JP2015206924A - image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that can make even a print result in printing performed with a middle tone density after high toner consumption printing, equivalent to a print result in printing performed with a middle tone density after low toner consumption printing.SOLUTION: An image forming apparatus includes: a print image analysis part for analyzing received print data; an image carrier; a charging member for charging the image carrier; an exposure part for forming an electrostatic latent image by exposing the image carrier; a developer carrier for carrying a developer used for development of the electrostatic latent image; and an exposure control part for controlling the exposure part. When the print image analysis part determines that in a print image formed on the basis of print data, a second area following a first area having an image formed thereon with a first density or more is formed with a middle tone image having a second density, the exposure control part controls the exposure part so that the exposure amount for the second area becomes higher than that for a forth area following a third area as a blank image and having a middle tone image formed thereon with the second density.

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a fax machine using an electrophotographic system.

  An image forming apparatus employing a general electrophotographic system includes a photosensitive drum, a charging device, an exposure device, a developing device, a transfer device, a fixing device, and a cleaning device. On the surface of the photosensitive drum uniformly and uniformly charged by the charging device, an exposure device exposes to form an electrostatic latent image corresponding to the printed image. The developing device supplies toner as a developer to the electrostatic latent image formed on the surface of the photosensitive drum, thereby reversely developing the electrostatic latent image to form a toner image. Then, the toner image on the surface of the photosensitive drum is transferred onto a sheet as a printing medium by a transfer device and fixed by a fixing device. The toner remaining on the surface of the photosensitive drum after the toner image is transferred is removed by a cleaning device.

  Some image forming apparatuses having such a configuration control the voltage applied to the charging device in accordance with the number of printed sheets in order to maintain a constant charging potential on the surface of the photosensitive drum (for example, Patent Documents). 1).

Japanese Patent Laid-Open No. 08-179594

  However, in the conventional technology having the above-described configuration, after printing with high toner consumption that consumes a large amount of toner, for example, solid black printing, in the sub-scanning direction (printing medium conveyance direction) on the printing medium, printing is then performed at a halftone density. When printing is performed, there is a problem that the print density is lower than that in the case of printing with halftone density after low toner consumption printing that does not consume much toner, for example, blank paper printing.

  The present invention has been made in view of such a situation, and an object of the present invention is to print at a halftone density after printing with low toner consumption even when printing at a halftone density after printing with high toner consumption. It is an object to provide an image forming apparatus capable of obtaining a printing result equivalent to the case of performing the above.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a print image analysis unit that analyzes received print data, an image carrier, a charging member that charges the image carrier, and the image carrier. Exposure unit for exposing the image carrier to form an electrostatic latent image on the image carrier, a developer carrier for carrying a developer used for developing the electrostatic latent image, and exposure control for controlling the exposure unit The exposure control unit includes a first area that follows the first region in which the print image analysis unit forms an image with a density equal to or higher than a first density on the print image formed based on the print data. When it is determined that the second area is formed with the halftone image having the second density, the exposure amount in the second area is set to the halftone at the second density following the third area which is a blank image. The exposure unit is controlled to be higher than the exposure amount in the fourth area where the image is formed. It is characterized in that.

  According to the present invention, even when printing is performed at a halftone density after high toner consumption printing, it is possible to obtain an image formation capable of obtaining a printing result equivalent to the case where printing is performed at a halftone density after low toner consumption printing. An apparatus can be provided.

1 is an apparatus configuration diagram of a printer 100 according to an embodiment. FIG. 2 is a functional block diagram for explaining a main configuration relating to control of a printer. FIG. 6 is a diagram for explaining a print pattern formed in a sub-scanning direction on a sheet. It is a graph which shows the printing result (density result) of the halftone pattern in the halftone pattern exposure amount immediately after the high toner consumption pattern printing and immediately after the blank paper pattern printing. FIG. 6 is a diagram showing fluctuations in surface potential on the photosensitive drum 3 when printing a print pattern formed in the sub-scanning direction on the paper 13; It is a graph which shows the printing result (density result) of the halftone pattern in the halftone pattern exposure amount according to the present embodiment immediately after the high toner consumption pattern printing and immediately after the blank paper pattern printing.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably.

