EP1354246A1 - Use of a packing strip as a holographic data carrier - Google Patents

Abstract

The invention relates to a packing strip (3) comprising a polymer film and used as a holographic data carrier. To this end, the packing strip (3) is designed to store holographic information. Holographic information can be entered into the packing strip (3) by means of a writing device (4), both before an object (1) is packed using the packing strip (3), and after.

Description

 Use of a packing tape as a holographic data carrier

The invention relates to the use of a packaging tape which has a polymer film.

Packing tapes containing a polymer film, the underside of which is usually provided with an adhesive layer, are used to a large extent in the packaging of objects. The polymer film is often reinforced by a fabric insert. Such a packing tape can e.g. be wrapped around a cardboard box to seal the cardboard box and, if necessary, also to seal or reinforce it.

In addition to conventional transport papers, barcodes are currently used for logistical purposes. For example, a label with a one-dimensional or two-dimensional barcode is stuck onto a package. The barcode contains, for example, a reference number, to which further information can be assigned using electronic data processing. However, the direct storage capacity of barcodes is very limited. In the near In the future, the use of transponders for logistical purposes can also be expected. The advantage of transponders is that they can be detected without a clear optical view. However, their storage capacity is low and the costs for mass use are still too high.

It is an object of the invention to provide a simple and inexpensive way to provide an object, in particular a packaged object or its packaging, with a larger amount of information.

This object is achieved by using a packing tape according to the features of claim 1. Advantageous refinements of the invention result from the subclaims.

According to the invention, a packing tape, which has a polymer film, is used as the holographic data carrier, the packing tape being set up for storing holographic information. The packaging tape is preferably used for packaging objects. Other applications, e.g. as a label, but are also conceivable. In a preferred embodiment, the packing tape has an adhesive layer so that it adheres to an object in a self-adhesive manner. It can also have other components, e.g. a fabric insert as reinforcement.

Since the packing tape is set up to store holographic information, it can hold large amounts of data. In contrast to conventional barcodes, larger amounts of information can therefore be directly assigned to an object. Examples of this for a package that is packed using the packing tape are the delivery address, the sender, transport documents, but also, for example, safety data sheets, manuals and the like. Thus, the invention makes it possible to pack objects quickly and inexpensively while saving on work steps and to provide them with information for logistical purposes, but also with additional information. The holographic information is preferably stored in the form of machine-readable data pages, as explained in more detail below. When using the packing tape, an object can first be packed using the packing tape, and then holographic information is entered into the packing tape. Alternatively, holographic information can first be entered into the packaging tape, for example after unwinding from a supply roll in a writing device provided for this purpose, and then the item is packaged using the packaging tape. Mixed forms are also conceivable in which holographic information is written into the packaging tape before and after the object is packaged. Conventional packaging machines can be used in such applications. An additional writing device is required only for entering the holographic information. Such writing devices, which have a laser lithograph, for example, have a relatively small volume, so that an existing packaging machine can be retrofitted with reasonable effort. The information to be entered into the packing tape can be specifically tailored to the given object to be packed without any problems.

Suitable materials for the polymer film are e.g. Polypropylene, polyvinyl chloride, polyester, polyethylene terephthalate (PET), polyethylene naphthalene, polymethylpentene (PMP; also poly-2-methylpentene) and polyimide. The polymer film preferably has a thickness which is customary in conventional packaging tapes and is required for the desired strength. If only a number of limited areas of the packaging tape are set up to store holographic information (see below), such areas can have their own polymer film, which is considerably thinner than the supporting structure of the packaging tape; in this case it is also conceivable that the support structure of the packaging tape itself does not have any polymer film at all.

The polymer film can be stretched and is preferably biaxially stretched, for example by being inside during production its plane is biased in two mutually perpendicular directions. This usually increases the strength of the polymer film. Furthermore, in the case of a stretched polymer film, a high energy density is stored in the film material. A relatively strong change in material with a change in the local properties of the polymer film can be achieved by local heating with deposition of a relatively small amount of energy per unit area, for example with the aid of a writing beam from a writing device.

Stretched polymer films are therefore particularly suitable for an advantageous embodiment of the invention. The polymer film can be changed locally by heating and is set up to store holographic information about the local properties of the polymer film. There are several ways to take advantage of this effect.

In one possibility, the refractive index of the polymer film can be changed locally by heating, wherein optical phase information about the local optical path length can be stored in the polymer film and it is provided that the polymer film is transmitted in transmission when information is read out. Phase information can therefore be stored locally in the polymer film, ie in an area provided for storing an information unit, by changing the refractive index in this area by heating (for example with the aid of a writing beam from a writing device). The local change in the refractive index causes a change in the optical path length of the radiation used when reading information from the polymer film (which radiates through the polymer film in transmission). The optical path length is namely the product of the geometric path length and the refractive index; By changing the refractive index, the local phase position of the radiation used when reading out information can be influenced, ie the desired holographic information can be stored as phase information. A hologram produced in this way in the polymer film of the packaging tape is accordingly a refractive phase hologram. In another possibility, the surface structure of the polymer film can be changed locally by heating, wherein holographic information about the local surface structure of the polymer film can be stored. In this case, the surface structure or topography of the polymer film can thus be changed locally, for example by focusing a laser beam serving as a writing beam onto the polymer film, preferably its surface zone, so that the light energy is absorbed there and converted into thermal energy. In particular, if the laser beam is irradiated for a short time (pulsed), the material change in the polymer film which leads to the local change in the surface structure remains limited to a very narrow volume due to the generally poor thermal conductivity of the polymer. If the holograpic information is entered point by point into the polymer film of the packaging tape, the area assigned to a point typically having linear lateral dimensions on the order of 0.5 μm to 1 μm, the height profile of the polymer film typically changes by 50 n to 500 nm, which depends in particular on the properties and operating conditions of the write beam and the properties of the packaging tape. The dot matrix, ie the center distance between two points (“pits”), is typically in the range from 1 μm to 2 μm. As a general rule, shorter light wavelengths of the write beam allow a tighter grid of points.

