JP2006330702A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a leading end of a transfer material from removing a toner image on an image carrier, thereby avoiding a deficit of the toner image. <P>SOLUTION: An image forming apparatus comprises: the image carrier which carries a toner image; a transferring member which forms a nip with the image carrier and transfers the toner image onto a transfer material which enters the nip; and a guide member which guides a leading edge of the transfer material in a transfer material moving direction so as to be brought into contact with the transferring member before the leading edge of the transfer material enters the nip. The transferring member guides the leading edge of the transfer material to the nip. In the image forming apparatus, the transferring member has a foamed layer such that a recessed part of a foamed cell do not appear in the surface of the transferring member which is in contact with the transfer medium. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that transfers a toner image carried on an image carrier to a transfer material.

  As a conventional electrophotographic technique, there is a technique of transferring a toner image on the image carrier onto a transfer material through a transfer material between an image carrier carrying a toner image and a transfer roller.

In this technique, there is a prior art that describes how a transfer material enters a transfer nip (Patent Document 1). The image forming apparatus described in Patent Document 1 includes a guide member that guides a transfer material toward a secondary transfer nip portion of an intermediate transfer belt. By this guide member, the leading edge of the transfer material first comes into contact with the intermediate transfer belt and enters the secondary transfer nip so that the transfer material follows the intermediate transfer belt.
JP 2001-356538 A

  However, the method of entering the transfer material into the secondary transfer nip as in the image forming apparatus of Patent Document 1 may cause a phenomenon that the tip of the transfer material scrapes off the toner image on the intermediate transfer belt. is there. Then, scraping off the toner image by the leading end of the transfer material causes an image defect. This image defect is difficult to occur when a sufficient margin is secured at the leading edge of the transfer material, but this image defect is noticeable when the margin is small or when an image without a margin is formed. Appear in.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, according to the first aspect of the present invention, an image carrier that carries a toner image, and a transfer member that forms a nip with the image carrier and transfers the toner image to a transfer material that enters the nip. And a guide member for guiding the leading edge of the transfer material to contact the transfer member before the leading edge in the transport direction of the transfer material enters the nip. In the image forming apparatus that guides the leading edge to the nip, the transfer member has a foam layer, and the concave portion of the foam cell does not appear on the surface of the transfer member that contacts the transfer material.

  According to a second aspect of the present invention, an image carrier that carries a toner image, a transfer member that forms a nip with the image carrier and transfers a toner image to a transfer material that enters the nip, and the image A transfer-facing member that is provided on the opposite side of the transfer member from the transfer member and forms a transfer electric field with the transfer member, and before the leading edge of the transfer material enters the nip, the transfer material In an image forming apparatus having a guide member that guides a leading edge to come into contact with the transfer member, in the transfer material transport direction, the most upstream position in the region where the transfer counter member and the image carrier are in contact with each other. The most upstream position of the nip is on the upstream side.

  According to a third aspect of the present invention, an image carrier that carries a toner image, an intermediate transfer member that receives the transfer of the toner image from the image carrier, and a nip formed between the intermediate transfer member and enters the nip A transfer member that transfers a toner image to the transfer material, a guide member that guides the front edge of the transfer material to contact the transfer member before the front edge of the transfer material enters the nip, In the image forming apparatus having the above, the transfer member is coated with a fluorinated compound on the surface that contacts the leading edge of the transfer material.

  According to a fourth aspect of the present invention, an image carrier that carries a toner image, an intermediate transfer member that receives the transfer of the toner image from the image carrier, and a nip formed with the intermediate transfer member, and enters the nip A transfer member that transfers a toner image to the transfer material, a guide member that guides the front edge of the transfer material to contact the transfer member before the front edge of the transfer material enters the nip, In the image forming apparatus, the transfer member is coated with a siloxane compound on the surface that contacts the leading edge of the transfer material.

  The effect of the present invention is to suppress the tip of the transfer material from scraping off the toner image on the image carrier, and to suppress loss of the toner image. Another effect is that the transfer material is smoothly guided by the transfer member and can enter the transfer nip, and the relative positional accuracy between the transfer material and the toner image is increased.

Example 1
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the following embodiments should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions. Further, unless specifically stated otherwise, the scope of the present invention is not limited to these.

