CA2125137A1 - Printing - Google Patents

Abstract

By using particulate material to take up an ink, the ink can be transferred to a plastics film at a high level of fidelity. The plastics film can then be laminated with another plastics film for security purposes to give a security document. Humidity and laminating temperature can be varied to produce a document which does not bleed or which bleeds after a certain length of time.

Description

I'RINTING ON PLASTIC FILMS
PRINTING
The present inver,tion relates to printing and more particularly, though not exclusively, to the printing of plastics to produce documen~s which are harder to copy; it also relates to the construction of the document produced, intermediate products made, and their methods of ~anufacture.
With improvements in photocopying~ documents ~an be more easily re-produced. Thus, the forging of documents is ~ecoming a major problem. The range of documents being forged is vast. The production of ~ecurity cards, money, tickets and mom~ership cards~
are just some exam~les of the areas in which forging and copying is proving difficult to control.
Since paper documents also wear quic~ly there has been a desire to produce plastics do~ments of, fo~ example, the type described. However, to date, the attempts to make plastics dot:uments, which meet the needs of the user or operator, have not proved satisfactory.
One of the pro~lems with printing onto plastics derives from the colourants used. Firstly, the colourants used can be removed from plastics by the use of solvents such as acetone, thereby leaving the documents open to alteration. To overcome this ~g 2 / 0 22'66 2 1 2 5 1 ~ 7 08 ~CEMBER 199 problem attempts have been made to bond a further plastics layer over the printed layer thereby enclo~ing the ink. Two major problems have, however, become apparent. Firstly, it ha~ been found that pla~tic~, for example, PVC or polyester/polyethylene film will not fully bond to itself or each oth~r where one or the oth~r ha~ been coloured with an ink or dye ~tuff. It ha~ also been found that printing directly onto pla~tic~ and then ~onding a further plastic ~ilm thereto, ther~by encap~ulating the ink or dy~, proves unsati~factory ~ince the ink or dye tend~ to run/bleed ~mmo~ately or within a ~hort tim~, re~ulting in a blurrcd psint. Whil~t thi~ problem can ~e dimini~hed by drying the ~nk u~ing high powered infra-red or ultra-violet light, the proce~ tLme con~uming and exp~n~ive.
It i~ an object of the i~vention to improve upon th~ known product~ and to d~ e a ~thod for doing ~o. T~e pre~ent inve~tio~ can be u~ed to provide prsduct~ which ~ub~tantially dc not bleed or which bleed at co~trolled rates.
In accordance with one aspect of the pre~ent invention there is provided a proce~ for printing a pla~tic~ film, comprisi~g printing a coloura~t onto a layer of particulate or colloidal ~aterial, which material i~ relea~ably bound to a backing;

Unite~ Kingdom Patent O~ ~
~ ~UBST~Tl~l~E S~

PC116B9 2 / ~ 22 6 G
212S137 ~8 IJ~ MBER 1993 tran~ferring the colourant onto a fir~t pla3tics ~:
film by placing the fir~t plasticQ film oYer the printed layer and subjecting the plastic~ film and printed layer to a substantially constant heat, and removing the backing characterised in that the particulate or colloidal material ha~ a particle ~ize of from 5 to 0.006 micron~.
Preferably the particulate or colloidal material iB inorganic.
Preferably a second plastics film is bonded to the first pla~tic~ film, thereby e~cap~ulating the colourant in the plastica.
By producing a document in thi~ way, avoidan~e of bleeding of the ink~ u~ed can be achieved, if de~ired, and, furthermore, if a ~econd layer of plastic~ is bonded to th~ printed pla~tic~ layer it wlll bond even where colour has taken. Thi~ i~ thought to be becau~e ths i~k plu~ the particulat~ material beco~es bonded within the poly~thylene. Al~o, ~y bonding a ~econd layer ther~to it become~ difficult or Lmpo~sible to tamper with the fir~t printed layer ~ince the ink~ are enclos~d within the pla~tics.
Preferably, the pla~tic~ film i~ a polye~ter film coated with polyethylene, ~uch a~ that purcha~ed from Morane (Ba~bury, U.R.) under the trade name Morafa~t.
Other pla tic~, ~uch a~, for example, polyvinyl _ Unlted Ki~gdom P. tent OffiC~ SU~STITUTE Sl~ T
PCT lnt~ n ~i.onc.l AppliC~tion , ~ .. . ~ . . .. _ ;B9 2/ 0226G
212~137 ~J ~ tg9~

