JP3728614B2 - Development method and multicolor image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a non-magnetic one-component contact developing method for performing printing using a mixed color toner obtained by arbitrarily mixing two or more basic color toners that are commercially available, and a multicolor image forming apparatus using the same. .
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been a demand for using a large amount of special colors for printing, for example, for POP (Point of Purchase) printing, which does not require full color. Relying on such a printing company for specialized printing is not only expensive, but also takes time to finish, which is inconvenient for POP. For this reason, electrophotographic full-color printers that have finally reached practical use in recent years have come to be used.
[0003]
[Problems to be solved by the invention]
By the way, full-color printers, which are currently mainstream, reproduce colors by area gradation. In the area gradation, the color density is not represented by the density of the ink itself, but is expressed by the spread of the ink, that is, the area, with the density of the ink being constant. For this reason, in color printing using three subtractive primary colors of magenta, cyan, and yellow, a color is expressed by a combination of ink spreading states within the maximum area of the printing dots of the three primary colors, that is, one pixel is represented by magenta, cyan, and yellow. Since three dots are expressed side by side, there is a technical problem that the color tone of the printed image is slightly rough. In addition, when printing a one-dot-width line such as a thin ruled line, color expression by mixed colors is impossible, and printing is performed with one of the basic colors, so the hue of the ruled line is limited. It also has the problem of end.
[0004]
In order to solve this problem, there is a method in which a desired color toner is manufactured in a special order and supplied to the user. However, the color toner manufactured by such a special order takes time to be completed and the product cost is high, which is uneconomical. Some of the highly demanded color toners are commercially available as off-the-shelf products, but it is practically impossible to prepare all the toners of the required hue, and this is not possible. For example, in the case of the kneading and pulverizing method, which is the mainstream of the current toner manufacturing method, every time the hue is changed, in order to avoid color mixing between the currently finished color and the next color to be manufactured, the inside of the manufacturing device is closely This requires a lot of labor and a lot of money. Therefore, increasing the hue (type) of the special color toner, which is limited in such applications and has little demand, only increases the cost of the toner, and has advantages for both the manufacturing side and the user side. Absent. For this reason, at present, toners of red, blue, and green are only commercially available other than the subtractive mixed primary color toners.
[0005]
Here, yellow, magenta, and cyan toners, which are the three primary colors of subtractive color mixing that are commercially available as described above, are prepared, and these are mixed in an arbitrary ratio in the toner state to obtain a color toner of a desired hue. Although it may be used for development, this method is considered to be impossible because of the problem of selective development, and there is no printer that has realized development by this method. The selective development which is the problem will be described below.
[0006]
FIG. 4 is a diagram showing toner development characteristics in a two-component development system used in a conventional full-color printer. In the drawing, the horizontal axis represents the potential difference between the photosensitive drum and the developing roll, and for the convenience of explanation, the potential of the photosensitive drum is set to 0 V, and in this case, the developing bias applied to the developing roll is represented. The vertical axis represents the amount of toner adhering to the photosensitive drum corresponding to the developing bias.
[0007]
As shown by the solid line in the figure, the toner adhesion amount does not increase and saturate as the potential difference increases, that is, there is no end point in the increase in adhesion amount, and no saturated development is observed. This is because there is a large amount of toner that contributes to the development sticking out in the form of a spike in the developing portion formed in a non-contact state between the developing roll and the photosensitive drum, so even if the toner is difficult to develop at the first low potential difference, the potential difference This is because as the electric field strength increases and the electric field strength increases, development is started.
[0008]
The nature of the toner, whether it is easy to develop or difficult to develop, depends on the adhesion between the toner particles and the carrier in the two components and depends on the individual characteristics such as the charging ability of the toner particles and the size of the particles. .
[0009]
Accordingly, the development characteristics as indicated by the solid line in the figure change as the curve indicated by the dotted line in the figure or the curve indicated by the alternate long and short dash line in the figure as printing (printing) is repeated. That is, when printing is continued with a constant development bias, the toner adhesion amount changes drastically in both shades. For example, assuming that printing is continued with a developing bias of −300 V, 0.7 mg / cm²To 1.4 mg / cm²The toner adhesion amount changes to the extent.
[0010]
  For this reason, in an actual developing method using a full-color printer, toner is detected for each color (for each developing device) by a sensor.WithA method has been adopted in which the amount of adhesion is measured, and the development bias is changed based on the measurement result to control the toner adhesion amount to be constant.