  The image forming apparatus according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a schematic configuration diagram of a color image forming apparatus using the intermediate transfer system according to the first embodiment.

  In the color image forming apparatus of the intermediate transfer system shown in FIG. 2, each color toner image is formed on each photoconductive drum 2 in a plurality of image forming units based on image input data. The plurality of image forming units are arranged side by side along an intermediate transfer belt (intermediate transfer member) 8 as an endless belt member. The intermediate transfer belt 8 functions as an image carrier that receives the transfer of the toner image.

  Each color image forming unit has a photosensitive drum 2 (2a, 2b, 2c, 2d) which is an image carrier. Around each photosensitive drum 2, as a means for forming a toner image, a charging roller 7 (7a, 7b, 7c, 7d) as a primary charging means, an exposure device 1 (1a, 1b, 1c, 1d), development A developing device 3 (3a, 3b, 3c, 3d) and a photosensitive drum cleaning blade 5 (5a, 5b, 5c, 5d) are arranged. Each developing device 3 houses toner cartridges 6 (6a, 6b, 6c, 6d) for the respective colors.

  A primary transfer roller 4 (4a, 4b, 4c, 4d) whose surface is covered with an elastic material such as foam rubber is in contact with the lower part of each photosensitive drum 2 via an intermediate transfer belt 8, and each photosensitive drum 2 is in contact with each photosensitive drum. A primary transfer portion for transferring the toner image formed on the body drum 2 to the intermediate transfer belt 8 is formed. Accordingly, the color toner images formed on the respective photosensitive drums 2 are sequentially transferred onto the intermediate transfer belt (intermediate transfer body) 8 by the primary transfer roller 4 in each primary transfer portion (the transfer process is referred to as “primary transfer”). ").

  The toner image superimposed on the intermediate transfer belt 8 is collectively transferred onto the transfer material P by a secondary transfer roller 10 as a transfer member that contacts the intermediate transfer belt 8 and forms a transfer region. The transfer materials P are fed one by one from the feed cassette 20 and are formed by the secondary transfer roller 10 and the intermediate transfer belt 8 by the pre-secondary transfer conveyance roller 18 as a transfer material conveyance unit. It is conveyed to. During the transfer of the transfer material P, the transfer material P is guided by the pre-transfer guide 17 which is a guide member, and the transfer material P is stably transferred to the regions α and β. The pre-rolling guide 17 guides the leading end of the transfer material P so as to come into contact with the secondary transfer roller 10 before entering the region α. The transfer material that has passed through the regions α and β is pressurized and heated by the fixing device 21, whereby the toner image transferred as described above is fixed on the transfer material. On the other hand, the toner remaining on the intermediate transfer belt 8 after the secondary transfer is scraped off from the intermediate transfer belt 8 by the intermediate transfer body cleaning blade 11. The toner scraped off is sent to the waste toner container 14 by the waste toner feeding mechanism 12 and stored therein.

  Here, the dimensions and materials of the main members constituting the secondary transfer portion such as the intermediate transfer belt 8 and the secondary transfer roller 10 will be described in detail.

The intermediate transfer belt 8 is stretched by a secondary transfer counter roller 15, a tension roller 9, and a secondary transfer pre-stretching roller 13 which are secondary transfer counter members. The intermediate transfer belt 8 is a single-layer and endless (seamless) resin belt having a thickness of 75 μm, a circumferential length of 1115 mm, and a length in the longitudinal direction (image forming width direction) of 310 mm. The intermediate transfer belt 8 is adjusted in electric resistance by dispersing carbon in a polyimide material which is a main material of the belt. The volume resistivity of the intermediate transfer belt 8 was 10 ⁹ Ω · cm as a result of measurement using an R8340 ultrahigh resistance meter (registered trademark) manufactured by Advantest, and the surface resistance was 10 ¹² Ω / □ or more. It was. The volume resistivity of the intermediate transfer belt 8 was measured according to JIS-K6911. During the measurement, conductive rubber having a low resistance value was sandwiched between the measurement electrode and the surface of the belt 8. This is to stabilize the contact between the electrode and the intermediate transfer belt 8. Then, the volume resistivity of the intermediate transfer member belt 8 was measured under the condition of 100 V for 10 seconds. Note that the measured values were the same whether measured from the front or back of the intermediate transfer belt 8.

