WO2002062915A1

WO2002062915A1 - Paper products containing triboluminescent materials

Info

Publication number: WO2002062915A1
Application number: PCT/GB2002/000452
Authority: WO
Inventors: Norman James Geddes; Ian Charles Sage; Christopher Frank Rozelaar; Ian Robert Mason; Grant Hannah Bourhill
Original assignee: Qinetiq Limited
Priority date: 2001-02-06
Filing date: 2002-02-04
Publication date: 2002-08-15
Also published as: WO2002062915A8; AU2002231937A1; GB0102876D0

Abstract

This invention relates to the use of triboluminescent materials in paper products.

Description

TRIBOLUMINESCENT MATERIALS IN ADHESIVE COMPOSITIONS FOR USE IN ADHESIVE TAPE

This invention relates to applications of triboluminescent materials, in particular it relates to the use of triboluminescent materials in paper products.

Triboluminescent materials are known - (L M Sweeting & L Guido, J. of Luminescence, 33, (1985), pl67, N Kitamura et al, Chem Phys Letts, 125, (1986), p360, B P Shandra, et al Pramana-J Phys, 29, (1987), p399, C R Hurt, et al Nature, 212, (1966), pl79; L M Sweeting & A L Rheingold, J Am Chem Soc, 109,(1987), p2652 M B Hocking, et al, J. of Luminescence, 43, (1989), p309). Triboluminescence is the effect seen when a material emits light when particles of the material are damaged/fractured or strained.

Currently only a limited number of applications have been disclosed utilising the triboluminescent effect. PCT GB96/02778 and corresponding US 5905260 describe the use of triboluminescent compounds in an environment where they are used to detect damage to objects. GB 2232119 discloses a security marking technique comprising the use of triboluminescent materials.

It is an objective of the present invention to find alternative uses for triboluminescent materials.

According to a first aspect of this invention a method of making paper that emits light when torn and/or pressed and/or gripped and/or folded comprises the steps of coating and/or impregnating the paper with triboluminescent material.

When coating and/or impregnating the paper it may be necessary to apply the triboliminescent material in one or more of a number of ways, for example:

• in an adhesive composition, in addition the triboluminescent material may be glued onto the paper either directly and/or in an encapsulant such as a polymer;

• in a solvent followed by solvent evaporation;

• by melting the triboluminescent material such that it soaks into the paper;

• by incorporating the triboluminescent material together with the pulp, fibre etc., during manufacture of the paper.

Preferably the solvent will be an organic solvent though this will be a function of the solvation properties of the triboluminescent material.

Examples of suitable polymers for use in encapsulation include the following:

Acrylic and methacrylic resins, polyimides, polyamides, melamine/formaldehyde resins, urea formaldehyde resins, epoxy resins, poly(p-xylylene), gelatin, poly(lactic acid), polyester resins and alkyd resins.

Typical adhesives include:

Epoxy adhesives based on adducts of bisphenol-A and epichlorhydrin cured by polyamine or anhydride initiators, and similar adhesives based on other epoxides UV curable and thermally curable adhesives based on acrylic, vinylic, styrenic, or thiol/ene monomer systems, cyanoacrylate adhesives, pressure sensitive adhesives, hot melt adhesives, latex based adhesives, PVA adhesives, solvent based adhesives, urea formaldehyde and melamine formaldehyde adhesives, anaerobic adhesives, bis- diallyamine derived adhesives etc. In addition to the adhesive and triboluminescent material the adhesive composition may also comprise one or more of the following additional reagents such as solvents, dispersants, plasticisers, curing agents, dyes, fillers, stabilisers, anti-oxidants etc as is understood in the art. The compositions may include water as a solvent or dispersant or an organic solvent such as dichloromethane, acetone, tetrahydrofuran etc. may be present in order to ensure that the composition is homogenous and will spread well.

According to a second aspect of this invention paper is provided which comprises one or more triboluminescent materials such that the paper triboluminesces when the paper is torn and/or pressed and/or gripped and/or folded.

