JP2005285167A - Optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium which can form a visible image which is finer and sharper in contrast on an image-recording layer on the opposite side of a recording layer by using a laser beam. <P>SOLUTION: The optical recording medium is formed with a recording layer to which the recording and reproduction of information can be made by the irradiation of a laser beam. In addition, the medium is formed with; an image-recording layer to which a visible image is recorded by the irradiation of a laser beam, the image-recording layer formed on the opposite side of the recording layer; and a groove for tracking in an image recording region on the image-recording layer side. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical recording medium, and more particularly to an optical recording medium capable of recording a visible image on a surface opposite to a recording surface.

  Conventionally, an optical recording medium (optical disc) capable of recording information only once by laser light is known. This optical disc is also referred to as a recordable CD (so-called CD-R), and its typical structure is a recording layer made of an organic dye on a transparent disk-shaped substrate, a light reflecting layer made of a metal such as gold, and a resin. A protective layer made of a metal is provided in this order in a laminated state. Information recording on this CD-R is performed by irradiating the CD-R with a near-infrared laser beam (usually a laser beam having a wavelength near 780 nm), and the irradiated portion of the recording layer emits the light. Information is recorded by absorbing and locally raising the temperature, causing a physical or chemical change (eg, pit generation) and changing its optical properties. On the other hand, reading (reproduction) of information is also performed by irradiating laser light having the same wavelength as the recording laser light, and the part where the optical characteristics of the recording layer have changed (recorded part) and the part that has not changed (unrecorded) Information is reproduced by detecting the difference in reflectance from (part).

  In recent years, an optical recording medium having a higher recording density has been demanded. In response to such a demand, an optical disk called a recordable digital vasatile disk (so-called DVD-R) has been proposed. This DVD-R is a transparent disk-shaped substrate in which the guide groove (pre-groove) for tracking the irradiated laser beam is narrower than half of the CD-R (0.74-0.8 μm). On top of that, a recording layer made of a dye, and usually two light reflecting layers on the recording layer, and further a protective layer if necessary, or a disk-shaped protective substrate having the same shape as the disk The recording layer has a structure in which the recording layer is bonded inside with an adhesive. Information recording / reproduction on a DVD-R is performed by irradiating visible laser light (usually laser light having a wavelength in the range of 630 nm to 680 nm), and recording at a higher density than CD-R is possible. Has been.

  By the way, the optical disc has visible information such as a title of music data recorded on the recording surface and a title for identifying the recorded data on the surface opposite to the recording surface on which the music data is recorded. One with a printed label is known. Such an optical disk is manufactured by printing a title or the like on a circular label sheet in advance by a printer or the like, and sticking the label sheet on a surface opposite to the recording surface of the optical disk.

  However, when producing an optical disc in which a desired visible image such as a title is recorded on the label surface as described above, a printer is required separately from the optical disc drive. Therefore, after recording on a recording surface of an optical disk using an optical disk drive, the optical disk is taken out from the optical disk drive, and a label sheet printed by a separately prepared printer is attached as described above. Need to do work.

  In view of this, an optical recording medium has been proposed in which a laser marker is used on the surface opposite to the recording surface to change the contrast between the surface and the background (for example, see Patent Document 1). By using such a method, a desired image can be recorded on the label surface of the optical disc by the optical disc drive without separately preparing a printer or the like. However, with this method, the sensitivity is low, and a high-power gas laser such as a carbon dioxide laser must be used, and the visible image formed by the laser light as described above has low contrast and poor visibility. It was.

As another example, an optical recording medium having a color-developing layer that develops different colors when irradiated with laser beams having different characteristics has been proposed (see, for example, Patent Document 2). However, this optical recording medium has a problem that the layer structure and recording apparatus are complicated and fine gradation cannot be applied.
JP-A-11-66617 JP 2003-272240 A

This invention is made | formed in view of the above conventional trouble, and makes it a subject to achieve the following objectives. That is,
An object of the present invention is to provide an optical recording medium capable of recording a denser and higher-contrast visible image using a laser beam on an image recording layer on the opposite side of the recording layer.

