JP2006053280A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for forming an image of high quality over passage of a time by suppressing image density irregularity generated when electrification capability is lowered to the minimum. <P>SOLUTION: The image forming apparatus is provided with a development apparatus. The image forming apparatus is changed over to delay latent image start timing more than normal start timing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to image formation using a toner for developer for revealing an electrostatic image formed on the surface of a photoreceptor in electrophotography, electrostatic recording, electrostatic printing, etc., such as a printer, a fax machine, and a copying machine. It relates to the device.

  Conventionally, various image forming apparatuses and developing apparatuses have been known including an image forming apparatus (for example, see Patent Document 1) proposed by the present applicant and adopting a partial configuration in the present invention (for example, (See Patent Documents 2 to 4).

JP 2002-148937 A JP-A-11-15262 JP-A-8-106208 JP-A-6-95481

  However, in Patent Document 1, the toner in the developer hopper is conveyed to the vicinity of the developing roller while being agitated by the developer conveying member, and the toner sandwiched between the developing roller and the supply roller mainly adheres to the surface of the developing roller by frictional charging. Then, the toner layer thickness is uniformly leveled by the regulating roller and charged to reach the developing area. Here, the toner is subjected to great mechanical stress not only in the thin layer forming portion but also in contact with the conveying member. In general, an external additive of an inorganic substance is attached to a toner to impart fluidity around the base resin, and the toner is buried in the base resin due to the stress. As a result, even if the toner is sufficiently charged, the fluidity is reduced and agglomerates, and the non-electrostatic adhesion force to the developing roller is increased. Occurrence, adverse effects such as scumming and density reduction appear over time.

  Patent Document 2 defines the surface friction coefficient of the developing roller in the one-component developing device, but since the toner charging depends on the friction with the surface of the developing roller, a reduction in the developing amount due to a decrease in the charging amount is predicted.

  Patent document 3 aims at sufficient filling of the developer into the developer carrier, and the product of the number of rotations of the agitating / conveying means and the amount of developer per rotation is the volume of the developer reservoir and the supply member. The developer is intended to follow the consumption of the developer by stipulating that the sum of the volume and the filling rate of the developer is equal to or less, and to minimize the hazard to the developer. Can not be suppressed.

  In Patent Document 4, the toner adhesion amount is kept constant by the bias voltage control means so that the potential difference is constant from the detection output from the photoreceptor surface potential sensor and the detection output from the surface potential sensor of the developing roller. It can be developed at a density. However, here, both outputs from the photoreceptor surface potential sensor are used, and control by the surface potential sensor for the developing roller is not performed. In order to sense on the photosensitive member side, it is necessary to develop the toner once, and it takes time until the output for that process, so that workability is lowered.

  As described above, the toner in the hopper is conveyed to the vicinity of the developing roller by the developer conveying member, passed between the developing roller and the regulating roller, and frictionally charged to form a uniformly charged toner thin layer on the developing roller. In an image forming apparatus that develops an electrostatic latent image that is opposed to the toner, a mechanical hazard is received when the toner is conveyed through the developing device. In the toner, CCA or CCR is mixed with a base resin, and an electric charge is obtained by friction with a member. Similarly, there is an additive mainly composed of inorganic materials driven around the base resin of the toner, and fluidity is given by reducing non-electrostatic adhesion with other toners or members. The additive itself may be charged, and often contributes to toner charging. However, the hardness of the base resin is extremely lower than that of metal or the like, and it has been reported that the toner additive is buried in the base resin as the process is repeated. When the additive is buried, the fluidity of the toner itself decreases and the toner tends to adhere to each other, so the amount of adhesion on the developing roller increases, and the coverage area of the additive on the toner base resin decreases, so the charge amount also decreases. As a result, the developing ability changes.

  In addition, in members that contribute to toner charging, such as a developing roller or a developing doctor that frictionally charges toner, a decrease in the ability to be charged over time is also considered a change in developing ability. On the image, the image density is excessive due to an increase in the adhesion amount on the developing roller, and the image density is decreased due to a decrease in charging ability. Particularly problematic is that when the charging ability is reduced, the toner obtains an electric charge by rubbing against the member, so that density unevenness occurs at the time of the next print output after the print output. Specifically, there is no problem when the print output is frequently performed, but if left for a long time, the toner adhered on the developing roller passes between the developing roller and the regulating roller (the toner is separated from the member). Since the charge amount is different between before and after the friction, the density on the image is different between the first round corresponding to the developing roller cycle and thereafter. Since the density of the first round of the developing roller is low, and after that, the density is normal, and density unevenness is observed in the entire image. This is inconspicuous when there are few solid images, such as a character image, but becomes noticeable when there are many solid images. In recent years, toner for low temperature fixing has been increasingly used for energy saving, and the toner base resin has become soft for fixing at low temperature, and this phenomenon has become a problem.

  Therefore, the present invention proposes an image forming apparatus that solves the problems of the conventional ones and can form high-quality images over time while minimizing image density unevenness that occurs when charging ability is reduced. For the purpose.

  In order to solve the above-mentioned problems, the invention described in claim 1 is provided with a developing device, and under a certain condition of the developing device, the latent image start timing is switched to be delayed from the normal start timing. Forming device. According to a second aspect of the present invention, in the first aspect, the latent image start timing is fed back based on a result of detecting the development density for each developing roller cycle. According to a third aspect of the present invention, in the first aspect, the latent image start timing is fed back based on the result of detecting the development density immediately after the end of one job of print output and after a certain period of time has elapsed since the end. It is characterized by comprising. According to a fourth aspect of the present invention, in the first aspect, the latent image start timing is fed back based on a result of detecting the toner remaining amount in the hopper of the developing device. According to a fifth aspect of the present invention, in the first aspect, the latent image start timing is fed back based on the detection of the toner remaining amount in the hopper and the print output pixel number count information. According to a sixth aspect of the present invention, in the first aspect, the latent image start timing is fed back based on the toner cartridge replacement information and the counter information after the replacement.

  According to a seventh aspect of the present invention, there is provided an image forming apparatus comprising a developing device, provided with a potential sensor for detecting a toner layer potential on a developing roller of the developing device, and detecting the toner layer potential of the developing operation. It is. The invention described in claim 8 is characterized in that, in claim 7, the detection of the toner layer potential on the developing roller is determined based on a comparison result with the end of the developing operation. A ninth aspect of the invention is characterized in that, in the seventh aspect, the detection of the toner layer potential on the developing roller is determined based on a comparison result with immediately after the start of the developing operation. According to a tenth aspect of the present invention, in the seventh aspect, when the toner layer potential on the developing roller is detected, the toner layer potential in the state of the new developing device and the current state are compared and detected. And According to an eleventh aspect of the present invention, in the tenth aspect, the toner layer potential in the state of a new developing device and the toner layer potential in each developing roller cycle in the current state are compared and detected. According to a twelfth aspect of the present invention, in any one of the eighth to eleventh aspects, the control different from the normal operation timing is performed based on the detection result of the rising potential immediately after the start of development.

  According to a thirteenth aspect of the present invention, in the twelfth aspect of the present invention, feedback is made to the latent image formation start timing based on the detection result of the rising potential immediately after the start of development. According to a fourteenth aspect of the present invention, in the twelfth aspect of the present invention, feedback is provided to the timing of developing bias control based on the detection result of the rising potential immediately after the start of development. According to the fifteenth aspect of the present invention, in the thirteenth or fourteenth aspect, in the case of continuous print output depending on the job mode, the first image latent image start timing is delayed from the normal start timing, and the second and subsequent sheets Is characterized in that it has a normal timing. A sixteenth aspect of the invention is characterized in that, in any one of the first to fifteenth aspects, the toner used has a circularity set to 0.9 or more.

  The invention according to claim 17 is the image forming apparatus according to any one of claims 1 to 16, which is of a tandem type. The invention according to claim 18 is a process cartridge using the developing device of the image forming apparatus according to any one of claims 1 to 17.

  The present invention is as described above, and by delaying the latent image start timing from the normal start timing, an image thinner than the normal image density due to a decrease in the charge amount of the developer on the first round of the developing roller is developed on the transfer paper. First, since the image on the developing roller is transferred from the position where the latent image start timing is shifted, the density unevenness on the image is made inconspicuous by minimizing the image density unevenness that occurs when the charging capability is reduced. be able to. Therefore, there is an effect that it is possible to provide an image forming apparatus capable of forming a high-quality image over time.

  In the following embodiments, a one-component developing device using one-component toner appears more remarkably, and therefore, an example using a one-component developing device will be described. In the case of a two-component developing device, the description can be made in substantially the same manner by replacing the one-component toner with a two-component developer and the toner thin layer with a developer layer.

  An example of an embodiment applied to an electrophotographic color printer (hereinafter referred to as a color printer) as an image forming apparatus will be described. First, the schematic configuration and operation of the color printer according to the present embodiment will be described with reference to FIG. The color printer 1 includes a photosensitive unit 10, a writing optical unit 20, a developing unit 30, an intermediate transfer unit 40, a secondary transfer unit 50, a fixing unit 60, a duplex printing paper reversing unit 70, and the like. Then, black: black (hereinafter referred to as “Bk”), cyan: cyan (hereinafter referred to as “C”), magenta: magenta (hereinafter referred to as “M”), and yellow: yellow (hereinafter referred to as “Y”) are transferred to the photosensitive unit 10. The image is sequentially visualized on the photosensitive belt 11, and these are superposed to form a final four-color full-color image.

  Around the photoreceptor belt 11, a photoreceptor cleaning device 12, a charging roller 13, a selected developing device of the developing unit 30, an intermediate transfer belt 41 of the intermediate transfer unit 40, and the like are disposed. The photosensitive belt 11 is stretched between a driving roller 14, a primary transfer counter roller 15, and a stretching roller 16, and is rotated in a direction indicated by an arrow A by a driving motor (not shown). When the photosensitive belt 11 having a joint is used, a joint mark is provided in a non-image forming area at the end of the photosensitive belt 11, and detection is performed by a sensor (not shown), and image formation is performed while avoiding the joint.

  The writing optical unit 20 converts the color image data into an optical signal, performs optical writing corresponding to each color image, and forms an electrostatic latent image on the photosensitive belt 11. The writing optical unit 20 includes a semiconductor laser as a light source, a laser light emission drive control unit (all not shown), a polygon mirror 22, three reflection mirrors 23a, b, and c.

  The developing unit 30 performs a contact / separation operation with respect to the photosensitive belt 11 by moving the developing units 31B, 31C, 31C, 31M and 31Y, and the developing units 31Y in the horizontal direction in the drawing. It consists of an approach / separation mechanism. Each developer storage case 32K, C, M, Y of each developing device 31K, C, M, Y stores a one-component developer composed of toner of each color as a developer. In the illustrated example, the Bk developing unit 31K containing black toner, the C developing unit 31C containing cyan toner, the M developing unit 31M containing magenta toner, and the Y developing unit 31Y containing yellow toner are sequentially arranged from the lower side of the apparatus main body. It has become. The contact / separation mechanism operates an electromagnetic solenoid (not shown) to move the developer containing case 32K, C, M, Y to the photosensitive belt 11 side (left side in the figure). At the time of development, any one selected from the developing devices 31K, 31C, 31M, and 31Y moves and contacts the photosensitive belt 11. On the other hand, when the electromagnetic solenoid is turned off, the developing device that is in contact with the photosensitive belt 11 is moved away from the photosensitive belt 11 (right side in the figure) by a pull-back spring built in the electromagnetic solenoid. The developing units 31K, C, M, and Y will be described in detail later.

  In the standby state of the main body of the color printer, the developing unit 30 has all the developing devices 31K, C, M, and Y set at positions separated from the photosensitive belt 11, and when the printing operation is started, the color image data is displayed. Based on this, optical writing with a laser beam and formation of an electrostatic latent image start (hereinafter, an electrostatic latent image based on Bk image data is referred to as a Bk electrostatic latent image; the same applies to C, M, and Y). Before the leading edge of the electrostatic latent image reaches the Bk development position so that development is possible from the leading edge of the Bk electrostatic latent image, the developing roller 110 is started to rotate, and the Bk electrostatic latent image is developed with Bk toner. To do. Thereafter, the developing operation of the Bk electrostatic latent image area is continued. When the rear end portion of the Bk electrostatic latent image passes the Bk developing position, the Bk developing unit 31K is separated from the photosensitive belt 11 and immediately proceeds to the next. The developing device of the color is in contact with the photosensitive belt 11. This is completed at least before the leading edge of the electrostatic latent image based on the next image data reaches the developing position.

