JP2007287298A - Optical recording medium and information-recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which can excellently record even with a short wavelength laser beam, clarify an optical constant required to a recording layer, in particular, a value of a real part (refractive index) of a complex refractive index and a variation in refractive index before and after recording, and is excellent in recording characteristics. <P>SOLUTION: A second optical recording medium 10B is provided with a second substrate 24, a second write once type recording layer 26 formed on the second substrate 24 and a second light-reflecting layer 30. The second write once type recording layer 26 is irradiated with laser light 46 having a wavelength of 450 nm or shorter to record/reproduce information. In this case, the real part of the complex refractive index of the second write once type recording layer 26 is 1.2-1.5 before the information is recoded to the second write once type recording layer 26 with the laser light 46, and the real part of the complex refractive index of the second write once type recording layer 26 is 1.7-1.9 after the information is recoded to the second write once type recording layer 26 with the laser light 46. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat mode type optical recording medium suitable for recording and / or reproducing information by irradiating a recording layer with laser light, and an information recording method for the optical recording medium.

  Recently, by using a laser beam having a wavelength shorter than that of a write-once DVD (so-called DVD-R), development of an optical disc having a larger recording capacity has been advanced. An optical recording medium used has been proposed.

  Examples of the dye used for the recording layer of such an optical recording medium include a dye having a low reflectance after recording (referred to as a first dye) and a dye having a high reflectance after recording (referred to as a second dye). . Information is recorded on the first dye at an absorption wavelength longer than the maximum absorption peak λmax of the first dye. For the second dye, information is recorded at an absorption wavelength shorter than the maximum absorption peak λmax of the second dye.

  In order to obtain good recording characteristics in a recording layer containing the first dye, it is generally known that the real part (n) of the complex refractive index of the recording layer before recording needs to be increased. . However, in an optical recording medium recorded / reproduced at 405 nm, it is difficult to obtain a first dye having a maximum absorption at a shorter wavelength than the recording / reproduction wavelength, and it is difficult to obtain a large real part of the complex refractive index. In addition to being difficult to obtain, it was difficult to achieve both light fastness.

  On the other hand, for the second dye, at present, in order to record information at an absorption wavelength shorter than the maximum absorption peak λmax of the second dye, the optical constant required for the recording layer and the change in the optical constant before and after recording are recorded. Is not clear.

  By the way, although the information recording by the short wavelength with respect to an optical recording medium is disclosed, for example in patent documents 1-6, there is no description regarding an optical constant.

  In Patent Documents 7 and 8, there is a description of n <1.2, k> 0.15 (k: imaginary part of complex refractive index), but only an optical constant related to a dye before recording, and changes before and after recording. For, there is no description of specific numerical values, only that n increases. In addition, the optical recording media described in Patent Documents 7 and 8 are configured on the assumption of a cover layer of 0.1 mm.

  In Patent Document 9, the real part of the complex refractive index before recording (refractive index nb) is 2.3 ≦ nb ≦ 4.0, and the real part of the complex refractive index after recording by decomposition (refractive index na). And the real part (refractive index nb) of the complex refractive index before recording is selected as 0.19 ≦ | na−nb | /nb≦0.62, The imaginary part (absorption coefficient k) is 0.01 ≦ k <0.1 and the film thickness d is 50 nm ≦ d ≦ 250 nm, and the imaginary part (absorption) of the complex refractive index before recording due to decomposition. An optical recording medium is described in which the coefficient k) is 0.01 ≦ k ≦ 0.2 and the film thickness d is 10 nm ≦ d ≦ 50 nm. However, the optical recording medium described in Patent Document 9 is also based on a 0.1 mm cover layer. In addition, recording is performed using reflectance modulation, and the thickness of the reflective layer is 20 nm or less. The principle is fundamentally different from the method of obtaining the signal amplitude by phase difference modulation.

Japanese Patent Laid-Open No. 2005-293772 JP 2005-293773 A JP 2005-288972 A JP-A-2005-297406 JP-A-2005-297407 JP 2002-74740 A JP 2004-98541 A JP 2004-98542 A JP 2001-273672 A

  The present invention can perform good recording even with a short-wavelength laser beam, and the optical constants required for the recording layer, in particular, the value of the real part n (hereinafter simply referred to as the refractive index) of the complex refractive index, and the refraction before and after recording. It is an object of the present invention to provide an optical recording medium and an information recording method in which a change in the rate n is clarified and recording characteristics are good.

  An optical recording medium according to a first aspect of the present invention includes a substrate, a recording layer formed on the substrate, and a reflective layer. The recording layer is irradiated with laser light to record and / or record information. Alternatively, in the optical recording medium to be reproduced, the real part of the complex refractive index of the recording layer before recording information on the recording layer by the laser beam is 1.2 to 1.5, and the recording is performed by the laser beam. The real part of the complex refractive index of the recording layer after recording information on the layer is 1.7 to 1.9.

  Thereby, information can be recorded satisfactorily even with a laser beam with a short wavelength of, for example, 450 nm or less, and an optical recording medium with good recording characteristics can be obtained.

  In the first aspect of the present invention, the recording layer may have an optical characteristic that a reflectance after information is recorded by the laser light is lower than a reflectance before the information is recorded. .

  In the first aspect of the present invention, the recording layer may contain a dye compound, and the dye compound may be a dye compound having trimethine oxonol as an anion and a metal complex as a cation.

  In this case, the dye compound is preferably a compound represented by the following general formula (1).

General formula (1)

  In the general formula (1), A, B, C and D are electron withdrawing groups in which the sum of the Hammett σp values of A and B and the sum of the Hammett σp values of C and D are each 0.6 or more. Yes, A and B or C and D may be linked to form a ring, R represents a substituent on the methine carbon, m = 1, n represents an integer of 0 to 2m + 1, and n is 2 In the case of the above integers, a plurality of R may be the same or different from each other, and may be connected to each other to form a ring, Yt + represents a t-valent cation, and t is an integer of 1 to 10 Represents.

  In the first aspect of the present invention, the groove depth of the substrate is preferably 30 to 130 nm. The groove width of the substrate is preferably 140 to 240 nm.

  In the first aspect of the present invention, the reflective layer preferably has a thickness of 50 to 200 nm. Thereby, there is almost no change in reflectance before and after recording, and phase difference modulation can be realized.

  In the first aspect of the present invention, the wavelength of the laser beam is 405 nm, the numerical aperture of the objective lens for condensing the laser beam on the recording layer is 0.65, and the distance from the end surface of the substrate to the recording layer is It may correspond to 0.6 mm.

