US3587459A - Thermographic stencil - Google Patents

Thermographic stencil Download PDF

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Publication number
US3587459A
US3587459A US746890A US3587459DA US3587459A US 3587459 A US3587459 A US 3587459A US 746890 A US746890 A US 746890A US 3587459D A US3587459D A US 3587459DA US 3587459 A US3587459 A US 3587459A
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US
United States
Prior art keywords
film
stencil
areas
heat
image
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US746890A
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English (en)
Inventor
Alexander Spencer
Alan Francis Blake
David Guthrie Burns
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NRG Manufacturing Ltd
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NRG Manufacturing Ltd
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Publication date
Application filed by NRG Manufacturing Ltd filed Critical NRG Manufacturing Ltd
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Publication of US3587459A publication Critical patent/US3587459A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
    • B41N1/00—Printing plates or foils; Materials therefor
    • B41N1/24—Stencils; Stencil materials; Carriers therefor
    • B41N1/245—Stencils; Stencil materials; Carriers therefor characterised by the thermo-perforable polymeric film heat absorbing means or release coating therefor
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T83/00—Cutting
    • Y10T83/02—Other than completely through work thickness
    • Y10T83/0237—Pricking

Definitions

  • the invention provides a novel duplicating stencil comprising a backing sheet and attached to one edge thereof a thin sheet of thermoplastic film softening not above 250 C. carrying a multiplicity of minute, closely spaced holes or artificially weakened areas. in use a heat absorbent image to be copied is placed in contact with the thermoplastic film and the assembly is exposed to heat, and the holes enlarge or the artificially weakened areas perforate in the image areas.
  • a sheet carrying a heat-absorbent image is placed in contact with a duplicating stencil of either kind with the heat-sensitive film and the image in contact, and the assembly is then irradiatedso that the heat-absorbent image areas are heated relative to the remainder of the assembly, the heat-sensitive film shrinks and splits in the areas corresponding to the image, thus producing an imaged duplicating stencil which can be used.
  • a duplicator in the same way as a duplicating stencil prepared in the usual manner with a typewriter. The splits occur in the film because the shrinkage forces are greater than the tensile strength of the film.
  • a heat-sensitive stencil can be made without the use of specially controlled heat-shrink film by the use of orientated r nonorientated thermoplastic film, which carries a multiplicity of minute, closely spaced holes or artificially weakened areas.
  • the said holes or areas ensure that the stencil perforates regularly in the image areas, while if the film is not heatshrinkable, it is surprisingly found that the said holes enlarge or the artificially weakened areas perforate in the image areas although under thesame conditions, but in the absence of the said holes or weakened areas, the film would not give a usable stencil.
  • the holes enlarge or the film Mark Cryovac S 254 (made from a 4:1 vinylidene chloride/vi- I nyl chloride copolymer produced by emulsion polymerizaperforates (as the case may be) in the image areas.
  • These holes or perforations will then pass ink when the imaged stencil is used on a conventional stencil duplicator.
  • the enlarged holes in the image areas pass more ink, so' that the" desired image is produced, when the stencil is used, against a toned background, which. in many cases is unobjectionable or even desirable.
  • the stencil perforates and only passes ink in the image areas, so that in use the image'is produced against an untoned plain background.
  • the thermoplastic film may be any of the commercially available films which soften not above 250 C., whether orientated or nonorientated e.g. of polystyrene, vinylchloride/vinylidene chloride copolymers, high density polyethylene, polypropylene or polyethylene terephthalate. Suitable commercially available films include those sold under the Trade tion), .Cryovac S 205 or Saran film (made from a similar copolymer produced by suspension polymerization).
  • Cryovac L an irradiated polyethylene film
  • Cryovac Y a biaxially orientated polypropylene film
  • Cryovac VPH a monoaxially orientated polyvinyl chloride film
  • Sordelli-Vinifoil a biaxially orientated polyvinyl chloridefilm
  • Melinex and Mylar films both of polyethylene terephthalate, and polythene film (made of polyethylene).
  • the thickness of the heat-shrinkable film is ordinarily of the order of 0.001 of an inch, say from one-fourth to twice this thickness.
  • Minute, artificially weakened areas in the film are conveniently (but not necessarily) made by embossing.