  The intermediate transfer unit 40 includes an intermediate transfer belt 41, a belt cleaning device 42, a position detection sensor 43, and the like. The intermediate transfer belt 41 is stretched around a drive roller 44, a primary transfer roller 45, a secondary transfer counter roller 46, a cleaning counter roller 47, and a tension roller 48, and is driven and controlled in the direction of arrow B by a drive motor (not shown). The A plurality of position detection marks (not shown) are provided in the non-image forming area at the end of the intermediate transfer belt 41, and one of these position detection marks (position detection at the start of the image forming operation). The position detection mark 43 that first passes through the sensor 43 is detected by the position sensor 43, and image formation is started at this detection timing. The belt cleaning device 42 includes a cleaning brush 42a, a contact / separation mechanism (not shown), and the like, while transferring the first color Bk image to the intermediate transfer belt 41, and 2, 3, 4 While the color image is transferred to the intermediate transfer belt 41, the cleaning brush 42a is separated from the surface of the intermediate transfer belt 41 by the contact / separation mechanism. The toner cleaned from the surface of the intermediate transfer belt 41 is stored in a waste toner tank 49 provided in the intermediate transfer unit 40.

  The transfer paper cassette 80 of the color printer 1 stores transfer paper and is fed and conveyed in the direction of the registration roller pair 82 by paper feed rollers 81a, b, and c. Further, a manual feed tray 83 for manual paper feed such as OHP paper or thick paper is provided on the right side surface of the color printer 1.

  The secondary transfer unit 50 is configured by a swinging mechanism (not shown) including a clutch for bringing the secondary transfer roller 51 and the secondary transfer roller 51 into and out of contact with the intermediate transfer belt 41. The secondary transfer roller 51 swings about the rotation axis of the swing mechanism in synchronization with the timing when the transfer paper reaches the transfer position. The secondary transfer roller 51 and the secondary transfer counter roller 46 bring the transfer paper and the intermediate transfer belt 41 into contact with each other at a constant pressure. The secondary transfer roller 51 maintains the positional accuracy of the parallelism with the secondary transfer counter roller 46 by a positioning member (not shown) provided in the intermediate transfer unit 40. Further, the contact pressure of the secondary transfer roller 51 with respect to the intermediate transfer belt 41 is made constant by a positioning roller (not shown) provided on the secondary transfer roller 51. At the same time as the secondary transfer roller 51 is brought into contact with the intermediate transfer belt 41, a transfer bias having a polarity opposite to that of the toner is applied to the secondary transfer roller 51, and the superimposed toner images on the intermediate transfer belt 41 are collectively transferred onto the transfer paper.

  Each unit can be easily detached from the apparatus. For example, in FIG. 1, when the intermediate transfer unit 40 is removed, it can be easily removed by opening a front cover (not shown) and sliding the unit from the back side to the front side of the sheet.

  In the color printer 1 configured as described above, when the image forming cycle is started, first, the photosensitive belt 11 is rotated counterclockwise as indicated by the arrow A and the intermediate transfer belt 41 is rotated clockwise as indicated by the arrow B by a driving motor (not shown). . A position detection mark (not shown) provided on the intermediate transfer belt 41 is detected by a position detection sensor 43, and Bk toner image formation and C toner image formation are performed on the photosensitive belt 11 in accordance with the detection timing of the position detection mark. M toner image formation and Y toner image formation are performed, and a toner image is finally formed on the intermediate transfer belt 41 in the order of Bk, C, M, and Y. At this time, the bias applied to the primary transfer roller 45 is generally increased in voltage sequentially, but differs depending on the resistance characteristics of the intermediate transfer belt 41 and the like.

  The Bk toner image is formed as follows. The charging roller 13 uniformly charges the photosensitive belt 11 by an applied voltage of a power source (not shown). The laser beam LD for writing is exposed based on the Bk color image signal. When this exposure is performed, in the exposed portion of the photosensitive belt 11 that is initially charged uniformly, the charge proportional to the exposure light amount disappears, and a Bk electrostatic latent image is formed. When the Bk toner on the developing roller 110 comes into contact with the Bk electrostatic latent image, the toner does not adhere to the remaining portion of the photosensitive belt 11, and the portion without charge, that is, the exposed portion is exposed. Bk toner is attracted to the portion, and a Bk toner image similar to the electrostatic latent image is formed. The Bk toner image formed on the photosensitive belt 11 contacts the intermediate transfer belt 41 at the primary transfer position. At this primary transfer position, a nip is formed between the intermediate transfer belt 41 and the photosensitive belt 11 by the primary transfer roller 45 and the primary transfer counter roller 15, and a Bk toner image is formed on the primary transfer roller 45. The Bk toner image is transferred to the intermediate transfer belt 41 by applying a reverse polarity bias.

  Some untransferred residual toner on the photoreceptor belt 11 is cleaned by the photoreceptor cleaning device 12 in preparation for reuse of the photoreceptor belt 11. The collected toner is stored in a waste toner tank (not shown) via a collection pipe.

  On the photosensitive belt 11 side, the process proceeds to the C image forming process after the Bk image forming process, and writing by the laser light LD is performed by the C image data in accordance with the detection timing of the position detecting sensor 43, and the C electrostatic latent image is obtained. Is formed. Then, after the rear end portion of the previous Bk electrostatic latent image has passed and before the front end portion of the C electrostatic latent image has arrived, the Bk developing device is retracted from the developing position, and the C developing device 31C is moved to the developing position. The C electrostatic latent image is developed with C toner. Thereafter, the development of the C electrostatic latent image area is continued, but when the rear end portion of the C electrostatic latent image passes, the C developing device 31C is retracted from the developing position as in the case of the previous Bk developing device 31k. Then, the next M developing unit 31M is moved to the developing position. This is also completed before the leading edge of the next M electrostatic latent image reaches the developing position. The M and Y image forming steps are the same as the Bk and C steps described above, and the description thereof is omitted here.

  On the intermediate transfer belt 41, Bk, C, M, and Y toner images sequentially formed on the photosensitive belt 11 are sequentially aligned on the same surface to form a four-color superimposed toner image. In the transfer process, the four color toner images are collectively transferred onto the transfer paper.

  At the time when the image forming operation is started, the transfer paper is fed from either the transfer paper cassette 80 or the manual feed tray 83 and is waiting at the nip of the registration roller pair 82. Then, when the leading edge of the four-color superimposed toner image on the intermediate transfer belt 41 approaches the secondary transfer roller 51, the registration roller pair 82 is driven so that the leading edge of the transfer paper coincides with the leading edge of the toner image. The transfer paper and the toner image are aligned. Then, the transfer paper is superimposed on the toner image on the intermediate transfer belt 41 and passes through the secondary transfer position. At this time, the transfer paper is charged by the transfer bias by the secondary transfer roller 51, and most of the toner image is transferred onto the transfer paper.

  Then, the transfer paper onto which the four-color superimposed toner images are collectively transferred from the intermediate transfer belt 41 is conveyed to the fixing unit 60, where the toner image is melted and fixed at the nip between the fixing belt 61 and the pressure roller 62 controlled to a predetermined temperature. Then, it is sent out of the apparatus main body (in the direction of arrow C) and stacked on the paper discharge tray 84 so as to obtain a full color copy.

  When performing duplex printing, the transfer paper that has passed through the fixing unit 60 is guided in the direction of arrow D by the discharge switching claw 85 and sent to the duplex printing paper reversing unit 70. After the transfer paper trailing edge passes through the paper conveyance switching claw 71, the conveyance roller pair 72 stops and the transfer paper also stops. Then, the transport roller pair 72 starts reverse rotation after a certain blank time, and the transfer paper starts to switch back. At this time, the paper conveyance switching claw 71 is switched, and the transfer paper is guided in the direction of arrow E and sent to the registration roller pair 82. The transfer sheet sent to the registration roller pair 82 stands by at the nip of the registration roller pair 82 with the front and back reversed. Then, the registration roller pair 82 is driven at a predetermined timing, the transfer paper is sent to the secondary transfer position, and the four-color superimposed toner image is collectively transferred from the intermediate transfer belt 41, and then the toner image is melted by the fixing unit 60. It is fixed and sent out of the main body.

  On the other hand, the surface of the photoconductor belt 11 after the primary transfer is cleaned by the photoconductor cleaning device 12 and is uniformly discharged by a charge removal lamp (not shown). Further, the surface of the intermediate transfer belt 41 after the toner image is transferred to the transfer paper is cleaned by pressing the cleaning brush 42a of the belt cleaning device 42 with a contact / separation mechanism. The toner cleaned from the intermediate transfer belt 41 is stored in a waste toner tank 49.

  In the color printer according to the present embodiment, a photosensitive belt is used as the latent image carrier. However, it is possible to use a drum-like latent image carrier by keeping the hardness of the developing roller low. .

  Next, the developing unit 30 will be described in detail. Since the color developing devices 31K, C, M, and Y of the developing unit 30 have the same configuration, the Bk developing device 31K will be described. FIG. 2 is a schematic configuration diagram of the Bk developing unit 31K. The Bk developing unit 31K transfers the developer to the photosensitive belt 11 to make a visible image, a developer supply roller 120 that supplies the developer roller 110 while pre-charging the developer, and the developer of the developing roller 110. A roller-shaped developer regulating roller 130 that regulates the amount of adhesion and frictionally charges the developer, a scraping member 131 that scrapes off the developer on the surface of the developer regulating roller 130, and the developer does not leak to the outside of the developing device. The developer hopper 101 is a storage space surrounded by a case to be stored, and three developer transport members 141, 142, and 143 that transport the developer from the developer hopper 101 to the developer supply roller 120. Yes.

  The developing roller 110 rotates at a linear speed ratio of 1.1 to 2.0 times with respect to the photosensitive belt 11 in the same direction as the traveling direction of the photosensitive belt 11, that is, in the direction of the arrow CW in the drawing (clockwise direction). is doing. The three developer conveying members 141, 142, and 143 rotate in the direction of arrow CW and convey the developer to the developer supply roller 120. The developer supply roller 120 is brought into contact with the development roller 110 with a predetermined nip and rotated to CW or CCW so as to have a relative linear velocity difference (CW in the example in the figure), and the developer on the surface of the developer supply roller 120 is By rubbing against the surface of the developing roller 110 within the nip, the developer is supplied while being preliminarily frictionally charged. The developer regulating roller 130 abuts the developing roller 110 with a predetermined load by urging the bearing portion 133 toward the developing roller 110 with a spring 132. By allowing the developer supplied from the developer supply roller 120 to pass through the nip of the contact portion, the amount of passage is made constant, and a uniform developer layer in the thrust direction on the surface of the developing roller 110 is formed. Further, since the developer that has passed is frictionally charged by the surfaces of both the developer regulating roller 130 and the developing roller 110, the developer supplied to the development on the photosensitive belt 11 has a stable charge amount. be able to.

  The electrostatic latent image formation and development operation timing will be described in more detail. Here, the solid development and halftone development operations in the Bk development single color will be described with reference to FIGS. In the state where the developing operation is stopped in the previous step, as the next developing step, the surface of the developing roller between the contact position of the photosensitive belt 11 and the developer regulating roller 130 has already passed the developer regulating roller 130. The toner is carried on the part A (about 1/3 round), the toner passing through the developer regulating roller 130 when the developing roller is driven next, the part B (one round), and the developer in the first round and thereafter There is toner that passes through the regulating roller 130. Normally, when the charging ability is maintained, the toners shown in the A part, the B part, and the B part and later (here, the C part is shown as an example) have different numbers of passages through the developer regulating roller 130. However, since there is not much difference in the charge amount of the toner, there is no density unevenness on the image.

