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Patent Searching and Data


Title:
OVENABLE FOOD CONTAINER
Document Type and Number:
WIPO Patent Application WO/2016/207587
Kind Code:
A1
Abstract:
A material (1) which is formable into an ovenable food container tray, the material (1) has a transparent deformable, heat resistant plastic top layer (3), a deformable, heat resistant decorative layer (5) applied to the top layer so that the decorative layer is visible through the top layer, a deformable, heat resistant adhesive layer (7) which bonds the decorative layer to the top layer and a deformable, heat resistant base layer (9) comprising a thermo-formable plastic. Embodiments of the invention comprise fully printed complex designs of many different colours on CPET trays and may combine metallic and printed effects with a paper look and feel to the outside of the tray.

Inventors:
URQUHART JAMES (GB)
PRITCHARD OWEN (GB)
Application Number:
PCT/GB2016/000126
Publication Date:
December 29, 2016
Filing Date:
June 22, 2016
Export Citation:
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Assignee:
DISCOVERY FLEXIBLES LTD (GB)
International Classes:
B65D81/34; B32B27/36; B65D1/34
Foreign References:
US5366791A1994-11-22
US4900594A1990-02-13
US20070212454A12007-09-13
US4327136A1982-04-27
US4327136A1982-04-27
US4595611A1986-06-17
Attorney, Agent or Firm:
BLACK, Simon John (4 Woodside Place, Glasgow G3 7QF, GB)
Download PDF:
Claims:
Claims

1. A material which is formable into an ovenable food container tray, the material comprising:

a transparent deformable, heat resistant plastic top layer;

a deformable, heat resistant decorative layer applied to the top layer so that the decorative layer is visible through the top layer;

a deformable, heat resistant adhesive layer which bonds the decorative layer to the top layer; and a deformable, heat resistant base layer comprising a thermo-formable plastic.

2. A material as claimed in claim 1 wherein the top layer is a film.

3. A material as claimed in claim 2 wherein the top layer is a cast film.

4. A material as claimed in claim 2 wherein the cast film comprises a

Polyethylene Terephthalate (PET) film.

5. A material as claimed in any preceding claim wherein the top layer is a biaxially oriented film.

6. A material as claimed in claim 4 wherein the top layer is a biaxially oriented PET film. 7. A material as claimed in claim 5 wherein the biaxially oriented film has substantially uniform stretching in the machine and transverse direction.

8. A material as claimed in claim 5 wherein the biaxially oriented film is stretched more in the transverse direction than in the machine direction.

9. A material as claimed in any preceding claim wherein, the layer is of thickness ranging from 12 to 100 microns.

IS

10. A material as claimed in any preceding claim wherein the decorative layer comprises a printed layer.

1 1. A material as claimed in claim 10 wherein the printed layer is created using a suitable ink system.

12. A material as claimed in claim 1 1 wherein, the ink system provides coverage of ink upon the top layer plastic which will maintain a desired level of ink coverage upon the surface after deformation of the finished material under the action of heat and/or pressure.

13. A material as claimed in claim 1 1 or claim 12 wherein the ink system is a pigmented nitrocellulose system. 14. A material as claimed in claim 1 1 or claim 12 wherein, the ink system is a vinyl modified polyurethane system.

15. A material as claimed in claim 1 1 or claim 12 wherein, the ink system is a polyurethane in an Ethyl Acetate solvent

16. A material as claimed in claim 1 1 or claim 12 wherein, the ink system is a polyurethane in an Ethanol/Ethyle Acetate solvent.

17. A material as claimed in claim 10 to 12 wherein, the printed layer is reverse printed to prevent damage or contamination in the thermoforming tool / process by sealing the ink in between the layers of film and not exposing it to the machine tooling surface.

18. A material as claimed in any preceding claim wherein, the material further comprises a filter layer positioned between the decorative layer and the base layer.

19. A material as claimed in claim 18 wherein, the filter layer is opaque and minimises the extent to which any colour component from the base layer shows through to the decorative layer.