The polymer film can be assigned an absorber dye which is set up to at least partially absorb a write beam used for entering information and to at least partially emit the heat generated thereby locally to the polymer film. Such an absorber dye enables sufficient local heating of the polymer film to change the local properties of the polymer film (for example the change in the local refractive index or the local surface structure) with a relatively low intensity of the writing beam. The absorber dye can be contained in the material of the polymer film. However, it can also be arranged in a separate absorber layer, which preferably has a binder; Mixed forms are also conceivable. For example, the absorber layer can have a thin layer (eg a thickness of 0.5 μm to 5 μm) made of an optically transparent polymer (eg made of polymethyl methacrylate (PMMA) or, for applications for higher temperatures, made of polyethylene pentene, polyether ether ketone (PEEK) or polyether id), which serves as a matrix or binder for the molecules of the absorber dye. The absorption maximum of the absorber dye should coincide with the light wavelength of the write beam used in order to achieve efficient absorption. For example, dyes from the Sudan red family (diazo dyes) or (for particularly polar plastics) eosin scarlet are suitable for a light wavelength of 532 nm of a writing beam generated by a laser. Green dyes, for example from the styryl family (which are commonly used as laser dyes), are more suitable for the customary laser diodes with a light wavelength of 650 to 660 nm or 685 nm.

In an alternative embodiment, the polymer film carries a dye layer with a dye that can be changed by exposure. The holographic information about the local absorption capacity can be stored in the dye layer. When the information is read out, the dye layer is irradiated, the absorption capacity in the dye layer which varies locally as a result of changes in the dye influencing the radiation, which enables the reconstruction of a holographic image. The local area for storing an information unit typically has linear dimensions (i.e. e.g. a side length or a diameter) of the order of 0.5 μm to 1 μm, but other sizes are also possible.

The molecules of the dye are preferably bleached or destroyed when exposed to radiation which is used to enter holographic information. "Bleaching" means damage to the chromophoric system of a dye molecule by excitation with intense light of a suitable wavelength without destroying the basic structure of the dye molecule. The dye molecule loses its color properties and becomes optically transparent with sufficient exposure for the light used for bleaching. If, on the other hand, the basic structure of a dye molecule is also destroyed, the change caused by the exposure is called "destruction" of the dye. The light used for exposing, i.e. for entering information, does not have to be in the visible wavelength range.

The dye layer preferably has a polymer matrix in which dye molecules are embedded. The dye molecules are preferably homogeneously distributed in the dye layer or in part of the dye layer. Polymers or copolymers, such as e.g. Polymethyl methacrylate (PMMA), polyimides, polyetherimides, polypentene, polycarbonate, cycloolefinic copolymers or polyether ether ketone (PEEK). When making the packaging tape, a polymer matrix containing dye, e.g. by application onto the polymer film serving as a support or onto a reflective layer previously applied to the polymer film (see below).

Easily bleachable dyes, such as azo and diazo dyes (for example the Sudan red family), are particularly suitable as the dye. In the case of dyes from the Sudan red family, information can be entered with a writing beam with a light wavelength of 532 nm. However, such dyes are preferably not so unstable against exposure that a bleaching process already begins due to ambient light (sun, artificial lighting). If the write beam is generated with a laser, significantly higher intensities can be achieved in the dye layer than when exposed to ambient light, so that dyes are available which are at least largely insensitive to ambient light for the desired application. The dye does not have to be sensitive to light, in contrast to a photographic film. If, on the other hand, the dye should not be bleached out, but rather destroyed with a higher laser power, you can use a variety of dyes To fall back on. The absorption maximum of the respective dye is preferably adapted to the wavelength of the laser used as the write beam. Other suitable dyes are poly ethyne dyes, aryl ethyne dyes, aza [18] annulene dyes and triphenylmethane dyes.

Since it should be possible to check the holograms of the packing tape, i.e. read out the holographic information entered into the packaging tape, even if the packaging tape e.g. is glued to a package, it is advantageous if the packing tape has a reflective layer which is set up to reflect light serving to read out holograpic information. The light is directed onto the packaging tape and reflected back by the reflection layer, wherein it is modulated by the changes on the packaging tape that are used to store holographic information. The reflected light can then be captured in a favorable geometric arrangement in order to reconstruct a holographic image of the holographic information. At which point on the packaging tape, based on its cross section, the reflection layer is most advantageously arranged depends on the effect that is used for storing holographic information. However, the reading process can also take place without an additional reflective layer, which, depending on the application, can even lead to better results.

If optical phase information about the local optical path length is stored in the polymer film, it is provided that the polymer film is preferably transmitted in transmission when reading out information. In this case, the reflection layer is preferably located between the polymer film and an adhesive layer. If holographic information about the local surface structure of the polymer film is stored, the reflection layer can also be arranged between the polymer film and an adhesive layer; in this case the surface structure of the polymer film is irradiated twice when reading out information. Alternatively, the reflection layer can be arranged on the surface of the polymer film, its local one Structure is changed when entering the holographic information, so preferably on the top of the polymer film. If a dye layer is used which is transmitted in transmission when information is read out, the reflection layer is, for example, between the polymer film and the dye layer or between an adhesive layer and the polymer film.

The holographic information to be stored can be entered into the packing tape by calculating the holographic information contained in a hologram of a storage object as a two-dimensional arrangement and directing a write beam from a writing device, preferably a laser lithograph, onto the packing tape and thus in accordance with the two-dimensional arrangement is controlled that the local properties of the packaging tape are set according to the holographic information. Since the physical processes involved in the scattering of light on a storage object are known, e.g. a conventional structure for generating a hologram (in which coherent light from a laser that is scattered by an object (storage object) is brought to interference with a coherent reference beam and the resulting interference pattern is recorded as a hologram) with the help a computer program is simulated and the interference pattern or the modulation of the local properties of the packaging tape are calculated as a two-dimensional arrangement (two-dimensional array).

