JP2004109550A - Image carrying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact image carrying device having improved cleaning performance. <P>SOLUTION: When a first full color image K1 is transferred to a recording medium by applying a positive bias voltage with a secondary transfer medium 36 and a secondary remaining toner RT2 which remains after removal with a secondary cleaning means 35 is removed, the secondary transfer means 36 applies a negative bias voltage to a secondary image carrier 30 to negatively charge the secondary remaining toner RT2. Once the toner RT2 reaches the secondary cleaning means 35, a bias roller 35b applies a positive bias voltage to the secondary image carrier 30 through a fur brush roller 35a, accordingly the toner RT2 sticks sequentially to the fur brush roller 35a and is removed from the carrier 30. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, when an image formed by a charged toner is carried on an image carrier, and the image on the image carrier is transferred to a transfer material, a transfer means having a polarity opposite to that of the charged toner by a transfer unit is transferred to the image carrier. The present invention relates to an image bearing device for applying a bias voltage while applying a bias voltage having a polarity opposite to the charging polarity of charged toner by a cleaning unit, and an image forming apparatus including the image bearing device, such as a printer, a facsimile, or a copying machine.
[0002]
[Prior art]
This type of conventional image forming apparatus includes an image forming unit that forms a full-color image using a charged toner, a primary image holding device that transfers and holds the formed image, and an image that is transferred by the primary image holding device. A secondary image carrying device for carrying the image, a fixing device for fixing the transferred image to a recording medium, and the like are provided. In addition, the secondary image bearing device includes one driving roller, a plurality of driven rollers, a belt-shaped secondary image bearing member wrapped around them, and a secondary image bearing member having the same polarity as the charged polarity of the charged toner. A transfer unit that applies a bias voltage to transfer an image to a transfer material; and a cleaning unit that removes untransferred toner on the secondary image carrier after transfer by applying a bias voltage having a polarity opposite to the charging polarity of the charged toner. Provide means.
[0003]
When an image is simultaneously formed on both sides of a recording medium using this image forming apparatus, the first full-color image formed by the image forming means using a charged toner charged in advance to a negative polarity is used as the primary image carrier. After the image is electrostatically transferred to the primary image carrier, the image is electrostatically transferred to the secondary image carrier in a transfer nip formed between the primary image carrier and the secondary image carrier. Thereafter, a second full-color image is formed by the image forming means and transferred to the primary image carrier.
[0004]
Then, the transfer material is fed into the transfer nip at the same time as the second full-color image carried by the primary image carrier and the first full-color image carried by the secondary image carrier, and the second full-color image is transferred. It is transferred electrostatically to the surface of the material. Thereafter, a positive bias voltage is applied from the front side of the transfer material by the transfer unit, the first full-color image is transferred to the back surface of the recording medium, and the first full-color image and the second full-color image are transferred to the recording medium by the fixing device. Are fixed, and the recording medium is discharged out of the apparatus.
[0005]
On the other hand, the untransferred toner on the secondary image carrier after the transfer is electrostatically removed by applying a positive bias voltage to the secondary cleaning means, and prepares for the next image transfer.
[0006]
However, some of the untransferred toner on the secondary image carrier may be positively charged by the transfer unit applying a positive bias voltage, or may not have a charged polarity, and may not be used for secondary cleaning. However, there is a problem that the cleaning performance is poor because it cannot be completely removed by the means.
[0007]
Therefore, a pre-cleaning charger or the like for applying a negative bias voltage is provided in front of the secondary cleaning means, and the untransferred toner on the secondary image carrier is negatively charged. There is one in which the cleaning performance is improved by surely removing the particles.
[Patent Document 1]
JP 2000-352889 A
[0008]
[Problems to be solved by the invention]
However, if the pre-cleaning charger is provided as a separate device, there is a problem that the image forming apparatus becomes complicated and large.
[0009]
Accordingly, a first object of the present invention is to provide an image bearing device that is compact and has improved cleaning performance.
[0010]
A second object of the present invention is to obtain a high-definition image.
[0011]
A third object of the present invention is to efficiently transfer an image.
[0012]
A fourth object of the present invention is to provide an image forming apparatus provided with an image carrier that achieves each of the above objects.
[0013]
[Means for Solving the Problems]
Therefore, according to the first aspect of the present invention, in order to achieve the first object, an image formed with charged toner is carried on an image carrier, and the image on the image carrier is transferred to a transfer material. An image bearing device that applies a bias voltage having a polarity opposite to the charging polarity of the charged toner to the image bearing member by a transfer unit, and applies a bias voltage having a polarity opposite to the charging polarity of the charged toner by a cleaning unit. When the untransferred toner on the image carrier is removed, a bias voltage having the same polarity as the charge polarity of the charged toner is applied to the image carrier by the transfer unit.
