JP4171872B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus miniaturized using an organic EL array exposure head.
[0002]
[Prior art]
Conventionally, in an image forming apparatus such as a copying machine, a printer, and a fax machine using electrophotography, a laser scanning optical system is generally used as a writing unit.
[0003]
Under such circumstances, Japanese Patent Application Laid-Open No. 2-273258 proposes an image forming apparatus using an LED array as writing means.
[0004]
Japanese Patent Application Laid-Open No. 11-198433 proposes an image forming apparatus using a one-chip light emitting element using an organic EL array.
[0005]
Japanese Patent Application Laid-Open No. 2000-127489 proposes an organic EL head for writing means of an image forming apparatus, in which a temperature sensor and a heating element are provided inside the element to keep the element temperature constant.
[0006]
[Problems to be solved by the invention]
However, since a conventional image forming apparatus using a laser scanning optical system requires a scanning optical system, it is difficult to realize a small-sized image forming apparatus with a large writing head. Further, in a color image forming apparatus having a tandem arrangement, it is difficult to improve the scanning position accuracy of the four scanning beams, and there is a problem in that color misregistration occurs and image quality deteriorates.
[0007]
In addition, in the case of an image forming apparatus using an LED array, a plurality of chips are connected in a row, so that the light emission characteristics are different for each chip, and streaks are generated in the output image. Although the pixel position accuracy is more advantageous than the laser scanning optical system, the relative position accuracy of the element deteriorates at the joint portion, and color misregistration occurs.
[0008]
Further, in order to reduce the number of electric wires between the main body and the head, a driver circuit is usually provided in the vicinity of the light emitting element, but it is difficult to form the light emitting portion and the driving circuit on the same substrate in the LED. For this reason, it is usually necessary to arrange the driver IC beside the element, and the width of the element is increased by the size of the driver IC. This is because when a small-diameter OPC (organic semiconductor) drum is used, it is difficult to dispose the drum between the charging device and the developing device, which hinders downsizing of the device.
[0009]
In Japanese Patent Application Laid-Open No. 11-198433 using an organic EL array as a writing means of an image forming apparatus, a light emitting unit and a driving unit can be configured on a single substrate. Can be small. However, there is a problem that the element deteriorates under the influence of humidity around the element, and the amount of emitted light and the light emission efficiency are lowered. In particular, when used in an image forming apparatus, the element deteriorates due to high-humidity hot air generated from the fixing device.
[0010]
Further, in the case of Japanese Patent Laid-Open No. 2000-127489 in which a temperature sensor and a heating element are provided inside the element to keep the element temperature constant, it is necessary to provide the element with a temperature sensor and a heating element, and the element structure is complicated and enlarged. As with LEDs, it is difficult to use a small-diameter photoreceptor.
[0011]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to realize an ultra-small image forming apparatus using an organic EL write head.
[0012]
[Means for Solving the Problems]
The image forming apparatus of the present invention that achieves the above object is provided with at least one image forming station in which a charging unit, an exposure unit, a developing unit, and a transfer unit are arranged around an image carrier, and is formed by the image forming station. In the image forming apparatus for transferring the toner image to the transfer medium,
An organic EL array exposure head is provided as the exposure means,
At least one heat source of the apparatus is arranged relative to the organic EL array exposure head.
[0013]
In the present invention, an organic EL array exposure head is provided as an exposure means, and at least one heat source of the apparatus is disposed below the organic EL array exposure head. By heating, the relative humidity in the vicinity of the exposure head is lowered, and the organic EL light emitting portion of the organic EL array exposure head is prevented from being deteriorated by humidity. Further, the organic EL light emitting portion is heated by the heat source and the temperature rises, so that the light emission efficiency of the exposure head increases.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An electrophotographic image forming apparatus fixes an image carrier (photosensitive member), a charging unit, an exposure unit, a developing unit, a transfer unit, and a toner image transferred to a recording medium (paper) disposed around the image bearing member (photosensitive member). Fixing means.
[0015]
When an organic EL element (head) is used as the exposure means (writing means) of such an electrophotographic image forming apparatus, there is a problem that the organic EL element deteriorates due to humidity. In addition, there is a problem that the organic EL element deteriorates due to temperature, but on the other hand, there is also a merit that the luminous efficiency of the organic EL element increases depending on the temperature.
[0016]
Therefore, in the present invention, the problem of deterioration due to humidity is prevented by isolating the organic EL head from a fixing device which is a humidity generation source of the electrophotographic image forming apparatus as described above. Further, by heating the periphery of the organic EL head and lowering the relative humidity around it, the problem of deterioration due to humidity is avoided and at the same time the luminous efficiency is increased.
[0017]
Further, the temperature around the organic EL head is prevented from rising as necessary.
[0018]
At the same time, the image forming apparatus can be reduced in size by using an organic EL head as an exposure unit.
[0019]
The image forming apparatus of the present invention will be described below based on examples.
[0020]
FIG. 2 is a schematic plan view of one embodiment of an organic EL array exposure head used in the present invention, and FIG. 3 shows a cross-sectional view of one pixel of the array along the line AA ′ of FIG.
[0021]
The organic EL array exposure head 1 of this embodiment is arranged such that two rows of arrays 2 and 2 'are parallel and the pixels are arranged in a staggered manner, and each array 2 and 2' is arranged in a straight line. Each pixel 3 has the same configuration, and includes an organic EL light emitting unit 4 and a TFT (thin film transistor) 5 that controls light emission of the organic EL light emitting unit 4.
[0022]
FIG. 3 shows a cross-sectional view including the organic EL light emitting portion 4 and the TFT 5 of one pixel 3, which will be described in the order of production. First, the TFT 5 is formed on the glass substrate 6. Various methods for manufacturing the TFT 5 are known. For example, a silicon oxide film is first deposited on the glass substrate 6 and an amorphous silicon film is further deposited. Next, the amorphous silicon film is crystallized by irradiating it with an excimer laser beam to form a polysilicon film serving as a channel. After patterning the polysilicon film, a gate insulating film is deposited, and a gate electrode made of tantalum nitride is formed. Subsequently, the source / drain portions of the N-channel TFT are formed by phosphorus ion implantation, and the source / drain portions of the P-channel TFT are formed by boron ion implantation. After activating the ion-implanted impurity, the first interlayer insulating film is deposited, the first contact hole is opened, the source line is formed, the second interlayer insulating film is deposited, the second contact hole is opened, and the metal pixel electrode is formed. The array of TFTs 5 is completed sequentially (see, for example, “8th Electronic Display Forum (2001.18)“ polymer organic EL display ”). Here, the metal pixel electrode serves as the cathode 7 of the organic EL light emitting unit 4 and also serves as a reflective layer of the organic EL light emitting unit 4, and is a metal thin film electrode such as Mg, Ag, Al, Li or the like. It is formed.
