JP3997296B2 - Optical recording medium manufacturing method, quality control method, film thickness measuring method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical recording medium capable of recording / reproducing with a laser beam having a relatively short wavelength, and more particularly to a method for manufacturing an optical recording medium using an organic dye in a recording layer, a quality control method thereof, and the like.
[0002]
[Prior art]
In recent years, not only computer information but also information such as voice, still images, and moving images has been digitized, and the amount of information handled has become extremely large. Along with this, it has become necessary to increase the capacity of optical recording media for storing such information. In response, optical recording media such as DVD-RAM and DVD-RW having a capacity 7 times or more that of conventional CD-R and CD-RW have been commercialized. As a means for realizing higher density, the laser spot diameter for recording / reproducing is reduced by using a technique such as reducing the laser wavelength or increasing the numerical aperture of the lens, thereby enabling DVD-RAM or DVD. -Commercialization of RW was realized.
These recording media that have been commercialized in the past have a structure in which a recording layer, a reflective layer, and a cover layer are sequentially laminated on a substrate. By making laser light incident from the substrate side, Recording / reproduction is performed (hereinafter, such a recording medium is appropriately referred to as a substrate incident type optical recording medium).
[0003]
However, the amount of information tends to increase further in the future. For example, in order to record high-quality video information for two hours or more, a medium having a capacity of 25 GB or more with a CD size of 12 cm is desired.
In order to meet this demand, an optical recording medium that uses a blue laser with a laser wavelength of 405 nm, increases the objective lens NA to 0.85, reduces the laser spot diameter, and records higher density information is proposed. (Jpn. J. Appl. Phys. Vol. 39 (2000) pp. 756-761, Part 1, No. 2B, Feb. 2000).
This optical recording medium is normally a rewritable optical recording medium using a phase change material made of an alloy for the recording layer, and has a structure in which a reflective layer, a recording layer, and a cover layer are sequentially provided on a substrate. This is because the focal length is shortened because the numerical aperture of the lens is larger than before, and it becomes impossible to record and reproduce the recording layer by irradiating the recording layer with the laser beam from the substrate side. This is a film surface incidence method in which laser light is irradiated from the opposite surface to perform recording and reproduction.
Recently, as such a film surface incidence type optical recording medium, a recording layer using a dye material has been developed.
[0004]
[Problems to be solved by the invention]
By the way, in the manufacturing process of the optical recording medium, particularly when a dye material is used for the recording layer, it is important to control the film thickness of the recording layer. Generally, when the thickness of the recording layer using a dye material is 50 to 200 nm, it is necessary to manage the error within a range of several nm.
In a conventional substrate-incidence type optical recording medium, a recording layer is formed on a substrate, and before the reflective layer is formed thereon, the measurement light of the film thickness measuring device is applied to the recording layer and the transmitted light is transmitted. The film thickness of the recording layer is measured by measuring the intensity of light absorption.
[0005]
On the other hand, in the case of a film surface incidence type optical recording medium corresponding to higher density, the reflection layer is formed on the substrate, and the recording layer is formed thereon. For this reason, at the time of measuring the film thickness of the recording layer in the manufacturing process, the reflective layer is already formed on the substrate, and the reflective layer does not transmit light. A similar problem is that the film thickness cannot be measured using transmitted light.
[0006]
The present invention provides an optical recording medium manufacturing method, a quality control method thereof, and a film thickness measuring method capable of measuring the film thickness of the recording layer in such a film surface incidence type optical recording medium. The purpose is to do.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, it is conceivable to irradiate the recording layer on the reflective layer with measurement light and measure the intensity of the reflected light.
However, when a blue laser having a laser wavelength of 405 nm is used for recording / reproduction, the absorption peak of light in the dye material used for the recording layer is 400 nm or less, and the measurement light (wavelength of the presently existing film thickness measuring device) No absorption is shown for wavelengths significantly longer than 400 nm. Therefore, as a matter of course, the film thickness of the recording layer cannot be measured.
[0008]
Therefore, it is conceivable to measure the film thickness of the recording layer using recording / reproducing light, that is, light having a laser wavelength of 405 nm or a wavelength close to this in the above example. However, the recording layer is originally designed with specifications such as film thickness so that the reflection is maximized when irradiated with recording / reproducing light, making it difficult to accurately measure the recording layer thickness. It has become.
This will be described in detail. As shown in FIG. 7, when the measurement light B1 is applied in a state where the reflection layer 2 and the recording layer 3 are formed on the substrate 1, the measurement light B1 is reflected between the reflection layer 2 and the recording layer 3. Reflected not only at the interface but also at the interface between the recording layer 3 and air (film thickness measurement environment atmosphere), the reflected lights B2 and B3 interfere with each other.
8 shows a case where a dye material having a large absorption for recording / reproducing light having a wavelength of, for example, 405 nm is used for the recording layer 3 and the recording layer 3 is irradiated with recording / reproducing light. The curve L1 indicates the relationship between the reflectance (absorption rate) of the reflected light B2 and B3 of the measurement light B1 and the film thickness of the recording layer 3. As shown in FIG. 8, as the film thickness of the recording layer 3 increases, the reflectance tends to decrease as a whole, but the curve L1 becomes wavy due to the influence of the interference described above. In such a relationship, in the example of FIG. 8, the reflectance has a maximum value in the vicinity of the film thickness of 80 nm and 170 nm, and the film thickness of the recording layer 3 indicates the film thickness in the vicinity of the maximum value in terms of recording characteristics. It is usual to design to.