  • the film is passed under pressure through thenip of a pair of rollers, one having a hard surface with minute projections, and the other having a plain, relatively resilient surface, e.g. of hard natural or synthetic rubber, cotton or compressed paper. This has the effect of reducing the thickness of the film around each projection thus creating weakened areas.
  • the minute projections on the hard roller may be arranged regularly or irregularly. A suitable irregular pattern of projections is readily obtained by mounting a sheet of fine sand, emery or carborundum or other abrasive paper on a hard roller.
  • the number of projections as measured in each of two directions at right angles to each other can be 60- --300 per inch, and is preferably from -200 per inch.
  • Practical consideration set an upper limit on the number of projections it is feasible to obtain.
  • too few projections, and hence too large or too widely spaced weakened areas give stencils which provide only poor quality copies.
  • the hard roller having the minute projections may be produced in conventional manner, e.g. by engraving a hard roller with a milled tool having the reverse pattern to that required on the roller. Alternatively the surface of the roller may be etched chemically into the desired pattern.
  • Thesize of the projections naturally depends on their number. For example, at 200 projections per inch, their spacing will be 0.005 inch, and each projection should be about 0.004 inch high.
  • the shape of the projections is not important, but will ordinarily be conical or pyramidal, with an apex angle below 45, e.g. 40.
  • the weakened areas must not coalesce. This sets a lower limit on the spacing of the weakened areas, and hence on the spacing of the projections on the hard roller.
  • the diameter of each projection at the base will generally not be more than 0.004 inch, thus allowing 0.005 inch between projections, and hence between weakened areas in the embossed film.
  • the best spacing willdepend both on the physical properties of the material from which the film is made and also on precise size and shape of the projections on the roller. The best combination of spacing, height and diameter of the projections can be found in any particular case by routine experiment.
  • the projections on the embossing roller completely penetrate the film; thus-giving'a sheet carrying'a multiplicity of minute holes, which preferablyvtaper so as to have a larger diameter on oneside of the film than the other.
  • These holes may be left unsealed, in which case the stencil inuse gives (as already mentioned) the desired image against a toned background, or, more usually,-sealed by calendering or with a suitable plastics coating, or preferably both.
  • the material used to seal the perforations must be such as not to prevent reopening of the holes-in the image areas during imaging of the stencil.
  • polystyrene used as an 0.5 to 20 percent solution in benzene
  • polyvinyl acetate and its copolymers used as an 0.1 to 30 percent solution in industrial methylated spirit
  • vinyl chloride copolymers used as an 0.5 to 10 percent solution in acetone
  • cellulose nitrate, acetate, or acetate/butyrate each used as an 0.5 to 25 percent solution in acetone or ethyl acetate
  • polyvinyl butyral used as an 0.l to 25 percent solution in 60:40 toluenezethanol
  • polyvinyl formal used as an 0.15 to 30 percent solution in 60:40 toluenezethanol
  • emulsions of similar polymers e.g. polystyrene in water.
  • the solvent in which the plastics material is applied must, of course, be selected so as
  • the embossed film is difficult to handle. It is therefore often convenient to laminate the film, before or after embossing, to a sheet of conventional stencil tissue containing to 30 percent of void area.
  • the lamination may be effected in conventional manner for laminating sheets of synthetic thermoplastic resins to paper. When a material is used in the manner already described to seal perforations in the film, this material may also if desired act as an adhesive in the lamination.
  • FIG. 1 is a greatly enlarged, diagrammatic partial cross section showing a thermoplastic film about to be embossed or perforated;
  • FIG. 2 is a greatly enlarged, diagrammatic partial cross section showing a thermoplastic film after embossing
  • FIG. 3 is a greatly enlarged diagrammatic partial cross section showing a thermoplastic film after perforation
  • FIG. 4a is a greatly enlarged, diagrammatic partial cross section showing a thermoplastic film after perforation and subsequent calendering
  • FIG. 4b is a greatly enlarged, diagrammatic partial plan view showing a thermoplastic film after perforation and subsequent calendering
  • FIG. 5 is a greatly enlarged, diagrammatic partial cross section showing a thermoplastic film after perforation, calendering, application of a sealing coating and lamination to stencil tissue;