[0023]
Next, a partition wall (bank) 9 having a hole 8 corresponding to the organic EL light emitting unit 4 and having a predetermined height is formed. The partition wall 9 can be formed by an arbitrary method such as a photolithography method or a printing method as disclosed in Japanese Patent Application Laid-Open No. 2000-353594. For example, when using the lithography method, an organic material is applied in accordance with the height of the bank by a predetermined method such as spin coating, spray coating, roll coating, die coating, dip coating, and a resist layer is applied thereon. Then, a mask is applied according to the shape of the partition wall 9, and the resist is exposed and developed to leave the resist matched to the shape of the partition wall 9. Finally, the partition wall material is etched to remove the partition wall material other than the mask. Moreover, you may form a bank (convex part) by two or more layers by which the lower layer was comprised with the inorganic substance and the upper layer was comprised with the organic substance. Further, as disclosed in JP-A-2000-323276, the material constituting the partition wall 9 is not particularly limited as long as it has durability against the solvent of the EL material, but it is made into Teflon by fluorocarbon gas plasma treatment. For example, organic materials such as acrylic resin, epoxy resin, and photosensitive polyimide are preferable. The laminated partition which made inorganic materials, such as liquid glass, the lower layer may be sufficient. The partition wall 9 is desirably black or opaque by mixing carbon black or the like with the above material.
[0024]
Next, immediately before the organic EL light emitting layer ink composition is applied, the substrate provided with the partition walls 9 is subjected to continuous plasma treatment of oxygen gas and fluorocarbon gas plasma. Thereby, for example, the polyimide surface constituting the partition wall 9 is water repellent and the cathode 7 surface is hydrophilized, and the wettability on the substrate side for finely patterning the ink jet droplets can be controlled. As an apparatus for generating plasma, an apparatus for generating plasma in a vacuum or an apparatus for generating plasma in the atmosphere can be used similarly.
[0025]
Next, the ink composition for the light emitting layer is discharged from the head 21 of the inkjet printing apparatus 20 into the hole 8 of the partition wall 9, and patterning is applied on the cathode 7 of each pixel. After application, the solvent is removed and heat treatment is performed to form the light emitting layer 10.
[0026]
Here, the ink jet system referred to in the present invention is a piezo jet system that ejects an ink composition using mechanical energy such as a piezoelectric element, and generates bubbles using the thermal energy of a heater. Any of the thermal methods for discharging the ink composition on the basis of the above (published “Fine Imaging and Hardcopy” 1999.1.7 (Corona) .43).
[0027]
After forming the light emitting layer 10 in the hole 8, the ink composition for hole injection layer is discharged from the head 21 of the ink jet printing apparatus 20 onto the light emitting layer 10 in the hole 8 and is applied by patterning onto the light emitting layer 10 of each pixel. I do. After coating, the solvent is removed and heat treatment is performed to form the hole injection layer 11.
[0028]
Note that the order of the light emitting layer 10 and the hole injection layer 11 may be reversed. It is desirable to arrange a layer that is more resistant to moisture on the surface side (the side farther from the substrate 6).
[0029]
Further, the light emitting layer 10 and the hole injection layer 11 can be formed by a known spin coat method, dip method or vapor deposition method instead of forming the ink composition by applying the ink composition by the ink jet method as described above. .
[0030]
As materials used for the light emitting layer 10 and materials used for the hole injection layer 11, various materials known in Japanese Patent Laid-Open Nos. 10-12377 and 2000-323276 can be used, and details thereof are omitted.
[0031]
After sequentially forming the light emitting layer 10 and the hole injection layer 11 in the holes 8 of the partition walls 9, a transparent electrode 12 serving as an organic EL anode is deposited on the entire surface of the substrate by vacuum deposition. Examples of the material of the transparent electrode 12 include a tin oxide film, an ITO film, a composite oxide film of indium oxide and zinc oxide, and a photolithography method, a sputtering method, a pyrosol method, and the like can be adopted in addition to the vacuum evaporation method. . By such a method, the transparent electrode 12 is formed on the upper surface of the partition wall 9 and the entire inner surface of the hole 8.
[0032]
Next, the surface of the transparent electrode 12 is subjected to water repellent treatment, and the transparent ink composition for the microlens is discharged from the head 21 of the inkjet printing apparatus 20 into the hole 8 of the partition wall 9, subjected to patterning application, cured after application, A convex microlens 13 is formed on the organic EL light emitting unit 4 of each pixel. The radius of curvature of the surface of the convex microlens 13, that is, the focal length is determined by the ejection amount of the ink composition, the diameter of the hole 8, the surface tension of the transparent ink composition for microlenses, the degree of water repellency with respect to the transparent electrode 12, and the ink composition. It is determined by the amount of shrinkage when the product is cured.
[0033]
As described above, an array of organic EL light emitting units 4 is provided on the substrate 6, and an array of TFTs 5 for light emission control of each organic EL light emitting unit 4 is provided, and an inkjet is formed on each organic EL light emitting unit 4. The organic EL array exposure head 1 according to one embodiment of the present invention in which the convex microlenses 13 having a predetermined focal length are formed by the method is a predetermined distance L from the organic EL array exposure head 1 as shown in a side view in FIG. The luminous flux from each organic EL light emitting unit 4 is condensed on the surface S that is separated by the same pattern as the arrangement of the pixels 3 of the organic EL array exposure head 1. Accordingly, the surface S is relatively moved in a direction orthogonal to the longitudinal direction of the organic EL array exposure head 1 and the light emission of each organic EL light emitting unit 4 of the organic EL array exposure head 1 is controlled by the TFT 5. A predetermined pattern can be recorded on the surface S.
