JP2010134978A - Method and device for manufacturing optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device to manufacture an optical recording medium which has uniform recording and reproducing characteristics over its inner and outer circumferences and less warping. <P>SOLUTION: This manufacturing method of an optical recording medium having at least a base plate with a guide groove and a pigment recording layer is provided. The manufacturing method includes steps of: coating pigments to form the pigment recording layer on the base plate by applying a solution containing organic pigments; and infrared processing by radiating an infrared ray to the optical recording medium by using an infrared lamp emitting an infrared ray after the step of coating pigments. The manufacturing device is also provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an optical recording medium having a dye recording layer, and more particularly to a method and apparatus for manufacturing an optical recording medium having uniform inner and outer peripheral characteristics and small warpage.

Conventionally, as a recording layer of a write-once optical recording medium such as a CD-R or DVD-R, an optical recording medium in which a dye recording layer is formed by applying a solution containing an organic dye by a spin coating method or the like has been widely used. Yes. In such an optical recording medium, it is desired to have uniform recording / reproduction characteristics on the entire surface of the disk-shaped optical recording medium. For this reason, the inner and outer circumferences are uniform by improving the spin coating method. A method for obtaining an optical recording medium having excellent recording / reproduction characteristics has been proposed (see, for example, Patent Document 1). Here, with respect to the treatment after the application of the organic dye solution, a method of heating for about 20 minutes with an oven heated to 70 ° C. or more is common.
JP 2007-152825 A

However, according to studies by the inventors, not only the improvement of the coating method itself as described above, but also the treatment after the application of the organic dye solution affects the uniformity of the recording / reproducing characteristics of the optical recording medium. It turns out. That is, controlling the drying state after the application of the organic dye solution is important in improving the uniformity of the recording / reproducing characteristics of the optical recording medium, and is also effective in suppressing warpage of the optical recording medium. It has been found.
The present invention has been made in view of such a situation. That is, the object of the present invention is to provide a technique for producing an optical recording medium having uniform recording / reproducing characteristics over the inner and outer circumferences and having a small warp by devising the treatment after the application of the organic dye solution. To do.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have performed uniform recording on the inner and outer circumferences by applying infrared treatment to irradiate infrared rays on the optical recording medium after application of the organic dye solution. The inventors have found that it is possible to produce an optical recording medium having reproduction characteristics and small warpage, and based on this finding, the present invention has been completed.
Thus, according to the present invention, the following (1) to (5) are provided.

(1) A method of manufacturing an optical recording medium having at least a substrate having a guide groove and a dye recording layer, wherein a dye coating step of forming a dye recording layer by coating a solution containing an organic dye on the substrate And an infrared treatment step of irradiating the optical recording medium with infrared rays using an infrared lamp that emits infrared rays after the dye coating step.

(2) The method for producing an optical recording medium according to (1) above, which is a method for producing an optical recording medium having a reflective layer between the substrate and the dye recording layer.
(3) The production of the optical recording medium according to (1) or (2), further comprising a heating step of holding the optical recording medium in a state heated to 50 ° C. or higher after the infrared treatment step. Method.

(4) The optical recording medium according to (1) or (2), further comprising a heating step of holding the optical recording medium in a state of being heated to 50 ° C. or more before the infrared treatment step. Production method.
(5) The method for producing an optical recording medium according to any one of (1) to (4), wherein a peak wavelength of infrared radiation emitted from the infrared lamp is 0.8 μm to 2.0 μm. .

(6) An apparatus for producing an optical recording medium having at least a guide groove and a dye recording layer, wherein the dye recording means forms a dye recording layer by applying a solution containing an organic dye on the substrate. And an infrared lamp that emits infrared rays, and has infrared processing means for irradiating the optical recording medium with infrared rays.

  According to the present invention, an optical recording medium having uniform recording / reproducing characteristics over the entire surface of the optical recording medium and having little warpage can be obtained.

  The best mode for carrying out the present invention (hereinafter, an embodiment of the present invention) will be described in detail below. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  The optical recording medium that can be manufactured by the optical recording medium manufacturing method to which the present embodiment is applied can be applied to any write-once type optical recording medium having a dye recording layer, and is not particularly limited. Depending on the incident direction of the recording / reproducing laser beam, it can be divided into a substrate surface incident type and a film surface incident type. As a specific example of a substrate surface incident type of an optical recording medium that is currently in practical use, for example, a CD-R having a polycarbonate substrate of 1.2 mm, the thickness of the polycarbonate is halved (0.6 mm), Examples include DVD-R and DVD + R for bonding substrates. A specific example of the film surface incidence type is a BD-R having a recording layer on one surface of a 1.1 mm thick substrate.

Here, in the case of the method for producing a film surface incidence type optical recording medium, usually, using a thermoplastic resin such as polycarbonate, a step of molding the substrate by injection molding or compression molding, and the like, A step of forming a reflective layer by sputtering or the like, a dye coating step of forming a dye recording layer containing an organic dye on the reflective layer by a spin coating method, and a protective layer (or cover layer) are further provided thereon. Process.
On the other hand, in the case of a substrate surface incident type optical recording medium, usually, a step of forming a substrate, a step of applying a dye by forming a dye recording layer by a spin coating method, and a step of providing a reflective layer and a protective layer in this order. And have. Each layer constituting the optical recording medium will be described later.

(Dye application process)
First, the dye application process in the present invention will be described. Here, the case where the most widely used spin coating method is used will be described as an example. However, the dye coating process in the present invention is not limited to the spin coating method, and a die coating method, a dip method, A screen printing method or the like may be used.