  However, when the charging ability is reduced, as shown in FIG. 3, the toner shown in the A part, the B part, and the B part and thereafter is changed in the charge amount of the toner due to the difference in the number of times the developer regulating roller 130 passes. Difference may occur, resulting in uneven density on the image. In particular, image density unevenness may be conspicuous at the time of the next print output after a certain time has elapsed after print output (hereinafter referred to as neglected). The toner on the developing roller after being left increases as the number of passages of the developer regulating roller 130 increases, and the charging amount Q rises to the normal charging amount after the second rotation of the developing roller. Display) is almost the same. Further, the amount of toner carried on the developing roller (indicated as M) is also different, and the difference between the two appears as density unevenness on the image. In one-component development, these characteristic values are expressed as M / A divided by unit area (indicated as A). As characteristic values, the A portion at the front end of the image is Q / M ... small, M / A ... normal. Part B is Q / M ... small, M / A ... small. After part B, Q / M ... normal, M / A ... normal. As the density on the image, the portion A at the front end of the image is dark. Part B is thin. Normal density after B part. Therefore, it will be noticeable as image unevenness.

  Therefore, as a method of making the density unevenness inconspicuous, the developing roller distance of A portion + B portion or more is driven first, and then delayed from the normal timing so that the leading edge of the latent image comes after that. Specifically, the developing roller was delayed by about 1.5 turns with a margin. In this example, since the driving time of the developing roller is about 0.3 sec for one rotation, the latent image leading edge writing position is reached after 0.45 sec, that is, light writing by laser light based on image data, electrostatic latent image formation Delayed the start of

  The main cause of the decrease in charging ability is mechanical stress or thermal stress on the toner, which appears when the proportion of toner remaining in the developing hopper for a long time without being developed increases. Specifically, the case where the toner remaining amount in the hopper is reduced is remarkable.

  In FIG. 6, a sensor 501 for detecting the toner density is provided toward the photosensitive belt 11, and detects the charging ability of the toner carried on the developing roller 110 shown in FIG. In this example, an optical sensor (represented as a P sensor) is used, but the present invention is not limited to this as long as the density can be detected. Corresponding to the position of the P sensor 501, a detection patch is set so that a certain size of patch is developed, and the density of the toner carried on the developing roller 110 can be determined for each developing roller cycle. In such a case, density unevenness can be made inconspicuous by delaying it from the normal latent image leading edge writing position (expressed as latent image start timing) at the time of print output. There are several methods for detecting the toner density by the P sensor 501, for example, the patch is developed before print output, and the latent image start timing at the actual print output is fed back based on the detection result.

  Also, in the state where charging ability is reduced, when the print output is continuous or when there is no time lapse until the next output even when outputting a single sheet (output immediately), the image density is hardly affected. It will not appear as an unevenness. However, image density unevenness appears on the first sheet when printed out after the passage of time (left). Therefore, as the toner density detection time by the P sensor 501, the first patch for comparison and discrimination is developed after the end of one job in the print output mode, and the next second patch is developed after a certain standing time, and the density is developed. If the difference exceeds a certain density difference, the latent image start timing at the actual print output is fed back based on the detection result. In this example, when 2 minutes have elapsed after the end of one job, when 5 minutes have elapsed, when 10 minutes have elapsed, etc. are set and compared with the density after the end of one job. When the next print output is started within the set time, the second patch for density comparison is not developed because it is difficult to be affected by the decrease in charging capability, and after completion of the output, 1 of the end of job comparison is made. Develop the second patch and finish. As this detection method, it is not necessary to detect the density for every cycle of the developing roller as in the above example, the density after the end of one job is set to the density after the second rotation of the developing roller, and the detection after being left is detected as the developing roller 1. It is sufficient to compare and discriminate as the density of the circumference.

  Further, the situation where the charging ability is lowered is conspicuous when the remaining amount of toner in the hopper is reduced. As shown in FIG. 7, a toner remaining amount detection sensor 502 is provided to feed back the latent image start timing at the time of actual print output based on the result of detecting a toner remaining amount below a certain level. In this example, an optical sensor is used. However, the present invention is not limited to this as long as the remaining amount of toner can be detected, such as a mechanical sensor that can detect a torque change.

  In addition, in order to make the image density unevenness due to the decrease in charging capability inconspicuous, in order to reflect a more accurate situation, the amount of toner consumed after the detection is calculated in conjunction with the detection of the remaining amount of toner in the hopper. Judgment is made by counting, and based on the result, the latent image start timing at the time of actual print output is fed back. Although the detection of the toner remaining amount in the hopper can be detected when the toner amount becomes a certain amount or less, a costly sensor is required to accurately detect the remaining toner amount thereafter. For this reason, a method of counting the number of pixels is employed in order to grasp the remaining amount of toner at a low cost. Here, the number of print output pixels is converted from the image data, and the toner consumption corresponding to the number of pixels is converted in advance into a table. The decrease in charging capability becomes more noticeable as the remaining amount of toner decreases, so the density unevenness can be corrected more accurately by feeding back the latent image start timing at the time of print output together with the toner consumption after detecting the remaining amount of toner. It can be made inconspicuous.

  In the one-component development method, a method in which the toner is used up and the development unit is replaced is generally used. The reason for this is that the members in the development unit are often in contact with each other. For example, the deterioration in image quality is faster compared to the two-component development method due to the life of the developer regulating member and the surface of the developing roller. Etc. In contrast, in this example, the developer regulating member is formed in a roller shape to extend the life by changing the wear position, so that the toner cartridge in the hopper is not used up, but the toner cartridge is replaced. As a result, it is possible to extend the replacement time of the developing unit.

  The situation where the charging capacity is reduced is conspicuous when the toner remaining in the hopper is reduced. Therefore, when the toner cartridge is replaced and new toner is replenished in the hopper, the charging ability is reduced from the state where the charging capacity is reduced. It gradually returns to a state close to its capacity in accordance with the ratio of new toner. An IC chip is attached to the toner cartridge, and when a new toner cartridge is replaced, the information is read into the main body. In FIG. 8, when the toner end is detected by the toner remaining amount detection sensor 502 and is replaced with a new toner cartridge 510, the ratio when the new toner is replenished and mixed with the toner remaining amount in the hopper at the time of the toner end, In the case of a fixed amount replenishment method, a table is prepared by converting in advance from the replenishment time and the number of times of replenishment driving. After reading the information on replacement of a new toner cartridge into the main body, the toner charging capability state in the hopper is predicted in correspondence with the replenishment time and the number of replenishment driving operations, and until it is determined that the normal state has been reached. By feeding back the latent image start timing in combination with the above detection method, density unevenness can be made inconspicuous. The toner cartridge 510 is provided with an agitator 511. When the toner cartridge 510 is attached to the developing unit, the toner cartridge 510 is regularly rotated by a driving gear in the unit, and is replenished from the toner replenishing port 512 and new toner is mixed in the hopper.

  Even in a state where the charging ability is lowered, in the case of continuous print output, it is difficult to be affected by this and does not appear as unevenness in image density. In each of the detection methods, the latent image start timing is fed back and delayed depending on the print output mode, or switched to normal latent image start timing. In this example, when the results based on the respective detection methods are fed back, in the continuous print output mode, the latent image start timing is fed back and delayed only for the first sheet, and the normal latent image starts for the second and subsequent sheets. Return to timing. Delaying the latent image start timing takes time until print output. Rather than delaying the start timing of the latent image every time based on the detection result, it is possible to prevent the output time from being increased as much as possible by returning the second and subsequent images to normal.

  9-12 show another embodiment. In this embodiment, the apparatus configuration is substantially the same as that of the previous embodiment. The difference is that the above embodiment delays the latent image start timing from the normal start timing to make the density unevenness on the image inconspicuous. However, in this embodiment, the sensor is provided near the surface of the developing roller. The toner layer potential formed on the roller is measured, and the image unevenness state is predicted from the potential fluctuation.

  As shown in FIG. 9, a potential sensor 601 a or 601 b is provided near the surface of the developing roller 110. Preferably, the potential sensor 601a is the most desirable because the potential of the toner layer formed on the developing roller is measured immediately after passing through the developer regulating roller 130. If the toner is not developed, the potential sensor 601b may be used. Alternatively, a double potential sensor may be provided. It is desirable that the potential sensor 601 is fixed on the main body side and a position where a measurable gap can be obtained when the developing unit comes to a position where it contacts the photoconductor. In some cases, it may be provided in the developing unit.

  FIG. 10 shows a development process model diagram. An image is created by each of the photosensitive member potential (hereinafter referred to as Vd), the image portion potential (V1), the developing roller potential (Vb). At this time, the toner layer potential on the developing roller is schematically expressed as Vt. As an example of illustration, each potential value is shown.

  FIG. 11 shows a potential drop model diagram when left unattended. When the time from the end of the developing operation to the start of the next developing operation is defined as the time after the stop of the developing operation, the toner layer potential (Vn) when the charge amount is not different from the normal amount (normal charge amount) hardly changes. However, in the case of a decrease in charge amount, the potential gradually decreases (Ve). The charge amount depends on toner characteristics, developing roller characteristics, and developer regulating member characteristics. Therefore, the cause of the decrease in the charge amount is the result of deterioration of the characteristic value due to deterioration individually or independently. Even when the charge amount is normal, if it has been stopped for several days, it may decrease after the development operation is stopped, but the method of attenuation is more gradual than the decrease in the charge amount.

  FIG. 12 shows a rising potential model diagram. The change in the toner layer potential over time after the development operation is started is shown. When the charge amount is normal, the rise to the toner layer potential Vmax is quick. On the other hand, when the charge amount is reduced, the rise to Vmax is slow as shown by the developing roller cycle. Even in the case of the decrease in the charge amount shown in FIG. 11, if the rise to Vmax is quick, there may be no problem on the image.

  As a specific example, when the toner layer potential at the end of the previous development operation is Ve, it is compared with Vn at the time of normal charging. In another embodiment, when the ratio Ve2 / Ve1 between the toner layer potential Ve1 immediately after the end of the operation and Ve2 after a certain time has passed, the charge amount is judged to be low.

  When the toner layer potential at the start of the developing operation is Vt1, it is determined that the charge amount is lowered when the toner layer potential is lower than a value that is a ratio of Vt1 / Vmax, for example, compared with the normal charge amount Vmax. In another example, the toner layer potential for each cycle of the developing roller 1st cycle Vt1, 2nd cycle Vt2, 3rd cycle Vt3,... From this, when the rise of the first round of the developing roller is poor, the toner is not developed on the photosensitive member correspondingly, so that it can be predicted that the density at the leading edge of the image is lowered and image unevenness occurs.

  In addition, when the sleeve period still does not reach Vmax, a considerable decrease in the charge amount has already occurred, and the toner and the charging member (developing roller and developer regulating roller) may be deteriorated. There is also a method of displaying an exchange signal as a judgment of development unit exchange.

  By storing the toner layer potential Vnew in the new development unit, it is possible to determine a decrease in the charge amount by comparing the current toner layer potential Ve / Vnew. For example, the degree of deterioration can be determined earlier by comparing the toner layer potential Ve at the end of development, the ratio Vt1 / Vnew of Vt1 immediately after the start of development, and the ratio Vt2 / Vnew of Vtn for each sleeve cycle. Also, by storing the toner layer potential in a new state, if the toner layer potential has changed over time, or if the potential fluctuates from cycle to cycle, contamination by foreign matter may occur due to foreign matter adhesion. There is also a possibility. In this case, in the developing roller reverse rotation mode, foreign matter can be removed by returning to the normal state by performing an abnormality handling mode such as rotating the developing roller, the developer regulating roller, and the supply roller at an angle opposite to the normal rotation. Is also possible. There is also a method of displaying a developing unit replacement signal when recovery is not performed even in the abnormality handling mode. In this example, the potential sensor is fixed at a certain position in the axial direction, but may be provided so as to be movable in the axial direction for detecting an abnormality or detecting an abnormal image in the axial direction.

  In addition, it is possible to more accurately determine the degree of charge reduction by combining the toner layer potential at the end of the developing operation and the toner layer potential comparison at the start of the developing operation.

  A method of applying a developing bias instead of shifting the latent image start operation timing will be described. When a decrease in the charge amount corresponding to the developing roller cycle is detected, the decrease in the charge amount and the development bias are applied in the direction of increasing the image density. If a data table of the relationship between the charge amount, the image density, and the developing bias is created in advance and the density is supplemented based on the data table, the density unevenness on the image can be made inconspicuous. Since there is no need to delay the operation timing, there is an effect that it is possible to cope with the same print output time as usual.