As already explained above, examples of the local properties of the packaging tape, which are set according to the holographic information, are the local refractive index of the polymer film, the local surface structure of the polymer film and the local absorption capacity of a dye layer carried by the polymer film.

The resolution of a suitable laser lithograph is typically about 50,000 dpi (dots per inch). The polymer film or a dye carrier carried by the polymer film can thus layer locally in areas or pits with a size of about 0.5 μm to 1 μm. The writing speed and other details depend, among other things, on the parameters of the writing laser (laser power, light wavelength) and the exposure time, as well as on the properties of the polymer film, the dye layer or any absorber dye.

The holographic information is therefore preferably entered in the form of pits of a predetermined size; the term "pit" is to be understood more generally in the sense of a changed area and is not restricted to its original meaning (hole or depression). The holographic information can be stored in binary coded form in a pit. This means that in the area of a given pit, the local properties of the packing tape only take on one of two possible basic forms (basic values). These basic forms preferably differ significantly, so that intermediate forms occurring in practice, which are close to one or the other basic form, can be clearly assigned to one or the other basic form in order to store the information reliably and unambiguously.

Alternatively, the holographic information can be stored in a pit in a continuously coded form, the local properties of the packing tape in the pit being set according to a value from a predetermined value range. If, for example, the local surface structure of the polymer film is to be set, the local maximum change in height of the surface structure in the pit is selected from a predetermined range of values. This means that in a given pit the surface structure of the polymer film can assume intermediate shapes between two basic shapes, so that the maximum change in height of the present intermediate shape takes on a value from a predetermined value range, the limits of which are given by the maximum changes in height of the two basic shapes. In this case, the information can be saved "in grayscale" so that each pit has more than comes to a bit. The same applies to the setting of the local refractive index of the polymer film or the local absorption capacity in the dye layer.

To read out holographic information from the packing tape, light, preferably coherent light (e.g. from a laser), can be directed onto the packing tape over a large area. The light is modulated by the locally varying properties of the packaging tape (e.g. the refractive index or the surface structure of the polymer film or the absorption capacity of the dye layer). After reflection on the packing tape, i.e. preferably after reflection on a reflective layer, a holographic image at a distance from the packing tape is acquired as a reconstruction of the holographic information contained in the area captured by the light, e.g. with a CCD sensor, which is connected to a data processing device.

The term "large area" is to be understood as an area which is significantly larger than the area of a pit. In this sense, for example, an area of 1 mm ^{2 is} large. There are many different options for the scheme according to which information is stored and read out. It is conceivable to read out a hologram on the packing tape at once by irradiating the entire area of the area of the packing tape set up as a hologram at once. Particularly in the case of larger areas, however, it is advantageous to divide the information to be stored into a number or a large number of individual areas (for example with a respective area of 1 mm ² ) and to read out the information only from a predetermined individual area at once.

When information is read out, the locally varying properties of the packaging tape lead to differences in the runtime of the light waves emanating from different points, that is to say essentially to periodic phase modulation (which applies in particular when the refractive index or the surface structure of the polymer film is set locally) or to one Amplitude modulation (especially with a locally varying absorption ability of a dye layer). The area of the packing tape that is captured by the light acts like a diffraction grating that deflects incident light in a defined manner. The deflected light forms an image of the storage object that represents the reconstruction of stored holographic information.

In principle, holographic information from different types of storage objects can be used with the packing tape. For example, the information contained in images, such as photographs, logos, writings, etc., can be saved and read out. However, the storage of machine-readable data is particularly advantageous since, for example, the data mentioned at the outset, such as the delivery address, sender, transport documents, safety data sheets, manuals and the like, can be stored. This takes place, for example, in the form of so-called data pages, the holographic information contained in a hologram of a graphic bit pattern (which represents the data information) being entered into the packing tape as explained. When reading out, a holographic image of this graphic bit pattern is created. The information contained therein can be recorded, for example, with the aid of a precisely adjusted CCD sensor and processed using the associated evaluation software. In principle, a simple matte screen or, for example, a camera with an LCD screen is sufficient for the reproduction of images where high accuracy is not important. With the holographic storage of machine-readable data, it is advantageous that the information does not have to be read out sequentially. but that an entire data set can be recorded at once, as explained. In contrast to a conventional data storage device, if the surface of the packaging tape is damaged, this does not lead to data loss, but merely to a deterioration in the resolution of the holographic image reconstructed when the information is read out, which is generally unproblematic. It is not necessary for the entire packaging tape to be set up to store holographic information. For the purposes explained, it is generally sufficient if the packaging tape has only a number of limited areas, each of which is set up to store holographic information. With such an embodiment, costs can be saved under certain circumstances, because a conventional, inexpensive packaging tape can be used as the starting material, which is designed to be more complex only in the limited areas in order to enable writing and reading out of holographic information. Such limited areas can be created, for example, by applying an absorber dye to a packing tape made of stretched polypropylene, polyvinyl chloride or polyester film using a printing process.

It is also conceivable that the limited areas each have their own piece of polymer film, to which additional layers such as an absorber layer, a dye layer or a reflection layer may have been applied, in order to store holographic information, for example, according to one of the options explained in more detail above to allow. Limited areas designed in this way can be applied to the supporting structure of the packaging tape (which can have a polymer film, but need not), e.g. be glued or welded on. However, it is preferred to provide as the polymer film a common polymer film for the entire packaging tape, for example a polymer film, which at the same time represents the load-bearing structure of the packaging tape. This polymer film can then be used e.g. by applying the additional layers mentioned, only provide zones in the limited areas in which there is the possibility of storing holographic information.

The delimited areas are preferably arranged on the packing tape at predetermined intervals. This makes it easier to enter and read out holographic information in automated systems. The limited areas can, for example be circular with a diameter of 6 mm and have mutual center distances in the longitudinal direction of the packing tape of 40 mm.

If holographic information is to be deleted from the packaging tape again, the holograms concerned are preferably destroyed with a strong writing beam. In this case, the destroyed area is no longer available for storing new information, which, however, is usually irrelevant, because due to the large storage density offered by holograms, there are mostly unused zones on the packaging tape that contain holographic information can be entered.

