Patent Application
20250085661
The present disclosure relates to a process cartridge used in a copying machine and a printer that use an electrophotographic method or an electrostatic recording method.
In an image forming apparatus such as a printer that uses an electrophotographic image forming method (electrophotographic process), an electrophotographic photoreceptor (hereinafter, referred to as “photoreceptor”) serving as an image carrying member is uniformly charged, and the charge photoreceptor is selectively exposed to light to form an electrostatic image on the photoreceptor. The electrostatic image formed on the photoreceptor is visualized as a toner image with a toner serving as a developer. Further, image recording is performed by transferring the toner image formed on the photoreceptor to a recording material such as recording paper or a plastic sheet and applying heat or a pressure to the toner image transferred onto the recording material so that the toner image is fixed on the recording material.
Such an image forming apparatus typically requires replenishment of a developer and maintenance of various process units. In order to facilitate an operation of replenish an image forming apparatus with a developer and maintenance of various process units, a system of forming a process cartridge that is attachable to and detachable from an image forming apparatus main body, by combining a photoreceptor, a charging unit, a developing unit, a cleaning unit, and the like in a frame to form a cartridge, has come into practical use. According to the process cartridge system, an image forming apparatus with excellent usability can be provided.
In recent years, a color image forming apparatus that forms a color image using developers of a plurality of colors has been widely used. A so-called in-line type image forming apparatus in which photoreceptors corresponding to each of image forming operations using developers of a plurality of colors are arranged in a row in a surface movement direction of a transfer material to which a toner image is transferred is known as the color image forming apparatus. Examples of the in-line type color image forming apparatus include an in-line type color image forming apparatus in which a plurality of photoreceptors are arranged in a row in a direction (for example, a horizontal direction) intersecting a vertical direction (gravitational direction). The in-line type image forming apparatus is a suitable image forming apparatus in terms that image formation is performed at a high speed and requirements such as development of a multifunction filter can be easily dealt with.
Examples of the image forming apparatus include an image forming apparatus in which a photoreceptor is disposed below an intermediate transfer member serving as a transfer material or a recording carrying member that conveys a recording material serving as a transfer material (see Japanese Patent Laid-Open No. 2011-253203).
In a case where the photoreceptor is disposed below the intermediate transfer member or the recording material carrying member, for example, a fixing device and a developing device (or exposure device) can be disposed at separate positions in a state of sandwiching the intermediate transfer member and the recording material carrying member in the image forming apparatus main body. Therefore, the developing device (or the exposure device) becomes to be difficult to be affected by heat of the fixing device.
In recent years, there has been an increasing demand for improving the productivity, and a printer capable of performing high-speed printing has been required. As a cartridge configuration that enables high-speed printing, a cartridge configuration in which a toner is satisfactorily supplied by causing a difference in peripheral speed between the developing roller and the toner supplying roller has been suggested (see Japanese Patent Laid-Open No. 2015-125258 and Japanese Patent Laid-Open No. 2020-79902).
Japanese Patent Laid-Open No. 2015-125258 discloses a technique with excellent flowability, in which density uniformity (so-called “solid adaptability”) defects and top coat disturbance (so-called “regulation defects”) do not occur in solid images even in a case where printing is performed at a high speed and a reduced load due to a combination of the cartridge configuration in which the developing roller and the toner supplying roller are in contact with each other with a peripheral speed difference and the surface of the developing roller and the surface of the toner supplying roller move in the same direction in the contact portion between the developing roller and the toner supplying roller and the toner obtained by controlling the particle diameter, the abundance ratio, the liberation ratio, and the coating state of the inorganic fine particles. However, with this configuration, the residual toner on the developing roller is not sufficiently recovered by the toner supplying roller when the printing is continuously performed at a low printing rate in a low-temperature and a low-humidity environment, and thus the toner on the developing roller is charged-up. In this manner, image defects called development ghosts, in which the history of the previous image appears on the image, occur. It has been found that density unevenness accompanied by the image defects occurs particularly in halftone images.
Meanwhile, Japanese Patent Laid-Open No. 2020-79902 discloses a cartridge configuration in which the developing roller and the toner supplying roller are in contact with each other with a peripheral speed difference and the surface of the developing roller and the surface of the toner supplying roller move in opposite directions in the contact portion. When printing is intended to be performed at a higher speed with this cartridge configuration, a problem in that circulation of the toner worsens due to a decrease in flowability inside the developing chamber in a low-temperature and low-humidity environment and toner aggregation occurs in a region below the toner supplying roller and the developing roller occurs. In this manner, a region where the residual toner on the developing roller cannot be sufficiently recovered by the toner supplying roller is generated. Therefore, it has been found that the property of coating the developing roller with the toner is degraded, and as a result, density unevenness occurs in halftone images.
The present disclosure provides a process cartridge that is capable of satisfactorily maintaining circulation of a toner inside a developing chamber and capable of maintaining a satisfactory image quality without worsening a property of coating a developing roller with the toner and particularly without causing density unevenness in a halftone image.
According to the present disclosure, there is provided a process cartridge that is mountable on an image forming apparatus, the process cartridge including: a developing chamber, in which the developing chamber includes a developing roller that develops an electrostatic latent image formed on a surface of a photosensitive drum using a toner to form a toner image, a toner supplying roller that supplies the toner to the developing roller, a toner regulating member that regulates a layer thickness of the toner on the developing roller, and a toner, a surface of the developing roller is in contact with a surface of the toner supplying roller, a movement direction of the surface of the developing roller is opposite to a movement direction of the surface of the toner supplying roller in a position where the surface of the developing roller is in contact with the surface of the toner supplying roller, the movement direction of the surface of the toner supplying roller includes an upward component at the position where the surface of the developing roller is in contact with the surface of the toner supplying roller in a mounting state where the process cartridge is mounted on an apparatus main body of the image forming apparatus, a toner flow path formed of an inner wall of the developing chamber and the surface of the toner supplying roller is formed upstream of the toner supplying roller in a rotation direction with respect to the position where the developing roller is in contact with the toner supplying roller in a cross section of the process cartridge in a direction perpendicular to a rotation axial line of the toner supplying roller, a closest distance between the inner wall of the developing chamber and the surface of the toner supplying roller in the toner flow path is 1.0 mm or greater and 5.0 mm or less, the developing roller and the toner supplying roller are formed such that a peripheral speed ratio R represented by Equation (E1) satisfies 1.1≤R≤2.5,
Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Hereinafter, a developing device, a process cartridge, and an image forming apparatus according to the present disclosure will be described in more detail with reference to the accompanying drawings. Here, the dimensions, the materials, the shapes, the relative dispositions, and the like of constituent components described in this embodiment are not intended to limit the scope of the present disclosure thereto unless otherwise specified. Further, the materials, the shapes, and the like of members described once in the following description are the same as those in the subsequent description. Well-known techniques or publicly known techniques in the technical field can be applied to the configurations or steps that are not described or shown in the drawings. Further, repeated description may not be provided.
The description of “XX or greater and YY or less” and “XX to YY” showing numerical ranges denotes numerical ranges including the lower limits and the upper limits as end points unless otherwise specified.
In a case where the numerical ranges are described in a stepwise manner, the upper limits and the lower limits of the respective numerical ranges can be optionally combined.
In order to deal with the above-described problems, a method of suppressing a toner from poorly circulating in a developing chamber has been examined, which may lead to a state where toner aggregation is likely to occur in a region below a toner supplying roller and a developing roller in a cartridge configuration in which a movement direction of a surface of the developing roller is opposite to a movement direction of a surface of the toner supplying roller.
As a result, it has been found that the above-described problems can be solved by limiting the distance between the inner wall of the developing chamber and the toner supplying roller and appropriately controlling the average circularity of the toner, the proportion of the particles with a relatively low circularity to be present, and the sticking ratio of silica particles in a certain range of R represented by Equation (E1).
That is, a process cartridge according to the present disclosure is a process cartridge that is mountable on an image forming apparatus, the process cartridge including: a developing chamber, in which the developing chamber includes a developing roller that develops an electrostatic latent image formed on a surface of a photosensitive drum using a toner to form a toner image, a toner supplying roller that supplies the toner to the developing roller, a toner regulating member that regulates a layer thickness of the toner on the developing roller, and a toner, a surface of the developing roller is in contact with a surface of the toner supplying roller, a movement direction of the surface of the developing roller is opposite to a movement direction of the surface of the toner supplying roller in a position where the surface of the developing roller is in contact with the surface of the toner supplying roller, the movement direction of the surface of the toner supplying roller includes an upward component at the position where the surface of the developing roller is in contact with the surface of the toner supplying roller in a mounting state where the process cartridge is mounted on an apparatus main body of the image forming apparatus, a toner flow path formed of an inner wall of the developing chamber and the surface of the toner supplying roller is formed upstream of the toner supplying roller in a rotation direction with respect to the position where the developing roller is in contact with the toner supplying roller in a cross section of the process cartridge in a direction perpendicular to a rotation axial line of the toner supplying roller, a closest distance between the inner wall of the developing chamber and the surface of the toner supplying roller in the toner flow path is 1.0 mm or greater and 5.0 mm or less, the developing roller and the toner supplying roller are formed such that a peripheral speed ratio R represented by Equation (E1) satisfies 1.1≤R≤2.5,
(in Equation (E1), VRs represents an absolute value [m/sec] of a peripheral speed of the surface of the toner supplying roller, and VD represents an absolute value [m/sec] of a peripheral speed of the surface of the developing roller), the toner contains a toner particle and a silica particle, the toner has a number average particle diameter of 4.0 μm or greater and 9.0 μm or less, the toner has an average circularity of 0.955 or greater and 0.975 or less, a proportion of the particle having a circularity of 0.900 or greater and 0.930 or less in a circularity distribution of the toner is 2.0% by number or greater and 15.0% by number or less, a content of the silica particle is 1.5 parts by mass or greater and 5.0 parts by mass or less with respect to 100 parts by mass of the toner particle, and a sticking ratio of the silica particle to the toner particle, which is measured by a water washing method, is 70% or greater and 82% or less.
Hereinafter, the process cartridge of the present disclosure will be described in detail.
An electrophotographic photosensitive drum (hereinafter, referred to as a photosensitive drum) 1 (1a, 1b, 1c, and 1d) is disposed in each process cartridge 70. Further, process units such as a charging roller 2 (2a, 2b, 2c, and 2d), a developing roller 25 (25a, 25b, 25c, and 25d), and a cleaning member 6 (6a, 6b, 6c, and 6d) are integrally disposed around the photosensitive drum 1 of each process cartridge 70. The charging roller 2 uniformly charges the surface of the photosensitive drum 1. The developing roller 25 develops a latent image formed on the photosensitive drum 1 with a developer (hereinafter, referred to as a toner) for visualization. Further, the cleaning member 6 transfers the toner image formed on the photosensitive drum 1 to a recording medium and removes the toner remaining on the photosensitive drum 1. In addition, the details of the configurations and the positional relationships of the photosensitive drum 1, the charging roller 2, the developing roller 25, and the cleaning member 6 will be described below with reference to
Further, a scanner unit 3 that selectively exposing the photosensitive drum 1 to light based on image information to form a latent image on the photosensitive drum 1 is provided below the process cartridge 70 in the gravitational direction.
A cassette 17 containing a recording medium S is mounted on a lower portion of an apparatus main body 100a.
Further, a recording medium conveying unit is provided such that the recording medium S passes through a secondary transfer roller 69 and a fixing unit 74 and is conveyed to above the apparatus main body 100a. Further, an intermediate transfer unit 5 is provided above each process cartridge 70 (70Y, 70M, 70C, and 70K) as an intermediate transfer unit for transferring a toner image formed on each photosensitive drum 1 (1a, 1b, 1c, and 1d). The intermediate transfer unit 5 includes a driving roller 56, a driven roller 57, primary transfer rollers 58 (58a, 58b, 58c, and 58d) at positions facing the photosensitive drums 1 of each color, and a facing roller 59 facing the secondary transfer roller 69, and a transfer belt 50 is stretched across these rollers. Further, the transfer belt 50 faces all the photosensitive drums 1, circulatingly moves to come into contact with the photosensitive drums 1, and performs primary transfer from the photosensitive drums 1 to the transfer belt 50 by applying a voltage to the primary transfer rollers 58 (58a, 58b, 58c, and 58d). Further, the toner of the transfer belt 50 is transferred to the recording medium S by applying a voltage to the facing roller 59 and the secondary transfer roller 69 disposed inside the transfer belt 50.
In image formation, each photosensitive drum 1 is allowed to rotate, and the photosensitive drum 1 uniformly charged by the charging roller 2 is selectively exposed to light from the scanner unit 3. In this manner, an electrostatic latent image is formed on the photosensitive drum 1. This latent image is developed by the developing roller 25. In this manner, a toner image of each color is formed on each photosensitive drum 1. In synchronization with the image formation, registration roller pairs 55 convey the recording medium S to a secondary transfer position where the facing roller 59 and the secondary transfer roller 69 are in contact with each other in a state of sandwiching the transfer belt 50 therebetween. Further, the toner image of each color on the transfer belt 50 is secondarily transferred to the recording medium S by applying a transfer bias voltage to the secondary transfer roller 69. In this manner, a color image is formed on the recording medium S. The recording medium S on which the color image has been formed is heated and pressurized by the fixing unit 74 to fix the toner image. Thereafter, the recording medium S is discharged to a discharge unit 75 by a discharge roller 72. In addition, the fixing unit 74 is disposed in an upper portion of the apparatus main body 100a.