[0011]
By the way, it is troublesome to perform the above control for each developing device, but even if it is attempted to control each developing device to be the same, it is technically impossible because the developing characteristics of the three primary color toners are not the same. . In other words, it is a very difficult attempt to make the development characteristics almost the same with the same three primary color toner external additives, and in particular, to make the charging characteristics of each color toner the same, the coloring agent pigment itself also has a charging characteristic. Difficult because it affects. Further, as shown in FIG. 4, it is difficult to maintain the same development characteristics until after the printing is repeated.
[0012]
Therefore, when color toners having different development characteristics are mixed and used as special color toners, the development bias is always applied to each mixed color toner in the same (equal) manner, and thus printing is repeated. Over time, the adhesion amount for each color toner changes according to the development characteristics (selective development), and an image with a stable hue cannot be obtained.
[0013]
In other words, the special color toner mixed in the toner state as described above includes easy-to-develop color toners and difficult-to-develop color toners due to characteristics such as charging characteristics, particle diameters, and shapes of the individual color toner particles. The amount of consumption precedes the color toner that is easily developed. In addition, the color toner has different characteristics depending on the colorant of the colorant, so that a difference in developability occurs. For this reason, the use of mixed color toners as described above causes a problem that the hue changes due to selective development.
[0014]
An object of the present invention is to realize and use a non-magnetic one-component contact development method capable of obtaining a stable hue image even when continuous printing is performed using a desired color toner obtained by mixing colors in a toner state. A multicolor image forming apparatus is provided.
[0015]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided an elastic developing roller which holds and conveys a non-magnetic one-component toner stored in a container and contacts the image carrier, and the elastic developing roller includes the image carrier. A regulating member that forms the toner on the developing roller in a thin layer on the upstream side of the developing unit that contacts the developing unit, and a bias applying unit that applies a developing bias to the developing roller, and passes the developing unit. The present invention is applied to a non-magnetic one-component contact developing method in which a latent image on an image carrier is developed with the toner conveyed by the elastic developing roller based on a developing bias applied by the bias applying means.
[0016]
  In the non-magnetic one-component contact development method of the present invention, the toner used for the development is a color toner containing a cyan pigment, a color toner containing a magenta pigment, a color toner containing a yellow pigment, and a color toner containing a black pigment. , And less than color toners containing white pigmentBothDevelop using mixed color toner that is a mixture of two kinds of arbitrarily selected color tonersAssuming thatTo do. And,The development density is saturated when each of the color toners before being mixed is developed with respect to the potential difference between the potential to be developed of the latent image on the image carrier and the developing bias potential applied to the developing roller. Development is performed with the above-described mixed color toner by setting the potential difference to be greater than the largest potential difference.
[0017]
  Next, the claim2The invention described herein includes an elastic developing roller that holds and conveys a non-magnetic one-component toner stored in a toner container on the surface and contacts the image carrier, and a development in which the elastic developing roller contacts the image carrier. A regulating member that forms the toner in a thin layer on the developing roller on the upstream side of the image forming unit, and a bias applying unit that applies a developing bias to the developing roller. A multi-color image forming apparatus that develops the latent image of the toner with the toner conveyed by the elastic developing roller based on the developing bias applied by the bias applying meansApplies to
[0018]
  In the multicolor image forming apparatus of the present invention, the toner used for the development is a color toner containing a cyan pigment, a color toner containing a magenta pigment, a color toner containing a yellow pigment, a color toner containing a black pigment, and Less than color toners containing white pigmentBothHoused in a single toner container in the form of a mixed-color toner in which two types of arbitrarily selected color toners are mixed.Assuming thatAnd,The development density is saturated when each of the color toners before being mixed is developed with respect to the potential difference between the potential to be developed of the latent image on the image carrier and the developing bias potential applied to the developing roller. It is configured to perform contact development with the above-described mixed color toner by setting the potential difference to be greater than or equal to the largest potential difference.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a side sectional view of a tandem type full color image forming apparatus used in an embodiment. A full-color image forming apparatus (main body apparatus) 10 shown in FIG. 1 is a small-sized image forming apparatus having a size that can be mounted on a desktop personal computer rack, for example. The full-color image forming apparatus 10 includes an open / close tray 11 on the front surface (right side in the drawing) and a paper cassette 12 in a detachable manner at the bottom. A large number of sheets are placed and stored in the sheet cassette 12. Further, an upper lid 13 is provided on the upper surface of the main body device 10. Although not visible in the drawing, a power switch, a liquid crystal display device, a plurality of input keys, and the like are disposed on the front side of the upper lid 13. The rear portion of the upper lid 13 forms a paper discharge tray 14 together with the upper surface of the rear portion of the main body device 10.
