MANUFACTURE OF TRAFFIC SIGNS

Abstract: The invention relates to a method for manufacturing traffic sign boards reflecting back light (L) and including sign figures. In the method a light-retroreflective layer (2) is attached on the base material (3), and colour materials (7) forming the sign figures are arranged on the outer surface of the layer. In accordance with the invention, the light-retroreflective layer is arranged uniformly over the entire traffic sign figure area so that it does not substantially change the colour of the reflected light. The necessary sign figures are arranged on one side of a separate coating film (4) in mirror image. The coating film is then adhered onto a retroreflective layer on the base material so that the reversed sign figures face the retroreflective layer. Thus, the sign figures consisting of colour materials are between the retroreflective layer (2) and the coating film (4) and protected from detrimental effects of the environment.

Description: Manufacture of Traffic Signs The present invention relates to a method for manufacturing traffic signs reflecting back light and including sign figures, and similar sign boards. In accordance with the method, a light-retroreflective layer is fastened on the surface of a rigid or flexible base material, and materials forming the sign figures are arranged on the outer surface. The invention further relates to a coating film combination for producing the traffic sign figures for such a traffic sign, and a base material combination applicable to the said traffic sign. As is known, besides the colours, the sign figures, such as symbols or an alphanumerical message as well as the shape of the board base of a traffic sign emphasises the function of the sign in traffic. So accordingly, round boards are used for forbidding and restriction; triangular signs give a warning; square or rectangular signs guide or inform; and turned to their points, they indicate the starting or ending of priority; an octagonal board is a shape used exclusively in STOP signs. Cutting the board base into shape and bending its edges before fastening the colours, symbols or an alphanumerical message, is one of the many working stages related with the manufacture of traffic signs. At some time, it has required considerable machine and tool investments from the base material manufacturer or the board factory; however, old board factories have recovered the costs as depreciations already years ago. When, for example, the suppliers of aluminium or plywood plate nowadays cut the material into shape, this cost item is of no notable consequence in the manufacture of traffic signs. In addition to the actual traffic signs, also other similarly manufactured sign boards, such as guides, are found by the roadside. Undoubtedly, the shape of the board base had an important task for the information conveyed by the traffic sign in times when materials reflecting in the dark were not yet known. It was possible to observe the shape of the contours of a "traffic board" painted onto an unreflecting base with unreflecting colorants, i.e. circle, triangle, square, or octagon, as a silhouette from a longer distance than other details of the board, i.e. its colours, symbol or message, especially in the dusk. When driving at night, it was impossible to discern the symbols on such a painted traffic sign with car lamps from farther away than a few metres. Inventing retroreflective materials which came on the market of western industrialised countries in 1955-1965, changed the situation dramatically. The shape of the board base is losing its meaning, as a reflective film returning light and colours back towards the light source in the dark, make it possible to discern the basic shape of the traffic sign already at a distance of a couple of hundreds of meters, irrespective of the shape of the board base on which the reflective sign symbol is fastened. Such test boards have already been made and mounted by the roadside in several countries in Europe. The said retroreflective colour surfaces and figures are attached to the board bases with two different, known methods. The oldest and still the most trustworthy way is the so-called vacuum heat lamination in which the colour surfaces of a traffic sign, e.g. the red edges and nowadays also the thin yellow "Euro edging", the yellow centre and black symbols as sign figures and, in some traffic signs, the blue areas, etc. are put together from single-coloured pieces of retroreflective films cut into desired shapes on the board base, i.e. as a rather laborious "puzzle". The assembly of the board base and of the coloured pieces of film placed on it is then baked under heating lamps in a temperature of about +83°C and under compression induced by vacuum in a vacuum heating apparatus generally for 3-4 minutes so that the dry adhesive layer on the back of the films melts and adheres to the board base. When this method is used, a single traffic sign requires a large number of pieces of reflective film of various shapes and colours be cut so that each piece of film always contains only one colour; and that these several pieces are manually and carefully placed to right places on the board base. In this method, the sign figures are formed from pieces of material that are both light-reflective and of a desired colour. The board base is non-reflective, and no optical requirements need to be set for it. The method is slow and consumes a lot of energy. The resulting traffic signs, however, are very durable in use, if the coating material for the traffic signs consists of such reflective materials that are disclosed e.g. in the publications JP-6- 43819(A), JP-2-93684(A), and JP-2-93685(A), and in which the retroreflective layer and the possible colour layer are protected from the influence of environment by a surface layer with high transmittance of light. A simpler and faster, but for the durability of the final result a considerably more unreliable method, is to first print all the sign figures of the traffic sign needed on the retroreflective film e.g. by silk-screen printing method and to then calender the film onto the board base by