JP2005116067A - Method for manufacturing optical information medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical information medium which is nearly unchanged in warpage by lapse of time and thermal storage, and sufficiently satisfies a standard for a radial tilt. <P>SOLUTION: The method for manufacturing the optical information medium comprises sticking together an information substrate having a recording layer or pits capable of recording information by irradiation with a laser beam and a protective substrate. The method has a process of subjecting the protective substrate to heat treatment at 60 to 90°C. The heat treatment time is preferably specified to 5 to 300 minutes. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an optical information medium, and more particularly to a method for manufacturing a bonded optical information medium such as a DVD.

A high-density optical information medium (DVD) for recording and reproducing large amounts of character information, image information, audio information, etc., and an optical information medium (DVD-R or DVD-RW) capable of recording information once or multiple times The demand for higher density is increasing. In such an optical information medium, in addition to making the shortest pit and track pitch less than half of the CD or the like, the information recording density is increased by bonding the optical information medium in two layers.
Such a bonded type optical information medium has a structure in which laminates (information substrates) having a recording layer or pits, a reflective layer, a protective layer, etc. on a substrate are bonded to each other between the surfaces of the protective layer, There is known a structure in which the laminate 1 described above and a protective substrate (dummy substrate) not provided with a recording layer or the like are bonded together.

In such a bonded optical information medium, it is known that the information substrate is subjected to heat treatment in order to suppress warpage change due to aging and thermo storage (80 ° C., dry, 24 hours) and deterioration of jitter over time. (For example, refer to Patent Document 1). When an information substrate subjected to heat treatment and a protective substrate not subjected to heat treatment are bonded together in this way, warpage (radial tilt, surface blur) changes due to aging or thermo storage, and the standard of radial tilt is not satisfied. There's a problem. This is considered because the residual distortion at the time of shaping | molding is relieve | moderated with time.
JP 2000-276787 A

This invention is made | formed in view of the said problem, and makes it a subject to achieve the following objectives. That is,
An object of the present invention is to provide a method for manufacturing an optical information medium that can manufacture an optical information medium that is less likely to change in warp due to aging or thermo storage and sufficiently satisfies the radial tilt standard.

As a result of intensive studies to achieve the above object, the present inventor has found that the object can be achieved by the following present invention.
That is, the present invention is a method for manufacturing an optical information medium in which an information substrate having a recording layer or pits capable of recording information by laser light irradiation and a protective substrate are bonded to each other, and the protective substrate has a temperature of 60 to 90 ° C. An optical information medium manufacturing method comprising a step of performing a heat treatment at a temperature.
The heat treatment time is preferably 5 to 300 minutes.
Furthermore, it is preferable to provide a step of performing the same heat treatment as the heat treatment applied to the protective substrate on the information substrate after forming the recording layer.

  According to the present invention, it is possible to provide a method of manufacturing an optical information medium that can manufacture an optical information medium that is less likely to change in warp due to aging or thermo storage and sufficiently satisfies the radial tilt standard.

  The method for producing an optical information medium of the present invention is a method for producing an optical information medium in which an information substrate having a recording layer or pits capable of recording information by laser light irradiation and a protective substrate are bonded to each other. And a step of performing a heat treatment at a temperature of 60 to 90 ° C. Hereinafter, an optical information medium manufactured by the method for manufacturing an optical information medium of the present invention will be described first.

<Optical information media>
The optical information medium according to the present invention is formed by laminating an information substrate having a recording layer or pits capable of recording information by laser light irradiation and a protective substrate. The information substrate is provided with a light reflection layer, a protective layer, or the like as necessary.
That is, the optical information medium according to the present invention includes an optical information medium having a recording layer capable of recording and reproducing information by laser light, and a light having a recording portion (pit) in which information reproducible by laser light is recorded. It can be applied to information media.
The former is a write-once or rewritable optical information medium such as DVD-R or DVD-RW, and the latter is an optical information medium in which information is written in advance such as a DVD-ROM. .

