GB2035212A - Method and apparatus for magnetic printing - Google Patents

Abstract

An image area 20 is created magnetically on a magnetizable layer 14 and developed using a liquid magnetic ink 22. The magnetic ink is applied to a non-wettable surface 16 that covers the magnetizable layer 14, and then transferred to a desired copy substrate 23. The magnetizable layer 14 may be supported on a base 12, and the non-wettable surface 16 may be solid or liquid. <IMAGE>

Description

SPECIFICATION Method and apparatus for magnetic printing Magnetic printing is known in the art wherein a web, tape, belt or drum will have a magnetizable surface which may have found thereon an image of an original to be copied. A plurality of methods are known for obtaining such magnetized image of the originals. A magnetizable development medium is placed upon the magnetized surface and so use quentlytransferred to a medium, such as paper, to form a copy of the original. A number of copies may be made by simply placing more development material onto the magnetized surface after each copy is made. Subsequent to the required number of copies being made, the magnetized image may then be erased.Heretofore the prior art has concerned itself primarily with using developer powders that are magnetizable and that will adhere to the magnetized image areas. In this respect the course taken by prior magnetic printing investigators has paralleled the route taken by those involved with electrostatic copiers in that dry toners are becoming the prevalent development medium. It is known that certain advantages exist when a liquid toner is utilized to develop an image. Liquid toners are less expensive and the equipment required to dispose the same is less complicated and less expensive. Additionaly, there are no fusing problems as neither heat fusing nor pressure fusing is required. Consequently, it would be beneficial to be able to develop magnetically produced images using a liquid developer.

In accordance with this invention, development with a liquid developer is made possible through the use of a magnetizable web or belt that includes a substrate or support member having a magnetic layerthereover and a thin non-wetting surface over the magnetic layer. In combination with this web, a magnetizable ink would be used wherein the ink would be attracted to the magnetized areas but would be free to flow away from those areas that were not magnetized, i.e., the non-image areas. A sheet of paper may then be placed overthe nonwetting surface and the ink would be transferred thereto to produce a copy.

The invention will be further described with reference to the accompanying drawings, in which: FIG. 1 shows a cross-sectional view of a web constructed in accordance with the principles of this invention.

FIG. 2 is a view similar to FIG. 1 showing the web after being magnetized.

FIG. 3 shows a view similar to FIG. 2 wherein the web has ink applied to one surface thereof.

FIG. 4 is an alternate embodiment of the invention showing a cross-sectional area of a web that may be utilized in accordance with the invention.

FIG. 5 is a cross-sectional view showing magnetic fields that may be set up in the web shown in FIG. 4 when used in accordance with this invention.

FIG. 6 is a cross-sectional view of an apparatus that may be used to carry of the method of the instant invention.

Referring now to FIGs. 1-3, a magnetizable web is shown generally at 10 and includes a substrate or support member 12 upon which a magnetic layer 14 may be supported. A non-wetting surface 16 is disposed over the magnetic layer 14to cover the magnetic layer. With this construction, the magnetic layer 14 is sandwiched between the support member 12 and the non-wetting surface 16.

A printing device 18 in the form of a magnetic writing head is provided for creating image areas 20 within the magnetic layer 14 by magnetizing discrete areas while the balance of the layer remains unmagnetized. As the writing head 18 is moved (by means not shown) across the web 10, relatively speaking, information is supplied to the magnetic layer 14 in the form of the image areas 20. After the image areas 20 are formed, magnetic ink 22 is applied to the non-wetting surface 16wherebythe ink will adhere through magnetic attraction to portions of the surface 16 that correspond to the image areas 20 and will flow from the balance of the non-wetting surface.Following the inking of the imaged areas 20, a sheet of paper 23 or any other similar substance may be brought into contact with the non-wetting surface 16 to transfer the ink 22 from the surface to the sheet by means of absorbtion thereby creating the copy.

The latent image under the surface 16 may be developed repeatedly with ink 22 after each transfer to a sheet 23 in orderto obtain additional copies until such time as the desired number of copies is obtained. After completing the printing of the required number of copies, the information or image areas 20 may be erased from the magnetic layer 14 by means well known in the art.