FIG. 1 is a diagram for explaining a spin coater used in the present embodiment.
As shown in FIG. 1, the spin coater 100 is provided with a coating solution supply device 10 that supplies a solution containing an organic dye (hereinafter sometimes referred to as “coating solution”), and a central hole in the central portion. A spinner head device 20 that holds a disk-shaped substrate S having a predetermined radius horizontally and rotates at a predetermined number of revolutions, and excess coating liquid discharged outward from the outer peripheral edge of the substrate S scatters to the periphery. And an anti-scattering device 30 for preventing the above.

  The coating liquid supply apparatus 10 includes a nozzle 11 that discharges the coating liquid from the tip and an arm 12 that supports the nozzle 11, and is swung from a standby position to a position above the substrate S by a handling mechanism (not shown). A predetermined amount of coating liquid is discharged onto the surface of the substrate S through the nozzle 11.

  The spinner head device 20 holds the substrate S horizontally on the rotary table 22 by a detachable fixture 21 and rotates at a predetermined number of rotations by a drive motor (not shown). The coating liquid discharged from the nozzle 11 of the coating liquid supply apparatus 10 is cast on the substrate S rotated by the spinner head device 20 on the outer peripheral side on the surface of the substrate S. Excess coating liquid is shaken off at the outer peripheral edge of the substrate S to form a dye recording layer on the surface of the substrate S.

  The anti-scattering device 30 includes a coater cover 31 that prevents the coating liquid released from the outer peripheral edge of the substrate S from scattering and a mist of the coating liquid that has been shaken off by the centrifugal force under the substrate S and the rotary table 22. And a rectifying member 32 for preventing the air from sneaking to the side. The inner cup 41 collects excess coating liquid discharged outward from the outer peripheral edge of the substrate S during spin coating. A gas such as a solvent in the coating solution is exhausted from an exhaust port provided below the coater cup 42.

  Next, the operation of the spin coater 100 will be described. The substrate S is loaded into the spin coater 100 and held horizontally by the fixture 21 on the rotary table 22 of the spinner head device 20. Next, a drive motor (not shown) is rotated at a low speed, and after the coating liquid is discharged from the nozzle 11 of the coating liquid supply apparatus 10 onto the substrate S in an annular shape or spirally, the drive motor is rotated at a high speed and together with the rotary table 22. The substrate S is rotated at a high speed to spread the coating solution on the substrate S. At this time, surplus coating liquid is spun off by centrifugal force, and the sprinkled coating liquid collides with the coater cover 31 and is discharged into the inner cup 41. Further, the arm 12 of the coating liquid supply apparatus 10 turns so that the tip of the nozzle 11 moves from the inner peripheral side to the outer peripheral side of the substrate S at a predetermined speed while discharging the coating liquid.

The rotation speed of the substrate S at the start of solution discharge is usually preferably 100 rpm to 500 rpm. The number of rotations when reaching the innermost circumferential position is preferably 100 rpm to 2000 rpm.
Even after the solution discharge is stopped, the rotational speed of a rotary motor (not shown) is further increased to the maximum rotational speed, and the maximum rotational speed is maintained. After a predetermined time has passed, the rotation of the rotary motor is stopped immediately. Such maximum rotational speed is usually 2000 rpm to 7000 rpm.

  If the rotation speed is slow, the film thickness tends to be too thick than the desired value. In addition, the maximum number of revolutions is limited by the restrictions of the motor used. Also, rotation close to the upper limit of the spindle motor capacity and rapid acceleration / deceleration tend to shorten the life of the rotating device, and a slight response time shift to the motor tends to make it difficult to control the film thickness. Therefore, the maximum rotational speed is preferably 7000 rpm or less, more preferably 5000 rpm or less.

  The concentration of the coating solution described above is variously selected according to the solvent to be used, the thickness of the dye recording film, and the like and is not particularly limited, but is usually 0.2% or more, preferably 0.3% or more, and usually 3%. Below, preferably 2.5% or less. When the concentration is low, the solution viscosity is low and the film thickness tends to be extremely thin, or the drying time tends to be long. On the other hand, when the concentration is too high, the film thickness becomes thicker than necessary, or the dye itself becomes difficult to dissolve, and as a result, precipitation tends to occur.

(Infrared treatment process)
The optical recording medium manufacturing method to which the present embodiment is applied is characterized in that an infrared treatment process is performed through the above-described dye coating process.
In the infrared treatment step, infrared rays are emitted to the optical recording medium that has undergone the dye coating step using an infrared lamp capable of emitting infrared rays. In the present invention, the term “infrared rays” means that the main wavelength of emitted electromagnetic waves is in the range of 0.8 μm to 3.0 μm. This is because the wavelength range with high absorption efficiency is 0.8 μm to 3.0 μm in water or coating solution contained in the substrate surface or in the substrate, and water and solvent can be vaporized most efficiently. . The radiance in the above wavelength range is preferably 0.8 (W / (cm ² · sr · μm)) or more.

The infrared light peak wavelength of the infrared lamp is preferably 0.8 μm to 2 μm, and the peak wavelength is generally determined by 2897 ÷ color temperature (K). The color temperature is preferably 3400K to 1450K. If the color temperature is too high, the peak shifts to the visible light side, the thermal efficiency of the heater is lowered, and if the color temperature is too low, the thermal damage to the substrate may increase. .
As the infrared lamp capable of emitting infrared rays, a commercially available lamp can be used as long as the main wavelength is in the above range. As the type of lamp, it is preferable to use a halogen lamp capable of efficiently emitting infrared rays. For example, UH-HA1-CL300 and UH-HA1-CL700 manufactured by USHIO Electric Co., Ltd. are available. The color temperature can correspond to various wavelengths by changing the filament temperature of the halogen lamp.

