EP0982127A1 - Method and means for hot foil printing - Google Patents

Abstract

The hot embossing method uses a rotary machine (1) with an embossing device (2) having a pair of cooperating rollers (3,4) defining an embossing gap (5) through which a material web (7) and an embossing foil web (8) are fed, for periodic contact by a heated embossing matrix (6), incorporated in the surface of one of the rollers. A pre-heating device (24) in front of the embossing gap is used for pre- heating the material web to a temperature of between 80 and 120 degrees centigrade. An independent claim for a hot embossing device is also included.

Description

The invention relates to a hot stamping process according to the Preamble of claim 1 and one in particular Execution of the method suitable hot stamping device according to the preamble of claim 7.

Hot stamping processes of this type become one for hot stamping impressing material layer with on an embossing film present embossed material used. An embossing foil points generally a thin, multilayer dry film, which is on a tear-resistant film carrier e.g. made of plastic is arranged. The film bears the embossed good that it is especially discrete ones, arranged side by side or one behind the other Embossing units such as pictures, texts or the like or to be stamped on parts or areas of layers of paint can act. A preferred application is with the embossed item for holographic images, such as her for example on banknotes or other securities Increase their counterfeit security. The Layer structure of the film is usually such that on the Foil carrier, for example, a wax-like separating layer is arranged, on which the color-determining or image-determining, the single or multi-layer layer containing the embossed material lies. On top of this is a thermally activatable layer of hot glue or adhesive layer provided.

In the process, the material layer, which is Sheet material or sheet material can act through a Embossing gap moves and the embossing foil web is also moved, that an embossing foil section at least during a Embossing interval at the same speed as the material layer moved through the embossing gap. During the minting interval the stamping foil section while heating to a stamping temperature pressed onto the material layer section to be embossed. The back side facing the material layer the adhesive layer arranged in the embossing film heats up during the embossing interval under the influence of a heated one and pressed embossing tool to an embossing temperature and softens. In conjunction with that during the minting interval briefly applied pressure is supposed to be a good adhesive bond between the printed material or the substrate and the embossed goods to be created. At the same time, it softens or evaporates through the acting Heat the separation layer, which makes it easy to remove the Embossed goods should be obtained from the film. A good, full surface adhesion between embossed goods and embossed material as well as a sufficiently secure separation of the transfer layers of the film carrier are essential from that by means of a heated to typical temperatures of more than 200 ° C Embossing tool generated via contact temperature, from the applied pressure in the embossing gap and from the Exposure time depending on the pressure and temperature act on embossing materials.

The most suitable embossing parameters should usually be at high pass speeds are provided. The Demand for high printing performance or throughput can be done mainly by two increasingly important Fulfill printing systems. In so-called flat-round embossing machines the printing nip between the printing material leading pressure cylinder and a flat embossing tool carrier plate formed in the direction of flow of the material to be embossed oscillating back and forth is that during the minting interval it will be sent to the Cylinder is pressed and at a peripheral speed of the cylinder at the embossing gap of the corresponding one linear velocity moves while rewinding is out of engagement with the cylinder. Even greater throughputs are equipped with so-called round-round machines or To achieve embossing rotary machines that are an embossing mill have, in which the embossing gap between an embossing tool load-bearing embossing cylinder and an impression cylinder is formed. With both methods is in the range of Embossing gap is only practically line-like or slightly compressible back pressure element narrow Pressure zone formed. This causes the effective connection time, in the sufficient contact pressure and the required Stamping temperature should prevail, becomes very short. Accordingly, especially with high throughput rates in high-speed embossing rotary machines Liability problems between embossed goods and the surface as well Replacement problems occurred.

Accordingly, the invention is based on the object Hot stamping process and a suitable hot stamping device propose a better liability between the mint and embossed material layer and easy detachment also with ensure high throughput speeds.

To achieve this object, the invention proposes a hot stamping process with the features of claim 1 and one for Execution of the method suitable hot stamping device with the features of claim 7.

