JP2006092710A - Optical information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical information recording medium whose reproducing characteristics of information can be satisfactorily kept even when the optical information recording medium is preserved under environment where humidity is changed after information is recorded. <P>SOLUTION: The optical information recording medium has at least a reflection layer, a dye recording layer, a barrier layer and a cover layer in this order on a resin substrate having ≤0.2 mass% hygroscopic rate and is irradiated with a laser beam from the cover layer side to perform recording and/or reproduction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical information recording medium capable of recording and reproduction using laser light having a specific wavelength.

  Conventionally, an optical information recording medium (optical disc) capable of recording information only once by laser light is known. This optical disk is also called a recordable CD (so-called CD-R), and its typical structure is a recording layer made of an organic dye on a transparent disk-shaped substrate, a reflective layer made of a metal such as gold, and further made of resin. These protective layers (cover layers) are laminated in this order. Information recording on this CD-R is performed by irradiating the CD-R with a near-infrared laser beam (usually a laser beam having a wavelength of around 780 nm), and the irradiated portion of the recording layer emits the light. Information is recorded by absorbing and locally raising the temperature, and changing the optical characteristics of the portion due to physical or chemical changes (for example, generation of pits). On the other hand, reading (reproduction) of information is also performed by irradiating the CD-R with laser light having the same wavelength as the recording laser light, and the optical characteristics of the recording layer (recording portion) change. This is done by detecting a difference in reflectance from a non-recorded part (unrecorded part).

  In recent years, an optical information recording medium having a higher recording density has been demanded. In response to such a demand, an optical disk called a write-once digital versatile disk (so-called DVD-R) has been proposed (for example, “Nikkei New Media”, separate volume “DVD”, published in 1995). This DVD-R has a transparent disk shape in which a guide groove (pre-groove) for tracking the irradiated laser beam is formed with a narrow groove width of less than half (0.74 to 0.8 μm) of the CD-R. A structure in which two recording disks, usually containing an organic dye-containing recording layer, a reflective layer, and a protective layer, are laminated together in this order on the substrate, with the recording layer inside, or a disk-shaped protection of the same shape as this disk It has a structure in which the substrate is bonded with the recording layer inside. Recording and reproduction of information on the DVD-R is performed by irradiating with visible laser light (usually laser light having a wavelength in the range of 630 nm to 680 nm), which has a higher density than the CD-R. Recording is possible.

  Recently, networks such as the Internet and high-definition TV are rapidly spreading. Also, the start of HDTV (High Definition Television) has started. Under such circumstances, a large-capacity recording medium capable of recording image information inexpensively and simply is required. DVD-R plays a role as a large-capacity recording medium at present, but the demand for larger capacity and higher density is increasing, and development of a recording medium that can meet these demands is also necessary. . For this reason, development of a recording medium having a larger capacity capable of performing high-density recording with light having a shorter wavelength than that of the DVD-R is underway.

  Usually, the density of an optical information recording medium can be increased by reducing the beam spot by shortening the wavelength of the recording and reproducing laser and increasing the NA of the objective lens. Recently, development has rapidly progressed from red semiconductor lasers with wavelengths of 680 nm, 650 nm, and 635 nm to blue-violet semiconductor lasers with wavelengths of 400 nm to 500 nm (hereinafter referred to as blue-violet lasers) that enable ultra-high density recording. Therefore, development of optical information recording media corresponding to this is also underway. In particular, since the launch of the blue-violet laser, development of an optical recording system using the blue-violet laser and a high NA pickup has been studied. A rewritable optical information recording medium and optical recording system having a phase-change recording layer are: It has already been announced as a DVR-Blue system (for example, see Non-Patent Document 1). In addition, a DVR-Blue disc, which is a write-once optical information recording medium using an organic dye and performs recording / reproduction with a blue-violet laser, has been announced (for example, see Non-Patent Document 2). With these optical information recording media, certain results have been obtained with respect to the problem of higher density.

