JP5348524B2 - Development method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development method, a developing device, a process cartridge and an image forming apparatus, capable of forming a proper halftone image adjacent to a solid image and which allows visual observation of dot reproducibility. <P>SOLUTION: In the developing method for developing a latent image formed on a photoreceptor drum 2, in a developing part where a developing roller 14 that is a developer carrier and a photoreceptor drum 2 that is a latent image carrier are opposed to each other, by using a developer composed of toner and carrier carried on the developing roller 14 an image pattern dependency ratio A/B that a ratio of a toner adhesive amount A per dot of floating island dots to a toner adhesive amount B per dot of isolated dots which are developed on the photoreceptor drum 2 is 0.40 or more. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

The present invention is, a printer, a facsimile, an image forming apparatus using a Re developing side Ho及 patron for use in an image forming apparatus such as a copying machine.

  In this type of image forming apparatus, an abnormality called a “halo image” in which the dot reproducibility of a halftone image adjacent to a solid image is deteriorated due to the influence of an edge electric field generated at the edge portion of the solid image, and is whitened. There is a known problem that an image is generated.

  White spots in the halftone image adjacent to the solid image occur as follows. In an image in which the solid image and the halftone image are adjacent to each other, the developing electric field at the edge of the halftone image is weakened by the edge electric field of the solid image, and the toner on the halftone image side adheres to the edge portion of the solid image. As a result, the toner adhesion amount at the edge of the halftone image is reduced, the dot reproducibility is deteriorated, and the edge of the halftone image is whitened. At this time, the toner adhesion amount increases at the edge portion of the solid image, but is not noticeable because it is originally a solid image. Accordingly, white spots in the halftone image adjacent to the solid image become a problem on the image.

  For such problems, set appropriate values for the developer amount and developer density in the developing section where the photosensitive drum and developing roller face each other, and optimize the developer amount and developer density in the developing section. By doing so, there are known ones that can suppress white spots in a halftone image adjacent to a solid image (Patent Document 1, Patent Document 2, etc.).

JP 2000-29308 A JP 2004-191881 A

  However, there is a possibility that the dot reproducibility of the halftone image adjacent to the solid image cannot be improved satisfactorily by just setting appropriate values for the developer amount and developer density in the developing unit.

The present invention has been made in view of the above problems, its object is good that dot reproducibility is acceptable visually, the developing direction Ho及 beauty image forming apparatus capable of forming a halftone image adjacent to the solid image Is to provide.

In order to achieve the above object, the invention of claim 1 uses a developer comprising a toner and a carrier carried on a developer carrying body, and the developer carrying body and the latent image carrying body face each other. In the developing method for developing the latent image formed on the latent image carrier in the developing section, one dot of floating island dots developed on the latent image carrier using a toner having an average particle size of 5 μm or less the ratio a / B is 0.40 or more der the toner adhesion amount B per dot of toner adhesion amount a and isolated dots per is, the pick-up amount of the developer carrying member of the developer C [mg / cm ² ], and the distance between the surface of the developer carrying member and the surface of the electrostatic latent image carrier in the developing unit is D [mm], the developer density C / D in the developing unit is a but 1950 [mg / cm ^3] or more, electrostatic the developing unit The distance D between the surface of the image carrier and the surface of the developer carrier is 0.3 [mm] or less, and faces the latent image carrier in a non-contact manner, and is formed on the latent image carrier. The toner adhesion amount detecting means for detecting the toner adhesion amount of the toner image detects the toner adhesion amounts of the floating island dots and the isolated dots formed on the latent image carrier, and 1 of the floating island dots is detected from the detection result. When the ratio A / B between the toner adhesion amount A per dot and the toner adhesion amount B per isolated dot is less than 0.40, the density of the developer in the developing portion is increased to Control is performed so that A / B is 0.40 or more .
The invention of claim 2 uses a developer comprising a toner and a carrier carried on a developer carrying member, and the latent image carrying member and the latent image carrying member are opposed to each other in the developing section. In a developing method for developing a latent image formed on an image carrier, a toner adhesion amount A per dot of floating island dots developed on the latent image carrier using a toner having an average particle diameter of 5 μm or less. The ratio A / B of toner to the toner adhesion amount B per isolated dot is 0.40 or more, the amount of developer pumped on the developer carrier is C [mg / cm ² ], and the development When the distance between the surface of the developer carrying member and the surface of the electrostatic latent image carrier in the portion is D [mm], the developer density C / D in the developing portion is 1950 [mg / cm ³ The surface of the electrostatic latent image carrier in the developing unit and the surface Distance D between the surface of the image-carrying member is not more 0.3 [mm] or less, the toner image from said image bearing member are opposed in a non-contact with the transfer member to be primarily transferred, the toner on said transfer Utsushitai the toner adhering amount detecting means for detecting a toner adhesion amount of the image, detects the island dots and the isolated dot each toner adhesion amount has been transferred to said transfer Utsushitai from the latent image bearing member, the floating island dot on the detection result 1 when the ratio a / B between the toner adhesion amount a per dot and the toner adhesion amount B per dot of isolated dots is less than 0.40, by increasing the density of the developer in the developing unit of Control is performed so that the ratio A / B is 0.40 or more.
According to a third aspect of the present invention, a developer composed of a toner and a carrier carried on a developer carrying member is used, and the latent image carrying member and the latent image carrying member are opposed to each other in the developing portion. In a developing method for developing a latent image formed on an image carrier, a toner adhesion amount A per dot of floating island dots developed on the latent image carrier using a toner having an average particle diameter of 5 μm or less. The ratio A / B of toner to the toner adhesion amount B per isolated dot is 0.40 or more, the amount of developer pumped on the developer carrier is C [mg / cm ² ], and the development When the distance between the surface of the developer carrying member and the surface of the electrostatic latent image carrier in the portion is D [mm], the developer density C / D in the developing portion is 1950 [mg / cm ³ The surface of the electrostatic latent image carrier in the developing unit and the surface Distance D between the surface of the image-carrying member is not more 0.3 [mm] or less, the recording finally the toner image via a transfer member the toner image from said image bearing member is primarily transferred is transferred the toner adhering amount detecting means for detecting a toner adhesion amount of the toner image on the medium, and finally the recording medium has been the island dots and the isolated dot of each transferred through said transfer Utsushitai from the latent image bearing member When the toner adhesion amount is detected, and the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot is less than 0.40 based on the detection result , in which by increasing the density of the developer in the developing unit is the ratio a / B and performs a control to be 0.40 or more.
According to a fourth aspect of the present invention, in the developing method according to the first , second, or third aspect , the control is performed between the toner adhesion amount A per floating island dot and the toner adhesion amount B per isolated dot dot. The distance between the surface of the latent image carrier and the surface of the developer carrier is narrowed until the ratio A / B becomes 0.40 or more.
According to a fifth aspect of the present invention, in the developing method according to the first , second, or third aspect , the control is performed between the toner adhesion amount A per floating island dot and the toner adhesion amount B per isolated dot dot. Until the ratio A / B becomes 0.40 or more, the distance between the developer carrying member and a regulating member that is provided facing the developer carrying member and regulates the amount of developer conveyed by the developer carrying member is set. It is characterized by spreading.
According to a sixth aspect of the present invention, there is provided a latent image carrier for carrying a latent image, a developer comprising a toner and a carrier on the developer carrier, and the developer carrier and the latent image carrier. In the image forming apparatus provided with developing means for developing the latent image on the latent image carrier in the developing portions facing each other, the average particle diameter of the toner is 5 [μm] or less. The ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more. Using the configured developing device, the amount of developer pumped on the developer carrier is C [mg / cm ² ], and the distance between the developer carrier and the latent image carrier in the developing unit is D [ mm], the density C / D of the developer in the developing portion is 1950 [ mg / cm ³ ] or more, and the distance D between the surface of the latent image carrier and the surface of the developer carrier in the developing portion is 0.3 [mm] or less, and the latent image carrier A toner adhesion amount detection means for detecting a toner adhesion amount of a toner image on the latent image carrier provided in contact with each other; and the floating island dots and the isolation on the latent image carrier by the toner adhesion amount detection means. Calculation means for detecting the toner adhesion amount of each dot and calculating a ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot based on the detection result And when the ratio A / B is less than 0.40 based on the calculation result of the calculation means, the density of the developer in the developing section is increased so that the ratio A / B is 0.40 or more. and having a control means for controlling the Than is.
According to a seventh aspect of the present invention, there is provided a latent image carrier that carries a latent image, a developer comprising a toner and a carrier carried on the developer carrier, and the developer carrier and the latent image carrier. In the image forming apparatus provided with developing means for developing the latent image on the latent image carrier in the developing portions facing each other, the average particle diameter of the toner is 5 [μm] or less. The ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more. Using the configured developing device, the amount of developer pumped on the developer carrier is C [mg / cm ² ], and the distance between the developer carrier and the latent image carrier in the developing unit is D [ mm], the density C / D of the developer in the developing portion is 1950 [ mg / cm ³ ] or more, and the distance D between the surface of the latent image carrier and the surface of the developer carrier in the developing portion is 0.3 [mm] or less, and the surface of the latent image carrier is A transfer means for transferring the toner image to a recording medium via a transfer body; a toner adhesion amount detection means for detecting the toner adhesion amount of the toner image on the transfer body provided in contact with the transfer body in a non-contact manner; The toner adhesion amount detection means detects the toner adhesion amounts of the floating island dots and the isolated dots transferred from the latent image carrier onto the transfer body, and based on the detection results, the floating island dots per dot are detected. A calculation means for calculating a ratio A / B between the toner adhesion amount A and the toner adhesion amount B per isolated dot, and the ratio A / B is less than 0.40 based on a calculation result of the calculation means. The developer in the developing section It is characterized in that a control means for controlling the degree to increase the by the the ratio A / B to 0.40 or more.
According to an eighth aspect of the present invention, there is provided a latent image carrier for carrying a latent image, a developer comprising a toner and a carrier carried on the developer carrier, and the developer carrier and the latent image carrier. In the image forming apparatus provided with developing means for developing the latent image on the latent image carrier in the developing portions facing each other, the average particle diameter of the toner is 5 [μm] or less. The ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more. Using the configured developing device, the amount of developer pumped on the developer carrier is C [mg / cm ² ], and the distance between the developer carrier and the latent image carrier in the developing unit is D [ mm], the density C / D of the developer in the developing portion is 1950 [ mg / cm ³ ] or more, and the distance D between the surface of the latent image carrier and the surface of the developer carrier in the developing unit is 0.3 [mm] or less, and the surface of the latent image carrier is Transfer means for transferring a toner image to a recording medium via a transfer member, toner adhesion amount detection means for detecting the toner adhesion amount of the toner image transferred to the recording medium, and toner adhesion amount detection means The toner adhesion amount of each of the floating island dots and the isolated dots transferred from the image carrier to the recording medium via the transfer body is detected, and the toner adhesion amount per dot of the floating island dots based on the detection result A calculating means for calculating the ratio A / B between A and the toner adhesion amount B per isolated dot, and when the ratio A / B is less than 0.40 based on the calculation result of the calculating means , Increase the density of the developer in the developing section It is characterized in that a control means for performing control of the said ratio A / B to 0.40 or more.
The invention according to claim 9 is the image forming apparatus according to claim 6 , 7 or 8 , wherein the control means controls the surface of the latent image carrier and the surface until the ratio A / B is 0.40 or more. The distance between the developer carrying member and the surface of the developer carrying member is narrowed.
The invention according to claim 10 is the image forming apparatus according to claim 6 , 7 or 8 , wherein the control control means faces the developer carrying member until the ratio A / B becomes 0.40 or more. The distance between the developer carrying member and the regulating member that regulates the amount of developer carried by the developer carrying member and the developer carrying member is increased.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the sixth, seventh, eighth, ninth, or tenth aspect, at least the latent image carrier and the developing means are integrally formed and detachable from the apparatus. It has a characteristic process cartridge.

