RECORDING APPARATUS AND METHOD

Abstract: This recording apparatus has an operation panel (8) for selecting a color image recording mode or a mono­ chromatic image recording mode, and color at monochro­ matic image recording mode time. When the color mode is selected by the panel (8), a photosensitive drum (22) is first charged by a charger (24). Then, a latent image formation and a development are repeated by latent image forming and developing unit (26, 30, 34, 38) on the drum (22) to form a color toner image. At this time, a bias electric field for arriving toner (T) flown from a de­ veloping roller (78) by electrostatic force at drum (22) unidirectionally and not returning from drum (22) is ap­ plied from a D.C. power supply (90) to between drum (22) and roller (78), and the latent image is developed with­ out contact between roller (78) and drum (22). Then, this color toner image is transferred to transfer sheet (P) by transfer charger (46) simultaneously. When mono­ chromatic mode is selected by the panel (8), the drum (22) is first charged by the charger (24). Then, a latent image is formed by the latent image forming and developing unit (26, 30, 34 or 38) on the drum, and de­ veloped. At this time, an A.C. electric field having sufficient intensity and frequency to cause toner (T) flown from the roller (l8) to reciprocate from the A.C. power supply (88) to between the drum (22) and the roll­ er (78). Then, the monochromatic developer image is transferred to a transfer sheet (P).

Description: The present invention relates to recording appara­ tus such as a color electrophotographic recorder and its recording method. In a conventional recording apparatus of this type, color recorders called "multiple-development and single-­ transfer type" and "multiple-development and multiple-­ transfer type" are known. In the multiple-development and single-transfer type, the electrostatic latent im­ ages formed sequentially on an image carrier, such as an electrophotographic photosensitive member, are de­ veloped by developers of different colors to form a multicolor toner image. Then, the images are simulta­ neously transferred to a record sheet. In the multiple-­ development and multiple-transfer type, electrostatic latent images are sequentially formed, developed and transferred to form a multicolor toner image on a re­ cording sheet. The multiple-development and single-transfer type is excellent in recording speed and superposing accuracy of the images, but has drawbacks such as a disorder of images and contamination with mixing colors of toners, occurring between developing units when unfixed images are superposed on an electrostatic recording medium. This type of a recording apparatus has not yet been put to practical use. There is proposed in Japanese Patent Application No. 233407/l982 a color recording apparatus which has a process for solving such drawbacks by preventing the same portions from being redeveloped. When this appara­ tus is used as a monochromatic recorder for a computer output unit, it is requested to improve the quality of images and recording speed. The above-mentioned drawbacks are not completely solved only by electrostatically preventing the mixing colors of toners. It is also confirmed that developing units necessitate no mechanical contact between toner and the image to be developed on the sheet. Therefore, a flying developing method is considered. This method can not only prevent mixing of colors and thus subse­ quent contamination, but also can provide excellent gradation and color recording as compared with the con­ ventional magnetic brush developing method. However, this method is apparently undesired for the purpose of copying a document full of characters. Consequently, it is difficult to provide a recording apparatus which can perform the above-mentioned both functions by one appa­ ratus. An object of the present invention is to provide recording apparatus and method capable of providing a preferable image in both color and monochromatic image recordings. According to an aspect of the present invention, there is provided a recording apparatus for recording a color image or a monochromatic image of a color selected from a plurality of colors on a recording member with a plurality of developing agent, comprising: selecting means for selecting color image recording mode or a monochromatic image recording mode and select­ ing the color at monochromatic image recording time, an image carrier provided movably in a predeter­ mined direction, charging means for charging the carrier, a plurality of latent image forming and developing means provided along the moving direction of the carrier for using the developing agents of the plurality of colors, said latent image forming and developing means respectively having latent image forming means