The invention is explained in more detail below on the basis of exemplary embodiments. The drawings show in

FIG. 1 is a schematic illustration that illustrates how holographic information is written into a packaging tape before the packaging tape is glued around a package.

FIG. 2 is a schematic diagram illustrating how holographic information is input into a packaging tape that is already glued to a package.

FIG. 3 shows a schematic plan view of a section of an area of the packaging tape that is set up for storing holographic information,

FIG. 4 shows a schematic longitudinal section through an area of the packaging tape set up for storing holographic information, in which holographic information about the local optical path length can be stored in a polymer film,

FIG. 5 shows a longitudinal section according to FIG. 4, the processes for reading out information being illustrated in a schematic manner, FIG. 6 shows a schematic longitudinal section through an area of the packaging tape set up for storing holographic information, in which holographic information about the local surface structure of a polymer film can be stored, with the aid of a

Write beam information is entered,

FIG. 7 shows a longitudinal section according to FIG. 6 after the surface structure has been changed locally to enter the information,

FIG. 8 shows a longitudinal section according to FIG. 7, the processes for reading out information being illustrated in a schematic manner,

FIG. 9 shows a schematic longitudinal section through an area of the packaging tape set up for storing holographic information, in which holographic information about the local absorption capacity can be stored in a dye layer, and

FIG. 10 shows a longitudinal section according to FIG. 9, the processes when reading out information being illustrated in a schematic manner.

FIGS. 1 and 2 schematically illustrate how a package is packed using a packing tape and in the process holographic information is input into the packing tape, which serves as a holographic data carrier. This information can be provided for logistical purposes and can include, for example, the delivery address and the sender as well as the shipping documents for the package. Since holographic data carriers have a high storage capacity, other data in the form of holograms can in principle also be stored on the packaging tape. Examples of this are safety data sheets, manuals and the like, ie data relating to the content of the package stand. In addition, other data content can be stored in holographic form on the packaging tape.

In Figure 1, a package 1 is transported on a treadmill 2. A packing tape 3 ("Carton Sealing Tape", CST) is fed over the treadmill 2 and against its direction of travel using a conventional packaging device. The packing tape 3 is set up for storing holographic information, as explained in more detail below. Above the packing tape 3 there is a writing device 4 which uses a laser beam as the writing beam 5 in order to enter holographic information into the packing tape 3. In the exemplary embodiment, the writing device 4 is a laser lithograph. The packing tape then runs through 3 deflection rollers 6 and is applied to the package 1.

The packing tape 3 is provided on its underside with an adhesive layer, so that it adheres to the package 1, which in the exemplary embodiment has a cardboard packaging, and closes and seals the package 1. These steps are carried out on a conventional system. The only new addition is the writing device 4, which due to its relatively small size can be easily installed on an existing system.

Figure 2 shows a variant of the process flow. Here, a package 1 'is moved on a treadmill 2'. The package 1 'is already closed with a packing tape 3 ¹ . A writing device 4 'with a writing beam 5', which is preferably designed as a laser lithograph, is arranged above the packet 1 '(ie at a point under which the packet 1' moves through). Here, the holographic information is thus entered into the packing tape 3 'after the object in the packet 1' has been packed using the packing tape 3 '.

It is also conceivable to write part of the holographic information into the packaging tape 3 or 3 'before it is glued to the package 1 or 1', and part of the holographic information afterwards. In the exemplary embodiment, the packing tape 3 or 3 'has a polymer film with a thickness of 35 μm made of biaxially stretched polypropylene. On the underside of the polymer film is the adhesive layer, which is 20 μm thick and consists of functionalized poly (meth) acrylate. In the exemplary embodiment, the holographic information is stored in accordance with the method explained with reference to FIGS. 9 and 10, the upper side of the entire packing tape being set up for storing holographic information. For this reason, a semitransparent reflective layer made of aluminum (about 10 to 20 nm thick) is applied to the top of the polymer film, and a dye layer and a protective layer are located above it.

The packing tape can also have other materials or dimensions or have additional components, e.g. a reinforcing fabric insert. Such a fabric insert is preferably arranged below a polymer layer and can also be embedded in additional polymer. Additional components of the packaging tape may be components required for storing holographic information (see below).

In other embodiments of the packing tape, only limited areas are provided, which are arranged at predetermined intervals from one another and are each set up for storing holographic information, while the packing tape in the intermediate zones is designed as a simple packing tape without the possibility of holographic data storage. Such limited areas can e.g. each have a diameter of 5 mm and distances of 50 mm to each other. For example, they can each have a piece of polymer film, have one of the configurations described below, and can be glued or welded onto a conventional packing tape.

Various possibilities for storing holographic information with the aid of a packing tape are explained in more detail below using examples. FIG. 3 is a schematic plan view of a section of an area 11 of a packaging tape that has been set up for storing holographic information and in which information is entered. In the exemplary embodiment, area 11 (hereinafter referred to as "storage area") is a limited area with its own carrier in the form of a square piece of polymer film of 8 mm side length and is together with similarly constructed limited areas (storage areas) 3 or 5, so that the entire packing tape is set up to store holographic information, such a variant may even be less expensive.

The storage area 11 has a polymer film 12 set up as a storage layer, which at the same time serves as a carrier (and in the above-mentioned variant forms the support structure of the packing tape) and in the exemplary embodiment consists of biaxially oriented polypropylene (BOPP) and has a thickness of 35 μm. The refractive index of bipolar oriented polypropylene can be changed locally by heating, which can be used to store information, as explained above. The polymer film 12 preferably has a thickness in the range between 10 μm and 100 μm, but other thicknesses are also possible. Examples of further advantageous materials for the polymer film 12 are given above.

