HK1113729A - Metallized cutlery and tableware - Google Patents

Description

Metallized cutlery

RELATED APPLICATIONS

The application is a divisional application of an invention patent application with the invention name of metallized cutlery, the international application date of 26/8/2002, the international application number of PCT/US02/27232, the national phase date of 2004-4/21, and the national application number of 02820864.1.

Technical Field

The present invention relates generally to the production of food service items for use in homes, fast food restaurants and restaurants, including commercial and institutional food items. More particularly, the present invention relates to plastic cutlery having a metallic appearance.

Background

Disposable plastic food service items are increasingly being used for storage, packaging and consumption of food products due to their reasonably low cost and the convenience they provide. Disposable food containers and articles range from non-returnable containers, such as yogurt cups and dinner service packaging, to storage containers for microwave ovens and common cutlery items, such as plastic plates, cups and cutlery. The increasing popularity of fast food chain stores further accelerates the demand for plastic tableware. In addition to fast food restaurants, catering operators also prefer disposable food service items because of the convenience, hygiene and competitive costs associated with disposable food service items. In this regard, it is important that the cost of replacement of disposable implements such as cutlery be balanced against the cost of cleaning (labor, materials and equipment) associated with metal cutlery.

The presence of non-disposable metal cutlery along with other disposable food items such as plates, cups and the like presents unusual problems for restaurants and catering operators. The problem arises from the waste of expensive metal cutlery that is thrown into trash and refuse containers along with disposable tableware and leftovers. This problem is further exacerbated during peak hours of operation, as the pressure of time further causes the food in the pan to be discarded along with the knife and fork or forks. Previous approaches to this problem are well known. U.S. patent No.4,632,253 discloses an apparatus for separating cutlery from restaurant waste, including a waste chute and inductive-type detector with associated evaluation logic that will issue an electronic switching signal when a cutlery item passes through the chute.

Another problem encountered by food service providers is the ability to clean metal flatware in certain locations and outdoor catering situations. To address this situation, catering operators tend to carry a large number of high-value metal cutlery. In such catering situations, the use of disposable plastic cutlery would eliminate the limitations of cleaning metal flatware, handling heavy metal cutlery, or maintaining a large inventory. In addition, it is noted that disposable cutlery has significant handling advantages over its corresponding metal article. For example, a typical set of cutlery comprising a fork, a knife, a spoon and a teaspoon weighs about 200 grams for metal cutlery and about 30 grams for premium plastic cutlery. Such a weight assumes a 250 person scenario, where the total weight of a metal cutlery item amounts to 110 pounds, while the weight of a plastic cutlery item amounts to only 16 pounds.

Due to the historical terrorist attack and potential threat of misusing stainless steel tableware as weapons in airplanes, most airlines are increasingly moving towards the use of disposable plastic cutlery when providing food during flight. However, the use of disposable plastic cutlery affects the image of airlines, particularly in premium class and higher priced flights.

Most advanced catering operating companies use disposable plastic cups, plates, bowls, etc. for catering functions. However, people generally prefer to continue to use conventional metal cutlery. The main reason is that plastic cutlery lacks the classic look, feel and image of stainless steel tableware. Although stainless steel cutlery is stronger than plastic cutlery, which is heavier in weight, is functionally suitable for most applications. Thus, the primary obstacle to the use of disposable cutlery in such catering situations is the feel and appearance associated with disposable cutlery, rather than its performance.

From the foregoing, it can be readily appreciated that there is a need for a eating utensil that provides the disposability of a plastic cutlery item, as well as the superior feel of a stainless steel cutlery item. In this way, a metallic appearance is provided to the disposable plastic cutlery which will enhance the sensory value and quality of the cutlery. The metallic appearance also makes disposable cutlery more acceptable because of the value of replacing metal cutlery used by catering operators and other food service companies in a variety of situations and situations.

This applies, albeit to a lesser extent, to other cutlery, such as cups and plates. The use of a metallic appearance, such as gold or silver, on the disc and cup, together with the cutlery, will enhance the aesthetics and give a more respectful feel. For the reasons discussed herein, the current state of the art is essentially incapable of providing metallized cups and trays. Thus, while the description herein focuses on cutlery, this information is applicable to other cutlery.

Various methods of providing a metallic appearance have been used in the prior art. One of the most common and inexpensive methods of providing a metallic appearance to plastic articles is to incorporate metallic pigments into the plastic resin during the molding process. Generally, metallic pigments have a high metal content. There are a number of pigment and masterbatch colorant manufacturers that make and market metallic pigment additives and colorants, such as Clariant, Engelhard, and EMIndustries. Other common methods of enhancing the visual effect and commercial attractiveness of plastic articles include finishing or painting portions of the article or the entire article. Many methods of decorating plastic articles are known, including printing, hot stamping, heat transfer, in-mold decoration, painting, and electroplating. The Printing process has been further classified into screen Printing, gravure or offset Printing, and pad transfer (see Hilestad, K., Decorting and Printing, Modern plastics encyclopedia 1999, F-7).

