Abstract: A method of producing a screen-printing stencil having open areas and blocked areas for respectively passage and blocking of a printing medium. The method includes providing a receptor element having an image-receiving layer capable of receiving a first chemical agent in areas corresponding to the blocked areas of the stencil to be produced. A first chemical agent is applied to the image-receiving layer of the receptor element in the corresponding areas. A second, stencil-forming chemical agent is then applied to a screen printing screen and the image-receiving layer fo the receptor element brought into contact with the stencil-forming agent to allow the first and second chemical agents to react to produce on the screen a stencil-forming layer having areas of lower solubility corresponding to the said blocked areas and areas of higher solubility in areas corresponding to the open stencil areas.

Abstract: Screen printing stencils are produced by a positive-working method which involves no light-sensitive materials and does not require the use of safe lights. A coated receptor film having a coating layer and a support layer is imaged using an ink-jet printer or plotter in areas corresponding to the open stencil areas. The film is then applied to a mesh and an emulsion applied. Chemical hardening of the emulsion takes place in the non-imaged areas. The stencil is then produced by removing the support layer of the film and washing away the unhardened emulsion. The receptor film may include a layer which is incorporated into the stencil layer to form a profile. In addition to screen production methods, coated films, coating compositions and compositions for imagewise application are disclosed.

Abstract: A coated film product comprises a support base, a stencil-forming layer and an intermediate release layer. The stencil-forming layer is a blend of two grades of polyvinyl alcohol having different degrees of hydrolysis. The stencil-forming layer is imaged by dropwise application (for example using an ink-jet printer or plotter) of a cross-linking agent which hardens the stencil-forming layer to resist washing out with water. The hardened areas remaining after washing out are however sufficiently tacky for the washed-out film to adhere to the screen mesh by application of pressure and, after removal of the support base, form the stencil layer of a screen-printing screen.

Abstract: A coated film product comprises a support base, a stencil-forming layer and an intermediate release layer. The stencil-forming layer is a blend of two grades of polyvinyl alcohol having different degrees of hydrolysis. The stencil-forming layer is imaged by dropwise application (for example using an ink-jet printer or plotter) of a cross-linking agent which hardens the stencil-forming layer to resist washing out with water. The hardened areas remaining after washing out are however sufficiently tacky for the washed-out film to adhere to the screen mesh by application of pressure and, after removal of the support base, form the stencil layer of a screen-printing screen.

Abstract: A method of producing a screen-printing stencil having open areas and blocked areas for respectively passage and blocking of a printing medium. The method includes providing a receptor element having an image-receiving layer capable of receiving a first chemical agent in areas corresponding to the blocked areas of the stencil to be produced. A first chemical agent is applied to the image-receiving layer of the receptor element in the corresponding areas. A second, stencil-forming chemical agent is then applied to a screen printing screen and the image-receiving layer fo the receptor element brought into contact with the stencil-forming agent to allow the first and second chemical agents to react to produce on the screen a stencil-forming layer having areas of lower solubility corresponding to the said blocked areas and areas of higher solubility in areas corresponding to the open stencil areas.

Abstract: Screen printing stencils are produced by a positive-working method which involves no light-sensitive materials and does not require the use of safe lights. A coated receptor film having a coating layer and a support layer is imaged using an ink-jet printer or plotter in areas corresponding to the open stencil areas. The film is then applied to a mesh and an emulsion applied. Chemical hardening of the emulsion takes place in the non-imaged areas. The stencil is then produced by removing the support layer of the film and washing away the unhardened emulsion. The receptor film may include a layer which is incorporated into the stencil layer to form a profile. In addition to screen production methods, coated films, coating compositions and compositions for imagewise application are disclosed.

Abstract: Screen printing stencils are produced by a positive-working method which involves no light-sensitive materials and does not require the use of safe lights. A coated receptor film having a coating layer and a support layer is imaged using an ink-jet printer or plotter in areas corresponding to the open stencil areas. The film is then applied to a mesh and an emulsion applied. Chemical hardening of the emulsion takes place in the non-imaged areas. The stencil is then produced by removing the support layer of the film and washing away the unhardened emulsion. The receptor film may include a layer which is incorporated into the stencil layer to form a profile. In addition to screen production methods, coated films, coating compositions and compositions for imagewise application are disclosed.

Abstract: The apparatus comprises a washing chamber and a washing brush on the end of a hose leading to a reservoir for liquid to be applied. The hose is connected to an outlet pipe of the reservoir having a one-way valve which is immersed in liquid in the reservoir and allows movement of the brush to pump liquid from the reservoir to the chamber. Liquid supplied to the chamber is collected in a sump, the overflow of which feeds the reservoir. A filter screen is positioned between the chamber and the sump, in which solid material precipitates, allowing liquid to be recycled. The apparatus can be used, for example, for removal of ink from a used screen, removal of stencil material from a used screen or application of a degreasing preparation to a screen prior to use.

Abstract: Water-processable screenprinting stencils and resists are based upon photopolymerizable systems in which the hydrogen donor compound is a modified polyvinylalcohol having pendant dialkylamino groups.

Abstract: Masking films, having the advantageous properties of both those masking films having an intermediate adhesive layer and those masking films having a high-adhesion masking layer without an intermediate adhesive layer, include a masking layer which incorporates a cellulose ester component, a polyurethane and one or more colorants selected from dyes and pigments.

Abstract: Masking films comprise a transparent base, preferably a polyester or a polycarbonate, directly carrying a masking film in the form of a dyed transparent plastics material based upon a vinyl chloride-vinyl acetate copolymer coating, which contains an aromatic polyester-based polyurethane. The amount of vinyl acetate and polyurethane in the coating preferably comprises 30% to 65% w/w of its total polymer content.

Abstract: Photopolymers which are derivatives of polyvinyl alcohol and are useful as resists, stencils and relief images are made by reacting a compound having one or two formyl or acetal groups, such as terephthaldehyde, a naphthalene dialdehyde or the reaction product of an acetal and hydroxy-benzaldehyde, with an aromatic or heterocyclic compound carrying an acetyl group, so as to produce an intermediate of the formula: ##STR1## and reacting this with a polyvinyl alcohol to yield a photosensitive product of the formula: ##STR2## wherein m is 0 or 1, n is an integer from 1 to 6, X is an aromatic or heterocyclic group carrying at least one polar group and Z is an aromatic group of the formula: ##STR3## wherein R' and R", when both are present, are the same or different and each represents a hydrogen or a halogen atom or an alkyl, alkoxy, hydroxyalkyl, hydroxy, nitro or cyano group.

Abstract: Light-sensitive compositions and materials incorporating such compositions, such as coated films for the production of polymeric resists, comprise a diazo-resin as a sensitizer for the composition and a water-soluble or water-dispersible colloid. In order to stabilize the diazo-resin sensitizer and increase the time between manufacture and use of such light-sensitive compositions and material, a poly-(vinylpyridine) is incorporated in the composition, preferably in the form of a water-soluble salt such as the hydrochloride or sulphate.