  • FIG. 6 is a greatly enlarged, diagrammatic partial cross section showing the film of FIG. 5 after exposure to heat.
  • FIG. 1 shows diagrammatically the embossed area 3 produced by a single projection 2. This area 3 is thinner and more highly stressed than the surrounding area of the film 1. It perforates when the film is heated.
  • FIG. 3 shows diagrammatically a single perforation 4 produced by a single projection 2 when impressed deeply enough to perforate rather than simply emboss the film l.
  • the materialS displaced from the hole 4 remains attached to the film 1 on the reverse side from that through which the projection 2 enters.
  • FIG. 4d shows the result of calendering the film of FIG. 3.
  • the ni'atcrial 5 is forced back toward the hole 4 thereby at least partially closing it.
  • FIG. 4b is a plan view of the calendered film.
  • FIG. 5 shows the film of FIG. 4a after the application by conventional means of a sealing. coating 6 consisting of a thin layer of a suitable plastics material, and lamination to a sheet of stencil tissue 7.
  • FIG. 6 shows the laminated film of FIG. 5 with the hole 4 reopened by the action of heat on the film l. y
  • the laminated or 'unlaminated sheet of thermoplastic film having minute holes or weakened areas may than be mounted in. the manner conventional for duplicating stencils by attaching one edge thereof to the edge of a backing sheet of similar size, the backing sheet being designed to be removed after the duplicating stencil has been imaged.
  • the duplicating stencil of this invention may be used in the following manner.
  • the original'to be copied carrying a heatabsorbent image is placed in contact with the duplicating stencil so that the heat-absorbent image is in contact with the thermoplastic film.
  • the assembly is then irradiated with infrared radiation which causes the image areas to become relatively hotter than the nonimage areas. This differential heating causes the weakened areas to rupture (or the minute holes to enlarge) and so produce ink-passing holes in the image areas.
  • the imaged duplicating stencil is then used -in the same manner as duplicating stencils imaged in conventional ways.
  • EXAMPLE 2 Heat-shrinkable polyethylene 'terephthalate film (Trade Name Melinex (I.C.I.) or Mylar (Du Pont) 0.0005 inch thick or polystyrene film 0.001 inch thick is passed through the rollers used in Example I and sufficient pressure is applied to perforate the film. The perforated film is then passed through two plain rollers under pressure and the material displaced from the perforated holes is flattened so that the film is of relative even thickness throughout. The film is then lightly coated with a solution or aqueous dispersion such as one or other of the following.
  • a solution or aqueous dispersion such as one or other of the following.
  • Polystyrene Aqueous Dispersion (Vinamul 710) 50 percent solids Water 10 parts by weight This solution or aqueous dispersion is coated onto the film and dried by a conventional technique. The coating weight is 0.5-3 grams per square meter.
  • the film is then sheeted'to normal stencil size and coated onto a suitable conventional backing paper.
  • Example 1 the hard roller maybe replaced by a roller covered with l600 grit size carborundum paper.
  • Nonorientated polypropylene film of thickness 0.0005 inch is passed through the roller used in Example 1 under sufficient pressure to enable the projections of the hard roller to penetrate nearly through the polypropylene film.
  • the film is laminated to conventional stencil tissue having a void area of 15 percent or a similar matrix using one or other of the laminant adhesives specified in Example 2, which is coated onto the film and dried by a conventional technique.
  • the coating weight is 0.S-7 grams per square meter.
  • This film is then sheeted to normal stencil size and mounted onto a suitable conventional backing paper.
  • embossing and laminating are not critical, and, if desired, the lamination can take place before the embossing.
  • Example 4 is repeated except that during the embossing sufficient pressure is used to cause the projections of the hard roller to penetrate the polyropylene film.
  • the perforated film is immediately coated with one or other of the adhesives mentioned in Example 2 at a coating weight of 0.5 to 7 grams per square meter. Before the coating is dry, the perforated film is laminated to a sheet of conventional stencil tissue.
  • the film After drying, the film is sheeted to normal stencil size and mounted onto a suitable conventional backing paper.
  • Example 4 the hard roller may be replaced by a roller covered with l80-600 grit size carborundum paper.
  • Method of producing an imaged duplicating stencil which comprises:
  • thermoplastic film having a softening temperature less than about 250 C.
  • thermoplastic film from the group consisting of polypropylene poly-(vinylidene/vinyl chloride), polystyrene and polyethylene terephthalate and thereafter producing said artificially weakened areas in said film.