20. A material as claimed in claim 18 or claim 19 wherein, the filter layer is solid white in colour. 2 . A material as claimed in any preceding claim wherein, the decorative layer comprises a metalised layer

22. A material as claimed in claim 21 wherein the metalised layer is vacuum deposited upon the top layer

23. A material as claimed in any preceding claim wherein the plastic material is recyclable.

24. A material as claimed in claim 23 wherein, the plastic material is recyclable through a thermoforming process.

25. A materia! as claimed in any preceding claim wherein, the adhesive of the adhesive layer is oven safe. 26. A material as claimed in any preceding claim wherein, the adhesive of the adhesive layer, the adhesive is solvent free,

27. A material as claimed in any preceding claim wherein, the adhesive of the adhesive layer, the adhesive is solvent based.

28. A material as claimed in claims 1 to 25 wherein, the adhesive is water based.

29. A material as claimed in any preceding claim wherein, the adhesive of the adhesive layer, a lengthy, temperature dependent curing processes.

30. A material as claimed in any preceding claim wherein, the adhesive of the adhesive layer, has sufficient flexibility to allow for the stretching required within the process.

31. A material as claimed in any preceding claim wherein, the adhesive of the adhesive layer, has a very high adhesive bond level to ensure that there is no delamination of layers when the thermoforming takes place. 32. A material as claimed in any preceding claim wherein, the adhesive of the adhesive layer, the base layer is flexible.

33. A material as claimed in any preceding claim wherein, the plastic is flexible. 34. A material as claimed in any preceding claim wherein, the plastic is able to withstand rapid changes in temperatures.

35. A material as claimed in any preceding claim wherein, the plastic is flexible in all directions and is able to withstand sudden high temperatures then low

temperatures in the manufacturing process without fracturing or tearing.

36. A material as claimed in any preceding claim wherein the cover layer is peelable and removable before putting it in an oven. 37. An ovenable food container comprising a material in accordance with the first aspect of the invention.

38. A method for making an ovenable food container tray, the method comprising the steps of:

Providing a transparent deformable, heat resistant plastic top layer;

Applying a deformable, heat resistant decorative layer to the top layer so that the decorative layer is visible through the top layer;

Applying a deformable, heat resistant adhesive layer which bonds the decorative layer to the top layer; and

Applying a deformable, heat resistant base layer comprising a thermo-formable plastic.

39. A method as claimed in claim 38 wherein, application of at least some of the layers is by lamination.

40. A method as claimed in claim 38 and claim 39 wherein the decorative layer may be printed using a printing process such as gravure printing. 41. A method as claimed in claims 38 to 40 wherein, the design is reverse printed onto the outer layer to prevent any damage or contamination in the thermoforming tool / process by sealing the ink in between the layers of film and not exposing it to the machine tooling surface. 42. A method as claimed in claims 38 to 41 wherein, the tray is thermoformed.

43. A method as claimed in claims 39 to 42 wherein, the material is heated in an oven to a high-enough temperature that permits it to be stretched into or onto a mould and cooled to a finished shape.

44. A method as claimed in claims 38 to 43 wherein, machines are utilised to heat and form the plastic sheet and trim the formed parts from the sheet in a continuous high-speed process. 45. A method as claimed in claims 38 to 44 wherein, the ovenable food container tray is as hereinbefore described in accordance with the first and second aspects of the invention.

Description:
Ovenable Food Container

Introduction The present invention relates to an ovenable food container which has a decorative appearance and in which foodstuffs may be heated or cooked within the container.

Background Supermarkets and the like sell a large amount of pre-prepared food such as ready meals, vegetable accompaniments and desserts. These foodstuffs are sold to the consumer in heat resistant preformed plastic trays that can be placed directly in a conventional oven, microwave oven or the like for the purpose of heating or cooking the food.

An ovenable food container may comprise a plastic tray which is able to withstand the heat necessary to cook or heat the contents of the tray and a sealed clear film lid which may be similarly heat resistant. The container may be designed for use in a microwave oven, where the maximum temperature is typically 120°C or in a conventional oven at temperatures of up to around 220°C. It should be noted that some foods and their trays are designed specifically to be cooked at the lower temperatures found in microwave ovens.

