Ultra-thin data carrier and reading method thereof

Abstract

The present invention relates to an ultra-thin plastic data carrier for long-term data storage and to a method for reading such a data carrier.

Description

[Technical field]

[0001] The present invention relates to an ultra-thin data carrier and a method for manufacturing such an ultra-thin data carrier. [Background technology]

[0002] It is estimated that humans, on average, generate about 2.5 quintillion bytes per day. Although most of the data may be generated only for short-term use, the demand for long-term data storage is growing day by day. Clearly, state-of-the-art data carriers such as flash, hard disk drives (HDDs), and magnetic tapes are not ideal from the perspective of long-term storage. Therefore, companies such as Microsoft are currently exploring alternative technologies for alternative storage technologies (see, for example, the so-called "Project Silica" and U.S. Patent No. 10,719,239).

[0003] WO 2021 / 028035 describes a different technique for long-term storage of information. The technique is based on the use of a ceramic substrate coated with layers of different materials and encoding information on the coated substrate, for example by using a laser to treat localized areas of the coated substrate. This technique has been proven to allow extremely resistant information storage against moisture, electromagnetic fields, acidic and corrosive substances, etc., so that the encoded writable ceramic plate offers a durability not available from other commonly used information storage media. However, one potential drawback of the technique is the use of a rather large ceramic plate with a thickness of about 1 mm. The data recording density per unit volume may therefore not reach the data recording density of currently used data carriers.

[0004] Therefore, there is a need for further improvements in data carriers suitable for long-term use and storage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021 / 028035 Summary of the Invention

[0006] Now, the inventors of the present invention have surprisingly found that the technique described in WO 2021 / 028035 can be used equally well for thin substrates made of certain plastic materials.

[0007] According to a first aspect, the present invention relates to a data carrier comprising a plastic substrate having first and second opposing surfaces and a thickness of at most 500 μm, preferably at most 200 μm, more preferably at most 150 μm, wherein the first surface of the substrate is covered with a first coating, the material of which differs from the material of the substrate, the first coating comprising a plurality of, preferably laser ablated, recesses encoding information.

[0008] The information encoded by the plurality of recesses may be analog and / or digital information. For example, the plurality of recesses may cooperate to form analog images, text, numbers, etc. Alternatively, the plurality of recesses may encode digital information similar to the digital information encoded in, for example, a CD, DVD, Blu-ray disc or Data Matrix code. In either case, the encoded information is preferably decodable visually by the naked eye or optically with the aid of suitable optical systems such as a microscope or by an optical decoder.

[0009] These recesses are generated by laser light, as detailed in WO 2022 / 002418, and may have various shapes and / or depths, which is hereby fully incorporated by reference, in particular with respect to any disclosure therein that details how information is encoded by the depth of the recesses. In the simplest form of this first embodiment, each recess has approximately the same depth, and the optical decoder detects the difference between the recess and the substrate area without a recess, for example by measuring the phase difference, or by detecting a change in reflectivity (for example, if the substrate surface is polished and the bottom of the recess is curved or roughened). In order to minimize distortion of the thin coating material, it is preferred that the recesses have a depth as small as possible, for example a depth of up to 100 nm, preferably up to 50 nm, even more preferably up to 30 nm. It is also preferred that the depth of each recess is less than 1%, preferably less than 0.1%, more preferably less than 0.05% of the thickness of the substrate.

[0010] To produce well-defined depressions that are easily detectable, the depressions are preferably produced by laser ablation utilizing a picosecond or femtosecond pulsed laser, which in effect results in cylindrical depressions with no edge of molten material at the periphery top of each depression.

[0011] The material of the first coating may have different optical properties compared to the optical properties of the substrate. For example, if the material of the substrate is light or white, while the material of the first coating is dark or black, ablating the material of the first coating to form recesses that extend towards or even into the substrate will result in a strong optical contrast between the entire surface of the first coating, on the one hand, and each recess, on the other hand. This contrast can be visible (e.g. to the naked eye) and create the impression of an image, text, etc., or provide a digital encoding (other than recess-to-recess) that is easily and reliably decoded by an optical decoder.

[0012] However, taking into account the envisaged long-term use of the data carrier of the invention, it must be ensured that the first coating remains reliably attached to the substrate, preferably even when the substrate is bent or wound on a roll. It is therefore preferred to apply a fairly thin coating layer having a thickness of at most 10 μm, preferably at most 1 μm, more preferably at most 200 nm, even more preferably at most 150 nm, even more preferably at most 100 nm, even more preferably at most 50 nm, even more preferably at most 30 nm, most preferably at most 20 nm. For optical effects, for example those realized by optical contrast, it is sufficient to have a thickness that allows substantial absorption, multiple scattering, reflection, etc.