As for the method of emitting infrared rays, the infrared lamp and the optical recording medium may be fixed and performed for a certain period of time, or while the infrared lamp is fixed and irradiated with infrared rays, the optical recording medium is conveyed at an appropriate speed. Also good. It is also possible to irradiate infrared rays while rotating the optical recording medium at a predetermined rotational speed.
The infrared lamp may be one lamp or a plurality of lamps. Alternatively, the arrangement of the infrared lamps may be linear or grid. Furthermore, the heat distribution distribution design of the filament of the infrared lamp can be changed so that the heating surface can be uniformly heated.

  By applying the infrared treatment process to the optical recording medium, the distribution of recording / reproducing characteristics on the inner and outer circumferences of the disk-shaped optical recording medium is remarkably improved as compared with the conventional drying process using an oven or the like. For example, in the recording sensitivity characteristic, the in-plane recording sensitivity difference is reduced, and a more uniform recording sensitivity characteristic can be obtained over the entire surface of the optical recording medium. This is presumed to be due to the following reason.

In the conventional hot air blow type oven, the temperature difference in the substrate is generated faster than the increase in the outer peripheral temperature of the substrate. In addition, it is estimated that the solvent and water are vaporized with thermal expansion of the substrate, and it is considered that partial unevenness is likely to occur when such evaporation occurs.
On the other hand, in the infrared lamp treatment, photothermal treatment can be efficiently performed with respect to the solvent or water on the disk surface, so that it can be uniformly dried in a short time. For this reason, it can be estimated that unevenness is unlikely to occur because the dye-dried film is formed before the thermal expansion of the substrate occurs.
For the above reasons, the uniformity of the mechanical properties of the optical recording medium can also be improved, so that the warp of the optical recording medium can also be reduced.

(Heating process)
In the method of manufacturing an optical recording medium to which the present embodiment is applied, a normal heating process using an oven or the like may be performed in addition to the above infrared processing process. The heating step is preferably performed after the infrared treatment step, but may be performed before the infrared treatment step. Moreover, you may perform an infrared treatment process in multiple times before and behind a heating process.
As the heating process, an oven or the like conventionally used in the drying process can be appropriately used as long as the optical recording medium can be held for a predetermined time while being heated to 50 ° C. or higher.

(substrate)
For the substrate on which the dye recording layer is formed by the above method, plastic, metal, glass or the like having appropriate processability and rigidity can be used. In the case of a substrate surface incident type optical recording medium, the substrate needs to be transparent to incident laser light. In the film surface incidence type optical recording medium, since the laser light does not normally pass through the substrate, the substrate does not need to be transparent to the laser light.

When the substrate is a metal or glass, it is necessary to provide a light or thermosetting thin resin layer on the surface and to form a groove there. In this respect, it is preferable from the viewpoint of manufacturing that a plastic material is used and the shape of the substrate, particularly a disc shape, and a guide groove on the surface are formed all at once by injection molding.
As the plastic material that can be injection-molded, polycarbonate resin, polyolefin resin, acrylic resin, epoxy resin, and the like conventionally used for CDs and DVDs can be used. The thickness of the substrate is preferably about 0.5 mm to 1.2 mm. Among them, generally, a substrate made of polycarbonate resin is used.

  Polycarbonate resin is transparent to recording / reproducing light, can accurately transfer fine patterns such as grooves and pits by injection molding, has necessary and sufficient heat resistance and strength, and is a general-purpose resin Therefore, it has many advantages as a substrate of an optical recording medium that is low in cost. As a method for producing the substrate, injection molding which is fast and excellent in transferability is preferable.

(Organic dye)
Here, the organic dye contained in the dye recording layer is not particularly limited, but is usually a macrocyclic azaannulene dye such as a phthalocyanine dye, a naphthalocyanine dye or a porphyrin dye; a polymethine dye such as a cyanine dye, a merocyanine dye or a squarylium dye Dyes: pyromethene dyes, anthraquinone dyes, azulenium dyes, metal-containing azo dyes, metal-containing indoaniline dyes, and the like. Furthermore, stilbene, (carbo) styryl, coumarin, pyrone, chalcone, triazole, sulfonylimine type, azlactone type compound and the like and mixtures thereof can be mentioned.

  The organic dye used in the dye recording layer has a maximum absorption wavelength λmax in the visible light to near infrared region of about 350 nm to 900 nm. In the case of an optical recording medium for blue laser, a dye compound suitable for recording with blue to near microwave laser is preferable. Specifically, a near-infrared laser (typically 780 nm, 830 nm, etc.) having a wavelength of about 770 nm to 830 nm as used for a CD-R or a wavelength 620 nm to 690 nm as used for a DVD-R is used. A dye suitable for recording with a red laser (typically 635 nm, 660 nm, 680 nm, etc.) or a so-called blue laser with a wavelength of 405 nm, 515 nm or the like is more preferable.

  One type of organic dye may be used, or two or more types of the same type or different types may be used. Furthermore, an organic dye suitable for recording in each of the recording lights having a plurality of wavelengths can be used in combination to form an optical recording medium corresponding to recording with laser light in a plurality of wavelength regions.

  In addition, the dye recording layer has a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone) as a singlet oxygen quencher to improve the stability and light resistance of the recording layer. Etc.) and a recording sensitivity improver such as a metal compound may be contained for improving the recording sensitivity. Here, the metal compound means a compound in which a metal such as a transition metal is contained in the compound in the form of atoms, ions, clusters, etc., for example, ethylenediamine complex, azomethine complex, phenylhydroxyamine complex, phenanthroline complex, Organic metal compounds such as dihydroxyazobenzene complex, dioxime complex, nitrosoaminophenol complex, pyridyltriazine complex, acetylacetonate complex, metallocene complex and porphyrin complex can be mentioned. Although it does not specifically limit as a metal atom, It is preferable that it is a transition metal.

