JP2006260667A - Single-sided two-layer optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provided a single-sided two layer optical recording medium capable of obtaining satisfactory recording and reproducing characteristics even from a deeper side recording layer. <P>SOLUTION: In the optical recording medium which has a first information layer, an intermediate layer and a second information layer which are sequentially provided between first and second substrates having guide grooves and wherein each information layer has a recording layer composed of an organic dye, a laser beam is made incident from the first substrate side and recording/reproduction of information is performed by modulation of a binary or more value of light intensity, the second information layer has a first protective layer, a second protective layer, an organic dye recording layer and a reflection layer which are sequentially layered from a light incident side and the first protective layer has 0.1×10E-6K<SP>-1</SP>to 2×10E-6K<SP>-1</SP>coefficient of thermal expansion. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a single-sided dual-layer optical recording medium capable of recording and reproducing information and additionally recording information by causing optical changes such as transmittance and reflectance of the recording material by irradiation with a light beam. The present invention relates to a recording / reproducing method and a recording / reproducing apparatus, and more particularly, to a single-sided double-layer optical recording medium capable of high-capacity and high-density recording.

In general a compact disc (CD) or DVD is performed to detect the recording and tracking signals of the binary signal using the reflectivity change caused by the interference of light from the bottom and mirror surface portion of the concave pits. In recent years, write-once compact discs (CD-R) having an organic dye film as a recording layer are being widely used as a medium that has reproduction compatibility (compatibility) with CDs. Various proposals have been made.
Conventionally, optical recording media using an organic dye thin film as a recording layer, those using a phthalocyanine compound, a cyanine dye, a phenalene dye, a naphthoquinone dye, etc. are used. It has been.
A write-once compact disc (CD-R) recording medium in which an organic dye, a metal reflective layer, and a UV resin protective layer are sequentially laminated on a substrate requires a high reflectivity to satisfy the CD standard, and therefore a reproduction wavelength range. It was necessary to develop an organic dye having a high refractive index (770 to 830 nm) and high stability (DVD ± R of a DVD write-once disc has a reproduction wavelength of 630 to 680 nm). Until now, CD-R and DVD ± R have been proposed as recording materials using cyanine dye / metal reflective layer, phthalocyanine dye / metal reflective layer or azo metal chelate dye / metal reflective layer as recording materials. (For example, Patent Document 1 or the like uses a cyanine dye / metal reflective layer as a recording material, Patent Document 2 uses a phthalocyanine dye as a recording material, and uses an azo metal chelate dye. Examples of the recording material used include Patent Document 3).

These all have one organic dye layer and have been developed as a recording medium for single-sided single-layer recording.
An optical disk has a groove with a concave and convex shape called a groove land for signal recording, and is concave in a direction farther away from the side irradiated with the laser beam for recording and reproduction (substrate side). The side that is recessed in the direction is called a land, and the side that protrudes in a direction close to it is called a groove. The recordable capacity is determined by the pitch (track pitch) of the guide grooves that can be recorded and reproduced. For example, DVD + R employs a groove recording method in which information is recorded only in the groove, and the track pitch is 0.74 μm when the recording capacity is 4.7 GB. Recently, multiple data layer systems have been proposed to increase the storage capacity of a single optical disk. For example, Patent Document 4 proposes a two-layer optical recording medium having a structure in which two information layers having a recording layer are stacked on one side of a substrate and these information layers are bonded with an ultraviolet curable resin or the like.
The transparent adhesive layer (corresponding to the intermediate layer in the present invention), which is an adhesive portion between the information layers, has a function of optically separating the two information layers, so that the recording / reproducing laser beam is not lost as much as possible. Since it is necessary to reach the information layer on the side, it is made of a material that does not absorb laser light as much as possible. Patent Document 4 proposes providing a buffer layer made of an inorganic material for the purpose of preventing mixing of the transparent adhesive layer and the dye recording layer on the back side, and the thickness is preferably 2 to 2000 nm. It is said that.

Since the refractive index of the buffer layer (referred to as a protective layer in the present invention) is usually different from the refractive index of the adhesive layer or the dye recording layer, the reflectance varies due to the interference effect depending on the film thickness of the protective layer. Therefore, this protective layer also has a role of adjusting the reflectance of the back recording layer. When reproducing the recording layer on the back side, a part of the laser light is absorbed and scattered by the recording layer on the front side, so the reflectance of the recording layer on the back side needs to be set high in advance. Reference 4 does not consider this.
Further, the recording characteristics of the single-sided double-layer optical recording medium depend on the physical properties (thermal conductivity, thermal expansion coefficient, etc.) of the protective layer. In order to realize a single-sided dual-layer optical recording medium exhibiting good recording characteristics, a prior application of the present applicant (Japanese Patent Application No. 2004-81173) using a protective layer mainly composed of ZnS has been proposed. However, good recording was not possible unless the protective layer thickness was 100 nm or more. However, if the thickness of the protective layer exceeds 100 nm, it takes time to form the film, and productivity may be reduced, or there may be a significant fluctuation in reflectance due to uneven film thickness. On the other hand, when the thickness of the protective layer is 100 nm or less, there is a problem that the intermediate layer is deformed during recording on the back recording layer and the characteristics are deteriorated. Therefore, a single-sided dual-layer optical recording medium that does not deteriorate in characteristics even when the protective layer is 100 nm or less is desired.
In the prior application (Japanese Patent Application No. 2004-261735 and Japanese Patent Application No. 2004-80007) of the present applicant, an invention in which the protective layer is formed in two layers has been proposed. The latter is intended to suppress deformation on the reflective layer side, and has a different purpose from the present invention.

