JPH065405B2 - Multicolor recorder - Google Patents

Description

Detailed Description of the Invention

(a) Field of Industrial Application The present invention relates to a multicolor recording apparatus using an electrophotographic recording method or an electrostatic recording method, and in particular, a multicolor recording apparatus capable of stably obtaining clear multicolor recording without color mixture for a long period of time. It is about. In recent years, with the diversification of information, colorization of recorded information is required, and electrophotographic recording and electrostatic recording are no exception, and various apparatuses and systems for multicolor recording have been proposed. In electrophotographic recording, an electrostatic latent image is formed by uniformly charging a latent image forming medium having a photoconductor layer with electric charges and exposing the photoconductor layer according to a desired image. In electrostatic recording, after the latent image forming medium having the dielectric layer is uniformly charged, the charge is removed by the discharge by the pin electrode, or the charge is simply added by the discharge by the pin electrode on the dielectric layer to make the electrostatic recording static. It forms a latent image. After forming an electrostatic latent image in any of these methods, the latent image is developed by a developing device to form a toner image, and the toner image is transferred to a recording sheet. Therefore, multi-color recording can be obtained by providing the latent image forming means and the developing means in multiple stages on the surface of the latent image forming medium and forming the toner image for each color in each development. However, in the above-described multicolor recording, the rabbit angle and the toner in the developer used in the previous development step are mixed in with the developer in the next development step, and the toner image formed in the next development step is mixed. However, deterioration of the developer due to mixing of other toners and other toners is likely to occur, and it is desired to surely eliminate such problems. (b) Conventional Technology FIG. 2 (a) is a schematic configuration diagram of a two-color recording apparatus applied for a simple explanation of a conventional multi-color recording apparatus of an electrophotographic recording system. Also, FIGS. 2 (b) to (g) are 2 of FIG. 2 (a).
FIG. 6 is a diagram showing a potential state on a latent image forming medium in each recording process in which two-color recording is performed by a color recording device. As shown in the configuration diagram and the potential state diagram, in the conventional recording apparatus, first, an initial charging device is provided on the latent image forming medium on which the photosensitive layer such as selenium (Se) is formed, that is, the surface of the photosensitive drum. 2 shows the initial charging potential level V as shown in Fig. 2 (b).
s is uniformly charged on the entire surface (positive charge). Next, negative exposure corresponding to the first color image is performed on the surface of the photosensitive drum 1 by the first exposure unit 3 including a laser scanning optical system using a gas laser such as He-Ne or a semiconductor laser. As shown in FIG. 2 (c), a first latent image 21 is formed in which the charging potential of the exposed portion on the surface of the photosensitive drum 1 is attenuated to approximately 0V. Next, the first latent image 21 is formed, for example, by using a two-component magnetic brush developer in which a red toner having a positive polarity and a carrier are mixed.
The magnetic brush reversal development is performed by the developing device 4, and the result shown in FIG.
As shown in (d), the first red toner image 22 is formed. After that, the recharger 5 causes the first red toner image 22
Recharging is performed so that the potential Vt of the portion becomes substantially the same as the background potential Vs of the surface of the photosensitive drum 1 as shown in FIG. 2 (e). This process is the first one already formed in the next development step.