However, when recording / reproducing light is used for film thickness measurement, the design value of the film thickness is in the vicinity of the maximum value, so that the slope of the curve L1 is very small, and the change in reflectivity with respect to the change in film thickness occurs. It becomes minute. For this reason, it is difficult to measure the film thickness of the recording layer 3 with high accuracy to such an extent that an error can be detected by measuring the reflectance of the reflected light B2 and B3.
[0009]
For this purpose, the method for producing an optical recording medium of the present invention comprises a reflective layer forming step of forming a reflective layer on a substrate having a tracking guide groove on the surface, and a recording layer is laminated on the reflective layer. A recording layer forming step to be formed, a reflectance measuring step for measuring the reflectance of the reflected light by irradiating the recording layer with measurement light for measuring the film thickness of the recording layer, and based on the measured reflectance And a film thickness specifying step for specifying the film thickness of the recording layer.
At this time, in the recording layer forming step, the recording layer is formed by containing a first dye having an absorption spectrum in a predetermined wavelength region and a second dye having a maximum absorption wavelength different from the first dye. In the reflectance measurement step, the light in the wavelength region where the second dye has an absorption spectrum can be applied to the recording layer as measurement light. Furthermore, it is preferable that the measurement light has a wavelength different from that of the recording / reproducing light for the recording layer.
In addition, in such a method, based on the thickness of the recording layer obtained, the supply amount of the material forming the recording layer of the optical recording medium to be manufactured later onto the reflective layer can be adjusted. Thus, quality control in the manufacturing process of the optical recording medium can be performed.
Further, if the reflectance measurement step and the film thickness identification step are performed before the recording layer is formed on the reflective layer and before the other layers are formed on the recording layer, the film thickness measurement result can be quickly obtained. Can provide feedback.
[0010]
An optical recording medium manufactured by such a manufacturing method includes a substrate having a tracking guide groove on the surface, a reflective layer formed on the substrate, and a recording layer formed on the reflective layer. Has an absorption maximum in a wavelength region corresponding to the wavelength of the recording / reproducing light and a wavelength region not corresponding to the recording / reproducing.
At this time, the recording layer has a maximum absorption wavelength for the first substance having the maximum absorption wavelength in the wavelength region corresponding to the wavelength of the recording / reproducing light and the wavelength region not corresponding to the recording / reproducing light. A second substance having.
In such an optical recording medium, if light in a wavelength region of an absorption spectrum that does not correspond to recording / reproducing light is applied to the recording layer, the film thickness of the recording layer can be specified based on the reflectance of the reflected light. it can. That is, it can be said that the second substance is for measuring the film thickness of the recording layer by irradiating the recording layer with film thickness measurement light in a wavelength region in which the second substance has an absorption spectrum.
Such a second substance preferably has a maximum wavelength on the longer wavelength side than the maximum absorption wavelength of the first substance. This is because an existing light source can be used as light for film thickness measurement on the long wavelength side.
In addition, the refractive index of the second substance at the wavelength of the film thickness measurement light is higher than the refractive index of the film thickness measurement environment atmosphere such as air, rather than the refractive index of the first substance at the wavelength of the recording / reproducing light. It can also be understood that it is characterized by closeness. With such a configuration, the influence of interference due to reflection at the interface between the recording layer and the film thickness measurement environment atmosphere can be reduced.
Furthermore, it can be understood that the second substance does not react to the recording / reproducing light.
Such a second substance is preferably 0.1 to 30% by weight of the substance forming the recording layer. This is because the recording / reproducing characteristics of the first substance are not adversely affected.
[0011]
By the way, the wavelength region corresponding to the wavelength of the recording / reproducing light is not necessarily one. When light of a plurality of types of wavelengths can be used for recording / reproducing, there are a plurality of wavelength regions corresponding to the wavelengths of the recording / reproducing light. That is, a plurality of types of substances having different absorption wavelength ranges may exist as the first substance in the recording layer.
[0012]
According to the quality control method of the present invention, in a manufacturing process of an optical recording medium in which a reflective layer and a recording layer are sequentially laminated on a substrate having a tracking guide groove on the surface, a film is formed on the recording layer formed on the reflective layer. A reflectance measuring step that applies measurement light for measuring thickness and measures the reflectance of the reflected light; and a film thickness identifying step that identifies the thickness of the recording layer based on the measured reflectance. It is characterized by.
At this time, the recording layer contains at least two dyes having different maximum absorption wavelengths, and the measurement light corresponds to the absorption wavelength region of one dye contained in the recording layer and is different from the recording / reproducing light. A wavelength is preferred.
In the reflectance measurement step, P-polarized light (vertically polarized light) can be incident on the recording layer at a Brewster angle as measurement light, and the reflectance of the reflected light can be measured.
In addition, as the measurement light, P-polarized light is incident on the recording layer at a plurality of angles, and the reflectance of the reflected light is measured. Based on the measured reflectance, the thickness of the recording layer is determined. It is also possible to specify.