Landscapes

  • Printing Plates And Materials Therefor (AREA)
  • Laminated Bodies (AREA)
  • Manufacture Or Reproduction Of Printing Formes (AREA)
US746890A 1967-07-25 1968-07-23 Thermographic stencil Expired - Lifetime US3587459A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB34075/67A GB1192452A (en) 1967-07-25 1967-07-25 Thermographic Stencil

Publications (1)

Publication Number Publication Date
US3587459A true US3587459A (en) 1971-06-28

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Family Applications (1)

Application Number Title Priority Date Filing Date
US746890A Expired - Lifetime US3587459A (en) 1967-07-25 1968-07-23 Thermographic stencil

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US (1) US3587459A (en:Method)
BE (1) BE718519A (en:Method)
DE (1) DE1771888A1 (en:Method)
FR (1) FR1575131A (en:Method)
GB (1) GB1192452A (en:Method)
NL (1) NL6810467A (en:Method)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3942440A (en) * 1972-11-14 1976-03-09 Gerhard Ritzerfeld Method of making a printing form
US4511520A (en) * 1982-07-28 1985-04-16 American Can Company Method of making perforated films
US4526098A (en) * 1977-02-22 1985-07-02 Dl Process Co. Laser formed rotary print plate with internal sintered titanium ink reservoir
US4547920A (en) * 1983-10-19 1985-10-22 Sears Manufacturing Company Process for developing porosity in air impervious film and articles produced by the process
US20050016395A1 (en) * 2001-08-02 2005-01-27 Yoshihide Sugiyama Plate making method for mimeographic printing and plate making device and mimiographic printing machine
EP1413454A4 (en) * 2001-08-02 2006-11-08 Duplo Seiko Corp THERMAL SENSITIVE PRINTING PLATE, MANUFACTURING METHOD AND DEVICE THEREFOR AND TEMPLATE PRINTING MACHINE
CN102458856A (zh) * 2009-06-09 2012-05-16 Nb科技股份有限公司 丝网印版

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3942440A (en) * 1972-11-14 1976-03-09 Gerhard Ritzerfeld Method of making a printing form
US4526098A (en) * 1977-02-22 1985-07-02 Dl Process Co. Laser formed rotary print plate with internal sintered titanium ink reservoir
US4511520A (en) * 1982-07-28 1985-04-16 American Can Company Method of making perforated films
US4547920A (en) * 1983-10-19 1985-10-22 Sears Manufacturing Company Process for developing porosity in air impervious film and articles produced by the process
EP0140623A3 (en) * 1983-10-19 1987-10-21 Sears Manufacturing Company Process for developing porosity in air impervious film and articles produced by the process
US20050016395A1 (en) * 2001-08-02 2005-01-27 Yoshihide Sugiyama Plate making method for mimeographic printing and plate making device and mimiographic printing machine
EP1413454A4 (en) * 2001-08-02 2006-11-08 Duplo Seiko Corp THERMAL SENSITIVE PRINTING PLATE, MANUFACTURING METHOD AND DEVICE THEREFOR AND TEMPLATE PRINTING MACHINE
EP1413431A4 (en) * 2001-08-02 2006-11-08 Duplo Seiko Corp PLATE MANUFACTURING METHOD FOR TEMPLATE PRINTING AND PLATE MANUFACTURING DEVICE AND TEMPLATE PRINTING MACHINE
US7278351B2 (en) 2001-08-02 2007-10-09 Duplo Seiko Corporation Plate-making method and plate-making apparatus for stencil printing and stencil printing machine
US20080017054A1 (en) * 2001-08-02 2008-01-24 Duplo Seiko Corporation Plate-making apparatus for stencil printing and stencil printing machine
US7448319B2 (en) 2001-08-02 2008-11-11 Duplo Seiko Corporation Plate-making apparatus for stencil printing and stencil printing machine
CN102458856A (zh) * 2009-06-09 2012-05-16 Nb科技股份有限公司 丝网印版

Also Published As

Publication number Publication date
GB1192452A (en) 1970-05-20
NL6810467A (en:Method) 1969-01-28
DE1771888A1 (de) 1972-02-17
FR1575131A (en:Method) 1969-07-18
BE718519A (en:Method) 1969-01-24

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