using an adhesive glue. In a coating film of this method, coloured surfaces, symbols and numbers, etc. of the traffic sign are thus printed onto the outer surface of a retroreflective film, i.e. onto the surface facing away from the board base and the light-reflective layers of the coating film so that the colorants are completely exposed to the influences of the environment. The reflectivity of the print, and thus its observability in the dark, depends on many factors, such as the trans lucency of the colorant, viscosity, the amount of thinner used, etc. Colorants on the outer surface of the sign endure poorly washing with a solvent, and change their colour relatively fast due to UN radiation. In addition, the consuming effect of wind, or ice, sand dust or icy snow flown by passing traffic can be seen as the wearing down, disappearance or fading of the colour surface in a short time. Also the fastening of the sign figure to the board base is dependent on the lamination method, temperature of the work room, storage time of the board figures, and temperature and cleanness of the board base before fastening. A sufficient number of corresponding board figures has to be stored for every dif- ferent traffic sign and size. Because it is difficult to anticipate the final need for every sign, the amount stored may be too big or too small, depending on the traffic sign in question. Thus, also this method includes considerable drawbacks, although with it is possible to avoid the cutting of many different-coloured pieces of reflective film needed in the first method, and the placing of the pieces onto the board base. A method of a different type for forming the symbol surface for a traffic sign is disclosed in the publication EP-0 089 215, in which the sign figure comprises a reflective layer consisting of liquid crystals so that a change in the ambient temper- ature makes the sign figure to appear and, correspondingly, to disappear. The purpose of the publication is to produce a guiding or warning traffic sign which changes in accordance with the temperature without outside control. Thus, in this publication, the reflective layer consists of a thermochrome liquid crystal material, and the reflectivity of the layer is found to be based on the Bragg reflection, i.e. scattering from the crystal lattice of the liquid crystals. This results in a distribution of radiation induced by the phase differences of the scattered radiation so that both the completely dark areas and points or lines of different intensities are generated in the half-space of the reflecting side, the places and intensities being dependent on the angle of incidence of radiation, and the theoretical maximum of the strongest point being 0.5, as is stated in the publication. The acting wavelength, again, is dependent on the properties of the crystal lattice. Such a reflection is in no way applicable to traffic signs, so also the publication uses means for improving the situation, such as orienting the liquid crystals so that they are perpendicular to the surface; in this way, one effective point of diffractive reflection is directed back to the direction-of incidence, but there is a poor reflection in the other incoming or respctively outgoing directions of radiation; alternatively, two layers, or two dif- ferent materials in one layer may be used so that the above-mentioned maximum reflectivity may be increased, but in this case, the distribution of reflection is as disadvantageous as before in the other incoming and outgoing directions of radiation. If reflection phenomena from the surface are thought about in general, they are divided into the following types. Scattering reflection in which the incident beam is reflected in a spotlike and/or linelike fashion to different directions which are dependent on the angle of incidence of the incident beam. Specular reflection in which the reflecting beam is directed at an angle to the surface normal which is as large as the angle of the incident beam to the surface normal. Diffuse reflection in which the reflecting radiation is distributed to all directions of the half-space, irrespective of the angle of incidence. Retroreflection in which the reflecting beam sets out back to the direction of the incident beam, irrespective of the angle of incidence of the incident beam. Usually, the reflection properties of generally occurring surfaces are between specularly reflective and diffusely reflective surfaces, i.e. they reflect more or less scattered or diffused radiation to directions near the specular reflection angle. Of these reflection types, only retroreflection is really effective in traffic signs. Scattering reflection may be effective only in one preadjusted direction so that the traffic sign cannot be seen at all from a direction deviating even slightly from the said preadjusted direction. Diffuse reflection again acts in all directions, but its efficiency is extremely low. Specular reflection, again, directs light completely to another direction from the approaching vehicle. In spite of the various solution propositions presented above, board bases still have maintained their old shapes; the reflective films and figures to be fastened to the signs are still made with the old methods, and no essential changes have occurred in the manufacturing technique of traffic signs over the last 30 years. Thus it is the object of the present invention to provide a method and part combinations or materials possibly used in connection with it, which make it possible to manufacture such retroreflective traffic signs in which the sign symbols with their colorants are well protected from the effects of weather and mechanically damaging factors. Another object of the invention is to provide such a method and parts combinations and materials possibly used in connection with it, with which the -production costs may be lowered, and with which part components for the traffic signs may be premanufactured as far as possible while simultaneously keeping the capital tied to them as small as possible. This means that as simple working stages and/or as few working stages as possible are required for the manufacture