(solvent)
Although it does not specifically limit as a solvent used in order to prepare the solution containing the organic pigment | dye mentioned above, For example, ketone alcohol solvents, such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; Methyl cellosolve, ethyl A cellosolve solvent such as cellosolve; a fluorine-based solvent such as 2,2,3,3-tetrafluoro-1-propanol and octafluoropentanol; a hydroxyethyl solvent such as methyl lactate and methyl isobutyrate is preferably used.

Furthermore, esters such as butyl acetate and cellosolve acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; amides such as dimethylformamide; hydrocarbons such as cyclohexane; Examples include ethers such as tetrahydrofuran, ethyl ether, and dioxane; alcohols such as ethanol, n-propanol, isopropanol, and n-butanol; and glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene glycol monomethyl ether. it can.
Among these, a fluorinated solvent is preferable. The above-mentioned solvents can be used alone or in combination of two or more in consideration of the solubility of the organic dye used.

  The thickness of the dye recording layer is not particularly limited because a suitable film thickness varies depending on the recording method or the like, but is usually 5 nm or more, preferably 10 nm or more in order to obtain a sufficient degree of modulation. Preferably it is 20 nm or more. However, since it is necessary to transmit light, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less. Especially for short wavelength laser applications of less than 660 nm, 100 nm or less is preferable, and 60 nm or less is more preferable.

(Optical recording medium)
Next, the optical recording medium will be described.
As described above, the optical recording medium to which the manufacturing method of the optical recording medium to which the present embodiment is applied can be applied to the substrate surface incident type and the film surface incident type depending on the incident direction of the recording / reproducing laser beam. Can be divided into

In the case of a film surface incidence type optical recording medium, a reflective layer, a dye recording layer, and a protective layer (or a cover layer) are usually provided on a disk-shaped substrate having a center hole in the center and having a predetermined radius. ) Are provided in this order. Here, a buffer layer formed of an inorganic material (for example, ZnS / SiO ₂ ) may be provided between the dye recording layer and the protective layer. In addition, a substrate surface incident type optical recording medium usually has a structure in which a dye recording layer, a reflective layer, and a protective layer are provided in this order on a substrate. In the substrate surface incident type optical recording medium, a hard coat layer may be provided on the substrate. Further, in the film surface incident type optical recording medium, a hard coat layer may be provided on the protective layer.

The method for producing an optical recording medium of the present invention is particularly preferably applied to a film surface incidence type optical recording medium. In a film surface incident type optical recording medium, a reflective layer exists between the dye recording layer and the substrate when the infrared treatment process is performed. For this reason, even if a part of the infrared energy irradiated from the dye recording layer surface side is once transmitted through the dye recording layer, it may be reflected by the reflective layer and absorbed again by the dye recording layer. For this reason, it is considered that the dye recording layer can be processed more efficiently than in the case where there is no reflective layer. In addition, when there is a reflective layer, the rate at which the infrared energy transmitted through the dye recording layer is absorbed by the substrate is relatively small, so thermal damage to the substrate can be suppressed, and the recording / reproduction characteristics of the optical recording medium can be reduced. It is thought to have a positive effect on mechanical properties.
Next, each layer constituting the optical recording medium will be described. The dye recording layer has already been described and is omitted here.

  Usually, a guide groove for tracking is formed on the substrate. The track pitch varies depending on the wavelength of the laser beam used for recording / reproducing on the optical recording medium. Specifically, in a CD-based optical recording medium, the track pitch is usually 1.5 μm to 1.6 μm. In a DVD-based (for red laser) optical recording medium, the track pitch is usually 0.7 μm to 0.8 μm. In an optical recording medium for blue laser, the track pitch is usually 0.2 μm to 0.5 μm. On the other hand, the depth of the groove also varies depending on the wavelength of the laser beam used for recording / reproducing of the optical recording medium. Specifically, in a CD-based optical recording medium, the groove depth is usually 10 nm to 300 nm. In a DVD optical recording medium, the groove depth is usually 10 nm to 200 nm. In the optical recording medium for blue laser, the groove depth is usually 10 nm to 130 nm.

  As a material for the reflective layer, a material having a sufficiently high reflectance at the wavelength of the reproduction light, for example, a metal such as Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, alone or in an alloy is used. Can be used. Among these, Au, Al, and Ag have high reflectivity and are suitable as a material for the reflective layer. In addition to these metals as main components, other materials may be added. Here, the main component means one having a content of 50% or more.

  Examples of materials other than the main component include Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Mention may be made of metals and semi-metals such as Ge, Te, Pb, Po, Sn, Bi, Ta, Ti, Pt, Pd, Nd. Among them, those containing Ag as a main component are particularly preferable because they are low in cost, easily produce high reflectivity, and obtain a beautiful white background when a print receiving layer described later is provided. For example, an alloy containing about 0.1 atomic% to 5 atomic% of one or more selected from Au, Pd, Pt, Cu, and Nd in Ag has high reflectivity, high durability, high sensitivity, and low cost. It is preferable.

  Specifically, for example, an AgPdCu alloy, an AgCuAu alloy, an AgCuAuNd alloy, an AgCuNd alloy, or the like. As a material other than the metal, a low refractive index thin film and a high refractive index thin film can be alternately stacked to form a multilayer film, which can be used as a reflective layer.