In FIG. 6, an example of a type of apparatus is shown that may be used with the web 10 to carry out the method of the instant invention. This apparatus includes a housing 25 that has a shaft 26 rotatably disposed therein. Means (not shown) may be provided for selectively rotating the shaft 26. Mounted upon the shaft 26 for rotation therewith is a magnetic decorating wheel or roller 28. Magnetic ink 22 is received within the housing 25, which housing serves as a sump, and the magnetic wheel or roller 28 is partially submerged within the magnetic ink. In vertical alignment with the magnetic wheel or roller 28 is a roller 30, therebeing an opening 32 within the housing 25 intermediate the magnetic wheel 28 and roller 30. The wheel or roller 28 and roller 30 are spaced from one another a small distance.The web 10 is trained about the roller 30 so as to be conveyed intermediate the roller and the magnetic wheel or roller 28 at the location of the opening 32. The web 10 is oriented so that the non-wettable surface 16 is exposed to the wheel or roller 28 and the support member 12 is in contact with the roller 30. As the magnetic wheel or roller 28 is rotated in the direction shown by the arrow, a sufficient quantity of ink 22 will adhere to its surface due to magnetic attraction and will contact or splash the underside of the web 10 as is conveyed by the roller 30. The distance between the wheel or roller 28 and roller 30 will be adjusted so that an appropriate thickness of ink 22 adheres to the non-wetting surface 16.That portion of the web 10 that has image areas 20 will retain the magnetic ink 22 to the corresponding areas of the non-wetting surface 16 again through magnetic attraction and the balance of the surface 16 will not retain the ink as the same will flow off and be attracted to the magnetic wheel or roller 28. As the web 10 is conveyed away from the opening 32 it may subsequently be engaged by a sheet whereby trans ferofthe ink 22 may take place.

The magnetic ink 22 useful in carrying out this invention may include either a dye or pigment that is combined with a magnetic material. This combination then may be used to form a magnetic colloidal suspension such as a diluted ferro fluid which is a water-based system. An example of a magnetic material that may be combined with the dye or pig ment is magnetite.

The substrate 12 may be any non-magnetic material that is able to support the other layers. A material that may be used is polyethyleneterephthalate, which is commercially available under the trademark MYLAR from E I Dupont De Nemours & Co.

The magnetic layer 14 may be a material such as any of the known magnetic tapes, as for example, ALNICO 5 which is a commercially available combination of 8% Al, 14% Ni, 24% Co, 3% Cu and 51% Fe.

The non-wetting surface 16 may be either in the liquid or solid state. An example of a liquid surface that may be used includes water when an oleophobic surface is required. When a hydrophobic surface is required a liquid hydrocarbon may be used. An example of such a liquid hydrocarbon is Isopar G available from Exxon Corp. Many materials are available for use as a non-wetting surface 16 in the solid state such as polyethyleneterephthalate, polytetrafluoroethylene, and polyester.

Writing heads 18 are commercially available for the purpose intended as for example, magnetic head type 12C 246 available from Gem Electromagnetics Company.

An alternate embodiment to the invention is disclosed in FlGs.4 & 5 wherein the web 10 includes the substrate 12 and non-wetting surface 16 and a pair of layers 34 and 36 therebetween. The layer 34 adjacent to the substrate 12 is a low coercivity, highpermeability material such as any of the iron-nickel alloys. Examples of commercially available materials that may be used as the low coercivity, high permeability layer 14 are alloy 2826 and alloy 2826 MB, both available from Allied Chemical Co. Alloy 2826 is a composition of Fe40 Ni40 P,4 B6 and alloy 2826 MB is a composition of Fe40 Ni30 Mo4 B,8. These are but two examples of a family of compositions that are refer red to as METGLASS alloy by Allied Chemical Co.

The layer 36 would be a high-coercivity material such ALNICO 5. By using such a web 10, oriented regions could be written which would either aid the magnetic fields, as indicated on the left in FIG. 5, or oppose the magnetic field as indicated on the right.

