JP2006163226A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus with which high-quality images are formed at a low price, by avoiding a blocking phenomenon while ensuring the quality of formed images by adjusting the constituent of contained toner without making a design change to the apparatus configuration so as to prevent occurrence of a thin spot in an image and detection of complete use of a toner before finishing up the contained toner in a developing cartridge. <P>SOLUTION: The image forming apparatus 10 with which monochrome images or color images are continuously formed, has: developing cartridges 13y-13k for toner development of an electrostatic latent image on the surface of a photoreceptor drum 12; and a developing rotary unit 14 for changeover of the developing cartridges by rotational transfer to a developing position facing the surface of the photoreceptor drum. The developing cartridge 13k which stands by in the lowest position as a home position contains a black (K) toner having a higher glass transition temperature than other color toner. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus, and more particularly, even after moving to a home position and waiting, a high-quality image can be formed without causing blur in the image to be formed. It relates to things that can be used up.

  2. Description of the Related Art Conventionally, an electrophotographic recording type image forming apparatus that exposes and forms an electrostatic latent image on the surface of a carrier made of a photoreceptor is known. In this image forming apparatus, the electrostatic latent image is developed with toner. The toner image on the surface of the carrier carried in this manner is transferred to a recording medium such as recording paper to form an image. The electrostatic latent image is developed by rotating a developing roller facing the surface of the carrier and transferring and adhering toner on the outer peripheral surface of the roller. Then, the toner is supplied by the supply roller rotating in the toner storage space being pressed and rotated.

  An image forming apparatus employing this electrophotographic recording system is detachably mounted with a developing cartridge including a developing roller and a supply roller that face a carrier, and a container that contains toner, and the developing cartridge is connected to a developing rotary unit. There is also a device configured to be able to accommodate a plurality thereof. In this image forming apparatus, the developing cartridge at the developing position where the developing roller faces the carrier can be switched by rotating the developing rotary unit about the rotation axis.

  For this reason, such an image forming apparatus is a developing cartridge that contains toner of yellow (Y), magenta (M), cyan (C), and black (K) as a developing cartridge that attaches toner to the surface of the carrier. By configuring the cartridge so that it can be stored (attached) in the developing rotary unit, it is possible to sequentially switch the developing cartridge and form a color image in which the respective color toners are superimposed (see, for example, Patent Document 1). In this configuration, it is needless to say that a monochrome image using a single color toner, for example, a black and white monochrome image (hereinafter also simply referred to as a monochrome image) using black (K) toner can be formed.

Further, as the toner in the developing cartridge to be mounted on such an image forming apparatus, the amount of various additives is adjusted in order to adjust the image quality, and gloss (gloss) is changed between a color image and a monochrome image. The wax content is adjusted to optimize the image (for example, see Patent Document 2), and the melting temperature (softening temperature) is used to optimize the transparency (light-shielding property) between the color image and the monochrome image. Has been proposed (see, for example, Patent Document 3). In addition, in order to effectively suppress so-called filming that covers a member in contact with the toner, it is also proposed to adjust the liberation rate of the external additive of the toner (for example, see Patent Document 4).
JP 2004-126089 A Japanese Patent No. 3342198 Japanese Patent No. 3521373 JP 2002-236386 A

  In an image forming apparatus including such a developing rotary unit, for example, a developing cartridge that contains black (K) toner for monochrome images that is frequently used can immediately start a sufficient developing operation. The home position is designed so that the position to be used is the standby position. Specifically, when the developing cartridge is designed so-called augerless in which the auger device is omitted by revolving and replenishing the toner stored on the supply roller side, the operation is started. The position at which the black (K) toner developing cartridge is at the lowest position is defined as the home position so as to supply as much toner as possible to the developing roller side while loosening the stored toner.

  For example, when the developing cartridge is heated by a motor disposed in the lower part as a heat source, the toner contained in the container becomes a mass having almost no fluidity and is supplied to the supply roller side or to the developing roller. So that the so-called blocking phenomenon may occur, and if the standby period without operation becomes longer, or if vibration is received, the contained toner is tightly contacted and the blocking phenomenon is further increased. Tends to occur.

  In particular, if a blocking phenomenon occurs in the developing cartridge that is waiting at the lowest position due to the consumption of the stored toner and the supply roller is exposed, the stored toner does not get on the outer peripheral surface of the supply roller, and the recording occurs. In some cases, the toner image transferred and formed on the medium is blurred, or the toner end is determined (detected) before the toner contained in the developing cartridge is used up.

  Here, the blocking phenomenon of the stored toner can be solved by stirring the stored toner by repeatedly rotating the developing rotary unit. For this reason, when forming a color image on a recording medium, the developing rotary unit repeatedly rotates to switch the developing cartridge at the developing position facing the carrier. As a result, the blocking phenomenon of the stored toner can be solved.