Japanese Patent Laid-Open No. 2-168446 Japanese Patent Laid-Open No. 5-139044 JP-A-5-279580 JP 2003-331473 A

  An object of the present invention is to provide a single-sided dual-layer optical recording medium that solves the above-described problems of the prior art and can obtain good recording / reproduction characteristics from the inner recording layer.

As a result of intensive studies to solve the problems of the prior art, the present inventors have found the following solution. That is, the said subject is solved by the following invention of 1) -7) (henceforth this invention 1-7).
Between the first substrate and the second substrate having 1) guide grooves, a first information layer, an intermediate layer, a second information layer sequentially provided, each information layer has a recording layer comprising an organic dye An optical recording medium that records and reproduces information by modulating laser light with a binary intensity or more upon incidence of laser light from a first substrate, wherein the second information layer is formed from the light incident side by the first protective layer. , The second protective layer, the organic dye recording layer, and the reflective layer are sequentially laminated, and the thermal expansion coefficient of the first protective layer is 0.1 × 10E-6K ⁻¹ to 2 × 10E-6K ^−1. Single-sided, dual-layer optical recording medium.
2) The single-sided two-layer optical recording medium according to 1), wherein the first protective layer has a thickness of 5 to 100 nm.
3) The single-sided two-layer optical recording medium according to any one of 1) and 2), wherein the total thickness of the first protective layer and the second protective layer is 8 to 103 nm.
4) _a first protective layer _SiO 2, _Al 2 O 3, of TiO ₂ either, characterized in that it consists of a material whose main component 1) to 3) single-sided two-layer optical recording medium according to any one of .
5) The single-sided dual-layer optical recording medium according to any one of 1) to 4), wherein the second protective layer is made of a material containing ZnS as a main component.
6) between the first substrate and the second substrate having a guide groove, a first information layer, an intermediate layer, a second information layer sequentially provided, each information layer has a recording layer comprising an organic dye An optical recording medium that records and reproduces information by modulating laser light with a binary intensity or more upon incidence of laser light from a first substrate, wherein the second information layer is formed from the light incident side by the first protective layer. The second protective layer, the organic dye recording layer, and the reflective layer are sequentially laminated, the first protective layer is made of an ultraviolet curable resin, and has a thermal expansion coefficient smaller than that of the intermediate layer. Two-layer optical recording medium.
7) The single-sided dual-layer optical recording medium according to 6), wherein the total thickness of the first protective layer and the intermediate layer is 20 to 70 μm.

FIG. 1 is a schematic cross-sectional view of a single-sided dual-layer optical recording medium according to an embodiment of the present invention.
The optical recording medium (optical disk) shown in FIG. 1 has two information layers. Each information layer is formed using an organic dye material. Information is recorded on each information layer by making a laser beam incident from the first substrate and recording a pattern called a mark. More specifically, the first information layer 100 is formed on the first substrate 101 having guide grooves. The first information layer 100 may be a single layer of the first organic dye recording layer 102, or a structure in which the first metal reflective layer 103 is laminated thereon. A transparent first heat diffusion layer may be provided on the first metal reflective layer 103. Further, an undercoat layer or a protective layer may be provided between the first organic dye recording layer 102 and the first substrate 101, or a structure in which they are laminated for improving the function may be used.
Meanwhile, the second information layer 200 is formed on the second substrate 201 having guide grooves. The second information layer 200 is laminated in order of the second metal reflective layer 202, the second organic dye recording layer 203, the second protective layer 204, and the first protective layer 205 from the second substrate side.
The first information layer 100 and the second information layer 200 are separated from each other by a predetermined distance with a substantially transparent adhesive layer as an intermediate layer 300, and are opposed to each other.

The first substrate 101 needs to sufficiently transmit light irradiated for recording and reproduction, and those conventionally known in the technical field are applied. As the material, a transparent resin such as polycarbonate, acrylic resin, polyolefin, or transparent glass can be used. Among these, polycarbonate resin is the most preferred material because it has a track record of being most widely used in CD and is inexpensive. The first substrate 101 is provided with a groove for guiding recording / reproducing light. Further, the thickness of the first substrate is preferably about 10 to 600 μm.
As the material of the second substrate 201, the same material as that of the first substrate 101 may be used, but a material opaque to the recording / reproducing light may be used. May be different. Although the thickness of the 2nd board | substrate 201 is not specifically limited, It is preferable to select thickness so that the sum total with the thickness of the 1st board | substrate 1 may be 1.2 mm. Further, a groove is provided on the side where the information layer 200 is formed.

The intermediate layer 300 is preferably small light absorption at a wavelength of light to be irradiated for recording and reproduction, as the material, moldability, and resin is preferable in terms of cost, ultraviolet curing resin, slow-acting resin, A thermoplastic resin or the like can be used. Also, a double-sided tape for bonding optical disks (for example, an adhesive sheet DA-8320 manufactured by Nitto Denko Corporation) can be used. The intermediate layer 300 is used to allow the pickup to distinguish the first information layer 100 and the second information layer 200 from each other and perform optical separation when recording / reproducing, and the thickness is preferably 10 to 70 μm. . When the thickness is less than 10 μm, interlayer crosstalk occurs. When the thickness is greater than 70 μm, spherical aberration occurs when recording / reproducing the second information layer, and recording / reproduction tends to be difficult. A range of 20 to 70 μm is more preferable.
As described later, the case of using an ultraviolet curable resin in the first protective layer, the total thickness of the first protective layer and the intermediate layer is preferably from 20 to 70 m, the thickness of the intermediate layer to the thickness of the first protective layer Corresponding adjustments can be made accordingly.

