JP2010049276A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which includes an image forming section for forming a tracking pattern for preventing improper use in an unfixed state on the circumference of an image part in the unfixed state, and forms a high-quality stable image. <P>SOLUTION: In heating by a selective heat source having low resolution, the tracking pattern p by yellow toner or the like is formed only on the circumference of the image part. The formation of the tracking pattern p is preferable from the view of saving energy. In addition, the formation of the tracking pattern p is effective not only in a secondary transfer system in fixing, but also in all fixing systems which are low in resolution and perform selective heating. In other words, even when the tracking pattern p is used for preventing illegal use, the tracking pattern p is formed only on the circumference of the image part f, so that the effect of the selective heating is improved to satisfy both of saving the energy and preventing the illegal use. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine or a printer.

  Generally known as a fixing device used in an electrophotographic image forming apparatus is a fixing device in which unfixed toner transferred onto a recording medium such as paper is nipped and conveyed together with the recording medium and is fixed on the recording medium by heating. Yes. In particular, there is known an image transfer member such as a photosensitive member, which is further transferred to a recording medium via an intermediate transfer member such as an intermediate transfer belt. In each transfer step in such an image forming apparatus, the quality of the transferred image is affected by the image stability due to the difference in the conveyance speed of the unfixed image, the humidity and thickness of the recording medium, the surface roughness, etc., and the stability of the transfer. It is known.

  Therefore, a technique has been proposed in which the toner on the intermediate transfer member is directly heated and pressed on the recording medium to fix it at the same time as the transfer. For example, there is a technique in which toner is heated by contact heating from an inner peripheral surface by a heating member in which an intermediate transfer member is stretched on the inner peripheral surface (see, for example, Patent Documents 1 and 2).

  In addition, the inventors of the present application have also proposed a secondary transfer method on fixing in which the toner is not heated on the intermediate transfer member but is further transferred onto the fixing member from the intermediate transfer member, and then the toner is heated from the outside. ing.

  However, in the technique disclosed in the above-mentioned patent document, the toner on the intermediate transfer member is heated by heating the intermediate transfer member, which is rotated and conveyed from the inner peripheral surface of the intermediate transfer member, at any time in contact with the heating member. Thus, since the toner is heated via the intermediate transfer member, the entire area of the intermediate transfer member becomes high temperature, and it takes time to cool down until it comes into contact with the image carrier that is the developing unit. In order to obtain such a cooling effect, it is necessary to increase the circumference of the intermediate transfer member, which leads to an increase in the size of the apparatus. Further, when a cooling member is added in order to obtain a cooling effect, the component cost increases. Furthermore, the need for time to heat the intermediate transfer member to a predetermined temperature increases the rise time of the apparatus.

  Further, the conveyed intermediate transfer member is heated as needed, and the plurality of recording media to be transferred is also heated, but this energy is disadvantageous for energy saving. The heat radiation from the heating member and the intermediate transfer member heated to a high temperature raises the temperature inside the image forming apparatus, and there is a concern that a defective image may be generated due to toner fusion or the like on the image carrier. .

  Also in the secondary transfer system for fixing, there is a point that the fixing member in the non-image area where there is no toner is heated more strongly than the part where the toner is present, and the intermediate transfer body is heated when contacting the intermediate transfer body. Since the temperature rise of the intermediate transfer member is slight, there is no situation that damages the toner or the photosensitive member between the transfer to the fixing and the next transfer from the photosensitive member to the intermediate transfer member. However, even if the temperature rises slightly, if this energy is accumulated, a large loss occurs.

  In order to solve the above-mentioned problems, an object is to selectively heat only an unfixed image portion to suppress an increase in an intermediate transfer member, a fixing member, and an in-machine temperature, and to provide a stable image with high image quality. However, in order to heat the toner, non-contact heating means must be the center. For this reason, it is necessary to use a toner containing an infrared absorbent in order to easily absorb the radiant energy, and the vivid color and the color reproduction range may be limited. In this technique, selective heating by contact heating, for example, heating with a heating member in contact with the fixing roller may be considered. However, in this case, there arises a problem that the surface of the fixing roller is easily worn.

  In order to solve these problems, the present invention proposes a technique for selectively heating an image corresponding portion on the recording medium side, instead of heating only the toner, the intermediate transfer member, and the fixing member.

An image forming apparatus according to a first aspect of the present invention includes an image forming unit that forms an unfixed image portion, and a heating unit that heats the unfixed image portion formed by the image forming unit. And
The image forming unit is an image forming unit that forms a tracking pattern for preventing unauthorized use in an unfixed state around the image unit in an unfixed state,
The heating unit is a heating unit that heats the unfixed image portion and the unfixed tracking pattern formed by the image forming unit.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the heating unit contacts and heats the transfer body onto which the unfixed image portion formed by the image forming portion is transferred. It is a heating means.

  According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the heating unit is in contact with a recording medium located at a portion corresponding to the unfixed image portion formed by the image forming portion. It is a heating means for heating.

  The intermediate transfer device, the fixing device, and the image forming apparatus according to the present invention suppress the increase in the temperature of the intermediate transfer member, the fixing member, and the apparatus by selectively heating only the unfixed image portion, and provide a stable image with high image quality. Can be provided.