  The optical information recording medium used in the optical recording system using the blue-violet laser and the high NA pickup as described above is a laser for focusing the high-NA objective lens when the recording layer is irradiated with the blue-violet laser light. A cover layer having a surface on which light is incident is thinned (see, for example, Patent Document 1). Here, as the cover layer, for example, a thin resin film made of the same material as that of the substrate is used, and is adhered to the recording layer using an adhesive or a pressure-sensitive adhesive. The thickness of the cover layer is usually about 100 μm including the adhesive layer or the adhesive layer formed by curing the adhesive or the adhesive, but is optimized by the wavelength of the irradiated laser and the NA.

As the cover layer is thus thinned, the optical information recording medium described above has an uneven thickness balance between the substrate and the cover layer when the recording layer is the center. Thus, for example, when the humidity changes, the moisture absorption / discharge amount in the substrate is large, while the cover layer has a relatively small moisture absorption / discharge amount. If such a situation is possible, a significant difference appears in the shrinkage rate and expansion rate of both, and the difference in the dimensional change causes the recording pits formed in the recording layer to be damaged, resulting in information reproduction characteristics. It had the problem of being lowered.
Also, since the recording layer is formed close to the substrate, it is particularly susceptible to dimensional changes due to moisture absorption / discharge on the substrate. For these reasons, it has been desired to improve an optical information recording medium in which the reproduction characteristics of recorded information do not deteriorate even when the humidity changes after the information is recorded.
“ISOM2000”, pages 210-211 “ISOM2001” pp. 218-219 Japanese Patent No. 3,431,612

  The present invention has been made in view of the above-described problems, and the object of the present invention is to maintain good reproduction characteristics of information even if the information is stored in an environment where the humidity changes after recording. An optical information recording medium is provided.

The above problems are solved by the present invention described below.
That is, the optical information recording medium of the present invention has at least a reflective layer, a dye recording layer, a barrier layer, and a cover layer in this order on a resin substrate having a moisture absorption rate of 0.2% by mass or less. Recording and / or reproduction is performed by irradiating a laser beam from the side.
In the optical information recording medium of the present invention, it is preferable that the thickness of the resin substrate is in the range of 0.7 to 2 mm, and the thickness of the cover layer is in the range of 0.01 to 0.5 mm. It is an aspect.

  ADVANTAGE OF THE INVENTION According to this invention, even if it preserve | saves in the environment where humidity changes after recording of information, the optical information recording medium with which the reproduction | regeneration characteristic of information is maintained favorable can be provided.

Hereinafter, the present invention will be described in detail.
The optical information recording medium of the present invention has at least a reflective layer, a dye recording layer, a barrier layer, and a cover layer in this order on a resin substrate having a moisture absorption rate of 0.2% by mass or less, and from the cover layer side. Recording and / or reproduction is performed by irradiation with laser light.
First, each element constituting the optical information recording medium of the present invention will be described in order.

[Resin substrate]
The resin substrate in the present invention has a moisture absorption rate of 0.2% by mass or less. Further, the moisture absorption rate is more preferably 0.18% by mass or less, and further preferably 0.16% by mass or less. Here, the “moisture absorption rate of the resin substrate” in the present invention refers to the mass change rate (mass increase rate) before and after leaving the resin substrate in pure water at 23 ° C. for 24 hours.

The material of the resin substrate is not particularly limited as long as the molded resin substrate has a specific moisture absorption rate as described above.
In the present invention, specific examples include acrylic resins such as polycarbonate and polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; amorphous polyolefins; If desired, these may be used in combination.
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, a resin substrate can be manufactured by injection molding.
The thickness of the resin substrate is preferably in the range of 0.7 to 2 mm, more preferably in the range of 0.9 to 1.6 mm, and in the range of 1.0 to 1.3 mm. Is more preferable.

