JP2004240129A - Developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a circumferential surface of a toner with a high molecular weight resin to achieve high image quality and to prevent the occurrence of an abnormal image due to colored deposits without increasing cost or upsizing an apparatus. <P>SOLUTION: A shell constituting a circumferential surface of a toner T comprises a high molecular weight resin Ta having such hardness and heat meltability that the resin does not adhere to additive agglomerates H even when the shell is rubbed against the additive agglomerates H. Accordingly, even when the toner T is slid on photoreceptor in rubbing manner and rubbed against surface layers of the additive agglomerates, part of the toner T does not adhere to the surface layers and the spherical shape can be maintained. Accordingly, the toner T is less liable to adhere to the surfaces of the additive agglomerates H and ensures condition free of the colored deposits M. Under such condition, the surfaces of the additive agglomerates are capable of transmitting laser light, poor exposure due to coloration of the additive agglomerates is avoided, and occurrence of such an abnormal image as an image with voids can be prevented. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly, to a developer used in an electrophotographic image forming apparatus and the image forming apparatus.
[0002]
[Prior art]
In a conventional electrophotographic image forming apparatus, an image is formed as follows. First, the surface of a photoreceptor as an image carrier is uniformly charged, and the surface of the uniformly charged photoreceptor is subjected to exposure processing according to image information to form an electrostatic latent image. A visible image is obtained by adhering a developer such as toner charged to negative or positive polarity thereto. Next, the visible image is transferred from the surface of the photoreceptor directly to a transfer member such as transfer paper or via an intermediate transfer member, and then fixed on the transfer member by heating or the like.
[0003]
In the image forming apparatus of this type, if the surface of the photoreceptor has a flaw, a colored adhering substance (medaka) is generated on the flaw, and this part is not exposed, so that an abnormal image is sometimes generated.
An example of a medaka and a mechanism of generating an abnormal image caused by the medaka will be described with reference to FIGS. 9 and 10. When a two-component developer composed of a toner and a carrier is used as the developer, when a pressure is applied while the carrier is attached to the surface of the photoconductor, an abnormal image is triggered on the surface of the photoconductor as shown in FIG. Crater-like scratches (hereinafter referred to as craters) may occur. On the other hand, various additives have been conventionally added to toner. Additives are added to the toner, for example, to compensate for problems related to the toner's electrostatic, thermal, or physical properties, fluidity, particle size distribution, and other various properties, such as silica and titanium oxide. Is used. When the development is repeatedly performed using the photoreceptor having a scratch on the surface, the additive Tc collects and accumulates on the scratch, and a nucleus composed of the additive aggregate is formed. From the nucleus, the additive aggregate grows on the upstream side in the rotation direction of the photoconductor. When a photoreceptor in which a core of an additive aggregate is formed is used, a dye contained in the toner T adheres to the additive aggregate over time and the core surface is colored, and as shown in FIG. An attached matter (hereinafter, referred to as medaka) M is generated. Since the surface of the photoreceptor on which the medaka M occurs does not transmit the exposure light, an abnormality occurs in the formation of the latent image, resulting in an abnormal image. For example, in the case of a negative / positive image, a latent image is not formed in a portion where the transmission of the exposure light is blocked, resulting in white spots. Is formed, and an abnormal image which becomes a background stain occurs.
[0004]
Conventionally, various proposals have been known to prevent abnormal images caused by medaka. In Patent Document 1, an electrostatic image developing toner composed of a binder resin component, a colorant, and an external additive is configured as follows. That is, the toner does not contain the THF-insoluble component of the binder resin, and has a molecular weight of 1 × 10 ³ ~ 1 × 10 ⁴ Containing the main peak and 1 × 10 ⁵ ~ 1 × 10 ⁷ , The content of the subpeak is 10 to 30% by weight, and the rheological characteristics of the subpeak component are determined by the frequency sweep method (150 ° C., 1 × 10 ^-2 ~ 1 × 10 ² rad / sec), the dynamic elastic modulus G ′ is 1 × 10 ⁵ ~ 5 × 10 ⁷ dyne / cm ² belongs to. This proposal proposes that the toner to be used is a pulverized toner and that the properties of the toner are specified so that even when copying is repeated for a long period of time, the additive is not released from the toner matrix and a stable charge can be maintained. ing. According to Patent Document 1, there is no occurrence of medaka on the photoreceptor due to the additives released from the toner matrix, and an abnormal image due to medaka can be prevented.