  However, when a monochrome image is continuously formed on a recording medium, after the developing cartridge to be used is rotated to the developing position, the developing operation is continued with the developing cartridge as it is. In this state, the blocking phenomenon of the stored toner cannot be eliminated. Therefore, it is conceivable as a countermeasure to repeatedly rotate the developing cartridge 360 degrees, but this reduces the processing speed (so-called throughput).

  Therefore, the present invention eliminates the occurrence of blocking phenomenon while ensuring the quality of continuously formed images by adjusting the constituent components of the stored toner, without changing the design of the apparatus, thereby reducing the stored toner in the developing cartridge. An object of the present invention is to provide an image forming apparatus capable of continuously forming a high-quality image at low cost without causing blurring in the image or becoming a toner end before it is used up.

  According to a first aspect of the present invention, there is provided an image forming apparatus for carrying a toner image on which an electrostatic latent image based on image data is formed and developing the electrostatic latent image, and the surface of the carrier A developing cartridge for developing the electrostatic latent image by selectively attaching toner to the electrostatic latent image, and a plurality of the developing cartridges are detachably accommodated around the rotating shaft, with the rotating shaft as a center. A developing rotary unit that rotates one of the developing cartridges to face the surface of the carrier, and the developer cartridge is a container that stores toner, and the outer circumference by rotating the outer surface while facing the carrier. A developing roller for adhering the toner on the surface to the carrier, and a supply roller for supplying the toner in the container to the outer peripheral surface of the developing roller when the developing roller rotates. Is stored in a container and mounted on a developing rotary unit, whereby an electrostatic latent image on the surface of a carrier of a single color image or a color image is developed with toner, and the toner image is transferred to a recording medium and fixed. In the forming device, when the developing rotary unit rotates to the home position and waits after the image forming operation is finished, the inside of the container of the specific developing cartridge that is mounted at a location where the toner storage space extends below the supply roller Is characterized in that it contains toner having a glass transition temperature set higher than that of the toner housed in a normal developing cartridge mounted in another location.

  In the present invention, when waiting at the home position after completion of the image forming operation, even if the supply roller or the like is exposed from the stored toner in the specific developing cartridge in which the toner storage space extends below the supply roller. The toner stored in the specific developing cartridge is heated to a temperature considerably lower than the fixing temperature (melting temperature) by setting the glass transition temperature higher than that of the toner stored in other normal developing cartridges. However, even if it is subjected to vibration at this time and tightened to some extent, it is difficult to achieve a blocking state that is a mass having almost no fluidity. That is, the toner accommodated in the specific developing cartridge can flow to the developing side when resuming the developing operation without causing a blocking phenomenon during standby, and does not expose the lower supply roller or the like in the normal developing cartridge. Similar to the toner stored, the toner can be smoothly supplied from the supply roller to the developing roller. Therefore, despite the fact that the toner is sufficiently contained, the developing operation can be resumed smoothly without causing fluctuations such as the amount of toner developing the electrostatic latent image on the surface of the carrier being reduced or being interrupted. Can continue.

  In a second invention of an image forming apparatus that solves the above problem, in addition to the specific matters of the first invention, the specific developing cartridge contains toner of a color that continuously forms a single color image on a recording medium. It is characterized by being.

  In this invention, since the toner contained in the developing cartridge used for forming a monochromatic image is kept in the developing position facing the carrier, the developing operation is continued. It is more difficult to eliminate the blocking state than the toner that is rotated and moved and stirred. However, the toner contained in the specific developing cartridge is not easily brought into a blocking state by setting the glass transition temperature to be high. Therefore, despite the fact that the toner for the monochromatic image is sufficiently contained, the development of the monochromatic image can be performed without causing fluctuations such as a decrease in the amount of toner developing the electrostatic latent image on the surface of the carrier or interruption. The operation can be resumed smoothly and continued.

  According to a third aspect of the image forming apparatus for solving the above-mentioned problems, in addition to the specific matters of the first or second aspect, the developing cartridge is configured to store the toner contained in the container without using the replenishing device. It is designed to be augerless that replenishes the supply roller side by rotational movement.

  In this invention, the toner stored in the augerless developing cartridge is supplied to the developing roller by the rotational movement of the developing rotary unit and supplied to the developing roller, and is replenished while stirring during the developing operation. It is difficult to eliminate the blocking state. However, the toner contained in the specific developing cartridge is not easily brought into a blocking state by setting the glass transition temperature to be high. Therefore, despite the fact that the toner is sufficiently contained, the developing operation can be resumed smoothly without causing fluctuations such as the amount of toner developing the electrostatic latent image on the surface of the carrier being reduced or being interrupted. Can continue.

