WO2009096972A1

WO2009096972A1 - Optical data recording medium and method, system and apparatus incorporating the same

Info

Publication number: WO2009096972A1
Application number: PCT/US2008/052634
Authority: WO
Inventors: Makarand P. Gore
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2008-01-31
Filing date: 2008-01-31
Publication date: 2009-08-06

Abstract

An optical data recording medium (100) includes a substrate (220) and a transparent markable coating (230) established therein. The transparent markable coating (230) includes an absorber dye (239) tuned to a predetermined write and read wavelength and a contrast-forming agent precursor (240) including a derivative of a contrast dye that converts to the contrast dye upon exposure to energy from the absorber dye (239).

Description

200704225 1

OPTICAL DATA RECORDING MEDIUM AND METHOD, SYSTEM AND APPARATUS INCORPORATING THE SAME

BACKGROUND

The present disclosure relates generally to optical data recording media, and method(s), system(s), and apparatus(es) incorporating the same.

Materials that produce color and/or contrast change upon stimulation with radiation are used in optical recording and imaging media and devices. Further, widespread adoption of and rapid advances in technologies relating to optical recording and imaging media have created a desire for greatly increased data storage capacity in such media. Thus, optical storage technology has evolved from the compact disc (CD) and laser disc (LD) to far denser data types, such as digital versatile disc (DVD) and blue laser formats such as BLU-RAY and high-density DVD (HD-DVD). "BLU-RAY" and the BLU-RAY Disc logo mark are trademarks of the BLU-RAY Disc Founders, which consists of 13 companies in Japan, Korea, Europe, and the U.S.

In each case, the optical recording medium includes a substrate, typically a disc, on which is deposited a layer on which a mark may be created. In some media, the mark is a "pit," or indentation in the surface of the layer, and the spaces between pits are called "lands." A marked disc can be read by directing a laser beam at the marked surface and recording changes in the reflected beam. An imaging medium consists of any surface coated with material activated by light. 200704225 2

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the present disclosure will become apparent by reference to the following detailed description and drawings, in which like reference numerals correspond to similar, though not identical, components. For the sake of brevity, reference numerals or features having a previously described function may or may not be described in connection with other drawings in which they appear.

Fig. 1 is a semi-schematic perspective view and block diagram illustrating an embodiment of an optical disc recording system; and Fig. 2 is a schematic side elevation view of an embodiment of a recording medium in conjunction with a partial block diagram of some of the elements of the system represented in Fig. 1.

NOTATION AND NOMENCLATURE Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, computer companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "comprising, but not limited to...."

Reference is made herein to BLU-RAY technologies. DVD specifications for BLU-RAY discs currently include the following: wavelength = 405 nm; numerical aperture (NA) = 0.85; disc diameter = 12 cm; disc thickness = 1.2 mm; and data capacity > 23.3/25/27 GB. BLU-RAY discs can currently be used to store 2 hours of high resolution video images or 13 hours of conventional video images. A blue- violet laser having a wavelength ranging from about 380 nm to about 420 nm, and particularly 405 nm is used as the light source for BLU-RAY discs. Another technology using blue light (380 ~ 420 nm radiation) is HD-DVD. 200704225 3

As used herein, the term "absorption band" refers to a band of radiation or absorbance +/- 30 nm from the stated value. For example, the 405 nm absorption band includes wavelengths ranging from 375 nm to 435 nm.

The term "dye derivative" refers to a chemically modified contrast dye that has low or no absorption in the wave band used for reading data, and is in a non- activated state. The dye derivative may be converted back to the contrast dye (i.e., to an activated state), which produces color, changes the color and/or changes the optical contrast in the desired wave band for reading the data.

As used herein, the term "absorber dye" describes a substance that absorbs a predetermined wavelength or range of wavelengths and transfers the absorbed energy to the dye derivative, thereby causing the dye derivative to alter its chemical and/or physical structure (i.e., revert back to the contrast dye).

The term "light" as used herein includes electromagnetic radiation of any wavelength or band and from any source.

DETAILED DESCRIPTION

Embodiments of the recording medium disclosed herein advantageously include dye components or other suitable colorants, a first of which captures radiation energy and a second of which initiates a color or contrast change reaction upon exposure to the radiation energy transferred from the first dye/colorant. Together, the function of the dyes/colorants is to cause sufficient refractive index and/or absorption coefficient changes in the areas of the medium exposed to the transferred radiation energy. As a non-limiting example, the second dye is a dye derivative that absorbs energy at least 100 nm from a predetermined read and write wavelength, and that, when exposed to energy from the first dye, forms an optically detectable mark that absorbs energy at the read wavelength. The transformation from the first and second dyes to the optically detectable mark is a thermal or photothermal transformation. In a photothermal transformation, transfer through heat and electronically excited complex (exciplex) states of the dyes may take part in the transformation. It is believed that the use of dyes advantageously 200704225 4

decreases the formation of particles in the coating, which may, in some instances, degrade signals for optical data reading and writing.