  The secondary transfer counter roller 15 is a roller that stretches the intermediate transfer belt 8 and has a function as a counter roller of the secondary transfer roller 10 and a function as a drive roller. Further, the secondary transfer counter roller 15 is grounded, and can form a transfer electric field with the secondary transfer roller 10. The secondary transfer counter roller 15 is obtained by coating a core metal having a diameter of 30 mm with an EPDM rubber whose resistance is adjusted with carbon black with a thickness of 500 μm.

  The tension roller 9 is an aluminum hollow tube having a diameter of 30 mm, has springs at both end bearing portions, and stretches the belt with a total pressure of 40N. The secondary transfer prestretching roller 13 is a stainless steel roller having a diameter of 14 mm, and is driven to rotate by the intermediate transfer belt 8.

  The secondary transfer roller 10 is a roller that forms three layers on a core metal having a diameter of 12 mm. FIG. 4 shows a cross-sectional view. An elastic body (elastic layer 10b) is coated on the cored bar 10a with a foamed hydrin rubber having a thickness of about 4 mm from the cored bar side so as to have a diameter of 20 mm over 310 mm, and a solid hydrin rubber having a thickness of about 1 mm is formed thereon. Constructed (coating layer 10c). Further, a urethane coating in which powdery PVDF (polyvinylidene fluoride) of about 20 microns is dispersed is applied thereon. The surface of the secondary transfer roller 10 is smooth due to the layer configuration and the coating of the fluorinated compound. In order to smooth the surface, it is also useful to use a silicone coat (coat with a siloxane compound). Even if the edge of the transfer material P hits, it is so smooth that the edge can slide on the surface of the secondary transfer roller 10. When the surface property of the secondary transfer roller 10 was measured with a contact angle using pure water, the contact angle θ was 100 °. Even if the surface was contaminated by durability, a contact angle of 60 ° or more could be secured. The contact angle θ of the secondary transfer roller 10 is measured by dropping about 3 ml of pure water on the surface of the secondary transfer roller and measuring the contact angle of pure water at the contact point between the pure water and the secondary transfer roller with a microscope. And measured. FIG. 3 shows the definition of the contact angle θ. In addition, the contact angle meter CA-X type of Kyowa Interface Science Co., Ltd. was used for the measurement. The secondary transfer roller 10 has an Asker-C hardness of 35 ° under a 500 g load. The secondary transfer roller 10 preferably has an Asker-C hardness of 45 ° or less. This is because the regions α and β are surely formed and the transfer material P is stably conveyed.

The so-called actual resistance value of the secondary transfer roller 10 is 10 ⁷ Ω. This resistance value measurement method is the result of measurement using an R8340 ultrahigh resistance meter (registered trademark) manufactured by Advantest while the roller to be measured is driven and rotated with respect to an aluminum cylinder having a diameter of 30 mm. The measurement conditions were applied voltage: 2 kV, application time: 30 seconds, contact pressure: 9.8 N, rotational peripheral speed of the secondary transfer roller 10; 190 mm / sec.

  Next, the path along which the transfer material P is conveyed to the regions α and β will be described. The transfer material P conveyed by the pre-transfer conveyance roller 18 is guided by the pre-transfer guide 17, and the front end of the transfer material P first contacts the secondary transfer roller 10. As described above, since the secondary transfer roller according to the present embodiment has good surface slipperiness, the leading edge of the transfer material P is conveyed and guided so as to slide on the surface of the secondary transfer roller 10. In the region α. With this configuration, the transfer material P can enter the first region α without contacting the intermediate transfer belt 8. The transfer material P is conveyed to the second region β, which is the transfer nip portion, while maintaining sufficient adhesion to the intermediate transfer belt 8 in the first region α, which is the nip portion immediately before transfer. It becomes.

