Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G15/00—Apparatus for electrographic processes using a charge pattern
  • G03G15/01—Apparatus for electrographic processes using a charge pattern for producing multicoloured copies
  • G03G15/0142—Structure of complete machines
  • G03G15/0147—Structure of complete machines using a single reusable electrographic recording member
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F3/00—Colour separation; Correction of tonal value
  • G03F3/10—Checking the colour or tonal value of separation negatives or positives
  • G03F3/105—Checking the colour or tonal value of separation negatives or positives using electro photographic materials

Definitions

• the invention relates to a method for the formation of a multi ⁇ colour proof print starting from a ⁇ least two (light-trans ⁇ mitting) colour separations.
• colour separations i.e. of partial images in each of the three basic colours (yellow, magenta, cyanogen) and usually supple ⁇ mented with a partial image in black.
• Different techniques are known for obtaining these colour separations, starting from the original to be reproduced and naturally before start- ing the final production printing run a check must be made that a good final result is obtained with the colour separat ⁇ ions formed.
• the present invention aims at providing a method for form ⁇ ing a multi-colour proof print which can be executed rapid ⁇ ly and cheaply and which provides a result which corresponds so well with a print formed on a printing press that it is possible to make a good assessment of the colour separations.
• the method according to the invention consists in a charge pattern being formed from each colour separation by ex ⁇ posure of a photoconductive coating which has been charged in advance to a certain charge level, this charge pattern being developed a predetermined period after the charge state has been achieved, using toner of a colour which corresponds with the colour separation concerned, and the transfer of the toner image thus obtained onto a receptor surface, so that the second and subsequent toner images are in registration with the preceding one(s), whereby the photoconductive coating for each of the partial images is charged up to an identical final charge state and the develop ⁇ ment with toner starts after a period of time after the coating has achieved the final charge state, which is iden- tical for all partial images.
• the present invention is based on the insight that fully re ⁇ producible and comparable results are obtained if, starting from a final charge state for the electrophotographic coating which is identical for all partial images, the development of the respective partial images starts at an identical point on the darkness decay curve of the corresponding coating
• the charging of the coating is preferably undertaken during a period which is identical for all the respective toner partial images, the same as the development by applying toner.
• Preferably several coatings having mutually identical charac- teristics are used for the formation of the respective par ⁇ tial images, whereby preferably the charging of a photocon ⁇ ductive coating is undertaken during the period of develop ⁇ ment of a coating which prior to this has already been charged up and exposed with a partial image of a different colour.
• the exposures for a certain colour separation are preferably effected with equal light quantities throughout the series, when using coatings sensitive to glare phenomena.
• the quality of the toner image is improved when the coating is moistened with a toner dispersant prior to the application of toner.
• the surface thereof is moistened with a suitable solvent and the applied solvent is then sucked off.
• the quality is still better when, prior to the transfer of toner, the receptor surface is moistened and dried after toner transfer.
• accordance with the invention comprises a housing which accommodates a flat support for a photoconductive coating, means for charging and exposure thereof, and means for the transfer to a receptor surface of a toner image obtained by interaction of the coating with one of a number of toner holders which are provided with toner application means and movable individually so as to bring about inter-action be ⁇ tween the coating and a certain, selected toner holder.
• a preferred embodiment of this device is such that the sup ⁇ port can be moved around a fixed axis" parallel with the surface from an initial position, in which the coating can be charged and exposed, to a second position which is ro ⁇ tated through 180 with respect thereto, in which the ex ⁇ posed surface can be provided with toner from one of the toner holders located one above the other in a magazine, which for this purpose can, by means of a drive mechanism be brought out of the magazine into a path which extends along the support and back into the magazine.
• the device is such that the support carries a photoconductive coating on both surfaces, the support be ⁇ ing horizontal in the two positions, the charging and ex ⁇ posure means being located above the level of the support
• the horizontal location of the support with the photoconduc ⁇ tive coatings and the arrangement described above of the means interacting therewith contributes to a compact con ⁇ struction and especially facilitates the supply of toner to the exposed photoconductive coating.