for form­ ing a latent image on the carrier charged by the charg­ ing means, and developing means for developing the latent image formed by the latent image forming means with the developing agents so that the plurality of latent image forming and developing means alternatively repeat the formation of the latent image on the carrier charged by the charging means and the development of the latent image at color image recording mode time to form a color developing agnet image, said latent image forming and developing means of the color selected by the selecting means forms the latent image on the carrier charged by the charging means, and develops the latent image at the monochromatic image recording mode time to form a mono­ chromatic developing agent image, and said developing means of at least the latent image forming and developing means for forming and developing latent images other than the first one develops the latent images without contact with the carrier, transfer means for transferring the color devel­ oping agent image and monochromatic developing agent image formed by the latent image forming and developing means on the recording member, and bias electric field applying means for applying a bias electric field between the carrier and at least the developing means other than the first one, said bias electric field applying means applying the bias electric field for moving the developing agent flown from the developing means by electrostatic force to move only in a direction toward the carrier at color image recording mode time and applying A.C. bias elec­ tric field having a sufficient intensity and frequency to cause the developing agnet flown from the developing means to reciprocate at monochromatic image recording mode time. According to another aspect of the present inven­ tion, there is provided a recording apparatus for re­ cording a color image or a monochromatic image of a color selected from a plurality of colors on a recording member with a plurality of developing agents, comprising: selecting means for selecting color image recording mode or a monochromatic image recording mode and select­ ing the color at monochromatic image recording time, an image carrier provided rotatably movably, drive means for rotating the carrier by plural rotations at color image recording mode time and by one revolution at monochromatic image recording mode time, charging means for charging the carrier rotated by the drive means at least first rotating time of the plural rotations at color image recording mode time and at one revolution time at monochromatic image recording mode time, latent image forming means for forming a latent image at every one revolution of the carrier on the carrier charged by the charging means, developing means for developing the latent image formed by the latent image forming means, said develop­ ing means having a plurality of developing units pro­ vided along the rotating direction of the carrier for developing the latent image with the plurality of devel­ oping agents so that the plurality of developing units sequentially develop the latent images formed at every one revolution on the carrier by the latent image form­ ing means at every one revolution at color image record­ ing mode time to form a color developer image, and the developing unit for developing with the developing agent corresponding to the color selected by the selecting means develops the latent image formed by the latent image forming means at monochromatic image recording mode time to form a monochromatic developing agent im­ age, the developing unit for developing at least the latent images other than the first one at color image recording mode time develops the latent image in noncon­ tact on the carrier, transfer means for transferring the color developer image and monochromatic developing agent image formed by the developing means on the recording member, and bias electric field applying means for applying a bias electric field between the carrier and at least the developing means other than the first one, said bias electric field applying means applying the bias electric field for moving the developing agent flown from the developing means by electrostatic force to move only in a direction toward the carrier at color image recording mode time and applying an A.C. bias electric field having a sufficient intensity and frequency to cause the developing agent flown from the developing means to reciprocate at monochromatic image recording mode time. According to further aspect of the present inven­ tion, there is provided a recording method for forming a developer image by developing a latent image formed on an image carrier by developing means to record a color image or a monochromatic image of a color selected from a plurality of colors on a recording member by transfer­ ring the developing agent image on the recording member, comprising the steps of: selecting a color image recording mode or a mono­ chromatic image recording mode and a color at monochro­ matic image recording mode time, charging the carrier at color image recording mode time when selecting the color image recording mode at the selecting step, forming and developing a latent image at color im­ age recording mode time to form a color developing agent image by repeating the formation of the latent image on the carrier charged in the charging step and the devel­ opment of the latent image, the latent image forming and developing step having a step of applying a bias electric field for moving the developing agent flown from the de­ veloping means by electrostatic force, between the car­ rier and at least the developing means other than the first one only in a direction toward the carrier, and the developing means performing at least the stepf of develo­ ping the latent image other than the first step of devel­ oping the latent image, without contacting the carrier, transferring the developing agent image formed by the forming and developing steps simultaneously on the recording member at color image recording mode time, charging the carrier at monochromatic image record­ ing mode time when monochromatic image recording mode is selected by the selecting step, forming a latent image on the carrier charged by the charging step at monochromatic image recording mode time, developing the latent image formed in the step of forming the monochromatic latent image at the monochroma­ tic image recording mode time to form a monochromatic developer image, said developing step applying an A.C. electric field having sufficient intensity and frequency to cause the developer flown from the developing means to reciprocate between the carrier and the developing means, and transferring the developer image formed in the de­ veloping means on the recording member at monochromatic image recording mode time. According to the recording apparatus and method of the present invention, at least second development is performed with the image carrier and the developing means without contact. Further, a D.C. electric field is sub­ stantially applied to between the developing means and the image carrier at color image recording time. An A.C. electric field is acted between the developing means and the image carrier at monochromatic image recording time. It can prevent the colors from mixing at color image re­ cording time, and provide a high contrast image at the monochromatic recording time. Therefore, the recording apparatus can record at equivalent speed as a color copy­ ing machine or a color printed without decreasing the functions as a conventional office copying machine or printer. This invention can be more fully understood from the following detailed description when taken in con­ junction with the accompanying drawings, in which: Fig. l is a schematic sectional view showing a first embodiment of a recording apparatus according to the present invention; Fig. 2 is a side view showing a light scanner of the apparatus of Fig. l; Fig. 3 is a perspective view of the light scanner; Fig. 4 is a view for describing the construction of a developing unit of the apparatus in Fig. l; Fig. 5 is a view showing a circuit for applying a bias voltage of the apparatus in Fig. l; Fig. 6 is a flowchart showing the image forming sequence of the apparatus in Fig. l; Fig. 7 is an explanatory view showing the state of the surface potential on a photosensitive member of the apparatus in Fig. l; Fig. 8 is a view showing the relationship between the electrostatic contrast voltage on the photosensitive member and the image density of the apparatus in Fig. l; and Fig. 9 is a schematic sectional view showing a second embodiment of a recording apparatus according to the present invention. Fig. l shows a first embodiment of a recording ap­ paratus according to the present invention. In Fig. l, reference numeral 2 designates a housing. Original platform 4, indicator 6 and Operation panel 8 are pro­ vided on the upper surface of housing 2. An original is placed on platform 4. Indicator 6 indicates record­ ing operation mode, for example, the number of copies. Panel 8 has selection keys l0 for selecting a color image recording mode or a monochromatic image recording mode, and selecting a color at monochromatic image re­ cording mode time. Original reader l2 for reading an original image by scanning the original on platform 4 is provided under platform 4. More particularly, reader l2 emits the original placed on platform 4 by lamp l4, and its reflected light is transmitted through color separa­ tion filter l6, and received by a photoelectric trans­ ducer l8. Thus, image information is converted into an electric signal. The