of traffic signs, or their parts combinations or materials. In addition, this means that it would be desirable to make products deviating as little as possible from each other, and that storing and transport would take as little space as possible and cause as low costs as possible. The above described drawbacks can be eliminated, and the above determined objects achieved by a method according to the present invention which is defined in the characterising part of claim 1, by a coating film which is defined in the characterising part of claim 8, and by a base material combination of the invention which is defined in the characterising part of claim 12. One advantage of the invention is that by following the method according to it, it is possible, if necessary, to manufacture sheetlike or platelike pieces of base materials of only one shape for all the different traffic signs, and these may be prepared in a similar way for all traffic signs with different symbols as sign figures. This keeps the manufacturing costs for sheet/platelike base material pieces for traffic signs very low, as well as the storing and transportation costs. Another advantage of the invention is that, by following its method, symbols may be formed onto the coating film with a fast and simple manufacturing technique; in addition, in the finished traffic sign, the symbols or sign figures are very well protected from, e.g. ultraviolet radiation and dust, abrasion and other mechanical effects. The manufacturing costs for coating films of the invention, storage costs, and transportation costs to the manufacturing site of the traffic signs are very low. The third advantage of the invention is that the finished traffic signs may be manufactured by using base material combinations of the invention already equipped with a light- retroreflective layer and coating film combinations so that these may be combined in a fast and simple way and thus, for example, near the intended site of use for the traffic sign. A further advantage of the invention is that coating film combinations and base material combinations of the invention may be industrially manufactured on a very large scale so that the unit prices become low. This advantage is still supported by the fact that the storage and transportation of these take very little space, thus keeping the costs low. The invention is next described in more detail referring to the enclosed drawings in which: Fig. 1 describes generally axonometrically a stage in accordance with the method of the invention, in which a coating film combination of the first type of the invention is being attached to a base material combination of the first type of the invention; Fig. 2 describes generally axonometrically a stage in accordance with the invention, in which a coating film combination of the second type of the invention is being attached to a base material combination of the second type of the invention; Fig. 3 is a schematic cross-section of the assembling phase of figure 2 in a traffic sign along the line I - 1 of Fig. 1 ; Fig. 4 is a schematic cross-section of the assembling phase of figure 2 in a traffic sign along the line II - II of Fig. 2; Fig. 5 is a cross-section of the first embodiment of a base material combination of the method at III in Fig. 3, but in an enlarged size; Fig. 6 is a cross-section of the second embodiment of a coating film combination of the invention at IN in Fig. 4, but in an enlarged size; Fig. 7 is an exemplary arrangement of three different traffic signs in the mirror image form in which they are formed to a coating film combination of the invention as seen from the direction N in Figs 3 and 4. The direction is equivalent to the side on which the symbols of the traffic sign are placed; and Fig. 8 is an exemplary arrangement of three traffic signs, which is the arrangement of Fig. 7, but as a finished traffic sign as seen from the direction of observation of the road user, i.e. from the direction NI in Figs 1 - 4. The figures 1 - 4 in particular show the sheetlike or platelike base material combination 9 of a traffic sign. It consists of a rigid base plate 3 and a light- retroreflective layer 2 attached to the plate. In this application, the concepts "light- reflective layer", "light-reflective material", and "light-reflection" refer to a layer reflecting back light, and to reflection of light back to the direction of the light source, i.e. retroreflection, if not stated otherwise. In accordance with the invention, the said base material combination 9 is a preliminary product comprising a base plate piece 13 cut into shape and surface treated. The said base plate piece 13 may be a metal sheet and, advantageously, a steel sheet coated with plastic layers 11a and l ib, as is shown in Fig. 5. Generally, traffic signs are relatively stable so that a steel sheet well protected by a plastic coating is a durable and a cost-effective solution. It is obvious that the base plate 3 may also be made of some kind of laminate, such as plywood or plastic-coated honeycomb board, or the like, and also of flexible material, such as plastic. When necessary, a flexible traffic sign or its base material combination may be transported e.g. on a roll. The most usual and most frequently used solution is, however, to use a rigid base plate 3, as mentioned above. Rigid refers here to a material which keeps it shape during handling and use. The base plate 3 may also be made of a composite material, such as fibreglass bonded with polyester plastic or epoxy plastic, carbon fibre or the like. If needed, the edges 25 of the base plate may be bent for increasing the rigidity of the base plate piece 13, as is shown in Fig. 2. The said bends may be carried out to opposite edges of the base plate 3, or to all edges. Also in accordance with the invention, the said base material combination 9 comprises on one surface 23 a a light-retroreflective layer 2 fastened permanently to it. This light-reflective layer 2 is of any type known in itself, and available on the market from several different manufacturers. The said light-reflective layers 2 vary from their inner structure according to the