[0013]
The present invention can also be understood as a method for measuring the thickness of a layer containing a first dye having a maximum absorption wavelength in a predetermined wavelength region. In this film thickness measurement method, when forming a layer, a second dye having a maximum absorption wavelength different from that of the first dye is added, and the wavelength corresponding to the wavelength region in which the second dye has an absorption spectrum. Is applied to the layer, and the thickness of the layer is measured based on the reflectance of the reflected light.
Further, as the light applied to the layer, P-polarized light can be incident on the layer at a Brewster angle.
Such a film thickness measurement method is particularly suitable for a film surface incidence type optical recording medium in which a recording layer contains a dye (first dye).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a cross-sectional view for explaining the configuration of the optical recording medium in the present embodiment. The optical recording medium of the present invention may or may not have any other layer as long as it has a substrate, a reflective layer, and a recording layer, which are basic components. It is not limited to the layer structure of FIG.
The optical recording medium is basically disc-shaped, and a reflective layer 12, a recording layer (layer) 13, and a cover layer 14 are formed on one side of the substrate 11, and further, between the recording layer 13 and the cover layer 14. In the structure, a separate layer 15 is formed. That is, on the one surface side of the substrate 11, the layers are laminated in the order of the reflective layer 12, the recording layer 13, the separate layer 15, and the cover layer 14.
[0015]
The substrate 11 has a diameter of 120 mm and a thickness of 1.1 mm, for example, and a tracking guide groove 16 is formed on one side thereof. For example, the tracking guide groove 16 is formed in a spiral shape that extends from the center side to the outer periphery side of the substrate 11. Note that disc recognition information, address information, and the like are recorded in advance on the substrate 11 by wobbles and prepits in the tracking guide groove 16. The tracking guide grooves 16 and pre-pits are preferably provided when the substrate 11 is formed, but can also be formed on the substrate 11 using an ultraviolet curable resin layer. When the tracking guide groove 16 has a spiral shape, the groove pitch is usually formed to be about 0.3 to 0.8 μm.
The material of the substrate 11 is not particularly limited as long as it has necessary strength and durability. Conventionally used as a substrate material, such as acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin (particularly amorphous polyolefin), polyester resin, polystyrene resin, epoxy resin, polyamide, polyethersulfone, A resin layer made of a resin such as polyarylate, polysulfone, polyimide, polyetheretherketone, econol, methylpentene polymer, ionomer resin, glass, or a radiation curable resin such as a photocurable resin on the glass. Any of these can be used. In view of high productivity, cost, moisture absorption resistance, etc., injection molded polycarbonate is preferred. Amorphous polyolefin is preferable from the viewpoint of chemical resistance, moisture absorption resistance and the like. Moreover, a glass substrate is preferable from the viewpoint of mechanical stability during high-speed rotation.
Since the substrate 11 does not have to be transparent at the wavelengths of the recording light and the reproduction light, the rigidity may be increased by adding a filler such as carbon fiber to a resin such as polycarbonate in order to prevent vibration during high-speed rotation. . Alternatively, in order to extend the life, an ultraviolet absorber, carbon black, or the like may be added.
[0016]
In the substrate 11, land portions 17 and groove portions 18 are alternately formed in the substrate 11 in the radial direction by the tracking guide grooves 16. In addition, although the cross-sectional shape of the land part 17 and the groove part 18 was substantially trapezoidal in FIG. 1, it is not necessarily restricted to this, It can be made into other cross-sectional shapes, such as a rectangular shape and V shape. is there.
[0017]
The reflective layer 12 is formed by depositing a metal or an alloy on the surface of the substrate 11 by sputtering or the like.
The reflective layer 12 is preferably made of a metal or an alloy, particularly an alloy having good corrosion resistance and low cost. Specifically, for example, Au, Al, Ag, Cu, Ti, Cr, Ni, Pt, Ta, Cr, and Pd metals can be used alone or as an alloy. Among these, Au, Al, and Ag have high reflectivity and are suitable as materials for the reflective layer 12. Other than these as main components, the following may be included. For example, Mg, Se, Hf, V, Nb, Ru, W, Mn, Re, Fe, Co, Rh, Ir, Cu, Zn, Cd, Ga, In, Si, Ge, Te, Pb, Po, Sn, Mention may be made of metals and metalloids such as Bi, Ta, Ti, Pt, Pd, Nd. Among these, those containing Ag as a main component are preferable from the viewpoint of low cost and high reflectivity, and an AgZn alloy is particularly preferable. Here, the main component means one having a content of 50% or more.
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 the reflective layer 12.
[0018]
The recording layer 13 is formed of a dye material containing at least a first substance and a second substance, and has a thickness indicating, for example, an absorbance (absorbance measured at a wavelength of 360 nm using air as a reference) 0.2. It is formed.
In the present embodiment, as shown in FIG. 2, the recording layer 13 includes a first dye having a large absorption (absorption spectrum) with respect to a laser beam having a wavelength used for recording / reproduction, for example, 405 nm. In addition to the laser beam used for recording / reproduction, a large absorption, for example, at least an attenuation coefficient k = 0, for a wavelength for film thickness measurement, for example, light having a thickness of 680 nm (film thickness measurement light, measurement light) A second pigment (second substance) having .05 or more is added. Furthermore, the second dye does not react to the recording / reproducing light.
