Particle and composition of particles with controlled dimensions

Abstract

A particle and a composition including a plurality of particles are provided, wherein the particles are platelets exhibiting a planar geometry which is circular or which is made up of a number (x) of planar (y)-sided polygon(s), wherein x is from 1 to 20 and y is at least 3 wherein if x is greater than 1 then said planar (y)-sided polygons are fused along one or more sides thereof, wherein the width (W.sub.P) of the platelets (P) at their widest point is no more than about 250 pm and the thickness of the platelets (P) is in the range of 10 nm to 50 nm.

Claims

1. A particle of controlled dimensions, consisting essentially of a platelet exhibiting a planar geometry which is circular or which is made up of a number (x) of planar (y)-sided polygon(s), wherein x is from 1 to 20 and y is at least 3 wherein if x is greater than 1 then said planar (y)-sided polygons are fused along one or more sides thereof, wherein the width (Wp) of the platelet (P) at its widest point is no more than about 250 μm and the thickness of said platelet is in the range of 10 nm to 50 nm.

2. A particle according to claim 1, wherein said platelet carries one or more micro-relief patterns on a surface thereof.

3. A particle according to claim 2, wherein said one or more micro-relief patterns is an optically variable effect structure.

4. A particle according to claim 1 wherein x is in the range from 1 to 10.

5. A particle according to claim 1 wherein y is 3 to 20.

6. A composition comprising a plurality of particles (P) of controlled dimension, wherein the number (n) of particles in said composition is at least 10, wherein said particles (P) consist essentially of platelets exhibiting a planar geometry which is circular or which is made up of a number (x) of planar (y)-sided polygon(s), wherein x is from 1 to 20 and y is at least 3 wherein if x is greater than 1 then said planar (y)-sided polygons are fused along one or more sides thereof, wherein the width (Wp) of the platelets (P) at their widest point is no more than about 250 μm and the thickness of the platelets (P) is in the range of 10 nm to 50 nm.

7. A composition according to claim 6 wherein x is in the range from 1 to 10.

8. A composition according to claim 6 wherein y is 3 to 20.

9. A composition according to claim 6, which is a pigment, security pigment, pigment concentrate, polymer masterbatch, paint, lacquer, coating, printing ink, glazing frit, ceramic frit, or security composition or concentrates therefor.

10. A formulation comprising the composition as defined in claim 6, and further comprising a vehicle, carrier, medium or diluent.

11. A formulation according to claim 10, which is a pigment, security pigment, pigment concentrate, polymer masterbatch, paint, lacquer, coating, printing ink, glazing frit, ceramic frit, or security composition or concentrates therefor.

12. A platelet consisting essentially of a planar geometry which is circular or which is made up of a number (x) of planar (y)-sided polygon(s), wherein x is from 1 to 20 and y is at least 3 wherein if x is greater than 1 then said planar (y)-sided polygons are fused along one or more sides thereof, wherein the width (Wp) of the platelet (P) at its widest point is no more than about 250 μm and the thickness of said platelet is in the range of 10 nm to 50 nm, said platelet carrying one or more micro-relief patterns on a surface thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is illustrated with reference to the following Figures.

(2) FIGS. 1A to 1C each show a laminar substrate comprising a support (1) and embossable layer (2) in which has been embossed a plurality of cells, in which each cell is defined by cell walls (3) and a cell floor (4). FIG. 1A illustrates the embodiment were the cell walls define positive relief in the z-dimension. FIG. 1B illustrates the embodiment were the cell walls define negative relief in the z-dimension. FIG. 1C illustrates the embodiment were the cell walls define both positive and negative relief in the z-dimension relative to the x-y plane of the cell floor.

(3) FIG. 2 shows an embossed substrate comprising a support (1) and embossable layer (2) in which has been embossed a plurality of cells, in which each cell is defined by cell walls (3) and a cell floor (4). A layer of material (6) has been deposited on the embossed substrate.

(4) FIG. 3 shows the embodiment wherein the embossable layer (2) exhibits a plurality of cells defined by cell walls (3) of height (H.sub.W) and an additional relief pattern (5) of height (h). The deposited material (6) has a thickness (T).

(5) FIG. 4 shows a plan view of the surface of a patterned substrate having a repeat pattern of 6 hexagonal discrete cells of identical cell geometry having cell walls (3) and floor portions (4) comprising a plurality of different and optional micro-relief patterns (5).

(6) FIG. 5 shows an embodiment wherein the embossable layer (2), for instance an acrylic thermo-embossable layer, is applied to the support (1) from a storage and supply means (10), the composite (coated) substrate then being provided with a release coating (not shown) by applicator (11) prior to contact with the embossing roller (12).

DETAILED DESCRIPTION

(7) The invention is further illustrated by the following examples. It will be appreciated that the examples are for illustrative purposes only and are not intended to limit the invention as described above. Modification of detail may be made without departing from the scope of the invention.

EXAMPLES

Example 1

(8) A polymer composition comprising polyethylene terephthalate was coextruded with a copolyester comprising terephthalic acid/isophthalic acid/ethylene glycol (82/18/100), cast onto a cooled rotating drum and stretched in the direction of extrusion to approximately 3 times its original dimensions at a temperature of approximately 90° C. The film was then passed through an inter-draw coater where a release coating comprising partially-esterified styrene maleic anhydride was applied as an aqueous solution at a concentration of 7% solids to one side of the film by a reverse roll direct coater. The coater speed was between 7 and 11 m.Math.min.sup.−1 and the line-speed was between 10 and 15 m.Math.min.sup.−1 The film was passed into a stenter oven at a temperature of 100° C. where the film was stretched in the sideways direction to approximately 3 times its original dimensions. The biaxially-stretched film was heat-set at a temperature of about 230° C. by conventional means. The total thickness of the coextruded film was 50 μm; the copolyester layer being approximately 10 μm thick, and the release coating being approximately 60 to 80 nm thick.

(9) The substrate was then heated to a temperature within the range 104 to 106° C. and pressed against an embossed roller (shim) bearing a repeat pattern comprising discrete cells of either regular hexagons, triangles or squares, the maximum planar dimension of a discrete cell being 25 μm between opposite walls. The depth of the negative image of the cell walls on the shim (prepared by electron-beam etching) was either 250 nm, 325 nm or 450 nm. The floor portion of each cell was coplanar with the surface of the support layer.

(10) A4 samples were then taken from the embossed reels and metallised in an Edwards laboratory scale bell jar metalliser, applying an aluminium film layer to a thickness in the range of 20 to 50 nm. The metallised film was then passed through a solvent-stripping process. The solvent used in the stripping process was acetone. The samples were either manually shaken or ultrasonically agitated, and the metal flakes were stripped from the film in about 30 seconds. A suspension of aluminium particles was collected having a concentration of about 1% by weight of aluminium particles. Optical magnification of the particles demonstrated that at least 30% of the particles exhibited the regular geometry of the cell pattern on the shim, i.e. were single hexagons, triangles or squares (x=1), and about 30% of the particles were particles consisting of fused hexagons, triangles or squares where the degree of fusion was x=2 or 4.