JP2003510748A - Data recording medium - Google Patents

Abstract

(57) Abstract: A data recording medium has an optical information carrier including a plurality of plies (10) of a polymer carrier (11), and information is transferred via the optical carrier to the preselected polymer. It can be read from the carrier ply (10) and optionally can be written to the preselected polymer carrier ply (10). The information carrier is formed around an optically transparent core, and the difference between the refractive index of the core and the refractive index of the polymer carrier (11) is less than 0.08.

Description

Detailed Description of the Invention

The invention relates to a data recording medium having an optical information carrier comprising a plurality of plies of polymer carrier.

In DE 298 16 802 a data recording medium with an optical information carrier is described which comprises a polymer carrier in the form of a polymer film. “Tesafilm kristall” by Beiersdorf AG, including polymethylmethacrylate as the material for the polymer film, and biaxially oriented polypropylene.
Mention may be made of polymer membranes sold under the name "klar". The polymer membrane is spirally wound around the core in a plurality of plies, with one adhesive layer each between adjacent plies. In this data recording medium, information can be written by locally heating the polymer film with the write beam of the data drive, and as a result, the refractive index at the interface of the polymer film and the reflectivity (reflectance) thereby However, it changes locally. This is detected using the read beam at the data drive. By focusing the writing beam or the reading beam, the information can be written in particular on a preselected ply of the information carrier or read out from a preselected ply of the information carrier. The core is optically transparent and has a recess in its central region that is utilized to house the read / write device of the data drive. In this case, the read / write device of the data drive moves with respect to the data recording medium, while the data recording medium is stationary, so that the data recording medium is balanced in view of the high speed rotational movement. Don't need that.

In the case of known data recording media, the wound core consists of polystyrene. Polystyrene is not particularly scratch resistant and has a refractive index (wavelength of the read beam used that is clearly different from that of the polymer film material (for the wavelength of the read beam, 1.49 for biaxially oriented polypropylene). In case of 1.59).
When the data recording medium is used in a data drive where the write / read device is located in the recess of the core, the walls of the core must be transmitted by the write beam and the read beam (and twice for each read step). ), Poor optical quality caused by scratches, and, in particular,
Reflection losses associated with large refractive index disparities give particularly undesirable results.

The object of the invention is to produce a data recording medium having an optical information carrier comprising a plurality of plies of polymer carrier, which data recording medium is due to the above-mentioned insufficient cores. There is no disadvantage.

This problem is solved by a data recording medium having the features of claim 1. Claim 13 relates to the use of such a data storage medium in a tailored drive. Advantageous embodiments of the invention are apparent from the dependent claims.

The data recording medium according to the invention comprises an optical information carrier comprising a plurality of plies of polymer carrier, readable by a preselected polymer carrier ply by said optical information carrier, optionally preselected polymer It is possible to write on the carrier ply. The information carrier is formed around an optically transparent core and the difference between its refractive index and that of the polymer carrier is 0.0.
It is less than 8. In this case, the index of refraction is related to the wavelength of the light at which the optical read-out device of the drive tuned for the data recording medium operates.

Due to the relatively small difference between the refractive index of the optically transparent core and the refractive index of the polymer carrier, the read beam transmitted from the read device of the drive and transmitted through the optically transparent core is It can penetrate into the polymer carrier without being reflected too strongly at the interface between and. Such reflections firstly attenuate the readout beam and secondly cause a background level of intensity that is superimposed on the actual readout signal. If the data recording medium is optionally arranged as a user writable data recording medium, the corresponding applies to the writing beam. The smaller the difference in refractive index, the less the reflection. If the data recording medium has one or more further layers between adjacent polymer carrier plies (see below), the refractive index of the further layers should also differ only slightly from that of the polymer carrier.

Suitably, the core is sleeve-like or cylindrical and has a recess in the central region of the core. From this it can be seen a design in which the circumference of the core is not circular in cross-section, but has steps, which allows the core to better fit the contours of the plies of the polymer carrier adjacent to the core. This will be explained in more detail below using examples.

The recess in the central region of the core may be arranged to accommodate the read device of the drive, which is adjusted to the data recording medium, and to accommodate any write device. Particularly advantageous is that when the data recording medium is used in a drive having a read device and an optional write device, the read device and the optional write device are arranged in a recess in the central region of the core to read and / or write information. Is moved with respect to the data recording medium, during which the data recording medium is stationary. In this case, the data recording medium does not have to be balanced in order to allow high rotational speeds, which favors production costs.

