IE44853B1 - A method of applying imprints to side surfaces of paper pads - Google Patents

Description

This invention relates to a method of applying an imprint to pads or blocks of sheet material, such as paper.

The pads may he of the kind having a flat surface defined hy a straight edge of the sheets, these straight edges being stuck together so that this flat surface defines a hinge or spine of the pad. In the case of a writing pad .or notepad, for example, the sheets may he detached one at a time by tearing them off from the hinge or spine surface. In the ease of other forms of pads or blocks, the sheets may he intended to be permanently stuck together so that they form leaves or pages in the manner of a book. Any such form of pad or block will be referred to as 'a pad of the kind specified It is sometimes desirable to provide an imprint on at least 'one side surface of a pad of the kind specified. The side surface may be the hinge or spine surface, or it may be any side surface of the pad defined by an edge of each of the sheets which constitute the pad. Such an imprint may be decorative.or may have a utilitarian or functional purpose.

For example, it may be desirable to provide a notepad having on one or more of its side surfaces an imprint in the form of advertising material or the like.

It is known to make a pad of the kind specified, carrying an imprint on at least one of its side surfaces, by applying the imprint to the pad by a silk screen printing process. However, difficulties sometimes arise in applying the imprint by a silk screen printing process, particularly where it is necessary to make more than one application of an imprint to the side surface, e.g. in the case of multicoloured printing. One such difficulty is to secure sufficiently accurate, registration of the successive silk screens to ensure a high quality print time after time 'in a repetition process. - 2 44-85^ One cause of this difficulty, particularly in the case of a thick pad consisting of a large number of sheets, is that it may not he feasible to clamp the pad sufficiently tightly to ensure that there \Ls no relative movement between any of the sheets during the successive stages of the printing process.

The present invention provides an improved method of applying an imprint to a side surface of a pad of the kind specified. .The advantages of the invention are ' ' particularly manifest where a multi-colour imprint is to be applied to one or more of the side surfaces of a thick pad.

According to the invention a method of applying an / I imprint to at least one side surface of a pad of the kind specified comprises! taking a transfer comprising the said imprint as a surface layer on a substrate; placing the transfer with the said surface layer in contact with a side surface of the pad; applying heat and pressure to the substrate to affix the surface layer to the side surface of the pad; and thereafter removing the substrate.

In the case where a multi-colour application is to be made, the transfer itself will carry the multi-colour material in the surface layer on the substrate and the several colours will be applied simultaneously to the pad, so that no problems of registration of successive colour imprints will arise.

The side surface of the pad to which the imprint is to be applied may be any of the side surfaces, including the hinge or spine surface..

The transfer may be made by forming an imprint, e.g. a mult'i-colour imprint, on a suitable substrate.. The substrate may be a sheet of paper having a vapour repellant surface coating, e.g, an agar derived coating such as that available - 3 & e1'· under the trade name Hycosol, The imprint may be made with a suitable ink capable of being transferred from the substrate to the side surface of the pad by the application of heat and pressure to the substrate, such as a vapour. diffusion ink» Such.inks are known in the art, e.g. for transfers for applying patterns or pictures to. synthetic textile fabrics. Suitable inks are available under the trade name MarlerTex.

Certain inks useful for making imprints do not 10 transfer well to the side surfaces of a pad of sheets of paper but have better adhesion to, for example, some synthetic polymeric materials. In such a case, satisfactory transfer may be achieved by first applying to the side surface of the pad a coating of a suitable material, e.g. of varnish based · on a synthetic plastics material, which is compatible with the imprint, i.e. to which the ink of the imprint, will adhere, both on application.and subsequently.

Alternatively the transfer may include a layer of such a suitable material over the layer of the imprint such that the layer of suitable material becomes disposed between the paper and the imprint on application to the pad.

To obtain satisfactory transfer of the imprint from the substrate to the side surface of the pad it is necessary that heat and pressure should be applied uniformly over the substrate. The transfer can therefore most simply be applied to a flat side surface of a pad, the heat and pressure being applied by the use of a press having a heated flat platen. A roller, preferably a heated roller, may however be used. -4 _ 44S53 The heat and· pressure necessary to give the optimum transfer of imprint from the substrate to the side surface of the pad will vary considerably, depending on the nature of the materials used. The best combination of pressure and temperature can be ascertained by simple experiments. The pressure applied to the transfer to affix the imprint to the pad may, for example, be in the range from 75 to 125 pounds per square inch, e.g. 100 pounds per square inch, and the application temperature in the range 200 to 300°C e.g..25O°C for an· application time in the range from 10 seconds to one minute, e.g. 20 seconds.

The invention resides not only in the method of applying the imprint to the pad, but to a pad carrying an imprint which has been applied-·by the said method? Also, according to another aspect of the invention, a pad of the kind specified has on at least one of its side surfaces a multi-colour imprint which has been applied to the side surface from a transfer in a single transfer operation.

A particularly striking product can be achieved by applying a multi-colour imprint to the four side surfaces of a pad consisting of a stack of square sheets of paper, the height of the pad being equal to the length of a side of a sheet so that the pad is in the form of a cube. One of the said four side surfaces constitutes the hinge or spine of the pad.

Claims (12)

1. CLAIMS:1. A method of applying an imprint to at least one side surface of a pad of the kind specified comprising: taking a transfer comprising the said imprint as a surface layer on a substrate; placing the transfer with the said surface layer in contact with a side surface of the pad; applying heat and pressure to the substrate to affix the surface layer to the side surface of the pad; and thereafter removing the substrate,

2. A method as claimed In Claim 1 wherein the imprint is a multi-colour imprint.

3. A method as'claimed in Claim 1 or Claim;2 wherein the imprint is applied to any or all of the side surfaces of the pad.

4. A method as claimed in any of the preceding Claims wherein the substrate is a sheet of paper having a vapour repellant surface coating,

5. A method as claimed in any of the preceding Claims wherein the side surface of the pad is coated with a layer of material compatible with .the imprint.

6.. A method as claimed in any of Claimsi 1 to 4 wherein the transfer is coated with a layer of material compatible with the imprint such that upon application to the side surface of the pad the layer of material compatible with the imprint is disposed between the side surface of the pad and the imprint. ·

7. A method as claimed in Claim 5 or Claim 6 wherein the material compatible with the imprint is a varnish based on a synthetic plastics' material.

8. , A method as claimed in any of the preceding Claims wherein the transfer is applied to the pad at a pressure in the range 75 to 125 pounds per square inch, and a temperature in the range 200 to 300°C, for a time in the range from 10 seconds to one minute. - 6 44883

9. A method as claimed in any of the preceding Claims wherein the transfer is applied with a roller.

10. A method of applying an imprint'to at least one side surface of a pad of the kind specified substantially as described 5 herein.,

11. A pad of the kind specified applied with an imprint by the method of any of the preceding Claims.

12. ,. A pad of the kind specified which has on at least one of its -side surfaces a multi-colour imprint which has been applied, 10 to the or each side surface from a transfer in a single transfer operation.