Here, the second dye may be any dye that exhibits a predetermined abnormal absorption with respect to a wavelength different from that of the laser beam used for recording / reproducing, and the wavelength is the wavelength of the laser beam used for recording / reproducing. Longer wavelength is preferable. This is because light emitted from an existing light source can be used on the long wavelength side.
The amount of the second dye added is preferably 0.1 to 30% by weight in the substance constituting the recording layer 13.
[0019]
Examples of the organic dye used for the first dye and the second dye of the recording layer 13 include a benzophenone dye, a phthalocyanine dye, a naphthalocyanine dye, a cyanine dye, an azo dye, a squarylium dye, and a metal-containing azo dye. Dyes, metal-containing indoaniline dyes, triarylmethane dyes, merocyanine dyes, azurenium dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes, pyrylium dyes, etc. be able to. In particular, it is preferable to use a benzophenone dye or a metal-containing azo dye as the first substance for the recording layer 13.
The recording layer 13 has a transition metal chelate compound (for example, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, bisdithio-α-diketone) as a singlet oxygen quencher in order to improve the stability and light resistance of the 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.
Moreover, a binder, a leveling agent, an antifoamer, etc. can also be used together as needed. Preferable binders include polyvinyl alcohol, polyvinyl pyrrolidone, nitrocellulose, cellulose acetate, ketone resin, acrylic resin, polystyrene resin, urethane resin, polyvinyl butyral, polycarbonate, polyolefin and the like.
The first substance, the second substance, these various additives, the binder resin, and the like that are the forming material of the recording layer 13 may be collectively referred to as “dye material”.
The film thickness of the recording layer 13 is not particularly limited because a suitable value varies depending on the recording method and the like, but is usually 5 nm to 1 μm, preferably 10 nm to 100 nm.
[0020]
The cover layer 14 is necessary to protect the reflective layer 12 from external force and perform recording / reproduction, and the film thickness is strictly defined by the use of the lens to be used. For example, in a lens designed for the cover layer 14 having a wavelength of 405 nm, NA 0.85, and 100 μm thickness, it is preferable that the thickness of the cover layer 14 be controlled within 100 μm ± 2 μm.
The material of the cover layer 14 is not particularly limited as long as it protects the reflective layer 12 from external force and transmits laser light used for recording / reproduction. Examples of the material of the organic substance include a thermoplastic resin, a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin.
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 in combination, and may be used not only as a single layer but also as a multilayer film.
The cover layer 14 can also be provided by adhering a thin film or sheet-like film made of the above resin with an adhesive. Various adhesives such as a room temperature curable adhesive, a thermosetting adhesive, an electron beam curable adhesive, and an ultraviolet curable adhesive can be used as the adhesive.
[0021]
The separate layer 15 is formed by the diffusion of the dye from the recording layer 13 to the cover layer 14 when the cover layer 14 is formed, the penetration of the coating liquid for forming the cover layer into the recording layer 13, or the adhesion when the cover layer 14 is adhered. This is to prevent mixing phenomena such as diffusion and penetration of the agent component into the recording layer 13.
For example, in the case of the recording layer 13 containing an organic dye, the adhesive layer invades the recording layer 13 when the film or sheet-like cover layer 14 is bonded to the recording layer 13 in the manufacturing process of the optical recording medium, and recording / recording is performed. Reproduction characteristics may deteriorate. Even when the cover layer 14 is provided on the recording layer 13 by using a coating liquid, the coating liquid may invade the recording layer 13 similarly to the adhesive, so that the recording / reproducing characteristics may be deteriorated.
On the other hand, providing the separate layer 15 between the recording layer 13 and the cover layer 14 prevents these problems. Thereby, the formed cover layer 14 does not affect the recording layer 13, and the recording / reproducing characteristics of the optical recording medium are improved.
By setting the arithmetic surface roughness Ra of the interface of the cover layer 14 side (recording / reproducing light incident side) in the separate layer 15 to 50 nm or less, scattering of laser light is prevented and recording / reproducing characteristics are improved.
[0022]
The material constituting the separate layer 15 is not particularly limited as long as it has the above-mentioned functions. For example, silicon oxide, particularly oxides such as silicon dioxide, zinc oxide, cerium oxide, yttrium oxide; zinc sulfide, sulfide Examples thereof include sulfides such as yttrium; nitrides such as silicon nitride; silicon carbide; a mixture of oxide and sulfur; Among these, those composed of at least one selected from silicon oxide, zinc sulfide, zinc oxide, silicon nitride, silicon carbide, cerium oxide, yttrium oxide, and a mixture of oxide and sulfur are preferable. A mixture of silicon oxide and zinc sulfide at a ratio of about 30:70 to 90:10 (weight ratio) is also suitable. In addition, a mixture of sulfur and yttrium dioxide is mixed with zinc oxide (Y₂O₂S-ZnO) is also suitable.
As the alloy, an alloy containing silver as a main component and further containing 0.1 to 15 atomic% of at least one element selected from the group consisting of titanium, zinc, copper, palladium, and gold is preferable. Further, those containing silver as a main component and containing 0.1 to 15 atomic% of at least one rare earth element are also suitable. As this rare earth, neodymium, praseodymium, cerium and the like are suitable.