FIG. 1A is a schematic diagram illustrating a first embodiment of an image forming apparatus according to the present invention, and FIG. The figure which shows the temperature distribution image of the intermediate transfer body 1 at the time of irradiation of light energy Schematic showing an example in which the first embodiment is applied to an image forming apparatus that outputs a monochrome image Sectional drawing of the principal part which shows the modification which replaced with the laser light source in Example 1, and used the flash lamp Schematic showing an image forming apparatus according to a second embodiment of the present invention. Schematic diagram showing Embodiment 3 of the image forming apparatus according to the present invention. Schematic showing Embodiment 4 of the image forming apparatus according to the present invention. Sectional drawing which shows the modification of Example 4 Schematic showing Embodiment 5 of the image forming apparatus according to the present invention. Schematic diagram showing Embodiment 6 of the image forming apparatus according to the present invention. Schematic showing Embodiment 7 of the image forming apparatus according to the present invention. Schematic showing an image forming apparatus according to an eighth embodiment of the present invention. Diagram showing other means that can be selectively heated The figure which shows the further means which can be heated selectively Schematic (A) and partial plan view (B) showing an embodiment 9 of the image forming apparatus according to the present invention. Sectional drawing which shows the irradiation part of the laser beam in Example 9 Schematic showing an image forming apparatus according to a tenth embodiment of the present invention. Schematic showing Embodiment 11 of the image forming apparatus according to the present invention. Schematic showing Embodiment 12 of the image forming apparatus according to the present invention. Diagram showing tracking pattern Diagram showing structure of infrared absorber

  The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings. In the following, a plurality of embodiments of the present invention will be described. However, in the second and subsequent embodiments, the description of the configuration, transfer, fixing process, operation, and effect common to the first embodiment will be omitted. The present invention does not heat the toner, the intermediate transfer member, and the fixing member, but selectively heats the image-corresponding portion on the recording medium side. However, the present invention is not limited unless the toner, the intermediate transfer member, and the fixing member are heated. . Although an image forming apparatus for forming a color image will be described as an example, the present invention includes a case where the image to be formed is a monochrome image. In addition, the intermediate transfer device, the fixing device, and the image forming device can be configured in various forms such as those configured as a single device, or configured as a unit in combination with other devices and means. The present invention is not limited to the illustrated form.

<Example 1>
1A and 1B are a schematic view (A) and a partial plan view (B) showing an embodiment 1 of an image forming apparatus according to the present invention. In the figure, reference numeral 1 denotes an intermediate transfer member, which has an endless belt-like shape stretched around a driving roller 2 and a fixing roller 3. Yellow (Y) and magenta (M) are located at positions facing the intermediate transfer member 1. , Cyan (C), black (Bk), and four image carriers 7... For forming four color toner images are disposed.

  For the toner used for development, a charged powder or liquid is used. In this embodiment, for example, the toner softening temperature is 100 ° C., and the toner has a sharp melt property using a crystalline polyester resin as a binder resin. Yes, toners other than Bk contain an infrared absorber. If the toner is made into a charm melt (low melting point) and the softening temperature is lowered, the toner 6 can be softened with a small amount of energy, so that the transfer and fixing can be speeded up.

  The image carrier 7 of the image forming unit 10 forms an electrostatic latent image on the surface. Although not shown, the surface of the image carrier 7 is uniformly charged around each image carrier 7. A charging device, an exposure device that irradiates the surface of the image carrier 7 with image light to form a latent image, and a toner image (unfixed image) by selectively transferring toner to the latent image formed on the image carrier 7. And a transfer roller 8 for transferring the toner image on the image carrier 7 onto the intermediate transfer member 1 so as to face the image carrier 7. A voltage necessary for the toner 6 to move is applied to the transfer roller 8 by a bias circuit (not shown).

  The intermediate transfer body 1 is formed by forming a surface layer with good releasability from toner on the surface of an endless belt-like base material, and a driving roller 2 disposed on the inside is rotated by a driving unit (not shown). By rotation, it moves around in the direction of the arrow shown in the circuit diagram. The intermediate transfer body 1 needs to have heat resistance. For example, a polyamide base material coated with PFA fluororesin having a good releasability with a thickness of 10 μm is used as a transparent member.

  The fixing roller 3 has a highly reflective member on the surface layer, and is rotated by the rotation of the intermediate transfer body 1 driven by the driving roller 2. A pressure roller 9 is arranged to face the fixing roller 3 so as to press the intermediate transfer body 1, and the recording medium P is connected to a pressure contact portion between the pressure roller 9 and the intermediate transfer body 1 via a conveyance path (not shown). The toner 6 on the intermediate transfer body 1 is transferred to the recording medium P. The toner on the intermediate transfer body 1 is usually in a layered form, but hereinafter it is simply referred to as toner unless particularly necessary.

  In the figure, reference numeral 4 denotes a laser light source, which is disposed above the fixing roller 3 as a toner heating source, and in the width direction (axial direction) of the fixing roller 3 perpendicular to the conveyance direction of the recording medium P, the toner 6 (unfixed image). And heating selectively in synchronization with Laser light L emitted from the laser light source 4 selectively irradiates the intermediate transfer member 1 at a position where the fixing roller 3 and the intermediate transfer member 1 are in contact with each other on the upstream side of the fixing roller 3. This laser light L is used when information on an exposure unit (not shown) irradiated on the image carrier 7 is used. When there is an unfixed image within a predetermined range of the intermediate transfer body 1 based on this information, irradiation is performed. The control unit of the image forming apparatus (not shown) performs the determination that the image is not performed, and based on the determination result, the irradiation is performed in synchronization with the position of the unfixed image transferred to the intermediate transfer body 1 from the front end position of the recording medium P. . As a result, the temperature of the entire intermediate transfer body 1 is not increased, and the durability of the intermediate transfer body 1 and the fusing and toner blocking due to the heat of the developing portion due to the temperature rise inside the image forming apparatus are prevented, and stable. Can be output.