  According to a fourth aspect of the image forming apparatus for solving the above-mentioned problems, in addition to the specific matter of any of the first to third aspects of the invention, the specific developing cartridge contains a toner contained in the normal developing cartridge rather than the toner contained in the normal developing cartridge. It is characterized by containing toner set with a small amount of wax.

  In the present invention, the toner stored in the specific developing cartridge that is likely to expose the supply roller during standby is set to have a glass transition temperature higher than that of the toner stored in the normal developing cartridge that is unlikely to be exposed. Thus, the amount of wax contained is set to be small, and it is further difficult to be in a blocking state in which a mass having almost no fluidity is formed. Therefore, the developing operation can be resumed smoothly and continued with higher reliability.

  According to a fifth aspect of the image forming apparatus for solving the above problem, in addition to the specific matter of the fourth aspect, a melting temperature is set higher in the specific developing cartridge than in a toner stored in a normal developing cartridge. In this case, the toner is stored.

  In the present invention, the toner stored in the specific developing cartridge that is likely to expose the supply roller during standby is set to have a glass transition temperature higher than that of the toner stored in the normal developing cartridge that is unlikely to be exposed. Thus, at the same time as the amount of wax contained is set to be small, the melting temperature is set to be high, and the fusion to the fixing device side at the time of heating and pressing when fixing to the recording medium is reduced. Therefore, a reduction in releasability due to a reduction in the amount of wax is ensured, and the formed toner image can be transferred and fixed on a recording medium without any problem.

  According to a sixth aspect of the image forming apparatus for solving the above-mentioned problems, in addition to the specific matter of any one of the first to fifth aspects of the invention, the specific developing cartridge contains more toner than the toner contained in the normal developing cartridge. It is characterized in that it contains toner having a large amount of external additive.

  In the present invention, the toner stored in the specific developing cartridge that is likely to expose the supply roller during standby is set to have a glass transition temperature higher than that of the toner stored in the normal developing cartridge that is unlikely to be exposed. Therefore, the amount of the external additive added for the purpose of securing fluidity is set to be large, and it is difficult to further achieve a blocking state of a lump having poor fluidity. Therefore, the developing operation can be resumed smoothly and continued with higher reliability.

  According to a seventh aspect of the image forming apparatus for solving the above-mentioned problems, in addition to the specific matter of any of the first to sixth aspects, a heat source is located at a position where the specific developing cartridge is closer to the normal developing cartridge during standby. It is characterized by being arranged.

  In the present invention, the toner accommodated in the specific developing cartridge close to the heat source at the home position during standby is highly likely to be heated to cause a blocking phenomenon. However, the accommodated toner is made difficult to be in a blocking state by setting the glass transition temperature to be high. Therefore, despite the fact that the toner is sufficiently contained, the developing operation can be resumed smoothly without causing fluctuations such as the amount of toner developing the electrostatic latent image on the surface of the carrier being reduced or being interrupted. Can continue.

  As described above, according to the present invention, the specific development cartridge in which the supply roller is easily exposed from the contained toner during the standby time has a glass transition temperature higher than that of the normal toner in the normal development cartridge in which the supply roller is not easily exposed from the contained toner during the standby time. Since the toner set at a high level is stored, the stored toner is unlikely to be in a blocking state of a lump having almost no fluidity, and can be continuously flowed to the developing side of the electrostatic latent image on the surface of the carrier. it can. For example, even when the developing cartridge is augerless or stands by at a position close to a heat source, the developing operation is smoothly resumed without causing blocking phenomenon in the stored toner, and the stored toner is removed from the electrostatic latent image. It can be made to flow continuously to the development side. Therefore, the developing operation can be resumed and continued without causing fluctuations such as a decrease in toner to be developed or interruption even though the toner is sufficiently contained. It is possible to eliminate the occurrence of blurring or toner end in the formed image before the stored toner is used up. As a result, high-quality images can be continuously formed at low cost without changing the structure of the apparatus.

  Furthermore, by setting the wax amount of the stored toner small or setting the external additive amount large, the stored toner can flow more reliably and continuously form high quality images at low cost. Can do. In addition, when setting the wax amount of the toner to be small, by setting the melting temperature higher, it is possible to reduce the fusion to the fixing device side, and to reduce the releasability by reducing the wax amount. Thus, it is possible to continuously form (transfer and fix) images without problems.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best embodiment of the invention will be described with reference to the drawings. 1 to 5 are diagrams showing an embodiment of an image forming apparatus according to the present invention.