Such paper is obtainable by the method of the first aspect of the invention.

For all of the above aspects of the invention the term paper is also taken to include paper-like products such as cardboard, kitchen-roll, tissue and the like.

According to a third aspect of the invention a product comprising the paper of the second aspect of the invention is provided.

Suitable triboluminescent materials may be chosen on the basis of one or more of the following characteristics:

Bright emission

Colour/wavelength of emission

Ability to excite secondary emission from fluorescent and phosphorescent colourants

Intrinsic colour or lack of colour

High stability to temperature and high melting point

Compatibility with adhesive resins

Mechanical properties including surface texture and ease of fracture

Low cost of manufacture

Low toxicity

Compatibility with foodstuff contact and packaging Low environmental impact

Long lifetime in storage without deterioration

For all of the above aspects of the invention preferably the triboluminescent materials are chosen from the following general formulae:

Formula I

Wherein M is Eu, Tb, Dy or Sm;

R2 is H or C1-C6 alkyi or phenyl;

Rl and R3 are independently of each other selected from phenyl, H, C1-C6 alkyl;

L is p-N,N-dimethylaminopyridine, N-methylimidazole or p-methoxypyridine-N-oxide.

The C1-C6 alkyl groups can be straight chain or branched and are typically methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, ter-butyl or the different positional isomers of pentyl and hexyl, cyclopentyl, cydohexyl or methyl cyclopentyl.

Preferably the alkyl groups contain 1-4 carbon atoms.

Preferably M is Eu, Tb or Dy.

R2 is preferably H.

Most preferably Rl and R3 are each tert-butyl or phenyl.

The synthesis of compounds of formula I is described in WO 96/20942 and references therein including Eisentraut et al, Inorg. Syn. 11, 1968, 94. Other suitable compounds include:

Coumarin, phenanthrene, acenaphthene, resorcinol, m-aminophenol, aniline hydrochloride, phthalic anhydride, triphenylamine, p-anisidine, europium/terbium/manganese coordination complexes, cis-4-octene, uranyl nitrate hexahydrate, menthol, 9-anthrylmethanol [L M Sweeting & J L Guido, J. of Luminescence, 33, (1985), pl67] various carbazoles [N Kitamura et al, Chem Phys Letts, 125, (1986), p360], zinc sulphide doped with luminescent impurities, uranyl nitrate, sucrose and sacharides, and the alkali halides such as sodium fluoride or lithium fluoride.

Further suitable compounds include tetrahedral manganese (II) complexes (for instance bis-triphenylphosphine oxide manganese II bromide) [B P Shandra, et al Pramana-J Phys, 29, (1987), p399j. Europium tetrakis (dibenzoylmethide)-triethylammonium [C R Hurt, et al Nature, 212, (1966), pl79; L M Sweeting & A L Rheingold, J Am Chem Soc, 109,(1987), p2652] and 1,2,5-triphenylphosphole [M B Hocking, et al, J. of Luminescence, 43, (1989), p309], menthyl 9 anthracene carboxylate, menthol, lithium sulphate:anhydrous, saccharin, m-nitrobenzonitrile, N-acetylanthranilic acid, nicotinium salicylate, Hexaphenylcarbodiphosphorane, 9-anthrylethanol, [CH₃NH₃]₃Mn₂CI₇

A single triboluminescent compound or a composition comprised of a plurality of triboluminescent compounds may be used. Different triboluminescent compositions may be applied to different regions of the paper in an overlapping or non-overlapping pattern. Triboluminescent compositions applied substantially to the surface of the paper may be applied to one side or to both sides. Different compositions may be applied to each side of the paper. In all of the above applications the triboluminescence is taken to be of sufficient intensity that the human eye is capable of seeing it in substantially day light and/or room lighting conditions.

According to a further aspect of the present invention the paper of the second aspect of the present invention or the product of the third aspect of the present invention may be such that the triboluminescence is of such intensity to be machine readable only.