Referring now to Figure 1 , an embodiment of a system for recording and/or transmitting optical data or visual images is semi-schematically depicted. Embodiments of the system include optical components 148, a light source 150 that produces the incident energy beam 152, a return beam 154 which is detected by the pickup 157, and a transmitted beam 156. When the system is used for transmitting, the transmitted beam 156 is detected by a top detector 158 (e.g., a photo detector) via lens or optical system 600, and is also analyzed for the presence of signal agents.

Figure 1 also illustrates a drive motor 162 and a controller 164 for controlling the rotation of the recording/imaging medium 100. Mark(s) (shown as 242 in Figure 2) may be read/detected by an optical sensor (e.g., optical pickup 157). The sensor (e.g., optical pickup 157) is positioned so as to detect at least one readable pattern of the optically detectable mark(s) 242 on the imaging medium 100.

Generally, the sensor reads at least one readable pattern as the imaging medium 100 moves in relation to the sensor. The sensor may send the readable pattern in the form of one or more signals to a processor 166.

The processor 166 and an analyzer 168 may be implemented together or in the alternative for processing the return beam 154 with a signal 165 from the pickup 157 to the processor 166, as well as processing a transmitted beam 156 from a signal 163 transmitted from the optical detector 158 and associated with the transmissive optical disc format.

A display monitor 114 may also be provided for displaying the results (generally in the form of data) of the processing. The system may also include a computer data base (not shown) which collects and stores the processed/analyzed data for subsequent retrieval.

Figure 2 shows an abbreviated block diagram of the read/write system 170 illustrating some of the same optical components shown in Figure 1. Specifically, 200704225 5

Figure 2 illustrates the read/write system 170 applying an incident energy beam 152 onto the imaging medium 100.

Imaging medium 100 includes a substrate 220 and a markable coating or marking layer 230 on a surface 222 of substrate 220. In the embodiment shown, the imaging medium 100 further includes a protective layer 235, as is generally known. It is to be understood that other embodiments of the imaging medium 100 do not include such a protective layer 235.

As described in detail below, marking layer 230 includes an absorber dye

239 and a contrast-forming agent precursor 240 dissolved or finely dispersed in a matrix or binder 241. Marking layer 230 may also include a fixing agent (not shown).

The substrate 220 may be any substrate upon which it is desirable to make a mark, such as, for example, the polymeric substrate of a CD-R/RW/ROM,

DVD±R/RW/ROM, HD-DVD or BLU-RAY disc. Substrate 220 may be paper (e.g., labels, tickets, receipts, or stationery), an overhead transparency, or another surface upon which it is desirable to provide marks. Marking layer 230 may be applied to substrate 220 via any acceptable method, such as, for example, rolling, spin-coating, spraying, lithography, screen printing or the like.

In many embodiments, it may be desirable to provide a marking layer 230 that has a thickness equal to or less than 200 nm. In order to achieve this, spin coating is one suitable application technique. In addition, it may be desirable to provide a marking composition that is capable of forming a layer that has a thickness equal to or less than 200 nm. Thus, in such cases, the marking layer

230 should be, inter alia, free from particles that would prevent formation of such a layer, i.e., free from particles having a dimension greater than 200 nm. In some instances, the absorber dye 239 and the contrast-forming agent precursor 240 are completely soluble in the marking composition solvent.

Furthermore, in many applications it may be desirable to provide a markable coating/marking layer 230 that is transparent. In such a case, any particles present in the coating 230 would have an average size less than half the wavelength of the 200704225 6

light to which the coating is transparent. While a coating 230 in which all particles are smaller than 200 nm would serve this purpose, it may be more desirable to utilize a coating 230 in which the marking components are dissolved, as opposed to one in which they are present as particles. Still further, as target data densities increase, the dot size, or mark size, that can be used for data recording decreases. Some currently available technologies require an average dot size of 200 nm or less. For all of these reasons, marking layer 230 is therefore desirably entirely free of particles that are larger than half the wavelength of the read and write radiation. In some embodiments, both the absorber dye 239 and the contrast-forming agent precursor 240 are soluble in the matrix 241 (a non-limiting example of which is a polymeric material). The matrix 241 may be provided as a homogeneous, single-phase solution at ambient conditions because the use of a dye derivative for the contrast-forming agent precursor 240 prevents the contrast-forming reaction from occurring prior to activation. In other embodiments, one of the components 239, 240 may be dispersed in the form of colloids in the matrix 241. In still other embodiments, an additional matrix 241 is not included, as the dye materials themselves serve as the matrix 241.

The matrix 241 may be any material or combination of materials suitable for dissolving and/or dispersing the absorber dye 239 and the contrast-forming agent precursor 240. Suitable matrix materials include, but are not limited to, UV-curable matrices such as acrylate derivatives, oligomers and monomers, with or without a photo package. A photo package may include a light-absorbing species which initiates reactions for curing of a matrix 241 , such as, for example, benzophenone derivatives. Other examples of photoinitiators for free radical polymerization monomers and pre-polymers include, but are not limited to, thioxanethone derivatives, anthraquinone derivatives, acetophenones and benzoin ether types. It may be desirable to choose a matrix 241 that can be cured by a form of radiation other than the type of radiation that causes a color and/or contrast change.