manufacturers. One known way to make a retroreflective layer which mainly reflects back light towards the starting point of the light and, additionally, at a relatively small angle around the return direction, is to place a number of small glass beads side by side on a background of an aluminium film so that the said aluminium film and glass beads are bound together by a plastic which is transparent to light. Another alternative for producing such a light-retroreflective layer is to use microprisms, the sharp apexes of which point away from the direction of view, i.e. from the direction of incidence of light. In this connection it is not necessary to explain the internal structure of the light-retroreflective layers 2 in more detail, as in this embodiment according to the invention any rigid or flexible light-reflective layers known in themselves may be used. The retroreflectivity coefficient R' of the said light-reflective layers varies between 40 cd/lx.m 2 - 1200 cd/lx.m 2 so that a light-retroreflective layer with sufficient reflectivity is selected for each particular purpose. The light-retroreflective layer 2 is fastened to the surface 23a of the base plate piece 13 with any way suitable for these materials, for example, by using a reaction adhesive or heat-setting adhesive. A special feature of the base material combination 9 of the invention, which is generated with the assistance of the other features of the invention, is that the shape and size HI and H2 of the base plate piece 13 are identical for all traffic signs 1 with the same maximum dimensions but with different- shaped sign figure areas. Thus it may, for example, be found in Fig. 8 showing the finished traffic signs of the invention from the user's point of view, that the horizontal width HI and height H2 of a base plate piece 13 for a speed restriction sign of 60 km/h are exactly identical with the width HI and height H2 of a base plate piece 13 for a triangular sign indicating the occurrence of a bend. It is obvious that the same dimensions and sizes may be used for forming a pointed triangle or STOP sign of similar size. The road number sign shown in the lower part of Fig. 8 again is slightly smaller but, again, it may be of the same size for all the road numbers, irrespective of the size of the road numbering. In accordance with the invention, the base plate pieces 13 are typically rectangular and advantageously square, as can be understood from Fig. 8. It is obvious that when one wants to make traffic signs of considerably varying sizes, it naturally is sensible to set the real widths HI and heights H2 near to the size of the traffic sign as needed. Thus it is possible to make the base plate pieces 13 in only a few sizes with rough differences in size, as in accordance with the invention, the desired size for the traffic sign can be made apparent in a way described later by using the black colour B for those areas of a base plate piece 13 that the user is not supposed to see. However, nothing prevents one from forming the base plate pieces 13 into other shapes, for example, circular, as is shown in broken lines in Fig. 1. In Fig. 4 there is shown a first embodiment of the base material combination 9 of the invention, the cross-section of which consists of a piece 13 of the said rigid base plate 3 with a light-reflective layer 2 permanently fastened onto the surface 23 a. A second embodiment of the base material combination 9 is shown more roughly in Fig. 3, and in more detail in Fig. 5. In this embodiment, the base material combination 9 further comprises an adhesive layer 6b on the outer surface 12 of the light-reflective layer 2, the adhesive layer being either an adhesive glue, a heat-setting adhesive glue, or dry adhesive. Thus, a coating film combination of either type of the invention described later may be fastened onto the base material combination 9 of the invention. The said adhesive or heat-setting adhesive glue or dry adhesive 6b may be any adhesive suitable for this purpose, and which is clear so that it diffuses light L passing through it as little as possible. Thus, the base material combination 9 comprises a light-retroreflective layer 2 and possibly an adhesive layer 6b on the surface 23a of either a rigid or flexible supporting base plate 3. The figures do not include an example of such a flexible base material combination. The light-retroreflective layer 2 on the base material combination 9 may also be of yellow colour Y so that, for example, the base colour for a traffic sign may be produced in this way. In the coating film combination 5, the said yellow points Y naturally have a colourless colour T described later. In Figs 1 - 4 and 6 - 7, there is shown a coating film combination for producing the sign figures for the traffic signs. The said coating film combination 5 is placed onto the base material combination 9 and fastened to its surface 12. The coating film combination 5 of the invention comprises a plastic sheet or plastic film 4 which forms the coating for the base material combination 9 with as good light transmission as possible and which diffuses light L transmitting it as little as pos- sible. In other words, it is a thin, clear transparent plastic which may be PNC plastic, acetate plastic, polycarbonate plastic, polyester plastic, or acrylic plastic, etc. The said coating film is uniformly continuous, i.e. uninterrupted at least in the area of the traffic sign symbols and, advantageously, continuing uniformly, i.e. uninterruptedly, into the area of the entire base material piece. At least part of the symbols 10 of a traffic sign 1 are fastened onto a surface 14a of this sheet or film material 4 in a mirror image P. In Fig. 7, there is shown the mirror images of the traffic signs in Fig. 8 and, in accordance with the invention, in this reversed form P, the sign figures 10 of the traffic signs are fastened onto a surface 14a of the coating film 4 seen from the side of the sheet or film 4 onto which the said sign figures 10 have been placed, i.e. from the directions N in Figs 1 - 4. With this special combination of the invention, it is possible to place the symbols 10 arranged onto the