Here, the floating island dot is one dot formed in a central pixel which is 9 × 9 pixels and is separated by two pixels in the vertical direction or the horizontal direction from the vertical and horizontal lines of the surrounding two pixels. This floating island dot, like a halftone image adjacent to a solid image, tends to reduce the amount of toner adhesion due to the influence of the edge electric field of the line and deteriorate dot reproducibility. The isolated dot is one dot in which the above-described line or the like that generates an edge electric field that affects dot reproducibility is not formed in other pixels around the one pixel on which it is formed. This isolated dot is not adjacent to the line that generates an edge electric field that affects dot reproducibility like a halftone image that is not adjacent to a solid image. Sexual deterioration does not occur.
For these reasons, as the toner adhesion amount of floating island dots approaches the toner adhesion amount of isolated dots, the decrease in toner adhesion amount of floating island dots due to the influence of the edge electric field is suppressed. The sex will be improved.

  In the present invention, as clarified in the experiment described later, the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot is 0.40 or more. As a result, it is possible to form a good floating island dot whose dot reproducibility is visually acceptable. Therefore, it is possible to form floating island dots that are deteriorated in dot reproducibility due to the influence of the edge electric field, such as a halftone image adjacent to a solid image, with good dot reproducibility that can be visually observed. A tone image can also be formed with good dot reproducibility acceptable by visual inspection.

  As described above, according to the present invention, there is an excellent effect that a halftone image adjacent to a solid image can be formed with good dot reproducibility and visually acceptable.

Hereinafter, the image forming apparatus according to the present embodiment will be described. FIG. 2 is a schematic configuration diagram showing an internal configuration of the image forming apparatus according to the present embodiment.
This image forming apparatus can form an image with a resolution of 600 [dpi]. As shown in FIG. 2, images of each color of yellow (Y), cyan (C), magenta (M), and black (K) are displayed. Four image forming units 1Y, 1C, 1M, and 1K for forming are provided. The color order of Y, C, M, and K is not limited to that shown in FIG.

  Each of the image forming units 1Y, 1C, 1M, and 1K includes photosensitive drums 2Y, 2C, 2M, and 2K as image carriers that are rotatably provided around a rotation axis, and the photosensitive drums 2Y, 2C, and 2M. As described later, a charging roller, a developing device, a cleaning device, and the like are provided around 2K. The image forming units 1Y, 1C, 1M, and 1K are arranged so that the rotation axes of the photosensitive drums 2 are parallel to each other and at a predetermined pitch in the surface movement direction of the intermediate transfer belt 4 described later. It is set to be. In the present embodiment, the linear velocity of the photosensitive drum 2 is 200 [mm / sec].

