WO2008121112A1

WO2008121112A1 - Self- contained thermal transfer label and method of preparation

Info

Publication number: WO2008121112A1
Application number: PCT/US2007/008276
Authority: WO
Inventors: Alfred Doi
Original assignee: INNOVATIVE LABEL TECHNOLOGY Inc
Current assignee: INNOVATIVE LABEL TECHNOLOGY Inc
Priority date: 2007-03-29
Filing date: 2007-03-29
Publication date: 2008-10-09
Anticipated expiration: 2009-09-29

Abstract

A thermal transfer label strip provides a peelable label stock over a carrier strip. The label stock is cut into separate labels arranged in single file order along the carrier strip. A thermal printing ribbon is placed over the label stock and adhered along transverse adhesive lines adjacent to the leading and trailing edges of the labels, or just the leading edges of the labels. The printing ribbon is severed into portions overlaying the individual labels with excess portions of the printing ribbon and the label stock removable leaving only the labels and the individual associated portions of the printing ribbon on the carrier strip in readiness for printing whereupon the individual labels may be easily peeled from the carrier strip for use.

Description

TITLE: Self-Contained Thermal Transfer Label And Method Of Preparation

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION:

This invention relates generally to self-contained thermal transfer labels and a process for making such labels.

BACKGROUND AND DESCRIPTION OF RELATED ART:

Thermal printing has made possible cost effective digital imaging under computer control. Thermal printing makes possible one of the most accurate methods of printing machine readable bar codes. Dots printed can be overlapped producing very distinct edges needed in bar codes.

Direct thermal printing functions to print an image directly on paper stock caged with heat sensitive chemicals. Because of the simplicity of the technology and cost effective in manufacturing, the population of the direct thermal printers in use today is numbered over three million world wide. Direct thermal images lack dimensional stability and resistance to physical and chemical reaction. The image thus made have problems in image stability, which gave rise to the introduction of thermal transfer printers. However, because of the higher costs of manufacturing, the population of direct thermal printers is greater than that of the thermal transfer printers. This invention is intended to allow direct thermal printers to produce images comparable to those produced by the more expensive thermal transfer printers.

Thermal printing techniques can generally be segregated into two principal categories: direct thermal printing and thermal transfer printing. Direct thermal printing functions to print an image directly on the paper stock, coated with heat sensitive material. In thermal transfer printing, a thermal transfer ribbon is applied upon the paper stock before the paper stock is passed through the thermal printer. The thermal transfer ribbon, or donor ribbon generally appears similar to carbon paper, with a wax or wax-resin coating formed on the undersurface. As the paper stock/donor ribbon is passed through the thermal printer, the print head functions to melt the wax onto the underlying paper stock in prescribed patterns. The donor ribbon is then removed from the paper stock, leaving the image formed by the thermal print head.

Thermal transfer printing has advantages that make this technology attractive. In thermal transfer printing, the ink is directly applied to the paper stock, whereas with the direct thermal transfer, no ink is used. Instead, the image arises from reaction of the heat sensitive coating as the paper stock passes adjacent the thermal print head. As a result, thermal transfer printing typically can result in a higher quality printing that resists fading and allows for long-term storage and scanability. Thermal transfer printing also lends itself to color printing, allows high graphics contrast capability and provides substantial flexibility in the papers stock or other receiving media to be printed on.

Despite the foregoing advantages, there are also disadvantages associated with thermal transfer printing. Many of those disadvantages arise from the requirement that the donor ribbon, be reliably applied in flat registry with the paper stock, then removable from the paper stock after printing. Typically, the thermal transfer ribbon is wound on a separate dispensing spool and mated to the paper stock as it reaches the thermal print head. Thereafter, the used ribbon is separated from the paper stock and rewound onto a retrieval roller. Such procedures require mechanisms that are incompatible with the large population of compact thermal printers that are currently used for many applications. Moreover, difficulties may arise in winding and rewinding the donor ribbon, wrinkling of the ribbon as it is applied to the paper, and recyclability of the donor ribbon after it is used. Disposability of the donor ribbon can be a significant problem, because many such ribbons do not readily degrade. Special treatments needed to dispose of the donor ribbon, adding cost to the labels.

