US3821931A

US3821931A - Copying-printing apparatus

Info

Publication number: US3821931A
Application number: US00229884A
Authority: US
Inventors: K Yamaji; A Kurahashi
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1971-03-04
Filing date: 1972-02-28
Publication date: 1974-07-02
Anticipated expiration: 1991-07-02

Abstract

An electrophotographic copier unit and an offset printer unit are combined together to constitute a copying-printing apparatus in accordance with the principles of the present invention, which utilizes an electrophotographic process to accomplish offset printing, utilizes preferably the wet type development to develop an electrostatic latent image, and utilizes an image transfer system to transfer the developed image to a transfer sheet. Such transfer sheet may in turn be used as an offset master sheet. Thus, the apparatus can perform copying and printing operations at high speeds and produce multiple copies in a short time and in an economical and hygienical manner.

Description

United States Patent [191 Yamaji et al.

[ COPYING-PRINTING APPARATUS [75] Inventors: Keizo Yamaii, Tokyo; Akira Kurahashi, Yokohama, both of Japan [73] Assignee: Canon Kabushiki Kaisha, Tokyo,

Japan [22] Filed: Feb. 28, 1972 [21] Appl. No.: 229,884

[30] Foreign Application Priority Data v Mar 4, 1971 Japan 46-11732 [52] US. Cl 101/132, lOI/DIG. 13, 101/451 [51] Int. Cl B411 11/08 [58] Field of Search lOI/DIG. 13, 132, 450, 101/451 [56] References Cited UNITED STATES PATENTS 2,357,809 9/1944 Carlson 101/D1G. 13 3,045,587 7/1962 Schwertz..... l0l/DlG. 13 3,052,213 9/1962 Schaffert..... lOI/DIG. 13 3,364,857 l/1968 Lein ct al lOl/451 .1 July 2', 1974 3,451,336 6/1969 Mignone l0l/l32.5 3,491,684 l/l970 Borinsky l0l/l32 3,648,603 3/1972 Kaminstein l [01/450 X 3,682,095 8/1972 Kaminstein l0l/450 X Primary Examiner-Robert E. Pulfrey Assistant Examiner-E. H. Eickholt Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto [57] ABSTRACT An electrophotographic copier unit and an offset printer unit are combined together to constitute a copying-printing apparatus in accordance with the principles of the present invention, which utilizes an electrophotographic process to accomplish offset printing, utilizes preferably the wet type development to develop an electrostatic latent image, and utilizes an image transfer system to transfer the developed image to a transfer sheet. Such transfer sheet may in tum be used as an offset master sheet. Thus, the apparatus can perform copying and printing operations at high speeds and produce multiple copies in a short time and in an economical and hygienical manner.

12 Claims, 4 Drawing Figures COPYING-PRINTING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a copying apparatus, and more particularly to an apparatus which comprises a novel combination of an electrophotographic copier and an offset printer.

2. Description of the Prior Art Multiple copies have heretofore been accomplished by repeating the copying cycle in a copying apparatus of the offset printing type or of the electrophotographic type.

In case of the former type, enormous energy and time was required to prepare an offset master and to mount such master on an offset printer before it is ready for operation, and these procedures required much skill.

The latter type of apparatus is superior to the former type in that such complex procedures are not involved in operation, but it still suffered from limitations in copying speed as is usual with the electrophotographic process, and thus this type has not been suitable for producing multiple copies within a short period of time. Moreover, the developing means employed with such copying apparatus is preferably of the wet or liquid type so as to attain simplification of the process and an increase in the copying speed. The wet type development employs an organic solvent as the carrier, and the supply of such carrier also presents a problem because a considerable amount of the solvent is consumed for multiple copies. There is a further problem because most of the carrier so consumed is discharged into the atmosphere, causing air pollution, which is hygienically very harmful.