Further, in Patent Document 2, a resin layer controller is provided on the surface of a photoreceptor drum and pressed and rotated in order to prevent the occurrence of medaka on the surface of the image carrier, thereby forming a minute thin film coating layer. are doing. According to this proposal, by forming a resin layer on the surface of the photoconductor drum, it is possible to prevent a substance causing a crater-like scratch, such as a carrier, from directly adhering to the surface of the photoconductor drum, thereby preventing the occurrence of medaka. It is like that. According to Patent Literature 2, an abnormal image caused by medaka can be prevented.
[0005]
[Patent Document 1]
JP 2000-338718 A
[Patent Document 2]
JP-A-6-314055
[0006]
[Problems to be solved by the invention]
However, in Patent Document 1, a crushed toner manufactured by a crushing method is used as a toner in order to prevent an abnormal image caused by medaka. FIG. 11 is an enlarged plan view of a certain pulverized toner. As shown in this figure, the pulverized toner has an irregular shape as compared with the spherical toner, and the size between the toner particles is also irregular, so it is difficult to express a smooth image, and it is difficult to achieve high image quality. There were side effects.
[0007]
Further, Patent Document 2 described above has a step of applying a resin such as fluorine to the surface of the photoconductor drum in order to form a minute thin film coating layer. For this reason, it is necessary to newly provide a coating device, which requires a cost and a space for the device, and has a side effect of increasing the cost and increasing the size of the device.
[0008]
In view of the above, it is desired to be able to realize high image quality and to prevent an abnormal image due to medaka without increasing the cost or the size of the apparatus.
The scratches on the surface of the photoconductor, which cause the above-mentioned medaka, may be caused not only by the adhesion of the carrier to the photoconductor but also by a cause other than the adhesion of the carrier. For this reason, an abnormal image caused by medaka is not limited to the case where a two-component developer composed of a toner and a carrier is used, but may also occur when a one-component developer is used. It is necessary to be able to prevent it.
[0009]
The present invention has been made in view of the above background, and an object of the present invention is to achieve high image quality and prevent an abnormal image caused by medaka without increasing the cost or the size of the apparatus. The purpose is to be.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 provides an image carrier, a latent image forming means for forming a latent image on the surface of the image carrier, and a developing device for visualizing the latent image with a developer. And a developer used in an electrophotographic image forming apparatus, wherein the developer contains at least a toner, and the toner is a polymerized toner whose outer peripheral surface is made of a high molecular weight resin. is there.
According to a second aspect of the present invention, in the developer of the first aspect, the toner has a core-shell structure in which the inside is made of a low molecular weight resin.
The invention according to claim 3 is the developer according to claim 1 or 2, wherein the developer is a two-component developer including a toner and magnetic particles.
According to a fourth aspect of the present invention, in the developer according to the first, second or third aspect, the amount of the additive to be added to the toner for various purposes is 1.0 [w% ] And 2.0 [w%] or less.
According to a fifth aspect of the present invention, in the developer of the fourth aspect, the toner has a circularity of 0.90 or more and 0.97 or less.
According to a sixth aspect of the present invention, there is provided an electrophotographic apparatus having an image carrier, a latent image forming unit for forming a latent image on the surface of the image carrier, and a developing unit for visualizing the latent image with a developer. In the image forming apparatus of the system, the developer used in the developing means is the developer according to claim 1, 2, 3, 4, or 5.
Here, if a soft material made of a low molecular weight resin is exposed on the surface of the toner, the low molecular weight resin is added compared to the high molecular weight resin when the toner is rubbed against the surface layer of the additive aggregate. Since it easily adheres to the surface layer of the agent aggregate, the surface layer may be colored. For this reason, the colored region cannot transmit the exposure light, and the exposure failure of the image carrier occurs, resulting in an abnormal image.
