A PACKAGE FOR STORING GOODS IN A PRESERVATIVE STATE, A METHOD FOR MARKING SUCH A PACKAGE, AS WELL AS A TEMPERATURE INDICATOR FOR THE PACKAGE Technical Field of the Invention In a first aspect, this invention relates to a package for storing goods in a preservative state in which the tem- perature should have a certain desired value, comprising, on one hand, a bar-code of the type that between two outer ; light-absorbing code bars includes a plurality of intermediate and likewise light-absorbing code bars or marks mutually spaced-apart by neutral, light-reflecting fields, and on the other hand a temperature indicator, which comprises a contrast medium contained between a front wall and a base wall, which medium has a certain colour or light-reflecting property in a first temperature state, but which on transition to another temperature state is triggered so far that the same is irre- versibly converted to a different colour or light-reflecting property.

Background Art Deep-frozen foods are handled in large amounts in the food sector. During the period between the production, when the goods are deep-frozen, and the retail sale to the final consumer, it is of vital importance that the temperature of the package and the goods contained therein does not exceed a certain recommended desired value, which for deep-frozen prod- ucts usually is-18 °C. If the goods during a certain time would unintentionally obtain a higher temperature than the recommended desired value, there is a risk that the quality of the goods is deteriorated, and if the exposure to the higher temperature would become long, the goods may become directly unhealthy by growth of bacteria. The handling of the goods from the producer to the consumer includes, in practice, a plurality of different steps, such as storage (long term as well as short term storage), trans-shipments, transports as well as handling in the shop. There are, per se, strict rules and recommendations how the temperature of the goods should be supervised and documented during these different steps, but in

practice the rules are difficult to completely observe. If the individual goods at some point, by misadventure or otherwise, would be exposed to a higher temperature than the recommended highest desired value, neither the consumers nor other parties in the chain between the producer and the consumer have previ- ously been able to see this on the proper package.

With the purpose of managing the above-mentioned prob- lems, it has by WO 01/72601 been proposed to provide packages for frozen goods with a temperature indicator, which comprises a means, which has a certain property when the temperature of the goods is lowered towards and past a predetermined limit value, which is at least somewhat higher than the desired value of temperature of the goods in question, but which alters said property in an irreversible way, if the tempera- ture during the storage would rise to or above the desired value. According to said document, said means consists of a contrast fluid, which is initially transparent and preserves the transparency thereof during temperature reduction past said limit and desired values, but is converted to an irre- versibly opaque state, if the temperature would increase above the desired value up to and past the limit value. In WO 01/72601, it is disclosed how the temperature indicator in question may be applied to the outside of a bar-code exposed on the external surface of the package in order to at least partially cover the same. The intention with this is that the temperature indicator, in the transparent state thereof, should enable scanning of the code, but in a triggered, opaque state make conventional scanning of the code impossible. Dur- ing the development of the temperature indicator which is the subject of WO 01/72601, it has, however, turned out that the normal scanning of the bar-code, i. e. scanning of fully useful goods on the packages of which the temperature indicator has not been triggered, is made more difficult in spite of the contrast medium in the temperature indicator still being transparent.

Bar-codes of the type that are applied to packages for food and other merchandise usually consist of so-called EAN codes, where the letters EAN stand for European Article Num- ber. This constitutes a worldwide system for article numbering

of all types of consumer goods. The system is administered by "International Article Numbering Association, EAN", which issues instructions for the users which are associated with the system. EAN is used in shops having computerized paydesks and a fixed or mobile bar-code scanner. When the symbol is scanned, a registration of the EAN code takes place in the computer system of the shop. The most common bar-codes consist of price codes and weight codes, respectively. When the regis- tration takes place a row of measures are triggered, if a code is in the price memory of the computer system. The price and the merchandise description, which the shop has entered into the computer system, are shown for the customer through a price window. The information is printed in plain text on the receipt of the customer and the computer adds the amount to be paid. On possible price changes, the goods does not need to be remarked. Furthermore, by using special programs in the com- puter system, there is a possibility to effectively assemble information, which may be combined in order to form a basis for order quantities, composition of class of goods, pricing, etc. The system could also be utilized for registering whether frozen goods has thawed, namely if the packages of the goods are provided with temperature indicators, which are combined with the bar-code of the packages. However, a condition for a scanning and computer system of a shop to be used in practice, is that the symbol scanning and registration becomes reliable, quick and correct. If a covering temperature indicator would delay the symbol scanning operation, e. g. by causing repeated re-scans, the possibility becomes less interesting.

