TECHNICAL FIELD

The present invention relates to taggants bearing data such as microscopic visual indicia, otherwise known as microdots, and more particularly to anodised metallic microdots.

BACKGROUND

Microdots and other taggants or identification devices are commonly attached, to or incorporated within items of value in order to identify ownership or origin and to hinder theft, diversion, or illegal use of such items. Typical examples of such items include, but are not limited to, motor vehicles, motorcycles, machinery, equipment, branded products, spirits, high-value consumer goods, documents, storage media, and financial and other instruments.

For at least the last sixty years, exceedingly small photographic reproductions have been employed to confidentially communicate sensitive information. In such techniques, letter-sized documents have, for example, been copied onto a "microdot" no larger than a typewritten period. Such microdots may be physically hidden as periods in written or typewritten communications. The data borne by the microdot may be read by observing the microdot using a suitable microscope or other optical magnification means. Such microdots are typically circular with a diameter of approximately 1 millimetre and a thickness of a fraction of a millimetre, Microdots of the type referred to above t pically have fiat surfaces bearing repetiti ve identifying indicia, such as numeric and alpha-numeric characters, which can be visually interpreted or retrieved under magnification. The indicia, whose smallest features (e.g., the middle stroke on a capital "E" character) are typically 2-5 micrometres in size, may provide part or all of a code that uniquely identifies the object to which a microdot is attached. On accoun t of being exceedingly small, such microdots are generally not readily apparent to the naked human eye when attached to an item of value. Multiple microdots may be attached at different locations on the item, thus making complete remo val of the microdots effectivel y impossible and thereby hindering attempts to hide the ownership or origi of the item. Microdots have been manufactured from various materials including polyester, ceramics, and metal substrates such as nickel and stainless steel. Metallic microdots have the distinct advantage of being relatively more durable and capable of withstanding adverse conditions such as weather, heat, direct sunlight, chemical exposure, and exposure to abrasion.

Traditional methods of manufacturing metallic microdots mcorporating variable and fixed data include:

* embossing a patter (e.g., a diffraetive pattern or a hologram) onto a surface of the microdot using a master i mpression ;

* laser ablating, discolouring and/or melting a surface of the microdot using a lase scribe and/or a mask; and

* creating a hole through the microdot (e.g., in the form of an alphanumeric character) using electroplating and or photochemical machining. in practice however, existing metal microdot manufacturing methods sutler from the following major disadvantages:

* High capita! and labour costs. For example, the electroplating and etching methods mentioned above are performed manually or by hand and are only viable in exceedingly low labour cost countries. Even then, production is slow and cannot easily be scaled. Furthermore, laser based systems involve exceedingly high capital and running costs; and

* Severe limitations regarding the amount of data that can be encoded on a microdot of practical size. Metallic microdots created by electroplating or photochemical machining methods have a practical character limit of six characters for a 1 mm diameter dot. This practical limitation in existing metal microdots represents a trade-off between microdot size and data capacity which, for example, precludes the use of such microdots in automotive applications where standard Vehicle identification Numbers (VlNs) are used fo identification purposes. VINs typically require 2-3 times the data capacity of existing 1mm metal dots. In addition, a data capacity of six unique numbers considerably limits the number of unique dots sets that can be created, m order to overcome this fundamental limitation manufacturers of these types of metal dots have resorted to adding background information, typically in the form of holograms and images adorned with diffractive elements; this process ensures that every client can have a unique logo or other background indicia, which is then allied with the six characters of penetrative variable data. The problem with this approach however is that the use of such background images typically requires the use of an e-beam to create the required shim; the process adds weeks to the production lead time and costs thousands of dollars for each new origination.

A need therefore exists for alternative and/or improved methods that are suitable for mass production of metal microdots.

Another need exists for methods of manufacturing metal microdots that are capable of holding relatively larger amounts of variable and/or fixed data.

Another need exists for new and improved methods for mamiiacturing metallic microdots in real-time, thus obviating the need for extended lead times.

Yet another need exists for methods of manufacturing metallic microdots that are capable of encoding data at high spatial densities such that Vehicle Identification Numbers (VINs) and Hull Identification Numbers (HINs) can be accommodated on microdots of diameter less man 1 ,0mm. Such methods should preferably have the ability to produce variable data in colour on a surface of a metallic microdot (e.g., to enable reproduction of client logos on a metallic microdot).

