GB1565243A - Recording data in eye-visible and machine readable magnetic form - Google Patents

Description

(54) RECORDING DATA IN EYE-VISIBLE AND MACHINE READABLE MAGNETIC FORM (71) We, EMI LIMITED, a British company of Blyth Road, Hayes, Middlesex, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the recording of information on a magnetic medium.

In general when information is recorded on a magentic medium no visible change of the medium occurs. If the recording is made by aligning some of the particles when they are mobile in the medium a alight texturing of the surface may occur which can be seen as a pattern of light and shade corresponding to the alignment but this is not always readily visible to an adequate amount.

It is an object of the invention to provide an information record which is both visually and magnetically detectable.

According to the invention there is provided a method of recording the same information at the same time in eye and machine readable forms including providing a record medium having in association a magnetic record material and a visual record material, placing the record medium at a recording location in a controlled magnetic field of such an intensity to cause no magnetisation of the magnetic record material at room temperature but sufficient to magnetise the magnetic record material when it is cooled in the presence of said field from a specific temperature in the region of the Curie temperature and heating said selected record area to said specific temperature and allowing it to cool whilst still in said controlled field, said visual record material being such that it irreversibly changes colour when heated to said specific temperature so that a record of the information is produced in each material in the same record area of the medium by change compared with the surrounding medium, whereby subsequent alteration of the magnetic record alone produces a detectable discrepancy between the eye and machine readable information records.

The method of recording information on a magnetic record medium, the information recorded being also visible, may include providing a record medium including overlaid layers of a thermo-magnetic record material and a thermo-chromic material.

The heat may be applied to the selected record area by a heated recording element which may have an arbitrary shape, e.g. a bar, to magnetise a similarly shaped region of magnetic material whose position is marked by the correspondingly shaped thermoplastic material region of changed colour.

The recording element may have a distinct shape from a set of such arbitrary shapes, e.g. the alpha-numeric or other graphic shapes, and the distinctly shaped magnetised regions may be distinctly detectable by reading apparatus by their distinct shape.

The recording element may also apply a magnetic recording field adjacent the visible record area of the thermochromic material of changed colour to make a further magnetic record.

The invention further provides a record medium including a non-magnetic substrate bearing a layer of magnetic record particles and a layer of material which irreversibly changes colour once heated above a specific temperature, the specific temperature being adjacent the Curie temperature of the particles, the substrate resisting change at the specific temperature.

A recording apparatus may be provided including means to transport a recording medium as described above through the apparatus to a recording location, means to apply a controlled magnetic field at the recording location, means to heat a distinctly shaped part of the medium at said location to the Curie temperature and then allow the medium to cool in said magnetic field to become magnetised in accordance with the applied field at said visually distinctly shaped part and means to transport the so-recorded medium away from said location.

The apparatus may include a character printer with dies or print elements having a range of shapes and being heatable to heat the medium.

A reading apparatus may also be provided to read a record medium bearing an associated visible and magnetic record including respective means to detect optically and magnetically recorded shapes and indicate the forms of such shapes.

The reading apparatus may include means to compare the detected forms and indicate the result of the comparison.

Embodiments of the invention will now be described with reference to the drawings accompanying the Provisional Specification in which: Figure 1 shows a portion of recording medium, Figure 2 shows a recording apparatus, Figure 3 shows recording in progress, Figure 4 shows a recorded recording medium in an operative arrangement, and Figure 5 shows a reading apparatus.

Figure 1 shows a portion 1 of a recording medium in the form of a length of tape. The tape has a flexible substrate 10 of polyvinylchloride and polyvinyl acetate or other plastics material suitable to withstand brief exposure to a temperature which may be as high as 1300C or 450"C. An underlayer 11 is of a dispersion of magnetisable material particles, e.g., a magnetic oxide, in a binder such as is well known in the tape manufacturing art. A top layer 12 is of a thermal indicating material, e.g. a thermochromic paint, exhibiting a colour change at a specific temperature e.g.

one in the range 1000C to 1500C, or 4000C to 500"C.

