JP2007042153A - Method for manufacturing optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical recording medium, wherein costs are low and productivity is high. <P>SOLUTION: The method for manufacturing an optical recording medium having a reflective layer, a recording layer and a cover layer sequentially formed on a substrate includes a groove forming step of forming a guide groove or pit in the substrate, a reflective layer forming step of forming the reflective layer on a surface side of the substrate where the guide groove or pit is formed after the groove forming step, a recording layer forming step of forming the recording layer on the cover layer, and a bonding step of bonding the reflective layer of the substrate and the recording layer of the cover layer. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical recording medium for computers, business use, consumer use, etc., and a method for manufacturing an optical recording method.

  Recently, networks such as the Internet and high-definition TV are rapidly spreading. Also, HDTV (High Definition Television) has been started. Under such circumstances, a large-capacity optical recording medium capable of recording image information inexpensively and simply is required. DVD-R (Digital Versatile Disc) currently plays a role as a large-capacity optical recording medium, but the demand for higher capacity and higher density is increasing, and these demands are met. It is also necessary to develop optical recording media that can be used. For this reason, it is possible to perform high-density recording with light having a shorter wavelength than that of DVD-R, and development of an optical recording medium having a larger capacity is being promoted.

For example, in an optical recording medium having a recording layer containing an organic dye, a recording / reproducing method for recording and reproducing information by irradiating laser light having a wavelength of 530 nm or less from the recording layer side toward the reflective layer side is disclosed. (For example, see Patent Documents 1 to 15).
In these methods, an optical recording medium having a recording layer containing a porphyrin compound, an azo dye, a metal azo dye, a quinophthalone dye, a trimethine cyanine dye, a dicyanovinylphenyl skeleton dye, a coumarin compound, a naphthalocyanine compound, etc. In addition, information is recorded and reproduced by irradiating with blue (wavelength 430 nm, 488 nm) or blue-green (wavelength 515 nm) laser light.

Further, from the viewpoint of compatibility with currently used CD-R systems, optical recording media capable of recording and reproducing information with laser beams in two different wavelength regions have been proposed.
For example, by using a mixture of a dye used for CD-R and a dye used for DVD-R, the laser light in the near infrared region near 780 nm and the visible laser light near 650 nm can be used. An optical recording medium capable of recording and reproduction has been proposed (see, for example, Patent Documents 16 to 20).

  However, according to the study by the present inventors, the optical recording medium described in the above publication is practically necessary when recording information by irradiation with a short wavelength laser beam having a wavelength of 600 nm or less, particularly 450 nm or less. It has been found that the sensitivity cannot be obtained, or other recording characteristics such as reflectance and modulation are not satisfactory, and further improvement is required. In particular, in the optical recording medium described in the above publication, it was confirmed that the recording characteristics deteriorated when a laser beam having a wavelength of 450 nm or less was irradiated.

Conventional optical recording media generally have a laser beam incident from the substrate side. However, in order to achieve higher density, a pickup using a short wavelength laser and a high numerical aperture (NA) objective lens has been used.
For example, a DVR-blue (“ODS 2001 Technical Digest” p.139-141) combining a blue-violet laser near 405 nm and an objective lens with NA of 0.85 is an example. In an optical recording medium using such a short wavelength, high NA optical system, the influence of coma aberration due to the warp of the disk becomes so large that it cannot be ignored.
Therefore, in order to eliminate the influence of coma aberration, the laser beam for recording / reproduction is passed through a cover layer having a thickness of about 0.1 mm which is much thinner than a conventional substrate (for example, 1.2 mm thickness for CD and 0.6 mm thickness for DVD). Incidence of recording and reproduction defects due to coma aberration is improved.