[0014]
According to a second aspect of the present invention, when the untransferred toner is removed, the transfer unit has the same polarity as the charging polarity in order to achieve the first object. Are superimposed on each other.
[0015]
According to a third aspect of the present invention, in order to achieve the first object, the image transfer apparatus according to the first or second aspect is characterized in that the untransferred toner is removed after a jam. And
[0016]
According to a fourth aspect of the present invention, in the image bearing device according to the first or second aspect, when the untransferred toner is removed, the transfer material is formed on the transfer material in order to achieve the first and second objects. It is characterized in that each image transfer is completed.
[0017]
According to a fifth aspect of the present invention, in the image bearing device according to the first or second aspect, the untransferred toner is removed every time a job is completed. Features.
[0018]
According to a sixth aspect of the present invention, in order to achieve the second object, in the image bearing device according to any one of the first to fifth aspects, the average circularity of the charged toner is 0.90 to 0. .99.
[0019]
According to a seventh aspect of the present invention, in order to achieve the second object, in the image bearing device according to any one of the first to sixth aspects, the shape factor SF-1 of the charged toner is 120 to 180. And the shape factor SF-2 is 120 to 190.
[0020]
According to an eighth aspect of the present invention, in order to achieve the second object, in the image bearing device according to any one of the first to seventh aspects, a volume average particle diameter with respect to a number average particle diameter of the charged toner is provided. Is 1.05 to 1.30.
[0021]
According to a ninth aspect of the present invention, in order to achieve the fourth object, an image forming apparatus includes the image bearing device according to any one of the first to eighth aspects.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows an overall schematic configuration of a simultaneous double-sided image forming printer which is an example of an image forming apparatus having an image bearing device of the present invention.
[0023]
The illustrated simultaneous double-sided image forming printer is capable of forming images almost simultaneously on both the front and back surfaces of a recording medium (transfer material) P such as a sheet of paper or an OHP film. As shown in FIG. For example, four image forming apparatuses A, B, C, and D, a primary image holding device E, a secondary image holding device F, a medium conveying device G, a fixing device H, a discharge stack device I, a toner replenishing device J, and the like are provided. ing.
[0024]
The four image forming apparatuses A, B, C, and D form different single-color images using toners (charged toners) of respective colors of yellow, magenta, cyan, and black, and each rotatably support a drum. Image forming carriers 12 are arranged in tandem, and charging means 13, developing means 14, image forming transferring means 15, image forming cleaning means 16, image forming and discharging means 17 are provided around each image forming body 12. Is placed. Under the image forming devices A, B, C, and D, a common exposing unit 18 for exposing each of the image forming members 12 separately is provided.
[0025]
The image carrier 12 is a photoconductor in which a layer of an organic semiconductor, which is a photoconductive substance, is provided on the surface of an aluminum cylinder having a diameter of about 30 to 100 mm. In this example, a drum shape is used, but a belt shape may be used.
[0026]
The exposure unit 18 irradiates light from an LD light source (not shown) toward the surface of the image carrier 12 with an optical component (not shown) by a known laser method, and scans the surface of the image carrier 12. To write to it. In this example, a laser method is used, but an exposure method using an LED array and an imaging component may be adopted.
[0027]
The primary image carrier E transfers and carries the images formed by the respective image forming devices A, B, C, and D, and the belt-shaped primary image carrier 20 is attached to each image carrier 12. In contact therewith, three primary rollers 21, 22 and 23 are passed between each image carrier 12 and each corresponding image transfer means 15, and a primary cleaning means 24 and a primary transfer means 25 are arranged around the three primary rollers 21, 22 and 23. are doing.
[0028]
The primary image carrier 20 is a belt made of a resin film or rubber having a thickness of 50 μm to 600 μm, and has a resistance value that enables transfer of toner from each image carrier 12.
[0029]
The secondary image carrying device (image carrying device) F is for carrying the image transferred by the primary image carrying device E by primary transfer, and carries the belt-like secondary image carrying material (image carrying material) 30 to the primary. A predetermined transfer nip is formed therebetween by contacting the image carrier 20, and is passed between the primary image carrier 20 and the primary transfer means 25 and wrapped around three secondary rollers 31, 33, and 34 to rotate around the image carrier 20. , A secondary cleaning unit (cleaning unit) 35 and a secondary transfer unit (transfer unit) 36 are disposed.