Information in the form of pits 14 is stored in the memory area 11. In the area of a pit 14, the polymer film 12 has a different refractive index than in the zones between the pits 14. The term “pit” is to be understood here in the sense of a changed area, that is to say more generally than in its original meaning (“hole”). The information can be stored in a binary coded form in a pit, in that the refractive index only takes on two different values (one of the two values also having the refractive index in the polymer film 12 in the zones between the pits 14 can match). It is also possible to store the information in a continuously coded form in a pit 14, the refractive index within the pit 14 being able to assume any value selected from a predetermined range of values. Clearly speaking, when stored in binary-coded form, a pit is "black" or "white", while when stored in continuously coded form it can also assume all the gray values in between (gradations of the amplitude or phase).

In the exemplary embodiment, a pit 14 has a diameter of approximately 0.8 μm. Shapes other than circular pits 14 are also possible, e.g. square or rectangular pits, but also other sizes. The typical dimension of a pit is preferably about 0.5 μm to 2.0 μm. FIG. 3 is therefore a greatly enlarged illustration and only shows a section of the memory area 11.

FIG. 4 shows a section of the storage area 11 in a schematic longitudinal section, and not true to scale. It can be seen that a pit 14 does not extend over the full thickness of the polymer film 12. In practice the transition zone in the lower area of a pit 14 to the lower region of the polymer film 12 is due to the writing method for inputting information, wherein the polymer film 12 is heated in the region of a pit 14 ^{'continuously,} ie the refractive index changes in this Zone gradually and not as sharply delineated as shown in Figure 4.

Under (i.e. behind) the polymer film 12 there is a reflection layer 16, which in the exemplary embodiment consists of aluminum. The reflection layer 16 can also fulfill its function if it is significantly thinner than the polymer film 12.

An absorber layer 18 is applied to the top of the polymer film 12. In the exemplary embodiment, the absorber layer has 18 on the absorber dye Sudan red 7B, the molecules of which are embedded in a matrix made of an optically transparent polymer, namely polymethyl methacrylate (PMMA). In the exemplary embodiment, the absorber layer 18 has a thickness of 0.5 μm. Sudan red 7B absorbs light particularly well in the wavelength range around 532 nm; this wavelength is suitable for a write beam of a laser lithograph for inputting information into the memory area 11. Examples of other materials of the absorber layer 18 are given above. Green dyes, for example from the styryl family, are particularly suitable for light lengths of 635 nm or 650 to 660 nm or 685 nm, in which the laser diodes of current DVD devices work; laser diodes of this type can be modulated directly, which considerably simplifies and reduces the cost of pulse generation. In the future, the range from 380 to 420 nm could also be interesting if corresponding blue laser diodes are commercially and inexpensively available. For this purpose, yellow absorber dyes are preferably to be used, such as stilbenes substituted with weak donors and acceptors, donor-substituted nitrobenzenes or coumarin dyes.

The absorber layer 18 has a preferred optical density in the range from 0.2 to 1.0; however, other values are also conceivable. The optical density is a measure of the absorption, here based on the light wavelength of a write beam. The optical density is defined as a negative decimal logarithm of the transmission through the absorber layer, which corresponds to the product of the extinction coefficient at the wavelength of the write beam used, the concentration of the absorber dye in the absorber layer 18 and the thickness of the absorber layer 18.

The absorber layer 18 facilitates the input of information into the memory area 11. Because when a write beam is focused on the area of a pit 14, it is at least partially absorbed in the absorber layer 18. The heat released in the process is largely transferred to the polymer film 12 and thus causes a local change in the refractive index in the polymer film 12 in the region of the pit 14. However, it is possible to do without the absorber dye entirely when using very short laser pulses.

In order to enter information into the memory area 11, phase information contained in a hologram of a memory object is first calculated as a two-dimensional arrangement. This can be carried out as a simulation of a classic setup for generating a photographically recorded hologram, in which coherent light from a laser, after scattering on the storage object, is brought into interference with a coherent reference beam and the resulting interference pattern is recorded as a hologram. The two-dimensional arrangement (two-dimensional array) then contains the information that is required to control the write beam of a laser lithograph. In the exemplary embodiment, the laser lithograph has a resolution of approximately 50,000 dpi (i.e. approximately 0.5 μm). The write beam of the laser lithograph is guided in pulsed operation (typical pulse duration of approximately 1 μs to 10 μs with a beam power of approximately 1 mW to 10 mW for inputting a pit 14) over the top of the memory area 11 in order to sequentially place the desired information into the memory area 11 (or a preselected area of the memory area 11). The write beam heats the absorber layer 18 in accordance with the two-dimensional array and thus generates the pits 14, as explained above.

FIG. 5 shows schematically how the information stored in the memory area 11 can be read out. For this purpose, coherent light is directed by a laser (preferably a wavelength that is only slightly absorbed by the absorber layer 18) onto the upper side of the storage area 11. For the sake of clarity, only a small section of this coherent light, which is preferably incident in parallel, is shown in FIG. 5, which is denoted by 20 (incident reading beam). In practice, the coherent light is directed and covered over a large area on the polymer film 12 a range of, for example, 1 mm ² . Because for the reconstruction of the stored information, the light coming from many pits 14 must be detected. The intensity of the incident reading beam 20 is too weak to change the refractive index in the polymer film 12 and thus the information stored.

The incident reading beam 20, which for practical reasons strikes the surface of the storage area 11 at an angle, is reflected at the interface 22 between the polymer film 12 and the reflection layer 16, so that a reflected reading beam 24 emanates from the interface 22 and thereby penetrates the pits 14. Since the local refractive index of the polymer film 12 differs depending on the pit 14, the local optical path length is varied so that phase shifts occur. As a result, spherical waves 26, which contain the stored phase information, emanate from the memory area 11 in the manner of a diffraction grating. A holographic image, which is produced by interference of the spherical waves 26, can be detected at a distance from the memory area 11 using a detector.

The effort required for the detector and the further processing of the recorded holographic image depend on the type of the storage object, as already explained above. A CCD sensor connected to a data processing device is particularly suitable for the reproduction of machine-readable data (data pages), while a simpler detector is also useful for pure image reproduction, especially if the image data are not to be further processed.