In some cases, the donor ribbon is not rewound after passing through the thermal print head, but rather remains on the paper stock, and separated in use. While such techniques avoid the need for retrieving the donor ribbon, they give rise to additional difficulties resulting from adhering the donor ribbon to the paper stock. In particular, as the donor ribbon is removed from the paper stock, adhesive may remain on the paper stock causing the paper stock to be gummy, interfering with the scanning of the printed image and interfering in the ability of the paper stock to pass through dispensing mechanisms and other devices.

Accordingly, there is a need for apparatus and techniques to allow for the thermal transfer printing of labels which allows the label to be printed on conventional direct thermal printers, without the need for retrieval rollers to collect the used thermal transfer ribbon. Additionally, it is desirable that the resulting labels be cut to size as desired, with little or no adhesive remaining on the face of the label after the thermal transfer ribbon is removed.

In some cases, the donor ribbon is not rewound after passing through the thermal print head, but rather remains on the paper stock, and is separated in use. While such techniques avoid the need for retrieving the donor ribbon, they give rise to additional difficulties resulting from adhering the donor ribbon to the paper stock. In particular, as the donor ribbon is removed from the paper stock, adhesive may remain on the paper stock causing the paper stock to be gummy, interfering with the scanability of the printed image and interfering in the ability of the paper stock to pass through dispensing mechanisms and other devices. An important need is for a thermal printing ribbon that may be made up without the need for surface treatment for adjustment of surface tension to assure the selective removal of one strip from the next and location of release and adhesive layers.

Accordingly, there is a need for apparatus and techniques to allow for the thermal transfer printing of labels which allows the label to be printed on conventional direct thermal printers, without the need for retrieval rollers to collect the used thermal transfer ribbon. Additionally, it is desirable that the resulting labels be sized as desired, with little or no adhesive remaining on the label after the thermal transfer ribbon is removed. Relevant references include:

U.S. patent number 6309498 to A. Doi which teaches a self-contained thermal transfer label. The product is formed as paper stock having an area of release material applied to a surface portion thereof. Lines of adhesive material are applied to the release material. A thermal transfer donor ribbon is joined to the label by the lines of adhesive material. The donor ribbon is treated, prior to being joined with the label, such that the surface tension at the donor ribbon is modified to a level substantially different from that of the release material. As a consequence, when the donor ribbon is removed from the label, after printing on the label, the adhesive remains secured to the donor ribbon, rather than the underlying label or its carrier strip. A result is a label that may support a higher quality image, but without adhesive residue after the donor sheet is peeled away.

Imamura, et al., U.S. 5,427,840 describes a co-winding type thermal transfer sheet that is constituted by forming on one surface side of a substrate film a heat-fusible ink layer comprising a pigment and a particulate binder, and causing a tracing paper to be peelably bonded onto the heat-fusible ink layer by the medium of an adhesive layer. The thus constituted co-winding type thermal transfer sheet is capable of providing an original image which can be reproduced by use of a blueprint process so as to provide blueprint images having a high precision and a high contrast. In addition, a co-winding type thermal transfer sheet may also be constituted by forming a heat-fusible ink layer on one surface side of a substrate film and causing a transparent resin sheet to be peelably bonded onto the heat-fusible ink layer by the medium of an adhesive layer containing a cross-linking agent. The thus constituted co-winding type thermal transfer sheet is capable of providing an image excellent in wear resistance on the transparent resin sheet. The transparent resin sheet after the image formation may be used as an OHP (overhead projector) sheet without contaminating the sheet having no liquid absorbing property.

Mitchell, Jr., U.S. 5,738,748 describes a label stock including a thermal transfer facestock and a thermal transfer ribbon that are laminated together. The face stock has a front face for receiving thermal transfer ink and a back face covered by an adhesive. The ribbon has a front face covered by thermal transfer ink and a back face covered by a release. The facestock and ribbon are laminated and wound together into a roll so that the ribbon also functions as a conventional release liner.

AIM, Thermal "Transfer Printing", AIM's 'Thermal Transfer Printing', 1993, pp. 1-7, AEVI USA Copyright.

Anonymous Author, "UV Silicone and Emulsion Adhesive Tandem Coating", North America, Nov./Dec. 1999, pp.44, 49.

SUMMARY OF THE INVENTION

The present invention teaches certain benefits in construction and use which give rise to the objectives described below.

A primary objective of the present invention is to provide an apparatus and method of use of such apparatus that provides advantages not taught by the prior art.

Another objective is to provide an inexpensive thermal label printing strip.