image information thus converted is supplied to memory information processor 20. Photosensitive drum 22 which rotates in a predeter­ mined direction is supported substantially to the center in housing 2. Around drum 22 are sequentially arranged along the rotating direction of drum 22, charger 24, first latent image forming and developing unit 26, first recharger 28, second image forming and developing unit 30, second recharger 32, third latent image forming and developing unit 34, third recharger 36, fourth latent image forming and developing unit 28. Units 26, 30 and 34 respectively have light scanners 40 and developing units 42. Drum 22 is rotatably driven through a drive force transmission mechanism, not shown, by motor 44. In this case, drum 22 is rotated by one revolution at one image recording time. Further, transfer charger 46, separator 48, dielec­ tric lamp 50 and cleaner 52 are sequentially arranged from unit 38 to charger 24. A toner image (developing agent image) on drum 22 is transferred to transfer sheet (transferring medium) p supplied from sheet supplying unit 54 by charger 46. Sheet p thus transferred with the toner image is separated from drum 22 by separator 48. The toner image transferred to sheet p is fixed by fixing unit 56. Sheet p on which the toner image is fixed is exhausted on tray 58 out of housing 2. After the toner image is transferred from drum 22 to sheet p, the sur­ face of drum 22 is deenergized by lamp 50. After this deenergization, the toner remaining on drum 22 is cleaned by cleaner 52. After cleaning, drum 22 enters next cycle. Input unit 60 is provided at the side of housing 2, and an image signal is inputted to unit 60 from external unit 62 (Fig. 5). Scanners 42 of first to fourth units 26, 30, 34 and 38 scan with lights on the surface of drum 22 ac­ cording to a signal fed through output circuit 64 from processor 20 or a signal fed through unit 60 from unit 62. As shown in Figs. 2 and 3, scanner 40 has an array of light emitting elements (hereinafter referred to as "an LED array") 66 provided on the optical axis of con­ vergent photoconductive members (Selfoc lens, trade name) 68. In LED array 66, light emitting diodes are arrayed per l mm. Array 66 is mounted on ceramic substrate 74 together with drive IC 70 and terminal pins 72. Members 68 are mounted through a pair of holders 76 (one of which is shown) on substrate 74. Unit 42 of first unit 26 is, for example as shown in Fig. 4, of one-component noncontact developing unit. Unit 42 has conductive developing roller 78, toner coating blade 80, recovery blade 82 and temporary sepa­ rating brush 84 of toner T. Roller 78 is rotated sub­ stantially at equal speed to drum 22 through a gap of l00 to 400 micron. Blade 80 is formed of phosphorus bronze or urethane rubber elastically contacted under pressure with roller 78, and a thin layer of high resistance-one-component nonmagnetic toner (having ll micron of mean diameter) T is coated on roller 78. De­ veloping units of second to fourth units 30, 34 and 38 have similar construction as unit 42 of first unit 26. Unit 42 of first unit 26 contains positively charged black toner, unit 42 of second unit 30 contains posi­ tively charged magenta toner, unit 42 of third unit 34 contains positively charged cyan toner, and unit 42 of fourth unit 38 contains positively charged yellow toner. As shown in Figs. 4 and 5, A.C. bias electric field from A.C. power supply 88 or D.C. bias electric field from D.C. power supply is applied through changeover switches 86 to between developing units 40 and drum 22. Switches 86 are driven by a signal supplied through con­ troller 92 from panel 8 or a signal supplied from unit 62 through interface 94 and controller 92. The image recording operation will be described. A color mode or a monochromatic mode is first sel­ ected and a color to be used at monochromatic mode time is selected by panel 8 or unit 62 in step l. Then, the operation is advanced to step 2. In step 2, whether is it color mode or monochroma­ tic mode is judged. If judged as color mode, the opera­ tion advances to step 3. In step 3, the bias electric fields of all units 42 are switched by switch 86 to the D.C. bias electric field. Then, the operation advances to step 4. In step 4, 5.6 kV of positive D.C. voltage is ap­ plied by charger 24 to set drum 22 to l000 V (V=l000 V). Then, the operation advances to step 5A. In step 5A, charged drum 22 is scanned by scanner 40 of first unit 26 in accordance with an image signal (black information) fed from reader l2 or unit 52. Thus, an electrostatic latent image according to black information is formed. Then, the latent image is de­ veloped by unit 52 of first unit 25. In other words, the image is developed by first color noncontact invert­ ing development with positive black toner T. At this time, an