  Next, in the information recording method according to the second aspect of the present invention, information is recorded by the phase difference modulation method by irradiating the optical recording medium according to the first aspect of the present invention with a laser beam having a wavelength of 450 nm or less. It is characterized by.

  Thereby, information can be recorded satisfactorily even with a laser beam having a short wavelength of 450 nm or less, for example, and the recording characteristics are good.

  As described above, according to the optical recording medium and the information recording method according to the present invention, an optical recording medium that can record information satisfactorily even with a laser beam having a short wavelength of, for example, 450 nm or less and has good recording characteristics. Obtainable.

  Embodiments of an optical recording medium and an information recording method according to the present invention will be described below with reference to FIGS.

  The optical recording medium of the present invention includes an optical recording medium according to the first aspect shown in FIG. 1 (hereinafter simply referred to as first optical recording medium 10A) and an optical recording medium according to the second aspect shown in FIG. Hereinafter, it is preferably simply referred to as the second optical recording medium 10B).

  As shown in FIG. 1, the first optical recording medium 10A has a first write-once recording layer 14 containing a dye on a first substrate 12 having a thickness of 0.7 to 2 mm, and a thickness of 0.01 to 0. And a cover layer 16 of 5 mm in this order. Specifically, for example, the first light reflection layer 18, the first write-once recording layer 14, the barrier layer 20, the first adhesive layer 22, and the cover layer 16 are provided in this order on the first substrate 12. .

  As shown in FIG. 2, the second optical recording medium 10B has a second write-once recording layer 26 containing a dye and a thickness of 0.1 on a second substrate 24 having a thickness of 0.1 to 1.0 mm. And a protective substrate 28 of ˜1.0 mm in this order. Specifically, for example, the second write-once recording layer 26, the second light reflection layer 30, the second adhesive layer 32, and the protective substrate 28 are provided on the second substrate 24 in this order.

  In the first optical recording medium 10A, as shown in FIG. 1, the track pitch of the first pregroove 34 formed on the first substrate 12 is 50 to 500 nm, the groove width is 25 to 250 nm, and the groove depth is 5 to 5. It is preferable that it is 150 nm.

  In the second optical recording medium 10B, as shown in FIG. 2, the track pitch of the second pregroove 36 formed on the second substrate 24 is 200 to 600 nm, the groove width is 50 to 300 nm, and the groove depth is 30 to. It is preferably 200 nm and the wobble amplitude is 10 to 50 nm.

  As shown in FIG. 1, the first optical recording medium 10 </ b> A has at least a first substrate 12, a first write-once recording layer 14, and a cover layer 16. explain.

[First substrate 12 of first optical recording medium 10A]
As shown in FIG. 1, the first substrate 12 of the preferred first optical recording medium 10A has a shape in which all of the track pitch, groove width (half width), groove depth, and wobble amplitude are in the following ranges. It is essential that the first pregroove 34 (guide groove) is formed. The first pregroove 34 is provided in order to achieve a higher recording density than that of a CD-R or DVD-R. For example, the first optical recording medium 10A corresponds to a blue-violet laser. It is suitable for use as a medium.

  The track pitch of the first pregroove 34 is essential to be in the range of 50 to 500 nm, the upper limit is preferably 420 nm or less, more preferably 370 nm or less, and further preferably 330 nm or less. preferable. Further, the lower limit is preferably 100 nm or more, more preferably 200 nm or more, and further preferably 260 nm or more.

  If the track pitch is less than 50 nm, it is difficult to form the first pregroove 34 accurately, and a problem of crosstalk may occur. If the track pitch exceeds 500 nm, the recording density may decrease. is there.

  The groove width (half width) of the first pre-groove 34 in the groove 40 (concave portion in the first substrate 12) is in the range of 140 to 240 nm, preferably 145 to 230 nm, and more preferably 150 to 220 nm. . If the groove width is too narrow, it is difficult to form the groove portion (groove 40), and if the groove width is too wide, it is difficult to form the inter-groove portion (land 38).

  The groove depth of the first pregroove 34 is in the range of 30 to 130 nm, preferably 33 to 110 nm, and more preferably 35 to 80 nm. If the groove depth is too deep, there is a problem that molding becomes difficult. If the groove depth is too shallow, tracking becomes unstable.

  Further, the upper limit of the groove inclination angle of the first pregroove 34 is preferably 80 ° or less, more preferably 70 ° or less, further preferably 60 ° or less, and 50 ° or less. It is particularly preferred. Further, the lower limit value is preferably 20 ° or more, more preferably 30 ° or more, and further preferably 40 ° or more.

  If the groove inclination angle of the first pre-groove 34 is less than 20 °, sufficient tracking error signal amplitude may not be obtained. If it exceeds 80 °, it is difficult to mold the first substrate 12 (such as injection molding). .

  As the first substrate 12 used in the first optical recording medium 10A, various materials used as substrate materials for conventional optical recording media can be arbitrarily selected and used.

  Specifically, glass; acrylic resin such as polycarbonate and polymethyl methacrylate; vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer; epoxy resin; amorphous polyolefin; polyester; metal such as aluminum; These may be used together if desired.

  Among the above materials, thermoplastic resins such as amorphous polyolefin and polycarbonate are preferable, and polycarbonate is particularly preferable from the viewpoints of moisture resistance, dimensional stability, and low price.

  When these resins are used, the first substrate 12 can be manufactured by injection molding.

  Moreover, the thickness of the 1st board | substrate 12 needs to be the range of 0.7-2 mm, and it is preferable that it is the range of 0.9-1.6 mm, and shall be 1.0-1.3 mm. Is more preferable.

  In addition, it is preferable to form an undercoat layer on the surface of the first substrate 12 on the side where the first light reflecting layer 18 described later is provided for the purpose of improving the flatness and the adhesive force.

  Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfone. Polymer materials such as chlorinated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate; silane coupling agents And the like.

  The undercoat layer is prepared by dissolving or dispersing the above materials in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the surface of the first substrate 12 by a coating method such as spin coating, dip coating, or extrusion coating. It can be formed by coating. The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, and preferably in the range of 0.01 to 10 μm.

[First Write-once Recording Layer 14 of First Optical Recording Medium 10A]
The first write-once recording layer 14 of the first optical recording medium 10A has an optical characteristic that the reflectance after information is recorded by the laser light 46 is higher than the reflectance before information is recorded.

