Holographic data-storage medium

[0001] The invention relates to a holographic data storage medium which, for example, can be used for storing pictorial data such as photographs, logos, text and so on but also for the storage of other data.

[0002] Contained in a hologram, distributed over the area of the hologram, is optical phase information about an object, from which, when irradiated with light, and in particular coherent light from a laser, an image of the object can be reconstructed. Holograms are used in many and various ways in technology, for example in the form of largely forgery-proof identifiers. Identifiers of this type will be found, for example, on credit cards or check cards; as what are known as white light holograms, even when illuminated with natural light, they show a three-dimensional image of the object depicted. Photographically produced holograms are widespread, as are embossed holograms, in which a relief structure is embossed into the surface of a material, at which the light used to reproduce the object is scattered in accordance with the phase information stored in the hologram, so that the reconstructed image of the object is produced by interference effects.

[0003] WO 00/17864 describes a data storage medium with an optical information. carrier, which contains a polymer film set up as a storage layer. The polymer film consists, for example, of biaxially. oriented polypropylene. In the data storage medium previously disclosed, the polymer film is wound spirally in a plurality of layers onto a core, there being an adhesive layer in each case between adjacent layers. Information can be written into the data storage medium by the polymer film being heated locally with the aid of a write beam from a data drive, as a result of which the refractive index of the polymer film and the reflective capacity at the interface of the polymer film are changed locally. This effect can be amplified by an absorber dye which is added to the adhesive layers, which at least partly absorbs the write beam and discharges the heat produced in the process locally to the polymer film. With the aid of a read beam in the data drive, the changes in the polymer film can be registered, since the read beam is locally reflected more or less intensely at the interface of the polymer film, depending on the information written in. By focusing the write beam or read beam, information can be written specifically into a preselected position on the information carrier or read out from it.

[0004] It is an object of the invention to provide a holographic data storage medium which is inexpensive, has wide areas of application and is largely insensitive to external influences.

[0005] This object is achieved by a holographic data storage medium having the features of claim 1 and the use of a data storage medium as claimed in claim 14. A method of putting information into a data storage medium of this type is specified in claim 19 a method of reading information out of a data storage medium of this type in claim 25. Advantageous refinements of the invention are cited in the dependent claims.

[0006] The holographic data storage medium according to the invention has a polymer film which is set up as a storage layer and which can be changed locally by heating. This polymer film is set up as a top layer of the data storage medium. Arranged underneath the polymer film is an absorber layer, which has an absorber dye which is set up to at least partly absorb a write beam serving to put information in and to discharge the heat produced in the process at least partly locally to the polymer film. The polymer film set up as a storage layer is preferably arranged in one layer in the data storage medium (preferably in a substantially flat arrangement), that is to say, for example, not wound up in a plurality of layers in spiral form.

[0007] Since the polymer film is set up as a top layer of the data storage medium, it can serve as the exposed outer side of the data storage medium and protects the generally relatively sensitive absorber layer located underneath. Furthermore, the changes in the polymer film which are effected by heating and using which holographic information is stored are primarily localized in the vicinity of the absorber layer, as explained in more detail further below. Therefore, this region of the polymer film provided with the stored information is likewise located in a protected zone. Undesired influences on the exposed outer side, such as scratches, therefore generally do not have any further effect and, above all, do not lead to a loss of data or to faults when putting information into the data storage medium.

[0008] The holographic data storage medium according to the invention is simply constructed, since an additional protective device can generally be dispensed with, and can therefore be produced inexpensively.

[0009] An adhesive layer is preferably arranged underneath the absorber layer, and makes it possible to stick the holographic data storage medium onto an object. If the adhesive layer is located immediately underneath the absorber layer, it simultaneously protects the absorber layer and the adjacent region of the polymer film with stored holographic information. The adhesive layer can, for example, contain an adhesive compound comprising an aqueous acrylate emulsion or can consist of functionalized poly(meth)acrylate. Other materials can also be used for the adhesive layer. One preferred thickness of the adhesive layer is about 20 μm, but other thicknesses are also possible.

[0010] In an advantageous refinement of the invention, a partly transparent reflective layer is arranged between the storage layer and the absorber layer. The reflective layer can have aluminum and preferably has a thickness in the range from 1 nm to 50 nm, other thicknesses also being possible. It is partly transparent, in order that the write beam penetrates as far as the absorber layer when information is being put in. Since the reflective layer is thin, it virtually does not hinder the discharge of heat to the polymer film. The reflective layer makes it easier to read out the stored holographic information in reflection, which represents a beneficial geometry in most applications. This is explained further below using examples. Furthermore, the reflective layer simplifies the operation of setting the focus of the write beam (see below).

[0011] It is also possible to arrange a reflective layer underneath the absorber layer. If there is an adhesive layer, this reflective layer is preferably located between the absorber layer and the adhesive layer. A layer structure of this kind permits the absorber layer to be penetrated in transmission when information is being read out of the holographic data storage medium, so that, for example, the contrast of the read-out signal is amplified if the absorption capacity of the absorber dye within the absorber layer varies in accordance with the information put in (amplitude effect; see below).

[0012] Suitable materials for the polymer film are, for example, polypropylene, polyvinylchloride, polyester, polyethylene terephthalate (PET), polyethylene naphthalate, polymethylpentene (PMP; also poly-2-methylpentene) and polyimide. The polymer film preferably has a thickness such that it is self-supporting and can carry out the protective function explained above. Suitable thicknesses lie in the range between 10 μm and 100 μm, but other thicknesses are likewise possible.

[0013] The polymer film can be oriented and is preferably biaxially oriented, for example it being pretensioned in two mutually perpendicular directions within its plane during production. This generally increases the strength of the polymer film. Furthermore, in the case of an oriented polymer film, a high energy density is stored in the film material. As a result of local heating with the deposition of a relatively small amount of energy per unit area, for example with the aid of a write beam from a writing device, which is absorbed in the absorber layer, a relatively intense material change with a change in the local properties of the polymer film can be achieved.

[0014] In addition to the absorber dye, the absorber layer preferably has a binder. The absorber dye permits local heating of the polymer film which is sufficient to change the local properties of the polymer film with a relatively low intensity of the write beam. The absorber layer can be thin and, for example, have a thickness in the range from 0.1 μm to 5 μm; other thicknesses are likewise possible. Preferred binders, which serve as a matrix for the molecules of the absorber dye are, for example, optically transparent polymers, for example of polymethyl methacrylate (PMMA) or, in the case of applications for higher temperatures, of polymethylpentene, polyether ether ketone (PEEK) or polyether imide. 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 a light wavelength of 532 nm of a write beam produced by a laser, for example dyes from the Sudan red family (diazo dyes) or (for particularly polar plastics) eosin scarlet are suitable. For the usual laser diodes with a light wavelength of 650 to 660 nm or 685 nm, green dyes, for example from the styryl family (which are usual as laser dyes), are better suited.

[0015] There are various possible ways to use the local change in the properties of the polymer film, effected by local heating of the latter, for the storage of information.

[0016] In one possible way, the refractive index of the polymer film can be changed locally by heating, it being possible for optical phase information to be stored in the polymer film via the local optical path length. In this case, provision is made to transilluminate the polymer film in transmission when reading out information (it being possible for the reflective layer to be helpful, see below). It is therefore possible to store phase information locally in the polymer film, that is to say in a region provided for the storage of a unit of information, by the refractive index -in this region being changed by heating (for example with the aid of a write beam from a writing device). The local change in the refractive index effects a change in the optical path length of the radiation used when reading information out of the polymer film (which transilluminates the polymer film in transmission). The optical path length is specifically the product of the geometric path length and the refractive index. Therefore, via a change in the refractive index, the local phase angle of the radiation used when reading out information can be influenced, that is to say the desired holographic information can be stored as phase information. A hologram produced in the polymer film in this way is accordingly a refractive phase hologram.