  In FIG. 1, an image forming apparatus 10 is a printer that is used by connecting to an external device such as a personal computer that creates and outputs an image such as a character. The image forming apparatus 10 includes image data such as a character that forms an image. The image recording device that records and forms on one or both sides of the recording paper (recording medium) by electrophotographic method, and the plurality of stacked recording papers are separated and fed one by one and conveyed to this image recording device And a sheet conveying device that unloads the recording sheet on which an image is recorded and that is loaded and stacked.

  The image recording apparatus will be briefly described. A laser beam scanning apparatus 11 that scans a laser beam with a polygon mirror 11a that rotates at high speed based on image data, and a laser beam from the laser beam scanning apparatus 11 is irradiated and scanned. Contains a photosensitive drum (carrier) 12 on which an electrostatic latent image based on image data is exposed and formed, and toners of yellow (Y), cyan (C), magenta (M), and black (K). A developing cartridge 13 (shown in the drawing as 13y, 13c, 13m, and 13k) for each color for developing toner by adhering the contained toner to the electrostatic latent image on the photosensitive drum 12, and this developing cartridge A developing cart which stores (installs) 13 in the installation space for each color and rotates the rotating shaft 14a to face the photosensitive drum 12 to perform a developing operation. Development rotary unit 14 for switching the wedge 13 and intermediate transfer for receiving a toner image of each color developed on the photosensitive drum 12 and forming a toner image (monochrome image or color image) that can be transferred and recorded on a recording sheet. The belt (intermediate transfer medium) 15 and the recording paper conveyed and fed are pressed (nip) so as to be sandwiched between the intermediate transfer belt 15 and conveyed downstream, and the toner carried by the intermediate transfer belt 15 The toner image is fixed by heating and pressing the transfer roller 16 for transferring the image onto the recording paper to be nipped and conveyed, and the recording paper to which the toner image has been transferred and conveyed, and the recording paper is further nipped downstream. The fixing roller pair (fixing device) 17 to be conveyed and the toner remaining on the photosensitive drum 12 are rotated by a cleaning blade (not shown). And the waste toner tank 18 for to storing, and a. Note that the intermediate transfer belt 15 and the transfer roller 16 and the fixing roller pair 17 of the image recording apparatus also have a function of conveying a recording sheet, and thus constitute a part of a sheet conveying apparatus described below. .

  Briefly, the paper transport device is detachably set on the lower part of the apparatus main body 10 and a paper cassette 21 on which a plurality of recording papers are stacked on the bottom lifting plate 21a, and the lifting plate 21a of the paper cassette 21. A pickup roller 22 that calls out (draws out) the uppermost recording paper and feeds it to the conveying path f by rotating to press against the separation pad 21b while being pressed against the bundle of recording paper raised by The first relay transport roller pair 23 that receives the recording paper sent from the cassette 21 and sandwiches and transports the recording paper to the downstream transport path f, and the recording paper that the first relay transport roller pair 23 transports into the transport path f. Received and held at the image recording (transfer) position by the intermediate transfer belt 15 and the transfer roller 16 of the image recording apparatus. A pair of registration rollers 24 to be fed (paper feed), and a pair of registration rollers 24 are conveyed along a conveyance path f passing between the intermediate transfer belt 15 and the transfer rollers 16 and between the pair of fixing rollers 17, thereby fixing the fixed image on one side. And a paper discharge roller pair 25 that receives the recording paper on which the paper is formed, and carries the paper on the paper discharge table 29 on the upper part of the apparatus main body 10 to discharge and stack it. This sheet conveying apparatus is arranged in a re-conveying path r for reversing the recording sheet on which the image is formed on one side and sending it to the conveying path f on the upstream side of the registration roller pair 24 and the path r. The second intermediate transport roller pair 26 receives the recording sheet sent into the re-transport path r when the paper discharge roller pair 25 is reversed and is received by the registration roller pair 24. By passing, it is possible to form an image on both sides of the recording paper.

  As a result, the image forming apparatus 10 transfers the toner image obtained by developing the electrostatic latent image by attaching toner on the surface of the photosensitive drum 12 to one side or both sides of the recording paper via the intermediate transfer belt 15. Thus, a color image formed by superimposing yellow (Y), cyan (C), magenta (M), and black (K) toner on the surface of the intermediate transfer belt 15 can be transferred onto a recording sheet. Or a monochrome image formed with black (K) toner can be transferred to a recording sheet to form an image.