-3a-chloride may be u~ed, but the ink can be removed with acetone. However, the bonding properties of polyethylene make it preferred and the ink i8, after bonding, unaffected by acetone. Thus, where a ...

r ~ ~ SUBSTITUT Sl~

WO93/11946 pcT/Gs92/o2266 212~137 polyethylene coated polyester film is used, it is preferred that the ink or dye is transferred to the polyethylene coated surface.
The colourant used may be any ink or dye but the following are preferred: diethylene glycol ba~ed ink using food dyes as colourants.
These inks are particularly favoured when used with polyethylene since they are cheap to use and print well.
The material of a particslate or colloidal nature is preferably silica, a sand, silicon, clay or chalk.
Silica is most preferred and is ~eferred to throughout the remainder of the specification, although the abo~e alternatives can be used also.
Preferably the particles are provided in a coating with latex (e.g. PVA) or starch.
Preferably the backing is a dense paper exceeding 80gms per square metre to avoid tearing when the paper is removed, although other materials could be used.
Preferably, the paper has a low level of loose fibres or no loose fibres. Parchment paper is preferred and is produced by dipping paper in conc. H2SO4 and then washing.
The colourant or in~ can be applied by hand, or by machine. Suitable machines include, for example, computer controlled printers, dot matrix, laser and PCT/6B ~ 2 / 0 2 2 6 B.

ink jet printer~ or printing plate~ etc, but ink jet printer~ are preferred.
The ink can be transferred to the plastic~ film by bringing the plastic~ film into contact with the ~urface of the material having a particulate na~ure, which material ha~ been printed over, and ~ubjecting it to a con~tant heat. Thi~ can be done by passing the two layer3 through a standard l~;nator. The temperature requir~d will depend on th~ plaRtic~ used and the thickne~ of the sheet~.
- The backing layer, u~ually paper, can then be p~oled off, with wa~hing and ~crubbing if nece~ary, to lea~e a printed pla~tic~ ~heet which ha~ ab~orbed the ink. Con~equently, it i8 more difficult to remove the ink~ by the u~e of solvent~ than with conv~ntionally pri~ted pla~tic~.
A~ pointed out above, printed pla~tics can also b~ bonded to a further pla3tic sheet to encap~ulat~
the i~k or dyQ maki~g the product "t~m~er proofn.
Thi~ i~ of particular Lmportance in ~ocument~ of A
security nat~re.
According to a further aspect of the invention there i~ provided a printed pla~tics document comprising a fir~t plastics film and a layer of particulate or colloidal material thereo~ onto which a coloursnt ha~ been print d, characteri~ed in ~9 C~ SUBSTITUTE SH~ET
PCT Int~ nal App~tcatlon ¦

PCT16~9 2 / 0 226B
2 1 2 5 1 3 7 0 8 DESEMBER l9g~

that the particulate or colloidal material has a partiele size of from S to 0.006 microns .
Aeeording to yet a further aspeet of the invention there i~ also provided a plasties ~heet eomprising ther~on a layer of a partieulate or eolloidal material eharacteri~ed in that the partieulate or eolloidal material has a partiele ~ize of from 5 to 0.0006 mierons.
Prefer~bly the partiele 8ize of most or sub~tantially all the partiele~ i8 from 5 mieron~ to _ ~ = SUBSTI~UTE SH~ET