Means for solving the problems are as follows. That is,
<1> An optical recording medium having a recording layer capable of recording and reproducing information by irradiating a laser beam, wherein a visible image is recorded by irradiating the laser beam on the surface opposite to the recording layer. An optical recording medium having a recording layer and having a tracking groove in an image recording area on the image recording layer side.
<2> The optical recording medium according to <1>, wherein the constituent component of the recording layer is different from the constituent component of the image recording layer.
<3> The optical recording medium according to <1> or <2>, wherein the groove pitch of the recording layer is different from the groove pitch of the image recording layer.
<4> The optical recording medium according to any one of <1> to <3>, wherein a groove shape of the recording layer is different from a groove shape of the image recording layer.

  According to the present invention, it is possible to provide an optical recording medium capable of forming a denser and higher-contrast visible image using a laser beam on the image recording layer on the opposite side of the recording layer.

The optical recording medium of the present invention is an optical recording medium having a recording layer capable of recording and reproducing information by irradiating a laser beam, and a visible image is irradiated on the surface opposite to the recording layer by irradiating the laser beam. Is recorded, and a tracking groove is provided in the image recording area on the image recording layer side.
The optical recording medium of the present invention will be described below.

  The type of the optical recording medium of the present invention may be any of a read-only type, a write-once type, a rewritable type, etc., but is preferably a write-once type. The recording format is not particularly limited, such as a phase change type, a magneto-optical type, and a dye type, but is preferably a dye type.

Examples of the layer configuration of the optical recording medium of the present invention include the following configurations.
(1) The first layer configuration is a configuration in which a recording layer, a reflective layer, and an adhesive layer are sequentially formed on a substrate, and an image recording layer and a dummy substrate are provided on the adhesive layer.
(2) The second layer configuration is a configuration in which a recording layer, a reflective layer, a protective layer, and an adhesive layer are sequentially formed on a substrate, and an image recording layer and a dummy substrate are provided on the adhesive layer.
(3) The third layer configuration is a configuration in which a recording layer, a reflective layer, a protective layer, an adhesive layer, and a protective layer are sequentially formed on a substrate, and an image recording layer and a dummy substrate are provided on the protective layer.
(4) The fourth layer configuration is a configuration in which a recording layer, a reflective layer, a protective layer, an adhesive layer, a protective layer, and a reflective layer are sequentially formed on a substrate, and an image recording layer and a dummy substrate are provided on the reflective layer. It is.
(5) The fifth layer configuration is a configuration in which a recording layer, a reflective layer, an adhesive layer, and a reflective layer are sequentially formed on a substrate, and an image recording layer and a dummy substrate are provided on the reflective layer.
Note that the layer configurations of (1) to (5) above are merely examples, and the layer configuration is not limited to the order described above, and may be partially replaced. A part may be omitted. Furthermore, each layer may be composed of one layer or a plurality of layers.
Hereinafter, the substrate and each layer will be described.

[Recording layer]
The recording layer is a layer on which code information (encoded information) such as digital information is recorded, and examples thereof include a dye type, a write-once type, a phase change type, and a magneto-optical type. Preferably there is.

Specific examples of the dye contained in the dye-type recording layer include a cyanine dye, an oxonol dye, a metal complex dye, an azo dye, and a phthalocyanine dye.
JP-A-4-74690, JP-A-8-127174, 11-53758, 11-334204, 11-334205, 11-334206, 11-334207 No. 2000-43423, JP-A 2000-108513, JP-A 2000-158818, and the like are preferably used.
Further, the recording material is not limited to a dye, but a triazole compound, triazine compound, cyanine compound, merocyanine compound, aminobutadiene compound, phthalocyanine compound, cinnamic acid compound, viologen compound, azo compound, oxonol benzoxazole compound, benzotriazole compound Organic compounds such as these are also preferably used. Among these compounds, cyanine compounds, aminobutadiene compounds, benzotriazole compounds, and phthalocyanine compounds are particularly preferable.

  The recording layer is prepared by dissolving a recording substance such as a dye in a suitable solvent together with a binder and the like to prepare a coating solution, and then coating the coating solution on a substrate to form a coating film, followed by drying. It is formed. 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%.

  The recording layer can be formed by a method such as vapor deposition, sputtering, CVD, or solvent coating, but solvent coating is preferred. In this case, a coating solution is prepared by dissolving a quencher, a binder, and the like in a solvent in addition to the above-described pigment, and then coating the coating surface on the substrate surface to form a coating film, followed by drying. Can be done.