For example, in the case of a rewritable phase change type optical recording medium, the optical recording medium has a cover layer / (transparent adhesive layer) / dielectric layer / recording layer / dielectric layer / reflection in order from the laser light incident surface side. A layer / substrate medium structure is employed (the cover layer and the transparent adhesive layer may be integrally formed by spin coating with an ultraviolet curable resin).
Here, in the case of DVR-blue, the total thickness of the cover layer and the transparent adhesive layer is about 0.1 mm, and the thickness of the substrate is about 1.1 mm.

  On the other hand, the dye-based write-once optical recording medium has a medium configuration of substrate / recording layer / reflective layer / protective layer in the CD-R in order from the laser light incident surface side, and substrate / recording in the DVD-R. A medium configuration of layer / reflective layer / (protective layer) / adhesive layer / (protective layer) / (reflective layer) / substrate is generally used. Note that the layers in parentheses in the case of DVD-R may be omitted.

If this is applied to an optical recording medium having the above-described cover layer, the following configuration is conceivable. That is, it is considered that the configuration is cover layer / (transparent adhesive layer) / transparent block layer / recording layer / reflection layer / substrate.
Here, the transparent block layer is used to prevent the dye of the dye layer from melting and damaging the dye layer when a transparent adhesive layer such as an ultraviolet curable resin is applied on the dye layer as the recording layer. Further, it is a transparent thin film layer formed by sputtering or the like. As the transparent block layer, a dielectric layer such as ZnS is used.
However, the formation of the dielectric layer requires a film formation cost and may damage the dye layer. In addition, there is a problem that the recording characteristics may be impaired due to the formation of a new interface.

  As another means, there is a method of sticking the transparent cover layer with a double-sided adhesive tape (including a case where there is no support), but there are problems such as high cost and loss of optical properties by the adhesive layer.

In any of the above optical recording medium manufacturing methods, since it is necessary to form a recording layer on a substrate, a film forming method such as so-called single wafer sputtering or spin coating is adopted, and film formation is performed in mass production. There is a problem that costs increase.
JP-A-4-74690 JP-A-7-304256 JP-A-7-304257 JP-A-8-127174 Japanese Patent Laid-Open No. 11-53758 JP-A-11-334204 JP 11-334205 A Japanese Patent Laid-Open No. 11-334206 JP 11-334207 A JP 2000-43423 A JP 2000-108513 A JP 2000-113504 A JP 2000-149320 A JP 2000-158818 A JP 2000-228028 A JP 2000-141900 A JP 2000-158816 A JP 2000-185471 A JP 2000-289342 A JP 2000-309165 A

  Accordingly, an object of the present invention is to provide a method for manufacturing an optical recording medium that is low in cost and excellent in productivity.

The above problems are solved by the present invention described below. That is, the present invention
<1> A method for producing an optical recording medium, wherein a reflective layer, a recording layer, and a cover layer are sequentially formed on a substrate,
A groove forming step of forming guide grooves or pits on the substrate;
A reflective layer forming step of forming the reflective layer on the surface side of the substrate where the guide grooves or the pits are formed after the groove forming step;
A recording layer forming step of forming the recording layer on the cover layer;
An optical recording medium manufacturing method comprising: a bonding step of bonding the reflective layer of the substrate and the recording layer of the cover layer.

  <2> At least the atmosphere at the time of bonding between the substrate and the cover layer in the bonding step is any one of a vacuum atmosphere, a reduced pressure atmosphere, a reduced nitrogen atmosphere, and a reduced inert gas atmosphere. <1> The method for producing an optical recording medium according to <1>, wherein

  <3> The method for producing an optical recording medium according to <1> or <2>, wherein a method of forming the recording layer in the recording layer forming step is web-type vacuum deposition or sputtering. .

  <4> The method for producing an optical recording medium according to <1> or <2>, wherein the film formation method of the recording layer in the recording layer forming step is application by a web method.

  <5> The method for manufacturing an optical recording medium according to any one of <1> to <4>, wherein the guide groove or the pit forming surface in the groove forming step is one surface of the substrate. is there.

  <6> The guide groove or the pit forming surface in the groove forming step is both surfaces of the substrate, and the formation of the guide groove or the pit is simultaneous on both surfaces <1> to <4> The method for producing an optical recording medium according to any one of the above.