This is to prevent the following different color toners from adhering to the red toner image 22 part. Next, a negative exposure corresponding to the second color image is performed on the recharged surface of the photosensitive drum 1 by the second exposure unit 6 including a laser scanning optical system using a He-Ne gas laser or a semiconductor laser. Then, as shown in FIG. 2 (f), a second latent image 23 is formed in which the charging potential of the exposed portion on the surface of the photosensitive drum 1 is attenuated to approximately 0V. Then, the second latent image 23 is subjected to magnetic brush reversal development by the second developing device 7 using a two-component magnetic brush developer in which, for example, a positive polarity black toner and a carrier are mixed,
A second black toner image 24 is formed as shown in FIG. Thus, the red, black, and 2 formed on the surface of the photosensitive drum 1
The color toner images 22 and 24 are collectively transferred onto the recording paper 13 by the transfer unit 8, and further fixed by thermocompression bonding or the like in the fixing unit 9 to record a two-color image. On the other hand, each toner remaining on the surface of the photosensitive drum 1 is discharged by the AC static eliminator 10 and removed by cleaning by the cleaner 11, and further, all charges on the surface of the photosensitive drum 1 are statically erased by the optical static eliminator 12 to remove the next charge. Enter the recording cycle. In the above recording apparatus, the first red toner image 22 already formed in the first developing step is not destroyed in the second developing step so that the first red toner image 22 is not destroyed in the second developing step. Diameter is 5
A two-component magnetic brush developer containing a magnetic carrier having a particle size of 10 to 100 μm and an electric resistance of 10 ¹² to 10 ¹⁶ Ω · cm mixed with a toner having a particle size of 10 to 20 μm is used. The soft-touch development is performed such that the tips of the magnetic brush slightly contact the surface of the photosensitive drum 1. Therefore, the problem that the first red toner image 22 already formed in the first developing step is destroyed and mixed into the developer in the second developing device 7 is remarkably improved, and good two-color image recording without color mixing is possible. I have to. (c) Problems to be Solved by the Invention However, even in the recording apparatus as described above, the red toner used in the first developing device 4 remains in the second developing device 7 as the recording operation is repeated over a long period of time. However, it is not possible to prevent it from gradually accumulating and accumulating. As a result, when the amount of the mixed red toner increases, the black toner having both positive polarity and the mixed red toner are developed together, and the second toner formed by the second developing step is developed. The black toner image 24 of No. 2 is mixed in color, and there is a disadvantage that a good two-color image recording cannot be obtained. Therefore, in order to prevent the occurrence of color mixture recording as described above, the present inventors have already proposed a method of separating the toner mixed in the second developing device by utilizing the difference in the triboelectric charging series.
It is proposed by the gazette No. 3. That is, in the above method, the first carrier 31 and the first toner 32 having the triboelectrification series shown in FIG.
The second carrier 33 and the second toner 34 are used. Each of the first toner 32 and the second toner 34 is a developing device.
In 4, 7, the first carrier 31 and the second carrier 33 are rubbed to be positively charged and, for example, the positive first toner 32 mixed in the second developing device 7 is conveyed on the developing roller. While in contact with the second carrier 33, the second carrier 33 is contacted and rubbed, and the negative polarity is reversed. As a result, the mixed first toner 32 is electrostatically coupled to the positive second toner 34, and the second carrier in the developing device 7 is
Since the adhesive strength with 33 decreases, the second electrostatically coupled second
The toner 34 is scattered along with the toner 34 from the surface of the developing roller to facilitate the separation of the mixed first toner 32. According to such a separation method, the mixed toner is not accumulated in the second developing device, so that it is possible to stably perform good two-color image recording without color mixing even if the recording operation is repeated for a long period of time. However, on the other hand, in the above-described method of separating the mixed toner, since carriers having different triboelectrification levels are used for the respective developing devices, a plurality of types of carriers having different triboelectrification characteristics are proportional to the number of developing devices arranged. Need to prepare. In addition, these carriers must have electrostatic characteristics that charge each toner combined with them to a predetermined polarity and frictionally reverse the charging polarity of the mixed toner. It had the drawback that it was not easy to create. In view of the above-mentioned conventional circumstances, the present invention reverses the polarity of the mixed toner to a negative polarity by contact friction with the mixed toner in each of the plurality of developing devices after the second developing device, or A configuration is provided in which a toner separation roller that attenuates the amount of electrified charge and separates the mixed toner easily and efficiently is provided.