coating film 4 between the said coating film or sheet and the light-retroreflective layer 2 of the base material so that they are very well protected from external influences, as can be understood especially on the basis of Figs 3 and 4. In accordance with the first embodiment of the coating film combination 5 of the invention presented e.g. in Fig. 3, it comprises merely the said plastic sheet or plastic film 4 and a sign figure 10 arranged onto the surface 14a in mirror image. The said coating film combination is pressed against the adhesive surface 6b of the first embodiment of the base material combination 9 in direction K so that a fixed traffic sign 1 is provided. In this traffic sign, the colour materials 7 or colorants forming the symbol 10 of the traffic sign are, according to the invention, tightly between the coating film 4 and the light-retroreflective layer 2 so that the sheet or film 4 protects the colorants from the influences of environment. In a second embodiment of the coating film combination shown, for example, in Figs 4 and 6, an adhesive layer 6a consisting either of adhesive glue, heat-setting adhesive glue, or dry adhesive is placed on the sign figure 10 formed by colour materials 7 on the surface 14a of the coating film 4. When such a coating film combination 5 is according to the invention placed on the outer surface 12 of a light-reflective layer 2 of the second embodiment of the base material combination 9 of the invention, as shown in Fig. 4, the adhesive layer 6a adheres to the said base material combination so that the colour materials 7 are very well protected between the plastic sheet or plastic film 4 and the base material combination 9, as in the embodiment described above. This arrangement is carried out as shown in Fig. 4 by pressing the coating film combination 5 against the base material combination 9 in direction K. In general, the coating film combination 5 of the invention thus has sign figures 10 for the traffic sign on the surface of a thin film or sheet 4 which is highly transparent, the sign figures 10 consisting of two or more different colours and figures, and the sign figures being in mirror image P, but this coating film combination does not have a light-reflective layer. In accordance with the invention, the coating film combination thus provides either all the figures or sign figures of the traffic sign, or at least more than one figure or symbol. It must be taken into account that in this application also the clear, i.e. colourless transparent area T is considered to be one colour among the colours of the coating film combination, because in this case, also it may form and often does form one of the symbols of the traffic sign. For example in Fig. 1, it may provide the base for the speed restriction number "80". In this description, colour thus refers to a transparent or reflective material which changes the distribution of spectrum of light passing through or reflecting from it, and/or the intensity of light, or changes these as little as possible. An extreme example of the latter is thus a colourless coating film, the extreme example of a colorant changing the intensity of light being black. In general, the materials do always change at least to some extent the spectrum distribution and intensity of light passed through and/or reflected from them, although this might not be discernible with the naked eye. Thus the coating film combination 5 of the invention, i.e. the uniformly continuing coating film, includes at least two colours, of which one may be a colourless colour or some other colour, forming all the areas with this colour for the symbols; or, the film may include more colours, such as three or four, forming with these colours all the areas inside the actual symbol area of the traffic sign, i.e. a circle, triangle, or octagon, or some other possible shape. As already has been mentioned in this description, in accordance with the invention, those areas E of the said coating film 4 that in the finished traffic sign are situated in those places of the base material 3 which are not supposed to be seen by the person moving on the road or observing the traffic sign, are covered by a black colour material B with as low light transmission as possible and absorbing and diffusing as much light as possible. As can be seen in Figs 1 - 2, 7 - 8, the intermediate area E around the speed restriction sign between the circle forming the symbol area and the square base plate piece 13, and the area between the triangular sign figure area of a bend sign and the square base plate piece have been coated with such a black colour material B. According to an advantageous embodiment of the invention, the light non-transmitting and light absorbing black colour material is arranged on the surface of the coating film combination 5 so that only the light-retroreflective layer 2 described above is found on the base material combination. In this way it is possible to simplify the arrangements. However, there is no reason why the black colour material B covering the edge area E should not be placed on the light-reflective layer 2, if necessary, as is shown with broken lines in Fig. 4. Even in this case, the black colour material B will in the final traffic sign 1 be placed between the plastic sheet or plastic film 4 of the coating and the light-reflective layer 2 of the base material so that it is protected. In order to make it possible for the observer of a traffic sign 1 to notice the sign figures 10 as clearly as possible, the symbols 10 consist of colour materials 7 which diffuse light L passing through them as little as possible, i.e. the colour materials 7 are translucent or clear. The different colours needed for the traffic signs, such as colourless T, yellow Y, red R, cyan C, etc. may be printing colours, e.g. silk-screen printing colorants or, alternatively, coloured films. In the first case, the colour materials 7 are printed on the surface 14a of a sheet or film 4 by silk-screen printing method, and in the latter case, they are adhered to the surface 14a of a sheet or film 4 by a suitable adhering method and appropriate adhesive. As has been