  As shown in FIG. 2, the developing cartridge 13 of the image forming apparatus 10 is formed in a similar shape so that it can be stored in each storage space (position) partitioned by the partition frame 14 b of the developing rotary unit 14. The container 31 to be accommodated and the photosensitive drum 12 facing the accommodated toner T on the outer peripheral surface 32a by being rotatably supported on the outer peripheral side in the container 31 separated from the rotating shaft 14a of the developing rotary unit 14. The developing roller 32 to be transferred and attached, and the developer roller 32 is supported by the developing roller 32 on the rotating shaft 14a side of the developing rotary unit 14 so that the developing roller 32 can be pressed against the developing roller 32 and is rotatably supported in the container 31. And a supply roller (supply means) 33 that is supplied by being attached to the outer peripheral surface 32a. The container 31 of the developing cartridge 13 is integrally formed with a partition plate 31a that partitions the first space S1 in which the developing roller 32 and the supply roller 33 are disposed and the second space S1 on the rotating shaft 14a side. The partition plate 31a communicates with the contained toner T through the upper portions of the first and second spaces S1 and S2. That is, the container 31 has a two-chamber structure that is partitioned into first and second spaces S1 and S2 that communicate with each other at the top. Needless to say, the supply roller 33 is not limited to such a roller type, and may be a supply unit that supplies the toner T by other methods.

  With this configuration, the developing cartridge 13 can supply the toner T contained in the first space S1 on the outer peripheral side of the container 31 partitioned by the partition plate 31a to the developing roller 32 in which the supply roller 33 is pressed and rotated. Further, when the developing cartridge 13 is rotated 90 degrees counterclockwise in FIG. 1 by the developing rotary unit 14 and rotated 180 degrees from the developing position facing the photosensitive drum 12, the first cartridge 31 of the container 31 is rotated. The toner T contained in the container 31 is agitated by rotating it 90 degrees and returning it to the developing position after the toner T is put together in the upper part of the second space S1, S2 (downward in FIG. 1). The stored toner T can be collected in the first space S1 on the supply roller 43 side so that the toner T can be supplied to the developing roller 32. That is, in the developing cartridge 13 mounted on the developing rotary unit 14 rotating in this way, the accommodation toner T is replenished while being agitated toward the supply roller 33 by the rotation, so that the accommodation toner T is agitated and replenished. A replenishment adjusting device (so-called agitator device or auger device) for performing the operation can be omitted as appropriate to make a so-called augerless. However, if the replenishment adjusting device is omitted, the developing cartridge 13 has, for example, a count value obtained by a toner counter and an image dot before at least the stored toner T supplied to the developing roller 32 runs out of the periphery of the supplying roller 33. The development rotary when the usage amount of the toner T detected by the number, the developing operation (image formation) time to be integrated, the integrated number of developed images, or the actually measured remaining amount of the stored toner T exceeds a preset value. It is necessary to supply and agitate the toner T that rotates the unit 14.

  The developing cartridge 13 has a developing roller 32 exposed from the inside of the container 31 so as to face the photosensitive drum 12 at the developing position, and between the outer peripheral surface 32 a of the developing roller 32 and the opening of the container 31. In the gap defined in FIG. 4, a seal member 34 that is urged by the urging member 34a and press-contacts the outer peripheral surface 32a, and a regulation blade 35 that is urged by the urging member 35a and press-contacts the outer peripheral surface 32a. , Is arranged. The seal member 34 prevents the contained toner T from leaking out of the container 31 and collects the toner T on the outer peripheral surface 32a of the developing roller 32 that has passed through the developing position without scraping it into the container 31. Further, the regulating blade 35 adjusts the flat portion on the rear end side with respect to the edge on the front end side so as to be in pressure contact with the surface of the outer peripheral surface 32a of the developing roller 32, whereby the toner T adhering to the outer peripheral surface 32a is adjusted to the front end. The thickness is controlled to be constant while scraping off at the side edge. Here, the toner T on the outer peripheral surface 32 a of the developing roller 32 is charged by applying a preset charging voltage to the regulating blade 35, and the supply roller 33 is pressed against the developing roller 32. When rotating, it is triboelectrically charged.

  The developing cartridge 13 accommodates yellow (Y), cyan (C), magenta (M), and black (K) color toners T. When the image forming operation is completed, the developing cartridge 13 is in the home position shown in FIG. The developing rotary unit 14 rotates and waits, and the developing cartridge 13k containing the black (K) toner T constitutes a specific developing cartridge, and the developing cartridges 13y, 13c, and 13m have other colors. A normal developing cartridge that accommodates the toner T is configured, and the developing cartridges 13y, 13c, 13m, and 13k for the respective colors accommodate toners T that are suitable for the respective toners.