  The spot diameter of the laser beam L is set to a range that satisfies the predetermined range described above. For example, it is assumed that irradiation is performed at 72 dpi with a range larger than that of a latent image recording pixel of 600 dpi. That is, since the intermediate transfer body 1 is divided into a plurality of parts and heated in a range larger than the minimum resolution in the image recording unit of the image forming apparatus, it is possible to absorb variations in the area where the toner 6 is placed and the heating position accuracy, Stable heating is possible. Irradiating and heating a smaller range with light energy can prevent the intermediate transfer body 1 from rising in temperature. However, the accuracy of the toner position and the heating position is important, and the spot diameter is larger than the latent image recording pixel in consideration of the position accuracy. It is more reliable to irradiate an unfixed image. FIG. 2 is a view showing a temperature distribution image of the intermediate transfer body 1 at the time of irradiation with light energy. In the figure, reference numeral 4a denotes a laser, and 4b denotes a polygon mirror, which scans along the axial direction of the fixing roller 3 using a lens (not shown) and irradiates the laser beam L.

  In the figure, reference numeral 11 denotes a cleaner, which is arranged on the downstream side in the rotational direction of the pressure contact portion between the intermediate transfer body 1 and the recording medium P, and collects the toner that is not transferred to the recording medium P but remains on the intermediate transfer body 1. In contact with the intermediate transfer member 1.

  The transfer and fixing operation of the toner 6 onto the recording medium P will be described. The toner 6 irradiated with the laser light L on the intermediate transfer body 1 is heated and softened, and then is pressed and conveyed while being nipped and conveyed with the recording medium P. 9 is pressed between the fibers of the recording medium P, pressed against the recording medium P, and transferred. Thereafter, the recording medium P is peeled off from the intermediate transfer member 1 having good releasability, and the transfer is completed. At this time, the heat of the toner 6 is absorbed by the recording medium P and is fixed on the recording medium P by solidification due to a temperature drop. Thereafter, the recording medium P is discharged out of the apparatus through a path (not shown).

  In order to perform such an operation, the toner on the intermediate transfer member 1 is positioned near the transfer position so that the time during which the temperature of the heated toner 6 does not decrease, that is, the time until contact with the recording medium P can be shortened as much as possible. 6 is preferably irradiated with laser light L. Further, the range of irradiation with the laser light L is an irradiation that takes into account variations such as the positional accuracy of forming a latent image on each image carrier 7 and the positional accuracy of transferring an image from each color image carrier 7 to the intermediate transfer member 1. By setting the range, it is possible to avoid excessive heating, effectively prevent the intermediate transfer body 1 from being heated, and reduce unnecessary energy for heating the range other than the toner. Note that the unfixed toner 6 on the intermediate transfer body 1 may be read by an optical sensor, and the range to be irradiated with the laser light L may be determined.

  The laser light L irradiated to the area having the toner 6 is absorbed by the toner 6 and heats the toner 6. However, the laser light L irradiated to the other area directly irradiates the intermediate transfer member 1, As described above, since the intermediate transfer member 1 is formed of a transparent material, it passes through the intermediate transfer member 1 and irradiates the fixing roller 3. Since the fixing roller 3 is driven to rotate with the intermediate transfer member 1, it does not irradiate a fixed position, and an uneven temperature rise due to irradiation of the fixed position does not occur. Further, the laser light L is reflected again toward the intermediate transfer member 1 by the high reflection member provided on the surface layer of the fixing roller 3, and the toner 6 is irradiated from the inside of the intermediate transfer member 1. If the intermediate transfer member 1 is made of a transmissive member, the absorption rate of the light energy of the irradiated laser beam L is low, which is effective for preventing the intermediate transfer member 1 from rising in temperature. In any case, since the non-fixed image surface on the intermediate transfer body 1 is heated in a non-contact manner, the toner state is not destroyed and the image quality is stabilized. In addition, the surface temperature of the toner 6 can be increased in advance to lower the heating from the lower intermediate transfer member 1, and the temperature of the intermediate transfer member 1 can be further prevented from rising.

  By being such a path of the laser light L, the laser light L that has passed through the intermediate transfer body 1 does not irradiate other devices and members in the image forming apparatus, and can prevent thermal destruction due to irradiation. Heating of the toner 6 on the intermediate transfer body 1 can be performed from the front and back, and energy can be used effectively. Furthermore, it is good also as a structure which provides a reflection plate or a reflection part in the part corresponding to the path | route of the laser beam L reflected from the back surface, and it reflects again.

  In the above-described embodiment, the structure is such that the roller is a rotating roller in order to reduce the sliding resistance with the intermediate transfer member 1, but the member that supports the intermediate transfer member 1 may be a member that can uniformly contact the recording medium P. What is necessary is just and it is not limited to the example of illustration. It is also effective to use a member that prevents the transmitted laser light L from irradiating other members, for example, a white member, and diffuse the energy by irregularly reflecting the light energy.