In addition to the layers that can be seen in FIG. 4, the storage area 11 can have additional layers, for example a transparent protective layer above the absorber layer 18. In the exemplary embodiment, below the reflection layer 16 there is an adhesive layer with which the storage area 11 is glued to the conventional packing tape. If, for example, an absorber dye that is invisible in visible light (that absorbs in the infrared, for example) or no absorber dye is used, or if an absorber layer is washed off after entering information in the storage area, the storage area can be made largely transparent and very inconspicuous.

A further possibility for storing holographic information by means of a packing tape is explained on the basis of FIGS. 6 to 8. In the exemplary embodiment, limited areas or storage areas, which are fastened at predetermined intervals on a conventional packing tape, are again provided for storing the information. Alternatively, however, the entire packing tape can again have the layer sequence explained with reference to FIGS. 6 to 8, so that the entire packing tape is set up for storing holographic information, similar to the example described above.

FIG. 6 shows a section of the storage area designated 31 here in a schematic longitudinal sectional view. The storage area 31 has a polymer film 32 set up as a storage layer, which in the exemplary embodiment consists of biaxially oriented polypropylene (BOPP) and has a thickness of 50 μm. On the underside of the polymer film 32 there is a 100 nm thick reflection layer 33 made of aluminum. Interfering interference effects as a result of reflections on the top of the polymer film 32 and the reflection layer 33 can, if appropriate, be avoided by suitable measures. If the entire packaging tape is set up to store holographic information, the polymer film can simultaneously serve as a support structure, and an adhesive layer is preferably arranged under the reflection layer.

An absorber dye is contained in the material of the polymer film 32, which absorbs light from a writing beam and converts it into heat. In the exemplary embodiment, Sudan red 7B is used as the absorber dye, which is particularly good light in the wave length range around 532 nm absorbed; this wavelength is suitable for a write beam of a laser lithograph for inputting information into the memory area 31. Examples of other absorber dyes have already been given above. Alternatively, the absorber dye can also be present in a separate layer, similar to the absorber layer 18 from the example according to FIGS. 3 to 5; in this case the absorber layer has a preferred optical density (see above) in the range from 0.2 to 1.0, although other values are also possible. If the absorber dye is distributed over the entire polymer film, a larger value for the optical density is recommended so that there is sufficient absorber dye in the surface zone of the polymer film that is to be heated especially during the writing process.

The absorber dye facilitates the input of information into the storage area 31. Because if a write beam 34 is focused on the polymer film 32, for example with the aid of a lens 35, and preferably in its surface zone, the light energy of the write beam 34 becomes particularly efficient Heat converted. FIG. 6 shows two writing beams 34 and two lenses 35 in order to illustrate the writing of information at two different locations on the polymer film 32. In practice, however, the writing beam 34 preferably moves sequentially over the surface of the polymer film 32. A laser lithograph with a resolution of approximately 50,000 dpi (ie approximately 0.5 μm) is suitable, for example, for entering the information. The write beam of the laser lithograph is guided over the upper side of the polymer film 32 in pulsed operation (typical pulse duration from approximately 1 μs to approximately 10 μs with a beam power of approximately 1 mW to approximately 10 mW for exposing or heating a point), that is to say generally in two directions to sequentially input the desired information into the storage area 31 (or a preselected area of the storage area 31). FIG. 7 shows the result of the action of the pulsed write beam 34. Because of the poor thermal conductivity of the material of the polymer film 32, there is a significant increase in temperature in a narrowly limited volume, at which the surface structure of the polymer film 32 changes locally. This creates a pit 36, ie the local area in which information is stored. A central depression 38, which is surrounded by a peripheral projection 39, belongs to each pit 36. The level difference between the lowest point of the depression 38 and the highest point of the projection 39, ie the local maximum change in height of the surface structure in the pit 36, is denoted by H in FIG. H is typically in the range from 50 nm to 500 nm. The distance between the centers of two adjacent pits 36, ie the dot pattern R, is preferably in the range from 1 μm to 2 μm. In the exemplary embodiment, a pit 36 has a diameter of approximately 0.8 μm. Shapes other than circular pits 36 are also possible. The typical dimension of a pit is preferably about 0.5 μm to 1.0 μm. When viewed from above, the polymer film 32 with the pits 36 looks similar to the illustration in FIG. 3.

In a pit 36, the information can be stored in binary-coded form, in that H only takes two different values (one of the two values preferably being 0). It is also possible to store the information in a pit 36 in a continuously coded form, H being able to take any value from a predetermined range of values for a given pit 36.

In order to enter information into the storage area 31, holographic information contained in a hologram of a storage object is first calculated as a two-dimensional arrangement. This can be carried out, for example, as a simulation of a classic setup for generating a photographically recorded hologram, in which coherent light from a laser that is scattered by the storage object is brought into interference with a coherent reference beam and the resulting module pattern is recorded as a hologram. The two-dimensional arrangement (two-dimensional array) then contains the information which is required to control the write beam of a laser lithograph already explained above. If the write beam of the laser lithograph is guided over the upper side of the storage area 31 in the pulsed mode, it heats the polymer film 32 in accordance with the two-dimensional array. The pits 36 are generated as seen above.

FIG. 8 shows schematically how the information stored in the memory area 31 can be read out. For this purpose, coherent light from a laser (preferably a wavelength which is not or only slightly absorbed by the absorber dye in the polymer film 32) is directed onto the upper side of the storage area 31. (Alternatively, a very bright LED can also be used, which may even lead to more favorable results, especially with a view to reducing so-called speckies noise.) For the sake of clarity, coherent light (incident reading beam ) only a small section is shown in FIG. 8, namely the incident light waves denoted by 42 and 43. In practice, the coherent light is directed over a large area onto the polymer film 32 and covers an area of, for example, 1 mm ² . Because to reconstruct the stored information, the light coming from many pits 36 must be detected. The intensity of the incident reading beam is too weak to change the surface structure of the polymer film 32 and thus the stored information.

