Brazilian publication Pi 9802274-1, to the same inventor, filed June 19,1998 and issued Feb. 20,2001, which does not constitute prior art, relates to a decorative plastic panel wherein a printed sheet is introduced between two fiberglass reinforced resin (FRP) layers, producing a bi-laminated panel, decorated on the front side only, and molded between two plastic films.

The aforementioned product, while having innovative characteristics at the time, proved to be difficult to manufacture, since it demanded the independent consolidation of the two layers of fiberglass reinforced resin (FRP) located on both faces of the printed sheet, the necessity of disintegrating the substratum aiming the union of the two opposed layers of FRP, one on each side of the sheet, so as to avoid any possibility of delamination, internal air bubbles and deformations of the panel thus made. Said panel had to be laminated by pultrusion and profiling devices and needed to be cured through several UV curing stations, located both above and below the laminate due to the barrier effect of the internal sheet.

Furthermore, the mandatory translucency of the front fiber reinforced resin layer of the panel restricted the choice of the resin, not allowing the use of some resins with exceptional structural and

ultraviolet radiation curability performances, such as epoxy resins, only because of the low weathering resistance of these resins.

Also, in the prior decorative panel, the substrate of the sheet was required to be white, because any other color would modify the printed image, due to the translucency caused by the impregnation with the resin. Therefore, it was impossible to print on both sides of the internal sheet, since light passing through the panel caused the superimposition of the opposed images printed on either side. Additionally, opaque printing ink could not be used without the color of the image being altered. These drawbacks precluded the ability to create a double-sided panel.

Regarding other types of one-side translucent decorative panels known in the prior art, from the point of view of quality, it is known by experts in the field that conventional decorated panels made using adhesive material, silk-screening or other, change their color tones depending on the lighting condition when illuminated by front light or back light. Furthermore, they are vulnerable to scratches, impacts, graffiti and other forms of aggression, or even to vandalism. They are not washable, especially by solvents, and are subject to a premature loss of brightness, splendor, optical impact, and resistance to weathering.

Similarly, from the point of view of industrial applicability, it is also known that the decoration of conventional translucent panels made using adhesives or silk screening is typically done by hand and its production may therefore be inconsistent, slow, and expensive.

It is therefore an object of the invention to provide a versatile decorated panel, one-side or double-side, composed of a multi-layer system of plastic films which allows variations in its form and constructive sequence, aiming to fulfill a wide range of applications in the visual communication, advertising, signs, and architecture fields, while providing innovative optical effects.

This object is achieved by a decorated panel comprising a translucent, structural core, which can be self-supporting depending on its thickness, composed of a fiber layer impregnated with synthetic resin, said core incorporating on one or both sides thereof a multi-layer system of translucent and opaque plastic films, printed in a predetermined sequence and coupled together by lamination, intermixing the printings with translucent ink layers, for instance white, enabling the reproducibility of the same color tones under different lighting conditions.

All the initially mentioned problems have been eliminated in the panel of the present application, which is of simple composition and improved appearance and quality, allows new visual effects, and expands, by its versatility, the range of use with numerous options related to printing features, according to the needs of a given application or desired effects.

As mentioned, decorative panels based on fiber reinforced plastic are known in the art, but none of them exploit the resources of a multi-layer system of printed film layers, laminated on one or both sides of a translucent structural fiber reinforced plastic core layer. The multi-layer system of printed film layers allows new optical effects, including reproduction of the same color tones under <BR> <BR> different lighting conditions, i. e. , with front light or back light ; pre- arranged superimposition of complementary images; double-sided printing; the combination of translucency and opacity; a greater choice of resins, printing inks, films and other components; and more graphic possibilities which will be described below.

An improvement can be achieved by a decorated panel having a core as described above, wherein the film layers of the multi-layer system are printed with different but complementary images so that, when lighted, they can superimpose, thereby producing a single, cohesive image, of pre-arranged composition,

resulting from the sum of all the printings; Another improvement can be achieved by a decorated panel having a core as described above, wherein the innermost film layer of the multi-layer system is opaque or printed with opaque ink so as to obstruct, either totally or partially, the light passing through the images printed on the external film layers, according to a predetermined layout, allowing creation of a double-sided panel having images presented on each side.

A further improvement can be achieved by a decorated panel having a core as described above, comprising a multi-layer system of film layers acting as a light diffuser element, wherein the light transmittance of the set can be easily controlled in the printing stage, being preferable near to 50%.

Still a further improvement can be achieved by a decorated panel having a core as described above, wherein whenever the printing inks used are not chemically compatible with the resin used for the impregnation of the fiber, said inks can be encapsulated between two plastic film layers of the multi-layer system so as to avoid direct contact between inks and resin.