[0030]
Like the primary image carrier 20, the secondary image carrier 30 is a resin film or rubber-based belt having a thickness of 50 μm to 600 μm, and has a resistance value at which toner can be transferred from the primary image carrier 20. Have.
[0031]
The medium conveying device G conveys the recording medium P through a medium conveying path extending from the lower side to the upper side in the figure by passing between the primary image carrier E and the secondary image carrier F, and is provided in two upper and lower stages. And a supply roller 41 for sequentially feeding the recording media P one by one from above from each medium storage container 40, and a medium guide for guiding the sent recording media P. 42, a registration roller 43 for abutting and stopping the leading end of the recording medium P guided and conveyed by the medium guide 42, a discharge guide 44 for guiding the recording medium P after image fixing, and a guide for the discharge guide 44. And a discharge roller 45 for discharging the recording medium P conveyed in the direction of arrow a.
[0032]
The fixing device H fixes a transfer image transferred from the primary image bearing device E and the secondary image bearing device F to the recording medium P, and includes a pair of heating rollers 47.
[0033]
The discharge stack device I is for stacking the recording medium P after image fixing by the fixing device H, and includes a stack portion 50 formed on the outer cover 10.
[0034]
The toner replenishing device J supplies new toner to each of the image forming devices A, B, C, and D using a powder pump or the like. The toner replenishing device J includes a toner cartridge 53 for each color in a toner storage unit 52.
[0035]
When a color image is formed on both the front and back sides of the recording medium P by the simultaneous double-sided image forming printer, the image forming body 12 and the primary rollers 21, 22 and 23 are controlled based on a print signal from a host (not shown). One of them, one of the secondary rollers 31, 33 and 34, the supply roller 41, etc., are rotated with timing.
[0036]
In each of the image forming apparatuses A, B, C, and D, as each image forming carrier 12 rotates clockwise in FIG. Writing is performed with the individual writing light from 18 to form a latent image for each color, and toner of each color is adhered by each developing unit 14 to form a toner image for each color on each image forming carrier 12. I do. In the illustrated example, at this time, the charge polarity of the toner on the image carrier 12 is negative.
[0037]
In the primary image carrier E, one of the primary rollers 21, 22, and 23 is rotated and the other two rollers are driven to rotate, so that the primary image carrier 20 is synchronized with the image carrier 12 in a reverse direction in the figure. The toner image is rotated and conveyed clockwise, and a positive bias voltage is applied to the primary image carrier 20 by each of the image forming / transferring means 15 to sequentially transfer the toner images on the image carrier 12, and four colors are superimposed. Form a first full-color image (image).
[0038]
After the image transfer, the image forming carriers 12 of the respective image forming apparatuses A, B, C, and D remove the residual toner by the image forming cleaning unit 16 and remove the charge by the image forming and removing unit 17. Thereafter, each of the charging means 13 is charged again, writing is performed by the exposure means 18, development is performed by each of the developing means 14, and a toner image of each color is formed again on each image forming carrier 12.
[0039]
In the secondary image carrier F, one of the secondary rollers 31, 33, and 34 is rotated and the other roller is driven to rotate, so that the secondary image carrier 30 is synchronized with the primary image carrier 20 in the figure. The paper is rotated clockwise, and the primary transfer unit 25 applies a positive bias voltage to the secondary image carrier 30 to transfer the image on the primary image carrier 20. At this time, the secondary cleaning unit 35 is in a non-cleaning state in which the secondary cleaning unit 35 is rotated about a support shaft (not shown) and separated from the secondary image carrier 30.
[0040]
After the image transfer, the primary image carrier 20 of the primary image carrier E electrostatically removes the residual toner by the primary cleaning unit 24. Thereafter, the images on the image carrier 12 are sequentially transferred onto the primary image carrier 20 again by the respective image transfer means 15 to form a second full-color image in which four colors are superimposed.
[0041]
After the image transfer, the image forming carriers 12 of the respective image forming apparatuses A, B, C, and D remove the residual toner by the image forming cleaning unit 16 and remove the charge by the image forming and discharging unit 17 to perform the next image forming cycle. Prepare for.
[0042]
On the other hand, in the medium transporting device G, one of the supply rollers 41 is selectively rotated as appropriate to feed out the recording medium P in the medium storage container 40, and guided by the medium guide 42 so that the leading end abuts between the registration rollers 43. The registration roller 43 is rotated in synchronization with the first full-color image and the second full-color image described above, and is sent to the transfer nip between the primary image carrier 20 and the secondary image carrier 30.