A further objective is to provide such a printing strip that is able to produce printed labels using a low cost and easily carried thermal printer. A still further objective is to provide such a printing strip whereby a donor ribbon is more easily stripped from the label after printing because of being attached alone only one, or at most, two edges.

These and other advantages and features are achieved in the present invention as described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the present invention. In such drawings:

Figure 1 is an exploded perspective view of a first preferred embodiment of the invention;

Figure 2 is a longitudinal cross-sectional view of a pressure sensitive label stock thereof as taken along line 2-2 in Fig. 1;

Figure 3 is a longitudinal cross-sectional view of the label stock of figure 2 with labels severed and an adhesive layer including micro spheres applied over the labels as taken along line 3-3 in Fig. 1 ;

Figure 4 is a longitudinal cross-sectional view of the assembly of Fig. 3 and additionally showing a transfer layer placed over the adhesive layer as taken along line 4- 4 in Fig. 1;

Figure 5 is a transverse cross-sectional view of the label stock of figure 4 as taken along line 5-5 in Fig. I₅ and

Figure 6 is an exploded perspective view of a second preferred embodiment of the invention; DETAILED DESCRIPTION OF THE INVENTION

The above described drawing figures illustrate the invention in at least one of its preferred embodiments, which is further defined in detail in the following description.

The present invention is a self-contained thermal transfer label assembly and the method of preparing it. As shown in Fig. 1, the assembly comprises a release stock 37, preferably of paper or plastic, supporting a release coating 39 and, over the release coating 39, a first adhesive coating or layer 35. The release stock 37 is preferably a series of separate sections connected by perforated interfaces 38. A face stock 10, preferably of paper or plastic 10, from which printed labels 11 will be derived, has an upper surface 12 and a lower surface 14. The face stock 10 is placed into registration with the release stock 37, with the lower surface 14 of the face stock is placed into contact with the adhesive coating 35. This four-layer assembly is referred to as a pressure sensitive label stock and is designated by the numeral 30 in Fig. 1.

Face stock 10 is severed by die cutting along lines 10', as best seen in Fig. 1 to form individual labels 11. Labels 11 may be rectangular, as shown, or any other shape. An adhesive layer 33 is disposed, preferably by printing onto the face stock 10 on its upper surface 12. Adhesive layer 33 is preferably contained in an emulsion containing micro spheres, such as produced by Gel-Tac® Adhesives, and printed in linear stripes just prior to the leading edge of each label 11 (Fig. 3), and optionally, also just subsequent to the trailing edge of each label 11 (Fig. 1). "Leading Edge" and "Trailing Edge" are terms used in relation to the direction in which the assembly, a long continuous strip, travels when being wound and unwound. Micro sphere adhesives form a discontinuous film thereby limiting physical contact resulting in low peel, removability and stable tack over time. The adhesive layer 33 is shown in Figs. 1 and 3 separated from the label stock 30, and in Figs. 3-5 in its location within the assembly. A donor ribbon strip 20, of paper or plastic film, is disposed in registry with the face stock 10; the donor ribbon strip 20 providing inclusively, a thermal transfer coating 21 which is placed in contact with the second adhesive 33. The transfer coating 21 is preferably of ink combined with either a wax, a wax and resin or resin alone, any one of which is thermally activated.

The donor ribbon strip 20 is severed along line 20' as best seen in Figs. 1 and 3. This cut is exterior to severance line 10' and enables portions of the donor ribbon 20 to remain in contact with the labels 11 when the remainder of the donor ribbon 20 is peeled off the finished assembiy after thermal transfer has taken place. As described, labels 11, defined by severance line 10' are aligned longitudinally on the face stock 10 with each one of the labels 11 positioned within one of the donor ribbon strip portions defined by severance lines 20'. The thermal transfer coating 21 has a surface tension greater than the surface tension of the second adhesive 33 so that when the donor ribbon strip 20 is peeled away from the pressure sensitive label stock 30, those portions of the face stock 10 that are peripheral to the labels 11 are also removed, leaving the labels 11 on the release stock 37.