<7> A method for producing an optical recording medium, wherein at least a recording layer and a cover layer are sequentially formed on a substrate,
A groove forming step for simultaneously forming a guide groove or pit on one surface of the substrate and a pit on the other surface;
A recording layer forming step of forming the recording layer on the cover layer;
The cover layer on which the recording layer is formed is bonded to one surface side of the substrate that has undergone the groove forming step so that the recording layer becomes an inner layer, and the cover layer on which the recording layer is not formed And a bonding step of bonding to the other surface side of the substrate.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the optical recording medium excellent in productivity at low cost can be provided.

<Method for Producing Optical Recording Medium of the Present Invention>
[1] First manufacturing method:
A first method for manufacturing an optical recording medium of the present invention is a method for manufacturing an optical recording medium in which a reflective layer, a recording layer, and a cover layer are sequentially formed on a substrate. A groove forming step for forming grooves or pits; (2) a reflective layer forming step for forming a reflective layer on the surface of the substrate on which the guide grooves or pits are formed after the groove forming step; and (4) A recording layer forming step of forming a recording layer on the cover layer; and (5) a bonding step of bonding the reflective layer of the substrate and the recording layer of the cover layer together.

  In the manufacturing method of the present invention, unlike the method of sequentially forming a reflective layer, a recording layer, and a cover layer on a substrate, the substrate on which the reflective layer and the like are formed and the cover layer on which the recording layer is formed are separately provided. It is characterized in that it is manufactured and bonded together. In the conventional method of sequentially forming a recording layer, a cover layer, etc. on a substrate, the recording layer must be formed on each disk substrate. For this reason, there has been a problem that the film formation cost in mass production increases.

  However, in the present invention, first, as shown in FIG. 1 (A), a coating film 3A to be a recording layer is continuously formed on a cover sheet 4A as a cover layer to produce a cover layer having the recording layer formed thereon. To do. As this formation method, it is preferable to adopt a web method application, a web method vacuum deposition or a sputtering method in consideration of the fact that it can be continuously processed. When the application by the web method is adopted, as shown in FIG. 1A, it is preferable to install the coating device 20 on the upstream side and provide the drying device 22 on the downstream side. Then, as shown in FIG. 1B, it is punched into the same shape as the substrate and bonded onto the reflective layer (FIG. 1C), or a cover layer is bonded onto the reflective layer of the substrate and then shaped into a predetermined shape. An optical recording medium can be manufactured by punching. As described above, since it is not necessary to form a recording layer on each disk substrate, it is possible to reduce the film formation cost in mass production.

  In addition, the recording layer of the optical recording medium manufactured in this way has a planar shape because the planar shape of the cover layer is reflected, and its thickness is substantially uniform. By being flat and substantially uniform, the signal level inner / outer difference and the inner / outer difference can be reduced, and the margin for signal error can be increased and the reliability can be increased.

  Hereinafter, the method for producing an optical recording medium of the present invention will be described while explaining the substrate and each layer of the optical recording medium.

(Substrate on which a reflective layer is formed)
As the substrate, various materials used as substrate materials for conventional optical recording media can be arbitrarily selected and used.
Specifically, glass; acrylic resin such as polycarbonate and polymethyl methacrylate; vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer; epoxy resin; amorphous polyolefin; polyester; metal such as aluminum; These may be used together if desired.
Among the above materials, polycarbonate and amorphous polyolefin are preferable, and polycarbonate is particularly preferable from the viewpoints of moisture resistance, dimensional stability, and low cost. The thickness of the substrate is preferably set to 0.3 to 1.2 mm in consideration of maintenance of strength, prevention of disc warpage, handling properties, and the like.