mentioned- above, the colour materials have to be as transparent and as non- diffusing materials as possible. The "colourless" colour T is naturally produced by leaving the area in question unprinted, or by not covering it with some other coloured film. Only the black colour B has to be of a type with as low light transparency as possible and which colour B absorbs and diffuses as much light as possible. Besides the said areas E which are meant to be non-visible, the black colour B is also used in other areas of the sign figure 10 which are supposed to look black in relation to the background, such as the numbers 80 and 60, and the arrow indicating the turning direction in the figures etc. In order to keep the reflection effect of the light-retroreflective layer 2 as good as possible, and to enable the light L to return back to the direction of the light source and the observer of the traffic sign as well as possible, also the plastic sheet or plastic film 4 of the coating film combination has to be sufficiently thin. Thus, the thickness S of the sheet or film 4 has to be in general at most about 1 mm and, advantageously, less than 0.5 mm. The sheet or film 4 is thus made of flat materials, and it may be relatively rigid or very flexible. For curved traffic signs, it is advisable to use material which is relatively flexible. Corresponding to Figs 1 and 2, the figures 3 and 4 show two different methods for placing the colour material 7. Fig. 3 shows an embodiment in which all different colorants are printed side by side. This entails that every colour needed for the traffic sign is printed separately, and that every colour area comprises empty spaces for other colours, if needed. For example in Fig. 3, the black colours B of the edge areas E and the number 80; the yellow W of the so-called "Euro edging"; the yellow or white base colour Y; and the red colour R of the circular edge are printed side by side. In another alternative shown in Figs 4 and 6, different colorants are printed on top of each other so that their joint effect creates the desired symbol 10 of the traffic sign. This is carried out in accordance with a so-called subtractive colour system. For example in the embodiment of Figs 2, 4 and 6, the colours for the no turn sign are thus printed so that e.g. the yellow colour Y is first printed over the whole plastic sheet or film. The area of the circular edge and the cross line are next printed on the sheet or film with the magenta colour M so that, in transmitting light L, these two colours Y and M are combined so that the user's eye sees the colour red R in these points. The magenta M may also be extended to the edge area E of the traffic sign. The black colour B is printed last to represent the arrow of the turning direction and the edge area E. In this embodiment, the colour materials are thus generally found on the said surface 14a of the plastic sheet or film in the order in which the symbol colour, in this case yellow Y, which must be discerned as uninterrupted or without the interference of other colours, lies closest to the sheet or film 4, and the symbol colour, which may partly be covered by the figures closer to the sheet or film, lies farthest away, i.e. in this case, the colour black B. Inbetween lies the colour which together with the colorant printed first forms the symbol colour cutting the outermost symbol colours, i.e. in the latter case, the black B. The colours most frequently used in traffic signs are generated this way. The colour blue replacing yellow in some signs may also be produced by the subtractive method if it is born in mind that it consists of cyan C and magenta M, just as red consists of magenta M and yellow Y. Thus all the colours occurring in traffic signs may be produced by using either one of the printing or placing arrangements described above. In this connection, it has to be emphasised that although it would appear in Fig. 1 that the superimposed arrangement of colours Y, M and B produced height differences to the plastic sheet or plastic film, the difference in thickness has no meaning whatsoever in practice, and that it has been shown in the figures only for the sake of understanding. In fact the films forming the colours or printing colour layers are extremely thin. As a summary it may be stated that above there is described a base material combination 9 in which the light-reflective layer 2 is arranged continuously at least on the dimension of the entire area of the traffic sign symbols and so that it does not substantially change the colour of the reflected light, and advantageously on the surface of the entire base plate piece 13. In addition, above there is described a coating film combination 5 in which at least part and, advantageously, all of the sign figures 10 needed for the traffic sign are arranged on one side of the coating film 4 in mirror image P and at least with two different colours, of which one may be a colourless colour, but no light-retroreflective layer. In accordance with the invention, the coating film combination 5 is then attached to the base material combination 9 with the light-reflective layer 2 so that the colour materials 7 of the sign figures 10 are placed between the said coating film 4 and the light-reflective layer 2 of the base material 3. For fastening the coating film combination to the base material combination, either an adhesive layer 6a may be arranged on colour layers on the other side 14a of the coating film combination or, alternatively, an adhesive layer 6b may be placed on the surface 23 of the light-reflective layer 2 on the base material combination 9. Taking into account the manufacturing technique for the base material combination, the adhesive layer 6b may be placed on the light-reflective layer 2 already before attaching the light-reflective layer to the base material 3, or the adhesive layer 6b may be arranged only after the light-reflective layer 2 has been attached to the base material 3. Depending on the type of adhesive joining the light-reflective layer 2 with the base material 3 of the sign board, either one of the described placing arrangements for the adhesive layer 6b may