Self adhesive labels

This invention relates to self adhesive labels and in particular concerns the application of labels to individual articles or objects.

In the field of produce marketing pressure sensitive labels find wide application because, for example, in supermarkets and other stores the products on sale are typically priced by means of a small pressure sensitive label which is applied to the product, and frequently these labels have to be changed because of price change, making consumption of the labels enormous.

Also, huge quantities of larger labels which are used for describing the articles or objects are applied to containers such as bottles and cans are used, and the present invention is concerned more with the application of these larger labels to articles.

Typically, these larger pressure sensitive labels are mounted on a carrier or backing web which is normally a web of paper coated with a suitable release material such as a silicone compound. The adhesive labels are applied to this carrier or backing web for transportation, storage and utilisation, but the labels can readily be peeled from the backing web as there is a much stronger bond between the adhesive and the material of the label, than between the adhesive and the release material.

-Not only is the backing web superflous after the labels have been peeled therefrom and consumed, but the manufacture of the backing web is a specialist process, and must be performed under carefully controlled conditions. The equipment to produce the backing web is expensive, and is extremely large, so that only a very few companies are able to finance and perform the backing strip manufacture.

There have been proposals to eliminate the backing strip in adhesive labels, but such proposals have been limited to small webs of the type for providing small price change labels. One of these proposals is set forth in U.S. Patent No. 3,575,788 wherein a backless roll of labels is produced by printing on clay coated paper on one side with a nitro cellulose base ink, and by covering the ink with a heat-cured thermosetting silicone resin release coating, the other side having a pressure sensitive adhesive applied thereto. The silicone release coating is cured at a temperature of 176.6°C to 260°C (350°F to 500°F). The said U.S. Patent No. 3,515,788 does not give any specific information as to how the labels are applied to the article or whether they are the small produce price labels or the larger labels which are applied to the articles such as containers, but it is believed that the small price change labels are envisaged.

It has been proposed as disclosed in U.S. Patent 2,845,728 to provide pressure sensitive labels in the form of a strip or tape, carried by a small dispenser for hand use. The strip of labels comprises an adhesive surface on one side, and a release characteristic on the other side so that the strip can be wound without a backing sheet into roll form. The individual labels are torn from the strip manually by a severing edge on the dispenser, and the labels are applied again manually to products such as fruit and grocery produce.

U.K. Patent Application 2,013,613 also discloses that it is known to provide a roll of labels, and on one side of the web is pressure sensitive adhesive whilst on the other side is a release coating to enable the web to be wound into roll form without the use of a backing strip. The roll of labels is placed in a "labelling gun" to enable the feeding of the web to unroll same, and the severing of individual labels from the roll by transverse cutting thereof. No detailed description is given of how the labelling gun operates, but such guns are probably small hand carried items such as they are described as being of a type which are carried by clerks to enable the prices of goods to be marked on the goods by application of the labels thereto. This specification as the United States patent 2,845,728 is therefore more concerned with the provision of small price labels as opposed to the somewhat larger labels which are applied to articles such as bottles and cans.

Where such larger labels are to be applied to articles such as bottles and cans, it has been traditional to use labels which carry heat or moisture activated glue, or to provide that the pressure sensitive labels are carried on a backing sheet which is release material coated.

In U.K. Patent No. 1,090,708 there is described a machine for applying labels to individual articles such as cans or bottles, wherein pressure sensitive labels are carried by a carrier web. The web is fed round a sharp angled edge to cause the labels to separate from the web, and a rotating vacuum drum picks up the partially separated labels and transports same to an application station whereat they are applied in sequence to the articles.

Further in US-A-3920122 there is disclosed a web supporting removable labels via bridges of web material, so that a skeletal waste web remains after detachment of individual labels.

There has been no disclosure of or attention given to the utilisation of a continuous web of material for the manufacture of the larger labels of a pressure sensitive nature, and which can be applied at relatively high speed.

The method provides for the application of labels individually to articles which are moved one by one relative to the station at which the labels are applied.

The present invention is concerned with a novel approach to the handling and applying of labels, with an adhesive which attaches to the articles by pressure.

According to the invention there is provided a method of applying adhesive coated labels to articles which move in turn relative to an application station including vacuum drum, characterised in that a web of material printed to define the labels therein and having adhesive on one side is fed at high speed to a removing station defined by said vacuum drum and a co-operating roller which act to remove individual labels from the web as it moves through the removing station and leaves a skeletal waste web, and including leading the skeletal waste web continuously away from the removing station, and further characterised in that the said adhesive is pressure sensitive and the label web is fed without a backing web to said removing station.