  As described above, the substrate has a tracking guide groove (groove representing information such as an address signal (hereinafter, the groove may mean “on-groove and in-groove”)), or A pit is formed. In order to achieve a higher recording density, it is preferable to use a substrate on which grooves having a narrower track pitch are formed as compared with CD-R and DVD-R. The track pitch of the groove is preferably in the range of 200 to 400 nm, and more preferably in the range of 250 to 350 nm. The in-groove depth (groove depth) is preferably in the range of 20 to 150 nm, and more preferably in the range of 25 to 80 nm. The pits and the guide grooves can be formed by a conventional molding method (injection molding) (groove forming step).

  The guide groove or pit forming surface in the groove forming step may be one side of the substrate, or both sides of the substrate, and the guide groove or pit may be formed simultaneously on both sides.

A light-reflective material having a high reflectivity with respect to laser light is used for the reflective layer arbitrarily formed on the surface of the substrate where the grooves are formed. The reflectance is preferably 70% or more.
As a light reflecting material having high reflectance, Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd , Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and other metals and semi-metals or stainless steel. These light reflecting materials may be used alone, or may be used in combination of two or more 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.

  The reflective layer can be formed on the substrate, for example, by vapor deposition, sputtering or ion plating of the light reflective material (reflective layer forming step). The thickness of the reflective layer is generally in the range of 10 to 300 nm and preferably in the range of 50 to 120 nm. As described above, a substrate on which a reflective layer and the like are formed is manufactured. The optical recording medium is generally in the form of an optical disk, but can be applied to, for example, a sheet type or a tape type depending on a card type or a substrate thickness.

(Cover film)
The cover film to be the cover layer is not particularly limited as long as it is a material transparent to the laser beam to be used, but is preferably a material having a moisture absorption rate of 5% or less at 23 ° C. and 50% RH, more preferably polycarbonate. , Cellulose triacetate, amorphous polyolefin, etc. are used.
Here, “transparent” means that the recording light and the reproduction light are so transparent that the light is transmitted (transmittance: 85% or more).
The thickness of the cover layer is preferably in the range of 30 to 130 μm, more preferably in the range of 50 to 110 μm, from the viewpoints of resistance to dust adhesion and scratches and reduction of coma aberration.

  The recording layer formed on the cover layer can record information with at least a laser beam having a wavelength of 450 nm or less, and contains a dye as a recording material. Examples of the dye contained in the recording layer include at least one of a metal complex dye, an azo dye, a benzotriazole dye, a phthalocyanine dye, and the like. Among these, a phthalocyanine dye is preferable. The recording layer may be either a rewritable type or a write once type, but is preferably a write once type. Further, not only heat mode recording but also photon mode recording may be used.

  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 as recording materials.

  The recording layer is prepared by dissolving a recording substance such as a dye in an appropriate solvent to prepare a coating solution, and then coating the coating solution on the cover film to form a coating film, followed by drying as necessary. (Recording layer forming step).

  As described above, it is preferable to apply means such as web application to the cover film or continuous vapor deposition as the application method of the application liquid. According to means such as web coating or continuous vapor deposition, it is possible to efficiently form a recording layer having a substantially uniform thickness. Further, according to such means, since the recording layer can be formed continuously, it is excellent in mass productivity and has a small thickness as compared with the method of forming the recording layer by spin coating or dip coating for each sheet. The occurrence of uniform defective products can be reduced, and productivity can be improved. Further, as described above, a sputtering method may be applied.

  The concentration of the recording substance 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, and most preferably. Is in 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 above solvents can be used alone or in combination of two or more in consideration of the solubility of the recording material used. Various additives such as an antioxidant, an ultraviolet absorber, a plasticizer, and a lubricant may be further added to the coating solution depending on the purpose.

