larger than 1 μm, it becomes difficult to control the electric resistance.
[0067]
The fluidity of the powder of the developed toner T was measured as a bulk density (g / ml) using a powder tester manufactured by Hosokawa Micron. The higher the flowability of the toner, the greater the bulk density. The relationship between the flowability and the bulk density is as follows. The bulk density of the developed toner T was 0.35 or more.
Fluidity ×: bulk density less than 0.25
Fluidity △: bulk density 0.25 to 0.30
Fluidity ：: bulk density 0.30 to 0.35
Fluidity ◎: bulk density 0.35 or more
[0068]
In addition, the haze degree of the single-color toner image was measured by a haze computer (HGM-2DP type). Further, the developed toner T can be used as a one-component non-magnetic toner or a magnetic toner. When used as a one-component magnetic toner, the following magnetic materials are included. That is, iron oxides such as magnetite, hematite and ferrite, metals such as cobalt and nickel, or these metals and aluminum, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium , Alloys with metals such as tungsten, vanadium and mixtures thereof. These magnetic materials preferably have an average particle size of about 0.1 to 2 μm, and the content of the magnetic material at this time is 20 to 200 parts by weight, particularly preferably 100 parts by weight of the binder resin. It is 40 to 150 parts by weight based on 100 parts by weight of the binder resin. Additives for use as a one-component developer include Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, and Cu. , Ag, V, Zr and the like, and composite oxides. In particular, silica, titania and alumina which are oxides of Si, Ti and Al are preferably used. In this case, the amount of the additive is preferably 0.5 to 1.8 parts by weight, particularly preferably 0.7 to 1.5 parts by weight, based on 100 parts by weight of the base particles. .
[0069]
By the way, conventionally, as for the developer, the toner replenishment rate is set to about 70% when the toner coverage of the magnetic carrier surface is completely covered with one layer of toner as 100%. Was implemented. On the other hand, in the present printer, toner is supplied so that the toner coverage on the magnetic carrier is about 150%. At this time, development is performed under the condition that the linear velocity ratio between the photosensitive member 1 and the developing sleeve 4a is 2.5 times or more. For example, the photosensitive member 1 having a diameter of 60 mm is rotationally driven at a linear speed of 240 [mm / sec], while the developing sleeve 4a having a diameter of 20 mm is rotationally driven at a linear speed of 600 [mm / sec]. Then, the toner is given an opportunity to be able to adhere to the electrostatic latent image on the photoreceptor 1 at a rate of 1 to 1.5 times in the developing gap. Can be obtained.
[0070]
It has been found that the toner coverage P on the magnetic carrier can be approximately approximated by the following equation under the condition of “volume average particle size of toner R << volume average particle size cR of magnetic carrier”.
(Equation 13)
P = 100 × C × ({3) / {2π (100−C) (1 + R / cR) 2 (R / cR) (ρ / ρc)}
* However,
ρ: True specific gravity of toner [g / cm ³ ]
ρc: true specific gravity of magnetic carrier [g / cm ³ ]
C: toner concentration [% by weight]
R: volume average particle size of the toner
cR: volume average particle size of the magnetic carrier
[0071]
In this printer, it is specified that the developed toner T having the above properties should be used. This designation is performed by, for example, shipping the printer body with the developed toner having such properties set, or shipping the printer body in a package with the developed toner T. Further, for example, in a document such as a printer main body or an instruction manual attached thereto, a product number or a product name of a toner applicable to the printer main body (each of which indicates a developed toner) or the like is attached to the printer main body or attached to the printer main body. This is done by attaching it to a document such as an instruction manual. In addition, for example, the manufacturer or the distributor of the printer body distributes information or information that associates the product number or product name of the developed toner T with the product number or product name of the printer body by distributing text or electronic data. . If the designation is performed in this manner, it is possible to reliably encourage the user to use the developed toner T, and to form a single-color toner image capable of realizing a projected image having excellent color tone reproducibility.
[0072]
Heretofore, as an image forming apparatus to which the present invention is applied, a printer that forms a single-color toner image using one developing unit 4 has been described. However, the present invention is also applicable to an image forming apparatus that forms a multi-color image by superimposing single-color toner images of different colors developed by a plurality of developing units. In this case, in the toner image, even if the above-mentioned relational expression 1 cannot be provided for the multicolor portion due to the superposition, the single color portion without the superposition can be provided. The present invention is also applicable to a so-called flight recording type image forming apparatus. In this case, by controlling the amount of toner to be attached to the intermediate recording medium or the sheet material from the toner flying device, it is possible to provide the above relational expression (1).
[0073]
As described above, in the printer according to the embodiment, the monochromatic toner image obtained by developing the electrostatic latent image carried on the photoconductor 1 as the latent image carrier by the developing unit 4 is transferred onto the recording medium P. . With such a configuration, the color tone of the projected image of the toner image formed by the electrophotographic process can be favorably reproduced. The same applies to the case where the monochromatic toner image on the photoconductor 1 is transferred to the recording medium P via the intermediate transfer medium.
Further, the development is performed under the condition that the maximum average toner adhesion amount after the development satisfies the relational expression of the above equation (10). Thus, the relational expression of the above equation 1 can be easily provided while adopting the electrophotographic method.
As a developer, a magnetic carrier having a larger volume average particle diameter R than the developed toner T has a magnetization in 1 [kOe] of 30 to 1000 [emu / cm]. ³ ] Is used. This effectively suppresses carrier adhesion to the photoconductor (1) due to insufficient magnetization of the magnetic carrier, and suppresses image roughness caused by scratching the toner image on the photoconductor (1) with the tip of the magnetic brush. be able to. Further, as described above, the dynamic resistance is set to 10 ⁷ A magnetic carrier of [Ω · cm] or less is used. As a result, even if the development time is kept short, a sufficient amount of toner corresponding to the development electric field can be attached to the photoconductor.
Further, by providing the relational expression of the above Expression 11, it is possible to avoid discharge between the background portion and the exposed portion while effectively suppressing toner adhesion to the background portion of the photoconductor (1).
Further, the type of the recording medium used for printing is determined by the control of the printer main body which is a determining means, and an image formation having the relational expression of Expression 1 is performed based on the determination result. As a result, for a paper output image for which it is not necessary to obtain a projected image, the image density can be increased by increasing the maximum toner adhesion amount Mmax for a single color toner image.
Also, by specifying that the developed toner is to be used, it is possible to reliably encourage the user to use the developed toner T, and to form a single-color toner image capable of realizing a projected image with excellent color tone reproducibility. it can.
[0074]
【The invention's effect】
According to the first to eighth aspects of the present invention, there is an excellent effect that it is possible to form an image suitable for a toner capable of reproducing the color tone of a projected image satisfactorily.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printer according to an embodiment.
FIG. 2 is an enlarged configuration diagram illustrating a main configuration of a developing unit of the printer.
FIG. 3 is a schematic view showing a developer set in the developing unit.
FIG. 4 is a graph showing the relationship between the maximum toner adhesion amount and the image quality in a single-color toner image on a recording medium.
FIG. 5 is an enlarged cross-sectional view showing a monochromatic toner image (after fixing) in which the haze degree of a projected image exceeds a target upper limit.
FIG. 6 is an enlarged sectional view showing the same single-color toner image before fixing.
FIG. 7 is an enlarged sectional view showing a single-color toner image transferred onto a recording medium by the printer.
FIG. 8 is an enlarged cross-sectional view showing the same single-color toner image after fixing.
FIG. 9 is a schematic view illustrating a developed toner developed by the present applicant.
[Explanation of symbols]
1 Photoconductor (latent image carrier)
2 Charging means
3 Optical writing means
4 Developing means
5 transfer means
6 Drum cleaning means
7 Static elimination means
8 Fixing means
T development toner
C magnetic carrier
P record