Examples of the solvent for the coating solution include esters such as butyl acetate, ethyl lactate, and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, and chloroform; and dimethylformamide. Amides; Hydrocarbons such as methylcyclohexane; Ethers such as dibutyl ether, diethyl ether, tetrahydrofuran, and dioxane; Alcohols such as ethanol, n-propanol, isopropanol, n-butanol, and diacetone alcohol; 2,2,3,3- Fluorinated solvents such as tetrafluoropropanol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, etc. And the like can be mentioned recall ethers.
The above solvents can be used alone or in combination of two or more in consideration of the solubility of the dye used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution depending on the purpose.

  When a binder is used, examples of the binder include natural organic polymer materials such as gelatin, cellulose derivatives, dextran, rosin and rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene and polyisobutylene; Vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl chloride / polyvinyl acetate copolymer; acrylic resins such as polymethyl acrylate and polymethyl methacrylate; polyvinyl alcohol, chlorinated polyethylene, epoxy resin, bunalal resin, Examples include 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 the binder used is generally in the range of 0.01 to 50 times the mass of the dye, preferably 0.1 to 5 times the amount. Is in range.

  Examples of the solvent application method include a spray method, a spin coating method, a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. The recording layer may be a single layer or a multilayer. The thickness of the recording layer is generally in the range of 10 to 500 nm, preferably in the range of 15 to 300 nm, and more preferably in the range of 20 to 150 nm.

  In order to improve the light resistance of the recording layer, the recording layer can contain various antichromic 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 Tokusho Sho Nos. 58-175893, 59-31194, 60-18387, 60-19586, 60-19587, 60-35054, 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, 60-47069, 68-209995, JP Listed in publications such as Nos. 4-25492, 1-38680, and 6-26028, German Patent No. 350399, and the Chemical Society of Japan, October 1992, page 1141 Can do.

  The amount of the anti-fading agent such as the singlet oxygen quencher used is usually in the range of 0.1 to 50% by mass, preferably in the range of 0.5 to 45% by mass, more preferably , In the range of 3 to 40% by mass, particularly preferably in the range of 5 to 25% by mass.

Specific examples of the material constituting the phase change recording layer include Sb—Te alloy, Ge—Sb—Te alloy, Pd—Ge—Sb—Te alloy, Nb—Ge—Sb—Te alloy, Pd—Nb—. Ge—Sb—Te alloy, Pt—Ge—Sb—Te alloy, Co—Ge—Sb—Te alloy, In—Sb—Te alloy, Ag—In—Sb—Te alloy, Ag—V—In—Sb—Te Alloys, Ag-Ge-In-Sb-Te alloys, and the like. Among these, Ge—Sb—Te alloy and Ag—In—Sb—Te alloy are preferable because they can be rewritten many times.
The layer thickness of the phase change recording layer is preferably 10 to 50 nm, more preferably 15 to 30 nm.

  The above phase change type recording layer can be formed by a vapor phase thin film deposition method such as sputtering or vacuum deposition.

[substrate]
The substrate of the optical recording medium of the present invention can be arbitrarily selected from various materials used as a substrate of a conventional optical recording medium.
Examples of substrate materials include acrylic resins such as glass, polycarbonate, and polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers, epoxy resins, amorphous polyolefins, and polyesters. You may use them together.
These materials can be used as a film or as a rigid substrate. Among the above materials, polycarbonate is preferable from the viewpoint of moisture resistance, dimensional stability, price, and the like.

  The thickness of the substrate is preferably 0.1 to 1.2 mm, and more preferably 0.2 to 1.1 mm. 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 conventional CD-R and DVD-R. In this case, the groove track pitch is preferably in the range of 200 to 400 μm, and more preferably in the range of 250 to 350 nm. Further, the depth of the groove (groove depth) is preferably in the range of 20 to 150 nm, and more preferably in the range of 50 to 100 nm.

  Further, the groove width of the groove is preferably in the range of 50 to 250 nm, and more preferably in the range of 100 to 200 nm. The groove inclination angle of the groove is preferably in the range of 20 to 80 °, and more preferably in the range of 30 to 70 °.

An undercoat layer may be provided on the substrate surface side (surface side on which the groove is formed) on which the recording layer is provided for the purpose of improving flatness, improving adhesive force, and preventing alteration of the recording layer. .
Examples of the material for the undercoat layer include polymethyl methacrylate, acrylic acid / methacrylic acid copolymer, styrene / maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene / vinyl toluene copolymer, chlorosulfonated. High molecular substances such as polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate / vinyl chloride copolymer, ethylene / vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate; and silane coupling agents And the like. The undercoat layer is formed by dissolving or dispersing the above substances in an appropriate solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. can do.
The thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably in the range of 0.01 to 10 μm.