In this connection, it should be pointed out that the code scanners on the market make use of infrared light, which illuminates the bars as well as the intermediate neutral fields in a bar-code, the contrast between the bars and said fields being crucial for the quality of scanning. In larger scanners the bars are illuminated by a grid of light rays. If the bars are of a dark colour, such as black or blue, at the same time as the neutral fields are light, e. g. white or yel- low, an optimum contrasting effect is obtained. However, also other combinations of colour may exist. The essential thing is that the infrared light is either absorbed or reflected by the

colours in question. Of large importance is naturally also the distinctness of the code bars.

By DE 19912529, a package having a temperature indicator in the form of a label is previously known, which, in addition to a thermally reactable layer having a variable colour, includes a transparent top coat in which a bar-code is inte- grated. As long as the goods in question keeps the desired temperature, the reactable layer remains unaffected and the bar-code scannable, but if the desired temperature is excee- ded, the lower layer changes its colour and makes the bar-code unscannable. However, a disadvantage of this label is that the same is intended to form individual price code or weight code of the goods package, which means that an extremely large number of different labels have to be manufactured, be dist- ributed, be stored and be applied to the thousands of differ- rent goods, which are in circulation in the convenience goods trade and which require individual code marking. Furthermore, the label excludes that obsolete goods are registered in the computer system of the shops, because the bar-code becomes illegible once and for all as soon as a colour alteration has taken place.

Objects and Features of the Invention The present invention aims at obviating the code scan- ning problems, which are associated with the known packages, and at providing an improved package. Thus, a primary object of the invention, in a first aspect, is that/to provide a package for goods having a bar-code as well as a temperature indicator, which indicator can separate saleable goods from obsolete without aggravating the scanning of a bar-code by means of a conventional, existing scanning equipment. An addi- tional object is to provide a package for goods which enables not only discovered of thawed, obsolete frozen goods, but also registration of the same in a computer system of a shop. Yet an object of the invention is to provide a package which enables discovery of obsolete frozen goods with double cer- tainty, viz. by detecting via a code scanning equipment of a shop as well as visual perception of the customer and/or the shop's staff.

According to the invention, at least the primary object is attained by the features defined in the characterizing clause of claim 1. Preferred embodiments of the package accor- ding to the invention are furthermore defined in the dependent claims 2-3.

In a second aspect, the invention also aims at providing a new temperature indicator particularly suitable for the package according to the invention. An object in this respect is to provide a temperature indicator, which may co-operate with arbitrary bar-codes, e. g. such primary bar-codes, which already are separately printed on different packages. The fea- tures of this temperature indicator are seen in claims 4-18.

In an additional aspect, the invention also aims at pro- viding a method for marking packages. The features of this method are seen in claim 19.

Summary of the Invention The present invention is based on the intention to pro- vide packages for goods, in particular packages for frozen goods, with an additional, secondary bar-code apart from the ordinary, primary price code and/or weight code marking, and utilize said secondary bar-code for detection and/or registra- tion of obsolete goods, more precisely by the fact that the secondary bar-code is integrated in a temperature indicator, which is unaffected as long as the goods are saleable at the same time as the bar-code is neutral or invisible, but which is triggered if the goods becomes obsolete, the indicator pro- viding a scannable bar-code. In practice, the bar-code toget- her with the temperature indicator may be incorporated in a label or label-like unit, which may separately be applied to the package besides an already printed, primary bar-code.