Specific examples of such a medium are as follows:- Example I A plastics film of polyethylene-terephthalate, e.g. the proprietary material Mylar (R.T.M.) some 15-50 micrometres thick is coated with an underlayer of a dispersion of chromium dioxide particles in a thermosetting binder to a final thickness of some 14 micrometres.Over this is a thin top layer of thermal indicating paint such as the proprietary material "Clearline single change paint" obtainable from Thermographic Measurements Ltd. of Ilchester. A range of such paints is obtainable and a suitable one is that which changes colour at 1200C which is adjacent the Curie temperature of the chromium oxide formulation at some 1300C. The coated film is prepared using conventional techniques, e.g. a trough coated in two stages, and dried and slit to form rolls of tape some 10--15 mm wide.

Example II A film of a high-temperature plastics or other non-magnetic material e.g. Kaptan (R.T.M.) some 40 micrometres thick is coated with an underlayer of a dispersion of fine particles of barium ferrite in a high temperature binder to a finished thickness of some 10 micrometres. The ferrite has a coercivity of some 4000 Oe at room temperatures, clSOC, and a Curie temperature of around 450"C so the plastics material must be chosen to resist such temperatures. The ferrite layer is coated with a layer some 5 micrometres thick of a multichange thermochromic material, in which the final colour is dependent on the highest temperature which the material attains. Such a thermochromic material is obtainable from the above suppliers. The film is coated and made into tape as described in Example I.The prepared tape may be hot stamped or laminated to a card material, e.g. a PVC/PVA copolymer provided the temperature of 100"C for Example I is not exceeded.

Clearly other forms of medium may be constructed. For example the recording medium may be a mixture of the magnetic and thermochromic materials in a single layer or several interleaved layers. The medium may be in or on formats other than tape. Thus strips or areas of medium can be coated on sheets of paper or cardboard. In particular other magnetisable material such as cobalt ferrites having coercivities of some 500 Oe or more at room temperature and 100 Oe at some 1500C to 2000C are appropriate.

The recording of information on a medium according to the invention will now be described.

One convenient form of recording apparatus includes what is basically a typewriter or other character printer in which a type die or print head is heatable to say 1500C or 450"C. A form of heatable print head is described in U.K. Patent Specification No. 973,200 and United States Patent Specification No. 3161457 and will not be described in detail. The printing location of the apparatus is positioned in a controlled magnetic field of intensity at least equal to the coercivity of the material on which a recording is to be made at the temperature attained when the heatable die is applied. Thus for the material of Example I at a die temperature initially of 1500C a field of some 150 Oe is suitable while for the material of Example II at an initial die temperature of some 450"C a field of up to 1800 Oe is desirable.

In operation to record data magnetically and visibly the medium described above is brought to the recording location by suitable, well-known, transport means, at which location the magnetic field exists, and an appropriate character recording element is applied to heat the medium in the shape of the character to about the Curie temperature of the magnetic material, thereby enabling magnetic recording in the heated shape bringing about the desired colour change.

One form of recording apparatus is shown at Figure 2. A type basket TB equipped with alpha-numeric or other suitable type faces such as arbitrary forms. e.g. bar code, graphic forms and the like e.g. ideographs.

The basket is positioned so that individual type elements can be operated to strike a piece of recording medium RM in tape form against an anvil AN. The tape is moved over anvil AN from reel Rl to reel R2 and in a preferred form the tape up reel R5 is driven by a stepping motor MS via toothed belt B in synchronism with the type-bars, moved by suitable means, to provide evenly spaced characters. Suitably the type-bars are operated by electrical signals supplied to a synchronising circuit SYN which directs the electrical signals to operate the respective type-bar and move the record medium. The electrical signals may be five or more level code signals of known form supplied, e.g.

from a punched tape reader, over the input connection INPUT. Clearly a hand-struck type basket can be used with suitable transport means.