  By the way, normally, the Bk toner is excellent in light absorption and is advantageous for heating, but color toners such as Y, M, and C are inferior in light absorption. Therefore, it is preferable to add an infrared absorbent to the toner other than Bk to improve the absorption efficiency of the irradiation energy of the laser light L, which is advantageous for heating. That is, the temperature increase rate of the intermediate transfer member 1 around the toner 6 is increased, and the toner temperature can be increased efficiently, so that transfer and fixing can be speeded up. In addition, due to the effect of the selective heating, it is possible to realize a color image forming apparatus in which the temperature of the entire intermediate transfer member 1 is not increased. Moreover, it is also preferable to make the softening point temperature low by containing crystalline polyester so that it can be sharp-melted and heated with a short irradiation energy.

  When the color toner does not contain an infrared absorber, it is effective to use a member having good light absorption for the intermediate transfer member 1. Since the light absorptivity is good, the heating rate is improved, the periphery of the toner 6 on the intermediate transfer 1 is quickly heated, and this heat can be propagated to the toner 6 and efficiently heated. In this case, since the range in which the toner 6 exists is selectively heated, it is possible to prevent the temperature of the entire intermediate transfer body 1 from rising. However, if the means of the above-described embodiment is employed, it is possible to cope with an increase in recording speed. It is more preferable. For this reason, in an image forming apparatus (for example, see FIG. 3) that outputs a monochrome image of only Bk that is advantageous in light absorption, making the intermediate transfer member 1 transparent is effective in preventing the temperature increase of the intermediate transfer member 1. It is. In this embodiment, the laser light source 4 is used as a heating source. However, it is needless to say that other means capable of selectively heating the range where the toner 6 exists on the intermediate transfer member 1 may be used. For example, means such as a plurality of regularly arranged lamps and heaters may be used. FIG. 4 is a cross-sectional view of an essential part showing a modification using a flash lamp 12 in place of the laser light source 4.

<Example 2>
FIG. 5 is a schematic view showing Embodiment 2 of the image forming apparatus according to the present invention. The intermediate transfer member 21 of the present embodiment is a transparent material obtained by coating a cylindrical glass substrate with a thin layer of PFA fluororesin, for example, 10 μm, and is rotationally driven by a drive source (not shown). The image forming unit 10, the image carrier 7, and the transfer roller 8 similar to those in the first embodiment are similarly arranged around the intermediate transfer member 21, and are arranged at the press contact portion between the pressing roller 9 and the intermediate transfer member 21. The recording medium P is fed through a conveyance path (not shown), and the toner 6 on the intermediate transfer member 21 is transferred to the recording medium P.

  The laser light source 4 is provided on the inner circumference of the intermediate transfer body 21 and is arranged so as to irradiate the laser light L from the inside. The laser light L irradiated from the laser light source 4 is upstream of the rotation direction of the intermediate transfer body 21. On the side, the vicinity of the contact portion with the pressing roller 9 (transfer, fixing portion) is selectively irradiated.

  The heating method and operation of this embodiment will be described. The laser beam L is irradiated from the inner peripheral surface of the intermediate transfer body 1 at the predetermined position described above, the toner 6 is irradiated through the intermediate transfer body 21 made of a transparent member, and the toner is heated. Further, the laser beam L transmitted around the toner 6 irradiates the recording medium P, and the surface layer of the recording medium P is also heated (shaded portion H in the figure). Since the irradiation position of the laser beam L is located near the position where the intermediate transfer body 21 contacts the recording medium P and upstream of the contact position in the rotation direction of the intermediate transfer body 21, the irradiation position of the recording medium P Is a position almost overlapping the unfixed image portion. The portion of the recording medium P irradiated with the laser light L then reaches a position (nip portion) sandwiched between the intermediate transfer member 21 and the pressing roller 9, and the softened toner is pressed by the pressing roller 9 and the fibers of the recording medium P are pressed. Penetration and establishment.

  This process is the same as that in the first embodiment. However, in this embodiment, the toner 6 is heated from the lower layer side, that is, the intermediate transfer member 21 side, and is softened. It becomes easy to transfer to P. In addition, since the corresponding portion of the recording medium P that contacts the toner 6 is also heated as described above, rapid cooling of the toner 6 can be prevented.

  When the toner 6 is rapidly cooled by contact with the recording medium P, the toner 6 is solidified without penetrating into the fibers of the recording medium P, and a binding force with the recording medium P cannot be obtained. There is a possibility that a problem of not transferring to the camera will occur. In order to avoid this, it is necessary to raise the heating temperature of the toner 6 to a sufficiently high temperature, or to increase the pressure on the contact surface and push it between the fibers. When the position corresponding to the toner transfer position on the recording medium P is also heated as in this embodiment, the softened toner easily permeates between the fibers of the recording medium P, and the fixing performance is improved. Therefore, it is not necessary to set the toner temperature so high that the temperature of the intermediate transfer member 21 is prevented from being raised, and light energy is used effectively. Further, the pressure of the pressing roller 9 may be low, and the intermediate transfer member 21 does not require rigidity, so that the thickness can be further reduced. Accordingly, transmission loss of light energy can be reduced, energy to be input can be reduced, and heat capacity and component cost can be effectively reduced.

<Example 3>
FIG. 6 is a schematic view showing Embodiment 3 of the image forming apparatus according to the present invention. Since the configuration of the present embodiment is almost the same as that of the second embodiment, the difference will be described. In this embodiment, the halogen lamp 30 is arranged at a position where the intermediate transfer member 21 and the recording medium P are not in contact with each other in the conveyance direction of the recording medium P, and the irradiation is performed in the axial direction beyond the maximum recording width. The reflector 32 is arranged so that the reflected light is in the direction in which the pressure roller 9 and the intermediate transfer body 1 are in contact with the halogen lamp 30.