Brief Description of the Appended Drawings In the drawings Fig 1 is a perspective view of a package according to the invention, a temperature indicator having an appurte- nant, secondary bar-code being shown applied beside a primary bar-code on a long-side edge surface on the package,

Fig 2 is an enlarged front view of the primary bar-code and the temperature indicator, the temperature indicator being shown in an unaffected or primed state, Fig 3 is an analogous front view showing the same tempera- ture indicator in a triggered state, Fig 4 is a perspective exploded view, which illustrates the construction of the temperature indicator, Figs 5-7 are exaggeratedly enlarged cross-sections through dif- ferent alternative temperature indicators, Fig 8 is a chart showing the function of the temperature indicator in different temperature states, Figs 9-12 are enlarged, schematic longitudinal sections through an alternative temperature indicator in dif- ferent functional states, Fig 13 is a longitudinal section through an additional, alternative embodiment of a temperature indicator, Fig 14 is a chart illustrating the melting point for an olive oil serving as contrast medium in the temperature indicator, Fig 15 is a perspective, partly cut exploded view of an addi- tional alternative embodiment of a temperature indica- tor according to the invention, and Fig 16 is an enlarged longitudinal section through yet an alternative embodiment of a temperature indicator according to the invention.

Detailed Description of Preferred Embodiments of the Invention In fig 1, numeral 1 generally designates a package for goods, such as a package for frozen goods, which in the exam- ple has a parallel-epipedic, flat basic shape. In practice, the package may consist of a capsule of comparatively stiff board or cardboard. On one of part surfaces of the package, in this case a long-side edge surface, a primary bar-code 2 as well as a temperature indicator 3 according to the invention are applied. The primary bar-code 2 may consist of a conventional price code and/or weight code (merchandise code), which may be printed on the package in connection with the same generally being provided with printing. Alternatively, the bar-code 2 may be included in a tape or the like, which is

applied to the package afterwards. By scanning in an available code scanner, the bar-code enables the usual data capture in a computer system of a shop.

As is seen from the enlarged views of figs 2 and 3, the bar-code 2 includes a plurality of code bars located between two outer bars 4 having mutually varying thickness and loca- tion. Together said code bars form an elongate, rectangular configuration. Under the code bars, there is usually also a numerical series of Arabic figures, which in the example are designated"X". In the area outside the two outer code bars 4, neutral fields 5 are left in order to enable scanning accord- ing to prevalent bar-code technique. In practice, said fields 5 should have a width of at least 2, 7 mm. An imaginary, rec- tangular surface field, is designated 2a, inside which extra- neous printing on the package must not be present. The code bars may have a black, blue or another dark colour, while the fields positioned between and outside the code bars may have a white, yellow or another light colour. The essential thing in this connection is that a contrasting effect is attained by the infrared light of a code scanner either being absorbed or reflected by the different colours.

The temperature indicator, in its entirety designated 3, which is shown on an enlarged scale in figs 2 and 3, has gen- eral similarities to the temperature indicator disclosed in WO 01/72601, inasmuch as it comprises a contrast medium contained between a front wall and a base wall, which medium has a cer- tain colour or light-reflecting property in a first tempera- ture state, and is arranged to be irreversibly converted to a different colour or light-reflecting property at transition to another temperature state. However, in contrast to the known temperature indicator, the temperature indicator according to the invention has inherent means in order to form a secondary bar-code generally designated 6. Said means consists of a plu- rality of transparent, window-like fields 7, which are sur- rounded by neutral, opaque or not transparent fields 8. The different fields 7 are generally long narrow and have varying width in order to be able to form individual code bars, which together may appear as a bar-code.

In order to explain the construction of the temperature indicator, reference is made now also to figs 4-7. In these figures is seen how the temperature indicator 3 includes a front wall 9 and a rear wall or base wall 10. Between said walls 9, 10, there is a contrast medium in its entirety desig- natedll, which will be described more in detail below. In the example, said contrast medium should have the ability to alter colour depending on prevailing temperatures. The casing 21, in which the contrast medium is contained and which includes said walls 9, 10, may be realized in various ways. In the example, the casing is assumed to be composed of two separate, compara- tively thin films, which are interconnected along the edges thereof, e. g. via welds 12. However, it should be pointed out that the casing also may be made in another way, e. g. from a tubular or pipe-shaped piece of film, which is flattened and sealed at opposite ends. In both cases, the casing 21 may advantageously form a label or label-like unit, which can be applied in a suitable way to the outside of the package 1. For this purpose, there may be a particular layer 13 of adhesive on the back side of the base wall 10.

