| WO2003012492A1 | 2003-02-13 |
| EP0405582A2 | 1991-01-02 | |||
| DE2417272A1 | 1975-10-23 | |||
| US6007888A | 1999-12-28 | |||
| US5376431A | 1994-12-27 |
| 1. | 1). A process for manufacturing a reflector laminate, wherein a structured surface is realised on a side of a laminate made of transparent or coloured transparent heatformable material and previously coated with a layer of reflective material, which structured surface gives backreflective properties to the laminate. 2). The process of claim 1, wherein at least one layer of protective material is distributed on the structured surface. 3). The process of claim 1 or 2, wherein the structured surface comprises a distribution of microprisms realised on a side of the laminate. 4). The process of any one of the preceding claims, wherein the reflective material is silver. 5). The process of claim 4, wherein a thickness of the silver is at least 0.5 micron, and is preferably comprised between 0.8 and 1.2 micron. 6). The process of any one of claims from 1 to 3, wherein the reflective material is aluminium. 7). The process of claim 6, wherein the structured surface is made by heat forming at a temperature of at least 120°C, preferably between 180°C and 250°C, by effect of which heatforming some optical properties of the reflective material are altered, in particular colour and luminosity. 8). The process of claim 6 or 7, wherein a thickness of the aluminium is at least 0.2 micron, and is preferably between 0.4 and 0.6 micron. 9). The process of any one of the preceding claims, wherein the laminate is shaped, preferably by heatforming, in order to realize, on a side thereof opposite to the structured surface, a distribution of macroscopic reliefs; on an opposite side of the laminate to the side exhibiting the macroscopic reliefs a plurality of cells are created, which cells are recessed and correspond to positions of the macroscopic reliefs. 10). The process of claim 9, wherein a layer of material is distributed on the laminate to fill the cells and cover the side of the laminate opposite the side exhibiting the distribution of macroscopic reliefs. 11). The process of claim 9 or 10, wherein the lamiante is heated before being subjected to the heatforming of the macroscopic reliefs, which heatforming includes an operation comprising two oppositelysituated embossing cylinders (11, 12), each peripherally provided with a matrix, one male and one female; the male matrix and the female matrix cooperating with one another in order to obtain, on the laminate, one surface exhibiting the macroscopic reliefs and another surface exhibiting the cells. 12). The process of claim 11, wherein a continuous protective film for protecting the laminate is made to pass between at least one of the male matrix and the female matrix and the laminate. 13). The process of claim 12, wherein the continuous protective film is made of thermoplastic material and is between 10 and 80 micron in thickness, and preferably is about 40 to 50 micron in thickness. 14). The process of claim 12 or 13, wherein the continuous protective film does not stably couple with the laminate and detaches, being rewound on a reel (13'). 15). The process of any one of the preceding claims, wherein the process is operated continuously starting from an unwinding of metallized film from a reel (1) and ending with a rewinding of a completed laminate (9, 17) on another reel (9,17). |
Technical Field The invention relates to a process for manufacturing a reflector laminate.
Specifically, though not exclusively, the reflector laminate can usefully be applied for making road signals.
Background Art The prior art teaches various types of reflector laminates, in particular of the type with a structured surface having micro-prisms to give the laminate back- reflecting properties, for example patents US 5376431, US 567162, US 6083607 and US 6139158.
The present invention provides a process for obtaining a laminate having high back-reflecting powers.
An advantage of the invention is that it provides a process for obtaining a back- reflecting laminate having the luminous, colour and back-reflecting characteristics required by the existing standards in the road-signal sector.
A further advantage is that the process is simple, economical, reliable and highly productive.
A further advantage is that the laminate is resistant and has a long working life.
These aims and advantages and more besides are all attained by the present invention as it is characterised in the claims that follow.
Disclosure of Invention Further characteristics and advantages of the present invention will better emerge from the detailed description that follows, of two preferred but non-exclusive
embodiments of the invention, illustrated purely by way of example in the figures of the drawings, in which: figure 1 is a diagram of a plant for manufacturing a first version of the laminate of the invention; figure 2 is a diagram of a second plant for manufacturing a second version of the laminate of the invention.
With reference to the figures of the drawings: 1 denotes a reel of metallized plastic film; 2 denotes an embossing cylinder bearing a matrix with micro-prisms ; 3 denotes a pressor cylinder cooperating in pressure with embossing cylinder ; 4 denotes a device for performing a roughening treatment on metallized plastic films with the aim of increasing the wettability of the surface thereof (to improve adhesion between the surface and the layer which will subsequently be applied thereon). 5 denotes a roller for distributing a layer of protective paint on the roughened metallized surface, and 6 denotes a reel of bi-adhesive film; 7 denotes a pair of rollers for coupling the biadhesive film with the film; 8 denotes a pair of roller-trimmers for trimming the laminate, and 9 denotes the rewinding reel of the obtained laminate.