Next, the first organic dye recording layer 102 and the second organic dye recording layer 203 will be described.
Optical characteristics can be mentioned as an item necessary for constituting the recording layer of the optical recording medium. The necessary condition for the optical characteristics is that the recording / reproducing wavelength has a large absorption band on the short wavelength side, and the recording / reproducing wavelength is in the vicinity of the long wavelength end of the absorption band. This means that it has a large refractive index and extinction coefficient at the recording / reproducing wavelength. Specifically, the recording layer single layer preferably has a refractive index n of 1.5 to 3.0 and an extinction coefficient k of 0.02 to 0.2. When n is less than 1.5, it is difficult to obtain a sufficient optical change and the recording modulation degree is low, which is not preferable. When n exceeds 3.0, the wavelength dependence becomes too high, and recording / reproduction is not possible. Even in the wavelength region, an error occurs, which is not preferable. Further, when k is less than 0.02, it is not preferable because the recording sensitivity is deteriorated. When k exceeds 0.2, it is difficult to obtain a reflectance of 18% or more. The layer is not preferable because the transmittance is too low and the recording sensitivity of the second information layer is deteriorated.

Next, specific examples of organic dye materials that can be used in the present invention include azo metal chelate dyes, formazan metal chelate dyes, dipyrromethene metal chelate dyes, polymethine dyes, squarylium dyes, azaannulene dyes, and the like. Metal chelate dyes, trimethine cyanine dyes, squarylium dyes, tetraazaporphyrin dyes.
As azo metal chelate dyes, the azo compound forming units on both sides of the azo bond are substituted / unsubstituted aromatic rings, pyridine residues, pyrimidine residues, pyrazine residues, pyridazine residues, triazine residues, imidazole residues. , triazole residue, pyrazole residue, thiazole residue, isothiazole residue, a metal chelate compound of azo compounds comprising a combination of such benzthiazole residue is particularly preferred.

式中、Ｚは、それが結合している炭素原子及び窒素原子と一緒になって複素環を形成する残基であり、具体的にはピリダジン環、ピリミジン環、ピラジン環、又はトリアジン環である。また、これらの複素環はアルキル基、アルコキシ基、アルキルチオ基、置換アミノ基、アリル基、アリルオキシ基、アニリノ基、ケト基等の置換基を有していてもよい。Ａは、アルキル基、アラルキル基、アリル基、又はシクロヘキシル基を表し、ハロゲン原子、アルキル基、アルコキシ基、ケト基、カルボキシル基又はそのエステル、ニトリル基、ニトロ基等の置換基を有していてもよい。Ｂは、アリル基を表し、ハロゲン原子、アルキル基、アルコキシ基、カルボキシル基又はそのエステル、ニトリル基、ニトロ基等の置換基を有していてもよい。 Examples of the formazan metal chelate dye include chelate compounds of a formazan compound represented by the following general formula and a divalent metal atom.

In the formula, Z is a residue that forms a heterocyclic ring together with the carbon atom and nitrogen atom to which it is bonded, and is specifically a pyridazine ring, a pyrimidine ring, a pyrazine ring, or a triazine ring. . These heterocyclic rings may have a substituent such as an alkyl group, an alkoxy group, an alkylthio group, a substituted amino group, an allyl group, an allyloxy group, an anilino group, or a keto group. A represents an alkyl group, an aralkyl group, an allyl group, or a cyclohexyl group, and has a substituent such as a halogen atom, an alkyl group, an alkoxy group, a keto group, a carboxyl group or an ester thereof, a nitrile group, or a nitro group. Also good. B represents an allyl group and may have a substituent such as a halogen atom, an alkyl group, an alkoxy group, a carboxyl group or an ester thereof, a nitrile group, or a nitro group.

式中、Ｒ_１〜Ｒ_９は、各々独立に、水素原子、ハロゲン原子、置換・未置換のアルキル基、アルコキシ基、アルケニル基、アシル基、アルコキシカルボニル基、アラルキル基、アリール基、又はヘテロアリール基を表す。
上記アゾ化合物、ホルマザン化合物、又はジピロメテン化合物とキレート化合物を形成する金属としては、例えば、Ｎｉ、Ｃｏ、Ｃｕ、Ｍｎ、Ｖ、Ｚｎ、Ｆｅ、Ｃｒ、Ａｌ等が挙げられ、製造上及びディスク特性上から、特にＮｉ、Ｃｏ、Ｃｕ、Ｍｎ、Ｖが好ましい。 Examples of the dipyrromethene metal chelate dye include chelate compounds of a dipyrromethene compound represented by the following general formula and a divalent metal atom.

In the formula, each of R _{1 to} R ₉ independently represents a hydrogen atom, a halogen atom, a substituted / unsubstituted alkyl group, an alkoxy group, an alkenyl group, an acyl group, an alkoxycarbonyl group, an aralkyl group, an aryl group, or heteroaryl. Represents a group.
Examples of the metal that forms a chelate compound with the azo compound, formazan compound, or dipyrromethene compound include Ni, Co, Cu, Mn, V, Zn, Fe, Cr, Al, etc. Therefore, Ni, Co, Cu, Mn, and V are particularly preferable.