In an optical information medium in which information is written in advance, such as a DVD-ROM, pits are formed at least on the bonding surface of the information substrate. Further, the protective substrate may have a configuration in which pits are formed in the same manner as the information substrate, or may have a configuration in which pits are not formed as a so-called dummy substrate.
Hereinafter, the substrate and each layer used in the present invention will be described using optical information media such as DVD-R and DVD-RW as examples. Note that the layer configuration, materials, and the like are merely examples, and the present invention is not limited to these.

[Information board, protective board]
As the information substrate and the protective substrate, various materials used as substrate materials for conventional optical information media can be arbitrarily selected and used.
Specifically, glass; acrylic resin such as polycarbonate and polymethyl methacrylate; vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer; epoxy resin; amorphous polyolefin; polyester; metal such as aluminum; These may be used together if desired.
Among the above materials, amorphous polyolefin and polycarbonate are preferable, and polycarbonate is particularly preferable from the viewpoints of moisture resistance, dimensional stability, and low price. Further, the thickness of the substrate is preferably 0.5 to 1.2 mm, and more preferably 0.6 to 1.1 mm.

The information substrate is formed with unevenness (pregroove) representing information such as a guide groove for tracking or an address signal.
The track pitch of the pregroove is preferably in the range of 300 to 900 nm, more preferably 350 to 850 nm, and still more preferably 400 to 800 nm.
If the thickness is less than 300 nm, it is difficult to form the pregroove accurately, and a crosstalk problem may occur. If the thickness exceeds 900 nm, the recording density may decrease.
The pregroove depth (groove depth) is preferably in the range of 80 to 200 nm, more preferably 110 to 180 nm, and even more preferably 110 to 160 nm.
If it is less than 80 nm, a sufficient recording modulation degree may not be obtained, and if it exceeds 200 nm, the reflectivity may be significantly lowered.
Furthermore, the half width of the pregroove is preferably in the range of 200 to 400 nm, more preferably 230 to 380 nm, and even more preferably 250 to 350 nm.
If the thickness is less than 200 nm, the grooves may not be sufficiently transferred at the time of molding or the recording error rate may be increased. If the thickness exceeds 400 nm, the pits formed at the time of recording spread and cause crosstalk. Or a sufficient degree of modulation may not be obtained.

[Recording layer]
In the case of DVD-R, the dye used in the recording layer is not particularly limited, but examples of usable dyes include cyanine dyes, phthalocyanine dyes, imidazoquinoxaline dyes, pyrylium / thiopyrylium dyes, azurenium dyes, squarylium dyes. Dyes, metal complex salt dyes such as Ni, Cr, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, merocyanine dyes, oxonol dyes, aminium dyes / diimonium dyes And nitroso compounds. Among these dyes, cyanine dyes, phthalocyanine dyes, azurenium dyes, squarylium dyes, oxonol dyes and imidazoquinoxaline dyes are preferable.
The recording layer may be a single layer or a multilayer. The recording layer generally has a thickness of 20 to 500 nm, preferably 30 to 300 nm, and more preferably 50 to 200 nm.

In the case of DVD-RW, the recording layer is preferably made of a phase change type optical recording material composed of at least Ag, Al, Te, and Sb that can take at least two states of a crystalline state and an amorphous state. Such a recording layer can be formed by a known method.
A known dielectric layer is formed on the recording layer as necessary.

[Light reflection layer]
For the light reflection layer, a light reflective material having a high reflectance with respect to laser light is used. The reflectance is preferably 70% or more.
As a light reflective material having a high reflectance, Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd , Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and other metals and semi-metals or stainless steel. These light reflecting materials may be used alone, or may be used in combination of two or more kinds or as an alloy. Among these, Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel are preferable. Particularly preferred is Au, Ag, Al or an alloy thereof, and most preferred is Au, Ag or an alloy thereof.
The thickness of the light reflecting layer is generally in the range of 10 to 300 nm, and preferably in the range of 50 to 200 nm.

