Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1998-08-28
2001-11-27
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S343000, C428S354000, C428S914000, C427S149000
Reexamination Certificate
active
06322876
ABSTRACT:
This invention relates to decalcamania or transfers in which one or more design indicia are supported on a temporary carrier sheet and are transferable to a substrate using a pressure-sensitive adhesive layer on the indicia.
Dry transfers of the above type are manufactured by printing onto a temporary carrier sheet and are over-printed with a pressure-sensitive adhesive. Because the nature of the carrier sheet is selected so that the indicia have a relatively poor adhesion to the carrier sheet, they can be transferred to a receptor surface under the influence of the tacky adhesive. Similarly, so-called water-slide transfers can be manufactured in which design indicia are printed onto a carrier sheet having a water-soluble surface coating, e.g. gummed paper. In preparation for use, the transfers are soaked in water, which releases them from the carrier sheet and adhered to a receptor surface. A pressure-sensitive adhesive layer on the indicia can be used to cause them to be bonded to the receptor surface. Both of the above kinds of transfers require the tacky adhesive layer to be protected from sticking to other carrier sheets or surface before the transfers are to be used.
In conventional practice, the transfers are interleaved with sheets which are coated with a material which easily releases from an adhesive surface, e.g. siliconised papers or films. Such siliconised sheets prevent the transfers sticking together when stacked or guillotined into smaller sizes, or delaminating or otherwise becoming unusable in storage or handling before the transfers are to be employed.
The siliconised paper or film is expensive, adds considerable weight to the product, and can be a problem if the level of the tack of the adhesive is relatively low and the paper becomes detached during such processes as the insertion of small transfers as novelties into other products, such as cereal packs.
Siliconised paper also presents an environmental problem because it must be separated from waste paper for recycling, since it interferes with paper-making processes.
It is an object of this invention to devise a transfer having a pressure-sensitive adhesive which does not require a siliconised paper or similar release material, but can be stored and handled without blocking or premature transfer.
According to the present invention there is provided a decalcamania in which at least one design indicium is supported on a temporary carrier sheet and is transferable to a substrate aided by pressure-sensitive adhesive on the indicium, said pressure-sensitive adhesive bearing a tack-reducing substance which enables several sheets of the decalcamania to be stacked without blocking, said tack-reducing substance being removable to restore tack to the adhesive by application of a differential solvent for the tack-reducing substance and the adhesive, said solvent being a non-solvent or poor solvent for tack inducing components of the adhesive and a good solvent for the tack-reducing substance.
The term “design indicium” as used in this specification includes a sign, figure, letter, picture or symbol. It may be formed from one ink or be a composite structure formed from two or more inks or ink layers.
The invention overcomes the problems of prior art pressure-sensitive transfers by application to the adhesive of a tack-reducing substance which is soluble in a solvent which is a non-solvent or a poor solvent for the adhesive. Conveniently, the tack-reducing substance is water-soluble since conventional components of pressure-sensitive adhesives, especially tackifiers, are not water-soluble. Also, water is always available to the user and is thus a convenient solvent for removing the tack-reducing substance and thus activates the adhesive.
One convenient way of carrying the invention into effect is to manufacture the transfer in the normal way up to coating or printing the adhesive onto the indicia. At this point, the surface of the adhesive is temporarily de-tackified by applying a tack-reducing substance to the exposed surface of the adhesive. The tack-reducing substance should not be soluble in or miscible with the adhesive, but should form a separate, superficial layer. In a currently preferred form of the invention, the tack-reducing substance is a solid material, e.g. a powder or crystalline material. When applied to the tacky surface, the solid material lies on the adhesive surface and prevents it bonding to another surface. The solid, powdery or crystalline tack-reducing substance is preferably water-soluble, and can be washed away by soaking the transfer or holding it under a stream of water.
Typical solid, water-soluble detackifiers are starch, modified starches, sugars, including natural and synthetic sugars, and cellulose derivatives such as alkyl- or alkoxy-celluloses and hydroxyalkyl celluloses.
The tack-reducing substance may be coloured so that the user is prompted to wash the adhesive layer until a colour change indicates that the tack-reducing substance has been sufficiently removed, and the tack of the adhesive restored.
It is not essential to apply the tack-reducing substance as a solid but it can, instead, be applied as a coating containing the tack-reducing substance. After drying, the tack reducing substance is deposited as a film (which may be continuous or in discrete areas) or as particles on the surface of the adhesive. In this case, it is often preferable for the coating to be formulated using solvents, such as alcohols, which are water-miscible but are not solvents for the pressure-sensitive adhesive.
An alternative way of rendering the adhesive temporarily non-tacky is by transferring a film of the tack-reducing substance from a carrier sheet to the adhesive surface. The film is generally water-soluble and is removed by washing with water to restore the tack level of the adhesive.
It will be understood that instead of activating by water as described, any solvent could be used which washes away the non-tackifying layer, but which leaves the tacky layer of adhesive. For example, if the adhesive were not soluble in alcohols, then an alcohol soluble layer could be used and removed with an alcoholic solvent.
The transfers in accordance with the invention may be dry transfers. However, the invention is especially useful in the manufacture of water-slide transfers which are coated with a pressure-sensitive adhesive on the exposed surface of the design indicia.
In the case of water slide transfers, it is normal and necessary to soak in water to release the transfer so there is no extra operation involved in preparing the transfer for application, except for rubbing the water-soluble layer from the surface of the pressure-sensitive adhesive.
A further means of applying the water-soluble layer is by use of a printing technique, e.g. ink-jet printing. In this case, the printing can consist of a single non-coloured layer over the area of the pressure-sensitive layer or, in addition or alternatively, a coloured layer or layers can be printed.
With this variant, the adhesive layer can be covered by the water-soluble layer for the primary purpose of obscuring the tackiness of the adhesive. This has the further advantage of enabling the water-soluble layer to be informative or decorative, or capable of having additional qualities. It is, for example, capable of being used as a method of marking paper by first wetting the paper, and then putting the water-soluble layer in contact with it and thereby transferring part or all of the water-soluble layer. When the water-soluble layer is removed, the coloured layer will have disappeared, leaving the pressure-sensitive layer visibly cleaned.
Another alternative is that the pressure-sensitive layer can be covered with a water-soluble powder layer which, for example, could be printed by ink jet printing, using water-based inks to provide information or decoration.
Furthermore, the water-soluble layer can be applied by hot melt applications using fine nozzles to express the molten water-soluble composition over the pressure-sensitive adhesive coating.
Referring to
Lythgoe Alan Lennox
van Heijningen Dick J.
Hess Bruce H.
McDermott & Will & Emery
Shewareged B.
Trip Industries Holding B.V.
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