It is an object of the present invention to provide a novel multicolor recording apparatus capable of stably performing good multicolor image recording without color mixture for a long period of time. (d) Means for Solving the Problems The above-mentioned object of the present invention is to provide a plurality of developing devices, each of which has a developing agent and a developing agent composed of a toner and a carrier for each color, around the latent image forming medium. A transfer means for transferring a multicolor toner image sequentially formed on the latent-agent forming medium by the plurality of developing devices to a recording sheet; and a cleaning means for removing residual toner on the latent-image forming medium. In the color recording apparatus, the triboelectrification characteristics of the respective carriers in the plurality of developing devices are common, the toner for each color has a triboelectrification level which becomes higher in order of the developing device to be used than the carrier, and Adjacent to the developing roller in each developing device after the second developing device, the polarity of the mixed toner is reversed, or the frictional charge level for attenuating the charge amount is higher than the mixed toner, and is higher than that of the toner in the second developing device. Low friction charging A multicolor recording apparatus according to the present invention having a structure in which a mixed toner separation roller formed by coating the mixed toner separation roller is provided, and the surface of the triboelectric charging layer coated on the mixed toner separation roller has minute irregularities. To be done. (e) Action That is, in the present invention, for example, a carrier constituting the developer used in each developing device, a first toner constituting the developer used in the first developing device, and a second developing device. The triboelectrification levels of the triboelectrification layer coated on the mixed toner separation roller disposed adjacent to the development roller inside and the second toner constituting the developer used in the second developing device in this order from the carrier. Since it has a large charging characteristic,
Only the first toner that has been charged to the positive polarity by rubbing with the carrier and that has entered the second developing device rubs against the triboelectrification layer coated on the mixed toner separation roller to be inverted to the negative polarity and to have the positive polarity. It electrostatically binds to the second toner and reduces the adhesive force of the carrier that adheres to the second toner, or attenuates the amount of electric charge charged. In this case, the surface of the triboelectrification layer formed on the outer peripheral surface of the mixed toner separation roller is made to be a finer uneven surface than the toner to increase the contact area with the developer. The contact frequency and the contact probability are increased, and the polarity of the mixed toner is reversed or the amount of charge is reduced more effectively. Therefore, the mixed first toner and the electrostatically coupled second toner can be scattered and separated by the rotational centrifugal force accompanying the conveyance on the mixed toner separating roller, and the recording operation is repeated for a long time. However, good multicolor image recording without color mixture can be performed stably and efficiently. Even if the second toner rubs against the triboelectric charging layer coated on the mixed toner separation roller, the triboelectric charging level is higher than that of the triboelectric charging layer, and therefore polarity reversal does not occur. Further, the carrier used in combination with the toner for each color only needs to satisfy the triboelectrification characteristics with respect to the toner, so that a carrier having a common triboelectrification level can be applied and the carrier can be easily prepared. (f) Embodiments In order to simplify the description of an embodiment of the multicolor recording apparatus according to the present invention with reference to the drawings, an example in which it is applied to the two-color recording apparatus shown in FIG. 2 (a). Will be described in more detail. First, the structure of the first developing device of the recording apparatus according to the present invention is the same as the conventional one, and one embodiment of the second developing device 41, which is a feature of the present invention, is shown in FIG. Show. That is, in the figure, 42 is a developing roller, 43 is a developer supplying roller, 44 is a mixed toner separating roller, 45 and 46 are scraping plates, and 47, 48 and 49.
Is a partition plate. Both the developing roller 42 and the developer supplying roller 43 are provided with magnetic rollers 42b and 43b inside non-magnetic sleeves 42a and 43a made of aluminum (Al) or the like. By rotating, the developer is conveyed to the photosensitive drum 1 side via the non-magnetic sleeve 42a. Further, a triboelectrification layer having a higher triboelectrification level than the mixed toner (the first red toner 32 in this embodiment) having a minute uneven surface on the outer peripheral surface in the vicinity of the developing roller 42 and the developer supplying roller 43. A non-magnetic sleeve 44a made of aluminum (Al) or the like covered with 44c and a mixed toner separation roller 44 having a magnetic roller 44b inside are arranged. The relationship between the triboelectric charge levels of the triboelectric charging layer 44c of the mixed toner separating roller 44, the first carrier 31, the first red toner 32, the second carrier 33, and the second black toner 34 used for the first development and the second development. Is determined as shown in the triboelectrification sequence diagram of FIG. 1 (b). Incidentally, the first developing device 4 and the second developing device 7 of the above two-color recording apparatus.
