Surface functionalized titanium dioxide nanoparticles

Abstract

The present invention relates to surface functionalized titanium dioxide nanoparticles, a method for its production, a coating composition, comprising the surface functionalized titanium dioxide nanoparticles and the use of the coating composition for coating holo-grams, wave guides and solar panels. Holograms are bright and visible from any angle, when printed with the coating composition, comprising the surface functionalized tita-nium dioxide nanoparticles.

Claims

1. Surface functionalized titanium dioxide nanoparticles treated with a) a phosphonate of formula: ##STR00041## or a mixture of phosphonates of formula (I), wherein: R.sup.1 and R.sup.2 are independently of each other hydrogen, or a C.sub.1-C.sub.4alkyl group, R.sup.3 is a group CH.sub.2═CH—, or a group of formula —[CH.sub.2].sub.n—R.sup.4, wherein n is an integer of 1 to 12, when n>3 one —CH.sub.2— may be replaced by —S— with a proviso that S is not directly linked to P, or R.sup.4, R.sup.4 is hydrogen, or a group of formula ##STR00042## R.sup.5 is hydrogen, or a C.sub.1-C.sub.4alkyl group, R.sup.6 is hydrogen, or a C.sub.1-C.sub.4alkyl group, X.sup.1 is O, or NH, and b) bonded with an alkoxide of formula R.sup.7O.sup.− (II) and/or ##STR00043## wherein: R.sup.7 is a C.sub.1-C.sub.8alkyl group, which may be interrupted one or more times by —O— and/or substituted one or more times by —OH, R.sup.8 is hydrogen, or a C.sub.1-C.sub.4alkyl group, R.sup.9 is hydrogen, —CH.sub.2OH, —CH.sub.2SPh, —CH.sub.2OPh, or a group of formula R.sup.10—[CH.sub.2OH—O—CH.sub.2].sub.n1—, n1 is an integer of 1 to 5, X.sup.2 is O, or NH, R.sup.10 is a group of formula —CH.sub.2—X.sup.3—CH.sub.2—C(═O)—CR.sup.11═CH.sub.2, X.sup.3 is O, or NH, and R.sup.11 is hydrogen, or a C.sub.1-C.sub.4alkyl group.

2. The surface functionalized titanium dioxide nanoparticles according to claim 1, which have a size from 1 nm to 40 nm.

3. The surface functionalized titanium dioxide nanoparticles according to claim 1, wherein a weight ratio of titanium dioxide nanoparticles to phosphonate(s) of formula (I) and alkoxide(s) of formula (II) and (III) is in the range of from 99-1 to 50-50.

4. The surface functionalized titanium dioxide nanoparticles according to claim 3, wherein the weight ratio of phosphonate(s) of formula (I) and alkoxide(s) of formula (II) and (III) varies from 1-99 to 50-50.

5. The surface functionalized titanium dioxide nanoparticles according to claim 1, which exhibit a refractive index of greater than 1.70, when coated on a glass plate and dried at 60° C.

6. The surface functionalized titanium dioxide nanoparticles according to claim 1, wherein in the phosphonate of formula (I): R.sup.1 and R.sup.2 are hydrogen, R.sup.3 is a group CH.sub.2═CH—, or a group of formula —[CH.sub.2].sub.n—R.sup.4, wherein n is an integer of 1 to 5, and R.sup.4 is hydrogen, or a group of formula ##STR00044##

7. The surface functionalized titanium dioxide nanoparticles according to claim 1, wherein the alkoxide of formula (III) is derived from at least one of the following alcohols: ##STR00045## ##STR00046## ##STR00047##

8. The surface functionalized titanium dioxide nanoparticles according to claim 1, which is: a) treated with a phosphonate of formula ##STR00048## and b) bonded with an alkoxide of formula EtO.sup.− (D-2), iPropO.sup.−(D-4) and ##STR00049## or a) treated with a phosphonate of formula ##STR00050## and b) bonded with an alkoxide of formula EtO.sup.− (D-2) and iPropO.sup.−(D-4).

9. A coating composition, comprising the surface functionalized titanium dioxide nanoparticles according to claim 1 and a solvent.

10. A method for forming a surface relief microstructure on a substrate, the method comprising: a) forming a surface relief microstructure on a discrete portion of the substrate; and b) depositing the coating composition according to claim 9, on at least a portion of the surface relief microstructure.