In addition to the above inorganic compounds, the separate layer 15 includes polyvinyl pyrrolidone, polyvinyl alcohol, vinyl acetate resin, vinyl chloride resin, polydimethylsiloxane, water-dispersed high molecular weight copolyester resin, sucrose, Organic substances such as tartaric acid and paraffin may be used. In these, it is preferable to use hydrophilic resins, such as polyvinylpyrrolidone and polyvinyl alcohol.
The thickness of the separate layer 15 may be adjusted so that the thickness of the cover layer 14 and the separate layer 15 becomes the design value of the objective lens in the optical pickup. Specifically, when formed by a dry process such as sputtering, the total film thickness of the cover layer 14 and the separate layer 15 is 10 to 100 μm, and when formed by a wet process such as spin coating, the thickness is about 0.1 to 10 μm. Is preferred.
[0023]
The above is a description of a single-sided recording type optical recording medium having the reflective layer 12 and the recording layer 13 on one side of the substrate 11. However, the invention is not limited to this, and the tracking guide grooves 16 are provided on both sides of the substrate 11. The reflection layer 12 and the recording layer 13 may be provided on each surface. Furthermore, an optical recording medium capable of double-sided recording can be configured by bonding two optical recording media having the reflective layer 12 and the recording layer 13 on one side, with each layer facing outward.
[0024]
The optical recording medium as described above records / reproduces data to / from the recording layer 13 while performing tracking by irradiating the reflection layer 12 in the groove portion 18 with laser light, for example.
Recording on the optical recording medium of the present invention obtained as described above is performed by irradiating the recording layer 13 provided on both sides or one side of the substrate with laser light focused to 1 μm or less. In the portion irradiated with the laser beam, thermal deformation of the recording layer 13 such as decomposition, heat generation, and dissolution due to absorption of laser beam energy occurs, and the optical characteristics change.
Reproduction of the recorded information is performed by reading the difference in reflectance between the portion where the change in optical characteristics has occurred and the portion where the change has not occurred with the laser beam.
[0025]
The optical recording medium can be manufactured in the following manufacturing process.
First, the substrate 11 is produced. Usually, the substrate 11 is formed by injection molding of a resin as a material, and tracking guide grooves 16 having a predetermined pitch and groove depth are formed on the surface thereof. Further, disc recognition information, address information, and the like are recorded in advance on the substrate 11 by wobbles in the grooves. Such information can also be formed by pre-pits. When a glass substrate is used as the substrate 11, the tracking guide groove 16 may be formed on the glass substrate by using a resin, or the glass substrate surface may be cut by etching or the like.
Next, the above-described various alloys and the like are formed on the surface of the substrate 11 by sputtering to form the reflective layer 12. In addition, a known inorganic or organic intermediate layer, adhesive layer, or the like can be provided on the substrate 11 or below the reflective layer 12 in order to improve reflectance, improve recording characteristics, improve adhesion, or the like. . At this time, the thickness of the reflective layer 12 is preferably about 50 to 200 nm.
[0026]
Subsequently, the recording layer 13 is formed on the reflective layer 12 with a thickness indicating a predetermined absorbance (absorbance measured at a wavelength of 360 nm with air as a reference) by applying the film thickness measuring method according to the present invention. Examples of the method for forming the recording layer 13 include a vacuum deposition method and a spin coating method, but the spin coating method is preferable from the viewpoint of mass productivity and cost. Further, depending on the material of the recording layer 13, the vacuum deposition method may be preferable to the coating method.
Further, the coating solvent for forming the recording layer 13 by a coating method such as a spin coating method is not particularly limited as long as it does not erode the reflective layer 12. For example, ketone alcohol solvents such as diacetone alcohol and 3-hydroxy-3-methyl-2-butanone; cellosolv solvents such as methyl cellosolve and ethyl cellosolve; chain hydrocarbon solvents such as n-hexane and n-octane Cyclic hydrocarbon solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane, n-butylcyclohexane, tert-butylcyclohexane and cyclooctane; fluoroalkyl alcohols such as tetrafluoropropanol, octafluoropentanol and hexafluorobutanol Solvent; Hydroxycarboxylic acid ester solvents such as methyl lactate, ethyl lactate, and methyl 2-hydroxyisobutyrate.
In the case of the vacuum vapor deposition method, the recording layer 13 is formed by evaporating the components of the material forming the recording layer 13 by resistance heating or heating by an electron beam and depositing on the reflective layer 12.
[0027]
After forming the recording layer 13 in this way, a separate layer 15 is formed on the recording layer 13. In the case where the separate layer 15 is formed using the above-described inorganic material, a known inorganic material thin film forming method such as various dry processes such as a sputtering method can be used. When a hydrophilic resin is used, the film is formed using a known coating method (wet process) such as a spin coating method using water or a solvent that does not dissolve the material of the recording layer 13 formed earlier. By separating this, the separate layer 15 can be formed.
