WO2004008192A1

WO2004008192A1 - A multi-layer reflector laminate, in particular of a type including micro-prisms

Info

Publication number: WO2004008192A1
Application number: PCT/IT2003/000181
Authority: WO
Inventors: Giorgio Corradi
Original assignee: Giorgio Corradi
Priority date: 2002-07-17
Filing date: 2003-03-27
Publication date: 2004-01-22
Also published as: ITMO20020205A1; AU2003219548A1; ITMO20020205A0

Abstract

The laminate comprises a transparent or coloured layer (2) made of a heat-formable material, having on a bottom side thereof a structured surface with micro-prisms to give optical back-reflecting properties thereto, a layer of silver reflective material (3) which covers the structured surface, a thin layer of anti-oxidant protective material (a metal primer) which covers the reflective layer, a thick protective layer (6) which fills valleys formed by the micro-prisms. The laminate has luminous, colour and back reflecting properties which satisfy existing road-signal standards.

Description

A Multi-layer Reflector Laminate, in particular of a Type including

Micro-prisms.

Technical Field

The invention relates to the field of multi-layer reflector laminates, in particular those including micro-prisms.

Specifically, though not exclusively, the reflector laminate can be usefully employed in the field of road signals. Background Art

The prior art teaches reflector laminates with micro-prisms, for example patents

US 5376431, US 567162, US 6083607 and US 6139158.

In general, reflector laminates with micro-prisms used in road signals comprise two superposed sheets, a first sheet bearing the micro-prism and a second sheet, anchored to the first at a heat-welded net-conformed zone which occupies 15-

20% of the total surface; between the two sheets there is a multiplicity of air- filled cells, where the micro-prisms conserve their reflective properties, delimited by the heat- welded non-reflector zone.

One of the problems with prior-art reflector laminates is that of respecting the optical characteristics, in particular reflecting capacity, luminosity and colour grades, all requested by the established standards for road signals.

A further problem, typical of laminates formed by two heat- welded sheets only in predetermined coupling zones of limited areas, consists in the instability of the coupling between the sheets. The present invention provides a laminate which is highly reflective. An advantage of the invention is that it provides a reflector laminate for road signals which has the characteristics of luminosity, colour grade precision and reflective capacity which are sufficient to satisfy the requisites of the existing standards and norms. A further advantage is that it provides a laminate which can be manufactured at reduced costs and with high production capacity.

A further advantage is that the laminate of the invention is resistant and has a long working life, even when used for horizontal signals, i.e. on or near the road surface. A still further advantage is that the invention makes available a multi -layer laminate with high coupling stability between the various layers, which can be coupled over up to 100% of their surfaces, thus providing a multi-layer laminate which is compact and for which there is only a very small risk of peeling between the layers. 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 a^* preferred but non-exclusive embodiment of the invention, illustrated purely by way of example in the drawing, in which: figure 1 is a section of part of a laminate made according to the invention. With reference to the drawing, 1 denotes in its entirety a reflector laminate, used in particular to make road signals, including horizontal signals, which comprises: a transparent or coloured-transparent layer 2 having on a bottom side thereof a structured surface for affording reflective properties thereto; a reflective layer 3 containing silver which covers the structured surface; at least a first protective layer 4 which covers the reflective layer 3.

The transparent or coloured transparent layer 2 is preferably made of a heat- formable plastic material (for example a methacrylate resin such as polymethyl methacrylate). The structured surface comprises a distribution of micro-prisms 5 impressed, preferably by embossing, on the bottom side of the transparent layer 2. The opposite, i.e. top side, is the side on view, which is destined to be struck by the incident light (the light coming from a vehicle) which is to be reflected back. The transparent layer 2 is about 150-300 micron in width. The micro-prisms 5 are preferably between 60 and 180 micron in height.