  Specifically, the home position of the developing rotary unit 14 is immediately rotated to the developing position where the developing cartridge 13k containing the black (K) toner Tk for monochrome images that is frequently used faces the photosensitive drum 12. In addition, since the developing cartridge 13k is designed in an augerless manner, the toner Tk for monochrome image that has been put together in the upper part of the first and second spaces S1 and S2 is loosened during the rotational movement. The developing cartridge 13k is set at the lowest position so that the first space S1 can be replenished. In this case, when the developing rotary unit 14 rotates to the home position and stands by, the developing cartridge 13k at the lowermost position has an accommodation space for the accommodation toner Tk below the supply roller 33, and the supply roller 33 May stand by while being exposed from the toner Tk. The standby position of the developing cartridge 13k is close to the laser beam scanning device 11 where the polygon mirror 11a rotates at high speed, and the toner Tk contained in the developing cartridge 13k is heated from the rotation motor (heat source) of the polygon mirror 11a. In this situation, a so-called blocking phenomenon is likely to occur, in which the supply roller 33 is exposed, and the supply roller 33 is exposed. And you will not be able to ride smoothly. Further, the toner Tk contained in the developing cartridge 13k is in a state of being in close contact with the standby state for a long period of time or receiving vibration, so that a blocking phenomenon is more likely to occur. This blocking phenomenon is caused by an image (toner) formed on the recording paper, because the toner T contained therein becomes a mass having almost no fluidity, and the supply to the supply roller 33 and the supply to the developing roller 32 cannot be performed smoothly. This is a phenomenon that causes blurring of the image) and causes the toner end to be determined (false detection) before the contained toner T is used up.

  Further, developing cartridges 13y, 13c, and 13m containing yellow (Y), cyan (C), and magenta (M) toners Tymc for color images are printed on a recording sheet in order to form a color image by superimposing colors. For each image to be formed, that is, for each development, the developing rotary unit 14 rotates and the developing operation can be repeated while stirring and refreshing the toner T contained in the container 31. When a monochrome image using the toner Tk of K) is formed on a plurality of recording papers, the electrostatic latent image on the photosensitive drum 12 is repeatedly developed with toner at the development position without rotating, and thus for color images. The components of toner T are adjusted for monochrome images. Note that the toner Tymc means toners Ty, Tm, and Tc, which are confused with the melting temperature Tm described later, and will be described as the toner Tymc.

The monochrome image toner Tk is set to have a glass transition temperature Tg higher than that of the color image toner Tymc. In addition, the wax amount WAX is smaller than that of the color image toner Tymc, and silica (SiO _2). ) And titania (TiO ₂ ) and the like are set to a large amount AD. Further, since the monochrome image toner Tk has a smaller wax amount WAX, the melting temperature (softening temperature) Tm is set higher than that of the color image toner Tymc.

  In short, the color image toner Tymc is adjusted to have the same general components as those of the conventional color image toner Tym, whereas the glass transition temperature Tg, the melting temperature Tm, the wax amount WAX, and the external additive The quantity AD is set to the components shown in FIG.

  Here, the glass transition temperature Tg, the melting temperature Tm, the wax amount WAX, and the external additive amount AD of the constituent components of the toner T are the blocking phenomenon, peeling characteristics, OHP translucency, gloss, It has been found that the characteristics can be adjusted. The blocking phenomenon of the stored toner T can be avoided by not impairing the fluidity of the stored toner T (by preventing it from agglomerating so as not to become a lump). The peeling characteristic is whether or not the toner image transferred onto the recording paper can be conveyed downstream without being wound around the outer peripheral surface of the fixing roller pair 17 after the fixing roller pair 17 is heated and pressed to fix the toner image. It is to judge whether. For OHP translucency, when an image is formed using an OHP (over head projector) sheet as a recording medium, in the case of a color image, it is determined whether or not it can be translucent by melting and mixing during fixing. In the case of a monochrome image, it is not necessary to be translucent and it is sufficient if it can be shielded from light. The gloss characteristic is the degree of gloss of the image surface when it is fixed on the recording paper.

  First, the blocking phenomenon depends on the ease of aggregation of the toners T at a low temperature that does not reach the fixing temperature. Therefore, the blocking phenomenon can be improved as the glass transition temperature Tg is set higher. As the amount of external additive AD that increases the fluidity of T is set to a larger value, the generation can be avoided, whereas the generation of wax can be avoided by reducing the amount of wax WAX. Further, since the peeling characteristics depend on the ease of adhesion of the toner T during fixing, it can be improved as the melting temperature Tm is set higher, whereas the wax amount WAX is reduced. Can improve. Since the OHP translucency and gloss characteristics depend on the melting characteristics of the toner T, the OHP translucency and gloss characteristics can be increased as the melting temperature Tm is set lower.

  Therefore, in order to satisfy the peeling characteristics, OHP translucency and gloss characteristics while avoiding the occurrence of blocking phenomenon, the glass transition temperature Tg is set high and the amount of external additive AD is also set large. When the melting temperature Tm and the wax amount WAX are set as parameters, the results shown in FIG. 5 are obtained.