be used. However, in all cases the adhesive layer 6a of the coating film combination 5 is always arranged only after the colour materials 7 have been spread to their places by using some method described above, and the said adhesive 6a is arranged on the outer surface of the colour materials. Depending on the type of adhesive used, a protective paper or protective film 8a is placed on the adhesive layer 6b of the base material combination, and a protective paper or protective film 8b on the adhesive layer 6a of the coating film combination. In this way, the said base material combinations and coating film combinations are made easily storable and transportable, because they do not have any outer surface susceptible to handling. Thus, they may be prefabricated in desired types and amounts for storage, and they may be transported to the site of use by any appropriate means. According to the invention, the general base colour yellow Y may thus be produced by a special colour area of the coating film combination 5, or by using the colour of the light- retroreflective layer 2 of the base material combination, and also by using a coloured adhesive layer, such as the adhesive layer 6a and/or adhesive layer 6b. For producing the finished traffic sign, the possible protective paper or protective film 8a and/or 8b is, when necessary, removed from the coating film combination and/or base material combination, and these are pressed against each other in the direction K showed in Figs 3 and 4. If necessary, the adhesive and/or colour materials 7 may be polymerised in a suitable temperature and under suitable pressure. After this stage, the adhesive layer 6a, 6b between the coating film combination and light-reflective layer is in a state maintaining adhesion. As can be understood, the adhesive layer may be placed either on the colour layer surface 24 of the coating film combination, or on the surface 12 of the light-reflective layer 2, or on both. One alternative is to place the actual adhesive layer onto one surface and an activator on the other surface so that after gaining contact after the pressing K, they provide the adhesion between the coating film combination 5 and the base material combination 9. Further, additional protective layers may be placed on the outer surface of the coating film combination vulnerable to the influence of weather, i.e. on the surface away from the colour materials M, R, Y, W, C, and also between the plastic sheet or plastic film 4 and the colour materials M, R, Y, W, C. Such layers may consist of dirt-repellent coatings, UV absorption coatings, layers improving the adhesion of colour materials, etc. After this it may clearly be understood that the light L coming from the direction of the light source and the observer of the traffic sign 1 passes through the colorants 7 between the plastic sheet or plastic film 4 and the light-reflective layer, is reflected from the light-reflective layer 2, passes again through the said colour layers 7 and further through the plastic sheet or plastic film 4 back to the observer's eye. These colorants are situated between the retroreflective layer 2 and the coating film 4, and on the back side of the said film as a mirror image P of the symbols, as is described above. In the coating film combination 5, part of the area corresponding to the symbols is of one colour, and part of some other colour, as is described above, so that also colourless T may be one colour. In this way, the traffic sign is observed in an appropriate way. Besides the manufacture of actual traffic signs, the present invention may also be used in and applied to the production of other similar boards, such as guide boards, etc., which require good visibility in light coming from the direction of the observer, i.e. a retroreflective surface and different sign figures on it. However, it normally concerns a road sign which has to be observed by the person in traffic. Generally it is most advantageous that all surfaces e.g. in finished traffic signs and similar products are not specularly reflective. This means that a traffic sign must not reflect to such an angle of incidence which is as large as the angle of incidence in relation to the surface normal. Generally it is most appropriate that a traffic sign or a similar product has one retroreflective surface, as is described above. Road signs are usually planar, if not bracing edge bendings are not taken into account, but they may also be shaped into a curved form from a rigid material so that they can be observed from incoming directions deviating even considerably from each other, irrespective of retroreflectivity. The invention also relates to such curved traffic signs or corresponding products.

Claims: Claims 1. Method -for manufacturing traffic signs (1) and analogous signs retroreflecting light (L) and including sign figures, in which method a light- retroreflective layer (2) is attached to a rigid or flexible base material (3), materials forming the sign figures (10) being attached on the outer surface of the said layer; the method is characterised in that it comprises as separate phases: [1] arranging the said light-retroreflective layer (2) uniformly over at least the dimensions (HI, H2) of the entire area of the traffic sign figures and said layer not substantially changing the colour of the light reflected therefrom; [2] arranging at least some of the sign figures (10) necessary for the traffic sign in question on one side of a coating film (4) in mirror image (P); and [3] adhering the coating film on top of the light-retroreflective layer on the surface of the base material so that the mirror image -type sign figures (10) point towards the light-retroreflective layer and are thus situated between the retroreflective layer (2) and the coating film (4). 2. Method according to claim 1, characterised in that the coating film (4) is a flexible or rigid sheet-like material transparent to light with as low absorption and as low diffusion as possible, and that a rigid sheet, e.g. a metal sheet is used as base material (3). 