  FIG. 1 is an apparatus configuration diagram of a printer 100 according to the present embodiment. The printer 100 includes black (Bk), yellow (Y), magenta (M), and cyan (C) image forming unit ID-K, image forming unit ID-Y, and image forming corresponding to each color of toner as a developer. This is an electrophotographic color printer that includes a section ID-M and an image forming section ID-C and can print a print image based on input print data on a sheet 13 as a print medium.

  The printer 100 includes an image forming unit along a medium transport path S formed in a substantially S shape starting from the paper feed tray 20 and ending with the transport roller 22, the transfer belt 14, the fixing device 19, and the discharge roller 23. ID-K, image forming unit ID-Y, image forming unit ID-M, and image forming unit ID-C are provided. Each of the image forming unit ID-K, the image forming unit ID-Y, the image forming unit ID-M, and the image forming unit ID-C is provided with a toner storage unit that stores toners of black, yellow, magenta, and cyan. The toner image is developed using the toner supplied from the toner container.

  The paper feed tray 20 stores paper 13 in a stacked state, and is detachably attached to the lower part of the printer 100. The hopping roller 21 provided on the upper side of the paper feed tray 20 takes out the paper 13 stored in the paper feed tray 20 one by one from the uppermost part and feeds it to the medium transport path S.

  The conveyance roller 22 corrects the skew of the sheet 13 fed from the hopping roller 21 and conveys the sheet 13 to the transfer belt 14.

  The transfer belt 14 is an endless belt member that electrostatically adsorbs the sheet 13 and conveys it in the direction of the arrow t in FIG. 1, and a drive roller 16 that rotates in the direction of the arrow in FIG. These are stretched by an idle roller 17 which is paired with the drive roller 16 and stabilizes the drive of the transfer belt 14. A belt cleaning device 18 for removing toner remaining on the transfer belt 14 is provided below the transfer belt 14.

  The fixing device 19 is disposed on the downstream side of the medium transport path S after the image forming unit ID-K, the image forming unit ID-Y, the image forming unit ID-M, and the image forming unit ID-C, and the heat roller 19a. And a backup roller 19b. For example, the heat roller 19a is formed by covering a hollow cylindrical cored bar made of aluminum or the like with a heat-resistant elastic layer of silicone rubber and coating a PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer) tube thereon. Is formed by. In the core bar, for example, a heater such as a halogen lamp is provided. The backup roller 19b has a configuration in which a core rubber made of aluminum or the like is coated with a heat-resistant elastic layer of silicone rubber and PFA is coated thereon, and is arranged so that a pressure contact portion is formed between the backup roller 19b and the heat roller. It is installed. When the paper 13 to which the toner image is transferred passes through a pressure contact portion formed by the heat roller 19a and the backup roller 19b maintained at a predetermined temperature, heat and pressure are applied to the toner on the paper 13, The toner melts and the toner image is fixed.

  The discharge roller 23 discharges the paper 13 that has passed through the fixing device 19 to a stacker that is formed using the upper outer casing of the printer 100.

  Next, the configurations of the image forming unit ID-K, the image forming unit ID-Y, the image forming unit ID-M, and the image forming unit ID-C will be described. The configurations of the image forming unit ID-K, the image forming unit ID-Y, the image forming unit ID-M, and the image forming unit ID-C are different only in the toner used for development, and the other configurations are all the same. . Therefore, in the following description, the image forming unit ID-C will be described as an example.

  The image forming unit ID-C rotates in the direction of the arrow in FIG. 1 and is arranged around the photosensitive drum 3 as the image carrier and the charging roller as the charging member that is arranged around the photosensitive drum 3 and rotates in the direction of the arrow in FIG. 4, an exposure device 5 as an exposure unit, a developing unit 7, a transfer device 12 having a transfer roller 15 rotating in the direction of the arrow in FIG. 1, and a developing device 1 having a cleaning blade 6.