[0017] In another possible way, the surface structure or interface structure of the polymer film can be changed locally by heating, it being possible for holographic information to be stored via the local interface structure of the polymer film. In this case, therefore, the interface structure or topography of the polymer film, in particular at the interface to the absorber layer or to the reflection layer, pointing away from the exposed outer side of the polymer film, can be changed locally, for example by a laser beam serving as a write beam being focused on to the absorber layer or the interface zone of the polymer film, so that the light energy is absorbed there and converted into heat energy. In particular if the laser beam is radiated in briefly (pulsed), the material change in the polymer film leading to the local change in the interface structure is limited to a very small volume, on account of the generally poor thermal conductivity of the polymer (or of a very thin reflective layer). If the holographic information is put into the polymer film point by point, the region associated with a point typically having linear lateral dimensions of the order of magnitude of 0.5 μm to 1 μm, the height profile of the polymer film typically changes by 50 nm to 500 nm, which depends in detail on the properties and operating conditions of the write beam and the properties of the polymer film, of the absorber layer and possibly of the reflective layer. The point grid, that is to say the center spacing between two points (“pits”), typically lies in the range from 1 μm to 2 μm. In general, it is true that shorter light wavelengths of the write beam permit a closer point grid.

[0018] Mixed forms are also conceivable, in which the holographic information can be stored both by a local change in the refractive index and by a local change in the interface structure of the polymer film.

[0019] The absorber dye can be set up such that its optical properties are changed locally when it absorbs a write beam serving to put information in. In this case, it is particularly advantageous if the absorber dye changes its absorption capacity locally, that is to say by being bleached partly or completely by the write beam. By means of local variation in the absorption capacity in the absorber layer, the effect achieved in the polymer film by the changes can be reinforced, so that the signal obtained when reading out the holographic data storage medium is more intense or more contrasty than if the absorber layer does not participate in the data storage. The weighting of the individual effects (local refractive index of the polymer film, local interface structure of the polymer film, amplitude effect as a result of locally bleached absorber dye) in the read signal may be influenced or set by choosing the layer structure of the holographic data storage medium. Thus, an amplitude effect is relatively high when a locally bleached absorber layer is transilluminated when information is being read out, such as is the case when a reflective layer is arranged underneath the absorber layer.

[0020] The information to be stored can be put into the holographic data storage medium by an item of holographic information contained in a hologram of a stored object being calculated as a two-dimensional arrangement and a write beam from a writing device, preferably a laser lithograph, being aimed at the polymer film and/or the absorber layer of the data storage medium and driven in accordance with the two-dimensional arrangement such that the local properties of the polymer film are set in accordance with the holographic information. Since the physical processes during the scattering of light at a stored object are known, a conventional structure for producing a hologram (in which coherent light from a laser, which is scattered by an object (stored object) is brought to interference with a coherent reference beam and the interference pattern produced in the process is recorded as a hologram) can be simulated for example with the aid of a computer program and the interference pattern or the modulation of the local properties of the polymer film can be calculated as a two-dimensional arrangement (two-dimensional array).

[0021] As already explained further above, examples of the local properties of the polymer film which are set in accordance with holographic information are the local refractive index and the local interface structure of the polymer film.

[0022] The resolution of a suitable laser lithograph is typically about 50 000 dpi (dots per inch). Therefore, the polymer film can be changed locally in regions or pits with a size of about 0.5 μm to 1 μm. The writing speed and other details depend, inter alia, on the parameters of the write laser (laser power, light wavelength) and the pulse duration and on the properties of the polymer film and the absorber layer.

[0023] The write beam is preferably aimed at the holographic data storage medium from the side of the top layer. In this case, it is possible, for example, to put information into the data storage medium if the adhesive layer does not have good optical properties or the data storage medium is bonded to a non-transparent substrate.

[0024] If the holographic data storage medium has a partly transparent reflective layer, as explained further above, then, in order to focus the write beam, its reflection from the reflective layer can be evaluated. A comparable reflection would also occur in the case of reflection at the interface between two media with different refractive indices if no reflective layer is arranged there but, in the present case, will be reinforced considerably by the reflective layer. The evaluation can be carried out, for example, via the magnitude of the reflection, measured with the aid of a detector, it being possible for the exact focus setting to be determined, for example, with the aid of calibration measurements. If the reflective layer is very thin (about 1 nm to 50 nm, but also more or less), it can be assumed that the focus of the write beam set to the reflective layer virtually coincides with the optimum focus in the absorber layer. Therefore, when information is put in, the absorber layer can be heated virtually in an optimum way.

[0025] As mentioned, the holographic information is preferably put in in the form of pits of predefined size. The term “pit” is to be understood here more generally in the sense of a changed region and not restricted to its original meaning (hole or depression). In this case, the holographic information can be stored in a pit in binary encoded form. This means that, in the region of a given pit, the local properties of the polymer film assume only one of two possible basic forms (basic values). These basic forms preferably differ considerably, in order that intermediate forms which occur in practice and which lie close to one or the other basic form can be assigned unambiguously to one or the other basic form, in order to store the information reliably and unambiguously.

[0026] Alternatively, the holographic information can be stored in a pit in continuously encoded form, the local properties of the polymer film in the pit being set in accordance with a value from a predefined value range. If, for example, the local interface structure of the polymer film is to be set, the local maximum height change in the interface structure in the pit is therefore selected from a predefined value range. This means that, in a given pit, the interface structure of the polymer film can assume intermediate forms between two basic forms, so that the maximum height change of the intermediate form which is present assumes a value from a predefined value range whose limits are given by the maximum height changes of the two basic forms. In this case, the information can therefore be stored “in gray steps”, so that each pit is assigned the information content of more than one bit. This is correspondingly true of the setting of the local refractive index of the polymer film.

[0027] In order to read information out from the holographic data storage medium according to the invention, light, preferably coherent light (for example from a laser) can be aimed at a large area of the storage layer of the data storage medium. In this case, the light is modulated by the locally varying properties of the polymer film (for example the refractive index or the interface structure). As a reconstruction of the information contained in the irradiated region, a holographic image is registered at a distance from the data storage medium, for example by a CCD sensor which is connected to a data processing device.

[0028] In principle, the reading operation can be carried out with transmission of the holographic data storage medium, that is to say the data storage medium is transilluminated completely and the holographic image is registered behind the data storage medium. However, for this purpose all the layers of the data storage medium must have a good optical quality, that is to say not just the polymer film but also the absorber layer and an optional adhesive layer. It is therefore more advantageous to read out the information in reflection, the light used for reading being reflected after passing through the polymer film. In this case, the holographic image is produced by light which has passed twice through the polymer film and, in the process, has been modulated, for example by local variations in the refractive index and/or the interface structure of the polymer film. In principle, reading can even be carried out in reflection if there is no separate reflective layer present; the only precondition is the presence of an interface between two media with different refractive indices. However, the reflective layer mentioned between the polymer film and the absorber layer improves the reproduction of the holographic image considerably.

[0029] The term “large area” is to be understood to mean an area which is considerably larger than the area of a pit. In this sense, for example an area of 1 mm2 is large. For the scheme in accordance with which information is stored and read out, there are many different possibilities. It is conceivable to read a hologram out of the polymer film in one operation by the entire area of the region of the holographic data storage medium set up as a hologram being irradiated in one operation. In particular in the case of relatively large areas, however, it is advantageous to divide up the information to be stored in to a number or large number of individual regions (for example with a respective area of 1 mm2) and to read out the information in one operation only from a predefined individual region.

[0030] During the reading of information, as a result of the locally varying properties of the polymer film, propagation time differences of the light waves originating from various points occur, that is to say substantially periodic phase modulation (which applies in particular in the case of local setting of the refractive index or the interface structure of the polymer film). The region of the polymer film covered by the light acts in the same way as a diffraction grating, which deflects incident light in a defined manner. The deflected light forms an image of the stored object, which constitutes the reconstruction of stored holographic information.