An inventive hot stamping process of the type mentioned is characterized in that a preheating of the impressing section of material before the embossing interval, i.e. before the effective passage of the to be connected Materials through the embossing gap, is performed. After Invention are thus those described, particularly at high throughput rates, very short contact times or Exposure times of embossing temperature and embossing pressure suitable preheating of the material to be embossed at least partially compensated. The preheating of the material layer leads to the fact that the adhesive layer to be activated not only e.g. is heated by means of the stamp, but also due to the pre-heated contact with the stamping foil Material layer. Since this already before entering the embossing gap area is preheated above the ambient temperature they pass little or when passing through the embossing gap no heat of usable for heating the adhesive layer this off, so that the usually initiated by the embossing stamp Heat essentially completely for activation the adhesive layer can be used. The film, especially its Adhesive layer, can be heated from both sides according to the invention which, compared to conventional methods, where the connection heat only through a heated embossing stamp or the like is applied in which Lower thermal gradients occur and a total gentle heating is effected. During the run the embossing gap ensures that the connection is good required adhesive layer temperature faster reached and prevails correspondingly longer under pressure, which significantly improves liability.

In addition, it has been shown that the embossed material if it was impressed by the method according to the invention, a shows significantly higher brilliance than conventional ones Process embossed. This may be possible explain that preheating generally makes it more gentle Treatment of the optical impression of the embossed Material-determining, possibly heat-sensitive surface areas is achievable. In particular, a better, Low-distortion, surface-friendly separation possible be through which the optically effective surface of the embossed material is less burdened. In the case of holograms, it may be added that the one-sided heating in conventional processes Distortions within the optical structure of the holographic Layer leads so that by microscopic Distortions in the light wavelength range are no longer those for a brilliant mapping required geometry of the holographic Structures. In the inventive The process, on the other hand, is thanks to the preheating of the material layer usually heated on both sides and therefore more gently, so that any distortion is not or only in one essential lesser dimensions occur, reflecting the brilliance of the holographic Figure increased.

It has proven to be advantageous in experiments if the section of material layer to be heated is used for preheating heated to temperatures below 150 ° C, especially at temperatures between approx. 80 ° C and approx. 120 ° C. This temperature range takes into account the problem that typical carrier film materials clearly at temperatures can often be plastically deformed above 90 ° C. This Temperature range should therefore be when heating the stamping foil not clearly by means of the material layer section be crossed, be exceeded, be passed.

Although it can be sufficient if only the material layer section is preheated, it can be beneficial to both embossing flat materials, including the stamping foil section, preheat, preferably one essentially same temperature of both materials is aimed at Thermal gradients to avoid declining distortions, though the materials in contact shortly before or in the embossing gap kick together.

To avoid an interim cooling between It is preheating and passage through the embossing gap advantageous if the preheating temporally to immediately before the embossing interval, preferably to less than 5 or 2 or 1 second before the start of the embossing interval. Accordingly, it can be advantageous if the preheating of the moving material in the immediate vicinity and / or in is carried out in the immediate vicinity of the embossing gap, whereby preferably a distance between a preheating section and the embossing gap less than 100 mm, in particular between 20 and 80 mm, preferably between 40 and 60 mm can lie. This can prevent the Material layer has been in the preheated state for too long which may result in heat-induced impairments or could be favored.

The preheating can, for example, by means of contact heat can be achieved in that the material section to be heated, in particular the material layer section over a heated deflection roller or deflection rod or the like is guided. To avoid damaging the possibly sensitive Material layer it is preferred if the preheating is contactless is carried out, in particular by means of hot gas and / or by means of thermal radiation.

It can be used for the effective use of the heat energy be advantageous if the material layer, preferably exclusively, from the side of the surface to be printed is heated. This is preferably the one used for gluing interacting with the embossing film web or with the adhesive layer Surface warms up while the print side faces away Back of the material layer is comparatively cooler can stay.