11. The method according to claim 10, wherein step a) comprises: a1) applying a curable compound to at least a portion of the substrate; a2) contacting at least a portion of the curable compound with surface relief microstructure forming means; and a3) curing the curable compound.

12. A process, comprising coating an article with the coating composition according to claim 9, where the article is selected from the group consisting of a hologram, a wave guide and a solar panel.

13. A security, or decorative element, comprising a substrate, which may contain indicia or other visible features in or on its surface, and on at least part of the said substrate surface, a coating, comprising the surface functionalized titanium dioxide nanoparticles according to claim 1.

14. A process for preparing titanium dioxide nanoparticles, the process comprising: (a) adding a solution of concentrated hydrogen chloride and diluting the solution with half volume of distilled water, diluting the solution with additional ethanol resulting in solution I to a solution of titanium-tetra-iso-propoxide first stirred in absolute ethanol resulting in a solution II, both volumes of the solutions I and II being equal, to obtain a clear solution, (b) stirring the obtained clear solution for 5 days at room temperature, and (c) evaporating the clear solution at 20-30° C./20 mm until a constant weight is achieved to obtain titanium dioxide nanoparticles.

15. The process according to claim 14, comprising: d) dissolving the titanium dioxide nanoparticles obtained in step c) in a solvent, e) adding a phosphonate(s) of formula (I) ##STR00051## and, optionally adding an alcohol of formula ##STR00052## obtaining a mixture having a weight, and stirring the mixture obtained in step (e) until a transparent solution is obtained, and evaporating the mixture until the weight remains constant, wherein: R.sup.8 is hydrogen, or a C.sub.1-C.sub.4 alkyl group, R.sup.9 is hydrogen, —CH.sub.2OH, —CH.sub.2SPh, —CH.sub.2OPh, or a group of formula R.sup.10—[CH.sub.2OH—O—CH.sub.2].sub.n1—, n1 is an integer of 1 to 5, X.sup.2 is O, or NH, R.sup.10 is a group of formula —CH.sub.2—X.sup.3—CH.sub.2—C(═O)—CR.sup.11═CH.sub.2, X.sup.3 is O, or NH, and R.sup.11 is hydrogen, or a C.sub.1-C.sub.4alkyl group.

16. Titanium dioxide nanoparticles obtained by the process according to claim 14, which have a particle size from 1 nm to 40 nm and a TiO.sub.2-content of at least 40% by weight, a film of which dried at 25° C. shows a refractive index of greater than 1.70 (589 nm).

17. The titanium dioxide nanoparticles according to claim 16, which are storable at 4° C. for at least 3 months and can be redissolved in methanol, ethanol, propanol, 2-methoxy ethanol, iso-propanol, 2-iso-propoxy ethanol, butanol, ethyl acetate, propyl acetate and butyl acetate.

Description

EXAMPLES

Example 1

(1) Preparation of Phosphonates:

(2) Phosphonate acrylamide and acrylate precursors have been synthesized according WO2006/094915 unless otherwise stated or are used as commercially available. All .sup.1H-NMR taken at 300.13 MHz and .sup.31P-NMR at 121.5 MHz.

Example 1.1

(3) Methyl Phosphonate of Formula

(4) ##STR00024##
(R.sup.4, R.sup.1 and R.sup.2=H; n=1):

(5) 50.0 g commercial dimethyl methyl phosphonic ester (Aldrich) are dissolved in 400 ml acetonitrile at room temperature and treated with 135.7 g trimethylsilyl bromide at 40° C. for 20 h. Then the mixture is evaporated and the residue treated with an excess of methanol to hydrolyze the silyl ester for 48 h at room temperature. Evaporation leaves 38.0 g of the methyl phosphonic acid (B1a) ready for further use.

(6) .sup.1H-NMR (DOCD.sub.3): 1.42 ppm (d). .sup.31P-NMR (DOCD.sub.3): +28.4 ppm.

Example 1.2

(7) Butyl Phosphonate of Formula (I) (R.sup.4, R.sup.1 and R.sup.2=H; n=4):

(8) According the procedure given for example 1.1, 35.0 g of butyl phosphonate (B1d) is obtained from 50.0 g of diethylbutyl phosphonic ester ready for further use.