[0028]
Thereafter, the cover layer 14 is formed to a thickness of, for example, 0.1 mm by applying a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or the like on the formed separate layer 15. Here, a thermoplastic resin, a thermosetting resin, etc. can be formed by dissolving in an appropriate solvent, applying a coating solution, and drying. 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. As a method for forming the cover layer 14 by coating, a coating method such as a spin coating method or a casting method is used in the same manner as the recording layer 13, but the spin coating method is preferable among them.
[0029]
In the present embodiment, in the manufacturing process as described above, the thickness of the recording layer 13 is measured before the recording layer 13 is formed and before the separation layer 15 is formed. Then, the measurement result is fed back to the formation process of the recording layer 13. For example, if the spin coating method is used to form the recording layer 13, after the film thickness of the recording layer 13 is measured, the amount of the dye material applied to form the recording layer 13 is changed thereafter. is there. More specifically, when the recording layer 13 is out of a predetermined range (design tolerance range) as a result of the film thickness measurement, the amount of the dye material to be applied is changed so as to fall within the range. To do.
[0030]
Thus, in order to measure the film thickness of the recording layer 13, the recording layer 13 formed on the reflective layer 12 is added to the material for forming the recording layer 13 from the direction substantially perpendicular to the recording layer 13. The second dye has a large absorption, for example, a film thickness measurement laser beam having a wavelength of 680 nm is applied, and the reflectance (absorption rate) of the reflected light is measured.
FIG. 3 shows, for film thickness measurement, for example, the reflectance (absorbance) of reflected light when light having a wavelength of 680 nm is applied to the recording layer 13 and the recording layer 13 when the attenuation coefficient k = 0.2. It is curve L2 which shows the relationship with the change (0-100 nm) of a film thickness. As shown in FIG. 3, as the film thickness of the recording layer 13 increases, the reflectance decreases substantially linearly.
For example, assuming that the design value of the film thickness of the recording layer 13 is 75 nm, the slope of the curve L2 is sufficiently larger in the vicinity of the design than the curve L1 as shown in FIG. Therefore, the actual film thickness of the recording layer 13 can be obtained in a one-to-one relationship from the measured reflectance, and the film thickness of the recording layer 13 including an error on the order of several nm can be accurately measured. it can.
Incidentally, the curve L3 shown in FIG. 3 shows a large absorption with respect to laser light having a wavelength of 405 nm when the second dye has an attenuation coefficient k = 0, that is, the second dye is not added to the recording layer 13. This is an example in which light having a wavelength of 680 nm is applied for film thickness measurement in the case where it is formed including only the first dye having the above. In this case, the slope of the curve L3 is small as a whole, and it is difficult to accurately measure the film thickness of the recording layer 13, and the effect of adding the second dye is clear.
[0031]
By the way, as shown in FIG. 4, the refractive index n of the recording layer 13 containing the second dye that absorbs light having a wavelength of 680 nm in the state of applying light having a wavelength of 680 nm for film thickness measurement is, for example, 1. 6 On the other hand, in the case of the conventional method as shown in FIG. 7, the refractive index n of the recording layer 3 is, for example, 2.2 in a state where light having a wavelength of 405 nm is applied for film thickness measurement.
Comparing both cases, in the configuration of the present embodiment and the configuration of the conventional method shown in FIG. 7, the film thickness measurement environment atmosphere (generally, in contact with the surfaces of the recording layers 13 and 3 in the film thickness measurement state). Is significantly different from the refractive index of air (refractive index n = 1.0 in the case of air). The recording layer 13 (refractive index n = 1.6) of the present embodiment is more in a film thickness measurement environment atmosphere (air: refractive index n) than the conventional recording layer 3 (refractive index n = 2.2). = 1.0). In general, interference is less likely to occur when the difference in refractive index between the substances on both sides of the interface is smaller. In other words, the recording layer 13 of the present embodiment including the second dye has a higher interference than the conventional configuration. The film thickness can be measured with less influence.
[0032]
As described above, in the recording layer 13, in addition to the first dye having a large absorption with respect to the wavelength of the recording / reproducing laser beam, the wavelength region exhibiting a large absorption is different from the first dye. It was set as the structure which adds a pigment | dye. And in order to measure the film thickness of the recording layer 13, it was set as the structure which irradiates the light of the wavelength corresponding to the wavelength range which a 2nd pigment | dye exhibits big absorption. As a result, the film thickness of the recording layer 13 can be measured by reflection even with a film surface incidence type optical recording medium. In addition, by setting the wavelength region in which the second dye exhibits a large absorption on the longer wavelength side than the first dye, for example, existing laser light sources and spectrum meters used for CD-R recording / reproduction can be used. It is possible to measure the film thickness of the recording layer 13 using a material, and it is possible to use a dye material for CD-R as the second dye, which is economical. In addition, the refractive index of the recording layer 13 containing the second dye having a larger absorption on the longer wavelength side than the first dye is the case where the second dye is not included, that is, the conventional recording layer 3 (see FIG. 7). Since the difference in refractive index with air is small compared to the above, the influence of interference is small, and the film thickness can be measured in a state where the influence of absorption is dominant. This makes it possible to measure the film thickness in a portion where the change in reflectance with respect to the change in film thickness is large, that is, in the portion where the slope of the curve L2 is large in FIG. Correspondingly, highly accurate measurement is possible.