According to another embodiment of the invention a decorated panel has the same core as described above, wherein whenever a film layer is not chemically compatible with the resin used for the impregnation of the fiber, said film can be coupled with other film layer which is compatible with both the chemically incompatible film layer and the resin of the core, thereby enabling lamination of the chemically incompatible film layer to the resin of the core.

The object of the invention is further achieved by a decorated panel made by a continuous, industrial and automated process, uniquely combining and juxtaposing rotary printing technology with a reinforced plastic continuous lamination, the

decorated plastic panel comprising a multi-layer system of film layers, made by the process comprising the steps of: impregnating a fiber layer, preferably structured by continuous strands, with a synthetic resin composition, thereby forming a translucent, continuous structural fiber and resin core ; feeding a multi-layer system of film layers through floating devices including cylinders which are properly joined so as to provide for geometrical adjusting and tensioning, and assuring the film layer's flatness after its being unwound from reels and subjected to lamination ; laminating said multi-layer system of film layers, coupled by adhesive resin, on one or both sides of the continuous fiber and resin core ; consolidating the laminate through a system of cylinders; curing the multi-layer laminate thus obtained; and collecting the multi-layer panel on a take-up reel.

Curing of the laminate can be done either by UV radiation or by heating. Thermal curing is cheaper, while radiation curing provides better quality to the panel, especially in regard to its superficial flatness or evenness. The main difference is the high cost of the photo-initiators required in the UV curing, which is much more expensive than the peroxide catalysts used in thermal curing.

The present invention discloses that mixing the normal quantity of thermal curing agents, usually peroxide catalysts, required in the thermal curing, with a very small quantity of UV photo-initiators, the panel can be cured in two subsequent and continuous stages, achieving the advantages of both thermal curing and UV curing, i. e. low cost and high quality.

So, according to a further embodiment of the invention, the curing is done using a mixed curing, by two subsequent stages: a first stage of UV curing where the laminate is partially hardened, sufficient to avoid the typical deformations caused by the subsequent thermal curing step (10-15 Barcol degrees is sufficient if polyester

resins are being used), followed by a second stage of thermal curing to complete the curing (up to 50 Barcol degrees, for polyester resins).

Advantages and features of the product according to the present invention will become more evident from the following detailed description of an embodiment of the invention, referring to the appended drawings, remarking the fact that they are not restrictive regarding other possible embodiments comprised by the invention, wherein: - Figure 1 shows the sequence of steps in the process of manufacturing the decorated panel as described in the preferred embodiments according to the invention; - Figure 2 shows a schematic view of a device for unwinding and feeding films which are part of the multi-layer system of the invention; - Figure 3 shows a partial cross-section through a panel illustrating a typical multi-layer structure of film layers laminated on both sides of a structural core, according to the method of Figures 1 and 2; and - Figure 4 shows a diagram illustrating the influence of the percentile fiber content on the tensile strength of fiber-reinforced plastics, with random orientation of the fiber, applicable to the structural core compositions of the panels according to the invention.

In Figure 1, fiber layer 6 is fed through vessel 8, which contains a curable resin 7 with which fiber layer 6 is to be impregnated. According to the present embodiment of the invention, said resin is a UV-curable resin. Of course, any other suitable curing method and curable resin may be used. Fiber layer 6 impregnated with resin 7 is passed between cylinders 9 which squeeze off the resin surplus, then immerged into a second batch of resin 10, located at the apex of two converging platforms 1, 1'for final adjustment of

the resin/fiber ratio and to prevent the entrapment of air in the compound. Then the impregnated fiber layer is consolidated along with multi-layer films systems 3,4, 5 and 3', 4', 5'by means of a set of consolidation cylinders 11 and passed through curing stations 12.

All the film layers are fed by carrier reels and unwound via tension control devices before their delivery to platforms 1 and 1'.

These platforms act as supports for their sliding and interconnecting by synthetic adhesive resin 2 and 2'provided at rollers 15 and 15', and cured through stations 17 and 17'.

The final product"P"thus formed is hauled off by a pair of powered rollers 13, collected on reel 16, and cut, when needed, by cutter 14.

Figure 2 shows the feeding of the film layers through a floating device which forms a braking labyrinth with cylinders 18, which are properly joined so that they automatically correct the possible geometrical variation in the carrier reels and, at the same time, control and adjust the tensioning of the film layers, thereby eliminating possible stretching and shrinking derived from its manufacturing by hot laminating and assuring the flatness of the panel surface.

Figure 3 represents in cross sectional view a preferred embodiment of the formation of the multi-layer panel"P", obtained according to the method illustrated in figures 1 and 2, wherein the multi-layer groups of film layers 3,4, 5 and 3', 4', 5'are bonded to respective sides of the structural core 6,7, 10.