The experience of the inventors of the present invention and those of ordinary skill in the art has been that conventional decorative and plastic color processes do not provide a commercially acceptable appearance to plastic cutlery for a variety of reasons.

First, it is a fundamental experience of those skilled in the art that these metallic pigments provide some gloss to the plastic surface but do not achieve a good polished metallic appearance of the cutlery item, and that certain metallic pigment formulations have undesirable off-flavors that are undesirable for food service items.

Second, metallic paint does not achieve the true appearance of polished stainless steel flatware.

Third, environmental and food contact issues associated with cutlery further limit the use of metallic paints and carrier solvents to provide a metallic appearance.

Fourth, good stainless steel flatware is often characterized by its elegant design, particularly on the handle of a cutlery item. Consistent with the objects of the present invention, providing plastic cutlery that is practically indistinguishable from fine metal cutlery, there is a need to make designs that tend to be substantially identical to conventional flatware for commercial acceptance. This presents a particular problem for in-mold labels (in-mold) where the label is strategically placed in the mold prior to molding and where the hot plastic entering the mold affects the adhesion of the label to the molded part. The delicate and elegant design provided on the surface of the plastic cutlery interferes with the attachment of the label and causes the label to crumple in areas containing fine design details.

Fifth, hot stamping, particularly metal foil stamping, when strategically placed on a plastic surface, provides a realistic metal appearance. However, hot foil stamping suffers from the same problems as described above for in-mold labels, where wrinkling of the foil and inconsistent adhesion of fine detail areas limit the use of foil stamping processes to achieve metallic looking cutlery.

Sixth, the use of electroplating methods is undesirable due to the environmental impact associated with electroplating chemistries that are known in the art.

Various metallization processes are known, including U.S. Pat. No.5,022,554, which describes metallized tableware made of a paper substrate, such as a dish, cup, etc., a metallized plastic film bonded to the substrate, and an FDA approved top coat of plastic film. This method of obtaining a metallic-looking food service item by laminating metallized films cannot be easily applied to cutlery because most plastic cutlery is typically produced by an injection molding process in which the feedstock is thermoplastic resin pellets rather than laminated films. The disadvantages of incorporating a metal foil or label during injection molding of a plastic cutlery item have been described above. Similar disadvantages also exist in the application of laminated metal films.

Other metallization methods, such as those used by Quest et al (U.S. patent nos. 5,177,124 and 5,280,052), describe utilitarian and/or decorative purposes, as well as methods of forming plastic articles having a metallic outer surface, appearance and handle. In this method, a mixture of a liquid monomer, a curing agent, a dispersion of metal particles and floatable particles is poured into a mould. The mold is then centrifuged to cause the metal particles to migrate toward the surface of the part before the monomer polymerizes and hardens to bond the particles. After removal from the mold, the outer surface of the part is polished and buffed to remove the plastic skin from the metal surface, thereby allowing the resulting plastic part to simulate the appearance of an actual metal part. This method is very cumbersome to apply to plastic cutlery because most plastic cutlery is made of polystyrene and/or polypropylene, which are thermoplastic polymer materials, rather than the monomers suggested in the above technical philosophy. In addition, the typical process for producing cutlery is injection molding, and rotating heavy injection molds is difficult and costly if not impossible. Also, the final secondary step of cleaning and polishing the plastic article is expensive and unacceptable for use in food service applications.

There are many references to plating on plastics by chemical deposition processes, electrodeposition processes, and/or a combination of both. U.S. patents 3,607,350, 3,629,922, 3,896,252, 3,962,494, 4,4,610,895, 3,445,350, 4,039,714, 4,073,743, 4,195,117, 4,810,333 and a host of other documents describe some methods of plating. These processes are essentially wet processes requiring the parts to be contacted with a solution containing metal ions, followed by a rinse to remove any residual chemicals, and for food service utensils this is true for basic hygiene reasons. These processes are quite unattractive for metallization of cutlery because of the high process and environmental costs.

Thus, it can be readily seen that there is a need for an elegant plastic cutlery item with enhanced visual and commercial appeal. The improved plastic cutlery should be inexpensive, allow for simple disposal and not require separation from food waste. This invention is generally practiced without the environmental disadvantages associated with wet metallization processes. The improved plastic cutlery should be made primarily of plastic with a true metallic appearance on its outer surface, and thus virtually visually indistinguishable from elaborate metal cutlery.

Disclosure of Invention

The present invention has been made keeping in mind the above problems occurring in the prior art described herein. It is therefore a primary object of the present invention to provide cutlery that addresses the problems described herein. It is an object of the present invention to provide high-end disposable cutlery, primarily made of plastic and having a metallic surface appearance that simulates real metal tableware.