output voltage (600 to 850 V) of D.C. power supply 90 is applied through switch 86 to roller 78 of unit 42. The operation goes to step 5B. Then, in step 5B, a voltage having 4.0 kV of D.C. component and 5.0 kV of A.C. component is applied to first corotron type recharger 28, and the potential of first exposure unit (i.e., developing unit) is recharg­ ed to become substantially equal to the potential of unexposure portion. Then, recharged drum 22 is exposed and scanned by scanner 40 of unit 30 according to a red image signal. Thus, an electrostatic latent image ac­ cording to red information is formed. Then, the latent image is developed by unit 42 of second unit 30. In other words, second color noncontact inverting develop­ ment of positive red toner T is performed. The develop­ ing conditions at this time are entirely the Same as unit 42 of first unit 26. In other words, a flying de­ velopment mainly using D.C. bias electric field is achieved. In this case, since the flying property of toner T is different depending upon the difference of toner T, the voltage is suitably regulated. Thus, toner T is transferred in noncontact under D.C. bias electric field. Thus, first unfixed toner image formed already on drum 22 is not mechanically disordered. Since toner T is transferred in unidirectional electric field (i.e., D.C. bias electric field), the movement of toner T is unidirectional similarly to electrostatic force. Thus, since toner T on drum 22 is not reversely transferred to unit 42 of second unit 30, it can prevent different color toners from mixing. Since the first exposure unit is reset to the initial potential by recharging, the portion which is not subjected to the second expo­ sure is not redeveloped. Accordingly, since it can simultaneously prevent the recording image from unde­ sirably mixing in colors, conditions necessary in color copying process are all satisfied. The developing bias may not always be complete D.C. bias electric field but may superpose A.C. bias electric field component thereon. This is because electrostatic vibration is acted on toner T on roller 78 to be acti­ vated to improve the developing sensitivity. However, if A.C. component increases to approx. 400 V or higher, an electric field for returning toner T reversely in­ creases to cause toner already recorded on drum 22 is separated, thereby inducing image noise or mixture of colors. Thus, if the A.C. component is approx. 400 V or higher, it is not preferable to superpose the A.C. bias electric field on the D.C. electric field bias. There­ fore, it is necessary to improve the developing property so as not to lose the unidirectivity of transfer of toner T when superposing the D.C. bias on the A.C. bias electric field. Thereafter, the operation advances to step 5C. In step 5C, second recharger 32, and third unit 34 are similarly driven, thus achieving third color noncon­ tact inverting developing by using positive upon toner T. Then, in step 5D, third recharger 36 and unit 38 are sequentially driven under the same conditions, thereby performing fourth color noncontact inverting developing by using positive yellow toner T. Thus, toner image of desired colors may be formed on drum 22. Then, the operation advances to step 6. In step 6, the color toner image is applied with -5.5. kV of voltage by charger 46, and transferred to transfer sheet p fed from sheet supply unit 54. The transferred sheet p is separated from drum 22 by separa­ tor 48, fixed by fixing unit 56, and exhausted to tray 58. In copying by color image recording process under the abovementioned conditions, unnecessary color mixture can be entirely eliminated to obtain a color print hav­ ing excellent color reproducibility. Fig. 7 shows the relationship between the surface potential of drum 22 and rotating position of drum 22 at this time. Potentials VR₁, VR₃, VR₅ after exposed by scanner 40 are recharged by all 750 V or higher not developed by rechargers 28, 32 and 36,respectively. Further, drum 22 is recharged by rechargers 28, 32 and 36 in the attenuated amount due to natural discharge (dark attenuation) of drum 22 to maintain potentials V₁ to V₃ not exposed of drum 22 at set voltage of l000 V. Rechargers 28, 32 and 36 are not limited to corotron type, but may be scorotron type. Then, when the monochromatic mode is judged in step 2, the operation is advanced to step 7. In step 7, the bias electric field of unit 42 of used color is switched by switch 86 to D.C. bias elec­ tric field. Then, the operation is advanced to step 8. In step 8, when cyan (blue) is, for example, desig­ nated as a color to be used, only second recharger 32 is operated as a print is started, and drum 22 is charged to approx. 