If a non-porous web is used in the process and a release characteristic is provided by applying a release coating to the non-adhesive side of the web there is the advantage that when the release coating is applied thereto, it can be applied in relatively small amounts, which means that the curing time for the release coating is reduced, and lower curing temperatures (as compared to the curing temperatures used in U.S. Patent No. 3,575,788 can be used). Moreover, it is not necessary to apply a nitrocellulose base ink to the web before application of the release coating.

The adhesive may cover the entire surface area or parts of the surface area of the web.

The web is printed to define the labels, the printing being on the side of the web to which the release coating is applied. Preferably, the web is of a synthetic resinous material containing an inorganic filler such as talc or chalk.

The web material defining the labels may be of a thickness consistent with the thickness of the labels as conventionally used and may be provided with sprocket feed holes at the edges thereof.

By way of example, when a release coating is applied to the web, it may be applied to the web by rollers, gravure cylinders or hot melt applicators to provide a surface having a release characteristic. The coating may for example contain non-migrant repellants, and in particular, polymerisable silicone polymers. The coating may for example be a solvent heat cured coating, an aqueous system, solvent free or UV cured, examples of the above are as follows:

Solvent heat cured

<tables id="tabl0001" num="0001"><img file="EP0081963B1_D0001.tif" /></tables>

Dry off solvent prior to cure approx. 5 seconds. <tables id="tabl0002" num="0002"><img file="EP0081963B1_D0002.tif" /></tables>

In the following proportions by volume. <tables id="tabl0003" num="0003"><img file="EP0081963B1_D0003.tif" /></tables>

Bath 1

Standard bath for in-line use or off-line on certain substrates such as PET.

Bath 2

Standard bath for off-line use, using Syloff 297 anchorage additive.

Bath 3

Special low solids bath for coating films such as polyethylene. Solvent choice important and ethyl acetate best. Uses Q2-7127 as accelerator.

Bath 4

Controlled release bath. Features Q2-7089 as release modifier and Syloff 297 as anchorage additive.

Bath 5

Premium release formulation involving incorporation Q2-7090 low viscosity fluid and additional Q2-7127 to restore catalyst level.

These are only typical baths and levels of accelerator, release modifier and premium release additive can all be varied to satisfy customer demands.

Curing conditions

Bath 1 and 2 cure in. 8-12 seconds at 140°C depending on substrate nature.

Bath 3 will cure in 15-20 seconds at 70°C.

Bath 4 cures typically in 15 seconds at 140°C.

Bath 5 cures in 30 seconds at 100°C or 10 seconds at 140°C.

Aqueous systems

<tables id="tabl0004" num="0004"><img file="EP0081963B1_D0004.tif" /></tables>

Solvent free silicone

<tables id="tabl0005" num="0005"><img file="EP0081963B1_D0005.tif" /></tables>

U.V. cured

<tables id="tabl0006" num="0006"><img file="EP0081963B1_D0006.tif" /></tables>

Cure rate 0.6 seconds with high pressure mercury Vapour U.V. Lamp (160 W/cm).

The amount of release coating applied may be in the order of 0.1 to 1.5 grams/sq. metre depending upon the web. The pressure sensitive adhesive may be applied by conventional means, and typically may be a solvent or water based emulsion of which the solvent or water is dried from the web after application. The pressure sensitive adhesive may for example be hot melt, water based, or solvent based, examples of which are as follows:

Hot melt

Elvax ^*40-P (Du Pont) (Ethylene-vinyl acetate resin)-40 parts by weight.

Piccovar^* L-60 (Hercules Inc.) (Hydrocarbon resin)-60 parts by weight.

Irganox ^*1010 (Ciba Geigy) (Antioxidant)-0.5 parts by weight.

Aqueous

Indatex SE2229S (Industrial Adhesives Ltd)

Solvent

Vinalak 5150 (Vinyl Products Ltd)

The labels may be colour printed by any suitable method such as letter press, flexographic, gravure or offset litho.

For the web material, it is preferred to use polypropylene or high density polyethylene film, including substantial proportions of particulate inorganic material.