The invention also relates to one for carrying out the above Hot stamping device suitable for the process. she has a Embossing, in which between a cylinder and a movable Back pressure element at least during an embossing interval an embossing gap is formed, and film transport means and material layer transport means for generating a at the same speed at least during an embossing interval Running an embossing foil section with one the embossing gap moved material layer section of a material layer and contact heating means for heating the material layer section and the stamping foil section during the Embossing interval, contact heat means the cylinder and / or can be assigned to the counter pressure element. A Hot stamping device according to the invention is characterized by a preheating device for preheating the material to be stamped Material layer section before effective passage through the embossing gap.

So it may be that the preheater at least one for heating the material layer section outside the Embossed gap formed material heat source. It can be advantageous if the heat output of the heat source is controllable, for example depending on the Throughput speed of the material to be heated. This allows at any suitable throughput speed about the same, particularly suitable preheating temperatures on End of the preheater are generated. A special one preferred because of the avoidance of mechanical damage Variant is characterized by non-contact working Heat sources, for example at least one on the material to be heated directed hot gas generator and / or at least one directed towards the material to be warmed up, preferably electric radiant heaters. Are preferred Here, embodiments in which a heat source is an in Transverse direction to the direction of movement substantially uniform Allows warming up of the material to be preheated. For example, a hot air blower can have one or more across the entire width of a layer of material Have longitudinal gas outlet slot.

These and other features go beyond the claims also from the description and the drawing, wherein the individual features individually or separately several in the form of sub-combinations in one embodiment of the invention and in other fields could be.

Fig. 1

eine schematische Seitenansicht einer erfindungsgemäß ausgerüsteten Präge-Rotationsmaschine.

An embodiment of the invention is shown in the drawing and is explained in more detail below. It shows:

Fig. 1

is a schematic side view of an embossing rotary machine equipped according to the invention.

The hot stamping rotary machine 1 in FIG. 1 can for example for stamping consecutive sheets or one Sheets of paper, cardboard or plastic can be used. in the The example shown is used to mint paper banknotes with embossing units in the form of holographic images used. The hot stamping rotary machine has an embossing unit 2 with a horizontal embossing cylinder 3 and an approximately equally large, underneath, rotating in opposite directions Impression cylinder 4, between which an embossing gap 5 is formed is. The embossing cylinder 3 has along its circumference at least one to a temperature of over 200 ° C, for example Embossing die 6 heated to 220 ° C., which in the Drawing figure on a continuous layer of material 7 a Embossing unit in the form arranged on the embossing foil web 8 of a hologram. The embossing foil web, its construction has already been explained in more detail at the beginning, has a rear side 9 and a sensitive one with a layer of hot glue Front 10, which in the area of the embossing gap impressing surface 11 of the material layer 7 is facing. The figure shows the device during an embossing interval, during which the material layer 7 and the embossing foil web 8 in the area of the embossing gap 5 the same direction of movement 12 and have the same speed through the embossing gap 5 to run.

The material layer 7 is by a material transport device, not shown uniform in the main direction of movement 12 moved through the embossing gap. The film transport are used to generate an uneven tracking of the embossing foil web trained, especially as a film accelerator for a forward / reverse operation of the embossing foil web. This film web guide with reversal of direction of movement the embossing foil web is particularly suitable for embossing combinations, where those are intended to save material is that successive embossing units to be embossed lie closer together on the embossing foil web than one behind the other Horizontal embossing locations on the material layer. It does it required that the embossing foil web outside the embossing interval slower than the material layer is performed before Embossing interval accelerated to the material layer speed is then braked again and if necessary also is withdrawn. The film transport device 13 for the The structure of embossing foil can be used to transport foils the embossing rotary machine described in EP 0 718 099 correspond to their characteristics by reference to the subject of this application. The film transport means 13 have an embossing gap 5 and one in the transport direction Deflection roller 14 downstream traction device 15 with a Slip drive for the stamping foil web and one with the Traction device interacting, the embossing gap and a this upstream guide roller 16 upstream, controllable film feed device 17. The slip drive the traction device is operated by an electric motor 18 driven suction belt 19 formed on the flat drive surface 20 the embossing film web in sections under construction can be sucked in by sliding friction. The film feeder 17 has a driven by an electric motor 21 a control device in rotational speed and / or Direction of rotation controllable control roller or clock roller 22, which in a circumferential section wrapped by the embossing foil web has effective suction openings through which a slip-proof, enables frictional guidance of the embossing foil web becomes. In the drawing it is indicated that the device several, for example up to six, lying side by side Film feed devices 17, 17 'can have the independent of each other several parallel stamping foil tracks control that through a common pulling device 15 by the Embossing gap are drawn.