A matrix 241 based on cationic polymerization resins may include photo- initiators based on aromatic diazonium salts, aromatic halonium salts, aromatic 200704225 7

sulfonium salts and metallocene compounds. An example of an acceptable matrix 241 includes Nor-Cote CLCDG-1250A or Nor-Cote CDGOOO (mixtures of UV curable acrylate monomers and oligomers), which contains a photoinitiator (hydroxy ketone) and organic solvent acrylates (e.g., methyl methacrylate, hexyl methacrylate, beta-phenoxy ethyl acrylate, and hexamethylene acrylate). Other acceptable matrixes include acrylated polyester oligomers such as CN292, CN293, CN294, SR351 (thmethylolpropane tri acrylate), SR395 (isodecyl acrylate), and SR256 (2(2-ethoxyethoxy) ethyl acrylate) available from Sartomer Co.

The chemical mechanisms that cause the dye derivatives to become dyes are much slower when the solid matrix 241 is below its glass transition temperature (Tg). Without subscribing to a particular theory, the chemical reactions in solids have an added energy barrier to heat the matrix 241 above its glass transition temperature T₉. Thus, in some embodiments, it may be desirable to provide sufficient photo or thermal energy in the region of the desired mark 242 to locally heat the matrix 241 above its glass transition temperature T₉. T₉ typically depends on the polymer composition of the matrix 241 , and can be determined by selecting one or more desirable polymers for the matrix 241. In some embodiments, T₉ will preferably be in the range of about 180⁰C to about 280⁰C.

It is to be understood that the absorber dye 239 at a concentration ranging from about 0.1 % to about 5% and the contrast-forming agent precursor 240 at a concentration of ranging from about 5% to about 25% in the marking layer 230 are sufficient to produce a detectable mark 242 when activated.

The absorber dye 239 is tuned to a predetermined wavelength (i.e., a single wavelength or a range of wavelengths), and is configured to capture radiation energy and transfer such captured energy to the contrast-forming agent precursor 240 to initiate color formation, color change and/or contrast change. The absorber dye 239 may be tuned to any desirable wavelength, for example, the absorber dye 239 may have a peak absorption at 405 nm, 650 nm, 780 nm, 984 nm or at 1084 nm. It is to be understood that the absorber dye 239 may also be tuned to any desirable absorption band (i.e., the 405 nm band, the 650 nm band, the 780 nm 200704225 8

band, the 984 nm band, or the 1084 nm band). As a non-limiting example, the dye may have a peak absorption in the 405 nm band (i.e., ranging from about 375 nm to about 435 nm). Non-limiting examples of suitable absorber dyes 239 with absorption at or near 405 nm (e.g., from about 375 nm to about 435 nm) include curcumin, crocetin, porphyrin and derivatives thereof (e.g., etioporphyhn 1 (CAS 448-71 -5), and octaethyl porphyrin (CAS 2683-82-1 )), azo dyes (e.g., Mordant Orange (CAS 2243-76-7), Merthyl Yellow (CAS 60-11-7), 4-phenylazoaniline (CAS 60-09-3), and Alcian Yellow (CAS 61968-76-1 )), or the like.

Examples of other absorber dyes 239 include C.I. Solvent Yellow 93 and C.I. Solvent yellow 163.

Additional examples of suitable absorber dyes 239 include the following: 1 ) those described in U.S. Patent No. 5,079,135, Japanese Patent 2,910,042 B2, European Patent 0376327B1 , and Hong Kong Patent 1007621 A1 , all of which are assigned to Sony Corporation, Tokyo, and incorporated herein by reference; and 2) those described in U.S. Patent Application Publication No. 2002/0015858 and

Japanese Patent Application Publication 2002-002112, both of which are assigned to Toyo Ink Mfg. Co. Ltd., Tokyo, and incorporated herein by reference. Commercial dyes used in conventional DVD recording, such as IRGAPHOR® Ultragreen MX, IRGAPHOR® LASERVIOLET, and IRGAPHOR® 1699 (all of which are commercially available from Ciba, Tarrytown, NY), may also be effectively used as absorber dyes 239.