It is another object of the present invention to provide a method by which plastic cutlery having a realistic metallic appearance can be mass produced for single use at a reasonable cost.

It is a further object of the present invention to provide a method of metallizing injection molded plastic cutlery at a reasonably increased cost.

It is yet another object of the present invention to provide disposable cutlery having the appearance of elaborate metal cutlery.

It is a further object of the present invention to obtain plastic articles, such as cutlery, which are shaped from a light-transmitting thermoplastic material and subsequently metallized.

It is a further object of the present invention to provide a plastic article, such as cutlery, which is formed from a light transmitting thermoplastic material, metallized on only one side.

It is a further object of the present invention to provide cutlery items having surface geometries that enhance the light reflecting appearance of metallized plastic cutlery items. The cutlery item surface geometry obtained in accordance with the present invention is characterized by a plurality of surface features, including concave and convex regions, ribs, flutes and other artistic features, that enhance the retroreflective appearance of the article.

It is a further object of the present invention to provide metallized plastic cutlery items in which the metal layer has enhanced adhesion and wear resistance, for example, by applying a surface coating to the thin metal layer to further enhance the wear characteristics of the metal layer. FDA approved surface coating compositions are readily available from a number of vendors.

In addition, it is another object of the present invention to provide metallized cutlery items in which optical density is enhanced by incorporating a color tone, such as a gray tone, into the base stock.

One object of the present invention is a metallized plastic food service item comprising: plastic tableware having a thin metal coating deposited on the plastic tableware, wherein the thin metal coating is deposited by a vacuum deposition process. Cutlery includes cutlery such as forks, spoons, knives, and other cutlery such as plates, bowls, and cups.

Still another object is a metallized plastic food service item wherein the thin metal coating comprises a metal selected from the group consisting of: silver, steel, stainless steel, chromium, aluminum, copper, and gold. The thin metal coating is typically less than 1000 nm. In addition, the dishware may also include a curable clear coating on the thin metal coating. Alternatively, the plastic tableware article may have a metal coating deposited on a single surface of the plastic tableware article.

Another object is a metallized plastic food service item wherein the plastic tableware article is made of polystyrene and is made by injection molding. The cutlery may also be made of a similar light-transmitting plastic. And wherein the metallized plastic food service item has an optical density of less than 2.0.

One object of the present invention is to metallize a plastic food service item by a process comprising the steps of: plastic tableware bodies are manufactured by injection molding, the plastic bodies are placed in a vacuum metallization system, and a thin metal coating is deposited on the plastic bodies by a vacuum deposition process. In one embodiment, the vacuum deposition process is physical vapor deposition, particularly sputter vapor deposition, wherein the sputter deposition process uses a plasma generated from a mixture of argon and nitrogen.

Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein we illustrate and describe only a preferred embodiment of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the spirit of the present invention.

Drawings

The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, and like reference numerals designate like structural elements. In the drawings:

FIG. 1A is an oblique view of a fork having a metal coating made in accordance with the present invention;

FIG. 1B is a side profile view of a fork having a metal coating;

FIG. 2A is an oblique view of a spoon according to the present invention having a metal coating;

FIG. 2B is a side profile view of a spoon with a metal coating according to the present invention;

FIG. 3A is an oblique view of a knife having a metal coating in accordance with the present invention;

FIG. 3A is a side profile view of a knife having a metal coating in accordance with the present invention;

FIG. 4 is a cross-sectional view of an exemplary cutlery item according to the present invention showing the metal coating.

Detailed Description

The terms knife and fork or knife and fork article or implement or eating utensil or food service item or food processing utensil or food serving implement as used in this specification or in any claim are used in a generic and broad sense. These terms include disposable plastic cutlery shaped into standard food processing utensils, such as forks, spoons, knives, kitchen utensils and/or combinations thereof, including spatulas, spork (spork), ladle, seafood forks, seafood picks (pick), spoons, and the like. Companion items, such as napkin rings, candle holders and center adornments, are sometimes designed to mate with cutlery. Finally, various goblets, glasses, soup bowls, dishes, plates, champagne wineglasses, lids and similar items, sometimes matched with other eating utensils, are within the scope of the invention. The preferred embodiments are merely illustrative of the techniques of this invention and many other variations and applications are possible within the scope of this invention.

Disposable cutlery items sold in supermarkets are typically made of polystyrene and/or polypropylene. However, it will be apparent to those skilled in the art that a variety of thermoplastic polymer types and/or resins can also be used to make the cutlery items of the present invention. The choice of materials for these applications is often governed by a number of factors, including consumer preference, cost, engineering requirements, practicality, and other economic and marketing factors. The main selection criteria for the substrate of the present invention are: high attractive appearance of the cutlery, high optical properties in terms of light transmission properties, high rigidity, and high surface energy or adhesion properties for metallization.