Typically, the inorganic material may be included in the range 20 to 50% of the web by volume, and in the preferred case the web is polypropylene ethylene sequential copolymer, as described in our British Patent No. 1,544,143 filled with 40% talc.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, wherein:- <ul id="ul0001" list-style="none"><li>Fig. 1 is a perspective view of a roll of labels for use in the present invention;</li><li>Fig. 2 illustrates how the labels of Fig. 1 are applied to box shaped products in accordance with the invention;</li><li>Fig. 3 illustrates apparatus for the coating of the web of labels with pressure sensitive adhesive and release coating according to one method;</li><li>Figs. 4 and 5 illustrate apparatus for the said coating according to two other methods; and</li><li>Fig. 6 illustrates apparatus which is a modification of the Fig. 5 apparatus.</li></ul>

Referring firstly to Fig. 1 of the drawings, in Fig. 1 there is shown a web 10 having boundaries 12 defining individual labels 14, each provided with printing 16. The web 10 is made up of a central substrate web which is of a non-fibrous and substantially inextensible material and on one side of which is applied a pressure sensitive adhesive coating and on the other side is applied a release coating. These coatings are applied as explained herein with reference to Figs. 3 to 6. The web is wound so that the adhesive coating is to the inner side of each coil and contacts directly on the release coating of the adjacent inner coil. This arrangement enables the web to be easily unrolled. The web may be wound on a suitable core 26.

In producing the web 10 as illustrated in Fig. 1, the printing 16 (single or multi coloured and of any desired pattern and/or content) is applied to the substrate prior to the application of the release coating. Fig. 2 shows how labels in rolls form as shown in Fig. 1 may be applied to box shaped products 40 in accordance with the invention. The roll of labels is indicated by numeral 42 and is unwound from this roll by a tractor unit 44 having a suitable sprocket feed device which engages the holes in the margins of the web 10 (the said holes are not shown in the drawings) and is fed through a removal and application station 46. The skeletal residue of the web 10 is wound into roll form as shown by numeral 48.

The adhesive side of the web 10 is the upper side and all surfaces which contact this adhesive side are required to be of a nature so as not to adhere to the adhesive. Such surfaces may be defined by silicone release material.

The removal and application station 46 comprises an upper pressure nip roller 50 (silicone coated) and a lower vacuum cylinder 52 around which the web 10 laps slightly as shown in Fig. 2, and which has a plurality of circumferentially spaced ports 54 which connect with axially extending passages 55, which are selectively connectable to a source of vacuum or, when at detachment position 56, with a blast of air under pressure. A valve plate 58 at one end of the cylinder controls the connection of the passage 55 to the source of vacuum and the blast of air in that said plate 58 has an arcuate port 60 coupled to the source of vacuum and a port hole at position 56 connected to the air under pressure. In use, the cylinder 52 rotates in the direction of arrow 62 whilst the plate 58 remains stationary and each passage 55 which registers with port 60 is connected to the source of vacuum. Each passage 55 which leaves register with port 60 arrives first at the position 56 where it receives a blast of air under pressure, and then the passage is blanked off until it once more reaches the port 60.

Operation of the unit 46 will be understood from the above. The individual labels 14 are detached by the vacuum at the nip between roller 50 and cylinder 52, and travel round with the cylinder 52 until they reach station 56 at which they are progressively applied to the products 40 which are moving as indicated by arrow 63, in synchronism with the feed of the labels. The labels and products are fed on a continuous basis, and at high speeds.

It is estimated that the apparatus shown in Fig. 2 will be capable of applying labels at the rate of approx. 200/min in part because the label roll has no backing strip.

Reference is now made to Figures 3 to 6, which shows methods of manufacturing labels according to the invention.

Referring to Fig. 3 of the drawings, a roll 110 of stock material in which labels are to be formed may suitably be of a width of 450 millimetres and thickness 80 micron, the material may be a blown film manufactured from a filled plastics material of the nature set out in British Patent No. 1,554,143, and preferably is of a non-fibrous and substantially non-extensible material. The web passes from roll 110 through silicone compound coating assembly 112 at which release coating is applied to one side (the first side) of the web, and then the web travels through a heating chamber 116 which is divided into two compartments 118 and 120 by means of a horizontal partition 122. The release coating is cured by passing the web back and forth through the chamber 118 with the first side initially face downwards then face upwards. The web 10 emerges from the chamber 118, after a traverse time of 20 seconds in an environment maintained at 120°C, and the web is engaged by a pair of guide rolls 124 and 126.