In the case of using 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; Vinyl resins such as vinyl chloride, polyvinylidene chloride, polyvinyl chloride / polyvinyl acetate copolymer, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resin, butyral resin, And synthetic organic polymers such as rubber derivatives and initial condensates of thermosetting resins such as phenol / formaldehyde resins. When a binder is used in combination as a material for the recording layer, the amount of binder used is generally in the range of 0.01 times to 50 times (mass ratio), preferably 0.1 times the recording substance. The amount is in the range of 5 to 5 times (mass ratio). The concentration of the recording substance in the coating solution thus prepared is generally in the range of 0.01 to 10% by mass, preferably in the range of 0.1 to 5% by mass.
The thickness of the recording layer is generally in the range of 20 to 500 nm, preferably in the range of 30 to 300 nm, and more preferably in the range of 25 to 80 nm.

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

  Specific examples thereof include JP-A Nos. 58-175893, 59-81194, 60-18387, 60-19586, 60-19587, and 60-35054. 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, JP-A-60-47069, JP-A-63-209995, JP-A-4-25492, JP-B-1-38680, JP-A-6-26028, etc., German Patent No. 350399, and Japan Examples include those described in Chemical Society Journal, October 1992, page 1141.

  The use amount of the antifading agent such as the singlet oxygen quencher is usually in the range of 0.1 to 50% by mass, preferably in the range of 0.5 to 45% by mass, based on the amount of the dye. More preferably, it is the range of 3-40 mass%, Most preferably, it is the range of 5-25 mass%.

  As described above, a cover film having a recording layer formed thereon is produced.

The substrate on which the reflective layer or the like is formed and the cover film on which the recording layer is formed are preferably bonded together as described below.
Although it does not specifically limit as a method of bonding the said cover film and a board | substrate, The following 1st-3rd methods are employable.
(1) As shown in FIGS. 1 and 2, the first method is a method of mechanically joining, for example, the innermost peripheral portion and the outermost peripheral portion without particularly providing an adhesive layer.
(2) In the second method, an adhesive layer (including a pressure-sensitive adhesive in this specification) is applied on the recording layer on the cover layer side to form an adhesive layer. In this method, the substrate side on which the layer is formed is bonded (bonded), or both are bonded via an adhesive sheet instead of the adhesive layer.
(3) In the third method, in the second method, a dielectric layer (also referred to as a transparent block layer or a barrier layer) is formed on the recording layer on the cover layer side (on the adhesive layer if an adhesive layer is formed). ) And pasting them together.

Here, as a dielectric layer which is a transparent block layer, it is a material such as oxide, nitride, carbide, sulfide, etc. composed of any one or more of Zn, Si, Ti, Te, Sm, Mo, Ge, etc. they may also be hybrid of as ZnS-SiO _2. As the transparent block layer, any material having a transmittance of 90% or more at the laser wavelength can be used without being limited to a dielectric. The thickness of the transparent block layer is preferably 1 to 100 nm, and more preferably 1 to 10 nm.

Hereinafter, the bonding process will be described in detail.
First, an adhesive is dissolved in a suitable solvent to prepare a coating solution. The prepared coating solution is coated on the recording layer of the cover film formed by web coating or the like. As the coating method, it is preferable to apply a method such as curtain coating or spray coating.
Thereafter, the surface on which the groove of the substrate is formed or the surface on which the reflective layer is formed is bonded to the coated surface. Then, the adhesive is cured by irradiating light from the top of the cover film or applying heat or the like, and the substrate and the cover film are brought into close contact with each other. In addition, hardening by light irradiation can be irradiated also from the board | substrate side especially when there is no reflection layer. Moreover, it is preferable that the cover film after the application is punched out to approximately the same size as the substrate before being bonded, and then bonded to the substrate.

As the atmosphere when the substrate and the cover film are bonded together, various atmospheres including atmospheric pressure can be adopted, but a vacuum atmosphere, a reduced pressure atmosphere, a reduced nitrogen atmosphere, and a reduced inertness. A gas atmosphere is preferred.
Here, the reduced pressure means less than atmospheric pressure, preferably about 0.3 to 10 ⁻⁵ Torr (39.9 Pa to 1.33 × 10 ⁻³ Pa).