(9) .sup.1H-NMR (CDCl.sub.3): 0.94 ppm (t, 3H); 1.48 ppm (m, 2H); 1.61 ppm (m, 2H); 1.76 ppm (m, 2H). .sup.31P-NMR (CDCl.sub.3): +36.6 ppm.

Example 1.3

(10) Octyl Phosphonate of Formula (I) (R.sup.4, R.sup.1 and R.sup.2=H; n=8):

(11) According the procedure given for example 1.1, 11.0 g of octyl phosphonate (B1e) is obtained from 15.0 g of diethyloctyl phosphonic ester ready for further use.

(12) .sup.1H-NMR (CDCl.sub.3): 0.90 ppm (t, 3H); 1.28-1.41 ppm (m, 8H); 1.57-1.82 (m, 6H). .sup.31P-NMR (CDCl.sub.3): +36.0 ppm.

Example 1.4

4-acryloylamido-butyl Phosphonate of Formula (I) (R.SUP.4.=acryloylamido-, R.SUP.1 .and R.SUP.2.=H, n=4)

(13) 112.0 g of Diethyl-4-amino butyl phosphonic ester (WO2006/094915) are reacted with 75.0 g of 2-chloro acetic acid chloride (Aldrich) in 600 ml dichloromethane in the presence of 59.7 g triethyl amine at 0° C. to room temperature for 24 h. The mixture is then subsequently extracted with 1N hydrogen chloride solution, water and brine and dried over sodium sulfate, filtered and evaporated to leave 111.1 g of a syrupy mass which is used in the next step. The product is dissolved in 450 ml of acetone containing 62.0 g of DBU (diaza-bicycloundecane) and 20 mg methoxy phenol and stirred at room temperature for 24 h. Subsequent evaporation leaves a residue which is extracted with 1 N hydrogen chloride, sat. sodium hydrogencarbonate solution and brine to give after removal of solvent 67.2 g of the phosphonic ester. The ester is treated according the procedure given in example 1 with 85.5 g trimethyl silylbromide in 475 ml acetonitrile to give 47.3 g of the title compound (B3b).

(14) .sup.1H-NMR (DOCD.sub.3): 1.44-1.80 ppm (m, 6H); 3.30 ppm (t, 2H); 5.67 ppm (dd, 1H); 6.24 ppm (dd, 2H). .sup.31P-NMR (DOCD.sub.3): +30.4 ppm.

Example 1.5

4-vinyl butyl Phosphonate of Formula (I) (R.SUP.4.=vinyl-, R.SUP.1 .and R.SUP.2.=H, n=4)

(15) 4.8 g of the starting diethyl phosphonate (R.sup.4=vinyl, R.sup.1=R.sup.2=Et, n=4) obtained according (WO2006/094915) are treated according the procedure in example 1.1 with 6.7 g trimethylsilyl bromide in acetonitrile to give 3.0 g of the title compound (B4b).

(16) .sup.1H-NMR (CDCl.sub.3): 1.55 ppm (m, 2H); 1.68 ppm (m, 2H); 1.81 ppm (m, 2H); 2.12 ppm (m, 2H); 5.00 ppm (m, 2H); 5.81 ppm (m, 1H). .sup.31P-NMR (CDCl.sub.3): +30.2 ppm

Example 1.6

2-methacroyloxy-butyl Phosphonate of Formula (I) (R.SUP.4.=methacroyloxy-, R.SUP.1 .and R.SUP.2.=H, n=2)

(17) The starting dimethyl 2-methacroyloxy derivative (R.sup.4=methacroyloxy, R.sup.1=R.sup.2=Me, n=2) is obtained according literature (K. Rajalakshmi et al. Polym. Sci. Ser. B, 2015, 57(5), 408). 28.0 g of this material is then treated with 41.0 g of trimethyl siliyl bromide in 120 ml acetonitrile according the procedure given in example 1.1 to give 24 g of the title compound (B2a) ready for further use.

(18) .sup.1H-NMR (CDCl.sub.3): 2.01 ppm (s, 3H); 2.22 ppm (m, 2H); 4.38 ppm (m, 2H); 5.58 ppm (s, 1H), 6.12 ppm (s, 1H). .sup.31P-NMR (CDCl.sub.3): +28.3 ppm.