An outer cover is provided which may comprise a sleeve or a cardboard box. One main purpose of the cover is to display information about the product including, for example, the brand, type of goods, cooking instructions, legislative requirements for food safety, ingredients and nutritional information.

Food processing companies rely heavily on packaging aesthetics for repeat retail sales of their products. Therefore, the cover must be able to meet printing requirements to truly replicate the brand and other information and colours that the vendor wishes to convey to a customer. For that reason cardboard and paper are

l the most frequently used media for the cover. However, the use of a sleeve or box creates additional production and disposal costs.

One way of saving cost would be to dispense with the sleeve or box. In order to do so, it would be necessary to print information and provide decoration directly onto the ovenable tray. Generally speaking, food-grade inks have weak colour are

transparent, do not withstand heating and are otherwise unsuitable.

Several attempts have been made at printing directly onto an ovenable tray. U.S. patent. No. 4,327,136 describes a tray in which the pigment is sandwiched between multiple layers of polymer. In this case, the container was specifically designed for use in the lower cooking temperatures created in microwave ovens and contained additional plastic barrier layers designed to prevent ink ingress to the food facing surface of the container.

US 4,595,61 1 discloses an ink-printed ovenable food container which has a layer of ink printed on paperboard with a pigment binder which is then coated with a sulfonated polyester. The resultant structure is further coated with a polyester resin sealing coating which is then formable into a container.

It is notable that the approaches described in the above prior art have not been widely adopted. The actual state of the art for ovenable containers comprises a plastic known as CPET (Crystalline Polyethylene Terephthalate). The production process is based on the esterification reaction between ethylene glycol and terephthalic acid and a controlled crystallisation of the plastic to make the material opaque. As a result of the partially crystalline structure, CPET retains its shape at high temperatures and is therefore suitable for use with products that are to be heated in both conventional domestic ovens and microwave ovens. The control of the material's crystallinity means that the product can be used within a temperature range of -40°C to +220X. This meets the needs of consumers, who require good impact resistance at low temperatures and shape retention at high temperatures. CPET also forms a highly effective barrier against oxygen, water, carbon dioxide and nitrogen. CPET food trays are typically black or white in colour although more recently, trays having a solid colour outside with a different colour inside have been manufactured. The colours are provided by introducing the required pigment into the mixture during manufacture of the CPET. The coloured trays are made by coextruding two different master batches together at the point of manufacturing the CPET.

Summary of the Invention It is an object of the present invention to provide an ovenable food container tray to which good quality, durable ink-printed graphics and/or other decoration may be applied such that the pigment and other ingredients of the printing, colouring or decorative composition remain in place without migrating or coming into contact with the food to be ingested.

Another object of the present invention is to produce an ovenable food container upon which fully printed complex designs of many differing colours or other decoration may be incorporated on the container. The ability to provide high quality print on the trays will greatly improve the aesthetic appeal and marketability of a product which has hitherto comprised a standard monochrome tray.

In accordance with a first aspect of the invention there is provided a material which is formable into an ovenable food container tray, the material comprising:

a transparent deformable, heat resistant plastic top layer;

a deformable, heat resistant decorative layer applied to the top layer so that the decorative layer is visible through the top layer;

a deformable, heat resistant adhesive layer which bonds the decorative layer to the top layer; and a deformable, heat resistant base layer comprising a thermo-formable plastic.

Optionally the top layer is a film. Optionally the top layer is a cast film. Optionally the cast film comprises a Polyethylene Terephthalate (PET) film. Optionally the top layer is an oriented film Optionally the top layer is an oriented PET film.

Optionally, the top layer is created using the Bubble process. Oprionally, the top layer is created using the Stenter process.

Optionally the layer is of thickness ranging from 12 micron to 100 microns.

Optionally the decorative layer comprises a printed layer. Optionally the printed layer is created using a suitable ink system.