The plant of figure 1 operates in line, starting from the reel 1 of metallized film and ending at the rewinding reel 9 of reflector laminate. The laminate obtained is particularly usable for making vertical road signs.
The metallized film on the reel 1 is made of heat-formable plastic material, either transparent or coloured-transparent (for example a methacrylate resin such as polymethyl methacrylate), on a side of which a thin layer of reflective material has been previously deposited, through a metallizing process using silver or aluminium. The transparent layer is between 150 and 300 micron in thickness.
The embossing cylinder 2, which is heated to the embossing temperature, generates a structured surface on the metallized side, which structured surface
comprises a distribution of micro-prisms M in relief, covered by layer of reflective material constituted by the metal. The micro-prisms M determine the properties of back-reflection of the laminate. The height of the micro-prisms is preferably comprised between 60 and 180 micron. The micro-prisms M are generated by heat-forming of the plastic material of the film. The thin reflective layer is not damaged. The reflective layer is relatively very thin in comparison with the height of the micro-prisms, being preferably less than the latter by at least one order.
If the metal used for metallization is sliver, the thickness of the silver reflective layer is preferably at least 0.5 micron; in the present embodiment the thickness is about 0.8-1. 2 micron. In the present embodiment the embossing temperature (about 215° C in the present embodiment and preferably between 180°C and 250°C) does not cause substantial alterations to the silver reflective material.
If the metal used is aluminium, the properties of the reflective layer have been seen to be considerably changed after the micro-prisms M have been heat-formed by the embossing machine 2. Owing to this change, the smooth side (not structured) of the laminate, destined to be in view and opposite the metallized and structured side, does not lose its back-reflecting properties (or at least only very minimally) but changes its visual aspect considerably, becoming lighter in colour, tending to white, and falling within the colour tone code established by the existing road signal standards. The luminosity is also changed and falls nonetheless into the range of luminosity required by the standards. The change in the properties of the aluminium reflective layer is caused by the oxidation of the aluminium. The thickness of the aluminium reflective layer is preferably at least 0.2 micron: in the present embodiment the thickness is about 0.4-0. 6 micron.
The device 4 performs a surface preparation of the metallized structured surface with micro-prisms, i. e. on the sub-strate on which a covering of protective paint
(layer S) will later be applied, to make the substrate suitable for bonding with the paint; in the illustrated embodiment this preparation consists of a roughening treatment which, as is known, increases the wettability of the sub-strate and thus the adherence of the further coating.
The rollers 5 distribute a thick layer S of a protective material which covers the metal and which is constituted by a paint for metals, preferably a bi-component polyurethane, which improves the grip of the protective and covering layer subsequently distributed (in the illustrated embodiment the bi-adhesive film).
The structured surface is composed of valleys and crests which are filled and covered by at least one protective layer P which, in the illustrated embodiment, is applied by means of the bi-adhesive film of the reel 6.
The rollers 7 couple the bi-adhesive paper onto the side bearing the micro-prisms.
The coupling causes the micro-prisms to fill with the layer P of adhesive material on the bi-adhesive paper. The layer P, which is made for example of a high- weight polyurethane resin, fills the valleys of the structured surface and covers the crests with a protective thickness, which protects the micro-prisms so that the shape thereof does not change when in use, since any change in conformation thereof would damage their optical properties.
If the material used for metallizing one side of tlle laminate is aluminium, the aluminium will undergo an oxidising process due to the temperature of the heat- forming of the micro-prisms and to the time it remains at the high temperature (in contact with the embossing cylinder 2), so that after the formation of the micro- prisms, on exiting the embossing cylinder 2, the reflective layer covering the micro-prisms is whitened with respect to the colour thereof on leaving the reel 1; no damaging effect to its continuity, however, results from the heat-forming of the micro-prisms M. The whitening effect means that the side of the laminate which will be in view is of a colour and luminosity which fall within the range
required by the standards for road signals. The desired whitening effect is already obtainable at minimum temperatures of heat-forming, around 120-130°C. The transparent material in the present embodiment is a plastic which is heat-formable at those temperatures, for example a vinyl-type material. In the illustrated embodiment, in which the transparent material is acrylic, the heat-forming temperatures are greater (in general at least 180°C), so that the whitening effect of the aluminium is guaranteed, even where working times are relatively short.