  In this embodiment, when the recording medium P is conveyed and reaches a predetermined position, light is irradiated from the halogen lamp 30 in accordance with the passage of the recording medium P, and an unfixed image on the intermediate transfer member 21, that is, the toner 6 is moved to a predetermined position. Is reached, the laser beam L is selectively irradiated to heat the toner 6. By irradiating the halogen lamp 30 and laser light, the intermediate transfer member 21 is heated from the lower layer side and the upper layer side of the toner 6, and the surface layer of the recording medium P is also heated uniformly (shaded portion H in the figure). Thereby, the rapid cooling at the time of contact between the recording medium P and the heated toner 6 is more effectively prevented. Further, since the upper layer surface of the toner 6 in contact with the recording medium P is also heated, the penetration of the toner 6 between the fibers of the recording medium P is further achieved, and the fixing performance is improved. Further, in this embodiment, the pressure of the pressing roller 9 is low, and the intermediate transfer member 21 does not need rigidity, so that it is possible to further reduce the thickness, thus reducing the transmission loss of light energy and reducing the input energy. Thus, it is possible to effectively reduce the heat capacity and component cost.

  Further, since the halogen lamp 30 is irradiated after the toner 6 is conveyed to a predetermined position, only the length corresponding to the recording medium P is heated. Therefore, the intermediate transfer member 21 is not always heated. Further, since a transmissive member is used for the intermediate transfer member 21, the temperature rise of the intermediate transfer member 21 can be suppressed, and the heat capacity is large by contact with the recording medium P at the transfer / fixing portion at the portion irradiated with light. Since the recording medium P absorbs heat and is cooled, the temperature increase of the intermediate transfer member 21 can be further suppressed. Further, since the upper layer of the toner 6 is heated by the lamp halogen lamp 30 and the upper and lower layers are heated by the laser beam of the lower layer of the toner, the heating can be performed for a short time, and the recording speed can be increased.

  Note that the portion of the intermediate transfer body 21 after the toner 6 is transferred is positively brought into contact with a member having a large heat capacity until the portion of the intermediate transfer body 21 is transferred to the image carrier 7, It is more effective if it is cooled by cooling air passing through a road or the like.

<Example 4>
FIG. 7 is a schematic view showing Embodiment 4 of the image forming apparatus according to the present invention. In this embodiment, when a light-transmitting member is used for the intermediate transfer body 1, protective members 22 and 23 are arranged at positions corresponding to the non-heating direction of the intermediate transfer body 1 with respect to the heating area by the laser light source 4. Heat damage of other parts due to light transmitted through the transfer body 1 is prevented.

  If a diffused reflection member is used for the protective members 22 and 23, light energy can be reduced by causing irregular reflection at a portion that receives the transmitted light, and thermal damage can be effectively prevented. Further, if a light reflecting member is used for the protective members 22 and 23, the reflected light from the light reflecting member irradiates the toner 6 again, and the light energy transmitted through the intermediate transfer body 1 is effectively used without loss. it can. In addition, since the light transmitted through the intermediate transfer body 1 can be irradiated with light energy from the non-image portion side (in the example in the figure) on which the toner is not placed, the transmitted light irradiates the recording medium P. It becomes possible. This can heat the recording medium corresponding to the image area, and reduces the difference between the recording medium temperature and the toner temperature, so that rapid cooling when contacted with the recording medium is prevented, thereby preventing the gap between the recording medium fibers. Since it penetrates easily, it is advantageous for fixing property.

  FIG. 8 is a cross-sectional view of a main part showing a modification of the fourth embodiment. In this example, a curved reflecting plate 24 is used, and the reflected light can be efficiently re-incident on a required portion of the intermediate transfer body 1 by the bending of the reflecting plate 24.

<Example 5>
FIG. 9 is a schematic view showing Embodiment 5 of the image forming apparatus according to the present invention. This embodiment has substantially the same configuration as that of the first embodiment, but a halogen lamp 13 is provided in the fixing roller 3 so that the intermediate transfer body 1 can be heated from both sides. In addition, the halogen lamp 13 is configured to heat the whole of the fixing roller 3 in the axial direction in synchronization with the toner 6 that is an unfixed image on the intermediate transfer body 1. In this example, since the intermediate transfer member 1 is not heated in the circumferential direction with respect to the whole, the temperature rise can be suppressed, and the toner 6 on the intermediate transfer member 1 is selectively heated from both sides of the intermediate transfer member 1. Thus, the heating temperature of the entire intermediate transfer member 1 can be lowered.

<Example 6>
FIG. 10 is a schematic view showing Embodiment 6 of the image forming apparatus according to the present invention. The present embodiment also has substantially the same configuration as that of the first embodiment, but a cooling roller 14 is provided on the downstream side of the fixing roller 3 in the moving direction of the intermediate transfer body 1 so that the temperature of the intermediate transfer body 1 can be raised early. In addition, the recording speed can be increased. The cooling roller as in this embodiment can be provided in the other embodiments described above.

<Example 7>
FIG. 11 is a schematic view showing Embodiment 7 of the image forming apparatus according to the present invention. This embodiment is called a secondary transfer system for fixing. Instead of heating the toner 6 on the intermediate transfer body 1, the toner 6 is further transferred from the intermediate transfer body 1 onto the fixing roller 3, The toner 6 on the fixing roller 3 is heated from the outside by a selective non-contact heat source such as a laser light source 4. Since heating is performed close to the fixing nip portion of the fixing roller 3 and on the upstream side in the rotation direction of the fixing roller 3, the heat radiation time from the heated toner 6 can be extremely shortened, and the temperature reduction is very efficient. Can be prevented. The intermediate transfer member 1 is wound around a driving roller 2 and a pair of secondary transfer rollers 3a and 3b, and the secondary transfer rollers 3a and 3b and a fixing roller which is in contact with the intermediate transfer member 1 with the intermediate transfer member 1 interposed therebetween. The secondary transfer of the toner 6 is performed between the toner 3 and the toner 3.