  FIG. 3 is a schematic configuration diagram showing the configuration of the image forming units 1Y, 1C, 1M, and 1K. Since the image forming units 1Y, 1C, 1M, and 1K have the same configuration except that only the color type of the toner to be used is different, the subscripts (Y, C, M, and K) representing the colors are omitted below. To explain.

  In the image forming unit 1, a photosensitive unit 15 including a photosensitive drum 2, a charging roller 13, a cleaning device, and the like, and a developing device 12 are integrally configured. The diameter of the photosensitive drum 2 is 40 [mm]. The charging roller 13 charges the surface of the photosensitive drum 2 with a charging voltage of 700 [V]. By configuring the image forming unit 1 as a process cartridge that can be attached to and detached from the apparatus main body, when the maintenance of the image forming unit 1 becomes necessary, the image forming unit 1 can be replaced for convenience. improves.

The developing device 12 develops the latent image on the photosensitive drum 2 using a two-component developer composed of toner and magnetic carrier housed in a developing case. As the toner in the developer, a toner having an average particle diameter of 5 [μm] or less is adopted based on the experimental results described later. The developing device 12 includes a developing roller 14 having a diameter of 20 [mm] that faces the photosensitive drum 2 through an opening of the developing case, a screw that stirs and conveys the developer contained in the developing case, and the developing roller 14. And a blade 18 including a magnetic material, which regulates the amount of the developer drawn up. Note that the amount of developer pumped up by the developing roller 14 (the amount of developer per unit area passing through the blade 18) is set to 58.5 [mg / cm ² ] by default based on the experimental results described later.

  In the present embodiment, the development gap D, which is the distance between the surface of the photosensitive drum 2 and the surface of the developing roller 14, is set to 0.30 [mm] by default based on experimental results described later.

  The developing roller 14 includes an outer rotatable sleeve, a magnet fixed on the inner side, and the like, and is configured such that a developing bias of 500 [V] is applied by a power source (not shown). The developer in the developing case agitated and conveyed by the screw is pumped and carried on the surface of the developing roller 14 by a magnet provided inside the developing roller 14 as the sleeve rotates, and on the surface of the developing roller 14. Form a magnetic brush. In this embodiment, the linear speed of the sleeve of the developing roller 14 is set to 400 [mm / sec].

  Then, in the developing portion formed at a position where the surface of the developing roller 14 and the surface of the photosensitive drum 2 face each other, the toner in the magnetic brush is light which will be described later from the developing roller 14 to which the developing bias is applied by the power source. The latent image on the photosensitive drum 2 formed by the writing unit 3 is transferred to the latent image, and the latent image is developed with toner to be visualized.

  The developing device 12 is also provided with a toner density sensor (not shown). Yellow (Y), cyan (C), magenta (M), black, and the like are supplied by a toner supply device (not shown) according to the output of the toner density sensor. The toner of the color corresponding to the developing device 12 of each color is replenished from the toner replenishing container 11 that accommodates the toner of (K).

  Below the image forming units 1Y, 1C, 1M, and 1K, an optical writing unit 3 that is a latent image forming unit that forms a latent image on the surface of each photosensitive drum 2 is disposed. The optical writing unit 3 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like. The surface of the photosensitive drums 2Y, 2C, 2M, and 2K charged to a potential of 700 [V] by the charging roller 3 is provided. Then, irradiation is performed while scanning with laser light based on the image data, and the surface potential of the photosensitive drum 2 at the portion irradiated with the laser light is lowered to 50 [V] to form a latent image.

  Above the image forming units 1Y, 1C, 1M, and 1K, a transfer unit 5 having an intermediate transfer belt 4 and primary transfer rollers 17Y, 17C, 17M, and 17K that are wound around and rotated by a plurality of rollers. Has been placed. In the transfer unit 5, the intermediate transfer belt 4 is sandwiched between the photosensitive drums 2Y, 2C, 2M, and 2K and the primary transfer rollers 17Y, 17C, 17M, and 17K to form primary transfer portions. The surface of the intermediate transfer belt 4 passes through the primary transfer portions of Y, C, M, and K along the endless movement (rotation operation) of the intermediate transfer belt 4 in the process of passing through the surface of the intermediate transfer belt 4. The Y toner image, the C toner image, the M toner image, and the K toner image formed on the photosensitive drums 2Y, 2C, 2M, and 2K are superimposed and transferred. As a result, a four-color superimposed toner image is formed on the surface of the intermediate transfer belt 4. At this time, each color toner image is transferred from the photosensitive drums 2Y, 2C, 2M, and 2K onto the surface of the intermediate transfer belt 4 from a power source (not shown) to the primary transfer rollers 17Y, 17C, 17M, and 17K. This is performed by supplying a current of 30 [μA] and forming a primary transfer electric field that attracts toner from the photosensitive drum 2 to the intermediate transfer belt 4.

  In addition, the transfer unit 5 forms a secondary transfer portion by sandwiching the intermediate transfer belt 4 between the secondary transfer backup roller 7 and the secondary transfer roller 8. In the secondary transfer portion, the transfer paper 9 is sandwiched between the intermediate transfer belt 4 and the secondary transfer roller 8 whose surfaces move in the forward direction and conveyed upward in FIG. The four-color superimposed toner image formed on the surface of the intermediate transfer belt 4 is transferred to the transfer paper 9 at this secondary transfer portion to become a full-color toner image. This transfer is performed by supplying a current of 40 [μA] from a power source (not shown) to the secondary transfer roller 8 and forming a secondary transfer electric field that attracts toner from the intermediate transfer belt 4 to the transfer paper 9. Is called.

  Foreign matter such as transfer residual toner remaining on the surface of the intermediate transfer belt 4 after passing through the secondary transfer portion is constituted by a brush roller, a cleaning blade, or the like provided so as to be in contact with the surface of the intermediate transfer belt 4. The surface of the intermediate transfer belt 4 is cleaned by the cleaning device 6.

  A fixing unit 38 is disposed on the upper right side of the transfer unit 5 in the drawing. In the fixing unit 38, a fixing belt is sandwiched between the pressure roller and the fixing roller to form a fixing nip portion. The toner image on the transfer paper 9 conveyed into the fixing unit 38 is fixed to the transfer paper 9 by pressure and heat received at the fixing nip portion. The transfer paper 9 on which the toner image is fixed is discharged out of the apparatus by a discharge roller.

  At the lower part of the image forming apparatus main body, paper feed cassettes 10a and 10b for accommodating the transfer paper 9 are arranged, and at the side of the image forming apparatus main body, a manual feed tray 10c for manually feeding paper is arranged. The transfer paper 9 fed from either the paper feed cassette 10a, 10b or the manual feed tray 10c stops once when it reaches the registration roller pair 16. Then, the transfer paper 9 is sent out from the registration roller pair 16 toward the secondary transfer portion at an appropriate timing, and the full-color toner image is transferred at the secondary transfer portion as described above.

  Next, features of the image forming apparatus according to the present embodiment will be described. The image forming apparatus according to the present embodiment is configured such that image formation can be performed by a developing method capable of forming a halftone image adjacent to a solid image having good dot reproducibility that is visually acceptable. Specifically, the image pattern dependence ratio A / B of floating island dots, which is the ratio of the toner adhesion amount A per floating dot to be described later and the toner adhesion amount B per isolated dot, is 0.40 or more. An image is formed by a developing method.