In carrying out this invention, the writing head 18 would be placed adjacent to the web 10 and moved relative thereto. Appropriate input would be sup plied to the writing head 18 so as to create the magnetic image areas required. As the writing head 18 moves relative to the web 10 the magnetic areas 20 are created in the magnetic layer 14 and the web is passed to a development station to be contacted by magnetic ink 22. The development station would apply ink 22 upon the non-wetting surface and the image areas of the magnetic layer 36 would attract the ink to the surface of the non-wetting area to be retained thereon. As the web 10 is conveyed past the development station, it would be contacted by a sheet of paper for transfer of the inking to take place.

An addition embodiment would involve the use of a thermo-magnetic approach to the formation of a latent image. The magnetic layer 26 may be prewritten in a suitable magnetic pattern such as alternating polarity dots or bars and then the latent image would be formed bythethermal bias of selected areas.

Thermal biasing may be accomplished by locally raising the temperature of the high remanence material momentarily beyond its cu rie temperature. The areas not erased would form the latent image which could then be developed.

Claims (12)

1. A method of printing using a magnetic, liquid printing ink which comprises forming a magnetic image on a magnetisable printing member having a surface which is non-wettable by said ink, applying the ink to said surface so atto be retained magnetically on said surface in the image areas of the print member but not in the non-magnetised, non-image areas, and transferring the printing ink image so formed from the magnetised printing member to a desired substrate.

2. A method according to claim 1, wherein the printing member is in the form of a continuous web having a magnetisable sub-layer and a surface layer which is non-wettable by said ink, and wherein the ink is applied to said surface as said web is driven along a path between an inking station and a printing station, the ink being applied to said surface at said inking station by a magnetic inking roller which is driven to pick-up said ink magnetically from an ink reservoir and to transfer the ink from said reservoir to said surface.

3. A method according to claim 2, wherein, in said inking station, the continuous web is constrained to run in a substantially horizontally path located above said roller, and with said non-wetting surface on the underside of the web, said roller being operated to pick up said ink from said reservoir to transfer it to the underside of said web.

4. A method according to claim 1, substantially as hereinbefore described with reference to the accompanying drawings.

5. A magnetic printing apparatus for printing with a magnetic, liquid printing ink comprising a magnetisable printing member having a surface which is non-wettable by said ink, means for forming a magnetic image on said printing member, means for applying said ink to said surface so atto be magnetically retained thereon in the image areas but not by the non-magnetised, non-image areas, and means for transferring the printing ink image so formed from the printing member to a desired substrate.

6. Apparatus according to claim 5, wherein said printing member is in the form of a continuous web having a magnetisable sublayer and a surface layer which is non-wettable by said ink, and wherein the means for applying the ink comprise a magnetic rol leroverwhich said web is driven and which is position to pick up the ink from an ink reservoir and rotatable to transfer the ink from the reservoir to said non-wettable surface of the web.

7. Apparatus according to claim 6 comprising means to drive said web along a substantially horizontal path over said roller and with the nonwettable surface forming the underside of the web, said roller being rotatabletotransferthe ink from the reservoir to the underside of the web as it passes thereover.

8. Apparatus according to claim 5,6 or7, wherein the printing member comprises a substrate layer, a layer of low coercivity, high magnetic permeability material overlying said substrate layer, a layer of high coercivity, high remanence material overlying said low coercivity layer, and a surface layer of material non-wettable by said ink overlying said high coercivity layer.

9. A magnetic printing member for use with a magnetic, liquid printing ink, comprising a substrate layer, a layer of magnetisable material applied over said substrate layer, and a surface layer of material non-wettable by the printing ink applied over said magnetisable layer.

10. A printing member according to claim 9 in the form of a continuous web.

11. A printing member according to claim 9 or 10, comprising a substrate layer, a layer of low coercivity, high magnetic permeability material laid over said substrate layer, a layer of high coercivity, high remanence magnetic material laid over said low coercivity layer, and a surface layer of material non-wettable by the ink laid over the high coercivity layer.

12. A printing member according to claim 9, substantially as hereinbefore described with reference to Figs. 1-5 of the accompanying drawings.