  The first write-once recording layer 14 contains a dye compound. This dye compound is preferably a dye compound having trimethine oxonol as an anion and a metal complex as a cation.

  In this case, the dye compound is preferably a compound represented by the following general formula (1).

General formula (1)

  In the general formula (1), A, B, C and D are electron withdrawing groups in which the sum of the Hammett σp values of A and B and the sum of the Hammett σp values of C and D are each 0.6 or more. Yes, A and B or C and D may be linked to form a ring, R represents a substituent on the methine carbon, m = 1, n represents an integer of 0 to 2m + 1, and n is 2 In the case of the above integers, a plurality of R may be the same or different from each other, and may be connected to each other to form a ring, Yt + represents a t-valent cation, and t is an integer of 1 to 10 Represents.

  Further, the first write-once recording layer 14 of the preferred first optical recording medium 10A is prepared by dissolving the dye compound in a suitable solvent together with a binder or the like, and then preparing the coating liquid on the substrate or It forms by apply | coating on the 1st light reflection layer 18 mentioned later, forming a coating film, and drying. Here, the first write-once recording layer 14 may be a single layer or a multilayer. In the case of a multilayer structure, the step of applying the coating liquid is performed a plurality of times.

  The concentration of the dye in the coating solution is generally in the range of 0.01 to 15% by mass, preferably in the range of 0.1 to 10% by mass, more preferably in the range of 0.5 to 5% by mass, most preferably. It is the range of 0.5-3 mass%.

  Examples of the solvent for the coating solution include esters such as butyl acetate, ethyl lactate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; dimethylformamide and the like Amides; Hydrocarbons such as methylcyclohexane; Ethers such as tetrahydrofuran, ethyl ether, dioxane; Alcohols such as ethanol, n-propanol, isopropanol, n-butanol diacetone alcohol; 2,2,3,3-tetrafluoropropanol, etc. Fluorinated solvents; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether; That.

  The above solvents can be used alone or in combination of two or more in consideration of the solubility of the dye used. In the coating solution, various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be added according to the purpose.

  Examples of the coating method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method.

  At the time of application, the temperature of the coating solution is preferably in the range of 23 to 50 ° C, more preferably in the range of 24 to 40 ° C, and particularly preferably in the range of 25 to 35 ° C.

  The thickness of the first write-once recording layer 14 formed in this manner is preferably 200 nm or less, more preferably 150 nm or less, and more preferably 100 nm on the groove 40 (concave portion in the first substrate 12). More preferably, it is more preferably 70 nm or less. The lower limit is preferably 10 nm or more, more preferably 15 nm or more, further preferably 20 nm or more, and particularly preferably 25 nm or more.

  Further, the thickness of the first write-once recording layer 14 is preferably 150 nm or less, more preferably 100 nm or less, and 70 nm or less on the land 38 (convex portion in the first substrate 12). Is more preferable. The lower limit is preferably 3 nm or more, more preferably 5 nm or more, and even more preferably 8 nm or more.

  Further, the ratio (t1 / t2) between the thickness t1 of the first write-once recording layer 14 on the groove 40 and the thickness t2 of the first write-once recording layer 14 on the land 38 is 0.1 or more. Is preferably 0.2 or more, more preferably 0.25 or more, and particularly preferably 0.7 or more. The upper limit value is preferably less than 1, more preferably 0.9 or less, further preferably 0.85 or less, and particularly preferably 0.8 or less.

  When the coating solution contains a binder, examples of the binder include natural organic polymer materials such as gelatin, cellulose derivatives, dextran, rosin, and rubber; hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene. , Polyvinyl chloride, polyvinylidene chloride, vinyl resins such as polyvinyl chloride / polyvinyl acetate copolymer, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resin, butyral And synthetic organic polymers such as resins, rubber derivatives, and initial condensates of thermosetting resins such as phenol / formaldehyde resins. When a binder is used in combination as the material of the first write-once recording layer 14, the amount of binder used is generally in the range of 0.01 to 50 times (mass ratio) with respect to the dye, preferably It is in the range of 0.1 times to 5 times (mass ratio).

  In addition, the first write-once recording layer 14 can contain various anti-fading agents in order to improve the light resistance of the first write-once recording layer 14. As the anti-fading agent, a singlet oxygen quencher is generally used. As the singlet oxygen quencher, those described in publications such as known patent specifications can be used.

  Specific examples thereof include JP-A Nos. 58-175893, 59-81194, 60-18387, 60-19586, 60-19587, and 60-35054. 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, JP-A-60-47069, JP-A-63-209995, JP-A-4-25492, JP-B-1-38680, JP-A-6-26028, etc., German Patent 350399, and Nihon Kagaku Listed in the October 1992 issue, page 1141, etc.

  The amount of the anti-fading agent such as the singlet oxygen quencher used is usually in the range of 0.1 to 200% by weight, preferably in the range of 0.5 to 180% by weight, based on the amount of the dye. Preferably, it is the range of 3-160 mass%, Most preferably, it is the range of 5-140 mass%.

  Here, optical characteristics before and after recording of the first write-once recording layer 14 containing a dye will be described. “Before recording” means a stage before information is recorded on the first write-once recording layer 14 by the laser light 46, and “after recording” means after recording information on the first write-once recording layer 14 by the laser light 46. A stage.

  As the optical characteristics of the first write-once recording layer 14, the real part of the complex refractive index of the first write-once recording layer before recording is 1.2 to 1.5, and the first write-once recording after recording is performed. The real part of the complex refractive index of the layer is preferably 1.7 to 1.9.

  Further, the lower limit of the imaginary part of the complex refractive index before recording of the first write-once recording layer is preferably 0.15 or more, more preferably 0.17 or more, and the upper limit is preferably 0.5 or less, more preferably. 0.4 or less. If the imaginary part of the complex index of refraction is too small, the sensitivity tends to deteriorate. On the other hand, if it is too large, the reflectance becomes too low. The imaginary part of the complex refractive index after recording is preferably 0.25 or less, more preferably 0.2 or less. If the imaginary part of the refractive index increases with recording, the signal amplitude decreases, which is not preferable, and the reproduction durability may deteriorate.

  With this configuration, information can be recorded favorably even with a laser beam having a short wavelength of, for example, 450 nm or less, and an optical recording medium with good recording characteristics can be obtained.

[Cover Layer 16 of First Optical Recording Medium 10A]
The cover layer 16 of the preferred first optical recording medium 10A is bonded to the first write-once recording layer 14 described above or a barrier layer 20 described later via a first adhesive layer 22 made of an adhesive, an adhesive, or the like. .