The first carrier 31 and the second carrier in each developer used for
33 has a particle size of 5 to 100 μm and an electric resistance of 10 ¹² to 10 ¹⁶ Ω.
・ Use the same one consisting of cm magnetic powder. Also the first
The red toner 32 and the second black toner 34 both have a particle size of 10 to 20.
It is made of non-magnetic and insulative powder having a particle size of μm, and the first and second carriers 31, 33, the first red toner 32, the second black toner 34, and the mixed toner separation roller 44 are frictionally charged. The triboelectrification levels of the layer 44c can be easily arranged in the order shown in the triboelectrification series diagram of FIG. 1 (b) by controlling the addition amount of the charge amount control material or the like. Next, the first and second magnetic carriers 31 and 33, the first red toner 32, and the second black toner 34, which have the above-mentioned triboelectric series,
A second developing device 41 further provided with a mixed toner separating roller 44 will be described with reference to an example in which the second developing device 41 is applied to the two-color recording device shown in FIG. First, the latent image medium on which a selenium (Se) photosensitive layer is formed, that is, the surface of the photosensitive drum 1 is uniformly charged by the initial charger 2 to an initial charging potential level of about + 600V. Next, negative exposure corresponding to the first color image is performed on the surface of the photosensitive drum 1 by the first exposure unit 3 by a laser scanning optical system using a semiconductor laser, and the potential of the exposed portion is attenuated to about 0V. Form a first latent image. Then, the first latent image is transferred to, for example, the first red toner 32 of positive polarity.
Using the first developer containing, and + 400V DC voltage or frequency: 1KHz, voltage: 1.5KVpp, offset voltage: +40
Magnetic brush reversal development is performed by the first developing device 4 to which an alternating voltage of 0 V is applied to form a first red toner image. After that, the recharger 5 recharges the first red toner image portion so that the potential of the first red toner image portion becomes substantially the same as the background potential level of the surface of the photosensitive drum 1. Next, negative exposure corresponding to the second color image was performed on the surface of the photosensitive drum 1 by the second exposure unit 6 by the laser scanning optical system also using the semiconductor laser, and the potential of the exposed portion was attenuated to about 0V. Second
To form a latent image of. Then, the second latent image is formed, for example, by using a second developer containing a second black toner 34 having a positive polarity and a DC voltage of + 400V,
Or frequency: 1KHz, voltage: 1.5KVpp, offset voltage:
A magnetic brush reversal phenomenon is performed by the second developing device 41, which is a feature of the present invention, to which an alternating voltage of +400 V is applied, to form a second black toner image. After that, the red, black, and
A two-color image can be recorded by collectively transferring the two-color toner images onto the recording paper 13 by the transfer device 8 and then fixing the toner images in the fixing unit 9 by thermocompression bonding or the like. In this two-color recording apparatus, even if the first red toner 32 used in the first developing device 4 may be mixed in the second developing device 41, the mixed first positive red toner 32 is scratched. By the take-up plate 45, it is transferred onto the triboelectric charging layer 44c of the admixed toner separation roller 44 adjacent thereto together with the developer conveyed on the developing roller 42. During this transfer, the polarity is efficiently inverted to the negative polarity due to the triboelectric charging with the triboelectric charging layer 44c in which the contact area is increased by the minute uneven surface, or the charged electric charge amount is attenuated to a substantially zero level. . As a result, the mixed first red toner 32 having the negative polarity is
The second black toner 34 is electrostatically coupled to the second black toner 34,
The adhesion with the carrier 33 is reduced. For this reason, the first red toner 32 electrostatically coupled to the second black toner 34 or the first red toner 32 whose charge amount is greatly attenuated is easily scattered from the developer. Therefore, the first red toner 32 is scattered by the centrifugal force from the surface of the mixed toner separation roller 44 due to the rotational movement of the tips generated by the rotation of the magnetic roller 44b, and enters the area immediately below the mixed toner separation roller 44 partitioned by the partition plate 48. It can be separated and housed easily. On the other hand, the other developers are transferred to the developer supplying roller 43 by the scraping plate 46 and then supplied to the developing roller 42 again. Therefore, even if the recording operation is repeated for a long period of time, good color mixing does not occur. Two-color image recording can be stably performed. In the above embodiment, an example in which the invention is applied to a two-color recording apparatus has been described in order to simplify the description, but the essence of the present invention is not limited to this example and is applied to a multicolor recording apparatus. Of course it is possible. That is, FIG. 3 shows an example of a triboelectrification series of the carrier, each toner and the polarity reversal layer of the toner separation roller applied to the second developing device and the third developing device when the present invention is applied to a three-color recording device. FIG. In the present embodiment, the carriers in the developer used in the first, second and third developing devices have the same triboelectric charging characteristics, and in the first developing device, the common carrier 51 and the common carrier 51 are used. 1
Of the toner 52 of the second developing device, the developer of the common carrier 51 and the second toner 53 in the second developing device, and the third developing device.