SUMMARY

An aspect of the present invention provides a method for manufacturing metallic microdots from a metallic substrate. The method comprises the steps of: anodising the metallic substrate; applying selected data to the metallic substrate at regular intervals; and separating a plurality of microdots from the metallic substrate. Each of the microdots comprises a portion of the metallic substrate having the selected data applied thereto.

The method may comprise the further steps of: applying a layer of photo sensitive material to one or more surfaces of the metallic substrate after anodising the metallic substrate; wherein the selected data is applied to the layer of photo sensitive material.

The selected data may be applied using imaging, laser scanning or direct light printing. The selected data may he applied to one or more anodised surfaces of the metallic substrate.

The step of applying selected data to the metallic substrate at regular intervals may comprise: generating an image mask based on the selected data; applying a layer of ^* photo sensitive material to one or more surfaces of the metallic substrate after anodising the metallic substrate; exposing the layer of photo sensitive material to light throug the image mask; and developing or fixing the exposed surfaces.

The step of applying selected data to the metallic substrate at regular intervals may comprise: applying a layer of photo sensiti ve material to one or more surfaces of the metallic substrate prior to anodising the metallic substrate; and forming a resist mask based on the selected data on the layer of photo sensitive material prior to anodising the substrate.

The largest diameter of the plurality of microdots ma be about 1mm,

The selected data may be applied to two surfaces of the substrate.

The metallic substrate may comprise aluminium.

The method may comprise titanium.

The metallic substrate may comprise metal tape of thickness approximately 0.1mm.

The metallic substrate ma comprise metal tape of width appro imately 20 mm.

The layer of photosensitive material may comprise silver halide.

The layer of photosensitive material may comprise a photoresist material,

The layer of photosensitive material may alternatively comprise a light cured coating such as a UV cured ink or paint.

The selected data may be applied to the layer of photoresist using one or more of the following: a digital archive writer (DAW); a high resolution light printer; and an ink printer.

The selected data may comprise one or more of the following: a number; a word; an alphanumeric character; a name: a batch number; a serial number; a supplier logo; an image; a barcode; and a hologram.

The method may comprise the further step of sealing the layer of photosensitive material and or photoresist with the data applied thereto.

The step of separating a plurality of microdots from the metallic substrate may comprise one or more of die following: punching the metallic substrate; slitting and chopping th metallic substrate; laser cutting the metallic substrate; and chemically etching the metallic substrate.

Another aspect of the present invention provides metallic microdots manufactured in accordance with any of the methods described above. BRIEF DESCR!PTION OF THE DRAWINGS

A limited number of embodiments of the present invention are described hereinafter with reference to the following drawings:

Fig. I is a flow diagram of a general method for manufacturin g metallic microdots from a metallic substrate in accordance with an embodiment of the present invention; and

Figs. 2 to 6 are flow diagrams of methods for .manufacturing metallic microdots in accordance with embodiments of the present invention. DETAILED DESCRIPTION

A small number of embodiments of the present invention are described hereinafter. The embodiments are illustrative in nature and are not intended to be limiting on the broadest forms or aspects of the present invention. Fig. 1 shows a flow diagram of a general method for manufacturing metallic microdots from a metallic substrate. More detailed embodiments of the method Fig. 1 are described hereinafter with reference to Figs. 2 to 5.

Referring to Fig. 1 , a metallic substrate is anodised at step 1 10.

At step 120, selected data is applied at regular intervals to the metallic substrate. The selected data may, for example, comprise one or more of the following: a number, a word., an alphanumeric character, a name, a batch number, a serial number, a supplier logo, an image, a barcode, and a hologram. The selected data may be digitally generated and/or formatted (e.g., using a computer system). Control marks may be added during generation and/or formatting to assist automated manufacturing of the microdots (i.e., downstream in the manufacturing process). Step 1 10 may be performed before or after step 120 in various ones of the embodiments described hereinafter.

At step 130, a plurality of microdots is separated from the metallic substrate. Separation of the microdots may, for example, be achieved by performing one or more of the following:

· punching the substrate;

* slitting and/or chopping the substrate:

» laser cuttin the substrate: and

* chemically etching the substrate; to produce a plurality of microdots of approximatel the same size. Each of the separated microdots comprises a portion of the metallic substrate having the selected data applied thereto.