  The thickness of the reflective layer is preferably 50 nm to 300 nm. Examples of the method for forming the reflective layer include sputtering, ion plating, chemical vapor deposition, and vacuum vapor deposition. In addition, a known inorganic or organic intermediate layer or adhesive layer may be provided on the substrate or under the reflective layer in order to improve reflectivity, improve recording characteristics, improve adhesion, or the like.

  In the case of an optical recording medium for a blue laser, examples of materials exhibiting a high reflectance in the blue wavelength region include Au, Ag, Al, Cu and alloys containing these as main components. More preferably, the alloy has a high reflectance at λ = 405 nm and a small absorption. For example, the main component is Ag, Au, Cu, rare earth elements (particularly Nd), Nb, Ta, V, Mo, Mn, Mg, Cr, Bi, Al, Si, Ge, and the like. Addition of atomic% is preferable because it can improve the corrosion resistance against moisture, oxygen, sulfur and the like. In addition, a dielectric mirror in which a plurality of dielectric layers are stacked can be used.

The material of the protective layer is not particularly limited as long as it protects the reflective layer from external force. For example, an organic material such as a thermoplastic resin, a thermosetting resin, an electron beam curable resin, or an ultraviolet curable resin; Examples thereof include inorganic materials such as silicon, silicon nitride, MgF ₂ and SnO ₂ . When a thermoplastic resin, a thermosetting resin or the like is used, a protective layer can be formed by applying a coating solution prepared by dissolving in a suitable solvent on the reflective layer and drying it. When using an ultraviolet curable resin, apply it directly on the reflective layer, or apply a coating solution prepared by dissolving in an appropriate solvent on the reflective layer and cure it by irradiating it with ultraviolet light. A protective layer can be formed.

  As the ultraviolet curable resin, for example, acrylate resins such as urethane acrylate, epoxy acrylate, and polyester acrylate can be used. These materials may be used alone or as a mixture of plural kinds. Further, the protective layer may be formed as a single layer or a multilayer.

  As a method for forming the protective layer, as with the dye recording layer, a coating method such as a spin coating method or a casting method, a sputtering method, a chemical vapor deposition method, or the like is used. Of these, a spin coating method is preferable. The film thickness of the protective layer is generally 0.1 μm or more, preferably 3 μm or more, because a certain degree of thickness is required to fulfill its protective function. However, if it is too thick, not only the effect does not change, but it may take time to form the protective layer and the cost may be high, so it is usually 100 μm or less, preferably 30 μm or less. In addition, when using plate-shaped members, such as resin (for example, polycarbonate) and a metal, for a protective layer, what is necessary is just to adhere | attach these members to a recording layer, a buffer layer, or a reflection layer using an adhesive agent.

  Further, in the case of a film surface incident type blue laser optical recording medium, the protective layer (or cover layer) is selected from a material that is transparent to recording / reproducing light and has little birefringence. (Referred to as a sheet) are bonded together with an adhesive, or after application, cured by light, radiation, heat, or the like. The protective layer preferably has a transmittance of 70% or more, more preferably 80% or more with respect to the recording / reproducing light wavelength.

  The plastic used as the sheet agent is polycarbonate, polyolefin, acrylic, cellulose triacetate, polyethylene terephthalate, or the like. For adhesion, light, radiation curing, thermosetting resin, or pressure sensitive adhesive is used. As the adhesive, an acrylic, rubber or silicon adhesive can be used.

  For example, in the case of forming a protective layer (or cover layer) for an optical recording medium for blue laser, a photocurable resin constituting the protective layer (or cover layer) is dissolved in an appropriate solvent, and a coating solution is prepared. After the preparation, the coating solution is applied onto the dye recording layer or the interface layer to form a coating film, and a polycarbonate sheet is overlaid on the coating film. Thereafter, the coating liquid is further stretched and developed by rotating the medium or the like in a superposed state as necessary, and then cured by irradiating with an ultraviolet ray with a UV lamp. Alternatively, a pressure sensitive adhesive is applied to the sheet in advance, and this sheet is overlaid on the dye recording layer or the interface layer, and then pressed and pressed with an appropriate pressure. In addition, when the protective layer is formed by a coating method, a spin coating method, a dip method, or the like is used, and in particular, a spin coating method is often used. As a material for the protective layer by coating, urethane, epoxy, acrylic resin or the like is used, and after coating, it is cured by irradiating with ultraviolet rays, electron beams, or radiation to accelerate radical polymerization or cationic polymerization.

Examples of the optical recording medium include a two-layer optical recording medium having two dye recording layers. The two-layer type optical recording medium usually has a first substrate, a first dye recording layer, a first (semi-transparent) reflective layer, a transparent adhesive layer, a second dye recording layer, a first dye recording layer, from the side on which recording / reproducing light is incident. It has a structure in which two reflective layers and a second substrate are laminated in this order.
In a two-layer type optical recording medium, the method for producing an optical recording medium of the present invention may be used when forming at least one dye recording layer. Of course, it is preferably used for the formation of all dye recording layers.
Examples of the material constituting the first substrate and the first dye recording layer include the same materials as those of the substrate and (organic dye) of the present invention described above.

The first (semi-transparent) reflective layer is a reflective layer having a certain light transmittance. That is, the reflective layer has a small absorption of recording / reproducing light, a light transmittance of 40% or more, and an appropriate light reflectance (usually 30% or more). For example, an appropriate transmittance can be provided by providing a thin metal with high reflectivity. Moreover, it is desirable that there is some degree of corrosion resistance. Further, it is desirable to have a blocking property so that the first dye recording layer is not affected by the seepage of the upper layer (here, the transparent adhesive layer) of the first (semi-transparent) reflective layer.
In order to ensure high transmittance, the thickness of the first (translucent) reflective layer is usually preferably 50 nm or less. More preferably, it is 30 nm or less. More preferably, it is 25 nm or less. However, since the first dye recording layer is not affected by the upper layer of the first (semi-transparent) reflective layer, a certain thickness is required and is usually 3 nm or more. More preferably, it is 5 nm or more.