  The resin substrate is provided with a tracking guide groove or unevenness (pregroove) representing information such as an address signal on the surface on which the dye recording layer is provided. In order to achieve a higher recording density, a pre-groove having a narrower track pitch is required as compared with CD-R and DVD-R. For example, when the optical information recording medium of the present invention is used as a suitable medium corresponding to a blue-violet laser, the pre-groove formed is preferably in the following range.

The upper limit of the track pitch of the pregroove is preferably 500 nm or less, more preferably 420 nm or less, still more preferably 370 nm or less, and particularly preferably 330 nm or less. Further, the lower limit is preferably 50 nm or more, more preferably 100 nm or more, further preferably 200 nm or more, and particularly preferably 260 nm or more.
The upper limit of the pregroove width (half width) is preferably 250 nm or less, more preferably 200 nm or less, still more preferably 170 nm or less, and particularly preferably 150 nm or less. Further, the lower limit is preferably 23 nm or more, more preferably 50 nm or more, further preferably 80 nm or more, and particularly preferably 100 nm or more.

The upper limit of the pregroove (groove) depth is preferably 150 nm or less, more preferably 100 nm or less, still more preferably 70 nm or less, and particularly preferably 50 nm or less. Further, the lower limit is preferably 5 nm or more, more preferably 10 nm or more, further preferably 20 nm or more, and particularly preferably 28 nm or more.
The upper limit of the pregroove angle is preferably 80 ° or less, more preferably 70 ° or less, still more preferably 60 ° or less, and particularly preferably 50 ° or less. Further, the lower limit value is preferably 20 ° or more, more preferably 30 ° or more, and further preferably 40 ° or more.
Each of the upper limit value and the lower limit value related to the pregroove can be arbitrarily combined.

  These pregroove values can be measured by an AFM (atomic force microscope). The angle of the pre-groove means that the groove depth of the groove is D, the surface of the resin substrate before the groove is formed as a reference, the inclined portion having a depth of D / 10 from the surface, and the most of the groove This is an angle formed by a straight line connecting a deep portion and an inclined portion having a height of D / 10 and a resin substrate surface (groove bottom surface).

In order to produce a resin substrate having a pregroove having such a groove shape, a stamper used at the time of injection molding must be formed by high-precision mastering. In order to achieve the above-mentioned groove shape, it is preferable to use DUV (wavelength 330 nm or less, deep ultraviolet) laser or EB (electron beam) cutting for this mastering.
On the other hand, with a UV laser or a visible light laser, it is difficult to perform good mastering for forming a groove shape as in the present invention.

In addition, it is preferable to form an undercoat layer on the surface of the resin substrate on the side where a light reflecting layer, which will be described later, is provided, for the purpose of improving flatness and adhesion.
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, and chloro. Polymer materials such as sulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate, etc .; silane coupling Surface modifiers such as agents;
The undercoat layer is prepared by dissolving or dispersing the above materials in an appropriate solvent to prepare a coating solution, and then applying the coating solution to the surface of the resin substrate by a coating method such as spin coating, dip coating, or extrusion coating. Can be formed. 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.

(Light reflection layer)
The optical information recording medium of the present invention has a light reflecting layer between the resin substrate and the dye recording layer in order to increase the reflectance with respect to the laser beam and to give the function of improving the recording / reproducing characteristics.
The light reflecting layer can be formed on the resin substrate by vacuum deposition, sputtering or ion plating of a light reflecting material having a high reflectance with respect to laser light.
The thickness of the light reflecting layer is generally in the range of 10 to 300 nm, and 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 metalloids or stainless steel. These light reflecting substances may be used alone, or may be used in combination of two or more kinds 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.

(Dye recording layer)
The dye recording layer in the present invention is a layer containing a dye as a recording substance.
The dye recording layer preferably contains a dye having absorption in the recording wavelength region. Examples of the dye include a cyanine dye, an oxonol dye, a metal complex dye, an azo dye, and a phthalocyanine dye.
JP-A-4-74690, JP-A-8-127174, 11-53758, 11-334204, 11-334205, 11-334206, 11-334207 The dyes described in JP-A No. 2000-43423, JP-A No. 2000-108513, JP-A No. 2000-158818, and the like are also preferably used.