In an advantageous embodiment of the invention, the polymer carrier, which preferably has a polymer membrane, is spirally wound on the core. Very high storage densities can be achieved with such a multi-ply structure of the data storage medium. For example, 10 to 30 polymer membrane plies may be rolled on top of each other, or the number of polymer membrane plies may be
It may be more or less than this. If the thickness of the polymer film is between 10 μm and 100 μm (preferably less than 50 μm, or about 35 μm), the information is read on different polymer film plies, for example from a read / write device known in the DVD technology. , Can be separated from each other with good resolution. Moreover, one can think of:
Rather than the polymer carrier being helically wrapped around the core, for example, a ply of the polymer carrier that is stretched around the core and placed substantially centrally.

The core may include plastic. Optically high quality plastics are preferably used as the core material. In this case, the refractive index of the plastic material needs to be included in the range of the refractive index of the polymer carrier. Thus, in particular when a biaxially oriented polypropylene (BOPP; see below) polymer membrane is used for the polymer carrier, for example polymethylmethacrylate (PMMA), or sold by Nippon Zeon under the name "Zeonex". Suitable are cycloolefin copolymers.

If the core has one plastic, or if it consists entirely of plastic, the core is preferably provided with an anti-scratch coating. Such an anti-scratch coating (for example as is known from spectacle optics) at least substantially prevents scratches on the surface of the core exposed to the read or write beam, which of the data recording medium. Improves reliability and life of operation. In this case, it is necessary to ensure that the anti-scratch coating does not lead to a sharp increase in refractive index.

The core may further include glass. Glass usually has better optical properties than plastic, and higher scratch resistance than plastic.
The glass core also has mechanical advantages. This is because the data recording medium including such a core cannot be easily modified. A particularly suitable type of glass for use with a polymer carrier comprising biaxially oriented polypropylene is the glass sold by Schott under the name "BK7".

To secure the polymer carrier plies to each other, an adhesive layer is preferably arranged between each adjacent polymer carrier. The adhesive layer is, for example,
It may have a thickness in the range between 1 μm and 40 μm, preferably less than 25 μm or about 2 μm. Suitable adhesives include, for example, bubble-free acrylate adhesives that are crosslinked chemically or by irradiation with UV or electron beams. Between adjacent polymer carrier plies, there may additionally be one or more layers with different or additional functions, eg layers containing absorber dye molecules (see below).

Suitably, at the interface between the polymer carrier ply and the adjacent adhesive layer, the refractive index of the adhesive layer is such that the interfering reflection of the read or write beam is minimized. And only slightly different. The difference in refractive index is 0.
It is particularly advantageous if it is less than 005. However, any difference in refractive index can be utilized to format the data storage medium.

In a preferred embodiment of the data recording medium according to the invention, the refractive index of the polymer carrier can be locally changed by heating. Suitable materials for the polymeric carrier include, for example, polymeric membranes composed of biaxially oriented polypropylene (BOPP), although any other material may be used. After extruding into a membrane, if polypropylene is pretensioned in two planes, a high intrinsic energy is stored in the material. For example, when the writing beam is used to locally heat, a sharp change in the strength material due to inverse deformation occurs, as well as when a relatively small amount of energy is allocated per unit area. Thus, for example, about 1
A refractive index change of about 0.2 can be achieved over the area for one recorded information unit with a diameter or side length of μm, which is well detectable by the readout beam.

The polymer carrier is assigned an absorber configured to at least partially absorb the writing beam and at least partially to release the heat generated thereby locally to the polymer carrier. The absorber is, for example, a polymer carrier,
Alternatively, the dye may be present in an adhesive layer adjacent to the polymer carrier to allow localized heating of the polymer carrier sufficient to change the index of refraction at a relatively low writing beam intensity.

[0018]   In the following, the present invention will be explained in detail with reference to examples.

FIG. 1 shows in a schematic diagram a data recording medium 1 and a write / read device 2 of a drive adjusted for the data recording medium 1. The data recording medium 1 functions as an information carrier and has a number of polymer carrier plies 10 in the form of a polymer film 11 spirally wound on an optically transparent core. The core is not shown in FIG. 1 for clarity. The core is located inside the innermost portion of ply 10 and will be described in detail with reference to FIG. To illustrate more specifically, the plies 10 are formed by helically winding them around the polymer membrane 11, although the individual plies 10 of the polymer membrane 11 in FIG.
Are shown as concentric rings. One adhesive layer 12 is arranged between the adjacent plies 10 of the polymer film 11. For reasons of clarity, the adhesive layer 12 in FIG. 1 is shown with a large thickness that is not scaled.