Other suitable absorber dyes 239 (i.e., radiation absorbing compounds) may be selected from aluminum quinoline complexes, porphyrins, porphins, indocyanine dyes, phenoxazine derivatives, phthalocyanine dyes, polymethyl indolium dyes, polymethine dyes or derivatives thereof (such as a pyrimidinetrione- cyclopentylidene), guaiazulenyl dyes, croconium dyes, polymethine indolium dyes, metal complex IR dyes, cyanine dyes, squarylium dyes, chalcogeno-pyryloarylidene dyes, indolizine dyes, pyrylium dyes, quinoid dyes, quinone dyes, azo dyes, and mixtures or derivatives thereof. 200704225 9

Still other suitable radiation absorbing compounds may also be used, and are known to those skilled in the art and can be found in such references as "Infrared Absorbing Dyes", Matsuoka, Masaru, ed., Plenum Press, New York, 1990 (ISBN 0- 306-43478-4) and "N ear- Infra red Dyes for High Technology Applications", Daehne, Resch-Genger, Wolfbeis, Kluwer Academic Publishers (ISBN 0-7923-5101 -0), both incorporated herein by reference.

Various radiation absorbing compounds/absorber dyes 239 may function as an antenna to absorb electromagnetic radiation of specific wavelengths and ranges. Generally, a radiation antenna which has a maximum light absorption at or in the vicinity of the desired development wavelength may be suitable for use in the embodiments disclosed herein. For example, the color forming composition may be optimized within a range for development using infrared radiation having a wavelength from about 720 nm to about 900 nm. Common CD-burning lasers have a wavelength of about 780 nm and can be adapted for forming images by selectively developing portions of the image layer. Radiation absorbing compounds/absorber dyes 239 which may be suitable for use in the infrared range include, but are not limited to, polymethyl indoliums, metal complex IR dyes, indocyanine green, polymethine dyes or derivatives thereof (such as pyhmidinetrione- cyclopentylidenes), guaiazulenyl dyes, croconium dyes, cyanine dyes, squarylium dyes, chalcogenopyryloarylidene dyes, metal thiolate complex dyes, bis(chalcogenopyrylo)polymethine dyes, oxyindolizine dyes, bis(aminoaryl)polymethine dyes, indolizine dyes, pyrylium dyes, quinoid dyes, quinone dyes, phthalocyanine dyes, naphthalocyanine dyes, azo dyes, hexafunctional polyester oligomers, heterocyclic compounds, and combinations thereof. Suitable pyhmidinethone-cyclopentylidene infrared antennae include, for example, 2,4,6(1 H,3H,5H)-pyrimidinethone 5-[2,5-bis[(1 ,3-dihydro- 1 ,1 ,3-dimethyl- 2H-indol-2-ylidene) ethylidene] cyclopentylidene]-1 ,3-dimethyl- (9Cl) (S0322 available from Few Chemicals, Germany).

Several specific polymethyl indolium compounds are available from Aldrich Chemical Company and include 2-[2-[2-chloro-3-[2-(1 ,3-dihydro-1 ,3,3-thmethyl-2/-/- 200704225 10

indol-2-ylidene)-ethylidene]-1 -cyclopenten-1 -yl-ethenyl]-1 ,3,3-trimethyl-3/-/-indoliunn perchlorate; 2-[2-[2-Chloro-3-[2-(1 ,3-dihydro-1 ,3,3-trimethyl-2H-indol-2-ylidene)- ethylidene]-1 -cyclopenten-1 -yl-ethenyl]-1 ,3,3-thnnethyl-3W-indoliunn chloride; 2-[2-[2- chloro-3-[(1 ,3~dihydro-3,3-dimethyl-1 -propyl-2H-indol-2-ylidene) ethyl idene]-1 - cyclohexen-1-yl] ethenyl]-3,3-dimethyl-1-propylindoliunn iodide; 2-[2-[2-chloro-3-[(1 ,3- dihydro-1 ,3,3-thnnethyl-2H-indol-2-ylidene) ethyl idene]-1 -cyclohexen-1 -yl]ethenyl]- 1 ,3,3-thmethylindolium iodide; 2-[2-[2-chloro-3~[(1 ,3-dihydro-1 ,3,v3-trimethyl-2H- indol-2-ylidene) ethylidene]-1 -cyclohexen-1 -yl]ethenyl]-1 ,3,3-thmethylindoliunn perchlorate; 2-[2-[3-[(1 ,3-dihydro-3,3-dimethyl-1 -propyl-2H-indol-2-ylidene) ethylidene]-2-(phenylthio)-1 - cyclohexen-1 -yl] ethenyl]-3,3-dimethyl-1 -propyl indolium perchlorate; and mixtures thereof.

Alternatively, the radiation absorbing compound/absorber dye 239 may be an inorganic compound (e.g., ferric oxide, carbon black, selenium, or the like).