Next, the process cartridge 70 to which the present disclosure has been applied will be described with reference to
The process cartridge 70 includes a cleaning unit 26 and a developing unit 4. The cleaning unit 26 includes the photosensitive drum 1, the charging roller 2, and the cleaning member 6. Further, the developing unit 4 includes the developing roller 25.
The charging roller 2 and the cleaning member 6 are disposed on the periphery of the photosensitive drum 1 as described above. The cleaning member 6 includes an elastic member 7 formed of a rubber blade and a cleaning support member 8. A tip portion of the elastic member 7 formed of a rubber blade is disposed in contact with the photosensitive drum in a counter direction with respect to a rotation direction of the photosensitive drum 1. Further, the residual toner removed from the surface of the photosensitive drum 1 by the cleaning member 6 falls into a removed toner chamber 27.
The photosensitive drum 1 is rotationally driven in response to an image forming operation by transmitting a driving force of a main body driving motor (not shown) serving as a driving source. Here, when a drum coupling fixed to a longitudinal end portion of the photosensitive drum 1 is engaged with a main body side coupling present on a longitudinal axial line of the photosensitive drum 1, the driving force is input to the photosensitive drum 1. The charging roller 2 is rotatably attached to the cleaning unit 26 via a charging roller bearing, is pressurized against the photosensitive drum 1 by a charging roller pressing member, and rotates in conjunction with the photosensitive drum 1.
The developing unit 4 is formed of the developing roller 25 that rotates in contact with the photosensitive drum 1 and a developing frame 31 that supports the developing roller 25. The developing frame 31 is formed of a developing chamber 31b and a toner accommodating chamber 31a (toner accommodating unit), and the toner accommodating unit is disposed below the developing chamber in the vertical direction.
Here, the developing chamber 31b of the present example will be described in detail with reference to the cross-sectional view. In the developing chamber 31b of the present example, a toner supplying roller 34 that rotates in a direction indicated by an arrow C in contact with the developing roller 25 and a regulating member (developing blade 35) for regulating a toner layer on the developing roller 25 are disposed on the periphery of the developing roller 25 as shown in
The configuration of the present disclosure is formed such that in a distance between the toner supplying roller 34 and an inner wall forming a supply path 37 that supplies the toner to the regulating member (developing blade 35), a closest distance 37a between the inner wall and the toner supplying roller 34 in a cross section of a surface perpendicular to the rotation axial line of the toner supplying roller 34 is 1.0 μm or greater and 5.0 mm or less.
The developing roller 25 and the toner supplying roller 34 are rotationally driven in response to the image forming operation by transmitting a driving force of a main body driving motor (now shown) different from the driving source of the cleaning unit to the developing unit 4. The driving force is input by a driving input method carried out via a coupling similar to the case of the cleaning unit 26. The driving input method using a coupling is suitable from the viewpoint of rotational stability as compared with a driving input method carried out via a gear.
The developing roller 25 is an elastic body roller formed such that a conductive elastic rubber layer having predetermined volume resistivity is provided as an elastic layer in the periphery of a metallic core metal. The developing roller 25 is formed of a base layer and a surface layer. The base layer is formed of silicone rubber, the surface layer is formed of urethane rubber, and urethane bead particles are dispersed in the urethane rubber of the surface layer so that desired roughness is set. The developing roller 25 and the photosensitive drum 1 respectively rotate such that the surfaces thereof move in the same direction (direction from bottom to top in the example described below) in a facing portion (contact portion). In the example described below, the toner negatively charged by triboelectric charging with respect to a predetermined DC bias applied to the developing roller 25 is transferred only to a bright area potential portion due to a potential difference thereof to visualize the electrostatic latent image.
The developing blade 35 is disposed below the developing roller 25, is in counter contact with the developing roller 25, and regulates the coating amount of the toner supplied by the toner supplying roller 34 and applies an electric charge. In the example described below, the developing blade 35 is formed of a plate-like member 35b having flexibility and a developing blade support 35a which fixes the plate-like member. The plate-like member is a member with a thickness of 80 μm, which is obtained by processing stainless steel (SUS) in a plate spring shape, and a contact portion positioned at a free end of the plate-like member is in contact with the developing roller 25 with a required contact pressure. The toner supplied onto the developing roller 25 is triboelectrically charged due to the friction between the developing blade 35 and the developing roller 25, and the layer thickness thereof is regulated at the same time as application of an electric charge. Further, in the example described below, a predetermined voltage is applied to the developing blade 35 from a blade bias power supply (not shown) to stabilize the toner coat.
The toner to which an electric charge has been applied adheres the surface of the developing roller 25 due to an image force with the developing roller 25. In a case where the adhesion force of the toner to the surface of the developing roller 25 exceeds the regulation force of the developing blade 35, the toner coat on the developing roller 25 is disturbed (so-called “regulation defects”). When regulation defects occur, image defects such as fogging in which the toner adheres to a white background of the image and an abnormal density occur.
Here, the developing blade 35 will be described in detail. The developing blade 35 is formed of a supporting plate 35a (blade supporting portion) obtained by processing stainless steel and a plate-like member 35b (blade portion) having flexibility as shown in
In the present embodiment, a part of a “tip edge portion 818” on a side to come into contact with the developing roller 25 is scraped off by polishing processing on a tip (free end) side of the plate-like member 35b as shown in
The developing blade 35 is provided at a free end of the plate-like member 35b in the transverse direction and includes a contact portion for coming into contact with the surface of the developing roller 25.
More specifically, before the tip of the developing blade 35 according to the present embodiment is subjected to polishing processing, a first surface 811 (first portion) that is a surface on a side to come into contact with the developing roller 25 intersects with a third surface 813 (third portion) orthogonal to the first surface 811 on a cross section orthogonal to the longitudinal direction to form “tip edge portion 818” described above. Further, the tip edge portion 818 is scraped off by performing polishing processing so that a second surface 812 (second portion) connects the first surface 811 with the third surface 813 is formed. A tip point of the first surface 811 on a free end side is defined as a point A, and a tip point of the second surface 812 on a free end side is defined as a point B in a state after the polishing processing. Further, a virtual line extending from the first surface 811 in a free end direction is defined as L1. Further, a point where a virtual line L2 orthogonal to the virtual line L1 and passing through the point B intersects with the virtual line L1 is defined as a point C. Here, a distance between the point B and the point C is defined as h1, and a distance between the point A and the point C is defined as d1. In the example described below, “h1=15 μm” and “d1=40 μm” are satisfied.
Here, a method of performing polishing processing on the developing blade 35 used in the present disclosure will be described. The plate-like member before being bonded to the support member is fixed to a pedestal in a state of being sandwiched between the pedestal and a pressing member.
An abrasive film wound around a rubber roller is in contact with the tip portion of the plate-like member in a state where a load is applied to the abrasive film. In the example described below, a wrapping film sheet with a grain size of #800 is used as the abrasive film, and a load of 500 g (4.9 N) is applied to the rubber roller.
The abrasive film on the rubber roller is disposed in a fixed state, and the pedestal moves right and left in the longitudinal direction so that the tip portion of the plate-like member is rubbed against the abrasive film and is thus finely scraped off.
The amount of the plate-like member to be scraped off is proportional to the distance where the plate-like member is rubbed against the abrasive film, and the scraped amount increases as the rubbed distance increases and the scraped amount decreases as the distance decreases. That is, the amount of the tip edge portion of the plate-like member to be scraped off can be changed by controlling the moving amount of the pedestal. The polishing method is merely an example, and the present disclosure is not limited thereto as long as the tip shape of the developing blade can be processed to a desired shape.
The toner supplying roller 34 is in contact with the developing roller 25 at a nip portion N2 (
The driving force from the main body driving motor is transmitted to a coupling 201 (driving force receiving unit) provided at an axial end portion of the toner supplying roller 34, and the driving force is transmitted to the toner supplying roller 34 through an intermediate 202 and a drive transmission member 203 (the intermediate 202 and the drive transmission member 203 are first driving force transmitting units). The driving force of the toner supplying roller 34 is transmitted to the developing roller 25 by gears (204a to 204c) provided between the toner supplying roller 34 and the developing roller 25 so that the developing roller 25 rotates (the gear 204 is a second driving force transmission unit, and the gear 204a is a third driving force transmission unit). Specifically, the gear 204c fixed to the toner supplying roller 34 rotates to transmit the driving force to an idler gear 204b, and thus the idler gear 204b rotates. When the idler gear 204b rotates, the driving force is transmitted to the gear 204a fixed to the developing roller 25, and thus the developing roller 25 rotates along with the gear 204a.
In the present embodiment shown in
On the contrary, in the present embodiment, since the driving force to the developing unit 4 is input from the longitudinal axial line of the toner supplying roller 34, the distance between the drive input position for the cleaning unit 26 and the drive input position for the developing unit 4 can be increased, which is more suitable when a drive input unit of the apparatus main body 100a is configured.
Meanwhile, since the configuration in which the driving force from the apparatus main body 100a is transmitted to the developing roller through the toner supplying roller 34 is required to drive the driving roller 25 through a plurality of gears, the rotational stability of the developing roller 25 is degraded as compared with the configuration in which the driving force is transmitted to the developing roller 25. As a result, the regulation force of the developing blade 35 is destabilized in some cases, and thus this configuration is disadvantageous in terms of regulation defects.
Further, the toner supplying roller 34 and the developing roller 25 rotate at the nip portion N2 in opposite directions with a peripheral speed difference, and the toner is supplied to the developing roller 25 while the residual toner on the developing roller 25 is recovered.
In the present disclosure, the developing roller and the toner supplying roller at the nip portion N2 rotate such that the peripheral speed ratio R represented by Equation (E1) satisfies 1.1<R≤2.5.
(In Equation (E1), VRs represents an absolute value [m/sec] of a peripheral speed of the surface of the toner supplying roller, and VD represents an absolute value [m/sec] of a peripheral speed of the surface of the developing roller.)
That is, a rotational angle speed ratio A represented by Equation (E2) “λ=ωRS/ωD” between the toner supplying roller 34 and the developing roller 25 satisfies “1.1 ≤λ×rRS/rD≤2.5” in a case where the radius of the toner supplying roller 34 is defined as rRS and the rotational angle speed thereof is defined as ωRS, and the radius of the developing roller 25 is defined as rD and the rotational angle speed is defined as @D. Further, in the example described below, since the radius of the toner supplying roller is 3.3 mm and the radius of the developing roller is 3.0 mm, “λ˜ 1.14” is satisfied.
When the peripheral speed ratio R is set to satisfy “1.1≤R≤2.5”, the recovery of the residual toner on the developing roller 25 and the supply of the toner to the developing roller 25 can be effectively performed. The peripheral speed ratio R is more preferably “1.2≤R≤1.5”.
In a case where the peripheral speed ratio R is less than 1.1, the residual toner on the developing roller is not sufficiently recovered by the toner supplying roller when the printing is continuously performed at a low printing rate in a low-temperature and a low-humidity environment, and thus the developing roller is unevenly coated with the toner. Particularly, density unevenness occurs in halftone images.
Meanwhile, in a case where the peripheral speed ratio R is greater than 2.5, the residual toner on the developing roller is sufficiently recovered by the toner supplying roller, but the toner deterioration is accelerated due to a high opposing speed between the developing roller and the toner supplying roller. Even in a case of the toner constituting the present disclosure, degradation of the flowability of the toner occurs due to the toner deterioration, and thus circulation of the toner is worsened. Accordingly, toner aggregation is likely to occur in a region below the toner supplying roller and the developing roller. As a result, the property of coating the developing roller with the toner is degraded, and thus density unevenness occurs in halftone images and fogging occurs due to charging unevenness accompanied by the toner deterioration.
Further, the toner supplying roller 34 and the developing roller 25 are in contact with each other with a predetermined inroad amount, that is, a recess amount ΔE in which the toner supplying roller 34 is formed into a recess shape by the developing roller 25.
The toner supplying roller 34 includes a conductive support and a foam layer supported by the conductive support. Specifically, the toner supplying roller 34 is provided with a core metal electrode having an outer diameter of φ5 (mm) as a conductive support and a urethane foam layer as a foam layer formed of an open-cell body (open-cell) formed by air bubbles being connected in the periphery of the core metal electrode, and rotates in a direction indicated by C in the figure. When urethane of the surface layer is formed into an open-cell body as described above, a large amount of toner can enter the inside of the toner supplying roller 34. Further, the resistance of the toner supplying roller 34 in the present example is 1×109 (Ω).
Further, in the present example, the inroad amount of the toner supplying roller 34 to the developing roller 25, that is, a recess amount ΔE in which the toner supplying roller 34 is formed into a recess shape by the developing roller 25 is set to 1.0 mm.
Here, a method of measuring the resistance of the toner supplying roller 34 will be described. The toner supplying roller 34 comes into contact with an aluminum sleeve having a diameter of 30 mm such that the inroad amount described below reaches 1.5 mm. When the aluminum sleeve is allowed to rotate, the toner supplying roller 34 rotates in conjunction with the aluminum sleeve at 30 rpm.
Next, a DC voltage of −50 V is applied to the developing roller 25. In this case, a resistor of 10 kΩ is provided on an earth side, and the resistance of the toner supplying roller 34 is calculated by measuring the voltage at both ends of the resistor and calculating the current. In the present embodiment, the surface cell diameter of the toner supplying roller 34 is set to be in a range of 50 μm to 1000 μm.
Here, the cell diameter denotes the average diameter of foam cells in an optional cross section, and the maximum cell diameter is obtained by measuring the area of the maximum foam cell from an enlarged image of the optional cross section and converting this area into a perfect circle-equivalent diameter. Further, the average diameter is an average value of respective cell diameters similarly converted from cell areas of respective remaining cells after foam cells having a cell diameter of ½ or less of the maximum cell diameter are eliminated as noise.