As such the paper products of the current invention may be used in devices for authenticating and identifying particular products and for applying security markings. Such devices encompass the use of triboluminescent paper wherein the triboluminescence is both capable and not capable of being seen by the human eye in substantially day light and/or room lighting conditions.

The invention will now be described by way of example.

A flashing form of paper, (e.g. writing paper, tissue or cardboard) according to the present invention may be fabricated as follows. Paper is soaked in a solution of triboluminescent material and any excess solvent is evaporated off. The paper may then be torn, folded or crumpled to test for a triboluminescent effect.

An alternative method of fabrication involves melting the triboluminescent material and allowing the melt to soak into the paper.

An alternative method of fabrication involves admixture of a triboluminescent (TL) material to paper pulp, which is then processed by normal known methods to provide a finished paper product.

A further method of providing a flashing form of paper according to the invention comprises forming a layer of pulp fibre onto which a triboluminescent composition is deposited, eg. by sprinkling the solid from a sieve or dispensing roller, or by ink jet printing of a suspension of TL material. A further layer of pulp fibre is deposited to laminate the TL material in place, and the whole is further processed to provide a paper product.

The above methods of fabrication have the advantage that the TL material is enclosed in the body of the paper and may be difficult to detect at the surface until its light emission is activated, thereby adding to the surprise of the effect or adding to the covert nature of the effect in the case that it is used as means for authentication of the article.

An alternative method of fabrication involves gluing triboluminescent material to the surface of the paper, alternatively the triboluminescent material is encapsulated, for example, in polymer which may then be coated on to the surface of the paper. Examples of suitable polymer include poly vinyl alcohol. The polymer may be applied whilst still in monomer form and subsequently cured. In all the above means of fabrication, the triboluminescent material may be used as an untreated additive. Alternatively the TL material may be encapsulated by known means before it is incorporated in the paper. Suitable means for encapsulation include suspending the TL material in a solution of a poly(amic acid), followed by spray drying and heat treatment. The TL material is thereby encapsulated in a poly(imide) coating. Suitable means for encapsulation also include exposure of the material to vapour of p- xylylene, obtained by thermal cracking of p-2,2-cyclophane. Preferably the material is agitated during this vapour treatment by such means as a fluidised bed or by ultrasound or by being placed on a vibrating surface.

Encapsulation, if applied, may contribute to the durability of the product, eg., by allowing the paper product to retain its TL effect after long storage, after washing or exposure to chemicals, or after exposure to conditions such as high temperature and humidity.

Encapsulation or indeed the general concept of the triboluminescent material being a part of the body of the paper means that the triboluminescent material is capable of being regenerated. For example the product may be melted and recrystallised in such a way that the crystals are effectively regenerated in terms of their triboluminescent effect.

Example 1

Paper was impregnated by soaking in a solvent (18.947g of chloroform) containing triboluminescent material (0.813g of Menthyl 9-anthracene carboxylate) and evaporating off any excess chloroform. This solution was poured over 80g/m² paper and allowed to soak in. The soaked paper was then left uncovered in a filter recirculation cabinet while the chloroform evaporated. After half an hour the paper was torn and bright flashes were observed. This work was repeated to test the application of this method to a lower grade of paper by substituting paper towelling for the 80g/m² paper. The results were similar. Example 2

Crystals of Menthyl 9-anthracene carboxylate (M9AC) were scattered over 80g/m² paper. A heat gun was used to melt the crystals and the melt was observed to soak into the paper. Flashes were observed on tearing the paper. This was repeated with the paper towelling and the results were similar.

Example 3

Triboliminescent crystals were glued onto the surface of the paper. "Spray Mount" a commercially available adhesive from 3M was sprayed onto 80g/m² paper. Crystals of Menthyl 9-anthracene carboxylate were then scattered over the adhesive. Excess crystals were shaken off the paper. Flashes were seen as the paper was torn. In order to test different triboluminescent materials, this experiment was repeated with crystals of Europium tetrakis dibenzoyl methide triethyl ammonium (ETBMTA) salt and similar results were obtained.