• each toner holder is closed at the top by a flat plate having at least two slots located transverse to the direction of movement of the holder, the level of which coincides with that of the outer surface of a toner transport roller mounted in the holder, which roller can be driven in rotary fashion in a direction opposed to the direction of movement of the holder, toner being applied by the roller to the plate from the holder during this rotation.
• the plate is electrically isolated with res ⁇ pect to the support and, in order to function as developing electrode, can be brought to a certain electrical potential with respect to the support. Satisfactory and uniform appli ⁇ cation of the toner is facilitated if the rollers can be displaced over a short distance transverse to the axial direction thereof.
• the toner which still remains behind on the photoconductive coating after image transfer is removed; for this purpose use can be made of one or several solvent discharge and suction nozzles having the discharge aperture facing upwards, covering the width of the coating, which are accommodated in an essentially horizontal direction in a frame which can move to and fro underneath the coating.
• a holder for solvent which can move to and fro in a horizontal direction underneath the " codting and one or several application rolls which pro ⁇ ject over a short distance from the upper confine thereof, which are driven in rotary fashion and connected with a narrow overflow chamber which passes over the photoconductive coating and which is open at the top, connected to a solvent feed pipe, accommodated in and projecting from a holder pro ⁇ vided with a liquid outlet, possibly combined with a suction nozzle which passes over the photoconductive coating.
• Fig. 1 shows aschematic frontal view of the mutual position of the different constituent parts of the arrangement in ac- cordance with the invention
• OM Fig. 2 provides ⁇ view in the direction of the arrow 2;
• Fig. 3 provides a view in the direction of the arrow 3;
• Fig. 4a - 4e show the positions and movements of the diffe ⁇ rent constituent components with respect to each other;
• Fig. 5 is a schematic side view, partially in section, of a toner holder employed in accordance with the invention;
• Fig. 6 is a schematic section of an arrangement for applying an accurately predetermined quantity of toner solvent to the photoconductive coating;
• Fig. 7 is a perspective representation of a part of the arrangement in accordance with the invention;
• Fig. 8 illustrates the left-hand portion of this arrangement;
• Fig. 9 gives a perspective view of the right-hand portion of this arrangement.
• the device consists of a flat support 1, shown in frontal view in fig. 1, which can rotate around the shaft 2 which is located in the plane of the drawing; the surface of the sup ⁇ port 1 is thus vertical to the plane of the drawing.
• the support 1 On each of the large surfaces the support 1 is provided with a photo ⁇ conductive coating, indicated by the reference numerals 3 and
• Both coatings possess the same characteristic properties.
• the source of radiation 7 is employed for image-wise exposing viathe colour separation 6, the photoconductive coating af ⁇ ter this latter has been charged up in the conventional man ⁇ ner; this charging up is undertaken by means of a corona device 8 (see fig. 2 and 3) which, when the frame 5 is tilted upwards in the direction of the arrows 9, can be moved over the surface of the coating 3.
• toner holders 13 - 16 accommodated in a frame 12 which is shown schematically, these being filled with toner of different colours.
• the frame 12 can move upwards and down ⁇ wards in the direction of the arrows 17, whilst a certain selected toner holder, the top edge of which lies below the level of the lowest photoconductive coating, shown y the dashed line 18, can be brought out of the frame and can move to and fro along the bottom of this photoconductive coating
• OMPI in the direction shown by arrow 19 so as to supply toner to the photoconductive coating.
• a device 20 for the removal of residual to- ner from the photoconductive coating comprises a pair of rotary application rollers 22 mounted in a holder 21 which is filled with solvent, and a suction nozzle 23 arranged close thereto.
• These elements are combined with the toner solvent application device 40, which will be described in greater detail by reference to fig. 6, by means of which an accurately determined quantity of solvent is applied to the photoconductive coating.
• Toner carriage 14 the construction of which will be des ⁇ cribed in greater detail later, is removed from the frame 12 by means of a suitable drive arrangement and moved in the direction of arrow 19 along the bottom of the exposed photoconductive coating, on which there is now a latent charge image, so as to apply toner to the charged surface portions of the coating 3.
• This toner feed operation for all the partial images which have to be produced with the diffe- rent colour separations commences a certain period of time after the coating has been charged up to a predetermined final charge state which is similarly identical for all partial images. Since the characteristics of.both coatings 3 and 4 are identical, image formation for all partial ima- ges takes place under mutually identical circumstances.
• the drum 11 comes away from the bottom surface and the photoconductive coating 3 is cleaned to re ⁇ move any residual toner by being washed with toner solvent.
• the arrangement 20 with the two application brushes 22 arranged in rotary fashion in holder 21 and the suction nozzle 23 which like the rollers 22 extend across the entire length of the coating.