As the polymethine dye, any dye having an absorption band at 530 to 600 nm can be used. Among them, a trimethine cyanine dye is preferable, and in particular, a trimethine chain having both substituted and unsubstituted indolenine and benzindolenin is particularly preferred. Preferably, the counter anion may be various metal chelate anions typified by a nickel dithiolate complex, in addition to a halogen anion, ClO ⁴⁻ , BF ⁴⁻ , PF ⁶⁻ , SbF ^{6−, and the} like.
As the squarylium dye, those composed of a combination of substituted / unsubstituted indolenine, benzindolenin, pyrazole, carbazole, quinoxaline, isoindole, aromatic ring and substituted amino group residues at both ends of the squalene ring are preferable.
Examples of azaannulene dyes include phthalocyanine, naphthalocyanine, tetrapyrazinoporphyrazine, tetrapyridinoporphyrazine, tetraazaporphyrin, etc. each having a specific substituent, and among these, tetraazaporphyrin is particularly preferred. Then, tetrapyridinoporphyrazine, tetrapyrazinoporphyrazine, and phthalocyanine are preferable in this order.

Regarding the thermal decomposition characteristics of the above-mentioned dye, it is preferable that the decomposition start temperature of the recording material is 360 ° C. or lower when the dye is used alone or in combination. 100-350 degreeC is especially preferable. When the decomposition temperature exceeds 360 ° C., pit formation at the time of recording is not performed well, and jitter characteristics are poor. If the temperature is lower than 100 ° C., the storage stability of the disk deteriorates.
The dye may be mixed or laminated with other organic dyes, metals, and metal compounds for the purpose of improving optical characteristics, recording sensitivity, signal characteristics, and the like.
Examples of other organic dyes include (poly) methine, naphthalocyanine, phthalocyanine, squarylium, croconium, pyrylium, naphthoquinone, anthraquinone (indanthrene), xanthene, triphenylmethane , Azulene, tetrahydrocholine, phenanthrene, triphenothiazine dyes, metal complex compounds, and the like.
Examples of metals and metal compounds include In, Te, Bi, Se, Sb, Ge, Sn, Al, Be, TeO ₂ , SnO, As, Cd, etc., each of which is used in the form of dispersion mixing or lamination. be able to.

In addition, various materials such as ionomer resins, polyamide resins, vinyl resins, natural polymers, silicones, liquid rubbers, or silane coupling agents may be dispersed and mixed in the dyes. For the purpose of improvement, stabilizers (for example, transition metal complexes), dispersants, flame retardants, lubricants, antistatic agents, surfactants, plasticizers and the like can be used together.
As a method for forming the organic dye recording layer, usual means such as vapor deposition, sputtering, CVD or solvent coating can be used. In the case of using the coating method, the above-described dye or the like can be dissolved in an organic solvent and can be performed by a conventional coating method such as spraying, roller coating, dipping and spin coating. Examples of the organic solvent used include alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide. Sulfoxides, tetrahydrofuran, dioxane, diethyl ether, ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, aliphatic halogenated hydrocarbons such as chloroform, methylene chloride, dichloroethane, carbon tetrachloride, and trichloroethane , Aromatics such as benzene, xylene, monochlorobenzene and dichlorobenzene, cellosolves such as methoxyethanol and ethoxyethanol, hexane and pen Down, cyclohexane, and hydrocarbons such as methylcyclohexane.
The film thickness of the recording layer is 10 nm to 10 μm, preferably 20 nm to 200 nm.

Examples of the metal reflective layer material include metals that are high in reflectance and hardly corroded, metalloids, and specific examples include Au, Ag, Cr, Ni, Al, Fe, Cu, and Sn. Au, Ag, and Al are most preferable from the viewpoint of reflectance and productivity. These metals and metalloids may be used alone or as two kinds of alloys. In particular, since the first information layer 100 requires high transmittance, it is preferable to use Ag or an Ag alloy having a low refractive index and a high thermal conductivity for the first metal reflective layer 103.
Examples of the film forming method include vapor deposition and sputtering.
The film thickness is 3 to 500 nm, preferably 3 to 300 nm. Regarding the 1st metal reflective layer 103, in order to ensure high transmittance, 3-20 nm is preferable. If the thickness is less than 3 nm, it is difficult to form a dense film having a uniform thickness.

Next, the 1st protective layer and the 2nd protective layer which are the characterizing parts of the present invention are explained.
The second information layer of the present invention is composed of a first protective layer, a second protective layer, a second organic dye layer, and a second metal reflective layer in this order from the light incident side.
The material of the second protective layer is determined in consideration of the refractive index, thermal conductivity, chemical stability, mechanical strength, adhesion, and the like. The lower thermal conductivity is desirable, but the standard is 1 × 10E ⁻³ pJ / (μm · N · nsec). Incidentally, it is difficult to measure the thermal conductivity of a thin film state of such a low thermal conductivity material directly, it is possible to obtain an indication from the measurement results of the actual recording sensitivity and thermal simulation as an alternative to direct measurement .
The material for the protective layer having a low thermal conductivity that brings about a preferable result includes 50 to 90 mol% of at least one of ZnS, ZnO, SiC, TaS ₂ , and rare earth sulfide, has high transparency, and has a melting point or A composite dielectric containing a heat-resistant compound having a decomposition point of 1000 ° C. or higher is desirable. More specifically, a composite dielectric containing 60 to 90 mol% of rare earth sulfides such as La, Ce, Nd, and Y, or a ratio of ZnS and ZnO of 70 to 90 mol% is desirable. Of these, a material mainly composed of ZnS is most suitable.
Examples of heat-resistant compounds having a melting point or decomposition point of 1000 ° C. or higher include Mg, Ca, Sr, Y, La, Ce, Ho, Er, Yb, Ti, Zr, Hf, V, Nb, Ta, Zn, Al, Si, Oxides such as Ge and Pb, nitrides, carbides, and fluorides such as Ca, Mg, and Li can be used.
Note that these oxides, sulfides, nitrides, carbides, and fluorides do not necessarily have a stoichiometric composition, and it is also effective to change the composition or use a mixture for controlling the refractive index and the like. It is.