3. Method according to claim 1, characterised in that it comprises a phase for spreading an adhesive layer (6a and/or 6b) adhering the coating film and the light- retroreflective layer to each other: [a] on the outer surface (12) of the retroreflective layer (2) either - before joining the layer to the base material (3); or - after the retroreflective layer has been fastened to the base material (3); or [b] on the surface (24) of colours (7) of sign figures being as mirror image on the coating film (4). 4. Method according to claim 3, characterised in that it further comprises a phase in which a protective film (8a; 8b), a protective paper or the like is placed on the spreaded adhesive layer (6a; 6b) for providing a prefabricated base material combination (9) or, respectively, a coating film combination (5), which combinations for traffic signs is readily transportable and manageable. 5. Method according to claim 1 or 2, characterised in that all sign figures (10) of a traffic sign-in question are arranged on one side of the coating film (4), that colorants transparent to light beams with as low diffusion as possible are used for other colours (T, Y, R, C, M, etc.) than black, and a colorant absorbing and diffusing light as strongly as possible is used for the black colour (B). 6. Method according to claim 4, characterised in that it comprises as phases: - removing the said protective film or protective paper (8a and/or 8b) from the adhesive layer (6a and/or 6b); - pressing (K) the outer surface (12) of the light-retroreflective layer of the base material combination (9) and the coating film combination (5) against each other; and - bringing the adhesive layer (6a and/or 6b) between the coating film combination and the retroreflective layer to a state maintaining adhesion. 7. Method according to claim 1 or 5, characterised in that the said sign figures (10) are arranged on the surface (14a) of the coating film by laminating from films of a desired colour and/or by printing, e.g. by silk-screen printing. 8. A coating film combination for providing traffic sign symbols for light- reflective traffic signs (1) with sign figures, in which combination the coating film continues uniformly at least over the area of the traffic sign figures and in which materials forming the sign figures (10) are arranged on the surface of a coating film (4), characterised in that the said coating film combination (5) comprises a light transparent plastic film (4) which diffuses transmitted light (L) as little as possible; that at least part of the sign figures 10) of the traffic sign (1) is fastened on one side (14a) of the film in mirror image (P); that the said sign figures mainly are colour materials (7) diffusing light (L) passing through them as little as possible; and that the coating film combination (5) is light-nonretroreflective. 9. Coating film combination of claim 8, characterised in that the said colour materials (7) are printing colorants, such as silk-screen printing colours or, alternatively, coloured films; that the black colorant (B) is a material transmitting as little light as possible and absorbing as much light as possible, and the other colorants (T, Y, R, C, M, etc.) are transparent to light and non-diffusing materials; and that these colour materials are placed on the said one side (14a) of the plastic sheet or plastic film in such an order that the symbol colour of the traffic sign in question, which is supposed to be visible uninterruptedly, lies closest to the sheet or plate, and the symbol colour, which may partly be covered by sign figures nearer the sheet or film, lies farthest away. 10. Coating film combination of claim 8, characterised in that an adhesive layer (6a) is on the surface (24) of the colour materials (7), the adhesive being an adhesive glue or a heat-setting adhesive glue or dry adhesive; that, if necessary, a releasable protective film or protective paper (8a) is on the adhesive layer; and that the thickness of the plastic film is less than 1 mm, advantageously less than 0.5 mm. 11. Coating film combination of claim 8 or 9, characterised in that the areas (E) of the said film (4), which in the final traffic sign are placed in the points of the base material (3) that are not supposed to be visible, are covered with a black colour material (B) transmitting as little light as possible and absorbing as much light as possible. 12. A sheet-like base material combination for light-retroreflective traffic signs (1) with sign figures, in which a light-retroreflective layer (2) is fastened to a rigid or flexible base plate (3), characterised in that the said base material combination (9) is a prefabricated product comprising a planar or alternatively bent and surface- treated base plate piece (13) cut into shape, and which further comprising a uniform light-retroreflective layer (2) on one side (23 a) of the base plate piece and attached permanently to it, the said layer being such that it does not substantially change the colour of the reflected light when compared with light directed thereto. 13. Base material combination of claim 12, characterised in that the shape and size (HI, H2) of the base plate piece (13) is identical for all traffic signs (1) with the same maximum dimensions but different-shaped sign figure areas, and that the base plate pieces are rectangular or, advantageously, square. 14. Base material combination of claim 12, characterised in that there is an adhesive layer (6b) on the outer surface (12) of the said light-retroreflective layer (2), the adhesive being an adhesive glue, a heat-setting adhesive glue or a dry adhesive, and that, when necessary, a releasable protective film or protective paper (8b) is on said adhesive layer. 15. Base material combination of claim 12, characterised in that the material of the base plate (3) is a rigid metal sheet, advantageously a steel sheet coated with plastic layers (11a, l ib) or, alternatively, a laminate or a composite material, and that the said rigid base plate is either straight or curved.

Inventors: VIROLAINEN REIMA EINARI, VIROLAINEN, REIMA, EINARI
Applicants: RAUTARUUKKI OY, VIROLAINEN REIMA EINARI, VIROLAINEN, REIMA, EINARI
Application year: 1998
Main classification: G09F13
IPC codes: G09F13