[0020]
Inside the main body device 10, the conveying belt 15 is arranged in a substantially loop shape in the front-rear direction, and both ends in the horizontal direction of the loop are held by the driving roller 16 and the driven roller 17. The conveyor belt 15 is driven by a driving roller 16 and circulates in the counterclockwise direction in the figure.
[0021]
Four photosensitive drums 18 (18a, 18b, 18c, 18d) are arranged in a multistage manner in the paper transport direction (from the right to the left in the figure) in the upper circulating portion of the transport belt 15. A cleaner, an initialization charging brush, a writing head 19 (19a, 19b, 19c, 19d), and a developing device 21 (21a, 21b, 21c, 21d) are provided so as to surround the photosensitive drum 18 (image carrier). ) And the transfer brush 22 (22a, 22b, 22c, 22d). The transfer brush 22 is disposed inside the conveyor belt 15 and presses against the photosensitive drum 18 via the conveyor belt 15 to form a transfer portion.
[0022]
Each of the developing devices 21 is provided with various devices that will be described in detail later. Normally, the developing unit 21 includes a magenta toner M, a cyan toner C, a yellow toner Y, and a black toner Bk in order from the developing unit 21a on the upstream side (right side in the figure) to the downstream developing unit 21d. Each toner (non-magnetic one-component toner) is accommodated.
[0023]
The writing head 19 is disposed on the back surface of the upper lid 13 and descends as the upper lid 13 is closed. The writing head 19 is positioned between the initialization charging brush and the developing roller of the developing device 21. Form. In the loop of the conveyor belt 15, a rotating arm 23 is disposed between the upper circulation part and the lower circulation part of the conveyor belt 15 and extends parallel to the conveyance direction. The rotating arm 23 includes a fixed support roller 24 at one end, and a movable support roller 25 at the other end.
[0024]
The fixed support roller 24 is rotatably fixed to and supported by the frame of the main body device 10. The fixed support roller 24 is provided in the vicinity of the upstream side of the transfer brush 22 d closest to the drive roller 16. The fixed support roller 24 is disposed in contact with the inner peripheral surface of the conveyance belt 15 so that the most downstream photosensitive drum 18 and the conveyance belt 15 are always in contact with each other.
[0025]
The rotating arm 23 rotates up and down on the free end side (right side in the figure) around the fixed support roller 24. The above-mentioned movable support roller 25 located at the free end contacts the inner peripheral surface of the conveyor belt 15 at a position between the transfer brush 22 a and the driven roller 17 closest to the driven roller 17 to support the conveyor belt 15. ing.
[0026]
When the rotating arm 23 rotates downward from the position shown in the drawing, the movable support roller 25 moves downward and is separated from the transport belt 15. The upper circulation portion of the transport belt 15 includes the drive roller 16, the fixed support roller 24, and the like. It is supported between the driven rollers 17. That is, the conveyance belt 15 contacts only with the photosensitive drum 22d and is separated from the remaining three photosensitive drums 22a to 22c. As a result, a mono-color printing mode is set only by the developing device 21d containing Bk toner, or only by the developing device containing special color toner mounted in exchange for the developing device 21d.
[0027]
In this mono-color printing mode, the three transfer brushes 22 a to 22 c are fixed to the rotating arm 23, moved downward together with the rotating arm 23, separated from the transport belt 15, and are attached to the frame of the main body device 10. Only the fixed transfer brush 22d is driven.
[0028]
A cam engaging portion 26 is formed on the lower portion of the rotating arm 23 so as to project laterally at a right angle, and a cam 27 is slidably in contact with the cam engaging portion 26. The cam 27 rotates 90 degrees in both forward and reverse directions around the fulcrum 28, and selectively positions the rotating arm 23 at the position shown in the drawing or the upper and lower positions descending below. This figure shows a state in which the cam 27 is rotated 90 degrees counterclockwise and the whole is set to the full-color printing mode. In this full-color printing mode, printing with a total of four colors of three primary colors of black and subtractive color shown in FIG. 1 by four developing devices 21a to 21d and printing with arbitrary four color toners described later are performed.