  The main cause of the decrease in charging ability is mechanical stress or thermal stress on the toner, which appears when the proportion of toner remaining in the developing hopper for a long time without being developed increases. Specifically, the case where the toner remaining amount in the hopper is reduced is remarkable.

  Compared with conventionally used pulverized toner, toner with a circularity of 0.9 or more has a spherical shape, so the toner is easy to roll and the torque applied to the developing unit is reduced, so the stress applied to the toner is reduced, As a result, the burying of the additive is suppressed. Accordingly, since the charging ability is less likely to be reduced than that of the pulverized toner, the frequency of delaying the latent image start timing by the feedback is reduced, and there is an advantage that it is less likely to take extra print output time.

  In general, a tandem lower image forming apparatus is represented by a color image output device, and constitutes a developing device for each color. Therefore, the effect is synergistically increased, and there is a great merit obtained compared to the case of using only the developing device. Specific effects are as follows: (1) The control method corresponding to each color can be adopted by using common parts and the cost can be reduced. (2) It can be easily controlled even in the process conditions corresponding to each color supply, and the image has a defect. (3) Since the stress received by the toner corresponding to each supply can be suppressed and the life of the toner can be extended, the frequency of toner replacement due to the deterioration of the toner is reduced, leading to an improvement in maintenance. Is mentioned.

  In general, a process cartridge refers to a configuration including at least a photoconductor and another image forming apparatus. In the present embodiment, a configuration including at least a photoconductor and a developing device is applicable. The process cartridge is generally used in common with other models, and the cost reduction effect due to the mass production effect due to the common use of parts is great. By deploying this configuration, the great cost reduction effect can be obtained. Also, due to environmental problems in recent years, process cartridges are not disposable but are generally recycled and reused, leading to a total cost reduction due to the cost reduction effect.

  Among the constituent elements such as the photoreceptor, the charging device, the developing device, and the cleaning device, a plurality of components can be integrally combined as a process cartridge. The process cartridge is configured to be detachably attached to an image forming apparatus main body such as a copying machine or a printer. In an image forming apparatus having a process cartridge in which at least a developing device and a photoconductor are integrally coupled, the photoconductor is rotationally driven at a predetermined peripheral speed. In the rotation process, the photoreceptor is charged uniformly with positive or negative predetermined potential on the peripheral surface by the charging device, and then receives image exposure light from an exposure device such as slit exposure or laser beam scanning exposure, and thus the photoreceptor. An electrostatic latent image is sequentially formed on the peripheral surface of the toner, and the formed electrostatic latent image is then developed with toner by a developing device, and the developed toner image is transferred between the photoreceptor and the transfer device from the paper feeding unit. The image is sequentially transferred by the transfer device to the transfer material fed in synchronization with the rotation of the photosensitive member. The transfer material that has received the image transfer is separated from the surface of the photosensitive member, introduced into the fixing device, fixed, and printed out as a copy (copy). The surface of the photoreceptor after the image transfer is cleaned by removing the residual toner by a cleaning device, and after being further neutralized, it is repeatedly used for image formation. The process cartridge can be removed independently and the life of the photosensitive unit and the developing device is extended. However, the lengths of the process cartridges may not always match, and at that time, they can be easily replaced separately. In addition, since it can be arranged independently, the addition of a simple mechanism makes it possible to retract the developing roller from the photosensitive member during non-development, thereby reducing the promotion of toner filming on the developing roller. The life of the developing device is extended.

  A supplemental explanation of the toner having a circularity of 0.9 or more will be given. The circularity of 0.9 or more defines the shape factor of the toner used. The ratio of the projected area to the area based on the average diameter of the toner particles was 96% or more. With normal pulverized toner, it is smaller than 96%. These toners are often produced by a polymerization method (emulsification, suspension, dispersion) or the like. It is also possible to make the toner diameter uniform. In this embodiment, the average particle diameter of the toner manufactured by the polymerization method is 6 μm, the main resin is polyester, and the additives are silica and titanium. The shape factor is 0.96. As a comparative example, a toner prepared by a conventional pulverization method has an average particle diameter of 6 μm, a main resin is polyester, and additives are silica and titanium. However, the shape factor is 0.85.

(Toner circularity measurement method)
It is important that the toner in the present invention has a specific shape. If the average circularity is less than 0.95 and the amorphous shape is too far from the spherical shape, a satisfactory high transfer quality and a high-quality image without dust are obtained. I can't get it. As a method for measuring the shape, an optical detection band method is suitable in which a suspension containing particles is passed through an imaging unit detection band on a flat plate, and a particle image is optically detected and analyzed by a CCD camera. A toner with an average circularity of 0.96 or more, which is a value obtained by dividing the perimeter of an equivalent circle having the same projected area obtained by this method by the perimeter of the actual particle, is a high-definition image with a reproducibility of an appropriate density It was found to be effective in forming. More preferably, the average circularity is 0.960 to 0.998. This value can be measured as an average circularity by a flow type particle image analyzer FPIA-2000 (manufactured by Toa Medical Electronics Co., Ltd.). As a specific measurement method, 0.1 to 0.5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of water from which impure solids have been removed in advance. About 0.1 to 0.5 g. The suspension in which the sample is dispersed is obtained by performing dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and measuring the shape and distribution of the toner with the above apparatus at a dispersion concentration of 3000 to 10,000 / μl. .

(Production method of spherical toner)
Examples of the method for producing a toner having a circularity of 0.96 to 1.00 described in this invention include suspension polymerization, emulsion aggregation, dispersion polymerization, interfacial polymerization, dissolution suspension, and phase inversion emulsification. The manufacturing method by wet granulation is mentioned. A toner having a high degree of circularity can also be produced by pulverizing and classifying a melt-kneaded product, but it is not desirable in terms of energy efficiency. Among the above-mentioned wet granulation methods, suspension polymerization method and dispersion polymerization method are excellent in that a toner with a high degree of circularity can be stably obtained, a sharp particle size distribution can be obtained, and in terms of toner charge control. ing. Further, the dissolution suspension method is excellent in that a polyester resin advantageous in terms of low-temperature fixability of the toner can be used. Hereinafter, the suspension polymerization method, the dispersion polymerization method, and the dissolution suspension method will be described in detail.

(Suspension polymerization method)
For a specific monomer described later, a dispersion stabilizer, a colorant, and, if necessary, a crosslinking agent, a charge control agent, a release agent, and the like are uniformly dispersed by a ball mill or the like, and then a polymerization initiator is added thereto. In addition, a monomer phase is obtained, and the aqueous dispersion medium phase prepared by stirring with the monomer phase in advance is placed in a stirring tank, stirred with a homogenizer, etc., and the resulting suspension is heated after nitrogen substitution and subjected to a polymerization reaction. By completing the above, colored resin particles are obtained, and by washing and drying, colored toner particles can be obtained.

  The polymerizable monomer used for suspension polymerization is a monomer having a vinyl group, and specific examples thereof include the following monomers. That is, styrene such as styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, 2,4-dimethyl styrene, butyl styrene, octyl styrene, and derivatives thereof, and the styrene monomer is most preferable. . Other vinyl monomers include ethylenically unsaturated monoolefins such as propylene, butylene and isobutylene, vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride, vinyl acetate and vinyl propionate. , Vinyl esters such as vinyl benzoate and vinyl butyrate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, acrylic acid-2 -Ethylhexyl, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, n methacrylate Α-methylene aliphatic monocarboxylic esters such as octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, acrylic acid or methacrylic acid such as acrylonitrile, methacrylonitrile, acrylamide Derivatives, vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methyl isopropenyl ketone, N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, N-vinyl pyrrolidone N-vinyl compounds such as vinyl naphthalene and the like can be used, and these monomers can be used alone or in combination.

  In the suspension polymerization method, in order to form a crosslinked polymer in the monomer composition, the following crosslinking agent may be present for suspension polymerization. As a crosslinking agent, divinylbenzene, divinylnaphthalene, polyethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexane glycol dimethacrylate, neopentyl glycol diacrylate, Dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, 2,2'-bis (4-methacryloxydiethoxyphenyl) propane, 2,2'-bis (4-acryloxydiethoxyphenyl) propane, trimethylolpropane trimethacrylate , Trimethylol methane tetraacrylate, dibromoneopentyl glycol dimethacrylate, diallyl phthalate and the like. When the amount of the crosslinking agent used is too large, the toner is hardly melted by heat, and heat fixability and heat pressure fixability are inferior. In addition, if the amount of the crosslinking agent used is too small, properties such as blocking resistance and durability required for the toner are deteriorated, and in heat roll fixing, a part of the toner does not adhere to the paper completely and adheres to the roll surface. As a result, a cold offset occurs in which the image is transferred to the next paper. Therefore, the amount of the crosslinking agent used is 0.001 to 15 parts by weight, preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer.

  The following can be used as the dispersion stabilizer in the suspension polymerization method. That is, water-soluble polymers such as polyvinyl alcohol, starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, sodium polyacrylate, sodium polymethacrylate, barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, clay, silica Soil, metal oxide powder, etc. are used. These are preferably used in the range of 0.1 to 10% by weight based on water.

  In the suspension polymerization method, the polymerization initiator may be added to the dispersion containing the monomer composition after granulation, but the polymerization initiator is uniformly applied to the individual monomer composition particles. From this, it is desirable to make it contain in the monomer composition before granulation. Such polymerization initiators include 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis- (cyclohexane-1- Carbonitrile), 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo or diazo polymerization initiators such as azobisbutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxide And peroxide polymerization initiators such as 2,4-dichloroylbenzoyl peroxide and lauryl peroxide.

  In the suspension polymerization method, a magnetic toner containing a magnetic material is possible. In order to obtain a magnetic toner, magnetic particles may be added to the monomer composition. Examples of magnetic materials that can be used in the present invention include powders of ferromagnetic metals such as iron, cobalt, and nickel, and powders of alloys and compounds such as magnetite, hematite, and ferrite. As the magnetic particles, particles having a particle size of 0.05 to 5 μm, preferably 0.1 to 1 μm are used. When producing a small particle toner, magnetic particles having a particle size of 0.8 μm or less are used. It is desirable to do. The magnetic particles are desirably contained in 10 to 60 parts by weight in 100 parts by weight of the monomer composition. These magnetic particles may be treated with a surface treatment agent such as a silane coupling agent or a titanium coupling agent, or an appropriate reactive resin. In this case, although depending on the surface area of the magnetic particles or the density of hydroxyl groups present on the surface, the surface treatment agent is usually 5 parts by weight or less, preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the magnetic particles. Thus, sufficient dispersibility in the polymerizable monomer is obtained, and the toner physical properties are not adversely affected.

(Dispersion polymerization)
A polymer dispersant that dissolves in the hydrophilic organic liquid is added to the hydrophilic organic liquid, and the polymer that is dissolved in the hydrophilic liquid is swollen by the hydrophilic liquid, or It is produced by adding one or two or more kinds of vinyl monomers which are hardly dissolved and polymerizing. Also included is a reaction in which polymer particles having a particle size distribution smaller than the target particle size and having a narrow particle size distribution are used to grow in the above-described system. The monomer used for the growth reaction may be the same monomer as that used to produce the seed particles or another monomer, but the polymer must not be dissolved in the hydrophilic organic liquid.

  Examples of the hydrophilic organic liquid as a monomer diluent used for the seed particle formation and seed particle growth reaction include methyl alcohol, ethyl alcohol, modified ethyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol. , T-butyl alcohol, s-butyl alcohol, t-amyl alcohol, 3-pentanol, octyl alcohol, benzyl alcohol, cyclohexanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, alcohols such as ethylene glycol, glycerin, diethylene glycol, Methyl cellosolve, cellosolve, isopropyl cellosolve, butyl cellosolve, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol mono Chirueteru, and ether alcohols such as diethylene glycol monoethyl ether as a representative.