[0031] In principle, holographic information from different types of stored objects can be used with the holographic data storage medium. For example, the information contained in images, such as photographs, logos, texts and so on, can be stored and read out. However, the storage of machine-readable data is particularly advantageous. This is carried out, for example, in the form of what are known as data pages, the holographic information contained in a hologram of a graphic bit pattern (which represents the data information) being put as explained into the polymer film serving as a storage layer. During reading, a holographic image of this graphic pattern is produced. The information contained therein can be registered, for example with the aid of a precisely adjusted CCD sensor, and can be processed by associated evaluation software. For the reproduction of images in which high accuracy is not important, a simple matt disk or, for example; a camera with and LCD screen is already in principle sufficient. During 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 registered in one operation, as explained. If, in spite of the protection by the exposed outer side of the polymer film of the regions of the data storage medium serving to store information, damage nevertheless occurs then, as opposed to a conventional data storage medium, this generally does not lead to a loss of data but merely to impairment of the resolution of the reconstructed holographic image when reading out the information. This is generally not a problem.

[0032] In the following text, the invention will be explained further using exemplary embodiments. In the drawings:

[0033]
FIG. 1 shows a schematic longitudinal section through a first embodiment of the holographic data storage medium according to the invention,

[0034]
FIG. 2 shows a schematic longitudinal section through a second embodiment of the holographic data storage medium according to the invention,

[0035]
FIG. 3 shows a schematic plan view of a detail of a holographic data storage medium according to the invention in accordance with the second embodiment, in which information can be stored via changes in the refractive index,

[0036]
FIG. 4 shows a schematic longitudinal section through the holographic data storage medium from FIG. 3, the input of information being illustrated,

[0037]
FIG. 5 shows a schematic longitudinal section through the holographic data storage medium from FIG. 3, the reading of information being illustrated,

[0038]
FIG. 6 shows a schematic longitudinal section through a holographic data storage medium according to the second embodiment, in which information can be stored via the local interface structure, the reading of information being illustrated, and

[0039]
FIG. 7 shows a schematic longitudinal section through a third embodiment of the holographic data storage medium according to the invention.

[0040]
FIG. 1 illustrates, in a schematic way and not to scale, a detail from a holographic data storage medium 1 according to a first embodiment in longitudinal section. The data storage medium 1 contains a polymer film 2 which serves simultaneously as a storage layer and as a top layer with an exposed outer side 3. In the exemplary embodiment, the polymer film 2 is self-supporting. Arranged underneath the polymer film 2 and adjacent to the polymer film 2 is an absorber layer 4 with an absorber dye. Underneath it there is an adhesive layer 6 which, in the delivered state of the data storage medium 1, is preferably covered by a film that can be pulled off or silicone paper. The terms “above” and “below” relate here and in the following text to the illustration in the figures; however, the data storage medium can also be arranged in any other orientation.

[0041] In the exemplary embodiment, the polymer film 2 is a biaxially oriented film of polypropylene (BOPP) with a thickness of 35 μm. Thinner or thicker films are likewise conceivable. Films of other materials are also suitable, as explained further above.

[0042] The absorber layer 4 in the exemplary embodiment contains polymethyl methacrylate (PMMA) as binder, to which the absorber dye Sudan red 7B is added. In the exemplary embodiment, the absorber layer is produced from a solution of 10.5% by mass of polymethyl methacrylate and 1.2% by mass of Sudan red 7B in toluene, which is applied to the underside of the polymer film 2 using a linearly engraved roll. The thickness of the absorber layer is about 0.5 μm and preferably lies in the range from 0.3 μm to 1.0 μm. However, other layer thicknesses are likewise conceivable. In order that the absorber layer 4 adheres better, before the application of the absorber layer 4 the underside of the polymer film 2 can be pre-treated in accordance with a process which is basically known.

[0043] The adhesive layer 6 in the exemplary embodiment is produced from an aqueous acrylate dispersion and has a layer thickness of 23±4 μm. Other layer thicknesses are likewise possible, and other adhesive compounds can also be used. The underside of the absorber layer 4 can be pre-treated before the application of the adhesive layer 6, in order to ensure better adhesion of the adhesive layer 6.

[0044] The absorber layer 4 and the zones of the polymer film 2 which are changed when information is put in (see below) lie in the internal region of the data storage medium 1 and are protected by the upper region of the polymer film 2 having the outer side 3 and the adhesive layer 6.

[0045]
FIG. 2 is an illustration similar to FIG. 1 of a second embodiment of a holographic data storage medium, which is designated 1′ here. Just like the data storage medium 1, the data storage medium 1′ has a polymer film 2 (here made of polyethylene terephthalate), which is set up as a storage layer and top layer with an exposed outer side 3, an absorber layer 4 and an adhesive layer 6. In addition, there is a reflective layer 8 between the polymer film 2 and the absorber layer 4.

[0046] In the exemplary embodiment, the reflective layer 8 consists of aluminum vapor-deposited on the underside of the polymer film 2 with a thickness such that the result is a transmission of 50%. Preferred layer thicknesses lie in the range from 1 nm to 50 nm, but smaller or larger values are also possible. Given such a low thickness, the reflective layer 8 is partly transparent, so that a write beam aimed at the outer side 3 of the polymer film 2 (for example from a laser lithograph, see below) can pass through the reflective layer 8 in order to reach the absorber layer 4.

[0047] As already mentioned, a series of materials are possible for the individual layers of the holographic data storage medium, and the layer thicknesses can also assume a large number of values. Furthermore, additional layers are conceivable. While the polymer film 2 is self-supporting in the case of the data storage media 1 and 1′, an additional rigid carrier layer can be provided in another embodiment, for example between the absorber layer and the adhesive layer.

[0048] In the exemplary embodiment explained by using FIG. 1, the absorber layer 4 has the absorber dye Sudan red 7B, whose molecules are embedded in a matrix of an optically transparent polymer, specifically polymethyl methacrylate (PMMA), the absorber layer 4 having a thickness of about 0.5 μ. Sudan red 7B absorbs light in the wavelength range around 532 nm particularly well; this wavelength is suitable for a write beam from a laser lithograph for putting information into the data storage medium. Examples of other absorber dyes are specified further above. For example, green dyes, for example from the styryl family, are suitable, particularly for light wavelengths of 635 nm or 650 to 660 nm or 685 nm, at which the laser diodes of current DVD devices operate; laser diodes of this type can be modulated directly, which makes the generation of pulses substantially simpler and cheaper. In the future, the range from 380 to 420 nm could also be of interest if appropriate blue laser diodes can be had commercially and inexpensively. For this purpose, yellow absorber dyes should then preferably be used, such as stilbenes substituted with weak donors and acceptors, donor-substituted nitrobenzenes or coumarin dyes.

[0049] The absorber layer 4 has a preferred optical density in the range from 0.2 to 1.0; however, other values are likewise 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 the negative decimal logarithm of the transmission through the absorber layer, which coincides with the product of the extinction coefficient at the wavelength of the write beam used, the concentration of absorber dye in the absorber layer 4 and the thickness of the absorber layer 4.

[0050] In the following text, using FIGS. 3 to 5, an explanation will be given as to how information can be put into a holographic data storage medium in accordance with the embodiment described using FIG. 2 and can be read out therefrom. The holographic data storage medium is designated 11 and has a polymer film 12 with an exposed outer side 13, an absorber layer 14, an adhesive layer 16 and a partly transparent reflective layer 18, see FIG. 4. In a way similar to FIGS. 1 and 2, FIGS. 3 to 5 are not to scale. The polymer film 12 here consists of biaxially oriented polyethylene terephthalate (PET) and has a thickness of 50 μm . The refractive index of biaxially oriented polyethylene terephthalate can be changed locally by heating, which is used to store information.

[0051] Within the polymer film 12, information is stored in the form of pits 20. In the region of a pit 20, the polymer film 12 has a refractive index which is different from that in the zones between the pits 20. The term “pit” is to be understood here in the sense of a changed region, that is to say more generally than in its original meaning (“hole”). In this case, the information can be stored in a pit in binary encoded form, by the refractive index assuming only two different values (it being possible for one of the two values also to coincide with the refractive index of the polymer film 12 in the zones between the pits 20). It is also possible to store information in a pit 20 in continuously encoded form, it being possible for the refractive index within the pit 20 to assume any desired selected value from a predefined value range. In clear terms, in the case of storage in binary encoded form, a pit is “black” or “white” while, in the case of storage in continuously encoded form, it can also assume all the gray values lying in between.