[0029]
A tension roller 29 is disposed in pressure contact with the back surface of the lower circulation portion of the conveyor belt 15. The tension roller 29 presses the transport belt 15 downward by a rotating member 29 biased downward by a biasing member 31. Thereby, the bending of the conveyor belt 15 is absorbed, and the entire conveyor belt 15 is stretched between the driving roller 16 and the driven roller 17 with a predetermined tension.
[0030]
An adsorption roller 33 is pressed against the driven roller 17 via the conveyor belt 15 at the upstream (right side in the drawing) side end of the conveyor belt 15 to form a sheet carry-in section. The suction roller 33 presses the conveyance belt 15 while applying an adsorption bias to the paper carried into the paper carry-in section, and electrostatically attracts the paper to the conveyance belt 15.
[0031]
A standby roll pair 34 and a paper detection sensor 35 are disposed on the upstream side of the transport belt 15 in the transport direction (right side in the figure). The paper feed roller 36, the separating member 37, and the opening / closing tray 11 described above are disposed. In addition, a conveyance path 38 formed by two guide plates is disposed below, and the above-described paper cassette 12 is located upstream (downward). A paper feed roller 39 is disposed above the paper feed end of the paper cassette 12.
[0032]
A separation claw 41, a fixing device 42, a paper discharge roller 43, and a switching lever 44 are provided downstream of the conveyance belt 15 in the sheet conveyance direction (left side in the drawing). The fixing device 42 is composed of a pressure roller, a fixing roller, a heat generating roller, a peripheral surface cleaning device, an oil application member, a thermistor, and the like assembled in a heat insulating casing, and heats the toner image transferred on the paper to the paper surface. Let it settle. As shown in the figure, the switching lever 44 guides the sheet to the upper discharge path 45 when it is in the lower position, and when it is rotated upward, the rear discharge port 46 opens the sheet to the rear surface of the apparatus. To guide. The downstream (upper side) of the discharge path 45 communicates with the upper discharge port 48 via the discharge roll pair 47.
[0033]
A cleaner bottle 51 is detachably disposed between the conveyor belt 15 and the paper cassette 12. A blade scraper 52 is attached to the upper portion of the cleaner bottle 51, and its tip abuts against the surface of the lower circulation portion of the conveyor belt 15. The blade scraper 52 scrapes off toner remaining on the surface of the conveyor belt 15 to clean the conveyor belt 15 and stores unnecessary toner scraped off in the cleaner bottle 51.
[0034]
Further, between the belt 15 and the paper cassette 12, an electrical component 53 is disposed behind the cleaner bottle 51 so that a predetermined number of circuit boards can be mounted. A control device composed of a plurality of electronic components is mounted on the circuit board disposed in the electrical component 53. Although not specifically shown, the control device is composed of a controller unit and an engine unit. The controller unit comprises a CPU (Central Processing Unit), ROM (Read Only Memory), EEPROM (Rewritable Read Memory), Frame Memory, Image Data Transfer Circuit, etc., and print data input from a host computer etc. Is generated, print data is created and transferred to the engine unit.
[0035]
The engine unit includes a CPU, a ROM, and the like. Data and command signals from the controller unit, an output of a developing device position detection sensor (not shown), an output of a paper detection sensor 35, and the like are input to the input side, and the output side A motor driver that drives a motor (not shown), a clutch driver that switches a drive system that transmits the drive of the motor to each unit, a print driver that drives the write head 19 based on the print data, an initialization charging brush, and a developing roller A bias power supply driver for supplying a predetermined bias current to the transfer brush 22 and the suction roller 33 is connected. The engine unit drives and controls each unit based on data from the controller unit, command signals, outputs from various sensors, and the like.
[0036]
A fan 54 is disposed behind the electrical component 53 to discharge heat dissipated from the electrical component 53 and heat leaked from the fixing device 42 to the outside of the apparatus.