Sets of microdots (e.g., having the same batch number and/or a sequence of serial numbers) may be automatically placed in separate receptacles or containers by way of control marks generated or located on the metallic substrate.

Fig. 2 shows a flow diagram of a method for manufacturing metallic microdots. Referring to Fig. 2, the method commences at step 210 with anodising of a metallic substrate. Anodisation of the metallic substrate provides a protective barrier to the substrate, which is nevertheless porous and thus capable of absorbing marking materials. The metallic substrate may, for example, comprise a metallic tape such as aluminium tape. Tft one particular embodiment, the metallic substrate comprises aluminium tape of 0. 1mm thickness and 20mm width. However, those skilled in the art will appreciate that numerous other metallic substrates capable of being anodised may be practiced. For example, substrates or tapes of other suitable metals and/or dimensions may be practiced.

At step 220, a layer of photosensitive material is applied to one or more surfaces of the metallic substrate anodised in step 210. The metallic substrate may be impregnated or coated with the photosensitive material. Such photosensitive material may, for example, include silver halide, photoresist, or any other suitable photosensitive material. The anodised surface is porous and exceedingly hard and the marking layer resides in the main within and below the surface of the anodised layer. It can be seen therefore that the data layer is protected by the presence of the anodised metallic substrate.

At step 230, selected data is applied at regular intervals to the layer/s of photosensitive material. The selected data may, for example, comprise one or. more of the following: a number, a word, an alphanumeric character, a name, a batch number, a serial number, a supplier logo, an image, a barcode, and a hologram. The selected data may be digitally generated and/or formatted (e.g., using a computer system) prior to being applied to the layer of photosensitive material. Control marks may be added during generation and/or fonnatting to assist automated manufacturing ^' of the microdots (i.e., downstream in the manufacturing process).

The selected data is applied to the layer/s of photosensitive material by way of imaging, laser scanning or direct light printing. This can be performed using an optical electronic device such as a digital archive writer (DAW), which is commonly used to apply images to microfilm, or a high-resolution light printer that can write directly to the photosensitive surface of the metallic substrate. An example of a suitable high-resolution light printer is the Lumejet S200. which has a feature resolution of some 3 microns, and which can be modified to image on metal rather than paper. After printing, the photosensitised .surface/s of the metallic substrate is/are developed to facilitate exposure of the selected data.

The porous, anodised metallic substrate may optionally be sealed by boiling in distilled water or another suitable solution, or fay application of a sealer. This optional step has the effect of sealing the selected data u der an effecti vely impervious layer or coating, which will protect the microdots from weathering, exposure to chemicals or other corrosive environments, and abrasion.

At step 240, a plurality of microdots is separated from the metallic substrate. Separation of the microdots may, for example, be achieved by performing one or more of the following:

« punching the substrate;

* slitting and/or chopping the substrate;

♦ laser cutting the substrate; and

• chemically etching the substrate;

to produce a plurality of microdots of approximately the same size. Each of the separated microdots comprises a portion of the metallic substrate having the selected data applied thereto. Sets of microdots (e.g., having the same batch number and/or a sequence of serial numbers) may be automatically placed in separate receptacles or containers.

Fig. 3 shows a flow diagram of another method for manufacturing metal lic microdots.

Referring to Fig. 3, the method commences at step 310 with anodismg of a metallic substrate. Anodisation of the metallic substrate provides a protective barrie to the substrate, which is nevertheless porous and thus capable of absorbing marking materials. The metallic substrate may, for example, comprise a metallic tape such as aluminium tape. In one particular embodiment, the metallic substrate comprises aluminium tape of 0.1mm thickness and 20mm width. However, those skilled in the art will appreciate that numerous other metallic substrates capable of being anodised may be practiced. For example, substrates or tapes of other suitable metals and or dimensions may be practiced.

At step 320, selected data is applied at regular intervals to one or more surfaces of the anodised metallic substrate. The selected data may, for example, comprise one or more of the following: a number, a word, an alphanumeric character, a name, a batch number, a serial number, a supplier logo, an image, a barcode, and a hologram. The selected data may be digitally generated and/or formatted (e.g., using a computer system) prior to being applied to the anodised metallic substrate. Control marks may be added during generation and/or formatting to assist automated manufacturing of the microdots (i.e., downstream in the manufacturing process).