  Note that when the slipperiness of the secondary transfer roller surface is poor, the leading edge (tip edge) of the transfer material P and the secondary transfer roller 10 are easily caught. Then, the resistance when the transfer material P comes into contact with the secondary transfer roller 10 disturbs the behavior of the front end of the transfer material P, and the front end of the transfer material P comes into contact with the toner image on the intermediate transfer belt 8 to display the image. It will be disturbed. Therefore, as described above, the slipperiness of the surface of the secondary transfer roller was ensured, and the transfer material immediately after the transfer material tip contacted the secondary transfer roller 10 stably entered the region α.

  As described above, the leading edge of the transfer material P prevents the contact of the leading edge of the transfer material P with the toner image on the intermediate transfer belt 8 before entering the first region α by the above behavior. be able to. This has the effect of suppressing certain image defects. The image defect occurs when the leading edge of the transfer material P scrapes off the toner image carried on the intermediate transfer belt 8. This is a phenomenon in which the front end portion of the transfer material P contacts the toner image on the intermediate transfer belt 8 before entering the nip region, and the toner image to be transferred is scraped off. This phenomenon causes two image defects, that is, an image defect due to the toner image being cut off itself and an image defect due to the tip of the transfer material P being stained with toner.

  The mechanism by which the above-mentioned image defect occurs will be further described in detail. The image forming apparatus as shown in the background art is configured such that the transfer material first contacts the toner image on the intermediate transfer belt at a predetermined position on the intermediate transfer belt. In this configuration, the image defect occurs depending on the transfer speed control of the transfer material and the setting of the entrance angle of the transfer material to the intermediate transfer belt. This time, as an easy-to-understand case, a case where the position where the transfer material contacts the intermediate transfer belt is shifted to the upstream side in the moving direction of the intermediate transfer belt will be described.

  The contact of the transfer material on the upstream side in the moving direction of the intermediate transfer belt means that the transfer material bypasses the path that is originally transported. When the transfer material detours and contacts the intermediate transfer belt, the intermediate transfer belt and the transfer material are moved, and therefore the toner image on the intermediate transfer belt precedes the detoured transfer material. Then, the tip of the transfer material comes into contact with the rear side in the moving direction of the intermediate transfer belt from the position where the tip of the transfer material is supposed to come into contact. Further, when the transfer material tip moves to the transfer nip while being in contact with the secondary transfer belt, the transfer material tip scrapes the toner image on the intermediate transfer belt while the intermediate transfer belt and the transfer material reach the transfer nip. become. This is because when the transfer material reaches the transfer nip, the relative position between the transfer material and the toner image on the intermediate transfer belt is a predetermined position, and the detour path is eliminated. In other words, the transfer material and the toner image on the intermediate transfer belt that are in contact with each other are misaligned. In the movement process, the posture of the transfer material is corrected and the misalignment is gradually eliminated. This is because the tip of the toner scrapes the toner image on the intermediate transfer belt.

  On the other hand, in the image forming apparatus according to the present embodiment, the leading end of the transfer material P conveyed so as to slide on the secondary transfer roller 10 is introduced into the region α without contacting the intermediate transfer belt 8. The image defect like this does not occur. This is particularly the case where a toner image is formed up to the edge of the transfer material (image formation with a small leading edge margin and image formation without a margin (hereinafter also referred to as “edgeless image”). In the case of transferring to the transfer material P), the effect appears remarkably. This is because the toner image near the tip of the transfer material is not disturbed during the transfer process. In the image forming apparatus of the present embodiment, it is possible to form a toner image neatly up to the edge of the transfer material P.

  Next, the conveyance speed of the transfer material P will be described. As for the transfer speed of the transfer material P, when the transfer speed of the transfer material P in the region β is 100%, the transfer speed of the transfer material P by the pre-secondary transfer roller 18 is set to 101%. . The following effects are exhibited by this speed relationship. When a certain transfer material P is in the regions α and β and is nipped by the secondary transfer conveyance roller 18, a slight loop of the transfer material P is formed between the regions α and β and the secondary transfer conveyance roller 18. Is done. By forming this loop, the transfer material P entering the region α is conveyed without being pulled by the pre-secondary transfer conveyance roller 18. This means that the transfer material P that has entered the region α is stably transported along with the movement of the intermediate transfer belt 8 in the transport process. In the transport process, the transfer material P is moved to the position of the intermediate transfer belt 8. It is possible to deter large deviations. That is, it is difficult for the toner image to shift on the transfer material P, and more stable transfer is realized.