The front wall 9 should have a light, e. g. white or yel- low colour so that the neutral fields 8 between and outside the bar-code windows 7 should reflect infrared light. In an analogous way, the front side on the base wall 10 should have a light colour in order to reflect infrared light. In the example, the light colour of the front wall is surrounded by a darker frame 14.

In fig 4, the surface defined inside the frame 14 is shown divided in two surface sections 15, 16, the surface sec- tion 15 of which occupies the bar-code windows 7. In the sec- ond surface section 16, a number of secondary, transparent symbol fields or symbol windows 17 are formed according to a preferred embodiment of the invention, which in the example are in the form of letters, which together form the word STOP.

The contrast medium, in its entirety designated 11, includes in this case two different liquids, a first one of which is designated 18 and is denominated indicator liquid.

The second liquid, which may contain colouring agent, is des- ignated 19 and is included in one or more burstable capsules

20, which at least partially are surrounded by the indicator liquid 18. The liquid 19 will henceforth be denominated phase- changing liquid. Characteristic of the liquids 18, 19 is, gen- erally, that they have different freezing points or eutectic temperatures. At least one of the liquids, viz. the phase- changing liquid 18, contains water and one or more freezing- point lowering agents. Advantageously, the liquids may consist of only water, although also alcohol could be included. Accor- ding to a preferred embodiment of the invention, salt of the type that is approved for use in foods is used as a freezing point lowering agent. Suitably, the medium may in the respect- tive liquid consist of a mixture of at least two salts, such as chlorides and sulphates of calcium, potassium and sodium respectively. Particularly, a mixture of sodium chloride (NaCl) and sodium sulphate (Na2SO4) is preferred, the eutectic temperatures of which in mixture with water can simply be established by varying the amount of salt in the water. Thus, in a mixture of H20, NaCl and Na2SO4 the desired eutectic temperature may with large accuracy be set within the tempera- ture range of-1 °C to-21 °C. The desired temperature value for quick-frozen foods is usually-18 °C. In these circum- stances, the eutectic temperature in the indicator liquid 18 may be set to-14 °C, while the eutectic temperature for the phase-changing liquid 19 is set to the higher value-12 °C.

In the same way as in the known temperature indicator according to WO 01/72601, the casing 21 formed by the walls 9, 10 is made from a material which resists low temperatures without becoming brittle or otherwise degradable. Simultane- ously, the burstable capsule or the covering 20 or the burst- able capsules or the coverings 20 are made from a film mate- rial, which preserves a fundamental elasticity or softness at degrees above zero, but becomes brittle and degradable at lower temperatures. When goods contained in the package 1 is frozen down, the following takes place in the temperature indicator: As the temperature falls from room temperature, heat is transported from the liquids 18, 19 via the respective casings out into the cooled environment. When the temperature in the phase-changing liquid 19 falls ; the volume of the liq- uid decreases at the same time as the volume of the individual

casing 20 decreases, the material therein becoming more brit- tle. When the temperature has fallen to-12 °C, the liquid 19 freezes to ice and begins to expand. Somewhat later (at - 14 °C), also the liquid 18 begins to freeze to ice and to expand. When the ice expands inside the capsules 20, the cap- sules break (so far that fine cracks arise in the capsule walls), whereby an irreversible way of communication to the ice/the liquid 18 arises. The ice formed by the indicator liq- uid 18 may expand without the surrounding casing 9, 10 being damaged or effected, since the material in said casing pre- serves the softness and density thereof at considerably lower temperature than the capsules 20. On this occasion, i. e. as long as the temperature is below-12 °C, no reaction takes place between the liquids 18, 19 because the same are in the state of ice. The temperature indicator is now primed.

If the temperature indicator 3 at a later occasion would come to be thawed by being exposed to temperatures-12 °C dur- ing a considerable time, initially the ice mass 18 and then the ice mass 19 will melt and revert to a liquid state. By the fact that the capsules 20 have cracked at the occasion of freezing, the liquid 19 may escape into the liquid 18 and col- our the same, thanks to the fact that the liquid 19 contains a colouring agent. Said colouring agent may in practice consist of pigments, e. g. pigment of the type that is approved for use in food. It is also feasible to provide the requisite colour- ing of the liquid 18 by a chemical reaction between the liq- uids. Thus, the initially transparent state of the liquid 18 is altered, in a known way per se, to an opaque, coloured state. This change of state is not reversible and will subsist also if the package and the content thereof are frozen down again.