[Protective layer]
A protective layer is preferably provided on the reflective layer or the recording layer for the purpose of physically and chemically protecting the recording layer and the like. Note that in the case of adopting the same form as in the case of manufacturing a DVD-R type optical information medium, that is, a structure in which two substrates are bonded with the recording layer inside, it is not always necessary to provide a protective layer. As a material for the protective layer, inorganic substances such as SiO ₂ , MgF ₂ , SnO ₂ , and Si ₃ N ₄ , organic substances such as thermoplastic resins, thermosetting resins, and UV curable resins can be used. The thickness of the protective layer is generally in the range of 0.1 to 100 μm.

Further, for example, a light transmission layer for improving adhesion to the recording layer may be provided between the reflective layer and the recording layer in accordance with the characteristics of the recording layer.
Any material can be used as the light transmission layer as long as it has a transmittance of 90% or more at the laser wavelength.
The light transmission layer can be formed by a conventionally known method, and the thickness of the light transmission layer is preferably 2 to 50 nm.

The protective layer prevents moisture from entering and scratching. The material constituting the protective layer is preferably an ultraviolet curable resin, a visible light curable resin, a thermosetting resin, silicon dioxide, or the like, and more preferably an ultraviolet curable resin. Examples of the ultraviolet curable resin include ultraviolet curable resins such as “SD-640” manufactured by Dainippon Ink and Chemicals, Inc. Further, SD-347 (manufactured by Dainippon Ink & Chemicals, Inc.), SD-694 (manufactured by Dainippon Ink & Chemicals, Inc.), SKCD1051 (manufactured by SKC), and the like can be used. The thickness of the protective layer is preferably in the range of 1 to 200 μm, and more preferably in the range of 50 to 150 μm.
In addition, the protective layer is required to have transparency in a layer configuration used as a laser optical path. Here, “transparency” means that the recording light and the reproduction light are so transparent that the light is transmitted (transmittance: 90% or more).

<Optical information medium manufacturing method>
The method for producing an optical information medium of the present invention capable of producing the above optical information medium will be described in detail below.

[Formation of information boards and protective boards]
The information substrate and the protective substrate can be formed by injection molding, compression molding, or injection compression molding using the aforementioned substrate material. Alternatively, the stamper can be compression-molded by attaching a stamper to one side of a molding die of a hydraulic press machine and pressing the resin heated to the vicinity of the melting point.

[Formation of recording layer]
The recording layer is prepared by dissolving the recording material such as the dye in a suitable solvent together with a binder and the like, and then applying the dye solution to the surface of the substrate (information substrate) on which the pregroove is formed. It is formed by drying after forming a coating film.
As a coating method, the temperature when applying the spin coating method is preferably 23 ° C. or higher, and more preferably 25 ° C. or higher. The upper limit of the temperature is not particularly limited, but the temperature needs to be lower than the flash point of the solvent, and preferably 35 ° C.
When the temperature is lower than 23 ° C., the drying of the solvent becomes slow, and the target dye film thickness (recording layer thickness) cannot be obtained, or the coating and drying time becomes long, and the productivity may decrease.

  As a method for dissolving the recording substance or the like, a method such as ultrasonic treatment, homogenizer, or heating can be applied.

  Solvents for preparing the dye 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; Amides such as dimethylformamide; Hydrocarbons such as methylcyclohexane; Ethers such as tetrahydrofuran, ethyl ether, dioxane; Alcohols such as ethanol, n-propanol, isopropanol, n-butanol diacetone alcohol; 2,2,3,3-tetra Fluorine solvents such as fluoropropanol; glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether; It can gel.