Such a dye recording layer is prepared by dissolving the dye in a suitable solvent together with a binder or the like to prepare a coating solution, and then coating the coating solution on the light reflecting layer to form a coating film. It is formed by drying.
In that case, it is preferable that the temperature of the surface which apply | coats a coating liquid is the range of 10-40 degreeC. More preferably, the lower limit is 15 ° C. or higher, more preferably 20 ° C. or higher, and particularly preferably 23 ° C. or higher. Moreover, as a lower limit, it is more preferable that it is 35 degrees C or less, It is still more preferable that it is 30 degrees C or less, It is especially preferable that it is 27 degrees C or less. As described above, when the surface temperature to be applied is in the above range, it is possible to prevent the occurrence of coating unevenness and coating failure and make the thickness of the coating film uniform.
Each of the upper limit value and the lower limit value can be arbitrarily combined.
Here, the dye recording layer may be a single layer or a multilayer. In the case of a multilayer structure, the dye recording layer is formed by performing the coating process 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 of 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 said solvent can be used individually or in combination of 2 or more types in consideration of the solubility of the pigment | dye to be 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 23 to 50 ° C.

The thickness of the dye recording layer formed in this manner is preferably 300 nm or less, more preferably 250 nm or less, and more preferably 200 nm or less on the groove (convex portion in the resin substrate). More preferably, it is particularly preferably 180 nm or less. The lower limit is preferably 30 nm or more, more preferably 50 nm or more, still more preferably 70 nm or more, and particularly preferably 90 nm or more.
Further, the thickness of the dye recording layer is preferably 400 nm or less, more preferably 300 nm or less, and further preferably 250 nm or less on the land (the concave portion in the resin substrate). The lower limit is preferably 70 nm or more, more preferably 90 nm or more, and further preferably 110 nm or more.
Further, the ratio of the thickness of the dye recording layer on the groove / the thickness of the dye recording layer on the land is preferably 0.4 or more, more preferably 0.5 or more, and 0.6 or more. More preferably, it is more preferably 0.7 or more. The upper limit is preferably less than 1, more preferably 0.9 or less, still more preferably 0.85 or less, and particularly preferably 0.8 or less.
Each of the upper limit value and the lower limit value can be arbitrarily combined.

  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 as a material for the dye recording layer, the amount of the binder used is generally in the range of 0.01 to 50 times (mass ratio), preferably 0.1 times the amount of the dye. The amount is in the range of 5 to 5 times (mass ratio).

The dye recording layer can contain various anti-fading agents in order to improve the light resistance of the dye recording layer.
As the antifading 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 No. 350399, and Japan Examples include those described in Chemical Society Journal, October 1992, page 1141.
The amount of the antifading agent such as the singlet oxygen quencher used is usually in the range of 0.1 to 50% by weight, preferably in the range of 0.5 to 45% by weight, based on the amount of the dye. Preferably, it is the range of 3-40 mass%, Most preferably, it is the range of 5-25 mass%.

Note that after the dye recording layer is formed on the light reflecting layer, it is preferable to perform an annealing treatment in order to remove excess solvent in the dye recording layer.
The temperature of the annealing treatment is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, and further preferably 60 ° C. or higher, as a temperature at which excess solvent can be efficiently removed. From the viewpoint of occurrence of alteration of the recording layer, the annealing temperature is preferably 100 ° C. or less, more preferably 95 ° C. or less, and further preferably 90 ° C. or less.
Further, although the annealing time depends on the treatment temperature, it is preferably 5 minutes or more, more preferably 10 minutes or more, and more preferably 30 minutes or more, as the time for removing excess solvent efficiently. More preferably. Further, from the viewpoint of shortening the production time and obtaining high productivity, it is preferably 6 hours or less, more preferably 4 hours or less, and even more preferably 3 hours or less.
The atmosphere for the annealing treatment is not particularly limited and is preferably set as appropriate.