The multi-layer system of plastic films, bonded by adhesive resin is typically composed of film layers having the main requirements of: linking film layers which have a face that bonds with the resin utilized for the impregnation of the fiber translucent core, becoming permanently incorporated to it by cross-linking chemical combination and lamination ; printing film layers decorated by printing

methods, preferably rotary printing; and finishing and protective film layers other perforating and impact efforts, its thickness depending on the use of the panel. Depending on the kind of panel some of the film layers composing the multi-layer system can be transparent, translucent, pigmented or opaque.

The materials and properties of each film layer may vary depending on the use of the panel. The embodiment shown in Fig. 3 with three film layers on each side of the core of the panel is just typical and represents the main functions of a film. Some of the film layers may be omitted or even may be multiplied. This occurs independently on each side of the panel.

Other reasons influence the project or the selection of the film layers composing the multi-layer system such as: the cost; the commercial availability ; the incompatibility with a determined resin of the core; the achievement of shading colors, like fume, rather difficult to obtain by printing; the protection to radiation, as UV; the sanitary or non-toxic properties ; and other special requirements for particular types of panel according with its use and performance.

Not always are the three film layers on each side of the core. One kind of panel has more than three whilst in another kind of panel a single printed film layer may be enough. Conceptually, the panels proposed in the invention are derivations of a same family of panels.

Decorated panels impressively bright can be produced by intermixing translucent white layers between the printing layers, adding glass micro-beads and metallic pigments to the laminating resins and adjusting the refraction indexes in the components, with unique characteristics which will be described below.

In one embodiment of the present invention, one printing film layer from the multi-layer system is printed with a first ink layer in any color, upon which are applied, sequentially, intermediate

translucent layers, preferably of white ink, intercalated with backing layers having similar color to the first. When lighted with a front light the panel will show just the color of the first layer, whilst when back lighted the panel will show the combination or sum of colors of the first and the backing layers. Properly formulating the color of the backing layers, especially its composition, resin, fillers, color, pigment concentration, and translucency, the panel will reproduce nuances of colors extremely similar under said different lighting conditions.

This effect results from the combination of color nuances of the printing materials making them capable of reflecting artificial light on the same frequencies of light observed with natural light, respecting tolerance limits and pre-established metamerism conditions.

Repeating the procedure utilizing more backing layers of printing films improves the quality of the resulting image of the system of multi-layer films.

The printing is preferably made by rotary printing methods and it can be made either on the internal side of the films facing the central core, in negative printing, when the film layers are transparent or translucent or on the external side of the film layers when they are pigmented or opaque, in positive printing, further laminated with an external finishing film layer.

In another embodiment of the present invention, one or more film layers are printed forming a first image, which might be polychromatic, upon which is printed, sequentially, a translucent white layer covering said first image, and one or more printed film layers forming a second image, whose layout is complementary with the first, with colors that can be different from the first. Thus, when lighted with front light the panel will show the first image only, whilst when back-lighted it will show the combination of both images

superimposed, according to a pre-determined layout. The same process can be repeated with three, four, or more complementary images, enhancing even more the optical perception of volume or a similar effect of depth on the resulting image, resulting from the sum of all the printings.

Similarly, by properly adjusting the translucency of the intermixing white layers, superimposed complementary images can also be observed with front light with effects similar to those observed when back-lighted. in another embodiment of the present invention, aimed at production of double-sided panels used as partition walls or for similar purposes, on one or both sides of the translucent structural core is provided at least one opaque film layer or a film layer printed with opaque ink, usually comprising metallic pigments or the like, so as to prevent the visual superimposition or overlapping of the two opposite printings through the panel.

Another embodiment of the invention allows the creation of panels where just some parts or spaces are translucent-a method likely to be used in visual communication-that consists in printing an opaque ink layer covering only a few parts of the panel image, according to a pre-determined layout, leaving translucent some other parts of the panel, for instance the logos. Therefore, when back- lighted, the panel will show only the translucent parts, whilst the opaque parts will be observed with day light or by the halo made by the translucent back-lighted parts.

Another possible embodiment of the invention gives some pre-established parts of the panel a superficial contrasting, rough, reflective or other particular finish, giving a differentiated visual effect, created when one or more film layers of the system is peeled off, after an intermediate curing step, leaving the printing ink layers

directly exposed on the surface of those parts of the panel or, as an alternative, on the whole panel.

In yet another possible embodiment of the present invention, further demonstrating the versatility of the multi-layer system panel offered by the invention, one or more plastic film layers printed with colored images or other decorations can be laminated on one side of the core and none or a single finishing film layer can be laminated on the other side.

The printing inks used can often be chemically incompatible with the resins used for the impregnation of the fiber translucent core. Thus, in another embodiment, the inks can be encapsulated between two plastic film layers so as to avoid direct contact between inks and resins.