The web next passes through a pressure sensitive adhesive coater assembly 128 of the form shown, which applies pressure sensitive adhesive composition to the other and second side of the web. The web is led by means of feed conveyor 130 into the upper heating chamber 120 which is maintained at 110°C, in order to drive off the solvents of the adhesive coatings, to dry same. The emergent web passes over guide rolls 132 and 134 (134 being silicone coated so that it will not stick to the adhesive side of the web which it contacts).

Compared to conventional methods of applying silicone coating to webs for the production of labels, the above equipment is simple and can be operated by converters of raw material on an in-house basis, the entire treatment having a cycle time of no more than half a minute to one minute and the overall length of the apparatus being no greater than 8-10 metres. The web material 110 will usually be pre-printed to define the label printed matter, and the silicone composition is applied over the printed side of the web.

In the arrangement shown in Fig. 4, the silicone release coating is an ultra violet curable material, and therefore after the coating is applied, the web is passed through an ultra violet dryer 140, which is quicker and less expensive than hot air drying. The adhesive is applied and dried as before.

In the arrangement of Fig. 5, both the silicone release coating and the adhesive are ultra violet curable and therefore there are two ultra violet driers 140 and 142 respectively for the silicone release coating and the adhesive, through which the web passes in turn after application of the respective coatings. Fig. 6 shows an arrangement similar to Fig. 5 in that ultra violet dryers are used. Only the path of travel of the web is different. The parts of the apparatus in Figs. 4, 5 and 6 already referred to in Fig. 3 are designated with the same reference numerals. In each of the arrangements shown in Figs. 3 to 6, the web travels first through the silicone coater 112 and second through the adhesive coater. This order could be reversed if desired. Also, an arrangement wherein a UV dryer is used for the adhesive and a hot air dryer is used for the release coating can be adopted. Another form of dryer which can be used at least for the adhesive is a radio frequency dryer.

In the production flow path in any of the apparatus of Figs. 3 to 6 after the stage of application of the adhesive, all of the rollers which contact the adhesive side are provided with a silicone coating in order to prevent sticking of the rollers to the adhesive, and of course it is possible directly to wind the web 110 after the adhesive and silicone materials have been applied in that the silicone side of the web will not adhere to the adhesive in the coiling and uncoiling of the web.

The speed and simplicity of production is enhanced by selecting a web material which is non-fibrous and therefore.will not absorb excessive amounts of the silicone material, which happens when paper webs are coated as in the conventional method of producing adhesive labels.

The web 110 may be provided with apertures in the margins thereof to enable the feeding of the web in the apparatus for removal of the labels from the web for application to articles before or after being coated. The said apertures may also serve for the driving of the web through the equipment shown in Figs. 3 and 6.

When the silicone coating is heat cured, the temperature at which the curing of the silicone coating takes place will be dictated in fact by the material of the web, the speed of the web and the thickness of the coating. Clearly, although the curing time can be reduced by increasing the curing temperature, the temperature cannot be so high as to cause disintegration of the web material itself.

It is preferred that the coating operation will proceed on a continuous basis, but it can be arranged to take place on a step by step basis with dwell times during which the silicone is cured and the adhesive is dried.

Any suitable form of pressure sensitive adhesive can be used.

The thickness of the web can depend upon the application, but typically labels are manufactured in a thickness of approximately 25 to 250 microns, with the filled plastics material web being typically 80 microns. The quantity of silicone coating which is required for such labels typically would be as little as 2 gms. per square metre, whereas with paper webs as much as 40 gms. per square metre may be required.

As concerns the method of producing the labels, an advantage of the preferred method of the invention resides in that the polymerisable release coating, which may be a silicone compound, can be polymerised in a relatively short time especially when the substrate web material is non-fibrous and therefore will not absorb the release coat material when applied. This means that only a fraction of the amount of release coat material normally applied will be used (as little as 5% as compared to the conventional method) and correspondingly the curing time is significantly reduced. With a slow curing time, correspondingly simpler and therefore smaller machinery can be employed for the manufacture of the labels.

Test using a silicone release coating material applied in amounts of 2 gm/sq metre have shown that 10 seconds in a chamber heated to 120°C achieves satisfactory cure of the silicone release coat material.

The materials described herein form embodiments of the invention claimed in European Patent Application No. 85110025.5 which is divided out of the present application.