  The cover layer 16 used in the first optical recording medium 10A is not particularly limited as long as it is a transparent material film, but is not limited to acrylic resins such as polycarbonate and polymethyl methacrylate; polyvinyl chloride, vinyl chloride copolymers and the like. It is preferable to use a vinyl chloride resin; an epoxy resin; an amorphous polyolefin; a polyester; cellulose triacetate or the like, and more preferably, polycarbonate or cellulose triacetate is used.

  Note that “transparent” means that the transmittance is 80% or more with respect to light used for recording and reproduction.

  The cover layer 16 may contain various additives as long as the effects of the present invention are not hindered. For example, a UV absorber for cutting light having a wavelength of 400 nm or less and / or a pigment for cutting light having a wavelength of 500 nm or more may be contained.

  Further, as the surface physical properties of the cover layer 16, it is preferable that the surface roughness is 5 nm or less for both the two-dimensional roughness parameter and the three-dimensional roughness parameter.

  Further, from the viewpoint of the concentration of light used for recording and reproduction, the birefringence of the cover layer 16 is preferably 10 nm or less.

  The thickness of the cover layer 16 is appropriately defined by the wavelength of the laser beam irradiated for recording and reproduction and the NA of the first objective lens 42. In the first optical recording medium 10A, the thickness of the cover layer 16 is 0.01. It is in the range of -0.5mm, and it is more preferable that it is the range of 0.05-0.12mm.

  The total thickness of the cover layer 16 and the first adhesive layer 22 is preferably 0.09 to 0.11 mm, and more preferably 0.095 to 0.105 mm.

  The light incident surface of the cover layer 16 may be provided with a hard coat layer 44 (protective layer) for preventing the light incident surface from being damaged when the first optical recording medium 10A is manufactured.

  As the adhesive used for the first adhesive layer 22, for example, a UV curable resin, an EB curable resin, a thermosetting resin, or the like is preferably used, and a UV curable resin is particularly preferably used.

  When using a UV curable resin as an adhesive, prepare the coating solution by dissolving the UV curable resin as it is or in an appropriate solvent such as methyl ethyl ketone or ethyl acetate, and supply it to the surface of the barrier layer 20 from the dispenser. Also good. Further, in order to prevent warpage of the first optical recording medium 10A to be manufactured, it is preferable that the UV curable resin constituting the first adhesive layer 22 has a small curing shrinkage rate. Examples of such UV curable resins include UV curable resins such as “SD-640” manufactured by Dainippon Ink and Chemicals, Inc.

  For example, a predetermined amount of the adhesive is applied onto the bonding surface including the barrier layer 20, and the cover layer 16 is placed thereon. Then, the adhesive is applied by spin coating to the bonding surface and the cover layer. It is preferable to cure the film after it has been uniformly spread between the two.

  The thickness of the 1st contact bonding layer 22 which consists of such an adhesive agent has the preferable range of 0.1-100 micrometers, More preferably, it is the range of 0.5-50 micrometers, More preferably, it is the range of 10-30 micrometers.

  In addition, as the pressure-sensitive adhesive used for the first adhesive layer 22, an acrylic, rubber-based, or silicon-based pressure-sensitive adhesive can be used. From the viewpoint of transparency and durability, an acrylic pressure-sensitive adhesive is preferable. . As such an acrylic pressure-sensitive adhesive, 2-ethylhexyl acrylate, n-butyl acrylate and the like are the main components, and in order to improve cohesion, short-chain alkyl acrylates and methacrylates such as methyl acrylate, ethyl acrylate, and methyl methacrylate are used. And acrylic acid, methacrylic acid, acrylamide derivatives, maleic acid, hydroxylethyl acrylate, glycidyl acrylate, and the like, which can be crosslinking points with the crosslinking agent, are preferably used. The glass transition temperature (Tg) and the crosslinking density can be changed by appropriately adjusting the mixing ratio and type of the main component, the short chain component, and the component for adding a crosslinking point.

  As a crosslinking agent used together with the said adhesive, an isocyanate type crosslinking agent is mentioned, for example. Such isocyanate-based crosslinking agents include tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine isocyanate, isophorone diisocyanate, triphenylmethane triisocyanate, and the like. Isocyanates, products of these isocyanates with polyalcohols, and polyisocyanates formed by condensation of isocyanates can be used. Commercially available products of these isocyanates include Coronate L, Coronate HL, Coronate 2030, Coronate 2031, Millionate MR, Millionate HTL manufactured by Nippon Polyurethane; Takenate D-102 and Takenate D-110N manufactured by Takeda Pharmaceutical Co., Ltd. , Takenate D-200, Takenate D-202; Death Module L, Death Module IL, Death Module N, Death Module HL;

  The pressure-sensitive adhesive may be uniformly applied in a predetermined amount on the surface to be bonded comprising the barrier layer 20, and the cover layer 16 may be placed thereon and then cured. A predetermined amount may be uniformly applied to one surface to form a pressure-sensitive adhesive coating, and the coating may be bonded to the surface to be bonded, and then cured.

  Moreover, you may use the commercially available adhesive film in which the adhesive layer was previously provided for the cover layer 16. FIG.

  The thickness of the 1st contact bonding layer 22 which consists of such an adhesive has the preferable range of 0.1-100 micrometers, More preferably, it is the range of 0.5-50 micrometers, More preferably, it is the range of 10-30 micrometers.

[Other Layers in First Optical Recording Medium 10A]
The preferred first optical recording medium 10A may have other arbitrary layers in addition to the above-described essential layers as long as the effects of the present invention are not impaired. Other optional layers include, for example, a label layer having a desired image formed on the back surface of the first substrate 12 (the back surface with respect to the formation surface of the first write-once recording layer 14), the first substrate 12 and the first layer A first light reflection layer 18 (described later) provided between the first write-once recording layer 14, a barrier layer 20 (described later) provided between the first write-once recording layer 14 and the cover layer 16, and a first light reflection. Examples include an interface layer provided between the layer 18 and the first write-once recording layer 14. Here, the label layer is formed using an ultraviolet curable resin, a thermosetting resin, a heat drying resin, or the like.

  These essential and optional layers may be a single layer or may have a multilayer structure.

[First Light Reflecting Layer 18 in First Optical Recording Medium 10A]
In the first optical recording medium 10 </ b> A, the first light is provided between the first substrate 12 and the first write-once recording layer 14 in order to increase the reflectance with respect to the laser light and to provide the function of improving the recording / reproducing characteristics. It is preferable to form the reflective layer 18.