Preferably, the ink system provides coverage of ink upon the top layer plastic which will maintain a desired level of ink coverage upon the surface after deformation of the finished material under the action of heat and/or pressure.

Accordingly, the ink composition has suitable bulk properties of flexibility and pressure resistance to withstand the thermoforming process.

Preferably, the ink system meets the required food safety standards for ovenable use.

Optionally, the ink system is a pigmented nitrocellulose system. Optionally, the ink system is a vinyl modified polyurethane system.

Optionally, the ink system is a polyurethane in an Ethyl Acetate solvent Optionally, the ink system is a polyurethane in an Ethanol/Ethyle Acetate solvent. In selecting the Ink system, consideration may be given to properties of the ink system such as good heat resistance, low solvent retention, gloss and colour strength and non-blocking characteristics. Preferably, the printed layer would typically be reverse printed to prevent damage or contamination in the thermoforming tool / process by sealing the ink in between the layers of film and not exposing it to the machine tooling surface.

Optionally, the material further comprises a filter layer positioned between the decorative layer and the base layer.

Preferably, the filter layer is opaque and minimises the extent to which any colour component from the base layer shows through to the decorative layer. Preferably, the filter layer is solid white in colour.

Optionally, the filter layer is coloured which provides for better density and reduces the risk of colour degradation. Optionally, the decorative layer comprises a metalised layer

Preferably the metalised layer is vacuum deposited upon the top layer

Preferably the plastic material is recyclable to minimise waste.

Preferably, the plastic material is recyclable through the thermoforming

process.

Preferably, the adhesive is oven safe.

Preferably, the adhesive is solvent free, Optionally, the adhesive is solvent based. Optionally, the adhesive is water based.

Preferably, the adhesive has a lengthy, temperature dependent curing processes. Preferably, the adhesive has sufficient flexibility to allow for the stretching required within the process.

Preferably, the adhesive has a very high adhesive bond level to ensure that there is no delamination of layers when the thermoforming takes place.

Preferably, the base layer is flexible.

Preferably, the plastic is flexible. Preferably, the plastic is able to withstand rapid changes in temperatures.

The plastic is flexible in all directions and is able to withstand sudden high temperatures then low temperatures in the manufacturing process without fracturing or tearing.

Advantageously, the embodiments of the present invention provides a cover which is removable by peeling the cover layer off before putting it in an oven.

In accordance with a second aspect of the invention there is provided an ovenable food container comprising a material in accordance with the first aspect of the invention.

In accordance with a third aspect of the invention there is provided a method for making an ovenable food container tray, the method comprising the steps of:

Providing a transparent deformable, heat resistant plastic top layer;

Applying a deformable, heat resistant decorative layer to the top layer so that the decorative layer is visible through the top layer;

Applying a deformable, heat resistant adhesive layer which bonds the decorative layer to the top layer; and Applying a deformable, heat resistant base layer comprising a thermo-formable plastic.

Preferably, application of at least some of the layers is by lamination.

Preferably, the decorative layer may be printed using a printing process such as gravure printing.

Preferably, the design would be reverse printed onto the outer layer to prevent any damage or contamination in the thermoforming tool / process by sealing the ink in between the layers of film and not exposing it to the machine tooling surface.

Preferably, the tray is thermoformed. Preferably, the material is heated in an oven to a high-enough temperature that permits it to be stretched into or onto a mould and cooled to a finished shape.

Optionally, machines are utilised to heat and form the plastic sheet and trim the formed parts from the sheet in a continuous high-speed process.

Preferably, the ovenable food container tray is as hereinbefore described in accordance with the first and second aspects of the invention.