  The photosensitive drum 3 includes a conductive support and a photoconductive layer. For example, a charge generation layer and a charge transport layer as a photoconductive layer are sequentially stacked on an aluminum element tube as a conductive support. Organic photoconductor.

  The charging roller 4 is a device for uniformly and uniformly charging the surface of the photosensitive drum 3. For example, the charging roller 4 has a configuration in which a conductor made of SUS material is coated with a semiconductive rubber layer such as epichlorohydrin. It arrange | positions so that the drum 3 may be contacted.

  The exposure device 5 includes, for example, a light emitting element such as an LED (Light Emitting Diode) element and a lens array, and selectively exposes the surface of the uniformly and uniformly charged photosensitive drum 3 to form an electrostatic latent image. Head. The exposure device 5 is disposed so that the irradiation light output from the LED element based on the print data is positioned on the surface of the photosensitive drum 3.

  The developing unit 7 is a device for developing the toner image by supplying the toner 2 to the electrostatic latent image formed on the surface of the photosensitive drum 3. The developing unit 7 rotates the photosensitive drum 3 in the direction of the arrow in FIG. A developing roller 9 as a developer carrying member that periodically supplies 2 and a toner roller 2 that are arranged in contact with the developing roller 9 and periodically rotate while rotating in the direction of the arrow in FIG. A supply roller 10 serving as a supply member, and a developing blade 11 disposed so as to press the tip portion against the developing roller 9. The inside of the developing unit 7 is configured to be supplied with toner 2 from the toner storage unit 8. ing.

  The developing roller 9 is disposed at a position in contact with the surface of the photosensitive drum 3. The developing roller 9 has a configuration in which an elastic layer is disposed in a roll shape on a conductive shaft (core metal) made of a SUS material and has a surface layer covering the elastic layer. Urethane rubber or silicone rubber can be used for the elastic layer, and a surface layer treated with a urethane solution or one coated with acrylic resin or acrylic-fluorine copolymer resin can be used. When an acrylic resin or an acrylic-fluorine copolymer resin is used as the surface layer, carbon black is blended to impart conductivity.

  The supply roller 10 has a configuration including a conductive shaft (core metal) made of SUS material and an elastic layer. As the elastic layer, a conductive silicone rubber foam layer or a conductive urethane rubber foam layer can be used. In order to give the elastic layer semiconductivity, acetylene black, carbon black or the like is added.

  The developing blade 11 is made of a SUS material having a thickness of 0.08 mm, and the tip portion thereof is bent (bent portion). The developing blade 11 is disposed so as to be pressed against the developing roller 9 through the tip portion, and regulates the layer thickness of the toner 2 on the surface of the developing roller 9.

  In addition, the toner 2 according to the present embodiment is non-magnetic using polyester as a binder resin, carbon black as a colorant, copper phthalocyanine pigment (CI Pigment Blue 15), quinacridone pigment (CI Pigment Red 122), CI Pigment Yellow 185, and the like. This is a one-component negatively chargeable toner. In this embodiment, the volume average particle diameter is 5.8 μm, and an external additive such as silica and titanium oxide is used for the purpose of controlling fluidization and chargeability.

  The transfer roller 15 is disposed in pressure contact with the photosensitive drum 3 via the transfer belt 14, and a toner image formed on the surface of the photosensitive drum 3 is applied by a predetermined transfer voltage applied from a transfer power source (not shown). This is a device for transferring to the paper 13. The transfer roller 15 can be configured as, for example, a conductive foaming elastic body.

  The cleaning blade 6 is a device for scraping and discarding the toner 2 remaining due to non-transfer on the surface of the photosensitive drum 3 and the waste toner moved from the developing unit 7 onto the surface of the photosensitive drum 3. The cleaning blade 6 is made of, for example, a rubber material, and its tip is disposed so as to be in contact with the surface of the photosensitive drum 3.