The toner supplied to the surface of the developing roller 25 from the toner supplying roller 34 is frictionally charged by friction between the developing blade 35 and the developing roller 25, and the layer thickness is regulated at the same time as the application of the electric charge. Thereafter, the toner is conveyed to the contact portion (developing unit) between the photosensitive drum 1 and the developing roller 25, and transferred to a bright area potential portion. The residual toner remaining on the surface of the developing roller 25 is returned to the inside of a developing container again, recovered from the surface of the developing roller 25 by the toner supplying roller 34, and accumulated inside of the toner supplying roller 34.
Here, the flow of the toner inside the developing chamber 31b will be described with reference to
Some of the toner G conveyed to an upper portion of the toner supplying roller 34 by the toner conveying member 36 is sucked into the toner supplying roller 34 due to restoration of the toner supplying roller 34 downstream of the nip portion N2 in the rotation direction of the toner supplying roller 34 (F1), and accumulated inside the toner supplying roller 34 along with the residual toner accumulated inside the toner supplying roller 34 recovered from the surface of the developing roller 25. Further, the toner is conveyed downstream of the nip portion N2 in the rotation direction of the toner supplying roller 34 due to the rotation of the toner supplying roller 34 in the direction indicated by C. The toner accumulated inside the toner supplying roller 34 is ejected due to deformation of the toner supplying roller 34 caused when the toner supplying roller 34 comes into contact with the developing roller 25 downstream in the rotation direction of the toner supplying roller 34 (F2).
The toner that has not reached the surface of the developing roller 25 in the toner ejected from the toner supplying roller 34 is gradually conveyed by the propulsive force in a direction of a developing opening (opening portion) due to the jetting force caused by the ejection from the toner supplying roller 34 through a toner flow path 37, passes through the developing opening, and is returned to the toner accommodating chamber 31a (F3).
When the toner is satisfactorily circulated between the developing chamber 31b and the toner accommodating chamber 31a as described above, deterioration of the toner is suppressed, occurrence of aggregation of the toner is suppressed even in a case where an image with a low printing ratio is continuously output, and thus a high-quality image can be stably output.
Here, when the flow (F3) of the toner returning to the toner accommodating chamber 31a is insufficient, the toner is compressed and aggregated in a region below the toner supplying roller 34 and the developing roller 25. In this manner, the toner enters the nip portion N2 between the toner supplying roller 34 and the developing roller 25, and the contact of the toner supplying roller 34 with the developing roller 25 is insufficient. A region where the residual toner on the developing roller 25 cannot be sufficiently recovered by the toner supplying roller 34 is generated, a specific toner is carried around by the developing roller 25 and passes through the contact portion between the developing blade 35 and the developing roller 25 more than necessary, and thus an over-charged toner is generated. As a result, the adhesion force of the toner exceeds the regulation force of the developing blade 35, and accordingly, regulation defects occur in some cases.
Since a width (closest distance between the inner wall of the developing chamber 31b and the surface of the toner supplying roller 34) 37a of the toner flow path is 1.0 mm or greater and 5.0 mm or less, the flow (F3) of the toner returning to the toner accommodating chamber 31a can be sufficiently ensured.
Such a phenomenon is likely to occur, for example, in a case where an image with a low printing ratio is continuously output in a low-temperature and low-humidity environment. This is because the residual toner recovered from the developing toner 25 by the toner supplying roller 34 is accumulated in the developing chamber 31b. Since the residual toner recovered from the developing roller 25 is charged, the toner is likely to be electrostatically aggregated. In this manner, the flowability of the toner inside the developing chamber 31b is degraded, the flow (F3) of the toner returning to the toner accommodating chamber 31a is insufficient, and the toner is likely to be aggregated in a region below the toner supplying roller 34 and the developing roller 25.
In order to deal with this, a method of disposing a toner stirring member below the toner supplying roller 34 inside the developing chamber 31b to create the flow (F3) of the toner returning to the toner accommodating chamber 31a may be used. However, since toner deterioration is accelerated due to the friction between the toner and the toner stirring member inside the developing chamber 31b when the toner stirring member is provided inside the developing chamber 31b, toner melt adhesion to the developing roller 25 is observed in a case where image with a low printing ratio is continuously output. Further, the toner stirring member is required to be provided as an additional member in addition to the toner supplying member 34 inside the developing chamber 31b, and thus the configuration of the apparatus is complicated. Therefore, in the present example, no members that are driven by motor drive are disposed inside the developing chamber 31b in addition to the developing roller 25 and the toner supplying roller 34.
Further, in the configuration in which no members other than the developing roller 25 and the toner supplying roller 34 are disposed inside the developing chamber 31b, the inner wall of the developing chamber 31b is set as follows with respect to the toner supplying roller 34 in order to efficiently use the toner inside the developing chamber 31b. The description will be provided in detail with reference to
R1 and R2 in
Further, as shown in
Further, the toner accommodating chamber 31a of the developing frame 31 is provided with the toner conveying member 36 for stirring the contained toner and conveying the toner to the toner supplying roller 34. As shown in
Next, the toner conveyance of the developing unit will be described. The sheet member 36b of the toner conveying member in the toner accommodating chamber 31a is provided such that the free end of the toner conveying member is in contact with the wall surface of the toner accommodating unit in a region A upstream of the opening portion 31c (communication port) in the rotation direction of the toner conveying member. Further, the sheet member 36b is deformed against elasticity as the toner conveying member rotates such that the free end side rather than the rotation axis side is upstream in the rotation direction of the toner conveying member.
That is, the sheet member 36b comes into contact with a deforming unit 31al on the inner surface of the toner accommodating unit in accordance with the rotation thereof. In this manner, the sheet member 36b receives a force from the deforming unit 31a1. As a result, the sheet member 36b is deformed against the elastic force of the sheet member 36b. Further, the sheet member 36b rotates in a state of being in contact with the deforming unit 31a1, the toner is conveyed in a state of being carried on the surface downstream in the rotation direction thereof. In the present example, the deforming unit 31al denotes a site (also referred to as a region A) of the inner wall of the toner accommodating chamber as shown in
Further, the free end of the toner conveying member is released from the contact with the wall surface of the toner accommodating unit in a predetermined position (also referred to as a position B) in a restoring unit 31a2 downstream of the region A in the rotation direction of the toner conveying member and upstream of the opening portion in the rotation direction of the toner conveying member. In this case, the deformed toner conveying member is elastically restored, and the conveyed toner flies toward the communication port. In the present example, the restoring unit 31a2 is disposed above the horizontal surface of the conveying member including the rotation axis.
Therefore, the contact of the restoring unit 31a2 with the inner wall of the sheet member 36b is released after the tip of the sheet member on the free end side passes through the deforming unit 31al as the sheet member 36b rotates. In this manner, the sheet member 36b is released from a state of being deformed by the deforming unit 31a1 and is restored to a natural state (original shape) by the elastic restoration force of the sheet member 36b. The toner conveyed by being carried on the sheet member 36b due to a change in shape of the sheet member 36b in the restoration direction flies against gravity toward the opening portion 31c. The opening portion 31c is positioned downstream of the restoring unit 31a2 in the rotation direction of the sheet member 36b. Some of the toner flied toward the opening portion 31c is conveyed to the developing chamber 31b. Meanwhile, the toner that has not reached inside the developing chamber 31b falls into the toner accommodating chamber 31a, remains at the bottom of the toner accommodating chamber 31a, and is returned to the original state again. The toner is stirred and conveyed by repeating this cycle.
Further, the boundary portion between the deforming unit 31al and the restoring unit 31a2 is below the lower end of the opening portion 31c (communication port), the rotation center of the toner conveying member 36 and the rotation center of the developing roller 25 are positioned on the same side with respect to the vertical line passing through the boundary portion as viewed in the axial line direction of the developing roller 25, and the maximum value of the radius of rotation of the toner conveying member 36 is greater than the distance between the rotation center of the conveying member and the lower end of the communication port.
The configuration in which the deforming unit 31al and the restoring unit 31a2 described above are provided is a configuration advantageous for increasing the efficiency of conveying the toner to the developing chamber 31b, but this configuration is likely to disrupt the flow (F3) of the toner returning to the toner accommodating chamber so that the regulation defects tend to occur.
In the present example, the length of the rotation axis of the sheet member 36b in the natural state in the radius direction of rotation is set to be greater than the distance from the rotation axis to the lower end of the developing opening in the same direction. The present configuration is advantageous for increasing the efficiency of conveying the toner to the developing chamber 31b, but is likely to disrupt the flow (F3) of the toner returning to the toner accommodating chamber 31a so that the regulation defects tend to occur.
Further, in the present example, two sets of sheet members 36b are attached in a position shifted from the attachment direction on the stirring shaft 36a in order to enable a sufficient amount of toner to be conveyed to the developing chamber 31b from the toner accommodating chamber 31a. The present configuration is advantageous for increasing the efficiency of conveying the toner to the developing chamber 31b, but is likely to disrupt the flow (F3) of the toner returning to the toner accommodating chamber 31a so that the regulation defects tend to occur.
The toner that has not reached the surface of the developing roller in the toner ejected from the toner supplying roller is conveyed by the propulsive force in a direction of a developing opening (opening portion) due to the jetting force caused by the ejection from the toner supplying roller, passes through the developing opening, and is returned to the toner accommodating chamber (F3).
When the toner is satisfactorily circulated between the developing chamber and the toner accommodating chamber as described above, a high-quality image can be stably output.
Hereinafter, the toner according to the present disclosure will be described in more detail.
As a result of intensive examination conducted by the present inventors by focusing on
That is, the toner according to the present disclosure is a toner containing toner particles and silica particles, in which the number average particle diameter of the toner is 4.0 μm or greater and 9.0 μm or less, the average circularity of the toner is 0.955 or greater and 0.975 or less, the proportion of particles having a circularity of 0.900 or greater and 0.930 or less is 2.0% by number or greater and 15.0% by number or less in the circularity distribution of the toner, the content of the silica particles is 1.5 parts by mass or greater and 5.0 parts by mass or less with respect to 100 parts by mass of the toner particles, and the sticking ratio of the silica particles to the toner particles, which is measured by a water washing method, is 70% or greater and 82% or less.
First, it is necessary to adjust the proportion of the particles having a circularity of 0.900 or greater and 0.930 or less to 2.0% by number or greater and 15.0% by number or less in the circularity distribution of the toner after the average circularity of the toner is adjusted to 0.955 or greater and 0.975 or less. This configuration is an intentional configuration in which a partially deformed toner is present in the toner. It is considered that an effect of suppressing the toner from being most densely packed and suppressing toner aggregation is exhibited by employing this configuration. Further, some of the silica particles are migrated and can adhere to the wall surface inside the developing chamber by setting the content of the silica particles in the toner to 1.5 parts by mass or greater and 5.0 parts by mass or less with respect to 100 parts by mass of the toner particles and setting the sticking ratio of the silica particles to the toner particles, which is measured by a water washing method, to 70% or greater and 82% or less. In this manner, the effect of suppressing toner aggregation by decreasing the adhesion force between the toner and the wall surface inside the developing chamber is considered to be exhibited. It is considered that the toner aggregation is suppressed by these two effects, and thus the effects of the present disclosure are exhibited.
The toner (toner which has the average circularity and allows a partially deformed toner to be present) is obtained by suitably a chemical toner production method of obtaining toner particles in an aqueous medium, such as an emulsion aggregation method or a suspension polymerization method, and particularly suitably an emulsion aggregation method.
Specifically, the above-described toner particles can be obtained by controlling the heat treatment temperature and the heat treatment time in the spheronization step of the production step. The details will be described in the method of producing toner particles below. Further, desired toner particles can be obtained by preparing particles with different heat treatment temperatures and different heat treatment times in the spheronization step and mixing these particles after the spheronization step.
The sticking ratio of the silica particles to the toner particles, which is measured by a water washing method, can be set to 70% or greater and 82% or less by controlling the kind, the particle diameter, the addition amount, the external addition strength, and the external addition time of the silica particles.
The content of the silica particles in the toner is more preferably 2.0 parts by mass or greater and 3.6 parts by mass or less with respect to 100 parts by mass of the toner particles. In a case where the content thereof is in the above-described range, the density unevenness and the density unevenness in halftone images can be suppressed by suppressing toner aggregation which is the effect of the present disclosure.
Further, the silica particles according to the present disclosure may include silica particles A having a particle diameter of 40 nm or greater and 300 nm or less and the coverage of the silica particles with respect to the toner particles be 10% or greater and 30% or less.
The spacer effect between toner particles can be exhibited by the silica particles A when the above-described configuration is employed. In this manner, the aggregation of toner particles can be further suppressed. Further, the property of recovering the residual toner on the developing roller by the toner supplying roller is improved by setting the coverage of the silica particles A to 10% or greater and 30% or less. As a result, the density unevenness and the density unevenness in halftone images can be further suppressed by suppressing toner aggregation which is the effect of the present disclosure.
Further, the average value of the solidities of the silica particles A according to the present disclosure, which is measured by a scanning electron microscope (SEM), is more preferably 0.40 or greater and 0.90 or less.
The silica particles A satisfying this requirement have a shape with a plurality of recesses.
With the above-described configuration, embedding of the silica particles into the surface of the toner particles is stably suppressed, and desorption (decrease in sticking ratio) of silica from the toner particles is suppressed. As a result, the density unevenness is suppressed by suppressing toner aggregation which is the effect of the present disclosure, and fogging due to charging unevenness accompanied by the toner deterioration can be suppressed.