The described thawing process is illustrated graphically in fig 8, the presumptions being that the indicator liquid has a freezing point of-14 °C and the phase-changing liquid 19 a freezing point of-12 °C. On thawing, the temperature in the indicator will increase linearly from-18 °C to-14 °C during the time T1 up to phase F1. The indicator then contains only ice. During the time T2, the outer ice mass 18 melts to liq- uid, and during this time, the temperature is constantly

- 14 °C up to phase F2. Then the temperature rises linearly to - 12 °C during the time T3 up to phase F3. During the time T4, the ice mass in the capsules melts and the temperature indica- tor begins to change colour during phase F4. In a fifth phase F5, the entire content of the temperature indicator has melted to liquid, the indicator being triggered inasmuch as the indi- cator liquid has been coloured.

If the temperature indicator would be exposed to a tem- perature rise up to the phase F3, and then be frozen again to a temperature below-14 °C, the indicator will return to an untriggered, uncoloured state. If the exposure passes the phase F3, the indicator will entirely or partly be triggered depending on how far the phases F4 and F5 are driven.

In practice, it should be ensured that the volume of the phase-changing liquid 19 is considerably smaller than the vol- ume of the indicator liquid 18. In this way, it can be guaran- teed that the capsules in the untriggered state do not become ocularly perceptible, in particular if they have the same col- our or light-reflecting property as the rest of the base wall.

It is also feasible to place the capsules outside the rectan- gular area that is occupied by the code bar fields 7. In other words, the presence of the capsules cannot be registered by a scanner as long as triggering of the temperature indicator has not taken place. However, after triggering, the coloured liq- uid 18 will distinctly appear via the code bar fields 7, whereby a scannable bar-code is formed. In the preferred embodiment, which includes the separate, transparent the sym- bol windows 17, also the human eye notices in a clear way that the temperature indicator has been triggered, i. e. that thaw- ing has taken place at some opportunity in the cold chain.

Reference being made to figs 5-7, it should be pointed out that the outwardly exposed front wall 9 advantageously may be thicker than the base wall 10 in order to, in this way, obtain a greater heat insulation capacity than the base wall.

By said increased heat insulation capacity, it is attained that the temperature in the indicator liquid 8 does not imme- diately rise already as a consequence of a short contact between the temperature indicator and a hand which seizes the package. Furthermore, in figs 5-7 is seen how the temperature

indicator may include a varying number of capsules 20 having phase-changing liquid 19. Thus, in fig 5 is shown how two cap- sules 20 are applied to or connected to the base wall 10. In fig 6, three capsules 20 are shown in a held-together set of, which is freely inserted in the outer casing 21. In fig 7, a number of capsules 20 are shown connected to the front wall 9 of the outer casing. In this connection, it should be pointed out that the storage and the delimitation of the phase-chang- ing liquid in relation to the indicator liquid may be realized in many other ways, e. g. by the fact that the phase-changing liquid is encapsulated in a plurality of extremely small and mutually spaced-apart balls or bubbles.

Reference is now'made to figs 9-12, which illustrate a second, alternative embodiment of a temperature indicator 3 according to the invention, more precisely in four different functional states.

In fig 9, the same temperature indicator is shown in an initial state after manufacture. Also this embodiment is intended for temperature or saleability supervision of deep- frozen goods.

In the example, the temperature indicator has the form of a label having, in the applied state, an exposed, visible top or outside 22 (the outside of the front wall 9) and a hid- den bottom side 23 (the back side of the base wall 10), which advantageously may include an adhesive (not shown) by means of which the label may be sticked onto the package 1. In prac- tice, also said label may be made as a casing 21 from a thin, transparent plastic foil or plastic film, which is folded along an end edge 25 and welded together along two long-side edges and an opposite end edge 26. The casing 21 defines a hollow space 27, which houses a porous, capillary suctioning means 11, which may be in the shape of a strip of paper or the like, and which in this case forms the contrast medium of the indicator. In other words, the film forms a casing which sur- rounds the strip 11, preferably in such a way that the casing is in close contact with the outside of the strip.