600 V. This charging potential was l000 V in the previous color mode, but since the developing pro­ perty is varied in this monochromatic mode, the charging voltage is regulated. Then, advanced to step 9. In step 9, a latent image is formed by scanner 40 of color to be used. Then, advanced to step l0. In step l0, unit 42 of color to be used is operat­ ed. At this time, A.C. power supply 88 is connected through switch 86 to roller 78 of unit 42. In other words, an A.C. bias electric field in which D.C. voltage of 350 to 500 V, A.C. voltage having executing value of 300 to 800 V and frequency of 0.8 to 3 kHz are super­ posed is applied. Thus, a latent image formed by scan­ ner 40 is inverted and developed by unit 42. In this case, toner T on roller 78 is repeated in vibration between roller 78 and drum 22 by A.C. bias electric field. Thus, since toner T is gradually attracted and converged to the latent image, the property that more toner T is adhered to the line or profile of the latent image is presented. Therefore, preferable image charac­ teristic as office print or copy can be provided. In this monochromatic mode, charging, exposing and developing units are selectively operated similarly to the case of selecting other any color, and charging output is switched and distributed to similarly provide preferable monochromatic line copy. Fig. 8 shows the comparison of the case (A) that the relationship between electrostatic contrast voltage and image density on drum when developing with black toner under D.C. bias electric field with the case (B) that the same relationship when developing under A.C. bias electric field, with respect to the image property at line of 0.l mm of width. From this comparison, the advantages of switching both modes are clarified. Thus, desired monochromatic toner image is formed on drum 22. Then, the operation is advanced to step ll. In step ll, the monochromatic toner image is transferred to sheet p fed from sheet supply unit 54 by applying -5.5 kV of voltage by transfer charger 46. The transferred sheet p is separated from drum 33 by separator 48, fixed by unit 56, and exhausted on dry 58. As described above, the noncontact type developing unit is used as unit 42. D.C. bias electric field is applied substantially between unit 42 and drum 22 at color image recording time, and A.C. bias electric field is acted between unit 42 and drum 22 at monochromatic image recording time. Thus, toner T is flown and trans­ ferred. Thus, mixture of colors can be prevented at color image recording time, and a high contrast image can be provided at monochromatic image recording time. Accordingly, this recording apparatus can provide equi­ valent speed as a color copying machine and a color printed without decreasing the functions as a conven­ tional office copying machine or printer for performing the monochromatic image recording. In the embodiments described above, unit 42 employs noncontact type developing unit. However, since a toner image is not formed on drum ll in the previous stage of unit 42 of first latent image forming and developing unit 26, a contact type developing unit may be used as unit 42 of first unit Further, rechargers 28, 32 and 36 may not always be necessarily provided. In the embodiment described above, a D.C. bias voltage is applied to all developing units 42 when the color mode is selected. Nontheless, the present invention is not limited to this. It suffices to apply the voltage to the second to fourth units 42. Fig. 9 shows a second embodiment of a recording apparatus according to the invention. In this second embodiment, recharger l02, light scanner l04, first developing unit l06, second developing unit l08, third developing unit ll0 and fourth developing unit ll2 are sequentially arranged along the rotating direction of drum 22 around drum 22. Drum 22 is rotatably driven through a drive force transmission mechanism, not shown, by motor 44. In this case, drum 22 is rotated by one revolution at first monochromatic image recording time, but rotated at plural revolutions (e.g., four revolu­ tions) at first color image recording time. Charging by charger l02, latent image formation by scanner l04 and development by first unit l06 are achieved by first rotation of drum 22 at color mode time. Then, charging by charger l02, latent image for­ mation by scanner l04 and development by second unit l08 are performed by second revolution of drum 22. Similar­ ly, charging, latent image formation and development of third and fourth revolutions are similarly carried out. Charging by charger l02, latent image formation and development by developing unit of color to be used are achieved by one revolution of drum 22 at monochromatic mode time. The other construction and operation are similar to those of first embodiment. According to the construction described above, scanners and chargers may be reduced. Therefore, the recording apparatus can be simplified and reduced in cost.