PCT/61~9 2 / 0 2266 2 1 2 ~ 1 3 ~ ~ a DECEMBER 1993 O.006 microns in diameter, more preferably from lym to 0.006 ~m.
The particle size can be determined by pa3~ing particles through a graded ~eries of sieves and determining which sieves the particles will or will not pa~s through.
The pla~tics film used m2y be formed from any of the plastics hereinbefore mentioned, but the preferred pla~tics film i~ a polyester/polyethyl~ns l~m;nate.
Preferably the layer of particle~ i8 formed on the polyethylene side of the laminate.
Without w~shing to b~ bound by theory it i~
b~lieved that the improved printi~g quality derives.
from the colourant being tran~ferred to the pla8tic8 from the particles i~ a "dry ~tate~.
By usi~g differe~t loading~ o~ sil~ca, different type~ of document ca~ be produced loading~ of 4 to 8 g/m~ (preferably 5-7 g/m~) give tran~pare~t documents.
Loadiny~ of 8-20g/m~ (preferably 10 to 15 g/m~) give opaque docum~nt~.
In order to produce document~ which ~ubstantially do not bleed when the backing i~ remo~ed, the layer of particulate or colloidal material preferably ~hould not be expo~ed to a~ atmosphere of above 40% humidity for any lengthy-period of tLme (e.g. not for longer than 20 minute~). De~irably, the second plastic~ film . ~F~ ~it ~ T~ n . rCT Inie,~ ,r~ ,.,r,'.ication should then be laminated to the first plastics film at a temperature of at or above 350F. This also applies to the silica, plastics layers and/or paper prior to being used for a product intended not to bleed.
In order to produoe documents having printing which is initially legible but which later begins to bleed, the said layer preferably should be exposed to an atmosphere of above 40% humidity (e.g. 40 to 80%
h~midity). Also, the first plastics film can be subjected to a ~ery fine water mist. Desirably the layer takes in no further moisture from the atmosphere. The second plastics film then desirably is laminated to the first at a temperature at or below 350F.
Having printed onto the plastics, further additional s~eps can be taken to Lmprove security, depending on the type of document being produced.
For a laminated document, for example, money, tickets etc. a mark akin to a "water mark" ca~ be introduced. The mark, as it is hereafter referred may be produced as follows:
A sheet of paper preferably with a weight in excess of 80 gms, but lower weights can be used, and having coated thereon fine particles of ~ilica has a design em~ossed thereon using a metal die or other means for embossing paper. Preferably, the impression 21~S137 is made on the coated side so that the coated side is depressed, although it will wor~, though less effectively, the other way round. ~he embossed sheet, is then placedt particle side down over a first plastics sheet and the two sheets are passed through a la~nator in the same way as has been described with reference to the transfer of inks from the coated sheet. The backing paper is then removed, and when a second plastics film is bonded to the first film, a mar~ is visible which mark contains no inks and does not appear to the hand to be raised or lowered in the end product.
Feature~ of the invention will now be des~ribed, by way of example only, with reference to the f~llowing specific em~odiments.
To produce a printed plastics document which also comprises a "watermark" the following procedure can be followed:
A sheet comprising a parchment paper backing and having thereon a layer of silica, has a design printed on the silic layer. The inks or dyes used are standard printing dyes and the design is applied by a computer controlled printer, printing plate or other means.
At another place along the sheet, prefera~ly a place which has not been printed, a part of the coated WO93/11946 PCT/~B92/02266 surface is raised by embossing the paper with a metal die having a raised design thereon.
The printed sheet is then covered, for example, with a lO0 microns thick polyester plastics sheet with a 16 micron thick polyethylene coat on at least one side, ~o that the polyethylene coat face~ the silica coated surface of the printed sheet. The two are heated to a te~perature at which the polyethylene melts sufficiently to take up ink. For the sheet of the given examples this temperature will desirably be between 32C (90F) and 60C (140F), preferably about 38C (about 100F) and can be achieved ~y passing the respective sheets through, for example, a pouch or ^
role laminator. I~ should ~e appreciated that the features exemplified above are not l~ting. The polye~ter sheet is prefera~ly above 30, e.g. up to 500 microns thick and the polyethylene coat is preferably from 12, e.g., up to 20 microns thick~ It is de~irable that the heat applied is constant and that sufficient pressure is exerted to expel any air from betwsen the sheets.
The backing paper is then removed. Generally it can be peeled off, but if it is well stuck down it can be soaked and scru~bed as necessary.
Where the paper was embossed, the raised parts caused the polyethylene to be "pushed out" as the 212~13~