  The transfer and fixing of the toner 6 to the recording medium P in the present embodiment is described above in that control is performed to reduce the heating amount for a portion where there is no unfixed image in a predetermined area as compared with a portion where there is an unfixed image. Similar to the embodiment, the toner 6 is heated and softened by irradiating the fixing roller 3 with the laser beam L, and thereafter, the fiber of the recording medium P is pressed by the pressing roller 9 by being nipped and conveyed with the recording medium P. The toner 6 is infiltrated and pressed between them to fix them. In the primary transfer by the transfer roller 8 and the secondary transfer by the secondary transfer rollers 3a and 3b, a voltage necessary for moving the toner is applied by a bias circuit (not shown).

<Example 8>
FIG. 12 is a schematic view showing Embodiment 8 of the image forming apparatus according to the present invention. This embodiment is also of the secondary transfer type on fixing, and shows an example in which a thermal head 15 is used as a selective heat source in contact with the toner 6 on the intermediate transfer body 1. Although it is difficult to heat the unfixed toner 6 with a contact heat source, in the secondary transfer system for fixing, the toner on the fixing roller 3 is subjected to secondary transfer onto the fixing roller 3 by the secondary transfer rollers 3a and 3b. It is possible to pre-selectively heat the position where the image is to be transferred. Since the toner 6 is always present at the position of the intermediate transfer member 1 where the heated position of the fixing roller 3 contacts, the intermediate transfer member 1 does not contact the high-temperature fixing roller 3 and the temperature of the intermediate transfer member 1 increases. This is because it hardly occurs.

  In Examples 7 and 8 described above, other means capable of selectively heating the range where the toner 6 exists can be used as the heating source. For example, as shown in FIG. 13, a plurality of heaters 17 having filaments 16 are used as selective heat sources, and each heater 17 is turned on and off in synchronization with the image position by a switching circuit 18 to perform selective heating. May be.

  Further, as shown in FIG. 14, a plurality of induction heating coils 16a can be used as selective heat sources, and the induction heating coils 16a can be turned on and off in synchronization with the image position by the high-frequency switching circuit 18a to perform selective heating. Since the fixing roller 3 has a conductive layer near the surface layer, the conductive layer can be heated by an induced current. The induction heating coil 16a can be arranged either inside or outside the fixing roller 3. A plurality of wirings may be switched, but it is also possible to switch the induction heating coil 16a by switching the frequency by adjusting the impedance with a capacitor or the like so that the resonance frequency is different for each induction heating coil 16a (for example, Japanese Patent Laid-Open No. 2003-017237).

<Example 9>
FIG. 15 is a schematic view (A) and a partial plan view (B) showing an embodiment 9 of the image forming apparatus according to the present invention, and FIG. 16 is a cross-sectional view showing a laser beam irradiation mode in this embodiment. Since the basic configuration is the same as that of the first embodiment shown in FIG. 1, the description thereof is omitted, but is different in the following points.

  In this embodiment, a laser light source 4, which is an example of a selective non-contact heat source, is disposed above the fixing roller 3 as a heating source, and the width direction (axial direction) of the fixing roller 3 orthogonal to the conveyance direction of the recording medium P. ), A required portion of the recording medium P is selectively heated in synchronization with the toner 6 (which is an unfixed image).

  Specifically, the laser light L emitted from the laser light source 4 is as close as possible to the position where the fixing roller 3 and the intermediate transfer body 1 are in contact with each other on the upstream side of the fixing roller 3 (upstream side in the conveyance direction of the recording medium P). Then, the recording medium P is selectively irradiated from the surface side. In FIG. 16, the irradiation site is indicated by the symbol A. The laser beam L is irradiated using information on an exposure unit (not shown) that irradiates the image carrier 7. If there is an unfixed image within a predetermined range of the intermediate transfer body 1 from this information, the laser beam L is irradiated and unfixed. The control unit of the image forming apparatus (not shown) determines that irradiation is not performed when there is no image, and synchronizes with the position of the unfixed image transferred from the leading end position of the recording medium P to the intermediate transfer body 1 based on the determination result. Do. That is, irradiation is performed in synchronization with both the main scanning direction and the sub-scanning direction in exposure of the image carrier 7. As a result, the temperature of the entire intermediate transfer body 1 is not increased, and the durability of the intermediate transfer body 1 and the fusing and toner blocking due to the heat of the developing portion due to the temperature rise inside the image forming apparatus are prevented, and stable. Can be output. In addition, since the heating position is in the vicinity of the position where the fixing roller 3 and the intermediate transfer member 1 are in contact with each other and on the upstream side in the rotation direction of the fixing roller 3, the heat radiation time from the heated recording medium P can be extremely shortened. And a temperature drop can be prevented very efficiently.