  These organic liquids can be used alone or in a mixture of two or more. In addition, by using the organic liquid other than alcohols and ether alcohols together with the above-described alcohols and ether alcohols, the organic liquid can be used under the condition that the organic liquid is not soluble in the generated polymer particles. It is possible to suppress the size of the generated particles, the coalescence of the seed particles, and the generation of new particles by carrying out the polymerization while changing the SP value of each. The organic liquid used in this case includes hydrocarbons such as hexane, octane, petroleum ether, cyclohexane, benzene, toluene, xylene, halogenated hydrocarbons such as carbon tetrachloride, trichloroethylene, tetrabromoethane, and ethyl ether. , Ethers such as dimethyl glycol, siloxane and tetrahydrofuran, acetals such as methylal and diethyl acetal, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexane, esters such as butyl formate, butyl acetate, ethyl propionate and cellosolve acetate , Acids such as formic acid, acetic acid, propionic acid, nitropropene, nitrobenzene, dimethylamine, monoethanolamine, pyridine, dimethyl sulfoxide, dimethylforma Sulfur, such as de, nitrogen-containing organic compounds, other water is also included. In addition, the type and composition of the mixed solvent can be changed at the start of polymerization, during polymerization, and at the end of polymerization to adjust the average particle size, particle size distribution, and drying conditions of the polymer particles to be produced.

  Suitable examples of the polymer dispersant used during seed particle production or growth particle production include acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, Acids such as fumaric acid, maleic acid or maleic anhydride, or acrylic monomers containing hydroxyl groups, such as β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-methacrylic acid β- Hydroxypropyl, γ-hydroxypropyl acrylate, γ-hydroxypropyl methacrylate, 3-chloro-2-hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate Glycerol monoacrylate, glycerol monomethacrylate, N-methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, etc. Esters of compounds containing vinyl alcohol and a carboxyl group, such as vinyl acetate, vinyl propionate, vinyl butyrate, acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic chloride, methacrylic chloride, etc. , Vinyl pyridine, vinyl pyrrolidone, vinyl imidazole, ethyleneimine, etc. Limer or copolymer, polyoxyethylene, polyoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonylphenyl ether, polyoxyethylene laurylphenyl Polyoxyethylenes such as ether, polyoxyethylene stearyl phenyl ester, polyoxyethylene nonyl phenyl ester, and celluloses such as methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, or the above hydrophilic monomers and styrene, α-methylstyrene, vinyl Those having a benzene nucleus such as toluene or derivatives thereof, acrylonitrile, methacrylonitrile, Copolymers with acrylic acid or methacrylic acid derivatives such as chloramide, and copolymers with crosslinkable monomers such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, allyl methacrylate, divinylbenzene and the like can also be used.

  These polymer dispersants are appropriately selected depending on the hydrophilic organic liquid to be used, the seeds of the intended polymer particles, and the production of the seed particles or the growth particles. In order to prevent stericity mainly, a polymer having a high affinity and adsorbability to the polymer particle surface and a high affinity and solubility to a hydrophilic organic liquid is selected. Further, in order to enhance the repulsion between particles in a three-dimensional manner, a molecular chain having a certain length, preferably a molecular weight of 10,000 or more is selected. However, when the molecular weight is too high, the liquid viscosity is remarkably increased, the operability and the stirrability are deteriorated, and the precipitation probability of the produced polymer on the particle surface is varied, so care must be taken. In addition, it is also effective for stabilization that a part of the monomer of the polymer dispersant listed above is allowed to coexist with the monomer constituting the target polymer particle.

  Further, together with these polymer dispersants, metals such as cobalt, iron, nickel, aluminum, copper, tin, lead, magnesium or alloys thereof (particularly those having a particle size of 1 μm or less are preferable), iron oxide, copper oxide, nickel oxide, Inorganic compound fine powders of oxides such as zinc oxide, titanium oxide, silicon oxide, higher alcohol sulfate ester salts, alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters and other anionic surfactants, alkylamine salts, Amine salt types such as amino alcohol fatty acid derivatives, polyamine fatty acid derivatives, imidazoline, and quaternary ammonia such as alkyltrimethylammonium salt, dialkyldimethylammonium salt, alkyldimethylbenzylammonium salt, pyridium salt, alkylisoquinolinium salt, benzethonium chloride, etc. Um salt-type cationic surfactants, fatty acid amide derivatives, non-ionic surfactants such as polyhydric alcohol derivatives, for example amino acids such as alanine type "for example dodecyldi (aminoethyl) glycine, di (octylaminoethyl) glycine" Even if the amphoteric surfactant of the type or betaine type is used in combination, the stability of the produced polymer particles and the improvement of the particle size distribution can be further enhanced.

  In general, the amount of the polymer dispersant used for producing the seed particles varies depending on the type of the polymerizable monomer for forming the target polymer particles, but is 0.1% by weight to 10% by weight with respect to the hydrophilic organic liquid. , Preferably 1 to 5% by weight. When the concentration of the polymer dispersion stabilizer is low, the polymer particles produced have a relatively large particle size, and when the concentration is high, a small particle size can be obtained. Even if it is used beyond, there is little effect on diameter reduction.

  The vinyl monomer is soluble in a hydrophilic organic liquid. For example, styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, α-methyl styrene, p-ethyl. Ethylene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-decylstyrene Styrenes such as pn-dodecyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, 3,4-dichloro styrene, methyl acrylate, ethyl acrylate, n-butyl acrylate, acrylic Isobutyl acid, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, acrylic 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacryl Α-methyl fatty acid monocarboxylic acid esters such as n-octyl acid, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, acrylonitrile , Vinyl halides such as acrylic acid or methacrylic acid derivatives such as methacrylonitrile and acrylamide, vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride Mixtures of singly or cross made of and their containing more than 50 wt% means a mixture of mutual with monomers capable of copolymerizable therewith.

  The polymer may be polymerized in the presence of a so-called crosslinking agent having two or more polymerizable double bonds in order to improve offset resistance. Preferred crosslinking agents include divinylbenzene, divinylnaphthalene and their aromatic divinyl compounds, other ethylene glycol dimethacrylate, diethylene glycol methacrylate, triethylene glycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, tert-butyl. Diethylenic carboxylic acid esters such as aminoethyl methacrylate, tetraethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, all divinyl compounds such as N, N-divinylaniline, divinyl ether, divinyl sulfide, divinyl sulfone, and three The compound which has the above vinyl group is mentioned, These are used individually or in mixture.

  When the growth polymerization reaction is subsequently performed using the seed particles thus crosslinked, the inside of the growing polymer particles is crosslinked. On the other hand, when the above-mentioned crosslinking agent is contained in the vinyl monomer solution used for the growth reaction, a polymer having a cured particle surface can be obtained. Examples of the purpose of adjusting the average molecular weight include compounds having a large chain transfer constant in the presence of polymerization, such as low molecular compounds having a mercapto group, carbon tetrachloride, and carbon tetrabromide.

  Examples of the polymerization initiator for the monomer include azo polymerization initiators such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile), and lauryl. Peroxide polymerization initiators such as peroxide, benzoyl peroxide, t-butyl peroctoate, peroxide polymerization initiators such as potassium persulfate, and systems using sodium thiosulfate, amine, etc. in combination with this Used. The polymerization initiator concentration is desirably 0.1 to 10 parts by weight with respect to 100 parts by weight of the vinyl monomer.

  The polymerization conditions for obtaining the seed particles are determined by the polymer dispersant in the hydrophilic organic liquid, the concentration of the vinyl monomer, and the compounding ratio according to the target average particle size and target particle size distribution of the polymer particles. Is done. In general, if the average particle size of the particles is to be reduced, the concentration of the polymer dispersant is set high, and if the average particle size is to be increased, the concentration of the polymer dispersant is set low. On the other hand, if the particle size distribution is to be made very sharp, the vinyl monomer concentration is set low, and if a relatively wide distribution may be used, the vinyl monomer concentration is set high.

  Particles are produced by completely dissolving a polymer dispersion stabilizer in a hydrophilic organic liquid, and then one or more vinyl monomers, a polymerization initiator, and other inorganic fine powders, surfactants, dyes if necessary. Add pigment, etc., and stir at normal speed of 30 to 300 rpm, preferably at low speed, and at a speed that makes the flow in the tank uniform using a turbine type stirring blade rather than a paddle type However, the polymerization is carried out by heating at a temperature corresponding to the polymerization rate of the polymerization initiator used. In addition, since the temperature at the initial stage of polymerization has a great influence on the kind of particles to be generated, it is desirable to increase the temperature to the polymerization temperature after adding the monomer, and to add the polymerization initiator dissolved in a small amount of solvent. In the polymerization, it is necessary to sufficiently expel oxygen in the air in the reaction vessel with an inert gas such as nitrogen gas or argon gas. If the oxygen purge is insufficient, fine particles are likely to be generated. In order to carry out the polymerization in a high polymerization rate range, a polymerization time of 5 to 40 hours is required, but the polymerization is stopped in a desired particle size, particle size distribution state, or a polymerization initiator is sequentially added, The polymerization rate can be increased by carrying out the reaction under high pressure.

  After completion of the polymerization, the polymer slurry may be used as it is in the dyeing process, or after removing unnecessary fine particles, residual monomers, polymer dispersion stabilizer, etc. by operations such as sedimentation separation, centrifugation, and decantation. However, if the dispersion stabilizer is not removed, the stability of the dyeing is higher and unnecessary aggregation is suppressed.

  Dyeing in the dispersion polymerization method is as follows. That is, the resin particles are dispersed in an organic solvent that does not dissolve the resin particles, the dye is dissolved in the solvent before or after this, the dye is infiltrated into the resin particles and colored, and then the organic solvent is removed. In the method for producing a dyed toner, the relationship between the solubility of the dye in the organic solvent (D1) and the solubility of the dye in the resin of the resin particle A (D2) is (D1) / (D2) A dye satisfying ≦ 0.5 is selectively used. As a result, a toner in which the dye has penetrated (diffused) to the deep part of the resin particles can be efficiently produced. The solubility in this specification is defined as measured at a temperature of 25 ° C. The solubility of the dye in the resin has the same definition as the solubility of the dye in the solvent, and means the maximum amount that the dye can be contained in the resin in a compatible state. Observation of the dissolved state or the deposited state of the dye can be easily performed using a microscope. In order to know the solubility of the dye in the resin, an indirect observation method may be used instead of the direct observation method described above. In this method, a liquid having a solubility coefficient close to that of the resin, that is, a solvent that dissolves the resin well, and the solubility of the dye in this solvent may be determined as the solubility in the resin.

As a dye used for coloring, the ratio (D1) / (D2) of the dye to the resin constituting the resin particles is 0.5 or less from the solubility (D1) of the dye in the organic solvent used as described above. Need to be. Furthermore, it is preferable that (D1) / (D2) be 0.2 or less. The dye is not particularly limited as long as it satisfies the above-mentioned solubility characteristics, but water-soluble dyes such as cationic dyes and anionic dyes may cause large environmental fluctuations, and the electrical resistance of the toner is lowered, resulting in a decrease in transfer rate. Since there is a possibility, use of a vat dye, a disperse dye, and an oil-soluble dye is preferable, and an oil-soluble dye is particularly preferable. Also, several kinds of dyes can be used in combination depending on the desired color tone. The ratio (weight) between the dye to be dyed and the resin particles is arbitrarily selected depending on the degree of coloring, but is usually used in a ratio of 1 to 50 parts by weight of the dye with respect to 1 part by weight of the resin particles. Is preferred. For example, when an alcohol such as methanol or ethanol having a high SP value is used as the dyeing solvent and a styrene-acrylic resin having an SP value of about 9 is used as the resin particle, examples of the dye that can be used include: And dyes such as
CI SOLVENT YELLOW (6,9,17,31,35,1,102,103,105)
CI SOLVENT ORANGE (2,7,13,14,66)
CI SOLVENT RED (5,16,17,18,19,22,23,143,145,146,149,150,151,157,158)
CI SOLVENT VIOLET (31,32,33,37)
CI SOLVENT BLUE (22,63,78,83-86,91,94,95,104)
CI SOLVENT GREEN (24,25)
CI SOLVENT BROWN (3,9) etc.