  Here, as shown in FIG. 4A, the floating island dot is formed in one pixel at the center, which is 9 × 9 pixels and separated by two pixels in the vertical or horizontal direction from the vertical and horizontal lines of the surrounding two pixels. 1 dot. This floating island dot, like a halftone image adjacent to a solid image, tends to reduce the amount of toner adhesion due to the influence of the edge electric field of the line and deteriorate dot reproducibility. On the other hand, as shown in FIG. 4B, an isolated dot is a line that generates an edge electric field that affects dot reproducibility on other pixels around one pixel on which it is formed. One dot is not formed. This isolated dot is not adjacent to the line that generates an edge electric field that affects dot reproducibility like a halftone image that is not adjacent to a solid image. Sexual deterioration does not occur. In this embodiment, as can be seen from FIG. 4B, adjacent isolated dots are formed by separating three pixels from each other.

  The image pattern dependency ratio is how much the toner adhesion amount of floating island dots is affected by the edge electric field of the above line (image pattern) around itself, that is, the toner adhesion amount of floating island dots is around It shows how much it depends on the above-mentioned line (image pattern). As can be seen from FIG. 4B, the isolated dots are different from the floating island dots and do not have the above-described line (image pattern) that generates an edge electric field that affects the toner adhesion amount.

  FIG. 4C is an example in which a plurality of floating island dots are actually output, and FIG. 4D is an example in which a plurality of isolated dots are actually output, but the dot reproducibility of floating island dots compared to isolated dots. It can be seen that there is a difference in the toner adhesion amount between floating island dots and isolated dots.

  From this, it can be said that the larger the difference between the toner adhesion amount of floating island dots and the toner adhesion amount of isolated dots, the greater the image pattern dependency of floating island dots. It can be said that the smaller the difference is, the smaller the image pattern dependency of floating island dots is. That is, as the image pattern dependency ratio of floating island dots approaches 0, the toner adhesion amount of floating island dots is greatly affected by the edge electric field of the line, indicating that the image pattern dependency of floating island dots is large. Conversely, the closer the image pattern dependency ratio of floating island dots is to 1, the less the toner adhesion amount of floating island dots is affected by the edge electric field of the line, indicating that the image pattern dependency of floating island dots is smaller.

  Next, an experiment conducted for evaluating the image pattern dependency ratio of floating island dots that can improve the dot reproducibility of floating island dots to an acceptable level by visual observation will be described.

  In the present embodiment, the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot were determined as follows. First, how to determine the toner adhesion amount A per floating island dot will be described. Thirty floating island dots are formed on the photosensitive drum 2, and each image information is read by a scanner provided in the apparatus main body so as to face the photosensitive drum 2 in a non-contact manner. Then, in the two-dimensional projection image of each floating island dot read by the scanner, black (toner-covered image portion) and white in the area S1 surrounded by a square shown in FIG. 4 (a), FIG. 4 (c), etc. (Non-image portion where toner is not applied). The optical density of each pixel is measured for a portion identified as black in the area S1, and the measurement results are integrated, and a control comprising a CPU as a calculation means and a memory as a storage means provided in the apparatus main body from the total sum. The toner adhesion amount A per floating island dot is obtained using a conversion table for the toner adhesion amount stored in advance in the memory of the unit. Similarly, with respect to the toner adhesion amount B per dot of isolated dots, 30 isolated dots are formed on the photosensitive drum 2 and the respective image information is read by the scanner, and FIG. 4B and FIG. d) The optical density of each pixel is measured for the portion identified as black in the area S2 surrounded by a square as shown in FIG. 4 and the like, the measurement results are integrated, and the sum total is used to calculate the isolated dot per dot from the conversion table. A toner adhesion amount B is obtained.

  Then, the image pattern dependence ratio A / B of the floating island dot is calculated from the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot determined in this way. Calculated by the above.

  In addition, as a result of intensive studies, the inventors of the present application have found that, when the dot diameter variation of isolated dots is 15% or less, good reproducibility of floating island dots that can be visually observed can be obtained. Yes.

In the present embodiment, the dot diameter variation of floating island dots was obtained as follows. Thirty floating island dots are formed on the photosensitive drum 2, and each image information is read by a scanner provided in the apparatus main body so as to face the photosensitive drum 2 in a non-contact manner. Then, in the two-dimensional projection image of each floating island dot read by the scanner, the area S1 surrounded by the square shown in FIG. 4A and FIG. (Non-image portion where toner is not applied). The equivalent circle diameter of the floating island dot (the diameter of a circle having an area equal to the area of the portion identified as black in the region S1) is obtained from the area of the portion identified as black in the region S1. The standard deviation of the equivalent circle diameter and the average equivalent circle diameter are obtained from the equivalent circle diameters of the 30 floating island dots thus obtained, and the value calculated by Equation 1 is used as the dot diameter variation.

In this experiment, the dot diameter variation of floating island dots in each of the four image pattern dependency ratios (0.23, 0.34, 0.47, 0.58) shown in Table 1 was obtained, The relationship with dot diameter variation was plotted as shown in FIG. Further, an approximate straight line representing the relationship between the image pattern dependency ratio and the dot diameter variation as shown in FIG. 1 was obtained from the relationship between each image pattern dependency ratio and the dot diameter variation by the least square method.

  From FIG. 1, the dot variation of floating island dots in the approximate straight line is 15% when the image pattern dependency ratio is 0.40. In the approximate straight line, as can be seen from FIG. 1, the dot variation decreases as the image pattern dependency ratio increases (closer to 1). From this, when the image pattern dependency ratio is 0.40 or more, the dot variation of floating island dots becomes 15% or less, and the dot reproducibility of floating island dots is improved satisfactorily to an acceptable level visually.

Further, by improving the dot reproducibility of floating island dots in this way, the granularity of floating island dots and the like is also improved. Here, the graininess is defined as follows, unlike “dot reproducibility” which is generally considered as an index of high image quality. In other words, “granularity” is defined as “subjective evaluation value indicating how rough an image that should be uniform” is, and the amount that objectively represents the granularity that is the subjective evaluation value is granularity. It is a measure of sex and is “granularity”. The granularity in the present embodiment is defined by Equation 2.

  For example, as shown in FIG. 1, when the image pattern dependency ratio is 0.23, the granularity of floating island dots and the like was 0.31, whereas when the image pattern dependency ratio was 0.58, the floating island The granularity of dots and the like is 0.23. As is generally known, the smaller the granularity, the better. Therefore, it can be seen that the image pattern dependency ratio is 0.40 or more and the dot reproducibility of the floating island dots is improved, thereby improving the granularity of the floating island dots and the like. This also means that the dot reproducibility and graininess of floating island dots have not been improved to an extent that is visually acceptable when the image pattern dependency ratio of floating island dots is 0.23 from FIG. It can be seen from the fact that the dot reproducibility and granularity of floating island dots are improved to an extent that is visually acceptable when the dependency ratio is 0.58.

  In this way, by improving the dot reproducibility and graininess of floating island dots, which are image patterns that are difficult to create such as a halftone image adjacent to a solid image or a character image with a large number of strokes, a solid image can be obtained. Dot reproducibility and granularity of adjacent halftone images and character images with a large number of strokes are also improved. Therefore, an image is developed using a development method that improves the dot reproducibility and granularity of floating island dots to such an extent that is visually acceptable, that is, a development method in which the above-described image pattern dependency ratio of floating island dots is 0.40 or more. By performing the formation, a halftone image or a character image adjacent to the solid image is faithfully reproduced with respect to the input data because the dot reproducibility and graininess are directly improved.