Brief Description of the Drawings

The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a side cross sectional view of a first embodiment of a material for making an ovenable container in accordance with the present invention;

Figure 2 is a side cross sectional view of a second embodiment of a material for making an ovenable container in accordance with the present invention; Figure 3 is a side cross sectional view of a third embodiment of a material for making an ovenable container in accordance with the present invention;

Figure 4 is a side cross sectional view of a fourth embodiment of a material for making an ovenable container in accordance with the present invention;

Figure 5 is a schematic diagram of a laminating process in accordance with the present invention; Figures 6a and 6b are schematic diagrams showing a gravure printing process which may be used in accordance with the present invention;

Figure 7 is a schematic diagram of an embodiment of a typical laminate structure in accordance with the present invention;

Figure 8 is a schematic diagram of a laminating process in accordance with the present invention;

Figure 9 is a schematic diagram of a thermoforming process in accordance with the present invention and

Figure 10 shows an ovenable tray in accordance with the present invention with printed coloured shapes on the side of the tray in orange, blue, yellow and green . Detailed Description of the Drawings

The present invention provides a product that removes the need for the cardboard box or sleeve in ovenable packaging and replaces it with a printable cover, removeably bonded to the lid and which is able to contain the information that would otherwise be presented to a consumer on a cardboard box or sleeve.

The present invention combines the thermal properties of heat resistance which are present in ovenable plastic trays and, in its embodiments, has created a new product which through a detailed understanding of the properties of the materials used, has created a printed, ovenable food tray which allows for accurate reproduction of brands and printed information on the side of the tray and removes the need for additional paper or plastic packaging. When considering the plastic tray used in this process, this invention specifically provides trays useable in conventional ovens.

Embodiments of the invention comprise fully printed complex designs of many different colours on CPET trays. In contrast, current standard ovenable trays are monochrome, typically black or white CPET trays. In addition, containers made in accordance with the present invention may combine metallic and printed effects with a paper look and feel to the outside of the tray.

The invention also provides for the production of fully registered trays by building in an allowance for distortion of the print due to the container forming process. To achieve this high quality printed CPET tray, the finished structure is created in layers. From the outside of the tray, the first layer is typically a cast or orientated clear, gloss or matt PET of thickness ranging from around 12 micron to 100 microns.

The decorative layer may be printed using a printing process such as gravure printing. Typically, the design would be reverse printed onto the outer layer to prevent any damage or contamination in the thermoforming tool / process by sealing the ink in between the layers of film and not exposing it to the machine tooling surface. The ink systems used provide a flexible and fracture resistant print upon the top layer which will not fracture during the thermoforming process. In one example, the ink system is a pigmented nitrocellulose system chosen for good heat resistance, low solvent retention, excellent gloss and colour strength and excellent non blocking characteristics. One alternative would be a vinyl modified polyurethane system which has similar properties to the pigmented nitrocellulose system.

An ink system is selected which, once printed, is able to stretch without a loss of colour strength which would be detrimental to the final appearance of the package. It should also work well with the adhesives which allow it to maintain an excellent bond strength.

Decoration may also be provided by vacuum deposition of a metallised layer. One important considerations in choosing the best material for this is its ability to be recycled through the thermoforming process to minimise waste.

The decorative layer is designed to withstand the sudden high temperatures then low temperatures which are experienced in the process of forming the container from the material. The material and its components should also be flexible in all directions so as to avoid fracture or tear when being formed and be approved for food use.

In embodiments of the invention, a second layer of cast or orientated PET of a thickness ranging from 20 to 100 microns may be used. This layer filters out any colour from the CPET layer, preventing it from showing through and dulling down the graphics from the outer layer. Making the layer white adds vibrancy to the finished product and the layer is often made from a cast CPET film similar or identical to the outer layer. In other embodiments of the present invention, the layer may be of a different colour to contribute to the overall colour effect given by the packaging.

In embodiments of the invention, the layers are laminated together utilising an oven safe adhesive. Solvent free, solvent based or water based technology is suitable. Suitable adhesives typically undergo lengthy, temperature dependent curing processes. In some cases the adhesives need to cure for up to ten days at a constant temperature of at least 40 degrees. The adhesive must be flexible enough to allow for the stretching required within the process but also have a very high adhesive bond level to ensure that there is no delamination of layers when the thermoforming takes place. These adhesives must also be food safe for oven use. These materials can be laminated together either simultaneously or with the curing process between each layer built in. Typically, for manufacturing efficiency it is expected to laminate them simultaneously to improve lead times. One or two printed or metallised layers may be supplied to the manufacturer of the CPET for lamination in line within their process directly after extrusion. The materials have the ability to withstand the temperatures associated with oven cooking

In the Cast Film process, the molten polymer is usually extruded through a slot die onto an internally cooled chill roll and then passes through a series of rollers which will determine the nature and properties of the cast film including thickness. The cast film is then cut to width as required by saws, shears or hot wire methods.