Further, the average circularity of the toner according to the present disclosure is 0.960 or greater and 0.975 or less, and the proportion (% by number) of the toner having a circularity of 0.900 or greater and 0.930 or less is more preferably 10.0% by number or greater and 15.0% by number or less.
With the above-described configuration, the density unevenness can be further suppressed by suppressing toner aggregation which is the effect of the present disclosure.
Further, the amount of boron atoms to be present in the toner according to the present disclosure is preferably 0.1 ppm by mass or greater and 100.0 ppm by mass or less. In this manner, the electric charge is appropriately received and transferred between or within the toner particles. When the chargeability between the toner particles is uniformized, embedding of the silica particles into the surface of the toner particles is stably suppressed, and desorption (decrease in sticking ratio) of silica from the toner particles is suppressed from the initial stage to the last stage of use. As a result, the density unevenness is suppressed by suppressing toner aggregation which is the effect of the present disclosure, and fogging due to charging unevenness accompanied by the toner deterioration can be suppressed.
Constituent component of toner
Each component constituting the toner and a method of producing the toner will be described in more detail below.
Binder resin
The toner particles contain a binder resin. The content of the binder resin is preferably 50% by mass or greater with respect to the total amount of the resin component in the toner particles.
The binder resin is not particularly limited, and examples thereof include a styrene acrylic resin, an epoxy resin, a polyester resin, a polyurethane resin, a polyamide resin, a cellulose resin, a polyether resin, and a mixed resin and a composite resin of these resins. Among these, a styrene acrylic resin and a polyester resin are suitable from the viewpoints of low cost, availability, and excellent low-temperature fixability. Polyester resin
The polyester resin can be obtained by selecting suitable compounds from among a polycarboxylic acid, a polyol, a hydroxycarboxylic acid, and the like, combining the compounds, and synthesizing the combined compounds by a known method of the related art, such as a transesterification method or a polycondensation method.
The polycarboxylic acid is a compound containing two or more carboxy groups in a molecule. Among examples of the polycarboxylic acid, a dicarboxylic acid is a compound containing two carboxy groups in one molecule and can be used.
Examples of the dicarboxylic acid include oxalic acid, succinic acid, glutaric acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-carboxylic acid, hexahydroterephthalic acid, malonic acid, pimelic acid, suberic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediacetic acid, o-phenylenediacetic acid, diphenylacetic acid, diphenyl-p,p′-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, and cyclohexanedicarboxylic acid.
Examples of the polycarboxylic acid other than the dicarboxylic acid include trimellitic acid, trimesic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, pyrenetetracarboxylic acid, itaconic acid, glutaconic acid, n-dodecylsuccinic acid, n-dodecenylsuccinic acid, isododecylsuccinic acid, isododecenylsuccinic acid, n-octylsuccinic acid, and n-octenylsuccinic acid. There may be used alone or in combination of two or more kinds thereof.
The polyol is a compound containing two or more hydroxyl groups in one molecule. Among examples of the polyol, the diol is a compound containing two hydroxyl groups in one molecule, and can be used.
Specific examples of the polyol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-hexanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,14-eicosanedecanediol, diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,4-butenediol, neopentyl glycol, 1,4-cyclohexanediol, polytetramethylene glycol, hydrogenated bisphenol A, bisphenol A, bisphenol F, bisphenol S, and alkylene oxide (ethylene oxide, propylene oxide, and butylene oxide) adducts of the above-described bisphenols.
Among these, alkylene glycol having 2 to 12 carbon atoms and alkylene oxide adducts of bisphenols are suitable, and combinations of alkylene oxide adducts of bisphenols and alkylene glycol having 2 to 12 carbon atoms is particularly suitable.
Examples of the tri-or higher valent include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylol benzoguanamine, tetraethylol benzoguanamine, sorbitol, trisphenol PA, phenol novolac, cresol novolac, and alkylene oxide adducts of the above-described tri-or higher valent polyphenols. These may be used alone or in combination of two or more kinds thereof.
Examples of the styrene acrylic resin include homopolymers formed of the following polymerizable monomers, copolymers obtained by combining two or more kinds of homopolymers, and mixtures thereof.
Examples of the styrene acrylic resin include a styrene-based monomer such as styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, or p-phenylstyrene;
a (meth)acrylic monomer such as methyl(meth)acrylate, ethyl(meth)acrylate, n-propyl(meth)acrylate, iso-propyl(meth)acrylate, n-butyl(meth)acrylate, iso-butyl(meth)acrylate, tert-butyl(meth)acrylate, n-amyl(meth)acrylate, n-hexyl(meth) acrylate, 2-ethylhexyl(meth) acrylate, n-octyl(meth) acrylate, n-nonyl(meth) acrylate, cyclohexyl(meth) acrylate, benzyl(meth) acrylate, dimethyl phosphate ethyl(meth) acrylate, diethyl phosphate ethyl (meth) acrylate, dibutyl phosphate ethyl(meth)acrylate, 2-benzoyloxyethyl(meth) acrylate, (meth)acrylonitrile, 2-hydroxyethyl(meth) acrylate, (meth)acrylic acid, or maleic acid; a vinyl ether-based monomer such as vinyl methyl ether or vinyl isobutyl ether; a vinyl ketone-based monomer such as vinyl methyl ketone, vinyl ethyl ketone, or vinyl isopropenylketone; and polyolefins such as ethylene, propylene, and butadiene.
A polyfunctional polymerizable monomer can be used as the styrene acrylic resin as necessary. Examples of the polyfunctional polymerizable monomer include diethylene glycol di(meth) acrylate, triethylene glycol di(meth) acrylate, tetraethylene glycol di(meth) acrylate, polyethylene glycol di(meth) acrylate, 1,6-hexanediol di(meth) acrylate, neopentyl glycol di(meth) acrylate, tripropylene glycol di(meth) acrylate, polypropylene glycol di(meth) acrylate, 2,2′-bis(4-((meth)acryloxydiethoxy)phenyl) propane, trimethylolpropane tri(meth) acrylate, tetramethylolmethane tetra(meth) acrylate, divinylbenzene, divinylnaphthalene, and divinyl ether.
Further, a known chain transfer agent and a known polymerization inhibitor can be further added to the toner in order to control the polymerization degree.
Examples of a polymerization initiator for obtaining the styrene acrylic resin include an organic peroxide-based initiator and an azo-based polymerization initiator.
Examples of the organic peroxide-based initiator include benzoyl peroxide, lauroyl peroxide, di-a-cumyl peroxide, 2,5-dimethyl-2,5-bis(benzoylperoxy) hexane, bis(4-t-butylcyclohexyl) peroxydicarbonate, 1,1-bis(t-butylperoxy) cyclododecane, t-butylperoxymaleic acid, bis(t-butylperoxy) isophthalate, methyl ethyl ketone peroxide, tert-butyl peroxy-2-ethylhexanoate, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, and tert-butyl peroxypivalate.
Examples of the azo-based polymerization initiator include 2,2′-azobis-(2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis(cyclohexane-1-carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, and azobismethylbutyronitrile, and 2,2′-azobis-(methylisobutyrate).
Further, a redox-based initiator obtained by combining an oxidizing substance and a reducing substance can also be used as the polymerization initiator.
Example of the oxidizing substance include hydrogen peroxide, an inorganic peroxide of a persulfate (a sodium salt, a potassium salt, or an ammonium salt), and an oxidizing metal salt of a tetravalent cerium salt.
Examples of the reducing substance include a reducing metal salt (a divalent iron salt, a monovalent copper salt, or a trivalent chromium salt, ammonia, a lower amine (an amine having 1 or more and 6 or less carbon atoms, such as methylamine or ethylamine), an amino compound such as hydroxylamine, a reducing sulfur compound such as sodium thiosulfate, sodium hydrosulfite, sodium hydrogen sulfite, sodium sulfite, or sodium formaldehyde sulfoxylate, lower alcohol (having 1 or more and 6 or less carbon atoms), ascorbic acid or a salt thereof, and a lower aldehyde (having 1 or more and 6 or less carbon atoms).
The polymerization initiator is selected with reference to a 10-hr half-life temperature, and is used alone or in the form of a mixture.
The amount of the polymerization initiator to be added changes depending on the target polymerization degree, but is typically 0.5 parts by mass or greater and 20.0 parts by mass or less with respect to 100.0 parts by mass of the polymerizable monomer. Release agent
A known wax can be used in the toner as a release agent.
Specific examples thereof include petroleum-based waxes such as paraffin wax, microcrystalline wax, and petrolatum, and derivatives thereof, montan waxes and derivatives thereof, hydrocarbon waxes obtained by using the Fischer-Tropsch method and derivatives thereof, polyolefin waxes such as polyethylene and derivatives thereof, and natural waxes such as carnauba wax and candelilla wax and derivatives thereof, and the derivatives include oxides, block copolymers with vinyl monomers, and graft modified products.
Further, examples of the waxes include alcohols such as higher aliphatic alcohol; fatty acids such as stearic acid and palmitic acid, acid amides, esters, and ketones thereof; hydrogenated castor oil and derivatives thereof, vegetable waxes, and animal waxes. These may be used alone or in combination.
Among these, polyolefin, hydrocarbon wax obtained by using the Fischer-Tropsch method, or petroleum-based wax can be used from the viewpoint that the developability and the transferability tend to be improved. Further, an antioxidant may be added to these waxes in a range where the characteristics of the toner are not affected.
Further, from the viewpoints of the phase separation properties with respect to the binder resin and the crystallization temperature, suitable examples thereof include higher fatty acid esters such as behenyl behenate and dibehenyl sebacate.
The content of the release agent is preferably 1.0 parts by mass or greater and 30.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin.
The melting point of the release agent is preferably 30° C. or higher and 120° C. or lower and more preferably 60° C. or higher and 100° C. or lower. In a case where a release agent having a melting point of 30° C. or higher and 120° C. or lower is used, a release effect is efficiently exhibited, and a wider fixing region is ensured.
A crystalline plasticizer in the toner of the present disclosure can be used for improving sharp melt properties. The plasticizer is not particularly limited, and known plasticizers used in toners as described below can be used.
Examples of the plasticizer include esters of monohydric alcohol and aliphatic carboxylic acid, such as behenyl behenate, stearyl stearate, and palmityl palmitate, or esters of carboxylic acid and aliphatic alcohol; esters of dihydric alcohol and aliphatic carboxylic acid, such as ethylene glycol distearate, dibehenyl sebacate, and hexanediol dibehenate, or esters of carboxylic acid and aliphatic alcohol; esters of trihydric alcohol and aliphatic carboxylic acid, such as glycerin tribehenate, or esters of trihydric carboxylic acid and aliphatic alcohol; esters of tetrahydric alcohol and aliphatic carboxylic acid, such as pentaerythritol tetrastearate and pentaerythritol tetrapalmitate, or esters of tetrahydric carboxylic acid and aliphatic alcohol; esters of hexahydric alcohol and aliphatic carboxylic acid, such as dipentaerythritol hexastearate and dipentaerythritol palmitate, or esters of hexahydric carboxylic acid and aliphatic alcohol; esters of polyhydric alcohol and aliphatic carboxylic acid, such as polyglycerin behenate, or esters of polyhydric carboxylic acid and aliphatic alcohol; and natural ester waxes such as carnauba wax and rice wax. These may be used alone or in combination.
The toner particles may contain a colorant. A known pigment or a known dye can be used as the colorant. From the viewpoint of excellent weather resistance, a pigment is suitable as the colorant.
Examples of a cyan-based colorant include a copper phthalocyanine compound and a derivative thereof, an anthraquinone compound, and a base dye lake compound. Specific examples thereof include C.I. Pigment Blue 1, 7, 15, 15:1, 15:2, 15:3, 15:4, 60, 62, and 66.
Examples of a magenta-based colorant include a condensed azo compound, a diketopyrrolopyrrole compound, an anthraquinone compound, a quinacridone compound, a base dye lake compound, a naphthol compound, a benzimidazolone compound, a thioindigo compound, and a perylene compound. Specific examples thereof include C.I. Pigment Red 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1, 122, 144, 146, 150, 166, 169, 177, 184, 185, 202, 206, 220, 221, and 254, and C.I. Pigment Violet 19.
Examples of a yellow-based colorant include a condensed azo compound, an isoindolinone compound, an anthraquinone compound, an azo metal complex, a methine compound, and an allylamide compound. Specific examples thereof include C.I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185, 191, and 194.
Examples of a black colorant include colorants toned to black using the yellow-based colorant, the magenta-based colorants, and the cyan-based colorants described above, and carbon black.
These colorants can be used alone or in the form of a mixture, and can also be used as a solid solution.
The content of the colorant is preferably 1.0 parts by mass or greater and 20.0 parts by mass or less with respect to 100.00 parts by mass of the binder resin. Charge control agent and charge control resin
The toner particles may contain a charge control agent or a charge control resin.
As the charge control agent, a known charge control agent can be used, and particularly a charge control agent that has a high triboelectric charging speed and is capable of stably maintaining a constant triboelectric charging amount is suitable. Further, in a case where the toner particles are produced by a suspension polymerization method, a charge control agent that has low polymerization inhibition properties and is substantially free from a solubilized substance in an aqueous medium is particularly suitable.
Examples of a charge control agent that controls the toner to be negatively charged include a monoazo metal compound, an acetylacetone metal compound, an aromatic oxycarboxylic acid-based metal compound, an aromatic dicarboxylic acid-based metal compound, an oxycarboxylic acid-based metal compound, a dicarboxylic acid-based metal compound, an aromatic oxycarboxylic acid, an aromatic monocarboxylic acid, an aromatic polycarboxylic acid, and metal salts thereof, anhydrides, esters, phenol derivatives such as bisphenol, urea derivatives, a metal-containing salicylic acid-based compound, a metal-containing naphthoic acid-based compound, a boron compound, a quaternary ammonium salt, a calixarene, an a charge control resin.