Example 1.7

5-methacryolyloxy-3 thia pentyl Phosphonate of Formula (I) (R.SUP.4.=5-methacryolyloxy-3 thia pentyl-, R.SUP.1 .and R.SUP.2.=H, n=5)

(19) 32.8 g of commercial diethyl vinylphosphonic ester are reacted with 15.6 g of 2-mercapto ethanol and 0.5 mg of sodium ethanolate (in 1.5 ml abs. ethanol) for 32 h at 107° C. After cooling down to room temperature the mixture is dissolved in dichloromethane and washed with water and dried over sodium sulfate. Filtration and evaporation leaves a residue which is purified by silica gel column chromatography (eluent: dichloromethane-methanol: 40-1) to give 38.2 g of the intermediate alcohol (R.sup.4=5 hydroxy-3-thia pentyl, R=Et, n=5).

(20) 34.9 g of this material is dissolved in 300 ml dichloromethane containing 22.6 g triethyl amine and 4-methoxy phenol as stabilizer and cooled to −10° C. Then 27 g of methacrylic acid chloride are added and the mixture stirred for 20 h. Subsequent extraction with 1 N hydrogen chloride, sat. hydrogen carbonate solution and brine and evaporation leaves a residue which is purified over silica gel column chromatography (eluent: dichloromethane-methanol: 40-1) to give 38.7 g of the title compound (B5a).

(21) .sup.1H-NMR (CDCl.sub.3): 1.97 ppm (s, 3H; 2.16 ppm (m, 2H); 2.87 ppm (m, 4H); 4.35 ppm (t, 2H); 5.63 ppm (s, 1H); 6.16 ppm (s, 1H). .sup.31P-NMR (CDCl.sub.3): +28.5 ppm.

Example 2

(22) ##STR00025##
(idealized with one potential ligand each only)
Preparation of Transparent, Soluble and Storable TiO.sub.2-Nanoparticles (Idealized with One Potential Ligand Each Only):

(23) A 5 l flask is first charged with 200 g (0.70 mol) commercial titanium-tetra-iso-propoxide (Aldrich) and filled up to a total volume of 2 l with dry absolute ethanol (Merck). This mixture is stirred smoothly (200 rpm) at room temperature. To this solution is subsequently funneled a second solution having been prepared from 60 ml of 33% hydrogen chloride (Aldrich) and 29.8 ml of distilled water filled up to a total volume of 2 l with ethanol. The resulting clear solution is stirred for 5 days at room temperature and then smoothly evaporated at 20°-30° C./20 mm until a constant weight is achieved.

(24) A transparent foamy material (118.9 g) is obtained which can be crushed to a solid when dry. This material can be stored at least over three months at 4° C. without any visible change and can be redissolved clearly in e.g. methanol, ethanol, propanol, 2-methoxy ethanol, iso-propanol, 2-iso-propoxy ethanol, butanol, N-methyl pyrrolidone, dimethyl formamide, dimethyl acetamide and the like. A TGA (thermogravimetric analysis) of this material up to 450° C. shows a weight loss of about 42%, which leaves a total TiO.sub.2 contents of at least 58%. A TEM (transmission electron microscopy) shows particle sizes <5 nm. A film of this material dried at 25° C. shows a refractive index (RI) (589 nm) of 1.72 and when dried at 120° C. an RI of 1.95, accordingly.

(25) The titanium dioxide nanoparticles are dissolved in ethanol, or isopropanol and spin-coated on float-glass substrates. The coated glass substrates are dried at temperatures of 25, or 120° C. until weight constancy and the Refractive Index (RI) of the coatings (layer thickness ca. 400 nm) is determined by white-light reflectometry using a Filmetrics F10-RTA-UV photospectrometer with an internal fitting algorithm (Cauchy fit). From the fitting the refractive indices were calculated for a wavelength of 589 nm.

Example 3

(26) Coating of Soluble & Storable TiO.sub.2-Nanoparticles:

(27) ##STR00026##

Example 3.1

(28) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Formula (I) of Example 1.1 (R.sup.4, R.sup.1 and R.sup.2=H; n=1):

(29) 1.00 g of dried TiO.sub.2-nanoparticles are dissolved at room temperature in 10 ml of ethanol together with various amounts from 0.01 g to 0.75 g (1% to 75%) of phosphonate of example 1.1 dissolved in 2 ml ethanol and stirred 18 h-24 h. All solutions are clear after being stirred for 1 h. The 1% sample stays clear as a 7% w/v solution in ethanol or as a 20% w/v in 2 iso-propoxy ethanol (R′—OH).