Furthermore, inside the casing at least one capsule is arranged which contains a liquid. In the shown, preferred embodiment, there are two such capsules 28, 28a, which are

placed fairly near each other in the area of the end edge 26 of the label. Each individual capsule is manufactured from a thin film of a material, e. g. a suitable plastic, which retains a fundamental elasticity or softness at a certain tem- perature, e. g. near 0 °C, but becomes brittle at lower tem- peratures, e. g. below-16 °C. The liquid contained in the individual capsule, which in fig 9 is designated 29, may for instance consist of a mixture of alcohol and water in such proportions that the freezing point of the liquid mix is at, for instance,-16 °C. Such a liquid mix is colourless and transparent.

Experiments that form the basis of the invention have shown that paper has different optical properties in dry and wet states, respectively. More precisely, the top side of a white or brightly coloured paper is in a dry state opaque so far that only the surface, but not the interior of the paper fibre web may be seen by the eye. However, as soon as the fibre web becomes wet, the same becomes transparent inasmuch as at least the outermost layer of the fibre web may be seen through. This phenomenon is utilized according to the inven- tion in this way that the strip 11 is provided with a print 30 which is invisible from the top side as long as the strip is dry, but which is made visible when the strip becomes wet.

More precisely, the print 30 is applied onto the back or bot- tom side of the strip. In this connection, it should be reminded that the top side of the strip is covered by the front wall 9 and is therefore always visible for the eye via the window fields 7, while the back side of the strip is fac- ing the package 1 and, therefore, not exposed in the direction of the observer. The colour in the strip may advantageously be white or at least light in order to reflect infrared light of the type that is used in code scanners. The colour in the print 30 should be generally darker than the white or the light colour in the strip. Advantageously, the colour in the print 30 may be black.

Although series manufacturing of the label according to figs 9-12 can be carried out in various ways, the strip 11 should be pre-printed on one side thereof, and then it is con- tained in a double-folded plastic film, which is welded along

three edges. Said plastic film is opaque with the exception of the bar-shaped window fields 7, which are transparent. Before sealing the plastic film, also the liquid capsules 28,28a are inserted either by being inserted in the strip (e. g. in coun- tersinks in the same) in advance or by being placed between the strip and the surrounding casing.

Arbitrarily long time after the manufacture, the dis- closed temperature indicator/the label may be primed for use, more precisely on the occasion when a storing period for a packaged frozen goods should be initiated. The only essential in this connection, is that the label before priming is not exposed to temperatures below the limit value that should be supervised (e. g.-16 °C). Conventionally, freezing of frozen goods is carried out at very low temperatures in order to has- ten the freezing process. Inside the temperature indicator, the following then takes place: As the temperature falls from the room temperature, heat is transported from the liquid cap- sules via the casing to the cooled surroundings. When the tem- perature has fallen to, for instance,-16 °C, the liquid 29 in the capsules freezes to ice and begins to expand. Simultane- ously, the material in the capsule walls has become brittle, said expansion resulting in that the capsules burst (in prac- tice fine cracks are formed in the capsule walls). The burst- ing means that an irreversible path of communication is estab- lished between the interior of the capsules and the surround- ing paper fibre web. However, as long as the temperature is below said limit value, no exit of liquid from the capsules takes place, because the liquid still exists in a solid state, more precisely as ice. The temperature indicator is now primed.

However, if the package 1 together with the temperature indicator 3 thereof, at some occasion during the handling from the producer to the consumer would unintentionally come to be thawed by being exposed to temperatures above the limit value during a considerable time, the ice will melt and return to liquid state. The accordingly triggered liquid (see fig 10) is first sucked into the fibre web in the immediate vicinity of the capsules 28, 28' (see fig 11), and then continued capil- lary implies that the strip is wet in its entirety, as is

shown in fig 12. In this connection, the strip becomes trans- parent so that the print 30 appears from the outside of the label.

In an additional, alternative embodiment of a tempera- ture indicator, particularly suited for chilled products, which is shown in fig 13, a liquid 29 that has a semi-plastic consistency at temperatures below a certain limit value, but becomes liquid at temperatures above the same is used as a wetting agent in the strip 11 serving as contrast medium. For chilled products in general and cooled foods in particular, the chosen limit value should be in the temperature range of 0 to +12 °C, suitably between +2 °C and +10 °C. For specific foods, the limit value may be established to either +4 °C or +8 °C.