Example 4

Crystals of triboluminescent material were encapsulated in a polymer which was then coated onto the surface of paper. Two systems were tested, one used Norland 65 (N65) a UV curable monomer system and the other used poly vinyl alcohol (PVA). In the case of the Norland - 0.626g of M9AC was mixed into 1.244g of N65. The M9AC did not dissolve but was dispersed evenly in the glue. This resulting material was then thinly coated onto a sample of the 80g/m² paper and polymerised in an Hereaus Suntest CPS+ apparatus. The resulting paper with polymer / M9AC layer was tested and flashes were seen on tearing the paper. This experiment was repeated with 0.438g ETBMTA, 1.162g N65. Similar results were obtained. A second encapsulation technique was tested substituting polyvinyl alcohol (PVA) for the N65. 2.927g of PVA was dissolved into lOOmL of de-ionised water. 1.832g of this PVA solution was taken, 0.793g of M9AC was added and mixed in. The M9AC did not dissolve but was evenly dispersed. This suspension was coated thinly onto the 80g/m² paper and allowed to dry. This left the M9AC encapsulated in the PVA on the paper. The paper flashed on tearing.

It is appreciated by the present inventors that the methods and products of the present invention may be used in such products such as wrapping paper and novelty crackers. Manufacturers are constantly looking for ways in which to make such products more visually appealing and typically this is limited to creating new designs. As such it is a further objective of the present invention to provide aesthetic effects in relation to paper products through the use of technical structures and/or other technical means.

Example 5

A card outer wrapper for a novelty Christmas cracker was provided with a spiral pattern perforated tear line in its central region. The perforated line alone was coated with a triboluminescent composition comprising terbium tris-tetramethylheptanedionate dimethylaminopyridine dispersed in a gum acacia binder. The novelty cracker was assembled and tested by pulling until breakage. A green novelty flash was visible under room lighting in addition to the other standard features of the cracker.

Claims

1. A method of making paper that emits light when torn and/or pressed and/or gripped and/or folded comprising the steps of coating and/or impregnating the paper with triboluminescent material.

2. A method according to claim 1 wherein the coating and/or impregnation is applied in one or more of the following ways:

• in an adhesive composition,

• in a solvent followed by solvent evaporation,

• by melting the triboluminescent material such that it soaks into the paper,

• by incorporating the triboluminescent material together with pulp and/or fibre during manufacture of the paper.

3. A method according to claim 2 wherein when an adhesive composition is used, the triboluminescent material may be glued onto the paper either directly and/or in an encapsulant.

4. A method according to claim 3 wherein the encapsulant is a polymer.

5. A method according to claim 4 wherein the polymer is chosen from acrylic and methacrylic resins, polyimides, polyamides, melamine/formaldehyde resins, urea formaldehyde resins, epoxy resins, poly(p-xylylene), gelatin, poly(lactic acid), polyester resins and alkyd resins.

6. A method according to claim 5 wherein the polymer is chosen from Norland 65 or polyvinyl alcohol.

7. A method according to any of claims 2-6 wherein the adhesive is chosen from epoxy adhesives, UV curable and thermally curable adhesives based on acrylic, vinylic, styrenic, or thiol/ene monomer systems, cyanoacrylate adhesives, pressure sensitive adhesives, hot melt adhesives, latex based adhesives, PVA adhesives, solvent based adhesives, urea formaldehyde and melamine formaldehyde adhesives, anaerobic adhesives, bis-diallyamine derived adhesives.

8. A method according to any of claims 2-7 wherein the adhesive composition further comprises one or more of the following: solvents, dispersants, plasticisers, curing agents, dyes, fillers, stabilisers or anti-oxidants.