The first protective layer is incompatible with the intermediate layer 300 and needs to have high transmittance, and a material having a thermal expansion coefficient of 2 × 10E-6K ⁻¹ or less is used. If the thermal expansion coefficient is larger than this, there is a risk that the characteristics will deteriorate due to deformation due to heat during recording. A preferable thermal expansion coefficient is 1 × 10E-6K ⁻¹ or less. Moreover, the minimum of a thermal expansion coefficient is 0.1 * 10E-6K- ¹ . If the thermal expansion coefficient is smaller than this, the difference in thermal expansion coefficient between adjacent films becomes large, and there is a possibility that breakage such as peeling occurs during recording. In addition, the storage characteristics deteriorate. Specific examples of the inorganic material suitable for the first protective layer include oxides such as SiO ₂ , Al ₂ O ₃ , and TiO ₂ or a mixture thereof. Moreover, you may contain an impurity as needed. The melting point of the protective layer needs to be higher than that of the recording layer.

When an inorganic substance is used for the first protective layer, the thickness of the first protective layer is preferably in the range of 5 to 100 nm. If it is thinner than 5 nm, the effect cannot be obtained. On the other hand, when the thickness is more than 100 nm, not only the productivity is deteriorated, but also the reflectance of the second information layer is lowered and the film stress is increased, so that the substrate is easily deformed and the light-transmitting protective layer is peeled off. A more preferable range is 5 to 60 nm, and a further preferable range is 5 to 40 nm.
The total film thickness of the first protective layer and the second protective layer is preferably in the range of 8 to 103 nm. The film thicknesses of the first protective layer and the second protective layer are designed in consideration of the sensitivity of the second information layer, the reflectance, and the effect of the first protective layer. A more preferable range is 8 to 63 nm, and a further preferable range is 8 to 43 nm.
Further, an ultraviolet curable resin having a smaller thermal expansion coefficient than that of the intermediate layer can be used for the first protective layer. If the thermal expansion coefficient of the first protective layer is smaller than that of the intermediate layer, the effect of the present invention can be obtained. Specifically, an ultraviolet curable resin having a low thermal expansion coefficient of about 0.1 × 10E-6K ⁻¹ to 1 × 10E-6K ⁻¹ is preferable. If the thermal expansion coefficient is larger than this, the effect cannot be obtained. If the thermal expansion coefficient is smaller than this, the difference in thermal expansion coefficient between adjacent films becomes large, and there is a possibility that breakage such as peeling occurs during recording.
When an ultraviolet curable resin is used for the first protective layer, the film thickness is preferably 1 to 55 μm. If it is thinner than 1 nm or thicker than 55 nm, it is difficult to form by spin coating.
When using a UV curable resin in the first protective layer, its optical properties, since similar to the intermediate layer, the total thickness of the first protective layer and the intermediate layer is in the range of 20~70μm are preferred, The thickness of the intermediate layer can be appropriately adjusted according to the thickness of the first protective layer.

The single-sided two-layer optical recording medium of the present invention may be provided with any other layer as necessary. Alternatively, any other layer may be provided on the outermost surface of the medium.
For example, a hard coat layer may be provided on the first substrate surface side, which protects the recording layer (reflection / absorption layer) from scratches, dust and dirt, and improves the storage stability of the recording layer (reflection / absorption layer). It is used for the purpose of improving the reflectance. For these purposes, SiO, SiO ₂ or the like can be used as an inorganic material, and polymethyl acrylate resin, polycarbonate resin, epoxy resin, polystyrene resin, polyester resin, vinyl resin, cellulose, aliphatic as organic materials. Thermosoftening and heat melting resins such as hydrocarbon resins, natural rubber, styrene butadiene resins, chloroprene rubbers, waxes, alkyd resins, drying oils and rosins can also be used. Particularly preferred is an ultraviolet curable resin excellent in productivity.
The film thickness of the substrate surface hard coat layer is 0.01 to 30 μm, preferably 0.05 to 10 μm. As in the case of the recording layer, the substrate surface hard coat layer may contain a stabilizer, a dispersant, a flame retardant, a lubricant, an antistatic agent, a surfactant, a plasticizer, and the like.

  In the single-sided two-layer optical recording medium of the present invention, a first heat diffusion layer may be provided on the first metal reflective layer 103. The first metal reflective layer 103 must be very thin from the viewpoint of transmittance. However, if the first metal reflective layer 103 is thin, the heat capacity is insufficient, and heat is trapped in the organic dye recording layer 102 to form minute marks. Can be difficult. In such a case, a first heat diffusion layer may be provided to supplement the heat capacity of the first metal reflective layer 103. The first heat diffusion layer also serves to prevent the first metal reflective layer from reacting with the intermediate layer. As the first thermal diffusion layer, it is desired that the thermal conductivity is high in order to quench the organic dye recording layer irradiated with the laser. It is also desired that the absorption rate at the laser wavelength is small so that the information layer on the back side can be recorded and reproduced. Furthermore, the extinction coefficient is preferably 0.5 or less, and more preferably 0.3 or less, at the wavelength of the laser beam used for recording / reproducing information. If it is greater than 0.5, the absorptance in the first information layer increases, and recording / reproduction of the second information layer becomes difficult. The refractive index is preferably 1.6 or more at the wavelength of the laser beam used for recording / reproducing information. If it is smaller than this, it becomes difficult to increase the transmittance of the first information layer.