Because the liquid in question should have the ability to transform or be converted from one viscosity state to another, more precisely between on one hand, a state of low viscosity and, on the other hand, a semi-plastic or probably a state of high viscosity-depending on the ambient temperature - said liquid will henceforth be denominated conversion liq- uid.

The choice of conversion liquid is determined by a plu- rality of factors, one of which is the nature of the packaged goods. Thus, if the product consists of a food, a liquid that is not toxic and/or chemically active should be chosen. There- fore, for the purpose, vegetable or animal oils are suitable of the type that has a melting point or a viscosity transition temperature within the range of 0-12 °C. Experiments which form the basis of the invention have shown that olive oil is particularly appropriate. Therefore, a brief account of a practical experiment will follow below, reference being made to the chart in fig 14.

An olive oil of the mark"BERTOLLI GENTILE, Extra Vergine"was cooled down in a refrigerator to a temperature of +3 °C, and then the sample was taken out in room temperature for measurement of the temperature change as well as the con- sistency of the oil once per minute during totally 6 min.

Below the result of these measurements follows in tabular form. Time Temperature Consistency (minutes) (°C) 0 +3, 4 Semi-plastic, honey-like 1 +4, 5 Semi-plastic, honey-like 2 +6,0 Indication of liquefaction 3 +7,5 Liquefaction initiated 4 +8,6 Viscous 5 +9, 8 Of low viscosity 6 +10,3 Of low viscosity

Thus, during the relatively narrow temperature interval 2, 6 °C between +6, 0 °C and +8, 6 °C, the olive oil in question transforms from a non-flowing, semi-plastic state to a state, which above +8, 6 °C becomes of low viscosity.

At the label according to fig 13, the conversion liquid 29 is contained in a capsule 28, which is connected to the label via a welded material portion 32 in which one or more weakened portions are included, which may form an open way of communication between the capsule and the inside of the casing 21. Furthermore, a constriction located up-stream the print 30 33 is included in the label, where the material in the paper strip 11 is compressed (there is a pre-chamber 34 between the constriction 33 and the material portion 32). In this way, penetration of the liquid in the direction of the end 25 is delayed or is counteracted. In this case, priming takes place by a mechanical pressure being applied against the capsule 28.

Said pressure may be provided either in a manual way, e. g. by means of fingers, or in a mechanical way by means of the tool, which is used in order to apply the label on the package. When the liquid pressure in the capsule is raised sufficiently high, the weakened material portion in welding 32 serving as a

valve, breaks, whereby a way of communication is opened for the liquid up to the strip. By initially executing the priming in an environment where the ambient temperature is below the limit value that is determined by the melting point of the liquid (e. g. +4°C), it is, however, guaranteed that the liquid is not immediately sucked into the strip. Thus, the still semi-plastic liquid will only reach the end of the strip. In practice, the capsule 28 is opened earliest in connection with the indicator being applied to the package 1 and/or the goods being brought into a cooling accomodation, for instance at a manufacturer/distributor or in shop. In this state, the strip 11 is unaffected by the liquid. In other words, the print 30 is still hidden under the surface layer turned outwards of the paper fibre web.

Suppose that the temperature limit value in question for the goods is set to +4 °C. As long as the ambient temperature is below the same value, the label remains in the initial state thereof. If, however, the temperature during storing of the goods would exceed +4 °C, the consistency of the liquid will be converted from a semi-plastic one to a liquid one. By the capillary effect in the porous strip 11, the liquid will then be sucked into the strip and completely wet the same, the print 30 appearing and becoming visibly from the outside of the label. In this way, a scannable bar-code in the window fields 7 is established.

A delay of the penetration of the liquid of low viscos- ity in the fibre web may also be provided by making the fibre web with spaced-apart sections, which have different porosity or varying capillary effect. By delaying the liquid penetra- tion in a suitable way, it is guaranteed that the article has to be exposed to a harmfully increased temperature during a certain. time in order to trigger the indicator. A short excee- ding of the temperature limit value, e. g. during the time which the customer stays in a shop (usually maximum approxi- mately 30 min), will therefore not lead to a triggering of the indicator.