The selected data is applied by way of ink printing. This can be performed using an mkjet printer of suitable resolution. A printer with the ability to print an alphanumeric character whose length and width do not exceed 50 microns is ideal Such printers are currently under development by major printer manufacturers.

The porous, anodised metallic substrate may optionally be sealed by boiling in distilled witter or another suitable solution, or by application of a sealer. This optional step has the effect of sealing the selected data under an effectively impervious layer or coating, which will protect the microdots from weathering, exposure to chemicals or other corrosive environments, and abrasion.

At step 330, a plurality of microdots is separated from the metallic substrate. Separation of the microdots may, for example, be achieved by performing one or more of the following:

• punching the substrate;

· slitting and/of chopping the substrate;

» laser cutting the substrate; and

• chemically etching the substrate;

to produce a plurality of microdots of approximately the same size. Each of the separated microdots comprises a portion of the metallic substrate having the selected data applied thereto. Sets of microdots (e.g., having the same batch number and/or a sequence of serial numbers) may be automatically placed in separate receptacles or containers.

Fig. 4 shows a flow diagram of another method for manufacturing metallic microdots.

Referring to Fig. 4, the method commences at step 410 with anodising of a metallic substrate. Anodisation of the metallic substrate provides protective barrier to the substrate, which is nevertheless porous and thus capable of absorbing marking materials. The metallic substrate may, for example, comprise a metallic tape such as aluminium tape. In one particular embodiment, the metallic substrate comprises aluminium tape of 0.1mm thickness and 20mm width. However, those skilled in the art will appreciate that numerous other metallic substrates capable of being anodised may be practiced. For example, substrates or tapes of other suitable metals and/of dimensions may be practiced.

At step 420, a layer of photosensitive material is applied to one or more surfaces of the metal lic substrate anodised in step 410, The metal lic substrate may be impregnated or coated with the photosensitive material Such photosensitive materia! may, for example, include silver halide, photoresist, or any other suitable photosensitive material.

At step 430, an image mask is generated based on selected data. The selected data may. for example, comprise one o more of the following: a number, a word, an alphanumeric character, a name, a batch number, a serial number, a supplier logo, an image, a barcode, and a hologram. The image mask may comprise the Inverse of the selected data and is typically digitally generated using a computer system and photosensitive microfilm. Control marks may be added during mask generation to assist automated manufacturing of the microdots (i.e., downstream in the manufacturing process).

A t step 440, the selected data is applied to a portion of microfilm tape using an optical electronic device such as a digital archive writer (DAW). The portion of microfilm is preferably of the same width as the metallic substrate for convenience (alignment).

At step 450, the portion of microfilm tape is developed or fixed in the conventional manner.

At step 460, the sensitised surface/s of the anodised metallic substrate is/are exposed through the image mask generated in step 430 and the image contained in the microfilm mask is then projected onto the underlying photosensitive anodised metal, using apparatus commonly known and used to make contact exposures. Alternatively the mask image can be projected onto the photosensitive anodised metal using apparatus commonly known and used to make photographic copies, reductions and enlargements.

At step 470, the exposed surfaces s of the anodised metallic substrate are developed and fixed to facilitate visibility of the selected data.

The porous, anodised metallic substrate may optionally be sealed by boiling in distilled water or another suitable solution, or by application of a sealer. This optional step has the effect of sealing the selected data under an effectively impervious layer or coating, which will protect the microdots from weathering, exposure to chemicals or other corrosive environments, and abrasion.

At step 480, a pluralit of microdots is separated from the metallic substrate.

Separation of the microdots may, fo example, be achieved by performing one or more of the following: • punching the substrate;

^« slitting and/or chopping the substrate;

• laser cutting the substrate; and

• chemically etching the substrate ;

to produce a plurality of microdots of approximately the same size. Each of the separated microdots comprises a portion of the metallic substrate having the selected data applied thereto. Sets of microdots (e.g., having the same batch number and/or a sequence of serial numbers) may be automatically placed in separate receptacles or containers. Fig. 5 shows a flow diagram of another method for manufacturing metal lic microdots.