From the above, the material of the first thermal diffusion layer preferably contains at least one of nitride, oxide, sulfide, nitride oxide, carbide and fluoride. For example, AlN, Al ₂ O ₃ , SiC, SiN, SnO ₂ , In ₂ O ₃ , ZnO, ITO (indium oxide-tin oxide), IZO (indium oxide-zinc oxide), ATO (tin oxide-antimony), DLC (Diamond like carbon), BN, etc. are mentioned.
The first thermal diffusion layer can be formed by various vapor deposition methods such as vacuum deposition, sputtering, plasma CVD, photo CVD, ion plating, and electron beam deposition. Among these, the sputtering method is excellent in mass productivity and film quality.
The thickness of the first thermal diffusion layer is preferably 10 to 200 nm. If it is thinner than 10 nm, the heat dissipation effect cannot be obtained. If it is thicker than 200 nm, the stress increases, and not only the repeated recording characteristics deteriorate, but also a problem arises in mass productivity.
The first information layer preferably has a light transmittance of 40 to 70% at a recording / reproducing laser beam wavelength of 350 to 700 nm, more preferably 40 to 60%.

Next, the manufacturing method of the single-sided double layer optical recording medium of the present invention will be described.
First, a first substrate on which the first information layer is formed on the surface of the first substrate and a second substrate on which the second information layer is formed on the surface of the second substrate are separately prepared. The first information layer is formed by applying an organic dye dissolved in a solvent to the surface of the first substrate on which the groove is provided by spin coating or the like, and forming a first metal reflective layer thereon. The second information layer is formed by forming a second metal reflective layer on the surface of the second substrate on which the groove is provided, applying an organic dye thereon by spin coating or the like, and further providing a second protective layer, The first protective layer is formed by sequentially forming a film.
The metal reflective layer and the protective layer constituting each of the first information layer and the second information layer can be formed by various vapor deposition methods such as vacuum deposition method, sputtering method, plasma CVD method, photo CVD method, ion plating method, electron It is formed by a beam evaporation method or the like. Among these, the sputtering method is excellent in mass productivity and film quality. In the sputtering method, film formation is generally performed while flowing an inert gas such as argon. At this time, reactive sputtering may be performed while oxygen, nitrogen, or the like is mixed.
Next, the first information layer formed on the first substrate surface and the second information layer formed on the second substrate surface, with the first information layer and the second information layer facing each other, Laminate through an intermediate layer. For example, after applying an ultraviolet curable resin as an intermediate layer on the information surface of one of the substrates by spin coating or the like, the other substrate is placed on the information surface with the film surfaces facing each other, and pressurization. The optical recording medium is manufactured by spreading the resin over the entire surface and then curing the resin by ultraviolet irradiation.

FIG. 2 is a schematic diagram of an apparatus for recording / reproducing a single-sided dual-layer optical recording medium according to the present invention. The optical recording medium is driven to rotate by a driving means consisting of a spindle motor, a light source consisting of a semiconductor laser is driven by a laser driving circuit which is a light source driving means, and a recording / reproducing pickup is used via an optical system (not shown), Optical recording is performed by irradiating an optical recording medium with an electromagnetic wave from the semiconductor laser light source, causing a change in the recording layer of the optical recording medium, and further receiving reflected light from the optical recording medium with a pickup for recording and reproduction. Records and reproduces information on the medium. In the waveform processing circuit, the signal level of the reproduced HF signal is measured, and an operation for obtaining Pwo is performed. The optimum recording power of the recording / reproducing pickup is set by a recording power setting circuit as recording power setting means.
An optical recording medium recording / reproducing apparatus irradiates an optical recording medium with laser light as an electromagnetic wave by a recording / reproducing pickup to cause a change in a recording layer, and records and reproduces information. There is provided recording means for modulating by the modulating section and recording on the optical recording medium by a recording / reproducing pickup. Also, a layer recognition means for identifying the first information layer and the second information layer, and for switching laser irradiation from the first information layer to the second information layer or from the second information layer to the first information layer. Layer switching means.

  According to the present invention, it is possible to provide a single-sided dual-layer optical recording medium capable of recording and reproducing both the first information layer and the second information layer.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited at all by these Examples.

[Examples 1-5, Comparative Examples 1-3]
On a first substrate made of polycarbonate resin having a diameter of 12 cm, a thickness of 0.58 mm, and a groove having a groove pitch of 0.74 μm, a groove width of 0.28 μm, and a groove depth of 150 nm, the following structural formula [Chemical Formula 3] The squarylium dye represented and the formazan chelate dye represented by the following structural formula [Chemical Formula 4] are mixed at a ratio of 7: 3, and the concentration is 1.0 mass% in 2,2,3,3-tetrafluoropropanol. The solution dissolved in was spin-coated to form a first dye-containing recording layer. This recording layer had a maximum absorption wavelength of 609 nm and an absorbance (Abs) at the maximum absorption wavelength of 0.65. The recording layer thickness in the groove at this time was 60 nm.
Further, a 12 nm-thick first metal reflective layer made of Ag ₉₈ Pd ₁ Cu ₁ was provided thereon by magnetron sputtering to obtain a first information layer.
Further, a film thickness of 160 nm made of Ag is formed on a second substrate made of a polycarbonate resin having a diameter of 12 cm, a thickness of 0.58 mm, and a groove having a groove pitch of 0.74 μm, a groove width of 0.28 μm, and a groove depth of 35 nm. The second metal reflective layer was formed, and the squarylium dye represented by the following structural formula [Chemical Formula 3] was added onto the second metal reflective layer in 2,2,3,3-tetrafluoropropanol at a concentration of 1.5% by mass. The dissolved solution was spin-coated so that the absorbance was 1.6, thereby forming a second dye-containing recording layer, and a second protective layer and a first protective layer were sequentially formed thereon.
Table 1 shows the materials and film thicknesses of the first protective layer and the second protective layer of each example and comparative example.
Subsequently, 1-methoxy-2-propanol was ejected to a position having a radius of 59.2 mm by a spin coater to remove the dye at the outer peripheral portion from the outer edge portion of the protective layer, thereby obtaining a second information layer.
Next, after applying UV-curing adhesive DVD-576M made by Nippon Kayaku on the film surface of the first information layer and bonding the second information layer surface side of the second substrate together, the ultraviolet light is transmitted from the first substrate side. A two-layer write-once optical recording medium having two information layers was prepared by irradiating light to cure DVD-576M as an intermediate layer. The thickness of the intermediate layer was 50 μm.
Next, for each optical recording medium, using a recording apparatus having an optical system with a laser wavelength of 657 nm and NA of 0.65, a linear velocity of 9.2 m / s, a linear density of 0.293 μm / bit, and a recording power of 18 to 20 mW Was recorded on the second information layer, and jitter was measured by a time interval analyzer under the conditions of a linear velocity of 3.8 m / s and a reproduction power of 0.7 mW.
The measurement results are shown in Table 1. The thermal expansion coefficient in the table is a value obtained by measuring a bulk sample in advance with a thermal expansion measuring device (TMA).
The jitters of the optical recording media of Examples 1 to 5 were 9% or less, and good recording and reproduction were possible for both the first information layer and the second information layer.