Field coils FCI and FC2, energised from a magnetising current source IM produce a magnetic field longitudinal of the medium in the region of anvil AN. Suitable field values have been considered above. The type faces to strike the recording medium are heated, either directly or indirectly, e.g. by infra red radiators IRH around the type basket.

Suitable power sources Sl, S2, S3 are also provided. In operation a selected type bar is operated to strike a heated type character shape against the recording medium tape on the anvil to heat the medium in the shape of the character to around the Curie temperature of the magnetic material and above the colour change temperature of the thermochromic material. The heat changes the colour of the material in the character shape and the heated magnetic material cooling in the magnetic field from near the Curie temperature becomes magnetised in the character shape, being magnetically very susceptible when so heated. The medium is then stepped on for the next character.

Figure 3 shows the recorded medium bearing visible characters which are also recorded as corresponding magnetised shapes. The magnetised part 310 of magnetic material layer 31 is indicated by shading in the sectional face, although clearly no visible change occurs, and the shape of changed colour 320 is shown in thermochromic layer 32. The type bar TBN carrying the heated die for the next letter, "N", is about to strike the tape RM on the anvil AN in the presence of a magnetic field F, indicated by arrow F, from coils FC I and FC2, not shown in Figure 3.

Clearly other methods of heating the medium in the shape of the data to be recorded are possible. For example ratio frequency heating using the shape of the type element to determine the heated area is possible. The form of the data can be chosen as desired and in addition to characters arbitrary shapes and binary data bars can be used.

Figure 4 shows an identity or like card 4 on which the material recorded as shown in Figure 3 has been secured in suitable manner, e.g. by lamination into sheets of polyvinyl acetate, the tape support 30 acting as an adhesive. The recorded indicia 41, John Doe, is repeated on the card at 42 in conventional printing. The whole provides a documents on which a recording or a considerable degree of security against unauthorised alteration is provided together with a check on authenticity.

The authenticity of the card is indicated visually by the correspondence of the thermally recorded and the conventionally printed information.

Alteration of the card is hampered by the presence of the thermally colour-changed material which change cannot be reversed to alter the recording. Even if this colourchange is simulated, e.g. by conventional colours, the magnetic recording remains unaltered and can be verified as described below. Clearly as yet unaltered parts of the colour-change material can be recorded.

However, this action can be made very difficult by use of the higher coercivity material. In this way a considerable degree of security against fraudulent alteration is attained.

Preferably the recording is in the form of alpha-numeric characters formed by elements of a dot matrix, e.g. a 7x5 element matrix. Such a matrix provides visible readily legible characters and also a matrix structure readily detectable by a magnetic reading head. Figure 5 shows an apparatus to read the colour-change and magnetic recording.

A card transport means 50 of any suitable form, e.g. a channel 51 with one or more powered card drive rollers 52 and a cover plate 53 to keep cards down the bottom of the channel is provided and supported in suitable manner, as is well-known in the art.

A card, such as card 4 of Figure 4, is inserted face down along the direction of arrow 54 and transported up to and past electronic reading station 55 and a magnetic reading station 56. Each station contains respective sensors of suitable form to read the visible and magnetic recording on adjacent record 41 of card 40. When the suggested 7x5 format is used five sensors at each station can be used to detect the condition of the five elements in one column at a time during transport of the record 41 on card 4 past them. (Clearly a source of illumination, not shown, may be required for the optical sensors). The electrical signals from the sensors are supplied to a comparator and display means 57 which displays the magnetically recorded information at 58 and at 59 indicates agreement (a tick) or lack of agreement (a cross) of the visible and magnetic record.

The card is ejected after reading.

Suitable electronic circuits for reception, storage and comparison of the signals from the sensors and the display of the result are well-known and will not be described further.