  The first light reflection layer 18 can be formed on the substrate by vacuum-depositing, sputtering, or ion plating a light-reflecting material having a high reflectance with respect to laser light.

  The layer thickness of the first light reflecting layer 18 is preferably in the range of 50 to 200 nm. The reflectance is preferably 70% or more.

  As a light reflective material having a high reflectance, Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd , Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and other metals and semi-metals or stainless steel. These light reflecting materials may be used alone, or may be used in combination of two or more or as an alloy. Among these, Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel are preferable. Particularly preferred is Au, Ag, Al or an alloy thereof, and most preferred is Au, Ag or an alloy thereof. More preferably, it is made of a metal containing 50 atm% or more of Ag.

[Barrier layer 20 (intermediate layer) in first optical recording medium 10A]
In the first optical recording medium 10 </ b> A, it is preferable to form a barrier layer 20 between the first write-once recording layer 14 and the cover layer 16.

  The barrier layer 20 improves the storability of the first write-once recording layer 14, improves the adhesion between the first write-once recording layer 14 and the cover layer 16, adjusts the reflectance, and adjusts the thermal conductivity. Provided for etc.

  The material used for the barrier layer 20 is not particularly limited as long as it is a material that transmits light used for recording and reproduction, and can express the above functions. Is a material with low permeability of gas and moisture, and is preferably a dielectric.

Specifically, materials made of nitrides, oxides, carbides, sulfides such as Zn, Si, Ti, Te, Sn, Mo, Ge are preferable. ZnS, MoO ₂ , GeO ₂ , TeO, SiO ₂ , TiO ₂ , ZuO, ZnS—SiO ₂ , SnO ₂ and ZnO—Ga ₂ O ₃ are preferable, and ZnS—SiO ₂ , SnO ₂ and ZnO—Ga ₂ O ₃ are more preferable.

  In addition, when Ag (silver) is included as a material of the 1st light reflection layer 18, it is desirable that the barrier layer 20 does not contain S (sulfur). This is because if S (sulfur) is included, for example, Ag (silver) that is a constituent material of the first light reflecting layer 18 is corroded. The barrier layer 20 is preferably made of a material that does not corrode with water. This is because materials that corrode water tend to have poor wet heat storage.

  The barrier layer 20 can be formed by a vacuum film formation method such as vacuum deposition, DC sputtering, RF sputtering, or ion plating. Among these, it is more preferable to use sputtering, and it is more preferable to use DC sputtering.

  The thickness of the barrier layer 20 is 1 to 80 nm, preferably 1 to 50 nm, and more preferably 1.5 to 30 nm. If it is too thin, the film quality will not be uniform and the barrier properties will deteriorate, and if it is too thick, it will take time to form the film and the efficiency will deteriorate.

  The film forming conditions of the barrier layer 20 are as follows.

  The pressure during film formation is 1E-02 to 1E-05 torr, the rate is 0.1 to 10 nm / sec, the gas flow rate is 1 to 50 sccm, and the gas type is Ar. The sputtering power is 0.2 to 4 kW, preferably 0.4 to 3 kW, and more preferably 0.5 to 2.5 kW.

  When the film is formed by the RF sputtering method, the tuning (matching) is adjusted, and the work of the film forming material separated from the target (the first write-once recording layer 14 and the first light reflecting layer 18 are formed on the first substrate 12). The amount (REF) of the film forming material separated from the target toward the target (REF) with respect to the amount (FWD) toward the target) is 10% or less, preferably 5% or less, more preferably 2.5% or less. is there. In the case of oxides and nitrides, these gases may be mixed in a sputtering gas to form a film by reactive sputtering.

  In the case of film formation by the DC sputtering method, it is preferable to combine a method of instantaneously removing the target charge by a pulse sputtering method or the like. In the case of oxides and nitrides, these gases may be mixed in a sputtering gas to form a film by reactive sputtering.

  The light transmittance of the barrier layer 20 is preferably 50 to 99%, preferably 55 to 98%, and more preferably 60 to 95%. If the light transmittance is low, the recording sensitivity is deteriorated and the medium reflectivity is lowered. When the light transmittance is high, the storage stability during the light resistance test tends to be poor. The inorganic layer used for the barrier layer 20 has a light absorption greater than the absorption at 405 nm in a region shorter than the recording / reproducing wavelength of 405 m, and also has a function of protecting the dye from light of ˜350 nm irradiated in the light resistance test. It is estimated that

  Next, the second optical recording medium 10B will be described.

  Here, the second optical recording medium 10B is an optical recording medium having a laminated type layer structure, and a typical layer structure is as follows.

(1) As shown in FIG. 2, the first layer structure is formed by sequentially forming a second write-once recording layer 26, a second light reflecting layer 30, and a second adhesive layer 32 on a second substrate 24. In this configuration, the protective substrate 28 is provided on the two adhesive layers 32.

(2) Although the second layer configuration is not shown, a second write-once recording layer 26, a second light reflecting layer 30, a protective layer, and a second adhesive layer 32 are sequentially formed on the second substrate 24. In this configuration, the protective substrate 28 is provided on the two adhesive layers 32.

(3) Although the third layer configuration is not shown, the second write-once recording layer 26, the second light reflecting layer 30, the protective layer, the second adhesive layer 32, and the protective layer are sequentially formed on the second substrate 24. The protective substrate 28 is provided on the protective layer.

(4) Although the fourth layer configuration is not shown, the second write-once recording layer 26, the second light reflection layer 30, the protective layer, the second adhesive layer 32, the protective layer, and the light reflection are formed on the second substrate 24. The layers are sequentially formed, and the protective substrate 28 is provided on the light reflecting layer.

(5) Although the fifth layer configuration is not shown, the second write-once recording layer 26, the second light reflecting layer 30, the second adhesive layer 32, and the light reflecting layer are sequentially formed on the second substrate 24. A protective substrate 28 is provided on the light reflecting layer.

  Note that the layer configurations (1) to (5) are merely examples, and the layer configuration is not limited to the order described above, and a part of the layer configuration may be replaced or a part of the layer configuration may be omitted. The second write-once recording layer 26 may also be formed on the protective substrate 28 side. In this case, the optical recording medium can be recorded and reproduced from both sides. Furthermore, each layer may be composed of one layer or a plurality of layers.