[Reflective layer]
A reflective layer may be provided adjacent to the recording layer for the purpose of improving reflectivity during information reproduction. The light-reflective substance that is the material of the reflective layer is a substance having a high reflectivity with respect to laser light. Examples thereof include Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and 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 metals such as semimetals and stainless steels. These substances may be used alone or in combination of two or more or as an alloy. Among these, Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel are preferable. Particularly preferred are Au metal, Ag metal, Al metal or alloys thereof, and most preferred are Ag metal, Al metal or alloys thereof. The reflective layer can be formed on the substrate or the recording layer, for example, by vapor deposition, sputtering or ion plating of the light reflective material. The thickness of the reflective layer is generally in the range of 10 to 300 nm, and preferably in the range of 50 to 200 nm.

[Adhesive layer]
The adhesive layer is an arbitrary layer formed in order to improve the adhesion between the reflective layer and the dummy substrate.
As a material constituting the adhesive layer, a photo-curing resin is preferable, and in particular, a material having a small curing shrinkage rate is preferable in order to prevent the disk from warping. Examples of such a photocurable resin include UV curable resins (UV curable adhesive) such as “SD-640” and “SD-347” manufactured by Dainippon Ink and Chemicals, Inc. it can. The thickness of the adhesive layer is preferably in the range of 1 to 1000 μm, more preferably in the range of 5 to 500 μm, and particularly preferably in the range of 10 to 100 μm in order to give elasticity.

[Dummy substrate]
The dummy substrate (protective substrate) can be made of the same material as the above-described substrate.

[Image recording layer]
As described above, the optical recording medium of the present invention has an image recording layer on the surface opposite to the recording layer. In the image recording layer, visible images (visible information) desired by the user, such as characters, graphics, and patterns, are recorded. Examples of visible images include disc titles, content information, content thumbnails, related patterns, design patterns, copyright information, recording date, recording method, recording format, and the like.

  The visible image recorded in the image recording layer means a visually recognizable image, and includes all visually recognizable information such as characters (rows), pictures, and figures. Also, as character information, usable person designation information, use period designation information, usable number designation information, rental information, resolution designation information, layer designation information, user designation information, copyright holder information, copyright number information, manufacturing Information, manufacturer date information, sales date information, dealer or seller information, use set number information, region designation information, language designation information, application designation information, product user information, use number information, and the like.

  The image recording layer only needs to be able to visually record image information such as characters, images, and patterns by laser light irradiation, and as the constituent material, the dye described in the recording layer described above can be suitably used. .

In the optical recording medium of the present invention, the recording layer component (dye or phase change recording material) described above and the image recording layer component may be the same or different. Since the required characteristics differ between the recording layers, it is preferable that the constituent components are different. Specifically, it is preferable that the constituent components of the recording layer have excellent recording / reproducing characteristics, and the constituent components of the image recording layer have high contrast of the recorded image. In particular, when a dye is used, it is preferable to use a cyanine dye, a phthalocyanine dye, an azo dye, an azo metal complex, or an oxonol dye among the dyes described above from the viewpoint of improving the contrast of a recorded image in the image recording layer. .
Further, one of the recording layer and the image recording layer may be a phase change type and the other may be a dye type. In this case, the recording layer is preferably a phase change type and the image recording layer is preferably a dye type.

  The image recording layer can be formed by preparing a coating solution by dissolving the above-described dye in a solvent and coating the coating solution. As the solvent, the same solvents as those used for preparing the recording layer coating liquid described later can be used. Other additives and coating methods can be performed in the same manner as the recording layer described above.

  The thickness of the image recording layer is preferably 0.01 to 200 μm, more preferably 0.05 to 100 μm, and further preferably 0.1 to 50 μm.

The optical recording medium of the present invention has a tracking groove in the image recording area on the image recording layer side. Since the image recording layer is formed adjacent to the above-described dummy substrate, the groove can be easily provided in the image recording region by providing the groove in the dummy substrate. In the present invention, since the position of the pickup can be precisely controlled by performing image recording while tracking the laser pickup with the formed groove, it is possible to record a precise image.
Further, by providing grooves in the image recording layer, there is an effect that light interferes and the surface looks like a beautiful rainbow color.