The method of preparing the above described self-contained thermal transfer label comprises the steps of providing the release stock 37 as a long strip of supportive material, coating the release stock 37 with the release coating 39; over coating the release coating 39 with the first adhesive coating 35, registering or aligning the face stock 10 with the release stock 37 and over laying the face stock 10 onto the adhesive coating 35. The method further comprises the steps of severing the face stock 10 at lines 10' into a sequence of labels aligned longitudinally on the face stock 10, placing, by printing or other selective lay-down technique, the second adhesive 33, onto the face stock, forward, and alternately rearward of the labels 11, and then placing the donor ribbon strip 20 including its transfer coating 21 in registry with the face stock 10, and in contact and in full adhesion with the second adhesive layer 33, and finally severing, along lines 20', the donor ribbon strip 20 along with the second adhesive 33, the face stock 10, and the first adhesive layer 35, peripheral to the labels 11 and spaced apart from it, as is clearly shown in Fig. 1. Further steps in the present method include the steps of stripping off the portions of the donor ribbon strip 20 not covering the labels 11 and coiling or fan-folding the face stock 30 with the labels 11 and remaining portions of the donor ribbon strips 30 for later use in a direct thermal printer. In the figures, separation lines 10' are cuts that define the extent of labels 11, while lines 20' are cuts that severe through layers 2O₅ 21, 33, 11 and 35, so that when peripheral portions of layers 20 and 21 are pulled away from the assembly, they take with them also terminal end portions of adhesive layer 33 and the peripheral portions of face stock 10. What is left after these portions are removed is separated and spaced apart labels 11 mounted on the individual perforated portions of release stock 37, and covering the labels 11, separate portions of layers 20 and 21 which are attached by adhesive 33 in lines just before and just after each of the labels 11. After the thermal transfer through layers 20 and 21 thereby marking on the face 12 of the labels 11, the layers 20 and 21 are easily peeled away leaving the exposed label 11. Because of severance lines 10% any corner of the label 11 is easily peeled up and the label then removed so it can be mounted onto a surface secured by adhesive layer 35.

While the invention has been described with reference to at least one preferred embodiment, it is to be clearly understood by those skilled in the art that the invention is not limited thereto. Rather, the scope of the invention is to be interpreted only in conjunction with the appended claims and it is made clear, here, that the inventor(s) believe that the claimed subject matter is the invention.

Claims

What is claimed is:

L A self-contained thermal transfer label strip apparatus comprising: a release stock supporting a release coating and, over the release coating, a first adhesive coating; a face stock in registration with the release stock and joined thereto by the first adhesive coating; the face stock severed into a series of labels aligned along the face stock; a second adhesive disposed on the face stock in linear transverse strips in at least one of a leading and a trailing positions peripheral to each of the labels; a donor ribbon strip providing a thermal transfer coating secured to the face stock by the second adhesive, the thermal transfer coating having a surface tension greater than a surface tension of the second adhesive; the donor ribbon strip severed exterior to the labels, enabling removal of portions of the donor ribbon strip while leaving further portions of the donor ribbon strip over the labels in preparation for thermal printing.

2. A self-contained thermal transfer label strip apparatus comprising: a release stock releasably supporting a face stock, the face stock severed into a series of labels aligned along the strip; an adhesive disposed on the face stock in linear transverse lines in at least one of a leading and a trailing positions peripheral to each of the labels; a donor ribbon providing a thermal transfer coating releasably secured to the face stock by the adhesive; the donor ribbon severed peripherally exterior to the labels, whereby, portions of the donor ribbon strip may be removed while leaving further portions of the donor ribbon strip over the labels in preparation for thermal printing.

3. A method of preparing a self-contained thermal transfer label strip, the method comprising: a) cutting a release stock into an elongated strip; b) coating the release stock with release coating and, over the release coating, a first adhesive coating; c) laying a face stock in registration with the release stock and joined thereto by the first adhesive coating; d) severing the face stock into a series of labels aligned along the release stock; e) disposing a second adhesive on the face stock in linear transverse lines peripheral to the labels in at least one of a leading and a trailing positions; f) adhering a donor ribbon strip providing a thermal transfer coating to the face stock by the second adhesive; g) severing the donor ribbon strip and thermal transfer coating peripheral to the labels; and h) removing portions of the donor ribbon strip while leaving further portions of the donor ribbon strip over the labels in preparation for thermal printing.

4. A method of preparing a self-contained thermal transfer label strip, the method comprising: a) releasab Iy joining a strip of face stock in registration with a strip of release stock; b) severing the face stock into a sequence of labels; c) adhering a transfer coating coated donor ribbon strip over the face stock along at least one of a leading and a trailing transverse linear positions peripheral to each of the labels; d) severing the donor ribbon strip peripheral to the labels; and e) removing portions of the donor ribbon strip while leaving further portions of the donor ribbon strip over the labels in preparation for thermal printing.