  Next, development conditions when the image pattern dependency ratio of floating island dots is set to 0.40 or more will be described.

In this embodiment, the agent density is 1050, 1500, 1950 [mg / mm ³ ], the development gap is 0.2, 0.3, 0.4 [mm], the toner particle size is 3, Experiments were performed to determine the image pattern dependency ratio of floating island dots as described above under the development conditions in which these are four combinations of 4, 5, and 5.8 [μm]. The results are shown in FIGS. 6 (a) and 6 (b).

Here, the agent density is expressed when the amount of developer pumped up on the developing roller 14 is the pumping amount C and the gap between the surface of the photoreceptor 2 and the surface of the developing roller 14 is the developing gap D. 7, the density of the developer in the developing section where the developing roller 14 and the photosensitive drum 2 face each other is calculated from Equation (3).

  FIG. 6A shows development conditions (agent density C / D, development gap D, toner particle size) in which the image pattern dependency ratio is 0.40 or more, and FIG. 6B shows the image pattern dependency ratio A. The development conditions (agent density C / D, development gap D, toner particle size) where / B is less than 0.40 are shown.

  6A and 6B, the horizontal axis of the graph indicates the value of the agent density C / D, and the vertical axis of the graph indicates the value of the development gap D. Further, the average particle diameter of the toner is indicated by a plot size. In addition, the value of the agent density C / D at the point where the imaginary line drawn downward from the center of the circle of the plot and the horizontal axis of the graph intersects is the value of the agent density C / D in the plot. The value of the development gap D at the location where the virtual line extending from the center of the circle toward the left side of the graph and the vertical axis of the graph intersects is the value of the development gap D in the plot.

When the agent density C / D is 1050 [mg / cm ³ ], as shown in FIG. 6A, when the development gap D is 0.2 [mm] and the toner particle size is 4 [μm], floating island dots The image pattern dependency ratio A / B is 0.40 or more. Further, from FIG. 6B, when the development gap D is 0.3 [mm] and the toner particle diameters are 3 [μm] and 5 [μm], the image pattern dependence ratio A / B of floating island dots is less than 0.40. become. Further, when the development gap D is 0.2 [mm] and the toner particle size is 3 [μm], the image pattern dependence ratio A / B of floating island dots is less than 0.40.

When the agent density C / D is 1500 [mg / mm ³ ], from FIG. 6A, the development gap D is 0.4 [mm] and the toner particle diameters are 3 [μm] and 5 [μm]. Sometimes the image pattern dependence ratio A / B of floating island dots becomes 0.40 or more. Further, from FIG. 6B, when the development gap D is 0.3 [mm], the toner particle size is any one of 3 [μm], 4 [μm], 5 [μm], and 5.8 [μm]. Even so, the image pattern dependency ratio A / B of floating island dots is less than 0.40. Further, when the development gap D is 0.2 [mm] and the toner particle size is 4 [μm] and 5 [μm], the image pattern dependence ratio A / B of floating island dots is less than 0.40.

When the agent density C / D is 1950 [mg / mm ³ ], as shown in FIG. 6A, when the development gap D is 0.3 [mm] and the toner particle size is 5 [μm], floating island dots are formed. The image pattern dependency ratio A / B is 0.40 or more. Further, when the development gap D is 0.20 [mm] and the toner particle size is 3 [μm] and 5 [μm], the image pattern dependence ratio A / B of floating island dots is 0.40 or more. Further, from FIG. 6B, when the development gap D is 0.4 [mm] and the toner particle size is 3 [μm] and 4 [μm], the image pattern dependence ratio A / B of floating island dots is 0.40. Less than.

  As described above, even when the agent density C / D is the same, the image pattern dependence ratio A / B of floating island dots becomes 0.40 or more or 0.40 due to differences in the development gap D, the toner particle size, and the like. Or less. That is, the toner reproducibility of floating island dots simply by setting the agent density C / D so that the image pattern dependency ratio A / B of floating island dots is 0.40 or more, in other words, a halftone image adjacent to a solid image. In some cases, the dot reproducibility of images and character images cannot be improved to an acceptable level visually. Therefore, an experiment is performed using an image forming apparatus actually used in advance or an experimental machine having a configuration equivalent to that of the image forming apparatus, and the image pattern dependency ratio A / B of floating island dots is 0.40 or more. What is necessary is just to obtain | require the combination of agent density C / D, the development gap D, and a toner particle size as development conditions.

6 (a) and 6 (b), the development conditions (agent density C / D, development gap D, toner particle size) when the image pattern dependence ratio A / B of floating island dots is set to 0.40 or more. As described above, the agent density C / D is set higher than 1500 [mg / cm ³ ], the development gap D is 0.4 [mm] or less, and the toner particle size is 5 [μm] or less. The shaded area shown in FIG. Preferably, as can be seen from FIG. 6B, when the agent density C / D is 1500 [mg / cm ³ ], the image pattern dependence ratio A / B of floating island dots tends to be relatively less than 0.4. In view of this, the agent density C / D may be 1800 [mg / cm ³ ] or more, the development gap D may be 0.4 [mm] or less, and the toner particle size may be 5 [μm] or less. Furthermore, from FIG. 6A, the image pattern dependency ratio A / B of floating island dots is 0.4 or more so that the image pattern dependency ratio A / B of floating island dots is 0.40 or more. The developer density C / D is 1950 [mg / cm ³ , which is a development condition that is recognized and from which the image pattern dependence ratio A / B of floating island dots is not less than 0.4 from FIG. 6B. As described above, it is desirable that the development gap D is 0.3 [mm] or less and the toner particle size is 5 [μm] or less. By setting such development conditions, the development capability and the fidelity to the latent image are increased, and the difference between the toner adhesion amount of floating island dots and the toner adhesion amount of isolated dots is small. In other words, the image pattern of floating island dots It is possible to form an image with good dot reproducibility with a dependency ratio A / B of 0.40 or more. As a result, the dot reproducibility and graininess of the halftone image and character image adjacent to the solid image are improved, and the halftone image and character image adjacent to the solid image are reproduced faithfully to the input data. Can do. Of course, the development conditions when the image pattern dependence ratio A / B of floating island dots is set to 0.40 or more are not limited to these.

From the experimental results as described above, the inventors of the present invention have increased the agent density C / D in the developing portion, reduced the toner particle size from the current value, and made the development gap D smaller than the current value. It has been found that the image pattern dependency ratio A / B of dots is 0.40 or more, and it is possible to form an image with good dot reproducibility and granularity of floating island dots. Note that to increase the developer density C / D of the developer in the developing portion is to set the agent density C / D so as to satisfy the relationship of Equation 4. Further, the agent density C / D satisfying the relationship of Equation 4 is a large agent density C / D with respect to an image forming apparatus such as a current printer.

  Here, when the image forming apparatus is used over time, the characteristics of the developer and the developing roller 14 may change, and the image pattern dependence ratio A / B of floating island dots may be reduced to less than 0.40. .