  Next, the configuration of the regions α and β will be described in detail.

  A secondary transfer voltage of about 2 kV is applied to the metal core of the secondary transfer roller 10 from a secondary transfer bias power source (not shown) via a power supply spring. The core of the secondary transfer counter roller 15 is grounded, and a transfer electric field is formed between the secondary transfer roller 10 and the secondary transfer counter roller 15. This transfer electric field is mainly formed in the region β in FIG. As shown in FIG. 1, the secondary transfer roller 10 is offset with respect to the secondary transfer counter roller 15 in the upstream in the belt moving direction. Further, a secondary pre-transfer stretching roller 13 is disposed upstream of the rollers 10 and 15 in the belt moving direction. The first region α and the second region β are formed by the arrangement of these rollers. The second area β is an area where both the secondary transfer roller 10 and the secondary transfer counter roller 15 are in contact with the front and back of the intermediate transfer belt 8. The first area α is a nip area where the transfer material P is nipped and conveyed by the intermediate transfer belt 8 and the secondary transfer roller 10 from the upstream side of the belt movement direction with respect to the second area β. By providing the area α in front of the area β, in the present embodiment, “scattering of toner and“ transfer omission ”due to discharge are suppressed, and the transfer quality of the toner image is improved. In the region α, the intermediate transfer belt 8 and the transfer material P are in close contact with each other, and the region β is reached in the close contact state. Therefore, the “scattering” and “transfer omission” are suppressed, and the image quality is maintained high.

  If the leading edge of the transfer material P is introduced into the transfer nip without sufficient adhesion to the intermediate transfer belt 8, so-called “toner scattering or“ transfer omission ”due to discharge occurs. become. The configuration of the present embodiment suppresses these.

  “Toner scattering” is a phenomenon in which toner in an image portion (portion where toner exists) of a toner image formed on a transfer material P spreads. For example, this is a phenomenon in which a line drawing of characters or the like is blurred.

  The mechanism of “toner scattering” will be described below. If the leading edge of the transfer material P is introduced into the transfer nip without obtaining sufficient adhesion between the transfer material P and the intermediate transfer belt 8, the transfer is performed with a gap between the transfer material P and the intermediate transfer belt 8. A transfer electric field is generated between the material P and the intermediate transfer belt 8. The toner tends to move from the intermediate transfer belt 8 to the transfer material P in accordance with the transfer electric field. Then, since there is a gap between the intermediate transfer belt 8 and the transfer material P, the toner flies between them, that is, the gap moves a long distance for the toner, and the movement of the toner becomes unstable. Further, the toner has a constant charge and tends to repel electrostatically between the toners. Therefore, the presence of the gap causes a phenomenon that the toner spreads during the transfer process. This phenomenon leads to “scattering of toner”.

  “Transmission omission” due to electric discharge is an image defect due to electric discharge, and is often accompanied by a so-called electric discharge pattern. In particular, the pattern tends to appear on the halftone image.

  The mechanism of “transfer loss” due to electric discharge will be described below. As described above, when the intermediate transfer belt 8 and the transfer material P enter the transfer nip without being in close contact with each other, a transfer electric field is generated in the gap. When the transfer electric field in the gap exceeds the Paschen's law, discharge occurs in the gap, and the charge polarity of the toner near the gap is reversed. The polarity of the negatively charged toner is reversed and becomes a positive polarity. As a result, the toner whose charge has been reversed reverses the direction of the original movement in the transfer process, and does not arrive at the transfer material P. The portion where the toner does not move is in a state where the toner image is missing, resulting in “transfer missing”. This is the formation mechanism of “transfer omission” due to electric discharge.

  The image forming apparatus shown in the present embodiment has the region α, and reaches the region β in a state where the intermediate transfer belt 8 and the transfer material P are in close contact with each other. Therefore, the “toner scattering” and “transfer omission” are caused. It is suppressed and the image quality is maintained high.

  As described above, the transfer speed of the transfer material P by the pre-secondary transfer transport roller 18 is higher than the transfer speed of the transfer material P in the area β. The transfer material P is transported without being pulled by the transport roller 18 before secondary transfer. The movement of the transfer material P at the time of transfer can be stabilized over the entire area of the transfer material, and the close contact state between the recording material P and the intermediate transfer belt 8 is maintained. “Transfer omission” can be suppressed.