Claims: 1. A recording apparatus for recording a color image or a monochromatic image of a color selected from a plurality of colors on a recording member (P) with a plurality of developing agents (T), comprising: select­ ing means (l8) for selecting color image recording mode or a monochromatic image recording mode and selecting the color at monochromatic image recording time, an im­ age carrier (22) provided movably in a predetermined direction, charging means (24) for charging the carrier (22), a plurality of latent image forming and developing means (26, 30, 34, 38) provided along the moving direc­ tion of the carrier (22) for using the developing agents (T) of the plurality of colors, the latent image forming and developing means (26, 30, 34, 38) respectively hav­ ing latent image forming means (40) for forming a latent image on the carrier (22) charged by the charging means (24), and developing means (42) for developing the latent image formed by the latent image forming means (40) with the developing agents (T) so that the plurality of latent image forming and developing means (26, 30, 34, 38) al­ ternatively repeat the formation of the latent image on the carrier (22) charged by the charging means (24) and the development of the latent image at color image re­ cording mode time to form a color developing agent im­ age, said latent image forming and developing means (26, 30, 34, 38) of the color selected by the selecting means (8) forms the latent image on the carrier (22) charged by the charging means (24) and develops the latent image at the monochromatic image recording mode time to form a monochromatic developing agent image, transfer means (46) for transferring the color developing agent image and monochromatic developing agent image formed by the latent image forming and developing means (26, 30, 34, 38) on the recording member (P), and bias electric field applying means (88, 90) for applying a bias electric field, characterized in that the developing means (42) of at least the latent image forming and developing means (26, 30, 34, 38) for forming and developing latent images other than the first one develops the latent image without contact with the carrier (22), and the bias electric field applying means (88, 90) applies the bias electric field, between the carrier (22) and at least the developing means other than the first one, for moving the developing agent flown from the developing means (42) by electrostatic force to move only in a direction toward the carrier (22) at color im­ age recording mode time and applying an A.C. bias elec­ tric field having a sufficient intensity and frequency to cause the developing agent flown from the developing means (42) to receiprocate at monochromatic image record­ ing mode time. 2. The recording apparatus according to claim l, characterized in that the developing means (42) of at least the latent image forming and developing means (26, 30, 34, 38) for forming and developing at least latent images other than the first one has a noncontact devel­ oping unit (42) using one-component developing agent (T). 3. The recording apparatus according to claim 2, characterized in that the noncontact developing unit (42) performs an inverting development. 4. The recording apparatus according to claim l, characterized in that the recording apparatus further comprises a plurality of recharging means (28, 32, 36), the recharging means (28, 32, 36) recharging the image carrier (22) prior to the image formation by at least the latent image forming and developing means (26, 30, 34, 38) other than the first one, at color image recording time. 5. The recording apparatus according to claim 4, characterized in that the recharging means (28, 32, 36) recharges the image carrier (22) by applying a D.C. corona voltage to the carrier (22). 6. The recording apparatus according to claim 4, characterized in that the recharging means (28, 32, 36) recharges the image carrier (22) to a level for elimi­ nating the potential difference generated by the forma­ tion of the latent image by the previous latent image forming and developing means (26, 30, 34, 38) to a level for not developing the electrostatic latent image formed by the previous latent image forming and developing means (26, 30, 34) by next latent image forming and de­ veloping means (30, 34, 38). 7. The recording apparatus according to claim l, characterized in that the developing means (42) of at least the latent image forming and developing means (26, 30, 34, 38) other than the first one develops the latent image without contact with developing agent adhered al­ ready to the image carrier (22). 8. The recording apparatus according to claim l, characterized in that the image carrier (22) has a photosensitive drum (22) rotating in a predetermined direction. 9. The recording apparatus according to claim 8, characterized in that the latent image forming means (40) and developing means (42) are alternately disposed along the rotating direction of said photosensitive drum (22). l0. A recording apparatus for recording a color image or a monochromatic image of a color selected from a plurality of colors on a recording member (P) with a plurality of developing agents (T), comprising: select­ ing means (8) for selecting color image recording mode or a monochromatic image recording mode and selecting the color at monochromatic image recording time, an im­ age carrier (22) provided rotatably movably, drive means (44) for rotating the carrier (22) by plural rotations at color image recording mode time and by one revolution at monochromatic image recording mode time, charging means (l02) for charging the carrier (22) rotated by the drive means (44) at least