  Commercially available dyes include, for example, Aizen SOT dyes Yellow-1,3,4, Orange-1,2,3, Scarlet-1, Red-1,2,3, Brown-2, Blue-1, manufactured by Hodogaya Chemical Co., Ltd. 2, Violet-1, Green-1, 2, 3, Black-1, 4, 6, 8 and Sudan dyes manufactured by BASF, Yellow-140, 150, Orange-220, Red-290, 380, 460, Blue -670 and Mitsubishi Chemical's dialresin, Yellow-3G, F, H2G, HG, HC, HL, Orange-HS, G, Red-GG, S, HS, A, K, H5B, Violet-D, Blue- Oil color made by J, G, N, K, P, H3G, 4G, Green-C, Brown-A and Orient Chemical, Yellow-3 , GG-S, # 105, Orange-PS, PR, # 201, Scarlet- # 308, Red-5B, Brown-GR, # 416, Green-BG, # 502, Blue-BOS, HN, Black-HBB, # 803, EE, EX, Sumitomo Chemical's Sumiplast, Blue GP, OR, Red FB, 3B, Yellow FL7G, GC, Nippon Kayaku Kayalon, Polyester Black EX-SH3, Kaya Set Red-B Blue A-2R or the like can be used. Of course, the dye is appropriately selected depending on the combination of the resin particles and the solvent used at the time of dyeing, and is not limited to the above example.

  As an organic solvent for dyeing used for dyeing a resin particle, one in which the resin particle to be used does not dissolve or that slightly swells, specifically, the difference in solubility parameter (SP value) is 1. 0.0 or more, preferably 2.0 or more is used. For example, for styrene-acrylic resin particles, alcohols such as methanol, ethanol and n-propanol having a high SP value, or n-hexane and n-heptane having a low SP value are used. If the SP value difference is too large, wetting with respect to the resin particles becomes poor, and good dispersion of the resin particles cannot be obtained. Therefore, the optimum SP value difference is preferably 2 to 5.

  After dispersing the resin particles in the organic solvent in which the dye is dissolved, it is preferable to keep the liquid temperature below the glass transition temperature of the resin particles and stir. Thereby, it is possible to dye while preventing aggregation of the resin particles. The stirring may be performed using a commercially available stirrer such as a homomixer or a magnetic stirrer. Alternatively, a dye may be directly added to a slurry obtained at the end of polymerization by dispersion polymerization or the like, that is, a dispersion in which polymer resin particles are dispersed in an organic solvent, and heated and stirred under the above conditions. When the heating temperature exceeds the glass transition temperature, fusion between the resin particles occurs. The method for drying the slurry after dyeing is not particularly limited, but may be directly dried under reduced pressure without filtering or filtering after filtration. In the present invention, the colored particles obtained by air-drying or drying under reduced pressure after being separated by filtration in the present invention are hardly agglomerated and are reproduced with almost no loss of the particle size distribution of the charged resin particles.

(Dissolution suspension method)
Next, a method for producing spherical toner particles by the dissolution suspension method will be described. The dissolution suspension method is a method in which a resin is dissolved in a solvent to prepare an oil phase, emulsified in an aqueous phase composed of an aqueous medium, and then the solvent in the emulsified dispersion is removed to obtain resin particles.

As the aqueous medium, water alone may be used, but a solvent miscible with water may be used in combination. Examples of miscible solvents include alcohol (methanol, isopropanol, ethylene glycol, etc.), dimethylformamide, tetrahydrofuran, cellosolves (methyl cellosolve, etc.), lower ketones (acetone, methyl ethyl ketone, etc.), and the like.
As the resin to be used, styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene, and a polymer of a substituted product thereof; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer Styrene-vinyl naphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate Copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, Styrene-butadiene copolymer, Styrene copolymers such as lene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polychlorinated Vinyl, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, Aromatic petroleum resins, chlorinated paraffin, paraffin wax and the like can be mentioned, and these can be used alone or in combination.

  As a solvent that can be used for oil phase preparation, a volatile solvent having a boiling point of less than 100 ° C. is preferable from the viewpoint of easy removal. Examples of the solvent include toluene, xylene, benzene, carbon tetrachloride, methylene chloride, 1,2-dichloroethane, 1,1,2-trichloroethane, trichloroethylene, chloroform, monochlorobenzene, dichloroethylidene, methyl acetate, ethyl acetate, Methyl ethyl ketone, methyl isobutyl ketone and the like can be used alone or in combination of two or more. In particular, aromatic solvents such as toluene and xylene and halogenated hydrocarbons such as methylene chloride, 1,2-dichloroethane, chloroform, and carbon tetrachloride are preferable. The amount of solvent used with respect to 100 parts of the toner composition is usually 10 to 900 parts.

  The oil phase is prepared by adding and mixing the colorant (or colorant masterbatch), the release agent, and the charge control agent, which are other toner compositions, at the same time when the dispersion is formed in the aqueous medium. However, it is more preferable to mix in the oil phase in advance.

  Further, other toner raw materials such as a colorant, a release agent, and a charge control agent do not necessarily have to be mixed when forming particles in an aqueous medium, and may be added after the particles are formed. Good. For example, after forming particles containing no colorant, the colorant can be added by a known dyeing method.

  For the dispersion of the oil phase and the aqueous phase, all normal stirring mixers can be used, but more preferably, a homogenizer having a high-speed rotating body and a stator, a high-pressure homogenizer, a ball mill, a bead mill, and a sand mill. Etc. are used.

  The dispersion method is not particularly limited, and known equipment such as a low-speed shear method, a high-speed shear method, a friction method, a high-pressure jet method, and an ultrasonic wave can be applied. In order to make the particle size of the dispersion 2 to 20 μm, a high-speed shearing type is preferable. The emulsifier having rotating blades is not particularly limited, and any emulsifier and disperser that are generally commercially available can be used. For example, Ultra Thalax (manufactured by IKA), Polytron (manufactured by Kinematica), TK auto homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), Ebara Milder (manufactured by Ebara Corporation), TK pipeline homomixer , TK homomic line flow (manufactured by Special Machine Industries Co., Ltd.), colloid mill (manufactured by Shinko Pantech Co., Ltd.), slasher, trigonal wet pulverizer (manufactured by Mitsui Miike Chemical Co., Ltd.), Cavitron (Eurotech Co., Ltd.) ), Fine flow mill (manufactured by Taiheiyo Kiko Co., Ltd.) and other continuous emulsifiers, CLEARMIX (manufactured by M Technique Co., Ltd.), fill mix (manufactured by Koki Kogyo Co., Ltd.), etc. Etc.

  When a high-speed shearing disperser is used, the rotational speed is not particularly limited, but is usually 1000 to 30000 rpm, preferably 5000 to 20000 rpm. The dispersion time is not particularly limited, but in the case of a batch method, it is usually 0.1 to 5 minutes. The temperature during dispersion is usually 0 to 150 ° C. (under pressure), preferably 10 to 98 ° C. The high temperature condition method is preferable in that the dispersion has a reasonably low viscosity and is easily dispersed.

  In the dissolution suspension method, a method of dispersing solid fine particles in an aqueous medium in advance is used for the purpose of stabilizing the dispersed oil phase.

  Furthermore, other dispersants can be used in combination to adjust the adsorptivity of the solid fine particle dispersant to the droplets. Other dispersants can be added before emulsification of the toner composition or after removal of volatile components after emulsification.

[Solid particulate dispersant]
The solid fine particle dispersant is present in a solid form hardly soluble in water in an aqueous medium, and is preferably fine particles having an average particle diameter of 0.01 to 1 μm.

  Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride. More preferably, tricalcium phosphate, calcium carbonate, colloidal titanium oxide, colloidal silica, hydroxyapatite and the like can also be used. In particular, hydroxyapatite synthesized by reacting sodium phosphate and calcium chloride in water under a basic condition is preferable.

  Examples of organic solid fine particle dispersants include microcrystals of low molecular weight organic compounds and polymer fine particles such as soap-free emulsion polymerization, suspension polymerization, polystyrene obtained by dispersion polymerization, methacrylate ester, acrylate ester copolymer, silicone, Examples of the polymer particles include polycondensation systems such as benzoguanamine and nylon, and thermosetting resins.

  In addition, hydrochloric acid or sodium hydroxide should be used when the solid fine particle dispersant is an acid such as calcium phosphate, or a polymer fine particle copolymerized with (meth) acrylic acid having a carboxyl group. The solid fine particle dispersant is removed from the toner particles whose shape has been adjusted by a method of dissolving the solid fine particle dispersant with an acid base such as water washing. It can also be removed by operations such as enzymatic degradation.

[Other dispersants used together during emulsification or added later]
Anionic surfactants such as alkylbenzene sulfonates, α-olefin sulfonates, phosphate esters, alkylamine salts, aminoalcohol fatty acid derivatives, polyamine fatty acid derivatives, amine salt types such as imidazoline, alkyltrimethylammonium salts, dialkyl Nonionic surfactants such as dimethylammonium salts, alkyldimethylbenzylammonium salts, pyridinium salts, alkylisoquinolinium salts, quaternary ammonium salt type cationic surfactants such as benzethonium chloride, fatty acid amide derivatives, polyhydric alcohol derivatives, etc. Agents such as amphoteric surfactants such as alanine, dodecyl di (aminoethyl) glycine, di (octylaminoethyl) glycine and N-alkyl-N, N-dimethylammonium betaine.

In addition, by using a surfactant having a fluoroalkyl group, the effect can be obtained in a very small amount. Preferred anionic surfactants having a fluoroalkyl group include fluoroalkyl carboxylic acids having 2 to 10 carbon atoms and metal salts thereof, disodium perfluorooctanesulfonyl glutamate, 3- [omega-fluoroalkyl (C6-C11). ) Oxy] -1-alkyl (C3-C4) sodium sulfonate, 3- [omega-fluoroalkanoyl (C6-C8) -N-ethylamino] -1-propanesulfonic acid sodium, fluoroalkyl (C11-C20) carboxylic acid And metal salts, perfluoroalkylcarboxylic acids (C7 to C13) and metal salts thereof, perfluoroalkyl (C4 to C12) sulfonic acids and metal salts thereof, perfluorooctanesulfonic acid diethanolamide, N-propyl-N- (2-hydroxyethyl) -Fluorooctanesulfonamide, perfluoroalkyl (C6-C10) sulfonamidopropyltrimethylammonium salt, perfluoroalkyl (C6-C10) -N-ethylsulfonylglycine salt, monoperfluoroalkyl (C6-C16) ethyl phosphate, etc. Is mentioned.
Product names include Surflon S-111, S-112, S-113 (Asahi Glass Co., Ltd.), Florard FC-93, FC-95, FC-98, FC-129 (Sumitomo 3M Co., Ltd.), Unidyne DS-1101 DS-102, (manufactured by Taikin Kogyo Co., Ltd.), Mega-Fac F-ll0, F-120, F-113, F-191, F-812, F-833 (Dainippon Ink Co., Ltd.), Xtop EF- 102, 103, 104, 105, 112, 123A, 123B, 306A, 501, 201, 204 (manufactured by Tochem Products), and Fagento F-100, F150 (manufactured by Neos).

  In addition, as the cationic surfactant, aliphatic quaternary ammonium salts such as aliphatic primary, secondary or secondary amic acid, perfluoroalkyl (C 6 -C 10) sulfonamidopropyltrimethylammonium salt which right the fluoroalkyl group, Benzalkonium salt, benzethonium chloride, pyridinium salt, imidazolinium salt, trade names include Surflon S-121 (Asahi Glass Co., Ltd.), Florard FC-135 (Sumitomo 3M Co., Ltd.), Unidyne DS-202 (Daikin Kogyo Co., Ltd.) ), Megafuck F-150, F-824 (Dainippon Ink Co., Ltd.), Xtop EF-132 (Tochem Products Co., Ltd.), Footgent F-300 (Neos Co., Ltd.) and the like.