  The spot diameter of the laser beam L is set to a range that satisfies the predetermined portion A as in the previous embodiment. For example, it is assumed that irradiation is performed at 72 dpi with a range larger than that of a latent image recording pixel of 600 dpi. That is, since the irradiation site A on the surface of the recording medium P is divided into a plurality of parts and heated within a range larger than the minimum resolution in the image recording unit of the image forming apparatus, the area where the toner 6 is placed and the heating position accuracy Variations can be absorbed and stable heating is possible. Irradiating and heating a smaller range with light energy can prevent the intermediate transfer body 1 from rising in temperature. However, the accuracy of the toner position and the heating position is important, and the spot diameter is larger than the latent image recording pixel in consideration of the position accuracy. It is possible to irradiate the required part A more reliably. In addition, the toner 6 approaching the portion A can also be irradiated and heated.

  The transfer and fixing operation of the toner 6 onto the recording medium P will be described. The toner 6 is heated in contact with the irradiated portion A of the heated recording medium P irradiated with the laser light L. Of course, since the laser beam L may be directly irradiated, it is also heated. Then, after being softened by heating, while being sandwiched and conveyed with the recording medium P, it is infiltrated between the fibers of the recording medium P by the pressure of the pressing roller 9, and is pressed against and transferred to the recording medium P.

  In order to perform such an operation, the time during which the temperature of the portion A of the heated recording medium does not decrease, that is, the time until contact with the toner 6 can be shortened as much as possible (for example, 10 to 100 milliseconds). As described above, it is preferable to irradiate the recording medium P with the laser light L at a position near the transfer position. Further, the range of irradiation with the laser light L is an irradiation that takes into account variations such as the positional accuracy of forming a latent image on each image carrier 7 and the positional accuracy of transferring an image from each color image carrier 7 to the intermediate transfer member 1. By setting the range, excessive heating can be avoided, the temperature of the intermediate transfer body 1 can be effectively prevented from being raised, and unnecessary energy for heating the range other than the irradiated portion A can be reduced. Note that the unfixed toner 6 on the intermediate transfer body 1 may be read by an optical sensor, and the range to be irradiated with the laser light L may be determined.

  The laser light L irradiated to the area having the toner 6 is absorbed by the toner 6 and heats the toner 6, but the laser light L irradiated to the other area directly irradiates the recording medium P. However, since the intermediate transfer body 1 is formed of a transparent material as described above, the laser light L leaked to the intermediate transfer body 1 is transmitted therethrough to irradiate the fixing roller 3. Since the fixing roller 3 is driven to rotate with the intermediate transfer member 1, it does not irradiate a fixed position, and an uneven temperature rise due to irradiation of the fixed position does not occur. Further, the laser light L is reflected again toward the intermediate transfer member 1 by the high reflection member provided on the surface layer of the fixing roller 3, and the toner 6 is irradiated from the inside of the intermediate transfer member 1. If the intermediate transfer member 1 is made of a transmissive member, the absorption rate of the light energy of the irradiated laser beam L is low, which is effective for preventing the intermediate transfer member 1 from rising in temperature. In any case, since the non-fixed image surface on the intermediate transfer body 1 is heated in a non-contact manner, the toner state is not destroyed and the image quality is stabilized. In addition, the surface temperature of the toner 6 can be increased in advance to lower the heating from the lower intermediate transfer member 1, and the temperature of the intermediate transfer member 1 can be further prevented from rising.

<Example 10>
FIG. 17 is a schematic view showing Embodiment 10 of the image forming apparatus according to the present invention. In this embodiment, a laser beam that is a heating source in the ninth embodiment is used as a resistance heating element that is in contact with or very close to the recording medium P, for example, the well-known thermal head 15. In the experiment conducted by the inventors of the present application, even when a thermal head is used, heating at a position as close as possible to the transfer position of the toner 6 resulted in excellent thermal efficiency. This is presumably because the toner 6 is pressed against the recording medium P without lowering the temperature of the surface or interface of the recording medium P to which the toner 6 is fixed.

  Unlike the non-contact heat source of the ninth embodiment, it is difficult to directly heat the unfixed toner 6 with a contact heat source such as the thermal head 15, but the position on the recording medium P where the toner image is to be transferred is determined in advance. It can be adopted by selective heating.

<Example 11>
FIG. 18 is a schematic view showing Embodiment 11 of the image forming apparatus according to the present invention. This embodiment relates to a system called a secondary transfer system on fixing. The toner 6 on the intermediate transfer body 1 is further transferred from the intermediate transfer body 1 onto the fixing roller 3, and the toner 6 on the fixing roller 3 is transferred. The image is transferred to the recording medium P. Also in this example, similarly to the first embodiment, the laser light source L is disposed above the fixing roller 3 as a heating source, and the toner 6 that is an unfixed image in the width direction of the fixing roller 3 perpendicular to the conveyance direction of the recording medium P is used. Selectively heat in sync with. Specifically, as in the first embodiment, the laser light L emitted from the laser light source 4 is irradiated on the upstream side of the rotation of the fixing roller 3 (upstream in the conveyance direction of the recording medium P) and on the fixing roller 3 and the intermediate transfer body 1. The recording medium P is selectively irradiated from the surface side at a position where the recording medium contacts, that is, as close as possible to the fixing nip portion. Since the heating position is close to the fixing nip portion of the fixing roller 3 and on the upstream side in the rotation direction of the fixing roller 3, the heat radiation time from the heated recording medium P can be extremely shortened, and the temperature drop is extremely reduced. It can be prevented efficiently. The intermediate transfer member 1 is wound around a driving roller 2 and a pair of secondary transfer rollers 3a and 3b, and the secondary transfer rollers 3a and 3b and a fixing roller which is in contact with the intermediate transfer member 1 with the intermediate transfer member 1 interposed therebetween. The secondary transfer of the toner 6 is performed between the toner 3 and the toner 3.