(30) The 1% sample e.g. gives a film after drying at 40° C. with thickness ca. 875 nm and RI=1.8240.

Example 3.2

(31) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Formula (I) of Example 1.1 (R.sup.4, R.sup.1 and R.sup.2=H; n=1) and

(32) ##STR00027##

(33) 10.00 g of dried TiO.sub.2-nanoparticles are dissolved at room temperature in 4.20 ml of ethanol to form a transparent solution; to this mixture a solution of 0.108 g of phosphonate of example 1.1, dissolved in 0.30 ml ethanol is added at room temperature and stirred for 3.5 h. Thereafter 0.96 g of compound (C-10), dissolved in 0.50 ml ethanol is added and the transparent mixture stirred for 24 h and subsequently evaporated until the weight remains constant to give a yellowish syrupy mass.

Example 3.3

(34) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Formula (I) of Example 1.1 (R.sup.4, R.sup.1 and R.sup.2=H; n=1) and Phosphonate of Formula (I) of Example 1.4 (R.sup.4=acryloylamido-, R.sup.1 and R.sup.2=H, n=4):

(35) 10.00 g of dried TiO.sub.2-nanoparticles are dissolved at room temperature in 50 ml of ethanol together with 0.20 g of phosphonate of example 1.1 to form a transparent solution and stirred for 2.5 h; to this mixture a solution of 0.800 g of phosphonate of example 1.4, dissolved in 20 ml ethanol is added at room temperature and stirred for an additional 18.5 h. Thereafter the transparent mixture evaporated until the weight remains constant to give a yellowish syrupy mass. This material shows an RI of 1.70 when dried at room temperature and an RI of 1.81 when dried at 80° C.

Example 3.4

(36) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Formula (I) of Example 1.1 (R.sup.4, R.sup.1 and R.sup.2=H; n=1) and Phosphonate of Formula (I) of Example 1.6 (R.sup.4=methacryloxy, R.sup.1 and R.sup.2=H, n=2):

(37) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Example 1.1 Methyl Phosphonate of Example 1.1 and Phosphonic Acid I (R.sup.4=methacryloxy, R=H, n=2):

(38) 160.00 g of dried TiO.sub.2-nanoparticles are dissolved at room temperature in 60 ml of ethanol, to this mixture are added 3.20 g of phosphonate of example 1.6 dissolved in 5 ml ethanol and stirred for 3 h to form a transparent solution; to this mixture a solution of 12.60 g of phosphonate of example 1.1, dissolved in 5 ml ethanol is added at room temperature and stirred for an additional 18.5 h. Fines are filtered off and the transparent mixture is evaporated until the weight remains constant to give a yellowish syrupy mass. This material shows an RI of 1.76 when dried at 80° C.

Example 3.5

(39) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Formula (I) of Example 1.1 (R.sup.4, R.sup.1 and R.sup.2=H; n=1) and Phosphonate of Formula (I) of Example 1.7 (R.sup.4=5-methacryolyloxy-3 thia pentyl-, R.sup.1 and R.sup.2=H, n=5):

(40) 1.00 g of dried TiO.sub.2-nanoparticles are dissolved at room temperature in 3.00 ml of ethanol, to this mixture are added 0.275 g of phosphonate of example 1.7 dissolved in 2 ml ethanol and stirred for 7 h to form a transparent solution; to this mixture a solution of 0.02 g of phosphonate of example 1.1, dissolved in 2 ml ethanol is added at room temperature and stirred for an additional 18.5 h. The transparent mixture is evaporated until the weight remains constant to give a yellowish syrupy mass.

Example 3.6

(41) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Formula (I) of Example 1.3 (R.sup.4, R.sup.1 and R.sup.2=H; n=8) and Phosphonate of Formula (I) of Example 1.7 (R.sup.4=5-methacryolyloxy-3 thia pentyl-, R.sup.1 and R.sup.2=H, n=5):

(42) 2.00 g of dried TiO.sub.2-nanoparticles are dissolved at room temperature in 20.00 ml of ethanol, to this mixture are added 0.100 g of phosphonate of example 1.3 and 0.50 g phosphonate of example 1.7 dissolved in 4 ml ethanol and stirred for 24 h to form a transparent solution. The transparent mixture is evaporated until the weight remains constant to give a white foamy mass which forms transparent solutions in ethanol.