paper was laminated to the plastics. When another plastics layer is placed into contact with the sheet, the paper having been removed, and laminated a distinctive mark is left. The amount of heat used in l~m;nation affects the clarity of the mark. The hotter the lamination the less clear the re~ulting mark. Generally a lamination temperature of greater than 49C (120F) is used.
Where lamination is used to encapsulate the ink it is possible, to incorporate other item~ between the sheets being laminated. Thus, for example, signature strips or electronic chips can be introduced and incorporated within the final product. In the 1Am; nate, desirabl~, the silica layer is sandwiched between two polyethylene layeræO
The results given in Table l beiow show how the present invention ~an be used to produce documents of different bleed times:
The Examples illustrat~d by the Table were performed u~ing parchment paper and a diethylene glycol ink comprising a food dye. The ink was prepared by treating yellow food dye obtainable under the trade mark "GOLD SEAL" (from Clayton & Jowett Ltd, Runcorn, England) until its volume was reduced by 7~% due to evaporation. l00 mls of the remaining liquid was then mixed with diethylene glycol to give a ~125137 level of 20% ulv glycol in the final ink. $he paper was loaded with an even layer of silica at a particle size of 0.010 microns and at a level of 10 g silica/m2 and was then printed with the dye. The printed layer ~as then placed against a polyester (150 microns thick) /polyethylene (16 microns thick) plastic~ film and heated at a temperature sufficient to transfer the printed layer to the plastics film polyethylene layer and the parchment paper was then removed. The resultant product comprising the plastics film and the printed layer was then left at the humidity level and exposure time given in the Table before finally la~inating a second layer of the plastics material to the first layer at the temperature gi~en in the Table.
The length of time taken for the ink used to bleed (i.e. for the printing to become blurred to the naked eye~ was determined by regular inspection and is given in the Table.
Bleeding could be effected with other ink jet inks provided that after removing the backi~g paper the layer of silica is exposed to an atmosphere of at least 40% humidity and the temperature at final lamination was below 177C (3S0F).
Yellow, magenta and cyan food dyes are obtainable under the trade mar~ "GOLD SEAL" and can be used to form ink jet inks as aforesaid, (except that 7S%

WO93/11946 PCT~GB92/02266 -l2-rather than 50% of the volume of the dye is evaporated). By mixing these dyes in appropriate proportions different colours can be produced, as desired.

Length of Temp.to Length Temp.
TLme to ~ransfer ~umidity of time at final Example Bl~ed Print % Exposed Lamination 1 1 year 100~ 40 15 mLns 325F
max .

2 6 months 100-200~75 30 mi~s. 325F

3 1 month 100-200-F 7560 min3. 325~

4 2 we~k~ 100-200-~ 40-5060 mln~. 325-F
S 1 woek 100-200~ 7~ 3 hours 325~

It is desirable in certain circumstances for bleedi~g to occur after a given tLme. This is the ca~e, for example, wher~ a tic~et or card is intended to be valid for a l;m;ted period only, the expiry of this period being indicated by bleeding of the ink.
By appropriate variation of humidity, temperature at final lamination and in~ used, the time can be varied at which bleeding occurs.
By appropriate variation of these parameters cards can be produced which will normally only bleed after several months (see e.g. Example 2~. ~owever, bleeding can be accelerated by puncturing or tearing the card to expose the silica to the atmosphere. One application of this is for consumer products havi~g 2125:~37 -l3-labels. The label can be formed with a line or point of wea~ness to which it is attached via a tag, to the consumer product. When the label is removed from the tag, tearing along the line of weakness exposes the silica to accelerate bleeding.
Even if the label is somehow reattached to the clothing, bleeding can still occur. This is advantageous in avoiding fraud by indicating to shopkeepers when a label has been removed from the consumer product. In the case of clothing, this lab~l, after being pierced, will then attract moisture from the body. lf the label shows signs of slight bleeding where it was pierced, this will show the ganment has just béen "tried on". If the article is worn for more than two hours the whole of the label wîll have bled (given the label is l" x l"). ~owever, the ink does not come out of the label. A further refinement of this technique is for the tag of the label to be attached to the consumer product via adhesive which eoats a removable holographic ;m~ge on the tag. Thus, if it is attempted to remove the label by pulling at the tag and avoiding the line or point of weakness the label and tag can be remo~ed together, but this destroys the holographic Lmage. A label comprising the remo~able holographic image and adhesive is also within the scope of the present invention.