According to the first to fifth aspects of the present invention, the outer peripheral surface of the toner is made of a polymer resin even if the developer is rubbed against the surface of the additive aggregate of the image carrier. The polymer resin is generally a resin having a molecular weight of 10,000 or more, and is a material that is relatively hard and has low heat-fusibility. For this reason, even when the surface of the photoreceptor is rubbed, the shape is not easily deformed, and it is hard to be melted by frictional heat or the like. Therefore, the developer containing the toner does not color the additive aggregate surface layer with the toner, and does not generate medaka caused by coloring the additive aggregate surface layer. Therefore, when this developer is used in an electrophotographic image forming apparatus, poor exposure of the image carrier due to medaka does not occur. This toner is a polymerization toner. The polymerized toner is a spherical toner having a more uniform particle size than the pulverized toner. Therefore, higher image quality can be achieved as compared with the pulverized toner. Furthermore, if this toner is used in an electrophotographic image forming apparatus, it is possible to prevent the occurrence of medaka even if the surface of the image carrier is damaged. Therefore, the above-mentioned abnormal image can be prevented without providing a device for forming a coating layer for preventing the surface of the image carrier from being scratched, so that it is possible to cause the medaka without increasing the cost or increasing the size of the device. To prevent abnormal images from occurring.
According to a sixth aspect of the present invention, an image is formed in an electrophotographic image forming apparatus using the developer according to the first to fifth aspects. As a result, exposure failure of the image carrier due to medaka does not occur. Further, it is possible to improve the image quality as compared with the pulverized toner, and further, it is not necessary to provide a device for forming a coat layer for preventing the occurrence of scratches on the surface of the image carrier, so that cost increases and An abnormal image caused by medaka is prevented without increasing the size of the apparatus.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment in which the present invention is applied to an electrophotographic laser printer (hereinafter simply referred to as a printer) as an image forming apparatus will be described below. The basic configuration of the printer will be described.
FIG. 1 is a schematic configuration diagram showing the printer. In the figure, a printer 200 includes a photosensitive drum 1 as an image carrier, a charging roller 2, a developing unit 3, a cleaning unit 4 for cleaning the photosensitive drum, and a light for writing an electrostatic latent image on the photosensitive drum 1. The image forming unit 100 includes the writing unit 6 and the like.
[0012]
The following can be used as the optical writing unit 6 for writing an optical signal corresponding to image information read by a scanner or the like. For example, an optical signal corresponding to image information is emitted from a semiconductor laser, and a laser beam L is scanned by a polygon mirror that is driven to rotate, and a convergence and polygon arranged in a scanning optical path of the laser beam L as exposure light. An optical signal corresponding to the color-separated image information is written on the photosensitive drum through a lens for correcting the surface tilt of the mirror, a mirror for deflecting the laser light, and the like.
[0013]
Further, below the image forming unit 100, a paper feed roller 9 for separating and feeding the transfer paper 8 as a transfer material stored in the paper feed cassette 7 one by one, and the paper is fed by the paper feed roller 9. After the fed transfer paper 8 is temporarily made to stand by before the photosensitive drum 1, the leading end of the image formed on the photosensitive drum 1 and the leading end of the transfer paper 8 are transferred to the photosensitive drum 1 and the transfer roller 10. A registration roller pair 11 is provided as transfer material transporting means for re-feeding the transfer paper 8 in synchronization with the rotation of the photosensitive drum 1 at a timing when the nip portion is almost simultaneously reached.
[0014]
Further, above the image forming unit 100, a fixing roller pair 15 composed of a fixing roller and a press roller each having a built-in heater rotatably disposed so as to be pressed against each other with the conveyance path 12 of the transfer paper 8 interposed therebetween. The fixing device 16 is provided as a fixing unit having the following. The transfer paper 8 that has passed through the fixing nip of the pair of fixing rollers 15 is discharged to a discharge tray (not shown) formed at the upper part of the main body of the printer 200 on the downstream side of the fixing device 16 in the transfer paper conveyance direction. Paper discharge roller 18 is provided.
[0015]
FIG. 2 is an enlarged view of an image forming unit provided in the printer of the present embodiment. The developing unit 3 in the image forming unit 100 includes transport screws 20, 21, a doctor blade 23, and a toner density sensor 24 in addition to the developing roller.