The ability to stretch and form in all directions is a preferred property because it helps to prevent the materials from splitting and tearing when stretched.

In examples of the present invention where the final tray or container is shallow, a material thickness of around 10mm is sufficient. In the case of deeper trays, a material thickness of around 25mm or more is suitable. In examples of the present invention, the film thicknesses have ranged from around 10mm to 40mm.

In the case of deeper trays, a cast film is preferred to allow it to stretch in all directions.

Biaxially oriented film is produced when the film is stretched in both machine and transverse directions directly following extrusion. The stretching process has the effect of orienting the polypropylene molecules. The degree to which a film can be oriented is dependent upon the polymer from which it is made. Polypropylene, polyethylene terephthalate (PET), and nylon are highly crystalline polymers that are readily heat stabilized to form dimensionally stable films. These films are well known to be capable of being biaxially stretched to many times the dimensions in which they are originally cast (e.g., 5X by 8X or more for polypropylene).

Biaxial orientation can be conducted simultaneously in both directions or sequentially where an apparatus stretches the film first in one direction and then in the other. A typical apparatus will stretch a film in the machine direction first and then in the transverse direction. Usually, the sheet is oriented sequentially, preferably being first stretched in the MD and then stretched in the TD. Thus, the cast material is typically heated (optionally including a pre-heating stage) to its orientation temperature and subjected to MD orientation between two sets of rolls, the second set rotating at a greater speed than the first by an amount effective to obtain the desired draw ratio. Then, the monoaxially oriented sheet is oriented in the TD by heating (again optionally including pre-heating) the sheet as it is fed through an oven and subjected to transverse stretching. The Bubble (sometimes referred to as the double bubble) process is a technique for producing film, the alternative being the Stenter process. The two methods give film with subtle differences in mechanical and physical properties.

Bubble film imparts a simultaneous orientation of 8x Machine Direction (MD) and 8x Transverse Direction (TD) compared to Stenter film which imposses 5x MD and 10x TD sequentially. This leads to several property benefits for Bubble film such as: i. Higher machine direction stiffness for improved control in Reel to Reel (R2R) processes;

ii. Balanced MD/TD properties. Improved cuttability in label production. Balanced shrink properties for shrink overwrap application.

Figure 1 shows a cross sectional view of a first embodiment of a material for making a printed food tray in accordance with the present invention. The material 1 comprises a transparent deformable, heat resistant plastic top layer 3 that in this example of the invention comprises a clear cast PET film.

A deformable, heat resistant decorative layer 5 is applied to the top layer 3 so that the decorative layer is visible through the top layer. In this example of the invention, the decorative layer is a gravure printed layer. The ink has been configured to be heat resistant, and deformable. In the context of the ink, deformable means that the printed ink may stretch and bend in response to the thermoforming process and the end product will be a print which faithfully represents the packaging design specified by the customer, typically a food processor/manufacturer.

The adhesive layer 7 is deformable and heat resistant. It sticks the printed layer 5 and top layer 3 to a heat resistant base layer that comprises a thermo-formable plastic base layer 9. In most cases, the printed layer 5 will not completely cover the top layer. In addition, where the base layer 9 is coloured, some of the base layer colour may be

transmitted through the printed layer 5, thus colouring the printed layer 5. Figure 2 shows a second embodiment of a material in accordance with the present invention. In this example, the material 21 comprises a transparent defonmable, heat resistant plastic top layer 23 which in this example of the invention comprises a clear cast PET film. A deformable, heat resistant decorative layer 25 is applied to the top layer 23 so that the decorative layer 25 is visible through the top layer 23. In this example of the invention, the decorative layer is a gravure printed layer. The ink has been configured to be heat resistant, and deformable. In the context of the ink, deformable means that the printed ink may stretch and bend in response to the thermoforming process and the end product will be a print which faithfully represents the packaging design specified by the customer, typically a food

processor/manufacturer.