The techniques described above provide a recording medium and operative system resistant to fradulent alteration which is suitable for the production of individual secure devices such as documents, cards, etc. in which the individual information can have a wide range of content and is easily applied. The information is made secure by the simultaneous recording in two ways and the irreversible alteration of the colour change material. For example the recording apparatus can be combined with a hot blocking device to transfer each section of recorded medium to a respective card, the apparatus being controlled by a tape punched with holes by an adjacent keyboard perforator. If required the security device, such as the card, can be encapsulated to protect it.The encapsulation may include thermochromic material with an operating temperature, say 60"C, lower than the material on the security device itself to prevent further undetected alteration of the record. The encapsulation, which may be an envelope or an adherent layer, may be damaged or modified when subjected to high local pressure to prevent further undetected printing action on the recording.

WHAT WE CLAIM IS: 1. A method of recording the same information at the same time in eye and machine readable forms including providing a record medium having in association a magnetic record material and a visual record material, placing the record medium at a recording location in a controlled magnetic field of such an intensity to cause no magnetisation of the magnetic record material at room temperature but sufficient to magnetise the magnetic record material when it is cooled in the presence of said field from a specific temperature in the region of the Curie temperature and heating said selected record area to said specific temperature and allowing it to cool whilst still in said controlled field, said visual record material being such that it irreversibly changes colour when heated to said specific temperature so that a record of information is produced in each material in the same record area of the medium by change compared with the surrounding medium, whereby subsequent alteration of the magnetic record alone produces a detectable discrepancy between the eye and machine readable information records.

2. A method according to Claim 1 including providing a medium of overlaid layers of a thermo-magnetic record material and a thermo-chromic record material.

3. A method according to Claim 2 in which heat is applied to the selected record area by a heated recording element in the shape of the information which it is desired to record.

4. A method according to Claim 3 including providing a plurality recording elements having shapes selected from the groups of distinct arbitrary shapes, alphanumeric character forms and graphic forms.

5. A method according to Claim 3 or Claim 4 including applying a magnetic recording field with the recording element adjacent the record area to make a further magnetic record.

6. A method according to Claim 2 including providing a layer of chromium dioxide as the thermo-magnetic material and applying a field of some 150 Oe around the recording location and heating the recording element to some 1500C.

7. A method according to Claim 1 including producing a secure document incorporating the recorded record medium to carry information securely by providing said eye and machine readable records of the information.

8. A record medium including a nonmagnetic substrate bearing a layer of magnetic record particles and a layer of material which irreversibly changes colour once heated above a specific temperature, the specific temperature being in the region of the Curie temperature of the particles, the substrate resisting damage at the specific temperature.

9. A medium according to Claim 8 in which the magnetic particles are chromium dioxide and the material to change colour is a colour-change paint.

10. A medium according to Claim 8 in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (16)

**WARNING** start of CLMS field may overlap end of DESC **. inserted face down along the direction of arrow 54 and transported up to and past electronic reading station 55 and a magnetic reading station 56. Each station contains respective sensors of suitable form to read the visible and magnetic recording on adjacent record 41 of card 40. When the suggested 7x5 format is used five sensors at each station can be used to detect the condition of the five elements in one column at a time during transport of the record 41 on card 4 past them. (Clearly a source of illumination, not shown, may be required for the optical sensors).The electrical signals from the sensors are supplied to a comparator and display means 57 which displays the magnetically recorded information at 58 and at 59 indicates agreement (a tick) or lack of agreement (a cross) of the visible and magnetic record. The card is ejected after reading. Suitable electronic circuits for reception, storage and comparison of the signals from the sensors and the display of the result are well-known and will not be described further. The techniques described above provide a recording medium and operative system resistant to fradulent alteration which is suitable for the production of individual secure devices such as documents, cards, etc. in which the individual information can have a wide range of content and is easily applied. The information is made secure by the simultaneous recording in two ways and the irreversible alteration of the colour change material. For example the recording apparatus can be combined with a hot blocking device to transfer each section of recorded medium to a respective card, the apparatus being controlled by a tape punched with holes by an adjacent keyboard perforator. If required the security device, such as the card, can be encapsulated to protect it.The encapsulation may include thermochromic material with an operating temperature, say 60"C, lower than the material on the security device itself to prevent further undetected alteration of the record. The encapsulation, which may be an envelope or an adherent layer, may be damaged or modified when subjected to high local pressure to prevent further undetected printing action on the recording. WHAT WE CLAIM IS:

1. A method of recording the same information at the same time in eye and machine readable forms including providing a record medium having in association a magnetic record material and a visual record material, placing the record medium at a recording location in a controlled magnetic field of such an intensity to cause no magnetisation of the magnetic record material at room temperature but sufficient to magnetise the magnetic record material when it is cooled in the presence of said field from a specific temperature in the region of the Curie temperature and heating said selected record area to said specific temperature and allowing it to cool whilst still in said controlled field, said visual record material being such that it irreversibly changes colour when heated to said specific temperature so that a record of information is produced in each material in the same record area of the medium by change compared with the surrounding medium, whereby subsequent alteration of the magnetic record alone produces a detectable discrepancy between the eye and machine readable information records.

2. A method according to Claim 1 including providing a medium of overlaid layers of a thermo-magnetic record material and a thermo-chromic record material.

3. A method according to Claim 2 in which heat is applied to the selected record area by a heated recording element in the shape of the information which it is desired to record.

4. A method according to Claim 3 including providing a plurality recording elements having shapes selected from the groups of distinct arbitrary shapes, alphanumeric character forms and graphic forms.

5. A method according to Claim 3 or Claim 4 including applying a magnetic recording field with the recording element adjacent the record area to make a further magnetic record.

6. A method according to Claim 2 including providing a layer of chromium dioxide as the thermo-magnetic material and applying a field of some 150 Oe around the recording location and heating the recording element to some 1500C.

7. A method according to Claim 1 including producing a secure document incorporating the recorded record medium to carry information securely by providing said eye and machine readable records of the information.

8. A record medium including a nonmagnetic substrate bearing a layer of magnetic record particles and a layer of material which irreversibly changes colour once heated above a specific temperature, the specific temperature being in the region of the Curie temperature of the particles, the substrate resisting damage at the specific temperature.

9. A medium according to Claim 8 in which the magnetic particles are chromium dioxide and the material to change colour is a colour-change paint.

10. A medium according to Claim 8 in

which the magnetic particles are of a ferrite material.

11. A medium according to Claim 8 in which the substrate is a plastics polymer selected to have a softening temperature range including or exceeding the Curie temperature of the particles.

12. A secure document including a medium according to Claim 8 or any dependent claim to provide a secure record of information checkable by comparison of the magnetic and visual records.

13. A secure document according to Claim 12 encapsulated in a material having a thermochromic property effective at a temperature below the record medium Curie temperature whereby undue heating of the document toward an easier magnetic recording state is indicated.

14. A system including at least one secure document according to Claim 12, at least one recording apparatus and at least one reading apparatus, the recording apparatus including means to transport the document through the apparatus to a recording location, means to apply a controlled magnetic field at the recording location, means situated at said recording location to heat a distinctly shaped part of the record medium of the document to the Curie temperature of the magnetic particles in said medium and means to allow said part to cool in said magnetic field, and the reading apparatus including a document transport path and a reading station for the visual and a reading station for the magnetic information arranged to supply information read-out signals to a comparator to indicate the agreement or otherwise of the readout signals and thereby the authenticity or otherwise of the document.

15. A record medium substantially as herein described with reference to Figure 1 of the drawings accompanying the Provisional Specification.

16. A secure document system substantially as herein described with reference to the drawings accompanying the Provisional Specification.