[0043]
First, a positive bias voltage is applied by the primary transfer unit 25 from the back surface side of the recording medium P at the transfer nip Tr, and the second full-color image on the primary image carrier 20 is transferred to the front surface of the recording medium P. Then, when the recording medium P is slightly conveyed upward, a positive bias voltage is applied by the secondary transfer means 36 from the front side to convert the first full-color image on the secondary image carrier 30 to the recording medium P. Transfer to back side. Thereafter, the recording medium P on which the image has been transferred to the front and back surfaces is guided to the fixing device H, and heat and pressure are applied through a pair of heating rollers 47 to fix the transferred images on both surfaces. At 45, the sheet is discharged out of the outer cover 10, and is stacked face down on the stack section 50 of the discharge stack apparatus I with its surface facing down.
[0044]
Therefore, the second page is formed first as a first full-color image, then the first page is formed later as a second full-color image, and the subsequent pages are similarly formed first to form a recording medium P When the image is transferred to the back side, the previous page is formed later, transferred to the front side, and output face down, the recording medium P can be arranged in the page order on the stack unit 50.
[0045]
At this time, using a known image processing technique, the second full-color image on the primary image carrier 20 is a normal image on the image carrier 12 and the first full-color image on the secondary image carrier 30. Needs to be a reverse image, ie, a mirror image, on the image carrier 12.
[0046]
After the image transfer, the primary image carrier 20 of the primary image carrier E removes residual toner by the primary cleaning unit 24. In addition, the secondary image carrier 30 of the secondary image carrier F rotates the secondary cleaning means 35 about the support shaft 56 in advance and comes into contact with the secondary image carrier 30 to be in a cleaning state. The residual toner is removed by the secondary cleaning unit 35 to prepare for the next image carrying.
[0047]
When the toner in each developing unit 14 is used up, the toner of the same color is supplied from a corresponding toner cartridge 53 of the toner storage unit 52 of the toner supply unit J by a powder pump or the like.
[0048]
When the conveyance of the recording medium P is hindered by the jam, the front cover 10A of the outer cover 10 is opened in the direction of the arrow d about the support shaft 55, and the medium conveyance path is opened to perform the jam processing.
[0049]
When a full-color image is formed on one side of the recording medium P by the simultaneous double-sided image forming printer, the image formed on each of the image forming members 12 of the image forming devices A, B, C, and D is used as a primary image holding device E After the image is transferred to the primary image carrier 20, the image is sequentially transferred directly to one side of the recording medium P conveyed by the medium conveying device G without being transferred to the secondary image carrier 30 of the secondary image carrier F. To do. Then, the transferred image is fixed by the fixing device H, and is discharged face-down to the discharge stack device I in a page order.
[0050]
Further, when a two-color image or a monochrome image is formed on the recording medium P by the illustrated printer, the image is formed using the image forming device of the corresponding color among the four image forming devices A, B, C, and D. Then, the image is transferred to the recording medium P via the primary image carrier 20 of the primary image carrier E and the secondary image carrier 30 of the secondary image carrier F.
[0051]
By the way, the secondary transfer unit 36 of the secondary image carrier F transfers the first full-color image K1 onto the recording medium P, and then removes the untransferred toner remaining on the secondary image carrier 30 when removing the secondary image. A negative bias voltage having the same polarity as that of the toner can be applied to the carrier 30.
[0052]
Further, the secondary cleaning means 35 has a fur brush roller 35a rotatably provided therein so that the tip of an elastic and conductive fine fiber comes into contact with the secondary image carrier 30. A conductive bias roller 35b is rotatably provided so that the tips of the fine fibers of the roller 35a are in contact with each other. Further, a blade 35c is provided so as to contact the surface of the bias roller 35b, and a toner storage section 35d for storing residual toner is provided below the blade 35c.
[0053]
The rotation of the fur brush roller 35a and the bias roller 35b is transmitted from a drive motor via a gear (not shown).
[0054]
In order to remove the residual toner on the secondary image carrier 30 by the secondary image carrier F configured as described above, as shown in FIG. It turns in the direction of f to be in the cleaning state. Then, the drive motor is rotated to rotate the fur brush roller 35a clockwise and the bias roller 35b counterclockwise in the figure. Further, a positive bias voltage is applied to the secondary image carrier 30 by a bias roller 35b via a fur brush roller 35a.
[0055]
Then, the residual toner RT1 remaining on the secondary image carrier 30 after the first full-color image K1 is transferred to the recording medium P by the secondary transfer means 36 is sequentially electrostatically adhered to the fur brush roller 35a. Remove. At this time, of the residual toner RT1, the negatively charged toner adheres to the fur brush roller 35a and is then transferred to the surface of the bias roller 35b. Then, the residual toner RT1 attached to the surface of the bias roller 35b is scraped off by the blade 35c, and is stored in the toner storage section 35d.