FIG. 2 is an enlarged view of the developing device 21 and is shown together with the photosensitive drum 18. The developing device 21 has the same configuration except that the color of the toner accommodated therein is different. As shown in the figure, the developing device 21 holds a developing roller (elastic developing roller) 21-2 rotatably in a lower opening of a housing (toner container) 21-1, and contains toner T therein. Contained. The toner T varies depending on the developing unit to be mounted, and may be M (magenta), C (cyan), Y (yellow), or Bk (black), or may be M (magenta) or C (cyan). , Y (yellow), and a special color toner prepared by mixing two or more color toners at an arbitrary ratio among four color toners obtained by adding white toner.
[0037]
A toner agitating member 21-3 is disposed below the housing 21-1, and the toner agitating member 21-3 rotates as indicated by a two-dot chain line in FIG. The toner T is fed to the supply roller 21-4. The supply roller 21-4 is made of a sponge member, presses against the developing roller 21-2, and supplies the toner T sent from the stirring member 21-3 to the peripheral surface of the developing roller 21-2 so as to rub. A bias power source (bias applying means) 21-6 is connected to the developing roller 21-2, and a predetermined bias voltage is applied to the developing roller 21-2.
[0038]
An edge portion formed by bending the tip of a doctor blade (regulating member) 21-5 made of a metal elastic body is in contact with the circumferential surface of the developing roller 21-2 in the rotational direction, and gives a frictional charge to the toner T. Thus, the adhesion to the developing roller 21-2 is assisted, and the adhering toner layer is suppressed to a constant thickness.
[0039]
The thickness of the toner layer is set to be constant by adjusting the spring force of the doctor blade 21-5. The adhesion of the toner T mainly depends on the adhesion force between the toner T and the developing roller 21-2. Therefore, the thickness cannot be increased without limitation, and the number of layers that can be formed is one (a state in which toner particles are closely arranged without overlapping) or two layers. As described above, since the toner layer is physically formed, even in the case of a mixed-color toner, the layer is not selectively formed according to the color in the toner. The layers are evenly formed as they are.
[0040]
This one-layer or two-layer toner T is transferred (developed) on the photosensitive drum 18 by the potential difference between the developing roller 21-2 and the photosensitive drum 18 by the bias voltage described above. As described above, the color density of the toner T is expressed by the size (width) at which the toner T is transferred within the area of one dot.
[0041]
FIG. 3 shows the development characteristics of toner in a development method called “non-magnetic one-component contact development method” in which the toner image is developed by contact development using the non-magnetic one-component toner performed in the present embodiment as described above. FIG. In the figure, the developing bias is indicated by V (volt) on the horizontal axis. In the figure, for the sake of convenience of explanation, the potential of the photosensitive drum 18 is set to 0 V, and the potential difference between this and the developing roller 21-2 is shown as a developing bias applied to the developing roller 21-2. The vertical axis of the figure shows the amount of toner adhesion transferred from the developing roller 21-2 to the latent image position (developing area) of the photosensitive drum 18 in accordance with the developing bias, in mg / cm.²(Per milligram / square centimeter).
[0042]
In this developing method, as described above, a toner layer consisting of one or two layers is formed on the developing roller 21-2 made of a conductive elastic body, and this is used as a photoconductor (photosensitive drum 18 in this example). In this method, development is performed using a potential difference between the photosensitive drum 18 and the developing roller 21-2. As shown in the figure, the feature of this method is that the adhesion amount gradually increases as the potential difference is increased, but reaches a saturation point at a certain point. That is, the yellow toner Y has a toner adhesion amount that increases as the developing bias (potential difference) increases from 0 V to the minus side, and the saturation point is “1.1 mg / cm” at about “−120 V”.²To reach. The magenta toner M also has a toner adhesion amount that increases as the developing bias increases from 0 V to the minus side, and reaches a saturation point of “1.1 mg / cm” at about “−200 V”.²To reach. The cyan toner C also has a toner adhesion amount that increases as the developing bias increases from 0 V to the minus side, and reaches a saturation point of “1.1 mg / cm” at about “−250 V”.²To reach.
[0043]
As described above, the toner adhesion amount at the saturation point is constant for the toner of any color, regardless of the difference in color, the thickness of the toner layer physically formed by the doctor blade 21-5 is constant. This is because, at this saturation point, the toner on the developing roller 21-2 corresponding to the developing area of the photosensitive drum 18 has moved (transferred) almost to the photosensitive drum 18. That is, the toner adhesion amount in the saturated state is determined by the thickness (one layer or two layers) of the toner layer when the toner layer is formed on the developing roller 21-2. As described above, the thickness of the toner layer cannot be increased beyond a certain level. Therefore, even if the development bias is increased, further development cannot be performed. That is, the saturation point is reached.