(Example 2)
An image forming apparatus according to the second embodiment will be described. Since the schematic configuration of the entire image forming apparatus is substantially the same as that of the above-described embodiment, only the configuration different from that of the above-described first embodiment will be described here. In the first embodiment described above, the configuration having the elastic body having a three-layer structure on the core metal is exemplified as the secondary transfer roller including two or more layers. However, in the second embodiment, the secondary transfer roller is illustrated. Is a two-layer structure. Hereinafter, the configuration and material of the secondary transfer roller will be described.

  The secondary transfer roller according to this embodiment has a two-layer structure, and a layer other than the surface layer is an elastic body having an Asker-C hardness of 45 ° or less. Specifically, in the secondary transfer roller having a two-layer structure, the base layer is a foamed rubber (elastic body) made of a blend rubber of epichlorohydrin and NBR, and the base layer portion has a hardness (base layer + core metal hardness). Asker-C hardness under a load of 500 g is 30 °.

  The surface layer is formed of a resin tube. The foam rubber is covered with a tube. The resin tube forming the surface layer of the secondary transfer roller is a resin tube having a thickness of 70 μm. In the present embodiment, a resin having high slipperiness with respect to the transfer material is selected as the resin tube forming the surface layer. Specifically, PVDF (polyvinylidene fluoride) whose resistance is adjusted with carbon black is used as the resin tube forming the surface layer. However, the present invention is not limited to this. For example, a tube using other resins such as polyimide, polycarbonate, polyester, polypropylene, and polyethylene terephthalate may be used.

  As described above, the secondary transfer roller according to this embodiment has a contact angle (contact angle of pure water) of the roller surface of 70 ° by covering with a resin tube having a high surface slipperiness.

  The resin tube forming the surface layer of the secondary transfer roller is coated with the foamed rubber of the base layer being compressed and deformed. The resin tube is fixed between the base layer and the surface layer by a clamping force. If a deviation or the like occurs between the surface layer and the base layer, an adhesive layer may be provided.

  In the case of a secondary transfer roller having a surface layer coated with a resin tube, there is a concern that the hardness of the roller surface becomes high. When used as a secondary transfer roller, if the hardness is too high, there is a problem that transferability and transferability of the transfer material are not stable. According to the experiment results of the present inventors, it is desirable that the hardness of the secondary transfer roller be 45 ° or less in order to obtain a stable nip at the secondary transfer portion and a stable transfer material transportability.

  Therefore, the present inventor has set the thickness of the resin tube covering the foamed rubber having an Asker-C hardness of 30 ° under a load of 500 g to 70 μm and the Asker-C hardness of the secondary transfer roller to 37 °. .

  In addition, when the hardness measurement which covered the resin tube made from PVDF with different thickness was performed, when the thickness [μm] of the resin tube is 30, 70, 150, 250, the Asker-C hardness of the entire roller is They were 34, 37, 45, and 49, respectively.

  As described above, by selecting a resin having a high surface slipperiness for the resin tube on the surface layer, the same effect as that of the first embodiment described above can be obtained, and a good image can be obtained.

(Example 3)
An image forming apparatus according to the third embodiment will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the configuration around the secondary transfer portion. Since the schematic configuration of the entire image forming apparatus is substantially the same as that of the above-described embodiment, only the configuration different from that of the above-described first embodiment will be described here.

  The image forming apparatus of the present embodiment has a mode “borderless image forming mode” in which a toner image is formed on the transfer material P without a blank space.

  In the image forming apparatus according to the present embodiment, the size of the transfer material is larger by 3 mm in the front-rear and left-right directions so that the toner image is formed up to the edge of the transfer material P even when the transfer timing of the transfer material P is shifted. A toner image was formed on the intermediate transfer belt 8. For this reason, the protruding toner that could not be transferred onto the transfer material P from the intermediate transfer belt 8 during the secondary transfer is directly transferred onto the secondary transfer roller 23.