9. A method according to claim 8 wherein the solvent or dispersant is water.

10. A method according to claim 8 wherein the solvent is an organic solvent.

11. A method according to claim 10 wherein the solvent is dichloromethane or acetone or tetrahydrofuran.

12. A method according to any of claims 1-11 wherein the triboluminescent material is chosen from:

Formula I

Wherein M is Eu, Tb, Dy or Sm;

R2 is H or C1-C6 alkyl or phenyl;

Rl and R3 are independently of each other selected from phenyl, H, C1-C6 alkyl;

L is p-N,N-dimethylaminopyridine, N-methylimidazole or p-methoxypyridine-N-oxide;

the C1-C6 alkyl groups can be straight chain or branched;

or the following: coumarin, phenanthrene, acenaphthene, resorcinol, m-aminophenol, aniline hydrocfiloride, phthalic anhydride, triphenylamine, p-anisidine, europium/terbium/manganese coordination complexes, cis-4-octene, uranyl nitrate hexahydrate, menthol, 9-anthrylmethanol, carbazole containing compounds, zinc sulphide doped with luminescent impurities, uranyl nitrate, sucrose and sacharides, the alkali halides, tetrahedral manganese (II) complexes, bis-triphenylphosphine oxide manganese II bromide, Europium tetrakis (dibenzoylmethide)-triethylammonium and 1,2,5-triphenylphosphole, menthyl 9 anthracene carboxylate, menthol, lithium sulphate:anhydrous, saccharin, m-nitrobenzonitrile, N-acetylanthranilic acid, nicotinium salicylate, Hexaphenylcarbodiphosphorane, 9-anthrylethanol, [CH₃NH₃]₃Mn₂CI₇

13. A method according to claim 12 wherein the C1-C6 alkyl groups are selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, ter-butyl or the different positional isomers of pentyl and hexyl, cyclopentyl, cydohexyl or methyl cyclopentyl.

14. A method according to claim 12 wherein the triboluminescent materials are chosen from general formula I and Rl and R3 contain 1-4 carbon atoms, M is Eu, Tb or Dy, R2 contains 1-4. carbon atoms or is H.

15. A method according to claim 14 wherein R2 is H and Rl and R3 are tert-butyl or phenyl.

16. Paper comprising one or more triboluminescent materials such that the paper triboluminesces when the paper is torn and/or pressed and/or gripped and/or folded.

17. Paper according to claim 16 wherein the triboluminescent materials are selected from:

Formula I

Wherein M is Eu, Tb, Dy or Sm;

R2 is H or C1-C6 alkyl or phenyl;

Rl and R3 are independently of each other selected from phenyl, H, C1-C6 alkyl;

the C1-C6 alkyl groups can be straight chain or branched;

or the following:

coumarin, phenanthrene, acenaphthene, resorcinol, m-aminophenol, aniline hydrochloride, phthalic anhydride, triphenylamine, p-anisidine, europium/terbium/manganese coordination complexes, cis-4-octene, uranyl nitrate hexahydrate, menthol, 9-anthrylmethanol, carbazole containing compounds, zinc sulphide doped with luminescent impurities, uranyl nitrate, sucrose and sacharides, the alkali halides, tetrahedral manganese (II) complexes, bis-triphenylphosphine oxide manganese II bromide, Europium tetrakis (dibenzoylmethide)-triethylammonium and 1,2,5-triphenylphosphole, menthyl 9 anthracene carboxylate, menthol, lithium sulphate: anhydrous, saccharin, m-nitrobenzonitrile, N-acetylanthranilic acid, nicotinium salicylate, Hexaphenylcarbodiphosphorane, 9-anthrylethanol, [CH₃NH₃]₃Mn₂CI₇

18. Paper according to claim 17 wherein the C1-C6 alkyl groups are selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, ter-butyl or the different positional isomers of pentyl and hexyl, cyclopentyl, cydohexyl or methyl cyclopentyl.

19. Paper according to claim 17 wherein the triboluminescent materials are chosen from general formula I and Rl and R3 contain 1-4 carbon atoms, M is Eu, Tb or Dy, R2 contains 1-4 carbon atoms or is H.

20. Paper according to claim 19 wherein R2 is H and Rl and R3 are tert-butyl or phenyl.

21. A product comprising the paper of any of claims 17-21.

22. A product according to claim 21 wherein the product is wrapping or gift paper.

23. A product according to claim 21 wherein the product is a novelty cracker.