[0044]
The operation of the full-color image forming apparatus 10 having such a configuration will be described with reference to FIGS. 1 to 3 described above again. First, the processing operation in the full-color printing mode will be described. In FIG. 1, when the apparatus main body 10 is turned on and the paper quality, the number of sheets to be used, the print mode, and other specifications are input as a key input or a signal from a connected host device, a drive mechanism (not shown) The cam 27 is driven, and the rotating arm 23 rotates upward. As a result, the movable support roller 25 moves upward to bring the conveyor belt 15 into contact with all four photosensitive drums 18 (18a, 18b, 18c, 18d).
[0045]
Then, the paper feed roller 39 feeds the paper P placed and accommodated in the paper cassette 12 to the standby roll pair 34 via the transport path 38. Alternatively, the paper feed roller 36 feeds the paper placed on the open / close tray 11 to the standby roll pair 34. The paper detection sensor 35 detects the fed paper P. The standby roll pair 34 stops rotating, and the leading edge of the paper P is brought into contact with the clamping portion to temporarily stop the paper feeding and wait for the conveyance timing.
[0046]
The driving roller 16 rotates in the counterclockwise direction, and the driven roller 17 is driven to rotate in the same counterclockwise direction. As a result, the conveying belt 15 is circulated and moved counterclockwise as a whole by the upper circulation portion coming into contact with the four photosensitive drums 18a to 18d.
[0047]
At the same time, the developing units 21a to 21d and the photosensitive drums 18a to 18d are sequentially driven in accordance with the printing timing. Each photosensitive drum 18 rotates clockwise, the initialization charging brush applies a uniform high negative charge to the circumferential surface of the photosensitive drum 18, and the writing head 19 is applied to the circumferential surface of the photosensitive drum 18. Exposure is performed according to the image signal to form a low potential portion. As a result, an electrostatic latent image composed of the high negative potential portion by the initialization and the low negative potential portion by the exposure is formed.
[0048]
In the present embodiment, the developing devices 21a to 21d accommodate R (red), B1 (blue), and Bk (black), which are POP colors, and G (green) toners that are commonly used. These color toners, except for Bk (black), are adjusted by appropriately mixing three primary colors of yellow, magenta, and cyan toners for the other R (red), Bl (blue), and G (green). It is a thing.
[0049]
Each developing device 21 accommodates the R (red), B1 (blue), G (green), and Bk (black) color toners from the upstream side in the paper conveyance direction, and the developing roller 21-2 has each color. The toner is transferred to the low potential portion of the electrostatic latent image on the photosensitive drum 18 to form a color toner image (reverse development) on the circumferential surface of the photosensitive drum 18.
[0050]
At this time, a developing bias is applied from the bias power source 21-6 to the developing roller 21-2 such that a potential difference of at least “−250 V” or more is generated between the photosensitive drum 18. This potential difference of “−250 V” is a potential difference at which the cyan toner, which is the most difficult to develop among the three primary color toners, reaches the saturation point (see FIG. 3).
[0051]
As a result, among the mixed color toners of R (red), Bl (blue), or G (green) in each developing device 21, any of the mixed three primary color toners has a portion corresponding to the development region up to the saturation point, that is, The entire amount is transferred to the photosensitive drum 18 and developed, thereby preventing selective development.
[0052]
At the timing when the leading edge of the R (red) toner image on the peripheral surface of the photosensitive drum 18a is rotated and conveyed to the point facing the conveying belt 15, the printing start position of the paper P coincides with the point facing the opposite point. Then, the standby roll pair 34 starts to rotate and feeds the paper P to the paper carry-in section.
[0053]
The driven roller 17 and the suction roller 33 convey and feed the fed paper P together with the conveying belt 15. The sheet P is attracted to the transport belt 15 and transported to the first (upstream) transfer section formed by the photosensitive drum 18a and the transfer brush 22a.
[0054]
The transfer brush 22 a applies a transfer current output from a transfer bias power source (not shown) to the paper P via the conveyance belt 15. By this applied transfer current, the R (red) toner image on the photosensitive drum 18 a is transferred to the paper P, and the R (red) toner image is formed on the paper P.