Also known is a system which comprises a combination of offset printing and electrophotography. This system employs a sheet containing zinc oxide as a photosesitive medium for electrophotography, on which an electrostatic latent image is formed, developed and fixed, whereafter the said sheet is subjected to a hydrophilic treatment (the treatment to impart a hydrophilic property) and used as a master sheet. In other words, this system may be called a direct type in which a photosensitive sheet directly serves as a master sheet. According to such a direct type of system, the use of a photosensitive sheet also as a master sheet makes the various means for the latent image formation, development, fixing, etc. very complicated in construction. In addition, the master sheet becomes very costly because it must have the electrophotographic sensitivity, which a master sheet usually does not need, unless also used as a photosensitive sheet. The master sheet suffers from another problem because the zinc oxide material usually forming such sheet, exhibits the great difficulty in the hydrophilic treatment, and readiness for such treatment is desirable for the master sheet.

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide an improved copying-printing apparatus which can accomplish copying and printing at very high speeds.

It is another object of the present invention to provide a copying-printing apparatus which is especially convenient for producing multiple copies.

It is still another object of the present invention to provide an improved copying-printing apparatus which can produce multiple printed copies with a reduced consumption of solvent during the electrophotographic process and, accordingly, with a reduced amount of gas produced from the solvent, thus minimizing the environmental pollution.

It is yet another object of the present invention to provide an improved copying-printing apparatus in which a master sheet may be prepared by the image transferred from the electrophotographic means so as to facilitate the selection of the materials for the master sheet.

It is still another object of the present invention to provide an improved copying-printing apparatus which can effect copying and printing very economically.

The invention will now be outlined hereunder. The recording medium used with the copying-recording means is formed of an inorganic or organic photoconductive material such as is normally used for the electrophotographic process and may take the form of a rotatable member such as rotatable drum or endless belt.

The electrophotographic process utilized with the present invention may be either of the direct type in which the image'is directly copied and fixed on a photosensitive sheet or of the indirect or transfer type in which the image isfinally fixed on a transfer sheet. However the latter type is preferred by the present invention.

The reason is that, in an application of electrophotographic means for offset printing, if the direct type or electrophotographic sensitive sheet is also used as the offset master sheet, such sheet must satisfy not only the conditions as a master sheet but also the requirement of sensitivity as an electrophotographic sensitive sheet, and thus, the sheet becomes costly and makes the apparatus more complicated in construction. In contrast, since the present invention utilizes the transfer type, i.e. electrophotographic transfer type of sheet as the master sheet,the material forming such sheet may be more freely selected so that the sheet may work well as a transfer sheet and a master sheet, respectively, and this leads to a simplified construction of the apparatus and a lower cost of the master sheet.

The transfer type of electrophotographic process, best suitable for use with the present invention, is the well-known one as disclosed in US. Pat. No. 2,221,776 issued to Carlson, 1938, wherein a photosensitive medium comprising a layer of photoconductive material superposed on an electrically conductive back-up member is charged uniformly over the surface thereof, which surface is then illuminated by image light to form an electrostatic latent image thereon, whereafter such latent image is developed with the aid of toner particles and then fixed by heat or solvent or transferred to separate paper or the like for fixing. Other various types of electrophotographic processes may be equally applicable to the present invention.

In either of these electrophotographic processes, the

electrostatic latent image formed on the photosensitive medium is visualized by developing means, whereafter the developed image is transferred to an offset printing master sheet. The master sheet with the image thus transferred thereto is wrapped securely around a rotatable member such as a master sheet holder drum or belt. if required, the toner image on the master sheet may then be fixed, and thereafter subjected to a hydrophilic and oil-proofing treatment, and then developed with the aid of printing ink, which in turn is transferred to other transfer sheet.

The developing method may be either of the dry type or of the wet type, but the latter type, i.e. liquid development is preferred by the present invention. One reason for this is that the dry type development requires the developing means to be considerably complex in construction, and further requires an infrared heater to be used for the fixing step. Another reason is that the dry type development limits the speed at which the developing and fixing steps are effected. In contrast, the wet type development only requires a very simple construction of the developing means and eliminates the fixing step, which contributes to a higher developing speed. Especially in the present invention, which utilizes the electrophotographic process of the transfer type to prepare the master sheet, the wet type development is advantageous over the dry type in that the resolving effect of the image during the image transfer step is superior, thus providing a clearer offset printed image.