  Here, as the second optical recording medium 10B, as shown in FIG. 2, a second write-once recording layer 26, a second light reflecting layer 30, a second adhesive layer 32, and a protective substrate 28 are provided on a second substrate 24. An example of the configuration having this order will be described below.

[Second substrate 24 of second optical recording medium 10B]
The second substrate 24 in the second optical recording medium 10B has a second pregroove 36 (guide) having a shape in which all of the track pitch, groove width (half width), groove depth, and wobble amplitude are in the following ranges. It is essential that grooves: grooves 50 and lands 52) be formed. The second pregroove 36 is provided in order to achieve a higher recording density than that of a CD-R or DVD-R. For example, the second optical recording medium 10B corresponds to a blue-violet laser. It is suitable for use as a medium.

  The track pitch of the second pregroove 36 is essential to be in the range of 200 to 600 nm, the upper limit is preferably 500 nm or less, more preferably 450 nm or less, and further preferably 430 nm or less. preferable. Further, the lower limit is preferably 300 nm or more, more preferably 330 nm or more, and further preferably 370 nm or more.

  If the track pitch is less than 200 nm, it is difficult to form the second pregroove 36 accurately, and a problem of crosstalk may occur. If the track pitch exceeds 600 nm, the recording density may decrease. is there.

  The groove width (half-value width) of the groove 50 (recessed portion in the second substrate 24) of the second pregroove 36 is essential to be in the range of 50 to 300 nm, and the upper limit is preferably 250 nm or less, and 200 nm. Or less, more preferably 180 nm or less. Further, the lower limit is preferably 100 nm or more, more preferably 120 nm or more, and further preferably 140 nm or more.

  If the groove width of the second pregroove 36 is less than 50 nm, the groove may not be sufficiently transferred during molding or the recording error rate may increase. If it exceeds 300 nm, the pits formed during recording spread. As a result, crosstalk may occur or a sufficient degree of modulation may not be obtained.

  The groove depth of the second pregroove 36 is essential to be in the range of 30 to 200 nm, and the upper limit is preferably 170 nm or less, more preferably 140 nm or less, and 120 nm or less. Further preferred. Further, the lower limit value is preferably 40 nm or more, more preferably 50 nm or more, and further preferably 60 nm or more.

  If the groove depth of the second pre-groove 36 is less than 30 nm, a sufficient recording modulation degree may not be obtained, and if it exceeds 200 nm, the reflectance may be significantly lowered.

  As the second substrate 24 used in the second optical recording medium 10B, various materials used as the substrate material of the conventional optical recording medium can be arbitrarily selected and used. Specific examples and preferable examples are as follows. This is the same as the first substrate 12 of the first optical recording medium 10A.

  In addition, the thickness of the second substrate 24 needs to be in the range of 0.1 to 1.0 mm, preferably in the range of 0.2 to 0.8 mm, and 0.3 to 0.7 mm. A range is more preferable.

  An undercoat layer is preferably formed on the surface of the second substrate 24 on the side where the second write-once recording layer 26, which will be described later, is provided, for the purpose of improving the flatness and the adhesive force. Specific examples and preferred examples of the material of the coating layer, the coating method, and the layer thickness are the same as those of the undercoat layer of the first optical recording medium 10A.

[Second Write-once Recording Layer 26 of Second Optical Recording Medium 10B]
The detailed description of the second write-once recording layer 26 of the preferred second optical recording medium 10B is the same as that for the first write-once recording layer 14 of the first optical recording medium 10A.

  Therefore, also in the second optical recording medium 10B, similarly to the first optical recording medium 10A described above, even if repeated reproduction is performed by the laser light 46, an increase in light absorption rate is suppressed. That is, the reproduction durability can be improved without lowering the content of the additive in the organic dye that is the material of the second write-once recording layer 26 and the output of the laser beam 46.

[Second Light Reflecting Layer 30 of Second Optical Recording Medium 10B]
In the second optical recording medium 10B, the second light reflecting layer 30 is formed on the second write-once recording layer 26 in order to increase the reflectance with respect to the laser light 46 and to provide the function of improving the recording / reproducing characteristics. There is. Details regarding the second light reflecting layer 30 of the second optical recording medium 10B are the same as those of the first light reflecting layer 18 of the first optical recording medium 10A.

[Second Adhesive Layer 32 of Second Optical Recording Medium 10B]
The second adhesive layer 32 in the preferred second optical recording medium 10 </ b> B is an arbitrary layer formed in order to improve the adhesion between the second light reflecting layer 30 and the protective substrate 28.

  As a material constituting the second adhesive layer 32, a photo-curing resin is preferable, and in particular, a material having a small curing shrinkage rate is preferable in order to prevent the disk from warping. Examples of such a photocurable resin include UV curable resins (UV curable adhesives) such as “SD-640” and “SD-347” manufactured by Dainippon Ink. The thickness of the second adhesive layer 32 is preferably in the range of 1 to 1000 μm in order to provide elasticity.

[Protective substrate 28 of second optical recording medium 10B]
As the protective substrate 28 (dummy substrate) in the preferred second optical recording medium 10B, the same material and the same shape as those of the second substrate 24 described above can be used. The thickness of the protective substrate 28 needs to be in the range of 0.1 to 1.0 mm, preferably in the range of 0.2 to 0.8 mm, and in the range of 0.3 to 0.7 mm. More preferably.

[Protective layer (not shown) of second optical recording medium 10B]
Depending on the layer configuration of the second optical recording medium 10B, a protective layer may be provided for the purpose of physically and chemically protecting the second light reflecting layer 30, the second write-once recording layer 26, and the like.

Examples of materials used for the protective layer include inorganic substances such as ZnS, ZnS—SiO ₂ , SiO, SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ , thermoplastic resins, thermosetting resins, and UV curable materials. Organic substances such as resins can be mentioned.

  The protective layer can be formed, for example, by bonding a film obtained by plastic extrusion onto the light reflecting layer via an adhesive. Moreover, you may provide by methods, such as vacuum evaporation, sputtering, and application | coating.

  Further, when a thermoplastic resin or a thermosetting resin is used as the protective layer, it is also formed by dissolving these in an appropriate solvent to prepare a coating solution, and then applying and drying the coating solution. be able to. In the case of a UV curable resin, it can also be formed by preparing a coating solution as it is or by dissolving it in a suitable solvent, and then applying the coating solution and curing it by irradiation with UV light. In these coating liquids, various additives such as an antistatic agent, an antioxidant, and a UV absorber may be added according to the purpose. The thickness of the protective layer is generally in the range of 0.1 μm to 1 mm.