[0034]
Therefore, in the present invention, the organic EL array exposure head 1 as in the above embodiment is used as an exposure head of an electrophotographic image forming apparatus. Before describing an embodiment of an image forming apparatus using such an organic EL array exposure head 1, a driving method of each light emitting unit 4 of the organic EL array will be described.
[0035]
This driving method is called current program gradation, and was developed for light-emitting polymer displays (Industry Research Committee "Electronic Materials" July issue separate volume "Liquid Crystal Display Technology 2001" (issued July 2001) ) "Low-temperature poly-Si thin-film transistor driven luminescent polymer display"). The current program gradation is for suppressing variations in light emission luminance due to all characteristic variations. FIG. 5 shows a pixel circuit of current program gradation. FIG. 6 shows the operating principle of the current program gradation. In the current program period, the gate electrode and the drain electrode of the TFT are short-circuited to Vgs = Vds, and the gradation signal is supplied to the TFT as an analog current, and the Vgs at this time is stored in the capacitor C1. In the holding period, the analog current is switched to the constant voltage VDD, and the operating point is an intersection of the IV characteristics of the TFT and the light emitting element OLED. Since the TFT operates in the saturation region in both the current program period and the holding period, the same amount of current as the program current is supplied to the holding period.
[0036]
A feature of this current program gradation is that since the saturation region of the TFT is used, it is possible to suppress variations in light emission luminance caused by variations in characteristics of all TFTs and light emitting elements. In addition, although constant current control is used, it is only necessary to connect to one constant voltage source VDD without requiring constant current sources as many as the number of light emitting units.
[0037]
FIG. 1 is a schematic cross-sectional view showing the overall configuration of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, the image forming apparatus of this embodiment is a color image forming apparatus of an intermediate transfer type vertical tandem arrangement, and includes a housing body 31 and an opening / closing member (door body) that is attached to the front surface of the housing body 31 so as to be freely opened and closed. ) 32 and a paper discharge tray (paper discharge unit) 33 formed on the upper part of the opening / closing member 32. In the housing main body 31, an electrical board 34 for driving and controlling the image forming apparatus, an image A forming unit 35, a blower fan 36 for cooling, a transfer belt unit 37, and a paper feeding unit 38 are disposed, and a paper conveying means 39 is disposed in the opening / closing member 32. The consumables in the image forming unit 35 and the paper feed unit 38 are configured to be detachable from the main body. In this case, the configuration including the transfer belt unit 37 can be removed and repaired or replaced. It has become.
[0038]
The transfer belt unit 37 is disposed below the housing main body 31 and is driven to rotate by a drive source (not shown), a tension roller 41 disposed above the drive roller 40, and a space between the two rollers. And an intermediate transfer belt 42 that is circulated and driven in the direction of the arrow shown in the figure (counterclockwise), and a cleaning means 43 that contacts the surface of the intermediate transfer belt 42, and the tension roller 41 and the intermediate transfer belt 42 are driven. The roller 40 is disposed above the figure.
[0039]
The drive roller 40 also serves as a backup roller for the secondary transfer roller 44. The tension roller 41 is also used as a backup roller for the cleaning means 43.
[0040]
A primary transfer member 45 made of a leaf spring electrode is in contact with the back surface of the intermediate transfer belt 42 by an elastic force so as to face the image carrier (photosensitive drum) 46 of each of the image forming stations Y, M, C, and K. Has been.
[0041]
The image forming unit 35 includes image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality (four in this embodiment) of different color images. The image forming stations Y, M, C, and K each include an image carrier 46 formed of a photosensitive drum, and a corona charging unit disposed around the image carrier 46 from upstream to downstream in the rotation direction. The organic EL array exposure head 1 as the exposure means (writing means) as described with reference to FIGS. 2 to 4 and the developing means 48 are included. The arrangement order of the image forming stations Y, M, C, and K is arbitrary.
[0042]
Then, the image carrier 46 of each image forming station Y, M, C, K is brought into contact with the belt surface facing downward in the transport direction of the intermediate transfer belt 42. As a result, each image forming station Y, M, C and K are also arranged on the left side of the driving roller 40 in the drawing. The image carrier 46 is rotationally driven in the conveyance direction of the intermediate transfer belt 42 as indicated by the arrows in the figure.
[0043]
The developing unit 48 includes a toner storage container 49 that stores toner (hatched portion in the drawing), a toner stirring member 50 disposed in the toner storage container 49, a toner supply roller 51, a development roller 52, The control blade 53 is configured.
[0044]
The paper feed unit 38 includes a paper feed unit including a paper feed cassette 54 in which the recording media P are stacked and held, and a pickup roller 55 that feeds the recording media P from the paper feed cassette 54 one by one.
[0045]
The paper transport unit 39 includes a registration roller pair 56 that defines the timing of feeding the recording medium P to the secondary transfer unit, and a secondary transfer roller as a secondary transfer unit that is pressed against the drive roller 40 and the intermediate transfer belt 42. 44, a recording paper conveyance path 57, a fixing unit 58, a discharge roller pair 59, and a duplex printing conveyance path 60.
[0046]
The fixing unit 58 includes at least one heating element such as a halogen heater incorporated therein and a rotatable fixing roller pair 58a, and at least one roller of the fixing roller pair 58a is pressed and urged to the other side. The secondary image secondarily transferred to the recording medium P has a pressing means for pressing the secondary image transferred onto the recording medium P, and the secondary image transferred to the recording medium is transferred at a predetermined temperature at the nip formed by the fixing roller pair 58a. It is fixed on the recording medium.
[0047]
In such a configuration, in each of the image forming stations Y, M, C, and K, the developing unit 48 uses, for example, non-magnetic one-component toner as a developer, and such a toner stored in the toner storage container 49 is used. The one-component developer is stirred by the toner stirring member 50, conveyed to the developing roller 52 by the toner supply roller 51, the film thickness of the developer adhering to the surface of the developing roller 52 is regulated by the regulating blade 53, and the developing roller 52 is The developer is attached to the image carrier 46 in accordance with the potential level of the image carrier 46 by contacting or pressing the image carrier 46. The image carrier 46 is uniformly charged by the charging means 47 and is exposed and discharged by the exposure head 1. The electrostatic latent image thus formed is developed as a toner image by the developing means 48. The yellow, magenta, cyan, and black toner images formed at the image forming stations Y, M, C, and K in this manner are sequentially transferred onto the intermediate transfer belt 42 by the primary transfer bias applied to the primary transfer member 45. The toner image that has been primarily transferred and is sequentially superimposed on the intermediate transfer belt 42 to become a full color is secondarily transferred to a recording medium P such as paper by a secondary transfer roller 44 and passes through a fixing roller pair 58 a of a fixing unit 58. As a result, the image is fixed on the recording medium P, and is discharged onto a paper discharge tray 33 formed on the upper part of the apparatus by a pair of paper discharge rollers 59.