[0052]
FIG. 3 is a schematic plan view of a detail from the data storage medium 11, which shows the arrangement of the pits 20 which are produced by the write beam from a laser lithograph (as explained further below using FIG. 4). In the exemplary embodiment, a pit 20 has a diameter of about 0.8 μm. Shapes other than circular pits 20 are likewise possible, for example square or rectangular pits, and also other sizes. The typical dimension of a pit is preferably about 0.5 μm to 2.0 μm. FIG. 3 is therefore a highly enlarged illustration.

[0053]
FIG. 4 indicates in a schematic way how, with the aid of a write beam 22 from a writing device (a laser lithograph in the exemplary embodiment), a pit 20 is produced. Firstly, the write beam 22 is focused in such a way that it has its smallest cross-section approximately in the absorber layer 14. In this case, the partly transparent reflective layer 18 is of great help, since it deflects the write beam 22 back into the writing device, where the reflection is evaluated. The focusing optics of the write beam 22 are then adjusted until the position of the focus is optimized. In the exemplary embodiment, the focus 23 is in the thin reflective layer 18, which is simplest to achieve. During the focusing operation, the write beam 22 can be operated at lower power, in order to prevent excessive heating in the vicinity of the focus.

[0054] The representation of the write beam 22 and its focus 23 in FIG. 4 is very schematic. Because of the wave nature of light, the focus 23 is not shaped like a point but has a size comparable with the diameter of a pit 20, so that the write beam 22 is capable of heating relatively uniformly a region of the size of a pit 20 within the data storage medium 11. The greatest heating in this case occurs within the absorber layer 14, since it is located in the region of the focus 23 and the absorber dye absorbs the write beam 22. The heat liberated in the process is largely transferred through the reflective layer 18 to the polymer film 12 and in this way effects a local change in the refractive index in the polymer film 12 in the region of a pit 20. Since the polymer film 12 is substantially heated in the lower region, the pit 20 does not extend over the full thickness of the polymer film 12. In practice, the transition zone in the upper region of a pit 20 to the central region of the polymer film 12 is continuous, that is to say the refractive index changes gradually in this zone and is not delimited as sharply as indicated in FIG. 4.

[0055] The distance between the upper region of a pit 20 and the outer side 13 of the polymer film 12 is relatively large, so that the pits 20 produced by the write beam 22 lie in a region of the polymer film 11 which is relatively safe against external influences.

[0056] In order to put information into the polymer film 11, first of all phase information contained in a hologram of a stored object is calculated as a two-dimensional arrangement. This can be carried out as a simulation of a classical structure for producing a photographically recorded hologram, in which coherent line from a laser, after scattering at the stored object, is brought into interference with a coherent reference beam, and the interference pattern produced in the process is recorded as a hologram. The two-dimensional arrangement (two-dimensional array) then contains the information which is necessary to drive the write beam of a laser lithograph. In the exemplary embodiment, the laser lithograph has a resolution of about 50 000 dpi (i.e. about 0.5 μm). The write beam from the laser lithograph is guided over the outer side 13 of the polymer film 12 in pulsed operation (typical pulse duration of about 10 ns to 10 μs with a beam power of about 1 mW to 20 mW in order to put in a pit 20), in order to put the desired information sequentially into the polymer film 12 (or a preselected region of the polymer film 12). In the process, the write beam 22 heats the absorber layer 14 in accordance with the two-dimensional array and in this way produces the pits 20, as explained above.

[0057]
FIG. 5 illustrates in a schematic way how the information stored in the polymer film 12 can be read out. For this purpose, coherent light from a laser is aimed at the outer side 13 of the data storage medium 11. For clarity, only a small section of this coherent light, preferably incident in parallel, is illustrated in FIG. 5, and is designated 24 (incident read beam). In practice, the coherent light is aimed at the polymer film 12 over a large area and covers a region of, for example, 1 mm2. This is because, in order to reconstruct the stored information, the light originating from many pits 20 must be registered. The intensity of the incident read beam 24 is too weak to change the refractive index in the polymer film 12 and thus the stored information.

[0058] Part of the incident read beam 24, which, for practical reasons, strikes the outer side 13 of the polymer film 12 at an angle, is reflected at the reflective layer 18 on the underside of the polymer film 12, so that a reflected read beam 26 originates from the reflective layer 18 and, in the process, passes through the pits 20. (The proportion of the incident read beam 24 let through by the reflective layer 18 is not shown in FIG. 5, for clarity). Since the local refractive index of the polymer film 12 is different, depending on the pit 20, the local optical path length is varied, so that phase shifts occur. The consequence of this is that spherical waves 28 originate from the data storage medium 11 in the manner of a diffraction pattern, containing the stored phase information. At some distance from the data storage medium 11, a holographic image, which is produced by interference between the spherical waves 28, can be registered by a detector.

[0059] The expenditure required for the detector and further processing of the registered holographic image depend on the type of stored object, as already explained further above. For the reproduction of machine-readable data (data pages), a CCD sensor connected to a data processing device is particularly suitable while, for pure image reproduction, a simpler detector is also expedient, in particular if the image data is not to be processed further.

[0060] Using FIG. 6, a further possible way of storing holographic information by means of a holographic data storage medium will be explained, said medium being constructed similarly to the holographic data storage medium according to FIG. 2. The holographic data storage medium designated 31 here again has a polymer film 32 with an outer side 33, an absorber layer 34, an adhesive layer 36 and a reflective layer 38.

[0061] In order to produce a pit for storing information, a pulsed write beam from a writing device (preferably a laser lithograph, as explained using FIGS. 3 to 5) is focused via the outer side 33 of the polymer film 32 and through the partly transparent reflective layer 38 onto a zone 42 which, in FIG. 6, is indicated by hatching. At the start of this process, the underside of the polymer film 32 (that is to say the interface to the reflective layer 38) and the reflective layer 38 are still flat. Since the zone 42 is located in the region of the absorber layer 34, the light energy from the write beam is converted efficiently into heat. Because of the poor thermal conductivity of the material, a significant increase in temperature occurs in a closely delimited volume, during which the interface structure of the polymer film 32 is changed locally. In this way, a pit 40 is produced, that is to say the local region in which information is stored. Each pit 40 includes a central depression 44 in the polymer film 32, which is surrounded by a peripheral, more or less annular, thrown-up portion 45. The difference in level between the lowest point of the depression 44 and the highest point of the thrown-up portion 45, that is to say the local maximum height change of the interface structure in the pit. 40, is designated H in FIG. 6. H lies typically in the range from 50 nm to 500 nm. The distance between the centers of two adjacent pits 40 is preferably about 1 μm to 2 μm. In the exemplary embodiment, a pit 40 has a diameter of about 0.8 μm. Shapes other than round pits 40 are likewise possible. The typical dimension of a pit is preferably about 0.5 μm to 1.0 μm.

[0062] The information can be stored in a pit 40 in binary encoded form, by H assuming only two different values (one of the two values preferably being 0). It is also possible to store information in a pit 40 in continuously encoded form, it being possible for H for a given pit 40 to assume any desired selected value from a predefined value range.

[0063] Otherwise, the information can be put into the data storage medium 31 in a manner similar to the data storage medium 11, that is to say preferably with the write beam from a laser lithograph which is guided over the polymer film 32 in pulsed operation and in the process produces the pits 40 in a previously calculated way. In plan view, the polymer film 32 with the pits 40 then appears similar to the illustration in FIG. 3.

[0064]
FIG. 6 also illustrates, in a schematic way, how the information stored in the data storage medium 31 can be read out. For this purpose, coherent light from a laser (preferably at a wavelength which is not absorbed or absorbed only slightly by the absorber layer 34) is aimed at the outer side 33 of the data storage medium 31. (Alternatively, use can also be made of a very bright LED which, under certain circumstances, even leads to more beneficial results, primarily with regard to a reduction in what is known as speckle noise) . For clarity, of this coherent light, which is preferably incident in parallel (incident read beam), only a small detail is illustrated in FIG. 6, namely the incident light waves designated 46 and 47. In practice, the coherent light is aimed at the polymer film 32 over a large area and covers a region of, for example, 1 mm2. This is because, in order to reconstruct the stored information, the light originating from many pits 40 must be registered. The intensity of the incident read beam is too weak to change the interface structure of the polymer film 32 and thus the stored information.