As described above, the optical recording medium of the present invention is produced.
According to the manufacturing method of the present invention, since it is not necessary to form a recording layer on each substrate, the film formation cost in mass production can be reduced. Further, it can be attached to the substrate in close contact with each other, so that the material cost can be reduced and the cost can be reduced. Furthermore, since the recording layer is formed on the cover film and then bonded to the substrate, a flat recording layer having a substantially uniform thickness can be efficiently formed. In addition, the said manufacturing method is an illustration, A various change in the range which can perform various well-known processes and those skilled in the art can be added.

As the material constituting the adhesive, various materials such as a photo-curable resin can be used, but a pressure-sensitive adhesive (adhesive) is preferable. As the adhesive, an acrylate resin adhesive can be used. It is preferable to add an isocyanate curing agent to the pressure-sensitive adhesive.
Moreover, when using photocurable resin as an adhesive agent, a thing with a small cure shrinkage rate is preferable in order to prevent the curvature of a disk. As such a photocurable resin, an ultraviolet curable resin is preferable. Specifically, an ultraviolet curable resin such as “SD-640”, “SD-347”, and “SD-318” manufactured by Dainippon Ink, Inc. is used. Resin (ultraviolet curable adhesive) can be mentioned. Further, the thickness of the adhesive layer is preferably in the range of 1 to 1000 nm, more preferably in the range of 2 to 100 nm, and particularly preferably in the range of 3 to 50 nm in order to provide elasticity.

For viscosity control, the coating temperature is preferably in the range of 23 to 50 ° C, more preferably in the range of 24 to 40 ° C, and still more preferably in the range of 25 to 37 ° C.
In order to prevent the disk from warping, it is preferable to irradiate the coating film with ultraviolet rays using a pulsed light irradiator (preferably, an ultraviolet irradiator). The pulse interval is preferably msec or less, and more preferably μsec or less. 1 pulse irradiation light amount is not particularly limited, and is preferably 3 kW / cm ² or less, 2 kW / cm ² or less being more preferred.
The number of times of irradiation is not particularly limited, but is preferably 20 times or less, and more preferably 10 times or less.

[2] Second manufacturing method:
A second method for producing an optical recording medium of the present invention is a method for producing an optical recording medium in which at least a recording layer and a cover layer are sequentially formed on a substrate, wherein one surface of the substrate is provided. A groove forming step for simultaneously forming guide grooves or pits on the other surface, a recording layer forming step for forming the recording layer on the cover layer, and the cover layer on which the recording layer is formed. Then, the recording layer is bonded to the one surface side of the substrate that has undergone the groove forming step, and a cover layer that is not formed with the recording layer is bonded to the other surface side of the substrate. And a laminating step.

  The groove forming step, recording layer forming step, and bonding step are the same as in the first manufacturing method. With this manufacturing method, a double-sided optical recording medium is manufactured in which one surface is a surface on which information can be recorded and the other surface is a surface on which information has already been recorded.

<Optical recording medium>
The optical recording medium manufactured by the first manufacturing method has a configuration as shown in FIG. 2, for example. As shown in FIG. 2, guide grooves (on-groove 1a and in-groove 1b) are formed on one surface of the substrate 1, and a reflective layer 2 is formed on the surface on which the on-groove 1a and in-groove 1b are formed. Further, the cover layer 4 on which the recording layer 3 is formed is bonded by the adhesive layer 5.

  Here, the on-groove 1a refers to a portion (see FIG. 2) where a convex portion is formed when viewed from the direction in which the laser beam 12 is irradiated onto the cover layer 4 through the objective lens 11. On the other hand, the in-groove 1b refers to a portion (see FIG. 2) where a recess is formed when viewed from the same direction as described above. The on-groove 1a or the in-groove 1b becomes an optical recording unit.

  The thickness of the recording layer 3 is substantially uniform. By being substantially uniform, the signal level inside / outside difference and the circumference difference can be reduced, and it becomes possible to widen a margin for signal error and increase reliability. Moreover, productivity can be improved by making it substantially uniform so that it may mention later.