Further, around the image forming unit 100, there is provided a static eliminator 20 for irradiating static elimination light b in order to eliminate residual charges on the photosensitive drum 1.
[0016]
When an image is formed in the printer 200 having such a configuration, the static elimination device 20 first irradiates the neutralizing light b with the rotation of the photosensitive drum 1 to average the surface potential to a predetermined reference potential. Next, the photosensitive drum 1 is uniformly charged by the charge from the charging roller 2 during rotation, and the surface potential becomes a predetermined charging potential.
Next, the optical writing unit 6 is driven based on the image information read from the outside, whereby an electrostatic latent image is formed on the charged area (image forming area) of the photosensitive drum 1. This electrostatic latent image is developed by the toner T in the developer supplied from the developing roller 3a of the developing unit 3, and becomes a toner image as a visible image.
[0017]
The formation of the toner image is performed as follows. A laser light L is irradiated by an optical writing device 6 (not shown), and the surface potential is changed to the image portion potential only in the portion irradiated with the laser light L to form an electrostatic latent image on the photosensitive drum. Thereafter, the electrostatic latent image is developed with the toner T in the two-component developer carried on the developing roller 3a to which a predetermined developing bias potential is applied, to form a toner image on the photosensitive drum.
[0018]
On the other hand, while the toner image is being formed on the photosensitive drum 1, the transfer paper 8 is pulled out from the paper supply cassette 7 by the paper supply roller 9, and the leading end thereof is applied to the nip portion of the registration roller 11. Stand by in contact. The transfer paper 8 is sent out to a transfer nip N formed by the photosensitive drum 1 and the transfer roller 10 by the rotation of the registration roller 11 at the timing of being superimposed on the toner image on the photosensitive drum 1. It is. Then, after the toner image on the photosensitive drum 1 is transferred at the transfer nip N, the charge is removed by contact with the charge removing brush 22. The transfer paper 8 that has been neutralized by the neutralization brush 22 is sent to the fixing device 16 after being mechanically separated from the photosensitive drum 1.
[0019]
The fixing device 16 fixes the toner image on the transfer paper 8 by heating and pressing the transfer paper 8 by sandwiching the transfer paper 8 between a fixing roller pair 15 including a fixing roller and a press roller. The so-called pressure fixing is performed. The transfer paper 8 on which the toner image has been fixed in this way is discharged by a discharge roller 18 to a discharge tray (not shown).
[0020]
The residual toner remaining on the surface of the photosensitive drum 1 after passing through the transfer nip N is removed from the photosensitive drum 1 by the cleaning blade 4a of the cleaning unit 4 and collected. On the other hand, the surface of the photosensitive drum from which the residual toner has been removed returns to the charging section again. The residual toner scraped off by the cleaning blade 4a is transported to a predetermined position by the toner transport coil 27.
By repeating these series of operations, a toner image is continuously formed on transfer paper.
[0021]
The developer is a two-component developer including a small iron ball called a carrier and a toner, and the charged toner adheres to the carrier by circulating while being stirred by the transport screws 20 and 21. Thereafter, the developer is carried to the surface of the photosensitive drum, and the toner is attached to the surface of the photosensitive drum by the action of electrostatic force. Further, an additive Tc for improving fluidity is added to the toner. Silica, titanium oxide, or the like is used as the additive Tc.
[0022]
In the printer having the above-described configuration, when development is repeatedly performed in a state in which a crater-shaped scratch is generated on the surface of the photoconductor, the additive Tc accumulates and aggregates in the scratch, and a nucleus formed of the additive aggregate is formed. was there. Then, the nucleus of the additive aggregate H grows upstream from the nucleus in the moving direction of the photoconductor surface. When development is performed using the photosensitive drum 1 on which the nucleus of the additive aggregate H is formed, the dye contained in the toner T adheres to the additive aggregate H over time, and the nucleus surface is colored. As shown in FIG. Since the exposure light does not pass through the surface of the photoconductor where the medaka M is generated, no latent image is formed and an abnormal image is formed. For example, in the case of a negative / positive printer as in the present embodiment, a portion where the laser light L is not irradiated occurs in a part of the image area irradiated with the laser light L, and the toner T does not adhere to this portion. Therefore, an abnormal image with white spots results. Therefore, in the present invention, even if the surface of the photoreceptor is scratched, such an abnormal image due to the medaka M is prevented from being generated.