[0065] The light waves 42 and 43 have a fixed phase Φ in relation to one another. For practical reasons, they fall on the outer side 33 of the polymer film 32 at an angle, pass through the polymer film 32 and are partly reflected at the reflective layer 38, so that reflected light waves 48 and 49 originate from the reflective layer 38 and in turn pass through the polymer film 32. For clarity, the proportion of the incident light waves 46 and 47 which passes through the partly transparent reflective layer 38 is not illustrated in FIG. 6. Since the local interface structure of the polymer film 32 varies over the pits 40, a phase shift occurs, and the reflected light waves 48 and 49 emerge with a phase Ψ, as illustrated in FIG. 6. The consequence of this is that light waves in which phase information is contained originate in many directions from the data storage medium 31 in the manner of a diffraction grating. At some distance from the data storage medium 31, a holographic image, which is brought about by interference between these light waves and constitutes a reconstruction of the stored information, can be registered by a detector.

[0066] By using FIGS. 5 and 6, two different possible methods by which a local change in the polymer film 12 or 32 can be used for storing information have been explained. Intermediate forms, that is to say both a change in the refractive index and in the interface structure of the polymer film in a pit, are likewise conceivable.

[0067] In principle, the methods explained for putting information in and reading information out can be used even when there is no reflective layer 18 or 38. For example, a write beam can also be focused without the aid of a reflective layer. When information is read out in reflection, a difference in the refractive index between two layers can be used. Furthermore, embodiments of the holographic data storage medium are conceivable in which the data storage medium is transilluminated in transmission when information is read out.

[0068] A third exemplary embodiment of a layer structure of the holographic data storage medium is illustrated in schematic longitudinal section in FIG. 7. The data storage medium designated 1″ contains a polymer film 2 which is used as a storage layer and top layer with an exposed outer side 3. Underneath the polymer film 2 and adjacent thereto is an absorber layer 4′. A reflective layer 8′ is arranged between the absorber layer 4′ and an adhesive layer 6, on the underside (which is covered by a protective layer in the delivered state). In the exemplary embodiment, the reflective layer 8′ consists of aluminum and is so thick that it is opaque and reflects maximally.

[0069] In the case of this layer structure, the reflective layer 8′ again makes it easier to focus the write beam onto the absorber layer 4′. Furthermore, when the information put in is read out, the absorber layer 4′ is transilluminated.

[0070] If the absorber dye contained in the absorber layer 4′ can be bleached locally when information is put in (for example with the aid of a laser lithograph), a change used for storing information can be achieved not only by the local heating of the absorber dye and the local change in the polymer film 2 effected by this (as explained above), but additionally also by a local change in the optical properties of the absorber dye, namely the absorption capacity. When information is read out from the data storage medium 1″, both effects are used in the layer structure according to FIG. 7, which results in amplification of the contrast of the read signal.

[0071] The following Table 1 lists dyes which are in principle suitable as an absorber dye for the absorber layer of the holographic data storage medium. In the first column, the wavelength (in nm) of the absorption maximum is specified; Table 1 is arranged by increasing wavelengths, if wavelengths are present. If available, the color index (CI) and a synonymous designation are also listed.