[Example 6, Comparative Example 4]
On the first substrate made of polycarbonate resin having a guide groove with a diameter of 12 cm, a thickness of 0.58 mm, a groove pitch of 0.74 μm, a groove width of 0.28 μm, and a groove depth of 150 nm, the above structural formula The squarylium dye represented and the formazan chelate dye represented by the above structural formula [Chemical Formula 4] are mixed at a ratio of 7: 3, and the concentration is 1.0 mass% in 2,2,3,3-tetrafluoropropanol. The solution dissolved in (1) was spin coated to form a first dye-containing recording layer. This recording layer had a maximum absorption wavelength of 609 nm and an absorbance (Abs) at the maximum absorption wavelength of 0.65. The recording layer thickness in the groove at this time was 60 nm.
Further, a 12 nm-thick first metal reflective layer made of Ag ₉₈ Pd ₁ Cu ₁ was provided thereon by magnetron sputtering to obtain a first information layer.
Further, a film thickness of 160 nm made of Ag is formed on a second substrate made of a polycarbonate resin having a diameter of 12 cm, a thickness of 0.58 mm, and a groove having a groove pitch of 0.74 μm, a groove width of 0.28 μm, and a groove depth of 35 nm. The second metal reflective layer was formed, and the squarylium dye represented by the following structural formula [Chemical Formula 3] was added onto the second metal reflective layer in 2,2,3,3-tetrafluoropropanol at a concentration of 1.5% by mass. The dissolved solution is spin-coated so that the absorbance is 1.6, thereby forming a second organic dye recording layer. Subsequently, the first protective layer material is spin-coated, and a 3 kW metal halide lamp is used. Cured by irradiation for 3 seconds. The first protective layer material was 94% by weight of acrylate monomer mixture (25% by weight of ethylene oxide 4 mol addition bisphenol A diacrylate, 10% by weight of tetraethylene glycol diacrylate, 34% by weight of 1,6-hexanediol diacrylate) 2-hydroxypropyl acrylate 5% by weight, dipentaerythritol hexaacrylate 10% by weight, tetrahydrofurfuryl acrylate 10% by weight), lithium perfluorooctyl sulfonate 1% by weight as a surfactant, methylphenyl as a photopolymerization initiator It is a photopolymerizable composition obtained by blending 5% by weight of glyoxylate and mixing it uniformly. The thermal expansion coefficient of the first protective layer was 1 × 10E-6K ⁻¹ .
Subsequently, 1-methoxy-2-propanol was ejected to a position having a radius of 59.2 mm by a spin coater, and the dye on the outer peripheral portion than the outer edge portion of the protective layer was removed to obtain a second information layer.
Next, Nippon Kayaku's UV curable adhesive DVD-576M is applied onto the film surface of the first information layer, the second information layer surface side of the second substrate is bonded, and then ultraviolet light is transmitted from the first substrate side. Was irradiated to cure the DVD-576M to form an intermediate layer, and a two-layer write-once optical recording medium of Example 6 was produced. The thickness of the intermediate layer was 50 μm. It was 60 * 10E-6K < ^-1 > when the thermal expansion coefficient of the intermediate | middle layer was measured.
Separately, a two-layer write-once optical recording medium of Comparative Example 4 was produced in the same manner as in Example 6 except that the first protective layer was not provided.
Next, for each optical recording medium, using a recording apparatus having an optical system with a laser wavelength of 657 nm and NA of 0.65, a linear velocity of 9.2 m / s, a linear density of 0.293 μm / bit, and a recording power of 18 to 20 mW When recording was performed on the second information layer under the following conditions, and the jitter was measured with a time interval analyzer under the conditions of a linear velocity of 3.8 m / s and a reproduction power of 0.7 mW, the jitter of Example 6 was good at 8.2%. However, the jitter of Comparative Example 4 was 14.3%.