[0048]
In this embodiment, when the recording medium (paper) P is heated by the fixing unit 58, moisture contained in the paper evaporates to generate high-temperature and high-temperature air, as shown in FIG. Since the intermediate transfer belt 42 is disposed between the organic EL array exposure head 1 and the fixing unit 58, the intermediate transfer belt 42 blocks the high-temperature and high-temperature air. It is possible to prevent the organic EL light emitting portion of the organic EL array exposure head 1 from deteriorating.
[0049]
Further, as described with reference to FIGS. 2 to 3, the organic EL array exposure head 1 has the organic EL light emitting unit 4 formed on the single substrate 6. And color unevenness can be prevented.
[0050]
Furthermore, the organic EL light emitting unit 4 and the drive circuit (TFT) 5 of the element can be easily formed integrally on the same single substrate 6, and the organic EL array exposure head 1 can be reduced in size. The image forming apparatus can be reduced in size.
[0051]
Further, it is desirable that each light emitting unit 4 of the organic EL array exposure head 1 is driven by constant current control as described with reference to FIGS. As shown in FIG. 1, even if the intermediate transfer belt 42 is interposed between the organic EL array exposure head 1 and the fixing unit 58 to prevent the influence of humidity, the periphery of the organic EL array exposure head 1 is generated by heat generated from the fixing unit 58. Some heating is inevitable. Such a temperature variation of the exposure head 1 changes the light emission efficiency of the organic EL light emitting unit 4 to change the light emission amount. However, driving by constant current control makes the light emission amount constant even if there is a temperature variation. And stable image formation becomes possible.
[0052]
The material of the intermediate transfer belt 42 is polyester having a low thermal conductivity (thermal conductivity: 0.16 Wm). ^-1 K ^-1 ), Resin such as polyimide, PET, polyurethane and the like is desirable. As shown in FIG. 1, when the intermediate transfer belt 42 is interposed between the organic EL array exposure head 1 and the fixing unit 58, the intermediate transfer belt 42 is heated on the fixing unit 58 side by the rotation operation of the intermediate transfer belt 42, and the exposure head 1 side. Therefore, there is a problem that the intermediate transfer belt 42 is condensed on the fixing side, and the condensed moisture moves to the image carrier 46 and is carried to the vicinity of the exposure head 1. Such condensation is caused by a metal belt having a high thermal conductivity (10 to 200 Wm) on the intermediate transfer belt 42. ^-1 K ^-1 ), The intermediate transfer belt 42 is made of resin (0.5 Wm). ^-1 K ^-1 ), The thermal conductivity is lower than in the case where metal is used for the intermediate transfer belt 42, and the temperature responsiveness to the outside air temperature on the surface of the intermediate transfer belt 42 becomes faster. Can be prevented. It should be noted that, even in the case where secondary transfer is not performed using a paper conveyance belt as in the examples described later, it is desirable to use a similar resin material having a low thermal conductivity as the paper conveyance belt.
[0053]
Further, it is desirable to use a hygroscopic material such as polyester (water absorption: 0.8% (test method ASTM 570-63)) as the intermediate transfer belt 42 or the paper conveying belt. By using a hygroscopic material (water absorption rate: 0.5% or more) as the material of the transfer belt, even if the intermediate transfer belt 42 or the paper transport belt is condensed, the condensed water is absorbed and the organic EL array exposure head is used. 1 can be prevented from being adversely affected.
[0054]
Further, the intermediate transfer belt 42 or the paper transport belt is desirably used that has an emissivity (= absorption rate) of about 0.8 or more, preferably 0.9 or more and can be regarded as a black body close to 1. In order to do so, carbon black may be dispersed in a resin or the like. By increasing the emissivity of the intermediate transfer belt 42 or the paper conveyance belt, the amount of heat transfer from the fixing unit 58 to the intermediate transfer belt 42 or the paper conveyance belt due to radiation can be increased. It is possible to efficiently heat, and as a result, the temperature around the exposure head 1 can be raised, and the exposure head 1 is heated to lower the relative humidity around it, thereby avoiding the deterioration of the exposure head 1 and at the same time emitting light. Efficiency can also be increased.
[0055]
Further, as shown in FIG. 1, the intermediate transfer belt 42 or the paper conveyance belt is stretched by two rollers (a driving roller 40 and a tension roller 41). The volume occupied by the apparatus can be minimized, which is desirable from the viewpoint of miniaturization of the apparatus.
[0056]
Although the image forming apparatus of FIG. 1 is an intermediate transfer system, in the case of an image forming apparatus using a paper transport belt described later, the paper transport path is complicated because the paper is guided to the fixing device after being peeled from the paper transport belt. become. On the other hand, the intermediate transfer method as shown in FIG. 1 has an advantage that the fixing unit 58 can be provided in the direction after the secondary transfer, and the paper transport path 39 is simplified.
[0057]
FIG. 7 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention. The same components as those in the embodiment of FIG. This embodiment is an example of a paper conveyance system using the above-described paper conveyance belt, and is a color image forming apparatus having an oblique tandem arrangement, and uses a paper conveyance belt 42 ′ instead of the intermediate transfer belt 42 in FIG.
[0058]
In this embodiment, a transfer unit 37 ′ and a paper transport unit 39 are provided in the opening / closing member 32. The transfer unit 37 ′ is disposed above the housing body 31 and is driven to rotate by a drive source (not shown), a tension roller 41 and a backup roller 61 disposed obliquely below the drive roller 40, A paper conveying belt 42 ′ stretched around these three rollers and driven to circulate in the direction of the arrow shown in the figure (clockwise), and a cleaning means 62 that contacts the surface of the paper conveying belt 42 ′ opposite the backup roller 61. The drive roller 40 and the paper transport belt 42 'are arranged in a direction inclined to the left in the drawing with respect to the tension roller 41. Further, a transfer member 63 made of a leaf spring electrode is brought into contact with the back surface of the paper conveying belt 42 ′ by the elastic force so as to face the image carrier 46 of each image forming station Y, M, C, K. .