As described hitherto, the present invention utilizes electrophotography to accomplish the offset printing, and utilizes the wet or liquid type development to develop a latent image, and utilizes the image transfer sys tem to transfer the developed image to a transfer sheet, which in turn is used as an offset master sheet. In this regard, the transfer-master sheet is highly effective inasmuch as the conditions required for such sheet to be used for the transfer of liquid-developed'image are just in coincidence with the conditions required for such sheet to be used for the purpose of offset printing after being subjected to a hydrophilic treatment. In a further embodiment of the present invention, such a transfermaster sheet may also be used as a sheet to be offsetprinted. Again in this case, the conditions therefor are well in accord with the conditions required for such sheet to be used for the offset printing.

BRIEF DESCRIPTION OF THE DRAWINGS- The invention will become more fully apparent from the following detailed description thereof taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of the copyingprinting apparatus of the present invention wherein a master sheet also serves as a sheet to be printed;

FIG. 2 schematically illustrates the copying-printing apparatus of the present invention wherein a web for the master sheet is stored in a master sheet holder drum;

FIG. 3 is a schematic representation of the copyingprinting apparatus of the present invention wherein a master sheet supply station is separate from the printing sheet supply station; and

FIG. 4 illustrates the method of testing the solvent resistivity of the master sheet, usable with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a photosensitive drum, designated by numeral 1, is rotatable in the direction of the arrow, and may be electrostatically charged uniformly over the entire surface thereof by charger means 2. An optical system 3 is provided to project image light therethrough from an original onto the surface of the photosensitive drum 1. An electrostatic latent image formed on the photosensitive drum 1 in accordance with the original image may be developed by developing means 5, which may be of the liquid type as shown, or of the dry or other suitable type. The image on the photosensitive drum 1, thus developed by the described process, may be transferred therefrom to a master sheet 8 held on and'over a master sheet holder drum 7. To enhance the efficiency of such image transfer effect, the master sheet holder drum 7 may preferably be in the form of an electrically conductive drum for applying or grounding the transfer voltage. Such an electrically conductive drum may be provided by a rotatable drum covered with an electrically conductive rubber material which is .commercially available. The master sheet 8 may be held on the holder drum 7 in advance of the transfer process, or alternatively the master sheet may be held on the holder drum 7 as it is fed for image transfer into the nip between the drums l and 7. Holder means for this purpose is provided as designated at 9. The master sheet 8 now having a toner image transferred thereto may then be subjected to a hydrophilic treatment by water supply means 10, whereafter ink is supplied only to thetoner image area (oleophilic) of the master sheet on the drum from oleophilic ink supply means 11. The oleophilic ink may be a paste-like mixture of pigment and printing varnish prepared by boiling linseed oil, resin type ink or the like. The master sheet holder drum 7 may continue to rotate so that the image thereon may be transferred onto a web of transfer paper 13 as fed from a printing sheet supply means 12. In the embodiment shown in FIG. 1, the master sheet 8 for offset printing is common with the transfer sheet 13 and this provides a limited variety of the material available for such a common printing and master sheet, but also provides a simplified construction of the apparatus. The material suitable for such master sheet may be a paper master which has already been subjected to a water-proofing treatment.

Since the image transferred from the master sheet 8 to the printing sheet 13 is a printed image, the printing sheet 13 with such transferred image, may be separated from the master sheet by separator means of the air blast type or the like, and discharged onto a tray 15.

The above-described steps may be repeated for the master sheet drum 7 to thereby obtain the number of copies, as desired.

The copying operation using the described system enables a number of copies to be provided irrespective of the limited processing time usually required in the electrophotographic process, and the solvent treatment may be greatly reduced, thus resulting in a higher speed and a higher efficiency of the copying operation.