[Examples 7 to 9, Comparative Example 5]
Except that the first protective layer having a film thickness of 10 nm was formed by simultaneously sputtering the SiO ₂ target and the C (carbon) target, Examples 7 to 9 and 2 of Comparative Example 5 were the same as Example 1. A layer write-once optical recording medium was prepared.
The composition and thermal expansion coefficient of the first protective layer are as follows.
Composition Thermal expansion coefficient
Example 7 (SiO ₂ ) ₉₇ C ₃ 0.8 × 10E-6K ⁻¹
Example 8 (SiO ₂ ) ₉₀ C ₁₀ 1.8 × 10E-6K ⁻¹
Example _{9 (SiO 2) 80 C 20} 2.0 × 10E-6K -1
Comparative Example 5 (SiO ₂ ) ₇₀ C ₃₀ 2.3 × 10E-6K ⁻¹
For each medium was evaluated jitter under the same conditions as in Example 1, but the jitter in Examples 7-9 was 9% or less, it has exceeded 9% in Comparative Example 5.
In addition to the above, except that adjusting the composition of the SiO ₂ and C of the first protective layer, in the same manner as in Example 1, the thermal expansion coefficient of 1.8~3.0 × ^{10E-6K -1} to create a two-layer write-once information recording medium having a first protective layer was evaluated jitter under the same conditions as in example 1, good properties when the thermal expansion coefficient of 2.0 × 10E-6K ^-1 or less showed that.

[Examples 10 to 11, Comparative Example 6]
Using an inorganic dielectric material having a composition of SiO ₂ : 68 wt%, Al ₂ O ₃ : 23 wt%, Li ₂ O: 5 wt%, and TiO ₂ : 4 wt%, a 10 nm-thick film having a thickness of 10 nm is formed by sputtering. A two-layer write-once optical recording medium of Example 10 was produced in the same manner as in Example 1 except that one protective layer was formed.
Similarly, using an inorganic dielectric material having a composition of SiO ₂ : 65 wt%, Al ₂ O ₃ : 27 wt%, Li ₂ O: 3 wt%, ZrO ₂ : 5 wt%, a film thickness of 10 nm by sputtering. A two-layer write-once optical recording medium of Example 11 was produced in the same manner as in Example 1 except that the first protective layer was formed.
Also, _SiO 2: 64 _wt%, Al ₂ O 3: 25 wt%, _Li 2 O: _5% by _weight, ZrO 2: 4.2 _{wt%, P} 2 O 5: a composition consisting of 1.8 wt% inorganic A two-layer write-once optical recording medium of Comparative Example 6 was prepared in the same manner as in Example 1 except that a first protective layer having a thickness of 10 nm was formed by ion plating using a dielectric material.
The thermal expansion coefficient of the first protective layer is 0.2 × 10E-6K ⁻¹ in Example 10, 0.14 × 10E-6K ⁻¹ in Example 11, and 0.05 × 10E in Comparative Example 6. It was -6K- ¹ .
When jitter was measured for each of the above media under the same conditions as in Example 1, both Examples 10 to 11 and Comparative Example 6 showed a good value of 9% or less.
However, for each of the above media, an acceleration test was performed under the conditions of 80 ° C., 85% RH, 300 hours, and jitter was measured under the same conditions as before the test. In Examples 10 and 11, a good value of 9% or less was obtained. However, in Comparative Example 6, it exceeded 9% and was found to be deteriorated.
In addition to the above, a two-layer write-once optical recording medium having a first protective layer having a thermal expansion coefficient of 0.05 to 2 × 10E-6K ⁻¹ by adjusting the inorganic dielectric material composition of the first protective layer The jitter was evaluated under the same conditions as in Example 1. As a result, the two-layer write-once optical recording medium having a thermal expansion coefficient of 0.1 × 10E-6K ⁻¹ or more has good characteristics even after the acceleration test. Indicated.

1 is a schematic cross-sectional view of a single-sided double-layer optical recording medium according to an embodiment of the present invention. 1 is a schematic view of an apparatus for performing recording / reproduction on a single-sided double-layer optical recording medium according to the present invention.

Claims (7)

A first information layer, an intermediate layer, and a second information layer are sequentially provided between the first substrate and the second substrate having the guide groove, and each information layer has a recording layer made of an organic dye. An optical recording medium that records and reproduces information by modulating a light intensity of at least two values by making a laser beam incident from one substrate, wherein the second information layer includes, from the light incident side, a first protective layer, a first protective layer, Two protective layers, an organic dye recording layer, and a reflective layer are laminated in order, and the first protective layer has a thermal expansion coefficient of 0.1 × 10E-6K ⁻¹ to 2 × 10E-6K ^−1. Two-layer optical recording medium.   The single-sided dual-layer optical recording medium according to claim 1, wherein the thickness of the first protective layer is 5 to 100 nm.   The single-sided dual-layer optical recording medium according to any one of claims 1 and 2, wherein the total thickness of the first protective layer and the second protective layer is 8 to 103 nm. Single-sided two-layer optical recording medium according to any one of claims 1 to 3 _{in which the} first protective layer, characterized in that it consists of a material mainly composed of either of _{SiO 2, Al 2 O 3,} TiO 2.   The single-sided dual-layer optical recording medium according to any one of claims 1 to 4, wherein the second protective layer is made of a material containing ZnS as a main component.   A first information layer, an intermediate layer, and a second information layer are sequentially provided between the first substrate and the second substrate having the guide groove, and each information layer has a recording layer made of an organic dye. An optical recording medium that records and reproduces information by modulating a light intensity of two or more by entering a laser beam from one substrate, wherein the second information layer includes a first protective layer, a first protective layer, Two protective layers, an organic dye recording layer, and a reflective layer are laminated in order, the first protective layer is made of an ultraviolet curable resin, and the thermal expansion coefficient thereof is smaller than the thermal expansion coefficient of the intermediate layer. Optical recording medium. The single-sided dual-layer optical recording medium according to claim 6, wherein the total thickness of the first protective layer and the intermediate layer is 20 to 70 µm.

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