[0059]
Also in this embodiment, since the paper conveyance belt 42 'is disposed between the fixing unit 58 that generates high-temperature and high-temperature air and the organic EL array exposure head 1, this high-humidity and high-temperature air is conveyed by paper. Since the belt 42 ′ blocks, it is possible to prevent the organic EL light emitting portion of the organic EL array exposure head 1 from being deteriorated by the humidity generated in the fixing unit 58.
[0060]
In the example of FIG. 7, since the fixing unit 58 is positioned relatively above the organic EL array exposure head 1, the air heated and absorbed by the fixing unit 58 moves upward, so that the organic EL array exposure is performed. Air with high humidity does not move in the vicinity of the head 1, and the deterioration of the organic EL light emitting unit can be prevented more reliably.
[0061]
FIG. 8 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention. The same components as those in the embodiment of FIG.
[0062]
In this embodiment, instead of tandemly arranging the image forming stations as shown in FIG. 1, a single image carrier (photosensitive drum) 46 is used, and the periphery of the image carrier 46 is upstream to downstream in the rotation direction. , A charging means 47 comprising a single corona charging means, an organic EL array exposure head 1 as a single exposure means (writing means), and Y (yellow) developing devices 48Y, M (magenta). Development unit 48M, C (cyan) development unit 48C, K (black) development unit 48K and rotary development device 64 arranged so as to be able to rotate and rotate around the rotation center. The electrostatic latent image formed by uniformly charging the body 46 by the charging means 47 and exposing and discharging the exposure head 1 is the developing device 4 selected in the order of the rotary developing device 64. Y, 48M, 48C, is developed as a toner image by 48K. The yellow, magenta, cyan, and black toner images sequentially formed in this manner are repeatedly subjected to primary transfer sequentially on the intermediate transfer belt 42 by the primary transfer bias applied to the primary transfer member (transfer roller) 45 ′. The full-color toner image that is sequentially superimposed on the intermediate transfer belt 42 is secondarily transferred to the recording medium P such as paper by the secondary transfer roller 44 and is recorded by passing through the fixing roller pair 58a of the fixing unit 58. The image is fixed on the medium P and discharged by a pair of paper discharge rollers 59 onto a paper discharge tray 33 formed in the upper part of the apparatus.
[0063]
Even in such an image forming apparatus using a single image carrier 46, a single organic EL array exposure head 1, and a rotary developing device 64 that uses a plurality of developing devices 48Y, 48M, 48C, and 48K in order. Heating the recording medium (paper) P by the fixing unit 58 evaporates the moisture contained in the paper and generates high-humidity and high-temperature air. As shown in FIG. Since the intermediate transfer belt 42 is disposed between the fixing units 58, the intermediate transfer belt 42 blocks this high-humidity and high-temperature air. Therefore, the organic EL array exposure head 1 is organically controlled by the humidity generated by the fixing unit 58. It is possible to prevent the EL light emitting unit from deteriorating.
[0064]
Next, in the color image forming apparatus as shown in FIG. 1, specific configuration examples for paper replacement, consumable replacement, exposure head 1 positioning, and the like will be described with reference to FIGS. 9 to 15. To do. The same components as those in the embodiment of FIG.
[0065]
FIG. 9 is a schematic cross-sectional view showing the overall configuration of the image forming apparatus of this embodiment. FIG. 10 is an enlarged view of the transfer belt unit 37 and the image forming unit 35 shown in FIG. The configuration of this embodiment is substantially the same as that of the embodiment of FIG. 1, and in the case of this example, the image forming stations Y, M, C, and K in the tandem arrangement are arranged at an angle only. (In the case of FIG. 1, the vertical type arranged vertically). Also in this example, the intermediate transfer belt 42 is arranged between the organic EL array exposure head 1 and the fixing unit 58, and the organic EL light emitting portion of the organic EL array exposure head 1 is deteriorated by the humidity generated in the fixing unit 58. Is preventing.
[0066]
In such an image forming apparatus, the paper feed cassette 54 on which the recording medium P is stacked and held is configured to be inserted and removed from the front (right side in the drawing) of the housing body 31 and replaced as shown in FIG. be able to.
[0067]
In the image forming apparatus of this embodiment, in order to replace the consumables, first, as shown in FIG. 12, the opening / closing member 32 is turned from the housing main body 31 in FIG. As a paper conveying means 39, a fixing unit 58, a secondary transfer roller 44, a registration roller pair 56, and a paper discharge roller pair 59 that are integrally attached to the opening / closing member 32, and are moved forward to form a housing. The transfer belt unit 37 in the main body 31 is exposed.
[0068]
In this state, as shown in FIG. 13, the frame 67 holding the transfer unit 37 and the image carrier unit 68 (FIG. 14) is rotated forward from the housing body 31 with the second rotation shaft 66 as a rotation fulcrum. Thus, for example, the K developing means 48 to be replaced in the image forming unit 35 is extracted from the housing body 31 and replaced with new developing means 48 so that the image forming unit 35 is exposed. At this time, the organic EL array exposure head 1 of the exposure means corresponding to the developing means 48 remains in the housing body 31 and is not replaced.
[0069]
Further, with the frame 67 tilted forward, the transfer unit 37 and the image carrier unit 68 can be removed from the frame 67 and replaced with a new one as shown in FIG. The image carrier unit 68 is integrally provided with an image carrier (photosensitive drum) 46 and a charging means 47 of each image forming station Y, M, C, K. In the state shown in FIG. Separated from the image forming stations Y, M, C, K.