[0023]
Hereinafter, features of the present embodiment will be described. FIG. 3 is an explanatory diagram of the toner T according to the present embodiment. In the present embodiment, a toner having a core-shell structure in which the outer shell constituting the outer peripheral surface of the toner T which is a component of the two-component developer used for development is made of a high molecular weight resin Ta and the inside is made of a low molecular weight resin Tb T is used. The high-molecular-weight resin Ta and the low-molecular-weight resin Tb are each made of a polyester resin.
In the present embodiment, the surface of the toner T is made of a high molecular weight resin Ta having low hardness and low heat melting property such that the outer shell does not adhere to the additive aggregate H even when the outer shell is rubbed against the additive aggregate H. Have been. Therefore, even if the surface of the additive aggregate H is rubbed against the photoconductor, a part of the toner T does not adhere to the surface of the additive aggregate H, and the spherical shape can be maintained. FIG. 4 is a front view of the photoconductor surface when an image forming operation is performed under the same image forming conditions as when obtaining FIG. 9 except for the toner T using this printer. The color of the surface of the additive aggregate H is lighter than that of the conventional photoreceptor surface shown in FIG. 9, and almost no medaka M is generated. In the state where the additive is hardly colored, the surface of the additive aggregate can transmit the laser beam L as shown in FIG. It is possible to prevent an abnormal image such as omission.
Further, the toner T is not the pulverized toner shown in FIG. 11, but a polymerized toner. The polymerized toner has a spherical shape and a uniform size as compared with the pulverized toner, so that higher image quality can be achieved as compared with the pulverized toner. Further, by using the toner T, it is not necessary to install a device for forming a coat layer on the surface of the photoreceptor in order to prevent an abnormal image caused by the medaka M, thereby increasing costs and increasing the size of the device. Can be avoided.
As described above, by using the toner T as described above in the printer of the present embodiment, it is possible to realize high image quality as compared with the case of using the pulverized toner, without increasing the cost and increasing the size of the apparatus. An abnormal image due to medaka can be prevented.
[0024]
As shown in FIG. 3, the toner T in the developer used in the present embodiment has a core-shell structure in which the inside is made of a low molecular weight resin Tb. Further, the fixing device 16 in the printer according to the present embodiment employs a pressure heating method using pressure and heating to fix an image transferred onto transfer paper. Since the inside is made of the toner T made of the low molecular weight resin Tb, the inside is soft and the heat melting property is high. Therefore, when the toner T transferred onto the transfer paper is pressed and heated, the toner T adheres to the transfer paper and the fixability is improved.
Here, conventionally, a toner containing a high molecular weight resin and a low molecular weight resin has been used as the toner. However, conventionally, since the toner was a mixture of a high-molecular resin and a low-molecular resin, when development was performed using a developer containing this toner, the surface of the photosensitive drum was softer than the high-molecular-weight resin. There is a case where the low molecular weight resin portion of the material comes into contact and is rubbed. Then, since the low molecular weight resin is more easily adhered to the surface layer of the additive aggregate due to its flexibility than the high molecular weight resin, the additive aggregate surface layer is colored to cause medaka M. In the present embodiment, while containing a low molecular weight resin which is effective for satisfactorily performing pressure fixing, the resin is positioned inside the outer shell covered with the high molecular weight resin. Therefore, the fixing property can be improved while maintaining the effect of preventing the occurrence of medaka M.
[0025]
Further, the printer of the present embodiment uses a two-component developer. For this reason, as described above, a crater is likely to be generated on the surface of the photosensitive member when pressure is applied while the carrier adheres to the surface of the photosensitive drum 1, and medaka M is generated as compared with the case where a one-component developer is used. Cheap. The present invention is applied to a printer using such a two-component developer, thereby preventing an abnormal image caused by medaka M which is likely to occur.