[Barrier layer]
The optical information recording medium of the present invention improves the storage stability of the dye recording layer, improves the adhesion between the dye recording layer and the cover layer, adjusts the reflectance, adjusts the thermal conductivity, etc. A barrier layer is provided between the dye recording layer and the cover layer.
The material used for the barrier layer 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 gas and moisture permeability and is preferably a dielectric.
Specifically, a material made of nitride, oxide, carbide, sulfide, etc. such as Zn, Si, Ti, Te, Sn, Mo, Ge is 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.

The barrier layer can be formed by a vacuum film forming 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 RF sputtering.
The thickness of the barrier layer in the present invention is preferably in the range of 1 to 200 nm, more preferably in the range of 2 to 100 nm, and still more preferably in the range of 3 to 50 nm.

[Cover layer]
The cover layer in the present invention is bonded onto the barrier layer via an adhesive or a pressure-sensitive adhesive.
The cover layer used in the present invention is not particularly limited as long as it is a transparent material film; however, an acrylic resin such as polycarbonate and polymethyl methacrylate; a vinyl chloride resin such as polyvinyl chloride and a vinyl chloride copolymer; It is preferable to use epoxy resin; amorphous polyolefin; polyester; cellulose triacetate and the like. Among them, it is more preferable to use polycarbonate or cellulose triacetate.
Note that “transparent” means that the transmittance is 80% or more with respect to light used for recording and reproduction.

Further, the cover layer 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, it is preferable that both the two-dimensional roughness parameter and the three-dimensional roughness parameter have a surface roughness of 5 nm or less.
Further, from the viewpoint of the concentration of light used for recording and reproduction, the birefringence of the cover layer is preferably 10 nm or less.

The thickness of the cover layer is appropriately determined depending on the wavelength and NA of the laser beam irradiated for recording and reproduction, but in the present invention, it may be in the range of 0.01 to 0.5 mm. Preferably, it is in the range of 0.05 to 0.12 mm.
The total thickness of the cover layer and the layer made of an adhesive or a pressure-sensitive adhesive 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 may be provided with a protective layer (hard coat layer) for preventing the light incident surface from being damaged when the optical information recording medium is manufactured.

For example, a UV curable resin, an EB curable resin, a thermosetting resin, or the like is preferably used as the adhesive used to bond the cover layer, and it is particularly preferable to use a UV curable resin.
When a UV curable resin is used as an adhesive, the UV curable resin may be used as it is or dissolved in an appropriate solvent such as methyl ethyl ketone or ethyl acetate to prepare a coating solution, which may be supplied from the dispenser to the barrier layer surface. . Further, in order to prevent warpage of the produced optical information recording medium, it is preferable that the UV curable resin constituting the adhesive layer 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.

The adhesive is applied, for example, on a surface to be bonded composed of a barrier layer, and after a cover layer is placed thereon, the adhesive is applied by spin coating to the surface to be bonded and the cover layer. It is preferable that the film is cured after being spread so as to be uniform.
The thickness of the adhesive layer made of such an adhesive is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.5 to 50 μm, and still more preferably in the range of 10 to 30 μm.

  As the pressure-sensitive adhesive used for laminating the cover layer, acrylic, rubber-based, and silicon-based pressure-sensitive adhesives can be used. From the viewpoint of transparency and durability, acrylic pressure-sensitive adhesive is used. 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 on the surface to be bonded made of the barrier layer, and may be cured after placing the cover layer thereon, or in advance on one side of the cover layer, A predetermined amount may be uniformly applied to form an adhesive coating film, the coating film 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.
The thickness of the pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive is preferably in the range of 0.1 to 100 μm, more preferably in the range of 0.5 to 50 μm, and still more preferably in the range of 10 to 30 μm.