[Other layers in the second optical recording medium 10B]
The second optical recording medium 10B may have other arbitrary layers in addition to the above-mentioned layers as long as the effects of the present invention are not impaired. The detailed description of such other optional layers is the same as the other layers in the first optical recording medium 10A.

<Optical information recording method>
The optical information recording method of the present invention is performed, for example, as follows using the first optical recording medium 10A or the second optical recording medium 10B.

  In the first optical recording medium 10A, first, recording of a semiconductor laser beam or the like from the cover layer 16 side while rotating the first optical recording medium 10A at a constant linear velocity (0.5 to 10 m / second) or a constant angular velocity. Is irradiated through the first objective lens 42 having a numerical aperture NA of, for example, 0.85. By irradiation with the laser light 46, the first write-once recording layer 14 absorbs the laser light 46 and the temperature rises locally, causing a physical or chemical change (for example, generation of pits) and its optical characteristics. It is considered that information is recorded by changing.

  At this time, the first light reflection layer 18 having a large reflectance and a large thickness with respect to the first write-once recording layer 14 is formed on the side opposite to the incident surface of the laser beam 46. Most of the incident laser light 46 is reflected by the surface of the first light reflection layer 18 and returns to the detector.

  Of the first write-once recording layer 14, the recorded mark (pit information) and the non-recorded portion have different optical constants (complex refractive indices), and therefore the optical path length during reciprocation to the first light reflecting layer 18 is different. Come. As a result, the pit information recorded on the first write-once recording layer 14 can be detected by the phase difference modulation method.

  Similarly, in the second optical recording medium 10B, first, while rotating the second optical recording medium 10B at a constant linear velocity (0.5 to 10 m / second) or a constant angular velocity, the semiconductor laser is started from the second substrate 24 side. A recording laser beam 46 such as light is irradiated through a second objective lens 48 having a numerical aperture NA of, for example, 0.65. By irradiation with the laser light 46, the second write-once recording layer 26 absorbs the laser light 46 and the temperature rises locally, causing a physical or chemical change (for example, generation of pits) and its optical characteristics. It is considered that information is recorded by changing.

  Also in the second optical recording medium 10B, the second light reflecting layer 30 having a large reflectance and a large thickness is formed on the side opposite to the incident surface of the laser light 46 with respect to the second write-once recording layer 26. Therefore, most of the incident laser light 46 is reflected by the surface of the second light reflecting layer 30 and returns to the detector.

  In the second write-once recording layer 26, the recorded mark (pit information) and the portion before recording have different optical constants (complex refractive index), so the optical path length during reciprocation to the second light reflecting layer 30 is different. Come different. As a result, the pit information recorded on the second write-once recording layer 26 can be detected by the phase difference modulation method.

  In the present embodiment, a semiconductor laser beam having an oscillation wavelength in the range of 390 to 450 nm is used as the recording laser beam 46. As a preferable light source, a blue-violet semiconductor laser beam having an oscillation wavelength in the range of 390 to 415 nm, and a blue-violet SHG having a central oscillation wavelength of 425 nm, which is half the wavelength of an infrared semiconductor laser beam having a central oscillation wavelength of 850 nm using an optical waveguide device. A laser beam can be mentioned. In particular, it is preferable to use a blue-violet semiconductor laser beam having an oscillation wavelength in the range of 390 to 415 nm in terms of recording density. Reproduction of information recorded as described above is performed by irradiating a semiconductor laser beam from the substrate side or the protective layer side while rotating the first optical recording medium at the same constant linear velocity as described above, and detecting the reflected light. Can be done.

  Hereinafter, Examples 1 and 2 having the same configuration as that of the second optical recording medium 10B are typically manufactured, and the refractive index before recording, the refractive index after recording, the modulation degree, and the PR (partial response) are recorded. The SN value was determined.

[Model calculation]
First, prior to measurement of various characteristics for the optical recording media according to Examples 1 and 2, two model calculations (first model calculation and second model calculation) are performed, and the value of the real part of the complex refractive index before recording is calculated. A preferable value was obtained.

  In the first model calculation, the thickness on the groove 50 of the second write-once recording layer 26 in the second optical recording medium 10B is 80 nm, and the thickness on the land 52 is 60 nm, which accompanies a change in the refractive index of the second write-once recording layer. The degree of modulation was calculated.

  In the second model calculation, the thickness of the second write-once recording layer 26 on the groove 50 was 40 nm and the thickness on the land 52 was 10 nm, and the degree of modulation accompanying the change in the refractive index of the second write-once recording layer was calculated.

  For the first model calculation and the second model calculation, calculation software diffractMOD of Nippon Softsoft Design Co., Ltd. was used.

  In the first model calculation and the second model calculation, the following parameters were used. That is, the groove width of the second pregroove 36 = 180 nm, the groove depth of the second pregroove 36 = 90 nm, the groove inclination angle of the second pregroove 36 = 45 deg, the refractive index n of the second light reflecting layer 30 = 0. 215, absorption coefficient k = 1.94, thickness of the second light reflecting layer 30 = 80 nm, refractive index n = 1.6 of the second substrate 24, absorption coefficient k = 0, calculation object area = 800 nm, decomposed dye The real part of the complex refractive index was 1.8 and the imaginary part was 0.1. The result of the first model calculation is shown in FIG. 3, and the result of the second model calculation is shown in FIG.

  In either case, it is shown that a modulation degree exceeding 0.1 is obtained when the real part of the complex refractive index before recording is in the range of 1.2 to 1.5. In addition, it is known that a sufficient modulation factor can be obtained even in the actual second optical recording medium 10B if a modulation factor of 0.1 is obtained in the calculation result.

[Example 1]
(Production of the second substrate 24)
A second substrate 24 having a thickness of 0.6 mm was molded by injection molding using a polycarbonate resin (Panlite AD5503) manufactured by Teijin Chemicals Limited. The track pitch of the second pregroove 36 of the second substrate 24 was 400 nm, the half width of the groove 50 was 190 nm, and the groove depth was 90 nm.

(Formation of the second write-once recording layer 26)
The following compound 1 was weighed and dissolved in a ratio of 2 g to 100 ml of 2,2,3,3-tetrafluoropropanol. The solution is irradiated with ultrasonic waves for 2 hours to dissolve the dye, then left in an environment at a temperature of 23 ° C. and a humidity of 50% for 0.5 hours or more, filtered through a 0.2 μm filter, and then the coating solution Got. This coating solution was applied onto the surface of the second substrate 24 on which the second pregroove 36 was formed by a spin coating method to form a second write-once recording layer 26 having a thickness of 55 nm. At this time, the real part of the complex refractive index of the dye was 1.34, and the imaginary part was 0.23.