The adhesive layer 27 is deformable and heat resistant. It sticks the printed layer 25 and top layer 23 to a backing layer 29. The backing layer prevents transmission of colour from the base layer into the decorative layer. In certain circumstances such transmission will detract from the decorative effect provided by the printed layer 25 and the backing layer solves this problem. In this example the backing layer 29 is white and made from a cast PET. A second adhesive layer 31 bonds the base layer 33 which is a standard thermoformable CPET. This variant may be used for high impact printed design requiring a layer of white to filter out the colour of the black base layer.

In other embodiments of the invention, the base or filter layer may be a coloured material for better density and to reduce the risk of colour degradation. So for example if trying to create a brown paper effect a cream film would be used which would be printed on as the base layer. Figure 3 shows a cross sectional view of a third embodiment of a material for making a printed food tray in accordance with the present invention. The material 41 comprises a transparent deformable, heat resistant plastic top layer 43 which in this example of the invention comprises a clear cast PET film.

A deformable, heat resistant decorative layer 45 is applied to the top layer 43 so that the decorative layer is visible through the top layer 43. In this example of the invention, the decorative layer is a metallised layer which is created by vacuum deposition of metal onto the top layer 43.

The adhesive layer 47 is deformable and heat resistant. It sticks the metallised layer 45 and top layer 43 to a heat resistant base layer which comprises a thermo- formable plastic base layer 49. This variant is used when a metallic outer is required. Figure 4 is a cross sectional view of a material for making a printed ovenable food tray in accordance with the present invention. This variant is used when a printed effect with a metallic background is required.

The material 61 comprises a transparent deformable, heat resistant plastic top layer 63 which in this example of the invention comprises a clear cast PET film.

In this example, the decorative layer comprises a printed layer 65 and a metalized layer 71. A deformable, heat resistant decorative layer 65 is applied to the top layer 63 so that the printed layer is visible through the top layer. In this example of the invention, the layer is a gravure printed layer.

In addition a metalized layer 71 is provided. The metalized layer 71 is deposited on a layer of clear film 69. A clear adhesive 67 bonds the clear film 69 to the printed layer. A second layer of adhesive 73 bonds the metallised layer to the CPET base layer 75.

Figure 5 is a flow diagram 101 which shows an embodiment of a process for making a material for creating a variety of different printed food containers in accordance with the present invention. The process steps which allow the creation of the materials through different combinations of the process steps. Step 103 comprises reverse printing the clear CAST PET with the required film design. Step 105 is the lamination of the reverse printed film from step 103 with a white CAST PET. Step 107 is the lamination of the reverse printed film from step 103 with a metalized CAST PET. Step 109 is the metallisation of a CAST PET. Step 1 is the lamination of the product of step 105, 107 or 109 to a thermoformable CPET. In each case the output from the process is a sheet of laminated printed material which is suitable for forming into a printed ovenable container.

Variant 1 1 3 follows the process steps shown by reference numeral 1 15, Variant 2 117 follows the process steps shown by reference numeral 1 19, Variant 3 121 follows the process steps shown by reference numeral 123 and Variant 4 125 follows the process steps shown by reference numeral 127.

Figure 6a is a schematic diagram of a roto-gravure printing process. It will be appreciated that this process is a known and convenient method for applying print to a surface and is frequently used for applying a high quality print to materials used in flexible packaging.

The Rotogravure machine 131 comprises an ink reservoir which contains the ink to be used in the present invention. As stated elsewhere herein, the ink is heat resistant and pressure resistant so as to provide a robust and reliable end product after being subjected to the heat and pressure of thermoformation of the ovenable container. In addition, the ink will not run or otherwise leech from its layer in the ovenable container when in use.

