FI82949B - Metallizing process - Google Patents

Description

! 82949

The present invention relates generally to a method for mirror-metallizing a substrate and to a product made by the method. The substrate may be in the form of a web or sheet and may be paper, cardboard, wood, plastic or any other material. A very shiny, smooth, polished mirror-like metal appearance can be applied to the substrate without special treatment or polishing.

Various methods are known in the art for metallizing a substrate in the form of a web 10 or sheet. In one method, a metal film is laminated to a substrate using a solvent based on polymerizable adhesives. This method is commonly used to metallize flexible materials and the most commonly used metal is aluminum foil. 15 In the method, the thickness of the metal film must be more than 1 micron. The use of thinner films is not possible in mass production and is only possible in small batch production. To achieve a mirror-like surface treatment, the metal film must have a polished surface treatment. The gloss and surface treatment of the final 20 products do not depend on the substrate, but rather on the gloss and surface treatment of the film.

In another known method, a very fine metal powder is dispersed in a binder and the powder-containing binder is applied to the surface to be metallized. The metallization methods of Edel-25 are performed by chemical precipitation and electrolysis methods. In these methods, the gloss and surface treatment of the metallized surface depends on the gloss and surface treatment of the substrate. Very good gloss and a mirror-like surface treatment are achieved when the substrate material is glossy, such as a plastic film or a polished surface. When the substrate is not flat, a smooth surface treatment is not achieved. Thus, in these methods, the gloss and surface treatment depend on the surface treatment of the substrate rather than the metal used.

Another commonly used method is vacuum metallization, in which vaporized metal is condensed on a substrate to be metallized. Here, the vessel is placed in a chamber, 2,82949, with a high vacuum of the order of 10-3 to 10-4 torr. Of course, this method is limited to a material that does not gasify and does not contain volatile substances such as moisture, plasticizers and resins. The disadvantage of this method is that the surface formed is generally quite rough, because the vaporized metal does not even out the roughness of the surface on which it is condensed. To improve the surface treatment of a substrate, such as paper, the paper substrate must be pre-polished or pre-varnished. In certain cases, each pretreatment is not sufficient to produce a mirror-like surface and the surface of the substrate must still be calendered at a high temperature. This extra step significantly increases the cost of the surface treated product.

Furthermore, when using this method with materials that are substantially gaseous, such as paper and board, high vacuum vacuum metallizing devices are required in the chamber to eliminate the loss of air caused by air and moisture in the paper or board. In some cases, degassing of the material before metallization is required.

The purpose of this method and the product produced by it is to provide a flat mirror-like surface which is independent of the flatness of the substrate or metal, without having to pre-treat the substrate and subject it to vacuum. The object of the invention is achieved by the means set out in the claims.

In carrying out the invention, a very thin coating of metal particles is placed on top of the finely treated transfer medium. A thin layer of varnish is applied to either the substrate or the transfer medium. The transfer medium and the substrate are laminated together before the varnish cures. The metal particles are absorbed or immersed in the lacquer coating, providing a substrate with the appearance of a mirror-like metal pin-35 back-treatment. After the varnish has hardened, the transfer medium and the substrate are separated. Transfer agents can be reused in the following processes.

3,82949 having a metal coating that is substantially thinner and significantly lighter than lamination with a metal film so as to provide a higher yield of coated substrate from the metal and significantly reduce material costs.

It is a further object of the present invention to provide a method of making a metal-coated substrate which has as good a mirror-like gloss as a metal film and which is substantially less expensive than film laminates.

It is a further object of the present invention to provide a metal-coated substrate which has the same chemical resistance as a metal film and which does not turn yellow or change in appearance over time, which is abrasion-resistant, flexible and hard so as to withstand various manufacturing and printing presses. 15 printing methods.

It is a further object of the invention to provide a metal-coated substrate which reflects infrared light and which is a barrier to visible and ultraviolet light so as to be suitable for packaging foodstuffs which, like a film, is relatively impermeable and can be manufactured together with a printing machine.

It is a further object of the present invention to provide a lacquer and metal coated substrate for bending tears.

Another object of the present invention will become apparent from the following detailed description.

In order to clarify the invention, reference is made to the accompanying drawings and the description, in which case FIG. 1 is a flow chart of a substrate storage method according to the invention, FIG. 2 shows an apparatus for vacuum precipitation of metal particles on a transfer medium, FIG. 3A-3C show the use of a varnish to smooth the surface of a substrate and a method for determining the amount of varnish used, FIG. 4A and 4C show a lamination method and a relationship between roll pressure and diameter, and Figs. 5 shows the separation of a metallized substrate from a transfer medium.