[0070]
FIG. 15 shows an example of a mechanism for accurately positioning each organic EL array exposure head 1 with respect to the image carrier (photosensitive drum) 46 attached to the image carrier unit 68. The image carrier 46 is rotatably attached to the frame 70 of the image carrier unit 68 by its shaft 69, while the organic EL array exposure head 1 is held by a long head holding member 71. The head holding member 71 is pressed against the frame 70 by elastic springs 72 at both ends with expandable springs 72. Accordingly, since the organic EL array exposure head 1 is accurately positioned with respect to the frames 70 at both ends of the image carrier 46, the exposure head 1 can be used as long as the mutual position between the image carrier 46 and the frame 70 is accurate. It is positioned accurately with respect to the carrier 46. Therefore, the exposure head 1 can be positioned with respect to the image carrier 46 in this manner, and the positional accuracy of the image can be improved and color misregistration and color unevenness can be prevented.
[0071]
As shown in FIGS. 12 to 14, when the fixing unit 58 rotates during the replacement of the consumables, the fixing that is a source of humidity from the exposure head 1 when the consumables such as the developing unit 48 and the image carrier 46 are replaced. The unit 58 can be moved away, and the influence of the humidity and temperature from the fixing unit 58 on the exposure head 1 when exchanging consumables can be eliminated.
[0072]
Further, since the image carrier unit 68 is attached to and detached from the housing main body 31 by the movement of each image carrier 46 in the radial direction, the frame holding the image carrier 46 is notched in the axial direction of the image carrier 46. Thus avoiding interference.
[0073]
By the way, when the image forming stations Y, M, C, and K are arranged in tandem, there are a vertical type that is arranged vertically as shown in FIG. 1, and an oblique type that is arranged obliquely as shown in FIGS. In addition, as shown in FIG. 16, there is a horizontal type that is arranged horizontally. In this embodiment, the configuration is substantially the same as that of the embodiment of FIG. 1, and an intermediate transfer belt 42 is disposed between the organic EL array exposure head 1 and the fixing unit 58. The organic EL light emitting part of the organic EL array exposure head 1 is prevented from deteriorating.
[0074]
As shown in FIG. 1, FIG. 7, FIG. 9, and FIG. 16, when a tandem type color image forming apparatus is configured, high-speed printing is possible, but usually four exposure means 48 need to be used. By combining with the organic EL array exposure head 1 as a means, the effect of miniaturization is great.
[0075]
Among them, when the vertical tandem arrangement is used as shown in FIG. 1, the process becomes a vertical type, and an image forming apparatus having a small size and a small installation area can be configured.
[0076]
Also, as shown in FIGS. 7 and 9, the oblique tandem arrangement in which the intermediate transfer belt 42 or the paper transport belt 42 ′ is stretched obliquely with respect to the vertical direction, and the process means is disposed in the lower direction. Then, by tilting the intermediate transfer belt 42 or the paper transport belt 42 ′, an arrangement space for the fixing unit 58 is provided obliquely above, and a small image forming apparatus with a small installation area can be configured. Further, since the fixing unit 58 can be arranged on the intermediate transfer belt 42 or the paper transport belt 42 'and the organic EL array exposure head 1 can be arranged on the bottom, the exposure head 1 is not easily affected by the heat generated by the fixing unit 58. Thus, the temperature fluctuation of the exposure head 1 can be reduced.
[0077]
As shown in FIG. 16, when the horizontal tandem arrangement is used, a small-sized image forming apparatus in which the vertical height is kept low can be configured.
[0078]
Further, when a color image forming apparatus is configured in a tandem type, the image carrier 46 is fixed to a common frame, and can be configured to be exchangeable as a unit. In this way, the frame of the photoconductor can be shared, the frame configuration is simplified, and the size can be reduced. In addition, maintenance becomes easy.
[0079]
Further, as shown in the example of FIG. 7, in the image forming apparatus of the vertical type or the oblique type tandem arrangement, the rotation direction of the intermediate transfer belt 42 or the paper transport belt 42 ′ moves downward and moves to the side where the exposure head 1 is located. In this case, the intermediate transfer belt 42 or the paper transport belt 42 ′ warmed by the fixing unit 58 moves from below to the side where the exposure head 1 is present, so that the exposure head 1 is warmed from below, so that the exposure is efficiently performed. Since the head 1 can be heated and the four exposure heads 1 can be heated more uniformly, the deterioration of the exposure head 1 can be avoided by heating the periphery of the exposure head 1 and lowering the relative humidity of the periphery. At the same time, the luminous efficiency can be increased.
[0080]
By the way, the image forming apparatus includes a drive motor for rotationally driving the electrical board 34, the image carrier 46, the intermediate transfer belt 42, or the paper transport belt 42 ′ as a heat source other than the fixing unit 58. Such a heat source is desirably disposed below the organic EL array exposure head 1 as in the embodiments of FIGS. 1, 7, 9, and 16. With such an arrangement, the heat source (in the case of these drawings, the electrical board 34) heats the organic EL array exposure head 1, and the relative humidity in the vicinity of the exposure head 1 is reduced to reduce the exposure head 1's relative humidity. In addition to avoiding deterioration, the light emission efficiency of the exposure head 1 increases as the temperature of the exposure head 1 increases.
[0081]
In addition, it is not necessary to provide a dedicated heat source such as a heater by utilizing heat generated from the electrical board 34 or the drive motor that is inherent in such an image forming apparatus.
[0082]
FIG. 17 shows an embodiment of FIG. 9 in which a gear train including a two-stage gear 74, a photosensitive member driving gear 75, an idle gear 76, and an intermediate transfer belt driving gear 77 indicated by dotted lines is driven. It is a figure which shows the Example arrange | positioned under the organic EL array exposure head 1 according to this invention by using the drive motor 73 which rotates the drive roller 40 synchronously as a heat source. However, in this embodiment, the driving roller 40 and the tension roller 41 are interchanged with respect to the arrangement shown in FIG.
[0083]
Further, these heat sources are arranged on the back side of the organic EL array exposure head 1 (on the side opposite to the intermediate transfer belt 42 or the paper transport belt 42 'side), particularly in a tandem color image forming apparatus. Problems due to temperature unevenness between the exposure heads 1 can be prevented. That is, if such a heat source is provided on one side of the exposure head 1 in the longitudinal direction, only one side of the exposure head 1 in the longitudinal direction is heated, and a temperature distribution is generated in the exposure head 1 in the axial direction, resulting in poor luminous efficiency. Uniformity occurs. If such a heat source is provided below the exposure head 1, the temperature of the exposure head 1 varies due to the difference in the location of the exposure head 1, resulting in non-uniform emission efficiency and the like. On the other hand, when such a heat source is provided on the back side of the exposure head 1, the four exposure heads 1 can be uniformly heated in the longitudinal direction, and the deterioration of the exposure head 1 and the light emission efficiency. Therefore, color misregistration and color unevenness can be prevented.