Several thermoplastic resins having desirable optical and functional properties, including Polystyrene (PS), Polymethylmethacrylate (PMMA), acrylonitrile-butadiene-styrene (ABS), styrene-acrylonitrile (SAN), and Polycarbonate (PC), may be used to achieve the objectives of the present invention. Polystyrene (PS) is the material of choice in the preferred embodiment of the present invention for several reasons. Polystyrene resins have a lower cost than ABS, PC and SAN. It is a fundamental experience of those skilled in the art that polystyrene cutlery is considered to be the higher grade disposable cutlery in the market. One criterion for selecting crystalline polystyrene as the material of choice for the present application is a higher flexural modulus compared to other resin materials in the same price range. More specifically, polystyrene has a flexural modulus exceeding that of polypropylene. Crystalline polystyrene has excellent light transmission characteristics because it has an amorphous polymer structure as opposed to polypropylene, which is highly crystalline in nature. In addition, varying cooling rates, such as those encountered during injection molding, have little effect on the light transmission characteristics of the molded article because polystyrene is an amorphous polymer structure. In other words, the crystalline polystyrene has a large process window in terms of its optical characteristics. And polystyrene has a higher surface energy than polypropylene and other polyolefins and is a better substrate for adhesion to other materials.

Thus, in the most preferred embodiment of the invention, the cutlery items are formed from a suitable crystalline polystyrene resin which has good physical properties and desirable flow, melt viscosity and forming characteristics from a manufacturing and fabrication standpoint.

Referring now to fig. 1A, 1B, 2A, 2B, 3A and 3B, there is shown a typical cutlery item made in accordance with the present invention, wherein like parts are designated by like reference numerals.

Fig. 1A shows an isometric perspective view of a fork, which is designated therein by reference numeral 10 and has a basic structure according to the invention. Fork 10 has a tine section 11 and a handle section 12. Fork 10 also has a grooved or other geometrically elegant contoured surface feature, generally indicated by reference numeral 13. A surface coating of metal is deposited on at least one surface of the plastic fork to create the appearance of a metal cutlery item. In the most preferred embodiment of the invention, the metal coating is applied on the side facing upwards, which is typically placed at meals. The metal coating on the plastic surface of the fork is indicated by reference numeral 14.

FIG. 1B shows a side view of fork 10, wherein various parts of the fork are identical to corresponding parts of FIG. 1A indicated by reference numerals. The metal coating is applied only to the upper surface of the plastic fork and is designated by reference numeral 14.

Referring now to fig. 2A, there is shown an isometric perspective view of a spoon, generally indicated at 20, having a basic construction in accordance with the present invention. Likewise, fig. 2B shows a side view of scoop 20, wherein like reference numerals represent like parts or features. The scoop 20 has a bowl-shaped portion 21 and a handle portion 22. Spoon 20 also has a grooved or other geometrically elegant contoured surface feature, generally indicated by reference numeral 23. A surface coating of metal is deposited on at least one surface of the plastic fork to create the appearance of a metal cutlery item. In the most preferred embodiment of the invention, the metal coating is applied on the side facing upwards, which is typically placed at meals. The metal coating on the plastic surface of the spoon is indicated by reference numeral 24.

Fig. 3A and 3B show an oblique view and a side view, respectively, of a knife, indicated in the figures with the reference number 30, having a basic structure according to the invention. The knife 30 has a blade portion 31 and a handle portion 32. The knife 30 also has a grooved or other geometrically elegant contoured surface feature, generally indicated by reference numeral 33. A surface coating of metal is deposited on at least one surface of the plastic fork to create the appearance of a metal cutlery item. In the most preferred embodiment of the invention, the metal coating is applied to only one side of the knife. The metal coating on the plastic surface of the knife is indicated by reference numeral 34.

Referring now to FIG. 4, a rear cross-section of a typical cutlery item 40 is shown. The stem portion of the fork 40 is indicated by reference numeral 42. In the illustrated embodiment, the stem 42 has various curved and grooved features on its surface, indicated by reference numeral 43. The cutlery item has a metal coating on one of its surfaces, indicated by reference numeral 44 in cross-section. The metal coating 44 is very thin (not shown to scale) compared to the entire dish and conforms to the contour shape on this portion of the surface. The thickness of the metal coating may vary depending on the particular application, but a thin layer is preferred in view of weight, cost and manufacturing time. For example, in a preferred embodiment, the thickness is about 200nm or less. Various patterns and ornamental features may decorate the stem, as is known to those of ordinary skill in the art, and the present invention is applicable to any such design.