  From this result, the target blocking phenomenon cannot be avoided under the condition 1 where the melting temperature Tm is set lower and the wax amount WAX is increased. However, in the case of the color image toner Tymc, the developing cartridges 13y, 13m, and 13c are rotated and agitated / refreshed for each development, so that a blocking phenomenon can be avoided in practice. This condition 1 is optimal because it can satisfy the peeling characteristics, OHP translucency and gloss characteristics. This condition 1 is close to the constituent components of the color image toner Tymc. In the case of this color image toner Tymc, it is possible to avoid the occurrence of the blocking phenomenon. The conventional setting is sufficient for the dosage AD. Also in the color image toner Tymc, if the glass transition temperature Tg is set high, the color transition is delayed when the color toners are overlaid and mixed (color overlap), so the glass transition temperature Tg is unnecessary. There is no need to set it higher.

  On the other hand, under the condition 4 where the melting temperature Tm is set high and the wax amount WAX is small, the OHP translucency and the gloss characteristics cannot be satisfied. However, in the case of the monochrome image toner Tk, OHP translucency is unnecessary and there is no problem even if gloss is not glossy. Under condition 4, after waiting for the lowest position after the image forming operation is completed, Condition 4 is optimal because it is possible to avoid the occurrence of the blocking phenomenon, which is a peculiar problem caused by repeating (continuing) the developing operation while stopped at the developing position.

  As described above, the developing cartridges 13y, 13m, and 13c contain the color image toner Tymc prepared with the conventional components equivalent to those in the condition 1, while the developing cartridge 13k contains the color image toner Tymc. All of the developing cartridges are accommodated by containing toner Tk for monochrome images in which the glass transition temperature Tg is high, the wax amount WAX is small, the external additive amount AD is large, and the melting temperature Tm is high. It is possible to prevent the blocking phenomenon from occurring in the accommodated toner T in the 13 containers 31. Therefore, the image forming apparatus 10 can smoothly resume the developing operation even after the developing cartridge 13k is kept at the lowest position, and a color image or monochrome image is printed on a plurality of recording sheets until the contained toner T is used up. Images can be formed continuously. In this case, the monochrome image toner Tk is set at a higher melting temperature Tm than the color image toner Tymc. It goes without saying that subsequent gloss (gloss) may be obtained even in a monochrome image.

  By the way, the monochrome image toner Tk in the developing cartridge 13k is not adhered to the electrostatic latent image on the surface of the photosensitive drum 12, but repeatedly in the container 31 to repeatedly develop the developing roller 32, the supply roller 33, the seal member 34, or the regulation. Even if the effect of the external additive amount AD is reduced by rubbing between the blade 35 and the containing toner Tk, the setting of the glass transition temperature Tg higher than that of the color image toner Tymc, and the wax By containing a small amount of WAX, it is possible to effectively avoid agglomeration into a block having almost no fluidity and a blocking state. In other words, the monochrome image toner Tk may be set to have a glass transition temperature Tg higher than that of the color image toner Tymc. However, as in the present embodiment, the wax amount WAX is reduced and the external toner Tk is reduced. It is advantageous to add a large amount of additive AD because the blocking phenomenon can be effectively avoided.

  Further, in this way, the developing cartridge 13 repeatedly performs a developing operation for forming an image on a plurality of recording sheets without causing a blocking phenomenon in the stored toner T (without being affected by the occurrence of the blocking phenomenon). Therefore, the toner T exceeding the capacity of the container 31 can be filled in a coarse density state with excellent fluidity. In particular, since there are many prints of text characters, monochrome images, and the like based on the usage status of the image forming apparatus 10, there is a demand to fill the container 31 of the developing cartridge 13k with as much monochrome toner Tk as possible. Therefore, the monochrome image toner Tk can be filled at a filling rate of 100% or more, which exceeds the capacity of the container 31 in the coarse density state (so-called loose apparent density).

  Further, such an image forming apparatus 10 repeatedly performs a developing operation by effectively using the stored toner T without causing a blocking phenomenon to occur in the stored toner T (without being affected by the occurrence of the blocking phenomenon). Therefore, for example, even if there is heating or vibration in the container during transportation, the developing operation can be started smoothly without any problem, and color images can be printed on multiple sheets of recording paper until the contained toner T is used up. And monochrome images can be formed continuously.