[0013] From the viewpoint of the ease of the coating process, especially the decoding / reading process, it is preferred that the average roughness Ra of both the substrate surface and the coating surface is less than 10 nm, preferably less than 5 nm, more preferably less than 3 nm, Ra being the arithmetic mean value of the filtered roughness profile determined from the deviation from the centerline along the evaluation length.

[0014] Since a first coating on the substrate may cause distortions in the data carrier, it may be beneficial to coat both sides of the substrate in order to achieve symmetrical distortions. The second surface of the substrate is therefore preferably covered with a second coating, the material of which is different from the material of the substrate (and preferably the same as the material of the first coating). Of course, when a second coating is provided, said second coating can be used to encode additional information, thereby doubling the amount of data recorded on the data carrier. Therefore, the second coating also preferably comprises a plurality of, preferably laser ablated, recesses encoding information.

[0015] As mentioned above, the data carrier according to the first aspect can provide an optical contrast or another difference in optical properties between the areas of the undisturbed coating and the areas with recesses. For this purpose, each recess of the first and / or second coating preferably has a depth equal to or greater than the thickness of the respective coating. In other words, the coating material is preferably substantially completely ablated (or evaporated or otherwise removed) in each recess in order to make the material of the substrate available for optical decoding (e.g. by the naked eye, a microscope, a camera or a more sophisticated optical decoder or reader). In this context, it would be ideal to remove all the coating material precisely at the recess location without affecting the substrate. However, this can be difficult to control reliably and reproducibly. Thus, for example, it may be preferable to control the laser system used for ablation such that each recess of the first and / or second coating has a depth slightly greater than the thickness of the respective coating. For example, the ratio between the depth of each recess and the thickness of the respective coating may range between 1.01 and 1.2, preferably between 1.01 and 1.1, more preferably between 1.02 and 1.05. Preferably, each recess extends into the substrate to a depth of at most 1 μm, preferably at most 100 nm, more preferably at most 50 nm, even more preferably at most 30 nm, even more preferably at most 20 nm, most preferably at most 10 nm.

[0016] It may also be preferred that each recess of the first and / or second coating has a depth smaller than the thickness of the respective coating. For example, the depth of each recess may be optimized so that it never touches the substrate and at the same time the bottom material below the recess of the respective coating is thin enough for the laser light of a certain wavelength to still at least partially penetrate said coating material and reach the material of the substrate in order to achieve the optical contrast mentioned above. To this end, it is preferred that the ratio between the depth of each recess and the thickness of the respective coating ranges between 0.9 and 0.99, preferably between 0.95 and 0.99, more preferably between 0.97 and 0.99. Alternatively, each recess of the first and / or second coating may have a depth significantly smaller than the thickness of the respective coating. In this case the substrate merely serves as a carrier substrate and the encoding and decoding is performed entirely on the coating material only.

[0017] Preferably, the first and / or second coating is made of the following materials: Cr, Co, Ni, Fe, Al, Ti, Si, W, Zr, Ta, Th, Nb, Mn, Mg, Hf, Mo, V, metal nitrides such as CrN, CrAlN, TiN, TiCN, TiAlN, ZrN, AlN, VN, Si3N4, ThN, HfN, BN, etc., metal carbides such as TiC, CrC, Al4C3, VC, ZrC, HfC, ThC, B4 C, SiC, etc.; metal oxides such as Al2O3, TiO2, SiO2, ZrO2, ThO2, MgO, Cr2O3, Zr2O3, V2O3, etc.; metal borides such as TiB2, ZrB2, CrB2, VB2, SiB6, ThB2, HfB2, WB2, WB4, etc.; or metal silicides such as TiSi2, ZrSi2, MoSi2, MoSi, WSi2, PtSi, Mg2Si, etc.

[0018] Preferably, the substrate comprises or consists of one or a combination of the following materials: polycarbonate, polyethylene naphthalate, polyester, fluoroethylene propylene, ethylene-propylene copolymer, ethylene-tetrafluoroethylene, perfluoroalkoxy polymer, polyetherimide, polyethersulfone, polyethylene terephthalate, polyimide, polymethypentene, polytetrafluoroethylene, polyvinylidene fluoride.

[0019] Preferably, the substrate is transparent for at least one wavelength range in the visible spectrum, preferably across the entire visible spectrum, i.e. between 400 nm and 700 nm, and / or for at least one wavelength range in the UV spectrum, preferably across the entire UV spectrum, i.e. between 100 nm and 400 nm. Preferably, the substrate exhibits a transmittance of at least 80%, preferably at least 90%, more preferably at least 95%, for at least one wavelength range in the visible spectrum, preferably across the entire visible spectrum, i.e. between 400 nm and 700 nm, and / or for at least one wavelength range in the UV spectrum, preferably across the entire UV spectrum, i.e. between 100 nm and 400 nm.