Similarly, the developing device uses a common carrier 51 and a developer composed of a third toner 54, respectively. The particle size, electric resistance value, etc. of each of the toners and carriers are the same as those in the embodiment using the two-color recording apparatus. Further, in the second developing device and the third developing device, similarly to the configuration of the developing device shown in FIG. 1 (a), there are a developing roller and a developer supplying roller, respectively, and a mixed toner separating roller adjacent to them. With the configuration provided, the sleeve surface of the mixed toner separating roller of the second developing device is covered with the A frictional charging layer 55 having the frictional charging level shown in FIG. On the sleeve surface of the toner separation roller of the developing device, a B triboelectric charging layer 56 having the triboelectric charging level similarly shown in FIG.
Are covered. However, the above-mentioned first, second, and third developing devices are arranged, for example, along the surface of the photosensitive drum in accordance with the structure of the above-mentioned two-color recording device so as to face each other along with the respective charging devices and the exposing means, thereby forming a three-color recording device. By doing so, the first toner 52 mixed in the second developing device and the first and second toners 52, 53 mixed in the third developing device are respectively A frictional charged on the toner separating roller. By the triboelectric charging with the layer 55 or the B triboelectric charging layer 56, the polarity thereof is reversed or the amount of charged electric charge is attenuated.
Similar to the description of the embodiment using the two-color recording apparatus, it is possible to easily separate the different color toners mixed in the second and third developing devices, and to maintain good three-color recording without color mixture for a long period of time. It becomes possible to do. Further, the present invention is not limited to the recording apparatus of the above-described embodiment, and for example, one latent image forming means, a plurality of developing devices, transfer means, cleaning means, etc. are provided around the photosensitive drum (latent image forming medium). The photosensitive drum is adapted to form a toner image corresponding to one color image by the latent image forming means and one developing device selected while the photosensitive drum makes one rotation, and the photosensitive drum is rotated by the required number of colors. The present invention is also applicable to a multicolor recording apparatus of the type in which a multicolor toner image is formed on a photosensitive drum by the above, and then the multicolor toner image is collectively transferred to a recording sheet by a transfer unit. Is obtained. Further, in each of the above-mentioned embodiments, the example of the constitution in which the toner separating roller for separating the toner mixed from the previous developing device side is provided in each developing device arranged after the first developing device has been described. The present invention is not limited to this example, and for example, the polarity reversal of the toner mixed directly on the outer peripheral surface of the non-magnetic sleeve of the developing roller in the developing device, or the triboelectrification layer having the triboelectrification level for attenuating the electrification charge amount Alternatively, the developing roller itself may have a function of separating the mixed toner. Further, although the present invention has been described with respect to a multicolor recording apparatus using an electrophotographic recording method, the invention is not limited to this method, and a latent image forming means such as a gas discharge method using a pin electrode or an ion flow control method is used. It goes without saying that the present invention can also be applied to the electrostatic recording type multicolor recording apparatus. (g) Effect of the Invention As is clear from the above description, according to the multicolor recording apparatus of the present invention, each of the developing devices arranged after the first developing device of the plurality of developing devices is arranged in each developing device. It is possible to efficiently invert the polarity of the different color toner mixed in from the preceding developing device, or to attenuate the charged charge amount to a substantially zero level, and easily scatter and separate from the developer on the mixed side. Therefore, the mixed toner from the previous developing device is not accumulated in each developing device after the first developing device, and it is possible to stably perform vivid multicolor recording without any color mixture. Have. Further, there is an advantage in practical use, such as an increase in the amount of developer consumed for replacement due to the mixed toner and the elimination of replacement maintenance work, which facilitates maintenance of the apparatus.