[0056]
On the other hand, of the residual toner RT1, those that are positively charged and those that are not positively or negatively charged do not adhere to the fur brush roller 35a, but remain on the secondary residual toner (untransferred toner) RT2. As a result, the sheet is conveyed while adhering to the secondary image carrier 30.
[0057]
When the secondary residual toner is removed after transferring the first full-color image K1 onto the recording medium P, the secondary transfer means 36 applies the same polarity as the charged polarity of the toner, that is, a negative bias voltage, to the secondary image carrier 30. Is applied. As a result, the secondary residual toner RT2 on the secondary image carrier 30 is sequentially charged negatively and transported while passing through the secondary transfer means 36.
[0058]
Then, as shown in FIG. 3, when the secondary residual toner RT2 reaches the secondary cleaning unit 35, the bias roller 35b applies a positive bias voltage to the secondary image carrier 30 via the fur brush roller 35a. Then, the secondary residual toner RT2 sequentially adheres to the fur brush roller 35a. Then, the secondary residual toner RT2 is removed from the secondary image carrier 30, and the secondary image carrier 30 is ready to carry the next full-color image. In this way, every time the first full-color image K1 is transferred to the recording medium P by the secondary transfer means 36, the secondary residual toner RT2 is removed.
[0059]
On the other hand, the secondary residual toner RT2 attached to the fur brush roller 35a is transferred to the surface of the bias roller 35b. Then, the secondary residual toner RT2 attached to the surface of the bias roller 35b is scraped off by the blade 35c, and is stored in the toner storage section 35d.
[0060]
Then, the secondary cleaning unit 35 rotates around the support shaft 56 in the direction of arrow g in preparation for the next transfer, and enters the non-cleaning state.
[0061]
In the above-described example, when the secondary residual toner RT2 is removed after the first full-color image K1 is transferred to the recording medium P, the secondary transfer unit 36 superimposes an AC bias having the same polarity as the toner. Is also good.
[0062]
In the above-described example, the secondary residual toner RT2 is removed by the secondary transfer unit 36 each time the transfer of the first full-color image K1 onto the recording medium P is completed. However, the present invention is not limited to this. Instead, for example, the secondary residual toner RT2 may be removed every time the job is completed.
[0063]
Further, a jam occurs in the medium conveyance device G, the secondary image carrier F, the fixing device H, and the like on the conveyance path of the recording medium P, and a part of the first full-color image K1 on the secondary image carrier 30 or When the transfer of the image is stopped while carrying all the untransferred toner, the untransferred toner may be removed after the jam is eliminated.
[0064]
In addition, in the above-described example, the secondary transfer unit 36 removes the secondary residual toner RT2 after transferring the first full-color image K1 onto the recording medium P, but the present invention is not limited to this. Instead, after the first full-color image K1 is transferred to the secondary image carrier 30 by the primary transfer means 25, or after the second full-color image K2 is transferred to the recording medium P by the primary transfer means 25, A negative bias voltage is applied to the image carrier 20 by the primary transfer unit 25 to remove the secondary residual toner (untransferred toner) on the primary image carrier 20 that cannot be removed by the primary cleaning unit 24. You may.
[0065]
Further, in the above-described example, the secondary transfer unit 36 is provided outside the rotation center of the secondary image carrier 30, but the present invention is not limited to this, and the rotation of the secondary image carrier 30 It may be provided inside the center. In this case, a foamed rubber sponge conductive roller, a brush made of fine fibers having elasticity and conductivity, a fur brush roller, and the like are provided in contact with the secondary image carrier 30. Then, a bias voltage having the same polarity as the charged polarity of the charged toner is applied to weaken the adsorbing force between the secondary image carrier 30 and the secondary residual toner RT2, so that the secondary cleaning unit 35 can easily adsorb and remove the toner. .
[0066]
The toner of each color used in the present invention has an average circularity of 0.90 to 0.99, a shape factor SF-1 of 120 to 180, a shape factor SF-2 of 120 to 190, and a number average particle diameter (Dn). When the ratio of the volume average particle diameter (Dv) to (Dv / Dn) is 1.05 to 1.30, a high-definition image can be obtained.
[0067]
The average circularity is more preferably 0.93 to 0.97, and particles having a circularity of less than 0.94 are preferably 10% or less. The dry toner having a ratio (Dv / Dn) of more preferably 1.10 to 1.25 is preferable.