  Here, “substantially uniform” means that when the average thickness is Ta, the thickness (Tmax) of the maximum thickness portion in one disk is “Ta ≦ Tmax ≦ 1.03 Ta (preferably Ta ≦ Tmax ≦ 1.02Ta) ”and the thickness (Tmin) of the minimum thickness portion is in the range of“ 0.97Ta ≦ Tmin ≦ Ta (preferably 0.98Ta ≦ Tmin ≦ Ta) ”. By being in the above range, it is possible to reduce the signal level internal / external difference.

Further, the gap 1c formed from the reflective layer 2 and the recording layer 3 is preferably an atmosphere of any one of a vacuum atmosphere, a reduced pressure atmosphere, a reduced nitrogen atmosphere, and a reduced inert gas atmosphere. . By setting the atmosphere to any one of the above, decomposition gas caused by the dye generated when recording information is easily released, so that the sensitivity can be increased. Such an effect can be similarly expected in a recording system accompanied by other shape changes such as a hole forming type.
In order to make the air gap 1c in any one of the above atmospheres, as described above, the substrate 1 on which the reflective layer 2 is formed and the cover film corresponding to the cover layer 4 on which the recording layer 3 is formed are bonded. Any one of the above-described atmospheres may be used when pasting with an agent or the like. The atmosphere of the void 1c can be confirmed by mass spectroscopy analysis in a vacuum atmosphere.

<Optical recording method and optical reproducing method>
Next, an optical recording method of information on an optical recording medium manufactured by the manufacturing method of the present invention and an optical reproduction method of recorded information will be described.

(Optical recording method)
In the optical recording method, a laser beam having a wavelength of 450 nm or less is condensed and irradiated through an objective lens having a numerical aperture of 0.7 or more from the cover layer side of the optical recording medium of the present invention described above to the optical recording unit. Information is recorded.

Specifically, this is performed as follows.
First, the optical recording medium is rotated at a constant linear velocity, for example, and recording laser light is irradiated from the cover layer side. When the laser beam is irradiated, the recording layer absorbs the light and the temperature rises locally, causing a physical or chemical change to change its optical characteristics, thereby recording information. The information is recorded by tracking on-groove or in-groove.

The light source of the recording laser light is not particularly limited as long as it is a light source that oscillates laser light having a wavelength of 450 nm or less. For example, a blue-violet semiconductor laser having an oscillation wavelength in the range of 390 to 415 nm, a central oscillation wavelength of 425 nm And a blue-violet SHG laser.
In order to increase the recording density, the NA of the objective lens used for the pickup is set to 0.7 or more, preferably 0.85 or more.

(Light regeneration method)
The optical reproducing method collects and irradiates laser light having a wavelength of 450 nm or less through an objective lens having a numerical aperture of 0.7 or more from the cover layer side of the optical recording medium, detects the reflected light, The information recorded in the recording unit is reproduced.

  Specifically, as in the optical recording method, information can be reproduced by irradiating a laser beam from the cover layer side while rotating the optical recording medium at a constant linear velocity and detecting the reflected light. it can.

  The present invention will be specifically described with reference to the following examples, but the present invention is not limited thereto.

(Example)
The stamper (master) produced in the mastering process is attached to a mold of an injection molding machine manufactured by Sumitomo Heavy Industries, and a stamper spiral groove (of the land portion) is placed on a disk substrate having a thickness of 1.1 mm, an outer diameter of 120 mm, and an inner diameter of 15 mm. The substrate was fabricated by transfer molding (groove formation step) with a height of 40 nm, a land portion width of 120 nm, and a track pitch of 300 nm. Ag was sputtered onto the surface having this group to form a reflective layer having a thickness of 100 nm (reflective layer forming step).

  On the other hand, 12 g of phthalocyanine-based organic compound Dye A (Orazol Blue GN: manufactured by Ciba Specialty Chemical Co., Ltd., maximum absorption: 340 nm, 640 nm) was mixed with 1 liter of 2,2,3,3-tetrafluoropropanol for 2 hours. Ultrasonic treatment was performed to dissolve, and a coating solution for forming a recording layer was prepared.