Fig. 1 shows a method for manufacturing a metal-coated substrate according to the invention. The transfer agent 20, which has a glossy, polished surface, is metallized. The transfer medium must be finely surface treated as it produces the final surface of the product. It must also be less sticky to metal particles than the varnish used. Suitable materials for the transfer medium 20 include e.g. untreated polypropylene, polyes-10 ter, polyethylene, polyvinyl chloride, polyamide, coextrudates and regenerated cellulose. The transfer agent 20 is then metallized at 22 by doping the metal particles by any known method, such as vacuum metallization, chemical precipitation, and other coating methods.

15 Suitable metals for deposition are aluminum, copper, silver, nickel, tin, platinum, gold, their alloys and other volatile metals. The amount of metal precipitation is controlled so that the precipitated metal particles form a very thin layer. The thickness of the precipitated particles is substantially less than the wavelength of light, e.g. less than 500 and preferably less than 300 Å, and the gap (where such a gap or metal film apertures occur due to a thinner thickness) is substantially less than the wavelength of visible light. Thus, the light is reflected substantially from the metal surface and the metal surface 25 appears uniform and has a completely mirror-like metallic surface.

As the transfer agent 20 undergoes metal deposition at step 22, a substrate is prepared (these steps need not be simultaneous). The substrate, optionally coated with metal particles, may be in the form of a web or sheet and may have a rough or flat surface. Suitable substrates include paper, cardboard, wood, leather, plastic, or any coating material that can be varnished. The substrate 24 is coated with a thin layer of lacquer 35 at step 26. A suitable lacquer for this purpose is polyurethane nilac. The lacquer acts both as a carrier to produce a smooth, mirror-like surface together with the transfer agent and to transfer the metal particles precipitated in step 22 from the transfer agent 20 to the substrate 24 and absorb them into the varnish. The varnish also smoothes the surface 24 of the substrate. It is a feature of the present invention that although the varnish adheres to the substrate, it does not adhere to the transfer agent 20.

Alternatively, the lacquer coating may be applied to the transfer agent 20 on top of the deposited metal particles. This alternative method produces a surface-treated product that is substantially similar to that produced when substrate 20 is varnished, although empirically, depending on the varnish and substrate, one or the other method is preferred. This alternative method is shown in Figure 1 as a flow line from step 22 to step 26.

After step 22, in which the metal particles are deposited on the transfer agent 20 and the substrate 24 or transfer agent 20 is coated 26, a lamination step 28 takes place. Step 28 is performed before the varnish has cured. In the lamination step 28, the substrate 24 is brought into contact with the metal-coated surface of the transfer medium 20. This is preferably accomplished by winding the substrate 24 and the transfer agent 20 into a single roll at low pressure. This step is similar to the conventional lamination process. The varnish transfers the metal particles from the transfer agent 20 to the substrate 24. The varnish absorbs the metal particles and assumes the uniform surface properties of the transfer agent 20 after it has been removed.

The laminated substrate 24 and transfer agent 20 may be dried at 30 by air drying or conventional drying processes. Once cured, dried or polymerized, the varnish does not bind to the transfer agent 20, but binds strongly 30 to the substrate 24. The curing step 30 may be natural or may be promoted by heat or irradiation. After curing 30, a separation step 32 takes place. The transfer medium 20 and the substrate 24 can be separated (in the case of flexible webs) into two separate rolls, and at this point 35 the lacquer and the metal particles absorbed or immersed have adhered to the substrate 24. After the separation 32, the transfer medium 24 can be reused several times. , which 6 82949 created very economic benefits.

The surface treated product 34 consists of a substrate 24 with a flat, mirror-like, metallic coating that appears continuous and even because the interstices or gaps between the metal particles allow low light transmission (i.e., less than 30%, preferably less than 20%). The varnish does not need to be applied to the substrate 24 over the entire surface, but rather can only be divided into certain parts in different patterns. Thus, only a few parts of the substrate 24 have a metallic luster. The surface-treated product 34 can be subjected to a variety of other processes, such as cutting, embossing, stamping, punching, and printing on a metallized surface by various printing systems, such as offset, gravure, flexographic, screen printing, and the like.

Having described above the various steps and the relationship between the steps of the method for making a metal-coated substrate, the apparatus and the processes of the individual steps will be explained in more detail below.