[0033]
In addition, in the manufacturing process of the optical recording medium, as described above, the film thickness is measured in a state where the recording layer 13 is formed on the reflective layer 12, and the measurement result is fed back to the forming process of the recording layer 13. As a result, the film thickness of the recording layer 13 can be efficiently managed in a form close to real time.
[0034]
[Other embodiments]
In the above embodiment, when measuring the film thickness of the recording layer 13 as described above, the light for measuring the film thickness is applied from the direction substantially perpendicular to the recording layer 13, but instead of this, A configuration as shown below can also be adopted.
[0035]
That is, as shown in FIG. 5, when measuring the film thickness of the recording layer 13 containing the first dye and the second dye, light for film thickness measurement is applied from a direction substantially perpendicular to the recording layer 13. Not Brewster angle θ₀And the reflected light is detected.
Brewster angle θ₀Is a value specific to a substance,
tanθ₀= N_d/ N₀
It is represented by Where n_dIs the refractive index of the substance (in this embodiment, the second dye), n₀Is the refractive index of air.
More specifically, in order to measure the film thickness of the recording layer 13, light having a wavelength corresponding to a wavelength region in which the second dye contained in the recording layer 13 exhibits large absorption (for example, laser light having a wavelength of 680 nm) is measured from the light source 30. ) P-polarized light with respect to the recording layer 13 Brewster angle θ₀The light intensity of the reflected light is detected by the light detector 31.
[0036]
Thus, the P-polarized light is changed to Brewster angle θ₀When the recording layer 13 is irradiated with the above, the reflection on the surface of the recording layer 13 can be eliminated, the reflection intensity relative to the absorption and film thickness of the recording layer 13 can be obtained, and the film thickness can be measured with higher accuracy. It becomes possible.
The incident angle of P-polarized light is the Brewster angle θ₀As long as they are substantially equal to each other, some deviation is allowed as long as the effects of the present invention are not impaired.
[0037]
By the way, when the Brewster angle corresponding to the second dye of the recording layer 13 is not known due to various conditions, or when the Brewster angle is likely to fluctuate, the incident angle of the light applied to the recording layer 13 is changed. The incident angle is changed by moving either the light source 30 or the holding unit (not shown) that holds the substrate 11 without being fixed, and the minimum value of the reflected intensity of the reflected light detected by the photodetector 31 at that time is changed. And the film thickness of the recording layer 13 can be obtained based on the minimum value of the reflection intensity.
FIG. 6 shows the change in the reflection intensity when the angle of incidence of the light for film thickness measurement is changed from 40 degrees to 70 degrees, for example, and is reflected in the range of 55 degrees to 60 degrees. The intensity shows the minimum value.
The incident angle indicating the minimum value of such reflection intensity is substantially equal to the Brewster angle, and by using this value for measurement, it is possible to perform highly accurate film thickness measurement.
[0038]
In the above embodiment, an example in which laser light having a wavelength of 680 nm is used as the film thickness measurement light is not limited to this, and visible light or infrared light can also be used. In that case, as a matter of course, the second dye added to the recording layer 13 is one having a large absorption with respect to the wavelength region of the light for film thickness measurement.
In addition, in the above embodiment, a blue laser with a wavelength of 405 nm is used for recording / reproduction, and the first dye having a large absorption with respect to this blue laser is used for the recording layer 13. Light in the wavelength region can also be used for recording / reproducing. Also in this case, the first dye of the recording layer 13 is one having a large absorption with respect to the wavelength region of recording / reproducing light.
In addition, recording with a plurality of wavelengths such as a near infrared laser having a wavelength of about 770 to 830 nm, which is usually used for a CD-R, and a red laser having a wavelength of about 620 to 690 nm, which is used for a DVD-R, as required It is also possible to form a recording layer 13 corresponding to recording with laser light in a plurality of wavelength ranges by using a dye suitable for recording using each as the first dye with respect to light for reproduction. In this case, for film thickness measurement, light having a wavelength other than a plurality of wavelength regions for recording / reproduction as described above is used for film thickness measurement, and the second dye added to the recording layer 13 is used. Uses a material having large absorption with respect to the wavelength region of light for film thickness measurement.
[0039]
Furthermore, in the above embodiment, the film thickness of the recording layer 13 is measured immediately after the recording layer 13 is formed in the manufacturing process, that is, without the cover layer 14 being formed. However, the present invention is not limited to this. It is also possible to measure the film thickness of the recording layer 13 after forming the cover layer 14. In this case, it is difficult to adjust the spin coating amount of the dye material for forming the recording layer 13 in a form close to real time, as in the above embodiment, by quickly feeding back the measurement results. In general, the material forming the cover layer 14 has an advantage that a better measurement condition can be secured because the refractive index is closer to that of air than the recording layer 13.
[0040]
In addition to this, as another embodiment, an example in which the film thickness of the recording layer 13 is measured using the Brewster angle has been described. In this case, it is essential to add the second dye to the recording layer 13. is not.
[0041]
【The invention's effect】
As described above, according to the present invention, the film thickness of the recording layer can be measured with high accuracy in the film surface incidence type optical recording medium.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a layer structure of an optical recording medium in the present embodiment.