[0084]
18, 19, and 20, respectively, in the case of the intermediate transfer method in the vertical tandem arrangement of FIG. 1, in the case of the paper conveyance method in the oblique tandem arrangement of FIG. 7, and in the intermediate transfer method in the oblique tandem arrangement of FIG. 9. In the case of the color image forming apparatus, the heat source electrical board 34 is disposed on the opposite side of the image forming stations Y, M, C, and K from the intermediate transfer belt 42 or the paper transport belt 42 'side. Other configurations are the same as those shown in FIGS. 1, 7, and 9, and will not be described.
[0085]
These heat sources may be arranged above the organic EL array exposure head 1. By disposing the heat source above the organic EL array exposure head 1 in this way, the exposure head 1 can be prevented from being heated from the heat source. In particular, in the case of a color image forming apparatus having a tandem arrangement, it is not easy to uniformly heat the four exposure heads 1, and the temperature of the exposure head 1 varies depending on the color. The difference in temperature becomes a difference in pixel position and light emission amount due to linear expansion, and color shift and color unevenness occur. This can be prevented by arranging a heat source above the organic EL array exposure head 1.
[0086]
21, 22, 23, and 24, respectively, in the case of the intermediate transfer method in the vertical tandem arrangement of FIG. 1, in the case of the paper conveyance method in the oblique tandem arrangement of FIG. 7, and in the middle of the oblique tandem arrangement of FIG. 9. In the case of the transfer method, in the color image forming apparatus in the case of the intermediate transfer method in the horizontal tandem arrangement shown in FIG. 16, the electrical substrate 34 of the heat source is arranged vertically above the image forming stations Y, M, C, and K. It is. Other configurations are the same as those shown in FIGS. 1, 7, 9, and 16, and will not be described.
[0087]
FIG. 25 shows an image carrier in the embodiment shown in FIG. 9 by driving a gear train including a two-stage gear 74, a photosensitive member driving gear 75, an idle gear 76, and an intermediate transfer belt driving gear 77 indicated by dotted lines. It is a figure which shows the Example which has arrange | positioned the heat source which consists of the drive motor 73 which rotates 46 and the drive roller 40 synchronously above the organic EL array exposure head 1 according to this invention. Other configurations are the same as those in FIG. 9, and a description thereof will be omitted.
[0088]
In these, since the heat source has the electric board 34 or the drive motor 73 disposed above the organic EL array exposure head 1, it is possible to prevent the exposure head 1 from being heated by the heat generated from these heat sources. it can.
[0089]
By the way, in the meaning of preventing the organic EL array exposure head 1 from being heated from the heat source, in the color image forming apparatus of the tandem arrangement, the rotation direction of the intermediate transfer belt 42 or the paper transport belt 42 ′ is as shown in FIGS. As shown in FIG. 25, it is desirable that the exposure head 1 moves to the side through the upper side. That is, the intermediate transfer belt 42 or the paper conveyance belt 42 ′ heated by the fixing unit 58 moves from above to the exposure head 1 side, so that the heated intermediate transfer belt 42 or the paper conveyance belt 42 ′ passes above. Sometimes it becomes easy to dissipate heat and the exposure head 1 can be prevented from being heated.
[0090]
In this case, it is desirable to use an intermediate transfer belt 42 or a paper transport belt 42 'having an emissivity (= absorption rate) of approximately 0, preferably 0.2 or less. By reducing the emissivity of the intermediate transfer belt 42 or the paper conveyance belt 42 ', the amount of heat transfer due to radiation from the fixing unit 58 can be reduced, and the intermediate transfer belt 42 or the paper conveyance belt 42' is prevented from being heated. It is possible to prevent the exposure head 1 from being heated. As such a low emissivity belt, for example, a Ni electroformed tube belt (emissivity 0.05) may be used.
[0091]
In the image forming apparatus that develops, transfers, and fixes a monochromatic toner image using the organic EL array exposure head 1, as shown in FIG. 26, the fixing unit 58 is disposed above the organic EL array exposure head 1 in the vertical direction. As a result, the high-temperature and high-humidity air generated in the fixing unit 58 moves to the upper part of the fixing unit 58 by convection, and the high-humidity air does not move around the exposure head 1. In this case, heat transfer is performed to the exposure head 1 by the radiant heat of the fixing unit 58, and the exposure head 1 can be heated to increase its luminous efficiency. .
[0092]
In FIG. 26, the outer peripheral surface of the image carrier (photosensitive drum) 46 rotating in the direction of the arrow is uniformly charged by the charging roller 78 and is exposed and discharged by the organic EL array exposure head 1. The electrostatic latent image is developed as a toner image by the developing means 48. The toner image is transferred onto the recording medium P fed from the paper feed cassette 54 by a transfer bias applied to the transfer roller 79, and the recording medium P passes through the fixing roller pair 58 a of the fixing unit 58, so that the recording medium P The recording medium P fixed on the toner image is discharged onto a paper discharge tray 33 formed at the top of the apparatus. Residual toner on the image carrier (photosensitive drum) 46 is cleaned by a cleaner 80.
[0093]
The image forming apparatus of the present invention has been described based on some embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made.
[0094]
【The invention's effect】
As is apparent from the above description, the image forming apparatus of the present invention includes an organic EL array exposure head as exposure means, and at least one heat source of the apparatus is disposed below the organic EL array exposure head. Therefore, when the organic EL array exposure head is heated by the heat source, the relative humidity in the vicinity of the exposure head is lowered, and the organic EL light emitting portion of the organic EL array exposure head is prevented from being deteriorated by humidity. Is done. Further, the organic EL light emitting portion is heated by the heat source and the temperature rises, so that the light emission efficiency of the exposure head increases.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an overall configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic plan view of one embodiment of an organic EL array exposure head used in the present invention.
3 is a cross-sectional view of one pixel of the array along the line AA ′ in FIG. 2;
FIG. 4 is a side view showing a state of light collection by the organic EL array exposure head.