Upstream of the embossing gap 5 in the transport direction 12 is in the area between the front deflection roller 16 and the embossing gap, a preheater 25 for preheating one that immediately passes through the embossing gap arranged to be embossed material web section. The preheating device 25 has a schematically shown Material heat source 27. The material heat source 27 is designed as a hot air blower and has one facing the film Top 11 of the web of material 7 directed transversely to Material web extending longitudinal air outlet slot, the extends over the entire width of the material web. The Heat source 27 is from a control device, not shown controlled in such a way that for a given throughput speed the web of material the top 11 on the whole Spread evenly to a preheating temperature of approx. 80 ° to Is preheated to 120 °. The material heat source 27 or her Air outlet is immediately in front of the embossing gap 5 with a Distance in the web direction of about 50 mm so that between the end of that defined by the heat source 27 Preheating section and the passage through the embossing gap in usually less than 1 second passes and an interim one Cooling is largely prevented. The air outlet the material heat source 27 is in one Distance of a few millimeters to the material web 7, so that in essentially the entire thermal energy contactless on that Usually thin material is transferred, which is quickly removed heats up.

The material heat source 27 is thus a non-contact one Hot air source formed through which the web of material 7 across its entire width from the surface to be printed 11 is preheatable. The warming can only over part of the width, for example if the Material web is wider than that used for embossing Stamping foil. The preheated area should at least be useful the area that comes into contact with the embossing foil web include. Alternatively or in addition to heating the Top 11 can also be heated from the film facing away Back of the material layer 7 take place.

By the heat source 27, which is immediately in front of the embossing gap between those in the embossing gap at an angle of approx. 10 ° to 20 ° converging material webs 7 and 8 is arranged, the material web 7 is so far, for example, on a Preheating temperature of about 100 ° to 120 ° warmed that at Meeting with the embossing foil web in the embossing gap as Heat source can serve, through which the embossing foil web of its adhesive layer side 10 is warmed up. Of the opposite back 9 is heated by means of the heated embossing tool 6, which is shown in the Example is heated to approx. 220 ° C surface temperature. Due to the preheating of the material layer, there is a bilateral Heating of the embossing foil web in the embossing gap area possible, with temperature gradients occurring in the embossing foil web are significantly flatter than with a cold material web. Because of the preheating of the material layer the over the embossing stamp 6 introduced thermal energy the material layer does not have to or only needs to heat up a little, the full thermal energy is available available for heating the embossed film. This makes it necessary for a good adhesive connection Adhesive layer temperature reached and prevails faster accordingly longer under embossing conditions, whereby the liability between the printed image and the printed material layer is significantly improved. The time in which the adhesive layer is fully activated under pressure conditions extended. Conversely, higher passage speeds can also be used of the material layers through the embossing gap at sufficient liability can be realized.

Although it is usually sufficient, only the material layer preheating can in certain cases be in addition to the material layer the embossing foil web can also be preheated. The Preheating can preferably be analogous to preheating the Non-contact material web immediately in front of the embossing gap be carried out, preferably heating be carried out exclusively from the adhesive side 10 can. A preheating device in the area of the embossing gap contact surfaces 10 that come into contact with one another the embossing foil web and 11 the material web at the same time preheats, can have a hot air blower, for example, at least one in the area immediately before the embossing gap air outlet opening directed onto the back of the stamping foil 10 and at least one on the surface 11 of the material layer 7 directed air outlet opening.