[0026]
Furthermore, the present inventor has found that there is a relationship between the amount of the additive Tc added to the toner T and the degree of occurrence of white spots due to medaka M. FIG. 6 shows that when the addition amount [w%] of the additive Tc added for improving the fluidity of the toner T is changed in a range of 0 [w%] to 3.0 [w%], 9 is a graph showing the results of examining the degree of occurrence of image white spots due to medaka M after repeatedly printing 2000 sheets for each addition amount. From this result, when the amount [w%] of the additive Tc is less than 1.0 [w%], image white spots occur. The smaller the amount of the additive Tc, the higher the degree of occurrence thereof. Almost no image white spots occurred.
FIGS. 7A and 7B are explanatory diagrams illustrating the relationship between the amount [w%] of the additive Tc and the occurrence of image white spots. When the amount of the additive Tc is small, as shown in FIG. 7A, since the amount of the additive Tc covering the surface of the toner T is small, the frequency of the toner surface directly rubbing against the additive aggregate H on the surface of the photoconductor increases. Then, during repeated rubbing, the surface of the additive aggregate H is colored as shown in the figure. On the other hand, as shown in FIG. 7B, when the amount of the additive covering the toner surface is increased, the frequency at which the toner surface is directly rubbed against the additive aggregate H is reduced, so that the surface of the additive aggregate H is hardly colored. Not done. The threshold value of the additive amount [w%] of the additive agglomerate H surface between the state where the surface of the additive aggregate H is easily formed and the state where the surface is difficult to be formed is 1.0 [w%]. The upper limit of the amount is usually 2.0 [w%] or less.
From the above, in the present embodiment, the addition amount [w%] of the additive Tc is set to be in the range of 1.0 to 2.0 [w%].
[0027]
In addition to limiting the range of the additive amount of the additive Tc, in the present embodiment, it has been found that the circularity of the toner T is related to the occurrence of medaka M. As the degree of circularity of the toner T approaches 1, which is a perfect circle, it becomes easier for the cleaning unit 4 to slip through the cleaning nip C, which is a position facing the cleaning blade 4a. If the amount of toner that passes through the cleaning nip C increases, the toner T is strongly rubbed against the surface of the photoconductor by the cleaning blade 4a when the toner passes through the cleaning nip C. At this time, if the additive aggregate H is present on the surface of the photoconductor, it is colored. Easier to do. Therefore, it is desirable that the toner T does not easily pass through the cleaning nip in order to prevent image white spots.
FIG. 8 shows the circularity of the toner T and the cleaning nip C using the toner T in which the additive amount [w%] of the additive Tc is in the range of 1.0 to 2.0 [w%]. 5 is a graph showing the result of examining the relationship with the slip-through amount. This is because, of the untransferred toner remaining on the surface of the photoreceptor without being transferred onto the transfer paper during image formation, the toner that has passed through the cleaning nip C and is located downstream of the cleaning nip C in the direction of movement of the photoreceptor surface. T was attached to a transparent tape, and the density was used as a characteristic value to collect data.
From FIG. 8, it was found that the amount of slip-through greatly changed around the circularity of the toner T of 0.97. When the circularity of the toner T is greater than 0.97, the slip-through amount increases sharply, and when the circularity of the toner T is 0.97 or less, the slip-through amount is maintained in a small state. Note that the lower limit of the circularity of the toner T is generally 0.90 or more because the toner T is close to a spherical shape in the case of the polymerization toner.
From the above, the toner T used in the present embodiment is limited not only in terms of the above-mentioned additive amount [w%] of the additive Tc but also in terms of circularity, and the circularity is 0.97 or less and 0.90 or more. And Accordingly, it is possible to suppress the toner T from slipping through the cleaning nip C, and it is possible to prevent the additive aggregate H on the photoconductor surface from being colored by the toner T slipping through the cleaning nip C. The more preferable upper limit of the circularity of the toner T is 0.95.
[0028]
As described above, the additive Tc added to the toner T of the present embodiment is added to improve the fluidity of the toner T. However, the present invention relates to the toner Tc to which the additive Tc is added. It is not limited to. However, depending on the type of the additive Tc, it is conceivable that the range of the desired addition amount or the like changes. Further, the printer to which the present invention can be applied is not limited to the configuration described in the above embodiment. For example, the present invention can be applied not only to a monochrome printer but also to a color printer.