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

The recording layer can contain various anti-fading agents in order to improve the light resistance of the recording layer.
As the antifading agent, a singlet oxygen quencher is generally used. As the singlet oxygen quencher, those described in publications such as known patent specifications can be used.
Specific examples thereof include JP-A Nos. 58-175893, 59-81194, 60-18387, 60-19586, 60-19587, and 60-35054. 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, JP-A-60-47069, JP-A-63-209995, JP-A-4-25492, JP-B-1-38680, JP-A-6-26028, etc., German Patent 350399, and Japan Examples include those described in Chemical Society Journal, October 1992, page 1141.

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

  Representative examples of the antifading agent include nitroso compounds, metal complexes, diimmonium salts, and aminium salts. Examples of these are described in, for example, JP-A-2-300288, JP-A-3-224793, and JP-A-4-146189.

  Examples of the binder include natural organic polymer substances such as gelatin, cellulose derivatives, dextran, rosin, rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene, polyisobutylene, polyvinyl chloride, polyvinylidene chloride, Vinyl resins such as polyvinyl chloride and polyvinyl acetate copolymers, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resins, butyral resins, rubber derivatives, phenol / formaldehyde resins And a synthetic organic polymer such as an initial condensate of a thermosetting resin. When the binder is used, the amount of the binder used is generally 0.2 to 20 parts by mass, preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the dye. It is.

  The application temperature is 20 to 40 ° C., but there is no particular problem, but it is preferably 25 to 35 ° C., more preferably 27 to 33 ° C. The relative humidity at the time of application may be 20 to 60% RH, preferably 30 to 50% RH, and more preferably 35 to 45% RH.

[Formation of light reflection layer]
The light reflecting layer can be formed on the recording layer, for example, by vapor deposition, sputtering or ion plating of the reflective material. In the present invention, for the purpose of improving storage stability or changing the appearance, the reflective layer may be formed by laminating the above materials as a single layer or by laminating two or more materials in multiple layers.

[Formation of protective layer]
In the case of an inorganic substance, the protective layer can be formed by a method such as vacuum vapor deposition, sputtering, or coating. In the case of an organic substance, the protective layer can be formed by laminating a plastic film, coating and drying a coating solution dissolved in a solvent, or the like. Alternatively, the protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic on the reflective layer via an adhesive. 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 preparing a coating solution as it is or by dissolving it in a suitable solvent, coating the coating solution, and curing it by irradiating 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.

In order to prevent warping of the disk, it is preferable to irradiate the coating film with ultraviolet rays using a pulsed light irradiator (preferably a UV irradiator). The pulse interval is preferably msec or less, and more preferably μsec or less. 1 pulse irradiation light amount is not particularly limited, and is preferably 3 kW / cm ² or less, 2 kW / cm ² or less being more preferred.
Further, the number of times of irradiation is not particularly limited, but is preferably 20 times or less, more preferably 10 times or less.

[Heat treatment of protective substrate]
The method for producing an optical information medium of the present invention includes a step of performing a heat treatment at 60 to 90 ° C. on the protective substrate. By performing the heat treatment, warpage due to aging or thermo storage can be reduced, and an optical information medium that sufficiently satisfies the radial tilt standard can be obtained. If the temperature of the heat treatment is less than 60 ° C., the effect of the heat treatment cannot be obtained, and if it exceeds 90 ° C., the protective substrate is deformed. As heat processing temperature, it is preferable to set it as 70-90 degreeC, and it is more preferable to set it as 75-85 degreeC.
In addition, it is preferable to provide the said process within 72 hours after formation of a protective substrate.

  The time for performing the heat treatment is preferably 5 to 300 minutes, more preferably 30 to 240 minutes, and still more preferably 60 to 210 minutes. By setting the heat treatment time to 5 to 300 minutes, the effect of the heat treatment can be sufficiently exhibited.

  In the present invention, the information substrate is preferably subjected to the same heat treatment as the heat treatment applied to the protective substrate. By subjecting the information substrate to heat treatment, it is possible to prevent the deterioration of jitter over time.