Examples of the charge control resin include a polymer or copolymer containing a sulfonic acid group, a sulfonate group, or a sulfonic acid ester group. The polymer containing a sulfonic acid group, a sulfonate group, or a sulfonic acid ester group is particularly preferably a polymer containing 2% by mass or greater of a sulfonic acid group-containing acrylamide-based monomer or a sulfonic acid group-containing methacrylamide-based monomer and more preferably a polymer containing 5% by mass or greater thereof in terms of the copolymerization ratio.
The charge control resin may have a glass transition temperature (Tg) of 35° C. or higher and 90° C. or lower, a peak molecular weight (Mp) of 10000 or greater and 30000 or less, and a weight-average molecular weight (Mw) of 25000 or greater and 50000 or less. In a case where such a charge control resin is used, preferred triboelectric charge characteristics can be imparted to the toner particles without affecting thermal characteristics required for the toner particles. Further, in a case where the charge control resin contains a sulfonic acid group, for example, the dispersibility of the charge control resin and the dispersibility of a colorant and the like in a polymerizable monomer composition are improved, and the coloring power, the transparency, and the triboelectric charge characteristics can be improved.
These charge control agents or charge control resins may be respectively used alone or in combination of two or more kinds thereof for addition.
The amount of the charge control agent or charge control resin to be added is preferably 0.01 parts by mass or greater and 20.0 parts by mass or less and more preferably 0.5 parts by mass or greater and 10.0 parts by mass or less with respect to 100.0 parts by mass of the binder resin.
Dry silica is suitable as the silica particles used as an external additive in the toner according to the present disclosure from the viewpoint of easily controlling a shape with a large number of recesses. The dry silica is formed of a silicon halogen compound or the like as a raw material. As the silicon halogen compound, silicon tetrachloride is used, but silanes such as methyl trichlorosilane and trichlorosilane can be used alone or silicon tetrachloride and silanes can be used in a mixed state as a raw material. After vaporization of the raw material, target silica is obtained by a so-called flame hydrolysis reaction of reacting the raw material with water generated as an intermediate in an oxyhydrogen flame. For example, a thermal decomposition oxidation reaction of silicon tetrachloride gas in oxygen and hydrogen is used, and the reaction formula is as follows.
SiCl4+2H2+O2→SiO2+4HCl
Hereinafter, a method of producing silica will be described.
Oxygen gas is supplied to a burner to ignite the ignition burner, hydrogen gas is supplied to the burner to form a flame, and silicon tetrachloride which is a raw material is added thereto for gasification. A flame hydrolysis reaction is carried out, and generated silica powder is recovered.
The average particle diameter and the shape can be arbitrarily adjusted to prepare silica particles in a shape with a large number of recesses by appropriately changing a silica tetrachloride flow rate, an oxygen gas supply flow rate, a hydrogen gas supply flow rate, and a retention time of silica in a flame. The shape with a large number of recesses may be controlled by a method of transferring the obtained silica powder to an electric furnace, spreading the silica powder in the form of a thin layer, and performing a heat treatment so that the silica powder is sintered. The coalescence strength of the silica particles is increased when the silica powder is sintered.
Further, the silica particles used in the present disclosure may be subjected to a surface treatment such as a hydrophobic treatment or a silicone oil treatment.
A hydrophobization method is performed by carrying out a chemical treatment with an organic silicon compound that reacts with or physically adsorbs on silica so that hydrophobicity is imparted. As a suitable method, silica generated by vapor phase oxidation of a silicon halogen compound is treated with an organic silicon compound.
Examples of such an organic silicon compound include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, a-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, 1-hexamethyldisoloxane, 1,3-divinyltetramethyldisiloxane, 1,3-diphenyltetramethyldisiloxane, and dimethylpolysiloxane.
These may be used alone or in the form of a mixture of two or more kinds thereof.
Further, silicone oil having a viscosity of 30 mm2/s or greater and 1000 mm2/s or less at 25° C. can be used as the silicone oil in the silicone oil-treated silica. Examples thereof include dimethyl silicone oil, methyl phenyl silicone oil, a-methyl styrene-modified silicone oil, chlorophenyl silicone oil, and fluorine-modified silicone oil.
Examples of a method of performing the silicone oil treatment include a method of directly mixing silicone oil with silica treated with a silane coupling agent using a mixer such as a Henschel mixer, a method of spraying silicone oil to silica serving as a base, and a method of dissolving or dispersing silicone oil in an appropriate solvent, adding silica thereto, mixing the mixture, and removing the solvent.
In the silicone oil-treated silica, silica after the treatment of silicone oil can be heated at a temperature of 200° C. or higher (more preferably 250° C. or higher) in an inert gas and the coating of the surface be stabilized. Preferred examples of the silane coupling agent include hexamethyldisilazane (HMDS).
The amount of the silica particles to be added is 1.5 parts by mass or greater and 5.0 parts by mass or less with respect to 100.0 parts by mass of the toner particles.
The sticking state of the external additive and the coating state of the toner particles with the external additive can be arbitrarily controlled by adjusting the rotation speed (rpm) of the stirring blade provided in an external adder and the external addition time as external addition conditions.
It is effective to increase the rotation speed and the external addition time in order to more firmly stick the toner particles, and particularly the sticking strength can be further increased by increasing the rotation speed. Further, since external additive particles with a small particle diameter form aggregates, the toner particles are subjected to a coating treatment with an external additive while a disintegration treatment is carried out by controlling the external addition conditions. The disintegration properties can be enhanced by increasing the rotation speed and the external addition time, but it is effective to reduce the rotation speed and to increase the external addition time in order to further promote disintegration while suppressing the sticking strength.
Further, the silica particles include silica particles A having a particle diameter of 40 nm or greater and 300 nm or less, and the coverage of the silica particles A with respect to the toner particles is preferably 10% or greater and 30% or less. These values can be controlled by adjusting the kind and the addition amount of the silica particles A, the rotation speed (rpm) of the stirring blade provided in an external adder, and the external addition time.
Method of producing toner
A method of producing the toner is not particularly limited, and the toner can be produced by using a known method such as a pulverization method, a suspension polymerization method, a dissolution suspension method, an emulsion aggregation method, or a dispersion polymerization method. The toner can be produced by an emulsion aggregation method from the viewpoint of easily obtaining the toner (toner which has the average circularity and allows a partially deformed toner to be present) of the present disclosure.
Hereinafter, the emulsion aggregation method will be described in detail. Emulsion aggregation method
The emulsion aggregation method is a method of producing toner particles by preliminarily preparing an aqueous dispersion liquid of fine particles formed of a constituent material of toner particles which are relatively small with respect to the target particle diameter, aggregating the fine particles until the particle diameter of the particles reach the particle diameter of the toner particles in an aqueous medium, and fusing the resin by being heated or the like.
That is, the emulsion aggregation method may include the following steps (1) to (5) in the following order: (1) a dispersion step of preparing a biner resin fine particle dispersion liquid containing the binder resin, (2) an aggregation step of aggregating binder resin fine particles contained in the binder resin fine particle dispersion liquid to form aggregates, (3) a shell formation step of further adding resin fine particles containing a resin for a shell to the dispersion liquid containing aggregates and aggregating particles to form aggregates having a shell, (4) a fusion step of heating and fusing the aggregates, and (5) a spheronization step of increasing the temperature and heating the aggregates.
Step of preparing resin fine particle dispersion liquid (dispersion step)
The resin fine particle dispersion liquid can be prepared by a known method, but the present disclosure is not limited thereto. Examples of the known method include an emulsion polymerization method, a self-emulsification method, a phase inversion emulsification method of adding an aqueous medium to a resin solution dissolved in an organic solvent to emulsify the resin, and a forced emulsification method of performing a high-temperature treatment in an aqueous medium to forcibly emulsify the resin without using an organic solvent.
Specifically, the binder resin is dissolved in an organic solvent that can dissolve the resin, and a surfactant and a basic compound are added thereto. In this case, when the binder resin is a crystalline resin having a melting point, the resin may be dissolved by being heated at the melting point or higher. Next, an aqueous medium is slowly added to the mixture while the mixture is stirred with a homogenizer or the like, to precipitate the resin fine particles. Thereafter, the solvent is removed by heating the mixture or reducing the pressure, thereby preparing an aqueous dispersion liquid of the resin fine particles. Any organic solvent can be used as the organic solvent used for dissolving the resin as long as the organic solvent can dissolve the resin, but an organic solvent that forms a homogeneous phase with water, such as toluene, can be used from the viewpoint of suppressing generation of coarse powder.
The surfactant used for the emulsification is not particularly limited, and examples thereof include an anionic surfactant such as a sulfuric acid ester salt-based surfactant, a sulfonate-based surfactant, a carbonate-based surfactant, a phosphoric acid ester-based surfactant, or a soap-based surfactant; a cationic surfactant such as an amine salt type surfactant or a quaternary ammonium salt type surfactant; and a nonionic surfactant such as a polyethylene glycol-based surfactant, an alkylphenol ethylene oxide adduct-based surfactant, or a polyhydric alcohol-based surfactant. The surfactant may be used alone or in combination of two or more kinds thereof.
Examples of the basic compound used in the dispersion step include an inorganic base such as sodium hydroxide or potassium hydroxide; and an organic base such as ammonia, triethylamine, trimethylamine, dimethylaminoethanol, or diethylaminoethanol. The basic compound may be used alone or in combination of two or more kinds thereof.
Further, the 50% particle diameter (D50) of fine particles of the binder resin based on volume distribution in the aqueous dispersion liquid of resin fine particles is preferably in a range of 0.05 μm to 1.0 μm and more preferably in a range of 0.05 μm to 0.4 μm. Toner particles having an appropriate number average particle diameter of 4.0 μm to 9.0 μm are easily obtained by adjusting the 50% particle diameter (D50) thereof based on volume distribution to be in the above-described ranges.
In addition, the 50% particle diameter (D50) of particles based on volume distribution is measured using a dynamic light scattering particle size distribution meter NANOTRAC UPA-EX150 (manufactured by Nikkiso Co., Ltd.).
Colorant Fine Particle Dispersion Liquid
A colorant fine particle distribution liquid may be used as necessary. The colorant fine particle distribution liquid can be prepared by a known method described below, but the present disclosure is not limited thereto. The colorant fine particle distribution liquid can be prepared by mixing a colorant, an aqueous medium, and a dispersant using a known mixer such as a stirrer, an emulsifier, or a disperser. A known dispersant such as a surfactant or a polymer dispersant can be used as the dispersant used here. Both dispersants, the surfactant and the polymer dispersant, can be removed in a washing step described below, but the surfactant is suitable from the viewpoint of washing efficiency.
Examples of the surfactant include an anionic surfactant such as a sulfuric acid ester salt-based surfactant, a sulfonate-based surfactant, a phosphoric acid ester-based surfactant, or a soap-based surfactant; a cationic surfactant such as an amine salt type surfactant or a quaternary ammonium salt type surfactant; and a nonionic surfactant such as a polyethylene glycol-based surfactant, an alkylphenol ethylene oxide adduct-based surfactant, or a polyhydric alcohol-based surfactant. Among these, a nonionic surfactant or an anionic surfactant is suitable. Further, a nonionic surfactant and an anionic surfactant may be used in combination. The surfactant may be used alone or in combination of two or more kinds thereof. The concentration of the surfactant in an aqueous medium is preferably in a range of 0.5% by mass to 5% by mass.
The content of the colorant fine particles in the colorant fine particle dispersion liquid is not particularly limited, but is preferably in a range of 1% by mass to 30% by mass with respect to the total mass of the colorant fine particle dispersion liquid.
In the dispersed particle diameter of the colorant fine particle in the aqueous dispersion liquid of the colorant, the 50% particle diameter (D50) based on the volume distribution is preferably 0.5 μm or less from the viewpoint of the dispersibility of the colorant in the toner to be finally obtained. Further, a 90% particle diameter (D90) based on the volume distribution is preferably 2 μm or less for the same reason. In addition, the dispersed particle diameter of the colorant fine particles dispersed in the aqueous medium is measured using a dynamic light scattering particle size distribution meter (NANOTRAC UPA-EX150, manufactured by Nikkiso Co., Ltd.).
Examples of the mixer such as a known stirrer, emulsifier, or disperser used when the colorant is dispersed in the aqueous medium include an ultrasonic homogenizer, a jet mill, a pressure homogenizer, a colloid mill, a ball mill, a sand mill, and a paint shaker. These may be used alone or in combination.
Release agent (aliphatic hydrocarbon compound) fine particle dispersion liquid
A release agent fine particle dispersion liquid may be used as necessary. The release agent fine particle dispersion liquid can be prepared by a known method described below, but the present disclosure is not limited thereto.
The release agent fine particle dispersion liquid can be prepared by adding a release agent to an aqueous medium containing a surfactant, heating the mixture at a temperature higher than or equal to the melting point of the release agent, dispersing the release agent in the form of particles using a homogenizer (for example, “CLEARMIX W-MOTION”, manufactured by M Technique Co., Ltd.) having a strong shearing ability or a pressure ejection type disperser (for example, “GAULIN HOMOGENIZER”, manufactured by Gaulin Corporation), and cooling the mixture at a temperature lower than the melting point of the release agent.
In the dispersed particle diameter of the release agent fine particle dispersion liquid in the aqueous dispersion liquid of the release agent, the 50% particle diameter (D50) based on the volume distribution is preferably in a range of 0.03 μm to 1.0 μm and more preferably in a range of 0.1 μm to 0.5 μm. Further, no coarse particles having a particle diameter of 1 μm or greater may be present.