  As described above, in the present embodiment, the heat source stands by at the lowest home position where the heat source is close, and the supply roller 33 is easily exposed because the heat source is located at the lowest position. The monotonic image toner Tk having a glass transition temperature Tg set higher than that of the color image toner Tymc is accommodated in the developing cartridge 13k which is in a disadvantageous condition for the occurrence of the blocking phenomenon. As a result, in the developing cartridge 13k, the stored toner Tk can be replenished to the supply roller 33 and supplied to the developing roller 32 without causing the developing roller 32 to be in a blocking state. High-quality monochrome images can be continuously formed without replenishment or supply interruption and causing toner end or image blurring.

  Further, the monochrome image toner Tk is more reliable than the color image toner Tymc by adding a larger amount of external additive AD and setting the melting temperature Tm higher while reducing the wax amount WAX. High and fluidity can be secured to prevent the occurrence of blocking phenomenon, and at the same time, the peelability at the fixing roller pair 17 can be secured, and continuous monochrome image formation (transfer fixing) can be realized without any problems. Yes.

  As a result, without changing the design of the image forming apparatus 10, the toner Tk for monochrome images in which no blocking phenomenon occurs (no toner running out or blurring) is contained in the developing cartridge 13 k having an augerless and inexpensive configuration. In addition to the color image, a monochrome image can be continuously formed with high quality.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea. For example, the case of an image forming apparatus including an intermediate transfer belt 15 that sets a plurality of developing cartridges 13 in the developing rotary unit 14 and transfers a toner image formed on the photosensitive drum 12 onto a recording sheet will be described as an example. However, the present invention is not limited to this, and it goes without saying that the present invention can also be applied to an apparatus for transferring and forming a toner image directly from a photosensitive drum onto a recording sheet.

1 is a perspective front view showing a schematic overall configuration of an image forming apparatus according to an embodiment of the present invention. It is a longitudinal cross-sectional view which shows the principal part structure. It is a see-through | perspective front view which shows the state in the home position at the time of the standby. It is a table | surface explaining the component of the toner. It is a table | surface which shows the characteristic when the component of the toner is adjusted.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Laser beam scanning apparatus 11a Polygon mirror 12 Photosensitive drums 13, 13c, 13k, 13m, 13y Developing cartridge 14 Developing rotary unit 15 Intermediate transfer belt 16 Transfer roller 17 Fixing roller pair 21 Paper cassette 23, 26 Relay conveyance Roller pair 24 Registration roller pair 31 Container 31a Partition plate 32 Developing roller 33 Supply roller 34 Sealing member 35 Restricting blade 43 Supply roller AD External additive amount S1, S2 Space T Toner Tg Glass transition temperature Tk Monochrome image toner Tm Melting temperature Tymc Color image toner WAX Wax amount

Claims (7)

An electrostatic latent image based on the image data is formed on the surface, and a carrier carrying a toner image obtained by developing the electrostatic latent image; and toner is selectively attached to the electrostatic latent image on the surface of the carrier. A developing cartridge that develops an electrostatic latent image, and a plurality of the developing cartridges are detachably accommodated around a rotating shaft, and one of the developing cartridges is opposed to the surface of the carrier by rotating about the rotating shaft. A developing rotary unit
The developing cartridge includes a container for storing toner, a developing roller that causes the toner on the outer peripheral surface to adhere to the carrier by rotating while the outer peripheral surface faces the carrier, and the developing roller when the developing roller rotates. A supply roller for supplying the toner in the container to the outer peripheral surface of the toner cartridge, and storing toners of different colors in the container and being mounted on the developing rotary unit, so that the surface of the single color image or color image carrier An image forming apparatus for developing an electrostatic latent image with toner and transferring and fixing the toner image on a recording medium,
When the developing rotary unit rotates to the home position and waits after completion of the image forming operation, there are other locations in the container of the specific developing cartridge that is mounted at a location where the toner storage space extends below the supply roller. An image forming apparatus for storing toner having a glass transition temperature set higher than that of toner stored in a normal developing cartridge mounted on the printer.   The image forming apparatus according to claim 1, wherein the specific developing cartridge contains toner of a color that continuously forms a single color image on a recording medium.   3. The image according to claim 1, wherein the developing cartridge is designed in an augerless manner that replenishes toner contained in a container to a supply roller side by a rotational movement of the developing cartridge without using a replenishing device. Forming equipment.   4. The image forming apparatus according to claim 1, wherein the specific developing cartridge stores toner having a smaller amount of wax than toner stored in the normal developing cartridge. 5.   The image forming apparatus according to claim 4, wherein the specific developing cartridge contains toner having a melting temperature set higher than that of the toner contained in the normal developing cartridge.   6. The image forming apparatus according to claim 1, wherein the specific developing cartridge contains toner whose amount of external additive is set larger than that of toner contained in the normal developing cartridge. apparatus.   The image forming apparatus according to claim 1, wherein a heat source is disposed at a position where the specific developing cartridge is closer to the normal developing cartridge during standby.

Images