In the example, the polymer membrane 11 consists of biaxially oriented polypropylene and is pretensioned in both surface directions before being rolled. In the example,
The polymer membrane 11 has a thickness of 35 μm, other thicknesses in the range of 10 μm to 100 μm, or thicknesses outside this range are likewise conceivable. The adhesive layer 12 is bubble-free and in this example comprises an acrylate adhesive with which the absorber dye is mixed.
The adhesive layer 12 is 23 μm thick, with a preferred layer thickness between 1 μm and 40 μm. In this example, the data recording medium 1 comprises 20 plies 10 of polymer film 11 and has an outer diameter of about 30 mm. The height of the data recording medium 1 is 19
mm. Any other number of plies 10 or any other dimensions are possible as well. The number of turns or the number of plies 10 can be, for example, between 10 and 30, but can be more than 30.

The write / read device 2 arranged in the recess of the central region of the data recording medium 1 comprises a write / read head 20, which is driven by a mechanism 21 in the direction of the arrow shown. It can be rotated and moved axially back and forth. The write / read head 20 has optical elements and a beam of light produced by a laser not shown in FIG.
30 nm or 532 nm) can be focused by the optical element onto the individual plies 11 of the polymer film 11. The write / read head 20 is moved by a mechanism 21 so that it can completely scan all plies 10 of the data recording medium 1. In this embodiment, the data recording medium 1 is stationary. Thus, the data recording medium, in contrast to the write / read head 20, need not be balanced (and need not be unwound or rewound) in view of the high rotational speed. The elements provided to balance the write / read head 20 for clarity are not shown in FIG. The laser described above is external to the write / read head 20 and is stationary. The laser beam is introduced into the write / read head 20 via an optical element.

In this embodiment, in order to record or write information on the data recording medium 1,
The laser is driven with a beam power of about 1 mW. In this case, the laser beam is used as a writing beam and is focused on the preselected ply 10 of the polymer film 11 so that the beam spot is less than 1 μm and the light energy is about 1 μm.
It is introduced in the form of short pulses of 0 μs duration. The energy of the writing beam is absorbed in the beam spot, which is promoted by the absorber in the adjacent adhesive layer 12. This leads to local heating of the polymer film 11 and thus local changes in refractive index and reflectance.

In order to read the recorded information from the data recording medium 1, the laser is driven in the continuous wave mode (CW mode). Depending on the information recorded, the read beam focused on the desired site is reflected and the intensity of the reflected beam is detected by a detector in the read / write device 2.

The data storage medium may also have embodiments that are not writable by the user. In this case, the data carrier comprises information units written by the manufacturer. At this time, the writing function in the user's data drive becomes unnecessary.

In the polymer film 11, the information units are formed by changing the optical properties in the region with a suitable size of less than 1 μm. The information may be recorded in binary form. That is, the local reflectance applies only two values at the site of the information unit. That is, if the reflectivity is greater than a fixed threshold, for example, a "1" is recorded at the site of interest on the information carrier and the reflectivity is less than or different than a different lower threshold. "0" if small
Is recorded accordingly. However, it is also conceivable that the information is recorded at multiple gray stages. This is possible if the reflectivity of the polymer film at the site of the information unit does not reach saturation and can be changed in a specific way by adjusting the defined refractive index.

In FIG. 2, a schematic sectional view of the data recording medium of FIG. 1 is shown. The core, designated here by 30, is in the form of a sleeve or a hollow cylinder and has a recess 32 in the central region. In the recess 32, the write / read device 2 of the drive can be housed (see FIG. 1). The optical information carrier including the spirally wound polymer film 11 and the adhesive layer 12 extends from the outer circumference 34 of the core 30 to the outer circumference 36.

In the example, the core 30 is made of polymethylmethacrylate (PMMA). It can be manufactured by injection molding or extrusion. Thereafter, the surface of the core 30 bordering the recess 32 is preferably anti-scratch coated.

Examples of other materials for the core are described in “Zeone” by Nippon Zeon.
It may be a cycloolefin copolymer marketed under the name "x", or other plastic. Particularly advantageous is glass, for example Schott's "BK
7 ”.

Importantly, the index of refraction of the core material is tailored to that of the polymer carrier. Thus, for a wavelength of light of 630 nm (ie, the wavelength of light associated with a read or write beam), biaxially oriented polypropylene has a refractive index of 1.503, while polymethylmethacrylate has a refractive index of 1.503. 1.491, the refractive index of "Zeonex" is 1.522, and the refractive index of glass "BK7" is 1.515. Therefore, the difference between the indices of refraction is small in all cases.