When a desired number of copies has been obtained, the master sheet 8 may be released from the master sheet holder means 9 on the master sheet drum 7 and removed outwardly by separator means.

After the image transfer from the photosensitive drum 1 to the master sheet 8 has been completed, the photosensitive drum 1 may be cleaned by cleaning means 20 and thereafter, during the offset printing process, may rotate at a high speed with no further image formed thereon and cooperate with the transfer drum 7 to hold the printing sheet therebetween for the impression on such sheet.

FIGS. 2 and 3 show further embodiments of the present invention. As compared with the FIG. 1 embodiment in which the master sheet and the printing sheet are used in common, the embodiment of FIG. 2 is such that a supply roll of master sheet is contained within the master sheet holder drum so that only a desired amount of the master sheet may be fed for use from a first roll 16 onto the surface of the drum and that after used, such amount of the master sheet may be taken up on a second roll 17 which is also contained within the drum. The printing sheet supply in this embodiment may be accomplished in the same manner as that described with respect to FIG. I. In the embodiment shown in FIG. 3, master sheet supply means 18 is provided separately from printing sheet supply means 19.

As will be seen, the embodiments of FIGS. 2 and 3 are a little more complicated in construction than the embodiment of FIG; 1, whereas the use of a discrete master sheet and printing sheet, for example, a sheet having a hydrophilic property and containing zinc or aluminum, leads to a wider range for selecting the materials for such sheets, which particularly gives rise to a merit that a number of copies may be obtained at a lower cost in spite of the cost of the master sheet such as zinc or aluminum sheet.

The copying-printing apparatus of the present invention has been described the foregoing detailed description. Now, description will be made of a master sheet, which is most suitable for use with the present invention, when carried out in the form of a liquid developing system. The liquid developer in use may be similar to the wet-type developer-as usually employed in the art of electrophotography. More particularly, the liquid developer may be composed of a carrier liquid having a specific volume resistivity of lOQcm or more and a toner dispersed therein, so that the liquid may not destroy the electrostatic latent image during the developing step and that the toner particles may be selectively deposited in accordance with the electric charges carried by the electrostatic image. If required, a dispersing agent may further be contained in the developing liquid.

The master sheet applicable for the present invention must satisfy the qualifications given below.

[I] Firstly, such sheet must have a suitable degree of resistivity to a solvent. For the liquid developer, use has chiefly been made of an organic solvent of high resistivity having the above-described characteristic, such as an organic paraffin solvent such as liquidous paraffin or liquidous isoparaffin, for example. An. organic isoparaffin solvent is commercially available under the tradename of lsopar, H, G or L" from Esso Chemicals Inc.

of the United States. A developer containing such solvent, when used for the purpose of image transfer, would therefore encounter the following inconveniences, unless the master sheet is provided with a suitable degree of solvent resistivity:

I. If the master sheet is provided with none, or an insufficient solvent resistivity, the organic solvent tends to permeate through the transfer paper during the image transfer step, thus resulting not only in a blurred or unsatisfactory image transfer effect but also in an unnecessarilygreat consumption of the developing liquid and a bad drying effect.

2. If the master sheet is provided with an excessive resistivity to solvent, it is desirable during the image transfer step that the solvent resistivity imparting substance be suitably softened in the interface with respect to the carrier liquid contained in the developer so that the toner material from the developer maybe contained therewith. Any excessive resistivity to the solvent would reduce the affinity to the carrier liquid, which in turn would aggravate the fixing effect of the developer and, accordingly, the transferred image could be destroyed as by friction even after being dried.