  The stabilization of the dispersed droplets may be adjusted with a polymer protective colloid. For example, acrylic acid, methacrylic acid, α-cyanoacrylic acid, α-cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid or maleic anhydride and other (meth) acrylic monomers containing hydroxyl groups Bodies such as β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, γ-hydroxypropyl acrylate, γ-hydroxypropyl methacrylate, 3-acrylate Chloro-2-hydroxypropyl, 3-chloro-2-hydroxypropyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, glycerol monoacrylate, glycerol monomethacrylate, N -Methylol acrylamide, N-methylol methacrylamide, etc., vinyl alcohol or ethers with vinyl alcohol, such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, etc., or esters of compounds containing vinyl alcohol and carboxyl groups, such as Vinyl acetate, vinyl propionate, vinyl butyrate, etc., acrylamide, methacrylamide, diacetone acrylamide or their methylol compounds, acid chlorides such as acrylic acid chloride, methacrylic acid chloride, pinyl pyridine, vinyl pyrrolidone, vinyl imidazole, ethyleneimine, etc. Homopolymers or copolymers such as those having nitrogen atoms or heterocyclic rings thereof, polyoxyethylene, polyoxypropylene, polymers Oxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl phenyl ether, polyoxyethylene stearyl phenyl ester, polyoxyethylene nonyl phenyl ester Polyoxyethylenes such as, celluloses such as methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and the like can be used. When a dispersant is used, the dispersant can remain on the surface of the toner particles, but it is preferable from the charged surface of the toner to wash away after the reaction.

  In order to remove the organic solvent from the obtained emulsified dispersion, a method in which the temperature of the entire system is gradually raised to completely evaporate and remove the organic solvent in the droplets can be employed. Alternatively, the emulsified dispersion can be sprayed into a dry atmosphere to completely remove the water-insoluble organic solvent in the droplets to form toner fine particles, and the aqueous dispersant can be removed by evaporation together. . As a dry atmosphere in which the emulsified dispersion is sprayed, a gas obtained by heating air, nitrogen, carbon dioxide gas, combustion gas, or the like, in particular, various air currents heated to a temperature equal to or higher than the boiling point of the highest boiling solvent used is generally used. Sufficient quality can be obtained with a short treatment such as spray dryer, belt dryer or rotary kiln.

  In the dissolution suspension method, solid fine particles usually adhere to the surface of emulsified oil droplets and stabilize the droplets in a spherical shape, but in the process of removing volatile components, the volume of the droplets decreases but the solids decrease. The fine particles remain attached as they are, and the surface area of the droplets decreases slowly, and the sphere cannot be maintained without catching up with the decrease in volume, and may become amorphous.

  In the suspension solution method, to obtain a spherical toner with a high degree of circularity, when removing the toner volatile components, the adsorption force at the interface of the solid fine particles is weakened, detachment from the droplets is promoted, and the sphere is maintained. However, it is necessary to form particles. For example, by adding a surfactant or polymer protective colloid for exchange adsorption, or adjusting the pH in the aqueous medium to change the charge of the droplet surface and the solid fine particles, adsorption at the solid fine particle interface Can weaken power.

(Sphericalizing of pulverized toner)
The toner by the pulverization / classification method is indefinite as it is, and depending on the pulverization method, the circularity is 0.930 to 0.950, and the circularity of the present invention is 0.96 to 1.00. However, the degree of circularity can be increased by a mechanical spheroidizing process or a heat treatment, which will be described later, and the toner having a circularity of 0.96 to 1.00 according to the present invention can be obtained.

[Mechanical processing]
For example, a method using a turbo mill (manufactured by Turbo Kogyo) described in JP 09-087441 A, a kryptron (manufactured by Kawasaki Heavy Industries), a Q-type mixer (manufactured by Mitsui Mining), a hybridizer (manufactured by Nara Machinery), a mechano By continuously processing with a fusion device (made by Hosokawa Micron etc.), the shape of the pulverized toner can be made spherical.

[Heat treatment (dry type)]
For example, the shape of the pulverized toner can be made spherical by semi-melting the surface of the toner particles with hot air of 100 to 300 ° C. using a surffusion system (Nippon Pneumatic Industry).

[Heat treatment (wet)]
The shape of the pulverized toner can be made spherical by immersing the toner obtained by the pulverization method in a high-temperature liquid at a temperature (about 200 ° C.) at which the toner has plasticity.

(Description of charge control agent)
The toner to be used may contain a charge control agent as required. Any known charge control agent can be used, for example, nigrosine dyes, triphenylmethane dyes, chromium-containing metal complex dyes, molybdate chelate pigments, rhodamine dyes, alkoxy amines, quaternary ammonium salts (fluorine-modified) Quaternary ammonium salts), alkylamides, phosphorus simple substances or compounds, tungsten simple substances or compounds, fluorine-based activators, salicylic acid metal salts, and metal salts of salicylic acid derivatives. Specifically, Nitronine-based dye Bontron 03, quaternary ammonium salt Bontron P-51, metal-containing azo dye Bontron S-34, oxynaphthoic acid metal complex E-82, salicylic acid metal complex E- 84, E-89 of a phenol-based condensate (manufactured by Orient Chemical Industry Co., Ltd.), TP-302 of a quaternary ammonium salt molybdenum complex, TP-415 (manufactured by Hodogaya Chemical Industry Co., Ltd.), quaternary ammonium Copy charge PSY VP2038 of salt, copy blue PR of triphenylmethane derivative, copy charge of quaternary ammonium salt NEG VP2036, copy charge NX VP434 (manufactured by Hoechst), LRA-901, LR-147 which is a boron complex (Nippon Carlit Co., Ltd.), copper phthalocyanine, perylene, quinacridone Azo pigments, sulfonate group, a carboxyl group, and a polymer compound having a functional group such as a quaternary ammonium salt. When toner particles are produced in an aqueous medium, a charge control agent that is difficult to dissolve in water is preferable from the viewpoint of controlling ionic strength and wastewater contamination.

  The amount of charge control agent used is determined by the type of binder resin, the presence or absence of additives used as necessary, and the toner production method including the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin. The range of 0.2 to 5 parts by weight is preferable. When the amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the main charge control agent is reduced, the electrostatic attractive force with the developing roller is increased, the flowability of the developer is reduced, and the image density is reduced. Incurs a decline. These charge control agents and release agents can be melt-kneaded together with the masterbatch and the resin, and of course, they may be added when dissolved and dispersed in an organic solvent.

(Description about colorant)
As the colorant, all known dyes and pigments can be used. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, Yellow lead, Titanium yellow, Polyazo yellow, Oil yellow, Hansa yellow (GR, A, RN, R), Pigment yellow L, Benzidine yellow (G, GR), Permanent yellow (NCG), Vulcan fast yellow (5G, R) ), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Red Dan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimon Zhu, Permanent Red 4R, Para Red, Phi Se Red, parachlor ortho nitro Nilin Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine B, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red F5R , Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Po Azo Red, Chrome Vermilion, Benzidine Orange, Perinone Orange, Oil Orange, Cobalt Blue, Cerulean Blue, Alkaline Blue Lake, Peacock Blue Lake, Victoria Blue Lake, Metal Free Phthalocyanine Blue, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue (RS, BC), indigo, ultramarine blue, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt purple, manganese purple, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridian, emerald green, pigment Green B, Naphthol Green B, Green Gold, Acid Green Lake, Malachite Green Lake, Phthalo Anine green, anthraquinone green, titanium oxide, zinc white, litbon and mixtures thereof can be used. The amount used is generally 0.1 to 50 parts by weight per 100 parts by weight of the binder resin.

  The toner colorant can also be used as a master batch combined with a resin. As the binder resin to be kneaded together with the production of the masterbatch or the masterbatch, in addition to the modified and unmodified polyester resins mentioned above, styrene such as polystyrene, poly p-chlorostyrene, polyvinyltoluene, and polymers of substituted products thereof; Styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α- Chloromethyl methacrylate copolymer, Tylene-acrylonitrile copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-malein Styrene copolymers such as acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, poly Acrylic resin, rosin, modified rosin, terpene resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. The

  The master batch can be obtained by mixing and kneading a resin for a master batch and a colorant under a high shear force to obtain a master batch. In this case, an organic solvent can be used in order to enhance the interaction between the colorant and the resin. Also, a so-called flushing method called watering paste containing water of colorant is mixed and kneaded with resin and organic solvent, and the colorant is transferred to the resin side to remove moisture and organic solvent components. Since it can be used as it is, it does not need to be dried and is preferably used. For mixing and kneading, a high shear dispersion device such as a three-roll mill is preferably used.

(Description of release agent)
Examples of the wax include solid paraffin wax, micro wax, rice wax, fatty acid amide wax, fatty acid wax, aliphatic monoketone, fatty acid metal salt wax, fatty acid ester wax, partially saponified fatty acid ester wax, Mention may be made of silicone varnishes, higher alcohols, carnauba wax and the like. Also, polyolefins such as low molecular weight polyethylene and polypropylene can be used. The wax has a melting point of 40 to 120 ° C., and preferably 50 to 110 ° C. When the melting point of the wax is excessive, the fixing property at low temperature may be insufficient. On the other hand, when the melting point is excessively low, the offset resistance and durability may be deteriorated. The melting point of the wax is determined by a differential scanning calorimetry ( DSC). That is, the melting peak value when a sample of several mg is ripened at a constant temperature increase rate, for example, (10 ° C./min) is defined as the melting point.

(Mixing of external additives)
In order to improve the fluidity, storage stability, developability, and transferability of the toner, inorganic fine particles such as hydrophobic silica fine powder may be further added to and mixed with the toner manufactured as described above. For mixing external additives, a general powder mixer is used, but it is preferable to equip a jacket or the like to adjust the internal temperature. In order to change the load history applied to the external additive, the external additive may be added in the middle or gradually. Of course, you may change the rotation speed of a mixer, rolling speed, time, temperature, etc. A strong load may be given first, then a relatively weak load, and vice versa. Examples of the mixing equipment that can be used include a V-type mixer, a rocking mixer, a Ladige mixer, a Nauter mixer, a Henschel mixer, and the like.

(Inorganic fine particles as external additives)
Inorganic fine particles can be used as an external additive for assisting the fluidity, developability, transferability, cleaning property, and chargeability of the toner. The primary particle diameter of the inorganic fine particles is preferably 0.01 to 2 μm. Moreover, it is preferable that the specific surface area by BET method is 20-500 m < ² > / g. The proportion of the inorganic fine particles used is preferably 0.1 to 15% by weight of the toner, and more preferably 0.5 to 10% by weight. Specific examples of the inorganic fine particles include, for example, silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, tin oxide, quartz sand, clay, mica, wollastonite, diatomaceous earth. Examples include soil, chromium oxide, cerium oxide, pengala, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride.

(Resin fine particles as external additives)
A resin fine particle may be used together with the fluidizing agent. For example, polystyrene particles obtained by soap-free emulsion polymerization, suspension polymerization, or dispersion polymerization, methacrylic acid ester or acrylic acid ester copolymer, polycondensation systems such as silicone, benzoguanamine, and nylon, and polymer particles by thermosetting resin can be mentioned. . By using in combination with such resin fine particles, the chargeability of the toner can be enhanced, the reversely charged toner particles can be reduced, and the background contamination can be reduced. The addition amount may be 0.01 to 5% by weight, preferably 0.1 to 2% by weight, based on the toner.

Toner A (suspension polymerization example, high circularity)

Add 40 parts by weight of styrene monomer, 20 parts by weight of carbon black MA100 (manufactured by Mitsubishi Kasei Co., Ltd.) and 0.5 parts by weight of 2,2'-azobisisobutyronitrile as a polymerization initiator. Into a 500 ml four-necked separable flask equipped with a gas introduction tube and a thermometer, the mixture was stirred for 30 minutes at room temperature under a nitrogen stream, and the inside of the flask was replaced with nitrogen. Then, it stirred at 60 rpm in a 70 degreeC hot water bath for 6 hours, and graft carbon black was obtained.

Then
Styrene monomer 50.0 parts by weight n-butyl methacrylate 14.5 parts by weight 1,3-butanediol dimethacrylate 0.5 parts by weight t-butylacrylamide sulfonic acid 3.0 parts by weight Low molecular weight polyethylene 2.0 parts by weight ( (Mitsui Petrochemicals, Mitsui High Wax 210P)
A mixture of 30.0 parts by weight of the graft carbon black was dispersed with a ball mill for 10 hours. After dissolving 1 part by weight of 2,2'-azobisisobutyronitrile and sodium nitrite in this dispersion, it was added to 250 parts by weight of a 2% aqueous solution of polyvinyl alcohol and added to a TK homomixer (Special Machine Co., Ltd.). The mixture was stirred at 6000 rpm for 10 minutes to obtain a suspension. The suspension was put into a 500 ml four-necked separable flask equipped with a three-one motor-driven stirring blade, a cooler, a gas inlet tube, and a thermometer, and stirred at room temperature for 30 minutes in a nitrogen stream to remove oxygen in the flask. Replaced with nitrogen. Thereafter, the mixture was stirred in a hot water bath at 70 ° C. for 8 hours at 90 rpm to complete the polymerization, thereby producing suspension polymerization particles. 100 parts by weight of these particles are redispersed in a mixed solution of water / methanol = 1/1 (weight ratio) so that the solid content is 30%, and 3 parts by weight of ditertiary butylsalicylic acid zinc salt is added as a charge control agent and stirred. Thereafter, filtration and drying were performed to obtain colored particles.