  The shape of the groove on the image recording layer side is preferably a spiral shape or a concentric shape since tracking is performed while the optical recording medium is rotated.

  The groove shape of the image recording layer can be different from the groove shape of the recording layer. Further, the groove pitch of the image recording layer and the groove pitch of the recording layer can be made different. Specifically, the pitch of the grooves in the image recording layer can be made wider than the grooves in the recording layer. Since tracking in image recording is the purpose, it is only necessary to be able to record a densely visible image, and it is not necessary to make the pitch narrower as the recording layer narrows the groove pitch (track pitch) in order to increase the recording density. is there.

From the viewpoint of the intensity distribution of the recording laser, the pitch of the tracking grooves formed in the image recording area of the image recording layer is preferably 0.3 to 2.0 μm, and preferably 0.4 to 1.6 μm. Is more preferable, and 0.6 to 1.0 μm is even more preferable.
The depth of the groove is preferably 50 to 200 nm, more preferably 80 to 150 nm, and still more preferably 100 to 130 nm.
Furthermore, the width of the groove is preferably 100 to 600 nm, more preferably 200 to 500 nm, and further preferably 250 to 450 nm.

Below, the protective layer employ | adopted by another structure is demonstrated.
(Protective layer)
A protective layer may be provided for the purpose of physically and chemically protecting the reflective layer and the recording layer.
In the case of adopting the same form as in the case of manufacturing a DVD-R type optical recording medium, that is, a structure in which two substrates (including the case where one is a dummy substrate) are bonded to each other with the recording layer inside. A protective layer is not necessary.

Examples of materials used for the protective layer include inorganic substances such as ZnS, ZnS—SiO ₂ , SiO, SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ , thermoplastic resins, thermosetting resins, and UV curable materials. Organic substances such as resins can be mentioned. The protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic on the reflective layer via an adhesive. Or you may provide by methods, such as vacuum evaporation, sputtering, and application | coating.

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

  As another configuration, for example, a reflective layer, a recording layer, and a cover layer may be sequentially formed on a substrate. The cover layer is preferably formed on the recording layer via an adhesive layer. In this case, the configuration other than the cover layer is as described above.

(Cover layer)
The cover layer is formed to prevent the inside of the optical recording medium from impact and the like, and is not particularly limited as long as it is a transparent material, but is preferably polycarbonate, cellulose triacetate, and more preferably at 23 ° C. and 50% RH. A material having a moisture absorption rate of 5% or less.
Note that “transparent” means that the recording light and the reproduction light are so transparent that the light is transmitted (transmittance: 90% or more).

The cover layer is prepared by dissolving a photocurable resin constituting the adhesive layer in an appropriate solvent to prepare a coating solution, and then coating the coating solution on the recording layer at a predetermined temperature to form a coating film. For example, a cellulose triacetate film (TAC film) obtained by, for example, plastic extrusion is laminated on the film, and light is irradiated from above the laminated TAC film to cure the coating film. The TAC film preferably contains an ultraviolet absorber. The thickness of the cover layer is in the range of 0.01 to 0.2 mm, preferably in the range of 0.03 to 0.1 mm, and more preferably in the range of 0.05 to 0.095 mm.
Moreover, a polycarbonate sheet etc. can also be used as a cover sheet.

  The cover layer can be provided as follows, for example. After the photocurable resin is dissolved in a suitable solvent to prepare a coating solution, this coating solution is applied on the recording layer at a predetermined temperature to form a coating film, and, for example, a plastic extrusion is formed on the coating film. It is formed by laminating a cellulose triacetate film (TAC film) obtained by processing, and irradiating light on the laminated TAC film to cure the coating film. The TAC film preferably contains an ultraviolet absorber. The thickness of the transparent sheet is in the range of 0.01 to 0.2 mm, preferably in the range of 0.03 to 0.1 mm, and more preferably in the range of 0.05 to 0.095 mm.

In addition, a polycarbonate sheet etc. can also be used as a cover layer. When the adhesive is given to the bonding surface of a transparent sheet, the said adhesive agent is unnecessary.
Moreover, you may form the light transmissive layer which consists of ultraviolet curable resin etc. instead of a cover layer.