Referring to Fig. 5, the method commences at step 510 with applying a layer of photosensitive material to one or more surfaces of a metallic substrate. The metallic substrate may, for example, comprise a metallic tape such as titanium tape. In one particular embodiment, the metallic substrate comprises titanium tape of 0.1mm thickness and 20mm width. However, those skilled in the ait will appreciate that numerous other suitable metallic substrates ma be practiced. For example, substrates or tapes of other suitable metals and/or dimensions may be practiced such as niobium and tantalum.

At step 520, selected data is generated and/or formatted for applying to one or more surfaces of the metallic substrate. The selected data may, for example, comprise one or more of the following: a number, a word, an alphanumeric character, a name, a batch number, a serial number,, a supplier logo, an image, a barcode, and a hologram. _The selected data may be digitally generated and/or formatted (e.g., using a computer system). Control marks may be added during generation and/or formatting to assist automated manufacturing of the microdots (i.e., downstream in the manufacturing process).

At step 530, a mask is formed on one or more surfaces of the metallic substrate using either a photo-resist masking method, or by printing of a resist mask. Where photo resist methods are used, the substrate is covered with a photosensitive material and then exposed to light, thereby forming the correct data image (or inverse) on the metal substrate. The resist mask is generated based on the selected data and may comprise the inverse of the selected data.

At step 540, the masked metallic substrate is placed in an anodising tank and subjected, to a voltage to anodise the areas not covered by the resist mask. This causes a thin layer of oxide to form on the unmasked surface's of the metallic substrate. On account of being relatively transparent, the oxide layer acts as an interference filter, thereby providing a colour contrast between the selected data (metallic substrate) and the oxide layer. As those skilled in. the art will appreciate, the thickness of the oxide layer and hence the colour performance of the oxid layer is a function of the voltage used in the anodising tank. The selected data will generally exhibit pure colour that is typical of structural colour and the colour will furthermore be angle dependent. Anodisafion of the unmasked portions of the metallic substrate has the effect of creating the data in the form of a relatively impervious and highly robust oxide layer that is relatively immune to weathering, exposure to most chemicals or other corrosive environments, and abrasion.

In an alternative embodiment, step 540 may comprise the masked metallic substrate being placed in a tank of organic acid mixed with sulfuric electrolyte and subjected to a pulsed current to mark the areas not covered by the resist mask.

The resist mask may be removed after creation of the anodised markings in the shape of the selected data (e.g., to improve asthetics or contrast) or may be retained as part of the selected data,

At step 550, a plurality of microdots is separated from the metallic substrate.

Separation of the microdots may, for example, be achieved by performing one or more of the following:

• punching the substrate;

• slitting and/or chopping the substrate;

· laser cutting the substrate; and

• chemically etching the substrate;

to produce a plurality of microdots of approximately the same size. Each of the separated microdots comprises a portion of the metallic substrate havin the selected data applied thereto. Sets of microdots (e.g., having the same batch number and/or a sequence of serial numbers) may be automatically placed in separate receptacles or containers.

Fig. 6 shows a flow diagram of another method for manufacturing metallic microdots.

Referring to Fig. 6, the method commences at step 610 with anodising of a metallic substrate. Aitodisation of the metallic substrate provides a protective barrier to the substrate, which is nevertheless porous and thus capable of absorbing marking materials. The metal lic substrate may, for example, comprise a metallic tape such as aluminium tape. In one particular embodiment, the metallic substrate comprises alumini m tape of 0, !mra thickness and 20mm width. However, those skilled in the art will appreciate that numerous other metallic substrates capable of being anodised may be practiced. For example, substrates or tapes of other suitable metals and/of dimensions may be practiced.

At step 620, selected data is applied one or more surfaces of the anodised metallic substrate by way of a layer of photosensitive material (as described hereinbefore, for example, with reference to steps 420 to 470 the method of Fig, 4) or a printed mask containing selected data (as described hereinbefore, for example, with reference to steps 520 to 540 the method of Fig. 5). The selected data may, for example, comprise one or more of the following; a number, a word, an alphanumeric character, a name, a batch number, a serial number, a supplier logo, an image, a barcode, and a hologram. Control marks may be added during mask generation to assist automated manufacturing of the microdots (i.e., downstream in the manufacturing process .