[0020] The data carriers of the present invention may be provided in thin sheets, which may be stacked on top of each other. For example, each data carrier may be a circular, disk-shaped, rectangular or square sheet, for example a sheet of 10 cm x 10 cm. Such sheets can be easily handled during encoding and decoding, and for example 50 or even 500 sheets may be used stacked on top of each other to form a stack.

[0021] Alternatively, the data carrier may be an elongated film, which may be wound into a roll. For this purpose, it is particularly advantageous if the substrate (and preferably the entire data carrier) has a Young's modulus of at most 80 GPa, preferably at most 75 GPa. It is further preferred that the data carrier does not break at a radius of curvature of 100 mm, preferably 50 mm, more preferably 25 mm, more preferably 10 mm, more preferably 5 mm, more preferably 2.5 mm. To achieve these mechanical properties, it is preferred to make the data carrier as thin as possible. Preferably, the thickness of the data carrier is at most 130 μm, more preferably at most 110 μm, even more preferably at most 100 μm, even more preferably at most 90 μm, most preferably at most 80 μm.

[0022] As mentioned above, the recesses may have any shape, be oval, circular, rectangular, square, etc. Different recesses of different shapes may be used to encode information. However, in its simplest and most straightforward approach, a plurality of essentially identical and substantially round recesses are generated by a laser beam, preferably using picosecond or femtosecond laser pulses. These recesses may be arranged in a regular pattern, such as a rectangular, square or hexagonal pattern, to encode digital information. Preferably, the diameter of said recesses is as small as possible, yet large enough to allow proper decoding. Preferably, each recess has a maximum extension perpendicular to the depth of each recess of at most 1 μm, preferably at most 500 nm, more preferably at most 300 nm, even more preferably at most 200 nm, most preferably at most 150 nm.

[0023] Preferably, the data carrier is 2 At least 10 megabytes of coded information per substrate surface, more preferably cm 2 At least 100 megabytes of coded information per cm 2 Each contains at least 1 gigabyte of information.

[0024] The present invention further relates to a method of manufacturing a data carrier as described above. To manufacture a data carrier according to the first aspect, a plastic substrate is provided, either or both surfaces of the substrate are coated with a first and / or second coating, and a plurality of recesses are generated in the first and / or second coating, preferably by laser ablation, more preferably using picosecond or femtosecond laser pulses.

[0025] Preferably, a Gaussian or Bessel shaped laser beam is used to achieve a preferably cylindrical recess.

[0026] Coating of either or both surfaces of the substrate with the first and / or second coating may be carried out by a variety of known techniques, particularly preferred techniques being physical vapor deposition or chemical vapor deposition.

[0027] The substrate may be treated on either or both surfaces with one or more of the following techniques: heating, sputtering, HiPIMS (High Power Impulse Magnetron Sputtering), application of forming gas such as nitrogen and / or hydrogen. These techniques can improve the quality of the substrate surface and / or provide a stronger bond between the substrate and the coating.

[0028] The substrate is preferably transparent to the wavelength of the laser light used for the laser ablation and the laser ablation is preferably performed with the laser light transmitted through the substrate, so that debris generated during ablation cannot affect the optics used for ablation, since the data carrier forms a barrier between the ablated material and the optics.

[0029] The invention further relates to a method for reading a data carrier as described above, according to which a data carrier of a first aspect is illuminated with light of a first wavelength. The light transmitted through and / or reflected by the data carrier is detected and analyzed in order to decode the information encoded in the recesses of the data carrier. For example, the light passing through the recesses and the light blocked by the data carrier where no recesses are present (e.g. by an opaque substrate or an opaque coating) are combined to generate a pattern (light / dark), such as a QR code, which can then be decoded using known techniques.

[0030] Preferably, the data carrier comprises a substrate and a coating on one surface of the substrate, the substrate being transparent to the first wavelength, and the light transmitted through the substrate is detected. This can occur both in transmission and reflection mode. In particular, the data carrier may be preferably illuminated through the substrate from the side opposite the coating. Furthermore, the light originating from the recesses may be detected through the substrate from the side opposite the coating. In this technique, the signal-to-noise ratio is improved, since the side opposite the coating with the recesses is usually cleaner and / or has a smoother surface that facilitates imaging. In case dust particles may be present on the side containing the recesses, it is particularly advantageous to illuminate from the opposite side and detect on the opposite side, with the illumination and / or detection focus being located at the bottom of the recesses, in order to minimize the influence of the dust particles (or other impurities) on the light beam.

