GB1602181A - Screen process printing - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO SCREEN PROCESS PRINTING (71) We, DAVID CECIL ADRIAN FRIEND and RACHEL MARGERY FRIEND,both British Subjects, residing respectively at 46 Rookery Place, Fenstanton, Huntingdon, Cambridge, and 15 Lodge Road, Sharnbrook, Bedford, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention is concerned with improvements in or relating to screen process printing.

In screen process printing, a negative image defined by a filler is provided on a screen stencil which may comprise, for example, a silk or nylon screen; and paint, for example, is forced through the stencil onto a substrate to be printed. The filler prevents passage of the paint except in the areas of the image itself, and thus a positive stencilled image is produced on the substrate.

It is an object of the present invention to provide an improved method of preparing a screen process printing stencil.

The invention provides, in one of its aspects, a method of preparing a screen process printing stencil comprising the steps of (a) providing a positive image on a screen area, (b) covering the screen area with a filler, and (c) selectively removing the positive image and corresponding portions of filler to leave a corresponding negative image defined by the remaining filler, wherein some positive image portions are drawn onto the screen by fine delineation, and at least one other positive image portion, comprised by a positive transfer image portion, is transferred from a backing member onto the screen area.

The delineated positive image on the screen area may be drawn for example in ink.

The finely delineated image lines are, for example, less than 1.0 mm. in thickness, e.g.

less than 0.5 mm., and may be 0.3 mm. or less.

The finely delineated ink and transfer image may, for example, be supplemented by additional image portions produced, prior to application of the filler, e.g. by crayons, oil pastels or paintbrush work.

The positive image may be formed by a water-insoluble image forming material, which is preferably non-soapy and free of fatty acids.

The invention also provides, in another of its aspects, a stencil prepared by a method according to the invention.

The invention also provides, in another of its aspects, a screen printing process using a stencil prepared by a method according to the invention.

The invention also provides, in another of its aspects, a substrate printed on by such a process.

The positive image may be for example removed by the action of a solvent which is selective to the positive image, the corresponding portions of filler being released by the removal of the positive image, which it will be realised, has masked said filler portions from adhearing directly to the screen area.

The above and other aspects of the invention will become more clear from the following description of methods embodying the invention. This description is given by way of example only, and not by way of limitation of the invention.

In a method embodying the invention, a screen process printing stencil is prepared by drawing in a free-flowing water-insoluble spiritbased ink using a felt or bonded fibre tip pen, a finely delineated positive image onto one surface of a fine mesh silk or nylon screen; allowing the ink to dry; adding one or more further positive image portions formed from transfers, by transferring it/them from a backing member onto the screen; then covering the whole of the said surface of the screen with a thin even layer of a settable water-based filler, the filler being applied using a rubber squeegee or a roller or a brush; allowing the filler to set; and applying a solvent to both surfaces of the screen, which solvent is selective to the positive image; the solvent is applied by vigorous rubbing with a cloth.The solvent removes the positive image and corresponding portions of the filler, which, having been masked by the positive image from direct adherence to the screen, are released by the removal of the positive image; this leaves a corresponding to both the finely delineated negative image corresponding to both the finely delineated and transferred positive images on the screen defined by the remaining filler. The treatment with the solvent is continued until all the relevant details are clear.

When the solvent has dried from the screen, the finished stencil is now used for printing onto a substrate by forcing, for example, paint, through the screen onto the substrate using a rubber squeegee. The filler prevents passage of the ink, except in the areas of the image itself, and thuse a positive stencilled image is produced on the substrate.

If a specially smooth surface is desired on which to draw the finely delineated positive image portions on the screen, the screen may be sized prior to forming the positive image portions. The size fills the screen mesh and is subsequently removed by the solvent at the same time as the positive image is removed from the screen. One example of a size is an aqueous suspension of corn flour.

The screen is, for example, supported in a rectangular wooden frame which presents a rectangular opening across which the screen is tautly stretched; alternatively, other suitable support means may be employed according to the nature of the substrate to be printed.

Examples of screen materials include silk, TERYLENE (DACRON), nylon, organdy, and wire cloth; the wire cloth is, for example, of stainless steel, bronze or copper. (TERYLENE and DACRON are Registered Trade Marks).

The mesh count of the screen varies according to the nature of the artwork and for example, a fine mesh screen is used to produce fine image detail. The mesh count is, for example, between 65 and 400 mesh openings per linear inch, e.g. between 140 and 280; and the screen thickness for example, between 55 and 200 microns.

Examples of suitable pens for the fine delineation include those known in the trade as: (a) YOKEN "Miracle Pen", Marking-Slender Type, which is glass-fibre-tipped; (b) PENTEL Pen 6A, which is nylon fibretipped and contains a permanent non-ether spirit ink; (c) PENTEL Jumbo Felt Pen M180, which is felt-tipped; (d) Maruzen "Wonder Marker" fine point No. 100, which is fibre-tipped.

(YOKEN and PENTEL are Registered Trade Marks).

The pens may be sold ready-filled with the appropriate inks and may be refillable or nonrefillable.