  FIG. 2 is a functional block diagram for explaining a main configuration relating to the control of the printer 100. The printer 100 is connected to a host device 300 such as a host computer via the interface unit 26, receives print data transmitted from the host device 300, and prints a print image based on the print data on the paper 13. Such a printer 100 includes a printer control unit 24, an interface unit 26, an exposure apparatus control unit 27, an exposure amount control unit 28, a drive unit 29, and a high voltage control unit 30.

  The printer control unit 24 includes at least a print image analysis unit 25 and controls functions related to the entire printer 100. The printer control unit 24 acquires print data transmitted from the host device 300 via the interface unit 26, and controls the exposure device control unit 27, the drive unit 29, and the high-voltage control unit 30 to thereby print a print image based on the print data. To print. The print image analysis unit 25 analyzes the received print data, and an image is formed on the print image formed based on the print data at a density equal to or higher than the first density that consumes much toner 2 such as solid black printing. It is determined whether or not the second area following the first area is formed with a halftone image of the second density.

  The interface unit 26 includes, for example, a network adapter that enables communication on a LAN (Local Aria Network), a USB (Universal Serial Bus) connector, and the like, and controls communication with the host device 300.

  The exposure device control unit 27 digitizes the print data as dot data, and controls the exposure amount control unit 28 based on the digitized dot data.

  The exposure amount control unit 28 adjusts the exposure amount with respect to the photosensitive drum 3 by controlling the light emission (number of light emitting dots) of the LED elements included in the exposure device 5 based on an instruction from the exposure device control unit 27.

  The driving unit 29 rotates a roller member such as the photosensitive drum 3, the charging roller 4, the transfer roller 15, the developing roller 9, the supply roller 10, the hopping roller 21, the transport roller 22, and the discharge roller 23, and a drum motor (not shown) The drive of a belt motor (not shown) that drives the transfer belt 14 is controlled by rotating a drive roller 16 that stretches the belt 14.

  The high voltage control unit 30 controls a voltage applied to the charging roller 4, the developing roller 9, the supply roller 10, the developing blade 11, and the transfer roller 14 by controlling a high voltage power source (not shown).

  Next, a normal printing operation of the printer 100 having the above configuration will be described with reference to FIGS.

  First, when receiving a print instruction from the host apparatus 300, the printer control unit 24 instructs the exposure apparatus control unit 27, the drive unit 29, and the high-pressure control unit 30 to start a printing operation.

  Specifically, the printer control unit 24 gives an instruction to the high voltage control unit 30 and applies a DC voltage of −1000 V to the charging roller 4 in contact with the surface of the photosensitive drum 3 by controlling a high voltage power source (not shown). The surface of the photosensitive drum 3 is uniformly and uniformly charged. Next, the printer control unit 24 instructs the high voltage control unit 30 to apply a DC voltage of −200 V to the developing roller 9 and −300 V to the supply roller 10 and the developing blade 11.

  Then, the printer control unit 24 gives an instruction to the drive unit 29, and controls the drum motor (not shown) to rotate the photosensitive drum 3 in the direction of the arrow in FIG. As the photosensitive drum 3 rotates, the developing roller 9 and the supply roller 10 also rotate in the direction of the arrow in FIG.

  Next, the printer control unit 24 acquires print data transmitted from the host apparatus 300 via the interface unit 26, digitizes the print data as dot data to the exposure apparatus control unit 27, and converts the print data into digitized dot data. Based on this, an instruction is given to control the exposure control unit 28. Receiving the instruction, the exposure apparatus control unit 27 uses the print data as dot data, and controls the exposure amount control unit 28 based on the dot data.

  The exposure amount control unit 28 adjusts the exposure amount by controlling the light emission of the LED elements provided in the exposure device 5, and irradiates the surface of the photosensitive drum 3 with a light beam corresponding to the dot data. An electrostatic latent image corresponding to the dot data is formed on the surface of the photosensitive drum 3 by the irradiation of the light beam.

  Subsequently, the printer control unit 24 gives an instruction to the high-voltage control unit 30 and controls a high-voltage power source (not shown) to apply a development voltage to the developing roller 9, thereby generating an electrostatic latent image on the surface of the photosensitive drum 3. Develop to form a toner image.