  A hard coat layer may be formed on the cover layer. The hard coat layer can be formed by coating or the like on the cover layer after forming a reflective layer, a recording layer, etc. on the substrate and forming a cover layer thereon. When the cover layer is a transparent sheet, before the transparent sheet is laminated on the recording layer, a hard coat layer is formed on the transparent sheet so that the hard coat layer is the outermost surface, and a transparent sheet is formed. The optical recording medium of the present invention may be produced by laminating on the recording layer.

  The optical recording medium of the present invention can be applied to a so-called read-only optical recording medium having a recording part (pit) in which information reproducible by laser light is recorded. is there.

[Image recording method]
Image recording on the image recording layer of the optical recording medium of the present invention is performed using the optical recording medium of the present invention and a recording apparatus capable of recording image information on at least the image recording layer of the optical recording medium.
First, a recording apparatus used for recording on the optical recording medium of the present invention will be described.

(Recording device)
In the optical recording medium of the present invention, recording of an image on the image recording layer and recording of optical information on the recording layer can be performed by one optical disk drive (recording apparatus) having a recording function on both layers. When one optical disk drive is used as described above, after recording on one of the image recording layer and the recording layer, it can be turned over and recording can be performed on the other layer. Examples of the optical disc drive having a function of recording a visible image on the image recording layer are described in JP2003-203348A, JP2003-242750A, and the like.

  In recording a visible image on the image recording layer, the recording apparatus tracks the optical recording medium and the laser pickup by a tracking groove formed in the image recording layer, and follows the surface of the optical recording medium. The laser beam is modulated in accordance with image data such as characters and pictures to be imaged and irradiated to the image recording layer in synchronization with the relative movement, and a visible image is recorded. Such a configuration is described in, for example, Japanese Patent Application Laid-Open No. 2002-203321.

  A recording apparatus for recording optical information on a recording layer has at least a laser pickup that emits laser light and a rotating mechanism that rotates an optical recording medium, and recording / reproduction on the recording layer is performed by optical recording in a rotated state. Laser irradiation is performed from a laser pickup toward the recording layer of the medium. The configuration itself of such a recording apparatus is well known.

  Next, recording of information (digital information) on the recording layer will be described. When the recording layer is a dye type, first, laser light is irradiated from a laser pickup while rotating the above-mentioned optical recording medium that has not been recorded at a predetermined recording linear velocity. By this irradiation light, the dye in the recording layer absorbs the light and the temperature rises locally, and a desired void (pit) is generated and its optical characteristics are changed to record information.

The recording waveform of the laser beam may be a pulse train or one pulse when one pit is formed. The ratio to the actual recording length (pit length) is important.
The pulse width of the laser beam is preferably in the range of 20 to 95%, more preferably in the range of 30 to 90%, and still more preferably in the range of 35 to 85% with respect to the length to be actually recorded. Here, when the recording waveform is a pulse train, the sum is in the above range.

The power of the laser beam varies depending on the recording linear velocity, but when the recording linear velocity is 3.5 m / s, the range of 1 to 100 mW is preferable, the range of 3 to 50 mW is more preferable, and the range of 5 to 20 mW is further increased. preferable. When the recording linear velocity is doubled, the preferable range of the laser beam power is ^21/2 times, respectively.

  In order to increase the recording density, the NA of the objective lens used for the pickup is preferably 0.55 or more, and more preferably 0.60 or more.

  In the present invention, a semiconductor laser having an oscillation wavelength in the range of 350 to 850 nm can be used as the recording light.

On the other hand, a case where the recording layer is a phase change type will be described. In the case of the phase change type, it is composed of the above-described material, and the phase change between the crystalline phase and the amorphous phase can be repeated by laser light irradiation.
At the time of information recording, a concentrated laser light pulse is irradiated for a short time to partially melt the phase change recording layer. The melted portion is rapidly cooled by heat diffusion and solidified to form an amorphous recording mark. During erasing, the recording mark portion is irradiated with laser light, heated to a temperature below the melting point of the recording layer and above the crystallization temperature, and then cooled to crystallize the amorphous recording mark. Return to the unrecorded state.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