  In the image forming apparatus according to the present embodiment, in order to establish a developing method so that the image pattern dependence ratio A / B of floating island dots is 0.40 or more, the floating island dots and the floating island dots are formed on the photosensitive drum 2 between jobs. Thirty isolated dots are formed and read by the scanner 19 disposed in the image forming unit 1 so as to face the surface of the photosensitive drum 2, and the image pattern dependence ratio A / B of floating island dots is determined by the method described above. Ask. When the image pattern dependence ratio A / B of floating island dots is less than 0.40, for example, the image is obtained by increasing the agent density C / D using any one of the following two control methods. The pattern dependence ratio A / B is set to 0.40 or more. FIG. 8 is an example of a control block diagram according to the above control method.

  First, the first control method will be described. As shown in FIG. 9, the blade 18 is held by a blade holding member 25 that is displaceable with respect to the developing device 14. The blade 18 is provided so as to be displaceable in the same direction as the displacement direction of the blade holding member 25 in conjunction with the displacement operation of the blade holding member 25. A screw 26 whose length is changed by a stepping motor 27 is attached to the blade holding member 25, and the blade holding member 25 is displaced in the axial direction of the screw 26 by changing the length of the screw 26 by the stepping motor 27. In conjunction with this, the blade 18 is also displaced in the axial direction of the screw 26.

  FIG. 10 is a flowchart according to this control. First, floating island dots and isolated dots are output on the photosensitive drum 2 between jobs (S1). Then, based on the images of floating island dots and isolated dots read by the scanner 19, the toner adhesion amount A per floating island dot and the toner adhesion amount B per isolated dot are obtained as described above (S2). ). Thereafter, the image pattern dependence ratio A / B of floating island dots is obtained by a calculation means such as a CPU of the control unit (S3). If the image pattern dependency ratio A / B of floating island dots is 0.40 or more (Y in S4), a series of control is terminated. When the image pattern dependency ratio A / B of the floating island dots is less than 0.40 (N in S4), the length of the screw 26 is increased by the stepping motor 27 in the direction of moving the blade holding member 25 away from the developing roller 14. The blade 18 is moved away from the developing roller 14, and the distance DG between the developing roller 14 and the blade 18 is increased by 0.02 [mm] (S5). Thus, by increasing the distance DG between the developing roller 14 and the blade 18, the amount of developer on the developing roller 14 after being regulated by the blade 18, that is, the pumping amount C increases. Therefore, as can be seen from Equation 3, the agent density C / D can be increased. In this way, by repeating the series of controls for increasing the agent density C / D by increasing the distance DG between the developing roller 14 and the blade 18, the image pattern dependence ratio A / B is 0.40 as shown in FIG. It can be made 0.40 or more from the state of less than. In the present embodiment, the interval DG between the developing roller 14 and the blade 18 is increased by 0.02 [mm], but is not limited thereto.

  Next, the second control method will be described. As shown in FIG. 12, the developing roller 14 is rotatably held around the rotation axis of the developing roller by a developing roller holding member 22 provided so as to be displaceable with respect to the developing device 14. Further, the developing roller 14 is provided so as to be displaceable in the same direction as the direction of displacement of the developing roller holding member 22 in conjunction with the displacement operation of the developing roller holding member 22. A screw 23 whose length is changed by a stepping motor 24 is attached to the developing roller holding member 22, and the developing roller holding member 22 is changed in the axial direction of the screw 23 by changing the length of the screw 23 by the stepping motor 24. In conjunction with this, the developing roller 14 is also displaced in the axial direction of the screw 23.

  FIG. 13 is a flowchart according to this control. First, floating island dots and isolated dots are output on the photosensitive drum 2 between jobs (S1 ′). Then, based on the images of floating island dots and isolated dots read by the scanner 19, the toner adhesion amount A per floating island dot and the toner adhesion amount B per isolated dot are obtained as described above (S2). ´). Thereafter, the image pattern dependence ratio A / B of floating island dots is obtained by a calculation means such as a CPU of the control unit (S3 ′). When the image pattern dependency ratio A / B of the floating island dots is 0.40 or more (Y in S4 ′), the series of control is terminated. When the image pattern dependency ratio A / B of floating island dots is less than 0.40 (N in S4 ′), the length of the screw 23 is reduced by the stepping motor 24 and the developing roller holding member 22 is moved to the photosensitive drum 2. The developing roller 14 is moved away from the developing roller 14 and the developing gap D, which is the distance between the photosensitive drum 2 and the developing roller 14, is narrowed by 0.02 [mm] (S5 ′). Thus, by reducing the developing gap D, which is the distance between the photosensitive drum 2 and the developing roller 14, the agent density C / D can be increased as can be seen from the above equation (3). In this way, by repeating the series of controls for narrowing the development gap D and increasing the agent density C / D, the image pattern dependence ratio A / B is less than 0.40, as in the first control method described above. From this state, it can be 0.40 or more. In the present embodiment, the developing gap D, which is the distance between the photosensitive drum 2 and the developing roller 14, is narrowed by 0.02 [mm], but is not limited to this.

  Further, the development gap D may be of a size such that the surface of the photosensitive drum 2 and the surface of the development roller 14 do not contact each other, but the lower limit of the development gap D is preferably set to 0.1 [mm]. In general, since the photosensitive drum 2 and the developing roller 14 have an assembly tolerance, the developing gap D varies in the direction of the developing roller rotation axis due to the tolerance. As described above, when the development gap D is different in the direction of the developing roller rotation axis, the agent density C / D is also different in the direction of the developing roller rotation axis of the developing unit. Since the gap D becomes larger as the gap D becomes smaller, it is not preferable to make the development gap D too small.

  Further, by narrowing the development gap D, which is the distance between the surface of the photosensitive drum 2 and the surface of the developing roller 14, or by widening the distance DG between the blade 18 and the developing roller 14, The degree of freedom to increase the agent density C / D is greater than that in the case where each is performed once, and the image pattern dependence ratio A / B of floating island dots can be easily set to 0.40 or more over time.

  Further, the position where the floating island dots and the isolated dots are read by the scanner is not limited to the photosensitive drum 2 using the scanner 19. Using the scanner 20 provided so as to face the surface of the intermediate transfer belt 4, the scanner 21 provided so as to face the transfer paper 9 discharged to the outside by the discharge roller, etc. Floating island dots and isolated dots may be read on the transfer paper 9 or the like. However, the image is finally formed on the transfer paper 9. In view of improving the dot reproducibility and graininess of the image on the transfer paper 9 and improving the image quality, the scanner 21 is used. It is desirable to read floating island dots and isolated dots on the transfer paper 9. The arrangement positions of the scanners 19, 20, and 21 are not limited to those shown in FIGS.