[Bonding of information board and protective board]
Various adhesives can be used for bonding the information substrate and the protective substrate. For example, an ultraviolet curable resin (Dai Nippon Ink Chemical Co., Ltd. SD640 or the like) is applied on the protective layer of the information substrate to a thickness of 20 to 60 μm by spin coating to form an adhesive layer. A protective substrate is placed on the formed adhesive layer, and the ultraviolet curable resin is cured by being irradiated with ultraviolet rays from the protective substrate and bonded together.

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

(Example 1)
Using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.), polycarbonate resin is mixed with a spiral groove (groove depth 150 nm, groove width 300 nm, track pitch 0.74 μm) and an outer diameter of 120 mm and an inner diameter having recesses. A transparent substrate (information substrate) having a thickness of 15 mm and a thickness of 0.6 mm was produced. Similarly, a protective substrate was produced.

  The produced protective substrate was heat-treated under a condition of 80 ° C. dry for 3 hours using a clean dry thermo made by Nippon Airtech.

  0.25 g of dye A represented by the following chemical formula and 0.06 g of dye B are mixed with 30 g of fluoroalcohol (2,2,3,3 tetrafluoropropanol solvent), subjected to ultrasonic treatment for 1 hour to dissolve, and a dye coating solution is obtained. Prepared.

・・・色素Ａ

... Dye A

・・・色素Ｂ

... Dye B

  At a temperature of 25 ° C. and a relative humidity of 45% RH, the prepared dye coating solution was applied to the surface of the information substrate on which the groove was formed by a spin coating method to form a recording layer having a thickness of 80 nm.

  The information substrate on which the recording layer was formed was heat treated under the same conditions as the protective substrate.

  Next, silver was sputtered on the formed recording layer by DC magnetron sputtering to form a light reflecting layer having a thickness of 80 nm.

The information substrate on which the recording layer and the light reflecting layer were formed as described above was set on a spin coater, and a UV curable adhesive was applied onto the light reflecting layer and spin coated at 60 rpm. Then, a protective substrate was placed on the information substrate, and further rotated at 4400 rpm, and a UV curable adhesive was filled between the two substrates.
The bonded substrate is transferred to another turntable, moved to the UV irradiation unit together with the turntable, irradiated with UV light to cure the UV curing adhesive, and the two substrates are bonded to each other to form an optical disc (optical information medium). ) Was produced.

(Comparative Example 1)
An optical disc was produced in the same manner as in Example 1 except that the protective substrate was not heat-treated.

[Evaluation]
For the optical disks produced in Example 1 and Comparative Example 1, the radial tilt value immediately after bonding, 4 days after bonding, and 80 ° C. dry storage for 24 hours (thermo storage) was measured using an optical disk mechanical property measuring machine (DLD4000 ( Table 1 shows the maximum value and the minimum value of each radial tilt value.

  From Table 1, the optical disk of Example 1 in which the protective substrate was heat-treated immediately after bonding, 4 days after bonding, and at any time point after storage at 80 ° C. for 24 hours, the radial tilt value (maximum value, It can be seen that there was no change in the (minimum value) and there was little warpage. In contrast, the optical disc of Comparative Example 1 had a very large change in the radial tilt value at each measurement point, and the optical disc was warped.

Claims (3)

A method for producing an optical information medium in which an information substrate having a recording layer or pits capable of recording information by laser light irradiation and a protective substrate are bonded together,
A method for producing an optical information medium, comprising a step of heat-treating the protective substrate at a temperature of 60 to 90 ° C.   The method of manufacturing an optical information medium according to claim 1, wherein the heat treatment time is 5 to 300 minutes.   The method of manufacturing an optical information medium according to claim 1, further comprising a step of performing a heat treatment on the information substrate after forming the recording layer, the same heat treatment as that performed on the protective substrate.