first rotating time of the plural rotations at color image recording mode time and at one revolution time at monochromatic image re­ cording mode time, latent image forming means (l04) for forming a latent image at every one revolution of the carrier (22) on the carrier charged by the charging means (l04), developing means (l06, l08, ll0, ll2) for developing the latent image formed by the latent image forming means (l04), said developing means (l06, l08, ll0, ll2) having a plurality of developing units (l06, l08, ll0, ll2) provided in the rotating direction of the carrier (22) for developing the latent image with the plurality of developing agents (T) so that the plurality of developing units (l06, l08, ll0, ll2) sequentially develop the latent images formed at every one revolution on the carrier (22) by the latent image forming means (l04) at every one revolution at color image recording mode time to form a color developing agent image, and the developing unit (l06, l08, ll0, ll2) for developing with the developing agent corresponding to the color selected by the selecting means (8) develops the latent image formed by the latent image forming means (l04) at monochromatic image recording mode time to form a mono­ chromatic developing agent image, transfer means (46) for transferring the color developer image and monochro­ matic developing agent image formed by the developing means (l06, l08, ll0, ll2) on the recording member (P), and bias electric field applying means (88, 90) for ap­ plying a bias electric field, characterized in that the developing unit (l06, l08, ll0, ll2) for devel­ oping at least the latent images other than the first one at color image recording mode time develops the latent images in noncontact on the carrier (22), and the bias electric field applying means (88, 90) applies the bias electric field, between the carrier and at least the developing means other than the first one, for moving the developing agent (T) flown from the developing means (l06, l08, ll0, ll2) by electrostatic force to move only in a direction toward the carrier (22) at color image recording mode time and applying an A.C. bias electric field having a sufficient intensity and frequency to cause the developing agent (T) flown from the developing means (l06, l08, ll0, ll2) to reciprocate at monochroma­ tic image recording mode time. 11. A recording method for forming a developing agent image by developing a latent image formed on an image carrier (22) by developing means (42, l06, l08, ll0, ll2) to record a color image or a monochromatic image of a color selected from a plurality of colors on a recording member (P) by transferring the developing agent image on the recording member (P), comprising: selecting step (St.l, St.2, St.3, St.7) for selecting a color image recording mode or a monochromatic image re­ cording mode and a color at monochromatic image record­ ing mode time, charging step (St.4) for charging the carrier (22) at color image recording mode time when selecting the color image recording mode at the select­ ing step (St.l, St.2, St.3, St.7), forming and develop­ ing step (St. 5) for forming and developing a latent image at color image recording mode time to form a color developing agent image by repeating the formation of the latent image on the carrier (22) charged in the charging step (St.4) and the development of the latent image, the latent image forming and developing step (St.5) having a step of applying a bias electric field, transferring step (St.6) for transferring the developing agent (T) image formed by the forming and developing steps (St.5) simul­ taneously on the recording member (P) at color image re­ cording mode time, charging step (St.8) for charging the carrier (22) at monochromatic image recording mode time when monochromatic image recording mode is selected by the selecting step (St.l, St.2, St.3, St.7), forming step (St.9) for forming a latent image on the carrier (22) charged by the charging step (St.8) at monochromatic image recording mode time, developing step (St.l0) for developing the latent image formed in the step (St.9) of forming the monochromatic latent image at the monochroma­ tic image recording mode time to form a monochromatic de­ veloper image, the developing step (St.l0) applying a bias electric field, and transferring step (St.ll) for transferring the developer image formed in the developing means (42, l06, l08, ll0, ll2) on the recording member (P) at monochromatic image recording mode time, characterized in that the developing means (42, l06, l08, ll0, ll2) de­ velops at least latent images other than the first one on the carrier (22) without contact, the bias electric field of the latent image forming and developing step (St.5) moves the developing agent (T) flown from the developing means (42, l06, l08, ll0, ll2) by electrostatic force only in a direction toward the carrier (22), and the bias electric field of the developing step (St.l0) in an A.C. electric field having sufficient intensity and frequency to cause the developing agent (T) flown flow the develop­ ing means (42, l06, l08, ll0, ll2) to reciprocate, the bias electric field being provided between the carrier (22) and at least the developing means other than the first one. 12. The recording method according to claim ll, characterized in that the forming and developing step (St.5) of color image recording mode has recharging the image carrier prior to at least the step of the formation later latent image, other than the first step of forming the latent image.

Inventors: KOHYAMA, MITSUAKI TOSHIBA K.K. PATENT DIVISION
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1986
Main classification: G03G15
IPC codes: G03G15