One example of a suitable filler for application to the screen is a water-soluble filler known as "Autotype Blue Filler 752" manufactured by Autotype of Wantage, Oxon, England; this filler is a viscous solution of blended polyvinyl alcohols and pigment in water, containing 0.01% of a phenolic fungicide. We believe the filler is repellent with respect to the inks used. The filler is applied in a moist treacly condition, and sets by drying. The thickness of the set filler above the screen is, for example, less than 1 micron.

If it is subsequently required to remove the negative image for re-use of the screen, this can simply be done by washing off the filler with water.

The squeegee comprises a piece of hard rubber held in a wooden handle. The rubber has a relatively sharp operative edge. The same squeegee may be used for applying the filler and for the subsequent printing operation.

One example of a suitable solvent for the pen ink is "General Purpose Cleaner 519" manufactured by E.T. Marler, Wimbledon, London, England. This is a blend of organic solvents including hydrocarbons and an alkaline soap, and has a flash point over 900F. Other examples of suitable solvents include turpentine and methylated spirits.

Stencils produced by a method embodying .he invention may be used in a variety of technical applications, and with a variety of substrate surface, texture, thickness and shape.

Substrate materials include, for example, wood, leather, plastics, paper, glass, cloth, metal, plaster, stone and ceramics. The stencils may be used in, for example, the production of letter headings, pictures, toys, flags, posters, greeting cards, games boards, book titles, book illustrations, certificates, house decorations, instrument panels, printed circuits, gaskets, and etchings on glass, metal or plastics. The substrate may be, for example, flat or curved. Metal powders or other types of applique materials, e.g.

glitter and tinsel, amy be applied to the substrate. Different colours may be used for the printing.

The finely delineated ink and transfer image may be supplemented by additional image portions produced prior to application of the filler by water-insoluble crayons or oil pastels. Wax crayons may be used, but non-waxy oil pastels are preferred.

Examples of non-waxy oil pastels include those known in the trade as: (a) "PANDA Oil Pastels", of Royal Talens BV, Apeldoorn, Holland; (b) "Cray-Pas", of Sakura Colour Products Corporation, Osaka, Japan; (c) "PENTEL Oil Pastels" of Pentel Co. Ltd.

Japan.

(PANDA and PENTEL are Registered Trade Marks).

One example of a wax crayon is known in the trade as Crayola, of Binney and Smith (Europe) Ltd., Ampthill Road, Bedford, England.

The preferred colour for the pastel or crayon is black.

Again, the image may be supplemented by water-insoluble paintbrush work prior to application of the filler.

It will be realised that the brushwork may also be carried out with the spirit-based ink itself.

For the crayoned, pastelled or painted image portions, a turpentine or white spirit solvent may for example be used, or a mixture of one or both of these with the pen ink solvent.

One example of a transfer which may be used is pressure-sensitive e.g. "LETRASET". The transferred image may include printed letters, symbols or other artwork. (LETRASET is a Registered Trade Mark).

WHAT WE CLAIM IS: 1. A method of preparing a screen process printing stencil comprising the steps of (a) providing a positive image on a screen area, (b) covering the screen area with a filler, and (c) selectively removing the positive image and corresponding portions of filler to leave a corresponding negative image defined by the remaining filler, wherein some positive image portions are drawn onto the screen area by fine delineation, and at least one other positive image portion, comprised by a positive transfer image portion, is transferred from a backing member onto the screen area.

2. A method according to Claim 1, wherein the positive image is formed by a water-insoluble image forming material.

3. A method according to Claim 1, wherein also positive image portions are formed by application of an oil pastel material to the screen area.

4. A method as claimed in Claim 1, wherein the finely delineated image portions are drawn on the screen area with a spirit-based ink.

5. A method as claimed in Claim 1, wherein also positive image portions are formed by application of a wax crayon material to the screen area.

6. A stencil prepared by a method according to any one of the preceding Claims.

7. A screen printing process using a stencil prepared by a method according to Claim 6.

8. A substrate printed on by a process according to Claim 7.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. or both of these with the pen ink solvent. One example of a transfer which may be used is pressure-sensitive e.g. "LETRASET". The transferred image may include printed letters, symbols or other artwork. (LETRASET is a Registered Trade Mark). WHAT WE CLAIM IS:

1. A method of preparing a screen process printing stencil comprising the steps of (a) providing a positive image on a screen area, (b) covering the screen area with a filler, and (c) selectively removing the positive image and corresponding portions of filler to leave a corresponding negative image defined by the remaining filler, wherein some positive image portions are drawn onto the screen area by fine delineation, and at least one other positive image portion, comprised by a positive transfer image portion, is transferred from a backing member onto the screen area.

2. A method according to Claim 1, wherein the positive image is formed by a water-insoluble image forming material.

3. A method according to Claim 1, wherein also positive image portions are formed by application of an oil pastel material to the screen area.

4. A method as claimed in Claim 1, wherein the finely delineated image portions are drawn on the screen area with a spirit-based ink.

5. A method as claimed in Claim 1, wherein also positive image portions are formed by application of a wax crayon material to the screen area.

6. A stencil prepared by a method according to any one of the preceding Claims.

7. A screen printing process using a stencil prepared by a method according to Claim 6.

8. A substrate printed on by a process according to Claim 7.