As described above, according to the present embodiment, the developer composed of the toner and the carrier carried on the developing roller 14 that is the developer carrying member is used to develop the developing roller 14 and the photosensitive drum 2 that is the latent image carrying member. In the image forming apparatus including a developing device that employs a developing method that develops a latent image formed on the photosensitive drum 2 in the developing units facing each other, floating island dots developed on the photosensitive drum 2 The image pattern dependence ratio A / B, which is the ratio of the toner adhesion amount A per dot to the toner adhesion amount B per isolated dot B, is 0.40 or more, which is apparent from the above-described experiment. In addition, it is possible to form a good floating island dot whose dot reproducibility is visually acceptable. Therefore, it is possible to form floating island dots that are deteriorated in dot reproducibility due to the influence of the edge electric field, such as a halftone image adjacent to a solid image, with good dot reproducibility that can be visually observed. A tone image can also be formed with good dot reproducibility acceptable by visual inspection.
Further, according to the present embodiment, the amount of developer drawn on the developing roller 14 is C [mg / cm ² ], and the distance between the surface of the developing roller 14 and the surface of the photosensitive drum 2 in the developing unit. When the development gap is D [mm], the developer density C / D, which is the density of the developer in the developing section, is 1950 [mg / cm ³ ] or more, and as described above, the image pattern of floating island dots The dependency ratio A / B can be set to 0.40 or more.
Further, according to the present embodiment, by using toner having an average particle size of 5 μm or less, the image pattern dependence ratio A / B of floating island dots can be set to 0.40 or more as described above.
According to the present embodiment, the development gap D, which is the distance between the surface of the photosensitive drum 2 and the surface of the developing roller 14 in the developing unit, is 0.3 [mm] or less, as described above. The image pattern dependency ratio A / B of floating island dots can be set to 0.40 or more.
In addition, according to the present embodiment, the scanner 19 that faces the photosensitive drum 2 in a non-contact manner and functions as a toner adhesion amount detection unit that detects the toner adhesion amount of the toner image formed on the photosensitive drum 2 is provided. The toner adhesion amounts of floating island dots and isolated dots formed on the photosensitive drum 2 are detected, and the toner adhesion amount A per floating island dot and the toner adhesion amount B per isolated dot based on the detection result. When the image pattern dependence ratio A / B, which is the ratio of the above, is less than 0.40, the agent density C / D, which is the density of the developer in the developing portion, is increased to obtain the image pattern dependence ratio A / B. By performing the control so as to be 0.40 or more, it is possible to maintain the dot reproducibility and graininess of floating island dots that have been improved to an acceptable level with time.
Further, according to the present embodiment, the toner image is transferred from the photosensitive drum 2 to the intermediate transfer belt 4 that is a transfer body on which the toner image is primarily transferred, in a non-contact manner, and the toner adhesion amount of the toner image on the intermediate transfer belt 4 is reduced. The scanner 20 functioning as a toner adhesion amount detection means for detecting detects the toner adhesion amounts of floating island dots and isolated dots transferred from the photosensitive drum 2 to the intermediate transfer belt 4, and 1 dot of floating island dots is detected from the detection result. When the image pattern dependency ratio A / B, which is the ratio between the toner adhesion amount A per contact and the toner adhesion amount B per isolated dot, is less than 0.40, the density of the developer in the developing portion is By controlling the image pattern dependency ratio A / B to be 0.40 or more by increasing a certain agent density C / D, floating island dots that have been improved to an acceptable level visually can be obtained. Tsu DOO reproducibility and graininess, etc. can be maintained over time.
In addition, according to the present embodiment, the toner image on the transfer paper 9 that is a recording medium to which the toner image is finally transferred via the intermediate transfer belt 4 onto which the toner image is primarily transferred from the photosensitive drum 2. The toner adhesion amounts of floating island dots and isolated dots that are finally transferred from the photosensitive drum 2 to the transfer paper 9 via the intermediate transfer belt 4 by the scanner 21 that functions as a toner adhesion amount detection unit that detects the toner adhesion amount. The image pattern dependence ratio A / B, which is the ratio of the toner adhesion amount A per floating dot to the toner adhesion amount B per isolated dot from the detection result, is less than 0.40. In this case, by controlling the image density dependency A / B to be 0.40 or more by increasing the agent density C / D, which is the density of the developer in the developing section, it is visually permitted. Dot reproducibility and granularity of the floating island dots improved enough to like can be maintained over time.
Further, according to the present embodiment, the above control is such that the image pattern dependency ratio A / B, which is the ratio of the toner adhesion amount A per floating island dot to the toner adhesion amount B per isolated dot, is 0. By reducing the developing gap D, which is the distance between the surface of the photosensitive drum 2 and the surface of the developing roller 14, until the value reaches 40 or more, as described above, the agent density C / D is increased, The image pattern dependency ratio A / B can be set to 0.40 or more.
Further, according to the present embodiment, the above control is performed so that the image pattern dependence ratio A / B, which is the ratio of the toner adhesion amount A per floating island dot to the toner adhesion amount B per isolated dot, is 0. As described above, the distance DG between the blade 18 and the developing roller 14 which is provided facing the developing roller 14 and regulates the amount of developer on the developing roller 14 is widened until it becomes 40 or more. Thus, the agent density C / D can be increased, and the image pattern dependency ratio A / B can be set to 0.40 or more.

The graph which showed the relationship between the image pattern dependence ratio of a floating island dot, and the dot diameter dispersion | variation of a floating island dot. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment. The enlarged view of an image forming unit. (A) Schematic diagram of floating island dots. (B) Schematic diagram of isolated dots. (C) Output image of floating island dots. (D) An output image of isolated dots. The schematic diagram and output image of a floating island dot and an isolated dot in case the image pattern dependence ratio of a floating island dot is 0.23 and 0.58. (A) The graph which showed the development conditions used as image pattern dependence ratio 0.40 or more. (B) A graph showing development conditions for an image pattern dependency ratio of less than 0.40. The enlarged view of an image forming unit. Control block diagram FIG. 6 is a schematic diagram when a blade that regulates the amount of developer on the developing roller is configured to be variable. The flowchart which concerns on a 1st control method. The graph which showed the relationship between agent density and image pattern dependence ratio. The schematic diagram at the time of comprising a developing roller so that a fluctuation | variation is possible. The flowchart which concerns on a 2nd control method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming unit 2 Photosensitive drum 4 Intermediate transfer belt 14 Developing roller 18 Blade 19 Scanner 20 Scanner 21 Scanner 22 Developing roller holding member 23 Screw 24 Stepping motor 25 Blade holding member 26 Screw 27 Stepping motor

Claims (11)