[Brief description of drawings]

FIG. 1 (a) is a cross-sectional view of an essential part showing an embodiment of a developing device having a separating function of mixed toner used in the developing device after the second developing device of the recording apparatus according to the present invention, FIG. 2 (a) is a triboelectrification sequence diagram showing an example of triboelectrification levels of the carrier, each toner and the triboelectrification layer of the toner separation roller of the second developing device when the present invention is applied to a two-color recording apparatus. ) Is a schematic diagram showing a two-color recording device applied to briefly explain a conventional multi-color recording device using an electrophotographic recording system, and FIGS. 2B to 2G are two-color recording devices shown in FIG. FIG. 2 is a diagram showing a potential state on the photosensitive drum (latent image forming medium) in each recording process in the recording apparatus. FIG. 2 (h) shows each carrier and each toner used in the conventional first development and second development. FIG. 3 is a series of triboelectrification charts showing triboelectrification levels, and FIG. Rear, each of the toner and the second developing device and the third
FIG. 7 is a triboelectric charging series diagram showing an example of triboelectric charging levels of each triboelectric charging layer that covers the mixed toner separation roller of the developing device. In the drawings, 1 is a photosensitive drum, 2 is an initial charging unit, 3 is a first exposing unit, 4 is a first developing unit, 5 is a recharging unit, 6 is a second exposing unit, 7 is a second developing unit, and 8 is Transfer device, 9 fixing unit, 13 recording paper, 31 first carrier, 32 first red toner, 33 second carrier, 34 second black toner, 41 second developing device, 42 developing roller 42a, 43a, 44a are non-magnetic sleeves, 42b, 43b, 44b are magnetic rollers, 43 is a developer supply roller, 44 is a mixed toner separation roller, 44c is a triboelectric charging layer, 45 and 46 are scraping plates, 47, 48 and 49 are partition plates, 51 is a common carrier, 52 is a first toner, 53 is a second toner, 54 is a third toner, 55 is an A triboelectric charging layer, and 56 is a B triboelectric charging layer.

Claims (2)

[Claims] 1. A plurality of developing rollers and a developing roller (42) each comprising a toner (32, 34) and a carrier (31, 33) for each color around the latent image forming medium (1). A developing device, a transfer unit for transferring a multicolor toner image sequentially formed on the latent image forming medium (1) by the plurality of developing devices to a recording sheet, and a residual toner on the latent image forming medium (1). In a multi-color recording apparatus provided with a cleaning unit for removing, each carrier (31, 33) in the plurality of developing devices has a common triboelectrification characteristic, and each color toner (32, 34) is (31, 33) has a triboelectric charge level which becomes higher in the order of the developing device used, and is admixed adjacent to the developing roller (42) in each developing device after the second developing device (41). Toner (3
The frictional charge level (44c) in which the polarity reversal of 2) or the frictional charge level that attenuates the amount of charge is higher than that of the mixed toner (32) and lower than that of the toner (34) in the second developing device (41). A multicolor recording apparatus comprising a mixed toner separation roller (44) formed by coating. 2. The friction charging layer (44c) coated on the mixed toner separating roller (44) has fine irregularities on the surface thereof, according to claim (1). Multicolor recording device.