FIG. 5 is a diagram showing a pixel circuit of a current program gradation of an organic EL array exposure head.
6 is a diagram illustrating an operation principle of the current program gradation of FIG. 5;
FIG. 7 is a schematic cross-sectional view showing an overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 8 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 9 is a schematic cross-sectional view showing an overall configuration of an embodiment for explaining a specific configuration example for replacement of paper, replacement of consumables, positioning of an exposure head, and the like in the image forming apparatus of the present invention. It is.
10 is an enlarged view of the transfer belt unit and the image forming unit of FIG.
FIG. 11 is a diagram for explaining a state of replacing a paper feed cassette in FIG. 9;
12 is a view for explaining a state in which a transfer belt unit is exposed by rotating an opening / closing member forward in FIG. 9;
13 is a diagram for explaining how the developing means is replaced in the next operation of FIG. 12. FIG.
14 is a diagram for explaining how the transfer unit and the image carrier unit are exchanged by the next operation of FIG.
FIG. 15 is a view showing an example of a mechanism for positioning an organic EL array exposure head with respect to an image carrier.
FIG. 16 is a schematic cross-sectional view showing an overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 17 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 18 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 19 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 20 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 21 is a schematic cross-sectional view showing an overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 22 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 23 is a schematic cross-sectional view showing an overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 24 is a schematic cross-sectional view showing an overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 25 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
FIG. 26 is a schematic cross-sectional view showing the overall configuration of another embodiment of the image forming apparatus of the present invention.
[Explanation of symbols]
1 ... Organic EL array exposure head
1 (K, C, M, Y): Organic EL array exposure head
2, 2 '... array
3 ... Pixel
4 ... Organic EL light emitting part
5 ... TFT
6 ... Glass substrate
7 ... Metal pixel electrode (cathode)
8 ... Hole
9 ... Bank (bank)
10 ... Light emitting layer
11 ... hole injection layer
12 ... Transparent electrode
13 ... Convex micro lens
20 ... Inkjet printer
21 ... Head
31 ... Housing body
32 ... Opening / closing member (door)
33 ... Paper discharge tray (paper output unit)
34 ... Electric circuit board
35. Image forming unit
36 ... Blower fan
37. Transfer belt unit
38 ... Paper feed unit
39: Paper conveying means
40 ... Driving roller
41 ... Tension roller
42. Intermediate transfer belt
42 '... paper transport belt
43. Cleaning means
44. Secondary transfer roller
45. Primary transfer member
45 '... Primary transfer member (transfer roller)
46: Image carrier (photosensitive drum)
47. Charging means
48. Developing means
48Y, 48M, 48C, 48K ... Developer
49. Toner storage container
50. Toner stirring member
51. Toner supply roller
52. Developing roller
53 ... Regulator blade
54. Paper cassette
55 ... Pickup roller
56 ... Registration roller pair
57 ... Recording paper transport path
58. Fixing unit
58a ... Fusing roller pair
59 ... Discharge roller pair
60 ... Conveying path for double-sided printing
61 ... Backup roller
62. Cleaning means
63 ... Transfer member
64. Rotary developing device
65 ... 1st rotation axis
66. Second rotation axis
67 ... Frame
68. Image carrier unit
69 ... axis of image carrier
70 ... Frame
71: Head holding member
72 ... Spring
73 ... Drive motor
74 ... Two-stage gear
75 ... Photoconductor drive gear
76 ... Idol Gear
77 ... Intermediate transfer belt drive gear
78 ... Charging roller
79. Transfer roller
80 ... cleaner
S ... surface
P ... Recording medium
Y, M, C, K ... Image forming station

Claims (8)

An image forming apparatus in which at least one image forming station having a charging unit, an exposing unit, a developing unit, and a transfer unit arranged around an image carrier is provided, and a toner image formed at the image forming station is transferred to a transfer medium. ,
As the exposure means, the cathode electrode comprises an organic EL array exposure head composed of a metal film of Mg, Al, Li,
At least one electrical component mounting board for driving and controlling apparatus which is a heat source of the device has been coordinating the bottom rear of the organic EL array exposure head in the housing of the image forming apparatus,
The transfer medium consists of a recording medium conveyed by an intermediate transfer belt or a paper conveyance belt,
A recording medium on which the toner image is secondarily transferred from the intermediate transfer belt, or a fixing means for fixing the toner image on the recording medium peeled off from the paper transport belt to the recording medium,
The intermediate transfer belt or the paper conveyance belt is disposed between the organic EL array exposure head and the fixing unit,
The fixing means is positioned relatively above the organic EL array exposure head,
The intermediate transfer belt or the paper transport belt is an oblique type arrangement arranged to run in an inclined oblique direction,
An image forming apparatus, wherein the intermediate transfer belt or the paper conveying belt is made of a material having an emissivity (= absorption rate) of 0.8 or more.   The image forming apparatus according to claim 1, wherein the light emitting portion of the organic EL array exposure head is formed on a single substrate.   3. The image forming apparatus according to claim 1, wherein the light emitting portion of the organic EL array exposure head and the drive circuit thereof are formed on the same single substrate.   4. The image forming apparatus according to claim 3, wherein a thin film transistor is used as the drive circuit.   The image forming apparatus according to claim 1, wherein the light emitting unit of the organic EL array exposure head is driven by constant current control. Ri Adair image forming station at least two provided in tandem arrangement, the transfer medium is an intermediate transfer belt, the closing member having the fixing means pivotable first pivot shaft as the fulcrum 6. The image forming station according to claim 1 , wherein the intermediate transfer belt is configured to be rotatable about a second rotating shaft, and the image forming station is configured to be detachable. The image forming apparatus according to Item.   6. The rotary developing device according to claim 1, wherein one image forming station is provided, and the developing unit is a rotary developing device in which a plurality of developing devices are arranged so as to be able to rotate and rotate around a rotation center. Image forming apparatus. The transfer medium is an intermediate transfer belt, said intermediate transfer belts are stretched between two rollers, part of the intermediate transfer belt rotating direction facing the image forming station of the intermediate transfer belt The image forming apparatus according to claim 1, wherein the image forming apparatus moves in a direction from the upper side to the lower side of the exposure unit .

Images