WO93/1t946 PCT/GB92/02266 212~1~7 -l4-It has also been found that if a hologram printed on polyester and placed, e.g. in the centre of a number of various other sheets of printed laminate, then the special effects can be made which to date no-one has been able to photocopy, or even copy using a scanning unit.
It has been found that anything printed above the hologram (which is itself transparent~ if tilted to the light appears to become embedded within that hologram. Also, any part of the top-most layer, if the item is tilted accordingly, is all that can be viewed, so that in the caæe of a credit card, this top part could be printed with the name, signature and account number of an authorised user.
In one embodLment a hy~rid document can be produced i.e, one em~odying the printed plastics descri~ed with an insert of printed paper or a material which can be mar~ed when pressure is applied thereto. Since the printed material used will e~entually fade in time, it-is preferred in some embodiments to coat the plastics with a material which reflects ultra-violet light or to use an ultra-violet resistant polyester, which light is responsible for the fading.
In other embodiments, however, the fading of the ink due to expoaure to U.V. light can be used advantageously. For example, tic~ets such as concert or football tic~ets may have certain information printed in an ink which on exposure to a high dosage of ultra-violet light will be destroyed.
Furthermore, the following additional features can be included:
1. Only one part of an image or pattern may be applied to a document. The other part of the pattern is held ~y the person receiving the tickets at the entrance to the establishment (theatre, football ground, Wimhledon etc.). That person can then quickly place the *ransparent ticket over the template he holds and if the pattern/image is complete then that ticket is "passed". Also a fingerprint can be applied, and because of the transparent nature of the document this can be placed over a recorded fingerprint for verification.
2. A heat sensitive material or chemical may be used on the ticket so that a pre-defined number/pattern or image etc. shows up under certain conditions.
3. Fibre optics may be incorporated into a document.
They can be applied so that either:
a) One or more fibres which have been et~hed via a laser or other means with either words or a design, are aff xed on or between the laminate sheets so that when a light is applied to the edge of the card, where viewed from the front of the card. It has also been found that if the amount of light is measured at the start of the fibres, the amount of light received at the other end will depend on the amount and size of the words or design etched onto the fibres due to light being diverted through the design. Therefore the amount of light received at the end can be anticipated and measured and if the light does not reach or is over a certain level, then, the card/document will be suspect.
b) A number of fibres are set in such a way that light transmitted onto one edse of the card is received at another edge. Light ~ensors can then be used to detect the received light and to read it at an angle which is oblique to the direction in which light enters the card, and if the correct message is not received then the card is considered "suspect".
c1 The fibres can be arranged in such a way that they can be read a5 a number i.e. using the same principle as a bar code. Each card can have its own unique number or bar code.
d) A fluorescent fibre can be also used whereby light is transmitted via the surface of the fibre to the fibre ends. ~hese too can be etched and read by a light sensor/reader.

WO93/11946 2 i 2 ~ 1 ~ 7 PCT/GB92/02266 If in the case of a credit card, for example, fibre optics are placed across the whole of the card information such as A/C number, name, etc., plus any other information, can be etched in and read by an automatic reader by moving the card relative to the reader.
Using this method a wealth of untamperable information can be held within the card so that a magnetic strip is no longer required. A magnetic strip can, however, be fixed/sprayed onto or into a product of the present invention if desired.
Generally, a person will read the transparent document against a plain ~ackground. If the document L8 placed against,~for example, a white background the details of the doc~ment will show up cle~rly.
In the ca~e of a doc~ment that may be used where there is no suitable background to hand, a plain hi~ged back can be affixed to the document~ The person in~pecting the card can both see the card clearly, and by raising th~ flap can see that no changes or insertions have been made.
It has also been found that if a num~er of printed films are laminated together, the colour is enhanced. Also "3D" Lmages can be made hy the fact that for example: - mountains and sky can be printed on a first film, trees and bushes on a second etc. If, as has been found, clear film is inserted between WO93/11946 PCT/GB92~02266 212~ 37 these printed films, an effective 3D effect can be made or at least some depth of field achieved.
Another addition to the security aspect includes printing a document so small, that it cannot be read by the naked eye, but can be read with the use of a magnifying glass.
In another em~odiment security can be enhanced by applying a prism effect.
In this embodiment the plastics incorporateC a number of prisms - some running in one direction and some running in another. To read a document a correcting card is required or the card can be tilted to a certain angle to be able to read it.
In another embodiment, security can be enhanced by the addition of a foil, prefera~ly metal which has been em~ossed with lettering or design. This foil is encapsulated between the sheets of plastics material.
Also, this foii ca~ be encapsulated in a plane state so that e.g., with credit cards, if the card is stamped with round letters a~d/or num~ers these can be easily read by the naked eye.
If an electrically conductive ink/dye/paint within the card is used, the card can ~e used as part of an electrical circuit or a switch to cause a short circuit to, say, light up a ~ulb or open a door (i.e.
as a key card).