  Therefore, in the present embodiment, a transfer member cleaning unit that removes the toner adhering to the secondary transfer roller 23 is provided. Specifically, as shown in FIG. 5, the transfer member cleaning means includes a cleaning blade 22 that contacts the secondary transfer roller 23 and writes off the toner. The cleaning blade 22 is made of urethane rubber, and is brought into contact with the secondary transfer roller 23 in a range of linear pressure of 20 to 100 g / cm. The toner scraped off by the cleaning blade 22 is stored in the waste toner container 19.

  Since the secondary transfer roller 23 according to the present embodiment is excellent in slipperiness similarly to the secondary transfer roller 10 according to the first embodiment described above, the toner can be easily removed. For this reason, the surface of the secondary transfer roller 23 has good cleaning properties. As the production process, the secondary transfer roller 23 is foamed in a cylindrical container to shape the elastic layer. During the shaping, a so-called skin layer is formed as a result in a portion that comes into contact with the cylindrical container, and the surface is a roller on which foamed cells do not appear.

  Further, according to the experiment results of the present inventors, by keeping the contact angle on the surface of the secondary transfer roller at 70 ° or more, there was little adhesion of water even in a high humidity environment, and stable cleaning could be realized. This is because the catching between the cleaning blade 22 and the secondary transfer roller 23 can be reduced.

  Furthermore, in this embodiment, the ten-point average roughness Rz of the surface of the secondary transfer roller 23 is 3 μm. This is because the toner can be more reliably cleaned by making Rz smaller than the toner particle diameter. This prevents the toner from slipping through the cleaning blade 22 to cause a cleaning failure.

  As described above, according to the present embodiment, the secondary transfer roller 23 is cleaned when an image having no margin is recorded on the transfer material by forming an image larger than the size of the transfer material on the intermediate transfer belt. Made possible. Further, the same effect as that of the first embodiment described above can be obtained.

  In the present embodiment, the cleaning means of the secondary transfer roller 10 is a blade, but the present invention is not limited to this, and other physical cleaning means such as a brush and a web, or secondary transfer, for example. You may employ | adopt the electrostatic cleaning means to which a cleaning roller etc. which can apply a bias to a roller contact | abut, and to collect | recover.

  In the above-described embodiment, four image forming units are used to form a color image. However, the number used is not limited, and may be set as needed. The image forming apparatus is not limited to a color image forming apparatus, and may be an image forming apparatus that forms a monochrome image.

  In the above-described embodiment, the printer is exemplified as the image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus may be another image forming apparatus such as a copying machine or a facsimile machine, or another image forming apparatus such as a multi-function machine combining these functions. An effect can be obtained.

  Moreover, while various embodiments of the invention have been shown and described, the spirit and scope of the invention are not limited to the specific descriptions and figures within the specification. For example, it goes without saying that the present invention can also be applied to a case where the image is directly transferred from a photoconductor to a transfer material.

1 is a schematic configuration diagram illustrating a secondary transfer unit of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the contact angle ((theta)) of the pure water of the transfer roller surface. It is a schematic block diagram which shows the secondary transfer part of the image forming apparatus which concerns on 3rd Example of this invention. 1 is a schematic configuration diagram illustrating a secondary transfer roller 10 of an image forming apparatus according to a first embodiment of the present invention.

Explanation of symbols

8 Intermediate transfer belt (intermediate transfer member)
10 Secondary transfer roller (transfer member)
10a Metal core 10b Elastic layer 10c Covering layer 15 Secondary transfer opposing roller (opposing member)
17 Pre-transfer guide (guide member)
18 Pre-secondary transfer conveyance roller (conveyance member)
22 Cleaning blade (cleaning member)
23 Secondary transfer roller (transfer member)

Claims (18)