It is given that a semi-plastic conversion liquid of the type that has been described above in connection with fig 13 may also be used in capsules of the type that are integrated

in the fibre web in the way which is shown in figs 9-12. It is even feasible to have, in a combination, a semi-plastic con- version liquid in one capsule, and a freezing liquid (e. g. water/alcohol) in another one.

Reference is now made to figs 15 and 16, which illus- trate an additional embodiment of a temperature indicator according to the invention. This embodiment is similar to the embodiment according to fig 13 so far that the same includes on one hand a wettable paper web or strip 11, and on the other hand a manually openable capsule 28 having a conversion liquid 29. However, in this case the print 30 is applied to the rear wall 10, which together with the front wall 9 form the casing surrounding the paper strip. In other words, the paper strip 11 in this case lacks print. However, when the paper strip is wet by liquid from the capsule 28 penetrating into the same, also the print 30 on the rear wall 10 becomes visible through the window fields 7 in the external wall 9 of the casing.

Furthermore, in the example according to figs 15 and 16, one or more additional prints 35,36 are arranged between the print 30 intended for forming the bar-code and the liquid cap- sule 28, more precisely prints that are applied on the back side of the paper strip. The pressure 35 positioned closest to the liquid capsule 28 has in the example the shape of a circu- lar spot with the purpose of indicating that the temperature indicator has been primed for use. The print 36 consists of a number of warning triangles. The different prints 35,36 may advantageously have different colours, which may deviate from the colour (e. g. black) in the print 30. The colour in the strip may advantageously be white or at least light in order to reflect infrared light of the type that is used in the code scanner. The colours in the prints 30,35, 36, should be gen- erally darker than white or the light colour in the strip.

Advantageously, the colour in the print 30 may be black, and in other prints 35,36, for instance green, yellow and/or red.

In this connection, it should be emphasized that only the print 30 has the purpose of forming a bar-code at wetting of the strip, while other prints are intended to be noticed by the human eye, more precisely with the purpose of giving

information about different functional state in the tempera- ture indicator.

Advantages of the Invention A primary advantage of bringing, according to the inven- tion, an initially invisible bar-code to become scannable first when a temperature limit value has been exceeded, is that the ordinary, primary price code or commodity code may be read without problem as long as the product is saleable. Would the product however have become obsolete, e. g. by thawing at arbitrary opportunity during the handling of the goods, a scannable bar-code appears by means of which a row of precau- tions may be taken. Above all, it is guaranteed that the obso- lete product does not leave the shop. Furthermore, it can be registered in the computer system of the shop that the indi- vidual product has become obsolete. In this way, statistics may be provided in a simple way of different line of goods and different types of packages which have thawed or been exposed to increased temperatures. Furthermore, information may be obtained whether thawing has occurred in connection with defrosting of freezers, cold-storage rooms, etc, as well as what season that is most frequent. Furthermore, manufacturers, forwarding agents, batch number, etc, may be tracked in a sim- ple way. Besides the detection via the formed bar-code, also the human eye may easy detect whether a product is saleable or not.

Feasible modifications The invention is not solely limited to the embodiments described above and illustrated in the drawings. Thus, the invention is applicable not only to such packages that contain frozen and cold foods, respectively. In the packages may, for instance, medicines, photographic films, etc be stored. Fur- thermore, it is feasible to utilize the temperature indicator according to the invention in order to detect/register whether freezing rather than thawing has taken place. Thus, in prac- tice, the temperature indicator could be utilized on pots for paint. Paint is frequently water-based and thereby affected by freezing. If a temperature indicator is applied, for instance,

on the outside of a lid, it will indicate if the container/ package has been exposed to unallowed temperatures. This takes place by a phase-changing liquid in the temperature indicator bursting the capsule and colouring the indicator liquid, if the temperature is lowered below an allowed value from 0 °C and downwards. Although EAN codes are the most common form of merchandise codes, in particular for foods, the invention is also applicable in connection with other types of commodity codes, which makes use of bars or bar-like symbols. Examples of such codes are Interleaved 2/5, Code 39, Code 128, as well as PDF-417. Characteristic of these codes too, is that the bars or the symbols form a rectangular configuration in the extension of which a temperature indicator according to the invention can be applied.