FIG. 2 is a diagram showing the relationship between the wavelength of irradiated light and the reflectance in a dye contained in a recording layer of an optical recording medium.
FIG. 3 is a diagram illustrating a relationship between a film thickness of a recording layer and reflectance.
FIG. 4 is a diagram showing a state of reflection on a recording layer.
FIG. 5 is a diagram showing a schematic configuration when measuring the film thickness of a recording layer by applying light at a Brewster angle.
FIG. 6 is a diagram showing the relationship between the angle and the reflectance when the angle of light applied to the recording layer is changed.
FIG. 7 is a diagram showing a state of reflection when light is reflected on a conventional optical recording medium.
FIG. 8 is a diagram showing the relationship between the thickness of a recording layer and the reflectance in a conventional optical recording medium.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Board | substrate, 12 ... Reflective layer, 13 ... Recording layer (layer), 16 ... Tracking guide groove, 30 ... Light source, 31 ... Photodetector

Claims (13)

A reflective layer forming step of forming a reflective layer on a substrate having a tracking guide groove on the surface;
A recording layer forming step of forming a recording layer by laminating on the reflective layer;
A reflectance measurement step of applying measurement light for measuring the film thickness of the recording layer to the recording layer formed on the reflective layer and measuring the reflectance of the reflected light;
Based on the measured reflectivity, have a, a thickness specifying step of specifying a thickness of the recording layer,
In the recording layer forming step, the first dye having an absorption spectrum with respect to the wavelength region of the recording / reproducing light and the maximum absorption wavelength that does not react to the recording / reproducing light unlike the first dye. Forming the recording layer by containing a second dye having
The method of manufacturing an optical recording medium, wherein, in the reflectance measurement step, light in a wavelength region in which the second dye has an absorption spectrum is applied to the recording layer as the measurement light . The measuring light process according to claim 1, wherein the optical recording medium, characterized in that the light for recording / reproducing with respect to the recording layer is a different wavelength.   Based on the film thickness of the recording layer obtained in the film thickness specifying step, on the reflective layer of the material for forming the recording layer in the recording layer forming step executed for an optical recording medium to be manufactured later 2. The method of manufacturing an optical recording medium according to claim 1, wherein an amount of supply to the optical recording medium is adjusted.   2. The reflectance measuring step and the film thickness specifying step are performed before the recording layer is formed on the reflective layer and before another layer is formed on the recording layer. 2. A method for producing an optical recording medium according to 1.   In the reflectance measurement step, as the measurement light, P-polarized light is incident on the recording layer at a Brewster angle determined based on the refractive index of the recording layer, and the reflectance of the reflected light is measured. The method of manufacturing an optical recording medium according to claim 1. In the reflectance measurement step, as the measurement light, P-polarized light is incident on the recording layer at a plurality of angles, and the reflectance of the reflected light is measured.
2. The method of manufacturing an optical recording medium according to claim 1, wherein in the film thickness specifying step, the film thickness of the recording layer is specified based on the lowest one of the measured reflectances. A quality control method in an optical recording medium manufacturing process in which a reflective layer and a recording layer are sequentially laminated on a substrate having a tracking guide groove on the surface,
A reflectance measuring step for irradiating the recording layer formed on the reflective layer with measurement light for measuring the film thickness of the recording layer and measuring the reflectance of the reflected light;
Based on said measured reflectance, have a, a thickness specifying step of specifying a thickness of the recording layer,
Unlike the first dye, the recording layer has a maximum absorption wavelength that does not react with the recording / reproducing light, and has a first absorption spectrum with respect to the wavelength region of the recording / reproducing light. Including a second dye,
The quality control method according to claim 1, wherein the measurement light corresponds to an absorption wavelength region of the second dye contained in the recording layer and has a wavelength different from that of the recording / reproducing light . In the reflectance measurement step, as the measurement light, P-polarized light is incident on the recording layer at a Brewster angle determined based on the refractive index of the recording layer, and the reflectance of the reflected light is measured. The quality control method according to claim 7 . In the reflectance measurement step, as the measurement light, P-polarized light is incident on the recording layer at a plurality of angles, and the reflectance of the reflected light is measured.
8. The quality control method according to claim 7, wherein in the film thickness specifying step, the film thickness of the recording layer is specified based on the lowest one of the measured reflectances. The supply amount onto the reflective layer of a material for forming a recording layer of an optical recording medium to be manufactured later is adjusted based on the film thickness of the recording layer obtained in the film thickness specifying step. Item 8. The quality control method according to Item 7 . 2. The reflectance measuring step and the film thickness specifying step are performed before the recording layer is formed on the reflective layer and before another layer is formed on the recording layer. 7. The quality control method according to 7 . A method for measuring a film thickness of a layer containing a first dye having an absorption spectrum for a predetermined wavelength region,
In forming the layer, a second dye having a maximum absorption wavelength different from the first dye is included,
A method for measuring a film thickness, comprising: applying light in a wavelength region in which the second dye has an absorption spectrum to the layer, and measuring the film thickness of the layer based on a reflectance of the reflected light. The film thickness measuring method according to claim 12 , wherein P-polarized light is incident on the layer at a Brewster angle determined based on the refractive index of the second dye as light applied to the layer.

Images