To 95 parts by weight of the obtained colored particles, 3 parts by weight of silica and 2 parts by weight of titanium oxide particles were mixed for 2 minutes with a Henschel mixer and sieved to obtain a toner.
This toner is referred to as toner A.
The circularity of the toner A was 0.98.
The weight average particle diameter of the toner A was 5.81 μm.
To 95 parts by weight of a silicone-coated carrier (magnetite core material) having a weight average particle diameter of 50 μm, 5 parts by weight of toner A was mixed with a rocking mixer to obtain a two-component developer.

Toner D (Comparison example with pulverized toner, low circularity)

The following raw materials were sufficiently mixed with a Henschel mixer, and then kneaded with a small two-roll mill at 150 ° C. for 2 hours.

Binder resin (styrene-methyl acrylate copolymer) 100.0 parts by weight Colorant (carbon black # 44, manufactured by Mitsubishi Carbon Corporation) 10.0 parts by weight Charge control agent (ditertiary butylsalicylate zinc salt)
(Orient Chemical Bontron E-84) 2.0 parts by weight Carnauba wax 5.0 parts by weight

The obtained kneaded product was coarsely pulverized with a pulverizer equipped with a 2 mm screen, then pulverized with a lab jet, and classified with 100 MZR to obtain colored particles.

To 95 parts by weight of the obtained colored particles, 3 parts by weight of silica and 2 parts by weight of titanium oxide particles were mixed for 2 minutes with a Henschel mixer and sieved to obtain a toner.
This toner is referred to as Toner D.
The circularity of the toner D was 0.93.
Toner D had a weight average particle diameter of 5.73 μm.
Two-component developer creation is the same as toner A

Toner G (Example of heat treatment of ground toner, high degree of circularity)

The colored particles obtained in the production example of Toner D were treated twice with a heat treatment temperature of 250 ° C., a hot air flow rate of 1000 l / min, and a supply air flow rate of 100 l / min using a Japan Pneumatic Surffusion System. Obtained.

To 95 parts by weight of the obtained colored particles, 3 parts by weight of silica and 2 parts by weight of titanium oxide particles were mixed for 2 minutes with a Henschel mixer and sieved to obtain a toner.
This toner is referred to as toner G.
The circularity of the toner G was 0.93.
The weight average particle size of the toner G was 5.56 μm.
In the preparation of the two-component developer, the circularity of each toner used was the same as that of the toner A, and the circularity of the toner A is 0.98, the toner D is 0.93, and the toner G is 0.97. When this toner was used and the change with time was examined, the rise of charging of the toner D was slow and the amount of scattering was larger than the initial value, which was 32 [mg / min]. It is considered that because of the amorphous shape, the dispersion efficiency of the additive is poor and the uniformity of charging cannot be obtained. On the other hand, toners A and G were in a state where the scattering amount was low with no problem. A: 15 [mg / min], G: 19 [mg / min].

  According to the second aspect of the present invention, development density unevenness is detected in the first and second rounds of the developing roller, and when density unevenness occurs, the latent image start timing is delayed to thereby develop the developing roller. Since the image thinner than the normal image density due to the decrease in the charge amount of the developer on the first round is not developed on the transfer paper, the image on the developing roller from the position where the latent image start timing is shifted is transferred. Unevenness can be made inconspicuous.

  According to the third aspect of the present invention, when developing density after a certain period of time has elapsed since the end of one job of print output, when there is a decrease in the charge amount of the developer, density unevenness appears. The density unevenness on the image can be made inconspicuous by feeding back the latent image start timing based on the result of detecting the development density.

  In the invention according to claim 4, when the toner in the toner cartridge decreases, new toner is not replenished, and the toner ratio in which the charge amount is likely to decrease tends to increase in the hopper of the developing device. By feeding back the latent image start timing based on the detection result of the remaining amount of toner in the hopper, density unevenness on the image can be made inconspicuous.

  According to the fifth aspect of the present invention, since the toner consumption can be converted by counting the number of print output pixels, the degree of decrease in the toner amount is predicted after detecting the remaining amount of toner in the hopper of the developing device. Thus, the density unevenness on the image can be made inconspicuous by feeding back the latent image start timing more accurately.

  According to the sixth aspect of the present invention, when a new toner is replenished from the toner cartridge, the toner ratio in which the charge amount is likely to decrease is reduced in the hopper of the developing device. The density unevenness on the image can be made inconspicuous by feeding back the latent image start timing based on the information at the time of exchanging and the counter information after the exchange.

  According to the seventh aspect of the invention, by measuring the toner layer potential on the developing roller, it is possible to detect a potential fluctuation from the start to the end of the developing operation, and predict an image unevenness state when developing on the image. can do.

  According to the eighth aspect of the present invention, it is possible to determine the decrease in the charge amount by measuring and comparing the toner layer potential on the developing roller after the end of the developing operation and at the start of the next operation, and the image unevenness state when the image is developed. Can be predicted.

  According to the ninth aspect of the present invention, it is possible to determine a decrease in the charge amount by measuring and comparing the toner layer potential on the developing roller immediately after the start of the developing operation and when a certain time has elapsed, and the unevenness of the image when the image is developed. The state can be predicted.

  The invention according to claim 10 determines the deterioration state of the developer and the state change of the member contributing to toner charging by measuring the toner layer potential on the developing roller between the new state and the current state. Can do.

  According to the eleventh aspect of the invention, by measuring the toner layer potential on the developing roller between the new state and the current state in the developing roller cycle, the deterioration state of the developer and the state change of the member contributing to toner charging In addition, it is possible to detect an abnormal value of the toner layer potential due to foreign matter contamination or foreign matter adhesion, and to determine abnormality of the developing device.

  The invention according to claim 12 predicts development density unevenness in the first and second rounds of the developing roller and performs control different from the normal operation timing, thereby changing the density in the first round to the density in the second and subsequent rounds. Accordingly, an image thinner than the normal image density due to a decrease in the charge amount of the developer on the first round of the developing roller is not developed on the transfer paper, and density unevenness on the image can be made inconspicuous.

  According to the thirteenth aspect of the invention, by delaying the latent image start timing, an image thinner than the normal image density due to a decrease in the charge amount of the developer on the first round of the developing roller is not developed on the transfer paper, and the latent image start timing is set. Since the image on the developing roller from the shifted position is transferred, density unevenness on the image can be made inconspicuous.

  According to the fourteenth aspect of the present invention, since the developing bias is controlled in a direction in which the image density is higher than the normal bias, it approaches the normal image density due to the decrease in the charge amount of the developer on the first round of the developing roller. Density unevenness can be made inconspicuous.

  According to the fifteenth aspect of the present invention, the image unevenness caused by the toner having a reduced charge amount is likely to occur in the first sheet during continuous output. Therefore, the output time becomes longer by changing the timing according to the job mode. This prevents printing output productivity from being reduced.

  In the invention according to the sixteenth aspect, since the toner with increased circularity is less likely to embed the additive than the toner with low circularity such as the pulverized toner, the decrease in the charge amount is suppressed. Image unevenness due to partial density reduction is difficult to occur.

  According to the seventeenth aspect of the present invention, in particular, in the case of a color tandem type image forming apparatus, when the toner characteristic value differs depending on various supplies, the configuration detection, control method, feedback timing, etc. are changed. Therefore, image unevenness due to a decrease in the density at the front end of the image can be made inconspicuous. As a result, the life of the developer can be extended, so that the frequency of replacement of the developing device can be reduced. In particular, maintenance is improved without frequently changing a plurality of developing devices. Costs can be reduced by using parts in common.

  The invention according to claim 18 can extend the life of the developer as in the case of claim 17, so that the replacement frequency of the process cartridge can be reduced, and maintenance performance can be improved without frequently changing a plurality of process cartridges. It leads to improvement. Costs can be reduced by using parts in common. In addition, since normal process cartridges are frequently recycled (used a plurality of times), they can be expanded to multiple types by sharing parts, which leads to a total cost reduction.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a schematic block diagram of a Bk developing device. It is a drawing for explaining solid development and halftone development operations in Bk development single color. It is a drawing for explaining solid development and halftone development operations in Bk development single color. It is a drawing for explaining solid development and halftone development operations in Bk development single color. 3 is a diagram illustrating an example in which a sensor for detecting toner density is provided. 6 is a diagram illustrating an example in which a remaining toner detection sensor is provided in a Bk developing device. 2 is a diagram illustrating an example in which a toner cartridge is further provided. It is a schematic block diagram of the Bk developing device which shows another embodiment of this invention. It is a development process model figure same as the above. It is a potential drop model diagram in the case of the same as above. It is a rising electric potential model figure same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color printer 10 Photoconductor unit 11 Photoconductor belt 12 Photoconductor cleaning apparatus 13 Charging roller 20 Writing optical unit 30 Developing unit 31K, C, M, Y Developer 32K, C, M, Y Developer accommodation case 40 Intermediate transfer unit 41 Intermediate transfer belt 50 Secondary transfer unit 60 Fixing unit 70 Double-sided printing paper reversing unit 501 Toner density detection sensor 502 Toner remaining amount detection sensor 510 Toner cartridge 511 Agitator 512 Toner replenishment port 601a, 601b Potential sensor

Claims (18)

  An image forming apparatus comprising: a developing device, wherein a latent image start timing is switched to be delayed from a normal start timing under a certain condition of the developing device.   The image forming apparatus according to claim 1, wherein a latent image start timing is fed back based on a result of detecting a developing density for each developing roller cycle.   The image forming apparatus according to claim 1, wherein the latent image start timing is fed back based on a result of detecting the development density immediately after the end of one job of print output and after a certain time has elapsed since the end.   The image forming apparatus according to claim 1, wherein the latent image start timing is fed back based on a result of detecting the toner remaining amount in the hopper of the developing device.   The image forming apparatus according to claim 1, wherein the latent image start timing is fed back on the basis of the toner remaining amount detection in the hopper and the print output pixel count information.   The image forming apparatus according to claim 1, wherein the latent image start timing is fed back based on the toner cartridge replacement information and the counter information after the replacement.   An image forming apparatus comprising a developing device, provided with a potential sensor for detecting a toner layer potential on a developing roller of the developing device, and detecting a toner layer potential in a developing operation.   The image forming apparatus according to claim 7, wherein the detection of the toner layer potential on the developing roller is determined based on a result of comparison with the end of the developing operation.   8. The image forming apparatus according to claim 7, wherein the detection of the toner layer potential on the developing roller is determined based on a comparison result with immediately after the start of the developing operation.   8. The image forming apparatus according to claim 7, wherein when detecting the toner layer potential on the developing roller, the toner layer potential of the new developing device is compared and detected with the current state.   The image forming apparatus according to claim 10, configured to compare and detect a toner layer potential in a new developing device state and a toner layer potential in each developing roller cycle in a current state.   12. The image forming apparatus according to claim 8, wherein the image forming apparatus is configured to perform control different from a normal operation timing based on a detection result of a rising potential immediately after the start of development.   13. The image forming apparatus according to claim 12, wherein the image forming apparatus is configured to feed back to a latent image formation start timing based on a detection result of a rising potential immediately after the start of development.   13. The image forming apparatus according to claim 12, wherein the image forming apparatus is configured to feed back to the timing of developing bias control based on the detection result of the rising potential immediately after the start of development.   15. The configuration is such that, depending on the job mode, the latent image start timing of the first image is delayed from the normal start timing in the case of continuous print output, and the normal timing is set for the second and subsequent images. The image forming apparatus described in 1.   The image forming apparatus according to any one of claims 1 to 15, wherein a toner having a circularity of 0.9 or more is used.   The image forming apparatus according to claim 1, which is a tandem type.   A process cartridge using the developing device of the image forming apparatus according to claim 1.