  Incidentally, in FIG. 1, the toner 2 stored in the toner storage unit 8 is held in the cell in the supply roller 10 and is rubbed between the supply roller 10 and the developing roller 9 to be charged negatively. To do. The negatively charged toner 2 adheres to the developing roller 9 due to an electric field generated by a potential difference between the supply roller 10 and the developing roller 9. The toner 2 on the developing roller 9 is regulated to a uniform toner layer thickness by the developing blade 11. Further, the toner 2 is frictionally charged by being rubbed by the developing blade 11 and the developing roller 9. The toner 2 on the developing roller 9 is conveyed to an electrostatic latent image on the surface of the photosensitive drum 3, and the electrostatic latent image is developed by the toner 2 adhering due to a potential difference between the electrostatic latent image and the developing roller 9. Is done.

  In accordance with the formation of the toner image on the surface of the photosensitive drum 3, the printer control unit 24 gives an instruction to the driving unit 29 and drives the hopping roller 21 and the conveying roller 22, whereby the paper 13 stored in the paper feed tray 20. Are taken out one by one from the top and fed out to the medium transport path S. The conveyance roller 22 corrects the skew of the sheet 13 fed from the hopping roller 21 and conveys the sheet 13 to the transfer belt 14.

  Then, the printer control unit 24 gives an instruction to the high voltage control unit 30 and controls a high voltage power source (not shown) to apply a transfer voltage to the transfer roller 15 and transfer the toner image on the surface of the photosensitive drum 3 to the paper 13. Let The sheet 13 on which the toner image has been transferred is conveyed to the fixing device 19 as the transfer belt 14 is driven in the direction of arrow t in FIG. In the fixing device 19, heat and pressure are applied, and the toner image on the paper 13 is fixed. The sheet 13 on which the toner image has been fixed is discharged to the stacker as the discharge roller 23 rotates, and the series of printing operations ends. The toner 2 remaining on the surface of the photosensitive drum 3 without being transferred is removed by the cleaning blade 6.

  As described above, in the sub-scanning direction (medium transport direction) on the paper 13, after printing with high toner consumption such as solid black printing, and then printing with halftone density, intermediate printing after low toner consumption printing such as blank paper printing is performed. The print density is lower than that in the case of printing with tonal density. Hereinafter, factors causing such a problem and operations according to the present embodiment capable of solving the problem will be described.

  FIG. 3 shows a high toner consumption pattern a (first region) having a length A and a width C in the sub-scanning direction on the paper 13 and a halftone density pattern having a length B and a width C immediately thereafter (FIG. 3). A white paper pattern c (third region), which is adjacent to the high toner consumption pattern a and a low toner consumption pattern having a length A and a width D, adjacent to the high toner consumption pattern a (hereinafter, referred to as a halftone pattern). Area) and a halftone pattern d having a length B and a width D (the fourth area and the same exposure amount as when the half pattern b is formed) immediately after that is printed. is there.

  In the present embodiment, the high toner consumption pattern “a” is formed when a 100% solid pattern is formed, in other words, when the maximum exposure amount of the exposure apparatus 5 is 100%, an image is formed with an exposure amount of 50% or more as the first density. It is assumed that the halftone pattern b and the halftone pattern d are formed with an exposure amount of 10% to 40% as the second density. The blank paper pattern c is a pattern in which an image is formed when the LED elements included in the exposure device 5 are not lit, and the consumption amount of the toner 2 is small.