At step 630, the anodised metallic substrate is marked using anodising dyes, which penetrate the anodising pores in the metallic substrate, in an alternative embodiment, the porous anodised metallic substrate may be electro-plated or electro-less plated, thus depositing a metal layer (e.g., tin) to provide a lightfast indicia.

At step 640, a plurality of microdots is separated from the metallic substrate. Separation of the microdots may, for example, be achieved by performing one or more of the following:

• punching the substrate;

· slitting and/or chopping the substrate;

» laser cutting the substrate; and

• chemically etching the substrate;

to produce a plurality of microdots of approximately the same size. Each of the separated microdots comprises a portion of the metallic substrate having the selected data applied thereto. Sets of microdots (e.g., having the same batch number and/or a sequence of serial numbers) may be automatically placed in separate receptacles or containers.

Photosenststive materials can play different roles in tire different embodiments described hereinbefore, in certain embodiments described hereinbefore, photosensitive materia! is used to create the selected data on a metallic substrate (e.g., the embodiments using silver halide). In this instance, the applied data is particularly durable on account of the process tending to be a one way polymerisation process. In other embodiments described hereinbefore, photosensitive material is used to create masks for applying the selected data. The selected data is then created on a metallic substrate by way of anodising the metallic substrate or by way of other similar processes. When such masks are used, the photosensiti ve material is typically cleaned after creation of the selected data on the metallic substrate. Photosensitive materials such as photo resist, and which can include ultraviolet (UV) inks, typically require exposure to light suitable for curing the photo resist (e.g., UV light).

Embodiments of the present invention advantageously enable both variable and mass (fixed) data to be generated or written on metallic microdots. Embodiments of the present invention also advantageously enable manufacture of metallic microdots on demand in real- time without the need for extended lead times.

In any of the foregoing embodiments, control marks located on the metallic substrate may be used to ensure that

• a set of microdots having a specific set of variable data are correctl placed in a container specifically allocated to microdots having that specific set of variable data; and

the microdot separation process is performed in correct registration with the data. That is, the control marks are used to ensure that the individual microdots ar separated appropriately between successive sets of data.

Use of control marks for the above purposes has the advantages of:

making the dots as small and as stealthy as possible;

* reducing material (metal) wastage; and

reducing production time.

In any of the foregoing embodiments, sealing can optionally be performed after the anodised metal lic microdots have been separated from the metallic substrate. This advantageously results in the entire microdot being sealed, as opposed to unsealed edges resulting from separation of the microdots from the metallic substrate after sealing. Such unsealed edges represent a possible point of entry for reactive materials or light (e.g., ultraviolet light), which would result in degradation of the microdots.

Sealing could, for example, be performed when the individual microdots have been placed in the panicular or allocated containers. The containers may be perforated to enable free movement of fluids or liquids but withot allowing the microdots to escape. Embodiments of die present invention provide methods for manufacturing metai microdots that are preferably and advantageously:

• durable and capable of ^' withstanding weathering, heat, direct sunlight, exposure to chemicals and exposure to abrasion:

• able to be produced at high speed and with little to no lead-time (this is particularly required whe supplying microdots for vehicle applications);

• able to be produced at low cost;

• able to be marked with a relatively large amount of data (this is particularly required when marking vehicles using YI numbers);

• able to be marked with aiphamimeric and graphics data simultaneously;

• able to be marked with colour graphics; and

• able to be mad from titanium, which is inert, heat tolerant, and biocompatible.

The league table hereinafter (Table 1) provides comparisons of microdots manufactured from various substrate materials (including polyester, lase written stainless steel, ceramic charms, nickel and anodised metal as per the present invention). The comparisons are based on data payload, batch sequence leadtime, labour content to produce, durability, cost, colour, bio-compatability, colour shift effect, and production rate. The table demonstates the relative advantages of anodised metallic microdots produced in accordance with the methods of the present invention.

TABLE 1

The foregoing description provides exemplary embodiments only, and is not intended to limit the scope, applicability or configurations of the invention. Rather, the foregoing description of exemplary embodiments provides those skilled in the art with enabling descriptions for implementing one or more embodiments of the invention. Various changes may be made in the function and arrangement of elements and/or features without departing from the spirit and scope of the in vention as set forth in the claims hereinafter.