The light waves 42 and 43 have a fixed phase to one another. For practical reasons, they fall at an angle on the upper side of the polymer film 32, penetrate the polymer film 32 and are reflected on the reflection layer 33, so that reflected light waves 44 and 45 emanate from the reflection layer 33 and in turn penetrate the polymer film 32. Since the local surface structure of the polymer film 32 via the pits 36 varies, a phase shift occurs, and the reflected light waves 44 and 45 emerge with a phase Ψ, as illustrated in FIG. As a result, light waves emanate from the storage area 31 in the manner of a diffraction grating in many directions, in which phase information is contained. At some distance from the storage area 31, a detector can be used to record a holographic image which is produced by interference of these light waves and which represents a reconstruction of the stored information.

FIGS. 9 and 10 illustrate a further possibility for storing holographic information using a packing tape. This time, in the exemplary embodiment, the entire packaging tape is set up for storing holographic information.

FIG. 9 shows a section of the packaging tape, designated 51, in a schematic longitudinal section, and not to scale; holographic information has already been entered. The packing tape 51 has a support structure 52 made of a 40 μm thick polymer film made of stretched polyvinyl chloride, on the underside of which there is a 25 μm thick or somewhat thinner acrylic adhesive layer (which is not shown in FIG. 9). A reflection layer 54 made of aluminum with a thickness of 100 nm is applied to the top of the support structure 52.

A polymer matrix is arranged above the reflection layer 54, in which dye molecules are embedded, as a result of which a dye layer 56 is formed. In the exemplary embodiment, the polymer matrix consists of polymethyl methacrylate (PMMA) and has a thickness of 1 μm. Other thicknesses are also possible. In the exemplary embodiment, Sudan red is used as the dye in such a concentration that an optical density of 0.8 results over the thickness of the dye layer 56, provided that the dye in the dye layer 56 is not changed by exposure. Preferred values for the optical density are in the range from 0.2 to 1.0; however, other values are also conceivable. On the A protective layer 57 is applied on top of the dye layer 56.

Information in the form of pits 58 is stored in the packing tape 51, the term “pit” being understood as before in the sense of a localized changed area. In the area of a pit 58, the absorption capacity in the dye layer 56 is different than in the zones between the pits 58. The information can be stored in a pit 58 in a binary-coded form in that the absorption capacity only assumes two different values (one of which Both values can also correspond to the absorption capacity in the dye layer 56 in the zones between the pits 58). It is also possible to store the information in a pit 58 in a continuously coded form, the absorption capacity within the pit 58 being able to assume any value selected from a predetermined range of values.

In the exemplary embodiment, a pit 58 has a diameter of approximately 0.8 μm. Shapes other than circular pits 58 are also possible, e.g. square or rectangular pits, but also other sizes. The typical dimension of a pit is preferably about 0.5 μm to 1.0 μm.

It can be seen that in the exemplary embodiment a pit 58 does not extend over the full thickness of the dye layer 56. In practice, due to the writing method for entering information, in which the dye in the dye layer 56 in the area of a pit 58 is changed with the aid of a focused write beam, the transition zone in the lower area of a pit 58 to the lower area of the dye layer 56 is continuously, ie the absorption capacity changes gradually in this zone and is not as sharply delimited as shown in FIG. 9. The same applies to the lateral edges of a pit 58. The distance between the lower regions of the pits 58 and the reflection layer 54 and the thickness of the dye layer 56 are preferably set up such that when the holographic layer is read out, interference and interference effects that interfere with the information.

In the exemplary embodiment, when the packaging tape 51 is produced, the reflection layer 54 made of aluminum is first evaporated onto the support structure 52, then the polymer matrix with the dye of the dye layer 56 is applied with an anilox roller and the protective layer 57 is finally laminated on.

10 In order to enter information into the packing tape 51, similarly as before, holographic information contained in a hologram of a storage object is first calculated as a two-dimensional arrangement (amplitude modulation). This can be used, for example, as a simulation of a classic setup to create a

1.5 photographically recorded hologram are carried out, in which coherent light from a laser after scattering on the storage object is brought into interference with a coherent reference beam and the interference pattern that arises is recorded as a hologram. The two-dimensional arrangement (two-dimensional

20 nale array) then contains the information required to control the write beam of a laser lithograph. In the exemplary embodiment, the laser lithograph has a resolution of approximately 50,000 dpi (i.e. approximately 0.5 μm). The write beam of the laser lithograph is used in pulsed mode (typical pulse duration

25 from about. 1 µs to 10 µs at a beam power of about 1 mW to 10 mW for inputting a pit 58) over the dye layer 56 of the packing tape 51 to sequentially place the desired information into the packing tape 51 (or a preselected area of the packing tape 51) to be entered. The writing beam changes

30 the dye in the dye layer 56 corresponding to the two-dimensional array and thus produces the pits 58, as explained above.

FIG. 10 shows schematically how the

35 information stored in the packing tape 51 can be read out. To do this, coherent light from a laser (preferably a wavelength emitted by the dye of dye layer 56 is significantly absorbed) directed to the top of the packing tape 51. For the sake of clarity, only a small section of this coherent light, which is preferably incident in parallel, is shown in FIG. 10, which is designated by 60 (incident reading beam). In practice, the coherent light is directed over a large area onto the dye layer 56 and covers an area of, for example, 1 mm ² . This is because the light emitted by many pits 58 must be detected in order to reconstruct the stored information. The intensity of the incident reading beam 60 is too weak to change the dye in the dye layer 56 and thus the stored information.

The incident reading beam 60, which for practical reasons strikes the surface of the packaging tape 51 at an angle, shines through the dye layer 56 and is reflected at the interface 62 between the dye layer 56 and the reflection layer 54, so that a reflected reading beam 64 from the interface 62 emanates. The pits 58 are penetrated with their different local absorption capacity, which causes an amplitude modulation with periodically different light absorption. The incident reading beam 60 is thus deflected in a defined manner, with the result that spherical waves 66, which reproduce the stored holographic information, emanate from the packing tape 51 in the manner of a diffraction grating. At some distance from the packing tape 51, a detector can record a holographic image that is created by interference of the spherical waves 66. The reading beam is also reflected and possibly modulated at the interface of the packing tape 51 with air (not shown in FIG. 10 for the sake of clarity), but significantly weaker. Nevertheless, a suitable choice of materials and layer thicknesses should ensure that there is no interfering interference between the different reflected rays. If a dye that is invisible in visible light is used (which absorbs in the infrared, for example), the packing tape can be made largely transparent and very inconspicuous.