The cutlery items of fig. 1A to 3A are shown as having particular structural and specific design feature ratios, for example, the ratio of the length of the tines of the fork to the overall fork length, the ratio of the length of the bowl portion of the spoon to the overall spoon length, and the ratio of the length of the blade edge of the knife to the overall knife length. Those of ordinary skill in the art will readily appreciate that these cutlery items are manufactured and sold in a variety of geometries, feature ratios, and sizes. The physical structures, design features and aspect ratios given herein are for illustrative purposes and are not meant to be limiting.

Furthermore, it is readily understood that depositing a metal layer on only one side of the article, as opposed to coating the entire article, yields several economic advantages. First, metal material is saved and only about half of the surface area is metallized. Secondly, there is only one passage through the metallization device and the part is not subjected to two deposition processes to deposit on both sides. Third, the metallization cycle-time is halved, since this requires half as long to deposit metal on only one side of the article. Finally, this process provides simpler article handling, as complex article handling mechanisms for rotating/flipping the article when two-sided metallization is avoided.

From an aesthetic standpoint, the metallized coating is applied to the side that is generally facing upward in a conventional table top layout for cutlery. The conventional arrangement typically includes the tines of the fork facing upward, the concave bowl of the spoon facing upward, the serrated edge of the knife facing to the left and away from the user, and the handle portion of all cutlery facing toward the user.

The metal coating on the cutlery item may be applied by any known vacuum deposition process. Vacuum metallization or deposition is the deposition of a film or coating in a vacuum or low pressure plasma environment. The term plasma generally refers to a gaseous environment rich in ions or electrons for providing significant electrical conductivity. Vacuum deposition is a term applied to processes that deposit atoms or molecules one at a time, such as Physical Vapor Deposition (PVD), or Low Pressure Chemical Vapor Deposition (LPCVD).

Typical PVD processes can be used to achieve the objectives of the present invention. In physical vapor deposition or (PVD) processes, metal particles are vaporized from a solid or liquid source and transported as a vapor in a vacuum or low pressure gaseous or plasma environment. The vaporized material may be an element, an alloy, or a compound. The agglomeration of the particles forms a thin metal coating or film on the surface of the substrate and provides the substrate with a metallic appearance. The thickness of the film ranges from a few nanometers to several thousand nanometers. However, PVD processes can be used to form thick deposits through multiple layers of coatings. Various variables of PVD processes have been described in the prior art including vacuum evaporation, sputter deposition or sputtering, arc vapor deposition and ion plating. Other evaporation techniques include hot wire evaporation, flash evaporation, and electron beam evaporation.

To ensure that a durable metal coating is deposited on the surface of the cutlery item, the resin used must be of high quality and non-volatile. Processing aids, such as mineral oils and surface waxes, conventionally added to commercial resins, flow out to the surface of the article and interfere with obtaining sufficient adhesion between the deposited metal and the surface of the article.

In a preferred embodiment of the invention:

(a) the cutlery items are made of light-transmitting grade thermoplastic polymer material. The resin is completely free of mineral oil and other volatile additives;

(b) the metal coating has the same composition as the stainless steel actually used with cutlery;

(c) the thickness of the metal coating is less than 200 nanometers;

(d) the metal coating is applied to only one side of the cutlery item;

(e) the metal coating is formed by a physical vapor deposition process.

In the most preferred embodiment of the invention, the metal coating is applied to the plastic cutlery item by vacuum sputter deposition (also known as sputter deposition or sputtering).

Sputtering is a PVD coating process that is performed in an evacuable coating or sputtering chamber. A source of coating material, i.e., a target, is placed in the sputtering chamber opposite the substrate, and the chamber is then evacuated, typically in the range of 1to 100 millitorr (1 Torr-1 mmHg), in the presence of an inert gas, such as argon. A negative DC or RF voltage is applied to a metal sputtering target (metal source) that is housed within the sputtering or coating chamber. A gas plasma or glow discharge is formed between the metal target and the article or substrate being coated. Positively charged gas ions generated in the plasma are directed at the target material (negative potential) at a high velocity, causing the neutral atomic size particles of the metal target material to be ejected. Sputtering is thus a non-thermal evaporation process in which surface atoms are physically ejected from a metal source after momentum transfer or exchange with kinetic energy bombarding particles or gas ions accelerated in a plasma. One particular advantage of sputtering techniques is the ability to deposit metals and metal alloys and is well suited for depositing the stainless steel components of conventional metal cutlery.

A useful method of making metallized plastic cutlery and other cutlery according to the present invention is as follows:

step 1: forming the plastic cutlery item using conventional injection molding processes known in the art;

step 2: the use of a part removal device to remove plastic cutlery from a mold, such as a side entry or top entry robot, is also well known in the art and is currently in use in equipment of the assignee;

and step 3: the individual cutlery items are placed in a non-abutting manner on a transfer or transport device, from where they are transferred to a vacuum deposition station. Each of the cutlery items is maintained in a separate or non-contiguous manner, preventing adjacent cutlery items from forming surface shadowing during metallization or coating;

and 4, step 4: carrying out a vacuum deposition process on the plastic knife and fork;

and 5: the plastic cutlery that has been metallized is collected and loaded into suitable packaging containers for shipping.