  Thereafter, annealing was performed in a clean oven. The annealing process was performed by supporting the second substrate 24 on a vertical stack pole while keeping a gap with a spacer, and holding at 80 ° C. for 1 hour.

(Formation of the second light reflecting layer 30)
On the second write-once recording layer 26, the second light reflecting layer 30 is formed to 100 nm by a vacuum film forming method using a target of Ag: 98.4 at%, Nd: 0.7 at%, and Cu: 0.9 at%. The film was formed with a thickness of. The input power was 2 kW and the Ar flow rate was 5 sccm.

(Lamination of protective substrate 28)
An ultraviolet curable resin (SD640 manufactured by Dainippon Ink Co., Ltd.) was dropped and applied onto the second light reflecting layer 30 by spin coating, and after the protective substrate 28 was placed thereon, 3600 r. p. m. After spreading the ultraviolet curable resin by rotating the substrate, the ultraviolet curable resin is cured by irradiating with ultraviolet rays, and the two substrates (second substrate 24 and protective substrate 28) are bonded together, An optical recording medium according to Example 1 having the same configuration as that of the second optical recording medium 10B was obtained.

[Example 2]
Example 2 having the same configuration as the second optical recording medium 10B in the same manner as in Example 1 except that the second write-once recording layer 26 was formed using the following compound 2 instead of the compound 1. An optical recording medium according to the above was produced. The real part of the complex refractive index of the dye before recording was 1.24, and the imaginary part was 0.4.

<Evaluation>
The produced Examples 1 and 2 were set in DDU-1000 (manufactured by Pulstec Industrial Co., Ltd.) equipped with a laser optical system having a wavelength of 406 nm and NA = 0.65, and a clock frequency of 64.8 MHz and a linear velocity of 6. An 11T signal (length 1.122 μm) was recorded at 61 m / s with a recording power of 4 to 10 mW, and the degree of modulation was measured. The degree of modulation was obtained by dividing the signal amplitude after 11T signal recording by the higher reflectance of the 11T signal.

  Further, an 8-12 modulated random signal was recorded, and an SN ratio (PRSNR) of PR (partial response) was obtained. Recording was performed by optimizing the light emission waveform.

  In the optical recording medium according to Example 1, the real part of the complex refractive index before recording is 1.34, the real part of the complex refractive index after recording is 1.75, the modulation factor is 0.38, and the PRSNR is 25.

  On the other hand, in the optical recording medium according to Example 2, the real part of the complex refractive index before recording is 1.24, the real part of the complex refractive index after recording is 1.8, the modulation factor is 0.51, and the PRSNR is 23.

  For this reason, it was shown that a sufficient degree of modulation can be obtained even with a dye that is not so large that the real part of the complex refractive index before recording is 1.24 and 1.34. The recording characteristics were also good.

  In addition, the optical recording medium and the information recording method according to the present invention are not limited to the above-described embodiments, and it is needless to say that various configurations can be adopted without departing from the gist of the present invention.

It is sectional drawing which abbreviate | omits and shows a part of 1st optical recording medium among the optical recording media which concern on this Embodiment. It is sectional drawing which abbreviate | omits and shows a part of 2nd optical recording medium among the optical recording media which concern on this Embodiment. It is a figure which shows the result of 1st model calculation. It is a figure which shows the result of 1st model calculation. It is a table | surface which shows the refractive index before recording of Examples 1 and 2, the refractive index after recording, a modulation degree, and PRSNR.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10A ... 1st optical recording medium 10B ... 2nd optical recording medium 12 ... 1st board | substrate 14 ... 1st write-once recording layer 16 ... Cover layer 18 ... 1st light reflection layer 20 ... Barrier layer 22 ... 1st adhesive layer 24 ... Second substrate 26 ... Second write-once recording layer 28 ... Protective substrate 30 ... Second light reflecting layer 32 ... Second adhesive layer 44 ... Hard coat layer

Claims (9)

In an optical recording medium comprising a substrate, a recording layer formed on the substrate, and a reflective layer, and recording and / or reproducing information by irradiating the recording layer with laser light,
The real part of the complex refractive index of the recording layer before recording information on the recording layer by the laser light is 1.2 to 1.5,
An optical recording medium, wherein a real part of a complex refractive index of the recording layer after information is recorded on the recording layer by the laser beam is 1.7 to 1.9. The optical recording medium according to claim 1,
The optical recording medium, wherein the recording layer has an optical characteristic that a reflectance after recording information by the laser light is higher than a reflectance before recording the information. The optical recording medium according to claim 1 or 2,
The recording layer contains a dye compound;
The optical recording medium, wherein the dye compound is a dye compound having trimethine oxonol as an anion and a metal complex as a cation. The optical recording medium according to claim 3,
The optical recording medium, wherein the dye compound is a compound represented by the following general formula (1).
General formula (1)

[In the general formula (1), A, B, C and D are electron withdrawing groups in which the sum of the Hammett σp values of A and B and the sum of the Hammett σp values of C and D are each 0.6 or more. A and B or C and D may be linked to form a ring, R represents a substituent on the methine carbon, m = 1, n represents an integer of 0 to 2m + 1, and n represents When the integer is 2 or more, a plurality of R may be the same or different from each other, and may be linked to each other to form a ring, Yt + represents a t-valent cation, and t is 1 to 10 Represents an integer. ] The optical recording medium according to any one of claims 1 to 4,
An optical recording medium, wherein the substrate has a groove depth of 30 to 130 nm. The optical recording medium according to any one of claims 1 to 5,
An optical recording medium characterized in that a groove width of the substrate is 140 to 240 nm. The optical recording medium according to any one of claims 1 to 6,
An optical recording medium, wherein the reflective layer has a thickness of 50 to 200 nm. The optical recording medium according to any one of claims 1 to 7,
The wavelength of the laser beam corresponds to 405 nm, the numerical aperture of the objective lens for condensing the laser beam on the recording layer is 0.65, and the distance from the end surface of the substrate to the recording layer is 0.6 mm. An optical recording medium characterized by the above.   An information recording method comprising: irradiating the optical recording medium according to any one of claims 1 to 7 with a laser beam having a wavelength of 450 nm or less to record information by a phase difference modulation method.

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