[0068]
Here, the average circularity is measured using a flow-type particle analyzer FPIA-2100 manufactured by Toa Medical Electronics Co., Ltd. in the following manner. That is, 0.1 to 0.5 ml of a surfactant, preferably an alkylbenzenesulfonate, is added as a dispersant to a container containing 100 to 150 ml of water from which impurity solids have been removed in advance. Then, about 0.1 to 0.5 g of a toner as a measurement sample is added. The suspension in which the toner has been dispersed is subjected to dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser to make the concentration of the dispersion 3000 to 10000 / μl, and then the shape and distribution of the toner are measured by the analyzer. Gain by doing.
[0069]
The following can be said about the average circularity measured in this way.
[0070]
With an irregularly shaped toner having an average circularity of less than 0.90 and too far from a sphere, satisfactory transferability and high quality images free of dust cannot be obtained. Further, when the average circularity exceeds 0.99, in a system employing blade cleaning or the like, poor cleaning of the photoreceptor and the transfer belt occurs to cause stain on an image.
[0071]
For example, when an image with a low image area ratio is output, the amount of residual toner is small, and there is no problem with cleaning failure. If an untransferred image remains on the photoreceptor due to a defect or the like, defective cleaning is likely to occur. If the above-described cleaning failure occurs frequently, the charging roller that contacts and charges the photoreceptor is contaminated, and the original charging ability cannot be exhibited.
[0072]
Further, as shown in FIG. 4, the shape factor SF-1 is a value indicating the ratio of the roundness of the shape of the spherical material, and the maximum length of the elliptical figure formed by projecting the spherical material on a two-dimensional plane. This value is obtained by dividing the square of Q by the figure area X and multiplying by 100π / 4. That is, the shape factor SF-1 is defined by the following equation.
[0073]
(Equation 1)
SF-1 = (Q ² / X) × (100π / 4)
[0074]
When the value of SF-1 is 100, the shape of the material becomes a true sphere, and as the value of SF-1 increases, the shape of the material becomes more unstable.
[0075]
Further, as shown in FIG. 5, the shape factor SF-2 is a numerical value indicating the ratio of the unevenness of the shape of the material, and the square of the perimeter P of the graphic formed by projecting the material on the two-dimensional plane is the graphic area. This is a value obtained by dividing by Y and multiplying by 100 / 4π. That is, the shape factor SF-2 is defined by the following equation.
[0076]
(Equation 2)
SF-2 = (P ² / Y) × (100 / 4π)
[0077]
When the value of SF-2 is 100, there is no unevenness on the surface of the material. As the value of SF-2 increases, the unevenness on the surface of the material becomes more prominent. In this example, the toner image was randomly sampled 100 times using an FE-SEM (S-800) manufactured by Hitachi, Ltd., and the image information was introduced into an image analyzer (LUSEX3) manufactured by Nireco. It is calculated by the above equation.
[0078]
The following can be said for the shape factor SF-1 and the shape factor SF-2 measured in this way.
[0079]
The present inventors have found that the transfer efficiency increases as the values of SF-1 and SF-2 both approach 100 and the shape of the toner approaches the spherical shape. This is because, due to point contact between the toner carrier and other toner particles or the image carrier due to the shape effect, the fluidity of the toner is increased, and the attraction force or the reflection force on the image carrier is weakened. This is considered to be due to being easily affected by the transfer electric field. On the other hand, as the shape of the toner approaches a sphere, mechanical cleaning performance such as blade cleaning tends to deteriorate.
[0080]
This means that, as described above, the fluidity of the toner is increased, the attraction force or the mirroring force on the image carrier or the like is weakened, and the toner easily passes through a small gap between the cleaning unit and the image carrier. It depends. Therefore, from the viewpoint of cleaning performance, it is preferable that the shape of the toner is somewhat deformed, that is, the value of SF-1 is larger than 100, and the toner has some irregularities, that is, the value of SF-2 is larger than 100. preferable.
[0081]
The ratio of the volume average particle size to the number average particle size is calculated in the following manner. First, a surfactant, such as an alkylbenzene sulfonate, is used as a dispersant in 100 to 150 ml of an approximately 1% NaCl aqueous solution (for example, ISOTON-II manufactured by Coulter, Inc.) prepared using primary sodium chloride. 5.0 ml, and then 2 to 20 mg of toner are added and suspended. Next, this suspension is subjected to dispersion treatment for about 1 to 3 minutes by an ultrasonic disperser, and the volume and number of toner particles or toner are measured by a particle size distribution measuring apparatus using a 100 μm aperture as an aperture. Calculate distribution and number distribution.