1TABLE 1Dyes which, in principle, are suitable as absorber dyesWave-lengthNameClSynonym2.3.4-TriazapentamethinecyanineAcridinium yellowAlizarin black SAmido yellow EAnalinee yellowAnalinee blackAnalinee sulfone phthaleinAnalinee violetAnthrasol blue IBCAntique purple6.6′-dibromoindigoArtisil blue GLFAstraphloxin FFAstrazone blue FGGLCl 11105Astrazone yellow 3 GLAstrazone red GBenzaurinBenzo light yellow 4GLBenzyl orangeBindschedler's GreenBrasileinBrilliant indigo 4BCiba blue 2BBrilliant orange RKBromophenol blueBromophenol redBromothymol blueBromoxylenol blueButter yellowCaledon red XB5Capri blueCapri blueCarbazolindanalineeCarbolan violet 2RCarthamineCelliton fast blue-green BQuinoline blueChlorantin light green BLLChlorantin light turquoise blue GLLChrome violet GyCibacetyl violetCibanon red 4BCibanon red GDoebner's violetEpsilon blueFanal colorsFluorenequinoneYellow-orange SCl 15985Green sensitizer MA2116HaemateinHelindon orangeHelindon pinkHelio fast yellow 5GKHeliogen green GHydron blue RHypericinImmedial brilliant blueImmedial yellow GGImmedial pure blueImmedial blackIndanthen yellowIndanthren blue GCDIndanthren blue RSIndanthren bordeaux RRIndanthren brilliant blue 4GIndanthren brilliant green FFBIndanthren brilliant orange GRIndanthren brilliant violet 2RIndanthren khaki GGIndanthren orange 2RTIndanthren red-brown 5RFIndanthren red-violetIndanthren turquoise blue 3GKIndanthren violet RRKIndathren yellow 5GKIndigo yellow 3GIndian yellowIndra redIrgalan brown-violet DLo.o′-dihydroxy-azo dyeIsoviolanthroneJuglonMadder lakesLake redLumogenMauveinMaxilon red BLMichler's Hydro blueMorinCl 75660MuscaflavinMuscarufinNaphthalene green VNeolan blue 2GNitramineOil yellow3.2′-dimethyl-4-aminoazobenzeneOxoninep-Xylenol bluePalanil pink RFParamethyl redPatent bluePatent blue VCl 42501Permanent violet RLPhenylene bluePhthalogen blue IBNPhthalogen blue-black IVMPinachrome blueProcinyl blue RPseudocyanineRubin pigment BKSambesi black VAcid fuchsineSulfur black TSupracen blue SESThioindigoHelindon red 2B; Algol red 5B; vat red BThionoultra green BThiopyronineToluylene blueVidal blackViolanthrone1080IR 261090IR 5229/345PrimulineCl 49000251BM-Terphenyl2,2″-dimethyl-p-terphenyl266TMQ3,3′,2″,3″′-tetramethyl-p-quaterphenyl275BMQ2,2″′-dimethyl-p-quaterphenyl275p-TerphenylPTP285DMQ2-methyl-5-t-butyl-p-quaterphenyl295TMI2,5,2″″,5″″-tetramethyl-p-quinquephenyl297p-QuaterphenylPQP302Butyl-PBD2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole302PBD2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole303PPO2,5-diphenyloxazole308Polyphenyl 1p-quaterphenyl-4,4″′-disulfonic acid disodium salt308Polyphenyl 2p-quaterphenyl-4,4″′-disullfonic acid dipotassiumsalt310QUI3,5,3″″,5″″-tetra-t-butyl-p-quinquephenyl313BiBuQ4,4″′-bis-(2-butyloctyoxy)-p-quaterphenyl314BBD2,5-bis-(4-biphenylyl)-1,3,4-oxadiazole320TBS3,5,3″″′,5″″′-tetra-t-butyl-p-sexiphenyl324PPF2,5-diphenylfuran327PBBO2-(biphenylyl)-6-phenyl-1,3-benzoxazole330Furan 22-(4-biphenylyl)-6-phenylbenzoxazotetrasulfonicacid potassium salt333a-NPO2-(1-naphthyl)-5-phenyl-phenyloxazole340BBO2,5-bis-(biphenylyl)-oxazole340DPS4,4′-diphenylstilbene341Direct yellow 62Cl 36900342Fast red violet salt LB3474-HydroxyazobenzolCl 11800350Bis-MSBp-bis(o-methylstyryl)-benzene350Carbostyryl 77-amino-4-methylcarbostyryl350Stilbene 1[1,1′-biphenyl]-4-sulfonic acid, 4,4″-1,2-ethene-diylbis-,dipotassium salt350Stilbene 32,2′-([1,1′-biphenyl]-4,4′-diyldi-2,1-ethenediyl)-bis-benzenesulfonic acid352Fast red salt PDCCl 37151354Coumarin 1207-amino-4-methylcoumarin354Cristal violet lactone354Mordant yellow 10Cl 14010355Furan 1Benzofuran,2,2′-[1,1′-biphenyl]-4,4′-diyl-bis-tetrasulfonic acid355Quinolone7-dimethylamino-1-methyl-8-azaquinolone-2356Fast korinth salt Vkz.Cl 37220357Celliton fast yellow GCl 11855357Fast red salt ITRCl 37150358POPOP1,4-di[2-(5-phenyloxazolyl)]benzene359Disperse yellow 9Cl 10375N-(2,4-dinitrophenyl)-p-phenylenediamine360Carbostyryl 37-dimethylamino-4-methylquinolone-2360Fast granite saltCl 37210362Alizarin yellow GGCl 14025Mordant yellow 1362Naphthochrome greenCl 44530Mordant green 31366Coumarin 27-amino-4-methylcoumarin368Walk yellow OCl 25135371Fast blue salt BCl 37235372Coumarin 47-hydroxy-4-methylcoumarin372Fast red salt RCCl 37120373Coumarin 477-diethylamino-4-methylcoumarin373/487Mordant brown 1Cl 20110374Thioflavin SCl 49010Direct yellow375Fast red salt B Tetrafluoroborate saltCl 37125377Variamine blue salt RTCl 37240378Thiazolyl blue3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazoliumbromide3801-MethoxyanthraquinoneCl 37325380Coumarin 4667-diethylaminocoumarin380Mordant yellow 12Cl 14045382Coumarin 1517-amino-4-trifluormethylcoumarin382Fast blueDiamidino 253/50385Alizarin yellow RCl 14030Mordant orange1, 5-(p-nitrobenzolazo)-salicylicacid385Celliton fast yellow 5RCl 260907,4′-benzolazo-4-hydroxy-3-methylazobenzene385Pinacryptol yellow386Mordant orange 10Cl 26560388Sudan orange GCl 119202,4-dihydroxyazobenzene389ChrysopheninCl 24895Direct yellow 12389Coumarin 1022,3,5,6-1H,4H-tetrahydro-8-methylquinolizino-[9,9a,1-gh]-coumarin390Direct yellow 50Cl 29025Siriuslichtgebret390Direct yellow 8Cl 13920392Supramine yellow RCl 18835Acid yellow 25393Direct yellow 27Cl 13950393Acid yellow 76Cl 18850Polar yellow 2G394Naphthol ASCl 375052-hydroxy-3-naphthanilide395Coumarin 3077-ethylamino-6-methyl-4-trifluoromethylcoumarin395Coumarin 5007-ethylamino-4-trifluoromethylcoumarin395Fast blue salt BBCl 37175396Coumarin 6H2,3,5,6-1H,4H-tetrahydroquinolzino-[9,9a,1-gh]coumarin397Brilliant yellowCl 24890397Coumarin 1527-dimethylamino-4-trifluormethylcoumarin400Mesoporphyrin-IX-dimethyl ester7,12-diethyl-3,8,13,17-tetramethyl-21H,23H-porphin-2,18-dipropionic acid dimethyl ester400Mordant brown 24Cl 118803-(3,5-dinitro-2-hydroxy-benzolazo)-2-hydroxy-5-methylacetanilide400Acid yellow 17Cl 18965401Mesoporphyrin-IX- dihydrochloride7,12-diethyl-3,8,13,17-tetramethyl-21H,23H-porphin-2,18-dipropionic acid402Thiazol yellow GCl 19540Titanium yellow403PyraninCl 590408-hydroxypyren-1,3,6-trisulfonic acid trisodiumsalt404Cibachron brilliant yellow 3G-PCl 18972Reactive yellow4051-Hydroxyanthraquinone405Coumarin 152A7-diethylamino-4-trifluoromethylcoumarin407Flavazin LCl 18820407Supramine yellow 3GLCl 18900Acid yellow 29408Fast light yellow D3GACl 18890Acid yellow 34410Coumarin 522N-methyl-4-trifluoromethylpiperidino-[3,2-g]-coumarin410Methyl redCl 130204′-(dimethylamino)-azobenzol-2-carbolic acid410Sulfon yellow RCl 22910Acid yellow 42412Quinoline yellow SCl 47005412Coumarin 303-(2′-N-methylbenzimidazolyl)-7-N,N-diethylaminocoumarin412Acid yellow 40Cl 18950412Thioflavin TCNCl 490053,6-dimethyl-2-(4-dimethylaminophenyl)-benzothiazoliumchloride413Mordant red 19Cl 187355-chloro-2-hydroxy-3-(5-hydroxy-3-methyl-1-phenyl-4-pyrazlolylazo)-benzosulfonic acidsodium salt414Fast silk yellow GCl 14170Acid yellow 65414Metanil yellowCl 13065Tropaeolin419Bromocresol purple5′,5″-dibromo-0-cresolsulfonphthalein422Brilliant sulfaflavin422Bromophenol blue3′,3″,5′,5″tetrabromophenolsulfonphthalein423Bromocresol