For these reasons, the master sheet must maintain a suitable degree of solvent resistivity, the range of which may be determined by a method, as will be described hereunder. As shown in FIG. 4, a sample sheet 21 for test is set on a metallic frame 22. A solvent dripping injector 24 is horizontally fixed to a support 26, whereafter a micrometer 25 is gradually rotated to let a drop of solvent (such as Isopar G produced by Esso Chemicals Inc.) onto the sample sheet. At the point of time when the drop of solvent has reached the sample surface, a stop watch is started. The stop watch is stopped at the point of time when the solvent has permeated throughout the area of the sample sheet, which is occupied by that drop of solvent (10 to 15 mm diameter). The length of time between these two points of time is adopted as a measure for the solvent resistivity. The distance from the needle end of the injector to the surface of the sample sheet may suitably be of the order of 5 cm. When measurement is carried out in this way, a sample having no resistivity to the solvent permits a drop of solvent to instantaneously permeate throughout the area of the sample sheet corresponding to the dimensions of the drop, thus providing a completely permeated condition. On the other hand, a sample having some solvent resistivity only permits gradual penneation of the solvent, and the length of time required until a drop of solvent has completely permeated through the thickness of the sample and throughout the area thereof corresponding to the size of such drop is variable with the degree of the solvent resistivity possessed by the sample. The solvent dripping injector may have a volume of 1 cc. or 2 cc. and its needle may be of A; type. One drop of solvent dripped from such injector has a volume of approximately 0.004 cc. When measured by such a method, the solvent resistivity suitable as the master sheet may practically be in the range of 0.14 to 25 seconds, and preferablyin the range of l to 12 seconds. i

[ll] Secondly, the master sheet must have a suitable degree of smoothness. As the result of the test effected in accordance with theforegoing' method on master sheets with various degrees of smoothness (i.e. the smoothness as measured of the paper grade J IS P8119 by a Bekk tester), it has been found that a smoothness in the range of 25 to seconds is satisfactory. Any degree of smoothness less than 25 seconds would cause non-uniformity of the image transfer, unless a great deal of developing liquid is present, thus resulting not only in an unsatisfactory transferred image but also in a much longer time required for drying up the developingliquid on such image. Conversely, any degree of smoothness exceeding 150 seconds has proved that a good transferred image may be obtained with little developing liquid, but the fixing effect subsequent to the transfer process is adversely affected, thus resulting in destruction of the transferred image due to friction. The smoothness may be adjusted to a suitable degree by application'of a coating material, but more practi- Cally-by physical means such as super calender, machine calender or the like.

Various materials and conditions were studied in order to obtain a master sheet satisfying the requirements of the solvent resistivity and smoothness as measured by the above-described method, and as the result, examples shown below were found satisfactory.

EXAMPLE 1 EXAMPLE 2 Vinyl acetate emulsion similar to that of EXAMPLE 1 was applied to a raw sheet of paper by size pressing, thereby obtaining a master sheet. The weight of the resin content was at the rate of 2 to 3 g/m EXAMPLE 3 2.5 parts by weight of emulsion composed chiefly of acrylic resin (available under the tradename of Primal P376 from Rhom and Haas), 1 part by weight of clay and 0.01 part by weight of dispersing agent (under the tradename of Primal 850) were mixed together and diluted by water to provide a viscosity of cp (25C). This liquid was applied to a raw sheet of paper by size pressing, to obtain a master sheet.

In the apparatus shown in F168. 1, 2 or 3, the master sheet on the master sheet holder drum is discharged therefrom when the last image transfer has been completed by the master sheet drum. To prevent the master sheet drum from being stained or contaminated during that time, the printing sheet may desirably be fed excessively enough to overlap the master sheet so that the two sheets may be removed in overlapping relationship. Also, where no offset printing process takes place, the optical system for illuminating the original image may be suitably changed so that an electrophotographic copying process may be effected directly on the printing sheet.

From the foregoing description, it will be appreciated that the present invention provides an apparatus which comprises a novel combination of a conventional offset printer unit and a conventional electrophotographic copier unit, but which has eliminated all the drawbacks peculiar to both units and utilizes their advantages as well as their combined effect. Such an application of the electrophotographic copier unit leads to the possibility of a master sheet for offset printing being producedreadily and simply in a short time, and such an application of the offset printer unit enables multiple copies to be provided at a high speed without any time loss, which would otherwise occur in the electrophotographic process.