A data recording medium having a central region, which is shown in the schematic sectional view of FIG.
0, the morphology of which is somewhat different from the data recording medium described with reference to FIGS. The core 40 has a cylindrical recess 41 for accommodating a drive and a write / read device. However, the outer contour portion 42 of the core 40 is formed in a spiral shape instead of a circle as in FIG. 2 and has a step 43. The height of the step 43 is the height of the outer contour portion 4 in contact with the step 43.
The size of the two radial protrusions is adapted to the thickness of the polymer film (including adjacent adhesive layers) wrapped around the core 40 and designated herein by 44.

FIG. 3 shows how the inner end 45 of the polymer film 44 (including the adhesive layer) is located on the step 43. The innermost ply 46 of the polymer membrane 44 is
The core 40 is in close contact with the outer contour portion 42 via an adhesive layer. Continued ply 4
At the beginning of 7, the step 43, as can be seen from FIG.
Ensure that 4 spreads ideally in a spiral. In particular, when the polymer film collides with the inner end, which represents the beginning of the first winding and represents the beginning of the first winding, the radial turbulence is such that it appears in a core including a circular perimeter, for example in the core 30. Protrusions are avoided. Thereby, in particular, the winding inside the helical configuration of the polymer film 44 has a relatively uniform flow, so that the focus of the read or write beam can be guided more effectively.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a data recording medium according to the invention having a helically wound polymer film, adjusted for the data recording medium in a recess in a central region of the data recording medium. Drive parts are located.

[Fig. 2]   FIG. 2 shows a schematic sectional view of the data recording medium from FIG.

FIG. 3 shows a schematic cross-sectional view of the design of the central area of a data recording medium with a surrounding core different from that of FIG.

─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Mussich, Bernhard             21218 Seevetal, Germany             Del Zener Wek 31 (72) Inventor Stadtler, Stephan             Germany 22391 Hamburg, Veri             Lux Butler Vek 117 (72) Inventor Nethe, Stephen             Germany 69469 Weinheim, Les             Berstraße 51 F-term (reference) 5D029 HA06 JA04 JB13 TB01                 5D090 AA08 BB12 BB16 CC12 CC14                       DD02

Claims (13)

[Claims] 1. Comprising a plurality of plies (10) of a polymer carrier (11),
A data recording medium having an optical information carrier, the information being readable via the optical carrier from a preselected polymer carrier ply (10), optionally the preselected polymer carrier Writable on the ply (10) and formed around an optically transparent core (30), the difference between the refractive index of the core and the refractive index of the polymer carrier (11) is less than 0.08. , Data recording medium. 2. The data recording medium according to claim 1, wherein the core (30) has a sleeve shape or a cylindrical shape, and has a recess (32) in a central region. 3. The recess (32) is arranged for accommodating a read device (2) and an optional write device (2) of a drive adjusted for a data recording medium (1). The data recording medium according to claim 2, characterized in that: 4. The polymer carrier (11) having the polymer film (11) is preferably spirally wound around the core (30). The data recording medium according to any one of the above. 5. The data recording medium according to claim 1, wherein the core (30; 40) contains plastic. 6. Data recording medium according to claim 5, characterized in that the core (30; 40) comprises one or more materials of polymethylmethacrylate or cycloolefin copolymers. 7. The data recording medium according to claim 5, wherein the core (30; 40) is provided with an anti-scratch coating. 8. The data recording medium according to claim 1, wherein the core (30; 40) contains glass. 9. The adhesive layer (12) according to claim 1, characterized in that an adhesive layer (12) is arranged between each adjacent polymer carrier ply (10). Data recording medium. 10. The refractive index of the adhesive layer (12) is determined by the polymer carrier (11).
Data carrier according to claim 9, characterized in that it is only slightly different from the refractive index (11) of). 11. Data recording medium according to claim 1, characterized in that the refractive index of the polymer carrier (11) can be changed by local heating. . 12. A writing beam is applied to the polymer carrier (11).
It is characterized in that it is assigned an absorber configured to at least partially absorb and at least partially, locally, release the heat generated thereby to the polymer carrier (11), The data recording medium according to claim 11. 13. A drive, adapted for the data recording medium, comprising a reading device (2) and an optional writing device (2), the reading device (2) and the optional writing device (2). Is the core (30
) Located in the recess (32) in the central region of the device, moved relative to the data recording medium (1) for reading and / or writing information, while the data recording medium (1) is stationary. Claims 1 to 1, which are related to Claim 3.
Use of the data recording medium according to any one of 2.