An image carrier that carries a toner image, a transfer member that forms a nip with the image carrier, and that transfers a toner image to a transfer material that enters the nip, and a leading edge in the transport direction of the transfer material are connected to the nip. A guide member that guides the front end of the transfer material to contact the surface of the transfer member before entering
The image forming apparatus, wherein the transfer member has a foam layer and a cover layer, and the cover layer is not foamed and constitutes a surface of the transfer member.   The image forming apparatus according to claim 1, wherein the coating layer is formed of a resin tube.   The image forming apparatus according to claim 1, wherein the coating layer is coated with a fluorinated compound. An image carrier that carries a toner image, a transfer member that forms a nip with the image carrier, and transfers a toner image to a transfer material that enters the nip, and a leading edge in the conveyance direction of the transfer material is formed in the nip A guide member that guides the leading edge of the transfer material so as to contact the transfer member before entering, and the transfer member guides the leading edge of the transfer material to the nip.
2. The image forming apparatus according to claim 1, wherein the transfer member has a foam layer, and a recess of the foam cell does not appear on a surface of the transfer member that contacts the transfer material.   The image bearing member has a transfer facing member that contacts a surface opposite to the surface on which the nip is formed and forms a transfer electric field with the transfer member. 5. The image forming apparatus according to claim 1, wherein a most upstream position of the nip is located upstream of a most upstream position of a contact area between the transfer facing member and the image carrier. . An image carrier that carries a toner image, a transfer member that forms a nip with the image carrier, and that transfers a toner image to a transfer material that enters the nip, and a side opposite to the transfer member with respect to the image carrier And a transfer counter member that forms a transfer electric field between the transfer member and the transfer member so that the front edge of the transfer material contacts the transfer member before the front edge of the transfer material enters the nip. In an image forming apparatus having a guide member for guiding
An image forming apparatus, wherein the most upstream position of the nip is upstream of a most upstream position in a region where the transfer facing member and the image carrier are in contact with each other in a transfer material transport direction.   The image forming apparatus according to claim 1, wherein a leading edge of the transfer material enters the nip without previously contacting the image carrier.   8. The apparatus according to claim 1, further comprising a mode in which a toner image larger than a transfer material is formed on the image carrier and a part of the toner image on the image carrier is transferred to the transfer material. The image forming apparatus according to claim 1.   9. The image forming apparatus according to claim 1, further comprising a photoconductor that carries a toner image, wherein the image carrier is an intermediate transfer body that receives a transfer of the toner image from the photoconductor. Image forming apparatus. An image carrier that carries a toner image, an intermediate transfer member that receives the transfer of the toner image from the image carrier, a nip formed with the intermediate transfer member, and the toner image is transferred to a transfer material that enters the nip In the image forming apparatus, comprising: a transfer member; and a guide member that guides the transfer material so that the leading edge of the transfer material contacts the transfer member before the leading edge of the transfer material enters the nip.
The image forming apparatus, wherein the transfer member is coated with a fluorinated compound on a surface with which a leading edge of the transfer material contacts. An image carrier that carries a toner image, an intermediate transfer member that receives the transfer of the toner image from the image carrier, a nip formed with the intermediate transfer member, and the toner image is transferred to a transfer material that enters the nip In the image forming apparatus, comprising: a transfer member; and a guide member that guides the transfer material so that the leading edge of the transfer material contacts the transfer member before the leading edge of the transfer material enters the nip.
The image forming apparatus, wherein the transfer member is coated with a siloxane compound on a surface that contacts the leading edge of the transfer material.   12. The image forming apparatus according to claim 10, wherein the leading edge of the transfer material enters the nip without previously contacting the intermediate transfer member.   The intermediate transfer member has a transfer counter member that contacts a surface opposite to the surface on which the nip is formed and forms a transfer electric field between the intermediate transfer member and the transfer material in the conveyance direction of the transfer material. 13. The image forming apparatus according to claim 10, wherein a most upstream position of the nip is upstream of a most upstream position of a contact region between the transfer facing member and the intermediate transfer member. .   14. The apparatus according to claim 10, further comprising a mode in which a toner image larger than a transfer material is formed on the intermediate transfer member, and a part of the toner image on the intermediate transfer member is transferred to the transfer material. The image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, wherein the transfer member has an Asker-C hardness of 45 degrees or less.   The image forming apparatus according to claim 1, wherein the transfer member is a roller capable of transporting a transfer material.   2. The apparatus according to claim 1, further comprising a conveying member that conveys the transfer material to the guide member, wherein a speed at which the conveying member conveys the transfer material is faster than a speed at which the transfer member conveys the transfer material. The image forming apparatus according to claim 16.   18. The image according to claim 1, further comprising a cleaning member that contacts the transfer member, wherein the cleaning member removes toner attached to the transfer member from the transfer member. Forming equipment.

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