Another embodiment of the invention is to print either some or all of the document with white ink/dye etc. This will stop photocopying, as no photocopier can print white.
Two other ways of printing in white are:-1. To cut out shapes/letter~/numberR etc. fromthe paper that has more than lO microns of silica a~d to transfer this silica to the laminate, by the normal means of this invention, then on final l~mination, this white print will remain.
2. To have a design/words/numbers etc. placed in the coating or rather on the coatir,g of the paper at the time of manufacture, i.e. the first coating of -less than 5 microns is applied, then, when dry, a se~ond coating is applied using rollers that will leave the design required etc. proud of the first coating. This second coating will have to be thick enough to give a total thickness (of the two coats) of lO microns or more.
2a. Using method l, a coloured design, printed arou~d this resulting white design can then ~e used with the intention that the colour bleeds into the design within a given period.
It has been found that the "watermar~" cannot be photocopied either.
If an overhead transDarency is made by photocopying one of the invention's documents ~ given 21251:~7 that any white print or "watermark" will not be present - and then placed on an overhead projector, the image will show on the screen. None of the invention's prints will show up clearly on the screen;
so this too could be used as a ~ecurity check.
It has also ~een found that if two layers of plastic are printed with the same details, but adhered together, slightly off-set, that a blurred print results, but if the card is tilted to one side, the prints line up and can be easily read.
Going further with this, two identical prints can be made and laminated off-set, so that when viewed ~traight on, the whole print appears as a black card, until the card is viewed at an anglen _O______________________________________________________

Claims (19)

PCT/GB92/0226?
- 21 -

1. A process for printing a plastics film, comprising printing a colourant onto a layer of particulate or colloidal material, which material is releasably bound to a backing; transferring the colourant onto a first plastics film by placing the first plastics film over the printed layer and subjecting the plastics film and printed layer to a substantially constant heat, and removing the backing characterised in that the particulate or colloidal material has a particle size of from 5 to 0.006 microns.

2. A process according to claim 1, wherein a second plastics film is bonded to the first plastics film to encapsulate the colourant and the particulate or colloidal material.

3. A process according to claim 1 or 2, wherein the particulate or colloidal material is silica.

4. A process according to any preceding claim, wherein the backing is parchment paper.

5. A process according to any preceding claim, wherein the layer comprises 4 to 8 g/m2 or 8 to 20 g/m2 of particulate or colloidal material.

6. A process according to any preceding claim for producing a document having a colourant which substantially does not bleed, comprising printing the colourant onto a layer of particulate or colloidal material, which layer is releasably bound to a backing;
transferring the colourant onto a first plastics film by placing the plastics film over the printed layer and subjecting the plastics film and printed layer to a substantially constant heat;
removing the backing and laminating a second plastics film to the first plastics film at a temperature at or above 177°C (350°F).

7. A process according to any of claims 1 to 5, for producing a document having a colourant which bleeds after a period of time, comprising printing the colourant onto a layer of particulate or colloidal material, which layer is releasably bound to a backing;
transferring the colourant onto a first plastics film by placing the plastics film over the printed layer and subjecting the plastics film and printed layer to a substantially constant heat;
removing the backing and exposing the layer of particulate or colloidal material to an atmosphere of above 40% humidity; and laminating a second plastics film to the first plastics film at a temperature below 177°C (350°F).

8. A process according to any preceding claim, wherein a U.V. sensitive or U.V. reflective material is inserted between first and second laminated plastics film.

9. A process according to any preceding claim, wherein one or more fibre optic fibres are inserted between the first and second plastics films.

10. A printed plastics document comprising a first plastics film and a layer of particulate or colloidal material thereon onto which a colourant has been printed, characterised in that the particulate or colloidal material has a particle size of from 5 to 0.006 microns.

11. A document as claimed in claim 10 in which the particulate or colloidal material is silica.

12. A document according to claim 10 or 11, wherein the first plastics film is laminated to a second plastics film to encapsulate the colourant and the layer of particulate or colloidal material.

13. A document according to claim 12, wherein a U.V. sensitive material, U.V. reflective material and/or one or more fibre optic fibres are encapsulated between the first and second plastics films.

14. A document according to claim 13, wherein the one or more fibre optics are etched.

15. A document according to any of claim 12, 13 or 14, wherein at least one of the plastics films comprises an embossed portion.

16. A document according to any of claims 12 to 15, wherein the document is a label and comprises a portion having a removable hologram and an adhesive overlying the hologram.

17. A document according to any of claims 11 to 16, wherein the document comprises at least one region of weakness where the document can be manually torn to expose the silica to the atmosphere.

18. A document as claimed in any of claims 10 to 17 which further comprises a mark akin to a watermark.

19. A plastics sheet comprising thereon a layer of a particulate or colloidal material characterised in that the particulate or colloidal material has a particle size of from 5 to 0.006 microns.