In addition to the possibilities for storing holographic data using a packing tape, which are explained here using examples, a packing tape can in principle also be used in connection with other holographic storage techniques.

Claims

claims 1. Use of a packing tape which has a polymer film (12; 32; 52) as a holographic data carrier, the packing tape (3; 3 ') being set up for storing holographic information. 2. Use according to claim 1, characterized in that an object (1; 1 ') is packaged using the packing tape (3; 3'). 3. Use according to claim 2, characterized in that the object (l ¹ ) is packaged using the packing tape (3 ¹ ) and then holographic information is entered into the packing tape (3 '). 4. Use according to claim 2 or 3, characterized in that holographic information is entered into the packing tape (3) and then the object (1) is packed using the packing tape (3). 5. Use according to one of claims 1 to 4, characterized in that the polymer film (12; 32; 52) is stretched, preferably biaxially stretched. 6. Use according to one of claims 1 to 5, characterized in that the polymer film (12; 32; 52) has a material which is selected from the following group: polypropylene, polyvinyl chloride, polyester, polyethylene terephthalate, polyethylene naphthalate, Polymethylpentene, polyimide. 7. Use according to one of claims 1 to 6, characterized in that the packing tape (3; 3 ¹ ; 51) has an adhesive layer. 8. Use according to one of claims 1 to 7, characterized in that the polymer film (12; 32) locally by heating is changeable and is set up for storing holographic information about the local properties of the polymer film (12; 32). 9. Use according to claim 8, characterized in that the refractive index of the polymer film (12) can be changed locally by heating, wherein optical phase information about the local optical path length can be stored in the polymer film (12) and it is provided that the polymer film (12) to be transmitted preferably in transmission when reading out information. 10. Use according to claim 8, characterized in that the surface structure of the polymer film (32) can be changed locally by heating, wherein holographic information about the local surface structure of the polymer film (32) can be stored. 11. Use according to claim 9 or 10, characterized in that the polymer film (12; 32) is assigned an absorber dye which is set up to at least partially absorb a writing beam (34) used for entering information and at least to absorb the heat generated in the process partially deliver locally to the polymer film (12; 32). 12. Use according to claim 11, characterized in that the material of the polymer film (32) contains absorber dye. 13. Use according to claim 11 or 12, characterized in that the absorber dye is arranged in a separate absorber layer (18), the absorber layer (18) preferably having a binder. 14. Use according to one of claims 1 to 7, characterized in that the polymer film (52) a dye layer (56) with a variable by exposure, preferably bleachable or destructible dye carries, holographic information about the local absorbency in the dye layer (56) being storable. 15. Use according to claim 14, characterized in that the dye layer (56) has a polymer matrix in which dye molecules are embedded, the polymer matrix preferably having at least one of the polymers or copolymers selected from the following group: poly-methyl methacrylate, polyimides, Polyetherimide, polymethylpen- ten, polycarbonate, cycloolefinic copolymer, polyether ether ketone. 16. Use according to claim 14 or 15, characterized in that the dye comprises at least one of the dyes selected from the following group: azo dyes, diazo dyes, polymethine dyes, aryl ethyne dyes, aza [18] annulene dyes, triphenylmethane dyes. 17. Use according to one of claims 1 to 16, characterized in that the packing tape (3; 3 '; 51) has a reflection layer (16; 33; 54) which is set up to read light serving for reading out holographic information to reflect. 18. Use according to one of claims 1 to 17, characterized in that for entering holographic information into the packing tape (3; 3 ';11;31; 51), holographic information contained in a hologram of a storage object is calculated as a two-dimensional arrangement and one Writing beam (5; 5 '; 34) of a writing device (4; 4'), preferably a laser lithograph, is directed onto the packing tape (3; 3 ';11;31; 51) and is controlled in accordance with the two-dimensional arrangement in such a way that the local inherent shadows of the packing tape (3; 3 ';11;31; 51) are set according to the holographic information. 19. Use according to claim 18, characterized in that the holographic information is entered in the form of pits (14; 36; 58) of predetermined size. 20. Use according to claim 19, characterized in that the holographic information is stored in a binary-coded form in a pit (14; 36; 58). 21. Use according to claim 19, characterized in that the holographic information is stored in a continuously coded form in a pit (14; 36; 58), the local properties of the packaging tape (3; 3 '; 11; 31; 51) in the pit (14; 36; 58) can be set according to a value from a predetermined value range. 22. Use according to one of claims 1 to 21, characterized in that the packing tape (3; 3 '; 11; 31; 51) has stored holographic information. 23. Use according to one of claims 1 to 22, characterized in that for reading out holographic information from the packing tape (3; 3 "; 11; 31; 51) light (20; 42, 43; 60), preferably coherent light, is directed over a large area onto the packing tape (3; 3 '; 11; 31; 51) and after reflection on the packing tape (3; 3'; 11; 31; 51) as a reconstruction of the holographic information contained in the irradiated area Image is captured at a distance from the packing tape (3; 3 '; 11; 31; 51). 24. Use according to claim 23, characterized in that the holographic image is captured by a CCD sensor connected to a data processing device. 25. Use according to one of claims 1 to 24, characterized in that the packing tape (3; 3 ') has a number of limited areas (11; 31), each of which is set up for storing holographic information. 26. Use according to claim 25, characterized in that the limited areas (11; 31) are arranged at predetermined intervals on the packing tape (3; 3 '). 27. Use according to one of claims 1 to 26, characterized in that the holographic information to be deleted from the packing tape (3; 3 '; 11; 31; 51) is destroyed by destruction with a strong writing beam. 28. Packing tape, characterized in that it is prepared for use according to one of claims 1 to 27.