In a case where the dispersed particle diameter of the release agent fine particle dispersion liquid is in the above-described ranges, the release agent can be present in a state of being finely dispersed in the toner, a bleeding effect during fixation can be maximized, and satisfactory separation properties can be obtained. Further, the dispersed particle diameter of the release agent fine particle dispersion liquid dispersed in the aqueous medium can be measured using a dynamic light scattering particle size distribution meter NANOTRAC UPA-EX150 (manufactured by Nikkiso Co., Ltd.). Mixing step
In the mixing step, a mixed solution is prepared by mixing the resin fine particle dispersion liquid with at least one of the release agent fine particle dispersion liquid and the colorant fine particle dispersion liquid as necessary. The mixed solution can be prepared by using a known mixing device such as a homogenizer or a mixer. Step of forming aggregate particles (aggregation step)
In the aggregation step, the fine particles contained in the mixed solution prepared in the mixing step are aggregated to form aggregates with a target particle diameter. Here, an aggregating agent is added thereto and mixed into the mixture, and the mixture is appropriately subjected to heating and mechanical power as necessary to form aggregates in which the resin fine particles and at least one of the release agent fine particles and the colorant fine particles are aggregated.
Examples of the aggregating agent include an organic aggregating agent such as a quaternary salt cationic surfactant or polyethyleneimine; an inorganic metal salt such as sodium sulfate, sodium nitrate, sodium chloride, calcium chloride, or calcium nitrate; an inorganic ammonium salt such as ammonium sulfate, ammonium chloride, or ammonium nitrate; and an inorganic aggregating agent such as a di-or higher valent metal complex. Further, an acid can also be added to the mixed solution so that the pH is decreased and the particles are softly aggregated, and sulfuric acid, nitric acid, or the like can be used as the acid.
The aggregating agent may be added to the mixed solution in any form of dry powder or an aqueous solution dissolved in an aqueous medium, but the aggregating agent can be added in the form of an aqueous solution in order to uniformly aggregate the particles. Further, the aggregating agent can be added to and mixed into the mixed solution at a temperature lower than or equal to the glass transition temperature or the melting point of the resin contained in the mixed solution. When the aggregating agent is mixed into the mixed solution under the above-described temperature conditions, relatively uniform aggregation proceeds. The aggregating agent can be mixed into the mixed solution using a known mixing device such as a homogenizer or a mixer. The aggregation step is a step of forming aggregates having a toner particle size in the aqueous medium. The number average particle diameter of the aggregates produced in the aggregation step is preferably in a range of 4.0 μm to 9.0 μm. The number average particle diameter can be measured by a coulter method using a particle size distribution analyzer (COULTER Multisizer III: manufactured by Beckman Coulter, Inc.). Shell formation step of further adding resin fine particles containing resin for shell to dispersion liquid containing aggregates and aggregating particles to form aggregates having shell
A shell formation step of forming a shell by further adding resin fine particles containing a resin for a shell and aggregating the particles can be provided after the formation of aggregated particles (core particles) in the aggregation step. That is, the toner particles may include core particles containing a binder resin and a shell on the core particle surface. As the resin for a shell, the same resin as the binder resin may be used, or other resins may be used. The amount of the resin for a shell to be added is preferably in a range of 5 parts by mass to 40 parts by mass and more preferably in a range of 10 parts by mass to 30 parts by mass or less with respect to 100 parts by mass of the binder resin contained in the core particles.
In this case, in order to allow the toner particles to easily contain boron, a boron compound can be added to the dispersion liquid containing the aggregates along with the resin fine particles containing the resin for a shell in the shell formation step.
The boron compound may be boric acid or a compound that can be changed to boric acid by controlling the pH in the production of the toner. Examples thereof include at least one selected from the group consisting of boric acid, borax, organic boric acid, a borate, boric acid ester, and the like. For example, the pH may be controlled by adding a boric acid source to the mixed solution so that the aggregates contain boric acid. The shell formation step can be performed by controlling the pH to be under an acidic condition in the aggregation step.
The boric acid may be present in the aggregates in the unsubstituted state. At least one selected from the group consisting of boric acid and borax is preferable as the boric acid source. In a case where the toner is produced in an aqueous medium, a borate can be added to the mixed solution as the boric acid source from the viewpoints of the reactivity and the production stability. Specifically, the boric acid source includes more preferably at least one selected from the group consisting of sodium tetraborate, borax, and ammonium borate and still more preferably borax.
Borax is represented by a sodium tetraborate decahydrate (Na2B4O7), and changed to boric acid in an acidic aqueous solution, and thus borax can be used in a case of being used in an aqueous medium in an acidic environment. According to an addition method, borax may be added in any form of dry powder or an aqueous solution dissolved in an aqueous medium, but borax can be added in the form of an aqueous solution in order to uniformly aggregate the particles. The concentration of the aqueous solution may be appropriately changed depending on the concentration thereof to be contained in the toner, and is, for example, in a range of 1% to 20% by mass. The pH can be controlled to be in an acidic condition before, during, or after the addition of borax in order to change borax to boric acid. The pH may be controlled to be, for example, in a range of 1.5 to 5.0 and preferably in a range of 2.0 to 4.0.
Step of obtaining dispersion liquid containing toner particles (fusion step)
In the fusion step, first, the aggregation is stopped while the dispersion liquid containing the aggregates obtained in the aggregation step is stirred in the same manner as in the aggregation step. The aggregation is stopped by adding an aggregation stopping agent such as a base, a chelate compound, or an inorganic salt compound such as sodium chloride, which can adjust the pH.
The dispersed state of the aggregated particles in the dispersion liquid is stabilized by the action of the aggregation stopping agent, the mixed solution is heated at a temperature higher than or equal to the glass transition temperature or the melting point of the binder resin to fuse the aggregated particles, and thus the particles having a desired particle diameter are prepared.
Further, the number average particle diameter of the toner particles is preferably in a range of 4.0 μm to 9.0 μm.
Step of obtaining desired surface shape of toner (spheronization step)
The spheronization step of further increasing the temperature and maintaining the temperature until the toner particles have a desired circularity or surface shape can be performed during or after the fusion step. The specific temperature of the spheronization step is, for example, preferably 90° C. or higher and more preferably 92° C. or higher, and preferably 95° C. or lower. The heating time in the spheronization step is, for example, 3 hours or longer, 5 hours or longer, or 8 hours or longer. In the present step, a hydrogen bond derived from boric acid is likely to be formed in the toner particles. Cooling step
The cooling step of decreasing the temperature of the dispersion liquid containing the obtained toner particles to a temperature lower than the crystallization temperature or the glass transition temperature of the binder resin can be performed by controlling the cooling rate after the spheronization step. When the cooling step is performed, formation of unevenness on the surface of the toner particles accompanied by a change in volume, such as expansion or contraction of the material in the toner particles is suppressed. The specific cooling rate is 0.1° C./sec or greater, preferably 0.5° C./sec or greater, more preferably 2° C./sec or greater, and still more preferably 4° C./sec or greater.
In the method of producing the toner, post-treatment steps such as a washing step, a solid-liquid separation step, a drying step, and the like may be performed, and toner particles in a dried state can be obtained by performing the post-treatment steps.
The toner of the present disclosure can be obtained by externally adding the silica particles to the obtained toner particles.
In the external addition step, silica fine particles are subjected to an external addition treatment to the toner particles obtained in the drying step. Specifically, the silica fine particles can be added to and mixed with the toner particles by applying a shearing force in a dry state. A known external adder can be used as an external adder that performs the external addition step.
Next, a method of measuring each physical property according to the present disclosure will be described.
The surface of the toner particle is photographed at a magnification of 30000 using FE-SEMS-4800 (manufactured by Hitachi, Ltd.). The particle diameter of the external additive is measured using this enlarged photograph, and the particle having a diameter of 40 nm or greater and 300 nm or less is determined as the silica particle A. The measurement is performed on 100 or more of the toner particles, and the average value of the particle diameters of the silica particles A is defined as the average particle diameter of the silica particles A.
Further, the toner containing a plurality of external additives in the surface of the toner particles can also be measured in the same manner as described above. The element of each fine particle can be specified using elemental analysis such as EDAX when a reflected electron image is observed using S-4800. Further, the same kind of fine particles can be selected based on the characteristics of the shape. The major axis of each silica particle can be calculated by performing the above-described measurement on the same kind of fine particles.
Coverage of silica particles A with respect to surface of toner particle
The coverage of the silica particles A according to the present disclosure with respect to the surface of the toner particles is measured by the observed image used to determine the particle diameter of the silica particles A. The coverage is calculated from the observed image in the following manner using image processing software “ImageJ”.
Only the particles derived from the silica particles A having a particle diameter of 40 nm or greater and 300 nm or less in the image are selected on the software by particle analysis. Next, the selection screen displays the area by performing the measurement setting. The coverage of the silica particles A in the visual field is obtained by dividing this value by the area of the entire visual field. This measurement is performed on 100 visual fields, and the average value of the obtained values is defined as the coverage of the silica particles A.
Method of measuring solidity of silica particles on toner particles
The calculation is performed by analyzing the images of the toner particle surfaces captured by a Hitachi ultra-high resolution field emission scanning electron microscope S-4800 (Hitachi High-Tech Corporation), using image analysis and image processing software ImageJ (developed by Wayne Rashand). The measurement procedures are as follows.
1) SEM observation
The observation is performed using the images obtained by observing the reflected electron images with S-4800. Inorganic fine particle images with high contrast are more easily obtained with the reflected electron images compared with secondary electron images, and thus the solidity of the silica particles A can be measured with high accuracy. The observation conditions are as follows.
The brightness is adjusted in an ABC mode, and a photograph is taken at a size of 640×480 pixels and stored. The following analysis is performed using this image file. The observation is performed by setting the observation magnification to 20k times in 100 visual fields, thereby obtaining 100 sheets of images.
3) Image analysis
Since the silica particles are shown with a high brightness and the toner particles are shown with a low brightness in the images obtained by observation, the coverage of the silica particles A in the visual field can be quantified by binarization. The coverage of the silica particles A can be calculated by performing a binarization treatment on the observed images obtained by the above-described method using image processing software ImageJ (developed by Wayne Rashand). The analysis conditions are as follows. The background brightness distribution is removed using 40 pixels with a flattening radius from the Subtract Background menu, and the images are binarized with a brightness threshold value of 50.
In the present disclosure, the solidity can be controlled by the kind and external addition conditions of the silica particles A to be used.
Measurement of weight-average particle diameter (D4) and number average particle diameter (D1) of toner or toner particles
The weight-average particle diameter (D4) and the number average particle diameter (D1) of the toner or toner particles are measured by 25000 effective measuring channels using a precision particle size distribution measuring device “COULTER COUNTER Multisizer 3” (registered trademark, manufactured by Beckman Coulter, Inc.) provided with an aperture tube having a diameter of 100 μm by an aperture impedance method and dedicated software “BECKMAN COULTER Multisizer 3. Version 3.51” (manufactured by Beckman Coulter, Inc.) attached to the device and calculated by analyzing measurement data.
An electrolyte solution obtained by dissolving special grade sodium chloride in ion exchange water and adjusting the concentration thereof to about 1% by mass, for example, “ISOTON II” (manufactured by Beckman Coulter, Inc.) can be used as the electrolyte solution used for the measurement.
In addition, the dedicated software is set up in the following manner before the measurement and the analysis.
In the dedicated software “screen for changing standard measuring method (SOM)”, the total count number in the control mode is set to 50000 particles, the number of times of measurement is set to once, and a value obtained by using “nominal particle 10.0 μm” (manufactured by Beckman Coulter, Inc.) is set as the Kd value. The threshold value and the noise level are automatically set by pressing the measurement button of the threshold value/noise level. Further, the current is set to 1600 μA, the gain is set to 2, the electrolyte solution is set to ISOTON II, and the aperture tube flash after measurement is checked.
In dedicated software “setting screen for converting pulse to particle diameter”, the bin interval is set to the logarithmic particle diameter, the particle diameter bin is set to 256 particle diameter bin, and the particle diameter range is set to 2 μm or greater and 60 μm or less.
The specific measuring method is as follows.
(1) A 250 ml round-bottom glass beaker for exclusive use of Multisizer 3 is charged with about 200 ml of the electrolyte solution and set on a sample stand, and the solution is stirred with a stirrer rod at 24 rotations/sec in a counterclockwise direction. Further, the stain and air bubbles inside the aperture tube are removed by the dedicated software “aperture tube flash”.
(2) A 100 ml flat-bottom glass beaker is charged with about 30 ml of the electrolyte solution, and about 0.3 ml of a diluent obtained by diluting “Contaminon N” (10 mass % aqueous solution of neutral detergent for washing precision measuring machine with pH of 7, which is formed of nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) to 3 times by mass with ion exchange water is added thereto as a dispersant.
(3) A predetermined amount of ion exchange water is poured into a water tank of an ultrasonic disperser “Ultrasonic Dispersion System Tetoral 150” with an electrical output of 120 W, which is provided with two built-in oscillators having an oscillation frequency of 50 kHz in a state of a phase shift of 180 degrees, and about 2 ml of Contaminon N is added to the water tank.
(4) The beaker of the item (2) is set in a beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Further, the position of the height of the beaker is adjusted such that the resonance state of the liquid level of the electrolyte solution in the beaker is maximized.
(5) The electrolyte solution in the beaker of the item (4) is irradiated with ultrasonic waves, and about 10 mg of the toner or the toner particles are added to the electrolyte solution little by little and dispersed therein. Further, an ultrasonic dispersion treatment is further continued for 60 seconds. In addition, the water temperature in the water tank is appropriately adjusted to 10° C. or higher and 40° C. or lower in the ultrasonic dispersion treatment.