green3′,3″,5′,5″-tetrabromo-m-cresolsulfonphthalein423Coumarin 1532,3,5,6-1H,4H-tetrahydro-8-trifluoromethylquinolizino-[9,9a,1-gh]coumarin423Phenol red sodium salt4243,3′-Diethyl-thiacyaniniodide424Acid orange 63Cl 22870425Coumarin 5102,3,5,6-1H,4H-tetrahydro-9-(3-pyridil)-quinolizino-[9,9a,1-gh]coumarin425TartrazinCl 19140427Disperse orange 13Cl 260801-benzolazo-4-(4-hydroxybenzolazo)-naphthalene427/452SafranCl 75100Saffron, Crocus428/392Citronin ACl 10316Naphthol yellow S; 2,4-dinitro-1-naphthol-7-sulfonic acid disodium salt430CurcuminCl 75300Diferuloylmethane430Martius yellow2,4-dinitro-1-naphthol433Coumarin 73-(2′-benzamidazylyl)-7-N,N-diethylaminocoumarin434/370Auramine OCl 410004,4′-(imidocarbonyl)-bis-(N,N-dimethylanaline)hydrochloride436Coumarin 3142,3,5,6-1H,4H-Tetrahydro-9-carboethoxyquinolizino-[9,9a,1-gh]coumarin439Quinoline yellow ACl 47000Quinophthalone440Fluorol 7GA440Naphthyl red hydrochloride4-benzolazo-1-naphthylamine hydrochloride440Palatin fast yellow BLNCl 19010Acid yellow 54442Acridine yellowCl 460253,6-diamino-2,7-dimethylacridine hydrochloride442Mordant brown 33Cl 13250443Celliton fast orange GRCl 110054-amino-4′-nitroazobenzene445Acid yellow 99Cl 13900446Supranol brown 4RCl 26550Acid orange 51449Chrysoidine GCl 112704504′,5′-DibromofluoresceinCl 45370450Coumarin 3342,3,5,6-1H,4H-tetrahydro-9-acetylquinolizino-[9,9a,1-gh]-coumarin451Oleobrown RRCl 112854522-hydroxy-1,4-naphthoquinoneCl 75480Lawson455Acid orange 74Cl 18745457Disperse orange 25457Fast black saltCl 37190458Chromazurol SCl 43825Mordant blue 29458Coumarin 63-(2′-benzothiazolyl)-7-diethylaminocoumarin462TrypaflavinAcriflavin4651-Aminoanthraquinone468Bismarck brown RCl 21010Vesuvin R472DASPI2-(p-dimethylaminostyryl)pyridylmethyl iodide472DCM4-dicyanmethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran475Orange GCl 16230Acid orange 10476/418Sudan ICl 12055Sudan yellow4801,5-Diaminoanthraquinone480Pyridine 11-ethyl-2-(4-(p-dimethylaminophenyl)-1,3-butandienyl)pyridinium perchlorate482AurinCl 438004-[bis-(4-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one482Crocein orange GCl 15970Ponceau 4 GB; 5-benzolazo-6-naphthol-2-sulfonic acid sodium salt483Celliton fast orange 5RCl 110804-analineo-4′-nitroazobenzene483Orange IICl 15510Acid orange A; 4-(2-hydroxy-1-naphthalinazo)-benzenesulfonic acid sodium salt485DOCI3,3′-diethyloxacarbocyanine iodide486Celliton orange RCl 607001-amino-2-methyl-anthraquinone489Fast yellow ex.Cl 13015Acid yellow-R; 4-aminoazobenzol-3,4′-disulfonicacid sodium salt490Astrazone orange GCl 48035490Orange ROFCl 15575Acid orange 8490Resorcin yellowCl 14270Tropaeolin O; 2,4-dihydroxy-azobenzol-4′-sulfonic acid sodium salt491Fast granite GBC BaseCl 111604-amino-2′,3-dimethylazobenzol492Acridine orangeCl 460053,6-bis-(dimethylamino)-acridin hydrochloridehydrate492Mordant brown 48Cl 113002-(5-chlor-2,4-diaminobenzeneazo)-4,6-dinitrobenzene493/420Sudan IICl 12140Sudan orange, Oleo scarlet G; 1-(2,4-dimethylbenzolazo)-2-naphthol494Pyrromethene 5464,4′-difluoro-1,3,5,7,8-pentamethyl-4-bor-3a,4a-diaza-s-indacene494Acid red 183Cl 18800494/388Remazole brilliant orange 3 RCl 17757Reactive orange 16495Disperse red 19Cl 111304-[bis-(2-hydroxyethyl)-amino]-4′-nitroazobenzene496FluoresceinCl 45350497Congo redCl 221204,4′-bis-(4-amino)-sulfo-3-naphthylazo)biphenyldisodium salt498Pyrromethene 556Disodium-1,3,5,7,8-pentamethylpyrromethene-2,6-disulfonate-difluoroborate complex498Acid anthracene red GCl 22890Acid red 97500Fast scarletCl 23500Saffrosin, benzopurpurin 4B500Pyridine 21-ethyl-4-(4-(p-dimethylaminophenyl)-1,3-butanedienyl)pyridinium perchloratee500UranineDisodium fluorescein500/374Mordant brown 4Cl 113352-(2,4-diamino-5-methyl-benzolazo)-4,6-dinitrophenol501Rhodamine 123 hydrate501Acid alizarin violet NCl 15670Mordant violet 5; Pontachrome violet SW502Celliton scarlet BCl 11110Dispersions red 1503Celliton fast ruby BCl 11115Dispersions red 13503Mordant black 11Cl 14645Eriochrome black T503/388Ponceau RCl 16150Xylidin-Ponceau 2R504Allura red ACCl 16035505Cl 12100Solvent orange 2505Fast red ACl 15620Roccellin, Acid red 88; 2′-hydroxy-(1,1′)-azonaphthalene-4-sulfonic acid sodium salt505Ponceau BSCl 26905Biebrich scarlet506/350Cochineal redCl 16255Neucoccin, Brilliant scarlet 4R,Scarlet N, Victoriascarlet 4R507Benzo fast scarlet 4BSCl 29160Direct red 23507Mercurochrome507Methyl orangeCl 13025507/354Sudan IIICl 26100507/398Toluidine redCl 121205081-Methylaminoanthraquinone508/376Fast acid red ECl 14710Acid red 4508/397Direct red 81Cl 28160Chlorantin light red-5BL508/532Cochineal scarlet PSCl 14900Acid red 8510Brilliant crocein MOOCl 27290Cotton scarlet; acid red 73510Cristal ponceauCl 16250510Rhodamine 110o-(6-amino-3-imino-3H-xanthene-9-yl)-benzoicacid510/530Chromotrop 2RCl 16570Acid red 29512Chromoxancyanine RCl 43820Mordant blue 3512Fluorescein 279-(o-carboxyphenyl)-2,7-dichloro-6-hydroxy-3H-xanthen-3-one512/356Fabric scarletCl 26900Acid red 151514Chromotrop 2BCl 16575514/351Ponceau SSCl 27190Fabric red G, Wool red B514/365Supranol red PBXCl 23635Acid red 114514/395Eosin BCl 45400Eosin scarlet515/383Azo rubineCl 14720Mordant blue 79; Chromotrope FB515/521PurpurinCl 58205Smoke brown G, madder purple516Azocarmin BXCl 50090Acid red 103516Mordant blue 9Cl 14855517Cibachron brilliant red 3B-ACl 18105Reactive red517Eosin light blue.517Eosin light yellowCl 45380518Fast red BCl 16180Bordeaux R518Helio fast ruby BBLCl 60760518Pyrromethene 5674,4-difluoro-2,6-diethyl-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene518/359Oil red OCl 26125Solvent red 27519PhenosafraninCl 50200Safranin B extra519Pyrromethene 5804,4-difluoro-2,6-di-n-butyl-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene5201-Hydroxy-4-aminoanthraquinone520Amidonaphthol red 6BCl 18055520Methyl eosinCl 45385520/352Ponceau SCl 27195520/357Sudan IVCl 26105(Biebrich) scarlet red521AmaranthCl 16185Azo rubine S, fast red D521Fast red DAzo rubine S521Emodine521Oil red EGNCl 26120Solvent red 26521Sudan red BCl 26110522DiiodofluoresceinCl 45425522Eosin B alcohol solubleCl 45400522Sirius pink BBCl 25380Direct red 75, benzo fast pink 2BL5241,1′-diethyl-2,2′-cyanine iodide524Pyrromethene 5974,4-difluoro-2,6-di-t-butyl-1,3,5,7,8-pentamethyl-4-bora-3a,4a-diaza-s-indacene524Rhodamine 6GCl 45160Benzoic acid, 2-[6-(ethylamino)-3-(ethylimino)-2,7-dimethyl-3H-xanthen-9-yl]ethyl ester,monohydrochloride525Erythrosin BCl 45430525Mordant violetCl 43810Eriochromcyanin RC525Murexide527Lanafuchsine 6BCl 18125Acid violet527Mordant blue 13Cl 16680Eriochrome blue SE528Quinaldine red528Direct red 80Cl 35780Sirius red F3B528Mordant black 3Cl 14640Eriochrome blue black B528Rhodamine 19Benzoic acid, 2-[6-(ethylamino)-3-(etnylimino)-2,7-dimethyl-3H-xanthen-9-yl], perchloratee529Fast acid violet ARRCl 45190Eriofuchsin A2R529SulfoRhodamine GCl 45220530DASBTI2-(p-dimethylaminostyryl)-benzothiazolylethyliodide530Safranin TCl 50240Safranine O531/563Carmin acidCl 75470Carmine532Eosin alcohol solubleCl 45386Ethyl eosin532/506Amidonaphthol red GCl 18050Acid red 1, azophloxin533/364Sudan