[0055]
Similarly, a B1 (blue) toner image is transferred from the upstream transfer portion formed by the photosensitive drum 18b and the transfer brush 22b, and subsequently formed by the photosensitive drum 18c and the transfer brush 22c. The G (green) toner image is transferred at the third transfer section from the upstream, and finally the Bk (black) toner image is sequentially transferred at the most downstream transfer section formed by the photosensitive drum 18d and the transfer brush 22d. Transcribed.
[0056]
The paper P to which the three special color toner images and the black toner image are transferred in this way is separated from the transport belt 15 by the separation claw 41 and is carried into the fixing device 42. The fixing device 42 heat-fixes the toner image on the paper P. After this image fixing, the paper P is discharged out of the machine by the paper discharge roller 43 with the toner image facing up from the rear paper discharge port 46 or from the upper paper discharge port 48 with the toner image facing down.
[0057]
In this way, based on the development characteristics of each of the three primary color single color toners, the potential difference of the toner that requires the largest potential difference to reach the saturation point is examined, and the developing roller so that a potential difference larger than this largest potential difference is generated. By setting the developing bias to 21-2, it is possible to obtain an image without selective development with mixed color toners, that is, with no hue change.
[0058]
Next, the operation in the mono color printing mode will be described. In the mono color printing mode, the rotating arm 23 rotates downward, the movable support roller 25 moves downward, and the movable support roller 25 is separated from the transport belt 15. As a result, the conveying belt 15 maintains the contact state of the photosensitive drum 18d between the driving roller 16 and the fixed support roller 24 on the one hand, and the other photosensitive resin remaining between the fixed support roller 24 and the driven roller 17 on the other hand. Separated from contact with the body drums 18a, 18b and 18c. As a result, only the most downstream photosensitive drum 18d and transfer brush 22d form the transfer section so that they can be operated, and monochromatic, that is, monocolor printing is performed by the color toner accommodated in the developing device 21d.
[0059]
In this case, the toner accommodated in the developing device 21d is not limited to Bk (black), and may be any single color toner obtained by mixing the three primary colors described above. In this case as well, the developing bias is applied so as to form a potential difference larger than the maximum potential difference required to reach the saturation point, so the hue does not change no matter what color toner is blended. A stable monochromatic image can be obtained.
[0060]
In the processing operation in the mono-color printing mode, the control of the exposure operation for the writing heads 19a to 19c is suspended, and the development bias output in the developing devices 21a to 21c is suspended. Other processing operations are the same as those in the above-described full-color printing mode, and will not be described.
[0061]
Although the toner to be mixed has been described as a subtractive three-primary color toner, the amount of toner contributing to development is constant, and thus there may be cases where light and dark cannot be expressed. Therefore, in addition to the three primary colors, white toner and black toner may be used for color mixing. Also in this case, a potential difference larger than the saturation potential difference of the toner requiring the largest potential difference among these toners is formed by the developing bias.
[0062]
As described above, if the printer using the above-described developing method is used, various kinds of arbitrary color toners (color mixture toners) that do not cause a hue change can be provided at low cost by using three primary color toners that are generally widely available at low cost. it can.
[0063]
Although there is no specific description on the preparation of the color mixture toner, it is used as appropriate according to commonly used mixing methods such as coloring of paints, mixing of chemicals by a pharmacist, mixing immediately before dyeing two-component hair dyes, etc. May be created. Further, for example, Y, M, and C color toners may be placed in individual graduated containers, and a separate recipe may be prepared so that a user can obtain a favorite color by mixing an appropriate amount. Further, the toner container of each developing device is formed in a toner replenishment type, and the toner container is replenished with a mixture of two or more color toners in a predetermined ratio by the above method. May be. In this case, if two or more color toners are simply weighed, it is convenient that the toner container is replenished and stirred and mixed on the developing device side, saving labor.
