Thermal transfer printing resistive ribbon

Description

[0001] The present invention relates to resistive ribbons for use in thermal transfer printing onto a receptor surface.

[0002] Resistive ribbon thermal transfer printing is known in the art and is, very briefly, summarised in US-4,103,066, _DE-2,842,772, FR-2,434,709 and GB-1,583,922, which disclose a resistive ribbon comprising a resistive polycarbonate layer or substrate with a transfer layer of wax, carbon black and a dye on one surface thereof.

[0003] The use in a resistive ribbon for thermal transfer printing of a "hold-off" layer as the layer closest to the receptor surface to be printed upon, is disclosed in European patent application No. 81103625.0, publication No. EP- , filed before but published after the priority.date of this application.

[0004] According to the present invention, a resistive ribbon for thermal transfer printing onto a receptor surface, is characterised by having a layer of polyvinyl acetate as the layer closest to the receptor surface being printed upon.

[0005] The layer of polyvinyl acetate may serve as the transfer layer. In such case, the layer of polyvinyl acetate contains a pigment, such as carbon, and/or one or more colouring dyes, and selected portions are transferred from the resistive ribbon to the receptor surface during printing to serve as the ink.

[0006] The layer of polyvinyl acetate layer may be used as a hold-off layer. In such case, the layer is uncoloured and serves to make subsequent correction of printing easier. When the polyvinyl acetate layer is used as a hold-off layer, it is used in conjunction with a transfer layer, which acts as the ink, and contains pigment and/or colouring material. The hold-off layer serves to prevent the ink from penetrating the pores of the receptor surface being printed upon. The polyvinyl acetate hold-off layer may be used with any of the known useful transfer layers, for example, a layer of polymerized fatty acid polyamide, as disclosed in GB-2,010,515.

[0007] Most preferred, however, is the use of a polyvinyl acetate uncoloured hold-off layer with a pigmented transfer layer of polyvinyl acetate.

[0008] The use of a polyvinyl acetate layer in a resistive ribbon according to the present invention, gives the advantages of rub resistance, waterfastness and correctability, while at the same time providing excellent print quality. An additional advantage is that such a layer is capable of formulation by water based application, rather than from an organic solvent. Thus, the use of organic solvents is avoided and an ecological advantage achieved.

[0009] The polyvinyl acetate layer, whether serving as hold-off layer or transfer layer, is suitable for use with any of the resistive layers and conductive layers known in the thermal transfer resistive ribbon making art. The polycarbonate ribbon of US-4,103,066 is one preferred resistive layer.

[0010] In general, the polyvinyl acetate layer, when used as a hold-off layer, should be from about 0.1 to 10 microns in thickness, and preferably from about 1 to about 2 microns. When the polyvinyl acetate layer is used as a transfer layer, whether with or without a polyvinyl acetate hold-off layer, it should be from about 1 to about 5 microns thick.

[0011] Polyvinyl acetate suitable for use in the present invention is available commercially from a number of sources. For exmaple, polyvinyl acetate latex is available from Union Carbide Corporation under the trademark Ucar Vehicle 4029. Carbon pigments suitable for use in conjunction with polyvinyl acetate for the transfer layer of the present invention are also readily available commercially. For example, Aqua Blak, a brand of carbon from the Borden company.

[0012] The following additional examples illustrate the invention, but many variations are possible without departing from the scope of the claims.

Example 1

[0013] A transfer layer was prepared by applying:

30 parts polyvinyl acetate latex;

40 parts water; and

7.5 parts carbon,

to a metallized polyurethane/polyester crosslinked resistive layer. The layer was dried with heat, and the ribbon was evaluated on a resistive ribbon thermal transfer robot. Excellent quality print was obtained at 35 to 40 milliamps current.

Example 2

[0014] A transfer layer was prepared as in Example 1, except that the formulation was applied to a metallized resistive layer of polycarbonate.

[0015] The ribbon was evaluated on a resistive ribbon thermal transfer robot and was found to produce excellent quality print at 30 to 35 milliamps current.

Example 3

[0016] A transfer layer was prepared by applying:

20 parts polyvinyl acetate latex;

5 parts carbon;

1 part polyethylene oxide;

50 parts water,

to a metallized polycarbonate resistive layer. The transfer layer was dried, and the ribbon was evaluated on a robot. Good quality print was obtained that could be removed with application of a pressured sensitive adhesive tape. The selected areas of print were lifted cleanly off the paper, demonstrating the correctability feature of the transfer layer.

Example 4

[0017] A hold-off layer was prepared by applying polyvinyl acetate latex in water to a polyamide transfer layer on a polycarbonate layer or substrate of a resistive ribbon. A thin clear layer of uncoloured polyvinyl acetate was formed on the polyamide ink surface of the ribbon.

[0018] The ribbon was printed onto paper. The latex layer prevented penetration of the ink into the paper. The print thus formed was lifted off the paper with adhesive tape, demonstrating the correctability of the material.

Claims

1 A resistive ribbon for thermal transfer printing onto a receptor surface, characterised by having a layer of polyvinyl acetate as the layer closest to the receptor surface being printed upon.

2 A ribbon according to claim 1, in which the layer of polyvinyl acetate is uncoloured.

3 A ribbon according to claim 2, in which the layer of uncoloured polyvinyl acetate covers a layer of coloured polyvinyl acetate.

4 A ribbon according to claim 2 or 3, in which the uncoloured polyvinyl acetate layer is from 0.1 to 10 microns thick.

5 A ribbon according to claim 4, in which the uncoloured polyvinyl acetate layer is from 1 to 2 microns thick.

6 A ribbon according to claim 1, in which the layer of polyvinyl acetate is coloured and contains pigment and/or dye.

7 A ribbon according to claim 3, or claim 4 as appendant to claim 3, or claim 6, in which the coloured polyvinyl acetate layer is from 1 to 5 microns thick.

8 A ribbon according to claim 6 or claim 7 as appendant to claim 6, in which the polyvinyl acetate layer also includes polyethylene oxide.