A latent image formed on the latent image carrier in a developing portion where the developer carrier and the latent image carrier are opposed to each other using a developer composed of toner and carrier carried on the developer carrier. In the developing method for developing
Using a toner having an average particle size of 5 μm or less,
Developed by the latent image bearing member, Ri ratio A / B is 0.40 or more der the toner adhesion amount B per dot of toner adhesion amount A and isolated dots per dot floating island dot,
The amount of developer pumped on the developer carrier is C [mg / cm ² ], and the distance between the surface of the developer carrier and the surface of the electrostatic latent image carrier in the developing portion is D [mm. ], The density C / D of the developer in the developing portion is 1950 [mg / cm ³ ] or more,
The distance D between the surface of the electrostatic latent image carrier and the surface of the developer carrier in the developing unit is 0.3 [mm] or less,
The floating island formed on the latent image carrier by a toner adhesion amount detection unit that faces the latent image carrier in a non-contact manner and detects a toner adhesion amount of a toner image formed on the latent image carrier. The toner adhesion amounts of the dots and the isolated dots are detected, and the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot is 0. A developing method comprising: controlling the ratio A / B to be 0.40 or more by increasing the density of the developer in the developing section when the ratio is less than 40 . A latent image formed on the latent image carrier in a developing portion where the developer carrier and the latent image carrier are opposed to each other using a developer composed of toner and carrier carried on the developer carrier. In the developing method for developing
Using a toner having an average particle size of 5 μm or less,
The ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more,
The amount of developer pumped on the developer carrier is C [mg / cm ² ], and the distance between the surface of the developer carrier and the surface of the electrostatic latent image carrier in the developing portion is D [mm. ], The density C / D of the developer in the developing portion is 1950 [mg / cm ³ ] or more,
The distance D between the surface of the electrostatic latent image carrier and the surface of the developer carrier in the developing unit is 0.3 [mm] or less,
The toner adhering amount detecting means on which the toner image from said image bearing member are opposed in a non-contact with the transfer member to be primarily transferred, detects the toner attachment amount of the toner image on said transfer Utsushitai, from the latent image bearing member detecting the island dots and the isolated dot each toner adhesion amount has been transferred to said transfer Utsushitai, toner adhesion amount per dot of toner adhesion amount a and isolated dots per dot floating island dot from the detection result B the ratio if a / B is less than 0.40, characterized in that the control which increases the density of the developer in the developing unit is the ratio a / B to be 0.40 or more and Development method. A latent image formed on the latent image carrier in a developing portion where the developer carrier and the latent image carrier are opposed to each other using a developer composed of toner and carrier carried on the developer carrier. In the developing method for developing
Using a toner having an average particle size of 5 μm or less,
The ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more,
The amount of developer pumped on the developer carrier is C [mg / cm ² ], and the distance between the surface of the developer carrier and the surface of the electrostatic latent image carrier in the developing portion is D [mm. ], The density C / D of the developer in the developing portion is 1950 [mg / cm ³ ] or more,
The distance D between the surface of the electrostatic latent image carrier and the surface of the developer carrier in the developing unit is 0.3 [mm] or less,
The toner adhesion amount detection means finally the toner image via a transfer member the toner image from said image bearing member is primarily transferred to detect the toner adhesion amount of the toner image on the recording medium to be transferred, latent finally detecting the recording the island dots and the toner adhesion amount of each said isolated dots transferred to the medium from the image carrier via said transfer Utsushitai, toner adhesion amount per dot floating island dot from the detection result If the ratio a / B of the toner adhesion amount B per dot of the a and isolated dots is less than 0.40, by increasing the density of the developer in the developing unit is the ratio a / B 0. A developing method characterized by performing control so as to be 40 or more. The developing method according to claim 1 , 2 or 3 ,
The above control is carried out until the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot becomes 0.40 or more. A developing method characterized by narrowing the distance from the surface of the developer carrying member. The developing method according to claim 1 , 2 or 3 ,
The control opposes the developer carrier until the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot becomes 0.40 or more. A developing method characterized by widening the distance between the developer carrying member and a regulating member that regulates the amount of developer carried by the developer carrying member. A latent image carrier for carrying a latent image;
A developer comprising a toner and a carrier is carried on the developer carrying member, and the latent image on the latent image carrying member is developed at a developing portion where the developer carrying member and the latent image carrying member face each other. In an image forming apparatus comprising a developing unit,
The toner has an average particle size of 5 [μm] or less,
As the developing means, the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more. Using a developing device configured to be
When the developer pumping amount on the developer carrier is C [mg / cm ² ], and the distance between the developer carrier and the latent image carrier in the developing unit is D [mm] The density C / D of the developer in the developing portion is 1950 [mg / cm ³ ] or more,
The distance D between the surface of the latent image carrier and the surface of the developer carrier in the developing unit is 0.3 [mm] or less,
A toner adhesion amount detecting means provided in a non-contact manner facing the latent image carrier to detect the toner adhesion amount of the toner image on the latent image carrier;
The toner adhesion amount detection means detects the toner adhesion amounts of the floating island dots and the isolated dots on the latent image carrier, and based on the detection result, the toner adhesion amount A of the floating island dots per dot and the isolation amount are isolated. A calculating means for calculating a ratio A / B of the toner adhesion amount B per dot;
Control where the ratio A / B is increased to 0.40 or more by increasing the density of the developer in the developing portion when the ratio A / B is less than 0.40 based on the calculation result of the calculation means. image forming apparatus characterized by a control means for performing. A latent image carrier for carrying a latent image;
A developer comprising a toner and a carrier is carried on the developer carrying member, and the latent image on the latent image carrying member is developed at a developing portion where the developer carrying member and the latent image carrying member face each other. In an image forming apparatus comprising a developing unit,
The toner has an average particle size of 5 [μm] or less,
As the developing means, the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more. Using a developing device configured to be
The amount pumping developer bearing member for the developer and C [mg / cm ^2], the distance between the developer carrying member and the latent image bearing member in the developing unit is taken as D [mm], The density C / D of the developer in the developing portion is 1950 [mg / cm ³ ] or more,
The distance D between the surface of the latent image carrier and the surface of the developer carrier in the developing unit is 0.3 [mm] or less,
Transfer means for transferring a toner image on the latent image carrier to a recording medium via a transfer member;
A toner adhesion amount detecting means provided to face the transfer body in a non-contact manner and detect a toner adhesion amount of a toner image on the transfer body;
The toner adhesion amount detection means detects the toner adhesion amounts of the floating island dots and the isolated dots transferred from the latent image carrier onto the transfer body, and based on the detection result, per toner dot of the floating island dots. Calculating means for calculating a ratio A / B between the toner adhesion amount A and the toner adhesion amount B per isolated dot;
Control where the ratio A / B is increased to 0.40 or more by increasing the density of the developer in the developing section when the ratio A / B is less than 0.40 based on the calculation result of the calculation means. And an image forming apparatus. A latent image carrier for carrying a latent image;
A developer comprising a toner and a carrier is carried on the developer carrying member, and the latent image on the latent image carrying member is developed at a developing portion where the developer carrying member and the latent image carrying member face each other. In an image forming apparatus comprising a developing unit,
The toner has an average particle size of 5 [μm] or less,
As the developing means, the ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot developed on the latent image carrier is 0.40 or more. Using a developing device configured to be
When the developer pumping amount on the developer carrier is C [mg / cm ² ], and the distance between the developer carrier and the latent image carrier in the developing unit is D [mm] The density C / D of the developer in the developing portion is 1950 [mg / cm ³ ] or more,
The distance D between the surface of the latent image carrier and the surface of the developer carrier in the developing unit is 0.3 [mm] or less,
Transfer means for transferring a toner image on the latent image carrier to a recording medium via a transfer member;
Toner adhesion amount detecting means for detecting the toner adhesion amount of the toner image transferred to the recording medium;
The toner adhesion amount detection means detects toner adhesion amounts of the floating island dots and the isolated dots transferred from the latent image carrier through the transfer medium to the recording medium, and based on the detection results. Calculating means for calculating a ratio A / B between the toner adhesion amount A per floating dot and the toner adhesion amount B per isolated dot;
Control where the ratio A / B is increased to 0.40 or more by increasing the density of the developer in the developing portion when the ratio A / B is less than 0.40 based on the calculation result of the calculation means. And an image forming apparatus. The image forming apparatus according to claim 6 , 7 or 8 ,
The image forming apparatus characterized in that the control means narrows the interval between the surface of the latent image carrier and the surface of the developer carrier until the ratio A / B becomes 0.40 or more. The image forming apparatus according to claim 6 , 7 or 8 ,
The control control means includes a regulating member provided facing the developer carrier and regulating the amount of developer conveyed by the developer carrier and the development until the ratio A / B reaches 0.40 or more. An image forming apparatus characterized in that the distance from the agent carrier is increased.   The image forming apparatus according to claim 6, 7, 8, 9 or 10.
An image forming apparatus, comprising: a process cartridge which is formed by integrating at least the latent image carrier and the developing unit and is detachable from the apparatus.