• the applied solvent is removed via het suction nozzle 23.
• an accurately determined quantity of solvent is applied to the coating 3 by means of the arrangement 40 (see fig. 6).
• the support 1 is rotated around shaft 2 through 180 until it reaches the position illustrated in fig. 4a and can again be charged up and exposed.
• the coating 4 which now carries a charge pattern corresponding with the colour separation 6' is now located on the underside of the support 1 and is developed using toner of the desired second colour, after which this toner image is transferred to the substrate, in registration with the first toner image.
• the horizontal position of the photoconductive coating during the various operations facilitates not only the operation of the device, especially the application of a colour separation onto the charged coating, but also the application of toner onto the charged coating and the cleaning thereof with sol ⁇ vent.
• Fig. 5 shows a cross section of a preferred toner holder, in ⁇ dicated in its entirety in this diagram by the notation figure 25.
• the holder comprises three application rollers 26, 27 and 28, rotatably mounted in a frame 29, which is mounted in holder 25 so as to be capable of free movement to and fro over a short
• Plates 31 and 34 which, as already stated, are arranged in insulated fashion with respect to the housing 25, can be connected with a voltage source of suitable potential and polarity, especially opposite to the toner polarity, so that during the development of the charge pattern by application of toner in the known manner a uniformly developed image is obtained.
• Fig. 6 shows in a schematic section a device for applying an accurately determined quantity of solvent to the coating.
• the toner fluid feed arrangement 40 comprises an overflow chamber 41 connected to the toner fluid feed pipe 42 and placed in a holder 43 to which a toner fluid discharge pipe 44 is connected.
• the overflow chamber 41 will be filled com ⁇ pletely with toner fluid 45.
• This fluid has a meniscus 63, the height of which depends on fluid characteristics and which is a constant for a certain fluid. Since the position of the photoconductive coating 3 during the various opera- tions is fixed, by adjusting the spacing between the over ⁇ flow chamber 41 with respect to this coating, the quantity of fluid which is fed to the coating can be governed extre ⁇ mely accurately.
• the whole assembly is guided along the coating: the excess toner applied by rollers 26, 27, 28 is sucked away by the nozzle 23 and by means of the toner fluid feed arrangement 40 the photoconductive coating is moistened to a predetermined extent; this during the return movement of the toner trolley.
• the object of this treatment is to prevent uncontrolled flows of toner particles along the photoconductive surface during the stage in which toner is transferred to the receptor me ⁇ dium.
• Fig. 7 gives a perspective view of part of the complete ar ⁇ rangement in accordance with the invention
• fig. 8 provides a perspective view of the portion with the support and photo-
• the cleaning unit 20 with rollers 22 and with a suction nozzle identical with 23 and an arrangement identical with 40 are visible in fig. 4a - 4e.
• the cleaning rollers 22 function whilst going from left to right; during the return movement they are adjusted downwardly after which the suction nozzle and the fluid feed nozzle come into action.
• the frame in which the entire assembly is accommodated is indicated by reference numeral 30.
• the left-hand portion 31 accommodates the support 1 with the photoconductive coating thereon visible.
• the corona arrangement 8 is similarly shown; this is guided past the guides 32, 33 and can be moved to and fro in the manner described previously across the coating 3.
• the frame 31 supports the pressure frame 5 accommodated in the tilting frame 34. Underneath the support 1 is the drum 11 for taking up the material on which the re ⁇ presentation is to be formed, the said drum being mounted on arms 35, 36.
• ancillary units are arranged such as a drum 38 which contains the various pipelines for fluid and the supply and discharge of medium required for normal operation; in the.right-hand por ⁇ tion of the frame 39 a frame 12 with the four toner holders 13 - 16.
• This frame 12 can be moved upwards and downwards by means of the threaded spindle 40 and brought to the
• fig. 8 requires no further explanation.
• Fig. 9 illustrates further details of the frame 12 with the four toner holders 13 - 16. The toner holder required can, guided in the guides 41, 42 of frame section 37 be brought in the manner described previously underneath the photoconductive coating.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Color Electrophotography (AREA)
• Ink Jet (AREA)
• Inks, Pencil-Leads, Or Crayons (AREA)
• Developing Agents For Electrophotography (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=19838561

Family Applications (1)

Country Status (6)

Citations (3)

Family Cites Families (2)

• 1981
  • 1981-12-16 NL NL8105675A patent/NL8105675A/nl not_active Application Discontinuation
• 1982
  • 1982-12-10 AT AT82201587T patent/ATE18702T1/de not_active IP Right Cessation
  • 1982-12-10 DE DE8282201587T patent/DE3270037D1/de not_active Expired
  • 1982-12-14 WO PCT/EP1982/000265 patent/WO1986004428A1/en unknown
  • 1982-12-15 JP JP57218515A patent/JPS58111051A/ja active Granted
  • 1982-12-16 AU AU91587/82A patent/AU551660B2/en not_active Ceased

Patent Citations (3)

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