(6) The electrolyte solution of the item (5) in which the toner or the toner particles have been dispersed using a pipette is added dropwise to the round-bottom beaker of the item (1) disposed in the sample stand, and the measurement concentration is adjusted to about 5%. Further, the measurement is performed until the number of measured particles reaches 50000.
(7) The weight-average particle diameter (D4) is calculated by analyzing the measurement data using the dedicated software attached to a device. Further, “average diameter” of the analysis/volume statistics (arithmetic average) screen is the weight-average particle diameter (D4) in a case where the graph/vol % is set with the dedicated software, and “average diameter” of “analysis/number statistics (arithmetic average)” screen is the number average particle diameter (D1) in a case where the graph/number % is set with the dedicated software.
Method of measuring average circularity of toner and proportion of particles having circularity of 0.900 or greater and 0.930 or less
The average circularity of the toner is measured using a flow type particle image analyzer “FPIA-3000” (manufactured by Sysmex Corporation) under measurement and analysis conditions during the calibration work.
An appropriate amount of alkylbenzene sulfonate serving as a surfactant is added to 20 mL of ion exchange water as a dispersant, 0.02 g of a measurement sample is added thereto, and a dispersion treatment is performed on the mixture for 2 minutes using a table top ultrasonic cleaner disperser (trade name: VS-150, manufactured by VELVO-CLEAR) at an oscillation frequency of 50 kHz and an electrical output of 150 watts to obtain a dispersion liquid for measurement. In this case, the dispersion liquid is appropriately cooled such that the temperature of the dispersion liquid is 10° C. or higher and 40° C. or lower.
The measurement is performed by using the flow type particle image analyzer equipped with a high-magnification objective lens (20 times) and a particle sheath “PSE-900A” (manufactured by Sysmex Corporation) as a sheath liquid. The dispersion liquid prepared by the above-described procedures is introduced to the flow type particle image analyzer, 3000 toner particles are measured in a total count mode and an HPF measurement mode, the binarization threshold value during particle analysis is set to 85%, and the particle diameter for analysis is limited to an equivalent circle diameter of 1.98 μm or greater and 19.92 μm or less to determine the average circularity of the toner. The external additive separated from the surface of the toner particles during the preparation of the dispersion liquid can be excluded from the measurement results by limiting the particle diameter.
The average circularity and the proportion (the deformation ratio or deformed toner ratio) of particles having a circularity of 0.900 or greater and 0.930 or less are calculated from the obtained analysis results.
In the measurement, automatic focus adjustment is performed using standard latex particles (for example, 5100A (trade name, manufactured by Duke Scientific Corporation) diluted with ion exchange water) before the start of measurement. Thereafter, focus adjustment can be performed every two hours from the start of measurement.
Method of removing external additive from toner to obtain toner particles
160 g of sucrose (manufactured by Kishida Chemical Co., Ltd.) is added to 100 mL of ion exchange water and dissolved in a hot water bath, thereby preparing a concentrated sucrose solution. 31 g of the concentrated sucrose solution and 6 mL of Contaminon N (10 mass % aqueous solution of neutral detergent for washing precision measuring machine with pH of 7, which is formed of nonionic surfactant, anionic surfactant, and organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) are poured into a centrifuge tube (volume of 50 ml). 1.0 g of the toner is added thereto, and the toner clumps are broken up with a spatula or the like. The centrifuge tube is shaken in a shaker (AS-IN, sold by AS ONE CORPORATION) at 300 spm (strokes per min) for 20 minutes.
After the centrifuge tube is shaken, the solution is transferred to a glass tube (50 mL) for a swing rotor and separated by a centrifuge (H-9R, manufactured by KOKUSAN Co., Ltd.) at 3500 rpm for 30 minutes.
The toner particles and the external additive are separated from each other by performing this operation. The toner particles separated into the uppermost layer are collected by a spatula or the like after visual confirming that the toner particles are sufficiently separated from the aqueous solution. The collected toner particles are filtered through a vacuum filter and dried by a dryer for 1 hour or longer, thereby obtaining a sample for measurement. This operation is performed a plurality of times to ensure the required amount.
Acid value of resin
The acid value is the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of the sample.
The acid value of the binder resin is measured in conformity with JIS K 0070-1992, and specifically, the acid value is measured by the following procedures.
(1) Preparation of reagent
1.0 g of phenolphthalein is dissolved in 90 ml of ethyl alcohol (95% by volume), and ion exchange water is added thereto to adjust the amount of the solution to 100 ml, thereby obtaining a phenolphthalein solution.
7 g of special grade potassium hydroxide is dissolved in 5 ml of water, and ethyl alcohol (95% by volume) is added thereto to adjust the amount of the solution to 11. The solution is poured to an alkali-resistant container such that contact with carbon dioxide or the like is avoided, and the resulting solution is allowed to stand for 3 days and filtered, thereby obtaining a potassium hydroxide solution. The obtained potassium hydroxide solution is stored in an alkali-resistant container. The factor of the potassium hydroxide solution is determined by placing 25 ml of 0.1 mol/l hydrochloric acid in an Erlenmeyer flask, adding several drops of the phenolphthalein solution thereto, performing titration with the potassium hydroxide solution, and calculating the amount of the potassium hydroxide solution required for neutralization. The 0.1 mol/l hydrochloric acid is prepared in conformity with JIS K 8001-1998 and used.
(A) Present test
2.0 g of a sample of a pulverized binder resin is precisely weighed in a 200 ml Erlenmeyer flask, and 100 ml of a mixed solution of toluene and ethanol (2:1) is added thereto to be dissolved therein for 5 hours. Next, several drops of the phenolphthalein solution are added thereto as an indicator, and the solution is titrated using the potassium hydroxide solution. Further, the time point when the light red color of the indicator continues for about 30 seconds is determined as the end point of the titration.
(B) Blank test
The titration is performed in the same manner as in the above-described operation except that the sample is not used (that is, only the mixed solution of toluene/ethanol (2:1) is used).
(3) The acid value is calculated by substituting the obtained results into the following equation.
Here, A represents the acid value (mgKOH/g), B represents the amount (ml) of the potassium hydroxide solution to be added in the blank test, C represents the amount (ml) of the potassium hydroxide solution to be added in the present test, f represents the factor of the potassium hydroxide solution, and S represents the sample (g). Content of boron in toner (ICP-AES)
The content of boron in the toner is quantified by an inductively coupled plasma atomic emission spectrometer (ICP-AES manufactured by Seiko Instruments Inc.).
As the pretreatment, 100.0 mg of the toner particles are subjected to acid decomposition by using 8.00 ml of 60% nitric acid (for atomic absorption spectrometry, manufactured by KANTO CHEMICAL CO., INC.). During the acid decomposition, the treatment is performed in a sealed container at an internal temperature of 220° C. for 1 hour using a microwave high-power sample pretreatment device ETHOS1600 (manufactured by Milestone General K.K.) to prepare a boron-containing solution sample. Thereafter, pure water is added thereto such that the total amount thereof reaches 50.00 g to obtain a measurement sample. A calibration curve is created, the amount of boron contained in each sample is quantified. Further, a blank obtained by adding pure water to 8.00 ml of nitric acid and adjusting the total amount thereof to 50.00 g is measured, and the amount of boron of the blank is subtracted from the amount of boron obtained above.
Hereinafter, the present disclosure will be described in more detail with reference to examples and comparative examples. The present disclosure is not limited to the following examples unless the gist thereof is overstepped. In the description of the following examples, “parts” are on a mass basis unless otherwise specified.
Synthesis of polyester resin 1
A flask provided with a stirring device, a nitrogen introduction pipe, a temperature sensor, and a rectifying tower was charged with the above-described monomers and heated to 195° C. for 1 hour, and it was confirmed that the mixture in the reaction system was uniformly stirred.
0.7 parts of tin distearate was added thereto with respect to 100 parts of these monomers. The temperature was increased from 195° C. to 240° C. over 5 hours while water which was further generated was distilled off, and a dehydration condensation reaction was further carried out at 240° C. for 2 hours. Next, the temperature was decreased to 190° C., 5 parts by mole of trimellitic anhydride was gradually added thereto, and the reaction was continued at 190° C. for 1 hour.
As a result, a polyester resin 1 having a glass transition temperature of 55.2° C., an acid value of 14.3 mgKOH/g, a hydroxyl value of 24.1 mgKOH/g, a weight-average molecular weight of 43600, and a number average molecular weight of 6200 was obtained.
A flask provided with a stirring device, a nitrogen introduction pipe, a temperature sensor, and a rectifying tower was charged with the above-described monomers and heated to 195° C. for 1 hour, and it was confirmed that the mixture in the reaction system was uniformly stirred.
0.7 parts of tin distearate was added thereto with respect to 100 parts of these monomers. The temperature was increased from 195° C. to 240° C. over 5 hours while water which was further generated was distilled off, and a dehydration condensation reaction was further carried out at 240° C. for 2 hours. Next, the temperature was decreased to 190° C., 5 parts by mole of trimellitic anhydride was gradually added thereto, and the reaction was continued at 190° C. for 4 hour.
As a result, a polyester resin 2 having a glass transition temperature of 56.2° C., an acid value of 10.0 mgKOH/g, a hydroxyl value of 20.1 mgKOH/g, a weight-average molecular weight of 74800, and a number average molecular weight of 10200 was obtained.
A flask provided with a stirring device, a nitrogen introduction pipe, a temperature sensor, and a rectifying tower was charged with the above-described monomers and heated to 195° C. for 1 hour, and it was confirmed that the mixture in the reaction system was uniformly stirred.
0.7 parts of tin distearate was added thereto with respect to 100 parts of these monomers. The temperature was increased from 195° C. to 240° C. over 5 hours while water which was further generated was distilled off, and a dehydration condensation reaction was further carried out at 240° C. for 2 hours. Next, the temperature was decreased to 190° C., 5 parts by mole of trimellitic anhydride was gradually added thereto, and the reaction was continued at 190° C. for 6 hours.
As a result, a polyester resin 3 having a glass transition temperature of 57.2° C., an acid value of 9.0 mgKOH/g, a hydroxyl value of 18.1 mgKOH/g, a weight-average molecular weight of 81000, and a number average molecular weight of 13200 was obtained.
Synthesis of polyester resin 4
A flask provided with a stirring device, a nitrogen introduction pipe, a temperature sensor, and a rectifying tower was charged with the above-described monomers and heated to 195° C. for 1 hour, and it was confirmed that the mixture in the reaction system was uniformly stirred.
0.7 parts of tin distearate was added thereto with respect to 100 parts of these monomers. The temperature was increased from 195° C. to 240° C. over 5 hours while water which was further generated was distilled off, and a dehydration condensation reaction was further carried out at 240° C. for 2 hours. Next, the temperature was decreased to 190° C., 8 parts by mole of trimellitic anhydride was gradually added thereto, and the reaction was continued at 190° C. for 1 hour.
As a result, a polyester resin 4 having a glass transition temperature of 58.5° C., an acid value of 30.0 mgKOH/g, a hydroxyl value of 18.1 mgKOH/g, a weight-average molecular weight of 38000, and a number average molecular weight of 9200 was obtained.
Synthesis of polyester resin 5
A flask provided with a stirring device, a nitrogen introduction pipe, a temperature sensor, and a rectifying tower was charged with the above-described monomers and heated to 195° C. for 1 hour, and it was confirmed that the mixture in the reaction system was uniformly stirred.
0.7 parts of tin distearate was added thereto with respect to 100 parts of these monomers. The temperature was increased from 195° C. to 240° C. over 5 hours while water which was further generated was distilled off, and a dehydration condensation reaction was further carried out at 240° C. for 2 hours. Next, the temperature was decreased to 190° C., 10 parts by mole of trimellitic anhydride was gradually added thereto, and the reaction was continued at 190° C. for 1 hour.
As a result, a polyester resin 5 having a glass transition temperature of 58.5° C., an acid value of 34.0 mgKOH/g, a hydroxyl value of 16.1 mgKOH/g, a weight-average molecular weight of 36000, and a number average molecular weight of 8700 was obtained.
Synthesis of polyester resin 6
A flask provided with a stirring device, a nitrogen introduction pipe, a temperature sensor, and a rectifying tower was charged with the above-described monomers and heated to 195° C. for 1 hour, and it was confirmed that the mixture in the reaction system was uniformly stirred. 1.0 parts of tin distearate was added thereto with respect to 100 parts of these monomers. The temperature was increased from 195° C. to 250° C. over 5 hours while water which was further generated was distilled off, and a dehydration condensation reaction was further carried out at 250° C. for 4 hours.
As a result, a polyester resin 6 having a glass transition temperature of 61.5° C., an acid value of 16.0 mgKOH/g, a hydroxyl value of 25.2 mgKOH/g, a weight-average molecular weight of 25200, and a number average molecular weight of 6100 was obtained.
Synthesis of polyester resin 7
A flask provided with a stirring device, a nitrogen introduction pipe, a temperature sensor, and a rectifying tower was charged with the above-described monomers and heated to 195° C. for 1 hour, and it was confirmed that the mixture in the reaction system was uniformly stirred. 1.0 parts of tin distearate was added thereto with respect to 100 parts of these monomers. The temperature was increased from 195° C. to 250° C. over 5 hours while water which was further generated was distilled off, and a dehydration condensation reaction was further carried out at 250° C. for 2 hours.