As a material for the first (semi-transparent) reflective layer, a material having a reasonably high reflectance at the wavelength of the reproduction light, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Pd, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, rare earth metals, etc. Metals and metalloids can be used alone or as an alloy. Among these, Au, Al, and Ag have high reflectivity and are suitable as materials for the first (translucent) reflective layer. In addition to these as main components, other components may be included. It is also possible to use a layer made of Si as the first (semi-transparent) reflective layer.
It is also possible to form a multilayer film by alternately stacking a low refractive index thin film and a high refractive index thin film using a material other than metal, and use it as a reflective layer.

  The transparent adhesive layer needs to be transparent, and has a high adhesive force and a low shrinkage during curing and adhesion is preferable because the shape stability of the medium is high. The refractive index of the transparent adhesive layer (refractive index with respect to the wavelength of recording light or reproducing light) is usually 1.40 or more and 1.80 or less. The transparent adhesive layer is preferably made of a material that does not damage the second dye recording layer. However, since the transparent adhesive layer is usually made of a resin, it is easily compatible with the second dye recording layer. In order to prevent this and prevent damage, it is desirable to provide a buffer layer described later between the two layers. Furthermore, the transparent adhesive layer is preferably made of a material that does not damage the first (semi-transparent) reflective layer. However, a known inorganic or organic protective layer may be provided between both layers in order to suppress damage.

It is preferable to accurately control the film thickness of the transparent adhesive layer. The film thickness of the transparent adhesive layer is usually preferably 5 μm or more. In order to separately apply focus servo to the two dye recording layers, it is necessary that there is a certain distance between the two recording layers. Although it depends on the focus servo mechanism, it is usually required to be 5 μm or more, preferably 10 μm or more.
In general, the higher the numerical aperture of the objective lens, the smaller the distance tends to be. However, if it is too thick, it takes time to adjust the focus servo to the two dye recording layers, and the moving distance of the objective lens tends to be long. Moreover, since time may be required for curing and productivity may be lowered, it is usually preferably 100 μm or less.
Examples of the material for the transparent adhesive layer include thermoplastic resins, thermosetting resins, electron beam curable resins, ultraviolet curable resins (including delayed curable resins), and the like.

  The transparent adhesive layer is prepared by dissolving a thermoplastic resin, a thermosetting resin, etc. in an appropriate solvent to prepare a coating solution, coating the first (semi-transparent) reflective layer, and drying (heating). Can be formed. The ultraviolet curable resin can be formed by preparing a coating solution as it is or by dissolving in an appropriate solvent, and then applying the coating solution and curing it by irradiating with ultraviolet light. There are various types of ultraviolet curable resins, and any of them can be used as long as it is transparent. These materials may be used alone or in combination, and may be used not only as a single layer but also as a multilayer film.

  As a coating method, a method such as a spin coating method or a casting method is used in the same manner as the dye recording layer. Among these, a spin coating method is preferable. Alternatively, a resin having a high viscosity can be formed by screen printing or the like. It is preferable to use an ultraviolet curable resin that is liquid at 20 ° C. to 40 ° C. so that the productivity can be applied without using a solvent. Moreover, it is preferable to adjust the viscosity to be 20 mPa · s to 1000 mPa · s. In addition, an adhesive layer can also be formed by using a pressure-sensitive double-sided tape and sandwiching and pressing the tape between laminated structures.

  Examples of the ultraviolet curable adhesive include a radical ultraviolet curable adhesive and a cationic ultraviolet curable adhesive, both of which can be used. As the radical ultraviolet curable adhesive, all known compositions can be used, and a composition containing an ultraviolet curable compound and a photopolymerization initiator as essential components is used. As the ultraviolet curable compound, monofunctional (meth) acrylate or polyfunctional (meth) acrylate can be used as the polymerizable monomer component. These can be used alone or in combination of two or more. Here, in the present invention, acrylate and methacrylate are collectively referred to as (meth) acrylate.

  In the second dye recording layer, since the power of the incident light beam decreases due to the presence of the first dye recording layer and the first (semi-transparent) reflecting layer, etc., recording is performed with about half the power. It is necessary to have higher sensitivity than a recording layer used for a recording medium (for example, CD-R, DVD-R, DVD + R). In order to realize good recording / reproducing characteristics, it is desirable to use a dye having low heat generation and high refractive index.

  The film thickness of the second dye recording layer is not particularly limited because the suitable film thickness varies depending on the recording method and the like, but in order to obtain a sufficient degree of modulation, it is usually preferably 10 nm or more, more preferably 30 nm or more. And particularly preferably 50 nm or more. However, since it is not necessary to be too thick in order to obtain an appropriate reflectance, it is usually 3 μm or less, preferably 1 μm or less, more preferably 200 nm or less. Here, the film thickness of the second dye recording layer usually refers to the film thickness in the thick film portion. The materials used for the first dye recording layer and the second dye recording layer may be the same or different.

  Examples of the material for the second reflective layer include the same materials as described above. The second reflective layer needs to have a high reflectance. Moreover, it is desirable that it is highly durable. In order to ensure high reflectivity, the thickness of the second reflective layer is usually preferably 20 nm or more. More preferably, it is 30 nm or more. More preferably, it is 50 nm or more. However, in order to shorten the production tact time and reduce the cost, it is preferable to be thin to some extent, and is usually 400 nm or less. More preferably, it is set to 300 nm or less.