Claims (8)

In a toner image forming apparatus in which a toner image is formed by attaching toner on a recording medium and then fixed by a fixing unit,
Mmax [mg / cm ² ], the true specific gravity of the toner ρ [g / cm ³ ], the apparent density of the toner ρr [G / cm ³ ], the volume average particle diameter of the toner is R [μm], and the closest packing ratio of true spheres is Br,
1.5 × ρr × R ≦ 10 × Mmax ≦ 1.2 × Br × ρ × R
A toner image forming apparatus which forms an image so as to satisfy the following relational expression: The toner image forming apparatus according to claim 1,
A toner image forming apparatus, wherein a toner image obtained by developing a latent image carried on a latent image carrier by a developing unit is transferred to the recording body directly or via an intermediate transfer body. 3. The toner image forming apparatus according to claim 2, wherein
The maximum average toner adhesion amount per unit area of the single color toner image on the latent image carrier is dMmax [mg / cm ² ], the true specific gravity of the toner is ρ [g / cm ³ ], and the apparent density of the toner is ρr [g / Cm ³ ], the volume average particle diameter of the toner is represented by R [μm], and the closest packing ratio of true spheres is represented by Br, respectively.
1.5 × ρr × R / 0.98 ≦ 10 × dMmax ≦ 1.2 × Br × ρ × R / 0.8
A toner image forming apparatus that performs development so as to satisfy the following relational expression: The toner image forming apparatus according to claim 2, wherein:
The developing means develops the latent image using a two-component developer containing a toner and a magnetic carrier, and as the two-component developer, 1 [kOe] of a magnetic carrier having a larger volume average particle diameter than the toner. A toner image forming apparatus, wherein a medium having a magnetization of 30 to 1000 [emu / cm ³ ] is used. The toner image forming apparatus according to claim 2, 3, or 4,
The developing unit develops the latent image with a two-component developer including a toner and a magnetic carrier carried on a developer carrier to which a developing bias is applied, and the developer carrier and the developer carrier when the developing bias is applied. A toner image forming apparatus characterized by using a magnetic carrier that has a dynamic resistance between a latent image carrier and 10 ⁷ [Ω · cm] or less. The toner image forming apparatus according to claim 2, 3, 4, or 5,
As the latent image carrier, a photosensitive member that carries the latent image by attenuating the potential of the exposed portion of the photosensitive layer formed on the surface is used, and a developer carrier to which a developing bias is applied is used as the developing unit. A developer which develops the latent image with a developer containing at least a toner carried on the photosensitive layer is used, and the potential of the non-exposed portion of the photosensitive layer is E _D , the potential of the exposed portion is E _L , and the value of the developing bias is E E _B , respectively,
_{0 <| E D | - |} E B | <| E D -E L | <400 [V]
A toner image forming apparatus satisfying the following relationship: The toner image forming apparatus according to claim 1, wherein
A toner image forming apparatus, comprising: a discriminating means for discriminating the type of the recording medium; and forming an image having the relational expression based on a discrimination result by the discriminating means. The toner image forming apparatus according to any one of claims 1 to 7,
As the toner set in the main body, the number average particle diameter of the particulate colorant dispersed in the base material is 0.5 [μm] or less, and the number of the particulate colorant having an average diameter of 0.7 [μm] or more is 5 [number]. %], The toner image forming apparatus comprising:

Images