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Title:
A PROCESS FOR MANUFACTURING REFLECTOR LAMINATES
Document Type and Number:
WIPO Patent Application WO/2003/011579
Kind Code:
A2
Abstract:
A reflective film (5) has a layer of microspheres (2) on one side and is heat-formed between two embossing cylinders (6). The embossing cylinders (6) peripherally exhibit two matrices which produce, on the side of the film (5) bearing the microspheres, a distribution of microscopic reliefs, and on the opposite side, corresponding cavities. A base layer (4) of material is applied to the side with the cavities, filling them. The heat-formed film comprises a first layer (31) of a transparent resin interpositioned between the microspheres (2) and a thin reflecting layer (32) containing metal, which in turn is covered by several layers (33 and 34) of protective material coupled to a layer (35) of heat-formable material. The reflector laminate is usefully applied in the field of horizontal road signals.

Inventors:
CORRADI GIORGIO (IT)
Application Number:
PCT/IT2002/000387
Publication Date:
February 13, 2003
Filing Date:
June 12, 2002
Export Citation:
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Assignee:
CORRADI GIORGIO (IT)
International Classes:
B29C69/00; B29D11/00; G02B5/128; (IPC1-7): B29D11/00; B29C69/00
Foreign References:
US5069964A1991-12-03
EP0602599A11994-06-22
US5620775A1997-04-15
US5896227A1999-04-20
Attorney, Agent or Firm:
Gianelli, Alberto (Via Emilia Est 25, Modena, IT)
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Claims:
Claims
1. 1). A process for manufacturing reflector laminate, comprising the following stages: preparation of a reflective film (5) having, on a reflecting side thereof, a layer of microspheres (2); embossing the film (5) in order to obtain, on the reflecting side thereof, a distribution of macroscopic reliefs to which cavities on a back side of the film (5) correspond; applying, on the back of the film (5), a base layer (4) of material which fills the cavities. 2). The process of claim 1, wherein during the embossing stage the film (5) passes through two opposing embossing cylinders (6) peripherally provided with two matrices reciprocally cooperating to obtain the reliefs and, on the back side, the cavities. 3). The process of claim 1 or 2, wherein, before the embossing stage, a support layer (35) made of a heatformable material is coupled to the back side of the film (5). 4). The process of any one of the preceding claims, wherein the preparation of the film (5) comprises the following stages: fixing the microspheres (2) on a temporary support film which is heated to produce a softening of the support film, into which the microspheres (2) sink to a predetermined degree; covering a side of the temporary support film housing the microspheres (2) with a thin first layer (31) of a transparent resin; depositing a thin reflective layer (32) of metal on an external surface of the thin first layer (31) ; covering the reflective layer (32) with one or more layers (33 and 34) of protective material; removing the temporary support film. 5). The process of claim 4, wherein, in order to improve the coupling between the microspheres (2) and the first layer (31), the resin of the first layer (31) contains additives comprising one or more silane derivatives, for example aminopropyltriethoxysilane, addition of which favours and makes possible an adhesion between inorganic surfaces, for example glass borosilicates, with organic polymers, for example polyurethane resins. 6). A reflector laminate, comprising: a layer of microspheres (2), partly sunk into a support layer (3) which is shaped to form, on a side thereof bearing the microspheres (2), macroscopic reliefs which are bigger than the support layer (3) and to form corresponding cavities on another side of the reflector laminate; a base layer (4) for filling the cavities formed on the support layer (3) of the microspheres (2). 7). The reflector laminate of claim 6, wherein the support layer (3) comprises: a layer (31) of a transparent resin in contact with the microspheres; a reflective layer (32) located on the resin layer (31) ; at least one layer (33) of primer for metals on the reflective layer (32); a layer (35) of heatformable material located beneath the other layers. 8). The laminate of claim 7, wherein the transparent resin in contact with the microspheres (2) contains additives of one or more silane derivatives.
Description:
Description A Process for Manufacturing Reflector laminates Technical Field The invention relates to a process for manufacturing a reflector film. Specifically, though not exclusively, the reflector laminate can be used for making horizontally-disposed road signs.

Background Art Particular reference is made to manufacture of a back-reflecting laminate having on a visible side thereof a plurality of macroscopic reliefs to which microspheres are anchored. A laminate of this type already exists in the prior art, for example in Italian patent IT 1,296, 759.

The main aim of the present invention is to provide a simple and economic process for manufacturing a laminate of the above-indicated type.

An advantage of the invention is that it makes available a reliable and high- productivity process.

A further aim of the invention is to manufacture a sturdy laminate, with long working life and high reflective capabilities.

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 a non-limiting example in the accompanying figures of the drawings, in which : Disclosure of Invention figure 1 is a plan view of a reflective laminate made according to the invention; figure 2 shows section II-II of figure 1 ;

figure 3 shows a diagram of a machine for making the laminate of the invention, in vertical elevation.