[Example 1]
This embodiment is a DVD-R type optical recording medium in which two discs are bonded together. A method for producing the optical recording medium will be described below.
A substrate having a thickness of 0.6 mm and a diameter of 120 mm having spiral grooves (depth: 130 nm, width: 300 nm, track pitch: 0.74 μm) was molded from polycarbonate resin by injection molding. A coating solution (1) is prepared by dissolving 1.5 g of the following dye (1) in 100 ml of 2,2,3,3-tetrafluoro-1-propanol, and the coating solution (1) is formed on the substrate by spin coating. The recording layer was formed by coating on the surface on which the groove was formed. Next, silver is sputtered onto the recording layer to form a reflective layer having a thickness of 120 nm, and then an ultraviolet curable resin (SD318 (manufactured by Dainippon Ink and Chemicals)) is applied by spin coating, and then ultraviolet rays are applied. Irradiation was cured to form a protective layer having a layer thickness of 10 μm, and the first disk was manufactured through the above steps.

  Next, in order to form an image recording layer, 1.0 g of the dye (1) and 0.5 g of the following dye (2) were dissolved in 100 ml of 2,2,3,3-tetrafluoro-1-propanol. A liquid (2) is prepared, and this coating liquid (2) is 0.6 mm in thickness and diameter having spiral tracking grooves (depth: 140 nm, width 300 nm, pitch: 0.74 μm). The film was formed on a 120 mm substrate by spin coating. Next, silver is sputtered onto the image recording layer to form a reflective layer having a thickness of 120 nm, and then an ultraviolet curable resin (SD318 (manufactured by Dainippon Ink and Chemicals)) is applied by a spin coating method, and then ultraviolet rays are applied. Then, a protective layer having a layer thickness of 10 μm was formed, and the second disk was manufactured through the above steps.

  Next, the following steps were performed in order to bond the first disk and the second disk to complete one disk. First, a slow-acting cationic polymerization adhesive (Sony Chemical Co., Ltd., SDK7000) was printed on the protective layers of both disks by screen printing. At this time, the mesh size of the screen printing plate was 300 mesh. Next, immediately after irradiating with ultraviolet rays using a metal halide lamp, the first disk and the second disk were bonded from the respective protective layer sides, pressed from both sides, and allowed to stand for 5 minutes, whereby the optical recording medium of Example 1 was obtained. Produced.

[Comparative Example 1]
An optical recording medium of Comparative Example 1 was produced in the same manner as in Example 1 except that a substrate having no grooves was used in the production of the second disk of Example 1.

[Evaluation]
The following evaluations were performed on the manufactured optical recording media of Example 1 and Comparative Example 1.
(Contrast evaluation)
-Image recording at DVD-R recording / reproducing wavelength (660 nm) Using a semiconductor laser with a wavelength of 660 nm used for recording / reproducing DVD-R, focusing was performed under conditions of a linear velocity of 3.5 m / s and a recording power of 8 mW. In this state, recording on the image recording layer was performed. In the optical recording medium of Example 1, the substrate on the image recording layer side also has a tracking groove, so that recording is performed in a state where tracking is applied. In Comparative Example 1, there is no tracking groove, so that the mechanical recording is performed. Recorded while moving the pickup. In order to quantify the difference in contrast before and after recording, the reflectance at the reflectance before and after recording (wavelength 550 nm) was measured using a spectrophotometer (manufactured by Shimadzu Corporation). The measurement results are shown in Table 1.

From Table 1, the optical recording medium of Comparative Example 1 has a reflectance difference of 12% before and after recording, whereas the optical recording medium of Example 1 has 17%, and the recorded portion is not recorded. It can be seen that the contrast with the part is high. In the optical recording medium of Example 1, the reflectance before recording is low because light interferes with the groove or is irregularly reflected.
Further, since the image recording on the optical recording medium of Example 1 is performed with tracking, it goes without saying that a finer image can be recorded as compared with Comparative Example 1.

Claims (4)

An optical recording medium having a recording layer capable of recording and reproducing information by irradiating a laser beam,
An image recording layer on which a visible image is recorded by irradiation with a laser beam is provided on a surface opposite to the recording layer, and a tracking groove is provided in an image recording area on the image recording layer side. Optical recording medium.   The optical recording medium according to claim 1, wherein a constituent component of the recording layer is different from a constituent component of the image recording layer.   The optical recording medium according to claim 1, wherein a pitch of the grooves of the recording layer is different from a pitch of the grooves of the image recording layer.   The optical recording medium according to claim 1, wherein a groove shape of the recording layer is different from a groove shape of the image recording layer.