In another embodiment, the radiation absorbing compound/absorber dye 239 may be selected for optimization of the color forming composition in a wavelength range from about 600 nm to about 720 nm, such as about 650 nm. Non-limiting examples of suitable absorber dyes 239 for use in this range of wavelengths include indocyanine dyes such as 3H-indolium,2-[5-(1 ,3-dihydro-3,3-dimethyl-1-propyl-2H- indol-2-ylidene)-1 ,3-pentadienyl]-3,3-dimethyl-1 -propyl-, iodide) (Dye 724 A_max 642 nm), 3H-indolium,1 -butyl-2-[5-(1-butyl-1 ,3-dihydro-3,3-dimethyl-2H-indo!-2-ylidene)- 1 ,3-pentadienyl]-3,3-dimethyl-, perchlorate (Dye 683 A_max 642 nm), and phenoxazine derivatives such as phenoxazin-5-ium,3,7- bis(diethylamino)-, perchlorate (oxazine 1 Amax = 645 nm). Phthalocyanine dyes having an A_max of about the desired development wavelength may also be used, such as, for example, silicon 2,3- napthalocyanine bis(thhexylsilyloxide) and matrix soluble derivatives of 2,3- napthalocyanine (both commercially available from Aldrich Chemical); matrix soluble derivatives of silicon phthalocyanine (as described in Rodgers, A.J. et al., 107 J. Phys. Chem. A 3503-3514, May 8, 2003), and matrix soluble derivatives of benzophthalocyanines (as described in Aoudia, Mohamed, 119 J. Am. Chem. Soc. 6029-6039, July 2, 1997); phthalocyanine compounds, such as those described in 200704225 1 1

U.S. Patent Nos. 6,015,896 and 6,025,486, which are each incorporated herein by reference, and Cirrus 715 (a phthalocyanine dye available from Avecia, Manchester, England having an A_max = 806 nm).

The contrast-forming agent precursor 240 used herein is a derivative of a contrast dye that converts to the contrast dye upon exposure to energy absorbed by the absorber dye 239. As such, the contrast-forming agent precursor 240 undergoes a detectable optical change in response to a threshold stimulus, i.e., energy absorbed by and transferred from the absorber dye 239. Generally, the contrast-forming agent precursor 240 is a contrast dye that has been reacted with a desirable protecting agent/group to form the dye derivative.

In an embodiment, the contrast dye used to form the dye derivative is selected from a dye having an amine function or a dye having an amide function. The amine or amide function reacts with the selected protecting group to produce the latent dye derivative. Non-limiting examples of suitable contrast dyes include 7,8-dimethylalloxazine (CAS 1086-80-2), 9-aminoacridine (CAS 52417-22-8), Solvent Brown 1 (CAS 6416-57-5), Sudan Orange G (CAS 2051 -85-6), diacetate (OAc₂), and diacyl (OCOR, where R is an alkyl or an aryl group) derivatives.

Any protecting agent that is capable of reacting with the selected contrast dye may be used in the embodiments disclosed herein. For amine or amide function protection, protecting agents such as amides, carbamates, tert.butyloxycarbonyl (t-BOC) (e.g., from reaction with t-BOC anhydride), 9- fluorenylmethyloxy (FMOC) (e.g., from reaction with FMOC chloride), 2- trimethylsilylethyl (TMSE), carbobenzyloxy (CBZ) (e.g., from reaction with CBZ chloride), arylsulfonyl amides, trityl derivatives, alkyloxycarbonyl, aryloxycarbonyl, and combinations thereof may be used.

Specific examples of the materials include BOC derivatives of dyes as shown below: 200704225 12

7,8-dιmethylalloxazιne CAS 1086-80-2 9-amιno acπdine CAS 52417-22-8 Solvent Brown 1 CAS 6416-57-5

BOC anhydride

Absorber+Light

quinazarin

In some instances, the modified dyes (i.e., the dye derivatives) have a light absorption maxima at a wavelength that is at least 100 nm apart from the wavelength of the radiation causing the contrast (i.e., the write/read wavelength). In other instances, the modified dyes (i.e., the dye derivatives) undergo a refractive index change of more than 0.2 at the write/read wavelength (due to its conversion to the contrast dye). As such, the dye derivative itself does not absorb energy at the wavelength of the radiation causing the contrast. As shown in Figure 2, when it is desired to make a mark 242, marking energy 110 (incident energy beam 152 shown in Figure 1 ) is directed in a desired manner at the recording/imaging medium 100. The form of the energy may vary depending, at least in part, upon the equipment available, ambient conditions, and desired result(s). Examples of energy (also referred to herein as radiation) that may be used include, but are not limited to, infra-red (IR) radiation, ultra-violet (UV) radiation, x-rays, or visible light. In these embodiments, imaging medium 100 is illuminated with light having the desired predetermined wavelength at the location where it is desirable to form a mark 242. Generally, the predetermined wavelength is absorbable by the absorber dye 239 and is at least 100 nm apart from the light absorption maxima of the dye derivative. 200704225 13

The absorber dye 239 in the marking layer 230 absorbs the energy and transfers the energy within the layer 230 to the contrast-forming agent precursor 240 (i.e., the dye derivative). The transferred energy triggers a chemical or physical change in the dye derivative. More specifically, the energy causes the protecting group to be removed, thereby producing the contrast dye (i.e., the parent of the dye derivative). The formation of the contrast dye results in absorption coefficient changes and/or refractive index changes in the exposed areas of the markable coating 230. As such, the detectable mark 242 is the result of a change in the optical properties of the markable coating 230 due to a change in the absorbance coefficient (k) of greater than 0.2, and/or a change in the refractive index (n) of greater than 0.2. Such changes may also occur due to a change in the physical dimension of the markable coating 230, such as a thickness change of >10 nm. The change(s) produce an optically detectable mark 242, which may manifest itself in the form of a produced color, a color change and/or a change in the contrast of the layer 230. Thus, if energy is applied to a desired region of the marking layer 230, an optically detectable mark 242 may be produced.