The material used for the reflective layer 3 is 99.9% silver, but in any case preferably the silver component should be at least 90%. The breadth of the reflective layer 3 of silver material is at least 0.5 micron. In the illustrated embodiment the breadth is about 0.8-1.2 micron. The reflective layer 3 is however relatively very slim in comparison to the height of the micro- prisms 5, and preferably should be slimmer by at least one order. The silver reflective layer 3 is covered by a thin layer of protective material 4 constituted by a metal primer, preferably polyurethane-based, which increases the grip of an overlaid layer of filler 6 of the micro-prisms. The micro-prism structured surface 5 comprises valleys and crests which are topped and covered by the filler layer 6, made of adhesive or self-adhesive material, and relatively thick with respect to the silver reflective layer 3 and the anti-oxidant protective primer 4. The filler layer 6 is distributed directly in contact with the layer, of protective primer 4. The adhesive material of the filler layer 6 is, for example, a high-weight polyurethane resin. It is in any case preferable that the protective layers overlying the reflective layer 3, especially the filler layer 6, be made of a material which does not contain solvents which could damage the micro-prisms. Possibly, for example, water-based materials could be used, or solventless resins. The filler layer 6 fills the valleys of the structured surface and tops the crests with a protective layer, with the aim of protecting the micro-prisms 5, in particular to avoid the risk of changing the conformation of the micro-prisms 5 (which would damage their optical capacities) in subsequent work operations.

The reflector laminate 1 of the invention, with a silver reflective layer 3, exhibits the colour, luminosity and back-reflective characteristics required by the standards relating to road signals, and especially responds to the characteristics required for seeing the laminate during the day in natural light conditions. The laminate 1, when destined for use as horizontal road signals, can be advantageously shaped, in known ways, to form a distribution of macroscopic reliefs (not illustrated) projecting from a top surface of the laminate, to which correspond, on the lower side, similarly-shaped "negatives", in the form of cells. On the bottom side of the laminate there is a layer of material filling the cells. The height of the macroscopic reliefs is about 1-4 millimetres, i.e. about one order of size larger than the dimensions of the micro-prisms, in order that the lateral surface of each relief exhibits a multiplicity of micro-prisms. This is because the lateral surface of the reliefs"is the side which is most responsible for the back-reflective effect when the laminate is used as a horizontal road signal. The reliefs (and the respective "negative" cells on the bottom side) in plan view preferably exhibit a hexagonal shape and are distributed in an ordered and regular fashion. They could be, for example trunco-pyramidal with a hexagonal base. They could also be of other shapes, even though preferably the reliefs should each exhibit a mostly flat top surface which is horizontal and parallel to the laminate, and an inclined lateral surface; at least a part of the micro-prisms is on the inclined lateral surface of the reliefs; the micro-prisms are protected against traffic-induced wear and are also the most exposed to the beam of light coming from the headlights of a motor vehicle, so as to optimise the back-reflective property and the visibility of the horizontal road signal, in any atmospheric condition and on any road surface condition and for any possible angle of incidence of the light beam emitted by the headlights of a motor vehicle. The filler layer 6 of the cells and for covering the lower shaped side is of a greater depth than the depth of the cells in order to provide a complete covering thereof and to form a continuous base over the entire bottom side of the laminate, opposite to the top, reflective side. The material used for the base layer is preferably a spreadable plastic material, for example a polyurethane resin, or a synthetic rubber.

The process for manufacturing the reflector laminate comprises the following stages, operated continuously on a sheet made as a continuous belt unwound from a bobbin which passes through the various work stages: stage a): forming (for example by continuous embossing) on one side of a continuous heat-formable plastic sheet, a structured surface exhibiting a distribution of micro-prisms made in relief; the micro-prisms are conformed in a known way, and give back-reflecting optical properties; stage b): treat the structured surface to increase the grip and stable anchoring qualities of the layer of material to be subsequently applied, for example using a treatment to increase the surface tension and roughness of the surface; stage c): distribute a layer of reflective silver material on the structured surface with the micro-prisms and treated as in stage b); the. silver is preferably applied using a known process of high-vacuum plating; alternatively a silver layer could be applied using other thin-layer plating techniques, for example spraying or rolling, etc; stage d): immediately after stage c) distribute a thin layer of anti-rust protective material on the reflective material, preferably a metal primer, for example a bi- component polyurethane, which enables a solid grip of the following layer of protective and covering material; alternatively to the primer, a surface treatment might be applied on the silver layer (for example a roughening treatment of known type) in order to improve the gripping ability of the protective and covering layer; subsequently, a second layer of protective material (for example a high-weight polyurethane resin) is applied which levels off the bottom side of the laminate by filling the valleys and covering the crests of the micro-prism in relief on the structured surface; the filler layer is thicker than the depth of the valleys on the structured side so as to obtain total protection and covering of the micro-prism.