In testing the preferred embodiment, plastic cutlery in the form of a fork, spoon and knife was placed into a laboratory-sized sputtering chamber. Sputtering equipment is provided by Soleras, inc. The stainless steel target is installed in the sputtering chamber. The specific composition of the glass fiber reinforced plastic is 304. The chamber was then evacuated until a vacuum of 10 degrees was reached^-3About mmHg. Argon gas is introduced into the chamber to generate plasma. When the vacuum is reached, a negative voltage of 5 to 10kW is applied to the cathode. The coating operation in this apparatus lasts 1to 5 seconds. After coating, the power is turned off and the vacuum is released to raise the pressure in the chamber to atmospheric pressure. Thereafter, the parts are taken out of the chamber and inspected. Various tests were performed on the plastic cutlery to check for peel adhesion. In some tests, coatings were applied to both sides of the article. In other tests, a coating was applied to only one side of the article.

It was found that polystyrene cutlery exhibited better coating adhesion than polypropylene cutlery. A power of 7.5kW and a sputtering time of 3 seconds are considered as the best conditions for obtaining good adhesion, surface appearance and coating uniformity. The most significant discovery in the experimental work was that the coating could be applied to one side of a clean polystyrene article to achieve the desired metallic appearance or effect. This unexpected result shortens manufacturing time and complexity while achieving a 2-fold utilization of the metal target.

The thickness of the metal deposit or layer is proportional to the duration of sputtering for a given hardware device and power setting configuration. An increase in the duration of sputtering (sputtering time) leads to a corresponding increase in the thickness of the metal layer. The increase in metal layer thickness is proportional to the optical density, and thus measuring the optical density can be used to determine the thickness of the metal deposited on the surface. To obtain a metallized cutlery item, an optical density value of around 1.5 is acceptable. At an optical density value of 1, the metal layer is very thin and lacks sufficient opacity to obtain an attractive metallic appearance of the article surface. Increasing the optical density can be achieved by increasing the metal deposition or by increasing the sputtering time. Another method of increasing optical density without extending the sputtering time is to add a light-transmissive dye or tint to the substrate. Generally, gray shades are preferred, but shades of multiple colors can be used to enhance the opacity of the cutlery item and to create other appearance effects.

Tape peel tests are commonly used to detect adhesion between the surface of the cutlery item and the metal layer deposited thereon. Adhesion is also related to the wear resistance or durability of the coating. The adhesion and abrasion resistance of the metal layer deposited on the surface of the substrate can be enhanced by various methods.

One method of providing abrasion resistance is to apply a light transmissive thermal or UV curable coating on the cutlery item for sealing the deposited metal layer. The composition of such coatings is well known in the art and is often used to provide a barrier top coating on a variety of articles, including CDs and DVDs. An FDA approved, curable, clear coating, which can be applied by spraying, can also be easily applied to food service items.

Another method of improving wear resistance is to subject the cutlery items to flame or corona treatment to increase the surface energy of the cutlery items. Surface treatments to increase the surface energy of plastic articles are also well known in the art. Typical corona treatment increases the surface energy of polystyrene from 35 dynes to 46 dynes.

The adhesion between the substrate or plastic and the deposited metal layer can be enhanced by a non-volatile resin completely free of mineral oil and the same lubricant.

Another technique for improving the adhesion of a metal coating to an article is to use a mixed gas of argon and nitrogen to generate a plasma in a sputtering chamber during the metal deposition process. In a mixed gas of nitrogen and argon, the nitrogen is generally present in a concentration of between 10% and 40%. The metal layer produced by sputter deposition using a mixed gas of nitrogen and argon has improved durability compared to an argon plasma alone.

Food items can affect the coating or cause it to peel off, and in order to confirm that the coated cutlery can be used with a variety of food items, validation tests were performed on cutlery in different food environments. The tests involved subjecting the cutlery to boiling water, boiling ketchup, boiling water-vinegar mixtures, lemon juice, coffee, ice, thermal cycles with alternate insertion of boiling and ice-water, transport of large batches of cutlery across countries, etc. It must be noted that coated cutlery, like any metal cutlery, is susceptible to scratching by abrasion.

While the invention has been described with particular reference to metallized plastic cutlery, it should be appreciated that the invention may be applied to common food service items, tableware and other industries where a metal coating is required on plastic and non-plastic parts. Moreover, those skilled in the art should appreciate that various modifications, substitutions and adaptations can be made without departing from the spirit and scope of the invention.