[0064]
【The invention's effect】
As described above in detail, according to the present invention, the development potential difference between the photosensitive drum and the developing roller is the largest of the potential differences that the development density should be saturated when each color toner of the mixed color toner is developed individually. Since the potential difference is set to be equal to or greater than the potential difference, selective development does not occur regardless of the color toner used, and therefore, a color toner of a desired color (single color) is created using an inexpensive commercially available color toner. Thus, it is convenient that an image having a stable hue can be obtained even if printing with a constant hue is continuously performed. In addition, it is possible to obtain a specific color toner that prints an image with a stable hue using an inexpensive color toner that is generally available on the market. Therefore, it is necessary to purchase a custom-made product or a very expensive special color toner with a small amount on the market. Therefore, it is economical and convenient.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a tandem type full-color image forming apparatus used in an embodiment.
FIG. 2 is an enlarged view showing a developing device together with a photosensitive drum.
FIG. 3 is a diagram illustrating development characteristics of toner in a non-magnetic one-component contact development method.
FIG. 4 is a diagram showing toner development characteristics in a two-component development system used in a conventional full-color printer.
[Explanation of symbols]
10 Image forming device (main device)
11 Opening and closing tray
12 Paper cassette
13 Upper lid
14 Output tray
15 Conveyor belt
16 Driving roller
17 Followed roller
18 (18a, 18b, 18c, 18d) Photosensitive drum
19 (19a, 19b, 19c, 19d) Write head
21 (21a, 21b, 21c, 21d) Developer
21-1 Housing (toner container)
21-2 Developing roller (elastic developing roller)
21-3 Toner stirring member
21-4 Supply roller
21-5 Doctor blade (regulating member)
21-6 Bias power supply (bias applying means)
T Toner
22 (22a, 22b, 22c, 22d) Transfer brush
23 Rotating arm
24 Fixed support roller
25 Movable support roller
26 Cam engagement part
27 cam
28 fulcrum
29 Tension roller
31 Biasing member
32 Rotating member
33 Suction roller
34 Waiting roll pair
35 Paper detection sensor
36 Paper feed roller
37 Thatched material
38 Transport path
39 Feed roller
41 Separating nails
42 Fixing device
43 Discharge roller
44 Switching lever
45 Discharge channel
46 Rear paper exit
47 Paper discharge roll pair
48 Upper paper exit
51 Cleaner bottle
52 Blade scraper
53 Electrical Department
54 fans

Claims (2)

An elastic developing roller that holds and conveys a non-magnetic one-component toner stored in a toner container on the surface and contacts the image carrier, and an upstream side of the developing unit where the elastic developer roller contacts the image carrier A regulating member that forms the toner in a thin layer on the developing roller; and bias applying means that applies a developing bias to the developing roller, and the latent image on the image carrier passing through the developing unit is A non-magnetic one-component contact developing method for developing with the toner conveyed by the elastic developing roller based on a developing bias applied by a bias applying means, wherein the toner used for the development is a color toner containing a cyan pigment; color toner containing a magenta pigment, a color containing a yellow pigment toner, color containing a black pigment toners, and at least two from among the color toners containing a white pigment In the non-magnetic one-component contact developing method of developing used in the form of a mixed color toner obtained by mixing color toner selected arbitrarily,
The development density is saturated when each of the color toners before being mixed is developed with respect to the potential difference between the potential to be developed of the latent image on the image carrier and the developing bias potential applied to the developing roller. A non-magnetic one-component contact development method, wherein development is performed with the mixed color toner by setting the potential difference to be greater than or equal to the largest potential difference. An elastic developing roller that holds and conveys a non-magnetic one-component toner stored in a toner container on the surface and contacts the image carrier, and an upstream side of the developing unit where the elastic developer roller contacts the image carrier A regulating member that forms the toner in a thin layer on the developing roller; and bias applying means that applies a developing bias to the developing roller, and the latent image on the image carrier passing through the developing unit is A multicolor image forming apparatus that performs contact development with the toner conveyed by the elastic developing roller based on a developing bias applied by a bias applying unit, wherein the toner used for the development is a color toner containing a cyan pigment, magenta color toner containing a pigment, color containing a yellow pigment toner, color containing a black pigment toners, and at least two kinds of responsibility among the color toners containing a white pigment In multicolor image forming apparatus to be accommodated in a single toner container with mixing the toner in the form of a mixture of color toner selected,
The development density is saturated when each of the color toners before being mixed is developed with respect to the potential difference between the potential to be developed of the latent image on the image carrier and the developing bias potential applied to the developing roller. A multicolor image forming apparatus that performs contact development with the mixed-color toner by setting the potential difference to be greater than or equal to the largest potential difference.

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