Thus the laminate of figure 1 is obtained. The following work operations can be made: stage e) heat-form the laminate to obtain a distribution of macroscopic reliefs to which the cells correspond on the "negative" side. During this stage the filler and covering layer has the task of protecting the micro-prism so as to conserve their conformation and their optical properties; the macroscopic reliefs project on the upper side of the laminate, the side in view i.e. the side on which there is the layer of transparent material, while the cells are on the bottom side of the laminate, on the same side as the protective layer; the laminate is heat-formed, passing between two embossing cylinders (not illustrated) peripherally provided with two matrices (male-female) which cooperate to produce the reliefs on one side of the laminate and on the other side the corresponding cells; preferably one of the two matrices (preferably the male matrix) is 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 can be made of metal (for example steel, nickel, etc.); before the heat-forming operation, the laminate is pre-heated, for example using infra-red batteries and/or heating rollers, and is then heat-formed by two embossing cylinders (cooled) which operate in phase so that each projection (male) of one matrix (male) corresponds to a recess (female) of the other matrix. The layer of heat-formable material guarantees good heat- forming of the laminate; stage f): distribute, as described herein above, a base layer to fill the cells and cover the bottom side of the laminate, on the side of the protective layer; stage g): deposit a layer of adhesive or self-adhesive (permanent or removable) on the base layer, which is for fixing the laminate on an external surface (for example a road surface) with paper or silicone film as protection. The smooth laminate of figure 1, obtained from stages a) to d), is ready for use as a back-reflecting laminate, in particular for vertical-type road signals, preferably after an adhesive-application stage, similar to stage g) as described above. The laminate with reliefs, obtained with the further stages from e) to g), enables a horizontal-type road signal to be produced, or a lateral signal (for example, for use on guard-rails and so on) which is durable and which needs no special maintenance.

The laminate, both in the smooth and macroscopic-relief versions, is provided with high reflective properties and provides high-capacity back-reflection over a long working life, even where subjected to wear, such as for example atmospheric agents or impacts caused by passing vehicles. The signals produced are highly visible to motorists, even when atmospheric conditions are unfavourable, such as for example at night or in fog or rain. Thus the signals contribute to road safety. The laminate has colour and luminosity specifications which satisfy standards (especially those relating to daytime visibility) and maintain high back-reflecting properties.

Claims

Claims.

1). A multi-layer reflector laminate, comprising: a transparent or coloured transparent layer (2) having a structured surface on a bottom side thereof to give back-reflecting properties; a reflective layer (3) made of a material containing silver, which covers the structured surface.

2). The laminate of the first claim, comprising at least one protective layer (4, 6) which covers the reflective layer (3).

3). The laminate of claim 1 or 2, wherein the structured surface exhibits a distribution of micro-prisms (5). 4). The laminate of any one of the preceding claims, wherein a thickness of the reflective layer (3) made of a material including silver is at least 0.5 micron.

5). The laminate of any one of the preceding claims, wherein a material of the reflective layer (3) is silver at a purity of not less than 90% and preferably of at least 99%. 6). The laminate of any one of the preceding claims, wherein the transparent or coloured transparent layer (2) is made of a heat-formable plastic material.

7). The laminate of any one of the preceding claims, wherein the structured surface forms valleys and crests which are topped and filled by at least one of the at least one protective layer (4, 6). 8). The laminate of any one of the preceding claims, wherein the reflective layer

(3) is covered by an anti-oxidant protective layer, preferably a metal primer, having a thickness which is smaller than a height of the micro-prisms (5).

9). The laminate of any one of the preceding claims, wherein the laminate is shaped so as to form an array of macroscopic reliefs, projecting from an upper side of the laminate, to which correspond cells formed on the bottom side of the laminate, which cells are negative shapes formed as a consequence of the macroscopic reliefs and corresponding in shape thereto; a layer of material being applied to fill the cells formed on the bottom side of the laminate.