Furthermore, the multiple copying operation effected by the offset printing technique does not include the liquid developing process as required for electrophotography, and this means that the use of the carrier liquid occurs only until the'image is transferred from the photosensitive drum to the master sheet, thus substantially eliminating the adverse effect of the gases, as produced from the carrier liquid.

. The electrophotographic process utilized with the present invention has been illustrated asCarlsons process, but it should be understood that the utilization of other various types of electrophotographic process is also within the scope of the present invention.

Summing up, the copying-printing apparatus of the present invention as described above in detail may provide the following effects:

At least in operation, the production of the master sheet is not required in particular, and multiple copies can be produced within a short time and with a greatly reduced consumption of the solvent, which in turn leads to a well-maintained hygienic environment. Moreover, when the number of copies to be obtained is limited to one hundred sheets or so, the master paper in use need not be of a special type, such as conventional offset master paper, thus reducing the cost of the master paper and, accordingly, the cost incurred in copying.

We claim:

1. A copying-printing apparatus comprising a photosensitive member for repetitive use, means for forming an electrostatic latent image on the surface of said photosensitive member, means for developing said electrostatic latent image, means for supplying a master sheet, means for transferring said developed image onto said master sheet, a conductive elastic drum for retaining said master sheet for winding therearound, means for applying a transfer bias voltage to said drum at least when said developed image is transferred onto said master sheet, means for supplying ink to said master sheet, means for supplying a printing sheet, and means for impressing said ink from said master sheet onto said printing sheet.

2. A copying-printing apparatus according to claim 1, wherein said developing means is a liquid developing device.

3. A copying-printing apparatus according to claim 2, wherein said master sheet has a solvent resistivity of 0.14 to 25 seconds and smoothness of 25 to seconds (according to Bekk indication).

4. A copying-printing apparatus according to claim 1, wherein said developing means is a dry type developing device.

5. A copying-printing apparatus according to claim 1, wherein said photosensitive member is in the form of cylindrical drum, and said developed image transfer means and said ink transfer means are provided by an area of contact between said two drums.

6. A copying-printing apparatus according to claim 1, wherein said master sheet supply means is provided within said conductive elastic drum.

7. A copying-printing apparatus according to claim 1, wherein said photosensitive medium and said master sheet holder member are in the form of cylindrical drums, and said developed image transfer means and said ink transfer means are provided by an area of contact between said two drums.

8. A copying-printing apparatus comprising a photosensitive member for repetitive use, means for forming an electrostatic latent image on the surface of said photosensitive member, means for developing said electrostatic latent image, means for supplying sheet material capable of use selectively as a master sheet and as a printing sheet, means for transferring said developed image onto said master sheet, a conductive elastic drum for retaining said master sheet for winding therearound, means for applying a transfer bias voltage to said drum at least when said developed image is transferred onto said master sheet, means for supplying ink to said master sheet, and means for impressing said ink from said master sheet onto said printing sheet.

9.. A copying-printing apparatus according to claim 8, wherein said photosensitive medium and said master sheet holder member are in the form of a cylindrical drum, and said developed image transfer means and ing device.

Claims

3. A copying-printing apparatus according to claim 2, wherein said master sheet has a solvent resistivity of 0.14 to 25 seconds and smoothness of 25 to 150 seconds (according to Bekk indication).

9. A copying-printing apparatus according to claim 8, wherein said photosensitive medium and said master sheet holder member are in the form of a cylindrical drum, and said developed image transfer means and said ink transfer means are provided by an area of contact between said two drums.

10. A copying-printing apparatus according to claim 8, wherein said developing means is a liquid developing device.

11. A copying-printing apparatus according to claim 10, wherein said master sheet has a solvent resistivity of 0.14 to 25 seconds and smoothness of 25 to 150 seconds (according to Bekk indication).

12. A copying-printing apparatus according to claim 8, wherein said developing means is a dry type developing device.