With reference to the figures of the drawings, 1 denotes in its entirety a reflector laminate comprising a layer of microspheres 2 partially sunk (to a predetermined degree) in a support layer 3 which is shaped in such a way as to form, on one side (the reflecting side) bearing the microspheres 2, macroscopic reliefs (a projection of which in height is around 1-4 mm.), much greater than the thickness of the support layer 3 and, on the other side of the support layer 3, the"negatives"of the reliefs.

Preferably the microspheres are made of a glassy material with a relatively high index of refraction, for example greater than 1.80 and preferably comprises between 1.90 and 1.97, in order to obtain a high back-reflecting result. The microspheres have, at least mostly, a diameter preferably comprised between 20 and 105 micron.

The support layer 3 is multi-layered and comprises at least: a layer 31 of a transparent resin, which may or may not be coloured, underlying and contacting microspheres, a layer 32 of reflective material, generally metallic, underlying the layer 31 of resin, and at least one layer underlying the metallic layer: in the present embodiment, various layers are provided below the reflecting layer 32, among which a primer 33 for metals situated below the metal layer 32, a layer of resin 34, for example a polyurethane resin, which is beneath the primer 33, and a heat-formable layer 35 which is beneath the other layers and is situated on the opposite side of the laminate with respect to the microspheres 2. The transparent resin (or coloured transparent resin) which forms the layer 31 in contact with the microspheres can have one or more derivates of silane added to it, as will be better explained herein below. The first layer 31 of transparent resin is interpositioned between the glass microspheres and the reflecting layer, to

improve the anchoring of the glass microspheres.

The laminate 1 further comprises a base layer 4 for filling the cavities which, apart from filling the preformed cavities in the microspheres'support layer 3, preferably also form a continuous base surface which covers the whole lower side of the laminate 1.

The process for manufacturing the reflector laminate 1 comprises the following stages.

1) Preparation of a reflective film 5 having, on a reflective side, a layer of microspheres 2 made of a transparent material (for example glass); preparation of the reflector laminate comprises the following stages (not illustrated): la) fixing the microspheres on a heated temporary support film to produce a softening of the film and enabling the microspheres to sink into the film to a predetermined degree; in the illustrated embodiment the temporary support film is a composite filin formed by a layer of polyethylene (on which the microspheres are distributed and into which they sink) supported by a layer of polyester; lb) covering the side of the temporary support film housing the microspheres 2 with a thin first layer 31 of a transparent resin, or a coloured transparent resin; the first transparent layer of resin, for example made of a polyurethane material (preferably a bicomponent polyurethane resin) can advantageously have a further component added to it to improve coupling with the glass microspheres : the additive is preferably a derivative of silane, for example aminopropyltriethoxysilane NH2 (CH2) 3 Si (OC2Hs) 3 and arninopropyltrimethoxysilane NH2 (CH2) 3Si (OCH3).

These substances are known to favour adhesion between inorganic surfaces (for example glass borosilicates, which is generally the material constituting the glass microspheres) and organic polymers (for example a polyurethane resin), inasmuch as they possess favourable characteristics of chemical affinity with the

inorganic surfaces and the organic polymers, creating electrostatic interactions, e. g. hydrogen bonds, between them. It has been advantageously found that the best results are obtained with use of the commercial product Dynasylan (S) AMEO or Dynasylant) AMEO-P. As an alternative a same type of additive, for example an aminoalkylsilane, can be used for treating, as described above, the external surface la of the glass microspheres 1, once more with the aim of improving the couple between the microspheres 1 and the first layer of primer 2; the external surface of the first layer 31 is specially treated to improve the grip of the next layer of material, as described in 1 c) ; Ic) depositing a thin layer 32 of reflective material (generally metal) on the external surface (previously subjected to the special treatment mentioned above) of the first layer 31 of resin; this operation (metallisation) is generally done under high-level vacuum; the layer of metal (constituted by example by aluminium) acts as a reflective material; ld) covering the layer 32 of metal with a second layer 33 of resin or primer for metals, which is preferably a bicomponent polyurethane, and subsequently with a third layer 34 of resin, for example high-weight polyurethane; le) removing by simple peeling-away of the temporary support film.

Before stage 2), the embossing stage, a support layer 35 made of heat-formable material is stably and permanently coupled, in a known way, to the opposite side of the laminate from the reflective side.

2). The laminate is now embossed so as to obtain, on the reflective side bearing the microspheres, a distribution of macroscopic reliefs which produce corresponding"negatives"i. e. cavities, on the other side. During the embossing operation, the film 5 passes through two opposite embossing cylinders 6 (see figure 3), peripherally provided with two matrices (male-female) which cooperate to produce reliefs on one side of the film 5 and the"negatives"i. e. cavities on the

other side of the film 5. Preferably one of the two matrices (preferably the male matrix) is made of an elastically-deformable material, and more deformable that the matrix of the other matrix. For example, the male matrix can be made of silicone rubber and the female matrix of metal (for example steel, nickel, etc.).