Also, some film layers made of very convenient materials, such as polypropylene, aren't chemically compatible with the resins used for the impregnation of the fiber in the core because they expand upon contact with some solvents, such as styrene. Thus, in a further embodiment, a chemically incompatible film layer is coupled with other film layer which is compatible with both the chemically incompatible film layer and the resin of the core, thereby enabling lamination of the chemically incompatible film layer to the resin of the core.

In another optional arrangement of the panel, especially in the case of back-light applications requiring thicker layers of printing inks going beyond the technical resources of the normally available printing equipment, more printing film layers can be added to the mentioned multi-layer system.

In another option, all film layers of the multi-layered system could be printed so as to obtain a stronger optical effect as desired.

Additionally, a sole polyvalent film layer adapted to be capable of linking, printing and finishing, could replace all films of the multi-

layer system on one or both sides of the core.

The panel"P"produced according to the invention has a core wherein the fiber layer comprises a composition of glass fiber in combination with synthetic fiber selected from the group consisting of chopped strand mat, woven roving fabric, and veil, preferably structured by continuous strands, so as to provide several finishing textures, the fiber layer being impregnated with synthetic resin.

Moreover, it allows the simultaneous incorporation of the multi-layer system of decorated film layers on one or both sides of the core during the very formation of the core during the manufacturing process of any of the variations of the panel, avoiding the need for additional separate steps of siding the core.

The continuous lamination machinery disclosed, while being quite simple, allows an exceptional consolidation of the FRP translucent core with a perfect structural composition of the laminate, making possible the continuous production of all kinds of high performance decorative panels, previously impossible to make, including a panel printed on both sides.

Obviously, the panel disclosed by the present invention, made of a single layer of fiber impregnated with synthetic resin, eliminates any possibility of delamination or separation of the composite material.

In composite materials such as the core of the present invention, which include in their formation resin and fiber, the resulting structural properties are more affected by the fiber/resin ratio than by any other cause or factor. Thus, high fiber content increases exponentially the mechanical resistance of the plastic laminate, as illustrated by the typical graph of Fig. 4.

High strength/weight ratios allow new market applications, otherwise impossible to achieve, for the formation of decorated panels, by using any one of the composition options proposed or

even others not described, as long as they are based upon the present concept or basic idea.

The use of fiber with oriented strands increases dramatically the fiber content in the compound, raising the fiber/resin ratio from figures that hardly exceed 20% to up to 70%, which allows the tensile strength to increase from about 650 kg/cm2 to up to 4500 kg/cm2, as indicated in the graph of figure 4, according to the reference: The Scott Bader Commonwealth Ltd. Polyester Handbook, Lund Humpries, London, 1969. In other words, the fiber content in the core structure of the panel can be adjusted to up to 70%, according to the requirements.

At the same time, minimization of the resin content in the translucent structural core diminishes the possibility of deformation, yellowing, aging and cracking, whilst increasing the thermal and dimensional stability. The panel becomes thinner and lighter, more durable and economically convenient.

Furthermore, the resulting product, due to its thinness, lightness and flexibility, allows for packaging in reels of up to several hundred meters, simplifying its storage, handling and transportation.

The inclusion of a simple mechanical disposition to feed the plastic films eliminates serious problems with the panel flatness.

Tensions and deformations in plastic films, typical of the hot lamination manufacturing, added to new tensions acquired during the printing and rewinding process, can create irregularities in the geometry of the reel body and stretching and shrinking in several parts of the film which are transferred to the panel, thus reproducing such irregularities in its surface. Said disposition comprises a floating device, illustrated in Fig. 2, which automatically corrects and adjusts the irregularities referred to.

As explained above, any suitable synthetic resin may be used in performing the process according to the invention. However,

the UV-curable resins are preferred in performing the method according to the present invention. These resins include unsaturated, photosensitive resins, preferably polyester, vinyl, epoxy, melamine, phenol, acrylic and polyurethane resins, or combinations thereof, and they can contain fillers, as glass beads, and pigments.

Below is appended a table, showing some properties of a multi-layer panel according to the method of the present invention.

Table 1

Typical Properties of a laminate-0, 7 mm Product characteristic Value Tolerance Standards Thickness [mm] 0,7 0, 1 Standard Chopped strand mat [g/m2]-Supplier Information Woven Roving [g/m2] 600 Supplier Information Density [g/cm3] 1, 55 05Standard Area weight [gim2] 1085 150 Standard Glass content [%] 51,4 1, 5 Standard Tensile strength [N/mm2] 211 + 10 DIN 61/íSO 527 Modulus of elasticity [N/mm2] 13100 500 DIN 61 Elongation at break [%] 1, 75 0, 2 DIN 61/iSO527 Hardness [° Barcol] 50 i 10 DIN 59

While the invention has been described in detail above, it is not intended to be limited to the specific embodiments described. It is evident that those skilled in the art may now make uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concepts and basic idea of the present invention.