Fig. 2 schematically shows a preferred embodiment 20 for performing step 22, to deposit metal particles on the transfer medium 20. The most efficient form of fabricating metal-coated surfaces arises when the transfer material 20 is in the form of an elongate web or material that can be fed by rollers. The transfer agent 20 is fed to a conventional vacuum chamber 36; the vacuum chamber has a plurality of metal (e.g., aluminum) containers deposited on the substrate 20. The number of containers is insufficient to form a uniform coating (e.g., 10 containers, 1 cm wide to 7.5 cm long for a 75 cmsn web). Each tank 38 is heated to a melting temperature 30 (e.g., 1500 ° C for all) and the web is maintained at room temperature by a water-cooled roll 40 passing about 15 cm above the tanks. As the transfer agent 20 passes through the vacuum chamber 36, the metal vapor 39 produced by the liquid metal passes into the transfer agent 20 and condenses at 39 due to the heat-35 gap. The speed of the transfer web 20 can be continuously adjusted as well as the temperature of the tanks so that the thickness of the metal precipitated by condensation is preferably less than about 82 Å on a substrate 20. This very small film thickness (depth) allows minimal use of the metal, but still produces a fully metallized continuous metal surface thanks to a lacquer surface treatment.

The monitoring of the vacuum deposition process can be performed by a suitable electronic or mechanical device so that the deposition rate is continuously monitored and fed to control the various heating electrodes and the feed rate of the transfer web 20.

Figures 3A and 3B show a lacquer coating step 26. As mentioned above, the substrate 24 may be of any suitable material, which may have either a rough or flat surface. No pretreatment is required because the lacquer coating provides a uniform mirror-like coating on all types of longitudinal surfaces and fills all the gaps present on the surface of the substrate 24. This is shown in Figure 3A, where the substrate 24 is coated with a varnish 42 which has completely smoothed the irregular surface of the substrate 24. Figures 3B and 3C show a method for determining the amount of varnish required to provide a uniform coating of substrate 24.

In general, the rougher or more absorbent the surface of the substrate 24, the greater the amount of varnish 42 required. The amount required is determined empirically by taking a test sample from substrate 24, placing it at an angle, and then applying lak-25 caprice 42 over the angled substrate 24 and then measuring in castings as shown at distance A. A similar test is performed with glass 44 instead of substrate 24. The length of the drain B is then measured. From the known amounts of varnish 42 required to properly coat the glass 44, the amount of varnish 42 required to coat the substrate 24 can be determined. The varnish may be coated on the substrate 24 or the transfer agent 26 in any known manner, but bath immersion has been found to be most preferred. The lacquer cover must be just sufficient to fill the valleys and 35 to cover the hills 24 '.

Figures 4A and 4B show the lamination of the substrate 24 and the metalloprecipitated transfer medium 20. The webs of the substrate 24 and the metallized β 82949 ti deposited transfer medium 20 are superimposed between the rollers 46, 48. Roll 46 is, for example, a rubber roll having a thickness of about 75 Shore, and roll 48 may be a suitable hard roll, such as a chrome-plated or stainless steel metal roll. Pressure is applied between the rollers 46 and 48 to laminate the substrate 24 to the metal-precipitated transfer medium 20. The dilution step is an uninterrupted step after the coating step 26 and the precipitation step 22 before the lacquer 42 has dried or cured. The pressure applied between the rollers 46 and 48 is inversely proportional to the diameter of the rollers as shown in Figure 4B. One pressure-diameter combination could be a pressure of 5-6 kg and a roll 46 with a diameter of 110 cm. Once the substrate 24 and transfer medium have been removed from the rollers 46 and 48, they are wrapped around a take-up roll 50 which, after winding, is set aside for curing.

The curing step 30 can take place in the coiled state within about 24 hours, or the curing can be accelerated by using a different varnish or by using heat or radiation. As mentioned above, as the lacquer 42 hardens on the transfer medium 20, the metal particles 39 '(see Fig. 40 are completely surrounded by the lacquer 42 on the substrate 24. Significantly the lacquer 42 obtains a smooth surface of the transfer medium 20 and is the key to mirror treatment. does not occur between the varnish 42 and the transfer agent 20 and the transfer agent can be reused several times, making the method very economical.