Example 3.7

(43) Coating of TiO.sub.2-Nanoparticles of Example 2 with Phosphonate of Formula (I) of Example 1.6 (R.sup.4=Vinyl-, R.sup.1 and R.sup.2=H, n=4) and Alcohol (C-10):

(44) 10.00 g of dried TiO.sub.2-nanoparticles are dissolved at room temperature in 4.20 ml of ethanol, to this mixture are added 0.300 g of phosphonic acid of example 1.6 dissolved in 0.30 ml ethanol and stirred for 3 h; thereafter 0.96 g of alcohol (C-10) dissolved in 0.50 ml ethanol are added and stirred for an additional 24 h. The transparent mixture is evaporated until the weight remains constant to give a yellowish syrupy mass which forms transparent solutions in ethanol.

Example 4

(45) Measuring of RI and Film Thickness of Titanium Nanoparticles Containing Films

(46) The titanium nanoparticles are diluted at a ratio 1:10 in ethanol. The solution is mixed at room temperature with a magnetic stirrer at low regime (roughly 50 rpm). Glass plates are cleaned with ethanol and wiped without leaving any fibers or contamination. Then the glass plates are Corona-treated twice (power 300 W). The glass plates are fixed on a spin coater by vacuum. The solution is visually transparent. After mixing, the solution, an amount of 0.1, resp. 0.2 g is taken with a pipette and applied on the center of the glass plate. The spin coater is turned on and runs at a rotational speed of 150 rpm during 10 seconds then immediately 10000 rpm during 4 seconds. A visual examination ensures that the coatings are transparent.

(47) The coated glass plates are dried at temperatures of from 60 to 120° C. until weight constancy and the Refractive Index (RI) of the coatings (layer thickness ca. 400 nm) are determined by white-light reflectometry using a Filmetrics F10-RTA-UV photospectrometer with an internal fitting algorithm (Cauchy fit). From the fitting the refractive indices were calculated for a wavelength of 589 nm.

(48) The results are summarized in the table below:

(49) TABLE-US-00002 Example (TiO.sub.2 Refractive Index nanop.) Phosphonate (I) Alkoxide (II)/(III) (RI) 3.1 (T-1) EtO.sup.− (D-2), iPropO.sup.− (D-4) RI of 1.82 when dried at 120° C. 3.2 (T-2) EtO.sup.− (D-2), iPropO.sup.− (D-4), RI of 1.82 when dried at 120° C. 0 3.3 (T-3) EtO.sup.− (D-2), iPropO.sup.− (D-4) RI of 1.81 when dried at 80° C. 3.4 (T-4) EtO.sup.− (D-2), iPropO.sup.− (D-4) RI of 1.76 when dried at 80° C. 3.5 (T-5) EtO.sup.− (D-2), iPropO.sup.− (D-4) RI of 1.76 when dried at 60° C. 3.6 (T-6) EtO.sup.− (D-2), iPropO.sup.− (D-4).sup.− RI of 1.75 when dried at 60° C. 3.7 (T-7) EtO.sup.− (D-2), iPropO.sup.− (D-4), RI of 1.75 when dried at 60° C. 0

(50) The coated glass plates are then stored in closed petri-dishes at room temperature.

Example 5

(51) Gravure Printing

(52) The titanium nanoparticles containing products of examples 3.1 to 3.7 (40% to 70% (w (weight)/v (volume)) solids in ethanol) are diluted to a final 6.5% (w/v) concentration (of solids:surface-treated TiO.sub.2 particles) with ethanol. The resulting ink is printed by gravure on PET foil containing holograms and no holograms using a 70 l/cm gravure cylinder at printing speed 10-90 m/min, heating 90° C.

(53) TABLE-US-00003 Surface OVD image OVD image visibility functionalized visibility after overlacquering TiO.sub.2 particle after printing with UV varnish T-7 Excellent, clear film Good, clear film (6.3% solids in ethanol) T-4 Excellent, clear film Good, clear film (5.8% solids in ethanol)

(54) The resulting foil is highly transparent and color less. Holograms are bright and visible from any angle, after overcoating the printed foil with 10 micron UV varnish, holographic structures remain visible.