The print cylinder has engraved cells 143 (shown in figure 6b). The cylinder rotates through the ink reservoir 133 to cover the engraved cells 143 with ink. Excess ink is removed from the cells using the doctor blade 137. The print substrate, which in this example of the invention is a sheet of CAST PET film 139, is threaded between the print cylinder 135 and the impression roller such that a print is applied to the CAST PET film 139. Figure 7 is a schematic diagram which shows an example of the lamination process used to create a laminate in accordance with the present invention.

The diagram 161 shows a reel 163 from which a first sheet of material 165 may be unwound. Rollers 167 apply adhesive from the adhesive station 169 to a surface of the sheet 65 and their rotation moves the sheet 165 through a drying tunnel 71 where the adhesive is cured. A second material 175 is stored on roller 73 from which it is unwound and presented to nip rollers 177 along with the first sheet 165. The materials are pressed together and bonded by the adhesive to form a laminate which is wound on to a reel 179.

The thermoforming process for making an ovenable container in accordance with the invention is shown in figure 8. Thermoforming is a manufacturing process where a plastic sheet is heated to a pliable forming temperature, formed to a specific shape in a mould, and trimmed to create a usable product. The sheet, or "film" when referring to thinner gauges and certain material types, is heated in an oven to a high-enough temperature that permits it to be stretched into or onto a mould and cooled to a finished shape.

Large production machines are utilised to heat and form the plastic sheet and trim the formed parts from the sheet in a continuous high-speed process, and can produce many thousands of finished parts per hour depending on the machine and mold size and the size of the parts being formed. Thin-gauge thermoforming is primarily the manufacture of disposable cups, containers, lids, trays, blisters, clamshells, and other products for the food, medical, and general retail industries.

In the most common method of high-volume, continuous thermoforming of thin- gauge products, plastic sheet is fed from a roll or from an extruder into a set of indexing chains that incorporate pins, or spikes, that pierce the sheet and transport it through an oven for heating to forming temperature. The heated sheet then indexes into a form station where a mating mould and pressure-box close on the sheet, with vacuum then applied to remove trapped air and to pull the material into or onto the mould along with pressurised air to form the plastic to the detailed shape of the mould. (Plug-assists are typically used in addition to vacuum in the case of taller, deeper-draw formed parts in order to provide the needed material distribution and thicknesses in the finished parts.) After a short form cycle, a burst of reverse air pressure is actuated from the vacuum side of the mould as the form tooling opens, commonly referred to as air-eject, to break the vacuum and assist the formed parts off of, or out of, the mould.

The sheet containing the formed parts then indexes into a trim station on the same machine, where a die cuts the parts from the remaining sheet web, or indexes into a separate trim press where the formed parts are trimmed. The sheet web remaining after the formed parts are trimmed is typically wound onto a take-up reel or fed into an inline granulator for recycling. In most cases, scrap and waste plastic from the thermoforming process is disposed of either by compressing in a baling machine or by feeding into a granulator (grinder) and producing ground flake, for sale to reprocessing companies or re-use in their own facility. Frequently, scrap and waste plastic from the thermoforming process is converted back into extruded sheet for forming again.

Figure 8 is a schematic diagram 191 which shows a thermoforming process in accordance with the present invention. The sheet material to be thermoformed is stored on a reel 193. After the laminated material 194 has been unwound heaters 195 increase the temperature of the material to increase its malleability. The sheet material 194 passes through a stamp 197 which shapes the laminate 194 to form a tray shape. Next the tray excess is trimmed from the trays 99 and sent to the recycled and the trays are stacked 201.

Figure 9 shows a typical laminate structure 151. In general there is a top web or film 153 upon which ink 155 has been printed. An adhesive 157 bonds a backing web or film to the ink 55 and top. Figure 10 shows an example of a tray 161 in accordance with the present invention which has orange 163, blue 165, yellow 167 and green print 169 visible at the outside of the tray. Improvements and modifications may be incorporated herein without deviating from the scope of the invention.