  The second substrate preferably has shape stability so that the two-layer optical recording medium has a certain degree of rigidity. That is, it is preferable that the mechanical stability is high and the rigidity is large. Examples of such materials include acrylic resins, methacrylic resins, polycarbonate resins, polyolefin resins (particularly amorphous polyolefins), polyester resins, polystyrene resins, epoxy resins, and the like, and glass. Things can be used.

  Further, the second substrate may be composed of a plurality of layers. For example, a substrate in which a resin layer made of a radiation curable resin such as a photo-curing resin is provided on a substrate made of glass or resin, etc. Can be used as If the first substrate does not have sufficient shape stability, the second substrate needs to have particularly high shape stability. In this respect, it is desirable that the hygroscopicity is small.

The second substrate does not need to be particularly transparent. As such a material, the same material as that which can be used for the first substrate can be used. For example, an Al alloy substrate such as an Al-Mg alloy containing Al as a main component, for example, Mg containing a main component such as Mg. A Mg alloy substrate such as a Zn alloy, a substrate made of any of silicon, titanium, and ceramics, a substrate that combines them, and the like can be used.
In addition, from the viewpoints of high productivity such as moldability, cost, low hygroscopicity, and shape stability, the above-described resins are preferable, and polycarbonate is particularly preferable. From the viewpoint of chemical resistance, low hygroscopicity, etc., amorphous polyolefin is preferred. Moreover, a glass substrate is preferable from the viewpoint of high-speed response.

  In order to give the two-layer type optical recording medium sufficient rigidity, the second substrate is preferably thick to some extent, and the thickness is preferably 0.3 mm or more. However, the thinner one is advantageous for thinning the recording / reproducing apparatus, and it is preferably 3 mm or less. More preferably, it is 1.5 mm or less.

The groove depth of the second substrate (groove depth) is preferably such that the groove depth of the first substrate is shallower than the groove depth of a general dye-based optical recording medium.
Here, it is preferable to provide a buffer layer as an intermediate layer between the transparent adhesive layer and the second dye recording layer. The buffer layer prevents the two layers from mixing and prevents compatibility. The buffer layer may also serve other functions than preventing the mixing phenomenon. Further, another intermediate layer may be interposed as required.

The material of the buffer layer is incompatible with the second dye recording layer and the transparent adhesive layer and needs to have a certain degree of light transmission, but known inorganic and organic materials can be used. In view of characteristics, an inorganic material is preferably used. For example, metal or semiconductor, metal or semiconductor oxide, nitride, sulfide, oxysulfide, fluoride or carbide, amorphous carbon, or the like is used. Among them, a layer made of a substantially transparent dielectric or a very thin metal layer (including an alloy) is preferable.
In addition, a resin layer may be used as long as it does not dissolve the organic dye of the second dye recording layer when the buffer layer is prepared. In particular, a polymer film that can be produced by vacuum deposition or CVD is useful.

The thickness of the buffer layer is usually 2 nm or more and 200 nm or less. In particular, in the case of a metal, 20 nm or less is preferable because the light transmittance is excessively lowered. In addition, a buffer layer as an intermediate layer may be provided between the first (translucent) reflective layer and the transparent adhesive layer.
Furthermore, in the two-layer type optical recording medium, any other layer may be sandwiched as necessary. Further, any other layer may be provided on the outermost surface of the optical recording medium.
Further, the recording layer may be three or more layers. Further, it is possible to make a larger-capacity medium having four recording layers by laminating two optical recording media of this layer configuration and the first substrate facing outside.

In addition, an ultraviolet curable resin layer, an inorganic thin film (for example, SiO ₂ ) or the like is provided on the mirror surface side of the optical recording medium (incident surface for recording light or reproducing light) in order to protect the surface and prevent adhesion of dust and the like. A film may be formed.
In addition, these optical recording media can accept prints that can be written (printed) by various printers such as ink jet and thermal transfer, or various writing tools, on the surface that is not the incident surface of recording light or reproducing light, if necessary. A layer may be provided.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples without departing from the gist thereof.

Example 1
In a clean booth having a temperature of 25 ° C. and a relative humidity of 42% on an injection-molded polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm having a guide groove having a track pitch of 0.74 μm, a width of 0.33 μm, and a depth of 160 nm, A tetrafluoropropanol solution of metal-containing azo dye (concentration: 1.4% by weight) was dropped and applied by a spinner method. The recording layer thickness was adjusted with a laser having a wavelength of 590 nm so that the OD value was 0.68.
After applying the dye recording layer, an infrared treatment process was performed at an output of 1000 W using a UH-HA1-CL300 infrared lamp manufactured by USHIO ELECTRIC CO., LTD.
The distance between the infrared lamp and the substrate is fixed at 200 mm, and 16.7 mm / sec. Infrared rays were emitted from above the optical recording medium while the optical recording medium was being transported in the horizontal direction at a transport speed of. In that case, the substrate surface temperature immediately after infrared irradiation was 85 degreeC.
Further, an Ag reflective layer having a thickness of 120 nm was formed on the dye recording layer by sputtering. Further, an adhesive layer was provided on the reflective layer by spin coating an ultraviolet curable resin. Then, a polycarbonate substrate having a diameter of 120 mm and a thickness of 0.6 mm was placed on the adhesive layer, and cured and adhered by irradiation with ultraviolet rays. In this way, an optical recording medium was produced.