[Other layers]
The optical information recording medium of the present invention may have other arbitrary layers in addition to the above essential layers as long as the effects of the present invention are not impaired. Examples of such other optional layers include an interface layer provided between the light reflecting layer and the dye recording layer.
Each of these essential and optional layers may be a single layer or may have a multilayer structure.

As described above, according to the optical information recording medium of the present invention, by using a resin substrate having a low hygroscopic property, the dimensional change of the resin substrate itself can be suppressed to be small, and formed in a recording layer provided in the vicinity. Damage to the recorded pit is suppressed.
In addition, even if the thickness balance between the resin substrate and the cover layer is biased, the difference in dimensional change between the resin substrate and the cover layer can be further reduced, so it is formed in the recording layer. Damage to the recorded pit is suppressed.
For these reasons, the optical information recording medium of the present invention can maintain good reproduction characteristics of information even when the information is stored in an environment where the humidity changes.

  The information recording method for the optical information recording medium of the present invention can be performed by irradiating laser light having a wavelength of 100 to 600 nm from the cover layer side and changing the dye recording layer physically or chemically. By recording on the optical information recording medium having the above structure by irradiating a laser beam having a suitable wavelength, good and stable recording / reproducing characteristics can be provided.

More preferably, the lower limit of the recording wavelength (laser light wavelength) is 200 nm or more, more preferably 300 nm or more, and particularly preferably 350 nm or more. Moreover, as an upper limit, it is more preferable that it is 500 nm or less, It is further more preferable that it is 450 nm or less, It is especially preferable that it is 420 nm or less.
Each of the upper limit value and the lower limit value can be arbitrarily combined.
Information may be recorded on the groove of the optical information recording medium of the present invention or on the land, but the groove is preferred.
Furthermore, information is also reproduced by the laser beam in the above wavelength region.

More specifically, information is recorded and reproduced using the optical information recording medium of the present invention, for example, as follows.
First, while rotating the optical information recording medium at a predetermined linear velocity (0.5 to 10 m / second) or a predetermined constant angular velocity, a blue-violet laser (for example, wavelength 405 nm) is passed through the objective lens from the cover layer side. ) Or other recording light. By this irradiation light, the dye recording layer absorbs the light and the temperature rises locally. For example, information is recorded by generating pits and changing the optical characteristics thereof. Reproduction of information recorded as described above is performed by irradiating a blue-violet laser beam from the cover layer side and detecting the reflected light while rotating the optical information recording medium at a predetermined constant linear velocity. Can do.

Examples of the laser light source having an oscillation wavelength of 500 nm or less as described above include a blue-violet semiconductor laser having an oscillation wavelength in the range of 390 to 415 nm, a blue-violet SHG laser having a central oscillation wavelength of 425 nm, and the like.
In order to increase the recording density, the NA of the objective lens used for the pickup is preferably 0.7 or more, and more preferably 0.85 or more.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
<Manufacture of optical information recording media>
(Resin substrate)
Polycarbonate resin (Teijin Bayer Polytech Co., Ltd.) having a thickness of 1.1 mm, an outer diameter of 120 mm, an inner diameter (center hole diameter) of 15 mm, and a spiral pregroove (track pitch of 320 nm, groove width of 107 nm, groove depth of 35 nm) , “ST-3000”). The moisture absorption rate of this resin substrate was 0.18% by mass.

(Formation of light reflection layer)
A light reflecting layer (Ag: 98% by mass, Nd: 1% by mass, Cu: 1% by mass) is formed by DC sputtering in an Ar atmosphere on a pregroove of a resin substrate by using Cube manufactured by Unaxis. ) Was formed. The film thickness of the light reflecting layer was adjusted by the sputtering time.