It is to be understood that the resulting optically detectable mark 242 absorbs energy at the wavelength of radiation causing the contrast (i.e., the write/read wavelength). It is believed that the use of the dye derivative as the contrast-forming agent precursor 240 substantially enables generating an optical change in desired regions of the markable coating 242. The contrast-forming agent precursor 240 does not become active as the dye until it has absorbed a stimulus which causes the protection group to detach. Depending on the contrast-forming agent precursor 240 selected, the marking layer 230 may become relatively more or relatively less absorbing at a desired wavelength upon activation. Many commercial and consumer products use a single wavelength for both read and write operations, and a contrast-forming agent precursor 240 that produces a mark 242 that is relatively absorbing (relative to the unmarked regions) at the read wavelength is particularly advantageous, as 200704225 14

such, it may be desirable to provide a contrast-forming agent precursor 240 that produces a mark 242 that is relatively absorbing at the read/write wavelength.

By way of example, if blue-violet light (radiation) is to be used as the read radiation, the marks 242 formed in the marking layer 230 are preferably a contrasting color, namely yellow to orange, indicating absorption of blue radiation. In certain embodiments, therefore, the marking layer 230 contains a dye derivative that, when activated to its dye, changes from being relatively non-absorbing at blue-violet wavelengths to being relatively absorbing at those wavelengths.

Laser light having blue, indigo, red and far-red wavelengths ranging from about 300 nm to about 980 nm may be used to develop the markable coatings 230 described herein. Therefore, recording/imaging media 100 may be selected for use in devices that emit wavelengths within this range. For example, if the light source 150 emits light having a wavelength of about 405 nm, the absorber dye 239 may be selected to absorb energy at or near that wavelength/wavelength band. In other embodiments, light sources 150 of other wavelengths/wavelength bands, including but not limited to 650 nm, 780 nm, 984 nm or 1084 nm may be used. In either case, the absorber dye 239 may be tuned to the selected wavelength/wavelength band so as to enhance localized energy absorption.

In still other embodiments, the embodiments disclosed herein may be used with a radiation source such as a laser or LED that emits light having blue and indigo wavelengths ranging from about 380 nm to about 420 nm. In particular, radiation sources such as the lasers used in certain DVD and laser disk recording equipment emit energy at a wavelength of about 405 nm.

The markable coatings 230 formed in the manner described herein can be applied to the surface of an imaging medium 100, such as a CD, DVD, HD-DVD, BLU-RAY disc or the like. Further, discs may be used in systems disclosed herein that include optical recording and/or reading capabilities. Such systems typically include a laser emitting light (e.g., light source 150) having a predetermined wavelength and power. Systems that include optical reading capability further 200704225 15

include an optical pickup unit 157 coupled to the laser. Lasers and optical pickup units are known in the art.

Referring again to Figures 1 and 2, an exemplary read/write system 170 includes the processor 166, the laser 150, and the optical pickup 157. Signals 163 from processor 166 cause laser 150 to emit light at the desired power level. Light reflected 165 from the disc surface is detected by pickup 157, which in turn sends a corresponding signal 165 back to processor 166.

When it is desired to record, the imaging medium 100 is positioned such that light emitted by laser 150 is incident on the marking surface 230. The laser 150 is operated such that the light incident on the marking layer 230 transfers sufficient energy to the surface to cause a mark 242. Both the laser 150 and the position of the imaging medium 100 are controlled by the processor 166, such that light is emitted by the laser 150 in pulses that form a pattern of marks 242 on the surface of the imaging medium 100. When it is desired to read a pattern of marks 242 on the surface of an imaging medium 100, the imaging medium 100 is again positioned such that light emitted by laser 150 is incident on the marked surface. The laser 150 is operated such that the light incident at the surface does not transfer sufficient energy to the surface to cause a mark 242. Instead, the incident light is reflected from the marked surface to a greater or lesser degree, depending on the absence or presence of a mark 242. As the imaging medium 100 moves, changes in reflectance are recorded by optical pickup 157 which generates a signal 165 corresponding to the marked surface. Both the laser 150 and the position of the imaging medium 100 are controlled by the processor 166 during the reading process.

While several embodiments have been described in detail, it will be apparent to those skilled in the art that the disclosed embodiments may be modified. Various modifications may be made, including the use of multiple lasers, processors, and/or pickups and the use of light having different wavelengths. The read components may be separated from the write components, or may be 200704225 16

combined in a single device. Therefore, the foregoing description is to be considered exemplary rather than limiting.