(Method for evaluating recording / reproduction characteristics of optical recording medium)
The recording / reproduction characteristics of the optical recording medium were evaluated by measuring the value of Asymmetry obtained after signal recording of the produced optical recording medium. The uniformity of the recording characteristics is better as the Asymmetry value with respect to the recording power is constant regardless of the measurement radius position.
Asymmetry is defined by the following equation.
Asymmetry = ((I14H + I14L) / 2− (I3H + I3L) / 2) I14
In the equation, I14H and I3H are the reflectances of the 14T and 3T signal spaces, respectively, and I14L and I3L are the reflectances of the 14T and 3T signal marks, respectively. I14L is the mark amplitude of the 14T signal.

  As an evaluation procedure, recording is performed while changing the recording laser power to the inner peripheral portion (radius 43.0 mm to 46.5 mm) and outer peripheral portion (53.5 mm to 56.3 mm) of the optical recording medium by a normal recording / reproducing drive. Went. Thereafter, reproduction was performed on DVD-CATS manufactured by Audio developer, and the recording power dependency of Asymmetry defined above was measured.

(Evaluation method of warpage of optical recording medium)
The warp of the optical recording medium indicates the angle when the reflected light from the substrate is received by the photodetector. Warpage of the substrate before the heat treatment was measured at a radius of 25 mm to 5 mm. Similarly, the warp of the optical recording medium after the heat treatment was measured, and the warpage change amount (r-tilt) was calculated when the warp before the treatment was 0 (zero). The closer the amount of warp change of the optical recording medium is to 0, the smaller the stress applied to the optical recording medium, and the smaller the warp after processing.

(Comparative Example 1)
An optical recording medium was produced in the same manner as in Example 1 except that after the dye recording layer was applied, it was kept in an oven at 85 ° C. for 18 minutes without using the infrared lamp.

(Evaluation results)
FIG. 2 and FIG. 3 show the results of measuring the recording power dependence of Asymmetry at the inner and outer peripheral portions of the optical recording media of Example 1 and Comparative Example 1, respectively. In Example 1 (FIG. 2), the values of Asymmetry with respect to the recording power almost coincide with each other on the inner and outer periphery, whereas in Comparative Example 1 (FIG. 3), the values of Asymmetry with respect to the recording power are shifted. That is, since the entire surface of the optical recording medium is normally recorded with a constant recording power, almost the same Asymmetry value is obtained on the entire surface of the optical recording medium in Example 1, whereas the Asymmetry value is obtained on the inner and outer circumferences in Comparative Example 1. A difference will occur, and the uniformity of the recording characteristics will be inferior.

Next, FIG. 4 shows the results of studying the warpage of the optical recording medium with respect to the optical recording media of Example 1 and Comparative Example 1. The warpage was measured by measuring the warpage of the optical recording medium before and after the infrared treatment step and the heating step in the manufacturing methods of Example 1 and Comparative Example 1, and evaluating the degree of change. The measuring apparatus is Dr. ARGUS manufactured by Schwab Inspection Technology was used. In Example 1 and Comparative Example 1, two sheets were produced and measured.
It is clear that the warpage of Example 1 is smaller than that of Comparative Example 1 over the inner and outer circumferences.
From the above, it can be seen that by applying a predetermined infrared treatment to the optical recording medium after the dye recording layer is applied, it is possible to obtain an optical recording medium having a small distribution of recording and reproducing characteristics on the inner and outer circumferences and a smaller warp. .

  According to the present invention, an optical recording medium having uniform recording / reproducing characteristics on the inner and outer circumferences and a small warp can be obtained, and can be applied to any write-once type optical recording medium having a dye recording layer. .

It is a figure for demonstrating a spin coat apparatus. In Example 1, it is the figure which showed the recording power dependence of Asymmetry. In Comparative Example 1, it is a diagram showing the recording power dependence of Asymmetry. In Example 1 and Comparative Example 1, it is the figure which showed the radius dependence of Tilt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Coating liquid supply apparatus 11 ... Nozzle 12 ... Arm 20 ... Spinner head apparatus 21 ... Fixing tool 22 ... Rotary table 30 ... Scatter prevention apparatus 31 ... Coater cover 32 ... Rectification member 41 ... Inner cup 42 ... Coater cup 100 ... Spin coat apparatus

Claims (6)

  A method for producing an optical recording medium having at least a substrate having a guide groove and a dye recording layer, comprising a dye coating step of forming a dye recording layer by applying a solution containing an organic dye on the substrate, A method for producing an optical recording medium comprising an infrared treatment step of irradiating the optical recording medium with infrared rays using an infrared lamp that emits infrared rays after the dye coating step.   2. The method for manufacturing an optical recording medium according to claim 1, wherein the method is a method for manufacturing an optical recording medium having a reflective layer between the substrate and the dye recording layer.   The method for producing an optical recording medium according to claim 1, further comprising a heating step of holding the optical recording medium in a state of being heated to 50 ° C. or higher after the infrared treatment step.   The method of manufacturing an optical recording medium according to claim 1, further comprising a heating step of holding the optical recording medium in a state of being heated to 50 ° C. or more before the infrared treatment step.   5. The method of manufacturing an optical recording medium according to claim 1, wherein the infrared light emitted from the infrared lamp has a peak wavelength of 0.8 μm to 2.0 μm.   An apparatus for producing an optical recording medium having at least a substrate having a guide groove and a dye recording layer, comprising: a dye applying means for applying a solution containing an organic dye on the substrate to form the dye recording layer An apparatus for manufacturing an optical recording medium, comprising: an infrared lamp that emits infrared rays, and comprising infrared processing means for irradiating the optical recording medium with infrared rays.

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