Next, a separation or delamination step takes place. The roll 50 is placed in contact with the rollers 52, 54 placed tangentially opposite. The tangent roll 52 removes the transfer material 20, which is found to be completely free of the metal coating that has migrated to the lacquer layer of the substrate 24. Thus, the tangent roll 54 removes the substrate 24, 39 ', 42 in which the metal particles are embedded in the lacquer layer and in which there is a flat, mirror-like metallic surface treatment.

After the substrate 20 has been removed from the roll, it can be reused several times and the surface-treated product 1.

9,82949 can be removed from roll 54 for further processing when printing or cutting, as described above. There is only a small amount of adhesion between the substrate 24 and the transfer medium 20 when they are separated. The bonding force is about 5 5 - 10 g / m2 and as long as it is less than the attraction of the varnish used, the performance requirements of the method are met. For my example, a 20 micron thick film of untreated bidirectional polypropylene (BOPP) is used as the transfer agent 10 and is vacuum metallized without prior coating. A very fine layer of aluminum, 0.03 g / m 2 thick, is deposited on the film. This layer precipitates a very thin aluminum

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a coating of about 105 A on the surface of the polypropylene film transfer agent. Preferably, the thickness is 50 to 250 A. This method is performed continuously on a spool.

In this example, the lacquer coating can be applied to the metal coating of the film transfer medium rather than to the substrate itself. The varnish used in this case is of the polyurethane type and, after coating, the film is allowed to evaporate (e.g. by passing it through rolls of rolls in a suction fan atmosphere) and is laminated to a substrate to be metallized. In this case, the substrate is paper with a weight of about 80 g / m2. The lamination is performed continuously in one gravure or flexographic printing machine (not shown). Lamination takes place at ambient temperature. The adhesive coating can weigh 8-10 g / m2 and contain 50% solids.

After lamination, the combined transfer medium and substrate are stored on the spool for a sufficient time so that the varnish hardens and allows easy removal from the transfer medium.

30 This is also best determined empirically and depends on the varnish, its thickness and substrate. The transfer medium and the substrate are detached from each other in a unwinder as shown. The transfer medium can then be reused. There are no inherent speed limits in the method.

35 Example _2 In this example, the transfer agent is metallized as shown in the example above. The metallized surface of the transfer medium is then coated with a solvent-free polyurethane-type varnish. In contrast to the previous example, in this case no evaporation of the varnish is required. After application, the varnish is laminated to a substrate weighing 80 g / m 2. As in the previous example, the material is allowed to rest long enough for the varnish to cure (e.g., 24 hours) and then the transfer agent and substrate are separated.

Example 3 10 Again, the transfer medium is metallized by a vacuum process. The metallized surface of the transfer medium is then bonded to the surface of the substrate with an ultraviolet-emitting, crosslinkable photopolymer resin. The solvents are dried by evaporation and the transfer agent is laminated to the substrate. In this example, lak-15 ka can be applied to either the vehicle or the substrate because the results are the same. After lamination, the polymerizable material is irradiated with UV radiation through a transfer medium. This allows the resin to cure immediately and the substrate can then be removed from the transfer medium continuously in the same machine. The resulting substrate has a very well-polished, mirror-like metallized surface that is also heat-resistant.

Although the present invention has been described in accordance with preferred embodiments, it is to be understood that variations and modifications may be made without departing from the scope of the invention, as will be apparent to those skilled in the art. Such variations and modifications are within the scope of the invention and the appended claims.

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Claims (4)

11 82949 A method for producing a high-gloss composite material comprising a substrate, a thin metal layer consisting of metal particles and a film 5 as an adhesive in which the metal particles are embedded and which holds the metal particles on a substrate, the metal particles first being applied in a layer less than 0.05 μm thick on the surface, then a layer of adhesive between the metal layer and the substrate is applied to this 10 and / or metal layer, then the transfer agent together with the metal layer is pressed onto the substrate and the metal particles are immersed in the adhesive and the transfer agent is removed from the composite material and solidified, that a polyurethane-curable plastic or a radiation-crosslinkable photopolymer plastic is used as the adhesive and that the removal of the transfer medium (20) is carried out by curing the plastic after it (30) and the metal particles have been absorbed into the plastic. Method according to Claim 1, characterized in that the metal layer is applied in a thickness of 0.005 to 0.025 μm. Method according to Claim 1 or 2, in which a radiation-crosslinkable photopolymer plastic is used, characterized in that the irradiation is carried out through a transfer medium (20). Method according to one of Claims 1 to 3, characterized in that the irradiation is carried out with ultraviolet radiation. 12 82949