The many features and advantages of the invention are set forth in the above description, together with details of the structure and function, some of which are novel and are set forth in the appended claims. The disclosure herein, however, is for the purpose of illustration only and various changes in arrangement and detail may be made therein without departing from the principles of the invention, the broad general meaning of the terms in which the claims are expressed.

The objects and advantages of the invention may be further realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.

Claims (47)

1. A metallized plastic food service item comprising:

plastic cutlery having a display surface and an underside, said plastic cutlery being adapted to be placed on a table top with the underside facing downwardly towards the table top and the display surface facing upwardly when a conventional set of cutlery is present; and

a thin metal coating deposited on said plastic tableware, wherein said thin metal coating is of a nature suitable for contacting food without the need for an outer coating and has a thickness sufficient to provide the plastic tableware with a reflective metal-like appearance to simulate real metal tableware, said thickness being less than 2000 nanometers, and wherein said thin metal coating is deposited by a vacuum deposition process.

2. The metallized plastic food service item according to claim 1, wherein said thin metal coating is at least one metal selected from the group consisting of: silver, steel, stainless steel, gold, and alloys thereof.

3. The metallized plastic food service item according to claim 1, wherein said thin metal coating has a thickness of less than 1000 nanometers.

4. The metallized plastic food service item according to claim 1, further comprising a thin outer coating of a hardenable transparent coating on said thin metal coating.

5. The metallized plastic food service item according to claim 1, wherein said plastic tableware article is an article for handling and eating food selected from the group consisting of: a fork, a knife and a spoon.

6. The metallized plastic food service item according to claim 1, wherein said plastic tableware article is made of a light-transmitting plastic.

7. The metallized plastic food service item according to claim 1, wherein said plastic tableware article is made of polystyrene.

8. The metallized plastic food service item according to claim 1, wherein said plastic tableware article is obtained from a plastic resin composition which is completely free of mineral oil and wax.

9. The metallized plastic food service item according to claim 1, wherein said metallized plastic food service item has an optical density of less than 2.0.

10. The metallized plastic food service item according to claim 1, wherein said plastic tableware article is produced by injection molding.

11. The metallized plastic food service item according to claim 1, further comprising decorative surface features for enhancing the reflective metal-like appearance of said plastic tableware article.

12. The metallized plastic food service item according to claim 1, wherein said vacuum deposition process is a sputter deposition process.

13. A metallized plastic food service item comprising:

plastic cutlery having a display surface and an underside, said plastic cutlery being adapted to be placed on a table top with the underside facing downwardly towards the table top and the display surface facing upwardly when a conventional set of cutlery is present; and

a thin metal coating deposited on the display surface of the plastic tableware, wherein the thin metal coating has a thickness sufficient to provide the plastic tableware with a reflective metal-like appearance, the thickness being less than several thousand nanometers, and wherein the thin metal coating is deposited by a vacuum deposition process; and wherein at least a portion of the underlying surface is free of the thin metal coating.

14. The metallized plastic food service item according to claim 13, wherein said thin metal coating is at least one metal selected from the group consisting of: silver, steel, stainless steel, chromium, aluminum, copper, and gold.

15. The metallized plastic food service item according to claim 13, wherein said thin metal coating has a thickness of less than 1000 nanometers.

16. The metallized plastic food service item according to claim 13, further comprising a thin outer coating of a hardenable transparent coating on said thin metal coating.

17. The metallized plastic food service item according to claim 13, wherein said plastic tableware article is an article for handling and eating food selected from the group consisting of: a fork, a knife and a spoon.

18. The metallized plastic food service item according to claim 13, wherein said plastic tableware article is made of a light-transmitting plastic.

19. The metallized plastic food service item according to claim 13, wherein said plastic tableware article is made of polystyrene.

20. The metallized plastic food service item according to claim 13, wherein said metallized plastic food service item has an optical density of less than 2.0.

21. The metallized plastic food service item according to claim 13, wherein said plastic tableware article is produced by injection molding.

22. The metallized plastic food service item according to claim 13, wherein said plastic tableware article is obtained from a plastic resin composition which is completely free of mineral oil and wax.

23. The metallized plastic food service item according to claim 13, further comprising decorative surface features for enhancing the reflective metal-like appearance of said plastic tableware article.

24. The metallized plastic food service item according to claim 13, wherein said vacuum deposition process is a sputter deposition process.

25. A utensil for treating and eating food comprising a light transmitting plastic and having a plurality of surfaces, wherein at least one of said plurality of surfaces is decoratively enhanced by a thin metal layer, said thin metal layer being deposited by a sputter deposition process thereby providing a light reflective metal-like appearance to at least a portion of said utensil, and said layer of said portion being less than 2000 nanometers.