  When the pattern shown in FIG. 3 is printed, the density of the halftone pattern b becomes lower than the density of the halftone pattern d, and a density difference occurs between the halftone pattern b and the halftone pattern d having the same exposure amount. When the high toner consumption pattern a is printed, the amount of toner 2 in the portion corresponding to the high toner consumption pattern a on the developing roller 9 decreases. At the same time, the toner 2 is newly supplied from the supply roller 10 to the portion where the amount of the toner 2 is reduced. Since the toner 2 is supplied to the portion where the amount of toner 2 is reduced, the amount of toner 2 on the developing roller 9 after printing of the high toner consumption pattern a is greater than after printing of the blank paper pattern c where the amount of toner 2 is not reduced. Less. As a result, a difference in density occurs between the halftone pattern b and the halftone pattern d due to the difference in the amount of toner 2 on the developing roller 9. As the exposure amount of the high toner consumption pattern a increases, the density difference increases. As the length A increases, the range in which the density difference occurs increases in the length B in the sub-scanning direction.

  FIG. 4 is a graph showing a halftone pattern printing result (density result) at a halftone pattern exposure amount immediately after printing a high toner consumption pattern and immediately after printing a blank paper pattern. The exposure amount during printing of the high toner consumption pattern was 50%, and the density of the halftone pattern was measured using a spectral color densitometer X-Rite 528 (manufactured by X-Rite).

  As shown in FIG. 4, there is a density difference between the result of printing the halftone pattern immediately after printing the high toner consumption pattern and the result of printing the halftone pattern immediately after printing the blank paper pattern. In particular, it can be seen that the density difference becomes significant in the region where the exposure amount is 10% or more and 40% or less.

The evaluation standard of the density difference ΔE in this embodiment is:
ΔE <0.05: A difference in density is felt faintly.
0.05 ≦ ΔE: A density difference is felt.
If the value of ΔE is less than 0.05, it is regarded as the same color and evaluated as having no problem. On the other hand, if the value of ΔE is 0.05 or more, a density difference is felt and it is evaluated that there is a problem.

  Table 1 is a table showing the result of FIG. 4 as a density difference for each exposure amount. As described above, a value having a density difference ΔE value of less than 0.05 is indicated by ◯, and a value having a density difference ΔE value of 0.05 or more is indicated by x.

  As is clear from Table 1, the evaluation is ○ when the exposure amount is in the range of 0% or more and 5% or less, evaluation × when the exposure amount is 10% or more and 40% or less, and evaluation ○ when the exposure amount is 45% or more and 50% or less. It can be seen that the density difference increases in the range of 40% or less.

  FIG. 5 is a diagram showing fluctuations in the surface potential on the photosensitive drum 3 when the print pattern formed in the sub-scanning direction on the paper 13 is printed. V0 is the surface potential on the photosensitive drum 3 when a charging voltage is applied to the charging roller 4, and Vb is the surface potential on the photosensitive drum 3 when irradiated with an exposure amount of 50% to 100%. Vh is the surface potential on the photosensitive drum 3 when irradiated with an exposure amount of 10% to 40%. When printing a blank paper pattern, there is no irradiation by the exposure device 5, so the surface potential on the photosensitive drum 3 is V0.

  In this embodiment, as a method of eliminating the density difference between the density of the halftone pattern printed immediately after printing the high toner consumption pattern and the density of the halftone pattern printed immediately after printing the blank paper pattern, the halftone pattern is printed immediately after printing the high toner consumption pattern. When the tone pattern printing continues, the exposure amount when forming the halftone pattern is larger than when the halftone pattern printing continues immediately after the blank paper pattern printing.

  For this reason, the printer 100 according to the present embodiment includes the print image analysis unit 25, analyzes the received print data, and the print image formed based on the print data has a halftone pattern after the high toner consumption pattern. It is determined whether or not it is formed. When it is determined that the halftone pattern is formed after the high toner consumption pattern, the printer control unit 24 determines the exposure amount related to the formation of the halftone pattern via the exposure device control unit 27 and the halftone pattern after the blank paper pattern. The exposure apparatus 5 is controlled to be higher than the exposure amount when the pattern is formed.

  Specifically, the printer control unit 24 increases the exposure amount by 5% in the printing of the halftone pattern with the exposure amount of 10% to 40% immediately after the high toner consumption pattern printing. As a result, the toner 2 on the developing roller 9 is easily moved to the photosensitive drum 3, and the density of the halftone pattern increases. As a result, the density difference between the density of the halftone pattern printed immediately after printing the high toner consumption pattern and the density of the halftone pattern printed immediately after printing the blank paper pattern can be eliminated.