(Formation of dye recording layer)
Dye A represented by the following chemical formula: 2 g was added and dissolved in 100 ml of 2,2,3,3-tetrafluoropropanol to prepare a dye-containing coating solution. And the prepared pigment | dye containing coating liquid was apply | coated on the conditions of 23 degreeC and 50% RH, changing the rotation speed to 300-4000 rpm with a spin coat method on the light reflection layer. Then, it was stored at 23 ° C. and 50% RH for 1 hour to form a dye recording layer (thickness on the groove: 45 nm, thickness on the land: 65 nm).

  After forming the dye recording layer, it was annealed in a clean oven. The annealing treatment was performed by supporting the resin substrate on a vertical stack pole while keeping a space with a spacer, and holding at 80 ° C. for 1 hour.

(Formation of barrier layer)
Then, on the dye recording layer, a Cube manufactured by Unaxis is used, and the thickness is made of ZnO.Ga ₂ O ₃ (ZnO: Ga ₂ O ₃ = 7: 3 (mass ratio)) by RF sputtering in an Ar atmosphere. A barrier layer having a thickness of 5 nm was formed.

(Covering the cover layer)
As the cover layer, a polycarbonate film (Teijin Pure Ace, thickness: 80 μm) having an inner diameter of 15 mm and an outer diameter of 120 mm and coated with an adhesive on one side, the thickness of the adhesive layer and the polycarbonate film is used. The total thickness was set to 100 μm.
Then, the cover layer was placed on the barrier layer so that the barrier layer and the pressure-sensitive adhesive layer were in contact with each other, and the cover layer was pressed and pressed with a pressing member.

<Evaluation of optical information recording media>
(Jitter evaluation)
The optical information recording medium immediately after manufacture was subjected to a random signal at a clock frequency of 66 MHz and a linear velocity of 5.28 m / s using a recording / reproduction evaluation machine (manufactured by Pulstec Inc .: DDU1000) loaded with a 403 nm laser and NA 0.85 pickup. Was recorded and reproduced, and jitter was measured with a spectrum analyzer (Pulstec MSG2). Recording was performed on the groove, and the recording power was 5.2 mW and the reproducing power was 0.4 mW. The measurement results are shown in Table 1. The measurement results are shown as initial data in Table 1. Here, when the jitter is 12% or less, it means that it is practically preferable.
The obtained optical information recording medium was stored for 12 hours at 40 ° C. and 85% RH, and then stored for 12 hours at 25 ° C. and 30% RH, followed by 6 times, and then at 23 ° C. and 50% RH. Jitter was measured by the same method as above for a sample that had been transferred to the environment and passed 24 hours. The measurement results are shown in Table 1. The measurement results are shown as data after storage in Table 1.

(Comparative Example 1)
A comparison was made in the same manner as in Example 1 except that the resin substrate material used in Example 1 was changed from polycarbonate resin (ST-3000) to polycarbonate resin (manufactured by Idemitsu Petrochemical Co., Ltd., “Toughlon MD1500”). The optical information recording medium of Example 1 was produced. The obtained optical information recording medium was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1. Moreover, the moisture absorption rate of the resin substrate used in Comparative Example 1 was measured by the same method as in Example 1, and is also shown in Table 1.

  From Table 1, the optical information recording medium of Example 1 is different from the optical information recording medium of Comparative Example 1 in the jitter immediately after manufacture and the jitter after storage in a high humidity environment. It was found that the reproduction characteristics were kept good. In addition, the optical information recording medium of Comparative Example 1 has a jitter value after storage exceeding 12%, and it has become clear that a practical problem has occurred.

Claims (2)

  By having at least a light reflection layer, a dye recording layer, a barrier layer, and a cover layer in this order on a resin substrate having a moisture absorption rate of 0.2% by mass or less, laser light is irradiated from the cover layer side. An optical information recording medium for recording and / or reproducing.   The optical information according to claim 1, wherein the thickness of the resin substrate is in a range of 0.7 to 2 mm, and the thickness of the cover layer is in a range of 0.01 to 0.5 mm. recoding media.