Turning to figure 2, the elements indicated with numbers from 1 to 5 are the same as the ones denoted by the same numbers in figure 1. Further: 10 denotes a radiating panel device (infrared rays) for heating the laminate exiting from the distributor roller 5 to a temperature of about 90-100°C ; 11 denotes an embossing cylinder arranged downstream of the heating device 10 and having a cylindrical matrix (male) on a periphery thereof, which matrix consists of macroscopic reliefs for forming the laminate; 12 denotes an embossing cylinder which cooperates with the cylinder 11 and has a matrix with recesses (female) corresponding to the above-mentioned macroscopic reliefs; 13 indicates a reel of thermoplastic film (for example polythene) having a thickness of between 10 and 80 micron (preferably about 40-50 micron) for the protection of the micro-prisms during the embossing operation to create the macroscopic reliefs ; 13'denotes a rewinding reel of the protection film after use; 14 denotes a first spreader for distribution of a filler resin of the cells created"negatively"to the macroscopic reliefs; 15 denotes a second spreader for distribution of an adhesive on the layer of resin; 16 denotes a pair of roller-trimmers for trimming, 17 denotes the rewinding reel of the obtained laminate, 18 a reel of anti-stick film, 19 two rollers to train the anti-stick film unwound from the reel 18, and 20 two contrast cylinders cooperating with the spreading groups 14 and 15.
In the plant of figure 2, as in the plant of figure 1, the laminate passes
continuously from the first, unwinding reel 1 to the rewinding reel 17, with no interruptions.
The laminate obtained with the plant of figure 2 is usable especially for horizontal or lateral road signals.
The heating device 10 brings the laminate up to the softening temperature for heat-forming by the embossing cylinders 11. The heating device 10 can comprise (in a non-illustrated version) a pair of heater rollers.
The two matrices, male and female, of the cylinders 11 and 12, are both made of a hard material (metal, for example steel or nickel); alternatively, one of the two matrices (preferably the male matrix) can be made of an elastically-deformable material, more deformable than the material of the other matrix. For example, the male matrix can be made of silicone rubber and the female matrix of metal.
The two embossing cylinders 11 (cooled) operate in phase so that at the heat- forming zone each projection (male) of a matrix corresponds with a recess (female) in the other matrix. The embossing cylinders 11 shape the laminate to form on a top side thereof a distribution of macroscopic reliefs to which, on the bottom side, there correspond cells. The height of the macroscopic reliefs is about 1-4 millimetres, i. e. about once again as big as the micro-prisms, so that the lateral surface of each relief exhibits a multiplicity of micro-prisms. This is because the lateral surface of the reliefs is more responsible for the back- reflecting effect when the laminate is used for horizontal road signals. The reliefs (and the respective cells on the other side) seen in plan view preferably exhibit a hexagonal shape and are distributed in an ordered and regular way. In the illustrated embodiment they are trunco-pyramidal with a hexagonal base. It is however possible to have other shapes, though it is preferable that the reliefs each exhibit a top surface which is mostly flat and parallel to the laminate, as well as having a lateral surface which is inclined with respect to the laminate. At least a
part of the micro-prisms are on the lateral surface, i. e. inclined surface of the reliefs; the micro-prisms are protected against traffic wear (in case of use of the laminate for horizontal road signals) and are also the most exposed to the beam of light coming from the headlights of a vehicle, so as to optimize the back- reflection and visibility of the horizontal road signal in all atmospheric conditions and with all road surface conditions, and for any angle of incidence of the light beam emitted by the headlights of the vehicle.
The protective polythene film, which is unwound from the reel 13 and is not pre- heated, prevents damage to the micro-prisms during the heat-forming of the cylinders 11 and 12. The protective film is interpositioned between the microprisms and the embossing cylinder 11, forming a protective barrier which maintains the conformation of the micro-prisms unaltered, and therefore preserves the back-reflecting properties of the laminate. The protective film does not stably couple but detaches immediately from the laminate and is rewound onto reel 13'.
The spreader 14 applies a layer of base on the laminate for filling the cells and for covering the bottom side of the shaped multi-layer laminate. The base layer with the filler material is thicker than the depth of the cells, so as to obtain a total covering and form a continuous base surface over'the whole bottom side of the laminate, opposite to the back-reflecting top side; the material of the base layer is preferably a spreadable plastic material, for example a polyurethane resin, or a synthetic rubber.
The spreader 15 deposits on a base layer a layer of adhesive or self-adhesive (permanent or removable) which is used for fixing the laminate to an external surface (for example a road surface) with paper or anti-stick protection unwound from the reel 18 and applied by the rollers 19.
The laminates obtained with the plants of figures 1 and 2 have a high degree of back-reflection properties and have those characteristics of colour and luminosity which satisfy the requisites of the existing standards in the field of road signals.