  This coating solution is applied onto a polycarbonate sheet (trade name: Pure Ace, manufactured by Teijin Ltd., thickness: 0.07 mm) as a cover film (cover layer) and dried (recording layer forming step) to form a recording layer. A cover film was prepared. In addition, drying was performed during web conveyance in 30 degreeC45% RH atmosphere.

The produced cover film was punched with a disk punching machine having a punching blade in the center hole portion and the outer shape portion (hereinafter, the punched cover film is referred to as “cookie”). The recording layer of this cookie and the reflective layer of the substrate were faced to each other and bonded together in a vacuum atmosphere of 3 × 10 ⁻³ Torr (bonding step) to produce an optical recording medium.

  In addition, the ultraviolet curable resin (Dainippon Ink Chemical Co., Ltd. product, SD-318) was previously apply | coated to the edge part of the inner edge part and outer edge part of a cookie in the case of bonding, and the ultraviolet-ray was irradiated.

  About the produced optical recording medium, 3D signal was recorded using DDU-1000 (manufactured by Pulstec) that oscillates 405 nm laser light, and a reproduction test was performed with laser light having a wavelength of 405 nm. When the degree of modulation was measured, the recording sensitivity, reflectivity, modulation degree, jitter, asymmetry inner and outer differences were small, and the recording / reproduction characteristics were excellent.

It is explanatory drawing explaining the one part process of the manufacturing method of this invention, (A) shows a recording layer formation process, (B) shows the cover layer after punching, (C) shows a bonding process. Show. It is a fragmentary sectional view which shows the example of the layer structure of the optical recording medium manufactured by the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 1a ... On-groove 1b ... In-groove 1c ... Gap part 2 ... Reflective layer 3 ... Recording layer 4 ... Cover layer 11 ... Lens 12 ... Laser light

Claims (7)

A method of manufacturing an optical recording medium, in which a reflective layer, a recording layer, and a cover layer are sequentially formed on a substrate,
A groove forming step of forming guide grooves or pits on the substrate;
A reflective layer forming step of forming the reflective layer on the surface side of the substrate where the guide grooves or the pits are formed after the groove forming step;
A recording layer forming step of forming the recording layer on the cover layer;
A method of manufacturing an optical recording medium, comprising: a bonding step of bonding the reflective layer of the substrate and the recording layer of the cover layer.   At least the atmosphere at the time of bonding between the substrate and the cover layer in the bonding step is any one of a vacuum atmosphere, a reduced pressure atmosphere, a reduced nitrogen atmosphere, and a reduced inert gas atmosphere. The method of manufacturing an optical recording medium according to claim 1.   3. The method of manufacturing an optical recording medium according to claim 1, wherein the recording layer is formed by a web method in the recording layer forming step.   3. The method of manufacturing an optical recording medium according to claim 1, wherein the recording layer forming method in the recording layer forming step is web-type vacuum deposition or sputtering.   5. The method of manufacturing an optical recording medium according to claim 1, wherein the guide groove or the pit forming surface in the groove forming step is a single side of the substrate.   The guide groove or the pit forming surface in the groove forming step is both surfaces of the substrate, and the formation of the guide groove or the pit is simultaneous on both surfaces. 2. A method for producing an optical recording medium according to 1. A method for producing an optical recording medium, wherein at least a recording layer and a cover layer are sequentially formed on a substrate,
A groove forming step for simultaneously forming a guide groove or pit on one surface of the substrate and a pit on the other surface;
A recording layer forming step of forming the recording layer on the cover layer;
The cover layer on which the recording layer is formed is bonded to one surface side of the substrate that has undergone the groove forming step so that the recording layer becomes an inner layer, and the cover layer on which the recording layer is not formed And a bonding step of bonding to the other surface side of the substrate.

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