Instead of the heating described in a very narrow, for example, only a few centimeters wide in the direction of travel Preheating section, it is also possible to refer to the Web running direction longer preheating section of 10, 20, 50 cm or to provide more, possibly even more gentle preheating enables. In particular, it is also possible to Preheating in stages on successive in the web direction Make places so that, for example, only one last preheating step the material web over a possibly critical temperature limit warmed.

Claims (15)

Hot stamping process for stamping a material layer with Embossed material present on an embossing film web, in which the material layer is moved through an embossing gap and the embossing foil web is moved so that a Embossing foil web section at least during an embossing interval at the same speed as the material layer moved through the embossing gap and during which Embossing interval of the stamping foil section under heating on a section of material to be embossed is pressed, characterized by preheating the Material layer section before the embossing interval. A method according to claim 1, characterized in that for preheating the material layer section to be heated to temperatures of less than 150 ° C, in particular to temperatures between approx. 80 ° C and approx. 120 ° C, is heated. Method according to one of claims 1 or 2, characterized characterized that the preheating temporally immediately before the embossing interval, preferably until less than five or two or a second before the start of the minting interval. Method according to one of the preceding claims, characterized in that the preheating of the moving Material in close proximity and / or in in the immediate vicinity of the embossing gap, preferably a distance between a preheating section and the embossing gap is less than 100 mm, in particular between 20 mm and 80 mm, preferably is between 40 mm and 60 mm. Method according to one of the preceding claims, characterized in that the material section to be heated heated without contact during preheating is, in particular by means of hot gas and / or by means of Heat radiation. Method according to one of the preceding claims, characterized in that the material layer, preferably exclusively from the side of the print Surface is preheated. Hot stamping device with an embossing unit, in which between a cylinder and a movable back pressure element at least during an embossing interval Embossing gap is formed with film transport and Material layer transport means for generating a at the same speed at least during an embossing interval Traversing an embossed film web section with a material layer section moved through the embossing gap a layer of material and with contact heat agents for heating the material layer section and the Stamping foil section during the stamping interval, characterized by a preheating device (25) for Preheating of the material layer section to be stamped (7) before passing through the embossing gap (5). Hot stamping device according to claim 7, characterized in that that the preheater (25) is at least 0 one for heating the material layer section outside of the embossing gap trained material heat source (27), preferably the heat output of the Material heat source, especially depending on the speed of movement of the material layer (7) is controllable. Hot stamping device according to claim 7 or 8, characterized characterized in that the preheating device (25) for contactless heating of the material layer section to be heated is formed, preferably the material heat source (27) at least one on the Material to be heated directed hot gas generator and / or at least one on the material to be heated directed, preferably electrical, heat radiation source having. Hot stamping device according to one of claims 7 to 9, characterized in that the preheating device (25) to transverse to the direction of movement of the to be heated Material essentially uniform warming up is trained. Hot stamping device according to one of claims 7 to 10, characterized in that the material heat source (27) designed and / or depending on the Movement speed of the material layer section can be controlled that the stamping foil (8) in contact with the material layer through the heated material layer section to a maximum temperature of less than 150 ° is warmed up, preferably to temperatures between 80 ° and approx. 120 °. Hot stamping device according to one of claims 7 to 11, characterized in that at least one material heat source (27) is arranged so that it is the material layer heated from the side to be stamped (11). Hot stamping device according to one of the preceding Claims, characterized in that a material heat source (27) of the preheating device (25) in the material flow direction (12) immediately before the embossing gap (5) is arranged, preferably between heat source and embossing gap less than a distance in the web direction 100 mm, in particular between 20 mm and 80 mm, preferably is between 40 mm and 50 mm. Hot stamping device according to one of claims 7 to 13, characterized in that the hot stamping device is an embossing rotary machine (1), the counter pressure element is an impression cylinder (4). Hot stamping device according to one of Claims 7 to 14, characterized in that the film transport (13) to produce an uneven tracking of the Embossing foil web are formed, in particular as Film accelerator for forward / backward operation the embossing foil web.

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