26. A metallized plastic food service item made by a process comprising the steps of:

forming a plastic tableware article by an injection molding process, wherein the plastic tableware article has a first surface and a second surface;

placing the plastic tableware in a vacuum metallization unit with the first surface facing the vacuum metallization unit;

depositing a thin metal coating on the first surface of the plastic tableware article by a vacuum deposition process, the coating having a thickness sufficient to provide the plastic tableware article with a light reflective metal-like appearance, wherein the thickness is less than several thousand nanometers, and wherein the thin metal coating is at least one metal selected from the group consisting of: steel, stainless steel, gold, silver and alloys thereof.

27. The metallized plastic food service item produced by the process according to claim 26, further comprising the step of spraying a clear coat layer and hardening said clear coat layer.

28. The metallized plastic food service item produced by the process according to claim 26, wherein said vacuum deposition process is physical vapor deposition.

29. The metallized plastic food service item produced by the process according to claim 26, wherein said physical vapor deposition is sputter vapor deposition.

30. The metallized plastic food service item produced by the process according to claim 29, wherein said sputter deposition process uses a plasma generated from a mixed gas of argon and nitrogen.

31. The metallized plastic food service item produced by the process of claim 26, wherein said thin metal coating is a stainless steel alloy.

32. The metallized plastic food service item produced by the process according to claim 26, wherein said plastic tableware article is formed of a light transmitting plastic having a color tint.

33. The metallized plastic food service item produced by the process of claim 26, wherein said thin metal coating has a thickness of less than 1000 nanometers.

34. The metallized plastic food service item according to claim 1, wherein said thin metal coating has a thickness of less than 500 nanometers.

35. The metallized plastic food service item according to claim 1, wherein said thin metal coating has a thickness of less than 200 nanometers.

36. The metallized plastic food service item according to claim 13, wherein said thin metal coating has a thickness of less than 500 nanometers.

37. The metallized plastic food service item according to claim 13, wherein said thin metal coating has a thickness of less than 200 nanometers.

38. A metallized plastic food service item comprising:

plastic cutlery having a display surface and an underside, said plastic cutlery being adapted to be placed on a table top with the underside facing downwardly towards the table top and the display surface facing upwardly when a conventional set of cutlery is present; and

a thin metal coating without an outer coating deposited on at least a portion of the plastic tableware, wherein the thin metal coating has a thickness sufficient to provide the plastic tableware with a reflective metal-like appearance, the thickness being less than 1000 nanometers, and wherein the thin metal coating is deposited by a vacuum deposition process.

39. The metallized plastic food service item according to claim 38, wherein said thin metal coating is at least one metal selected from the group consisting of: silver, steel, stainless steel, and gold.

40. A metallized plastic food service item comprising:

plastic cutlery consisting essentially of polystyrene polymer and having a display surface and an underside, said plastic cutlery being adapted to be placed on a table top with said underside facing downwardly toward said table top and said display surface facing upwardly when a conventional set of cutlery is present; and

a thin metal coating having no outer coating deposited on said plastic tableware, wherein said thin metal coating has a sufficient thickness to provide the plastic tableware with a reflective metal-like appearance, said thickness being less than 2000 nanometers, and wherein said thin metal coating is deposited by a vacuum deposition process.

41. The metallized plastic food service item according to claim 40, wherein said thin metal coating is stainless steel.

42. The metallized plastic food service item according to claim 40, wherein said plastic tableware article is an article for handling and eating food selected from the group consisting of: a fork, a knife and a spoon.

43. A metallized plastic food service item comprising:

plastic cutlery having a display surface and an underside, said plastic cutlery being adapted to be placed on a table top with the underside facing downwardly towards the table top and the display surface facing upwardly when a conventional set of cutlery is present; and

a thin metal coating deposited on the plastic tableware by a vacuum deposition process, wherein the thin metal coating has a sufficient thickness to provide the plastic tableware with a reflective metal-like appearance, the thickness being less than 2000 nanometers, and wherein the thin metal coating comprises at least one metal selected from the group consisting of: silver, steel, stainless steel, gold, and alloys thereof.

44. The metallized plastic food service item according to claim 43, wherein substantially all of said plastic tableware article is coated with said thin metal coating.

45. A metallized plastic food service item comprising:

plastic cutlery having a display surface and an underside, said plastic cutlery being adapted to be placed on a table top with the underside facing downwardly towards the table top and the display surface facing upwardly when a conventional set of cutlery is present; and

a thin metal coating deposited on the plastic tableware by a vacuum deposition process, wherein the thin metal coating has a thickness sufficient to provide the plastic tableware with a reflective metal-like appearance, the thickness being less than 2000 nanometers, and wherein the thin metal coating is stainless steel.

46. The metallized plastic food service item according to claim 45, wherein said thin metal coating is deposited on only a portion of said plastic tableware article.

47. The metallized plastic food service item according to claim 45, wherein said plastic tableware article is at least one selected from the group consisting of: a fork, a knife and a spoon.