[0029]
The two-component developer used in the printer of the present embodiment has a core-shell structure in which the toner T, which is a component thereof, is made of a low-molecular-weight resin. Thereby, the fixing property can be improved while maintaining the effect of preventing the occurrence of medaka M.
Further, in the present embodiment, the present invention is applied to a printer using a two-component developer in which medaka M, which causes an abnormal image, is likely to occur. Therefore, the effect of preventing abnormal images caused by medaka M is also greater than when a one-component developer is used.
In the present embodiment, the amount [w%] of the additive Tc added to the toner T is set to 1.0 [w%] or more and 2.0 [w%] or less. This makes it possible to more effectively prevent image white spots caused by the medaka M.
In the present embodiment, the toner T having a circularity of 0.97 or less and 0.90 or more is used. As a result, the effect of preventing the occurrence of medaka M can be enhanced, and image white spots caused by medaka M can be more effectively prevented.
[0030]
【The invention's effect】
According to the first to sixth aspects of the present invention, it is possible to achieve high image quality as compared with the case where pulverized toner is used, and to prevent an abnormal image due to medaka without increasing the cost or increasing the size of the apparatus. Has an excellent effect.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printer according to an embodiment.
FIG. 2 is an enlarged view of an image forming unit provided in the printer of the embodiment.
FIG. 3 is an explanatory diagram of a toner according to the exemplary embodiment.
FIG. 4 is a front view of a photosensitive member surface when an image forming operation is performed using the printer of the embodiment.
FIG. 5 is a cross-sectional view of the surface of a photoconductor to which an additive aggregate is attached when an image forming operation is performed using the printer of the embodiment.
FIG. 6 is a graph showing the result of examining the relationship between the amount [w%] of an additive added to a toner and the degree of occurrence of image white spots caused by medaka M;
FIGS. 7A and 7B are diagrams illustrating the relationship between the additive amount [w%] of an additive and occurrence of image white spots.
FIG. 8 is a graph showing the result of examining the relationship between the circularity of the toner and the amount of slippage of the cleaning nip.
FIG. 9 is a front view of the surface of the photoconductor when a medaka M which is a conventional problem occurs.
FIG. 10 is an explanatory diagram showing a mechanism of occurrence of an abnormal image by medaka M.
FIG. 11 is an enlarged plan view of one crushed toner.
[Explanation of symbols]
1 Photoconductor drum
2 Charging roller
3 Developing unit
3a Development roller
4 Cleaning unit
4a Cleaning blade
6 Optical writing unit
7 Paper cassette
8 Transfer paper
9 Paper feed roller
10 Transfer roller
11 Registration roller pair
15 Fixing roller pair
16 Fixing device
18 Discharge roller
20 Static eliminator
100 Image forming unit
200 printer
H additive aggregate
M Medaka
N transfer nip
T toner
Ta high molecular weight resin
Tb low molecular weight resin
Tc additive

Claims (6)

A developer for use in an electrophotographic image forming apparatus, comprising: an image carrier; a latent image forming unit that forms a latent image on the surface of the image carrier; and a developing unit that visualizes the latent image with a developer. At
A developer characterized in that the developer contains at least a toner, and the toner is a polymerized toner whose outer peripheral surface is made of a high molecular weight resin. The developer according to claim 1,
A developer, wherein the toner has a core-shell structure in which the inside is made of a low molecular weight resin. The developer according to claim 1 or 2,
The developer is a two-component developer comprising a toner and magnetic particles. The developer according to claim 1, 2, or 3,
A developer characterized in that the amount of the additive to be added to the toner for various purposes is from 1.0 [w%] to 2.0 [w%] by weight with respect to the toner. The developer according to claim 4,
A developer, wherein the circularity of the toner is 0.90 or more and 0.97 or less. An image carrier, an electrophotographic image forming apparatus having a latent image forming unit that forms a latent image on the surface of the image carrier, and a developing unit that visualizes the latent image with a developer;
An image forming apparatus, wherein the developer used for the developing unit is the developer according to claim 1, 2, 3, 4, or 5.

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