red 7BCl 26050Oleored blueish538Procion red MX-5BReactive red 2540DMETCI3,3′-dimethyl-9-ethylthiacarbocyanine iodide540Neutral redCl 50040543Rhodamine BCl 45170544Fuchsin SCl 42685544Para rosanalineeParafuchsin base545Formyl violet S4BCl 42650Acid violet 4B545Parafuchsin acetateCl 42500Para rosanalinee acetate547Bismarck brown YCl 21000Vesuvin548Alizarin blue black BCl 63615548Pyronin YCl 45005548/510Eosin 10 BCl 45410Cyanosin, Phloxin B549Bengal pink disodium saltCl 45440Acid red 94549Brilliant benzo fast violetCl 27905Sirius violet BB; direct violet 515501,4-Diaminoanthraquinone550Phenoxazone 99-diethylamino-5H-benzo(a)phenoxazin-5-one550Pyridine 41-ethyl-4-(4-(9-(2,3,6,7-tetrahydro-1H,5H-benzo(i,j)-quinolizinium))-1,3-butadienyl)pyridinium perchlorate552/374Phenolphthalein552/630Rhodanil blue553New fuchsin 90 Plv.Cl 42520New magenta, Magenta III553Nil red553Pyronin BCl 45010554SulfoRhodamine BCl 45100Xylylene red B556/596Alzarin red S hydrateCl 58005557DTCI3,3′-diethylthiacarbocyanine iodide557/360Phenol red558Ethyl red1,1′-diethyl-2,4′-cyanine iodide5603,3′-Diethyl-thiacarbocyanine iodide565Nigrosin alcohol solubleCl 50415566Sulfoncyanine 5R ex.Cl 26360Acid blue 113567/629Sulfonazo III569Palatinchrome black 6BNCl 15705Mordant black 17570New fast blue 3RCl 51175Meldola's blue570Nigrosine water soluble.Cl 50420570Styryl 82-(4-(p-dimethylaminophenyl)-1,3-butadienyl)-3-ethylbenzothoazolium perchlorate570/367Cresol red570/407Brilliant black BNCl 28440571Sulfonic acid blue RCl 13390Anazolene sodium, acid blue 92 FG572Chlorophenol red572Sulfoncyanine black BBCl 26370574Sulfoncyanine GR ex.Cl 26400Acid blue 120575Litmus575Styryl 111-ethyl-4-(4-(p-dimethylaminophenyl)-1,3-butadienyl)-quinolinium perchloratee576Rhodamine 101576SulfoRhodamine 101 hydrate579OrceinNatural red 28579/371Cresol purple580Methylene violetCl 52041582DODCI3,3′-diethyloxadicarbocyanine iodide584Janus blackDiazin black584Methyl violet 2BCl 42535585Brilliant blue RCl 42660Brilliant indocyanine 6B585Styryl 9M2-(6-(4-dimethylaminophenyl)-2,4-neopentylene-1,3,5-hexatrienyl)-3-methyl-benzothiazoliumperchloratee585/379Bromocresol purple sodium salt586Nitrazine yellowCl 14890588Styryl 14589Janus blueCl 12210590Crystal violetCl 42555590Pyrromethene 6504,4-difluoro-8-cyano-1,2,3,5,6,7-hexamethyl-4-bora-3a,4a-diaza-s-indacene590Resorcinol crystal violet592DQOCI1,3′-diethyl-4,2′-quinolyloxacarbocyanine iodide592Remazol Brilliant blue RCl 61200Reactive blue 19592Victoria blue BCl 44045Corn blue B592/396Thymolphthalein594Benzo light blue FFLCl 34140594/376Thymol blue595Alizarinsaphirol BCl 63010595Procion blue MX-RCl 61205Reactive blue 4596Ethyl violetCl 42600596Cresyl violet acetate597Remazole black BCl 20505Reactive black 5598Thionin acetateCl 52000Lauth's violet598/415Sudan black BCl 26150Grease black599/374Alizarin direct blue ARCl 62130600Alizarinsaphirol ACl 62055600Oxonol 595601GallocyaninCl 51030602Indigo602IndigotinCl 73000602Cresyl violet perchlorate5,9-diaminobenzo[a]phenoxazonium perchloratee602Acid blue 29Cl 20460603Alkali blue 6B/Nicholson blueCl 42750604/560Quinaldin blue1,1′-Diethyl-2,2′-carbocyanine chloride6052,6-DichlorophenolindophenolTillmann's reagent605Analinee blue605/388Tetrabromophenol blue605/642Acid green 27Cl 61580606Astra blue base 6 GLL606Astrazone blue GLL606DCI-21,1′-diethyl-2,2′-carbocyanine iodide607Celliton blue exCl 645001,4,5,8-Tetraaminoanthraquinone607Pinacyanolbromide1,1′-diethyl-2,2′-carbocyanine bromide607Procion blue HBCl 61211Reactive blue 2607Trypan blueCl 23850Niagara blue 3B, Diamine blue 3B608IndigocarmineCl 73015608Phenol blue609/567AlizarinCl 580001,2-dihydroxyanthraquinone6101,4,5,8-tetraaminoanthraquinone610/380Alizarin direct blue A2GCl 62125611Evans blueCl 23860612/400Bromocresol green sodium salt614Pinacyanol1,1′-diethyl-2,2′-carbocyanine iodide615Alcian blue 8 GXCl 74240615Lissamine blue FFNCl 42135Xylolcyanol FF615Oxazine 43-ethylamino-7-ethylimino-2,8-dimethylphenoxazin-5-ium perchlorate615Stenacril blue RLCl 11075615Styryl 62-(4-(p-dimethylaminophenyl)-1,3-butadienyl)-1,3,3-trimethyl-3H-indolium perchloratee615Victoria blue RCl 44040615/425Malachite greenCl 42000616Azure CCl 52002618Amido black 10BCl 20470Naphthol blue black 6B618Chicago blue 6BCl 24410Diamine pure blue FF618Guinea green BCl 42085619Victoria pure blue BOCl 425956201,4-dianalineoanthraquinone622Brilliant cresyl blue ALDCl 51010622/427Fast green FCFCl 42053625/406Erioglaucin disodium saltCl 42090Alphazurin FG625/428Brilliant greenCl 42040Malachite green626Toluidine blue OCl 52040Tolonium chloride627Oxazine 1709-ethylamino-5-ethylimino-10-methyl-5H-benzo(a)phen oxazonium perchloratee627/582Alizarin pure blue RCl 61585628Nil blue A perchloratee5-amino-9-diethyliminobenzo[a]phenoxazoniumperchlorate629Alizarin brilliant blue RFFCl 62058629DQTCI1,3′-diethyl-4,2′-quinolylthiacarbocanine iodide630Oxonol blue630/422Light green SF yellowishCl 42095Acid green 5630/591New methylene blue NCl 52030633Azure ACl 52005633Wool greenCl 44090Lissamine green BN635/410Patent blue VFCl 42045635/420Methyl greenCl 42590637/409Patent blue ACl 42080Alphazurin A638Azure B Thiocyanate638Nil blue BXCl 51180Nil blue chloride639HIDCI1,1′,3,3,3′,3′-hexamethylindocarbocyanin iodide640/594Celliton fast blue FFRCl 61505640/595Sudan blueCl 61552Calco oil blue N642Coelestin blue BCl 51050Mordant blue 14642/608Alizarincyanine green G extraCl 61570643Rhodamine 700644/595Celliton fast blue BCl 615001,4-bis-(methylamino)anthraquinone644/596Oil blue NCl 61555Solvent blue 14644/607Alizarincyanine green oleosolubleCl 61565645Styryl 20645/522Eosin-methylene blueMay-greenwood-dye646Oxazine 13-diethylamino-7-diethyliminophenoxazoniumperchloratee648Styryl 15652/604Sudan blue IICl 61554Grease blue B, solvent blue 35653DTDCI3-diethylthiadicarbocyanine654Rhodulin pure blue 3GCl 51004Zapon fast blue 3G655Carbazine 122655Dithiazanine iodide3,3′-diethyl-thiadicarbocyanine iodide657Azure IICl 52010657/618Methylene greenCl 52020660Chlorophyll aCl 75810660/395Janus green BCl 11050Diazine green663Acid black 48Cl 65005665Methylene blueCl 52015667Oxazine 750675Cibachron turquoise blue GF-PCl 74459Reactive blue682Methyl-DOTCI3,3′-dimethyloxatricarbocyanine iodide682Rhodaminee 800694Copper phthalocyanineCl 74160Heliogen blue B; Monastral blue B7071,1′-diethyl-2,2′-dicarbocyanine iodide710DDI1 ,1′-diethyl-2,2′-dicarbocyanine iodide714Naphthol green BCl 10020741HITCI1,1′,3,3,3′,3′-hexamethylindotricarbocyanine .iodide7431,1′-diethyl-2,2′-quinotricarbocyanineiodide750IR 1447603,3′-diethyl-thiatricarbocyanineperchlorate760DTTCI3,3′-diethylthiatricarbocyanine iodide7653,3′-diethyl-thiatricarbocyanine iodide765DNTTCI3,3′-diethyl-9,11-neopentylenethiatricarbocyanineiodide780HDITCI1,1′,3,3,3′,3′-hexamethyl-4,4′,5,5′-dibenzo-2,2′-indotricarbocyanine iodide795IR 125798DDTTCII3,3′-diethyl-4,4′,5,5′-dibenzothiatricarbocyanineiodide810IR 1408141,1′-diethyl-4,4′-dicarbocyanine iodide815DDCI-41,2′-diethyl-4,4′-dicarbocyanine iodide830IR 132

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