As a result, a polyester resin 7 having a glass transition temperature of 60.2° C., an acid value of 19.8 mgKOH/g, a hydroxyl value of 28.2 mgKOH/g, a weight-average molecular weight of 11200, and a number average molecular weight of 4100 was obtained.
Preparation of resin particle dispersion liquid 1
The methyl ethyl ketone and the isopropyl alcohol were added to a container. Thereafter, the polyester resin 1 was gradually added thereto, the mixture was stirred for complete dissolution, thereby obtaining a polyester resin 1-dissolved solution. The temperature of the container containing the polyester resin 1-dissolved solution was set to 65° C., a 10% ammonia aqueous solution was gradually added dropwise to the container so that the total amount of the solution reached 5 parts while the mixture was stirred, and 230 parts of ion exchange water was further gradually added dropwise thereto at a rate of 10 ml/min to cause phase inversion emulsification. Further, desolvation was performed under reduced pressure using an evaporator, thereby obtaining a resin particle dispersion liquid 1 of the polyester resin 1. The volume average particle diameter of the resin particles was 135 nm. Further, the solid content of the resin particles was adjusted to 20% with ion exchange water.
Preparation of resin particle dispersion liquids 2 to 7
Resin particle dispersion liquids 2 to 7 were obtained in the same manner as described above except that the polyester resins 2 to 7 were used in place of the polyester resin 1 in the preparation of the resin particle dispersion liquid 1. The obtained resin particle dispersion liquids are listed in Table 1.
An aqueous dispersion liquid (colorant fine particle dispersion liquid) in which the concentration of colorant fine particles was 20% was prepared by mixing the above-described components, dispersing the components using a high-pressure impact type disperser NANOMIZER (manufactured by YOSHIDA KIKAI CO., LTD.) for about 1 hour, and dispersing the colorant.
Preparation of release agent particle dispersion liquid 1
A mixing container equipped with a stirring device was charged with the above-described components, and the mixture was heated to 90° C., circulated through CLEARMIX W-MOTION (manufactured by M Technique Co., Ltd.), and subjected to a dispersion treatment for 60 minutes. The dispersion treatment was performed under the following conditions.
The mixture was cooled to 40° C. under cooling treatment conditions of a rotor rotation speed of 1000 r/min, a screen rotation speed of 0 r/min, and a cooling rate of 10° C./min after the dispersion treatment, thereby obtaining a release agent particle dispersion liquid having a volume average particle diameter of 160 nm and a solid content of 20%.
Preparation of release agent particle dispersion liquid 2
A mixing container equipped with a stirring device was charged with the above-described components, and the mixture was heated to 90° C., circulated through CLEARMIX W-MOTION (manufactured by M Technique Co., Ltd.), and subjected to a dispersion treatment for 60 minutes. The dispersion treatment was performed under the following conditions.
The mixture was cooled to 40° C. under cooling treatment conditions of a rotor rotation speed of 1000 r/min, a screen rotation speed of 0 r/min, and a cooling rate of 10° C./min after the dispersion treatment, thereby obtaining a release agent particle dispersion liquid having a volume average particle diameter of 170 nm and a solid content of 20%.
Production of toner suspended particles 1
First, the above-described materials were added to a round stainless steel flask and mixed in a core formation step. Next, the mixture was dispersed using a homogenizer ULTRA-TURRAX T50 (manufactured by IKA) at 5000 r/min for 10 minutes. A 1.0% nitric acid aqueous solution was added thereto to adjust the pH to 3.0, and the mixed solution was heated to 45° C. while the rotation speed at which the mixed solution was stirred in a heating water bath using a stirring blade was appropriately adjusted.
The volume average particle diameter of the formed aggregated particles was appropriately confirmed by using COULTER Multisizer III, and in a case where aggregated particles (cores) having a diameter of 5.0 μm were formed, the following materials were added thereto in a shell formation step and further stirred for 1 hour, thereby forming a shell.
Thereafter, the pH of the mixture was adjusted to 9.0 by using a 5% sodium hydroxide aqueous solution, continuously stirred, and heated to 90° C. in the spheronization step.
Thereafter, the average circularity of the formed aggregated particles was appropriately measured by a flow type particle image analyzer “FPIA-3000” (manufactured by Sysmex Corporation).
The aggregated particles were heated (the heating time was 3 hours) until the average circularity thereof reached 0.970. Next, the particles were cooled to 25° C. by quickly adding ice thereto in the cooling step such that the cooling rate was set to 10° C./sec or greater, thereby obtaining a toner particle dispersion liquid 1.
Production of toner suspended particles 2 to 17
Toner suspended particles 2 to 17 were obtained in the same manner as described above except that the conditions were changed as listed in Table 2 in the production of the toner suspended particles 1.
Production of toner suspended particles 18
Toner suspended particles 18 were obtained in the same manner as that for the toner suspended particles 1 except that the shell formation step was performed after aggregated particles (cores) having a number average particle diameter of 3.4 μm were formed in the production of the toner suspended particles 1.
Production of toner suspended particles 19
Toner suspended particles 19 were obtained in the same manner as that for the toner suspended particles 1 except that the shell formation step was performed after aggregated particles (cores) having a number average particle diameter of 6.8 μm were formed in the production of the toner suspended particles 1.
Magnesium sulfate aqueous solution: 2 mass % magnesium sulfate aqueous solution Production of toner particles 1
100 parts of the toner suspended particles 1 were filtered, subjected to solid-liquid separation, and washed with ion exchange water.
100 parts of the toner suspended particles were washed by performing filtration washing 20 times using 200 parts of ion exchange water.
After completion of the washing, the toner suspended particles were dried using a vacuum dryer, thereby obtaining toner particles 1 having a number average particle diameter (D1) of 6.7 μm. The physical properties of the obtained toner particles 1 are listed in Table 3.
Production of toner particles 2 and 5 to 21
Toner particles 2 and 5 to 21 were obtained in the same manner as described above except that the conditions were changed as listed in Table 3 in the production of the toner particles 1. The physical properties of the obtained toner particles are listed in Table 3.
Production of toner particles 3
Toner particles 3 were obtained in the same manner as that for the toner suspended particles 1 after 80 parts of the toner suspended particles 3 and 20 parts of the toner suspended particles 4 were mixed. The physical properties of the obtained toner particles are listed in Table 3.
Production of toner particles 4 and 22 to 24
Toner particles 4 and 22 to 24 were obtained in the same manner as described above except that the conditions were changed as listed in Table 3 in the production of the toner particles 3. The physical properties of the obtained toner particles are listed in Table 3.
Production Example of silica particles A1
Silica particles A1 were produced in the following manner.
Oxygen gas was supplied to a burner to ignite the ignition burner, hydrogen gas was supplied to the burner to form a flame, and silicon tetrachloride which was a raw material was added thereto for gasification, thereby obtaining silica powder. The specific method was based on the description of Japanese Patent Laid-Open No. 2002-3213. The obtained silica powder was recovered, transferred to an electric furnace, and spread in a thin layer, and subjected to a heat treatment at 900° C. to be sintered and aggregated. Thereafter, 100 parts of the obtained silica fine particles were subjected to a hydrophobic treatment by adding 10 parts of hexamethyldisilazane thereto as a surface treatment agent, thereby obtaining silica particles A1. The physical properties (the solidity and the major axis) of the silica particles A1 are listed in Table 4.
Production Examples of silica particles A2 to A4
Silica particles A2 to A4 were obtained by adjusting the amount of silicon tetrachloride, the amount of oxygen gas, the amount of hydrogen gas, the silica concentration, the retention time, and the surface treatment based on the description of Japanese Patent Laid-Open No. 2002-3213. The physical properties (the solidity and the major axis) of the silica particles A2 to A4 are listed in Table 4.
Production Examples of silica particles A5
Silica particles A5 were produced in the following manner.
A 1.5 L glass reaction container equipped with a stirrer, a dropping nozzle, and a thermometer was charged with 150 parts of 5% ammonia water to obtain an alkaline catalyst solution.
The temperature of the alkaline catalyst solution was adjusted to 50° C., 100 parts of tetraethoxysilane and 50 parts of 5% ammonia water were simultaneously added dropwise thereto while the solution was stirred, and the solution was allowed to react for 8 hours, thereby obtaining a silica fine particle dispersion liquid. Thereafter, the obtained silica fine particle dispersion liquid was dried by spray drying, and disintegrated in a pin mill, thereby obtaining silica particles A5. The physical properties (the solidity and the major axis) of the silica particles A5 are listed in Table 4.
Production Example of toner 1
The above-described materials were mixed at 3000 rpm for 7.5 minutes using a Henschel mixer FM10C (manufactured by NIPPON COKE & ENGINEERING CO., LTD.), thereby obtaining a toner 1. The external addition conditions for the toner 1 are listed in Table 5.
Further, the results obtained by performing various analysis on the toner 1 are listed in Table 5.
Toners 2 to 39 were obtained in the same manner as described above except that the conditions were changed as listed in Tables 5-1 and 5-2 in the production example for the toner 1.
Color Laser Jet Enterprise 6701dn (manufactured by HP) was prepared as an evaluation machine and modified such that the printing speed thereof was changeable. Further, a process cartridge of the present disclosure which was mountable on the above-described evaluation machine and set to have a peripheral speed ratio R of 1.2 was prepared and filled with 150 g of the toner 1.
The process cartridge was allowed to stand in a low-temperature and low-humidity environment (at a temperature of 15° C. and a humidity of 10% RH). The image evaluation was performed by allowing the process cartridge to stand for 3 days, outputting solid black images and halftone images, continuously feeding (printing) 100 sheets of paper of horizontal lines with an image ratio of 1%, and outputting solid black images and halftone images. Further, A4 size GF-C081 (manufactured by Canon Inc., 81.4 g/m2) was used as the transfer material, and the density was measured by using X-rite exact advance (manufactured by X-rite, Inc.). The evaluation results are listed in Table 6. Evaluation of density unevenness in halftone images (evaluation of adverse effects in images accompanied by initial development ghosts)
A 15 mm square solid black image and then a full halftone image were printed on the lead edge portion of one sheet as an image pattern. Further, density unevenness with a developer carrying roller cycle, which appeared in the halftone portion, was evaluated, and a difference in image density between the image area where the density unevenness occurred and the halftone portion was confirmed.
Rank A: The density unevenness was not found.
Rank B: Extremely slight density unevenness was found (density unevenness was confirmed, and the difference in image density was less than 0.05).
Rank C: Slight density unevenness was found (density unevenness was confirmed, and the difference in image density was less than 0.10).
Rank D: Significant density unevenness was found (density unevenness was confirmed, and the difference in image density was 0.10 or greater).
Next, the image evaluation was performed by continuously feeding (printing) 100 sheets of paper of horizontal lines with an image ratio of 1% and outputting solid black images and halftone images.
Evaluation of density unevenness in halftone images (evaluation 1 of adverse effects in images accompanied by toner aggregation)
A 15 mm square solid black image and then a full halftone image were printed on the lead edge portion of one sheet as an image pattern. Further, density unevenness with a developer carrying roller cycle, which appeared in the halftone portion, was evaluated, and a difference in image density between the image area where the density unevenness occurred and the halftone portion was confirmed.
Rank A: The density unevenness was not found.
Rank B: Extremely slight density unevenness was found (density unevenness was confirmed, and the difference in image density was less than 0.05).
Rank C: Slight density unevenness was found (density unevenness was confirmed, and the difference in image density was less than 0.10).
Rank D: Significant density unevenness was found (density unevenness was confirmed, and the difference in image density was 0.10 or greater).
Evaluation of development stripes in halftone images
Next, full halftone images were printed as the image pattern. Further, the presence or absence of development stripes which appeared in halftone portion was evaluated.
Rank A: Development stripes were not found.
Rank B: Extremely slight development stripes were found (about one extremely thin stripe was found).
Rank C: Slight development stripes were found (about two to three extremely thin stripes were found).
Rank D: Significant development stripes were found (four or more extremely thin stripes or clear stripes were found).
Fogging evaluation
The fogging was measured by using REFLECTOMETER MODEL TC-6DS (manufactured by Tokyo Denshoku Co., Ltd.). A green filter was used as the filter. A drum (electrostatic latent image carrying member) when a solid white image was output was taped with Mylar tape, the fogging was calculated by subtracting the reflectivity of the Mylar tape attached onto paper from the Macbeth density of the Mylar tape attached directly onto paper, and the evaluation was performed according to the following determination criteria.
Fogging (%)=reflectivity (%) of tape directly attached onto paper−reflectivity (%) of tape taped on drum
Determination criteria for fogging evaluation
Rank A: The fogging was less than 1.0%.
Rank B: The fogging was 1.0% or greater and less than 2.0%.
Rank C: The fogging was 2.0% or greater and less than 4.0%.
Rank D: The fogging was 4.0% or greater.
The process cartridge configuration was changed as described below, and the evaluation was performed in the same manner as in Example 1. The evaluation results of Examples 2 to 37 and Comparative Examples 1 to 11 are listed in Table 6. Toner: The toner was changed to the toner described in the production example of the toner.
Rotation: The movement direction of the surface of the developing roller was adjusted to be opposite to (counter) or same as (with) the movement direction of the surface of the toner supplying roller in the position where the development roller was in contact with the toner supplying roller.
Peripheral speed ratio R: The peripheral speed ratio between the developing roller and the toner supplying roller was adjusted.
Closest distance: The closest distance 37a between the inner wall and the toner supplying roller 34 was adjusted.
While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2023-147440, filed Sep. 12, 2023 and Japanese Patent Application No. 2024-139816, filed Aug. 21, 2024, which are hereby incorporated by reference herein in their entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-147440 | Sep 2023 | JP | national |
| 2024-139816 | Aug 2024 | JP | national |
