IE980582A1

IE980582A1 - A thermal printing ink

Info

Publication number: IE980582A1
Application number: IE980582A
Authority: IE
Inventors: James Lacey; John Downing; Milo Slattery
Original assignee: Inx Res And Dev Ltd
Priority date: 1998-07-17
Filing date: 1998-07-17
Publication date: 2000-03-08

Abstract

A printing ink for thermal printing applications comprises a mixture of a varnish, a dispersion colour and a wax. The varnish comprises in combination a very hard styrene-acrylic emulsion and a solution acrylic resin.

Description

A thermal printing ink This invention relates to a printing ink, and in particular to a printing ink for use in thermal printing applications .

Thermal printing is widely used, for example, in supermarkets for printing labels indicating the contents and price of goods being purchased. It is difficult to produce a problem-free printing ink for thermal printing. One of the main difficulties arises in trying to achieve good heat resistance while at the same time having good water resistance. Relatively long drying times are common with a result that smudging and ill defined printing of the label can occur.

The present invention is directed towards overcoming this problem.

According to the invention, there is provided a printing ink for use in thermal printing applications comprising a mixture of a dispersion colour and a varnish, the varnish comprising in combination a very hard styrene-acrylic emulsion having a tg (glass transition temperature) in the range 90-100°C and an MFT (minimum film forming temperature) in the range 70-75JC, a solution acrylic resin having a tg in the range 90-100°C and a wax.

It has been found that the combination of these types of hard styrene acrylic emulsion and solution acrylic resin produces a particularly desirable printing ink for thermal printing applications which combines good heat resistance with water resistance. Advantageously, the ink dries relatively quickly - typically within about 2 minutes of printing. —--.......

OPEN TO PU0UC INSPECTION UNDER SECTION 26 AND RULE 23 - j-iT-imnriO Tl - 2 Preferably, the emulsion, resin and wax are combined in the ratio 20:74:6 by weight.

In another aspect of the invention, there is provided a process for producing a printing ink for use in thermal printing applications, the process comprising:preparing a varnish by combining a very hard styreneacrylic emulsion having a tg in the range 90-100=C and an MFT in the range 70-75'C with a solution acrylic resin having a tg in the range 90-100cC and a wax, adding a dispersion colour and optionally conditioning additives to the varnish and mixing the dispersion colour and the varnish to produce an homogenous printing ink.

In a further embodiment, the styrene-acrylic emulsion, solution acrylic resin and the wax are combined in the ratio 20:74:6 by weight.

The invention will be more clearly understood by the following description of an example thereof.

Example wt. % Dispersion colour 1-50 Antifoam 1 Varnish balance The varnish is prepared as follows:IE 980582 Wt . % Styrene acrylic emulsion Solution acrylic resin Wax The above-mentioned varnish ingredients are mixed to produce a varnish which is subsequently mixed with the desired quantities of dispersion colour and antifoam to produce a printing ink of the invention.

The styrene acrylic emulsion has a tg in the range 9010 100°C and an MFT in the range 70-75°C. The solution acrylic resin has a tg in the range 90-100°C.

It has been found that the printing ink of the invention is particularly suited to thermal printing applications as it combines good water resistance with good heat resistance which facilitates thermal printing. This particular combination provides a particularly advantageous balance of soft and hard polymers to achieve this end result.

The invention is not limited to the embodiment hereinbefore described which may be varied in construction and detail.

Claims

1. A printing ink for use in thermal printing applications comprising a mixture of a dispersion colour and a varnish, the varnish comprising in combination a very hard styrene-acrylic emulsion having a tg in the range 90-100 : C and an MFT in the range 70-75°C, a solution acrylic resin having a tg in the range 90-100'C and a wax.

2. A printing ink as claimed in claim 1, wherein the emulsion, resin and wax are combined in the ratio 20:74:6 by weight.

3. A printing ink for use in thermal printing applications substantially as hereinbefore described with reference to the example.

4. A process for producing a printing ink for use in thermal printing applications, the process comprising:preparing a varnish by combining a very hard styrene-acrylic emulsion having a tg in the range 90-100 c C and an MFT in the range 70-75°C with a solution acrylic resin having a tg in the range 90-100°C and a wax, and mixing the varnish with a dispersion colour to produce the printing ink.

5. A process as claimed in claim 4, wherein the emulsion, resin and wax are combined in the ratio 20:74 :6 by weight.

6. A process for producing a printing ink substantially as hereinbefore described with reference to the example.

7. A printing ink for use in thermal printing 5 applications whenever produced by the process as claimed in any of claims 4 to 6.