  The transfer and fixing of the toner 6 to the recording medium P in the present embodiment is described above in that control is performed to reduce the heating amount for a portion where there is no unfixed image in a predetermined area as compared with a portion where there is an unfixed image. Similar to the embodiment, the toner 6 is heated and softened by irradiating the laser beam L in the vicinity of the nip portion of the fixing roller 3, and then is nipped and conveyed with the recording medium P, whereby the recording medium is pressed by the pressing roller 9. The toner 6 is infiltrated and pressed between the P fibers and fixed. In the primary transfer by the transfer roller 8 and the secondary transfer by the secondary transfer rollers 3a and 3b, a voltage necessary for moving the toner is applied by a bias circuit (not shown). Further, by selectively heating the position on the recording medium P where the toner image is to be transferred in advance, the intermediate transfer member 1 can be prevented from coming into contact with the high-temperature fixing roller 3, and the temperature of the intermediate transfer member 1 is almost increased. Can not be.

<Example 12>
FIG. 19 is a schematic view showing Embodiment 12 of the image forming apparatus according to the present invention. This embodiment also relates to the secondary transfer system for fixing, and as a selective heat source that contacts the recording medium P, the thermal head 15 is used as a resistance heating element as in the second embodiment. Since other configurations and operations are the same as those in the second and third embodiments, description thereof will be omitted.

  As the heating source, other means capable of selectively heating the recording medium P in a range corresponding to the presence of the toner 6 can be used, and the heating source is limited to a laser light source, a thermal head, or the like as shown in the illustrated example. There is nothing. For example, a plurality of heaters having filaments may be used as a selective heat source, and each heater may be turned on and off in synchronization with the image position by a switching circuit to perform selective heating.

  Although all of the embodiments described above use a fixing roller as a fixing member, the present invention can be configured to use a belt material as the fixing member.

It is also important to use a selective heat source and an overall heat source that heats the entire image including the non-image area. For example, a laser may only have a heat conversion efficiency of about 10 to 20%, and a halogen heater, induction heating, etc. are expected to have a heat conversion efficiency of 70 to 80%. It is preferable to determine the total power based on the distribution ratio of both. In addition, the toner needs heat energy necessary for softening, and this energy must reach the sum of both. Therefore, it is possible to save energy by increasing the energy distribution of the selective heat source in an image forming apparatus having a low image ratio even if the heat conversion efficiency is low, and increasing the ratio of the entire heating heat source in an image forming apparatus having a high image ratio.

  Furthermore, not only heating from one side of the recording medium P but also heating from the other side at the corresponding part may be used in combination.

  FIG. 20 shows a tracking pattern. In the figure, f indicates an image portion, and p indicates a tracking pattern using yellow toner or the like. Conventionally, tracking patterns are often formed even in non-image areas (FIG. 20A). This is because the conventional image forming apparatus is premised on the entire surface heating. In heating with a low-resolution selective heat source, it is preferable from the viewpoint of energy saving to form the tracking pattern p only around the image area (FIG. 20B). This is effective not only for the secondary transfer system for fixing but also for all fixing systems that perform selective heating with low resolution. That is, even when the tracking pattern p is used for crime prevention, since the tracking pattern p is formed only around the image portion, the effect of selective heating is enhanced, and both energy saving and crime prevention can be achieved. A technique for enabling printing of a tracking pattern for preventing forgery is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-010057.

  FIG. 21 is a diagram showing a chemical structure of an infrared absorber. An infrared absorber having the structure shown in the figure is disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-357927. In the formula, R1 to R8 are substituents added to the benzene ring or naphthalene ring, and are hydrogen, a halogen atom, a saturated or unsaturated hydrocarbon group having 1 to 18 carbon atoms, and 1 to 13 carbon atoms. An oxygen and / or nitrogen-containing hydrocarbon group, M represents a hydrogen atom or two hydrogen atoms, a divalent metal, or a trivalent to tetravalent metal derivative.

1: Intermediate transfer member 2: Driving roller 3: Fixing roller 3a: Secondary transfer roller 4: Laser light source 6: Toner 7: Image carrier 8: Transfer roller 9: Pressing roller 10: Image forming unit 11: Cleaner 13: Halogen Lamp 15: Thermal head 16: Filament 16a: Induction heating coil 17: Heater 18: Switching circuit 18a: High-frequency switching circuit 21: Intermediate transfer member 22: Protection member 24: Reflecting plate 30: Halogen lamp 32: Reflecting plate A: Laser light Irradiation part L: laser beam P: recording medium f: image part p: tracking pattern

Japanese Patent No. 3042414 Japanese Patent Application Laid-Open No. 07-225524

Claims (3)

An image forming unit for forming an unfixed image unit;
Heating means for heating the unfixed image portion formed by the image forming portion;
Comprising
The image forming unit is an image forming unit that forms a tracking pattern for preventing unauthorized use in an unfixed state around the image unit in an unfixed state,
The image forming apparatus, wherein the heating unit is a heating unit that heats the unfixed image portion and the unfixed tracking pattern formed by the image forming unit.   The image forming apparatus according to claim 1, wherein the heating unit is a heating unit configured to contact and heat a transfer body onto which the unfixed image unit formed by the image forming unit is transferred. 2. The image according to claim 1, wherein the heating unit is a heating unit that heats the recording medium in contact with a recording medium located at a portion corresponding to the unfixed image unit formed by the image forming unit. Forming equipment.