[0031] An example of the invention will now be described with reference to the drawings in which: FIG. [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a bright field microscope image of an exemplary data carrier at 100x magnification. [Diagram 2] FIG. 2 is a back-illuminated microscope image of an exemplary data carrier at 100x magnification. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] In the example, a polycarbonate substrate with a size of 10 mm × 10 mm and a thickness of 500 μm was coated with a coating of CrN with a thickness of 100 nm by physical vapor deposition (PVD). A circular recess with a diameter of about 1 μm was ablated from the coating using a 300 femtosecond laser with a wavelength of 514 nm.

[0034] The resulting data carrier was imaged at 100x magnification from the front and back with a Sensofar Sneox as shown in Figures 1 and 2, respectively.

[0035] As is evident from these figures, it is possible to reliably and irreversibly form recesses in the coating so as to achieve excellent optical contrast between the material of the polycarbonate substrate (transparent) and the material of the coating layer (light absorbing). Moreover, the CrN coating adhered reliably to the polycarbonate substrate and could not be mechanically displaced.

Claims

1. a plastic substrate having opposing first and second surfaces and a thickness of up to 500 μm; the first surface of the substrate is coated with a first coating; the material of the first coating is different from the material of the substrate; the first coating includes a plurality of laser-ablated depressions encoding information; Data carrier.

2. The thickness of the substrate is up to 200 μm; 2. The data carrier according to claim 1.

3. the second surface of the substrate is coated with a second coating; the material of the second coating is different from the material of the substrate; the second coating includes a plurality of laser-ablated depressions encoding information; 2. The data carrier according to claim 1.

4. the thickness of the first coating and / or the second coating is at most 1 μm; 4. The data carrier according to claim 3.

5. each recess in the first coating and / or the second coating has a depth of at most 100 nm; 4. The data carrier according to claim 3.

6. each recess in the first coating and / or the second coating has a depth that is less than the thickness of the respective coating; 4. The data carrier according to claim 3.

7. each recess in the first coating and / or the second coating has a depth substantially equal to the thickness of the respective coating; 4. The data carrier according to claim 3.

8. each recess in the first coating and / or the second coating has a depth greater than the thickness of the respective coating; 4. The data carrier according to claim 3.

9. each recess extends into the substrate to a depth of at most 100 nm; 9. The data carrier according to claim 8.

10. The first coating and / or the second coating may be made of the following materials: metals such as Cr, Co, Ni, Fe, Al, Ti, Si, W, Zr, Ta, Th, Nb, Mn, Mg, Hf, Mo, and V; CrN, CrAlN, TiN, TiCN, TiAlN, ZrN, AlN, VN, Si ３ N ４ , metal nitrides such as ThN, HfN, and BN, TiC, CrC, and Al ４ C ３ , VC, ZrC, HfC, ThC, B ４ Metal carbides such as C and SiC, Al ２ O ３ , TiO ２ , SiO ２ , ZrO ２ , ThO ２ , MgO, Cr ２ O ３ , Zr ２ O ３ , V ２ O ３ Metal oxides such as TiB ２ , ZrB ２ , CrB ２ , V.B. ２ , SiB ６ , ThB ２ , HfB ２ , W.B. ２ , W.B. ４ or metal borides such as TiSi ２ , ZrSi ２ , MoSi ２ , MoSi, WSi ２ , PtSi, Mg ２ metal silicides such as Si, 4. The data carrier according to claim 3.

11. the substrate comprises one or a combination of the following materials: polycarbonate, polyethylene naphthalate, polyester, fluoroethylene propylene, ethylene-propylene copolymer, ethylene-tetrafluoroethylene, perfluoroalkoxy polymer, polyetherimide, polyethersulfone, polyethylene terephthalate, polyimide, polymethypentene, polytetrafluoroethylene, polyvinylidene fluoride; 2. The data carrier according to claim 1.

12. The data carrier is wound in a roll.

2. The data carrier according to claim 1.

13. 2. A method for manufacturing a data carrier according to claim 1, comprising the steps of: providing a plastic substrate; coating either or both surfaces of the substrate with a first coating and / or a second coating; creating a plurality of recesses in the first coating and / or the second coating by laser ablation; A method comprising:

14. the substrate is transparent to the wavelength of laser light used for laser ablation; The laser ablation is performed using laser light transmitted through the substrate. The method of claim 13.

15. 2. A method for reading a data carrier according to claim 1, comprising: illuminating the data carrier with light at a first wavelength; detecting light transmitted through and / or reflected by the data carrier; analyzing the detected light to decode information encoded in the plurality of recesses of the data carrier; A method comprising:

16. the data carrier comprises a plastic substrate and a coating on one surface of the substrate, the coating having a plurality of laser-ablated recesses; the substrate is transparent to the first wavelength; Light transmitted through the substrate is detected.

16. The method of claim 15.

17. the data carrier is illuminated from the side opposite the coating and / or light reflected by the data carrier is detected on the side opposite the coating, 17. The method of claim 16.

Images