Claims

200704225 17What is claimed is:

1. An optical data recording medium (100), comprising: a substrate (220); and a transparent markable coating (230) established on the substrate (220), the coating (230) including an absorber dye (239) tuned to a predetermined write and read wavelength and a contrast-forming agent precursor (240) including a derivative of a contrast dye that converts to the contrast dye upon exposure to energy from the absorber dye (239).

2. The optical data recording medium (100) as defined in claim 1 wherein i) the dye derivative has a light absorption maxima at a wavelength that is at least 100 nm apart from the predetermined write and read wavelength, ii) the markable coating (230) undergoes a refractive index (n) change of more than 0.2 at the predetermined write and read wavelength, iii) the markable coating (230) undergoes an absorption coefficient (k) change of more than 0.2 at the predetermined write and read wavelength, or iv) combinations of i, ii and iii.

3. The optical data recording medium (100) as defined in any of claims 1 and 2 wherein the dye derivative includes the contrast dye reacted with a protecting group selected from t-BOC, CBZ, FMOC, alkyloxycarbonyl, aryloxycarbonyl, and combinations thereof.

4. The optical data recording medium (100) as defined in any of claims 1 through 3 wherein the contrast dye is selected from a dye having an amine function or an amide function that reacts with a protecting group.

5. The optical data recording medium (100) as defined in any of claims 1 through 4 wherein the contrast dye is selected from 7,8-dimethylalloxazine, 9- aminoachdine, Solvent Brown 1 , Sudan Orange G, diacetate, and diacyl derivatives. 200704225 18

6. The optical data recording medium (100) as defined in any of claims 1 through 5 wherein the absorber dye (239) is selected from a dye having a peak absorption at a 405 nm band, a dye having a peak absorption at a 650 nm band, a dye having a peak absorption at a 780 nm band, a dye having a peak absorption at a 984 nm band, or a dye having a peak absorption at a 1084 nm band.

7. A system (170) for at least one of recording or transmitting optical data or visual images, comprising: an optical data or visual image recording medium (100) including: a substrate (220); and a transparent markable coating (230) established on the substrate (220), the transparent markable coating (230) including an absorber dye (239) tuned to a predetermined write and read wavelength and a contrast-forming agent precursor (240) including a derivative of a contrast dye that converts to the contrast dye upon exposure to energy from the absorber dye (239); and a light source (150) positioned so as to illuminate the recording medium (100) in a predetermined manner to i) cause the absorber dye (239) to capture light energy from the light source (150) and transfer such light energy to the contrast- forming agent precursor (240) to convert the dye derivative to the contrast dye to form at least one optically detectable mark (242), or ii) cause at least one optically detectable mark (242) previously formed on the markable coating (100) to produce at least one readable pattern.

8. The system (170) as defined in claim 7 wherein i) the dye derivative has a light absorption maxima at a wavelength that is at least 100 nm apart from the predetermined write and read wavelength, ii) the markable coating (100) undergoes a refractive index (n) change of more than 0.2 at the predetermined write and read wavelength, iii) the markable coating (100) undergoes an absorption 200704225 19

coefficient (k) change of more than 0.2 at the predetermined write and read wavelength, or iv) combinations of i, ii and iii.

9. The system (170) as defined in any of claims 7 and 8 wherein the at least one optically detectable mark (242) has a light absorption maxima at the predetermined write and read wavelength.

10. The system (170) as defined in any of claims 7 through 9 wherein the dye derivative includes the contrast dye reacted with a protecting group selected from t-BOC, CBZ, FMOC, alkyloxycarbonyl, aryloxycarbonyl, and combinations thereof.

11. The system (170) as defined in any of claims 7 through 10 wherein the contrast dye is selected from a dye having an amine function or an amide function that reacts with a protecting group.

12. The system (170) according to any of claims 7 through 11 wherein for optically transmitting data and visual images, the system (170) further comprises: a sensor (157) positioned so as to detect the at least one readable pattern of the at least one optically detectable mark (242) previously formed on the medium (100), the sensor (157) reading the at least one readable pattern as the medium (100) moves in relation to the sensor (157); a processor (166) to which the sensor (157) sends at least one signal based on the at least one readable pattern detected by the sensor (157); an analyzer (168) to which the processor (166) sends the at least one signal, the analyzer (168) configured to analyze the at least one signal and generate data therefrom; and a computer data base configured to receive and store the data from the analyzer (168), wherein the is accessible via the computer data base. 200704225 20

13. A method for at least one of i) optically recording data or visual images, or ii) reading optically recorded data or visual images, the method comprising: providing an optical data or visual image recording medium (100) including: a substrate (220); and a transparent markable coating (230) on the substrate (220), the transparent markable coating (230) including an absorber dye (239) tuned to a predetermined write and read wavelength and a contrast-forming agent precursor (240) including a derivative of a contrast dye that converts to the contrast dye upon exposure to energy from the absorber dye (239); and beaming light from a light source (150) to i) cause the absorber dye (239) to capture light energy from the light source (150) and transfer such light energy to the contrast-forming agent precursor (240) to convert the dye derivative to the contrast dye to form at least one optically detectable mark (242), or ii) cause at least one optically detectable mark (242) previously formed on the markable coating (100) to produce at least one readable pattern.