  Vha shown in FIG. 5 is a surface potential on the photosensitive drum 3 when the exposure amount is increased by 5% in the printing of the halftone pattern at the exposure amount of 10% to 40% immediately after the high toner consumption pattern printing. It can be seen that by increasing the exposure amount, the surface potential of the photosensitive drum 3 is lowered, and the toner 2 on the developing roller 9 is easily moved to the photosensitive drum 3.

  FIG. 6 is a graph showing a halftone pattern printing result (density result) with a halftone pattern exposure amount immediately after printing a high toner consumption pattern and immediately after printing a blank paper pattern.

  Compared to FIG. 4, it can be seen that the density difference of the halftone pattern is smaller immediately after printing the high toner consumption pattern and immediately after printing the blank paper pattern.

  Table 2 shows the result of FIG. 6 as a density difference for each exposure amount. As described above, a value having a density difference ΔE value of less than 0.05 is indicated by ◯, and a value having a density difference ΔE value of 0.05 or more is indicated by x.

  As is apparent from Table 2, in this embodiment, the evaluation is ○ when the exposure amount is in the range of 0% or more and 50% or less, and the density difference of the halftone pattern is immediately after printing the high toner consumption pattern and immediately after printing the blank paper pattern. You can see that it is decreasing.

  As described above, according to the present embodiment, when a halftone pattern is formed immediately after the high toner consumption pattern is formed, printing is performed by increasing the printing of the halftone pattern beyond a predetermined exposure amount. As a result, the density of the halftone pattern can be increased, and the density difference from the case where the halftone pattern is formed immediately after the blank paper pattern is formed can be eliminated.

  The present invention is applicable to an electrophotographic color or monochrome image forming apparatus. In the description of the present invention, a printer has been described as a preferred example of an image forming apparatus. However, the present invention is not limited to this, and can be applied to, for example, a copying machine, a FAX, and an MFP. .

DESCRIPTION OF SYMBOLS 1 Developing device 2 Toner 3 Photosensitive drum 4 Charging roller 5 Exposure device 6 Cleaning blade 7 Developing portion 8 Toner accommodating portion 9 Developing roller 10 Supply roller 11 Developing blade 12 Transfer device 13 Paper 14 Transfer belt 15 Transfer roller 16 Drive roller 17 Idle roller 18 Belt cleaning device 19 Fixing device 19a Heat roller 19b Backup roller 20 Paper feed tray 21 Hopping roller 22 Transport roller 23 Discharge roller 24 Printer control unit 25 Print image analysis unit 26 Interface unit 27 Exposure device control unit 28 Exposure amount control unit 29 Drive Unit 30 high pressure control unit 100 printer 300 host device

Claims (4)

A print image analysis unit for analyzing the received print data;
An image carrier;
A charging member for charging the image carrier;
An exposure unit that exposes the image carrier to form an electrostatic latent image on the image carrier;
A developer carrying member carrying a developer used for developing the electrostatic latent image;
An exposure control unit for controlling the exposure unit,
The exposure control unit
A second area following the first area in which the print image analysis unit forms an image at a density higher than the first density on the print image formed based on the print data is a halftone image having a second density The exposure amount in the second area is set to the exposure in the fourth area where a halftone image is formed at the second density following the third area which is a blank image. An image forming apparatus, wherein the exposure unit is controlled to be higher than the amount. The exposure control unit
The image forming apparatus according to claim 1, wherein an exposure amount for forming the halftone image is controlled by changing a light emission amount or a light emission number of the exposure unit. 3. The image according to claim 1, wherein the image formation at the first density is performed with a light emission amount of 50% or more when a maximum light emission amount of the exposure unit is 100%. Forming equipment. The halftone image formation at the second density is performed at a light emission amount of 10% or more and 40% or less when the maximum light emission amount of the exposure unit is 100%. 4. The image forming apparatus according to any one of items 3.