[0082]
The volume average particle diameter (Dv) and the number average particle diameter (Dn) of the toner are obtained from the volume distribution and the number distribution, and the ratio of the volume average particle diameter to the number average particle diameter (Dv / Dn) is calculated. As a particle size distribution measuring device, a Coulter Counter TA-II or Coulter Multitizer II manufactured by Coulter Co., Ltd. is used.
[0083]
In addition, as a channel, 2.00 to less than 2.52 μm, 2.52 to less than 3.17 μm, 3.17 to less than 4.00 μm, 4.00 to less than 5.04 μm, and 5.04 to less than 6.35 μm , 6.35 to less than 8.00 μm, 8.00 to less than 10.08 μm, 10.08 to less than 12.70 μm, 12.70 to less than 16.00 μm, 16.00 to less than 20.20 μm, 20.20 to less Using 13 channels of less than 25.40 μm, 25.40 to less than 32.00 μm, and 32.00 to less than 40.30 μm, and targeting particles having a particle size of 2.00 μm or more and less than 40.30 μm.
[0084]
The following can be said about the ratio (Dv / Dn) of the volume average particle diameter to the number average particle diameter measured in this way.
[0085]
Generally, it is said that the smaller the particle diameter of the toner, the more suitable it is to obtain a high-resolution and high-quality image, but on the other hand, the transfer performance and the cleaning performance tend to decrease. Further, when the volume average particle diameter is smaller than the range of the present invention, in a two-component developer, the toner is fused to the surface of the carrier in a long-term stirring in the developing device, and the charging ability of the carrier is reduced.
[0086]
When used as a one-component developer, filming of the toner on the developing roller and fusion of the toner to a member such as a blade for thinning the toner are likely to occur. These phenomena are the same in the toner having a fine powder content higher than the range of the present invention. Conversely, when the volume average particle diameter of the toner is larger than the range of the present invention, it is difficult to obtain a high-resolution image with high resolution, and when the balance of the toner in the developer is performed. In many cases, the fluctuation of the particle diameter of the toner becomes large.
[0087]
It was also found that the same applies when the volume average particle diameter / number average particle diameter (Dv / Dn) is larger than 1.30. When the ratio (volume average particle diameter) / (number average particle diameter) is smaller than 1.05, there is a preferable surface in terms of stabilizing the behavior of the toner and making the charge amount uniform. On the other hand, it is difficult to separate functions according to the particle size of the toner, such as developing a solid image mainly with large-sized particles.
[0088]
Therefore, the volume average particle diameter (Dv) of the toner is 4 to 8 μm, and the ratio of the volume average particle diameter to the number average particle diameter (Dv / Dn) is 1.05 to 1.30, preferably 1.10 to 1. .25, the particle size distribution of the toner becomes narrow, and the following effects can be obtained.
[0089]
First, since it is difficult for selective development in which toner particles having a toner particle diameter corresponding to an image pattern are selectively developed to occur, a stable image can be always formed. Further, since the particle size distribution of the toner is narrowed, the effect that occurs when the toner recycling system is mounted, that is, the effect of recycling a large amount of small-sized toner particles that are difficult to transfer is hardly affected by the toner, and the toner is always stable. An image can be formed.
[0090]
Furthermore, in the case of the two-component developer, even when the toner balance is performed for a long period, the fluctuation of the toner particle diameter in the developer is reduced, and good and stable developability can be obtained even when the developing device is stirred for a long time. Can be In addition, even when the toner is used as a one-component developer, fluctuations in the particle diameter of the toner are reduced even when the balance of the toner is performed, and the filming of the toner on the developing roller and the thinning of the toner are performed. There is no fusion of the toner to members such as blades, and good and stable developability and images can be obtained even when the developing device is used for a long period of time by stirring or the like.
[0091]
The average circularity, the shape coefficient SF-1, the shape coefficient SF-2, and the volume average particle diameter with respect to the number average particle diameter do not need to be all within the above numerical ranges. Within this range, a high-definition image can be obtained.
[0092]
In the above-described example, the example of the printer that forms a full-color image on both sides simultaneously has been described. However, the present invention is not limited to this. It can be applied to the printer. Further, the present invention is not limited to a printer, and can be applied to any image forming apparatus such as a facsimile and a copying machine.
[0093]
【The invention's effect】
As described above, according to the first aspect of the invention, when removing the untransferred toner on the image carrier, a bias voltage having the same polarity as the charging polarity of the charged toner is applied to the image carrier by the transfer unit. Therefore, there is no need to provide another unit before the cleaning unit and apply a bias voltage having the same polarity as the charged polarity of the charged toner to the untransferred toner, so that the image bearing device is compact and has improved cleaning performance. Can be provided.