14. The method as defined in claim 13 wherein the at least one previously formed optically detectible mark (242) produces the at least one readable pattern, and wherein the method further comprises: detecting by a sensor (157) the at least one readable pattern of the at least one previously formed optically detectable mark (242) illuminated by the light on the medium (100), the sensor (157) reading the at least one readable pattern as the medium (100) moves in relation to the sensor (157); and sending from the sensor (157) to a processor (166) at least one signal based on the at least one readable pattern detected by the sensor (157).

15. The method as defined in any of claims 13 and 14 wherein i) the dye derivative has a light absorption maxima at a wavelength that is at least 100 nm apart from the predetermined write and read wavelength, ii) the markable coating (100) undergoes a refractive index (n) change of more than 0.2 at the 200704225 21

predetermined write and read wavelength, iii) the markable coating (100) undergoes an absorption coefficient (k) change of more than 0.2 at the predetermined write and read wavelength, or iv) combinations of i, ii and iii.

16. The method as defined in any of claims 13 through 15 wherein the dye derivative includes the contrast dye reacted with a protecting agent selected from t- BOC, CBZ, FMOC, alkyloxycarbonyl, aryloxycarbonyl, and combinations thereof, and wherein the contrast dye is selected from a dye having an amine function or an amide function that reacts with a protecting group.

17. The method as defined in any of claims 13 through 16 wherein providing the optical data or visual image recording medium (100) includes establishing the transparent markable coating (230) on the substrate (220).

18. A method of making an optical data recording medium (100), the method comprising: chemically modifying a contrast dye to form a dye derivative that converts to the contrast dye upon exposure to energy from an absorber dye (239) tuned to a predetermined write and read wavelength; mixing the absorber dye (239) with the dye derivative to form a transparent markable coating (230); and establishing the transparent markable coating (230) on a substrate (220).

19. The method as defined in claim 18 wherein chemically modifying the contrast dye includes reacting the contrast dye with a protecting group.

20. The method as defined in any of claims 18 and 19 wherein i) the dye derivative has a light absorption maxima at a wavelength that is at least 100 nm apart from the predetermined write and read wavelength, ii) the markable coating (100) undergoes a refractive index (n) change of more than 0.2 at the 200704225 22

21. An apparatus for at least one of recording or transmitting optical data or visual images, comprising: an optical data or visual image recording medium (100) including a substrate

(220) and a transparent markable coating (230) on the substrate (220), the markable coating (230) including an absorber dye (239) tuned to a predetermined write and read wavelength and a contrast-forming agent precursor (240) including a derivative of a contrast dye that converts to the contrast dye upon exposure to energy from the absorber dye (239); and a recording or transmitting device (170) including a light source (150) positioned to transmit light beams to at least one of i) cause the absorber dye (239) to capture light energy from the light source (150) and transfer such light energy to the contrast-forming agent precursor (240) to convert the dye derivative to the contrast dye to form an optically detectable mark (242), or ii) cause at least one optically detectable mark (242) previously formed on the markable coating (100) to produce at least one readable pattern.

22. The apparatus as defined in claim 21 wherein i) the dye derivative has a light absorption maxima at a wavelength that is at least 100 nm apart from the predetermined write and read wavelength, ii) the markable coating (100) undergoes a refractive index (n) change of more than 0.2 at the predetermined write and read wavelength, iii) the markable coating (100) undergoes an absorption coefficient (k) change of more than 0.2 at the predetermined write and read wavelength, or iv) combinations of i, ii and iii.

23. The apparatus as defined in any of claims 21 and 22 wherein the absorber dye (239) is selected from a dye having a peak absorption at a 405 nm 200704225 23

band, a dye having a peak absorption at a 650 nm band, a dye having a peak absorption at a 780 nm band, a dye having a peak absorption at a 984 nm band, or a dye having a peak absorption at a 1084 nm band; wherein the dye derivative includes the contrast dye reacted with a protecting group selected from t-BOC, CBZ, FMOC, alkyloxycarbonyl, aryloxycarbonyl, and combinations thereof; and wherein the contrast dye is selected from a dye having an amine function or an amide function that reacts with the protecting group.

24. The apparatus as defined in any of claims 21 through 23 wherein for optically transmitting data or visual images, the apparatus further comprises: a sensor (157) positioned so as to detect the at least one readable pattern of the at least one previously formed optically detectable mark (242) on the recording medium (100), the sensor (157) reading the at least one readable pattern as the recording medium (100) moves in relation to the sensor (157); and a processor (166) to which the sensor (157) sends at least one signal based on the at least on readable pattern detected by the sensor (157).