The film 5 is pre-heated by heating means 9 (for example infrared ray batteries and/or heating rollers) before being heat-fonned by the two embossing cylinders 6 (cooled) which are synchronised so that in the heat-forming zone each protuberance (male) collaborates with a recess (female) of the other matrix. The heat-formable support layer 35 ensures good heat-fonning of the film 5.

The reliefs (and the respective cavities on the other side) seen in plan view (figure 1) 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. Other shapes could be used, however.

3). A base layer 4 of material covering the cavities is applied on the opposite side of the laminate. The base layer 4 is thicker than the depth of the cavities, so that a total covering of the"negative"is obtained, forming a continuous base over the whole bottom side of the laminate opposite to the side with the reliefs, the reflective side. The material is preferably a plastic spreadable material, for example a polyurethane resin or a synthetic rubber. The material can contain, as additives, a percentage of pigments, for example whites or colours according to needs. The material can also contain a percentage (for example about 0.5%) of bleaching agent, preferably of the type normally used for example in the textile or paper industries, to improve the visibility of the laminate when used for road signals. The material also preferably contains particles of relatively hard abrasive materials, which give the laminate a good resistance to wear, both mechanical and atmospheric, thanks to which the reliefs on the external reflective side keep their original shape, and in particular their thickness, over a long time even where

subjected to strong wearing agents. The abrasive particles can be either granular or scales having very irregular cutting edges; for example the abrasive substances can be powder or granular, of the type normally used for making glass-paper, mills, emery paper and so on; in the illustrated embodiment, the particles are mostly constituted by grains or scales of corundum or other abrasive substances having a hardness of about the same or even greater than corundum (i. e. 9 in the Mohs scale), such as for example carborundum, boron carbide, aluminium sesquioxide, diamond, etc. Less hard substances than corundum can be used, however, although they should preferably be above 8 in the Mohs scale, i. e. harder than topaz. It has been noted however that laminates for high-quality horizontal signals can be made with abrasive particles having a hardness of less than 8 in the Mohs scale, but preferably harder than silica glass (which is between 6 and 7 in the Mohs scale) such as for example garnet or quartz in very fine grains; other usable abrasive materials are, for example, the following: pumice, sepia, tripoli powder, fossil powder, tantalum carbide, tungsten carbide, sandstone, very fine glass powder, granular and powder emery, iron oxide and/or chrome oxide in powder form. A mixture of powders can also be used, made of various abrasive materials, reduced to granular or powder form and having different hardnesses and granulometries. The abrasive particles can be mixed up together with the other ingredients of the base layer 4 (for example polyurethane resin, white pigment and bleach), after which the mixture obtained can be spread on the side exhibiting the cavities, advancing the laminate in direction F towards a base layer 4 forming device, comprising a feeder 7 which distributes the mixture and a doctor 8 which fills the cavities and scrapes and smooths the mixture.

Preferably but not indispensably, the reliefs can each exhibit a top surface which is flat and parallel to the laminate, and can also exhibit an inclined lateral surface

with respect to the laminate. At least a part of the microspheres is anchored to the inclined lateral surface of the reliefs. The microspheres arranged on these lateral surfaces are protected against traffic wear and are also exposed to the light beams coming from the headlights of a vehicle, giving an excellent back-reflecting effect and very good visibility of the road signal, in all atmospheric conditions and road surface conditions and for any possible angle of incidence of the light beam emitted by the headlights of the vehicle. The majority of the back-reflecting power is provided by the microspheres situated on the lateral surface of the reliefs. The top surface of the reliefs can be without microspheres, without this leading to a significant drop in the back-reflecting capacity of the laminate. The microspheres which are arranged on the top surfaces contribute less to the reflective power of the laminate when the laminate is used to make horizontal signals. Also, the microspheres in that position are the most exposed to traffic wear and are therefore destined to wear out and detach from the laminate before the others. The top surfaces of the reliefs can therefore be subjected to a mechanical operation which removes the microspheres anchored to the top surfaces, leaving the base layer 4 (white or coloured) in view, thus obtaining the desired colour scheme.

In a known way, below the base layer 4 a layer of adhesive or self-adhesive, either removable or permanent, is attached (not illustrated). This serves to fix the laminate to an external surface (for example the road surface).

The application of the reflector laminate on the road surface, or other surfaces, is done in known ways and using known methods.

The laminate is particularly useful for horizontal road signals, has a high back- reflecting power, and can maintain a high reflective capacity over a long period of time, even where subject to wear and stress, such as for example atmospheric agents or passage of motor vehicles. The laminate provides a horizontal signal

which will last over a long period of time and which does not require any particular maintenance. The horizontal signal offers very high visibility for drivers even in very bad weather, such as for example at night or when it is foggy or raining, thus improving road safety. The laminate has excellent anti-skid surface characteristics, especially for vehicle tyres.

In the above-described example, the reflective layer 32 is lid over the whole surface of the laminate. It is however possible to metallize in zones (for example stripes or bands) so as to form metalized zones adjacent to non-metallized zones, for example as described in Italian patent IT 1,296, 759 which is incorporated into the present description for reasons of reference.