[0094]
According to the second aspect of the present invention, when removing the untransferred toner, an AC bias voltage having the same polarity as the charging polarity is superimposed on the transfer means, so that the image bearing apparatus is compact and has improved cleaning performance. Can be provided.
[0095]
According to the third aspect of the present invention, since the time when the untransferred toner is removed is after the jam, when the transfer of the image is stopped by the jam while the image carrier carries some or all of the untransferred toner. By applying a bias voltage having the same polarity as the charging polarity of the charged toner to the image carrier by the transfer means, the untransferred toner can be reliably removed, and the image is compact and has improved cleaning performance. A carrying device can be provided.
[0096]
According to the fourth aspect of the present invention, the untransferred toner is removed every time the image transfer to the transfer material is completed, so that the untransferred toner can be more reliably removed. Thus, it is possible to provide an image bearing device that is compact, has improved cleaning performance, and can obtain a high-definition image.
[0097]
According to the fifth aspect of the present invention, since the time when the untransferred toner is removed is each time the job is completed, the time for removing the untransferred toner in the entire job processing time can be reduced, and the image can be efficiently displayed. Can be transcribed.
[0098]
According to the sixth aspect of the present invention, the average circularity of the charged toner is 0.90 to 0.99. Therefore, when transferring an image having a toner shape close to a sphere and a high image area ratio, the cleaning performance is improved. And a high-definition image can be obtained.
[0099]
According to the seventh aspect of the invention, since the shape factor SF-1 of the charged toner is 120 to 180 and the shape factor SF-2 is 120 to 190, the toner shape is appropriately close to spherical and the toner fluidity is high. And the attraction force to the image carrier or the like is weakened, so that it becomes easy to adapt to the transfer electric field, and a high-definition image can be obtained.
[0100]
According to the present invention, the ratio of the volume average particle diameter to the number average particle diameter of the charged toner is 1.05 to 1.30. A selection phenomenon in which the toner particle size is selectively used is less likely to occur, and a high-definition image can be obtained.
[0101]
According to the ninth aspect of the present invention, it is possible to provide an image forming apparatus including an image bearing device that achieves the above effects.
[Brief description of the drawings]
FIG. 1 is a simultaneous double-sided image forming printer shown as an example of an image forming apparatus, and is an overall schematic configuration diagram of an internal mechanism thereof.
FIG. 2 is a diagram illustrating a state where residual toner is removed by the secondary image holding device.
FIG. 3 is a diagram illustrating a state in which a secondary residual toner is removed by the secondary image holding device.
FIG. 4 is a diagram showing the maximum length of an elliptical figure formed by projecting a spherical substance on a two-dimensional plane.
FIG. 5 is a diagram showing a perimeter of a substance.
[Explanation of symbols]
30 Secondary image carrier (image carrier)
35 Secondary cleaning means (cleaning means)
36 Secondary transfer means (transfer means)
F Secondary image carrier (image carrier)
K1 First full-color image (image)
P Recording medium (transfer material)

Claims (9)

When an image formed by the charged toner is carried on an image carrier and the image on the image carrier is transferred to a transfer material, a bias voltage having a polarity opposite to the charge polarity of the charged toner is applied to the image carrier by a transfer unit. In the image bearing device, while applying a bias voltage having a polarity opposite to the charging polarity of the charged toner by the cleaning unit,
An image carrier device, wherein when removing untransferred toner on the image carrier, a bias voltage having the same polarity as the charging polarity of the charged toner is applied to the image carrier by the transfer unit. 2. The image bearing device according to claim 1, wherein when removing the untransferred toner, an AC bias voltage having the same polarity as the charging polarity is superimposed on the transfer unit. 3. 3. The image bearing device according to claim 1, wherein the untransferred toner is removed after a jam. 3. The image bearing device according to claim 1, wherein the untransferred toner is removed each time image transfer to the transfer material is completed. 4. 3. The image bearing device according to claim 1, wherein the untransferred toner is removed every time a job is completed. The image bearing device according to any one of claims 1 to 5, wherein the charged toner has an average circularity of 0.90 to 0.99. 7. The image bearing device according to claim 1, wherein the shape factor SF-1 of the charged toner is 120 to 180, and the shape factor SF-2 is 120 to 190. 8. The image bearing device according to claim 1, wherein a ratio of a volume average particle diameter to a number average particle diameter of the charged toner is 1.05 to 1.30. An image forming apparatus comprising the image bearing device according to any one of claims 1 to 8.

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